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We formulate a numerical framework, in both 2d and 3d, to model the structural patterns emerging from creeping viscous flow typically encountered in long‐term ductile lithospheric deformation by coupling the discontinuous Galerkin level set method with a finite element Stokes‐like flow solver. The level set formulation has the advantage of retaining information on the interface geometry, decreased memory requirement and improved computational efficiency from the two‐way particle‐mesh information transfer compared to particle‐in‐cell methods. Furthermore, our formulation fully exploits the advantages of the finite element method (e.g., the flexibility of mesh geometry and the ease of handling anisotropic materials) by using a unified finite element framework. The novelty of our formulation is the capability to offer a fully dynamic approach for modeling structural patterns resulting from a tectonic flow that is non‐steady and inhomogeneous. The material distribution and the finite deformation patterns predicted from the numerical model can be directly compared with geological map patterns (e.g., lithological distribution at specified depths and on cross‐sections) and field structural analyses (e.g., foliation, lineation and strain patterns), thus offering the possibility of ground‐truthing the modeling results by field evidence. As examples for potential applications of our method, we apply our method to the modeling of a competent inclusion in simple shear flow, as well as a Rayleigh‐Taylor type density overturn. Our models demonstrate good agreement with previous 2d benchmark results and produce 3d lithological and deformation patterns comparable to field observations. Plain Language Summary: A novel modeling method is proposed to simulate the ductile deformation patterns resulting from viscous tectonic flow. Domains of different material properties are efficiently captured by the scalar level set function, which describes the signed distance to the domain interface. The level set field, paired with passive tracer particles, enables the modeling of the spatial distribution of lithological units, regional fold patterns of stratigraphic layers as well as finite deformation patterns (in terms of foliation/lineation patterns, strain history and strain intensity) in 3d block model, horizontal slices at certain depth level and vertical cross‐sections. Simulated cross‐sections and geological maps can be constructed along any direction and at any depth, thus allowing direct comparison between numerical models and field data obtained from geological mapping. Key Points: We implement a method for simulating tectonic flow in both 2d and 3d capable of predicting ductile deformation patternsAreas of different material properties are efficiently captured with the level set method on a stationary meshTracer particles record simulated strain ellipsoids, thus facilitating comparisons between model results and field data [ABSTRACT FROM AUTHOR]

The Gubaoquan area is located in the southern part of the Palaeozoic Beishan Orogenic Collage of the Central Asian Orogenic Belt in northwest China. Structural analysis of the Gubaoquan area has documented multiple phases of deformation, which challenge previous tectonic models and suggest that the eclogites formed through in-situ metamorphism. The study area is a highly deformed belt of metamorphic tectonites, intruded by syn-tectonic granitoids. The belt largely consists of D3 fabrics that developed after peak metamorphism, with only local preservation of D1 eclogite-facies fabrics in the cores of mafic boudins. Fabrics associated with D1–D4 document a clockwise metamorphic trajectory, characterised by eclogite–facies metamorphism (D1) followed by a large decrease in pressure and small decrease in temperature (D2), high-temperature low-pressure conditions (D3) and greenschist-facies metamorphism (D4). D2–D4 is associated with widespread N–S shortening and local extension. We propose that the metamorphic tectonite belt hosting the Gubaoquan eclogite represents Meso- to Neo-Proterozoic crust that underwent Ordovician–Silurian, north-directed subduction to various depths. The eclogite and its host were detached from the down-going slab, probably due to slab break-off and leading to extensive syn-tectonic magmatism. Exhumation probably occurred in an extruding-wedge-type setting. Convergence continued until the emplacement of the Silurian–Devonian granitoids. [ABSTRACT FROM AUTHOR]

Abstract The Dunhuang Tectonic Belt (DTB) is located about 100 km south of the Beishan–Tianshan orogen in the Central Asian Orogenic Belt in NW China. It was previously considered as a part of the Tarim or North China craton. Detailed structural analyses reveal two episodes of deformation in the central DTB, D1 and D2. D1 is a north-side-up reverse shear, and D2 a dextral strike slip. Mineral assemblages, microstructures and quartz C-axis patterns indicate that D1 deformation took place under amphibolite facies conditions (500 to 600 °C) and D2 mostly under greenschist-facies conditions (300–450 °C). U–Pb zircon dating of eight granitoid/intermediate intrusions (mostly dikes, with well constrained cross-cutting relationships with the D1 and D2 structures) and an amphibolite gneiss indicates that D1 deformation took place before ca. 349 Ma and most likely at ca. 406 Ma, and D2 between ca. 249 Ma and ca. 241 Ma. The DTB has a structural, metamorphic and magmatic signature in the Paleozoic–Mesozoic that is typical of an orogenic belt. It shares a similar geological history with the Beishan–Tianshan orogen and is likely a part of the Central Asian Orogenic Belt. The DTB and the Beishan-Tianshan orogen might represent two separate Paleozoic mountain belts that developed more or less synchronously on the south and north sides, respectively, of the last vestige of the Paleo-Asian Ocean before its terminal closure in the Permian. The D1 reverse shearing in the DTB is interpreted to be related to a Silurian–Devonian terrane accretion/collision and the D2 dextral strike slip to post-accretional/collisional movement among terranes in Late Permian–Middle Triassic time. Highlights • Two episodes of deformation are recognized in the Dunhuang Tectonic Belt (DTB): D1, a N-side-up reverse shear, and D2, a dextral strike slip. • U–Pb zircon dating indicates that D1 took place before ca. 349 Ma and most likely at ca. 406 Ma, and D2 at ca. 249–241 Ma. • The DTB has characteristics in the Paleozoic–Mesozoic that are typical of an orogenic belt and is likely a part of the Central Asian Orogenic Belt. • The DTB might represent a Paleozoic mountain belt that developed on the south side of the last vestige of the Paleo-Asian Ocean. [ABSTRACT FROM AUTHOR]

U–Pb ages and Hf isotope compositions of zircons from the Chencai complex in Zhejiang Province have been determined to provide constraints on mechanisms of migmatization and tectonic evolution related to the early Palaeozoic orogeny in the Cathaysia Block, South China. Zircons from leucosome samples of migmatites are characterized by nebulous overgrowths enclosing inherited cores or occur as newly formed grains with weak zoning. Five samples gave weighted mean ages ranging from 438±3 Ma to 432±4 Ma, which are interpreted as recording the time of anatexis of a regional tectono-thermal event. Their ε Hf(t) values range from −21.4 to −4.8 (with peak at −11), with corresponding T DM2 ages of 1.73–2.77 Ga (with peak at c. 1.9–2.3 Ga), suggesting that the protoliths formed by reworking of ancient crust evolved from Late Palaeoproterozoic – early Archaean crust–mantle differentiation. The migmatization was spatially and temporally associated with reported 460–435 Ma metamorphism with a clockwise pressure–temperature (P – T) path and was most likely controlled by crustal thickening driven by the early Palaeozoic orogenesis. The T DM2 ages of the Chencai complex are consistent with those of the Wuyi–Yunkai structural belt in the Cathaysia Block, but distinct from those (with peak at 2.7–3.0 Ga) of the Badu complex which lacks early Palaeozoic tectono-thermal records. The data support the suggestion that a postulated geological entity, instead of the east domain (the Badu complex being its main part) of the Cathaysia Block, was probably involved in the early Palaeozoic orogeny. [ABSTRACT FROM AUTHOR]

An integrated study of zircon U-Pb geochronology and geochemistry, together with Nd-Hf isotopes, have been carried out on the rhyodacite and rhyolitic tuff of the Jingtan Formation in the eastern part of the Jiangnan orogen. SIMS zircon U-Pb dating of two samples yielded weighted mean 206 Pb/ 238 U ages of 784 ± 6 Ma and 788 ± 6 Ma, respectively. Geochemically, they are peraluminous (A/CNK mostly around 1.2) and are characterized by enrichments in Rb, Th, REEs and HFSEs (e.g. Zr and Y) but depletions in Ba, Sr, P, Eu and Ti. The volcanic rocks show a clear A-type granite geochemical signature with high total alkalis (K 2 O + Na 2 O = 5.3–7.64 wt%), FeO t /MgO ratios and low CaO, MgO and TiO 2 contents. They have negative whole-rock ε Nd (t) (−4.2 to −1) and positive zircon ε Hf (t) (+1.26 to +11.6) values, illustrating decoupled Nd-Hf isotopes which may be genetically related to their petrogenesis process. The positive ε Hf (t) values and juvenile T Hf DM1 (0.89–1.3 Ga) of zircons indicate that the volcanic rocks may have been derived from the partial melting of the Neoproterozoic to late Mesoproterozoic crustal materials. Combined with the occurrence of significant volumes of contemporary bimodal volcanic rocks in eastern section of the Jiangnan orogen, it is inferred that the Jingtan felsic volcanic rocks formed during post-collisional extension shortly after the final amalgamation of Yangtze and Cathaysia blocks. [ABSTRACT FROM AUTHOR]

