Burial Conditions Research Articles

Origin of dolomites in oolitic carbonates of the Middle Jurassic Dorgali Formation, eastern Sardinia, Italy: Petrographic and geochemical constraints

The Bathonian-Callovian (Middle Jurassic) Dorgali Formation in eastern Sardinia (Italy) consists of dolomitized oolitic grainstone and records a complex diagenetic history. Petrographic examinations revealed three main phases of replacive (D1, D2) and fracture-filling (D3) dolomites with crystal-size ranges of <4–50 μm (dolomicrite to dolomicrosparite D1), 50–200 μm (eu-to subhedral dolomite D2), and 50–400 μm (sub-to anhedral crystals of dolomite D3). The early D1 exhibits dull luminescence (CL) under cathodoluminoscope, whereas the later D2 shows dull to zoned CL, and D3 consistently zoned CL. The near-micritic grainsize, low Sr contents (136 ± 43 ppm) and estimated δ18O values of the parent dolomitizing fluids (−1.3‰ to −0.9‰ VSMOW) suggest an early-diagenesis origin for D1 at low temperatures of near-surface conditions. In contrast, the larger crystal size and microthermometric measurements of primary two-phase fluid inclusions (Th = 101.7 ± 8.0 °C) reveal that D2 precipitated during later stages at higher temperatures of mid-to deeper burial settings, which is supported by the high calculated δ18O values of D2 parent dolomitizing fluids (10.0‰–10.7‰ VSMOW). Petrographic examinations suggest that the vug- and fracture-filling D3 and coarse calcite cement (C3, up to 2 mm) precipitated at deeper burial conditions, which is consistent with the low δ18O (−5.2 ± 1.0‰ VPDB) and δ13C (−5.1 ± 2.6‰ VPDB) compositions of C3. The similarity in shale-normalized REESN patterns, strong negative Ce anomalies and lack of Eu anomalies, suggest a seawater origin for the parent dolomitizing fluids.

Modeling uplift failure of pipes buried in sand using material point method

Uplift of underground pipelines is frequently encountered in urban tunneling and landslide-prone areas, seriously affecting their structural integrity and serviceability. However, the uplift resistance of pipelines and the failure modes of surrounding soils under permanent ground deformation have not been fully understood. In numerical simulations, the element distortion phenomenon significantly restricts the application of mesh-based numerical methods in addressing such issues. In this paper, the material point method (MPM) is used to investigate the upward movement of pipes buried in dense sand and the mobilization of uplift resistance. Two typical constitutive models are used, and their model parameters are estimated using state index, whose values are dependent on relative density and confining pressure. The post-peak softening characteristics of soil have also been considered and a series of numerical simulations are conducted. The results from physical model tests in the literature are used to verify the numerical model. It is found that the experimental and numerical results agree well with each other in terms of force–displacement relationships and soil deformation patterns. The effects of burial depths on the uplift failure mechanism of pipes are investigated in detail. The numerical results show that for shallow burial conditions, the inclination of shear bands is approximately identical to the maximum dilation angle of sand at the peak resistance and then decreases when the pipe undergoes larger uplift displacement, leading to a reduction of uplift resistance. For deeply buried pipes, the inclination of shear bands does not change in the post-peak phase, but a failure pattern with a series of progressive shear zones gradually forms, which is analogous to the bearing failure modes of foundations. At large uplift displacements, significant flow-around phenomena are observed for various burial depths of the pipe. Finally, the distribution profiles of earth pressure acting on the pipe surface are explored. It is found that the normal pressure concentration area mainly rangesfrom 0°–45° from the pipe crown. In comparison, the tangential contact pressure primarily concentrates on the pipe shoulder within 15°–45° from the crown. Finally, the peak uplift forces and corresponding failure modes within the maximum embedment ratio of 50 are investigated to provide practical guidance for the design of underground pipelines.

