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• 1. [Article] New 40Ar/39Ar age progression for the Louisville hot spot trail and implications for inter–hot spot motion

  In this study we present 42 new ⁴⁰Ar/³⁹Ar incremental heating age determinations that contribute to an updated age progression for the Louisville seamount trail. Louisville is the South Pacific counterpart ...

  Citation × Citation Citation Abstract Copy Title: New 40Ar/39Ar age progression for the Louisville hot spot trail and implications for inter–hot spot motion Author: Gee, Jeffrey S., Lonsdale, Peter F., Colwell, Lauren E., Koppers, Anthony A. P., Mahoney, John J., Duncan, Robert A., Gowen, Molly D. In this study we present 42 new ⁴⁰Ar/³⁹Ar incremental heating age determinations that contribute to an updated age progression for the Louisville seamount trail. Louisville is the South Pacific counterpart to the Hawaiian‐Emperor seamount trail, both trails representing intraplate volcanism over the same time interval (~80 Ma to present) and being examples of primary hot spot lineaments. Our data provide evidence for an age‐progressive trend from 71 to 21 Ma. Assuming fixed hot spots, this makes possible a direct comparison to the Hawaiian‐Emperor age progression and the most recent absolute plate motion (APM) model (WK08G) of Wessel and Kroenke (2008). We observe that for the Louisville seamount trail the measured ages are systematically older relative to both the WK08G model predictions and Hawaiian seamount ages, with offsets ranging up to 6 Myr. Taking into account the uncertainty about the duration of eruption and magmatic succession at individual Louisville volcanoes, these age offsets should be considered minimum estimates, as our sampling probably tended to recover the youngest lava flows. These large deviations point to either a contribution of inter–hot spot motion between the Louisville and Hawaiian hot spots or to a more easterly location of the Louisville hot spot than the one inferred in the WK08G model. Both scenarios are investigated in this paper, whereby the more eastern hot spot location (52.0°S, 134.5°W versus 52.4°S, 137.2°W) reduces the average age offset, but still results in a relatively large maximum offset of 3.7 Myr. When comparing the new ages to the APM models (S04P, S04G) by Steinberger et al. (2004) that attempt to compensate for the motion of hot spots in the Pacific (Hawaii) or globally (Hawaii, Louisville, Reunion and Walvis), the measured and predicted ages are more in agreement, showing only a maximum offset of 2.3 Myr with respect to the S04G model. At face value these more advanced APM models, which consider both plate and hot spot motions, therefore provide a better fit to the new Louisville age data. The fit is particularly good for seamounts younger than 50 Ma, a period for which there is little predicted motion for the Louisville hot spot and little inter–hot spot motion with Hawaii. However, discrepancies in the Louisville age‐distance record prior to 50 Ma indicate there is an extra source of inter–hot spot motion between Louisville and the other Pacific hot spots that was not corrected for in the global S04G model. Finally, based on six new ⁴⁰Ar/³⁹Ar age dates, the 169°W bend in the Louisville seamount trail seems to have formed at least 3 Myr before the formation of the Hawaiian‐Emperor bend. The timing of the most acute parts of both bends thus appears to be asynchronous, which would require other processes (e.g., plume motions) than a global plate motion change between 50 and 47 Ma to explain these two observations. Title: New 40Ar/39Ar age progression for the Louisville hot spot trail and implications for inter–hot spot motion Author: Gee, Jeffrey S., Lonsdale, Peter F., Colwell, Lauren E., Koppers, Anthony A. P., Mahoney, John J., Duncan, Robert A., Gowen, Molly D. In this study we present 42 new ⁴⁰Ar/³⁹Ar incremental heating age determinations that contribute to an updated age progression for the Louisville seamount trail. Louisville is the South Pacific counterpart to the Hawaiian‐Emperor seamount trail, both trails representing intraplate volcanism over the same time interval (~80 Ma to present) and being examples of primary hot spot lineaments. Our data provide evidence for an age‐progressive trend from 71 to 21 Ma. Assuming fixed hot spots, this makes possible a direct comparison to the Hawaiian‐Emperor age progression and the most recent absolute plate motion (APM) model (WK08G) of Wessel and Kroenke (2008). We observe that for the Louisville seamount trail the measured ages are systematically older relative to both the WK08G model predictions and Hawaiian seamount ages, with offsets ranging up to 6 Myr. Taking into account the uncertainty about the duration of eruption and magmatic succession at individual Louisville volcanoes, these age offsets should be considered minimum estimates, as our sampling probably tended to recover the youngest lava flows. These large deviations point to either a contribution of inter–hot spot motion between the Louisville and Hawaiian hot spots or to a more easterly location of the Louisville hot spot than the one inferred in the WK08G model. Both scenarios are investigated in this paper, whereby the more eastern hot spot location (52.0°S, 134.5°W versus 52.4°S, 137.2°W) reduces the average age offset, but still results in a relatively large maximum offset of 3.7 Myr. When comparing the new ages to the APM models (S04P, S04G) by Steinberger et al. (2004) that attempt to compensate for the motion of hot spots in the Pacific (Hawaii) or globally (Hawaii, Louisville, Reunion and Walvis), the measured and predicted ages are more in agreement, showing only a maximum offset of 2.3 Myr with respect to the S04G model. At face value these more advanced APM models, which consider both plate and hot spot motions, therefore provide a better fit to the new Louisville age data. The fit is particularly good for seamounts younger than 50 Ma, a period for which there is little predicted motion for the Louisville hot spot and little inter–hot spot motion with Hawaii. However, discrepancies in the Louisville age‐distance record prior to 50 Ma indicate there is an extra source of inter–hot spot motion between Louisville and the other Pacific hot spots that was not corrected for in the global S04G model. Finally, based on six new ⁴⁰Ar/³⁹Ar age dates, the 169°W bend in the Louisville seamount trail seems to have formed at least 3 Myr before the formation of the Hawaiian‐Emperor bend. The timing of the most acute parts of both bends thus appears to be asynchronous, which would require other processes (e.g., plume motions) than a global plate motion change between 50 and 47 Ma to explain these two observations. Close

