Sumit Mishra1, Pradip K Singh2*, Vinod K Singh3, Alexander I Slabunov4, HC Nainwal1 and Neeraj Chaudhary3
1 Department of Geology, Hemvati Nandan Bahuguna Garhwal University, India
2 División de Geociencias Aplicadas, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), Mexico
3 Department of Geology, Institute of Earth Science, Bundelkhand University, India
4 Institutes of Geology, Karelian Research Centre, Russia
*Corresponding author: Pradip K Singh, División de Geociencias Aplicadas, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), Camino a la Presa,San José 2055, San Luis Potosí, Mexico
Submission: July 02, 2018;Published: October 17, 2018
ISSN: 2577-1949 Volume3 Issue3
The orthoclase granite and granodiorite-granite series rocks are extensively exposed in the Bundelkhand granite greenstone belt around Jhansi, Babina and Mauranipur in central part of the craton which are mostly calc-alkaline in nature, low Sr (12-436ppm), low Y (9.1-67) and low Sr/Y (0.24- 21.37) ratio characteristics. These rocks have high Rb (77.7-539), moderate Nb (7.2-42.2) and Nd (21.92-115), and geochemically vary from mostly I- to A-type granites generally formed during syn-to post collision. The chondrite normalized rare earth element distribution pattern is poorly fractionated LaN/LuN=(3.4-31.79) with a negative Europium (Eu) anomaly (Eu/Eu*=0.2-0.82) showing subduction environment. The granodiorite-granite series rocks show mostly volcanic arc setting while orthoclase- granites plots within the syn-collosion to post-collisional granite fields on the Yb+Ta versus Rb and Nb versus Y discrimination diagram. Geochemical characteristics indicate that anhydrous partial melting of the Paleo-Mesoarchean TTG or mafic crustal through subduction setting responsible for formation of these rocks.
Keywords:Neoarchean granitoids; Subduction tectonics; Geodynamics settings; Bundelkhand craton
The early earth crust formation still remains immense wide scope for in depth research on the Precambrian crustal growth which evolving a wide range of geological processes including plate tectonics and magmatism [1-4]. Understanding the early earth evolution and its geodynamics is one of most fundamental scientific issues in geology, because the evolutionary trends of the planet earth cannot be resolved without adequate knowledge of Archean period. To understand the tectonic growth of continental crusts in Archean cratons the granites are playing most important role in this context. The Bundelkhand craton is nestled in the northern margins of Peninsular India. The Bundelkhand craton begin with the ~3.5Ga crustal component growth signatures, as preserve in the form of TTG and gneisses rocks [5-7]. The craton mainly constitutes older basement of TTG and mafic gneisses and is associated with migmatites, amphibolites, schist, and supra-crustal belt of meta-sedimentary and meta-volcanics. The ample orthoclase granites and granodiorite-granite series rocks mostly inhabit of the craton and crustal growth takes place during Neoarchean period in multiple phases [7-9]. Recently, Singh & Slabunov [10-13] depict the Greenstone Belts (GB) and establish tectonic evolution of the craton, based on SHRIMP-dating of zircon from the felsic volcanic rocks from the Babina belt. The present paper deal with the geochemistry of granitiods (granodioritegranite series and orthoclase-granite) rocks from mostly central part of the Bundelkhand craton to establish tectonic settings and the continental growth of the craton during Neoarchean period.
The Bundelkhand craton covers 29,000 square km, lying between 24°11’ to 26°27’ N and 78°10’ to 81°24’ E, represents a semicircular outcrop. The low grade metamorphic rocks of the Bijawar Group (Palaeoproterozoic) to the south, southeast, and Vindhyan Supergroup (Meso-to Neoproterozoic) to the southeast, south, southwest, and west are resting over on Bundelkhand craton [7,14,15]. The major part of the craton comprises the different phases of magmatism, low-grade metamorphism and deformation of Archean TTG-gneissic rocks, mafic dykes and undeformed quartz veins [8,9,16-18]. The doleritic dykes are usually dark grayish green in color and have NNW-SSE to NW-SE trend [14,19]. A general characteristic of highly jointed quartz veins occur mostly about NE- SW to NNE-SSW trend. Singh  mapped the older crustal components from the central part of Bundelkhand craton which are scattered in the E-W shear zones of 3-5kms width. The potash-rich granites (~2500Ma) occurring around Babina, Dhaura, and 3km south of Mauranipur regions. The pegmatites veins are also observed at many places. TTG-gneisses are exposed at Babina, Dhaura, Gora and Mauranipur areas (Figure 1).
