Enrichment Of Nb Research Articles

Origin of the alkali tonsteins from southwest China: Implications for alkaline magmatism associated with the waning stages of the Emeishan Large Igneous Province

ABSTRACTA unique type of Nb–Zr–REE–Ga-enriched alkali tonstein of pyroclastic origin occurs exclusively within the late Permian coal measures of southwest China. The alkali tonsteins are located within the lowest Xuanwei or Longtan formations of Wuchiapingian age, indicating that their age is later than the main episode of Emeishan Large Igneous Province (ELIP) magmatism. The alkali tonsteins have intermediate–felsic Al2O3/TiO2 values (12.6–34.2, mean 22.0), light rare earth element-enriched chondrite-normalised patterns, negative δEu and incompatible element ratios similar to those of ELIP alkaline Nb–Ta-enriched syenites. All available evidence shows that the alkali tonsteins from southwest China originated from coeval ELIP alkaline magmatism. The enrichment of Nb–Zr–REE–Ga in alkali tonsteins is derived from the ELIP alkaline Nb–Ta-enriched volcanic ashes and may represent the last stage of mineralisation associated with the Emeishan mantle plume activity.

Mineralogy and Beneficiation of Lamujärvi Syenites

The Lamujarvi syenites intrusions occur within Svecofennian (ca. 1.92 Ga) gneisses, ca. 70 km west of the Otanmaki alkaline area in central Finland. Previous studies have revealed zones in the syenites that display strong enrichment in Zr (1587 ppm), Nb (up to 685 ppm), Ta (up to 82 ppm), and REE (up to 5350 ppm). The major REE-bearing minerals in the Lamujarvi syenites are allanite and monazite. A sample of the Lamujarvi syenites with the REE content of 4700 ppm was studied on the mineralogy and beneficiation at GTK Mintec. The mineralogical analysis was conducted by MLA. The REE-bearing minerals allanite, parisite, zircon, and apatite were identified at significant concentrations and high contents of titanite (15.4%), biotite (30.9%) and magnetite (8.2%) were displayed in the sample. The beneficiation experiments by flotation, wet low and high gradient magnetic separations and gravity separation with a shaking table were carried out. A composite REE-Ti concentrate with REE 23,000 ppm, Zr 5000 ppm, Nb 3400 ppm and TiO2 25.5% at REE and Ti recoveries of 57% and 54% was obtained. In addition, biotite and magnetite concentrates were gained as by-products.

Geochemistry and geochronology of the blueschist in the Heilongjiang Complex and its implications in the late Paleozoic tectonics of eastern NE China

The Paleozoic to early Mesozoic tectonic framework and evolution of Northeast China, especially the Jiamusi block and its related structural belts, are highly debated. In this paper, geochemical, geochronological and isotopic analyses were carried out on the blueschist in the Heilongjiang Complex to address these issues. The Heilongjiang Complex defines the suture belt between the Jiamusi block and the Songliao block in NE China, and the blueschist is a major composition for this complex, coexisting with mafic-ultramafic rocks, greenschist, quartzite and mica schist. The blueschist has a mineral association of sodic amphibole, epidote, chlorite, phengite, albite and quartz with accessory phases of apatite, titanite, zircon and ilmenite. Together with the lithological association, the major and trace element compositions present that the protoliths of the blueschist can be divided into the alkaline and tholeiitic basalts and have OIB affinities, formed in an ocean island setting, indicated by the (La/Yb) N values of 3.57 – 11.54, and the (La/Sm) N values of 0.69 – 3.64. The high and positive εNd (t) values of+3.7 to +9.0, and relative enrichment in Nb (vs. Th) and Ta (vs. U) show that both the alkaline and tholeiitic basalts may be derived from the asthenospheric mantle with insignificant crustal contamination. Magmatic zircons from the blueschist in Yilan area yield a 206Pb/238U age of 281±3Ma, interpreted as its protolithic age. The youngest ages of~200Ma of the detrital zircons in the associated mica schist from Mudanjiang area place constraints on the timing of metamorphism for the blueschist. These indicate that a big ocean existed between the Jiamusi and Songliao blocks at least since the early Permian, and the blueschist formed since the late Triassic to late Jurassic by the subduction of this ocean. Such an ocean during the Permian – Jurassic is difficult to be interpreted by the tectonic evolution of the Paleo-Asian Ocean.

Petrogenesis of high-Ti mafic dykes from Southern Qiangtang, Tibet: Implications for a ca. 290 Ma large igneous province related to the early Permian rifting of Gondwana