Forensic examination and application of areca nuts as material evidence

In this study, we aimed to explore the possibility of DNA analysis of areca nut as material evidence and the value of short tandem repeat (STR) typing of areca nut as material evidence under the condition of simulating external environment. In this study, water soaking, soil burial, sun exposure, and wet environment were used to treat areca nut residues. Chelex 100 was used to extract DNA, the PowerPlex21 kit to amplify, and the ABI PRISM® 310 Genetic Analyzer to analyze the DNA of areca nut residues. DNA and STR typing were performed to analyze the residue after chewing. The results showed that the number of residual sites decreased with time under the conditions of water soaking, soil burial, sun exposure, and wet environment. Thus, areca nut can be used as forensic material evidence for DNA analysis and individual identification.

Buckling Mechanism of Offshore Pipelines: A State of the Art

The buckling analysis of an offshore pipeline refers to the analysis of temperature-induced uplift and lateral buckling of pipelines by analytical, numerical, and experimental means. Thus, the current study discusses different research performed on thermal pipe-buckling and the different factors affecting the pipeline’s buckling behaviour. The current study consists of the dependency of the pipe-buckling direction on the seabed features and burial condition; the pre-buckling and post-buckling load-displacement behaviour of the pipeline; the effect of soil weight, burial depth, axial resistance, imperfection amplitude, temperature difference, interface tensile capacity, and diameter-to-thickness ratio on the uplift and lateral resistance; and the failure mechanism of the pipeline. Moreover, the effect of external hydrostatic pressure, bending moment, initial imperfection, sectional rigidity, and diameter-to-thickness ratio of the pipeline on collapse load of the pipeline during buckling were also included in the study. This work highlights the existing knowledge on the topic along with the main findings performed up to recent research. In addition, the reference literature on the topic is given and analysed to contribute to a broad perspective on buckling analysis of offshore pipelines. This work provides a starting point to identify further innovation and development guidelines for professionals and researchers dealing with offshore pipelines, which are key infrastructures for numerous maritime applications.

Thermal Alteration History of the Fenghuoshan Group, Hoh Xil Basin, Northern Tibetan Plateau: Insights From Clumped Isotope Thermometry

AbstractThe carbonate clumped isotope (Δ47) thermometer has been widely used for paleoclimatic and paleo‐elevation reconstructions in sedimentary basins. Its reliable use requires that carbonates are free from later diagenetic alteration and retain their depositional Δ47 compositions, which is not always the case during the burial history of a basin. Therefore, identifying the alteration mechanisms that occurred during burial is essential for the correct interpretation of Δ47 signatures. In this study, we used the Δ47 thermometer to investigate possible carbonate alteration during burial of the Fenghuoshan Group (FHSG) in the Hoh Xil Basin, northern Tibetan Plateau, China. The Δ47 temperatures [T(Δ47)] of 30 carbonate samples through the ∼4.5 km thickness of the FHSG range from 51 to 132°C and exceed the surface temperature, implying the effects of thermal alteration on FHSG carbonates. The T(Δ47) values combined with the water‐rock exchange model, indicating that the alteration occurred under closed burial conditions at low water:rock ratios. The solid‐state reordering model fails to predict the Δ47 values, even with a modified time‐temperature history. In contrast, most measured Δ47 values are in agreement with predictions from recrystallization models. Therefore, the proposed alteration scenario is that FHSG carbonates underwent progressive microscale recrystallization during deep burial and subsequent exhumation, during which process recrystallized carbonate equilibrated with ambient burial temperature and therefore modified Δ47 values. This study highlights the potential of Δ47 thermometry and related models for evaluating the burial history and diagenesis of carbonates in sedimentary basins.

