内蒙古双尖子山银多金属矿床S、Pb同位素特征及成矿机制探讨

Isotopic characteristics of sulfur and lead and metallogenic mechanism of Shuangjianzishan silver polymetallic deposit in Inner Mongolia

双尖子山银多金属矿处于黄岗梁—甘珠尔庙多金属成矿带中,是近年新发现的超大型矿床,银的储量超过了2万t。矿体产于中二叠统大石寨组粉砂岩中,多以北西走向为主,其次为北东向,呈陡倾状。矿石类型主要为块状硫化物矿石和石英—硫化物细网脉状矿石,矿石矿物主要为闪锌矿、方铅矿和银的矿物。S、Pb同位素显示,闪锌矿、方铅矿S同位素组成为-52‰^-08‰,反映深源岩浆S的特征。铅同位素组成^(206)Pb/^(204)Pb为18.267~18.295,^(207)Pb/^(204)Pb为15.522~15.553,^(208)Pb/^(204)Pb为38.084~38.181,显示壳幔混源特征。矿区中具有高演化特征的正长花岗岩,矿石中存在锡矿化,表明该矿为岩浆热液型矿床,属于锡钨多金属成矿系统。

The Shuangjianzishan silver polymetallic ore deposit is a large-sized deposit discovered in recent year, which is located in Huanggangliang - Ganzhuermiao polymetallic metallogenic belt. The silver metal reserve is more than 20 000 t. The silver ore body occurs in the siltstone of the Dashizhai formation in the middle Permian. The main ore body dip in steep angle and mostly northwest-trending and minor NE-trending. The ore types are mainly massive sulfide type and quartz-sulfide fine veinlets, the ore metal minerals are sphalerite, galena and silver minerals. The S isotope composition of sphalerite and galenais -5.2‰ ~ -0.8‰, which indicated the sulfur originated from magma. The lead isotope composition of galena is as followings：206Pb /204Pb ranging from 18.267 to 18.295,207Pb /204Pb from 15.52 to 15.553,208Pb /204Pb from 38.08 to 38.118, which reflects mixed sources of crust and deep mantle magma for lead sources. Fully shows that the mine is a magmatic hydrothermal deposit. The existence of high-evolution syenitic granite and tin mineralization in the ore indicate that the deposit belongs to the magmatic hydrothermal type deposit, and it is a tin-tungsten polymetallic metallogenic system.