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The timing and duration of silicic magmatism at relatively small volcanic centres in the geological record remain poorly constrained but are vital for understanding the temporal evolution of magmatic provinces. The Palaeogene Central Arran Igneous Complex (CAIC), and the nearby North Arran Granite, show spatial and temporal relationships between silicic intrusions and intra-caldera volcanic deposits. High-precision UPb zircon geochronology, integrated with detailed field observations, allows a timeline of silicic magmatic activity on Arran to be constrained. Silicic magmatism in north and central Arran occurred as a very short-lived (∼0.5 Ma) ‘pulse’ during the protracted (>8 Ma) evolution of the British Palaeogene Igneous Province (BPIP). Evolution of the CAIC volcano from caldera collapse to eruption of the youngest preserved unit (including several phases of eruption punctuated by quiescent periods of land surface erosion and deposition of sediments) took no more than 185 ka. Silicic magmatism at the complex (volcanism followed by intrusion of granites) lasted no more than 330 ka, with the North Arran Granite was emplaced shortly prior to the CAIC. This evidence of a short magmatic pulse accompanied by drastic land-surface changes has major implications for our understanding of localised silicic magmatism in other igneous provinces, both in the geological record and the present day.

The Early–Middle Jurassic period represented a crucial juncture for the Northeast Asian continent, marked by significant geological transformations. These included the initial thinning of the North China Craton (NCC), the closure of the Mongol-Okhotsk Ocean (MOO), and the subduction of the Izanagi Plate. Despite the acknowledged significance of these events, the specific temporal and spatial extents of the two tectonic regimes influencing the Northeast Asian continent remain uncertain. This study aims to elucidate these ambiguities, focusing on the spatiotemporal extents of magmatic activity and deformation driven by these distinct tectonic regimes. To achieve this, our research integrates comprehensive analyses of magmatism, stratigraphy, and deformation across the Northeast Asian continent. Our findings highlight the spatially non-uniform intensity of magmatism in Northeast China and the NCC during the Early–Middle Jurassic, pointing to a heterogeneous influence of the tectonic regimes over time and space. This early stage of the orogeny was also signed by local extensional tectonics within the NCC's eastern parts, as opposed to the compressional deformation in the western part, within the Songliao basin. However, the overall extension intensity over the entire region may not have been very pronounced. During the middle to late Middle Jurassic, there was a shift in the scenario, with compression-dominated deformation expanding across the Northeast Asian continent, indicating a significant change in tectonic dynamics. Further analysis reveals the distinct impacts of the Izanagi Plate's subduction beneath the Jiamusi–Khanka Block and the Yanshan fold-and-thrust belt, as well as the MOO tectonic regime's influence on the western Songliao basin, extending to the northern Ordos basin. Interestingly, a substantial portion of the craton remained relatively unaffected during the initial stages of Izanagi Plate's subduction and MOO's closure. However, these events laid the groundwork for the extensive destruction of the craton witnessed during the Late Jurassic–Early Cretaceous period. This study significantly contributes to our understanding of the geological processes in the Northeast Asian continent during the Mesozoic, offering valuable insights into the dynamic interplay of tectonic regimes that shaped this region. By delineating the spatial and temporal extents of magmatic activity and deformation, we provide a clearer picture of the geological evolution of the Northeast Asian continent, highlighting the complexity and variability of tectonic influences during the Early–Middle Jurassic.

