Large Depletion Research Articles

Cyclin-dependent kinase inhibitor 1 plays a more prominent role than activating transcription factor 4 or the p53 tumour suppressor in thapsigargin-induced G1 arrest.

Thapsigargin (Tg) is a compound that inhibits the SERCA calcium transporter leading to decreased endoplasmic reticulum (ER) Ca2+ levels. Many ER chaperones are required for proper folding of membrane-associated and secreted proteins, and they are Ca2+ dependent. Therefore, Tg leads to the accumulation of misfolded proteins in the ER, activating the unfolded protein response (UPR) to help restore homeostasis. Tg reportedly induces cell cycle arrest and apoptosis in many cell types but how these changes are linked to the UPR remains unclear. The activating transcription factor 4 (ATF4) plays a key role in regulating ER stress-induced gene expression so we sought to determine if ATF4 is required for Tg-induced cell cycle arrest and apoptosis using ATF4-deficient cells. Two-parameter flow cytometric analysis of DNA replication and DNA content was used to assess the effects of Tg on cell cycle distribution in isogenic HCT116-derived cell lines either expressing or lacking ATF4. For comparison, we similarly assessed the Tg response in isogenic cell lines deleted of the p53 tumour suppressor and the p53-regulated p21WAF1 cyclin-dependent kinase inhibitor important in G1 and G2 arrests induced by DNA damage. Tg led to a large depletion of the S phase population with a prominent increase in the proportion of HCT116 cells in the G1 phase of the cell cycle. Importantly, this effect was largely independent of ATF4. We found that loss of p21WAF1 but not p53 permitted Tg treated cells to enter S phase and synthesize DNA. Therefore, p21WAF1plays an important role in these Tg-induced cell cycle alterations while ATF4 and p53 do not. Remarkably, the ATF4-, p53-and p21WAF1-deficient cell lines were all more sensitive to Tg-induced apoptosis. Taken together, p21WAF1 plays a larger role in regulating Tg-induced G1 and G2 arrests than ATF4 or p53 but these proteins similarly contribute to protection from Tg-induced apoptosis. This work highlights the complex network of stress responses that are activated in response to ER stress.

Giant ionospheric density hole near the 2022 Hunga-Tonga volcanic eruption: multi-point satellite observations

A giant ionospheric hole was simultaneously detected in the in situ measurements of FORMOSAT-7/COSMIC-2 (F7/C2), Ionospheric Connection Explorer (ICON), Swarm missions, and ground-based total electron content (TEC) by global navigation satellite system receivers, and F7/C2 Global Ionosphere Specification (GIS) data near Tonga, following the explosive volcano eruption on 15 January 2022. The TEC maps displayed the huge depletions that developed near Tonga after the eruption and gradually evolved. The ICON IVM, F7/C2 IVM and Swarm-LP detected large depletions not only near Tonga, but also in the EIA trough region. The GIS observations clearly show the ionospheric hole that extends spatially near Tonga, especially strongly south/southward. The simultaneous observations showed that the ionosphere hole near Tonga combined with the EIA trough and finally evolved into a giant ionosphere hole around 07 UT. The ionospheric hole, which occurred at 05 UT near Tonga, extended over a wide area of 160°-200°E and 25°S-20°N and lasted for about 11 h. The F7/C2 and ICON satellites overpasses showed large ion density depletions by the hole at orbit altitudes, accompanied by enhancements in ion temperature and field-aligned and perpendicular ion drift. Such a long-lasting giant ionospheric hole by a seismic event has not been reported earlier, creating a unique ionospheric environment near Tonga after the eruption. The strong successive impulses by multiple volcano eruptions, together with O/N2 decrease in the summer hemisphere, interhemispheric wind, and water vapor injection into high altitudes apparently yielded such a giant ionospheric hole, 4–6 times larger than that observed during the Tohoku earthquake.Graphical

The Paleocene high-silica granites and their associated diorite enclaves in central Lhasa subterrane, Xizang, China: Insights to crust-mantle mixing and crustal reworking

The history of crustal growth in the western Central Lhasa (CL) subterranean during India-Eurasian collision remains unclear. The crucial problem is lack of suitable and ideal magmatism recorded information of the early stages of continental collision. Here, we report the newly discovered high-silica granites (K-feldspar granite with aplite granite) hosting diorite enclaves from the Geji area in western CL subterrane. This suite of magmatic rocks is of great significance to reveal the crustal growth of CL during the India-Eurasia collision. Zircon U-Pb dating results show that the K-feldspar granite, aplite granite, and diorite enclaves were formed at 57.2–57.9 Ma, 58.7 Ma and 58.2 Ma, respectively. Petrology, mineralogy, and mineral chemistry of the plagioclase from the diorite enclave indicates that it was generated by magma mixing between mafic and felsic magmas. The mafic melt was sourced from partial melting of mantle wedge and metasomatized by subduction fluid and sediment melt. This has been supported by the positive zircon εHf(t) values (+0.6 to + 4.9), enrichment of large ion lithophile elements (Rb, K, Th, and U) and depletion of high field strength elements (Nb and Ta), and the high Th/Ce ratios of diorite enclaves. The K-feldspar granite also has positive zircon εHf(t) values (+1.3 to +6.2), arc magma geochemical features, and a lower crust Nb/Ta ratio (8.3). These indicate that the K-feldspar granite was originated from the juvenile lower crust. In conclusion, we think that the crust-mantle magma mixing has a substantial impact on the crustal growth of the western CL subterrane during the subduction slab roll-back of the Paleocene Neo-Tethys Ocean when paired with other research and the context of regional tectonic development.

U-Pb Geochronology, Geochemistry and Geological Significance of the Yongfeng Composite Granitic Pluton in Southern Jiangxi Province

The Yongfeng composite granitic pluton, located in the southern section of the Nanling area, is composed of the Yongfeng and Longshi biotite monzonitic granites. In order to reveal the genesis of this composite granitic pluton and its relationship with mineralization, this study conducted zircon U-Pb dating, whole-rock major and trace element analysis, and biotite electron probe analysis. The results show that the Yongfeng composite granitic pluton is rich in silicon and alkali, weakly peraluminous, and poor in calcium and iron. It shows the enrichment of light rare earth elements and a significant fractionation of light and heavy rare earth elements. It also shows the enrichment of large ion lithophile elements and depletion of Ba, K, P, Eu, and Ti relative to the primitive mantle. The contents of TFe2O3, MgO, CaO, TiO2, and P2O5 are low and decrease with increasing SiO2 content. The Yongfeng composite granitic pluton does not contain alkaline dark minerals. Its average zircon saturation temperature is 776 °C, average TFe2O3/MgO is 4.81, and average Zr + Nb + Ce + Y is 280.6 ppm, which correspond to a highly fractionated I-type granite. The Yongfeng and Longshi granites were respectively formed at 152.0 ± 1.0 Ma–151.3 ± 1.1 Ma and 148.9 ± 1.2 Ma. They were formed in the extensional tectonic setting during the post-orogenic stage, under the control of the breakup or retreat of the backplate after the subduction of the Pacific Plate into the Nanling hinterland. The magmatic system of the Yongfeng composite granitic pluton is characterized by high fractionation, high content of F, high temperature, and low oxygen fugacity, which is conducive to mineralization of Sn, Mo, and fluorite.

A 1D Model for Nucleation of Ice From Aerosol Particles: An Application to a Mixed‐Phase Arctic Stratus Cloud Layer

AbstractMixed‐phase clouds (MPCs) have been identified as significant contributors to uncertainties in climate projections, attributable to model representation of processes controlling the formation and loss of supercooled water droplets and ice particles from the atmosphere. Arctic MPCs are commonly widespread and long‐lived, with sustained ice crystal formation processes that challenge current understanding. This study examines the ice‐nucleating particle (INP) reservoir dynamics governing immersion‐mode heterogeneous freezing in an observed case of Arctic MPCs using a simplified 1D aerosol‐cloud model. The model setup includes prescribed dynamical forcings and thermodynamic profiles, and represents INPs as multicomponent and polydisperse particle size distributions. Diagnostic and prognostic approaches to immersion freezing parameterization are compared, including time‐independent (singular) number‐ and surface area‐based descriptions and a time‐dependent description following classical nucleation theory (CNT). The choice of freezing parameterization defines the size of the INP reservoir. The CNT‐based description yields an orders of magnitude larger INP reservoir than the singular parameterizations, which is the dominant factor for sustained ice crystal formation. The efficiency of the freezing process and cloud cooling are of secondary importance. A diagnostic treatment neglecting INP loss is only accurate when the INP reservoir size is large and INP depletion weak. Since a larger INP reservoir sustains ice crystal formation substantially longer, and ice water path scales with ice crystal concentrations for the conditions considered, resolving the source of differences in INP reservoir dynamics due to model implementation is a high priority for advancing climate model physics.

Zircon U–Pb–Hf and whole‐rock Sr–Nd isotopic insights on the Silurian syenite–monzonite shoshonitic magmatism of Central Iran

