Magmatic history of the Eastern Creek Volcanics, Mt Isa, Australia: insights from trace-element and platinum-group-element geochemistry

Gregory, Melissa Joy; Keays, Reid R.; Wilde, Andrew Robert

doi:10.1080/08120090802266618

Cited by 5 publications

(7 citation statements)

References 46 publications

(62 reference statements)

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“…Basaltic rocks were erupted through an older ≥ 1840 Ma continental basement and in sufficiently large volumes across northern Australia to warrant the term large igneous province (Gibson et al, ; Scott et al, ). They have been compared to 180 Ma continental flood basalts in southern Africa (Karoo) and share many of the same compositional characteristics, including a subduction or arc‐like geochemical signature thought to reflect decompressional melting of a metasomatically enriched or crustally contaminated lithospheric mantle (Gibson et al, ; Gregory et al, ; Scott et al, ). A backarc intracontinental rift setting for basaltic magmatism is widely accepted although no corresponding agreement has yet been reached on the position of the contemporary subduction zone and magmatic arc which have been variously located (Figures a and a) along the southern edge of the Arunta Block in central Australia (Betts et al, ; Betts et al, ; Giles et al, ; Karlstrom et al, ; Scott et al, ) or farther outboard along the eastern or western margins of conjoined Australian and Antarctic continents (Betts et al, ; Gibson et al, ; Gibson et al, ).…”

Section: Paleoproterozoic Eastern Australia: Basin History and Tectonmentioning

confidence: 99%

Orogenesis in Paleo‐Mesoproterozoic Eastern Australia: A response to Arc‐Continent and Continent‐Continent Collision During Assembly of the Nuna Supercontinent

et al. 2020

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Northern and southern Australia preserve a common record of 1790-1655 Ma intracontinental rifting and backarc extension culminating in formation of a marginal sea that subsequently collapsed following a 1650-1640 Ma reversal in plate motion and onset of arc-continent collision. Arc-continent collision was accompanied by intermediate-pressure Barrovian-type metamorphism (6-8 kb) and widespread crustal thickening as reflected in a clockwise pressure-temperature-time path. Later metamorphism during the 1620-1580 Ma Isa and Olary orogenies occurred under intrusion-enhanced lower pressure conditions (4-6 kb) and followed a counterclockwise pressure-temperature-time path incompatible with either significant amounts of crustal thickening or tectonic models which have Australia and Laurentia commencing collision at this time. Continent-continent collision more likely followed on closely behind arc-continent collision (Riversleigh Tectonic Event), precipitating a switch in crustal shortening from northeast-southwest to west-east as the older rift template and underlying basement structures were reactivated in a transpressive or multicollisional tectonic regime not unlike that which produced the Himalayan-Tibet orogenic system. As in the latter, ongoing collision was accommodated by thrusting, extensional collapse and lateral extrusion of still thermally weak crust on orogen-parallel strike-slip faults, resulting in formation of the west-east-striking Isa Superbasin, isothermal decompression and granite intrusion from 1620 Ma. A comparable record of deformation, metamorphism, and magmatic intrusion from 1650 until 1600 Ma has been documented for northern and southern North America (Forward/Racklan and Mazatzal orogenies) indicating that Laurentia and Australia were likely proximal to each other throughout this period.

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Section: Paleoproterozoic Eastern Australia: Basin History and Tectonmentioning

confidence: 99%

Orogenesis in Paleo‐Mesoproterozoic Eastern Australia: A response to Arc‐Continent and Continent‐Continent Collision During Assembly of the Nuna Supercontinent

et al. 2020

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“…Significantly, volcanic rocks in both these sequences were erupted at roughly similar times and in similarly discrete pulses at 1790 Ma, 1780Ma, 1760Ma, and 1740. Compositions of basaltic rocks erupted at these times are also very similar, showing moderately high enrichment in lithophile elements coupled to conspicuous depletions in high field strength elements like Nb, P, and Ti, consistent with melting of a metasomatically enriched or crustally contaminated lithospheric mantle Gregory et al, 2008;. Geochemical and isotopic analyses for these and other basaltic rocks compared in this study are listed in Tables DR1 and DR2 in the GSA Data Repository Item 1 .…”

Section: Short Researchmentioning

confidence: 58%

Antipodean fugitive terranes in southern Laurentia: How Proterozoic Australia built the American West

Gibson

Champion

2019

Lithosphere

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Paleoproterozoic arc and backarc assemblages accreted to the south Laurentian margin between 1800 Ma and 1600 Ma, and previously thought to be indigenous to North America, more likely represent fragments of a dismembered marginal sea developed outboard of the formerly opposing Australian-Antarctic plate. Fugitive elements of this arc-backarc system in North America share a common geological record with their left-behind Australia-Antarctic counterparts, including discrete peaks in tectonic and/or magmatic activity at 1780 Ma, 1760 Ma, 1740 Ma, 1710–1705 Ma, 1690–1670 Ma, 1650 Ma, and 1620 Ma. Subduction rollback, ocean basin closure, and the arrival of Laurentia at the Australian-Antarctic convergent margin first led to arc-continent collision at 1650–1640 Ma and then continent-continent collision by 1620 Ma as the last vestiges of the backarc basin collapsed. Collision induced obduction and transfer of the arc and more outboard parts of the Australian-Antarctic backarc basin onto the Laurentian margin, where they remained following later breakup of the Neoproterozoic Rodinia supercontinent. North American felsic rocks generally yield Nd depleted mantle model ages consistent with arc and backarc assemblages built on early Paleoproterozoic Australian crust as opposed to older Archean basement making up the now underlying Wyoming and Superior cratons.

