Precipitation and dissolution of chromite by hydrothermal solutions in the Oman ophiolite: New behavior of Cr and chromite

Arai, Shoji; Akizawa, Norikatsu

doi:10.2138/am.2014.4473

Cited by 90 publications

(61 citation statements)

References 39 publications

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“…Some spinel grains can be found as exsolution lamellae in orthopyroxene, whereas some are also present as mineral inclusions in olivine that appear to have precipitated from the fluids. Arai and Akizawa (2014) have suggested that spinel (chromite) grains precipitate from hydrothermal fluids. If the quartz and the spinel in the fluid inclusions had indeed precipitated from the fluids, the original fluids must have contained dissolved Si, Al, Cr, Fe, and Mg, in addition to volatile components.…”

Section: Fluid Compositionmentioning

confidence: 99%

Evolution of carbon dioxide-bearing saline fluids in the mantle wedge beneath the Northeast Japan arc

Kumagai

Kawamoto

Yamamoto

2014

Contrib Mineral Petrol

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Section: Fluid Compositionmentioning

confidence: 99%

Evolution of carbon dioxide-bearing saline fluids in the mantle wedge beneath the Northeast Japan arc

Kumagai

Kawamoto

Yamamoto

2014

Contrib Mineral Petrol

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“…We prefer fluid to melt as an agent for the dike formation, because of the presence of fine euhedral chromian spinel, indicating the Cr-rich character of the high-Al agent. The solubility of Cr in silicic melts is very low (e.g., Irvine, 1977), but high-T aqueous fluids can dissolve appreciable amounts of Cr to precipitate chromian spinel (e.g., Arai and Akizawa, 2014). The coarse chromian spinel, with a high Cr# core and low Cr# rims (Table 1), are of xenocrystal origin from the wall dunite and/or chromitite.…”

Section: Discussionmentioning

confidence: 99%

“…Plagioclase occasionally contains fluid inclusions, of which the main components are HCO 3 − , SO 4 2− , and Cl − (Scherbakova, 1975). Rubies may be effectively formed within the fluid metasomatic processes because the fluids with appreciable Cl − , CO 3 2− , and SO 3 2− are capable of dissolving Cr 3+ from chromian spinel (Arai and Akizawa, 2014).…”

Section: Discussionmentioning

confidence: 99%

Ruby–bearing feldspathic dike in peridotite from Ray–Iz ophiolite, the Polar Urals: Implications for mantle metasomatism and origin of ruby

Ishimaru

Arai

Miura

et al. 2015

Journal of Mineralogical and Petrological Sciences

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Crystallization of ruby requires excess Al and appreciable amounts of Cr in the system. A ruby-bearing feldspathic dike crosscuts dunite in the Ray-Iz massif, the Polar Urals, and the dominant mineral of the dike changes from plagioclase at the center to amphibole outward. Ruby has been observed in between, and the zone is composed of plagioclase and phlogopite with minor chromian spinel and ruby as primary phases, and paragonite as a secondary phase. The Cr 2 O 3 content of the ruby is <7.5 wt% and close to the values of those found in serpentinite and chromitite from other localities. The petrographical and highly LREE-enriched and HREE-depleted features of the ruby-bearing rock imply a metasomatic origin for the dike through the interaction between feldspathic component-rich aqueous fluid and wall rock dunite with chromitite. Based on the primary occurrence of plagioclase, it is inferred that the fluid infiltration possibly occurred at 1.0-1.5 GPa, and the fluid interacts with peridotite. The lithological change of the dike indicates effective consumption of Si, Ca, and K and assimilation of Cr and Mg in the fluid at the contact with the wall-rock dunite, and the fluid composition could have evolved to be peraluminous through the interaction. Chromium is effectively transported by aqueous fluid with some anions, e.g., Cl − , CO 3 2− , and SO 3 2− , and the interaction of peridotite as a source of Cr with such fluids is one of the important formation processes of ruby within the mantle wedge where fluids are available from the downgoing slab.

