Enrichment Of Zr Research Articles

The application of trace elements and Sr–Pb isotopes to dating and tracing ruby formation: The Aappaluttoq deposit, SW Greenland

Trace element characteristics of rubies from the Aappaluttoq deposit, SW Greenland, were measured using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), laser ablation - inductively coupled plasma-time of flight-mass spectrometry (LA-ICP-TOF-MS) and offline laser ablation followed by solution ICP-MS. LA-ICP-TOF-MS - applied to rubies for the first time - effectively maps trace element spatial variation in these gems. With the exception of a small number of elements that can substitute for Al3+ in the crystal structure (e.g., Ti, Fe, V, Cr, Mg), trace element mapping clearly demonstrates that most elements such as Th, U, Sr and Rb are hosted in mineral and fluid inclusions or are present along fractures. Primitive mantle normalized trace element patterns show characteristics that are broadly correlative to mineral inclusions within the analysed rubies. These minerals include rutile (enrichment of HFSE over LREE, high Ta/Nb and Hf/Zr ratios and low Th/U ratios), phlogopite (enrichment in Rb and Ba and positive Sr anomalies), and zircon (extreme enrichment in Zr–Hf, U and Th, HREE enrichment over LREE and positive Ce anomalies).The sample suite analysed here is derived from a bulk sample of ore composed of three different rock types (sapphirine-gedrite, leucogabbro and phlogopitite). Two different populations of ruby were identified at Aappaluttoq; these can be defined on the basis of their different V content within the corundum lattice. Therefore, V content may be able to geochemically define rubies from different host rocks within the same deposit.Using offline laser ablation followed by thermal ionization mass spectrometry (TIMS) we measured the radiogenic isotope compositions in ruby for the first time. A Pb–Pb isochron age of 2686 +300/−74 Ma, was defined for gem formation at Aappaluttoq. We believe that this is the first ever direct age determined on a ruby suite, independent of associated minerals, derived by bulk sampling sub-micron to micron sized inclusions in the corundum lattice. This age likely reflects the re-crystallization and re-setting of the ruby (and its U–Pb system) during the Neoarchean in SW Greenland, due to regional granulite to upper-amphibolite facies metamorphism.

Dissolution of silica component of glass network at early stage of corrosion in initially silica‐saturated solution

AbstractCorrosion of glass in silica‐saturated solution has been performed with the assumption that dissolution of silicate species from the glass network would not occur. Using surface‐sensitive analytical techniques, we report experimental evidence suggesting the dissolution of silicate network species from a model nuclear waste glass, called international simple glass (ISG), in an aqueous solution initially saturated with soluble silica species. Results from low energy ion scattering and X‐ray photoelectron spectroscopy reveal a complete depletion of mobile element species (B, Na) from the ISG surface and an enrichment of Zr on the outmost surface. In support of spectroscopic analyses, results from topographic imaging with atomic force microscopy show a stochastic dissolution of glass surface resulting in a higher surface roughness with increasing corrosion time in aqueous solution. This study shows that a true equilibrium between soluble silica species in the solution phase and silicate species in the glass network could not be warranted by performing corrosion experiments in the solution where dissolved silica species are initially equilibrated with amorphous silica in the presence of KOH. The leaching of mobile species (B, Na) could affect the saturation level of aqueous solution and induce further dissolution of the glass surface.

Dolomite-illitic rocks (dolillite) – the product of hydrothermal replacement of carbonate rocks in the Holy Cross Mts., Poland – a possible guide to ores

The dolomites altered to dolomite-illitic rocks were found accompanying marcasite-pyrite-hematite mineralization within the Middle Devonian carbonate rocks in the eastern part of the Holy Cross Mts. (Poland) in the fault zones and their close vicinity. The alteration consist of dolomite recrystallization and replacement by illite, accompanied by small amounts of silica, K-feldspars and disseminated pyrite or hematite. The final product of dolomite replacement by illite are massive, dolomite-illitic rocks unevenly distributed within the unaltered dolomites or in fault breccia. They form irregular metric-sized nest-like bodies most often with blurred boundaries, or in some places sharp delineated veins and lenses. Illite crystallinity, demonstrates its hydrothermal origin. Altered rocks are characterized by elevated contents of REE, Rb, and sometimes other trace metal (Zr, Ti, Zn, U, Th, Ba and al.), compared to unaltered dolomites. The enrichment in REE, Zr and Ti implies their mobility in hydrothermal solutions. The lamprophyre intrusions present in the close vicinity may be considered as the probable source of potassium rich hydrothermal fluids. The peculiar features of dolomite-illitic rocks such as: their composition and occurrence close to the sulphide and hematite mineralization, allow supposing, that they may be a guide to deeply seated unknown ore deposits. Normal 0 21 false false false PL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Arial,sans-serif; mso-bidi-font-family:CG Times 12pt; mso-fareast-language:EN-US;}

