In situ determination of Os, Ir, and Ru in chromites formed from komatiite, tholeiite and boninite magmas: Implications for chromite control of Os, Ir and Ru during partial melting and crystal fractionation

Pagé, Philippe; Barnes, Sarah‐Jane; Bédard, Jean H.; Zientek, Michael L.

doi:10.1016/j.chemgeo.2011.06.006

Cited by 118 publications

(48 citation statements)

References 75 publications

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“…This mineralization phase has characteristic PGE patterns with high IPGE contents compared to PPGE (samples MA 226, 400 and 422; Fig. 15) which fits relatively well with that of chromitites from ophiolites, komatiites and layered intrusions (Cabri, 2002;Naldrett et al, 2012;Pagé et al, 2012). Chromite crystallized in komatiitic and tholeiitic melts concentrates IPGE.…”

Section: Pgm Crystallization and Pge Fractionationsupporting

confidence: 53%

“…Chromite crystallized in komatiitic and tholeiitic melts concentrates IPGE. These elements may be present in chromite as solid solution (Pagé et al, 2012;Brenan et al, 2012) or co-crystallized with IPGE minerals due to their low solubilities in basic magmas (Pagé et al, Table 3) contents suggest that the PGE (and especially IPGE) have been entrapped by sulphide phases that now form inclusions within chromite grains. The igneous PGE mineralization most probably originated through separation of a sulphide fraction from the silicate melt, in agreement with the more compatible behaviour of IPGE relative to PPGE in sulphide melts compared to silicate magmas (Sattari et al, 2002).…”

Section: Pgm Crystallization and Pge Fractionationmentioning

confidence: 99%

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Petrogenesis of Archean PGM-bearing chromitites and associated ultramafic–mafic–anorthositic rocks from the Guelb el Azib layered complex (West African craton, Mauritania)

Berger¹,

Diot²,

Lô³

et al. 2013

Precambrian Research

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a b s t r a c tThe Archean Guelb el Azib layered complex (GAC) in the West African craton of Mauritania is composed of an association of serpentinites, chromitites, amphibolites and anorthosites with few fine-grained amphibolite dykes. The complex forms tectonic slices in 2.9-3.5 Ga TTG gneiss terrains in close association with supracrustal rocks (BIFs, impure marbles, amphibolites). It was affected by a main granulite-facies grade metamorphism (up to 900• C at 5-6 kbar) with subsequent retrogression in amphibolite and greenschist facies conditions.The preserved igneous macrostructures, the mineral compositions and the nature of relic magmatic assemblages have been used to constrain the composition of the parental melts and the conditions of crystallization. According to petrological observations and to comparison with experimental data, the formation of the complex can be explained by fractionation of a slightly hydrous high-alumina basaltic melt at low pressure. The early fractionation of olivine and the absence of massive clinopyroxene fractionation before plagioclase saturation led to crystallization of highly calcic plagioclase with Fe-, Al-rich but Cr-poor chromite from a hydrous tholeiitic parental magma, similar to worldwide Archean tholeiites.The complex shares many similarities with Archean anorthosite layered complexes, possibly formed in a supra-subduction zone environment according to results obtained on similar 2.9-3.0 Ga complexes from Greenland and India (namely Fiskenaesset and Sittampundi). Three phases of PGE mineralization affected the GAC chromitites: (i) igneous crystallization of laurite; (ii) formation of late magmatic IPGE sulpho-arsenides (irarsite-hollingworthite) and (iii) hydrothermal Pt-Pd mineralization represented by sperrylite and rustenburgite.

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Section: Pgm Crystallization and Pge Fractionationsupporting

confidence: 53%

Section: Pgm Crystallization and Pge Fractionationmentioning

confidence: 99%

Petrogenesis of Archean PGM-bearing chromitites and associated ultramafic–mafic–anorthositic rocks from the Guelb el Azib layered complex (West African craton, Mauritania)

Berger¹,

Diot²,

Lô³

et al. 2013

Precambrian Research

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“…The first hypothesis is based on experimental studies that have shown that Ir, Ru, Rh and Pd could partition into spinel phases (Brenan et al 2012;Capobianco and Drake 1990;Capobianco et al 1994;Righter et al 2004;Sattari et al 2002). Recently, homogeneous Ru laser ablation ICP-MS spectra in chromite from komatiites have been interpreted as evidence of partitioning of the IPGE in solid solution within natural chromite crystals (Locmelis et al 2011;Pagé et al 2012). Several laser-ablation ICP-MS analyses have been carried out on chromite crystals from the Merensky Reef of the Bushveld Complex (Ballhaus and Sylvester 2000;Godel et al 2008;Osbahr et al 2013), and on chromite and secondary magnetite grains of the J-M Reef of the Stillwater Complex , in order to test whether the PGE partitioned into natural spinel phases in sulfide-rich PGE-reef environments.…”

Section: Oxidesmentioning

confidence: 99%

Platinum-Group Element Deposits in Layered Intrusions: Recent Advances in the Understanding of the Ore Forming Processes

