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We integrate the existing detrital zircon data from multiple modern river sediment samples on Viti Levu, Fiji, with the most current available geological and topographic mapping of the respective river drainage basins to compare detrital populations with potential bedrock sources. The temporal and spatial variations in zircon geochemistry supplement what is known from igneous rocks and confirm the petrological differences between plutonic and volcanic rocks from the Eocene to early Oligocene (Yavuna age, >30 Ma), middle Oligocene to middle Miocene (Wainimala age, 30–12.5 Ma), late Miocene (Colo age, 12.5–6.5 Ma) and latest Miocene (Namosi age, 6.5–5 Ma). The >30 Ma Yavuna-age zircons are restricted to areas that drain the previously mapped Yavuna Group. The 30–12.5 Ma zircons are found across central Viti Levu from west to east, and the 30–15 Ma zircons have distinctively low U/Yb and high Dy/Yb ratios. They are the best radiometric evidence of widespread early to middle Miocene arc magmatism in Fiji that was relatively U-poor. Peak deconvolution of the Colo age zircons from individual basins suggests the following ages for undated or poorly dated plutons from central Viti Levu. The large Mavuvu pluton is probably composed of multiple intrusions in the 12–10 Ma range, the Waiqa pluton is probably ca 10 Ma, and the Noikoro pluton is probably ca 9 Ma. There are zircons from unknown plutonic or volcanic sources between 8 and 7 Ma in western Viti Levu that have distinct Eu/Eu* ratios. We attribute the highest U/Yb ratios in some Colo age zircons to crustal anatexis. Namosi-age zircons are abundant in the Medrausucu Group and can be found scattered across Viti Levu. Detrital zircon samples have aided geological mapping of the tropical and poorly exposed terrain in Fiji and elucidated the magmatic history. Detrital zircons indicate widespread early to middle Miocene arc magmatism across central Viti Levu. Detrital zircon ages have provided further constraints on the ages of 12-9 Ma plutons in central Viti Levu. Detrital zircon ages indicate that there is an unknown igneous source of 8-7 Ma zircons in western Viti Levu. [ABSTRACT FROM AUTHOR]

An aerobic, rod-shaped, non-motile, endospore-forming bacterium, strain V-9T, was found in the frozen volcanic ash, Kamchatka peninsula, Russia. Phylogenies based on 16S rRNA gene and genome sequences demonstrated that strain V-9T was affiliated with the family Paenibacillaceae and clustered outside the clade that includes the type species of this genus, Paenibacillus polymyxa, and closely related species. V-9T showed the highest 16S rRNA gene sequences similarity to Paenibacillus chartarius CCUG 55240T (96.7%). The similarity to type strains of other Paenibacillus species were below 94.7%, with 91.8% determined to Paenibacillus polymyxa IAM 13419T. The AAI and POCP values between V-9T and type species of the genera of Paenibacillaceae with available genomes, including Paenibacillus polymyxa, were below the thresholds for defining novel genera. The cell wall of new strain contained a lysine-based peptidoglycan and two teichoic acids, unsubstituted 1,3-poly(glycerol phosphate) and 1,3-poly(glycerol phosphate) substituted at the C(2) of glycerol by glucose. Acid hydrolysates of the cell wall included glucose, galactose and glycerol. Strain V-9T contained menaquinone MK-7 as the sole isoprenoid quinone, anteiso-C15:0, anteiso-C17:0, iso- C15:0 and iso-C16:0a as the dominant fatty acids, and phosphatidylglycerol, diphosphatidylglycerol, acylphosphatidylglycerol, and phosphatidylinositol as the major polar lipids. The DNA G+C content calculated from the whole genome sequence was 55 mol %. Based on the data obtained, a new genus and species, Gordonibacillus kamchatkensis gen. nov., sp. nov., is proposed with the type strain V-9T (=VKM B-2647T = DSM 26726T). [ABSTRACT FROM AUTHOR]

The modern turbines aimed to work at enhanced efficiencies demand the use of a novel high-performance thermal barrier coating (TBC) which may be susceptible to multiple failure modes. Specifically, ingestion of calcium–magnesium–alumino–silicate (CMAS) or volcanic ash (VA) at elevated temperatures induce accelerated deterioration of conventional yttria-stabilized zirconia (YSZ) TBCs. The ability to form an impervious and rapidly crystallizing rare earth-based apatite layer upon interaction with CMAS/VA salt favors the choice of rare earth zirconates (REZs) as novel TBCs. Among diverse REZs, Yb2Zr2O7 (YbZ) exhibits ideal TBC characteristics. A detailed insight into YbZ coating characteristics and performance is vitally needed to qualify these materials for TBC applications. Accordingly, in this study indigenously developed YbZ and commercial YSZ were deposited by air plasma spraying. Subsequently, the VA infiltration resistance of deposited coatings was comprehensively compared up to 1350 °C. The SEM analysis of VA-infiltrated YSZ and YbZ coatings revealed the thickness of the infiltration zone and the corresponding mechanism. YbZ coatings displayed significantly better VA infiltration resistance attributed to forming an impervious Yb-apatite-based arresting layer and pinning the further seepage of the VA salt front. Besides, VA rapidly infiltrated YSZ coatings, which failed to form an arresting layer. Overall, the study provides essential insights and thrust in developing next-generation TBCs. [ABSTRACT FROM AUTHOR]

The late Archean Western Dharwar Craton supergroup has volcanic and sedimentary rocks deposited during 2900–2600 Ma underlain by the Sargur Group basement of 3.36–3.2 Ga granitic gneiss and older supracrustal rocks. The western part of the craton, known as the western province (Dharwar Foreland), comprises four major schist belts (Western Ghats-Bababudhan-Shimoga-Chitradurga). A regional gravity and magnetic (Total Field) survey was done in the Shimoga region. The geophysical data of the study area reveal the subsurface extension and behaviour of the exposed rocks of the area. The Euler deconvolution was used to define the depth of the anomaly sources. Euler depth solution for the spherical body (structural index 2), window size = 10, and depth tolerance = 5% depicts the depth of the various sources. The Euler depth solutions cluster over the hook-shaped schist rock of the Medur group (at the northern part of the area) reveals that the body's depth varies from 1 to 4 km in the central part, and at the northern flank, it goes up to 7 km. The solution also brought out the depth of the anomalous body near Hithala, within 4 km. The 2D forward depth modelling of the anomalous zone brings out the involvement of the tectonic forces in the generation of this anomalous body. The more precise depth from the model has been estimated between 2 and 3 km. The model clearly shows the relationship between schist rocks and the basement. However, the high-gravity anomaly has been modelled as the manganese bearing horizon, which has come to optimum depth because of folding and faulting in the region, thus providing a favourable zone for manganese deposition. [ABSTRACT FROM AUTHOR]

The abundant natural volcanic ash (NVA) in East Africa is a prospective supplementary cementitious material that may be used to produce green and economical railway concrete. To mitigate the shrinkage of concrete with NVA, internal curing using a superabsorbent polymer (SAP) is employed in this study. The compressive strength, autogenous shrinkage, and drying shrinkage of internally cured concrete with NVA were measured. In addition, the water loss and internal relative humidity of internally cured concrete with NVA were analyzed. The results indicate that the compressive strength of concrete with NVA shows a linear decreasing trend with SAP. In addition, SAP significantly reduces the autogenous shrinkage but slightly increases the drying shrinkage of concrete with NVA. The internal curing using SAP increases the water loss of concrete, whereas the water released from SAP still significantly improves the internal relative humidity (IRH) of concrete. The positive influence of internal curing on the autogenous shrinkage overwhelms the unexpected influence on the drying shrinkage, resulting in the mitigated shrinkage of concrete with NVA. [ABSTRACT FROM AUTHOR]

Oceanic volcanic islands have a complex internal structure due to their geological evolution. La Palma is the second youngest in the Canary Islands. Historical eruptions occurred in the Cumbre Vieja (CV) volcanic system, including the last 2021 Tajogaite eruption. The seismicity before, during, and after the Tajogaite eruption provides valuable information for a better understanding of deep volcanic processes. We applied the receiver function technique to image the crustal and upper mantle structures beneath the CV volcanic complex. We investigated the first 50 km of the lithosphere, identifying various seismic discontinuities. After a thin layer of recent volcanic rocks, we found a layer corresponding to the old oceanic crust. Beneath the Moho, we found a significant decrease in the seismic velocities until about 37 km of depth. This low‐velocity layer corresponds to a zone of partial melting with interconnected magmatic chambers that feed the volcanic activity in CV. Plain Language Summary: Oceanic volcanic islands have a complex internal structure. Our study is important to understand volcanic activity in its geodynamic context better. The last eruption occurred in the Cumbre Vieja volcanic complex on La Palma Island (2021) and had an unexpected magnitude in terms of lava volume, explosivity, and a significant impact on the economy and society of the island. This study used receiver function analysis to image the lithosphere up to a depth of 50 km. This seismological technique exploits the recordings of teleseismic events (i.e., earthquakes located between 30 and 90° from the stations) for this purpose. We used an advanced inversion technique to study the structure of the crust and the upper mantle beneath the volcano. The most relevant finding is a zone of anomalous low seismic velocities extending from 13 to 37 km depth. This zone is likely to host partial melt and magma chambers and extends over a much wider and thicker volume than expected from previous studies. Previous studies also identified two magma chambers: the upper one, located at about 10–15 km, and the lower one, beneath 25 km depth. These findings provide new insights into the current paradigms about the internal active oceanic volcanic islands. Key Points: Receiver function analysis allowed us to image the crustal and upper mantle seismic structure beneath Cumbre Vieja volcano in La PalmaMain velocity discontinuities in the crust show the contacts between the recent volcanic rocks, the old oceanic crust and the upper mantleA low‐velocity zone extending from the Moho up to about 37 km of depth indicates the presence of a broad zone of partial melting [ABSTRACT FROM AUTHOR]

