Enriched Source Research Articles

Zircon double-dating, trace element and O isotope analysis to decipher late Pleistocene explosive-effusive eruptions from a zoned ocean-island magma system, Ascension Island

In this first detailed study of zircon from Ascension Island, South Atlantic, we take a novel approach combining trace element and O isotope compositional data with double-dating (disequilibrium 238U–230Th and (U–Th)/He) to decipher timescales and dynamics of magmatic processes. The Echo Canyon (EC) sequence comprises small-volume explosive-effusive eruptions of trachyte that tapped a compositionally zoned magma system. Associated volcanic hazards may be constrained from the age of volcanism, duration of magma storage, and magma source and plumbing system character. Zircon U–Th–Pb dating of lithic lava clasts has revealed recurrent evolved volcanism at 1.34 and 0.6 Ma, and 95 ka. The (U–Th)/He zircon cooling ages indicate that most of the EC explosive-effusive sequence erupted in a brief episode at ca. 95 ka. Additionally, uniform 238U–230Th zircon crystallisation ages suggest moderately protracted magma storage with melt present at depth for at most 103–104 years before eruption. The enriched character of zircon trace element compositions, relative to MORB, in the absence of a continental crustal signature in the oxygen isotope values (δ18O range 2.67–5.63‰), suggests the presence of an enriched component in the EC magma source. Furthermore, low δ18O zircon compositions imply assimilation of high temperature hydrothermally altered country rock by the source magma. The mineral assemblage in crystal-poor pumices indicates equilibrium storage conditions: zircon saturation and Ti-in-zircon crystallisation temperatures are consistent with alkali feldspar-melt temperatures. Significantly, zircon crystals were preserved both as macrocryst inclusions and in the groundmass of EC explosive and effusive deposits. These rocks preserve evidence of magma evolution by fractional crystallisation. This process led to pre-eruptive compositional stratification, which is evidenced in the range of whole-rock major and trace element compositions and zircon Zr/Hf values. Notably, zircon crystallisation and cooling ages derived from pumice, lava, and accidental lithic lava clasts in highly explosive pyroclastic deposits, have revealed episodes of evolved magmatism that would otherwise have gone undetected. In addition, the zircon trace element and isotope compositions, in combination with the range of crystallisation ages, evidence progressively deeper tapping of less evolved magma stored in discrete lenses. Thus, a combined zircon geochronological-geochemical approach can place constraints on the ca. 0.6 Ma recurrence of past explosive-effusive pulses of millennial to decamillennial duration and their enriched magma sources. This information is relevant for assessing hazards and informing monitoring and forecasting efforts to assist in managing associated risks for small ocean island volcanoes with particularly vulnerable populations and infrastructure.

Magnesium isotopic constraints on the lithospheric mantle metasomatism beneath the craton margin

The magnesium (Mg) isotopic distinction between surficial carbonate and mantle rock makes the Mg isotopes a potential tracer for recycled crustal materials (especially the carbonate-bearing materials) within the mantle. However, whether or to what extent recycled carbonate-bearing crustal materials could influence the Mg isotopes of the lithospheric mantle is still in debate. Here, we report the Mg isotope data for three well-characterized alkaline complexes from the northern margin of the North China Craton, i.e., the Hekanzi, Yaojiazhuang and Saima alkaline complexes. These alkaline rocks were all derived from enriched lithospheric mantle sources beneath the craton margin that were variably metasomatized by carbonate-bearing recycled crustal materials. However, they have relatively homogeneous and normal mantle-like δ26Mg values, i.e., −0.23 to −0.25‰ for the Hekanzi, −0.20 to −0.30‰ for the Yaojiazhuang and − 0.25 to −0.30‰ for the Saima alkaline rocks, respectively. These Mg isotopic characteristics were unrelated to shallow crustal processes (i.e., surface alteration, fractional crystallization and crustal assimilation) but inherited from the mantle sources. The mantle-like Mg isotopes suggest that the recycled carbonate-bearing crustal materials did not change the Mg isotopic compositions of the lithospheric mantle overlying the subduction zone, which mainly ascribes to the large contrast of MgO contents between the recycled crustal materials and the lithospheric mantle peridotite. The MgO contents of calcite-rich carbonates in the metasomatic agents released from the subducted crustal materials are too low to induce Mg isotopic anomaly in the MgO-rich peridotite. Our work reveals that Mg isotopes might not be a sensitive tracer of carbonate melt/fluid metasomatism in the lithospheric mantle beneath the craton margins.