Quantitative estimations of iron oxide minerals in the Late Pleistocene paleosol of the Yangtze River Delta: Implications for the chemical weathering, sedimentary environment, and burial conditions

Iron oxide minerals are widely present in soil and known to be closely associated with soil-forming environments. In this study, a detailed quantitative analysis of the iron oxide minerals in the Late Pleistocene hard clay of the Yangtze River Delta (YRD) was conducted using new integrated methods of magnetism, selective chemical-dissolution, and diffuse reflectance spectroscopy. A variety of established chemical weathering indexes and optically stimulated luminescence (OSL) chronology were also applied in the investigations of the hard clay in the study area. These methods allowed for detailed examinations of the chemical weathering, sedimentary environmental conditions, and the post-depositional processes of the hard clay deposits in the YRD. This study’s A-CN-K diagram revealed that the hard clay had entered an intermediate weathering stage. In addition, various chemical weathering indexes demonstrated that the hard clay had undergone three stages of chemical weathering from bottom to top as follows: 1) A relatively high stage of chemical weathering; 2) A low chemical weathering stage with a slightly increasing trend; and 3) A relatively high chemical weathering stage with a weakly decreasing trend. It was found that when χ, χfd, Fed/Fet, Gt, and Hm/Gt were not reliable indicators of chemical weathering for the hard clay, Fed could be a useful proxy. In the current study, based on the OSL ages and several paleoclimatic proxies, it was suggested that the climate conditions in the YRD had transitioned from a relatively weak to a strong East Asian summer monsoon phase during the periods between the marine oxygen isotope stages (MIS) 4 and MIS 3. Furthermore, the low values of χ and χfd in the hard clay indicated an intense dissolution of fine-grained strong magnetic minerals. Meanwhile, the relatively high Feo/Fed ratios in the superficial horizon displayed the predominance of poorly crystalline forms of iron oxides. In summary, the analysis results implied that the hard clay had undergone post-burial processes of ferrolysis, as well as dissolved organic matter translocation from the overlying Holocene sediment. The aforementioned post-burial processes for the hard clay had occurred under reduction–oxidation cycles, which were mainly driven by the rise of the groundwater levels with the Holocene transgression.

Dolomitization micro-conditions constraint on dolomite stoichiometry: A case study from the Miocene Huangliu Formation, Xisha Islands, South China Sea

The micro-conditions that control dolomitization processes were still not well known in natural environments. Cenozoic “island dolostones” are ideal for examining the processes since they are geologically young and have not experienced deep burial conditions. Miocene dolostones from the Xisha Islands, located in the South China Sea, are similar to those found on Grand Cayman Island, located in the Caribbean Sea. These dolostones are composed of low-Ca dolomite (LCD, < 55 mol % CaCO3; hereafter referred to as %Ca) and high-Ca dolomite (HCD, > 55 %Ca). Individual dolomite crystals are commonly formed entirely of LCD or HCD, and/or HCD cores that are encased by LCD and alternating zones of HCD and LCD (1–10 μm thick). The crystal textures indicate that the LCD and HCD are primary growth features (no obvious recrystallization) that formed as the dolomite replaced the limestone precursor. The compositional features (%Ca in LCD and HCD, average %Ca, and proportion of LCD and HCD) and geochemical parameters (O/C isotopes, Sr, Fe and Mn) of dolomite indicate that the Mg was incorporated into dolomite crystals in an orderly manner that was mainly controlled by the interaction of fluid properties and crystal structure. The fact that dolomite stoichiometry varied laterally and vertically throughout the successions shows that micro-scale physicochemical conditions played a critical role in the evolution of individual dolomite crystals. The similarities between the dolostones of the Xisha Islands and Grand Cayman, which are 15,795 km apart, indicate that the factors that control the micro- and large-scale features of these dolostones must have undergone similar processes or experienced similar physicochemical conditions despite their disparate settings.

Unique chemical parameters and microbial activity lead to increased archaeological preservation at the Roman frontier site of Vindolanda, UK

Waterlogged burial conditions impact upon artefact preservation. One major determinant of preservation is presence and behaviour of microorganisms, however, unravelling the mechanisms, especially in waterlogged conditions is challenging. In this study, we analysed elemental composition, bacterial diversity and community structure from excavation trenches at the Roman Site of Vindolanda, Northumberland, UK, using pXRF and 16S rRNA gene amplicon sequencing. Excavation trenches provide information of different occupation periods. The results indicated that microbial communities were dominated by Firmicutes, Bacteroidetes and Proteobacteria at a phylum level. Samples which also had visible vivianite presence showed that there were marked increases in Methylophilus. Methylophilus might be associated with favourable preservation in these anaerobic conditions. More research is needed to clearly link the presence of Methylophilus with vivianite production. The study emphasises the need for further integration of chemical and microbiome approaches, especially in good preservation areas, to explore microbial and chemical degradation mechanisms.

