Academic literature on the topic 'Cu-Au mineralisation'

The Au-Ag-Cu mineralisation in the Paliomylos area is associated with quartz segregations and pegmatoids in the form of boudinaged bodies. The Au, Ag and Cu contents in the ore bodies reach 6.8 ppm, 765 ppm and 0.80 wt%. The ore minerals consist of pyrite, chalcopyrite, sphalerite, pyrrhotite, galena, bismuthinite, argentopentlandite, gersdorffite, cobaltite, aikinite, hessite, native bismuth and gold. Pentlandite contains significant amounts in Ag (13.15 wt%), Au (1.59 wt%) and PGM, demonstrating a formula of Fe5.37 Ni2.56 Ag1.03 Ir0.03 S8.01. On the basis of geological, textural and chemical data, the mineralisation in the studied area was formed under high temperatures.

Abstract Situated about 130 km northeast of Tabriz (northwest Iran), the Mazra’eh Shadi deposit is in the Arasbaran metallogenic belt (AAB). Intrusion of subvolcanic rocks, such as quartz monzodiorite-diorite porphyry, into Eocene volcanic and volcano-sedimentary units led to mineralisation and alteration. Mineralisation can be subdivided into a porphyry system and Au-bearing quartz veins within andesite and trachyandesite which is controlled by fault distribution. Rock samples from quartz veins show maximum values of Au (17100 ppb), Pb (21100 ppm), Ag (9.43ppm), Cu (611ppm) and Zn (333 ppm). Au is strongly correlated with Ag, Zn and Pb. In the Au-bearing quartz veins, factor group 1 indicates a strong correlation between Au, Pb, Ag, Zn and W. Factor group 2 indicates a correlation between Cu, Te, Sb and Zn, while factor group 3 comprises Mo and As. Based on Spearman correlation coefficients, Sb and Te can be very good indicator minerals for Au, Ag and Pb epithermal mineralisation in the study area. The zoning pattern shows clearly that base metals, such as Cu, Pb, Zn and Mo, occur at the deepest levels, whereas Au and Ag are found at higher elevations than base metals in boreholes in northern Mazra’eh Shadi. This observation contrasts with the typical zoning pattern caused by boiling in epithermal veins. At Mazra’eh Shadi, quartz veins containing co-existing liquid-rich and vapour-rich inclusions, as strong evidence of boiling during hydrothermal evolution, have relatively high Au grades (up to 813 ppb). In the quartz veins, Au is strongly correlated with Ag, and these elements are in the same group with Fe and S. Mineralisation of Au and Ag is a result of pyrite precipitation, boiling of hydrothermal fluids and a pH decrease.

ABSTRAK Pegunungan Kulon Progo merupakan produk magmatisme Busur Sunda-Banda tersusun atas formasi andesit tua. Daerah Sumbersari merupakan bagian dari gunung api Gajah, batuan gunung api tertua Kulon Progo. Indikasi mineralisasi tipe porfiri ditemukan di daerah ini sehingga menarik untuk diteliti lebih lanjut. Penelitian ini bertujuan untuk mengetahui potensi keterdapatan mineral logam berharga (Cu-Au). Metode penelitian yang digunakan adalah pemetaan geologi, analisis petrografi dan mikroskopi bijih, serta analisis geokimia menggunakan XRF dan ICP-MS. Geologi daerah penelitian terletak pada fasies sentral-proksimal Khuluk Gajah, terususun atas intrusi mikrodiorit, mikrodiorit kuarsa, andesit, andesit basaltik-diorit, dan batugamping. Alterasi hidrotermal berkembang pada batuan beku diorit, mikrodiorit, dan sebagian pada andesit. Alterasi hidrotermal dibagi menjadi beberapa kelompok, yaitu ilit-serisit±biotit sekunder, epidot-aktinolit-kalsit±ilit, epidot-kalsit±ilit, dan ilit-serisit±kuarsa. Beberapa fase mineralisasi berkembang, antara lain fase epidot-aktinolit yang diikuti mineralisasi magnetit-kalkopirit, fase biotit-magnetit-kalkopirit-bornit, dan fase akhir serisit-mineral lempung-pirit menggantikan keseluruhan sistem. Analisis geokimia pada batuan teralterasi menunjukan indikasi mineralisasi Cu-Au dengan kadar 491–1447 ppm (0,14%) Cu dan 0,02–0,3 ppm Au dengan rasio elemen Cu:Au adalah 1,01. Karakter geokimia menunjukkan adanya korelasi kuat Cu terhadap Au.ABSTRACT Kulon Progo Mountain is Sunda-Banda Arc magmatism product composed of an old andesite formation. Sumbersari Area is part of the Gajah volcanic, which is the oldest rock of Kulon Progo volcanics. Indication of porphyry type mineralisation has been found in the area which makes the area interested for further research. The research methodologies are geological mapping, petrography and ore microscopy, and geochemical analysis using XRF and ICP-MS. Geology of the area located in central-proximal facies of Khuluk Gajah, consist of microdiorite, quartz-microdiorite, andesite, basaltic-dioritic andesite intrusions, and limestone. Hydrotermal alteration is developing into certain groups like illite-sericite ± secondary biotite, epidote-actinolite-calcite ± illite, epidot-calcite ± illite, and illite-sericite ± quartz. Some mineralisation phases are developed like epidote-actinolite followed by magnetite-chalcopyrite mineralisation, biotite-magnetite-chalcopyrite-bornite phase and the late phase of sericite-clay-pyrite replacing the entire system. Geochemical analysis on altered rocks show Cu-Au mineralisation indication ranging from 491-1,447 ppm (0.14%) and 0.02-0.3 ppm respectively, with Cu:Au ratio is 1.01. Geochemical characteristic shows strong correlation of Cu to Au.

