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The A-type granites are an important component of the Earth's continental crust and play a significant role in understanding crustal evolution and tectonic processes. This study presents a comprehensive assessment of A-type granites from Ataitir El Dehami granites (ADG), which are located in the northwestern part of the Wadi Seih area in South Sinai, using geochemistry, zircon geochemistry and geochronology characteristics. The geochemical analysis reveals that ADG are characterized by high silica content, relatively high FeO* and high alkali concentration, consistent with A-type granites derived from the melting of tonalite sources. Zircons from Ataitir El Dehami granites have high REE contents with Ce enrichment and depletion of Eu, which, together with the high U/Yb ratios, suggest that the studied granites were generated from melting of continental crustal rocks. Zircon U–Pb geochronological data indicate that the granite emplacement occurred around 575–603 Ma throughout continuous exhumation pulses. The isotopic analyses also indicate the presence of inherited zircon grains (735 ± 9 Ma). The present data suggest that the studied granites were formed in a post-collisional setting, and represent the transition stage from convergence to extension that occurred at 600 Ma. [ABSTRACT FROM AUTHOR]

Whether the North China Block (NCB) remained in extension from its cratonization to the mid-Paleozoic is questionable. Here, we conduct a synthesis of zircon U–Pb data of Statherian–Ordovician sandstones to provide a historical review of provenance changes in the western NCB through time. In contrast to typical NCB basement sources characterized by c. 2.7–1.8 Ga ages with spectral peaks at c. 2.5 and 1.9 Ga during much of c. 1.8–0.45 Ga, Ediacaran to Cambrian Stage 3 succussions contain abundant zircons with Meso- to Neoproterozoic ages. The exotic provenance, further verified by southeastward palaeo-flow, implies sources from the western Bainaimiao arc terrane (BAT), where basement rocks with suitable ages exist. Hence, the BAT should have evolved at the NCB margin before c. 0.56 Ga, but after rifting of the NCB (until c. 773 Ma). This event led to a craton-wide stratigraphic break during the Mesoproterozoic–Ediacaran. The presence of 521–515 Ma detrital zircons in Cambrian Stage 3 strata indicates subduction onset of the Palaeo-Asian Ocean before c. 515 Ma, coincident with the Precambrian–Cambrian boundary paraconformity. A sequence of depositional shifts triggered by the tectonic activities of the BAT unveils a complicated plate reorganization history of the northern NCB, contesting the view that the NCB remained passive from the Statherian. Supplementary material: Figures S1, S2 and Tables S1 and S2 are available at https://doi.org/10.6084/m9.figshare.c.7040743 [ABSTRACT FROM AUTHOR]

The Altai region of China features abundant granitoids, which can be used to reconstruct the tectonic evolution of the orogen. We conducted petrological, geochronological, geochemical and isotopic analyses on several representative granitoids from the Altai region. U‒Pb dating revealed ages of 444 ± 3 Ma for gneissic granites, 406 ± 8 Ma for syenogranites, 280 ± 6 Ma for diorites, 278 ± 3 Ma for two-mica monzonitic granites and 269 ± 3 Ma for muscovite granites. The Ordovician gneissic granites have I-type arc-related element characteristics and are derived from volcanic magmas extracted from the mantle wedge and then metasomatized by subducted sediment in a continental arc. The Devonian syenogranites show dual I-type arc and within-plate granite geochemical signatures, suggesting derivation from volcanic magmas extracted from the lithospheric mantle metasomatized by subducted fluid/melt in a back-arc basin. The Permian diorites are Mg-diorites derived from a mixed-magma source involving residual subducted basaltic oceanic crust and lithospheric mantle. The two-mica monzonitic granites are S-type granites originating from the crustal recycling of sedimentary rocks, whereas the muscovite granites are leucogranites resulting from the anatexis of ancient metasedimentary rocks. Their tectonic setting is syn-/post-collisional. By combining these results with previously published data, we propose that the Chinese Altai region experienced mid- to late Ordovician continental arc magmatism, early to mid-Devonian back-arc extension and early to mid-Permian arc–arc syn-/post-collision. Supplementary material: Supplementary Tables S1–S3 are available at https://doi.org/10.6084/m9.figshare.c.6420236 [ABSTRACT FROM AUTHOR]

We studied the zircon U–Pb ages, whole-rock geochemistry and Sr–Nd isotopic compositions of a Paleozoic gabbro–diabase–granite association in the Shangdan suture zone to constrain the petrogenesis of these intrusive rocks and identify their tectonic implications. These rocks have distinctive crystallization ages: the Guchenggou gabbro yielded zircon U–Pb ages of 424–423 Ma, the average age of the Yueritan diabase was 411 Ma and the Danfeng granites yielded zircon U–Pb ages of 414–411 Ma. The Guchenggou gabbro was formed by partial melting of a phlogopite-bearing garnet lherzolite modified by subduction fluids in a continental arc setting. The Yueritan diabase was generated by mixing a phlogopite-bearing garnet lherzolite modified by subduction melts with continental crustal rocks in a post-collision setting. The Danfeng granites were weakly peraluminous I-type granites formed by mixing juvenile crust with metagreywackes at high temperatures and pressures in a tectonic environment transitioning from compression to extension. We suggest that the subduction of the Shangdan Ocean induced the formation of the gabbro. The diabases and granites are related to relamination of the continental crust in response to the collision of the North Qinling Belt with the South Qinling Belt, suggesting that closure of the Shangdan Ocean may have occurred at c. 410 Ma. [ABSTRACT FROM AUTHOR]

