青藏措勤盆地下白垩统则弄群火山岩岩石地球化学特征

青藏高原措勤盆地早白垩世火山活动十分强烈，则弄群火山岩主要分布在措勤盆地中央隆起带的冈底斯构造岩浆岩带中，则弄群以安山岩—英安岩—流纹岩钙碱性系列火山熔岩及火山碎屑岩为主，盆地北部坳陷带中火山活动相对较弱，见有少量玄武安山岩、安山岩。则弄群火山岩岩石化学、地球化学特征分析表明，该火山岩形成于岛弧区构造环境中，这与古特提斯洋壳沿雅鲁藏布江结合带向北俯冲作用有关

LITHOGEOCHEMICAL CHARACTERISTICS OF THE VOLCANIC ROCKS IN THE EARLY CRETACEOUS OF ZENONG GROUP IN CUOQIN BASIN OF QINGHAI-XIZANG AREA

The volcanic activities were extensive in Cuoqin Basin of Qinghai Xizang plateau during the Early Cretaceous. The volcanic rocks of Zenong Group in the Early Cretaceous occurred mainly in Gangdisi volcanic rock belt in the central uplift of the basin. The Zenong Group was dominated by calcalkaline volcanic suite (andesite dacite rhyolite) and pyroclastic rocks. The volcanic activities were light in the northern depression with a little basaltic andesite and andesite. The lithochemical and lithogeochemical analyses of the Zenong Group show that the volcanic rocks formed in the tectonic enviroment of inland arc, which is related to the palaeotethys ocean crust subduce towards north along the Yarlung Zangbo river.