Mechanochemical preparation of ceria-zirconia catalysts for the total oxidation of propane and naphthalene Volatile Organic Compounds

A range of ceria-zirconia mixed metal oxide catalysts were synthesised by mechanochemical milling from nitrate precursors and tested for propane and naphthalene total oxidation. The mixed CeZrOx metal oxide catalysts were more active compared to pure CeO2 and ZrO2, with the Ce0.90Zr0.10Ox catalyst the most active for both propane and naphthalene total oxidation. Catalysts were characterised by XRD, TGA, Raman spectroscopy, BET surface area, XPS, TEM and SEM-EDX techniques. Formation of CeZrOx solid solutions were observed for Zr content ranging from 5 to 25%, and phase separated materials were observed for higher Zr content of 50%. The incorporation of Zr into the CeO2 lattice increased the surface area compared to pure CeO2 and ZrO2, with evidence of a surface enrichment of Zr when concentrations were compared to the bulk. Incorporation of Zr was found to increase the surface concentration of oxygen defects in the CeZrOx mixed metal oxides, the concentration of these defect on the catalysts follows a similar trend to the propane and naphthalene total oxidation activity: The increased presence of oxygen defects and reducibility are factors responsible for the enhanced total oxidation activity of the mixed metal oxide catalysts and the mechanochemical method is an effective preparation route for these active catalysts.

Constraints on the formation of the Baogutu reduced porphyry copper deposit (West Junggar, NW China): Assessing the role of mafic magmas in mineralization

The Baogutu porphyry copper deposit is a typically reduced porphyry copper deposit (RPCD), characterized by reduced, calc-alkaline, felsic shallow intrusions. A newly discovered gabbro, which contains 1182–1260 ppm Cu, provides an ideal window to reveal the genesis and formation of the Baogutu RPCD. A combined study of the petrological, geochronological, geochemical and isotopic characteristics of the Cu-bearing gabbro and granitoids in the Baogutu RPCD has been completed. The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating of zircons from a gabbro, diorite and porphyritic diorite are 318.2 ± 0.8 Ma (MSWD = 0.01, n = 16), 315.8 ± 1.0 Ma (MSWD = 1.50, n = 16), and 314.9 ± 0.6 Ma (MSWD = 0.12, n = 20), respectively. The geochemical and isotopic characteristics of the gabbro, diorite, and porphyritic diorite at Baogutu RPCD are all metaluminous, calc-alkaline series rocks with depletion in Nb, Ta, and Ti and enrichment in light rare earth elements (LREE) and large ion lithophile elements consistent with an arc-related setting. The relatively high Nd and Hf isotopes (εNd(t) = +6.9 to +7.5, εHf(t) = +8.8 to +14.4) and wide variations of major and trace elements suggest that the gabbro and diorite in the Baogutu RPCD were all derived from a mixture of melts of metasomatized mantle wedge, the hydrous slab, and old crustally derived materials. The high Mg andesites (HMA)/sanukite features (high Mg#, Cr and Ni content) of the gabbro suggest it was derived mainly from a metasomatized mantle-hydrous slab-derived melt source with only slightly contamination by the old crustal materials, whereas adakitic features of the diorite (high Al2O3 and Sr contents and Sr/Y ratios) suggest a greater role the melting of residual subducted oceanic crust with juvenile mantle materials. The porphyritic diorite, which inherited the geochemical characteristics of diorite, was probably derived from a similar parental magma but the low εNd(t) of +1.4, old T2DM (Nd) age of 961 Ma and enrichment in Zr and Hf suggest a greater degree of crustal contamination. The high content of Cu and high oxidation state of the gabbro is consisted with it having formed early from an unusually Cu-rich parental magma. This magma would have provided abundant metal and sulfides which would have been mobilized and reconcentrated by later ore bearing fluids linked to the intermediate to acid porphyry intrusions in the Baogutu RPCD.

