Structure of the Central Altyn Tagh Fault revealed by magnetotelluric data

New insights into the structure of the northern margin of the India-Asia collision

Letian Zhang, Martyn Unsworth, Sheng Jin*, Wenbo Wei, Gaofeng Ye, Alan G. Jones, Jianen Jing, Hao Dong, Chengliang Xie, Florian Le Pape, Jan Vozar

*Corresponding author for this work

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

The Altyn Tagh Fault (ATF) is a left-lateral, strike-slip fault that forms the northern margin of the Tibetan Plateau and plays a significant role in accommodating the convergence between the colliding Indian and Eurasian plates. As a part of the fourth phase of the INDEPTH project, magnetotelluric (MT) data were collected across the central segment of the ATF to determine the lithospheric-scale structure of the fault system. Dimensionality analyses demonstrated that the MT data can be interpreted using two-dimensional approaches, but some localized 3-D effects are seen. Consequently, both 2-D and 3-D inversions were carried out, and a joint interpretation was made on the basis of these two types of models. Inversion models revealed two major conductors beneath the Qaidam Basin (QB) and Altyn Tagh Range (ATR), respectively. The conductive region beneath the QB was interpreted as a ductile layer in the lower crust to upper mantle that might represent flow beneath the western margin of the QB, whereas the large scale south-dipping conductor beneath the ATR is interpreted as a region with high fluid content formed by metamorphism associated with the oblique underthrusting of the Tarim Block beneath the northern Tibetan Plateau. These fluids migrate upwards through the fault system and have formed serpentinized zones in the crust. Combining these interpretations, a structural model compatible with diverse geophysical observations is proposed, in which we suggest the competing end-member rigid block model and continuum model are reconcilable with the continuum model locally dominant for the study region, as evidenced by a thickened crust.

Original languageEnglish
Pages (from-to)67-79
Number of pages13
JournalEarth and Planetary Science Letters
Volume415
DOIs
Publication statusPublished - 1 Apr 2015
Externally publishedYes

Keywords

  • 2-D inversion
  • 3-D inversion
  • Altyn Tagh Fault
  • Lithospheric electrical structure
  • Magnetotellurics
  • Northern margin of the Tibetan Plateau

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