Contributions to the geochemistry, economic geology, and geochronology of the Yemen Arab Republic

Abstract

Results of major-element analyses of a group of Precambrian granitoid rocks exposed around Rida 1 and Al Bayda, Yemen Arab Republic (YAR), are compared with data on Precambrian granitoid rocks in the Kingdom of Saudi Arabia. The comparison shows that the rocks at Rida 1 and Al Bayda comprise a posttectonic suite of latest Precambrian age, probably between 620 Ma and 560 Ma years, making them among the youngest Precambrian rocks in the YAR. Some are so shown on the geologic map of the YAR. However, the most strongly gneissic of these rocks were mapped with the oldest Precambrian gneissic granite. The chemical data indicate that the difference between the gneissic and the massive rocks reflects syntectonic and posttectonic emplacement with reference to the end of the Precambrian orogeny and final cratonization of the Shield. For strict classification of the Precambrian granitoid rocks of the YAR, definition of the stratigraphic succession of the Precambrian metavolcanic and metasedimentary rocks, major-element geochemistry, and geochronology are required.spike related to sand choke in wadis, suggest that traditional views of mean bed scour and fill during floods in ephemeral streams in semi arid climate are not fully applicable in the arid part of the YAR. Therefore, the possibility for proximate eluvial and alluvial gold placers must not be dismissed on theoretical grounds alone.Exploration by inclined diamond-drill holes under the gossan at Jabal Al Maidan and Jabal Al Ma'aden in the Sa'dah area is urged to determine the metal contents of unweathered sulfide minerals. Concentrations as high as 550 ppm As, 1,000 ppm Ni, 60 ppm Cu, 300 ppm Co, and 6,000 ppm Zn reported by the German Geological Advisory Group in the YAR may reflect co-precipitation and concentration in secondary iron minerals during weathering, but across the border in Saudi Arabia surface gossan similar to that at Sa'dah was shown to be depleted by factors of 5-10 relative to the unoxidized sulfides below the gossan for the metals Cu, Pb, Zn, Ni, and Co.

Impact of Climate Change on Groundwater in Dhamar Basin (Yemen)

“…The eastern and northeastern parts of the Dhamar basin are dominated by Pre-Cambrian metamorphic rocks along with presence of post tectonic granite and diorites outcrops. The central part of Dhamar basin is dominated by Quaternary basaltic lava flows having prominent older volcanic features with radial obscured Thrust-Faults near Jabal-Isbil (Chiesa, 1985;Overstreet, 1985;Al-Kohlani, 2009;Minissale, 2013). Amran Group Pre-Cambrian Precambrian Basement Hydrological Characteristics: Can be described of geological formations and their natural characteristics and their relation to groundwater in Dhamar basin as follows: Ground reservoirs in sediments and volcanoes of quaternary: These sediments are composed of gravel and sand with primary permeability and are located on solid rocks that help to prevent groundwater infiltration through them.…”