Weathering of Ilmenite in a Lateritic Pallid Zone

Abstract

Abstract--In a lateritic pallid zone ilmenite crystals alter via pseudorutile to porous leucoxene grains composed of randomly oriented aggregates of ~0.06/~m anatase crystals. This style of alteration differs from that in beach sands where parallel oriented futile crystals develop from pseudorutile. Increased Si and A1 in the altered grains is due to the crystallization from soil solution of halloysite, kaolinite and gibbsite within pores rather than to the incorporation of these elements into anatase crystals. Manganese was a significant constituent (3.2% Mn203) of the original ilmenite but was not retained by the leucoxene grains. The minor constituents Ni, Zn, Cu, Mg, Co and Ca were also lost, but Cr and V were retained.

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] .…”

Geochemical properties and saline-water intrusion in the Valle de Yabucoa alluvial aquifer, southeastern Puerto Rico

“…Individual ilmenite grains contain patches and streaks of leucoxene (a combination of rutile, TiO2; anatase, TiO2; and sphene, CaTiO(SiO4)), indicating that leaching of iron and manganese from the original ilmenite has resulted in the formation of the iron and manganese-free alteration product and the release of the manganous and ferrous ions into the reducing ground water without oxidation or reduction reactions. The liberation of iron and manganese during the progressive alteration of ilmenite to leucoxene (possibly including the intermediate alteration product pseudo-rutile) has been reported by other workers (Morad and Aldahan, 1985;Anand and Gilkes, 1984).…”

Weathering trends and parent material characteristics of polygenetic oxisols from Minas Gerais, Brazil: I. Mineralogy

“…Ilmenites present in saprolites and soils of group SJR-sap, as well as in group SJR-sed are weathered, whereas this is not clearly observed in group SL-sap. Weathering of ilmenite under oxidizing conditions has been frequently reported (Anand and Gilkes, 1984;Ramakrishnan et al, 1997). In group SJR-sap, ilmenite grains show altered surfaces, characterized in thin section by a pellicular, dotted and/or complex alteration pattern, similar to the pattern described by Anand and Gilkes (1984) for a lateritic layer in Australia.…”