南岭锡钨多金属矿区碱长花岗岩的厘定及其意义  

Characteristics of alkali feldspar granite in tungsten(tin) deposits of Nanling region

作　　者：祝新友[1,2] 王京彬[1,2,3] 王艳丽[3] 程细音[4] 何鹏[5] 傅其斌[4] 李顺庭 

机构地区：[1]北京矿产地质研究院,北京100012 [2]中色地科矿产勘查股份有限公司,北京100012 [3]有色金属矿产地质调查中心,北京100012 [4]昆明理工大学,云南昆明650093 [5]中国地质大学,北京100083

出　　处：《中国地质》2012年第2期359-381,共23页Geology in China

基　　金：全国危机矿山接替资源找矿项目"湘南-粤北地区锡钨多金属矿床成矿规律总结研究"(20089927);国家科技支撑课题"湖南锡田地区深部成矿岩体空间结构与成矿预测"(2011BAB04B08);广西"地质工程中心重点实验室建设"项目(11-031-20-K2)联合资助

摘　　要：南岭地区锡钨多金属矿成矿作用主要与燕山早期花岗岩岩浆活动有关,这些花岗岩一直被认为是黑云母花岗岩、二长花岗岩、细粒二长花岗岩等,少量矿区岩体顶部出现钠长石花岗岩。通过对湖南瑶岗仙钨矿岩体的深入解剖,以及对杮竹园、黄沙坪、锡田、邓阜仙、栗木、梅子窝等矿区花岗岩全面的岩矿鉴定和电子探针分析,确定钨矿区致矿花岗岩的长石主要为碱性长石,其中绝大部分样品中钠长石An<5,因此确定这些花岗岩均属于碱长花岗岩。与成矿有关的由浆液过渡态流体形成的云英岩包体中的钠长石更加富Na,An<3。碱长花岗岩的成分以及钠长石成分在岩体顶部约1 000 m深度范围内无明显垂向变化。致矿花岗岩体中部分早期花岗岩包体、晚期花岗斑岩,部分花岗岩基以及印支期花岗岩、加里东期花岗闪长岩等,钠(斜)长石An值明显高,很多属更长石、中长石甚至基性长石。这种包含有两种碱性长石的碱长花岗岩由富挥发分的岩浆形成,在岩体顶部附近广泛发生液态不混溶作用,是导致锡钨多金属矿富集成矿的主要分异方式。钨锡矿区碱长花岗岩钠长石An值明显低于区域大花岗岩基或不致矿花岗岩,可作为花岗岩的钨锡成矿评价标志之一。The early Yanshanian granites related to tungsten and tin deposits in Nanling region have been considered to be biotite granite,monzogranite,albite granite etc.However,microscope and electron microprobe analyzes of the granite related to tungsten mineralization in Yaogangxian,Shizhuyuan,Xitian,Dengfuxian,Limu and Meiziwo show that all the feldspars of the granite consist of K-feldspar and albite（An5）,which suggests that the name should be alkali feldspar granite.The albite of greisen inclusions in the alkali feldspar shows the character An 3.There is no obvious vertical regular variation or zoning of the compositions of the albite and granite within the depth range of 1000m.On the contrary,the plagioclases of the granite inclusions（xenoliths）,some granite porphyry dykes,giant batholiths,and Triassic and Paleozoic monzogranite or granodiorite have a wide range of An value of 0～93,belonging to oligoclase,andesine or even basic plagioclase.The alkali-feldspar granite that contains two kinds of alkali feldspar was usually formed from the rich-volatile（Li-F） magma,with the extensive development of liquid immiscibility at the top of the granite,which caused the enrichment and mineralization of W,Sn,Bi,Mo in the hydrothermal-magma.The An value of the albite in alkali-feldspar granite could be used as an indicator for evaluating granite in search for W-Sn mineralization,because the value is obvious lower than that of barren granite.

关 键 词：南岭 锡钨矿 花岗岩 碱长花岗岩 

分 类 号：P588.121[天文地球—岩石学]