Journal articles: 'Greenstone belts Western Australia Norseman'

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Schandl, Eva S., and Frederick J. Wicks. "Two stages of CO2 metasomatism at the Munro mine, Munro Township, Ontario: evidence from fluid-inclusion, stable-isotope, and mineralogical studies." Canadian Journal of Earth Sciences 28, no. 5 (May 1, 1991): 721–28. http://dx.doi.org/10.1139/e91-062.

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The Munro asbestos mine is hosted by a differentiated ultramafic sill of Archean age. Localized carbonate alteration at the mine has resulted from two separate episodes of CO2 metasomatism, and the fluids were unrelated. The first episode affected only the serpentinized peridotite and occurred at 250 °C. The fluid was a saline brine (up to 24 wt.% NaCl–CaCl2), and had an oxygen isotopic composition of −3‰, and δ13C was equal to −7.8‰. Calcite veins were emplaced into the overlying, fractured pyroxenite at approximately 300–400 °C during the second episode. The salinity of this fluid was only 1–5 equiv. wt.% NaCl, the oxygen isotopic composition was +7.5‰, and δ13C equaled −3 to −5‰. The first episode was probably associated with burial metamorphism (diagenesis) and the second episode with regional metamorphism. The widespread occurrence of two separate stages of CO2 metasomatism in the Abitibi belt and in other well-documented Archean terranes, such as the Norseman–Wiluna greenstone belt in Western Australia, suggests that this may be an important factor in the tectonic evolution and metamorphic history of Archean greensone belts.

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Spray, John G., and Lyle A. Burgess. "Landsat MSS imagery applied to geological investigation of the Norseman area granitoid–greenstone terrain, southeast Yilgarn Block, Western Australia." Geological Magazine 122, no. 6 (November 1985): 587–94. http://dx.doi.org/10.1017/s0016756800032003.

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AbstractInteractively processed Landsat MSS imagery has been used as an aid to studying the regional geology of approximately 10 800 km2 of terrain at the southeast margin of the Archaean Yilgarn Block in Western Australia. The technique proved successful in extending positions of known lithological contacts and lineaments into poorly exposed, inaccessible areas and in revealing new geological features, especially faults, previously unrecognized at ground level. During this investigation the distribution of granitoids and greenstones was more precisely defined, internal greenstone structures highlighted and three main fault trends were identified: (1) NW–NNW and (2) ENE, both within Archaean shield, and (3) NE–NNE within the transition to adjacent Proterozoic mobile belt. In order for the most information to be extracted from Landsat MSS images it is recommended that, whenever possible, image processing should follow ground-based studies as well as precede them, and that field geologist and Landsat specialist should work at the image processing system together.

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Mamuse, Antony, and Pietro Guj. "Rank statistical analysis of nickel sulphide resources of the Norseman-Wiluna Greenstone Belt, Western Australia." Mineralium Deposita 46, no. 3 (February 8, 2011): 305–18. http://dx.doi.org/10.1007/s00126-011-0333-z.

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Hill, R. E. T., S. J. Barnes, M. J. Gole, and S. E. Dowling. "The volcanology of komatiites as deduced from field relationships in the Norseman-Wiluna greenstone belt, Western Australia." Lithos 34, no. 1-3 (January 1995): 159–88. http://dx.doi.org/10.1016/0024-4937(95)90019-5.

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Ririe, G. Todd. "A comparison of alteration assemblages associated with Archean gold deposits in Western Australia and Paleozoic gold deposits in the southeast United States." Canadian Journal of Earth Sciences 27, no. 12 (December 1, 1990): 1560–76. http://dx.doi.org/10.1139/e90-168.