مکی عہد میں خواتین کی تہذیبی و عائلی سرگرمیاں اوران کے عصری اطلاقات

With the advent of Islam, the reforms at cultural, social, economic, educational, medical, political, domestic and militant levels were introduced and simultaneously implemented. According to these reforms, women were given the right to participate in all social, cultural, educational, medical and domestic activities. In all spheres of life, Islam allows, both men and women to participate actively within their gender limits. Tolerance in social interaction, mutual assistance and other social behaviors of Muslim women in early period of Meccan era, are enriched exemplary source for Muslim women of modern age. During the Meccan era, women were active in the economic field like the first lady of Islam Ḥaḍrat Khadīja who used to do business activities and she spent a major portion of his wealth in promoting Islam. Contemporary Muslim women may participate in the economic field according to their feminine limits. Islam encourages them. Other activities among Muslim women of early period of Islam are adornment, telling stories to each other, visiting each other’s home, sewing, embroidering and nursing. In this research paper, cultural and domestic accomplishments of women in the Meccan era have been briefly analyzed and their contemporary applications are also highlighted.

Carbonatite and ultrabasic magmatism at Toro Ankole and Virunga, western branch of the East African Rift system

The western branch of the East African Rift hosts four main Neogene-Quaternary volcanic provinces, characterized by products with wide chemical and mineralogical variability. This study focuses on the two northernmost volcanic provinces, Toro Ankole where ∼0.2 Ma-old carbonatites, melilitites and kamafugites, erupted together with foidites, and Virunga where ∼13–9 Ma-old strongly and mildly alkaline rocks, from nephelinite up to trachytes crop out. Petrographic and whole/rock geochemical characteristics (low SiO2, high CaO and K2O, coupled with LILE enrichment) of 49 samples from Toro Ankole and 5 samples from Virunga (tephrites, trachybasalts and trachyandesites) point out enriched and heterogeneous sub-lithospheric mantle sources. The nature of the ultramafic nodules occasionally associated to the investigated samples highlights the presence of metasomatic veins variably enriched in clinopyroxene, phlogopite, carbonate, apatite, Ti-magnetite and titanite. 143Nd/144Nd ratios of Toro Ankole rocks are below ChUR (0.51249–0.51260), and all but two carbonatite lavas have 87Sr/86Sr ˃ BSE (0.7046–0.7056). Virunga lavas display less radiogenic 143Nd/144Nd (0.51235–0.51249) and more radiogenic 87Sr/86Sr ratios (0.7058–0.7071). Lead isotopes are all above the NHRL (206Pb/204Pb mostly in the range 19.12–19.63). δ11B values cover the whole OIB range (−8.3 to −3.3 ‰), but with the exception of some Toro Ankole samples with notably heavier compositions (−1.9 to 6.6), here linked to the carbonate enrichment. The differences in the isotopic features observed between Toro Ankole and Virunga products may reflect a north to south change of the lithospheric mantle source in terms of composition, mineralogy and depth of melting. Toro Ankole phlogopite-bearing mantle is more intensely metasomatized by a 87Sr- and 11B-rich component (as altered oceanic crust or subducted carbonates) compare to that one beneath Virunga, in which the metasomes might contain amphibole rather than phlogopite. Low degree of partial melting of the metasomatized mantle produces magmas of carbonatitic and ultrabasic/ultrapotassic compositions of the western rift branch.

Noble and base metal geochemistry of late- to post-orogenic mafic dykes from central Spain