The presence and/or generation mechanism of a mantle plume associated with early Permian rifting on the northern margin of Gondwana are topics of debate. Here we report LA–ICP–MS U–Pb zircon ages, whole-rock geochemistry, and Sr–Nd isotope data for high-Ti mafic dykes from southern Qiangtang, Tibet, with the aim of assessing if a mantle plume formed in this region during the early Permian. Zircon U–Pb dating of diabase dykes yielded ages of 290.6±3.5Ma and 290.1±1.5Ma, indicating they were emplaced during the early Permian. Whole-rock geochemistry shows that these mafic dykes are alkaline (Nb/Y=0.73–0.99), have high TiO2 (3.6%–4.8%), and have ocean-island basalt (OIB)-like trace element patterns with enrichments in Nb, Ta, and Ti. Whole-rock Sr–Nd isotope data show a relatively narrow range of εNd(t) (+2.29 to +3.53), similar to basalts produced by a mantle plume (e.g., Emeishan continental flood basalts (ECFB)). Elemental and isotope data suggest that the dykes have undergone fractionation crystallization of mafic minerals and have experienced negligible crustal contamination. These mafic rocks show an affinity to OIB and may have been generated by partial melting of an OIB-type, garnet-bearing asthenospheric mantle source. On the basis of a similar emplacement age to the Panjal Traps basalts in the Himalayas, combined with a tectonic reconstruction of Gondwana in the early to middle Permian, our work suggests that the high-Ti mafic dykes in the Southern Qiangtang terrane and the coeval Panjal Traps basalts in the Himalayas together comprise a ca. 290Ma large igneous province linked to a mantle plume, which probably played an active role in early Permian rifting on the northern margin of Gondwana and was related to circum-Pangea subduction.

Study on the microstructure, phase transition and hardness for the TiAl–Nb alloy design during directional solidification

Bridgman-type directional solidification experiments were conducted for the TiAl–Nb alloys. The microstructure, phase transition and the hardness were investigated for the composition design. The S- and β-segregation are observed corresponding to solute Nb enrichment in primary β/α phase during the solidification and in the retained β phase during the β → α transition respectively. The improved Nb addition can promote the L + β + α peritectic solidification to the fully β solidification in Ti–46Al alloy, and even the fully α solidification to the β solidification in Ti–50Al alloy. During the peritectic solidification the S-segregation and the further β-segregation lead to the highly solute enrichment and the inhomogeneous multi-phase structure, in which B2 phase and massive γ lamellar from the Nb enrichment in the core of dendrites and the coarse α2/γ lamellar from the Al enrichment in the interdendritic region greatly decrease the hardness in TiAl–Nb alloy, leading to the scatter mechanical properties. Finally the low-(Al, Nb) TiAl–Nb alloy with the fully β solidification is proper for the favorable mechanical property due to its homogeneous microstructure with the weak solute segregation.

Geochemistry, petrogenesis and tectonic setting of Neoproterozoic mafic–ultramafic rocks from the western Jiangnan orogen, South China

The Jiangnan orogenic belt (JOB) has been interpreted as a suture zone between the Yangtze craton and Cathaysian terranes in South China. The Neoproterozoic mafic–ultramafic rocks are extensively exposed in the western JOB, providing an ideal opportunity to study the Neoproterozoic assembly and tectonic evolution of South China. We present integrated field and geochemical studies including LA-ICP-MS zircon U–Pb dating, and whole-rock major and trace element and Sm–Nd isotope analyses of the Neoproterozoic mafic–ultramafic rocks exposed in the northern Guangxi Province, South China. Geochronological results show that the magmatic events took place in two distinct periods: the early Neoproterozoic (861–834Ma) and the late Neoproterozoic (770–750Ma). Early Neoproterozoic ultramafic rocks of the Sibao Group have positive εNd(t) values (+2.7 to +6.6) whereas mafic rocks exhibit negative εNd(t) values (−5.8 to −0.9). The basaltic rocks show TiO2 contents of 0.62–0.69wt.% and Mg-number of 59–65, and also display an enrichment of light rare earth elements (LREEs) and pronounced negative Nb, Ta and Ti anomalies on chondrite- and primitive mantle-normalized diagrams, consistent with subduction-related geochemical signatures. Late Neoproterozoic rocks of the Danzhou Group show εNd(t) values (−1.23 to +3.19) for both ultramafic and mafic rocks. The basaltic rocks have TiO2 contents of 1.01–1.33wt.% and Mg-number of 57–60, and have a mixture of MORB- and arc-like geochemical affinities, inferred to have formed in an extensional arc environment. Geochemical signatures suggest that all rock types in this study were derived from subarc mantle wedge sources and underwent various degrees of crustal contamination. Thus, we suggest that subduction may have continued to ca. 750Ma in the western JOB, implying that the amalgamation event between the Yangtze craton and Cathaysian terranes was later than 750Ma.

Geochemistry, geochronology and Sr–Nd–Pb–Hf isotopic compositions of Middle to Late Jurassic syenite–granodiorites–dacite in South China: Petrogenesis and tectonic implications

