滇西凤庆习谦泥盆系温泉组地层新认识

NEW UNDERSTANDING OF THE DEVONIAN WENQUAN FORMATION IN FENGQING,WESTERN YUNNAN

昌宁—孟连结合带是地质学研究的热点地区,泥盆系温泉组对研究其构造背景及地质演化意义重大。习谦温泉组以黑云石英片岩、云母片岩和浅变质砂岩为主,夹少量千糜岩、变粒岩、硅质岩、含构造角砾的千枚质碎裂岩、碳质板岩等,原岩恢复后为石英砂岩、粉砂岩、粉砂质(泥)页岩、含碳质层,夹薄层硅质岩组合。野外研究及选取其中6件样品进行岩相学、岩石地球化学分析、构造背景分析及原岩恢复剖面对比研究,认为其可对比泥盆系温泉组。印支期习谦地区温泉组地层存在浅变质改造作用;原岩沉积于洋盆初始化阶段被动大陆边缘大陆斜坡—半深海环境;与西侧更戛向阳寺组地层沉积物源一致,环境不同,沉积时水位体系交替变化。

The Changning-Menglian belt has been a research focus area for geologists, because the Devonian Wenquan Formation in this area is of great significance to the study of the tectonic and geological history. The Wenquan Formation in Xiqian is mainly composed of biotite quartz schist, mica schist and metamorphosed sandstone, with a small amount of phyllonite, granulite, siliceous rocks, and massive cataclastic rock containing tectonic breccia and carbonaceous slate. The protolith includes quartz sandstone, siltstone, silty(mud) shale,carbonaceous layers, and thin layers of siliceous rock. Through field study and analysis of six samples for petrographic, geochemical, and tectonic data, it is considered that these rocks can be correlated with the Devonian Wenquan Formation. According to the data, the Devonian Wenquan Formation in the Xiqian area was metamorphosed during the late Permian and Indo-China period. The protolith was deposited in continental-slope and bathyal environments on a passive continental margin. Its provenance is similar to, although its depositional environment is different from, the Xiangyangsi Formation in the Gengga area to the west.