Geochronology Constraints on Transformation Age from Ductile to Brittle Deformation of the Shangma Fault and Its Tectonic Significance, Dabieshan, Central China
- 责任者：Wang Guocan (Faculty of Earth Sciences ; China University of Geosciences ; Wuhan 430074 ; China ; State Key Laboratory of Geological Processes and Mineral Resources ; China University of Geosciences ; Wuhan 430074 ; China ) ; Wang Pu
- 刊名：Journal of China University of Geosciences
- 出版年：2008
- 卷期：19(2)
- 关键词：ductile to brittle deformation ; zircon U-Pb dating
- 页码：p.97-109
- 图表：8 illus., 1 table, 25 refs.
- issnNo：ISSN1002-0705
- isbnNo：CN42-1279/P
By a detailed investigation of geometry and kinematics of the Shangma fault in Dabieshan, three different crust levels of extension movement have been recognized in sequence from the deep to the shallow: 1) low-angle ductile detachment shearing with top to the NW; 2) low-angle normal fault with top to the NW or NWW in brittle or brittle-ductile transition domain; 3)high-angle brittle normal fault with top to the W or NWW. Two samples were chosen for zircon U-Pb age dating to constrain the activity age of the Shangma fault. A bedding intrusive granitoid pegmatite vein that is parallel to the foliation of the low-angle ductile detachment shear zone of the country rock exhibits a lotus-joint type of boudinage deformation, showing syn-tectonic emplacing at the end of the ductile deformation period and deformation in the brittle-ductile transition domain. The zircon U-Pb dating of this granitoid pegmatite vein gives an age of (125.9±4.2) Ma, which expresses the extension in the brittle-ductile transition domain of the Shangma fault. The other sample, which is collected from a granite pluton cutting the foliation of the low-angle ductile detachment shear zone, gives a zircon U-Pb age of (118.8±4.1) Ma, constraining the end of the ductile detachment shearing.