Zirconia Composites Research Articles

Geochronology and geochemistry of zircon and columbite–tantalite group minerals from the Weilasituo Sn–polymetallic deposit, northeastern China: Implications for the relationship between mineralization and the magmatic–hydrothermal transition

The Weilasituo Sn–polymetallic deposit, located in the southern portion of the Great Xing'an Range of Inner Mongolia, China, is a super-large Sn deposit associated with abundant Li, Rb, Nb, Ta, Zn, and Cu resources. Despite that previous studies have characterized the age, hydrothermal evolution, and genetic relationship between the alkali feldspar granite porphyry and associated Sn–polymetallic mineralization, the magmatic–hydrothermal evolution and ore–forming processes remain ambiguous. To address these ambiguities and bridge this knowledge gap, this contribution characterizes the texture, geochemistry, and U–Pb isotope composition of zircon and columbite–tantalite group minerals (CGMs) from amazonitized alkali feldspar granite (AMG) and albitized alkali feldspar granite (ABG) in the Weilasituo deposit. Type-I zircon (Zr1) is inclusion-poor, translucent, and is characterized by low light rare earth element (LREE) contents, high (Sm/La)N ratios (mean = 655.7), and low Th/U (mean = 0.21 < 0.3), Zr/Hf (mean = 5.46), and Y/Ho ratios (mean = 4.42), indicating that it formed during the magmatic–hydrothermal transition. Type-II zircon (Zr2) is inclusion-rich, porous, has a low CL response, and is characterized by low Th/U ratios (0.08–0.32, mean = 0.17), high LREE contents, weakly positive Ce anomalies, and low (Sm/La)N ratios (mean = 20.7), indicating that it formed via hydrothermal alteration of Zr1 (i.e., magmatic–hydrothermal zircon). Type-I CGM (CGM1) generally lacks oscillatory zoning, and has similar and positively correlated Ta/(Nb + Ta) and Mn/(Mn + Fe) values (AMG: R2 = 0.93; ABG: R2 = 0.75), indicative of a magmatic origin. Type-II CGMs (CGM2) occur as rims on CGM1 and are characterized by higher Ta/(Nb + Ta) and lower Nb/Ta ratios than CGM1, indicative of precipitation from a hydrosilicate liquid during the magmatic–hydrothermal transition. Based on the characteristics of CGMs, two stages are evident in the evolution of the Weilasituo granite porphyry: an earlier magmatic differentiation stage and a later magmatic–hydrothermal transition stage. Furthermore, the magmatic–hydrothermal transition stage can be subdivided into the AMG and ABG substages within the porphyry system based on petrological and mineralogical characteristics. The U–Pb ages for zircons and CGMs from the alkali feldspar granite porphyry range from 137.2 ± 2.0 Ma to 129.8 ± 1.4 Ma, without a notable age gap. The similarity in U–Pb ages between CGM1–CGM2 and Zr1–Zr2 indicates that the magmatic stage and the magmatic–hydrothermal transition at Weilasituo were continuous processes that occurred during the Early Cretaceous.

Zircon in tin granite as tracer for fluid metasomatism and Sn mineralization

Most tin deposits in the world are genetically related to tin granite and form during complex magmatic-hydrothermal processes. Zircon is a common accessory mineral in granite and related ore systems and can host a number of ore metals, such as Sn, W, Nb, Ta, U and Th, in its crystal lattice. However, whether metal enrichment/depletion can trace ore-forming processes is still unclear. Here, we report that the metal concentrations in various types of zircons from the Mopanshan tin granites in the southern Great Xing'an Range (Northern China) can be used as good indicators of fluid metasomatism and Sn mineralization. Two lithological zones are developed in the Mopanshan pluton, including porphyritic syenogranite (PG) in the center and fine-grained syenogranite (FG) at the margin. Zircons in the PG (PGZ-1, PGZ-2, and PGZ-3) are all magmatic in origin, while zircons in the FG can be categorized into magmatic zircons (FGZ-1 and FGZ-2) and metasomatic zircons (FGZ-3). The PGZ-1 and FGZ-1 grains are transparent prismatic crystals with bright oscillatory zonation, whereas the PGZ-2 grains are murky crystals with dark oscillatory zonation. PGZ-3 and FGZ-2 grains occur as overgrowths of previously formed zircon (PGZ-1, PGZ-2, and FGZ-1) or as brown individual crystals, showing dark and homogeneous cathodoluminescence (CL) textures. The metasomatic FGZ-3 grains are translucent-opaque porous crystals with vermicular CL zonation and commonly replace FGZ-2. The trace element compositions of magmatic zircons are completely melt controlled, providing a record of magmatic evolution as a constant decrease in Zr/Hf ratios and a gradual increase in Th, U, Nb, and Ta contents. Moreover, the structure of magmatic zircons transforms from a crystalline state to an amorphous state as a consequence of radioactive decay of U and Th. A coupled dissolution-reprecipitation process is proposed for the formation of metasomatic FGZ-3. The reactive fluid is the magmatic fluid that exsolved from the melt in the late magmatic stage. The magmatic fluid replaced biotite and rare earth phosphates (mainly monazite and apatite) enclosed within biotite, resulting in significant amounts of Nb, Ta, Sn, P, Al, Ca, Fe, and REEs, which subsequently reacted with the FGZ-2 zircons to leach Th, U, Y, and HREEs. Eventually, REEs, Y, Th, and U in the fluid combined with P to form monazite and xenotime, while the other elements partially precipitated with the crystallization of the FGZ-3 zircons. Although the alteration of biotite only released approximately 190 ppm of Sn into the fluid, this is still a significant Sn source for the Sn deposits surrounding the Mopanshan pluton, taking the granite size (∼50 km2) and the volume proportion of biotite (∼5%) into account. Furthermore, based on previous studies on tourmaline from the Mopanshan granite and regional geochemistry, it may be inferred that the addition of wall rock components may also play an important role in Sn mineralization.

