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[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]

• Granitoids of Singhbhum Craton. • Two generation of TTGs at 3.42 and 3.32 Ga formed by melting of juvenile mafic crust. • Later K-rich, silicic granites at 3.28 and 3.25 Ga formed by melting of tonalites. • Recurring crustal melting in a gradually thickening oceanic plateau. • Final cratonisation of the Singhbhum Craton at 3.25 Ga. A significant part of many Archean cratons formed during Paleoarchean. Yet, the mechanism and tectonic setting of formation of Paleoarchean continental crust remain highly debated. In this contribution, we present field, petrographic, geochemical, zircon U-Pb age and Hf isotope data on Paleoarchean granitoids from west-central part of the Singhbhum Craton (Champua-Hat Gamharia corridor), India. The whole process starting from nucleation of a juvenile continent to its evolution and final stabilization is documented. The core of the craton nucleated with formation of 3.45–3.40 Ga TTGs showing juvenile character (zircon ɛHf t = +0.6 to +7.1). These rocks show slightly depleted HREE and Y, negligible Eu-anomaly (Eu/Eu* = 0.90 to 1.00) and moderate Sr/Y (25–64), consistent with derivation from a low-K mafic crust at a pressure near the lower end of the garnet stability field, causing subordinate garnet retention in the residue and negligible role of plagioclase. A second generation of TTG formation took place at 3.32 Ga in the area by deeper melting of a juvenile mafic crust (zircon ɛHf t = +1.3 to +5.7) as suggested by strongly depleted HREE and Y, and high Sr/Y (52–155) implying significant amount of garnet retention in the residue. Subsequently, the area witnessed intracrustal melting at 3.28 and 3.25 Ga which tapped moderately old to juvenile (zircon ɛHf t = −1.9 to +4.5), mostly TTG sources at variable depths generating potassic, LILE-enriched, high-silica granites. Intrusion of these potassic granites marks the final cratonization of the Singhbhum Craton. The sequence of events is interpreted in terms of repeated crustal melting and granitoid generation in a gradually thickening oceanic plateau with a progressive change in granitoid source from mafic to felsic in composition. A synthesis of rock assemblage, regional geological setting and structural pattern also supports intraplate nature of the magmatism in Singhbhum Craton, which might have been a significant mechanism of crustal growth worldwide during Paleoarchean. Further, a comparison of juvenile crustal growth and crustal reworking events of the Singhbhum and other Indian cratons show that these cratons record distinct evolutionary histories and were probably nucleated at different sites. [ABSTRACT FROM AUTHOR]

Palaeoarchaean granitoids are exposed over wide area in the Singhbhum craton whose origin and role in crustal evolution are not well constrained. This study presents whole-rock and mineral chemical data coupled with zircon U-Pb dating and Hf isotope results on such granitoids from the central part of the craton to understand their petrogenesis, tectonic setting and role in continental crustal evolution. The first phase of granitoid magmatism in this area is represented by a 3.47 Ga Na-rich, gneissic tonalite belonging to the Archaean TTG (tonalite-trondhjemite-granodiorite) suite. This rock is characterized by high-HREE (heavy rare earth elements), negative Eu anomaly, low Sr/Y ratio and positive zircon Hf isotope signature (εHf t = +2.1 to +4.8). It is interpreted to be formed by shallow melting of a juvenile mafic source. At 3.35 Ga a silicic, ferroan porphyritic biotite granite formed. It shows variable K/Na, low Y and high Sr/Y, moderately fractionated HREE and positive zircon εHf t (+1.8 to +4.0), and is explained as a product of high-temperature melting of a heterogeneous, juvenile source consisting of tonalites and mafic rocks at lower crustal depth. The final phase of granitoid magmatism is marked by a 3.30 Ga non-porphyritic ferroan, silica-rich biotite granite. Geochemical characteristics like moderately high K, moderately fractionated HREE, low Ca and Sr/Y, and zircon εHf t (+0.8 to +3.7) suggest that the granite was formed by high-pressure melting of a tonalite-dominated source with short crustal residence. All the three granitoid phases display low Mg, Ni and Cr contents and magnesium number (Mg#) precluding direct involvement of mantle in their origin. Rather, crustal reworking caused by episodic plume-related mafic-ultramafic magma underplating and intraplating in an oceanic plateau setting is suggested as the possible mechanism for formation of the granitoids. Successive crustal reworking events involved progressively greater amount of previously formed felsic crust generating more evolved, K-rich granitoids. It appears to be a globally important process which led to effective crustal differentiation and maturing of the cratons during Palaeoarchaean. [ABSTRACT FROM AUTHOR]