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A comparison of high-alumina mineral assemblages spatially associated with the Haile and Brewer gold deposits in the Paleozoic Carolina slate belt (CSB) of the southeast United States and the Sons of Gwalia and Mount Celia gold deposits in the Archean Norseman–Wiluna greenstone belt (NWGB) in Western Australia suggests a similar hydrothermal origin and subsequent metamorphic and deformational history. A common hydrothermal origin is supported by the striking similarity in whole-rock chemistry, even though there were probably significant variations in original unaltered protoliths. An analysis of rocks from each of the deposits that contain high-alumina minerals demonstrates that the protoliths were leached of alkalis with respect to aluminum and have a ratio of Al2O3/Na2O + CaO + K2O greater than three. Although the rocks contain abundant high-alumina minerals, the aluminum content in these rocks is not unusually high, and it does not appear that there has been any significant transport of aluminum either into or out of the rocks that were altered.The most common high-alumina minerals found in rocks affected by the feldspar destructive alteration event include andalusite, kyanite, pyrophyllite, kaolinite, and sericite. Other minerals present in variable amounts include diaspore, chloritoid, alunite, natroalunite, paragonite, and topaz. It is possible that some of these minerals formed during the early hydrothermal alteration event and were recrystallized during metamorphism. Regardless of when the high-alumina minerals formed, textural relations suggest that the rocks had been hydrothermally altered by the time the metamorphic minerals formed. A comparison of alteration from the deposits studied in the CSB and the NWGB suggests there are many similarities to acid-sulfate alteration associated with geothermal areas, such as Yellowstone Park, Wyoming, and with acid-sulfate gold deposits, such as Goldfield, Nevada. Thus, it is possible that the protolith of the metamorphosed rocks in the CSB and NWGB contained an alteration assemblage that included alunite, pyrophyllite, and kaolinite.A generalized paragenetic sequence determined from petrographic and field observations, beginning with regional metamorphism, follows: (i) formation of andalusite, kyanite, chloritoid, and topaz during prograde metamorphism, depending on whole rock chemistry, (ii) formation of pyrophyllite and quartz-rich pods during silicification of aluminosilicate-bearing rocks, (iii) bedding parallel schistosity and fracturing produced by a deformational event, (iv) fractures filled by quartz, sericite, pyrophyllite, or calcite, (v) folding of early layering in the rocks to form a crenulation cleavage accompanied by introduction of quartz veins at high angles to foliation; and (vi) retrograde metamorphism of andalusite–kyanite-pyrophyllite to produce an assemblage of kaolinite ± diaspore.The spatial association of the acid-sulfate alteration with gold mineralization, together with comparison of analogous alteration associated with younger unmetamorphosed acid-sulfate gold deposits, suggests that at least some of the gold was introduced during the early premetamorphic alteration event. The present location of gold in each deposit is a result of local changes brought about by later metamorphic and deformational events.

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Dentith, M. C., M. House, J. R. Ridley, and A. Trench. "Three-Dimensional Structure of Greenstone Belts in Western Australia: Implications for Gold Exploration." Exploration Geophysics 23, no. 1-2 (March 1992): 105–9. http://dx.doi.org/10.1071/eg992105.

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Giraud, Jeremie, Mark Lindsay, Vitaliy Ogarko, Mark Jessell, Roland Martin, and Evren Pakyuz-Charrier. "Integration of geoscientific uncertainty into geophysical inversion by means of local gradient regularization." Solid Earth 10, no. 1 (January 25, 2019): 193–210. http://dx.doi.org/10.5194/se-10-193-2019.

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Abstract. We introduce a workflow integrating geological modelling uncertainty information to constrain gravity inversions. We test and apply this approach to the Yerrida Basin (Western Australia), where we focus on prospective greenstone belts beneath sedimentary cover. Geological uncertainty information is extracted from the results of a probabilistic geological modelling process using geological field data and their inferred accuracy as inputs. The uncertainty information is utilized to locally adjust the weights of a minimum-structure gradient-based regularization function constraining geophysical inversion. Our results demonstrate that this technique allows geophysical inversion to update the model preferentially in geologically less certain areas. It also indicates that inverted models are consistent with both the probabilistic geological model and geophysical data of the area, reducing interpretation uncertainty. The interpretation of inverted models reveals that the recovered greenstone belts may be shallower and thinner than previously thought.

