用户名: 密码: 验证码:
Structure Implication in Tanjianshan Group on Southern Qilian Caledonian Orogeny and Exhumation of UHP Metamorphic Rocks in Northern Qaidam
详细信息   
摘要


     The original Tanjianshan Group in Northern Qaidam can be decomposed into three parts by its stuc-ture and lithology.The lower rock formation is island-arc intermediate-basic volcanic rock series deformed and metamorphosed to greenschist facies mylonite .The middle rock formation is back-arc basin jet-sedimentary rock series in which deformational partitioning of greenschist facies occurred , belonging to the ore-bearing layer of Xitieshan-type Pb-Zn ore deposit.The upper rock formation is purple-red pebbled sandstone with slight de-formation and metamorphism .Structural analysis suggests that the lower rock formation of the original Tanjians-han Group belongs to Upper Cambrian-lower Ordovician,which is the product of ocean -continent collision sys-tem .The middle rock formation belongs to the middle-late Ordovician, the product of the Back-arc basin.The upper rock formation belongs to the early Silurian , the product of the foreland basin in the continent-continent collision system.The lower or middle rock formation and the gneiss of early Proterozoic Dakendaba Group are contacted with the base Detachment fault, while the upper rock formation or the thrust sheet of the Dakendaba Group and the middle rock formation are contacted with the upper detachment fault .The two detachment faults are characteristed by duplex thrust structure.Before the extensional collapse of the orogenic belt, the Dakenda-ba Group without eclogite was thrusted and stacked on the Tanjianshan Group , subsequently setback loss by the upper detachment fault during the Post-orogenic extensional, only partialy remaining relics.After the extension of orogenic belt, the Northern Qaidam was superimposed by intracontinental orogeny, the original Tanjianshan Group, thrust sheets.Nappe faults and detachment faults are transferred into the podiform inverted syncline to-gether, and superimposed on the late Devonian molasse basin .In Caledonian orogenic extensional period, the Altyn strike-slip fault was adjusted by early exhumation between north Qaidam and South Altyn UHP metamor-phic rocks, and the tectonic erosion of the UHP metamorphic belt at the follow-up of the extrusion and exten-sional system.

© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号

地址:北京市海淀区学院路29号 邮编:100083

电话:办公室:(+86 10)66554848;文献借阅、咨询服务、科技查新:66554700