Characterizing arsenic mineralization in the Carmen Quartz-Pyrite-Gold (QPG) Veins, Mankayan Mineral District, Philippines: A geometallurgical approach

Geometallurgy has emerged as a critical approach for understanding unconventional ore deposits, leveraging advanced techniques such as automated mineralogy and diagnostic leaching to characterize the behavior of complex ores. In the Philippines, the Carmen quartz-pyrite-gold (QPG) veins in the Mankayan Mineral District exemplify such a deposit, where copper occurs as arsenic-bearing tennantite and enargite. The ore's complexity is emphasized by intricate mineral textural relationships and its deleterious nature. Understanding its ore’s mineralization characteristics is imperative for the improvement of mineral processing and metal extraction.

The main orebody of the Carmen QPG vein is a silicic hydrothermal breccia intersected by multiple sulfide veins. Petrographic analysis reveals a predominance of tennantite with minor enargite-luzonite, closely associated with quartz and pyrite, the primary gangue minerals. Trace inclusions of chalcopyrite, bornite, chalcocite, and covellite are also observed replacing the primary minerals. Automated mineralogy, performed using a Mineral Liberation Analyzer (MLA) on whole and ground ore, provided valuable insights into the processing behavior of these arsenic-bearing minerals. Mineral maps of whole and comminuted samples reveal complex and pervasive textures at the microscopic scale. Tennantite is commonly associated with enargite (22.79%), pyrite (21.71%), and quartz (30.07%), while enargite is associated with tennantite (34.45%), pyrite (6.72%), and quartz (17.98%). Particle size distribution data indicate a convergence in the grinding behavior of enargite and tennantite with increasing fineness. Both minerals exhibit similar liberation trends, where larger size fractions contain a higher proportion of binary and ternary+ particles that progressively liberate with finer grinding. However, enargite consistently shows a higher proportion of liberated particles per size fraction compared to tennantite. Diagnostic leaching studies are currently underway to further evaluate the leaching behavior of arsenic, aiming to inform strategies for the effective beneficiation of this unconventional ore.