Search Results (28)

This work investigated the structural response and phase transformation dynamics of silica-bearing cherts subjected to high-temperature processing (up to 1400 °C) and prolonged mechanochemical activation. Through a combination of X-ray diffraction (XRD) with Rietveld refinement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and transmission electron microscopy (HRTEM), we trace the crystallographic pathways of quartz, moganite, tridymite, and cristobalite under controlled thermal and mechanical stress regimes. The experimental results demonstrated that phase behavior is highly dependent on intrinsic properties such as initial phase composition, impurity presence, and crystallinity. Heating at 1400 °C induced irreversible conversion of quartz, moganite, and tridymite into cristobalite. Samples enriched in cristobalite and tridymite exhibited notable increases in crystallinity, whereas quartz-dominant samples showed either stability or a decline in structural order. Rietveld analyses underscored the critical influence of microstrain and crystallite size on thermal resilience and phase persistence. Thermal profiles revealed by DSC and TGA expose overlapping processes including polymorphic transitions, minor phase dehydration, and redox-driven changes, likely associated with trace components. Mechanochemical processing resulted in partial amorphization and the emergence of phases such as opal and feldspar minerals (microcline, albite, anorthite), interpreted as the product of lattice collapse and subsequent reprecipitation. Heat treatment of chert leads to a progressive rearrangement and recrystallization of its silica phases: quartz collapses around 1000 °C before recovering, tridymite emerges as an intermediate phase, and cristobalite shows the greatest crystallite size growth and least deformation at 1400 °C. These phase changes serve as markers of high-temperature exposure, guiding the identification of heat-altered lithic artefacts, reconstructing geological and diagenetic histories, and allowing engineers to adjust the thermal expansion of ceramic materials. Mechanochemical results provide new insights into the physicochemical evolution of metastable silica systems and offer valuable implications for the design and thermal conditioning of silica-based functional materials used in high-temperature ceramics, glasses, and refractory applications. From a geoarchaeological standpoint, the mechanochemically treated material could simulate natural weathering of prehistoric chert tools, providing insights into diagenetic pathways and lithic degradation processes. Full article

The Heilongjiang Complex provides a crucial geological record of the evolutionary history of the Mudanjiang Ocean, making it significant for understanding the accretion process between the Jiamusi Block and the Songliao Block. In this study, we analyzed samples from the Heilongjiang Complex in the Huanan region using zircon U-Pb and ⁴⁰Ar/³⁹Ar isotopic dating. The LA-ICP-MS U-Pb dating results show that the deposition time of the mica quartz schist is Late Triassic (237–207 Ma), while the protolith age of the amphibolite is Middle Triassic (245.5 ± 1.2 Ma). Detrital zircon ages from the mica quartz schist reveal four groups: 155–229 Ma, 237–296 Ma, 485–556 Ma, and 585–2238 Ma. The provenances are related to the magmatic and metamorphic activities at the junction of the Jiamusi Block and Songliao Block. ⁴⁰Ar/³⁹Ar isotopic dating yielded a plateau age of 183.40 ± 1.83 Ma for phengite in the mica quartz schist, with the metamorphic ages obtained from zircon U-Pb dating. We identify three major metamorphic events in the Heilongjiang Complex: (1) ~229 Ma, marking the earliest tectonic thermal disturbance in the complex; (2) 207–202 Ma, corresponding to the metamorphic event related to the collision between the Jiamusi Block and Songliao Block; and (3) ~183 Ma, indicating the closure of the Mudanjiang Ocean. Integrating these new findings with the results of previous research on magmatism and metamorphism, we reconstruct the tectonic evolution of the Mudanjiang Ocean from the Late Paleozoic to the Mesozoic. During the Early Permian, the Mudanjiang Ocean had already opened. Between the Middle Permian and Middle Triassic, bidirectional subduction occurred. In the Late Triassic, the Mudanjiang Ocean entered a subduction dormancy period. By the Early to Middle Jurassic, the Mudanjiang Ocean closed due to continental collision, leading to the final positioning of the Heilongjiang Complex. Full article

