Zr Content Research Articles

Gemology, Mineralogy, and Spectroscopy of Gem-Quality Diopside from Pakistan and Russia: New Insights for the Chromogenic Mechanism and Possible Origin

Green diopside is currently popular in the jewelry market due to its attractive color and excellent transparency. Gem-quality diopsides are mainly sourced from Pakistan, Italy, Russia, and other places. The color, geographic origin, and formation mechanism are the main factors affecting the value of gemstones, which can be determined by examining their gemology and composition characteristics. This study systematically characterizes the standard gemology of green diopsides from Pakistan and Russia and compares them with the blue diopsides produced within the skarn process and the diopsides from the nearby region in Russia from previous studies by gemological microscopy, spectral testing (infrared, Raman and ultraviolet-visible spectroscopy), and chemical analyses (electron probe and laser ablation inductively coupled plasma mass spectrometry). The results show that the spectral characteristics and phase composition of the green diopside samples from Pakistan and Russia have excellent uniformity and similarity. The high Cr, Fe, V, and Ni contents are the reasons why they appear as green. Meanwhile, the elemental characteristics of the diopside are effective tools for distinguishing different origins of different diopsides. The Russian green diopsides have higher contents of Sr, Sc, Zr, and rare earth elements (REE), indicating that they are related to alkaline ultrabasic rocks, and the source of the diopside sample from Pakistan is metamorphic rock.

Synergistic effect of Zr and Hf alloying on cross fluvial microstructure of CoCrFeNi eutectic high-entropy alloys

In this study, selective vacuum arc furnace is used to fabricate CoCrFeNi-M0.4 (M = Zr, Hf, 50 %Zr + 50 %Hf) EHEAs, and the content of Zr and Hf element is controlled to solve the balance of strength and plasticity in HEAs. Through alloying with Zr or Hf, the cross fluvial eutectic structure of CoCrFeNiZr0.4 and CoCrFeNiHf0.4 are consists of FCC-CoCrFeNi matrix phase and intermetallic. CoCrFeNiZr0.2Hf0.2 EHEAs, which is synergistic alloying with Zr and Hf, have a brawny river eutectic structure of both soft FCC and hard Ni7Hf2 intermetallic. The synergistic precipitation strengthening and solid solution strengthening result in the fracture strength and ductility of CoCrFeNiZr0.2Hf0.2 reaching 3475.7 MPa and 14.1 %, respectively. Furthermore, CoCrFeNiZr0.2Hf0.2 exhibit a good combination of strength and plasticity through synergistic alloying effect compared with other CoCrFeNi HEAs.

Novel strategies to tune the color emission of Bi2Ti2-xZrxO7:Er3+,Yb+3 upconversion phosphors: Substituting Ti by Zr and annealing at high temperatures

Bi2Ti2-xZrxO7:Er3+,Yb3+ phosphors were synthesized with different content of Zr (X = 0–1.5) by combustion method at 550 °C, producing a mixture of Bi2Ti2O7/Bi4Ti3O12 phases. After increasing the synthesis temperature to 1000 °C, a pure Bi2Ti2O7 (BiTiO) phase was obtained as well as porous coalesced microparticles (2–10 µm) with pore sizes of 110–420 nm. Those samples produced green (548 nm)/red (655 nm) and NIR (1530 nm) emission bands after excitation with 980 nm and their color emission was tuned from green to yellow–red or viceversa using two strategies: i) by increasing the Zr content in the Bi2Ti2-xZrxO7:Er3+,Yb3+ host (from X = 0 to 1) or ii) by increasing the synthesis temperature from 550 to 1000 °C. Interestingly, the intensity of the NIR and red emission bands was enhanced with the content of OH groups on the surface of the BiTiO:Yb,Er phosphors.

