Two Types of Archaean Supracrustal Belts in the Bundelkhand Craton, India: Geology, Geochemistry, Age and Implication for Craton Crustal Evolution

Abstract

Two Archaean supracrustal complexes are documented in the Bundelkhand craton viz. 1) the Central Bundelkhand greenstone complex (formed the Babina and Mauranipur belts), and 2) the Southern Bundelkhand metasedimentary (paragneisses, schists) complex (formed the Girar belt). The Central Bundelkhand greenstone complex consists of (i) an early assemblage composed of basic-ultrabasic, felsic volcanics, banded iron formation (BIF), and (ii) a late assemblage which contains felsic volcanics. The U-Pb zircon ages of felsic volcanics from the early assemblage, formed in an arc-type subduction setting, are 2813 Ma (Mesoarchaean). The U-Pb zircon ages of felsic volcanics from the late assemblage, which also occur in subduction settings as an active continental marginal type, are 2542 Ma (Neoarchaean). The Girar belt, located in the southern part of the craton, consists generally of metasedimentary rocks namely quartzites and BIFs. Quartzites are represented by fuchsite- and hematite-bearing quartz arenite and lesser quartz pebble conglomerates that have been subjected to low-grade metamorphism. BIF is represented by thinly-bedded quartz–hematite (±magnetite) rocks. Some lenses of marble and chlorite schist are present at the contact between the two formations. BIF is fairly rich in Cr and Ni, poor in Zr, Hf, Ba, Th, Sr, Yb and Lu, and displays a distinct positive Euanomaly (Eu/Eu* = 1.14-2.46). Zircons from quartzites give two U-Pb ages: 3432±9.7 Ma and 3252±6.4 Ma. The Sm-Nd isotope study of quartzite from the Girar belt shows that the TDM is 3.29 Ga. This TDM correlates well with the U-Pb ages of zircon and indicates that the continental crust in the Girar area began to form in the Paleoarchaean (3.4-3.2 Ga). The Central Bundelkhand greenstone complex was thus formed in a subduction-accretion setting in Mesoarchaean (ca 2.8 Ga) and Neoarchaean (2.54 Ga) time, and the Southern Bundelkhand metasedimentary complex originated in a sedimentary basin on the old continental crust apparently at ca ~ 2.7 Ga.

Paleoarchean Zircons from Quartzite of South Bundelkhand Supracrustal Complex:Origin and Implications for Crustal Evolution in Bundelkhand Craton, Central India

“…PeridotiteGabbro-Diorite layered intrusions, viz. meta-peridotite, serpentinite, meta-gabbro and meta-pyroxenites occur in Madawara-Ikauna area 19 . The sedimentary sequence of Girar belongs to the Berwar Formation and comprises two assemblages: quartzite and BIF 19,29 .…”

“…meta-peridotite, serpentinite, meta-gabbro and meta-pyroxenites occur in Madawara-Ikauna area 19 . The sedimentary sequence of Girar belongs to the Berwar Formation and comprises two assemblages: quartzite and BIF 19,29 . The quartzite assemblage near Berwar village is around 300 m thick and is represented by muscovite-bearing arkosic quartzite (Figure 2 a), fuchsite-bearing quartzite, hematite-bearing quartzite, quartz pebble conglomerates (Figure 2 b), traces of dolomitic marble and chlorite schist near the quartzite/BIF boundary 19 .…”

“…km and consists of Archean potassium-rich granitoids 14 , Archean (3.55-2.8 Ga) sodium-rich TonaliteTrondjhemite-Granodiorites (TTGs) and Mesoarchean (ca. 2.84 Ga) to Neoarchean (2.57-2.52 Ga) greenstone complexes [15][16][17][18][19][20] . The Paleoproterozoic rocks (low metamorphosed sedimentary along with mafic flows and sills) of the Bijawar and Gwalior Groups are exposed in the southern and northern parts of BC (Figure 1 a).…”

“…These quartz veins are cut by Paleoproterozoic (~2.15 Ga) mafic dykes having NNW-SSE to NW-SE trend 21,27,28 . There are two supracrustal complexes in BC 18,19 : (i) Central Bundelkhand and (ii) South Bundelkhand. The Central Bundelkhand Supracrustal Complex includes Babina and Mauranipur greenstone belts.…”

“…This complex essentially consists of two associations (i) the early (Mesoarchean) sequence consisting of metamorphosed tholeiitic basalt and high Mg-basalt (basaltic association), meta-dacite-rhyolite and Banded Iron Formation (BIF), and (ii) the late (Neoarchean) felsic volcanics. On the basis of geochemical and geochronological data, subductional setting has been proposed for the formation of volcano-sedimentary rocks from Central Bundelkhand greenstone complex 18,19 . The South Bundelkhand Supracrustal Complex consists of Girar supracrustal belt (Figure 1 b).…”