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Sample records for ca 3700ma zircons

  1. Chemical abrasion-SIMS (CA-SIMS) U-Pb dating of zircon from the late Eocene Caetano caldera, Nevada

    Science.gov (United States)

    Watts, Kathryn E.; Coble, Matthew A.; Vazquez, Jorge A.; Henry, Christopher D.; Colgan, Joseph P.; John, David A.

    2016-01-01

    Zircon geochronology is a critical tool for establishing geologic ages and time scales of processes in the Earth's crust. However, for zircons compromised by open system behavior, achieving robust dates can be difficult. Chemical abrasion (CA) is a routine step prior to thermal ionization mass spectrometry (TIMS) dating of zircon to remove radiation-damaged parts of grains that may have experienced open system behavior and loss of radiogenic Pb. While this technique has been shown to improve the accuracy and precision of TIMS dating, its application to high-spatial resolution dating methods, such as secondary ion mass spectrometry (SIMS), is relatively uncommon. In our efforts to U-Pb date zircons from the late Eocene Caetano caldera by SIMS (SHRIMP-RG: sensitive high resolution ion microprobe, reverse geometry), some grains yielded anomalously young U-Pb ages that implicated Pb-loss and motivated us to investigate with a comparative CA and non-CA dating study. We present CA and non-CA 206Pb/238U ages and trace elements determined by SHRIMP-RG for zircons from three Caetano samples (Caetano Tuff, Redrock Canyon porphyry, and a silicic ring-fracture intrusion) and for R33 and TEMORA-2 reference zircons. We find that non-CA Caetano zircons have weighted mean or bimodal U-Pb ages that are 2–4% younger than CA zircons for the same samples. CA Caetano zircons have mean U-Pb ages that are 0.4–0.6 Myr older than the 40Ar/39Ar sanidine eruption age (34.00 ± 0.03 Ma; error-weighted mean, 2σ), whereas non-CA zircons have ages that are 0.7–1.3 Myr younger. U-Pb ages do not correlate with U (~ 100–800 ppm), Th (~ 50–300 ppm) or any other measured zircon trace elements (Y, Hf, REE), and CA and non-CA Caetano zircons define identical trace element ranges. No statistically significant difference in U-Pb age is observed for CA versus non-CA R33 or TEMORA-2 zircons. Optical profiler measurements of ion microprobe pits demonstrate consistent depths of ~ 1.6

  2. Dating Intrusions in the Salinian Block Using Single Zircon U-PB CA-TIMS Analysis

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    DeNicola, S.; Mundil, R.; Wang, C. Y.; Sprain, C. J.; Manga, M.

    2015-12-01

    The Salinian block (SB) consists largely of metasedimentary basement intruded by suites of compositionally heterogeneous Early to Late Cretaceous rocks. Exposed throughout Central and Northern California, it is bordered to the northwest by the Naciemiento fault, to the southwest by the Big Pine fault and to the east by the San Andreas Fault. These faults are thought to have caused a dextral offset of the SB; however, its original position is still debated. Published radioisotopic ages from various techniques on SB intrusives suggest that the initial magmatic activity of the Salinian arc began at around 100 Ma and concluded some 40 myr later, but the timing of individual magmatic pulses are yet to be fully understood because arguably most of the available geochronological data are compromised with respect to precision and accuracy. Previous studies include U-Pb zircon ages from different lithologies and areas using multi-crystal TIMS as well as ICPMS, and SIMS techniques. Whereas the former technique is now known to be prone to producing inaccurate, although precise, ages due to averaging effects from older inheritance and open system behavior, the latter are often associated with analytical uncertainty at the several percent level as well as unrecognized open system behavior, making the interpretation of age data notoriously difficult. Complementary geochemical, petrological and structural studies have been conducted, but are also difficult to interpret in absence of precise and accurate geochronological data because geochemical trends and intrusion rates cannot be reconstructed. Here, we examine a group of intrusive rocks from the Northern California SB that include a biotite-hornblende granodiorite host rock which is intruded by a complex array of igneous dikes of varying lithology ranging from ~5% to ~50% mafic components. We perform closed system single zircon U-Pb CA-TIMS analysis and obtain 206Pb/238U ages of ~98 Ma and ~92 Ma (with permil level resolution

  3. High-Resolution Zircon U-Pb CA-TIMS Dating of the Carboniferous—Permian Successions, Paraná Basin, Brazil

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    Griffis, N. P.; Mundil, R.; Montanez, I. P.; Isbell, J.; Fedorchuk, N.; Lopes, R.; Vesely, F.; Iannuzzi, R.

    2015-12-01

    The late Paleozoic Ice Age (LPIA) is Earth's only record of a CO2-forced climatic transition from an icehouse to greenhouse state in a vegetated world. Despite a refined framework of Gondwanan ice distribution, questions remain about the timing, volume, and synchronicity of high-latitude continental ice and the subsequent deglaciation. These questions ultimately preclude our understanding of linkages between ice volume, sea level, and high- and low-latitude climate. Poor constraints on the timing and synchronicity of glacial and interglacial transitions reflect a lack of high-resolution radioisotopic dates from high-latitude, ice-proximal Carboniferous-Permian successions. The Rio Bonito Fm in Rio Grande do Sul State of southern Brazil hosts the oldest non-glaciogenic Carboniferous- Permian deposits of the Paraná Basin, thus recording the icehouse-to-greenhouse transition. Despite a widespread effort over the last two decades to constrain these deposits in time by means of U-Pb zircon geochronology, published data sets of the Candiota and Faxinal coals of the Rio Bonito Fm host discrepancies that may reflect post- eruptive open system behavior of zircon and analytical artifacts. These discrepancies have hindered the correlation of the Candiota and Faxinal sediments within the larger Gondwanan framework. Here we present the first U-Pb ages on closed system single zircons using CA-TIMS techniques on Permo-Carboniferous ash deposits of the Paraná Basin. Preliminary results indicate two major and distinct coal-forming periods that are separated by ca 10 Ma. Our results and conclusions are not in agreement with multi- crystal U-Pb TIMS and SIMS ages that suggest coeval deposition of the Candiota and Faxinal coals. CA-TIMS analyses applied to zircons from additional ash deposits are aimed at constructing a robust chronostratigraphic framework for the Carboniferous- Permian succession of the Paraná Basin, which will facilitate a better understanding of the timing and

  4. Development of CA-ID-TIMS zircon U–Pb dating technique at Guangzhou Institute of Geochemistry, Chinese Academy of Sciences

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    Yu-Ting Zhong

    2017-06-01

    Pretreatment protocols for zircon analysis, and community-wide innovations spurred on by EARTHTIME tends to be at the leading edge of technological development. Also, more and more Chinese researchers perform lots of laboratory work in improving the technique in China. Here we present the running condition, procedural blanks and zircon standards measurement results in the clean laboratory of the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS. The results show the total procedural blanks (Pbc are below ∼1 pg mostly, suitable for the sample pretreatment and operation. The 206Pb/238U dates of R33 and 500 Ma solution are 419.88 ± 0.94 Ma (n = 7; MSWD = 6.8 and 500.50 ± 0.19 Ma (n = 9; MSWD = 0.84, respectively. These results demonstrate that the CA-ID-TIMS procedure is well established at GIGCAS. Our efforts are beneficial to the development of EARTHTIME-CN program. In particular, when this technique is combined with the SIMS technique, it provides an efficient way to solve a number of geochronological problems encountered in China and worldwide.

  5. Middle Neoproterozoic (ca. 705-716 Ma) arc to rift transitional magmatism in the northern margin of the Yangtze Block: Constraints from geochemistry, zircon U-Pb geochronology and Hf isotopes

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    Wang, Ruirui; Xu, Zhiqin; Santosh, M.; Xu, Xianbing; Deng, Qi; Fu, Xuehai

    2017-09-01

    The South Qinling Belt in Central China is an important window to investigate the Neoproterozoic tectono-magmatic processes along the northern margin of the Yangtze Block. Here we present whole-rock geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes of a suite of Middle Neoproterozoic intrusion from the Wudang Uplift in South Qinling. Zircon LA-ICP-MS U-Pb ages reveal that these rocks were formed at ca. 705-716 Ma. Geochemical features indicate that the felsic magmatic rocks are I-type granitoids, belong to calcic- to calc-alkaline series, and display marked negative Nb, Ta and Ti anomalies. Moreover, the enrichment of light rare earth elements (LREEs) and large ion lithophile elements (LILEs), combined with depletion of heavy rare earth elements (HREEs) support that these rocks have affinity to typical arc magmatic rocks formed in Andean-type active continental margins. The REE patterns are highly to moderately fractionated, with (La/Yb)N = 5.13-8.10 in meta-granites, and 2.32-2.35 in granodiorite. The granitoids have a wide range of zircon εHf(t) values (-29.91 to 14.76) and zircon Hf two-stage model ages (696-3482 Ma). We suggest that the ca. 705-716 Ma granitoids were sourced from different degrees of magma mixing between partial melting of the overlying mantle wedge triggered by hydrous fluids released from subducted materials and crustal melting. The hybrid magmas were emplaced in the shallow crust accompanied by assimilation and fractional crystallization (AFC). Both isotopic and geochemical data suggest that the ca. 705-716 Ma felsic magmatic rocks were formed along a continental arc. These rocks as well as the contemporary A-type granite may mark a transitional tectonic regime from continental arc to rifting, probably related to slab rollback during the oceanic subduction beneath the northern margin of Yangtze Block.

  6. Ti-in-Zircon Thermometer: Preliminary Results

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    Fu, B.; Cavosie, A. J.; Clechenko, C. C.; Fournelle, J.; Kita, N. T.; Lackey, J.; Page, F.; Wilde, S. A.; Valley, J. W.

    2005-12-01

    , permissive of low rutile activity. Peraluminous granites have lower whole-rock TiO2 content (0.02-0.21 wt.%) than metaluminous granites (0.54-0.91 wt.%), and both have similar zircon saturation temperatures (710-780°C). The low Ti content and apparent temperature in zircons from anorthosite and metagabbro (magmatic T = ca. 1000-1100°C) and the homogeneity of igneous zircon cores vs. metamorphic rims in metagabbro suggest that Ti content was reset during granulite-facies metamorphism (750°C, 1.0 Ga), in contrast to the current estimate of extremely low diffusivity of Ti in zircon. The Ti contents of >3.9 Ga Jack Hills detrital zircons are consistent with previously published data that were used to constrain magmatic temperature and thus the composition of unknown host rocks (W&H, 2005, Science 308:841). However, these values overlap those from both felsic and mafic rocks, and the Ti data are not sufficient to independently identify parent melt chemistry unless post-crystallization changes can be ruled out. The best evidence of pre-4 Ga evolved crust is provided by previously reported oxygen isotope ratios and felsic mineral inclusions in zircon (see Cavosie et al., 2005, EPSL 235:663).

  7. Li diffusion in zircon

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    Cherniak, D. J.; Watson, E. B.

    2010-09-01

    Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0-1.2 GPa) conditions has been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted to evaluate possible rate-limiting effects on Li diffusion of slow-diffusing REE+3 that might provide charge balance. Diffusion experiments performed in the presence of H2O-CO2 fluid were run in a piston-cylinder apparatus, using a source consisting of a powdered mixture of spodumene, quartz and zircon with oxalic acid added to produce H2O-CO2 fluid. Nuclear reaction analysis (NRA) with the resonant nuclear reaction 7Li(p,γ)8Be was used to measure diffusion profiles for the experiments. The following Arrhenius parameters were obtained for Li diffusion normal to the c-axis over the temperature range 703-1.151°C at 1 atm for experiments run with the spodumene source: D_{text{Li}} = 7.17 × 10^{ - 7} { exp }( - 275 ± 11 {text{kJmol}}^{ - 1} /{text{RT}}){text{m}}2 {text{s}}^{ - 1}. Diffusivities are similar for transport parallel to the c-axis, indicating little anisotropy for Li diffusion in zircon. Similar Li diffusivities were also found for experiments run under fluid-present conditions and for the experiment run with the Dy-bearing source. Li diffusion is considerably faster than diffusion of other cations in zircon, with a smaller activation energy for diffusion. Although Li diffusion in zircon is comparatively rapid, zircons will be moderately retentive of Li signatures at mid-crustal metamorphic temperatures, but they are unlikely to retain this information for geologically significant times under high-grade metamorphism.

  8. Zircon U-Pb dating of eclogite from the Qiangtang terrane, north-central Tibet: a case of metamorphic zircon with magmatic geochemical features

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    Zhai, Qing-guo; Jahn, Bor-ming; Li, Xian-hua; Zhang, Ru-yuan; Li, Qiu-li; Yang, Ya-nan; Wang, Jun; Liu, Tong; Hu, Pei-yuan; Tang, Suo-han

    2017-06-01

    Zircon is probably the most important mineral used in the dating formation of high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks. The origin of zircon, i.e., magmatic or metamorphic, is commonly assessed by its external morphology, internal structure, mineral inclusions, Th/U ratios and trace element composition. In this study, we present an unusual case of metamorphic zircon from the Qiangtang eclogite, north-central Tibet. The zircon grains contain numerous eclogite-facies mineral inclusions, including omphacite, phengite, garnet and rutile; hence, they are clearly of metamorphic origin. However, they display features similar to common magmatic zircon, including euhedral crystal habit, high Th/U ratios and enriched heavy rare earth elements pattern. We suggest that these zircon grains formed from a different reservoir from that for garnet where no trace elements was present and trace element equilibrium between zircon and garnet was achieved. U-Pb dating of zircon gave an age of 232-237 Ma for the eclogite, and that of rutile yielded a slightly younger age of ca. 217 Ma. These ages are consistent with the reported Lu-Hf mineral isochron and phengite Ar-Ar ages. The zircon U-Pb and mineral Lu-Hf isochron ages are interpreted as the time of the peak eclogite-facies metamorphism, whereas the rutile U-Pb and phengite Ar-Ar ages represent the time of exhumation to the middle crust. Thus, the distinction between metamorphic and magmatic zircons cannot be made using only Th/U ratios and heavy REE compositions for HP-UHP metamorphic rocks of oceanic derivation.

  9. Chemical characteristics of zircon from A-type granites and comparison to zircon of S-type granites

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    Breiter, Karel; Lamarão, Claudio Nery; Borges, Régis Munhoz Krás; Dall'Agnol, Roberto

    2014-04-01

    The trace element content in zircons from A-type granites and rhyolites was investigated by using back-scattered electron images and electron microprobe analyses. The studied Proterozoic (Wiborg batholith, Finland and Pará, Amazonas and Goiás states, Brazil) and Variscan (Krušné Hory/Erzgebirge, Czech Republic and Germany) plutons cover a wide range of rocks, from large rapakivi-textured geochemically primitive plutons to small intrusions of F-, Li-, Sn-, Nb-, Ta-, and U-enriched rare-metal granites. While zircon is one of the first crystallized minerals in less fractionated metaluminous and peraluminous granites, it is a late-crystallized phase in peralkaline granites and in evolved granites that may crystallize during the whole process of magma solidification. The early crystals are included in mica, quartz, and feldspar; the late grains are included in fluorite or cryolite or are interstitial. The zircon in hornblende-biotite and biotite granites from the non-mineralized plutons is poor in minor and trace elements; the zircon in moderately fractionated granite varieties is slightly enriched in Hf, Th, U, Y, and HREEs; whereas the zircon in highly fractionated ore-bearing granites may be strongly enriched in Hf (up to 10 wt.% HfO2), Th (up to 10 wt.% ThO2), U (up to 10 wt.% UO2), Y (up to 12 wt.% Y2O3), Sc (up to 3 wt.% Sc2O3), Nb (up to 5 wt.% Nb2O5), Ta (up to 1 wt.% Ta2O5), W (up to 3 wt.% WO3), F (up to 2.5 wt.% F), P (up to 11 wt.% P2O5), and As (up to 1 wt.% As2O5). Metamictized zircons may also be enriched in Bi, Ca, Fe, and Al. The increase in the Hf content coupled with the decrease in the Zr/Hf value in zircon is one of the most reliable indicators of granitic magma evolution. In the zircon of A-type granites, the Zr/Hf value decreases from 41-67 (porphyritic granite) to 16-19 (equigranular granite) in the Kymi stock, Finland, and from 49-52 (biotite granite) to 18-36 (leucogranite) in the Pedra Branca pluton, Brazil. In the in situ strongly

  10. Applications of biotite inclusion composition to zircon provenance determination

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    Bell, Elizabeth A.; Boehnke, Patrick; Mark Harrison, T.

    2017-09-01

    Detrital zircons are the only confirmed surviving remnants of >4.03 Ga crust while younger detrital zircons provide a parallel record of more recent crustal evolution to that preserved in crystalline rocks. Zircons often preserve inclusions that may provide clues as to the origins of out-of-context grains in the sedimentary record. Previous studies have established that inclusions of biotite in magmatic zircon are compositionally well-matched to biotite in the source rock matrix, although a direct application to ancient detrital zircons has not been made. A number of studies have documented variations in the Fe, Mg, and Al contents of magmatic biotite from different source rocks and tectonic settings, suggesting that biotite inclusions may indeed serve as provenance indicators for detrital zircons. Consistent with earlier studies, we find that the FeO*/MgO ratio of magmatic biotite from continental arcs, collisional, and within-plate settings varies with relative oxidation state as well as whole-rock FeO*/MgO, while its Al2O3/(FeO* + MgO) varies with whole-rock A/CNK (molar Al/(2 ṡ Ca + Na + K)). Biotite from oxidized metaluminous and reduced S-type granitoids can be readily distinguished from each other using FeO*/MgO and Al2O3/(FeO* + MgO), while biotite from reduced I-type and oxidized peraluminous granites may in some cases be more ambiguous. Biotite from peralkaline and reduced A-type granites are also distinguishable from all other categories by Al2O3/(FeO* + MgO) and FeO*/MgO, respectively. Biotite inclusions in Hadean zircons from Jack Hills, Western Australia indicate a mixture of metaluminous and reduced S-type host rocks, while inclusions in 3.6-3.8 Ga detrital zircons from the Nuvvuagittuq Supracrustal Belt indicate more oxidized peraluminous magmas. These results highlight the diversity of felsic materials on the early Earth and suggest that biotite inclusions are applicable to zircon provenance throughout the sedimentary record.

  11. Late accretion to the Moon recorded in zircon (U-Th)/He thermochronometry

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    Kelly, Nigel M.; Flowers, Rebecca M.; Metcalf, James R.; Mojzsis, Stephen J.

    2018-01-01

    We conducted zircon (U-Th)/He (ZHe) analysis of lunar impact-melt breccia 14311 with the aim of leveraging radiation damage accumulated in zircon over extended intervals to detect low-temperature or short-lived impact events that have previously eluded traditional isotopic dating techniques. Our ZHe data record a coherent date vs. effective Uranium concentration (eU) trend characterized by >3500 Ma dates from low (≤75 ppm) eU zircon grains, and ca. 110 Ma dates for high (≥100 ppm) eU grains. A progression between these date populations is apparent for intermediate (75-100 ppm) eU grains. Thermal history modeling constrains permissible temperatures and cooling rates during and following impacts. Modeling shows that the data are most simply explained by impact events at ca. 3950 Ma and ca. 110 Ma, and limits allowable temperatures of heating events between 3950-110 Ma. Modeling of solar cycling thermal effects at the lunar surface precludes this as the explanation for the ca. 110 Ma ZHe dates. We propose a sample history characterized by zircon resetting during the ca. 3950 Ma Imbrium impact event, with subsequent heating during an impact at ca. 110 Ma that ejected the sample to the vicinity of its collection site. Our data show that zircon has the potential to retain 4He over immense timescales (≥3950 Myrs), thus providing a valuable new thermochronometer for probing the impact histories of lunar samples, and martian or asteroidal meteorites.

  12. Detrital zircon geochronology and provenance of the Chubut Group in the northeast of Patagonia, Argentina

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    Navarro, Edgardo L.; Astini, Ricardo A.; Belousova, Elena; Guler, M. Verónica; Gehrels, George

    2015-11-01

    The Chubut Group constitutes the most widespread sedimentary unit in NE Patagonia, characterized by variable-energy fluvial deposits. U-Pb analysis of detrital zircons from two sections of the Chubut Group constraint the age of the oldest sedimentary rocks in the northeast of the Somuncurá - Cañadón Asfalto Basin. In the Cañadón Williams area, at San Jorge section, 20 km NW of Telsen locality, dating of 56 detrital zircons from a medium to coarse sandstone indicated a maximum depositional age of 109 ± 1 Ma (n = 4). These sandstones were interpreted to represent shallow channels, associated with a lacustrine system. In the Telsen locality, a laser ablation analysis of 115 detrital zircons from a medium to coarse-grained sandstone, from fluvial channel facies, yielded a maximum depositional age of ca. 106 ± 1 Ma (n = 8). Both ages are consistent with volcanic events of the Barremian to Albian age in the central Patagonian Andes Region. Cathodoluminescence images of zircons from the San Jorge sample suggest an igneous origin, which is further supported by Th/U values above 0.5 in most of the grains. The distribution of the statistical modes of the main age populations of detrital zircons for the two samples [182, 185 and 189 Ma for Telsen sample (T2S) and 181 ± 1 Ma for San Jorge sample (SJS)] matches the age of the volcanic Marifil Formation. The rocks of the Marifil Formation of these ages are exposed NE to SE of the study area. The abundance of zircons of similar Jurassic ages (n = 52 for SJS and n = 105 for T2S) and the external morphology of the zircons in the sample SJS, implies a close proximity of the source area. Suggestion that the Marifil Formation was the main provenance source is also supported by northeast-southeasterly paleocurrents measured at the San Jorge and Telsen sections.

