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.

Apatite and Zircon Geochemistry in Yao’an Alkali-Rich Porphyry Gold Deposit, Southwest China: Implications for Petrogenesis and Mineralization

The Yao’an gold deposit is located in the middle of the Jinshajiang-Ailaoshan alkali-rich metallogenic belt, and this belt hosts many porphyry-type Cu-Au-Mo deposits formed at 46–33 Ma. Yao’an porphyry gold-mineralization is intimately associated with biotite syenite porphyry, whereas the contemporaneous quartz syenite porphyry is barren. In this study, we compared the major and trace elements of apatite and zircon and isotopic compositions of zircon from the biotite syenite porphyry and quartz syenite porphyry, to explore their geochemical differences that may affect their mineralization potential. The results show that both porphyries were derived from the partial melting of the thickened lower crust, which has been modified by slab-derived fluids, but has different mineral crystallization sequences, magma fluid activities, and magma oxidation states, respectively. REE contents in apatite and zircon can be used to reveal the crystallization sequence of minerals. A rapid decrease of (La/Yb)N ratio in apatite from both porphyries may be caused by the crystallization of allanite. Large variation of Cl contents and negative correlation between F/Cl and (La/Yb)N in apatite from fertile porphyry indicate that it has experienced the exsolution of Cl-bearing hydrothermal fluid. Higher Y/Ho and lower Zr/Hf in zircon from fertile porphyry indicate a stronger fluid activity than barren porphyry. The high S, V, As contents, δEu, low δCe in apatite, as well as high Ce4+/Ce3+ and log(fO2) estimated from zircon geochemistry from fertile porphyry, indicate high a oxidation state of fertile porphyry, similar to other fertile porphyries in this metallogenic belt. High fluid activity and fluid exsolution are conducive to the migration and enrichment of metal elements, which are very important for mineralization. High oxygen fugacity inhibits the precipitation of metal in the form of sulfide, thereby enhancing the mineralization potential of rock. Therefore, the exsolution of Cl-bearing hydrothermal fluid and high oxygen fugacity are the key factors promoting mineralization in Yao’an area.

The Changshagou gold deposit, Eastern Tianshan, NW China: Orogenic gold mineralization overprinting a Porphyry gold occurrence

The temporal-spatial relationships of porphyry and orogenic gold mineralization in the Eastern Tianshan Orogenic Belt are ambiguous. The newly-discovered Changshagou deposit in this belt contains both porphyry and orogenic gold mineralization, which are characterized by polymetallic-sulfide veinlets and quartz-pyrite veins, respectively. Fluid inclusions in the porphyry mineralization episode were trapped at 290–340 °C with salinities of 3.0–8.0 wt.% NaClequiv. The homogenization temperatures and salinities in the orogenic mineralization episode range from 240 to 300 °C and 1.0–5.0 wt.% NaClequiv. Coexisting V-type and L-type fluid inclusions with similar homogenization temperatures are indicative of fluid immiscibility. The δ18Ow and δDw values range from 7.6 to 9.1 ‰ and −70.9 to −84.0 ‰ in the porphyry mineralization episode, and from 6.4 to 7.1 ‰ and −65.7 to −72.1 ‰ in the orogenic mineralization episode, overlapping magmatic and metamorphic ranges, respectively. The pyrite δ34S values range from 3.5 to 4.9 ‰, falls into the magmatic range. Pyrite in porphyry and orogenic mineralization episodes yield Re-Os isotopes ages of 269.1±2.9 Ma and 257.4±2.4 Ma. The porphyry and orogenic gold mineralizations are genetically associated with the quartz syenite porphyry and Kanggur strike-slip shear activity, respectively.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5635584

Decoupling of Sr-Nd Isotopic Composition Induced by Potassic Alteration in the Shapinggou Porphyry Mo Deposit of the Qinling–Dabie Orogenic Belt, China

