HAN xue¹, YE Tai-ping^2*, CHEN Ren¹, WANG Min¹, CHEN Jian-shu¹, LIU Ai-min¹, MO Bing³

(1.Guizhou Academy of Geological Survey, Guiyang 550081, China;
2. Guizhou Central Laboratory of Geology and Mineral Resources, Guiyang 550018, China;
3. Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China)

Abstract: In the classification of deposits, the process and controlling factors of mineral precipitation of the cave phosphorus deposit are not analyzed. In this paper, by using the combination of optical microscope and double beam scanning electron microscope, ore structures of the Banqi phosphorite deposit in Guizhou Province have been studied. It is found that ores of the cave phosphorus deposit contain mineral components of apatite, rhodochrosite, pyrolusite, and a small quantity of siderite, authigenic quartz and calcite, etc., and have dominant colloidal, banded, ctenoid, and honeycomb structures. It is inferred from the high similarity of the mineral structure characteristics of the Banqi phosphorite deposit and micro flow stones in Karst caves of the phreatic zone that the deposition of phosphorus and manganese in the cave phosphorus deposit was actually resulted from the decrease of phosphorus and manganese solubilities caused by the change of pH value of water medium. After comparing with the formation mechanism of calc-sinter, the apatite formed by the precipitatation of phosphorus due to the change of pH value of water medium has been named "phos-sinter".

Keywords: The cave phosphorus deposit; ore structure; precipitation process; Banqi, Ceheng

ACTA MINERALOGICA SINICA Vol. 40, No.6, 2020, page 758-764