Experimental and Thermodynamical Modeling of Ore-Forming Processes in Magmatic and Hydrothermal Systems

This special issue book includes 10 original research papers that discuss and solve some problems of ore-forming processes in magmatic and hydrothermal systems. Some of these papers in the issue deal with experimental and thermodynamical modeling, while the others are devoted to analytical geochemistry, geochronology and genesis of some ore occurrences. I hope that these papers will be useful for scientists who work on the fundamental problems of ore-forming processes and the genesis of ore deposits, and will provide new ideas for future research

Geo-Information Technology and Its Applications

Geo-information technology has been playing an ever more important role in environmental monitoring, land resource quantification and mapping, geo-disaster damage and risk assessment, urban planning and smart city development. This book focuses on the fundamental and applied research in these domains, aiming to promote exchanges and communications, share the research outcomes of scientists worldwide and to put these achievements better social use. This Special Issue collects fourteen high-quality research papers and is expected to provide a useful reference and technical support for graduate students, scientists, civil engineers and experts of governments to valorize scientific research

Mineralogy and geochemistry of iron-oxides in the Olympic Dam IOCG-deposit and adjacent prospects, South Australia

Iron-oxide copper gold (IOCG) mineralisation is defined by an abundance of hematite and/or magnetite. The predominance of one Fe-oxide over the other and their textural relationships can, however, differ significantly within a single deposit or within the same metallogenic province, as a response to variations in the genetic conditions. Analysis of Fe-oxides, bridging scales of observation from deposit down to the nanoscale, highlights different formation conditions within deposits and prospects from the ~1.6 Ga Olympic Dam district, South Australia. In addition, Fe-oxides from the ~5.3-1.6 Ma El Laco Volcanic Complex (Chile), which are debated in terms of magmatic and/or hydrothermal origins, were analysed for comparison with those formed in IOCG systems. At Olympic Dam, a characteristic oscillatory-zoned hematite, containing up to wt% concentrations of U-W-Sn-Mo (‘granitophile’ elements), is the predominant Fe-oxide over the ~6 km-strike and ~2 km-depth of the breccia-hosted mineralisation. Complex textural and compositional zoning patterns within the hematite indicate overprinting and replacement of pre-existing minerals, including earlier hematite, during subsequent episodes of fluid-assisted brecciation and mineralisation. A diverse range of features at the micron- to nanoscale indicates that pseudomorphic replacement of hematite occurred via coupled dissolution and reprecipitation reactions leading to grain-scale (re)mobilisation of minor/trace elements. Primary geochemical signatures are nevertheless partially or selectively preserved. This allows the use of hematite as a reliable U-Pb geochronometer. Mineralogical-geochemical study of Fe-oxides from the outer shell, a weakly-mineralised domain between the host granite and the Olympic Dam orebody, allows for re-interpretation of deposit formation. Iron-oxide assemblages comprise oscillatory-zoned, silician magnetite, high field strength element-bearing hematite, and various interconversion products between the two oxides. Formation of such assemblages is associated with early alkali-calcic alteration (calc-silicate inclusions in silician magnetite), breakdown of magmatic Fe-Ti-oxides, and replacement of igneous magnetite by silician magnetite. Geochemical modelling at 400 °C suggests magnetite-replacement at pH/fO₂ conditions that coincide with stability shifts of K-feldspar → sericite, and ilmenite → rutile. Outer shell formation was initiated at the depth of granite emplacement (~6-8 km), following volatile release from fluids ponding at intrusion margins. Mineralisation continued during uplift to shallower depth, with cupola collapse following extensive fluid release that facilitated brecciation and orebody formation. Nanoscale analysis of Fe-oxides by scanning transmission electron microscopy using Z-contrast imaging and mapping provides further insights into ore-forming processes. Fingerprinting of fluid-mineral interactions during subsequent overprint of U-W-Sn-Mo-bearing hematite show that twins provide pathways for fluid percolation and trap elements exchanged during cycles of coupled dissolution-reprecipitation. Metal nanoparticles (NP) are also trapped within pores developed during transient porosity, which can be hosted by fluid inclusions. Unusual Cu-As-zoning at the micron-scale correlates with Cu-(As)-NPs along fluid inclusion trails and Si-Al-K-bearing twin planes linking such metal enrichment to hydrolytic alteration. W-Pb-enrichment occurs along 2-3 nm-wide twin crests and as W-(Pb)-bearing NPs in hematite displaying ‘granitophile element’-signature with preferential removal of W and preservation of Sn, as shown by grain-scale element patterns. A two-fold superstructure model with oxygen vacancies is constructed to explain W-release from hematite. Nanoscale features observed in relation to twins also allow prediction of disturbances to the U/Pb-systematics of hematite with implications for geochronology. Nanomineral inclusions in magnetite are valuable petrogenetic indicators that can clarify ore-forming processes. At Acropolis, vein titanomagnetite, within ~1.6 Ga volcanic rocks, features nanoscale inclusions with ulvöspinel-hercynite pairs and ilmenite-trellis exsolutions followed by subsequent overprinting (rutile replacement of Ti-phases). Spinel-group associations and ilmenite/magnetite oxythermobarometry supports hydrothermal-magnetite formation at ≥500 °C. Silician magnetite from Wirrda Well hosts nanoinclusions of the rare Al-amphibole, tschermakite. Considering the metamorphism of the host ~1.85 Ma granite, the presence of tschermakite could represents a metamorphic phase that crystallised prior to IOCG-style mineralisation. In contrast, magnetite from Fe-ores at El Laco contains nm-scale inclusions of paired clinopyroxenes (augite-pigeonite/clinoenstatite) with intergrowths indicative of rapid growth and exsolution at low pressures/high temperatures, typical of crystallisation from melts. Sulfur-bearing coatings on comparable but finer-grained pyroxene-bearing magnetite are indicative of ‘magnetite flotation’ via attachment to bubbles of vapour+fluid, allowing transport from a deep magma reservoir to surface. Iron-oxides show remarkable variation in compositional signatures and nanoscale heterogeneity. Detailed petrographic, geochemical and mineralogical analysis of Fe-oxides represents a rich and often untapped source of information that can assist in constraining ore formation conditions and contribute to improved genetic models.Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering and Advanced Materials, 202

