Hydrothermal-biogenic controls on critical metal enrichment in Ediacaran-early Cambrian stone coal of the Qinling-Daba Mountains

Five correlatable stone coal layers formed in the Ediacaran-early Cambrian succession. • Critical metals display pronounced spatial-stratigraphic heterogeneity. • Layer 3 hosts anomalous Se-Mo and significant Cd-V enrichment. • Metal enrichment was dominated by hydrothermal fluids and enhanced by algal activity. • Ga, V, Mo, and Cd indicate substantial critical-metal resource potential. The Qinling-Daba Mountains represent one of the major stone coal bearing areas in China, where multiple stone-coal layers occur within the Ediacaran-early Cambrian strata. These stone coal are commonly enriched in critical metals; however, their spatial and stratigraphic enrichment patterns remain poorly understood. In this study, we investigated the enrichment characteristics of 14 critical metals across three major belts (southern, central, and north) in the Qinling-Daba stone coal area. The results show that the Ediacaran-early Cambrian strata contain five regionally correlatable stone coal layers, three within the Ediacaran and two within the lower Cambrian. Critical metal enrichment exhibits pronounced spatial and stratigraphic pattern: the southern belt displays the strongest enrichment, whereas layer 3 ( Z 2 3 $Z_2^3$ ) consistently hosts the highest enrichment of critical metals. Within this layer, Se and Mo reach anomalous enrichment levels (EF max  > 100), and Cd and V are significantly enriched (EF max  > 10) across all three belts. Four critical metals, Ga, V, Mo, and Cd, show significant mining potential. Inorganic and organic geochemical evidence indicates that hydrothermal input was the primary control on metal enrichment across the five layers, whereas the exceptionally high metal enrichment in layer 3 were further amplified by biogenic contributions, particularly from marine algae. These findings clarify the spatial and stratigraphic controls on critical metal enrichment in the Qinling–Daba stone coal area and provide new insights into hydrothermal–biological interactions and metalliferous sedimentation in Ediacaran-Cambrian basins. Download: Download high-res image (201KB) Download: Download full-size image