Search

U-Pb baddeleyite ages for key mafic dykes of the Amazonian Craton reveal four significant intraplate episodes that allow connections with global igneous activity through time and supercontinent cycles. The oldest dykes (Carajas-Rio Maria region) are diabases with ages of 1880.2 ± 1.5 Ma and 1884.6 ± 1.6 Ma, respectively, corresponding with the Tucuma swarm which crops out to the west and is age-equivalent. The magmatic activity has a genetic link with the ca. 1.88 Ga Uatuma Silicic Large Igneous Province (SLIP), characterized by felsic plutonic-volcanic rocks. There is an age correlation with LIP events (ca. 1880 Ma) in the Superior, Slave, Indian and other cratons. This magmatism could be derived from significant perturbations of the upper mantle during the partial assembly of Columbia. Gabbronorite of the Rio Perdido Suite (Rio Apa Terrane) crystallized at 1110.7 ± 1.4 Ma, and is identical to that of the Rincon del Tigre-Huanchaca LIP event of the Amazonian Craton. This event was synchronous with the initiation of Keweenawan magmatism of central Laurentia (Midcontinent Rift) and also with coeval units in the Kalahari, Congo and India cratons. The two youngest U-Pb dates (535 and 200 Ma) occur in the Carajas region. Diabase of the Paraupebas swarm yields an age of 535.1 ± 1.1 Ma, which may be correlative with the giant Piranhas swarm located ca. 900 km apart to the west. The Paraupebas swarm is correlative with post-collisional plutonism within the Araguaia marginal belt. Therefore, the Cambrian dykes may reflect reactivation of cooled lithosphere, due to crustal extension/transtension active along the craton’s margin during assembly of West Gondwana. This magmatism is also contemporaneous with the 539–530 Ma Wichita LIP of southern Laurentia. The youngest studied Carajas region dyke was emplaced at ca. 200 Ma, corresponding with 40 Ar/ 39 Ar ages for the Periquito dykes west of Carajas and with most K-Ar ages of the giant Cassipore swarm, located north of the study area. The newly dated ca. 200 Ma dyke fits well into the known, brief span of ages for the CAMP Large Igneous Province event, around the present central and northern Atlantic Ocean.

The Scourie dyke swarm has long been important to unravelling the geological history of the Lewisian Gneiss Complex (LGC) and the North Atlantic Craton. Recent dating has documented that the majority of those dykes were emplaced between c. 2418–2375 Ma. Here we show that a quartz dolerite dyke in the Rona Terrane of the LGC has a U-Pb zircon age of 1989.08 +4.3/−0.99 Ma. This is the first mafic dyke to be dated from the Rona terrane, the southernmost of those proposed for the terrane model of the LGC. Our new age also overlaps with the c. 1992 Ma age of a previously dated olivine gabbro dyke in the Northern region of the LGC and shows that the LGC contains at least three, and possibly four, temporally discrete episodes of Palaeoproterozoic mafic magmatism: The Scourie dyke swarm ‘sensu stricto’ at c. 2.4 Ga; a suite of younger dykes at c. 1.99 Ga, referred to here as the Strathan dyke swarm; and the c. 1.99–1.90 Ga mafic rocks that are part of the Palaeoproterozoic Loch Maree Group. A c. 2.04 Ga dyke in the Assynt terrain may be part of the younger suite of dykes or perhaps records a temporally separate event. Crucially, our new age data demonstrate that suites of mafic dykes emplaced across the mainland LGC are similar in age and supports the correlation of structural and metamorphic features across that Complex.

Tonalite–trondhjemite–granodiorite (TTG) suites constitute dominant components of Precambrian continental crust and provide important insights into the crustal evolution history of the early Earth. Here we investigate a suite of TTGs and associated greenstones from the Luxi Terrane in the south–eastern part of the North China Craton (NCC). We present data from petrology, geochemistry, zircon U–Pb geochronology and Lu–Hf isotopes to characterize these rocks and understand their genesis. Mineral assemblage in the greenstones and TTGs suggests that the rocks have undergone amphibolite–facies metamorphism with regression under greenschist–facies. Zircon U–Pb data from the magmatic grains yield upper intercept ages of 2753 ± 37 and 2582 ± 40 Ma for greenstone, 2552 ± 13 Ma for TTG gneiss and 2476 ± 18 Ma for tonalite, and weighted mean 207Pb/206Pb age of 2507 ± 22 Ma for granodiorite. Lu–Hf isotope systematics show eHf(t) values ranging from −2.13 to 7.29 and crustal model ages (TCDM) in the range of 2603–3125 Ma for the TTGs, whereas the eHf(t) values are up to 8.53 with TCDM ages of 2644–3006 Ma for the greenstone. The results suggest that the protolith for the greenstone was derived from a Meso- to Neoarchean mantle contaminated by the crust source, whereas the TTGs were mostly sourced from juvenile crustal sources with reworking of older basement. The geochemical features of greenstone are similar to island arc basalt, with low Na2O, K2O and TiO2, low total rare earth elements (REEs) values, relative enrichment in light REEs and depletion in heavy REEs absence of obvious Ce anomaly, and negative Nb, Ta and Ti anomalies. The TTGs show similar features, except for the high K2O content and moderate total REEs values. We propose that the greenstone likely represent a part of the early and initial crustal growth at ca. 2750–2600 Ma, and the TTGs were generated subsequently at ca. 2550–2450 Ma. Our results are consistent with the previous models on the crustal growth models in the NCC and provide further insights into the Neoarchean to Paleoproterozoic tectonic history of the craton.

The Paleoproterozoic (centred at ∼2.054 Ga) Bushveld LIP is one of the largest intracratonic LIPs in the world. Its components are primarily distributed within the Archean Kaapvaal Craton. This study reports dyke-like and sill-like norite intrusions from Lose quarry within the Mahalapye Complex, a Paleoproterozoic granitoid-migmatitic gneiss terrane along the northern edge of Kaapvaal Craton. Field relations indicate the norite postdate the ∼2.061 Ga diorite gneiss and predate the ∼2.039 Ga granodiorite. Significantly, it exhibit structures indicative of comingling with ∼2.053 Ga leucosome/leucogranite, a product of partial melting of diorite gneiss. The cross-cutting relations provide unequivocal evidence that the norite and the leucogranite were liquid at the same time, and should be of similar age. Fe-rich orthopyroxene (XMg = 0.43–0.46) constitutes the dominant mafic mineral in the norite. Geochemical characteristics of the Mahalapye Complex norites are similar to those of marginal facies norites from the Bushveld Complex (B1 sills) and Molopo Farms Complex layered intrusions, two of the prominent constituents of the Bushveld LIP. This is the first solid evidence that the original extent of the Bushveld LIP covered an area larger than the current known limits of the Archean Kaapvaal Craton – into the youngest and westernmost terrane of the high-grade Limpopo Complex. The potential of high-grade terranes along Archean cratonic margins as locales to look for LIP fragments is explored.

The Tarim block in NW China consists of a Precambrian basement and late Neoproterozoic to Paleozoic cover sequences. In order to better understand its roles in Precambrian supercontinent evolution, we used SHRIMP and LA-ICPMS U-Pb methods to date late Paleoproterozoic rifting-related mafic dykes and Mesoproterozoic igneous activity in the Precambrian of the southwestern Tarim terrane (STT): 1) WNW trending mafic dyke swarm emplaced at ca. 1785 Ma; 2) Mesoproterozoic bimodal volcanic sequence (the lower member) and marble- clastic-quartzite sequences (the upper member) deposited at ca. 1525 Ma and 1500–1400 Ma, respectively; 3) late Mesoproterozoic granodiorite-augen granite-leucogranite complex emplaced at ca. 1117 Ma. Geochemistry revealed that the 1784 ± 12 Ma mafic dykes were derived from an E-MORB – like mantle source suggesting an extensional setting, and likely linked with coeval major large igneous provinces (LIPs) on several crustal blocks which collectively suggest a pulse of rifting associated with assembly of the Columbia supercontinent. The obtained U-Pb age of 1525 ± 4 Ma from a meta-rhyolite in the bimodal sequence matches a recently discovered 1525–1529 Ma Large Igneous Province from the southern West African craton (Essakane-Sambarabougou swarm) and formerly adjacent Amazonian craton (Kayser event). Geochemistry of the ca. 1117 Ma granitic intrusions defines their A-type signature. These may be linked to coeval intraplate mafic magmatism of a reconstructed 1110 Ma LIP involving Kalahari, Congo, India (Bundelkhand block), Amazonia cratons. In line with these three newly recognized pulses of Precambrian igneous activities in STT and the significant diachroneity of the Precambrian tectono-magnetic events between the STT and the Northern Tarim terrane (NTT), we argue that the Precambrian basement of the Tarim were most likely composed of two distinct terranes (i.e., the STT and the NTT). These originated from different Precambrian nuclei and they did not amalgamate as the Tarim block until to the early middle Neoproterozoic.

The Middleback Ranges is a 60 km-long BIF-endowed iron ore belt located in the southeastern Gawler Craton and is the largest exploited iron resource in South Australia. The belt is hosted within an Archean- to Paleoproterozoic-aged granitic-gneissic basement terrane. Petrographic and geochronological constraints are given for a suite of granites associated with deposits throughout the Middleback Ranges and compared with other regional granites. Granites from the Middleback Ranges show complex mineralogical and geochemical features indicating multiple overprinting events. Sensitive high-resolution ion microprobe U-Pb zircon ages from all granites across the Middleback Ranges yield Archean ages, suggesting the existence and a more extensive distribution of Mesoarchean crust than previously recognized beneath the entire Middleback Ranges BIF sequence. Grey and pink granites from the central Middleback Ranges (Sultan prospect) produced the oldest 207Pb/206Pb weighted mean ages within the sample suite (3241 ± 6 and 3238 ± 9 Ma, respectively). Zircon in the latter granite also features overgrowths dated at ∼2.6 Ga and interpreted to be metamorphic. A second group of younger granites from the Iron Monarch deposit and a sample of Cooyerdoo Granite (northern Middleback Ranges) have a minimum crystallization age of 3165 ± 8 Ma and a 207Pb/206Pb weighted mean magmatic age of 3134 ± 18 Ma, respectively. The youngest granites analyzed here derive from the Iron Baron deposit in the central part of the belt, which display strong deformation and have a minimum crystallization age of 3089 ± 9 Ma, and from the Iron Magnet deposit in the southern part of the belt (207Pb/206Pb weighted mean age of 3023 ± 33 Ma). Petrographic and geochemical features observed within the sample suite indicate that post-Archean overprinting events led to alteration of the granitic basement and may infer that fluid-rock interaction and granite leaching were important for BIF upgrading processes and iron-oxide formation.

