湘南长城岭锑铅锌矿床方解石Sm-Nd同位素年代学、地球化学特征及地质意义  

Sm-Nd Isotope Chronology, Geochemical Characteristics andSignificance of Calcite from the Changchengling Sb-Pb-Zn Depositand Geological Significance in Hunan, Southern China

作　　者：王雷[1] 许嘉劲 任雯琪 朱恩异 蒋宗和 WANG Lei;XU Jiajin;REN Wenqi;ZHU Enyi;JIANG Zonghe(Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming 650093,Yunnan,China;Energy Bureau of Hezhang County,Bijie 553206,Guizhou,China;Bureau of Geophysical Prospecting INC.,CNPC,Chengdu 610000,Sichuan,China)

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650093 [2]贵州省毕节市赫章县能源局,贵州毕节553206 [3]中国石油东方地球物理公司西南物探分公司,四川成都610000

出　　处：《大地构造与成矿学》2023年第5期933-952,共20页Geotectonica et Metallogenia

基　　金：国家重点研发计划课题(2018YFC0603902);国家自然科学基金项目(42362009);云南省兴滇英才支持计划“青年人才”专项联合资助。

摘　　要：长城岭矿区位于南岭成矿带与钦杭成矿带的叠合部位,发育多期次的岩浆活动,同时产出锑铅锌多金属矿床和铷等稀有金属矿床,锑铅锌矿床的成矿时代和成矿物质来源研究较为薄弱,本文对与锑铅锌矿共生的脉石矿物方解石开展Sm-Nd同位素年代学、元素地球化学和C-O同位素分析。结果显示:①方解石Sm-Nd同位素等时线年龄为151.5±3.2 Ma,表明锑铅锌矿是南岭燕山期成矿大爆发产物,与矿区内花岗斑岩型铷矿(222.5±1.8 Ma)属于两期不同成矿作用的产物;②方解石稀土元素配分模式为轻稀土元素富集型,Y/Ho-La/Ho分布特征显示方解石为同源热液产物;不同矿物组合的方解石稀土元素变化特征表明,成矿过程中成矿流体的稀土元素总量随成矿作用进行而减少;较负的Eu异常值指示,原始成矿流体亏损Eu元素;③热液方解石δ13CPDB值为−5.12‰~−0.63‰,δ18OSMOW值为3.80‰~12.69‰,具有明显较低的δ18OSMOW值,表明成矿CO_(2)源于深源地幔。εNd(t)值为−12.48~−12.37,表明成矿物质来自于地壳与地幔的部分熔融。综合研究表明,锑铅锌矿床与铷矿床形成时代不同,二者具有两期叠合成矿特点,推测矿区存在燕山期隐伏的岩浆岩,深部具有较好的找矿前景。The Changchengling deposit is located on the overlapping portion of the Nanling and Qinhang metallogenic belts,which is characterized by multiple stages of magmatism and the associated mainly Sb-Pb-Zn mineralization.In order to determine the age of mineralization,source of ore-forming materials,and characteristics of ore-forming fluids of the deposit,we carried out Sm-Nd isotope chronology,C-O isotope,and trace element analyses of the calcite samples from the main mineralization period.The calcite Sm-Nd isotope isochron yielded an age of 151.5±3.2 Ma,therefore,the Sb-Pb-Zn metallogenic system is part of the Nanling Yanshanian mineralization explosion which is irrelevant to the granite porphyry Rb mineralization(222.5±1.8 Ma).The calcite samples from different mineral assemblages have similar REE patterns and Y/Ho-La/Ho distribution characteristics,which indicate that they are homologous hydrothermal products.The decreasing REE contents of the early to late stage calcite samples and the negative Eu anomalies may reflect the signature of the ore-forming fluids.The hydrothermal calcite has 13CPDB values ranging from−5.12‰to−0.63‰,and 18OSMOW ranging from 3.80‰to 12.69‰,indicating a deep mantle origin for the ore-forming CO_(2).The hydrothermal calcite samples haveεNd(t)values ranging from−12.48 to−12.37,implying that the ore-forming material was formed by crust-mantle mixing.Comprehensive research reveals that the antimony lead zinc deposit and granitic porphyry Rb deposit formed in different periods,therefore,a hidden Yanshanian intrusion may exist in the mining area,and thus the area may have a promising prospecting potential.

关 键 词：南岭成矿带 方解石 Sm-Nd同位素年代学 C-O同位素 稀土元素 

分 类 号：P611[天文地球—矿床学] P597[天文地球—地质学]