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New data on the geological position, U‒Pb SIMS zircon ages, petrogeochemical features, Sr‒Nd isotopic composition, and geodynamic setting of the granitoids and volcanics of the Northern volcanic-plutonic belt of the Verkhoyan–Kolyma fold area are presented. Magmatic rocks of the belt include granitoids of Elikchan, Kuranakh, and Bakyn plutons, composed of Elikchan granite–granodiorite complex and volcanics of predominantly intermediate-felsic Tumusskaya sequence with subvolcanic bodies of the same composition. They form a single Early Cretaceous (127–121 Ma) volcanic-plutonic assemblage. Granitoid plutons are elongated in a sublatitudinal and northwestern direction and are discordant to main fold-and-thrust structures. Granitoids intrude and metamorphose Jurassic terrigenous and Early Cretaceous volcanics of Tumusskaya sequence and are intruded by younger Late Cretaceous subvolcanic bodies. Granitoids of Bakyn, Elikchan, and Kuranakh plutons combine petrogeochemical features of I-, S-, and A-type granites. Such diversity of petrogeochemical granitoid types, as well as interrelations of major ( –TiO2–MgO) and rare (Ba/La–Nb × 5–Yb × 10) elements in granitoids and the same age volcanics of the Tumusskaya sequence, allow us to refer them to igneous rocks of transform or sliding plate boundaries. Collision between the Chukotka microcontinent and the Siberian continent with the earlier accreted Kolyma–Omolon microcontinent in Barremian–Aptian time changed to postcollisional extension and formation of volcanic-plutonic assemblage of the Northern volcanic-plutonic belt. Postcollisional extension took place at the transform or sliding plate boundaries. Sr–Nd isotopic characteristics of granitoids of all granite plutons indicate the interrelation of mantle and crustal sources of granitoid melts in this process. [ABSTRACT FROM AUTHOR]

The Late Carboniferous volcanic magmatic evolution in the Bogda Orogenic Belt is considerably important for understanding the evolution history of the Eastern Tianshan in the Central Asian Orogenic Belt. Our study focuses on the Upper Carboniferous Liushugou Formation in the Liudaogou and Qidaogou sections of Xishan Township in eastern Bogda. By analyzing the volcanics and sedimentary sequences, we present paleontological evidence, new zircon U–Pb ages, and geochemical data of the volcanics. The lithological composition of volcanics ranges from basic to acidic. The rhyolite has an age of 311.2 ± 1.7 Ma, which, when combined with guide fossils Plerophyllum sp., Zaphrentoides sp., and Zaphrentites sp., indicates its formation in the Late Carboniferous. The geochemical and zircon Lu–Hf isotopic data (εHf(t) = 8.0–11.9) indicate that the basalts originated from a metasomatized subcontinental lithospheric mantle, while andesites and rhyolites were products of crystallization differentiation of the basalts that underwent assimilative mixing. Based on the published data, we propose that the tectonic evolution, transitioning from island arc magmatic systems to post-collisional orogenic belts, commenced in the Bogda Orogenic Belt toward the end of the Late Carboniferous.

This paper deals with the isotope composition of helium (3Не/4Не = R) in the groundwater of the Southern Baikal volcanic area (SBVA) and Southern Khangai volcanic area (SKhVA) during the Late Cenozoic Period. We have found differences in the behavior and value of that parameter. It was found that the differences in the concentrations of 3Не/4Не in the SBVA and the SKhVA resulted from mantle reservoirs that have different isotope compositions of helium. This confirms that the Late Cenozoic volcanism in the SBVA and SKhVA is controlled by mantle sources related to mantle plumes of the Central Asian hot mantle field. [ABSTRACT FROM AUTHOR]

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The Jehol and Yanliao biotas of northern China, two world‐class Lagerstätten with abundant biomass and biodiversity, provide critical clues to Mesozoic terrestrial ecosystems. Their evolution is a response to the destruction of the North China craton. However, the impetus for the rapid bloom of the biotas remains a mystery. Mesozoic large‐scale volcanic‐sedimentary strata in northern China are rich in terrestrial organisms. Statistical analyses show that volcanic nutrient element delivery, biomass, and biodiversity in these stratigraphic sequences increase synchronously, while harmful elements have the opposite change with them. These observations reveal the coevolutionary relationship between volcanism and terrestrial biotas. The increased nutrient element supply and inhibited harmful element delivery to terrestrial ecosystems from the voluminous volcanic products, produced under the geodynamic regime of paleo‐Pacific subduction and cratonic destruction, could create a conducive environment for the biodiversity and high prosperity of Mesozoic terrestrial biotas. Plain Language Summary: The weathering of volcanic products can quickly provide material supply for ecosystems, including nutrient and harmful elements. The availability of these elements in volcanic‐sedimentary sequences can provide key evidence for the intrinsic relations between volcanism and terrestrial biological evolution. Through statistically‐based big data analyses, we determine the changes in nutrient/harmful element delivery, biomass, and vertebrate and entomic diversity of the Mesozoic fossil‐bearing volcanic‐sedimentary strata in northern China. Excluding the interference of pyroclastic flows on the fossil records, the results reveal the significant contributions of elevated volcanic nutrient supply to the flourishing of the Jehol and Yanliao biotas. Meanwhile, the inhibited release of harmful elements has limited impacts on the biotas. This study opens a new path for multidisciplinary investigations to explore the feedback relationship among regional tectonics, volcanism, and terrestrial biotas. Key Points: Mesozoic terrestrial biotas in northern China coevolved with volcanism during the paleo‐Pacific subduction and cratonic destructionThe increasing supply of volcanic nutrients promoted the flourishing of the Jehol and Yanliao biotasInhibited volcanic toxic delivery facilitated the rapid bloom of the terrestrial biotas [ABSTRACT FROM AUTHOR]

The Northern Calcareous Alps in the Western Tethys realm were affected in Middle to Late Jurassic times by a mountain building process triggered by ophiolite obduction similar to that in the Inner Western Carpathians or Inner Dinarides. In contrast to these other mountain ranges, in the Northern Calcareous Alps the obducted ophiolites or ophiolite derived components in the Bathonian-Oxfordian mélanges are missing. Cr-spinels in Kimmeridgian basinal deposits are the oldest known relics of a Jurassic ophiolite obduction. This study reveals new data from a newly detected Hallstatt Mélange below the Late Jurassic Plassen Platform in the southeastern Northern Calcareous Alps (Raucherschober/Schafkogel area). Upper Triassic Hallstatt Limestone blocks from the former distal northwestern continental margin of the Neo-Tethys Ocean, as well as ophiolite and radiolarite blocks from the Neo-Tethys Ocean floor rest within an upper Middle to lower Upper Jurassic radiolaritic-argillaceous matrix. Ophiolitic blocks show calc-alkaline volcanic arc affinity, defining the rocks as the product of intra-oceanic subduction and the formation of an early arc during stacking of the oceanic crust. Resedimented ribbon radiolarite blocks deposited above the newly formed suprasubduction (SSZ) ophiolites in the Neo-Tethys Ocean east of the island arc have a Middle Jurassic age. Later, at a time of decreasing tectonic activity, the Hallstatt Mélange was sealed by the Kimmeridgian-Tithonian Plassen Carbonate Platform, showing a shallowing-upward trend.