The granitoids of the Kalba–Narym batholith and the Irtysh shear zone (ISZ) are among the main geological features of the late Paleozoic Altai accretion–collision system (AACS) in Eastern Kazakhstan. Traditionally, it is believed that late Paleozoic strike-slip faults played a pivotal role at all stages of the development of the AACS, they were supposed to control deformation, magmatism, and ore deposits. This work is devoted to solving the problem of the tectonic evolution of the AACS based on the reconstruction of the thermal history of granitoids of the Kalba–Narym batholith in connection with the Chechek metamorphic dome structure, which is one of the highly metamorphosed blocks mapped within the ISZ. The new geological and geochronological data presented in this work allowed us to establish the sequence of formation of the Kalba–Narym granitoid batholith and link it with the evolution of the Irtysh shear zone (ISZ). It was revealed that in the late Carboniferous–early Permian (312–289 Ma), during the NE–SW compression, the Irtysh shear zone formed as a gently dipping thrust system into which gabbro of the Surov massif intruded. The combined manifestation of magmatic and tectonic processes caused the formation of tectonic mélange with cataclastic gabbro and metamorphic rocks of the Chechek metamorphic dome structure (312–289 Ma). Compression caused the formation of a cover-thrust structure. The thickening of the crust under the probable thermal action of the Tarim plume led to the formation of the early Permian Kalba–Narym batholith (297–284 Ma) within the Kalba–Narym terrane. Denudation of the orogen occurred before the Early Triassic (280–229 Ma). In this way the sequence of formation of the Kalba–Narym batholith and the ISZ is consistent with the concepts of the stages of plume-lithosphere interaction within the AACS under the influence of the late Carboniferous–early Permian Tarim igneous province, but in the cover-thrust tectonic setting. Full article

Background/Objectives: Mastectomy is a surgical option for breast cancer when conservative treatment is unsuitable, and it is also performed prophylactically in high-risk women. Various surgical techniques can be used for mastectomy, including electrosurgery, which can cause thermal damage to tissues, reducing surgical precision and delaying wound healing. This study aims to compare electrical plasma surgery and hydrodissection, which appear to be the least traumatic methods, to determine the better option for performing mastectomy with immediate reconstruction. Methods: Conducted at the “Breast Unit” of AO “OrdineMauriziano Umberto I”, this study analyzed 56 patients undergoing 65 mastectomies (9 bilateral, 47 unilateral). A total of 16 were prophylactic, and 49 were oncologic. All patients received immediate subpectoral reconstruction. Data collected included preoperative medical history, pain, drain flow, blood transfusions, hemoglobin levels, and hospital stay duration. Complications were graded using the Clavien-Dindo classification. Results: Both groups were similar in age, body mass index (BMI), smoking habits, and comorbidities. Patients who underwent hydrodissection reported more pain on the first and second postoperative day and had longer hospital stays. The drop in hemoglobin from pre- to postoperative and the volume of surgical drains on the day of surgery and the first and second postoperative days were comparable between groups. Early complications and reintervention rates (Clavien-Dindo grade 3) were similar between techniques. Conclusions: Electrical plasma surgery offers better early postoperative outcomes in terms of pain and hospital stay, although overall complication and reintervention rates are unaffected by the technique used. Larger randomized studies are needed to confirm these findings and optimize patient management. Full article

