西藏冈底斯成矿带(斑岩-)矽卡岩矿床钴富集特征及成因研究  

Study on cobalt enrichment and genesis of the(porphyry-)skarn deposit in Gangdese metallogenic belt,Tibet

作　　者：王硕 曹明坚 单鹏飞 黄新硕 斯郎旺堆 李光明[1,2] 皮静怡 秦克章 WANG Shuo;CAO MingJian;SHAN PengFei;HUANG XinShuo;SILANG WangDui;LI GuangMing;PI JingYi;QIN KeZhang(State Key Laboratory of Lithospheric and Environmental Coevolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;No.6 Geological Brigade,Tibet Bureau of Geology and Mineral Resources,Lhasa 851414,China)

机构地区：[1]岩石圈演化与环境演变全国重点实验室,中国科学院地质与地球物理研究所,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049 [3]西藏地质矿产勘查开发局第六地质大队,拉萨851414

出　　处：《岩石学报》2025年第2期492-509,共18页Acta Petrologica Sinica

基　　金：第二次青藏科考(2019QZKK0801);国家重点研发计划项目(2022YFC2903503);国家自然科学基金项目(42122013、92162102、92162323);中国科学院地质与地球物理研究所重点部署项目(IGGCAS-202204)联合资助.

摘　　要：冈底斯成矿带位于拉萨地体南部,发育多个超大型斑岩铜-钼矿床及众多的矽卡岩矿床,是青藏高原重要矿集区。冈底斯成矿带的矽卡岩矿床存在钴的差异富集,主要体现在东段富钴、西段贫钴。根据钴的富集程度,可将矽卡岩矿床分为三类:富钴矿床、较富钴矿床和贫钴矿床。其中富钴矿床——浦桑果铜多金属矿床、甲玛铜多金属矿床、知不拉铜矿床主要位于冈底斯中东段南部;较富钴矿床——春哲铁矿床、勒青拉铅锌矿床、邦雄巴铅锌矿床、程巴铜多金属矿床、蒙亚啊铅锌矿床、龙马拉铜多金属矿床主要位于冈底斯东段北部;贫钴矿床代表——帮布勒铅锌矿床、查个勒铅锌矿床位于冈底斯西段。在冈底斯成矿带区域对比研究中,发现中新世形成的铜多金属矿床中钴的富集最为显著,全岩及单矿物的主微量数据显示埃达克质(高Sr低Y高La低Yb)的成矿岩体更有利于钴的富集矿化。H-O-S同位素显示这些矽卡岩矿床均不同程度地存在大气降水的加入,但成矿流体主要为岩浆来源,Pb-Os-Hf同位素特征进一步指示富钴矿床的成矿物质主要来源于新生下地壳或幔源岩浆,富钴幔源岩浆或新生镁铁质下地壳的加入更有利于钴的富集。而贫钴矿床多为晚白垩世晚期-始新世期间形成的铅锌矿床,其成矿岩体多显示或继承普通弧岩浆特征。此外,根据浦桑果铜多金属矿床、甲玛铜多金属矿床、知不拉铜矿床的成矿环境对比,发现物理化学条件的差异可能是形成不同独立钴矿物的主要原因。矽卡岩矿床钴的富集标志主要包括独立钴矿物的形成,载钴矿物(闪锌矿)和手标本矿石块样中的高钴含量,以及成矿岩体埃达克质特征;此外,较低的^(206)Pb/^(204)Pb、^(207)Pb/^(204)Pb、^(208)Pb/^(204)Pb值、较高的ε_(Hf)(t)、接近地幔的初始Os值揭示了其与幔源岩浆或新生下地壳的紧密成因联系。冈底斯�The Gangdese metallogenic belt is located in the southern part of the Lhasa terrane,and it is an important ore-concentration area on the Tibetan Plateau.It hosts large porphyry copper-molybdenum deposits and numerous skarn deposits.There is a differential enrichment of cobalt in the skarn deposits of the Gangdese metallogenic belt,with the eastern segment being rich in cobalt and the western segment being poor in cobalt.Based on the degree of cobalt enrichment,skarn deposits can be classified into three types:cobalt-rich deposits,moderately cobalt-rich deposits,and cobalt-poor deposits.The cobalt-rich deposits,such as Pusangguo copper polymetallic deposit,Jiama copper polymetallic deposit,and Zhibula copper deposit,are mainly located on the southern part of the central-eastern segment of Gangdese,while the moderately cobalt-rich deposits,including Chunzhe iron deposit,Leqingla lead-zinc deposit,Bangxiongba lead-zinc deposit,Chengba copper polymetallic deposit,Mengyaa lead-zinc deposit,and Longmala copper polymetallic deposit,are primarily situated on the northern part of the eastern segment of Gangdese.The representative cobalt-poor deposits,Bangbule lead-zinc deposit,and Chagele lead-zinc deposit,are found in the western segment of Gangdese.Regional comparisons within the Gangdese metallogenic belt reveal that cobalt enrichment is most significant in the Miocene copper-polymetallic deposits.Whole-rock and single-mineral major and trace element data indicate that adakitic rocks(characterized by high Sr,low Y,high La and low Yb)are more conducive to the enrichment and mineralization of cobalt.H-O-S isotope analyses indicate that these skarn deposits involve varying degrees of meteoric water,with a primarily magmatic origin.Pb-Os-Hf isotope characteristics further suggest that the formation of cobalt-rich deposits involves the mixing of juvenile lower crustal or mantle-derived magma.Contributions from mantle-derived magma or the addition of juvenile lower crust is more conducive to cobalt enrichment.Conversely,coba

关 键 词：冈底斯 (斑岩-)矽卡岩矿床 钴富集特征 钴差异富集 钴富集标志 

分 类 号：P612[天文地球—矿床学] P618.62[天文地球—地质学]