A new U–Pb ID–TIMS baddeleyite date of 2252.4 ± 5.5 Ma is obtained for an ENE-trending mafic dyke in the central-western Bastar craton that signifies its link with the ca. 2.25 Ga Chhura dyke swarm within the craton. This suggests that the ca. 2.25 Ga magmatic event is more widely distributed across the Bastar craton, despite its comparatively low dyke density. The studied dykes exhibit evolved basaltic compositions with restricted major- and trace-element variability. Geochemical systematics indicate that magma differentiation was governed by fractional crystallization, involving early olivine ± clinopyroxene removal followed by plagioclase-dominated crystallization within transient crustal magma reservoirs. The absence of systematic variation in contamination-sensitive trace-element ratios indicates negligible crustal assimilation. Instead, arc-like trace-element characteristics, including LILE enrichment and Nb–Ta–Ti depletion, are consistent with moderate degree of partial melting (10–15%) of a spinel-rich subcontinental lithospheric mantle source previously metasomatised by slab-derived fluids during Archean subduction. Comparison with coeval 2.26–2.25 Ga dyke swarms of the Dharwar and Singhbhum cratons reveals strong geochemical coherence, with subtle spatial variation in plume–lithosphere interaction. Anisotropy of magnetic susceptibility (AMS) data, supported by shape-preferred orientation (SPO) analyses and reported here for the first time from Bastar mafic dykes, record sub-horizontal to moderately inclined K1 axes, indicating lateral magma transport within ENE-trending fractures. Imbricated fabrics consistently indicate southwest-directed magma flow, suggesting a plume centre northeast of the Bastar craton. Integration of geochemical and structural constraints supports a two-stage geodynamic model in which plume-related thermal perturbation triggered melting of previously subduction-modified lithospheric mantle.
The formation and reconstruction of the North China Craton (NCC) occurred predominantly from the Neoarchean to late Paleoproterozoic, during which multiple tectono-thermal events induced polyphase granulite facies metamorphism in various terranes. This study documents two distinct phases of late Neoarchean and late Paleoproterozoic granulite facies metamorphism from mafic granulites at the Habuqin iron deposit in the southwest Yinshan Block based on petrographic observation, phase equilibrium modelling and zircon U-Pb dating. The late Neoarchean metamorphism is characterised by an anticlockwise P-T path with UHT peak conditions of >930 °C and ∼10 kbar, registering a low-P/T type geothermal gradient of >25 °C/km. The late Paleoproterozoic metamorphism represents high-pressure granulite overprinting, marked by garnet coronae, and clockwise P-T paths with the peak conditions reaching 900–910 °C and 11–12.5 kbar, registering a medium-P/T type geothermal gradient of 20–21 °C/km. Zircon U-Pb dating yields weighted mean ages of 2501.5 ± 4.5 Ma and 2498.6 ± 4.4 Ma for the first-phase metamorphism, and a weighted mean age of 1811 ± 20 Ma for the second-phase overprint; both are interpreted to represent the post-peak cooling stages. Two phases of granulite facies metamorphism are also reported in the high-grade domain of the Yinshan Block and other regions along the northern margin of the NCC. The late Neoarchean UHT metamorphic event is interpreted to reflect a vertical sagduction regime, whereas the Paleoproterozoic HP granulite overprinting is likely to represent an orogenic event that is widely distributed along the whole northern margin of the NCC. These findings demonstrate that the Yinshan Block, which was traditionally considered as a stable Archean terrane, was partially reworked during Paleoproterozoic orogenesis.