The Jingdezhen ductile shear zone is evolved from the Neoproterozoic Zhangyuan ophiolite mélange belt in the eastern Jiangnan Orogen, South China. Comprehensive study of geometry, kinematics, quartz c-axis fabric, temperature-pressure conditions and geochronology were conducted in this study. The Jingdezhen shear zone extends ∼180 km along the NE orientation with two groups of subvertical foliation and subhorizontal lineation. One group of foliation strikes NEN orientation whereas another one NEE orientation. Field investigation, microscopic observation and quartz c-axis fabric show that sinistral shearing along NEN-striking foliation occurred earlier than dextral shearing along NEE-striking foliation. Syn-tectonic staurolite porphyroblasts and deformation manner of feldspar imply that sinistral shearing occurred at 530-420 ºC and 6-2 kbar. Deformation manner and c-axis fabric of quartz and pre-tectonic staurolite porphyroblasts indicate that dextral shearing took place at 420-300 ºC. LA-ICP-MS zircon U-Pb and mica 40Ar/39Ar dating indicate that the sinistral shearing occurred during Neoproterozoic orogeny (830-800 Ma) whereas the dextral shearing at 447±12 Ma. The sinistral shearing resulted from the Neoproterozoic final assembly between the Yangtze and Cathaysia blocks. The dextral shearing was caused by Early Paleozoic orogen parallel extension and clockwise rotation. [ABSTRACT FROM AUTHOR]

Abstract: Large‐scale magmatism affected the Tongbai‐Dabie orogenic belt during post‐collisional lateral tectonic extension in the Cretaceous, which was suggested to account for the widespread deformation and migmatization in the Tongbai‐Dabie complexes. However, it cannot explain the most deformations in the shear zones. The northwest‐southeast shear zones are developed around or wrapped the Tongbai‐Dabie complexes. They play an important role for the interpretation of the tectonic evolution of the Tongbai‐Dabie orogenic belt. By a systematically observation and description of the geometry and kinematics of these shear zones, we found that the shear zones to the north dip NE and have a uniform sinistral shear sense, the shear zone to the south dips SW and has a uniform dextral shear sense, and the shear zones at the core are sub‐horizontal and have a uniform top‐to‐NW sense of shear. Combining with the comparison of previous and our geochronological studies, we interpret these associations as indicating that these shear zones were originally a single, more flat‐lying and sub‐horizontal shear zone with a uniform top‐to‐NW shear sense before the folding‐doming of the Tongbai‐Dabie complexes and suggest that the Tongbai‐Dabie orogenic belt experienced a uniform top‐to‐NW orogen‐parallel extension in the ductile lithosphere before the widespread magmatism in the Cretaceous. [ABSTRACT FROM AUTHOR]

The detrital zircon geochronological record of Permian-Triassic clastic rocks of the Beishan region in the southern Central Asian orogenic belt indicates a pattern of cyclical, successive Paleozoic accretion events. Comparison of zircon age spectra derived from two individual arc terranes reveals similar age patterns offset by 30-40 m.y. Detrital samples with a provenance interpreted as the southern arc terrane indicate magmatic peaks at 275, 370, and 430 Ma with a 50 m.y. hiatus from 350 to 300 Ma. Samples with a provenance interpreted as the northern arc terrane exhibit a similar pattern yet with consistently earlier component peaks at 310, 400, and 445 Ma with a 40 m.y. hiatus from 380 to 340 Ma. This is interpreted to reflect that subduction developed successively between terranes and progressed until Silurian-Devonian sequential docking of the arcs along separate suture zones. Detrital geochronology of accreted sediments (single peak at 445 Ma) within the northern suture, with coincident tuff and pillow basalt U-Pb zircon ages of 409 ± 2.9 and 416.6 ± 15.0 Ma, respectively, may redefine a principal phase of amalgamation as Devonian, over previously interpreted ages in the Carboniferous-Permian. Initiation and cessation of arc magmatism are shown to correlate with regional phases of ophiolite generation and emplacement, respectively. This supports regional models that ophiolite belts in the Central Asian orogenic belt correlate with suture zones developed from multiple contemporaneous subduction systems between arcs. We explore whether a pericratonic archipelago of crustal slivers around the Tarim craton may have initiated successive arc formation. [ABSTRACT FROM AUTHOR]

The Tongbai orogenic belt has an overall antiformal geometry and the hinge of the antiform is sub-horizontal and trends NW–SE. The Tongbai complex (TBC) in the core of the antiform is bounded by the S-dipping Yindian–Malong shear zone in the south, the sub-horizontal Taibaiding shear zone at the top and the N-dipping Hongyihe–Tongbai shear zone in the north. The three shear zones have dextral, top-to-NW and sinistral movement, respectively. They are parts of a single shear zone, termed the Tongbai shear zone, that has a uniform top-to-NW sense of shear. Three samples of deformed granitoid (mylonite or protomylonite) from the shear zone have U–Pb zircon ages of 145 ± 6 Ma, 142 ± 2 Ma and 131 ± 6 Ma, respectively. An L-tectonite in the TBC yielded a metamorphic age of 137 ± 8 Ma and a migmatite an age of 137 ± 1 Ma. The Tongbai shear zone is intruded by undeformed Early Cretaceous granite and dykes and deformation in the shear zone is constrained to ca. 140–135 Ma, synchronous with metamorphism and migmatization in the TBC. Early Cretaceous magma emplacement and the associated uplift modified the TBC into a gentle antiform and the uplift may have continued to ca. 102–85 Ma. Similar geometry and kinematics have been documented in the Dabie orogenic belt to the east, which suggests that the Central Orogenic Belt in China probably experienced a uniform orogen-parallel extension and top-to-NW shearing in the ductile lithosphere in the Early Cretaceous. [ABSTRACT FROM PUBLISHER]

L tectonite is well developed and widely distributed in the Tongbai orogenic belt in central China. The orogenic belt as a whole has an antiformal geometry and the hinge of the antiform is subhorizontal and trends NW-SE. The L tectonite occurs in the core of the antiform, in a zone that is 10–30 km wide and over 100 km long. Lineations in the L tectonite are sub-horizontal, parallel to the hinge of the antiform. Sheath folds are also well developed associated with the L tectonite, with the hinges parallel to the lineations. Migmatite occurs in the core and structurally below the L tectonite and has a gradational relationship with the L tectonite. The domain of L tectonite is bounded by three ductile shear zones, on the north, at the top and on the south, respectively. Well-developed shear sense indicators indicate that the southern, the overlying and the northern shear zones have a dextral, top-to-NW and sinistral sense of shear, respectively. These geometrical and kinematic data indicate that the three shear zones are likely part of a single shear zone that wraps around the L-tectonite domain. The L-tectonite zone in the core moves southeast relative to the hanging wall. The development of the tectonite is interpreted to be a result of this special geometry and kinematics and reflects a post-collisional orogen-parallel extension synchronous with migmatization and the continuing convergence between the Yangtze Block and the North China Block in the Early Cretaceous. [ABSTRACT FROM AUTHOR]

The Central Manitoba mine trend is one of the most important lode gold districts in the Rice Lake greenstone–granitoid belt of the western Uchi subprovince within western Superior Province, Manitoba, Canada. Neoarchean host rocks consist of a south-facing metavolcano-sedimentary succession (2.75–2.73 Ga) intruded by voluminous gabbroic sills and tonalitic–granodioritic plutons (2.73–2.72 Ga), as well as late aplite dikes (2.73–2.72 Ga) and quartz-feldspar porphyry dikes (2.73–2.71 Ga). Five generations (G 1 –G 5 ) of deformation structures have been recognized through detailed geological mapping. The entire succession was folded during G 1 and G 2 prior to rare late aplite dike emplacement. All fault-fill veins and extension veins cut all lithologic units, and are structurally governed by late (G 3 and G 4 ) conjugate shear zones. Main gold mineralization occurs within fault-fill veins hosted by west-trending steeply-dipping (G 4 ) dextral brittle–ductile and ductile shear zones, which occur along or across contacts of metabasalt, metagreywacke and metagabbro or entirely within metagabbro. Microstructural and paragenetic analyses on main gold-bearing veins have revealed that gold is intimately associated with quartz, pyrrhotite and tellurobismuthite. Main gold introduction is interpreted to have taken place contemporaneously with pyrrhotite and tellurobismuthite deposition early during G 4 shearing. These results in structural and mineralogical aspects at the Central Manitoba mine trend provide new constraints on structural evolution and gold mineralization of the southeastern Rice Lake belt, and can be used to improve exploration models for gold deposits in Archean terranes. [ABSTRACT FROM AUTHOR]