Cosmogenic nuclide exposure dating is an important technique for reconstructing glacial histories. Many of the most commonly applied cosmogenic nuclides are extracted from the mineral quartz, meaning sampling of felsic (silica-rich) rock is often preferred to sampling of mafic (silica-poor) rock for exposure dating studies. Fieldwork in remote regions such as Antarctica is subject to time constraints and considerable logistical challenges, making efficient sample recovery critical to successful research efforts. Remote sensing offers an effective way to map the geology of large areas prior to fieldwork and expedite the sampling process. In this study, we assess the viability of multispectral remote sensing to distinguish felsic from mafic rock outcrops at visible-near infrared (VNIR) and shortwave infrared (SWIR) wavelengths using both the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and very high-resolution Worldview-3 (WV-3) imagery. We applied a combination of spectral mapping and ground truth from spectral measurements of 17 rock samples from Mount Murphy in the Amundsen Sea sector of West Antarctica. Using this approach, we identified four dominant rock types which we used as a basis for felsic–mafic differentiation: felsic granites and gneisses, and mafic basalts and fragmental hydrovolcanic rocks. Supervised classification results indicate WV-3 performs well at differentiating felsic and mafic rock types and that ASTER, while coarser, could also achieve satisfactory results and be used in concert with more targeted WV-3 image acquisitions. Finally, we present a revised felsic–mafic geological map for Mt Murphy. Overall, our results highlight the potential of spectral mapping for preliminary reconnaissance when planning future cosmogenic nuclide sampling campaigns in remote, unvisited areas of the polar regions. Full article

Basal metabolic rates (BMRs) increase with temperature and body mass. Environmental temperatures rapidly change in tropical mountains due to elevation (macro scale) and vegetation structure (micro scale). Thus, tropical mountains are good settings for testing the effects of temperature on BMRs. We measured the BMRs at four temperature ranges on six territorial and closely related species of Rubyspot damselflies (Hetaerina, Calopterygidae), which also share very similar behavior and morphology and are segregated by habitat and elevation across the Western Colombian Andes. We analyzed the effects of body mass, habitat, elevation, temperature, and sex on their BMRs, using a phylogenetic framework. We found that the main factors regulating their niche partition seemed to be environmental temperature, body size, and BMR. We found differences in their BMRs related to elevation when the temperatures were close to those experienced by the damselflies at their elevational range. As predicted, the larger species associated with colder habitats, forests, and highlands had higher BMRs. However, at high stressful temperatures, only the body mass was positively related to the BMR, showing that smaller individuals can keep their BMRs lower under high temperatures compared to bigger ones. Habitat use was not associated with changes in the BMR. Finally, phylogenetic reconstruction showed all species clustered in three clades. Each clade in the phylogenetic tree shares similar habitat preferences, pointing to a mixture of evolutionary history, thermal adaptations, and body mass differences as a possible explanation for the great diversity of these damselflies in a small area. Under the global warming scenario, we expect Rubyspots with smaller body sizes to be favored since they will tolerate higher temperatures, which would ultimately lead to populations with smaller body sizes overall, which could negatively affect their fitness. Full article

We aim to constrain the stellar initial mass function (IMF) during the epoch of reionization. To this purpose, we build up a semi-empirical model for the reionization history of the Universe based on various ingredients: the latest determination of the UV galaxy luminosity function from JWST out to redshift $z\lesssim 12$; data-inferred and simulation-driven assumptions on the redshift-dependent escape fraction of ionizing photons from primordial galaxies; a simple yet flexible parameterization of the IMF $\varphi \left(m_{\star }\right)$∼$m_{\star }^{\xi }{e}^{-m_{\star ,\mathrm{c}}/m_{\star }}$ in terms of a high-mass end slope $\xi <0$ and a characteristic mass $m_{\star ,\mathrm{c}}$, below which a flattening or a bending sets in (allowing description of a variety of IMF shapes from the classic Salpeter to top-heavy ones); the PARSEC stellar evolution code to compute the UV and ionizing emission from different stars’ masses as a function of age and metallicity; and a few physical constraints related to stellar and galaxy formation in faint galaxies at the reionization redshifts. We then compare our model outcomes with the reionization observables from different astrophysical and cosmological probes and perform Bayesian inference on the IMF parameters via a standard MCMC technique. We find that the IMF slope $\xi$ is within the range from $-2.8$ to $-2.3$, consistent with direct determination from star counts in the Milky Way, while appreciably flatter slopes are excluded at great significance. However, the bestfit value of the IMF characteristic mass $m_{\star ,\mathrm{c}}$∼a few $M_{\odot }$ implies a suppression in the formation of small stellar masses at variance with the IMF in the local Universe. This may be induced by the thermal background of ∼20–30 K provided by CMB photons at the reionization redshifts. We check that our results are robust against different parameterizations for the redshift evolution of the escape fraction. Finally, we investigate the implications of our reconstructed IMF for the recent JWST detections of massive galaxies at and beyond the reionization epoch, showing that any putative tension with the standard cosmological framework is substantially alleviated. Full article