The Eastern Kunlun Orogenic Belt (EKOB), located north of the Qinghai-Tibetan Plateau, recorded voluminous late Palaeozoic – early Mesozoic intermediate-acid volcanic rocks. The tectonic evolution of the Palaeo-Tethys Ocean from initial subduction and final closure and post-collision extension has been hotly debated. This study examines the petrogenesis of Palaeozoic to Early Mesozoic volcanic rocks at six locations: Xiahe, Elashankou, Jirimai, Harizha, Nagengkangqieer, and Yazigounan. The investigation involves detailed field observations, petrology, zircon U-Pb geochronology, Lu-Hf isotopes, and whole-rock geochemical analysis. The rocks analysed represent three episodic volcanic events. The ca. 257–245 Ma volcanic rocks were derived from magma mixing response to the subduction. The ca. 227–220 Ma highly fractionated I-type volcanics were derived from partial melting of the ancient lower crust, with varying contribution proportions of mantle materials. The ca. 216 Ma A-type volcanic rocks derived from partial melting of the juvenile crust. In this study, using existing regional geological data and spatiotemporal distribution of the magmatic region, combined with our new data, we attempt to propose more rational models to reveal the tectonic evolution of the Palaeo-Tethys Ocean, and we recognize three significant time nodes: (1) Ca. 240 Ma marks the final closure time of the Palaeo-Tethys Ocean. (2) Ca. 230 Ma indicates the vital tectonic regime transition from compression to extension response to slab break-off and continued lithospheric delamination. (3) Ca. 216 Ma mark the beginning of the final stage of orogeny in the EKOB, and mild magmatism lasts to ca. 200 Ma in response to the mountain collapse. [ABSTRACT FROM AUTHOR]

Volcanic glass has been used extensively as a paleoaltimeter. Deuterium (2H) concentrations in glass have been found to be stable over geologic timescales, making δ2H (also known as δD) a reliable proxy for ancient water chemistry. However, continued work revolves around better understanding how different factors affect preserved water in volcanic ash. Here, we analyze δD in the Rattlesnake Tuff (RST), a widespread ca. 7 Ma ash-flow tuff, and create a paleoisoscape to assess variations in δD across Oregon during that time. To this end, 16 ash samples were collected across central and eastern Oregon from various flow units within the RST. Samples were analyzed for δD using a temperature conversion elemental analyzer (TC/EA) connected to a mass spectrometer and elemental composition using a scanning electron microscope (SEM). We compared the isotopic results to modern water and published ancient water proxy data to better constrain changes in climate and topography across Oregon throughout the Neogene. We also estimated wt. % H2O by calculating excess (non-stoichiometric) oxygen from SEM elemental data. We did not observe significant variations in δD among the flow units from single locations, nor was there a significant relationship between the prepared glass shard composition and wt. % H2O or δD, supporting the use of volcanic glass as a reliable paleoenvironmental indicator. Our results show significant spatial variation in δDwater values of RST, ranging from −107‰ to −154‰. δD values of ancient glass were similar to modern water near the Cascade Mountains but became relatively negative to the east near the inferred eruptive center of the RST, suggesting that a significant topographic feature existed in the vicinity of the RST eruptive center that has since subsided. [ABSTRACT FROM AUTHOR]

A new tectonic model is presented to explain the tectono-stratigraphic evolution of the Paleoproterozoic Karrat Group in central West Greenland and the polyphase deformation, magmatism, and metamorphism of the Rinkian orogen. Sedimentation of the Karrat Group initiated after ca. 2000 Ma in an intracratonic rift basin with basal quartzites overlying Archean gneisses of the Rae craton. Rift-related alkaline volcanic rocks and synrift siliciclastic sediments were deposited in the north while an evaporite-carbonate platform developed in the south. The rift basin evolved to a back-arc basin, with associated subalkaline volcanic rocks, concomitant with the intrusion of arc-related granitoids of the Prøven igneous complex along the basal contact of the Karrat Group between 1900 Ma and 1850 Ma. The Karrat Group and magmatic arc rocks underwent metamorphism ca. 1830-1800 Ma during the collisional phase of the Rinkian orogeny. The metamorphic grade of the Karrat Group increases from greenschist facies in the south to granulite facies in the north, where it is marked by migmatization and emplacement of S-type leucogranites. Extensive east-southeastward thrust emplacement and fold vergence characterize the Rinkian orogen south of the Prøven igneous complex magmatic arc, where the arc-continent collision is established along a top-to-the-ESE shear zone postdating the Rinkian metamorphism. In summary, the Karrat Basin developed on the upper plate above eastward-dipping subduction and, together with the Rinkian orogen, represents the result of arc-continent collision that initiated the structuring of a backarc fold-and-thrust system antithetic to the subduction system. [ABSTRACT FROM AUTHOR]

The Samba Cu deposit is located in pre-Katangan Supergroup basement metavolcanic rocks of the Central African Copperbelt in Zambia. To better understand the formation of the Cu deposit, we use geochronologic, geochemical, and S isotopic data obtained for the deposit's host rocks and sulfide minerals. Laser ablation-inductively coupled plasma-mass spectrometric (LA-ICP-MS) dating of zircon from host rocks, including quartz-sericite schist and biotite-sericitechlorite schist, yields ages of 1967 ± 17 Ma and 1960 ± 20 Ma, which are interpreted as the crystallization ages of the original volcanic rocks. Re-Os analyses of molybdenite intergrown with chalcopyrite constrain sulfide deposition to 548.1 ± 7.5 Ma and 524.1 ± 7.3 Ma, which correspond to the timing of the Cu mineralization. LA-ICPMS U-Pb analyses of metamorphic rutile from the biotite-sericite-chlorite schist yield a U-Pb age of 508.3 ± 6.6 Ma, which is interpreted to represent the age of regional metamorphism. The new data suggest that the Cu mineralization at Samba was synchronous with the Lufilian orogeny. [ABSTRACT FROM AUTHOR]

Slab tearing is widely reported in oceanic slabs; however, tearing in continental slabs is still not very well understood. Geophysical data have shown the existence of tearing of the Indian lithosphere underneath the Yadong-Gulu rift in southern Tibet. Along this rift, the Jiacun lamprophyres and the Yangying trachytes comprise the youngest alkaline volcanic rocks in the Himalayan-Tibetan orogen, and hence provide evidence for understanding the operation of continental slab tearing. Jiacun lamprophyres, with an age of 13 Ma as determined by Ar-Ar dating, are the only outcrop of alkaline volcanic rocks in the Himalayan block. Geochemical analysis indicates that they were derived from a peridotite source in the Indian lithospheric mantle near the spinel field. Yangying trachytes, dated at 8.81 ± 0.15 Ma by the U-Pb dating method, were derived from a pyroxenite melt in the Tibetan lithospheric mantle with a higher crustal influence. Both sites show high phlogopite and pyroxene temperatures, indicating a hot influx favoring the melting of these magmas, which is likely associated with the tearing of the Indian slab. Ages of this magmatism suggest that the activity along the rift lasted at least 4 m.y. and migrated from south to north. This shows that slab tearing can trigger over-thickened lithospheric melting in a collisional orogen. [ABSTRACT FROM AUTHOR]

The petrogenesis of Nb-enriched basalts (NEBs) is controversial. NEBs are generally considered to form by melting of either a mixed enriched and depleted mantle source or a mantle wedge metasomatized by adakitic melts. Here we present geochronological, petrological, geochemical, and Sr-Nd-Os isotope data for Early Permian volcanic rocks from the Tuotuohe area in the northern Qiangtang Terrane, China. The studied volcanic rocks can be divided into two groups: arc basalts and basaltic andesites in the lower sequence and NEBs in the upper sequence. Zircon grains from one basaltic andesite sample in the lower sequence yielded a concordia age of 302.0 ± 1.1 Ma. The geochemical and isotopic characteristics suggest that the NEBs were derived from a mixed source consisting of enriched mid-oceanic ridge basalts (MORB)- to oceanic-island basalt-like ambient mantle and slab-derived fluids, whereas the arc basalts and basaltic andesites originated from a source made of the MORB-type ambient mantle modified by slab-derived melts. We propose for the first time that the Nb enrichment of the NEBs was most likely inherited from high-Nb ambient mantle and is independent of the addition of slab-derived components. In addition to slab-derived components, the nature of the ambient mantle is also an important factor controlling the diversity of arc magmatism. Our new findings show that the Late Carboniferous-Early Permian magmatism in the northern Qiangtang Terrane was related to northward subduction of the Paleo-Tethys Ocean, suggesting that subduction might have occurred in at least the Early Permian rather than in the previously thought Middle Permian. [ABSTRACT FROM AUTHOR]

Alkalic magmatism occurred in the Selwyn Basin, Yukon, Canada throughout the Paleozoic, concurrent with extension during passive margin sedimentation. To examine magmatism associated with this extension, geochemical data were obtained from several locations in the Selwyn Basin (MacMillan Pass, Anvil District, Keno Hill, and the Misty Creek Embayment). Volcanic rocks from the Anvil District and the Misty Creek Embayment are dominated by alkalic basalts with light rare earth element (LREE)-enriched geochemical signatures, whereas metavolcanic and dike samples from Keno Hill comprise subalkaline basalts with enriched mid-ocean ridge basalt (E-MORB) signatures. The Early Ordovician Menzie Creek volcanic rocks of the Anvil District display trace element geochemical signatures intermediate between ocean island basalt (OIB) and E-MORB, whereas the Middle–Late Ordovician volcanic rocks from the Misty Creek Embayment have OIB signatures. Differences in the trace element geochemistry of the sample suites are attributed to the degree of partial melting. The Menzie Creek volcanic rocks formed from large volume melts of enriched mantle that diluted incompatible element signatures in the Early Ordovician. Late Ordovician magmatism produced the Misty Creek Embayment samples, where restricted melt volumes of an enriched mantle source resulted in the most enriched samples geochemically. The Keno Hill samples represent the shallowest melting of the analysed samples and may have resulted from melting of heterogenous subcontinental lithospheric mantle. Magmatic zircons from a Keno Hill metavolcanic sample analysed by chemical abrasion thermal ionization mass spectrometry resulted in a primary deposition age of c. 296 ± 0.36 Ma (Early Permian), during a period with little magmatism in the Selwyn Basin and representing a previously unknown unit in the area. [ABSTRACT FROM AUTHOR]