The tectonic history of the Yangtze block of South China prior to the Ediacaran Period has been a matter of debate. In particular, the tectonic history of the Shennongjia terrane in the central-northern margin of the Yangtze block is poorly understood, and the tectonic relationship between the Shennongjia terrane and the Huangling massif (exposed in the Huangling anticline) is unclear. Previous researchers have reported U-Pb dates of detrital zircons and Nd isotopic compositions of clastic rocks from Cryogenian successions in the Shennongjia terrane to identify ancient crustal remnants and the provenance of clastic sediments, and to constrain the age and crustal evolution of the Yangtze block. Here, we describe abundant graphite discs from silty mudstone of the Cryogenian Nantuo Formation in the Shennongjia area of the Yangtze block. These graphite discs are opaque, ∼23–171 μm in size, and highly reflective. Most are abraded or rounded, although some show hexagonal crystalline morphology. Their Raman spectra are distinct from those of indigenous carbonaceous material (CM) in the sedimentary matrix from the Nantuo Formation at the same locality. Raman CM geothermometric analysis indicates that graphite discs experienced a maximum metamorphic temperature of nearly 600 °C, which is inconsistent with the relatively low metamorphic grade of the host rock. These observations indicate that the graphite discs are of detrital origin, most likely derived from high-grade metamorphic rocks in the basement of the Yangtze block (e.g., the Archean-Paleoproterozoic Kongling terrain in the core of the Huangling anticline), consistent with the hypothesis that the Shennongjia region was a part of Yangtze block by the end of the Cryogenian Period.

The Jiangnan orogenic belt in South China, formed by the collision of the Yangtze and Cathaysia sub-blocks, represents a key to reconstruct the assembly of the Rodinia supercontinent. Here we investigated the Fuchuan ophiolite melange and Shexian magmatic units in the eastern Jiangnan belt, and report the first findings of anorthosite and leucogranite that are dated at 848 ± 4 and 840 ± 5 Ma, respectively. The anorthosites yield positive eNd(t) values (2.3–4.2) and lower initial 87Sr/86Sr ratios (0.704616–0.704679), along with zircon eHf(t) of ∼9.2, suggesting a depleted mantle contribution with minor crustal assimilation. The mafic-ultramafic rocks and anorthosite within the Fuchuan ophiolite display N-MORB & E-MORB signatures, likely generated in back-arc marginal sea spreading center and metasomatized by subduction-related fluids. The intermediate-felsic igneous suites from Shexian area in the eastern margin of the Zhanggong Terrane were formed at 850–830 Ma and display continental-arc-related geochemical features. Zircons within these rock suites mostly show eHf(t) values of 3–12, whereas inherited grains yielded negative eHf(t) values with model ages of 2.7–1.9 Ga, implying an active continental marginal environment. Overall relations and data indicate that the disrupted Fuchuan mafic-ultramafic rocks, anorthosite and leucogranite constitute the remnants of an 860–830 Ma ophiolite, whereas the northwestward subduction beneath the Zhanggong terrane occurred at ca. 870–860 Ma to ca. 830 Ma. A ca. 817 Ma muscovite-bearing K-granitic pluton dated at 817 ± 5 Ma emplaced in a post-collisional setting constrains the upper age limit of continental assembly along the Shaoxing- Jiangshan- Pingxiang- Qidong-Quanzhou- Longsheng-Yongfu fault zone. The timing of the final assembly of South China occurred at 830–800 Ma as referred from a collisional-type granitic magmatism ca. 830–815 Ma and an external dynamic process of uplifting-erosion-transpotation-deposition presented by the regional-scale unconformity with ages 820–795 Ma. Age and nature of the Jiangnan orogenic belt, along with sedimentary records and paleomagnetic constraints, indicate that the South China Block was possibly located along the northern Rodinia margin, adjacent to the Tarim and northwestern Australia blocks.

High-pressure (HP) pelitic granulites have been used as important targets in evaluating ancient geodynamic processes similar to subduction, collision and exhumation operating in modern plate tectonics. In this contribution, relic HP pelitic granulites were identified from the Pingdu-Laiyang areas of the Jiaobei terrane that are dominated by low- to medium-pressure (LMP) pelitic granulites, suggesting their linear distribution and that at least some of LMP types should be retrograde products of the HP pelitic granulites. Their metamorphic P-T-t paths were traced by integrated methods of petrographic observation, mineral chemistry, P-T-X pseudosection modeling, Zr-in-rutile thermometry, and zircon and monazite geochronology. These HP pelitic granulites record consistent clockwise P-T-t paths that are manifested by similar peak metamorphism of high-pressure granulite-facies, with P-T conditions of P > 13 kbar, T > 850 °C possibly during 1950–1900 Ma, followed by near isothermal decompression (ITD) to mid-crustal level at 1900–1850 Ma and subsequent near isobaric cooling (IBC) to low temperature during 1850–1800 Ma. The consistent clockwise P-T-t paths and linear distribution of HP pelitic granulites explicitly indicate a sequence of geodynamic processes similar to modern-style plate tectonics must have operated during formation of the Paleoproterozoic Jiao-Liao-Ji belt (JLJB). These include a process similar to subduction that brought sedimentary precursors of HP pelitic granulites down, which was followed by continental orogeny during 1950–1900 Ma, leading to crustal thickening (40–50 km) and high-pressure granulite-facies metamorphism, and a post-orogenic collapse during 1900–1800 Ma that resulted in exhumation and cooling of HP granulites along ITD and IBC paths. Therefore, it is argued that ancient HP pelitic granulites can be regarded as relics of orogen and ascertain tectonic interpretation of the dominated LMP pelitic granulites in the same Precambrian metamorphic terranes. Notably, the apparent thermal gradients estimated from peak metamorphism are 15–20 °C/km, much higher than those of typical products in Phanerozoic plate tectonics, and the HP pelitic granulites that contain well-preserved kyanite probably require relatively high exhumation rates during ITD to middle crustal level. These seem to mark the differences in thermal regimes and tectonic mechanisms between Paleoproterozoic and Phanerozoic collisional orogenic systems.

The detrital zircon record yields important information on crustal evolution that may be missing from extant magmatic rocks. The Palaeoarchaean to Neoarchaean East Pilbara Terrane (EPT), Western Australia, is the ancient core of the Pilbara Craton, and the archetypal granite-greenstone terrane. Magmatic zircon U–Pb crystallization ages from the EPT record crustal magmatism spanning 3.53–3.22 Ga. However, detrital zircons with ages as old as 3.65 Ga have been identified in EPT supracrustal sequences, which may provide key insights into the EPT’s early Archaean history. The Strelley Pool Formation (SPF), one of the earliest EPT siliciclastic sedimentary successions, is a critical unit in the field of Precambrian palaeobiology, containing multiple lines of evidence for some of Earth’s earliest life forms. The SPF was deposited on a continental shelf in a shallow water environment, upon perhaps the oldest preserved terrestrial erosion surface on Earth; it thus provides a record of a newly-emergent Palaeoarchaean continent. We report U–Pb, Lu–Hf and O isotope data from a suite of detrital zircon crystals sourced from the type locality of the SPF. Two hundred and five U–Pb detrital zircon analyses were undertaken via SIMS and LA–ICPMS. Four analyses define a young age peak of 3414 ± 34 Ma (2σ), which we interpret as a maximum depositional age. Zircon Hf isotope analyses yield eHfi of −3.5 to +5.2, clustering around chondritic values, with two-stage Hf crustal model ages of 3.9–3.5 Ga. Zircon O isotopes give a range in δ18O values from mantle-like (5.3‰) to more elevated (∼6.4‰). Taken together, the Hf and O isotope record, from new and published detrital and magmatic zircon crystals, implies a juvenile (mafic) source for evolved rocks of the EPT until ca. 3.3 Ga, after which time it experienced a period dominated by reworking of existing crust, possibly reflective of a change in geodynamics. The relationship between the cryptic core of the EPT, which is perhaps as old as 3.8–3.7 Ga, and the extant magmatic rocks that comprise the exposed Palaeoarchaean granite domes, remains uncertain.

The NE Jiangxi ophiolitic melange separates the Huaiyu and Jiuling terranes in the eastern Jiangnan Orogen of the South China Block. Two phases of S-type granites, which are geochemically and mineralogically similar to the Himalayan leucogranites, are newly recognized in mantle peridotites of the NE Jiangxi ophiolite. The first phase, a tourmaline-bearing granite porphyry, has a SIMS zircon U–Pb age of 904.4 ± 4.8 Ma and is strongly enriched in K2O (4.00–4.26 wt%) and strongly peraluminous (A/CNK = 2.94–3.24). It further shows high Rb/Sr ratios and highly fractionated REE patterns, indicating an origin due to fluid-absent melting of metapelites at relatively high temperatures. The granite porphyry exhibits highly evolved zircon Hf (−6.0 to −1.0) and whole-rock Nd (−4.2 to −5.1) isotopes, which is in contrast to juvenile-derived magmatic rocks in the Huaiyu Terrane. We thus propose that the granite porphyry was formed by melting of the metapelites sourced from the Yangtze Block subsequent to the accretion of the Huaiyu arc to the Jiuling Terrane (the continental margin of the Yangtze Block). The second phase, a muscovite-bearing quartz porphyry, is strongly peraluminous (A/CNK = 1.29–1.34) with low CaO/Na2O ratios (0.11–0.14) and low FeOt + MgO + TiO2 contents (2.39–2.75 wt%), similar to melts derived from fluid-fluxed melting of metapelites. Zircon grains from the quartz porphyry yielded U–Pb ages of ca. 803–801 Ma with mainly positive eHf(t) values (+1.9 to +8.7), which are younger than the depositional ages of the basement sequences and nearly identical to the accumulation of the overlying unmetamorphosed cover in the Jiangnan Orogen. Therefore, it is suggested that the quartz porphyry was formed in a post-collisional extensional setting subsequent to the final assembly of the Yangtze and Cathaysia blocks. In conjunction with published data, we conclude that multiple subduction-accretion events may have been involved in the formation of the South China Block during Neoproterozoic times.

The Cuchilla Dionisio (or Punta del Este) Terrane of the southern Dom Feliciano Belt, eastern Uruguay, experienced a prolonged Neoproterozoic to Cambrian tectonothermal evolution. Zircon and monazite age data from orthogneisses of the basement of the terrane (Cerro Olivo Complex) provide evidence of widespread magmatism at c. 780 Ma and high-grade, up to granulite-facies metamorphism between 655 and 632 Ma. Isotope data imply that the orthogneiss protolithic melts formed in a within-plate, rift-related setting by Neoproterozoic (re-) melting of lower crustal material that was extracted from the mantle during the Palaeoproterozoic. We show that the terrane extends further north than previously thought. The presence of inherited Meso- and Palaeoproterozoic zircon grains indicates the existence of older crustal components in the terrane. The ages of the detrital zircon grains and their Hf isotope signatures cannot be explained by a Rio de la Plata Craton provenance but are consistent with a southern African Kalahari Craton origin. Ar-Ar ages of 628 and 625 Ma were obtained on magnesiohornblende in amphibolite from the northern Cuchilla Dionisio Terrane, whose protolith formed in an Ediacaran back-arc basin. These ages are interpreted as the time of amphibolite-facies metamorphism. Thus, crustal convergence between the Kalahari (or Congo?) and the Rio de la Plata Craton and subduction of the intervening oceanic basin must have been underway between 655 and 625 Ma. The early Neoproterozoic basement of the Cuchilla Dionisio Terrane is part of the southern African Namaqua Province that was separated from the Kalahari Craton during Rodinia break-up and opening of the southern Adamastor Ocean in the Tonian. Closure of this ocean in the late Cryogenian to early Ediacaran was associated with arc magmatism and high-temperature metamorphism of the Cuchilla Dionisio Terrane basement. A back-arc basin formed and was closed between this arc and the western African margin. Relics of this basin were obducted onto the Cuchilla Dionisio Terrane at c. 625 Ma. Late Neoproterozoic intrusive igneous rocks from the Cuchilla Dionisio and the Coastal terranes were emplaced in a supra-subduction setting (at least in Uruguay) and have the same Hf isotope signature.

