Abstracts from the early-career researchers virtual International Platinum Symposium, May 2022

This issue contains abstracts from a variant of the biennial International Platinum Symposium that was held virtually in May 2022. This symposium di ff ered from previous events in that the organising committee, keynote speakers, and symposium presenters were made up entirely of students and early-career researchers. The event was organised to facilitate dis-cussions, networking, and collaboration amongst bud-ding researchers, something that has been hampered throughout the COVID-19 pandemic. The organising committee and reviewers are thanked for their contributions to this abstract volume, and hopefully these studies become full journal articles in the future. The presented research encompassed traditional meet-ing themes of igneous petrology and economic geology pertaining to ma fi c-ultrama fi c rocks, as well as novel themes of non-conventional platinum-group element repositories and the applications of machine learning in mineral exploration. Several studies focussed on the world-class Bushveld Complex of South Africa, particularly the complex ’ s northern limb which has become one of the world ’ s most exciting exploration frontiers for platinum-group elements, nickel, copper, chromium, and vanadium. The mobility of magmatic sulphide liquids intrans-crustalsystemsalsofeaturesinseveralstudies,and more speci fi cally, the roles in which volatile phases may play to facilitate the migration of immiscible sulphide liquid. Lastly, someabstracts focus on petrogenetic aspects of established ma fi c-ultrama fi c complexes, such as the Noril ’ sk-Talnakh, Coldwell, and Stillwater complexes. Not only did our symposium celebrate the academic achievements of early-career researchers in our fi eld, but it also celebrated diversity and inclusivity. Amongst the presenters, six continents and thirty countries were represented. Approximately 73% of participants were early-career researchers, ranging from those currently studying for bachelors ’ degrees to those completing post-doctoral studies. One third of participants were female, a statistic that extends to the keynote speakers and organising committee. I am very pleased to be part of a The northern limb of the Bushveld Complex, South Africa, is globally recognised as one of the world ’ s largest resources of platinum-group elements (PGEs). These metals are essential to the growth of sustainable and environmentally friendly technologies, particularly within the electric vehicle industry; a market which is expected to grow exponentially in the coming decades. The PGE-Ni – Cu – Co mineralisation is hosted within the Platreef, a magmatic package thought to be analo-gous to the Critical Zone of the western and eastern limbs. It has PGE grades comparable with the Merensky Reef, commonly 3 – 4 g/t (Pt + Pd + Rh + Au), but up to 15 g/t, over a much greater thickness, along with sub-stantially more associated Ni – Cu – Co in the form of magmatic sulphides. The Platreef is thought to have formed from discrete magmatic units or sills, each with their own variable metal budgets and thicknesses. Previous workers have divided the Platreef into three to four discrete magmatic units at various locations in the southern sector of the northern limb. At Turfspruit, this has been achieved via examining changing mineralogy, Pt:Pd and Ni:Cu ratios [1], and at Townlands, via trace element and S isotope analysis [2]. In the central sector, north of Sandsloot, the Platreef has been divided into three units based on mineralogy and grade [3]. Better understanding the stratigraphy of the Platreef, both in terms of along strike and down-dip variations, is vital for developing genetic and exploration models, which will in turn aid in the prediction of the locations of economically important horizons within the intrusion. In study, the Exploration geoscience practitioners use spatial data to derive insights into the spatial distribution and other characteristics of target geological objects (e.g., an orebody). However, interpretation of large datasets by human interpreters is often highly subjective. This study tests the possibility of using data science techniques on complex and very large databases in order to produce more systematic and robust results. The stratigraphy of the Rustenburg Layered Suite in the northern limb is di ff erent from that of the eastern and western limbs south of the Thabazimbi-Murchi-son Lineament. In the northern limb, the Lower Zone occurs as chonolith-like bodies that intruded into Archaean granite-gneisses and metasedimentary rocks of the Transvaal Supergroup [1]. These bodies host Cr and Ni – Cu – PGE sulphide deposits, whereas the Lower Zone in the rest of the complex is barren. The Uitloop Lower Zone intrusion is exposed as two separate bodies (Uitloop I and Uitloop II) which lie along the eastern periphery of the northern limb. Nickel sulphide mineralisation in Lower Zone serpentinised ultrama fi c rocks as well as PGE – Cu – Ni mineralisation in Critical Zone lithologies are targets of the recent exploration campaign by Lesego Platinum Uitloop (Pty) Ltd on the Uitloop II body [2] (Figure 1). An extension of the Platreef intrusion, nestled between metasedimentary packages of the Transvaal Supergroup, has been recognised in southeastern part of the Uitloop II body. styles of PGE – Cu-Ni mineralisation are hosted in the Critical sequences: basal the intrusions and within the footwall and (ii) reef-style (strata-bound) PGE horizon the upper part of the intrusions The northern limb of the Bushveld Complex, South Africa, contains various mineralised horizons, one of which is the Flatreef. The Flatreef is the correlative equivalent of the Upper Critical Zone in the eastern and western limbs of the Bushveld Complex. In the northern limb, the Flatreef is emplaced in direct contact with the Transvaal Supergroup sediments and shows signi fi cant petrological and geochemical evidence for magma-footwall interaction. Ultrama fi c rocks in the Lower Flatreef comprise distinctive hybrid lithologies that form the Footwall Assimilation Zone (FAZ) and are associated with fragments of partially melted sedimentary xenoliths. In this study, we investigate the petrography and geochemistry of the various mineral assemblages that are associated with dolomitic xenoliths with the aim of providing further understanding of the processes of carbonate assimilation that occurred. We have identi fi ed di ff erent types of mineral assemblages in the hybrid units by means of phase relations, mineral chemistry, and whole-rock chemistry. These mineral assemblages are derived from the interaction of dolomitic material with either a primitive melt or a di ff erentiated melt. Samples containing olivine (Fo 84 – 86 ) + clinopyroxene (19 – 35 mol-% Ca-Tscher-mak) and intercumulus spinel were classed as being derived from the interaction of a carbonate melt (CaO-, CO2-rich) with primitive melt. Samples that were derived from an interaction of a dolomitic xenolith with di ff erentiated melt contained olivine The Bushveld Complex is an economically important and scienti fi cally fascinating intrusion due to the thick chromitite layers contained in its Critical Zone (Figure 1). These laterally extensive chromitite layers are mined for chromium and, for some layers, platinum-group elements. They are subdivided into Lower Group, Middle Group and Upper Group chromitites (LG, MG and UG respectively) of which the LG and MG chromitites were analysed in this study. Field observations from open pit and underground exposures in the eastern and western Lobes of the Bushveld Complex were used to describe the chromitite morphology on a regional scale. The studied chromitite layers are traceable over long distances and may occur as one, two or three chromitite layers at distinct locations, with several changes in the number of their layers and their thickness occurring along a distance of a few kilometres. This is best understood as a structure of regionally bifurcating chromitites with small-scale bifurcations being visible even at the scale of individual outcrops. This study reports evidence of magmatic erosion of fl oor cumulates, as several chromitite layers transgressing their footwall have been observed. Among these features are large inclusions of orthopyroxenite in chromitite that are partly attached to the footwall rocks, suggesting that they are erosional remnants of these rocks. Fur-thermore, two potholes, roughly circular depressions in the chamber fl oor, were documented, which reveal transgressive relations of chromitites with their footwall rocks. To explain the regional bifurcations, we propose a model of chromitite formation involving the in fl ux of several pulses of superheated melt. Each pulse caused thermochemical erosion of the chamber fl oor, as shown by transgressive relationships between chromitites and their Platinum-group element (PGE) mineralisation in the northern limb [1] of the Bushveld Complex is located in disseminated base metal sulphides and subordinate chromitites hosted in ma fi c-ultrama fi c cumulates. Visual logging to di ff erentiate between and mineralised rocks interpretation of the technique samples. re (Pt, and (Co, and (Drenthe, determine a of The orebodies of Norilsk contain some of the world ’ s most valuable accumulations of Ni, Cu and platinum-group elements (PGEs). The PGEs occur throughout the deposit, but are particularly abundant within the upper ‘ taxitic ’ zones (i.e. zones with variable grain size distributions, reworked country rock xenoliths, and mm to cm-scale irregular spinel-rich aggregates that occur as patches or disrupted seams and strin-gers). These taxitic gabbrodolerites contain ore-grade PGE concentrations alongside 2 – 3 wt-% magmatic sulphides, associations that are referred to as low-sul-phide PGE-rich mineralisation. A key feature in these units are the spherical and sub-spherical features that we interpret as former gas bubbles, partially or entirely with low-temperatu