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In this study we report laser ablation-inductively coupled plasma-mass spectrometer U-Pb ages of granitoids from the so-called early granodiorites of the northwest Iberian Variscan belt. The U-Pb results attest to significant magmatic activity in Visean time (ca. 347-337 Ma) that generated a hitherto poorly constrained granitoid suite in the northwest Iberian tract of the western European Variscan belt realm. This early Carboniferous suite (ECS) is mainly composed of peraluminous cold and hot crustal granodiorites and monzogranites with minor associated mafic rocks that attest to minor involvement of mantle melting. Based on the geochronological and geochemical data, we compare the Visean granitoids with younger Variscan granitoids in northwest Iberia and, in view of the tectonothermal scenarios of the Variscan collision in northwest Iberia, propose a model for the genesis of the ECS in northwest Iberia that involves rapid melting upon fast exhumation of the thickened Gondwanan crust in the course of the protracted Variscan collision.

Major, minor, and trace element abundances in titanite crystals from four granitic plutons in southern Yidun arc, SW China, have been determined using electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The selected plutons are the Cretaceous Xiuwacu (CXWC) pluton, with quartz vein-type Mo mineralization (economic-Mo), the Tongchanggou (TCG) pluton, with porphyry-type Mo mineralization (economic-Mo), the Triassic Pulang (PL) pluton, with porphyry-type Cu mineralization (subeconomic-Mo), and the Triassic Xiuwacu (TXWC) pluton, without any Mo mineralization (Mo-barren). Our study reveals that the chemical compositions of titanite crystals from these plutons such as REE, Sr, Ga, δEu, δCe, Fe2O3/Al2O3, halogens, and Mo can be used to track magma compositions, oxidation states, metal fertility, and crystallization history. The data from this study also show that titanite crystals from these plutons with different potential of Mo mineralization have similar Mo contents and exhibit an irregular variation between Mo and Sr abundances (indicating non-Mo enrichment in the residual melt during the progressive crystallization) for some Mo-mineralized plutons. Our new observations support the recent hypothesis that high initial Mo contents in magma and the enrichment of Mo in residual melts formed by fractional crystallization are not the only requirements to form a granite-related Mo ore deposit. Efficient extraction of the residual melts, possibly facilitated by high concentrations of magmatic F is also critical to the ore formation. Evidence for high-F concentration in felsic magma, which facilitates melt and fluid separation and economic Mo mineralization during magma evolution, may be traced by the presence of F-rich titanite crystals in the two Mo-mineralized granite plutons (CXWC and TCG). These new findings from this study confirm that titanite is indeed a good petrogenetic and metallogenic indicator. However, in light of the limited contribution of metal fertility to Mo mineralization, we suggest that titanite Mo concentrations should be used along with other crucial proxies, such as titanite F contents and Fe2O3/Al2O3 ratios to better evaluate the Mo-mineralized potential of granites.

We report four late Palaeozoic zircon sensitive high-resolution ion microprobe (SHRIMP) U-Pb ages for granitic plutons from the Inner Mongolia Palaeo-uplift on the northern margin of the North China block. These cast a new light on the poorly understood tectonic history of the northern margin of the North China block and the Central Asian Orogenic Belt during the late Palaeozoic. The plutons have for a long time been considered to belong to the early Precambrian basement of the North China block. Our new SHRIMP U-Pb zircon dating of four plutons at Longhua, Daguangding, Boluonuo and Hushiha has yielded intrusive ages of 311±2 Ma, 324±6 Ma, 302±4 Ma and 310±5 Ma, respectively. Geochemical data suggest that these granitoids have a calc-alkaline, subduction-related I-type signature, indicating the existence of an Andean-style continental arc along the northern margin of the North China block during the late Palaeozoic. Our results also indicate that the Palaeo-Asian Ocean still existed during latest Carboniferous-earliest Permian time, and that the final collision between the southern Mongolia composite terranes and the North China block occurred later than c. 290 Ma. We suggest that the northern margin of the North China block was an active continental margin and the Inner Mongolia Palaeo-uplift is a deeply exhumed mid-crustal \"root\" of a late Palaeozoic Andean-style continental arc.