High-precision ages of Cenozoic volcanic rocks in northeast China are widely reported recently. However, the systematic analysis of spatio-temporal distribution of Cenozoic volcanism, which is important for reconstructing and constraining regional tectonic evolution, is still limited. Here, we collected published geochronological data from more than 400 Cenozoic volcanic samples in northeast China. Combined with field observations of volcanic rock samples and three valid 40Ar-39Ar geochronological data obtained in this study, we compile geochronological data in northeast China and explore a new spatio-temporal distribution pattern for the Cenozoic volcanism in order to constrain geodynamic models for northeast China. Our results show that the Cenozoic volcanism in northeast China has a horseshoe-shaped distribution, and the volcanism almost existed from Paleocene to Quaternary, which can be roughly divided into six volcanic belts. Our results suggest that the volcanism in this region is centred on around the Songliao Basin, then migrates eastward, and eventually has end up with a series of intense activity around the Songliao Basin. This may be related to the upwelling of the asthenosphere caused by the subduction of the Pacific plate and the opening of the Japan Sea. Our study also reveals that Chuandishan basalt in Dunhua area formed by Early Oligocene volcanic activity, which differs from the Pliocene or Miocene stratigraphic ages assumed before. [ABSTRACT FROM AUTHOR]

The volcanic rocks in the deep depth of Nanpu sag is the main formation of oil and gas enrichment. It has huge resource potential and prospects for exploration and development. Accurate characterization of lithology and pore space is the basis of reservoir quality prediction. Through petrography studies of cores and thin sections, explosive and sedimentary facies represent the dominant oil and gas-bearing reservoirs, and intergranular pores and fractures are major pore and seepage space. In order to predict favorable reservoirs and improve the efficiency of fracturing, according to composite well loggings and electrical images, logging response features of different lithofacies are characterized and five types of pore structure facies are classified. Further, five types of petrophysical facies are proposed. Among them, Type I and Type II are the most favorable petrophysical facies in the study area. The petrophysical facies typing approach show consistency with oil test data, which verifies that this approach can well predict reservoir quality and provide technical support for the exploration and development of the oil and gas-bearing volcanic rocks. [ABSTRACT FROM AUTHOR]

Asian dust delivers highly reactive iron (FeHR) to the Pacific Ocean, affecting marine biogeochemical cycles and Earth's climate. Tracing the source of dust deposited in the Pacific is vital for assessing global nutrient cycles but poses challenges. This work applies the (234U/238U) activity ratio to determine the pre‐deposition time and provenance of dust in North Pacific Ocean sediments (Ocean Drilling Program site 1209B). Results indicate a consistent dust pre‐deposition time (134 ± 10 ka) over the past 300,000 years, except during Marine Isotope Stage 7 when volcanic ash input shortened it to 31 ± 19 ka. Comparing the dust pre‐deposition times to those of the potential source deserts, we identify the dust transported to the North Pacific Ocean was primarily from the Taklamakan Desert, which contains higher FeHR content than other deserts. This finding enhances our understanding of soluble Fe supplied to the oceans, especially in dust circulation models. Plain Language Summary: Unraveling the provenance of aeolian dust deposited in the oceans is critical for understanding marine biogeochemical cycles, past climate changes, and dust transport mechanisms. Here we measured the (234U/238U) activity ratio of marine sediments in the North Pacific Ocean to understand the source and pre‐deposition time of dust deposited in the Pacific. The source of dust in the Pacific has remained debated because of the non‐unique geochemical signatures of possible source regions and the complexity introduced by the volcanic ash. The (234U/238U) of the dust fraction in marine sediments informs the source‐to‐sink transport time for dust particles, providing a new source tracer. We compared the (234U/238U)‐derived pre‐deposition time, Nd isotopes, grain size, magnetic susceptibility and aeolian dust flux of the North Pacific marine sediments to those of potential dust source regions, and identify the Taklamakan Desert as a major source delivering dust to the North Pacific. Our work highlights the (234U/238U) and associated particle pre‐deposition time as a promising tool for tracing sources of dust in marine sediments, holding profound implications for our understanding of global dust‐nutrient cycles. Key Points: Uranium isotope‐based pre‐deposition time serves as a novel tool to trace the provenance of Asian dust transported to the North Pacific OceanDust pre‐deposition time at site 1209B remains relativity stable (134 ± 10 ka), but decreases during MIS 7 due to volcanic ash inputTaklimakan Desert is the major source of dust delivered to the North Pacific Ocean, supplying dust with highly reactive iron [ABSTRACT FROM AUTHOR]

High-pressure and ultra-high-pressure metamorphic terrains display an internal architecture consisting of a pile (or stack) of several coherent tectonic thrust sheets or units. Their identification is fundamental for understanding the scale and mechanisms active during subduction and exhumation of these crustal slices. This study investigates the geometry of the northern Dora-Maira Massif and the kinematics of the major tectonic boundaries, combining field and geochronological data. The tectonic stack of the northern Dora-Maira Massif comprises the following units. The lowermost unit (the Pinerolo Unit) is mainly characterized by Upper Carboniferous fluvio-lacustrine (meta-)sediments. The Pinerolo unit is overthrust by a pre-Carboniferous basement. The latter is subdivided in two tectonic units (the Chasteiran and Muret Units) with different Alpine metamorphism (ultra-high-pressure and high-pressure, respectively). The pre-Carboniferous basement of the Muret Unit is thicker than previously thought for two main reasons. Firstly, some paragneisses, traditionally assumed to be Carboniferous and/or Permian in age, display detrital zircon ages indicating a main source at about 600 Ma. Secondly, three samples of the Granero Orthogneiss, previously assumed to be a Permian intrusive body, have provided zircon U–Pb ages of 447 ± 1 Ma, 456 ± 2 Ma and 440 ± 2 Ma, indicating a late Ordovician or early Silurian age for the protoliths. The uppermost unit (the Serre Unit) comprises porphyritic (meta-) volcanic and volcaniclastic rocks dated to the Permian (271 ± 2 Ma), on top of which remnants of the Mesozoic cover is preserved. Detailed mapping of an area about 140 km2 shows that (i) the ultra-high pressure Chasteiran Unit is localized at the boundary between the Pinerolo and Muret Units, (ii) the Granero Orthogneiss may be considered as the mylonitic sole of the Muret Unit, characterized by a top-to-W sense of shear, and (iii) the contact between the Muret and Serre Units displays ductile-to brittle structures (La Fracho Shear Zone), indicating a top-to-the-NW displacement of the hangingwall with respect to the footwall. A final episode of brittle faulting, cutting across the nappe stack (the Trossieri Fault), indicates an extensional stage in the core of the Alpine belt, as previously documented in more external zones. This work provides a necessary and robust basis before an accurate discussion of processes acting during continental subduction of the Dora-Maira Massif may be understood. [ABSTRACT FROM AUTHOR]

The Okinawa Trough is an incipient back-arc basin formed by the subduction of the Philippine Sea Plate beneath the Eurasian Plate and is a natural laboratory for studying basin evolution, magmatism, and crust-mantle interactions during the early stages of back-arc spreading. Back-arc spreading and recent magmatism are occurring mainly in the Middle Okinawa Trough (MOT) and Southern Okinawa Trough (SOT). In order to investigate the magmatism in the Okinawa Trough, volcanic rock samples from the MOT and SOT were analysed for Fe – Sr – Nd – Pb – Hf isotopic compositions. The Fe isotopic compositions of basaltic andesite samples from the SOT are similar to or lower than MORBs. The fluid/melt derived from the subducted slab, especially the fluid dehydrated from slab serpentinites and sediment-derived melts, entered the overlying depleted mantle wedge and participated in magma generation, which resulted in the low δ56Fe values of the SOT basaltic magmas. The δ56Fe values of volcanic rocks from the MOT increase with increasing SiO2 contents, suggesting a gradual enrichment of heavy Fe isotopes during the evolution of the magma as it ascended to the surface. While the Sr – Nd – Pb – Hf isotopic compositions do not vary significantly, suggesting that the different samples are the products of different degrees of crystal fractionation of comagma. The fractional crystallization of olivine, pyroxene, and ilmenite minerals, which enrich in light Fe isotopes, resulted in the gradual increase in Fe isotopic values of magma during its evolution. The dacites and rhyolites from the southernmost Okinawa Trough have the similar δ56Fe values with the basaltic andesite and the basalt from the SOT and MOT, accompanied by significantly lower Nd and Hf isotope ratios relative to basalts, reflecting that the contamination of crustal materials would not change the magma in Fe isotope compositions evidently. Compared with the MOT, the volcanic rocks from the SOT was more affected by subduction components on their underlying mantle, and those from the southernmost experienced more contamination by crustal materials in the evolving magma. [ABSTRACT FROM AUTHOR]

Located in the central part of the Central Asian Orogenic Belt, East Junggar represents one of the most important sites of juvenile crustal growth during the Phanerozoic. However, the mechanism of juvenile crustal growth during the Permian remains controversial. The Daheishan granites in the eastern segment of East Junggar are dated at ~292 Ma (Early Permian) and 269 Ma–267 Ma (Middle Permian). The Early Permian granites are coarse-grained with very high SiO2 (76.64 wt%–80.02 wt%), Al2O3 (10.72 wt%–12.96 wt%), and K2O/Na2O (1.27‒2.14), and low TiO2 (0.12 wt%–0.18 wt%), CaO (0.27 wt%–0.90 wt%), Mg# (25–32), and Sr/Yb (16–25). The Middle Permian granites are medium‒fine-grained with relatively high SiO2 (71.84 wt%–76.26 wt%), Al2O3 (11.26 wt%–13.00 wt%), and K2O/Na2O (0.53–1.54), and low TiO2 (0.17 wt%–0.21 wt%), CaO (0.37 wt%–3.20 wt%), Mg# (33–43), and Sr/Yb (5–9). These Permian granites display slightly positive whole-rock εNd(t) (+0.77 to + 1.04) and highly positive zircon εHf(t) (+7.3 to + 8.7) values, and low Ga/Al (2.04–2.55 < 2.6), P2O5 (0.02%–0.05% <0.14%), and zircon saturation temperature (690°C–749°C, take the median for each sample). Moreover, they display characteristic tetrad rare earth element patterns and non-CHARAC (CHArge-and-RAdius-Controlled) trace element behaviour, suggesting that the Daheishan granites are I-type granites that underwent both fractional crystallization (K-feldspar and plagioclase, e.g.) and crustal contamination prior to their emplacement. In combination with data from volcanic rocks in the Santanghu Basin, we infer that the Early Permian granitic magmas were derived from delamination of a thickened lithospheric mantle base and partial melting of pre-Permian arc components, while the Middle Permian granites formed during the subsequent stretching and thinning of the lithosphere. [ABSTRACT FROM AUTHOR]

Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting the population and infrastructure. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma–Vesuvius and Campi Flegrei volcanoes, along with the Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. This study focuses on the analysis of pyroclastic fall and flow deposits and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius in 472 CE (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory), and archeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are also referenced to the finding of ash beds in more distal areas, which were included in new isopach maps for the two sub-Plinian eruptions. The results show that for both eruptions the distribution of the primary deposits is wider than previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such a distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions, which involved distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), and it was possible to calculate the velocities and dynamic pressures of the lahars and ultimately infer the lahar transport and emplacement mechanisms. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas even at distances of several to tens of kilometers from active volcanoes. This especially applies to large parts of the densely populated areas around Somma–Vesuvius up to the nearby Apennine valleys. [ABSTRACT FROM AUTHOR]

The study of the volcano–sedimentary sequence in the lower part of the Zaonega formation in the Paleoproterozoic Onega structure (Karelian craton, Fennoscandian Shield) has shown that tuffaceous and high-silica rocks predominate in its composition. High-silica rocks (SiO2 up to 94 wt %) are depleted in all elements and probably represent chemogenic siliceous silts. Tuffaceous rocks vary broadly in composition and were formed during mixing of tuffogenous basalt material and high-silica chemogenic sediments. In terms of levels of contents and the distribution character of trace elements, tuffogenous rocks are close to N-MORB volcanic rocks. This rock association is typical of the early stages of continental rifting in the Phanerozoic and may indicate the formation of volcano–sedimentary complexes of the Zaonega formation in the environment of continental rifting. The tuffaceous rocks in the lower part of the Zaonega formation are geochemically identical to dolerite dikes and MORB-type volcanic rocks 2.10–2.14 Ga in age. Their formation was probably related to this episode of large-scale extension and thinning of the continental lithosphere of the Karelian craton in the Middle Paleoproterozoic. In this case, the age limit of the Zaonega and underlying Tulomozero formations should be somewhat older than the 2.06–2.10 Ga interval accepted in the modern regional stratigraphic schemes of the Paleoproterozoic Fennoscandian shield. [ABSTRACT FROM AUTHOR]

This work investigates the relationships between partial melting, melt extraction, pluton growth and silicic volcanism in garnet-bearing felsic volcanic rocks that were extruded in the Iberian Pyrite Belt, at ca. 345 Ma. The garnets are of peritectic origin, displaying textural and chemical features of disequilibrium crystallization during partial melting reactions involving biotite at high temperatures (up to 870 °C) in the middle-lower crust. Major element composition suggests compositional equilibrium with the entrained and pinitized peritectic cordierite, but reveals some subsequent homogenization by diffusion. Trace element maps and spot analyses of garnet show, nonetheless, significant trace element variations, reflecting biotite and Y-REE-P-rich accessory phase breakdown during partial melting reactions. Peritectic garnet and cordierite growth resulted in the preservation of Th- and Y-rich prograde suprasolidus monazite, which constrains the timing of partial melting of the metapelitic protolith at ca. 356.8 ± 2.4 Ma. The zircon cargo further shows that a significant amount of zircon crystals from previously crystallized felsic melts were also remobilized and erupted. These were likely stored in an upper crustal pluton that grew episodically since ca. 390 Ma during voluminous melt generation periods within the middle to lower crust, which also resulted in voluminous volcanism. The geochemical trends of the felsic volcanic rocks reflect the entrainment of xenoliths of peritectic garnet, cordierite and feldspar, and as such, the garnet-bearing felsic volcanic rocks represent an erupted mixture of a lower-temperature (ca. 770 °C) silicic melt and autocrysts, and peritectic phases and zircon crystals from previously crystallized and stored felsic melts. [ABSTRACT FROM AUTHOR]

To better understand the geodynamic evolution of northeastern China during the Late Mesozoic, we analyzed zircon U–Pb geochronological, Lu–Hf isotopic, and geochemical data for Early Cretaceous volcanic rocks from the southeastern margin of the Songliao Basin. Newly identified A-type rhyolite and trachyandesite yielded zircon 206Pb/238U ages of ca. 123 Ma and 117 Ma, respectively. The rhyolites are high in SiO2 (72.24–78.89 wt%) and total alkali (K2O + Na2O = 8.81–10.03 wt%), and low in MgO (0.10–0.26 wt%), CaO (0.32–0.36 wt%), Ni (0.08–2.69 ppm), and Cr (0.39–4.87 ppm) concentrations, with negative Nb, Ta, and Sr anomalies. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) and depleted in high-field-strength elements (HFSEs); the calculated Zr saturation temperatures are high (828–915 °C). The A-type rhyolites possess variable zircon εHf(t) values ranging from + 5.69 to + 10.49. Petrogenetic analysis leads us to propose that the A-type rhyolites were probably formed by partial melting of a Neoproterozoic–Early Paleozoic juvenile lower crust. The trachyandesites have Nb/Ta (14.9–17.25), Zr/Hf (35.04–42.75), Rb/Sr (0.25–0.40), and Lu/Yb (0.14–0.15) ratios that are similar to those of mantle-derived magma, indicating a mantle source. They have εHf(t) values of + 4.71 to + 7.29 and show enrichment in LILEs and LREEs, and weak depletion in HFSEs, suggesting that the parent magma originated from partial melting of a depleted lithospheric mantle, and was subsequently metasomatized by subduction-related fluids, followed by extensive fractional crystallization during the magma evolution. Combined with the temporal and spatial distribution of Late Mesozoic igneous rocks from the southeastern margin of the Songliao Basin, we propose that Early Cretaceous volcanic rocks formed in an extensional tectonic setting that was closely related to rollback of the Paleo-Pacific (Izanagi) oceanic slab. [ABSTRACT FROM AUTHOR]

The Yermak Plateau (YP) north of Svalbard is a prominent bathymetric feature in the Eurasia Basin of the Arctic Ocean, forming the northwesternmost margin of the Eurasian plate. Seismic data indicate that the YP comprises continental basement; however, little is known about its geology. New petrographic, geochemical, Sr–Nd isotopic, and Ar–Ar geochronological data were obtained on rock fragments, which were previously recovered from basement highs of the northeastern and southwestern YP and are dominantly of magmatic origin. These new data combined with available literature data, and comparisons with volcanic and sedimentary rocks from onshore and offshore areas adjacent to the YP indicate that the northeastern YP and the southwestern YP are different regarding their geological evolution. The southwestern YP comprises an alkaline basaltic suite for which an Ar–Ar biotite age of 51 Ma was previously reported. The suite was formed in a continental extensional regime offshore northern Svalbard. Associated sedimentary rocks (sandstone, several limestones) show petrographic similarity with rocks of the Devonian Old Red Sandstone on Svalbard. From the northeastern YP, in contrast, we recovered mildly alkaline basaltic rocks with mid-Cretaceous Ar–Ar ages (102 ± 3 and 98 ± 3 Ma). The rocks show certain geochemical characteristics (partial enrichments of P, Ba, and Eu), which overlap with similar-aged Cretaceous basaltic rocks from northern Ellesmere Island of Canada and North Greenland. We suggest that the northeastern YP is a continental fragment derived from the North American plate, which was separated from the conjugate Morris Jesup Rise and juxtaposed to the geologically distinct southwestern YP by the propagation of the Gakkel Ridge spreading center since the early Oligocene. [ABSTRACT FROM AUTHOR]

The Aqishan-Caixiashan polymetallic ore cluster, located in the eastern Tianshan Orogenic Belt, is part of the southern Central Asian Orogenic Belt (CAOB) and experienced extensive tectono-magmatic events with polymetallic mineralization during the Carboniferous. However, the Carboniferous tectonic affinity and magmatic evolution of the ore cluster are still controversial, which limits further understanding of the tectonic evolution and regional metallogeny. With the aim of solving these problems, we have carried out geochronological and geochemical studies on Carboniferous intrusive rocks and volcanic rocks from the ore cluster. The samples of the Carboniferous magmatic rocks are enriched in LREEs and LILEs but depleted in HFSEs, which attest to the I-type affinity and are similar to those formed in a continental arc. The early Carboniferous granodiorites and granites (350–343 Ma) in the Central Tianshan Block (CTB), with high Mg# values of 37–66, low Y values of 2.3–17.2 ppm, and high Sr/Y ratios (34–85), show characteristics of adakites that are formed by partial melting of delaminated oceanic crust and/or lower crust. Additionally, they have a wide range of εHf(t) values (5.4–15.9), high εNd (t) values (1.78–6.31) and low ISr values (0.705–0.706), indicating a mixed source of depleted mantle and lower crust for its origin. The Late Carboniferous volcanic rocks (314–306 Ma) in the Aqishan-Yamansu Tectonic Belt (AYTB) north of the CTB have obviously negative Nb–Ta-Ti anomalies, as well as high Y contents (12–20 ppm) and low Sr/Y ratios (5.6–29.9) compared to primitive mantle, which has a relatively flat chondrite-normalized REE pattern, resembling arc-related magmas. Additionaly, they have positive values of εHf(t) values (8.7–14.7), high εNd(t) values (3.04–4.45) and low ISr ratios (0.704–0.707), showing a depleted mantle source, which is weakly affected by the contamination of ancient crustal material. Combining this study and previous works, we suggest that the continuous southwards subduction of the North Tianshan Ocean during the Carboniferous generated the continental arc and forearc basin in the northern part of the CTB. The expansion of the Aqishan-Yamansu forearc basin formed intrusions and volcanic formations along the arc belt. The early Carboniferous intermediate-felsic mantle-derived adakitic magmas in the CTB are probably related to regional Zn-Pb enrichment and mineralization, and the Late Carboniferous intrusions and volcanic formations in the AYTB are related to large-scale Fe-Cu-Zn-Pb-Ag mineralization. [ABSTRACT FROM AUTHOR]

