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本文根据近年内取得的资料,提出对滇东寒武纪早期磷块岩形成条件的认识,着重于沉积相带的划分:(1)磷块岩属半封闭海湾浅水型滨海相的潮坪沉积环境,有一系列浅水与暴露的相标志。(2)磷块岩的分布依附于沉积相。富磷矿赋存于潮间相带,而潮下“台盆”相带沉积有贫的厚层磷块岩。矿石结构既反映了沉积时水动力能量上的差异,也显示出不同的沉积环境:内碎屑结构具化学——机械特征,形成于强搅动环境中;凝胶状结构属化学沉积,形成于宁静低能环境中;球粒结构属于上两种结构的过渡产物。(3)磷块岩的岩性序列为:白云岩——磷质磷块岩、白云质磷块岩、硅质磷块岩——硅质岩。磷块岩矿床的贫富、厚薄、类型上有变化,主要反映在白云质、硅质两者配比不同。
Based on the data obtained in recent years, this paper puts forward the understanding of the formation conditions of phosphorite in the early Cambrian of the eastern Yunnan, focusing on the division of sedimentary facies: (1) Phosphorite is a tidal flat sediment of the semi-enclosed bay coastal facies Environment, with a series of shallow water and exposed phase signs. (2) The distribution of phosphorite is dependent on the sedimentary facies. Phosphate-rich ore occurs in the intertidal facies belt, while the subtidal “basin” facies sediments poor, thick phosphorite. The ore structure not only reflects the difference in hydrodynamic energy during deposition, but also shows different depositional environments. The inner detrital structure has chemical-mechanical characteristics and forms in a strong agitating environment. The gel-like structure is chemically deposited and forms in Quiet and low energy environment; pellet structure belongs to the transition between the two products. (3) The lithologic sequence of phosphorite is dolomite-phosphorite, dolomitic phosphorite and siliceous phosphorite-siliceous rock. Phosphorite deposit rich and poor, thickness, type changes, mainly reflected in the dolomitic, siliceous ratio of the two different.