准噶尔盆地腹部二叠系火山岩岩石学及演化分异研究

STUDY ON PETROLOGY AND MAGMA EVOLUTION OF THE PERMIAN VOLCANIC ROCKS IN CENTER REGION OF JUNGGAR BASIN

准噶尔地区晚古生代火山岩及岩浆演化研究主要集中于准噶尔盆地周边褶皱造山带,盆地腹部地区因被中、新生代连续沉积覆盖,研究较少.通过对准噶尔盆地腹部二叠系火山岩岩石学特征及岩浆分异演化地球化学特征研究,得到如下认识:①准噶尔盆地腹部二叠系火山岩岩性从下向上逐步由玄武岩演化成为安山岩,表明岩浆不断地从基性向酸性演化;②通过分异指数、SI(固结指数)、地球化学及火山岩K2O和Na2O含量随深度变化关系分析,得知该区火山岩向富含碱铝硅酸盐方向演化;③准噶尔盆地腹部二叠系火山岩岩浆从基性向中酸性及不断富碱分异演化的结论,与二叠纪准噶尔处于大洋消亡、闭合阶段后期,碰撞活动趋于减缓的整体构造背景相吻合.

The study of late Paleozoic volcanic rocks and magma evolution in Junggar Basin was concentrated on the fold mountain belts around. This is due to lacking rock samples in the central region where lied with continuous sedimentary layer from Mesozoic up to now. This paper pays attention on petrology and magma evolution of the drilled rock specimens from the Center Region of Junggar Basin. It has been suggested that three conclusions as below： （1） Permian volcanic rocks in Center Region of Junggar Basin mainly evolved from basalts to andesites vertically; （2）based on the study of differentiation index, consolidation index（SI）, geochemistry and the content of K2O（%）和 Na2O（%） with depth, this paper concludes that the volcanic rocks in Permian Junggar Region evolve with the trend of rich aluminosilicate; and （3） differentiation and evolution of the volcanic rocks in Permian Junggar Region fits well with general tectonic settings, which was late stage of an closed ancient ocean and collision had become mitigation.