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Detrital zircon populations from Silurian--Devonian clastic rocks of NW Svalbard were analysed by U--Pb laser ablation inductively coupled plasma mass spectrometry to investigate the pre-Caledonian provenance of Svalbard's Northwestern Terrane. Changes in the resulting age spectra suggest a major shift in sources from the Laurentian--Avalonian suture in the latest Silurian to the local metasedimentary basement of the Northwestern Terrane in the Late Silurian--Early Devonian, and in the Lochkovian to Grenvillian-Sveeonorwegian sources. These data, together with structural, additional geochronological and metamorphic data from Svalbard, East Greenland and Avalonia, support the amalgamation of Svalbard as the result of long-distance transport along sinistral strike-slip faults. A unifying model for the final amalgamation of Svalbard, consistent with the stratigraphical and tectonothermal history of Svalbard, involves fragments from the Grampian orogen and Avalonian ernst originally accreted to the Laurentian margin being subsequently transported northward along sinistral strike-slip faults during Scandian deformation. Supplementary material: The sample preparation procedures, laser ablation ICP-MS analytical methods, and data table are available at http://www.geolsoc.org.uk/SUP18421. doi: 10.1144/0016-76492010-062.

New secondary ionization mass spectrometry U-Pb and O isotope analyses of detrital zircons from the Sa'al schist in Sinai coupled with whole-rock Nd isotopic analyses provide new evidence of preNeoproterozoic crust in the northernmost Arabian-Nubian Shield (ANS). The detrital zircon age population is bimodal, with concordia ages of 1029 [+ or -] 7 Ma and 1110 [+ or -] 8 Ma. The whole-rock [epsilon].sub.Nd](t = 1.0 Ga) value of +2 is significantly lower than found for juvenile Neoproterozoic rocks in the region. Thus, the Sa'al schist is interpreted to represent Kibaran (Grenville) age crust incorporated into the northernmost ANS. The [[delta].sup.18]O (zircon) values (6.1%-9.4%) imply that supracrnstal recycling was involved in the formation of this ca. 1.0-1.1 Ga crust. A compilation of reported xenocrystic and detrital pre-ANS zircons and the variability ofNd, Sr, Pb, and O isotopic compositions within the shield suggests that its northernmost and eastern margins were more strongly contaminated by older crust ca. 0.9-3.0 Ga old. The distribution of 0.9-1.1 Ga xenocrystic and detrital zircons mainly in the east and north of the ANS suggests that such crust characterized parts of the northeastern margin of western Gondwana prior to ANS formation, and that 0.9-1.1 Ga old zircons detected in lower Paleozoic sandstone cover may have a proximal provenance.

Quartz veins in high-pressure (HP) to ultrahigh-pressure (UHP) rocks are the products of fluid-rock interaction, and thus provide insight into fluid processes in subduction zones. In this paper, we report an integrated study of mineral inclusion, trace-element, U-Pb age, and Lu-Hf isotope compositions of hydrothermal zircon grains from a quartz vein within an UHP eclogite outcrop from the Hong'an area, western Dabie Mountains. These data are used to decipher the age, conditions of formation, and source of fluid for zircon formation during the exhumation of UHP rocks. Zircon grains from the vein have perfect euhedral shape, and show sector zoning or weak zoning, indicating that they precipitated from the aqueous fluid responsible for the vein formation. Raman spectroscopy analysis reveals that the zircon grains contain inclusions of garnet, omphacite, rutile, quartz, and [H.sub.2]O, implying that they crystallized from aqueous fluid under HP eclogite-facies conditions. The zircon grains show low Th/U and Lu/Hf ratios, nearly flat HREE patterns, absent Eu anomalies and low LREE contents. These characteristics are consistent with their precipitation in the presence of garnet and epidote, and absence of feldspar, and thus suggest that trace-element concentrations in hydrothermal zircon are controlled by co-precipitation of mineral assemblages. Crystallization temperatures of 670 to 712[degrees]C, which were calculated using the Ti content of zircon, are consistent with their formation under eclogite-facies conditions and may correspond to the temperature of the infiltrating fluid. The weighted mean [sup.206]Pb/[sup.238]U age of 224.7 [+ or -] 1.3 Ma is taken as the best estimate for the age of quartz-vein formation and records aqueous fluid flow during the early exhumation stage of UHP rocks. The zircon grains in the quartz-vein have Hf compositions similar to those in the host eclogite, which demonstrates isotopic equilibrium between fluid and rocks and that the fluid-rock ratio was likely low. Keywords: Hydrothermal zircon, trace element, Lu-Hf isotope, U-Pb age, HP-UHP metamorphism, quartz vein, western Dabie Mountains

