东昆仑那更康切尔银矿床S-Pb-C-O同位素地球化学特征

Constrains of S-Pb-C-O Isotope Compositions on the Origin of Nagengkangqieer Silver Deposit, the Eastern Kunlun Mountains, China

那更康切尔银矿床位于东昆仑成矿带中部,紧邻昆中构造带。矿体主要以脉状产出于古元古代金水口群片麻岩以及晚古生代花岗闪长岩和二长花岗岩中。本文在矿床地质特征研究基础上,采集12件样品对其硫化物(黄铁矿、方铅矿、闪锌矿)和方解石分别开展了S-Pb和C-O同位素研究。结果表明,矿床硫同位素组成稳定,δ^(34)S主要集中于-3.4‰~0.6‰之间,主要来源于岩浆作用;硫化物^(206)Pb/^(204)Pb值介于18.28~18.62,平均值为18.37,^(207)Pb/^(204)Pb值介于15.60~15.73,平均值为15.65,^(208)Pb/^(204)Pb值介于38.38~39.10,平均值为38.63,铅同位素组成稳定,矿石铅主要来源于地壳;方解石δ^(13)C值介于-6.0‰^-2.8‰,平均值为-4.25‰,δ^(18)O值介于6.1‰~20.5‰,平均值为12.49‰,表明C可能主要由岩浆作用提供。综合矿床地质特征和区域成矿背景认为该矿床应属于岩浆期后热液矿床,受构造和岩浆作用的双重控制。

.Nagengkangqieer silver deposit is located in the central part of the Eastern Kunlun Mountains. Ore bodies occurring as vein are mainly hosted in gneiss of the Jinshuikou Group and Late Paleozoic granodiorite and monzonitic granite. Based on the study of geological characteristics of deposit, twelve samples of sulfides and calcites were studied with S-Pb-C-O isotopes analysis. Sulphur isotope values range from-3.4‰ to 0.6‰,implicating that the sulfur sources were probably derived from magmatism process. The ^206Pb/^204Pb, ^207Pb/^204Pb, and ^208Pb/^204Pb ratios of sulfides range from 18.28 to 18.62, 15.6 to 15.73, and 38.38 to 39.10, with an average of 18.37, 15.65, and 38.63, respectively. Most of Pb isotope compositions were plot in the field of the upper Pb evolution curve. Carbon and oxygen isotope compositions range from-6‰~ to 2.8‰ and 6.1‰ to 20.5‰,with an average of-4.25‰ and 12.49‰, respectively, suggesting that the carbon was mainly derived from magmatism. Geological and isotopes studies of Nagengkangqieer silver deposit reveal that the deposit is similar to the postmagmatic hydrothermal type controlled by structure and magmatism.