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Thermal Anomaly (thermal + anomaly)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Synthesis, structural and thermal studies of tetrathioureacopper(I) chloride crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2005
M. Dhandapani
Abstract Tetrathioureacopper(I) chloride, hereafter abbreviated as TCC, was synthesised and single crystals were obtained from saturated aqueous solution by slow evaporation (solution growth) method at room temperature. The crystals obtained are bright, colourless and transparent having well defined external faces. The grown crystals were characterized through elemental analysis, single crystal X-ray diffraction study, thermal analysis, electron spin resonance spectroscopy and Fourier Transform infrared spectroscopy. The elemental analysis confirms the stoichiometry of the compound. The single crystal diffraction studies indicate that TCC crystallises in the tetragonal lattice and the unit cell parameters are a = b = 13.4082 Å, c = 13.8074 Å, V = 2482.29 Å3, , = , = , = 90°. Space group and the number of molecules per unit cell (Z) are found to be P41212 and 8 respectively. The TG curve of the sample shows a prolonged decomposition from 210 to 628.3 °C, from which the decomposition pattern has been formulated. The endothermic peaks in the DTA curve indicate melting and decomposition of the compound at 165.2 and 633.8 °C respectively. An exothermic peak in high temperature DSC indicates a phase transition in the compound at 274.8 °C. Thermal anomalies observed in the low temperature DSC at ,163.3, ,152.0, ,141.5, ,108.3, 1.0 and 12.1 °C in the heating run and ,157.1 and ,153.9 °C in the cooling run reveal first order phase transitions in the crystal. The peaks observed at ,146.2 °C in both the heating and cooling runs suggest occurrence of a second order phase transition in this compound. The IR spectroscopic data were used to assign the characteristic vibrational frequencies of various groups present in the compound. The ESR study confirms that the copper is in the +1 oxidation state in the complex. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Thermal anomaly around the Nojima Fault as detected by fission-track analysis of Ogura 500 m borehole samples

ISLAND ARC, Issue 3-4 2001
Takahiro Tagami
Abstract To better understand heat generation and transfer along earthquake faults, this paper presents preliminary zircon fission-track (FT) length data from the Nojima Fault, Awaji Island, Japan, which was activated during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake). Samples were collected of Cretaceous granitic rocks from the Ogura 500 m borehole as well as at outcrops adjacent to the borehole site. The Nojima Fault plane was drilled at a depth of 389.4 m (borehole apparent depth). Fission-track lengths in zircons from localities > 60 m distance from the fault plane, as well as those from outcrops, are characterized by the mean values of ,10,11 ,m and unimodal distributions with positive skewness, which show no signs of an appreciable reduction in FT length. In contrast, those from nearby the fault at depths show significantly reduced mean track lengths of ,6,8 ,m and distributions having a peak around 6,7 ,m with rather negative skewness. In conjunction with other geological constraints, these results are best interpreted by a recent thermal anomaly around the fault, which is attributable to heat transfer via focused fluids from the deep interior of the crust and/or heat dispersion via fluids associated with frictional heating by fault motion. [source]

