Hydrothermal alteration mapping and structural features in the Ain Smara basin, Constantine (Northeastern Algeria): contribution of Landsat OLI8 data

2021 ◽  
Vol 14 (21) ◽  
Author(s):  
Nouh Rebouh ◽  
Abdelkader Oudni ◽  
Abdelkader Khiari ◽  
Chaouki Benabbas ◽  
Nevzat Özgür
Keyword(s):  
Hydrothermal Alteration ◽  
Structural Features ◽  
Northeastern Algeria

Hydrothermal alteration mapping and structural features in the Guelma basin (Northeastern Algeria): contribution of Landsat-8 data

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Baya Nait Amara ◽  
Djamal Eddine Aissa ◽  
Saïd Maouche ◽  
Massinissa Braham ◽  
Djamel Machane ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Structural Features ◽  
Landsat 8 ◽  
Northeastern Algeria

scholarly journals Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

2017 ◽  
Vol 14 (6) ◽  
pp. 1461-1492 ◽  
Author(s):  
Laura A. Casella ◽  
Erika Griesshaber ◽  
Xiaofei Yin ◽  
Andreas Ziegler ◽  
Vasileios Mavromatis ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Fossil Record ◽  
Marine Invertebrates ◽  
Structural Features ◽  
Geochemical Data ◽  
Replacement Reaction ◽  
Bulk Analysis ◽  
Arctica Islandica ◽  
Experimental Conditions ◽  
Living Organisms

Abstract. Biomineralised hard parts form the most important physical fossil record of past environmental conditions. However, living organisms are not in thermodynamic equilibrium with their environment and create local chemical compartments within their bodies where physiologic processes such as biomineralisation take place. In generating their mineralised hard parts, most marine invertebrates produce metastable aragonite rather than the stable polymorph of CaCO3, calcite. After death of the organism the physiological conditions, which were present during biomineralisation, are not sustained any further and the system moves toward inorganic equilibrium with the surrounding inorganic geological system. Thus, during diagenesis the original biogenic structure of aragonitic tissue disappears and is replaced by inorganic structural features. In order to understand the diagenetic replacement of biogenic aragonite to non-biogenic calcite, we subjected Arctica islandica mollusc shells to hydrothermal alteration experiments. Experimental conditions were between 100 and 175 °C, with the main focus on 100 and 175 °C, reaction durations between 1 and 84 days, and alteration fluids simulating meteoric and burial waters, respectively. Detailed microstructural and geochemical data were collected for samples altered at 100 °C (and at 0.1 MPa pressure) for 28 days and for samples altered at 175 °C (and at 0.9 MPa pressure) for 7 and 84 days. During hydrothermal alteration at 100 °C for 28 days most but not the entire biopolymer matrix was destroyed, while shell aragonite and its characteristic microstructure was largely preserved. In all experiments up to 174 °C, there are no signs of a replacement reaction of shell aragonite to calcite in X-ray diffraction bulk analysis. At 175 °C the replacement reaction started after a dormant time of 4 days, and the original shell microstructure was almost completely overprinted by the aragonite to calcite replacement reaction after 10 days. Newly formed calcite nucleated at locations which were in contact with the fluid, at the shell surface, in the open pore system, and along growth lines. In the experiments with fluids simulating meteoric water, calcite crystals reached sizes up to 200 µm, while in the experiments with Mg-containing fluids the calcite crystals reached sizes up to 1 mm after 7 days of alteration. Aragonite is metastable at all applied conditions. Only a small bulk thermodynamic driving force exists for the transition to calcite. We attribute the sluggish replacement reaction to the inhibition of calcite nucleation in the temperature window from ca. 50 to ca. 170 °C or, additionally, to the presence of magnesium. Correspondingly, in Mg2+-bearing solutions the newly formed calcite crystals are larger than in Mg2+-free solutions. Overall, the aragonite–calcite transition occurs via an interface-coupled dissolution–reprecipitation mechanism, which preserves morphologies down to the sub-micrometre scale and induces porosity in the newly formed phase. The absence of aragonite replacement by calcite at temperatures lower than 175 °C contributes to explaining why aragonitic or bimineralic shells and skeletons have a good potential of preservation and a complete fossil record.

Overprinting of early, redistributed Fe and Pb–Zn mineralization by late-stage Au–Ag–Cu deposition at the Dumagami mine, Bousquet district, Abitibi, Quebec

1990 ◽  
Vol 27 (12) ◽  
pp. 1651-1671 ◽  
Author(s):  
P. Marquis ◽  
C. Hubert ◽  
A. C. Brown ◽  
D. M. Rigg
Keyword(s):  
Hydrothermal Alteration ◽  
Narrow Band ◽  
Early Stage ◽  
Hydrothermal Activity ◽  
Structural Features ◽  
White Mica ◽  
Ductile Deformation ◽  
Sulphide Mineralization ◽  
Abitibi Greenstone Belt ◽  
Two Stages