Effect of Zr on isothermal oxidation behavior of TC4 alloy at 600 °C

The oxidation behavior of TC4-xZr (x = 0, 20, 30, 47) alloys at 600 °C is studied. The oxidation kinetics of TC4 alloy and TC4-20Zr alloy at 600 °C follows a parabolic rule, while the oxidation of TC4-30Zr alloy and TC4-47Zr alloy at 600 °C follows the linear law. The thickness of the oxide film increases obviously with the increase of Zr content. The surface of TC4 alloy is a dense oxide layer composed of TiO2 compound. With the addition of Zr, ZrO2 and ZrTiO4 compounds are gradually formed, and cracks are formed at the oxide film and oxide film/matrix interface. In short, the addition of Zr reduces the oxidation resistance of TC4 at 600 °C.

The occurrence of anthophyllite–phlogopite-bearing schist in the Seridó belt, northeastern Brazil: Geological significance and potential guide of prospecting for gold and emerald deposits

In the Bonfim W–Mo and Au–Bi–Te skarn deposit, Northeastern Brazil, Archean metamafic–ultramafic rocks are similar to those found in greenstone belt sequences worldwide. The Bonfim emerald deposit comprises metric layers of lenticular-shaped phlogopite-rich schist developed at the symmetrical contacts between metamafic–ultramafic rocks and Be-rich granite intrusions. They formed near these rocks by metasomatic fluids emanating from granitic magma. Metasomatism also transformed the marble and schists into skarns at the marble–schist contact and within the marble. This contribution describes the drill cores containing Mg-rich schist in the Neoproterozoic metapelitic sequence. Detailed petrographic observations and geochemical analysis reveal that it contains phlogopite, anthophyllite, fuchsite, and anomalous Cr–Ni–V–Co–Sc contents. These characteristics contrast those of the common schists at Bonfim or regionally and indicate a probable komatiitic affinity. The anthophyllite–phlogopite-bearing schist contains a metamorphic paragenesis of phlogopite + anthophyllite + garnet + tourmaline + zircon + monazite + plagioclase + quartz, followed by two successive retrograde metasomatic parageneses comprising (i) clinozoisite–zoisite + apatite and (ii) white mica (±fuchsite) + clinochlore + quartz. It exhibits a peculiar texture containing prismatic pseudomorphs (1–7 mm long) composed of anthophyllite, clinozoisite–zoisite, and white mica. The relict orthogonal cleavage suggests that they could represent preexistent Mg-rich pyroxene. Similar to the common schist in Bonfim, the anthophyllite–phlogopite-bearing schist near the skarns is metasomatically converted in places into actinolite–anthophyllite–phlogopite-bearing schist. The anthophyllite–phlogopite-bearing schist contains phlogopite and biotite with low Fe/(Fe + Mg) (between 0.2 and 0.4) and anthophyllite with a composition close to Mg5Fe2Si8O22(OH)2 (MgO approximately 22 wt% and Al2O3 <0.7 wt%). In the actinolite–anthophyllite–phlogopite-bearing schist, the metasomatically formed amphibole has a composition varying from actinolite to magnesiohornblende with a high MgO (>16.5 wt%). The whole-rock geochemical analyses of three representative samples indicate that the anthophyllite–phlogopite-bearing schist contains high MgO (approximately 15%), Cr (up to 574 ppm), and Ni (up to 237 ppm) contents, besides V (up to 198 ppm), Co (up to 51 ppm), and Sc (up to 25 ppm). The anthophyllite–phlogopite-bearing schist has higher MgO, K2O, S, Cr, Co, Ni, and Rb contents, and lower Na2O, P2O5, Zn, Sr, Zr, and Pb contents than the average composition of the Seridó regional schist. The 87Sr/86Sr ratio in two representative samples of the Bonfim schists revealed that the anthophyllite–phlogopite-bearing schist has higher ratio (0.89455) than the enclosing common schist (0.74514), indicating distinct ages of the source rocks for the sedimentary protolith of these two schists, with evidence for an older age of the former source. The original sediments of the anthophyllite–phlogopite-bearing schist could have had an Archean komatiitic source (e.g., komatiitic basalt, peridotite, websterite or pyroxenite), as indicated by the Mg-rich metamorphic minerals (phlogopite and anthophyllite), Cr–K-rich metasomatic ones (fuchsite), and the peculiar MgO, Cr, Ni, Co, Sc, and K2O contents. This source could be part of an Archean greenstone belt now dismantled and/or removed by tectonic and erosion processes. Alternatively, the Mg-rich schist could be a remnant of the upper sedimentary unit of such an ancient rock sequence. The unusual schist could potentially guide gold and emerald deposit prospecting in the region.

