新疆西准地区古生界火山岩岩石特征及其与金矿化的关系

PETROLOGICAL CHARACTERISTICS OF PALAEOZOIC ERATHEM VOLCANIC ROCKS FROM WESTERN JUNGGAR,XINJIANG AUTONOMOUS REGION AND RELATIONSHIP BETWEEN THEM AND GOLD MINERALIZATION

新疆西准噶尔地区三个构造层各有其相应的火山建造:前泥盆系为基底构造层,细碧角斑岩建造位于该层加里东期俯冲碰撞型蛇绿杂岩带内.中晚泥盆系至早石炭系为弧后盆地构造层,西区火山岩为张裂早期形成的钙碱性岛弧火山岩,安齐火山岩带石炭系火山岩为亚碱性低钾拉斑玄武岩.晚石炭——二叠系为陆相火山——磨拉石沉积构造层,其中的火山岩以壳源的流纹岩为主,含少量碱性大陆玄武岩.石炭系太勒古拉组玄武岩是西准最重要的矿源层,哈图金矿即位于该层的破火山口中,为火山晚期热液成因.

In the Western Junggar,Xinjiang,each of the three tectonic sequences——basement,island arc-back basins and continental facies volcano—molassesediments has its correspondent volcanic formation.The basement consists of pre-devonian stratum.The spilite-keratohyre formation is included in the Caledoniansubduction and collision ophiolite complex belt.The island arc-back basinsformed during middle-late Devonian and early Carboniferous.The Devonian-Caboniferous volcanic rocks in the west area of the assemblage,which are closeto calc-alkali island volcanic rocks,formed during the early stage of the tensionof the island arc-back basins.The Carboniferous volcanic rocks in the Angivolcanic rock belt,however,are subalkali,and low-K tholeiitic basalts.Theyare of the transitional basalt of rift belt,and the eruption environment was inthe island arc-back basins.Most of the volcanic rocks in the continental faciesvolcano-molasse sediments,which developed during the late Carboniferous andPermian,is rhyolite driven from continental crust,while a few of that isalkalic continental basalt.In the gold minerogenetic region of Western Junggar,more than 70% ofgold deposits and mineralized places occur in the Carboniferous volcanic layers.The basalt layer of the Tailegula formation is the most important gold minero-genetic layer in Western Junggar.Hatu gold deposit,which precipiteted fromhydrothermal fluid of the late stage of the volcanism,occur in the caldera,andits age is in the range of 310-340Ma.