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• 791. [Article] Active tectonics of the Kashmir Himalaya (NW India) and earthquake potential on folds, out-of-sequence thrusts, and duplexes

  Active tectonics of a deformation front constrains the kinematic evolution and structural interaction between the fold-thrust belt and the most-recently accreted foreland basin. At the Himalayan deformation ...

  Citation × Citation Citation Abstract Copy Title: Active tectonics of the Kashmir Himalaya (NW India) and earthquake potential on folds, out-of-sequence thrusts, and duplexes Author: Gavillot, Yann G. Active tectonics of a deformation front constrains the kinematic evolution and structural interaction between the fold-thrust belt and the most-recently accreted foreland basin. At the Himalayan deformation front, the thrust front is blind, characterized by a broad fold (the Suruin-Mastgarh anticline (SMA)), and displays no emergent faults cutting the southern limb. Dated deformed terraces on the Ujh River constrain the structural style of deformation and shortening rates. Six terraces are recognized, and three yield OSL ages of 53 ka, 33 ka, and 0.4 ka. Terrace restorations through long profiles reveal a deformation pattern characterized by uniform uplift across the anticlinal axis and northern limb, and variable uplift due to rotation of the southern limb. Offset terraces occur between the fold trace and the northern limb. Bedrock dips, stratigraphic thicknesses, and cross sections suggest that a SW-directed duplex at depth drives uniform uplift in the north, and a NE directed wedge thrust drives variable tilt in the south. Localized faulting at the fold axis introduces asymmetrical fold geometry. Folding of the oldest dated terrace suggests rock uplift rates across the SMA range between 1.8 and 2.0 mm/yr. Assuming a 25°-dip for the duplex ramp on the basis of dip data constraints, the shortening rate across the SMA ranges between 3.8-5.4 mm/yr or ~4.6 mm/yr since ~53 ka. Of that rate, 2.7-1.1 mm/yr is likely absorbed by faulting at the fold axis. In comparison, long-term bedrock shortening rates are consistent with our data of Pleistocene shortening rates. Cross sections at the Ujh River transects and Chenab reentrant indicate 6.5 mm/yr and ~4 mm/yr, respectively, using an onset age of thrusting of ~ 3 Ma. Within the Sub-Himalaya deformation belt, new geomorphic mapping demonstrates that active emergent thrust faulting occurs north of the deformation thrust front in the Kashmir Himalaya. The Riasi thrust (RT) comprises the southeastern strand of a ~250 km-long seismically active fault system in Pakistan and Indian Kashmir. Multiple fault strands with Quaternary activity characterize the fault zone near the Chenab River. Vertical separation of ~272 m of Pleistocene fluvial deposits marks the main strand of the RT, or the Main Riasi thrust (MRT). A shortening rate of 10.8-2.8 mm/yr characterizes a ~91-39 ka time interval for the MRT at this location. A fault scarp and offset Holocene terrace mark the southernmost and frontal splay of the RT fault zone, called here the Frontal Riasi thrust (FRT). Differential uplift (21.6±1m) of a Holocene terrace yields a preferred shortening rate of 8.8-4.4 mm/yr. Contact relationships in a trench across the FRT date the last surface rupture of the RT fault zone at ~4,500 yrs ago. Average shortening rates since ~100 ka across the MRT and the FRT range from 10.8 mm/yr to 4.4 mm/yr (7.6±3.3 mm/yr), consistent with long-term bedrock shortening of ~10-14 mm/yr since 5 Ma. Given that Himalayan-Indian convergence is ~11-18 mm/yr, the sum of the intermediate-term shortening rates for the RT (10.8-4.4 mm/yr) and the deformation front (5.4-3.8 mm/yr), accounts for most of the total geological shortening in Kashmir. Using average rates, internal faults (RT) absorb 50% of the Himalayan shortening, comparatively more than the deformation front (~30%) in Kashmir. Similarities in the structural setting between the Riasi thrust and the Balakot-Bagh fault, including millennia recurrence, suggest the potential of Mw 7 to 8 earthquakes on the RT fault zone, similar to the source of the Mw 7.6 2005 Kashmir earthquake on the Balakot-Bagh fault segment. Lower rate at the deformation front may suggest an even longer recurrence interval, but nonetheless potentially devastating with predicted Mw of 7.5-7.6 along the 180-250 km-long structure. Apatite and zircon (U-Th)/He cooling ages are used to quantify the pattern of distributed deformation and overall thrust-belt kinematics at longer timescales across the Kashmir Himalayas. Apatite (U-Th)/He (AHe) cooling ages for the foreland molasse sediments are consistently younger than the sediment age, indicating that ages of Sub-Himalayan belt samples are reset. We interpret regional pattern of young AHe cooling ages (<3 Ma) in the foreland with peak cooling at 1.9-3.2 Ma to represent rapid coeval fault-related exhumation on multiple structures across the Sub-Himalaya. In the hinterland front ranges of the Pir Panjal, the MBT and MCT thrusts are characterized by older cooling (>4.7 Ma). For zircon (U-Th)/He (ZHe), probability density plots of samples from both detrital cooling ages in the foreland and reset cooling ages in the hinterland show a pronounced spike in cooling between ~16 and 20 Ma, a period where MCT motion is well documented throughout the Himalaya. Estimates of exhumation rates for the sum of Sub-Himalayan structures are higher (2.8-2.2 mm/yr) than across the MCT/MBT (<1 mm/yr) in the Pir Panjal Range. Cooling patterns across the Kashmir Himalayas do not correlate with monsoon precipitation gradients, suggesting climate forcing is decoupled from erosion and exhumation. Distributed rather than localized forward-propagating deformation characterizes fault-related exhumation for the orogenic wedge development in the Sub-Himalayan belt since at least ~2-3 Ma. In the hinterland, coeval young cooling ages (< 3 Ma) and high exhumation rates (2.8-1.3 mm/yr) across the Kishtwar Window, >100 km north of the deformation front, suggest tectonic-driven rapid exhumation across the orogenic wedge coincides with localities of predicted changes in ramp geometry and/or active orogenic growth. We attribute a pattern of distributed deformation and coeval faulting across the Sub-Himalaya to the effects of pre-existing basin architecture in Kashmir. Title: Active tectonics of the Kashmir Himalaya (NW India) and earthquake potential on folds, out-of-sequence thrusts, and duplexes Author: Gavillot, Yann G. Active tectonics of a deformation front constrains the kinematic evolution and structural interaction between the fold-thrust belt and the most-recently accreted foreland basin. At the Himalayan deformation front, the thrust front is blind, characterized by a broad fold (the Suruin-Mastgarh anticline (SMA)), and displays no emergent faults cutting the southern limb. Dated deformed terraces on the Ujh River constrain the structural style of deformation and shortening rates. Six terraces are recognized, and three yield OSL ages of 53 ka, 33 ka, and 0.4 ka. Terrace restorations through long profiles reveal a deformation pattern characterized by uniform uplift across the anticlinal axis and northern limb, and variable uplift due to rotation of the southern limb. Offset terraces occur between the fold trace and the northern limb. Bedrock dips, stratigraphic thicknesses, and cross sections suggest that a SW-directed duplex at depth drives uniform uplift in the north, and a NE directed wedge thrust drives variable tilt in the south. Localized faulting at the fold axis introduces asymmetrical fold geometry. Folding of the oldest dated terrace suggests rock uplift rates across the SMA range between 1.8 and 2.0 mm/yr. Assuming a 25°-dip for the duplex ramp on the basis of dip data constraints, the shortening rate across the SMA ranges between 3.8-5.4 mm/yr or ~4.6 mm/yr since ~53 ka. Of that rate, 2.7-1.1 mm/yr is likely absorbed by faulting at the fold axis. In comparison, long-term bedrock shortening rates are consistent with our data of Pleistocene shortening rates. Cross sections at the Ujh River transects and Chenab reentrant indicate 6.5 mm/yr and ~4 mm/yr, respectively, using an onset age of thrusting of ~ 3 Ma. Within the Sub-Himalaya deformation belt, new geomorphic mapping demonstrates that active emergent thrust faulting occurs north of the deformation thrust front in the Kashmir Himalaya. The Riasi thrust (RT) comprises the southeastern strand of a ~250 km-long seismically active fault system in Pakistan and Indian Kashmir. Multiple fault strands with Quaternary activity characterize the fault zone near the Chenab River. Vertical separation of ~272 m of Pleistocene fluvial deposits marks the main strand of the RT, or the Main Riasi thrust (MRT). A shortening rate of 10.8-2.8 mm/yr characterizes a ~91-39 ka time interval for the MRT at this location. A fault scarp and offset Holocene terrace mark the southernmost and frontal splay of the RT fault zone, called here the Frontal Riasi thrust (FRT). Differential uplift (21.6±1m) of a Holocene terrace yields a preferred shortening rate of 8.8-4.4 mm/yr. Contact relationships in a trench across the FRT date the last surface rupture of the RT fault zone at ~4,500 yrs ago. Average shortening rates since ~100 ka across the MRT and the FRT range from 10.8 mm/yr to 4.4 mm/yr (7.6±3.3 mm/yr), consistent with long-term bedrock shortening of ~10-14 mm/yr since 5 Ma. Given that Himalayan-Indian convergence is ~11-18 mm/yr, the sum of the intermediate-term shortening rates for the RT (10.8-4.4 mm/yr) and the deformation front (5.4-3.8 mm/yr), accounts for most of the total geological shortening in Kashmir. Using average rates, internal faults (RT) absorb 50% of the Himalayan shortening, comparatively more than the deformation front (~30%) in Kashmir. Similarities in the structural setting between the Riasi thrust and the Balakot-Bagh fault, including millennia recurrence, suggest the potential of Mw 7 to 8 earthquakes on the RT fault zone, similar to the source of the Mw 7.6 2005 Kashmir earthquake on the Balakot-Bagh fault segment. Lower rate at the deformation front may suggest an even longer recurrence interval, but nonetheless potentially devastating with predicted Mw of 7.5-7.6 along the 180-250 km-long structure. Apatite and zircon (U-Th)/He cooling ages are used to quantify the pattern of distributed deformation and overall thrust-belt kinematics at longer timescales across the Kashmir Himalayas. Apatite (U-Th)/He (AHe) cooling ages for the foreland molasse sediments are consistently younger than the sediment age, indicating that ages of Sub-Himalayan belt samples are reset. We interpret regional pattern of young AHe cooling ages (<3 Ma) in the foreland with peak cooling at 1.9-3.2 Ma to represent rapid coeval fault-related exhumation on multiple structures across the Sub-Himalaya. In the hinterland front ranges of the Pir Panjal, the MBT and MCT thrusts are characterized by older cooling (>4.7 Ma). For zircon (U-Th)/He (ZHe), probability density plots of samples from both detrital cooling ages in the foreland and reset cooling ages in the hinterland show a pronounced spike in cooling between ~16 and 20 Ma, a period where MCT motion is well documented throughout the Himalaya. Estimates of exhumation rates for the sum of Sub-Himalayan structures are higher (2.8-2.2 mm/yr) than across the MCT/MBT (<1 mm/yr) in the Pir Panjal Range. Cooling patterns across the Kashmir Himalayas do not correlate with monsoon precipitation gradients, suggesting climate forcing is decoupled from erosion and exhumation. Distributed rather than localized forward-propagating deformation characterizes fault-related exhumation for the orogenic wedge development in the Sub-Himalayan belt since at least ~2-3 Ma. In the hinterland, coeval young cooling ages (< 3 Ma) and high exhumation rates (2.8-1.3 mm/yr) across the Kishtwar Window, >100 km north of the deformation front, suggest tectonic-driven rapid exhumation across the orogenic wedge coincides with localities of predicted changes in ramp geometry and/or active orogenic growth. We attribute a pattern of distributed deformation and coeval faulting across the Sub-Himalaya to the effects of pre-existing basin architecture in Kashmir. 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• 792. [Article] Biological Soil Crusts of the Great Basin : An Examination of their Distribution, Recovery from Disturbance and Restoration

  We are at risk of losing the sagebrush steppe in the floristic Great Basin to the invasion of Bromus tectorum L., cheatgrass. The floristic Great Basin includes the Central Basin and Range, the Northern ...

