Jon Hronsky - Academia.edu (original) (raw)

Papers by Jon Hronsky

In recent years it has become clear that the deposit scale footprint for mafic intrusion-hosted N... more In recent years it has become clear that the deposit scale footprint for mafic intrusion-hosted NiCu deposits of massive sulfide deposits hosted at the base of intrusions or funnel shaped intrusions does not apply to the entire class of the deposit and in particular not to the world class deposits. We propose a new classification for Ni-Cu deposits based on intrusion geometry i.e. the definable distal footprint of Ni-Cu deposits. We find this a useful practical guide in exploration as opposed to mineralization style or geotectonic setting, both of which are poorly or unknown during area selection in exploration.

The composition of the subcontinental lithospheric mantle (SCLM) varies broadly with the age of t... more The composition of the subcontinental lithospheric mantle (SCLM) varies broadly with the age of the last major tectonothermal event in the overlying crust. Archean SCLM is highly depleted, commonly is strongly stratified, and contains rock types that are essentially absent in younger SCLM. Its composition reflects processes that do not operate today. Phanerozoic terrains are generally underlain

Ore Geology Reviews, 2019

Despite many decades of development, spatial prospectivity modelling is not yet widely used or ac... more Despite many decades of development, spatial prospectivity modelling is not yet widely used or accepted throughout the global mineral exploration industry. A common criticism of the method is that it is not practically useful because it has a bias to mature, well-known areas and generates excessively large areas of high-prospectivity. It is suggested that the reason for this is not primarily related to limitations in the prospectivity mapping algorithms but rather to issues relating to the use of input data sets. Specifically, it is common that the input data (such as geological interpretations) do not uniformly and objectively represent the search space of interest, omit critical targeting-relevant geoscientific elements (such as major, deepseated ore-controlling structures) and have a large degree of unrecognised dependence. It is considered that these problems are not in principle barriers to the eventual successful deployment of this technology. However, future approaches to spatial prospectivity modelling need to explicitly address these concerns. It is suggested that the most effective method may be a hybrid of subjective human geological interpretation and objective, machine-based analysis, that captures the best aspects of these alternative approaches; i.e., an intelligence amplification (IA) rather than an artificial intelligence (AI) approach. A roadmap is proposed for improving the effectiveness of spatial prospectivity modelling that has implications for the broader community interested in mineral exploration targeting.

Mineral Deposit Research: Meeting the Global Challenge, 2005

ABSTRACT Mineral deposits exhibit extremely heterogeneous distributions, with each major deposit ... more ABSTRACT Mineral deposits exhibit extremely heterogeneous distributions, with each major deposit type showing a distinctive, commonly unique, temporal pattern. Individual temporal patterns reflect a complex interplay between formational and preservational forces that, in turn, largely reflect changes in tectonic processes and environmental conditions in an evolving Earth. The first-order drivers were the super continent cycle and evolution from plume-dominated to modern-style plate tectonics in a cooling Earth. Consequent decrease in the growth rate of continental crust, and change from thick, buoyant sub-continental lithospheric mantle (SCLM) in the Precambrian to thinner, negatively buoyant SCLM in the Phanerozoic, led to progressive decoupling of formational and preservational processes through time. This affected the temporal patterns of deposit types including orogenic gold, porphyry and epithermal deposits, VHMS, palaeoplacer Au, iron-oxide Cu-Au, PGE, diamond and probably SEDEX deposits. KeywordsMineral deposits–temporal distribution–tectonics–lithosphere

The Nebo and Babel Ni-Cu-PGE deposit is one of the largest nickel sulphide discoveries worldwide ... more The Nebo and Babel Ni-Cu-PGE deposit is one of the largest nickel sulphide discoveries worldwide in the last ten years. The known mineralisation inventory is 392 Mt at 0.3 % Ni, 0.3 % Cu, 0.18 g/t PGE with Co and Au credits. The deposit is a fault-offset, ~5 km long, tube-like, basic layered intrusion intruded into S-poor, granulite facies granitic gneiss. The principal rock type is gabbronorite with variable proportions of plagioclase, ortho– and clinopyroxene, minor olivine, oxides and apatite. Oxide-apatite rich gabbronorite occurs at the eastern end of Nebo. Mineralised zones are confined to the top and upper parts of the intrusion and comprise disseminated magmatic sulphides and massive sulphide lenses. Field, mineralogical and geochemical data suggest that the marginal units crystallised first under open system conditions. After magma supply ceased, inner units which exhibit 'normal' vertical fractionation trends, crystallised under closed system conditions. Systematic...