Analysis of Low Mechanical Properties of 1420 Al-Li Alloy in Tensile Test

The mechanical properties of 1420 Al-Li alloy tensile specimen were tested after T6 heat treatment. The mechanical properties of some specimens were lower than the standard requirements. In this paper, the reasons for the low mechanical properties of tensile specimens were analyzed by means of electron microscope observation, metallographic examination and hardness examination. The results show that after T6 heat treatment, the surface of the sample is rough and the depth of the oxide layer is different, and the notch sensitivity of 1420 alloy is very high. During the mechanical properties testing, the deep oxide layer becomes the stress concentration point and the source zone of tensile fracture, which reduces the overall mechanical properties of the sample. After heat treatment, the surface of the specimen is formed with low hardness white bright band structure, which also reduces the mechanical properties of the specimen. The high content of Zr in the fracture source region of some samples also leads to the unqualified mechanical properties.

Indicators of restoration strategies in land uses: metallic and non-metallic elements

Land management practices can have an impact on the environmental quality of soil and contribute to identifying the source of its pollution. The objective of this study was to determine presence of metallic and non-metallic elements as indicators of land use impact (livestock management, restoration strategies and without management practices) in the Monte Caldera communal lands located in Cerro de San Pedro, San Luis Potosi, Mexico. Eighteen samples were collected at depths of 0-10 cm and 10-20 cm for each land use. Total concentrations of Zr, Sr, U, Th, Pb, As, Rb, Cr, V, Ti, Zn, and Cu were determined by X-ray fluorescence. Mean concentrations ranged in the following order: Ti&gt;Zr&gt;Rb&gt;V&gt;Sr&gt;Zn&gt;Cr&gt;Pb&gt; Cu&gt;Th&gt;U&gt;As, with concentrations for Ti, Cr, Th, U and As exceeding technical reference values for phytotoxic soils. Significant differences were evidenced by ANOVA between land use (Th, Pb, Rb, Cu) and soil depth (U, Pb, and As). Land use practices associated with restoration resulted in a positive environmental impact. These findings underscore the need to conduct follow-up studies in the area and further examine the relationship of such practices with other environmental factors. Highlights: Soil management practices can affect the environmental quality of this resource and help diagnose the source of its contamination. It is necessary to evaluate the Impact of land use on livestock management, restoration strategies, and without management or conservation areas. By X-ray fluorescence technique the total concentration of Zr, Sr, U, Th, Pb, As, Rb, Cr, V, Ti, Zn, and Cu was determined. Ti, Cr, Th, U and As exceed the technical reference values for consideration as phytotoxic in soils. Land use associated with reclamation practices is an indicator of a positive influence on improving soil quality.

Preparation and characterization of metastable β-type titanium alloys with favorable properties for orthopedic applications

Titanium (Ti)-based alloys with good mechanical properties are highly desirable for bone implants to achieve long-term clinical success. As non-toxic alloying elements, zirconium (Zr) and molybdenum (Mo) have been employed to improve the mechanical properties of Ti-based alloys. In this work, a series of Ti-Zr-Mo alloys, including Ti-18Zr, Ti-13Mo, and Ti-18Zr-13Mo were prepared and compared for potential orthopedic applications for the first time. The phase composition, microstructure, mechanical properties, corrosion resistance, biocompatibility, and osteointegration performance were systemically investigated. It is found that Ti-18Zr displayed an acicular α′ phase, whereas Ti-13Mo and Ti-18Zr-13Mo exhibited a metastable β phase. Compared with commercially pure Ti (CP-Ti), the prepared Ti-Zr-Mo alloys possessed a higher compressive yield strength and a greater microhardness, because of the solid solution and phase precipitation strengthening of Zr and Mo elements. Furthermore, Ti-18Zr-13Mo and Ti-13Mo demonstrated better corrosion resistance than that of CP-Ti, while Ti-18Zr exhibited an inferior result. The cytocompatibility and osteointegration of prepared alloys were similar to those of CP-Ti. Taken together, the Ti-Zr-Mo alloys investigated in this study present a promising alternative to CP-Ti for orthopedic applications, among which the metastable β-type alloy Ti-18Zr-13Mo is most attractive. Moreover, an appropriate Mo content enhances the mechanical and corrosion resistance properties of Ti-based alloys, whereas a high Zr content may pose an adverse influence on the corrosion resistance, which provides valuable insights into the design and further optimizing of new Ti-Zr-Mo alloys for future biomedical applications.