Pre-Palaeozoic metasedimentary rocks are widespread in the Cathaysia Block but their accurate depositional ages are poorly constrained. Here we report a detailed study on U–Pb dating for zircons from the metasedimentary rocks in both Mamianshan and Mayuan groups from NW Fujian Province. The data show two models of age spectrum, i.e. multimodal and unimodal. Multimodal samples include detrital zircons from Daling and Longbeixi Formations of Mamianshan Group, Dajinshan Formation of Mayuan Group and Dikou Formation. Their age spectra are characterized by two prominent age groups of 1.3–0.9 Ga and 0.9–0.7 Ga, and two minor age groups of 0.7–0.5 Ga and 2.7–2.4 Ga. They all have the youngest age group of Ediacaran-Cambrian (ca. 0.61–0.53 Ga). Their age spectra resemble those of early Cambrian strata in Nanling and Yunkai regions of the Cathaysia Block, indicating that their depositional age is most likely Cambrian rather than previously proposed mid-Neoproterozoic or Paleoproterozoic. Therefore it is suggested that the originally named Mamianshan Group, Mayuan Group and Dikou Formation metamorphic strata are probably not anymore a traditional lithostratigraphic unit but a “complex” with rocks of multiple ages. The unimodal samples are all from Nanshan Formation of Mayuan Group, which show age spectra characterized by the dominating age cluster of mid-Neoproterozoic (ca. 0.88–0.74 Ga). The age spectra are very similar to those of the Cryogenian strata in Nanhua rift basin of the South China Block. Therefore, we suggest that the depositional age of those unimodal samples from Nanshan Formation is likely Cryogenian. In addition, detrital zircons from our Cryogenian samples are mostly euhedral-subhedral and they could be derived mainly from the South China Block itself. In contrast those Cambrian samples may have exotic East Gondwana derived detrital zircon compositions. Comparing age spectra of detrital zircons from different terranes, our studied Cambrian strata in the Cathaysia Block show a similarity to those of western and central North India-Himalaya. It is suggested that the Cathaysia Block should be more close to west and central India-Himalaya during Cambrian.

The Pontiac Subprovince is located in the Superior Province, south of the Abitibi Subprovince. The metasedimentary rocks of the Pontiac Group are characterized by a Barrovian metamorphic gradient increasing from north to south from biotite- through garnet- to staurolite-zone conditions. The Pontiac Subprovince has been interpreted as an accretionary wedge or alternatively as an exotic terrane that was tectonically docked to the Abitibi Subprovince during Archean subduction. However, few studies have attempted to characterize its pressure-temperature-time path to test this hypothesis and little is known about the timing relationship between regional metamorphism and the gold mineralization. An E-W lepidoblastic ductile micaceous foliation defines the regional fabric related to the second episode of deformation. Garnet and staurolite porphyroblasts are interpreted to be late- to post-kinematic to the regional fabric. Locally, cordierite or andalusite porphyroblasts fully pseudomorphed by a polymineralic assemblage of muscovite, feldspar and quartz are wrapped by the main foliation indicating that a potential low pressure - high temperature metamorphism (M1) preceded the main episode of deformation and Barrovian metamorphism (M2). Pressure and temperature (P-T) forward thermodynamic modelling on a water-saturated pseudosection yielded peak conditions of 550–600 °C and 5–6 kbar during a prograde, clockwise P-T path for M2. Lu-Hf dating of garnet from three different locations within the staurolite zone yielded a weighted average age of 2657.5 ± 4.4 Ma (95% confidence level) that is inferred to be representative of these conditions. The age of garnet growth calls into question the previous tectonic interpretation of the Abitibi and Pontiac Subprovinces and is coherent with the new rafted ribbon continent model of Bedard (2018) . Because the Canadian Malartic gold mineralization is older or synchronous with the garnet growth episode in the staurolite zone south of the ore body, this garnet age also provides an estimate of the minimum age of the mineralization event, previously dated at 2664 ± 11 Ma with Re-Os on molybdenite.

Cimmerian terranes in Tibet are thought to be as old as Archean or as young as Neoproterozoic or even early Paleozoic in age. However, their Precambrian history and their role in the assembly and dispersal of early supercontinents (e.g., Rodinia) are still poorly known. Here, U-Pb dating, trace-element geochemistry and Lu-Hf isotopes of detrital zircons (351 grains) from the Nyainqentanglha-Group clastic rocks, the earliest strata overlying the Lhasa Block (South Tibet), are used to constrain the provenance of the sediments and test paleogeographic and tectonic models for the Lhasa Block during the breakup of the Rodinia supercontinent. The youngest detrital zircon cluster (803 ± 5 Ma) in the clastic rocks and granitic dykes (797 ± 10 Ma) intruding them constrain the deposition age close to 800 Ma. Four main groups of detrital zircons in these sediments record several sources, including Mesoproterozoic and Neoproterozoic juvenile terranes, a Grenvillian orogenic belt and an Archean continental-crust component. Detrital-zircon age distributions and Lu-Hf isotopic data reveal the variation of the sedimentary provenance and suggest its affinity to the Himalaya and/or the East Africa Orogen. These results show that the Lhasa Block was probably located within a giant convergent plate margin system surrounding the Rodinia supercontinent during its breakup in the Tonian time.

The vast Tin Begane batholith (5000 km2) is located in the Laouni terrane, LATEA metacraton, Central Hoggar and emplaced in the middle crust (c. 4.2 kbar). High-K calc-alkaline, metaluminous and magnesian as a whole, it comprises two distinct groups: i/ a porphyritic amphibole-biotite monzogranite (598 ± 3 Ma, U–Pb zircon) display a LREE enriched pattern and a negative Eu anomaly while ii/ a porphyritic biotite monzogranite (596 ± 4, U–Pb zircon) and a fine-grained monzogranite (591 ± 6 Ma, U–Pb zircon) show a highly fractionated REE patterns and slight Eu anomalies. Both groups enclosed numerous microgranular magmatic enclaves with the same contrasted chemical characteristics. In the center of the batholith, a basement sheet bounded by faults comprises migmatitic country rocks and leucogranites (595 ± 6 Ma, U–Pb zircon) and a garnet-muscovite dyke swarm. Geochemical compositions of the Tin Begane magmatic rocks, including magmatic enclaves, and inherited zircons point to a Paleoproterozoic composite lower crustal metasedimentary source with a psammitic garnet-free component and a garnet-bearing greywacke melted at c. 900 °C with a minor basaltic mantle component. Leucogranites originated from the same sources but at a lower temperature (c. 780 °C) not far from the emplacement of the Tin Begane batholith. A detailed structural study shows that the Tin Begane batholith is post-collisional, syn-kinematic, bounded and controlled by large scale detachment shear zones, which restricted the flow by channeling the magma from depth to the middle crust and accommodated the magma emplacement. Late, when the batholith was largely crystallized, the subhorizontal magmatic fabric was progressively replaced by pronounced subvertical planar fabric when approaching the shear zones. The Tin Begane area shows a local but major high-temperature NNE-SSW (subvertical) extensional deformation, especially marked by a large NW-SE detachment, within the WNW-ESE regional compression (subhorizontal shortening) induced by the global transpressive system linked to the tectonic escape of the Tuareg terranes toward the north. This contrasted behavior is favored by the metacratonic character of LATEA.

The Precambrian basement of the Lhasa terrane provides important information for understanding the formation and evolution of the Tibetan Plateau. However, due to the paucity of exposure, the properties of the Precambrian basement of the Lhasa terrane remain poorly known. Here we report zircon U–Pb ages, bulk-rock geochemical and zircon Hf isotopic data on the orthogneisses in the Milin area of the southeastern Lhasa terrane, southern Tibet. Inherited magmatic zircon cores of these gneisses yield protolith crystalline ages of 1556–1517 Ma, whereas the zircon rims give metamorphic ages of 1197–1192 Ma, both could be local provenance for the Mesoproterozoic detrital zircons in the Neoproterozoic–Paleozoic strata in the Lhasa terrane. Geochemical data indicate that the protoliths of the Mesoproterozoic rocks are continental arc-like granitoids with bulk-rock eNd(t) values of −3.7 to +0.7 (TDM2 = 1.99–2.34 Ga) and zircon core eHf(t) values of +1.8 to +8.6 (TDM2 = 1.71–2.17 Ga), suggesting their most likely derivation from partial melting of Paleoproterozoic crustal materials. We propose that the Mesoproterozoic gneisses in the Milin area represent the Precambrian metamorphic basement of the Lhasa terrane, likely related to the growth of Columbia supercontinent. Local exposure of the Precambrian metamorphic basement may be caused by crustal rapid uplift and erosion in the late Cenozoic and their inhomogeneous distribution.

The Micangshan terrane is located along the NW margin of the Yangtze block and contains the second oldest Precambrian basement in South China. It comprises the Beiba and the Wangcang-Nanjiang segments, while the oldest suites (∼2.1 Ga Houhe complex) occur in the Beiba. The Hekou and the Wangjiaping metamorphic volcano-sedimentary sequences in the Wangcang are characterized by intensive metamorphism and deformation, long being regarded as the equivalent of the Houhe suite. This contribution presents an integrated study of zircon U-Pb geochronology and Hf isotope, whole rock elemental and Sr-Nd isotope geochemistry on volcanic rocks of the metastrata. It reveals that they formed at ∼ 865–860 Ma and underwent upper amphibolite facies metamorphism at ∼ 815 Ma with lower limits in P-T conditions of ∼ 5.0 kbar and ∼ 650–660 °C. The Hekou metavolcanics comprise dacitic-rhyolitic and alkaline basaltic rocks with minor tholeiitic mafics, whereas those of the Wangjiaping are composed of dacitic and tholeiitic mafic rocks. The Hekou alkaline metamafics show affinity to high-Nb to Nb-enriched basalts (HNB-NEB) with eNd(t) values of + 5.80 to + 6.25, whereas tholeiitic metamafics of the both sequences display characteristics typifying high-Al basalt (HAB) with eNd(t) value ∼+2.66. The Hekou and the Wangjiaping metafelsics have eNd(t) ranges of −2.33 to + 5.60 and −0.82 to + 0.99 (except one + 2.29), respectively, and the dacitic rocks show features akin to the high Mg-number andesites. The ∼ 865–860 Ma magmatism is suggested to have occurred in an extensional basin with a post-subduction affinity. It was induced by upwelling of convective asthenosphere succeed the ceased slab subduction: the Wangjiaping metafelsics were derived from partial melting of juvenile lower crust, the Hekou dacitic rocks were produced by partial melts of the relict of subducted oceanic crust interacted with mantle wedge; the Hekou HNB-BEB were sourced by metasomatized mantle wedge, whereas the HAB lavas were generated by anhydrous partial melts of the upwelling asthenosphere. The ∼ 815 Ma metamorphism was caused by an amalgamation between the South Qinling belt and the proto margin of the northwestern Yangtze block. This event was followed by an expanding rift from the Micangshan successively to the South Qinling.