We report the lattice thermal expansion of zircon-(xenotime-)type LuP[O.sub.4] and LuV[O.sub.4] in the temperature range of 25-1000[degrees]C from high-temperature powder XRD studies. The details of the high-temperature crystal chemistry of both phases have been determined from Rietveld analysis of the powder XRD data. Both the compounds show appreciably higher thermal expansion than analogous zircon-type silicates. Despite isomorphism, the axial thermal expansion of LuV[O.sub.4] shows significant anisotropy compared to LuP[O.sub.4]. In the studied temperature range, the average axial thermal expansion coefficients of LuV[O.sub.4] are [[alpha].sub.a] = 6.0 x [10.sup.-6] and [[alpha].sub.c] = 7.2 x [10.sup.-6] ([degrees][C.sup.1] and those of LuV[O.sub.4] are [[alpha].sub.a] = 3.6 x [10.sup.-6] and [[alpha].sub.c] = 11.8 x [10.sup.-6] ([degrees][C.sup.-1]). However, the average volume thermal expansion coefficients are almost identical. The differences in the thermal expansion behavior of the two structures originate from differences in the expansion and distortion of the Lu[O.sub.8] polyhedra. The Lu[O.sub.8] polyhedron in LuV[O.sub.4] shows about 30% higher thermal expansion than that in LuP[O.sub.4]. The overall thermal expansion behaviors of these two structures are predominantly related to the distortion in the Lu[O.sub.8] unit, inter-cation distances and spatial arrangement of the Lu-O bonds in the structure. Keywords: Thermal expansion, crystal chemistry, zircon, xenotime, phosphates, vanadates

Ion microprobe analysis with a sub-micrometer diameter spot reveals a sharp, 2 [micro]m gradient in oxygen isotope ratio proving that oxygen diffusion in zircon is slow even under prolonged high-grade metamorphism. The data are consistent with an oxygen diffusion coefficient of [10.sup.-23.5[+ or -]1] [cm.sup.2]/s. Furthermore, this gradient is found in a zircon that contains clear textural evidence of recrystallization in nearby regions. This finding shows that through careful textural and chemical analysis, primary information can be extracted from a zircon that has also undergone partial recrystallization. The oxygen isotope ratios found in zircon have been used to infer magmatic and pre-magmatic histories, including the presence of liquid water on the surface of earliest Earth. Recently, these interpretations have been questioned with the assertion that zircon may not retain its primary oxygen isotope signature through metamorphism. The slow diffusion confirmed by these results supports interpretations that assume preservation of magmatic compositions. Keywords: Ion microprobe, SIMS, zircon, diffusion, oxygen isotopes, stable isotopes, granulites facies, migmatites

There is no consensus as to how the extreme metamorphic conditions required to form granulites are attained, or how these rocks relate to crustal growth and differentiation processes. Studying young granulites offers two advantages: the tectonic setting is likely to be well constrained, and the ambiguities that result from overprinting by younger metamorphic events are potentially avoided. We report the first ion microprobe U-Pb (zircon) ages for orthopyroxene-bearing granulites, tonalites, and gabbros of the Cenozoic Hidaka metamorphic belt (Hokkaido, Japan) to clarify the magmatic-metamorphic connection in this area. The data support a two-stage evolution for this terrane, which is attributed to episodes of supra-subduction zone magmatism (late Eocene) and back-arc extension (early Miocene). We relate granulite facies metamorphism and garnet-orthopyroxene tonalite generation to mafic magma under-accretion and lithosphere thinning due to the opening of the Japan Sea at 19 Ma. The Hidaka granulites are thus among the youngest exposed granulites on Earth, and manifest the thermal response to continental growth. Keywords: Granulite, zircon, U-Pb dating, Hidaka metamorphic belt.