Geology at ANU (1959-2009)

This history was undertaken to celebrate the 50th anniversary of the Geology Department at ANU, and to honour its founding professor David A. Brown. It includes contributions from some 100 former students outlining their career successes. This history was compiled by Dr Mike Rickard, a staff member of the Department of Geology from 1963 to 1997, who also served as Head of Department for seven years. He graduated BSc and PhD from Imperial College London in 1957 and has specialised in mapping the structure of mountain chains in Ireland, Canada, Norway, and southern South America. He also mapped volcanic rocks for the Geological Survey of Fiji. He taught Structural Geology and Tectonics and has supervised field work in south eastern and central Australia. After retirement he has taught U3A courses in Earth Science

Geology at ANU (1959-2009)

This history was undertaken to celebrate the 50th anniversary of the Geology Department at ANU, and to honour its founding professor David A. Brown. It includes contributions from some 100 former students outlining their career successes. This history was compiled by Dr Mike Rickard, a staff member of the Department of Geology from 1963 to 1997, who also served as Head of Department for seven years. He graduated BSc and PhD from Imperial College London in 1957 and has specialised in mapping the structure of mountain chains in Ireland, Canada, Norway, and southern South America. He also mapped volcanic rocks for the Geological Survey of Fiji. He taught Structural Geology and Tectonics and has supervised field work in south eastern and central Australia. After retirement he has taught U3A courses in Earth Science

2009 GREAT Day Program

SUNY Geneseo’s Third Annual GREAT Day.https://knightscholar.geneseo.edu/program-2007/1003/thumbnail.jp

Multispectral and Hyperspectral Remote Sensing Data for Mineral Exploration and Environmental Monitoring of Mined Areas

In recent decades, remote sensing technology has been incorporated in numerous mineral exploration projects in metallogenic provinces around the world. Multispectral and hyperspectral sensors play a significant role in affording unique data for mineral exploration and environmental hazard monitoring. This book covers the advances of remote sensing data processing algorithms in mineral exploration, and the technology can be used in monitoring and decision-making in relation to environmental mining hazard. This book presents state-of-the-art approaches on recent remote sensing and GIS-based mineral prospectivity modeling, offering excellent information to professional earth scientists, researchers, mineral exploration communities and mining companies

