甘肃柳园地区花岗质岩石时代及成因

The Age and Origin of the Liuyuan Granitoid, Northwestern Gansu

柳园花岗质岩石在空间上与榴辉岩共生，是探讨区域构造演化的关键岩石类型之一。岩石学、地球化学和锆石Ｕ－Ｐｂ同位素测年研究表明，这套花岗岩侵入时代系新元古代（８８０Ｍａ），具有先存地壳与幔源岩浆混合的特点。推断系陆陆碰撞地壳增厚的产物。

The Liuyuan granitoid, associated with eclogite, serves as a key to understand the regional tectonic evolution. U-Pb single zircon gives an upper intercept age of 880±31Ma. The REE pattern shows LREE_enriched and Eu negative anomaly, and the whole_rock sample gives εNd value of -0.9 at 880 Ma and Nd model age of 1530 Ma related to a depleted mantle. The authors conclude that the Liuyuan granitoid crystallized at Neoproterozoic of 880 Ma and was derived from a source composed of the mixture of a deep_seated Paleoproterozoic crust_derived (probably 1800～2200Ma) and a mantle_derived magma. It is inferred that the granitoid was formed against the setting of continental_continental collision.