In our previous study on petrogenesis of quartz syenite and granite porphyry, the host rocks of the Late Mesozoic Shapinggou Mo deposit in the Qinling–Dabie orogenic belt, we found that the initial Sr isotopic composition of the host rocks is strongly affected by the degree of K-alteration. Here, we provide further isotopic evidence of the host rocks and their minerals to investigate the geochemical behaviour of trace elements and isotopes during the alteration and to explain the phenomenon of decoupling of Sr–Nd isotopic composition. The quartz syenite and granite porphyry are altered by K-alteration in varying degrees and have high K2O and Rb contents and low Na2O, CaO, Sr, and Ba contents. Rock samples of both quartz syenite and granite porphyry have variable Rb/Sr ratios and initial 87Sr/86Sr values (even < 0.70) but contain quite homogeneous εNd(t) values (−12.8 to −14.8). Minerals from the rocks of moderate to intense K-alteration have very low initial 87Sr/86Sr values (even < −17), while those from the weakly altered rocks have 87Sr/86Sr(t) values of 0.7044 to 0.7084. The same phenomenon of the decoupling in Sr–Nd isotopic composition can be observed from several Mo deposits within the eastern Qinling–Dabie orogenic belt. This fact suggests similar hydrothermal features and a comparable origin for both the magmatic rocks and hydrothermal fluids in this belt. A comparison between porphyry Mo and porphyry Cu deposits shows that elements and the Rb–Sr isotope system have different behaviours during the K-alteration, implying distinct material sources and igneous rocks for porphyry Mo and porphyry Cu deposits, respectively.

The Levels, Sources, and Spatial Distribution of Heavy Metals in Soils from the Drinking Water Sources of Beijing, China

Our study area is the upstream watershed of the Guanting and Miyun Reservoirs; together, these two reservoirs comprise the main drinking water source of Beijing, China. In order to prevent crop contamination and preserve the quality of the water and soil, it is important to investigate the spatial distribution and the sources of the heavy metals in farmland soils on the watershed scale. For this study, we collected 23,851 farmland surface soil samples. Based on our analysis of the concentrations of eight heavy metals in these samples, we found that the overall soil quality in our study area is excellent, but that the Cd, Cu, Zn, and Cr contamination risks are relatively high. Moreover, a percentage of samples exceeded the Cd (1.54%,), Cu (0.28%), Zn (0.25%), Cr (0.13%), Pb (0.09%), As (0.05%), Ni (0.04%), and Hg (0.02%) risk screening values for soil contamination in agricultural land. In addition to determining the spatial distribution characteristics of the heavy metal concentrations of the soil samples, we also conducted a factor analysis and an R cluster analysis (CA) whcih can gathered the similar variables to track the sources of the heavy metals. We found that the Cd, Pb, and Zn are likely sourced from a quartz syenite porphyry body and from coal-fired enterprises, while the Cr, Cu, and Ni contaminations are mainly caused by runoff from iron ore smelting. Additionally, agricultural production contributes to the local accumulation of Cu, and industrial (smelting) discharge is partially responsible for the As contamination. As a result of the atmospheric deposition of pollutants, areas with high Hg concentrations are generally centered on large- and medium-sized cities. Due to these high natural heavy metal background values, the existing and future heavy metal contamination in the watershed poses a serious ecological risk to both the soil and the surface water.

On the possible analogy between the Dizi Series of the Southern slope zone of the Greater Caucasus and the folded basement of the plain Crimea: composition, metamorphism, magmatism and age