The Palaeozoic magmatic history of Central Iran is related to the subduction of the Proto‐Tethys Ocean and the amalgamation of Gondwana continental fragments. This study presents whole‐rock geochemistry, Sr–Nd isotope and zircon U–Pb–Hf ages of shoshonitic plutonic rocks (e.g., monzonite–syenite) from the north Posht‐e‐Badam (NPB) district with a view to constrain their petrogenetic and tectono‐magmatic evolution during the Palaeozoic. The geochemical data show moderate enrichment in large‐ion lithophile elements and Ti, large positive Pb anomalies, and depletion or moderate enrichment in high‐field‐strength elements (e.g., Nb and Ta), typical of continental arcs. Zircon LA–ICP–MS U–Pb ages are in the range of 444–428 Ma. The Sr–Nd–Hf isotope data, for example, (87Sr/86Sr)i = 0.7073 to 0.7089, εNd(t) = −1.4 to −0.2, and εHf(t) = −3.6 to +7.7, indicate derivation of the magma from a mantle source. The numerical modelling shows a contribution of less than 10% crustal assimilation and ~3% sediment into the melt‐derived mantle. We propose that metasomatic enrichment occurred during the subduction of Proto‐Tethyan Ocean between the Iranian microcontinents, leading to the formation of a shoshonitic melt. We infer that the recorded ages coincide with a continental rift episode followed by a rear arc tectonic region that spread along the northern active margin of Gondwana. Further, the change in magma affinity from calc‐alkaline (~474–512 Ma) to shoshonitic (444–428 Ma) in Central Iran is probably related to the gradual steepening of the slab dip angle and trench‐ward migration of the front arc into the region above metasomatically enriched rear arc mantle.

Petrogenesis and tectonic implications of the Late Cretaceous to Paleogene calc-alkaline volcanic rocks, Ladakh Himalaya

One of the most widespread volcanic suites exposed in the northwest Himalaya is the Khardung volcanic suite sandwiched between the Ladakh Batholith in the south and the Karakoram Batholith in the north. These volcanic rocks show a transition from andesite, dacite to more evolved rhyolite and have a calc-alkaline affinity. They display large ion lithophile elements (Rb, Sr, Ba, U, Pb) enrichment and depletion of high field strength elements (Nb, Ta, Hf, Ti) with increasing Eu negative anomaly from andesite to rhyolite. Bulk-rock Liquid Line of Descent (LLD) modelling shows that fractional crystallization played a dominant role in their petrogenesis. The calculated zircon saturation temperature (TZr) in andesitic magma (745 °C) is higher than the dacitic and rhyolitic magmas (682 °C). Andesites have zircon ages of 69–68 Ma, whereas more evolved dacite and rhyolite yield younger ages (59–64 Ma) that are consistent with their generation in the last stage of magmatism in an active continental marginal setting. Geochemical and geochronological findings of this study demonstrate that Khardung volcanic rocks were derived through two major magmatic events. These events occurred during the Late Cretaceous to the Paleocene Epoch due to the subduction of the Neo-Tethyan oceanic slab underneath the Eurasian plate boundary before the main collision between India and Eurasia.

Geochemical characteristics of arc fractionated I-type granitoids of eastern Tak Batholith, Thailand

Abstract The Tak Batholith is located in the western part of Thailand’s eastern granitoid belt. To better understand the geochemical characteristics of granitoid and identify their occurrence, rock samples collected from the eastern part of the Tak Batholith were used for petrographical, mineralogical, and geochemical analyses. According to field investigation and lithology, petrography classifies these granitic rocks as medium-grained granodiorite and granodioritic dike. The granodiorites are composed chiefly of plagioclase, orthoclase, quartz, hornblende, and biotite, with tiny amounts of zircon, apatite, and opaque minerals. Meanwhile, the granitic dike shows a highly porphyritic texture, presenting mostly plagioclase phenocrysts, with a small amount of orthoclase and unidentified mafic phenocrysts sitting in a fine-grained groundmass comprising K-feldspar and quartz with a small amount of plagioclase and present granophyric intergrowth. Geochemical data of the amphiboles classified them as Ferro-edenite symbolizing the I-type granite. Whole-rock geochemistry indicates that these rock suites are I-type metaluminous granodiorite, and diorite fractionated from the high K calc-alkaline magma melted from the mafic crust of arc magmatism agreeable with the enrichment of large ion lithophile elements and depletion of highfield-strength elements, and rare earth element patterns.

Development of a back-arc basin from initial rifting to seafloor spreading: Constraints from Paleozoic basic rocks in the North Qinling accretionary orogen, central China

