International Journal of Research and Innovations in Earth Science Volume 2, Issue 3, ISSN (Online) : 2394-1375 Geology of Rajpura-Dariba Group of Rocks P. K. Yadav Email: [email protected] Abstract – Stratigraphic position of Rajpura-Dariba Group collection of new data and in totality adopting a holistic of rocks has been worked out by different workers and integrated approach to find new sites for exploration. varied status has been given by them. These different views Study area lies around village Sindesar Khurd which is have been discussed in the present paper, Considering accessible by road from Dariba mines and Rail Magra; a lithology, airborne and ground geophysics and Tehsil headquarter. The area consists of a physiographic geochronological data in the present paper an attempt has been made to compare these different views on the ridge composed of series of hills looking like a chain of stratigraphy. On the basis of presence of basal conglomerate, train bogies. volcanics and variation in the environment of deposition a Stratigraphically the sequence in the Rajpura-Dariba new threefold classification has been proposed. Stratigraphic Group of rocks was considered by Gupta (1934) to belong status of host lithology has been identified for use as tool for to Aravalli “system.” Later Raja Rao et al. (1971) of prognostication of base metals in the Rajpura-Dariba Grou[ Geological Survey of India recognized the cover sequence of rocks. to be Pre-Aravalli meta-sediments on the basis of differences with the Aravalli‟s in lithology and grade of Keywords – Lithological Setup, Host Lithology, metamorphism. In the major stratigraphic revision, Prognostication, Stratigraphy, Structure. Geological Survey of India grouped the basement rocks under the Mangalwar Complex and the cover meta- INTRODUCTION sediments of Dariba area were grouped under Rajpura Dariba Group of the Bhilwara Supergroup of Archean age Rocks of the Rajpura-Dariba-SindesarKhurd-Bethumbi- (Gupta et.al, 1980; 1995). Surawas area belong to Precambrians. Stratigraphic On the basis of Pb-Pb model ages of stratiform galena position of these rocks has been worked out by different occurrences which lie in Bhilwara Supergroup; showed workers and status of these rocks has been differently that they are all around 1.8 Ga old (Deb and Thorpe, given by them. According to these workers in general an 1989,2004) it was supported by Roy et al. (1981) on the ensemble of gneiss-granite-amphibolite and associated basis of tracing the structural and physical continuity of high grade sediments constitute the basement over which the Aravalli superacrustals into Bhilwara rocks. Roy et al. successive younger metasediments and metavolcanic (1981) have claimed that they have traced continuity of cover sequences were deposited. According to a few an band of quartzite from southeast of Nathdwara, Nathuwas, unconformity separate basement rocks from the overlying and Dhanera (south of Rajpura Dariba mines) to the west cover rocks. Status of high grade meta-sediments and south of Bhinder. (Naha and Roy, 1983; Roy 1988, according to these workers is either Lower Proterozoic or 1999) an idea originally mooted by Heron (1953) and Archean. According to a few workers Rajpura-Dariba Crookshank (1948) and have indicated that the rocks of group of rocks rest on migmatised Aravallis. Rocks of Rajpura-Dariba rest on migmatised Aravallis. Rocks of Rajpura-Dariba are equivalent to the Aravalli Supergroup Rajpura-Dariba are thus equivalent to the Aravalli of rocks. The age for basement gneiss is Meso–Archean Supergroup of rocks. and age for intrusive Untala granite is Neo-Archean. The rocks of Rajpura-Dariba unconformably overlie the However there is no dispute about status of Aravalli Potla formation of the Mangalwar Complex in the north Supergroup of rocks starting above unconformity and they where as in the south near Dhanera and Akola an are of Lower Proterozoic age. unconformable relation is seen with the Lasaria Formation In Rajpura–Dariba belt mineralisation of lead and zinc of the Mangalwar Complex (Gupta et al., 1995, p.27).The was established on the basis of gossan. Lead and Zinc are geological map of study area and surroundings (Roy, the basic requirement of many industries. Almost all the 2004) lacks study of aerogeophysical and gravity and areas in Rajpura–Dariba belt which show oxidation and integrated data based evidences which have been earlier also in the extension of all these areas gossans have been studied by (Saurabh Ray and R. Srinivas Rao, 2000). searched for Lead and Zinc mineralisation. Recent deep Tracing continuity of the band of quartzite from southeast drilling by HZL in Rajpura-Dariba-SindesarKhurd has of Nathdwara, to Nathuwas, and Dhanera (south of increased