High-Temperature Mechanical and Dynamical Properties of γ-(U,Zr) Alloys

High-temperature body-centered cubic (BCC) γ-U is effectively stablized by γ-(U,Zr) alloys that also make it feasible to use it as a nuclear fuel. However, relatively little research has focused on γ-(U,Zr) alloys due to their instability at room temperature. The effect of Zr composition on its mechanical properties is not clear yet. Herein, we perform molecular dynamics simulations to investigate the mechanical and dynamical stabilities of γ-(U,Zr) alloys under high temperatures, and we calculate the corresponding lattice constants, various elastic moduli, Vickers hardness, Debye temperature, and dynamical structure factor. The results showed that γ-U, β-Zr, and γ-(U,Zr) are all mechanically and dynamically stable at 1200 K, which is in good agreement with the previously reported high-temperature phase diagram of U-Zr alloys. We found that the alloying treatment on γ-U with Zr can effectively improve its mechanical strength and melting points, such as Vickers hardness and Debye temperature, making it more suitable for nuclear reactors. Furthermore, the Zr concentrations in γ-(U,Zr) alloys have an excellent effect on these properties. In addition, the dynamical structure factor reveals that γ-U shows different structural features after alloying with Zr. The present simulation data and insights could be significant for understanding the structures and properties of UZr alloy under high temperatures.

Potential dust sources for loess deposits in Central Italy: A geochemical case study from the Loess-Paleosol-Sequence of Ponte Crispiero (Marche)

Identifying potential dust sources of Loess-Paleosol-Sequences (LPS) is important to understand past climatic and environmental conditions. For loess deposits of Central Italy different hypothesis on particle sources have been proposed, but none of them has been tested using a comprehensive geochemical approach yet.Here we present geochemical, mineralogical and grain-size data from selected deposits of a LPS situated at Ponte Crispiero (Marche, Central Italy) to obtain first insights on the provenance of particles deposited here.Loess deposits within the Ponte Crispiero succession are rather coarse (mostly coarse silt and fine sand) indicating a dominance of proximal dust sources. Applied geochemical indices suggest the alluvial plains of the Po River (Northern Italy) and its discharging area as major particle sources.According to these findings, the so-called “Great Po Plain” hypothesis, that claims the presence of a vast alluvial landscape related to the sea-level drop of the Adriatic Sea during the Pleniglacial (i.e. Marine Isotope Stage MIS 4–2), may be considered as a realistic scenario. Such a considerable alluvial plain would have the potential as major source for silt and sand particles not only for the Ponte Crispiero LPS, but also for the loess on the Adriatic side of Central Italy. The main geochemical characteristics of Ponte Crispiero loess are the low concentrations of Zr and Hf and the high contents of carbonate and transition elements compared to the Upper Continental Crust and other European loess sections. Overall, this study contributes towards a better understanding of the provenance and origin of Italian loess. However, for further testing the “Great Po Plain” hypothesis, more (geochemical) investigations need to be conducted, especially in the surrounding areas of the Po plain.

Vacuum brazing TiAl intermetallic to K4169 alloy using amorphous filler metals Ti56.25–xZrxNi25Cu18.75

A series of Ti56.25–xZrxNi25Cu18.75 (x = 0–25, at.%) filler metals were designed based on a cluster-plus-glue-atom model to vacuum braze TiAl intermetallic to K4169 alloy. The impact of Zr content on the interfacial microstructure and shear strength of joints was examined. And the relationship between the interfacial lattice structure and the fracture behavior of the joint was investigated. The findings reveal a sectionalized characteristic with three reaction zones (Zone I, Zone II and Zone III) in the microstructure of the TiAl intermetallic to K4169 alloy joint. As the Zr content in filler metals increased, the diffusion of Ti transitioned from long-distance to short-distance in Zone I, changing the initial composition from TiNi3/TiNi/NiNb/(Cr, Fe, Ni)SS to NiCrFe/(Cr, Fe, Ni)SS/TiNi. In Zone II, the initial composition altered from TiNi3/TiNi to TiNi/Ti2Ni/TiNi3/TiCu/TiNi. The interface between Zones II and III altered from a non-coherent and semi-coherent interface of TiNi/TiAl/Ti3Al with significant residual stress to a semi-coherent interface of TiNi/TiNi3/TiAl2/Ti3Al with a gradient distribution. The shear strength of the joint initially decreased and then increased. When the Zr content of filler metal was 25 at.%, the shear strength of the joint reached 288 MPa. The crack initiation position changed from non-coherent TiNi/TiAl interface with high angle grain boundaries (HAGBs) and lattice mismatch of 65.86 at.% to a semi-coherent Ti3Al/TiAl2 interface with a lattice mismatch of 20.07 at.% when the Zr content increased. The brittle fracture was present on the fracture surfaces of all brazed joints.

Glass forming ability of Zr-based Zr–Cu–Ni–Al–(Ag) alloys

A series of Zr-based glasses has been obtained by rapid melt quenching and their thermal characteristics (Tg, Tx, Tl) were determined by DSC/DTA. Some of the most recognized glass forming ability (GFA) criteria were applied to predict the glass forming ability of the alloys and to study its dependence on the alloy composition. As a result, the best glass forming compositions among the studied alloys could be selected. It was found that as a general trend an increase of the Zr content results in Tx and ΔTx (= Tx − Tg) decrease. The determined liquidus temperatures of chosen compositions with substantially different ΔTx were found to vary relatively little. Therefore, it was concluded that the variation in the GFA of the studied alloys is mainly due to difficulties in the crystallization process, rather than to different stability of the melts.

Two pulses of Mesoproterozoic intra-plate magmatism in the heart of the Palaeoproterozoic Ubendian Domain of northern Malawi

Two Mesoproterozoic anorogenic igneous events are recorded in the Palaeoproterozoic Ubendian Domain in northern Malawi. The oldest is represented by the Mwakikome orthogneiss, a small peraluminous, sub-alkaline and ferroan syenogranite that has a U–Pb zircon emplacement age of 1411 ± 3 Ma, an initial εNd of −4.5 and a Nd TDM2 model age of 2.27 Ga. These data are interpreted to suggest that the Mwakikome intrusion was derived mainly from the melting of the adjacent Palaeoproterozoic country rocks during Kibaran-aged extension. The second anorogenic igneous event is defined by the more widespread Mwenga Suite, a series of small (<100 km2) NW-SE oriented and elongated plutons that occur in a narrow belt in the north of the Ubendian Domain. Seven samples from different intrusions gave U–Pb zircon emplacement ages between ∼1150 and 1110 Ma. The Mwenga Suite is comprised of rocks that are also ferroan, potassic and sub-alkaline in composition and shows a range of major element compositions from monzogranite to alkali-feldspar granite. Nd isotopic data from one sample yielded an initial εNd of −2.2 and a Nd TDM2 model age of 1.88 Ga, suggesting that the suite was also largely derived from melting of the Ubendian host rocks, but with some additions from an enriched mantle source. Both the Mwakikome and Mwenga rocks are characterised by high concentrations of Zr, Hf, Nb, Ta, Y and REE and high Ga/Al, imparting a within-plate, A-type, trace element signature. The rocks have no direct temporal correlatives beyond northern Malawi and SW Tanzania and appear unique to this region. They do, however, build on a theme of long-lived Mesoproterozoic (∼1400–1100 Ma) intra-plate extension, basin formation, and bimodal A-type magmatism that is better established in areas of central Africa located over 500 km NW of the study area.

