Zirconia Composites Research Articles

Evolution of magma oxidation states and volatile components in the Cenozoic porphyry ore systems in the western Turkey, Tethyan domain: Constraints from the compositions of zircon and apatite

特提斯成矿域中段的土耳其西部集中产出了与俯冲、碰撞-后碰撞、伸展动力学背景有关的斑岩型铜、钼、金矿床。前人已完成了针对这些斑岩型矿床构造背景的大量研究工作，但对于区内不同构造背景下斑岩型矿床的成矿岩浆源区性质、成矿元素-挥发分含量和成矿物质演化关系尚未有系统研究。而这些研究将对认识中特提斯构造域晚白垩世以来在新特提斯洋俯冲、欧亚板块-Tauride-Anatolide板块碰撞和伸展过程中斑岩矿床形成时地壳厚度、壳幔相互作用方式及成矿物质演化过程具有重要意义。本研究选择土耳其西段三个斑岩成矿带（Tavsanli带、Biga半岛成矿带和Afyon-Konya带）内五个斑岩型矿床的成矿岩体与同期侵入岩-火山岩，开展锆石微量元素和磷灰石主量元素研究，限定碰撞与伸展环境下斑岩型矿床成矿岩浆的形成温度、氧逸度条件及其与岩浆形成时地壳厚度的关系，利用磷灰石F-Cl-S含量组成揭示熔体挥发分和硫元素的物质组成，进而约束新特提斯洋俯冲-碰撞-伸展过程中斑岩系统的深部物质演化规律。研究结果表明，土耳其西部新生代斑岩型矿床成矿岩浆锆石大部分落于高水含量-高氧逸度区间，具有相似的稀土元素标准化配分曲线。从始新世到中新世，锆石氧逸度Ce4+/Ce3+比值呈现出先降低（斑岩型Cu-Mo矿到斑岩型Mo矿）后升高（斑岩型Mo-Cu矿到斑岩Au矿）的趋势，且相对于斑岩型Mo矿和Mo-Cu矿，斑岩型Au矿和Cu-Mo矿成矿岩体的锆石形成时具有相对较高的氧逸度。绝大部分斑岩型矿床成矿岩体的锆石EuN/EuN*位于0.4~0.7之间，但斑岩型Mo矿和斑岩型Mo-Cu矿床的锆石具有相对较低的EuN/EuN*比值，可能是由于在结晶时熔体受斜长石结晶影响较大。锆石微量元素显示（Yb/Gd和Hf/Y-Th/U）锆石组成大部分受岩浆房中角闪石±榍石±磷灰石分离结晶控制。根据锆石Ti温度计估算土耳其西部斑岩型矿床成矿岩体及其相关岩体的形成温度在650~900℃之间，结晶温度从斑岩型Au矿、斑岩型Cu-Mo/Mo-Cu矿至斑岩型Mo矿呈现递减趋势。对于熔体的挥发分与硫含量组成，始新世-渐新世斑岩型Cu-Mo与Mo矿床成矿岩浆相对具有高F和低Cl组成，中新世伸展环境形成的斑岩型Mo-Cu矿和斑岩型Au矿床成矿岩浆Cl含量普遍较高。与成矿岩体同期的暗色包体或基性岩脉中磷灰石计算获得的熔体硫含量均大于侵入体对应熔体的硫含量，且具有不均一的含量组成，表明基性岩浆注入可能为岩浆房提供硫。结合区域动力学和地壳厚度估算，本文认为触发土耳其西部新生代斑岩矿床形成的动力学机制是：在新特提斯洋向北单向汇聚的背景下，北部始新世-渐新世斑岩矿床受控于碰撞后俯冲的新特提斯洋板片（Vardar洋）后撤-回转-断离过程；南部中新世斑岩矿床的形成则受控于爱琴海板片俯冲控制的地壳伸展-减薄过程。北侧Izmir-Ankara-Erzincan缝合带附近的Tavsanli与Biga半岛斑岩成矿带始新世-渐新世斑岩型矿床的形成与熔融-同化-储存-均一过程（MASH）有关，深部地壳热区过程（DCHZ）与中新世Afyon-Konya带斑岩型矿床的形成有关。

Age and Composition of Zircons From the Devonian Petrivske Kimberlite Pipe of the Azov Domain, the Ukrainian Shield

