(1. 北京科技大學(xué) 土木與資源工程學(xué)院，北京 100083；
2. 中國地質(zhì)科學(xué)院 南京地質(zhì)礦產(chǎn)研究所，南京 210016)
摘 要: 沙坪溝鉬礦床位于安徽省金寨縣，大地構(gòu)造位置屬于大別造山帶東段，是世界第二大斑巖型鉬礦床。沙坪溝鉬礦外圍發(fā)現(xiàn)有銀山、蓋井等多處鉛鋅礦床，但其與斑巖型鉬礦的成因聯(lián)系不明。以沙坪溝斑巖型鉬礦及礦區(qū)北部的銀山鉛鋅礦為研究對象，在野外地質(zhì)調(diào)研的基礎(chǔ)上，通過流體包裹體巖相學(xué)、顯微測溫學(xué)、顯微激光拉曼和穩(wěn)定同位素等研究，系統(tǒng)闡明斑巖型鉬礦與外圍鉛鋅礦的成礦流體來源、成礦流體特征及演化、成礦物質(zhì)來源，初步建立斑巖型鉬礦與周邊鉛鋅礦的成因聯(lián)系。流體包裹體巖相學(xué)結(jié)果表明，沙坪溝斑巖型鉬礦主要發(fā)育3類流體包裹體，包括AV類(氣液兩相包裹體)、AC類(富CO2三相包裹體)、ADV類(含子晶多相包裹體)。成礦早階段三種類型均有發(fā)育，均一溫度范圍為325~420 ℃，AV和AC類鹽度介于0.8%~15.4% NaCleqv(質(zhì)量分?jǐn)?shù))之間，ADV類鹽度介于33%~46% NaCleqv之間。成礦中階段發(fā)育AV類、AC類和ADV類，均一溫度范圍為226~367 ℃，AV類與AC類鹽度介于0.4%~13.2% NaCleqv之間，ADV類鹽度介于33.3%~39.6% NaCleqv之間。成礦晚階段主要發(fā)育AV類包裹體，均一溫度范圍為185~300 ℃，鹽度介于0.7%~8.4% NaCleqv之間。銀山鉛鋅礦主成礦階段石英中只發(fā)育AV類包裹體，其均一溫度范圍為175~315 ℃，鹽度介于0.6%~4.9% NaCleqv之間。流體包裹體中水的H-O同位素結(jié)果表明，沙坪溝鉬礦成礦早階段流體主要來自巖漿水，晚期鉛鋅礦化階段，成礦熱液為巖漿水與大氣水的混合，與銀山鉛鋅礦主成礦階段石英中流體包裹體中水的H-O同位素相似。S同位素數(shù)據(jù)表明兩礦床主成礦階段硫化物的硫元素主要來自深源巖漿，Pb同位素數(shù)據(jù)顯示礦石鉛具有殼幔混源的特征。S、Pb、H、O同位素及流體包裹體特征均指示，研究區(qū)鉬礦及鉛鋅礦床具有一致的物質(zhì)來源，成礦流體具有由高溫-高鹽度巖漿熱液流體向中低溫-低鹽度流體和從富CO2至貧CO2的演化趨勢，沙坪溝周邊鉛鋅礦為斑巖成礦系統(tǒng)的組成部分。
關(guān)鍵字: 流體包裹體；H-O-S-Pb同位素；鉬鉛鋅成礦系統(tǒng)；沙坪溝；大別造山帶
（1. School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China;
2. Nanjing Institute of Geology and Mineral Resource, Chinese Academy of Geological Sciences, Nanjing 210016, China）
Abstract:The Shapinggou molybdenum deposit, located in Jinzhai County, Anhui Province, China, is the second largest porphyry molybdenum deposit in the world. Several Pb-Zn deposits have been discovered in the periphery of Shapinggou Mo deposit, such as Yinshan and Gaijing deposits, but their genetic relationship with porphyry Mo deposit is misunderstood. In this work, we base on data from field work investigation combined with laboratory analyses data such as fluid inclusions petrography, microthermometry, laser Raman microprobe and stable isotopes to characterize the source and evolution of Shapingguo porphyry Mo deposit and surrounding Yinshan Pb-Zn deposits in order to establish a genetic relationship between both deposits. Petrography fluid inclusion of lithofacies from Shapinggou porphyry Mo deposit reveals 3 types of fluid inclusions including gas-liquid phase inclusions (AV), CO2-rich three phase inclusions (AC),and crystalline-bearing inclusions (ADV),developed in three stages of mineralization. In the early stage of mineralization, the homogeneous temperature of fluid inclusions ranges from 325 to 420 ℃ with relatively low salinity of AV and AC types ranging from 0.8% to 15.4% NaCleqv and moderately high salinity of ADV type ranging from 33% to 46% NaCleqv. In the middle stage of mineralization, AV, AC and ADV have uniform temperature at around 226-367 ℃ with low salinity of AV and AC types ranging from 0.4% to 13.2% NaCleqv and relatively high salinity of ADV type ranging from 33.3% to 39.6% NaCleqv. The late stage of mineralization develops AV type of fluid inclusion with homogeneous temperature ranging from 185 to 300 ℃, and the salinity ranges from 0.7% to 8.4% NaCleqv. However, in the Yinshan Pb-Zn deposits, only one stage of mineralization has been developed and displaying AV fluid inclusions. The homogeneous temperature of fluid ranges from 175 to 315 ℃ with salinity of 0.6%-4.9% NaCleqv, which correspond to the late stage of Shapinggou porphyry Mo deposit. It clearly appear that the homogeneous temperature and salinity decrease from the earlier to the late stage of mineralization. H-O isotope results of water in fluid inclusions show that the early stage fluid of Shapinggou Mo deposit is principally originated from magmatic source, while in the late stage of Pb-Zn mineralization, the ore-forming hydrothermal fluid is a mixture of magmatic water and meteoric water, similar to H-O isotopes of water in quartz fluid inclusions in the main metallogenic stage of Yinshan Pb-Zn deposit. It appears that the early hydrothermal fluid was originated from magmatic source with a small amount of meteoric water, which has, therefore, gradually increased during the middle and late stage of mineralization. S-isotope data indicated that sulfur of the two deposits derives from deep magmatic source and Pb-isotope, however, has characteristic of crust-mantle mixed source. The characteristics of S, Pb, H, O isotopes and fluid inclusions indicate that, the Mo deposits and Pb-Zn deposits in the study area have the same material sources. The ore-forming fluid has an evolution trend from high-temperature-high-salinity magmatic hydrothermal fluid to low-temperature-low-salinity magmatic-meteoric mixed fluid and from CO2-rich to CO2-poor. The Yinshan Pb-Zn deposits around Shapinggou are part of the porphyry metallogenic system.
Key words: fluid inclusion; H-O-S-Pb isotope; molybdenum lead zinc metallogenic system; Shapinggou molybdenum deposit; Dabie orogenic belt
