Characterisation of Kalalikhera Felsic Volcanics, Pur-Banera Belt, Rajasthan: Insights from Monazite–Xenotime Geochemistry and Chemical Ages
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J. Earth Syst. Sci. (2021) 130:84 Ó Indian Academy of Sciences https://doi.org/10.1007/s12040-021-01572-8 (0123456789().,-volV)(0123456789().,-volV) Characterisation of Kalalikhera felsic volcanics, Pur-Banera belt, Rajasthan: Insights from monazite–xenotime geochemistry and chemical ages 1, 2 1 SURESH CHANDER * ,SANTANU BHATTACHARJEE ,MANIDEEPA ROY CHOUDHURY 1 and NIKHIL AGARWAL 1Geological Survey of India, Western Region, 15-16 Jhalana Dungri, Jaipur 302 004, India. 2Geological Survey of India, Training Institute, Bandlaguda, Hyderabad 500 068, India. *Corresponding author. e-mail: [email protected] MS received 15 October 2020; revised 5 January 2021; accepted 6 January 2021 Geological and geochemical characteristics of the litho units exposed in and around Kalalikhera area of Pur-Banera belt have conBrmed the presence of felsic volcanic rock unit named Kalalikhera felsic volcanic, with characteristic features such as (i) abundance of lapilli composed of polygonal quartz and feldspar and (ii) presence of relict bipyramidal quartz. These volcanics are associated with thin bands of chert. Geo- chemically, the volcanics are found to be of rhyolitic composition. Development of garnet porphyroblasts along with preferred orientation of the silicate minerals of rhyolite indicates a low to medium grade meta- morphism and deformation of the units. Monazite geochemistry of the volcanics indicated towards the metamorphic origin of monazites, with REE pattern show steep fractionation trend from La to Lu. The in- situ chemical age of 2192 ± 57 Ma recorded from xenotime is interpreted as indicative of the opening of the Aravalli basin with the onset of rifting leading to the formation of Kalalikhera volcanics. The estimated ages of 1784 ± 92, 1351 ± 45 and 1026 ± 57 Ma from monazite analyses are interpreted as different metamor- phic events associated with (i) closure of the basin and the onset of Aravalli orogeny, (ii) further imprints of Delhi orogeny, and (iii) with late Grenvillian age imprints. Keywords. Pur-banera; Kalalikhera; monazite; xenotime; volcanics; REE. 1. Introduction from the Proterozoic cover sequence of the PBB was reported by Ozha et al.(2016) of mesoproterozoic The NNE–SSW trending Pur-Banera Belt (PBB) (*1.37–1.35 Ga) age. They also reported the constitutes an early Proterozoic cover sequence over preservation of Grenvillian ages of *1.05–0.99 Ga in Archaean Mangalwar Complex in south-central both the basement and supracrustal rocks. D’Souza Rajasthan. It is known to host several base metal et al.(2019) recorded monazite ages of 1.3–0.8 Ga prospects of sub-economic significance. Many and suggested multiple post-depositional workers have studied the metamorphic and struc- tectonothermal events in the PBB. tural evolution of the Pur-Banera Belt (PBB) of the The study of major oxides, trace elements south-central Rajasthan based on the monazite and including rare-earth elements (REE) and high Beld xenotime geochemistry and geochemical ages. The strength (HFS) elements can deBne the emplace- monazite geochronology of the metapelitic rocks ment of various felsic volcanic rocks in different 84 Page 2 of 14 J. Earth Syst. Sci. (2021) 130:84 Figure 1. (a) Geological map Pur-Banera Belt, Bhilwara District, Rajasthan (modiBed after Gupta et al. 1980). (b) Detailed geological map of Kalalikhera area. tectonic settings including the oceanic plateau, In the present work, the authors place the new subducted oceanic crust as well as in the spreading crystallization age of the felsic volcanic from the ridges (Andrehs and Heinrich 1998; Kerr et al. 2000; PPB by EPMA chemical dating of monazite and Hazarika et al. 2013; Ozha et al. 2016). REE-bearing xenotime and aim to geochemically characterize minerals such as monazite and xenotime are gener- felsic volcanics in the Pur-Banera basin. ally used as petrogenetic indicators which occur as accessory phases in felsic and alkaline magmatic rocks as well as in hydrothermal veins (Pearce et al. 2. Geology 1984; Ahmad and Tarney 1991; Ward and Miller 1993;Forster€ 1998b; Zhu et al. 1999; Spear and Pyle The NNE–SSW trending Pur-Banera Belt (PBB) 2002; Ondrejka et al. 2007; Ahmad et al. 2008a; (Bgure 1a) forms an isolated basin that rests over Berger et al. 2008; Singh and Singh 2012; Quach and the Archaean Gneissic Complex in south-central Hans 2015). Compositional variations in monazite Rajasthan. The belt extends from near Bhinder in and xenotime can provide valuable information on the south to Banera in the north. The geological fractionation, rock–Cuid interaction, and meta- framework of the PBB has been given by Gupta morphic overprint in host-rock. (1934) and Heron (1953) who considered the J. Earth Syst. Sci. (2021) 130:84 Page 3 of 14 84 Figure 2. Field photographs showing (a, b and c) lapilli bearing felsic volcanics in Kalalikhera area, (d) contact between felsic volcanics and mica-schist, (e and f) chert band intercalated with mica-schist. metasediments of the Pur-Banera basin to be The geochronological framework of Archaean equivalent of Aravalli rocks. Gupta et al.(1980) Gneissic Complex is fairly well understood. The have mapped the lithosequence of the PBB as Pur- oldest basement gneisses have yielded a whole rock Banera Group that forms part of the Archaean six-point isochron age of 3307 ± 33 Ma by Sm–Nd Bhilwara Supergroup. Sinha-Roy (1989), on the method (Gopalan et al. 1990). Rb–Sr whole-rock other hand, invoked the coevality of the PBB and isochron ages of the oldest granites of Untala area, the Proterozoic Aravalli basin. He suggested that intrusive into BGC, have been obtained as the intracratonic basins like that of Pur-Banera in 2900 ± 100 Ma (Sastry 1992). The potassic gran- the Archaean gneissic complex evolved as pull- ites exposed around Berach have been dated at apart basins that were contemporaneous with the 2533 Ma (Rb–Sr whole-rock isochron age) and opening of the Aravalli basin. The main rock types 2440 ± 8 Ma (ion microprobe study) by Crawford comprising the PBB include impure carbonates, (1970) and Wiedenbech et al. (1996); respectively. quartzites, calc-silicate rocks, garnetiferous quartz Radiometric dating of PBB and adjoining isolated mica schist, amphibolites and banded iron forma- basins of Rajpura–Dariba has been attempted by tions. The rocks of PBB are intensely deformed Deb et al. (1989). They determined Pb–Pb model into large scale folds that have NNE–SSW axial ages that hover around 1.8 Ga. The south-central trace. part of the PBB near Kalalikhera (KK) comprises 84 Page 4 of 14 J. Earth Syst. Sci. (2021) 130:84 Figure 3. Photomicrograph of the felsic volcanics showing (a) chloritisation of biotite grains, (b) post-tectonic garnet porphyroblast with orientation of inclusion trails (yellow dash line) parallel to outer schistosity orientation (red dash line), (c) relict bipyramydal quartz crystal rimmed by epidote, and (d) muscovite and biotite in quartzofeldspathic matrix. of multiple bands of garnetiferous quartzite, Chloritisation of biotite is observed at places quartzofeldspathic rocks, mica-schist and chert (Bgure 3a). Garnet porphyroblasts are post-tec- (Bgure 1b). The quartzofeldspathic rocks are Bne- tonic with inclusion rich core, with an orientation grained with aphyric texture and also consist of of internal inclusion trails matching with the lapillae that vary from 0.2 to about 0.5 cm in size external schistosity (Bgure 3b). The monazite (Bgure 2a–d). The width of these quartzofeld- grains are subhedral to euhedral while xenotime is spathic bands is about 30 m trending NNE–SSW. mostly euhedral. The quartzofeldspathic unit The lapillae bearing rocks contain pin-head size shows a relict bipyramidal shape of quartz at places garnets. Quartzite is a major lithounit exposed in rimmed by epidote (Bgure 3b). Bipyramidal quartz the area. In the northwestern part of the Kala- is indicative of its volcanic nature (Bgure 3d). likhera area, a well laminated thin band of chert is Biotite to chlorite alteration is noted at places present (Bgure 2e and f). (Bgure 3a). The presence of bipyramidal quartz and abundance of lapilli comprising of polygonal quartz and feldspar in felsic volcanic unit and 3. Petrology presence of associated chert band signiBes towards the felsic volcanic nature of the litho assemblage. Petrographically, the quartzofeldspathic rock dis- play microlites of quartz, k-felspar, biotite, mus- covite, and garnet as the major mineral constituents; and sphene, epidote, monazite, etc., 4. Analytical methods as accessory phases (Bgure 3c). The rock displays evidence of deformation with well-developed The whole-rock (WR) analyses of six representa- foliation and lineation. Foliation is deBned by tive samples of felsic volcanics were carried out. biotite and recrystallized quartz and feldspar. Major oxides were analyzed by X-ray Cuorescence J. Earth Syst. Sci. (2021) 130:84 Page 5 of 14 84 Table 1. Major oxide (wt.%) and trace element (ppm) composition of representative samples of Kalalikhera felsic volcanics. *SRM (JG-2) Sample KK-1 KK-2 KK-6 KK-7 KK-8 KK-9 CertiBed values Observed values (wt.%) SiO2 82.11 83.15 82.97 82.13 80.15 82.95 76.83 75.73 Al2O3 8.41 7.47 8.14 8.39 8.5 8.16 12.47 12.05 Fe2O3 2.57 1.4 2.74 2.37 2.89 2.7 0.97 0.92 MgO 0.94 0.22 0.59 0.94 0.7 0.63 0.04 0.05 CaO 0.22 0.16 0.2 0.22 0.55 0.18 0.70 0.50 Na2O 2.3 4.95 4.12 2.3 3.8 4.14 3.54 3.21 K2O 1.58 1.62 0.05 1.78 1.26 0.08 4.71 4.48 TiO2 0.58 0.36 0.47 0.58 0.38 0.44 0.04 0.03 P2O5 0.08 0.06 0.07 0.08 0.07 0.68 0.00 0.02 Total 98.79 99.39 99.35 98.79 98.3 99.96 99.302 96.989 (ppm) V 182 142 166 180 140 164 3.78 3.79 Cr 92 63 113 94 65 115 6.37 6.31 Ni 13 4 22 11 3 25 4.35 4.31 Co215422 3.62 3.57 Cu 23 7 52 25 6 50 0.49 0.50 Pb 27 26 13 29 27 15 31.5 30.78 Zn 155 6 16 150 6 18 13.6 13.7 Ba 559 387 150 564 385 148 81 75 Sr 20 16 17 21 18 14 17.9 17.74 Rb 42 10 2 41 9 5 301 304 Zr 223 169 143 220 170 141 97.6 96.88 Y 11 2 2 13 3 5 86.5 85.64 Nb756647 14.7 14.63 La 17 2 4 18 1 2 19.9 19.6 Ce 22 1 1 23 2 2 48.3 47.56 Nd311211 26.4 26.2 *Imai et al.