Evolution of gold mineralization in the Ashanti Gold Belt,Ghana: Evidence from carbonate compositions and parageneses     

A. Hamid Mumin  M. E. Fleet 《Mineralogy and Petrology》1995,55(4):265-280

Summary Ankerite, siderite, calcite and magnesite occur in variable proportions within all host and mineralized rocks of the Bogosu and Prestea mining districts of the Ashanti Gold Belt, Ghana. The compositions of coexisting ankerite-siderite grains establish that complex rhythmically zoned growth banding and replacement textures are present. This compositional variation is attributed to episodic fluctuation in the temperature and composition of fluids in the Bogosu-Prestea mesothermal gold system. Temperatures derived from the ankerite-siderite composition geothermometer are generally consistent with those from calcite-dolomite, arsenopyrite, carbon and oxygen stable isotope, and fluid inclusion geothermometers, and are about 360°C for the metamorphic peak, 400 to 350°C for carbonate alteration of mafic dikes, and 340 to 140°C for gold deposition. The latter range occurs on a thin-section scale and represents separate pulses of fluid in the ore conduit.

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Entstehung der Goldvererzung im Ashanti Gold Belt, Ghana: Rückschlüsse aus Karbonat zusammensetzungen und Paragenesen

Zusammenfassung In allen Wirtsgesteinen und mineralisierten Gesteinen der Bergbaureviere von Bogosu und Prestea im Ashanti Gold Belt, Ghana treten Ankerit, Siderit, Calcit und Magnesit in unterschiedlichen Verhältnissen auf. Die Zusammensetzung von koexistierenden Ankerit-Siderit-Körnern zeigt eine komplexe, rhythmisch zonierte Wachstumsstreifung und Verärdngungsstrukturen. Diese Änderungen in der Zusammensetzung sind auf episodische Fluktuationen der Temperatur und der Zusammensetzung der Fluide im mesothermalen Goldsystem von Bogosu-Prestea zurückzuführen. Temperaturen nach dem Ankerit-Siderit-Geothermometer stimmen im allgerneinen mit jenen aus Geothermometern, die auf Calcit-Dolomit, Arsenopyrit, den stabilen Isotopen von Kohlenstoff and Sauerstoff und auf Flüssigkeitseinschlüssen beruhen, überein. Sie liegen bei rund 360°C für den Höhepunkt der Metamorphose, bei 400 bis 350°C für die Karbonat Alteration der matischen Gänge and bei 340 bis 140°C für die Gold-Fällung. Der letztgenannte Bereich tritt in Dünnschlif Maßstab auf and repräsentiert einzelne Schübe von Fluid in den Erzgängen.

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Simulating the interactions between the water and the socio-economic system in a stressed endorheic basin     

Sajad Enteshari  Hamid R. Safavi 《水文科学杂志》2020,65(13):2159-2174

ABSTRACT

The endorheic basin of Zayandehrud in Iran suffers from environmental problems, social tensions, and economic instability. Lack of understanding how the water system and the socio-economic system interact may explain these challenges. A system dynamics model, being a holistic simulation tool, was developed for the Zayandehrud basin and used to evaluate several policy scenarios. The indices of employment, gross regional product, the volume of groundwater and surface water stored, flow into the basin’s end lake, and the water flow in the river were used to evaluate the scenarios. The findings demonstrate that focusing on supply-based activities or water demand management cannot solely improve the condition of the Zayandehrud basin. It is required to reconsider the development policies of the region in a broader context. Reducing the irrigated area by 15% and developing new industries up to a certain limit may make the combined water and socio-economic system sustainable.  相似文献   

The Mesozoic–Cenozoic structural framework of the Bay of Kiel area, western Baltic Sea     

Martin Bak Hansen  Holger Lykke-Andersen  Ali Dehghani  Dirk Gajewski  Christian Hübscher  Morten Olesen  Klaus Reicherter 《International Journal of Earth Sciences》2005,94(5-6):1070-1082

A dense grid of multichannel high-resolution seismic sections from the Bay of Kiel in the western Baltic Sea has been interpreted in order to reveal the Mesozoic and Cenozoic geological evolution of the northern part of the North German Basin. The overall geological evolution of the study area can be separated into four distinct periods. During the Triassic and the Early Jurassic, E–W extension and the deposition of clastic sediments initiated the movement of the underlying Zechstein evaporites. The deposition ceased during the Middle Jurassic, when the entire area was uplifted as a result of the Mid North Sea Doming. The uplift resulted in a pronounced erosion of Upper Triassic and Lower Jurassic strata. This event is marked by a clear angular unconformity on all the seismic sections. The region remained an area of non-deposition until the end of the Early Cretaceous, when the sedimentation resumed in the area. Throughout the Late Cretaceous the sedimentation took place under tectonic quiescence. Reactivated salt movement is observed at the Cretaceous Cenozoic transition as a result of the change from an extensional to compressional regional stress field. The vertical salt movement influenced the Cenozoic sedimentation and resulted in thin-skinned faulting.  相似文献   