Late Devonian felsic volcanic rocks of the Grand Beach complex (GBC) of Avalonia from the Burin Peninsula, southeastern Newfoundland (northwestern Appalachians) are part of an overstep sequence overlying the Neoproterozoic basement. The volcanic complex is composed of volcanic and volcaniclastic rocks deposited in a post-tectonic extensional setting proximal to the St. Lawrence granite (SLG), a Devonian pluton associated with a prominent vein-type fluorite mineralization. The volcanic rocks are alkali rhyolites, which are weakly peraluminous and exhibit geochemical characteristics of A-type felsic magmas, such as low FeOt, MgO, CaO, and TiO2 but high contents of alkalis, Nb, Y, and Zr and high Ga/Al and FeOt/MgO ratios. They have positive ɛNd(t) values (~ + 2.5) and their Nd-depleted mantle model ages (~ 0.9 Ga) are consistent with derivation of the parental magma from metasomatized dry Avalonian lower crustal basement via partial melting followed by fractional crystallization. The U–Pb zircon age for the volcanic complex (375.6 ± 1.1 Ma) is closely comparable to the age of the SLG, suggesting that they were emplaced during the same magmatic episode. They also have similar chemical and isotopic compositions, suggesting that the GBC represents a volcanic equivalent of the SLG. The compositional differences between the volcanic rocks and the main phase of the granite pluton, including higher oxidation state of the GBC, reflect the interaction of the parental magma with crustal material and fluids. The close proximity of SLG and GBC suggests that the volcanic complex could host fluorite mineralization. [ABSTRACT FROM AUTHOR]

Changbaishan volcano (China/North Korea) is one of the most active and hazardous volcanic centers in Northeast Asia. Despite decades of intensive research, the eruption history of this stratovolcano remains poorly constrained. One of the major puzzles is the timing of the eruption that produced the Tianwen Yellow Pumice (TYP) deposit at the caldera rim. Here we identify a new cryptotephra layer in sediment core 13PT‐P4 from the East Sea. Grain‐specific major, minor, and trace element analyses of glass shards allow a clear correlation of this distal tephra to the proximal TYP deposit of Changbaishan. Age‐depth modeling using radiocarbon (14C) dates of sediment bulk organic fractions and other tephrochronological markers from the sediment sequence constraints the age of the cryptotephra and thus the TYP eruption to 29,948–29,625 cal yr BP (95.4% confidence interval). Our findings lead to a revision of the history of Changbaishan explosive activity, and show that the volcano has been particularly active during ca. 51–24 ka BP in the last 100 ka. Using high resolution palaeo‐proxy records, we find the TYP tephra almost coeval with regional to hemispheric‐scale climatic changes known as Heinrich Event 3 (H3). With its precise age determination and wide geographic dispersion, the tephra offers a key isochron for dating records of past climatic changes and addressing the phasing relationships in environmental response to H3 across East Asia. Plain Language Summary: Improving the knowledge of past volcanism is critical for volcanic hazard mitigation. Changbaishan volcano is one of the most dangerous volcanic centers in Northeast Asia, but its eruption history is not clearly understood. A classic example is the eruption that produced the magnificent Tianwen Yellow Pumice (TYP) deposited at the crater rim. Previous studies suggested a range of very different ages for this major eruption. In this study we trace its volcanic ash into a marine sediment core from the East Sea. By radiocarbon age‐depth modeling we are able to say with a high level of certainty that the eruption occurred sometime between 29,948 and 29,625 cal yr BP. The new results demonstrate the dispersal potential of ash from the eruption and shed light on the history and frequency of Changbaishan explosive activity. In addition, the TYP eruption is found to coincide with hemispheric‐scale and regional environmental changes. As a consequence, the volcanic ash can be used as a key time mark for dating sediment sequences and for investigating past environmental changes in East Asia. Our study also demonstrates the potential of using distal volcanic ash in reconstructing past explosive volcanism. Key Points: Timing of the Changbaishan Tianwen Yellow Pumice (TYP) eruption is resolved through proximal‐distal tephra correlation and radiocarbon age‐depth modelingEruption history of the Changbaishan volcano is revised, and dispersal potential of the TYP tephra is shown for the first timeA demonstration that the TYP tephra, as a regional marker, has great potential for sediment sequence‐based palaeoenvironmental studies [ABSTRACT FROM AUTHOR]

In the view of the recycling and upscaling processes of waste materials, three different precursors, namely metakaolin, fly ash and volcanic ash, were mixed with Na- or K-silicate to produce binders aimed for the synthesis of geopolymer mortars based on construction and demolition wastes (CDWs). These later, used as aggregates in amount of 50 wt.%, were sampled in two geologically different Italian areas. A comparative study was carried out through a multidisciplinary approach using mineralogical–chemical analyses and physical–mechanical tests for the characterization of six binders and twelve mortars. The aim was to verify the effects of CDW interactions on binders as well as the extent of their compositional influences on the final properties. The chemical and mineralogical results evidenced strong compositional differences among the CDWs, differently influencing the physical–mechanical performances (i.e., compressive strength, density, water absorption and porosity) of the mortar samples. Regardless of the types of precursors and CDWs used, a better influence of K-silicate than sodium on the synthetised samples was observed. Furthermore, the higher versatility of metakaolin mortars with any type of CDW used was noted. Contrary, fly ash and volcanic ash mortars showed better properties with CDWs based on their high silica content and volcanic minerals. The study highlighted the critical roles of the CDW composition and precursor selection in mortar production. It confirmed that CDWs can be recycled for geopolymeric synthesis through proper characterisation and binder selection. Optimising these parameters allows for the successful integration of CDWs into geopolymeric materials. This process supports the advancement of a circular economy in the construction industry. [ABSTRACT FROM AUTHOR]

The Neotectonic period of deformation in Anatolia has been embraced by a location between the complex interaction of Afro-Arabian and Eurasia plates. During this ongoing deformation, the eastern part was under the continuing influence of subduction by the Neotethyan Ocean in the Eastern Mediterranean Region resulting in the indentation of the Arabian Plate into Anatolia. As the Red Sea opened deformation became increasingly focused on a fault system comprising the Dead Sea, North Anatolian, and East Anatolian fault systems. To help constrain the age and deformation history of this last phase we have conducted a paleomagnetic study from a total of 28 sites at Lower-Middle Miocene Mazgirt volcanic rocks and Pliocene Karakoçan basalts in the Anatolian Plate, and the Quaternary Cizre basalts of the Arabian Plate. The mean paleomagnetic direction in Early-Middle Miocene time identifies a clockwise rotation of 12.38° ± 5.1° in the Anatolian Plate. In contrast, counterclockwise rotation of 19.2° ± 6.1° and 14.8° ± 5.7° is obtained in the Middle Miocene-Pliocene and Quaternary periods in the Anatolian and Arabian Plate, respectively. According to our findings, we point to the importance of two distinct tectonic events. The first phase defines a period between Lower Miocene to Pliocene which is defined by a clockwise rotation of 31.5°. It is concluded that during this time interval, the collision between Arabia and Eurasia and the motion of Arabia in the northeast direction gave rise to the clockwise rotation of Anatolia. The North Anatolian Fault (NAF) is thought to be inactive, while the East Anatolian Fault (EAF) was not generated in this time interval. In the second phase, the northwest-directed movement of the Arabian Plate led to counterclockwise rotations both in the Anatolian and Arabian Plate. We suggest that the North Anatolian Fault provided a contribution to this movement in the Pliocene, while the East Anatolian Fault accompanied this tectonic westward escape of the Anatolian Plate after the Quaternary. [ABSTRACT FROM AUTHOR]

Mantle xenoliths hosted in volcanic rocks from the island of Lutao offer a glimpse into the nature of the mantle beneath the northern Luzon volcanic arc. The xenoliths are spinel-bearing and composed mostly of harzburgite with one lherzolite and one olivine orthopyroxenite. The olivine (Fo92.5–88.9), orthopyroxene (Mg# = 94.6–89.2), and clinopyroxene (Wo49.1–38.1En57.0–45.4Fs3.0–11.0) compositions are similar to those of abyssal peridotites. The spinel compositions are variable and can be principally divided into high-Al (Cr# < 45) and low-Al (Cr# > 45) groupings. The whole rock compositions are similar to abyssal peridotite (Al2O3 = 0.95–2.07 wt %; Mg# = 88.5–90.9) and have U-shaped chondrite normalized rare earth element patterns. The Sr-Nd isotopes of the xenoliths are broadly chondritic (87Sr/86Sri = 0.704400–0.707908; εNd(t) = 0.0 − +1.5). The two-pyroxene equilibrium temperatures range from 900 to 1200 °C with the majority of temperature estimates >1000 °C. The olivine-orthopyroxene-spinel oxygen barometry estimates yielded ΔFMQ values from 0 to +2 and correspond to moderately oxidizing to oxidizing conditions. The xenoliths are likely derived from the Philippine Sea Plate lithospheric mantle that was modified by melt extraction and/or fluid enrichment processes. Trace element and isotopic mixing modeling indicate that 1–2% contamination by subducted South China Sea sediment can explain the Sr-Nd isotopic enrichment and Th and U elemental variability within the xenoliths assuming an initial composition similar to enriched depleted mid-ocean ridge mantle (E-DMM). The anomalously high two-pyroxene equilibrium temperatures of the Lutao xenoliths relative to other regions of the northern Luzon volcanic arc (Iraya <1000 °C) indicate that they were affected by a high-temperature event that was likely a consequence of recent intra-arc rifting that occurred after collision (<6 Ma) between the Luzon arc and the Eurasian margin. [ABSTRACT FROM AUTHOR]

In this study, zircon U‐Pb dating of volcanic rocks from the Zhongba ophiolite of the Yarlung Zangbo Suture Zone (YZSZ) in southern Xizang (Tibet) yielded an age of 247 ± 3 Ma. According to whole rock geochemical and Sr‐Nd‐Pb isotopic data, the Early Triassic samples could be divided into two groups: Group 1 with P‐MORB affinity, showing initial 87Sr/86Sr ratios of 0.70253–0.70602, εNd(t) values of 4.2–5.3, (206Pb/204Pb)t ratios of 16.353–18.222, (207Pb/204Pb)t ratios of 15.454–15.564, and (208Pb/204Pb)t ratios of 35.665–38.136; Group 2 with OIB affinity, showing initial 87Sr/86Sr ratios of 0.70249–0.70513, εNd(t) values of 4.4–4.9, (206Pb/204Pb)t ratios of 17.140–18.328, (207Pb/204Pb)t ratios of 15.491–15.575, and (208Pb/204Pb)t ratios of 36.051–38.247. Group 2 rocks formed by partial melting of the mantle source enriched by a former plume, and assimilated continental crustal material during melt ascension. The formation of Group 1 rocks corresponds to the mixing of OIB melts, with the same components as Group 2 and N‐MORBs. The Zhongba Early Triassic rocks belong to the continental margin type ophiolite and formed in the continental–oceanic transition zone during the initial opening of the Neo‐Tethys in southern Xizang (Tibet). [ABSTRACT FROM AUTHOR]

