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Papers by Gemechu Bedassa

Research paper thumbnail of Stratigraphy and eruptive history of Gedemsa caldera volcano, Central Main Ethiopian Rift

Journal of Volcanology and Geothermal Research, Jan 31, 2024

Research paper thumbnail of Structural controls on magma pathways in Bora-Baricha-Tullu Moye (BBTM) volcanic system, Main Ethiopian Rift

Volcanica

The Bora-Baricha-Tullu Moye (BBTM) volcanic complex is located at a transitional zone in the Main... more The Bora-Baricha-Tullu Moye (BBTM) volcanic complex is located at a transitional zone in the Main Ethiopian Rift where tectonic and volcanic features show complex interplays. We mapped and characterised volcanic and tectonic features using high-resolution digital elevation models and performed morphometric and vent spatial distribution analyses. Structural analysis reveals NNE–SSW, NE–SW, and NW–SE trending faults in the region. The dominant post-caldera volcanic landforms are lava domes, pumice cones, scoria cones, maars, obsidian coulees and lava flows, which have distinct morphological characteristics. Vent elongation and alignment highlight close association between these landforms and the caldera(s) as well as with tectonic structures, suggesting these structures acted as the main magma pathways during the BBTM recent eruptions. We estimate that during the entire BBTM post-caldera phase a total bulk volume of 10.9 km3 of material was erupted. This would represent a time-average...

Research paper thumbnail of The significance of volcanic segments and rifts in faults characterization within the Amagmatic graben of the Afar Depression, Ethiopia

Journal of Structural Geology

Research paper thumbnail of Geochemical and mineralogical evidence for the supergene origin of kaolin deposits – Central Main Ethiopian Rift

Journal of African Earth Sciences, 2019

Abstract The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was ... more Abstract The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The geological, mineralogical and geochemical studies indicate that supergene alteration played a major role in the formation of the Belessa kaolin deposit. The absence of quartz veining and alteration zones containing high temperature minerals precludes significant hypogene alteration. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) also show that the host rock experienced strong alteration and weathering. Furthermore, high Ce+Y+La values correspond to supergene-type alteration. The low P and high Cr+Nb concentrations also support a supergene origin. The physical properties, chemistry, mineralogy and crystal morphology indicate that the Belessa kaolin has potential applications for paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics.

Research paper thumbnail of Multi-Disciplinary Approach for Surface Mining Effects on Shallow Groundwater Potential Using Remote Sensing and Gis

Ground water is becoming a major concern with respect to surface mining. Two major concerns are g... more Ground water is becoming a major concern with respect to surface mining. Two major concerns are ground‐water quality and ground‐water quantity, but only the quantity aspects are addressed in this paper. Mining exerts pressure on environment at many stages such as exploration, extraction, processing, and post closure operations. Increase in production and opening of new mines do generate pressure on environment. The key environmental problems arising out of mining activities are land degradation, surface water and groundwater, degradation of forest and loss of biodiversity, soil contamination, deterioration of natural drainage system, air pollution, noise and vibrations. The principle aim of this research is to evaluate the value of integration of remote sensing and GIS techniques in monitoring the impact of mining activity on groundwater resources in around the Pallakkapalayam Limestone Mine lease areas of Komarapalayam, Namakkal district, Tamil Nadu.

Research paper thumbnail of Data of Remote Sensing and GIS - To Demarcate the Potential Sector of Groundwater in Debre Berhan, Amhara region, Ethiopia

Research paper thumbnail of Characterization of the Genesis of Belessa Kaolin Occurrences, Hosaina Area, Central Main Ethiopian Rift

Research paper thumbnail of Geochemical and mineralogical evidence for the supergene origin of kaolin deposits -Central Main Ethiopian Rift

The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied u... more The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The...

Research paper thumbnail of Data of Remote Sensing and GIS - To Demarcate the Potential Sector of Groundwater in Debre Berhan, Amhara region, Ethiopia

Data in Brief, Oct 1, 2019

Research paper thumbnail of Data of remote sensing and GIS -to demarcate the potential sector of groundwater in Debre Berhan, Amhara region, Ethiopia

Research paper thumbnail of Geochemical and mineralogical evidence for the supergene origin of kaolin deposits -Central Main Ethiopian Rift

The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied u... more The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The geological, mineralogical and geochemical studies indicate that supergene alteration played a major role in the formation of the Belessa kaolin deposit. The absence of quartz veining and alteration zones containing high temperature minerals precludes significant hypogene alteration. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) also show that the host rock experienced strong alteration and weathering. Furthermore, high Ce+Y+La values correspond to supergene-type alteration. The low P and high Cr+Nb concentrations also support a supergene origin. The physical properties, chemistry, mineralogy and crystal morphology indicate that the Belessa kaolin has potential applications for paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics.

