West Pacific-type convergent boundaries and their role in the formation of the Central Asian Fold Belt

The type of convergent boundaries forming in the area of mantle plumes is considered. These convergent boundaries (West Pacific type) are characteristic of the western margin of the Pacific. West Pacific-type boundaries are a regular succession of structures from ocean to continent: island arcs, marginal basins, rift basins, and associated OIB-type volcanics at the continental edge. The convergence zones are up to a thousand kilometers wide.Studies of the history of the part of the Central Asian Fold Belt forming the folded periphery of the Siberian continent have shown that the continent drifted above the African plume or corresponding low-velocity mantle province for most of the Phanerozoic (up to the Early Mesozoic inclusive). This fact determined the West Pacific type of convergent boundaries for the accretionary structures of the Central Asian Fold Belt. The drift of Siberia from African to Pacific province in the Late Cenozoic determined the structure and development of the convergent boundary in the western Pacific, including extensive intraplate magmatism in continental Asia in the Late Mesozoic and Cenozoic.     

First Data on Au–Sb Mineralization of the Ariadnoe Ultramafic Intrusion,Primor’e

Doklady Earth Sciences - A new promising source of mineral deposits is found in the southern part of the Far East of Russia: the Ti-bearing intrusions of ultramafic rocks of the Sikhote-Alin...     

Seismotectonics of the Calabrian arc

Relocation of intermediate and deep earthquakes of Tyrrhenian Sea area through joint hypocenter determination for the period 1962–1979, has allowed a more detailed definition of the geometry of this peculiar Benioff zone. Earthquakes dip along a quasi-vertical plane to 250 km depth; there is a 50° dip in the 250–340 km depth range, and a low dip angle to 480 km depth. The structure sketched from the hypocenters is almost continuous, but most energy has been released in the 230–340 km depth interval. An evaluation of fault plane solutions of intermediate earthquakes in this area indicates predominance of down-dip compressions in the central part of the slab. At the border, strike-slip motion occurs independent of depth. Some earthquakes that occurred at intermediate depth (less than 100 km) along the Ionian margin of Calabria show predominance of reverse faulting, with the P-axis oriented SE-NW. However, shallow earthquakes in the Calabria-Sicily region indicate a more complex motion, with predominance of normal faulting. A possible interpretation of these features according to the available geological history, which involves subduction of continental lithosphere, is discussed.     

Mineral magnetic characterization of the Godavari river sediments: Implications to Deccan basalt weathering

Mineral magnetic analysis including thermo-magnetic studies and clay mineralogy on bed load and floodplain sediments from the Godavari river indicate distinct mineral assemblages. The floodplain sediments up to the delta region are characterised by unimodal ferrimagnetic mineralogy marked by the presence of maghemite and single domain magnetites derived from Deccan basalts. On the other hand the bed loads show varied magnetic mineral assemblages depicting greater local mixing from the non-basaltic bedrock province. The temperature dependent magnetic susceptibility and clay mineralogy of the floodplain samples show titanomagnetites (Fe₃O₄-Fe₂TiO₄), maghemite (χ _LF-Fe₂O₃) and smectite that are characteristic of the Deccan Volcanic Province (DVP). Presence of this ferrimagnetically dominant unimodal assemblage up to the delta region and probably into the Bay of Bengal off the Godavari river is attributed to extensive chemical weathering of the basalt. The quantitative approach of mineral magnetism, therefore, can be used to study the paleomonsoon variability and its relation to Deccan basalt weathering from the Godavari-Bengal fan system.     

