High Pressure Low Temperature Research Articles

Cretaceous thermal evolution of the closing Neo-Tethyan realm revealed by multi-method petrochronology

A Cretaceous paleo-accretionary wedge, the Ashin Complex, now exposed along the Zagros suture zone in southern Iran, exhibits mafic, metasedimentary and ultramafic lithologies. Field, geochemical and petrological observations point to an anomalous high-temperature event that gave rise to the formation of peritectic (trondhjemitic) melts associated with restitic garnet-bearing amphibolites. Lu-Hf isotopic dating of centimetre-sized garnet in amphibolite-facies metasediments yielded a crystallization age of 113.10 ± 0.36 Ma, possibly representing the age of prograde to near-peak metamorphic conditions. SHRIMP U-Th-Pb zircon dating from trondhjemitic leucosomes yields crystallization ages of 104 ± 1 Ma, interpreted as the age of the temperature peak, which occurred in the upper amphibolite-facies (c. 650–680 °C at 1.1–1.3 GPa), according to thermodynamic modelling and Ti-in-zircon thermometry. Rutile crystals from two leucosomes yield Zr-in-rutile temperatures in the range of 580–640 °C and a LA-ICP-MS U-Pb age range from 85 to 112 Ma, interpreted as a consequence of partial re-equilibration during incipient cooling. A late static recrystallization event is indicated by the presence of sodic-calcic clinopyroxene, sodic amphibole, Si-rich phengite, titanite overgrowths after rutile and lawsonite within former leucosomes and late fractures. This mineral assemblage is a typical blueschist-facies (high pressure-low temperature) paragenesis and is interpreted as reflecting long-term isobaric cooling that occurred until the end of the Cretaceous as a consequence of increasing slab thermal age. This first report of a melting event in the Zagros paleo-accretionary wedge reveals the presence of a transient, abnormally high thermal gradient of c. 18 °C/km that occurred at c. 105–113 Ma. We speculate that this could be explained by the subduction of a thermal anomaly such as a seamount chain, a transform fault system or, more likely, a spreading ridge under the southern Iranian margin. Indeed, paleogeographic reconstructions of the Tethyan realm suggest the entrance of the Northern Tethyan basin ridge into the subduction zone shortly after 120 Ma.

Trace and Rare Earth Element Compositions of Lawsonite as a Chemical Tracer of Metamorphic Processes in Subduction Zones

AbstractLawsonite is a major host mineral of trace elements (TEs; e.g. REE, Sr, Pb, U, Th) and H2O in various rock types (metabasite, metasediment, metasomatite) over a wide range of depths in subduction zones. Consequently, the composition of lawsonite is a useful archive to track chemical exchanges that occurred during subduction and/or exhumation, as recorded in high-pressure/low-temperature (HP/LT) terranes. This study provides an extensive dataset of major element and TE compositions of lawsonite in HP/LT rocks from two mélanges (Franciscan/USA; Rio San Juan/Dominican Republic), two structurally coherent terranes (Tavşanlı/Turkey; Alpine Corsica/France), and the eclogite blocks of the Pinchi Lake/Canada complex. Bulk major and TE compositions were also determined for lawsonite-bearing host rocks to understand petrogenesis and assess compositional evolution. Most analyzed mélange and coherent-terrane metabasalts have normal mid-ocean ridge/back-arc basin basalt signatures and they preserve compositional evidence supporting interactions with (meta)sediment ± metagabbro/serpentinite (e.g. LILE/LREE enrichments; Ni/Cr enrichments). Most lawsonite grains analyzed are compositionally zoned in transition-metal elements (Fe, Ti, Cr), other TEs (e.g. Sr, Pb), and/or REE, with some grains showing compositional variations that correlate with zoning patterns (e.g. Ti-sector zoning, core-to-rim zoning in Fe, Cr-oscillatory zoning). Our results suggest that compositional variations in lawsonite formed in response to crystallographic control (in Ti-sector zoning), fluid–host rock interactions, modal changes in minerals, and/or element fractionation with coexisting minerals that compete for TEs (e.g. epidote, titanite). The Cr/V and Sr/Pb ratios of lawsonite are useful to track the compositional influence of serpentinite/metagabbro (high Cr/V) and quartz-rich (meta)sediment (low Sr/Pb). Therefore, lawsonite trace and rare earth element compositions effectively record element redistribution driven by metamorphic reactions and fluid–rock interactions that occurred in subduction systems.