The post-tectonic and post-orogenic mafic rocks from the Spanish Central System (SCS) (Iberian Massif) include dyke swarms of shoshonitic (microgabbros) and alkaline (lamprophyres and diabases) geochemical affinity, which register the nature of the metasomatic lithospheric mantle under central Spain. Such magmas sometimes show a direct (or indirect) relationship with the formation of orogenic and intrusion-related gold deposits, which are relatively abundant in the Iberian Massif. The noble and base metal composition of these intrusions shows Primitive Mantle-normalized patterns characterized by positive Au and Co anomalies and fractionated platinum group elements (PGE): from lower Ir-group PGE (IPGE; Ir–Ru) to higher Pd-group PGE (PPGE; Rh–Pt–Pd). The low contents of PGE, together with the base metal contents of pyrite (which is the dominant sulphide phase in the alkaline dykes), is in accordance with low degrees of mantle partial melting and the early segregation of sulphides during magma differentiation. The scarcity of PGE mineral deposits in the Iberian Massif could be explained in part by the apparent lack of PGE enrichment in the Iberian lithospheric mantle. On the contrary, the positive Au anomaly of the SCS mafic dykes represents relatively high Au contents, similar to (and higher than) those of mafic rocks derived from metasomatized subcontinental lithospheric mantle underlying Au-endowed cratons. Several geochemical features point to subduction-related metasomatism of either oceanic or continental nature as the main source of Au enrichment. The Au re-fertilization of the lithospheric mantle under central Spain makes it a potential source in the formation of gold mineralizations.

Genome-wide identification, molecular structures and functional exploration of the membrane attack complex/perforin domain-containing proteins and validation of GmmiRNA169o-GmMACPF-9 module in soybean cold stress

Soybean (Glycine max L.) is a widely cultivated legume and an enriched source of edible oil and protein. Membrane Attack Complex/Perforin Domain-Containing Proteins (MACPFs) played significant roles in plant growth and biotic and abiotic stresses. Here, we performed a genome-wide scanning for the putative GmMACPFs and a total of 20 GmMACPFs were identified in soybean. The conserved domain and phylogenetic analysis of MACPF showed the evolutionary diversification of MACPF genes family among legumes. The GmMACPFs protein characteristics were predicted, including theoretical molecular weight (38.06 to 68.38 kDa), protein isoelectric point (6.61 to 9.41), subcellular localization (nucleus, cytoplasm or mitochondria) and various TFs binding sites. GmMACPFs are located on 12 chromosomes out of a total 20 chromosomes in soybean. The 2 kb promoter analysis revealed that GmMACPFs contains a large number of phytohormones and stress responsive cis-acting elements (CAE) and transcription factor binding sites. We explored the 3D protein structure of GmMACPFs, their posttranscriptional regulators especially abiotic stress responsive miRNAs, and the evolutionary relationship among different legumes and Arabidopsis. GmMACPFs expression pattern was retrieved from RNA-seq libraries for tissue specific and under various abiotic stresses in soybean. According to the results, GmMACPF genes exhibited spatiotemporal, tissue, development stage and abiotic stress specific expression patterns in soybean. Our RT-qPCR analysis indicates the antagonistic expression pattern between GmmiRNA-GmMACPF modules under cold, salt, drought and heat stresses. Transient over expression of GmmiRNA169o-GmMACPF-9 module in soybean hairy root and biochemical analysis showed that GmmiRNA169o-OE plants accumulated less reactive oxygen species (ROS), malondialdehyde (MDA) and accumulated higher superoxide dismutase (SOD) and peroxidase (POD) to enhance cold stress tolerance. These results enriched our knowledge of the functions of GmmiRNA169o and GmMACPF-9 and provided candidate miRNAs-GmMACPFs modules especially GmmiRNA169o for environmental stress resilient soybean breeding through genetic engineering.

Production of reduced graphene oxide from activated rice husk charcoal using a high-energy ball milling method

Production of high-quality graphene at a commercial scale with low cost remains challenging. Thus, we used a high-energy ball milling approach to make reduced graphene oxide (rGO) from activated rice husk charcoal as an enriched carbon source. The as-produced rGO samples were characterized to determine the effect of various milling times (0, 50, 100, 150, and 200 min) on their structure, morphology, specific surface area, pores volume, and size distribution. The variation in the ball milling times was found to introduce the structural defects and remove the oxygen functional groups, thus improving the overall characteristics of the obtained rGO. The wrinkle sheet-like structures of rGO evolved into numerous paper balls-like transparent rumple morphologies due to the milling process-enabled compression mechanism. In addition, due to the increase of milling times, the amount of carbon in rGO was increased to 89.9 atomic%, and oxygen was reduced to 9.3 atomic%, wherein the thermal agitation-mediated collisions of particles played a significant role. The specific surface area (121.483 m2 g−1) and pore volume (0.133 cm3 g−1) of rGO prepared at a milling time of 50 min were observed to be optimum. It was asserted that a high-energy ball milling technique with controlled milling times could help produce high-quality rGO from activated rice husk charcoal at low cost, leading to the development of sustainable and environmentally friendly material required for diverse applications.