Late Miocene ultrapotassic rocks are widely exposed in the Saray Peninsula of northwestern Iran. These rocks are mainly classified as tephrite-tephritic phonolite with some trachyte and lamprophyre dikes with porphyritic textures. Ca-rich pyroxene and leucite are the main phenocrysts. Olivine and phlogopite with some sodic amphiboles occur locally as phenocrysts. Chemically, the rocks are characterized by low contents of SiO₂ (45.4–47.3 wt%), with high contents of K₂O (3.4–6.6 wt%), K₂O/Na₂O (1.2–5.7), MgO (5.6–9.1 wt%), CaO (10.3–12.7 wt%) and Sr (826–2020 ppm) with low P₂O₅/Al₂O₃ (0.08–0.14). Chondrite normalized REE and primitive mantle-normalized patterns indicate the involvement of a LREE (La, Ce) and LILE (Cs, Ba, Pb) enriched mantle, and weak negative Ti-Nb-Ta anomalies are observed. Isotopically, the rocks show high ⁸⁷Sr/⁸⁶Sr ratios (0.7071–0.7084) and low εNd(t) values (–3.8 to –1.8). Their δ¹³C values show a variation from –13.4 ‰ to –6.5 ‰, confirming some organic carbon recycling in the subduction zone, and the absence of Ce/Ce* and Eu/Eu* negative anomalies confirm the redox system melting. The SrNd isotopic values, higher contents of incompatible elements, and lower δ¹³C values suggest a continental crustal material involvement for the sources of these rocks. The presence of calcite in the matrix, the inclusion of melt droplets with some calcite, and the carbonation of leucite and pyroxene grains confirm the high CO₂ content during magmatic evolution and/or the late stages of reaction of CO₂-fluid rocks with earlier minerals. Due to the situation of the Saray ultrapotassic rocks near the junction of the Van microplate and the NW Iran block, dragging of the Van microplate beneath NW Iran is likely to have transported some carbonate rocks and biogenetic organic carbon into the mantle and converted the primitive mantle to carbonate peridotite. A very low rate of partial melting at a pressure of less than 3 GPa around the garnet-spinel stable zone produced ultrapotassic melts. The correlation with some neighboring ultrapotassic rocks shows that this process is a dominant factor to generate the kamafugite and/or interval of kamafugite-Roman type ultrapotassic series in a collision system, without considering the role of mantle phlogopite present in the deep metasomatized mantle. This work shows why most of the ultrapotassic rocks in Iran have developed near the suture zone after the closure of Neotethys.

Intracrystalline chemical diffusion offers valuable insights into the durations of metamorphic and igneous processes. However, it can yield timescale estimates for orogenic and subduction zone events that are considerably shorter than those obtained via isotopic geochronology. One potential explanation that has been offered for the discrepancy is that the interdiffusion of species with different atomic or ionic radii may generate intracrystalline, compositional stresses that alter or limit diffusional relaxation. In this study we test this idea by developing and applying the compositional stress theory of materials scientists F. Larché and J. Cahn to garnet from the Barrovian sillimanite zone, Scotland. Relaxed contacts from the garnet, independent diffusion chronometers, and thermal modeling all indicate a >100 kyr duration for peak temperature metamorphism. Nonetheless, the garnet records sharp, μm-scale variations in calcium and iron contents that standard diffusion treatments predict should relax in 1–10 kyr at peak temperature conditions. Our results show that the development of compositional stress during diffusional relaxation can explain the preservation of the observed short wavelength compositional oscillations at a >100 kyr timescale. Thus, it may be necessary to account for compositional stress when modeling diffusion in solid solutions with appreciable differences in their endmember molar volumes. This will be particularly relevant when considering sharp, μm-scale chemical gradients involving grossular, the garnet endmember with the largest molar volume relative to pyrope, almandine, and spessartine. Neglecting compositional stress in such cases could result in the underestimation of the timescales of lithospheric processes by potentially orders of magnitude. The effects of compositional stress in garnet are predicted to be the most pronounced under amphibolite and blueschist–eclogite facies conditions. At lower temperatures diffusion is limited, and at higher temperatures both plastic deformation and more ideal solid solution behavior will act to diminish the impact of stress.