Abstract The Jehol and Yanliao biotas of northern China, two world‐class Lagerstätten with abundant biomass and biodiversity, provide critical clues to Mesozoic terrestrial ecosystems. Their evolution is a response to the destruction of the North China craton. However, the impetus for the rapid bloom of the biotas remains a mystery. Mesozoic large‐scale volcanic‐sedimentary strata in northern China are rich in terrestrial organisms. Statistical analyses show that volcanic nutrient element delivery, biomass, and biodiversity in these stratigraphic sequences increase synchronously, while harmful elements have the opposite change with them. These observations reveal the coevolutionary relationship between volcanism and terrestrial biotas. The increased nutrient element supply and inhibited harmful element delivery to terrestrial ecosystems from the voluminous volcanic products, produced under the geodynamic regime of paleo‐Pacific subduction and cratonic destruction, could create a conducive environment for the biodiversity and high prosperity of Mesozoic terrestrial biotas.

In operation for >16 years to date, the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) sounder has acquired data at its nominal 300–450 m along-track and 3-km cross-track resolution covering >55% of the Martian surface, with nearly 100% overlap in coverage at that scale in the polar regions and in a number of smaller mid-latitude areas. While SHARAD data have opened a new window into understanding the interior structures and properties of Martian ices, volcanics, and sedimentary deposits up to a few kilometers in depth, they have also led to new revelations about the deeper interior and the behavior of the planet's ionosphere. Here we summarize the data collected by SHARAD over this time period, the methods used in the analysis of that data, and the resulting scientific findings. The polar data are especially rich, revealing complex structures that comprise up to several dozen reflecting interfaces that extend to depths of 3 km, which inform the evolution of Martian climate in the late Amazonian period. SHARAD observations of mid-latitude lobate debris aprons and other glacier-like landforms detect strong basal reflections and low dielectric loss, confirming that they are ice-rich debris-covered glaciers. In other mid-latitude terrains, SHARAD data demonstrate the presence of widespread ground ices, likely at lower concentrations. SHARAD signals also probe non-icy materials, mapping out stacked lava flows, probing low-density materials thought to be ash-fall deposits, and occasionally penetrating sedimentary deposits, all of which reveal the structures and interior properties diagnostic of emplacement processes. SHARAD signals are impacted by their passage through the Martian ionosphere, revealing variations in time and space of the total electron content linked with the remanent magnetic field. Advanced techniques developed over the course of the mission, which include subband and super-resolution processing, coherent and incoherent summing, and three-dimensional (3D) radar imaging, are enabling new discoveries and extending the utility of the data. For 3D imaging, a cross-track spacing at the nominal 3-km resolution is more than sufficient to achieve good results, but finer spacing of 0.5 km or less significantly improves the spatially interpolated radar images. Recent electromagnetic modeling and a flight test show that SHARAD's signal-to-noise ratio can be greatly improved with a large (∼120°) roll of the spacecraft to reduce interference with the spacecraft body. Both MRO and SHARAD are in remarkably fine working order, and the teams look forward to many more years in which to pursue improvements in coverage density, temporal variability in the ionosphere, and data quality that promise exciting new discoveries at Mars. • SHARAD has revealed the internal structure, composition, and history of Mars' polar caps and constrained current heat flow. • SHARAD settled a long-standing debate by showing that mid-latitude glacial landforms are ice-rich debris-covered glaciers. • SHARAD has provided first constraints on the interior composition and stratigraphy of volcanic and sedimentary layers. • SHARAD has provided a new understanding of Martian ionospheric variability and its relationship to crustal magnetic fields. [ABSTRACT FROM AUTHOR]

The newly proposed Middle Cretaceous “Bibai Group”, named after the Bibai peak, is exposed in Kach-Ziarat, Spera Ragha-Chingun areas of the Western Sulaiman Fold-Thrust Belt, Pakistan. It comprises thick succession of the mafic volcanic rocks, volcanic conglomerate, mudstone and sandstone. The stratigraphic nomenclature proposed by previous workers was not clear enough, as they used different names for the succession, such as “Kahan Conglomerate Member” of the Mughal Kot Formation, “Parh-related volcanics” by considering it as part of the “Parh Group, “Bibai Formation” and “Bela Volcanic Group”, which were confusing and misleading. Also previous workers did not realize that the succession may be further classified into distinct mappable lithostratigraphic units and deserved the status of a “Group”. Therefore, we carefully examined and mapped the area and hereby propose the name “Bibai Group” for the overall volcanic and volcaniclastic succession of the Middle Cretaceous age. Based on distinct lithostratigraphic characters we further subdivided the “Group” into two lithostratigraphic units of formation rank, for which we propose the names “Chinjun Volcanics” and “Bibai Formation”. Also based on distinct lithostratigraphic characters we further propose to subdivide our “Babai Formation” into three lithostratigraphic units of member rank, which we named as the “Kahan Conglomerate Member”, “Ahmadun Member” and “Kach Mudstone Member”. In this paper we have defined and briefly described the Bibai Group, its constituent formations and their members. Also we examined and discussed the validity and status of the proposed subdivisions; e.g. formations and members, of the Bibai Group, and are fully satisfied that the proposed subdivisions are appropriate and comply with the Article 24 and 25 of the North American Stratigraphic Codes (2005) and that the previous nomenclatures are inconsistent, confusing and do not comply with the International Stratigraphic Codes.

The volcanics of the Navysh complex of the Lower Riphean Ai Formation in the Southern Urals are well studied petrochemically and dated by several methods. In 2013 zircons from a trachybasalt porphyrite (sample 2152) gave a concordant SHRIMP date 1752±11 Ma, which was used as a fundamental for the lower boundary of the Riphean with no special arguments against it. The later attempts to repeat this date for the Navysh volcanics were not successful: the collected zircons were either more ancient (> 2500 Ma), or more young (< 500 Ma). From the beginning, the zircons with such ages were regarded as xenogenic or secondary metasomatic, or belonging to paleozoic dykes intruding the Riphean volcanics. However, the clearly expressed mineralogical properties of the Paleozoic zircons and their frequent presence in volcanics, not dykes, led to a conclusion that the zircons and Navysh volcanics, containing them, and exposed within the area of development of the Ai Formation, are polychronous. To support this conclusion, the authors studied in more detail the zircons of the Navysh trachybasalts, developed in the Ai Formation. The main conclusion, obtained from this new data, was that the volcanics attributed to the Navysh complex, form a polychronous system, including both the Lower Riphean (1750 Ma) and Paleozoic (450 Ma) rocks. The zircons of these age groups differ in their mineralogical and geochemical properties supporting the idea that they belong to different primary sources which may be due to repeating plume processes, which partly reanimated – heated and melted-rocks of the previous cycle and/or created new sources of melts.

