Fluid inclusion studies of the Changpai area in Zhuguang Mountain, northern Guangdong Province
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摘要:
长排矿区位于诸广山岩体南部，是近年来铀矿找矿重点突破的新成果。流体包裹体岩相学特征显示，该矿区成矿期主要发育2种类型包裹体：含CO2三相包裹体（Ⅰ型）和气液两相包裹体（Ⅱ型）。其中，Ⅱ型包裹体又可分为富液相包裹体（Ⅱ-1型）和富气相包裹体（Ⅱ-2型）。根据流体包裹体岩相学特征和显微测温结果，可将成矿期流体包裹体划分为2组：第1组均一温度主要集中在291~388℃之间，盐度范围为3.23%~7.87% NaCleqv，为Ⅰ型含CO2三相和Ⅱ-2型富气相包裹体；第2组均一温度范围主要集中于140~260℃之间，盐度为1.74%~10.24% NaCleqv，属Ⅱ-1型富液相包裹体，分别代表成矿期早阶段和晚阶段流体性质。晚阶段流体包裹体相对于早阶段具有较低的均一温度和较大的盐度变化范围，说明成矿期晚阶段很可能发生了不同来源流体的混合作用。激光拉曼分析显示，成矿期流体包裹体气相成分主要为CO2、CH4、H2等。硫同位素分析结果显示，成矿期黄铁矿δ34S值在-10.2‰~-3.2‰之间，与华南地区其他铀矿床成矿期硫化物的δ34S值相近。结合区域地质特征可知，长排矿区成矿物质主要来源于古老含铀地层部分熔融形成的富铀花岗岩；温度降低和流体混合作用可能是导致铀络合物水解沉淀的重要因素。
Abstract:The Changpai area, located within the southern part of the Zhuguang Mountain, is an important prospecting area in South China. In this paper, the authors present new fluid inclusion and stable isotopic data of the study area to discuss the nature of the oreforming fluids and uranium mineralization. Two types of fluid inclusions of the mineralization stage were recognized by petrographic observations:three-phase CO2-rich (type Ⅰ) and two-phase vapor-liquid (type Ⅱ) fluid inclusions. Type Ⅱ fluid inclusions include two sub-types, i.e. liquid-rich (type Ⅱ-1) and vapor-rich (type Ⅱ-2). Based on petrographic features and the results of microthermometry, the fluid inclusions from the mineralization stage can be classified into two suites:(1) type Ⅰ and Ⅱ-2 fluid inclusions with homogenization temperatures of 291~388℃ and salinities of 3.23%~7.87% NaCl equivalent; (2) type Ⅱ-1 fluid inclusions with homogenization temperatures of 140~260℃ and salinities of 1.74%~10.24% NaCl equivalent. The fluid inclusions of suite 1 and 2 represent the early and late sub-stages of fluids during the mineralization stage, respectively. Raman analyses of fluid inclusions show that the vapor ingredient of the ore-forming fluid inclusions contains CO 2, CH4 and H2. S isotopic compositions (δ34S=-10.2‰~-3.2‰) of the pyrites associated uranium mineralization are similar to those from other U deposits in South China. The fluid inclusions of suite 2 are characterized by wide range of salinities and have lower homogenization temperatures than those of suite 1, indicating that fluid mixing process took place. Combined with geological features, the authors hold that U was derived from the granite which was associated with partial melting of uranium-rich ancient crust, and that temperatures declining and fluid mixing played a key role in U precipitation.
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Key words:
- fluid inclusion /
- Raman spectroscopy /
- S isotope /
- Changpai area /
- Zhuguang Mountain
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表 1 长排矿区流体包裹体显微测温结果
Table 1. The temperature determination of fluid inclusions at Changpai
成矿期次 包裹体类型 测试
数目CO2包裹体 均一温度/℃ 冰点/℃ 盐度/%NaCleqv 初溶温度/℃ 笼形物消失温度/℃ 部分均一温度/℃ 范围 平均 范围 平均 成矿期 I 17 -61.9~-58.9 5.5~8.2 19.7~29.4 291~388 338 - 3.52~7.87 5.40 Ⅱ-1 149 - - - 113~356 199 -6.8~-1 1.74~10.24 5.52 Ⅱ-2 12 - - - 222~378 314 -4.4~-1.9 3.23~7.02 4.63 成矿后期 Ⅱ-1 56 - - - 80~179 134 -3.9~-0.2 0.35~6.3 3.8 
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表 2 长排矿区黄铁矿硫同位素组成
Table 2. S isotopic compositions of the pyrite from the Changpai area
序号 样号 矿物 δ34s/‰ 岩石名称 1 GZN201-3 黄铁矿 -9.1 产于灰色微晶石英脉屮 2 GZN201-1 黄铁矿 -3.2 产于灰色微晶石英脉屮 3 GZN201-11 黄铁矿 -9.7 产于猪肝色赤铁矿化蚀变花岗岩屮 4 ZK11-2-2 黄铁矿 -10.7 产于肉红色微晶硅质脉屮
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