Geology

The punctuated distribution of major gold deposits along orogenic belts is poorly understood. In ... more The punctuated distribution of major gold deposits along orogenic belts is poorly understood. In northern Perú, gold deposits cluster along trends that transect the subparallel Phanerozoic belts that accreted onto the western margin of the Archean–Proterozoic Amazonian craton. This suggests the influence of as yet unrecognized pre-Andean basement structures in controlling the localization of Phanerozoic deposits. We report the newly discovered Tomac ophiolite, which represents a missing link in tracing a cryptic basement collisional suture striking obliquely to the Peruvian Andes. The Tomac ophiolite signals the opening of a former Neoproterozoic ocean basin between the Amazonian craton and a continental ribbon of dispersed microterranes. Re-accretion of the continental ribbon resulted in the formation of a collisional belt between ca. 465 and 440 Ma. Rifting and re-accretion occurred parallel to the strike of the ca. 1400–1000 Ma Grenvillian-Sunsás orogen, indicating that structura...

Processes and Ore Deposits of Ultramafic-Mafic Magmas through Space and Time, 2018

Large orthomagmatic Ni-Cu(-PGE) and platinum-group-element (PGE) deposits dominantly form during ... more Large orthomagmatic Ni-Cu(-PGE) and platinum-group-element (PGE) deposits dominantly form during the assembly and peak of supercontinents, when mantle plumes bombard the Subcontinental Lithospheric Mantle (SCLM) roots. The thinner edges of thick resilient SCLM at (paleo)craton margins internal to continents focus mantle melting and transfer of melts into the crust via active translithospheric faults. An interconnected intrusive network provides the plumbing system to upper-crustal sites of deposit formation. Most PGE reef deposits form slightly inboard of margins at major subhorizontal crustal interfaces. Os isotope data are consistent with melt interaction with the SCLM, which may increase PGE contents of the melts. The degree of mantle melting, regional geodynamics, and interaction with lithospheric architecture determine the crustal setting, melt composition (High MgO versus Low MgO end-members), mechanisms of sulfide saturation, and deposit style. Tectonic stress switches can initiate dynamic injection of key ore-forming sulfide melts from deeper in the magmatic conduit system. Ore-forming concepts are translated into global- to deposit-scale exploration parameters.

Mineralogical Magazine, 2013

Anniversary volume. This knowledge has substantially improved our ability to mine and explore wit... more Anniversary volume. This knowledge has substantially improved our ability to mine and explore within the immediate environs of ore deposits. However, over the same period it has become increasingly clear that this knowledge is of limited relevance to the exploration challenge of predicting the location of new major ore districts and to discriminating between camps and provinces with different endowment potential.

Journal of Geochemical Exploration, 2021

Abstract Mineral exploration targeting is a highly complex decision-making task. Two key risk fac... more Abstract Mineral exploration targeting is a highly complex decision-making task. Two key risk factors, the quality of exploration data and robustness of the underlying conceptual targeting model, have a strong impact on the effectiveness of this decision-making. Geographic information systems (GIS) can be used not only for compiling, integrating, interrogating and interpreting diverse exploration data, but also for targeting by employing powerful mathematical algorithms, an approach that is commonly referred to as mineral potential modelling or mineral prospectivity mapping (MPM). Here, we pose and examine key aspects around the question of “how can we get better at mineral exploration targeting using GIS?” We do this by (1) reviewing the fundamental aspects of MPM, (2) identifying significant deficiencies of MPM, and (3) discussing possible solutions to alleviating or eliminating these deficiencies. In particular, we discuss how these deficiencies can be overcome by adopting an intelligence amplification system, such as the recently proposed exploration information system (EIS) for translating critical ore-forming processes into spatially predictive criteria (i.e., predictor maps and spatial proxies) and improving decision-making in mineral exploration targeting.

Economic Geology, 2020

The North and South Flank deposits are located on the flanks of the Weeli Wolli anticline at Mini... more The North and South Flank deposits are located on the flanks of the Weeli Wolli anticline at Mining Area C in the central Hamersley Province. Supergene martite-goethite mineralization is hosted within the Marra Mamba Iron Formation and is developed over a strike length of more than 60 km. This multibillion metric ton resource has been drilled out on a 150- × 50- to 50- × 50-m grid, thus providing us with an unprecedented data set for analysis. This study synthesizes the drill hole data and presents a physical process model that can account for the observed distribution of mineralization. A fluid and mass flux model is proposed which envisages a three-stage process: (1) leaching of Fe from banded iron formation (BIF) in the vadose zone by reduced, acidic, meteoric-derived fluids; (2) penetration of an Fe-rich supergene-fluid plume, driven by gravity and focused by bedding-parallel permeability into the body of ambient alkaline groundwater, effecting nonredox, mimetic replacement of m...

Mineralium Deposita, 2019