Forming and preserving aragonite in shear zones: First report of blueschist facies metamorphism in the Jabal Akhdar Dome, Oman Mountains

We report the first occurrence of high-pressure metamorphic aragonite in Precambrian carbonates of the Jabal Akhdar Dome in the Oman Mountains (northern Oman). We propose a model for both its formation at blueschist facies conditions and its subsequent preservation to the surface within the tectonic framework of the Late Cretaceous obduction of the Semail Ophiolite. Aragonite formed at temperature ∼350 °C and pressure ≥0.9 GPa and is preserved within mylonitic shear zones and in stretched-fiber dilational veins where the necessary conditions for its formation and preservation, such as plastic strain accommodation, fluid-enhanced mineralogical reactions, and an anisotropic permeability structure, were preferentially met with respect to the surrounding rock. High-strain structural domains are ideal sites to look for and study prograde and retrograde high-pressure metamorphic histories in deeply subducted and exhumed terrains

Relatively oxidized conditions for diamond formation at Udachnaya (Siberia)

Thanks to the physical strength of diamonds and their relatively unreactive chemical nature, their mineral inclusions may remain exceptionally preserved from alteration processes and chemical exchanges with surrounding minerals, fluids and/or melts following diamond formation. Cr-bearing spinels are relatively common inclusions found in peridotitic diamonds and important oxybarometers providing information about the oxygen fugacity (fO2) of their source mantle rocks. Here, we investigated a magnesiochromite-olivine touching pair in a diamond from the Udachnaya kimberlite (Siberia) by in situ single-crystal X-ray diffraction and energy-domain synchrotron Mossbauer spectroscopy, aiming to constrain the physical-chemical conditions of diamond formation and to explore the redox state of this portion of the Siberian craton when the diamond was formed. The P-T-fO(2) entrapment conditions of the inclusion pair, determined by thermo- and oxybarometric analyses, are similar to 5.7(0.4) GPa and similar to 1015(50) ? (although entrapment at higher T and re-equilibration during subsequent mantle storage are also possible) and fO(2) near the enstatite-magnesite-olivine-diamond (EMOD) buffer. The determined fO(2) is similar to, or slightly more oxidized than, those of xenoliths from Udachnaya, but whilst the xenoliths last equilibrated with the surrounding mantle just prior to their entrainment in the kimberlite at similar to 360 Ma, the last equilibration of the inclusion pair is much older, occurring at 3.5-3.1, similar to 2 or similar to 1.8 Ga before final encapsulation in its host diamond. Hence, the similarity between xenoliths and inclusion fO(2) values indicates that the modern redox state of this portion of the Siberian lithosphere was likely attained relatively early after its formation and may have persisted for billions of years after diamond formation, at least at the local scale. Moreover, the oxygen fugacity determination for the inclusion pair provides direct evidence of diamond formation near the EMOD buffer and is consistent with recent models suggesting relatively oxidized, water-rich CHO fluids as the most likely parents for lithospheric diamonds

Synchrotron M\uf6ssbauer Source technique for in situ measurement of iron-bearing inclusions in natural diamonds

