【摘要】 元素和Pb-Sr-Nd同位素地球化学示踪结果表明,西藏芒康盆地内拉屋乡组高钾火山岩是在转换压缩引起的陆内俯冲背景下产生的,其可能源区为EMII型富集地幔端元。高场强元素Nb和Ta出现明显的负异常,表明在该火山岩源区内有陆壳物质的加入。稀土元素模拟结果显示岩浆源区成岩过程中有单斜辉石、斜长石和石榴子石的分离结晶。更多还原

【Abstract】 Elemental and Pb-Sr-Nd isotopic geochemistry tracing indicates that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin were derived from an EMII enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs (such as Nb and Ta) made clear that there was an input of continental material into the mantle source. REE numerical modeling suggests that the REE patterns of the residual magma would be similar to the high-K volcanic rocks with SiO2<65% in the Mangkang basin if a standard intermediate magma underwent 72% fractional crystallization with a crystallized residual of clinopyroxene (60%), plagioclase (25%) and garnet (15%), suggesting the onset of fractional crystallization of clinopyroxene, plagioclase and garnet in the evolution of magma.更多还原