The Effect of Different Coverings on Total Body Score Development of Buried Carcasses.

BackgroundExamination of post-mortem changes is one of the ways to assess decomposition process on buried bodies. Nonetheless, studies on such assessment are still lacking, especially on the effects of body coverings by different materials in burial conditions. The aim of this research is to study the effect of different types of covering towards decomposition on buried rabbit carcasses by using Total Body Score (TBS) system.MethodsTwenty-seven rabbit carcasses were divided into: (i) No Clothing; (ii) Thick Clothing and (iii) Plastic Wrapping groups, and buried into individual shallow graves. One subject was exhumed from first to ninth post-burial week and assessed by using TBS system.Results and DiscussionThere are significant differences among TBS between different coverings while controlling the time factor, F (2, 23) = 4.80, P < 0.05, partial η2 = 0.294. TBS score for Plastic Wrapping group is significantly lower than No Clothing group over times at α = 0.05, P < 0.05. The slightly delaying effect of thick clothing is caused by design of jacket, which allows arthropods access and microbial activity. Relatively strong delaying effect by plastic covering could be caused by impermeable property that caused accumulation of decompositional products and slow down the degradation.ConclusionIn conclusion, TBS system is a potential tool in describing rate of decomposition for buried cases in Malaysia.

Examining collagen preservation through glutamine deamidation at Denisova Cave

The use of glutamine deamidation has been controversially proposed as a means of measuring relative decay in archeological bones using peptide mass fingerprinting data. If reliable, it could be used to identify intrusive fossils in stratigraphic layers and relatively date unprovenanced remains. However, growing empirical evidence suggests that there is no reliable link between glutamine deamidation and chronological age. To explore this and understand what contribution, if any, glutamine deamidation can make to our understanding of the archeological record we analyze 2459 fossils using MALDI-TOF MS from the East Chamber of Denisova Cave where robust chronological studies have been carried out and burial conditions are well understood. We then compare these results with additional data from 15 fossils measured using LC-MS/MS and the recently published deamiDATE tool. Our results reveal that intra and inter layer variability is too high to be able to detect a pattern of deamidation at Denisova Cave, suggesting caution should be applied when attempting to link deamidation with relative decay or chronological age.

Raman approach to the forensic study of bronze patinas

Illicit trade in archaeology is a widespread phenomenon connected to the market of archaeological objects from clandestine excavations or faking manufacture, which includes bronze objects. As a consequence, authentication and provenance studies are required on objects of unknown provenance when they are recovered thanks to the investigation activity of the police, before returning them to the museums. Various strategies and approaches can be used to identify fake bronzes, as for instance patinas studies, since the corrosion can spontaneously occur over time, due to the interaction of the surface with the environment, or induced by artificial treatments, performed to mimic the archaeological aging effects in short time. The artificial patina has outward appearance and colours very similar to the natural patinas, but with different mineralogical composition. In this work, Raman spectroscopy is used to discriminate between artificial and natural patinas by a non-destructive approach, supported by the microanalysis SEM-EDS and optical microscope observations in the case of two ‘Etruscan-Roman’ bronze statuettes of illicit and unknown provenance, and demonstrates their recent and fake manufacture. Indeed, the patinas of both statuettes contain covellite, antlerite, langite, chalcanthite and rouaite, minerals or metastable chemical species traced back to corrosion induced by chemical attack and thermal treatment, as distinct from their stable polymorphs usually formed in burial condition. Moreover, we have not found evidence of the presence of malachite and azurite, typical of natural aged patinas. Finally, the abundance of Zn in the alloy suggest a modern manufacture.

