Can a primary remanence be retrieved from partially remagnetized Eocence volcanic rocks in the Nanmulin Basin (southern Tibet) to date the India-Asia collision?

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

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Paleomagnetic dating of the India-Asia collision hinges on determining the Paleogene latitude of the Lhasa terrane (southern Tibet). Reported latitudes range from 5°N to 30°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 (∼10°N). New zircon U-Pb dates indicate an age of ∼52 Ma. 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° (35.7°, 40.5°) (95% significance) and a secondary remanence with inclination of 42.9° (41.5°,44.4°) (95% significance). The paleolatitude defined by the modeled primary remanence - 21°N (19.8°N, 23.1°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 ∼20°N and took place by ∼50 Ma.

Original languageEnglish (US)
Pages (from-to)42-66
Number of pages25
JournalJournal of Geophysical Research: Solid Earth
Volume120
Issue number1
DOIs
StatePublished - Jan 2015

Keywords

  • India-Asia collision
  • paleomagnetism applied to tectonics
  • remagnetization
  • rock and mineral magnetism

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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