We present newly acquired trace element compositions for more than 300 zircon grains in 36 gabbros formed at the slow-spreading Mid-Atlantic and Southwest Indian Ridges. Rare earth element patterns for zircon from modern oceanic crust completely overlap with those for zircon crystallized in continental granitoids. However, plots of U versus Yb and U/Yb versus Hf or Y discriminate zircons crystallized in oceanic crust from continental zircon, and provide a relatively robust method for distinguishing zircons from these environments. Approximately 80% of the modern ocean crust zircons are distinct from the field defined by more than 1700 continental zircons from Archean and Phanerozoic samples. These discrimination diagrams provide a new tool for fingerprinting ocean crust zircons derived from reservoirs like that of modern mid-ocean ridge basalt (MORB) in both modern and ancient detrital zircon populations. Hadean detrital zircons previously reported from the Acasta Gneiss, Canada, and the Narryer Gneiss terrane, Western Australia, plot in the continental granitoid field, supporting hypotheses that at least some Hadean detrital zircons crystallized in continental crust forming magmas and not from a reservoir like modern MORB. Keywords: detrital zircon, trace elements, provenance, mid-ocean ridge, Hadean.

Nepheline-bearing gneisses from the 75 k[m.sup.2] Tambani body in the Mozambique Belt of southern Malawi, are miaskitic biotite-nepheline monzodiorites, reflecting an absence of K-feldspar, alkali amphiboles or pyroxenes, and contain euhedral zircon megacrysts up to 5 cm across. The zircons contain U = 1-1,860 ppm, Th = 0-2,170 ppm and Y = 400-1,100 ppm, and very low concentrations of all other measured trace elements except Hf (Hf[O.sub.2] = 0.53-0.92 wt. %). Cathodoluminescence images reveal oscillatory sector growth zoning and no evidence for xenocrystic cores, indicating that the zircons represent primary magmatic crystallization products that have survived amphibolite grade metamorphism. U-Pb isotopic analyses (by TIMS) yield an upper intercept age of 730 [+ or -] 4 Ma (MSWD = 1.7), which we interpret as the time of magmatic crystallization of the zircons. This is coincident with 11 SHRIMP spot analyses, which yield a mean age of 729 [+ or -] 7 Ma (MSWD = 0.37). Metamorphism, at 522 [+ or -] 17 Ma as suggested by monazite, caused partial Pb-loss during local recrystallization of zircon. Lu-Hf isotopic data for three whole-rock samples of nepheline-bearing gneiss are collinear with those for zircon megacrysts, and correspond to an age of 584 [+ or -] 17 Ma (MSWD = 0.37. We interpret the Lu-Hf array to represent a mixing line defined by the Hf isotopic signature of primary zircon and that of the rock-forming minerals reset during metamorphic (re-)crystallization; hence the 584 Ma age is likely geologically meaningless. Given the well-defined association of nepheline syenites (and phonolitic volcanic equivalents) with continental rifting, we suggest that the Tambani body represents a magmatic product formed at 730 Ma during the break-up of the Rodinia supercontinent. The 522 Ma age is akin to other Pan-African metamorphic ages that record collisional suturing events during the final assembly of Gondwana. Zircon-bearing nepheline gneisses thus preserve a record of intra-continental rifting and of continental collision in southern Malawi.

An entirely different approach is presented that is based on use of the zirconocene-mediated ring contraction of a vinyl furanoside to generate an enantiopure cyclobutanol and subsequent adaptation of a 3.3 sigmatropic rearrangement. Extended functionalization gives the opportunity to generate stereodefined cyclooctane -1,2,3-triols and 1,2,3,4,5-pentaols and to elaborate authentic carbasugar analogues as well.