ABSTRACT:Ore element ratios in intrusion-related mineralisation are in part a function of the relative oxidation state and degree of fractionation of the associated granite suite. A continuum from Cu-Au through W to Mo dominated mineralisation related to progressively more fractionated, oxidised I-type magmas can be traced within single suites and supersuites. Such systematic relationships provide strong evidence for the magmatic source of ore elements in granite-related mineral deposits and for the production of the observed ore element ratios dominantly through magmatic processes. The distribution of mineralised intrusive suites can be used to define a series of igneous metallogenic provinces in eastern Australia. In general, there is a correlated evolution in the observed metallogeny (as modelled based on the compatibility of ore elements during fractionation) with increasing degree of chemical evolution of the associated magmatic suite. This is from Cu-Au associated with chemically relatively unevolved magmas, through to Sn and Mo-rich mineralisation associated with highly evolved magmas that had undergone fractional crystallisation. Provinces recognised in that way do not necessarily correlate with the tectonostratigraphic boundaries defined by the near-surface geology, indicating that the areal distribution of some granite source regions in the deep crust is unrelated to upper crustal geology.

The Olympic Cu-Au Province is a metallogenic province in South Australia that contains one of the world’s most significant Cu-Au-U resources in the Olympic Dam deposit. The Olympic Cu-Au Province also hosts a range of other iron oxide-copper-gold (IOCG) deposits including Prominent Hill and Carrapateena. This paper reviews the geology of the Olympic Cu-Au Province by investigating the lithospheric architecture, geodynamic setting and alteration systematics. In addition, since the province is almost entirely buried by post-mineral cover, the sedimentary cover sequences are also reviewed. The Olympic Cu-Au Province formed during the early Mesoproterozoic, ca. 1.6 Ga and is co-located with a fundamental lithospheric boundary in the eastern Gawler Craton. This metallogenic event was driven in part by melting of a fertile, metasomatized sub-continental lithospheric mantle during a major regional tectonothermal event. Fluid evolution and multiple fluid mixing resulted in alteration assemblages that range from albite, magnetite and other higher temperature minerals to lower temperature assemblages such as hematite, sericite and chlorite. IOCG mineralisation is associated with both high and low temperature assemblages, however, hematite-rich IOCGs are the most economically significant. Burial by Mesoproterzoic and Neoproterozoic-Cambrian sedimentary successions preserved the Olympic Cu-Au Province from erosion, while also providing a challenge for mineral exploration in the region. Mineral potential modelling identifies regions within the Olympic Cu-Au Province and adjacent Curnamona Province that have high prospects for future IOCG discoveries. Exploration success will rely on improvements in existing potential field and geochemical data, and be bolstered by new 3D magnetotelluric surveys. However, drilling remains the final method for discovery of new mineral resources.

