Assessment of the Acid Generation Potential of Wall Rocks Associated with Niğde Özyurt Epithermal Au-Ag Mineralization in Compliance with National Legislation

Abstract

The leaching of sulfide minerals can lead to serious environmental issues, including acid generation and metal contamination in metallic ore deposits. In Niğde province, Çamardı district, mineral exploration activities were conducted to assess reserves and evaluate the feasibility of mining operations for epithermal Au-Ag deposits. As part of this study, core samples, with lithological and geochemical investigations performed, were selected and sampled from the vicinity of Özyurt-Üçkapılı villages. The aim was to determine and characterize the acid generation potential of wall rock samples within the framework of national regulations in Turkey, specifically the Mine Waste Management Directive. A total of 84 samples representing different locations and depths were collected from the cores. Based on ASTM 1915-20 standards, 83 samples were identified as having a total sulfur content below 0.1% via infrared spectroscopy. One sample (NOP-85), with total sulfur content above 0.1%, was subjected to the Modified Sobek method and found to have an NP/AP ratio of 8.11, well above the threshold of 3.0, classifying it as "non-acid generating inert mining waste." Furthermore, the carbonate neutralization potential and Sobek acid potential of the samples were evaluated, revealing that all samples, except NOP-85, were in the acid-consuming zone. The low abundance or absence of sulfide minerals in the field, along with the dominance of marble as the primary lithology and the abundance of alkaline minerals such as calcite and aragonite, corroborate the quantitative acid generation potential chemical analysis data. Additionally, hierarchical cluster analysis, a multivariate statistical method, was performed, indicating that the acid generation potential of the samples exhibited similarities across five distinct clusters. © 2025 Elsevier B.V., All rights reserved.