The formation of Archean continental crust is a core frontier in Precambrian geology, with tonalite-trondhjemite-granodiorite (TTG) suites—the dominant component of Archean felsic continental crust—holding the key to deciphering early Earth geodynamic regimes. The petrogenesis of Archean TTG has long been at the center of a critical debate between plate tectonic model and non-plate tectonic regimes (e.g., mantle plume, sagduction). The Eastern Hebei province in the North China Craton’s Eastern Block preserves well-exposed Neoarchean basement rocks, yet the tectonic setting of its late Neoarchean TTG remains unresolved. Previous studies relied heavily on whole-rock geochemistry and geochronology, lacking systematic constraints on the coupled magmatic water content and oxygen fugacity (fO2), a robust proxy to distinguish competing geodynamic models. In this study, we systematically sampled TTG gneisses and cogenetic dioritic/granitic gneisses across different tectonic units in Eastern Hebei. We conducted comprehensive analyses including whole-rock major and trace elements, in-situ zircon U-Pb geochronology and Lu-Hf isotopes, and mineral chemistry of zircon and apatite inclusions. A combined oxybarometer-hygrometer approach, with cross-validation from zircon Ce-U-Ti and apatite sulfur valence oxybarometers, was applied to quantify the water content and fO2 of the TTG parental magma. Our results show that the Eastern Hebei TTG formed at 2.59–2.50 Ga. The cogenetic rock suites display a continuous geochemical evolutionary trend, recording amphibole-dominated fractional crystallization from a common parental magma. The TTG parental magma has a median water content of 7.72 ± 1.20 wt% and elevated fO2 (median ΔFMQ=+0.97 ± 0.46), with a strong positive correlation between water content and fO2 (R2 = 0.67)—a signature highly consistent with modern subduction zone island arc felsic magmas. Zircon Hf isotopes further indicate the high water content and fO2 were modulated by input of oceanic crust formed no later than 2.9 Ga. This study provides new robust geochemical evidence that late Neoarchean continental crust formation in the Eastern Block of the North China Craton was dominantly controlled by early plate tectonic regime, and also offers novel quantitative insights into the petrogenesis of TTG suites across other regions and time geological periods worldwide.
Understanding how early Paleoproterozoic tectono-magmatic processes shaped the Yangtze Craton is critical for reconstructing Precambrian cratonization and its role in the assembly of Columbia. However, this history remains enigmatic in the southwestern Yangtze Craton because well-preserved Archean-Paleoproterozoic rocks are scarce. Here we present integrated whole-rock geochemical, zircon U-Pb geochronological, and zircon Hf-O isotopic data for 2.37–2.33 Ga granitoids and diorites from the Cuoke Complex. Our results define four distinct magmatic suites. 2.37–2.35 Ga sodic granites with trondhjemitic affinity exhibit high Na2O/K2O ratios, low K2O and Rb contents, low Sr/Y and (La/Yb)N ratios, and enriched Hf-O isotopic compositions, indicating partial melting of Mesoarchean mafic crust under low- to moderate-pressure conditions. 2.36–2.33 Ga strongly peraluminous granites with S-type affinity display low FeO/MgO ratios and HFSE contents, variable CaO/Na2O, K/Rb, and Rb/Sr ratios, and enriched Hf-O isotopic compositions, favoring derivation from a heterogeneous metasedimentary source. 2.35 Ga granites with A-type geochemical affinity show enriched Hf-O isotopic compositions, reflecting high-temperature remelting of compositionally heterogeneous crust involving TTG-like basement and metasedimentary components. 2.35 Ga diorite exhibits low Mg# and Nb/Ta ratios, high Rb/Sr values, and enriched Hf-O isotopic signatures, favoring derivation from partial melting of Mesoarchean mafic lower crust with possible mantle thermal contribution. These magmatic suites record a progressive tectonic transition from late syn-collision to post-collisional extension, likely driven by orogenic collapse, lithospheric delamination, and asthenospheric upwelling, which promoted large-scale reworking of heterogeneous Mesoarchean crust. Synthesis of previous data suggests that a magmatic shift from regional 2.37–2.35 Ga syn-collisional S-type granites and sodic granites to 2.35–2.31 Ga post-collisional granitoids with increasing proportions of A-type affinity and dioritic-mafic rocks likely marks a tectonic switch of the southwestern Yangtze Craton from syn-collision to post-collision at ca. 2.35 Ga. This collisional event was followed by a within-plate tectonic regime from ca. 2.33 Ga and renewed convergence with the northern Yangtze domain after ca. 2.15 Ga, culminating in final craton amalgamation at 2.0–1.93 Ga. The comparable Paleoproterozoic tectonothermal evolution of the Yangtze and North China cratons may further indicate a close geodynamic linkage during the assembly of Columbia.