&lt;p&gt;The Dizi Series is exposed within the Southern slope zone of the Greater Caucasus that occurs as a complex geological structure, which constitutes an integral part of the Mediterranean (Alpine-Himalayan) collisional orogenic belt. It is built up of terrigenous and volcanogenic-sedimentary rocks faunistically dated from the Devonian to Triassic inclusive (Somin, 1971; Somin, Belov, 1976; Kutelia 1983). Most of them are metamorphosed under conditions of chlorite-sericite subfacies of the greenschist facies of regional metamorphism (chlorite-phengite-albite&amp;#177;quartz, graphite-sericite-quartz phyllites and marbleized limestones), and only a minor part represented by clay-carbonaceous, phengite-chlorite-carbonaceous and prehnite-chlorite-carbonate schists underwent anchimetamorphism (Shengelia et al., 2015). The Dizi Series is intruded by numerous magmatic bodies of gabbro-diabases, diabases, diorites, diorite-porphyries, syenites, monzo-syenites and granitoids. The age of the intrusions was defined by K-Ar method at 176-165 Ma (Dudauri, Togonidze, 1998) and by U-Pb LA-ICP-MS zircon dating at 166.5 &amp;#177; 4.6 Ma (authors` unpublished data) and corresponds to the Bathonian orogeny. The Middle Jurassic intrusions caused intense contact metamorphism of the rocks of the Dizi Series resulted in the formation of various hornfelses containing andalusite, cordierite, corundum, biotite, plagioclase, potassium feldspar, clinozoisite, hornblende, cummingtonite, clinopyroxene, wollastonite and scapolite. These rocks correspond to albite-epidote-hornfels, andalusite-biotite-muscovite-chlorite-hornfels and andalusite-biotite-muscovite-hornfels subfacies of the contact metamorphism (Javakhishvili et al., 2020). The analogues of the Dizi Series rocks have not previously been established either in the Greater Caucasus or in the neighboring regions. In our view, Paleozoic rocks similar to the Dizi Series occur under the Cretaceous and Jurassic deposits within the folded basement of the plain Crimea where they were recovered by wells. Most of these rocks, as in the Dizi Series, underwent metamorphism of chlorite subfacies of the greenschist facies and, to a lesser extent, deep epigenesis (clayey-carbonaceous, sericite-carbonaceous, actinolite-chlorite-prehnite, muscovite-albite-chlorite, epidote-actinolite-chlorite and graphite-talc-quartz schists) (Chernyak, 1969). These rocks are also intruded by Middle Jurassic igneous rocks, including gabbro-diabases, diabases, diorites, syenites, monzo-syenites, granite-porphyries, etc. (Shniukova, 2016; Shumlyanskyy, 2019). As a result of the contact metamorphism of the basement rocks, muscovite-quartz-cordierite and cordierite-quartz-feldspar micaceous hornfelses were formed. Quartz syenite yielded a K-Ar age of 158 Ma (Scherbak, 1981), while monzo-syenite was dated at 170 &amp;#177; 5 Ma applying 40Ar/39Ar method (Meijers, 2010). Thus, based on the rock associations, the nature of metamorphism, the age of the metamorphic and igneous rocks, and on the spatial position of the Dizi Series and folded basement of the plain Crimea we assume that these units developed coevally in similar environment and geological conditions.&lt;br&gt;&lt;br&gt;Acknowledgements.This work was supported by Shota Rustaveli National Science Foundation (SRNSF) [PHDF-19-159, Regional and Contact Metamorphism of the Dizi Series].&lt;/p&gt;

The importance of in situ crystallisation and loss of interstitial melt during formation of the Kærven Syenite Complex, Kangerlussuaq, East Greenland

The Kærven Syenite Complex (KSC) is one of the oldest felsic intrusions in the Tertiary East Greenland province. Here we update our previous description of the KSC and supply a greatly expanded and comprehensive geochemical dataset. New data allow us to present a more detailed petrogenetic model for the evolution of the KSC and to investigate the geochemical characteristics of igneous cumulates subjected to loss and, occasionally, replacement of residual liquid. The KSC comprises eleven mappable units that generally young westwards. Rock types range from quartz syenite to quartz alkali feldspar syenite and alkali feldspar granite. Individual intrusive units are relatively narrow and steep-sided and are collectively suggested to represent a ring dyke complex. Basement gneiss and gabbro host rocks have locally contaminated the oldest quartz syenite KSC unit, but most of the main part of the complex escaped significant influence from host rocks. A late suite of E–W to NE–SW striking peralkaline dykes of trachytic to phonolitic compositions intrude the KSC. Compositions of the KSC rocks span a considerable range in SiO2, 59–73 wt%. Concentrations of several elements vary widely for a given SiO2 (especially at SiO2 < 66 wt%), and variation diagrams do not suggest a single model for the evolution of the units of the complex. A cumulative origin is envisaged for several KSC units. Geochemical modelling suggests that KSC magmas were derived from more than one primary magma, and that the complex evolved through a four-stage process: fractional crystallisation in precursory magma chambers was followed by final emplacement of each unit, establishment of a crystal/melt mush, expulsion of part of the residual melt and, finally, crystallisation of the remaining melt. Trace element disequilibria between alkali feldspar and host rocks in two closely associated quartz alkali feldspar syenite units indicate that highly evolved residual melt was replaced by a less evolved melt phase. Modelling of potential parent melt compositions to the Kærven magmas suggests an origin not in the Iceland plume asthenosphere, but rather in a moderately enriched source, possibly in the continental lithosphere. The course of melt evolution by fractional crystallisation is indicated to have taken place in magma chambers at depth, and repeated rise of magma into the upper crustal magma chambers and crystallisation there formed the KSC. Based on our survey of published geochemical data, the inferred parental magmas seem to have few equivalents in the North Atlantic Igneous Province and may have been generated mainly from melting of enriched dry lithospheric mantle of possibly Archaean age.