In situ zircon U–Pb ages and Hf isotope data, major and trace elements and Sr–Nd–Pb isotopic compositions are reported for coeval syenite–granodiorites–dacite association in South China. The shoshonitic syenites are characterized by high K2O contents (5.9–6.1wt.%) and K2O/Na2O ratios (1.1–1.2), negative Eu anomalies (Eu/Eu*=0.65 to 0.77), enrichments of Rb, K, Nb, Ta, Zr and Hf, but depletion of Sr, P and Ti. The adakitic granodiorite and granodiorite porphyry intrusions are characterized by high Al2O3 contents (15.0–16.8wt.%), enrichment in light rare earth elements (LREEs), strongly fractionated LREEs (light rare earth elements) to HREEs (heavy rare earth elements), high Sr (438–629ppm), Sr/Y (29.2–53.6), and low Y (11.7–16.8ppm) and HREE contents (e.g., Yb=1.29–1.64ppm). The calc-alkaline dacites are characterized by LREE enrichment, absence of negative Eu anomalies, and enrichment of LILEs such as Rb, Ba, Th, U and Pb, and depletion of HFSEs such as Nb, Ta, P and Ti.Geochemical and Sr–Nd–Hf isotopic compositions of the syenites suggest that the shoshonitic magmas were differentiated from parental shoshonitic melts by fractional crystallization of olivine, clinopyroxene and feldspar. The parent magmas may have originated from partial melting of the lithospheric mantle with small amount contribution from crustal materials. The adakitic granodiorite and granodiorite porphyry have Sr–Nd–Pb isotopic compositions that are comparable to that of the mafic lower crust. They have low Mg# and MgO, Ni and Cr contents, abundant inherited zircons, low εNd(t) and εHf(t) values as well as old whole-rock Nd and zircon Hf model ages. These granodiorites were likely generated by partial melting of Triassic underplated mafic lower crust. The Hf isotopic compositions of the dacites are relatively more depleted than the Cathaysia enriched mantle, suggesting those magmas were derived from the partial melting of subduction-modified mantle sources. The coeval shoshonitic, high-K calc-alkaline and calc-alkaline rocks in Middle to Late Jurassic appear to be associated with an Andean-type subduction. This subduction could have resulted in the upwelling of the asthenosphere beneath the Cathaysia Block, which induced partial melting of the mantle as well as the mafic lower crust, and formed an arc regime in the coastal South China during Middle to Late Jurassic.

Mineralogical and geochemical aspects of Miocene laterite, Sharm Lollia area, South Eastern Desert, Egypt

A lateritic soil profile formed on the top of the middle Miocene was identified in the south of the Eastern Desert of Egypt. It is located about 55 km south of Marsa Alam and far about 3 km from the Red Sea coast. The mineral identification of samples was carried out using X-ray diffraction (XRD) and scanning electron microscope (SEM). The study revealed the relative predominance of kaolinite and gibbsite beside iron minerals (hematite and goethite), evaporates (halite and anhydrite), carbonate (dolomite and calcite), quartz, and cryptomelane. Accessory minerals are represented by columbite, tapiolite, thorite, monazite, zircon, barite, atacamite, anarkite, romanchite, hemimorphite, cerussite, garnet, ilmenite, nickel, and flurorichterite. The geochemical data of the bulk samples reflect enrichment in SiO2, Al2O3, Fe2O3, Zn, Pb, Ba, Sr, As, Nb, Cu, and Zr. This lateritic soil shows high Uc/Th ratio indicating addition of uranium under suboxic to anoxic condition. The LREE predominance was over the HREE due to the presence of monazite mineral. Negative Eu anomaly confirms the saturated source rocks of these laterites.

Sources of rare-metal-bearing A-type granites from Jabel Sayed complex, Northern Arabian Shield, Saudi Arabia

Jabel Sayed, in the northern part of the Arabian Shield, is an alkaline granite complex. It consists of syenogranites and aegirine–riebeckite alkali feldspar granites intruded into an older granodiorite–tonalite suite. Elemental geochemistry attests that the syenogranite and the alkali feldspar granite represent a genetically related post-collisional A2-type granite intrusion (e.g., high K2O+Na2O, FeO∗/MgO, Ga/Al, and Y/Nb, and low CaO, Ba, and Sr). U–Pb zircon dating and Nd isotopes of the alkali feldspar granites indicate an age of 593Ma, εNd(t) values of +4.9 to +5.3 (mean=+5.1), and depleted mantle model ages (tDM) between 0.78 and 0.88Ga. These isotope results are in agreement with a juvenile magma source of Neoproterozoic age like that responsible for forming most other Arabian–Nubian Shield crust. The alkali feldspar granites have substantial modal content of albite and fluorite, wide variation of HFSE and REE and exhibit tetrad effects in REE patterns that indicate interaction with hydrothermal F-rich fluids. The fluids caused secondary metasomatic alteration superimposed on the granitic rocks. The result of the fluids–granitic rock interaction is a metasomatic pegmatite rim, which carries economic levels of HFS elements and REE, and a red granite variety (altered syenogranite) characterized by large variation in trace element abundances. Geochemical features in the granitic rocks such as strong linear positive correlation of Ta versus Nb and Zr versus Hf indicate magmatic origin of the fluids and emphasize that the behavior and enrichment of Ta and Nb are largely controlled by magmatic processes. Based on the geochemical and Nd isotopes compositions, we propose an origin for the Jabel Sayed granites which involved fractional crystallization of a parental magma derived by the partial melting of a crustal protolith accreted between 780Ma and 880Ma. This crustal protolith has juvenile geochemical and isotopic composition and was extracted from a subduction modified mantle source.

