内蒙古安家营子金矿与侵入岩的关系及其地球动力学意义  

Relationship between intrusive rocks and gold mineralization of the Anjiayingzi gold deposit, Inner Mongolia and its implications for geodynamics.

作　　者：李永刚[1] 翟明国[1] 苗来成[1] 朱嘉伟 薛良伟 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]河南省地质科学研究所,郑州450053

出　　处：《岩石学报》2003年第4期808-816,共9页Acta Petrologica Sinica

基　　金：中国科学院重大知识创新项目(编号:KZCX1-07)的研究成果

摘　　要：位于华北陆块北缘金矿成矿带的安家营子中型金矿属赤峰-朝阳金矿化集中区。金矿体主要赋存于安家营子花岗岩岩体内。区内广泛分布着与金矿化相伴生的流纹斑岩脉。与金矿化密切相关的安家营子花岗岩具有轻稀土富集、重稀土亏损、较低的^(87)Sr/^(86)Sr初始比值、Ba-Sr含量高等特点,暗示该花岗岩浆形成深度较大。这些特点与我国胶东地区与金矿有关花岗岩的特征非常相似,但区别于较早期的喀喇沁花岗岩和成矿后的流纹斑岩脉。锆石U-Pb年龄表明,安家营子花岗岩侵位时代为132～138 Ma,而穿切矿体的流纹斑岩岩脉的成岩时代为124.9～126.5 Ma,进而金矿成矿时代可以限定在126～132Ma。这一年龄结果与华北克拉通中生代动力学体制发生转折的时间相吻合。研究表明,早中生代前后华北东部曾发生了动力学机制的重大转折,如挤压向伸展转变和岩石圈的减薄达到高峰导致岩浆作用增强等。华北克拉通绝大多数金矿床集中形成于这一转折时期暗示成矿作用可能与深部作用过程有关,即早白垩世地幔物质-能量强烈上涌的同时,使金等成矿元素活化迁移至地壳层次,并在有利的构造部位富集成矿。The Anjiayingzi gold mine, an intermediate-size deposit located in the Chifeng-Chaoyang gold-concentrated area in the north margin of the North China craton, is hosted in the Anjiayingzi granite, and is spatially associated with rhyolitic porphyry. The granite is geochemically characterized by rich-LREE, depleted-HREE, relative high initial Sr-87/Sr-86 ratio, and high Ba and Sr contents, indicative of a deep-source of the granite magma. These geochemical features are consistent with those of the granitoids that are closely related to gold mineralization in eastern Shandong Province, whereas are contrast to those of early-formed Kalaqin granite and post-gold mineralization rhyolite dikes. Zircon U-Pb dates suggest that the Anjiayingzi granite was formed at 132similar to138 Ma, and the rhyolite dike that cut gold lodes was formed at 125similar to127 Ma. Therefore, gold mineralization in the area is constrained at 126similar to132 Ma. This timing of gold mineralization is coeval with the Mesozoic geodynamic regime reverse of the North China Craton. Researches suggest that the geodynamic reverse in the North China Craton took place during early Mesozoic time, such as changing of tectonism from compression to extension and thinning of the lithosphere to a peak at that time and causing much more extensive and intensive magmatism. Most gold deposits were formed during the reverse period, which indicates that gold mineralization is probably related to these deep processes. That is to say along with going up of mantle materials and energy, metallogenic elements including Au were reactivated and transported to upper crustal level, and then deposited at preferred structural sites.

关 键 词：金矿床 侵入岩 地球动力学 内蒙古 安家营子 

分 类 号：P597.3[天文地球—地球化学] P588.121[天文地球—地质学]