Conditions for uranium biomineralization during the formation of the Zoovch Ovoo roll-front-type uranium deposit in East Gobi Basin, Mongolia

The Zoovch Ovoo uranium roll-front-type deposit is hosted in the Sainshand Formation, a Late Cretaceous siliciclastic reservoir, which constitutes the upper part of the post-rift infilling of the Mesozoic East Gobi Basin in SE Mongolia. The Sainshand Formation consists of unconsolidated medium-grained sand, silt and clay intervals deposited in fluvial-lacustrine settings. The uranium deposit is confined within a 60–80 m thick siliciclastic sequence inside aquifer-driven systems. The overall system experienced shallow burial and was never subjected to temperatures higher than 40 °C. This study proposes a comprehensive metallogenic model for this uranium deposit. Sedimentological and mineralogical observations from drill core samples to the microscopic scale (optical and Scanning Electron Microscopy) together with in situ geochemistry of late-formed phases (Laser Ablation–Inductively Coupled Plasma Mass Spectrometry, Electron Probe Microanalysis, Fourier Transform–Infrared Spectroscopy) were considered for the reconstruction of the main stages of U trapping.In the mineralized zone, the uranium ore is expressed as Ca–enriched uraninite (UO2) and less commonly as Ca–enriched phospho-coffinite (U, P)SiO4. Trapping mechanisms include i) complexation (i.e. uranyl-carboxyl complexes), ii) adsorption on organic or clay particles) and iii) reduction by pyrite and by bacterial activity to amorphous uraninite. In all cases, the organic matter plays either the role of trap for uranium or nutrient for bacteria that can trap uranium through their metabolism. The shallow burial diagenesis conditions do not allow direct reduction of U(VI) by organic carbon. The δ34S values of the iron disulfide are very diverse, fluctuating in extreme cases between −50 to + 50‰, with an average δ34S value for framboidal pyrite at 2‰, and −20‰ for euhedral pyrite. The positive and negative values reflect close versus open fractionation systems, while bacterial sulphate reduction (BSR) is active during the whole diagenetic history of the deposit as an essential source of reduced sulfur. Therefore, using detrital organic matter as a carbon source, microorganisms play a significant role in uranium trapping, either as a direct reducing agent for uranium or pyrite formation, which will trap uranium through redox driven epigenetic processes.

Cd absorption characteristics of Suaeda salsa under different sediment burial and exogenous Cd input conditions in the Yellow River estuary, China.

Suaeda salsa (L.) Pall., a typical halophyte plant in the Yellow River estuary, has high enrichment capacity for heavy metals. However, few studies have investigated the Cd absorption characteristics of S. salsa under different sediment burial and exogenous Cd input conditions, especially following the water-sediment regulation scheme (WSRS), which brought sediment burial and exogenous substances to the estuary. So, we established a greenhouse pot culture experiment with four sediment burial depths (0 cm, 3 cm, 6 cm, and 12 cm) and exogenous Cd input levels (0 mg·kg-1, 0.5 mg·kg-1, 1.0 mg·kg-1, and 1.5 mg·kg-1) and analyzed the leaf, stem, root, and total biomass; leaf, stem, and root Cd content; and storage, sediment Cd content, accumulation factor, root/leaf (R/L), root/stem (R/S), and stem/leaf (S/L) ratios to study the Cd absorption characteristics of S. salsa under the different sediment burial and exogenous Cd input. Results showed that high Cd content in roots, stems, and leaves was harmful to S. salsa growth, and then led to a decrease in biomass (characterized by stem, leaf, and total biomass). Suaeda salsa exhibited a survival strategy to deal with Cd toxicity, which involved the roots absorbing Cd from the sediment and storing it in stems and leaves (stem and leaf Cd content peaked at 0.5 mg·kg-1 Cd input) at low Cd input, whereas roots stored more Cd and reduced Cd transport to stems and leaves at high Cd input. Therefore, we observed the maximum value of leaf (500.63 ± 19.15 g·m-2), stem (648.22 ± 50.08 g·m-2), and total biomass (1246.92 ± 55.49 g·m-2) in the treatment with 1.5 mg·kg-1 Cd input and 3-cm sedimentdepth due to the Cd content in leaves and stems being relatively low. The accumulation factors of leaves, stems, and roots varied (0.39-0.99, 0.19-2.58, and 0.80-20.45, respectively), and most of the accumulation factors for roots and leaves and the R/L and R/S ratios were >1, which indicated that S. salsa had high enrichment levels of Cd, which mostly accumulated in the roots. Shallow or moderate burial depth was beneficial to S. salsa growth, but sediment burial was not beneficial to Cd absorption because the sum of leaf, stem, and root Cd storage was higher at 0-cm depth compared with the other depths. Variance analysis showed that the influence of Cd input on leaf, stem, root, and sediment Cd content and stem and root Cd storage was significant (P < 0.05), whereas sediment burial, interaction of sediment burial and Cd input on Cd content, storage, and biomass were not significant (P > 0.05). Therefore, we concluded that more attention should be paid to the control of sediment burial and heavy metal input, especially during the WSRS, in the Yellow River estuary.