Electrodeposition and Characterisation of Novel Ni-NbOx Composite Coatings as a Diffusion Barrier for Liquid Solder Interconnects - Part II: Diffusion Barrier Performance

The control of interfacial microstructural stability is of utmost importance to the reliability of liquid solder interconnects in high temperature electronic assemblies. This is primarily due to excessive intermetallic compounds (IMCs) that can form and continuously grow during high temperature operation, which renders conventional barrier metallisations inadequate. With the intention of reducing such excessive IMC growth, electrically conducting, NbOx containing Ni coatings were developed using electrodeposition and were assessed as solder diffusion barrier layers in terms of their electrical conductivity and barrier property. The present work adopts a novel electrochemical route to produce Ni-NbOx composite coatings of good uniformity, compactness and purity, from non-aqueous glycol-based electrolytes consisting of NiCl2 and NbCl5 as metal precursors. The effects of cathodic current density and NaBH4 concentrations on the surface morphology, composition and thickness of the coatings were examined. Increased NaBH4 concentrations were found to elevate the maximum deposit thickness (above 10 µm), although these led to a reduction in the co-deposited Nb content. The composite coatings generally exhibited good electrical conductivity. The reaction between a liquid 52In-48Sn solder and Ni-NbOx, with Nb contents up to 6 at.%, was studied at 200ºC. The results indicate that, Ni-NbOx with sufficient layer thickness and higher Nb content, offered longer service lifetime. Nb enrichment was generally observed at or close to the reaction front after high temperature storage which suggests evident effectiveness of the enhanced diffusion barrier characteristics. A mechanism for the role of Nb as a barrier performance enhancer was postulated.

The olivine macrocryst problem: New insights from minor and trace element compositions of olivine from Lac de Gras kimberlites, Canada

This study presents detailed petrographical and geochemical investigations on remarkably fresh olivines in kimberlites from the EKATI Diamond Mine™ located in the Tertiary/Cretaceous Lac de Gras kimberlite field within the Slave craton of Canada.Olivine, constituting about 42vol.% of the analyzed samples, can be divided into two textural groups: (i) macrocrystic olivines, >100μm sub-rounded crystals and (ii) groundmass olivines, <100μm subhedral crystals. Olivines from both populations define two distinct chemical trends; a “mantle trend” with angular cores, showing low Ca (<0.1wt.% CaO) and high Ni (0.3–0.4wt.% NiO) at varying Mg# (0.86–0.93), contrasts with a “melt trend” typified by thin (<100μm) rims with increasing Ca (up to 1.0wt.% CaO) and decreasing Ni (down to 0.1wt.% NiO) contents at constant Mg# (~0.915). These findings are in agreement with recent studies suggesting that virtually all olivine is composed of xenocrystic (i.e. mantle-related) cores with phenocrystic (i.e. melt-related) overgrowths, thereby challenging the traditional view that the origin of kimberlitic olivine can be distinguished based on size and morphology.The two main trends can be further resolved into sub-groups refining the crystallization history of olivine; the mantle trend indicates a multi-source origin that samples the layered lithosphere below the Slave craton, whereas the melt trend represents multi-stage crystallization comprising a differentiation trend starting at mantle conditions and a second trend controlled by the crystallization of additional phases (e.g. chromite) and changing magma conditions (e.g. oxidation). These trends are also seen in the concentrations of trace elements not routinely measured in olivine (e.g. Na, P, Ti, Co, Sc, Zr). Trace element mapping with LA-ICP-MS reveals the distribution of these elements within olivine grains. The trace element distribution between the two trends appears to be consistent with phenocrystic olivine overgrowths mainly originating from dissolved orthopyroxene, showing enrichment in Zr, Ga, Nb, Sc, V, P, Al, Ti, Cr, Ca and Mn in the melt trend.In a sample of magmatic kimberlite from the Leslie pipe, the amount of xenocrystic and phenocrystic olivine is estimated to be around 23vol.% and 19vol.%, respectively. Subtraction of this xenocrystic olivine from the Leslie bulk composition, aimed at estimating the parental kimberlite melt, results in a minor decrease of Mg# (by about 0.01) and SiO2 content (by about 3wt.%), whereas CaO increases (by about 3wt.%).

Transition from I‐type to A‐type magmatism in the Sanandaj–Sirjan Zone, NW Iran: an extensional intra‐continental arc

The South Dehgolan pluton, in NW Iran was emplaced into the Sanandaj–Sirjan magmatic–metamorphic zone. This composite intrusion comprises three main groups: (1) monzogabbro–monzodiorite rocks, (2) quartz monzonite–syenite rocks, and (3) a granite suite which crops out in most of the area. The granites generally show high SiO2 content from 72.1%–77.6 wt.% with diagnostic mineralogy consisting of biotite and amphibole along the boundaries of feldspar–quartz crystals which implies anhydrous primary magma compositions. The granite suite is metaluminous and distinguished by high FeOt/MgO ratios (av. 9.6 wt.%), typical of ferroan compositions with a pronounced A‐type affinity with high Na2O + K2O contents, high Ga/Al ratios, enrichment in Zr, Nb, REE, and depletion in Eu. The quartz monzonite–syenites show intermediate SiO2 levels (59.8%–64.5 wt.%) with metaluminous, magnesian to ferroan characteristics, intermediate Na2O + K2O contents, enrichment in Zr, Nb, REE, Ga/Al, and depletion in Eu. The monzogabbro–monzodiorites show overall lower SiO2 content (48.5%–55.9 wt.%) with metaluminous and calc‐alkaline compositions, relatively lower Na2O + K2O contents, low Ga/Al ratios, and FeOt/MgO (av. 1.6 wt.%) ratios, low abundances of Zr, Nb, and lower REE element concentrations relative to the granites and quartz monzonite–syenites. These geochemical differences among the three different rocks suites are likely to indicate different melt origins. We suggest that the South Dehgolan pluton resulted from a change in the geodynamic regime, from compression to extension in the Sanandaj–Sirjan zone during Mesozoic subduction of the Neo‐Tethys oceanic crust beneath the Central Iranian microcontinent. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Petrogenesis of basalt–high-Mg andesite–adakite in the Neoarchean Veligallu greenstone terrane: Geochemical evidence for a rifted back-arc crust in the eastern Dharwar craton, India