Strata in the Huron (2.5–2.0 Ga) and Animikie (2.2–1.85 Ga) basins were deposited on the southern margin of the Archean Superior province. These rocks were deformed during the Penokean orogeny (∼1850 Ma) followed by subsequent accretionary orogens to the south at 1750 Ma (Yavapai) and 1630 Ma (Mazatzal). Strain patterns are unique to each orogenic belt with no far-field effect: Archean Wawa terrane rocks in the Penokean foreland preserve deformation associated with Archean accretion with no younger Penokean, Yavapai or Mazatzal strain overprint. The Penokean orogeny deformed Huron-Animikie basin sediments into a north-vergent fold-and-thrust belt with no Yavapai or Mazatzal strain overprint. Yavapai orogen strains (SW-NE margin-parallel shortening) are unique when compared to the younger Mazatzal shortening (N20°W) shortening, with no strain overprint. Penokean deformation is characterized by shortening from the south including uplifted Archean gneisses and a northerly thin-skinned fold-and-thrust belt, with north-vergent nappes and a gently-dipping foreland. Our study of finite and calcite twinning strains (n = 60) along (∼1500 km) and across (∼200 km) the Penokean belt indicate that this orogeny was collisional as layer-parallel shortening axes are parallel across the belt, or parallel to the tectonic transport direction (∼N-S). Penokean nappe burial near the margin resulted in vertical shortening strain overprints, some of which are layer-normal. The Sudbury impact layer (1850 Ma) is found across the Animikie basin and provides a widespread deformation marker with many local, unique strain observations. We also report new geochronology (U-Pb zircon and apatite) for the gneiss-mafic dike rocks at Wissota (Chippewa Falls, WI) and Arbutus (Black River Falls, WI) dams, respectively, which bears on Penokean-Yavapai deformation in the Archean Marshfield terrane which was accreted during the Penokean orogen. Pseudotachylite formation was common in the Superior province Archean basement rocks, especially along terrane boundaries reactivated by contemporaneous Penokean, Trans-Hudson, Cape Smith and New Quebec deformation. In the hinterland (south), the younger Yavapai orogen (1750 Ma; n = 8) deformation is preserved as margin-parallel horizontal shortening (∼SW-NE) in Yavapai crust and up to 200 km to the north in the Penokean thrust belt as a strain and Barrovian metamorphic overprint. Mazatzal deformation (1630 Ma; n = 16) is preserved in quartzites on Yavapai and Penokean crust with layer-parallel and layer-normal shortening strains oriented N20°W.

New igneous and detrital zircon laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb geochronology and Lu-Hf isotopic data are presented for the Mesoproterozoic Kgwebe Formation and the unconformably overlying Ghanzi Group in northwestern Botswana. The Makgabana Hills porphyritic rhyolite flow from the Ghanzi area yielded a U-Pb concordia age of 1085.5 ± 4.5 Ma and provides a new maximum depositional age for the unconformably overlying Ghanzi Group. Detrital zircon (n = 448) from the Ghanzi Group yielded a 207Pb/206Pb age distribution with a dominant (70 to 90%) Mesoproterozoic population (∼1450 to ∼1050 Ma), a smaller (5 to 20%) Paleoproterozoic (∼2200 to ∼1700 Ma) population, and a few (n = 4) older (∼3000 Ma to ∼2450 Ma) grains. A maximum depositional age constraint of ∼1060 to ∼1050 Ma was obtained for middle and upper Ghanzi Group based on the weighted-mean 207Pb/206Pb age of the youngest clusters of overlapping zircon ages for each sample. Initial hafnium ratios (eHfi) and corresponding crustal residence model ages (TCDM) for the Paleoproterozoic zircon populations indicate either fractionation from a chondritic uniform reservoir (CHUR) or mixing between juvenile mantle and older crustal components. Mesoproterozoic zircon with eHfi values between −20 and +15 and TCDM model ages between 3000 and 1200 Ma suggest that the source terrane(s) contained magmatic rocks including both juvenile material and substantially reworked Paleoproterozoic and possibly Archean crust. Comparison with a compilation of published U-Pb, Lu-Hf, and Sm-Nd data from the Kalahari Craton suggests that the predominant Mesoproterozoic zircon population was derived from the Namaqua Sector, Rehoboth Basement Inlier, Kwando Complex, and Choma-Kalomo Block; some zircon may have had distal sources in adjacent Rodinia landmasses. Both Archean cratonic components and juvenile ∼1200 to ∼1000 Ma magmatic rocks of the Natal Sector and the Maud and Mozambique belts on the eastern margin of the craton are unlikely sources for the detrital zircon based on isotopic composition. Sediment transported from the western margin of the Kalahari Craton entered the northwest Botswana rift and mixed with sediments from the Rehoboth Basement Inlier and Paleo- to Mesoproterozoic terranes that bound the northwest Botswana rift.

The Neoproterozoic amalgamation and timing of collision between the Yangtze and Cathaysia sub-blocks along the Jiangnan Orogen in South China remain disputed. With a view to constrain the crustal evolution in this major orogen, here we present new results from petrology, geochemistry, zircon U-Pb chronology and Lu-Hf isotopes, on a suite of meta-sedimentary rocks from the Shuangqiaoshan Group and tuffaceous rock from the Liantuo Formation in the Jiuling terrane of central Jiangnan Orogen. Magmatic zircon grains in meta-sedimentary and sedimentary samples from the bottom to top part of the lower and upper Shuangqiaoshan groups constraints the deposition during 863–820 Ma and 797–780 Ma, respectively. The unconformities were formed during 820–797 Ma, reflecting the final amalgamation of Yangtze with Cathaysia sub-blocks along the central Jiangnan Orogen. Our data also identify four major events at 1000–800, 1500–1900, 1900–2200, 2300–2600 Ma. The Neoproterozoic detrital zircons in the lower Shuangqiaoshan Group possess variable eHf(t) values of −44.0 to +13.4. Combined with the geochemical features, these data suggest that the lower Shuangqiaoshan Group was deposited in a back-arc basin with a mixed provenance of granitic and felsic volcanic components, whereas the upper Shuangqiaoshan Group was formed in a rift basin with more granitic or felsic components in the source region. Integrating the results presented in this study with those from previous works, a five-stage crustal evolution model is proposed for the Neoproterozoic Jiangnan Orogen involving (1) intra-oceanic subduction beneath the Huaiyu oceanic island arc (1000–880 Ma), (2) collision between Huaiyu arc and Yangtze Sub-block (880–860 Ma), (3) back-arc extension beneath the Yangtze Sub-block (860–830 Ma), (4) collision between Cathaysia and Yangtze sub-blocks (830–800) and (5) intracontinental rifting throughout South China Block (800–750 Ma).

The lithologic diversity and protracted geologic history of the Minnesota River Valley (MRV) gneiss terrane at the southern margin of the Archean Superior Province provide key perspectives on the growth and modification of this craton. Innovations in geochronology, specifically the application of the chemical abrasion technique to remove Pb-loss domains in zircon, and the tandem use of in situ geochemistry and precise isotope dilution age analysis for establishing the petrologic context of radioisotopic ages, are yielding new insights into these old rocks. First, U-Pb geochronology on a variety of plutonic to mesoscale intrusive rocks from the Morton and Montevideo blocks of the MRV provide precise constraints on the Neoarchean (2603–2584 Ma) Sacred Heart orogeny, which sutured the Mesoarchean gneisses of the MRV to the southern margin of the Superior craton in an episode of contractional deformation, high-grade metamorphism, and voluminous plutonism. Second, we report the first radioisotopic age constraints on the St. Leo and Taunton belts of greenstone and supracrustal rocks within the Yellow Medicine shear zone, an inferred lithosphere-scale structure juxtaposed between the Morton and Montevideo gneisses. Titanite from a metadiorite intrusion into the St. Leo belt yields igneous (∼2539 Ma) and metamorphic (∼2510 Ma) ages, confirming the Archean provenance of the host greenstones and revealing a latest Neoarchean episode of magmatism and deformation focused along and within the shear zone. Third, a new ∼1781 Ma U-Pb zircon age for one of a number of small granitic plugs in the southern Montevideo block confirms its correlation to the more voluminous East-Central Minnesota Batholith and its origin in the Yavapai orogeny. Again later magmatism was focused along the Yellow Medicine shear zone suggesting the lithosphere-scale significance of that structure. This more resolved history for the Neoarchean to Proterozoic evolution of the southern Superior craton provides new opportunities to test Archean craton correlations and reconstructions, including links to the Wyoming and Slave cratons.

The North and South Lhasa terranes in the central Tibetan Plateau were traditionally considered to be one block in the Precambrian and originate from the northeastern India or northern Australia. In this contribution, we report Middle Neoproterozoic (ca. 760 Ma) gabbros in the North Lhasa terrane. The gabbros can be subdivided into two groups. The group-1 gabbros (ca. 766 Ma) are calc-alkaline and exhibit arc-like geochemical features. They have high ISr (0.708 to 0.710) and low zircon eHf(t) (−2.0 to +1.0) and whole-rock eNd(t) (−2.4) values, and were probably generated by partial melting of an enriched subduction-modified lithospheric mantle. By contrast, the group-2 gabbros (ca. 766 and 758 Ma) belong to the tholeiitic series and are geochemically similar to N-MORB. Their low ISr (0.705 to 0.706) and high positive zircon eHf(t) (+5.6 to +8.8) and whole-rock eNd(t) (+2.6 to +3.8) values are indicative of an N-MORB-type depleted mantle source. The presence of these coeval N-MORB- and arc-type gabbros is related to an arc and back-arc system, and indicates an age equivalent to the northern EAO (East African Orogen). Integrating previous studies with the data presented in this contribution, we suggest that the North Lhasa terrane was most likely separated with the South Lhasa terrane in the Precambrian and originated from the northern EAO.

The question of whether high-grade metamorphism and crustal melting in the early Archaean were associated with modern-style plate tectonics is a major issue in unravelling early Earth crustal evolution, and the eastern Kaapvaal craton has featured prominently in this debate. We discuss a major ca. 3.2 Ga tectono-magmatic-metamorphic event in the Ancient Gneiss Complex (AGC) of Swaziland, a multiply deformed medium- to high-grade terrane in the eastern Kaapvaal craton consisting of 3.66–3.20 Ga granitoid gneisses and infolded greenstone remnants, metasedimentary assemblages and mafic dykes. We report on a 3.2 Ga granulite-facies assemblage in a metagabbro of the AGC of central Swaziland and relate this to a major thermo-magmatic event that not only affected the AGC but also the neighbouring Barberton granitoid-greenstone terrane. Some previous models have related the 3.2 Ga event in the eastern Kaapvaal craton to subduction processes, but we see no evidence for long, narrow belts and metamorphic facies changes reflecting lithospheric suture zones, and there is no unidirectional asymmetry in the thermal structure across the entire region from Swaziland to the southern Barberton granite-greenstone terrane as is typical of Phanerozoic and Proterozoic belts. Instead, we consider an underplating event at ca. 3.2 Ga, giving rise to melting in the lower crust and mixing with mantle-derived under- and intraplated mafic magma to generate the voluminous granitoid assemblages now observed in the AGC and the southern Barberton terrane. This is compatible with large-scale crustal reworking during a major thermo-magmatic event and the apparent lack of a mafic lower crust in the Kaapvaal craton as shown by seismic data.