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Campbell, I. H., and R. I. Hill. "A two-stage model for the formation of the granite-greenstone terrains of the Kalgoorlie-Norseman area, Western Australia." Earth and Planetary Science Letters 90, no. 1 (September 1988): 11–25. http://dx.doi.org/10.1016/0012-821x(88)90107-0.

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Whitaker, A. "A geophysical model of the Precambrian of the Albany 1:1M sheet, Western Australia, and its relevance to economic geology." Exploration Geophysics 20, no. 2 (1989): 195. http://dx.doi.org/10.1071/eg989195.

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In the Albany 1:1M sheet, the 10-50 km wavelength gravity and aeromagnetic anomalies define major boundaries and subdivisions of the Precambrian blocks/provinces and large bodies of granite, while the short wavelength magnetic anomalies define lithological banding and lineaments. The Yilgarn Block in the sheet area is readily subdivided into two major north-northwest to north trending zones of low magnetization separated by a 30 km wide zone of high magnetization. The eastern zone is considered to be due to granite-greenstone terrane, the western boundary of which is located 100 km west of that currently recognised from outcrop geology. The western zone is considered to be due to granite-geiss terrane while the 30 km wide zone between coincides with strongly magnetised granulites. The Albany Province is composed of two structurally distinct east-west trending zones. The southern zone of relatively low magnetization and density coincides with acid gneiss and granites, whereas the highly magnetised, relatively dense zone to the north and west, correlates with highly metamorphosed acid and mafic granulites. Thrusting of the Albany Province during the Mid-Proterozoic has demagnetised and or deformed the margin of the southern Yilgarn Block to at least 50 km north of the block boundary. Throughout the region, significant mineral deposits of Au, Ni, Sn, Ti, and Fe are located within greenstone and high grade metamorphic belts. These belts have characteristic signatures which contrast with extensive areas of relatively homogeneous, low economic mineral potential, granite-gneiss terrane.

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Hill, R. I., B. W. Chappell, and I. H. Campbell. "Late Archaean granites of the southeastern Yilgarn Block, Western Australia: age, geochemistry, and origin." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, no. 1-2 (1992): 211–26. http://dx.doi.org/10.1017/s0263593300007902.

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ABSTRACTLate Archaean granitic rocks from the southern Yilgarn Craton of Western Australia have a close temporal relationship to the basaltic and komatiitic volcanism which occurs within spatially associated greenstone belts. Greenstone volcanism apparently began ∼2715 Ma ago, whereas voluminous felsic magmatism (both extrusive and intrusive) began about 2690 Ma ago. A brief but voluminous episode of crust-derived magmatism ∼2690-2685 Ma ago resulted in the emplacement of a diverse assemblage of plutons having granodioritic, monzogranitic and tonalitic compositions. This early felsic episode was followed immediately by the emplacement of mafic sills, and, after a further time delay, by a second episode of voluminous crust-derived magmatism dominated by monzogranite but containing plutons covering a wide compositional range, including diorite, granodiorite and tonalite. The products of this 2665–2660 Ma magmatic episode now form a significant fraction of the exposed southern Yilgarn Craton. Later magmatism, which continued to at least 2600 Ma ago, appears largely restricted to rocks having unusually fractionated compositions.The magmatic sequence basalt-voluminous crust-derived magmatism-later diverse magmatism, is interpreted in terms of a dynamically-based model for the ascent of the head of a new mantle plume. In this model basalts and komatiites are derived by decompression melting of rising plume material, and the crust-derived magmas result after conductive transport of heat from the top of the plume head into overlying continental crust. This type of magmatic evolution, the fundamentally bimodal nature of the magmatism, the presence of high-Mg volcanics (komatiites), and the areal extent of the late Archaean magmatic event, are all suggested to be characteristic of crustal reworking above mantle plumes rather than resulting from other processes, such as those related to subduction.

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Morris, Paul A., and Andrew J. Sanders. "The effect of sample medium on regolith chemistry over greenstone belts in the northern Eastern Goldfields of Western Australia." Geochemistry: Exploration, Environment, Analysis 1, no. 3 (August 2001): 201–10. http://dx.doi.org/10.1144/geochem.1.3.201.