New U‒Pb SIMS and 40Ar‒39Ar geochronological, petrogeochemical, and isotope geochemical data for the granitoids of the Chimalga pluton in the central part of the Main batholith belt of the Chersky Range within the Verkhoyan–Kolyma fold area are presented. It is shown that the zircon crystallization ages of 150 and 152 Ma for granodiorites and leucogranites coincide within the error with the 40Ar‒39Ar amphibole age of 148.6 ± 5.6 Ma for the granodiorites of the pluton, as well as the ages of the felsic and intermediate volcanic host rocks of the Uyandina–Yasachnaya volcanic belt (150–152 Ma) and the peak of granitoid intrusion within the Main batholith belt (150 ± 3 Ma). The granitoids of the Chimalga pluton have petrogeochemical characteristics, which provide a possibility to classify them into I-type as well as S‑type granites. They are similar to I-type granites in the presence of biotite, hornblende, and clinopyroxene among mafic minerals; the absence of primary muscovite; and the prevalence of calc-alkalic and metaluminous varieties. Like S-type granites, the highly silicic compositions are characterized by the presence of ferroan and magnesian varieties. The granitoids contain high-alumina mineral aggregates associated with potassium feldspar, albite, and spinel, which suggest the presence of granulite-facies metapelites in magma source area. The Sr‒Nd isotope characteristics of the granitoids of the Chimalga pluton, as well as the interrelationship of certain rock-forming oxides indicate a heterogeneous source of granite melts. Negative εNd(Т) values that vary from –2.98 to –6.23, high primary 87Sr/86Sr values from 0.7073 to 0.7091, and the Mesoproterozoic model ages of the granitoids attest to the contribution of fairly mature continental crustal material to their petrogenesis. The granitoids are assumed to have formed in a marginal continental setting during the activity of the Uyandina–Yasachnaya volcanic arc. [ABSTRACT FROM AUTHOR]

The N–S trending Neoarchaean to Palaeoproterozoic Dongargarh–Kotri belt in the Bastar Craton in central India exposes bimodal volcanics and volcaniclastics of the Nandgaon Group. In this contribution, lithofacies analysis of the Nandgaon Group has been attempted mainly based on distribution of rhyolites, basalts and pyroclastics in this ancient volcanic terrain, their field characteristics and petrography. The study area in the central part of the belt around Dongargaon–Gotatola area can be two distinct domains based on distribution and composition of volcanics and volcaniclastics. Domain-I comprises coherent and autoclastic rhyolite, and Domain-II with basic lava and pyroclastics. The rhyolites of Domain-I can be further divided into feldspar quartz phyric, quartz phyric, aphyric, and autoclastic rhyolites. Basic lava of Domain-II includes basalt and andesitic basalt. The associated volcaniclastics are mainly coarse lapilli tuff, fine lapilli tuff and ash beds. Field characteristics of coherent lavas and volcaniclastics attest to phreato-magmatically controlled plinian to sub-plinian style of eruptions. Effusive and explosive eruptive processes through multiple vents gave rise to the observed volcanic sequences. This study indicates that subaerial volcanism initially led to formation of felsic ignimbrites and ash deposits followed by effusive rhyolite lava flows. Subsequently, mafic volcanism occurred giving rise to pyroclastic flows and surges, followed by effusive mafic lava flows. [ABSTRACT FROM AUTHOR]

The article demonstrates a method for quantitative-qualitative geodiversity assessment based on core elements of abiotic nature (geology and geomorphology) according to a proposed weight multiplied by the area of spread through the studied region. The territory of the Coromandel Peninsula was selected as a case study due to its diverse geology and geomorphology. The north part of the Peninsula (Port Jackson, Fletcher Bay and Port Charles districts) was chosen because of the variety of rock types (sedimentary and volcanic groups) covering the region, while historical stratovolcano remnants and old sediments provide a good variety of meadow hills and weathered coastal cliffs. Meanwhile, the method utilizes easily accessible data (topographical and geological map) to assess slope angle (morphometry) and rock groups, including their age (geology) to identify areas in the sample region with significant geodiversity values. Moreover, the aim of this research is to make the assessment of geodiversity simpler and more accessible for various parts of the world with minimal required information. In this paper, we provide access to improve and utilize this method in geologically diverse territories to select the best areas for geotourism, geoeducation and geconservation planning. [ABSTRACT FROM AUTHOR]

Geological and geochemical characteristics of the litho units exposed in and around Kalalikhera area of Pur-Banera belt have confirmed the presence of felsic volcanic rock unit named Kalalikhera felsic volcanic, with characteristic features such as (i) abundance of lapilli composed of polygonal quartz and feldspar and (ii) presence of relict bipyramidal quartz. These volcanics are associated with thin bands of chert. Geochemically, the volcanics are found to be of rhyolitic composition. Development of garnet porphyroblasts along with preferred orientation of the silicate minerals of rhyolite indicates a low to medium grade metamorphism and deformation of the units. Monazite geochemistry of the volcanics indicated towards the metamorphic origin of monazites, with REE pattern show steep fractionation trend from La to Lu. The in-situ chemical age of 2192 ± 57 Ma recorded from xenotime is interpreted as indicative of the opening of the Aravalli basin with the onset of rifting leading to the formation of Kalalikhera volcanics. The estimated ages of 1784 ± 92, 1351 ± 45 and 1026 ± 57 Ma from monazite analyses are interpreted as different metamorphic events associated with (i) closure of the basin and the onset of Aravalli orogeny, (ii) further imprints of Delhi orogeny, and (iii) with late Grenvillian age imprints. [ABSTRACT FROM AUTHOR]

Abstract Widespread recent volcanic rocks occur across the Cordillera landward of the current/recent volcanic arc Mexico to Alaska and most other subduction backarcs. We conclude that most are produced by partial melt in the upper asthenosphere where two conditions are met: (1) thin lithosphere, shallow hot asthenosphere. Most of the Cordillera is uniformly hot with thin lithosphere such that the hot asthenosphere extends up to a sufficiently shallow depth to intersects the wet solidus; (2) wet upper asthenosphere. There is substantial water in the upper asthenosphere that reduces the solidus sufficiently for partial melting. We integrate geochemical analyses that constrain the partial melt source temperature and depth, seismic velocities that define the upper mantle temperature and partial melt zones, and seismic receiver functions that define the lithosphere‐asthenosphere boundary (LAB). Geochemical data for the Canadian Cordillera are integrated with data from the western United States. Upper mantle xenoliths indicate a dry strong lithosphere, 250 ppm, is indicated by the volcanics, facilitating small‐scale convection. Geochemical equilibration averages ∼1,350°C, at ∼65 km. Receiver functions also define the LAB at ∼65 km for the western Cordillera, deeper in the eastern US Cordillera, and asthenosphere tomography velocities indicate ∼1,350°C. Low velocities above ∼150 km suggest a few percent partial melt that percolates upward and ponds at the base of the lithosphere until enough accumulates to locally penetrate upward. The 65‐km depth may be controlled by the spinel‐garnet phase transition. Mechanisms are discussed for the spatial distribution of recent volcanics.

