Partial Melting Processes Research Articles

Geochemistry and petrogenesis of late Ediacaran (605–580 Ma) post-collisional alkaline rocks from the Katherina ring complex, south Sinai, Egypt

The Katherina ring complex (KRC) in the central part of south Sinai, Egypt, is a typical ring complex of late Neoproterozoic age (605–580Ma). It was developed during the final tectono-magmatic stage of the north Arabian–Nubian Shield (ANS) during evolution of the Pan-African crust. The KRC includes Katherina volcanics, subvolcanic bodies, ring dykes and Katherina granitic pluton. The Katherina volcanics represent the earliest stage of the KRC, which was subsequently followed by emplacement of the subvolcanic bodies and ring dykes. The Katherina granitic pluton depicts as the latest evolution stage of the KRC that intruded all the early formed rock units in the concerned area. The Katherina volcanics are essentially composed of rhyolites, ignimbrite, volcanic breccia and tuffs. Mineralogically, the peralkaline rhyolites contain sodic amphiboles and aegirine. The rhyolite whole rock chemistry has acmite-normative character. The subvolcanic bodies of the KRC are represented by peralkaline microgranite and porphyritic quartz syenite. The ring dykes are semicircular in shape and consist mainly of quartz syenite, quartz trachyte and trachybasalt rock types. The Katherina subvolcanic rocks, volcanic rocks as well as the ring dykes are alkaline or/and peralkaline in nature. The alkaline granitic pluton forms the inner core of the KRC, including the high mountainous areas of G. Abbas Pasha, G. Bab, G. Katherina and G. Musa. These mountains are made up of alkaline syenogranite and alkali feldspar granite. The mantle signature recorded in the KRC indicates a juvenile ANS crust partial melting process for the generation of this system. The evolution of the KRC rocks is mainly dominated by crystal fractionation and crustal contamination. Mineral geothermometry points to the high temperature character of the KRC, up to 700–1100°C.

Bi2Sr2CaCu2O8 + x round wires with Ag/Al oxide dispersion strengthened sheaths: microstructure–properties relationships, enhanced mechanical behavior and reduced Cu depletion

Ag/Al alloys with various Al content (0.50 wt%, 0.75 wt%, 1.00 wt%, and 1.25 wt%) are made by powder metallurgy and used as the outer sheath material for Bi2Sr2CaCu2O8 + x (Bi2212)/Ag/AgAl multifilamentary round wires (RW). Bi2212/Ag/AgAl RW microstructural, mechanical and electrical properties are studied in various conditions, including as-drawn, after internal oxidation, and after partial melt processing (PMP). The results are compared with the behavior of a Bi2212/Ag/Ag0.20Mg wire of the same geometry. The grains in as-drawn Ag/Al alloys are found to be ∼25% smaller than those in the corresponding Ag/0.20 wt%Mg, but after PMP, the Ag/Al and Ag/0.20 wt%Mg grain sizes are comparable. Tensile tests show that Bi2212/Ag/AgAl green wires have yield strength (YS) of ∼115 MPa, nearly 65% higher than that of Bi2212/Ag/Ag0.20Mg. After PMP, the Bi2212/Ag/AgAl YS is about 35% greater than that of Bi2212/Ag/Ag0.20Mg. Furthermore, Bi2212/Ag/AgAl wires exhibit higher ultimate tensile strength and modulus and twice the elongation-to-failure. Atomic resolution high-angle annular dark-field scanning transmission electron microscopy, high resolution transmission electron microscopy and energy dispersive spectroscopy demonstrate the formation of nanosize MgO and Al2O3 precipitates via internal oxidation. Large spherical MgO precipitates are observed on the Ag grain boundaries of Ag/0.20 wt%Mg alloy, whereas the Al2O3 precipitates are distributed homogenously in the dispersion-strengthened (DS) Ag/Al alloy. Furthermore, it is found that less Cu diffused from the Bi2212 filaments in the Bi2212/Ag/Ag0.75Al wire during PMP than from the filaments in the Bi2212/Ag/Ag0.20Mg wire. These results show that DS Ag/Al alloy is a strong candidate for improved Bi2212 wire.