Results of a study of U-Pb and Hf isotope systematics and trace element concentrations in five zircon crystals separated from the Devonian Petrivske kimberlite are reported in the paper. Four zircons have yielded Paleoproterozoic and Archean ages, while one zircon grain gave a Devonian age of 383.6±4.4 Ma (weighted mean 206Pb/238U age). The Precambrian zircons have been derived from terrigenous rocks of the Mykolaivka Suite that is cut by kimberlite, or directly from the Precambrian rock complexes that constitute continental crust in the East Azov. The Devonian zircon crystal has the U-Pb age that corresponds to the age of kimberlite emplacement. It is 14 m.y. younger than zircon megacrysts found in the Novolaspa kimberlite pipe in the same area. In addition, Petrivske zircon is richer in trace elements than its counterparts from the Novolaspa pipe. Petrivske and Novolaspa zircons crystallized from two different proto-kimberlite melts, whereas the process of kimberlite formation was very complex and possibly included several episodes of formation of proto-kimberlite melts, separated by extended (over 10 M.y.) periods of time.

Comparison of surface topography and roughness in different yttrium oxide compositions of dental zirconia after grinding and polishing.

PURPOSEThe purpose of this study was to compare the surface roughness, phase transformation, and surface topography of dental zirconia with three different yttrium oxide compositions under same grinding and polishing conditions.MATERIALS AND METHODSThree zirconia disks (IPS e.max ZirCAD LT, MT, MT multi, Ivoclar Vivadent AG, Schaan, Liechtenstein) were selected for experimental materials. Sixty-nine bar-shaped specimens were fabricated as 12.0 × 6.0 × 4.0 mm using a milling machine and glazing was conducted on 12.0 × 6.0 mm surface by same operator. With a custom polishing device, 12.0 × 6.0 mm surfaces were polished under same condition. Surface roughness (Ra[µm]) was measured before grinding (C), after grinding (G), and at every 3 steps of polishing (P1, P2, P3). X-ray diffraction and FE-SEM observation was conducted before grinding, after grinding, and after fine polishing (P3). Statistical analysis of surface roughness was performed using Kruskal-Wallis test and Mann-Whitney-U test was used as a post hoc test (α = .05).RESULTSThere were no significant differences of surface roughness between LT, MT, and MM groups. In LT, MT, and MM groups, P3 groups showed significantly lower surface roughness than C groups. X-ray diffraction showed grinding and polishing didn't lead to phase transformation on zirconia surface. In FE-SEM images, growths in grain size of zirconia were observed as yttrium oxide composition increases.CONCLUSIONPolished zirconia surface showed clinically acceptable surface roughness, but difference in yttrium oxide composition had no significant influence on the surface roughness. Therefore, in clinical situation, zirconia polishing burs could be used regardless of yttrium oxide composition.

Study of Lu/Hf isotopic composition of zircons using a Neptune Plus multicollector inductively coupled plasma mass spectrometer with an NWR 213 laser ablation attachment

A technique of analyzing the isotopic composition of Lu and Hf and for determining the Lu/Hf and Hf/Hf isotopic ratios in zircons is presented using a Neptune Plus (Thermo Scientific) mass spectrometer with inductively coupled plasma with an NWR 213 (ESI) laser ablation attachment. On the example of Mud Tank, GJ-1, 91500, Plesovice and Temora-2 standard zircon samples, the uncertainty of a single measurement of the 176Hf/177Hf ratio has been obtained in the range of 0.002-0.008% in the form of 2σ (with a crater diameter of 50 μm; when it decreased to 25 μm the measurement uncertainty of the 176Hf/177Hf ratio increased by 1.5-2 times). Under the optimum parameters of the NexION 300S with NWR213 with the aim of increasing the locality of the sequential study of U/Pb and Lu/Hf isotope systems, a comparative characteristic of the application of two approaches has been obtained: in adjacent grain areas (approach 1) and in one crater (approach 2). The metrological characteristics of analyzing the isotopic composition of Lu and Hf and for determining the Lu/Hf and Hf/Hf isotopic ratios in zircons have been determined. To establish the application limits of the developed technique, the factor planning of the experiment has been developed. It was established that with a Lu/Hf ratio of 1/50 or more, the technique is not recommended to be applied due to the incorrect allowance of the isobaric effect. The procedures for measuring and calculating the Lu/Hf isotopic ratios of the isotope system in zircon have been tested on zircon grains (samples NP-46 and NP-47) of the Neplyuevsky pluton (South Urals). The data obtained was in satisfactory agreement with the data of the A. P. Karpinsky Russian Geological Research Institute (VSEGEI).