Natural diamonds containing silicate, oxide and sulfide inclusions are a popular focus of investigation as they uniquely provide a window into the conditions of the Earth\u2019s interior at extreme depths. Recent discoveries based on investigations of deep diamonds have considerably improved our knowledge of the Earth\u2019s deep carbon and water cycles and the oxygen fugacity of the Earth\u2019s interior. Super deep diamonds are those that are believed to have formed at depths of at least 300 km and some evidence suggests depths of at least 800 km. A common inclu- sion in these diamonds is ferropericlase, (Mg,Fe2+)O. Ferropericlase is the second most abundant mineral in the lower mantle, constituting up to about 20 mol% of its volume. The Fe3+/Fetot of ferropericlase is a strong func- tion of oxygen fugacity, and provides a measure of the most recent redox conditions under which it equilibrated. Conventional M\uf6ssbauer spectroscopy using a 57Co point source has been used in the past decades to study the Fe3+/Fetot content in inclusions still trapped in their diamond\u2019s host, however its limitations are the low spatial resolution (not below 3c100 \u3bcm2) and the long acquisition time. The Flank method was also proposed, it is fast, it has high spatial resolution (down to 3c20 \u3bcm2) but it measures the bulk value of Fe3+/Fetot since it cannot distinguish between different phases. An ideal method to measure Fe3+/Fetot values of ferropericlase would com- bine (1) the advantage of M\uf6ssbauer spectroscopy to distinguish Fe3+ in different phases and measure inclusions while still in the diamond, with (2) the advantage of the Flank method to conduct rapid measurements with high spatial resolution. The only method that offers the possibility to satisfy all these requirements is the Synchrotron M\uf6ssbauer Source (SMS). We used the SMS for the first time, to study the iron content and iron distribution in ferropericlase inclusion still contained within its diamond host from Juina (Brazil). This definitive non-destructive technique with extremely high spatial resolution ( 3c15 \u3bcm2) enabled measurements in multiple regions of the 150 7 150 \u3bcm2 inclusion to be sampled and showed that while Fe3+/Fetot values in ferropericlase were below the detection limit (0.02) overall, there was a magnetic component whose abundance varied systematically across the inclusion. Hyperfine parameters of the magnetic component are consistent with magnesioferrite, and the absence of superparamagnetism allows the minimum particle size to be estimated as 3c30 nm. Bulk Fe3+/Fetot values are similar to those reported for other ferropericlase inclusions from Juina. Their variation across the inclusion can provide constraints on its history, and ultimate on the deep carbon processes behind diamonds formation and their exhumation from the transition zone and shallow lower mantle regions

First in-situ measurements of Fe3+/Fetot for oxides and silicates included in natural diamonds with Synchrotron M\uf6ssbauer Source

Diamond is the paramount phase to understand the evolution and the physico- chemical condition of the deep portions of the Earth\u2019s mantle, mainly because: (i) it is the stable phase through which carbon is stored in the deep mantle for long geologic time; (ii) it does contain and preserve different types of inclusions (fluid, mineral, etc.); (iii) it is the only material sampling the mantle to depths of 800 km (e.g. Harte, 2010), although the majority of the mined diamonds worldwide derive from shallower depth (150 to 250 km). The study of mineral inclusions trapped in diamonds allows the retrieval of different pieces of information about the Earth\u2019s interior and its active geodynamics, providing important clues on the initiation of subduction processes (Shirey & Richardson, 2011; Smart et al., 2016), tracking the transfer of material through the mantle transition zone (Stachel et al., 2005; Walter et al., 2011), recording the timing of ingress of fluids to the continental lithosphere (e.g. Shirey et al., 2004), preserving carbonatitic fluid that trigger deep mantle melting (e.g. Schrauder & Navon, 1994; Kopylova et al., 2010), providing samples of primordial noble gases (e.g. Ozima & Igarashi, 2000), and capturing the redox state of the mantle (e.g. Rohrbach & Schmidt, 2011). Unfortunately the majority of the techniques used so far to study the mineral inclusions are destructive. It is only in the last decade that the studies on inclusions in diamond have started to use non-destructive techniques, providing new information which would otherwise be lost using earlier destructive techniques. Such an example is the rim fluids around inclusions in diamonds. In this study we present details of the experimental setup on the determination of Fe3+/Fetot ratios of mineral inclusions whilst still within the diamonds by a non-destructive approach using the Synchrotron M\uf6ssbauer Source (SMS; Potapkin et al., 2012) at the Nuclear Resonance beamline SOURCE ID18 (R\ufcffer & Chumakov, 1996), European Synchrotron Radiation Facility (ESRF), Grenoble. The extremely small X-ray spot size (10 7 15 \u3bcm2) is perfectly suited for our purposes as some inclusions are smaller than 30-50 \u3bcm and the Fe3+/Fetot variation over the same inclusion cannot be performed by using standard laboratory radioactive sources because of the larger beam size. The average collection time for thicker inclusions (~ 200 \u3bcm) was 2 hours per spectrum, whilst the smallest inclusion (~ 30 730 730 \u3bcm3) required a collection time of approximately 10-12 hours in order to get a spectrum with nicely distinguishable features and a high signal-to-noise ratio. In general, application to a suite of silicate and oxide inclusions in diamonds produced comparable results with respect to those obtained using conventional M\uf6ssbauer sources (e.g. McCammon et al., 2004)