A reconstruction of the tectonothermal evolution of the Laojunshan–Song Chai granite gneiss massif (North Vietnam, South China) was carried out, based on summaries of the latest isotopic and fission-track dating results. The recorded wide range (420–465 Ma) of the age of granite gneiss rocks testifies to the long-term existence of a partially molten layer at a depth of 20–30 km for several tens of Ma. By the Devonian–early Carboniferous, a section of the excessively thickened crust was denudated, the massif was exhumated to the level of the upper crust, and isotope systems were “frozen”. The rate of uplift of the rocks of the massif is estimated to be about 0.2–0.5 mm/year. In the further history of the granite gneiss massif, episodes of repeated burial to a depth of about 13 km are recorded, associated with the Indosinian collision. The rocks have experienced metamorphism of the amphibolite-green schist facies, accompanied by tectonic transport in the form of a thrust sheet. Over the next 200 Ma, the uplift of the massif and the erosion of the overlying strata occurred in discrete pulses, during a sequence of active tectonic events. Thus, the thermochronological and P-T history of the Laojunshan–Song Chai massif is a kind of chronicle of regional tectonic–thermal events. In the history of the massif, traces of two orogenic cycles associated with the collision of the Cathaysia and Yangtze blocks in the Lower Paleozoic and the Indosinian collision in the Triassic are recorded. Full article

The Ordos Basin is rich in oil and gas resources in the Paleozoic strata. The southern part of the basin boasts a thick Paleozoic sedimentary sequence, enriched organic matter, favorable sedimentary facies, and hydrocarbon source rocks with an over-mature thermal evolution stage. However, the lack of in-depth study of the tectono-thermal evolution in the southern basin limits regional oil and gas exploration. In this study, drill core and outcrop samples were collected from the Shanbei Slope and the Weibei Uplift, respectively. These samples were subjected to apatite fission track (AFT) and (U-Th)/He dating (AHe). The results were used to reconstruct the thermal history of the southern basin, calculate exhumation rates, and analyze the tectonic evolution of the basin. The seven annealed AFT data values from the Shanbei Slope range from 21.4 to 52.8 Ma, with mean track lengths of 13.24 μm, and the twelve unannealed AFT data values from the Weibei Uplift range from 111.9 to 204.6 Ma. The seven AHe data values from the Shanbei Slope range from 17.0 to 31.8 Ma, and the eight AHe data values from the Weibei Uplift range from 31.7 to 47.5 Ma. The thermal history is characterized by a prolonged phase of burial and heating from the Triassic to the Late Early Cretaceous, followed by a phase of uplift and cooling that continued into the Cenozoic. This cooling phase exhibits three distinct stages with varying rates of uplift and cooling. According to the dating results, the cooling timing of the southern basin was earlier than that of the central part, and the southern basin experienced higher uplift rates during the Paleogene than in other periods of the Cenozoic. This may be attributed to the far-field effects of the collision between the Indian Plate and the Eurasian Plate during the Paleogene. Full article