The progression from initial back-arc rifting to back-arc opening in ancient orogenic collages is important for reconstructing subduction histories, constraining tectonic switching, and understanding crustal growth and evolution. However, it is difficult to constrain this transition in ancient arcs. The Qinling-Dabie orogenic belt is one of the most important orogenic belts in eastern Asia, yet the history of Paleozoic accretionary processes in this belt remains equivocal, owing to a poor understanding of back-arc opening processes in the Erlangping unit. In this study, we present whole-rock geochemical analyses of mafic dikes in the Erlangping unit, along with U-Pb ages and Hf-O isotope compositions of zircon from these dikes. Zircon secondary ion mass spectrometry (SIMS) dating of these mafic dikes yielded U-Pb ages of 453 ± 3 Ma. The mafic dikes are calc-alkaline and are characterized by high K2O contents (1.16−3.16 wt%). They have enriched ([La/Yb]N = 4.3−14.9) light rare earth elements (REEs) and relatively flat heavy REE ([Dy/Yb]N = 0.9−1.5) patterns, and they exhibit enrichment in large ion lithophile elements (LILEs) but depletion in high field strength elements (HFSEs), resembling arc-like magmatism. These mafic dikes are characterized by relatively enriched initial 87Sr/86Sr (0.7049−0.7059), chondritic to slightly radiogenic εNd(t) (−0.36 to 1.33), and radiogenic whole-rock and zircon εHf(t) (+7.2−7.6 and +7.5−7.8, respectively). The zircons have δ18O values (5.0‰ ± 0.1‰) similar to those of normal mantle zircon. Accordingly, we interpret that the mafic dikes were derived from an enriched lithospheric mantle source metasomatized by subducted Proto-Tethys (Shangdan) ocean material. In contrast, previously reported ca. 440 Ma gabbros from the Erlangping unit are tholeiitic and have lower incompatible trace-element concentrations with less enrichment in LILEs and less depletion in HFSEs than the mafic dikes presented here. Whole-rock Nd and zircon Hf isotopic compositions suggest that these Silurian gabbros were derived from partial melting of a more depleted mantle with the involvement of asthenosphere, and they have a close geochemical affinity with back-arc basin basalts. In addition, trace-element ratios and geochemical modeling suggest higher melting pressures for the mafic dikes than the gabbros. The geochemical differences show systematic variations from island-arc basalt into back-arc basin basalt types, which is consistent with the magma source evolution of the Mariana Trough. Thus, we interpret that the ca. 454 Ma mafic dikes were emplaced when the infant arc split, and they record initial back-arc rifting in the Erlangping unit, whereas the Silurian gabbros subsequently formed during the opening of the back-arc basin. Our study provides a paradigm for deciphering the evolution of back-arc basins through the study of spatiotemporal geological and geochemical variations of mafic intrusions in ancient accretionary orogens.

On the quiet-time occurrence rates, severity and origin of L-band ionospheric scintillations observed from low-to-mid latitude sites located in Puerto Rico

In December 2021 three Global Navigation Satellite System (GNSS) ionospheric scintillation and Total Electron Content (TEC) monitors were installed in Puerto Rico (∼24.5° N dip latitude). The installation is part of an effort to better understand the occurrence of ionospheric irregularities and scintillation at mid-latitudes. Puerto Rico (PR) is commonly referred to as being located at mid-latitudes or at the boundary between low and mid-latitudes. Previous reports already presented observations of ionospheric irregularities and scintillation detected from PR. These observations, however, were limited in number. Additionally, the reports related the observed scintillation and irregularities events with different types of mid-latitude ionospheric disturbances. Here we present results from the analyses of the first three months of observations, December 21st, 2021 to March 20th, 2022. The analyses focus on the occurrence rate, severity and origin of scintillation detected on the signals tracked by the PR monitors during geomagnetically quiet times. We show that, out of the 43 geomagnetically quiet nights, 34 (∼80%) showed the occurrence of L-band scintillation. The results also indicate the recurrent existence of severe scintillation (S4 ∼ 1.0) accompanied by large TEC depletions. The temporal evolution of the observed scintillation showed that scintillation-causing plasma irregularities first occurred near the magnetic equator and propagated towards PR (reaching up to ∼22o dip latitude). Simultaneous space-based observations of the ionospheric F-region peak electron densities made by the GOLD mission confirmed that the quiet-time scintillation observed by the monitors in PR was associated with equatorial plasma bubbles. GOLD observations also show enhanced background F-region densities at the location of the Ionospheric Pierce Points of the affected GNSS signals, indicating conditions that favor the occurrence of intense scintillation.

Characteristics of labile organic carbon fractions under different types of subsidence waterlogging areas in a coal mining area: A case study in Xinglongzhuang Coal Mine, China

The restoration of subsidence waterlogging areas has the potential to facilitate carbon accumulation in coal mining areas with high ground water tables. However, the soil organic carbon (SOC) and labile organic carbon (LOC) have not been sufficiently investigated in different types of subsidence waterlogging areas. In this study, SOC and LOC fractions, including light fraction organic carbon (LFOC), particulate organic carbon (POC), and dissolved organic carbon (DOC) within 0–50 cm soil profiles, were determined in a reference cropland (RC) and three types of subsidence waterlogging area in Xinglongzhuang Coal Mine, Shandong Province, China, including an aquaculture waterlogging area (AWA), deep waterlogging area (DWA) and shallow waterlogging area (SWA) with water depths of 1.8, 3.2, and 0.65 m, respectively. Compared with RC, SOC and LOC decreased by 4.13%, 25.03%, and 77.91% in SWA, DWA, and AWA, respectively. The largest depletion was in the 0–10 cm layer, indicating that there was a time lag for the recovery of the total functional pools of SOC after subsidence. The lability of POC was highest among the three types of LOC fractions, indicating that mining subsidence triggered soil redistribution and impacted on carbon accumulation. With comparatively little soil profile interference in DWA and SWA, the lability of LFOC and POC decreased with soil depth, while the DOC increased. There was a large discrepancy in AWA, with the lability of LOC fractions fluctuating because of soil disturbance by intensive engineering. The LOC fractions were closely associated and correlated with soil properties, especially total nitrogen (TN) and total phosphorus (TP). Restoration and management of the subsidence waterlogging areas have a vital impact on the SOC pool. It was concluded that shallow water and a natural geomorphology-based topography, with little soil disturbance, well-developed vegetation communities, and continuous monitoring of soil and water properties would facilitate the carbon accumulation process.

