南京大学学报（自然科学版）2018，Vol.54Issue(2)：351-365,15.DOI:10.13232/j.cnki.jnju.2018.02.010
安徽省池州市马头钼矿床成矿流体特征和矿床成因
The characteristics of ore-forming fluid and genesis of the Matou Mo deposit,Chizhou,Anhui province
摘要
Abstract
The Matou Mo deposit is located in the Anqing-Guichi ore cluster area of the Middle-Lower Yangtze Valley metallogenic belt.The mineralization types are divided into shallow quartz vein type and deep veinlet disseminated type.The alteration types in shallow parts mainly include phyllic alteration,propylitization,with minor potassic alteration and carbonatation.The deep parts are mainly composed of intense potassic alteration and silicification.The ore minerals in the Matou Mo deposit are mainly molybdenite and chalcopyrite,with a small amount of scheelite,magnetite,pyrrhotite,sphalerite,and galena.Gangue minerals are mainly K-feldspar,quartz,sericite,and calcite. Three main types of inclusions can be identified in the hydrothermal veins:two-phase aqueous inclusions(type Ⅰ), two-phase CO2rich inclusions(Type Ⅱ)and three-phase CO2-bearing inclusions(Type Ⅲ).The dominant fluid inclusions in the shallow part are type Ⅰ,while deep quartz veins contain type Ⅰ,Ⅱ and Ⅲ inclusions.Type Ⅰinclusions in the shallow quartz vein exhibit low to moderate salinities ranging from 3.8 wt.% to 7.6 wt.% NaCl equivalent,and homogenization temperatures from 224 ℃ to 283 ℃.Type Ⅰ and coexisting type Ⅱ inclusions in deep veinlet disseminated mineralization show higher homogenization temperatures ranging from 263 ℃ to 316 ℃and from 311 ℃ to 331 ℃,with salinities of 5.1 wt.% to 10.3 wt.% and 0.6 wt.% to 2.0 wt.% NaCl equivalent, respectively.Type Ⅲ inclusions in deep veinlet disseminated mineralization yield homogenization temperatures of 335 ℃ to 362 ℃,with salinities 2.7 wt.% to 6.7 wt.% NaCl equivalent.The ore-forming fluid of shallow quartz vein orebody is NaCl-H2O system,while the ore-forming fluid in deep mineralization belongs to NaCl-H2O-CO2system. A large number of type Ⅰ,type Ⅱ and type Ⅲ inclusions coexist in the same quartz from the deep mineralization. Their similar homogenization temperature indicated that the fluid immiscibility may occurred in the deep part.The dramatic changes in chemical properties of fluids resulted from immiscibility lead to the decomposition of complex and molybdenite precipitation.The pressures of mineralization were 65 MPa~90 MPa,obtained from the microthermo-metric data of typeⅠandⅡfluid inclusions from the deep part,which is corresponding to the depth of 2.4 km to 3.3 km. Alteration mineralogy research shows that the Matou Mo deposit exerts typical porphyry deposit alteration characteristics, with potassic alteration,silicified zone and sericitic zone.The identification of fluid immiscibility during mineralization pro-vides new evidence for ore genesis and precipitation mechanism of Matou deposit.关键词
马头钼矿床/斑岩型钼矿床/流体包裹体/流体不混溶/成矿机制Key words
Matou Mo deposit/porphyry molybdenum deposit/fluid inclusion/fluid immiscibility/metallogenic mechanism分类
天文与地球科学引用本文复制引用
顾建峰,倪培,李文生,王国光,潘君屹,刘政..安徽省池州市马头钼矿床成矿流体特征和矿床成因[J].南京大学学报（自然科学版）,2018,54(2):351-365,15.基金项目
国家重点研发计划(2016YFC0600206) （2016YFC0600206）
