Geochemical evolution of the Doushantuo economic phosphorite in Central Guizhou, South China: Quantified multi-stage metallogenic process.

[Display omitted] • The Doushantuo phosphorites are petrographically subdivided into pristine and reworked type. • Major element results suggest a concentration of P from pristine to reworked phosphorites. • Mass change calculation reveals the enrichment and loss of different elements. • A three-stage model of chemical/biochemical enrichment, hydrodynamic reworking, and chemical leaching is proposed. • Such multi-stage metallogenic processes contribute to enrichment of P and loss of impurities. Economic phosphorite from Ediacaran Doushantuo Formation is the first true phosphorite giant and represents the onset of the Precambrian-Cambrian global phosphogenic event. The Doushantuo phosphorite may have deposited during the early-middle Ediacaran (ca. 632–574 Ma) according to the latest radiochronological data. Petrographically, in central Guizhou, it can be subdivided into two types of lithofacies: pristine phosphorite (micritic phosphorite, phosphatic shale, banded phosphorites) and reworked phosphorite (intraclastic phosphorite, vuggy intraclastic phosphorite, unconsolidated phosphorite). Geochemical data show that chemical/biochemical enrichment is the most effective process to condense the phosphatic sediments and obviously improve the grade of P 2 O 5 (can reach 38.8 wt%). Hydrodynamic reworking may not play an important role in the further enrichment of P 2 O 5 content but effectively got rid of SiO 2 and Al 2 O 3 components in phosphorite by the removal of lighter terrigenous particles and clays. Mass change calculation shows that Ca and Mg are heavily depleted in the chemical leaching process, implying it is a key process to upgrading the quality of phosphorite by separating the carbonate constituents from phosphorite. Therefore, a multi-stage metallogenic model of chemical/biochemical enrichment, hydrodynamic reworking, and chemical leaching is proposed, quantified the composition changes and elucidated the constrained factors in the formation of high-graded phosphorite. Such a metallogenic process effectively produced high-quality phosphorite deposits and bring great benefits to metallurgy. [ABSTRACT FROM AUTHOR]