  13. Post-Hadean transitions in Jack Hills zircon provenance: A signal of the Late Heavy Bombardment?

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    Bell, Elizabeth A.; Harrison, T. Mark

    2013-02-01

    Hadean Jack Hills (Western Australia) detrital zircons represent the best documented terrestrial resource with which to observe the pre-4 Ga Earth. The >4 Ga component of this semi-continuous 4.38 to 3.0 Ga zircon record has been investigated in detail for age, δ18O, Lu-Hf systematics, and Ti thermometry. The more abundant post-Hadean population is less well-characterized, but a previous study (Bell et al., 2011) suggests a more restricted range of δ18O source materials together with a ca. 4.0-3.6 Ga discontinuity in Lu-Hf evolution. These differences could reflect a transformation in the character of the older zircon source region or their sourcing from different terranes entirely. The relative scarcity of 4.0-3.6 Ga zircons corresponds to a discontinuity in Lu-Hf evolution after which 176Hf/177Hf in zircon reverts to more radiogenic values relative to the >4 Ga population. We present new oxygen isotope, titanium, and trace element results for 4.0-3.6 Ga Jack Hills zircons in a search for apparent transitions in petrological conditions. Post-3.8 Ga zircons show a marked decrease in the occurrence of heavy oxygen (>6.5‰), but remain close to the average of the Hadean distribution despite their restricted range. This may point to the decreased importance of sedimentary materials in post-3.8 Ga magmas. Ca. 3.9 Ga zircons fall into two categories: “Group I” displays temperatures and compositions similar to the Hadean zircons whereas “Group II” zircons have higher U and Hf, and lower (Th/U), Ce and P. Group II zircons also have anomalously low Ti, and are remarkably concordant in the U-Pb system. Group II's geochemical characteristics are consistent with formation by transgressive recrystallization (Hoskin and Black, 2000), in which non-essential structural constituents are purged during high-grade thermal metamorphism. The restricted age range of Group II occurrence (3.91-3.84) and its coincidence with the postulated intense bolide flux in the inner solar

  14. The first discovery of Hadean zircon in garnet granulites from the Sutam River (Aldan Shield)

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    Glukhovskii, M. Z.; Kuz'min, M. I.; Bayanova, T. B.; Lyalina, L. M.; Makrygina, V. A.; Shcherbakova, T. F.

    2017-09-01

    For the first time in Russia, a Hadean zircon grain with an age of 3.94 Ga (ID-TIMS) has been discovered in high-aluminous garnet granulites of the Aldan Shield among the U-Pb zircons with an age from 1.92 Ga. In this connection, the problems of its parental source, the petrogenesis of granulites that captured this zircon, and the mechanism of occurrence of these deep rocks in the upper horizons of the crust have been solved. The comparison of the geochemistry of garnet granulites and the middle crust has shown that the granulites are enriched in the entire range of rare-earth elements (except for the Eu minimum), as well as in Al2O3, U, and Th and are depleted in the most mobile elements (Na, Ca, Sr). In the upper part of the allitic weathering zone of the middle crust, which formed under conditions of arid climate, this zircon grain was originated from the weathered granites from the middle crust. In the latter case, they were empleced discretely in the upper granite-gneiss crust under high pressure conditions (the rutile age is 1.83-1.82 Ga). The zircon with an age of 3.94 Ga is comparable to the Hadean zircons from orthogneisses of the Acasta region (Canadian Shield, 4.03-3.94 Ga).

  15. Trace element chemistry of zircons from oceanic crust: A method for distinguishing detrital zircon provenance

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    Grimes, Craig B.; John, Barbara E.; Kelemen, P.B.; Mazdab, F.K.; Wooden, J.L.; Cheadle, Michael J.; Hanghoj, K.; Schwartz, J.J.

    2007-01-01

    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. ?? 2007 The Geological Society of America.

  16. Zircon saturation in silicate melts: a new and improved model for aluminous and alkaline melts

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    Gervasoni, Fernanda; Klemme, Stephan; Rocha-Júnior, Eduardo R. V.; Berndt, Jasper

    2016-03-01

    The importance of zircon in geochemical and geochronological studies, and its presence not only in aluminous but also in alkaline rocks, prompted us to think about a new zircon saturation model that can be applied in a wide range of compositions. Therefore, we performed zircon crystallization experiments in a range of compositions and at high temperatures, extending the original zircon saturation model proposed by Watson and Harrison (Earth Planet Sci Lett 64:295-304, 1983) and Boehnke et al. (Chem Geol 351:324-334, 2013). We used our new data and the data from previous studies in peraluminous melts, to describe the solubility of zircon in alkaline and aluminous melts. To this effect, we devised a new compositional parameter called G [ {( {3 \\cdot {{Al}}2 {{O}}3 + {{SiO}}2 )/({{Na}}2 {{O}} + {{K}}2 {{O}} + {{CaO}} + {{MgO}} + {{FeO}}} )} ] (molar proportions), which enables to describe the zircon saturation behaviour in a wide range of rock compositions. Furthermore, we propose a new zircon saturation model, which depends basically on temperature and melt composition, given by (with 1σ errors): ln [ {{Zr}} ] = ( {4.29 ± 0.34} ) - ( {1.35 ± 0.10} ) \\cdot ln G + ( {0.0056 ± 0.0002} ) \\cdot T( °C ) where [Zr] is the Zr concentration of the melt in µg/g, G is the new parameter representing melt composition and T is the temperature in degrees Celsius. The advantages of the new model are its straightforward use, with the G parameter being calculated directly from the molar proportions converted from electron microprobe measurements, the temperature calculated given in degrees Celsius and its applicability in a wider range of rocks compositions. Our results confirm the high zircon solubility in peralkaline rocks and its dependence on composition and temperature. Our new model may be applied in all intermediate to felsic melts from peraluminous to peralkaline compositions.

  17. Late magmatic stage of the zoned Caleu pluton (Central Chile): insights from zircon crystallization conditions

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    Molina, P. G.; Parada, M.; Gutierrez, F. J.; Chang-Qiang, M.; Jianwei, L.; Yuanyuan, L.

    2012-12-01

    The Caleu pluton consists of three N-S elongated lithological zones: Gabbro-Diorite Zone (GDZ), Tonalite Zone (TZ) and Granodiorite Zone (GZ); western, middle and eastern portions of the pluton, respectively. The zones are thought to be previously differentiated in a common, isotopically depleted (Sr-Nd), subjacent magma reservoir at a 4 kbar equivalent depth. The emplacement should have occurred at the climax of the Cretaceous rifting. We present preliminary results of U238/Pb206 zircon geochronology; zircon saturation, Tsat(Zrn), and crystallization temperatures (Ti-in-Zrn); as well as relative oxidation states at time of crystallization, based on: (i) the sluggish REE and HFSE subsolidus diffusivities in zircon; (ii) the behavior of Ti4+↔Si4+ and Ce4+↔Zr4+ isovalent replacement, in addition to a constrained TiO2 activity in almost all typical crustal rocks; and (iii) relative oxidation states at time of crystallization, respectively. The latter are obtained by interpolation of the partition coefficients of trivalent (REE) and tetravalent (HFSE) curves in Onuma diagrams for each zircon, and then estimating relative Ce(IV)/Ce(III) ratios. Results obtained from 4 samples (a total of 77 zircon grains) collected from the three mentioned lithological zones indicate U/Pb ages of approximately 99.5 ±1.5 Ma, 96.8 ±0.6 Ma, and 94.4 +2.2 -0.8 Ma; and Ti-in Zrn ranges of ca. 720-870°C, ca. 680-820°C and ca. 750-840°C, for the GDZ, TZ and GZ samples, respectively. On the other hand Tsat(Zrn) of ca. 750-780°C in the TZ, and ca. 830-890°C in the GZ, were obtained. As expected saturation temperatures are similar or higher than Ti-in-Zrn obtained in zircon grains of TZ and GZ, respectively. Cathodoluminiscence images in zircon suggest a magmatic origin, due to absence of complex zoning patterns and fairly well conserved morphologies. Exceptionally the GDZ sample zircons show evidence of inheritance, indicating a xenocrystic and/or antecrystic origin. A relative Ce

  18. Crustal growth history of the Korean Peninsula: Constraints from detrital zircon ages in modern river sediments

    Directory of Open Access Journals (Sweden)

    Taejin Choi

    2016-09-01

    Full Text Available U-Pb analyses were carried out on detrital zircon grains from major river-mouth sediments draining South Korea to infer provenance characteristics and the crustal growth history of the southern Korean Peninsula, using a laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS. The Korean Peninsula is located in the East Asian continental margin and mainly comprises three Precambrian massifs and two metamorphic belts in between them. We obtained 515 concordant to slightly discordant zircon ages ranging from ca. 3566 to ca. 48 Ma. Regardless of river-mouth location, predominance of Mesozoic (249–79 Ma and Paleoproterozoic (2491–1691 Ma ages with subordinate Archean ages indicates that the zircon ages reflect present exposures of plutonic/metamorphic rocks in the drainage basins of the South Korean rivers and the crustal growth of the southern Korean Peninsula was focused in these two periods. Comparison of detrital zircon-age data between the North and South Korean river sediments reveals that the Paleoproterozoic zircon age distributions of both regions are nearly identical, while the Neoproterozoic–Paleozoic ages exist and the Mesozoic ages are dominant in southern Korean Peninsula. This result suggests that Precambrian terrains in Korea record the similar pre-Mesozoic magmatic history and that the influence of Mesozoic magmatism was mainly focused in South Korea.

  19. New experimental constraints for Hadean zircon source melts from Ce and Eu anomalies in zircon

    Science.gov (United States)

    Trail, D.; Watson, E. B.; Tailby, N.

    2010-12-01

    A common feature of zircon rare earth element profiles is that they often have enriched chondrite normalized Ce abundances relative to bracketing rare earth elements (REEs) La and Pr. The magnitude of a zircon Ce anomaly is generally attributed to an increase in Ce4+/Ce3+ of the crystallizing medium (Ce4+ is more compatible than Ce3+ in zircon), which is associated with more oxidizing environments. Zircons may also have depleted chondrite normalized Eu abundances relative to Sm and Gd. A negative Eu anomaly may be indicative of more reducing conditions (Eu2+ is incompatible in zircon) or depletion of Eu in the melt from plagioclase prior to or during zircon crystallization. We report experimental data from zircons crystallized in hydrous peralkaline, metaluminous, and peraluminous melts (800-1300oC; 10 kbar) with the oxygen fugacity buffered from ~IW to HM+1 in order to constrain magnitude of zircon Ce and Eu anomalies. Zircon Ce anomalies increase in magnitude with higher oxygen fugacities and lower crystallization temperatures; Eu anomalies are more negative at ~IW vs. NNO for the same temperature and melt composition. Our experiments also show that with the oxygen fugacity buffered at NNO, zircons may have both positive Ce anomalies and negative Eu anomalies. Thus, Eu2+ and Ce4+ may co-exist in terrestrial melts; furthermore, melt depletion of Eu by plagioclase fractionation prior to (or during) zircon crystallization may not be a requisite for the presence of zircon Eu anomalies in (Hadean) zircons. The magnitude of the anomalies is also a function of the melt composition; peraluminous melts yield the largest positive Ce (or negative Eu) anomalies at a given oxygen fugacity and temperature. Extrapolation of our preliminary empirical calibration to the crystallization temperatures of the Jack Hills Hadean zircons (~700oC) suggests the magnitude of Ce anomalies in approximately half of the Hadean zircons cannot be produced in metaluminous or peralkaline melts

  20. Proterozoic to Mesozoic evolution of North-West Africa and Peri-Gondwana microplates: Detrital zircon ages from Morocco and Canada

    Science.gov (United States)

    Marzoli, Andrea; Davies, Joshua H. F. L.; Youbi, Nasrrddine; Merle, Renaud; Dal Corso, Jacopo; Dunkley, Daniel J.; Fioretti, Anna Maria; Bellieni, Giuliano; Medina, Fida; Wotzlaw, Jörn-Frederik; McHone, Greg; Font, Eric; Bensalah, Mohamed Khalil

    2017-05-01

    The complex history of assemblage and disruption of continental plates surrounding the Atlantic Ocean is in part recorded by the distribution of detrital zircon ages entrained in continental sedimentary strata from Morocco (Central High Atlas and Argana basins) and Canada (Grand Manan Island, New Brunswick). Here we investigate detrital zircon from the latest Triassic (ca. 202 Ma) sedimentary strata directly underlying lava flows of the Central Atlantic magmatic province or interlayered within them. SHRIMP (Sensitive High-Resolution Ion MicroProbe) and LA-ICP-MS (Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry) U-Pb ages for zircon range from Paleozoic to Archean with a dominant Neoproterozoic peak, and significant amounts of ca. 2 Ga zircon. These ages suggest a prevailing West African (Gondwanan) provenance at all sampling sites. Notably, the Paleoproterozoic zircon population is particularly abundant in central Morocco, north of the High Atlas chain, suggesting the presence of Eburnean-aged rocks in this part of the country, which is consistent with recent geochronologic data from outcropping rocks. Minor amounts of late Mesoproterozoic and early Neoproterozoic zircon ages (ca. 1.1-0.9 Ga) in Moroccan samples are more difficult to interpret. A provenance from Avalonia or Amazonia, as proposed by previous studies is not supported by the age distributions observed here. An involvement of more distal source regions, possibly located in north-eastern Africa (Arabian Nubian Shield) would instead be possible. Paleozoic zircon ages are abundant in the Canadian sample, pointing to a significant contribution from Hercynian aged source rocks. Such a signal is nearly absent in the Moroccan samples, suggesting that zircon-bearing Hercynian granitic rocks of the Moroccan Meseta block were not yet outcropping at ca. 200 Ma. The only Moroccan samples that yield Paleozoic zircon ages are those interlayered within the CAMP lavas, suggesting an increased dismantling

  1. Records of magmatic change as preserved in zircon: examples from the Yellowstone Volcanic Field

    Science.gov (United States)

    Rivera, T. A.

    2015-12-01

    Zircon crystals have been used as proxies for their host magmatic composition and as records of the evolution and differentiation of silicic magma systems through the use of integrated techniques such as cathodoluminescence imaging, LA-ICPMS trace element analysis, thermometry, and high-precision CA-IDTIMS U/Pb dating. This petrochronologic approach can aid in identifying crystal populations arising from discrete pulses of magmatism, reconstructing the growth histories of those populations, quantifying the chemical evolution of the host magma, and determining the timing and tempo of that chemical evolution. The Yellowstone Volcanic Field hosts both large and small volume silicic eruptions whose zircon records can provide insights to magmatic processes using a petrochronologic approach. Morphological and thermochemical trends preserved in zircon grains extracted from the three Yellowstone super-eruptions and a small volume precursory eruption indicate that magmatism in the volcanic field is punctuated, characterized by numerous pulses of melting, differentiation, and solidification occurring prior to eruption. U/Pb zircon dating constrains magma assembly to geologically short timescales, with populations of earlier solidified zircon incorporated into the nascent magma just prior to eruption. This requires punctuated intervals of high magmatic flux be superimposed on longer durations of a much lower background flux. Thus super-eruptions within the Yellowstone Volcanic Field result from rapid production and evolution of magma, and preceded by periods of smaller volume magma production that undergo similar differentiation processes over comparable timescales.

  2. Simulation of radiation damage in zircon

    Energy Technology Data Exchange (ETDEWEB)

    Weber, W.J.; Maupin, G.D.

    1988-05-01

    Radiation damage in natural zircon minerals due to alpha decay over geologic time has been simulated in laboratory studies extending over 5.5 years using Pu-doped synthetic zircon. These studies confirm for the first time that laboratory testing of actinide-doped materials can accurately predict the radiation-damage behavior of radioactive waste forms over geologic time and also provide new insights into interpretation of radiation damage in natural minerals.

  3. Simulation of radiation damage in zircon

    Energy Technology Data Exchange (ETDEWEB)

    Weber, W.J.; Maupin, G.D.

    1987-06-01

    Radiation damage in natural zircon minerals due to alpha decay has been simulated in laboratory studies using Pu-doped synthetic zircon. These studies confirm that laboratory testing of actinide-doped materials can accurately predict the radiation-damage behavior of radioactive waste forms over geologic time, and also provide new insights into interpretation of radiation damage in natural minerals. 15 refs., 4 figs., 2 tabs.

  4. Contrasting Cu-Au and Sn-W Granite Metallogeny through the Zircon Geochemical and Isotopic Record

    Science.gov (United States)

    Gardiner, Nicholas; Hawkesworth, Chris; Robb, Laurence; Whitehouse, Martin; Roberts, Nick; Kirkland, Chris

    2017-04-01

    -hydrothermal deposit, and empirical observations suggest that this threshold may be marked by zircon Eu/Eu* values of ca. < 0.08. The isotope and trace element signatures of both magmatic and detrital zircons can be developed into a useful exploration tool.

  5. Detrital zircon U-Pb geochronology of metasediments from southwestern Svalbard's Caledonian Province

    Science.gov (United States)

    Kośmińska, Karolina; Schneider, David A.; Majka, Jarosław; Lorenz, Henning; Gee, David G.; Manecki, Maciej; Barnes, Chris

    2015-04-01

    We conducted SIMS U-Pb geochronology on detrital zircons from metasedimentary rocks of Svalbard's Southwestern Caledonian Province, including: Prins Karls Forland, Wedel Jarlsberg Land, and Sørkapp Land. Quartzite from the northernmost area, Prins Karls Forland, was collected from the amphibolite facies Pinkie Unit, which was thought to be Mesoproterozoic. Preliminary detrital zircon dating obtained for this unit yielded ages as young as early Neoproterozoic to late Mesoproterozoic (0.95-1.05 Ga), with dominant populations around 1.4 and 1.6 Ga. Samples from Wedel Jarlsberg Land were collected from the Eimfjellet, Deilegga and Sofiebogen groups, and except for one quartzite from the Gulliksenfjellet Formation (Eimfjellet Group), samples also possess ages as young as early Neoproterozoic to late Mesoproterozoic (0.9-1.1 Ga). Older zircon age signatures are dominated by Mesoproterozoic populations at ca. 1.3 Ga and 1.45-1.6 Ga, with older Paleoproterozoic ages also present. The Gulliksenfjellet Formation is characterized by 1.75-1.9 and 2.5-3.0 Ga detrital zircon ages; no detrital grains younger than 1.7 Ga are present. The samples from Sørkapp Land were collected from an unnamed complex, which is thought to be an equivalent of the Neoproterozoic Isbjørnhamna Group of Wedel Jarlsberg Land. Youngest detrital zircons of early Neoproterozoic to late Mesoproterozoic (ca. 0.95-1.1 Ga) age are abundant. The older populations are dominated by Mesoproterozoic to Paleoproterozoic zircon, with clusters at 1.3-1.35, 1.65, and 1.8 Ga. Single Archean grains were also identified. The detrital zircon age signatures for metasedimentary rocks from Sørkapp are similar to those identified within Wedel Jarlsberg Land. In summary, our data from the southwestern Svalbard's Caledonian Province indicate: a) an early Neoproterozic maximum sedimentation age for the units; and b) a distinct late Mesoproterozoic to early Neoproterozoic provenance. The exception is the Gulliksenfjellet

  6. Sample-scale zircon geochemical and geochronological heterogeneities as indicators of residual liquid infiltration events in the incrementally assembled Caleu Pluton, Central Chile

    Science.gov (United States)

    Molina, P. G.; Parada, M. A.; Gutiérrez, F. J.; Ma, C.; Li, J.; Liu, Y.

    2013-12-01

    The Upper Cretaceous metaluminous Caleu Pluton is emplaced at a depth equivalent of 2kbar and consists of four lithological zones: the Gabbro-Dioritic Zone (GDZ), the Quartz-Monzodioritic Zone (QMDZ), the Granodioritic Zone (GZ) and the Monzogranitic Zone (MGZ). The zones would have been fed from a deeper magma reservoir emplaced at a 4 kbar. U238/Pb206 LA-ICP-MS geochronology of zircon grains of the four lithological zones (82 analyzed spots, 4 samples) indicates a maximum zircon crystallization range of ca. 106-91 Ma for the pluton as a whole. The U-Pb zircon age distribution of the four samples shows three inflection points at about 101, 99 and 96 Ma, separating four zircon crystallization events with the following weighted average ages and 2σ confidence intervals: 103.×1.6 Ma (n=4), 100.3×0.68 Ma (n=14), 97.49×0.49 Ma (n=25) and 94.66×0.44 Ma (n=30). The GDZ sample records the first three events, the GZ and QMDZ samples record the last three events while the MGZ only have zircons formed during the last two events. It is interesting to note that the youngest event of zircon formation coincide with the Ar/Ar cooling ages (95-93 Ma) previously obtained in hornblende, biotite and plagioclase of the four lithological zones, as a consequence of a rapid pluton exhumation. Temperatures of zircon crystallization (Ti-in-Zrn) obtained in each sample are variable and roughly lower than the zircon saturation temperatures. Most of the Ti-in-Zrn temperatures indicate late-stage crystallization conditions, consistent with the calculated melt composition from which zircons would have crystallized and the observed coexistence of zircons with quartz-orthoclase symplectites, hornblende and interstitial anhedral biotite. There are variable and overlapped total incompatible element concentrations in zircons of the four lithological zones regardless its age and Ti-in-Zrn temperatures, indicating that the melts from which zircon crystallized at different moments, were equivalent

  7. Coeval Formation of Zircon Megacrysts and Host Magmas in the Eifel Volcanic Field (Germany) Based on High Spatial Resolution Petrochronology

    Science.gov (United States)

    Schmitt, Axel; Klitzke, Malte; Gerdes, Axel; Ludwig, Thomas; Schäfer, Christof

    2017-04-01

    Zircon megacrysts (approx. 0.5-6 mm in diameter) from the Quaternary West and East Eifel volcanic fields, Germany, occur as euhedral crystals in porous K-spar rich plutonic ejecta clasts, and as partially resorbed xenocrysts in tephrite lava. Their relation to the host volcanic rocks has remained contentious because the dominantly basanitic to phonolitic magma compositions in the Eifel are typically zircon undersaturated. We carried out a detailed microanalytical study of zircon megacrysts from seven locations (Emmelberg and Rockeskyll in the West Eifel; Bellerberg, Laacher See, Mendig, Rieden, and Wehr in the East Eifel). Crystals were embedded in epoxy, sectioned to expose interiors through grinding with abrasives, diamond-polished, and mapped by optical microscopy, backscattered electron, and cathodoluminescence imaging. Subsequently, isotope-specific analysis using secondary ionization mass spectrometry (SIMS) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was carried out placing 100 correlated spots on 20 selected crystals. Concordant U-Th disequilibrium and U-Pb ages determined by SIMS are between ca. 430 ka (Rieden) and 170 ka (Mendig) and indicate that the megacryst zircons crystallized almost always briefly before eruption. A significant gap between zircon megacryst crystallization (ca. 230 ka) and eruption (ca. 45 ka) ages was only detected for the Emmelberg location. SIMS trace element abundances (e.g., rare earth elements) vary by orders-of-magnitude and correlate with domain boundaries visible in cathodoluminescence; trace element patterns match those reported for zircon from syenitic origins. Isotopic compositions are homogeneous within individual crystals, but show some heterogeneity between different crystals from the same locality. Average isotopic values (δ18O SMOW = +5.3±0.6 ‰ by SIMS; present-day ɛHf = +1.7±2.5 ‰ by LA-ICP-MS; 1 standard deviation), however, are consistent with source magmas being dominantly mantle

  8. 1.8 billion years of fluid-crust interaction: A zircon oxygen isotope record for the lower crust, western Churchill Province, Canadian Shield

    Science.gov (United States)

    Petts, Duane C.; Moser, Desmond E.; Longstaffe, Frederick J.; Davis, William J.; Stern, Richard A.