The Northern Liaoning Complex in northeastern China constitutes an important component of the Eastern Block in the North China Craton. The major lithologies consist of Archean granitoid gneisses with minor supracrustal rocks occurring as tectonic lenses. This study presents zircon Lu–Hf isotopic data for the first time as well as new SHRIMP zircon U–Pb data of the major lithologies from the Northern Liaoning Complex, in order to elucidate the crustal evolution of the complex and provide new constraints on the Neoarchean crustal evolution of the Eastern Block in the North China Craton. Magmatic zircon U–Pb data from this study show that the protolith magmas of the supracrustal rocks and granitoid gneisses were generated during ∼2.55–2.50 Ga. Metamorphic zircons document consistent metamorphic ages at 2.49–2.48 Ga, suggesting a regional metamorphic event immediately after the magmatism at the end of the Neoarchean in the Northern Liaoning Complex. Inherited/detrital zircons of 2.79–2.60 Ga suggest possible existence of ancient crust in this region. Zircon Lu–Hf isotopic compositions show that the magmatic zircons have variable ɛ Hf ( t ) values from −4.0 to +9.0 with depleted mantle model ages of 3.6–2.5 Ga, of which most ɛ Hf ( t ) values are positive with a model age peak at 2.9–2.7 Ga. These zircon Hf signatures reveal major juvenile crustal growth with additions of older crustal materials during 2.9–2.7 Ga, and a crustal reworking event with minor juvenile additions at 2.6–2.5 Ga in the studied area. Integrated with previous data from other Neoarchean complexes in the Eastern Block, both the major juvenile crustal growth during 2.9–2.7 Ga and the strong crustal reworking at 2.6–2.5 Ga contribute to the extensive Neoarchean crust formation of the Eastern Block in the North China Craton. The North China Craton share similar Neoarchean continental crustal evolution to other cratons in the world, though it is distinctively featured by intensive tectonothermal overprinting at the end of the Neoarchean. [ABSTRACT FROM AUTHOR]

The volcanic rocks in the eastern part of Jiangnan orogen provide an important suite to investigate magma petrogenesis and tectonic evolution of South China Block. We carried out a combined study of geochronology and geochemistry for the bimodal association of basalts and rhyolitic tuffs from the Shuangqiaoshan Group in south Anhui Province. Zircons from a basalt and two rhyolitic tuff samples yield crystallization ages of 829 ± 12 Ma, 832 ± 9 Ma and 832 ± 10 Ma, respectively. The basalts are characterized by left-sloping REE distribution patterns, enriched large iron lithosphere elements (LILEs, e.g. Rb, Ba, K) and depleted high field strength elements (HFSEs, e.g. Nb, Ta) relative to those in N-MORB, resembling those of modern Central Lau back-arc basin basalts (BABB). In addition, they have positive ɛ Nd ( t ) values (+4.6 to +5.7) with initial 87 Sr/ 86 Sr ratios in the range of 0.70706–0.70719. These geochemical and isotopic signatures indicate that the basalts were derived from an N-MORB-like source modified by slab-derived fluids. The rhyolitic tuffs have high SiO 2 (72.9–78.3 wt %) contents and high 10,000*Ga/Al ratios (mostly >2.6). Taking into account their aluminous nature (A/CNK > 1.1), they are affinitive to aluminous A-type granites. They invariably show a relative enrichment in light-REE, and strong negative Eu anomalies (Eu/Eu* = 0.16–0.31) and negative anomalies in HFSE, Sr and P compared with the neighboring elements in their trace element spidergrams. Their ɛ Nd ( t ) values range from −2.1 to +0.1. Detailed elemental and isotopic data suggest that the rhyolitic tuffs formed by partial melting of mafic lower crust triggered by asthenosphere upwelling. The occurrence of bimodal volcanic rocks with the basalts showing geochemical affinity to intra-oceanic BABB appears to support the development of a Neoproterozoic back-arc basin in the eastern part of Jiangnan orogen at ca. 830 Ma. Combined with the published data from central and western part of Jiangnan orogen, it is inferred that the back-arc basin developed in the entire Jiangnan orogen during 850–810 Ma. Considering the age of the strata overlying the folded basement sequence, we suggest that the final collision of the Yangtze and Cathaysia blocks happened during 820–810 Ma along the Jiangnan orogen. [ABSTRACT FROM AUTHOR]

The Hongliuhe ophiolite is a fragment of the early Paleozoic oceanic crust situated in a suture zone central to the Beishan orogenic collage, which is a subset to the Central Asian Orogenic Belt in Northwest China. It has lithologic, geochemical and chronological similarities to the Yueyashan–Xichangjing ophiolite 400 km east, along strike, allowing for correlative interpretations of marginal seafloor spreading processes. The Hongliuhe ophiolite is explored in this study with complete petrologic, geochemical and structural descriptions. The ultramafic body comprises cumulate-layered lherzolite and gabbro plutonic lithologies, tectonized with syn-magmatic extension. A U–Pb age of 520.3 ± 5.8 Ma was obtained by SHRIMP analysis of zircons from a pegmatitic gabbro. The ultramafic rocks are variably depleted and some show refertilization of LILE’s consistent with slab dehydration in a supra-subduction mantle wedge. Mineral chemistry shows high Cr# (36–82) populations of spinel, and wide-ranging lower Mg# (8–50), consistent with known forearc peridotite chemistry partially re-equilibrated by tectonism or through staged magmatism. Olivine and pyroxene chemistries are consistent with this interpretation. A thin volcanic cover is interlayered with red cherts, and has a bimodal set of geochemical signatures, both island-arc tholeiite and calc-alkaline. They bear distinct Nb–Ta anomalies consistent with slab-derived fluid initiated melting in a supra-subduction environment. Coarse volcaniclastic turbidites infilled paleo-topography along the ophiolite, and they are interbedded with quartzofeldspathic sandstones, indicating an initial proximity to an arc. The sandstones contain detrital spinel with analyses showing relation to both the ophiolite and possibly a secondary alkalic volcanic source. The supracrustal sequence continues with a thick, contiguous covering of margin-related rocks, including interlayered limestone, pyroclastic and siliciclastic rocks, and basalts. As a constraint on emplacement we provide an U–Pb Zircon SHRIMP date (413.6 ± 3.5 Ma) from an undeformed granitoid body intruded within the overlying stratigraphy. The entire analysis paints a picture of subduction rollback-related extension affecting the margin of an emerging or mature arc just prior to a known magmatic cycle that ended with a collision in the Devonian at the latest. This suture is one of many in the Beishan, and our interpretation provides evidence in a long running debate supporting accretionary orogenesis in an island-arc archipelago as the main system for growing sialic crust in the Paleozoic central Asia. [ABSTRACT FROM AUTHOR]

The Pikwitonei Granulite Domain (PGD), located in the northwestern Superior Province, is one of the largest Neoarchean high‐grade metamorphic domains in the world, and is a key to understanding the Neoarchean crustal evolution of the Superior Province. Here we report results of a study on ultrahigh temperature (UHT) granulites with a sapphirine + quartz‐bearing peak assemblage from the Sipiwesk Lake area in the PGD. Three stages of metamorphic assemblage development are recognized based on petrographic observations: Pre‐peak stage is marked by garnet, sillimanite, K‐feldspar, and biotite inclusions within sapphirine and orthopyroxene. Peak stage is charactered by the typical UHT associations of sapphirine + quartz and sapphirine + orthopyroxene. The retrograde stage is represented by the retrograde formation of cordierite, biotite and sillimanite in the matrix. Phase equilibrium modelling based on the bulk compositions of sapphirine‐bearing granulites suggest that the rocks have experienced extensional UHT metamorphism in excess of 1035°C at pressures of 7.9–9.0 kbar, followed by isobaric cooling process. SHRIMP U–Pb dating of metamorphic zircons in sapphirine‐bearing granulite record the timing of the UHT event in the PGD with a weighted mean 207Pb/206Pb age of 2681 ± 13 Ma. This study in combination with other metamorphic P–T paths and age information reveals that this UHT metamorphism at 2.68 Ga in PGD was generated by upwelling asthenosphere due to slab break‐off in collision during the amalgamation of the Superior Province. [ABSTRACT FROM AUTHOR]

