Magnesium-iron compositional variance in hornblende pyroxene granulites

Hornblende-orthopyroxene-calcic pyroxene-plagioclase (andesine-labradorite) — magnetite-ilmenite±quartz assemblages are evidently the most common granulite facies representatives of basic rocks throughout the world, and they must represent a variance of more than one. Ramberg (1948) invoked an additional degree of freedom arising out of unequal fractionation of Mg and Fe in the ferromagnesian silicates in such rocks. This is examined in detail on the basis of chemical data on twentytwo hornblende-orthopyroxenecalcic pyroxene triads, half of them from the type charnockite area near Madras.Theoretical consideration of a magnesium-iron distribution model shows that in quartz-bearing hornblende pyroxene granulites, the Mg/Mg+Fe ratios of hornblende, orthopyroxene and calcic pyroxene are uniquely determined by temperature at constant pressure. But these assemblages contain quartz rarely and Mg-Fe distribution among the three can be best described by three exchange equilibria where, at constant temperature, there is a fixed relation between the Mg/Mg+Fe ratios of the minerals. Among these, the exchange equilibria between hornblende-orthopyroxene and hornblende-calcic pyroxene appear to be interdependent; however, they are known to be significantly modified by varying tetrahedral aluminium contents of hornblendes. Comparison of molecular Mg/(Mg+Fe) ratios of hornblendes and parent rocks strongly points to an absence of Mg-Fe compositional variance in the total system, a petrologically important corollary being that the hornblendes in these rocks are highly unlikely to be secondary after pyroxenes. The general variance of the assemblages is also discussed.     

Bulk Transfer Relations for the Roughness Sublayer

In the roughness sublayer (RSL), Monin–Obukhov surface layer similarity theory fails. This is problematic for atmospheric modelling applications over domains that include rough terrain such as forests or cities, since in these situations numerical models often have the lowest model level located within the RSL. Based on empirical RSL profile functions for momentum and scalar quantities, and scaling the height with the RSL height z _*, we derive a simple bulk transfer relation that accounts for RSL effects. To verify the validity of our approach, these relations are employed together with wind speed and temperature profiles measured over boreal forest during the BOREAS experimental campaign to estimate momentum and heat fluxes. It is demonstrated that, when compared with observed flux values, the inclusion of RSL effects in the transfer relations yields a considerable improvement in the estimated fluxes.     

New U–Pb isotopic data for detrital zircons from metasedimentary sequences of northwestern Taimyr

This work presents the U–Pb (LA–ICP–MS) data of detrital zircons from metasedimentary sequences of northwestern Taimyr. An analysis of the youngest populations of detrital zircons testifies to the wide distribution of Cambrian sequences in the study area, but not Precambrian sequences as was considered earlier, and the need for a substantial revision of the stratigraphic scheme of this area. The detrital zircon age distribution shows that the Timan margin of the Baltic paleocontinent was a major provenance area of the Cambrian sediments in northern and northwestern Taimyr, as well as the coeval sediments of the Severnaya Zemlya archipelago.     

Geodynamic interpretation of the earthquake distribution in the kermadec subduction zone

Summary The morphology of the Wadati-Benioff zone in the Kermadec region, based on the distribution of 1100 earthquake foci, verified the existence of an intermediate aseismic gap and its relation to active andesitic volcanism, and the non-uniformity of subduction due to the hampering effect of the main structural features of the subducting Pacific plate. Two cycles of the recently active subduction in the Tonga-Kermadec island arc were found.     

Long-term soil moisture dynamics derived from GNSS interferometric reflectometry: a case study for Sutherland,South Africa

Soil moisture is a geophysical key observable for predicting floods and droughts, modeling weather and climate and optimizing agricultural management. Currently available in situ observations are limited to small sampling volumes and restricted number of sites, whereas measurements from satellites lack spatial resolution. Global navigation satellite system (GNSS) receivers can be used to estimate soil moisture time series at an intermediate scale of about 1000 m². In this study, GNSS signal-to-noise ratio (SNR) data at the station Sutherland, South Africa, are used to estimate soil moisture variations during 2008–2014. The results capture the wetting and drying cycles in response to rainfall. The GNSS Volumetric Water Content (VWC) is highly correlated (r ² = 0.8) with in situ observations by time-domain reflectometry sensors and is accurate to 0.05 m³/m³. The soil moisture estimates derived from the SNR of the L1 and L2P signals compared to the L2C show small differences with a RMSE of 0.03 m³/m³. A reduction in the SNR sampling rate from 1 to 30 s has very little impact on the accuracy of the soil moisture estimates (RMSE of the VWC difference 1–30 s is 0.01 m³/m³). The results show that the existing data of the global tracking network with continuous observations of the L1 and L2P signals with a 30-s sampling rate over the last two decades can provide valuable complementary soil moisture observations worldwide.     