Laurentthomasite, Mg₂K(Be₂Al)Si₁₂O₃₀: a new milarite-group-type member from the Ihorombe region, Fianarantsoa Province, Madagascar

Laurentthomasite, ideally Mg2K(Be2Al)Si12O30, is a new milarite-group member found within quartz-syenite pegmatites from the Ihorombe region, Fianarantsoa Province, Madagascar. It occurs as euhedral {0001} hexagonal crystals, maximum 15 mm large and 5 mm thick. The crystals show a very strong dichroism with cobalt blue and green-yellow colours when observed along [0001] and [1000], respectively. The mineral is transparent, uniaxial (+) and its lustre is vitreous. The hardness is about 6 (Mohs scale), showing a poor {0001} cleavage, irregular to conchoidal fracture, and a measured density of 2.67(8) g cm−3. Laurentthomasite is hexagonal, space group P6/mcc (no. 192), with a=9.95343(6) Å, c=14.15583(8) Å, V=1214.54(1) Å3 and Z=2. The strongest nine lines in the X-ray powder diffraction pattern [d in Å – (I) – hkl] are 3.171 – (10) – 211, 4.064 – (8) – 112, 2.732 – (8) – 204, 4.965 – (6) – 110, 2.732 – (4) – 204, 3.533 – (3) – 004, 7.055 – (2) – 002, 4.302 – (2) – 200 and 3.675 – (2) – 202. Chemical analyses by electron microprobe and several spectroscopies (inductively coupled plasma, ICP; optical emission, OES; mass, MS; and Mössbauer) give the following empirical formula based on 30 anions per formula unit: (Mg0.86 Sc0.54 Fe0.352+ Mn0.26)∑=2.01(K0.89 Na0.05 Y0.02 Ca0.01 Ba0.01)∑=0.98[(Be2.35 Al0.50 Mg0.11 Fe0.033+)∑=2.99(Si11.90 Al0.10)O30]; the simplified formula is (Mg, Sc)2(K, Na)[(Be, Al, Mg)3(Si, Al)12O30]. The crystal structure was refined to an R index of 1.89 % based on 430 reflections with Io > 2σ(I) collected on a four-circle diffractometer with CuKα radiation. By comparison with the general formula of the milarite group, A2B2C[T(2)3T(1)12O30](H2O) x (0<x<n, with n<2 pfu, per formula unit), the laurentthomasite structure consists of a beryllo-alumino-silicate framework in which the T(1) site is occupied by Si and minor Al and forms [Si12O30] cages linked by the T(2) site mainly occupied by (Be + Al). The A and C sites occur in the interstices of the framework while the B site is vacant. The origin of the strong dichroism is related to a charge transfer process between Fe2+ and Fe3+ in octahedral A sites and tetrahedral T(2) sites, respectively.

Early Permian granitoids of the East Magnitogorsk zone (South- ern Urals): petrology, geochemistry, and geodynamic formation environment