Sc/Zr ratio-dependent mechanisms of strength evolution and microstructural thermal stability of multi-scale hetero-structured Al–Mg–Sc–Zr alloys

• A tensile strength of ∼605 MPa and ∼10% elongation were obtained in Al–7Mg–0.3Sc–0.1Zr. • The strength-ductility synergy owes to a multi-scale heterogeneous microstructure. • While Al–7Mg–0.1Sc–0.3Zr had higher thermal stability at ≥ 400 °C than high-Sc/Zr ratio alloys. • High-content Zr atoms are helpful in enhancing precipitation and coarsening resistance of Al 3 (Sc,Zr). Microstructure and its thermal stability are critical in the development of high-performance Al–Mg alloys. Here, we attempt to tailor Al 3 (Sc,Zr) precipitates and thus microstructure characteristics to manipulate mechanical properties and microstructural stability of Al–7Mg alloys fabricated by hot extrusion combined with two-pass hard-plate rolling via changing Sc/Zr ratio. Increasing Sc/Zr ratio leads to improved strength without any loss of ductility. A strength-ductility synergy, i.e. yield strength of ∼548 MPa and ultimate tensile strength of ∼605 MPa with an impressive ductility of ∼10% elongation was achieved in the Al–7Mg–0.3Sc–0.1Zr alloy. The good strength-ductility synergy is ascribed to the multi-scale heterogeneous microstructure promoted by the high Sc/Zr ratio, i.e. a bimodal grain structure, profuse low angle grain boundaries, dispersed nano-sized Al 3 (Sc,Zr) precipitates coexisting with intragranular Mg-Zr co-clusters segregated at dislocations. Upon thermal exposure, the Al–7Mg–0.3Sc–0.1Zr alloy maintained higher hardness at below 250 °C, whereas Al–7Mg–0.2Sc–0.2Zr and Al–7Mg–0.1Sc–0.3Zr alloys exhibited higher hardness in moderate- and high-temperature range of 250-350 °C and ≥ 400 °C, respectively. Atom-probe tomography analysis illustrates that slow-diffusing Zr atoms enhance Al 3 (Sc,Zr) coarsening resistance through forming a higher-content Zr-enriched protective shell around a Sc-enriched core in Al–7Mg–0.1Sc–0.3Zr. Meanwhile, the high Zr content promotes concurrent Al 3 (Sc,Zr) precipitation during thermal exposure at high temperatures. The improved microstructural thermal stability in Al–7Mg–0.1Sc–0.3Zr alloy is further discussed in terms of the recrystallization resistance and grain growth behavior. The present study reveals the feasibility for designing high-strength and thermally stable hetero-structured Al–Mg–Sc–Zr alloys via tailoring Sc/Zr ratios for different application temperature ranges.

Petrogenesis and Tectonic Implications of the Cryogenian I-Type Granodiorites from Gabgaba Terrane (NE Sudan)

The widely distributed granitic intrusions in the Nubian Shield can provide comprehensive data for understanding its crustal evolution. We present new bulk-rock geochemistry and isotopic (zircon U-Pb and Lu-Hf) data from the Haweit granodiorites in the Gabgaba Terrane (NE Sudan). The dated zircons presented a 206Pb/238U Concordia age of 718.5 ± 2.2 Ma, indicating that they crystallized during the Cryogenian. The granodiorites contain both biotite and amphibole as the main mafic constituents. The samples exhibit metaluminous (A/CNK = 0.84–0.94) and calc-alkaline signatures. Their mineralogical composition and remarkable low P2O5, Zr, Ce, and Nb concentrations confirm that they belong to I-type granites. They exhibit subduction-related magma geochemical characters such as enrichment in LILEs and LREEs and depletion in HFSEs and HREEs, with a low (La/Yb)N ratio (3.0–5.9) and apparent negative Nb anomaly. The positive Hf(t) values (+7.34 to +11.21) and young crustal model age (TDMC = 734–985 Ma) indicates a juvenile composition of the granodiorites. The data suggest that the Haweit granodiorites may have formed from partially melting a juvenile low-K mafic source. During subduction, the ascending asthenosphere melts might heat and partially melt the pre-existing lower crust mafic materials to generate the Haweit granodiorites in the middle segment of the Nubian Shield.

