Radiological Investigation on Sediments: A Case Study of Wadi Rod Elsayalla the Southeastern Desert of Egypt

The presence of heavy radioactive minerals in the studied granitoids from which the Wadi sediments leads to the study of the exposure to emitted gamma rays from the terrestrial radionuclides, such as 238U, 232Th, and 40K. The geological study revealed that the Wadi sediments derived from the surrounding granitoids, such as syenogranite, alkali feldspar granite, and quartz syenite. The mineral analysis confirmed that the granitoids were enriched with radioactive minerals, such as uranothorite as well as monazite, zircon, yttrocolumbite, and allanite. The mean activity of the 238U, 232Th, and 40K concentrations are 62.2 ± 20.8, 84.2 ± 23.3, and 949.4 ± 172.5 Bq kg−1, respectively, for the investigated Wadi sediments, exceeding the reported limit of 33, 45 and 412 Bq kg−1, respectively. Public exposure to emitted gamma radiation is detected by estimating many radiological hazard indices, such as the radium equivalent content (Raeq), external and internal hazard indices (Hex and Hin), annual effective dose (AED), annual gonadal dose equivalent (AGDE), and excess lifetime cancer (ELCR). The obtained results of the radiological hazards parameters showed that public exposure to emitted gamma radiation can induce various dangerous health effects. Thus, the application of the investigated sediments in different building materials and infrastructures fields is not safe. A multivariate statistical analysis (MSA) was applied to detect radionuclide correlations with the radiological hazard parameters estimated in the granite samples.

Architectural Significance of Granite and Other Durable Rocks in the Context of India – An Analytical Study

Architectures created through the cutting of naturally occurred massive rocks include different structures, buildings, tombs, monuments, caves and sculptures. On account of hard and tough property, the granite is considered as strong construction stone in human history. Granite is very common in the continental crust of our mother earth. It is characterised as coarse grained plutonic intrusive igneous rock and is composed of quartz, alkali feldspar and plagioclase. Typical mineralogical character and textural varieties of granite facilitates to develop a wide range of colours, which include white, pink and grey etc. Granite rocks established itself as praiseworthy architecture stone since historical past because of its distinctive character like durability, appreciable finishing, fascinating polish nature and above all its magnificent colour diversities. As architectural stone, the granitic rocks demand attraction owing to the combination of style and elegance. The application of granitic rocks is witnessed in the ancient world through the mesmerising major architectures in India and around the world like Mount Rushmore, Washington Monument, Great Pyramid of Giza; Ajanta and Ellora caves, monolithic structure in the Zagwe-built Lalibela in Ethiopia along with in most of the long-lived old Indian temples, old forts and monuments etc. The monolithic free-standing architecture is generally rock-cut structures as depicted in the Ellora Kailasanathar Temple. The biggest monolithic statue in world, the Gommateshwara statue of Bahubali at Shravanabelagola present in the Indian state at Karnataka was carved in the 983 CE from a single block of granite rock. The radioactivity stuff in the granite is an important concern to the people in recent world. Even though the impact of radioactivity is proved mostly very less harmful to mankind, current research indicates that few granite products are showing radioactive substance index beyond permissible limit of the specified standard, which is responsible for environmental pollution during the use for long. Therefore, due attention is required towards the pertinent issue of radioactivity in the granite stones. Apart from granite, many of the architectures in India are created by the other rock types that include rocks like sedimentary, metamorphic and igneous rocks.

Albite ± Actinolite-Altered Porphyry Dykes in Archean Gold Deposits of the Boulder Lefroy-Golden Mile Fault System, Yilgarn Craton, Western Australia: Petrography, Chronology, and Comparison to Canadian Albitites

The Boulder Lefroy-Golden Mile fault system in the Archean Yigarn Craton is the most productive gold-mineralized structure in Australia (>2300 t Au). The New Celebration deposit (51 t Au) is part of a group of hematite- and anhydrite-bearing mesothermal deposits and Fe-Cu-Au skarns associated with monzodiorite-tonalite intrusions in the strike-slip fault system. Ore-grade biotite-carbonate and late sericite-carbonate-alkali feldspar replacement is bound to the contacts of a felsic (low Cr, Ni, V) quartz-plagioclase porphyry dyke dated at 2676 ± 7 Ma. The sodic-potassic alteration of the felsic boudinaged dyke contrasts with the albite-actinolite alteration in the adjacent mafic (high Cr, Ni, V) plagioclase porphyry dated at 2662 ± 4 Ma, although both share the same sulfide-oxide assemblage: pyrite ± chalcopyrite, magnetite ± hematite. The younger porphyry locally crosscuts foliation and is bordered by post-kinematic actinolite-pyrite selvages overprinting talc-chlorite-phlogopite-dolomite schist. It contains auriferous pyrite (70 ppb Au; 610 ppb Ag) where sampled for zircon U-Pb chronology at +224 m elevation. Above the sample site, the dyke was mined as gold ore (1–6 g/t Au) at +300–350 m. Temperature estimates based on actinolite-albite pairs (300–350 °C) agree with the fluid inclusion trapping temperature of main-stage auriferous veins (330 ± 20 °C). These relationships are interpreted to indicate syn-mineralization emplacement. Gold-related albite-altered porphyry dykes (albitites) also occur in the world-class Hollinger-McIntyre (986 t Au) and Kerr Addison-Chesterville deposits (336 t Au), Abitibi greenstone belt, Canada.

