Structural Characterization of and Geochronological Constraints on Sinistral Strike-Slip Shearing along the Southern Segment of Chongshan Shear Zone, Western Yunnan
详细信息
- 责任者：Tang Yuan (Chengdu Institute of Geology and Mineral Resources ; Chengdu 610081 ; China) ; Yin Fuguang
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(4)
- 关键词：剪切带 ; shear zones ; 走滑断层 ; strike-slip faults ; 云南 ; Yunnan Province
- 页码：p.1311-1324
- 图表：illus., 1 table, 53 refs.
- 分类号：0300
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
As the important boundary between Baoshan block and Lanping-Simao basin, the Chongshan shear zone has undergone multi-stage tectonic evolution in Cenozoic. The most obvious structural deformation along the shear zone shows large-scale ductile strike-slip shearing, which is characterized by a dextral-dominated strike-slip shearing in northern segment and a sinistral strike-slip shearing in southern segment. Based on macro- and micro-structural observations and fabric analysis of quartz in the deformed rocks, two stages of ductile deformation in the southern segment of Chongshan shear zone have been established in this paper. During the first stage (D1), the deformation along the Chongshan belt is dominated by contractional deformation under pure shearing at high temperature conditions (550～650℃), characterized by symmetrical folds, boudinages, tectonic lenses and symmetrical patterns of quartz c-axis fabrics. The second stage deformation (D2) is characterized by sinistral strike-slip shearing along the shear zone under simple shearing, showing highly developed foliation and/or lineation and various mylonites related to the strike-slip shearing. In addition, it can be found that some tourmaline-bearing granitic dykes are intensely developed in the Chongshan shear zone. According to the temporal relationships between granitic dykes and shearing, we interpret such granitic dykes are syn-shearing intrusions which account for crystallization of anatectic magma formed during the early stage of sinistral ductile strike-slip shearing. In this paper, two samples of those granitic dykes in the Chongshan shear zone were chosen for LA-ICP-MS zircon U-Pb dating, giving ages of 21.7±0.3Ma and 22.7±0.3Ma respectively. The zircon U-Pb ages of these syn-shearing granitic dykes reveal that the sinistral ductile strike-slip shearing along the southern segment of Chongshan shear zone started at about (or a little earlier than) 22Ma.
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