Zircon U-Pb-Hf constraints on the geological evolution of the Bihar Mica Belt, Central Indian Tectonic Zone, and its link to Columbia assembly

In this study, U-Pb-Hf isotope composition and trace element chemistry of zircon from basement gneisses and quartzites of the Bihar Mica Belt (BMB), a belt of supracrustal rocks within the Central Indian Tectonic Zone, is used to constrain crustal growth and reworking. The protoliths of BMB gneisses were emplaced at 1651 ± 5 Ma. The magmas were derived from juvenile and 1747 ± 7 Ma I-type long-lived felsic precursors that survive as xenocrystic cores. Zircon grains from quartzites display two distinct morphologies. Grains with little rounding of edges have internal structures comprising 1750 ± 5 Ma inherited cores mantled by 1657 ± 4 Ma igneous zones that are identical to those from the granite gneisses. The εHf (t) and trace element composition of both the xenocrystic cores and the igneous mantles in these detrital grains are identical to those of zircon in the gneisses. They constitute molasse-like sediments derived from the nearby basement. More rounded grains furnish age clusters between 1857 and 2848 Ma, suggestive of long-distance transport and derivation from multiple sources. In-situ formed metamorphic rims around zircons in gneisses and quartzites furnish 1476–1466 Ma ages, dating the earliest metamorphic overprint. The age of sedimentation is bracketed between 1657 Ma and 1466 Ma. The 1651 ± 5 Ma gneisses and its 1747 ± 7 Ma felsic precursor were I-type, and emplaced in an arc setting. They constitute part of the expansive suite of Paleoproterozoic gneisses of the Chhota Nagpur Gneiss Complex emplaced during protracted period of arc-magmatism between 1.75 Ga and 1.65 Ga. Strongly positive εHf(t) of 2.0–2.85 Ga detrital zircons conforms to the global trend of positive εHf(t) excursions and high dT/dP gradients, and may correspond to passive margin juvenile magmatism associated with the break-up of Archean supercratons prior to Columbia assembly. The 1.86 Ga and 1.75 Ga detrital and xenocrystic zircons from the BMB have enriched εHf(t), in accordance with negative excursions seen in global zircon between 2.0 Ga and 1.70 Ga, reflecting progressive assembly of Columbia through collisional orogenesis. An excursion to strongly positive εHf(t), coinciding with low dT/dP gradients at ca. 1.65 Ga, reflects wide-spread formation of arcs linked to accretionary growth of Columbia.

Effect of silica addition on the photocatalytic activity of MO2@SiO2 (M=Ti, Zr, Sn, Ce) nanocomposites prepared by sol-gel

AbstractPhotocatalysis uses wide band gap ceramic semiconductors (anatase, zirconia, ceria, cassiterite…) that have the ability to promote electron-hole pairs by UV light irradiation producing both reducing and oxidants ions and radicals. In general, oxidizing species are more efficient, using photocatalysis as an advanced oxidation process (AOP) for the biodegradation of organic substances refractory to conventional treatments, such as azo dyes, or atmospheric pollutants as NOx. In this communication, the photocatalytic activity of xSiO2@(1-x)MO2 (M = TiO2, ZrO2, SnO2, CeO2, x = 0, 0.1, 0.3 and 0.5) composites on the Orange II azo dye in solution, as well as on NOx in air, was analysed. The composites were obtained by Sol-Gel methods based on the hydrolysis-condensation of alcoholic solutions of silicon tetraethoxide (TEOS) and titanium n-butoxide, zirconium iso-propoxide, SnCl2.2H2O and Ce(NO3)3.6H2O as precursors of MO2 oxides. The resulting xerogels were studied by XRD, bandgap measurements from UV-Vis-NIR diffuse reflectance spectroscopy, photocatalytic activity against Orange II in dissolution and NOx in air (efficiency in nitrate abatement), and SEM-EDX microstructural analysis. In the case of non-stabilized samples, charring samples at 300 °C/1 h and fired samples at 500 °C/1 h were also studied. The cassiterite-silica composite stands out for its photocatalytic activity against Orange II in solution and the cerianite-silica composite against NOx in air. Silica increases the photocatalytic activity on NOx in zirconia, tin oxide and ceria composites and also on Orange II in zirconia and tin oxide. Graphical Abstract

The Relationship between Granitic Magma and Mineralization in the Darongxi Skarn W Deposit, Xiangzhong District, South China: Constrained by Zircon and Apatite