Three deep Alpine-permafrost boreholes in Svalbard and Scandinavia

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2001
Ketil Isaksen
Abstract The presence and thermal character of permafrost reflect past and present surface energy balances plus the heat flux from the Earth's interior. Analysis of permafrost ground temperatures constitutes a key research tool for detecting thermal anomalies caused by twentieth-century warming. Three deep boreholes in alpine permafrost were drilled in Svalbard and Scandinavia and form part of the latitudinal transect of mountain permafrost boreholes through the mountains of Europe established under the EU PACE (Permafrost and Climate in Europe) project. The northernmost borehole in the transect, at Janssonhaugen (depth 102 m), western Svalbard (78°10,46,,N, 16°28,01,,E, 270 m ASL) was drilled in May 1998. In Scandinavia, boreholes were drilled at Tarfalaryggen (depth 100 m), northern Sweden (67°55,09,,N, 18°38,29,,E, 1550 m ASL) in March 2000 and at Juvvasshøe (depth 129 m), southern Norway (61°40,32,,N, 08°22,04,,E, 1894 m ASL) in August 1999. Permafrost thickness at Janssonhaugen is estimated as approximately 220 m. The temperature profiles on Tarfalaryggen and Juvvasshøe show anomalously low geothermal gradients, indicating low heat flow through thick permafrost (,350 m and ,380 m respectively). Palaeoclimatic analysis based on inversion modelling of the ground temperature measurements at Janssonhaugen shows near surface warming of 1.5 ± 0.5 °C during the twentieth century. Both the Tarfalaryggen and Juvvasshøe boreholes also reveal thermal anomalies, which reflect a surface warming over the past decades, with a magnitude of approximately 0.5,1.0 °C. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ L'existence d'un pergélisol ainsi que ses caractères thermiques reflètent la balance entre l'énergie de surface (passée et actuelle) et le flux de chaleur interne de la terre. L'étude des températures du pergélisol constitue ainsi une recherche fondamentale pour détecter les anomalies thermiques dues au réchauffement du vingtième siècle. Trois sondages profonds dans le pergélisol alpin ont été réalisés au Svalbard et en Scandinavie. Ils constituent une partie du transect en latitude de sondages du pergélisol de montagne réalisé dans le cadre du projet de l'Union Européenne Pace (Pergélisol et Climat en Europe). Le sondage le plus septentrional du transect a été foré en mai 1998 à Janssonhaugen (profondeur 102 m), à l'ouest de Svalbard (78°10,46,,N, 16°28,01,,E, à 270 m d'altitude). En Scandinavie, des sondages ont été réalisés en mars 2000 à Tarfallaryggen (profondeur 100 m) au nord de la Suède (67°55,09,,N, 18°38,29,,E, à 1550 m d'altitude) et en août 1999 à Juvvasshoe (profondeur 129 m), au sud de la Norvège (61°40,32,,N, 08°22,04,,E, à 1894 m d'altitude). L'épaisseur du pergélisol à Janssonhaugen est approximativement de 220 m. Les profils de température à Tarfalaryggen et à Juvvasshoe montrent des gradients géothermiques anormalement faibles, indiquant un faible écoulement de chaleur au travers d'un pergélisol épais (respectivement d'environ 350 m et 380 m). Des analyses paléoclimatiques basées sur un modèle d'inversion des mesures de la température du sol à Janssonhaugen indiquent un réchauffement près de la surface de 1.5 0.5 °C pendant le 20e siècle. A la fois à Tarfalarygen et à Juvvasshoe, les anomalies thermiques existantes révèlent un réchauffement de la surface d'une ampleur de approximative de 0.5 à 1.0 °C au cours des dernières décades [source]

Synthesis and characterization of potassium magnesium sulphate hexahydrate crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2006
M. Dhandapani
Abstract Potassium magnesium sulphate hexahydrate (picromerite) was synthesized and single crystals were obtained from saturated aqueous solution by slow evaporation method at room temperature. The crystals were bright, colourless and transparent having well defined external faces. The grown crystals were characterized through Fourier Transform Infrared (FTIR) spectral studies and thermal analysis. The FTIR data were used to assign the characteristic vibrational frequencies of the various chemical bonds in the compound. The compound crystallizes in monoclinic lattice with the space group P21/c. The thermogravimetry (TG) indicates the removal of only two water molecules around 100 °C. A suitable decomposition pattern was formulated based on the percentage weight losses observed in TG of the compound. The results of differential thermal analysis (DTA) conform to the results of TGA. Differential scanning calorimetry (DSC) analysis carried out at high temperature suggests that the occurrence of two phase transitions in the crystal between 140 and 180 °C. When the crystal was cooled below the room temperature up to ,170 °C, no thermal anomaly was observed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Using Temperature to Test Models of Flow Near Yucca Mountain, Nevada

GROUND WATER, Issue 5 2003
Scott Painter
Ground water temperatures in the fractured volcanic aquifer near Yucca Mountain, Nevada, have previously been shown to have significant spatial variability with regions of elevated temperatures coinciding roughly with near-vertical north-south trending faults. Using insights gained from one-dimensional models, previous investigators have suggested upwelling along faults from an underlying aquifer as a likely explanation for this ground water temperature pattern. Using a three-dimensional coupled flow and heat-transport model, we show that the thermal high coinciding with the Paintbrush fault zone can be explained without significant upwelling from the underlying aquifer. Instead, the thermal anomaly is consistent with thermal conduction enhanced slightly by vertical ground water movement within the volcanic aquifer sequence. If more than -400 m3/day of water enters the volcanic aquifer from below along a 10 km fault zone, the calculated temperatures at the water table are significantly greater than the measured temperatures. These results illustrate the potential limitations in using one-dimensional models to interpret ground water temperature data, and underscore the value in combining temperature data with fully coupled three-dimensional simulations. [source]