Petrogenesis and Rb-Sr Isotopic Characteristics of PaleoMesoproterozoic Mirgarani Granite Sonbhadra Uttar Pradesh India: Geodynamics Implication for Supercontinent Cycle

The Rb-Sr whole-rock isochron, age 1636 ± 66 Ma of Mirgarani granite, is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex (CGGC). The initial Sr ratio is 0.715 ± 0.012 (MSWD = 0.11), showing an S-type affinity. The Mirgarani granite has intruded the migmatite complex of the Dudhi Group and forms the Mirgarani formation comparable to the granites of the Bihar Mica Belt around Hazaribagh (1590 ± 30 Ma). The present studies have established the chronostratigraphy of the Dudhi Group and adjoining areas in CGGC. Petro graphic and geochemical studies revealed that the granite is enriched in Rb (271 ppm), Pb (77 ppm), Th (25 ppm), and U (33 ppm) and depleted in Sr (95 ppm), Nb (16 ppm), Ba (399 ppm) and Zr (143 ppm) contents as compared to the normal granite. The Mirgarani granite is a peraluminous (A/CNK = 1.23), high potassic (K2O 6.42%), Calc-Alkalic to Alkali-Calcic {(Na2O+K2O)-CaO = 6.29} S-Type granite, a feature supported by the presence of modal garnet and normative corundum (2.68%). The Mirgarani granite is considered to have been formed by the anatexis of a crustal sedimentary protolith at a depth of approximately 30 km with temperatures ranging from 685-700 °C during the Co lumbian - Nuna Supercontinent.

Synthesis of novel Zr-rich 312-type solid-solution MAX phase in the Zr-Ti-Si-C system

A novel 312-type MAX-phase solid solution series in the Zr-Ti-Si-C system has been synthesized by the vacuum carbosilicothermic reduction method using mixtures of TiO2, ZrO2, SiC, and Si powders as starting materials. The upper limit for Zr content in metal sublattice of the synthesized (Zr,Ti)3SiC2 MAX phase solid solutions was found to be as much as approximately 66 at%, closely corresponding to a hypothetical quaternary Zr2TiSiC2 MAX phase. A wide miscibility gap inside the interval of Zr content in metal sublattice ranging between 22 at% and 55 at% was found. Crystal structure of the synthesized MAX-phase solid solutions was studied by HR-STEM/HAADF and XRD Rietveld analyses. The lattice constants were determined to be linearly correlated with Zr content as predicted by Vegard's law. A significant inhomogeneity in distribution of metal atoms similar to that of out-of-plane ordered quaternary MAX phases has been established for both Ti-rich and Zr-rich MAX-phase solid solutions.

A Quantitative Method for the Composition of 7B05 Cast-Rolled Aluminum Alloys Based on Micro-Beam X-ray Fluorescence Spectroscopy and Its Application in Element Segregation of Recrystallization

Microscopic content segregation is among the important reasons for the anisotropy of mechanical properties in the cast-rolled sheets of the 7B05 aluminum alloy. It is of great significance to study the uniformity of aluminum alloys in terms of the microscopic composition and structure. In this study, a precise method for composition quantification based on micro-beam X-ray fluorescence spectroscopy is established by parameter optimization and a calibration coefficient. Furthermore, this method was applied for exploring and quantifying the relationship between recrystallization and deformation microstructures. The results show that the comprehensive measurement effects of all elements are the best when the X-ray tube voltage is 50 kV, the current is 150 μA, and the single-pixel scanning time is 100 ms. After verification, the sum of differences between the measured values and the standard values for all elements using the calibration coefficient is only 0.107%, which confirms the accuracy of the optimized quantitative method. Three types of segregation indexes in national standards were used to capture small differences, and finally ensure that the segregation degrees of elements are Ti > Fe > Cr > Cu > Mn > Zr > Zn > Al. The quantitative segregation results obtained by the spatial-mapping method show that the difference in the content of Al and Zn is approximately 0.2% between the recrystallization region and the deformation region, the difference in the content of Fe and Ti is 0.018% and 0.013%, the difference in the content of Cr, Cu and Zr is approximately 0.01%, and the difference in the content of Mn is not obvious, only 0.004%.

