Early Cretaceous uplift history of the Dabie orogenic belt: Evidence from pluton emplacement depths  

作　　者：WANG YongSheng WANG HaiFeng SHENG Yong XIANG BiWei 

机构地区：[1]School of Resource and Environmental Engineering, Hefei University of Technology [2]Faculty of Earth Sciences, China University of Geosciences

出　　处：《Science China Earth Sciences》2014年第5期1129-1140,共12页中国科学（地球科学英文版）

基　　金：supported by the Anhui Natural Science Foundation (Grant No. 1108085J12);China Geological Survey Project of Science and Technology (Grant No. 1212011121114)

摘　　要：The North Dabie complex unit （NDC） is a widely exposed petro-tectonic unit. To understand post-orogenic uplift history and mechanism of the Dabie orogenic belt, many samples of granite, granodiorite, diorite, and alkali feldspar granite with precise zircon U-Pb ages were collected for electron microprobe analysis of hornblende. Emplacement pressure values were then cal- culated by using an Al-in-hornblende geobarometer. The result shows that total A1 （A1T） values in hornblende range from 1.17 to 1.97 p.f.u., XFe（=Fe/（Fe＋Mg）） from 0.4 to 0.65, and corresponding pressure values from 256.8 to 676.2 MPa for A1T greater than 1.17. It is suggested that although the main mechanism for the uplift is tectonic extension, inhomogeneous uplift related to the pluton emplacement is also important during post-orogenic evolution of the Dabie orogenic belt. Emplacement depth dis- tribution of the plutons shows that uplift in the NDC is affected by horst-graben structures since 120 Ma.The North Dabie complex unit(NDC)is a widely exposed petro-tectonic unit.To understand post-orogenic uplift history and mechanism of the Dabie orogenic belt,many samples of granite,granodiorite,diorite,and alkali feldspar granite with precise zircon U-Pb ages were collected for electron microprobe analysis of hornblende.Emplacement pressure values were then calculated by using an Al-in-hornblende geobarometer.The result shows that total Al(AlT)values in hornblende range from 1.17to 1.97 p.f.u.,XFe(=Fe/(Fe+Mg))from 0.4 to 0.65,and corresponding pressure values from 256.8 to 676.2 MPa for AlT greater than 1.17.It is suggested that although the main mechanism for the uplift is tectonic extension,inhomogeneous uplift related to the pluton emplacement is also important during post-orogenic evolution of the Dabie orogenic belt.Emplacement depth distribution of the plutons shows that uplift in the NDC is affected by horst-graben structures since 120 Ma.

关 键 词：Dabie orogenic belt North Dabie complex belt Early Cretaceous plutons Al-in-hornblende geobarometer 

分 类 号：P542[天文地球—构造地质学]