Geochronology and Geochemistry of the Granites from the Longtoushan Hydrothermal Gold Deposit in the Dayaoshan Area, Guangxi: Implication for Petrogenesis and Mineralization

The gold mineralization in the Longtoushan hydrothermal gold deposit is concentrated within the contact zone of the granitic complex. Whole rock geochemistry and in-situ U-Pb and Hf isotopic data were used to constrain the genesis and age of the granites and related Cu-Au mineralization in the Longtoushan Deposit. The granites mainly consist of the granite porphyry, rhyolite porphyry, porphyritic granite and quartz porphyry. LA-ICP-MS U-Pb dating of zircons from the granite porphyry, rhyolite porphyry and quartz porphyry indicates that they intruded from ca. 94 to 97 Ma. These intrusions exhibit similar trace element characteristics, i.e., right-dipping REE patterns, depletion of Ba, Sr, P and Ti, and enrichment of Th, U, Nd, Zr and Hf. The eHf (t) values of zircons from the granite porphyry, rhyolite porphyry and quartz porphyry range from −26.81 to −8.19, −8.12 to −5.33, and −8.99 to −5.83, respectively, suggesting that they were mainly derived from the partial melting of the Proterozoic crust. The Cu-Au mineralization is mainly related to the rhyolite porphyry and porphyritic granite, respectively. The Longtoushan granites were most likely formed in a post-collisional extensional environment, and the deposit is a part of the Late Yanshanian magmatism related mineralization in the Dayaoshan area and its adjacent areas.

Cover Feature: Effect of Vapor‐phase‐treatment to CuZnZr Catalyst on the Reaction Behaviors in CO2 Hydrogenation into Methanol (ChemCatChem 5/2019)

The Cover Feature shows the formation of methanol from CO2 hydrogenation on CuZnZr catalyst. In their Full Paper, S. Chen et al. investigate the reasons that vapor-phase-treatment (VPT) leads to the changes in reaction behavior on the catalysts. The VPT with TPABr induces obvious increases in the particles size of CuO, ZnO and ZrO2, promotes the formation of the rod-like structure, Zn and Zr enrichments on surface and the presence of more concentration of oxygen vacancies. These synergetic effects of the changes in surface properties and morphology restrain the competitive reverse water-gas shift (RWGS) reaction furthest, subsequently leading to the supremacy of catalyst for methanol selectivity. More information can be found in the Full Paper by S. Chen et al. on page 1448 in Issue 5, 2019 (DOI: 10.1002/cctc.201801988).

Effect of Vapor‐phase‐treatment to CuZnZr Catalyst on the Reaction Behaviors in CO2 Hydrogenation into Methanol

AbstractCuZnZr catalysts prepared by co‐precipitation method were treated by vapor‐phase‐treatment (VPT) method, and used for the synthesis of methanol for CO2 hydrogenation. Compared with conventional co‐precipitation method, this VPT with TPABr (TPABr: tetrapropylammonium bromide) induces obvious increases in the particles size of CuO, ZnO and ZrO2, promotes the formation of the rod‐like structure, Zn and Zr enrichments on surface and the presence of more concentration of oxygen vacancies. Due to the increases of particle size especially for CuO particles, the activity of the catalyst for CO2 hydrogenation to CO (RWGS reaction) is furthest suppressed, leading to dramatical decrease in conversion of CO2. However, methanol productivity is affected relatively modestly due to the enrichments of Zn and Zr as another active species on the catalyst surface. In addition, catalyst properties and methanol selectivity can be regulated through adjusting the processing time. The catalyst with the processing time of 3 day (CuZnZr‐TPABr‐3d catalyst) shows a methanol selectivity above 90 % and no obvious deactivation appeared in a period of 100 h reaction.