Relationship between microstructure and thermoelectric properties of Bi2Sr2Co2Ox bulk materials

Abstract

Characterization of weathering and heterogeneous mineral phase distribution in brachinite Northwest Africa 4872

AbstractTerrestrial weathering of hot desert achondrite meteorite finds and heterogeneous phase distributions in meteorites can complicate interpretation of petrological and geochemical information regarding parent‐body processes. For example, understanding the effects of weathering is important for establishing chalcophile and siderophile element distributions within sulfide and metal phases in meteorites. Heterogeneous mineral phase distribution in relatively coarsely grained meteorites can also lead to uncertainties relating to compositional representativeness. Here, we investigate the weathering and high‐density (e.g., sulfide, spinel, Fe‐oxide) phase distribution in sections of ultramafic achondrite meteorite Northwest Africa (NWA) 4872. NWA 4872 is an olivine‐rich brachinite (Fo63.6 ± 0.5) with subsidiary pyroxene (Fs9.7 ± 0.1Wo46.3 ± 0.2), Cr‐spinel (Cr# = 70.3 ± 1.1), and weathered sulfide and metal. Raman mapping confirms that weathering has redistributed sulfur from primary troilite, resulting in the formation of Fe‐oxide (‐hydroxide) and marcasite (FeS2). From Raman mapping, NWA 4872 is composed of olivine (89%), Ca‐rich pyroxene (0.4%), and Cr‐spinel (1.1%), with approximately 7% oxidized metal and sulfide and 2.3% marcasite‐dominated sulfide. Microcomputed tomography (micro‐CT) observations reveal high‐density regions, demonstrating heterogeneities in mineral distribution. Precision cutting of the largest high‐density region revealed a single 2 mm Cr‐spinel grain. Despite the weathering in NWA 4872, rare earth element (REE) abundances of pyroxene determined by laser‐ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) indicate negligible modification of these elements in this mineral phase. The REE abundances of mineral grains in NWA 4872 are consistent with formation of the meteorite as the residuum of the partial melting process that occurred on its parent body. LA‐ICP‐MS analyses of sulfide and alteration products demonstrate the mobility of Re and/or Os; however, highly siderophile element (HSE) abundance patterns remain faithful recorders of processes acting on the brachinite parent body(ies). Detailed study of weathering and phase distribution offers a powerful tool for assessing the effects of low‐temperature alteration and for identifying robust evidence for parent‐body processes.

Helium isotopic textures in Earth's upper mantle

AbstractWe report 3He/4He for 150 mid‐ocean ridge basalt (MORB) glasses from the Southeast Indian Ridge (SEIR). Between 81°E and 101°E 3He/4He varies from 7.5 to 10.2 RA, encompassing more than half the MORB range away from ocean island hot spots. Abrupt transitions are present and in one case the full range occurs over ∼10 km. Melting of lithologically heterogeneous mantle containing a few percent garnet pyroxenite or eclogite leads to lower 3He/4He, while 3He/4He above ∼9 RA likely indicates melting of pyroxenite‐free or eclogite‐free mantle. Patterns in the length scales of variability represent a description of helium isotopic texture. We utilize four complementary methods of spectral analysis to evaluate this texture, including periodogram, redfit, multitaper method, and continuous wavelet transform. Long‐wavelength lobes with prominent power at 1000 and 500 km are present in all treatments, similar to hot spot‐type spectra in Atlantic periodograms. The densely sampled region of the SEIR considered separately shows significant power at ∼100 and ∼30–40 km, the latter scale resembling heterogeneity in the bimodal distribution of Hf and Pb isotopes in the same sample suite. Wavelet transform coherence reveals that 3He/4He varies in‐phase with axial depth along the SEIR at ∼1000 km length scale, suggesting a coupling between melt production, 3He/4He and regional variations in mantle temperature. Collectively, our results show that the length scales of MORB 3He/4He variability are dominantly controlled by folding and stretching of heterogeneities during regional (∼1000 km) and mesoscale (∼100 km) mantle flow, and by sampling during the partial melting process (∼30 km).