The Lower Coverdale plutonic suite is located in the Ganderian Brookville terrane of southern New Brunswick, Canada. It does not outcrop at surface but has been intersected in 11 drill holes at depths of 100–200 m below unconformably overlying Carboniferous sedimentary rocks, and extends to a depth of at least 1100 m. No host rocks are present in the drill core, which consists entirely of plutonic and meta-plutonic rocks. The dominant rock types are anorthosite, mela-anorthosite, and ferronorite with layers of ilmenite and ilmenite-apatite rocks. They are intruded by abundant undated mafic dykes and minor ca. 390 Ma felsic dykes. A ferronorite sample yielded a Tonian age of 975.5 ± 2.3 Ma, interpreted to be the igneous crystallization age of the plutonic suite. A mela-anorthosite sample yielded a similar but less precise age of 979 ± 16 Ma, likely also the igneous crystallization age. The anorthosite has characteristics of alkali anorthosite massifs, including andesine (An30-35) commonly with exsolution lamellae of K-feldspar. The Lower Coverdale suite is interpreted to have been emplaced during orogen-scale extension following crustal thickening associated with the Grenvillian orogeny. The Lower Coverdale anorthosite and ferronorite have more isotopically evolved signatures (higher 206Pb/204Pb and 207Pb/204Pb and lower ∊Nd) compared to typical Laurentian Grenville-age plutons. We infer from these data that the Lower Coverdale plutonic suite originated in the Amazonian part of the Grenville orogen during the early stages of Tonian breakup of Rodinia. It was then incorporated into Ganderia before accreting to Laurentia as part of the Brookville terrane during the Pangean phase of supercontinent assembly.

Recent geochronological and petrographic studies in the Nuuk region, West Greenland, have established that modern-style tectonic processes were active in the Neoarchean. However, more limited work has addressed Neoarchean processes elsewhere in West Greenland. In particular, conflicting models have been proposed for the tectonothermal history of the Akia terrane, to the north of the Nuuk region. In this study, the depositional and metamorphic history of supracrustal rocks in the Akia terrane have been investigated using field relationships, petrography, phase equilibria modelling, and zircon and apatite U-Pb geochronology. The Akia terrane is a Palaeo- to Mesoarchean tonalite-trondhjemite-granodiorite (TTG) gneiss terrane with subordinate supracrustal rocks, mafic to ultramafic intrusions – all metamorphosed at amphibolite to granulite facies – Proterozoic mafic dyke suites, Neoproterozoic and Jurassic kimberlitic rocks, and a Mesoarchean and a Jurassic carbonatite. Some of the supracrustal rocks are known to be Mesoarchean, whilst others lack age constraint. New detrital and metamorphic zircon ages show that the metasedimentary rocks studied – the Kangerluarsuk Supracrustal Belt – were sourced from TTG gneisses within the host Akia terrane and deposited in the period ≤2877 Ma to ≥2857 Ma; this requires exhumation of the Akia terrane after c. 3010–2970 Ma magmatism and low-pressure granulite facies metamorphism. After exhumation, the Kangerluarsuk Supracrustal Belt was buried and underwent prolonged high-temperature metamorphism, reaching ∼820–850 °C and 8–10 kbar during regional ductile deformation in the period 2857–2700 Ma. The same rocks grew metamorphic zircon and neoblastic apatite at c. 2630 Ma and >450 to

The Precambrian origin and evolution of the Lhasa Terrane remain unclear. Here, we present new zircon U–Pb isotopic and whole-rock geochemical data for the RenTso gabbros of the central Lhasa Terrane. These data indicate that these gabbros formed during the early Neoproterozoic (∼925 Ma) and have affinities with high-Fe–Ti basaltic rocks, given that they contain low concentrations of SiO2 (39.8–49.0 wt%) and high concentrations of FeOT (11.3–23.5 wt%), TiO2 (2.19–5.70 wt%), and V (333–1204 ppm). These gabbros also have N-MORB-like trace element features such as low (La/Sm)N ratios (0.50–0.57) and the absence of negative Nb–Ta anomalies. Combining these features with the high whole-rock eNd(t) (+5.04 to +7.55) and zircon eHf(t) (+7.8 to +13.0) values for these samples indicate that the RenTso gabbros formed by the partial melting of depleted asthenospheric mantle. The Fe–Ti enrichment in these gabbros reflects conditions of low oxygen fugacity during magma fractionation. These gabbros are spatially associated with troctolite and peridotite units, indicating that together these units form a typical ophiolitic lithological assemblage. These geochemical and field observations suggest that the study area contains a subduction-unrelated-type ophiolite that most likely represents the embryonic crust of the Mozambique Ocean following continental rifting and breakup. The results therefore indicate that the Lhasa Terrane has a Precambrian affinity with the East African orogen and occupied a different position to the Qiangtang Terrane within the Rodinia supercontinent.

We report here new zircon U-Pb age and Hf-isotope as well as geochemical analyses of the recently discovered Archean-Paleoproterozoic Zhongxiang Complex in the northern-central Yangtze Craton, South China, and interpret the early crustal evolution of the Yangtze Craton. Zircon LA-ICP-MS dating yielded magmatic crystallization ages of ca. 2.90–2.87 Ga for two monzogranites, ca. 2.77 Ga for a trondhjemitic gneiss, and ca. 2.67–2.62 Ga for three potassic granites. The trondhjemitic gneiss also contains zircon rims that record a metamorphic event at ca. 2.08 Ga. These results demonstrate that the Zhongxiang Complex is significantly older than previously thought, and it contains the only potential TTG with ages of 2.8–2.7 Ga for the Yangtze Craton. These granitoids vary considerably in zircon Hf isotopic and geochemical characteristics. The ca. 2.90–2.87 Ga monzogranites correspond in composition to alkaline and calc-alkalic peraluminous granites originated from mixing of ancient and juvenile crustal components at relatively shallow depths. In contrast, the ca. 2.77 Ga trondhjemitic gneisses are calc-alkalic and peraluminous with relatively high Sr/Y and (La/Yb)N ratios and slightly evolved zircon Hf signatures, but without significant Eu anomaly that is, typical of a medium-pressure TTG component. Consequently, they are interpreted to be the products of partial melting of a basaltic source with appreciable involvement of pre-existing crustal components (i.e., tonalites), with garnet and amphibole in the residue. The ca. 2.67–2.62 Ga potassic granites are alkaline, faintly peraluminous and ferroan, exhibiting a high-silica A-type granite affinity. They are characterized by low Al2O3/TiO2 ratios with dominantly undepleted zircons, suggesting their derivation from melting of meta-sedimentary rocks under high-temperature conditions with plagioclase as the main residual phases. The Zhongxiang Complex thereby differs from the Kongling Complex and other Archean provinces in the Yangtze Craton by preserving distinct magmatic pulses (ca. 2.90–2.87 Ga; ca. 2.77 Ga; ca. 2.67–2.62 Ga) with different nature and sources. A comparative analysis of the crustal evolution of the Zhongxiang Complex and other Archean provinces of the Yangtze Craton indicates a compositionally heterogeneous Archean Yangtze Craton, which likely comprises several Archean terranes that accreted together to form a uniform craton during the late Archean to Paleoproterozoic time.

Late Neoarchean plutonic rocks in the eastern range of the Western Shandong (WSD) terrane, North China Craton, consist of fine-grained monzogranites (Group #1), fine-grained monzogranitic gneisses (Group #2), coarse-grained granodioritic gneisses (Group #3) and coarse-grained gabbro-diorites (Group #4). The first three groups of granitoids exhibit high SiO2 and K2O contents and plot in the quartz monzonite, granodiorite and granite fields in the TAS classification diagram and the high-K calc-alkaline series field in the SiO2 and K2O diagram. These granitoids show meta- to peraluminous characteristics in the A/NK versus A/CNK plot. In contrast, the gabbro and diorite samples display low SiO2 and K2O contents. LA-ICP-MS zircon U-Pb isotopic dating reveals that the high-K granitoids (Groups #1, 2 and 3) were emplaced at ∼2511–2497 Ma and that the gabbro-diorites were emplaced at ∼2511 Ma. All of these samples generally underwent regional metamorphism at ∼2475–2451 Ma. Detailed petrogenetic and geochemical studies suggest that the fine-grained monzogranites (Group #1) were derived from the hydrous partial melting of juvenile sediments at mid-crustal levels, while the fine-grained monzogranitic gneisses (Group #2) were most likely derived from the partial melting of metagreywackes at lower to mid-crustal levels. The gabbro-diorites (Group #4) were derived from the partial melting of a fluid-metasomatized mantle source at relatively deeper levels of the upper mantle. The granodioritic gneisses (Group #3) were generated from magma mixing between melts derived from the partial melting of metagreywackes (∼90%) and melts derived from a metasomatized depleted mantle source (∼10%) with minor ancient basement material additions. These findings, combined with previously obtained zircon U-Pb dating and Lu-Hf isotope data, suggest that crust-mantle interaction constituted the essential mechanism for the formation of high-K granitoids in the WSD terrane. The upwelling and underplating of mantle-derived magmas (Group #4) not only provided sufficient heat for melting crustal materials at various levels (Group #1 and #2) but also mixed mantle materials with crustal-derived melts, thereby generating the magmatic precursors of the granodioritic gneisses (Group #3).

Two prominent features separate the Archean Wyoming and Hearne cratons: the Paleoproterozoic Great Falls tectonic zone (GFTZ) and the Medicine Hat block (MHB), neither of which is well defined spatially because of Phanerozoic sedimentary cover. Based on limited data, the MHB is thought to be a structurally complex mix of Archean (2.6–3.1 Ga) and Proterozoic (1.75 Ga) crust, but is recognized primarily by its geophysical signature, and its influence on the geochemistry of younger igneous rocks. Similarly, the GFTZ was recognized on the basis of broad differences in geophysical patterns, isopachs of Paleozoic sedimentary sections, and lineaments; however, juvenile arc rocks in the Little Belt Mountains (LBM) and strongly overprinted Archean rocks in southwestern Montana show it to be a dominantly Paleoproterozoic feature. The Little Rocky Mountains (LRM) of Montana provide access to exposures of the northeastern-most Precambrian crust in the MHB-GFTZ region. U/Pb ages of zircons from Precambrian rocks of the LRM range from 2.4 to 3.3 Ga, with most ages between 2.6 and 2.8 Ga. Whole-rock analyses yield Sm-Nd TDM from 3.1 to 4.0 Ga and initial eNd(T) values calculated at U-Pb zircon crystallization ages range from −0.9 to −10.5, indicating significant contributions from older Archean crust. The high proportion of 2.6–2.8 Ga U/Pb ages differentiates LRM crust from arc-related Paleoproterozoic magmatic rocks exposed in the LBM to the southwest. The age and isotopic composition of the LRM gneisses are similar to crust in the northern Wyoming Province (2.8–2.9 Ga), but Paleoproterozoic K-Ar cooling ages suggest crust in the LRM experienced the Paleoproterozoic metamorphism and deformation that characterizes the GFTZ. Consequently, its history differs markedly from the adjacent Beartooth-Bighorn magmatic zone of the northern Wyoming Province, which does not record Paleoproterozoic tectonism, but has a strong correlation with the Montana metasedimentary terrane that was strongly overprinted during the Paleoproterozoic Great Falls orogeny that defines the GFTZ. The LRM, therefore, likely provides a unique, and perhaps the only, opportunity to characterize Archean crust of the MHB.