Evidence of crustal reworking in the Mesoarchean: Insights from geochemical, U-Pb zircon and Nd isotopic study of a 3.08–3.12 Ga ferro-potassic granite-gneiss from north-eastern margin of Singhbhum Craton, India

Evidences of Mesoarchean crustal reworking are not very common in geological records, being only found from Precambrian terrains like Kaapvaal and Pilbara Cratons where it is preserved as anorogenic/post-collisional granitic activity of 3–3.2 Ga age. The present study focuses on a granitoid unit of similar age, found near the eastern margin of the Precambrian Singhbhum Craton of eastern India. This ellipsoidal, N-S trending, well-foliated granite-gneiss body is found within the polydeformed, metasedimenatry rocks of Singhbhum Group, belonging to the North Singhbhum Mobile Belt. LA-ICP MS U-Pb analysis of zircon grains from one sample give crystallization ages ranging from 3079.4 ± 6.8 Ma to 3115 ± 10 Ma. These rocks hereby dubbed as “Bangriposi Granite Gneiss”, are composed of quartz, alkali feldspar, ferroan biotite (Fe/Fe + Mg: 0.7–0.9), titanite, illmenite, hastingsite, apatite, and numerous U-Th-REE- bearing accessory phases. They have high SiO2 (67–77 wt%) and Na2O + K2O (8.19–9.01 wt%), low CaO (0.35–1.5 wt%), MgO (0.05–0.36 wt%) and shows enrichment of Nb, Rb, Zr, Y, Th, and REEs, and depletion of Cr, Ni, U, with high FeOt/FeOt + MgO (~0.9), Ga/Al (2.04–3.51), (La/Yb)N (6.5–13), and low Eu/Eu* (0.11–0.47). Geochemically and mineralogically they are categorized as metaluminous to weakly peraluminous (A/CNK: 0.9–1.1) ferro-potassic alkali feldspar granites. These rocks show unequivocal affinities towards ‘A-type” granites and from geochemical evidences it is suggested that the parent magma was produced in response to crustal anatexis under low fO2 with P-T estimates of ~900 °C and 7–8 kbar. Geochemical modelling has revealed that the probable source was lower crustal amphibolites belonging to the Paleoarchean Older Metamorphic Group, which suffered low degrees (5–15%) of melting. Negative ƐNd values (−0.5 to −1.5) are also in favour of reworking of older crust and their Nd isotopic signature bears similarities with other coeval anatectic granites. Bangriposi Granite-Gneiss, along with Mayurbhanj Granite and Bonai Granite, represent a major phase of Mesoarchean anorogenic/post-collisional granitic activity in Singhbhum Craton, indicating the onset of its stabilization. Similar Mesoarchean crustally reworked felsic units are encountered in Pilbara and Kaapvaal cratons suggesting a possibility of correlation with the hypothesized “Vaalbara” supercontinent.

Mg-RE Alloy Anode Materials for Mg-Air Battery Application

Commercial purity Mg, Mg-RE alloys ZE10A (UNS M11600), and EV31A (UNS M12310) were evaluated in the as-received condition for potential application as anode for Mg-air battery. Anodic and cathodic polarization studies were performed in 0.6 M of NaCl, 0.5 M of NaNO3 and 0.1 M of Na2SO4. Hydrogen evolved during anodic polarization was measured at different current densities. Electrochemical impedance spectroscopy was carried out at open circuit conditions, and galvanostatic conditions. The results showed that commercial purity magnesium had higher corrosion resistance than the Mg-RE alloy specimens in all the electrolytes tested. All the specimens showed negative difference effect (NDE) where the rate of hydrogen evolution increased with increased anodic polarization. The NDE was more pronounced on ZE10A than on other materials. The results suggest that EV31A could be a potential anode material for Mg-air battery due to its better discharge capabilities. The surface layer formed on the Mg specimen showed predominantly a p-type semiconductivity with a charge carrier density in the order of 1021 cm−3. The Mg-RE alloys showed a dual layered surface layer with bottom n-type and top p-type characters. The p-type behavior could be associated with the formation cation vacancies due to dissolution of Mg from its lattice site, and the n-type semiconductivity could be attributed to segregation of trivalent rare earth cations at the metal/oxide interface. The enhanced NDE behavior of the Mg-RE alloys could also be attributed to the surface enrichment of Zr, and presence of MgxREy type secondary phases.

