TY  - JOUR
A1  - Huang, Wentao
A1  - Dupont-Nivet, Guillaume
A1  - Lippert, Peter C.
A1  - van Hinsbergen, Douwe J. J.
A1  - Dekkers, Mark J.
A1  - Waldrip, Ross
A1  - Ganerod, Morgan
A1  - Li, Xiaochun
A1  - Guo, Zhaojie
A1  - Kapp, Paul
T1  - What was the Paleogene latitude of the Lhasa terrane? A reassessment of the geochronology and paleomagnetism of Linzizong volcanic rocks (Linzhou basin, Tibet)
JF  - Tectonics
N2  - 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.
KW  - remagnetization
KW  - rock magnetism
KW  - geochronology
KW  - India-Asia collision
Y1  - 2015
U6  - https://doi.org/10.1002/2014TC003787
SN  - 0278-7407
SN  - 1944-9194
VL  - 34
IS  - 3
SP  - 594
EP  - 622
PB  - American Geophysical Union
CY  - Washington
ER  -