Search Results (56)

Continental rifts represent one of the most important settings geologically and economically. The Suez Rift represents more than 74% of the Egyptian crude oil. It represents the northern end of the Red Sea, which understanding is vital to reconstructing the tectonics, dynamics, and time–temperature history of the whole region. An effective method to reveal rift-related history is by studying its flanks, which are represented here by the Arabian-Nubian Shield Neoproterozoic basement rocks. We applied an approach integrating new fission-track thermochronology data, new time–temperature modeling, stratigraphic information, and geological knowledge, which has proven its effectiveness in such geological settings. The collected samples from the Wadi Hebran area on the eastern flank of the Suez rift showed two differentiated cooling histories: The first has a Carboniferous zircon fission-track and a Cretaceous apatite fission-track age, and the second has a Triassic zircon fission-track and an Oligocene–Miocene apatite fission-track age. The time–temperature history modeling supported four distinct cooling events activated through the Neoproterozoic post-accretion erosional event, Variscan tectonic event, Gondwana disintegration, and the Suez Rift initiation. The rock uplift that accompanied the Suez Rift reaches up to 4 km, explaining the extraordinary elevations of the Catherina region, and supports an active rift component in the southern segment of the Suez Rift eastern flank. Full article

(1) Background: Generation IV supercritical water-cooled reactors (SCWRs), including small modular reactor (SCW-SMR) variants, are pivotal in nuclear technology. Operating at 300–500 °C and 25 MPa, these reactors require detailed understanding of radiation chemistry and transient species to optimize water chemistry, reduce corrosion, and enhance safety. Boron, widely used as a neutron absorber, plays a significant role in reactor performance and safety. This study focuses on the yields of radiolytic species in subcritical and supercritical water exposed to ⁴He and ⁷Li recoil ions from the ¹⁰B(n,α)⁷Li fission reaction in SCWR/SCW-SMR environments. (2) Methods: We use Monte Carlo track chemistry simulations to calculate yields (G values) of primary radicals (e⁻_aq, H^•, and ^•OH) and molecular species (H₂ and H₂O₂) from water radiolysis by α-particles and Li³⁺ recoils across 1 picosecond to 0.1 millisecond timescales. (3) Results: Simulations show substantially lower radical yields, notably e⁻_aq and ^•OH, alongside higher molecular product yields compared to low linear energy transfer (LET) radiation, underscoring the high-LET nature of ¹⁰B(n,α)⁷Li recoil nuclei. Key changes include elevated G(^•OH) and G(H₂), and a decrease in G(H^•), primarily driven during the homogeneous chemical stage of radiolysis by the reaction H^• + H₂O → ^•OH + H₂. This reaction significantly contributes to H₂ production, potentially reducing the need for added hydrogen in coolant water to mitigate oxidizing species. In supercritical conditions, low G(H₂O₂) suggests that H₂O₂ is unlikely to be a major contributor to material oxidation. (4) Conclusions: The ¹⁰B(n,α)⁷Li reaction’s yield estimates could significantly impact coolant chemistry strategies in SCWRs and SCW-SMRs. Understanding radiolytic behavior in these conditions aids in refining reactor models and coolant chemistry to minimize corrosion and radiolytic damage. Future experiments are needed to validate these predictions. Full article

Hainan Island is the only large island located on the northern margin of the South China Sea and is surrounded by Cenozoic graben basins, including the Qiongdongnan, Yinggehai, and Beibuwan basins. The uplift and denudation history of the Jianfeng pluton on southwestern Hainan Island is significant for understanding the formation of the regional geomorphology and adjacent basin evolution. This paper presents apatite and zircon fission-track (FT) analyses conducted on the Jianfeng pluton. The zircon FT (ZFT) ages of the pluton range are from 63 ± 4 to 108 ± 8 Ma, and the apatite FT (AFT) ages are from 19.4 ± 1.8 to 43.9 ± 4.4 Ma. The average confined track lengths in apatite are relatively short (11.9–12.8 μm). An age–elevation plot indicates that two rapid cooling events occurred during 73–63 and 44–40 Ma. Thermal modeling revealed four stages of 73–63 Ma, 44–40 Ma, 40–11 Ma, and 11–0 Ma. From the Late Cretaceous to the middle Eocene (73–40 Ma), the Jianfeng area underwent episodic rapid uplift and denudation. At the end of the Late Cretaceous (73–63 Ma), the area was affected by mid-ocean ridge spreading in the Proto-South China Sea. During the middle Eocene (44–40 Ma), the Yinggehai Basin underwent abrupt expansion and subsidence, which increased the elevation difference between the Jianfeng area and the Yinggehai Basin. From the middle Eocene to the middle Miocene (40–11 Ma), the Jianfeng area underwent slow denudation, and the Yinggehai Basin was rapidly infilled, which eliminated the original elevation difference between the two areas. From the middle Miocene to the present (11–0 Ma), the Jianfeng area has undergone reactivated rapid uplift and denudation, which was driven by the remote effects of the India–Eurasia collision. Full article