The atypical 'hippocampal' glutamate receptor coupled to phospholipase D that controls stretch-sensitivity in primary mechanosensory nerve endings is homomeric purely metabotropic GluK2.

A metabotropic glutamate receptor coupled to phospholipase D (PLD-mGluR) was discovered in the hippocampus over three decades ago. Its pharmacology and direct linkage to PLD activation are well established and indicate it is a highly atypical glutamate receptor. A receptor with the same pharmacology is present in spindle primary sensory terminals where its blockade can totally abolish, and its activation can double, the normal stretch-evoked firing. We report here the first identification of this PLD-mGluR protein, by capitalizing on its expression in primary mechanosensory terminals, developing an enriched source, pharmacological profiling to identify an optimal ligand, and then functionalizing it as a molecular tool. Evidence from immunofluorescence, western and far-western blotting indicates PLD-mGluR is homomeric GluK2, since GluK2 is the only glutamate receptor protein/receptor subunit present in spindle mechanosensory terminals. Its expression was also found in the lanceolate palisade ending of hair follicle, also known to contain the PLD-mGluR. Finally, in a mouse model with ionotropic function ablated in the GluK2 subunit, spindle glutamatergic responses were still present, confirming it acts purely metabotropically. We conclude the PLD-mGluR is a homomeric GluK2 kainate receptor signalling purely metabotropically and it is common to other, perhaps all, primary mechanosensory endings.

Review of the influence of farrowing and lactation housing and positive human contact on sow and piglet welfare

Farrowing crates continue to be the most common system of housing farrowing and lactating sows, however continuous confinement is one of the most contentious welfare issues in livestock production. This review aims to critically evaluate the scientific literature on the implications of two important determinants of sow and piglet welfare: housing and human contact. While the evidence in sows is contradictory, there is consistent evidence of a greater short-term cortisol response in gilts introduced to farrowing crates than pens and there is limited evidence of changes in the HPA axis consistent with sustained stress in gilts during the fourth week of lactation. Confinement of sows during lactation increases stereotypic behaviour, reduces sow-piglet interactions, nursing duration and lying behaviour, and may contribute to leg and shoulder injuries in sows. Piglets reared by sows in pens display more play and less oral manipulative behaviours and generally have better growth rates than those reared in farrowing crates. However, there is increasing interest in developing alternate housing systems with minimal sow confinement and reduced piglet mortality risk. Recent research on temporary crating of sows suggests that confinement briefly around farrowing may be the best compromise between continuous housing in farrowing crates and pens, as it may reduce live-born piglet mortality, while providing the opportunity for the sow to move more freely prior to parturition. Together with housing, the behaviour of stockpeople is a key determinant of pig welfare. Recent evidence shows that positive handling of piglets during lactation reduces fear behaviour and physiological stress responses of pigs to humans, novelty and routine husbandry practices, and thus may be enriching for piglets. As a source of enrichment, positive human interactions provide several advantages: close interactions with piglets usually occur several times daily, positive interactions can be combined with routine checks, human interactions invariably provide variability in their predictability which will minimise habituation, and positive interactions may not require additional physical resources. There is a clear need for comprehensive research examining both the short- and long-term welfare implications and the practicality of less confinement of the sow, and positive handling of both sows and piglets during lactation.

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.

Litho-bio-stratigraphy model and palaeoenvironments of the Babouri-Figuil Basin (NE Cameroon): A lacustrine/fluvial/deltaic setting associated to the Benue Trough (Nigeria)

This paper focuses on the lithostratigraphy and the palaeoenvironmental evolutions of the Babouri-Figuil Basin depositional system. Facies analysis, palynology and organic geochemistry were investigated to propose a 2D sedimentary model of the basin. The study reveals that, this basin is made up of four main facies (sandstones, siltstone, claystone/shale and marls) resting on the granite-gneissic basement. The general trend of the beds is E-W; they dip to the S (SW or SE) and NE, with angles ranging between 4 and 30°. The sedimentary analysis indicates an arid to semi-arid climate. The pollen assemblage strongly suggests a Cenomanian-Turonian age for the sedimentary interval which contains the black shale formations. The presence of the mixture of marine and terrestrial organic matter (type II, I and III) in the same interval indicates a possible marine shallow-water deposit in the basin. The deposits were also influenced by volcanic events and hydrothermal fluid circulation during diagenesis, which are the source of carbonate enrichment in the sediments. The analysis of the sedimentary bodies, the encountered palynology assemblage and the 2D reconstruction show that the sedimentary formations of the Babouri-Figuil Basin were deposited in a lacustrine/fluvial/deltaic sedimentary environment.