Orogenic gold systems are important sources of Paleoproterozoic gold mineralization in cratonic settings worldwide and are commonly associated with convergent-margin tectonics and crustal-scale fluid flow. In the northern São Francisco Craton, eastern Brazil, several Rhyacian-Orosirian gold occurrences are known; however, the geodynamic context and structural framework controlling mineralization in the Contendas-Mirante volcanosedimentary belt remain poorly constrained. This study integrates geological and structural mapping, core sample analysis, whole-rock geochemistry, U–Pb detrital zircon geochronology, and aerogeophysical data to constrain the tectonic setting and mineralization processes of the Contendas-Mirante belt. Metabasalts of the Neoarchean lower unit display light rare earth element-enriched patterns, elevated Th and U contents, and pronounced negative Nb–Ta–Ti anomalies, consistent with a continental geochemical signature. Elevated Th/Yb, La/Yb, and Th/Nb ratios may have been partly modified by secondary processes and are therefore considered supportive, but not restricted to an arc-like continental geochemical signature, as they may also reflect crustal contamination during the evolution of basaltic magma. U–Pb detrital zircon ages from associated phyllites yield a maximum depositional age of 2626 ± 31 Ma, indicating provenance from proximal Neoarchean volcanic sources along a continental margin. Structural analyses reveal a dominant north–south-trending crustal-scale lineament formed during the Rhyacian-Orosirian tectonothermal event, itself associated with the accretion of oceanic and continental arcs and older continental blocks in the northern São Francisco Craton. Subordinate northwest-southeast and northeast-southwest structures controlled the distribution of lithologies and fluid migration. Gold mineralization in the Contendas-Mirante belt is hosted by brecciated ferruginous metacherts of the lower unit and is spatially associated with quartz-sericite schists, reflecting fluid focusing within brittle-ductile deformation zones where iron-rich sedimentary rocks acted as effective chemical and rheological traps. The results support a tectonic evolution involving Neoarchean continental-margin volcanism, followed by the Rhyacian-Orosirian tectonothermal event and orogenic gold mineralization, most likely within a continental arc system. The Contendas-Mirante belt mineralization exhibits key temporal, structural, and geodynamic characteristics of Paleoproterozoic orogenic gold systems in the Congo, Amazonian, and West African cratons, contributing to broader reconstructions of crustal growth, metallogenesis, and gold exploration models in the São Francisco Craton and analogous cratonic provinces worldwide.
The Kuibis Subgroup (lower Nama Group) in Namibia was deposited during the late Ediacaran in mainly shallow marine environments of a foreland basin that was separated into a northern (Zaris) and southern (Witputs) sub-basin by the Osis Ridge. The succession was correlated between the two sub-basins based on lithostratigraphy, and, more recently, carbonate carbon isotope (δ13Ccarb) chemostratigraphy. Here, we use satellite imagery integrated with field data to establish a refined stratigraphic framework and correlation of the Kuibis Subgroup across the two sub-basins, independent of δ13C chemostratigraphy. The succession consists of alternations between resistant and recessive intervals, reflecting second- and third-order sequences, many of which are traceable throughout the sub-basins and even across the Osis Ridge over distances of ∼300 km. The proposed correlation differs from previous δ13C-based correlations, but is similar to older lithostratigraphic correlations, and identifies three second-order sequences in the Kuibis Subgroup in both sub-basins. This correlation scheme is supported by the continuity of distinctive flat-topped surfaces between the sub-basins, which are interpreted to reflect transgressive–regressive sequence boundaries. The integration of published δ13C data shows that during deposition of the first two sequences, little sediment accumulated on the ridge crest and the sub-basins each record different δ13C values. The third second-order sequence, however, was deposited across the ridge and δ13C values are comparable in both sub-basins. Therefore, we suggest that the Zaris and Witputs sub-basins were separated and geochemically distinct during the early stages of the Nama foreland basin. Continued subsidence eventually buried the ridge and connected the two sub-basins.
The Mesoproterozoic Kunene Complex of Angola and Namibia is the world’s largest massif-type anorthosite complex, and represents an exceptional area for studying the large-scale magmatic and thermal record of long-lived Proterozoic anorthosites. We examined evolved pegmatoidal enclaves and their host anorthosites from the central part of the complex to clarify their crystallisation sequence and investigate the magma emplacement dynamics and post-crystallisation thermal and metasomatic history. In combination with detailed petrography and mineral mapping, zircon, apatite and titanite were analysed for U-Pb isotope and trace element concentrations. Zircon dates for both the enclaves and the host anorthosites are ca. 1500 Ma, indicating contemporaneous crystallisation, but some zircon grains underwent coupled dissolution-reprecipitation, likely driven by high-temperature fluids related to protracted regional Kunene magmatism. The oldest age for one Kunene anorthosite, at 1510 ± 4 Ma, attests to a total duration for the magmatism reaching 150 Myr. Apatite also crystallised at ca. 1500 Ma as it mostly preserves magmatic textures and igneous trace element compositions, but records resetting ages of ca. 1400 Ma, corresponding with a subset of zircon dates and the crystallisation ages of secondary titanite, which may reflect a major Kunene magmatic pulse at this time. Overall, zircon age variability in single samples, combined with trace element decoupling, suggest localised post-crystallisation disturbance of the magmatic system. This study shows the contribution that multiple geochronological datasets from large igneous bodies can provide to explain prolonged histories of magma recharge, thermal rejuvenation and fluid-rock interaction.