The present work describes the first results of the project “Lipari Obsidian and Neolithic Human Communities in the Aeolian Islands”, which aims to study the connection between obsidian sources on the island of Lipari and Neolithic populations on the Aeolian archipelago in Italy. Obsidian is a natural volcanic glass used to produce chipped tools; in the Neolithic period it was the sharpest known material and its trade played an important role in the Mediterranean area. It is thus of particular interest for tracing prehistoric trading patterns. Indeed, Lipari obsidian has a wide distribution and has been found even in southern France, Dalmatia, Sicily and mainland Italy. To reach the project goal, we considered both raw materials from different obsidian geological samples and artefacts from Neolithic settlements on the Aeolian islands, and performed fission-track dating (FT), a radiometric technique that can be used for uranium-bearing minerals and glasses. The preliminary results facilitated the age determination of geological samples, which we could relate to the different eruption phases. Archaeological samples were also dated; their link with the studied volcanic deposits and lava flows made it possible to shed some new light on raw material procurement and on the ability of the Neolithic populations to move from their locations, with particular attention to the consequences of environmental features on the first human settlements on the Aeolian islands. Full article

Interpretation of ⁴⁰Ar/³⁹Ar dates of alkali feldspar and U-Pb dates of apatite depends on the dominant mechanism of isotopic transport in these minerals, which can be either diffusion or fluid-assisted dissolution-reprecipitation. To clarify the contributions of these processes, we have conducted a holistic study of alkali feldspar, apatite and other minerals from the Mt. Isa Inlier in NE Australia. Mineral characterisation by electron microscopy, optical cathodoluminescence imaging and element mapping reveal a complex interplay of textures resulting from magmatic crystallisation, deuteric recrystallisation, local deformation with subsequent higher-temperature alteration, and finally ubiquitous low-temperature alteration. U-Pb and Pb isotopic data for zircon, apatite, fluorite and alkali feldspar suggest that the latter event occurred at ~300 Ma and was associated with fluid-assisted exchange of Pb isotopes between minerals in the same rock, causing some apatite grains to have ²⁰⁷Pb-corrected U-Pb dates that exceed their crystallisation age. However, this event had no unequivocal effect on the ⁴⁰Ar/³⁹Ar or Rb-Sr systematics of the alkali feldspar, which were disturbed by higher-temperature alteration at ~1450 Ma. The age of the latter event is derived from Rb-Sr data. ⁴⁰Ar/³⁹Ar dates are very scattered and suggest that ⁴⁰Ar redistribution proceeded by diffusion in the presence of traps in some places and by dissolution-reprecipitation with variable amounts of recycling in other places. Our results demonstrate the complex effects that interaction with limited amounts of fluids can have on ⁴⁰Ar/³⁹Ar dates of alkali feldspar and U-Pb dates of apatite and thereby reinforce previous critique of their suitability for thermochronological reconstructions. We further identify and discuss potential implications for noble gas geochronology of groundwaters and fission track dating of apatite. Full article

The effects of different regional tectonic events on the Neoproterozoic basement rocks of the Arabian–Nubian Shield in Sinai, as well as the Egyptian unstable and stable shelves, remain uncertain. Coupling fission-track thermochronometry findings with the modeling of the time–temperature history has proved to be an effective method for tackling these issues. The obtained zircon fission-track ages were differentiated into two groups from the Ediacaran–Cambrian and the Ordovician–Carboniferous periods, while the apatite fission-track data revealed two separate groups of cooling ages of the Carboniferous–Triassic and Late Cretaceous ages. The integration of these cooling ages and modeling of the time–temperature history revealed four discrete cooling pulses during the Neoproterozoic, Devonian–Carboniferous, Cretaceous, and Oligocene–Miocene eras. After integrating our findings with the regional tectonic historical and sedimentological records, these could be identified as cooling/exhumation pulses activated in response to the post-accretional event of erosion, Variscan tectonism, the disintegration of Gondwana, and the Gulf of Suez rifting, respectively. Furthermore, the southern border of the Egyptian unstable shelf was found to extend southward to South Sinai and south of the Bahariya depression. Full article

