西藏玉龙铜矿带南段吉措Pb-Zn-Ag-Au矿床类型及岩石成因  

Deposit types and petrogenesis of the Jicuo Pb-Zn-Ag-Au deposit in the southern section of the Yulong copper belt, Tibet

作　　者：谢富伟 周敖日格勒 曹阳[1] 何亮[1,3] 周宇航 高鲁通[1] 李文昊 邓夏雨 XIE FuWei;ZHOU AoRiGeLe;CAO Yang;HE Liang;ZHOU YuHang;GAO LuTong;LI WenHao;DENG XiaYu(College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu 610059,China;SinoProbe Laboratory,Chinese Academy of Geological Sciences,Beijing 100094,China;No.6 Geological Party,Xizang Bureau of Geological Exploration and Mineral Development.Lhasa 851400,China)

机构地区：[1]成都理工大学地球与行星科学学院,成都610059 [2]中国地质科学院,自然资源部深地科学与探测技术实验室,北京100094 [3]西藏自治区地质矿产勘查开发局第六地质大队,拉萨851400

出　　处：《岩石学报》2025年第5期1531-1546,共16页Acta Petrologica Sinica

基　　金：本文受国家重点研发计划项目(2022YFC2905002);中国地质调查局项目(DD20230361);中国地质科学院矿产资源研究所基本业务费(KK2221);中央引导地方科技发展资金项目(XZ202401YD0006);珠峰科学研究计划项目(2024ZF11426)联合资助详细信息。

摘　　要：玉龙铜矿带是全球典型的碰撞型斑岩铜矿带, 但其南、北段矿化规模、矿床类型和矿化元素组合差异较大。吉措作为南段新发现的一中型Pb-Zn-Ag-Au矿床, 尚未系统开展过科学研究, 制约了对矿床成因的认识与找矿方向的确定。本文通过野外地质调查、岩矿鉴定、电子探针、LA-ICP-MS锆石U-Pb测年及Hf同位素、全岩主微量元素及Sr-Nd同位素等方法分析技术, 以确定矿床类型和岩石成因。研究显示, 矿区发育Au-Ag-Pb-Zn→Pb-Zn-Ag矿化元素分带, 其矿石构造、蚀变矿物组合、金属矿物组合、闪锌矿的FeS(16~20mol/mol)等都与中硫型浅成低温热液矿床相似, 其Ag主要赋存于方铅矿、硫锑铅矿、硫砷铜银矿, Au赋存于毒砂、黄铁矿中, 黄铁矿Au、As、Co等元素呈现核部低、边部高的特征, 且As/Sb比值变化较大, 指示热液流体成分的较大波动, 沸腾作用可能是Au沉淀的主要机制。吉措矿区花岗斑岩与成矿密切相关, 2件样品的锆石U-Pb年龄分别为39.38±0.28Ma和39.41±0.32Ma, 属于钾玄系列, 具有高SiO_(2)、高全碱、低MgO、Cr, 明显富集大离子亲石元素(K、Rb、LREE等), 相对亏损高场强元素(Nb、Ta、Ti、HREE等);其(^(87)Sr/^(86)Sr)_(i)值为0.7080~0.7082, ε_(Nd)(t)介于-3.49~-3.34之间;锆石ε_(Hf)(t)值-0.40~+1.00(平均值为+0.19), 二阶段模式年龄分布在1140~1047Ma之间;表明岩浆起源于加厚下地壳部分熔融, 并有少量幔源岩浆的混入, 形成于印度-欧亚碰撞走滑的地壳增厚构造背景。吉措中硫型浅成低温热液矿床的确立指示玉龙铜矿带南段同样具有寻找碰撞型斑岩成矿系统的找矿潜力, 对区域找矿方向的确定有重要指导意义。The Yulong copper belt is a globally representative collision-type porphyry copper belt, yet significant differences exist in mineralization scale, deposit types, and elemental assemblages between its northern and southern segments. As a newly discovered medium-sized Pb-Zn-Ag-Au deposit in the southern segment, the Jicuo deposit has not undergone systematic scientific investigation, hindering understanding of its genesis and exploration targeting. This study integrates field geological surveys, petrographic analysis, electron probe microanalysis, LA-ICP-MS zircon U-Pb dating, Hf isotopes, whole-rock major-trace elements, and Sr-Nd isotopes to determine deposit type and petrogenesis. Results reveal a metal zoning pattern of Au-Ag-Pb-Zn→Pb-Zn-Ag mineralization. Ore textures, alteration assemblages, metallic mineral associations, and sphalerite FeS contents (16~20mol/mol) align with intermediate-sulfidation epithermal systems. Silver primarily resides in galena, boulangerite, and selenian polybasite, while gold occurs in arsenopyrite and pyrite. Pyrite exhibits core-to-rim increases in Au, As, and Co concentrations, with variable As/Sb ratios indicating significant hydrothermal fluid fluctuations, suggesting boiling as the primary gold precipitation mechanism. Granite porphyry related to mineralization yields zircon U-Pb ages of 39.38±0.28Ma and 39.41±0.32Ma. These shoshonitic rocks show high SiO_(2), alkalis, low MgO and Cr, enriched LILEs (K, Rb, LREEs), and depleted HFSEs (Nb, Ta, Ti, HREEs). Their isotopic characteristics ((^(87)Sr/^(86)Sr)_(i)=0.7080-0.7082, ε_(Nd)(t)=-3.49~-3.34, zircon ε_(Hf)(t)=-0.40~+1.00 with tDM2=1140~1047Ma) indicate derivation from thickened lower crustal melting with minor mantle input, formed under crustal thickening during India-Eurasian collision. Identification of the Jicuo intermediate-sulfidation epithermal deposit confirms the southern Yulong belt's potential for collision-related porphyry systems, providing important guidance for regional mineral exploration.

关 键 词：中硫型浅成低温热液矿床 吉措Ag±Au多金属矿床 玉龙铜矿带 矿床类型 西藏 

分 类 号：P588.13[天文地球—岩石学] P597.3[天文地球—地质学] P611.1