The Yunzhongshan (YZS) massif, located in the central Trans-North China Orogen (TNCO), preserves crucial Neoarchean to Paleoproterozoic volcanic records for understanding the tectonic evolution of the North China Craton (NCC), and offers valuable insights into global Archean geodynamic processes. However, the precise magmatic processes and the tectonic setting of these rocks remain contentious. This study presents an integrated investigation of field geology, petrography, whole-rock geochemistry, whole-rock Nd-Hf isotopes, and zircon U–Pb-Hf isotopes for the YZS meta-volcanic rocks. We report crystallization ages of 2516 ± 7 Ma for meta-basalt and 2519 ± 13 Ma for meta-dacite, alongside captured zircon ages of ∼ 2.55 Ga and ∼ 2.70 Ga. The volcanic suite displays significant geochemical diversity, evolving from tholeiitic basalts to calc-alkaline dacites, yet consistently preserves subduction-related signatures (e.g., Nb, Ta depletion) and homogeneous, depleted mantle-like isotopic compositions (εNd(t) = +1.9 to + 4.0; εHf(t) = +5.7 to + 12.2). Petrogenetic analysis and modeling suggest these rocks formed via fractional crystallization transitioning to assimilation fractional crystallization from a slab-fluid-modified depleted mantle source. Critically, the coexistence of arc-like signatures with extensional indicators (flat HREE patterns, high Ti/V ratios) and regional coeval alkaline granites supports a continental back-arc setting. Therefore, we interpret the ∼ 2.52 Ga YZS meta-volcanic rocks as products of a back-arc basin. This study reveals that the YZS magmatism records a pivotal tectonic transition from subduction-driven compression to back-arc extension within the central NCC, providing robust evidence for the operation of modern-style plate tectonic regimes.
The 1.33 Moz Katanning Gold Deposit (KGD) is hosted by Neoarchean granulite-facies volcanosedimentary rocks of the Katanning Greenstone Belt (KGB), Southwest Yilgarn Craton, Western Australia. The pressure–temperature-time (P-T-t) evolution of these high-grade metamorphic rocks remains poorly constrained, limiting our understanding of the tectono-thermal framework in which gold mineralisation developed. We present P-T estimates and in situ Lu-Hf garnet geochronology for mafic, felsic, and metasedimentary migmatites to establish the timing and conditions of metamorphism across the KGD. Mafic samples yield slightly lower pressures and higher apparent thermal gradients (4.4–6.4 kbar; ∼135–210°C/kbar) than felsic (6.5–7.5 kbar; ∼140–110°C/kbar) and metasedimentary samples (∼5.5 kbar; ∼140°C/kbar). The P-T estimates at the KGD reflect high-temperature–moderate-pressure, granulite–facies conditions (780–930°C; 4.4–7.5 kbar), with modelled melt fractions from ∼0–25 vol% and approximate burial to mid-crustal paleodepths (∼22 km), in agreement with estimates for the Corrigin Tectonic Zone (CTZ). Almandine-rich garnets display subdued yttrium-rich cores and flattened major-element compositional zoning, including Y-Cr-Mn enrichment in narrow rims, consistent with prograde growth followed by intracrystalline diffusion and continued garnet growth during prolonged granulite-facies residence. These garnets yield an in situ Lu-Hf weighted mean age of 2702 ± 15 Ma, interpreted to record the time-integrated garnet growth from prograde through peak metamorphic conditions. Maximum depositional and Lu-Hf garnet ages of metasedimentary migmatitic gneiss indicate apparent burial rates for the KGB consistent with active tectonic burial. The high-temperature thermal regime that affected the KGD was relatively long-lived, initiating shortly after or coeval with the KGB volcanosedimentary deposition (∼2710–2680 Ma) and culminating at ∼2650 Ma with the cooling of anatectic melts. This event overlaps locally with the emplacement of a TTG intrusion at ∼ 2670 Ma and, regionally, with widespread high-Ca TTG magmatism between ∼2680–2660 Ma across the Yilgarn Craton, the UHT metamorphism in the Narryer Terrane (∼2690–2660 Ma), and the low- to high-temperature metamorphism in the Kalgoorlie Terrane (∼2680–2665 Ma). The high to ultrahigh apparent thermal gradients and older metamorphic ages obtained for the KGD are consistent with the involvement of diverse heat sources during a dynamic and protracted Neoarchean tectono-metamorphic evolution throughout the Yilgarn Orogeny (∼2730–2630 Ma).