    2014-04-01

    The western Churchill Province of the Canadian Shield experienced a prolonged and complex formation history (ca. 4.04 to 1.70 Ga), with evidence for multiple episodes of orogenesis and regional magmatic activity. Here we report on the oxygen isotopic compositions of garnet and zircon recovered from lower crustal xenoliths, which have U-Pb ages between ca. 3.5 and 1.7 Ga. Overall, zircon from four metabasite xenoliths from the Rankin Inlet sample suite have δ18O values ranging from + 5.5 to + 8.6‰. Zircon from three metatonalite/anorthosite xenoliths and five metabasite xenoliths from the Repulse Bay sample suite have δ18O values of + 5.6 to + 8.3‰. High δ18O values (> + 6.0‰) for the oldest igneous zircon cores (ca. 3.5 Ga and 3.0-2.6 Ga) indicate that their metatonalite/anorthosite protolith magmas were generated from, or had assimilated, supracrustal rocks that interacted previously with surface-derived fluids. Igneous zircon cores (ca. 2.9-2.6 Ga) from one metabasite xenolith have δ18O values of + 5.6 to + 6.4‰, which suggests a formation from a mantle-derived basaltic/gabbroic magma. Metamorphic zircon cores (ca. 2.0-1.9 Ga) from one metabasite xenolith commonly have δ18O values between + 6.0 and + 6.3‰, which is indicative of a basalt/gabbro protolith and localized reworking of the lower crust caused by regional-scale plate convergence. The wide range of δ18O values (+ 5.5 to + 8.3‰) for ca. 1.75-1.70 Ga metamorphic zircon rims (identified in all xenoliths) indicates regional transient heating and reworking of mantle- and supracrustal-derived crust, induced by magmatic underplating along the crust-mantle boundary.

  9. Geochronology of the Voisey's Bay intrusion, Labrador, Canada, by precise U Pb dating of coexisting baddeleyite, zircon, and apatite

    Science.gov (United States)

    Amelin, Yuri; Li, Chusi; Naldrett, A. J.

    1999-06-01

    The emplacement history of the Voisey's Bay troctolite intrusion, that hosts the major Ni-Cu-Co sulfide deposit of the same name, has been studied using precise U-Pb geochronology of baddeleyite, zircon and apatite. The baddeleyite U-Pb ages of multiple drill core samples of troctolite and gabbro indicate that all of the mafic rocks studied from different components of the Voisey's Bay intrusion: Eastern Deeps, Discovery Hill Zone and Reid Brook Zone, and from the adjacent Red Dog area, were emplaced at 1332.7±1.0 Ma. On the basis of combined geological and geochronological evidence, it is suggested that the Voisey's Bay Ni-Cu-Co deposit was formed during the same period. The zircons coexisting with the ca. 1333 Ma baddeleyite show a diversity of ages. The zircons from normal troctolite and some of the olivine gabbro samples are coeval with the baddeleyite, while zircon from the varied textured troctolite and feeder olivine gabbro are much younger at 1305.0±0.8 Ma. The identical ages of the younger zircon population and the Voisey's Bay syenite that cuts the mafic rocks indicate a link between zircon growth in the mafic rocks and contact metamorphism, related to the emplacement of the syenite. Various mechanisms of zircon growth were probably involved, including reaction of the 1333 Ma baddeleyite with a silica-enriched fluid with formation of a secondary polycrystalline zircon, and zircon crystallization from syenite micro-veins in the mafic rocks. The mean 207Pb/ 206Pb age of 1303.5±2.6 Ma of the Voisey's Bay apatites is similar to the age of the younger zircon population. The apatite age may either be a result of resetting the U-Pb system in response to the syenite intrusion, or may reflect the closure of the system during regional cooling and cessation of fluid circulation. The presence of xenocrystic zircon in a Discovery Hill Zone feeder olivine gabbro indicates that the Voisey's Bay magmas were contaminated with 1.90 Ga crustal rocks.

  10. Geology, zircon geochronology, and petrogenesis of Sabalan volcano (northwestern Iran)

    Science.gov (United States)

    Ghalamghash, J.; Mousavi, S. Z.; Hassanzadeh, J.; Schmitt, A. K.

    2016-11-01

    to ca. 110 ka. Because zircon crystallization predates eruption, this age represents the upper limit for the youngest eruptions of Sabalan. Valley-filling ignimbrites yielded variable U-Pb zircon ages which argue against these pyroclastic rocks being generated in a single caldera forming event. These results indicate that eruptions occurred more recently than previously indicated by K-Ar dating. Paleo-Sabalan and Neo-Sabalan volcanic rocks have similar geochemical characteristics, including enrichment of LILE and LREE relative to HFSE and HREE, respectively, and prominent negative Ti, Nb, and Ta anomalies. The trachyandesitic to dacitic rocks of Sabalan also share negative Eu anomalies. This, together with horizontal or slightly increasing Y vs. Rb trends, indicates fractionation of plagioclase-amphibole or plagioclase-clinopyroxene assemblages with negligible crustal assimilation (based on low and invariant Rb/Th). High degrees of mantle partial melting are inferred from high (La/Yb)N (from 28 to 48). Overall, the subduction-affinity of Sabalan volcanic rocks agrees with models of melt generation following a Quaternary slab break-off event coeval with continental collision.

  11. Lithium in low-temperature fluid-affected zircons. Paleoproterozoic weathering horizon (Karelia, the Baltic shield).

    Science.gov (United States)

    Alfimova, Nadezhda; Klimova, Ekaterina; Matrenichev, Vjacheslav; Zinger, Tatjana

    2017-04-01

    Zircon is a mineral, which is widely used in geochronology. At the same time, low-temperature fluids had been shown to affect the inner structure, chemical and even isotopic composition of zircons (Geisler et al., 2007, Pidgeon et al., 2013). Here we report changes in the inner structure and chemical composition of zircon grains, preserved in Paleoproterozoic weathering horizon from Karelia craton (N. Ladoga region, Russia) in spite of greenschist metamorphism. Detailed zircon SEM and CL study revealed that zircons in weathered samples can be classified into two groups depending on their microstructural characteristics: 1- the zircons with an unusual and complex (breccia-like) structure with almost no relics of magmatic zonation. The inner structure of that grains is often composed of a mosaic of angular crystal pieces cemented with silicates or even other generation of zircon itself. Group 2- zircons with clearly seen relics of magmatic (oscillatory) zonation. Both groups have outer rims which are forming the facets of the grains. These two groups are also different in chemistry. Group 1 zircons contain more than 10 ppm of Ba and Sr, >1000 ppm U and Th/U there is ≤0.1, REE spectra show LREE/HREE > 0.5, positive Cean (enrichment of non-formula elements (Ca, Mg, Fe, Al) and water. Lithium varies broadly - from 33 to 136 ppm (av.value around 60 ppm). Group 2 zircons are characterized by Th/U >0.3, Ba and Sr are less than 10 ppm each, LREE/HREE+2.0, Euan ≤ +1.0, Li is from 19 to 73 ppm with average meaning 49 ppm. A separate geochemical group can be identified within "a-structural" grains (group 1) -parts of zircons and grains light-colored in SEM. These part of group 1 zircons demonstrate specific REE spectra - LREE/HREE < 0.1, ∑REE ≤750 ppm, thus being lower, then LREE part of spectra from grains with magmatic structure. These group also has the highest concentration of Li (up to 136 ppm with av. 88 ppm) and lowest Ba/Sr ratio of all measured points, thus

  12. A search for thermal excursions from ancient extraterrestrial impacts using Hadean zircon Ti-U-Th-Pb depth profiles.

    Science.gov (United States)

    Abbott, Sunshine S; Harrison, T Mark; Schmitt, Axel K; Mojzsis, Stephen J

    2012-08-21

    Few terrestrial localities preserve more than a trace lithic record prior to ca. 3.8 Ga greatly limiting our understanding of the first 700 Ma of Earth history, a period inferred to have included a spike in the bolide flux to the inner solar system at ca. 3.85-3.95 Ga (the Late Heavy Bombardment, LHB). An accessible record of this era may be found in Hadean detrital zircons from the Jack Hills, Western Australia, in the form of μm-scale epitaxial overgrowths. By comparing crystallization temperatures of pre-3.8 Ga zircon overgrowths to the archive of zircon temperature spectra, it should, in principle, be possible to identify a distinctive impact signature. We have developed Ti-U-Th-Pb ion microprobe depth profiling to obtain age and temperature information within these zircon overgrowths and undertaken a feasibility study of its possible use in identifying impact events. Of eight grains profiled in this fashion, four have overgrowths of LHB-era age. Age vs. temperature profiles reveal a period between ca. 3.85-3.95 Ga (i.e., LHB era) characterized by significantly higher temperatures (approximately 840-875 °C) than do older or younger zircons or zircon domains (approximately 630-750 °C). However, temperatures approaching 900 °C can result in Pb isotopic exchange rendering interpretation of these profiles nonunique. Coupled age-temperature depth profiling shows promise in this role, and the preliminary data we report could represent the first terrestrial evidence for impact-related heating during the LHB.

  13. Reaction Sintering of Mexican Dolomite – Zircon Mixtures

    Directory of Open Access Journals (Sweden)

    Rodríguez-Galicia, J. L.

    2005-08-01

    Full Text Available The present work has been conducted aiming to develop additional phase [Ca3SiO5, Ca2SiO4 and/or Ca3Mg(SiO42]-bonded magnesia refractory materials via reaction sintering of dolomite-zircon mixtures, employing a Mexican dolomite containing an excess of 3 wt% of CaCO3. The study was based on phase equilibrium data extracted from the quaternary system CaO – MgO – SiO2 – ZrO2, to put it more precisely, base on the projection from the MgO-apex of the liquidus surface of the primary crystallization volume of MgO onto the opposite face of the above mentioned quaternary system. The refractory materials designed within this system were obtained by attrition milling, followed by cold isostatic pressing and high temperature reaction sintering. All initial and produced materials were characterized by ICP-AES, XRF, XRD, SEM-EDX, DTA and TG analyses. The results obtained indicated that reaction sintering of dolomite-zircon mixtures is an interesting route to produce MgO-CaZrO3-additional phase refractory materials.

    El propósito de este trabajo ha sido obtener materiales refractarios de magnesia, aglomerados con una fase adicional [Ca3SiO5, Ca2SiO4 y/o Ca3Mg(SiO42], mediante la sinterización reactiva de mezclas de dolomita-circón, empleando para ello una dolomita mexicana que contiene un exceso de 3% en peso de CaCO3. El estudio se basa en la información relativa al equilibrio de fases del sistema CaO – MgO – SiO2 – ZrO2. En concreto se usa la proyección, desde el vértice del MgO, de la superficie de liquidus del volumen de cristalización primaria de este, hacia la cara opuesta de sistema cuaternario. Los materiales refractarios diseñados se han obtenido por molienda de atrición, seguida de un prensado isostático en frío y sinterización reactiva a alta temperatura. Todos los materiales, iniciales y finales, han sido caracterizados mediante ICPAES, FRX, DRX, MEB-EDX, ATD y TG. Los resultados obtenidos indican que la sinterizaci

  14. Component geochronology in the polyphase ca. 3920 Ma Acasta Gneiss

    Science.gov (United States)

    Mojzsis, Stephen J.; Cates, Nicole L.; Caro, Guillaume; Trail, Dustin; Abramov, Oleg; Guitreau, Martin; Blichert-Toft, Janne; Hopkins, Michelle D.; Bleeker, Wouter

    2014-01-01

    The oldest compiled U–Pb zircon ages for the Acasta Gneiss Complex in the Northwest Territories of Canada span about 4050–3850 Ma; yet older ca. 4200 Ma xenocrystic U–Pb zircon ages have also been reported for this terrane. The AGC expresses at least 25 km2 of outcrop exposure, but only a small subset of this has been documented in the detail required to investigate a complex history and resolve disputes over emplacement ages. To better understand this history, we combined new ion microprobe235,238U–207,206Pb zircon geochronology with whole-rock and zircon rare earth element compositions ([REE]zirc), Ti-in-zircon thermometry (Tixln) and 147Sm–143Nd geochronology for an individual subdivided ∼60 cm2 slab of Acasta banded gneiss comprising five separate lithologic components. Results were compared to other variably deformed granitoid-gneisses and plagioclase-hornblende rocks from elsewhere in the AGC. We show that different gneissic components carry distinct [Th/U]zirc vs. Tixln and [REE]zirc signatures correlative with different zircon U–Pb age populations and WR compositions, but not with 147Sm–143Nd isotope systematics. Modeled  [REE] from lattice-strain theory reconciles only the ca. 3920 Ma zircons with the oldest component that also preserves strong positive Eu∗ anomalies. Magmas which gave rise to the somewhat older (inherited) ca. 4020 Ma AGC zircon age population formed at ∼IW (iron–wüstite) to ca. 3920 Ma emplacement age for the AGC is contemporaneous with bombardment of the inner solar system. Analytical bombardment simulations show that crustal re-working from the impact epoch potentially affected the precursors to the Acasta gneisses.

  15. Magma mixing and crystal exchange at Yellowstone caldera revealed though sub-crystal-scale age, trace-element, and Hf-isotopic analyses of zircons

    Science.gov (United States)

    Stelten, M. E.; Cooper, K. M.; Vazquez, J. A.; Wimpenny, J.; Yin, Q.

    2011-12-01

    We examine magma mixing and crystal exchange in a young magma reservoir by correlating sub-crystal-scale SIMS age, SIMS trace element, and LA-MC-ICPMS Hf-isotopic data from zircons in the coeval ca. 100ka, yet compositionally distinct rhyolites of the Solfatara Plateau flow (SPF) and Hayden Valley flow (HVF) at Yellowstone Caldera. The SPF and HVF lavas are part of the Central Plateau Member (CPM) of the Plateau Rhyolite that is composed of the youngest intracaldera rhyolite flows at Yellowstone, erupted between ca. 170-70ka. We compare these data to age and trace element data from zircons in 1) the Pitchstone Plateau Flow, West Yellowstone Flow, and Dry Creek Flow of the CPM as representative of main reservoir zircons, 2) the ca. 118ka extracaldera Gibbon River Flow rhyolite (GRF), and 3) the ca. 260ka Scaup Lake Flow of the Upper Basin Member rhyolites. Additionally, we compare the zircon data to new MC-ICPMS Hf-isotopic data from CPM glasses. Correlating age, trace element, and Hf-isotopic data from zircons in the HVF and SPF reveals the presence of four zircon populations. Main reservoir-like (MR-like) zircons have trace element compositions similar to main CPM reservoir zircons, young ages (Lastly, a population of zircons (which we interpret to be inherited) have cores with older ages (>350ka), a range in trace element compositions, and high ɛHf (-5.8 to -3.6) whereas the rims have restricted MR-like trace element compositions and ɛHf within error of CPM glasses. The sense of core to rim zoning specific to each population suggests that each population has its own unique history. The core to rim zoning in MR-like and inherited zircons, from cores with a range of Hf-isotopic compositions to rims similar to CPM glasses, suggests that MR-like and inherited zircons in the SPF and HVF came from distinct high ɛHf magmas and were incorporated into the CPM reservoir. For mixed zircons, the zoning from MR-like or EC-like cores to intermediate rim compositions

  16. Geochemical fingerprints and pebbles zircon geochronology ...

    Indian Academy of Sciences (India)

    (figures 2c and 3a). We selected gravel samples. (clast diameters >4 cm) from conglomerates with clasts composed of granitic gneiss and then selected zircon grains from granitic gneiss. ...... 4.3.2 Laiyang Group, Neoproterozoic granitic gneiss and Mesozoic intrusive rocks. The curved shape of the trace element plot for the.

  17. Geochemical fingerprints and pebbles zircon geochronology ...

    Indian Academy of Sciences (India)

    The zircon ages of the granitic gneiss material in the conglomerates at the base of the Laiyang Group are 790±8.4 Ma, close to the ages of the Neoproterozoic granitic gneiss in the Jiaonan Orogen (739–819 Ma), and very different from the ages of the Early Cretaceous intrusive rocks. Combiningwith paleocurrent directions ...

  18. MORPHOMETRY OF ZIRCON FROM BETLIAR GRANITE

    Directory of Open Access Journals (Sweden)

    Jakabská Katarína

    1997-10-01

    Full Text Available Morphometrical analyse has been provided, using the method of [10] , on zircon from granite porphyry at Betliar. The result of this investigation indicate a comagmatic origin of Betliar and other granite bodies in the Gemericum. The source materila for at the granite magma formation originated by hybridization of crust-mantle rocks.

  19. Mass-spectrometric mining of Hadean zircons by automated SHRIMP multi-collector and single-collector U/Pb zircon age dating: The first 100,000 grains

    Science.gov (United States)

    Holden, Peter; Lanc, Peter; Ireland, Trevor R.; Harrison, T. Mark; Foster, John J.; Bruce, Zane

    2009-09-01

    The identification and retrieval of a large population of ancient zircons (>4 Ga; Hadean) is of utmost priority if models of the early evolution of Earth are to be rigorously tested. We have developed a rapid and accurate U-Pb zircon age determination protocol utilizing a fully automated multi-collector ion microprobe, the ANU SHRIMP II, to screen and date these zircons. Unattended data acquisition relies on the calibration of a digitized sample map to the Sensitive High Resolution Ion MicroProbe (SHRIMP) sample-stage co-ordinate system. High precision positioning of individual grains can be produced through optical image processing of a specified mount location. The focal position of the mount can be optimized through a correlation between secondary-ion steering and the spot position on the target. For the Hadean zircon project, sample mounts are photographed and sample locations (normally grain centers) are determined off-line. The sample is loaded, reference points calibrated, and the target positions are then visited sequentially. In SHRIMP II multiple-collector mode, zircons are initially screened (ca. 5 s data acquisition) through their 204Pb corrected 207Pb/206Pb ratio; suitable candidates are then analyzed in a longer routine to obtain better measurement statistics, U/Pb, and concentration data. In SHRIMP I and SHRIMP RG, we have incorporated the automated analysis protocol to single-collector measurements. These routines have been used to analyze over 100,000 zircons from the Jack Hills quartzite. Of these, ca. 7%, have an age greater than 3.8 Ga, the oldest grain being 4372 +/- 6 Ma (2[sigma]), and this age is part of a group of analyses around 4350 Ma which we interpret as the age when continental crust first began to coalesce in this region. In multi-collector mode, the analytical time taken for a single mount with 400 zircons is approximately 6 h; whereas in single-collector mode, the analytical time is ca. 17 h. With this productivity, we can produce

  20. Zircon ion microprobe dating of high-grade rocks in Sri Lanka

    Energy Technology Data Exchange (ETDEWEB)

    Kroener, A.; Williams, I.S.; Compston, W.; Baur, N.; Vitanage, P.W.; Perera, L.R.K.

    1987-11-01

    The high-grade gneisses of Sri Lanka display spectacular in-situ granulitization phenomena similar to those observed in southern India and of current interest for evolutionary models of the lower continental crust. The absolute ages of these rocks are poorly constrained and so, using the SHRIMP ion microprobe, the authors have analyzed small spots on zircons from upper amphibolite to granulite grade quartzitic and pelitic metasediments. Detrital grains from a metaquartzite of the Highland Group preserve premetamorphic U-Pb ages of between 3.17 and 2.4 Ga and indicate derivation of the sediment from an unidentified Archean source terrain. The Pb-loss patterns of these zircons and the other samples suggest severe disturbance at ca 1100 Ma ago, which the authors attribute to high-grade regional metamorphism. Two pelitic gneisses contain detrital zircons with ages up to 2.04 Ga and also record an approx. = 1100 Ma event that is also apparent from metamorphic rims around old cores and new zircon growth. A granite intrusive into the Highland Group granulites records an emplacement age of 1000-1100 Ma as well as metamorphic disturbance some 550 Ma ago but also contains older, crustally derived xenocrysts. Zircons from a metaquartzite xenolith within the granitoid Vijayan Complex are not older than approx. 1100 Ma; therefore the Vijayan is neither Archean in age nor acted as basement to the Highland Group, as previously proposed. The authors suggest that the Vijayan Complex formed significantly later than the Highland Group and that the two units were brought into contact through post-1.1 Ga thrusting. Although the granulitization phenomena in India and Sri Lanka are similar, the granulite event in Sri Lanka is not Archean in age but took place in the late Proterozoic.