Dynamic mechanical characters of PEG/zircon composites around PEG glassy region

Abstract Polyethylene glycol (PEG)/zircon (ZrSiO4) composites with various zircon sizes have been fabricated using a liquid method to study the effect of crystallite size on the thermo-mechanical properties of the composites around the glass temperature of PEG. The zircon powders were prepared by different heat treatment, i.e., 500, 1000, and 1200 °C, to acquire different crystallite size. The characterization included XRD, FTIR, and DMA. Results showed that the powders exhibited pure zircon with crystallite size of 226, 321, and 391 nm. Meanwhile, analyses of the FTIR and XRD data confirmed the successful synthesis of the composites. DMA analysis revealed the storage moduli, loss moduli, and tan delta characters of the PEG/zircon composites. The maximum storage moduli and glass transition temperature (Tg) were achieved by the 5 wt% zircon calcined at 500 °C (LPZ500), while the maximum loss moduli were achieved by the 5 wt% zircon calcined at 1200 °C (LPZ1200).

Critical Influence of the Processing Route on the Mechanical Properties of Zirconia Composites with Graphene Nanoplatelets

Graphene-based nanostructures, used as potential reinforcement in ceramic composites, have a great tendency to agglomerate. This requires the use of homogenization techniques during the powder processing, posing the need to evaluate how these techniques affect the microstructure and the mechanical properties of the resulting composites. The influence of the processing route on the properties of 3YTZP (3 mol % yttria tetragonal zirconia polycrystals) ceramic composites with 10 vol % cost-effective GNP (graphene nanoplatelets) has been addressed. Four different powder processing routines combining ultrasonic powder agitation (UA) and planetary ball milling (PBM) in wet and dry media have been used and all the composites were densified by spark plasma sintering (SPS). The mechanical properties at room temperature in the macroscale have been assessed by Vickers indentations, four-point bending tests and the impulse-echo technique, while instrumented indentation was used to measure the hardness and Young’s modulus at the nanoscale. The application of dry-PBM enhances greatly the mechanical and electrical isotropy of the composites, slightly increases the hardness and lowers the elastic modulus, independently of the application of UA. The combination of UA and dry-PBM enhances the flexure strength by 50%, which is desirable for structural applications.

Late Mesoproterozoic–early Neoproterozoic quartzite–schist sequences of the Aktau–Mointy terrane (Central Kazakhstan): Provenance, crustal evolution, and implications for paleotectonic reconstruction

Metasedimentary complexes represented by quartzite–schist Kiik Group quartzite–schists play a significant role in the Aktau–Mointy terrane structure, which is one of the largest Precambrian blocks in the western Central Asian Orogenic Belt (CAOB). U-Pb LA-ICP-MS dating of detrital zircons from quartzites in different Kiik Group areas and related magmatic age data establish that accumulation occurred in the late Mesoproterozoic to early Neoproterozoic (from 1150 to 920 Ma). Concordant age estimates of detrital zircons from Kiik Group quartzites predominately fell within intervals of 1149–2105 and 2272–2850 Ma with the prominent peaks at 1217, 1332, 1466, 1582, 1621, 1748, 1849, 2517 and 2689 Ma, and minor peaks at 1992, 2282, 2791 and 2823 Ma. Hf-in-zircon and Nd whole rock data suggest that the primary stages of continental crustal growth in the Aktau–Mointy terrane were associated with the tectono-magmatic processes of the Neoarchean, Paleoproterozoic, and Mesoproterozoic. Juvenile continental crust production occurred during the Neoarchean and Paleoproterozoic, with older complex tectono-magmatic reworking, and juvenile crust production finally prevailed in the mid-Mesoproterozoic. Based on the age patterns and Hf isotopic compositions of detrital zircons from the Aktau–Mointy terrane and other terranes in the western CAOB, the crustal basement of the Aktau–Mointy terrane exhibits certain similarities with those of the Northern Kazakhstan and Issyk–Kul terranes. They all exhibit a close tectonic affinity with the Chinese Central Tian Shan terranes, Yili Block, North and China Craton, while differing from the Tarim Craton. In the Rodinia supercontinent structure, the Aktau–Mointy terrane was probably located near the Sveconorwegian Orogen in the western Baltica with other Kazakhstan and Northern Tian Shan Precambrian blocks.

