上扬子陆块北缘晶质石墨矿地质特征及成因  

Geological characteristics and genesis of crystalline graphite deposits in the North margin of Upper Yangtze Block

作　　者：马志鑫[1] 罗茂金[1] 师洪亮 黄腾 孙志明[1] MA Zhixin;LUO Maojin;SHI Hongliang;HUANG Teng;SUN Zhiming(Chengdu Center,China Geological Survey,Chengdu 610081,Sichuan,China;No.604 of Sichuan Province Metallurgical Geological Bureau,Guangyuan 628017,Sichuan,China;No.605 of Sichuan Province Metallurgical Geological Bureau,Meishan 620860,Sichuan,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]四川省冶金地质勘查局六O四大队,四川广元628017 [3]四川冶金地质勘查局六O五大队,四川眉山620860

出　　处：《地质通报》2022年第5期857-872,共16页Geological Bulletin of China

基　　金：第二次青藏高原综合科学考察研究《典型地区岩石圈组成、演化与深部过程》(编号:2019QZKK0702);中国地质调查局项目《三江造山带昌都-澜沧地区区域地质调查》(编号:DD20190053);《西南重大工程地质安全调查与评价》(编号:DD20221811);《龙门山-滇中成矿带通安—宁蒗地区地质矿产调查》(编号:DD20160017)。

摘　　要：石墨矿是重要的国家战略保护资源,为了深化对上扬子陆块北缘晶质石墨矿成因的认识,对研究区多个石墨矿床的含矿地层、矿体特征、矿石结构构造、矿石地球化学特征进行了对比研究。结果发现,上扬子陆块石墨矿主要分布于四川南江—旺苍一带,形成一个南西—北东向延伸约60 km的矿化带。由南西至北东,石墨矿具有矿体厚度增加、结晶程度变高的趋势。主量和微量元素指标(SiO_(2)、Al_(2)O_(3)、V/Cr、Ni/Co等)反映出含矿岩系整体形成于相对局限缺氧的浅水碳酸盐台地环境,这种环境有利于炭质保存,从而为石墨成矿提供物质来源。石墨矿的δ^(13) C在-24.9‰~-14.2‰之间,与有机质的δ^(13) C分布范围一致,表明石墨矿的炭质来源于生物有机质。石墨矿围岩含有绢云母、黑云母、石榴子石、红柱石等特征变质矿物,指示其经历了低绿片岩相变质作用。在岩浆岩与石墨矿接触部位固定碳含量明显增加,并伴有石墨片径增大的现象,表明岩体热接触变质促进了石墨矿进一步富集。初步提出了研究区石墨矿三阶段成矿模式,即中元古代原生碳质沉积阶段、中新元古代区域变质石墨晶核形成阶段、新元古代岩体热变质晶体生长成矿阶段。研究结果为深入认识上扬子陆块北缘石墨矿形成机制和中国晶质石墨矿成因提供基础材料。Graphite ore is a kind of important national strategic protection resource.In order to deepen the understanding of the genesis of crystalline graphite ore in the northern margin of the Upper Yangtze Block,the ore-bearing strata,ore body characteristics,ore structure and ore geochemical characteristics of many graphite deposits in the area have been studied.It was found that graphite ore was mainly distributed in the Nanjiang-Wangcang area of Sichuan,forming a graphite mineralization zone extending about 60 km from the northeast-southwest direction,and graphite ore has a tendency to increase the thickness of the ore body and the degree of crystallinity in this direction.The main and trace element proxies(SiO_(2),Al_(2)O_(3),V/Cr,Ni/Co,etc.)reflect the formation of the ore-bearing rock series in a relatively limited,oxygen-deficient shallow carbonate platform environment.This environment is conducive to the preservation of carbon,which provide material sources for graphite ore formation.Theδ^(13) C of graphite ore is between-24.9‰and-14.2‰,which overlaps the distribution range ofδ^(13) C of organic matter,indicating that the carbon of graphite ore comes from biological organic matter.The surrounding rock of the graphite mine contains characteristic metamorphic minerals such as sericite,biotite,garnet,andalusite,indicating that it is a set of low-green schist facies shallow metamorphic rocks.The fixed carbon content in the contact part of the magmatic rock and the graphite ore increases significantly and is accompanied by the increase of the scale structure,indicating that the thermal contact metamorphism of the rock mass promotes the further enrichment of the graphite ore.A three-stage metallogenic model of graphite deposits in the study area is initially proposed,inclunding the Mesoproterozoic primary carbonaceous sedimentation enrichment stage,Mesoproterozoic to Neoproterozoic regional metamorphic graphite nucleation stage,and Neoproterozoic rock mass thermal metamorphic crystal growth and mineralization st

关 键 词：扬子陆块 石墨矿 地质特征 成矿模式 四川 地质调查工程 

分 类 号：P619.252[天文地球—矿床学]