Geochemical Characterization of Pit Wall Rocks: A Preliminary Step in Predicting the Water Quality of Pit Lake

Abstract

The quality of pit lake water during development and final condition is affected by various factors, including geochemical characterization of materials of a pit wall, which may consist of in-situ and backfilling materials. This research aims to obtain a geochemical characterization of pit wall materials using 3 main laboratory tests and analysis, namely static test, mineralogical and elemental composition analysis, and kinetic test using free draining column leach test. Static test results show that 5 of 6 samples exhibit low paste pH and NAG pH. Pyrite is found in four samples and is responsible for acid mine drainage production. Some samples contain acid-consuming carbonates and oxides such as calcite and periclase. Four samples exhibit leachates’ pH values lower than 3,00, mostly during all cycles. Alongside the lithostratigraphic distribution of pit wall rocks, these results imply a potential occurrence of acid mine drainage that will become a critical issue for water quality development and final condition in pit lake formation. Therefore, these results become essential feedback for the stakeholders to plan and implement acid mine drainage management to minimize the adverse impact of acid mine drainage in pit lakes. Immediate understanding of the geochemical characteristics of leachates from pit wall rock, which control the overall mine water quality.