The east–west-trending South Tibetan Detachment System (STDS) and north–south-trending rifts (NSTRs) are the two main types of extensional structures that have developed within the Tibetan Plateau during continent–continent collision since the early Cenozoic. They have played significant roles in the evolution of the plateau, but it is unclear how they are related genetically. In the Yadong area of the eastern Himalaya, the NSTRs cross-cut the STDS. Apatite and zircon fission track ages of a leucogranite pluton in the footwall of the two extensional faults can be used to reconstruct the cooling and exhumation history and thereby constrain the activity of extensional structures. The new AFT ages range from 10.96 ± 0.70 to 5.68 ± 0.37 Ma, and the ZFT age is 13.57 ± 0.61 Ma. Track length distributions are unimodal, albeit negatively skewed, with standard deviations between 1.4 and 2.1 µm and mean track lengths between 11.6 and 13.4 µm. In conjunction with previously published datasets, the thermal history of the region is best explained by three distinct pulses of exhumation in the last 16 Ma. The first pulse (16–12 Ma) records a brittle slip on the STDS. The two subsequent pulses are attributed to the movement on the Yadong normal fault. The normal fault initiated at ~12 Ma and experienced a pulse of accelerated exhumation between 6.2 and 4.7 Ma, probably reflecting the occurrence of two distinct phases of fault activity within the NSTRs, which were primarily instigated by slab tear of the subducting Indian plate. Full article

Patterns of Phanerozoic burial and erosion across the cratonic interior of North America can help constrain the continental hypsometric history and the potential influence of dynamic topography on continental evolution. Large areas of the Canadian Shield currently lack Phanerozoic sedimentary cover, but thermochronology data can help reconstruct the previous extent, thickness, and erosion of Phanerozoic strata that once covered the craton. Here, we report apatite (U-Th)/He (AHe) data for 15 samples of Precambrian basement rocks and 1 sample of Triassic kimberlite from a 1400 km–long east–west transect across the southern Canadian Shield. Single-grain basement AHe dates range from >500 Ma in the west to <250 Ma in the east. AHe dates for the kimberlite in the middle of the transect overlap with the pipe’s Triassic eruption age. These data, combined with previous apatite fission-track data, geologic constraints, and thermal history modeling, are used to constrain the first-order regional thermal history that we interpret in the context of continental burial and erosion. Our burial and erosion model is characterized by Paleozoic burial that was greater to the east, unroofing that migrated eastward through Jurassic time, and little to no post-Triassic burial. This pattern suggests dynamic and tectonic forces related to Appalachian convergence, subduction cessation, and later rifting as drivers. The AHe data contribute to efforts to collect thermochronology data across the Canadian Shield to map out continental-scale burial and erosion patterns. The outcomes can be used to refine mantle dynamic models and test how dynamic topography, far-field tectonics, and other effects influence the surface histories of continental interiors. Full article

The clumped isotope paleo-thermometer has become a valuable proxy for the burial history reconstruction of carbonate formations. To maximise the accuracy of these reconstructions, post-depositional alterations, such as recrystallisation and Δ₄₇ isotope exchange reactions, must be understood. In this study, we examine the isotopic behaviour of calcites and early dolomite samples from the same stratigraphic intervals, and thus with similar burial history. This approach provides additional constraints on the kinetics of Δ₄₇ reordering in dolomite during exhumation. Clumped isotope measurements were performed on 19 calcites and 15 early dolomites from the Permian, Jurassic, and Cretaceous periods from four locations in Oman spanning different burial regimes. The calcite and dolomite samples were collected from the rock matrix, based on the assumption that fine material was more susceptible to recrystallisation. Our results show that calcites and dolomites record different Δ₄₇ values despite being subjected to the same thermal history. The maximum Δ₄₇ temperature recorded in dolomites (181 ± 13 °C) corresponds to the oldest and most deeply buried Permian rock. This value is approximately 35 °C higher than those measured in the co-located and coeval calcite matrix (145 ± 14 °C). This discrepancy suggests that calcite and dolomite have different kinetic parameters. Our data confirm (1) that dolomite Δ₄₇ values are more resistant to alteration during burial and exhumation than Δ₄₇ calcite values, and (2) that dolomite has a higher Δ₄₇ closing temperature than calcite during cooling. The presence of two mineral phases with distinct kinetic parameters in the same stratigraphic unit provides additional constraints on models of burial and uplift. In addition, mineralogical data coupled with Δ₄₇ and burial depths suggest that the progressive development of dolomite cation ordering is driven by temperature elevation, as previously suggested. Full article