UCP4C mediates uncoupled respiration in larvae of Drosophila melanogaster

Larvae of Drosophila melanogaster reared at 23\ub0C and switched to 14\ub0C for 1 h are 0.5\ub0C warmer than the surrounding medium. In keeping with dissipation of energy, respiration of Drosophila melanogaster larvae cannot be decreased by the F-ATPase inhibitor oligomycin or stimulated by protonophore. Silencing of Ucp4C conferred sensitivity of respiration to oligomycin and uncoupler, and prevented larva-to-adult progression at 15\ub0C but not 23\ub0C. Uncoupled respiration of larval mitochondria required palmitate, was dependent on Ucp4C and was inhibited by guanosine diphosphate. UCP4C is required for development through the prepupal stages at low temperatures and may be an uncoupling protein

TOXOPLASMOSIS: FOOD SAFETY AND RISK COMMUNICATION

Toxoplasmosis, parasitic pathology supported by Toxoplasma gondii, is a typical example of multi-issue and inter-disciplinary on which, with equal intensity, converge the interests of various branches of human and veterinary medicine. The aim of research was the assessment of risk communication to pregnant women by doctors gynecologists involved in ASL's territorial about toxoplasmosis, which can have serious effects on pregnancy and the unborn child. The results acquired during the investigation showed the need to develop and implement appropriate information campaigns and proper nutrition education

Reduction in primary production followed by rapid recovery of plant biomass in response to repeated mid-season droughts in a semiarid shrubland

The frequency and severity of extreme weather events, including droughts, are expected to increase due to the climate change. Climate manipulation field experiments are widely used tools to study the response of key parameters like primary production to the treatments. Our study aimed to detect the effect of drought on the aboveground biomass and primary production both during the treatments as well as during the whole growing seasons in semiarid vegetation. We estimated aboveground green biomass of vascular plants in a Pannonian sand forest-steppe ecosystem in Hungary. We applied non-destructive field remote sensing method in control and drought treatments. Drought treatment was carried out by precipitation exclusion in May and June, and was repeated in each year from 2002. We measured NDVI before the drought treatment, right after the treatment, and at the end of the summer in 2011 and 2013. We found that the yearly biomass peaks, measured in control plots after the treatment periods, were decreased or absent in drought treatment plots, and consequently, the aboveground net primary production was smaller than in the control plots. At the same time, we did not find general drought effects on all biomass data. The studied ecosystem proved resilient, as the biomass in the drought-treated plots recovered by the next drought treatment. We conclude that the effect of drought treatment can be overestimated with only one measurement at the time of the peak biomass, while multiple within-year measurements better describe the response of biomass

High-brilliance X-ray system for high-pressure in-house research: applications for studies of superhard materials

Newly installed, at Bayerisches Geoinstitut, X-ray system consists of three major components: RIGAKU FR-D high-brilliance source, Osmic’s Confocal Max-Flux optics, and SMART APEX 4K CCD area detector. We tested the system for single-crystal structural studies on example of garnet, Co3Al2Si3O12, for powder diffraction analysis on example of a small sample of boron carbide, B4C, recovered after treatment in a multi-anvil apparatus, and for in situ experiments at high pressure on example of FeO compressed in a diamond anvil cell to >100 GPa. In all the cases, the system demonstrated its reliability and provided results comparable with those obtained using the best currently available instruments. Using a new X-ray system, we measured the compressibility of superhard nanocrystalline diamond at pressures up to 26 GPa and found it to be extremely incompressible with KT = 488(4) GPa, K' = 3.1(2), and V0 = 3.401(6) cm3/mol

The origin of water on Earth: stars or diamonds?: A conversation among astronomers and geologists

This contribution deals with two different hypotheses on the origin of superficial water on the Earth: the Endogenous hypothesis and the Exogenous one. They proposed that water either was brought to the surface of the Earth from the deep interior of the Earth or would have come to the Earth from celestial bodies that bombarded the planet billions of years ago. The evidence from recent astronomical and geological findings supporting the two alternative hypotheses will be discussed