摘要
CCSD PP3超镁铁岩表现为高 Mg 和 Cr,低 Ca 和 Al 特征,是中国东部和超高压变质带上极其罕见的亏损地幔岩,通过地球化学和矿物学和 Re-Os 同位素研究发现岩石来自古元古代岩石圈地幔,并在地幔浅部尖晶石相条件下发生部分熔融,最近一次部分熔融作用发生在中-晚元古代,后经岩石圈厚度加大、拆沉或深俯冲过程,岩石转变为石榴石橄榄岩。
The mantle rocks from the CCSD PP3 drilling cores in the Sulu UHPM belt are characterized by high contents of Mg and low A1 and Ca,suggesting a much highly depleted mantle rocks than those in the east of China.Geochemical,mineralogical and Re-Os isotope data indicate that the mantle rocks in PP3 were originated from early Proterozoic lithospheric mantle and partial melted at shallow depth under spinel facies during medium-late Proterozoic time.The spinel facies peridotites were transformed into garnet facies peridotites,due to the deep subduction during the collision between the Yangtze and the North China blocks.