Major element, trace element, and Sr–Nd–Pb isotopic compositions of Cenozoic diabase in southeastern China provide insights into the nature of their mantle sources and processes. The diabases are alkaline in lithochemistry (Na2O + K2O = 4.37–5.19 wt.%) and have overall oceanic island basalt-like trace element patterns, without negative Nb–Ta anomalies. In addition, they are characterized by lower La/Nb (<1.5) and La/Ta (<22), and higher Ce/Pb (>15) and Nb/U (>30) ratios, indicating an origin in the asthenospheric mantle. The relatively lower143Nd/144Nd (0.512632–0.512648) and206Pb/204Pb (18.20–18.22), but intermediate87Sr/86Sr (0.7061–0.7063) ratios of the diabases are similar to enriched mantle type 1, suggesting crustal contamination or mixing with metasomatized lithsopheric mantle. However, the low Th and U contents and lack of correlations of Nd isotope compositions and MgO preclude significant crustal contamination. Alternatively, the moderate TiO2contents (2.01–2.09 wt.%) and high Cr concentrations (>240 ppm) suggest interaction between asthenosphere-derived melts and metasomatized lithospheric mantle. Petrological modelling suggests that the diabases were generated from a low degree (~3–5%) of partial melting of lherzolite with ~2–3% garnet. Jiangxi diabase was generated in a within-plate extensional regime, probably related to the far effect of the Himalaya–Tibetan orogen. [ABSTRACT FROM PUBLISHER]

The Kongling terrane is a high grade metamorphic complex, exposed in the northern part of the Yangtze Block. It mainly consists of TTG gneisses, amphibolites, migmatites and metasedimentary rocks. The amphibolites occur as enclaves or layers in the TTG gneisses, and both the amphibolites and the TTG gneisses are intruded by granitic and diabasic dykes. U–Pb ages of zircons from the amphibolite, migmatite, granite and diabase are determined by LA-ICP-MS. Igneous zircons from an amphibolite have an upper intercept age of 2945 ± 13 Ma (MSWD = 1.2) while metamorphic zircons yield an upper intercept age of 2870 ± 13 Ma (MSWD = 0.9). Igneous zircons from a migmatite and a granite have weighted average 207 Pb/ 206 Pb age and upper intercept age of 1987 ± 5 Ma (MSWD = 1.7) and 1985 ± 6 Ma (MSWD = 1.3), respectively. Igneous zircons from a diabase dyke yield an upper intercept age of 1783 ± 23 Ma (MSWD = 0.86). The protoliths of the amphibolites are tholeiitic basalts and exhibit slightly depleted to variably enriched LREE patterns with moderate enrichment of Rb and Ba and depletion in Nb and Zr, similar to oceanic island arc volcanics. They have high Cr, Co, Ni, MgO and FeO T content with negative ɛ Nd ( t ) values, indicating that the tholeiitic basalts resulted from high degree batch melting of enriched mantle wedge. The granites are strongly peraluminous with A/CNK > 1.1 and they have relatively low HREE and Y and negative ɛ Nd ( t ) values. Detailed elemental and isotopic data suggest that they formed by partial melting of recycled products of the TTG gneisses, amphibolites and older crustal material in a continental collisional setting. The diabases are characterized by relatively high Al 2 O 3 , FeO T and TiO 2 contents and low Zr/Ba ratios. Their high initial 87 Sr/ 86 Sr ratios and negative ɛ Nd ( t ) values indicate that they were derived from enriched lithospheric mantle in extensional setting. Therefore, the Kongling terrane occurred as an oceanic island arc at ca. 2.95 Ga, and experienced earliest metamorphism at ca. 2.87 Ga which probably contributed to the formation of the high grade metamorphic terrane. This terrane experienced a strong collisional event at ∼2.0 Ga which may have led to cratonization over all of the Yangtze Block, and also experienced lithospheric extension during 1.85–1.78 Ga. The global ∼2.0 Ga Paleoproterozoic collisional events were related to the assembly of supercontinent Columbia. [ABSTRACT FROM AUTHOR]

The basis for understanding continental tectonics to a large degree relies on terrane recognition. However, discrepant identifications and interpretations of the same terrane as well as its boundary are still commonly seen in South China. For years, the central debate has been revolving around the Yangtze-Cathaysia boundary and West-East Cathaysia boundary. Here we characterized the geochemical patterns (or differences) of the proposed terranes and located their boundaries by using a big geochemical dataset of South China, which consists of compositions of 75 elements in 5231 sediment samples. To extract valuable information from this big geochemical dataset, we applied multiple data mining techniques, including principal component analysis, sequential binary partition, Sobel operator, and support vector machine. Our results show that the geochemical patterns vary distinctly at regional scale across both the subblocks (i.e., Yangtze and Cathaysia) and terranes (i.e., Jiuling, Huaiyu, and Youjiang). Accordingly, we conclude that 1) the Northeast Jiangxi fault marks not only the Jiuling-Huaiyu boundary but also the north-eastern Yangtze-Cathaysia boundary; 2) the Yangtze-Cathaysia boundary extends westward along the Jiangshan-Pingxiang-Chaling fault; and 3) a fault zone comprising the Northwest Fujian fault and Zhenghe-Dapu fault possibly demarcates the West and East Cathaysia. The boundaries defined by the contrasting geochemical patterns in this study are also supported by geophysical, Nd isotopic, and geological evidence. Our observations will allow better explanation of where the proposed terranes originated and how South China was assembled. Our work demonstrates that data mining techniques are effective in deriving and integrating information for solving geoscience problems. • We characterized geochemical patterns of multiple terranes of South China. • Big geochemical dataset containing 75 element compositions in 5231 sediments were used. • We located terrane boundaries in South China by applying multiple data mining methods. • Geophysical, isotopic, and geological studies support the boundaries defined herein. [ABSTRACT FROM AUTHOR]

Special Issue on Tectonic, Magmatic and Metallogenetic Evolution of the Central China Orogenic Belt. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report the detailed deformational structures of the Matachewan area. [•] We confirm that the Matachewan area is a western part of the CLLDZ. [•] Syenites are syntectonic intrusions and act as a competent trap for gold mineralization. [•] Major stages of auriferous veins were formed during the development of the CLLDZ. [Copyright &y& Elsevier]

Highlights: [•] Two stages (Meso- and Neoarchean) of south-dipping subduction along northern margin of North Caribou Terrane are proposed. [•] U–Pb zircon age data show two events of deformation at >∼2.72Ga and ∼2.70Ga. [•] Terminal collision occurred at ca. 2.70Ga. [Copyright &y& Elsevier]

Abstract: This paper presents petrography, zircon U–Pb ages and Hf isotopic data as well as whole-rock Sm–Nd isotopic data for mafic granulites, metapelitic rocks and high-grade marble from the Kongling Complex in the Yangtze Block, South China. Petrographic observations indicate that these three types of rocks experienced high-pressure metamorphism. Their mineral assemblages and P–T conditions define a clockwise P–T path involving isothermal decompression following the peak high-pressure metamorphism, which is considered to record a continent–continent collisional event. This is systematic documentation of the tectonic evolution of the Kongling Complex from 2.1-2.0Ga deposition (constrained by youngest detrital zircon and metamorphic zircon) through ~2.0Ga collision (high-pressure metamorphism) and syn-collisional partial melting (S-type granite and migmatization of TTG gneiss) to ~1.85Ga post-collisional extension (A-type high-K granite and mafic dyke). These ages are broadly coincident with global collisional events (2.1–1.8Ga) that led to the assembly of the Palaeo-Mesoproterozoic Columbia (or Nuna) supercontinent. Therefore, this study provides strong evidence that the Yangtze Block in South China was a component of the Columbia supercontinent. [Copyright &y& Elsevier]

Highlights: [•] We present ages of detrital zircons from a Neoarchean sedimentary sequence. [•] The age pattern supports basin formation by diapirism and sagduction. [•] Sagduction can bring such sedimentary rocks deep into the crust soon after deposition. [•] This is evidenced by a conglomerate in the mid to lower crust in the Kapuskasing uplift. [Copyright &y& Elsevier]

Highlights: [•] We identify a ca. 830–810Ma back-arc basin in the southeastern Yangtze Block. [•] The basalts of Shaojiwa Formation might have been derived from a slightly depleted mantle source metasomatized by fluid. [•] The rhyolites of Shaojiwa Formation can be explained by fractional crystallization of the basaltic magma. [•] The precursor magma of the amphibolites might have been originated from an N-MORB source modified by slab-derived fluids. [•] Widespread Neoproterozoic igneous rocks (850–810Ma) in the Jiangnan Orogen most likely occurred in back-arc environment. [Copyright &y& Elsevier]

Highlights: [•] A back-arc basin developed along the southeastern Yangtze Block at 842–825Ma. [•] Neoproterozoic juvenile crustal growth in the southeastern Yangtze Block. [•] Orogen-parallel motion played a significant role in amalgamation of South China. [ABSTRACT FROM AUTHOR]