Identification and anatomy of oceanic arcs within ancient orogenic belt are significant for better understanding the tectonic framework and closure process of paleo‐ocean basin. This article summarizes the geological, geochemical, and geochronological characteristics of upper crust of Proto‐Tethyan Lajishan intra‐oceanic arc and provides new data to constrain the subduction evolution of the South Qilian Ocean. The intra‐oceanic arc volcanic rocks, including intermediate–mafic lava, breccia, tuff, and minor felsic rocks, are distributed along southern part of the Lajishan ophiolite belt. Geochemical and isotopic compositions indicate that the intermediate–mafic lava were originated from depleted mantle contaminated by sediment melts or hydrous fluids, whereas the felsic rocks were likely generated by partial melting of juvenile mafic crust in intra‐oceanic arc setting. Zircons from felsic rocks yield consistent and concordant ages ranging from 506 to 523 Ma, suggesting these volcanic rocks represent the relicts of upper crust of the Cambrian intra‐oceanic arc. Combined with the Cambrian forearc ophiolite and accretionary complex, we suggest that the Cambrian intra‐oceanic arc in the Lajishan ophiolite belt is belonging to the intra‐oceanic arc system which was generated by south‐directed subduction in the South Qilian Ocean at a relatively short interval between approximately 530 and 480 Ma. [ABSTRACT FROM AUTHOR]

The tight tuff reservoir is an unusual type of unconventional reservoir with strong heterogeneity. However, there is a lack of research on the microscopic pore structure that causes the heterogeneity of tuff reservoirs. Using the Chang 7 Formation in Ordos Basin, China as a case study, carbon-dioxide gas adsorption, nitrogen gas adsorption and high-pressure mercury injection are integrated to investigate the multi-scale pore structure characteristics of tuff reservoirs. Meanwhile, the fractal dimension is introduced to characterize the complexity of pore structure in tuff reservoirs. By this multi-experimental method, the quantitative characterizations of the full-range pore size distribution of four tuff types were obtained and compared in the size ranges of micropores, mesopores and macropores. Fractal dimension curves derived from full-range pores are divided into six segments as D1, D2, D3, D4, D5 and D6 corresponding to fractal characteristics of micropores, smaller mesopores, larger mesopores, smaller macropores, medium macropores and larger macropores, respectively. The macropore volume, average macropore radius and fractal dimension D5 significantly control petrophysical properties. The larger macropore volume, average macropore radius and D5 correspond to favorable pore structure and good reservoir quality, which provides new indexes for the tuff reservoir evaluation. This study enriches the understanding of the heterogeneity of pore structures and contributes to unconventional oil and gas exploration and development. [ABSTRACT FROM AUTHOR]

The Beyşehir-Hoyran Nappes, one of the tectonostratigraphic units of the Taurides, are thought to be originated from the Izmir-Ankara Ocean (northern branch of Neotethys). In this study, Late Paleozoic rock units from the blocks of Beyşehir-Hoyran Nappes were studied in detail using foraminiferal assemblages in two different locations from the southwest of Karaman City (southern Turkey). In both places, blocks/slices and pebbles of various origins are embedded within a highly sheared matrix of Late Cretaceous Age, and the whole unit can be regarded as a sedimentary mélange. The ages of the blocks from the southwest of Karaman City range from the Late Serpukhovian (Late Mississippian) to Late Capitanian (Middle Permian) with some depositional breaks (e.g., Bashkirian, Kasimovian). Combined with the previous data from the Mersin Mélange, which also include the remnants of the Beyşehir-Hoyran Nappes, our new findings suggest that a shallowing-upward sequence, characterized by a shallow water environment with foraminifera-bearing limestones, was deposited over the Tournaisian pelagic sequence in the Beyşehir-Hoyran Nappes till the Early Moscovian (Early Middle Pennsylvanian). This shallowing-upward sequence in the Beyşehir-Hoyran Nappes could be related to the Late Paleozoic Glaciation on the Gondwana supercontinent (Glacial II), which resulted in a sea-level drop and deposition of platform carbonates during the Viséan–Early Moscovian (Middle Mississippian to Early Middle Pennsylvanian) time interval. The absence of the main part of the Middle-Upper Pennsylvanian deposits (continental phase during the Middle Moscovian–Middle Gzhelian) in the Beyşehir-Hoyran Nappes can be mainly attributed to the occurrence of a mantle plume and partially to the effect of Late Paleozoic Gondwanan Glaciation (Glacial III). Progressive uplifting by the buoyant mantle plume material has resulted in rifting at the center of the basin where the Beyşehir-Hoyran Nappes have deposited. The rifting process led to tectonic destabilization of the platform in the basin, causing accumulation of the Upper Gzhelian (uppermost Pennsylvanian) detrital limestone with broken and abraded foraminiferal shells. Following this, deep basinal conditions prevailed during the Late Asselian–Kungurian (Early Permian), as revealed in the Mersin Mélange, where radiolarian cherts are associated with continental within-plate lavas of extreme incompatible trace element enrichment. Similar processes were responsible for the continual deposition of detrital limestones in the same basin until the end of Late Capitanian (Middle Permian). Based on all these, the uplifting process followed by rift-related volcanic rocks and detrital limestones can be interpreted as the opening of the Izmir-Ankara Ocean (northern Neotethys). [ABSTRACT FROM AUTHOR]

Basaltic hydrovolcanic environments on Earth produce abundant glass (sideromelane), which readily alters and acts as an important source of chemical energy for lithotrophic microorganisms; as such, these sites are significant for potential origins-of-life and early life research. Similar environments were identified on Mars and should be considered potential targets for astrobiological investigation. Pleistocene to recent phreatomagmatic and glaciovolcanic structures on Earth include tuff cones, tuff rings, maars, tuyas, and tindars. Such hydrovolcanic deposits contain abundant glass that is variably hydrothermally altered, and some areas contain published evidence of putative microbial habitation and microbially mediated alteration, including microtubules and granular alteration. We analyzed the literature on terrestrial hydrovolcanic environments and created a global database of 45 volcanic fields on Earth with compositions, alteration histories, and structures relevant to Mars. These sites have geochemistry, mineralogy, and syn-and post-eruptive environmental conditions that make them suitable targets for Mars-analogue astrobiological research. Relevant alteration products include palagonite, zeolites, clays, and calcite. Seven of these sites have evidence of microbially mediated alteration, which could be considered a useful biosignature in a Mars-analogue context. The sites are Wells Gray-Clearwater Volcanic Field, Canada; Fort Rock Volcanic Field, Western Snake River Plain Volcanic Field, and Upsal Hogback, USA; Reykjanes Volcanic Field and Western Volcanic Zone, Iceland; and Carapace Nunatak, Antarctica. Based on the properties of these already confirmed sites, along with comparing the remaining 38 Earth volcanic fields to volcanic rocks on Mars, we recommend 11 volcanic fields in particular from our database for future investigations: Auckland and South Auckland volcanic fields, New Zealand; O'ahu, Black Rock Desert, and Black Point, USA; Tuya Volcanic Field, Canada; Karapınar Volcanic Field, Türkiye; Vestmannaeyjar Archipelago, Iceland; Llancanelo Volcanic Field, Argentina; São Miguel Volcanic Field, Azores; and Icefall Nunatak, Antarctica. We recommend reviewing palagonitized tuff samples from these sites for evidence of microbial alteration, in addition to performing geochemical and mineralogical analyses to constrain their magmatic and alteration properties. By studying the rock record of hydrovolcanic environments on Earth to infer habitability and biological alteration, we contribute to establishing the conditions favorable for the origination, survival, and proliferation of life in a Mars-relevant setting. [ABSTRACT FROM AUTHOR]

The Dulate arc, located in East Junggar (NW China) in the southern Central Asian orogenic belt, records a Devonian magmatic arc evolution, offering a window to understanding the orogenic processes of the Central Asian orogenic belt. Here we present new geochemical and isotopic data for Late Devonian high-Mg andesite (HMA) and Nb-enriched basalt (NEB) suites from the Qiakuerte area, East Junggar. The HMA samples are typical subduction-related volcanic rocks. They have SiO2 contents ranging from 53.30 to 54.59 wt%, high MgO (5.0-5.26 wt%), and high Mg# values (~55) and show enrichments in large ion lithophile elements (LILEs) and depletions in high field strength elements (HFSEs). The HMA samples have high (La/Yb)N ratios and Sr/Y (~6.5 and 50-59, respectively) with no Eu anomalies. The HMA samples have high Na2O (~3.3 wt%) and low K2O (~2.5 wt%) and Th (~2.4 ppm) contents, combined with positive εNd(t) and low (87Sr/86Sr)i values. These characteristics suggest that the samples were formed mainly through interactions between subducted oceanic melts and mantle peridotites. Compared to normal arc basalts, the NEB samples have higher concentrations of Nb (~20 ppm), higher primitive mantle-normalized Nb/La (0.50-0.58), and higher ratios of Nb/U (9.4-14.6). The NEB samples also have positive εNd(t) and low (87Sr/86Sr)i values, indicating that their source was mantle wedge that had been metasomatized by slab melt. Considering the widespread presence of A-type granites, the abnormally high heat flow, and the tectonic characteristics of East Junggar, we conclude that a slab window created by the subduction of an ocean ridge was responsible for the melting of slab and the formation of the NEB-HMA suites. These processes may have also played a key role in the tectonic evolution processes of East Junggar during the Late Devonian. [ABSTRACT FROM AUTHOR]