Petrology and mineralogy of the martian olivine gabbroic shergottite Northwest Africa 13581: Insights into the enriched martian mantle source

Gabbroic and microgabbroic shergottites are intrusive igneous rocks on Mars and exhibit a wide variety of mineralogical and geochemical properties. However, their source reservoirs, magmatic processes and the link to other shergottite subtypes are not well constrained. Northwest Africa (NWA) 13581 is a newly found permafic olivine gabbro, representing a cumulate member in the shergottite group. This sample provides new critical constraints on the characteristics of mantle sources and magmatic evolution of shergottites. The texture and mineral chemistry of NWA 13581 indicate a polybaric crystallization condition, with an increase in oxygen fugacity of approximately 1 log unit after ascent and emplacement. Geochemical studies suggest that the sample is young (150 ± 25 Ma) and may share a similar enriched mantle reservoir (initial ε176Hfi = −18.4, initial ε143Ndi = −7.1) with shergottites like Zagami (basaltic shergottite), NWA 10169 (poikilitic shergottite) and Larkman Nunatak 06319 (olivine-phyric shergottite). In addition, the presence of potassium-rich melt inclusions enclosed in early-formed minerals of NWA 13581 implies a fertile source, probably originating from a metasomatized mantle. The occurrence of similar potassium-rich components in other enriched shergottites may suggest a common process in their mantle reservoir and during crystallization. Overall, NWA 13581 resembles poikilitic shergottites closer than typical gabbroic shergottites in several aspects such as poikilitic texture, mineral chemistry, magmatic evolutionary path, and emplacement conditions. A simplified model is proposed for the formation of NWA 13581 and poikilitic shergottites in the same magma series. Magma mixing and/or assimilation are not the major mechanism that account for their slightly varied mineral modal abundances and quantitative textural characteristics. For samples derived from similar mantle sources, the textural and mineralogical diversities of shergottites are largely related to crystallization at different crustal levels.

Nucleosynthesis in outflows of compact objects and detection prospects of associated kilonovae

ABSTRACT We perform a comparative analysis of nucleosynthesis yields from binary neutron star (BNS) mergers, black hole-neutron star (BHNS) mergers, and core-collapse supernovae (CCSNe) with the goal of determining which are the most dominant sources of r-process enrichment observed in stars. We find that BNS and BHNS binaries may eject similar mass distributions of robust r-process nuclei post-merger (up to third peak and actinides, A ∼ 200−240), after accounting for the volumetric event rates. Magnetorotational (MR) CCSNe likely undergo a weak r-process (up to A ∼ 140) and contribute to the production of light element primary process (LEPP) nuclei, whereas typical thermal, neutrino-driven CCSNe only synthesize up to first r-process peak nuclei (A ∼ 80−90). We also find that the upper limit to the rate of MR CCSNe is $\lesssim 1~{{\ \rm per\ cent}}$ the rate of typical thermal CCSNe; if the rate was higher, then weak r-process nuclei would be overproduced. Although the largest uncertainty is from the volumetric event rate, the prospects are encouraging for confirming these rates in the next few years with upcoming surveys. Using a simple model to estimate the resulting kilonova light curve from mergers and our set of fiducial merger parameters, we predict that ∼7 BNS and ∼2 BHNS events will be detectable per year by the Vera C. Rubin Observatory (LSST), with prior gravitational wave (GW) triggers.

