Search

[Display omitted] • Juvenile crust in Singhbhum Craton formed at ∼3.51, ∼3.45, 3.38–3.25, 3.15–3.05 and ∼2.80–2.75 Ga. • Reworking of older crust in the craton occurred at ∼3.46, ∼3.3, ∼3.1 and ∼2.8 Ga. • Maximum crustal thickness was attained at ∼3.3 Ga followed by a possible reduction over ∼3.1–2.8 Ga. • Paleo-Meso–Archean continental growth occurred through episodic intraplate juvenile magmatism and resultant crustal reworking. The composition of continental crust and its temporal variation, the mechanism of crust-mantle interaction, and the degree of mantle depletion during the early Archean have been widely debated. To address these issues related to the Singhbhum Craton, we present whole-rock sediment geochemistry, detrital zircon U-Pb date, trace element and Hf isotope data from four Archean clastic sedimentary successions. The rocks have high whole-rock K 2 O/Na 2 O, relatively high La and Th compared to Ni and Sc, distinct negative Eu anomaly and flat HREE patterns, and high detrital zircon U/Yb ratios. These features suggest attainment of early crustal stability with the sediments derived from a strongly weathered basement dominated by granitoids formed through shallow intracrustal melting. Detrital zircon U-Pb and Hf isotope data indicate episodic crust formation at ∼3.51, ∼3.46, 3.38–3.25, 3.15–3.05 and ∼2.80–2.75 Ga. Each major crust formation event is marked by addition of depleted mantle-derived juvenile crust and its quick reworking. Besides, episodic tapping of older crust, as indicated by a wide range (both positive and negative) of zircon εHf t values, are evident at ∼ 3.46, ∼3.3, ∼3.1 and ∼2.8 Ga. Pressure-sensitive zircon trace element ratios suggest that the crust attained the maximum thickness at ∼3.3 Ga followed by a possible reduction in thickness over ∼3.1–2.8 Ga. In the absence of strong evidence of subduction, the rock association and their temporal distribution (coeval granitoid and mafic-ultramafic magmatism) suggest that the Paleoarchean-Mesoarchean crustal growth in the Singhbhum Craton was a result of episodic, depleted mantle-derived, intraplate magmatic injection and attendant crustal reworking. [ABSTRACT FROM AUTHOR]

The processes responsible for the origin and evolution of Early Archean continental crust are not properly understood. Questions regarding the pattern of crustal growth (episodic vs. continuous) and the role of crust-mantle interaction in the temporal change of crustal composition and thickness are still being widely debated. In order to address the above issues, we present whole-rock geochemistry and detrital zircon U-Pb-Hf isotopes, and trace-element data from Mesoarchean clastic rocks of two selected greenstone belts of western Dharwar Craton. The mineralogically mature character of the sampled sandstones along with their high K 2 O/Na 2 O, Rb/Sr and CIA values, relatively enriched concentrations of La and Th over Cr and Sc, variably negative Eu-anomaly, and high U/Yb values of detrital zircons are indicative of their derivation from strongly weathered stable continental provenance dominated by low-HREE TTGs and K-rich granites of shallow crustal origin. Detrital zircon U-Pb ages indicate the maximum age of deposition for these sandstones is ∼3.1 Ga. The detrital zircon U-Pb and Lu-Hf data suggest two major crust formation events at 3.54–3.33 Ga and 3.27–3.12, mainly via juvenile crustal addition and subsequent rapid reworking. Besides, ∼3.6 Ga detrital zircons with negative εHft values suggest that the antiquity of the western Dharwar Craton can be traced back at least up to 3.8 Ga. Reworking of the older continental crust occurred during ∼ 3.25 Ga and ∼ 3.15–3.07 Ga, the last one represented by emplacement of K-rich granites. Zircon trace element ratios indicate a maximum increase in crustal thickness at ∼3.2 Ga followed by a crustal thinning at around ∼3.15 Ga. The detrital record in combination with geological setting suggests an episodic crustal growth and reworking in the western Dharwar Craton during Paleoarchean to early Mesoarchean period which was possibly related to intraplate processes. • Juvenile crust in Western Dharwar Craton formed at 3.54–3.33 Ga. • The juvenile crust reworked during 3.27–3.12 Ga. • Reworking of older crust occurred at ∼3.25 Ga, ∼3.15–3.07 Ga and ∼ 3.02 Ga. • Maximum crustal thickness attained at ∼3.2 Ga followed by thinning up to ∼3.1 Ga. • Link between crustal thickening and partial convective overturn is suggested. [ABSTRACT FROM AUTHOR]