Alteration and chemical U-Th-total Pb dating of heterogeneous high-uranium zircon from a pegmatite from the Aduiskii massif,middle Urals,Russia

Mineralogy and Petrology - The U-Th-Pb isotope system in the accessory mineral zircon may be disturbed, as for instance by the secondary loss of radiogenic lead. The recognition of such alteration...     

Reconstruction of Late Pleistocene events in the periglacial area in the southern part of the East European Plain

An integrated study of the loess–soil sequence in the coastal exposure near the settlement of Beglitsa (Rostov oblast) allowed us, for the first time, to reconstruct the landscape-climatic changes that occurred in the eastern Azov region over the course of the Late Pleistocene. In the south of the periglacial zone, considerable differences between intensity of the loess accumulation in the Early and Late Valdai Cryochrons were revealed. In the Early Valdai Epoch, which corresponds roughly to the end of Marine Isotope Stage (MIS) 5 and MIS 4, loess accumulation occurred after completion of development of the Mezin pedocomplex and before the beginning of the Bryansk stage of soil development, i.e., over more than 20 000 years. In the much shorter Late Valdai Cryochron MIS 2 (10 000–12 000 years), loess accumulation reached 5 m. The data evaluation shows that the loess accumulation rates in the Early Valdai Epoch (~0.07 mm/year) and the Late Valdai Epoch (~0.5 mm/year) differ from each other by an order of magnitude.     

Condor-E Spacecraft with a Synthetic Aperture Antenna and Its Capabilities

Izvestiya, Atmospheric and Oceanic Physics - The main parameters of a small spacecraft (SSC) (Condor-E) and its onboard radar with a synthetic aperture antenna (SAR) are presented in the paper. Two...     

Analysis of climate policy targets under uncertainty

Although policymaking in response to the climate change threat is essentially a challenge of risk management, most studies of the relation of emissions targets to desired climate outcomes are either deterministic or subject to a limited representation of the underlying uncertainties. Monte Carlo simulation, applied to the MIT Integrated Global System Model (an integrated economic and earth system model of intermediate complexity), is used to analyze the uncertain outcomes that flow from a set of century-scale emissions paths developed originally for a study by the U.S. Climate Change Science Program. The resulting uncertainty in temperature change and other impacts under these targets is used to illustrate three insights not obtainable from deterministic analyses: that the reduction of extreme temperature changes under emissions constraints is greater than the reduction in the median reduction; that the incremental gain from tighter constraints is not linear and depends on the target to be avoided; and that comparing median results across models can greatly understate the uncertainty in any single model.     

Fast data assimilation using a nonlinear Kalman filter and a model surrogate: An application to the Columbia River estuary

A fast and adjoint-free nonlinear data assimilation (DA) system was developed to simulate 3D baroclinic circulation in estuaries, leveraging two recently developed technologies: (1) a nonlinear model surrogate that executes forward simulation three orders of magnitude faster than a forward numerical circulation code and (2) a nonlinear extension to the reduced-dimension Kalman filter that estimates the state of the model surrogate. The noise sources in the Kalman filter were calibrated using empirical cross-validation and accounted for errors in model and model forcing.The DA system was applied to assimilate in situ measurements of water levels, salinities, and temperatures in simulations of the Columbia River estuary. To validate the DA results, we used a combination of cross-validation studies, process-oriented studies, and tests of statistical and dynamical consistency. The validation studies showed that DA improved the representation of several important processes in the estuary, including nonlinear tidal propagation, salinity intrusion, estuarine residual circulation, heat balance, and response of the estuary to coastal winds.     

Mineralogy, geochemistry and stratigraphy of the Maslovsky Pt–Cu–Ni sulfide deposit, Noril’sk Region, Russia

We report new data on the stratigraphy, mineralogy and geochemistry of the rocks and ores of the Maslovsky Pt–Cu–Ni sulfide deposit which is thought to be the southwestern extension of the Noril’sk 1 intrusion. Variations in the Ta/Nb ratio of the gabbro-dolerites hosting the sulfide mineralization and the compositions of their pyroxene and olivine indicate that these rocks were produced by two discrete magmatic pulses, which gave rise to the Northern and Southern Maslovsky intrusions that together host the Maslovsky deposit. The Northern intrusion is located inside the Tungusska sandstones and basalt of the Ivakinsky Formation. The Southern intrusion cuts through all of the lower units of the Siberian Trap tuff-lavas, including the Lower Nadezhdinsky Formation; demonstrating that the ore-bearing intrusions of the Noril’sk Complex post-date that unit. Rocks in both intrusions have low TiO₂ and elevated MgO contents (average mean TiO₂ <1 and MgO?=?12?wt.%) that are more primitive than the lavas of the Upper Formations of the Siberian Traps which suggests that the ore-bearing intrusions result from a separate magmatic event. Unusually high concentrations of both HREE (Dy+Yb+Er+Lu) and Y (up to 1.2 and 2.1?ppm, respectively) occur in olivines (Fo_79.5 and 0.25% NiO) from picritic and taxitic gabbro-dolerites with disseminated sulfide mineralization. Thus accumulation of HREE, Y and Ni in the melts is correlated with the mineral potential of the intrusions. The TiO₂ concentration in pyroxene has a strong negative correlation with the Mg# of both host mineral and Mg# of host rock. Sulfides from the Northern Maslovsky intrusion are predominantly chalcopyrite–pyrrhotite–pentlandite with subordinate and minor amounts of cubanite, bornite and millerite and a diverse assemblage of rare precious metal minerals including native metals (Au, Ag and Pd), Sn–Pd–Pt–Bi–Pb compounds and Fe–Pt alloys. Sulfides from the Southern Maslovsky intrusion have δ ³⁴S?=?5–6‰ up to 10.8‰ in two samples whereas the country rock basalt have δ ³⁴S?=?3–4‰, implying there was no in situ assimilation of surrounding rocks by magmas.     

Lake ice simulation using a 3D unstructured grid model

Ocean Dynamics - We develop a single-class ice and snow model embedded inside a 3D hydrodynamic model on unstructured grids and apply it to lake studies using highly variable mesh resolution. The...     

Undersea Buried Pipeline Reconstruction Based on the Level Set and Inverse Multiquadric Regularization Method

The electric inversion technique reconstructs the subsurface medium distribution from acquired data. On the basis of electric inversion, objects buried under the earth or seabed, such as pipelines and unexploded ordnance, are detected and located in a contactless manner. However, the process of accurately reconstructing the shape of the target object is challenging because electric inversion is a nonlinear and ill-posed problem. In this work, we present an inverse multiquadric (IMQ) regularization method based on the level set function for reconstructing buried pipelines. In the case of locating underwater objects, the unknown inversion area is split into two parts, the background and the pipeline with known conductivity. The geometry of the pipeline is represented based on the level set function for achieving a noiseless inversion image. To obtain a binary image, the IMQ is used as the regularization term, which 'pushes' the level set function away from 0. We also provide an appropriate method to select the bandwidth and regularization pa-rameters for the IMQ regularization term, resulting in reconstructed images with sharp edges. The simulation results and analysis show that the proposed method performs better than classical inversion methods.