This study presents the structural and petrological characteristics of mantle peridotites in relation to the rock-hydrous melt reaction found in the Hayachine ultramafic complex, NE Japan. We conducted sampling, microstructural observations, crystal-orientation analyses, and major element composition analyses of the major constituent minerals in the peridotites. We used 17 serpentinized peridotites that preserved better mantle textures. The peridotites are composed of lherzolite to harzburgite, consisting of olivine, orthopyroxene, clinopyroxene, amphibole, and spinel. The peridotites were classified into two textures according to olivine grain size: coarse-grained (ca. 2–3 mm) and fine-grained (ca. 0.3–0.5 mm). Fine-grained peridotites were newly found in this study and were characterized by aggregates of orthopyroxene and amphibole with a large number of spinel inclusions. Based on olivine crystal-preferred orientation (CPO), we found that the coarse-grained peridotites were further classified into Group 1 (A type CPO) and 2 (AG type CPO) and the fine-grained peridotites were accordingly classified into Group 3 (weak CPO). The systematic continuity in the chemical compositions of the minerals suggests that Group 1 peridotites partially melted to form Group 2 peridotites, followed by Group 3 peridotites, due to further reaction of Group 2 peridotites with hydrous melts. These textural and chemical variations in the peridotites could have resulted from rock-hydrous melt reactions under back-arc spreading and subsequent processes.

The Pamir Plateau contains critical information on the tectonic evolution of the Tethys domain. In this study, we report geochronology, geochemistry, and Sr-Nd-Hf isotopic compositions of the Cenozoic adakitic monzogranite in the Reskam and Taxkorgan areas, NE Pamir, to provide new insights into the post-collisional tectonic evolution following the India-Eurasian collision. Zircon UPb ages reveal these granitoids were emplaced at ca 12–8 Ma. Geochemically, they exhibit relatively uniform whole-rock major and trace element compositions, and share typical adakitic signatures with high SiO₂ (68.55–73.30 wt%), moderate Al₂O₃ (14.11–15.84 wt%), elevated Sr (399–1710 ppm) and La (34–182 ppm), but low Y (5.53–15.10 ppm) and Yb (0.39–1.26 ppm), and thus in high Sr/Y (32−200) and (La/Yb)_N ratios (20–236). Isotopically, these adakitic rocks show significantly enriched whole-rock SrNd (ε_Nd(t) = −7.97 to −5.76; ⁸⁷Sr/⁸⁶Sr(t) = 0.7072–0.7110) and zircon Hf (mostly ε_Hf(t) -5 to −2) isotopic compositions. Elemental and isotope signatures indicate their origin from partial melting of mafic-intermediate sources under high pressure, with a residuum of negligible feldspar but dominant garnet. Integrating the new findings with reported data of granitoids in the Pamir, we estimate the crustal thickness variations from the Cretaceous to Miocene. The crustal thickness in the Pamir region largely remained no more than 45 km before India-Asia collision, after which a significant increase in crustal thickness occurred, reaching a peak of 80–100 km around 10 Ma. We propose that the break-off of the subducted Neo-Tethys oceanic slab (ca. 40 Ma) and lithospheric delamination (ca. 25 Ma) led to two-stage rapid continental uplift events in Pamir Syntax.

Alpine subduction of a block of olivine gabbro produced a plethora of different assemblages and local structures typical of high-pressure and low-temperature metamorphism. However, gabbro with the locally well-preserved igneous assemblage olivine - augite - plagioclase occurs in some domains of a 2 km long outcrop (Allalinhorn, western Alps).

A large variety of hydrate minerals including zoisite, glaucophane, talc, Mg-chloritoid, chlorite, paragonite and muscovite formed during Alpine subduction of the metagabbro. The three primary igneous minerals have been replaced by hydration reactions during Eocene subduction. Talc, omphacite, and zoisite + jadeite and are the main minerals in the local domains after olivine, augite and plagioclase respectively. The rocks preserved the coarse grained igneous texture.