  1. Mechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry

    Science.gov (United States)

    Stelten, Mark; Cooper, Kari M.; Vazquez, Jorge A.; Calvert, Andrew T.; Glessner, Justin G

    2015-01-01

    We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (ca. 170 – 70 ka) Central Plateau Member eruptive episode – the most recent post-caldera magmatism at Yellowstone. We present 238U-230Th crystallization ages and trace-element compositions of the interiors and surfaces (i.e., unpolished rims) of individual zircon crystals from each rhyolite. We compare these zircon data to 238U- 230Th crystallization ages of bulk sanidine separates coupled with chemical and isotopic data from single sanidine crystals. Zircon age and trace-element data demonstrate that the magma reservoir that sourced the Central Plateau Member rhyolites was long-lived (150 – 250 kyr) and genetically related to the preceding episode of magmatism, which occurred ca. 256 ka. The interiors of most zircons in each rhyolite were inherited from unerupted material related to older stages of Central Plateau Member magmatism or the preceding late Upper Basin Member magmatism (i.e., are antecrysts). Conversely, most zircon surfaces crystallized near the time of eruption from their host liquids (i.e., are autocrystic). The repeated recycling of zircon interiors from older stages of magmatism demonstrates that sequentially erupted Central Plateau Member rhyolites are genetically related. Sanidine separates from each rhyolite yield 238U-230Th crystallization ages at or near the eruption age of their host magmas, coeval with the coexisting zircon surfaces, but are younger than the coexisting zircon interiors. Chemical and isotopic data from single sanidine crystals demonstrate that the sanidines in each rhyolite are in equilibrium with their host melts, which considered along with their near-eruption crystallization ages suggests that nearly all CPM sanidines are autocrystic. The paucity of antecrystic sanidine crystals relative to

  2. Significance of zircon U-Pb ages from the Pescadero felsite, west-central California coast ranges

    Science.gov (United States)

    McLaughlin, Robert J.; Moore, Diane E.; ,; Martens, UWE C.; Clark, J.C.

    2011-01-01

    Weathered felsite is associated with the late Campanian–Maastrichtian Pigeon Point Formation near Pescadero, California. Poorly exposed, its age and correlation are uncertain. Is it part of the Pigeon Point section west of the San Gregorio–Hosgri fault? Does it rest on Nacimiento block basement? Is it dextrally offset from the Oligocene Cambria Felsite, ∼185 km to the southeast? Why is a calc-alkaline hypabyssal igneous rock intrusive into the outboard accretionary prism? To address these questions, we analyzed 43 oscillatory-zoned zircon crystals from three incipiently recrystallized pumpellyite ± prehnite ± laumontite-bearing Pescadero felsite samples by sensitive high-resolution ion microprobe–reverse geometry (SHRIMP-RG) and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) techniques. Thirty-three zircons gave late Mesozoic U-Pb ages, with single-grain values ranging from 81 to 167 Ma; ten have pre-Mesozoic, chiefly Proterozoic ages. A group of the four youngest Pescadero zircons yielded an apparent maximum igneous age of ca. 86–90 Ma. Reflecting broad age scatter and presence of partly digested sandstone inclusions, we interpret the rest of the zircons (perhaps all) as xenocrysts. Twenty-three zircons were separated and analyzed from two samples of the similar Cambria Felsite, yielding a unimodal 27 Ma U-Pb age. Clearly, the origin of the Upper Oligocene Cambria Felsite is different from that of the Upper Cretaceous Pescadero felsite; these rocks are not correlated, and do not constrain displacement along the San Gregorio–Hosgri fault. Peak ages differ slightly, but relative probability curves for Mesozoic and pre-Mesozoic Pescadero zircons compare well, for example, with abundant U-Pb age data for detrital zircons from Franciscan metaclastic strata ∼100 km to the east in the Diablo Range–San Francisco Bay area, San Joaquin Great Valley Group turbidites, Upper Cretaceous Nacimiento block Franciscan strata, and Upper

  3. Modeling of Carbochlorination of Zircon in Fluidized Bed Reactor

    Science.gov (United States)

    Jazini, M. H.; Ghoreishi, S. M.; Dadkhah, A. A.

    2010-02-01

    The chlorination of zircon is an integral part of the overall process for the production of zirconium. A two-phase hydrodynamic-type model was used to simulate the fluidized bed zircon carbochlorination reactor. In the plug-plug (P-P) model, the flow of gas in both dense and bubble phases was considered as a plug flow compared with the plug-mixed (P-M) model in which the flow in dense phase was assumed to be mixed. The zircon conversion obtained by model was compared with experimental measurements for model validation. The results of the P-M model indicated a stronger correlation with experimental data. Using the validated model, the effects of the zircon inlet size distribution, reactor temperature, inlet gas concentration, chlorine conversion velocity, and converted zircon were investigated. The results demonstrated that higher reactor temperature, smaller zircon size, and higher inlet gas velocity and concentration enhanced the chlorination rate.

  4. Thermoluminescence of zircon: a kinetic model

    CERN Document Server

    Turkin, A A; Vainshtein, D I; Hartog, H W D

    2003-01-01

    The mineral zircon, ZrSiO sub 4 , belongs to a class of promising materials for geochronometry by means of thermoluminescence (TL) dating. The development of a reliable and reproducible method for TL dating with zircon requires detailed knowledge of the processes taking place during exposure to ionizing radiation, long-term storage, annealing at moderate temperatures and heating at a constant rate (TL measurements). To understand these processes one needs a kinetic model of TL. This paper is devoted to the construction of such a model. The goal is to study the qualitative behaviour of the system and to determine the parameters and processes controlling TL phenomena of zircon. The model considers the following processes: (i) Filling of electron and hole traps at the excitation stage as a function of the dose rate and the dose for both (low dose rate) natural and (high dose rate) laboratory irradiation. (ii) Time dependence of TL fading in samples irradiated under laboratory conditions. (iii) Short time anneali...

  5. Micrometer-scale U–Pb age domains in eucrite zircons, impact re-setting, and the thermal history of the HED parent body

    Science.gov (United States)

    Hopkins, M.D.; Mojzsis, S.J.; Bottke, W.F.; Abramov, Oleg

    2015-01-01

    Meteoritic zircons are rare, but some are documented to occur in asteroidal meteorites, including those of the howardite–eucrite–diogenite (HED) achondrite clan (Rubin, A. [1997]. Meteorit. Planet. Sci. 32, 231–247). The HEDs are widely considered to originate from the Asteroid 4 Vesta. Vesta and the other large main belt asteroids record an early bombardment history. To explore this record, we describe sub-micrometer distributions of trace elements (U, Th) and 235,238U–207,206Pb ages from four zircons (>7–40 μm ∅) separated from bulk samples of the brecciated eucrite Millbillillie. Ultra-high resolution (∼100 nm) ion microprobe depth profiles reveal different zircon age domains correlative to mineral chemistry and to possible impact scenarios. Our new U–Pb zircon geochronology shows that Vesta’s crust solidified within a few million years of Solar System formation (4561 ± 13 Ma), in good agreement with previous work (e.g. Carlson, R.W., Lugmair, G.W. [2000]. Timescales of planetesimal formation and differentiation based on extinct and extant radioisotopes. In: Canup, R., Righter, K. (Eds.), Origin of the Earth and Moon. University of Arizona Press, Tucson, pp. 25–44). Younger zircon age domains (ca. 4530 Ma) also record crustal processes, but these are interpreted to be exogenous because they are well after the effective extinction of 26Al (t1/2 = 0.72 Myr). An origin via impact-resetting was evaluated with a suite of analytical impact models. Output shows that if a single impactor was responsible for the ca. 4530 Ma zircon ages, it had to have been ⩾10 km in diameter and at high enough velocity (>5 km s−1) to account for the thermal field required to re-set U–Pb ages. Such an impact would have penetrated at least 10 km into Vesta’s crust. Later events at ca. 4200 Ma are documented in HED apatite 235,238U–207,206Pb ages (Zhou, Q. et al. [2011]. Early basaltic volcanism and Late Heavy Bombardment on Vesta: U–Pb ages of small

  6. Zircon U-Pb geochronology and Hf isotopes from the Sanbagawa Metamorphic Belt, Western Shikoku, Japan: evidence for the prevalence for the Late Cretaceous protoliths

    Science.gov (United States)

    Walia, Monika; Knittel, Ulrich; Suzuki, Shigeyuki; Nishizaka, Naoki; Kimura, Kazunari; Lee, Yuan-Hsi; Lee, Hao-Yang

    2017-04-01

    Sanbagawa Metamorphic Belt lies to the south of Median Tectonic Line and is exposed on Kyushu, Shikoku and Honshu Islands in Japan. This belt has been the focus of many studies in recent years since the discovery of young detrital zircon grains (80 - 95 Ma). Samples for this study come from a 2000 m bore hole from north-western Shikoku drilled in an area considered to be part of the Jurassic to Early Cretaceous part of the Sanbagawa Belt. Dating of single zircon grains using the LA-ICP-MS U-Pb dating method shows that all but one sample contain zircons younger than 100 Ma and thus the protoliths are younger than the previously accepted age of metamorphism of the Sanbagawa Belt at ca. 110 Ma. The single sample that contains only zircons dated at 136 ± 3 Ma, apparently is of volcanic origin and could be a clast representing the source of 130-140 Ma zircons of the sample taken about 120m above this sample. In addition, three surface samples were analyzed. Two of these also contain zircons younger than 100 Ma, whereas the third sample contains only zircons older than 159 Ma. Hf-isotope values for the younger age group 82-116 Ma, ɛHf(T) range from -2.4 to +9.6. Zircon grains of 127-146 Ma ages have more positive ɛHf(T) values of +11.5 to +19.0 indicating depleted mantle source. We envisage these zircons to have been derived from the ocean side of a magmatic arc. All grains in the range 215-250 Ma are characterized by negative ɛHf(T) ranging from -2.3 to -15.2, suggesting re-melting of already existent crust. Within the detrital zircon populations contained in the Sanbagawa meta-sediments age groups are recognized that are also known from SE China. However, compared to those from mainland China, zircons from the Sanbagawa meta-sediments are usually characterized by higher ɛHf(T) values suggesting higher input of material derived from the depleted mantle.

  7. Significance of detrital zircons in upper Devonian ocean-basin strata of the Sonora allochthon and Lower Permian synorogenic strata of the Mina Mexico foredeep, central Sonora, Mexico

    Science.gov (United States)

    Poole, F.G.; Gehrels, G.E.; Stewart, John H.

    2008-01-01

    U-Pb isotopic dating of detrital zircons from a conglomeratic barite sandstone in the Sonora allochthon and a calciclastic sandstone in the Mina Mexico foredeep of the Minas de Barita area reveals two main age groups in the Upper Devonian part of the Los Pozos Formation, 1.73-1.65 Ga and 1.44-1.42 Ga; and three main age groups in the Lower Permian part of the Mina Mexico Formation, 1.93-1.91 Ga, 1.45-1.42 Ga, and 1.1-1.0 Ga. Small numbers of zircons with ages of 2.72-2.65 Ga, 1.30-1.24 Ga, ca. 2.46 Ga, ca. 1.83 Ga, and ca. 0.53 Ga are also present in the Los Pozos sandstone. Detrital zircons ranging in age from 1.73 to 1.65 Ga are considered to have been derived from the Yavapai, Mojave, and Mazatzal Provinces and their transition zones of the southwestern United States and northwestern Mexico. The 1.45-1.30 Ga detrital zircons were probably derived from scattered granite bodies within the Mojave and Mazatzal basement rocks in the southwestern United States and northwestern Mexico, and possibly from the Southern and Eastern Granite-Rhyolite Provinces of the southern United States. The 1.24-1.0 Ga detrital zircons are believed to have been derived from the Grenville (Llano) Province to the east and northeast or from Grenvilleage intrusions or anatectites to the north. Several detrital zircon ages ranging from 2.72 to 1.91 Ga were probably derived originally from the Archean Wyoming Province and Early Paleoproterozoic rocks of the Lake Superior region. These older detrital zircons most likely have been recycled one or more times into the Paleozoic sandstones of central Sonora. The 0.53 Ga zircon is believed to have been derived from a Lower Cambrian granitoid or meta-morphic rock northeast of central Sonora, possibly in New Mexico and Colorado, or Oklahoma. Detrital zircon geochronology suggests that most of the detritus in both samples was derived from Laurentia to the north, whereas some detritus in the Permian synorogenic foredeep sequence was derived from the

  8. Resolution, the key to unlocking granite petrogenesis using zircon U-Pb - Lu-Hf studies

    Science.gov (United States)

    Tapster, Simon; Horstwood, Matthew; Roberts, Nick M. W.; Deady, Eimear; Shail, Robin

    2017-04-01

    Coarse-scale understanding of crustal evolution and source contributions to igneous systems has been drastically enhanced by coupled zircon U-Pb and Lu-Hf data sets. These are now common place and potentially offer advantages over whole-rock analyses by resolving heterogeneous source components in the complex crystal cargos of single hand-samples. However, the application of coupled zircon U-Pb and Lu-Hf studies to address detailed petrogenetic questions faces a crisis of resolution - On the one hand, micro-beam analytical techniques have high spatial resolution, capable of interrogating crystals with complex growth histories. Yet, the >1-2% temporal resolution of these techniques places a fundamental limitation on their utility for developing petrogenetic models. This limitation in data interpretation arises from timescales of crystal recycling or changes in source evolution that are often shorter than the U-Pb analytical precision. Conversely, high-precision CA-ID-TIMS U-Pb analysis of single whole zircons and solution MC-ICP-MS Lu-Hf isotopes of column washes (Hf masses equating to ca. 10-50 ng) have much greater temporal resolution (bridging the gap in resolving power between in-situ and isotope dilution coupled zircon U-Pb - Lu-Hf studies. We demonstrate the potential of this approach to unravel intra- and inter-sample heterogeneity and address models for granite genesis using a new regional data set for 21 samples encompassing all major granite types within the Early Permian Cornubian Batholith (SW England). The data provide a refined chronological framework for magma source evolution over 20 Myrs of crust-mantle melt extraction and upper crustal batholith construction. The resulting petrogenetic model will also be evaluated through the lens of low- temporal resolution commonly employed in granitic zircon U-Pb - Lu-Hf studies in order to highlight the enhanced insights into geological processes gained though our approach. The current limitations to data

  9. Detrital zircons of deep-sea sediments of the Arctic ocean - key to the understanding of High Polar Arctic tectonics

    Science.gov (United States)

    Shokalsky, S.; Morozov, A.; Petrov, O.; Belyatsky, B.; Rekant, P.; Shevchenko, S.; Sergeev, S.

    2012-04-01

    Zircons from sedimentary rocks bear the information on composition of vast territories often inaccessible for geologic investigation but which are the source of material. The studies of modern beaches and fluvial deposits demonstrate the efficiency of reconstruction of composition and distribution of rock types based on clastic zircon characteristics (Zircon, 2003). We have studied nine 0,5 kg specimens (every meter) from gravity-corer sample of deep sea-bottom sedimentary cover within the Geophysicists Spur region (Lomonosov Ridge) which represent first 9 meters of the section formed during 70 000 years. Heavy fraction is composed by garnet, tourmaline, titanite, rutile and by 200-300 grains of zircon per sample. Zircons in all samples are different in morphology and inner structure: from faceted needle-like to perfectly rounded, from colorless to brown opaque, with thin growth zones and inherited cores, as well as homogeneous. U-Pb SIMS SHRIMP isotope dating (50 grain analyses for each sample) was applied to two key specimens from the depth of 12-14 and 505-507 cm. The age probability distribution diagrams show that the main age peaks are of 138-147, 200-300, 400-800 and 1845-2000 Ma; few grains of 2700 Ma and one grain is 3000 Ma old. Our previous data for the zircon age distribution for box-corer sample of hemipelagic sediment from the North Pole (Grikurov et al., 2011) revealed peaks of 160, 200-450 (max 260-300 Ma), 800, 1855, 2000 and 2600 Ma. Zircons from three samples above show common features: 1) presence of Archean grains (>2400 Ma), 2) defined age peak of 1800-2000 Ma (ca 30% of grains), 3) lack of Grenvillian age zircons, 4) youngest ages of 40-160 Ma. Thus, all three studied samples have very similar provenance source, the deposition time of sandstones, from which had mainly formed the modern (<30 000 years) sediments, is Jurassic (≤140-160 Ma). About 50% of analyzed zircons falls to the age interval 200-500 Ma. However, grains distribution is

  10. Assessing the isotopic evolution of S-type granites of the Carlos Chagas Batholith, SE Brazil: Clues from U-Pb, Hf isotopes, Ti geothermometry and trace element composition of zircon

    Science.gov (United States)

    Melo, Marilane G.; Lana, Cristiano; Stevens, Gary; Pedrosa-Soares, Antônio C.; Gerdes, Axel; Alkmin, Leonardo A.; Nalini, Hermínio A.; Alkmim, Fernando F.

    2017-07-01

    The Carlos Chagas batholith (CCB) is a very large ( 14,000 km2) S-type granitic body formed during the syn-collisional stage of the Araçuaí orogen (southeastern Brazil). Zircons extracted from the CCB record a wide range of U-Pb ages (from 825 to 490 Ma), indicating a complex history of inheritance, magmatic crystallization and partial melting during the evolution of the orogeny. Magmatic zircons (ca. 578-588 Ma) are marked by similar Hf isotope compositions and REE patterns to those of inherited cores (ca. 825-600 Ma), indicating that these aspects of the chemical signature of the magmatic zircons have likely been inherited from the source. The U-Pb ages and initial 176Hf/177Hf ratios from anatectic and metamorphic zircon domains are consistent with a two-stage metamorphic evolution marked by contrasting mechanisms of zircon growth and recrystallization during the orogeny. Ti-in-zircon thermometry is consistent with the findings of previous metamorphic work and indicates that the two metamorphic events in the batholith reached granulite facies conditions (> 800 °C) producing two generations of garnet via fluid-absent partial melting reactions. The oldest metamorphic episode (ca. 570-550 Ma) is recorded by development of thin anatectic overgrowths on older cores and by growth of new anatectic zircon crystals. Both domains have higher initial 176Hf/177Hf values compared to relict cores and display REE patterns typical of zircon that grew contemporaneously with peritectic garnet through biotite-absent fluid partial melting reactions. Hf isotopic and chemical evidences indicate that a second anatectic episode (ca. 535-500 Ma) is only recorded in parts from the CCB. In these rocks, the growth of new anatectic zircon and/or overgrowths is marked by high initial 176Hf/177Hf values and also by formation of second generation of garnet, as indicated by petrographic observations and REE patterns. In addition, some rocks contain zircon crystals formed by solid

  11. High temperature behaviour of a zircon ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Carbonneau, X.; Olagnon, C.; Fantozzi, G. [INSA, Villeurbanne (France). GEMMPM; Hamidouche, M. [Lab. Science des Materiaux, Univ. de Setif (Algeria); Torrecillas, R. [Inst. Nacional del Carbon, Oviedo (Spain)

    1997-12-31

    The high temperature properties of a sintered zircon material has been tested up to 1200 C. A significant creep rate is observed, mainly attributed to the presence of glassy phase. The sub-critical crack growth measured in double torsion showed that above 1000 C, the crack velocity is reduced either by stress relaxation or by crack healing. The thermal shock analysis under a heat exchange coefficient of 600 W/m{sup 2}/K showed a regular decrease rather that a sudden fall off of properties. (orig.) 3 refs.

  12. Silica–calcium zirconate nanocomposite, studying its thermal and ...

    Indian Academy of Sciences (India)

    Silica–calcium zirconate nanocomposite was prepared in a two-step procedure. First, nanocalcium zirconate was synthesized by the modified sol–gel method; then, silica was added to the prepared sol and the resulting product was calcined at 700–1000° C. Dilatometric measurements were performed to determine the ...

  13. Natural radioactivity and radon specific exhalation rate of zircon sands

    Energy Technology Data Exchange (ETDEWEB)

    Righi, S.; Verita, S.; Bruzzi, L. [Bologna Univ., Centro Interdipartimentale di Ricerca per le Scienze Ambientali and Dipt. di Fisica, Ravenna (Italy); Albertazzi, A. [Italian Ceramic Center, Bologna (Italy)

    2006-07-01

    The study focuses on the radon emanation from zircon sands and their derivatives, which are widely used in many sectors of industry. In particular, the results obtained by experimental measurements on samples of zircon sands and zircon flours commonly used in Italian ceramic industries are reported. Zircon sands contain a significant concentration of natural radioactivity because Th and U may substitute zirconium in the zircon crystal lattice. The relevant routes of exposure of workers to T.E.N.O.R.M. from zircon materials are external radiation and internal exposure, either by inhalation of aerosols in dusty working conditions or by inhalation of radon in workplaces. The main objective of this investigation is to provide experimental data able to better calculate the internal exposure of workers due to radon inhalation. Zircon samples were surveyed for natural radioactivity, radon specific exhalation rate and emanation fraction. Measurements of radioactivity concentration were carried out using {gamma}-spectrometry. Methods used for determining radon consisted in determining the {sup 222}Rn activity accumulated in a vessel after a given accumulation build-up time. The average activity concentrations of {sup 238}U and {sup 232}Th in samples result about 2600 and 550 Bq kg-1, respectively; these concentrations are significantly higher than the world average noticed in soils, rocks and Earth crust. The {sup 222}Rn specific exhalation rates result very low probably due to the low porosity of the material and the consequent difficulty for radon to be released from the zircon crystal lattice. (author)

  14. Latest Pleistocene crustal cannibalization at Baekdusan (Changbaishan) as traced by oxygen isotopes of zircon from the Millennium Eruption

    Science.gov (United States)

    Cheong, Albert Chang-sik; Sohn, Young Kwan; Jeong, Youn-Joong; Jo, Hui Je; Park, Kye-Hun; Lee, Youn Soo; Li, Xian-Hua

    2017-07-01

    The silicic volcanism of Baekdusan (Changbaishan), which is on the border between North Korea and China, was initiated in the Late Pleistocene and culminated in the 10th century with a powerful (volcanic explosivity index = 7) commendite-trachyte eruption commonly referred to as the ;Millennium Eruption.; This study presents oxygen isotope data of zircon in trachydacitic pumices ejected during the Millennium Eruption, together with whole-rock geochemical and Sr-Nd-Pb isotopic data that manifest once again the A-type and EM1 affinities of the Millennium Eruption magma. The zircon crystals, dated by previous studies at ca. 12-9 ka, show a moderate inter-grain variation in δ18O from 3.69‰ to 5.03‰. These values are consistently lower than the normal mantle range, and interpreted to have resulted from the digestion of meteoric-hydrothermally altered intracaldera rocks in the shallow magma chamber beneath Baekdusan just prior to the crystallization of the zircons, rather than from derivation from low-δ18O sources deep in the mantle. The whole-rock geochemical/isotopic considerations suggest that the magma mainly self-cannibalized the earlier erupted volcanic carapace around the magma chamber. This study highlights the usefulness of zircon oxygen isotopes for characterizing past volcanic activity that has now been commonly eroded away and implies that the generation of Yellowstone-type low-δ18O magma is not a rare phenomenon in large-volume silicic eruptions.

  15. Pre-Variscan evolution of the Western Tatra Mountains: new insights from U-Pb zircon dating

    Science.gov (United States)

    Burda, Jolanta; Klötzli, Urs

    2011-10-01

    In situ LA-MC-ICP-MS U-Pb zircon geochronology combined with cathodoluminescence imaging were carried out to determine protolith and metamorphic ages of orthogneisses from the Western Tatra Mountains (Central Western Carpathians). The metamorphic complex is subdivided into two units (the Lower Unit and the Upper Unit). Orthogneisses of the Lower Unit are mostly banded, fine- to medium-grained rocks while in the Upper Unit varieties with augen structures predominate. Orthogneisses show a dynamically recrystallised mineral assemblage of Qz + Pl + Bt ± Grt with accessory zircon and apatite. They are peraluminous (ASI = 1.20-1.27) and interpreted to belong to a high-K calc-alkaline suite of a VAG-type tectonic setting. LA-MC-ICP-MS U-Pb zircon data from samples from both units, from crystals with oscillatory zoning and Th/U > 0.1, yield similar concordia ages of ca. 534 Ma. This is interpreted to reflect the magmatic crystallization age of igneous precursors. These oldest meta-magmatics so far dated in the Western Tatra Mountains could be linked to the fragmentation of the northern margin of Gondwana. In zircons from a gneiss from the Upper Unit, cores with well-developed oscillatory zoning are surrounded by weakly luminescent, low contrast rims (Th/U grade metamorphic event, connected with the formation of crustal-scale nappe structures and collision-related magmatism.

  16. Composition of coexisting zircon and xenotime in rare-metal granites from the Krušné Hory/Erzgebirge Mts. (Saxothuringian Zone, Bohemian Massif)

    Science.gov (United States)

    René, Miloš

    2014-08-01

    Zircon and xenotime, from two mineralogically and chemically contrasting granite suites occurring in the Krušné Hory/Erzgebirge Mts., display extended compositional variability with respect to abundances of Zr, Hf, REE, Y, P, Th, Ca, Al, Fe and As. According to their geochemical signatures, P-rich (S-type) and P-poor (A-type) granites could be distinguished here. Both granite suites display high Ga/Al ratios (>2.6) and according to FeOtot./(FeOtot. + MgO) ratio can be classified as ferrous granites. Consequently, the both ratios cannot be used for discrimination S- and A-type granites. Both minerals are characterized by a variety of complex zircon-xenotime textures. They are usually strong hydrated and enriched in F. Zircon from P-rich granites displays a significant enrichment in P (up 0.24 apfu P), whereas zircon from P-poor granites has lower P and higher Y (up to 0.15 apfu Y). The xenotime-type substitution is the most important mechanism of isomorphic substitution in zircon in both granite suites. Zircon from both granite suites is typically enriched in Hf, especially unaltered zircon from P-rich granites (up to 8.2 wt. % HfO2). However in altered zircons the Hf/Zr ratio is higher in the P-poor granites. The Hf-rich zircon from unaltered P-rich granite crystallised from low temperature granite melt, whereas altered zircons crystallised during post-magmatic hydrothermal alteration (greisenization). Xenotime from P-poor granites displays a considerable enrichment in HREE (up to 40 mol. % HREEPO4) compared to xenotime from P-rich granites (up to 20 mol. % HREEPO4). Xenotime compositions from P-rich granites are influenced by brabantite-type substitution, whereas for xenotime from P-poor granites the huttonite-type substitution is dominant. Unusual enrichments in HREE is significant for xenotime from P-poor granites, especially in Yb (up to 0.17 apfu Yb) and Dy (up to 0.11 apfu).

  17. Zircon-pyrochlore ores of Proterozoic Gremyakha-Vyrmes polyphase massif, Kola Peninsula: source and evolution

    Science.gov (United States)

    Sorokhtina, Natalia; Belyatsky, Boris; Antonov, Anton; Kononkova, Natalia; Lepekhina, Elena; Kogarko, Lia

    2017-04-01

    The alkaline-ultrabasic Gremyakha-Vyrmes massif occurs within the Central Kola terrane in the northern part of the Fennoscandian Shield and consists of diverse rock complexes: basic-ultrabasic rocks, foidolites, alkaline metasomatic rocks and carbonatites, alkaline granites and granosyenites. Nb-Zr ore deposit is confined to alkaline metasomatic rocks developed over foidolites. The metasomatites are represented by albitites and aegirinites occur as submeridionally orientated zones extending up to 6-8 km and several hundred meters thickness. They are mainly composed of albite and aegirine, but amphibole, annite, microcline, fluorapatite, titanite, ilmenite, pyrochlore group minerals, zircon are present [Sorokhtina et al., 2016]. Carbonatites are developed sporadically and accessory zircon but not the pyrochlore is observed only in contact zones with albitites and aegerinites. In metasomatites, zircon and pyrochlore are main rare metal minerals, which are formed at the latest stages of crystallization. Ca-dominant fluorcalcio- and hydroxycalciopyrochlores are the most abundant, whereas U-dominant pyrochlore, oxyuranobetafite, zero-valent-dominant (Ba, Sr-dominant) pyrochlore, hydro- or kenopyrochlore are rare. The pyrochlore-group minerals form heterogeneous metacrystals containing inclusions of host rock minerals, calcite, ilmenite, zircon, sulfides, and graphite. While pyrochlore is replaced by Si-rich "pyrochlore" (SiO2 is up to 18 wt.%.), cation-deficient hydrated pyrochlore, Fe-Si-Nb, U-Si-Nb, and Al-Si-Nb phases along fracture zones and margins. The early generation zircon is represented by large heterogeneous metacrystals filled with inclusions of various host rock minerals, calcite, ilmenite, thorite, thorianite and sulfides, while the late zircons are empty of inclusions. Zircons are nearly stoichiometric in composition; but intermediate zones are enriched in Pb, Y and Th, and overgrowths are enriched Hf only. According to CL and ion-microprobe analysis

  18. Cast aluminum alloys containing dispersions of zircon particles

    Science.gov (United States)

    Banerji, A.; Surappa, M. K.; Rohatgi, P. K.

    1983-06-01

    A process for preparing Al-alloy castings containing dispersions of zircon particles is described. Composites were prepared by stirring zircon particles (40 to 200 µm size) in commercially pure Al (99.5 pct)* and Al-11.8 pct Si melts and subsequently casting these melts in permanent molds. It was found to be necessary to alloy the above two melts with 3 pct Mg to disperse substantial amounts of zircon particles (25 to 30 pct). Further, it was possible to disperse up to 60 wt pct zircon by adding up to 5 pct Mg; however, the melts containing above 30 wt pct zircon showed insufficient fluidity for gravity diecasting and had to be pressure diecast. Microstructural studies of cast composites indicated the presence of a reaction zone at the periphery of zircon particles, and electron probe microanalysis showed concentrations of Mg and Si at the particle-matrix interface. Hardness, abrasive wear resistance, elastic modulus, 0.2 pct proof stress, and tensile strength of cast Al-3 pct Mg alloy were found to improve with the dispersions of zircon particles. Scanning electron micrographs of abraded and fractured surfaces did not show any evidence of particle pull-outs or voids at the particle matrix interface, indicating strong continuous bonding.

  19. Coordinated U-Pb geochronology, trace element, Ti-in-zircon thermometry and microstructural analysis of Apollo zircons

    Science.gov (United States)

    Crow, Carolyn A.; McKeegan, Kevin D.; Moser, Desmond E.

    2017-04-01

    We present the results of a coordinated SIMS U-Pb, trace element, Ti-in-zircon thermometry, and microstructural study of 155 lunar zircons separated from Apollo 14, 15, and 17 breccia and soil samples that help resolve discrepancies between the zircon data, the lunar whole rock history and lunar magma ocean crystallization models. The majority of lunar grains are detrital fragments, some nearly 1 mm in length, of large parent crystals suggesting that they crystallized in highly enriched KREEP magmas. The zircon age distributions for all three landing sites exhibit an abundance of ages at ∼4.33 Ga, however they differ in that only Apollo 14 samples have a population of zircons with ages between 4.1 and 3.9 Ga. These younger grains comprise only 10% of all dated lunar zircons and are usually small and highly shocked making them more susceptible to Pb-loss. These observations suggest that the majority of zircons crystallized before 4.1 Ga and that KREEP magmatism had predominantly ceased by this time. We also observed that trace element analyses are easily affected by contributions from inclusions (typically injected impact melt) within SIMS analyses spots. After filtering for these effects, rare-earth element (REE) abundances of pristine zircon are consistent with one pattern characterized by a negative Eu anomaly and no positive Ce anomaly, implying that the zircons formed in a reducing environment. This inference is consistent with crystallization temperatures based on measured Ti concentrations and new estimates of oxide activities which imply temperatures ranging between 958 ± 57 and 1321 ± 100 °C, suggesting that zircon parent magmas were anhydrous. Together, the lunar zircon ages and trace elements are consistent with a ⩽300 My duration of KREEP magmatism under anhydrous, reducing conditions. We also report two granular texture zircons that contain baddeleyite cores, which both yield 207Pb-206Pb ages of 4.33 Ga. These grains are our best constraints on

  20. Records of Sedimentation and Palaeofluid Events in Detrital Zircon U-Th-Pb Ages From Northern Greeland.

    Science.gov (United States)

    Morris, G. A.; Pease, V.; Kirkland, C. L.

    2008-12-01

    The Neoproterozoic (1.0 Ga to 550 Ma) is an important interval of dramatic change in the global environment. Several fragments of Neoproterozoic crust occur in the circum-Artic region and are thought to have been dispersed during the break-up of Rodinia/Pannotia. The correlation between these fragments and the models for their dispersion however remains controversial. We present U-Th-Pb detrital zircon age profiles from turbidite trough sediments (the Cambrian Polkorridoren and Vølvedal, and the Silurian Sydgletscher groups) of Northern Greenland and use the results to assess the source(s) of these sediments. These results allow us to test possible correlation(s) with dispersed circum-Arctic Neoproterozoic fragments. U-Th-Pb zircon ages from the two younger units (Vølvedal and Sydgletscher groups) show a significant number of discordant analyses. These are routinely ignored in detrital zircon studies, but when plotted on a standard inverse Concordia diagram define a pattern of radiogenic Pb-loss which occurred at ca. 400 Ma. Indeed, one zircon from the Sydgletcher Group yields a re-set pseudo-concordant age of 407 ± 13 Ma. Partial or total resetting of zircon U-Pb systematics at low temperatures (<200°C) is well- documented, particularly in U rich grains. The stratigraphically confined nature of the reset units, coupled with the presence of quartz/calcite veining, suggests that, rather than regional metamorphism, a major palaeofluid event at approx. 400 Ma was responsible for this resetting. We propose that this fluid event was driven by uplift of the Caledonian Orogen to the east.

  1. A Raman spectroscopic study of zircons on micro-scale and Its significance in explaining the origin of zircons

    CERN Document Server

    Bao, Xuezhao; Lu, Songnian

    1998-01-01

    The magmatic and metamorphic zircons were investigated with Raman spectrum microprobe analysis. We found notable differences between these two kinds of zircons exhibited by the variation trend of Raman peak intensity from core to rim of a crystal. In magmatic zircons, the intensity and the ratio H/W of Raman spectrum peaks gradually decrease from core to rim of a crystal, which is produced by an increase in metamictization degree and suggests an increase in U and Th concentrations from core to rim. In metamorphic zircons, there are two kinds of crystals according to their Raman spectra: the first group of zircons exhibits a variation trend opposite to those of magmatic zircons, tending to increase in the Raman peak intensity and H/W value from core to rim of a crystal, which is produced by a decrease in metamictization degree and indicates a decrease of U and Th concentrations from core to rim of a crystal. The second group of zircons exhibits no change in Raman peak intensity and H/W value through a crystal....

  2. Reactions of calcium orthosilicate and barium zirconate with oxides and sulfates of various elements

    Science.gov (United States)

    Zaplatynsky, I.

    1979-01-01

    Calcium orthosilicate and barium zirconate were evaluated as the insulation layer of thermal barrier coatings for air cooled gas turbine components. Their reactions with various oxides and sulfates were studied at 1100 C and 1300 C for times ranging up to 400 and 200 hours, respectively. These oxides and sulfates represent potential impurities or additives in gas turbine fuels and in turbine combustion air, as well as elements of potential bond coat alloys. The phase compositions of the reaction products were determined by X-ray diffraction analysis. BaZrO3 and 2CaO-SiO2 both reacted with P2O5, V2O5, Cr2O3, Al2O3, and SiO2. In addition, 2CaO-SiO2 reacted with Na2O, BaO, MgO, and CoO and BaZrO3 reacted with Fe2O3.

  3. The Dynamics of the Post-Caldera Magmatic System at Yellowstone: Insights from Age, Trace Element, and Isotopic Data of Zircon and Sanidine

    Science.gov (United States)

    Stelten, M. E.; Cooper, K. M.; Vazquez, J. A.; Calvert, A. T.; Glessner, J. J.; Wimpenny, J.; Yin, Q. Z.

    2014-12-01

    Yellowstone hosts a voluminous magmatic system that produced three silicic caldera-forming eruptions over the past 2.1 My. Following the most recent of these (the Lava Creek Tuff at 639 ka), the magma system at Yellowstone underwent two episodes of intracaldera eruptions, the latest of which produced the Central Plateau Member (CPM) rhyolites. The CPM rhyolites erupted intermittently from ca. 170 ka to ca. 70 ka and can be viewed as snapshots of the magma system through time, which provides a unique opportunity to study the dynamics of an evolving caldera system. To constrain the nature and timescales of magmatic processes at Yellowstone we examine four CPM rhyolites that erupted from ca. 116 ka to ca. 74 ka and present a comprehensive data set that integrates (1) 238U-230Th ages, trace-elements, and Hf isotope compositions of the surfaces and interiors of single zircons, (2) bulk 238U-230Th ages and in situ Ba and Pb isotope compositions of sanidines, (3) sanidine 40Ar-39Ar ages, and (4) trace-element and isotopic compositions of the CPM glasses. Zircon 238U-230Th ages and Hf isotope data demonstrate that isotopically juvenile magmas, derived from Yellowstone basalts, were added to the Yellowstone magma reservoir over time and were fundamental to its post-caldera isotopic evolution. We use zircon Hf isotope data along with new Hf isotope data (and existing O isotope data) for the Yellowstone basalts (whole-rocks), older Yellowstone rhyolites (glasses), and local crustal sources to quantify the role of isotopically juvenile magma in the evolution of the magmatic system. Additionally, linking age, trace-element, and isotopic data from zircon and sanidine demonstrates that eruptible CPM rhyolites were generated by extracting melt and antecrystic zircon from a long-lived (>200 ky) crystal mush, while sanidine remained trapped in the crystal network. The extracted melts amalgamated and then crystallized new sanidines and rims on the antecrystic zircons that were in

  4. Zircon U-Pb Ages of Tuffs and Volcaniclastic Sandstone of the Core Sample of IODP Exp. 322 at the Northern Part of the Shikoku Basin.

    Science.gov (United States)

    Shinjoe, H.; Nakajima, T.; Orihashi, Y.; Saito, S.; Oda, H.; Danhara, T.

    2014-12-01

    We determined U-Pb ages of zircons from core samples of IODP Exp. 322 using the laser abrasion ICP-MS (VG Plasma Quad 3 with New Wave Research UP-213). Zircon crystals were separated from four felsic tuffs from the Unit V of Site C0011, and a volcaniclastic turbidite sandstone of the lowermost horizon of the Unit V of Site C0012. Both of the drilling sites are located off the Nankai trough on the Shikoku Basin of the Philippine Sea plate, southwest Japan. Zircons from two felsic tuffs from Site C0011 are euhedral crystals, and most of their 238U-206Pb ages range 13 - 16 Ma. Weighted means of the 238U-206Pb ages of these samples are ca. 14.3 Ma. The other two felsic tuffs include zircon grains with older ages (80 - 260 Ma), however, weighted means of the 238U-206Pb ages of population with young ages ranges 14.5 - 14.7 Ma. These ages are coincide with those of the intense felsic magmatism occurred in the forearc region of southwest Japan (14 - 15 Ma) just after the opening of the Japan Sea and consequent clockwise rotation of the southwest Japan. Some of the felsic igneous bodies of the middle Miocene southwest Japan ejected large amount of felsic materials resulting caldera formation. So the provenance of felsic tuffs from the core of the Site C0011 are presumed to be one of the felsic igneous bodies of the forearc region of southwest Japan. Turbidite sandstone from Site C0012 also includes Miocene zircon grains of which their weighted mean of the 238U-206Pb ages is ca. 14.2 Ma. Moreover turbidite sandstone contains zircons with various ages (19 - 2500 Ma). One of the possible origin of such old zircon grains is reworking from sediments of the accretionary complex in the forearc of southwest Japan. If we assume the present rate of convergence of the Philippine sea plate (ca. 4 cm/y) is invariant, the turbidite including both clastic sediment and coeval felsic igneous materials traveled ca. 600 km across the trench.

  5. Extrusion and properties of lead zirconate titanate piezoelectric ceramics

    DEFF Research Database (Denmark)

    Cai, S.; Millar, C.E.; Pedersen, L.

    1997-01-01

    The purpose of this work was to develop a procedure for fabricating electroceramic actuators with good piezoelectric properties. The preparation of lead zirconate titanate (PZT) piezoelectric ceramic rods and tubes by extrusion processing is described. The microstructure of extrudates was investi......The purpose of this work was to develop a procedure for fabricating electroceramic actuators with good piezoelectric properties. The preparation of lead zirconate titanate (PZT) piezoelectric ceramic rods and tubes by extrusion processing is described. The microstructure of extrudates...

  6. CO2 fluid inclusions in Jack Hills zircons

    Science.gov (United States)

    Menneken, Martina; Geisler, Thorsten; Nemchin, Alexander A.; Whitehouse, Martin J.; Wilde, Simon A.; Gasharova, Biliana; Pidgeon, Robert T.

    2017-08-01

    The discovery of Hadean to Paleoarchean zircons in a metaconglomerate from Jack Hills, Western Australia, has catalyzed intensive study of these zircons and their mineral inclusions, as they represent unique geochemical archives that can be used to unravel the geological evolution of early Earth. Here, we report the occurrence and physical properties of previously undetected CO2 inclusions that were identified in 3.36-3.47 Ga and 3.80-4.13 Ga zircon grains by confocal micro-Raman spectroscopy. Minimum P-T conditions of zircon formation were determined from the highest density of the inclusions, determined from the density-dependence of the Fermi diad splitting in the Raman spectrum and Ti-in-zircon thermometry. For both age periods, the CO2 densities and Ti-in-zircon temperatures correspond to high-grade metamorphic conditions (≥5 to ≥7 kbar/ 670 to 770 °C) that are typical of mid-crustal regional metamorphism throughout Earth's history. In addition, fully enclosed, highly disordered graphitic carbon inclusions were identified in two zircon grains from the older population that also contained CO2 inclusions. Transmission electron microscopy on one of these inclusions revealed that carbon forms a thin amorphous film on the inclusion wall, whereas the rest of the volume was probably occupied by CO2 prior to analysis. This indicates a close relationship between CO2 and the reduced carbon inclusions and, in particular that the carbon precipitated from a CO2-rich fluid, which is inconsistent with the recently proposed biogenic origin of carbon inclusions found in Hadean zircons from Jack Hills.