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“…The concentrations of transition metals in such rocks have been used in the past to assess the relative contribution of hydrothermal (e.g., Mn, Zn, Cr, Cd), hydrogenous (e.g., Mg, V, Co, Ni), and detrital (e.g., Cr, Ti) components to the protolith (e.g., Bonatti, 1975;Heimann et al, 2011;Hein et al, 2005). Although Cr is generally not considered an element that is enriched in hydrothermal fluids, Arai and Akizawa (2014) showed that Cr in high-temperature hydrothermal solutions may be more elevated. However, its behavior in lower temperature hydrothermal fluids (i.e., temperatures associated with exhalations from metal-bearing hydrothermal vents) remains unclear.…”

Section: Discussionmentioning

confidence: 99%

Gahnite composition as a means to fingerprint metamorphosed massive sulfide and non-sulfide zinc deposits

O'Brien

Spry

Teale³

et al. 2015

Journal of Geochemical Exploration

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Gahnite occurs in and around metamorphosed massive sulfide (e.g., Broken Hill-type Pb-Zn-Ag (BHT), volcanogenic massive sulfide Cu-Zn-Pb-Au-Ag (VMS), sedimentary exhalative Pb-Zn (SEDEX)), and nonsulfide zinc (NSZ) deposits. In addition to occurring in situ, gahnite occurs as a resistate indicator mineral in unconsolidated sediments (e.g., glacial till) surrounding such deposits. The spatial association between gahnite and metamorphosed ore deposits has resulted in its use as an empirical exploration guide to ore. Major and trace element compositions of gahnite from BHT, NSZ, SEDEX, and VMS deposits are used here to develop geochemical fingerprints for each deposit type. A classification tree diagram, using a combination of six discrimination plots, is presented here to identify the provenance of detrital gahnite in greenfield and brownfield terranes, which can be used as an exploration guide to metamorphosed massive sulfide and nonsulfide zinc deposits. The composition of gahnite in BHT deposits is discriminated from gahnite in SEDEX and VMS deposits on the basis of plots of Mg versus V, and Co versus V. Gahnite in SEDEX deposits can be distinguished from that in VMS deposits using plots of Co versus V, Mn versus Ti, and Co versus Ti. In the Sterling Hill NSZ deposit, gahnite contains higher concentrations of Fe3+ and Cd, and lower amounts of Al, Mg, and Co than gahnite in BHT, SEDEX, and VMS deposits. Plots of Co versus Cd, and Al versus Mg distinguish gahnite in the Sterling Hill NSZ deposit from the other types of deposits. Gahnite occurs in and around metamorphosed massive sulfide (e.g., Broken Hill-type Pb-Zn-Ag (BHT), volcanogenic massive sulfide Cu-Zn-Pb-Au-Ag (VMS), sedimentary exhalative Pb-Zn (SEDEX)), and nonsulfide zinc (NSZ) deposits. In addition to occurring in situ, gahnite occurs as a resistate indicator mineral in unconsolidated sediments (e.g., glacial till) surrounding such deposits. The spatial association between gahnite and metamorphosed ore deposits has resulted in its use as an empirical exploration guide to ore. Major and trace element compositions of gahnite from BHT, NSZ, SEDEX, and VMS deposits are used here to develop geochemical fingerprints for each deposit type. A classification tree diagram, using a combination of six discrimination plots, is presented here to identify the provenance of detrital gahnite in greenfield and brownfield terranes, which can be used as an exploration guide to metamorphosed massive sulfide and non-sulfide zinc deposits. The composition of gahnite in BHT deposits is discriminated from gahnite in SEDEX and VMS deposits on the basis of plots of Mg versus V, and Co versus V. Gahnite in SEDEX deposits can be distinguished from that in VMS deposits using plots of Co versus V, Mn versus Ti, and Co versus Ti. In the Sterling Hill NSZ deposit, gahnite contains higher concentrations of Fe 3+ and Cd, and lower amounts of Al, Mg, and Co than gahnite in BHT, SEDEX, and VMS deposits. Plots of Co versus Cd, and Al versus Mg distinguish gahnite in the Sterlin...

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Precipitation and dissolution of chromite by hydrothermal solutions in the Oman ophiolite: New behavior of Cr and chromite

Cited by 90 publications

References 39 publications

Evolution of carbon dioxide-bearing saline fluids in the mantle wedge beneath the Northeast Japan arc

Evolution of carbon dioxide-bearing saline fluids in the mantle wedge beneath the Northeast Japan arc

Ruby–bearing feldspathic dike in peridotite from Ray–Iz ophiolite, the Polar Urals: Implications for mantle metasomatism and origin of ruby

Gahnite composition as a means to fingerprint metamorphosed massive sulfide and non-sulfide zinc deposits

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