Absence of low-δ18O magmas despite widespread assimilation of altered crust in a large magmatic and hydrothermal province

Magmas with low δ18O values, which require a contribution of isotopically light oxygen from hydrothermally altered rocks, are globally rare despite the common association of large-scale magmatism with intense hydrothermal activity. Here we consider this paradox in the central Taupō Volcanic Zone (TVZ, New Zealand), one of the most intense regions of Quaternary silicic magmatism and hydrothermal activity on Earth. We present new data on phenocryst δ18O values from 62 magma batches erupted since ∼1.6 Ma, ranging from basalt to rhyolite, and match these against existing and new Sr and Nd isotopic data. Basalt δ18Omelt values (typically ≥+6.3 to +6.5‰) calculated from phenocrysts are mostly high relative to mid-ocean ridge basalts (MORB), whereas basaltic andesites extend to +7.1‰. Rhyolite δ18Omelt values are mainly +7.0 to +8.5‰, which is considered high-δ18O in most settings. However, assimilation and fractional crystallisation (AFC) models show a mismatch between the amount of greywacke basement assimilation required to explain the Sr-Nd isotopic ratios and the δ18O values of many TVZ rhyolites. We attribute this mismatch to shallow assimilation of low-δ18O altered rocks after prior assimilation of unaltered greywacke at deeper levels. We infer that interactions between large silicic magmatic systems and shallow altered crustal rocks are common and widespread in the TVZ, despite the absence of silicic magmas with low δ18O values (<∼+6.0‰). This absence reflects the combined influence of high δ18O values inherited from the slab in parental basalts, and the limited isotopic leverage available in the TVZ to drive large 18O depletions via hydrothermal alteration. The TVZ example suggests that large-scale interactions between magmas and altered host rocks are likely to be important in many silicic magmatic provinces and not restricted to the sparse occurrences of low-δ18O magmas. Spatial clustering of the lowest TVZ rhyolite δ18Omelt values (+6.3 to +7.0‰) occurs along a western corridor of presently weak hydrothermal activity, implying that hydrothermal activity was more intense there in the past, and may have represented a focus of heat flow similar to the present-day eastern TVZ margin. Magma δ18O values can thus be useful for tracing areas of past alteration even in settings where conventionally normal to high δ18O values are retained in erupted products.

Isoelectronic aluminum-doped gallium nitride alpha-voltaic cell with efficiency exceeding 4.5%

Although alpha-voltaic cells have shown great potential in unattended miniaturized systems for compact, long-lifetime and independence of external energy input, the power conversion efficiency of state-of the-art alpha-voltaic cells is still much lower than the theoretical limit. Here, an alpha-voltaic cell based on a gallium nitride transducer with PIN structure is designed and investigated. We find that isoelectronic aluminum-doping is an effective way for boosting the performance of the gallium nitride transducer by decreasing the unintentional doping concentration, deep trap concentration, and dislocation density in the gallium nitride epilayer. The isoelectronic aluminum-doped cell demonstrates a large depletion region of 1.89 μm and a charge collection efficiency of 61.6% at 0 V bias, resulting in a high power conversion efficiency of 4.51%, comparable to the best gallium nitride beta-voltaic cells. This work increases alpha-voltaic cell efficiency, bridging the gap between nuclear micro-batteries and real applications in extreme environments.

An Early Paleozoic Ultramafic Complex in the North Wulan Metamorphic Complex, North Qaidam: Contraints on the Nature of the Alaskan‐type Continental Arc Root

