Abstract-The newly discovered Dhala structure, Madhya Pradesh State, India, is the eroded remnant of an impact structure with an estimated present-day apparent diameter of about 11 km. It is located in the northwestern part of the Archean Bundelkhand craton. The pre-impact country rocks are predominantly granitoids of ∼2.5 Ga age, with minor 2.0-2.15 Ga mafic intrusive rocks, and they are overlain by post-impact sediments of the presumably >1.7 Ga Vindhyan Supergroup. Thus, the age for this impact event is currently bracketed by these two sequences. The Dhala structure is asymmetrically disposed with respect to a central elevated area (CEA) of Vindhyan sediments. The CEA is surrounded by two prominent morphological rings comprising pre-Vindhyan arenaceousargillaceous and partially rudaceous metasediments and monomict granitoid breccia, respectively. There are also scattered outcrops of impact melt breccia exposed towards the inner edge of the monomict breccia zone, occurring over a nearly 6 km long trend and with a maximum outcrop width of ∼170 m. Many lithic and mineral clasts within the melt breccia exhibit diagnostic shock metamorphic features, including multiple sets of planar deformation features (PDFs) in quartz and feldspar, ballen-textured quartz, occurrences of coesite, and feldspar with checkerboard texture. In addition, various thermal alteration textures have been found in clasts of initially superheated impact melt. The impact melt breccia also contains numerous fragments composed of partially devitrified impact melt that is mixed with unshocked as well as shock deformed quartz and feldspar clasts. The chemical compositions of the impact melt rock and the regionally occurring granitoids are similar. The Ir contents of various impact melt breccia samples are close to the detection limit (1-1.5 ppb) and do not provide evidence for the presence of a meteoritic component in the melt breccia. The presence of diagnostic shock features in mineral and lithic clasts in impact melt breccia confirm Dhala as an impact structure. At 11 km, Dhala is the largest impact structure currently known in the region between the Mediterranean and southeast Asia.

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The occurrence of metamorphosed basaltic pillow lava in close association with serpentinized ultramafic rock, metamorphosed basaltic komatiite, volcaniclastic metasediment, and banded iron formation (BIF) in the Mauranipur area is the first explicit evidence for subduction related submarine volcanism in the Archean Bundelkhand craton, Central India. The Mauranipur pillow lava underwent greenschist to amphibolite facies metamorphism while retaining a geochemical signature of its igneous protolith. The pillow lava and associated massive volcanic rock is subalkalic, low − K tholeiitic basalt to basaltic andesite with SiO 2 = 51.9 − 55.9 wt% and Mg/(Mg + Fe .44, and depicts a nearly flat chondrite normalized HREE pattern with a low MREE/HREE ratio (Gd/Yb) N = 1.24 − 1.58. The basaltic komatiite displays remarkably similar geochemical characteristics to modern boninite. The present study, combined with available geological data, suggests that the supracrustal rocks of the Mauranipur area represent an Archean ophiolite sequence formed in a plate convergent setting.

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A comprehensive study based on U-Pb and Hf isotope analyses of zircons from gneisses has been conducted along the western part (Babina area) of the E-W-trending Bundelkhand Tectonic Zone in the central part of the Archaean Bundelkhand Craton. 207 Pb-206 Pb zircon ages and Hf isotopic data indicate the existence of a felsic crust at ß 3.59 Ga, followed by a second tectonothermal event at ß 3.44 Ga, leading to calc-alkaline magmatism and subsequent crustal growth. The study hence suggests that crust formation in the Bundelkhand Craton occurred in a similar time-frame to that recorded from the Singhbhum and Bastar cratons of the North Indian Shield.