earlier estimated reserves of Lead and Zinc. It Rajpura Dariba mines) to the west and south of Bhinder has given a new hope for searching additional targets of has evoked serious doubts (Saurabh Ray and R.Srinivas Lead and Zinc in the Rajpura–Dariba belt. Rajpura–Dariba Rao, 2004, GSI). According to Saurabh Ray and has been explored extensively for several years using R.Srinivas Rao (2004) there is absence of correlation sophisticated means. Thus, exploration geologists are factor between aerogeophysical and gravity data with the posed with a question of searching new ore sites based on formations of Aravallis and Rajpura-Dariba belt. cost effective integrated techniques and discovery of According to him in the geophysical data there is clear mineralised targets is thus, a challenge. Therefore, difference in basement and cover. The exploration of lead and zinc requires review of all the data, linear/elliptical/ovoid shaped Proterozoic basins Copyright © 2015 IJRIES, All right reserved 89 International Journal of Research and Innovations in Earth Science Volume 2, Issue 3, ISSN (Online) : 2394-1375 equivalent to pre Aravalli sediments within Archean such linear zones. Depositional basin had parallel horst gneisses geophysicaly comes out sharply in contrast to the and half-graben structures. In these sites volcano- BGC. Similar to Roy (2004) based on discordant structural sedimentary and exhalites of metal rich fluids were relations, presence of folded unconformity, metamorphic deposited. The rifting was accompanied by development brakes and lithofacies contrasts between the migmatitic of parallel minor shears, faults and fractures could have substrate and the sedimentary cover, and intrusive resulted in formation of basement slices between adjacent relationship of the Berach Granite (ca.2.5 Ga) with the packages of Supracrustals. substrate migmatite and not with the cover rocks has led The Rajpura–Dariba Group of rocks in Sindesar Khurd Sinha Roy (1984 b) and Sinha-Roy et al. (1998) also to area has been covered by airborne and ground geophysical give a judgment that the enclave rocks of BGC in survey. From the study of airborne geophysical map, Bhilwara belt are isolated Proterozoic cover sequences in depicting total intensity magnetic contours, Airborne synformal keels within the BGC gneisses. These belts Electro Magnetic (A.E.M.) zones and mineralised have been considered Paleo-Mesoproterozoic pull-apart prospects the following features emerge: basins, genetically linked with regional strike slip faults by i) In the total magnetic contour maps cover rocks stand Sinha-Roy in 1989.These strike slip faults were out prominently in the background of rocks of Mangalwar responsible for opening of main Aravalli basin. The complex. Cover rocks are characterised by abrupt change lithostratigraphy of BGC is a composite rock sequence in in the magnetic intensity i.e. with higher amptitude/wave which Sinha-Roy (1985) first recognized dismembered length ratio of isomagnetic contours. Cover rocks are granite- greenstone sequence. Later Sinha-Roy (1993); characterised by narrow elongated zones like chains of Mohanty and Guha, (1998, 1993a) have identified Airborne Electro Magnetic (AEM) zones. All the komatiites, ultramafics, cherts, basic tuffs, graywackes, prospects containing base metals have recorded strong amphibolites and carbonates. Greenstone affinity of BGC magnetic and AEM anomalies (6 to 5 channels i.e. IP/OP, is also indicated by Upadhyaya et.al. (1992). input, output, ratio >3) and are associated with the magnetic discontinuities. The magnetic discontinuities REVIEW OF GEOPHYSICAL CHARACTERS OF also reflect faults or ductile shear zones e.g. those trending RAJPURA-DARIBA GROUP OF ROCKS N-S, NNW-SSE, E-W and NS-SE in the present area. Over the basement rocks magnetic contours 7200 gamma Rajpura-Dariba Group of rocks occurs as a linear (except patchy highs over metabasics or magnetic bearing northeast-southwest basin. The Bhilwara rocks e.g. metapellites) have much lower isomagnetic metasedimentaries Rajpura-Dariba Group of rocks (cover contour gradient that becomes gentler on cover rocks. rocks), are flanked by the basement rocks of the Banded ii) The metallotects are characterised by intersection of Gneisses, Mangalwar Complex (Gupta et al. 1995). This faults in N-S and E-W which are reflected by magnetic linear alignment is further depicted in linearly arranged breaks and also associated with magnetic anomalies. volcano-sedimentaries and sulphide facies within Rajpura-Dariba-Sindesar Khurd area has registered strong northeast-southwest extending shear. There are several magnetic response >13000 gamma due to presence of sub-parallel NE-SW trending faults indicating banded iron formations, magnetite quartzite, iron