Abstract: A SHRIMP U–Pb zircon age along with geochemical and Nd–Hf isotopic results are reported for the Tieshajie volcanic rocks in the southeastern Yangtze Block, South China. The Tieshajie volcanic rocks are bimodal in composition and are dominantly transitional alkaline basalts and alkaline rhyolites, with an eruption age of 1159±8Ma. The basaltic samples have high TiO2 (2.14–3.12%) and relatively low Mg# (36–49) with variable ɛ Nd(t) values (−2.2 to +1.2), and display OIB-like incompatible elemental patterns, similar to many alkali basalts in continental rifts. These geochemical characteristics indicate that the primary magma of these basalts was probably derived from a moderately depleted asthenospheric mantle source and underwent fractional crystallization plus minor crustal contamination. The rhyolitic rocks are highly enriched in Th, Ta, Nb, REE, Zr, Hf and Y and depleted in Sr, P, Eu and Ti, showing affinity to A1-type granites. Combined with their slightly positive ɛ Nd(t) values (+1.3 to +1.6) and negative ɛ Hf(t) values (−2.45 to −12.7), the Tieshajie rhyolites were most likely generated by partial melting of mafic lower crust induced by basaltic underplating following asthenospheric ascent. The Tieshajie alkaline bimodal volcanic sequence is proposed to have developed within a continental rift setting on a passive continental margin. Combined with documented rift events in Yangtze Block during the late Mesoproterozoic, they may indicate onset of the amalgamation of Yangtze Block with other blocks within the Rodinia supercontinent. Integrating our data with the oldest arc-related igneous events in eastern Zhejiang, the transition of the regional tectonic regime from intracontinental rifting to interplate convergence occurred between ca. 1159Ma and 970Ma in the southeastern Yangtze Block. [Copyright &y& Elsevier]

Abstract: The Superior Boundary Zone separates the Neoarchean Superior Province to the southeast from the Paleoproterozoic Reindeer Zone of the Trans-Hudson Orogen to the northwest. In northern Manitoba, late convergence along the zone in the Paleoproterozoic has previously been interpreted in terms of a promontory model, where the Superior Province indents the Reindeer Zone towards the northwest. We present a modified promontory model that includes a WNW transport direction of the Superior Province and lateral escape of a segment of the Superior Province (the Split Lake Block) along the northern margin of the promontory. The model is based on the kinematics of an array of shear zones along the Superior Boundary Zone that are interpreted as having been active concurrently. Tectonic escape of the Split Lake Block occurred in a manner similar to the extrusion and rotation of the Indochina block along the eastern margin of the Himalayas, but at a much smaller scale. Our model explains shear zone kinematics, but also the curvilinear nature of some of the shear zones and a high component of along-strike stretch along one of the shear zones. [Copyright &y& Elsevier]

Abstract: The partitioning of triclinic flow into domains of apparent monoclinic and apparent orthorhombic flow is described and discussed, using the Aiken River shear zone (ARSZ) as an example. The ARSZ is a 1–1.5 km wide east–west trending, dextral, north-side-up, mylonite zone, within the northern part of the Superior Province in Manitoba. It displays a high along-strike stretch (∼10), which is most likely indicative of an escape-tectonic setting. Although the central mylonite zone exhibits an apparent monoclinic fabric symmetry, the actual flow field was probably triclinic with a high simple shearing over pure shearing ratio, which resolves potential strain compatibility problems with neighbouring domains. The simple shearing-dominated zone is relatively narrow and has well-defined boundaries. An up to ∼20 km wide zone adjacent to the ARSZ shows an apparent orthorhombic fabric symmetry with shear zone boundary-parallel horizontal stretch and shear zone-orthogonal shortening. However, the actual flow may have been triclinic with a low simple shearing over pure shearing ratio. Either way, the pure shear component of the ARSZ is distributed over a much broader area than the simple shear component and has diffuse boundaries. This is consistent with simple shearing being a softening and pure shearing a hardening process. [Copyright &y& Elsevier]

The Neoarchean Pukaskwa batholith consists of pre-, syn-, and post-tectonic phases emplaced over an interval of 50 million years. Pre-tectonic phases are broadly synvolcanic and have a high-Al tonalite-trondhjemite-granodiorite (TTG) affinity interpreted to reflect derivation by partial melting of basaltic crust at lower crustal or upper mantle depths. Minor syn-tectonic phases slightly post-date volcanism and have geochemical characteristics suggesting some involvement or interaction with an ultramafic (mantle) source component. Magmatic emplacement of pre- and syn-tectonic phases occurred in the midcrust at paleopressures of 550-600 MPa and these components of the batholith are thought to be representative of the midcrust underlying greenstone belts during their development. Subsequent to emplacement of the syntectonic phases, and likely at approximately 2680 Ma, the Pukaskwa batholith was uplifted as a structural dome relative to flanking greenstone belts synchronously with ongoing regional sinistral transpressive deformation. The driving force for vertical tectonism is interpreted to be density inversion (Rayleigh-Taylor-type instabilities) involving denser greenstone belts and underlying felsic plutonic crust. The trigger for initiation of this process is interpreted to be an abrupt change in the rheology of the midcrust attributed to introduction of heat from the mantle attendant with slab breakoff or lithospheric delamination following the cessation of subduction. This process also led to partial melting of the intermediate to felsic midcrust generating post-tectonic granitic phases at approximately 2667 Ma. We propose that late density inversion-driven vertical tectonics is an inevitable consequence of horizontal (plate) tectonic processes associated with greenstone belt development within the Superior Province. Le batholite néoarchéen de Pukaskwa comprend des phases pré-, syn- et post-tectoniques mises en place durant une période de 50 Ma. Les phases pré-tectoniques sont largement synvolcaniques et elles ont une affinité Al et TTG (« tonalite-trondhjemite-granodiorite ») élevée qui est interprétée comme étant le reflet de la dérivation par fusion partielle d'une croûte basaltique à des profondeurs de croûte inférieure ou de manteau supérieur. Des phases syntectoniques mineures sont légèrement plus tardives que le volcanisme et elles ont des caractéristiques géochimiques qui suggèrent une certaine implication ou interaction avec une composante de source ultramafique (manteau). La mise en place magmatique des phases pré- et syntectoniques a eu lieu dans le milieu de la croûte à des paléopressions de 550-600 MPa et ces composantes du batholite seraient représentatives des ceintures de roches vertes sous-jacentes, au centre de la croûte durant leur développement. Après la mise en place des phases syntectoniques, et probablement vers 2680 Ma, le batholite de Pukaskwa a été soulevé en dôme structural par rapport aux ceintures de roches vertes de part et d'autre, et ce, de manière synchrone avec la déformation transpressive régionale senestre en cours. La force motrice derrière le tectonisme vertical serait une inversion de densité (instabilités de type Rayleigh-Taylor) impliquant les ceintures de roches vertes plus denses et la croûte felsique plutonique sous-jacente. Le déclencheur pour l'initiation de ce processus est interprété comme étant un changement abrupt dans la rhéologie de la croûte moyenne attribué à l'introduction de chaleur du manteau auxiliaire à la rupture de la dalle ou à la délamination lithosphérique suivant la cessation de la subduction. Ce processus a aussi mené à une fusion partielle de la croûte moyenne intermédiaire à felsique générant des phases granitiques post-tectoniques vers 2667 Ma. Nous proposons que la tectonique verticale poussée par l'inversion de densité tardive soit une conséquence inévitable des processus tectoniques horizontaux (plaques) associés au développement de ceintures vertes dans la Province du Supérieur. [ABSTRACT FROM AUTHOR]

Abstract: The Archean Bird River greenstone belt (BRGB) is located on the southwestern edge of the Superior Province between the 3.2Ga old Winnipeg River subprovince to the south and the metasedimentary belt of the English River subprovince (ERSP) to the north. This position between two major subprovinces makes the BRGB a primary target for investigating the geodynamic and kinematic evolution of a major structural boundary. New structural and geochronological data have allowed us to present an evolutionary framework for the southern boundary of the North Caribou superterrane. The BRGB underwent 3 main deformation phases. The D1 event took place ca. 2698Ma and displays a north-side-up shearing. The D2 event, occurring at ca. 2684Ma in a transpressive context, presents a complex structural pattern mixing vertical tectonics in the BRGB and strike-slip tectonics along the boundaries of the greenstone belt with other subprovinces. Between the BRGB and the ERSP, the 2832–2858Ma old Maskwa batholith acted as a rigid passive block during the collision and marks the boundary between pure dextral strike-slip tectonics along his northern boundary with the ERSP and vertical south-side-up motion in the BRGB. The BRGB can be considered as a pop-up structure with anastomosed shear zones displaying different horizontal offset according to the orientation of the shear zones. The southern boundary with the Winnipeg River subprovince is represented by a sinistral south-side-up shear zone. The same pattern is found at the regional scale where major shear zones acted as a conjugate set in the horizontal plane. At ca. 2640Ma, the D3 event occurred in a general dextral transpressive tectonic regime coeval with the emplacement of rare-elements pegmatitic plutons in a still hot (400–500°C) country rock. The geodynamical and mechanical significance of the partitioning between pure strike-slip tectonics in the English River subprovince and vertical motion in the BRGB can be explained by the rheological behaviour of a hot and weak lithosphere undergoing transpressive strain. The structural framework of the BRGB is the result of strong interactions between hot and weak domains, coeval with widespread plutonism, and a rigid older domain (Maskwa batholith) during the D2 transpressive event. [Copyright &y& Elsevier]