An excellent overview of the complex coarse textures of the eclogite facies rocks has been provided by element distribution maps produced from up to 25 cm large polished slabs of typical samples of Allalingabbro using a μXRF instrument. The RGB images suggest that the minerals formed at the high-pressure in the presence of an aqueous fluid. The pseudomorphing reactions progressed close to volume conservation. The hydration reactions required an H₂O fluid containing dissolved solids. The mapped distribution of elements including trace elements provides important clues on the origin and mobility of these elements in the hydration fluid. The homogeneously distributed immobile Cr in omphacite portrays primary augite. The irregular patchy Sr distribution resulted from small-scale migration of components replacing plagioclase by Sr-bearing zoisite and jadeite. Coherent Ni signals are related to the presence of talc. The talc occurs as a late infill of structures produced by dissolving olivine. Mg-chloritoid, kyanite and mica coat the former grain-boundary of olivine and plagioclase suggesting that olivine dissolved at eclogite facies conditions. Talc formed at distinctly lower pressures, however, as implied by computed model reactions. The olivine replacement structures are often larger than the size thin section and can be excellently studied by the large size μXRF patterns used in this study.

The fractured surroundings of the locations of olivine provided the necessary hydraulic conductivity for hydration reactions to progress. The fractures and small veinlets contain late Ni-bearing talc. Cl is only present in very late vein amphibole suggesting that hydration fluids in the subduction zone transported dissolved components as hydrous complexes (and their dissociated ions). There is no evidence for the presence of a Cl-brine during subduction. In addition to primary olivine as a local Ni source, the element may also have partly been imported with the hydration fluid and originate from dehydration of ophiolitic serpentinites in the slab.

The Mesozoic magmatic activation in Central and Northeast Asia resulted in the formation of a large volume of volcanic rocks with diverse compositions. The most dramatic compositional change occurred at the end of the Early Cretaceous, when mainly alkaline basaltic lavas began to erupt after subalkaline differentiated lavas. The nature of crustal and mantle processes that led to this change in volcanism remains unclear. The Torey Volcanic Field (TVF) of Eastern Transbaikalia (Russia) demonstrates a similar compositional change. Therefore, the TVF is crucial to studying the cause of the difference in geochemical and isotopic signatures of the Mesozoic volcanism in Central and Northeast Asia.

TVF belongs to the northeastern end of the Eastern Mongolia Volcanic Area (EMVA). Like other volcanic fields of the EMVA, TVF formed in two stages: early (∼121–129 Ma) and late (∼101–119 Ma). The TVF is composed of subalkaline and alkaline basaltic trachyandesites – trachyandesites. All TVF rocks are characterized by negative Ti and Sr anomalies and positive Ba and Pb anomalies. Compared to the late TVF rocks, the early TVF rocks have distinct negative Ta and Nb anomalies and are highly enriched in light rare earth elements relative to heavy rare earth elements. TVF rocks have the following isotopic characteristics: ⁸⁷Sr/⁸⁶Sr_(t) = 0.70477–0.70540, ε_{Nd(t) =} − 0.9 – +2.4, ²⁰⁶Pb/²⁰⁴Pb_(t) = 17.9–18.4, and ²⁰⁷Pb/²⁰⁴Pb_(t) = 15.5–15.6. However, older rocks mainly have higher ε_Nd(t) values and ²⁰⁶Pb/²⁰⁴Pb_(t) and ²⁰⁷Pb/²⁰⁴Pb_(t) ratios.

Geochemical and isotopic data of samples suggest that the TVF formed by melting in the continental metasomatized lithospheric mantle (CMLM). Phlogopite-amphibole-rutile-bearing pyroxenite veins played a major role in the formation of older rocks. Eclogite, represented by the recycled oceanic crust or the buried lower continental crust, was dominant in the source of younger rocks. The common source for both groups of the TVF rocks was metasomatized hydrous peridotite.

Lithospheric extension and subsequent asthenospheric upwelling led to melting in the CMLM and the formation of the TVF. At the early stage of the volcanism, melting occurred at relatively low temperatures where amphibole, phlogopite, and rutile were stable. Due to ongoing lithosphere extension, the melting of eclogite occurred at a higher temperature and/or lower pressure at the late stage of the volcanism.