Synthetic glass and jute fabric reinforced soy-based biocomposites: Development and characterization

In this work, both glass fabric and jute fabric reinforced nanoclay modified soy matrix-based composites were developed and characterized. Glass fabric (60 wt.%) reinforced composite showed maximum tensile strength of 70.2 MPa and thermal stability up to 202°C, which are 82.8% and 12.2% higher than those observed with corresponding jute composite. Water absorption and contact angle values of glass-soy specimens were tested, and found composites are water stable. Biodegradation study of composites under soil burial condition revealed that glass-soy composite with 40 wt.% glass fabric lost maximum 32.6% of its original weight after 60 days of degradation. The developed glass fabric-soy hybrid composites with reasonable mechanical, thermal, and hydrolytic stability can be used in different sectors as an alternative to the nondegradable thermoplastic reinforced glass fabric composites.

Biosynthesized Poly(3-Hydroxybutyrate) on Coated Pineapple Leaf Fiber Papers for Biodegradable Packaging Application.

This paper is aimed at investigating the usage of biosynthesized poly(3-hydroxybutyrate) (P(3-HB)) for a coating on pineapple leaf fiber paper (PLFP). For this purpose, (P(3-HB)) was produced by Rhodococcus pyridinivorans BSRT1-1, a highly potential P(3-HB) producing bacterium, with a weight-average molecular weight (Mw) of 6.07 × 10 −5 g/mol. This biosynthesized P(3-HB) at 7.5% (w/v) was then coated on PLFP through the dip-coating technique with chloroform used as a solvent. The respective coated PLFP showed that P(3-HB) could be well coated all over on the PLFP surface as confirmed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The brightness and mechanical properties of PLFP could be improved by coating with biosynthesized P(3-HB) in comparison to commercially available P(3-HB) and non-coated PLFP. Furthermore, coating of P(3-HB) significantly increased the water drop penetration time on the surface of PLFP and was similar to that of the commercial P(3-HB) with the same content. The results showed that all the coated PLPF samples can be degraded under the soil burial test conditions. We have demonstrated that the P(3-HB) coated PLFP paper has the ability to prevent water drop penetration and could undergo biodegradation. Taken together, the P(3-HB) coated PLFP can be applied as a promising biodegradable paper packaging.

Fast Preparation of Flexible Wet-Resistant and Biodegradable Films From a Stable Suspension of Xylan/Chitosan Polyelectrolyte Complexes

Novel hemicellulose-based films from polyelectrolyte complexes (PECs) of chitosan and xylan from sugar cane bagasse were prepared and characterized. PEC suspension from two different xylan to chitosan mass ratios (70/30 and 80/20) were considered. With the aim of shorten the whole film preparation process, PEC suspension was concentrated through a fast evaporation stage before casting. Results show that the concentration stage did not modify neither the size of the complexes, i.e., a size distribution with a mode at 450 nm and other at 5000 nm, nor the mechanical properties of the films. By the increment in xylan content from 70 to 80%, the strain at break was decreased (up to a value of 7%), the stress at break was increased (up to 22 MPa) and the swelling of the films was increased from 80 to 90%. After 25 days under aerobic burial conditions, degradation of the films was similar to cellulose.

