Mineralogy of the fuchsites from Gattihosahalli, Chitradurga District

Abstract

The fuchsites described here occur in the lower portions of a precambrian quartzite bed, which typically encloses small bands and lenses of barytes. Of the two fuchsites studied, one occurs in the main relatively fine grained quartzite and the other forming one of the small schistose segregations in the quartzite. While the commonly measured axial angles average 34°and 32°, small angles of 14°and 19°, which are possibly related to the formation of the mineral under high pressure, have been recorded in both the fuchsites, There is a close similarity in x-ray powder pattern between the two fuchsite samples studied and between these and muscovite. This observation is in accordance with the interpretation that fuchsites exhibit the same two layered mica structure as muscovite 2M t. Chemically the fuchsites of Gattihosahalli are closely similar to the one reported from Manitoba and the cell contents are comparable to di-octahedral micas of muscovite character with Cr substituting for octahedarl AI. It is inferred that the fuchsites of Gattihosahalli are of sedimentary origin and the constituents required for their formation were all present in the shaly component of the sandstone or were partly or completely supplied by volcanic exhalations.

Chromite‐bearing quartzite in the southern fringe of Singhbhum Craton around Ghutrigaon, Eastern India: Petrogenetic implication

“…In addition to the above geological setting, Ramiengar, Devadu, Viswanatha, Chayapathi, and Ramakrishnan (1978) and Argast (1995) reported a completely different geological set-up where the chromite mineralization occurs in the form of banded chromite-fuchsitequartzite within the supracrustal sequences of Karnataka. Similar chromiferous quartzites from southern peninsular India have also been studied by Devaraju and Murthy (1975) and Raase, Raith, Ackermand, Viswanatha, and Lal (1983). The typical minerals in such association form during a wide range of metamorphic conditions and comprises of chrome-spinel, fuchsite, quartz, kyanite, rutile, tourmaline, and magnetite.…”

Green micas in the Archaean Isua and Malene supracrustal rocks, southern West Greenland, and the occurrence of a barian-chromian muscovite

“…We suggest that the chemical characteristics of the Malene green micas are explained adequately by invoking chromite as a source for Cr, and sedimentary barite, which was mixed into the clastic rocks, as a source for Ba. The interlayered 'fuchsite' schist -barite deposits described recently by Devaraju & Murthy (1978) in Archaean rocks from the Chitradurga District, India may be a direct analogue to the Malene occurrences. Unfortunately, these authors did not report Ba analyses of their green micas.…”

“…Several papers reporting on the chemical compositions of green micas have appeared within the last few years (e.g. Chen & Lee, 1974;Sadashivaiah & Karisiddaiah, 1976;Ghisler, 1976;Devaraju & Murthy, 1978;Cooper, 1980), but in general the literature on 'fuchsite' is sparse and incomplete, especiaIly in view of the high Ba-contents reported here, as most previous investigators either negiected to analyze for that element or did not report a measurement. The original analysis of 'fuchsite' from the type locality (Schwartzenstein, Zillerthal, Austria) lists more than 5 Wt % CrZ03 (Dana, 1892).…”