Abstract: The Northern Superior superterrane in the northwestern Superior Province is characterized by an ancestry back to ca. 3.8Ga and contains one of the largest and best-preserved high-grade terranes on Earth, the Pikwitonei Granulite Domain and its northeast extension, the Split Lake Block. This high-grade terrane occurs in the Superior Boundary zone, a complex transitional zone that bounds the northwestern margin of the Archean Superior Province and separates it from the Paleoproterozoic crust of the Trans-Hudson Orogen. Detailed structural and geochronological data from the exceptionally well-exposed Gull Rapids area at the eastern margin of the Split Lake Block shows evidence for both Neoarchean (Kenoran) and Paleoproterozoic (Trans-Hudson) deformation and metamorphism. More importantly, it indicates that the uplift of the Split Lake Block was achieved by shear zone movement in the Neoarchean, not in the Palaeoproterozoic, synchronous with peak metamorphism and dyke emplacement at ca. 2686Ma. This indicates that uplift of the high-grade domains in the Northern Superior superterrane was neither related to its collision with the North Caribou superterrane at ca. 2.72Ga, nor to the ca. 1.8Ga Trans-Hudson orogeny. Instead, this uplift might have occurred during a major period of Superior-wide active tectonism toward the end of the Neoarchean Kenoran orogenesis. [Copyright &y& Elsevier]

• The ca. 1885 Ma I- and S-type granites are different in their source rocks. • The adakitic granites suggest thickened crust in the JLJB syn-orogenic process. • The granitoids reflect a heterogeneity of the JLJB in the Late Paleoproterozoic. A suite of Paleoproterozoic syn-orogenic magmatism with distinctive natures in the Jiao-Liao-Ji Belt (JLJB) of North China Craton is studied, including I-type monzogranite, related quartz gabbro, S-type granites, and adakitic granites. The Caiyuan monzogranite and quartz gabbro intrusions yield zircon U-Pb ages of 1881 ± 31 Ma and 1889 ± 19 Ma, respectively. They exhibit light rare earth element enriched patterns, and are rich in Rb, Ba, and K, but depleted in Nb, Ta, and Ti. These granites have relatively low (87Sr/86Sr) i ratios of 0.701985–0.706703, εNd(t) values of −13.0 to −0.3 and dominantly negative zircon εHf(t) values. Two Siping porphyritic granite samples give U-Pb ages of 1877 ± 11 Ma and 1881 ± 11 Ma respectively. They display enriched REE patterns, characterized by high Al 2 O 3 and A/CNK ratio (>1.1), similar to S-type granites, with high (87Sr/86Sr) i ratios up to 0.711142 and negative εNd(t) values of −8.0 to −2.2. The Wafang and Xujiapu granites intrusions yield zircon U-Pb age of 1887 ± 11.0 Ma and 1885 ± 9.7 Ma and have high Sr/Y, (La/Yb) N and strikingly positive Eu anomalies, likely belonging to adakite. The association of quartz gabbro, I-type, and S-type granites in the Caiyuan region indicate that they were derived from mafic parental magma triggered by slab subduction. Crustal materials mixed in further AFC processes of the magma, before the monzogranite and porphyritic granite crystallized. The Wafang adakitic granite was probably related to the partial melting of a thickened crust. A complex syn-orogenic evolution model is thus proposed in the Late Paleoproterozoic of the JLJB, as slab subduction and partial melting of thickened crust simultaneously occurred at ~1885 Ma. [ABSTRACT FROM AUTHOR]

Abstract: Shear direction is an important parameter in the kinematic interpretation of high-strain zones. Recent developments in the study of high-strain zones show that there is no simple relationship between the orientation of stretching lineations and the shear direction and it is difficult to use the former to determine the latter. In contrast, striations on C-surfaces, a product of ductile deformation, form parallel to the shear direction. It is therefore important for the kinematic interpretation of high-strain zones to differentiate such striations from stretching lineations. Ductile striations are much more common in natural high-strain zones than reported in the literature. We discuss how to differentiate the two types of lineations and describe a natural high-strain zone example from the Superior craton of Canada. The striation data show that the shear direction of the high-strain zone varies from subhorizontal to moderately plunging across the strike of the zone. We conclude that well-developed ridge-in-groove type striations are a reliable indicator of the shear direction. We also discuss situations where the orientation of stretching lineations can potentially be used as an indicator of shear direction. [Copyright &y& Elsevier]

Abstract: The long and narrow Carrot River greenstone belt in the northwestern Superior craton is a synclinal keel between two broad granitoid domes. Its unique structural geometry and kinematics place significant constraints on the timing relationship between vertical and horizontal tectonism. A high-strain zone spatially coincident with the belt records evidence for synchronous greenstone-down/granitoid-up dip-slip and dextral strike-slip components. Kinematic and regional considerations lead to the conclusion that the dip-slip component was a result of vertical tectonism and the strike-slip component was a result of horizontal tectonism, and therefore that the vertical and horizontal tectonism were synchronous. It is emphasized that vertical and horizontal tectonism do not have to act exclusively of each other. It is not necessary to downplay the significance of vertical tectonism to validate horizontal tectonism, and vice versa. Evidence for synchronous vertical and horizontal tectonism reported here makes it necessary that both processes (as opposed to either one or the other) and their potential interactions are considered in interpretations of Archean terrains. It is suggested that synchronous vertical and horizontal tectonism was a common process in the Neoarchean and might represent a transition from dominant vertical tectonism in the Mesoarchean (and Paleoarchean?) to dominant horizontal tectonism in the Proterozoic and Phanerozoic. It might be an important process for gold mineralization at the late stages of Archean cratonization. [Copyright &y& Elsevier]

• The volcanic rocks formed in an arc setting at 756-740 Ma. • The late Tonian arc in the Wuyi domain was part of a major arc system in the West Cathaysia terrane. • The Wuyi arc system was different from the arc system along the western margin of the Yangtze Block at the late Tonian. • The West Cathaysia terrane was distinct from the southeastern margin of the Yangtze Block and they were not amalgamated until after the late Tonian. The late Tonian tectonic setting of the West Cathaysia terrane in South China is highly controversial and is key to better understanding the timing of amalgamation between the Yangtze Block and the West Cathaysia terrane and the positions of these two terranes in Rodinia and Gondwana. A detailed field-based study was conducted on the petrology, zircon U-Pb geochronology and Lu-Hf isotopes, and whole-rock geochemistry of a series of Neoproterozoic meta-volcanic and meta-sedimentary rocks in the Wuyi domain in the northeastern West Cathaysia terrane. The results indicate that the meta-volcanic rocks formed in an arc setting at 756-740 Ma, and the meta-sedimentary rocks were developed in an arc-related basin with single zircon age peaks of 765-728 Ma. We propose that the late Tonian arc in the Wuyi domain was part of a major arc system in the West Cathaysia terrane. An arc setting for the West Cathaysia terrane is distinct from the continental rift setting for the southeastern margin of the Yangtze Block at the time, supporting an interpretation that the two terranes were not amalgamated until after the late Tonian and occupied separate positions in Rodinia. [ABSTRACT FROM AUTHOR]