The Borborema Province BP (NE Brazil) consists of a complex rock mosaic composed mainly by Proterozoic metasedimentary belts that amalgamate Archean-to-Paleoproterozoic gneiss-migmatite complexes. It is a key region to understand the West Gondwana amalgamation, during the Pan-African/Brasiliano orogeny because it is an important portion of the orogen located between the Sao Francisco-Congo and West African cratons. We present the deep-rooted crustal framework of the BP interpreting the lateral contrasts of density and magnetization using the first available regional coverage of gravity and aeromagnetic data. The external boundaries of the BP having deep-rooted crustal significance are the Transbrasiliano shear zone, to the west, and the limit with the Sao Francisco craton, to the south. The latter limit is marked by a gravity anomaly which is the typical gravity signature of collisional sutures. Inside the BP crustal block, the Pernambuco, Patos, and Jaguaribe shear zones are identified as the major structures, based on termination and/or truncation criteria of geophysical anomalies. The three shear zones correspond to geophysical lineaments which conform with the Transbrasiliano shear zone, forming a single splay that opens to the northeast/east direction. The external boundaries and major shear zones divide the BP crustal block into four internal major domains of contrasting geophysical characteristics, namely the Southern, Transversal Zone, Rio Grande do Norte, and Ceara geophysical domains in analogy with the division based on surface geology. However, compared with the delimitations based on surface geology, there are three differences: the Medio Coreau belt is not positioned over the BP crustal block, a portion of the Parnaiba basin baseament should be included in the BP crustal block, and the basement beneath the folded-and-thrusted metasedimentary rocks of the Casa Nova Group (which form the nappes of the Riacho do Pontal belt) is part of the Sao Francisco craton crustal block. A subdivision of each major domain is also presented. Of special relevance is a pattern of alternate-polarity, quasi-parallel aligned geophysical anomalies present in the Transversal Zone domain, suggesting a clear alternation of high-density/high-susceptibility with low-density/low-susceptibility deep-rooted crustal subdomains. This geophysical pattern is compatible with a tectonic model of terrane collage.

LA-ICP-MS U-Pb dating of zircon, monazite, titanite and rutile was carried out to investigate the temperature-time evolution of eclogite-facies rocks in the Kuummiut Terrane of the Paleoproterozoic Nagssugtoqidian Orogen in South-East Greenland. The terrane is dominated by Archean TTG gneiss and a variety of supracrustal rocks; basic dykes intruded the gneiss during Paleoproterozoic deformation. Detrital zircon in garnet-kyanite schist gives Archean to Paleoproterozoic dates and confines the maximum deposition of the metasediment precursor to 2107 ± 21 Ma. Intrusion of the metabasic dykes occurred at 2146 ± 63 and 2092 ± 22 Ma, within error of the detrital zircon date, possibly indicating near-contemporaneous dyke emplacement and sedimentation. About 200 m.y. after dyke emplacement, the Kuummiut Terrane underwent a clockwise PT-evolution, involving eclogite-facies metamorphism and subsequent exhumation into the mid crust. The majority of zircon, monazite and titanite give metamorphic dates between 1891 ± 10 and 1882 ± 3 Ma. Although the REE patterns in metamorphic zircon reflect growth at eclogite-facies conditions, the zircons are associated with retrograde mineral assemblages and their dates are indistinguishable from amphibolite-facies titanite. This may be interpreted to indicate that the timing of eclogite- and high-pressure amphibolite-facies metamorphism overlap within error, consistent with rapid and tectonically-controlled exhumation. However, previous studies have shown that the REE and U-Pb systematics in zircon may be decoupled during retrograde metamorphism, and the range in dates is thus best interpreted to reflect mineral growth and recrystallization during high-pressure amphibolite-facies retrogression. Monazite and titanite dates between 1872 ± 70 and 1821 ± 31 Ma reflect regional medium-pressure amphibolite-facies metamorphism and mark the final stages of compressional deformation in the Kuummiut Terrane. The subsequent thermal evolution was associated with titanite growth until 1738 ± 61 Ma, a time where the majority of rutile cooled below its closure temperature. The youngest rutile dates at 1645 ± 63 and 1617 ± 91 Ma correlate with the emplacement of post-tectonic intrusive complexes. Collectively, the data show that after an initial tectonically-controlled exhumation, the Kuummiut Terrane experienced relatively slow, erosion-controlled cooling with only minor thermal perturbations during the waning stages of metamorphic and magmatic activity.

The Sveconorwegian orogeny is a more than 250 Myr-long multiphase orogenic event that contributed to the amalgamation of Fennoscandia into Rodinia at the end of the Mesoproterozoic. We propose a new lithospheric-scale tectonic model for the pre- to early Sveconorwegian orogenic evolution between 1280 and 1080 Ma. This evolution is recorded in southern Norway by two c. 25 km wide belts of up to granulite-facies rocks, the Bamble and Kongsberg Lithotectonic Units, and a c. 80 km belt in the Telemarkia Lithotectonic Unit, which contains lower-grade rocks and evidence of widespread plutonism. New zircon U–Pb geochronological data from 54 samples confirm magmatic activity between 1575 and 1485 Ma, and 1210 and 1140 Ma. The new data constrain peak amphibolite to granulite-facies metamorphism in Bamble and Kongsberg to between 1145 and 1130 Ma. New geological mapping shows that the Kongsberg Lithotectonic Unit is characterized by a regional, N–S trending highly transposed lithological banding reflecting E–W orthogonal shortening as expressed by tight to isoclinal folds, and a penetrative subvertical foliation bearing a steep peak-metamorphic lineation. Telemarkia is instead characterized by crustal extension-related bimodal magmatism and intermontane basin sedimentation between 1280 and 1080 Ma. Paired and in part coeval extension and compression are interpreted as reflecting asthenospheric upwelling, orogenic plateau development and delamination of the sub-continental lithospheric mantle beneath Telemarkia, followed by foundering (dripping-off) of the lithospheric mantle slab under the Kongsberg and Bamble Lithotectonic Units. This model stresses the pull effect of a foundering mantle slab in an actively shortening orogen to facilitate highly localised compression and granulite-facies metamorphism in the crust. It accounts for the well-known, first-order geological characteristics of the orogen and does not require the accretion of exotic terranes to explain the early-Sveconorwegian orogenic evolution.

The origin of ancient continental blocks in the Tibetan plateau and their paleogeographic locations in the Rodinia supercontinent remain enigmatic. Here, we report the early Cryogenian metamorphic magmatic rocks (including amphibolites and granitic gneisses) from the North Lhasa terrane of the central Tibetan Plateau. The amphibolites (ca. 822 Ma) are tholeiitic and exhibit both MORB- (e.g., flat patterns of rare-earth and high field strength elements) and arc-like (e.g., elevated Th/Yb tatios) geochemical affinities. In combination with high positive zircon eHf(t) (+6.9 to +12.4) and whole-rock eNd(t) (+4.4 to +10.4) and low zircon δ18O (4.87 to 5.81‰) values, their geochemical data indicate a depleted mantle source affected by subduction components. The granitic gneisses (ca. 810 and 806 Ma) are A2-type granitoids and have relatively lower zircon eHf(t) (+4.7 to +6.9) and whole-rock eNd(t) (+3.5) and higher zircon δ18O (5.44–8.08‰) values. Their protoliths were probably generated by partial melting of Mesoproterozoic crustal rocks. The amphibolites and granitic gneisses are geochemically distinct from the Cryogenian rift-related magmatic rocks in the interior of the Rodinia supercontinent but similar to the coeval back-arc magmatic rocks at the northwestern edge of the Rodinia supercontinent, thus providing new constraints on the early Cryogenian paleogeographic location of the North Lhasa terrane.

NJG acknowledges Curtin University for financial support. The Proterozoic assembly of Australia involved the convergence of three main Archean cratonic entities: the North, West and South Australian Cratons, and is recorded in the Proterozoic orogenic belts surrounding these continental nuclei. The Rudall Province of northern Western Australia is the sole exposure of a Paleo- to Mesoproterozoic orogen lying between the North and West Australian Cratons, and may record the effects of their amalgamation. We present new zircon O, U–Pb and Lu–Hf isotope data from magmatic rocks across the Rudall Province, to which we add existing isotope data to yield a crustal evolution overview. Hf evolution trends for the ca. 1804–1762 Ma Kalkan Supersuite, the ca. 1589–1549 Ma Krackatinny Supersuite and the ca. 1310–1286 Ma Camel Suite, indicate a significant input of Archean East Pilbara Basement material, albeit as a mix with more juvenile material, including a possible ca. 1900 Ma component. Zircon δ18O data suggest a contribution from supracrustal material into the magmatic source of the Kalkan Supersuite, which may have been emplaced in an extensional setting. In contrast, the Krackatinny Supersuite and Camel Suite have mantle-like δ18O which may reflect partial melting of deeper Archean sources. Geochemical data for the Krackatinny Supersuite shows geochemical trends implying that melting of thickened mafic crust progressed from deeper to shallower levels, possibly in a rift setting. Camel Suite K-rich leucogranites may also have been emplaced in an extensional setting towards the end of high-P metamorphism. All terranes of the Rudall Province are para-autochthonous with respect to the Pilbara Craton, with no requirement for arc-related magmatism. We outline two potential scenarios for the Paleo- to Mesoproterozoic geodynamic evolution of the Rudall Province: an early cratonic amalgamation between the West and North Australian Cratons ca. 1680 Ma followed by Mesoproterozoic intraplate events; or a later assembly ca. 1377–1275 Ma. We lean towards this later amalgamation scenario. Publisher PDF

The Precambrian basement of the Jiaobei terrane consists of Archean metavolcanic and metasedimentary rocks, tonalitic – trondjhemitic – granodioritic gneisses (TTGs), Paleoproterozoic metasedimentary sequences, as well as lenses of metamorphic mafic–ultramafic rocks. Petrological, geochemical and in situ zircon U-Pb studies were conducted on meta-calcsilicates, which occur as irregular blocks within TTG gneisses. Samples were collected at Nanshankou, Jiaobei terrane of Shandong Peninsula at the north-eastern part of the North China Craton (NCC).Two groups of meta-calcsilicate rocks were distinguished, which originate from a metavolcanic-metasedimentary series. The respective bulk rock composition is a result of different proportions of source rock material involved. One group which is higher in CaO and lower in Na2O demonstrates a higher contribution material from a sedimentary source, whereas volcanoclastic to pyroclastic precursor dominates in the second group. The meta-calcsilicates are generally composed of Ca-bearing silicates with a peak preassure assemblage of Grt-Cpx-Zo-Am-Qz-Ttn; they experienced epidote amphibolite facies metamorphism constrained by P-T conditions of 580°C / 1.08–1.13 GPa. Late prehnite-, albite-, calcite- and actinolite-bearing veins refer to the subgreenschist conditions at the late exhumation stage.In situ zircon U-Pb dating of 173 detrital zircons from the meta-calcsilicate rocks yield Archean ages up to 3.04 Ga; a further predominant age population clusters at ca. 2.68 Ga with subordinate clusters at ca. 2.87, 2.78, which are interpreted to represent magmatic ages. A subordinate cluster at 2.51 Ga associated with zircon rim domains reflects a metamorphic event. Further frequently textureless rims of zircon of an age range between ca. 2.5 and –2.1 Ga indicate subsequent metamorphic events. The deposition of the meta-calcsilicate precursors occurred around of shortly after 2.1 Ga on an Archaean basement.

