投稿时间：2018-10-06
修订日期：2019-01-22
网络发布日期：2019-04-30
中文摘要:帕奔金矿床位于老挝西北部，为韧-脆性剪切带控制的方解石脉型金矿床。文章在系统的野外和镜下工作基础上，对比了方解石脉、红化蚀变岩、弱碳酸盐化蚀变灰岩、未蚀变灰岩以及方解石脉内雄黄和雌黄的稀土元素特征，结合灰岩和方解石的C、O同位素组成以及雄黄/雌黄的S同位素组成，探讨了成矿流体的性质、来源及矿床成因。载金方解石、蚀变岩和灰岩的稀土元素配分曲线总体相近，均表现出重稀土元素平坦以及Eu、Ce负异常特征；但方解石轻微亏损轻稀土元素，且具有较高的Tb/La和Sm/Nd比值。在Y/Ho-La/Ho和Tb/Ca-Tb/La图解中，灰岩→蚀变岩→方解石投点分别与重结晶趋势线和重新活化趋势线基本吻合，灰岩和方解石C、O同位素组成也表现出了基本一致的海相碳酸盐岩成因。因此，推断帕奔金矿的含金方解石脉及相关的热液蚀变是同一成矿期内同源流体体系的产物，相对形成顺序由早到晚为弱蚀变灰岩、红化蚀变岩、方解石大脉，且与赋矿灰岩存在继承性。结合矿床地质特征，认为帕奔金矿床成矿流体可能主要来源于区域动力变质作用过程中，下二叠统灰岩的脱水和脱碳酸盐化作用。雄黄和雌黄δ34S值接近0‰，且方解石脉稀土元素总量较低，表明可能混入了深部岩浆流体和大气降水。综合区域地质背景，认为帕奔金矿床成矿作用很可能发生于晚三叠世-侏罗纪的滇缅马泰地体与印支陆块碰撞导致的区域韧-脆性构造活动，并受到岩浆活动驱动。
Abstract:The Phapon gold deposit, located in northwestern Laos, is a calcite vein-type gold deposit controlled by NEtrending brittle-ductile shear zone. Based on detailed field and microscopic work, the authors compared the characteristics of rare earth elements (REE) between calcite vein, red altered rock, weak carbonation limestone, unaltered limestone, and realgar and orpiment from the calcite veins. Combined with the C,O isotope compositions of limestone and calcite and S isotope compositions of realgar and orpiment, the authors investigated the nature and source of the ore-forming fluids and ore genesis. The auriferous calcite, altered rocks and unaltered limestone show generally consistent HREE-flat patterns and negative anomalies of Eu and Ce, whereas the calcites show slight LREE-depleted patterns and relatively high Tb/La and Sm/Nd ratios. In the Y/Ho-La/Ho and Tb/Ca-Tb/La diagrams, the points of limestone, altered rock, and calcite are basically consistent with the trend line of recrystallization and remobilization, respectively. The C,O isotopic compositions of limestone and calcite also show similar geneses of marine carbonate. These data suggest that the auriferous calcite vein and the related hydrothermal alterations in Phapon are products of one fluid system in the same mineralization period. The relative formation sequence, from early to late, is in order of weak carbonation, red alteration, and calcite vein. The altered rocks and calcites have genetic relations with the wall rocks. Considering the ore deposit geology, the ore fluids might have been mainly derived from dehydration and decarbonation of the Lower Permian limestone during the dynamic metamorphism. The δ34S values of realgar and orpiment range around 0‰, and the calcite veins contain lower ΣREE, suggesting that the magmatic and meteoric waters might have been involved in ore fluids. Combined with the regional geological background, it is believed that the mineralization of the Phapon gold deposit probably occurred during the regional brittle-ductile tectonic activity caused by the collision between the Sibumasu Block and the Indochina Block in Late Triassic-Jurassic, and was driven by magmatic activities.
keywords:geochemistry rare earth elements C,O,S isotopes ore-forming fluids ore genesis Phapon gold deposit
文章编号：
中图分类号：P618.51
文献标志码：
基金项目:中国地质调查局地质调查项目（编号：121201010000150013）和自然科学基金青年基金项目（编号：41702069）的资助
引用文本：
郭林楠,侯林,刘书生,张启明,徐思维,施美凤,曾祥婷.2019.老挝帕奔金矿床成矿流体来源与矿床成因:稀土元素和C、O、S同位素证据[J].矿床地质,38(2):233~250GUO LinNan,HOU Lin,LIU ShuSheng,ZHANG QiMing,XU SiWei,SHI MeiFeng,ZENG XiangTing.2019.Ore-fluid sources and genesis of Phapon gold deposit, Laos:Constraint from REE and C, O, S isotopic characteristics[J].Mineral Deposits38(2):233~250
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