The ∼2.7Ga Veligallu greenstone terrane in the eastern Dharwar craton is one of the least studied Neoarchean greenstone belts in India. To our knowledge, there is no published dataset that provides a detailed account of the petrogenetic processes, which culminated into the evolution of this greenstone belt. This paper presents a comprehensive account of field, petrography and geochemistry of the basalt–high-Mg andesite–adakitic volcanic rock association in the Veligallu greenstone belt.The basalts are tholeiitic in nature and are characterized by primitive geochemical compositions with ∼49wt% SiO2, ∼9wt% MgO, Mg# 54, Cr∼197ppm, Ni∼122ppm, Y∼27ppm, Yb∼2.7ppm; Zr/Y<3 and Ce/Yb<5. They do not plot on a mixing line between Mesoarchean TTG and N-MORB, therefore, inconsistent with any interaction with the upper continental crust. Accordingly, they are interpreted to have erupted in an oceanic setting. On the basis of Nb/Th ratio the Veligallu basalts are divided onto two groups. The basalts with Nb/Th>8 display systematically flat to light-REE depleted chondrite normalized REE patterns (LaN/YbN=0.76–1.0), in contrast to the samples with Nb/Th<8, which display slight enrichments in light-REE (LaN/YbN=1.0–1.6). The depleted basalts are characterized by primitive mantle normalized Nb concentrations lower than La but equal to Th, in contrast to the enriched basalts, which are characterized by slight depletions of Nb relative to both La and Th. Collectively, as a group, they display Nb/Yb ratio higher than the N-MORB. The enrichment in Nb is attributed to moderate to low degree (∼10%–4%) partial melting of a depleted MORB source. The trace, REE and their interelement ratios in the Veligallu basalts exhibit transitional characteristics between the average N-MORB and the typical Phanerozoic island arc basalts. Overall, the geochemical characteristics of the Veligallu basalts are identical to basalts erupted in the Phanerozoic back-arc basins.The Veligallu high-Mg andesites are orthopyroxene-bearing calc-alkaline andesites and are characterized by moderate SiO2 (∼56wt%), high MgO (∼8wt%), Mg# (61–67), Cr (174–330ppm) and Ni (173–242ppm) contents; low Y (∼13ppm) and Yb (∼1.2ppm) concentrations, relative to typical island arc andesites. They exhibit light-REE enriched (LaN/SmN∼1.7) and heavy-REE depleted (GdN/YbN∼1.9) fractionated REE patterns. On a primitive mantle normalized trace element variation diagram they exhibit negative Nb and Ti, and contrasting positive Zr anomalies relative to the neighboring REE. The La–Yb systematics suggest that these high-Mg andesites were generated by hydrous partial melting of a slab-melt metasomatized mantle wedge in the sub-arc mantle. The felsic volcanic rocks are characterized by high SiO2∼73wt%, Na2O∼4.5wt%, and significantly low concentrations of MgO (∼0.72wt%), Cr∼19ppm, Ni∼23ppm, Y∼5.9, and Yb∼0.44ppm; strongly fractionated chondrite normalized REE patterns (LaN/YbN∼30) with occasionally minor positive Eu anomaly, and primitive mantle normalized negative Nb and Ti, and contrasting positive Zr anomaly. The geochemical attributes of the Veligallu felsic volcanic rocks are analogous to the Cenozoic high silica-type adakites that are produced by partial melting in the sub-arc mantle, and presumably without any significant interaction of the slab-melts with the overlying mantle wedge.The juxtaposed occurrence of basalts with the banded iron formations, and their close spatial association with the high-Mg andesites, in the Veligallu greenstone belt, indicates that the petrogenesis of these volcanic rocks is consistent with their eruption in an intraoceanic setting. The close proximal association of the back-arc type basalts, and the high-Mg andesites and adakites within the Veligallu greenstone belt potentially suggests that this greenstone belt represents a rifted back-arc crust. This event appears to have significantly contributed to the peak of crustal growth activity in the eastern Dharwar craton at 2.7Ga.

Diffusion Barrier Characteristics of Ni-NbOx Composite Electrodeposits for Liquid In-Sn Solder Interconnects

The control of interfacial microstructural stability is of utmost importance to the reliability of liquid solder interconnects in high temperature electronic assemblies. This is primarily due to excessive intermetallic compounds (IMCs) that can form and continuously grow during high temperature operation, which renders conventional barrier metallizations inadequate. With the intention of reducing such excessive IMC growth, electrically conducting, NbOx containing Ni coatings were developed using electrodeposition and were assessed as solder diffusion barrier layers in terms of their electrical conductivity and barrier property. The present work adopts a novel electrochemical route to produce Ni-NbOx composite coatings of good uniformity, compactness and purity, from non-aqueous glycol-based electrolytes consisting of NiCl2 and NbCl5 as metal precursors. The effects of cathodic current density and NaBH4 concentrations on the surface morphology, composition and thickness of the coatings were examined. Increased NaBH4 concentrations were found to elevate the maximum deposit thickness (above 10 μm), although these led to a reduction in the co-deposited Nb content. The composite coatings generally exhibited good electrical conductivity. The reaction between a liquid 52In-48Sn solder and Ni-NbOx, with Nb contents up to 6 at.%, was studied at 200°C. The results indicate that, Ni-NbOx with sufficient layer thickness and higher Nb content, offered longer service lifetime. Nb enrichment was generally observed at or close to the reaction front after high temperature storage which suggests evident effectiveness of the enhanced diffusion barrier characteristics. A mechanism for the role of Nb as a barrier performance enhancer was postulated.

