滇西北衙金矿蚀变斑岩中的流体包裹体研究

STUDY OF THE FLUID INCLUSIONS IN ALTERED PORPHYRES IN THE BEIYA GOLD DEPOSIT, WSTERN YUNNAN

位于爆破角砾岩筒边缘的接触带矿化斑岩中早期流体包裹体以CO2-H2O包裹体为主,而岩体内无或弱矿化斑岩中对应的流体包裹体以高盐度H2O-NaCl包裹体为主,反映来源于富碱岩浆的流体在它的早期阶段即分异出富碳相和盐水相,富碳相位于流体的外层,成矿元素主要在富碳相中迁移。因此,外接触带及其附近的围岩是成矿的有利部位。岩体内部蚀变岩石样品石英斑晶中的次生流体包裹体可大致划分为4个阶段。根据显微测温结果、形成温度和压力的估算及均一温度-盐度关系,结合H2O-NaCl体系P-T投影图,包裹体的4个阶段反映了环境条件的变化过程及相关的地质过程。

The early stage fluid inclusions in the mineralized porphyry in contact zone (also on the edge of the breccia pipe) are dominated by CO_2-H_2O type,and the inclusions in none- or weakly mineralized porphyry from the inner rock body are by hypersaline H_2O-NaCl type.It illustrated that the fluid derived from alkali-rich magma had fractionated into CO_2-rich and hypersaline phases in its early stage,and the ore-forming metals were initially transplanted in the CO_2-rich phase,which occurred at the exterior of the fluid.Therefore,a conclusion might be drawn that the exo-contact zone and nearby was the favorable position for ore formation.The secondary fluid inclusions in quartz phanerocryst in altered rock samples from the inner rock body can approximately be divided into four generations.According to the result of microthermometry,estimation of the formation temperature and pressure,homogenization temperature-salty relation,and P-T plot of H_2O-NaCl system,the four generations of fluid inclusions reflected the change processes of environmental conditions (relative to the trapped fluids) and corresponding geological processes.