  Citation × Citation Citation Abstract Copy Title: Biological Soil Crusts of the Great Basin : An Examination of their Distribution, Recovery from Disturbance and Restoration Author: Condon, Lea A. We are at risk of losing the sagebrush steppe in the floristic Great Basin to the invasion of Bromus tectorum L., cheatgrass. The floristic Great Basin includes the Central Basin and Range, the Northern Basin and Range, and the Snake River Plain. The Great Basin receives most of its precipitation as winter snow and experiences hot and dry summers. Early accounts of invasion by cheatgrass associated it with farming and grazing practices. The non-farmed areas in the region are still actively grazed and referred to as rangelands. On invaded sites, cheatgrass changes the flammability of fuels on invaded landscapes, across the Great Basin, from coarser fuels that are widely spaced to fine fuels that are continuous, filling interspaces between perennial plants. The fuel load created by cheatgrass regenerates annually. This has resulted in a change in the fire regime of the Great Basin from infrequent, small fires to more frequent large fires. In arid lands globally, soil interspaces between perennial plants are typically filled by biological soil crusts (biocrusts). This is also true for ecoregions in and surrounding the Great Basin. Biocrusts are known to influence many ecosystem processes that cheatgrass influences, specifically nutrient cycling and availability of soil moisture. However, little work has been done on biocrusts of the Great Basin and to my knowledge, no one had restored biocrusts within the Great Basin. I attempt to fill some of this knowledge "interspace" by relating biocrust presence to disturbances and cheatgrass invasion and to demonstrate the potential for biocrust restoration within this region. Previous work in eastern Oregon demonstrated relationships between declines in biocrusts and increases in cheatgrass with increasing grazing intensity, soil temperature, and decreasing soil moisture. Grazing intensity influences the cover of biocrusts as well as the abundance and composition of native bunchgrasses. Native bunchgrasses influence the interspace gap size between perennial herbaceous vegetation which is directly associated with the cover of cheatgrass. In a region where grazing records may be incomplete and may exist in various forms of data, having a simple indicator of grazing impacts would be useful. It is also crucial that we have an understanding of what leads to loss of site resistance to cheatgrass. This previous work suggested that cover of biocrusts, in addition to bunchgrass composition, were associated with increased site resistance to cheatgrass. In Chapter 2, I used current grazing records from a range of suspected grazing intensities, to examine the ability of both biocrusts and perennial vegetation to maintain site resistance to cheatgrass after fire. I examined the ability of mosses and lichens to maintain site resistance separately given that these are two very different kinds of organisms. Mosses are non-vascular plants and early colonizers of sites in primary succession. Lichens have a symbiotic relationship between a fungus and a photosynthesizing partner, a cyanobacteria, an algae or both. Using structural equation models, I corroborated that perennial vegetation and lichens are associated with increased site resistance to cheatgrass and that mosses are associated with and may facilitate both lichens and perennial herbaceous vegetation. Also in Chapter 2, I identified that burned sites were associated with increased grazing pressure by livestock as shown by increases in cow dung density and increases in gap size between perennial herbaceous vegetation. The Great Basin is managed for cover of perennial vegetation but it could also be managed for morphogroups of biocrusts. Considering morphogroups of biocrusts, which were shown in the Chapter 2 to be important for site resilience and resistance, I wanted to determine if there were site characteristics associated with biocrust distribution and recovery from disturbance, across the Great Basin. Outside of the Great Basin on the Columbia Plateau, others had found that mosses were still present on disturbed sites whereas lichens were often lost. In addition, biocrust species were more associated with soil properties than with grazing by livestock. Given that grazing by livestock and fire are common disturbances across the region, I wanted to know if the same relationships between biocrusts, soil properties and disturbance were true in the Great Basin. I found that cover of the lichen component of biocrusts was higher on sites that were both ungrazed and unburned. Factors related to disturbance characteristics were correlated with the recovery of biocrusts, even after accounting for time since fire. Factors related to disturbance, a composite of grazing and fire, were more important for structuring the cover and composition of morphogroups as opposed to environmental conditions. Lichens were the most sensitive morphogroup, compared to tall mosses, followed by short mosses which were favored by some disturbance but reduced in cover immediately after fire. Perennial grasses were also favored by some disturbance and perennial forbs did not show an obvious relationship with a disturbance gradient. Chapter 3 highlights that grazing by livestock and fire are common disturbances across the region so much so that the effects of one on the abundances of morphogroups could not be separated from the other. Given the observed contributions of biocrusts to site resilience and resistance, I wanted to know if we could restore biocrusts in the field. Others have grown mosses in a lab setting but this was the first study to restore mosses in the Great Basin. I tested the influence of factors that are commonly used in the field of restoration for facilitating plant establishment. I tested the influence of season of inoculation (fall versus spring), the addition of organic matter (in the form of jute net), irrigation (in the spring season) and the climatic setting of moss the collection sites (for moss propagation), in comparison to the experiment site (warm, dry versus cool, moist) on moss growth. I used two moss species: a ruderal (Bryum argenteum) and a later successional species (Syntrichia ruralis). Moss cover increased when the climatic setting of the collection site matched the experiment site. Mosses were facilitated by the addition of the organic jute netting, putting on most of their growth in winter. Although there is still a great deal of work to be done developing moss material for restoration and working out inoculation rates of moss fragments, similar to seeding rates, land managers have another tool to consider when rehabilitating sites after disturbance. Managing the Great Basin for biocrusts in the presence of grazing and fire will not only increase site resistance to cheatgrass but it will add to the conservation of ecosystem functions related to nutrient cycling, hydrologic cycling and soil erosion. Site resistance will be improved with increased periods of rest from grazing following fire. The lichen component of biocrusts is a more sensitive indicator of disturbance when compared with mosses or perennial vegetation but we are currently actively managing for perennial vegetation and not biocrusts. The moss component of biocrusts can be successfully restored in the Great Basin, without irrigation. This dissertation shows that land managers should consider a suite of organisms, in addition to perennial plants to achieve management goals and maintain site resistance to cheatgrass. Title: Biological Soil Crusts of the Great Basin : An Examination of their Distribution, Recovery from Disturbance and Restoration Author: Condon, Lea A. We are at risk of losing the sagebrush steppe in the floristic Great Basin to the invasion of Bromus tectorum L., cheatgrass. The floristic Great Basin includes the Central Basin and Range, the Northern Basin and Range, and the Snake River Plain. The Great Basin receives most of its precipitation as winter snow and experiences hot and dry summers. Early accounts of invasion by cheatgrass associated it with farming and grazing practices. The non-farmed areas in the region are still actively grazed and referred to as rangelands. On invaded sites, cheatgrass changes the flammability of fuels on invaded landscapes, across the Great Basin, from coarser fuels that are widely spaced to fine fuels that are continuous, filling interspaces between perennial plants. The fuel load created by cheatgrass regenerates annually. This has resulted in a change in the fire regime of the Great Basin from infrequent, small fires to more frequent large fires. In arid lands globally, soil interspaces between perennial plants are typically filled by biological soil crusts (biocrusts). This is also true for ecoregions in and surrounding the Great Basin. Biocrusts are known to influence many ecosystem processes that cheatgrass influences, specifically nutrient cycling and availability of soil moisture. However, little work has been done on biocrusts of the Great Basin and to my knowledge, no one had restored biocrusts within the Great Basin. I attempt to fill some of this knowledge "interspace" by relating biocrust presence to disturbances and cheatgrass invasion and to demonstrate the potential for biocrust restoration within this region. Previous work in eastern Oregon demonstrated relationships between declines in biocrusts and increases in cheatgrass with increasing grazing intensity, soil temperature, and decreasing soil moisture. Grazing intensity influences the cover of biocrusts as well as the abundance and composition of native bunchgrasses. Native bunchgrasses influence the interspace gap size between perennial herbaceous vegetation which is directly associated with the cover of cheatgrass. In a region where grazing records may be incomplete and may exist in various forms of data, having a simple indicator of grazing impacts would be useful. It is also crucial that we have an understanding of what leads to loss of site resistance to cheatgrass. This previous work suggested that cover of biocrusts, in addition to bunchgrass composition, were associated with increased site resistance to cheatgrass. In Chapter 2, I used current grazing records from a range of suspected grazing intensities, to examine the ability of both biocrusts and perennial vegetation to maintain site resistance to cheatgrass after fire. I examined the ability of mosses and lichens to maintain site resistance separately given that these are two very different kinds of organisms. Mosses are non-vascular plants and early colonizers of sites in primary succession. Lichens have a symbiotic relationship between a fungus and a photosynthesizing partner, a cyanobacteria, an algae or both. Using structural equation models, I corroborated that perennial vegetation and lichens are associated with increased site resistance to cheatgrass and that mosses are associated with and may facilitate both lichens and perennial herbaceous vegetation. Also in Chapter 2, I identified that burned sites were associated with increased grazing pressure by livestock as shown by increases in cow dung density and increases in gap size between perennial herbaceous vegetation. The Great Basin is managed for cover of perennial vegetation but it could also be managed for morphogroups of biocrusts. Considering morphogroups of biocrusts, which were shown in the Chapter 2 to be important for site resilience and resistance, I wanted to determine if there were site characteristics associated with biocrust distribution and recovery from disturbance, across the Great Basin. Outside of the Great Basin on the Columbia Plateau, others had found that mosses were still present on disturbed sites whereas lichens were often lost. In addition, biocrust species were more associated with soil properties than with grazing by livestock. Given that grazing by livestock and fire are common disturbances across the region, I wanted to know if the same relationships between biocrusts, soil properties and disturbance were true in the Great Basin. I found that cover of the lichen component of biocrusts was higher on sites that were both ungrazed and unburned. Factors related to disturbance characteristics were correlated with the recovery of biocrusts, even after accounting for time since