区域岩石圈组成和热状态对岩浆作用和成矿的制约——以秦巴地区为例

遵循区域岩石圈系统的组成和状态制约区域各类地质—地球化学作用过程的性质和特征,以及各类地质—地球化学过程引起的物质分异和循环反映区域岩石圈发展和演化的构想,分析了秦巴地壳的化学和岩石组成特征及岩石圈的高热流状态,并据之阐明秦巴花岗岩类多具有Ⅰ型和Ⅰ—S混合型特征及该区缺乏与花岗岩类有关的典型岩浆期后热液矿床的原因,同时由该区花岗岩类岩石多具有黑云母组合和角闪石组合脱水熔融特征,揭示了多数花岗岩浆形成的较高熔融程度及有大量未经风化沉积旋回的岩浆岩加入了岩浆的源区,从而为秦巴上、下地壳化学成分差异小、物质分异弱找到了较合理的解释。本例表明在区域成岩和成矿研究中,区域岩石圈组成和状态的分析具有重要意义。

Constraints of Regional Lithospheric Constitution and Thermal State on Magmatism and Ore-forming Processes:as an Example of Qinba Area

The crust of the Qinling region is characterized by low contente of the chemical clemente related to granites, and a larger proportion of metamorphosed volcanic rocks and TTG gneisses. The lithospheric heat flows are high both at present and in the past. Under such con-ditions granitic magmas could be generaled not only by higher partial melting of sedimentary and felsic igneous rocks, but also with hornblende-and biotite-bearing metamorphosed igneous rocks as the sources. This resulte in that most of the granitoids in the region are the I-type and l and S transitional type, more basic in chemical composition with lower initial "Sr/^Sr ratio, relatively poor in ore-forming clemente, and associated with no past - magmatic hydrothermal deposits. The smaller difference between the upper and deep crustal compositions in the region can also be ascribed to the higher partial melting of the crustal rocks. This exam-ple emphasizes the significance of studing the regional lithosphere during making researches on rock-forming and ore -forming processes.