Widespread recent volcanic rocks occur across the Cordillera landward of the current/recent volcanic arc Mexico to Alaska and most other subduction backarcs. We conclude that most are produced by partial melt in the upper asthenosphere where two conditions are met: (1) thin lithosphere, shallow hot asthenosphere. Most of the Cordillera is uniformly hot with thin lithosphere such that the hot asthenosphere extends up to a sufficiently shallow depth to intersects the wet solidus; (2) wet upper asthenosphere. There is substantial water in the upper asthenosphere that reduces the solidus sufficiently for partial melting. We integrate geochemical analyses that constrain the partial melt source temperature and depth, seismic velocities that define the upper mantle temperature and partial melt zones, and seismic receiver functions that define the lithosphere‐asthenosphere boundary (LAB). Geochemical data for the Canadian Cordillera are integrated with data from the western United States. Upper mantle xenoliths indicate a dry strong lithosphere, <50 ppm H2O. A wet asthenosphere source, >250 ppm, is indicated by the volcanics, facilitating small‐scale convection. Geochemical equilibration averages ∼1,350°C, at ∼65 km. Receiver functions also define the LAB at ∼65 km for the western Cordillera, deeper in the eastern US Cordillera, and asthenosphere tomography velocities indicate ∼1,350°C. Low velocities above ∼150 km suggest a few percent partial melt that percolates upward and ponds at the base of the lithosphere until enough accumulates to locally penetrate upward. The 65‐km depth may be controlled by the spinel‐garnet phase transition. Mechanisms are discussed for the spatial distribution of recent volcanics. Plain Language Summary: There are widespread recent volcanic rocks in most of the North American Cordillera from Mexico to Alaska and most 200–1,000 km wide global subduction zone backarcs. We interpret them to result mainly from partial melting in upper wet asthenosphere where there is small‐scale solid‐state convection. There is substantial geochemical modification and differentiation in transit to the surface through the dry strong lithosphere. Partial melt is inferred to pond and chemically equilibrate at the lithosphere‐asthenosphere boundary which is near 65 km for most of the Cordillera from geochemical and seismic structure constraints. This depth may be stabilized by the spinel‐garnet phase transformation. The boundary in most areas is at about 1,350°C which strongly constrains upper mantle and crust temperatures, with the Cordillera Moho generally at 800°C–850°C. Local concentrations of volcanics may result from upward movement into the asthenosphere melt window. Key Points: Similar mafic backarc volcanics are widespread in the Cordillera from Mexico to AlaskaMost of Cordillera is uniformly hot with base of the lithosphere at ∼1,350°C and ∼65 km from geochemical equilibria, seismic tomography, and receiver functionsVolcanics produced mainly by partial melting in wet asthenosphere, ponding at base of dry lithosphere; depth controlled by the spinel‐garnet phase change [ABSTRACT FROM AUTHOR]

Abstract—Paleomagnetic studies of several Late Cretaceous volcanic sections of the Okhotsk–Chukotka volcanic belt have been carried out in the Bilibino region of the Chukotka Autonomous Okrug and along the Pevek–Egvekenot road. Extensive collections have been acquired and analyzed. The laboratory experiments isolated the ancient characteristic magnetization component reflecting the direction of the geomagnetic field at the time of formation of the studied rocks (~85 Ma ago). The primary character of the revealed characteristic magnetization component is supported by the positive regional fold test and by the coincidence of the paleomagnetic pole calculated from this component with that previously obtained for Chukotka from the rocks of similar age (Stone et al., 2009). The paleomagnetic pole calculated from the combination of the previous and our newly obtained data (Plat = 69.3°, Plong = 180.7°, N = 99, A95 = 5.1°) indicates that the sampled rocks were formed in the immediate vicinity of the geographic pole. The reliability of the existing Late Cretaceous paleomagnetic poles for Eurasia and North America is analyzed, and the refined poles are calculated for these plates for the time of ~85 Ma. The reconstruction of the Chukotka–Kolyma–Omolon block's position relative to Eurasia and North America allowing for the paleomagnetic poles calculated for that time is proposed. The reconstruction implies that from the formation time of the studied rocks up to the present, the Chukotka–Kolyma–Omolon block has undergone relatively small (tens to first hundreds of km) southward movements relative to the North American plate and has been noticeably shifted (by a few hundred km) relative to the Eurasian plate. Our reconstruction is close to that proposed in (Otofuji et al., 2015) but, in contrast to the latter, it does not require a collision between the Chukotka–Kolyma–Omolon block and Eurasia after 80 Ma ago. [ABSTRACT FROM AUTHOR]

Hydrothermally active submarine volcanoes are mineral-rich biological oases contributing significantly to chemical fluxes in the deep sea, yet little is known about the microbial communities inhabiting these systems. Here we investigate the diversity of microbial life in hydrothermal deposits and their metagenomicsinferred physiology in light of the geological history and resulting hydrothermal fluid paths in the subsurface of Brothers submarine volcano north of New Zealand on the southern Kermadec arc. From metagenome-assembled genomes we identified over 90 putative bacterial and archaeal genomic families and nearly 300 previously unknown genera, many potentially endemic to this submarine volcanic environment. While magmatically influenced hydrothermal systems on the volcanic resurgent cones of Brothers volcano harbor communities of thermoacidophiles and diverse members of the superphylum "DPANN," two distinct communities are associated with the caldera wall, likely shaped by two different types of hydrothermal circulation. The communities whose phylogenetic diversity primarily aligns with that of the cone sites and magmatically influenced hydrothermal systems elsewhere are characterized predominately by anaerobic metabolisms. These populations are probably maintained by fluids with greater magmatic inputs that have interacted with different (deeper) previously altered mineral assemblages. However, proximal (a few meters distant) communities with gene-inferred aerobic, microaerophilic, and anaerobic metabolisms are likely supported by shallower seawater-dominated circulation. Furthermore, mixing of fluids from these two distinct hydrothermal circulation systems may have an underlying imprint on the high microbial phylogenomic diversity. Collectively our results highlight the importance of considering geologic evolution and history of subsurface processes in studying microbial colonization and community dynamics in volcanic environments. [ABSTRACT FROM AUTHOR]

Arabian Shield offers a strong potential for geothermal energy. However, only a limited amount of exploration effort has taken place. Harrat Rahat is a recent volcanic area located along the Makkah-Madinah-Nafud volcanic line in western Saudi Arabia. This study is oriented to identify the geothermal potential of Harrat Rahat. The geologic data was collected and processed. In the current study, we focus on evaluating the potential sources of subsurface heat and groundwater. Subsurface heat is based on the age of erupted volcanoes and the expected volume of subsurface magma chambers. An analogy with an existing geothermal field in a similar setting as Mexico suggests that the faults and the coincident seismicity may be associated with higher permeability. It is concluded that Harrat Rahat is characterized by a good geothermal potential for future geothermal energy source production. [ABSTRACT FROM AUTHOR]

