Equation of state of Fe3+-bearing phase-X

We investigated the high-pressure behaviour of Fe³⁺-bearing hydrous phase-X, (K_1.307Na_0.015)(Mg_1.504Fe _0.373 ³⁺ Al_0.053Ti _0.004 ⁴⁺ )Si₂O₇H_0.36, up to 34?GPa at room temperature by synchrotron X-ray powder diffraction. The lattice parameters behave anisotropically, with the [001] direction stiffer than [100]. In the 10^?4 to 22?GPa pressure range, the axial bulk moduli are K _0a ?=?112(3) GPa and K′?=?4, and K _0c ?=?158(2) GPa and K′?=?4, and the anisotropy of the lattice parameters is β_0c :β_0a ?=?0.71:1. The cell volumes are fitted by a second-order Birch–Murnaghan equation of state giving a bulk modulus of K ₀?=?127(1) GPa and K′?=?4 in the same pressure range. After 22?GPa, a discontinuity in volume and lattice parameters can be recognized. Sample did not become amorphous up to 34?GPa. The coupled substitution K?+?Mg?=?[]?+?Fe³⁺ has only a limited influence on the bulk modulus and structural stability of phase-X.     

Authigenic carbonates in methane seeps from the Norwegian sea: Mineralogy, geochemistry, and genesis

Authigenic carbonates in the caldera of an Arctic (72°N) submarine mud volcano with active CH₄bearing fluid discharge are formed at the bottom surface during anaerobic microbial methane oxidation. The microbial community consists of specific methane-producing bacteria, which act as methanetrophic ones in conditions of excess methane, and sulfate reducers developing on hydrogen, which is an intermediate product of microbial CH₄ oxidation. Isotopically light carbon (δ¹³C_av =−28.9%0) of carbon dioxide produced during CH₄ oxidation is the main carbonate carbon source. Heavy oxygen isotope ratio (δ¹⁸O_av = 5%0) in carbonates is inherited from seawater sulfate. A rapid sulfate reduction (up to 12 mg S dm⁻³ day⁻¹) results in total exhausting of sulfate ion in the upper sediment layer (10 cm). Because of this, carbonates can only be formed in surface sediments near the water-bottom interface. Authigenic carbonates occurring within sediments occur do notin situ. Salinity, as well as CO ₃ ²⁻ /Ca and Mg/Ca ratios, correspond to the field of nonmagnesian calcium carbonate precipitation. Calcite is the dominant carbonate mineral in the methane seep caldera, where it occurs in the paragenetic association with barite. The radiocarbon age of carbonates is about 10000 yr.     

Evaluation and treatment of seepage problems at Chapar-Abad Dam, Iran

Engineering geological properties of the ground at the Chapar-Abad Dam were investigated in order to evaluate seepage problems and to select a proper method of water-proofing prior to construction. The dam is located to the northwest of Iran and is undergoing construction phase. The geology of the site consists of a series of Early Cambrian limestones and shales that crop out on the abutments and a valley that is filled by 60 m of alluvium deposits. The presence of thick alluvium deposits with various coefficients of permeability along the foundation demonstrates a possible seepage problem after water impoundment in the reservoir. The potential of water seepage was evaluated by the study of joint systems of the rock units, the use of numerical analysis to simulate water flow in the ground, and by conducting in-situ tests to estimate the permeability's values. Based on the obtained results and by reviewing many types of water-proofing methods regarding cost, feasibility and safety factors, the installation of a grout curtain is suggested.     

Estimation of drought-related yield loss using the dynamic statistical model of crop productivity forecasting

The methodological approach is proposed to the estimation of drought-related crop yield loss based on the dynamic statistical model of crop productivity forecasting. The obtained results agree well with the total actual crop yield loss. The approach under consideration is the first stage of creation of operational assessment of expected loss.     

VLA observations of class I methanol masers in the region of low-mass star formation L1157

We present the results of VLA observations of a maser candidate in the low-mass star formation region L1157 in the 7₀-6₁ A ⁺ transition at 44 GHz. The line is emitted by a compact, undoubtedly maser source associated with clump B0a, which is seen in maps of L1157 in thermal lines of methanol and other molecules. A much weaker compact source is associated with clump B1a, which is brighter than B0a in thermal methanol lines. The newly detected masers may form in thin layers of turbulent post-shock gas. In this case, the maser emission may be beamed, so that only an observer located in or near the planes of the layers can observe strong masers. On the other hand, the maser lines are double with a “red” asymmetry, indicating that the masers may form in collapsing clumps. A detailed analysis of collapsing-cloud maser models and their applicability to the masers in L1157 will be developed in subsequent papers.     

Geochronology of West Indonesia and its implication on plate tectonics

The results of radiometric dating of granitic rocks around Kotanopan near the west coast of Central Sumatra indicate an average age of 45 million years.Granites from the Lassi Mass in the Padang Highlands, Central Sumatra, and the Lampong Mass, South Sumatra, possess radiometric ages of ca. 112 and ca. 88 m.y., respectively. Granites and other rocks from the offshore areas north of Java indicate an average age of 100 m.y.Late Cretaceous granitic rocks are present in the islands of the Sunda Shelf namely Anambas (ca. 86 m.y.), Tembelan (ca. 85 m.y.) and Natuna (ca. 75 m.y.).Late Paleozoic granites possessing ages of ca. 276–298 m.y. are encountered in the basement rocks near Djambi, South Sumatra.The outcome of this radiometric age dating proves to be significant for it permits a fresh analysis of the geological evolution of Indonesia based on the plate-tectonics concept.The Tertiary volcano-plutonic arc exposed along the west coast of Sumatra can be traced to the south coast of Java. The corresponding subduction zone can be found in the islands west of Sumatra and the submarine ridge south of Java.The Late Cretaceous plutonic belt of Sumatra does not continue to Java but passes north of it, running however parallel to the subduction zone of Java. These two zones merge in the Meratus Mountains of Southeast Kalimantan.Sumatra was already a volcano-plutonic arc during Permian time, suggesting that since this Period the margins of at least four lithospheric plates have remained near the side of the active Sumatran arc.The presence of Permian volcanic and granitic rocks in the Malay Peninsula and West Kalimantan, and the results of the radiometric age determination of granitic rocks from the islands situated in the Sunda Shelf area, point to the existence of other Permian and Cretaceous volcano-plutonic arcs east and north of the arcs previously described in Sumatra and Java. Thus a double volcano-plutonic arc with opposing Benioff zones must have existed during Permian and Cretaceous time in this area.The Schwaner Mountains of West Kalimantan are considered to be the place where volcano-plutonic arcs of different ages have merged together. The correlative subduction zones have to be sought in the so-called Danau Formation of West Kalimantan and the northern part of the Kuching zone, the Sibu zone of Serawak situated north of the Schwaner Mountains.The evolution and complex geology of the western part of Indonesia can only be understood by the supposition of the existence of megaplates and sub-plates generated from spreading centers situated in the Indian Ocean and presumably in the area of the South China Sea, respectively.     

Bemerkungen zu Sonders Arbeit: „Zur Theorie und Klassifikation der eruptiven vulkanischen Vorgänge“

Ohne Zusammenfassung     

Stokes problem for infinite vertical plate with constant heat flux

An exact solution for the Stokes problem for an infinite vertical plate has been derived on taking into account the constant heat flux at the plate. It has been observed that the velocity of the fluid increases with increasingt (time) orG (the Grashof number).