Study On Geology And Geochemistry Of Wheathered Phosphate Deposits, South China

Weathered phosphate is a new industrial type of phosphate. Compared to original phosphate, Weathered phosphate, not only has high grade but also two outstanding qualities:First,owing to carbonate decomposition after the phosphate ore weathered, the content of detrimental impurity, say MgO, which is not got rid of through processing, would decline, and therefore, made the phosphate enriched naturally; Secondly, because of silicate clay material cemented by carbonate decomposing, after work like scrubing and desliming, the content of R₂O₃ type detrimental impurity, would decline, and then the phosphate meets the high concentration production requirements. Therefore, Weathering phosphate is not equal toâ… grade rich phosphate as people often thought of. Thanks to the low content of detrimental impurity, the value of it is better thanâ… grade rich phosphate. Therefore, the study of weathered phosphate is very necessary.Weathered phosphate mainly distributes in districts, like Dianchi ,Yunnan Province, Dongshanfeng, Hunan and Hubei province, as well as Sichuan, Guizhou, Guangxi and other provinces. Source of weathered phosphate includes phosphorite forming strata in different geologic ages, such as Doushantuo Formation of Upper Sinian, Meishucun formation of Lower Cambrian, as well as Late Paleozoic and Mesozoic strata. According to the occurrence, the weathered phosphate deposits, are divided into two kinds of genetic type: Supergene weathering type and weathering and leaching residual type, of which the former type is always characterized with associated originated ores and high grade, while the latter one is without originated ores and grade is lower than the former. Ores of weathered phosphate, are mainly with textures of pore, sandy formation cutting, chiltern sandy formation cutting and shaliness sandy formation cutting and structures are predominated with secondary structure such as obvious earthy structure and honeycomb structure. There are no carbonate minerals existing in weathered phosphate ores, minerals of which are mainly secondary, such as devonite, secondary apatite as well as calcium aluminum phosphate minerals. Based on the analysis of major and trace elements and REE of weathering phosphate ore samples, the characteristics in weathering phosphate ores are as follows: In terms of chemical composition, compared to the originated ores, weathering phosphate ores are riched in P₂O₅ and the contents of MgO, CaO and CO₂ decline while the Fe₂O₃ and Al₂O₃ inccrease; in the aspects of trace elements, after standardization of mantle rocks, they are generally enriched in alkali metals, alkaline earth metals, halogens, and radioactive elements while depleted in mantle elements; as for REE, the total amount of REE are relatively high, with enrichment of LREE, loss of HREE, as well as common Eu anomalies.