The Gutiolo volcanic unit belongs to the Aptian Bilbao Formation and crops out 6 km SE of Bilbao (N Spain) within marine marlstones. It is 300 m thick and up to 1 km long. The volcanics consist of lava in the lower part and volcaniclastic sediments above, with metatrachytes and metatrachybasalts, similar to others of the alkali Cretaceous sequence in the Basque–Cantabrian Basin. The palaeontological age is top early Aptian (Dufrenoyiafurcata Zone) near the Bedoulian–Gargasian substage transition, and the isotopic age (K–Ar) is 123 ± 3 Ma but most probably, 122 Ma. E–W and N–S trending faults bounding the Gutiolo volcanics controlled magma eruption. Other NW‐ and SE‐oriented major faults in the Bilbao area favoured several Valanginian to Santonian eruptions including Gutiolo. The eruptions moved progressively in space and time from SW to NE. These faults make up a 15‐km‐wide tectonic belt, the magma‐leaky Bilbao Fault Zone. A similar magmatic fault zone NE of Bilbao, Gernika‐Elgoibar, poured magma onto the sea floor during the late Albian–Cenomanian up to the Santonian, continuing the north‐easterly younging trend of volcanic inceptions recognized in Bilbao. All this Cretaceous volcanism is related to the Bay of Biscay opening processes, and the Gutiolo event is correlated with the first appearance of oceanic crust in the Bay of Biscay. From stratigraphic, volcanic, geochemical, and mineralization evidence, we attribute Gutiolo to an early phase of mafic intrusion emplacement in the Bilbao area, underplated by magmatism during the Valanginian to Santonian (Cretaceous). Volcanic hydrothermal fluids associated to the Gutiolo event are considered responsible for metallic ore emplacement in the Basque–Cantabrian Basin during the early Aptian. [ABSTRACT FROM AUTHOR]

Abstract—The paper summarizes material on the chemical composition of Walvis Ridge volcanics. Analysis showed that the formation of the eastern and central parts of the ridge in the Cretaceous and Paleogene was determined primarily by the appearance of fractured decompression centers, which resulted from strike-slip–pull-apart dislocations during the Gondwana breakup. Basalts of the central part of the Walvis Ridge show signs of crustal contamination. Apparently, in the Cretaceous and Paleogene, the Tristan plume indirectly participated in the formation of Walvis Ridge rocks, partially enriching with its material melting centers that occurred in thick (>20 km) deformed crust. The spreading factor manifested itself in the Upper Cretaceous (tholeiitic volcanism of the eastern part of the ridge) and in the Neogene–Quaternary, when the thickness of the newly formed oceanic crust began to decrease. This allowed the "dying" Tristan plume to form a system of volcanic seamounts in the western part of the Walvis Ridge. [ABSTRACT FROM AUTHOR]

Abstract The Bass Basin, a Mesozoic-Cenozoic intra-continental rift basin along the southern Australian continental shelf, offers an excellent natural laboratory for examining igneous rocks in the subsurface. Igneous material within the basin is manifested as a mixture of predominately mafic extrusive and intrusive rocks, mainly Cretaceous-Palaeocene and Oligocene-Miocene in age. Igneous rocks have been encountered in 20 out of 36 (55.6%) exploration wells drilled within the Bass Basin, but the presence of these has historically been poorly predicted; of the first 11 exploration wells to penetrate igneous rocks, their presence was not predicted in pre-drill interpretations. We present a series of case studies from wells that unexpectedly encountered igneous rocks. The first of these wells (Bass-1) targeted a carbonate reef structure which instead penetrated the flank of a submarine volcano. In another notable example (Flinders-1 well), a relatively discontinuous high-amplitude seismic reflection thought to be a clastic reservoir was found to be an igneous intrusion with a relatively unusual composition. A number of these incidents, where igneous rocks were unexpectedly encountered, can be accounted for by human factors, such as a sparsity of good quality data and a lack of knowledge transfer as companies entered and left basin during different phases of exploration. However, a number of examples, particularly the unexpected occurrence of igneous intrusions, appear to have been caused by anomalously low acoustic impedance contrasts between igneous rocks and surrounding sedimentary sequences. Our findings have generic implications for other sedimentary basins impacted by magmatic activity, such as the importance of integrating available outcrop data in the absence of nearby well control, and the value of fully appraising previous exploration results. Highlights • The Bass Basin is a Mesozoic-Cenozoic intra-continental rift basin along southern Australian. • Igneous rocks encountered in 20 out of 36 (55.6%) exploration wells drilled within the Bass Basin. • In 13 of 20 exploration wells (65%) the igneous rocks encountered were not predicted pre-drill. • Low impedance contrast between igneous and sedimentary rocks in Bass Basin relative to other magmatic basins (e.g. North Atlantic Margin). [ABSTRACT FROM AUTHOR]

The Li-bearing claystone and carbonate are sedimentary rocks deposited in the lacustrine environment hosting the Bigadiç borate deposits in western Anatolia. The purpose of this paper is to explain the mineralogical, geochemical, stable isotope characterizations and formation of Li-rich claystone (hectorite, saponite), and have strategic, technological, and economic importance for the country's economy, which have not been sufficiently studied previously. In the rhyolitic and dacitic tuffs, sanidine and plagioclase crystals were altered, biotite and hornblende, Fe-oxidized, locally opaque, and chloritized in a sericitized, Fe-oxidized, argillized, calcified, and zeolitized glassy matrix. The claystone consists mainly of smectite and minor illite, volcanogenic quartz, feldspar, mica, hornblende, and occasionally calcite, aragonite, dolomite, and gypsum/anhydrite. Hectorite and saponite were determined based on the expansion of their basal peaks following heating at 500 °C and solvation with ethylen-glycol; additionally, hectorite expanded, and saponite was not affected after glycerine-saturated Cs-smectite and heating at 100 °C for 20 h. Smectite shows webby to crenulated forms, and coexist with feldspar, volcanic glass, rhomboidal calcite, blocky gypsum/anhydrite, and Fe-oxide phases. The Li values increase up to 2650 ppm in the smectite-rich claystone and marl, and up to 449 ppm in the volcanic rocks. The positive correlation of REE with each of SiO 2 , Al 2 O 3 , and K 2 O; positive correlation of MgO vs. Li, and increase of MgO + CaO, Sr, Li, LREE relative to MREE and HREE; negative Eu anomaly and high values of As and S suggest that the feldspar, mica, and hornblende alteration originating from the Miocene volcanic and pyroclastic materials and presence of gypsum/anhydrite during the hydrothermal alteration activities were the sources for the smectite formation. The high negative δ18O values of calcite, the δD and δ18O values of smectite and δ34S‰ and δ18O‰ values of gypsum, and the 87Sr/86Sr isotope ratios range of calcite and gypsum suggest the contribution of mixing meteoric and hydrothermal environmental conditions during the depositional and diagenetic process(es) in the playa lake environment. [Display omitted] • Investigates sedimentary and depositional characteristics of the Neogene Bigadiç deposits. • Examines the alteration of volcanic components and their relationship with authigenic clay formation. • Determines the formation of Li-rich authigenic clays during diagenesis and hydrothermal activities. • Emphasis importance of Li-rich deposits as industrial raw materials for technology applications. [ABSTRACT FROM AUTHOR]

Keywords: Marion Island; Clinopyroxene megacrysts; Volcanics; Geographical location EN Marion Island Clinopyroxene megacrysts Volcanics Geographical location 357 359 3 07/15/20 20200801 NES 200801 Roberts et al. ([9]) document clinopyroxene megacrysts from Marion Island, Antarctic Ocean to present evidence for a late stage shallow origin. This paper makes a valuable contribution in terms of the geochemical characteristics of the clinopyroxene megacrysts and the magmatic evolution of scoria cones on Marion Island. The Marion and Prince Edward Islands are young islands that represent the peaks of Hawaiian type shield volcanoes which has been associated with a mantle plume (McDougall et al. [7]). [Extracted from the article]

