Thermomechanical erosion of ore-hosting embayments beneath komatiite lava channels: Textural evidence from Kambalda, Western Australia

Staude, Sebastian; Barnes, Stephen J.

doi:10.1016/j.oregeorev.2017.05.001

Cited by 32 publications

(29 citation statements)

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“…The fine intergrowth with sulfide, the presence of these textures suggestive of crystallisation from a previously superheated melt (Lofgren, 19080), and the distinctive cuspate geometry of the clast margins suggest that this sample is a melt-emulsion "breccia" formed as a physical mixture of molten silicate and sulfide magma. Such hybrid emulsion rock types have been described at silicate-sulfide contacts at Sudbury (Hawley, 1962) and in two examples of Western Australian komatiitehosted ores: Moran shoot, Kambalda (Staude et al, 2016;Staude et al, 2017), and Silver Swan (Dowling et al, 2004).…”

Section: Sample Ab-rp1mentioning

confidence: 93%

“…An alternative mechanism that needs to be considered is whether reverse Cr zoning is the result of reaction of cumulus pyroxenes (and pre-existing mafic rock xenoliths) with sulfide liquid. This possibility is raised by the common presence of narrow zones of strong enrichment in chromite at sulfide-silicate contacts in komatiite-hosted deposits (Ewers et al, 1976;Barrett et al, 1977;Frost and Groves, 1989;Dowling et al, 2004;Fonseca et al, 2008;Staude et al, 2016;Staude et al, 2017). Two critical observations are relevant here.…”

Section: Origin Of Reverse-zoned Pyroxenesmentioning

confidence: 94%

“…Evidence from other deposits is that Cr is a very minor component in magmatic sulfide liquids; while chromite is found at contacts between molten sulfide and silicate in komatiite settings (e.g. Staude et al, 2017) the dominant oxide phase in mafic-hosted magmatic sulfide deposits is invariably magnetite, not chromite (e.g. Dare et al, 2014).…”

Section: Origin Of Reverse-zoned Pyroxenesmentioning

confidence: 99%

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Textural development in sulfide-matrix ore breccias in the Aguablanca Ni-Cu deposit, Spain, revealed by X-ray fluorescence microscopy

Barnes

Piña

2018

Ore Geology Reviews

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The intrusion-hosted Ni-Cu sulfide deposit at Aguablanca in southwestern Spain contains a high proportion of ores in the form of sulfide-matrix ore breccias. These are polymict, with autolith and xenolith inclusions in sulfide-rich and/or sulfide-poor matrices. Inclusion lithologies include calc-silicate skarn rocks from the adjacent marbles, ultramafic and mafic cumulates, and remelted and recrystallized mafic rocks containing spinifex-like textures. Breccia textures have been investigated at mm to cm scale using desk-top and synchrotronbased microbeam XRF mapping which reveals a number of distinctive common features: disaggregation of inclusions into adjacent sulfide along original silicate grain boundaries; complex reverse and oscillatory zoning in Cr content of clinopyroxene grains within sulfide and inside inclusions; narrow reaction rims between country rock clasts and enclosing silicates; and preferential disposition of pyroxene crystals within pyrrhotite-pentlandite aggregates (original MSS) relative to inclusion-poor chalcopyrite. The observed range of textures is explained by a model of percolation of molten sulfide through a pre-existing silicate-matrix intrusion breccia, preferentially displacing a cotectic or eutectic plagioclase-pyroxene melt. The process is analogous to that believed to have formed interspinifex ore in komatiite-hosted deposits, and also to that responsible for superficially similar sulfide matrix ore breccias at Voisey's Bay. The preserved range of textures is interpreted as being due to late stage gravity-driven percolation of sulfide liquid from above into a pre-existing partially molten intrusion breccia. This intrusion breccia itself may have been emplaced into the neck of the Aguablanca stock, in the waning stages of magma flow.

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Section: Sample Ab-rp1mentioning

confidence: 93%

Section: Origin Of Reverse-zoned Pyroxenesmentioning

confidence: 94%

Section: Origin Of Reverse-zoned Pyroxenesmentioning

confidence: 99%

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Textural development in sulfide-matrix ore breccias in the Aguablanca Ni-Cu deposit, Spain, revealed by X-ray fluorescence microscopy

Barnes

Piña

2018

Ore Geology Reviews

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“…Where geometries are mappable, it appears that extremely high ux, giant komatiite ows in the Perseverance area have physically and thermally eroded hundreds of meters into the substrate and may have owed for 10s to 100s of km down-channel 44 . Ten-km scale lava channels, forming erosional troughs tens of metres deep and up to 200m wide are developed associated with the nickel sul de ores at Kambalda 45 . Lava temperature and effusion rate clearly affect the turbidity of ows and their erosive potential, but a signi cant factor controlling erosion by komatiite lavas is the geology of the substrate.…”

