Wenxiao Zhou

The eastern Tianshan region in the Central Asian Orogenic Belt (CAOB) is characterized by multiple complex tectonic activity of uncertain historical contribution to the construction of the CAOB. This study utilizes a multi-proxy geochemical approach to characterize I-type monzogranite pluton rocks and their associated hornblende-rich dioritic enclaves to decipher the tectonic and magmatic evolution of the Xigebi area, eastern Tianshan. Zircon geochronology indicates a Triassic and Permian crystallization age of ca. 224.2 ± 1.7 Ma and ca. 268.3 ± 3.0 Ma for the host monzogranites and the dioritic enclaves, respectively. Major, trace and rare earth element distribution, together with Hf isotope systematics displaying noticeable positive εHf(t) anomalies for both rock types, point to partial melting of meta-mafic rocks in an intraplate extensional setting. The diorite was formed by the melting of lower crustal meta-igneous rocks mixed with mantle melts, and the monzogranite, predominantly from deep crustal meta-basalts contaminated by shallow metasedimentary rocks, with some degree of mixing with deeply sourced mantle magma. While both the host monzogranites and their dioritic enclaves are the products of upwelling magma, the younger Triassic monzogranites captured and preserved fragments of the dioritic Permian lower continental crust during crystallization. These multiple stages of magmatic underplating and crustal reworking associated with vertical stratification of the juvenile paleo-continental crust suggest the monzogranites and diorites indicate a change from a post-collisional setting to a regional intraplate regime on the southern margin of the CAOB.

Zircon U–Pb dating of the Penggongmiao granite batholith in the western part of Cathaysia block, Hunan Province, South China, together with Hf isotopes and whole-rock elemental analyses, reveal critical insights into its depositional history. Zircon U–Pb geochronology traces the primary crystallization phase to between 445.3 ± 2.0 and 440.5 ± 1.9 Ma. An earlier onset indicated by 464.1 ± 0.9 Ma for fine- and medium-grained porphyritic granodiorite, suggests emplacement began before the Middle Ordovician. Geochemically, the rocks exhibit a calc-alkaline, ferruginous, and peraluminous composition, characterized by K₂O + Na₂O content of 6.46–8.32 wt %, Mg^# values of 21–42, and A/CNK ratios of 1.11–1.31. High ε_Hf(t) values ranging from –7.50 to –4.20, with T_DM2 ages of 1.54–1.73 Ga, point to magma derived predominantly from sedimentary sources, with strongly mantle contributions. Major and trace element data indicate that the batholith formed in a post-orogenic extensional setting during a transition from compressional orogeny to non-orogenic conditions. The evidence suggests that formation was the likely result of asthenospheric mantle upwelling due to the rollback of the Yangtze and Cathaysia blocks during subduction. This tectonic process caused partial melting of the lithospheric mantle and overlying ancient crustal material, producing a granite of mixed crust-mantle origin dominated by crustal sources.

The Late Paleozoic strata on the northwestern margin of the Tarim Block provide valuable insights into the subduction and collision processes that formed the Southwest Tianshan Orogenic Belt. This study integrates detrital zircon U-Pb dating and sandstone geochemical analysis of the Balikelike and Kalundaer formations to examine sedimentary provenance and tectonic settings during the Cisuralian–Guadalupian Epoch in the Keping area on the northwestern margin of the Tarim Block. Three of five Precambrian detrital zircon U-Pb age populations, 2500–2300 and 2000–1800 Ma and 900–600 Ma, are likely related to the fragmentation of the Columbia supercontinent and Rodinia’s assembly, respectively. Two Paleozoic detrital zircons, 500–380 Ma, are associated with Paleozoic magmatism. Among them, ~295 Ma zircons are associated with post-collisional extension and emplacement of the Tarim Large Igneous Province. Geochemical analysis of sandstones, coupled with tectonic reconstruction, indicates a passive continental margin setting in the northwestern margin of the Tarim Block during the Silurian Period, later transitioned to a foreland basin from the Pennsylvanian to the Guadalupian Epochs. The crustal transformation from the Middle-late Devonian to Early Mississippian marked the closure of the South Tianshan Ocean (STO), involving a soft collision and significant uplift, with major orogenesis occurring in the Late Guadalupian. Five key stages are identified in the evolution of the foreland basin: (1) Middle-late Devonian to Early Mississippian initiation (remnant ocean basin stage); (2) Late Mississippian to Early Pennsylvanian early stage; (3) Late Pennsylvanian to Early Cisuralian middle stage; (4) the Late Cisuralian stage; and (5) the terminal Guadalupian stage. These findings provide new constraints on when STO closed and propose an innovative foreland basin evolution model during the late post-collisional phase from the Late Mississippian to Guadalupian. Collectively, the data advance our understanding of the tectonic processes that shaped the northwestern Tarim Block, with broader implications for Paleozoic geodynamics.

