Beitrag
Metamorphic "rims" in chromites from Sukinda, Orissa, India
Mitra, Sachinath
Neues Jahrbuch für Mineralogie - Monatshefte Jg. 1972 Heft 8 (1972), p. 360 - 375
25 Literaturangaben
veröffentlicht: Oct 19, 1972
DOI: 10.1127/njmm/1974/1974/360a
ArtNo. ESP156197208004, Preis: 19.00 €
Abstract
Layered chromite bodies in neo-alpine ultramafic intrusives occurring around Saruabil, Sukinda region, Prov. Orissa, India, were emplaced in two separate intrusions; the earlier one being more deficient in Mg and Al than the latter. These bear impressions of regional metamorphism, which not only made the body easily cleavable into platy ores, but also produced features of micro-deformation like micro-faulting, brecciation, mylonitisation etc. in chromites. Metamorphism not only caused physical deformations in chromites but also effected chemical zoning in chromites, accompanied often by the formation of some Cr-chlorites from serpentines etc. The zones or rims in chromites often show high values in Cr and Fe with corresponding low values in Mg and Al. The zoned areas of chromite are more opaque than the central part, which often transmits light feebly in thin sections. The rims are commonly lighter in colour than the body of the grain. Dark rims have also been observed in Sukinda ores. Various stages of formation of these rims have been observed under microscope in deformed ores, and the possible mechanism of formation of these rims also been discussed in this paper.
Schlagworte
Chromite • stratiform • ultrabasic • regional metamorphism • microtectonics • zoning • electron probe; Orissa (Sukinda)