fire. Factors related to disturbance, a composite of grazing and fire, were more important for structuring the cover and composition of morphogroups as opposed to environmental conditions. Lichens were the most sensitive morphogroup, compared to tall mosses, followed by short mosses which were favored by some disturbance but reduced in cover immediately after fire. Perennial grasses were also favored by some disturbance and perennial forbs did not show an obvious relationship with a disturbance gradient. Chapter 3 highlights that grazing by livestock and fire are common disturbances across the region so much so that the effects of one on the abundances of morphogroups could not be separated from the other. Given the observed contributions of biocrusts to site resilience and resistance, I wanted to know if we could restore biocrusts in the field. Others have grown mosses in a lab setting but this was the first study to restore mosses in the Great Basin. I tested the influence of factors that are commonly used in the field of restoration for facilitating plant establishment. I tested the influence of season of inoculation (fall versus spring), the addition of organic matter (in the form of jute net), irrigation (in the spring season) and the climatic setting of moss the collection sites (for moss propagation), in comparison to the experiment site (warm, dry versus cool, moist) on moss growth. I used two moss species: a ruderal (Bryum argenteum) and a later successional species (Syntrichia ruralis). Moss cover increased when the climatic setting of the collection site matched the experiment site. Mosses were facilitated by the addition of the organic jute netting, putting on most of their growth in winter. Although there is still a great deal of work to be done developing moss material for restoration and working out inoculation rates of moss fragments, similar to seeding rates, land managers have another tool to consider when rehabilitating sites after disturbance. Managing the Great Basin for biocrusts in the presence of grazing and fire will not only increase site resistance to cheatgrass but it will add to the conservation of ecosystem functions related to nutrient cycling, hydrologic cycling and soil erosion. Site resistance will be improved with increased periods of rest from grazing following fire. The lichen component of biocrusts is a more sensitive indicator of disturbance when compared with mosses or perennial vegetation but we are currently actively managing for perennial vegetation and not biocrusts. The moss component of biocrusts can be successfully restored in the Great Basin, without irrigation. This dissertation shows that land managers should consider a suite of organisms, in addition to perennial plants to achieve management goals and maintain site resistance to cheatgrass. Close

• 793. [Article] Conserving energy by safe and environmentally acceptable practices in maintaining and procuring transmission poles ; August 1984

  Improved Fumigants After 14 years, chloropicrin, Vapam and Vorlex continue to effectively control internal decay of pressure-treated Douglas-fir transmission poles, but 6 years after application of methylisothiocyanate (MIT) ...

  Citation × Citation Citation Abstract Copy Title: Conserving energy by safe and environmentally acceptable practices in maintaining and procuring transmission poles ; August 1984 Author: Oregon State University, Oregon State University. Dept. of Forest Products Improved Fumigants After 14 years, chloropicrin, Vapam and Vorlex continue to effectively control internal decay of pressure-treated Douglas-fir transmission poles, but 6 years after application of methylisothiocyanate (MIT) some poles are becoming reinfested by decay fungi although NIT residues remain high in these poles. The closed-tube bioassay, developed through our research, is an effective method for detecting fumigant persistance, and future studies will aim at determining the actual fumigant concentrations detected in wood by this bioassay. A study of MIT movement through Douglas-fir pole sections following treatment with gelatin encapsulated MIT was completed and results indicate that addition of small quantities of water along with the capsules will give excellent fumigant release and movement into the wood. Decay fungi were virtually eliminated from in service transmission poles 21 months after treatment with gelatin encapsulated MIT near the groundline. In poles treated up to 12 feet above the groundline with encapsulated MIT and chloropicrin, no decay fungi could be isolated 1 year after treatment. Both fumigants were well distributed through the poles and appear to have moved laterally from the treatment holes. One of the goals of our research has been eventual fumigant application to poles at the treatment plant shortly after conventional preservative treatments. This would provide predrilled holes for later fumigant retreatment and would effectively protect the entire i iipole cross section. While the most economical application method would involve incorporating the fumigant treatment holes into the conventional predrilling process, it would also result in preservative treated fumigant holes. Consequently we have initiated studies to determine the influence of creosote and pentachlorophenol on fumigant movement into treated wood. Preliminary results indicate that creosote and P-9 penta base oil slow movement of MIT into wood but do not prevent the build up of fungitoxic concentrations in the wood. The new, pelletized MIT formulation has been evaluated in our laboratory assay for wood fumigants. The results indicate that pelletized MIT is as effective as pure MIT on an active ingredient basis. Since pelletized MIT has many similar application and safety advantages as encapsulated MIT, we intend to further evaluate pellets in poles in service. Cedar Sapwood Decay Control The effectiveness of seventeen chemicals (3 oil-borne, 14 water-borne) for controlling above-ground decay of cedar sapwood was evaluated using a modified soil block test and an Aspergillus bioassay. Pentachlorophenol (10%) in diesel oil, currently used for protecting cedar poles, was markedly superior to all other chemicals evaluated probably because of the increased penetrability of the oil, since penta in water at the same strength did not perform as well. Three other formulations, copper-8-quinolinolate (oil), pentachlorophenol (2% in water), and 3-iodo propynyl butyl carbamate (2% in water), exhibited some residual effectiveness; however, more time is necessary to determine if these chemicals will remain effective. An additional five chemicals will be evaluated this coming spring. iii The persistence of chloropicrin 5 years after treatment in western redcedar was also evaluated using open tube bioassays, closetube bioassays and gas chromatographic determinations. The open tube bioassay indicated that chioropicrin still effectively limited growth of the assay fungus, P. placenta. Similarly, closed tube bioassays indicated strong inhibition in the pole interior and lower inhibitions near the surface. Extraction/gas chromatographic procedures detected chloropicrin in all cores examined with the highest concentrations towards the pole interior. Chioropicrin concentration did not correlate with closed tube results, suggesting that these tests are measuring different fumigant properties. The results indicate that chloropicrin should be an effective treatment for preventing cedarbutt rot and may provide some protection to pole sapwood. Bolt Holes Control poles for the bolt hole protection study were again sampled and insufficient decay was found in these poles to warrant evaluation of the various decay prevention treatments. We will reevaluate the control poles this summer. Detecting decay and estimating residual strength in poles An infrared spectrophotometric method of analyzing warm water extracts of decayed and non-decay wood was evaluated with a number of brown and white rot fungi. Brown rot was highly correlated with absorption peaks produced at wavelength 17201cm. Work is now underway to identify this peak to determine if less involved detection methods might be employed. iv Fluorescent labeled lectins, which have high specificity for selected carbohydrates, were also evaluated as potential fungal indicators. Of the lectins tested, wheat germ agglutinin appears the most promising since it strongly reacted with chitin in the fungal cell wall, making decay hyphae visible at very early stages of decay. Evaluation of Douglas-fir beams air-seasoned for 1 or 2 years using Pilodyn pin penetration, longitudinal compression, radial compression, bending and culturing indicated that, while there is a well established fungal flora in the wood, this flora has not yet affected strength. These tests will be performed on the 3 year airseasoned beams this coming year. Of the strength tests employed, longitudinal compression appears promising for estimating pole bending strength and we intend to further evaluate this method. As a second phase of this evaluation, the effect of moisture content on Pilodyn pin penetration was examined. This information is necessary since pin penetration varies with moisture content and must be corrected to compare values from different poles. Pin penetration increased with increasing moisture content up to fiber saturation and stabilized above this point. The moisture content at 0.5 inches was highly correlated with pin penetration, and this depth might be a convenient standard measuring point. En a new phase of the project, preliminary acoustic testing was begun using small beams from poles at varying stages of decay. These beams were sonically evaluated and then loaded to failure in three point bending tests. Sonic evaluation was highly correlated with NOR; however, much more testing will be necessary before such an apparatus can be applied to posts or poles. V Initiation of decay in Douglas-fir poles prior to pressure treatment The ability of basidiomycetes isolated from air-seasoning poles to reduce wood strength was evaluated in rapid tests for toughness by impact bending and changes in the breaking radius of Douglas-fir test wafers. Although some fungi behaved differently in the two tests, the test correlations were relatively high (r2 = O.78S). Of 26 basidiomycetous species evaluated, Poria placenta, P. carbonica, P. xantha and Crustoderma dryinum most rapidly decayed Douglas-fir heartwood, but at least one isolate of most of the other species tested significantly reduced toughness. While the wood decaying ability of each fungus is important, the frequency of isolation also must be considered when determining the overall importance of a species. To determine the influence of wood temperature and moisture content on establishment of P. carbonica in Douglas-fir heartwood, a method was developed for direct observation of germinating spores on wood. In this test, chiamydospores and basidiospores failed to germinate or colonize wood at moisture content below fiber saturation suggesting that free water is necessary for infection. Chiamydospores germinated most readily and colonized wood at 22°C, while germination was significantly lower and the fungus failed to become established in wood at 5 or 35°C. Similar temperature responses were obtained with basidiospores although these spores failed to germinate at 5 and 35°C. Nevertheless, basidiospores may remain viable and retain the potential to establish colonies once conditions become more favorable. vi Exposure of sterilized pole sections at four Pacific Northwest air-seasoning sites for successive 3-month periods showed a significant increase in basidiomycete isolation frequency for the period Nov. '81-Jan.'82. Furthermore, the frequency increased from the northern to the southern most site. Detailed study of the site weather patterns strongly suggests that increased basidiomycetous infection can be related to number of days with measurable rain fall and temperatures conducive to fungal growth. During the other periods studied, temperature or precipitation conditions were unfavorable for infection and pole section moisture contents fell below fiber saturation. This in turn limited spore germination and fungal colonization of the wood. About 30 different basidiomycetous species have been identified from isolates cultured from sterilized pole sections exposed at the four sites. In general, the species were the same as those