Figure 1:General geological map of central Bundelkhand craton showing sample locations. Abbreviations: B: Babina; D: Dhala; Dh: Dhaura; G: Gora; J: Jhansi; K: Karera; Kb: Kabrai; M: Mauranipur; Mh: Mahoba; P: Pichhore
Fresh samples of granodiorite-granite series rocks and orthoclase granite, from central Bundelkhand region have been collected and pulverized in agate ball mill for geochemistry. For major element analysis, 1.2g sample powder was weighed and mixed with 6g lithium borate flux (consisting of 35.3% tetraborate and 64.7% metaborate). Further, the fusion bead method was used to prepare the glass bead at 1000 °C for ≈8 min in Pt-Au crucible for only major elements analysis. For selected trace element analysis, 9g of sample powder was pressed into a pellet using 1.2g Wax binding agent. Both, glass bead and pressed pellet analysis were carried out at Institute of Geosciences, University of Campinas (UNICAMP), Brazil for seven samples. Major oxides concentrations were determined by X-ray fluorescence spectrometer (XRF), utilizing fusion beads and trace elements by inductively coupled plasma-mass spectrometry (ICP-MS) using lithium borate fusion techniques. The loss of ignition (LOI) determined by TGA furnace. The base metals were analyzed using four acid digestions method by ICP- atomic emission spectroscopy (ICP-AES). Whereas total carbon and sulfur obtained by Leco combustion techniques. Five samples (SCB-1,SCB-2,SCB-3,SCB-4 and SCB-5) for whole rock geochemical analyses were conducted at Australian Laboratory services Pty. Ltd., Malaga, Western Australia, Australia. Five orthoclase granite samples (BL-5,BL-6,BL-29,BL-30,SB-31) for whole rock geochemistry are analyzed at Petrozavodsk, Russia and detail methodology is given in Singh & Slabunov .
Geochemical compositions of Neoarchean granitoids samples from the Bundelkhand craton were summarized in Table 1 and Table 2. The samples classified by TAS  as Dacite (SCB-04,BH- 8,BM-6), Trachyte (SCB-01,SCB-05), Rhyolite (SCB-02,SCB-03,BH- 11,UM-4,BJ-1;PL-1). The majority of orthoclase granite rocks are classified as rhyolite, while granodiorite-granite series rocks fall in dacite and trachydacite field (Figure 2a). The granodioritegranite series rocks are mostly high-K calc-alkaline and orthoclase granites are varies from high-K calc-alkaline to shoshonite series in nature (Figure 2b) . In granodiorite-granite series rocks Na2O varies from 3.29 to 3.83wt% and K2O content varies from 2.44 to 4.04wt.%. The Al2O3 content varies from 12.61 to 15.79wt. % (av. Al2O3: 14.79wt. %) and SiO2 having range from 61.63 to 74.2wt %. The Titania (TiO2) content is low ranging from 0.25 to 1.32 wt.%.
Table 1:Major (wt.%) and trace (ppm) element analytical data of granodiorite (1-6) and granite (7-17) rocks from the central part of the Bundelkhand craton.
Figure 2:Classification diagram SiO2 vs. Na2O+K2O .
Figure 2b: SiO2 vs. K2O diagram .
The orthoclase granite rocks having Na2O varies from 3.19 to 4.06wt. % and K2O content varies from 3.45 to 5.42wt %. The Al2O3 content varies 10.18 to 15.18wt. % and SiO2 having range from 64.62 to 75.28wt %. The Titania (TiO2) content are low ranging from 0.1 to 1.83wt. %. Most of the samples from granodioritegranite series rocks are poor in potash (K2O/ Na2O varies from 0.66 to 1.22) while K2O/ Na2O > 1 for orthoclase granite.
The granodiorite-granite series belongs to high-K calc alkaline magma series, with metaluminous character while orthoclase granite shows metaluminous to peraluminous character  (Figure 3). These granodiorite-granite series and orthoclase granite rocks mostly occur in I-type to A-type granitoids field of Whalen et al.  diagram (Figure 4). On Harker diagram (Figure 5), the abundances of TiO2, Al2O3, MgO, CaO, P2O5, Fe2O3 total and MnO decrease with linear or near-linear trends increasing SiO2 on variation diagrams indicate a typical feature of I-type granites . In the Yb+Ta versus Rb and Nb versus Y discrimination diagram of Pearce et al. , the granodiorite-granite series rocks plot within volcanic arc granite field whereas orthoclase granitic rocks plots within the syncollosion to post-collisional granite fields (Figure 6). This is also supported by the R1-R2[R1=4Si4+-11(Na++K+)2(Fe3++Ti4+), molar; R2=6Ca2++2Mg2++Al3+, molar] tectonic discrimination diagram (Figure 7) .