Abstract A paucity of displacement markers can make constraining the kinematics and interaction of regional-scale strike-slip faults difficult. In this study, a high-resolution aeromagnetic survey allows quantitative analysis of kilometre-scale Paleogene faulting in the north of Ireland. Mapping offset dykes and igneous centres reveals the presence of two orientations of Cenozoic strike-slip faults attributed to broadly N-S Alpine shortening arising from the convergence of Africa and Europe. Reactivated NE-SW striking faults accommodated up to 2.3 km of sinistral displacement mainly during the Paleocene. Following tectonic quiescence, up to 2.5 km of Oligocene-aged dextral movement was accommodated on newly-formed NNW-SSE striking faults. Displacement analysis suggests that the faults were kinematically linked and experienced a switch in polarity of the predominantly active fault orientation during the Paleogene, forming an apparent conjugate system with asymmetric displacement distributions. The switch in fault polarity is attributed to a rotation in the regional maximum horizontal stress orientation and the locus of deformation moving from pre-existing reactivated structures to newly formed faults. The analysis also illustrates that, despite low strain rates, the interaction of the principal components of the fault system controlled the formation of sedimentary basins and defined the present-day geography of the region, far from an active plate boundary. Highlights • Kilometre-scale displacement on regional Cenozoic strike-slip faults in Ireland have been analysed. • Locus of faulting shifted from sinistral to dextral structures during the Paleocene. • Faults controlled the distribution of Oligocene sediments in the north of Ireland. • Formation of an apparent conjugate system with asymmetric displacement distributions is attributed to S Hmax rotation. • Faults developed in an intraplate setting under the effects of far-field Alpine collision. [ABSTRACT FROM AUTHOR]

Abstract: Many previous studies on lacustrine basins in the East African Rift System have directed their attention to climatic controls on contemporary sedimentation or climate change as part of palaeoenvironmental reconstruction. In contrast, this research focuses on the impact of tectonism and volcanism on rift deposition and develops models that help to explain their roles and relative importance. The study focuses on the spatial and temporal variability in bulk sediment geochemistry from a diverse range of modern and ancient rift sediments through an analysis of 519 samples and 50 major and trace elements. The basins examined variously include, or have contained, wetlands and/or shallow to deep, fresh to hypersaline lakes. Substantial spatial variability is documented for Holocene to modern deposits in lakes Turkana, Baringo, Bogoria, Magadi and Malawi. Mio‐Pleistocene sediments in the Central Kenya Rift and Quaternary deposits of the southern Kenya Rift illustrate temporal variability. Tectonic and volcanic controls on geochemical variability are explained in terms of: (i) primary controlling factors (faulting, subsidence, uplift, volcanism, magma evolution and antecedent lithologies and landscapes); (ii) secondary controls (bedrock types, rift shoulder and axis elevations, accommodation space, meteoric and hydrothermal fluids and mantle CO2); and (iii) response factors (catchment area size, orographic rains, rain shadows, vegetation densities, erosion and weathering rates, and spring/runoff ratios). The models developed have, in turn, important implications for palaeoenvironmental interpretation in other depositional basins. [ABSTRACT FROM AUTHOR]

The ability of Kula volcanics (the youngest volcanic rocks of western Anatolia) to remove Pb(II) and Cu(II) from aqueous solutions has been demonstrated, for the first time, in this study. The optimum parameters viz., pH, contact time and sorbent amount/solution volume ratio were evaluated using batch experiments. Langmuir isotherm model excellently described the sorption process and both of the ions followed pseudo-second-order kinetics. The method was applied to the natural river water samples and it was observed that the sorbent can successfully be used for the removal Pb(II) and Cu(II) ions with acceptable accuracy and precision. [ABSTRACT FROM PUBLISHER]

In the southwestern part of the Korean Peninsula, Cretaceous volcanic rocks occur along a NE–SW-trending, sinistral strike-slip fault (Hamyeol Fault). Based on their spatial distribution, the volcanic rocks are classified into three lithostratigraphic units: the Buan, the Seonunsan, and the Beopseongpo Volcanics. These volcanics are composed of various types of pyroclastic, sedimentary, and lavas/intrusive rocks. SHRIMP U Pb ages of zircon crystals were isolated from each unit. For the Buan Volcanics, Cheonmasan Tuff = 87.23 ± 0.92 Ma; Udongje Tuff = 86.79 ± 0.71 Ma; Seokpo Tuff = 87.30 ± 0.99 Ma; and Yujeongje Tuff = 86.66 ± 0.93 Ma. For the Seonunsan Volcanics, Gyeongsusan Tuff = 84.9 ± 1.1 Ma and Yeongije Tuff = 86.61 ± 0.67 Ma. For the Beopseongpo Volcanics, Seongsan Tuff = 87.73 ± 0.89 Ma and Gyema Rhyolite = 86.2 ± 1.7 Ma. The ages correspond well to recent mapping results of volcanic rocks in the southwest and south parts of the Korean Peninsula. In addition, the age data are comparable to those of the Aioi and Arima volcanic rock groups in southwestern Japan. This suggests that regional volcanic activity in the Japanese Islands and the southwestern part of the Korean Peninsula is related, and results from magmatism together with crustal deformation due to slab rollback of the Izanagi Oceanic Plate underneath the Eurasian Plate. [ABSTRACT FROM AUTHOR]

A paleomagnetic study performed in Plio-Pleistocene volcanic rocks of two localities in the Southern Central Andes is presented. The region corresponds to the transition zone between the Central and the Patagonian Andes. In the latter, deformation is almost exclusively controlled by the dextral-strike slip Liquiñe-Ofqui Fault Zone, that extends from ∼47 °S to ∼38 °S and accommodates the deformation generated by the oblique subduction of the Nazca Plate below South America. To the north of ∼36 °S, deformation is mainly contractional. Our study was carried out in the transition zone between both tectonic regimes. Sampling consisted of 31 paleomagnetic sites distributed in two localities: the Loncopué (∼38.0 °S, 70.7 °W) and Andacollo (∼37.2 °S, 70.8 °W) areas. We sampled Pliocene and Pleistocene volcanic rocks with ages younger than 5 Ma. After stepwise demagnetization and principal component analysis, site mean remanence directions were computed. Both localities show non-significant clockwise rotations of 1.7° ± 14.4° (Loncopué) and 8.1° ± 8.4° (Andacollo). Although the presently available database does not support significant tectonic rotation of the Andacollo lavas, preliminary results obtained from upper Miocene volcanics in a nearby area indicating ∼20° of clockwise rotation, encourage further studies to improve the resolution of the paleomagnetic data to determine if crustal block rotations have been, or still are, part of the Andean deformational processes. A revision of previously published paleomagnetic data in the northern Patagonian Andes suggests that, against original claims, no significant tectonic rotations associated to the Liquiñe-Ofqui Fault Zone, between ∼39 and 37.5 °S, can be unambiguously demonstrated. • Paleomagnetic study carried out on Plio-Pleistocene lavas in Southern Central Andes. • Test of tectonic rotations performed in the Antiñir-Copahue Fault Zone (ACFZ). • Data from northern ACFZ compatible with small clockwise rotations but yet uncertain. • Paleomagnetic data in northern Liquiñe-Ofqui Fault Zone reassessed. • No significant tectonic rotations can be unambiguously demonstrated there. [ABSTRACT FROM AUTHOR]