  7. Evolution of the African continental crust as recorded by U-Pb, Lu-Hf and O isotopes in detrital zircons from modern rivers

    Science.gov (United States)

    Iizuka, Tsuyoshi; Campbell, Ian H.; Allen, Charlotte M.; Gill, James B.; Maruyama, Shigenori; Makoka, Frédéric

    2013-04-01

    To better understand the evolutionary history of the African continental crust, a combined U-Pb, Lu-Hf and O isotopic study has been carried out by in situ analyses of approximately 450 detrital zircon grains from the Niger, Nile, Congo, Zambezi and Orange Rivers. The U-Pb isotopic data show age peaks at ca. 2.7, 2.1-1.8, 1.2-1.0, ca. 0.8, 0.7-0.5 and ca. 0.3 Ga. These peaks, with the exception of the one at ca. 0.8 Ga, correspond with the assembly of supercontinents. Furthermore, the detrital zircons that crystallized during these periods of supercontinent assembly have dominantly non-mantle-like O and Hf isotopic signatures, in contrast to the ca. 0.8 Ga detrital zircons which have juvenile characteristics. These data can be interpreted as showing that continental collisions during supercontinent assembly resulted in supermountain building accompanied by remelting of older continental crust, which in turn led to significant erosion of young igneous rocks with non-mantle-like isotopic signatures. Alternatively, the data may indicate that the major mode of crustal development changed during the supercontinent cycle: the generation of juvenile crust in extensional settings was dominant during supercontinent fragmentation, whereas the stabilization of the generated crust via crustal accretion and reworking was important during supercontinent assembly. The Lu-Hf and O isotope systematics indicate that terreigneous sediments could attain elevated 18O/16O via prolonged sediment-sediment recycling over long crustal residence time, and also that reworking of carbonate and chert which generally have elevated 18O/16O and low Hf contents is minor in granitoid magmatism. The highest 18O/16O in detrital zircon abruptly increased at ca. 2.1 Ga and became nearly constant thereafter. This indicates that reworking of mature sediments increased abruptly at that time, probably as a result of a transition in the dynamics of either granitoid crust formation or sedimentary evolution

  8. Deformation Behavior across the Zircon-Scheelite Phase Transition

    Science.gov (United States)

    Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang

    2016-09-01

    The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO4 ) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO4 develops a (001) compression texture associated with dominant slip along ⟨100 ⟩{001 } starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.

  9. Creation of a continent recorded in zircon zoning

    Science.gov (United States)

    Moser, D.E.; Bowman, J.R.; Wooden, J.; Valley, J.W.; Mazdab, F.; Kita, N.

    2008-01-01

    We have discovered a robust microcrystalline record of the early genesis of North American lithosphere preserved in the U-Pb age and oxygen isotope zoning of zircons from a lower crustal paragneiss in the Neoarchean Superior province. Detrital igneous zircon cores with ??18O values of 5.1???-7.1??? record creation of primitive to increasingly evolved crust from 2.85 ?? 0.02 Ga to 2.67 ?? 0.02 Ga. Sharp chemical unconformity between cores and higher ??18O (8.4???-10.4???) metamorphic overgrowths as old as 2.66 ?? 0.01 Ga dictates a rapid sequence of arc unroofing, burial of detrital zircons in hydrosphere-altered sediment, and transport to lower crust late in upper plate assembly. The period to 2.58 ?? 0.01 Ga included ???80 m.y. of high-temperature (???700-650 ??C), nearly continuous overgrowth events reflecting stages in maturation of the subjacent mantle root. Huronian continental rifting is recorded by the youngest zircon tip growth at 2512 ?? 8 Ma (??? 600 ??C) signaling magma intraplating and the onset of rigid plate behavior. This >150 m.y. microscopic isotope record in single crystals demonstrates the sluggish volume diffusion of U, Pb, and O in zircon throughout protracted regional metamorphism, and the consequent advances now possible in reconstructing planetary dynamics with zircon zoning. ?? 2008 The Geological Society of America.

  10. The Minerageny of Two Groups of Zircons from Plagioclase- Amphibolite of Mayuan Group in Northern Fujian

    CERN Document Server

    Bao, Xuezhao

    1996-01-01

    Zircon can crystallize in a wide range of physical and chemical conditions. At the same time, it has very high stability and durability. Therefore zircon can grow and survive in a variety of geological processes. In addition, the diffusivity of chemical compositions in its crystal is very low. Consequently, we can trace back the evolution history of the planetary materials containing zircon by zircon U-Th-Pb geochronology and geochemistry studies. However, this depends on our ability to decipher its genesis, namely magmatic or metamorphic origins. In this paper, magmatic and metamorphic zircons were found from plagioclase-amphibolite samples. Their geneses have been determined by zircon morphology, chemical composition zonations and geological field setting combined with their zircon U-Th-Pb ages. We have found obvious differences in micro-scale Raman spectra between these magmatic and metamorphic zircons. The magmatic zircons exhibit a high sloping background in their Raman spectra, but the metamorphic zirco...

  11. Geochemical, zircon U-Pb and Hf isotopic study on metabasalt in the Cathaysia Block: Implications of Paleozoic migmatization of Precambrian crustal and mantle materials in South China

    Science.gov (United States)

    Zeng, Wen; Zhou, Hanwen; Li, Zheng-Xiang; Fitzsimons, Ian C. W.; Zhong, Zengqiu; Xiang, Hua; Liu, Rui; Jin, Song

    2017-04-01

    Metamorphic rocks scattered in northeastern Cathaysia Block experienced upper-amphibolite to granulite facies metamorphism. This study focuses on the mafic metamorphic rocks (including biotite-amphibolite and amphibolite) found in migmatite. The whole rock geochemical characteristics of ten mafic metamorphic rock samples suggest that their protoliths are subalkaline basalts, including tholeiites and calc-alkaline basalts resemble those in E-MORB, within-plate and volcanic-arc tectonic settings. Eighty zircon grains from three representative samples (samples FJ39-1, FJ61-3 and FJ125-4) were picked for geochronology analyses. Cathodo-luminescence images show that most zircons are elongated subhedral to eueuhedral crystals with oscillatory zoning. Some of them are surrounded by thin, homogeneous luminescent overgrowth rims, which may present a later thermal event. LA-ICP-MS analyses indicate that most analyzed zircon grains have high Th/U ratios (0.16-1.41, n = 69) and yield U-Pb zircon ages of 444 ± 3 Ma (FJ39-1), 445 ± 2 Ma (FJ61-3), 448 ± 3 Ma and 473 ± 4 Ma (FJ125-4), respectively for each sample. The Hf model ages calculated for these zircons ranges from ˜3613 to ˜853 Ma with ɛHf(t) values from -20.0 to +7.1; zircons with model ages of 1121-853 Ma show positive ɛHf(t) values (+0.2 - +7.1). This implies that the protoliths of the mafic metamorphic rocks contain diverse basalts erupted in various tectonic settings during the Precambrian, rather than being Ordovician new crustal addition. The data suggest that there could be an Archaean basement component in the Cathaysia Block and the basement possibly had crustal additions during the Meso- to Neoproterozoic. The zircon U-Pb ages of the mafic metamorphic rocks are the same as those of leucosomes (471 ± 4 Ma and 445 ± 3 Ma). The metamorphic P-T conditions are constrained by the zircon Ti-content thermometer, the Amp-Pl thermobarometer and mineral stability fields of titanite and garnet to be 722-779

  12. Zircon U-Pb age of the Pescadero felsite: A late Cretaceous igneous event in the forearc, west-central California Coast Ranges

    Science.gov (United States)

    Ernst, W.G.; Martens, U.C.; McLaughlin, R.J.; Clark, J.C.; Moore, Diane E.

    2011-01-01

    Weathered felsite is associated with the late Campanian-Maastrichtian Pigeon Point Formation near Pescadero, California. Poorly exposed, its age and correlation are uncertain. Is it part of the Pigeon Point section west of the San Gregorio-Hosgri fault? Does it rest on Nacimiento block basement? Is it dextrally offset from the Oligocene Cambria Felsite, ~185 km to the southeast? Why is a calc-alkaline hypabyssal igneous rock intrusive into the outboard accretionary prism? To address these questions, we analyzed 43 oscillatory-zoned zircon crystals from three incipiently recrystallized pumpellyite ?? prehnite ?? laumontite-bearing Pescadero felsite samples by sensitive high-resolution ion microprobe-reverse geometry (SHRIMPRG) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) techniques. Thirty-three zircons gave late Mesozoic U-Pb ages, with single-grain values ranging from 81 to 167 Ma; ten have pre-Mesozoic, chiefl y Proterozoic ages. A group of the four youngest Pescadero zircons yielded an apparent maximum igneous age of ca. 86-90 Ma. Refl ecting broad age scatter and presence of partly digested sandstone inclusions, we interpret the rest of the zircons (perhaps all) as xenocrysts. Twenty-three zircons were separated and analyzed from two samples of the similar Cambria Felsite, yielding a unimodal 27 Ma U-Pb age. Clearly, the origin of the Upper Oligocene Cambria Felsite is different from that of the Upper Cretaceous Pescadero felsite; these rocks are not correlated, and do not constrain displacement along the San Gregorio-Hosgri fault. Peak ages differ slightly, but relative probability curves for Mesozoic and pre-Mesozoic Pescadero zircons compare well, for example, with abundant U-Pb age data for detrital zircons from Franciscan metaclastic strata ~100 km to the east in the Diablo Range- San Francisco Bay area, San Joaquin Great Valley Group turbidites, Upper Cretaceous Nacimiento block Franciscan strata, and Upper Cretaceous

  13. Early Mesozoic paleogeography and tectonic evolution of the western United States: Insights from detrital zircon U-Pb geochronology, Blue Mountains Province, northeastern Oregon

    Science.gov (United States)

    LaMaskin, Todd A.; Vervoort, J.D.; Dorsey, R.J.; Wright, J.E.

    2011-01-01

    This study assesses early Mesozoic provenance linkages and paleogeographic-tectonic models for the western United States based on new petrographic and detrital zircon data from Triassic and Jurassic sandstones of the "Izee" and Olds Ferry terranes of the Blue Mountains Province, northeastern Oregon. Triassic sediments were likely derived from the Baker terrane offshore accretionary subduction complex and are dominated by Late Archean (ca. 2.7-2.5 Ga), Late Paleoproterozoic (ca. 2.2-1.6 Ga), and Paleozoic (ca. 380-255 Ma) detrital zircon grains. These detrital ages suggest that portions of the Baker terrane have a genetic affinity with other Cordilleran accretionary subduction complexes of the western United States, including those in the Northern Sierra and Eastern Klamath terranes. The abundance of Precambrian grains in detritus derived from an offshore complex highlights the importance of sediment reworking. Jurassic sediments are dominated by Mesozoic detrital ages (ca. 230-160 Ma), contain significant amounts of Paleozoic (ca. 290, 380-350, 480-415 Ma), Neoproterozoic (ca. 675-575 Ma), and Mesoproterozoic grains (ca. 1.4-1.0 Ga), and have lesser quantities of Late Paleoproterozoic grains (ca. 2.1-1.7 Ga). Detrital zircon ages in Jurassic sediments closely resemble well-documented age distributions in transcontinental sands of Ouachita-Appalachian provenance that were transported across the southwestern United States and modified by input from cratonal, miogeoclinal, and Cordilleran-arc sources during Triassic and Jurassic time. Jurassic sediments likely were derived from the Cordilleran arc and an orogenic highland in Nevada that yielded recycled sand from uplifted Triassic backarc basin deposits. Our data suggest that numerous Jurassic Cordilleran basins formed close to the Cordilleran margin and support a model for moderate post-Jurassic translation (~400 km) of the Blue Mountains Province. ?? 2011 Geological Society of America.

  14. Crustal formation in the Nanling Range, South China Block: Hf isotope evidence of zircons from Phanerozoic granitoids

    Science.gov (United States)

    Shu, Xu-Jie; Wang, Xiao-Lei; Sun, Tao; Chen, Wei-Feng; Shen, Wei-Zhou

    2013-09-01

    Granitic rocks are the principle agent of crustal differentiation, therefore their origins yield important information on crustal formation and reworking. An extensive survey of zircon Hf isotopes from granitic rocks in a large region can provide a profile of crustal characteristics that may be further linked to previous crustal evolution. In this study, we measured U-Pb ages and Hf isotope compositions of zircon grains extracted from twenty-five Jurassic, five Triassic and two Ordovician granitic plutons from the Nanling Range, South China Block (SCB). Combined with the published Lu-Hf isotopic data for the granitic rocks in the studied and adjacent areas, three domains with different crustal formation histories have been identified in the southern part of the SCB: eastern side, middle part and western side. The eastern side extends to the coastal area of the SCB, with dominant Hf crustal model ages (TDM2) in zircons falling within the range of 2.2-1.6 Ga. The middle part is partly coincided with the low-Nd model age belt proposed by Chen and Jahn (1998), with zircon Hf TDM2 ranging from 1.6 to 1.0 Ga. The western side covers the westernmost Nanling Range and the western end of the Jiangnan orogen, in which the granitoids have zircon Hf TDM2 model ages spanning 2.2-1.8 Ga. The Paleo- to Meso-Proterozoic model ages of the Phanerozoic granitoids in the Nanling Range imply a long-term crustal reworking. Zircons from the western and eastern sides have an average ɛHf(155 Ma) at around -10, about 4 epsilon units lower than the middle part (ɛHf(155 Ma) = -6). Hf TDM2 histogram from the western Nanling Range is similar to that of the Neoproterozoic granitoids in northern Guangxi Province to the west but much lower to the granites in the middle part to the east. The eastern side has a broader range of Hf model ages in zircons, with the main peak low to ca 1.6 Ga, suggesting the reworking of Mesoproterozoic crust. However, granitoids in the middle part have zircon Hf TDM2

  15. Detrital zircon U-Pb ages of the Proterozoic metaclastic-sedimentary rocks in Hainan Province of South China: New constraints on the depositional time, source area, and tectonic setting of the Shilu Fe-Co-Cu ore district

    Science.gov (United States)

    Wang, Zhilin; Xu, Deru; Hu, Guocheng; Yu, Liangliang; Wu, Chuanjun; Zhang, Zhaochong; Cai, Jianxin; Shan, Qiang; Hou, Maozhou; Chen, Huayong

    2015-12-01

    The Shilu Fe-Co-Cu ore district, located at Hainan Province of South China, is well known for high-grade hematite-rich Fe ores and also two Precambrian host successions, i.e. the Shilu Group and the overlying Shihuiding Formation. This district has been interpreted as a banded iron formation (BIF) deposit-type, but its depositional time, source area and depositional setting have been in debate due to poor geochronological work. Detrital zircon U-Pb dating aided by cathodoluminescence imaging has been carried out on both the Shilu Group and Shihuiding Formation. Most of the zircon grains from both the successions are subrounded to rounded in morphology and have age spectra between 2000 Ma and 900 Ma with two predominant peaks at ca. 1460-1340 Ma and 1070 Ma, and three subordinate peaks at ca. 1740-1660 Ma, 1220 Ma and 970 Ma. The similar age distribution suggests the same depositional system for both successions. Linked to the geological and paleontological signatures, the Shihuiding Formation is better re-interpreted as the top, i.e. Seventh member of the Shilu Group, rather than a distinct Formation. The youngest statistical zircon age peaks for both successions, i.e. ca. 1070-970 Ma may define the maximum depositional time of the Shilu Group and interbedded BIFs. At least two erosional sources are required for deposition of the studied detrital zircons, with one proximal to provide the least abraded zircons and the other distal or recycled to offer the largely abraded zircons. The predominance of rounded or subrounded zircons over angular zircons probably implies a relatively stable tectonic setting during deposition. Given the Precambrian tectonics of Hainan Island, a retro-arc foreland basin is proposed for the deposition of the Shilu Group and interbedded BIFs. In comparison with those from the South China and other typical Grenvillian orogens, the detrital zircon age populations reveal that Hainan Island had crystalline basement similar to neither the Yangtze

  16. Provenance shift in Cambrian mid-Baltica: detrital zircon chronology of Ediacaran–Cambrian sandstones in Estonia

    Directory of Open Access Journals (Sweden)

    Yukio Isozaki

    2014-12-01

    Full Text Available In order to clarify the tectono-sedimentary history of Paleozoic Baltica, age spectra of detrital zircon grains from the Ediacaran (Kotlin Regional Stage and Lower Cambrian sandstones (lowermost Lontova and Lükati formations in western Estonia in central Baltica were analyzed by LA-ICPMS. The abundant occurrence of Archean to Mesoproterozoic (2800–1000 Ma zircon grains was confirmed in all samples. The new data provided the following information on the provenance of siliciclastic material as well as a major change in the sedimentary regime of the Paleo-Baltic basin during the Early Cambrian: (1 the Ediacaran–Lower Cambrian Paleo-Baltic basin received abundant terrigenous clastics from the core of Baltica underlain by the Archean–Mesoproterozoic crystalline crust, (2 the exposed surface area of the 1600 Ma Rapakivi granites apparently was more extensive during the Ediacaran–Early Cambrian than at present, (3 a major re-organization of the basin geometry occurred in the middle Early Cambrian (ca 530–515 Ma in central Baltica, inducing a change in the sediment supply system, (4 in contrast to the total absence of Neoproterozoic detrital zircon grains before the middle Early Cambrian, their sudden appearance at this time, together with consistent occurrence at least until the mid-Devonian, suggests a significant uplift event located in southeast Baltica and/or in a more easterly land domain (e.g., in Sarmatia, (5 possible sources for the Neoproterozoic zircon grains include the peripheral mobile belts with pan-African signatures around Baltica, e.g., the so-called Gondwanan fragments along the Tornquist margin to the southwest and the Timanian belt along the northeastern margin.

  17. Comparison of U-Th and U-Pb zircon ages from erupted plutonic clasts and 40Ar/39Ar eruption ages from Newberry Volcano, Oregon

    Science.gov (United States)

    Sullivan, K. M.; Stelten, M. E.; Leech, M. L.; Donnelly-Nolan, J. M.

    2016-12-01

    The magmatic plumbing systems of Quaternary volcanoes are poorly understood due to insufficient uplift and erosion to expose their intrusive roots. These intrusive bodies remained in the plumbing system for longer timescales than the eruptive melt; therefore, plutonic rocks record a more extensive history of the entire magmatic system. Occasionally, large-scale eruptions can expose regions of the plumbing system and/or erupt plutonic clasts (EPC) to the surface. We are investigating EPCs found within Newberry ash flow tuffs and hydrothermal drill cores to understand subsurface processes occurring within the magmatic plumbing system. Newberry Volcano is a large shield-shaped composite volcano located in central Oregon that has experienced recurrent volcanism from ca. 500 ka to 1,300 ybp. This study uses the EPC ages to link the intrusive rocks inferred to be representative of the Newberry magmatic plumbing system, and to discern a systematic relationship with volcanism. SHRIMP U-Th disequilibrium and U-Pb zircon ages were analyzed from six EPCs and two hydrothermal granitoids from separate drill cuttings. We compare these new SHRIMP ages to existing 40Ar/39Ar geochronology of Newberry volcanic strata. Three EPCs have unimodal zircon ages of 140 ka, two EPCs display ages of 300 ka, and one has three distinct zircon age populations of 120 ka, 200 ka, and 300 ka. Zircons from separate drill cuttings have ages of 350 ka and 1.9 Ma. All the EPC zircon ages are less than 500 kyr, implying that these clasts are related to the Newberry magmatic system. The granitoid with 1.9 Myr zircons was penetrated by drilling at 2.6 km depth, and could be related to Newberry magmatism and represent an earlier phase of intrusive activity. The 140 kyr zircons record a single crystallization event that took place during a period of frequent volcanism, while the three remaining age populations represent multiple periods of growth that overlap with timeframes of waning activity. Combining

  18. U-Pb zircon and biostratigraphic data of high-pressure/low-temperature metamorphic rocks of the Talea Ori: tracking the Paleotethys suture in central Crete, Greece

    Science.gov (United States)

    Zulauf, G.; Dörr, W.; Krahl, J.; Lahaye, Y.; Chatzaras, V.; Xypolias, P.

    2016-10-01

    Inherited deformation microfabrics of detrital quartz grains and U-Pb (Laser ablation (LA)-ICPMS and ID TIMS) ages of detrital zircons separated from the Phyllite-Quartzite Unit s.l. of the Talea Ori, central Crete, suggest strikingly different source rocks. Albite gneiss of the lower Rogdia Beds includes Cambrian and Neoproterozoic rounded zircons with main U-Pb age peaks at 628 and 988 Ma. These and minor Paleoproterozoic and Archean peaks, together with the lack of Variscan-aged and Mesoproterozoic zircons, are similar to the age spectra obtained from the Phyllite-Quartzite Unit s.str. of the Peloponnesus and eastern Crete and from the Taurides. All of these zircons should be derived from the northeastern passive margin of Gondwana (Cimmeria). Metatuffites of the uppermost Rogdia Beds and metasandstone of Bali beach, on the other hand, include euhedral detrital zircons displaying a Variscan U-Pb age spectra at ca. 300 Ma with concordia ages at 291 ± 3, 300 ± 1 Ma (Rogdia) and 286 ± 3, 300 ± 3, 313 ± 2 Ma (Bali). Both types of metasediments and their zircons are similar to those of the pre-Alpine basement and overlying Tyros Beds of eastern Crete, revealing a provenance at the southern active margin of Laurasia. Thus, in central Crete the Paleotethys suture should be situated inside the Rogdia Beds. Magmatic zircons separated from a rhyolite boulder of the lower Achlada Beds yielded a concordant U-Pb zircon age at 242 ± 2 Ma placing a maximum age for the deposition of the (meta)conglomerate from which the boulder was collected. This age is compatible with an Olenekian-early Anisian age of the underlying Vasilikon marble suggested by new findings of the foraminifera Meandrospira aff. pusilla. Both the Achlada Beds and the Vasilikon marble can be attributed to the lower Tyros Beds of eastern Crete. The Alpine deformation led to a pervasive mylonitic foliation, which is affecting most of the studied rocks. This foliation results from D2 top

  19. Growth of Zircone on Nanoporous Alumina Using Molecular Layer Deposition

    Science.gov (United States)

    Hall, Robert A.; George, Steven M.; Kim, Yeongae; Hwang, Woonbong; Samberg, Meghan E.; Monteiro-Riviere, Nancy A.; Narayan, Roger J.

    2014-04-01

    Molecular layer deposition (MLD) is a sequential and self-limiting process that may be used to create hybrid organic/inorganic thin films from organometallic precursors and organic alcohol precursors. In this study, films of a zirconium-containing hybrid organic/inorganic polymer known as zircone were grown on nanoporous alumina using MLD. Scanning electron microscopy data showed obliteration of the pores in zircone-coated nanoporous alumina. An in vitro cell viability study indicated that the growth of human epidermal keratinocytes was the greatest on zircone-coated nanoporous alumina than on uncoated nanoporous alumina. Our results suggest that MLD may be used to create biocompatible coatings for use in many types of medical devices.