• 2. [Article] Implications of a nonlinear ⁴⁰Ar/³⁹Ar age progression along the Louisville seamount trail for models of fixed and moving hot spots

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Implications of a nonlinear ⁴⁰Ar/³⁹Ar age progression along the Louisville seamount trail for models of fixed and moving hot spots Author: Koppers, Anthony A. P., Steinberger, Bernhard, Duncan, Robert A. Copyrighted by American Geophysical Union. Title: Implications of a nonlinear ⁴⁰Ar/³⁹Ar age progression along the Louisville seamount trail for models of fixed and moving hot spots Author: Koppers, Anthony A. P., Steinberger, Bernhard, Duncan, Robert A. Copyrighted by American Geophysical Union. Close

• 3. [Article] Age systematics of two young en echelon Samoan volcanic trails

  The volcanic origin of the Samoan archipelago can be explained by one of three models, specifically, by a hot spot forming over a mantle plume, by lithospheric extension resulting from complex subduction ...

  Citation × Citation Citation Abstract Copy Title: Age systematics of two young en echelon Samoan volcanic trails Author: Staudigel, Hubert, Hart, Stanley R., Koppers, Anthony A. P., Jackson, Matthew G., Russell, Jamie A., Wright, Dawn J., Roberts, Jed, Konter, Jasper G. The volcanic origin of the Samoan archipelago can be explained by one of three models, specifically, by a hot spot forming over a mantle plume, by lithospheric extension resulting from complex subduction tectonics in the region, or by a combination of these two processes, either acting sequentially or synchronously. In this paper, we present results of 36 high-resolution ⁴⁰Ar/³⁹Ar incremental heating age analyses for the initial (submarine) phase of Samoan volcanoes, ranging from 13.2 Ma for the westernmost Samoan seamounts to 0.27 Ma in the eastern Samoan volcanic province. Taken as a whole, our new age data point to a hot spot origin for the shield-building volcanism in the Samoan lineament, whereby seamounts younger than 5 Ma are consistent with a model of constant 7.1 cm/yr plate motion, analogous to GPS measurements for the Pacific Plate in this region. This makes our new ⁴⁰Ar/³⁹Ar ages of the submarine basalts all older compared to recent absolute plate motion (APM) models by Wessel et al. (2008), which are based on the inversion of twelve independent seamount trails in the Pacific relative to a fixed reference frame of hot spots and which predict faster plate motions of around 9.3 cm/yr in the vicinity of Samoa. The Samoan ages are also older than APM models by Steinberger et al. (2004) taking into account the motion of hot spots in the Pacific alone or globally. The age systematics become more complicated toward the younger end of the Samoan seamount trail, where its morphology bifurcates into two en echelon subtracks, termed the VAI and MALU trends, as they emanate from two eruptive centers at Vailulu'u and Malumalu seamount, respectively. Spaced ~50 km apart, the VAI and MALU trends have distinct geochemical characters and independent but overlapping linear ⁴⁰Ar/³⁹Ar age progressions since 1.5 Ma. These phenomena are not unique to Samoa, as they have been observed at the Hawaiian hot spot, and can be attributed to a geochemical zoning in its underlying mantle source or plume. Moreover, the processes allowing for the emergence of two distinct eruptive centers in the Samoan archipelago, the stepped offset of these subtracks, and their slight obliqueness with respect to the overall seamount trail orientation may very well be controlled by local tectonics, stresses, and extension, also causing the rejuvenated volcanism on the main islands of Savai'i, Upolu, and Tutuila since 