The Siah Cheshmeh-Khoy-Misho-Tabriz fault (NW Iran) is a cryptic neotethys suture: evidence from detrital zircon geochronology, Hf isotopes, and provenance analysis

ABSTRACT Provenance analysis including sandstone modal compositions, heavy mineral assemblages, and LA-ICP-MS U-Pb dating with in-situ Hf isotopic compositions of detrital zircons defines two types of Late Cretaceous-Eocene turbiditic sequences separated by the Siah Cheshmeh-Khoy-Misho-Tabriz Fault in the Azerbaijan Province, Northwest Iran: (1) Volcaniclastic turbidites to the southwest and (2) terrigenous turbidites to the northeast. The first appearance of Cr-spinel in Upper Cretaceous sandstones of both sequences indicates the erosion of ophiolites at that time. The southwestern volcaniclastic sandstones contain few Late Triassic and dominantly Late Cretaceous zircon grains whose Hf isotopic compositions suggest a continental magmatic arc provenance. In the northeastern terrigenous sandstones, detrital zircon U-Pb ages cluster in five main age groups from Paleoproterozoic-Neoproterozoic with Hf isotopic compositions typical of continental crust to Late Cretaceous-Palaeocene zircon grains with Hf isotopic compositions similar to those of the southwest turbidites. The provenance characteristics define, along with sedimentary structures, two separate basins, a marginal basin to the northeast, and a deep oceanic basin to the southwest. We conclude that the Siah Cheshmeh-Khoy-Misho-Tabriz Fault overprints a boundary between two lithospheres separated by ophiolite outcrops; therefore, the Siah Cheshmeh-Khoy-Misho-Tabriz Fault is a reworked suture. The Cretaceous arc, witnessed by clastic material, has been largely eroded and/or subducted.

First Data on the Age (U–Pb, SHRIMP-II) and Composition of Zircon from the Unique Yarega Oil–Titanium Deposit, South Timan

Isotope–geochemical study of zircon from leucoxene–quartz sandstone of the Yarega deposit in South Timan was conducted for the first time using the Sensitive High-Resolution Ion Microprobe II (SHRIMP), Secondary Ion Mass Spectrometer (SIMS) technique. Two groups of zircons were established. The first group has signs of hydrothermal processing with a high content of Light Rare Earth Elements (LREEs), Y, Ca, Sr, and other nonformula elements. Zircon that had been hydrothermal altered from titanium deposits of Middle Timan (Pizhma and Ichet’yu) is characterized by similar geochemical features. The second group of zircons has signs of magmatic genesis, including enrichment in Heavy Rare Earth Elements (HREEs), a positive Ce-anomaly, and a negative Eu-anomaly. The concordant ages of magmatic zircon grains lie in the range of 1100–2100 Ma with maxima around 1230 and 1540 Ma. The age of the magmatic zircon grains indicates the predominance of detrital material in sandstones, which was received during erosion of the ancient Mesoproterozoic basement, and excludes the participation of clastic material from the Timan–Ural folded region.

The Lu–Hf Isotope Composition of Zircon from Syenites of the Saharjok Alkaline Massif, Kola Peninsula

Zircon crystals from the alkaline and nepheline syenites of the Saharjok massif, which were formed during the magmatic (2645 ± 7 Ma), hydrothermal (1832 ± 7 Ma), and metamorphic (1784 ± 22 Ma) crystallization stages, were studied. Zircon from alkaline syenites displays lower eHf and eNd values than zircon from ocean island basalts (OIB); these values indicate their affinity to mantle-derived protoliths, which are similar to CHUR in isotope composition. It is assumed that the Neoarchean Keivy alkaline province formed as a result of the plume–lithosphere interaction, induced by the upwelling of a Neoarchean plume, which facilitated metasomatic alteration and the subsequent partial melting of rocks of the subcratonic lithospheric mantle and the crust. The parental melts of the Saharjok massif could have been formed during the resumption of plume activity 20–30 million years after alkaline granite emplacement in the province by the selective melting of the metasomatized lithospheric mantle rocks.