A Burst with Double Radio Spectrum Observed up to 212 GHz

We study a solar flare that occurred on 10 September 2002, in active region NOAA 10105, starting around 14:52 UT and lasting approximately 5 minutes in the radio range. The event was classified as M2.9 in X-rays and 1N in Hα. Solar Submillimeter Telescope observations, in addition to microwave data, give a good spectral coverage between 1.415 and 212 GHz. We combine these data with ultraviolet images, hard and soft X-ray observations, and full-disk magnetograms. Images obtained from Ramaty High Energy Solar Spectroscopic Imager data are used to identify the locations of X-ray sources at different energies, and to determine the X-ray spectrum, while ultraviolet images allow us to characterize the coronal flaring region. The magnetic field evolution of the active region is analyzed using Michelson Doppler Imager magnetograms. The burst is detected at all available radio frequencies. X-ray images (between 12 keV and 300 keV) reveal two compact sources. In the 212 GHz data, which are used to estimate the radio-source position, a single compact source is seen, displaced by 25″ from one of the hard X-ray footpoints. We model the radio spectra using two homogeneous sources, and we combine this analysis with that of hard X-rays to understand the dynamics of the accelerated particles. Relativistic particles, observed at radio wavelengths above 50 GHz, have an electron index evolving with the typical soft–hard–soft behavior.     

Photometric and polarimetric studies of three W UMa-type binaries: FZ Ori,V407 Peg and LP UMa

We present analyses of new optical photometric observations of three W UMa-type contact binaries FZ Ori, V407 Peg and LP UMa. Results from the first polarimetric observations of the FZ Ori and V407 Peg are also presented. The periods of FZ Ori, V407 Peg and LP UMa are derived to be 0.399986, 0.636884 and 0.309898 d, respectively. The O?C analyses indicate that the orbital periods of FZ Ori and LP UMa have increased with the rate of 2.28×10^?8 and 1.25×10^?6 d?yr^?1, respectively and which is explained by transfer of mass between the components. In addition to the secularly increasing rate of orbital period, it was found that the period of FZ Ori has varied in sinusoidal way with oscillation period of ～30.1 yr. The period of oscillations are most likely to be explained by the light-time effect due to the presence of a tertiary companion. Small asymmetries have been seen around the primary and secondary maxima of light curves of all three systems, which is probably due to the presence of cool/hot spots on the components. The light curves of all three systems are analysed by using Wilson-Devinney code (WD) and the fundamental parameters of these systems have been derived. The present analyses show that FZ Ori is a W-subtype, and V407 Peg and LP UMa are A-subtype of the W UMa-type contact binary systems. The polarimetric observations in B, V, R and I bands, yield average values of polarization to be 0.26±0.03, 0.22±0.02, 0.22±0.03 and 0.22±0.05 per cent for FZ Ori and 0.21±0.02, 0.29±0.03, 0.31±0.01 and 0.31±0.04 per cent for V407 Peg, respectively.     

Anatomy of individual agglutinates from a lunar highland soil

Abstract— We report results of our investigation of the relationship between values of I_s/FeO (relative concentration of nanophase Fe⁰ divided by total FeO content), glass abundance, total Fe content, and degree of digestion of <20 μm clasts for 22 individual agglutinates (250–1000 μm) from the mature Apollo 16 soil 61181 (I_s/FeO = 82 units in the <250 μm fraction). Agglutinates are important products of space weathering on the Moon, and they influence spectral observations at visible and near-IR wavelengths. Values of I_s/FeO for individual agglutinates (250–1000 μm) within this single soil span a range from 3 to 262 units which is larger than the range observed for all Apollo 16 bulk soils (～0 to 110 units). No correlation was observed between I_s/FeO and glass abundance and FeO concentrations for either agglutinitic glass or whole agglutinate particles under investigation. Our results suggest that the variation in I_s/FeO for agglutinates from a single soil may be in part a consequence of natural mixing processes on the Moon that produce highly-variable environments (with respect to surface exposure) for agglutinate formation and in part to variable kinetics of reactions in an agglutinate melt, which are influenced by a variety of factors including melt composition, temperature, impactor velocity, and quench rate. We cannot exclude but do not see evidence for other processes including addition of exotic agglutinates, micrometeoritic bombardment into compositionally-diverse microtargets, recycling of agglutinates, preferential melting of very fine soil particles, and production of nanophase Fe⁰ in amorphous rims of very fine irradiated lunar grains contributing to the observed variation of I_s/FeO.