| 西藏昌都哇了格铅-银矿床成因:矿床地质、流体包裹体和同位素地球化学制约 |
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| 引用本文： | 刘兴平,周联生,尤静,李随云,刘锐.西藏昌都哇了格铅-银矿床成因:矿床地质、流体包裹体和同位素地球化学制约[J].矿物学报,2020(2):223-236. |
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| 作者姓名： | 刘兴平 周联生 尤静 李随云 刘锐 |
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| 作者单位： | 湖北省地质局第六地质大队;中国地质大学（武汉） |
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| 基金项目： | 国家自然科学基金项目(批准号:41002025);中央高校基本科研业务费专项资金(批准号:CUGL140406)。 |
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| 摘 要： | 哇了格铅银矿床位于西藏昌都市卡若区北东(5°)约150km处,矿区出露地层主要为上三叠统,含矿层位为甲丕拉组灰岩段第2亚段(T3j^2-2)。矿区无岩浆岩出露,构造以断裂为主,构造行迹主要为北西向。共圈定7个工业矿体,Pb资源量(50.4×10^7 kg)以及伴生Ag资源量(580×10^3 kg)均达到大型矿床规模。本文在详细的矿床地质研究基础上,通过流体包裹体和C-O-S-Pb同位素地球化学研究,探讨该矿床的成矿流体性质和成矿物质来源,以期为理解该矿床成因提供更加丰富的地球化学信息。研究结果表明:1)该矿床明显受地层和构造控制;2)成矿温度主要集中在130~180℃,盐度集中于6%~17%,具低温、中低盐度特征;3)赋矿沉积岩和热液碳酸盐矿物的C-O同位素组成(分别为-2.7‰~4.3‰和2.6‰~4.0‰)与正常海相碳酸盐岩相当,暗示其来源于赋矿围岩,方铅矿的S同位素组成介于-3.8‰~1.6‰,与幔源硫(-3‰~3‰)颇为相似,但考虑到矿区无岩浆活动,而沉积地层的δ34S值为6.2‰~20.5‰,表明成矿流体中的硫很可能地层中硫酸盐热化学还原作用的产物,硫化物Pb同位素具有壳源特征,绝大多数矿石样品与赋矿围岩相似的Pb同位素特征指示成矿金属很可能主要来源于赋矿围岩。综上,本文认为哇了格铅银矿床成矿物质主要来源赋矿地层本身,成因类型上应属于低温热液矿床。
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| 关 键 词： | 流体包裹体 C-O-S-Pb同位素 成矿物质来源 哇了格铅-银矿床 西藏 |
Genesis of the Waliaoge Pb-Ag deposit in Qamdo City,Tibet,China:constraints from ore deposit geology,fluid inclusions,and isotope geochemistry |
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| LIU Xing-ping,ZHOU Lian-sheng,YOU Jing,LI Sui-yun,LIU Rui.Genesis of the Waliaoge Pb-Ag deposit in Qamdo City,Tibet,China:constraints from ore deposit geology,fluid inclusions,and isotope geochemistry[J].Acta Mineralogica Sinica,2020(2):223-236. |
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| Authors: | LIU Xing-ping ZHOU Lian-sheng YOU Jing LI Sui-yun LIU Rui |
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| Institution: | (Sixth Geological Team of Hubei Geological Bureau,Xiaogan 432000,China;Faculty of Earth Resources,China University of Geosciences,Wuhan 430074,China) |
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| Abstract: | The Waliaoge Pb-Ag deposit is located in the northeastern part of Karuo District(about 150 km away from the downtown of Qamdo City),Qamdo City,Tibet,China.The stratum exposed in the deposit is the Upper Triassic Jiapila Formation in which orebodies are mainly hosted in its second sub-member limestone(T3j2-2).There is no magmatic rock outcropped in the deposit.There are main structures of dominant NW-trending faults.7 industrial ore bodies were outlined in the deposit,with the Pb metal resource of 504 kt and associated Ag metal resource of 580 t,respectively.This means that the deposit is a large scale one in terms of both Pb and Ag resources.Based on the detailed study of the geological characteristics of the deposit,studies of fluid inclusions and multiple isotopes(C-O-S-Pb)geochemistry of the deposit have been carried out in this paper,in order to explore properties of ore-forming fluids and sources of ore-forming materials of the deposit and to provide more abundant geochemical information for understanding genesis of the deposit.The results show that:(1)orebodies of this deposit are obviously controlled by stratum and structures;(2)the measured homogenization temperatures(concentrated in 130-180℃)and salinities(concentrated in 6%-17%Na Cl equiv.)of fluid inclusions indicate that the ore-forming fluid was characterized with low temperature and medium-low salinity.(3)the C and O isotopes of ore-bearing strata(δ13CPDB values varying from-2.7‰to 4.3‰)and hydrothermal calcite(δ13CPDB values varying from 2.6‰to 4.0‰)samples are similar to those of the normal marine sedimentary limestone,inferring that the carbon of hydrothermal fluid could mainly be sourced from wallrocks.The sulfur isotopic compositions(δ34S values),varying from-3.8‰to 1.6‰,of galena samples are quite similar to mantle sourced sulfur(from-3‰to 3‰).However,considering that there is no magmatic activity and theδ34S values of sedimentary rocks vary from 6.2‰to 20.5‰in the deposit area,it is speculated that the sulfur of ore-forming fluid could be mainly sourced from strata as the product of thermochemical reduction of sulfates.In addition,lead isotopes of sulfides,which have crustal sourced lead characteristics,and the similarity of Pb isotopes of most ore samples to those of host rocks indicate that the metallogenic metals could be mainly sourced from ore-hosted wallrocks.In summary,it is believed that the ore-forming materials of the Waliaoge Pb-Ag deposit were mainly sourced from the ore-hosted strata,.In terms of the genetic type,the Waliaoge deposit belongs to the low temperature hydrothermal Pb-Ag one. |
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| Keywords: | fluid inclusions C-O-S-Pb isotopes the source of ore-forming materials the Waliaoge Pb-Ag deposit Tibet |
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