Structural Deformation in the Dongmozhazhua Deposit, Northern Segment of the Sanjiang Belt
详细信息
- 责任者：Zhang Hongrui (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Yang Tiannan
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(4)
- 关键词：构造变形 ; tectonic deformation ; 西南地区 ; Southwest China
- 页码：p.1145-1155
- 图表：illus., 30 refs.
- 分类号：0300
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The uplift models of Qinghai-Tibetan plateau are mostly based on Cenozoic deformation but lack of the information from Paleozoic and Mesozoic structures, the later is important to understand the uplift process as the early structures always providing a framework. In this paper, we document the deposit-region structures and then try to analyze the deformation sequence in the Dongmozhazhua area, northern segment of the Sanjiang belt. Detailed geological mapping reveals four lithostratigraphic associations in Dongmozhazhua area, i.e., the Lower to Middle Permian Jiushidaoban Formation, consisting mainly of limestones; the Upper Permian Nayixiong Formation composed of clastic and volcanic rocks; the Upper Triassic Jiapeila Formation comprising clastic rocks intercalated with volcanics; and the Upper Triassic Bolila Formation of carbonate rocks. Between the Permian and Triassic is a regional angular unconformity, but this contact interface is replaced by nearly north-south trend thrust locally. Northwestward thrust in Dongmozhazhua dips 40°～50° to the north and juxtaposes Triassic carbonate and clastic sequence over Permian-Triassic strata. The Triassic rocks in the footwall are squeezed out by right-lateral and left-lateral strike-slip faults both sides. Two stages of folding that deformed the Permian-Triassic strata in the map and outcrop view. They were represented by tight plunging folds in NS section and open inclined folds in EW section. Then deformation history in Dongmozhazhua can be rebuilt: the first stage (D1) is characterized by nearly E-W trend folds and formed during the close of Paleo-Tethyan oceans in Late Triassic; the second stage (D2) is associated with a NE directed shortening in Late Eocene that produced NW trend thrusts and open folds and caused by the continent collision between India and Eurasian; the third stage (D3) is characterized by nearly N-S trend thrust and possibly triggered by the left-slip faulting in the eastern Indo-Asian collision zone.
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