Accretionary and collisional orogeny are often accompanied by the disturbance of the geothermal gradient, leading to high-temperature metamorphism. High-temperature metamorphic rocks are significant in their ability to help the reconstruction of the thermal histories of orogenic belts. The Tianshan Orogenic Belt, at the southwest margin of the Central Asian Orogenic Belt, is a record of the long-term subduction–collision–post-collision orogenic process that has taken place in the Phanerozoic Eon. Here, we report the discovery of mafic granulites in the Muzhaerte area, SW Tianshan. Petrographic observation reveals that the mafic granulites underwent two metamorphic stages. The peak mineral assemblage of the first stage is dominated by clinopyroxene + orthopyroxene + plagioclase + quartz + hornblende (hb¹) ± biotite, and the post-peak mineral assemblage of the second stage is dominated by clinopyroxene + plagioclase + quartz + hornblende (hb²) + biotite. The calculated results obtained from the two-pyroxene thermobarometers and the Al-in-hornblende barometer for the mafic granulites indicate that the metamorphic conditions of mafic granulites are 760–860 °C, <0.39–0.41 Gpa. The mafic granulites recorded a high-grade granulite facies thermal metamorphic event with the highest temperature limit currently recorded in the Central Tianshan Block. Full article

The Arabian–Nubian Shield envelops the entire regional tectonic history from its formation during the Ediacaran to the Red Sea/Gulf of Suez rifting in the Oligocene–Miocene. The occurrence and extent of the expected successive tectonic events on Sinai basement rocks remain uncertain. Integration of thermochronological techniques with time–temperature modelling has proven to be a powerful tool for thermal-tectonic history reconstruction. Therefore, we collected representative samples from the Arabian–Nubian Shield basement rocks of the Wadi Agar area at the eastern flank of the Suez rift. Zircon fission-track data show two cooling age possibilities of Ediacaran and Devonian ages. Meanwhile, apatite fission-track data represent three cooling age spans of Carboniferous, Triassic, and Cretaceous. The integration of these data with the modelled time–temperature histories reveals four different cooling events synchronous with the regional events; (1) the Neoproterozoic post-accretion erosional event that causes near-surface rock uplift, (2) the Devonian–Carboniferous Hercynian tectonic event which affected the region with rocks exhumation of ca. 4.2 ± 1.4 km, (3) the Triassic Gondwana breakup initiation, and (4) the Oligocene–Miocene Gulf of Suez rifting which caused flanks uplift in the studied region of ca. 1.2 ± 0.4 km. The Gulf of Suez is a passive rift with a dominant mechanical component that is divided into two differently exhumed northern and southern segments, where an additional far-field thermal overprint was restricted to the southern segment. Full article

Methanogens can produce methane in anaerobic environments via the methanogenesis pathway, and are regarded as one of the most ancient life forms on Earth. They are ubiquitously distributed across distinct ecosystems and are considered to have a thermophilic origin. In this study, we isolated, pure cultured, and completely sequenced a single methanogen strain DL9LZB001, from a hot spring at Tengchong in Southwest China. DL9LZB001 is a thermophilic and hydrogenotrophic methanogen with an optimum growth temperature of 65 °C. It is a putative novel species, which has been named Methanothermobacter tengchongensis—a Class I methanogen belonging to the class Methanobacteria. Comparative genomic and ancestral analyses indicate that the class Methanobacteria originated in a hyperthermal environment and then evolved to adapt to ambient temperatures. This study extends the understanding of methanogens living in geothermal niches, as well as the origin and evolutionary history of these organisms in ecosystems with different temperatures. Full article