Late Carboniferous extension-related magmatism in the southwestern Alxa block of NW China: geochronology, geochemistry, and tectonic implications

ABSTRACT Whether the northern margin of the North China Craton (NCC) was a continental arc or in a lithospheric extensional setting during the Carboniferous is the primary divergence among different tectonic models about the terminal evolutionary history of the southeastern Central Asian Orogenic Belt (CAOB). The Alxa block is the western segment of the northern NCC and contiguous to the southeastern CAOB, and therefore the tectonic setting of the Carboniferous magmatic intrusions in this block can shed light on this controversy. In this contribution, new zircon U–Pb ages, elemental geochemistry, and Sr-Nd isotopes are presented for thirteen Late Carboniferous (~318–300 Ma) magmatic intrusions in the southwestern Alxa block. Among them, seven calc-alkaline I-type granites and one aluminous A2-type granite were probably generated by the partial melting and crystallization differentiation of various crustal sources (perhaps including earlier orogenic materials) under different temperature conditions. Four quartz diorites and one hornblende gabbro may be the partial melts of subduction-modified basaltic lower crust sources and sub-continental lithospheric mantle sources, respectively. According to the integration of the new results and regional geological correlations, the Alxa block and the southeastern CAOB were most likely in a uniform tectonic regime during the Carboniferous. At that time, this region was characterized by the lithospheric extension-related magmatic rock associations, the increasing mantle inputs over time, the clockwise P–T paths of high temperature-low pressure metamorphic rocks, and the transgression sedimentary sequences. All these lines of evidence suggest an intra-continental lithospheric extensional setting rather than a continental arc setting for the southeastern CAOB during the Carboniferous.

Experimental and numerical study of the thermal and hydraulic performance of fin array with wedge shield in bypass

In this study, the thermal and hydraulic performances of fin array with a wedge shield installed in the bypass to alter the flow were experimentally and numerically investigated. The effect of the wedge shield inclination angle was explored at Reynolds numbers ranging from 2753 to 20,825. The mean Nusselt number and friction factor were measured in a wind tunnel with the varying volume rate of inlet air flow. The comprehensive performance evaluation criteria under identical pressure drop and identical pumping power were adopted to evaluate the effect of the wedge shield. The velocity, temperature and pressure fields, and the local Nusselt number were characterized using ANSYS Fluent. The results indicated that the heat transfer enhanced and the flow resistance increased by the wedge shield effect. At a same Reynolds number, the mean Nusselt number and friction factor reach their maximum values at θS=10∘ and θS=60∘, respectively. According to the comprehensive performance evaluation, the applicable condition of wedge shield to enhance fin array performance was the inclination angle θS=135∘ at Reynolds number Re=3286, in which the enhancement was approximately 9% under identical pressure drop and 14% under identical pumping power. The numerical results showed that the velocity increase in fin channel and recirculation zone, caused by the blockage of the wedge shield, was the fundamental mechanism of wedge shield to enhance the heat transfer and increase the flow resistance. The velocity increase and recirculation zone, along with the low temperature region and high pressure in the entrance region of the fin channel caused by them, were all affected by the wedge shield inclination angle.

The Maira-Sampeyre and Val Grana Allochthons (south Western Alps): review and new data on the tectonometamorphic evolution of the Briançonnais distal margin

Here we describe the structure, the high-pressure, low-temperature (HP-LT) metamorphism and tectonic evolution of the Briançonnais distal margin units from the south Western Alps. The studied area extends southwest of the Dora-Maira (U)HP basement units and east-southeast of the classical Briançonnais nappes. A new structural map accompanied by geological profiles shows the thrusting of the oceanic nappes (Monviso and Queyras units) onto the distal Briançonnais units (D1 and D2 late Eocene deformation phases) under blueschist-facies conditions. Subsequent deformation during the Early Oligocene (D3 deformation phase) took place under greenschist-facies conditions and was associated with back-folding and -thrusting in the units overlying the Dora-Maira massif and with exhumation related to normal reactivation of former thrusts within the latter massif. Two large cover units, detached from their former distal Briançonnais basement, are redefined as the Maira-Sampeyre and Val Grana Allochthons (shortly: Maira-Grana Allochthons = MGA) including, (i) the Val Maira-Sampeyre unit involving Lower and Middle Triassic formations, seemingly detached from the Dora-Maira units during the subduction process, and (ii) the Val Grana unit with Middle-Upper Triassic and Early-Middle Jurassic formations, which was probably detached from the Maira-Sampeyre unit and correlates with the “Prepiemonte units” known from the Ligurian Alps to the Swiss Prealps. Three major shear zones involving tectonic mélanges of oceanic and continental rocks at the base of the Val Grana, Maira-Sampeyre and Dronero units testify to an early phase of exhumation within the subduction channel in front of the Adria plate. We present a new metamorphic map based on published and new petrological data, including new thermometric data obtained by Raman spectroscopy of carbonaceous material (RSCM). The TRSCM values range from ~ 400 °C to > 500 °C, going from the most external Val Grana unit and overlying Queyras schists to the uppermost Dora-Maira unit. During the Late Triassic, the width of the Briançonnais s.l. domain can be restored at ~ 100 km, whereas it reached ~ 150 km after the Jurassic rifting. A significant, second rifting event affected the Briançonnais domain during the Late Cretaceous-Paleocene, forming the Longet-Alpet chaotic breccias, which deserve further investigations.

Subduction, Underplating, and Return Flow Recorded in the Cycladic Blueschist Unit Exposed on Syros, Greece

AbstractExhumed high‐pressure/low‐temperature (HP/LT) metamorphic rocks provide insights into deep (∼20–70 km) subduction interface dynamics. On Syros Island (Cyclades, Greece), the Cycladic Blueschist Unit preserves blueschist‐to‐eclogite facies oceanic‐ and continental‐affinity rocks that record the structural and thermal evolution linked to Eocene subduction. Despite decades of research, the metamorphic and deformation history (P‐T‐D) and timing of subduction and exhumation are matters of ongoing discussion. We suggest that Syros comprises three coherent tectonic slices and that each slice underwent subduction, underplating, and syn‐subduction return flow along similar P‐T trajectories, but at progressively younger times. Subduction and exhumation are distinguished by lineations and ductile fold axis orientations, and are kinematically consistent with previous studies that document top‐to‐the‐S‐SW shear (prograde‐to‐peak subduction), top‐to‐the‐NE shear (blueschist facies exhumation), and then E‐W coaxial stretching (greenschist facies exhumation). Amphibole zonations record cooling during decompression, indicating return flow above a cold slab. Multi‐mineral Rb‐Sr isochrons and compiled metamorphic geochronology show that the three slices record distinct stages of peak subduction (53–52, ∼50, and 45 Ma) that young with structural depth. Retrograde blueschist and greenschist facies fabrics span ∼50–40 and ∼43–20 Ma, respectively, and also young with structural depth. Synthesized data sets support a revised tectonic framework for Syros, involving subduction of structurally distinct coherent slices and simultaneous return flow of previously accreted tectonic slices in the subduction channel shear zone. Distributed, ductile, dominantly coaxial return flow in an Eocene‐Oligocene subduction channel proceeded at rates of ∼1.5–5 mm/yr and accommodated ∼80% of the total exhumation of this HP/LT complex.