Section: Comparison To the Archean Earthmentioning

confidence: 99%

“…Jumbled blocks of disrupted terrain termed "chaos" are spatially linked with out ow channels. These channels are seen by some as analogous to glacial outburst oods on Earth that form due to rapid and catastrophic melting of glacial ice, sometimes associated with warming climate and other times associated with subglacial volcanism [4][5][6][7][8] . On Mars, potentially contentious elements of the aqueous hypotheses include the existence, rapid release and recharge of vast quantities of groundwater and ground ice 2 .…”

Section: Introductionmentioning

confidence: 99%

The volcanic geology of Morella Crater, Ganges Cavus and Elaver Vallis, Mars

Michalski¹

2021

Preprint

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Mars contains a large number of yet unexplained collapse features, sometimes spatially linked to large outflow channels. These pits and cavi are often taken as evidence for collapse due to the release of large volumes of pressurized groundwater. One such feature, Ganges Cavus, is an extremely deep (~ 6 km) collapse structure nested on the southern rim of Morella Crater, a 78-km-diameter impact structure breached on its east side by the Elaver Vallis outflow channel. Previous workers have concluded that Ganges Cavus, and other similar collapse features in the Valles Mariners area formed due to catastrophic release of pressurized groundwater that ponded and ultimately flowed over the surface. However, in the case of Ganges Cavus and Morella Crater, I show that the groundwater hypothesis cannot adequately explain the geology. The geology of Morella Crater, Ganges Cavus and the surrounding plains including Elaver Vallis is dominantly volcanic. Morella Crater contained a large picritic to komatiitic lava lake (> 3400 km3), which may have spilled through the eastern wall of the basin. Ganges Cavus is a voluminous (> 2100 km3) collapsed caldera. Morella Crater, Ganges Cavus and Elaver Vallis illustrate a volcanic link between structural collapse, formation and potential spillover of a large lake, and erosion and transport, but in this case, the geology is volcanic from source to sink. The geologic puzzle of Morella Crater and Ganges Cavus has important implications for the origins of other collapse structures on Mars and challenges the idea of pressurized groundwater release on Mars.

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Interspinifex Ni sulfide ore from Victor South-McLeay, Kambalda, Western Australia

2020

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Spinifex-textured olivine plates hosted in sulfides are usually named “interspinifex ore” in komatiite-hosted sulfide deposits. This ore type is rare but provides important genetic information on sulfide deposits, komatiite volcanology and thermomechanical erosion processes. Occurrences in Victor South-McLeay and Moran South (Kambalda, Western Australia) differ significantly from previously reported occurrences in their stratigraphic location, position within the ore profile and textural appearance. Thus, their formation process has to be reconsidered. Interspinifex ore reported here is situated in the lower portion of the basal lava flow between massive and net-textured sulfides in the centre of the embayment and between massive sulfides and older basalt in a “pinchout” where the sulfides melted sideways into older basalt on the embayment edge. Interspinifex ore is composed of up to 10-cm-long aggregates of parallel plates in the upper portion of massive sulfides and is overlain by barren komatiite. The texture does not allow for a classic single explanation. Thus, two possible formation mechanisms are envisaged: (1) A younger komatiite melt intrudes into its own olivine and sulfide liquid cumulate pile, while the sulfides are still liquid. The injection on top of the sulfides causes the formation of an emulsion, from which the spinifex forms due to the temperature gradient between the melts. (2) Interspinifex ore is a relic of an early komatiite flow formed in a series of successive pulses of komatiite and sulfide liquid. The spinifex of the komatiite is invaded by a younger batch of sulfide liquid replacing interstitial silicate melt.

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Thermomechanical erosion of ore-hosting embayments beneath komatiite lava channels: Textural evidence from Kambalda, Western Australia

Cited by 32 publications

References 54 publications

Textural development in sulfide-matrix ore breccias in the Aguablanca Ni-Cu deposit, Spain, revealed by X-ray fluorescence microscopy

Textural development in sulfide-matrix ore breccias in the Aguablanca Ni-Cu deposit, Spain, revealed by X-ray fluorescence microscopy

The volcanic geology of Morella Crater, Ganges Cavus and Elaver Vallis, Mars

Interspinifex Ni sulfide ore from Victor South-McLeay, Kambalda, Western Australia

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