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The subduction of the Paleo‐Pacific Plate beneath the NE Asian continental margin induced extensive magmatism, providing an excellent opportunity to investigate the interplay between plate dynamics, arc magmatism, continental crust formation, and porphyry mineralization. Here, we integrate mineralogical, geochronological, geochemical, and isotopic analyses of diverse Early Cretaceous magmatic assemblages in the Yanbian Fold Belt (NE China), aiming to reconstruct the evolution of a transcrustal magmatic plumbing system and constrain the key factors controlling porphyry mineralization during slab rollback. Dioritic enclaves (∼123 Ma) represent rapidly ascending mantle‐derived magmas that underwent magma mixing/mingling and quenching before solidification. Granitic intrusions (∼118 Ma) with low Sr/Y were attributed to a depleted crustal source with plagioclase and biotite fractionation. Mafic dikes (∼116 Ma) from a bimodal suite originated from a slab‐fluid‐metasomatized lithospheric mantle with increased input from the depleted mantle, whereas felsic dikes (∼115 Ma) with high Sr/Y resulted from melting of a juvenile lower crust under garnet amphibolite facies conditions. These rock assemblages record back‐arc crustal growth, reworking, and maturation. Compared with earlier (peaking at ∼130 Ma) back‐arc magmatism farther west in the Great Xing'an Range, our newly identified bimodal magmatism (initiated at ∼118 Ma) in the Yanbian area reveals a rapid rollback of ∼600 km within ∼12 Myr. Moreover, the late Early Cretaceous magmas exhibit significantly higher magmatic oxygen fugacity (ΔFMQ > +1, where FMQ is the fayalite‐magnetite‐quartz oxygen fugacity buffer) than their Jurassic counterparts (with ΔFMQ values generally below +0.5), paralleling regional porphyry‐related mineralization and revealing the critical role of slab rollback in modulating arc magmatic fertility. Our findings highlight how transient rollback episodes can generate diverse magmatic differentiation pathways and metallogenic triggers in supra‐subduction zone settings.

This paper explores the evolutional process of back-arc basin (BAB) magma system at final spreading stage of extinct BAB, Shikoku Basin (Philippine Sea) and assesses its tectonic evolution using a newly discovered oceanic core complex, the Mado Megamullion. Bulk and in-situ chemical compositions together with in-situ Pb isotope composition of dolerite, oxide gabbro, gabbro, olivine gabbro, dunite, and peridotite are presented. Compositional ranges and trends of the igneous and peridotitic rocks from the Mado Megamullion are similar to those from the slow- to ultraslow-spreading mid-ocean ridges (MOR). Since the timing of the Mado Megamullion exhumation corresponds to the very end of the Shikoku Basin opening, the magma supply was subdued and highly episodic, leading to extreme magma differentiation to form ferrobasaltic, hydrous magmas. In-situ Pb isotope composition of magmatic brown amphibole in the oxide gabbro is identical to that of depleted source mantle for mid-ocean ridge basalt (MORB). In the context of hydrous BAB magma genesis, the magmatic water was derived solely from the MORB source mantle. The distance from the back-arc spreading center to the arc front increased away through maturing of the Shikoku Basin to cause MORB-like magmatism. After the exhumation of Mado Megamullion along detachment faults, dolerite dikes intruded as a post-spreading magmatism. The final magmatism along with post-spreading Kinan Seamount Chain volcanism were introduced around the extinct back-arc spreading center after the opening of Shikoku Basin by residual mantle upwelling.

New zircon U–Pb ages and whole-rock chemical data from four adakitic and two non-adakitic igneous rocks as tectonic blocks in the southern West Junggar accretionary complexes, northwestern China and one gabbro enclave in adakitic block provide further constraints on the initial subduction and following rollback process of the Junggar Ocean as part of southern Palaeo-Asian Ocean. The oldest adakitic monzonite in Tangbale is intruded by the non-adakitic quartz monzonite at 549 Ma, and the youngest adakitic diorite in Tierekehuola formed at 520 Ma. The Ediacaran–Cambrian magmatism show a N-wards younger trend. The high-SiO 2 adakitic rocks have high Sr (300–663 ppm) and low Y (6.68–12.2 ppm), with Sr/Y = 40–84 and Mg no. = 46–60, whereas the non-adakitic rocks have high Y (13.2–22.7 ppm) and Yb (2.32–2.92 ppm), with Mg no. = 36–40. The gabbro has high MgO (14.81–15.11 wt%), Co (45–48 ppm), Cr (1120–1360 ppm) and Ni (231–288 ppm), with Mg no. = 72–73. All the samples show similar large-ion lithophile element (LILE) and light rare earth element (LREE) enrichment and Nb, Ta, Ti and varying Zr and Hf depletion, suggesting that they were formed in a subduction-related setting. The adakitic rocks were produced by partial melting of subducted oceanic slab, but the melts were modified by mantle wedge and slab-derived fluids; the non-adakitic rocks were likely derived from partial melts of the middle-lower arc crust; and the gabbro originated from the mantle wedge modified by slab-derived fluids. The magmatism could have been generated during the Ediacaran initial subduction and Cambrian slab rollback of the Junggar Ocean.

The western Hellenic subduction zone (WHSZ) exhibits well‐documented along‐strike variations in lithosphere density (i.e., oceanic versus continental), subduction rates, and overriding plate extension. Differences in slab density are believed to drive deformation rates along the WHSZ; however, this hypothesis has been difficult to test given the limited seismic constraints on the structure of the WHSZ, particularly beneath northern Greece. Here, we present high‐resolution seismic images across northern and southern Greece to constrain the slab composition and mantle wedge geometry along the WHSZ. Data from two temporary arrays deployed across Greece in a northern line (NL) and southern line (SL) are processed using a 2D teleseismic migration algorithm based on the Generalized Radon Transform. Images of P‐ and S‐wave velocity perturbations reveal N60E dipping low‐velocity layers beneath both NL and SL. The ∼8 km thick layer beneath SL is interpreted as subducted oceanic crust while the ∼20 km thick layer beneath NL is interpreted as subducted continental crust. The thickness of subducted continental crust inferred within the upper mantle suggests that ∼10 km of continental crust has accreted to the overriding plate. The relative position of the two subducted crusts implies ∼70–85 km of additional slab retreat in the south relative to the north. Overall, our seismic images are consistent with the hypothesis that faster sinking of the denser, oceanic portion of the slab relative to the continental portion can explain the different rates of slab retreat and deformation in the overriding plate along the WHSZ. Key Points Seismic images show subducted oceanic crust beneath southern Greece Seismic images show subducted continental crust beneath northern Greece The subducted crusts' position implies ~70 km more retreat of the oceanic slab