A Low-Temperature-Sensitivity Resonant Pressure Microsensor Based on Eutectic Bonding

This paper presented a temperature-insensitive resonant pressure microsensor where silicon based resonators anchored on a pressure-sensitive diaphragm were vacuum packaged by a silicon cap based on eutectic bonding. Incoming pressures deformed the pressure-sensitive diaphragm and built stresses around resonators for frequency modulation while under temperature challenges, deformations of silicon based resonators and the vacuum cap were consistent and thus no stresses were generated on resonators. The temperature-insensitive resonant pressure microsensor was analyzed in both theoretical analysis and numerical simulations with confirmed high pressure sensitivities and low temperature disturbances. The resonant pressure microsensor was then fabricated by key steps of photolithography, deep reactive ion etching, and eutectic bonding and characterized in both open-loop and close-loop testing systems. Characterization results showed that the quality factors of resonators were <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 10000$ </tex-math></inline-formula> with pressure sensitivity of 82.98 Hz/kPa and temperature disturbance of −0.63 Hz/° (the lowest result among previously reported resonant pressure microsensors). In summary, the temperature-insensitive resonant pressure microsensor developed in this study exhibited a fitting accuracy better than 0.02% FS within the pressure range of 10 to 120 kPa and the temperature range of −45 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$85^{\circ }\text{C}$ </tex-math></inline-formula> .

Serpentinite Diapirs and the Evolution of Oceanic Core Complexes

Serpentinites and peridotites are the predominant lithological components of Oceanic Core Complexes (OCCs), located commonly at triple junctions of slow-spreading oceanic accreting ridges, fracture zones and transform faults. These lithologies differ from the surrounding oceanic brittle lithosphere, built of basalt and gabbro, and the structural evolution of these OCCs is enigmatic. The present investigation suggests that the tectonics of OCCs is derived from the ascent of serpentinic diapirs generated by the unique proximity of shallow asthenosphere, faulted lithosphere and the juxtaposition of oceanic crusts of contrasting densities. Such setting initiated two structural stages in the evolution of the OCC, the first is spontaneous subduction of old and dense oceanic crust under the fresh and lighter basalt at the edge of the MOR across its intersection with transform fault - fracture zone. The sub ducted slab would be affected by the combined effect of the steep thermal gradient and the availability of volatiles there to enhance the alteration of pyroxene into serpentine. Analog and numeric experiments show that spontaneous subduction can initiate spontaneously if the density contrast between the juxtaposed slabs is significant, as is the case between fresh basalt (ρ~2.7 g/cm3 ) and older basalt (ρ~2.9 g/cm3 ). Since the average thermal gradient under the MOR is ca. 130o /km, then at depth of 4-5 km the pyroxene and plagioclase would start their alteration, mostly to serpentine. The abundant faults of MOR normal rifting and strike-slip transform faulting could enable the light and malleable serpentinite to form diapirs, which would ascent to the seafloor at the rift-fracture zone intersections. The friction at the top of the diapirs during their ascent would probably generate breccia at their tops. Highlights a) OCCs are built mostly of serpentinite diapirs that carry peridotite inclusions. b) Serpentinization occurs under low pressure-high temperature conditions. c) OCC source rock is slab of cold oceanic crust sub ducted under fresh crust. d) Such subduction occurs mostly where large density contrast between slabs exists. e) The link between OCCs and detachment normal faults requires support.

Analyzing structural features of proteins from deep-sea organisms.

Protein adaptations to extreme environmental conditions are drivers in biotechnological process optimization and essential to unravel the molecular limits of life. Most proteins with such desirable adaptations are found in extremophilic organisms inhabiting extreme environments. The deep sea is such an environment and a promising resource that poses multiple extremes on its inhabitants. Conditions like high hydrostatic pressure and high or low temperature are prevalent and many deep-sea organisms tolerate multiple of these extremes. While molecular adaptations to high temperature are comparatively good described, adaptations to other extremes like high pressure are not well-understood yet. To fully unravel the molecular mechanisms of individual adaptations it is probably necessary to disentangle multifactorial adaptations. In this study, we evaluate differences of protein structures from deep-sea organisms and their respective related proteins from nondeep-sea organisms. We created a data collection of 1281 experimental protein structures from 25 deep-sea organisms and paired them with orthologous proteins. We exhaustively evaluate differences between the protein pairs with machine learning and Shapley values to determine characteristic differences in sequence and structure. The results show a reasonable discrimination of deep-sea and nondeep-sea proteins from which we distinguish correlations previously attributed to thermal stability from other signals potentially describing adaptions to high pressure. While some distinct correlations can be observed the overall picture appears intricate.