0.4 Ma. Title: Age systematics of two young en echelon Samoan volcanic trails Author: Staudigel, Hubert, Hart, Stanley R., Koppers, Anthony A. P., Jackson, Matthew G., Russell, Jamie A., Wright, Dawn J., Roberts, Jed, Konter, Jasper G. The volcanic origin of the Samoan archipelago can be explained by one of three models, specifically, by a hot spot forming over a mantle plume, by lithospheric extension resulting from complex subduction tectonics in the region, or by a combination of these two processes, either acting sequentially or synchronously. In this paper, we present results of 36 high-resolution ⁴⁰Ar/³⁹Ar incremental heating age analyses for the initial (submarine) phase of Samoan volcanoes, ranging from 13.2 Ma for the westernmost Samoan seamounts to 0.27 Ma in the eastern Samoan volcanic province. Taken as a whole, our new age data point to a hot spot origin for the shield-building volcanism in the Samoan lineament, whereby seamounts younger than 5 Ma are consistent with a model of constant 7.1 cm/yr plate motion, analogous to GPS measurements for the Pacific Plate in this region. This makes our new ⁴⁰Ar/³⁹Ar ages of the submarine basalts all older compared to recent absolute plate motion (APM) models by Wessel et al. (2008), which are based on the inversion of twelve independent seamount trails in the Pacific relative to a fixed reference frame of hot spots and which predict faster plate motions of around 9.3 cm/yr in the vicinity of Samoa. The Samoan ages are also older than APM models by Steinberger et al. (2004) taking into account the motion of hot spots in the Pacific alone or globally. The age systematics become more complicated toward the younger end of the Samoan seamount trail, where its morphology bifurcates into two en echelon subtracks, termed the VAI and MALU trends, as they emanate from two eruptive centers at Vailulu'u and Malumalu seamount, respectively. Spaced ~50 km apart, the VAI and MALU trends have distinct geochemical characters and independent but overlapping linear ⁴⁰Ar/³⁹Ar age progressions since 1.5 Ma. These phenomena are not unique to Samoa, as they have been observed at the Hawaiian hot spot, and can be attributed to a geochemical zoning in its underlying mantle source or plume. Moreover, the processes allowing for the emergence of two distinct eruptive centers in the Samoan archipelago, the stepped offset of these subtracks, and their slight obliqueness with respect to the overall seamount trail orientation may very well be controlled by local tectonics, stresses, and extension, also causing the rejuvenated volcanism on the main islands of Savai'i, Upolu, and Tutuila since 0.4 Ma. Close

• 4. [Article] High-resolution ⁴⁰Ar/³⁹Ar dating of the oldest oceanic basement basalts in the western Pacific basin

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: High-resolution ⁴⁰Ar/³⁹Ar dating of the oldest oceanic basement basalts in the western Pacific basin Author: Staudigel, Hubert, Koppers, Anthony A. P., Duncan, Robert A. Copyrighted by American Geophysical Union. Title: High-resolution ⁴⁰Ar/³⁹Ar dating of the oldest oceanic basement basalts in the western Pacific basin Author: Staudigel, Hubert, Koppers, Anthony A. P., Duncan, Robert A. Copyrighted by American Geophysical Union. Close

• 5. [Article] Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism? Author: Staudigel, Hubert, Koppers, Anthony A. P., Wijbrans, Jan R., Pringle, Malcom S. Copyrighted by American Geophysical Union. Title: Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism? Author: Staudigel, Hubert, Koppers, Anthony A. P., Wijbrans, Jan R., Pringle, Malcom S. Copyrighted by American Geophysical Union. Close