川西甲基卡花岗伟晶岩型锂矿床中熔体、流体包裹体固相物质研究

川西甲基卡二云母花岗岩和伟晶岩内发育大量原生熔体包裹体和富晶体流体包裹体。为了查明甲基卡成矿熔体、流体性质与演化特征,运用激光拉曼光谱和扫描电镜鉴定了甲基卡花岗伟晶岩型锂矿床中二云母花岗岩及伟晶岩脉不同结构带内的原生熔体、流体包裹体的固相物质。分析结果表明,甲基卡二云母花岗岩石英内熔体包裹体的矿物组合为磷灰石+白云母、白云母+钠长石、白云母+石墨;伟晶岩绿柱石内富晶体流体包裹体的矿物组合主要为刚玉、富铝铁硅酸盐+刚玉+锂辉石、锂辉石+石英+锂绿泥石;伟晶岩锂辉石内富晶体流体包裹体的矿物组合主要为磷灰石、锡石、磁铁矿、石英+钠长石+锂绿泥石、萤石、富钙镁硅酸盐+富铁铝硅酸盐+富铁硅酸盐+石英;花岗岩浆熔体与伟晶岩浆熔体(流体)具有一定的差异,成矿熔体、流体成分总体呈现出碱质元素(Na、Si、Al)、挥发分(F、P、CO_2)含量增高及基性元素(Fe、Mg、Ca)降低的特征;包裹体中子矿物与主矿物的化学成分具有一定的差别,揭示出伟晶岩熔体(流体)存在局部岩浆分异作用,具不混溶性及非均匀性。因此认为,伟晶岩熔浆(流体)为岩浆分异与岩浆不混溶共同作用的产物,挥发分含量的增高(F、P、CO_2)使伟晶岩能够与稀有金属组成各类络合物或化合物,这对于稀有金属成矿起到了至关重要的作用。

A study of solid minerals in melt inclusions and fluid inclusions from the Jiajika pegmatite-type lithium deposit

A large number of primary melt inclusions and crystal-rich fluid inclusions are developed in two-mica granites and pegmatites in Jiajika deposit, western Sichuan. In this study, the authors identified the mineral types of glass from melt inclusions of quartz in two-mica granite and daughter minerals from fluid inclusions of beryl and spodumene in pegmatites by means of laser Raman and scanning electron microscopy. According to the experimental results, Jiajika glass from melt inclusions of quartz in two-mica granite consists mainly of apatite+muscovite, muscovite+albite and muscovite+graphite. Crystals from fluid inclusions of beryl comprise mainly corundum, alumina-rich ferrosilicate+corundum+spodumene, spodumene+quartz+lithium chlorite. Crystals from fluid inclusions of spodumene are composed mainly of apatite, cassiterite, magnetite, quartz+albite+lithium chlorite, fluorite, calcium-magnesium-rich silicate+alumina-rich ferrosilicate+ferrosilicate+quartz. From early granite to pegmatite, the melts and fluids in the metallogenic melt and fluid in general showed high values of Na, Si, Al and F, and decrease of Fe, Mg and Ca. The ore-forming fluid of early granitic pegmatite magma to beryl and spodumene subminerals showed inheritance and some differences, with the existence of local pegmatite magma, magma immiscibility and non-uniformity. The increase of volatilization content of F, P and CO₂ in pegmatite played an important role in the mineralization of rare metals.