Effect of Graphene Addition on the Thermal and Persistent Luminescence Properties of Gd2.994Ce0.006Ga3Al2O12 and Gd2.964Ce0.006Dy0.03Ga3Al2O12 Ceramics.

The gadolinium, gallium, aluminum garnet doped with cerium and co-doped with dysprosium ions were prepared using sol gel method. The SEM images show that after synthesis, the grains are below 100 nm. The powders were ultrasonically mixed with graphene nanoflakes and ceramics were prepared using the high pressure low temperature sintering technique. A series of the ceramics was prepared using different graphene content. The structure of the samples was examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman techniques. The spectroscopic properties were checked using conventional and persistent luminescence spectra measurements. The thermoluminescence glow curves and fading time of persistent luminescence measurements were performed to check how the graphene presence affects the electron traps number and depth. It was found that the addition of graphene improved the thermal conductivity of co-doped samples. This resulted in faster release of deeper traps and an increase in fading of persistent luminescence. The possibility of releasing energy from deep traps without additional stimulation may allow the use in different applications, the matrices and luminescent ions, which so far did not show persistent luminescence at room temperature.

Spatial declustering of zircon data indicate rapid Archean crustal growth and Neoproterozoic plate tectonic equilibrium

Constraining the growth and evolution of the continental crust provides insight into the secular change of tectono-magmatic processes through time. Radiogenic isotope pairs such as 176Lu/176Hf are commonly used to track the growth rates of the continental crust. Previous studies utilizing global compilations of LuHf isotopes of zircon to query continental growth through time. However, we show that sample clustering and spatial bias lead to erroneous interpretations and casts doubt as to the representativeness of global zircon compilations. To ameliorate this issue, we apply a geographic declustering algorithm to remove the spatial bias in the nonrepresentative dataset. A more representative declustered dataset indicates that the continental crust grew much faster than previous assessments have proposed. We further speculate that the transition to modern-style tectonics (as heralded by the appearance of low temperature–high pressure metamorphism) was accompanied by little to no net continental growth and propose that continental growth may be a feature of pre-plate tectonic magmatic processes.

Volume dependent fracture energy and brittle to quasi-brittle transition in intermetallic alloys

Intermetallic alloys such as titanium aluminide (TiAl) are lightweight with superior specific strength and high temperature oxidation resistance. They have a potential to replace heavier nickel based super alloys in low pressure high temperature sections of an aero engine. To facilitate an industry wide implementation, it is however indispensable to develop physically accurate computational methods which account for key deformation and fracture mechanisms. This assists the virtual prototyping required for the new product development using TiAl alloys. In this work, the quasi-brittle and volume dependent behavior of TiAl alloys is experimentally and numerically investigated. A total number of 29 geometrically identical TiAl specimens of three different sizes are tested in a three-point bending setup to investigate the volume dependence of fracture properties. In addition, three compact tension tests with identical specimen geometries are performed to analyze brittle to quasi-brittle transition and a switch in failure mechanism. Since the material fracture is observed to be preceded by plasticity, a theoretical and numerical framework of phase field ductile fracture which accounts for both elastic and plastic work densities is applied. The averaged fracture energy density for each test is evaluated numerically which is found to be lower for larger volumes. The work concludes with the proposal of an empirical law relating the fracture energy density with the specimen volume. Data from literature for different classes of materials is used for validation of the proposed empirical law. The mechanisms of transition from brittle to quasi-brittle fracture are investigated on the basis of local stress triaxiality in three-point and compact tension simulations.

