黑龙江省大兴安岭地区大黑山钼矿床流体包裹体特征及成矿机制探讨  

Characteristics of Ore-Forming Fluids and the Metallogenic Mechanism of the Daheishan Mo Deposit in the Great Xing′an Range,Heilongjiang Province

作　　者：沈军[1,2] 何谋惷[1,3] 胡新露[1] 熊索菲[1] 姚书振[1] 孟宇[1] 王翔[1] 

机构地区：[1]中国地质大学资源学院,武汉430074 [2]西安地质矿产勘查开发院,西安710100 [3]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《地质科技情报》2015年第3期150-159,共10页Geological Science and Technology Information

基　　金：黑龙江省国土资源补偿费专题研究项目"大兴安岭北段典型矿床剖析及成矿模式"(SDK2010-25)

摘　　要：大黑山钼矿床位于黑龙江省大兴安岭北段,是一个与花岗闪长岩有关的钼矿床。根据矿物组合和脉体穿插关系,将成矿过程划分为4个阶段:石英-钾长石阶段(Ⅰ)、石英-辉钼矿阶段(Ⅱ)、石英-多金属硫化物阶段(Ⅲ)和石英-方解石阶段(Ⅳ)。流体包裹体岩相学、显微测温以及显微激光拉曼探针研究显示,该矿床成矿流体为H2O-NaCl-CO2体系,第Ⅰ、Ⅱ、Ⅲ阶段均可见水溶液包裹体(L+V型)、含子晶多相包裹体(S型)和含CO2包裹体(C型);而第Ⅳ阶段仅发育水溶液包裹体(L+V型)和纯液相包裹体(L型)。成矿流体演化从早到晚,流体包裹体的均一温度峰值分别为:330~430,320~360,280~340,180~240℃,呈现逐步降低的趋势;对应的盐度w(NaCleq)分别为5.86%~54.10%,4.07%~51.70%,3.23%~46.20%和0.70%~9.08%,也逐步降低。主成矿阶段的流体最低捕获压力为17~58 MPa,对应的成矿深度约为1.7~5.8km。成矿流体的δ18Ow值为-5.8‰~4.2‰,δDW值为-139.8‰^-127.2‰,成矿流体可能为岩浆水与雨水的混合流体。主成矿阶段发生了流体沸腾作用,使CO2大量逸出,导致流体还原性增强,造成大量MoS2的沉淀而形成钼矿床。The Daheishan Mo deposit located in the northern Great Xing＇an range is a porphyry metallogen- ic system, and granodiorite intrusions contributed to the mineralization. Based on mineral assemblage and vein crosscutting relationships, the ore-forming process could be divided into four mineralization-alteration stages, I. Quartz-potash feldspar stage; Ⅱ. Quartz-molybdenite stage; Ⅲ. Quartz-polymetallic sulfide stage; IV. Quartz-calcite stage. Ore minerals were mainly precipitated in the middle stage. Researches based on petrography, fluid inclusion tests and Laser Raman spectroscopic analysis suggest that ore-form- ing fluids are mainly composed of CO2-H2 O-NaC1. There is boiling process in the fluid system. The hydro- thermal quartz formed in the I, II, and III stages contain three types of fluid inclusions （FIs）, i. e. NaCI- H2O （l-V-type）, CO2-H2O （C-type） and daughter mineral-bearing （S-type） fluid inclusions; while the Ⅳ-stage minerals contain only NaC1-HzO fluid inclusions（L-b-V-type） and pure H2O （L-type）. The hom- ogenization temperatures of ore-forming fluids from stage I to stage 1V are 330--430℃, 320--360℃, 280 --340℃ and 180--240℃ respectively with the corresponding average salinities being 5.86%--54.10%Na- Cleqv, 4.07%--51. 70% NaCleqv, 3. 23%--46. 20% NaCleqv and 0. 70%--9. 08% NaCleqv. The esti- mated pressures range from 17--58 MPa in the Ⅱ stage, corresponding to depth of 1.7--5.8 km. The 818Ow values of the ore-forming fluid vary from --5.8‰--4.2‰, and δDw values vary from --139.8‰-- --127.2‰, indicating that the ore-forming fluid was derived mainly from magmatic fluid mixed with mete- oric water. The strong boiling action of the ore-forming fluid seems to have been the dominant factor for molybdenite deposition.

关 键 词：流体包裹体 大黑山钼矿床 成矿机制 大兴安岭 

分 类 号：P575.9[天文地球—矿物学]