(Invited) Mechanical Challenges in up-Scaling SOEC

For solid oxide fuel cells there are numerous applications calling for units in the power range from 10-50 kW range, for instance for domestic CHP units and APUs for mobile applications. The situation is different for solid oxide electrolysis cells. Here, the most important applications (energy storage or production of synthetic fuels) are characterized by requiring large scale – in the 10 – 100 MW range. Also the electrolysis applications typically require even longer operational life-times than SOFCs.In this paper we shall discuss some recent achievements in improving both cell toughness/reliability and durability.In thin-electrolyte cell designs the fuel electrode (a porous mixture of Ni and ZrO2) is typically designed to be the mechanically carrying component. Its mechanical properties are strongly dependent on the amount of porosity [1] and for a given porosity the strength/toughness is dictated by the properties of the zirconia [2]. To maximize toughness, the zirconia chosen is typically a tetragonal composition like “3YSZ” (3 mol% Y2O3 doped zirconia) which because of the transformation toughening mechanism is much tougher than fully stabilized cubic zirconia.To facilitate manufacture of larger foot-print SOEC cells we have investigated a series of Ce-Y-co-doped zirconias with the aim to identify compositions superior to the currently preferred 3Y-composition. Fifteen compositions have been characterized with respect to phase stability [3] and a subset of 6 of them with respect to mechanical properties. A composition with 1.5%CeO2 and 2.25%Y2O3 substitution in ZrO2 was found to increase the achievable toughness of a porous NiO/Zirconia support by 30% [4] whilst maintaining hydrothermal stability, which may enable a scale up in footprint by a factor of ~15 for a constant risk of failure.Besides a discussion of how to improve reliability by optimizing the zirconia composition it will be presented how it, in a mechanical perspective, can be advantageous to handle cells in reduced state rather than as presently preferred in oxidized state. Introducing a reduction step converting the NiO to Ni as one of the last steps in the cell manufacture further has the advantage that the porous Ni/YSZ support/electrode lends itself well to modification by infiltration. Recently, it has been shown that the degradation of Ni/YSZ fuel electrode during electrolysis operation can be strongly reduced by Ce-oxide infiltration [5,6]. Recent progress along this line of work shall be presented.Reducing a full cell with both electrodes or a cell, with a porous CGO-backbone infiltration layer for the oxygen electrode to be, is feasible [7], but this requires careful control of the reduction conditions not to damage the cell due to “expansion on reduction” [8] of any of the CGO parts of the cell. This phenomenon and its relation to the lattice defects will be discussed highlighting some specific works clarifying the latter [8,9].

Theoretical versus empirical secular change in zircon composition

We generate theoretical curves for zircon growth during cooling of tonalitic and A-type granitic magmas and compare these with empirical Ti-in-zircon populations from the Paleoarchean Pilbara Craton, Australia, Mesoarchean Akia Terrane, Greenland, and the Mesoproterozoic Musgrave Province, Australia. Our models predict variable zircon growth rates on magma cooling dependant on magma composition, crystallizing assemblage, and zircon growth process. In most modelled magma compositions, higher-temperature grains growing close to the zircon saturation temperature are more abundant, with yields decreasing continuously thereafter. However, there are important dissimilarities in the cumulative zircon growth curve for different magma compositions and whether zircon growth is by equilibrium or disequilibrium processes. For a given starting melt Zr concentration, A-type granite magmas grow zircon at higher temperatures than tonalitic magmas. This compositional distinction is most pronounced at lower starting melt Zr concentrations, and in low Zr tonalite the rate of zircon growth may even increase on cooling. The dependence of zircon growth on magma composition and crystallization process leads to predictive differences in cumulative Ti-in-zircon distributions. Greater disequilibrium growth yields more sigmoidal cumulative growth curves that are dissimilar to predictions from phase equilibrium models. When applied to Mesoarchean-aged zircon grains from the Akia Terrane, calculated Ti-in-zircon temperatures decrease over the 3100–2900 Ma interval. This magmatic episode also reveals a change in cumulative zircon growth curve topology from steeper to shallower, consistent with a reduction in the relative proportion of disequilibrium growth, greater crystal–liquid communication, and enhanced infracrustal reworking. The temporal variability in cumulative zircon growth and its implication for melt interconnectedness are powerful tools in understanding magmatic processes and indicate an important secular change point at c. 3.0 Ga in the Akia Terrane where zircon growth dynamics changed.

