Forecasting Geoenvironmental Risks: Integrated Applications of Mineralogical and Chemical Data

Anita Parbhakar-Fox,Laura Jackson,Nathan Fox,Rebekah Cornelius

doi:10.3390/min8120541

Abstract

Management of solid mine wastes requires detailed material characterisation at the start of a project to minimize opportunities for the generation of acid and metalliferous drainage (AMD). Mine planning must focus on obtaining a thorough understanding of the environmental properties of the future waste rock materials. Using drill core obtained from a porphyry Cu project in Northern Europe, this study demonstrates the integrated application of mineralogical and geochemical data to enable the construction of enviro-geometallurgical models. Geoenvironmental core logging, static chemical testing, bulk- and hyperspectral mineralogical techniques, and calculated mineralogy from assay techniques were used to critically evaluate the potential for AMD formation. These techniques provide value-adding opportunities to existing datasets and provide robust cross-validation methods for each technique. A new geoenvironmental logging code and a new geoenvironmental index using hyperspectral mineralogical data (Hy-GI) were developed and embedded into the geochemistry-mineralogy-texture-geometallurgy (GMTG) approach for waste characterisation. This approach is recommended for new mining projects (i.e., early life-of-mine stages) to ensure accurate geoenvironmental forecasting, therefore facilitating the development of an effective waste management plan that minimizes geoenvironmental risks posed by the mined materials.

Highlights

Porphyry systems are defined as large volumes (10 to 100 km3 ) of hydrothermally altered rock typically centered on porphyry stocks that may contain skarn, carbonate-replacement, sediment hosted and high and intermediate sulphidation epithermal base and precious metal mineralization [1].They are considered the hallmark of magmatic arcs, constructed above active subduction zones at convergent plate margins [2,3], though a minority occupy post-collisional and other tectonic settings that develop after subduction ceases [1]
Whilst several acid and metalliferous drainage prediction methodologies were performed in this study, this section presents a snapshot of key results with a focus on (1) describing the lithological characteristics of the sampled drill core in AMD terms; and (2) critically evaluating data from new methodologies compared to traditionally derived AMD data with a focus on waste drill holes
A breccia facies containing highly silicified-matrix supported sub-angular clasts was identified at the base of the drill hole and classified as not acid forming (NAF) by the acid rock drainage index (ARDI) with 0.25% total sulphides

Summary

Introduction

Porphyry systems are defined as large volumes (10 to 100 km3 ) of hydrothermally altered rock typically centered on porphyry stocks that may contain skarn, carbonate-replacement, sediment hosted and high and intermediate sulphidation epithermal base and precious metal mineralization [1].They are considered the hallmark of magmatic arcs, constructed above active subduction zones at convergent plate margins [2,3], though a minority occupy post-collisional and other tectonic settings that develop after subduction ceases [1]. Porphyry systems are defined as large volumes (10 to 100 km3 ) of hydrothermally altered rock typically centered on porphyry stocks that may contain skarn, carbonate-replacement, sediment hosted and high and intermediate sulphidation epithermal base and precious metal mineralization [1]. The median global Cu composition for porphyry mines is around 0.5% and as such they are commonly regarded as “low-grade, large-tonnage” [6], e.g., Aitik mine, Sweden (1227 Mt reserves at 0.23% Cu) and Bingham Canyon, US (cumulative production of 2829 Mt at 0.7% Cu) [7].

Methods

Results

Discussion

Conclusion