投稿时间：2021-05-06
修订日期：2021-08-17
网络发布日期：2021-10-22
中文摘要:龙口-土堆金矿大地构造位于胶莱盆地东北缘，胶-辽-吉构造带南段，华北克拉通东南缘，成矿地质条件优越。研究区虽经多年的勘探开采，但其成矿流体和成矿物质来源研究薄弱且存在较大争议，严重制约了成矿机理研究和进一步勘探工作。文章从与成矿密切相关的方解石脉和其他矿物的微量元素与C-H-O-S同位素地球化学特征入手，探讨了龙口-土堆金矿床流体地球化学特征和矿床成因。微量元素分析表明，不同类型方解石具有明显不同的Fe、Mn含量，其中主成矿期含矿方解石具有最高的w （Fe+Mn）（114 070×10-6），荆山群大理岩w （Fe+Mn）最低（3971×10-6），而不含矿的方解石的w （Fe+Mn）（5410×10-6）介于前两者之间。不含矿方解石样品δ13CPDB值在-6.90‰~-0.19‰之间，δ18OSMOW值在5.38‰~12.15‰之间；含矿方解石样品δ13CPDB值在-8.56‰~-6.41‰之间，δ18OSMOW值在8.66‰~10.61‰之间；荆山群大理岩样品δ13CPDB值在-3.83‰~-6.73‰之间，δ18OSMOW值在14.39‰~16.28‰之间。研究表明：方解石的C-O同位素组成指示含矿碳酸盐脉形成于花岗岩和地幔多相体系；不含矿碳酸盐形成于火成碳酸岩和地幔多相体系；含矿方解石形成于地幔多相体系。石英和方解石流体包裹体氢氧同位素分别为δDwater=-51.5‰~-119.9‰和δ18Owater=0.6‰~7.81‰，表明成矿流体主要为岩浆水，同时可能存在大气降水和地层建造水的参与。矿石硫化物的δ34S值介于8.5‰~12.7‰之间，硫同位素组成呈明显的正态分布，以富集34S为特征，显示了岩浆硫和壳源硫混合的同位素组成特征。结合区域成矿地球动力学背景，文章认为龙口-土堆金矿床为岩浆热液有关的构造蚀变岩型金矿，其流体来源于壳幔混源的多相体系。综合成矿条件分析，文章完善了胶东金矿成矿模式，指出矿区中碳酸盐脉富Fe+Mn的地球化学特征可能指示围岩含矿或近矿。该研究成果可为胶东金矿床的深部及外围找矿勘查提供新的科学依据。
Abstract:The Longkou-Tudui gold deposit is tectonically located in the northeastern margin of Jiaolai Basin, the southern segment of Jiao-Liao-Ji tectonic belt, and the southeast margin of North China Craton. The study area has been intensively explored since many years ago, but the source of ore-forming fluid and metallogenic materials is still debatable and controversial, which seriously restricts the study of metallogenic mechanism and further exploration. In this paper, various analyses including trace element geochemical characteristics and C-H-O-S isotopes of calcite veins and other minerals closely related to mineralization were carried out, and the fluid geochemical characteristics and genesis of Longkou-Tudui gold deposit were discussed. The trace element analysis shows that the contents of Fe and Mn in different types of calcites are variable. The calcites formed in the main metallogenic period have the highest w(Fe+Mn) (114 070×10-6), but the marbles from the Jingshan Group have the lowest w(Fe+Mn) (3971×10-6), and the w(Fe+Mn) values (5410×10-6) of barren-calcites is between the former two. The δ13CPDB values of barren calcite samples are between -6.90‰ and -0.19‰, and the δ18OSMOW values are between 5.38‰ and 12.15‰. The δ13CPDB values of calcite samples bearing ore are between -8.56‰ and -6.41‰, and the δ18OSMOW value is between 8.66‰ and 10.61‰. The δ13CPDB values of marble samples of the Jingshan Group are between -3.83‰ and -6.73‰, and the δ18OSMOW values are between 14.39‰ and 16.28‰. The C-O isotopic compositions of calcites indicate that the barren carbonate veins were formed in the multiphase system involving granite and mantle, and the ore-bearing carbonate veins were formed in a multiphase system involving igneous carbonate and mantle. The hydrogen and oxygen isotopes of quartz and calcite are δDwater=-51.5‰ to -119.9‰ and δ18Owater=0.6‰ to 7.81‰, respectively, indicates that the ore-forming fluids were mainly magmatic water, and may also have involved both meteoric water and strata water. The δ34S values of sulfides in the ore range from 8.5‰ to 12.7‰, and the sulfur isotopic compositions show a significant normal distribution. The enrichment of 34S represents the isotopic compositional characteristics of crust-derived sulfur. Together with the regional metallogenic and geodynamics setting, it is considered that the Longkou-Tudui deposit is a magmatic-hydrothermal related, structure-controlled, altered rock-type gold deposit, and the fluids came from the multiphase system with a mixed source of mantle and crust. Finally, a metallogenic model is established based on the comprehensive metallogenic conditions revealed in this study. The results highlight that the Fe+Mn enriched geochemical characteristics of carbonate veins may possibly indicative significance for gold prospecting. Overall results from this study can provide new scientific basis for the deep and peripheral prospecting of gold deposits in the Jiaodong region.
keywords:geochemistry gold deposit ore-forming fluid ore-forming materials Fe-Mn elements carbonates
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基金项目:本文得到国家重点研发计划"华北东部巨量金来源、迁移与富集机理"（编号：2016YFC0600104）和中国黄金集团公司-山东烟台鑫泰黄金矿业有限责任公司地质科研"山东省海阳市龙口-东刘家金矿床流体地球化学与深部找矿预测研究"（编号：XY-DZ2020081）项目的联合资助
引用文本：
陈原林,李欢,郑朝阳,冯波,段留安,李大兜.2021.胶莱盆地龙口-土堆金矿床成因：微量元素特征与C-H-O-S同位素约束[J].矿床地质,40(5):977~996CHEN YuanLin,LI Huan,ZHENG ChaoYang,FENG Bo,DUAN LiuAn,LI DaDou.2021.Genesis of Longkou-Tudui gold deposit, Jiaolai Basin: Constraints of trace element characteristics and C-H-O-S isotopes[J].Mineral Deposits40(5):977~996
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