摘要
内蒙古阿鲁科尔沁旗敖仑花铜钼矿床位于华北克拉通北缘西拉沐伦钼矿带,是典型的斑岩型铜钼矿床。对6件辉钼矿样品进行了铼-锇同位素分析,获得的等时线年龄为129.4±3.4Ma,表明成矿作用发生在早白垩世。根据成矿中的流体过程可分为三个阶段:早阶段以发育石英-黄铁矿脉为标志,中阶段是主要的成矿阶段,以发育石英-多金属硫化物脉为标志。这两个阶段的流体包裹体均一温度分别集中在330～430℃和250～350℃,盐度分别为1.06～>58.41 wt%NaCl eqv和0.88wt%～48.21 wt%NaCl eqv,两个阶段均为多种类型包裹体密切共生,均一温度接近而盐度相差悬殊,且两个阶段的包裹体均一方式多样,这些特征指示了这两个阶段的流体皆发生过沸腾作用。晚阶段以发育石英-碳酸盐细脉为标志,只有少量黄铁矿沉淀,该阶段仅发育富液相包裹体,均一温度<270℃.盐度低,范围为0.71 wt%～8.41 wt%NaCl eqv。激光拉曼光谱分析表明,早、中阶段包裹体的气相成分为H_2O和CO_2,而晚阶段气相中只含H_2O。总体来看,初始流体可能直接来自岩浆房中岩浆流体的上涌,具有高温、高盐度、高氧逸度和富CO_2等特点,在430℃和350℃时流体发生了两次沸腾作用,致使成矿物质快速沉淀,流体氧逸度降低,CO_2逃逸,到了晚期,流体包裹体中基本不再含有子晶和CO_2。
The Aolunhua Cu-Mo deposit in Arhorqin Area, Inner Mongolia, located in the Xilamulun Mo-metallogenic belt in the northern margin of North China Craton, is a typical porphyry Cu-Mo deposit. Re-Os isotope dating for six molybdenite samples gives an isochrot age of 129.4 +/- 3.4 Ma, that indicates the deposit formed in the early Cretaceous. The hydrothermal ore-forming process could be diviled into three stages: the early stage is characterized by mineral assemblages of quartz-pyrite veins while the most important stage, the middle stage, is characterized by mineral assemblages of quartz-polymetallic sulfides veins. Fluid inclusions in minerals formed in early and middle stages yield homogeneous temperatures of 330 similar to 430 degrees C and 250 similar to 350 degrees C, respectively, with salinities of 1.06 wt% - > 58.41 wt% NaCl eqv and 0.88 wt% similar to 48.21 wt% NaCl eqv. Some fluid inclusions with contrasting salinities are homogenoized to divergent phases at similar temperatures, and daughter mineral-bearing inclusions coexist with the vapor-and liquid-rich fluid irclusions, which strongly suggests that fluid-boiling have occurred in the early and middle stage. The late stage is characterized by quartz-carbonate-pyrite veinlets. In late-stage minerals, only liquid-rich fluid inclusions can be observed with homogeneous temperatures mainly below 270 degrees C and salinities between 0.71 wt% similar to 8.41 wt% NaCl eqv. Laser Raman spectroscopy indicate that the principal gas components of the fluid inclusions trapped in early and middle stages are H(2)O and CO(2), whereas in those formed late stage are only H(2)O. Hence it is believed that the original fluid, which is characterized by high temperature, high salinity, high oxygenfugacity, and CO(2)-rich, have be sourced from magma or magma chamber. The fluid boiled at least twice when the primary magmatic fluid cooled down to 430 degrees C and 350 degrees C, and resulted in rapid ore-metal precipitation, oxygen-fugacity decrease and CO(2)-release. The late-stage fluid inclusions are lack of daughter mineral and poor in CO(2).
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第10期2601-2614,共14页
Acta Petrologica Sinica
基金
国家973项目(2006CB403501)
中国地质调查局项目(1212010813045)
北京大学校长基金资助