Petrography And Field Study Of Andesitic Ignimbrite In Temangan, Kelantan

The volcanic rocks in Temangan, Kelantan consist of felsic to intermediate volcanic rocks, that is mainly of pyroclastic with rhyolitic, dacitic, and andesitic tuff. A geological review has been carried out in Kampung Bukit Besi, Temangan, in Kelantan, Malaysia, which is composed of schist, shale, andesite, and ignimbrite. In Temangan, andesite and ignimbrite show an intimate relationship, as the ignimbrite exists as the fragments and andesite as the matrix. The methodology used in this study are petrography and X-ray Diffraction (XRD) analyses, to determine the mineralogical composition of andesitic ignimbrite. Andesite shows aphenitic and porphyritic textures and consist of pyroxene, plagioclase, alkali feldspar, quartz, biotite and iron oxides. A range of plagioclase textures indicate imperfect equilibrium condition from andesite, reflecting plagioclase dissolution and regrowth. The structural analysis suggest that thrust fault occurred in the study area. Andesite and ignimbrite of the two stages are suggested to have derived from the andesite magma eruption which produced pyroclastic flow eruptions in small amount in most caldera volcanoes at high temperature gradient.

Geochronology, geochemistry and tectonic implications of early Carboniferous plutons in the southwestern Alxa Block

The southeastern Central Asian Orogenic Belt (CAOB) records the assembly process between several micro-continental blocks and the North China Craton (NCC), with the consumption of the Paleo-Asian Ocean (PAO), but whether the S-wards subduction of the PAO beneath the northern NCC was ongoing during Carboniferous–Permian time is still being debated. A key issue to resolve this controversy is whether the Carboniferous magmatism in the northern NCC was continental arc magmatism. The Alxa Block is the western segment of the northern NCC and contiguous to the southeastern CAOB, and their Carboniferous–Permian magmatism could have occurred in similar tectonic settings. In this contribution, new zircon U–Pb ages, elemental geochemistry and Sr–Nd isotopic analyses are presented for three early Carboniferous granitic plutons in the southwestern Alxa Block. Two newly identified aluminous A-type granites, an alkali-feldspar granite (331.6 ± 1.6 Ma) and a monzogranite (331.8 ± 1.7 Ma), exhibit juvenile and radiogenic Sr–Nd isotopic features, respectively. Although a granodiorite (326.2 ± 6.6 Ma) is characterized by high Sr/Y ratios (97.4–139.9), which is generally treated as an adikitic feature, this sample has highly radiogenic Sr–Nd isotopes and displays significantly higher K2O/Na2O ratios than typical adakites. These three granites were probably derived from the partial melting of Precambrian continental crustal sources heated by upwelling asthenosphere in lithospheric extensional setting. Regionally, both the Alxa Block and the southeastern CAOB are characterized by the formation of early Carboniferous extension-related magmatic rocks but lack coeval sedimentary deposits, suggesting a uniform lithospheric extensional setting rather than a simple continental arc.

Evolution of the Late Mesozoic Magmatism of the Omulevka Terrane of the North Part of the Verkhoyansk–Kolyma Orogenic Region

