The paper describes the composition of skarn garnets of the Novonikolaevskoe Cu deposit (South Urals) in comparison with that of garnets of the Gumeshki and Tarutino skarn copper porphyry deposits in the Urals. Three generations of the andradite-grossular group garnets typical of skarn depositsare distinguished at the Novonikolaevskoe deposit. The median TiO2 content of garnet-1 and garnet-2 is 0.37 wt. % reaching 2.38 wt. % in garnet-3. This TiO2 content of garnets and relatively low Fe contents in some garnets from exoskarns (And40–54) possibly indicates a temperature increase during the skarn formation stage of garnets at the Novonikolaevskoe deposit, as well as relatively higher-temperature conditions of formation of garnet at the deposit compared to those from the Tarutino and Gumeshki deposits. Low fluid redox conditions during the formation of skarns at the Novonikolaevskoe deposit compared to the Tarutino deposit may be another reason for the low Fe contents in exoskarn garnets. According to the composition of garnet, the Novonikolaevskoe and Gumeshki deposits can be classified as Au-Fe-Cu skarn deposits, whereas the Tarutino deposit can be ascribed to a Cu-skarn deposit.
Wondem Habtamu, Teferi Minyahl, Jothimani Muralitharan
et al.
This study investigates the petrological and geochemical characteristics of basalts from the Gomer area in the Northwestern Ethiopian Volcanic Province to explore their petrogenesis and mantle source characteristics. Traverse-based field mapping, petrographic investigation, and whole-rock geochemical analysis were conducted. The whole-rock geochemical analysis of basalts for major and trace elements was performed using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry, respectively. The Gomer area comprises different textured basalts, including vesicular, amygdaloidal, scoriaceous, massive basalt, and interbedded agglomerates. These basalts are primarily composed of minerals such as olivine, clinopyroxene, plagioclase, and opaque phases in varying proportions. They exhibit highly porphyritic to glomeroporphyritic textures with abundant phenocrysts of clinopyroxene and plagioclase and subordinate olivine set in an intergranular textured groundmass of the same mineral assemblage. Based on the proportion of phenocryst mineral assemblage, the studied samples are grouped as plagioclase-pyroxene phyric basalt and plagioclase phyric basalt. Geochemically, the analyzed samples are tholeiitic in composition, with hypersthene- and quartz-normative mineralogy. The Gomer basalts exhibit trace element characteristics and ratios (e.g., Zr/Nb = 12.4–19.8, La/Nb = 1.13–1.5) similar to E-MORB. Low (La/Yb) N ratios (2.19–3.85) and relatively flat HREE patterns [(Tb/Yb) N = 1.29–1.7 and (Dy/Yb) N = 1.27–1.57] indicate a high degree of partial melting of an E-MORB-type mantle in the spinel stability field. Overall, the petrogenesis of the Gomer basalts is primarily governed by fractional crystallization involving olivine, clinopyroxene, plagioclase, and occasional spinel, with minimal crustal interaction. The geochemical characteristics and trace element ratios support derivation from an E-MORB-type mantle source. These findings provide new insights into mantle heterogeneity in continental rifting settings and allow comparisons with other large igneous provinces, such as the Deccan Traps and Icelandic basalts.
A. P. Zhgilev, A. B. Perepelov, S. S. Tsypukova
et al.
Studies have been made on pyroxene (Cpx) and garnet (Grt) megacrysts from the rocks related to two-stage formation of the Tesiingol volcanic field in Northern Mongolia. The rocks related to the initial stage of the volcanic field formation, basanites and phonotephrites of the Early Miocene Bod-Uul volcano (40Ar/39Ar, 17.0±0.5 Ma), do not contain xenogenic material. Megacrysts and associated peridotite and pyroxenite xenoliths were discovered in eruptive deposits and lavas of basaltic trachyandesites of the Middle Miocene Uguumur volcano (40Ar/39Ar, 12.5±0.2 Ma) at the second stage of activity. The volcanic field rocks show the presence of carbonate matter. Cpx and Grt megacrysts have traces of melting and transformation and are associated with sanidine, ilmenite and apatite megacrysts. Pyroxenes have elevated contents of Al and Na and are similar in composition to omphacites (Di71–72Jd16–19Ae9–12). Garnets are characterized by chromium-free almandine-grossular-pyrope composition (Alm58–66Grs17–20Pyr14–19) and correspond to minerals of eclogite paragenesis. Pyroxene megacrysts, compared in composition to pyroxenes from eclogites and peridotites, are enriched in REE, Y, Nb, Ta and Hf. Garnets show relatively high contents of LREE, Zr and Hf. It has been found that the early-stage basanite and phonotephrite magmas were formed in the asthenospheric mantle at 21–28 kbar and 1359–1432 °C. The formation of basaltic trachyandesite melts occurred near the crust and upper mantle at 10–13 kbar and 1192–1237 °C. Megacrysts of the Cpx+Grt association crystallized at 20–24 kbar and 1190–1331 °C in the area of the garnet facies of the lithospheric mantle depth and near its boundary with the asthenosphere. Based on the data for P-T formation conditions, crystal chemistry, trace element and isotopic composition of Cpx and Grt megacrysts, a model of the origin of the latter has been proposed. It is suggested that megacrysts formed above the deep magma chamber as a result of the process similar to pneumatolytic, due to the separation and subsequent crystallization of a silicate-carbonate phase above the solidus of carbonated peridotites, mainly in the lithospheric mantle.
We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R _⊕ ) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M _⊕ . Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% ± 37%) consistent with that of Earth (∼33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day–night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.
The paper represents a literary translation of the late ancient poem “Lithica” (“On stones”). Scholars date the poem by the period from 2nd to 4th centuries. Along with the “Orphic Argonautica” the “Litica” is a part of the Orphic corpus. From the point of view of the genre it is a lapidary in verse (a literary work about stones, mostly precious and unusual). Lapidaries were very popular in the epoch of late antiquity and Middle age. The author of the “Litica” borrows his knowledge from different sources; his work has intersections with the works of Theophrastus, Pliny the Elder, Galenus, Dioscorides and with the prosaic lapidaries of different times. Stories about the stones are located into the double narrative frame: these is a bucolic plot, in which the narrator on the way to the temple meets the “divine man” Theodamas who tells him about some stones. In the middle of the narration Theodamas inserts in his own story the one of the diviner Helenus (this fact should be evidence of the deep antiquity of the information given in the poem). The main content of the poem is information about approximately 30 different minerals, their useful proprieties as therapeutic, so magic; in the commentaries are given the modern hypotheses of their identification. The information about the stones in the poem is given unevenly; from the simple mention up to the detailed story including medical or magic recipes and mythological digressions connected with the origin of each stone. As well as the “Orphic Argonautica” the ”Litica” reflects the decline of ancient rationalism and the domination of the religious interests over the “scientific” ones which is typical for the late ancient mentality.
Yoel Ochoa-Mc-Intosh, Tomás Hernaldo Fernández-Columbié, Ledennis Suárez-Torres
et al.
El trabajo tuvo el propósito de caracterizar, desde el punto de vista químico, físico, granulométrico y mineralógico, un residuo industrial de hidróxido de calcio generado en el proceso de fabricación de acetileno. Las muestras se analizaron, primeramente, sin neutralizar; luego se realizó el mismo procedimiento, usando ácido sulfúrico a un 98 % de pureza. Para ambos casos, las temperaturas de calentamiento fueron de 500 oC y 900 oC. Para identificar las fases, los patrones de difracción fueron obtenidos usando fuente de radiación de cobre (CuKα, λ = 1,5418 Å). Se determinó que el residual presenta CaO y MgO, lo que garantiza su pureza. Al calentarlo sin neutralizar a 500 oC se transforma el hidróxido de calcio y a los 900 oC hay pérdida del carbonato y del agua. En el residual tanto sin tratamiento como neutralizado está presente el hidróxido de calcio.
Abstract Red ceramic waste (RCW) is one of the main by-products generated by the production of ceramic materials. Its application in lightweight aggregates (LWAs) has not yet been tested. Thus, this review intends to evaluate the perspectives of using RCW in the manufacture of LWAs. The search was carried out in the ScienceDirect database. 47 articles were selected. A significant amount of data on the chemical, physical, mineralogical, and morphological properties of RCW are discussed. In most studies, the chemical constituents of RCW complied with the swelling parameters. The mineralogy of the residue usually has constituents capable of controlling the viscosity and aiding gas formation. The data of granulometry, microstructure, and loss of mass denote the need for special care with the methodology adopted for grinding and sintering of the residue. This review indicates that there is a high potential for the use of RCW in the manufacture of LWAs.
The 40Ar/39Ar dating of ultrapotassic rocks from Central Chukotka shows that these rocks are Early Cretaceous, and yields a narrow range of age variations (109 to 107 Ma), which correlates fairly well with the range of age variations of granitoids typical of the study area (117–105 Ma). There are thus grounds to suggest that the ultrapotassic magmas and granitoids resulted from the same geological process that can be identified from the material characteristics of the ultrapotassic magmas.In the modern concepts of the regional geological development, the formation of the granitoid and ultrapotassic magmas can be related to the continental lithosphere extension due to the collision of Eurasian plate and the Chukotka – Arctic Alaska continental block.Using modern genetic models based on the interpretations of the material characteristics of ultrapotassic magmas, it is possible to limit the number of genetic hypotheses and to relate the continental lithosphere extension to the processes that took place in the upper mantle of the study area.
Effective energy-dispersive X-ray spectroscopy analysis (EDX) with a scanning electron microscope of fine-grained materials (submicrometer scale) is hampered by the interaction volume of the primary electron beam, whose diameter usually is larger than the size of the grains to be analyzed. Therefore, mixed signals of the chemistry of individual grains are expected, and EDX is commonly not applied to such fine-grained material. However, by applying a low primary beam acceleration voltage, combined with a large aperture, and a dedicated mineral classification in the mineral library employed by the Zeiss Mineralogic software platform, mixed signals could be deconvoluted down to a size of 200 nm. In this way, EDX and automated quantitative mineralogy can be applied to investigations of submicrometer-sized grains. It is shown here that reliable quantitative mineralogy and grain size distribution assessment can be made based on an example of fault gouge with a heterogenous mineralogy collected from Ikkattup nunaa Island, southern West Greenland.
Asad Ali Narejo, Abdul Majeed Shar, Noor Fatima
et al.
Abstract We have studied geochemical characteristics, mineralogy and origin of the manganese deposits in Bela ophiolitic complex. Geochemical investigation was conducted in order to discuss the elemental correlations and to infer the probable origin of manganese deposits in Bela ophiolites. Ore microscopy was conducted to identify different manganese minerals and their paragenesis. Psilomelane and braunite were found to be the major ore minerals. Mineral paragenesis sequence as observed was braunite forming first. Psilomelane formed in later stages because it has been found that psilomelane is altering the braunite. Magnetite was observed as a secondary mineral as vein filling and cutting through both the braunite and psilomelane, therefore, younger than the psilomelane and braunite. The gangue minerals observed in the studied samples were quartz, cryptocrystalline silica and calcite. The correlations among different major and trace elements showed diversity of relations. MnO showed negative correlation with Fe2O3 (− 0.73), Si2O (− 0.27), positive correlation with Al2O3 (0.54), TiO2 (0.36), MgO (0.22), Pb (0.23), Ni (0.07), Cr (0.12), and no correlation was established with Zn, Cu, Co. Binary diagram of Si versus Al and ternary discrimination diagrams of Fe–(Ni + Co + Cu) × 10–Mn and Ni–Zn–Co showed hydrothermal-diagenetic-type deposits. Furthermore, the present study suggests that the enriched manganiferous fluid during its upward movement within the Tethys oceanic crust near spreading center started precipitating Mn along with Fe on the sea floor. Later on, these manganese minerals were obducted on land between Indian plate and Helmond block of Eurasian plate in existing position accompanying pillow basalt and pelagic sediments.
Morphological features of amazonite cause some onthogenic models of K-feldspars. The crystals of amazonite are zonal and sectorial. «Microcline lattice» of stresses in K-feldspar is formed after its growth during polymorphic transformation of monoclinic to triclinic structure. The «annealing» of tense structure of microcline is accompanied by formation of microporosity. Only exsolution and syntax «perthites» are identified in K-feldspar. Eutectic crystallization of amazonite suggests its broad assemblage with many minerals, including galena.
Abstract After publication of the article (Orywall et al. 2017), it has been brought to our attention that there are a number of errors. The authors have listed them below.