Ureilites are meteorites derived from the mantle of a reduced differentiated asteroid, the “Ureilite Parent Body” (UPB), which was later disrupted by impact with another Solar System body. They have ultramafic compositions dominated mostly by olivine and pigeonite with rare orthopyroxene and augite; aluminous phases are generally absent. Ureilites vary from abundant peridotites to much rarer pyroxenites, and their core olivine compositions range from Fo₇₄ to Fo₉₇ across different samples. The UPB experienced sufficiently high temperatures to undergo silicate partial melting, as shown by depletion in the Light Rare Earth Elements (LREE) in bulk restitic ureilites. Plagioclase and merrillite were probably present in the UPB mantle but have been completely removed during silicate partial melting. Partial melts of the UPB mantle are represented by glassy melt inclusions, igneous clasts in ureilite breccias, cumulus augite in some ureilites, and rare trachyandesitic fragments. These melts are generally intermediate and sub-alkaline in composition, although a few are alkaline. They have more enriched and flatter bulk REE patterns than the restitic ureilites and often show positive Eu anomalies. Glasses (representing melts) in ureilites from this study range from 57 to 79 wt% SiO₂. One sample (AhS 22) shows petrographic and geochemical evidence for interaction between magma and the solid UPB mantle by forming metasomatic augite.

Silicate minerals in ureilites analysed by LA-ICP-MS are generally LREE-depleted, with negative Eu anomalies. Ureilitic olivines have the lowest REE contents and the smallest negative Eu anomalies. Low-Ca pyroxenes have similar patterns with slightly stronger Eu anomalies. Augites have the highest REE contents and the most negative Eu anomalies. Augites show REE disequilibrium with olivine and low-Ca pyroxene, suggesting that they were not part of the restitic assemblage but were added by silicate melts passing through the UPB mantle, i.e. they are metasomatic in origin. We also discuss the size of the original UPB, using silicate minerals as evidence for it being a typical asteroid rather than a planet-sized object.

The Cordillera Central on the island of Hispaniola comprises a section through the crust of the Late Cretaceous phase of the Greater Antilles Arc. The gabbroic-tonalitic batholiths of the Cordillera Central are widely considered to represent the temporal main axis of this island arc. Although they have been studied extensively, the timing of batholith emplacement is not well constrained. We present new LA-ICP-MS U-Pb zircon ages and whole-rock geochemical data from diorites, tonalites, and granites of the El Río, El Bao, Jumunuco, and Loma de Cabrera batholiths, and from tonalite boulders deposited in the Eocene-Oligocene Velázquitos Formation. The sample ages range from 97 to 80 Ma with small differences between the intrusive bodies. Samples from the El Río, Jumunuco, and Loma de Cabrera batholiths cover most of the above age range, while the rocks of the El Bao pluton yield a well-defined maximum around 87 Ma. In the El Río batholith, U-Pb ages are in good agreement with the exposed contact relationships. Based on their composition and existing geochronological data, we divide the intrusive history of the Cordillera Central into four stages reflecting different magma compositions: ultramafic to dioritic magmatism lasted from 105 to 87 Ma, tonalite units formed between 96 and 84 Ma, felsic tonalites and granites intruded from 87 to 80 Ma overlapping with a younger phase of dioritic magmatism between 84 and 78 Ma.

The geochemical signatures of the felsic tonalites of the Jumunuco batholith and the granites of the El Río batholith are similar to the rhyolitic and dacitic island-arc volcanics from the Restauración Formation of the Tireo Group, thus confirming the relationship between the volcanic and plutonic units of the Greater Antilles Arc. Based on petrographical, geochemical, and geochronological data of the tonalite samples from the Velázquitos Formation, we interpret these boulders as being eroded from the Jumunuco batholith or the related Buena Vista pluton.