The Randu Kuning prospect is situated at Selogiri area, Wonogiri, Central Java, Indonesia. This location is about 40 km to the south-east from Solo city or approximately 70 km east of Yogyakarta city. Many Tertiary dioritic rocks related alterationmineralisation were found at the Randu Kuning area and its vicinity, including hornblende microdiorite, hornblende-pyroxene diorite and quartz diorite. Mineralisation type of the Randu Kuning prospect was interpreted as porphyry Cu-Au and a number epithermal Au-base metals deposits in its surrounding. The closed existing of porphyry Cu-Au and epithermal Au-base metals type deposits at the Randu Kuning area produced a very complex of veins and hydrothermal breccias crosscutting relationship. A lot of porphyry veins types were found and observed at the Randu Kuning area, and classified into at least seven types. Most of the porphyry veins were cross cut by epithermal type veins. Many epithermal veins also are found and crosscut into deeply porphyry vein types. There are genetically at least two type of hydrothermal breccias have recognized in the research area, i.e. magmatic-hydrothermal breccia and phreatomagmatic breccia. Magmatic hydrothermal breccias are mostly occured in contact between hornblende microdiorite or quartz diorite and hornblende-pyroxene diorite, characterized by angular fragments/clasts supported or infilled by silicas, carbonates and sulphides matrix derived from hydrothermal fluids precipitation. Phreatomagmatic breccias are characterized by abundant of the juvenile clasts, indicated contact between hot magma with fluid or water as well as many wall rock fragments such as altered diorites and volcaniclastic rock clasts set in clastical matrix. The juvenile clasts usually compossed by volcanic glasses and aphanitic rocks in rounded-irregular shape. Both veining and brecciation processes have an important role in gold and copper mineralisation of the Randu Kuning Porphyry Cu-Au and epithermal Au-base metals deposits, mostly related to the presence of quartz veins/veinlets containing significant sulphides, i.e., quartz with thin centre line sulphides (Abtype) veins, pyrite±chalcopyrite (C type) veinlets, pyrite+quartz± chalcopyrire±carbonate (D type) veins of porphyry types as well as epithermal environment quarts+ sulphides+carbonate veins.

Abstract The Almoughlagh batholith intruded the dioritic Baba Ali pluton during the Oligo-Miocene; the pluton and is now exposed as a big enclave within the batholith. The pluton intruded the Songhor Series during the Late Kimmeridgian (~136 Ma) orogeny. The intrusion by the batholith transformed the diorite to metadiorite and the impure carbonate units of the Songhor Series. The batholith consists of rock types such as quartz syenite and syenogranite, which have a low average quartz content, and which are metaluminous to peraluminous and calc-alkaline in composition. Comparison of the compositions of the Almoughlagh batholith and the pluton with its Cu, Mo, Fe, Sn, W, Au, and Zn skarn deposits, indicates that the Baba Ali diorite geochemically shows much resemblance with those which could bring about Fe-Cu skarn mineralization, whereas the compositions of the Almoughlagh granitoids resembles those of the plutons associated with Mo and Zn skarn deposits. The associated hydrothermal activity related to the Almoughlagh batholith culminated in magnetite mineralisation in the Baba Ali and the Chenar mines in which copper mineralisation also is considerable.

Brambang is one of the porphyry copper-gold prospects/deposits situated along eastern Sunda arc. This study is aimed to understand geological framework, alteration geochemistry and ore fluid characteristics of the prospect. Fieldworks and various laboratory analyses were performed including petrography, ore microscopy, rock geochemistry, chlorite chemistry and fluid inclusion microthermometry. The prospect is composed of andesitic tuff and diorite which are intruded by tonalite porphyries. Tonalite porphyries are interpreted as ore mineralisation-bearing intrusion. Various hydrothermal alterations are identified including potassic, phyllic, propylitic, advanced argillic and argillic types. Ore mineralisation is characterized by magnetite and copper sulfides such as bornite and chalcopyrite. Potassic alteration is typified by secondary biotite, and associated with ore mineralisation. Mass balance calculation indicates SiO2, Fe2O3, K2O, Cu and Au are added during potassic alteration process. Ore forming fluid is dominated by magmatic fluid at high temperature (450-600ºC) and high salinity (60-70 wt. % NaCl eq.). Hydrothermal fluid was diluted by meteoric water incursion at low-moderate temperature of 150-400ºC and salinity of 0.5-7 wt. % NaCl eq.

