Illite Crystallinity Mapping of Very Low Grade Metamorphism of Triassic Metapelites in the Zoigê Area,Western China

作     者：TANG Yan SANG Longkang YUAN Yanming YU Jishun ZHANG Yunpeng QI Xianmao YANG Yunlong 

作者机构：Faculty of Earth SciencesChina University of GeosciencesWuhan 430074China College of Earth Science and ResourcesChang'an UniversityXi'an 710054China State Key Laboratory of Geological Processes and Mineral ResourcesChina University of GeosciencesWuhan 430074China Xi'an Center of Geological SurveyChina Geological SurveyXi'an 710054China Chengdu Institute of Geology and Mineral ResourcesChengdu 610082China Sinopec Exploration Southern CompanyChengdu 610082China 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2012年第86卷第1期

页      面：96-105页

核心收录：

学科分类：081803[工学-地质工程] 0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：SINOPEC Exploration Southern Company,part of the National Oil and Gas Special Project XQ-04 the Special Fund for Basic Scientific Research of Central Colleges,Chang'an University(CHD2011JC185) for supporting this study 

主　　题：X-ray diffraction metapelitic zone illite crystallinity percentage of illite in I/S mixed layers percentage of I/S mixed layers the metamorphic map 

摘      要：X-ray diffraction methods for estimating the metamorphic grade of diagenetic, anchizone and epizone in metapelites are reviewed and applied to samples from a 7000 m＋ borehole in western China and surface samples from the surrounding Zoige area. Kiibler＇s illite crystallinity （IC） measurements provide more consistent results than calculated values of percentage of illite in the I/S mixed layers and percentage of I/S mixed layers. Down-borehole IC values display a typical burial metamorphic relationship between stratigraphic level and IC. A method for preparing very low grade metamorphic maps is described, and isograds plotted on a regional geological map at selected values of IC, delineating a high temperature diagenetic zone, an anchizone, and an epizone. The map shows that IC values are controlled by stratigraphic level in the north of the study area （i.e. burial metamorphism）, and proximity to an igneous intrusive body in the south （i.e. contact metamorphism）.