Neoproterozoic continental arc volcanism at the northern edge of the Arabian Plate, SE Turkey

New geochemical, Sr/Nd isotope and zircon U–Pb LA-ICP-MS data from the Derik Volcanics in the Southeast Anatolian Autochthone Belt of Turkey are consistent with an Andean-type Cadomian arc that developed along the northern edge of the Arabian Plate during the Late Neoproterozoic. The Derik Volcanics represent a volcanic complex including andesites, rhyolites and basalts, with volcanoclastic and fluvial sediments. They are unconformably overlain by playa sediments with Early Cambrian ichno-fossils, followed by Middle Cambrian-Silurian shallow marine deposits.Geochemically, the Derik Volcanics (DV) display transitional-calcalkaline affinities. On Th/Nb–Ti/Zr diagram, DV display negative trends from rhyolites to late to early-stage andesites and mafic dykes, respectively. The REE patterns are highly to moderately fractionated, with [(La/Yb)N=5.20–6.77 in late-stage andesites, 4.38–10.51 in rhyolites, 2.58–4.65 in the early-stage andesites, and 2.51–4.21 in mafic dykes]. Normalized trace element and REE diagrams display Th, La, Ce, Sm enrichment and depletion of Nb, Ti and Eu as is typical for Andean-type active continental margin igneous rocks. The enrichment of LILE and LREE, combined with depletion of HREE also suggests that the Derik Volcanic rocks were formed in relation with a subduction zone. Negative Eu anomalies (Eu/Eu)N, range from 0.50 to 1.81, indicates fractional crystallization of feldspar. The DV have positive ɛNd (+0.15 to +4.20) and mean model ages of 1.28Ga for the early-stage andesites, 1.34Ga for rhyolites, 1.35 for late-stage andesites, and 1.36Ga for mafic dykes. The positive ɛNd(T) data show that DV are product of mantle-derived magmas. Lower 143Nd/144Nd isotope ratios than the depleted MORB mantle (DMM) source indicate that the DV may have been contaminated by crustal material during magma genesis. Geochemical modeling shows that all four volcanic rock types may have been formed by different percentages of batch melting of DMM and subducting slab sources.Zircon LA-ICP-MS data give crystallization ages of 581.4±3.5Ma (n=7) and 559.2±3.2Ma (n=3) for the early and late-stage andesitic rocks, as well as ages of 569.6±1.6Ma (n=17), 571.6±1.9Ma (n=18), 575.4±4.3Ma (n=6) for the rhyolites.The geological and geochemical features together with the new age data suggest that the Derik Volcanics formed along a continental arc in the course of the southward subduction of Prototethys oceanic lithosphere along the northern margin of the Arabian Plate, which is attributed to a late-stage phase of the Cadomian Orogeny of the Pan-African cycle.

Petrology and Sr–Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province

Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69–75), clinopyroxene (Mg# = 75–84), intercumulus plagioclase (An53–86) and Fe–Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than plagioclase and Fe–Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35–39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive εNdi values (4·3–4·8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr–Nd isotopic disequilibrium between clinopyroxene and plagioclase separates: 87Sr/86Sri (0·7038–0·7041) and εNdi (1·0–1·9) of clinopyroxene are lower and higher than the respective ratios of intercumulus plagioclase (87Sr/86Sri = 0·7042–0·7043, εNdi = 0·4–1·0). The 87Sr/86Sri and εNdi of clinopyroxene separates correlate positively and negatively with Zr/Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. 87Sr/86Sri increases and εNdi decreases with increasing Ca content of plagioclase, indicating that higher An plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and εNdi of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean–Neoproterozoic basement and carbonates as contaminants.

In situ analyses of micas in the Yashan granite, South China: Constraints on magmatic and hydrothermal evolutions of W and Ta–Nb bearing granites

