Chromites from meta-anorthosites, Sittampundi layered igneous complex, Tamil Nadu, southern India

Ghosh, Biswajit; Konar, Ritam

doi:10.1016/j.jseaes.2011.07.024

Cited by 27 publications

(12 citation statements)

References 57 publications

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“…Most chromitites form meter-scale lenses in the ultramafic, olivine-bearing units but some lenses have also be found in close association with leuco-amphibolites and anorthosites. These characteristics allow us to link this complex to well-known, worldwide Archaean anorthosite complexes [28], such as Fiskenaesset in Greenland [40] and Sittampundi in India [41,42].…”

Section: Methodsmentioning

confidence: 99%

Following the Amphibolite to Greenschist Metamorphic Path through the Structural Parameters of Spinels from Amsaga (Mauritania)

et al. 2018

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Abstract:We investigated the crystal and structural behavior of several Cr-bearing spinels from the Archean chromitites of Amsaga (Mauritania). The chemical and structural data testified a retrograde metamorphism from amphibolite to greenschist facies, witnessed by relative changes in the amount of all the major oxides (Cr, Al, Mg, Fe 2+ , Fe 3+ ), the relative proportion of Fe 3+ /Fe tot as well as the structural parameters, including the cell edge and the oxygen coordinate. The general agreement between electron microprobe and Mössbauer data indicates that the analyzed spinels are stoichiometric. The structural data revealed that the oxygen positional parameter of amphibole-bearing samples is the highest observed among Cr-bearing spinels with similar Cr# and Mg#. Consequently, it is suggested that a structural study of detrital Cr-spinels could be important in discriminating an amphibole-chromitite source from an ophiolite source.

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Section: Methodsmentioning

confidence: 99%

Following the Amphibolite to Greenschist Metamorphic Path through the Structural Parameters of Spinels from Amsaga (Mauritania)

et al. 2018

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“…The Cr# values [Cr/(Cr + Al) atomic ratio] of the spinels of ultramafics from SMUC range from 0.81 to 0.98, and their Mg# values [Mg/ (Mg + Fe 2+ ) atomic ratio] show a range of 0.11 to 0.30 (Table 1), which are generally higher than those of spinels reported from the other parts of CSZ (Ghosh & Konar, 2011). On tectonic discrimination plots, the spinels show typical arc environment (Figure 16a) with high Ti concentrations suggesting fore-arc setting (Figure 16b,c).…”

Section: Spinelmentioning

confidence: 85%

The mafic–ultramafic complex of Salem, southern India: An analogue for Neoproterozoic Alaskan‐type complex

2019

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The Salem Mafic–Ultramafic Complex occurs within the northern part of Cauvery Suture Zone (CSZ), Southern Granulite Terrane (SGT), India. The complex occurs as semicircular to elongated linear body with a thick mantle section and comparatively well‐developed crustal section comprising different lithological units, also referred to as the Chalk Hills of Salem. The major rock types in the complex comprise ultramafic cumulates of dunite, peridotite, wherlite, pyroxenite, and hornblendite, mafic and felsic intrusions of gabbros and amphibolites, and quartzo–feldspathic alkaline rocks together with several ultrapotassic dykes. Geochemical studies of amphibolites from this complex indicate tholeiitic parent magma with enrichment of LIL elements (Rb, Ba, Th, and Sr) and are relatively more enriched than N‐MORB as compared with arc‐related rocks. The enrichment of LIL elements over the HFS elements and with distinct Nb, Ta, and Ti depletion relative to other HFS elements suggest the involvement of subduction‐related components in the depleted mantle source and that the magmatism occurred in an oceanic convergent realm. The mineral chemistry of dunite and peridotite shows high content of forsterite (86.9–92.2) in olivine and high Cr# value (80.85–98.73) for spinel. The tectonic discrimination plots of spinel and olivine mineral chemistry together with clinopyroxene chemistry of amphibolites reveal arc signature typical of Alaskan type of complex. The U–Pb zircon analysis of quartz monzonite intrusion within the hornblendite from the complex yielded a weighted mean age of 819 ± 2.4 Ma, suggesting that the complex formed during the Neoproterozoic and can be correlated to the Alaskan‐type complexes described from the Arabian–Nubian Shield.

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“…Taking into consideration the fact that >95% of spinels from mantle rocks have TiO 2 < 0.2 wt.% and volcanic spinels with <0.2 wt.% are uncommon and with TiO 2 < 0.1 wt.% are exceptionally rare a compositional boundary between peridotitic and volcanic spinels has been arbitrarily set at TiO 2 = 0.2 wt.% (figure 4). Titanium (Ti 4+ ), present in magma, can enter into the spinel structure by couple substitution together with Fe 2+ , replacing two Fe 3+ in the octahedral site (Ghosh and Konar 2011). Therefore, incorporation of titanium in the spinel lattice demands the spinel to be of partly inverse structure which is favoured if the spinel crystallizes under higher oxygen fugacity condition.…”

Section: Discussionmentioning

confidence: 99%

Chromian spinel-rich black sands from eastern shoreline of Andaman Island, India: Implication for source characteristics

Bhatta

Ghosh

2014

J Earth Syst Sci

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Black sands rich in chromian spinel commonly occur in pockets along the eastern shoreline of Andaman Island where various types of peridotites and volcanics belonging to the Andaman ophiolite suite are exposed in close vicinity. The chemistry of these detrital chromian spinels has been extensively used here in identifying the source rocks vis-à-vis deciphering the source characteristics. The composition of the chromian spinels (Cr#: 0.20-0.88, Mg#: 0.26-0.77, Al 2 O 3 : 5.04-48.21 wt.%, TiO 2 : up to 1.39 wt.% and Fe 2+ /Fe 3+ : 1.73-9.12) varies widely signifying multiple sources, of which mantle peridotites and volcanic rocks are relevant in an ophiolitic terrain. The volcanic chromian spinels are relatively fresh, commonly euhedral, sometimes with compositional variations, and contain inclusions in contrast to the mantle peridotitic chromian spinels which are rounded, extensively fractured, and altered. We used a number of geochemical bivariate plots in order to know the provenance protoliths. The volcanic chromian spinels show geochemical characters of MORB, related to spreading centers (either MOR or back-arc) and also boninites/arc-tholeiites, related to active subduction. On the other hand, the peridotitic spinels indicate partially depleted lherzolite and depleted harzburgite source of the ophiolite suite.

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Chromites from meta-anorthosites, Sittampundi layered igneous complex, Tamil Nadu, southern India

Cited by 27 publications

References 57 publications

Following the Amphibolite to Greenschist Metamorphic Path through the Structural Parameters of Spinels from Amsaga (Mauritania)

Following the Amphibolite to Greenschist Metamorphic Path through the Structural Parameters of Spinels from Amsaga (Mauritania)

The mafic–ultramafic complex of Salem, southern India: An analogue for Neoproterozoic Alaskan‐type complex

Chromian spinel-rich black sands from eastern shoreline of Andaman Island, India: Implication for source characteristics

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