岩浆热侵位对煤变质型石墨富集成矿的控制——以西秦岭凤县隐晶质石墨矿为例

Late Carboniferous graphitic Caoliangyi formation is distributing at Caotangou- Honghuapu- Luobo′an- Laochang- Meigou area of Feng town in Shaanxi province North Qinling Orogen. The ore bodies are scattered around by same Yanshan period magmatite numerous intrusive bodies. The genesis of this graphite ore is closely related with the surrounding rock mass of Baoji thermal emplacement role, that the study on these rocks in which time sequence and spatial position relationship that thermo-emplaced at Feng Town Caoliang yi formation graphite mine construction is lacked. The influence degree caused by thermodynamic conditions of magmatic emplacement on graphite mine in the plane and longitudinal needs ot be further studied. This study take magmatic thermo-emplacement in the coal metamorphic graphite ore richintegration role as the object, analysising petrology and petrography characteristics of hornfels in contact zone in order to determine the thermal contact metamorphism, carrying out temperature and pressure conditions of the magmatic rocks, Finding out change regulation of the content of fixed carbon, metamorphic grade, graphite crystal size and its euhedral degree in the plane and vertical.The study may helps to determine the influence of magma intrusion in which thermal effects graphite metamorphic mineralization, in order to offer same reference on investigation of the magma thermo-emplacement during mineralization enrichment of coal metamorphic type aphanitic graphite ore.

西秦岭凤县草滩沟—煤沟一带分布着晚石炭世草凉驿组煤变质土状隐晶质石墨变成矿床，矿体周围分布着众多的燕山期岩浆岩侵入体，石墨矿成因跟周围宝鸡岩体的热侵位作用密切相关，这些岩体以何种时间顺序和空间位置关系热侵位于凤县草凉驿组含石墨矿建造的研究尚浅，岩体热侵位热力条件对该石墨矿在平面上与纵向上影响程度的大小尚待深入研究。本项目以岩浆热侵位在煤变质富集成石墨矿的作用为对象，分析接触带角岩岩石学与岩相学特征确定热接触变质作用程度，开展各岩浆岩体温压条件分析，查明石墨矿层固定碳含量、变质程度、石墨晶形大小及自形程度等在平面和纵向上的变化规律。该研究有助于确定各岩浆侵入体以何种热力作用对石墨变质成矿产生何种影响，为探讨煤变质型隐晶质石墨富集矿成矿中岩浆热作用研究提供依据。

秦岭造山带是我国石墨矿资源丰富的五大主要分布区之一，西秦岭凤县隐晶质石墨矿床是我国重要的石墨矿产地之一，目前仅开展过初步调查，研究程度很低，矿床特征和成因等研究尚浅。本研究以秦岭造山带已发现的数十处石墨矿床/点/远景区的基础资料为依据，揭示出秦岭造山带石墨矿床受秦岭东西向区域性构造的控制大致呈近东西向展布的三大矿带展布：Ⅰ华北板块南缘新太古界—元古界基底型晶质石墨矿床富集成矿带；Ⅱ西秦岭商丹缝合带山间盆地群石炭系隐晶质石墨矿床成矿富集带；Ⅲ东秦岭西部秦岭古微板块古生界晶质石墨矿成矿富集带。. 以西秦岭凤县地区基础地质资料、煤系石墨矿露头和煤矿资料为依据，通过野外地质调查、煤系石墨矿老硐编录及测试分析，运用地质综合分析方法，研究表明西秦岭隐晶质石墨矿床矿石为土状石墨，矿体呈似层状、透镜状。发育上下叠置的Ⅰ号和Ⅱ号两个主要矿层，Ⅰ号矿层矿体厚度0～1.8m，固定碳含量67.38%，视密度1.87；Ⅱ号矿层矿体厚度0～1.4m，有时可见矿体出现分叉现象，固定碳84.64%，视密度1.90。西秦岭凤县煤变质型石墨矿床是草凉驿组煤层在岩浆热侵位加热烘烤和构造运动双重作用下的产物，岩浆热侵位为煤层受热形成石墨提供了充足的热动力条件，构造运动控制石墨矿层的空间分布。煤层经热接触变质作用发生煤层→石墨化煤→煤化石墨→石墨的系列变化，岩浆热侵位对煤层受热变质形成石墨的程度具有控制性，距离越近变质程度越高，石墨的晶体自形程度越高，晶体也越大。该矿床成因类型属于热接触变成矿床。