ABSTRACTThe ore-element associations of granite-related ore deposits in the eastern Australian Palaeozoic fold belts can be related to the inferred relative oxidation state, halogen content and degree of fractional crystallisation within the associated granite suites. Sn mineralisation is associated with both S- and I-type granites that are reduced and have undergone fractional crystallisation. Cu and Au are associated with magnetite- and/or sphene-bearing, oxidised, intermediate I-type suites. Mo is associated with similar granites that are more fractionated and oxidised. W is associated with a variety of granite types and shows little dependence on inferred magma redox state. The observed ore deposit-granite type distribution in eastern Australia, and the behaviour of ore elements during fractionation, is consistent with models of ore element sequestering by sulphides and Fe-Ti phases (e.g. pyrrhotite, ilmenite, sphene, magnetite) whose stability is nominally fO2-dependent. Fractional crystallisation acts to amplify this process through the progressive removal of compatible elements and the concentration of incompatible elements into decreasing melt volumes. The halogen content is also important. S-type granites are poorer in Cl than I-types. Cl decreases and F increases in both S- and I-type granites with fractional crystallisation. Low Cl contents combined with low magma fO2 in themselves seem to provide an adequate explanation for the rarity of Mo, Cu, Pb and Zn type mineralisation with S-type granites. Although such properties of granite suites seem adequately to predict the associated ore-element assemblage to be expected in associated mineral deposits, additional factors determine whether or not there is associated economic mineralisation.

The Kansanshi Cu-Au deposit located in the Domes region of the North West province of Zambia is characterised by structurally controlled high angle veins and associated alteration halos. The northwest trending Kansanshi antiform flanks the Solwezi syncline to the north and hosts the Kansanshi deposit and consists of tillites and metasedimentary rocks. Mineralisation is associated with Neoproterozoic Pan African deformation events experienced during the formation of the Lufilian fold belt; however recent findings confirm that structures in the form of reverse and normal faults and drag folds are critical controls on mineralisation within the deposit, Main pit in particular. Low angle faults occurring below the current pit are believed to have served as major fluid pathways during mineralisation. Age dating data from the Kansanshi deposit suggest that mineralisation took place between 512 and 503 Ma indicating that the event was associated with metamorphism. Two types of alteration are dominant within the Main pit (Kansanshi deposit) with the type and intensity of alteration being largely controlled by lithological units. Albite alteration occurs dominantly in phyllites and schists whereas dolomitisation is prevalent in calcareous units. Alteration is associated with mineralisation, and therefore is used as a condition for predicting vein or disseminated mineralisation. The high Au tenor at Kansanshi can be attributed to gold grains occurring in association with melonite (NiTe₂) and microfractured pyrite intergrown with chalcopyrite in sulphide and quartz dominated veins and veinlets. Analysis of gold grade distribution within the Main pit shows a clear concentration of the element along the major north-south trending structures like the 4800 and 5400 zones, possibly through supergene enrichment in the oxide-transition-sulphide zones. It is imperative that exploration for Kansanshi-type deposits will require geochemical and geophysical studies, understanding of the geology of an area to identify the three lithostratigraphic units (red beds, evaporites and reducing strata).

This thesis investigates the tectonic and magmatic setting of a Copper-rich seafloor massive sulfide deposit. Integrated multi-scale data analysis produced a regional to deposit-scale framework to constrain how, why and where these types of mineral deposits form. Outcomes from this research advance our understanding of 1) regional tectonic evolution of the East Manus Basin, and 2) volcanic and magmatic processes conducive to seafloor massive sulfide deposit formation.

The genesis of the Minto copper-gold deposit, YT, Canada, has been variously interpreted since its discovery although no existing model accounts for ductile deformation as a control on mineralization. Results from this study show that Minto ore is hosted within ductiley deformed granitoid host rocks emplaced as multiple intrusions into an actively deforming environment, with the variably sheared host rocks separated by incipiently deformed granodiorites essentially barren of mineralisation. Contacts between deformed/mineralized rock and incipiently deformed/barren rock range from abrupt to gradational, and are the product of pre-existing igneous contacts, variably partitioned deformation, or a combination of these. Deformation of granitoids is interpreted to have controlled fluid flow, with associated alteration promoting further deformation and fluid flow. Potassic alteration, in the form of biotite-magnetite, is the dominant alteration associated with mineralisation, and analysis of alteration using isocon diagrams indicates that K, Fe, Si, Cu, Au, and Ag have been added during alteration, although mass has been lost overall due to a relative reduction in Na and Ca. Host rock intrusion, mineralization, and deformation are interpreted via geochronology and crosscutting relationships as ongoing over at least 5 m.a., from about 202 Ma until about 197 Ma, based on U-Pb SHRIMP geochronology of zircons in granitoids and Re-Os ICP-MS geochronology of molybdenite. The trend of mineralisation is now coincident with the strike of foliation on short steep limbs and of axial planes of folded foliation. This geometry may not be representative of original processes, but of remobilization of ore during continued deformation. The above observations, coupled with data from existing studies, strongly suggest Minto is representative of deposit generation within an arc subduction environment at depths not typically considered for copper-gold deposit formation.

