Magmatism in the epochs of ural paleocean closure and mobile belt development: Composition, distinctive evolutionary features, and sources

The paper reports major evolutionary trends of Paleozoic magmatism in the Urals in relation to the closure of the oceanic basin and associated subduction, obduction, and collision. An attempt is undertaken to use these data as a basis for reproducing the geodynamic and thermal regime during various stages of the regional geological evolution. Distinctive compositional features of the rocks, the discrete character of magmatism reflecting changes in the geodynamic environments, and the transition from predominantly mantle sources of magmatism (at 460-380 Ma) to mantle-crustal (at 360-310 Ma) and finally crustal (290-250 Ma) ones, alternating epochs of relatively “dry” and “hydrous” mantle magmatism at 460-430 Ma and the “hydrous” type of later magmatism make it possible to reproduce the thermal regime of the orogen. During the intense low-hydrous basite magmatism (460-430 Ma), the temperature in the magma generation region was 1300-1100°C and decreased to 1100-900°C during predominantly hydrous magmatism (425-400 Ma). The P-T parameters of hydrous anatexis (360-310 Ma) that gave rise to tonalites and granodiorites were 7-9 kbar and 800 ± 50°C; they constrain the maximum temperature in the lower crust. The next stage of the hydrous anatexis of tonalites and granodiorites resulted in intense granite-forming processes (290-250 Ma) and occurred at pressures close to 5-6 kbar and temperatures of 700 ± 50°C. In the situation of the adiabatic heat transfer with fluids, the minimum temperatures in the upper mantle in the Ural suprasubduction epioceanic mobile belt at a depth of approximately 80 km can be provisionally estimated as follows: 1300 ± 100°C at 450-425 Ma, 1100 =- 100°C at 425-400 Ma, and 900 ± 100°C at 375-250 Ma. Data reported in the paper testify that the temperature in the upper mantle and crust of the Ural Mobile Belt was 150-200°C lower than in neighboring oceanic and continental areas, and this places the Urals among orogens of the “cold” type (Maruyama et al.,2007).     

Simulation of high-impact tropical weather events: comparative analysis of three heavy rainfall events

Episodes of heavy rainfall, although relatively rare, significantly contribute to the hydrological cycle due to the large quantum of rainfall in a short span of time. Accurate simulation of such heavy or extreme rainfall events therefore is an important benchmark for a model. Here, we consider the simulation of three heavy rainfall events (Mumbai, Bangalore and Chennai) that occurred over the Indian monsoon region in different geographical locations and seasons during 2005, using a mesoscale meteorological model, namely MM5V3. Simulations have been carried out at high resolution (2 km) to resolve orographic features and land–ocean gradients over the event locations with a 3-nest, 2-way configuration. The primary objective of this study is to carry out a multi-event, multi-location evaluation of the model configuration for simulating a class of heavy rainfall events and to compare some important meteorological features of the events. Our results have shown that a very high relative humidity, low-level convergence, convective instability in terms of equivalent potential temperature, high vertical velocity, smaller mixing ratio at low level and higher mixing ratio at upper level essentially dominated and sustained the convective dynamics in all the three events. It was also found that the latent heat flux (LHF) dominated coastal events (Mumbai and Chennai) with relatively much higher values compared to sensible heat flux (SHF) throughout the event life cycle. In the case of the Bangalore event, both LHF and SHF are comparable during the event life cycle.     

Ophiolite complexes as collision zone markers: making the case for the Antique Ophiolite Complex, Panay Island, central Philippines

The collision between the North Palawan Block (NPB) and Philippine Mobile Belt (PMB) has been the subject of studies considering its significance in help-ing define the tectonic evolution of the Philippine is-land arc system. The geology of the western Panay island reveals the presence of a continent-related block (Buruanga Peninsula) juxtaposed to an oceanic frag-ment (Antique Ophiolite Complex). Our recent work in the Buruanga Peninsula helped us define the terrane boundary between the Peninsula and the Antique Ophiolite Complex. However, considering available published data, the Antique Ophiolite Complex has never been considered to be a part of the NPB and to mark the collision zone between Palawan and the PMB.     

