REE characteristics and genesis of alkaline-rich porphyry, Yunnan Province

来源期刊：中南大学学报(英文版)2001年第1期

论文作者：LAI Jian-qing WU Cheng-jian PENG Sheng-lin

文章页码：45 - 49

Key words：alkaline-rich porphyry; REE; genesis; Sr isotope; Yunnan

Abstract: The Yunnan Himalayan alkaline-rich porphyry occurs as a compound rock belt and consists of cal-ca-alkalic, alkaline and peralka line intrusions. Its origin is in debate. The paper deals with its origin by studying rock′s REE and Sr isotope. Although the rocks are different in their REE contents varyingfrom77.53μg/g to 1 798.3μg/g, they have very similar features in REE parameters. On the triangalar diagram of REEs, the sample dots are concentrated on the end area of light REEs, representing a product of low-degree melting of upper mantle or lower crust materials. The initial　87Sr/86Sr values of rocks vary between 0.706 4and 0.709 8, showing a feature of mantlecrust mixed source. Moreover, REEs show a logarithmic linear positive correlation between them. This type of correlation strongly supports the fractional-partial melting model.The result of geochemistry inversion shows that the source rock of alkaline-rich porphyry is plagioclase-bearing harzburgite and of mantle-crust mixed type. At the early state of melting, some crust components of the source rock were partiallymelted into intermediate-acidic magma; with the crust components consumed, the magma evolved to basic.