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“…The Paroo Fault is crosscut by a series of faults (the Bernborough and J46 Faults; Fig. 2) that have been interpreted as conduits for the fluid that leached copper out of the ECV and deposited it in the Urquhart Shales (e.g., Heinrich et al, 1989;Heinrich et al, 1995;Gregory et al, 2008). The copper orebodies have irregular shapes, with highest grades in zones of most structural complexity (Fig.…”

Section: Regional and Deposit Geologymentioning

confidence: 99%

“…The lighter δ 65 Cu values close to the Paroo Fault can be explained by fluid ingress along the fault, at intersections with the steeper structures, and the contact with the Urquhart Shale which constitutes a strong chemical contrast. The mafic rocks of the underlying ECV constitute the most likely metal source (e.g., Heinrich et al, 1995;Gregory et al, 2008) whereas the crosscutting steep structures such as the Bernsborough and J46 Faults represent the fluid pathways. Fluid inclusion studies, alteration and ore mineral chemistry all suggest that copper deposition at Mount Isa occurred at temperatures between 300 and 350 °C (e.g., Heinrich et al, 1989;Cave et al, 2020).…”

Section: Copper Isotopes As Indicators Of Hydrothermal Fluid Pathwaysmentioning

confidence: 99%

“…The first model proposes that copper was sourced within the basin from ferruginous red beds by oxidised basinal brines and transported along permeable mud and silt horizons to the pyritic Urquhart Shales where chalcopyrite deposition occurred due to reduction reactions (e.g., McGoldrick and Keays, 1990;Wilde et al, 2006). The second model proposes that copper was sourced from basement mafic rocks by oxidised basinal or metamorphic brines, transported along fractures and deposited in the overlying Urquhart Shales either by cooling, pH change or an increase in sulfur fugacity (e.g., Heinrich et al, 1989;Heinrich et al, 1995;Gregory et al, 2008). In this contribution, we present, for the first time, 65 Cu/ 63 Cu isotope data (reported as δ 65 Cu) from chalcopyrite across the Mount Isa deposit and discuss the results in terms of metal source, transport, precipitation and the two most prominent competing genetic models.…”

Section: Introductionmentioning

confidence: 99%

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A magmatic copper and fluid source for the sediment-hosted Mount Isa deposit

Sanislav,

Mathur,

Rea

et al. 2023

Geochem. Persp. Let.

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The world class Mount Isa deposit is a unique, sediment-hosted, copper deposit with no known equivalent around the world and a controversial origin. We report δ 65 Cu values (n = 90) from chalcopyrite grains collected systematically across the entire deposit. The δ 65 Cu shows a unimodal distribution with limited variability (min = −0.87 ‰; max = 0.88 ‰) and an average value (þ0.13 ‰) comparable to average igneous rocks. In general, the δ 65 Cu values in chalcopyrite are lower near major structures and heavier further away, consistent with equilibrium fractionation with distance from the fluid source. The range in δ 65 Cu of chalcopyrite from the Mount Isa deposit is less variable compared to sedimentary copper, VMS and porphyry/ epithermal deposits, but similar to Michigan deposits; meanwhile, average δ 65 Cu at Mt. Isa is distinctly higher than sedimentary copper deposits, but similar to VMS, porphyry/epithermal and Michigan deposits. These data suggest that, from a copper isotope perspective, the Mount Isa deposit is clearly different from sedimentary copper deposits and more like VMS, porphyry copper/ epithermal and Michigan style deposits. The average δ 65 Cu (þ0.13 ‰) is almost identical to the average δ 65 Cu (þ0.14 ‰) from Proterozoic basalts and suggests that copper was sourced from the underlying mafic rocks; the limited fractionation and the normal distribution of the δ 65 Cu indicate a very effective leaching mechanism and transport by a hot fluid from which chalcopyrite precipitated without significant fractionation of copper isotopes.

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Magmatic history of the Eastern Creek Volcanics, Mt Isa, Australia: insights from trace-element and platinum-group-element geochemistry

Cited by 5 publications

References 46 publications

Orogenesis in Paleo‐Mesoproterozoic Eastern Australia: A response to Arc‐Continent and Continent‐Continent Collision During Assembly of the Nuna Supercontinent

Orogenesis in Paleo‐Mesoproterozoic Eastern Australia: A response to Arc‐Continent and Continent‐Continent Collision During Assembly of the Nuna Supercontinent

Antipodean fugitive terranes in southern Laurentia: How Proterozoic Australia built the American West

A magmatic copper and fluid source for the sediment-hosted Mount Isa deposit

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