青藏高原北羌塘榴辉岩质下地壳及富集型地幔源区——来自新生代火山岩的岩石地球化学证据

Enriched upper mantle and eclogitic lower crust in north Qiangtang, Qinghai-Tibet Plateau: petrological and geochemical evidence from the Cenozoic volcanic rocks.

利用岩石地球化学的方法 ,研究了北羌塘新生代火山岩。结果表明 ,北羌塘第三纪火山岩可区分为碱性 (钾玄岩质 )和高钾钙碱两套不同的火山岩组合 ,它们分别起源于一个特殊的、不均一的富集型上地幔和一个加厚陆壳的榴辉岩质下地壳。由于青藏陆块之下软流层物质的上涌而形成幔源碱性岩浆活动 ,而幔源岩浆在 Moho面的底侵作用又为下地壳中酸性高钾钙碱系列火山岩的起源提供了热动力条件。

Using the petrological and geochemical method, the Cenozoic volcanic rocks collected from north Qiangtang, Qinghai Tibet plateau were dealt with in this paper. The research results indicate that the Tertiary volcanic rocks can be devided into two different associations: alkaline (shoshonitic) series and high potassium calc alkaline series. They originated from a special inhomogeneously enriched upper mantle and a eclogitic lower crust, respectively. It shows that the north part of Qinghai Tibet plateau develops a enriched mantle source and a eclogitic lower crust in Cenozoic period at the specific tectonic setting of plates collision. This recognization is significant for further discussions about the uplift mechanism and continental dynamics of the Qinghai Tibet plateau.