This study presents new fission track data from 40 apatite and 40 zircon samples in the Southern Altai Mountains (SAMs), revealing apatite fission track (AFT) ages of 110 ± 8 Ma to 54 ± 4 Ma and zircon fission track (ZFT) ages of 234 ± 24 Ma to 86 ± 7 Ma. The exhumation rates derived from three thermochronological methods range from 0.01 to 0.1 km/Ma (Age-Elevation method), 0.01 to 0.14 km/Ma (Half-Space thermal model), and 0.027 to 0.075 km/Ma (Age2exhume model). Thermal history modeling using HeFTy software reveals similar thermal histories on both sides of the Kangbutiebao Fault, with a notable cooling event and higher exhumation rates to the northeast. The Late Cretaceous (100–75 Ma) rapid cooling is associated with tectonic reactivation, likely linked to the collapse of the Mongol–Okhotsk Orogen and slab rollback in the southern Tethys Ocean. In the Late Cenozoic (10–0 Ma), cooling and uplift reflect the influence of tectonic stresses from the India–Eurasia collision, which also drove the reactivation of the Kangbutiebao Fault. These findings suggest a complex interplay of tectonic processes driving exhumation in the SAMs from the Late Jurassic to the Early Paleogene. Full article

The Zheduo–Gongga Mountain, an enormous tower located at the boundary of the eastern Tibetan Plateau, is an ideal place to study the contribution of the climate and/or tectonics to the mountain building. Here, we report new zircon U–Pb ages, biotite ⁴⁰Ar–³⁹Ar, and apatite fission track (AFT) ages of granites along the Zhonggu transect in the northern part of the Zheduo–Gongga massif to investigate the detailed exhumation history and mechanism. The results show zircon U-Pb ages of 14.3 ± 0.3 and 11.3 ± 0.2 Ma, Biotite ⁴⁰Ar–³⁹Ar ages of 4.39 ± 0.07 and 3.62 ± 0.05 Ma, and AFT ages of ~2.6–0.9 Ma. Combining previous structural and geochronological studies, we argue that the growth and exhumation of the Zheduo–Gongga Mountain experienced the following stages. Late Oligocene–early Miocene crust shortening and magmatism marked the initiation of the crustal thickening and surface uplift during ~32–11 Ma, forming a migmatite–granitic belt along the Xianhuihe fault, in response to the northward advancing of the Indian plate into the Eurasian plates. Subsequently, the massif experienced episodic phases of exhumation with variable rates. The exhumation occurred at a rate of ~1–1.5 km/Ma with a cooling rate of 70 ± 20 °C/m.y. during ~11–5 Ma coinciding with the coeval intensification of the Asian monsoon and clockwise rotation of the Chuandian block, south of the Xianshuihe fault. During ~5–2 Ma, a phase of accelerated exhumation (~2–5 km/Ma) started, followed by a possible phase of decelerated exhumation (~1–1.5 km/Ma, corresponding to a cooling rate of 120 ± 20 °C/m.y.) since ~2 Ma, when alpine glaciations initiated due to global cooling. This study highlights the importance of tectonic deformation during ~11–5 Ma in controlling the early growth and exhumation of high mountains in the eastern Tibetan Plateau. The climate may account for the later exhumation of the Zheduo–Gongga mountain since ~5 Ma. Full article

