秦岭造山带东江口花岗岩体群的地球化学研究及其构造环境

陕南秦岭造山带东江口花岗岩体群含磁铁矿极高,并含镁质黑云母,稀土元素负铕异常极不明显,氧同位素和锶初始比值都较低.因此,东江口岩体肛为一典型的Ⅰ型花岗岩.用数学地质和图解法与全球重要造山带花岗岩的地质地球化学特征类比后发现,本岩体群花岗岩为碰撞型花岗岩,是秦岭造山带碰撞造山的产物.据此分析了晚古生代秦岭造山带的演化.讨论了花岗岩成因类型与其构造环境的关系,认为碰撞型花岗岩既可是S型花岗岩,也可以是Ⅰ型花岗岩,这主要与花岗岩的源区岩石有关.而与构造环境没有必然的关系.

THE GEOCHEMICAL STUDY OF DONGJIANGKOU GRANITIC PLUTON GROUPS AND ITS TECTONIC ENVIRONMENT IN QINLING OROGEN, SOUTERN SHAANXI PROVINCE

Dongjangkou granitic pluton groups in Qinling orogen, Southern Shaanxi Contain extraordinarily high content of magnitite, with less amount of magnesium-bearing biotite and weak nagatiue Eu anomaly of REE. Therefor ,Dongjongkon pluton groups are typocal of I-type granite. The comparison of geological and geo-chemical characteristics of the granite with that of the granites in worldwide famous orogens shows that the granite in the pluton groups are collision-type granites resulting from the collision and orogenic processes. The paper also deals with the evolution of Qinling Orogen in Later Palaeozoic Era. The discussion on the relationship between the genetic types of granites and their tectonic environments has concluded that the collision -type granites may be S-type granites or I-type granites,mainly associated with the rocks in the granite source areas,and not necessarily with the tectonic environment.