The Arabian Shield comprises early Neoproterozoic to Cambrian (∼850–530 Ma) tectonostratigraphic terranes formed by the closure and accretion of juvenile volcanic arcs and back-arc basins associated with Gondwana assembly. Unlike the Nubian Shield which preserves crustal isotopic signatures, the Arabian Shield is distinctly juvenile with the exception of the Paleoproterozoic (∼1800–1670 Ma) Khida subterrane in Saudi Arabia and the terranes of Yemen. This study presents the first combined zircon U-Pb, O and Hf isotope data of metavolcanic and metasedimentary rocks from southwestern most Saudi Arabia, near the Yemen border – a region thought to contain some of the oldest (>815 Ma) lithologies in Saudi Arabia, including the Atura Formation and the Tayyah Belt. One volcaniclastic metasediment sample from the Atura Formation yields zircon U-Pb age peaks of 741, 672, 646 Ma (n = 131), δ18O(V-SMOW) ranging from 4.6 to 8.3‰ and ɛHf (t) from +7.7 to +12.5. Two samples from the Tayyah Belt include an older metasandstone and a late intruding granitic dyke which provides a minimum age for the Tayyah Belt. The former yields two significant U-Pb peaks of 812 (n = 8) and 999 (n = 6) Ma, δ18O and ɛHf (t) values ranging from 4.4 to 9.6‰ and −10.1 to +12.4, respectively; the later yields a concordia age of 645.8 [±1.7] Ma (n = 29), δ18O ranging from 5.7 to 6.6‰, and ɛHf (t) of +5.9 to +9.6. The zircon age and juvenile Hf signatures from the Atura Formation are consistent with the synorogenic phase in the Shield. Sedimentation was likely associated with arc volcanism during the previously documented eastward phase of accretion at ∼740–640 Ma and the closure of the Mozambique Ocean. In contrast, the data from the texturally more mature Tayyah Belt metasediment indicate a more distal, and more evolved crustal input at the time of sediment deposition which is unusual for the Saudi Arabian Shield. Consequently, the Tayyah metasediments are likely sourced from areas with greater continental affinity, such as the cratonic basement and/or reworked crust of the Sahara metacraton in NE Africa.

The remnants of an island arc system of Pinwarian age, the Escoumins supracrustal belt (ESB), are exposed for over 100 km in the Low-pressure belt of the Central Grenville Province (Canada), and are part of the Quebecia terrane. The ESB mainly consists of amphibolite-facies supracrustal rocks with well preserved primary textures (Saint-Simeon Group; SSG), and their plutonic counterpart (Tadoussac Intrusive Suite; TIS) that provide a record of the evolution of a Mesoproterozoic arc system. Granodiorite (1502 ± 6 Ma) and tonalite of the TIS have calc-alkalic oceanic arc signatures, positive eNd (+2.66) with old model age (1672 Ma) consistent with remelting of previously formed juvenile mafic crust and interaction with an older crustal component, and are crosscut by younger within-plate granitoids. Tectonically above the TIS, the lowest formation of the SSG (Saint-Paul-du-Nord) consists of sedimentary, and minor basalt, intruded by syn-volcanic juvenile (eNd = +5.21) tholeiitic gabbro and is interpreted to represent the remnants of an oceanic basin adjacent to an arc. The middle formation (Moulin-a-Baude) records an evolution from: (a) subalkaline tholeiitic to transitional arc basaltic andesite, basalt, and minor calc-alkalic volcanic arc 1492 ± 3 Ma dacite with crustal-derived signature (eNd = −0.77, model age of 1936 Ma), to (b) transitional to tholeiitic dacite–rhyodacite and 1464 + 38/−32 Ma rhyolite, and (c) subalkaline juvenile (eNd = +3.91–+4.92) tholeiitic basalts and FeTi basalts of arc rift and back-arc affinities. This formation is interpreted to represent an oceanic arc undergoing rifting. Finally, the upper formation (Port-aux-Quilles) is composed of epiclastic sedimentary rocks with detrital zircon of Laurentian affinities, indicating proximity of the arc to Laurentia, but dominated by 1.5–1.47 Ga ages, showing a maximum age of deposition of 1476 ± 10 Ma. The eNd and Nd-model ages indicate an association of mixed crustal and mantle-derived signatures typical of Quebecia crust combined with younger depleted mantle-derived basaltic magma. The data provide new insights on the organisation of Quebecia, and show that crust formed in an oceanic arc setting during late Geon 15 to Geon 14 constitutes a significant component of the central Grenville Province.

The Central Zone of the Limpopo Belt in southern Africa is a classical example of a polymetamorphic terrane that experienced three metamorphic events at 3.22 Ga (M1), 2.66–2.61 Ga (M2) and 2.02 (M3). However, the geodynamic significance of these events is controversial as their P-T evolution was poorly constrained. We present new petrological and geochronological data for the M2 and M3 events. The Neoarchean M2 event is well-preserved in samples from a newly discovered enclave of supracrustal and magmatic rocks in the 2.612 Ga Bulai pluton that shielded the enclave against a Paleoproterozoic M3 overprint, which is dominant in rocks exposed outside the pluton. P-T pseudosection modelling for migmatitic Grt-Crd metapelites from the enclave and the rock sequence outside the pluton indicates an opposite metamorphic evolution, a counterclockwise P-T path for M2 but a clockwise path for M3. Spinel-quartz assemblages in the enclave metapelites record early heating to UHT conditions (ca. 930 °C, 5.5 kbar) at intermediate crustal levels. The peak-pressure M2-assemblage garnet-cordierite-sillimanite-K-feldspar-plagioclase-quartz ± rutile formed at ca. 860 °C and 7.5 kbar during a moderate pressure increase. Cordierite coronas around garnet record subsequent decompression. We interpret the counterclockwise P-T evolution during M2 to result from convergence of the Zimbabwe and Kaapvaal Cratons, which has led to subduction of oceanic lithosphere beneath the Zimbabwe Craton. Subsequent slab retreat has caused asthenosphere upwelling, thereby inducing delamination of the lithospheric mantle. Intrusion of hot asthenospheric material beneath the crust induced early UHT metamorphism at mid-crustal levels. The subsequent moderate pressure increase was related to the ensuing collision of the cratons. Post-peak decompression records incorporation of the enclave into the Bulai pluton melt and uplift in the ascending granitoid melt. The peak M3-assemblage garnet-cordierite-sillimanite-K-feldspar-rutile-plagioclase-quartz formed in metapelites occurring outside the pluton during near-UHT conditions (ca. 880 °C, 7.5 kbar). Cordierite coronas around garnet record subsequent decompression. New growth of garnet and sillimanite at the expense of cordierite documents late near-isobaric cooling to

The Central Zone of Limpopo Belt is a polymetamorphic and complexly deformed Precambrian terrane whose tectonic evolution is still uncertain because details on the timing of its evolution are not well established. We report zircon ages for newly discovered rocks in the Central Zone which document three distinct high-grade tectono-metamorphic events at 3.22, 2.62 and 2.02 Ga. The youngest of these has been well established, but the older two events were so far largely based only on rare zircon overgrowth rims. Most of our samples were collected from a large enclave in the 2.61 Ga Bulai pluton and constitute a strongly deformed, brecciated high-grade assemblage of supracrustal rocks, meta-anorthosite and granitoid gneisses, some of which are most likely equivalents of the pre-3.33 Ga Beit Bridge Complex. Magmatic zircon ages of 3.34–3.33 Ga for anorthositic and tonalitic gneisses in the enclave breccia support this correlation. Ca. 3.22 Ga metamorphic zircons, possibly reflecting the D1/M1 event, were only found in one felsic granulite sample, and their regional significance remains uncertain. Abundant metamorphic zircons grew at ca. 2.62 Ga under granulite-facies conditions (D2/M2), and some of these experienced variable degrees of recrystallization and/or Pb-loss during the third granulite-facies event at ca. 2.0 Ga (D3/M3). Rocks outside the Bulai enclave contain abundant newly-formed ca. 2.02 Ga metamorphic zircons but only rarely preserve evidence for the ca. 2.62 Ga event since these late Archaean zircons show strong recrystallization and/or Pb-loss at ca. 2.0 Ga. We suggest that the Bulai pluton “protected” the rocks inside the enclave from severe overprinting at ca. 2.0 Ga because these rocks remained dry, whereas the assemblages outside the Bulai pluton experienced fluid-assisted metamorphic overprinting at ca. 2.0 Ga. Our new data sugggest that the tectonic evolution of the Central Zone was more complex than previously thought. We favour a scenario where collision involving the Limpopo Belt occurred in the Neoarchaean, whereas the high-grade Palaeoproterozoic event was most likely intracontinental and records far-field effects of plate movements elsewhere. The tectonic setting controlling the early Archaean D1/M1 event remains unknown, largely because of insufficient data and extensive overprinting during later times.

The U-Th-Pb isotopic data from detrital zircon grains from five samples of Archean quartzite from the Mt. Alfred area of the Illaara greenstone belt in the Yilgarn Craton of Western Australia are presented in this study. The zircon grains are typically fractured and contain both irregular and oscillatory zoned internal structures as revealed by cathodoluminescence imaging. Concordant 207Pb/206Pb ages range between 3109 ± 17 and 3918 ± 16 Ma (2σ), with three main age peaks at ca. 3640, 3690 and 3760 Ma. Older 207Pb/206Pb ages up to 4067 ± 5 Ma are strongly affected by at least one recent disturbance event, however one single-grain discordia yields an upper intercept age of 4107 ± 12 (MSWD = 1.2). A further sixteen zircon grains with multiple analyses define discordia that suggest U-Pb disturbance events in the Neoarchean and the Mesozoic, the latter as a result of invasive low temperature weathering solutions. The notable lack of grains with ages less than ∼3.6 Ga in the Mt. Alfred detrital zircon population differentiates it from other quartzite samples from both the Illaara Formation and the Eoarchean zircon-bearing metasedimentary rocks of the Narryer Terrane. Also, the limited spread of zircon ages between 3640 and 3760 Ma suggests a relatively uniform and possibly local source region. However, no rocks of this age have been found in the Youanmi Terrane. This implies either the distal transport of similarly aged clastic sediments at 3.1 Ga from the Narryer Gneiss Complex (NGC) to the Mt. Alfred area, or the previous existence of NGC-like rocks near the Illaara greenstone belt that are either not currently recognised or have since been destroyed.