Controls on metal fertility of dioritic intrusions in the Laiwu district, North China Craton: Insights from whole-rock geochemistry and mineral compositions

Several large high-grade iron skarn deposits in the Laiwu district of Shandong Province (North China Craton) are developed along the contact zone between the Early Cretaceous Kuangshan diorite pluton and Middle Ordovician dolomitic limestone. In sharp contrast, no iron skarn mineralization has been recognized in association with other contemporaneous dioritic intrusions (Jiaoyu, Jinniushan, Tietonggou) in this district. The reason for this contrast remains elusive. Here we present a comparative study of the ore-related Kuangshan pluton and its barren equivalents using whole-rock and mineral (zircon, apatite) geochemistry combined with existing Sr-Nd isotope data to provide new insights into the critical controls on iron skarn mineralization and shed light on future mineral exploration. Geochemical and Sr-Nd isotope data suggest that both the ore-related and barren intrusions were derived from a common enriched lithospheric mantle source following variable degrees of fractional crystallization and crustal assimilation. Modeling based on whole-rock Sr-Nd isotopes implies that the magmas responsible for the Kuangshan and Jinniushan diorite plutons assimilated significant quantities of the Ordovician evaporite-bearing carbonates. Both the fertile and barren diorites show high whole-rock Sr/Y ratios, high zircon Eu/Eu* and Eu/Eu*/Y ratios, and low zircon Dy/Yb ratios. These data, combined with high magmatic water contents (4.4−8.0 wt%) calculated from amphibole compositions, indicate that those four plutons crystallized from hydrous magmas. High whole-rock Fe2O3/FeO, and high ΔFMQ values (mostly >1; fayalite-magnetite-quartz oxygen buffers) estimated from zircon, apatite, and amphibole suggest that the magmas from which the diorite intrusions crystallized were all oxidized. Using available partitioning coefficients for Cl between apatite and magma, the parental melts of the Kuangshan and Jinniushan diorite are estimated to have had higher Cl contents (0.15−0.77 wt%) than the Jiaoyu and Tietonggou diorites (0.06−0.34 wt%). Two types of apatite from the intrusions studied are recognized based on their paragenetic relations: Type 1 apatite (Ap1) is an early-formed phase enclosed in euhedral amphibole, plagioclase, and biotite, whereas type 2 (Ap2) is a late-formed variety hosted in, or intergrown with, anhedral K-feldspar (± anhedral amphibole ± subhedral to anhedral quartz). In the fertile Kuangshan diorite, Cl and OH contents of apatite decrease, but Sr contents increase from Ap1 to Ap2. However, those parameters show reverse trends or remain constant from Ap1 to Ap2 in barren diorites. Such distinctive apatite geochemical signatures are best interpreted as reflecting more efficient fluid exsolution from the parental magma of the Kuangshan diorite than from the barren intrusions. This view is supported by the presence of abundant fluid inclusions in apatite and quartz exclusively from the mineralized intrusion, indicating its crystallization from volatile oversaturated melts. The results presented here indicate that elevated magma Cl contents and efficient separation of magmatic hydrothermal fluid from cooling magmas have been the critical factors controlling iron skarn mineralization in the Laiwu district. Mass balance constraints on Cl budget indicate that a minimum of 44−60 km3 of magma was required to form the Fe deposits associated with the Kuangshan pluton. Our preliminary results suggest that decreasing OH and Cl contents from early to late apatite in intermediate rocks can be used as an indicator for efficient fluid exsolution and consequently metal fertility of those rocks.

Geochemistry, petrology, and isotopic characteristics of the Enseada da Caieira intrusions: Insights from mineral chemistry and Nd and Sr isotopes from Fernando de Noronha, South Atlantic, Brazil

The alkaline magmatism found in the Brazilian Equatorial Margin (BEM) in the Southwest Atlantic Ocean, such as that observed in Fernando de Noronha Archipelago, poses intriguing questions about its origin and its relationship to guyots and onshore magmatism of similar alkaline compositions in northeast Brazil. The Fernando de Noronha Archipelago (FNA) exhibits a broad spectrum of alkaline magmatism, ranging from foiditic to phonolitic/trachytic compositions. At the Enseada da Caieira, a group of intrusions reflects this wide variety from FNA. This paper presents a complete description of these intrusions based on petrography, lithogeochemistry, and mineral and isotopic chemistry, as well as thermobarometry and petrogenetic modeling. The new data are compared with data compiled from the FNA, BEM onshore and offshore magmatism, and the Vitória-Trindade Ridge (VTR). The intrusions are classified as trachyte, alkali-basalt/basanite, phonotephrite, and picrobasalt. The compositional diversity of dikes outcropping in a relatively small area suggests a complex petrogenetic evolution for the feeding system of the Fernando de Noronha Island. This is supported by the presence of porphyritic clinopyroxenes (for example) with compositional zoning, indicating multistage crystallization processes. Flow, resorption, and glomeroporphyritic textures are common. Skeletal crystals also occur as phenocrysts of olivine and clinopyroxene due to supercooling. Secondary minerals such as zeolites and carbonate commonly occur as fillers in amygdules. Values for ƐNd range from +0.2 to +3.1. The Sr–Nd isotopic signatures suggest a mixture between an enriched component (EMII) and a depleted mantle component (DMM). A multi-approach thermobarometer using clinopyroxene, amphibole, and zircon mineral chemistry reveals different stages for crystallization, with pressure and temperature ranging from 320 to 1300 MPa and 750 to 1240 °C, respectively. The whole-rock lithogeochemistry modeling suggests a low degree of partial melting (around 2% or less) of an enriched source with variable proportions from spinel and garnet-lherzolite melting zones.