• SJC experienced multiple magmatism of ~2.78, ~2.69 and ~2.55 Ga. • Neoarchean magma derived from episodic juvenile crust growth and crustal reworking. • Recycling of sediments was not intense or extensive in SJC during Neoarchean. • A bottom-up tectonic regime related to plume activity is favored for NCC in Neoarchean. Recent advances in high-precision in-situ analysis of zircon U-Pb-Hf-O isotopes have significantly improved our approach to studying the origin and evolution of Archean crust. This study presents high-precision in-situ zircon U-Pb-Hf-O isotopes for the Southern Jilin Complex (SJC) on the northeastern margin of the North China Craton (NCC) and explores the potential of such an integrated approach in understanding the Archean crust evolution and its tectonic implications. The SJC consists mainly of Archean granitoid gneisses hosting minor supracrustal rock xenoliths. Zircon U-Pb data from representative lithologies reveal three episodes of magmatism at ~2.78, ~2.69 and ~2.55 Ga, respectively. The former two granitoid magmatic events are recognized for the first time in NE NCC, while the latest one is widespread over the NCC. All metamorphic zircon domains document similar metamorphic ages of 2.51–2.48 Ga, consistent with the widespread metamorphism of ~2.50 Ga in the NCC. Most concordant magmatic zircons preserve "mantle-like" O isotopic signatures, indicating the magma sources were not contaminated by large amounts of high δ18O supracrustal sediments. Hf depleted mantle model ages of magmatic zircons display one predominant peak at 2.9–2.8 Ga and two subordinate peaks at 3.3–3.2 Ga and 2.7–2.6 Ga, indicating possible episodic crust-mantle differentiation in Southern Jilin. Integrated zircon U-Pb-O-Hf data from the SJC suggest that magma sources were mainly derived from multiple episodes of reworking of juvenile or ancient crust with mantle component addition, while recycling of sediments was trivial during the Neoarchean in this region. The spatial–temporal relations of magmatism, lack of supracrustal addition to magma sources, and other geological evidence from the NCC are in favor of a bottom-up geodynamic regime possibly related to plume activities, arguing against a widespread top-down mechanism involving modern-style subduction in the NCC during the Neoarchean. [ABSTRACT FROM AUTHOR]

Reports an example of promontory-promontory collision from the Canadian Appalachians. Proposed model that relates transverse wrench faulting and tectonic wedging to promontory-promontory collision; Silurian syncollisional deformation, metamorphism and magmatism of the rocks of the Central mobile belt in Cape Breton and Southwestern Newfoundland.

• The central Dunhuang Orogenic belt (DOB) can be split into two contrasting terranes. • The granitoid rocks were emplaced in two phases: ca. 284–275 Ma and ca. 255–238 Ma. • The two phases of granitoids are arc-related and post-collisional rocks, respectively. The Dunhuang orogenic belt (DOB), located in the southern Central Asian Orogenic Belt (CAOB), exposes Precambrian and Paleozoic intrusive-metamorphic rocks. To better understand its evolution, we carried out detailed petrological and geochronological investigations on the major lithologies of the central DOB. The central DOB can be divided into two terranes, the north and the south, with contrasting geological history. The north is characterized by Precambrian crystalline rocks (ca. 3.1–1.6 Ga) overprinted by Devonian tectono-thermal events. The Precambrian rocks show evidence for major juvenile crust growth with additions of older crustal materials at 2.7–2.5 Ga, a major crustal reworking event at 2.0–1.9 Ga, and juvenile additions with minor crustal reworking at 1.8–1.7 Ga. In contrast, the south is characterized by early Devonian (ca. 406 Ma) TTG-gneiss and amphibolite gneiss, and some Late Paleozoic–early Mesozoic granitoid rocks (ca. 284–238 Ma). The Late Paleozoic–early Mesozoic granitoid rocks from the south were emplaced in two phases: early Permian (ca. 284–275 Ma) and late Permian–middle Triassic (ca. 255–238 Ma). They belong to the high-K calc-alkaline I-type series which were generated from mixing juvenile materials with Mesoproterozoic continental crust. The early Permian and the late Permian–middle Triassic granitoid rocks are considered as arc/subduction-related and post-collisional rocks, respectively. These suggest that the final assembly of the DOB with the Beishan or final assembly within the DOB happened in the middle Permian (ca. 275–255 Ma). The DOB formed by accretion/collision of multiple terranes/microcontinents, similar to other areas in the CAOB. [ABSTRACT FROM AUTHOR]

The North Qinling Orogen underwent subduction and collision processes during the Palaeozoic, but the tectonic framework remains unclear. To investigate the tectonic evolution of the North Qinling Orogen, we selected the Devonian granites from the northeastern margin of the North Qinling Terrane. Integrated petrographic, geochemical, and geochronological studies, as well as Sr–Nd–Hf isotopic analyses, were carried out on the newly identified Devonian granites from the Hengjian area in the northeastern North Qinling Terrane, Qinling Orogenic Belt. Zircon laser ablation inductively coupled plasma mass spectrometry U–Pb dating reveals that these granites were crystallized at 396–387 Ma. The granite samples are metaluminous to weakly peraluminous (A/CNK = Al2O3/(CaO+Na2O+K2O) = 0.86 to 1.12), with high SiO2 (60.6–76.5 wt%) and high total alkaline (Na2O + K2O = 8.45–11.0 wt%) contents. The granites are enriched in Th, rare‐earth element, Zr, and Hf and depleted in Sr, Nb, Ta, P, Eu, and Ti. They are characterized by high Zr + Nb + Ce + Y contents (511–990 ppm) and 10,000*Ga/Al ratios (2.71–3.32), as well as high zircon‐saturation temperatures (TZr = 819–885°C, average = 845°C), which indicate that they are typical A‐type granites. The granites have low Y/Nb (0.39–0.67) and Yb/Ta (0.56–0.83) ratios, resembling those of the A1‐type granite, which indicates that they are formed in anorogenic settings. They also have low (87Sr/86Sr)i ratios (0.7055–0.7071) and negative εNd(t) values (−10.1 to −8.40) and variable zircon εHf(t) values (−8.46 to +14.7), with the two‐stage model ages of 2.0–1.8 Ga and 1.9–0.4 Ga, respectively. These geological features suggest that the granites of the Hengjian area were most likely generated by partial melting of mafic lower crust induced by asthenospheric ascent. The A‐type granites were generated in a continental rift environment during 396–387 Ma, corresponding to the closure of the Shangdan Ocean and the opening of the Palaeo‐Tethyan Ocean during the Early Devonian. [ABSTRACT FROM AUTHOR]

• Cees's papers had had a transformative effect on our understanding of accretionary orogenic processes. • Examples of accretionary and post accretionary processes are provided from the Appalachian, circum-Atlantic, Cordilleran and Central Asian orogenic belts. [ABSTRACT FROM AUTHOR]

A Neoproterozoic subduction-accretion complex have been identified along the Zhenghe-Dapu fault (ZDF) zone in the inner Cathaysia Block, South China. The serpentinites are characterized by low 187Os/188Os ratios of 0.11621 to 0.12008 and very low 187Re/188Os values of 0.031-0.129, which are similar to those from highly refractory mantle residues, indicating that they are tectonic rather than igneous origin. The meta-ultramafic rocks, including pyroxene hornblende schist and hornblende schist, are characterized by high Ni, Cr and low K2O content. Their convex upward REE partterns, along with lower concentrations of highly incompatible elements indicate that their protolith were cumulate origin. Low initial 87Sr/86Sr and high 143Nd/144Nd ratios suggest that they were derived from partial melting of an depleted mantle source. Low Nb/Yb, Th/Yb and Ti/V imply they have IAT-like geochemical features which occurred in oceanic island arc setting. The associated metasedimentary rocks have low chemical index of alteration (CIA) values (34.7-58.2) and relatively high index of compositional variability (ICV) values (0.98-3.22) suggested weak chemical weathering and an immature source. Low K2O/Al2O3 (0.01-0.03), low zirconδ18O values (4.4 to 5.3‰) and high zircon ɛHf (t) values (+13.5 to +16) of the metasedimentary rocks point to mantle-derived material supply for their protolith. TDM1 (616-719 Ma) of the zircons reflect the source material was derived from a mantle source with Neoproterozoic model ages. Low La/Sc and Th/Sc values infer that their source material were derived from an ocean island arc setting. These rocks have experienced strong mylonitization. Shear-sense indicators show that the mylonitized rocks experienced sinistral strike-slip motion parallel to the ZDF zone. Metamorphic zircons from the mylonitized rocks yield SIMS U-Pb age of ca.522-520 Ma, suggesting that the subduction-accretion complex experienced intensive Pan-African metamorphic event. All these features prefer that there was a Pan-African accretionary orogeny in the South China Block. The ZDF zone probably marks the collisional belt between the west Cathaysia Block and the west Australia, corresponding to the assembly of the Gondwanaland. [ABSTRACT FROM AUTHOR]