Linear chains of Deformed Alkaline Rocks and Carbonatites (DARCs) mark sutures where continents had rifted apart and later amalgamated. Since DARCs are products of two well-defined components of Wilson cycle, i.e., continental rifting and subsequent collision, geochronological constraints from DARCs along the Singhbhum/Bastar Craton-Eastern Ghats Belt contact in eastern India is used to unravel the history of continental breakup and amalgamation in the Indo-Antarctic Enderbia continent. Proto India and East Antarctica were involved in several episodes of collision and breakup during the assembly of past supercontinents. The Napier Complex of East Antarctica collided with the Dharwar Craton and Ongole Domain at 1.60 Ga forming the central-eastern Indian shield. Zircon U-Pb ages from DARCs at the craton-Eastern Ghats Belt margin show that the alkaline complexes (Kamakhyanagar: 1350 ± 14 Ma; Rairakhol: 1379 ± 6 Ma; Koraput: 1387 ± 34 Ma; Kunavaram: 1360 ± 5 Ma; Jojuru: 1352 ± 6 Ma) were emplaced between 1320 Ma and 1370 Ma. The alkaline magmatism marks an episode of rifting in the Indo-Antarctic continental fragment, correlatable with the breakup of the Columbia supercontinent. The Khariar alkaline complex was emplaced at 1478 ± 5 Ma during an earlier phase of crustal extension coeval with the formation of the Mesoproterozoic Chattisgarh rift basin. Metamorphic zircons from the alkaline rocks furnish age populations at 953–930 Ma, 808–795 Ma, and 661–563 Ma. The 953–930 Ma ages are correlated with oceanic closure between Ruker Terrane of East Antarctica and India during Rodinia assembly. The resultant collision of the Ruker Terrane with India-Napier Complex composite produced the Grenville-age Eastern Ghats Province-Rayner Complex orogen. The 808–795 Ma ages record disintegration of Rodinia when India broke away from East Antarctica. In the early Paleozoic, India redocked with East Antarctica and Australia during Gondwanaland assembly. The 661–563 Ma zircon ages date the resulting collisions during Pan-African orogenesis. The assembly of the Eastern Ghats Province and the Rayner Complex with the Bastar-Singhbhum Craton occurred in the early Neoproterozoic during the final stages of Rodinia assembly, supporting the existence of Enderbia continent comprising crustal units from India and East Antarctica.

The origin of the North Lhasa terrane in Tibet remains enigmatic. Our study reports the first evidence for Ediacaran magmatic rocks, including gabbros (ca. 572 Ma), tonalites (ca. 568 Ma), and rhyolites (ca. 547–541 Ma), in the North Lhasa terrane, Tibet. Gabbros are calc–alkaline and exhibit arc-like (e.g., enrichments of Rb and Pb and depletions of Nb, Ta, P, and Ti) geochemical affinities. These gabbros have variable zircon eHf(t) values (−5.5 to +0.9) and they are probably derived from partial melting of an enriched lithospheric mantle source triggered by a subduction event. Tonalites are high-K calc–alkaline and exhibit negative zircon eHf(t) values (−9.1 to −0.8). They can be attributed to partial melting of a thickened lower continental crust with minor mantle-derived component. Rhyolites have negative zircon eHf(t) values (−6.1 to −1.2) and they were probably products of partial melting of Paleoproterozoic metasedimentary rocks. These Ediacaran magmatic rocks were interpreted as a result of the Andean-type subduction along the Gondwanan Proto-Tethyan margin. Coeval Andean-type magmatism has been documented along the northern Arabian margin but absent in the northern India or Australia. Integrating previous studies with the data presented in this contribution, we suggest that the North Lhasa terrane was most likely located in the transitional area between the Arabian and Indian–Australian proto-Tethyan margins in the Ediacaran and it originated from the northern segment of the East African orogen.

Petrography, whole rock geochemistry, and in-situ U-Pb zircon geochronology on quartz potassic syenite in Iwo area, southwestern Nigeria have been performed. The results indicate that the syenite was syn-tectonically emplaced during the Pan-African orogeny and shows heterogeneous deformation. On the basis of geochemical data, the rock is defined as high potassic calc-alkaline derived from metasomatised mantle with slight crustal contamination. The small negative europium (Eu) anomalies (Eu/Eu∗ = 0.87) displayed by the rock could be an indication of separation of amphibole and pyroxene. In-situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry U-Pb zircon dating yielded a Concordia age of 642 ± 6 Ma which could be taken as that of emplacement and deformation. The relative position of the Iwo quartz potassic syenite in respect to the other undeformed syenite bodies in southwestern Nigeria and the main Pan-African suture zone suggest amalgamation of at least four terranes or micro blocks in the southwestern Nigeria during the Neoproterozoic time. The emplacement and deformation of the Iwo quartz potassic syenite were synchronous with basin closure around Ilesha-Ife and subsequent collision of two terranes/micro blocks. The collision resulted from a west-dipping subduction related tectonics which was different from the main Pan-African subduction zone at the margin of the West African craton. The amalgamation of these terranes contributed to the accretion of the Gondwanaland in the southern part of the Trans Saharan fold belt.

The Neoproterozoic geology of East Africa records the events leading up to the formation of Gondwana and subsequently Pangea, and hence understanding the geodynamic history of this area offers a unique insight into supercontinent development. Eighteen new U-Pb zircon and two U-Pb monazite ages were collected in conjunction with 110 whole-rock lithogeochemistry analyses from a region of south-east Tanzania we designate the ‘Ntaka Terrane’. These new data suggest this area of the East African Orogen constitutes an exotic nappe terrane that was part of the Mozambique Ocean in the Neoproterozoic. The lithological sequence in the region consists of a 770–720 Ma ‘basement’ of intermediate-felsic paragneiss possibly derived from a volcano-sedimentary sequence and recording arc-like geochemical signatures. These are intruded by 700–650 Ma amphibolites (±garnet) with mafic-intermediate magmatic protoliths that also have arc-like geochemistry. This sequence is then intruded by a set of ca. 670–650 Ma ultramafic, dominantly pyroxenitic sills collectively termed the Ntaka Ultramafic Complex, which have a much more mantle-like, non-arc origin, possibly formed as the island-arc intersected a mantle plume ‘hot spot’. The mafic-intermediate intrusives occur synchronous with, and outlast, the high-Mg basalt magmatism, suggesting that this latter event was transient in the context of the overall tectonic regime. The final magmatic event in the terrane is the intrusion of 640–620 Ma syn-orogenic granites that are coeval with 640–600 Ma upper amphibolite-granulite facies metamorphism. The broader geodynamic setting consisted of the Congo-Tanzania-Bangweulu Block of east Africa to the west and the Azania Block to the east of the Neomozambique Ocean, both of which contain Archean-Paleoproterozoic detritus. Based on the island arc-like geochemical characteristics of the 700–650 Ma mafic intrusive rocks and the lack of detrital zircons >1000 Ma, we suggest that the Ntaka Terrane represents a Neoproterozoic intra-oceanic island arc which was accreted to either East Africa or Azania shortly before full continental collision (the East African Orogeny) at ca. 640–620 Ma. Data from the Ntaka Terrane correlate with the Vohibory Terrane (Madagascar), Eastern Granulites (northern Tanzania) and Cabo Delgado Nappe Complex (Mozambique), suggesting these areas represent a set of broadly correlative oceanic terranes.

The basement of the Tarim Craton in NW China is divided into northern and southern terranes by the central 1500 km long Central Tarim Terrain (CTT) demarcated by a high aeromagnetic anomaly. However, the nature of the CTT remains enigmatic because of sparse data from basement below the deep basin. In this contribution we report new U-Pb ages from Precambrian granites from boreholes in the CTT to constrain the timing of the assembly of the northern and southern Tarim terranes. Zircon U-Pb ages from four samples of metagranite yielded four U-Pb ages of 1927.3 ± 7.5 Ma and 1920.4 ± 9.8 Ma, 1915.3 ± 5.4 Ma and 1968 ± 8.4 Ma along the CTT. Geochemically, the granitoids display high K2O and high K2O/Na2O ratios, showing their high-potassium calc-alkaline nature. They are rich in Ba, Sr, LREE and LILE, and depleted in Nb, Ta, Ti and Nd, Zr, Y, with variable negative Eu anomaly. The zircons have a large range of eHf(t) values (−14.6–16.1). Geochemical and isotopic characteristics suggest that the granites were derived from partial melting of crust and partial of the depleted mantle, and are geodynamically related to subduction in an arc setting. Collectively, our study argues that the assembly of the northern and southern Tarim terranes took place in the late Paleoproterozoic rather than the Neoproterozoic. We suggest that the amalgamation between the southern and northern terranes was completed by ∼1.91 Ga, which led to extensive contemporaneous magmatism rather than the assembly with the Columbia supercontinent.

According to present views, the crustal terranes of the Anabar province of the Siberian craton were initially independent blocks, separated from the convecting mantle at 3.1 (Daldyn terrane), 2.9 (Magan terrane) and 2.5 Ga (Markha terrane) (Rosen, 2003, 2004; Rosen et al., 1994, 2005, 2009). Previous studies of zircons in a suite of crustal xenoliths from kimberlite pipes of the Markha terrane concluded that the evolution of the crust of the Markha terrane is very similar to that of the Daldyn terrane. To test this conclusion we present results of U-Pb and Hf-isotope studies on zircons in crustal xenoliths from the Zapolyarnaya kimberlite pipe (Upper Muna kimberlite field), located within the Daldyn terrane, and the Botuobinskaya pipe (Nakyn kimberlite field) in the center of the Markha terrane. The data on xenoliths from the Botuobinskaya kimberlite pipe record tectonothermal events at 2.94, 2.8, 2.7 and 2 Ga. The event at 2 Ga caused Pb loss in zircons from a mafic granulite. U-Pb dating of zircons from the Zapolyarnaya pipe gives an age of 2.7 Ga. All zircons from the studied crustal xenoliths have Archean Hf model ages ranging from 3.65 to 3.11 Ga. This relatively narrow range suggests that reworking of the ancient crust beneath the Nakyn and Upper Muna kimberlite fields was minor, compared with the Daldyn and Alakit-Markha fields (Shatsky et al., 2016). This study, when combined with dating of detrital zircons, implies that tectonic-thermal events at 2.9–2.85, 2.75–2.7 and 2.0–1.95 Ga occurred everywhere on the Anabar tectonic province, and could reflect the upwelling of superplumes at 2.9, 2.7 and 2 Ga. The presence of the same tectonic-thermal events in the Daldyn and Markha terranes (Rosen et al., 2006a,b) supports the conclusion that the identification of the Markha terrane as a separate unit is not valid.

Declining gold discoveries underscore the importance of informed geological models for future exploration. The genesis of many gold deposits remains ambiguous, but integrated structural and chronological studies shed light on key questions of source, timing and geodynamic setting. The Hammond Reef gold deposit is unusual in that it is hosted in Mesoarchean tonalite of the Wabigoon superterrane, rather than in Neoarchean greenstone belt terranes, as is common elsewhere in the Superior Province. Gold deposition at Hammond Reef occurred in two stages: The main stage of disseminated low-grade mineralization was followed by discrete, channelized veins, both tied to regional tectonic events. Disseminated mineralization is associated with localized sulfidation and chlorite breakdown within a sericitized deformation zone adjacent to the locked greenstone-gneiss boundary. Chlorite-leached halos around small fractures at the deposit margins indicate that fluid penetration into the tonalite was guided by fractures concentrated in the broad deformation corridor. Pervasive alteration was enhanced by grain-scale flow. Hammond Reef may have been particularly susceptible to sulfidation and associated gold precipitation due to the greater local abundance of mafic dykes and chlorite-rich enclaves in the tonalite. The secondary gold mineralization phase is associated with younger and discrete auriferous quartz-carbonate veins that were episodically emplaced along pre-existing structures. Cross-cutting relationships show that both mineralization phases post-date the emplacement of the 2.889 Ga Diversion Stock. The kinematics of mineralized structures relate Hammond Reef to the 2.7 Ga northward subduction of the Wawa terrane beneath the Wabigoon superterrane. This places Hammond Reef in a supra-subduction setting, where an older dormant fault zone with enhanced permeability was infiltrated by auriferous fluids during the an orogeny up to 200 million years later. The two phases of gold enrichment present disseminated and channelized fluid flow through the available permeable pathways within the same regional tectonic setting.