AbstractOrogenic peridotite is an important component of orogenic belts and retains crucial information on mantle magmatic activity, slab subduction, and melt or fluid metasomatism. To determine the source of the mantle‐derived parental magma of the peridotite and to investigate the metasomatism that it experienced, we undertook an integrated study of the petrography, whole‐rock major‐ and trace‐element compositions, in situ zircon U–Pb geochronology, and mineral major‐ and trace‐element compositions of an early Paleozoic ultramafic complex in the North Wulan area of North Qaidam. The Halihatu ultramafic–mafic complex is composed of dunite, pyroxene peridotite, and gabbro, which are characteristic of Alaskan‐type complexes. The dunite yields a weighted mean 206Pb/238U age of 479 ± 5 Ma (MSWD = 0.7), which reflects the age of the metasomatism rather than the crystallization age of the ultramafic magma. The peridotites have high Mg# (89.8–91.8) and Cr contents (2419–5190 ppm), low Al2O3 (0.20–1.68 wt.%) and Ni (289–1012 ppm) contents, and high olivine Fo contents (87–91), suggesting a large degree (~15%–22%) of partial melting of lithospheric ultramafic rocks followed by variable degrees of fractional crystallization of olivine and pyroxene. This is consistent with estimates of 15%–22.3% partial melting calculated using the Cr# of spinel crystals and with the low Yb (0.04–0.33 ppm) and Y (0.72–1.29 ppm) contents of clinopyroxene crystals. Whole‐rock trace‐element patterns show enrichment in large ion lithophile elements and depletion in high field strength elements, along with high Al2O3 (2.10–6.47 wt.%) and low TiO2 (0.01–0.21 wt.%) contents of clinopyroxene crystals, suggesting an arc magma cumulate trend. These features, along with the high olivine Fo contents (87–91 ppm), imply that the Halihatu peridotite is an Alaskan‐type crustal cumulates derived from Mg‐rich hydrous basaltic melts. The high estimated fO2 (FMQ +1.97 to FMQ +3.81) further supports the idea that they formed in an arc setting. The Ni/Co and Ni/Mn ratios and cumulate textures of the olivine, quenched boundaries between mafic and felsic melts, and the occurrence of tremolite and phlogopite reflect interactions between the Halihatu peridotite and injected silicate and carbonatitic melts in the lower crust. Therefore, we propose a new cumulate‐infiltration model for the petrogenesis of Alaskan‐type ultramafic complexes, which improves our understanding of the nature of Alaskan‐type continental arc root.

Suppressed polaronic conductivity induced sensor response enhancement in Mo doped V2O5 nanowires

In this paper, we show the direct correlation between the suppression of the polaronic oxygen vacancy defect (Vo) density and gas sensor response of 1 at. % Mo-doped V2O5 nanowires (MVONWs). Doping 1 at. % Mo5+ leads to substitution at the V5+ site in V2O5 nanowires (VONWs) and, therefore, reduction in Vo defects. This, in turn, affects the charge carrier hopping sites and, subsequently, enhances the sensor response at lower temperatures (&amp;lt;320 °C). The Mo5+ dopants lead to the lowering of Fermi energy (EF) toward valence band maxima due to the reduced Vo donor density. The polaron suppression is confirmed with the activation energy of polaron hopping, increasing from 195 to 385 meV in VONWs and MVONWs. As a result, the response to ethanol gas enhanced as the depletion width is widened for the given cross section of the nanowires. This may lead to a large depletion controlled cross-sectional area and, therefore, better sensitivity. At about 350 °C, VONWs show a change in the slope of resistance vs temperature (MIT), which is not observed in the case of MVONWs. This is attributed to the presence of the enhanced non-stoichiometry of V ion resulting in metallic behavior and accompanied by a sudden rise in the sensor response at this temperature. Moreover, the absence of MIT may be attributed to the lack of such a sudden rise in the response in MVONWs.

An Experimental Research on Partial Replacement of Fine Aggregate with Granite Powder

Abstract: The most commonly used fine aggregate across world is river sand. River sand is expensive due to excessive cost of transportation from natural sources. The use of sand in construction activities results in the excessive mining. Due to excessive mining natural resources are getting exhausted results in increase in scour depth and sometimes flood possibility. Thus becoming inevitable to use alternative material in concrete. Also large scale depletion of the source creates environmental problems as environmental transportation and other constraints make the availability and use of river sand less attractive. A substitute or replacement product for concrete industry needs to be found. Granite is an igneous rock which is widely used as construction material in different forms. Granite industries produce lot of dust and waste materials. The wastes from the granite polishing units are being disposed to environment which causes health hazards. Granite fines are used as a filler material in the concrete, replacing the fine aggregate which will help in filling up the pores in the concrete. Filling up of the pores by granite fines to increase the strength of the concrete and also a material which is abundantly to investigate the strength behaviour of concrete with use of granite fines as an additive .In this project an attempt is made experimentally to investigate the Strength and durability behaviour of ordinary and high strength concrete with the use of granite fines as an additive. Concrete is prepared with granite fines as a replacement of fine aggregate in 6 different proportions namely 0%,10%,20%,30%,40%and 50%.To improve the workability of concrete 1% superplasticizer added to ordinary strength concrete. The test results indicate that granite as replacement for fine aggregate with has beneficial effect on the mechanical durability properties such as compressive strength, split tensile strength.