Geophysical Mapping of a Buried Basalt/Sedimentary Interface, Eastern Sudan     

Hamid O. Ali 《Ground water》1987,25(1):14-20

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HAZMAP: A REMOTE DIGITAL MEASUREMENT SYSTEM FOR WORK IN HAZARDOUS ENVIRONMENTS     

D. P. Chapman  A. T. D. Deacon  A. Hamid 《The Photogrammetric Record》1994,14(83):747-758

In a continuing drive to reduce the radiation exposure of nuclear workers, many routine aspects of nuclear plant maintenance and refurbishment are increasingly undertaken by robotic or remote handling tools. Accurate “as built” documentation of plant records is vital to the successful planning and execution of such operations since an unexpected obstruction or undocumented site modification may result in a costly disruption or even failure of the intervention. In recognition of the importance of such documentation, a recent European Community ? ? Teleman-Robotics and remote sensing operations in hazardous nuclear environments
sponsored project has been directed towards the development of techniques for cost effective survey and modelling of such plant. This paper will detail the rationale behind the design of such a system and will describe typical results from a number of pilot projects.  相似文献   

Synthetic light curves of two eclipsing binary systems,U Sge and AW UMa     

Hamid M. K. Al-Naimiy 《Astrophysics and Space Science》1978,56(1):219-238

Photometric curve fits have been investigated by means of numerical quadratures to develop theoretical light curves appropriate to stars built up in accordance with the Roche model. The method has been applied previously to β Per (Al-Naimiy and Budding, 1977) on the basis of available observations in red and infrared, while presently applied to two systems with contact components.

1. U Sge, spherical primary totally eclipsed by a contact component secondary. Improved photometric elements of the system have been found, and compared with those obtained by Kopal's method in the frequency domain. The outcome of the curve fitting corresponds well with the results of an analysis in the frequency domain.
2. AW UMa, exhibiting the shallowest minima known for totally eclipsing W UMa systems. The physical and geometrical elements of the system have been found, and the contact nature of the two components confirmed.

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Time series forecasting of river flow using an integrated approach of wavelet multi-resolution analysis and evolutionary data-driven models. A case study: Sebaou River (Algeria)     

Mousaab Zakhrouf  Hamid Bouchelkia  Madani Stamboul  Sungwon Kim  Salim Heddam 《自然地理学》2018,39(6):506-522

The complexity of hydrological processes and lack of data for modeling require the use of specific tools for non-linear natural phenomenon. In this paper, an effort has been made to develop a conjunction model – wavelet transformation, data-driven models, and genetic algorithm (GA) – for forecasting the daily flow of a river in northern Algeria using the time series of runoff. This catchment has a semi-arid climate and strong variability in runoff. The original time series was decomposed into multi-frequency time series by wavelet transform algorithm and used as inputs to artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) models. Several factors must be optimized to determine the best model structures. Wavelet-based data-driven models using a GA are designed to optimize model structure. The performances of wavelet-based data-driven models (i.e. WANFIS and WANN) were superior to those of conventional models. WANFIS (RMSE = 12.15 m³/s, EC = 87.32%, R = .934) and WANN (RMSE = 15.73 m³/s, EC = 78.83%, R = .888) models improved the performances of ANFIS (RMSE = 23.13 m³/s, EC = 54.11%, R = .748) and ANN (RMSE = 22.43 m³/s, EC = 56.90%, R = .755) during the test period.  相似文献   

Analyse multi-échelle par ondelettes des contacts géologiques : application à la carte gravimétrique du Maroc nord-oriental     

Driss Khattach  Hamid Mraoui  Driss Sbibih  Touria Chennouf 《Comptes Rendus Geoscience》2006,338(8):521-526

The multiscale wavelet analysis has been applied to the gravity data from northeastern Morocco to map the major geological contacts, such us faults. Hence, the faults affecting the survey area were outlined with their importance level and dip direction. Seismic data confirm these results and testify the efficiency of this method, particularly in studying structure of plains. The structural map established is a very useful document in the planning of natural resources investigations (i.e. water, mines) to be undertaken in the area of study. To cite this article: D. Khattach et al., C. R. Geoscience 338 (2006).  相似文献   

Monitoring of dust storm and estimation of aerosol concentration in the Middle East using remotely sensed images     

Taheri Shahraiyni  Hamid  Karimi  Khadijeh  Habibi Nokhandan  Majid  Hafezi Moghadas  Naser 《Arabian Journal of Geosciences》2015,8(4):2095-2110

Arabian Journal of Geosciences - Dust storms are one of the major environmental disasters in the arid regions of Middle East, occurring in very high frequency. As a result, monitoring dust storms...  相似文献   

Application of analytical hierarchy process,frequency ratio,and certainty factor models for groundwater potential mapping using GIS   总被引：4，自引：1，他引：3  

Yousef Razandi  Hamid Reza Pourghasemi  Najmeh Samani Neisani  Omid Rahmati 《Earth Science Informatics》2015,8(4):867-883

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