延边东部杨金沟金矿床成矿时代与成矿物质来源

Metallogenic age and ore-forming material source of Yangjin'gou Gold Deposit in eastern Yanbian region

杨金沟金矿床位于吉林省珲春市春化镇,大地构造位置上地处兴蒙造山带最东端。为了确定其成矿时代以及成矿物质来源,选取金矿石中与金矿化密切相关的辉钼矿和黄铁矿分别进行Re-Os定年和S同位素测试分析。辉钼矿的Re-Os等时线年龄为(247.6±5.8)Ma,模式年龄的加权平均年龄为(250.6±1.8)Ma,结合已有白云母Ar-Ar测年和含矿岩体锆石U-Pb测年结果,确定杨金沟金矿床的形成时代为晚二叠世末至早三叠世初。金矿石中黄铁矿的δ^(34)S值介于0.59‰~2.70‰,接近陨石硫δ^(34)S值,故硫源主要来自于上地幔;辉钼矿的Re质量分数介于2.87×10^(-4)~5.64×10^(-4),也表明其成矿物质主要来源于地幔。根据成矿地质条件、矿床地质特征、成矿物质来源、成矿构造背景以及同类矿床对比研究,认为杨金沟金矿床是东北地区晚古生代金矿床的典型代表,其成因上属与造山作用有关的中温热液脉型金矿床。

Yangjin^gou Gold Deposit is located in Chunhua Town,Hunchun City, Jilin Province, and tectonically in the easternmost part of Xing^an - Mongolia Orogenic Belt. The Re - Os isotopic dating and S isotopic analysis are conducted on molybdenite and pyrite respectively, which are closely related to gold mineralization in the gold ores, to determine the metallogenic age and ore-forming material source. The Re - Os isotopic dating of the molybdenite shows that the isochron age is （247. 6 ±5. 8） Ma and the weighted average age of the model age is （250. 6 ± 1. 8） Ma,which, combined with the existing results of muscovite Ar - Ar dating and zircon U - Pb dating for ore-bearing rock, can conclude that the Yangjin^ou Gold Deposit formed at the end of Late Permian or the beginning of Early Triassic. The 34S values in the pyrite range from 0. 59 %c to 2. 70 close to the meteorite sulfur ^34S value, indicating that the sulfur resource mainly comes from the upper mantle. Besides that,the Re mass fraction of molybdenite ranges from 2. 87 × 10 4 to 5.64 ×104 , which suggests that the metallogenic minerals also mainly come from the mantle. Such re-search data as geological conditions, geological features, tectonic setting and ore-forming material source and the com-parison with other similar deposits indicated that the Yangjin gou Gold Deposit is one representative Neopaleozoic gold deposit in NE China,whose genesis belongs to the mesothermal vein-type gold deposit formed in the orogenic tectonic activities.