Multilevel structured PASS nanofiber filter with outstanding thermal stability and excellent mechanical property for high-efficiency particulate matter removal

Particulate matter (PM) pollution from industrialization poses a great threat to people’s health. Although fiber-based filters are used effectively to capture PM, the traditional filters with large diameter suffer from low filtration efficiency, high pressure drop and low temperature resistance. In this study, multilayer poly arylene sulfide sulfone (M-PASS) composite filter was designed and fabricated via electrospinning technology. The M-PASS composite filter is sandwich-structure. Due to the unique structure and composition, the M-PASS filter exhibited outstanding removal efficiency of 99.97 ± 0.0050%, extremely low air resistance of 44.3 ± 0.7 Pa, excellent quality factor (QF) of 0.19 ± 0.0019 Pa−1, and desirable mechanical strength of 7.0 ± 0.2 MPa. Furthermore, the as-prepared M-PASS filter can remain outstanding filtration performance at 200.0 ℃ due to the high thermal stability of PASS and the removal efficiency was still above 95.2 ± 0.4% after long-term filtration test. These results demonstrate that the structure of filter is the important one for air filtration and the M-PASS nanofiber filters have great potential in PM removal, especially under high temperature conditions.

40Ar/39Ar Age Constraints on HP/LT Metamorphism in Extensively Overprinted Units: The Example of the Alpujárride Subduction Complex (Betic Cordillera, Spain)

AbstractWidespread overprinting of early high‐pressure/low‐temperature (HP/LT) subduction stages due to subsequent collisional or late‐orogenic tectono‐metamorphic events is a common feature affecting the interpretation of geochronologic data from HP/LT orogens. The Betic‐Rif orogen is exemplary in this connection as a great majority of published radiometric ages are found to cluster around 20 Ma. This clustering is commonly interpreted as reflecting a short, yet complex, succession of tectono‐metamorphic events spanning only over a few Myr, including back‐arc extension and overthrusting of the Internal Zones on the External Zones. An alternative explanation consists in the poor preservation of a much earlier HP/LT metamorphic event, presumably Eocene, coeval with subduction and crustal thickening in the Internal Zones, and particularly the Alpujárride Complex. However, this age is vividly debated due to widespread resetting by the Early Miocene HT/LP overprint. In this study, we provide new 40Ar/39Ar evidence from white micas selected along an E‐W section of the Internal Betics, from the central to the eastern Alpujárride Complex. Our new data show (a) that exceptionally well‐preserved HP/LT parageneses in this unit retain a well‐defined Eocene age around 38 Ma, and (b) that widespread 20 Ma ages recorded all along the section correspond to a regional stage of exhumation, coeval with a major change in the kinematics of back‐arc extension. Our study provides conclusive evidence that 40Ar/39Ar dating of carefully targeted HP/LT associations can overcome the problem of extensive late‐orogenic overprinting, testifying for an Eocene HP event around 38 Ma in the Betic‐Rif orogen.

P-T paths and U-Pb ages of pelitic and semi-pelitic granulites in the Yunkai massif and implication for the tectonic evolution of the Wuyi-Yunkai orogen, South China

Understanding the tectono-metamorphic evolution of the Wuyi-Yunkai orogen is crucial to constraining the Early Paleozoic geodynamic history of the South China Block. Here, we present petrological and geochronological characteristics of the pelitic and semi-pelitic granulites from Yunkai massif that occur as lenses or enclaves within orthogneisses and charnockites. These granulites have garnet-cordierite-spinel-sillimanite-bearing and garnet-orthopyroxene-bearing assemblages, respectively, showing typical low-pressure–high-temperature (LP-HT) granulite-facies mineral assemblages. Based on petrological characteristics, P-T calculations and phase equilibrium modelling in the NCKFMASHTO system, three-stage metamorphic evolution can be distinguished: 1) prograde stage (M1) characterized by biotite-plagioclase- or sillimanite-bearing assemblages present as inclusions in garnet or cordierite porphyroblasts, with P-T conditions of 7.0–8.0 kbar/730–780 °C; 2) peak LP-HT stage (M2) featured by garnet-orthopyroxene- or cordierite-bearing assemblages, with P-T conditions of 4.7–5.1 kbar/825–875 °C, suggesting high geothermal gradients (∼50–56 °C/km); and 3) post-peak stage (M3) represented by garnet+quartz corona or spinel-cordierite-bearing intergrowth, with P-T conditions of 4.0–4.3 kbar/650–750 °C. P-T estimates and pseudosection modelling define two consistent clockwise P-T paths involving a pre-peak prominent heating with decompression followed by a post-peak nearly isobaric cooling process. LA-ICP-MS zircon U-Pb dating results reveal that the granulite-facies metamorphism occurred at ∼445 Ma. Combined with previous studies, we proposed that the LP-HT metamorphism in the Yunkai massif might be attributed to the ridge subduction in the Early Paleozoic, which caused asthenosphere upwelling and supplied high heat flux to the lower crust when the slab window opened.