The Tonian represents a critical interval for eukaryote evolution, yet whether the oceans remained predominantly anoxic or underwent progressive oxygenation remains a longstanding debate, highlighting the need of robust proxies for reconstructing benthic redox conditions. Carbonate-associated iron (Fecarb) has recently been proposed as a promising redox proxy, but its sensitivity to early diagenetic alteration has not been systematically evaluated. Here, we investigate microbial carbonates from the Tonian Jiudingshan Formation (North China Craton) using Fecarb, Mg/Ca ratios, carbonate contents, δ13Ccarb, petrographic observations, and a one-dimensional diffusion–advection-reaction (DAR) model. The results reveal two contrasting carbonate facies: low-Mg limestones exhibit consistently low Fecarb, stable Mg/Ca ratios, and minimal evidence for recrystallization, whereas Mg-rich stromatolitic and partially dolomitized facies display a positive relationship between Fecarb and Mg/Ca, reflecting enhanced Fe incorporation during early diagenesis. The diffusion–advection-reaction (DAR) model reproduces these contrasting geochemical characteristics and demonstrates that porewater evolution and Mg-rich carbonate precipitation exert fundamental controls on Fecarb incorporation. Consequently, only the low-Mg limestones reliably preserve primary benthic redox signals. Their average Fecarb concentration (∼45 ppm) corresponds to oxygenated sediment–water interface conditions (>250 μmol/L), which notably exceed typical oxygen level in the oxygen oases under the anoxic water column. These findings demonstrate that Fecarb can be used as a robust proxy for reconstructing local seafloor oxygenation when integrated with petrographic, mineralogical, and diagenetic constraints, and confirm locally oxygenated seafloor environment in Tonian, which may provide a suitable environment for early eukaryotic evolution.
The Oki belt preserves a rare Paleoproterozoic continental basement in the Japanese Islands. The belt is composed mainly of migmatitic paragneisses and granitic gneisses. This study constrains the provenance, depositional age, and tectonothermal evolution of the Oki belt using zircon U–Pb geochronology, whole-rock geochemistry, and Nd isotopic data. Detrital zircon age spectra from migmatitic paragneisses are dominated by Paleoproterozoic populations between ca. 2.16 and 1.99 Ga, indicating source mainly from contemporaneous Paleoproterozoic crust. The youngest concordant zircon cores constrain the maximum depositional ages to ca. 1.99–1.93 Ga, possibly as young as ca. 1.85 Ga locally. The high alumina saturation index values, variable negative Nb anomalies, and εNd(t) values of −5.1 to +0.1, taken together, suggest partial melting of arc-related, old terrigenous sediments deposited along an active continental margin. Granitic gneiss and anatectic leucosomes in the migmatite reflect ca. 1.87 Ga igneous activity and ca. 1.84 Ga anatexis related to the previously recognized regional M1 granulite-facies metamorphism. The Oki belt was subsequently overprinted during the Triassic at ca. 233–226 Ma, recording the renewed partial melting during the M2 high-grade metamorphism. These results indicate that the Oki belt is tectonically correlated with the northern Gyeonggi Massif on the basis of comparable Paleoproterozoic high-grade metamorphism (ca. 1.86–1.84 Ga), coeval ca. 1.87 Ga magmatism, and Triassic anatexis. However, unlike the northern Gyeonggi Massif, its detrital zircon spectra, dominated by 2.16–1.99 Ga ages, indicate derivation from Paleoproterozoic continental crust, including arc-related magmatic sources, in the Jiao–Liao–Ji Belt and the Nangrim Massif, implying a more northeasterly paleogeographic position along the eastern margin of the North China Craton.