Formation of refractory inclusions by evaporation of condensate precursors

Berman’s (1983) activity-composition model for CaO-MgO-Al₂O₃-SiO₂ liquids is used to calculate the change in bulk chemical and isotopic composition during simultaneous cooling, evaporation, and crystallization of droplets having the compositions of reasonable condensate precursors of Types A and B refractory inclusions in CV3 chondrites. The degree of evaporation of MgO and SiO₂, calculated to be faithfully recorded in chemical and isotopic zoning of individual melilite crystals, is directly proportional to evaporation rate, which is a sensitive function of P_H2, and inversely proportional to the droplet radius and cooling rate. When the precursors are partially melted in pure hydrogen at peak temperatures in the vicinity of the initial crystallization temperature of melilite, their bulk chemical compositions evolve into the composition fields of refractory inclusions, mass-fractionated isotopic compositions of Mg, Si, and O are produced that are in the range of the isotopic compositions of natural inclusions, and melilite zoning profiles result that are similar to those observed in real inclusions. For droplets of radius 0.25 cm evaporating at P_H2 = 10⁻⁶ bar, precursors containing 8 to 13 wt.% MgO and 20 to 23% SiO₂ evolve into objects similar to compact Type A inclusions at cooling rates of 2 to 12 K/h, depending on the precise starting composition. Precursors containing 13 to 14 wt.% MgO and 23 to 26% SiO₂ evolve into objects with the characteristics of Type B1 inclusions at cooling rates of 1.5 to 3 K/h. The relatively SiO₂-poor members of the Type B2 group can be produced from precursors containing 14 to 16 wt.% MgO and 27 to 33% SiO₂ at cooling rates of <1 K/h. Type B2’s containing 27 to 35 wt.% SiO₂ and <12% MgO require precursors with higher SiO₂/MgO ratios at MgO > 15% than are found on any condensation curve. The characteristics of fluffy Type A inclusions, including their reversely zoned melilite, can only be understood in the context of this model if they contain relict melilite.     

Decolorization of different azo dyes by Phanerochaete chrysosporium RP78 under optimal condition

Detoxification of synthetic dyes is one of the main challenges in clearing textile industry wastes. Biodegradation of azo-dyes using Phanerochaete chrysosporium is one the most environmentally friendly methods available. The main enzymes responsible for mycodecolorization process are lignin and manganese peroxidases. Here, optimization of expression conditions has been carried out with manipulating culture condition and nutrient sources. Therefore, the effects of buffer and temperature as well as nitrogen source on lignin peroxidase and manganese peroxidase production were investigated at two levels and four levels, respectively. For this purpose, P. chrysosporium RP78 based on Taguchi design of experiment has been applied. Maximum lignin and manganese peroxidase activities of 182 ± 2.5 U/L and 850 ± 41 U/L were obtained under predicted optimum conditions, respectively. Thereby, about 100 % decolorization was achieved after 24 h for two most widely used groups of azo dyes in textile industry consisting reactive and acidic. The physical adsorption of the azo dyes by mycelia was not significant which indicated that the enzymatic degradation of the dyes was occurred. Time profile of these enzymes showed that manganese peroxidase was peaked on 9^th day while lignin peroxidase peaked on 13^th day and remained stable in the culture. The extracellular expression profiles of both were studied by 2 dimensional gel electrophoresis to partially characterize the enzymes.     

Dissociative velocity rates of oxygen and ozone in the ionosphere

Summary On the basis of the exponential approximation for the distribution of the concentration of molecular oxygen and ozone in given parts of the ionosphere, expressions have been derived for the changes of the dissociative velocity rates of the oxygen components in the ionosphere. The numerical calculations made reveal negligible changes of these rates for heights above 100 km and sufficiently strong variations in the low ionosphere.     

Silicate and salt melts in the genesis of the industrial’noe tin deposit: Evidence from inclusions in minerals

The data obtained on melt and fluid inclusions in minerals of granites, metasomatic rocks, and veins with tin ore mineralization at the Industrial’noe deposit in the southern part of the Omsukchan trough, northeastern Russia, indicate that the melt from which the quartz of the granites crystallized contained globules of salt melts. Silicate melt inclusions were used to determine the principal parameters of the magmatic melts that formed the granites, which had temperatures at 760–1020°C, were under pressures of 0.3–3.6 kbar, and had densities of 2.11–2.60 g/cm³ and water concentrations of 1.7–7.0 wt %. The results obtained on the fluid inclusions testify that the parameters of the mineral-forming fluids broadly varied and corresponded to temperatures at 920–275°C, pressures 0.1–3.1 kbar, densities of 0.70–1.90 g/cm³, and salinities of 4.0–75.0 wt % equiv. NaCl. Electron microprobe analyses of the glasses of twelve homogenized inclusions show concentrations of major components typical of an acid magmatic melt (wt %, average): 73.2% SiO₂, 15.3% Al₂O₃, 1.3% FeO, 0.6% CaO, 3.1% Na₂O, and 4.5% K₂O at elevated concentrations of Cl (up to 0.51 wt %, average 0.31 wt %). The concentrations and distribution of some elements (Cl, K, Ca, Mn, Fe, Cu, Zn, Pb, As, Br, Rb, Sr, and Sn) in polyphase salt globules in quartz from both the granites and a mineralized miarolitic cavity in granite were assayed by micro-PIXE (proton-induced X-ray emission). Analyses of eight salt globules in quartz from the granites point to high concentrations (average, wt %) of Cl (27.5), Fe (9.7), Cu (7.2), Mn (1.1), Zn (0.66), Pb (0.37) and (average, ppm) As (2020), Rb (1850), Sr (1090), and Br (990). The salt globules in the miarolitic quartz are rich in (average of 29 globules, wt %) Cl (25.0), Fe (5.4), Mn (1.0), Zn (0.50), Pb (0.24) and (ppm) Rb (810), Sn (540), and Br (470). The synthesis of all data obtained on melt and fluid inclusions in minerals from the Industrial’noe deposit suggest that the genesis of the tin ore mineralization was related to the crystallization of acid magmatic melts. Original Russian Text@ V.B. Naumov, V.S. Kamenetsky, 2006, published in Geokhimiya, 2006, No. 12, pp. 1279–1289.     

