Differences in composition of chromites from low-Ti and …
Chromite is among the first minerals to crystallize from mantle derived magmas and one of the last to be consumed during partial melting of the mantle. Chromite is also an important mineral in major ore deposits of Cr and Pt. The composition of chromite could, therefore be of use in interpreting the petrogenetic conditions during partial melting …
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Peridotite: Igneous Rock
Chromite in Peridotite. Some peridotites contain significant amounts of chromite. Some of these form when a subsurface magma slowly crystallizes. During the early stages of crystallization, the highest-temperature minerals such as olivine, orthopyroxene, clinopyroxene, and chromite begin to crystallize from the melt.
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Chromite
Chromite is a dark grey, metallic, oxide mineral. Due to its metallic luster and occasional magnetic properties, chromite is often mistaken for magnetite. Chromite can often be found in basic igneous rocks, and in the metamorphic and sedimentary rocks created by rocks containing chromite that were affected by weather.
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Chromitite
The Kemi Chromite Deposit. T. Huhtelin, in Mineral Deposits of Finland, 2015 The Chromite Mineralization. The main chromitite layer that parallels the basal contact zone of the Kemi intrusion is known to occur over the whole length of the complex, extending for 15 km from the town of Kemi to the northeast. In the central part of the intrusion, where the …
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Genesis of hexavalent chromium from natural sources in soil and
Although chromite [FeCr(III) 2 O 4] is the primary source of Cr in ultramafic and serpentinite rocks (), it exhibits very low solubility under most geologic and industrial refining conditions (14–16), and there are few naturally occurring oxidants of Cr(III).The only natural oxidants of aqueous Cr(III) at pH < 9 are Mn(IV/III)-oxides (17–21) and hydrogen …
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Chromite and Other Mineral Deposits in Serpentine …
CHROMITE AND OTHER MINERAL DEPOSITS IN SER PENTINE ROCKS OF THE PIEDMONT UPLAND, MARY LAND, PENNSYLVANIA, AND DELAWARE By NANCY C. PEARRE and ALLEN V. HEYL, JR. ABSTRACT The Piedmont Upland in Maryland, Pennsylvania, and Delaware is about 160 miles long and at the most 50 miles wide.
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Petrogenetic insights from chromite in ultramafic cumulates …
Chromite is one of the earliest crystallized minerals from mafic melts and has been used as an important "petrogenetic indicator." Its composition may be modified by interaction with intercumulate melt and adjacent minerals. Thus, chromite in mafic-ultramafic rocks contains clues to the geochemical affinity, evolution, and mantle source of its parent …
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Chromitites from an Archean layered intrusion in the …
The PGE patterns display positive Ru-anomalies, which are typical for chromite-rich rocks, because this mineral and its inclusions is a major Ru host in ultramafic rocks (Pagé et al., 2012; Pagé and Barnes, 2016). The overall PGE patterns, generally high Os contents and in particular the fractionation of Ir from Os in several samples are not ...
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Occurrence and mineral chemistry of chromite and related
The Hongshishan mafic-ultramafic complex is located in the western Beishan Terrane, NW China, and hosts an economic Ni-Cu deposit. Chromite as accessory mineral from the complex is divided into three types based on its occurrence and morphology. Quantitative electron probe microanalysis (EPMA) have been conducted on the different …
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Peridotites, chromitites and diamonds in ophiolites
Diamond is a typical UHP mineral that forms at depths >150 km (~5 GPa) and is commonly found in certain types of volcanic rocks (for example, kimberlites, lamproites and lamprophyres) 118, UHP ...
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Occurrence, Origin and Transformation Processes of …
48 Citations. Metrics. Abstract. Weathering of ultramafic rocks has been linked to the occurrence of elevated concentrations of hexavalent chromium (Cr (VI)) in …
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(PDF) Geophysical Hunt for Chromite in Ophiolite
Chromite is found in the mantle rocks such as peridotite and its altered products. Large economic deposits are generally found in stratiform structure and the smaller ones in pod-like or tabular ...
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Genesis of chromite deposits by dynamic upgrading of Fe …
There are oxide-silicate–facies iron formations and Fe-Ti oxide-bearing gabbros in underlying rocks, the intrusions contain iron-formation and gabbro xenoliths, the parental magma was a chromite-saturated low-Mg komatiite (Mungall et al., 2010), and the chromite-bearing intrusions are dominated by cumulates and interpreted to represent …
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Chromite in the Platreef (Bushveld Complex, South Africa …
Chromite in olivine-bearing rocks is rare and disseminated. Olivine often shows a disequilibrium texture, and less commonly, ortho-pyroxene has rounded edges or corroded margins. Reaction rims of ortho-pyroxene at the contact between olivine and intercumulus plagioclase are a typical feature.