Fabrication of High-Strength Zr-Based Composites by Spark Plasma Sintering

Zirconium (Zr) partially stabilized zirconia (PSZ) composites were fabricated using the spark plasma sintering technique with the aim of producing medical implants with reduced metal-related artifacts in magnetic resonance imaging. Composites with compositions ranging from 100% Zr to 100% PSZ were fabricated, and they exhibited high mechanical performance. Optical microscopy and density measurements revealed that dense composites were successfully produced, irrespective of the PSZ content. Hardness and bending tests were performed to evaluate the influence of the addition of PSZ on the mechanical properties of the composites. The results showed that the hardness and bending strength increased with increasing PSZ content. The elastic modulus of the composites was higher than that predicted by the rule of mixtures, and this was due to the formation of Zr oxide around the Zr phase during sintering. It was concluded that the mechanical properties of the composites could be controlled within the range of those of monolithic Zr and monolithic PSZ, and that the use of PSZ was effective for improving the mechanical properties.

Identification of Forearc Sediments in the Milin-Zedong Region and Their Constraints on Tectonomagmatic Evolution of the Gangdese Arc, Southern Tibet

Abstract The Xigaze forearc sediments revealed the part of the tectonomagmatic history of the Gangdese arc that the bedrocks did not record. However, the sediments’ development is restricted to the region around and west of Xigaze City. Whether the eastern segment of the arc had a corresponding forearc basin is yet to be resolved. In this study, a field-based stratigraphic study, detrital zircon U-Pb geochronology (15 samples), and Hf isotopic analyses (11 of the 15 samples) were carried out on four sections in the Milin-Zedong area, southeast Tibet. The analytical results revealed the existence of three distinct provenances. The lower sequence is characterized by fine-grained sandstone, interbedded mudstone, and some metamorphic rocks (e.g., gneiss and schist). The detrital zircon U-Pb age distribution of this sequence is analogous to those of the Carboniferous-Permian strata and metasediments of the Nyingtri group in the Lhasa terrane. The middle and upper sequences are predominantly composed of medium- to coarse-grained volcaniclastic/quartzose sandstones, which are generally interbedded with mudstone. The detrital zircon U-Pb ages and Hf isotope signatures indicate that the middle sequences are Jurassic to Early Cretaceous in age (~200–100 Ma) and show clear affinity with the Gangdese arc rocks, that is, positive εHft values. In contrast, the upper sequences are characterized by Mesozoic detrital zircons (150–100 Ma) and negative εHft values, indicative of derivation from the central Lhasa terrane. The overall compositions of the detrital zircon U-Pb ages and Hf isotopes of the middle to upper sequences resemble those of the Xigaze forearc sediments, implying that related forearc sediments may have been developed in the eastern part of the Gangdese arc. It is possible that the forearc equivalents were eroded or destroyed during the later orogenesis. Additionally, the detrital zircons from these forearc sediments indicate that this segment of the Gangdese arc experienced more active and continuous magmatism from the Early Jurassic to Early Cretaceous than its bedrock records indicate.

The Utility of Implant-Supported Fixed Dental Prosthesis Material for Implant Micromovement and Peri-implant Bone Microstrain: A Study in Rabbit Tibia

