Yemen is characterized by a considerable number of metallic and non-metallic raw materials, including base metals, precious metals, and dimension stones. The Wadi Masilah Basin, in the southeasternmost part of Yemen, hosts very promising base metal and barite prospects. This terrain has undergone a complex geological and structural history, including oblique divergence (transtension) related to the opening phases of the greater Red Sea - Gulf of Aden rift system, with NW-SE and NE- SW major fault zones. Barite occurs either singly or in association with galena, hemimorphite, willemite, zincite, smithsonite, descloizite, celestine, quartz, calcite, dolomite, iron and manganese oxides, and gypsum, connected mainly to the Cretaceous carbonates (Saa'r Formation). The mineralisations crop out as either vein fillings or stratiform type. BaSO4 contents between 95 and 98% and specific gravity values up to 4.37 g/cm3 are indicative of high quality ores. Sulfide mineralisations consist of sphalerite, galena and pyrite. They occur in association with barite veins or form fracture-filling in limestones and silicified dolostones. Available data indicate several lead- zinc ore bodies at various depths, some of which are considerably large with dimensions attaining 60 m x 30 m x 50 m, and tonnages reaching thousands of tons. Nonsulfide minerals comprise hemimorphite, willemite, smithsonite, hydrozincite, and zincite, as well as cerussite, hydrocerussite, anglesite, wulfenite, and rarely pyromorphite. Zinc contents in the mineralised veins range from low (1-8 wt.%) to high grades (30-50 wt.%). The above mentioned minerals occur in a variety of structures, such as: shear zones, fractures, vugs, cavities, brecciated veins, and open spaces of the vein barite sidewalls, and connected mainly to the dolostone sequence. Vanadium ores mostly occur as descloizite and rarely vanadinite, in association with barite, calcitized veins and brecciated zones, and dolomitic limestones, with vanadium contents up to 12.30 wt.%. These prospects contain one of the most remarkable occurrences of descloizite known, and besides lead-zinc, descloizite is probably the mineral resource for which the Wadi Masilah Basin is most promising. Mn and Fe ores are also present, whose mineralogy consists of hollandite, romanechite, cryptomelane, pyrolusite, hematite, goethite and limonite. They include several discordant irregular veins. The results of geochemical analyses reveal high quality Mn ores, with an average MnO content of 64%. The orebodies in all prospects consist mainly of fracture-filling in limestones, dolostones, and silicified limestones. They originated from both hydrothermal processes and the action of slightly acidic groundwater. The prospecting area is structurally controlled and located in a NW-SE major fault zone and its parallel lineaments. Tectonic uplift and intensive fracturing systems, along with favorable climatic conditions, gave rise to the development of supergene Zn, Pb, V, Mn and Fe mineralisations.
Mineral resources in the Red Sea/Gulf of Aden: Polymetallic-Barite mineralizations at Wadi Masilah Basin (Yemen).
Pinarelli L;
2018
Abstract
Yemen is characterized by a considerable number of metallic and non-metallic raw materials, including base metals, precious metals, and dimension stones. The Wadi Masilah Basin, in the southeasternmost part of Yemen, hosts very promising base metal and barite prospects. This terrain has undergone a complex geological and structural history, including oblique divergence (transtension) related to the opening phases of the greater Red Sea - Gulf of Aden rift system, with NW-SE and NE- SW major fault zones. Barite occurs either singly or in association with galena, hemimorphite, willemite, zincite, smithsonite, descloizite, celestine, quartz, calcite, dolomite, iron and manganese oxides, and gypsum, connected mainly to the Cretaceous carbonates (Saa'r Formation). The mineralisations crop out as either vein fillings or stratiform type. BaSO4 contents between 95 and 98% and specific gravity values up to 4.37 g/cm3 are indicative of high quality ores. Sulfide mineralisations consist of sphalerite, galena and pyrite. They occur in association with barite veins or form fracture-filling in limestones and silicified dolostones. Available data indicate several lead- zinc ore bodies at various depths, some of which are considerably large with dimensions attaining 60 m x 30 m x 50 m, and tonnages reaching thousands of tons. Nonsulfide minerals comprise hemimorphite, willemite, smithsonite, hydrozincite, and zincite, as well as cerussite, hydrocerussite, anglesite, wulfenite, and rarely pyromorphite. Zinc contents in the mineralised veins range from low (1-8 wt.%) to high grades (30-50 wt.%). The above mentioned minerals occur in a variety of structures, such as: shear zones, fractures, vugs, cavities, brecciated veins, and open spaces of the vein barite sidewalls, and connected mainly to the dolostone sequence. Vanadium ores mostly occur as descloizite and rarely vanadinite, in association with barite, calcitized veins and brecciated zones, and dolomitic limestones, with vanadium contents up to 12.30 wt.%. These prospects contain one of the most remarkable occurrences of descloizite known, and besides lead-zinc, descloizite is probably the mineral resource for which the Wadi Masilah Basin is most promising. Mn and Fe ores are also present, whose mineralogy consists of hollandite, romanechite, cryptomelane, pyrolusite, hematite, goethite and limonite. They include several discordant irregular veins. The results of geochemical analyses reveal high quality Mn ores, with an average MnO content of 64%. The orebodies in all prospects consist mainly of fracture-filling in limestones, dolostones, and silicified limestones. They originated from both hydrothermal processes and the action of slightly acidic groundwater. The prospecting area is structurally controlled and located in a NW-SE major fault zone and its parallel lineaments. Tectonic uplift and intensive fracturing systems, along with favorable climatic conditions, gave rise to the development of supergene Zn, Pb, V, Mn and Fe mineralisations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
