A long‐lived metamorphic history in the contact aureole of the Mooselookmeguntic pluton revealed by in situ dating of monazite grains preserved as inclusions in staurolite porphyroblasts

Emplacement of the Mooselookmeguntic pluton, located in the western Maine region of the northern Appalachians, was thought to have occurred towards the end of the Acadian deformation at around 370 Ma. Crystallization ages from different parts of the pluton suggest a more sequential emplacement history over a period of c. 20 Myr. Foliation inflection/intersection axes (FIAs) within porphyroblasts from its aureole reveal at least five periods of garnet and staurolite growth. The orientation of FIAs in both garnet and staurolite porphyroblasts trend successively from ESE–WNW, NNW–SSE, E–W, ENE–WSW to NE–SW. Electron probe microanalysis dating of monazite grains included in staurolite porphyroblasts containing one of these five periods of FIA development reveals a succession of apparent ages from 410 Ma to 345 Ma. A similar spread of crystallization ages can be observed for plutons from Maine and adjacent regions. This succession indicates that deformation and metamorphism began well before and continued long after what is classically regarded as the Acadian orogeny. The thermal structure of the orogen progressively evolved to enable pluton emplacement, and it continued to develop afterwards with magmatic fluids still forming at depth.     

Long-term variability of UV radiation in the spectral range of 300–380 nm in Moscow

The seasonal and interannual variability of global ultraviolet (UV) radiation in the spectral range of 300-380 nm (0380) in Moscow in 1968-2014 is analyzed. The effect of cloudiness on the magnitude of 0380 is assessed. The smallest (-22...-26%) losses due to cloudiness are registered in May-August, and the highest ones (to -45%) are observed in October-November. According to the UV radiation reconstruction model and measurement data, the long-term deviations of 0380 from the average (for 1968-1997) due to clouds can reach + (11-12)%. The statistically significant positive linear trend in total annual 0380 is revealed from the data of both the reconstruction model and observations (about 1.5% per decade for 1968-2014 and 3% per decade for 1979-2014).     

Extended finite element framework for fault rupture dynamics including bulk plasticity

We present an explicit extended finite element framework for fault rupture dynamics accommodating bulk plasticity near the fault. The technique is more robust than the standard split‐node method because it can accommodate a fault propagating freely through the interior of finite elements. To fully exploit the explicit algorithmic framework, we perform mass lumping on the enriched finite elements that preserve the kinetic energy of the rigid body and enrichment modes. We show that with this technique, the extended FE solution reproduces the standard split‐node solution, but with the added advantage that it can also accommodate randomly propagating faults. We use different elastoplastic constitutive models appropriate for geomaterials, including the Mohr–Coulomb, Drucker–Prager, modified Cam‐Clay, and a conical plasticity model with a compression cap, to capture off‐fault bulk plasticity. More specifically, the cap model adds robustness to the framework because it can accommodate various modes of deformation, including compaction, dilatation, and shearing. Copyright © 2013 John Wiley & Sons, Ltd.     

Ophiolitic association of Cape Fiolent area,southwestern Crimea

An ophiolitic association consisting of serpentinized ultramafic rocks and serpentinite, layered mafic–ultramafic complex, gabbro and gabbrodolerite, fragments of parallel dike complex, pillow lava, black bedded chert, and jasper has been identified for the first time by authors in the Cape Fiolent area. The chemistry of pillow lavas and dolerites, including REE patterns and a wide set of other microelements, indicates suprasubduction nature of the ophiolites and their belonging to a backarc basin that has reached the stage of spreading in its evolution.     

Silver and silver microparticles of the Cretaceous-Paleogene boundary sediment of Fish Clay Højerup (Stevns Klint,Denmark)

We report the occurrence of micrometer-sized silver particles in the red (“impact” or “ejecta”) layer of the Fish Clay. These appear to be embedded into the biogenic/abiogenic calcite matrix. Energy dispersive X-ray analysis indicates that these microparticles are composed of pure silver (>99% of the total weight). Scanning electron microscopy images reveal irregular and predominantly rounded shapes with rugged surfaces. Numerous silver microparticles are spherical, and some exhibit dendritic textures. These microparticles were probably originated during the Chicxulub asteroid impact event, or immediately afterwards, and dispersed globally.     

Solubility and migration ability of rhodium in natural conditions: model experimental data

The contents of dissolved rhodium species in the near-neutral environments have been studied for the first time and data on the interaction of Rh with organic matters of natural waters and its sorption behavior during contact with the components of geochemical barriers were obtained. The solubility method was used to analyze the behavior of rhodium hydroxide in the Rh(OH)_x–H₂O and Rh(OH)_x–H₂O–FA (fulvic acids) systems. The possible contents of inorganic species of rhodium and its compounds with humic organic ligands were determined within the pH range typical of surface waters. The solubility of rhodium shows a twoorder- of magnitude increase in the presence of humic matters (FA). The sorption interaction of the soluble rhodium species with the main components of geochemical barriers such as iron oxyhydroxides (III), (including fulvic-acid modified ones), alumosilicates, and precipitates of humic acids in contact with natural waters was studied. It was revealed that rhodium has the high affinity to all studied materials; its species are sorbed by ferrihydrite within several hours. It is suggested that rhodium is mainly transferred as colloid with suspended particulate matters of waters and then is accumulated in bottom sediments. The differences revealed in the sorption behavior of Pt(IV), Pd(II) and Rh(III) may be used to predict the distribution of the considered platinum group elements between the components of ecosystems.     

Age and geochemistry of zircon from the oldest metamorphic rocks of the Omolon Massif (Northeast Russia)

This study provides SHRIMP-RG data on zircons from garnet gedritites, the products of retrograde metamorphism of eclogite-like rocks constituting belonging to the basement of the Omolon Massif. The earliest episode recorded by oscillatory-zoned cores having high HREE and Ti contents occurred at 3.25–3.22 Ga (Paleoarchean) and is interpreted to represent an upper age limit of a metamorphic or magmatic protolith. One zircon core with a pronounced negative Eu anomaly yielded a concordant age of 2.6 Ga, which is interpreted to mark a Neoarchean episode of granite formation. The studied population of zircons provides the most distinct record of a Paleoproterozoic (1.9 Ga) event, which is marked by formation of garnet gedritites under amphibolite-facies conditions. This event is recorded by transparent recrystallization rims of preexisting large zircon grains and small newly-formed grains, which are characterized, compared with their cores, by lower crystallization temperatures and one order of magnitude lower concentrations of U, Th, and HREE, and the presence of garnet micro-inclusions.     

Tectonic setting discrimination diagrams for terrigenous rocks: a comparison

An attempt is made to compare discrimination diagrams of the first (mid-1980s) and second (early 2010s) generations compiled using data for sedimentary successions of different ages. Our results suggest that the diagrams of different generations allow more or less correct discrimination only between the platform, rift, passive margin, and island arc settings. The data for collision sediments do not form separate fields in these diagrams.