Oxygen isotope (δ18O) trends measured from Ordovician conodont apatite using secondary ion mass spectrometry (SIMS): Implications for paleo-thermometry studies

Abstract The oxygen isotopic compositions (δ18O) of minimally altered phosphate minerals and fossils, such as conodont elements, are used as a proxy for past ocean temperature. Phosphate is thermally stable under low to moderate burial conditions and is ideal for reconstructing seawater temperatures because the P-O bonds are highly resistant to isotopic exchange during diagenesis. Traditional bulk methods used to measure conodont δ18O include multiple conodont elements, which can reflect different environments and potentially yield an aggregate δ18O value derived from a mixture of different water masses. In situ spot analyses of individual elements using micro-analytical techniques, such as secondary ion mass spectrometry (SIMS), can address these issues. Here we present 108 new δ18O values using SIMS from conodont apatite collected from four Lower to Upper Ordovician stratigraphic successions from North America (Nevada, Oklahoma, and the Cincinnati Arch region of Kentucky and Indiana, USA). The available elements measured had a range of thermal alteration regimes that are categorized based on their conodont alteration index (CAI) as either low (CAI = 1–2) or high (CAI = 3–4). Though individual spot analyses of the same element yield δ18O values that vary by several per mil (‰), most form a normal distribution around a mean value. Isotopic variability of individual spots can be minimized by avoiding surficial heterogeneities like cracks, pits, or near the edge of the element and the precision can be improved with multiple (≥4) spot analyses of the same element. Mean δ18O values from multiple conodonts from the same bed range between 0.0 and 4.3‰ (median 1.0‰), regardless of low or high CAI values. Oxygen isotopic values measured using SIMS in this study reproduce values similar to published trends, namely, δ18O values increase during the Early–Middle Ordovician and plateau by the mid Darriwilian (late Middle Ordovician). Twenty-two of the measured conodonts were from ten sampled beds that had been previously measured using bulk analysis. SIMS-based δ18O values from these samples are more positive by an average of 1.7‰ compared to bulk values, consistent with observations by others who attribute the shift to carbonate- and hydroxyl-related SIMS matrix effects. This offset has implications for paleo-temperature model estimates, which indicate that a 4 °C temperature change corresponds to a 1‰ shift in δ18O (‰). Although this uncertainty precludes precise paleo-temperature reconstructions by SIMS, it is valuable for identifying spatial and stratigraphic trends in temperature that might not have been previously possible with bulk approaches.

Mechanical and Biodegradation Behaviour of Jute/ Polylactic Acid Green Composites

Global warming, diminution of fossil fuels, escalating oil price’s are the major reasons which forces the researchers to develop green products for the sustainable development. In this research work, green composites have been developed with jute fibers as reinforcement and poly lactic acid as matrix material using compression moulding technique. All composites were developed with maintaining the reinforcement as 30% fiber volume fraction. The influence of curing temperature with the range of 160°C, 170°C and 180°C was investigated for various mechanical properties of developed composites and degradation behaviour of developed composites were analysed using soil burial test. Results acquired from the tests specify that the tensile and flexural strength decreases with upsurge in curing temperature. Morphology study using scanning electron microscopy is further justified the findings obtained from mechanical tests. Biodegradation study was done on the all the three different composites under the soil burial conditions for 9 months and results indicate that composites developed at 160°C degrade faster as compared to others. This study also gives an optimum curing temperature for the development of jute/PLA composites.

