豫西熊耳山矿集区栾灵金矿床辉钼矿Re-Os同位素年龄及其地质意义

Re-Os isotopic dating of molybdenite from Luanling gold deposit in Xiong'er Mountain ore concentration area of western Henan Province and its geological significance

豫西栾灵金矿床地处熊耳山金多金属矿集区南部马超营断裂带北侧,金矿体产于构造破碎带中,呈钾长石石英脉体和蚀变岩产出,为本区一种新的金矿化类型。文章为厘定栾灵金矿床的成矿时代,采用辉钼矿Re-Os同位素定年方法,测得栾灵金矿6件辉钼矿样品的Re-Os同位素模式年龄为(161±3)Ma^(164±2)Ma,加权平均年龄(163±1)Ma(MSWD=0.68),等时线年龄(163±2)Ma(MSWD=1.5),表明栾灵金矿床形成于晚侏罗世早期。与祁雨沟、前河金矿等早白垩世(125 Ma)金矿相比,栾灵金矿的成矿作用早约38 Ma。这些年龄数据表明,该矿床在区域上可能与南泥湖-三道庄、上房沟钼矿等形成于同一成矿系统,它的发现为在熊耳山地区寻找相似成矿地质条件的金、钼矿床提供了依据。

The Luanling gold deposit is located on the northern side of Machaoying fault zone in the southern part of the Xiong er Mountain gold polymetallic ore district,Henan Province. The gold orebodies mainly occur as the K-feldspar-quartz vein or altered rock in the structural fracture zone. For the purpose of studying the chronology of the gold mineralization in the Luanling gold deposit, the authors purified molybdenite from the gold-bearing feldspar quartz veins in the Luanling gold deposit. Re-Os dating of these minerals yielded modal ages from（ 161 ± 3） Ma to（ 164 ± 2） Ma, a weighted average age of（ 163 ± 1） Ma（ MSWD = 0. 68）, and an isochron age of（ 163 ± 2） Ma（ MSWD = 1. 5）, implying that the Luanling gold deposit formed in the Late-Jurassic. Compared with the Cretaceous（ 125 Ma） Qiyugou gold deposit and Qianhe gold deposit, the Luanling gold deposit formed about 38 Ma earlier, indicating a new late Jurassic mineralization period in the Xiong er ore concentration area. The Luanling gold deposit and Nannihu-Sandaozhuang as well as Shangfanggou Mo deposits were produced by the same mineralization system. The discovery of the Luanling Au deposit provides the basis for the study of Au-Mo deposits of the similar ore-forming conditions in the Xiong＇er Mountain region.