The Suursaari volcanic sequence represents volcanic activity related to Wiborg Batholith rapakivi intrusions in the southern part of the Fennoscandian Shield. The estimated pressure conditions for batholith granitic rocks are 1–5 kbar and crystallization temperatures range from 670 to 890 °C. To describe the temperature regime of the Suursaari volcanic system, a rock sample was taken from the Mäkiinpäällys Mountain outcrop and analysed with laser ablation inductively coupled plasma mass spectrometry. Sample spots were selected from quartz phenocrysts and groundmass. Quartz crystallization temperatures were calculated by the Ti-in-quartz method that takes into account rutile equilibrium and Ti activity in each phase. The calculated crystallization temperatures of the Suursaari quartz porphyry are in the range of 647–738 °C. The results show that the Suursaari quartz porphyry contains two generations of quartz which can be distinguished on the basis of crystallization temperatures: phenocrysts crystallized at higher and groundmass quartz at lower temperature.

The granites El Mogote, Mata Oscura and Piñero outcrop in the El Baúl massif, next to metasedimentary, volcanic and   sub volcanic rocks, to the south of Cojedes state, Venezuela. El Mogote  Granite, is sintectonic respect to the Taconic orogenesis (Caledonian) and is the most representative of the massif. The lower Permiangranitoids are controlled by the Apalachian event (Hercinian or equivalent) and are post-orogeny to this event. El Mogote Granite was emplaced at shallow crustal and represents a magmatic event-granite of the Early Paleozoic. The Mata Oscura and Piñero granites, were emplaced in middle and higher crustal levels, respectively, together with the Volcanic of Guacamayas. The aplitic dykes of this last event cut metasedimentary   units and granite. El Mogote Granite is characterized by presenting porphydic seudo rapakivi texture with alkalifeldspar.The Mata Oscura Granite are of medium to coarse grain and The Piñero Granite have fine grain and present myrmekite, micrographic, symplectite, grano phydicandperthite textures. The diferente textures and mineralogical compositions described in this work have provided novel geological subunits contributing new petrological information on the evolution of El Baúl massif. Â

Although the Permian-Triassic Semanggol Formation is widely distributed in northwestern Peninsula Malaysia and is made of various lithofacies, its sedimentology and possible relation with the Permian-Triassic boundary (PTB) were not considered before. In this study, detailed facies analysis was conducted for two sections of the Semanggol Formation at the Bukit Kukus and Baling areas, South Kedah to clarify its sedimentology and relation to the PTB. Four facies from the Permian part of the Semanggol Formation that were identified at the Bukit Kukus section include laminated black mudstone, interbedded mudstone and sandstone, volcanogenic sediments, and bedded chert. In Baling area, the Triassic part of the formation is classified into three members. The lower member comprises of claystone and bedded chert facies, while the middle member is composed of sandstone and claystone interbeds (rhythmite). On the other hand, the upper member is grouped into two main units. The lower unit is mainly claystone and includes two facies: the varve-like laminated silt and clay and massive black claystone. The upper unit is composed of various sandstone lithofacies ranging from hummocky cross stratified (HCS) sandstone to thinly laminated sandstone to burrowed sandstone facies. The HCS sandstones occur as two units of fine-grained poorly sorted sandstone with clay lenses as flaser structure and are separated by a hard iron crust. They also show coarse grains of lag deposits at their bases. The laminated black mudstone at the lowermost part of the Semanggol Formation represents a reducing and quite conditions, which is most probably below the fairweather wave base in offshore environment that changed upwards into a fining upward sequence of tide environment. Abundance of chert beds in the volcanogenic sediments suggests the deposition of tuffs and volcanic ashes in deep marine setting which continues to form the Permian pelagic bedded chert and claystone. The bedded chert in the lower member of the Triassic section suggests its formation in deep marine conditions. The rhythmic sandstone and claystone interbeds of the middle member are suggestive for its formation as a distal fan of a turbidite sequence. Lithology and primary sedimentary structure of the upper member suggest its deposition in environments range from deep marine represented by the varve-like laminated silt and clay to subtidal environment corresponds to the massive black claystone to coastal environment represented by the hummocky sandstone units and reaches the maximum regression at the hiatus surface. Another cycle of transgression can be indicated from the second hummocky unit with transgressive lag deposits that develops to relatively deeper conditions as indicated from the formation of relatively thick laminated sandstone and bioturbated massive sandstone facies that represent tidal and subtidal environment, respectively. Late Permian lithological variation from the radiolarian chert into early Triassic claystone probably resulted from a decrease in productivity of radiolarians and might represent a PTB in the Semanggol Formation. Volcanogenic sediments in the studied section can be used as an evidence for volcanic activities at the end of the Permian, which is probably connected to the nearby volcanic ash layers in the eastern China, the ultimate cause of the PTB in this area. Black mudstone in the Permian part of the studied section may be interrelated to the Latest Permian Anoxia that started to build in the deep ocean well before the event on shallow shelves. [ABSTRACT FROM AUTHOR]

New field observations on granitoids and associated lithounits in some parts of Indus-Shyok Suture Zones have been documented in order to re-establish the geological relationships between various volcano-plutonic magmatic lithounits. Careful examination of outcrops and contact relationships between the various lithounits have pin-pointed the sequence of geological events. Field features of granitoids exposed along Leh-Saboo-Khardung_La suggest multiple pulses of mafic-felsic magma interactions (mingling to mixing) with almost 25% of the mafic to hybrid magma input in the evolution of the eastern part of Ladakh batholith. Along Khardung_La-Shyok-Diskit, thick sequence of volcanic lithounits is exposed, which dominantly consist of massive basaltic andesite, porphyritic andesite, dacite and rhyolite forming Khardung Formation. On the other hand Shyok Formation, dipping opposite to the Khardung Formation, composed predominantly of meta-sedimentary lithounits and subordinate amount of volcanic materials at present exposed level. Spectacular intrusive contacts of Ladakh granitoids with metavolcanics and meta-sedimentary country rocks of Shyok Formation near Diskit can be observed, which are manifested by ubiquitous xenoliths near the marginal parts. Although the nature of granitoid melt invasion into country-rocks was relatively winty, granitoid melt has produced leucogranite-pegmatite system because of devolatization and decompression effects. Frequent xenoliths of porphyritic andesite and dacite roof pendants are being reported in Tirit granitoids, which strongly suggest sub-volcanic emplacement of granitoid melt, extensive assimilation and roof collapse of overlying volcanic materials. It is more likely that the xenoliths hosted in Tirit granitoids belong to Shyok volcanics. It is suggested that multiple pulses of coeval mafic and felsic magmatism occurred extensively and emplaced at differential crustal levels. [ABSTRACT FROM AUTHOR]