Tin deposits are widespread throughout the Kibaran Metallogenic Province (KMP) of Central Africa. Although studies from the Karagwe-Ankole and Kibara Belts have linked cassiterite mineralization to fluid mixing and greisenization, the processes controlling tin mineralization in the Kivu Belt (KVB) remain poorly constrained. This study investigates the timing and mechanisms of tin mineralization in the Meso- to Neoproterozoic KVB, Democratic Republic of the Congo, by integrating in situ LA-ICP-MS U-Pb geochronology and trace-element analyses of cassiterite from the Lemera leucogranite, Numbi pegmatite, and associated quartz veins. Cassiterite U-Pb ages range from 566.1 ± 9.8 Ma to 541 ± 12 Ma, corresponding to late Neoproterozoic-early Cambrian tectono-magmatic activity in Central and southern Africa. Granite- and pegmatite-hosted cassiterite yields the oldest apparent ages, whereas vein-hosted cassiterite is generally younger. However, the overlap within analytical uncertainties indicates that these ages most likely record a single Pan-African tin-mineralizing event or a series of closely spaced mineralizing pulses. Cassiterite from the Numbi pegmatite is enriched in Nb (up to 9433 ppm), Ta (up to 4992 ppm), Zr (1204–2691 ppm), and Hf (average ∼762 ppm), but depleted in W (average ∼43 ppm), consistent with crystallization in a highly fractionated pegmatitic system. In contrast, cassiterite from the Lemera leucogranite and associated quartz veins is characterized by elevated W concentrations (>5000 ppm) and low Nb and Ta contents (≤352 ppm), indicating precipitation from evolved magmatic-hydrothermal fluids. Collectively, these results indicate that tin mineralization in the Kivu Belt is genetically linked to collisional Pan-African magmatism during Gondwana assembly. The Lemera and Numbi districts represent a younger Pan-African granite-related tin system, distinct from the dominant ca. 1.0–0.9 Ga tin mineralization systems in the KMP. These findings refine the regional metallogenic framework and provide new insights for tin exploration in Central Africa.
The Huronian Ice Age (ca. 2.45–2.22 Ga) represents one of the most extensive glacial events in Earth history, yet its geological record in South China remains poorly constrained. This study documents new evidence for cold climatic conditions from the Paleoproterozoic (2.35–2.29 Ga) Abudu Formation in central Yunnan, South China, based on an integrated analysis of chemical weathering indices, carbon–oxygen isotopes of dolostone, and stratigraphic sequences. Major–element compositions from 24 siliciclastic samples were used to calculate the Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), Plagioclase Index of Alteration (PIA), and Weathering Index of Parker (WIP), while carbon and oxygen isotopes were obtained from 11 dolostone samples. CIA values range from 40.8 to 78.5 (average 65.9) and display one distinct low–CIA interval in the lower Abudu Formation. Given the tropical paleogeographic location of the South China Craton at ∼2.3 Ga, this low–CIA interval likely records the Paleoproterozoic Huronian Ice Age. The δ13C values (–1.85 to +0.82‰; average –0.36‰) and δ18O values (–13.56 to –9.62‰; average –11.00‰) are comparable to those reported from the second Huronian glacial episode in North America. Furthermore, the vertical succession of diamictite, sandstone, siltstone, shale, and dolostone is similar to that of the Huronian glacial succession in Canada, southern Africa, and Western Australia. Together, these results indicate that the Abudu Formation most likely represents a regional expression of the Huronian Ice Age in South China.
