Keywords: 
• authigenic monazite /
• Precambrian /
• sedimentary rocks /
• biomineralization /
• rare earth elements

Abstract: The authigenic monazite have been discovered for the first time in the Shisanlitai Formation, Sinia System of Precambrian sedimentary rock from Dalian area. That was inspired by the discovery of auhtigenic galena in the Gejiatong Formation. There are listed in this paper same examples of North China, where are abnormal high contents of Ce and REE in the Precambrian sedimentary rocks being expected to find authigenic monazite either in above areas or to offer the possibility using U,Th-Pb isotopic method for geo-age determination. This paper introduces new data of authigenic monazite, which recently have been found in Mid-Proterozoic strata of the Ming Tombs District, Beijing. The electron scattered forms of authigenic monazite are quiet different with crystalline forms of magmatic, metamophzeic, and placer monazite grains. This paper recognizes that high contents of REE, especially, higher LREE of Proterozoic mudstones are deposits near old continental crust. The statistical data of La+Ce+Nd, Yb+Y, and Sm+Gd+Dy ratio and plotting in a triangle diagram with Preterozoic mudstones of the Ming Tombs District, Beijing, Golden Pebble Beach, Dalian, and Liaoning Province shows that those samples with more La+Ce+Nd belong to near old continental crust deposits. This paper compares for the first time with the Proterozoic sedimentary rocks of North China and phosphate rocks of Sinian System of South China showing the later plotted points far away from La+Ce+Nd end point due to the phosphorus element from ocean upwelling. According to analysis of sedimentary environment of the Shisanlitai Formation, Sinian System of Dalian the authigenic monazite should be formed by biomineralization processes. It is demonstrated that local sub-reducing environment under entire oxidation environment created authigenic monazite formation, based on which a reef-back lagoon biomineralization model has been established in this paper. Meanwhile, it is supposed that the Precambrian sedimentary rocks with rich rare earth elements of North China might be the ore-source beds of the huge rare earth mineral deposits of the Baiyun Obo, Inner Mongolia.