Alteration of Ilmenite in the Manavalakurichi Deposit, India

Abstract

Magnetic fractionation, chemical, and structural analyses prove that alteration ofilmenite from Manavalakurichi deposit extends only up to the formation of pseudorutile with traces of rutile. The data indicate that ferrous to ferric iron transformation, ferric iron oxide formation, and iron removal contribute to the alteration sequence. The first two highly magnetic fractions are not unaltered ilmenite. A reduction in ilmenite unit cell volume indicates the ferrous-ferric conversion occurred during alteration.

Alteration Characteristics Of Ilmenites From South India

“…Thus, the sum total of the percentages from the altered portions of ilmenite varies from 95.061% to 98.780% for Navaladi and from 97.224% to 98.935% for Teri, which may be due to the incorporation of hydroxyl ions into the structure during weathering. Similar observations have also been made by many authors [2,5,[16][17] .…”

“…The heavy mineral assemblage in this sector is suggestive of provenance consisting principally of high-grade metamorphic (granulite facies) rocks, principally of khondalite (garnet-sillimanite-graphite-gneisses), charnokites and granitic gneisses (unclassified crystalline rocks), bordered by the sedimentary rocks exposed along the eastern coastal plains which are the rock types of Tamilnadu [14] . However, the extent of alteration depends on the geological history of the deposit and also the weathering environments [2,11] . The degree of alteration of different ilmenite deposits in the world is quite varied; those of Zululand (South Africa) and Brazil being altered relatively very little but those of Australia and Florida (U.S.A.) show extensive alteration [11,19] .…”

“…The degree of alteration due to weathering is significant and is independent of the provenance. Hence, it attracts the attention of scientists in different disciplines with totally different approaches [2][3][4][5] . Several workers have studied ilmenite from across the world to assess the qualitative variation from deposit to deposit [6][7][8][9] , Many articles were published on the alteration of ilmenite [4,[10][11][12][13] .…”

Differential Alteration of Ilmenite in a Tropical Beach Placer, Southern India: Microscopic and Electron Probe Evidences

“…The same trend is shown by the a axis with lengths of about 5.10 Å for all samples except M3 (5.07 Å). The leaching of iron from the ilmenite structure result in the reduction of the cell volume as alteration advances (Suresh Babu et al, 1994). The TGA data reveal the relatively higher structural water content and hence the higher alteration state of sample M3, as signified by the weight loss at 500-600°C.…”

“…Mössbauer techniques were applied and found suitable to estimate the pseudorutile formation in ilmenite grains (Subrahmanyam et al, 1982;Nair, 2001). Magnetic fractionation of ilmenite and the study of its qualitative variation are helpful in delineating the general progressive alteration of the mineral (Suresh Babu et al, 1994).…”