Multiple melting behavior of poly(lactic acid)-hemp-silica composites using modulated-temperature differential scanning calorimetry

Abstract Poly(lactic acid) (PLA)-hemp-nanosilica (PHS) composites were prepared by impregnation of hemp woven fabric with PLA solution. Nanosilica was dispersed in the PLA solution to introduce a matrix reinforcing nanophase within the composite. The melting behavior of PLA composites was obtained by using differential scanning calorimetry (DSC) and modulated-temperature DSC (mT-DSC). Multiple melting which appeared in the non-isothermal heating curve showed that the temperature of a low melting peak increased when using a slower scanning rate. The incorporation of nanosilica in PLA composites affected the melting temperature (Tm) and sufficiently formed nucleation sites that promoted the growth of PLA crystals. Composites analyzed by a temperature-modulated program showed a broad exothermic peak before the melting peak in the non-reversing heat capacity and endothermic melting in the reversing heat capacity curve. This behavior was explained by a process of partial melting, recrystallization and remelting (mrr). The mT-DSC resolved that hemp fiber induced recrystallization and nanosilica acted as an effective nucleating agent, which promoted small and imperfect crystals that changed successively into more stable crystals through a melt-recrystallization process.

Synthesis of Bi2Sr2CaCu2Ox superconductors via direct oxidation of metallic precursors

Bi2Sr2CaCu2Ox(Bi2212)/Ag multifilamentary wires are manufactured via the powder-in-tube process using oxide powders. After deformation, the wires undergo a partial-melt process, resulting in a complex, heterogeneous microstructure containing multiple secondary phases and porosity, limiting the wires’ electrical and mechanical performance. Here, an alternative approach using the direct conversion of metallic precursors (MPs) to Bi2212 is studied. The formation of metallic precursor powders via a mechanical alloy is discussed. The MP powder is then converted to superconducting Bi2212 through a simple two-step heat treatment. By introducing oxygen at a temperature at which Bi2212 is in a stable phase, and holding at an elevated temperature for a sufficient time, the metallic precursors are oxidized and transformed into Bi2212. Several factors that impact the formation and growth of Bi2212 grains are discussed. Peak temperature, holding time and heating rate are shown to affect the MP →Bi2212 conversion, the Bi2201 content and the Bi2212 morphology and density. It is found that Bi2Sr2CuOy (Bi2201) can be the only phase impurity after heat treatment, which is quite different from what is observed in partial-melt processed wires derived from oxide precursors. Lastly, the microstructure at the sample/silver interface suggests larger size and preferred orientation of Bi2212 grains with the aid of a silver surface. Implications for MP Bi2212 wires are discussed.

Geochemical and Sr-Nd isotopic evidence for origin and evolution of the Miocene Pangeon granitoids, Southern Rhodope, Greece

The Sr-Nd isotopic ratios of selected post-collisional, calc-alkaline, I-type granitoids from the Pangeon pluton, intruding the lower tectonic unit (LTU) in the Southern Rhodope in the Miocene, support the existence of two types of granitoids (PTG porphyritic tonalite granodiorite and MGG biotite granodiorite to two-mica granite) unrelated by crystal fractionation and likely derived by partial melting of the same source under different P-T conditions. The Sr-Nd isotopic ratios of mafic enclaves in the granitoids as well as metamorphic rocks from the LTU have also been determined. At 22 Ma, the IRSr range between 0.706850 and 0.708381, whereas the εNd(22) range from –3.86 to –1.05, with no relationship to granitoid types. The relationships between Sr and Nd isotopes as well as these isotopes and SiO2 provide evidence of contamination of mafic melts by interaction with crust during magma differentiation. Both partial melting and AFC processes (r = 0.2) may account for compositional variations in the Pangeon magmas. The mafic enclaves display IRSr from 0.706189 to 0.707139, and εNd(22) from –2.29 to –1.94, similar to the granitoids, supporting the hypothesis of a common origin. Amphibolites inferred to be subduction-enriched metabasalts under-plated crust during old subduction can represent the source of the Pangeon melts. The TDM of the Pangeon granitoids is in the range 0.7–1.1 Ga for the inferred extraction age of the LILE-enriched subcontinental lithospheric mantle source. The upper crustal geochemical signatures and the relatively small isotopic composition of the Pangeon granitoids make these rocks similar to the coeval eastern-Mediterranean lamproites emplaced within the same geodynamic setting; this prompts similar melt sources. Lastly, the Pangeon granitoids display geochemical characteristics, isotopic ratios, and TDM also similar to other Tertiary magmatic rocks from the Southern Rhodope and Biga peninsula, western Anatolia, suggesting a similar tectonic environment and co-magmatic evolution throughout the area.