Godel

2015

Springer Geology

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“…Ln (wt % TiO 2 в расплаве) = 0,82574 î Ln (wt % TiO 2 в хромите) + 0,20203; использование данных математических зако номерностей, ранее апробированных на при мере офиолитовых комплексов и базальтов срединно океанических хребтов [Page, Barnes, 2009], позволяет оценить интервал содержаний Al 2 O 3 и TiO 2 в расплавах на мо мент излияния. Для коматиитов изучаемых структур интерпретация химического состава хромитов с помощью данных закономерно стей позволила получить следующие характе ристики первичных расплавов (вес.…”

Section: геохимия шпинелидов как отражение условий магмогенерации породunclassified

“…Однако проведение измерений в режиме увеличенного времени набора спектра в точ ках анализа до 300 секунд показало, что в яд рах первично магматических хромитов, из коматиитов Совдозерской и Костомукшской структур, диагностируются высокие содер жания ЭИПГ (Os, Ir, Ru до 100 ppb) и ЭППГ (Pt и Pd до 200 ppb). Данное наблюдение со гласуется с высокими значениями коэффи циентов разделения хромит расплав для ЭПГ: Kd (Os, Ir) (хромит расплав) > 8 и Kd (Ru) (хро мит расплав) > 79 [Page et al, 2012].…”

Section: геохимия шпинелидов как отражение условий магмогенерации породunclassified

Relicts of the Primary Magmatic Accessory Spinels in the Archean Komatiites of the Eastern Fennoscandia

Рыбникова¹,

Rybnikova

2015

Proceedings of KarRC of RAS

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Институт геологии Карельского научного центра РАНВ статье приводятся результаты комплексного изучения реликтов первично магматических шпинелидов из архейских (3,02,7 млрд лет) коматиитовых серий зеленокаменных структур восточной части Фенноскандинавского щита. Проана лизированы акцессорные минералы из массивных и мезокумулятивных зон расслоенных лавовых потоков коматиитов (содержащих 2430 вес. % MgO). В коматиитах установлено сосуществование нескольких генераций шпинелидов, в том числе реликтов первично магматического хромит алюмохромита (Cr 2 O 3 44,6451,80, Al 2 O 3 9,3913,74, #Cr 68,9778,52, #Mg 3,9812,14, #Fe < 12), являющегося равновесной минеральной фазой в коматиитовых расплавах и кри сталлизующегося в интервале температур 1340-1370 C после выделения оливи на. Выявленная геохимическая зональность в первичных шпинелидах является результатом равновесной кристаллизации коматиитового расплава с постепен ным понижением температуры, приводящей к образованию твердых растворов алюмохромит субферриалюмохромитов. Показано, что метаморфические преоб разования пород при давлении 5 кбар и температурах 500 C приводят к пол ной перекристаллизации первичных шпинелидов. К л ю ч е в ы е с л о в а : хромиты, коматииты, архей. Z. P. Rybnikova. RELICTS OF THE PRIMARY MAGMATIC ACCESSORY SPINELS IN THE ARCHEAN KOMATIITES OF THE EASTERN FENNOSCANDIAThe article presents the results of a complex study of the relicts of the primary magmatic spinels from the Archean (3.0-2.7 Ga) komatiitic series of the greenstone structures of the eastern Fennoscandian Shield. The accessory minerals of the massive and mesocumulate zones of differentiated komatiite flows (containing 24-30 wt. % MgO) are analyzed. The coexistence of several generations of spinels including relicts of the primary magmatic chromite alumochromite (Cr 2 O 3 44.64-51.80, Al 2 O 3 9.39-13.74, #Cr 68.97-78.52, #Mg 3.98-12.14, #Fe <12), which is an equilibrium mineral phase in komatiitic melts crystallizing in the temperature range of 1340-1370 C after the extraction of olivine, is established in the komatiites. The identified geochemical zoning in the primary spinels is the result of the equilibrium crystallization of komatiitic melt with a gradual decrease in temperature, which leads to the formation of alumochromite subferrialumochromite solid solutions. It is shown that the metamorphic transformation of rocks at pressure 5 kbar and temperatures 500 C leads to a complete recrystallization of the primary spinels.K e y w o r d s : chromite, komatiites, archean.

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In situ determination of Os, Ir, and Ru in chromites formed from komatiite, tholeiite and boninite magmas: Implications for chromite control of Os, Ir and Ru during partial melting and crystal fractionation

Cited by 118 publications

References 75 publications

Petrogenesis of Archean PGM-bearing chromitites and associated ultramafic–mafic–anorthositic rocks from the Guelb el Azib layered complex (West African craton, Mauritania)

Petrogenesis of Archean PGM-bearing chromitites and associated ultramafic–mafic–anorthositic rocks from the Guelb el Azib layered complex (West African craton, Mauritania)

Platinum-Group Element Deposits in Layered Intrusions: Recent Advances in the Understanding of the Ore Forming Processes

Relicts of the Primary Magmatic Accessory Spinels in the Archean Komatiites of the Eastern Fennoscandia

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