The Maronia Magmatic Corridor is a NE-trending belt of Oligocene plutons that intrudes the Kechros Dome of the northern Rhodope Core Complex in northeastern Greece. The post-collisional magmatism transitions from early high-K calc-alkaline magmatism in the NE to a younger, shoshonitic phase in the SW. We use a full suite of whole-rock geochemical analyses, including rare earth elements, to show a shared metasomatized mantle source of the magmatism. Evidence of plagioclase saturation from the onset of crystallization and amphibole-pyroxene-controlled fractionation in the high-K calc-alkaline magmatism suggest a drier (<4.75 wt% H2O) parental magma than is typical of subduction-related magmatism. Continued H2O depletion of the metasomatized source mantle resulted in the transition to a shoshonitic trend where deep crustal fractionation of an H2O-poor (< ∼2 wt% H2O) magma in the absence of major olivine resulted in incompatible enrichment over a small range of SiO2. High-precision U-Pb zircon geochronology is presented here for the first time to provide chronological markers for the transition in the magmatic evolution of the Kechros dome. A 2.2 Myr break in magmatism separates the intrusion of the shoshonitic Maronia pluton at 29.8 Ma from the emplacement of the rest of the high-K calc-alkaline Maronia Magmatic Corridor between 32.9-32.0 Ma. The Maronia pluton is the hottest, driest, and youngest episode of post-collisional magmatism in the Kechros dome; we suggest that the emplacement of Maronia marks the cessation of magmatism in the northern Rhodope Core Complex as asthenospheric mantle upwelling migrated southward.

The North Qilian Orogen witnessed the opening, subduction, and closure of the Proto-Tethys Qilian Ocean and the post-subduction of multiple exhumation events from Late Neoproterozoic to Early Paleozoic. The Early Paleozoic dioritic-granitic magmatic suites, prominently exposed in the eastern North Qilian Orogen, offer valuable insights into the evolution of the Proto-Tethys Ocean. However, their petrogenesis, magma source, and tectonic evolution remain controversial. Here, we investigate the Leigongshan, Zhigou, and Dalongcun intrusions and present geochronological, geochemical, and isotopic data, aiming to refine the comprehension of their timing and petrogenesis, which will contribute to understanding the tectonic evolution of the Proto-Tethys Ocean. Zircon U-Pb dating reveals mean ages of 471-427 Ma for these intrusions, consistent with compiled formation ages of dioritic-granitic intrusions in the eastern North Qilian Orogen, indicating close temporal links with the tectonic evolution of the Proto-Tethys Ocean during the Early Paleozoic. The studied magmatic rocks could be categorized into two major types: granitoids and diorites. The granitoids are majorly I-type granitoids that are generated through partial melting of the mafic lower crust and fractional crystallization at the middle-upper crust, with the involvement of mantle-derived materials. The diorites underwent limited crustal contamination and fractionation of hornblende, plagioclase, and some accessory minerals. They were derived mainly from the mixture of fertile mantle and reworked crustal components, with minor contributions from subduction-related slab fluids and sediment melts. In addition, all the studied Early Paleozoic dioritic-granitic intrusions (ca. 471-427 Ma) formed within subduction-related arc settings. Combined with the tectonic evolution of the Early Paleozoic Qilian orogenic system, we interpret these Cambrian to Silurian dioritic-granitic intrusions as tectonic responses to the subduction (ca. 520-460 Ma) and closure (∼440 Ma) of the Proto-Tethys Ocean, whereas the Devonian Huangyanghe intrusion witnessed the final stage of extensional collapse of the Qilian orogenic system at ca. 400-360 Ma.

Late Cambrian to Devonian granitic magmatism in the Chinese Altai provides a critical view of geodynamic processes active during crustal growth in the Central Asian orogenic belt. In this study, we report results of zircon U-Pb and Hf-O isotopic compositions, whole-rock geochemical signatures, and Nd isotopic data for late Cambrian-Early Devonian granites in the Chinese Altai. These granites were emplaced between 497 and 397 Ma and have high SiO2 (66.02-72.07 wt%) and K2O (3.18-5.19 wt%) contents, and low Fe2O3t (1.94-5.63 wt%), MgO (0.21-2.23 wt%), and CaO (0.62-1.25 wt%) contents, with A/CNK ratios of 1.16-1.53 (where A/CNK = molar ratio of Al2O3/[CaO + Na2O + K2O]). Moreover, these granites are geochemically similar to S-type granites. They are characterized by negative εNd(t) values (-3.84 to -1.54), high δ18O values (+9.34 ppm to +13.82 ppm), and low CaO/Na2O and (Na2O + K2O)/(MgO + FeO + TiO2) ratios, implying a mafic-metapelitic source. The εHf(t) values of the granites (-11.17 to +13.27) are decoupled from the εNd(t) and δ18O isotope values. This is suggested to be a result of disequilibrium during melting of the source wherein residual zircons were preserved and retained large amounts of Hf, producing Hf-depleted melts and Hf-enriched xenocrystic zircons. Variable zircon dissolution rates during melting and melt loss are ascribed to explain the observed variance in Hf concentrations. Based on the results and published data, a ridge subduction model was established to explain the 497-397 Ma high-temperature magmatism in the Chinese Altai.

