摘要
攀西裂谷复合分异的火山岩系及双峰式火山岩套,具有壳幔混染成因特点。火山岩的平衡矿物共生组合类型受二次岩浆房的埋藏深度控制,而TiO_2、LREE及大离子亲石元素的富集受低压条件下的液体不相容性分离作用和陆壳的同化混染作用控制。
Complex differentiated volcanic series of the early, middle and late eruption stages in the Panzihua-Xichang ancient rift originated from secondary magma chambers at deep, medium and shallow levels of the upper mantle, experienced fractional crystallization in the chambers, then were contaminated and assimilated by the continental crust and displayed some immisibility. The depth of and the pressure in the secondary chambers are responsible for mineral associations in equilibrium, in each of the three rock series from the bottom to the top: the Dongchuan tephrite formation of Ne-norm alkali basalt series→ the Emeishan basalt formation of Hy-norm alkali basalt series→ the acid volcanic rock formation of alkali series. The enrichment of TiO2, LREE and hydromagmaphile elements is attributed to the immiscibility separation of liquids, and continental crust contamination at low pressures (below 5kbar). Thus, the evolution of the magma is characterized by negatively correlated bimodal and complex differentiation. The REE distribution patterns indicate that the magma was derived from an enriched mantle.
出处
《地球化学》
CAS
CSCD
北大核心
1989年第2期158-166,共9页
Geochimica