“Pure” supernovae and accelerated expansion of the Universe

A special class of type Ia supernovae that is not subject to ordinary and additional intragalactic gray absorption and chemical evolution has been identified. Analysis of the Hubble diagrams constructed for these supernovae confirms the accelerated expansion of the Universe irrespective of the chemical evolution and possible gray absorption in galaxies.     

Theoretical investigation of large-amplitude waves in granular soils

A theoretical investigation of plane waves in granular soils is presented. Dynamic equations are derived with the use of the hypoplasticity theory for granular materials. For numerical calculations the material parameters of Karlsruhe sand are used. Wave speeds as slopes of characteristics of the dynamic equations are calculated for various stresses and densities. It is shown that under certain conditions the dynamic equations lose hyperbolicity and the initial boundary value problem thus becomes ill-posed. Two types of ill-posedness are found, known as flutter ill-posedness and stationary discontinuity. The latter is shown to arise at higher shear stress than the former. A comparison is made between dynamic ill-posedness and stability of static equilibrium. With the use of the second-order work stability criterion it is found that the dynamic equations lose hyperbolicity when the static equilibrium under a dead load is still stable. Numerical solutions to the problem of propagation of boundary disturbance in a half-space are obtained. Owing to dilatancy and contractancy of the granular material, a purely transverse disturbance induces a longitudinal component of velocity in the wave, and vice versa.     

Water Quality Estimation Based on the Structural Analysis of Diatomic Complexes

Two types of plots characterizing the undisturbed structure of the biotopic spectrum of diatom algae are recognized. The first of them has a hyperbolic form and the second is a sigmoid curve (normal distribution). It was shown that, under adverse external impact, both types of plots change their shape and the extent of their distortion reflects the general level of anthropogenic load on this water body or its part. The proposed method of graphical comparison was developed for lakes of Kola Peninsula. Later it was successfully used in the biomonitoring of watercourses of the Volga–Akhtuba interfluve area (Astrakhan Province) and in paleoenvironmental reconstruction for Galichskoe Lake (Kostroma Province).     

Hα emission objects in Circinus

We present a new survey for Hα emission objects in the Circinus cloud complex and introduce an efficient photometric method for detecting Hα emission via observations in a narrow‐band filter. The observed flux is compared to a blackbody fit of the continuum. Our search strategy reveals 20 stars with strong Hα emission (EW > 10 Å), eight of them being new detections. All Hα stars display infrared excess corroborating their youth. On the other hand, the region contains a number of infrared excess objects that do not show Hα emission. Our results support the picture that accretion – as witnessed by Hα emission – is a highly variable phenomenon. Therefore, Hα surveys can only trace the temporarily active objects. In contrast, infrared excess is a more robust tracer that reveals most of the population of young stellar objects in a star forming region. Our analysis of the general stellar content of the region yields a reliable distance of 450 pc for the Circinus cloud. Moreover, we find a ratio of total‐to‐selective extinction of R^V = 2.8 suggesting that smaller‐than‐normal dust grains may be present. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Global Context of Solar Activity During the Whole Heliosphere Interval Campaign

The Whole Heliosphere Interval (WHI) was an international observing and modeling effort to characterize the 3-D interconnected ??heliophysical?? system during this solar minimum, centered on Carrington Rotation 2068, March 20??C?April 16, 2008. During the latter half of the WHI period, the Sun presented a sunspot-free, deep solar minimum type face. But during the first half of CR 2068 three solar active regions flanked by two opposite-polarity, low-latitude coronal holes were present. These departures from the quiet Sun led to both eruptive activity and solar wind structure. Most of the eruptive activity, i.e., flares, filament eruptions and coronal mass ejections (CMEs), occurred during this first, active half of the interval. We determined the source locations of the CMEs and the type of associated region, such as active region, or quiet sun or active region prominence. To analyze the evolution of the events in the context of the global solar magnetic field and its evolution during the three rotations centered on CR 2068, we plotted the CME source locations onto synoptic maps of the photospheric magnetic field, of the magnetic and chromospheric structure, of the white light corona, and of helioseismological subsurface flows. Most of the CME sources were associated with the three dominant active regions on CR 2068, particularly AR 10989. Most of the other sources on all three CRs appear to have been associated with either isolated filaments or filaments in the north polar crown filament channel. Although calculations of the flux balance and helicity of the surface magnetic features did not clearly identify a dominance of one region over the others, helioseismological subsurface flows beneath these active regions did reveal a pronounced difference among them. These preliminary results suggest that the ??twistedness?? (i.e., vorticity and helicity) of subsurface flows and its temporal variation might be related to the CME productivity of active regions, similar to the relationship between flares and subsurface flows.