Early Cretaceous subduction of an oceanic plateau at the Northern Andes; geochemical, metamorphic, and cooling age constraints of the Raspas Metamorphic Complex

The Raspas Metamorphic Complex is a high-pressure unit that includes eclogites, blueschists, and metapelites, with minor garnet amphibolites and greenschists. Although its geochemistry and ages are relatively well known, metamorphic constraints and the origin of its protolith remain unclear. In this study, we present new geochemical, metamorphic, and cooling age data to understand the protolith, metamorphic conditions, and the tectonic implications of this feature for the Northern Andes.Geochemical analyses reveals rocks with N- to E-MORB signatures and trace element ratios typical of a heterogeneous mantle source, like oceanic plateau lavas. Blueschists originated from a deep enriched source, similar to primitive mantle, while eclogites are similar to MORB. Iterative thermodynamic modeling of an eclogite indicates a low T/P gradient of ∼406 °C/GPa during the formation of the assemblage garnet (core), quartz, katophorite, and omphacite cores at ∼598 °C and 1.43 GPa, followed by the formation of atoll garnets and zoisite at 661 °C and 1.63 GPa, around 133 Ma. Peak metamorphic conditions were attained after isobaric heating at 709 °C and 1.61 GPa, resulting in the assemblage of garnet (rim), zoisite (rim), omphacite (rim), and katophorite. 40Ar/39Ar ages around 129 Ma indicate fast exhumation rates of 1.25 to 0.5 cm/yr.We propose that the Raspas Metamorphic Complex represents the interaction of the South American plate with an oceanic plateau during the Early Cretaceous. During the early stages of subduction, it created a flat slab geometry around 130 Ma. As the plateau transformed to eclogite, the decrease in buoyancy caused an increase in subduction dip during a regional roll-back at 129–123 Ma, which triggered the exhumation along the high-pressure belt.

Formation stages of the Kholodninskoye pyrite-polymetallic deposit ore zone

The Kholodninskoe pyrite-polymetallic deposit (Baikal-Patom plateau, Russia) was discovered in 1968, but the questions of its genesis still remain controversial. It is assumed that the explosive activity of volcanic apparatuses of the southern part of the Baikal-Muya zone as well as underwater exhalations of the scattered spreading zone of the back-arc basin could have most likely influenced the geochemical features of amagmatic deposits of the Bodaibo and Patom zones. To investigate the influence of underwater hydrothermal activity on the geochemical features of Neoproterozoic carbonbearing sediments of the Baikal Mountain region, the Olokit zone, which is a fragment of the spreading zone of the backarc basin, was chosen. According to the geochemical parameters, the sediments of the Itykit and Ondokskaya formations hosting the Kholodninskoye deposit fall into the sedimentation area of DalnyaTaiga period paleobasins. Having compared the development of sulfide mineralization of ore objects of the Bodaibo and Olokit structural-formation zones, the authors suggest the unity of deposit formation processes within the Baikal Mountain area. The presence of framboidal pyrite indicates that the early stages of ore formation of the Kholodninskoe hydrothermal-stratiform polymetallic deposit were synchronous with sedimentation. The source of deposit ore zone enrichment with zinc lead, silver and other elements typical for low- and medium-temperature associations was a hydrothermal solution of the scattered spreading zone of back-arc basins. It is likely that the explosive and exhalation activities of the southern Baikal-Muya zone within the studied region also spread further northward, thus influencing the formation of siderochalcophilic geochemical specialization of amagmatic black shale strata of the Bodaibo and Patom zones.

