黄陵背斜核北部黄凉河组混合岩化作用及泥质变质岩P-T轨迹对石墨成矿的启示  

Implication of Migmatization and P-T Path of Metapelite in HuangliangheFormation on Graphite Mineralization in Northern Hangling Anticline Core

作　　者：陈冰寒 卢金祥 熊丽 周舟 裴银 龚银 Chen Binghan;Lu Jinxiang;Xiong Li;Zhou Zhou;Pei Yin;Gong Yin(Seventh Geological Brigade of Hubei Geological Bureau,Yichang,Hubei 443100;Hubei Geological Exploration Fund Management Center,Wuhan,Hubei 430071)

机构地区：[1]湖北省地质局第七地质大队,湖北宜昌443100 [2]湖北省地质勘查基金管理中心,湖北武汉430071

出　　处：《资源环境与工程》2023年第5期496-503,共8页Resources Environment & Engineering

基　　金：湖北省宜昌市夷陵区蔡家冲矿区石墨矿普查(鄂地勘基金合〔2020〕17号)。

摘　　要：黄陵背斜核北部黄凉河组产出大鳞片晶质石墨矿,现有研究认为石墨片度分布与混合岩化作用有关,但这些研究多侧重于经验判断和特定样品的对比,缺乏统计学证据。以蔡家冲矿区的石墨矿为研究对象,根据不同层位样品中石墨片度的统计结果,分析混合岩化作用对石墨成矿的影响;对黄凉河组代表性样品进行相平衡模拟,探讨P-T轨迹对石墨成矿的启示。结果表明,蔡家冲地区的混合岩造成距离其0~20 m范围内的石墨片度增大,≥50目的石墨鳞片含量相较于蔡家冲地区整体平均值提高了5.77%~19.55%,因此石墨片度受石墨矿体与混合岩距离的影响,石墨矿体距混合岩越近,其大鳞片石墨含量越高;同时混合岩影响距离的远近与混合岩规模有关,混合岩规模越大,受其影响的距离越远。采用黄凉河组含石墨红柱石十字石二云片岩样品进行相平衡模拟,得到其峰期变质条件为640~660℃、0.31~0.38 GPa;结合该样品变质矿物世代变化和对应的变质反应,在P-T视剖面图中得到升压升温+减压升温的两阶段P-T轨迹,升压升温阶段对应碰撞造山过程,石墨矿的主体形成于该时期;减压升温阶段指示造山后伸展之前的热松弛期,混合岩化作用发生于该时期,并造成部分石墨矿体的石墨片度明显增大。Large-scale crystalline graphite occur in the Huanglianghe Formation in the northern Huangling anticline core.It is believed that the distribution of graphite flakes is related to migmatization.However,these studies mostly focus on empirical judgment and comparison of specific samples,lacking statistical evidence.Taking the graphite ore in Caijiachong mining area as the research object,according to the statistical results of graphite flakes in different samples,the influence of migmatization on graphite mineralization is analyzed.The phase equilibrium modeling of representative samples of Huanglianghe Formation is carried out,and the enlightenment of P-T path on graphite mineralization is discussed.The results show that the migmatite in Caijiachong area causes the increase of graphite flake size in the range of 0-20 m.The content of graphite flake with≥50 mesh increases by 5.77%-19.55%compared with the overall average value in Caijiachong area.Therefore,the graphite flake size is affected by the distance between graphite ore body and migmatite.The closer the graphite ore body is to the migmatite,the higher the large-scale crystalline graphite content is.At the same time,the influence distance of migmatite is related to the scale of migmatite.The larger the scale of migmatite,the farther the distance affected by it.The phase equilibrium modeling is carried out by using the andalusite-staurolite-mica schist with graphite of Huanglianghe Formation,and the peak metamorphic conditions are 640-660℃and 0.31-0.38 GPa.According to the generational changes of metamorphic minerals and the corresponding metamorphic reactions in the sample,the two-stage P-T path compression heating and decompression heating is obtained.The compression heating stage corresponds to the collision orogeny,and the main graphite ore is formed in this period.The decompression heating stage indicates the thermal relaxation period before the post-orogenic extension,during which the migmatization occurred and caused the graphite flake to increase s

关 键 词：晶质石墨 混合岩化 P-T轨迹 相平衡模拟 黄陵背斜 

分 类 号：P511.5[天文地球—地质学] P619.25