Thermal anomaly around the Nojima Fault as detected by fission-track analysis of Ogura 500 m borehole samples

Granulite facies thermal aureoles and metastable amphibolite facies assemblages adjacent to the Western Fiordland Orthogneiss in southwest Fiordland, New Zealand

JOURNAL OF METAMORPHIC GEOLOGY, Issue 5 2009
A. H. ALLIBONE
Abstract In southwest New Zealand, a suite of felsic diorite intrusions known as the Western Fiordland Orthogneiss (WFO) were emplaced into the mid to deep crust and partially recrystallized to high- P (12 kbar) granulite facies assemblages. This study focuses on the southern most pluton within the WFO suite (Malaspina Pluton) between Doubtful and Dusky sounds. New mapping shows intrusive contacts between the Malaspina Pluton and adjacent Palaeozoic metasedimentary country rocks with a thermal aureole ,200,1000 m wide adjacent to the Malaspina Pluton in the surrounding rocks. Thermobarometry on assemblages in the aureole indicates that the Malaspina Pluton intruded the adjacent amphibolite facies rocks while they were at depths of 10,14 kbar. Similar P,T conditions are recorded in high- P granulite facies assemblages developed locally throughout the Malaspina Pluton. Palaeozoic rocks more than ,200,1000 m from the Malaspina Pluton retain medium -P mid-amphibolite facies assemblages, despite having been subjected to pressures of 10,14 kbar for > 5 Myr. These observations contradict previous interpretations of the WFO Malaspina Pluton as the lower plate of a metamorphic core complex, everywhere separated from the metasedimentary rocks by a regional-scale extensional shear zone (Doubtful Sound Shear Zone). Slow reaction kinetics, lack of available H2O, lack of widespread penetrative deformation, and cooling of the Malaspina Pluton thermal anomaly within c. 3,4 Myr likely prevented recrystallization of mid amphibolite facies assemblages outside the thermal aureole. If not for the evidence within the thermal aureole, there would be little to suggest that gneissic rocks which underlie several 100 km2 of southwest New Zealand had experienced metamorphic pressures of 10,14 kbar. Similar high- P metamorphic events may therefore be more common than presently recognized. [source]

Fluid evolution and thermal structure in the rapidly exhuming gneiss complex of Namche Barwa,Gyala Peri, eastern Himalayan syntaxis

JOURNAL OF METAMORPHIC GEOLOGY, Issue 9 2005
D. CRAW
Abstract High-grade gneisses (amphibolite,granulite facies) of the Namche Barwa and Gyala Peri massifs, in the eastern Himalayan syntaxis, have been unroofed from metamorphic depths in the late Tertiary,Recent. Rapid exhumation (2,5 mm year,1) has resulted in a pronounced shallow conductive thermal anomaly beneath the massifs and the intervening Tsangpo gorge. The position of the 300 °C isotherm has been estimated from fluid inclusions using CO2,H2O immiscibility phase equilibria to be between 2.5 and 6.2 km depth below surface. Hence, the near-surface average thermal gradient exceeds 50 °C km,1 beneath valleys, although the thermal gradient is relatively lower beneath the high mountains. The original metamorphic fluid in the gneisses was >90% CO2. This fluid was displaced by incursion of brines from overlying marine sedimentary rocks that have since been largely removed by erosion. Brines can exceed 60 wt% dissolved salts, and include Ca, Na, K and Fe chlorides. These brines were remobilized during the earliest stages of uplift at >500 °C. During exhumation, incursion of abundant topography-driven surface waters resulted in widespread fracture-controlled hydrothermal activity and brine dilution down to the brittle,ductile transition. Boiling water was particularly common at shallow levels (<2.5 km) beneath the Yarlung Tsangpo valley, and numerous hot springs occur at the surface in this valley. Dry steam is not a major feature of the hydrothermal system in the eastern syntaxis (in contrast to the western syntaxis at Nanga Parbat), but some dry steam fluids may have developed locally. [source]