Figure 3:A/NK versus A/CNK diagram .
Figure 4:Classification of granitoids after Whalen et al. .
Figure 5:Harker diagrams for granitoid rocks from Bundelkhand craton. Symbols are the same as in Figure 2.
Figure 6:Discrimination diagrams Rb:Y+Nb, Nb:Y  for the TTG:gneiss and granite of the central Bundelkhand craton. Symbols are the same as in Figure 2. ORG: Ocean Ridge Granites; syn: COLG: Syn: Collision Granites; VAG: Volcanic Arc Granites; WPG: Within Plate Granites
Figure 7:R1:R2 multicationic variation diagram [R1 = 4Si4+:11(Na++K+): (Fe3++Ti4+), molar; R2 = 6Ca2++ 2Mg2+ +Al3+, molar], .
The granodiorite-granite series samples are classified as dacite to rhyolite composition occur in subduction environment and orthoclase granites formed during syn-collision at shallow depth. The silica percentage ranging from 61-75wt% suggests acidic, calcalkaline nature. It is characterized by low Sr (12-436ppm), low Y (9.1-56) and low Sr/Y (0.34-21.37) ratios. Most of the orthoclase granite samples are rich in potash (K2O/ Na2O>1), with high Rb (77.7-539), moderate Nb (7.2-42.2) and Nd (21.92-115). The chondrite normalized rare earth element distribution pattern is poorly fractionated LaN/LuN=(3.4-31.79) with a negative Europium (Eu) anomaly (Eu/Eu*=0.2-0.82) showing subduction environment (Figure 8a; [10,12,28]). A primitive mantle normalized  multi-element diagram (Figure 8b) showed a wide range in the concentration of the trace elements. Most of the samples show enrichment of large-ion lithophile elements (LILE) but depletion of Nb, Ta and Ti . The depletion of Nb and Ta in the rocks is most significant with Nb/La ratios (Figure 8b). It is noted that the granodiorite-granite series and orthoclase granitic rocks are characterized by the Ba-poor, Sr, P, Nb-Ta and Ti anomalies. The negative Nb-Ta anomalies and a positive Pb anomaly are generally interpreted as subduction-related magma generation. Similarly, High-Field-Strength Elements (HFSE) depletions are common in rocks formed in arc environments, those that have interacted with continental crust, or those, which crystallized Ti-rich phases .
The Harker diagram of granitoids show positive correlation of K2O vs. SiO2 suggest that K-feldspar fractionation is an important differentiation process during the late stages of crystallization for the orthoclase granite in Bundelkhand craton . Most of the samples are occur in I- to A-type granitic field of the Whalen et al.
 diagram which indicates that the granitoids are formed during syn-collision to post-collision tectonic environment. Singh & Singh  have established similar observation for the granites and TTG from central part of the Bundelkhand craton. The geochemical analysis suggests a subduction tectonic setting for granodioritegranite series formed in active continental edge where oceanic crust subducted under continental block in Neoarchean time by accretion-collision system. Chauhan et al.  also indicate that anhydrous partial melting of the Paleo-Mesoarchean TTG or mafic crustal materials in an extensional regime produce K-rich granites. The plagioclase-orthoclase granite advanced in post-accretionary processes after granodiorite-granite series formed in the craton. The Bundelkhand craton is stabilized at around 2.5Ga.
Figure 8:REE Chondrite spider plot after Nakamura .
Figure 8b: Primitive mantle:normalized elements  for the Neoarchean granitoids.
DST Inspire fellowship (DST/INSPIRE/03/2015/000761) is thanks for financial support to SM. PKS thanks to ALS laboratory, Western Australia for analysis of 5 samples in AAG. VKS is thanks to Department of Science and Technology, Gov. of India for grant (INT/RUS/RFBR/P-279) and AIS is thanked to RFBR for grant (17- 55-45005 IND-а). VKS and SKV thanks to Bundelkhand University, Jhansi, India and IPICYT, Mexico, under MOU for supporting local field mapping.
© 2018 Pradip K Singh. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and build upon your work non-commercially.