Mechanisms of Initial Enrichment of Organic Matter and Metallogenic Elements in Black Rock Series: Evidence From the Lower Cambrian Zhalagou Formation, Eastern Guizhou, China

ABSTRACT Black rock series enriched in organic matter and metallogenic elements are potential source rocks for Mississippi Valley‐Type (MVT) Pb–Zn deposits, yet their syn‐sedimentary co‐enrichment mechanism remains unclear. This study uses TOC, major/trace elements, REE, TIMA, and SEM‐EDS analyses to investigate the lower shales of the Cambrian Zhalagou Formation in eastern Guizhou. The aim is to characterise the paleo‐sedimentary environment, identify the controls on organic matter enrichment, and determine the sources of metals. The results show an average TOC of 1.63% and strong enrichment of Ba (EF = 52) and Mo (EF = 16). Positive Eu anomalies (average δEu = 1.35) and low Y/Ho ratios indicate hydrothermal activity. Mo/TOC and U–Mo covariation suggest an anoxic–euxinic, semi‐restricted water column, which is further supported by framboidal pyrite sizes (3.75–6.05 μm). Low P/Ti ratios indicate low paleoproductivity. However, the positive TOC–Ni ex correlation and the nonlinear δEu response imply that moderate hydrothermal input enhanced reducibility and nutrient supply, thereby favouring organic preservation. Excessive input, in contrast, caused dilution. Ba, Cu, Zn, and Pb are mainly hydrothermal in origin, Mo is seawater‐derived, and Ni is multi‐sourced. We propose a coupled model of ‘tectonic triggering – hydrothermal driving – environmental conditioning – biological participation’: Late Ediacaran–Early Cambrian extension reactivated faults, allowing hydrothermal fluids to ascend, bringing metallogenic elements and reinforcing reducing conditions in a semi‐restricted stratified basin, thus leading to synchronous initial enrichment of organic matter and sulfides. This model links organic matter to MVT mineralisation at the source rock stage.