热液导致的白云石重结晶过程中的原位地球化学记录:以塔里木盆地巴楚地区上寒武统白云岩为例  

Evolution of in-situ geochemical records in hydrothermal recrystallization of dolomite:A case study from Upper Cambrian dolostones in the Bachu area,Tarim Basin

作　　者：刘明铭 鲁子野 李飞 陈曦[1] 叶宁 黄柏文 李映涛 张歆妍 张哨楠[1] LIU Mingming;LU Ziye;LI Fei;CHEN Xi;YE Ning;HUANG Baiwen;LI Yingtao;ZHANG Xinyan;ZHANG Shaonan(School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610050,China;Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 100083,China;Exploration and Development Research Institute,PetroChina Southwest Oil and Gasfield Company,Chengdu 610094,China)

机构地区：[1]西南石油大学地球科学与技术学院,四川成都610050 [2]中国石化石油勘探开发研究院,北京100083 [3]中国石油西南油气田分公司勘探开发研究院,四川成都610094

出　　处：《沉积与特提斯地质》2025年第1期120-133,共14页Sedimentary Geology and Tethyan Geology

基　　金：国家自然科学基金项目(42102191)。

摘　　要：塔里木盆地巴楚地区上寒武统白云岩遭受了大量的热液改造。基于岩石学、原位微量元素特征分析及前人的研究成果,本研究从BT5井上寒武统白云岩中识别出了3种组构的白云石:基质白云石(MD)、环带状鞍形白云石(SD1)和巨晶鞍形白云石(SD2)。其中,SD1自形程度较好,其核部(SD1-1)具有污浊的晶面和亮红色阴极光,边缘(SD1-2)具有明亮的晶面并在阴极光下显示无规则明暗环带;SD2具有波状消光和亮红色阴极光。原位微量元素分析显示,从MD到SD1和SD2核部(SD2-1),样品呈现Sr元素含量逐渐下降、稀土元素总含量逐渐增加且轻稀土元素的富集程度逐渐增加的规律。综合上述研究,推测SD2-1是从热液中沉淀的白云石充填物,而SD1与热液导致的MD重结晶改造有关。本研究显示热液导致的重结晶形成的白云石具过渡性质稀土元素构成(介于MD和SD2之间),这种特征可以用来识别热液导致的重结晶过程。The Upper Cambrian dolostones in the Tarim Basin have undergone widely alteration by hydrothermal fluids.In this study,based on petrological and trace element analyses,three types of dolomites were identified in the Upper Cambrian dolostones of Well BT5 in the Bachu area:matrix dolomites(MD),dolomite cements with cathodoluminescence zonation(SD1),and blocky dolomite cements(SD2).SD1 occurs as euhedral crystals,consisting of a core(SD1-1)and a rim(SD1-2).SD1-1 is characterized by cloudy crystal surfaces and bright red luminescence under cathodoluminescence(CL),while SD1-2 displays bright crystal surfaces with irregular bright-dark zoning under CL.And SD2 exhibits wavy extinction and shows bright red under CL.From the host dolostone(MD)to the last generation of dolomite cements(SD1,and SD2's core SD2-1),the Sr concentrations decreased,and the total rare earth element concentrations(ƩREE)as well as light rare earth element enrichment increased.Consequently,SD2-1 is interpreted to be dolomite fillings precipitated from hydrothermal fluids,while SD1 results from hydrothermal recrystallization of MD.This study suggests that the dolomites formed from hydrothermal recrystallization show transitional REE characteristics,which can serve as a useful tool to identify recrystallization process in dolomites.

关 键 词：塔里木盆地 上寒武统 白云岩 热液重结晶 微量和稀土元素 

分 类 号：P618.13[天文地球—矿床学]