The Dumagami Au–Ag–Cu deposits are hosted by strongly deformed and altered Archean felsic metavolcanites of the Blake River Group (BRG), southern Abitibi greenstone belt, Canada. Textural and structural features recorded within the lithologies of the BRG at Dumagami indicate that two stages of hydrothermal alteration, separated by a dynamometamorphic event, have affected the volcanic protoliths in the deposit area. Advanced argillic and sericitic alteration zones, massive pyrite bodies, and massive sphalerite–galena bodies resulted from the first stage of hydrothermal activity. Sericitic shells surround peraluminous cores, which host the massive pyrite bodies and massive sphalerite–galena bodies within the altered zones.This early-stage alteration was followed by a dynamometamorphic event that reached the greenschist–amphibolite grade and almost completely recrystallized both fresh and altered rocks and the enclosed massive sulphide bodies. White-mica schists and andalusite–kyanite schists represent the dynamometamorphic equivalents of the earlier sericitic and advanced argillic zones. Mesoscopic and microscopic structures and textures attest to the ductile behaviour of the massive pyrite bodies during this deformation and accompanying metamorphism.Portions of the deformed and metamorphosed altered zones are characterized by a late cataclastic deformation and by the development of fractures postdating the ductile deformation. The late hydrothermal alteration is concentrated within these cataclastic rocks and is characterized by the retrogression of the greenschist–amphibolite assemblages. Andalusite and kyanite are replaced by diaspore, kaolinite, and pyrophyllite assemblages, and pyrite is replaced by chalcopyrite–gold, chalcopyrite–bornite–gold, and bornite–stromeyerite assemblages. The concentration of the pre-dynamometamorphic alteration and sulphide mineralization within a narrow band along the southern BRG could indicate that this part of the BRG was the locus of a major Archean synvolcanic fault zone.

scholarly journals Using of remote sensing and aeromagnetic data for predicting potential areas of hydrothermal mineral deposits in the Central Eastern Desert of Egypt

2018 ◽  
Vol 7 (1) ◽  
Author(s):  
Mohamed Ismail Abdelkareem
Keyword(s):  
Remote Sensing ◽  
Hydrothermal Alteration ◽  
Principal Component ◽  
Eastern Desert ◽  
Shuttle Radar Topography Mission ◽  
Structural Features ◽  
Central Eastern Desert ◽  
Structural Density ◽  
Predictive Map ◽  
Central Eastern

<p>This article explored mineral resources and their relation to structural settings in the Central Eastern Desert (CED) of Egypt. Integration of remote sensing (RS) with aeromagnetic (AMG) data was conducted to generate a mineral predictive map.  Several image transformation and enhancement techniques were performed to Landsat Operational Land Imager (OLI) and Shuttle Radar Topography Mission (SRTM) data. Using band ratios and oriented principal component analysis (PCA) on OLI data allowed delineating hydrothermal alteration zones (HAZs) and highlighted structural discontinuity. Moreover, processing of the AMG using Standard Euler deconvolution and residual magnetic anomalies successfully revealed the subsurface structural features. Zones of hydrothermal alteration and surface/subsurface geologic structural density maps were combined through GIS technique. The results showed a mineral predictive map that ranked from very low to very high probability. Field validation allowed verifying the prepared map and revealed several mineralized sites including talc, talc-schist, gold mines and quartz veins associated with hematite. Overall, integration of RS and AMG data are powerful techniques in revealing areas of potential mineralization involved with hydrothermal processes.      </p>

scholarly journals Using of remote sensing and aeromagnetic data for predicting potential areas of hydrothermal mineral deposits in the Central Eastern Desert of Egypt

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Mohamed Abdelkareem ◽  
Abdelhady Akrby ◽  
Mousa Fakhry ◽  
Mohamed Mostafa
Keyword(s):  
Remote Sensing ◽  
Hydrothermal Alteration ◽  
Principal Component ◽  
Eastern Desert ◽  
Shuttle Radar Topography Mission ◽  
Structural Features ◽  
Central Eastern Desert ◽  
Structural Density ◽  
Predictive Map ◽  
Central Eastern

This article explored mineral resources and their relation to structural settings in the Central Eastern Desert (CED) of Egypt. Integration of remote sensing (RS) with aeromagnetic (AMG) data was conducted to generate a mineral predictive map. Several image transformation and enhancement techniques were performed to Landsat Operational Land Imager (OLI) and Shuttle Radar Topography Mission (SRTM) data. Using band ratios and oriented principal component analysis (PCA) on OLI data allowed delineating hydrothermal alteration zones (HAZs) and highlighted structural discontinuity. Moreover, processing of the AMG using Standard Euler deconvolution and residual magnetic anomalies successfully revealed the subsurface structural features. Zones of hydrothermal alteration and surface/subsurface geologic structural density maps were combined through GIS technique. The results showed a mineral predictive map that ranked from very low to very high probability. Field validation allowed verifying the prepared map and revealed several mineralized sites including talc, talc-schist, gold mines and quartz veins associated with hematite. Overall, integration of RS and AMG data is a powerful technique in revealing areas of potential mineralization involved with hydrothermal processes.

