喀喇昆仑阿克塔河地区龙山组火山岩地球化学特征及构造环境分析

喀喇昆仑阿克塔河地区中侏罗统龙山组地层内所见火山岩夹层,岩石类型为粗安岩。岩石富碱、高钾,属碱性钾玄岩系列火山岩;镁铁质相对富集,反映火山岩岩浆为上地幔部分熔融产物;微量元素呈现强不相容元素强富集、弱不相容元素弱富集特征,指示火山岩源区为富集地幔;LREE/HREE值较高,属轻稀土富集型,具大陆边缘钾玄岩的稀土配分形式。结合区域地质背景及构造环境判别,本区粗安岩形成于板内拉张环境。

Geochemical Characteristics and Tectonic Environment Analysis of the Longshan Volcanic Rock in Aketahe Area,Karakoram

Volcanic rock intercalation is found in the Middle Jurassic Longshan formation in aketahe area,Karakoram,and the rock type is trachyandesite.The rocks are rich in alkali and high potassium,belonging to alkaline shoshonite series volcanic rocks;the mafic rocks are relatively enriched,reflecting that the volcanic magma is the product of partial melting of upper mantle;the trace elements are characterized by strong enrichment of strongly incompatible elements and weak enrichment of weakly incompatible elements,indicating that the source area of volcanic rocks is enriched mantle;the LREE/hree value is high,belonging to LREE enriched type It has REE distribution pattern of shoshonite in continental margin.Comprehensive study shows that the formation environment of the Longshan volcanic rocks in aketahe area is marine environment under the background of local extensional structure.