青海省卡尔却卡铜多金属矿床流体包裹体特征及成矿流体

摘要

There are two mineralization types in Kaerqueka copper polymetallic deposit in Qimantage area, Qinghai Province, which are skarn-type mineralization and porphyry-type mineralization. Both of the two mineralization types are closely related to Indosinian granodiorite. Fluid inclusions (FI) host in porphyry-type mineralization granodiorite and skarn-type ore, and the fluid inclusions in skarn-type ore typically are aqueous FI (type I ) while those in porphyry-type mineralization granodiorite are usually aqueous FI (type I ) or daughter mineral-bearing FI (type II) as well. The bomogenization temperatures of the fluid inclusions in the skarn-type ore and the porphyry-type mineralized granodiorite vary from 137 'C to 322 ℃ and 274℃ to 495 ℃, respectively. The salinities of skarn-type ore range from 0.7% to 12.7% (mass fraction, NaClequiv); and those in porphyry-type mineralized granodiorite range from 5.9% to 59.1%. The study demonstrates that the ore-forming fluids originate from magma which is high-temperature (up to 500 ℃), hypersaline (up to 60%), rich in Na* and metallogenic material, with the characteristics of ultrahigh pressure. Fluid-boiling occurs when the ore-forming temperatures are between 290 ℃and 320℃because of breaking of wall rocks. Then the composition and physicochemical properties of ore-forming fluids are changed by mixed extraneous fluids, leading to the precipitation and enrichment of metallogenic material.%卡尔却卡多金属矿床位于祁漫塔格成矿带,矿区主要有斑岩型和矽卡岩型两种矿化类型,均与印支期花岗闪长岩关系密切.流体包裹体研究表明,矽卡岩矿石中可见水溶液包裹体(Ⅰ型)；斑岩型矿化岩体中发育有水溶液包裹体( Ⅰ型)和含子矿物的包裹体(Ⅱ型).斑岩型矿化岩体中的流体包裹体气液均温度在274～495℃,盐度介于5.9％～59.1％(质量分数,NaCl equiv,下同)之间:矽卡岩矿石样品的气液均(一)温度集中在137～322℃,盐度介于0.7％～12.7％之间.研究显示矿区成矿流体来源于富Na+及成矿物质的高温(达500℃)、高盐度(达60％)的岩浆流体,具有超高压特征.流体演化至290～320℃时由于围岩碎裂减压而发生沸腾现象,并和外来流体混合,改变流体的成分和物理化学性质,有利于成矿物质沉淀富集.