Characteristics of Plasma Sprayed BSCCO Superconductor Coatings with Annealing Time After Partial Melt Process

<TEX>$Bi_2Sr_2CaCu_2O_x$</TEX>(Bi-2212) and <TEX>$Bi_2Sr_2Ca_2Cu_3O_y$</TEX>(Bi-2223) high-Tc superconductors(HTS) have been manufactured by plasma spraying, partial melt process(PMP) and annealing treatment(AT). A Bi-2212/2223 HTS coating layer was synthesized through the peritectic reaction between a 0212 oxide coating layer and 2001 oxide coating layer by the PMP-AT process. The 2212 HTS layer consists of whiskers grown in the diffusion direction. The Bi-2223 phase and secondary phase in the Bi-2212 layer were observed. The secondary phase was distributed uniformly over the whole layer. As annealing time goes on, the Bi-2212 phase decreases with mis-orientation and irregular shape, but the Bi-2223 phase increases because a new Bi-2223 phase is formed inside the pre-existing Bi-2212 crystals, and because of the nucleation of a Bi-2223 phase at the edge of Bi-2212 crystals by diffusion of Ca and Cu-O bilayers. In this study the spray coated layer showed superconducting transitions with an onset Tc of about both 115 K, and 50 K. There were two steps. Step 1 at 115 K is due to the diamagnetism of the Bi-2223 phase and step 2 at 50 K is due to the diamagnetism of the Bi-2212 phase.

The 36–18 Ma Central Nevada ignimbrite field and calderas, Great Basin, USA: Multicyclic super-eruptions

The 36–18 Ma Central Nevada ignimbrite field and calderas, Great Basin, USA: Multicyclic super-eruptions

Petrogenesis of Tarom high-potassic granitoids in the Alborz–Azarbaijan belt, Iran: Geochemical, U–Pb zircon and Sr–Nd–Pb isotopic constraints

Large-scale Upper Eocene plutons in the Western Alborz–Azarbaijan orogenic belt mostly show calc-alkaline and I-type geochemical features contrasted by the Tarom complex with its high-potassic to shoshonitic affinity. The pluton was emplaced in the Tarom subzone of the orogenic belt and its laser ICP-MS zircon U–Pb age of 41Ma is interpreted as the age of magma crystallization. The Tarom complex is composed of quartz monzodiorite, quartz-monzonite and monzogranite, the SiO2 contents range from 57 to 70wt.%, the K2O+Na2O content is high (5.0–8.9wt.%) and K2O/Na2O ratio ranges from 0.4 to 1.9. All the investigated rocks are enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs), and bear a weak Eu anomaly (Eu/Eu*=0.46 to 1.38) in chondrite-normalized trace element patterns. The samples display some variety in initial Sr and Nd isotopic compositions, marked with low ISr=0.704–0.705 and εNd (40Ma)=−4.2 to +3.4 (−5.7 for an enclave) values. The Pb isotopic ratios are (206Pb/204Pb)=18.52–18.86, (207Pb/204Pb)=15.57–15.72 and (208Pb/204Pb)=38.47–39.08. Comparison with experimental studies, together with mantle-like isotopic ratios and comparisons of REE patterns, points to an origin of chemically enriched lithospheric mantle source for the Tarom plutonic complex. Partial melting process involving different partial melting degrees affecting heterogeneously metasomatized mantle is a process that seems likely to have occurred in the studied complex as the major differentiation process. The Tarom monzonitic plutons are considered to be post-orogenic intrusions that were emplaced in an environment of lithospheric extension, causing asthenospheric upwelling. Asthenospheric upwelling induced a thermal anomaly which caused partial melting of metasomatized subcontinental lithospheric mantle in the Tarom area.

Geochemistry, U–Pb geochronology, and genesis of granitoid clasts in transported volcanogenic massive sulfide ore deposits, Buchans, Newfoundland

The Buchans Group, central Newfoundland, represents an Ordovician continental bimodal calc-alkaline arc sequence that hosts numerous volcanogenic massive sulfide (VMS) occurrences, including both in situ and mechanically transported sulfide breccia–conglomerate orebodies. Diverse lithic clasts associated with transported deposits include rounded granitoid clasts. Earlier workers have suggested that Buchans Group VMS-hosting felsic extrusive units, small granodiorite intrusions (e.g., Wiley’s Brook), and granitoid cobbles associated with transported ore represent co-genetic products of the same magmatic system. The granitoid cobbles and small granodiorite intrusions are geochemically similar and closely resemble Buchans Group felsic volcanic units. U–Pb zircon age determinations show a (i) 466.7 ± 0.5 Ma crystallization age for the Wiley’s Brook granodiorite (WBG), (ii) 464 ± 4 Ma crystallization age for a granitoid cobble, and (iii) 466 ± 4 Ma maximum deposition age for a conglomerate–sandstone sequence associated with transported ore. Thus, Buchans Group felsic plutonic rocks are within experimental error of felsic volcanism and VMS deposition. Furthermore, εNd (T) (T, time of crystallization) values of four granitoid cobbles (–1.95 to –4.0) overlap values obtained from Buchans Group felsic volcanic units. Our results are compatible with plutonic and volcanic rocks being related through fractional crystallization or partial melting processes but do not support a petrogenetic link between VMS deposition and exposed felsic plutons. Comparisons to modern arc analogues favour exhumation of plutonic rocks by extension along caldera or rift walls and (or) subaerial erosion. Enigmatic rounding of Buchans granitoid clasts was likely accomplished in a subaerial or shallow marine environment, and the clasts transported into a VMS-active basin by mass flows.

High strength oxide dispersion strengthened silver aluminum alloys optimized for Bi2Sr2CaCu2O8+x round wire

High strength dispersion strengthened (DS) Ag/Al alloys with various Al content are studied as candidates for sheathing Bi2Sr2CaCu2O8+x (Bi2212) wire. The Ag/Al alloys are fabricated by powder metallurgy and internally oxidized in pure oxygen. The time and temperature of the internal oxidation heat treatment is varied to maximize the strength after undergoing the Bi2212 partial melt process (PMP). Vickers micro-hardness number (HVN), room temperature tensile behavior, optical and scanning electron microscopy, ion channeling contrast imaging using a focused ion beam and electrical resistivity measurements are used to characterize the alloys. An Ag/0.2wt%Mg (Ag/Mg) alloy is used for comparison. Results show that internal oxidation at 650–700 ° C for 4 h produces the highest HVN for the DS Ag/Al alloy; when oxidized at 675 ° C for 4 h the HVN, yield strength and tensile strength of the DS Ag/Al are 50% higher than the corresponding values of Ag/Mg. Microstructural observations show that Al2O3 precipitates play the main role in strengthening the DS Ag/Al alloy. The alloy retains its fine grain structure and strength after PMP heat treatment.

Slab flattening trigger for isotopic disturbance and magmatic flare-up in the southernmost Sierra Nevada batholith, California