The Carboniferous tectonic evolution of Western Junggar is crucial to understanding the subduction–accretion process of the Central Asian Orogenic Belt, but the nature of this setting is still controversial. In this work, composite mineralogical, geochemical and detrital zircon U–Pb geochronological investigations have been conducted on Carboniferous clastic rocks in the Darbut region. The chemical compositions and sedimentary features show low sediment maturity and limited recycling, suggesting short-distance transportation and rapid accumulation. The samples contain igneous rock debris, mainly andesite and small amounts of basalt and granite, and a heavy mineral assemblage of Zr + Ap + Aug + Hbl + iron-bearing minerals (Hem-Lm, Ilm, Mag and Py). The samples feature moderate ratios of Zr/Sc (average 15.47) and Th/Sc (average 0.61), and low ratios of La/Sc, Co/Th and La/Th, as well as low Hf content, suggesting intermediate to felsic arc-related igneous provenances. Detrital zircon grains from the clastic rocks show prominent age peaks in the Devonian and Carboniferous with positive ε Hf(t) values, indicating a consistent provenance associated with the Tiechanggou–Halaalate island arc. Combining the petrology, geochemistry and geochronology of the sedimentary and magmatic rocks, we conclude that the Darbut Carboniferous volcanic–sedimentary strata were deposited in a back-arc basin during c. 327–311 Ma. Supplementary material: Tables S1-S6 and Figures S1-S6 are available at https://doi.org/10.6084/m9.figshare.c.5357293 [ABSTRACT FROM AUTHOR]

Geochronological, elemental and Sr–Nd–Hf isotopic data for intermediate–acid volcanic sequences from the western North Huaiyang Belt of the Dabie Orogen, China, provide new constraints for the nature of the lithosphere and the potential involvement of subducted Yangtze crust. These rocks are calc-alkaline andesite, trachyandesite and dacite. They yield ages of 129–127 Ma and show a geochemical affinity to arc volcanic rocks. (87Sr/86Sr)i ratios and εNd(t) values range from 0.7065 to 0.7080 and −16.9 to −13.2, respectively. Zircon in situ εHf(t) values range from −29.4 to −20.2 and Hf model ages from 3.03 to 2.46 Ga. These volcanic rocks were likely derived from a hybridized source involving enriched lithosphere of the North China Craton (NCC) and deep-recycled continental crust of Yangtze Block. Our data, along with geological observations from early Cretaceous igneous rocks, suggest an east–west extensional magmatic pulse at 130–120 Ma along the entire North Huaiyang Belt. The extent of involvement of the Yangtze continental crust with the lithosphere of the NCC decreases from East to West. This reflects along strike changes in Triassic northward deep subduction and subsequent exhumation of the Yangtze crust. Further lithospheric extension in the early Cretaceous led to unrooting of the thickened lithosphere and generation of Cretaceous volcanic rocks along the North Huaiyang Belt. Supplementary material: Microprobe data for all samples are available at https://doi.org/10.6084/m9.figshare.c.4611911 [ABSTRACT FROM AUTHOR]

The widespread migmatites in the Precambrian basement of the North Qinling Belt are products of partial melting of the Earth's crust and record the tectono-thermal response to Late Paleozoic collision along the Shangdan suture. The morphology and trace element geochemistry of zircons from the migmatites suggest a metamorphic origin related to partial melting. The zircons from leucosome, melanosome and banded migmatites yield U–Pb weighted mean ages of 408 ± 2, 403 ± 2 and 400 ± 2 Ma, respectively, constraining the timing of migmatization. The granitic dyke intruded into the migmatites gives a zircon U–Pb weighted mean age of 396 ± 2 Ma, constraining the minimum time of migmatization. Zircons from the melanosome and banded migmatite yield upper intercept ages of 1088–1061 Ma, representing the protolith ages of the basement of the North Qinling Belt. The zircon rims of the melanosome and banded migmatite predominantly display negative and positive εHf(t) values, respectively, suggesting the variable input of mantle material. Together with the regional geology and previous geochronological data, we propose that the thickening and partial melting in the North Qinling Belt was induced by the collision along the Shangdan suture between the North and South China Blocks from c. 408 to 400 Ma. Supplementary material: LA-ICP-MS U–Pb data, Lu–Hf isotopic compositions and trace element geochemistry data of the zircons and Ti-in-zircon thermometry are available at https://doi.org/10.6084/m9.figshare.c.4521389 [ABSTRACT FROM AUTHOR]