Orientation contrast imaging and quantitative electron back-scatter diffraction analysis of a zircon collected from an Indian Ocean gabbro reveal intragrain crystallographic misorientations (up to 14[degrees]) and low-angle orientation boundaries concentrated in the zircon tips. These features represent the formation and migration of dislocations and provide the first evidence of crystal-plastic deformation of zircon under crustal conditions. Panchromatic and wavelength cathodoluminescence (CL), combined with quantitative rare earth element (REE) ion microprobe analyses, demonstrate modification of zircon REE chemistry within the areas of crystal plasticity. These data indicate that the enhanced diffusion of REEs into the zircon is spatially linked to the presence of dislocations that behave as high-diffusivity pathways, increasing bulk diffusion rates and effective diffusion distances in the zircon by several orders of magnitude. In addition, discrete ~2 [micro]m zones of reduced panchromatic CL correspond exactly to the position of low-angle orientation boundaries and demonstrate a defect dependence on CL signal at high dislocation densities. The presence of deformation-related crystal-plastic microstructures in zircon, and their role in modifying elemental diffusion, questions the commonly made assumption of chemical robustness and has fundamental implications for the interpretation of zircon trace-element and isotopic data. Keywords: microstructure, diffusion, deformation, geochemistry, EBSD.

Mafic-layered intrusions and sills and spatially associated andesitic basalts are well preserved in the Funing area, SW China. The 258 [+ or -] 3 Ma-layered intrusions are composed of fine-grained gabbro, gabbro and diorite. The 260 [+ or -] 3 Ma sills consist of undifferentiated diabases. Both the layered intrusions and volcanic rocks belong to a low-Ti group, whereas the diabases belong to a high-Ti group. Rocks of the high-Ti group have FeO, Ti[O.sub.2] and [P.sub.2][O.sub.5] higher but MgO and Th/Nb ratios lower than those of the low-Ti group. They have initial [sup.87]Sr/[sup.86]Sr ratios (0.706-0.707) lower and [epsilon]Nd (-1.5 to -0.6) higher than the low-Ti equivalents (0.710-0.715 and -9.6 to -4.0, respectively). The high-Ti group was formed from relatively primitive, high-Ti magmas generated by low degrees (7.3 -9.5%) of partial melting of an enriched, OIB-type asthenospheric mantle source. The low-Ti group may have formed from melts derived from an EM2-like, lithospheric mantle source. The marie rocks at Funing are part of the Emeishan large igneous province formed by a mantle plume at ~260 Ma.

Analysis of [[delta].sup.18]O in igneous zircons of known age traces the evolution of intracrustal recycling and crust-mantle interaction through time. This record is especially sensitive because oxygen isotope ratios of igneous rocks are strongly affected by incorporation of supracrustal materials into melts, which commonly have [[delta].sup.18]O values higher than in primitive mantle magmas. This study summarizes data for [[delta].sup.18]O in zircons that have been analyzed from 1,200 dated rocks ranging over 96% of the age of Earth. Uniformly primitive to mildly evolved magmatic [[delta].sup.18]O values are found from the first half of Earth history, but much more varied values are seen for younger magmas. The similarity of values throughout the Archean, and comparison to the composition of the 'modern' mantle indicate that [[delta].sup.18]O of primitive mantle melts have remained constant ([+ or -] 0.2[per thousand]) for the past 4.4 billion years. The range and variability of [[delta].sup.18]O in all Archean zircon samples is subdued ([[delta].sup.18]O(Zrc)=5-7.5[per thousand]) ranging from values in high temperature equilibrium with the mantle (5.3 [+ or -] 0.3[per thousand]) to slightly higher, more evolved compositions (6.5-7.5[per thousand]) including samples from: the Jack Hills (4.4-3.3 Ga), the Beartooth Mountains (4.0-2.9 Ga), Barberton (3.5-2.7 Ga), the Superior and Slave Provinces (3.0 to 2.7 Ga), and the Lewisian (2.7 Ga). No zircons from the Archean have been analyzed with magmatic [[delta].sup.18]O above 7.5[per thousand]. The mildly evolved, higher Archean values (6.5-7.5[per thousand]) are interpreted to result from exchange of protoliths with surface waters at low temperature followed by melting or contamination to create mildly elevated magmas that host the zircons. During the Proterozoic, the range of [[delta].sup.18]O(Zrc) and the highest values gradually increased in a secular change that documents maturation of the crust. After ~1.5 Ga, high [[delta].sup.18]O zircons (8 to > 10[per thousand]) became common in many Proterozoic and Phanerozoic terranes reflecting [[delta].sup.18]O(whole rock) values from 9 to over 12[per thousand]. The appearance of high [[delta].sup.18]O magmas on Earth reflects non-uniformitarian changes in the composition of sediments, and rate and style of recycling of surface-derived material into magmas within the crust.