Whether the voluminous Early Cretaceous magmatism in the Tengchong and Baoshan blocks, western Yunnan, China, was related to subduction of the Meso-Tethys or the Neo-Tethys is controversial. Here, we report SHRIMP and LA-ICP-MS U Pb zircon ages, bulk-rock major and trace elements, and Sr Nd isotope data from volcanic rocks in the Lameng area of the Baoshan block, SW China, investigate their genesis, and discuss the evolution of the Tengchong and Baoshan blocks. These rocks yield U Pb zircon ages of 120.3 ± 1.7 and 120.8 ± 1.4 Ma and constitute a bimodal volcanic suite (group 1 and group 2). Group 1 samples show alkaline basaltic signatures (SiO 2 = 46.2–53.1 wt.%), enrichments in Zr, Hf, Ti, and light rare earth elements, and slight depletions in Nb, Ta, and heavy rare earth elements. They have ε Nd (t) = −1.0–+3.7 and initial 87Sr/86Sr = 0.70503–0.70709. Group 2 samples display higher silica contents (SiO 2 = 61.7–65.0 wt.%) and evolved ε Nd (t) (−4.3 to −3.6) and initial 87Sr/86Sr (0.70653–0.70678) values. These features suggest that the group 1 melts were derived from an asthenospheric mantle source mixed with subcontinental lithospheric mantle components and that the group 2 samples were produced by partial melting of the lower crust in a continental back-arc setting. From an affinity with widespread coeval magmatic rocks in the Tengchong and Lhasa blocks, we suggest that the Bangong-Nujiang Ocean between the Tengchong and Baoshan blocks had closed by 120 Ma and that the Early Cretaceous magmatism in the Tengchong and Baoshan blocks formed in an arc–back-arc system associated with Neo-Tethyan slab rollback. • The first report on the Early Cretaceous bimodal volcanic rocks in the Baoshan block. • The Tengchong and Baoshan blocks constituted an arc–back-arc system at ca. 120 Ma. • The Bangong-Nujiang Ocean had closed in the Early Cretaceous. [ABSTRACT FROM AUTHOR]

The tectonics of the Chenoua massif suggests block rotations of Neogene nappes associated with the African-European plate convergence. To estimate the extent of these rotations, a Paleomagnetic study on rhyolites and andesites of Langhian-Serravallian age and sandstones of Burdigalian age was carried out on 23 sites (200 specimens). The sites are distributed in the northwestern, southeastern and southern Chenoua massif. One or two components of magnetization, mainly carried by magnetite, pyrrhotite and/or hematite, were isolated in sandstones and volcanics. The sandstone sites reveal magnetizations in sandstones from the Cap Blanc syncline that are post-folding. However, both polarities are found, which is consistent with data from Africa during the Upper Miocene. Clockwise and counterclockwise rotations were recorded, dating back to the Neogene times in volcanics and sediments. From the faulted Cap Blanc syncline counterclockwise rotations of 1 ± 4° to 18 ± 28° around a vertical axis occurred in sediments since the Miocene with respect to Africa. In fact, remagnetizations occurred at several periods of time and in different sites, providing information on the evolution of post-tectonic rotations. Some volcanics record counterclockwise rotations of about 30° since the Miocene, whereas others do not show any significant rotation. This can be explained by the direction of the principal compressive stress axis σ and by lateral extrusions related to an indentation model, in which we expect both clockwise and counterclockwise rotations. [ABSTRACT FROM AUTHOR]

The current kinematic patterns of northeast Greece remain largely unknown. This is mainly because this region is characterised by low seismicity rates and is poorly covered by GPS stations. Here, we analyse new homogeneous GPS data collected over a period of 5.5 years from the first permanent network in northeast Greece (HEPOS) to shed light in the kinematics of this region. We find that GPS displacement vectors that derive from either side of the natural depression of the Strymon Valley differ significantly in orientation and magnitude. Specifically, we find that across a distance of ca. 30 km the GPS displacement vectors change orientation by > 130° (from NNW to SSW), producing a mean horizontal strain rate of 3.3 ± 0.3 mm/yr. We attribute this kinematic translation to result from movement along the Strymon Fault System (SFS), a > 200 km-long structure that strikes NW-SE and extends from SW Bulgaria to North Aegean (where possibly abuts against the North Anatolian Fault). Up to date, the SFS was considered to be a major Alpine and Neogene geotectonic boundary of unclear Holocene activity. If the interseismic strain stored currently across the fault system is released seismically, large earthquakes (M > 7) and associated coseismic lateral displacements should be expected in the area. These results call for a better assessment of the earthquake risk in northeast Greece, which is currently evaluated as a low seismic hazard region. [ABSTRACT FROM AUTHOR]

Classic low-albedo regions of the martian surface are investigated using combined reflectance and emission (“pan-spectral”) data to constrain the types of alteration mineral phases that are present at spectrally significant abundances (>10–15%). The lack of hydrated mineral species observed using near-infrared data suggests that anhydrous chemical alteration dominates at the regional scale. Spectral characteristics in the VNIR and TIR are consistent with those associated with weathering processes identified in the hyper-arid, hypo-thermal, and geologically stable McMurdo Dry Valleys of Antarctica, where oxidative weathering processes dominate and significant aqueous alteration does not occur. In addition, the spectral trends associated with oxidative weathering processes are similar to regional trends in VNIR spectral characteristics observed on Mars and potentially complicate the spectral interpretation of basaltic terrains. Collectively, these relationships suggest that the martian surface has been dominated by cold, dry, and stable conditions since the formation of these low-albedo regions. While significant at regional scales early in martian history, aqueous alteration appears to be predominantly absent from large-scale basaltic regions on Mars. [ABSTRACT FROM AUTHOR]

Krauklis waves are a special wave mode that is bound to and propagates along fluid-filled fractures. They can repeatedly propagate back and forth along a fracture and eventually fall into resonance emitting a seismic signal with a dominant characteristic frequency. They are of great interest because this resonant behavior can lead to strongly frequency-dependent propagation effects for seismic body waves and may explain seismic tremor generation in volcanic areas or affect microseismic signals in fractured fluid reservoirs. It has been demonstrated that Krauklis waves can be initiated by a seismic source inside the fracture, for example by hydrofracturing. Here, the aim is to study Krauklis wave initiation by an incident plane P- or S-wave in numerical simulations. Both seismic body waves are reflected and scattered at the fracture, but also, two Krauklis waves are initiated with significant amplitude, one at each fracture tip (i.e., at the diffraction-points of the fracture). Generally, the incident S-wave initiates larger-amplitude Krauklis waves compared to the incident P-wave case. For both incident wave modes, the initiation of Krauklis waves strongly depends on the fracture orientation. In the case of an incident P-wave, large-amplitude Krauklis waves are initiated at moderate (12°-40°) and high (>65°) inclination angles of the fracture with a distinct gap at approximately 50°. The dependency of Krauklis wave initiation on fracture orientation is almost inversed in the case of an incident S-wave and the largest-amplitude Krauklis waves are initiated at an S-wave incidence angle of approximately 50°. The initiation of large-amplitude Krauklis waves by both P- and S-waves has important implications for earthquake signals propagating through fluid-bearing fractured rocks (volcanic areas, fluid-reservoirs) or for seismic exploration surveys in fractured reservoir situations. [ABSTRACT FROM AUTHOR]