IDENTIFICATION OF ALBITITE ZONE USING MULTISENSOR DATA IN EASTERN RAJASTHAN

Abstract

Albitite is a coarse grained, deep pink to brick red colour porphyritic rock which has randomly oriented subhedral laths of feldspar as the principal mineral. Albitite occurrences are very rare even on global scale and only a few reported occurrences have been documented so far from India. The generation of albitite is attributed to the replacement of alkali feldspar and plagioclase of the original granite by pure albite. Almost all descriptions associate the deposits with zones of extensive tectonic activity. Belevtsev (1980) and Grechishnicov (1980) described albitites in the Kirovograd-Krivoi Rog district. They reported that in this area the albitites are located adjacent to deeppenetrating fault extending over 100 km at surface and are associated with a combination of pegmatite intrusion, cataclasis and mylonitisation. Belevtsev (1980) studied albitites in The Beaverlodge district. Here the albitites are hosted within a major fault zone, the St Louis Fault. Albitites at Lagoa Real are developed along shear zones (Lobato and Fyfe, 1990). Occurrence of albitite in Guyana is reported from two sub-parallel, east-west trending fault zones (Alexandre, 2009). Potential sources of uranium are known to be hosted in albitites, albitised granitoids, and albitised metasedimentary rocks. Several such economically viable uranium deposits have been reported from Krivoy Rog and Zheltye Vody in Ukraine, Espinharas and Lagoa Real in Brazil, Pleutajokk and Arjeplog in Sweden, Kitongo in North Cameroon (Barthel, 1987). A few occurrences of albitite have been reported from a narrow linear zone in Khetri Copper Belt (KCB) in eastern Rajasthan, India. The detailed field survey in KCB has located albitite bodies distributed in a narrow zone of 170 km length. This zone is designated as ‘albitite zone’ of northern Rajasthan. The different albitite bodies occur in three linear sectors viz., the Sakhun Ladera, Khandela-Guhala and Maonda-Sior sectors. 17 The KCB forms the northern boundary of the Aravalli mountain range in Rajasthan, northwest India. It extends from Singhana in the NE to Raghunathgarh in the SW and is about 80 km long. The Kantli fault which strikes NW-SE divides the belt into two parts - viz., North KCB (NKCB) and South KCB (SKCB) (Das Gupta, 1968; Gupta et al., 1998). The geological interest in the area is mainly because of the copper mineralization. KCB is a well studied, thoroughly documented, regionally metamorphosed mineralized belt, and is among the main indigenous sources of base metals (Cu, Co, Pb, Zn and related metals) in the country. The geological investigation in the area were mainly focused on description of the regional geology and the nature of mineralization in the area. Hacket (1877, 1880, and 1881) and Heron (1923, 1925) carried out detailed survey and documented the regional geology. The studies were also focused on exploring the potential of copper (Cu) mineralization and also to locate other economically viable Cu deposits in the area. Varma and Krishnanni (1963) analysed the mineralization in selected pockets of the study area. Further studies on ore mineralization were also carried out by Roy Chowdhury and Venkatesh (1971). The geological history of the area has been researched and discussed by various geoscientists. Researches indicate that the geological evolution of the area has been inferred by multistage development and sinking of intracratonic basin, deposition of different sedimentary facies and associated Cu mineralization. This was followed by events related to various deformational activities and multiphase metamorphism of the strata (Roy et al., 1998). KCB is characterized by an unconformable basement-cover relationship between the high grade paragneissquartzite- calc-silicate rock sequence and copper hosted metasedimentary sequence. The metasedimentary rocks of the KCB display a NNE—SSW to NE—SW trend and are folded into a number of regional anticlines and synclines with culminations and depressions (Das Gupta, 1968).