Along-dip variations of subduction fluids: The 30–80 km depth traverse of the Schistes Lustrés complex (Queyras-Monviso, W. Alps)

The Queyras-Monviso traverse of the Schistes Lustrés complex, is a stack of underplated nappes of oceanic rocks subducted from blueschist- to eclogite-facies conditions.This study reports on salinities and gas contents of primary fluid inclusions trapped in high pressure veins from metasediments and metamafic rocks (445 fluid inclusions in 22 samples). These data provide snapshots of the compositions of fluids present at peak burial conditions, varying from ~30 to 80 km depth and illustrate the evolution of fluid composition with burial along a cold subduction zone.Fluid inclusions trapped in lawsonite- and carpholite-bearing veins in metasediments contain moderately saline aqueous fluids (average salinity of 4.6 wt% NaCl eq.) with subordinate amounts of CO2 and CH4 in the vapor phase. The observed salinity decrease with increasing grade is interpreted as reflecting progressive dilution of initial seawater-like pore fluid by low-salinity fluids released locally by dehydration reactions. Less-frequently measured higher salinities in the uppermost metasedimentary-dominated tectonic unit suggest brine infiltration from embedded blocks of margin units containing evaporites. CO2 and CH4 (and scarce potential hydrocarbons) appear to be locally released from fluid interaction with carbonates and carbonaceous matter-rich pelitic horizons, respectively.Fluid inclusions in high pressure omphacite veins in metagabbros record higher salinities (mean salinity about 17 wt% NaCl eq.) with small amounts of N2 in eclogitic veins only, and a variety of minerals (calcite, white mica, salts) indicative of complex chemical systems. These high salinities are interpreted as partly inherited from seafloor high-temperature hydrothermal alteration of gabbros, resulting in phase separation and brine formation. Progressive breakdown of hydrothermal Cl-rich amphibole to glaucophane (blueschist-facies) and then omphacite (eclogite-facies) and release of brines trapped in fluid inclusions could account for the high salinity fluids. Therefore, in metagabbros, fluid inclusions record progressive release of Cl in the fluid phase with increasing grade.Fluid signatures of metasediments and metamafics appear characteristic of each rock type. Local fluid signatures and redox conditions were preserved within units, possibly due to restricted and transient fluid circulation (at the hm-scale at most).Fluid inclusions in Alpine metasediments show salinities and gas contents comparable with other subducted fragments of oceanic lithosphere worldwide, whereas fluid salinities of Alpine metagabbros are higher than salinities recorded elsewhere, either due to (1) higher-temperature hydrothermal alteration and brine formation in Alpine metagabbros (compared to metavolcanics) or (2) more restricted infiltration by sediment-derived fluids compared to block-in-mélange subduction complexes.

Quartz Vein Geochemistry Records Deformation Processes in Convergent Zones

AbstractIn several examples of subduction zones, we compared pairs of quartz veins formed either at the lower temperatures of the seismogenic zone (260°C or below), or at the higher temperatures of its downdip limit (∼330°C). All the veins analyzed here are mode I cracks that formed contemporaneously with the host‐rock main stage of deformation at peak burial conditions. Lower‐temperature veins show examples of quartz crystals with euhedral shapes and growth rims, while higher‐temperature veins contain crack‐seal microstructures. In the lower‐temperature realm, quartz growth rims have alternatingly either: (1) high cathodoluminescence (CL), CL‐blue color and high concentration in trace elements and fluid inclusions, or (2) low luminescence, CL‐brown color and low concentration in trace elements and fluid inclusions. In contrast, the quartz from higher‐temperature samples is homogeneously low luminescent and CL‐brown, except for very restricted domains of the crack‐seal microstructures where patches of CL‐blue quartz are present. The highly luminescent quartz contains high concentrations of aluminum and lithium, up to 3,000 and 400 ppm, respectively. Variations in Al and Li correlate well, so that Li appears as the main charge‐compensating cation for Al. We propose that the incorporation of Al and Li reflects the amplitude of the fluid pressure variations, which control crystal growth rates. Quartz geochemistry might therefore unravel the contrast between the seismogenic zone, where large fluid pressure variations are present, and its downdip limit, where fluid pressure variations are much more limited in amplitude.