A hypothesis of origin for podiform chromite deposits

Dickey, John S.

doi:10.1016/b978-0-08-019954-2.50026-3

Cited by 43 publications

(67 citation statements)

References 19 publications

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“…1982;Nicolas and Violette 1982). We agree that the chromitites of the Zambales ophiolite are crystallized in situ, but reject a crystallization in channels as well as a later subsidence of the chromitites into the mantle peridotites (Dickey 1975), or an infolding of the chromitites as suggested by Greenbaum (1977). Our arguments are:…”

Section: Origin Of the Chromititesmentioning

confidence: 65%

Refractory- and metallurgical-type chromite ores, Zambales ophiolite, Luzon, Philippines

et al. 1986

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Abstract. The Zambales ophiolite is the major source of chromite ore in the Philippines. The chromitites are concordant cumulates and are associated with distinct chromitite-bearing sequences within the mantle peridotites. Refractory and metallurgical chromite deposits are spatially separated and related to different lithologic associations, which crystallized from different parental magmas. -Refractory chromite ores (30-44 wt% Cr203 ; 20-30 wt% A1203) are linked with the peridotite-troctolite-olivine gabbro lineage. Two main types were found: (1) N-rich refractory ores associated with harzburgites and feldspathic peridotites and (2) more Cr-rich varieties associated with lherzolites. -Metallurgical chromite ores (45-53 wt% Cr203 ; 12-18 wt% A1203) are linked with the peridotite-pyroxenite-norite lineage. Two main types were also found: (1) Cr-rich metallurgical ores associated with orthopyroxenites and (2) more N-rich varieties related to clinopyroxenites. -The chemical composition of chromite within the deposits varies depending on the chromite/ silicate ratios of the ore types and grades continuously into accessory chrome spinels in the wall-rock peridotites. -The geochemistry of accessory chrome spinels in various peridotites and mafic cumulates depends on the mineralogical composition and the stratigraphic position of their host rocks.

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Section: Origin Of the Chromititesmentioning

confidence: 65%

Refractory- and metallurgical-type chromite ores, Zambales ophiolite, Luzon, Philippines

et al. 1986

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“…Previous works assigned the primary importance to fractional crystallization and subsequent deformation (Dickey, 1975;Thayer, 1964). Later on, almost all of the investigations were undertaken to find a pertinent Compositional variations of chrome spinels in the ore-bearing zones… 143 condition for chrome spinel crystallization during different melts interaction, mixing or mingling .…”

Section: Discussionmentioning

confidence: 99%

“…It was established that the ophiolite chrome spinel grains are characterized by a wide variation of Cr/Al ratio, a small difference in Mg/Fe ratio and low concentration of TiO2 (Dickey, 1975;Thayer, 1964). Ophiolite ore-forming spinels were grouped into two types.…”

Section: Discussionmentioning

confidence: 99%

Compositional Variation of Chrome Spinels in the Ore-bearing Zones of the Kraka Ophiolite and the Chromitite Origin

Saveliev¹,

Blinov²

2017

ВПУГ

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The article considers a chemical variation of accessory and ore-forming chrome spinels from the Kraka ultramafic massif at the different scales, from the deposit to the thin section. A correlation analysis of compositional and structural features of ultramafic rocks and ores was performed. The ultramafic rocks and chromitites in the studied massif show the distinct deformation structures and tectonite olivine fabric. A typical chemical gap (i.e. Cr#=Cr/(Cr+Al)) was observed between peridotite, on the one hand, and dunite and chromitite, on the other hand, on the scale of deposits and ore-bearing zones. The location and size of this gap depend on the type of deposit. The gap becomes wider from the disseminated tabular bodies to the typical podiform ones. It has been found that in the thin initial dunite veinlets in peridotite the chrome spinels chemistry changes gradually and there is no Cr# gap between peridotite and dunite. The dunite venlets show a strong olivine fabric, which is an evidence of their high-temperature plastic flow origin. It has been revealed that new chrome spinel grains previously formed as rods or needles and then coarsened. We explained this observation as the result of impurity segregation, coalescence and spheroidization induced by the plastic deformation of olivine. It is inferred that a solid crystal flow is the main requirement for the dunite and chromitite body formation in the Kraka ophiolite massif. In the solid stream, the mineral phase separation takes place. For example, olivine and orthopyroxene grains of parental peridotite separate from one another, and weaker (more mobile) olivine grains form dunite bodies in which chromitite appears as a result of impurity segregation.

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“…Il aura donc tendance à entrer dans le réseau de l'olivine qui avec la chromite se trouve souvent sur la cotectique lors la cristallisation. Dickey (1975), Dick et Bullen (1984), etQasimetal. (1985.…”

Section: Le Manganèseunclassified

Formation des latérites nickélifères et mode de distribution des éléments du groupe du platine dans les profils latéritiques du complexe de Musongati, Burundi /

Bandyayera¹

1997

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A hypothesis of origin for podiform chromite deposits

Cited by 43 publications

References 19 publications

Refractory- and metallurgical-type chromite ores, Zambales ophiolite, Luzon, Philippines

Refractory- and metallurgical-type chromite ores, Zambales ophiolite, Luzon, Philippines

Compositional Variation of Chrome Spinels in the Ore-bearing Zones of the Kraka Ophiolite and the Chromitite Origin

Formation des latérites nickélifères et mode de distribution des éléments du groupe du platine dans les profils latéritiques du complexe de Musongati, Burundi /

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