The early Mesozoic was a critical era for the geodynamic evolution of the Sakarya Zone as transition from accretion to collision events in the region. However, its complex evolutionary history is still debated. To address this issue, we present new in situ zircon U–Pb ages and Lu-Hf isotope data, whole-rock Sr-Nd isotopes, and mineral chemistry and geochemistry data of plutonic rocks to better understand the magmatic processes. The Gokcedere pluton is mainly composed of gabbro and gabbroic diorite. LA-ICP-MS zircon U–Pb dating reveals that the pluton was emplaced in the early Jurassic (177 Ma). These gabbros and gabbroic diorites are characterized by relatively low SiO 2 content of 47.09 to 57.15 wt% and high Mg# values varying from 46 to 75. The samples belong to the calc-alkaline series and exhibit a metaluminous I-type character. Moreover, they are slightly enriched in large ion lithophile elements (Rb, Ba, Th and K) and light rare earth elements and depleted in high field strength elements (Nb and Ti). Gabbroic rocks of the pluton have a depleted Sr-Nd isotopic composition, including low initial 87 Sr/ 86 Sr ranging from 0.705124 to 0.705599, relatively high ε Nd ( t ) values varying from 0.1 to 3.5 and single-stage Nd model ages ( T DM1  = 0.65–0.95 Ga). In situ zircon analyses show that the rocks have variable and positive ε Hf ( t ) values (4.6 to 13.5) and single-stage Hf model ages ( T DM1  = 0.30 to 0.65 Ga). Both the geochemical signature and Sr-Nd-Hf isotopic composition of the gabbroic rocks reveal that the magma of the studied rocks was formed by the partial melting of a depleted mantle wedge metasomatized by slab-derived fluids. The influence of slab fluids is mirrored by their trace-element characteristics. Trace-element modeling suggests that the primary magma was generated by a low and variable degree of partial melting (~5–15%) of a depleted and young lithospheric mantle wedge consisting of phlogopite- and spinel-bearing lherzolite. Heat to melt the mantle material was supplied by the ascendance of a hot asthenosphere triggered by the roll-back of the Paleo-Tethyan oceanic lithosphere. The rising melts were accompanied by fractional crystallization and encountered no or minor crustal contamination en route to the surface. Taking into account these geochemical data and integrating them with regional geological evidence, we propose a slab roll-back model; this model suggests that the Gokcedere gabbroic pluton originated in a back-arc extensional environment associated with the southward subduction of the Paleo-Tethyan oceanic lithosphere during the early Jurassic period. Such an extensional event led to the opening of the northern branch of the Neotethys as a back-arc basin. Consequently, we conclude that the gabbroic pluton was related to intensive extensional tectonic events, which peaked during the early Jurassic in response to the roll-back of Paleo-Tethyan oceanic slab in the final stage of oceanic closure.

