江西北武夷地区老虎洞铅锌矿床成因研究——硫化物原位微量元素及硫同位素证据

Genesis of the Laohudong Pb-Zn deposit in the north Wuyi area in Jiangxi Province:Evidence from in situ trace element and sulfur isotope of sulfides

江西北武夷地区处于钦杭成矿带上的萍乡-广丰结合带南侧,多期构造事件和岩浆活动在该区形成了复杂的地质构造格局,铜铅锌多金属矿床成矿潜力巨大。但由于江西北武夷地区铅锌矿床普遍规模较小,研究程度不足,缺乏物质来源、成矿条件、矿床成因等问题的深入认识。本文以铅山老虎洞铅锌矿床为研究对象,通过原位主量、微量元素和硫同位素分析技术,揭示主要硫化物的主量、微量元素和硫同位素组成特征,以此探讨成矿温度、物质来源和矿床成因。EPMA测试显示闪锌矿内Fe含量(质量分数)在7.58%~8.27%之间,结合LA-ICP-MS微量元素测试结果,闪锌矿富集Fe、Mn、Cu、Cd元素,Co、Ni、Ag、In、Pb元素含量次之,Ga、Ge、As、Se、Sn、Bi元素含量相对较低。其中,Mn、Fe、Cd、In、Co主要以类质同象的形式赋存于闪锌矿中,Cu、Ag、Pb以类质同象和显微包体两种形式赋存于闪锌矿中。闪锌矿的Fe元素含量、Ga/In值(0.001~0.129)、Zn/Cd值(262~312)及相关公式计算结果均指示闪锌矿形成于中高温条件(327~337℃)。闪锌矿和黄铁矿的δ34S值分别集中在2.07‰~4.16‰和0.82‰~3.19‰之间,指示矿床硫源为岩浆硫。与国内多个典型矿床相比,老虎洞铅锌矿床内闪锌矿微量元素组成与典型矽卡岩型矿床的闪锌矿相吻合。老虎洞铅锌矿床与葛仙山花岗岩杂岩体具有密切的成因联系,矿区附近黑云母花岗斑岩和二长花岗岩的成岩时代(153.9±2.7 Ma和162.8±1.2 Ma)可代表成矿时间的下限,与北武夷地区主要多金属铅锌矿床成矿时代范围一致。

The north Wuyi area in Jiangxi Province is located on the southern side of the Pingxiang-Guangfeng junction zone on the Qinhang mineralization belt.Multiple tectonic events and magmatic activities formed a complex geological structure pattern in this area,and metallogenic potential of copper and lead-zinc polymetallic deposits is enormous.However,due to the generally small scale and insufficient research of lead-zinc deposits in the northern Wuyi area of Jiangxi Province,there is a lack of in-depth understanding of material sources,metallogenic conditions,and deposit genesis.This paper takes Laohudong Pb-Zn deposit in the northern Wuyi area of Jiangxi Prov-ince as the research object.EPMA,LA-ICP-MS and LA-MC-ICP-MS were used to reveal the major and trace element and sulfur isotope composition of sulfides,then many important information concerning the mineralization temperature,the source of metallogenic materials and the genesis of the deposit were investigated.EPMA testing shows that the Fe content in sphalerite ranges from 7.58%to 8.27%.Combined with LA-ICP-MS trace element testing,sphalerite is rich in Fe,Mn,Cu,Cd elements,followed by Co,Ni,Ag,In and Pb elements,the contents of Ga,Ge,As,Se,Sn and Bi elements are low.In sphalerite,Mn,Fe,Cd,In and Co exist in the form of isomorphism,while Cu,Ag,Pb exist in the form of isomorphism and microscopic inclusions.The content of Fe,the values of Ga/In(0.001~0.129),Zn/Cd(262~312)and calculation results of relevant formulas of sphalerite all indicated that sphalerite was formed under medium to high temperature mineralization conditions(about 327~337℃).Theδ34S of sphalerite and pyrite respectively concentrated between 2.07‰~4.16‰and 0.82‰~3.19‰,they all indicated magmatic sulfur.Compared with multiple Pb-Zn deposits in China,the trace element composition of sphalerite in Laohudong Pb-Zn deposit is consistent with typical skarn deposits.The Laohudong Pb-Zn deposit has a close genetic relationship with the Gexianshan granite complex,and the age of Gexianshan granite complex(153.9±2.7 Ma and 162.8±1.2 Ma)can represent the lower limit of the mineralization time,which is consistent with the range of the main polymetallic Pb-Zn deposits in the north Wuyi area.