Research paper thumbnail of Stratigraphy and eruptive history of Gedemsa caldera volcano, Central Main Ethiopian Rift

Journal of Volcanology and Geothermal Research, Jan 31, 2024

Research paper thumbnail of Structural controls on magma pathways in Bora-Baricha-Tullu Moye (BBTM) volcanic system, Main Ethiopian Rift

Volcanica

The Bora-Baricha-Tullu Moye (BBTM) volcanic complex is located at a transitional zone in the Main... more The Bora-Baricha-Tullu Moye (BBTM) volcanic complex is located at a transitional zone in the Main Ethiopian Rift where tectonic and volcanic features show complex interplays. We mapped and characterised volcanic and tectonic features using high-resolution digital elevation models and performed morphometric and vent spatial distribution analyses. Structural analysis reveals NNE–SSW, NE–SW, and NW–SE trending faults in the region. The dominant post-caldera volcanic landforms are lava domes, pumice cones, scoria cones, maars, obsidian coulees and lava flows, which have distinct morphological characteristics. Vent elongation and alignment highlight close association between these landforms and the caldera(s) as well as with tectonic structures, suggesting these structures acted as the main magma pathways during the BBTM recent eruptions. We estimate that during the entire BBTM post-caldera phase a total bulk volume of 10.9 km3 of material was erupted. This would represent a time-average...

Research paper thumbnail of The significance of volcanic segments and rifts in faults characterization within the Amagmatic graben of the Afar Depression, Ethiopia

Journal of Structural Geology

Research paper thumbnail of Geochemical and mineralogical evidence for the supergene origin of kaolin deposits – Central Main Ethiopian Rift

Journal of African Earth Sciences, 2019

Abstract The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was ... more Abstract The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The geological, mineralogical and geochemical studies indicate that supergene alteration played a major role in the formation of the Belessa kaolin deposit. The absence of quartz veining and alteration zones containing high temperature minerals precludes significant hypogene alteration. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) also show that the host rock experienced strong alteration and weathering. Furthermore, high Ce+Y+La values correspond to supergene-type alteration. The low P and high Cr+Nb concentrations also support a supergene origin. The physical properties, chemistry, mineralogy and crystal morphology indicate that the Belessa kaolin has potential applications for paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics.

Research paper thumbnail of Multi-Disciplinary Approach for Surface Mining Effects on Shallow Groundwater Potential Using Remote Sensing and Gis

Ground water is becoming a major concern with respect to surface mining. Two major concerns are g... more Ground water is becoming a major concern with respect to surface mining. Two major concerns are ground‐water quality and ground‐water quantity, but only the quantity aspects are addressed in this paper. Mining exerts pressure on environment at many stages such as exploration, extraction, processing, and post closure operations. Increase in production and opening of new mines do generate pressure on environment. The key environmental problems arising out of mining activities are land degradation, surface water and groundwater, degradation of forest and loss of biodiversity, soil contamination, deterioration of natural drainage system, air pollution, noise and vibrations. The principle aim of this research is to evaluate the value of integration of remote sensing and GIS techniques in monitoring the impact of mining activity on groundwater resources in around the Pallakkapalayam Limestone Mine lease areas of Komarapalayam, Namakkal district, Tamil Nadu.

Research paper thumbnail of Data of Remote Sensing and GIS - To Demarcate the Potential Sector of Groundwater in Debre Berhan, Amhara region, Ethiopia

Research paper thumbnail of Characterization of the Genesis of Belessa Kaolin Occurrences, Hosaina Area, Central Main Ethiopian Rift

Research paper thumbnail of Geochemical and mineralogical evidence for the supergene origin of kaolin deposits -Central Main Ethiopian Rift

The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied u... more The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The...

Research paper thumbnail of Data of Remote Sensing and GIS - To Demarcate the Potential Sector of Groundwater in Debre Berhan, Amhara region, Ethiopia

Data in Brief, Oct 1, 2019

Research paper thumbnail of Data of remote sensing and GIS -to demarcate the potential sector of groundwater in Debre Berhan, Amhara region, Ethiopia

Research paper thumbnail of Geochemical and mineralogical evidence for the supergene origin of kaolin deposits -Central Main Ethiopian Rift

The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied u... more The Belessa kaolin deposit in the western margin of the Central Main Ethiopian Rift was studied using geological, mineralogical, chemical and physical methods to understand its genesis and evaluate its potential suitability for different industrial applications. X-ray diffraction and Scanning Electron Microscopy were used to establish the mineralogical composition. Bulk chemical compositions were determined using ICP-MS and ICP-AES. The geology of the kaolin district is comprised of Miocene to Quaternary age rhyolite and pyroclastic tuff. The kaolin occurrence is located in the central part of the study area and is associated with rhyolite. The host rock is composed of quartz and alkali feldspar phenocrsyts set in a groundmass of very fine grained quartz, alkali-feldspar and plagioclase. The rhyolite is partially to completely altered to kaolin. The kaolin deposit is composed predominantly of kaolinite and quartz. The kaolinite minerals of the deposit have high structural order. The geological, mineralogical and geochemical studies indicate that supergene alteration played a major role in the formation of the Belessa kaolin deposit. The absence of quartz veining and alteration zones containing high temperature minerals precludes significant hypogene alteration. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) also show that the host rock experienced strong alteration and weathering. Furthermore, high Ce+Y+La values correspond to supergene-type alteration. The low P and high Cr+Nb concentrations also support a supergene origin. The physical properties, chemistry, mineralogy and crystal morphology indicate that the Belessa kaolin has potential applications for paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics.