【摘要】 潜花岗班岩为火山颈相,其锆石U-Pb同位素年龄为32±0.2Ma。岩石具有富Al、Th和LREE特征,Eu负异常不明显,表明不是由基性浆演化而成,而是由加厚陆壳底部熔融形成的。结合区域构造、沉积记录和火山岩组合特征,潜花岗斑岩形成于大陆拉张环境。潜花岗斑岩年龄的确定制约了新生代沉积地层的年代,同时也为藏北地区陆内拉张时代的确定提供了依据。更多还原

【Abstract】 Hidden granite porphyry is of volcanic neck facies and gives isotopic age of zircon being 32±0.2 Ma.The rock is characterized by enrichment of Al,Th and LREE and shows indistinctive negative anomaly of Eu.This indicates that the porphyry is resulted from melting of thickened continental crust at the bottom rather than from basic magma.With regional structure,sedimentary records and the features of volcanic rock association being taken into consideration,we can conclude that the rock formed in the extensional environment of continent.Dating of the hidden granite porphyry confines the age of Neozoic sedimentary stratum and also provides a basis for timing of intracontinental extension in northern Tibet.更多还原