The impact of rare events on the chemical enrichment in dwarf galaxies

ABSTRACT In the environments where the abundance of heavy elements is low, rare events are expected to impact the chemical enrichment. Dwarf galaxies have small masses, low average metallicities and in general low star formation rates, and thus investigating the chemical enrichment provides understanding on the impact of each source of elements on the chemical abundance. Using a chemical evolution model in which the rarity is introduced, we investigate the impact of rare events on the chemical enrichment for Local Group dwarf galaxies. In the model, the occurrence of individual sources of elements is estimated with the star formation history derived by the colour–magnitude diagram. The abundance ratios of trans-iron elements to iron predicted by the model show the oscillation at the lowest metallicities because of the r-process events. In the case of a galaxy of a lower mass, the oscillation caused by neutron star mergers is also seen at higher metallicities, which suggests that the rarity can be important in lower-mass systems. Regarding the source of the chemical enrichment, we observe that the r-process sites seem to contribute more to the production of trans-iron elements at low metallicities, but massive stars of different rotating velocities also contribute to create part of the dispersion of the abundance ratios through the s-process. Both observational and theoretical data, including nucleosynthesis calculations and the chemical abundance of metal-poor stars, are needed to obtain deeper insights into the sources of the chemical enrichment at low metallicities.

Contrasting trends in water quality between adjacent ocean‐ and river‐dominated estuaries: Evidence for marsh porewaters as a source of nutrient enrichment?

AbstractDegradation of estuarine water quality during the Anthropocene has largely resulted from discharges of nutrients leading to eutrophication. Recently, upstream management practices have led to comparatively reduced nutrient input into estuaries. Concurrently, climate cycles and impacts associated with anthropogenic climate warming can affect the long‐term conditions observed within estuaries. Using long‐term monitoring data from adjacent southeastern U.S. estuaries, we show that decadal‐scale trends in nutrient concentrations and phytoplankton standing stock differ between the two connected systems. These contrasting trends appear to result from differences in oceanic influence, the extent of adjacent vegetated marsh, watershed size, and upstream degradation. In the minimally impacted, ocean‐dominated North Inlet estuary, we document increasing ammonium and chlorophyll a (Chl a), while in the adjacent, river‐dominated Winyah Bay, ammonium, and Chl a concentrations are more variable but do not appear to have increased over the same time period. Surprisingly, total nitrogen exhibits the opposite pattern: temporal stability in North Inlet but increasing in Winyah Bay. We hypothesize that sea level rise associated with climate change has driven a complex set of interactions between salt marsh porewaters and tidal pumping, leading to the spillover of nutrients from salt marshes into tidal creeks in North Inlet. In Winyah Bay, this mechanism is less evident as a driver of ammonium concentrations, likely due to the outsized effect of watershed nutrient input and the narrow fringing marsh platform. The degree to which this mechanism operates in other estuaries, which vary in tidal range, the extent of vegetated marsh, watershed size, and degree of anthropogenic degradation warrants further study.

Towards further understanding the applications of endophytes: enriched source of bioactive compounds and bio factories for nanoparticles.

The most significant issues that humans face today include a growing population, an altering climate, an growing reliance on pesticides, the appearance of novel infectious agents, and an accumulation of industrial waste. The production of agricultural goods has also been subject to a great number of significant shifts, often known as agricultural revolutions, which have been influenced by the progression of civilization, technology, and general human advancement. Sustainable measures that can be applied in agriculture, the environment, medicine, and industry are needed to lessen the harmful effects of the aforementioned problems. Endophytes, which might be bacterial or fungal, could be a successful solution. They protect plants and promote growth by producing phytohormones and by providing biotic and abiotic stress tolerance. Endophytes produce the diverse type of bioactive compounds such as alkaloids, saponins, flavonoids, tannins, terpenoids, quinones, chinones, phenolic acids etc. and are known for various therapeutic advantages such as anticancer, antitumor, antidiabetic, antifungal, antiviral, antimicrobial, antimalarial, antioxidant activity. Proteases, pectinases, amylases, cellulases, xylanases, laccases, lipases, and other types of enzymes that are vital for many different industries can also be produced by endophytes. Due to the presence of all these bioactive compounds in endophytes, they have preferred sources for the green synthesis of nanoparticles. This review aims to comprehend the contributions and uses of endophytes in agriculture, medicinal, industrial sectors and bio-nanotechnology with their mechanism of action.