西秦岭中生代花岗岩类岩浆作用及成矿

西秦岭是我国重要的有色金属和贵金属成矿省。本文论述了该地区主要矿床的空间分布特点;分析讨论了主要成矿带和矿集区中的矿化组合及其与花岗岩类的空间、时间和成因关系。提出该地区大规模成矿作用出现在220~100Ma之间,最高峰值为170Ma左右。花岗岩类岩浆作用及成矿相应的地球动力学背景为陆—陆碰撞造山运动的晚期表现为一侧陆壳向另一侧陆壳之下的俯冲叠置过程。中生代花岗岩类在成因上与陆壳的俯冲有联系,大多属高钾钙碱性系列。部分为钾玄武岩系列,它们来自加厚的下地壳。部分花岗岩类具壳幔混合成因。一个地区花岗岩类的Pb-Sm-Nd同位素主要受该地区源岩基底地层的控制,因此同一地区花岗岩类具有相近的Pb-Sm-Nd同位素特征。基底地层对花岗岩类的分布成因类型、有关的成矿作用具有重要的控制作用。依据花岗岩Sr和Yb的含量,本文将该地区花岗岩类大致分为两类:埃达克岩和喜马拉雅型花岗岩。铜钼矿大都同埃达克岩有关,而两类花岗岩均可形成金矿。

Mesozoic Granitoid Magmatism and Mineralization in West Qinling

The paper introduced the distribution of the important mineral deposits in the study area, and discussed relationships between mineral assemblage and granitoid at space, period and genesis. The author points out the intensive and large scale mineralization occurred at 220~100Ma, the peak at 170 Ma. The geodynamic settings of mineralization and granitoid magmatism should be occurred at the late period of orogenic movement of intercontinental collision, which was a subduction and superposition process of one continental crust down another continental crust. In genesis, Mesozoic granitoid occurred with intercontinental subduction, the most are high-K calc-alkaline series, some are K basalt series which came from thickened crust, and the other granitoid should the crust-mantle mixing type. Pb-Sm-Nd isotope are controlled by basement strata of source rock in a certain area, therefore, the characteristics of granitoids in same area should be similar. The basement rock should be an important factor controlling granitoid type and related mineralization. According Sr and Yb content of granitoids in study area, they are grouped roughly to 2 type: adakite and Himalayan type granite. Most Cu-Mo deposits are related with adakite, but gold may occurred from these two type granite.