Bauxite formation on Tertiary sediments in the coastal plain of Suriname

Lateritic bauxites in the coastal lowlands of Suriname form part of a belt along the northern margin of the Guiana Shield that has long been one of the world's major bauxite producing regions. The Surinamese deposits, many of which with an extensive mining history, originated on Tertiary siliciclastic sediments and were mostly buried under a layer of young sediments. The bauxite-bearing sequences are generally topped with an iron-rich layer largely made up of hematite and goethite. It covers a gibbsite-rich bauxite horizon that passes downward into a kaolinitic bottom section containing anatase and zircon as main accessory minerals. Weathering profiles across formerly mined deposits were analyzed for geochemical and mineralogical properties aimed at exploring compositional diversity, underlying controls of bauxite-formation and the nature of precursor sediments.Studied profiles in different parts of the coastal plain reveal overall similarities between individual deposits in showing significant depletion of Si, K, Na, Mg and Ca and strong, primarily residual, relative enrichment of Al, Ti, Zr, Nb, Hf, Ta and Th. In detail, however, there are distinct differences in major and trace-element signatures, accessory mineral assemblages, facies distribution and provenance of the terrigenous precursor sediments. Enrichments in high field-strength elements and heavy rare earth elements are largely attributable to accumulation of heavy minerals like zircon in the precursor. Petrological and trace-element evidence does not support a direct genetic relationship between bauxite and the underlying saprolitic clays. The complex petrologic characteristics and compositional heterogeneity of the coastal-plain deposits can essentially be explained by element fractionation, primarily through selective leaching, in combination with relative and absolute enrichment processes, erosion and reworking during two-stage, polycyclic bauxitization of a heterogeneous precursor.

High Nb\u2013Ta rhyolites of the Kyihe region, north Daxingan Mountains, China: geochemistry, petrogenesis, and zircon U\u2013Pb geochronology

Rhyolites with high Nb–Ta contents were recently discovered in the north Daxingan Mountains, China. We determined the geochemical characteristics and zircon U–Pb ages of these rhyolites to elucidate their tectonic setting of formation and petrogenesis. Zircons from the high Nb–Ta rhyolites are idiomorphic or hypidiomorphic, short prismatic crystals with oscillatory zoning; the zircon trace element has a higher Th/U ratio (> 0.4); zircon rare earth element (REE) content is high (average is 1729 × 10−6) and indicates heavy REE (HREE) enrichment (average is 1561 × 10−6) and shows positive Ce (Ce/Ce* = 2.1–103.4) and negative Eu (Eu/Eu* = 0.18–0.64) anomalies typical of crustal magmatic zircons. Their weighted-mean LA–ICP–MS U–Pb age of 155 ± 1 Ma indicates that they formed in the Upper Jurassic. The rhyolites are characterized by high SiO2 and alkali contents and low Fe, Ca, Mg, and Mn contents, and are weakly peraluminous, indicating that they are high-K calc-alkaline rocks. Trace element compositions are characterized by enrichments in Nb, Ta, Zr, Hf, Ce, and Rb and depletions in Sr, Eu, Ba, P, Ti, Co, and Ni, with significant positive Ce (Ce/Ce* = 2.4–2.7) and negative Eu (Eu/Eu* = 0.06) anomalies. Niobium and Ta are hosted in the zircons. In (Na2O+K2O+FeOT+MgO+TiO2) vs (Na2O+K2O)/(FeOT+MgO+TiO2) and (Al2O3+FeOT+MgO+TiO2) vs Al2O3/(FeOT+MgO+TiO2) mineral characterization diagrams, data for the samples plot in the metamorphic greywacke or basic argillaceous rock fields, indicating that the magma originated from partial melting of crustal material. εSr(t) values cover a wide range (− 18.2 to + 102.9), whereas εNd(t) values have a narrow range (1.9–2.0) with T2DM model ages of 789–785 Ma, indicating that the source was the Neoproterozoic Xinghua Ferry Group crustal basement. This crustal rock suite comprises a volcanic–sedimentary formation of metamorphosed mafic volcanic and terrigenous clastic rocks derived from a mixture of mantle and crustal materials. Residual phases in the source region include Ca-rich plagioclase, amphibole, orthopyroxene, and zircon + garnet. Together with the positive Ce anomalies and low-Sr/high-Yb characteristics of the rhyolites, this indicates that the source rocks melted at relatively shallow depths (< 30 km), low pressures (< 0.8 GPa), and high O2 fugacity. Ga × 104/Al > 2.6, Ta vs Yb, and (Rb/30) vs Hf vs (3Ta) discrimination diagrams, data for the samples plot in the A-type rhyolite and intraplate granite fields, whereas in the Nb vs Y vs Ce diagram, the data plot in the A1-type field. It is concluded that an extensional tectonic setting, resulting from closure of the Mongolia–Okhotsk Ocean at the end-Triassic, or northward subduction of oceanic lithosphere under the Siberian Plate, caused underplating of mantle-derived basaltic magma and partial melting of metamorphic crustal rocks.

