Komatiite-associated Ni–Cu–PGE deposits (by C. M. Lesher …
Komatiite - July 2008. Introduction. There are two main types of ore deposits associated with komatiites: primary magmatic sulfide deposits, mined chiefly for their nickel content with minor by-product Cu and PGEs, and secondary laterite deposits enriched in nickel and cobalt, developed over thick olivine cumulate units, the latter known thus far only in the …
From the mantle source to the crustal sink: magmatic …
Paleoproterozoic (2.05 Ga) komatiites are widespread in the Central Lapland Greenstone Belt (CLGB), northern Finland. Close association with sulfur (S)-rich country rocks and spatiotemporal connection with the Cu-Ni(-PGE) deposits of Kevitsa and Sakatti make these komatiites interesting targets for sulfide deposit exploration. We …
Expanding the metamorphic devolatilization model: Komatiites …
Combined with the availability of gold and mineralogically bound water in hydrated komatiites, metamorphic devolatilization of komatiites can well account for hypozonal gold mineralization in amphibolite-facies rocks, as well as the close temporal and spatial association between hypozonal gold and komatiites in greenstone belts.
Chromite in komatiites: 3D morphologies with implications …
In this contribution, we present the first 3D study of chromite morphologies obtained by high-resolution X-ray computed tomography of komatiitic rocks selected from an extensive collection made during three decades of study of the komatiites in the Yilgarn Craton, Western Australia (Fig. 1).The samples were selected to represent the observed …
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In situ determination of Os, Ir, and Ru in chromites formed …
For whole-rock analyses, the chromitite samples were crushed in a steel jaw crusher and then pulverised in a W-carbide shatterbox for 3 ... Komatiites are richer in IPGE than all other magmas. This probably reflects the fact that komatiites formed by very high degrees of partial melting, sufficient to dissolve all the sulphides in the mantle ...
Komatiite | Atlas of magmatic rocks
Komatiite is an ultramafic, high-magnesian volcanic rock typical of a spinifex texture originated during fast cooling of a silicate melt enriched in olivine and other Mg-Fe silicates. Komatiites occur only in Archean …
Helium in the Archean komatiites revisited: significantly
In order to provide constraints on 3 He/ 4 He ratios in the Archean mantle source, we have analyzed helium isotopic compositions in 2.7 Ga old Archean komatiites from the Abitibi green stone belt, Ontario, Canada. Two spinifex-textured komatiites yielded significantly high 3 He/ 4 He ratios of about 30 Ra (where Ra denotes the atmospheric …
Ore Deposition Associated with Magmas
The komatiites are host to Ni sulfide ores in Western Australia, Zimbabwe and Canada; these ores and their origin are discussed by C.M. Lesher in this volume. Examples of mineralization associated with the picritic sub-class of tholeiites include ‹ Prev;
Re-Os isotopic constraint to the age of in komatiites in the …
The 2.5 Ga Guyang greenstone belt is a major lithological unit in the northwestern part of the North China Craton. Komatiites have recently been identified to occur within the lower part of the meta-volcanic sedimentary sequence of the greenstone belt. The biggest komatiite near Guyang has been mapped out, which is 500 m long and …
Komatiites
Komatiites represent primitive mantle melts and require high degree partial melting of the mantle (up to 50 %) (Nesbitt & Sun 1976, Sun & Nesbitt 1978). The formation of komatiites has generally been attributed to mantle plume upwelling and related volcanism in a variety of geodynamic settings mainly during the Archean and early Proterozoic ...