Post-collisional (23–8 Ma), potassium-rich (including ultrapotassic and potassic) mafic magmatic rocks occur within the north–south-trending Xuruco lake–Dangre Yongcuo lake (XDY) rift in the Lhasa terrane of the southern Tibetan Plateau, forming an approximately 130-km-long semi-continuous magmatic belt. They include both extrusive and intrusive facies. Major and trace element and Sr–Nd–Pb isotopic data are presented for all of the known exposures within the XDY rift. The potassium-rich, mafic igneous rocks are characterized by high MgO (5.9–10.8 wt.%), K 2 O (4.81–10.68 wt.%), Ba (1,782–5,618 ppm) and Th (81.3–327.4 ppm) contents, and relatively high SiO 2 (52.76–58.32 wt.%) and Al 2 O 3 (11.10–13.67 wt.%). Initial Sr isotopic compositions are extremely radiogenic (0.712600–0.736157), combined with low ( 206 Pb/ 204 Pb) i (18.28–18.96) and ( 143 Nd/ 144 Nd) i (0.511781–0.512046). Chondrite-normalized rare earth element patterns display relatively weak negative Eu anomalies. Primitive mantle-normalized incompatible trace element patterns exhibit strong enrichments in large ion lithophile elements relative to high-field-strength elements and display strongly negative Ta–Nb–Ti anomalies. The combined major and trace element and Sr–Nd–Pb isotopic characteristics of the K-rich igneous rocks suggest that the primitive magmas were produced by 1–10 % partial melting of an asthenospheric mantle source enriched by both fluids and partial melts derived from Indian passive continental margin sediments subducted into the shallow mantle as a consequence of the northward underthrusting of the Indian continental lithosphere beneath Tibet since the India–Asia collision at ~55 Ma. The best-fit model results indicate that a melt with trace element characteristics similar to those of the K-rich rocks could be generated by 8–10 % partial melting of a metasomatized mantle source in the south and 1–2 % melting in the north of the XDY rift. Trace element and Sr–Nd–Pb isotopic modeling indicate that the proportion of fluid derived from the subducted sediments, for which we use as a proxy the Higher Himalayan Crystalline Sequence (HHCS), in the mantle source region increases from north (rear-arc) to south (front-arc), ranging from 0 to 5 %, respectively. Correspondingly, the proportion of the melt derived from the subducted HHCS in the source increases from north (2 %) to south (15 %). The increasing proportion of the fluid and melt component in the mantle source from north to south, together with a southward decreasing trend in the age of the K-rich magmatism within the XDY rift, is inferred to reflect rollback of the subducted Indian lithospheric mantle slab during the period 25–8 Ma. Slab rollback may be linked to a decreasing convergence rate between India and Asia. As a consequence of slab rollback at 25 Ma beneath the Lhasa terrane, its geodynamic setting was transformed from a convergent (55–25 Ma) to an extensional (25–8 Ma) regime. The occurrence of K-rich magmatism during the period 25–8 Ma is a consequence of the decompression melting of an enriched mantle source, which may signal the onset of extension in the southern Tibetan Plateau and provide a petrological record of the extension process.

Slab rollback during subduction plays a key role in controlling continental growth at convergent plate boundaries. The dynamics of currently subducting slabs can be precisely constrained using geophysical techniques. In contrast, ancient episodes of slab rollback can be difficult to constrain, yet are critical to unlocking the tectonic evolution of long‐lived orogens such as the Phanerozoic Australian Tasmanides of eastern Gondwana. Recognition of ancient slab rollback relies on the identification of the progressive migration of magmatic arcs. Here, we investigate the timing and isotopic variation of ∼90 km of the trans‐orogen migration of the Carboniferous Bathurst Batholith as a potential indicator of slab rollback. U–Pb–Hf isotopes, combined with a regional zircon Hf isotope data set, suggest that the eastward migration of the batholith over ∼18 Myr, from 340.1 to 322.4 Ma, records a maximum slab steepening rate of ∼0.6–1.2° Myr−1 in a relatively stable trench setting. These results provide a magmatic record of Carboniferous slab rollback and establish a missing link between the long‐lived Lachlan and New England orogens of the eastern Gondwanan Tasmanides. Plain Language Summary Slab rollback occurs at convergent plate boundaries, which is key to understanding the evolution of subduction processes. However, for ancient subduction zones where the geometry of long since subducted slabs no longer exists, the evolution of slab dynamics remains unclear. Occasionally though, the progressive migration of magmatic trends is observable and provides constraints on slab rollback, which aid in reconstructing the tectonic evolution of long‐lived orogens, such as the Phanerozoic orogens of eastern Australia. Here, we focus on how the unique magmatism of the Carboniferous Bathurst Batholith progressively migrated in the direction of the trench and analyze and interpret the geochronological and geochemical evolution of the batholith to better constrain subduction dynamics. We find that the Bathurst Batholith records the Carboniferous slab rollback of eastern Gondwana and reveals the relationship between the two key orogens of eastern Australia. Thus, the migration of magmatism in convergent settings can be used to track the slab rollback processes and evolution of the long‐lived orogens. Key Points The Bathurst Batholith is part of a Carboniferous continental arc formed as a result of westward subduction in eastern Gondwana Eastward migration of the batholith over ∼18 Myr recorded a maximum slab steepening rate of ∼0.6–1.2° Myr−1 in a stable trench setting The batholith as a trans‐orogen “missing link” reveals continental arc magmatism extended across the Lachlan and New England orogens

About 45% of tungsten, ∼20% of tin, and ∼9% of fluorite of known world reserves are associated with Late Mesozoic igneous rocks, Southeast (SE) China. Here we demonstrate that Fogang granite, the largest inland batholith, is mainly of A2-type that is commonly found in post-orogenic settings and experienced plate subduction induced metasomatism. In contrast, the Yajishan syenite and Nankunshan granite intruding the Fogang granite ∼20 Ma later are of A1-type formed in intraplate settings. We found that F-rich fluid fractionation, which could make the decline of Ga/Al ratio, total (Nb + Y + Ce + Zr) and Zr concentrations, Nb/Ta and Zr/Hf ratios, leads to chemical variations of a few Fogang granites changing from A2-type to highly fractionated or I- and S-type granitoids. Crystal and F-rich fluid fractionations, as well as crustal contamination most likely derived from the Fogang granite, result in some Nankunshan granites developing from A1-type into A2-type. These late- or post-magmatic processes should be taken into account carefully when discriminating the petrogenetic types of igneous rocks, especially for the A2-type suites. Combining with the distribution of 180–140 Ma A1- and A2-type igneous rocks, rare metal deposits, and fluorite deposits in SE China, we highlight the significant role of slab-released F-rich fluids in formation of A-type suites and subsequent chemical differentiation and rare metal and fluorine mineralization. A model of flat-slab northeastward rollback is thus proposed, in which the subduction front reached somewhere near Fogang and then started to roll back at ∼165 Ma. The inland Jurassic granites of SE China represent a unique locality for formation of A-type suites and their associated mineralization. These granites are not anorogenic, but they are the result of slab rollback from a flat slab, founding of that slab at shallow levels, and metasomatism of by F-rich fluids related to slab heating by the asthenosphere.

We present crustal deformation results from a geodetic experiment (Retreating‐Trench, Extension, and Accretion Tectonics (RETREAT)) focused on the northern Apennines orogen in Italy. The experiment centers on 33 benchmarks measured with GPS annually or more frequently between 2003 and 2007, supplemented by data from an additional older set of 6 campaign observations from stations in northern Croatia, and 187 continuous GPS stations within and around northern Italy. In an attempt to achieve the best possible estimates for rates and their uncertainties, we estimate and filter common mode signals and noise components using the continuous stations and apply these corrections to the entire data set, including the more temporally limited campaign time series. The filtered coordinate time series data are used to estimate site velocity. We also estimate spatially variable seasonal site motions for stations with sufficient data. The RMS scatter of residual time series are generally near 1 mm and 4 mm, horizontal and vertical, respectively, for continuous and most of the new campaign stations, but scatter is slightly higher for some of the older campaign data. Velocity uncertainties are below 1 mm/yr for all but one of the stations. Maximum rates of site motion within the orogen exceed 3 mm/yr (directed NE) relative to stable Eurasia. This motion is accommodated by extension within the southwestern and central portions of the orogen, and shortening across the foreland thrust belt to the northeast of the range. The data set is consistent with contemporaneous extension and shortening at nearly equal rates. The northern Apennines block moves northeast faster than the Northern Adria microplate. Convergence between the Northern Apennines block and the Northern Adria microplate is accommodated across a narrow zone that coincides with the northeastern Apennines range front. Extension occurs directly above an intact vertically dipping slab inferred by previous authors from seismic tomography. The observed crustal deformation is consistent with a buried dislocation model for crustal faulting, but associations between crustal motion and seismically imaged mantle structure may also provide new insights on mantle dynamics. Key Points Syn‐convergent extension is active in the northern Apennines There is net divergent motion across the northern Apennines Geodetic data are most consistent with slab rollback plus upper plate retreat

The Pacific Northwest (PNW) has a complex tectonic history and over the past ∼17 Ma has played host to several major episodes of intraplate volcanism. These events include the Steens/Columbia River flood basalts (CRB) and the striking spatiotemporal trends of the Yellowstone/Snake River Plain (Y/SRP) and High Lava Plains (HLP) regions. Several different models have been proposed to explain these features, which variously invoke the putative Yellowstone plume, rollback and steepening of the Cascadia slab, extensional processes in the lithosphere, or a combination of these. Here we integrate seismologic, geodynamic, geochemical, and petrologic results from the multidisciplinary HLP project and associated analyses of EarthScope USArray seismic data to propose a conceptual model for post‐20 Ma mantle dynamics beneath the PNW and the relationships between mantle flow and surface tectonomagmatic activity. This model invokes rollback subduction as the main driver for mantle flow beneath the PNW beginning at ∼20 Ma. A major pulse of upwelling due to slab rollback and upper plate extension and consequent melting produced the Steens/CRB volcanism, and continuing trench migration enabled mantle upwelling and hot, shallow melting beneath the HLP. An additional buoyant mantle upwelling is required to explain the Y/SRP volcanism, but subduction‐related processes may well have played a primary role in controlling its timing and location, and this upwelling likely continues today in some form. This conceptual model makes predictions that are broadly consistent with seismic observations, geodynamic modeling experiments, and petrologic and geochemical constraints. Key Points We propose a conceptual model for mantle dynamics beneath the Pacific Northwest The main drivers for mantle processes are rollback subduction and extension Our model is consistent with the volcanic history over the past ~20 Ma

The South Tianshan records the latest accretionary and collisional events in the southwestern Altaids, but the internal subduction-related processes are controversial. This study provides an integrative analysis of a newly identified Late Carboniferous adakitic granodiorite from the South Tianshan, incorporating geochronological, zircon U-Pb and Lu-Hf isotopic, whole-rock geochemical, and Sr-Nd isotopic data. Zircon U-Pb analysis indicates that the granite was emplaced at 310 ± 2.5 Ma. Based on major element compositions, the granodiorite belongs to medium-K calc-alkaline weakly peraluminous series (A/CNK = 0.95–1.09). The samples exhibit typical high-silica adakitic affinity, as evidenced by the elevated contents of SiO2 (67.75–69.27 wt.%), Al2O3 (15.29–15.90 wt.%), Sr (479–530 ppm), and Ba (860–910 ppm); low concentrations of Yb (0.43–0.47 ppm) and Y (7.12–7.44 ppm); high Sr/Y ratios (67–72); and slight Eu anomalies (δEu = 0.89–1.03). The sodium-rich composition (K2O/Na2O = 0.48–0.71) is comparable to adakitic rocks from slab-derived melts. Elevated concentrations of Ni (22.12–24.25 ppm), Cr (33.20–37.86 ppm), Co (6.32–6.75 ppm), and V (30.33–32.48 ppm), along with high Mg# values (55–57), suggest melt–mantle interaction during magma ascent. The slightly enriched isotopic signatures, characterized by higher initial 87Sr/86Sr ratios (0.706086–0.706205) and lower εNd(t) (−3.09 to –2.47) and εHf(t) (−3.11 to +7.66) values, point to notable sedimentary contributions, potentially through source contamination and/or shallow-level crustal contamination. By integrating the new results with previously published data, we consider that the adakitic granodiorite was generated by partial melting of the subducted oceanic crust, triggered by asthenospheric upwelling associated with the southward rollback of the north-dipping South Tianshan oceanic lithosphere. Our data provide new insights into Late Carboniferous retreating subduction along the southern active margin of the Yili-Central Tianshan and the accretionary architecture of the southern Altaids.