Geological characteristics and metallogenic potential of bentonite deposits in Yangfan area, Guangshan County, Henan Province

Objective This study aims to elucidate the geological characteristics, genetic mechanisms, and metallogenic potential of the newly discovered medium−sized bentonite deposit in Yangfan, Guangshan County, southern Henan Province, providing a scientific basis for regional mineral exploration.

Methods Integrated methodologies were employed, including drilling engineering, methylene blue absorption analysis, multi−element chemical analysis, cation exchange capacity (CEC) testing, and mathematical statistics, to systematically investigate the deposit’s geological features, ore mineral composition, chemical characteristics, and genetic mechanisms.

Results The bentonite ore bodies in Yangfan predominantly occur within the Lower Cretaceous Chenpeng Formation and its unconformity contact zones with other strata. Topographically subdued areas constitute favorable prospecting targets. The main ore body is shallowly buried with high montmorillonite grade. Compared to other bentonite deposits, it is rich in Fe₂O₃, CaO, K₂O, Na₂O and less SiO₂. Both ore thickness and montmorillonite grade exhibit an increasing trend with decreasing elevation.

Conclusions The Yangfan bentonite deposit is a volcanic−sedimentary type formed by devitrification and hydrolysis of intermediate−acid pyroclastic rocks from the Chenpeng Formation in an alkaline aqueous medium, controlled by paleotopography. Proven resources total ~14.93 million tons. Extensive ore bodies with characteristics identical to Yangfan bentonite have been identified in the peripheral area, indicating significant prospecting potential.