After removing any sledge hammer marks using sand paper, pieces of rock were crushed in an alumina-faced jaw crusher. A 200-g aliquot of each crushed sample was ground in an alumina shatter box and then finely re-ground in an alumina-faced disk mill. This ground material was further used for the chemical studies. ... Gorgona komatiites: Aitken ...
Geochemical diversity in oceanic komatiites and basalts from the late Archean Wawa greenstone belts, Superior Province, Canada: trace element and Nd isotope evidence for a heterogeneous mantle. Derek Wyman. Precambrian Research, 1999. download Download free …
Study with Quizlet and memorize flashcards containing terms like Archean greenstones are interpreted as being formed in __________. Select one: a. volcanic arcs b. back arc basins c. meteorite impacts d. mid-oceanic ridges, Continental crust formed at __________. Select one: a. shields b. subduction zone c. mid-oceanic ridges d. meteorite impacts e. transform faults, …
Petrography and geochemistry of Mesoarchaean komatiites from the eastern Iron Ore belt, Singhbhum craton, India, and its similarity with 'Barberton type komatiite' ... After crushing in a metal jaw crusher, all samples were ground in an agate ball mill. Major and trace elements were analyzed at the Activation Laboratories Ltd. (Ancaster, ...
Samples were crushed with a steel jaw crusher at the University of Western Australia to a size of 0.2–2 ... komatiites, tholeiitic basalts, and boninites. Komatiites have been subdivided into Al-undepleted (AUK, or Munro-type) and Al-depleted (ADK, or Barberton-type) varieties, and ADK into Al-depleted and Al-depleted–Ti-enriched subtypes ...
I. Weltevreden Formation komatiites formed approximately 3.3 billion years ago. II. By 3.3 Ga, the terrestrial mantle had absolute and relative HSE abundances similar to those in the modern mantle. III. Weltevreden komatiites formed via anhydrous and high degree, high temperature partial melting, likely in a mantle plume source. II.
It should be also taken into account that, although most models for the generation of komatiites involve hot melting of dry peridotite (e.g., Arndt, 1976; Herzberg and O'Hara, 1985; Herzberg and Zhang, 1996), some authors have suggested derivation of komatiites by hydrous melting in island arcs (e.g., Allègre, 1982; Parman et al., 1997 ...
samples were first coarsely crushed in a steel jaw crusher, then powdered using ceramic ball milling equipment during initial characterisation of the Winnipegosis Komatiite Belt (Hulbert et al ...
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 ...
Komatiites are igneous rocks mainly of Archaean age. Their ultramafic origin is controversial and has been attributed to either high degrees of dry melting of peridotite in deep mantle plumes at temperatures up to 500°C hotter than today, or to melting at shallow depth, in volatile-rich (hydrous) mantle with temperatures not much different than the 1200–1500°C (for …
Komatiites also provide a link between crustal building and the formation of the Earth's early lithosphere with a view that they are melts removed from the Archaean mantle to …
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 provide whole-rock …
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 ...
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komatiites is metasomatic introduction or depletion of elements during metamorphic and/or hydrothermal fluid–rock interaction. In the Agnew–Wiluna greenstone belt, some portions of …
The komatiites are divided into three groups based on total REE, shape of the patterns and Eu anomalies. Group I komatiites are characterized by low to moderate total REE (8.77–22.26 ppm) and show flat REE patterns with (Gd/Yb) N ratios (0.62–1.42) except few samples which show either slight depletion or enrichment in MREE (Fig. 16 a).
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Whole rock samples were crushed into mm-sized pieces using a ceramic jaw crusher. The freshest pieces were cleaned with Milli-Q water in an ultrasonic bath for ½ h and were subsequently dried in an oven at 60°C for ∼ 1 h. ... The Dundonald komatiites and komatiitic basalts show strong olivine control on MgO vs. Al 2 O 3 (Fig. 1) and TiO 2 ...
Komatiites are particularly useful for determining absolute and relative abundances of the highly siderophile elements (HSE, including Os, Ir, Ru, Pt, Pd, and Re) in their mantle sources. ... and crushed in an alumina-faced jaw crusher. A 100-g aliquot of crushed sample was ground in an alumina shatter box and re-ground in an alumina-faced disk ...
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...
Komatiites are ultra-hot ultramafic lavas, largely restricted to the Archaean. They represent an extreme endmember of terrestrial magmatism and challenge our understanding of …
1.. IntroductionThe precise tectonic setting of komatiites in the Archaean is a contentious subject. The prevalent model is that all komatiites were the result of varying, but usually high degrees of mantle partial melting under conditions of high temperature (Arndt and Nisbet, 1982) and most likely to have originated as plumes generated close to the core mantle …
The komatiites of the Southern Cross greenstone belt form an intermediate group between the intracontinent (low-MgO, unchannelized) and the continent edge (high-MgO, channelized) type komatiites. These magmas have high-MgO contents ( 18 ), but are unchannelized, cumulate-poor, and unmineralized ( 18 ).
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 Yilgarn Craton of Western …
komatiites from the Pilbara Craton in Western Australia. Major-, lithophile trace element-, and HSE abundances, as well as Re-Os isotopic data are reported for a set of drill core and surface …
Whole rock samples were crushed using a steel jaw crusher and small chips (3–15 mm) were then separated and washed in an ultrasonic cleaner for 10 min. Clean chips were then dried and milled using agate or mild steel mills. ... Komatiites appear further to the east, and these komatiites have been intruded by granitoids, which are in turn ...
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 28–30 wt % MgO. ... and crushed in an alumina-faced jaw crusher. A 100-g aliquot of crushed sample was ground in an alumina shatter box and re-ground ...
Komatiites often have exquisite disequilibrium mineral textures seldom seen in younger rocks. These spinifex textures give komatiite a mystical aura, keenly sought after, …
Les komatiites contiennent des olivines spinifex (minéraux en forme de baguettes), témoins d'une cristallisation extrêmement rapide. Affleurements et répartitions dans le temps Sur Terre, les komatiites sont très rares et essentiellement limités aux roches d'âge archéen.
The precise tectonic setting of komatiites in the Archaean is a contentious subject. The prevalent model is that all komatiites were the result of varying, but usually high degrees of mantle partial melting under conditions of high temperature (Arndt and Nisbet, 1982) and most likely to have originated as plumes generated close to the core mantle boundary (Boehler et …
Komatiites and komatiitic basalts in the Abitibi greenstone belt exhibit pronounced spatial and temporal variations in major and trace element geochemistry that provide important constraints on their petrogenesis and tectonic setting. ... -27, …
Komatiites erupted billions of years ago as pulsating streams of white-hot lava. Their unusual chemical compositions and exceptionally high formation temperatures produced highly fluid lava that crystallized as spectacular layered flows. Investigation of the extreme conditions in which komatiites formed provides important evidence about the ...
