摘要
磷块岩中存在着大量硅质组分和硅质层。硅质矿物以自生石英、硅质条带、燧石结核、硅质胶结物和硅质交代物的形式产出。硅质胶结物有四种结构形式,在剖面和平面上与其它成分胶结物有一定的演变关系。硅化作用有众多的宏观和微观形态,硅化结果使P_2O_5含量大大下降。盆地型磷块岩硅化作用的硅源可能来自海底火山活动,台地型磷块岩硅化作用的硅源主要与陆源水的混合有关。
A lot of siliccous components and even siliccous rocks existed in phosphorusbcaring series. They appeared as authigenous quartz, siliceous band, chert coneretion, siliccous cement and silicified products.The texture of siliccous cements can be divided into four types: microquartz cement, microchalcedony cement, fine crystalline quartz filling void or rounding grain in pectinate form, and mediumcoarse quartz filling void.Compared with carbonate, phosphate and mud cement, the siliceous cement usually occurred in lower part of columnar section of phosphorite deposit,in deep water area of platform in plane.This may indicate the direction of phosphorite prospecting. There are various macro-and microshape textures of silicification in phosphorite deposit, such as banded, patchy, lenticular,organismpseudomorphic, mineral-pseudocrystal, replaced residual, antisequence texture and so on.The antisequence texture is similar to the first generation cement inthe form of pectination, but it is not earliest cement.Instead, it is later cement formed by replacement.The result of replacement reduced seriously the P_2O_5 content.
The siliceous components in basin type phosphorite mainly came from diagenetic differentiation of mudstone that is rich in silica and phosphate.Together with other evidences it indicates that the formation of phosphorite deposit may be associated with seafloor volcanism.The siliceous components in platform type phosphorite mainly came from mixing seawater with terrigenous water. It can be explained with the model of mixing water silicification proposed by L. P. Knauth in 1979.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1990年第1期46-55,T002,共11页
Acta Petrologica Sinica
关键词
磷块岩
硅质岩
成岩作用
Phosphorite
Siliceous rock
Diagenesis
Siliceous cement
Silicification in mixing water