The Late Devonian postorogenic Cobaw Batholith, in southeastern Australia, is an oval, east-west-orientated, terrane-stitching lopolith that intruded low-grade metaturbidites. The initial intrusion (at 370 Ma) was the small, hypabyssal, S-type Rainy Creek Rhyolite (RCR). At 369 Ma, the foliated S-type Pyalong Pluton was emplaced, apparently along an east-west-orientated fracture zone. Around 367 Ma, the main I-type Baynton pluton intruded as numerous shallow-dipping sheets. The last plutonic event was the intrusion of the broad, thin, flat-lying, and crosscutting sheet of the I-type Beauvallet Pluton. The Cobaw Plutons had independent origins, with magmas derived from contrasting, internally heterogeneous source rocks. For both the RCR and the Pyalong pluton, the sources were old metasedimentary rocks, while the magmas for the Baynton and Beauvallet Plutons formed through partial melting of metadacitic to meta-andesitic rocks, probably with an admixture of immature volcaniclastic graywackes. The source rocks for the Baynton magmas were more crustally evolved than those for the Beauvallet magmas. Heterogeneity in the Baynton Pluton did not result from crystal fractionation or magma mixing, despite the relatively high abundance of igneous-textured microgranular enclaves (MEs). The MEs show neither chemical nor isotope mixing trends with each other or with the host magmas. Variations in the Baynton magmas were derived from the heterogeneity of the source terrane, with individual magma batches formed from mixtures of metaigneous and metasedimentary rocks. Baynton MEs are isotopically less evolved than their host rocks. Their chemistry, textures, and field relations suggest that they represent small volumes of hybrid magmas formed through near-source mixing between crustal melts and mantle-derived mafic magmas. Further modification occurred through melt loss and ingestion of host crystals as the MEs were deformed, in the plastic state, during magmatic flow of their hosts

Granitoids of the tonalite–trondhjemite–granodiorite (TTG) series dominate Earth’s earliest continental crust. The geochemical diversity of TTGs is ascribed to several possible geodynamic settings of magma formation, from low-pressure differentiation of oceanic plateaus to high-pressure melting of mafic crust at convergent plate margins. These interpretations implicitly assume that the bulk-rock compositions of TTGs did not change from magma generation in the source to complete crystallization. However, crystal–liquid segregation influences the geochemistry of felsic magmas, as shown by the textural and chemical complementarity between coeval plutons and silicic volcanic rocks in the Phanerozoic Eon. We demonstrate here that Paleoarchean (ca. 3,456 million years old) TTG plutons from South Africa do not represent liquids but fossil, crystal-rich magma reservoirs left behind by the eruption of silicic volcanic rocks, being possibly coeval at the million-year scale as constrained by high-precision uranium–lead geochronology. The chemical signature of the dominant trondhjemites, conventionally interpreted as melts generated by high-pressure melting of basalts, reflects the combined accumulation of plagioclase phenocrysts and loss of interstitial liquid that erupted as silicic volcanic rocks. Our results indicate that the entire compositional diversity of TTGs could derive from the upper crustal differentiation of a single, tonalitic magma formed by basalt melting and/or crystallization at <40 km depth. These results call for a unifying model of Hadean–Archean continent nucleation by intracrustal production of TTG magmas.The chemical diversity of Earth’s early continental building blocks can be explained by differentiation of a single melt, without complex geodynamic settings, according to petrological and geochemical analysis of samples from South Africa.

Magma reservoirs typically form through the incremental emplacement of smaller magma pulses over extended timescales. Pulsed reservoir growth significantly impacts a magma body's temperature evolution, chemical differentiation potential, and the probability, scale, and timing of volcanic eruptions. Moreover, the addition of thermal energy and magmatic fluids reheat and hydrothermally alter previously emplaced magma. Consequently, it may be difficult to distinguish individual magma pulses in exposed solidified intrusions (plutons), obscuring evidence of magma body construction and evolution. In this study, we employ geological mapping combined with petrofabric and Anisotropy of Magnetic Susceptibility (AMS), Anisotropy of Anhysteretic Remanent Magnetization (AARM), hysteresis, First‐Order Reversal Curves (FORCs) and susceptibility versus temperature analyses to investigate pulsed magma emplacement and its consequences in terms of fabric overprinting and hydrothermal alteration within the Slaufrudalur pluton in Southeast Iceland. The field mapping documents distinct emplacement styles, including magma ascent in marginal zones, subhorizontal sheet emplacement, and bulk intrusion below the sheets. The AMS fabrics show high Km values (∼1 × 10−2 SI), but overall weak degrees of anisotropy (Pj < 2%). The weak magnetic fabrics reflect the destructive interference between the magnetite fabric and the fabric of hematite and iron hydroxides. Later, pulses of magma are less oxidized, which indicates that the alteration was caused by volatile release from magma that intruded below already emplaced magma. Our results demonstrate that rock magnetic data provide a novel approach to detecting magma pulse interactions and associated alteration in plutons, offering insights into magma body dynamics.