The synthetic route to the manufacture of bifunctional zirconocene/borane complex is described. This complex was characterized by X-ray diffraction method.

The effects of electron-withdrawing perfluoroaryl groups on the zirconocene coupling of alkynes are described. Mechanistic studies on zirconocene couplings indicate that the observed regioselectivities are determined by an electronic factor that controls the orientation of at least one of the two alkynes as they are coupled.

The electrochemistry of zirconocene dichlorides and the IR spectroscopy of zirconocene dicarbonyls were experimentally examined to address the electronic influence of ansa bridges in more detail. The results demonstrate that inferences pertaining to the relative electron-donating properties of the ring substituents are influenced by the method used to probe the effect.

It is observed that the relative energetic stability of the 'rac' and the 'meso' rational isomers of metallocene-based Ziegler-Natta catalysts plays an important role in determining the structural, physical and chemical properties of synthesized polymers. A cluster can be defined for which the hybrid approach yields meaningful results when compared to full quantum mechanics calculations.

The reactions of unbridged zircocene complexes with diisobutylaluminum hydride and the corresponding reactions of several ansa-zirconocene dichlorides are studied by using NMR spectroscopy. The results have shown that reactions with HAl[super i][Bu.sub.2] has given different reaction products from unbridged zirconocenes dichlorides with a single-atom bridge.

[1] New apatite and zircon fission track and (U-Th)/He analyses serve to document the bedrock cooling history of the central Nepalese Himalaya near the Annapuma Range. We have obtained 82 apatite fission track (AFT), 7 zircon fission track (ZFT), and 7 apatite (U-Th)/He (AHe) ages from samples collected along the Marsyandi drainage, including eight vertical relief profiles from ridges on either side of the river averaging more than 2 km in elevation range. In addition, three profiles were sampled along ridge crests that also lie ~2 km above the adjacent valleys, and a transect of >20 valley bottom samples spans from the Lesser Himalaya across the Greater Himalaya and into the Tethyan strata. As a consequence, these data provide one of the more comprehensive low-temperature thermochronologic studies within the Himalaya. Conversely, the youthfulness of this orogen is pushing the limits of these dating techniques. AFT ages range from >3.8 to 0 Ma, ZFT ages from 1.9 to 0.8 Ma, and AHe ages from 0.9 to 0.3 Ma. Most ridges have maximum ages of 1.3-0.8 Ma at 2 km above the valley bottom. Only one ridge crest (in the south central zone of the field area) yielded significantly older ZFT and AFT ages of ~2 Ma; we infer that a splay of the Main Central Thrust separates this ridge from the rest of the Greater Himalaya. ZFT and AFT ages from a vertical transect along this ridge indicate exhumation rates of ~1.5 km [Myr.sup.-1] ([r.sup.2] > 0.7) from ~2 to 0.6-0.8 Ma, whereas AHe ages indicate a faster exhumation rate of ~2.6 km [Myr.sup.-1] ([r.sup.2] = 0.9) over the last 0.8 Myr. Exhumation rates calculated for six of the remaining seven vertical profiles ranged from 1.5 to 12 km [Myr.sup.-1] (all with low [r.sup.2] values of

The results of several reactions of Me3Sn-substituted zirconocene dichloride (1) with electrophiles (BBr3, BCl3, I2, ICl and HCl), and the comparison of the reactivities of the Me3Sn and Me3Si substituents towards such electrophiles are reported. The results suggest that Me3Sn substituents undergo electrophilic halodemethylation more readily than corresponding Me3Si substituents, whereas the reactivities of the halostannylated complexes toward nucleophiles such as airborne moisture are much lower than those of their halosilylated counterparts.