isolated form air-seasoning poles although there were some significant differences between the species obtained from the different sites. The frequency of P. placenta mono- and dikaryons was particularly high with monokaryons more abundant at three of the four locations. Individual species exhibited distinct colonization patterns from different pole zones. For example, P. placenta was isolated most frequently from heartwood exposed at the pole ends while Peniophora spp. and llaemotostereum sanguinolentum were recovered most frequently from the upper surfaces of the pole sections. vii Preventing infection of poles by decay fungi during air-seasoning Pole sections treated with ammonium bifluoride (NH4HF2) or gelatin encapsulated MIT and chioropicrin were extensively sampled after air seasoning to determine the influence of these chemicals on wood colonization by decay fungi. Preliminary results indicate that after 2 years NH4HF2 and the fumigants significantly reduced basidiomycetous colonization of sterile wood. Surface Decay Poles treated with Vapam 14 years ago were extensively cored, the cores were cultured and the resulting fungi were identified to evaluate the fungal flora of fumigant treated wood. A well developed fungal flora was identified that differed from that found in nonfumigant treated wood. These fungi will be further evaluated to determine their role in fumigant effectiveness. Title: Conserving energy by safe and environmentally acceptable practices in maintaining and procuring transmission poles ; August 1984 Author: Oregon State University, Oregon State University. Dept. of Forest Products Improved Fumigants After 14 years, chloropicrin, Vapam and Vorlex continue to effectively control internal decay of pressure-treated Douglas-fir transmission poles, but 6 years after application of methylisothiocyanate (MIT) some poles are becoming reinfested by decay fungi although NIT residues remain high in these poles. The closed-tube bioassay, developed through our research, is an effective method for detecting fumigant persistance, and future studies will aim at determining the actual fumigant concentrations detected in wood by this bioassay. A study of MIT movement through Douglas-fir pole sections following treatment with gelatin encapsulated MIT was completed and results indicate that addition of small quantities of water along with the capsules will give excellent fumigant release and movement into the wood. Decay fungi were virtually eliminated from in service transmission poles 21 months after treatment with gelatin encapsulated MIT near the groundline. In poles treated up to 12 feet above the groundline with encapsulated MIT and chloropicrin, no decay fungi could be isolated 1 year after treatment. Both fumigants were well distributed through the poles and appear to have moved laterally from the treatment holes. One of the goals of our research has been eventual fumigant application to poles at the treatment plant shortly after conventional preservative treatments. This would provide predrilled holes for later fumigant retreatment and would effectively protect the entire i iipole cross section. While the most economical application method would involve incorporating the fumigant treatment holes into the conventional predrilling process, it would also result in preservative treated fumigant holes. Consequently we have initiated studies to determine the influence of creosote and pentachlorophenol on fumigant movement into treated wood. Preliminary results indicate that creosote and P-9 penta base oil slow movement of MIT into wood but do not prevent the build up of fungitoxic concentrations in the wood. The new, pelletized MIT formulation has been evaluated in our laboratory assay for wood fumigants. The results indicate that pelletized MIT is as effective as pure MIT on an active ingredient basis. Since pelletized MIT has many similar application and safety advantages as encapsulated MIT, we intend to further evaluate pellets in poles in service. Cedar Sapwood Decay Control The effectiveness of seventeen chemicals (3 oil-borne, 14 water-borne) for controlling above-ground decay of cedar sapwood was evaluated using a modified soil block test and an Aspergillus bioassay. Pentachlorophenol (10%) in diesel oil, currently used for protecting cedar poles, was markedly superior to all other chemicals evaluated probably because of the increased penetrability of the oil, since penta in water at the same strength did not perform as well. Three other formulations, copper-8-quinolinolate (oil), pentachlorophenol (2% in water), and 3-iodo propynyl butyl carbamate (2% in water), exhibited some residual effectiveness; however, more time is necessary to determine if these chemicals will remain effective. An additional five chemicals will be evaluated this coming spring. iii The persistence of chloropicrin 5 years after treatment in western redcedar was also evaluated using open tube bioassays, closetube bioassays and gas chromatographic determinations. The open tube bioassay indicated that chioropicrin still effectively limited growth of the assay fungus, P. placenta. Similarly, closed tube bioassays indicated strong inhibition in the pole interior and lower inhibitions near the surface. Extraction/gas chromatographic procedures detected chloropicrin in all cores examined with the highest concentrations towards the pole interior. Chioropicrin concentration did not correlate with closed tube results, suggesting that these tests are measuring different fumigant properties. The results indicate that chloropicrin should be an effective treatment for preventing cedarbutt rot and may provide some protection to pole sapwood. Bolt Holes Control poles for the bolt hole protection study were again sampled and insufficient decay was found in these poles to warrant evaluation of the various decay prevention treatments. We will reevaluate the control poles this summer. Detecting decay and estimating residual strength in poles An infrared spectrophotometric method of analyzing warm water extracts of decayed and non-decay wood was evaluated with a number of brown and white rot fungi. Brown rot was highly correlated with absorption peaks produced at wavelength 17201cm. Work is now underway to identify this peak to determine if less involved detection methods might be employed. iv Fluorescent labeled lectins, which have high specificity for selected carbohydrates, were also evaluated as potential fungal indicators. Of the lectins tested, wheat germ agglutinin appears the most promising since it strongly reacted with chitin in the fungal cell wall, making decay hyphae visible at very early stages of decay. Evaluation of Douglas-fir beams air-seasoned for 1 or 2 years using Pilodyn pin penetration, longitudinal compression, radial compression, bending and culturing indicated that, while there is a well established fungal flora in the wood, this flora has not yet affected strength. These tests will be performed on the 3 year airseasoned beams this coming year. Of the strength tests employed, longitudinal compression appears promising for estimating pole bending strength and we intend to further evaluate this method. As a second phase of this evaluation, the effect of moisture content on Pilodyn pin penetration was examined. This information is necessary since pin penetration varies with moisture content and must be corrected to compare values from different poles. Pin penetration increased with increasing moisture content up to fiber saturation and stabilized above this point. The moisture content at 0.5 inches was highly correlated with pin penetration, and this depth might be a convenient standard measuring point. En a new phase of the project, preliminary acoustic testing was begun using small beams from poles at varying stages of decay. These beams were sonically evaluated and then loaded to failure in three point bending tests. Sonic evaluation was highly correlated with NOR; however, much more testing will be necessary before such an apparatus can be applied to posts or poles. V Initiation of decay in Douglas-fir poles prior to pressure treatment The ability of basidiomycetes isolated from air-seasoning poles to reduce wood strength was evaluated in rapid tests for toughness by impact bending and changes in the breaking radius of Douglas-fir test wafers. Although some fungi behaved differently in the two tests, the test correlations were relatively high (r2 = O.78S). Of 26 basidiomycetous species evaluated, Poria placenta, P. carbonica, P. xantha and Crustoderma dryinum most rapidly decayed Douglas-fir heartwood, but at least one isolate of most of the other species tested significantly reduced toughness. While the wood decaying ability of each fungus is important, the frequency of isolation also must be considered when determining the overall importance of a species. To determine the influence of wood temperature and moisture content on establishment of P. carbonica in Douglas-fir heartwood, a method was developed for direct observation of germinating spores on wood. In this test, chiamydospores and basidiospores failed to germinate or colonize wood at moisture content below fiber saturation suggesting that free water is necessary for infection. Chiamydospores germinated most readily and colonized wood at 22°C, while germination was significantly lower and the fungus failed to become established in wood at 5 or 35°C. Similar temperature responses were obtained with basidiospores although these spores failed to germinate at 5 and 35°C. Nevertheless, basidiospores may remain viable and retain the potential to establish colonies once conditions become more favorable. vi Exposure of sterilized pole sections at four Pacific Northwest air-seasoning sites for successive 3-month periods showed a significant increase in basidiomycete isolation frequency for the period Nov. '81-Jan.'82. Furthermore, the frequency increased from the northern to the southern most site. Detailed study of the site weather patterns strongly suggests that increased basidiomycetous infection can be related to number of days with measurable rain fall and temperatures conducive to fungal growth. During the other periods studied, temperature or precipitation conditions were unfavorable for infection and pole section moisture contents fell below fiber saturation. This in turn limited spore germination and fungal colonization of the wood. About 30 different basidiomycetous species have been identified from isolates cultured from sterilized pole sections exposed at the four sites. In general, the species were the same as those isolated form air-seasoning poles although there were some significant differences between the species obtained from the different sites. The frequency of P. placenta mono- and dikaryons was particularly high with monokaryons more abundant at three of the four locations. Individual species exhibited distinct colonization patterns from different pole zones. For example, P. placenta was isolated most frequently from heartwood exposed at the pole ends while Peniophora spp. and llaemotostereum sanguinolentum were recovered most frequently from the upper surfaces of the pole sections. vii Preventing infection of poles by decay fungi during air-seasoning Pole sections treated with ammonium bifluoride (NH4HF2) or gelatin encapsulated MIT and chioropicrin were extensively sampled after air seasoning to determine the influence of these chemicals on wood colonization by decay fungi. Preliminary results indicate that after 2 years NH4HF2 and the fumigants significantly reduced basidiomycetous colonization of sterile wood. Surface Decay Poles treated with Vapam 14 years ago were extensively cored, the cores were cultured and the resulting fungi were identified to evaluate the fungal flora of fumigant treated wood. A well developed fungal flora was identified that differed from that found in nonfumigant treated wood. These fungi will be further evaluated to determine their role in fumigant effectiveness. Close

• 794. [Article] The Geology and Geochemistry of the Haquira East Porphyry Copper Deposit of Southern Peru : Insights on the Timing, Temperature and Lifespan of the Magmatic-hydrothermal Alteration and Mineralization

  This dissertation is informally divided into three major sections. In the first section (Chapter 2) I use data from field mapping, isotopic geochronology, whole rock geochemistry and trace element concentrations ...