The Masumbi Au-Cu deposit in the Ndori Greenstone Belt of western Kenya is hosted in dacitic volcanics of the Nyanzian Group (2710 ± 340 Ma) and dioritic to granodioritic felsic intrusives (2504 ± 48 Ma). The deposit is characterised by gold and copper mineralisation that is associated with quartz-sulphide veins and veinlets. The copper mineralisation typically occurs as chalcopyrite. Gold is closely associated with pyrite in mineralogy and its pathfinder elements silver, bismuth, tellurium and selenium in geochemistry. The gold occurs in two forms that may indicate two generations of precipitation: the equant and the elongate forms. Based on Au/Ag ratios, the equant gold grains can be classified as native gold as their gold content is greater than 90 wt%. The elongate gold grains can be classified as electrums as their silver content is greater than 38 wt%. While there is a strong Au-Ag association within individual gold grains supporting an orogenic model for the gold mineralisation, mineralisation at the Masumbi Prospect appears atypical of Archaean orogenic gold deposits because of the abundance of copper (up to 0.43%). The enrichment of silver, copper, bismuth and tellurium in ore assemblages is common in porphyry, VMS and epithermal systems, but their presence at Masumbi does not preclude the formation as an orogenic deposit. Assay results from three Masumbi diamond drill-holes show an apparent correlation between gold and copper. However, petrography and electron probe microanalyses results from this study indicate that chalcopyrite is an earlier phase than pyrite as it occasionally occurs as inclusions in pyrite. This petrogenetic relationship between pyrite and chalcopyrite suggests that there is no temporal relationship between gold and copper mineralisation. Statistical analysis of the assays shows no linear correlation between gold and copper thereby supporting the above findings. The gold and copper mineralisation have been interpreted as forming as two separate events with copper forming first followed by gold. These events are both related to the intrusion of the felsic rocks that are associated with the Aruan metamorphic event that has been responsible for the bulk of the gold mineralisation on the Tanzanian Craton. The common alteration assemblage in the Masumbi rocks comprises chlorite and epidote. This alteration assemblage is typical of regional greenschist metamorphic facies grading into amphibolite metamorphic facies in the Nyanzian Group of Kenya. However, these alteration minerals could possibly be products of propylitic alteration in the rock groundmass. Other alteration mineral assemblages, possibly of hydrothermal origin, comprise muscovite, sericite, quartz, carbonate, associated with the sulphides pyrite and chalcopyrite. Although the occurrence of gold appears to be controlled by the presence of pyrite, it is also associated with silicification. Exploration methods have been proposed to target undiscovered gold deposits in the Ndori Greenstone Belt that are similar to the Masumbi deposit. These methods could probably be applied to vein-type gold deposits in other granite-greenstone terranes in the Lake Victoria Goldfields.

Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1995?
National Grid Reference Maitland Sheet I-553/12 (1:250 000) Whyalla I-53/8 (1:250 000). Three folded maps in pocket inside back cover. Includes bibliographical references (leaves 74-78).

Continental magmatic arcs host economically important porphyry ore deposit types for copper, gold, and molybdenum, and, if preserved, epithermal high- to intermediate-sulfidation gold and silver deposits. These deposits are genetically and/or spatially associated with magmatism, so understanding the link between magmatism and mineralisation is seen as a crucial endeavor to assist knowledge of mineralisation processes and strategies for regional-scale mineral exploration. This thesis examines aspects of the mineralisation potential of continental arc magmatic rocks that are exposed as part of the Permo-Carboniferous Kennedy Igneous Association (KIA) from northeastern Queensland. This belt of upper crustal intermediate to felsic granitoids and associated volcanic rocks is recognised to host many economic ore deposits related to igneous activity. Using well-established analytical techniques to analyze whole-rock and mineral major- and trace element compositions combined with Sm-Nd isotopes, I investigate two different localities related by their occurrence in time and space, with the aim to better understand magma fertility, or more specifically the petrogenetic processes contributing to Permo-Carboniferous Cu-Au mineralisation in northeast Queensland. This work strives to improve the applicability of magma fertility concepts to confidently identify fertile igneous terranes potentially covering high grade Cu-Au deposits at depth. The first location investigated lies to the south of Townsville at the northern edges of the Bowen Basin, where the early Permian Lizzie Creek Volcanic Group (LCV) hosts the Mount Carlton high-sulfidation epithermal Au-Cu deposit. Established whole-rock geochemical parameters, e.g. Sr/Y, V/Sc, used to distinguish fertile porphyry Cu-Au hosting intrusive rocks from barren intrusions, were tested on the "fertile" LCV succession, hosting the Mt. Carlton deposit and compared to contemporary "barren" volcanic rocks of the same group. The results reveal that the key control on generating the fertile LCV sequence was a high magmatic water content, reflected by early fractionation of amphibole at the source level, whereas the barren sequence was comparably dry, and formed by typical fractionation of plagioclase and clinopyroxene. This outcome has major implications for the applicability of whole rock geochemistry as a magma fertility indicator. The here presented results suggest that for volcanic rocks, which tend to be affected by hydrothermal alteration; a) Sr/Y is not a reliable fertility proxy and; b) Rare earth element ratios (e.g. La/Yb, Dy/Yb), which are relatively resistant to alteration, can be used to reveal differences in magmatic evolution. This supports previous research on magma fertility, and provides strong evidence that fertile magmatic suites can be identified from volcanics sequences that evolved from basalt to rhyolite with a progressive increase in La/Yb, decreasing Dy/Yb, and consistent or slightly increasing V/Sc ratios, despite having experienced some degree of alteration. The second location investigated in this thesis is the Tuckers Igneous Complex (TIC); a calc-alkaline, I-type igneous complex which intruded the Ravenswood Batholith between ~300-290 Ma and formed within the same convergent margin as the LCV. The TIC is part of the KIA and its relevance for this project lies within its close association with the major early Permian, breccia-hosted Mt. Leyshon Au deposit. The TIC contains a sequence of intrusive rocks from gabbro to felsic granodiorite, and hence offers the opportunity to investigate geochemical evolution, particularly volatile element evolution, of arc magmas at upper crustal levels. Here, I build on previous geochemical and petrographic data for the complex using newly acquired whole-rock geochemistry and in-situ mineral analyses of the major rock forming minerals plagioclase-clinopyroxene-orthopyroxene, and the halogen-bearing minerals apatite and biotite (and amphibole) to monitor and track volatile evolution (Cl and F). As volatile element behavior is recognised to have a fundamental control on magma fertility, this study, offers new insights into the fertility of this Permo-Carboniferous arc, which can be applied to other arc worldwide. My new results show that the TIC formed through closed-system crystal fractionation from gabbro to mafic granodiorite varieties with only minor mixing and/or assimilation, and likely became an open system during cooling and crystallisation of the more felsic granodiorites. Based on apatite halogen contents, volatile saturation is suggested to have occurred at around ~63-65 wt.% bulk-rock SiO₂, up to which point estimated Cl melt contents steadily rise, and then suddenly drop from ~0.8 to 0.4 wt.%. This abrupt change likely relates to the exsolution of a Cl-rich volatile phase, and also marks important changes within the mineral assemblage from a dry Plag ± Px ± Fe-Ti oxide assemblage, towards a more hydrous and slightly more oxidised Plag ± Hbl ± Bt ± Mag assemblage. Fluorine enriches in the melt with fractionation, even once saturation in a volatile phase is reached, consistent with what is expected from experimental partitioning studies in the system apatite – melt – fluid. Local or temporal changes in the magma's fO₂ is indicated by a measurable increase in apatite S contents in evolved felsic granodiorite, as apatite preferentially incorporates S as its oxidised species S⁶⁺, which also coincides with the general observed changes in the rock forming mineral assemblages as described above. Indicated volatile exsolution, causing loss of significant proportions of Cl together with oxidising conditions at which the bulk of dissolved S may have been present and possibly degassed as S⁴⁺O₂ (and causing the presence of low amounts of available S²⁻ to precipitate base metals) from the TIC magma may have caused mineralization within overlying, but now eroded rocks. A second possibility may be that the TIC was never able to produce mineralising fluids due to early segregation of sulfides, scavenging ore forming metals (e.g. Cu, Au, and Ag) prior to the crystallisation of TIC gabbro, and thereby stripping the TIC of its ore-forming potential early on. However, an exsolved Cl-rich fluid is very capable of transporting ore metals, therefore the role and true nature of such fluid(s) originating from the TIC can be subject of further investigations. The here presented results help to understand Cu-Au fertility on a regional, magmatic arc terrane (both volcanic and intrusive) from initial lower crustal petrological processes to the surface, but also on a local scale; within confined individual igneous bodies, their respective mineral assemblages, and their potential role towards regionally present Cu-Au mineralisation. In particular the findings on volcanic rocks offer great potential as easily accessible first-order fertility assessment tool for magmatic-hydrothermal Cu-Au exploration worldwide.

Transported regolith has the capacity to mask underlying mineralisation by restricting the migration of most trace elements to the surface. Oxidation of sulphides generates highly mobile H+ which may migrate to surface, resulting in alteration of minerals and redistribution of elements within transported regolith cover. A detailed geochemical and geophysical study has been conducted at the Mandamah Cu-Au deposit in central-western New South Wales, where sub-economic mineralisation is covered by ~50 m of transported regolith and ~30 m of in situ regolith. A shallow-penetration electromagnetic survey was undertaken on nine transects and detailed mineralogical and selective extraction/ICP-MS geochemical analysis performed on regolith samples obtained from 107 soil cores and 16 pits spanning three extensive traverses across buried mineralisation. The selective extractions used were ammonium acetate, hydroxylamine.HCl and aqua regia. A distinct vertical zonation exists in the upper two metres of the transported regolith cover across the site and is related to soil mineralogy, soil pH, electrical conductivity and the amount of selectively extractable elements using the different geochemical extractions. The upper zone of near-neutral soil pH contains organic material but little carbonate; the intermediate high-pH zone has up to 2% Mg-calcite; the underlying low-pH zone displays Fe mottling. This zonation results from precipitation of salts due to evaporation, changes in redox potentials and accumulation of organic materials, in an otherwise relatively homogeneous quartz-clay alluvium. Ground conductivity measurements and selective extraction geochemistry display a strong response to parts of the underlying mineralisation. The principal signature is the depletion of Ca, S and Na, a reduction in the cation exchange capacity, the presence of non-carbonate alkalinity and a low electrical conductivity. A model to account for these patterns has been developed and involves a "prograde" stage of alteration of clay mineralogy and a redistribution of carbonates and various trace elements due to the development of an "acid chimney" above the oxidizing mineralisation during a period of elevated water tables and a "retrograde" stage involving a redistribution of some mobile elements back into the former acid chimney zone following the onset of more arid conditions. The results of this research demonstrate that the effects of sulphide mineralisation on the upper transported regolith at Mandamah can be detected using a combination of selective extraction geochemistry and shallow depth conductivity measurements. This technique has potential application in similar arid to semi-arid terrains.

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The Kanmantoo Cu-Au deposit has been in episodic operation since 1846, one decade after the capital city of Adelaide was established some 40 kilometres to the NW. Regionally and within the host stratigraphy there exists archetypal evidence of the Cambrian Delamerian Orogeny through a complex structural, metamorphic and intrusive history. Consequently, numerous theories exist within the literature regarding a syngenetic or epigenetic style of mineralisation and the debated contribution, if any, of magmatic hydrothermal fluids. This study has documented numerous felsic intrusive vein sets within the Kanmantoo Cu-Au deposit which have been utilised to constrain the role of igneous activity on mineralisation within a wider Delamerian context. Monazite U–Pb ages of felsic veins show that intrusion first occurred at syn-peak metamorphic, syn-orogenic conditions (495.11 ± 2.79 Ma), continuing periodically until post-peak metamorphic, extensional conditions (483.43 ± 2.52 Ma). Intrusions are coeval with mineralisation and are temporally and geochemically analogous to magmatic activity in the adjacent Monarto and Murray Bridge provinces. Analysis of trace elements in monazites identifies the Kanmantoo Cu-Au deposit as a syn- to post-peak metamorphic hydrothermal anomaly which, combined with the presence of felsic veins, indicates that mineralisation resulted partly from fluids generated by a pluton at depth. These findings broadly confirm the prospectivity of Delamerian-affected terranes throughout large parts of South Eastern Australia where pervasive intrusive geology exists.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018

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The Palaeoproterozoic Poodla Granite within the Olary Domain, Curnamona Province, South Australia, has been suggested as a direct contributor to Cu-Au mineralisation within the region on the basis of age correlations. Alteration present within the Poodla Granite consists of four styles that have been interpreted as two events. The first event includes pervasive potassic alteration followed by pervasive Na-Ca alteration. Sm/Nd isotope analysis indicates fluids for this event were sourced from the Willyama Supergroup sediments. The second event consists of fracture-controlled sodic and Ca-Na-Si alteration with associated actinolite/clinopyroxene brecciation. Utilisation of magmatic major element trends obtained from a natural analogue (Mt Angelay Complex, Cloncurry District) has allowed greater accuracy in chemical characterisation of alteration. Fluid inclusion analysis has identified two distinct fluids involved in the later fracture-controlled sodic and Ca-Na-Si alteration event. Namely, a low salinity (18-26wt% NaCl equivalent) and a high salinity (35-45wt% NaCl equivalent) fluid. A later fluid mobilisation event related to the Palaeozoic Delamerian Orogeny is indicated by re-equilibration of the Rb/Sr isotopic system. New age constraints from other granites in the I-type suite, to which Poodla Granite belongs, suggest the Poodla Granite did not have direct hydrothermal input into regional Cu-Au mineralisation. Analysis of alteration chemistry suggests that Cu and Au mobilisation occurred during the first alteration event. These results offer evidence for previously untested Cu-Au mineralising models within the region and may encourage exploration for Cu-Au resources.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2003

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The world-class Boddington Cu-Au-Mo deposit has a complex genetic history. The relative importance of different ore-forming processes during the period 3.0 – 2.6 Ga is debated, particularly with respect to the role played by the 2611±3 Ma Wourahming granite. LA-ICP- MS analysis of trace element concentration in molybdenite represents a valuable new metallogenetic tool to track mineralising events in deposits with protracted geologic histories. The Re content and trace-element signatures in molybdenite from diorite and granite show three distinct populations, attributed to porphyry-style (hundreds of ppm) orogenic- and granite-related systems (<1 to a few ppm, respectively). Rhenium concentrations in molybdenite are highly variable on the deposit-scale. Economic concentrations of Re occur only at shallower levels in both Central Diorite and ABreccia. The Au content correlates with high-concentrations of chalcophile elements (CE). This is seen in the association of Au- minerals and Bi-(Pb)-tellurides present as inclusions in the molybdenite from diorite and is inferred from an LA-ICP-MS element map for molybdenite in granite. The FIB-SEM and TEM study show that visible telluride inclusions extend down to the nanoscale as coherent intergrowths with host molybdenite. Nanoporosity is accompanied by a whole range of structural defects and twinning. The telluride species identified include unnamed Bi4Pb7Te4S9. Analysis of stacking sequences show co-precipitation of Bi-tellurides and molybdenite under equilibrium conditions. In corroboration with EPMA data, this is the first confirmation that minerals from the aleksite series are characteristic components of the ore at Boddington. Molybdenite with high-concentration of chalcophile elements is present as the 2H polytype only, contrary to previous hypothesis that incorporation of trace elements is assisted by 3R structural modification. Instead, a new mechanism is presented in which coherent lattice-scale intergrowths between molybdenite and tellurides are reasons for the measured high CE concentrations. Knowing that Bi-(Pb)-tellurides are Au-carriers, this may also explain the observed, unusual Au-enrichment in molybdenite from Boddington. Nucleation of Au fine particles is inferred from element map correlations but further work is necessary to prove if Au nanoparticles are also present. Petrographic, mineralogical and geochemical evidence support a three-stage model for Boddington. An early porphyry event can account for the bulk of the Cu mineralisation, as well as some of the Au and Mo. A subsequent orogenic-Au event led to shearing and remobilisation of ore components. New constraints on metamorphic conditions are offered by chlorite and stannite-sphalerite geothermometry (200-420 °C) and the occurrence of two co- existing pyrrhotite species. The granite introduced some Au, Mo and other „granitic‟ elements, notably Bi leading to substantial upgrading of Au grades by Bi-melt scavenging. The study concludes however that hydrothermal activity associated with granite was not the most important concentrator of ore minerals.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2011