Geochronology of Iron Oxides and Development of Matrix-Matched Reference Material for Routine U-Pb Dating

Iron oxides, hematite and magnetite, are common minerals throughout rocks and ores of all types and ages. The discovery of U-bearing hematite at Olympic Dam, the largest iron oxide copper-gold (IOCG) deposit in the Gawler Craton (South Australia) prompted development of this mineral as a new U-Pb geochronometer. Unlike accessory minerals routinely used to track hydrothermal mineralisation, iron oxides are dominant components of Precambrian IOCG systems and therefore geochronology of iron oxides is pivotal to understand deposit evolution. Iron oxide minerals are studied in terms of U-Pb systematics and reliability for dating Olympic Dam and surrounding IOCG prospects formed at ~1.6 Ga. The temporal window between crystallisation of magmatic zircon and hydrothermal Fe-oxides is investigated to define the onset and lifespan of mineralisation and assess magma fertility. A matrix-matched reference material for routine microbeam geochronology is synthesised and tested for U/Pb isotope homogeneity by ID-TIMS. The U-Pb systematics of hematite are complex, exhibiting U-Th-Pb concentration and ratio heterogeneity at the nano- to micron-scales. Nevertheless, using a multi-instrument approach, high- precision data is routinely obtained. Reconnaissance SEM imaging in BSE mode and LA-ICP-MS isotope mapping allows pinpointing of U/Pb-homogeneous, inclusion-free grain domains. Dating of such domains via LA-ICP-MS using both mixed-(U/Pb)-solution and zircon reference materials produced successful results and a steppingstone to investigate at higher resolution and precision. The first application of both SHRIMP and ID-TIMS to hematite dating confirmed the robust U-Pb system in natural hematite, yielding 207Pb/206Pb (ID-TIMS) precision of up to ~0.05%. Coupled with (CA-)ID-TIMS analysis of magmatic zircon, hematite sampled throughout the Olympic Dam deposit provides a well constrained magmatic-hydrothermal timeline of events. The granite intrusion hosting Olympic Dam was emplaced rapidly at 1593.28 ± 0.28 Ma. The orebody was formed during a major mineralising event following granite uplift and during cupola collapse over a period of ~2 Ma, whereby the earliest hydrothermal activity is recorded in the early, deep ‘outer shell’ of the deposit at 1591.27 ± 0.89 Ma. Findings discredit a shallow origin for the deposit based on irreconcilable differences between the depth of granite emplacement and timeframes of uplift and fluid exsolution. Recognition of U-bearing hematite with a comparable W-Mo-Sn-bearing signature and age as Olympic Dam hematite within other IOCG systems, Wirrda Well and Acropolis, links the fluid forming the wider Olympic Cu-Au Province to a common source and time period. LA-ICP-MS U-Pb dating of U-bearing, silician magnetite from Fe-rich lithologies in the outer shell at Olympic Dan yields an age of 1761 ± 19 Ma, distinct from any other ages found within the deposit. The age is likely linked to ca. 1750 Ma intrusive/extrusive magmatism reported across the Gawler Craton. This shows the presence of older ore protoliths within Olympic Dam and represents the first successful application of U-Pb dating to magnetite. Magmatic zircon studied down to the nanoscale from two granite suites in the Gawler Craton shows crystal zoning with respect to ‘non-formulae’ elements such as Fe, Ca, and Cl, and also chloro-hydroxy-zircon nanoprecipitates when associated with IOCG mineralisation. This is indicative of early Fe-Cl-metasomatism prior to metamictisation, a diagnostic tool for assessing ‘fertility’ of granitic magmas. In contrast, metamict zircon from high-grade bornite ores shows patchy amorphisation throughout domains with pervasive enrichment in U-, Y- and non-formula elements. Hydrated ferric oxide doped with U-Pb solutions was converted to Fe-oxide and assessed by SEM imaging, XRD and LA-ICP-MS indicating the presence of homogenous U-Pb domains in cm-sized chips of hematite. Micro-sampled domains were measured by ID-TIMS confirming U-Pb isotope homogeneity at high precision. Hematite is a remarkably robust U-Pb geochronometer for dating hydrothermal ore deposits. Dissemination of the synthesized reference material to the wider community will allow routine LA-ICP-MS dating.Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering & Advanced Materials, 202