Evaluation of Marwit Rod El Leqah deposit as pegmatite high purity quartz source for advanced applications was conducted through the geological, mineralogical and geochemical studies. Elemental analysis of a represent...Evaluation of Marwit Rod El Leqah deposit as pegmatite high purity quartz source for advanced applications was conducted through the geological, mineralogical and geochemical studies. Elemental analysis of a representative quartz sample showed that the quartz deposits were classified as medium purity quartz with 99.575% average SiO2 content and about 0.422% (4220 ppm) of accompanied mineral. Field study and petrography investigation using optical polarized transmitted microscope and reflected light microscope revealed that these impurities were mainly found as solid particulates of iron oxide, muscovite, rutile, orthoclase, granitic rafts, and as fluid inclusions as well. Moreover, structural undesirable trace elements were also presented in the quartz sample.展开更多
The presence of glass microspherules enclosing relict grains, shattered quartz and silicon carbide in white sandstone beds near the Jurassic-Cretaceous boundary in west central Sinai indicates a cosmic impact event. C...The presence of glass microspherules enclosing relict grains, shattered quartz and silicon carbide in white sandstone beds near the Jurassic-Cretaceous boundary in west central Sinai indicates a cosmic impact event. Characterization of the impact microspherules and proposing a reasonable scenario for their origin are the aims of this work. Field observations, optical, binocular, scanning electron and high-resolution transmitted electron microscopy investigations and chemical analyses were carried out. The study revealed that glass microspherules have high Al<sub>2</sub>O<sub>3</sub> and FeO contents and low CaO and MgO contents. The high content of Al<sub>2</sub>O<sub>3</sub> indicates that the source of microtektite-like microspherules is attributed to the melting of a clay-rich sandstone and carbonaceous matter, while the high content of FeO indicates admixing with projectile matter. The reaction between silica and carbon was carried out under conditions of high temperature (T > 1000°C) and carbon (C/Si > 1) which resulted in the production of silicon carbide with microdiamond intergrowth. Consequently, this intergrowth is in accordance with the impact origin via rapid condensation and growth within a vapor phase. In spite of the fact that no source crater has been recognized to date in the study area, the authors propose at least a single cosmic impact event scenario for the recorded glass microspherules in west central Sinai. The impact excavated the Paleozoic siliciclastic sedimentary rocks and then the glass microspherules showered the area of study. The deposition of microtektite-like glass particles within the white sandstone beds of the Malha Formation took place in the fluvial plain terrestrial environment. This setting precluded severe post-depositional reworking, yielding preservation of the glass particles in a primary layer. Eventually, lateral migration of the braided channels led to the reworking of the microspherules layer and the spatial dispersal of the shattered quartz.展开更多
文摘Evaluation of Marwit Rod El Leqah deposit as pegmatite high purity quartz source for advanced applications was conducted through the geological, mineralogical and geochemical studies. Elemental analysis of a representative quartz sample showed that the quartz deposits were classified as medium purity quartz with 99.575% average SiO2 content and about 0.422% (4220 ppm) of accompanied mineral. Field study and petrography investigation using optical polarized transmitted microscope and reflected light microscope revealed that these impurities were mainly found as solid particulates of iron oxide, muscovite, rutile, orthoclase, granitic rafts, and as fluid inclusions as well. Moreover, structural undesirable trace elements were also presented in the quartz sample.
文摘The presence of glass microspherules enclosing relict grains, shattered quartz and silicon carbide in white sandstone beds near the Jurassic-Cretaceous boundary in west central Sinai indicates a cosmic impact event. Characterization of the impact microspherules and proposing a reasonable scenario for their origin are the aims of this work. Field observations, optical, binocular, scanning electron and high-resolution transmitted electron microscopy investigations and chemical analyses were carried out. The study revealed that glass microspherules have high Al<sub>2</sub>O<sub>3</sub> and FeO contents and low CaO and MgO contents. The high content of Al<sub>2</sub>O<sub>3</sub> indicates that the source of microtektite-like microspherules is attributed to the melting of a clay-rich sandstone and carbonaceous matter, while the high content of FeO indicates admixing with projectile matter. The reaction between silica and carbon was carried out under conditions of high temperature (T > 1000°C) and carbon (C/Si > 1) which resulted in the production of silicon carbide with microdiamond intergrowth. Consequently, this intergrowth is in accordance with the impact origin via rapid condensation and growth within a vapor phase. In spite of the fact that no source crater has been recognized to date in the study area, the authors propose at least a single cosmic impact event scenario for the recorded glass microspherules in west central Sinai. The impact excavated the Paleozoic siliciclastic sedimentary rocks and then the glass microspherules showered the area of study. The deposition of microtektite-like glass particles within the white sandstone beds of the Malha Formation took place in the fluvial plain terrestrial environment. This setting precluded severe post-depositional reworking, yielding preservation of the glass particles in a primary layer. Eventually, lateral migration of the braided channels led to the reworking of the microspherules layer and the spatial dispersal of the shattered quartz.
