川西北松潘-甘孜地块大石包组玄武岩成因及其形成构造背景

Petrogenesis and tectonic setting of Dashibao Group basalts from Songpan-Ganze block,northwestern Sichuan province,China.

川西北松潘-甘孜地块内二叠世大石包组玄武岩富集大离子亲石元素和高场强元素,具有与洋岛玄武岩相似的地球化学性质,形成于大陆板内环境。通过与典型峨眉山玄武岩之地球化学组成的对比研究,认为大石包玄武岩与峨眉山玄武岩中的高钛类玄武岩性质相同,两者具有一个共同的成因,即部是峨眉山地幔柱活动的产物。由此推测峨眉山玄武岩不仅分布在扬子地块内部,向西还有一定的延伸,同时暗示了峨眉山地幔柱头部可能具有比现在所认识的更大的规模。

The early late Permian Dashibao basahs, which distributed at the Songpan-Ganze block, NW Sichuan Province, display significant enrichment of large ion lithophile elements and high field strength elements, and similar to oceanic island basalts and the Emeishan flood basahs. These geochemical characteristics are comparable with the high-Ti Emeishan basalts from Binchuan, suggesting that they were formed within continental plate and were resulted from the Emeishan mantle plume. This implies that the Emeishan flood basalts distributes beyond the Yangtze block, has extended to the Songpan-Ganze block and the Emeishan plume head is bigger than that estimated before.