云南香格里拉县洛吉地区基性杂岩的地球化学特征

云南香格里拉县洛吉地区出露由洛吉组玄武岩和基性岩墙群组成的基性杂岩,其母岩浆起源于亚碱性-碱性系列的拉斑玄武系列,地球化学特征表明该基性杂岩体形成于构造变动的复杂环境,并与不同源区岩浆混合及一定程度的壳幔混染有关,其中的碱性玄武岩与基性岩墙属具有相似性OIB玄武岩,是深部地幔石榴石橄榄岩与尖晶石橄榄石小部分熔融的产物,形成于大陆内或陆缘裂谷转变为盆缘造山带的过渡环境,亚碱性玄武岩属于E-MORB并有向OIB过渡趋势,由源区相对浅的尖晶石橄榄石熔融形成,为洋中脊向大陆过渡环境的蛇绿岩质分子,属甘孜-理塘结合带残余产物。

Geochemical Characteristics of Mafic Rocks in the Luoji Area, Shangri-La County, Yunnan Province

Abstract: At the Luoji area of Shangri-La county in Yunnan Province, a suit of mafic rocks composed of Luoji Fm. basalts and basic dikes are outcropped, of which the parental magma derived from alkaline and sub-alkaline tholeiite series. Geochemical characteristics suggest that the mafic rocks formed in a complex environment of tectonic movement, associated with a mixture of magma from different source areas as well as crust-mantle hybridization of some degree. In this area, alkaline basalts and basic dikes belong to OIB basalts, which are the products of deep mantle garnet peridotite and spinel peridot partial melting, formed in continent interior or a transition from a continental marginal rift to an orogenic belt at a basin margin. Sub-alkaline basalts belong to E-MORB basalts and have a trend of transforming to OIB basalts. They are the products of relatively shallow spinel peridot melting, and reflect the Mid-ocean ridge turning into continent, which are the composition of ophiolite and residual products of the Gaze-Litang suture belt.