To evaluate and compare the effects of two restorative materials with different stiffness on peri-implant bone microstrain and implant micromovements during occlusal loading in implant-supported single and adjacent splinted crowns. Two 3 × 10-mm implants were inserted into the tibia of four rabbits. During the osseointegration process, prosthetic restorations were performed. Before suturing the flap, each implant's position and direction were obtained by fastening two splinted transfer abutments, onto which implant analogs were placed and fastened; the splinted transfer abutments were subsequently unfastened. Splinted transfer abutment/analog complexes were cast using type IV plaster to obtain eight different working models. Two single mandibular premolar crowns of monolithic zirconia and acrylate polymer composite were generated using CAD/CAM technology, and 16 adjacent splinted crowns (eight of each material) with the same design were also generated. After 6 weeks of implant osseointegration, the animals were sacrificed. Tibial sections with the implants were extracted, and prosthetic restorations (performed during implant osseointegration) were fastened to the implants. Static loading tests were performed with 100-N force application and an inclination of 6 degrees over the central fossa of the premolars. Implant micromovement was measured using an image analysis technique. Bone microstrain was quantified using two strain gauges placed on the crestal bone around the implants. Data were analyzed using two-way analysis of variance. The mean implant micromovement values were lower for monolithic zirconia single and splinted crowns (61.5 ± 26.3 μm and 57.7 ± 8.8 μm, respectively) than for acrylate polymer composite-based single and splinted crowns (78.9 ± 37.3 μm and 59.61 ± 11.5 μm, respectively). No significant differences between the materials were noted. Bone microstrain around the implants was lower for splinted crowns (303.7 ± 281.3 με for acrylate polymer composite; 312.4 ± 226.8 με for monolithic zirconia) than for single crowns (539.7 ± 8.8 με for acrylate polymer composite; 574.6 ± 271.9 με for monolithic zirconia). Using restorative materials of different stiffness did not significantly affect the micromovement of already-osseointegrated implants supporting single or splinted crowns. Independent of material stiffness, single crowns transfer significantly more microstrain than splinted crowns.

The effects of selective contamination on the early Paleozoic intracontinental mafic rocks in the South China Block: New insights from high-δ18O zircon

The petrogenesis of continental mafic rocks that are enriched in large-ion lithophile elements (LILE) and that have enriched Sr–Nd–Hf isotope compositions is debated, with some models suggesting an enriched mantle source and others arguing for crustal contamination. Crustal contamination has generally not been favored as numerical models indicate that this would require the addition of significant amounts of crustal materials. Here we present the first detailed study of the oxygen isotope composition of zircons from representative early Paleozoic mafic, intermediate, and felsic magmatic rocks in the South China Block (SCB), and combine this information with available geochemical data to re-examine whether crustal contamination or an enriched mantle source is the principal cause of the crustal geochemical signatures in these rocks. Zircon grains in the high-MgO mafic rocks (MgO > 8 wt%) with low εNd(t) values (< −6) have similar, or slightly lower, mean δ18Ozrn values (e.g., 8.3 ± 0.1‰ and 8.5 ± 0.2‰ for zircons in the Fuxi monzonorite and Xinchuan hornblendite, respectively) than those in coeval granitoids (9.2 ± 0.2‰ and 8.6 ± 0.3‰ for zircons in the Fuxi granite and Xinchuan quartz monzonite, respectively). Zircon grains in the Yonghe low-MgO olivine-bearing gabbro (εNd(t) = −2.9 to −1.5) and the Guantian quartz diorite (εNd(t) = −3.5 to −3.0) are characterized by relatively low mean δ18Ozrn values (7.2 ± 0.1‰ and 7.7 ± 0.1‰, respectively). Considering that the early Paleozoic mafic rocks in the SCB have heterogeneous Sr–Nd–Hf isotope signatures (whole-rock initial 87Sr/86Sr = 0.7041–0.7114; εNd(t) = −8.4 to +1.8; weighted mean zircon εHf(t) = −8.7 to +5.2) and crustal Ce/Pb, Nb/U, Rb/Sr, and Th/La ratios (0.59–13.1, 3.3–20.9, 0.05–0.68, and 0.11–0.51, respectively), it is suggested that crustal contamination, rather than an ancient subduction-modified enriched mantle source, was the principal cause of the crustal geochemical signatures in these rocks. A refined model is proposed in which water played a key role in the preferential transfer of fluid-mobile elements from crust-derived hydrous felsic magmas to mantle-derived mafic magmas, leading to the enrichment of fluid-mobile elements (e.g., LILE), the fractionation of these elements (e.g., elevated La/Sm, La/Ta, Rb/Sr, and Th/La, and depressed Ce/Pb, Nb/U, and Sm/Nd), and the enrichment in 18O in the selectively contaminated mafic magmas.

Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.