The San Emigdio Schist of the southwestern Sierra Nevada batholith (SNB) permits examination of partial melting and devolatilization processes along a Late Cretaceous shallow subduction zone. Detrital and metamorphic zircon of the structurally highest and earliest subducted portions of the San Emigdio Schist constrain the depositional age to between ca. 102 and 98 Ma. Zircon oxygen isotope data from both lower plate schist and upper plate batholithic assemblages reveal a δ^(18)O shift of ~ 1.5‰ between igneous (~ 5.5‰) and metamorphic (~ 7‰) domains. These results, taken with previous zircon and whole-rock δ^(18)O measurements, provide evidence for massive devolatilization of the San Emigdio Schist and fluid traversal of upper plate batholithic assemblages, thereby altering the isotopic composition of overlying material. Furthermore, the timing of fluid-rock interaction in the southwestern SNB is coincident with eastward arc migration and an associated pulse of voluminous magmatism. We posit that during flattening of the Farallon slab the schist was rapidly emplaced beneath the magmatic source, where ensuing devolatilization triggered a magmatic flare-up in the southeastern SNB. This short-lived (< 15 Myr) high-flux event was followed by the termination of arc magmatism as the shallow subduction zone approached thermal equilibrium.

Understanding processing–microstructure–properties relationships in Bi2Sr2CaCu2Ox/Ag round wires and enhanced transport through saw-tooth processing

Superconducting magnets generating magnetic fields above 25 T are needed for many scientific applications. Due to fundamental limitations in NbTi and Nb3Sn, such high-field superconducting magnets require alternative high-field conductors. One candidate conductor is round wire composites of Bi2Sr2CaCu2Ox sheathed in a Ag-alloy matrix (Bi2212/Ag). The performance of such wires is sensitive to the heat treatment, so improvements in the critical current density (Jc) require a thorough understanding of the processing–structure–properties relationships. Here we present a two-part study. In part I, a new heat treatment approach, saw-tooth processing (STP), is introduced based upon previous results showing that Bi2212 nucleation is site-saturation limited. The microstructural evolution of Bi2212 filaments during processing is discussed and results from STP are compared with those from other processes. STP is shown to increase Jc by 120% and 70% relative to partial-melt processing at 5 T and self-field respectively, and by 65% and 34% relative to split-melt processing. Yet STP also complicates the heat treatment by introducing a number of new heat treatment variables that affect the grain morphology, phase assemblage and oxygen content of the Bi2212 filaments and thus the transport properties. In part II, the effects of STP heat treatment parameters on the microstructure and transport properties are discussed. It is shown that wires with the highest transport critical current densities primarily have filaments with two types of microstructures, one comprised primarily of highly textured Bi2212 grains, and another with a noticeable amount of Bi2Sr2CuOx with the Bi2212.

Geochemistry of Huyanshan Alkaline Complex, Shanxi Province, China: Evidences for the Sources of Magma

The Huyanshan alkaline complex outcrops in the middle part of the eastern wing of the Lvliang Mountain in Shanxi Province. Due to its typical alkaline rock type, the Huyanshan alkaline complex has attracted much attention from the geological field all the time. This paper describes the characteristic of trace elements of the Huyanshan alkaline complex and discussed the scientific problems such as magma sources and substance composition. The primitive mantle-normalized trace element spider diagram shows that the Huyanshan alkaline complex are enriched in Pb, Hf, Sr, Ba, Cs, Th, U and depleted in Cr, Ni and Co. The data presented indicates that the complex has deep source characteristic and derives from enriched mantle controlled by spinel peridotite partial melting process.

Geochronology and geochemistry of Neoproterozoic Mt. Abu granitoids, NW India: Regional correlation and implications for Rodinia paleogeography