The Xiangho Zng district is the largest low-temperature W-Au-Sb metallogenic area in the world. The Darongxi skarn W deposit in the north of the Xiangzhong district is closely related to biotite monzonite granite, muscovite monzonite granite, and felsophyre, but the nature of granitic magma and its relationship with mineralization is relatively weak. In this paper, U-Pb dating, Lu-Hf isotope, the in situ composition of zircon, and the apatite of biotite monzonite granite, muscovite monzonite granite, and felsophyre in the Darongxi mining area are systematically studied, and the formation age, magma property and source, and their relationship with mineralization are discussed. The values of zircon U-Pb age and the εHf(t) of biotite monzonite granite are 222.2 ± 0.54 Ma and −2.9~−6.4, respectively. The values of zircon U-Pb age and the εHf(t) of muscovite monzonite granite are 220.8 ± 0.58 Ma and −2.7 to −8.1, respectively. The values of zircon U-Pb age and the εHf(t) of felsophyre are 222.3 ± 2.20 Ma and −2.2~−5.4, respectively. Magmatic apatite grains from biotite monzonite granite and muscovite monzonite granite show distinctive core–rim and oscillatory zoning textures in CL images, and demonstrate a bright yellow in colorful CL images. The magmatic apatite has a total rare earth concentration (3766~4627 ppm), exhibiting right-inclined nomorlized rare earth element patterns and obvious negative Eu anomalies. The geochemical data of magmatic zircon and apatite indicate that magma sources are responsible for these intrusions in the Darongxi mining area, mainly derived from the partial melting of the Mesoproterozoic crust, which is rich in W; the magma is rich in F and poor in Cl (F = 2.4~3.3 wt%, Cl = 0.0024~0.0502 wt%). The oxygen fugacity of magmatic zircon (ΔFMQAVG = −4.02~−0.26), the high negative Eu anomaly (δEu = 0.06~0.12) and the low positive Ce anomaly (δCe = 1.09~1.13) of magmatic apatite, and the occurrence of ilmenite all indicate that the redox condition of magma from the Darongxi mining area is reduced. The reduced F-rich crust-source granitic rock and W-rich source provide favorable conditions for the mineralization of the Darongxi reduced skarn W deposit.

Chemical and Textural Peculiarities of Zircon from Peralkaline Granites and Quartz-Bearing Syenites

Zircon from four plutons of peralkaline granites and quartz-bearing syenites, differing in geotectonic positions, petrological and mineralogical compositions, and contents of volatile and trace elements, was studied using SEM, CL, and EPMA with the intention to define typical textural and chemical features of zircon from peralkaline rocks. In strongly peralkaline Na-pyroxene-bearing rocks represented by the Khan Bogd and Khalzan Buregte plutons (Mongolia), the primary zircon is scarce or missing. Most zircon grains are secondary, originating in hydrothermal stage from primary Zr silicates. They often form globular or radial aggregates. Chemical compositions of zircon in these rocks typically show high contents of Y, moderate contents of REE (thus high Y/Yb values) together with low contents of U and Th and low analytical totals. In mildly peralkaline mica-bearing rocks represented by Ivigtut stock (Groenland) and Madeira pluton (Brazil), the exclusive primary Zr mineral is zircon, mostly of orthomagmatic origin. Its analytical totals approach 100 wt%, enrichment in HREE, resulting in low Y/Yb values, is typical. Zircon populations from two types of peralkaline granitoids can be distinguished from each other and from zircon from S-type granites based on combination of the Zr/Hf, Y/Yb, and U/Th values, or on the Y-Hf-P ternary diagram.

Fabrication of translucent graded dental crown using zirconia-yttrium multi-slurry tape casting 3D printer

This paper aims to fabricate functionally graded dental crown using a multi-slurry tape casting additive manufacturing technology. The different luminescence of the dental crown was obtained with different composition of zirconia and yttria. Zirconia with tunable mechanical properties and translucency are obtained by adding 3, 3.5, 4, 4.5, and 5 mol% of yttrium oxide to zirconia powder. After obtaining the printable slurry with maximum solid loading, the green bodies are prepared using the in-house built high-speed multi-ceramic tape casting technology. They are later sintered with two-stage sintering method. After the successful fabrication, the mechanical properties and translucency of the specimens were evaluated with Vickers hardness, three-point bending and translucency parameter tests. Finally, an FGM tooth crown with five photocurable slurries is proposed to demonstrate the translucent gradient effect of sintered part. The solid loading of 80% zirconia and 20% resin delivered samples without any surface cracks. The shrinkage ratio analysis showed that the sintered sample dimension was reduced by 20%, 20%, and 23% along X, Y, and Z directions. The samples fabricated with 3% yttrium oxide to zirconia delivered excellent hardness (1687 HV) and flexural strength (650.6 MPa). However, the relative luminescence increased with increasing the yttrium oxide for 3–5 mol%. With the optimized process parameters, the proposed dental crown is fabricated and analyzed for their shrinkage ratio, mechanical, and translucency properties. The study proposes the potential of fabricating customized dental crown with gradient translucent appearance.

Zircon Trace‐Element Compositions in Cenozoic Granitoids in Japan: Revised Discrimination Diagrams for Zircons in I‐Type, S‐Type, and A‐Type Granites

ABSTRACTOwing to high resistance to alteration, detrital zircons retain information about their formation ages and parental magmas for a long period of time. Many geochemical researchers have proposed various indicators for zircon to constrain tectonic settings and to identify source rock. Because most detrital zircons analyzed by geochronologic studies are derived primarily from granitoids, we focus on the classification of zircon within granitoids. In the style of alphabetical classification scheme (Igneous, I; Sedimentary, S; and Alkaline, A types), some discrimination diagrams have been proposed. To improve the database and enhance discriminating studies, we examined trace‐element compositions of zircons extracted from some Cenozoic granitoids exposed in the Japan Islands. The zircons showed systematic differences in Nb, Ta, Ce, and P contents. Zircons in Oceanic Arc I‐type granite are poor in Nb and Ta, and these signatures clearly reflect those elements in their parental bodies. Despite their low abundance at the whole‐rock level, zircons in Oceanic Arc I‐type granite are characterized by high Ce content. This is attributable to the relatively oxidizing conditions of Oceanic Arc I‐type magma. Zircons in S‐type granite are characterized by high P and low Ce contents. The former can be explained by high apatite solubility in Al‐rich magma, whereas the reducing environment of S‐type magma is accountable for the latter. The zircon crystallized at the later stage during S‐type granite solidification is slightly depleted in Nb and Ta. This is attributable to the depletion of these elements in the magma by Ti‐bearing minerals such as ilmenite prior to zircon crystallization. In analogy with whole‐rock composition, zircons in transitional I‐A‐type granite have intermediate composition between I‐type and A‐type zircons. On the basis of the updated database, we demonstrated that the Nb/P–Ce/P or Ta/P–Ce/P crossplots are the most useful for discriminating zircons in Oceanic Arc I‐type, I‐type, S‐type, and A‐type granites.

Conductivity Increase As a Result of the Disappearance of Short-Range Ordering in a Scandia-Zirconia Electrolyte

Solid oxide cell electrolytes and structures have been greatly optimised to offer high performance and good durability for commercial implementation. This has highlighted an underlying issue where the slow, long-term conductivity degradation in the generally used fluorite structured oxide-ion conducting doped zirconias known to be related to reorganisation of their defect short-range structures. Among the doped zirconia systems, scandia stabilised zirconia (SSZ) gives the highest ionic conductivity due to the smallest mismatch between the dopant and host cations. However, owing to these similar and small sizes, the system is more prone to defect short-range ordering. This leads to a complex phase diagram of the Sc2O3-ZrO2 system and, depending on the composition, its ionic conductivity ages more significantly than other zirconia systems on high temperature annealing. Here, we report a magnesia and india co-doped scandia stabilised zirconia (IMSSZ) composition that offers high ionic conductivity, 0.14 at 850 ℃ and 0.4 at 1000 ℃, improved phase stability in both macro- and micro scales, and long-term conductivity stability. The conductivity after annealing the sample at 850 ℃, for different times, 0 (as-sintered), 167 and 426 hours, is correlated to the microdomain structural evolution. We show the initial of conductivity increase over time as a result of eliminating the defect short-range ordering using electron diffraction and powder neutron diffraction, resulting in a long-term stable disordered structure with improved conductivity. We will discuss here the thermodynamic driving forces for the breakdown of defect short-range ordering, and how right co-dopant sizes may play a role. Figure 1

Review of temporal trend in Archean granitoid chemistry- implications for Eoarchean (3.7–3.9 Ga) transition in geodynamic regime of crust formation

In this study, we review changes in Archean granitoid chemistry using stacked probability density estimation and statistical change-point analyses. A significant change in Archean sodic granitoid composition occurs in the 3.9–3.75 Ga period, marked by a shift of SiO2, Al2O3, Na2O, V, Cr, Sr, Sr/Y to higher, and TiO2, FeOT, MnO, P2O5, A/NK, A/CNK, Sc, Ba, Ta, Nb, Hf, Y, and rare earth elements to lower values, which reflects different formation P-T regime and petrogenetic processes. Using phase equilibria and trace element modelling, we demonstrate that the pre-3.9 Ga Acasta Tonalite Gneiss (ATG)-like granitoids formed at shallow depths (∼3 km) but are chemically distinct from impactites of all known large impact craters with basaltic/mixed target rocks. Impact melting produces MgO-rich melts at relatively greater “apparent” depths, reflecting target rock chemistry and contribution from the upwelling mantle, and is unlikely to have produced the shallow-seated ATG rocks. The ATG trace element chemistry is similar to many modern-day non-arc settings felsic rocks, which suggests that the melting regime in these extensional settings also existed before 3.9 Ga and ATG formed in a mantle plume-driven extensional tectonic regime involving melting of long-lived mafic proto-crust at shallow crustal depths above mantle upwelling. In contrast, the 3.9–3.75 Ga transitional and post-3.75 Ga TTGs formed by deep-seated (25–50 km) melting in equilibrium with garnet-bearing amphibolite. When considered together with Ti isotopic evidence of shift from tholeiitic to calc-alkaline magmatism in the 4.0–3.75 Ga period, the evidence for a transition from a regime dominated by crustal reworking to one of significant juvenile input at 3.60–3.85 Ga, noted in trace element/Hf-isotope composition of detrital zircon from several cratons and the reported ultra-high pressure metamorphism/interleaving arc-plume sequence, require a greater depth of melting. We interpret this transition to mark a gradual shift from stagnant-lid to intermittent mobile-lid-type plate tectonics involving deeper subduction of oceanic lithosphere. However, from the single occurrence of pre-3.9 Ga ATG rocks and their similarity with some Archean Fe-rich silica-saturated rocks chemistry, it is unknown whether plume magmatism was the only active mechanism or operated in conjunction with mobile-lid tectonics on early Earth, like in Archean.

Enhancing the Properties of Yttria-Stabilized Zirconia Composites with Zeolitic Imidazolate Framework-Derived Nanocarbons.

Ceramic matrix composites (CMCs) reinforced with nanocarbon have attracted significant interest due to their potential to enhance mechanical, thermal, and electrical properties. Although the investigation of carbon-based materials such as graphene and carbon nanotubes as additives for advanced ceramics has been widespread, the utilization of metal-organic framework (MOF)-derived nanocarbons in CMCs remains largely unexplored. We extended our previous proof-of-concept investigations by demonstrating the effectiveness of a different type of MOF-derived carbon as a reinforcing phase in an alternative ceramic matrix. We employed spark plasma sintering (SPS) to consolidate yttria-stabilized zirconia (YSZ) and zeolitic imidazolate framework (ZIF-67) powder blends at 1300 °C and a uniaxial pressure of 50 MPa. YSZ serves as the ceramic matrix, whereas ZIF-67 serves as the nanocarbon source. The composite exhibits a highly significant improvement in fracture toughness with an increase of up to 13% compared to that of the YSZ monolith. The formation of ZIF-derived nanocarbon interlayers is responsible for the observed enhancement in ductility, which can be attributed to their ability to facilitate energy dissipation during crack propagation and inhibit grain growth. Furthermore, the room-temperature electrical conductivity of the sintered samples demonstrates a substantial improvement, primarily due to the in situ formation of nanocarbon-based fillers, reaching an impressive 27 S/m with 10 wt % ZIF-67 content. Based on the results, it can be inferred that the incorporation of in situ MOF-derived nanocarbons into CMCs leads to a substantial improvement in both the mechanical and electrical properties.

Zircon and cassiterite U-Pb geochronology and petrochemical characteristics of early Tertiary tin mineralization at Mayo Darlé, Cameroon Volcanic Line

Tin mineralization at Mayo-Darlé in the Cameroon Volcanic Line is associated with highly evolved anorogenic ferroan granite magmatism with a pervasive hydrothermal overprint. Mineralization occurs as cassiterite-quartz-muscovite stockwork and disseminated in quartz-mica and quartz-topaz greisen in low-Ca alkali feldspar granite with a composition near the 1 kbar haplogranitic thermal minimum. The trace element composition of zircon indicates elevated temperature (880 ± 55 °C) and very low oxidation state below the quartz-fayalite-magnetite buffer. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) identifies a partly disturbed U-Pb system for igneous zircon (U and Th contents >1000 ppm) but defines Tera-Wasserburg concordia ages and common-lead-corrected weighted 206Pb/238U ages of about 54 Ma, similar to a previous 87Rb/86Sr vs 87Sr/86Sr regression with a date of 56.1 ± 1.7 Ma (MSWD = 58; n = 9) and an initial 87Sr/86Sr ratio of 0.7085 ± 0.0035 (2 s). Hydrothermal cassiterite gives a pooled LA-ICPMS Tera-Wasserburg concordia age of 56.7 ± 0.6 Ma on two samples (each about 20 points, MSWD = 0.54 and 1.3). These new age data define a period of early Cenozoic intraplate calc-alkalic felsic magmatism as a precursor to abundant Oligocene to Recent alkali basalt volcanism along the Cameroon Volcanic Line. Geochemical and Sr–Nd–Hf isotopic data suggest that the granitic rocks from Mayo Darlé were largely derived by partial melting of Mesoproterozoic basement and modified by strong differentiation, all likely powered by heat (and possibly fluids) from the mantle. The Tertiary age of the rare-metal magmatism sets this system apart from the widespread Late Neoproterozoic to Early Paleozoic rare-metal pegmatites and granites in the Pan-African collisional belts of Africa, and also from the anorogenic Mesozoic ring complexes in Central Nigeria.

Bio-inspired nacre-like zirconia/PMMA composites for chairside CAD/CAM dental restorations

ObjectivesTo introduce a versatile fabrication process to fabricate zirconia/PMMA composites for chairside CAD/CAM dental restorations. These zirconia composites have nacre-like lamellar microstructures, competent and tooth-matched mechanical properties, as well as crack resistance behaviours. MethodsBi-directional freeze casting was used to fabricate ceramic green bodies with highly aligned lamellar structure. Pressure was then applied to control the ceramic volume fraction. PMMA was infiltrated into the ceramic scaffold. Mechanical tests including 3-point bending, Vickers hardness, and fracture toughness were performed on the composites. The machinability of the composites was also characterised. ResultsTwo types of nacre-like zirconia/PMMA composites, i.e., 3Y-YZP/PMMA and 5Y-PSZ/PMMA composites were fabricated. The microstructure created was similar to the ‘brick and mortar' structure of nacre. Excellent flexural strength (up to 400 MPa and 290 MPa for 3Y-TZP/PMMA and 5Y-PSZ/PMMA composite, respectively), tuneable hardness and elastic modulus within the range similar to enamel, along with improved crack-resistance behaviour were demonstrated on both zirconia composites. In addition, both zirconia/PMMA composites showed acceptable machinability, being easy to mill, as would be required to produce a dental crown. SignificanceNacre-like zirconia/PMMA composites therefore exhibit the potential for use in the production of chairside CAD/CAM dental restorations.

The Ahadawa deposit—A newly discovered porphyry Cu–Mo system in the North Qaidam, Northern Qinghai-Tibet Plateau, NW China

Ongoing exploration in the North Qaidam, Northern Qinghai-Tibet Plateau, NW China, has led to the identification of a porphyry Cu-Mo system centered on Ahadawa. In this study, we conducted a detailed geochronological and geochemical study on porphyritic monzogranite from the Ahadawa deposit, which hosts the Cu-Mo mineralization. The weighted mean zircon U-Pb ages for three mineralized porphyritic monzogranite samples from different sites range from 218.8 ± 1.2 Ma (MSWD = 1.5) to 224.7 ± 1.6 Ma (MSWD = 1.8), and finally to 233.1 ± 0.9 Ma (MSWD = 1.4, n = 23). These results, combined with antecrystic grains as old as ∼ 245.7 Ma, collectively indicate more than 25 Ma multi-stage magmatic emplacement activity in the Ahadawa deposit. Corresponding to complex magma episodes, six studied molybdenite samples yielded variable Re-Os model ages ranging from 436.7 ± 6.6 to 232.6 ± 1.2 Ma, with the three youngest dates constraining a weighted mean Re-Os age of 234.0 ± 6.8 Ma. The 234 Ma mineralization age is consistent with the observed Late Triassic magmatism, whereas the Re-Os model ages of 436.7 to 245.7 Ma, if they remain robust through future investigation, may highlight a long-lived hydrothermal activity in the Ahadawa deposit. Whole-rock and zircon compositions indicate that the Late Triassic porphyries occurring at the surface display distinct geochemical features, with the early porphyritic monzogranite of 233.1 Ma characterized by much higher whole-rock Sr/Y, and zircon Eu/Eu* and Ce/Ce* than the younger (218.8 Ma and 224.7 Ma, respectively) porphyritic monzogranite. This suggests that the Late Triassic magmas were initially characterized by high water content and high oxidation state and the differences between the old and two younger groups might be related to plagioclase-dominated fractionation. The finding of the Ahadawa porphyry system highlights the need for ongoing exploration (especially in poorly studied remote areas) and systematically geochronological and geochemical studies to constrain the temporal and spatial evolution of mineralized episodes within a complex, protracted magmatic history.

Accretionary and collisional processes of the Brasiliano Orogeny recorded by the Tonian La Tuna ophiolite, Dom Feliciano Belt, Uruguay

Accretionary to collisional orogenies such as the Brasiliano Orogeny of eastern South America present the opportunity to distinguish between oceanic-continental (accretionary) and continental (collisional) processes. However, the multitude of geotectonic processes involved and the reduced degree of preservation of the accretionary stage restrain the interpretation of evidence. This study focuses on a metasomatite associated with the La Tuna Ophiolite in the southern Dom Feliciano Belt of the Uruguayan Shield, as these can provide crucial insights into the accretionary stage of the Brasiliano Orogeny. The metasomatite occurs as a meter-sized massive tourmalinite body surrounded by a meter-wide chloritite lens, both enclosed by the La Tuna serpentinite. Our SEM-EDS and EPMA data revealed that the serpentines from the La Tuna ophiolite are antigorite and lizardite, while chlorite was identified as clinochlore. Abundant inclusions of sheridanite chlorite in dravite tourmaline suggests that tourmaline overgrew chlorite. Dravite crystals revealed the presence of three diffuse zones with minor compositional variations, mainly enrichments in Ca and Fe towards the rims. The U-Pb LA-ICP-MS dating of metasomatic zircon yielded ages of 743.2 ± 3.4 Ma (n = 22) for the chloritite and 743.1 ± 2.4 Ma (n = 31) for the tourmalinite. High δ11B values (+12.1‰ to + 18.1‰) of tourmaline (LA-ICP-MS) suggest that the metasomatic event was caused by seawater-derived fluids in a fluid-dominated environment. The single metasomatic U-Pb age combined with the high δ11B values suggest that the metasomatites underwent more intense metasomatic events than those associated with the Bossoroca (−8.5‰ to +1.8‰) and the Ibaré ophiolites (+3.2‰ to +5.2‰) further north in the São Gabriel Terrane of the Dom Feliciano Belt. Nonetheless, a few spots in tourmaline located within fracture zones and in contact with chlorite displayed negative (c. −5‰) and low positive δ11B values (c. 2‰). These are interpreted as overprinting by crustal fluids, either during the tectonic emplacement of the La Tuna Ophiolite or during exhumation. The calculated TDM Hf model ages for zircon in tourmalinite and chloritite range from 0.74 to 1.09 Ga and their ɛHf(T) values range from +4.9 to +11.2, indicating derivation from depleted mantle sources. The data corroborate earlier results indicating that the associated La Tuna amphibolites have composition similar to N-MORB. Furthermore, the trace element composition of zircon in the metasomatites is consistent with an oceanic environment (U/Yb < 0.1). Geotectonically, the La Tuna metasomatites formed at 743 ± 2 Ma in an oceanic setting, most likely in a juvenile Adamastor Ocean basin. During the collisional stage of the Brasiliano Orogeny, the La Tuna Ophiolite was tectonically emplaced within the <666 Ma La Micaela Schist of the Paso del Drágon Complex. As such, this study on the La Tuna Ophiolite contributes direct evidence on the oceanic evolution leading up to the accretionary stage of the Brasiliano Orogeny and provides new constraints on the transition towards the collisional stage.

Effect of different surface and heat treatments on the surface roughness, crystallography, and phase composition of high translucency zirconia for monolithic restorations

Statement of problemHigh translucency zirconia (HTZ) has gained popularity as an esthetic computer-aided design and computer-aided manufacturing (CAD-CAM) material for monolithic restorations. A detailed comparison between different common surface and heat treatments with a non-treated HTZ control to explain the behavior of the material under stress is lacking. PurposeThe purpose of this in vitro study was to evaluate the effect of different surface and heat treatments on the surface roughness parameters (SRPs), topography, crystallography, and phase composition of HTZ used for monolithic restorations. Material and methodsNinety Ø11.9×1.18-mm HTZ disks (Prettau Anterior) were milled, sintered, and distributed into 9 groups (n=10); 8 experimental (coarse diamond grinding GC, fine diamond grinding GF, fine diamond grinding and 3-step polishing kit GF+P1, fine diamond grinding and 3-step polishing kit and diamond paste GF+P1+DP, fine diamond grinding and 2-step polishing kit GF+P2, fine diamond grinding and GF+Gl, fine diamond grinding and 3-step polishing and glazing GF+P1+Gl, airborne-particle abrasion with 50-µm alumina), and a control group (C, as-sintered). SRPs (AveSa, AveSv, AveSz) and 3-dimensional (3D) images were obtained using a noncontact 3D-optic-profilometer. The crystal structure was determined with scanning electron microscopy. Phase composition was analyzed by X-ray diffraction (XRD). Surface roughness parameters data were statistically analyzed by 1-way ANOVA and the Tukey HSD test (α=.05). ResultsThe applied surface and heat treatment resulted in significantly different SRP mean values (P<.001) with different topographies. GC had the highest AveSa, AveSv, and AveSz mean values (0.95, 8.8, 17.4 µm, respectively) with significant microcracks. GF had significantly lower SRP with finer microcracks. GF+P1 had a significantly smoother surface, but GF+P2 resulted in SRP comparable with the GF group. GF+P1+DP had the smoothest homogenous surface (mean Sa: 0.08 µm). GF+P1 and GF+GL were equally effective, while GF+P1+GL was not superior. Airborne-particle abrasion produced a low Sa mean value (0.11 µm) with relatively high Sv and Sz mean values (5.9, 9.2 µm, respectively) and microcracks. A monoclinic phase was detected in all groups. All experimental groups had broadened XRD-peaks with lower intensity, suggesting the presence of the rhombohedral phase. ConclusionsThe different surface and heat treatments altered the HTZ crystals and their surface roughness with distinct topographies. Cubic crystal changes take place under stress as shown by the scanning electron microscope and the XRD diffraction pattern and may transform to the rhombohedral phase.

A Clean, Rapid, and Controllable Approach for Establishing Bioactive Surfaces on Zirconia Implants

AbstractZirconia implants have great application prospects due to their favorable biocompatibility and esthetic properties. However, the percentage of osseointegration of zirconia implants is lower than that of titanium implants. This study, structures bioactive surfaces on zirconia using a femtosecond laser combined with hydroxyapatite (HA) crystals and evaluates the surface morphology, functional groups, crystal phase, mechanical performance, and cell response. The results revealed that calcium phosphate deposition coincided with the establishment of micro‐grooves on the zirconia surface. The crystal composition and flexural strength of zirconia showed no significant changes after the surface treatment. Furthermore, the modified surface promoted cell adhesion and proliferation through adjustments in cell morphology. The findings suggest that the combination of femtosecond laser and HA crystals offers a clean, rapid, and controllable approach to preparing bioactive surfaces for zirconia implants.

Petrogenesis of the Mesozoic granitoids from the Yuanlinzi Sn-Cu deposit, Northeast China: Implications for Cu-rich Sn mineralization

Granite-related hydrothermal Sn deposits are commonly expected to contain little or no Cu because Cu and Sn have markedly different geochemical properties. However, examples of Sn deposits rich in Cu are well-known in many Sn belts worldwide. So far, the magmatic processes of ore-related rocks and genesis of Cu-rich Sn deposits remain controversial. The newly discovered Yuanlinzi Sn-Cu deposit is located in the southern Great Xing’an Range (SGXR), Northeast China. It is a typical Cu-rich Sn deposit in the SGXR. This contribution reports new cassiterite and zircon U-Pb ages, geochemical compositions, and Sr-Nd isotopic data for the granitoids in the Yuanlinzi deposit to decipher the genesis of Cu-rich Sn deposit. Cassiterite U-Pb dating reveals that the Sn mineralization at Yuanlinzi was formed at ∼ 138 Ma. Zircon U-Pb dating of the granitoids yielded two age clusters: Early Triassic (247.6–246.3 Ma) for the granodiorite, and Early Cretaceous (145.3–141.9 Ma) for the granites, including K-feldspar granite (145.3 ± 0.5 Ma), granite porphyry (143.6 ± 0.9 Ma), fine-grained granite (142.8 ± 1.1 Ma) and albite granite (141.9 ± 1.3 Ma). The Early Cretaceous granites have geochemical affinities for A-type granites, for example, A/CNK = 0.98–1.07, high TFeO/(TFeO + MgO) ratios, total alkali (Na2O + K2O), and Ga/Al ratios. The Early Triassic granodiorite have relatively low (87Sr/86Sr)i values of 0.7034–0.7041, whereas the Early Cretaceous granite has slightly variable and higher (87Sr/86Sr)i values, varying from 0.7020 to 0.7065. The Early Triassic granodiorite and Early Cretaceous granites have similar bulk-rock εNd (t) values and TDM2 ages, ranging from + 1.89 to + 3.53 and 732 to 845 Ma, respectively. The geochemical data and Sr-Nd isotopes indicate that the Early Cretaceous granites were derived from partial melting of the juvenile middle-upper crust. This study further suggests that the 145.3–141.9 Ma granites are associated with back-arc extension environment during the low-angle subduction of Paleo-Pacific plate. In addition, the whole-rock and zircon compositions show that the Cu-Sn magma is characterized by relatively oxidized and less evolved features compared to the Cu-poor Sn deposits in the region. The rapid increase of oxygen fugacity of the latest episode of the Early Cretaceous magma is supposed to have initiated by the injection of mafic magma, which supported the Cu source for the deposit. Our studies suggest that the Cu-bearing mafic magma/fluid injection plays a key role on the formation of Cu-rich Sn deposit.

Trace element composition of zircon from granitoids of the Neoarchean alkaline province of the Kola Peninsula

Research subject. Zircon from granitoids of the A- and I-types of the Neorchean Kola alkaline province of the Baltic (Fennoscandian) shield. Aim. To determine the trace element composition of zircon in order to characterize the conditions of its formation in different types of granitoids. To use these data, along with the available results of U-Pb dating and Lu-Hf isotope composition of the studied zircon crystals, to assess the amount of mantle and core matter in the protolith composition and the effect of crystallization conditions on the rare element composition of zircon. Materials and Methods. 50 zircon crystals from 5 samples of the main types of granitoids of the province were studied. Concentrations of trace elements were determined using a Cameca IMS-4f ion microprobe (NF FTIAN, Yaroslavl). Points for analysis were selected using optical and cathodoluminescent images. The size of the crater did not exceed 20 µm, the relative measurement error for the predominant part of the elements was set at 10–15%, the threshold for detecting elements was 10 ppb. Results. There are two main types of zircon of Neoarchean age – zircon-1 and zircon-2, formed, respectively, at the magmatic and autometasomatic stages of crystallization, zircon-4 in inclusions in zircon-1, and Paleoproterozoic zircon-3 of metamorphic genesis. The average isotopic composition of Hf in zircon-1 and zircon-2 of different arrays varies slightly, with the amount of mantle component (Xm) ranging from 23 to 30%, which may indicate a relatively constant and significantly core composition of their protoliths. Conclusions. The change in the trace element composition of Neoarchean zircons was controlled mainly by the composition of protoliths and redox crystallization conditions. Under reducing conditions, the greatest chemical activity was acquired by light (La-Nd) lanthanides, for which a direct dependence on the Ce/Ce* value was established. For heavy lanthanides with similar ion sizes relative to Zr+4, crystallochemical factors were more important and a decrease in the dependence of heavy lanthanide concentrations in zircon on Ce/ Ce* was determined.

Detrital zircon and tourmaline unravel polycyclic provenance of sedimentary infill of the Cretaceous Tupanciretã formation, southern Brazil

The recognition and evaluation of polycyclic processes in sedimentary units are critical for proper provenance analysis and sedimentary system interpretation. The chemical composition and textural maturity of detrital tourmalines and zircons allow identification of sediment source areas, transport, and deposition. This study investigates the origin and history of post-Gondwanan sediments of the Tupanciretã Formation in southern Brazil, which lacks provenance studies. The Tupanciretã Formation is in a similar setting of the Bauru Supersequence at the uppermost portion of the Paraná Basin. Detrital zircon ages indicate sediment provenance from the Transamazonian, Grenvillian, and Brasiliano orogenic cycles of the Rio Grande do Sul Shield and younger grains (280-128 Ma) record contribution from the Choiyoi and Serra Geral igneous events, with a maximum deposition age of 127 Ma. Detrital tourmaline chemical analyses points to the Sul-riograndense Shield as the ultimate source, with metapelitic, metapsamitic and granitic origins. The predominant degrees of roundness are well rounded to rounded suggest evidence of sediment recycling from sedimentary units of the Paraná Basin, with important aeolian reworking involved. Zircon U–Pb signatures are compatible with the eastern sector of the Botucatu Formation in Rio Grande do Sul as the immediate source and the northeastern Sul-riograndense Shield as the ultimate source. Intermediate sources between the Sul-riograndense Shield and the Tupanciretã Formation were Gondwanan sedimentary units of the Paraná Basin, with possible participation from the Camaquã Basin.