Life and FCT Failure of Yttria- and Ceria-Stabilized EBPVD TBC Systems on Ni-Base Substrates

The lifetime at 1100 °C of furnace oxidation tested TBC samples having YSZ (ZrO2-7 wt.% Y2O3) and CeSZ (ZrO2-25 wt.% CeO2-2.5 wt.% Y2O3) topcoats on four Ni-base alloys including a no-bond coat NiCrAl alloy were studied. The thermally grown oxide (TGO) was investigated by energy-dispersive spectroscopy. The outer zone of the TGO revealed preferred enrichment of Zr and of rare earth elements Ce and Y in dependence of the stage of life. The oxygen potential gradients in the TGO have been rated; they are stronger for the YSZ TBC systems than for the CeSZ systems and cause a more intensive interaction of the outer zone alias mixed zone with the metal substrate than with the ceramic topcoat. When comparing the chemical composition data of the mixed zone as a function of the test period, the average lifetime as well as the particular composition of the two topcoats and the refractory element content of the substrates allowed conclusions to be drawn about the mechanisms which influence the lifetime.

Geochemistry and grain size distribution of surface sediments of a large semi-enclosed lagoon connected to the western Bay of Bengal

Batticaloa is a large (135.5 km2), semi-enclosed, micro-tidal lagoon that formed by barrier deposits in eastern Sri Lanka and has a unique geographic position due to its tropical monsoonal climate and absence of tectonics. The recent soft bottom sediments of Batticaloa lagoon were studied on the basis of geochemistry and grain size distribution in order to interpret their characteristics and provenance. Poor to moderately sorted medium sands are the dominant sedimentary deposits for the lagoon; therefore, a medium energy condition is suggested for sediment deposition. The average silt and clay fraction of the lagoon sediments is less than 3%, indicating medium or high energy flows. Coarser deposits are restricted to channel and lagoon mouths. The scatter plots of Nb, Zr, Cr and Sc vs. Th and Cr/V vs. Y/Ni show a felsic provenance for the sediments. The normalized diagrams of major element oxides and trace elements for the regional rocks (Vijayan Complex of Sri Lanka) indicate high country rock influence for the sedimentation for the semi-enclosed setting. The enrichment and distribution of Zr, Th, Nb, Cr and TiO2 suggest the possibility of mineral sands that are fractionated with hydrodynamic setting of the lagoon.

Geochemical, petrographic, and uranium–lead geochronological evidence for multisourced polycyclic provenance of deep-water strata in a hybrid tectonic setting: The upper Miocene upper Mount Messenger Formation, Taranaki Basin, New Zealand