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Crocoite
Chromite is also found in metamorphic rocks such as serpentites. As is indicated by its early crystallization, chromite is resistant to the altering affects of high temperatures and pressures, thus it is generally unaffected by the metamorphic processes. This characteristic explains the use of chromites as a refractory component in the bricks ...
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Electrical resistivity tomography of Mesoarchaean chromitite …
Chromite is one of the early crystallised magmatic minerals associated with ultramafic rocks. Chromitite, a mono-minerallic rock of chromite, is found in abundant as pockets and lenses hosted in ultramafic rocks. A chromite exploration strategy basically involves locating the host and identifying the domains of chromitite lenses.
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Petrogenesis of the Neoarchean zincian chromite within
Chromite is a common mineral in the layered mafic–ultramafic, ophiolite, and Alaskan-type complex. However, chromium concentration has been reported from sedimentary and metamorphic terrains, i.e., laterite and saprolite derived from ultrabasic rocks, beach placer and metamorphosed limestones, serpentinites many times host …
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Massive chromitite layers of the Bushveld Complex, South …
As concentration of chromium in natural magmas rarely exceeds 1 wt %, and chromite in ultramafic rocks typically occurs as an accessory phase, the formation of large chromite deposits requires ...
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Origin of the UG2 chromitite layer, Bushveld Complex
In these chromite-rich rocks chromite forms a net-texture surrounding granular orthopyroxene. The constituent minerals of four samples from the footwall and three from the hanging wall of the E chromitite have been analyzed. As can be seen in Fig. 9, there are no significant variations in orthopyroxene Mg-number throughout the sequence. …
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On the rocks
The researchers reacted chromite with birnessite, a manganese-containing mineral that often forms in weathered rocks and soils containing chromite. In water, powders of the two solids produced ...
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Frontiers | Ultramafic Rocks and Their Alteration Products …
The presence of ores such as chromite and magnetite is shown by X-ray diffraction of bulk ophiolite rocks (serpentinites and listwaenite) samples. Antigorite, calcite, dolomite, quartz, bustamite, and ore deposits are found in the studied X-ray diffraction patterns of serpentinites ( Figures 15A, B ; magnetite and chromite).
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Chromite: The mineral Chromite information and …
Detailed description, properties, and locality information guide about the chromium mineral chromite. Minerals Complete Information Guide to Rocks, Minerals, & Gemstones
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Chromite | Ores, Mining, Processing | Britannica
Chromite is commonly found as brittle masses in peridotites, serpentines, and other basic igneous and metamorphic rocks; an unusual occurrence is as a crystalline inclusion in diamond. The earliest worked deposits were …
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Formation and modification of chromitites in the mantle
Section snippets Definition of chromitite. As far as we know, there is no clear definition of chromitite. In the case of the Tari-Misaka ultramafic complex in Japan, Arai (1980) recognized a modal gap between ca. 5 vol.% and 20 vol.% chromite in a peridotite-chromitite series of rocks (Fig. 3).We can define chromitite as rocks containing > 20 …
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The influence of chromite on osmium, iridium, ruthenium …
Chromite-rich plutonic rocks are enriched in Os, Ir, Ru (IPGE) and Rh which is usually attributed to the presence of micron-size inclusions of platinum-group minerals. It is also known that volcanic rocks show positive correlations between Cr and IPGE and Rh with the most primitive lavas (olivine + chromite phyric) being enriched in these elements …
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Genesis and tectonic setting of high-Cr podiform chromitites …
Chromitites are defined as rocks containing > 20 vol.% chromite; meanwhile, those containing 5–20 vol.% are called chromite-rich rocks (Arai and Murau, 2016). Most ophiolites, as pieces of oceanic crust and upper mantle, tectonically emplaced on continental crust, contain chromitites which consist mainly of Cr- and Al-rich spinel occurring ...
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Occurrence, Origin and Transformation Processes of …
The primary sources of Cr in rocks are chromite and Cr-magnetite, as well as other mixed-(Al, Mg, Fe, Cr) composition spinels [2, 5, 36, 46].Chromite is typically not pure FeCr 2 O 4 [] but contains high levels of Cr (>35 % Cr 2 O 3 in the majority of the data), while Cr-magnetite typically hosts less than 15 % Cr 2 O 3 in its structure ().The Cr …
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Chromite
Chromite, the only commercial source of chromium, is a spinel group mineral that occurs in ultramafic igneous rocks and further occurs exclusively in rocks formed by the intrusion and solidification of molten lava or magma, which is very rich in the heavy iron-containing minerals such as pyroxenes and olivine. In addition, it is also found in metamorphic rocks …
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Compositional variations in the Mesoarchean chromites of …
The chromite deposits in the Archean Nuggihalli schist belt are part of a layered ultramafic–mafic sequence within the Western Dharwar Craton of the Indian shield. The 3.1-Ga ultramafic–mafic units occur as sill-like intrusions within the volcano-sedimentary sequences of the Nuggihalli greenstone belt that are surrounded by the …
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