39101
2015
2015
eng
594
622
29
3
34
article
American Geophysical Union
Washington
1
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--
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What was the Paleogene latitude of the Lhasa terrane? A reassessment of the geochronology and paleomagnetism of Linzizong volcanic rocks (Linzhou basin, Tibet)
The Paleogene latitude of the Lhasa terrane (southern Tibet) can constrain the age of the onset of the India-Asia collision. Estimates for this latitude, however, vary from 5 degrees N to 30 degrees N, and thus, here, we reassess the geochronology and paleomagnetism of Paleogene volcanic rocks from the Linzizong Group in the Linzhou basin. The lower and upper parts of the section previously yielded particularly conflicting ages and paleolatitudes. We report consistent Ar-40/Ar-39 and U-Pb zircon dates of similar to 52Ma for the upper Linzizong, and Ar-40/Ar-39 dates (similar to 51Ma) from the lower Linzizong are significantly younger than U-Pb zircon dates (64-63Ma), suggesting that the lower Linzizong was thermally and/or chemically reset. Paleomagnetic results from 24 sites in lower Linzizong confirm a low apparent paleolatitude of similar to 5 degrees N, compared to the upper part (similar to 20 degrees N) and to underlying Cretaceous strata (similar to 20 degrees N). Detailed rock magnetic analyses, end-member modeling of magnetic components, and petrography from the lower and upper Linzizong indicate widespread secondary hematite in the lower Linzizong, whereas hematite is rare in upper Linzizong. Volcanic rocks of the lower Linzizong have been hydrothermally chemically remagnetized, whereas the upper Linzizong retains a primary remanence. We suggest that remagnetization was induced by acquisition of chemical and thermoviscous remanent magnetizations such that the shallow inclinations are an artifact of a tilt correction applied to a secondary remanence in lower Linzizong. We estimate that the Paleogene latitude of Lhasa terrane was 204 degrees N, consistent with previous results suggesting that India-Asia collision likely took place by similar to 52Ma at similar to 20 degrees N.
Tectonics
10.1002/2014TC003787
0278-7407
1944-9194
wos:2015
WOS:000353837100013
Huang, WT (reprint author), Peking Univ, Sch Earth & Space Sci, Minist Educ, Key Lab Orogen Belts & Crustal Evolut, Beijing 100871, Peoples R China., W.Huang@uu.nl
U.S. NSF Continental Dynamics [EAR-1008527]; Netherlands Organization
for Scientific Research (NWO) [864.08.005, 864.11.004]; China
Scholarship Council; ERC [306810]; Alexander von Humboldt foundation;
Cai Yuanpei program; Chinese Ministry Of Education
Wentao Huang
Guillaume Dupont-Nivet
Peter C. Lippert
Douwe J. J. van Hinsbergen
Mark J. Dekkers
Ross Waldrip
Morgan Ganerod
Xiaochun Li
Zhaojie Guo
Paul Kapp
eng
uncontrolled
remagnetization
eng
uncontrolled
rock magnetism
eng
uncontrolled
geochronology
eng
uncontrolled
India-Asia collision
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
39380
2015
2015
eng
42
66
25
1
120
article
American Geophysical Union
Washington
1
--
--
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Can a primary remanence be retrieved from partially remagnetized Eocence volcanic rocks in the Nanmulin Basin (southern Tibet) to date the India-Asia collision?
Paleomagnetic dating of the India-Asia collision hinges on determining the Paleogene latitude of the Lhasa terrane (southern Tibet). Reported latitudes range from 5 degrees N to 30 degrees N, however, leading to contrasting paleogeographic interpretations. Here we report new data from the Eocene Linzizong volcanic rocks in the Nanmulin Basin, which previously yielded data suggesting a low paleolatitude (similar to 10 degrees N). New zircon U-Pb dates indicate an age of similar to 52Ma. Negative fold tests, however, demonstrate that the isolated characteristic remanent magnetizations, with notably varying inclinations, are not primary. Rock magnetic analyses, end-member modeling of isothermal remanent magnetization acquisition curves, and petrographic observations are consistent with variable degrees of posttilting remagnetization due to low-temperature alteration of primary magmatic titanomagnetite and the formation of secondary pigmentary hematite that unblock simultaneously. Previously reported paleomagnetic data from the Nanmulin Basin implying low paleolatitude should thus not be used to estimate the time and latitude of the India-Asia collision. We show that the paleomagnetic inclinations vary linearly with the contribution of secondary hematite to saturation isothermal remanent magnetization. We tentatively propose a new method to recover a primary remanence with inclination of 38.1 degrees (35.7 degrees, 40.5 degrees) (95% significance) and a secondary remanence with inclination of 42.9 degrees (41.5 degrees,44.4 degrees) (95% significance). The paleolatitude defined by the modeled primary remanence21 degrees N (19.8 degrees N, 23.1 degrees N)is consistent with the regional compilation of published results from pristine volcanic rocks and sedimentary rocks of the upper Linzizong Group corrected for inclination shallowing. The start of the Tibetan Himalaya-Asia collision was situated at similar to 20 degrees N and took place by similar to 50Ma.
Journal of geophysical research : Solid earth
10.1002/2014JB011599
2169-9313
2169-9356
wos:2015
WOS:000350152000003
Huang, WT (reprint author), Peking Univ, Key Lab Orogen Belts & Crustal Evolut, Minist Educ, Sch Earth & Space Sci, Beijing 100871, Peoples R China., W.Huang@uu.nl
U.S. NSF [EAR-1008527]; Netherlands Organization for Scientific Research
(NWO); China Scholarship Council; ERC [306810]; Marie Curie CIG
HIRESDAT; Alexander von Humboldt foundation; French Ministry of Foreign
Affairs; French Ministry of Higher Education and Research; Chinese
Ministry of Education
Wentao Huang
Guillaume Dupont-Nivet
Peter C. Lippert
Douwe J. J. van Hinsbergen
Mark J. Dekkers
Zhaojie Guo
Ross Waldrip
Xiaochun Li
Xiaoran Zhang
Dongdong Liu
Paul Kapp
eng
uncontrolled
remagnetization
eng
uncontrolled
paleomagnetism applied to tectonics
eng
uncontrolled
rock and mineral magnetism
eng
uncontrolled
India-Asia collision
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften