Indiana University-Purdue University Indianapolis (IUPUI) / The Sudbury Igneous Complex (SIC) in Sudbury, Canada is a remnant geologic structure from a meteor impact that occurred ~1.85 Ga. The impact produced ~30,000 km3 of superheated melt which reached >2200 °C. The existing SIC is composed of three compositionally distinct layers, norite, quartz gabbro, and granophyre, which stretch the entire lateral distance of the complex. The presentation of layers in the SIC is unusual for impact melts, and the crystallization path has been debated by scientists. The SIC differs from more common layered mafic complexes because of its intermediate composition, crustal isotopic signature, and large volume of granophyre. This thesis is an investigation of some of the main theories surrounding the SIC and how it crystallized to form such distinct layers. There are two main theories of how the SIC formed its compositionally distinct layers: (1) fractional crystallization and (2) separation by viscous emulsion. The viscous emulsion theory involves isolated droplets of melt separating from the surrounding melt body due to differences in viscosity and density, similar to an emulsion of oil and water. In this study, viscous emulsion theory was investigated experimentally by heating samples of rock from the SIC to the extreme temperatures associated with the Sudbury impact, and then analyzing the cooled experimental products using electron microscopy to determine if there was evidence of textures that would be consistent with expectations for a viscous emulsion. Fractional crystallization was investigated by modeling using the vii software EasyMELTS to evaluate compositions from the SIC to estimate how they would crystallize according to the temperature, pressure, and other properties of the melt. There was no textural evidence of a viscous emulsion found in the experimental products. The models produced compositions similar to what is seen in the SIC but had limited application to fractional crystallization theory.

<p> Forty-Three cores were collected from the region of the Killarney Igneous Complex, southeast of the town Killarney. These cores were analysed by measuring geophysical properties such as bulk susceptibility, percent anisotropy, magnetic foliation and lineation and remanence. The magnetic fabric measured indicated a regional fabric. In some areas the fabric was completely overprinted due to localised deformation. Measured remanence may make it possible to determine the effect of previous deformations; however, none was seen in this study. </p> <p> The petrological fabric was also investigated by taking thin sections perpendicular to the long axis of the core. Again it was possible to see a regional and localized deformation pattern due to reduced grain size, grain alignment and recrystallization. </p> <p> Measurements collected from the samples determined that both the magnetic fabric and petrological fabric showed indications of being near areas of greater deformational intensities. A relationship was then established between the magnetic fabric and petrological fabric on a fine scale. This relationship may aid in determining direction and extent of deformation in the rock bodies when it is not easily identifiable in the field. </p> / Thesis / Bachelor of Science (BSc)

Philosophiae Doctor - PhD / The Platreef is a platinum group elements (PGE) deposit located in the Northern limb of the Bushveld Igneous Complex (BIC). It is a series of mafic and ultramafic sills that are overlain by rocks from the Main Zone (MZ) of the BIC. In comparison to PGE deposits (i.e., Merensky Reef and the UG-2 chromitite) occurring in the Critical Zone (CZ) of the Eastern and Western Limbs of the BIC, which are less than 1 m in thickness, the Platreef is 10 to 400 m in thickness and is comprised of a variety of rocks. PGE mineralisation in the Platreef is not confined to a specific rock type, and its distribution and styles also vary with depth and along strike. Despite the numerous researches that have been conducted, the genesis of Platreef is still poorly understood. New major and trace elements in conjunction with Sr–Nd isotope data, generated from whole-rock analyses of different Platreef rocks, were collected from four drill cores along its strike. The data were examined to determine the source of the magmas and identify the processes involved in its genesis. The study also aimed at establishing whether a genetic link exists between the Platreef magmas and the magmas that formed the Lower Zone (LZ), CZ and MZ in the Rustenburg Layered Suite (RLS) of the BIC. The petrography revealed that the Platreef in the four drill cores consists of harzburgite, olivine pyroxenite, pyroxenite, feldspathic pyroxenite and norite. Based on the textural and modal mineralogy variations, feldspathic pyroxenite was subdivided into five types (I, II, III, IV and V). The variation in the average contents of MgO, LaN/YbN and ΣREE for the Platreef rocks are consistent with the modal mineralogy from the least to the most differentiated rocks. However, the Sr–Nd isotope data of the Platreef rocks have revealed two distinct groups of samples with decreasing ɛNd2060. Group 1 consists of pyroxenite and feldspathic pyroxenite II, III and V having ɛNd2060 values that range from –8.4 to –2.9, and 87Sr/86Sr2060 values from 0.707281 to 0.712106. The Platreef rocks of group 2 consist of olivine pyroxenite and feldspathic pyroxenite Type I with ɛNd2060 ranging from –12.6 to –10.8, and 87Sr/86Sr2060 ranging from 0.707545 to 0.710042. In comparison to the LZ, CZ and MZ rocks, which have ɛNd values ranging from –8.5 to –5.1, and 87Sr/86Sr ranging from 0.704400 to 0.709671, Platreef pyroxenite of group 1 have lower negative ɛNd2060 values (from –3.8 to –2.9) and higher 87Sr/86Sr2060 values from 0.709177 to 0.710492, whereas feldspathic pyroxenite of group 1 have overlapping ɛNd2060 values (from –8.4 to –4.9) but also higher 87Sr/86Sr2060 values (from 0.707281 to 0.712106). Instead, the Platreef olivine pyroxenite and feldspathic pyroxenite in group 2 highly negative ɛNd2060 values and overlapping 87Sr/86Sr2060 values. It is therefore suggested that the Platreef magmas derived from the partial melting of an heterogeneous mantle source comprising depleted mantle melts and both metasomatized slightly unradiogenic Nd enriched melts and highly unradiogenic Nd enriched melts from the subcontinental lithospheric mantle. These magmas ascended via the continental crust using different paths and interacted with rocks of different Sr–Nd isotopic compositions which resulted in the formation the hybrid magmas. The study speculates that sulphide saturation in the Platreef magmas was reached in the staging chambers at depth, and the varying styles of the PGE mineralisation in the Platreef rocks are the result of the varying degree of partial melting of the heterogeneous source for their magmas. In conlusion, this study suggests that the genesis of the Platreef is much more complex and should be considered very much independent from processes involved in the genesis of the RLS in the Eastern and Western Limbs of BIC in agreement with earlier studies. / NRF Inkaba ye Africa Iphakade / 2020-08-31

This study comprises a petrographical and mineralogical investigation of rocks from an area 850 sq. km in size, situated about 80km northeast of Middelburg. Roughly half of the area is occupied by rocks of the epicrustal phase of the Bushveld Complex, and consists largely of Rooiberg Felsite and granophyre as well as leptite, microgranite and granodiorite. Numerous veins of finegrained granite traverse the leptite which is considered to be highly metamorphosed felsite. These veins of fine-grained granite probably owe their origin to the melting of the leptite. The coalescence of these products of melting gave rise to the thick sheet of._granophyre between the leptite and the felsite. Rocks of the Layered Sequence occupy the eastern half of the area and consist of the Main and Upper Zones which were subdivided into various subzones on the basis of characteristic rock types and marker horizons. Mineralogical investigations are restricted to the minerals from rocks of the Layered Sequence, namely orthopyroxene, plagioclase, apatite and the sulphides of the Upper Zone. In Subzone A of the Main Zone, the orthopyroxene is present as cumulus crystals, but it changes in texture to ophitic in the lower half of Subzone B where small discrete grains of inverted pigeonite are also developed. Inverted pigeonite is present in the upper half of Subzone B and in rocks of the Upper Zone, whereas the orthopyroxene-pigeonite relationships in Subzone C of the Main Zone are a repetition of those observed in the underlying rocks. The phase-change from orthopyroxene to pigeonite takes place over a transition zone in which both phases crystallized from the magma. It is envisaged that the first pigeonite to have crystallized from the magma at high temperatures had a lower Fe/Mg ratio than the hypersthene precipitating at slightly lower temperatures, with the result that the early formed pigeonite was unstable and reacted with the magma to form hypersthene. This caused the formation of groups of grains of hypersthene which are optically continuous over large areas and which may contain a few blebs of augite exsolved from the original pigeonite. A few pigeonite grains were effectively trapped in other minerals, mostly augite, and consequently escaped reaction with the liquid. These inverted to hypersthene at the appropriate temperature and contain numerous exsolution-lamellae of augite. As fractional crystallization of the magma continued, it moved further into the stability field of pigeonite and out of the stability field of hypersthene with the result that the formation of hypersthene by the reaction of pigeonite with magma was replaced by inversion of pigeonite to hypersthene. This inverted pigeonite is also present as groups of grains optically continuous and contains pre-inversion exsolution-lamellae of augite orientated at random, and post-inversion exsolution- lamellae which are orientated parallel to the (100) plane of the orthopyroxene throughout a unit. The inverted pigeonite is orientated in such a way that its crystallographic c-axis lies close to or in the plane of layering. This is explained as being due to the load pressure of the superincumbent crystal mass during the inversion. Textural features of the plagioclase revealed interesting information on the postcumulus changes in the rock. Reversed zoning, interpenetration and bending of plagioclase crystals as well as the presence of myrmekite are described. These are considered to be due to increased load pressure prior to and during crystallization of the intercumulus liquid. It is considered that the various types of pegmatoids may have originated by an increase in pressure on the intercumulus liquid which was concentrated to form pipe-like bodies by lateral secretion or filter pressing. Cumulus apatite is developed in the olivine diorites of Subzone D of the Upper Zone. From unit cell dimensions it seems as if it changes in composition from a fluor-rich hydroxyapatite at the base of this subzone to a relatively pure hydroxyapatite 70m below the roof. There seems to be a substantial increase in the fluor content of the apatite in the topmost 70m of the intrusion. Rocks of the Upper Zone contain considerably more sulphides than those of the Main Zone. This is ascribed to an increase in the sulphur content of the magma owing to fractional crystallization. The magma reached the saturation point of sulphur when rocks of Subzone D of the Upper Zone started to crystallize with the result that these rocks contain numerous small droplets of sulphide which constitute on an average about 0, 5 per cent by volume of the rocks. A concentration of the sulphides in these rocks would not yield a deposit of economic interest because of the unfavourable composition of the sulphide phase, which consits of more than 90 per cent pyrrhotite. Sulphides in the rocks below this subzone are intercumulus and a concentration could be of economic importance because the sulphide phase contains appreciable amounts of chalcopyrite and pentlandite. Although no economic concentration of sulphides are known from the Upper Zone, this study has revealed the presence of a mineralized anorthosite below Lower Magnetitite Seam 2 which contains in places up to 1 per cent Cu, 0, 18 per cent Ni and 1, 6g/ton platinum metals. Continuous, slow convection and bottom crystallization probably gave rise to the homogeneous rocks of the Main Zone. Injection of a considerable amount of fresh magma took place at the level of the Pyroxenite Marker which resulted in a compositional break and gave rise to a repetition in Subzone C of the rocks of the Main Zone below this marker. The oxygen pressure during crystallization of the magma was probably low, causing a gradual enrichment in iron in the magma and gave rise to the appearance of magnetite at the base of the Upper Zone. Intermittent increase in the oxygen fugacity is considered to be important in the formation of magnetitite seams. As a result of fractional crystallization the volatile content of the remaining magma gradually increased. This is seen firstly, by the appearance of biotite secondly by the appearance of cumulus apatite and droplets of sulphide and lastly by hornblende in the rocks of the Upper Zone. Some water-rich residual liquids apparently also intruded the overlying leptite, causing additional melting of the latter and the formation of irregularly shaped veins and pockets of granodiorite. A lateral change in facies of the rocks of the Layered Sequence in a souther ly direction is described. This is considered to be due to crystallization of the magma at slightly lower temperatures because of the more effective heat loss where the magma chamber was thinner. Two parameters of differentiation for layered intrusions are proposed, viz. a modified version of the differentiation index and a modified version of the crystallization index. The former seems more applicable for intrusions such as the Bushveld Complex, whereas the latter seems to be more applicable for intrusions in which there is a considerable development of ultramafic rocks. These two parameters can also be used to indicate the differentiation trend if they are plotted against height in the intrusion. / Thesis (PhD)--University of Pretoria, 1971. / gm2013 / Geology / unrestricted

The Bushveld Igneous Complex (BIC) is the largest layered mafic intrusion in the world and contains the largest known deposits of vanadium, chromium and Platinum group elements on the planet, as well as large deposits of iron, nickel, copper, tin and fluorite. To aid and improve our understanding of the tectonics that prevailed during the emplacement of the Bushveld Complex relevant data can still be extracted from the metamorphic aureole of the Complex, not the least among which are accurate determinations of pressure conditions during peak metamorphism. A relatively large number of geothermobarometric investigations have been performed on the Bushveld Complex aureole. The summation of all the thermobarometric studies on the Bushveld Complex aureole produces a dataset with largely divergent pressure-estimates, ranging from 1.5 kbar to 5.5 kbar. This study’s main aim was to produce new thermobarometric data for the Eastern Bushveld Complex aureole. To this ends metapelites from the aureole were sampled between Lydenburg and somewhat northwest of Penge. Polished thin-sections were produced for a number of samples and studied under microscope. After XRF analyses were performed on a refined number of samples, pseudosections for these samples were produced using Perplex. Electron microprobe analyses were used to analyze mineral chemistries of five samples and the resultant data used to construct isopleths for these samples in Perplex. The isopleth data was then used to scrutinize and, where possible, refine PT-estimates. The principal results obtained from mineral equilibrium modeling were the pseudosections and isopleths of samples DY09-54 and DY09-56. These samples’ cumulate results suggest that the metapelites of their sampling locality, which lies roughly ~36 km northwest of Penge, reached 530-565 ºC and 2230-2960 bar during peak metamorphism. Modelled isopleths of MnO/(MnO+CaO+FeO+MgO) suggest that these estimates be refined to 550 ± 5 ºC and 2650 ± 20 bar. These pressure estimates agree well with the majority of barometric studies in the literature that post-date the nineteen-eighties. The pressure estimates of 2230-2960 bar suggest that DY09-54 and DY09-56 were at a crustal depth of 7.9-10.4 km during peak metamorphism, assuming that a roughly 1.5 km thick load of rock, mainly of the Rooiberg Group and/or the Lebowa Granite Suite, were situated above the Rustenburg Layered Suite and at the top of the pile that overlay the samples. In such a case the Rustenburg Layered Suite’s contribution to the load would have represented a 4.2-6.7 km thick pile of these mafic rocks and, assuming that the load of Pretoria Group strata in the floor to the Complex had a thickness of 2350 m, the base of the Rustenburg Layered Suite would have been at a crustal depth of 5.6-8.0 km during peak metamorphism and directly above samples DY09-54 and DY09-56. Modelled palaeogeotherms together with the peak-metamorphic crustal depths estimated for samples DY09-54 and DY09-56 suggest that at peak metamorphism the samples’ temperatures had been elevated by no less than 320-355 °C, assuming that no thermal metamorphic effect was active on the samples just prior to the intrusion of the Bushveld Complex. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Geology / unrestricted

The presence of trace transition metal species in the atmosphere can be attributed to the emission of particulate matter into the atmosphere by anthropogenic activities, as well as from natural sources. Trace metals emitted into the atmosphere can cause adverse health–related and environmental problems. At present, limited data exists for trace metal concentrations in South Africa. In this investigation, the general aim was to determine the concentrations of trace metals in atmospheric aerosols in the industrialised western Bushveld Igneous Complex, as well as to link the presence of these species in the atmosphere to possible sources in the region. The measurement site was placed in Marikana, a small rural town situated 35 km east from Rustenburg in the North West Province of South Africa. It is surrounded by numerous industrial and metallurgical operations. MiniVolumeTM samplers and Teflon® filters (2 ;m pores) were utilised to collect PM2.5 and PM10 particulate samples. The MiniVolumeTM samplers were programmed to filter 5 litres of air per minute for 12 hours per day, over a six–day period. The starting time for sampling was altered every six days, in order to obtain both day and night samples. Sampling was performed for a period of one year. The collected samples were chemically analysed with inductively coupled plasma mass spectroscopy (ICP–MS). Surface analysis of the sampled filters was performed with a scanning electron microscope (SEM) in conjunction with energy–dispersive spectroscopy (EDS). The dataset was also subjected to factor analysis in an attempt to identify possible sources of trace metal species in the atmosphere. The concentrations of 27 trace metals (Be, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Pd, Cd, Ba, Pt, Au, Hg, Tl, Pb, U) were determined. Pd, Hg, Tl, U, Ca, Co, As, Cd, Ba and Au were above the detection limit 25% or less of the time during the sampling period. With the exception of Ni, none of the trace metals measured at Marikana during the sampling period exceeded local and international standards. Higher Ni levels were possibly due to base metal refining in the region. Pb, which is the only metal species that has a standard prescribed by the South African Department of Environmental Affairs (DEA), did not exceed any of the standards. It is also significant to refer to Hg that was below the detection limit of the analytical instrument for the entire sampling period. The impact of meteorological conditions revealed that wet removal of atmospheric PM10 trace metals was more significant than the wind generation thereof. During the dry months, the total trace metal concentrations in the PM10 fraction peaked, while PM10 particles were mostly washed out during the wet season. Wind speed showed an unexpected inverse pattern compared to wet deposition. A less significant seasonal trend was observed for the trace metal concentrations in the PM2.5 fraction, which was attributed to a faster replenishment of smaller particles into the atmosphere after rain events. Separation of trace metal concentrations into PM10–2.5 and PM2.5 fractions indicated that 79% of the total trace metal levels that were measured were in the PM2.5 fraction, which indicated a strong influence of industrial and/or combustion sources. Fractionalisation of each of the trace metal species detected showed that for each metal species, 40% and more of a specific metal was in the PM2.5 fraction, with Cr, V, Ni, Zn and Mn occurring almost completely in the PM2.5 fraction. Surface analysis with SEM supported results from the chemical analysis, which indicated that a large fraction of the particles was likely to originate from anthropogenic activities and from wind–blown dust. SEM–EDS also detected nonmetallic S that is usually associated with the Pt pyrometallurgical industry that is present in the western Bushveld Igneous Complex. Correlations between Cr, V, Ni, Zn and Mn revealed that the main sources of these species were pyrometallurgical industries. Explorative factor analysis of the unprocessed and Box–Cox transformed data for all 27 metals detected, resolved four meaningful emission sources, i.e. crustal, vanadium related, base metal related and chromium related. Comparison of trace metal species to other parameters measured (e.g. CO, BC) also indicated pyrometallurgical activities and wind–blown dust to be the main sources of trace metals in this region. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011.

The presence of trace transition metal species in the atmosphere can be attributed to the emission of particulate matter into the atmosphere by anthropogenic activities, as well as from natural sources. Trace metals emitted into the atmosphere can cause adverse health–related and environmental problems. At present, limited data exists for trace metal concentrations in South Africa. In this investigation, the general aim was to determine the concentrations of trace metals in atmospheric aerosols in the industrialised western Bushveld Igneous Complex, as well as to link the presence of these species in the atmosphere to possible sources in the region. The measurement site was placed in Marikana, a small rural town situated 35 km east from Rustenburg in the North West Province of South Africa. It is surrounded by numerous industrial and metallurgical operations. MiniVolumeTM samplers and Teflon® filters (2 ;m pores) were utilised to collect PM2.5 and PM10 particulate samples. The MiniVolumeTM samplers were programmed to filter 5 litres of air per minute for 12 hours per day, over a six–day period. The starting time for sampling was altered every six days, in order to obtain both day and night samples. Sampling was performed for a period of one year. The collected samples were chemically analysed with inductively coupled plasma mass spectroscopy (ICP–MS). Surface analysis of the sampled filters was performed with a scanning electron microscope (SEM) in conjunction with energy–dispersive spectroscopy (EDS). The dataset was also subjected to factor analysis in an attempt to identify possible sources of trace metal species in the atmosphere. The concentrations of 27 trace metals (Be, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Pd, Cd, Ba, Pt, Au, Hg, Tl, Pb, U) were determined. Pd, Hg, Tl, U, Ca, Co, As, Cd, Ba and Au were above the detection limit 25% or less of the time during the sampling period. With the exception of Ni, none of the trace metals measured at Marikana during the sampling period exceeded local and international standards. Higher Ni levels were possibly due to base metal refining in the region. Pb, which is the only metal species that has a standard prescribed by the South African Department of Environmental Affairs (DEA), did not exceed any of the standards. It is also significant to refer to Hg that was below the detection limit of the analytical instrument for the entire sampling period. The impact of meteorological conditions revealed that wet removal of atmospheric PM10 trace metals was more significant than the wind generation thereof. During the dry months, the total trace metal concentrations in the PM10 fraction peaked, while PM10 particles were mostly washed out during the wet season. Wind speed showed an unexpected inverse pattern compared to wet deposition. A less significant seasonal trend was observed for the trace metal concentrations in the PM2.5 fraction, which was attributed to a faster replenishment of smaller particles into the atmosphere after rain events. Separation of trace metal concentrations into PM10–2.5 and PM2.5 fractions indicated that 79% of the total trace metal levels that were measured were in the PM2.5 fraction, which indicated a strong influence of industrial and/or combustion sources. Fractionalisation of each of the trace metal species detected showed that for each metal species, 40% and more of a specific metal was in the PM2.5 fraction, with Cr, V, Ni, Zn and Mn occurring almost completely in the PM2.5 fraction. Surface analysis with SEM supported results from the chemical analysis, which indicated that a large fraction of the particles was likely to originate from anthropogenic activities and from wind–blown dust. SEM–EDS also detected nonmetallic S that is usually associated with the Pt pyrometallurgical industry that is present in the western Bushveld Igneous Complex. Correlations between Cr, V, Ni, Zn and Mn revealed that the main sources of these species were pyrometallurgical industries. Explorative factor analysis of the unprocessed and Box–Cox transformed data for all 27 metals detected, resolved four meaningful emission sources, i.e. crustal, vanadium related, base metal related and chromium related. Comparison of trace metal species to other parameters measured (e.g. CO, BC) also indicated pyrometallurgical activities and wind–blown dust to be the main sources of trace metals in this region. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011.

Thesis (M. Sc.(Geography)) -- University of Limpopo, 2019 / Global production of Platinum Group Metals (PGMs) is dominated by South Africa due to its large economic resources base in the Bushveld Igneous Complex (BIC). PGMs are used in a wide range of high technology applications worldwide including medicinal, industrial and commercial purposes, and its contribution to the Gross Domestic Product (GDP) and creating jobs for many. In an area where mining activities dominate, there are likely to be problems that need effective environmental management approaches, which can be facilitated through legislations. Marula Platinum Mine (MPM) is located in Limpopo province BIC which has the second largest number of mining productivity in South Africa. Environmental legislations have been put in place by the South African government in order to avoid or minimise the footprints caused by PGM mining. This study looked at environmental compliance with solid waste management practices by Marula Platinum Mine (MPM) as guided by Mineral and Petroleum and Resource Development Act (MPRDA) and National Environmental Management Act (NEMA) as well as the environmental impacts of MPM in the surrounding communities. Both primary (questionnaires, field observations and key informant interviews) and secondary (NEMA, MPRDA, journals, reports, pamphlets, internet and books) data was used to address the objectives of the study. Descriptive method and Statistical Package for Social Sciences (SPSS) version 25 were used for the analysis of data. The key research results revealed that MPM was compliant with 65% and 21% partially compliant with solid waste management practices. Only 14% of information on solid waste management practices could not be accessed because MPM is still operational. MPM had also had negative footprints on the surrounding villages such as dust generation and cracks on walls and floors on houses of community members, strikes and increase in the usage of substance abuse. Recommendations of the study are that MPM should address challenges that hinder environmental compliance so as to be 100% compliant with MPRDA and NEMA regulations. MPM should also provide other mitigation measures for blasting of explosives to reduce dust generation and problems of cracks on houses of surrounding village members.

The Station Creek Igneous Complex (SCIC) is one of the largest Middle-Late Triassic plutonic bodies in the northern New England Orogen of Eastern Australia. The igneous complex comprises of five plutons - the Woonga Granodiorite (237 Ma), Woolooga Granodiorite (234 Ma), Rush Creek Granodiorites (231 Ma) and Gibraltar Quartz Monzodiorite and Mount Mucki Diorite (227 Ma respectively), emplaced as high-level or epizonal bodies within the Devonian-Carboniferous subduction complex that resulted from a westward subduction along the east Australian margin. Composition of the SCIC ranges from monzogabbro to monzogranite, and includes diorite, monzodiorite, quartz monzodiorite and granodiorite. The SCIC has the typical I-type granitoid mineralogy, geochemistry and isotopic compositions. Its geochemistry is characteristics of continental arc magma, and has a depleted-upper mantle signature with up to 14 wt% supracrustal components (87Sr/86Srinitial = 0.70312 to 0.70391; Nd = +1.35 to +4.9; high CaO, Sr, MgO; and low Ni, Cr, Ba, Rb, Zr, Nb, Ga and Y). The SCIC (SiO2 47%-76%) has similar Nd and Sr isotopic values to island-arc and continentalised island-arc basalts, which suggests major involvement of upper mantle sourced melts in its petrogenesis. SCIC comprises of two geochemical groups - the Woolooga-Rush Greek Granodiorite group (W-RC) and the Mount Mucki Diorite-Gibraltar Quartz Monzodiorite group (MMD-GQM). The W-RC Group is high-potassium, calc-alkalic and metaluminous, whereas the MMD-GQM Group is medium to high potassium, transitional calc-alkalic to tholeiitic and metaluminous. The two geochemical groups of the SCIC magmas are generated from at least two distinct sources - an isotopically evolved Neoproterozoic mantle-derived source with greater supracrustal component (10-14 wt%), and an isotopically primitive mafic source with upper mantle affinity. Petrogenetic modeling using both major and trace elements established that the variations within respective geochemical group resulted from fractional crystallisation of clinopyroxene, amphibole and plagioclase from mafic magma, and late fractionation of alkalic and albitic plagioclase in the more evolved magma. Volcanic rocks associated with SCIC are the North Arm Volcanics (232 Ma), and the Neara Volcanics (241-242 Ma) of the Toogoolawah Group. The major and trace element geochemistry of the North Arm Volcanics is similar to the SCIC, suggesting possible co-magmatic relationship between the SCIC and the volcanic rock. The age of the North Arm Volcanics matches the age of the fractionated Rush Creek Granodiorite, and xenoliths of the pluton are found within epiclastic flows of the volcanic unit. The Neara Volcanics (87Sr/86Sr= 0.70152-0.70330, 143Nd/144Nd = 0.51253-0.51259) differs isotopically from the SCIC, indicating a source region within the HIMU mantle reservoir (commonly associated with contaminated upper mantle by altered oceanic crust). The Neara Volcanics is not co-magmatic to the SCIC and is derived from partial melting upper-mantle with additional components from the subducting oceanic plate. The high levels emplacement of an isotopically primitive mantle-derived magma of the SCIC suggest periods of extension during the waning stage of convergence associated with the Hunter Bowen Orogeny in the northern New England Orogen. The geochemical change between 237 to 227 Ma from a depleted-mantle source with diminishing crustal components, to depleted-mantle fractionate, reflects a fundamental change in the source region that can be related to the tectonic styles. The decreasing amount of supracrustal component suggests either thinning of the subduction complex due to crustal attenuation, leading to the late Triassic extension that enables mantle melts to reach subcrustal levels.