华南富锂氟含稀有金属花岗岩的成因分析  

GENETIC INTERPRETATION OF Li-F-RICH RARE METAL-BEARING GRANITES IN SOUTH CHINA

作　　者：李福春[1] 朱金初[1] 金章东[1] 

机构地区：[1]南京大学地球科学系,成矿作用国家重点实验室,南京210093

出　　处：《矿床地质》2000年第4期376-395,共20页Mineral Deposits

基　　金：国家自然科学基金!(编号 :495 73185和 498730 17);南京大学成矿作用国家重点实验室开放课题资助

摘　　要：雪球结构的产出特征、钠长石电子探针分析及其它间接证据都说明 ,雪球结构是在岩浆结晶过程中形成的。雪球结构形成与否主要与岩浆熔体中 Na2 O/ K2 O比值和 F、H2 O含量有关。较大的 Na2 O/ K2 O比值 ( >1)使钠长石首先从熔体中晶出 ;较高的 F含量使岩浆固相线温度大大降低 ,有利于岩浆分异演化并形成接近端员组分的钠长石和钾长石 ;较高的 H2 O含量有利于石英以较快的速度生长并逐渐包裹钠长石形成雪球结构。自形的 α-石英斑晶、接近各自端员组分的钾长石和钠长石等说明该类花岗岩形成温度较低。众多的地质、地球化学依据都证明了 ,华南富锂氟含稀有金属花岗岩是从过铝富氟富钠的残余熔体中直接结晶而成的。The mode of occurrence of snowball texture,the electron microprobe analysis of albite from quartz and K feldspar phenocrysts as well as other evidence suggest that the snowball texture might have been generated during the crystallization of magmatic melt.The formation of snowball texture was closely related to the Na 2O/K 2O ratio as well as the fluorine and H 2O content of the granitic melt.The relative high Na 2/K 2O ratio(>1) probably caused the first crystallization of albite.The increase of fluorine content might have resulted in the decrease of solidus temperature and benefited the evolution of magma and the formation of K feldspar and albite approximately with end member composition.Comparatively high content of H 2O was favorable for the faster growth of quartz than albite.Finally,the quartz phenocrysts which contained albite laths might form snowball texture.Snowball texture,together with low melting temperature of the granites, euhedral α type quartz phenocrysts as well as K feldspar and albite approximately with end member composition,indicates that L F rich rare metal bearing granites in South China were directly crystallized from the peraluminous F Na rich residual granitic melt.

关 键 词：雪球结构 花岗岩 岩浆结晶 成因 稀有金属矿床 

分 类 号：P618.701[天文地球—矿床学] P588.121[天文地球—地质学]