  20. Linking zircon U-Pb and garnet Sm-Nd ages to date loading and metamorphism in the lower crust of a Cretaceous magmatic arc, Swakane Gneiss, WA, USA

    Science.gov (United States)

    Gatewood, Matthew P.; Stowell, Harold H.

    2012-08-01

    Synorogenic basin development and subsequent collapse and loading provide important constraints on the Late Cretaceous crustal structure of the North America Cordillera. High grade metasedimentary rocks of the Swakane Gneiss in the North Cascades have been interpreted to include ca. 73 Ma detrital zircon that requires a protolith age considerably younger than metamorphic ages of adjacent terranes. This detrital interpretation requires rapid loading rates of 7-8 mm/yr, heating to 750 °C in dates for the Swakane Gneiss that directly date metamorphism and provide a basis for evaluating this model of Late Cretaceous deposition, loading, and crustal structure. Garnet preserves compositional evidence for growth during high pressure amphibolite-facies metamorphism and little subsequent modification. New garnet-rock Sm-Nd isochrons of 73.5 ± 1.2, 71.3 ± 2.8, and 65.8 ± 0.7 Ma, tightly constrain the timing of garnet growth. Swakane Gneiss zircons preserve complex magmatic, detrital, and metamorphic histories. Most zircons have distinct cores and homogeneous overgrowths. Detrital zircon cores include significant Proterozoic and Mesozoic components with low U/Th ratios. Homogeneous metamorphic zircon rims have high U/Th (> 5) and define an array of concordant U-Pb dates from 75 to 63 Ma. The new zircon U-Pb and garnet Sm-Nd ages establish that the youngest regional metamorphism was diachronous and occurred between 75 and 63 Ma. Our dataset precludes post 73 Ma deposition and instead suggests that sedimentation occurred after ca. 91 Ma and ended before ca. 75 Ma. Using these age constraints for deposition and metamorphism, we propose new loading rates of 1-3 mm/yr and conclude that the Swakane Gneiss protolith was likely deposited in a small, short-lived, intra-arc basin that subsided, filled in, and collapsed quickly due to overthrusting of arc crust.

  1. U-Pb dating of magmatic and xenocryst zircons from Mangakino ignimbrites and their correlation with detrital zircons from the Torlesse metasediments, Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    McCormack, Kenneth D.; Mary Gee, M. A.; McNaughton, Neal J.; Smith, Richard; Fletcher, Ian R.

    2009-05-01

    Mangakino ignimbrites are a sequence of voluminous eruptive units in the rhyolitic Mangakino Volcanic Centre (MVC) caldera complex, Taupo Volcanic Zone, New Zealand. U-Pb dating of 113 zircons extracted from four Mangakino ignimbrites reveals magmatic and xenocrystic zircons. Magmatic zircon ages from three ignimbrites are slightly older than K/Ar and 40Ar/ 39Ar ages. Magmatic zircon age-spectra are tightly clustered and support a simple crystallisation history for these three ignimbrites. It is possible that the assimilation of zircon antecrysts leads to magmatic zircon spectra for the Ahuroa ignimbrite being ≥ 70 ka older than the 40Ar/ 39Ar age. Xenocrystic zircon age spectra correlate with spectra of detrital zircons from the underlying Mesozoic Torlesse metasediments. Our data are consistent with significant assimilation of metasediments and the incorporation of zircon prior to eruption. Systematic variations in the age spectra of xenocrystic zircons in successive Mangakino ignimbrites may be related to the structural development of the North Island, New Zealand.

  2. Molecular dynamics modelling of radiation damage in zircon

    Science.gov (United States)

    Grechanovsky, A. E.

    2009-04-01

    Zircon (ZrSiO4) is among actinide-bearing phases which has been proposed as a crystalline confinement matrix for nuclear waste management, especially for weapon-grade plutonium and UO2 spent fuel in the USA. Zircon is also widely used in geochronology. But, with accumulating α-decay damage, zircon undergoes a radiation induced transition to an amorphous (or metamict) state. So, in the present work molecular dynamics simulations (MD simulations) of zircon structure have been performed to study radiation damage in zircon. In this technique, one simulates the propagation of an energetic particle in a system of atoms interacting via model potentials, by integrating the Newton equations of motion. Author has used version 3.09 of the DL_POLY molecular simulation package. Zircon structure containing 181944 atoms (19x19x21 unit cells) was equilibrated at 300 K for 10 ps, and one Zr atom (usually called the primary knock-on atom, PKA) was given a velocity corresponding to an implantation energy of about 20 keV. MD simulations were performed in the microcanonical ensemble that is under conditions of constant particle number, volume and energy. Results of the MD simulations show that the number of interstitials is equal to 840 atoms. This is very close (4000-5000 atoms for 70 keV recoil atom 234Th) to what is measured in the diffuse x-ray scattering and NMR experiments on amorphous metamict samples (damaged by natural irradiation) of geological age. It has been shown that the damaged structure contains several depleted regions with characteristic sized up to 2,5 nm after single event and up to 4,5 nm after three overlapping events. Furthermore, these events produce channels of depleted matter between the overlapping damaged regions. These channels provide a high-diffusivity path for radiogenic Pb (percolation effect). Loss of radiogenic Pb may result in to incorrect dating of rocks.

  3. Gondwana to Pangea: a detrital zircons tale from NW Iberia

    Science.gov (United States)

    Pastor-Galán, Daniel; Gutiérrez-Alonso, Gabriel; Brendan Murphy, J.; Fernández-Suárez, Javier; Hofmann, Mandy; Linnemann, Ulf

    2013-04-01

    The Cantabrian Zone of NW Iberia preserves a voluminous, almost continuous, sedimentary sequence that ranges from Neoproterozoic to Early Permian in age. Its tectonic setting is controversial and recent hypotheses include (i) passive margin deposition along the northern margin of Gondwana or (ii) an active continental margin or (iii) a drifting ribbon continent. In this paper we present detrital zircon U-Pb laser ablation age data from 13 samples from the Cantabrian Zone sequence ranging from Early Silurian to Early Permian in depositional age, which, together with previously published detrital zircon ages from Ediacaran-Ordovician strata, allow a comprehensive analysis of changing provenance through time. Laser ablation U-Pb geochronological analysis of detrital zircons in thirteen samples of the Cantabrian Zone of the NW Iberian Variscan belt reveal that this portion of Iberia was part of the northern passive-margin of Gondwana from the Ordovician to Late Devonian, until the onset of collision between Gondwana and Laurentia. Zircon populations in these samples show important similarities with zircons found in coeval detrital rocks from central North Africa. Additionally, the populations found in NW Iberia are coherent with a Saharan source. We suggest that NW Iberia was situated from Ordovician to Late Devonian along the Gondwana northern passive margin close to the paleoposition of central North Africa and Saharan craton. Additionally, the Carboniferous-Permian samples studied record the provenance changes produced during the Variscan collision and basement exhumation, the Cantabrian orocline formation and the subsequent detachment of the lithospheric mantle. The provenance changes reflect major topographic variations due to the afore mentioned processes during Late Devonian to Early Permian times. Detrital zircon studies are a useful tool that can complement regional syntheses in deducing paleogeographic locations, the occurrence of major tectonic events such

  4. Field, petrologic and detrital zircon study of the Kings sequence and Calaveras complex, Southern Lake Kaweah Roof Pendant, Tulare County, California

    Science.gov (United States)

    Buchen, Christopher T.

    U-Pb dating of detrital zircon grains separated from elastic sedimentary rocks is combined with field, petrographic and geochemical data to reconstruct the geologic history of Mesozoic rocks exposed at the southern end of the Lake Kaweah metamorphic pendant, western Sierra Nevada. Identification of rocks exposed at Limekiln Hill, Kern County, CA, as belonging to the Calaveras complex and Kings sequence was confirmed. Detrital zircon populations from two Calaveras complex samples provide Permo-Triassic maximum depositional ages (MDA) and reveal a Laurentian provenance indicating that continental accretion of the northwest-trending Kings-Kaweah ophiolite belt was in process prior to the Jurassic Period. Rock types including radiolarian metachert, metachert-argillite, and calc-silicate rocks with marble lenses are interpreted as formed in a hemipelagic environment of siliceous radiolarian deposition, punctuated by extended episodes of lime-mud gravity flows mixing with siliceous ooze forming cafe-silicate protoliths and limestone olistoliths forming marble lenses. Two samples of the overlying Kings sequence turbidites yield detrital zircons with an MDA of 181.4 +/-3.0 Ma and an interpreted provenance similar to other Jurassic metasediments found in the Yokohl Valley, Sequoia and Boyden Cave roof pendants. Age peaks indicative of Jurassic erg heritage are also present. In contrast, detrital zircon samples from the Sequoia and Slate Mountain roof pendants bear age-probability distributions interpreted as characteristic of the Snow Lake block, a tectonic sliver offset from the Paleozoic miogeocline.

  5. Phase relations and conductivity of Sr-zirconates and La-zirconates

    DEFF Research Database (Denmark)

    Poulsen, F.W.; Vanderpuil, N.

    1992-01-01

    phase orthorhombic SrZrO3 and somewhat impure, tetragonal Sr2ZrO4 were observed, whereas the formation of ordered Ruddlesden-Popper phases, SrnZrn-1O3n-2, where n = 4 and 3, could not be verified. The conductivity of La2Zr2O7 was 3.7 X 10(-6) S/cm at 750-degrees-C and 3.8 x 10(-5) S/cm at 1000-degrees......-C. The conductivity of the Sr-zirconates increases with increasing Sr/Zr ratio. Samples with a nominal composition corresponding to Sr2ZrO4 have a conductivity of 7.5 x 10(-5) and 5.9 x 10(-4) S/cm at 750 and 1000-degrees-C, respectively. For all samples one observes low activation energies for ionic conduction (0...

  6. Syntesis of lanthanum zirconate hydrosols by the ion exchange method

    Science.gov (United States)

    Bovina, E. A.; Tarasova, J. V.; Chibirova, F. Kh

    2011-04-01

    Ion exchange of LaCl3 and ZrOCl2 aqueous solutions with anion-exchanger AV-17-8 was used to synthesize finely dispersed hydrosol of amorphous lanthanum zirconate La2Zr2O7. Heat treatment of dried La2Zr2O7 hydrosols at 700°C and 1100°C resulted in the formation of powders with fluorite and pyrochlore type structures, respectively. Epitaxial La2Zr2O7 films were obtained on SrTiO3 (001) single crystals. The substrate has an influence on the lanthanum zirconate crystal orientation, as well as strong inhibitory effect on sintering processes.

  7. Simulation of optically-stimulated luminescence of zircon

    Energy Technology Data Exchange (ETDEWEB)

    Turkin, A.A. [National Science Center, Kharkov Institute of Physics and Technology, Kharkov (Ukraine); Vainshtein, D.I.; Hartog, H.W. den [University of Groningen (Netherlands)

    2007-03-15

    Mineral zircon, ZrSiO{sub 4}, belongs to a class of materials that can be used as a chronological tool in geology and archaeology for measurements of the natural radiation dose and the sample age by optical methods. The model of optically stimulated luminescence developed earlier is used to investigate the applicability of the single-aliquot regenerative-dose method (SAR) for dating with zircon. Various implementations of the SAR method are considered and practical recommendations are formulated. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Oxalate co-precipitation synthesis of calcium zirconate and calcium titanate powders.

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Sanchez, Bernadette A.; Tuttle, Bruce Andrew

    2009-06-01

    Fine powders of calcium zirconate (CaZrO{sub 3}, CZ) and calcium titanate (CaTiO{sub 3}, CT) were synthesized using a nonaqueous oxalate co-precipitation route from Ca(NO{sub 3}){sub 2}{center_dot}4 H{sub 2}O and group(IV) n-butoxides (Ti(OBu{sup n}){sub 4} or Zr(OBu{sup n}){sub 4}). Several reaction conditions and batch sizes (2-35 g) were explored to determine their influence on final particle size, morphology, and phase. Characterization of the as-prepared oxalate precursors, oven dried oxalate precursors (60-90 C), and calcined powders (635-900 C) were analyzed with TGA/DTA, XRD, TEM, and SEM. Densification and sintering studies on pressed CZ pellets at 1375 and 1400 C were also performed. Through the developed oxalate co-precipitation route, densification temperatures for CZ were lowered by 125 C from the 1500 C firing temperature required for conventional mixed oxide powders. Low field electrical tests of the CZ pellets indicated excellent dielectric properties with dielectric constants of {approx}30 and a dissipation factor of 0.0004 were measured at 1 kHz.

  9. The final collision of the CAOB: Constraint from the zircon U–Pb dating of the Linxi Formation, Inner Mongolia

    Directory of Open Access Journals (Sweden)

    Jie Han

    2015-03-01

    Full Text Available The Linxi Formation occupies an extensive area in the eastern Inner Mongolia in the Central Asian Orogenic Belt (CAOB. The Linxi Formation is composed of slate, siltstone, sandstone and plant, lamellibranch microfossils in the associated strata. Major and trace element data (including REE for sandstones from the formation indicate that these rocks have a greywacke protolith and have been deposited during a strong tectonic activity. LA-ICPMS U–Pb dating of detrital zircons yield ages of 1801 to 238 Ma for four samples from the Linxi Formation. 425–585 Ma, together with the ∼500 Ma age for the metamorphism event previously determined for Northeast China, indicates that their provenance is the metamorphic rocks of Pan-African age that have a tectonic affinity to NE China. A few older zircons with U–Pb ages at 1689–1801 Ma, 1307–1414 Ma, 593–978 Ma are also present, revealing the Neoproterozoic history of NE China. The youngest population shows a peak at ca. 252 Ma, suggesting that the main deposition of the Linxi Formation was at late Permain. Moreover, the ca. 250 Ma zircon grains of all four samples yield weighted mean 206Pb/238U ages of 250 ± 3 Ma, 248 ± 3 Ma, 249 ± 3 Ma, and 250 ± 2 Ma, respectively. These ages, together with the youngest zircon age in the sample ZJB-28 (ca. 238 Ma, suggest that the deposition of the Linxi Formation extended to the early Triassic. Combining with previous results, we suggest that the final collision of the Central Asian Orogenic Belt (CAOB in the southern of Linxi Formation, which located in the Solonker–Xra Moron–Changchun suture, and the timing for final collision should be at early Triassic.

  10. The origin of zircon and the significance of U-Pb ages in high-grade metamorphic rocks: a case study from the Variscan orogenic root (Vosges Mountains, NE France)

    Science.gov (United States)

    Skrzypek, E.; Štípská, P.; Cocherie, A.

    2012-12-01

    U-Pb zircon dating is combined with petrology, Zr-in-rutile thermometry and mineral equilibria modelling to discuss zircon petrogenesis and the age of metamorphism in three units of the Variscan Vosges Mountains (NE France). The monotonous gneiss unit shows results at 700-500 Ma, but no Variscan ages. The varied gneiss unit preserves ages between 600 and 460 Ma and a Variscan group at 340-335 Ma. Zircon analyses from the felsic granulite unit define a continuous array of ages between 500 and 340 Ma. In varied gneiss samples, zoned garnet includes kyanite and rutile and is surrounded by matrix sillimanite and cordierite. In a pseudosection, it points to peak conditions of ~16 kbar/850 °C followed by isothermal decompression to 8-10 kbar/820-860 °C. In felsic granulite samples, the assemblage K-feldspar-garnet-kyanite-Zr-rich rutile is replaced by sillimanite and Zr-poor rutile. Modelling these assemblages supports minimum conditions of ~13 kbar/925 °C, and a subsequent P-T decrease to 6.5-8.5 kbar/800-820 °C. The internal structure and chemistry of zircons, and modelling of zircon dissolution/growth along the inferred P-T paths are used to discuss the significance of the U-Pb ages. In the monotonous unit, inherited zircon ages of 700-500 Ma point to sedimentation during the Late Cambrian, while medium-grade metamorphism did not allow the formation of Variscan zircon domains. In both the varied gneiss and felsic granulite units, zircons with a blurred oscillatory-zoned pattern could reflect solid-state recrystallization of older grains during HT metamorphism, whereas zircons with a dark cathodoluminescence pattern are thought to derive from crystallization of an anatectic melt during cooling at middle pressure conditions. The present work proposes that U-Pb zircon ages of ca. 340 Ma probably reflect the end of a widespread HT metamorphic event at middle crustal level.

  11. Dielectric Strontium Zirconate Sprayed by a Plasma Torch.

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Janata, Marek

    2017-01-01

    Roč. 10, č. 4 (2017), s. 226-230 ISSN 2008-2134 Institutional support: RVO:61389021 Keywords : Plasma spraying * Electrical properties * Strontium Zirconate * Insulators Subject RIV: JH - Ceramics , Fire-Resistant Materials and Glass www.pccc.icrc.ac.ir/Articles/18/1/18/1010/

  12. Characterization and microstructure of porous lead zirconate titanate ...

    Indian Academy of Sciences (India)

    Porous lead zirconate titanate (PZT) ceramics are widely used because of their low acoustic impedance, high figure of merit and high hydrostatic sensitivity. In the present work, porous PZT ceramics were fabricated by incorporating polyethylene oxide (PEO) as pore-forming agent. Both PZT powder and PEO were mixed ...

  13. Creep and crack growth of zircon and mullite base materials

    Energy Technology Data Exchange (ETDEWEB)

    Carbonneau, X.; Olagnon, C.; Fantozzi, G. [INSA, Villeurbanne (France). GEMPPM

    1999-03-01

    The creep and crack propagation properties of mullite and zircon ceramics were compared. In the investigated temperature range, mullite presents a simple crack propagation of a unique macrocracks, although a change of mechanism is observed at 1200 C. The zircon material present a rather more complex crack propagation, with multicracking and branching, due to a significant crack healing. The creep behaviours also appeared as different for both materials. The mullite creep curves present only two stages, even when fracture occurs, while a tertiary regime is observed in the case of zircon. The results show that grain boundary sliding is the main deformation mechanism for the two different materials. In fact, they exhibit similar overall real behaviours with a different characteristic temperature. At low stress, the minimum creep rate can be considered as a stationary creep, but at a higher stress, generalised or localised damage interfere, leading to a higher apparent stationary creep exponent. Sub-critical crack growth and deformation act as parallel mechanisms for mullite, while the interaction is more complex in zircon where crack healing induce multi-cracking. (orig.) 9 refs.

  14. Zircon U–Pb geochronology and geochemistry of rhyolitic tuff ...

    Indian Academy of Sciences (India)

    The Lengshuikeng rhyolitic tuff, granite porphyry and syenogranite yielded zircon U–Pb ages of. 161, 155 and 138 Ma, respectively. The Lengshuikeng granite porphyries belong to calc-alkaline series and show fractionated I-type affinities. The rhyolitic tuffs show almost similar characteristics as the granite porphyries.

  15. A preliminary geochemical study of zircons and monazites from ...

    Indian Academy of Sciences (India)

    On the basis of structural conformity of the felsic and basaltic dikes, K-Ar ages and trace element considerations, a previous study concluded that the felsic rocks are coeval with the Deccan Volcanics and originated by crustal anatexis. The felsic rocks contain two populations of zircons and monazites, one that crystallized ...

  16. Dielectrics of lead zirconate bonded with barium borate glass

    Indian Academy of Sciences (India)

    K SINGH and ARUNA INDURKAR. Department of Physics. Nagpur University, Nagpur 440 010, India. MS received 25 May 1987; revised it July 1988. Abstract. Dielectric constant variation with temperature and frequency is reported for barium-borate glass-bonded lead zirconate. Lowering of the relative permittivity of the.

  17. Paleo- to Eoarchean crustal evolution in eastern Hebei, North China Craton: New evidence from SHRIMP U-Pb dating and in-situ Hf isotopic study of detrital zircons from paragneisses

    Science.gov (United States)

    Liu, Shoujie; Wan, Yusheng; Sun, Huiyi; Nutman, Allen P.; Xie, Hangqiang; Dong, Chunyan; Ma, Mingzhu; Liu, Dunyi; Jahn, Bor-ming

    2013-12-01

    In the Caozhuang complex in eastern Hebei, North China Craton, the Paleo- to Eoarchean crustal evolution was earlier revealed by the preservation of detrital zircon grains older than (or as old as) 3.8 Ga in fuchsite-quartzite. In order to test if the Eoarchean antiquity is also preserved in rocks other than the fuchsite quartzite, we collected two paragneisses, a hornblende gneiss and a garnet-biotite gneiss, from Huangbaiyu village and dated their detrital zircon grains. The zircon dating of the hornblende gneiss yielded concordant 207Pb/206Pb ages ranging from 3684 to 3354 Ma. However, an older date of 3782 Ma with 18% discordancy was also obtained. Detrital zircon grains from the garnet-biotite gneiss gave a similar 207Pb/206Pb age range, from 3838 to 3342 Ma. The metamorphic domains of the zircon grains from both samples, including the strongly recrystallized cores and rims, recorded an overprinting metamorphism at ca. 2.5 Ga, which correlates with the most widespread tectono-thermal event in the North China Craton. In situ zircon Hf-isotope analyses on the dated zircon grains yielded a wide range of model ages (TDM1) from 4.0 to 3.3 Ga with corresponding ɛHf(T) from -36.0 to +4.8. This suggests that the evolution of the crustal segment in this area has involved multiple phases of juvenile crustal addition as well as recycling of older crustal rocks. The new geochronological results imply the presence of a significant amount of Eoarchean crustal fragments in the eastern Hebei area. The sedimentary protoliths of the paragneisses and other high-grade metamorphic rocks in the Caozhuang complex were probably deposited between 3.4 and 2.5 Ga.

