ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00180.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00181.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTCurrent pollution of the total environment is caused by waste products of the extrasomatic metabolism ofHomo sapienswho, since the beginnings of the industrial revolution, has raised his energy consumption by a factor of 10–20 above the basic metabolic rate of the single individual. While the increased energy flow through the human ecosystem has brought about an improvement of the human condition unprecedented in the history of mankind (including a doubling of the average life expectancy), it is beset also with an intrinsic maladaptive potential for the possible emergence of an autotoxic effect. The future of high‐energy (industrial) societies will, accordingly depend on man's capability to maintain an adequate energy flow while hopefully minimizing the potential impact of autotoxicity on his environment by suitable technological fi

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00182.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe aim of this paper is to demonstrate all aspects of the way in which chemistry affects exploitation of geothermal fluids: through scaling and corrosion and their treatment, through its influence on production characteristics, environmental considerations and also in the possible recovery of valuable by‐products. It is therefore essential that the chemical characteristics and behaviour of fluids are evaluated fully in order to optimize the design, operating conditions and management of a commercial geothermal system. Careful sampling and accurate measurements are thus indispensable. Chemical computer models are shown to be valuable tools for studying the chemical behaviour of a fluid in various situations; a brief illustration using the TPDEGAZ code is give

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00183.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTField observations on deep parts of the root zone of the Caledonian orogen are combined with the geophysical data available for recent continental collision zones such as the Alps, to provide a model for dynamics of crustal root zones.Rocks descending into the root zone are locally infiltrated by fluids which cause eclogitization along shear zones and fluid pathways. The eclogite facies rocks vary in density from 3.1 to 3.6 g cm‐3, reflecting the compositional variation in their protoliths. Where the amount of highly ductile eclogitic material reaches about 40% the descending crustal segment loses its coherence and disintegrates into a breccia where blocks of granulite facies rocks float in a matrix of eclogite material. A density‐stratified root zone develops, where light unreacted or partly eclogitized material floats on an ‘ocean’ dominated by eclogite facies rocks, the top of which may correspond to the Moho. Catastrophic decent of this eclogitic layer may (1) transport blocks of light material to depths of>90 km, which upon further disintegration due to eclogitization are released and return by buoyancy forces to the crust; (2) result in extension and uplift of the partly‐eclogitized lighter

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00184.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTA method is exhibited for assessing the time of onset of diapirism and salt flow‐speed. Using vitrinite reflectance measurements from wells drilled on top of a salt structure it is possible to determine the excess maturity caused by the focusing of heat due to the higher thermal conductivity of salt. The method is based on calculation of the thermal anomaly surrounding a rising salt diapir. For a given salt speed, predicted vitrinite reflectance values are calculated and compared with the observed values at given depths. The process is repeated with various speeds of the rising salt until consistency of predicted and observed values is obtained, thus constraining an assessment of the velocity of the salt. The method can easily be tailored to thermal indicators other than vitrinite reflectance, thereby enhancing the resolution of the thermal history, and constraining both the onset of salt rise as well as the speed. The well, Lulu‐1, from the Danish North Sea, is used to illustrate the proced

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00185.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTCorrelative fractionation relationships of sulphur isotope data for coexisting sulphate and sulphide pairs from hydrothermal ore deposits on δ38S versus Δ34S diagrams are deciphered theoretically. Taking into account dissolved H2S and SO42‐in hydrothermal fluids during precipitation of both sulphate and sulphide minerals, a 4‐species closed system is suggested for describing the conservation of mass among all sulphur‐bearing species on the δ‐Δ diagrams. The covariation in the δ34S values of both sulphate and sulphide is ascribed to isotopic exchange between oxidized and reduced sulphur species during mineral precipitation. The isotopic exchange could be a thermodynamic process due to simple cooling of high temperature fluids, which results in an equilibrium fractionation, or a kinetic process due to mixing of two sulphur reservoirs, which leads to a disequilibrium fractionation. The δ34S value of total sulphur in a hydrothermal system could change due to the precipitation of minerals, or due to the escape of H2S and/or SO42‐. Sulphur isotope data for anhydrite and pyrite pairs from the Luohe porphyrite iron deposit in the Yangtze River Valley is used to illustrate the mixing responsible for the disequilibriu

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00186.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe small, arctic Jan Mayen Island, site of the World's northernmost active volcano, Beerenberg, is part of the mid‐Atlantic ridge system and located along the Jan Mayen Fracture Zone (JMFZ). Recent data from the local seismic network, and fault plane solutions from the global network, indicate that the island is located at a ridge‐crest intersection, which might explain the origin of the island and the associated volcanism. Moreover, the new data suggest a series of offset segments of the Mohn's Ridge, overlapping in anen echelonpattern.In January 1985, a flank eruption was for the first time observed with the local seismic network. Volcanic tremors and low‐frequency events were observed on 5 January at 2230 h and 10 hours later the first large earthquake occurred. No visual confirmation of the eruption was made until 6 January at 1630 h. The seismic observations rule out the possibility that the large earthquake caused the eruption; it seems more likely that the changes in local stress conditions triggered the earthquake and that the eruption started before the first large earthquake. Recent observations show that the local network provides an efficient tool for monitoring and warning of volcanic activity. However, since there was no change in the local seismicity in the days or months before the 1985 eruption, it seems to be difficult to make long‐term predictions of Beerenberg flank eruptions without using other techniques such as observations

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00187.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTWe examine the long‐term seismicity of the Marmara Sea region in Turkey over a period of twenty centuries to attempt to answer two questions: (1) how well recorded in history is the earthquake activity of this region? and (2) does seismicity over this long period of time differ from that over the present century? We study this densely‐populated and fast‐developing region because it is one of the most tectonically active regions on the continents that appears today to be relatively quie

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00188.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe integrated analysis of geological, seismological and field observations with lineament data derived from satellite images allows the identification of a possible seismogenic fault zone for an earthquake which occurred near Etne in southwestern Norway, on 29 February 1989. The hypocentre of the earthquake was located at the mid‐crust at a depth of 13.8±0.9 km which is typical of small intraplate earthquakes. The Etne earthquake occurred as a result of normal faulting with a dextral strike‐slip component on a NW–SE trending fault. Available geological and lineament data indicate correlation of the inferred seismogenic fault with the NW–SE trending Etne fault zone. An aeromagnetic anomaly related to the Etne fault zone forms a regional feature intersecting both Precambrian basement and allochthonous Caledonian rocks. Based on these associations the occurrence of the Etne event is ascribed to the reactivation of a zone of weakness along the Etne fault zone. Slope‐instabilities developed in the superficial deposits during the Etne event demonstrate the existence of potentially hazardous secondary‐effects of such earthquakes even in low seismicity areas such as southwe

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1991.tb00189.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY