喀喇昆仑地区火烧云巨型铅锌碳酸盐矿床形成机制与成矿构造背景

The Huoshaoyun lead-zinc deposit is a new discovered giant lead-zinc deposit with a Pb+Zn reserve of 16 Mt in the Karakorum area, China. It is characterized by well-development of sedimentary ores. It is classified as a sedimentary exhalative lead-zinc deposit. The ore-forming minerals include smithsonite, cerussite, sphalerite and galenite. The Pb+Zn reserve of lead-zinc carbonate ore bodies is more than 15 Mt. The Huoshaoyun sedimentary exhalative lead-zinc carbonate deposit is a new subtype of sedimentary rock-host lead-zinc deposits and the largest lead-zinc carbonate deposit in the world. However, as a new discovered deposit, its formation mechanism and tectonic setting are unclear. This applying research project will firstly and detailedly study on the formation mechanism and tectonic setting of the Huoshaoyun giant lead-zinc carbonate deposit in the Karakorum area, including 1) host rocks and structure, mineralogy and zoning, alteration, ore textures, deposit morphology, age of ore deposition, nature of the ore fluids, metal sources, precipitation processes and ore controls of the Huoshaoyun lead-zinc deposit, creating a genetic model of sedimentary exhalative lead-zinc carbonate deposits; and 2) genetic type and tectonic setting of the Linjitang basin where the Huoshaoyun lead-zinc deposit formed, mineralization of the Duobaoshan and Tianshuihai lead-zinc sulfide deposit in the Huoshaoyun area, creating a tectonic evolution and regional metallogeny model of the Linjitang basin. This study is a great significance to understand the origin of sedimentary exhalative lead-zinc carbonate deposits, and to guide the finding and exploring similar deposits in the Karakorum and Qiangtang area, Tibet, China.

火烧云铅锌矿为喀喇昆仑地区新发现的巨型铅锌矿，矿石沉积结构构造发育，为喷流沉积成因铅锌矿床。矿床成矿矿物为菱锌矿、白铅矿、方铅矿与闪锌矿，其中菱锌矿与白铅矿Pb+Zn资源量大于1500万吨。火烧云喷流沉积成因铅锌碳酸盐矿为沉积型铅锌矿新类型，为世界最大铅锌碳酸盐矿床；但矿床研究程度低，其形成机制与成矿构造背景不清楚。本项目针对“火烧云铅锌碳酸盐矿床形成机制与成矿背景”开展原创性研究，研究工作包括：1）火烧云铅锌矿床的容矿围岩与控矿构造、矿物学与分带、蚀变、矿石结构构造、矿体形态、成矿年代、成矿流体与成矿物质来源，研究其形成机制与控制因素，创建喷流沉积成因铅锌碳酸盐矿床成因模型；2）火烧云铅锌矿成矿盆地形成构造背景与区域成矿作用，建立成矿盆地构造演化与区域成矿模型。本研究将揭示沉积成因铅锌碳酸盐矿床形成机制，科学意义重大；区域成矿模型建立对于喀喇昆仑与羌塘盆地寻找同类型铅锌矿具重要指导意义。

研究团队克服研究区高寒缺氧等艰辛条件（研究区为高原无人区，火烧云矿区海拔5800米），开展了大量的野外调查与样品采集，圆满完成各项研究工作与目标，在以下4个方面取得重要进展：. 1）查明火烧云铅锌矿床特征，包括：①矿床主要由菱锌矿（块状、层状与脉状；>85%）、白铅矿（脉状；<10%）、硫化物（脉状；<5%）组成，为铅锌碳酸盐矿床；②主矿体顺层产出，具层控特征；③矿床成矿经历了铅锌碳酸盐成矿阶段与硫化物阶段成矿。. 2）查明火烧云铅锌碳酸盐矿床成因机制，指出其为原生与深成矿床，成因于喷流沉积作用，为非硫化物矿床新类型，其主要特征包括：①具典型的二元结构，由近水平的层状菱锌矿矿体和近直立的菱锌矿脉组成。层状矿体具从块状向纹层状侧向相变与变化特征； ②菱锌矿与白铅矿为深成成因，具有与表生菱锌矿和白铅矿不同的且相对高的13C同位素值，具与硫化物不同的、相对高的66Zn同位素值,具相对高的REE含量与明显的Y正异常；③菱锌矿成矿温度105-145 ºC，白铅矿成矿温度186-206 ºC；④Pb-Zn成矿物质源于地壳；⑤成矿流体为岩浆流体+海水；⑥形成于弧后陆基裂谷盆地。. 3）查明火烧云铅锌矿床形成的构造背景，建立喀喇昆仑地区中新生代构造演化格架，主要进展有：①在甜水海地块发现0.97Ga火山岩，指出甜水海地块存在2.47-2.5Ga基底；②厘定大红柳滩210-220Ma碰撞带花岗岩带，指出喀喇昆仑地区侏罗纪林济塘盆地不是前陆盆地；③厘定喀喇昆仑地区弧－盆体系，指出林济塘盆地为弧后裂谷盆地；④在甜水海矿区西北部发现102Ma辉长岩；⑤建立喀喇昆仑地区中新生代构造演化模型。. 4）开展区域成矿作用研究，发现宝塔山矿床为构造破碎带角砾岩型（构造热液型）锌铁碳酸盐矿床、并确定其成矿年龄为102Ma，建立区域成矿模型，将火烧云地区铅锌矿床按成因分为沉积－交代型、MVT型与岩浆热液型三种类型。. 已发表期刊论文5篇、其中SCI论文2篇，完成博士论文1篇，已撰写并投稿的SCI期刊论文5篇。培养博士研究生2名。. 火烧云巨型铅锌碳酸盐矿床的发现与喷流沉积成因的提出是世界铅锌非硫化物矿床研究的重大进展。在区域成矿构造背景与成矿模型方面的研究成果不仅丰富了区域地质与成矿作用的认识，对喀喇昆仑地区乃至青藏高原地区寻找新的铅锌矿资源具有重要指导意义。