Characterization of magnesium oxide nanoparticle for water-based drilling mud formulation

This research is based on the synthesis and analysis to determine the efficiency and cost effectiveness of nanoparticle materials used in drilling fluid during oilfield exploration process. The study was carried out in the formulation of a waterbased drilling fluid, in which the prepared additives were treated with magnesium oxide (MgO) nanoparticles. The rheological properties of nanoparticle materials, such as flow time, viscosity, shear rate, shear stress, torque difference, and separation of solids and liquids, have been determined. The study also analyzed the fluid loss with respect to time in a manual filter press for low temperature and low pressure versus high pressure and high temperature using filter press hydraulic dead weight assembly in high temperature and high pressure. The nanoparticle used for the study was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer and particle size analyzer. Viscosity parameters were optimized using a multi-speed viscometer, lubricity tester and pH meter at effective concentration, as well as contact time, temperature and pressure changes as a function of concentration. The study suggests the use of MgO nanoparticle as an additive for water-based mud exploration in oilfields.

Native corn and potato starch as CO[formula omitted] gas bubble nucleation agent for low-temperature high-pressure foaming applications

Gas bubble nucleation and its control is one of the most important parameters in industrial foaming applications defining the physical and chemical properties of the end product. It is possible to enhance this process by adding gas bubble nucleation supporting agents. In this work, the potency of native corn and potato starch as bubble nucleating agents for low-temperature high pressure (HP) foaming applications have been evaluated at 30 barg. In a first work step, the physical properties of the starches were assessed using scanning electron microscopy (SEM), Washburn rise method, nitrogen adsorption, Hg porosimetry as well as light scattering and compared to those of talcum, a well know and widely used nucleating agent in non-food systems. Secondly, the effect of the addition of these starch particles on CO2 gas bubble nucleation in highly viscous watery hydroxy-methyl-propyl-cellulose dispersions was determined applying HP rheology. Results of the surface properties evaluation suggested that the investigated native starch particles are suitable natural nucleating agents for HP foaming applications but are less efficient than talcum particles. The critical supersaturation value of a 1 wt% HPMC dispersion was reduced from 2.9±0.4 to 1.1±0.7 and 1.3±0.6 after the addition of 1 wt% corn and potato starch particles, respectively. The applied HP rheology technique developed to measure the critical supersaturation revealed, that the starches can compete with the talcum. These findings also allowed to validate the suitability of HP rheology to investigate gas bubble nucleation under defined shear conditions thus, enabling new insights into the mechanism of this process for low-temperature foaming applications in food and pharmaceutical product systems.

Performance Enhancement of InGaZnO Top-Gate Thin Film Transistor With Low-Temperature High-Pressure Fluorine Treatment

In this work, the suppression of hydrogen diffusion in top-gate InGaZnO thin film transistors (TFTs) was observed. Under positive-bias temperature stress, the threshold voltage in short-channel devices was negatively shifted; this shift was attributed to hydrogen diffusion. To inhibit hydrogen migration, low-temperature high-pressure (LTHP) fluorine treatment was subsequently utilized. Under supercritical fluid states, fluorine, the most electronegative species of all elements, acted as a reactant and reduced mobile hydrogen. It was confirmed that the treatment benefited the characteristic properties of InGaZnO TFTs with varied channel lengths, especially in devices with short channels. The reliability of devices under stress improved through the LTHP treatment; the effects of suppression of hydrogen diffusion were illustrated by the energy band and capacitance–voltage curves of devices. Energy-dispersive X-ray spectroscopy of the specimen treated with LTHP indicated the presence of fluorine, which ensured the contribution of the treatment. Thus, LTHP treatment enables the realization of small-sized high-performance top-gate InGaZnO TFTs.

