Unified stratigraphic model of Western Iron Ore Supergroup, Singhbhum Craton, India: New insights from its deformation history and Sm–Nd geochronological data of the Basal Malangtoli volcanic suite.

The present work attempts to establish lithostratigraphy of the Western Iron Ore Group (WIOG), i.e., the Bonai–Kendujhar Belt (BK Belt) and the Darjing Basin occurring to the west of it near contiguously. Malangtoli Group of the BK Belt, represented by Basal Kendujhar Quartzite and Malangtoli volcanic suite, overlies the surrounding granitoid with a profound unconformity at its base. This is overlain by the Koira Group of the BK Belt, consisting largely of volcaniclastic with subordinate epiclastic material and chemogenic precipitates represented by dolomite and BIF. Darjing Group commences with rudaceous facies with clasts of Koira and Malangtoli Groups and is further succeeded by arenaceous to argillaceous to calcareous facies. Based on the identical deformation history amongst the lithopackages of the BK Belt and Darjing Basin, Iron Ore Supergroup-West (IOSG-W) is proposed. IOSG-W has undergone three distinct phases of deformations. A detailed account of the first deformational event in an NW–SE shortening regime, which is accompanied by later overturned folding and penetrative fabric development, is being established here. Lithopackage of IOSG-W is marked by a series of low plunging, NE–SW trending, F1, and F2 folds. The F1 is invariably overturned with a vergence towards the east contrary to the near upright F2, and their superposition has led to a 'hook-shaped' interference pattern. Shortening in the NE–SW direction has resulted in F3 cross folds and a 'dome and basin' pattern. The overall structure of the Bonai–Kendujhar Belt is a series of low plunging synclines and anticlines with BIF preserved in the form of synclinal ridges flanked by stratigraphically older phyllite. The disposition of the lithounits is further modified by several major faults, some of which are related to the thrusting during the first deformational episode. The Sm–Nd TDM model age between 3.0 and 3.3 Ga of the Malangtoli volcanic suite represents the lower stratigraphic horizon of the IOSG-W. Based on the structural disposition and age of basaltic rocks distributed both within and in the periphery of the belt, a major stratigraphic revision is proposed in this study. [ABSTRACT FROM AUTHOR]