Electrical resistivity structure beneath the central Cona-Oiga rift, southern Tibet, and its implications for regional dynamics

doi:10.13745/j.esf.sf.2022.2.3

Abstract

Abstract:

As one of the most significant extensional structural styles of the Tibetan Plateau, the rifts in southern Tibet are an important window for studying the growth of the plateau. However, the formation mechanism of these deep rifts remains controversial. In this paper, magnetotelluric data from the central part of the Cona-Oiga rift were used to study the rifts in southern Tibet. The Magnetotelluric sounding curves and phase tensors were calculated and analyzed, and the electrical resistivity structure beneath the Qiongduojiang and Oiga grabens was obtained through 3D MT inversion. The 3D inversion result showed that an obvious continuous high-conductivity anomaly develops beneath the Cona-Oiga rift in a “subduction” pattern overlaying with high-resistivity structures, while low-resistivity anomalies distribute in the relatively shallow parts beneath either side of the Qiongduojiang graben. Combined with the previous studies, the continuous high-conductivity anomaly beneath the Cona-Oiga rift is believed to be originated from crustal partial melting, probably related to the southward crustal flow. We suggest that, under the N-S compression driven by the India-Eurasia collision, the weakened crust promotes the development of the rifts in southern Tibet by decoupling the upper crust and the lower lithosphere.

Key words: Cona-Oiga rift, magnetotelluric, rifts in southern Tibet, electrical resistivity structure, crustal flow, extensional structures

CLC Number:

XUE Shuai, LU Zhanwu, LI Wenhui, WANG Guangwen, WANG Haiyan, LIANG Hongda. Electrical resistivity structure beneath the central Cona-Oiga rift, southern Tibet, and its implications for regional dynamics[J]. Earth Science Frontiers, 2022, 29(2): 393-401.

Figures/Tables 4

Fig.1 (a) Geological sketch maps of the Himalayan orogenic belt (modified from [19]) and the Cona-Oiga rift (modified from [19,38]) in southern Tibet

Fig.2 Typical MT sounding curves for the Cuonadong dome (see Fig.1b for locations of sites 033, 048, 055, 061). Red hollow circles and blue hollow rhombi represent observation modes xy and yx. Red and blue solid lines denote the corresponding inversion results.

Fig.3 MT phase tensors in the research area

Fig.4 N-S vertical cross section 3D inversion result. C1/C2, LR1/LR2, R1/R2 indicate high conductivity and low- and high-resistivity features, respectively.

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