Timing of Transition from Proto- to Paleo-Tethys: Evidence from the Early Devonian Bimodal Volcanics in the North Qaidam Tectonic Belt, Northern Tibetan Plateau

The transition from the Proto- to the Paleo-Tethys is still a controversial issue. This study reports a new petrology, zircon U–Pb geochronology, and whole-rock geochemistry of volcanic rocks from the Maoniushan Formation in the Nankeke area, northern Qaidam (NQ) of the Tibetan Plateau, to provide new evidence for the transition from the Proto- to the Paleo-Tethys oceans. The volcanic suite consists mainly of rhyolitic crystal lithic tuff lavas and minor basalts. Zircon U–Pb data indicate that the bimodal volcanic rocks were formed during the Early Devonian (ca. 410–409 Ma). Geochemically, the basalts have low contents of SiO2 (48.92 wt.%–51.19 wt.%) and relatively high contents of MgO (8.94 wt.%–9.99 wt.%), TiO2 (1.05 wt.%–1.29 wt.%), K2O (2.35 wt.%–4.17 wt.%), and K2O/Na2O ratios (1.04–2.56), showing the characteristics of calc-alkaline basalts. Their rare earth element (REE) patterns and trace element spider diagrams are characterized by enrichments in LREEs (LREE/HREE = 18.31–21.34) and large ion lithophile elements (LILEs; Rb, Th, and K) and depletion in high-field-strength elements (HFSEs; Nb, Ta, P, and Ti), with slight negative Eu anomalies (Eu/Eu* = 0.82–0.86), which are similar to Etendeka continental flood basalts (CFB). These features suggest that the basalts were most likely derived from low degree (1%–5%) partial melting of the asthenospheric mantle, contaminated by small volumes of continental crust. In contrast, the felsic volcanics have high SiO2 (68.41 wt.%–77.12 wt.%), variable Al2O3 (9.56 wt.%–12.62 wt.%), low MgO, and A/CNK ratios mostly between 1.08 and 1.15, defining their peraluminous and medium-K calc-alkaline signatures. Their trace element signatures show enrichments of LREEs and LILEs (e.g., Rb, Th, U, K, and Pb), depletion of HFSEs (e.g., Nb, Ti, Ta, and P), and negative Eu anomalies (Eu/Eu* = 0.22–0.66). These features suggest that the felsic volcanics were derived from partial melting of the middle crust, without interaction with mantle melts. Considering all the previous data and geochemical features, the Maoniushan Formation volcanic rocks in NQ formed in a post-collisional extensional setting associated with asthenospheric mantle upwelling and delamination in the Early Devonian. Together with the regional data, this study proposed that the Proto-Tethys Ocean had closed and evolved to the continental subduction/collision orogeny stage during the Middle to Late Ordovician, evolved to the post-collisional extensional stage in the Early Devonian, and finally formed the Zongwulong Ocean (branches of the Paleo-Tethys Ocean) in the Late Carboniferous, forming the tectonic framework of the Paleo-Tethys Archipelagic Ocean in the northern margin of the Tibetan Plateau.

Effect of Cu or Ni addition to ZnO nanostructures on their n-butanol sensing performance

ZnO nanostructures with two shapes were routinely synthesised using a direct-current heating technique. These structures were coated with metals such as Cu and Ni to enhance the sensor response to n-butanol vapour. The surface modification approach associated with semiconductor materials used in gas sensor applications is essential for improving sensing performance, including the sensor response, selectivity, and stability for specific gases. Previously investigated surface modification approaches mostly involved the addition of noble metals, such as Pd, Pt, and Au. However, these metals are expensive for commercial applications. Herein, surface modification by the addition of non-noble metals is presented as a p–n junction for sensor fabrication. Cu and Ni sputter-coated onto ZnO nanostructures were transformed into CuO and NiO, respectively. The results of the gas-sensing characteristics show that the p–n junction formation of the ZnO–CuO and ZnO–NiO sensors remarkably enhanced the sensor response toward n-butanol. The sensor response of the ZnO–NiO sensor upon exposure to n-butanol at a concentration of 1000 ppm was 1400.0 at a working temperature of 450 °C, whereas that of the ZnO–CuO sensor was 775.9 at the optimum working temperature of 400 °C and an n-butanol concentration of 1000 ppm. Furthermore, these sensors exhibited excellent selectivity toward n-butanol compared to other gases. The sensing mechanism is explained by the large depletion layer width at the boundary of the p–n junction, which improves the sensor response. These results demonstrate a viable approach for manufacturing n-butanol sensors and possibly for constructing a functional active layer in e-nose applications.