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Fox, David C. M., Samuel C. Spinks, Milo Barham, Christopher L. Kirkland, Mark A. Pearce, Mehrooz Aspandiar, Renee Birchall, and Ed Mead. "Working up an Apatite: Enigmatic Mesoarchean Hydrothermal Cu-Co-Au Mineralization in the Pilbara Craton." Economic Geology 116, no. 7 (November 1, 2021): 1561–73. http://dx.doi.org/10.5382/econgeo.4842.

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Abstract Globally, significant examples of hydrothermal Cu-Co mineralization are rare within Archean greenstone belts, especially relative to the endowment of these terranes with other world-class hydrothermal ore deposits, particularly Au deposits. Using U-Pb geochronology of hydrothermal apatite, this study provides the first absolute age constraints on the timing of mineralization for the Carlow Castle Cu-Co-Au deposit. Carlow Castle is a complex, shear zone-hosted, veined Cu-Co-Au mineral system situated within the Paleo-Mesoarchean Roebourne greenstone belt of the Pilbara craton of northwestern Western Australia. Although U-Pb geochronology of this deposit is challenging due to low levels of radiogenic Pb in synmineralization apatite, mineralization is best estimated at 2957 ± 67 Ma (n = 61). Additionally, analysis of alteration phases associated with Carlow Castle mineralization suggests that it is dominated by a propylitic assemblage that is characteristic of alkaline fluid chemistry and peak temperatures >300°C. Within proximal portions of the northwest Pilbara craton, the period of Carlow Castle’s formation constrained here is associated with significant base-metal volcanogenic massive sulfide mineralization and magmatic activity related to back-arc rifting. This rifting and associated magmatic activity are the most likely source of Carlow Castle’s unique Cu-Co-Au mineralization. Carlow Castle’s Mesoarchean mineralization age makes it among the oldest discovered Cu-Co-Au deposits globally, and unique in the broader context of hydrothermal Cu-Co-Au deposits. Globally, hydrothermal Cu-Co mineralization occurs almost exclusively as Proterozoic and Phanerozoic stratiform sediment-hosted Cu-Co deposits due to the necessity of meteorically derived oxidized ore fluids in their formation. This research therefore has implications for exploration for atypical Cu-Co deposits and Cu-Co metallogenesis through recognition of comparably uncommon magmatic-hydrothermal Cu-Co-Au ore-forming processes and, consequently, the potential for analogous Cu-Co-Au mineralization in other Archean greenstone belts.

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Hayman, Patrick C., Ray A. F. Cas, Richard J. Squire, Ian A. Campbell, Mimi Chen, and David Doutch. "Emplacement origins of coarsely-crystalline mafic rocks hosted in greenstone belts: Examples from the 2.7 Ga Yilgarn Craton, Western Australia." Precambrian Research 324 (May 2019): 236–52. http://dx.doi.org/10.1016/j.precamres.2019.01.023.

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Thomson, B. "Petrology and stratigraphy of some texturally well preserved thin komatiites from Kambalda, Western Australia." Geological Magazine 126, no. 3 (May 1989): 249–61. http://dx.doi.org/10.1017/s0016756800022342.

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AbstractArchaean komatiite volcanics at Kambalda, Western Australia have been metamorphosed to upper greenschist–lower amphibolite grade and have experienced intense though heterogeneously developed polyphase deformation. Despite this, preservation of igneous textural features is often good, particularly in areas which underwent only ‘static style’ metamorphism. Thin lavas from the Tripod Hill Member of the Kambalda Komatiite Formation over the western margin of the Hunt nickel shoot display textural elements and facies variations which are virtually identical to those found in fresher thin komatiite sequences in other Archaean greenstone belts. Four principal flow profile (facies) types are defined, comprising nine subtypes. These represent stages in a facies continuum, ranging from ‘mature’ profiles which comprise thick spinifex textured tops and close packed cumulate bases through to massive, jointed ‘immature’ profiles devoid of mesoscopic spinifex texture. The causes of textural diversity within and between profiles are many and complex. However, facies variations can be attributed mainly to the effects of lava velocity at the time of major heat loss, combined with relative lateral position within any flow. The most mature textural (and geochemical) profiles developed in parts of lavas which had become ponded prior to major heat loss, whereas the least evolved profiles developed along the lateral margins (levees) of moving lavas. The study area komatiites occur as alternating stacks of flows of similar type. This stratigraphy records temporal and spatial shifts in the locus of lava ponding over the western margin of the Hunt nickel shoot. Such shifts may have been caused by irregularities in the underlying volcanic topography and/or by synvolcanic faulting and subsidence.

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Urosevic, Milovan, Ganesh Bhat, and Marcos Hexsel Grochau. "Targeting nickel sulfide deposits from 3D seismicreflection data at Kambalda, Australia." GEOPHYSICS 77, no. 5 (September 1, 2012): WC123—WC132. http://dx.doi.org/10.1190/geo2011-0514.1.

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The greenstone belts of the Yilgarn Craton, Western Australia, host numerous Archaean gold, nickel, and iron ore deposits. These deposits typically are found in complex geologic structures hidden by a deep, heterogeneous, and often conductive regolith profile. This added complexity limits the depth of penetration for the potential field methods, but at the same time opens new revenue possibilities through the application of seismic methods. To explore this opportunity, we acquired high-resolution, experimental, 3D seismic data over Lake Lefroy in Kambalda, Western Australia. The main objective was to map exceptionally complex, deep structures associated with Kambalda dome. Survey design used 3D ray tracing to improve the distribution of the common reflection points across ultramafic-basalt contacts which host numerous small, high-grade nickel sulfide deposits. A combination of small explosive sources, high-shot/receiver density, and exceptionally good coupling over the ultrasalty lake surface produced seismic data of very high quality. Processing focused on computation of accurate static and dynamic corrections, whereas imaging was helped by the existing geologic model. Advanced volumetric interpretation supported by seismic forward modeling was used to guide mapping of the main lithological interfaces and structures. Forward modeling was carried out using rock properties obtained from ultrasonic measurements and one borehole, drilled in the proximity of the 3D seismic volume. Using this information, geometric constraints based on the typical size of ore bodies found in this mine and a simple window-based seismic attribute, several new targets were proposed. Three of these targets subsequently have been drilled and new zones of mineralization were intercepted. The case study presented demonstrates that high-quality, high-resolution, 3D seismic data combined with volumetric seismic interpretation could become a primary methodology for exploration of deep, small, massive sulfide deposits distributed across the Kambalda area.

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Barley, M. E., and D. I. Groves. "Deciphering the tectonic evolution of Archaean greenstone belts: the importance of contrasting histories to the distribution of mineralization in the Yilgarn Craton, Western Australia." Precambrian Research 46, no. 1-2 (January 1990): 3–20. http://dx.doi.org/10.1016/0301-9268(90)90064-w.

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Garde, Adam A., Henrik Stendal, and Bo Møller Stensgaard. "Pre-metamorphic hydrothermal alteration with gold in a mid-Archaean island arc, Godthåbsfjord, West Greenland." Geological Survey of Denmark and Greenland (GEUS) Bulletin 13 (October 12, 2007): 37–40. http://dx.doi.org/10.34194/geusb.v13.4971.

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Recently discovered volcaniclastic rocks of andesitic composition form major parts of the mid-Archaean, amphibolite facies supracrustal belts at Qussuk, on Bjørneøen and on part of Storø in western Godthåbsfjord (Fig. 1). These rocks are interpreted as an island arc that represents the onset of the magmatic accretion of the Akia terrane 3070 Ma ago; this terrane is the north-westernmost of several Archaean tec tono-stratigraphic terranes in the Nuuk region, which were all amalgamated by 2720 Ma (cf. Hollis et al. 2006). The presence of the arc in the Akia terrane points to similarities between high-grade orthogneiss-amphibolite associations in West Greenland and lower-grade granite-greenstone terrains of other Archaean cratons e.g. in Canada and Western Australia. Volcaniclastic rocks belonging to the ancient arc have been subject to intense synvolcanic, hydrothermal alteration associated with gold-copper mineralisation especially in parts of the Qussuk area. Another important gold prospect occurs on central Storø, which is currently being explored by NunaMinerals A/S (Knudsen et al. 2007 – this volume). This contribution presents new field observations from some of the best preserved parts of the ancient arc at Qussuk and on Bjørneøen, while it remains unclear if the volcano-sedimentary associations and their gold mineralisation at Qussuk, Bjørneøen and the nearby Storø share a common midArchaean geological history.