We carried out an integrated study of zircon U–Pb geochronology, Hf isotopes and geochemistry on the paragneisses and amphibolites from the Chencai area, South China. The detrital zircon ages of four paragneisses range from 2974 to 501 Ma with the main peak at ca. 820 Ma. The detrital materials with Neoproterozoic age may derive from the Jiangnan Orogen and those of Palaeo–Mesoproterozoic age may come from the Wuyi terrane. The youngest age indicates that the protoliths of the paragneisses were formed after ca. 501 Ma. The εHf(t) values (−20.6 to +20.9) of the detrital zircons suggest that the detrital materials of the protoliths are composed of old crustal and juvenile materials. The geochemical characteristics suggest that the protoliths of the paragneisses are greywackes, which formed in an active continental margin or continental island arc environment. The metamorphic ages of the three amphibolites are 428 ± 4, 430 ± 4, and 438 ± 3 Ma. The protoliths of the amphibolites are tholeiites, which can be divided into two groups. Group 1 is characterized by low ∑REE contents and (La/Yb)N ratios showing left‐inclined REE patterns and Nb, Ta depletion which resembles N‐MORB. Group 2 has higher ∑REE contents and (La/Yb)N ratios, with Eu negative anomalies showing affinity to E‐MORB. The data show that the Chencai Group is composed of oceanic crust remnants and continental crust materials, indicating it should be a subduction accretionary complex rather than a metasedimentary sequence and thus it cannot be regarded as the Precambrian basement of the Cathaysia Block. [ABSTRACT FROM AUTHOR]

Hardly any previous studies have focused on the granitic dykes which intrude into the Paleoproterozoic Liaohe Group in the Liaodong Peninsula, northeast of the North China Craton. In situ zircon U-Pb dating, Lu-Hf isotopic and geochemical analyses on three representative monzogranite dykes were taken in this study. These dykes have relatively high content of SiO2 (72.20%–74.78%) and K2O (2.83%–6.37%), and have characteristics of high-K calc-alkaline to shoshonite series. Two dyke samples have I-type granite features and have high Sr/Y ratios and positive Eu anomalies, showing an adakitic feature. Another dyke has a high ratio of Ga/Al, but has a low Zr saturation temperature, which differs from the typical A-type granite. Zircon grains from these three dykes have typical magmatic zoning in CL images and yield consistent U-Pb ages of ~1859–1852 Ma, which are interpreted as the crystallization ages of these dykes. Hf isotopic analyses yield mainly negative εHf(t) values and TDM2 ages of 2782–2430 Ma, similar to those of the 2.2–2.1 Ga granitoids and meta-sedimentary rocks (the Liaohe Group), indicating these monzogranitic dykes may have been sourced from melting of Paleoproterozoic granitoids and meta-sedimentary rocks. The monzogranitic dykes were generated under a post-collisional geological setting after the Jiao-Liao-Ji orogeny process. [ABSTRACT FROM AUTHOR]

Includes a supportive view of Zheng-xiang Li's tectonic model for continent-continent collision between the North and South China blocks. Requirements for a nonsynchronous collision; Conflicting views on the need for a promontory for the South China block.

• ∼785 Ma mafic-ultramafic cumulates in West Cathaysia formed from hydrous basaltic magmas. • Their geochemical data are consistent with arc-related cumulate petrogenesis. • They were probably formed at a crustal depth in a subduction setting. • Yangtze and West Cathaysia were not amalgamated in the Tonian, but more likely in the early Paleozoic. The Neoproterozoic tectonic setting of the West Cathaysia terrane and its relationship with the Yangtze Block are critical to understanding the formation and tectonic evolution of South China. A detailed study of late Tonian mafic-ultramafic cumulate slivers embedded in the Shenshan tectonic mélange along the northwest margin of West Cathaysia is presented here with the aim of elucidating its Neoproterozoic tectonic history. These partly-altered mafic-ultramafic rocks include olivine-bearing cumulates (olivine pyroxene hornblendite or olivine hornblende pyroxenite), pyroxene hornblendite, and gabbroic cumulates. The early crystallization of clinopyroxene and the abundance of hornblende indicate that they formed from hydrous magmas. The rocks have similar geochemical distribution patterns and show variable initial 87Sr/86Sr ratios of 0.702679 to 0.709742 and positive εNd(t) values of +2.10 to +4.52. The mineral compositions of the clinopyroxene and hornblende and their whole-rock extended normalized trace element patterns show features (e.g., negative Nb anomalies, LILE enrichment) typical of rocks with an arc affinity. The high calculated Mg# values (58–77, average 71) of the equilibrium magmas are close to those of primary mantle-derived basalts. We conclude that these mafic and ultramafic cumulates were derived from a subduction-related, hydrous, magnesian basalt in a subduction setting. The estimated crystallization temperature and pressure, based on the composition of the amphiboles, suggest that the minerals accumulated in magma chambers at middle to lower crustal depths. LA-ICP-MS U-Pb dating of zircon from the gabbroic cumulate indicates crystallization at ca. 785 Ma. A previous interpretation for West Cathaysia at this time involved a continental rift basin (the Nanhua basin) that straddled the southeastern margin of the Yangtze Block and the northwestern margin of West Cathaysia. In contrast, our results suggest that West Cathaysia was an arc at ca. 785 Ma, which supports the interpretation that the amalgamation between Yangtze and West Cathaysia did not occur in the Tonian, but more likely in the early Paleozoic. [ABSTRACT FROM AUTHOR]

The Neoproterozoic magmatism along the Jiangnan Orogen preserves significant information for understanding the tectonic evolution of the South China Block (SCB). We conducted a systematic zircon U–Pb geochronological and whole‐rock geochemical study on the basalts from the Yingchuan Formation in the eastern Jiangnan Orogen, SCB. The basalts yielded a weighted mean 206Pb/238U age of 817 ± 13 Ma, enriched in Rb, Th, U, LREE and HFSE (e.g., Zr and Ti). The basalts have positive εNd(t) (+1.9 to +2.1) and high (87Sr/86Sr)i (0.69853–0.70737), indicating a slightly depleted mantle source. The high La/Nb (2.14–2.35) and La/Ta (28.6–33.3) ratios indicate a lithospheric mantle source for the basalts. Their high Ba/Yb (7.85–44.3) and Th/Yb (0.59–0.74) ratios and high absolute Nb contents (7.64–11.6 ug/g) indicate that the lithospheric mantle source has been metasomatized by melts and fluids derived from a subducted slab. The basalts are characterized by (La/Yb) N ratios (3.0–3.5) and Sm/Nd ratios (0.24–0.26), comparable to intra‐continental back arc basin basalts (BABBs). Their Ta/Yb (0.14–0.16) and Th/Yb (0.59–0.74) ratios are similar to those of Okinawa Trough basalts and contemporary mafic rocks formed in the back‐arc basin in the Jiangnan Orogen. Combined with their source features, we propose that the basalts were formed in a back‐arc basin setting. The identification of BABBs from the Yingchuan Formation shows that there were Neoproterozoic back‐arc basins in the south‐eastern Yangtze Block, indicating that the final assembly between the Yangtze and Cathaysia blocks did not occur before ca. 817 Ma. [ABSTRACT FROM AUTHOR]

To better reveal the early Neoproterozoic tectonic process of South China with respect to the assembly of the Rodinia supercontinent, an integrated dataset of geochronology, whole-rock geochemistry, and Sr-Nd-Hf isotopic compositions for diabases that intruded the Kunyang Group in the southwestern Yangtze Block is herein presented. Zircon U-Pb dating gives four weighted mean 206Pb/238U ages of 946 ± 4 Ma, 948 ± 6 Ma, 939 ± 4 Ma, and 918 ± 7 Ma, suggesting mafic magmatism in the earliest Neoproterozoic. The diabases possess Nb = 12.3–30.5 ppm, Nb/U = 19.99–37.06, Nb/La = 0.78–1.05, (Nb/Th) PM = 0.44–0.80, and (Nb/La) PM = 0.75–1.02, geochemically resembling those of typical Nb-enriched basalts. They are tholeiitic in composition with low SiO 2 (49.49–51.95 wt%), high TiO 2 (2.03–4.65 wt%), MgO (2.50–6.14 wt%), and Fe 2 O 3 T (15.38–18.84 wt%) contents. They are enriched in light rare earth elements (LREEs) with weak negative Eu anomalies (Eu/Eu* = 0.75–0.96) and show E-MORB-like characteristics with slight to moderate Nb-Ta depletion. The samples show zircon ε Hf (t) values ranging from + 5.8 to + 10.3 and whole-rock ε Nd (t) values from + 0.5 to + 0.9. These elemental and isotopic characteristics suggest that the 0.95–0.92 Ga diabases may have derived from an E-MORB-like magma source with the injection of metasomatized slab melts. Integrating previous studies with our results, we propose that the southwestern Yangtze Block evolved from an intracontinental rift to a passive continental margin in the late Mesoproterozoic, followed by the development of an earliest Neoproterozoic continental arc-back-arc basin system analogous to the Northern Okinawa Trough. The distinct tectonic processes between the southern and northern parts of the Yangtze Block at ca. 1.0–0.9 Ga favour the hypothesis that the final cratonization of the present-day Yangtze Block occurred slightly later than ∼ 0.9 Ga in response to the Rodinia supercontinent assembly. [ABSTRACT FROM AUTHOR]