Structure-controlled mineralization resulted from Paleoproterozoic orogenesis in the Dahenglu Cu-Co deposit, NE China

Abstract

Paleoproterozoic orogenic-related (or orogenic-like) ore deposits play a significant role in the metal and non-metal metallogenic systems in the North China Craton. This study focuses on detailed field structural of the Dahenglu Cu-Co deposit to reveal relationship between structural controls and enrichment process of cobalt (Co)-bearing hydrothermal fluids in the metasedimentary rock. In the context of Paleoproterozoic orogenesis, at least three phases of deformation were identified within the ore-bearing country rocks: an early DPl-1, the peak-orogenic deformation phase called DPl-2 and a final exhumation stage of deformation designated as DPl-3. Through meticulous structural analysis, microscopic examination of drilling cores, and the application of the TESCAN Integrated Mineral Analyzer, we have discerned that thrust faults, operating at both outcrop-scale and microscale, function as substantial conduits for the migration of ore-forming hydrothermal fluids. Additionally, fractures within thrust faults, the core of folds, and the high strain micro-scale shear zone between overturned folds provided ideal spaces for the precipitate of Co-bearing hydrothermal fluid. Based on the regional geological correlations, the second phase of deformation (DPl-2) is characterized by S2 foliation, crenulation cleavage, and thrust fault, which played a crucial role in the enrichment of cobalt in minerals such as siegenite and pyrite. This cobalt enrichment is attributed to the peak-orogenic stage, DPl-2, which likely occurred between 1.95 and 1.90 Ga. The ore-forming geodynamic was associated with Paleoproterozoic orogenesis, characterized by intense deformation and metamorphism. This conclusion aligns with cobalt enrichment observed in the Paleoproterozoic Trans North China orogen in the central North China Craton and the Paleoproterozoic Peräpohja belt in northern Finland. The structures generated by significant tectonic events, such as Paleoproterozoic orogenesis, represent key controlling factors of Co-rich ore deposits.