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Le Vaillant, Margaux, Stephen J. Barnes, Marco L. Fiorentini, Sarah-Jane Barnes, Adam Bath, and John Miller. "Platinum-group element and gold contents of arsenide and sulfarsenide minerals associated with Ni and Au deposits in Archean greenstone belts." Mineralogical Magazine 82, no. 3 (April 13, 2018): 625–47. http://dx.doi.org/10.1180/minmag.2017.081.100.

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ABSTRACTPost-magmatic alteration of certain magmatic Ni sulfide ores in Western Australia, the Miitel deposit and the Sarah's Find prospect, produced Ni–As–PGE haloes around massive sulfides. A study of the composition of arsenide grains from these hydrothermal haloes, along with arsenides from various magmatic and hydrothermal mineralized environments in other localities, was conducted in order to compare their composition, and assess their potential use as indicator minerals for exploration vectoring, as well as to gain knowledge on their crystallization history. Concentrations in trace elements such as platinum-group elements (PGEs), Au and other metals was obtained by laser ablation inductively coupled plasma mass spectroscopy analyses. Results show that variations in PGEs and Au compositions can be related to the magmaticvs.hydrothermal origin of the grains; and to their provenance from deposits enriched in either Ni, Au or both. Magmatic NiCoFe sulfarsenides have strongly correlated, high IPGE (Os, Ir, Ru, Rh) contents up to 100 ppm Ir, compared with maximum values in hydrothermal sulfarsenides of ~1 ppm. Gold in hydrothermal sulfarsenides from Au-mineralized ultramafic rocks extends up to 500 ppm, with typical values of 3–30 ppm; similar values are also found in nickeline (also called niccolite). These results suggest that nickel arsenides could potentially be used as indicator minerals for nickel and gold exploration. Trace-element contents of arsenide grains in shear zones could be used to deduce the presence of Ni or Au mineralization upstream in the fluid pathway.

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Gardiner, N. J., J. A. Mulder, C. L. Kirkland, T. E. Johnson, and O. Nebel. "Palaeoarchaean TTGs of the Pilbara and Kaapvaal cratons compared; an early Vaalbara supercraton evaluated." South African Journal of Geology 124, no. 1 (March 1, 2021): 37–52. http://dx.doi.org/10.25131/sajg.124.0010.