Fission-track modeling rests on etching, counting and measuring the lattice damage trails from uranium fission. The tools for interpreting fission-track data are advanced but the results are never better than the data. Confined-track samples must be an adequate size for statistical analysis, representative of the track population and consistent with the model assumptions and with the calibration data. Geometrical and measurement biases are understood and can be dealt with up to a point. However, the interrelated issues of etching protocol and track selection are more difficult to untangle. Our investigation favors a two-step protocol. The duration of the first step is inversely proportional to the apatite etch rate so that different apatites etch to the same Dpar. A long immersion reveals many more confined tracks, terminated by basal and prism faces. This allows consistent length measurements and permits orienting each track relative to the c-axis. Long immersion times combined with deep ion irradiation reveal confined tracks deep inside the grains. Provided it is long enough, the precise immersion time is not important if the effective etch times of the selected tracks are calculated from their measured widths. Then, whether the sample is mono- or multi-compositional, we can, post hoc, select tracks with the desired properties. The second part of the protocol has to do with the fact that fossil tracks in geological samples appear to be under-etched compared to induced tracks etched under the same conditions. This should be assumed if the semi-axes of a fitted ellipse plot above the induced-track line. In that case, an additional etch can increase the track lengths to a point where they are consistent with the model based on lab-annealing of induced tracks, a condition for valid thermal histories. Here too, it is possible to select a subset of tracks with effective etch times consistent with the model if the widths of confined tracks are measured along with their lengths and orientations. Full article

Developments in scanning electron microscopy (SEM) have introduced instant live coloured SEM images based on elemental composition. Here, we use a technique utilising a Unity BEX detector system, with collection speeds up to 100 times faster than typical standard energy-dispersive X-ray (EDX) analysis systems, to obtain large area backscattered and elemental composition maps of heavy mineral (HM) suites from a sample from an Oligocene fluvio-deltaic system in the Central Myanmar Basin. The fast X-ray collection rate and a high-resolution backscattered (BSE) detector allow for rapid imaging of polished blocks, thin sections, and stubs. Individual HM species can be rapidly classified, allowing for the subsequent collection of compositional and morphological metrics. In addition, the identification of grains such as zircon and apatite allow for further analysis by cathodoluminescence (CL) to identify and record the presence of growth zonation, which is critical for further U-Pb geochronology and thermochronology, using fission track analysis of apatite, zircon, and titanite. The sample used in this study contains a diverse heavy mineral suite due to the complex tectonic history of Myanmar, juxtaposing multiple metamorphic basement terranes alongside volcanic arcs and obducted ophiolites. This, along with the textural and mineralogical immaturity of the sediments themselves (governed by short transport systems and the rapid weathering of the sources), means that a wide variety of heavy mineral species can be identified and tested using this new technique, which provides a time-efficient method in comparison to traditional optical techniques. As the Unity BEX detector is located at the polepiece, it is relatively insensitive to working distance; in addition, the geometry of paired X-ray detectors on either side of the polepiece (at 180°) means that the system is also capable of fully characterising individual particles, on uncut and unpolished grain mounts, without artefacts such as particle shadowing. The development of a more comprehensive heavy mineral EDX database (library) will improve the accuracy of this new technique, as will the correlation with other techniques such as Raman spectroscopy. Full article

Fission yeast, a single-cell eukaryotic organism, shares many fundamental cellular processes with higher eukaryotes, including gene transcription and regulation, cell cycle regulation, vesicular transport and membrane trafficking, and cell death resulting from the cellular stress response. As a result, fission yeast has proven to be a versatile model organism for studying human physiology and diseases such as cell cycle dysregulation and cancer, as well as autophagy and neurodegenerative diseases like Alzheimer’s, Parkinson’s, and Huntington’s diseases. Given that viruses are obligate intracellular parasites that rely on host cellular machinery to replicate and produce, fission yeast could serve as a surrogate to identify viral proteins that affect host cellular processes. This approach could facilitate the study of virus–host interactions and help identify potential viral targets for antiviral therapy. Using fission yeast for functional characterization of viral genomes offers several advantages, including a well-characterized and haploid genome, robustness, cost-effectiveness, ease of maintenance, and rapid doubling time. Therefore, fission yeast emerges as a valuable surrogate system for rapid and comprehensive functional characterization of viral proteins, aiding in the identification of therapeutic antiviral targets or viral proteins that impact highly conserved host cellular functions with significant virologic implications. Importantly, this approach has a proven track record of success in studying various human and plant viruses. In this protocol, we present a streamlined and scalable molecular cloning strategy tailored for genome-wide and comprehensive functional characterization of viral proteins in fission yeast. Full article