The relevance of the problem. The Early Permian magmatism of the Southern Urals is poorly studied with the help of modern methods. The granitoid massifs of this age locally developed in the East Magnitogorsk zone contain important information about the geodynamic conditions of their formation. Clarification of this issue makes an important contribution to the understanding of the geodynamic development of the Urals. The nature of granitoids is still debatable. The connection with the massifs combined in the Balkan complex of gold-tungsten mineralization indicates the need for a comprehensive study. The purpose of the study is to determine the petrological and geochemical features of the rocks of the Balkan complex, to identify the mechanism of their petrogenesis and to establish the geodynamic conditions of their formation. Results. The petrological and geochemical study of the formations of the Balkan complex was carried out and their place in the typical taxonomy of granitoids was determined. Their belonging to the I-type is shown. Mineralogical and petrogeochemical methods were first studied for shonkinite xenoliths in granitoids. The mechanism of petrogenesis of rocks is proposed and the geodynamic setting of their formation is determined. It is shown that the monzonitemonzodiorite-quartz syenite-granosyenite-leucogranite series of rocks was formed as a result of crystallization differentiation of a single parental melting, and it was also concluded that the massifs of the complex are formed under conditions of early collision conditions with the important role of the subduction process. The mechanism of formation of the massifs of the complex is largely similar to mechanism for granitoids in other conflict areas, although it has its own specifics. Conclusions. 1). The Early Permian granitoids of the Balkan complex relates to type I. 2). All rocks of the complex, from monzonites to quartz syenites and leucogranites, including xenolith shonkinites, form a petrogenetic series formed as a result of crystallization differentiation of a single parent alkaline-gabbroic melting with increased water pressure. 3). The Balkan complex was formed in an early collisional setting under the action of deep subduction. 4). Transpression in the upper part of the crust induced formation of the massifs of the complex. 5). The Balkan complex is a kind of indicator of the growth of the newly formed crust as a result of collision and accretion processes.

Eocene post-collisional magmatism in Himalaya orogenic belt: evidence from petrography, zircon U-Pb age and Sr-Nd-Hf isotope of the Mayum alkaline complex, southern Lhasa subterrane

&lt;p&gt;Alkaline magmatism is commonly generated in extensional settings, playing an important role in constraining the timing of slab breakoff. Eocene post-collisional magmatism is widely distributed along the Gangdese belt of southern Tibet. However, few Eocene post-collisional alkaline magmatism has been identified. Here, we present a comprehensive study of whole-rock geochemistry, zircon U-Pb ages and Sr-Nd-Hf isotopes of the Mayum alkaline complex from the Southern Lhasa Subterrane, providing an insight into the timing of breakoff of the Neo-Tethyan slab. The alkaline complex is composed of amphibolite syenite, quartz syenite and alkaline granite. The mafic microgranular enclaves are ubiquitous in the syenites. Zircon U-Pb analyses indicates that the alkaline rocks were generated in Early Eocene (ca. 53-50 Ma). These ages suggest that the alkaline rocks emplaced shortly (10-15Ma) after the continental collision between the Indian and Eurasian plates. The alkaline rocks have high SiO&lt;sub&gt;2 &lt;/sub&gt;(64.32-77.36 wt.%), Na&lt;sub&gt;2&lt;/sub&gt;O + K&lt;sub&gt;2&lt;/sub&gt;O (6.63-9.03 wt.%) contents, low MgO (0.14-2.52 wt.%) contents. These rocks show obvious arc-like geochemical features in trace elements, i.e., enrichment in LILEs (e.g., Rb, K), LREEs, Th and U, and depletion in HFSEs (e.g., Nb, Ta, Ti), HREEs with strongly to moderately negative Eu anomalies (&amp;#948;Eu=0.28&amp;#8211;0.72). These features together with high FeO&lt;sup&gt;T&lt;/sup&gt;/MgO, Ga/Al, Ce/Nb and Y/Nb values, and low Ba, Sr contents, suggesting that the Mayum alkaline rocks belong to an A2-type granitoids. Besides, the alkaline rocks have homogeneous initial &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr ratios (0.7052-0.7059) and negative &amp;#949;&lt;sub&gt;Nd&lt;/sub&gt;(t) values (-2.1 to -0.9) for whole-rock, and positive zircon &amp;#949;&lt;sub&gt;Hf&lt;/sub&gt;(t) values (+0.73 to +11.16). Nd-Hf isotope decoupling suggests that the alkaline was likely produced by mixing of mantle- and crust-derived magmas under a post-collisional extensional setting. Combined with previous published results, we propose that the slab breakoff of the subducting Neo-Tethyan oceanic lithosphere at least prior to Early Eocene (ca. 53Ma). The Eocene Mayum alkaline complex might be related to asthenosphere upwelling trigged by the slab breakoff.&lt;/p&gt;