Future exploration for mineral resources will target greater depths and submarine settings, which is costly and technically challenging. For this development, numerical modeling can be used to identify the governing processes within entire ore-forming systems. Capturing the dynamics of magmatic-hydrothermal interface processes requires to resolve mass and energy fluxes as a continuum that extends beyond the roots of hydrothermal systems and bridges the gaps between fluid flow and magma dynamics. Magma is mobile during intrusion events and can convect until it reaches a crystal lockup due to cooling and crystallization. During this process, the magma reservoir reaches fluid saturation and exsolves metal-bearing magmatic volatiles to the host rock. We developed a consistent formulation for fluid generation and transport in a coupled model for viscous flow according to the Navier-Stokes-Equations and porous flow with Darcy’s Law, using an up-scaled description of volatile release from reservoir to host rock and realistic magma properties from published experimental and modelling works. We explore the consequences of exsolved volatile phases on magma dynamics and its implications on fluid release and ore formation within the host rock. We distinguish three distinct stages during the evolution of magmatic bodies and their associated porphyry copper deposits with a preparation, a brecciation-stockwork-veining and an ore-formation stage.

Mineralogy evaluation is critical to understand a deposit’s mineralogical variability, and inform decisions associated with ore beneficiation. Elemental-to-mineral conversion techniques (EMC) are a popular method to rapidly estimate a sample’s modal mineralogy from an assay dataset. EMC techniques are based in the principle that the bulk chemistry of a sample is proportional to the product of its modal mineralogy and the mineral’s elemental composition.

In this work, we present a Baeysian framework to infer modal mineralogy from compositional data, Pedras. It builds upon the works of Escolme et al. (2019) and Berry et al. (2011), an EMC method that uses linear programming to minimize coefficients representing the energy required to generate a given mineral assemblage. The minimization process implies thermodynamic equilibrium, which is rarely the case for hydrothermal environments. Instead, the thermodynamic coefficients are defined as a logistic probability distribution function, centred at the mineral assemblage’s equilibrium, which relaxes the thermodynamic coefficient’s minimization.

The framework is tested on synthetic alteration assemblages within a porphyry copper deposit and applied to a geochemical dataset from the Wainaulo porphyry copper deposit (Fiji). The results show that by relaxing thermodynamic minimization constraint, accurate modal mineralogy can be approximated at different stages of hydrothermal alteration in porphyry copper deposit systems. Major mineralogical domains are obtained from mineral approximations, reflecting different lithotypes, alteration and mineralization patterns. The modal mineralogy outputs also provide invaluable insights of mineral associations that vector towards mineralization, The method’s accuracy is enhanced when prior knowledge is objectively included in the modelling stage.

The Ruwai Pb-Zn-Ag skarn deposit is located within the Schwaner Mountain Complex in Central Kalimantan, Indonesia. It is the largest polymetallic skarn deposit in Kalimantan with the resources is estimated up to 14.43 Mt. at 4.94 wt.% Zn, 3.28 wt.% Pb, 108.11 g/t Ag which hosted by Jurassic limestones of the Ketapang Complex and Cretaceous granitoids of Sukadana Complex. In order to study the complex mineralogy and deportment of critical-elements (Ag, Bi, Sb, In, Te, Cd) pulp samples from the main stages of the processing plant (Ball mill/feed, Pb concentrate, Zn concentrate, Pb scavenger, Zn scavenger, Fe screw, and tailings) as well as 66 core samples of Pb-Zn-Ag mineralization were obtained.

Preliminary results on the pulp samples from X-ray diffraction (XRD), X-ray fluorescence (XRF) and mineral liberation analysis (MLA) agree within analytical uncertainties. The data allows a preliminary assessment of the deportment and distribution of Ag and Bi in the skarn ores and processing products. Particularly, acanthite (Ag₂S) and freibergite ((Ag,Cu,Fe)₁₂(Sb,As)₄S₁₃) are likely to be important hosts of Ag, while Bi occurs within bismuthinite (Bi₂S₃) and native bismuth (Bi). For the core samples, µ-XRF measurements of slabs have so far provided a broad overview of elemental distribution within the samples, while XRD results indicate more complex mineralogical compositions than the pulp samples.

Further analytical work including electron probe microanalysis (EPMA) and laser ablation ICP-MS are planned for all samples to be also able to evaluate the resource potential of other critical elements of interest such as Sb, In, Te, Cd.

Indonesian laterite deposits are a major source of Ni and Co. Here, we present new geological data on the Sebuku laterites (SE Kalimantan, Indonesia), with a resource of ~390 Mt at 42.5 wt.% Fe, 0.9 wt.% Ni, and 0.15 wt.% Co. The deposits are mostly limonitic, oxide-dominated Fe-Ni-Co-rich horizons, which formed by weathering of Jurassic-Cretaceous ophiolitic units. Although the Fe ore has been mined since 2006, little mineralogical and geochemical data are available, which would allow optimizing beneficiation and recovery of Ni and Co.

Typical laterite profiles at Sebuku consist of: 1) weathered bedrock composed of serpentinized dunites and harzburgites overlain by 2) a 0.2-7 m-thick saprolite zone, 3) a 2-8.5 m-thick yellow limonite zone, and 4) a 1-3.5 m-thick red-limonite zone.

Preliminary XRF, XRD, and mineral liberation analysis (MLA) data show a decrease in Mg and Si and an increase in Fe moving upwards through the laterite profile, corresponding to a transition from silicate- to oxide-rich mineralogy. Oxides and (oxy)-hydroxides comprise goethite, maghemite, hematite, magnetite, chromium spinel, gibbsite/bayerite, and various Mn-minerals, whereas silicates consist of serpentine, chlorite, talc, quartz, pyroxene, olivine, and clay minerals. Ni is hosted by various minerals, which include goethite, Mn-oxides, serpentine, and clays, whereas Co is mainly hosted by Mn-oxides.

Mineral chemical analyses (EPMA) are planned to further understand critical metal variability and distribution within the host minerals and throughout the deposits. Our ultimate goal is to characterize and quantify the distribution of Ni and Co in order to develop more efficient beneficiation processes.

Securing a predictable and affordable supply of critical metals for the high-tech industry, coupled with tightening supplies and augmented competition for available resources, leads to increasing exploration of complex and/or unconventional deposits. Complex ores often require extensive metallurgical processing and thus suffer from high capital and/or operational expenditures (CAPEX and OPEX). The Fe, Co, Ni, and Sc extraction from Sebuku Fe-(Ni)-Laterite was studied. The study compares conventional and alternative extraction methods, considering both the metal value of the deposit and the operational expenditures involved.

Conventional methods, such as roasting, stirred leaching, and pressure leaching, showed high extraction efficiencies for the target elements but also a significant demand in energy and chemicals. Alternative reducing agents in combination with conventional methods benefit faster leaching times and reduced energy demand at similar extraction efficiencies and might result in a more cost-effective and environmentally friendly process chain. Unconventional approaches, such as ionic liquids and deep eutectic solvents, report lower recovery rates necessitating further basic investigations to optimize the leaching agents and/or to develop efficient process designs with respect to the specific requirements.

Independent on the approach used, a basic process design including the implementation of potential recycling processes and waste/wastewater streams is mandatory for a first economic assessment of the individual routes. Based on this evaluation, the study highlights the need for further optimization to make beneficiation approaches feasible and attractive for potential investors especially viewing the current market prices for metals and chemicals.

This study is part of the StratOre Project (Client II).