Hadal fauna of the South Sandwich Trench, Southern Ocean: Baited camera survey from the Five Deeps Expedition.

The South Sandwich Trench is a 965 km long arcuate subduction trench spanning the South Atlantic and Southern oceans, isolated from most other hadal (areas where water depths exceed 6000 m) environments by thousands of kilometres. This feature represents the coldest known hadal ecosystem with ambient sub-zero temperatures recorded from bathyal depths to over 7000 m water depth. Very little research has been carried out into the hadal fauna of this trench since the Russian expeditions of the 1960s and 70s. Here, we report the first visual assessment of hadal fauna from the South Sandwich Trench from a series of seven baited camera and trap deployments between 6044 m and the deepest point at 8265 m water depth, a location called Meteor Deep. Three species of hadal fish (Liparidae), with very low population densities were observed at depths shallower than expected, likely due to the piezo-thermal effect decreasing their depth range. Four species of scavenging amphipods were recovered, extending the known distribution of Eurythenes andhakarae, Hirondellea dubia, and Bathycallisoma schellenbergi to the South Sandwich Trench. Large densities of brittle stars (Ophiuroidea) were seen in the shallower hadal depths, while dense aggregations of holothurians (Elpididae) were observed within trench-fill basins located along the deep trench axis coincident with a visible surficial layer of surface derived detritus. In addition, gastropods, sponges, and stalked crinoids were observed. Importantly, this study highlights the endemic community present at hadal depth within this somewhat unique high pressure-low temperature environment.

Zircon U-Pb and geochemical signatures in high-pressure, low-temperature metamorphic rocks as recorders of subduction zone processes, Sikinos and Ios islands, Greece

Zircon U-Pb dating is a powerful and widely used geochronologic technique to constrain the timing and rates of magmatic and high and lower-grade metamorphic processes, as well as sediment provenance. Zircon trace element (TE) compositions also record magmatic and metamorphic processes during zircon growth. In this study, zircon laser ablation split-stream (LA-SS)-ICP-MS U-Pb and TE depth-profiling and novel two-dimensional zircon mapping techniques are used in combination with oxygen isotope analyses (secondary ion mass spectrometry, SIMS) to reconstruct the timing and metamorphic conditions recorded by recrystallization and growth of zircon rims, which provide valuable insight into the petro-tectonic evolution of high-pressure/low-temperature (HP/LT) metamorphic rocks formed in subduction zones. These techniques are applied to zircon grains from HP/LT metamorphic rocks of the Cycladic Blueschist Unit (CBU) and Cycladic Basement (CB) on Sikinos and Ios islands, Greece, which experienced metamorphism and deformation associated with subduction and subsequent back-arc exhumation. Zircon records multiple episodes of non-magmatic zircon rim growth at ~50 Ma and ~ 26 Ma. Eocene metamorphic rims are associated with HP/LT metamorphism and are observed in both units, suggesting likely juxtaposition prior to or during subduction and associated HP metamorphism. The similarity between TE concentrations and δ18O values of the Eocene rims and their corresponding cores is an indicator for re-crystallization and precipitation as a mechanism of zircon growth. In contrast, Oligocene zircon rims appear to be restricted to a < 0.5 km thick zone along the CB-CBU contact, characterized by garnet break-down, and show HREE enrichment and higher ẟ18O values in the rims compared to the cores, consistent with a model suggesting metasomatic infiltration of fluids derived from dehydrating sedimentary rocks during progressive subduction and underplating prior to back-arc extension. This metamorphism appears to be static in nature and does not support major late Cenozoic reactivation of the contact as an extensional shear zone during back-arc extension.