This article presents the results of a study of Late Mesozoic intrusive formations of the Omulevka terrane of the Verkhoyansk–Kolyma orogenic region. The research area covers the Selennyakh block of the Omulevka terrane and the territory adjacent to the south. The compositions of rock-forming, accessory and restitic minerals and geochemical features of intrusive rocks are considered. The methods of optical microscopy, microprobe, silicate and spectral analyses were used. There are the following several stages in the evolution of magmatism: (1) the Late Jurassic supra-subduction (gabbro, dolerites), (2) the beginning of the Early Cretaceous-transitional from supra-subduction to marginal-continental (gabbro-diorites, diorites, granodiorites), (3) the Early Cretaceous of active continental margin (granodiorites, granites), (4) the Late Cretaceous postorogenic or continental-riftogenic (alkali-feldspar granites of A-type), (5) the Late Cretaceous continental riftogenic (subalkaline gabbroids and basaltoids). In the process of evolution from stage one to stage four, there was an increase in the silicic acid content, total alkalinity and ferruginousity of rocks with the movement of magmogeneration levels to higher and higher horizons of the lithosphere (calculated pressure from 1.6–1.4 GPa to 0.6–0.9 GPa). At the same time, the preservation of high temperatures of magmogeneration (1000–1150 °C) and crystallization implies the supply of additional heat from an external (deep) source during the formation of granitoid melts. The magmatic activity is completed by the intrusion of subalkaline derivatives of a deep hearth, formed by metasomatized lherzolites. All the studied igneous rocks are either direct mantle fusions, or bear signs of the participation of mantle matter in the generation of parent melts in crustal substrates: the presence of tschermakite in gabbroids, nonequilibrium structures, the composition of early generations of biotites corresponding to biotites of mantle and crust-mantle derivatives, the presence of pyroxenes and accessory minerals characteristic of mantle magmas in granitoids. In the diagram Al-Na-K-2Ca–Fe + Ti + Mg, the composition points of the studied intrusive rocks tend to the mixing trend. In general, the research results suggest that the evolution of the Late Mesozoic intrusive magmatism of the studied territory and the specific matter of rock compositions were caused by the crust-mantle interaction as a result of the rise of mantle diapirs in the crust from a long-existing deep hearth of the main melt.

Thermochronology of Alkali Feldspar and Muscovite at T > 150 °C Using the 40Ar/39Ar Method: A Review

The 40Ar/39Ar method applied to K-feldspars and muscovite has been often used to construct continuous thermal history paths between ~150–600 °C, which are usually applied to structural and tectonic questions in many varied geological settings. However, other authors contest the use of 40Ar/39Ar thermochronology because they argue that the assumptions are rarely valid. Here we review and evaluate the key assumptions, which are that (i) 40Ar is dominantly redistributed in K-feldspars and muscovite by thermally-driven volume diffusion, and (ii) laboratory experiments (high temperatures and short time scales) can accurately recover intrinsic diffusion parameters that apply to geological settings (lower temperatures over longer time scales). Studies do not entirely negate the application of diffusion theory to recover thermal histories, although they reveal the paramount importance of first accounting for fluid interaction and secondary reaction products via a detailed textural study of single crystals. Furthermore, an expanding database of experimental evidence shows that laboratory step-heating can induce structural and textural changes, and thus extreme caution must be made when extrapolating laboratory derived rate loss constants to the geological past. We conclude with a set of recommendations that include minimum sample characterisation prior to degassing, an assessment of mineralogical transformations during degassing and the use of in situ dating.

Petrography and Mineral Chemistry of Monte Epomeo Green Tuff, Ischia Island, South Italy: Constraints for Identification of the Y-7 Tephrostratigraphic Marker in Distal Sequences of the Central Mediterranean

The 56 ka Monte Epomeo Green Tuff (MEGT) resulted from the largest volume explosive eruption from Ischia island (south Italy). Its tephra is one of the main stratigraphic markers of the central Mediterranean area. Despite its importance, a detailed characterisation of the petrography and mineral chemistry of MEGT is lacking. To fill this gap, we present detailed petrographic description and electron microprobe mineral chemistry data on samples collected on-land from the MEGT. Juvenile clasts include pumice, scoria, and obsidian fragments with porphyritic/glomeroporphyritic, vitrophyric, and fragmental textures. The porphyritic index is 13–40 vol.%, and phenocryst phases include alkali-feldspar, plagioclase, clinopyroxene, ferrian phlogopite, and titano-magnetite, in order of decreasing abundance; accessory phases include sphene, hydroxy-fluor-apatite, and rare edenite. Plagioclase varies from predominant andesine to subordinate oligoclase, whereas alkali-feldspar is more variable from sanidine to anorthoclase; quasi-pure sanidine commonly occurs as either rim or recrystallisation overgrowth of large phenocrysts due to hydrothermal alteration. Secondary minerals include veins and patches of carbonate minerals, Fe-Mn oxyhydroxides, clay minerals, and zeolites. Clinopyroxene is ferroan diopside (En45–29Fs7–27) and never reaches Na-rich compositions. This feature allows the discrimination of MEGT from aegirine-bearing, distal tephra layers erroneously attributed to MEGT, with implications for the areal distribution of Ischia explosive deposits.