Most rare-metal granites in South China host major W deposits with few or without Ta–Nb mineralization. However, the Yashan granitic pluton, located in the Yichun area of western Jiangxi province, South China, hosts a major Nb–Ta deposit with minor W mineralization. It is thus important for understanding the diversity of W and Nb–Ta mineralization associated with rare-metal granites. The Yashan pluton consists of multi-stage intrusive units, including the protolithionite (-muscovite) granite, Li-mica granite and topaz–lepidolite granite from the early to late stages. Bulk-rock REE contents and La/Yb ratios decrease from protolithionite granite to Li-mica granite to topaz–lepidolite granite, suggesting the dominant plagioclase fractionation. This variation, together with increasing Li, Rb, Cs and Ta but decreasing Nb/Ta and Zr/Hf ratios, is consistent with the magmatic evolution. In the Yashan pluton, micas are protolithionite, muscovite, Li-mica and lepidolite, and zircons show wide concentration ranges of ZrO2, HfO2, UO2, ThO2, Y2O3 and P2O5. Compositional variations of minerals, such as increasing F, Rb and Li in mica and increasing Hf, U and P in zircon are also in concert with the magmatic evolution from protolithionite granite to Li-mica granite to topaz–lepidolite granite. The most evolved topaz–lepidolite granite has the highest bulk-rock Li, Rb, Cs, F and P contents, consistent with the highest contents of these elements and the lowest Nb/Ta ratio in mica and the lowest Zr/Hf ratio in zircon. Ta–Nb enrichment was closely related to the enrichment of volatile elements (i.e. Li, F and P) in the melt during magmatic evolution, which raised the proportion of non-bridging oxygens (NBOs) in the melt. The rims of zoned micas in the Li-mica and topaz–lepidolite granites contain lower Rb, Cs, Nb and Ta and much lower F and W than the cores and/or mantles, indicating an exotic aqueous fluid during hydrothermal evolution. Some columbite-group minerals may have formed from exotic aqueous fluids which were originally depleted in F, Rb, Cs, Nb, Ta and W, but such fluids were not responsible for Ta–Nb enrichment in the Yashan granite. The interaction of hydrothermal fluids with previously existing micas may have played an important role in leaching, concentrating and transporting W, Fe and Ti. Ta–Nb enrichment was associated with highly evolved magmas, but W mineralization is closely related to hydrothermal fluid. Thus these magmatic and hydrothermal processes explain the diversity of W and Ta–Nb mineralizations in the rare-metal granites.

Lithospheric influences on magma compositions of late Mesozoic and Cenozoic intraplate basalts (the Older Volcanics) of Victoria, south-eastern Australia

Abstract Basaltic volcanism, ranging in age from Late Cretaceous to Holocene and extending across the southern part of the state of Victoria in south-eastern Australia was initiated during the earliest stages of rifting associated with opening of the Tasman Sea and Southern Ocean. Volcanism has continued sporadically since that time with major breaks in activity occurring between 77 and 62 Ma and 18 and 7 Ma. Basaltic rocks with ages in the range 95 to 18 Ma occur in small lava fields scattered across eastern and south-eastern Victoria and they have also been recovered from bore holes in the west of the state. They have been referred to as the “Older Volcanics” to differentiate them from more volumetrically extensive and younger (mainly Older Volcanics vary in composition from SiO 2 -undersaturated nephelinites, basanites, basalts and hawaiites through transitional basalts to hypersthene and quartz normative tholeiites. Strontium, Nd and Pb isotopic compositions lie between depleted (DM) and enriched (EM1 and EM2) end member mantle components in Sr–Nd–Pb isotopic space. Trace element compositions are generally characterised by enrichment of Cs, Ba, Rb, Th, U, Nb, K and light REE over heavy REE, Ti, Zr and Y and the overall patterns of major and trace element behaviour can be explained in general terms by petrogenetic models involving partial melting of a complex spectrum of mantle compositions with subsequent but limited additional modification by fractional crystallisation with or without assimilation of crust. Among basalts with relatively high Mg# [100 ∗ Mol. MgO/(MgO + FeO) > 65], two distinct end member compositions can be differentiated using primitive mantle normalised extended element patterns. Group 1 basalts have convex upward patterns with enrichment of light over heavy REE and depletion of Rb, Ba, Th and U relative to Nb. Group 2 basalts also have distinctive convex upwards patterns but are characterised by strong depletions of K, Rb and Ba relative to Nb. In both groups there is additional subtle variation with some samples having patterns with relative enrichments in Nb, Sr and Eu and/or depletions in Pb. Group 1 basalt compositions can be approximated by quantitative models involving 2 to 10% partial melting of an originally depleted mantle composition that has been metasomatised by the addition of 2 to 3% of an enriched component with a composition similar to EM1 intraplate basalt. The trace element patterns of Group 2 basalts can be modelled by 2 to 10% partial melting of an originally depleted mantle metasomatised by the addition of 1% of a calci-carbonatite composition. When Sr isotope data for Older Volcanics are projected onto an east–west profile across the state of Victoria, they outline distinctive discontinuities in isotopic composition that appear to be related to surface and subsurface structural features within the basement. One such discontinuity has previously been identified using data for the Newer Volcanics of the Western District Province of Victoria. Lithospheric blocks present beneath southern Victoria range in age from NeoProterozoic or Cambrian to Palaeozoic and some of the lowest 87 Sr/ 86 Sr ratios are observed in basalts erupted above an older basement unit (the Selwyn Block). The inference is that there is some form of lithospheric control on basaltic magma chemistry and since a substantial proportion of Older Volcanics have the geochemical characteristics of primary magmas (high Mg# and moderate to high abundances of Ni and Cr), this could indicate that magmas have been sourced from regionally heterogeneous, variably metasomatised, sub-continental lithospheric mantle. Neither the temporal and spatial relationships of the magmatic activity that followed continental breakup nor the uplift history of the south-eastern Australian passive margin are readily explained in terms of deep mantle plume tectonic models. Edge-driven convection across the irregular base of the southern Australian lithosphere, within the asthenosphere offers an elegant explanation for the longevity of the magmatic activity, its distribution, the small magma volumes involved and the uplift history as well as the geochemical variation observed in the eruptives.

Pyroxenite and peridotite xenoliths from Hexigten, Inner Mongolia: Insights into the Paleo-Asian Ocean subduction-related melt/fluid–peridotite interaction

The in situ major, trace-element and Sr-isotopic compositions of the peridotite and pyroxenite xenoliths from the Hexigten region in the Xing-Meng orogenic belt (XMOB) were examined to evaluate the influences and contributions of the Paleo-Asian Oceanic slab subduction on the lithospheric mantle transformation. Pyroxenes in the Type 1 pyroxenite exhibit low and variable Mg# (67–85) and relatively high 87Sr/86Sr ratios (0.7036–0.7053), indicating that they were formed by assimilation and fractional crystallization processes during a basaltic underplating event. The peridotite and Type 2 pyroxenite xenoliths sampled the lithospheric mantle and recorded subduction-related metasomatism. The mineral chemistries of the Type 1 peridotite suggest that the lithospheric mantle beneath this area suffered 1–15% melt extraction. Clinopyroxene (Cpx) in some Type 1 peridotites are characterized by high (La/Yb)N coupled with marked depletions in high field strength elements (HFSE) (Nb, Ta, Zr, Hf and Ti) and negative correlations between the low Ti/Eu (Nb/La) and 87Sr/86Sr ratios (0.7037–0.7055), suggesting metasomatism by subduction-related CO2-rich fluids. Olivine (Ol) and orthopyroxene (Opx) in the Type 2 peridotite are characterized by a relatively low Mg# but high Ni contents. In addition to the normal incompatible element-depleted Opx, Opx with enrichments in Rb, Ba, Th, U, Nb, Ta and LREE were observed, as well. The Mg# of incompatible element-depleted Opx exhibits weak zonations (i.e., decreasing from the cores to the rims). Cpx and Opx of the Type 2 pyroxenite exhibit similarly high Mg# and Ni contents. Rb, Ba, Th, U, Nb, Ta and LREE contents and 87Sr/86Sr ratios of the Cpx increase from the cores to the rims. Moreover, Opx in the Type 2 peridotite and Cpx in the Type 2 pyroxenite exhibit increased Nb/Ta ratios and Ni contents relative to those in the Type 1 peridotites. These observations collectively suggest a rutile-bearing eclogite-derived silicic melt–peridotite reaction as the origin for the Type 2 peridotite and pyroxenite. Considering the geological setting, it is suggested that the melt/fluid–peridotite interactions were caused by the Paleo-Asian Ocean subduction, which could have contributed significantly to the transformation of the lithospheric mantle beneath the northern margin of the NCC, as well.

The genesis of Zr–Nb–REE mineralisation at Khalzan Buregte (Western Mongolia) reconsidered

The sources and formation conditions of unconventional Zr–Nb–REE mineralisation (REE=rare earth elements) presently found in increasing number worldwide are still poorly constrained. One particular problem is the specific role of magmatic and hydrothermal processes active in various geological settings. Investigation of Zr–Nb–REE mineralisation at Khalzan Buregte and Tsakhir, Western Mongolia, enables to evaluate magmatic processes preceding economic mineralisation and, in a second step, to compare similar ore-forming processes developing in host rocks of contrasting rock composition (low- vs. high-silica rocks). The genesis of the Zr–Nb–REE mineralisation is re-assessed using field observations, whole rock analysis (chemical composition, quantitative modal analysis by X-ray diffraction) and by the application of various transmitted light and electron microscopic techniques. Coarse-grained intrusive bodies, dikes and volcanic rocks of alkaline, silica-saturated composition were found to be contemporarily emplaced at subvolcanic to volcanic levels forming four alkaline massifs within the Khalzan Buregte area. The whole rock composition of weakly altered magmatic rocks ranges from syenite to quartz monzonite and alkaline granite (alkali feldspar syenite to alkali feldspar granite according to their modal composition). Magmatic and at least two subsequent hydrothermal processes contributed significantly to the formation of economic concentrations of high field strength elements (HFSE) such as Zr, Hf, Nb, Ta, REE and Y in the Khalzan Buregte deposit and in the nearby Tsakhir prospect. Mixing of magma from at least three sources and the formation of potassium feldspar cumulates resulted in local enrichment of Zr, Nb and light rare earth elements (LREE) in the rocks up to sub-economic levels. There was no significant increase in Y and heavy rare earth elements (HREE) during magmatism.Multistage metasomatic alteration resulted in a pronounced chemical and mineralogical heterogeneity of associated alteration assemblages. The main hosts of Zr and Hf in the ores are zircon and other zirconium silicates (gittinsite, catapleiite-(Ca) and elpidite). The rare metals Nb and Ta are mainly contained in various types of pyrochlore (Khalzan Buregte) and, to a lesser extent, in fergusonite and other minerals (Tsakhir). A large variety of REE- and Y-bearing minerals have been identified, including oxides, fluorocarbonates and silicates. Early hydrothermal alteration by silica- and carbonate-rich fluids yielded extreme concentrations of Zr, Nb and LREE. Later alteration resulted in enrichment of Y and HREE. In the latter case, fluids were very rich in fluorine. Our preliminary genetic model assumes a carbonatite-related fluid system responsible for the early alteration that occurred late during or postdating the intrusion/extrusion of the silica-saturated magmas. A “Li-F granite-type” fluid system was active during the late alteration. The interplay of all these processes resulted in the formation of a complex, economic Zr–Nb–REE mineralisation at Khalzan Buregte.