The genesis of ca. 1.78 Ga granitoids in the Xiong’er large igneous province: Implications for continental crust generation

The genesis of intermediate-felsic rocks and the implications for crustal growth are highly controversial. These issues are particularly relevant to large igneous provinces, which are one of the most effective methods of crustal generation. Mafic magmas, even those with continental marks, have been considered as the contribution from mantle to crust, whereas the intermediate-felsic series in large igneous provinces has uncertain implications for crustal growth due to uncertainty about their modes of generation. In this paper, we focus on the intermediate-felsic granitoids, i.e., Gushicun diorites and granites, in the Xiong’er large igneous province (ca. 1780‒1750 Ma) through detailed study of their petrology, chronology, and geochemistry. Our new data show that both diorites and granites have the same emplacement age of ca. 1780 Ma and were synchronized with the Xiong’er large igneous province. The granitoids are characterized by enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., Li, Ba, and Rb) but depletion in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti). They have almost the same ΣREE (rare earth element) contents and TTi-Zircon (∼850 °C), whole-rock Nd (εNd(t) from −8.24 to −5.76), zircon Hf (εHf(t) isotope ratios of −14 to −8 isotope ratios), and O-isotope compositions (average δ18O = 5.3‰). The fine-grained Gushicun diorites have low Sr/Nd (&amp;lt;10) and Eu/Sm (&amp;lt;0.3) but high Si/Al (&amp;gt;3.2) ratios and are similar to the basaltic andesites in the Xiong’er large igneous province, which suggests that the diorites are crystallization melts that differentiated along the liquid line of descent. The Rayleigh fractionation model based on the REE contents shows that the Gushicun diorites were formed by 40%‒50% fractional crystallization of Xiong’er basaltic melts. The characteristics of high K2O (3.8‒4.7 wt%) and Yb contents (4.0‒6.5 ppm), low Sr/Y (1.4‒3.3), and low metaluminous values (A/CNK = 0.8‒1.1) of the Gushicun granites with mantle-like O-isotope values rule out the melting genesis of low K2O (&amp;lt;0.5 wt%) amphibolite and trondhjemite−tonalite−granodiorites (TTGs) of the surrounding Taihua Complex. The Gushicun granites show a geochemical affinity with andesites in the Xiong’er large igneous province. The alphaMELTs simulation based on the major elements argues against the partial melting of amphibolite and TTGs but supports the melting genesis of Xiong’er intermediate igneous rocks with low water contents (&amp;lt;1 wt%). These findings shed light on the formation of the felsic series in large igneous provinces, which remelted the previous mafic-intermediate rocks via underplating basaltic magmas. Despite having enriched Nd- and Hf-isotope features, the Gushicun diorites represent juvenile crust, while the granites were formed by the reworking of juvenile crust instead of ancient crust. This paper also suggests that radiogenic isotopic ratios cannot be reliably used to assess types of continental crust.

Diachronous subduction, closure of the Proto-Tethys Ocean, and collisional accretion of microcontinents: Insights from the early Paleozoic intermediate-mafic rocks in the Amdo microcontinent of the Tibetan Plateau

The Proto-Tethys Ocean played an important role in the formation and evolution of the East Asian continental blocks, and the final closure of the Proto-Tethys Ocean may have led to the first assembly of nearly all East Asian blocks at the northern margin of Gondwana. However, controversy remains about the reconstruction of East Asian blocks at the northern margin of Gondwana. The Tibetan Plateau is located in the northern margin of Gondwana and recorded the entire tectonic evolution from continental rift and drift to subduction and collision during the early Paleozoic. Therefore, it is an important region in which to address tectonic evolution processes of the Proto-Tethys Ocean and Gondwana. Here, we present petrology, zircon U-Pb, Sr-Nd-Hf isotope, and whole-rock geochemical data from newly recognized intermediate-mafic magmatic rocks from the Amdo microcontinent of central Tibet, with a view to gain insights into the nature and geotectonic evolution of the northern margin of Gondwana. Zircon grains from meta-andesites and meta-basites in Amdo yielded magmatic crystallization ages of 490 Ma and 455−450 Ma, respectively. The meta-andesites are characterized by enrichment in large ion lithophile elements (e.g., Rb, Th, U, and K) and depletion in high field strength elements (e.g., Nb, Ta, and Ti) with positive zircon εHf(t) values (+3.4 to +6.4), which were probably derived from partial melting of a depleted mantle source enriched by minor fluids from subducted sediments in a continental arc setting. The meta-basites are tholeiitic and exhibit both mid-ocean-ridge basalt (e.g., flat rare earth element patterns) and arc-like (e.g., elevated Th/Yb ratios) geochemical affinities, in combination with negative zircon εHf(t) (−4.6 to −0.3) and whole-rock εNd(t) (−0.21 to −0.45) values, suggesting that they were probably generated by varying degrees of partial melting of a spinel peridotite source with ∼5%−10% crustal assimilation in a back-arc setting. In this regard, we favor the interpretation that the Amdo microcontinent experienced long-lasting (ca. 530−450 Ma) subduction of the Proto-Tethys Ocean slab before the subsequent collisional accretion of microcontinents. Integrating results from previous studies, we propose that the Amdo microcontinent, South Qiangtang terrane, Qilian-Qaidam terrane, and other East Asian blocks were all located at the northern margin of East Gondwana, which recorded the arc-related magmatism along the proto-Tethyan margin in the early Paleozoic. The closure of the Proto-Tethys Ocean and initial collision along the East Gondwana Proto-Tethyan margin may have been diachronous between ca. 455 and 430 Ma.