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Abstract The continental crust that dominates Earth’s oldest cratons comprises Eoarchaean to Palaeoarchaean (4.0 to 3.2 Ga) felsic intrusive rocks of the tonalite-trondhjemite-granodiorite (TTG) series. These are found either within high-grade gneiss terranes, which represent Archaean mid-continental crust, or low-grade granite-greenstone belts, which represent relic Archaean upper continental crust. The Palaeoarchaean East Pilbara Terrane (EPT), Pilbara Craton, Western Australia, and the Barberton Granite-Greenstone Belt (BGGB), Kaapvaal Craton, southern Africa, are two of the best exposed granite-greenstone belts. Their striking geological similarities has led to the postulated existence of Vaalbara, a Neoarchaean-Palaeoproterozoic supercraton. Although their respective TTG domes have been compared in terms of a common petrogenetic origin reflecting a volcanic plateau setting, there are important differences in their age, geochemistry, and isotopic profiles. We present new zircon Hf isotope data from five granite domes of the EPT and compare the geochemical and isotopic record of the Palaeoarchaean TTGs from both cratons. Rare >3.5 Ga EPT evolved rocks have juvenile εHf(t) requiring a chondritic source. In contrast, younger TTG domes developed via 3.5 to 3.4 and 3.3 to 3.2 Ga magmatic supersuites with a greater range of εHf(t) towards more depleted and enriched values, trace element signatures requiring an enriched source, and xenocrystic zircons that reflects a mixed source to the TTGs, which variously assimilates packages of older felsic crust and a more juvenile mafic source. EPT TTG domes are composite and record multiple pulses of magmatism. In comparison, BGGB TTGs are less geochemically enriched than those of the EPT and have different age profiles, hosting coeval magmatic units. Hafnium isotopes suggest a predominantly juvenile source to 3.2 Ga northern Barberton TTGs, limited assimilation of older evolved crust in 3.4 Ga southern Barberton TTGs, but significant assimilation of older (Hadean-Eoarchaean) crust in the ca. 3.6 Ga TTGs of the Ancient Gneiss Complex. The foundation of the EPT is younger than that for the oldest components of the Eastern Kaapvaal. Although the broader prevailing Palaeoarchaean geologic framework in which these two cratons formed may reflect similar a geodynamic regime, the superficial similarities in dome structures and stratigraphy of both cratonic terranes is not reflected in their geochemical and age profiles. Both the similarities and the differences between the crustal histories of the two cratons highlights that they are formed from distinct terranes with different ages and individual evolutionary histories. Vaalbara sensu lato represents typical Palaeoarchaean cratonic crust, not in the sense of a single homogeneous craton, but one as diverse as the continents are today.

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Giraud, Jérémie, Mark Lindsay, Mark Jessell, and Vitaliy Ogarko. "Towards plausible lithological classification from geophysical inversion: honouring geological principles in subsurface imaging." Solid Earth 11, no. 2 (March 31, 2020): 419–36. http://dx.doi.org/10.5194/se-11-419-2020.

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Abstract. We propose a methodology for the recovery of lithologies from geological and geophysical modelling results and apply it to field data. Our technique relies on classification using self-organizing maps (SOMs) paired with geoscientific consistency checks and uncertainty analysis. In the procedure we develop, the SOM is trained using prior geological information in the form of geological uncertainty, the expected spatial distribution of petrophysical properties and constrained geophysical inversion results. We ensure local geological plausibility in the lithological model recovered from classification by enforcing basic topological rules through a process called “post-regularization”. This prevents the three-dimensional recovered lithological model from violating elementary geological principles while maintaining geophysical consistency. Interpretation of the resulting lithologies is complemented by the estimation of the uncertainty associated with the different nodes of the trained SOM. The application case we investigate uses data and models from the Yerrida Basin (Western Australia). Our results generally corroborate previous models of the region but they also suggest that the structural setting in some areas needs to be updated. In particular, our results suggest the thinning of one of the greenstone belts in the area may be related to a deep structure not sampled by surface geological measurements and which was absent in previous geological models.

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Calvert, Andrew J., Michael P. Doublier, and Samantha E. Sellars. "Seismic reflections from a lithospheric suture zone below the Archaean Yilgarn Craton." Nature Communications 12, no. 1 (December 2021). http://dx.doi.org/10.1038/s41467-021-27516-w.

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AbstractSeismic reflectors in the uppermost mantle, which can indicate past plate tectonic subduction, are exceedingly rare below Archaean cratons, and restricted to the Neoarchaean. Here we present reprocessed seismic reflection profiles from the northwest Archaean Yilgarn Craton and the Palaeoproterozoic Capricorn Orogen of western Australia that reveal the existence of a ~4 km thick south-dipping band of seismic reflectors that extends from the base of the Archaean crust to at least 60 km depth. We interpret these reflectors, which lie south of a ~50 km deep crustal root, as a relict suture zone within the lithosphere. We suggest that the mantle reflectors were created either by subduction of an oceanic plate along the northern edge of the Yilgarn Craton, which started in the Mesoarchaean and produced the rocks in northern Yilgarn greenstone belts that formed in a supra-subduction zone setting, or, alternatively, by underthrusting of continental crust deep into the lithosphere during the Palaeoproterozoic.

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Journal articles on the topic 'Greenstone belts Western Australia Norseman'

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