The ∼125km2 Mt. Abu granitic pluton in Rajasthan, northwestern India, consists of variably deformed, subsolvus, dominantly metaluminous, I-type, porphyritic hornblende-biotite granitoids that are crosscut by both rhyolitic and mafic dykes. Weakly deformed varieties occur mainly in the central regions of the pluton, and gneissic varieties, including distinctive augen gneisses are found on the margins, especially on the northwestern side. Modest diversity in major and trace element chemistry (SiO2=72.8±2.8wt.%; La=100–400× chondrites) is attributed to variable partial melting processes rather than to fractional crystallization. U–Pb zircon analyses (TIMS method) for three samples representing both deformed and undeformed granitoid types yield nearly concordant dates of 765±5Ma, which we interpret as the time of magmatic crystallization. This demonstrates that the Mt. Abu granitoids are coeval and correlative with volcanic and plutonic rocks of the nearby Malani Igneous Suite, rather than with the Erinpura granites, which are demonstrably older by ∼100m.y. We further show that Mt Abu granitoids are geochemically and petrologically distinct from Erinpura granitoids, but match those from the Malani Igneous Suite and Praslin Group granitoids of the Seychelles, which, along with northern Madagascar, formed now-fragmented components of an Andean-type magmatic arc on the margin of the Rodinia supercontinent. 40Ar/39Ar isotopic data on a hornblende separate from a weakly deformed Mt. Abu granite yield an age of 509±2Ma, and a biotite separate from the type locality of Erinpura granitic augen gneiss yields an age of 514±2Ma; we interpret these ages as representing the time of a fabric-forming event that reached amphibolite grade. This late Pan-African age demonstrates that the effects of Gondwana assembly and collapse extend into northwestern India, and must have also affected sedimentary rocks of the Marwar Supergroup, which are likely equivalents of the extensive earliest Paleozoic sandstones of North Africa. Deformation of the Mt. Abu granitoids and Marwar supracrustal rocks may be related to late Pan-African collisional events, and/or to collapse of the mountains formed during the final assembly of the Gondwana supercontinent.

The 36–18 Ma Indian Peak–Caliente ignimbrite field and calderas, southeastern Great Basin, USA: Multicyclic super-eruptions

The 36–18 Ma Indian Peak–Caliente ignimbrite field and calderas, southeastern Great Basin, USA: Multicyclic super-eruptions

The carbonated source region of Cenozoic mafic and ultra-mafic lavas from western Qinling: Implications for eastern mantle extrusion in the northeastern margin of the Tibetan Plateau

Cenozoic Indo-Asian collision caused significant crustal shortening in central Tibet. The strike-slip faults around the Tibetan Plateau (TP) are generally attributed to extrusion tectonics, resulting from lower crust flow. Therefore, the mantle extrusion site corresponding to the Cenozoic elevation of the TP needs to be identified. This paper reports the petrology and geochemistry of Cenozoic mafic and ultra-mafic volcanic rocks in the Xiahe and Lixian areas, at the northeastern margin of the TP. Detailed analysis indicates a regular change in partial melting conditions and source regions of the volcanic rocks from west to east, revealing a Cenozoic eastward mantle extrusion in the eastern margin of the TP. The Xiahe volcanic rocks display ocean island basalt affinity with negative K anomalies and positive Nb and Ta anomalies. They are alkaline with extremely high Na2O/K2O ratios and relatively enriched Sr–Nd–Pb isotopic compositions, indicating that these basalts were derived from partial melting of carbonated pyroxenite. The Lixian picro-basalts are closely associated with igneous carbonatites. They have relatively high TiO2 (3.47–4.66%) and MgO (11.24–18.88%) contents and low SiO2 (41.14–44.82%) and Al2O3 (5.84–9.18%) contents. Based on the depleted Sr–Nd–Pb isotopic compositions, we propose that the Lixian picro-basalts may have originated from the partial melting of carbonated lithosphere mantle peridotites at relatively high pressure (>3GPa). Minor hornblendite in their source region can account for the high TiO2 and Na2O+K2O contents. Thus, we argue that these volcanic rocks were formed by episodic decompression melting of the carbonated mantle lithosphere during the eastward extrusion of the Tibetan lithosphere, in contrast to the conventional view that they were formed in a continental rift setting. Their partial melting and eruption processes may be closely related to the Cenozoic strike-slip fault activities in the northeastern margin of the TP.

Progress of long coated conductors fabrication with fluorine-free CSD method at SWJTU

Recent progress on the fabrication of long high-Tc superconducting coated conductors with a fluorine-free chemical solution deposition (CSD) method is presented. Developments including such novel methods as single buffer technology, partial-melting process on YBa2Cu3O7 (YBCO), slot-die coating and drying; reel-to-reel facilities for continuous process have been achieved in the effort on high-Tc superconducting coated conductors at SWJTU, which form a comprehensive technology to fabricate long coated tapes with high performances.