Archean cratons display spatial and temporal changes in the composition and thickness of the crust, which has important implications for intracrustal differentiation, attainment of long-term stability, and operation or absence of plate tectonics. The geodynamic reason(s) for these changes, though, is a controversial subject. To address this issue, the present contribution investigates the spatial and temporal changes in granitoid compositions of the well-exposed Singhbhum Craton. It reports new zircon U-Pb and Lu-Hf, and whole-rock geochemical data on Paleoarchean granitoids from some of the less-studied parts of the Singhbhum Craton. The new information is then collated with previously reported data from the central part (cratonic core) of the Singhbhum Craton to illustrate the spatial and temporal changes in granitoid chemistry, using selected major oxide and pressure-sensitive elemental ratios. Temporal changes in the characteristics of the granitoids suggest that the crust building in Singhbhum Craton possibly started in a relatively thin oceanic plateau with the emplacement of low-pressure TTGs and diorites during ∼3.53–3.47 Ga. The ∼3.47–3.42 Ga period marks a gradual increase in crustal thickness, inferred from progressively increasing Al 2 O 3 and pressure-sensitive trace element ratios of the TTGs. Subsequently, as a result of protracted mantle upwelling and consequent juvenile TTG addition, the composition of the bulk continental crust differentiated into a more evolved felsic composition by ∼3.35 Ga, when the first potassic granite was emplaced. Spatial distribution of the granitoids suggests partial convective overturn (contemporaneous sinking of greenstones and diapiric rise of shallow- to mid-crustal granitoid domes) played a role in bringing the older as well as juvenile TTGs to a melting depth, generating ∼3.35–3.25 Ga spatially restricted high-silica, high-potassic, low-pressure K-rich granite and transitional granitoid domes. TTG magmatism also continued contemporaneously during this period. During ∼3.33–3.32 Ga, continental crust in Singhbhum Craton reached the maximum thickness, inferred from the formation of high-pressure (or low-HREE) TTGs. Afterward, possibly delamination of dense lower crustal residue caused the crust to become thinner, as recorded by progressively low-pressure K-rich granite and transitional granitoid emplacement until ∼3.28 Ga. Near the end of Paleoarchean (∼3.26–3.25 Ga), the crust became thicker again, further yielding high-pressure TTGs and K-rich granites. We suggest an oceanic plateau-like setting (characterized by relatively inefficient heat extraction compared to a modern-day subduction zone) where plume magmatism and delamination of anatectic residues of crustal melting caused the time-transgressive thickening and thinning of the continental crust, respectively. This process resulted in change in melting depth and, in turn, in the granitoid chemistry. Therefore, the Paleoarchean crustal architecture and the bulk crustal composition of the Singhbhum Craton controlled the temporal change in granitoid chemistry in an ongoing tectonic regime (partial convective overturn-dominated setting) without any distinct tectonic shift. [ABSTRACT FROM AUTHOR]

Highlights: [•] Granitoid magmatism changed in composition with evolution of Kadiri greenstone belt. [•] Initial sanukitoid magmatism was followed by transitional TTG, leucogranite and A-type granite. [•] A convergent setting characterized by repeated slab break-off and crustal reworking. [•] Finally post-subduction anorogenic granite magmatism. [•] Reworking of Mesoarchaean crust in eastern Dharwar craton identified. [Copyright &y& Elsevier]