湖南骑田岭花岗岩与锡成矿的关系  

RELATIONSHIP OF QITIANLING GRANITE TO Sn MINERALIZATION IN HUNAN PROVINCE

作　　者：汪雄武[1] 王晓地[2] 刘家齐[2] 常海亮[2] 

机构地区：[1]成都理工大学,四川成都610059 [2]宜昌地质矿产研究所,湖北宜昌443003

出　　处：《地质科技情报》2004年第2期1-12,共12页Geological Science and Technology Information

基　　金：中国地质调查局地质大调查项目"南岭地区锡矿成矿规律研究"( 2 0 0 3 10 2 0 0 0 72 ) ;南京大学内生金属矿床成矿机制研究国家重点实验室开放基金资助项目 ( 0 9-0 3 -0 9) ;国家自然科学基金资助项目 ( 4 0 0 73 0 2 5 ) ;宜昌地质矿产研究所科研发展基金资助

摘　　要：骑田岭花岗岩是燕山早期深源浅成的高钾钙碱性复式花岗岩岩体。最晚的细粒花岗岩 Rb-Sr等时线年龄为 ( 15 1± 5 )Ma,低温蚀变和矿化的时代约为 13 6Ma。锡矿化分布于外接触带矽卡岩和岩体内部隐爆角砾岩充填的断裂中 ,细粒花岗岩岩浆作用与蚀变和矿化作用在空间上紧密伴生 ,成因上密切相关。骑田岭花岗岩具有花岗岩岩浆作用与矿化作用密切相关的直接证据——岩浆 -热液过渡阶段典型的地质地球化学特征 :1结构构造变化大 ,出现许多不平衡的结构构造 ,如斑状结构、蠕虫结构、连续不等粒结构、文象结构、花斑结构、细晶结构、环带结构、伟晶岩壳和晶洞构造 ;2石英中含有熔体包裹体和熔体—流体包裹体 ,并与 CO2 流体包裹体和高盐度流体包裹体共存 ;3蚀变广泛 ,特别是存在高温自交代蚀变钠长石化和条纹长石的微斜长石化。这种高温蚀变的花岗岩具有四重效应 ,表现出惰性元素的活动性 ,w( K) /w ( Rb)、w ( Sr) /w( Eu)、w( Y) /w( Ho)和 w( Zr) /w( Hf)等值大大偏离球粒陨石中的值。这些特征反映了富挥发分的晚期花岗岩岩浆由于高位减压“过冷”及淬火从而导致挥发分出溶、顶盖沿构造薄弱带隐爆垮塌以及出溶流体与正在结晶的花岗岩间的流—岩相互作用。岩体冷却及其高热产率驱动长期的热液循环 ,形成广泛的?Qitianling granite is a post-collisional,deep-sourced and hypabyssal,early Yanshanian high-K calc-alkaline granite complex pluton.The latest fine-grained granite Rb-Sr isochronic age is (151±5) Ma.The age of alteration and mineralization is about 136 Ma. The alteration and mineralization is closely related to fine-grained granite in space and origin. The magmatic-hydrothermal transitional geologic-geochemical characteristics directly evidence the magmatism related to mineralization in Qitianling granite. ①Greatly variation of texture and structure, and many unequilibrium textures and structures, such as porphyritic, seriate, graphic, granophyric, myrmekitic,aplitic texture, pegmatoid and miarolitic structure;②Quartz in Qitianling granite containing melt inclusion and melt-fluid inclusion coexisted with CO_2 inclusion and high-salinity inclusion;③Qitianling granite, widely altered, especially, with the occurrence of high-temperature autometasomatism albitization and microclinization of perthite. The high-temperature altered granite shows REE tetrad effect , mobility of inert element and departure of w(K)/w(Rb),w(Sr)/w(Eu),w(Y)/w(Ho) and w(Zr)/w(Hf) from chronitic ratios. These characteristics indicate that the super-cooling and quenching of volatile-enriched late granitic magma at high level results in volatile exsolution ,cryptoexplosion and fluid/rock interaction of exsolved fluid with crystalling granite,cooling pluton and its high heat production drives the cycling of hydrothermal fluid,thus leading to widespread alteration and mineralization.

关 键 词：骑田岭 细粒花岗岩 锡矿化 流体包裹体 流体出溶 REE四重效应 流-岩相互作用 

分 类 号：P618.44[天文地球—矿床学]