Petrographic, detrital zircon, major, trace, and rare earth element data from the deep-water slope upper Miocene upper Mount Messenger Formation, Taranaki Basin, New Zealand have been characterized to examine their provenance, tectonic setting, grain size, and source-to-sink implications. Sandstone samples have an average quartz–feldspar–lithic framework composition of Q37F9L54. Lithic fragments are metasedimentary and commonly quartz and epidote bearing, having been recycled through at least two phases of erosion and deposition from an original orogenic to transitional arc setting. Detrital zircon U–Pb ages (total 304 single-grain ages) range from 37 to 2466 Ma, with large Triassic to Permian modes and small mid-Cretaceous, Early Jurassic, Devonian–Ordovician, Cambrian, and Proterozoic modes. The ages show subtle variation from the base to the top of the formation and statistical similarity with the Torlesse composite terrane and Waipapa Group. Trace and rare earth element analyses indicate enrichment in Th and Zr compared with Sc and Cr, and a strong Eu anomaly. The depositional system is overwhelmingly fine- to very fine–grained and probably reflects grain recycling and mechanical breakdown, either through an intermediate depositional cycle or derived directly from metasedimentary basement sources. Basement sources appear to be primarily the Torlesse composite terrane (Rakaia, Pahau, and Kaweka terranes) and Waipapa Group located east and southeast of the study area. This study documents source-to-sink elements in a profoundly regressive depositional system within an active margin setting. It also contributes new information on the composition and depositional history of a stratigraphic interval that contains important petroleum reservoirs in the nearby subsurface.

Petrogenesis of boninitic lavas from the Troodos Ophiolite, and comparison with Izu–Bonin–Mariana fore-arc crust

Supra-subduction zone (SSZ) ophiolites such as the Troodos Ophiolite of Cyprus are thought to have formed at spreading centres close to subduction zones. Similarities in the geochemistry between lavas from SSZ ophiolites and fore-arc lavas from active subduction zones, and the presence of boninites in both, have led to the suggestion that SSZ ophiolites represent fragments of fore-arc crust and mantle, formed during subduction initiation. Here we present major and trace element and Sr, Nd and Pb isotope data for fresh volcanic glasses from a section through the lava pile on the southern margin of the Troodos Ophiolite, and compare these to lavas from the Izu–Bonin–Mariana fore-arc. In Troodos, boninites and tholeiitic basalts are interbedded and were derived from a highly depleted mantle source that was later enriched by both fluids and melts derived largely from subducted sediment, before melting beneath the spreading axis. Troodos boninites differ from Izu–Bonin–Mariana boninites by their greater source depletion, enrichment in Nb by small degree melts, and lack of Zr enrichment relative to Sm. Together with the lack of fore-arc basalts in Troodos, our data imply that the Troodos Ophiolite was formed in a fore-arc location at a back-arc spreading centre that propagated into arc crust. The Troodos Ophiolite was thus not formed during subduction initiation and thus may not be used as analogue for the formation of fore-arc basalts.

Petrogenesis and tectonic implications of Late Carboniferous continental arc high-K granites in the Dongwuqi area, central Inner Mongolia, North China

Central Inner Mongolia is located in the southeastern segment of the Central Asian Orogenic Belt (CAOB), and controversy has long surrounded its late Paleozoic tectonic evolution. Here, we present an integrated study of zircon U-Pb ages, whole rock major and trace elements, and zircon Hf isotopes for five less studied alkali feldspar granitic plutons in the Dongwuqi area to the north of the Erenhot-Hegenshan-Heihe suture zone. Zircon U–Pb dating by laser ablation-inductively coupled plasma–mass spectrometry (LA–ICP–MS) indicates that these granitic plutons were emplaced in the Late Carboniferous (315–300 Ma). The Late Carboniferous alkali feldspar granites belong to high-K calc-alkaline series and are evolved I-type granites. They are high in SiO2 (73.22–77.36%), and low in MgO (0.07–0.49%) with enrichments in light rare earth elements (LREEs), Zr, Hf, Rb, Th, and U, and depletions in Ba, Nb, Ta, Sr, and Eu. The Dongwuqi granitic rocks are characterized by high positive zircon εHf(t) values (+7.6 to +15.1), and relatively young two-stage Hf model (TDM2) ages (364–835 Ma). These geochemical data, together the common miarolitic texture, indicate that they were derived from partial melting of juvenile arc-related mafic to intermediate rocks in the lower crust, and eventually emplaced in low-pressure conditions or at shallow crustal levels, with involvement of extensive fractional crystallization during magma evolution. Our new results, along with the published regional data, delineate a NE-trending Carboniferous continental arc belt (more than 1700 km) in the northern accretionary zone of the Erenhot-Hegenshan-Heihe suture. Accordingly, we invoke that the Dongwuqi Late Carboniferous high-K granites were emplaced in an active continental margin setting, which was probably related to the northwestward subduction of the Hegenshan oceanic plate beneath the Xing'an-Uliastai-Nuhetdavaa block.