Although considered a crucial component of the Rodinia supercontinent, it remains uncertain how the Yangtze craton relates to the accretion and breakup of Rodinia. Here, the Huanglingmiao granitic complex (HGC), an intermediate-acid rock series that intruded on the southern Kongling terrane of the northern Yangtze craton margin, is investigated to help resolve this conundrum. Our analysis indicates that these rocks consist of tonalite, trondhjemite, granodiorite, oligoporphyritic granodiorite, porphyric biotite granodiorite, and fine- to medium-grained granodiorite dyke compositions. Collectively, this assemblage is further subdivided into two categories by their temporal, spatial, and geochemical features into early TTG-like and later granitic–dioritic units, which are composed of tonalite, trondhjemite, granodiorite, porphyritic granodiorite, and the fine- to medium-grained granodiorite dykes, respectively. Zircon U-Pb dating yields ages of 865~850 Ma for the TTG-like rocks, 844~825 Ma for the porphyritic granodiorites, and ~800 Ma for the granodiorite dykes. Combined with geochemical evidence, the data suggest that the early- and late-series rocks were formed by a partial melting of Mesoproterozoic and Paleoproterozoic crustal materials, respectively, suggesting that the vertical layering of the crust controlled the composition of the independent units. In addition, isotopic evidence points to different sources for the various rocks in the Kongling terrane and that mantle-derived materials influenced the early-series lithologies. Combined with previous studies on the northern margin of the Yangtze craton, it is inferred that the early-series rocks formed in an active continental margin environment, while the late-series rocks display within-plate boundary formation characteristics. The multiple magmatic activities revealed by this study record sequential partial melting with tectonic transition characteristics from an Andean-type to within-plate magmatism in the northern margin of the Yangtze craton. Taken together, these observations point to a strong association between these rocks, convergence, and incorporation of the northern Yangtze craton margin into the Rodinia supercontinent during the Tonian Period.

Text: Analytical methods. Table S1: Representative electron microprobe analyses of garnet in eclogite samples. Table S2: Representative analyses of clinopyroxene (omphacite) in eclogite samples. Table S3: Representative microprobe analyses of low-sodic clinopyroxene in eclogite samples. Table S4: Representative microprobe analyses of amphibole in eclogite samples. Table S5: Representative microprobe analyses of plagioclase in eclogite samples. Table S6: Representative microprobe analyses of other minerals (orthopyroxene and epidote) in eclogite samples. Table S7: Whole-rock major (wt%) and trace element (ppm) analyses of eclogites in Nuomuhong area, East Kunlun orogenic belt. Table S8: SHRIMP Zircon U–Pb isotopic data from the eclogite in Nuomuhong area, East Kunlun orogenic belt. Table S9: Rare earth elements (ppm) analyses of the tested zircons from the retrograde eclogites.

Text: Analytical methods. Table S1: Representative electron microprobe analyses of garnet in eclogite samples. Table S2: Representative analyses of clinopyroxene (omphacite) in eclogite samples. Table S3: Representative microprobe analyses of low-sodic clinopyroxene in eclogite samples. Table S4: Representative microprobe analyses of amphibole in eclogite samples. Table S5: Representative microprobe analyses of plagioclase in eclogite samples. Table S6: Representative microprobe analyses of other minerals (orthopyroxene and epidote) in eclogite samples. Table S7: Whole-rock major (wt%) and trace element (ppm) analyses of eclogites in Nuomuhong area, East Kunlun orogenic belt. Table S8: SHRIMP Zircon U–Pb isotopic data from the eclogite in Nuomuhong area, East Kunlun orogenic belt. Table S9: Rare earth elements (ppm) analyses of the tested zircons from the retrograde eclogites.

Text: Analytical methods. Table S1: Representative electron microprobe analyses of garnet in eclogite samples. Table S2: Representative analyses of clinopyroxene (omphacite) in eclogite samples. Table S3: Representative microprobe analyses of low-sodic clinopyroxene in eclogite samples. Table S4: Representative microprobe analyses of amphibole in eclogite samples. Table S5: Representative microprobe analyses of plagioclase in eclogite samples. Table S6: Representative microprobe analyses of other minerals (orthopyroxene and epidote) in eclogite samples. Table S7: Whole-rock major (wt%) and trace element (ppm) analyses of eclogites in Nuomuhong area, East Kunlun orogenic belt. Table S8: SHRIMP Zircon U–Pb isotopic data from the eclogite in Nuomuhong area, East Kunlun orogenic belt. Table S9: Rare earth elements (ppm) analyses of the tested zircons from the retrograde eclogites.

The Early Permian Yuejin Sumu intrusive rocks are located approximately 40 km northwest of Xilinhot City, Inner Mongolia. The magmatic rocks primarily composed of gabbro, diorite, and syenogranite. Through the study of zircon LA-ICP-MS U–Pb geochronology and rock geochemistry, age dates of the three lithologies show that the three formed simultaneously in the late Early Permian (gabbro formation age is 276.7 ± 1.3 Ma; diorite is 276.9 ± 0.8 Ma; syenogranite is 275.0± 1.4 Ma). The geochemical characteristics of the three lithologies are primarily calc-alkaline, and some samples, such as gabbro and diorite, show a transition to the alkaline series. The oxides in the gabbro and diorite are linearly related to SiO₂. With magma MgO content, Al₂O₃ content increases first and then decreases, while CaO content decreases sharply, suggesting that the magma for the gabbro and diorite is a mantle-derived magma that undergoes separation and crystallization. The crystalline minerals include magnesia-rich pyroxene in the early stage and the plagioclase and pyroxene in the late stage. The syenogranite has high aluminum content (12.8–14.6%), and the ratio of FeO^T/Mg^# is high. Rare earth elements are characterized by a mid-range of the light and heavy rare earth elements. Eu shows significant negative anomalies, and the whole rare earth elements (REEs) are characterized by V-shaped distribution. The syenogranite are enriched in K, Rb, Th, U, Zr, and depleted in Eu, Ba, Sr, Ti, P, Nb, Ta, indicating that the magma may derived from crust in a typical post-orogenic environment. Petrology and geochemical characteristics of the Early Permian intrusive rocks indicate that in the Early Permian (~274–278 Ma) in the Xilinhot area was back-arc extensional environment at the active continental margin. Mantle-derived magma caused partial melting of the crustal material. The mantle-derived magma and the melt of the crustal material formed the Early Permian bimodal-like Yuejin Sumu intrusive rocks.