Thermal, mechanical and morphological properties of polyurethane–zirconia loading

Abstract The polyurethane (PU) has been showing a dramatic increase in applications related to material science and technology. However, the mechanical, physical and thermal properties could be further improved by loading PU with zirconia (Zr) to create renewable materials known as polyurethane–zirconia (PUZ) composites. In this study, PU matrix was treated with wt.% Zr at 0.5, 1.0, 1.5 and 2.0. In this study, the thermo-mechanical properties and the morphology were investigated of PU and PUZ nano-samples. The images of the scanning electron microscope (SEM) were the prime tool in investigating PU and PUZ surfaces and fractured surfaces showing vanishing the cracks and formation of agglomeration on the sample PUZ-1.5%. In addition, the tensile strength, Young’s modulus and maximum loading were improved by 36.7, 31.8 and 39.1%, respectively, at Zr loading of 1.5 wt.%. The flexural stress and the load were improved by 94.3% and 93.6%, respectively, when Zr loading was 1.5 wt.%. The impact without and with a notch was improved by 110.7% and 62.6%, respectively, at Zr loading of 1.5 wt.%. The the morphologies of the PU surface and Zr surface supported by SEM images. Regarding the storage modulus ability of PU and PUZ composites, Zr loading has negatively influenced E. The E functioning temperature was observed to move from 142 to 183°C. Another effect was determined by adding a small amount of Zr. This small amount was enough to shift the crystallization temperature (${T}_c$) and the melting temperature (${T}_m$) of PU from 125 to 129°C and from 150 to 144°C, respectively.

Genesis and timing of Mo mineralization in the Mada Ring Complex, north-central Nigeria: insights from whole-rock geochemistry, Nd-Sr isotopes, zircon U-Pb-Hf isotopes, and molybdenite Re-Os systematics

The genesis and timing of molybdenum (Mo) mineralization in the Mada Ring Complex, north-central Nigeria, have been constrained using a combination of whole-rock elemental geochemistry, Nd-Sr isotopes, zircon U-Pb-Hf isotopes, and molybdenite Re-Os geochronological data. The Mada Ring Complex is one of fifty-three within-plate alkaline ring complexes with economically significant Sn and Nb production from largely alluvial placer deposits in north-central Nigeria. Molybdenum mineralization in the ring complex is dominantly disseminated with minor stockwork veins hosted within biotite granite. Integrated zircon U-Pb and molybdenite Re-Os geochronology constrain initial magma emplacement to between 152 and 151 (± 1) Ma and the Mo-mineralization event to ≤ 150 (± 1) Ma. The granites associated with Mo mineralization are highly silicic and display elevated whole-rock concentrations of Nb, Zr, Y, and REE (except Eu), as well as high 87Rb/86Sr ratios, but low concentrations of Sr, Ba, CaO, MgO, and TiO2, consistent with highly differentiated A-type granites. They yield moderately negative whole-rock eNd(t) (− 5.87 to − 5.47) and zircon eHf(t) (− 4.97 to − 10.06), suggesting that their parental magmas were largely derived from the lower crust with a contribution from the upper mantle. Magmatic oxygen fugacity (ƒO2) of the A-type granites (log FMQ = +1.16), constrained from zircon compositions, is lower than values reported from typical within-plate porphyry molybdenum deposits (log FMQ = +2 to + 3). However, compared to regional Sn ± Nb-mineralized A-type granites, the Mada A-type granites have higher ƒO2 and Ce4+/Ce3+, but are less differentiated.

Detrital Zircon U-Pb Geochronology and Hf Isotope Geochemistry of the Hayang Group, SE Korea and the Himenoura and Goshoura Groups, SW Japan: Signs of Subduction-Related Magmatism after a Long Resting Period

There was a hiatus in magmatism in Korea and Japan, located on the eastern continental margin of Asia, during a period of about 40 Ma from 160 Ma to 120 Ma. The cause of the resumption of magmatism since then is not yet well understood. In this study, we analyzed the Hf isotope composition of detrital zircons in the Cretaceous sediments of Korea (Hayang Group) and Japan (Goshoura and Himenoura groups) to investigate the tectonic evolution of eastern Asia in the Early Cretaceous period. εHf(t) in Cretaceous zircons from Japanese samples values from +8.2 to +0.1, suggesting that magmatism was sourced from the depleted juvenile materials, which is compatible with ridge subduction and subsequent melting of the young oceanic crust. εHf(t) values from Cretaceous zircons in the Hayang Group are negative, except for the Jindong Formation, which had a sediment supply from Japan, indicating that the old continental crust material of the Korean Peninsula was included in the magma generation. The detrital zircons of this study exhibit a depleted isotopic character at the beginning of subduction-related magmatism in Permian and Early Cretaceous, and then gradually change to a more enriched composition. This trend may be a typical example of the Pacific-type orogenic cycle.