Multiple Sulfur Isotope Geochemistry of the
Komatiites, greenstone volcanic rocks, and mafic dyke swarms are constituents of early earth magmatic activity, crucial for understanding the chemical evolution of the Archean mantle. The composition of the subcontinental lithospheric mantle (SCLM) is systematically modified throughout the Earth's history by the addition of …
Geological evidence for high H2 production from komatiites …
Komatiites are highly magnesian lavas, which contain evidence of extensive serpentinization and magnetite (Fe 2+ Fe 3+2 O 4) production close to the Archaean …
Ir, Ru, Pt, and Pd in basalts and komatiites: new constraints …
The major, trace, and platinum-group element abundances of the samples are summarized in Table 2. The MgO contents of the six Kolbeinsey Ridge samples range from <7% to >10% and MgO correlates well with Al 2 O 3, CaO, and compatible trace elements such as Ni (Fig. 1). The PGE concentrations of the Kolbeinsey MORB vary by …
Geochemistry of a komatiitic, boninitic, and tholeiitic basalt
Samples were crushed with a steel jaw crusher at the University of Western Australia to a size of 0.2–2 ... Komatiites of the Koolyanobbing suite lie just above the …
Komatiites and Ni-Cu-PGE deposits | Geology for Investors
Komatiites are exclusive ancient rock types which exhibit a unique spinifex texture. The Ni-Cu-PGE mineralisation generally occurs as massive sulfide ore at the floor of the komatiitic flow or as disseminated sulfides through olivine-rich layers. It is worth noting that the critical features whether the mineralisation will occur are the flow ...
Komatiite-associated Ni–Cu–PGE deposits (by C. M. Lesher …
Summary. Introduction. There are two main types of ore deposits associated with komatiites: primary magmatic sulfide deposits, mined chiefly for their nickel content with …
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Komatiites reveal a hydrous Archaean deep-mantle reservoir
Archaean komatiites are shown to originate in hot mantle plumes that entrained hydrous material from deep in the mantle. Komatiites are a rare type of volcanic rock, formed uniquely during the ...
Komatiites: Petrology, Volcanology, Metamorphism, and …
Nickel sulfide deposits of the Yilgarn craton are almost exclusively associated with komatiites, a distinctive suite of ultramafic volcanic rocks characterized by very high MgO contents implying extreme eruption temperatures. Komatiites have a remarkable array of igneous textures, including spectacular dendritic "spinifex" olivine and ...
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Expanding the metamorphic devolatilization model: …
Komatiites are ultramafic lava flows that originate from the mantle with high MgO contents and similar components as peridotite (mainly olivine and pyroxene). The …
Chapter 1 Archean Komatiites
11 Chapter 1 ARCHEAN KOMATIITES N.T. ARNDT INTRODUCTION Twenty-five years have passed since komatiites were first recognized in South Africa by Richard and Morris Viljoen (Viljoen and Viljoen, 1969a,b; 1982) and the existence of ultramafic volcanic rocks is now generally accepted.
Mantle heterogeneity and crust-mantle interaction in the …
1. Introduction. Komatiites are high magnesian, low alkali, predominantly Archean ultramafic extrusive rocks, and are important in understanding the lower mantle processes in early Earth (Arndt et al., 2008; Dostal, 2008; Furnes et al., 2013; Hanski et al., 2001; Le Bas, 2000; Viljoen and Viljoen, 1969).Quenched from very high temperature …
Komatiites
Komatiites represent primitive mantle melts and require high degree partial melting of the mantle (up to 50 %) (Nesbitt & Sun 1976, Sun & Nesbitt 1978). The formation of komatiites has generally been attributed to …
(PDF) Komatiites
Komatiites are ultramafic volcanic rocks that occur mainly in Archean and Paleoproterozoic greenstone belts. These olivine-rich rocks are assumed to have crystallized from magmas that have about ...
Nickel isotope fractionation in komatiites and associated …
The Hart deposit consists of two mineralized zones. The main zone is located at the base of the lowermost komatiite flow of the middle Tisdale volcanic assemblage, within a large embayment where several stacked komatiite flows overlie and crosscut the felsic to intermediate volcanic succession of the lower Tisdale assemblage and …
The discovery and petrogenetic significance of komatiites
Komatiites are now recognized in many greenstone belts around the world and in some places associated with high-magnesium, high silica basalts called boninites …
Komatiites and Ni-Cu-PGE deposits | Geology …
Komatiites are exclusive ancient rock types which exhibit a unique spinifex texture. The Ni-Cu-PGE mineralisation generally occurs as massive sulfide ore at the floor of the komatiitic flow or as disseminated …