Biogeochemical Features of the Formation of the Holocene Sediments in Lake Dukhovoe at the Stage of Early Diagenesis in Eastern Baikalia

Abstract —A 6-meter core of the Holocene sediments in Lake Dukhovoe is studied. The material composition of the core is heterogeneous and has clear bedding. Lacustrine sediments are represented by the upper 293 cm. Each bed of the sediments is subjected to microbiological analysis. A high total number of heterotrophic bacteria is revealed in the upper (0–15 cm) and deeper (110–150 cm) sapropel intervals. Sulfate-reducing bacteria are identified only in Chrysophyceae cysts. The CaO/Fe2O3 ratio shows the degree of “carbonate content” of bottom sediments. It is low in the lake sapropel (0.2), which indicates the geochemical specificity (carbonate-free sapropel). Na, Mg, Al, Si, Al, Ca, Fe, Mn, Zr, and Cr concentrations in sapropel are within the average concentrations for the Earth’s crust, shale, and oceanic pelagic clays, while U and Mo concentrations exceed them. Phytoplankton is enriched in phosphorus (biogenic element) and chalcophile elements (Zn, Cd, Sn, Sb, Hg, Pb, and Cu), which characterize the pollution of the modern atmosphere of the Baikal region. Diagenetic processes result in the transformation of the pore waters, namely an increase in mineralization as compared to lake water, an increase in the concentrations of biogenic components (HCO3-, NH4+, NO3-, and PO43-) and a decrease in SO42-. Pyrite framboid accumulations are revealed in organomineral sediments below the horizon of 200 cm, and iron phosphates represented by vivianite are identified in sapropel.

Origin and implication of two newly identified peraluminous A-type granites in the early Paleozoic orogeny, Southeast Asia

Abstract: The amalgamation of the Yangtze and the Cathaysia Block in Neoproterozoic time led to the formation of the South China Block (SCB) and generated the Jiangnan Orogen with the occurrences of juvenile magmatic rocks. After this orogeny, a typical collisional orogen formed during the early Paleozoic period in Southeast Asia which is mainly distributed in the Wuyi-Nanling-Yunkai area in the SCB. However, the transitional time from syn-collisional compression to post-collisional extension is debatable. Here, we present new data on zircon U-Pb zircon ages, Lu-Hf isotopes, and geochemistry for the Guzhang and Shadi granites from the Nanling area, South China. Both plutons have similar zircon 238U/206Pb ages of ca. 430 Ma. Petrographic and geochemical characteristics (e.g., FeOt/(FeOt+MgO) = 0.82–0.95) indicate that both granites are peraluminous A-type, with high Ga/Al ratios (2.43–2.91) as well as high concentrations of Zr, Nb, Ce, Y (sum values from 327 to 527 ppm), and formation temperature (820°C–845°C). Shadi granite exhibit high positive εHf(t) values (clustering within 0 to +6) while Guzhang granite show relatively lower εHf(t) values (−8.7 to −2.9). Their mildly negative to positive zircon εHf(t) values are higher than that of many coeval granites and can be derived from anhydrous melting of tonalitic genesis in the middle crustal depth, with the Shadi pluton having more orthometamorphite in the source. The ages and Hf isotopic compositions of inherited zircons (εHf(t = 960 Ma) = 9.2, εHf(t = 950 Ma) = 7.3) suggest that the Neoproterozoic juvenile magmatic rocks in the Jiangnan Orogen were a significant source for these granites. We interpret these A-type granites derived at the post-collisional stage. Their occurrence indicates that the geological setting of this Paleozoic orogen shifted from compression to extension no later than 430 Ma.