The Proterozoic ultramafic and mafic lavas and tuffs of the Dalma greenstone belt, Singhbhum, eastern India

Abstract

A detailed petrochemical study of the Proterozoic "Dalma Epidiorites" of Singhbhum leads to a completely new interpretation of this dominantly volcanic belt. The initial igneous activity is represented by mafic and ultramafic intrusives and lavas of tholeiitic. alkaline, and komatiitic affinities. Interlayered are lithic tuffs and tuffaceous sediments. Also present is an analcite basalt heretofore unreported from the Dalma. This suite is overlain by a high-magnesian vitric tuff horizon, which along with its comagmatic intrusives shows quench textures and its chemistry is closely comparable to peridotitic-pyroxenitic komatiites of Archean greenstone terrains. It is noteworthy that the komatiitic magma in this belt is dominantly pyroclastic. The vitric tuff horizon is followed upwards by a thick sequence of high-iron, low-potassium, pillowed tholeiites with ocean-floor affinities.The proposed evolutionary model of the Dalma belt suggests that stretching of Archean proto-continental crust gave rise to the Dalma graben within the Proterozoic (Chaibasa) basin and unique thermal conditions coupled with a disrupted crust led to a high degree of melting and direct tapping of the mantle producing the komatiitic extrusives at a particular stage of the development of the belt.

∼1.6 Ga ultrahigh‐temperature granulite metamorphism in the Central Indian Tectonic Zone: insights from metamorphic reaction history, geothermobarometry and monazite chemical ages

“…The majority of these models envisage an early N-S extension, leading to the opening of a volcano-sedimentary basin (cf. NSMB) either in ensialic (Gupta et al, 1980;Mukhopadhyay, 1984;Sarkar et al, 1992;Ghosh et al, 2006;Acharyya et al, 2006), or marginal basin (Bose and Chakrabarty, 1981;Bose et al, 1989) settings, and succeeded by compressional deformation, causing basin inversion following either intraplate subduction (Sarkar and Saha, 1977), microcontinental subduction (Sarkar, 1982) or collision (Ghosh et al, 2006;Mahato et al, 2008). Available geochronological data, however, do not support an intracontinental rift related setting for the evolution of the NSMB, as Archaean ancestry of the CGC, which is required for a uniform cratonic basement across the NSMB, has not been established.…”

Pressure–temperature-deformation history for a part of the Mesoproterozoic fold belt in North Singhbhum, Eastern India

“…The earliest metamorphic event (M1), characterized by stabilization of greenschist facies mineralogy (muscovite, chlorite, biotite and andalusite), essentially preceded the folding events. Tectonic models proposed for the NSFB envision that it developed either as an ensialic basin (Gupta et al, 1980;Mukhopadhyay, 1984;Fig. 11.…”

Neoarchean–Paleoproterozoic stratigraphy of the Dhanjori basin, Singhbhum Craton, Eastern India: And recording of a few U–Pb zircon dates from its basal part

“…Index for inset map: B -Bastar craton, BN -Bundelkhand craton, D -Dharwar craton, S -Singhbhum North Orissa craton. (b) Geological map of the study area, showing sample locations for U-Pb zircon dating (compiled from Saha (1994), Sarkar and Saha (1962), Gupta et al (1980Gupta et al ( , 1985). Sample numbers designated by last three digits.…”

“…Geological setting and stratigraphy of the Dhanjhori basin Dunn and Dey (1942) considered the Dhanjori sequence to have covered the 'denuded surface' of the Iron Ore Series (renamed later as Iron Ore Group or IOG), and many later workers Saha, 1962, 1977;Sarkar et al, 1969;Saha, 1994 and references therein) assigned the sequence a much younger (Mesoproterozoic) stratigraphic position, placing it above the Chaibasa and Dhalbhum formations of the Singhbhum Group. The perception, however, changed with further studies in this belt and the Dhanjori sequence was placed stratigraphically below the Chaibasa Formation (Sarkar and Deb, 1971;Gupta et al, 1980Gupta et al, , 1985Mukhopadhyay, 1976Mukhopadhyay, , 1988Sarkar et al, 1992;Gupta and Basu, 2000), with a presumed Palaeoproterozoic age status.…”