  Citation × Citation Citation Abstract Copy Title: The Geology and Geochemistry of the Haquira East Porphyry Copper Deposit of Southern Peru : Insights on the Timing, Temperature and Lifespan of the Magmatic-hydrothermal Alteration and Mineralization Author: Cernuschi Rodilosso, Federico This dissertation is informally divided into three major sections. In the first section (Chapter 2) I use data from field mapping, isotopic geochronology, whole rock geochemistry and trace element concentrations in zircons to examine the petrology, geochemistry and ages of the Haquira East porphyry copper deposit of southern Peru. In the second section (Chapters 3 - 6) I investigate the timing, temperature, zonation and lifespan of the magmatic-hydrothermal alteration and Cu-Mo mineralization by applying field mapping, whole rock geochemistry, petrography, geothermometry, spectral, X-ray and cathodoluminiscense imaging of rock samples. The timescales of the magmatic-hydrothermal system was constrained by isotopic dating, diffusion of titanium in quartz and the novel approach of oxygen diffusion via δ¹⁸O of quartz analyzed by secondary ion mass spectrometry. These data are also used construct cross-sections and 3D models. In the final section (Chapter 7) I describe the production and evaluation of a calibration for portable X-ray spectrometers that could potentially be applied to further investigate porphyry copper deposits. Haquira East is a moderate grade porphyry copper-molybdenum-gold deposit (688 Mt ore at 0.59 wt. % Cu, containing 4.7 Mt Cu, 37,000 t Mo and 0.9 M oz Au) in the Eocene-Oligocene Andahuaylas-Yauri porphyry belt of southern Peru. Based on a Re/Os age of molybdenite, the copper and molybdenum mineralization and hydrothermal alteration at Haquira East formed at ~33.85 Ma. These ores are associated with dominantly granodioritic intrusions that range from 34.5 to 33.5 Ma in age and represent some of the youngest intrusions of the Andahuaylas-Yauri batholith between 40 and 32 Ma. In this study, new U-Pb zircon ages of these intrusions ages were determined via laser ablation inductively coupled mass spectroscopy (LA-ICP-MS¬) and sensitive high resolution ion microprobe in reverse geometry (SHRIMP-RG). At Haquira East, the regional Eocene-Oligocene shortening of the Incaic orogeny resulted in the folding of Jurassic-Cretaceous meta-sedimentary rock into the northwest-trending and northeast-overturned Tocone syncline that is associated with northwest-striking and southwest-dipping thrust faults. The magmatism was synchronous with the deformation and began with the ~34.5 Ma andesitic to dacitic Lahuani sills and was followed by the ~34.2 to 33.5 Ma Haquira granodiorite stock and the slightly younger, narrow and subvertical Haquira porphyry dikes of similar composition. Several sets of Haquira porphyry dikes were emplaced synchronously with the porphyry copper and molybdenum mineralization, veining and K-silicate hydrothermal alteration. At the waning stages of the magmatism (~33.5), the dacitic Pararani porphyry dikes were emplaced along a north-south strike and closely followed in time with D veins, sericitic halos and sericitically-altered hydrothermal breccias. Whole-rock trace element modeling indicates that the Haquira East magmas originated in a garnet-bearing basaltic-andesite to andesite zone of melt-assimilation-storage-hybridization (MASH) in the lower crust below ~25 km depth. Andesite melts from the MASH zone were injected into an inferred granodiorite magma chamber at ~10km depth beneath Haquira East, where the oxidized and water-rich magma fractionated hornblende and small amounts of plagioclase, together with traces of titanite, apatite, zircon and magnetite. Intrusions sourced in this chamber have enrichments in Sr/Y (>60) and V/Sc (>12), depletions in the light rare earth elements (REE) and high mid-REE/heavy-REE ratios inherited from melts derived from the MASH zone where garnet is residual. Similarly, the intrusions that were emplaced closely in time with the mineralization have high Eu[subscript N]/Eu[subscript N]* (0.4 to 0.8) and Ce[subscript N]/Ce[subscript N]* (200 to 5000) in zircon compared to older intrusions (LA-ICP-MS, and SHRIMP-RG) further evidencing the high oxidation state and water content of the magma. New core logging observations, ICP-MS whole rock geochemical data and short wave infrared spectroscopy data document the sequence and spatial distribution of veins, hydrothermal alteration zones and Cu-Mo-bearing sulfide ore zones and are summarized in cross-sections and three-dimensional models. From oldest to youngest, the sequence of veins consists of biotite veins/micro-breccias, aplite dikes, deep quartz (DQ) veins, actinolite veins with plagioclase halos and epidote veins, early dark micaceous (EDM) halos with bornite-chalcopyrite, Cu-sulfide±quartz veinlets with chalcopyrite and/or bornite, banded molybdenite-quartz (BMQ) veins, B-type quartz-bornite-chalcopyrite veins, D-type pyrite-quartz-sericite veins with sericitic halos, and fractures with green and white intermediate argillic halos containing mixtures of illite-smectite-chlorite-kaolinite ± pyrite. The areas with the highest density of EDM halos constitute the high-grade copper ore. Scanning electron microscopy imaging (QEMSCAN) have been used to identifiy mineralogy, textures and zoning of hydrothermal alteration zones. The EDM halos are formed by hydrothermal biotite, muscovite, K-feldspar, with rare quartz and corundum replacing magmatic plagioclase and hornblende and carry up to 10-15 volume % disseminated bornite and chalcopyrite. Later BMQ veins host the high-grade molybdenum ore, whereas late B veins contribute both copper and molybdenum to the ores. The copper ore shell forms a continuous high-grade ore zone (>0.5 wt. %) in the Haquira stock, but is lower grade where it projects into the relatively non-reactive meta-sedimentary, mostly quartzite, wall rock, likely as a result of a limited supply of iron to enable copper-iron sulfide precipitation. In contrast, molybdenite mineralization forms a roughly symmetric shell overlapping both the stock and quartzite with an axis of symmetry located along the southwest flank of the Haquira granodiorite stock. The abundance of EDM halos, lack of A veins and the dearth of unmixed fluid inclusion assemblages in quartz veins and prescense of two phase (liquid + vapor) fluid inclusions (P>1.5 kbar) suggest that Haquira East was emplaced at significant depths. The emplacement depth of Haquira is estimated at ~10 km, at greater depth than shallower and outcropping Acojasa intrusion to the south, emplaced at ~ 8 km according to hornblende barometry (~2.0 ± 0.5 kb). The veining, hydrothermal alteration and mineralization formed at this depth magmatic hydrothermal fluid was released from an inferred magmatic cupola, hydro-fractured the wall rock and depressurized from ~3 kb at lithostatic pressure to >1.2 kb at close to hydrostatic pressure without unmixing into a vapor and brine phase. The temperature evolution of the magmatic-hydrothermal system was estimated by mineral phase equilibria and the application of different geothermometers. For TitaniQ geothermometry, Ti-in-quartz of veins and dikes was measured by electron microprobe (EMP) and LA-ICP-MS (1 ppm to > 100 ppm) on samples that were previously imaged by secondary electron microscope cathodoluminescense, Temperatures were also estimated through Ti-in-zircon (2 ppm to 13 ppm, via SHRIMP-RG), Ti-in-biotite (~1.0 to 2.3wt.%, via EMP) and the δ³⁴S compositions of pyrite-anhydrite and chalcopyrite-anhydrite pairs (-1.4 ‰ to -0.1‰ and 7.5 ‰ to 10.2‰ respectively). Porphyry dikes, aplites and DQ veins formed first between ~720ºC and 650ºC. Copper was introduced later in EDM halos at ~500ºC and was followed by molybdenite in BMQ veins at ~650ºC during a thermal reversal. A second stage of copper and molybdenum was introduced in B veins at ~550°C. Late D veins with pyrite and sericite formed first at ~450ºC and later at ~350ºC. Diffusion modeling of both Ti (EMP) and δ¹⁸O gradients (via secondary ion mass spectrometry, ~10.7 ‰ to ~12.7‰) across initially abrupt quartz growth boundaries yields a calculated maximum lifespan for the Haquira East porphyry of 170,000 years for the period from initial fluid injection at >650 ºC to cooling below ~ 350 ºC. However, the high-grade copper and molybdenum ore formed relatively rapidly in less than 30,000 years. In the last chapter of this dissertation two calibrations were produced and tested for a Bruker Tracer IV portable X-ray fluorescence portable spectrometer (pXRF). Concentrations of Al₂O₃, CaO, FeO*, K₂O, MnO, TiO₂ and, in lesser degree, SiO₂ were accurately reproduced together with Cr, Cu, Nb, Ni, Sr, Y, Zr and less accurately V in powdered basaltic samples, and Nb, Pb, Rb, Sr, Y, Zn, Zr and, less accurately, Ba in powdered rhyolitic samples. The pXRF is particularly reliable for measuring relatively immobile elements (e.g. Nb, Zr, Ti and Y), which are often resistant to hydrothermal alteration and weathering. Therefore pXRFs may be useful for lithogeochemical mapping of hydrothermally altered rocks that are zoned around porphyry copper deposits. Title: The Geology and Geochemistry of the Haquira East Porphyry Copper Deposit of Southern Peru : Insights on the Timing, Temperature and Lifespan of the Magmatic-hydrothermal Alteration and Mineralization Author: Cernuschi Rodilosso, Federico This dissertation is informally divided into three major sections. In the first section (Chapter 2) I use data from field mapping, isotopic geochronology, whole rock geochemistry and trace element concentrations in zircons to examine the petrology, geochemistry and ages of the Haquira East porphyry copper deposit of southern Peru. In the second section (Chapters 3 - 6) I investigate the timing, temperature, zonation and lifespan of the magmatic-hydrothermal alteration and Cu-Mo mineralization by applying field mapping, whole rock geochemistry, petrography, geothermometry, spectral, X-ray and cathodoluminiscense imaging of rock samples. The timescales of the magmatic-hydrothermal system was constrained by isotopic dating, diffusion of titanium in quartz and the novel approach of oxygen diffusion via δ¹⁸O of quartz analyzed by secondary ion mass spectrometry. These data are also used construct cross-sections and 3D models. In the final section (Chapter 7) I describe the production and evaluation of a calibration for portable X-ray spectrometers that could potentially be applied to further investigate porphyry copper deposits. Haquira East is a moderate grade porphyry copper-molybdenum-gold deposit (688 Mt ore at 0.59 wt. % Cu, containing 4.7 Mt Cu, 37,000 t Mo and 0.9 M oz Au) in the Eocene-Oligocene Andahuaylas-Yauri porphyry belt of southern Peru. Based on a Re/Os age of molybdenite, the copper and molybdenum mineralization and hydrothermal alteration at Haquira East formed at ~33.85 Ma. These ores are associated with dominantly granodioritic intrusions that range from 34.5 to 33.5 Ma in age and represent some of the youngest intrusions of the Andahuaylas-Yauri batholith between 40 and 32 Ma. In this study, new U-Pb zircon ages of these intrusions ages were determined via laser ablation inductively coupled mass spectroscopy (LA-ICP-MS¬) and sensitive high resolution ion microprobe in reverse geometry (SHRIMP-RG). At Haquira East, the regional Eocene-Oligocene shortening of the Incaic orogeny resulted in the folding of Jurassic-Cretaceous meta-sedimentary rock into the northwest-trending and northeast-overturned Tocone syncline that is associated with northwest-striking and southwest-dipping thrust faults. The magmatism was synchronous with the