Provenance studies of Kalabsha kaolin deposits, Egypt: a petrographical and geochemical approach

The present study focuses on the kaolin deposit in Kalabsha area south Western Desert of Egypt in an attempt to determine its possible source, tectonic setting, and weathering history by means of integrated petrographical and geochemical approaches. The petrographical study was worked by microscopic investigation and supported by X-ray diffraction analysis. X-ray fluorescence and inductively coupled plasma-mass spectrophotometry methods were used for the determination of the bulk elemental composition. Mineralogical analysis revealed that kaolinite is the main clay mineral component indicating a severe chemical weathering of Al-rich source rocks and complete leaching under warm, semiarid climatic conditions. The nonclay minerals are represented by quartz, iron oxides and hydroxides, Ti-bearing minerals, and zircon. Geochemical data show a prevalence of SiO2 and Al2O3 and enrichment of Hf, Nb, Ta, Th, U, and Zr that support the kaolinitic nature of the deposits and their derivation from a felsic granitic terrain. The high values of the chemical index of alteration and the lower values of the index of compositional variability also suggest an intensive weathered source area and the geochemical maturity of the sediments. Other relevant geochemical discriminant functions and plots reveal felsic igneous parent rock for the kaolin deposits. Q-mode hierarchical cluster analysis combined with the normalized rare earth element patterns played a crucial role in unraveling the origin of the studied deposits. The results show that the most probable source rock of the Kalabsha kaolin deposits is the intense weathering of relatively proximal Adara Adatalob granites and their similar rock types in the Arabian-Nubian Shield from the south Eastern Desert of Egypt.

Enhancement in age hardenability of sintered Ti–5Fe alloy by Zr addition processed by pulsed electric current sintering

ABSTRACTThe age-hardenable Ti–5Fe–5Zr (wt. %, 5Zr) alloy has been consolidated by pulsed electric current sintering, following a β solution treatment, and the results are compared with a Ti–5Fe (0Zr) alloy. The precipitation sequence measured at 640°C ageing is β + athermal ω → β + isothermal ω → β + α. At the peak hardness isothermal ω phase forms at 20 s of ageing. The Zr addition retards the precipitation kinetics of the α phase; as a result, the α phase nucleates at latest at 300 s ageing in the overaged state. Fe is partitioned into β, while it is depleted from the α phases. There is Zr enrichment near the α/β interface when the α phase precipitates due to a solute drag effect; the growth rate of the α phase in the 5Zr alloy is significantly reduced compared with that in the 0Zr alloy.

Hydrothermal alteration and evolution of Zr-Th-U-REE mineralization in the microgranite of Wadi Ras Abda, North Eastern Desert, Egypt

Ras Abda plutonic suite, North Eastern Desert of Egypt, consists predominantly of Neoproterozoic calc-alkaline older granites. Minor exposures of pink microgranite are occurring along Wadi Ras Abda within the older granites. Previous studies on this area demonstrated that the microgranite is altered in some parts and contains anomalous concentrations of rare metal elements (Zr, Th, and U). These altered and mineralized zones are re-assessed using field observations, chemical analysis, and by the application of various transmitted light and electron microscopic techniques. The rare metals exist as mineral segregation grew freely into open cavities of the microgranite and concordant with the NNE strike-slip fault movement. The mineralized zones contain an assemblage of secondary magnetite, zircon, uranothorite, columbite-(Mn), fergusonite-(Y), and allanite-(Ce). The extreme abundance of zircon in the mineralized zone, along with other evidence, indicates a hydrothermal origin of this zircon together with associated rare metals. The geochemical investigation and mass balance calculations revealed extreme enrichment of Zr, Th, U, Y, Nb, Ta, and REE. Post-magmatic hydrothermal alterations resulted in such pronounced chemical and mineralogical heterogeneity. The hydrothermal fluids are thought to be oxidizing, alkaline and of medium temperature (> 250 °C). The average contents of the elements Zr (1606 ppm), Th (1639 ppm), U (306 ppm), Nb (955 ppm), and REE (1710 ppm) in the mineralized microgranite reach sub-economic levels and could be a potential source of these elements.