紫金山地区中生代岩浆系统的时空结构及其地质意义
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引用本文:张德全,李大新,丰成友,董英君.2001.紫金山地区中生代岩浆系统的时空结构及其地质意义[J].地球学报,22(5):403-408.
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作者单位
张德全 中国地质科学院矿产资源研究所北京100037 
李大新 中国地质科学院矿产资源研究所北京100037 
丰成友 中国地质科学院矿产资源研究所北京100037 
董英君 中国地质科学院矿产资源研究所北京100037 
基金项目:国家重点基础研究项目“大规模成矿作用与大型矿集区预测”(项目编号 :G1999043209)
中文摘要:紫金山地区中生代岩浆系统可以划分成晚侏罗世和早白垩世 2个主要的子系统。晚侏罗世岩浆子系统形成于陆内挤压造山的构造背景下 ,侵位于 15 7~≤ 14 1Ma之间 ,先后由深至浅地侵位于区域中部 ,形成由 3个单元复合而成的紫金山超单元花岗岩。其中的金龙桥单元正长花岗岩是晚期分异相 ,应作为紫金山地区锡矿重要的预测标志。早白垩世岩浆岩定位于 12 8~ 94Ma之间 ,是区域伸展作用体制下的产物 ,形成了由上部火山岩和下部侵入岩构成的具双层结构的岩浆子系统。在火山间歇期 (± 10 5Ma) ,花岗闪长斑岩侵入 ,并大规模地隐伏于该区的深部 ,从而导致本区大规模的铜金矿化作用。早白垩世岩浆子系统中的穹状火山构造、隐伏的花岗闪长斑岩岩体的顶面产状和形态 ,应该作为本区铜金矿床成矿预测的重要找矿信息和预测标志。详细的岩石学研究及时空关系显示 ,才溪二长花岗岩是这两个岩浆子系统之间的过渡产物 ,其年龄 ( 13 3Ma)应该是本区中生代区域挤压向区域拉伸转换的时间记录。
中文关键词:岩浆作用  时空结构  紫金山地区
 
The Temporal and Spatial Framework of the Mesozoic Magmatic System in Zijinshan Area and Its Geological Significance
Abstract:The Mesozoic magmatic system in Zijinshan area can be divided in to two subsystems, namely the Late Jurassic and the Early Cretaceous magmatic subsystems. The Late Jurassic magmatic subsystem was emplaced in upward succession at the center du- ring 157~≤141 Ma under intracontinental compression-orogeny, forming composite granite of the Zijinshan Superunit composed of medium-coarse-grained syenogranite of Jingmei Unit, medium-fine-grained monzogranite of Wulongshi Unit and fine-grained syenogranite of Jinlongqiao Unit. The fine-grained syenogranite of Jinlongqiao Unit is the differentiated lithofacies of this magmatic system, and can serve as the criteria for tin ore-prospecting in this area. The Early Cretaceous magmatic subsystem was formed during 128~94 Ma under regional extension, and exhibits a two-layer structure composed of the upper volcanic rocks and the lower intrusive rocks. During the period when volcanism was inactive (105 Ma), granodiorite porphyry invaded and was extensively buried in the depth of this area, resulting in large-scale Cu-Au mineralization. Volcanic domes and attitude of the superface of the buried granodio- rite porphyry in the Late Cretaceous magmatic subsystem can serve as the criteria for Cu-Au ore prospecting in the region. As detailed petrological study and temporal-spatial relationship show that the Chaixi monzogranite was the transitional magmatic product from the Late Jurassic magmatic subsystem to the Early Cretaceous magmatic subsystem, the age of 133 Ma of the Chaixi monzogranite should be the time record of transformation from compression to extension in this area.
keywords:magmatism  temporal and spatial framework  Zijinshan area
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