The Otowi Member of the Bandelier Tuff erupted at ca. 1.60 Ma from the Valles caldera (New Mexico, USA). It consists of as much as 400 km3 (dense rock equivalent) of strongly differentiated high-silica rhyolite and shows systematic upward variations in crystallinity, mineral chemistry, and trace element concentrations through its thickness, but the major element composition is almost constant and is near the low-pressure granite minimum. Incompatible trace elements in whole pumice fragments and glasses show well-correlated linear covariations. Upward zoning to lower abundances of incompatible trace elements is accompanied by development of overgrowths on quartz and alkali feldspar, although earlier-formed interiors of quartz and feldspar have nearconstant compositions throughout the tuff, modified by cation diffusion in the case of feldspar. Melt inclusions in remnant quartz cores show diverse Pb isotope ratios, pointing to a wide range of distinct protoliths that contributed rhyolitic melt to the Otowi magma. Mineral thermometers suggest a modest temperature gradient through the melt body, perhaps of 40 °C, at the time of eruption. Chemical, textural, and mineralogical variations and volumecomposition relations through the tuff are consistent with an origin for zoning by melting of a high-crystallinity cumulate layer beneath cognate supernatant liquid to produce denser, remobilized liquid of accumulative composition (i.e., the "modified mush model"). Melting may have occurred in several episodes. The latest of these episodes, probably thousands of years prior to eruption, introduced new rhyolitic liquid into the system and was associated with a thermal excursion, recorded in core compositions of pyroxene, during which much of the earlier crystal mass was dissolved. This left inherited cores and interiors of accumulated quartz and feldspar mantled with new growth having less-evolved compositions (higher Ti, Sr, and Ba). Changing solubility of zircon during cumulate melting produced a reversal of Zr concentrations. There is no clear petrologic evidence of a recharge eruption trigger; nonetheless, compositional zoning resulted mainly from repeated recharge-induced remobilization of quartz-feldspar cumulate. The Otowi system was built, evolved, and modified by several events over the course of a few hundred thousand years. [ABSTRACT FROM AUTHOR]

In the lacustrine succession F4‐F5 of the Fucino Basin, central Italy, 20 visible tephra layers were identified in the time interval 250–315 ka (Marine Isotope Stages 8–9). Fifteen of them contained suitable material to explore their volcanic sources. Among these tephra some well‐known eruptions and eruptive sequences of the Roman and Roccamonfina volcanoes were identified, such as the Tufo Giallo di Sacrofano and the Lower White Trachytic Tuff, respectively. Furthermore, the sediment succession documents a more complex eruptive history of the Sabatini, Vulsini, Colli Albani and Roccamonfina volcanic complexes during the investigated period, as inferred from previously undescribed tephra deposits. Single‐crystal‐fusion 40Ar/39Ar dating of two of the inspected tephra layers combined with two already published tephra ages provided the basis for a Bayesian age‐depth model. The modelled tephra ages allow chronological constraining of so‐far undefined eruptions of the Sabatini (272.5±4.7, 281.8±4.7, 308.5±2.8, 312.8±2.1 ka), the Vulsini (311.7±2.3, 311.9±2.3 ka) and the Colli Albani (301.0±3.6 ka) volcanic districts. Two tephra layers of an undefined volcanic source from the Roman volcanoes have modelled ages of 309.5±2.7 and 310.5±2.6 ka. The new 40Ar/39Ar and modelled ages were further used for a reassessment of the timing of already known and dated eruptive units, such as the Tufo Giallo di Sacrofano (40Ar/39Ar: 289.3±4.8 ka). Tephra tentatively correlated with the Valle Santa Maria, Case Pisello and the White Trachytic Tuff Unit E3 or Unit F offer modelled ages for these eruptions of 296.6±3.9, 301.8±3.5 and 303.6±3.4 ka, respectively. The results complete the tephrostratigraphical investigations of the c. 425 ka old F4‐F5 record, extend the Mediterranean tephrostratigraphical framework and provide a significant contribution for improving knowledge on Italian volcanic explosive activity. [ABSTRACT FROM AUTHOR]

The Chagai belt to the north of the Afghan block and the east of the Iranian block in the western part of Pakistan is known for occurrence of Oligocene to Miocene calc‐alkaline magmatic belt. The present study discusses the characteristics of episodic magmatic activities that contributed to mineralization for the Reko Diq porphyry complex in the western part of the Chagai belt. U–Pb dating of zircons from volcanic rocks of the Reko Diq porphyry complex yielded ages of 25.8 ± 1.8 and 12.29 ± 0.44 Ma for two phases of magmatic crystallization. Geochemical analyses of whole‐rock rhyolite and dacite indicate that the rock units are peraluminous calc‐alkaline, derived from Andean‐type subduction. The magma was formed due to partial melting of the thickened mafic lower crust in a continental arc setting in relation to the subduction of the Neotethys along the Makran subduction zone. The abundance of zircons, Hf, REE, U/Pb and Th indicates high degrees of magmatic evolution. Moreover, the Sr and Nd isotopic data indicate the fractional contribution of depleted N‐MORB mantle to the Reko Diq magmas through bulk mixing with magmas derived from the lower continental crust. Short‐lived magmatic systems repeated magma injection, and various episodes of hydrothermal fluid flow have led to the formation of porphyry mineralization. Emplacement of the Reko Diq porphyry complex and related Cu–Au mineralization is associated with a series of tectonic–magmatic events at different episodes of the Oligocene–Miocene times. [ABSTRACT FROM AUTHOR]

This study provides new constraints on the causes of the chemical and isotopic variability in the central Victorian, Devonian, silicic, magmatic rocks and relates these to crustal architecture in the region. Synthesising present and previous work, it is concluded that the Selwyn Block, which forms the main source region for the Devonian silicic magmas (granitic and silicic volcanic rocks), is heterogeneous in three dimensions, on scales of 1 km and less. The sources of both the I- and S-type magmas were formed in Paleoproterozoic to Mesoproterozoic times, in the distal back-arc region of an Andean-type margin, in a basin that was extending and deepening eastward with time. The prominent rock types are high-grade metamorphosed greywackes, potassic andesites and dacites, with smaller volumes of pelitic rocks. The metasediment-dominated source rocks generally lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. This means that the I-type magmas were generally at lower temperatures and were also more hydrous than the S-type magmas. Heat for the metamorphism and partial melting of the source rocks of the silicic magmas was advected into the crust by mantle-derived magmas. These probably formed an underplate, to drive the regional metamorphism, but numerous, scattered, sill-like mafic bodies caused local contact anatexis and silicic magma production. Along with the emplacement of mafic magma bodies, the ascent of the silicic magmas to the upper crust rendered the deeper parts of the Selwyn Block denser and more mafic. The largely unexposed Selwyn Block, which forms the crustal basement in central Victoria, is heterogeneous in three dimensions, on scales of 1 km and less. The sources of the Devonian I- and S-type silicic magmas here formed in the Paleoproterozoic to Mesoproterozoic distal back-arc of an Andean-type margin. The metasedimentary S-type source rocks lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. Heat for the metamorphism and partial melting was advected by both underplating and numerous sill-like mafic bodies scattered throughout the deep crust. [ABSTRACT FROM AUTHOR]

This article employs a nonlinear creep constitutive model and explores the microscopic deformation features of hard tuff during the creep process, incorporating damage effects. Utilizing the particle flow program (PFC2D), a creep contact model is developed to simulate hard tuff under triaxial compression conditions. The study analyzes the creep mechanism of hard tuff under varying confining pressures, focusing on microscopic evolutions. Triaxial compression tests, conducted with confining pressures ranging from 10 to 30 MPa and axial pressures from 50 to 80% of peak strength, reveal significant influences of the confining pressure on the strength, deformation, and failure mode of hard rock. The results reveal that higher confining pressures enhance peak strength and peak strain, while the elastic modulus reduces continuously with increasing deviatoric stress, accompanied by pronounced attenuation creep features and cumulative deformation. The numerical results indicate that the mixed model accurately represents creep behavior in hard rocks. The meso-crack propagation pattern reveals that tensile fracture is the predominant mode of particle failure under triaxial compression. At low axial pressure, micro-crack propagation in attenuation creep and steady-state creep is limited, although internal damage accumulates continuously. As axial pressure increases, the rate of fracture formation rises, making creep failure more apparent. The numerical results align with the experimental data, with the mixing ratio of the mixed model effectively representing the creep characteristics of various rock types. The developed approach has significant implications for ensuring the enduring stability and structural integrity of rock masses in challenging sedimentary rock formations. [ABSTRACT FROM AUTHOR]

Many massive sulfide deposits have been discovered in the Upper Paleozoic rift-related volcaniclastic sequence in South China, among which the Yushui copper deposit is the most important due to its high grade. The deposit has been variably attributed as SEDEX (sedimentary exhalative) or MVT (Mississippi valley type). The Yushui copper deposit in Guangdong (South China) contains stratiform bornite-chalcopyrite orebodies (102.1 kt Cu @ 3.5%, 186.6 kt Pb @ 4.29%, 117.6 kt Zn @ 2.91%, and 339 t Ag @ 112 g/t) developed along the contact between Upper Carboniferous dolostone and Lower Carboniferous pebbly quartz sandstone, which indicates a shallow marine deposition environment. The Yushui deposit comprises an upper massive sulfide orebody and a lower stockwork orebody with intense alteration. In this study, we newly identified Carboniferous tuffs and syn-volcanic faults in the footwall, and exhalites in the hanging-wall. Hematite from the Cu ores yielded a U-Pb age of 320 ± 15 Ma (MSWD = 2.1, n = 57), and hydrothermal dolomite yielded a Sm-Nd isochron age of 308.1 ± 4.6 Ma (n = 7; MSWD = 0.94), which constrains the timing of mineralization at Yushui. These ages are coeval with the Carboniferous host rocks. Combining the evidence from the geological features (syn-volcanic faults, volcanic rocks, exhalites) and hematite trace element compositions, we suggest that the Yushui is a shallow marine VMS (volcanogenic massive sulfide) deposit. The Sr-Nd isotope composition of hydrothermal dolomite (εNd ~−12) indicates that the ore-forming materials were originated from the crustal basement. The Yushui copper deposit was likely formed during the Late Carboniferous continental back-arc extension in eastern South China. The regional extension may have caused enhanced heat flow, which promoted fluid convection in the basement rocks. In addition, we suggest that volcanic rocks and disseminated chalcopyrite-pyrite mineralization in the Lower Carboniferous quartz sandstone and exhalites are good indicators for regional VMS prospecting. [ABSTRACT FROM AUTHOR]