deformation and began with the ~34.5 Ma andesitic to dacitic Lahuani sills and was followed by the ~34.2 to 33.5 Ma Haquira granodiorite stock and the slightly younger, narrow and subvertical Haquira porphyry dikes of similar composition. Several sets of Haquira porphyry dikes were emplaced synchronously with the porphyry copper and molybdenum mineralization, veining and K-silicate hydrothermal alteration. At the waning stages of the magmatism (~33.5), the dacitic Pararani porphyry dikes were emplaced along a north-south strike and closely followed in time with D veins, sericitic halos and sericitically-altered hydrothermal breccias. Whole-rock trace element modeling indicates that the Haquira East magmas originated in a garnet-bearing basaltic-andesite to andesite zone of melt-assimilation-storage-hybridization (MASH) in the lower crust below ~25 km depth. Andesite melts from the MASH zone were injected into an inferred granodiorite magma chamber at ~10km depth beneath Haquira East, where the oxidized and water-rich magma fractionated hornblende and small amounts of plagioclase, together with traces of titanite, apatite, zircon and magnetite. Intrusions sourced in this chamber have enrichments in Sr/Y (>60) and V/Sc (>12), depletions in the light rare earth elements (REE) and high mid-REE/heavy-REE ratios inherited from melts derived from the MASH zone where garnet is residual. Similarly, the intrusions that were emplaced closely in time with the mineralization have high Eu[subscript N]/Eu[subscript N]* (0.4 to 0.8) and Ce[subscript N]/Ce[subscript N]* (200 to 5000) in zircon compared to older intrusions (LA-ICP-MS, and SHRIMP-RG) further evidencing the high oxidation state and water content of the magma. New core logging observations, ICP-MS whole rock geochemical data and short wave infrared spectroscopy data document the sequence and spatial distribution of veins, hydrothermal alteration zones and Cu-Mo-bearing sulfide ore zones and are summarized in cross-sections and three-dimensional models. From oldest to youngest, the sequence of veins consists of biotite veins/micro-breccias, aplite dikes, deep quartz (DQ) veins, actinolite veins with plagioclase halos and epidote veins, early dark micaceous (EDM) halos with bornite-chalcopyrite, Cu-sulfide±quartz veinlets with chalcopyrite and/or bornite, banded molybdenite-quartz (BMQ) veins, B-type quartz-bornite-chalcopyrite veins, D-type pyrite-quartz-sericite veins with sericitic halos, and fractures with green and white intermediate argillic halos containing mixtures of illite-smectite-chlorite-kaolinite ± pyrite. The areas with the highest density of EDM halos constitute the high-grade copper ore. Scanning electron microscopy imaging (QEMSCAN) have been used to identifiy mineralogy, textures and zoning of hydrothermal alteration zones. The EDM halos are formed by hydrothermal biotite, muscovite, K-feldspar, with rare quartz and corundum replacing magmatic plagioclase and hornblende and carry up to 10-15 volume % disseminated bornite and chalcopyrite. Later BMQ veins host the high-grade molybdenum ore, whereas late B veins contribute both copper and molybdenum to the ores. The copper ore shell forms a continuous high-grade ore zone (>0.5 wt. %) in the Haquira stock, but is lower grade where it projects into the relatively non-reactive meta-sedimentary, mostly quartzite, wall rock, likely as a result of a limited supply of iron to enable copper-iron sulfide precipitation. In contrast, molybdenite mineralization forms a roughly symmetric shell overlapping both the stock and quartzite with an axis of symmetry located along the southwest flank of the Haquira granodiorite stock. The abundance of EDM halos, lack of A veins and the dearth of unmixed fluid inclusion assemblages in quartz veins and prescense of two phase (liquid + vapor) fluid inclusions (P>1.5 kbar) suggest that Haquira East was emplaced at significant depths. The emplacement depth of Haquira is estimated at ~10 km, at greater depth than shallower and outcropping Acojasa intrusion to the south, emplaced at ~ 8 km according to hornblende barometry (~2.0 ± 0.5 kb). The veining, hydrothermal alteration and mineralization formed at this depth magmatic hydrothermal fluid was released from an inferred magmatic cupola, hydro-fractured the wall rock and depressurized from ~3 kb at lithostatic pressure to >1.2 kb at close to hydrostatic pressure without unmixing into a vapor and brine phase. The temperature evolution of the magmatic-hydrothermal system was estimated by mineral phase equilibria and the application of different geothermometers. For TitaniQ geothermometry, Ti-in-quartz of veins and dikes was measured by electron microprobe (EMP) and LA-ICP-MS (1 ppm to > 100 ppm) on samples that were previously imaged by secondary electron microscope cathodoluminescense, Temperatures were also estimated through Ti-in-zircon (2 ppm to 13 ppm, via SHRIMP-RG), Ti-in-biotite (~1.0 to 2.3wt.%, via EMP) and the δ³⁴S compositions of pyrite-anhydrite and chalcopyrite-anhydrite pairs (-1.4 ‰ to -0.1‰ and 7.5 ‰ to 10.2‰ respectively). Porphyry dikes, aplites and DQ veins formed first between ~720ºC and 650ºC. Copper was introduced later in EDM halos at ~500ºC and was followed by molybdenite in BMQ veins at ~650ºC during a thermal reversal. A second stage of copper and molybdenum was introduced in B veins at ~550°C. Late D veins with pyrite and sericite formed first at ~450ºC and later at ~350ºC. Diffusion modeling of both Ti (EMP) and δ¹⁸O gradients (via secondary ion mass spectrometry, ~10.7 ‰ to ~12.7‰) across initially abrupt quartz growth boundaries yields a calculated maximum lifespan for the Haquira East porphyry of 170,000 years for the period from initial fluid injection at >650 ºC to cooling below ~ 350 ºC. However, the high-grade copper and molybdenum ore formed relatively rapidly in less than 30,000 years. In the last chapter of this dissertation two calibrations were produced and tested for a Bruker Tracer IV portable X-ray fluorescence portable spectrometer (pXRF). Concentrations of Al₂O₃, CaO, FeO*, K₂O, MnO, TiO₂ and, in lesser degree, SiO₂ were accurately reproduced together with Cr, Cu, Nb, Ni, Sr, Y, Zr and less accurately V in powdered basaltic samples, and Nb, Pb, Rb, Sr, Y, Zn, Zr and, less accurately, Ba in powdered rhyolitic samples. The pXRF is particularly reliable for measuring relatively immobile elements (e.g. Nb, Zr, Ti and Y), which are often resistant to hydrothermal alteration and weathering. Therefore pXRFs may be useful for lithogeochemical mapping of hydrothermally altered rocks that are zoned around porphyry copper deposits. Close

• 795. [Article] Defect Mechanisms in Bismuth-based Perovskites

  The aim of this research is to develop a fundamental understanding of the dominant defect species and the relevant defect equilibrium conditions for bismuth-containing perovskites to help guide the development ...

  Citation × Citation Citation Abstract Copy Title: Defect Mechanisms in Bismuth-based Perovskites Author: Kumar, Nitish The aim of this research is to develop a fundamental understanding of the dominant defect species and the relevant defect equilibrium conditions for bismuth-containing perovskites to help guide the development of these materials for emerging applications. This is of paramount importance for many demanding applications, because ultimately the defect equilibria have a profound influence on phenomena such as piezoelectric fatigue, reliability, and leakage current. At the same time, they can be used to tailor properties to make these materials better suited for specific applications. Perovskite materials with Bi³⁺ on the A-site have been the focus of great technical interest over the last decade. A number of compositions based on Bi-perovskites (e.g. (Bi,Ba)(B²⁺,Ti)O₃) are being studied for high energy density (or high temperature) capacitor applications. In addition, a number of Bi-based perovskite materials have shown great promise as a replacement for Pb(Zr,Ti)O₃ (PZT) for piezoelectric applications. Compounds such as (Bi₁/₂K₁/₂)TiO₃ (BKT) and (Bi₁/₂Na₁/₂)TiO₃ (BNT), and their solid solutions with BaTiO₃ and other tetragonal perovskites exhibit useful piezoelectric properties and are considered to be promising candidates to replace Pb-based materials if the underlying defect chemistry can be controlled. The technological impact of these materials is expected to grow because research in this area is being driven by increased environmental regulations and energy efficiency considerations. While much of the current research and progress on Bi-perovskites have been focused on primary materials properties like the piezoelectric coefficient, relative permittivity, etc., there have been few studies on the underlying fundamental defect chemistry and they are not fully understood. This research focuses mainly on two material systems to study their defect chemistry and transport properties. First is Bi(Zn₁/₂Ti₁/₂)O₃–BaTiO₃, for high performance capacitor applications. Conventional approaches to this technical challenge include utilizing ferroelectric or antiferroelectric materials with permittivities in excess of 1000. However, these non-linear materials derive their high permittivity from domain contributions that saturate at relatively low fields ultimately resulting in limited energy densities. However, solid solutions based on BiMO₃-BaTiO₃ that exhibit relaxor behavior can potentially demonstrate high energy densities. The second material system investigated was BNT-BKT- Bi(Mg₁/₂Ti₁/₂)O₃. This material features a field-induced relaxor-to-ferroelectric transition that is accompanied by a large piezoelectric strain values. The first part of the thesis focuses on polycrystalline BaTiO₃-Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) ceramics, which have been shown to exhibit superior dielectric properties for high temperature and high energy density applications as compared to the existing materials. As miniaturization without compromising cost and performance is vital for several applications, chapter 9.1 shows the results on multilayer ceramic capacitors based on relaxor BT-BZT ceramics. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ > 1 GΩ-cm at 300°C), and negligible saturation up to fields as high as 150 kV/cm. The multilayer capacitor embodiments exhibited similar dielectric and resistivity properties. The energy density for the multilayer ceramics reached values of ~2.8 J/cm³ at room temperature at an applied electric field of ~330 kV/cm. This represents a significant improvement compared to commercially available multilayer capacitors. The dielectric properties were also found to be stable over a wide range of temperatures with a temperature coefficient of approximately -2000 ppm/K measured from 50 to 350 °C, an important criteria for high temperature applications. Finally, the compatibility of inexpensive Ag-Pd electrodes with these ceramics was also demonstrated, which can have implications on minimizing the device cost. Having demonstrated that BT-BZT exhibits promising properties, the primary focus of this thesis research is developing a fundamental understanding of the transport properties and defect chemistry. A significant improvement in insulation properties was measured with the addition of BZT to BT. Both low-field AC impedance and high field direct DC measurements indicated an increase in resistivity of at least 2 orders of magnitude at 400 °C with the addition of just 3% BZT (~10⁷ Ω-cm) into the solid solution as compared to pure BT (~10⁵ Ω-cm). This effect was also evident in dielectric loss data, which remained low at higher temperatures as the BZT content increased. In conjunction with band gap measurements, it was also concluded that the conduction mechanism transitioned from extrinsic for pure BT to intrinsic-like for 7.5% BZT suggesting a change in the fundamental defect equilibrium conditions. It was also shown that this improvement in insulation properties was not limited to BT-BZT, but could also be observed in SrTiO₃-BZT system. While pure BT exhibits extrinsic p-type conduction, it is reported that BT-BZT ceramics exhibit intrinsic-like n-type conduction using atmosphere dependent conductivity measurements. Annealing studies and Seebeck measurements were performed and confirmed this result. For BT, resistivity values were higher for samples annealed in nitrogen as compared to oxygen, while the opposite responses were observed for BZT-containing solid solutions. This suggested a possibile unintentional donor doping upon addition of BZT to the solid solution, which may also be linked to the improvement in resistivity in BT-BZT ceramics as compared to pure BT. Impedance spectroscopy in conjunction with small DC-bias provided further proof of the p-type to n-type transition and also demonstrated the field-stable properties of BT-BZT ceramics. For p-type BaTiO₃, the ceramics deviated from Ohm’s law behavior at very low voltage levels along with a reversible drop in bulk resistivity by several orders of magnitude starting at bias fields as low as 0.1 kV/cm (~8 V). In contrast, n-type BT-BZT ceramics exhibited a small (i.e. less than one order of magnitude) increase in resistivity on application of small field levels. These data indicate a hole-generation mechanism which becomes active at a low voltage threshold. The bulk capacitance values calculated using AC impedance spectroscopy, however, were relatively unaffected (<15% change) by this application of a DC bias (up to ~0.25 kV/cm). These findings provide further insights into the electric transport mechanisms in BT-based ceramics. To investigate the possible presence of Bi⁵⁺ in BT-BZT ceramics, which was postulated to be one of the possible mechanisms for n-type behavior in BT-BZT ceramics, some BT-BaBiO₃ solid solutions were fabricated. The BaBiO₃ ceramics were sintered in oxygen to obtain a single phase with monoclinic I2/m symmetry as suggested by high-resolution x-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states – 3+ and 5+. Optical spectroscopy showed presence of a direct band gap at ~2.2 eV and a possible indirect band gap at ~0.9 eV. This combined with determination of the activation energy for conduction of 0.25 eV, as obtained from ac impedance spectroscopy, suggested that a polaron-mediated conduction mechanism was prevalent in BaBiO₃. These BaBiO₃ ceramics were crushed, mixed with BaTiO₃, and sintered to obtain BaTiO₃-BaBiO₃ solid solutions. All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response. Using ac impedance and optical spectroscopy, it was shown that resistivity values of BaTiO₃-BaBiO₃ were orders of magnitude higher than BaTiO₃ or BaBiO₃ alone, indicating a change in the fundamental defect equilibrium conditions. A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity. To investigate the effect of A-site nonstoichiometry in BT-BiMO₃ ceramics, BaTiO₃-BiScO₃ (BT-BS) and SrTiO₃-Bi(Zn₁/₂Ti₁/₂)O₃ (ST-BZT) were fabricated. The effect of nonstoichiometry on the dielectric and transport properties was studied using temperature- and oxygen partial pressure-dependent AC impedance spectroscopy. For p-type BT-BS ceramics, the addition of excess Bi led to effective donor doping along with a significant improvement in insulation properties. A similar effect was observed on introducing Ba vacancies onto the A-sublattice. However, Bi deficiency had an opposite effect with effective acceptor doping and a deterioration in the bulk resistivity values. For n-type intrinsic ST-BZT ceramics, the addition of excess Sr onto the A-sublattice resulted in a decrease in resistivity values, as expected. Introduction of Sr vacancies or addition of excess Bi on A-site did not appear to affect the insulation properties in air. These results indicate that minor levels of non-stoichiometry can have an important impact on the material properties and furthermore it demonstrates the difficulties encountered in trying to establish a general model for the defect chemistry of Bi-containing perovskite systems. Finally, the other prospective candidates for n-type behavior in BT-BZT were studied—loss of volatile cations, oxygen vacancies, bismuth present in multiple valence states and precipitation of secondary phases. Combined x-ray and neutron diffraction, prompt gamma neutron activation analysis and electron energy loss spectroscopy suggested much higher oxygen vacancy concentration in BT-BZT ceramics as compared to BT alone. X-ray photoelectron spectroscopy and x-ray absorption spectroscopy did not suggest presence of bismuth in multiple valence states. At the same time, using transmission electron microscopy, some secondary phases were observed, whose compositions were such that they could result in effective donor doping in BT-BZT ceramics. Using experimentally determined thermodynamic parameters for BT and slopes of conductivity-oxygen partial pressure curves, it has been suggested that an ionic compensation mechanism is prevalent in these ceramics instead of electronic compensation. However, these defects in BT-BZT ceramics have an effect of shifting the conductivity minimum in conductivity-oxygen partial pressure curves to higher oxygen partial pressure values, resulting in significantly higher resistivity values in air atmosphere. This provides an important tool to tailor transport properties and defects in BT-BiMO₃ ceramics, to make them better suited for dielectric applications. The second Bi-based ceramic system which was looked at was lead-free Bi(Mg₁/₂Ti₁/₂)O₃-(Bi₁/₂K₁/₂)TiO₃-(Bi₁/₂Na₁/₂)TiO₃ for sensors and actuator applications. There has been a huge drive to replace Pb from existing ceramics (e.g. lead zirconate titanate) due to health and environmental concerns. The dielectric spectra showed a T[subscript max] of more than 320 °C for all compositions and the transitions became increasingly diffuse as the Bi(Mg₁/₂Ti₁/₂)O₃ content increased. A lower temperature transition, indicating a transformation from an ergodic to a non-ergodic relaxor state, was also seen for all compositions and this transition temperature decreased as the mole fraction of Bi(Mg₁/₂Ti₁/₂)O₃ increased. The composition with 1% Bi(Mg₁/₂Ti₁/₂)O₃ showed characteristic ferroelectric-like polarization and strain hysteresis. However, compositions with increased Bi(Mg₁/₂Ti₁/₂)O₃ content became increasingly ergodic at room temperature with pinched polarization loops and no negative strain. Among these compositions, the magnitude of d₃₃* increased with Bi(Mg₁/₂Ti₁/₂)O₃ content and the composition with 10% Bi(Mg₁/₂Ti₁/₂)O₃ exhibited a d₃₃* of 422 pm/V . Fatigue measurements were conducted on all compositions and while the 1% Bi(Mg₁/₂Ti₁/₂)O₃ composition exhibited a measurable, but small loss in maximum strain after a million cycles; all the other compositions from 2.5% to 10% Bi(Mg₁/₂Ti₁/₂)O₃ were essentially fatigue-free. Lastly, optical and AC impedance measurements were employed to identify intrinsic conduction as the dominant conduction mechanism. These compositions were also highly insulating with high resistivities (~10⁷ Ω-cm) at high temperatures (440 °C). To investigate the role of point defects on the fatigue characteristics, the composition 5%BMT-40%BKT-55%BNT was doped to incorporate acceptor and donor defects on the A and B sites by adjusting the Bi/Na and Ti/Mg stoichiometries. All samples had pseudo-cubic symmetries based on x-ray diffraction, typical of relaxors. Dielectric measurements showed that the high and low temperature phase transitions were largely unaffected by doping. Acceptor doping resulted in the observation of a typical ferroelectric-like polarization with a remnant polarization and strain hysteresis loops with significant negative strain. Donor-doped compositions exhibited characteristics that were indicative of an ergodic relaxor phase. Fatigue measurements were carried out on all of the compositions. While the A-site acceptor-doped composition showed a small degradation in maximum strain after 10⁶ cycles, the other compositions were essentially fatigue free. Impedance measurements were used to identify the important conduction mechanisms in these compositions. As expected, the presence of defects did not strongly influence the fatigue behavior in donor-doped compositions owing to the nature of their reversible field-induced phase transformation. Even for the acceptor-doped compositions, which had stable domains in the absence of an electric field at room temperature, there was negligible degradation in the maximum strain due to fatigue. This suggests that either the defects introduced through stoichiometric variations do not play a prominent role in fatigue in these systems or it is compensated by factors like decrease in coercive field, an increase in ergodicity, symmetry change, or other factors. The results obtained for these ceramic systems have provided significant insights in the defect chemistry and transport properties and are expected to help improve performance of these emerging materials for energy and MEMS technologies. Title: Defect Mechanisms in Bismuth-based Perovskites Author: Kumar, Nitish The aim of this research is to develop a fundamental understanding of the dominant defect species and the relevant defect equilibrium conditions for bismuth-containing perovskites to help guide the development of these materials for emerging applications. This is of paramount importance for many demanding applications, because ultimately the defect equilibria have a profound influence on phenomena such as piezoelectric fatigue, reliability, and leakage current. At the same time, they can be used to tailor properties to make these materials better suited for specific applications. Perovskite materials with Bi³⁺ on the A-site have been the focus of great technical interest over the last decade. A number of compositions based on Bi-perovskites (e.g. (Bi,Ba)(B²⁺,Ti)O₃) are being studied for high energy density (or high temperature) capacitor applications. In addition, a number of Bi-based perovskite materials have shown great promise as a replacement for Pb(Zr,Ti)O₃ (PZT) for piezoelectric applications. Compounds such as (Bi₁/₂K₁/₂)TiO₃ (BKT) and (Bi₁/₂Na₁/₂)TiO₃ (BNT), and their solid solutions with BaTiO₃ and other tetragonal perovskites exhibit useful piezoelectric properties and are considered to be promising candidates to replace Pb-based materials if the underlying defect chemistry can be controlled. The technological impact of these materials is expected to grow because research in this area is being driven by increased environmental regulations and energy efficiency considerations. While much of the current research and progress on Bi-perovskites have been focused on primary materials properties like the piezoelectric coefficient, relative permittivity, etc., there have been few studies on the underlying fundamental defect chemistry and they are not fully understood. This research focuses mainly on two material systems to study their defect chemistry and transport properties. First is Bi(Zn₁/₂Ti₁/₂)O₃–BaTiO₃, for high performance capacitor applications. Conventional approaches to this technical challenge include utilizing ferroelectric or antiferroelectric materials with permittivities in excess of 1000. However, these non-linear materials derive their high permittivity from domain contributions that saturate at relatively low fields ultimately resulting in limited energy densities. However, solid solutions based on BiMO₃-BaTiO₃ that exhibit relaxor behavior can potentially demonstrate high energy densities. The second material system investigated was BNT-BKT- Bi(Mg₁/₂Ti₁/₂)O₃. This material features a field-induced relaxor-to-ferroelectric transition that is accompanied by a large piezoelectric strain values. The first part of the thesis focuses on polycrystalline BaTiO₃-Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) ceramics, which have been shown to exhibit superior dielectric properties for high temperature and high energy density applications as compared to the existing materials. As miniaturization without compromising cost and performance is vital for several applications, chapter 9.1 shows the results on multilayer ceramic capacitors based on relaxor BT-BZT ceramics. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ > 1 GΩ-cm at 300°C), and negligible saturation up to fields as high as 150 kV/cm. The multilayer capacitor embodiments exhibited similar dielectric and resistivity properties. The energy density for the multilayer ceramics reached values of ~2.8 J/cm³ at room temperature at an applied electric field of ~330 kV/cm. This represents a significant improvement compared to commercially available multilayer capacitors. The dielectric properties were also found to be stable over a wide range of temperatures with a temperature coefficient of approximately -2000 ppm/K measured from 50 to 350 °C, an important criteria for high temperature applications. Finally, the compatibility of inexpensive Ag-Pd electrodes with these ceramics was also demonstrated, which can have implications on minimizing the device cost. Having demonstrated that BT-BZT exhibits promising properties, the primary focus of this thesis research is developing a fundamental understanding of the transport properties and defect chemistry. A significant improvement in insulation properties was measured with the addition of BZT to BT. Both low-field AC impedance and high field direct DC measurements indicated an increase in resistivity of at least 2 orders of magnitude at 400 °C with the addition of just 3% BZT (~10⁷ Ω-cm) into the solid solution as compared to pure BT (~10⁵ Ω-cm). This effect was also evident in dielectric loss data, which remained low at higher temperatures as the BZT content increased. In conjunction with band gap measurements, it was also concluded that the conduction mechanism transitioned from extrinsic for pure BT to intrinsic-like for 7.5% BZT suggesting a change in the fundamental defect equilibrium conditions. It was also shown that this improvement in insulation properties was not limited to BT-BZT, but could also be observed in SrTiO₃-BZT system. While pure BT exhibits extrinsic p-type conduction, it is reported that BT-BZT ceramics exhibit intrinsic-like n-type conduction using atmosphere dependent conductivity measurements. Annealing studies and Seebeck measurements were performed and confirmed this result. For BT, resistivity values were higher for samples annealed in nitrogen as compared to oxygen, while the opposite responses were observed for BZT-containing solid solutions. This suggested a possibile unintentional donor doping upon addition of BZT to the solid solution, which may also be linked to the improvement in resistivity in BT-BZT ceramics as compared to pure BT. Impedance spectroscopy in conjunction with small DC-bias provided further proof of the p-type to n-type transition and also demonstrated the field-stable properties of BT-BZT ceramics. For p-type BaTiO₃, the ceramics deviated from Ohm’s law behavior at very low voltage levels along with a reversible drop in bulk resistivity by several orders of magnitude starting at bias fields as low as 0.1 kV/cm (~8 V). In contrast, n-type BT-BZT ceramics exhibited a small (i.e. less than one order of magnitude) increase in resistivity on application of small field levels. These data indicate a hole-generation mechanism which becomes active at a low voltage threshold. The bulk capacitance values calculated using AC impedance spectroscopy, however, were relatively unaffected (<15% change) by this application of a DC bias (up to ~0.25 kV/cm). These findings provide further insights into the electric transport mechanisms in BT-based ceramics. To investigate the possible presence of Bi⁵⁺ in BT-BZT ceramics, which was postulated to be one of the possible mechanisms for n-type behavior in BT-BZT ceramics, some BT-BaBiO₃ solid solutions were fabricated. The BaBiO₃ ceramics were sintered in oxygen to obtain a single phase with monoclinic I2/m symmetry as suggested by high-resolution x-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states – 3+ and 5+. Optical spectroscopy showed presence of a direct band gap at ~2.2 eV and a possible indirect band gap at ~0.9 eV. This combined with determination of the activation energy for conduction of 0.25 eV, as obtained from ac impedance spectroscopy, suggested that a polaron-mediated conduction mechanism was prevalent in BaBiO₃. These BaBiO₃ ceramics were crushed, mixed with BaTiO₃, and sintered to obtain BaTiO₃-BaBiO₃ solid solutions. All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response. Using ac impedance and optical spectroscopy, it was shown that resistivity values of BaTiO₃-BaBiO₃ were orders of magnitude higher than BaTiO₃ or BaBiO₃ alone, indicating a change in the fundamental defect equilibrium conditions. A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity. To investigate the effect of A-site nonstoichiometry in BT-BiMO₃ ceramics, BaTiO₃-BiScO₃ (BT-BS) and SrTiO₃-Bi(Zn₁/₂Ti₁/₂)O₃ (ST-BZT) were fabricated. The effect of nonstoichiometry on the dielectric and transport properties was studied using temperature- and oxygen partial pressure-dependent AC impedance spectroscopy. For p-type BT-BS ceramics, the addition of excess Bi led to effective donor doping along with a significant improvement in insulation properties. A similar effect was observed on introducing Ba vacancies onto the A-sublattice. However, Bi deficiency had an opposite effect with effective acceptor doping and a deterioration in the bulk resistivity values. For n-type intrinsic ST-BZT ceramics, the addition of excess Sr onto the A-sublattice resulted in a decrease in resistivity values, as expected. Introduction of Sr vacancies or addition of excess Bi on A-site did not appear to affect the insulation properties in air. These results indicate that minor levels of non-stoichiometry can have an important impact on the material properties and furthermore it demonstrates the difficulties encountered in trying to establish a general model for the defect chemistry of Bi-containing perovskite systems. Finally, the other prospective candidates for n-type behavior in BT-BZT were studied—loss of volatile cations, oxygen vacancies, bismuth present in multiple valence states and precipitation of secondary phases. Combined x-ray and neutron diffraction, prompt gamma neutron activation analysis and electron energy loss spectroscopy suggested much higher oxygen vacancy concentration in BT-BZT ceramics as compared to BT alone. X-ray photoelectron spectroscopy and x-ray absorption spectroscopy did not suggest presence of bismuth in multiple valence states. At the same time, using transmission electron microscopy, some secondary phases were observed, whose compositions were such that they could result in effective donor doping in BT-BZT ceramics. Using experimentally determined thermodynamic parameters for BT and slopes of conductivity-oxygen partial pressure curves, it has been suggested that an ionic compensation mechanism is prevalent in these ceramics instead of electronic compensation. However, these defects in BT-BZT ceramics have an effect of shifting the conductivity minimum in conductivity-oxygen partial pressure curves to higher oxygen partial pressure values, resulting in significantly higher resistivity values in air atmosphere. This provides an important tool to tailor transport properties and defects in BT-BiMO₃ ceramics, to make them better suited for dielectric applications. The second Bi-based ceramic system which was looked at was lead-free Bi(Mg₁/₂Ti₁/₂)O₃-(Bi₁/₂K₁/₂)TiO₃-(Bi₁/₂Na₁/₂)TiO₃ for sensors and actuator applications. There has been a huge drive to replace Pb from existing ceramics (e.g. lead zirconate titanate) due to health and environmental concerns. The dielectric spectra showed a T[subscript max] of more than 320 °C for all compositions and the transitions became increasingly diffuse as the Bi(Mg₁/₂Ti₁/₂)O₃ content increased. A lower temperature transition, indicating a transformation from an ergodic to a non-ergodic relaxor state, was also seen for all compositions and this transition temperature decreased as the mole fraction of Bi(Mg₁/₂Ti₁/₂)O₃ increased. The composition with 1% Bi(Mg₁/₂Ti₁/₂)O₃ showed characteristic ferroelectric-like polarization and strain hysteresis. However, compositions with increased Bi(Mg₁/₂Ti₁/₂)O₃ content became increasingly ergodic at room temperature with pinched polarization loops and no negative strain. Among these compositions, the magnitude of d₃₃* increased with Bi(Mg₁/₂Ti₁/₂)O₃ content and the composition with 10% Bi(Mg₁/₂Ti₁/₂)O₃ exhibited a d₃₃* of 422 pm/V . Fatigue measurements were conducted on all compositions and while the 1% Bi(Mg₁/₂Ti₁/₂)O₃ composition exhibited a measurable, but small loss in maximum strain after a million cycles; all the other compositions from 2.5% to 10% Bi(Mg₁/₂Ti₁/₂)O₃ were essentially fatigue-free. Lastly, optical and AC impedance measurements were employed to identify intrinsic conduction as the dominant conduction mechanism. These compositions were also highly insulating with high resistivities (~10⁷ Ω-cm) at high temperatures (440 °C). To investigate the role of point defects on the fatigue characteristics, the composition 5%BMT-40%BKT-55%BNT was doped to incorporate acceptor and donor defects on the A and B sites by adjusting the Bi/Na and Ti/Mg stoichiometries. All samples had pseudo-cubic symmetries based on x-ray diffraction, typical of relaxors. Dielectric measurements showed that the high and low temperature phase transitions were largely unaffected by doping. Acceptor doping resulted in the observation of a typical ferroelectric-like polarization with a remnant polarization and strain hysteresis loops with significant negative strain. Donor-doped compositions exhibited characteristics that were indicative of an ergodic relaxor phase. Fatigue measurements were carried out on all of the compositions. While the A-site acceptor-doped composition showed a small degradation in maximum strain after 10⁶ cycles, the other compositions were essentially fatigue free. Impedance measurements were used to identify the important conduction mechanisms in these compositions. As expected, the presence of defects did not strongly influence the fatigue behavior in donor-doped compositions owing to the nature of their reversible field-induced phase transformation. Even for the acceptor-doped compositions, which had stable domains in the absence of an electric field at room temperature, there was negligible degradation in the maximum strain due to fatigue. This suggests that either the defects introduced through stoichiometric variations do not play a prominent role in fatigue in these systems or it is compensated by factors like decrease in coercive field, an increase in ergodicity, symmetry change, or other factors. The results obtained for these ceramic systems have provided significant insights in the defect chemistry and transport properties and are expected to help improve performance of these emerging materials for energy and MEMS technologies. Close