Extensional Detachment and Magmatism of the Lushan Metamorphic Core Complex: Constraints From 40Ar/39Ar and U-Pb Geochronology
详细信息
- 责任者：Zhu Qingbo (MOE Key Laboratory of Tectonic and Petroleum Resources ; China University of Geosciences ; Wuhan 430074 ; China) ; Yang Kunguang
- 刊名：Geotectonica et Metallogenia
- 出版年：2010
- 卷期：34(3)
- 关键词：滑脱构造 ; decollement ; 变质核杂岩 ; metamorphic core complexes ; 氩‐氩计时 ; 铀—铅计时 ; U-Pb dating ; 庐山 ; Lushan Mountains
- 页码：p.391-401
- 图表：7 illus., 2 tables, 44 refs.
- 分类号：0300
- issnNo：ISSN1001-1552
- isbnNo：CN44-1595/P
摘要
The Lushan metamorphic core complex (MCC) is the shallow response of lithospheric extending and thinning during the Mesozoic in South China. Studying the relationship between extensional detachment and magmatism during the forming process of MCC, is of great significance in understanding the extension-thinning process of shallow crust as well as the forming mechanism of MCC. Based on the mesoscopic and microscopic investigation, 40Ar/39Ar geochronological studies on the basement detachment fault and U-Pb zircon geochronology studies on the Yujing granite were carried out. The geochronology data provide new constrains for extensional detachment and magmatism. It is concluded that: 1) the Yujing granite was formed at (133.0±2.1) Ma (LA-ICP-MS U-Pb zircon dating), and the intrusion of the granite signifies the beginning of magmatism of MCC; 2) the muscovite 40Ar/39Ar dating of ductile shear zone on the foot wall of basement detachment fault was (140.4±1.7) Ma, which represents both the forming time of Lushan MCC and the time of lithospheric extension-thinning in the Lushan region. Regional lithospheric extension-thinning began in Late Jurassic; and 3) the Lushan MCC was the result of different scale extensional detachment and magmatism during the Mesozoic. The forming processes of shallow crust are as follows: Extensional detachment took place earlier than magmatic emplacement. Decompression of the basement detachment fault led to the ascending and emplacing of magma at depth. Then magmatic emplacement led to the Lushan massif uplifting which provided the motivity for the gravitational detachment of the cover.