东秦岭钼矿类型、特征、成矿时代及其地球动力学背景

Geology, distribution, types and tectonic settings of Mesozoic molybdenum deposits in East Qinling area

文章在总结前人研究成果的基础上,综合论述了东秦岭钼矿床的时空分布、分类和基本特征。东秦岭钼矿带沿区域构造线呈近东西向狭长带状展布,钼矿床主要集中分布于金堆城—南泥湖地区内;其形成与燕山期中酸性浅成_超浅成小花岗斑岩体有关,钼矿床直接产于岩体内外接触带及其附近;矿床类型主要为斑岩型、斑岩_矽卡岩型,少量热液碳酸盐脉型。结合Re_Os同位素年龄数据,探讨了东秦岭钼矿床的成矿时代及其成矿物质来源、成矿环境、大规模成矿作用时限及其特征,以及成矿地球动力学背景、演化特点和成矿过程。研究结果表明:除黄龙铺钼矿床形成于(221.5±0.3)Ma外,东秦岭地区钼矿床的大规模成矿主要出现在(144.8±2.1)^(132.4±2.0)Ma时限之间,对应的地球动力学背景为华北克拉通与扬子克拉通的碰撞造山后陆内造山局部伸展过程、中国东部地球动力学体制大转换晚期岩石圈拆沉及伸展时期。

Located on the southern margin of the North China craton, the East Qinling molybdenum metallogenic belt is one of several regions in China characterized by the distribution of some important large-size molybdenum deposits. Molybdenum deposits generally occur in nearly E-W direction along the tectonic lineament and are mostly concentrated in a zone stretching from Jinduicheng area of Shaanxi Province in the west to Nannihu-Sandaozhuang-Shangganggou area of Luanchuan and Leimenggou of Songxian in western Henan Province. They are genetically related to Yanshanian intermediate-acid granites distributed extensively in East Qinling area and occur along the endo- and exo-contact zones of the porphyry. The molybdenum deposits are mainly of porphyry and porphyry-skarn type and subordinately of carbonatite vein type. The ore-forming ages of the molybdenum deposits in East Qinling area are within (221.5±0.3) Ma～(132.4±2.0) Ma, and cluster mainly into two pulses of (221.5±0.3) Ma and (144.8±2.1)～(132.4±2.0) Ma. The former pulse geodynamically correspond to the extensional period of post-collision orogenic process between North China and Yangtze cratons. The latter pulse results from the transformation of the tectonic regime from NS- to nearly EW-directions in East China.