Deterioration of the volcanic kerb and pavement stones in a humid environment in the city centre of Izmir, Turkey

?zmir is the third largest city in Turkey and has being the centre of art, culture, tourism and trade activities throughout the 5,000 years of its history. Natural stones brought from different parts of the world have been widely used for construction of the prestigious buildings, monuments and roads etc., in the past in the city. Renovation of the street pavements and public gathering areas in the city centre has been undertaken by the Metropolitan Municipality in 2000 and continued through the year of 2001. These renovation activities have mainly been carried out in the streets running parallel to the sea shore. Volcanic rocks brought from the Central Anatolia Ankara-Gölba?? (andesites) and Kayseri-?ncesu (tuffs) have been used in the renovation works. These rocks have shown extensive deteriorations within 4 years of their usage between 2001 and 2005 under the influence of different environmental factors. In this study, the deteriorations developed in the recently placed volcanic rocks used as kerb and pavement stones in the city centre of ?zmir in the light of their mineralogical, chemical, physical and mechanical properties, used locations and the environmental factors are presented.     

Pyroxenite and granulite xenoliths from beneath the Scottish Northern Highlands Terrane: evidence for lower-crust/upper-mantle relationships

Xenolith suites from Permian host rocks in Orkney and the extreme NE of the Scottish mainland (Duncansby Ness) are described and compared to those from elsewhere in the Northern Highlands Terrane. Those from the Tingwall dyke, Orkney, comprise roughly equal proportions of ultramafic rocks (wehrlites, clinopyroxenites, websterites, hornblendites) and mafic to felsic rocks (gabbroic, noritic and dioritic granulites, with subordinate tonalites and trondhjemites). Those from Duncansby (45 km to the south) are dominantly olivine-poor ultramafic rocks (clinopyroxenites, pargasite pyroxenites, biotite-pyroxenites), together with granulites grading from gabbroic through to tonalites and trondhjemites. Most of the granulites are meta-igneous, comprising plagioclase and one- or two-pyroxene species with equilibration temperatures of 810-710 °C, and are regarded as samples of the lower crust. Absence of garnet and olivine, together with the association of relatively sodic plagioclase and aluminous pyroxenes, is consistent with derivation from depths corresponding to 5-10 kbar. Positive Eu anomalies in the granulites imply that most originated as plagioclase-rich cumulates from basaltic magmas. Scarce peraluminous quartzo-feldspathic xenoliths, such as a garnet-sillimanite-bearing sample from Duncansby, are regarded as metasedimentary in origin. Pyroxenes (and biotites) in the ultramafic xenoliths tend to have higher mg numbers than those of the granulites, reflecting higher temperatures of formation. Whereas the pyroxene-rich ultramafic rocks may be partly interleaved with the granulites in the lower crust, it is concluded that they also constitute a zone of substantial thickness at or around Moho level, separating the granulites from underlying peridotites, and that they originated as cumulates cognate to the granulites. They have, however, been variably metasomatised with formation of amphibole. This zone may constitute a density trap at which melt fractions, rich in K, Fe, Ti and OH and ascending from the asthenosphere, interact with the ultramafic cumulates, modifying them texturally and modally to produce a complex veined assemblage of clinopyroxene- and pargasite-rich rocks. The metasomatism involved an increase in LREE, HFSE and LILE contents. Some modal and cryptic metasomatism may also have affected the granulites, accounting for the presence of amphibole and relatively high LREE/HREE values (La/Lu 38-206). Since closely comparable xenolith assemblages also occur in Mull at the southwestern extremity of the Northern Highland Terrane, such metasomatised olivine- and orthopyroxene-deficient ultramafic rocks may characterise the shallowest part of the mantle beneath the entire terrane. The strongly bimodal character of the xenolith populations (either ultramafic or mafic grading to felsic) is taken to reflect the sharpness of the petrological Moho in this region.