scholarly journals Experimental diagenesis: Insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

2016 ◽  
Author(s):  
Laura A. Casella ◽  
Erika Griesshaber ◽  
Xiaofei Yin ◽  
Andreas Ziegler ◽  
Vasileios Mavromatis ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Fossil Record ◽  
Marine Invertebrates ◽  
Organic Matrix ◽  
Structural Features ◽  
Geochemical Data ◽  
Replacement Reaction ◽  
Bulk Analysis ◽  
Arctica Islandica ◽  
Experimental Conditions

Abstract. Biomineralised hard parts form the most important physical fossil record of past environmental conditions. However, living organisms are not in thermodynamic equilibrium with their environment and create local chemical compartments within their bodies where physiologic processes such as biomineralisation take place. Generating their mineralized hard parts most marine invertebrates thus produce metastable aragonite rather than the stable polymorph of CaCO3, calcite. After death of the organism, the physiological conditions which were present during biomineralisation are not sustained any further and the system moves toward inorganic equilibrium with the surrounding inorganic geological system. Thus, during diagenesis the original biogenic structure of aragonitic tissue disappears and is replaced by inorganic structural features. In order to understand the diagenetic replacement of biogenic aragonite to non-biogenic calcite, we subjected Arctica islandica mollusc shells to hydrothermal alteration experiments. Experimental conditions were between 100 °C and 175 °C with reaction durations between one and 84 days, and alteration fluids simulating meteoric and burial waters, respectively. Detailed microstructural and geochemical data were collected for samples altered at 100 °C (and at 0.1 MPa pressure) for 28 days and for samples altered at 175 °C (and at 0.9 MPa pressure) for 7 and 84 days, respectively. During hydrothermal alteration at 100 °C for 28 days, most but not all of the biopolymer matrix was destroyed, while shell aragonite and its characteristic microstructure was largely preserved. In all experiments below 175 °C there are no signs of a replacement reaction of shell aragonite to calcite in X-ray diffraction bulk analysis. At 175 °C the replacement reaction started after a dormant time of 4 days, and the original shell microstructure was almost completely overprinted by the aragonite to calcite replacement reaction after 10 days. Newly formed calcite nucleated at locations which were in contact with the fluid, at the shell surface, in the open pore system, and along growth lines. In the experiments with fluids simulating meteoric water, calcite crystals reached sizes up to 200 micrometres, while in the experiments with Mg-containing fluids the calcite crystals reached sizes up to one mm after 7 days of alteration. Aragonite is metastable at all applied conditions. A small bulk thermodynamic driving force exists for the transition to calcite, which is augmented by stresses induced by organic matrix and interface energies related to the nanoparticulate architecture of the biogenic aragonite. We attribute the sluggish replacement reaction to the inhibition of calcite nucleation in the temperature window from ca. 50 °C to ca. 170 °C, or, additionally, to the presence of magnesium. Correspondingly, in Mg2&amp;plus;-bearing solutions the newly formed calcite crystals are larger than in Mg2&amp;plus;-free solutions. Overall, the aragonite-calcite transition occurs via an interface-coupled dissolution-reprecipitation mechanism, which preserves morphologies down to the sub-micrometre scale and induces porosity in the newly formed phase. The absence of aragonite replacement by calcite at temperatures lower than 175 °C contributes to explain why aragonitic or bimineralic shells and skeletons have a good potential of preservation and a complete fossil record.

scholarly journals Lithological, structural and hydrothermal alteration mapping utilizing remote sensing datasets: a case study around Um Salim area, Egypt

2021 ◽  
Vol 942 (1) ◽  
pp. 012032
Author(s):  
A Shebl ◽  
Á Csámer
Keyword(s):  
Remote Sensing ◽  
Hydrothermal Alteration ◽  
Spatial Relationship ◽  
Eastern Desert ◽  
Detailed Examination ◽  
Structural Features ◽  
Ore Deposits ◽  
Band Ratio ◽  
Density Slicing ◽  
Lineament Extraction

Abstract Remote sensing datasets have introduced remarkable advancements in mapping rock units, structural elements, and hydrothermal alteration zones. This study applied Landsat Operational Land Imager (OLI) multispectral dataset in discriminating the intricate basement of Um Salim area, Central Eastern Desert (CED), Egypt. Moreover, a panchromatic 15m pixel size band is implemented to extract the study area’s linear structural features. Several image processing methods including False Color Combination (FCC), Band Ratio (BR), Optimum Index Factor (OIF), and Density slicing were utilized in lithological and alteration mapping. The widely used, LINE module of the PCI Geomatica is applied for lineament extraction. Results reasonably discriminate the complicated rock units using selected composites depending on OIF results. A photo-geological map is constructed and shows greater coincidence with recently published maps. Lineaments map and its density revealed the preponderance of NE-SW and WNW-ESE structural trends. The spatial relationship between the resultant hydrothermally-altered zones and the detected structural features strongly recommends further detailed examination for ore deposits within the study area besides manifesting the efficiency of the utilized data and methods.

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