Early detection of volcanic ash clouds is crucial to aviation safety and airspace surveillance. With the increase in air traffic and the frequency of volcanic eruptions, the need for effective warning procedures and improved detection methods has become obvious. The eruption of the Eyjafjallajökull volcano in 2010 showed that air traffic operations were severely disrupted and highlighted the importance of effective communication strategies between stakeholders. To improve monitoring capabilities, satellite techniques have become essential due to their wide coverage and rapid response. This article presents the HOTVOLC 3.0 web-Geographic Information System (GIS) interface, an enhanced version of the French operational monitoring platform developed at the Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) and certified by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS-INSU). By integrating data from the Meteosat Second Generation (MSG) satellites, HOTVOLC 3.0 enables early detection of volcanic activity and monitoring of ash plumes and clouds. The HOTVOLC service is designed to support volcanic observatories, volcano research institutes, Volcanic Ash Advisory Centers (VAAC), and other operational actors who play a crucial role in decision-making and the implementation of effective risk management strategies for aviation safety. After a description of how the system works, we provide details of the updated web interface, which enhances the user experience by offering an interface with an operational mode and an archive mode, enabling easy access to past eruptions for training purposes. In the second part, we look at the various ash-related observation products (detection algorithms and quantitative products) that are disseminated via the new interface. Finally, we explore future developments of the platform, including the use of machine learning for ash detection, the integration of data from other geostationary satellites to improve product quality, and the forthcoming arrival of data from Meteosat Third Generation (MTG) satellites. [ABSTRACT FROM AUTHOR]

Magmatic rocks host different types of uranium deposits that can range from magmatic/high-temperature hydrothermal systems to post-magmatic, low-temperature hydrothermal deposits. The uranium mineralization in the syn- or late-magmatic systems could be divided into three types. (1) Magmatic deposits related to differentiated peralkaline complexes that are typically rich in SiO2 (>72 wt%) and poor in (B: Fe+Mg+Ti)<100 (in cation values). The Na/K ratio in these rocks is > 1 and they have high contents of incompatible lithophile elements such as Nb, Ta, Zr, REE, Th and U. (2) Magmatic deposits related to strongly peraluminous magmas, derived from partial melting of crust. They are the result of a low degree partial melting of crustal arkosic (quartz-feldspathic) rocks with high SiO2 (>74 wt%), low B < 40 and positive values for (A: Al-[Na+K + 2Ca]) (in cation values)), and are mostly accompanied by Li and F minerals. (3) Magmatic deposits related to the evolved hot peralkaline or metaluminous (A [A2] - to I- types) magma that assimilated fertile materials of the crust and endured a high rate of crystal fractionation. They mostly form high-temperature (vein-type and hybrid system) deposits. The rate of fluid in magma is important for the formation of this type of deposit. Therefore, the fertile magmas for this type of deposits typically have SiO2 >72 wt%, positive values of A, B < 50 and K/Rb < 150. They are possibly rich in Mo and F. Dry-hot alkaline felsic volcanic rocks are more suitable for post-magmatic low-temperature hydrothermal deposits. The altered intrusive rocks with about 200 Ma age and higher contents of refractory minerals, are suitable candidates for supporting the post-magmatic, low-temperature hydrothermal uranium mineralization. [ABSTRACT FROM AUTHOR]

We report the whole-rock major and trace element and Sr – Nd – Pb isotopic compositions of volcanic rocks from the Nansatsu area in South Kyushu. We analysed samples from the Oldest stage (middle Miocene), Older stage (late Miocene), and Middle stage (early Pliocene) Nansatsu volcanic rocks, which are andesite to dacite in composition, with an island-arc trace element signature. The compositional variabilities within the Older and the Middle stage rocks are relatively small compared to those in the Oldest stage and Quaternary volcanic rocks. Isotopic characteristics suggested that the Oldest stage volcanic rocks had magma sources similar to regional ilmenite-series granitoids of later ages (Outer Zone granitoids), which incorporated a substantial amount of graphite-bearing accretionary sediments (Shimanto Supergroup). The sources for the Older and Middle stage magmas were similar to those of primary Quaternary basalts in South Kyushu, indicating that Pliocene and Quaternary volcanic rocks in South Kyushu share a common mantle source, despite the change in the nature of volcanic activity from andesite-dominated to more variable volcanism of basalt to rhyolite. [ABSTRACT FROM AUTHOR]

Subduction-related magmatism is a significant contributor to arc building and continental growth. In the active convergent margin of the SW Japan arc, voluminous volcanic rocks and mafic dykes formed through subduction and back-arc rifting during Miocene. In this study, we investigate a suite of felsic volcanic rocks (rhyolite and dacite) and lamprophyres from central Shikoku Island, which occur in the north-central part of the Chichibu belt and Sanbagawa belt in the Outer zone of the SW Japan arc. Whole-rock geochemistry results show that the rhyolite and dacite samples are peraluminous, belong to the high-K calc-alkaline series, show LREE and LILE enrichment, HREE and HFSE depletion that suggest arc volcanic affinity. The lamprophyre samples belong to alkali lamprophyre, show LREE and HFSE enrichments, and display OIB (oceanic island basalt)-like geochemical features. The 206Pb/238U weighted mean ages of the zircons from the rhyolite and dacite samples range from 14.39 ± 0.21 Ma to 13.92 ± 0.30 Ma, whereas the lamprophyre shows 206Pb/238U weighted mean age of 12.21 ± 0.35 Ma. Zircon Lu-Hf isotope data suggest that the rhyolite and dacite were derived from the remelting of the arc crustal rocks and that the lamprophyre was derived from depleted mantle sources and was contaminated by crustal materials. The felsic volcanic rocks (rhyolite and dacite) can be correlated to Miocene (15.5 Ma to 13.5 Ma) magmatism in the Outer Zone of the SW Japan arc. The formation of lamprophyre dykes in the SW Japan arc may be related to the subhorizontal mantle flows beneath the SW Japan arc associated with the opening of the Japan Sea back-arc basin or asthenosphere upwelling through the slab-tear of the Philippine Sea Plate beneath the SW Japan arc. Our study shows that the SW Japan Arc was built by multiple magmatism from diverse sources in an active convergent margin. [ABSTRACT FROM AUTHOR]

The Qinling Orogenic Belt (QOB) is a composite orogenic belt located between the North China Craton (NCC) and the South China Block (SCB), and formed as a result of multiple episodes of collision and accretion. Although the tectonic history of the QOB has been extensively studied and reviewed, the evolution of the belt remains controversial. This contribution mainly reviews the geological, geochemical, and geochronological data of all the Early Palaeozoic intrusive and volcanic rocks of different genetic types in different tectonic units of the QOB and investigates their tectonic implications, together with the records of sediments, fossils and metamorphic rocks, to synthesize a new model for the Early Palaeozoic tectonic framework of the QOB. The QOB contains four discrete tectonic units (from north to south): the southern margin of the NCC, the North Qinling Terrain (NQT), the South Qinling Terrain (SQT), and the northern margin of the SCB. The Kuanping Ocean (represented by the Kuanping suture between the NQT and NCC) was a long-lived ocean rather than a backarc basin. Southward subduction of the Kuanping oceanic slab probably had begun before the Neoproterozoic and continued until the closure of the oceanic basin during the Early Palaeozoic. The subsequent retreat of the subducting slab caused the exhumation of deeply subducted arc volcanic rocks, forming high-pressure – ultrahigh-pressure metamorphic rocks at 500 My and the Erlangping backarc basin later. The closure of this basin and the subsequent collision between the NQT and NCC occurred at ca. 440 Ma. The Shangdan Ocean was a proto-Tethyan Ocean that had existed as early as the Neoproterozoic, the oceanic slab eventually underwent northward subduction towards the NQT at ca. 520 Ma, and this ocean closed by ca. 420 Ma. Marginal rifting and tectonic extension within the northern margin of the SCB formed the Mianlue oceanic basin during the Early Devonian. The complex interactions between the four discrete tectonic units within the QOB also led to the multiple-phase Early Palaeozoic metamorphic events, with the closure of the Kuanping, Erlangping, and Shangdan oceanic basins resulting in the HP – UHP and granulite- and amphibolite-facies metamorphism occurred at ca. 500, ca. 440, and 420 Ma, respectively. [ABSTRACT FROM AUTHOR]

The continental crust of Iran is dominated by abundant calc-alkaline and alkaline plutonic and volcanic rocks and by rifted basins filled with mostly terrigenous sedimentary rocks that formed at a Late Ediacaran to Cambrian extensional convergent plate margin along the northern margin of Gondwana. Here we present new zircon U–Pb age, geochemical, and isotopic data from plutonic (granite-granodiorite) and metamorphic (gneiss) rocks in the Kariznou region of NE Iran to provide insights into the nature of the Cadomian convergent margin of Iran. Geochemical data indicate calc-alkaline signatures, characterized by strong depletions in Nb, Ta, P, and Ti and arc-like trace element patterns. New zircon U–Pb ages show that calc-alkaline granitoids and granitic gneiss formed at ~564 to 537 Ma and 538 Ma, respectively. Bulk rock Sr-Nd isotopic data of calc-alkaline rocks have εNd(t) = –5.42 to −5.53 and −6.93 to −7.43 for granite and gneiss, respectively. The gneisses show stronger interaction with and/or re-melting of older continental crust than do granitic rocks. We interpret Kariznou magmatic rocks as forming in association with strong extension accompanied by crustal assimilation. Extension initiated ~570 Ma with the deposition of Late Ediacaran sediments, and magmatism began at 545–535 Ma, generating calc-alkaline magmas. The tectonomagmatic evolution of the Kariznou region encapsulates the prolonged transition of Cadomian Iran from a strongly extensional convergent margin, possibly as a result of oblique oceanic subduction and slab roll-back of the subducting Proto-Tethys oceanic lithosphere, culminating in the formation of an Early Palaeozoic passive margin on the northern side of Gondwana. [ABSTRACT FROM AUTHOR]

Hydration of rock during drilling will lead to wellbore instability. The wellbore stability can be effectively improved by accurately evaluating the hydration damage of rocks. However, there are few studies on the hydration damage of volcanic rocks. Based on the S-wave frequency domain, nuclear magnetic resonance and effective porosity, this article establishes a hydration damage variable, and discusses the influence of hydration on the microstructure, acoustic properties and mechanical properties of basalt and tuff. The results show that volcanic rocks produce new cracks during soaking, accompanied by mineral spalling and clay expansion. The correlation between the new hydration damage variable and the existing hydration damage variable is greater than 0.8. At the same time, the stress–strain curve simulated by the hydration constitutive model is in good agreement with the results of uniaxial compression experiments, and the average relative error of the elastic parameters of the two is small. The average relative errors of the peak stress, peak strain, and elastic modulus of basalt are 2.45%, 1.07%, and 1.72%, respectively, and the average relative errors of tuff are 1.49%, 0.45%, and 3.55% respectively. This study provides a new idea for evaluating the hydration damage of volcanic rocks. [ABSTRACT FROM AUTHOR]