The geodynamic evolution of the Precambrian basement of the North China Craton (NCC) has been a forefront subject of geosciences over the past three decades. The Central Orogenic Belt (COB), formed by accretion of arc(s) to the Eastern Block, preserves important geological information on the Precambrian tectonic evolution of the craton. The Linshan Massif, situated in the southern segment of the COB, is primarily composed of tonalitic-trondhjemitic-granodioritic (TTG)-diorite gneisses, metamorphic volcanic-sedimentary rocks and monzogranites. The monzogranites mainly occur as plutons and dikes/veins intruding TTG gneisses and metabasites. Zircon U-Pb dating of two monzogranite samples yield ages of 2535 ± 25 Ma and 2526 ± 32 Ma, suggesting their emplacement at ca. 2.53 Ga. Geochemically, they have high SiO2 and K2O contents, exhibiting high-K calc-alkaline and peraluminous characteristics. On REE and multi-element normalized diagrams, they are characterized by light REE enrichment and pronounced negative Eu anomalies, and significant depletions in Sr, Ba, and Ti. The monzogranites have high Ga/Al ratios and Zr + Nb + Ce + Y values with high zircon saturation temperatures (∼803 °C on average), resembling those of typical fractionated A-type granites. Low Sr/Y ratios (0.59–11.21) indicate the absence of garnet residue in the source. Positive whole-rock εNd(t) values (from + 4.8 to + 6.2) and zircon εHf(t) values (from + 2.4 to + 7.8) with TDM2 ages around ca. 2.7 Ga, suggest that the monzogranites were derived primarily from the partial melting of 2.7 Ga juvenile crusts. Considering co-existence of ca. 2.5 Ga back-arc mafic rocks with mixed MORB-IAT affinities and I-type granites in the region, we propose that the ca. 2.53 Ga monzogranites in the Linshan Massif formed in an intra-arc rifting setting of TTG-dominated island arc terranes, which resulted in the formation of a Neoarchean back-arc basin. Several Neoarchean “forearc-island-arc-backarc” systems, analogous to modern examples, may have existed in the NCC, suggesting that plate tectonics has been active since at least 2.55–2.50 Ga.
Cooling processes and their signatures (i.e., mineralogical, textural, and geochemical modifications) from peak temperature–pressure conditions to stable continental geotherms are rarely preserved in Precambrian shields. Metasomatic reaction zones (MRZs) formed at the contrasting lithological contacts due to fluid-rock interaction can provide critical insights into this post-peak cooling process in such ancient shields. This study investigates MRZs formed at the contact between a metabasic dyke and pelitic schist in the Proterozoic North Singhbhum Mobile Belt (NSMB), using an integrated approach of field observations, petrography, mineral and whole-rock geochemistry, mass balance calculations, pseudosection modeling, reaction-path simulations, and hydrothermal experiments. The MRZs developed from pelitic schist through mass transfer (i.e., gain / loss) and chemical exchange of elements with the dyke in the presence of saline fluid across their contact. The MRZs get enriched in Ca, Na, and Sr, but depleted in K, Al, Rb, Ba, Cs, rare earth elements and high field strength elements (Nb, Y, Th, U). These depleted components are enriched in the dyke, demonstrating substantial redistribution of elements traditionally considered immobile. The results show that such transfer is strongly localized at lithological boundaries where fluids equilibrated with one rock interact with another. Associated mass and volume changes resulted in formation of fluid-pathways that facilitated element transport within MRZs. Thermodynamic modelling suggests that fluid-rock interactions occurred during thermal relaxation from peak metamorphic conditions (5.5–10 kbar, 550–700 °C) to mid-crustal depths (1–3 kbar, 300–500 °C). Our results show that, lithological contacts can act as localized sites for critical element redistribution/concentration during post-metamorphic cooling.
Quantitative comparison of detrital zircon age spectra emphasizes stratigraphic correlation and tectonic reconstruction. However, analytical workflows implicitly combine provenance similarity, depositional timing, statistical significance, and ordination structure, potentially concealing their distinct geological implications. Using the Paleoproterozoic Western Succession of the Mount Isa Inlier (Australia) as a case study, we demonstrate that provenance similarity and maximum depositional age (MDA) represent related but partially independent aspects of basin evolution. Southern Mount Guide Quartzite predate northern equivalents by >100 Myr, but they display very similar zircon age spectra and only small differences in distribution shape. A similar pattern is observed in the Warrina Park Quartzite and Moondarra Siltstone, where the units that are considered stratigraphically equivalent show different depositional ages but comparable source signatures. In contrast, some intra-formational transitions (e.g., within the Myally Subgroup) reveal abrupt shifts in provenance that are not reflected in mapped supersequence boundaries. To investigate these relationships, we combine several statistical frameworks, including measures of distribution dissimilarity (effect size), statistical testing, uncertainty assessment, grain-count sensitivity analysis, multidimensional scaling, and stratigraphy-aware change-point detection. Applied to the Mount Isa Inlier, this framework facilitates distinguishing between continuing provenance, differences in depositional timing, and structural juxtaposition of rock units. By explicitly separating dissimilarity metrics, statistical confidence, uncertainty, ordination quality, and depositional constraints, we propose a diagnostic workflow that improves interpretation of detrital zircon data. This framework refines superbasin assignment at the sample scale and provides a broadly applicable approach for detrital zircon studies in basins with complex tectono-stratigraphic evolutions.