The radioactive fission product ⁹⁰Sr has a sufficient half-life (28.8 years) to be detected long after its appearance in the environment. After its uptake into the soil-edible plant system, it enters the food chain and represents a potential source of contamination that threatens human health. Due to these facts, tracking the distribution of the artificial radionuclide ⁹⁰Sr in the soil–edible plant system is a subject of intense research. The tracking of the ⁹⁰Sr radionuclide distribution in the soil profile, as well as in the crops on the long-term experimental fields was carried out using beta radiation spectrometry. The radiochemical analytical method was used to analyze the ⁹⁰Sr content in cultivated soil and crops. The conducted study focused on the experimental substantiation of the developed model for predicting the behavior of ⁹⁰Sr in the cultivated soil–crop system. The results of using the applied radioecological model for the transfer of ⁹⁰Sr from the soil to the above-ground part of crops showed a relatively good agreement with the experimentally determined values of the soil–crop transfer factor, which indicates that the used model can be successfully applied for the prediction of the behavior of ⁹⁰Sr in the soil–soil solution–crop system. Full article

SE Anatolia is witnessing the final stage of the Wilson Cycle, where a continental collision between the Tauride–Anatolide block and Arabian platform occurred, and a 1.5 km Eastern Tauride mountain chain formed. We present new low-temperature thermochronology (LTT) ages, including eight apatite fission track (AFT) and seven apatite and zircon U-Th-Sm/He (AHe, ZHe) ages, for the metamorphic rocks from the Nappe Zone of the Southeast Anatolian Orogenic Belt. The ZHe ages vary from 51.2 ± 0.7 Ma to 30.4 ± 0.6 Ma, the AFT ages range from 33.1 ± 1.6 Ma to 18.1 ± 0.9 Ma, and the AHe ages range from 23.6 ± 2.5 Ma to 6 ± 1.9 Ma. The LTT data show a continuous slow uplift of the region. However, the thermal modeling results suggest an Eocene and middle–late Miocene fast uplift of the region. Similar to our results, the LTT studies along the SAOB show that the vertical movements initiated during the Eocene period have continued in a steady-state regime to recent times. The Eocene epoch is identified by arc–back-arc setting in the region, whereas the Miocene epoch is marked by the continental collision. Within this tectonic framework, vertical movements on the overriding plate are controlled by both extensional and compressional tectonics. The LTT data obtained along the SAOB show fingerprints of thrust propagation from north to south. Full article

The Kaiyang phosphate mining area in Guizhou, which is located in the central–southern part of the Yangtze Block, hosts one of China’s more significant phosphate-enriched strata within the Doushantuo Formation. This formation is essential for phosphate mining and also preserves multiple magmatic events, which are closely linked to the assembly and breakup of the Rodinia supercontinent. Our comprehensive studies in petrology, geochemistry, zircon U-Pb geochronology, and fission-track dating reveal that the primary ore mineral in phosphorite is collophane, which is accompanied by dolomite, quartz, pyrite, and zircon. The majority of detrital zircons in the phosphorite, as well as the overlying dolostone and underlying sandstone, are of magmatic origin, with a record of multiple stages of magmatic ages. Among these, the older age groups of ~2500 Ma and ~2000–1800 Ma represent the ancient crystalline basement of the Yangtze Block from the Paleoproterozoic era. The three main age peaks at ~880 Ma, ~820 Ma, and ~780 Ma indicate that the magmatic event at ~880 Ma was related to the assembly of the Rodinia supercontinent during the Grenvillian period. The most prominent age peak at ~820 Ma marks a critical time point for the transition from assembly to the breakup of the Rodinia supercontinent, with the Yangtze Block’s response to the supercontinent breakup events lasting at least until ~780 Ma. The youngest group of zircon ages from the phosphorite (~594 Ma), and the underlying sandstone (~529 Ma) establishes the minimum age for the phosphorite formation, indicating that the Doushantuo phosphorite layer in the Kaiyang area was formed after 594 Ma, i.e., even later than 529 Ma. The zircon fission-track ages in the three rock types of the phosphorite-bearing rocks can be divided into three groups: 501–489 Ma, ~366 Ma, and 53–39 Ma. All of these groups are presumed to be associated with the tectonic uplift events that follow mineralization. The first two age groups correspond to the two major tectonic uplift events during the Caledonian period, which resulted in the formation of the Qianzhong Uplift. The ages of 53–39 Ma are related to the late uplift of the Himalayan orogeny, and they represent its response in the Kaiyang area of Guizhou. Full article