ZHOU Ke-lin1,2, FU Yong1*, YE Yuan-mou1, LONG Ke-shu1, ZHOU Wen-xi3
(1. College of Resource and Environment of Guizhou University, Guiyang 550025, China;
2. Geological Party 117, Guizhou Provincial Bureau of Geology and Mineral Exploration and Development, Guiyang 550018, China;
3. Geological Party 111, Guizhou Provincial Bureau of Geology and Mineral Exploration and Development, Guiyang 550018, China)
Abstract: The Early Cambrian is another important phosphorus-forming period besides the Ediacaran Doushantian Period. The Early Cambrian phosphorites are widely distributed in Asia, Western Europe, North America, and Oceania. The extensively distributed phosphorite in Guizhou Province is an important part of this event. Two typical phosphorite profiles including the Gezhongwu profile in Zhijin County and Bahuang profile in Tongren City of Guizhou Province have been selected in this paper for studying and transversely comparing their sedimentary characteristics, total REE contents (ΣREY) and P2O5 contents, and their correlations with indexes of redox sensitive elements. The results show that there is a relatively consistent variation trend between the total REE contents (ΣREY) and P2O5 contents of rocks in the longitudinal direction of both the Gezhongwu and Bahuang profiles. Neither the total REE contents (ΣREY) nor the P2O5 contents have synergistic changes with indexes of redox sensitive elements. The linear regression of ΣREY and P2O5 contents shows that there is a significant positive correlation between the ΣREY and P2O5 contents, implying a close genetic connection between each other. In addition, there is no obvious correlation between the index of redox sensitive elements and the respective total REE contents (ΣREY) and P2O5 contents, indicating that the REE enrichment is not mainly controlled by the redox condition of sedimentary medium. The NASC-normalized REE+Y patterns of samples from the Gezhongwu and Bahuang profiles are characterized with “hat shape” and relatively enrichment of the MREE. This is because ions of the MREE are easier to substitute calcium ions in the apatite lattice than other REE ions in the diagenetic process of the phosphorite, as the ion radii of MREE are more similar to the calcium ion radius than those of other REE.
Keywords: phosphorus-rich rocks; the REE enrichment; diagenesis; redox conditions; Guizhou
ACTA MINERALOGICA SINICA Vol. 39, No.4, 2019, page 420-431