  18. Evaluating the paleomagnetic potential of single zircon crystals using the Bishop Tuff

    CERN Document Server

    Fu, Roger R; Lima, Eduardo A; Kehayias, Pauli; Araujo, Jefferson F D F; Glenn, David R; Gelb, Jeff; Einsle, Joshua F; Bauer, Ann M; Harrison, Richard J; Ali, Guleed A H; Walsworth, Ronald L

    2016-01-01

    Zircon crystals offer a unique combination of suitability for high-precision radiometric dating and high resistance to alteration. Paleomagnetic experiments on ancient zircons may potentially constrain the earliest geodynamo, which holds broad implications for the early Earth interior and atmosphere. However, the ability of zircons to record accurately the geomagnetic field has not been fully demonstrated. Here we conduct thermal and room temperature alternating field (AF) paleointensity experiments on 767.1 thousand year old (ka) zircons from the Bishop Tuff, California. The rapid emplacement of these zircons in a well-characterized magnetic field provides a high-fidelity test of the zircons intrinsic paleomagnetic recording accuracy. Successful dual heating experiments on nine zircons measured using a superconducting quantum interference device (SQUID) microscope yield a mean paleointensity of 46.2 +/- 18.8 microtesla (1sigma), which agrees closely with high-precision results from Bishop Tuff whole rock (43...

  19. Dating sub-20 micron zircons in granulite-facies mafic dikes from SW Montana: a new approach using automated mineralogy and SIMS U-Pb geochronology

    Science.gov (United States)

    Ault, A. K.; Mahan, K. H.; Flowers, R. M.; Chamberlain, K.; Appleby, S. K.; Schmitt, A. K.

    2010-12-01

    Geochronological data is fundamental to all tectonic studies, but a major limitation for many lithologies is a paucity of sizeable zircons suitable for conventional U-Pb techniques. In particular, mafic dike swarms provide important time markers for tectonometamorphic activity in Precambrian terranes, but commonly yield little or no zircon or baddeleyite sufficient for TIMS or standard ion-probe analysis of crystal separates. We apply a new approach involving in-situ automated mineralogy and high spatial resolution Secondary Ion Mass Spectrometry (SIMS) geochronology to a mafic dike swarm exposed in the Northern Madison Range of SW Montana. The dikes cross-cut early fabrics but are also variably deformed and metamorphosed to P-T conditions as high as 1.2 GPa and 850 C. The swarm emplacement age is inferred to be ca. 2.1 Ga based on similarities to dated dikes in the adjacent Tobacco Root Mountains. Resolving the timing of dike emplacement and high-grade metamorphism in the study area is important for understanding the extent of post-Archean modification to the northwest margin of the Wyoming craton. Identification and textural characterization of zircons were facilitated by in-situ automated mineralogical analysis, in contrast to a standard elemental X-ray mapping approach. Our technique uses an SEM-based platform coupling calibrated BSE data with X-ray data collected by multiple energy dispersive spectrometers to rapidly identify target accessory phases at high spatial resolution. Whole thin section search maps were generated in ~30 minutes at 4 µm pixel resolution. Our dike thin sections commonly contained >300 zircons in a variety of textural settings, with 80% having a short dimension dated in-situ by adjusting the field aperture of the CAMECA ims1270 to preferentially collect secondary ions emitted from within the inner few microns of the ~15 µm diameter analysis pit. This allows us to analyze zircon grains with a minimum dimension as small as 8 μm at

  20. Magma mixing and the generation of isotopically juvenile silicic magma at Yellowstone caldera inferred from coupling 238U–230Th ages with trace elements and Hf and O isotopes in zircon and Pb isotopes in sanidine

    Science.gov (United States)

    Stelten, Mark E.; Cooper, Kari M.; Vazquez, Jorge A.; Reid, Mary R.; Barfod, Gry H.; Wimpenny, Josh; Yin, Qing-Zhu

    2013-01-01

    The nature of compositional heterogeneity within large silicic magma bodies has important implications for how silicic reservoirs are assembled and evolve through time. We examine compositional heterogeneity in the youngest (~170 to 70 ka) post-caldera volcanism at Yellowstone caldera, the Central Plateau Member (CPM) rhyolites, as a case study. We compare 238U–230Th age, trace-element, and Hf isotopic data from zircons, and major-element, Ba, and Pb isotopic data from sanidines hosted in two CPM rhyolites (Hayden Valley and Solfatara Plateau flows) and one extracaldera rhyolite (Gibbon River flow), all of which erupted near the caldera margin ca. 100 ka. The Hayden Valley flow hosts two zircon populations and one sanidine population that are consistent with residence in the CPM reservoir. The Gibbon River flow hosts one zircon population that is compositionally distinct from Hayden Valley flow zircons. The Solfatara Plateau flow contains multiple sanidine populations and all three zircon populations found in the Hayden Valley and Gibbon River flows, demonstrating that the Solfatara Plateau flow formed by mixing extracaldera magma with the margin of the CPM reservoir. This process highlights the dynamic nature of magmatic interactions at the margins of large silicic reservoirs. More generally, Hf isotopic data from the CPM zircons provide the first direct evidence for isotopically juvenile magmas contributing mass to the youngest post-caldera magmatic system and demonstrate that the sources contributing magma to the CPM reservoir were heterogeneous in 176Hf/177Hf at ca. 100 ka. Thus, the limited compositional variability of CPM glasses reflects homogenization occurring within the CPM reservoir, not a homogeneous source.

  1. Three Proterozoic orogenic cycles in the Livingstone Mountains, Tanzania: Evidence from petrology and ion microprobe dating of zircon and monazite

    Science.gov (United States)

    Nitsche, Christoph; Schenk, Volker; Schmitt, Axel; Kazimoto, Emmanuel

    2017-04-01

    The Livingstone Mountains at Lake Nyasa in southern Tanzania are situated in an area where three orogenic belts seem to be overlapping: the Ubendian-Usagaran belts, the Irumide Belt and the East African Orogen, whose formations are linked to the assembly of the Proterozoic supercontinents of Columbia, Rodinia and Gondwana. Granulite-facies migmatitic metapelites and two orthogneisses were studied petrologically and by ion microprobe dating of monazite and zircon to decipher their tectono-metamorphic history and to find out if and to which degree the rocks of the Livingstone Mountains were affected by the different orogenies. Zircon dating of orthogneiss yielded a magmatic age of ca. 2.2 Ga. Texturally controlled ion microprobe U-Pb dating of monazite inclusions in garnet of a Grt-Sil-Bt migmatite in combination with discordant zircon data point to sillimanite-garnet grade metamorphism at 1857±27 Ma during the Ubendian-Usagaran orogeny. Oscillatory zoned concordant zircon of another orthogneiss was dated at 997±8.6 Ma, whereas the age of monazite inclusions in garnet and matrix of a garnet-sillimanite-gneiss revealed an associated high-grade metamorphism at 1067±20 Ma during the Irumide orogeny. Low Th/U overgrowths on orthogneiss zircon and concordant matrix monazite in metapelite are dated at 653±9.1 Ma, which is in agreement with the known ages of Pan-African events in the East African Orogen and in the Ubendian Belt (655-550 Ma) (Möller et al., 2000; Boniface et al, 2012). Garnet is homogeneous in Fe and Mg, but cores are mantled by Ca-rich garnet which shows rim-ward depletion in Ca. Thermobarometry using compositions of garnet rims and matrix minerals yielded 770-820 °C and 7-8 kbar, which we interpret to represent conditions during the Neoproterozoic metamorphic event. The high-grossular mantle might reflect earlier conditions of kyanite-grade metamorphism tentatively correlated with high-pressure metamorphism during the Mesoproterozoic Irumide orogeny

  2. Timing and conditions of metamorphism and melt crystallization in Greater Himalayan rocks, eastern and central Bhutan: insight from U-Pb zircon and monazite geochronology and trace-element analyses

    Science.gov (United States)

    Zeiger, K.; Gordon, S. M.; Long, S. P.; Kylander-Clark, A. R. C.; Agustsson, K.; Penfold, M.

    2015-05-01

    Within the eastern Himalaya in central and eastern Bhutan, Greater Himalayan (GH) rocks are interpreted to have been thickened by the Kakhtang thrust (KT). In order to understand the metamorphic and exhumation history of the GH and to evaluate the structural significance of the KT, zircon and monazite from twenty samples were analyzed by laser-ablation split-stream ICPMS. In eastern Bhutan, zircon and monazite from samples collected in the KT hanging wall revealed ca. 36-28 Ma metamorphism. Subsequently, the initiation of melt crystallization shows a trend with structural distance above the KT, with early melt crystallization (ca. 27 Ma) in the structurally highest samples and younger melt crystallization (ca. 16 Ma) for leucosomes within the KT zone. Melt crystallization was protracted and continued until ca. 14-13 Ma in both the KT hanging wall and the footwall. In comparison, in central Bhutan, two leucosomes revealed extended melt crystallization from ca. 31 to 19 Ma. The youngest zircon dates from samples exposed structurally above and below the KT are similar, indicating that the KT was not as significant of a structure as other fault systems to which it has been correlated. However, the younging trend in the initiation of melt crystallization with decreasing structural distance above the KT argues that progressive underplating of ductile material assisted in the initial emplacement of the GH unit in central and eastern Bhutan. The KT likely represents a minor shear zone that aided in this underplating process.

  3. U-Pb SHRIMP zircon dating of high-grade rocks from the Upper Allochthonous Terrane of Bragança and Morais Massifs (NE Portugal); geodynamic consequences

    Science.gov (United States)

    Mateus, A.; Munhá, J.; Ribeiro, A.; Tassinari, C. C. G.; Sato, K.; Pereira, E.; Santos, J. F.

    2016-04-01

    Bragança and Morais Massifs are part of the mega-klippen ensemble of NW Iberia, comprising a tectonic pile of four allochthonous units stacked above the Central-Iberian Zone autochthon. On top of this pile, the Upper Allochthonous Terrane (UAT) includes different high-grade metamorphic series whose age and geodynamic meaning are controversial. Mafic granulites provided U-Pb zircon ages at 399 ± 7 Ma, dating the Variscan emplacement of UAT. In contrast, U-Pb zircon ages of ky- and hb-eclogites, felsic/intermediate HP/HT-granulites and orthogneisses (ca. 500-480 Ma) are identical to those of gabbros (488 ± 10 Ma) and Grt-pyroxenites (495 ± 8 Ma) belonging to a mafic/ultramafic igneous suite that records upper mantle melting and mafic magma crustal underplating at these times. Gabbros intrude the high-grade units of UAT and did not underwent the HP metamorphic event experienced by eclogites and granulites. These features and the zircon dates resemblance among different lithologies, suggest that extensive age resetting of older events may have been correlative with the igneous suite emplacement/crystallisation. Accordingly, reconciliation of structural, petrological and geochronological evidence implies that the development and early deformation of UAT high-grade rocks should be ascribed to an orogenic cycle prior to ≈ 500 Ma. Undisputable dating of this cycle is impossible, but the sporadic vestiges of Cadomian ages cannot be disregarded. The ca. 500-480 Ma time-window harmonises well with the Lower Palaeozoic continental rifting that trace the Variscan Wilson Cycle onset and the Rheic Ocean opening. Subsequent preservation of the high heat-flow regime, possibly related to the Palaeotethys back-arc basin development (ca. 450-420 Ma), would explain the 461 ± 10 Ma age yielded by some zircon domains in felsic granulites, conceivably reflecting zircon dissolution/recrystallisation till Ordovician times, long before the Variscan paroxysm (ca. 400-390 Ma). This

  4. Provenance analysis and detrital zircon geochronology on the onshore Makran accretionary wedge, SE Iran: implication for the geodynamic setting

    Science.gov (United States)

    Mohammadi, Ali; Burg, Jean-Pierre; Winkler, Wilfried; Ruh, Jonas

    2014-05-01

    The Makran, located in Southeast Iran and South Pakistan, is one of the largest accretionary wedges on Earth. In Iran it comprises turbiditic sediments ranging in age from Late Cretaceous to Holocene. We present a provenance analysis on sandstones, which is aimed at reconstructing the assemblages of source rocks and the tectonic setting from which the clastic material was derived. Sandstone samples collected from different units span the regional stratigraphy from Late Cretaceous to Miocene. Laser ablation ICP-MS resulted in ca 2800 new U-Pb ages of individual detrital zircons from 18 samples collected in onshore Makran. 101 detrital zircons from a Late Cretaceous fine grained sandstone range from 180 to 160 Ma (Middle Jurassic). 478 detrital zircons from mid- to late Eocene sandstones allow differentiating a NE and NW sector of the Makran Basin. Zircon grains in the NE basin belong to two populations peaking at 180 to 160 Ma (late Early to Middle Jurassic) and 50 to 40 Ma (Mid-Eocene), with the noticeable absence of Cretaceous grains. In the NW basin, detrital zircons are 120 to 40 Ma (late Early Cretaceous to Lutetian, Eocene). 587 detrital zircon grains from fine to medium grained Oligocene sandstones collected over the whole area also range from 120 to 40 Ma (late Early Cretaceous to Eocene, Lutetian). 1611 detrital zircons from early Miocene sandstones show again distinctly different ages in the eastern and western parts of the basin. They range from 120 to 40 Ma (late Early Cretaceous to Eocene) in the eastern and from 80 to 40 Ma (Late Cretaceous to Eocene) in the western basin. Hf isotopes analyses were performed on 120 zircon grains from 6 samples. Negative values (-2 to -15) in Middle Jurassic and late Early Cretaceous zircons indicate minor or no influence of mantle reservoirs which implies a rifting setting during crystallization of the zircons. Low negative to positive (-5 to +10) values in Late Cretaceous and Eocene zircons indicate mixed crustal and

  5. Heavy mineral compositions and zircon U-Pb ages of Cenozoic sandstones in the SW Qaidam basin, northern Tibetan Plateau: Implications for provenance and tectonic setting

    Science.gov (United States)

    Zhu, Wen; Wu, Chaodong; Wang, Jialin; Zhou, Tianqi; Li, Jijun; Zhang, Changhao; Li, Linlin

    2017-09-01

    The Qaidam basin is the largest intermountain basin within the Tibetan Plateau. The spatio-temporal evolution of the basin and the provenances of the deposits in the SW Qaidam basin were greatly influenced by the boundary ranges. Comprehensive research is needed to identify the relationships between the basin and the surrounding ranges. Therefore, 4682 heavy mineral data from 70 wells and 720 detrital zircon ages from 8 samples were used to investigate the provenances of the deposits in the SW Qaidam basin and to further constrain the tectonic evolution of the boundary ranges. The heavy mineral data, zircon U-Pb ages, and paleocurrent data indicate that the Qimen Tagh Range and the Altyn Tagh Range were two provenances of the sediments deposited in the SW Qaidam basin during the Cenozoic. The variations of heavy mineral assemblages and ZTR index (100 ∗ (zircon + tourmaline + rutile)/total transparent heavy minerals) on the northern flank of the Qimen Tagh Range suggest that the Qimen Tagh Range experienced rapid uplift in the Early to Middle Miocene. Furthermore, according to the greatly increased quantities of epidote and hornblende sourced from the Altyn Tagh Range and the obvious decrease in the ZTR index values, the Altyn Tagh Range underwent fast uplift in the Late Oligocene to Early Miocene. In addition, based on the ages of the granitic plutons in the Altyn Tagh Range and the zircon ages in the Ganchaigou and Qigequan sections, the strike-slip movement of the Altyn Tagh Fault (ATF) initiated during or no later than the Middle Eocene, resulting in the ATF offsets of ca. 200 km between the Middle Eocene and the Miocene and of ca. 345 km between the Middle Eocene and the present.

  6. LA-ICP-MS dating of Archean Metamorphic Zircons From the Kapuskasing Structural Zone, Ontario: Evidence for the Geodynamic Origin and Evolution of the Abitibi-Opatica Terrane

    Science.gov (United States)

    Benn, K.; Kamber, B.

    2007-12-01

    The Late Archean Abitibi greenstone belt, in SE Superior Province, is one of the largest contiguous greenstone belts on Earth. Geochronological data from upper crustal rocks indicate it was formed by volcanism and plutonism that spanned 2760 Ma through 2660 Ma. The classical model for the Abitibi belt is one of tectonic accretion and thrust stacking of magmatic arcs, and possibly plateau fragments, resulting in a thick crust, with a granulitic base. A Proterozoic uplift, the Kapuskasing structural zone, on the western side of the Abitibi belt, is believed to represent the lower to middle crust of the Abitibi. Previous U-Pb zircon dates from the Kapuskasing uplift correspond to a period of granitic plutonism at the end of the Abitibi magmatic history (ca. 2660 Ma), consistent with underthrusting and underplating, during and following tectonic collision. An alternative model for the Abitibi belt is that it represents part of a single, large oceanic plateau, modified by subduction and slab-window magmatism. The Abitibi greenstone belt and the Opatica gneiss belt, to the north, would then represent a single tectonic terrane, called the Abitibi-Opatica terrane. That model requires the existence of a thick crust prior to tectonic accretion, rather than thickening of crust as the result of collision. The plateau model can be tested by dating metamorphic minerals from lower to middle crustal rocks in the Kapuskasing uplift. We have used laser ablation (LA) -ICP-MS, to carry out "in-situ" dating of zircons from a mafic clinopyroxene- garnet granulite and from two hornblende-biotite-garnet metatonalites. Zircons in the rocks are less than 100 microns in size, mostly 40 microns or less. BSE and CL images of the zircons reveal that some are unzoned, some are patchwork zoned, and others are sector zoned. The crystals are devoid of oscillatory zoning and their morphologies are mainly anhedral to subhedral; they are interpreted to be of metamorphic in origin. That interpretation

  7. An Integrated Analytical Approach to Obtaining Reliable U-Pb and Hf Isotopic Data from Complex (>3.9 to 3.3 Ga) Zircon from the Acasta Gneiss Complex

    Science.gov (United States)

    Bauer, A.; Bowring, S. A.; Vervoort, J. D.; Fisher, C. M.

    2014-12-01

    The Acasta Gneiss Complex (AGC) of northwestern Canada preserves some of Earth's oldest granitic crust (>4.03 Ga) and thereby contains important insight into crust forming processes on the early Earth. In general, rocks of the AGC have undergone a complex history of metamorphism and deformation (Archean and Paleoproterozoic)1,2, and, as a consequence, the zircons retain a complex history including inheritance, magmatic and metamorphic overgrowths, recrystallization, and multi-stage Pb loss. Previously published Hf isotopic data on zircons show within sample variability in excess of analytical uncertainty2,3,4. In order to assess the meaning and significance of this apparent isotopic variability, we are using two different methods to obtain coupled U-Pb and Lu-Hf isotopic data in zircon from a suite of rocks ranging in age from ca. > 3.9 Ga to 3.3 Ga. To obtain these data from the same volume of zircon, our approach involves: 1) split stream LA-ICPMS for U-Pb and Lu-Hf; 2) mechanical isolation of zircon domains for chemical abrasion and ID-TIMS U-Pb analyses and solution ICPMS for Lu-Hf recovered from U-Pb ion exchange chromatography. The deconvolution of complex histories requires this integrated approach and permits us to take advantage of both high spatial resolution and highest precision measurements to ultimately decipher the age and isotopic composition of discrete domains of multi-phase zircon. We demonstrate our approach with both relatively simple and complex grain populations in an attempt to understand within and between grain heterogeneity. The samples with the simplest zircon systematics have increasingly negative ɛHf from oldest to youngest, consistent with involvement of 4.0 Ga or older crust in later generations; also, none of our samples have been derived solely from strongly depleted sources. The presence of intra-zircon variability within samples from the AGC reflects a complex history of magmatic additions requiring melting/assimilation of older

  8. Syntesis of lanthanum zirconate hydrosols by the ion exchange method

    Energy Technology Data Exchange (ETDEWEB)

    Bovina, E A; Tarasova, J V; Chibirova, F Kh, E-mail: bovina@rambler.ru [LLC ' Superconductor' , Varshavskoe shosse, 46, 115230, Moscow (Russian Federation)

    2011-04-01

    Ion exchange of LaCl{sub 3} and ZrOCl{sub 2} aqueous solutions with anion-exchanger AV-17-8 was used to synthesize finely dispersed hydrosol of amorphous lanthanum zirconate La{sub 2}Zr{sub 2}O{sub 7}. Heat treatment of dried La{sub 2}Zr{sub 2}O{sub 7} hydrosols at 700 deg. C and 1100 deg. C resulted in the formation of powders with fluorite and pyrochlore type structures, respectively. Epitaxial La{sub 2}Zr{sub 2}O{sub 7} films were obtained on SrTiO{sub 3} (001) single crystals. The substrate has an influence on the lanthanum zirconate crystal orientation, as well as strong inhibitory effect on sintering processes.

  9. The anatectic effect on the zircon Hf isotope composition of migmatites and associated granites

    Science.gov (United States)

    Chen, Yi-Xiang; Gao, Peng; Zheng, Yong-Fei

    2015-12-01

    Zircon Hf isotope composition is widely used to trace the growth and evolution of continental crust. However, it is controversial whether the Hf isotope composition of magmatic zircons can faithfully reflect that of their sources, especially for S-type granites. In order to provide an insight into this issue, we have revisited the published Lu-Hf isotope data of zircons from well-studied migmatites and associated granites in the Sulu orogen and the Cathaysian terrane, respectively. The results show greatly elevated 176Hf/177Hf ratios (by more than 10ε units) for newly grown zircon domains compared to the relict zircon domains. This indicates considerable contributions from non-zircon Hf to anatectic melts during crustal anatexis and subsequent magmatism. Furthermore, this more radiogenic Hf isotope signature was not erased during magmatic processes such as crystal fractionation during melt ascent and emplacement. The budget of Hf isotopes in source rocks with respect to mineral Lu/Hf ratios suggests the involvement of Hf-bearing major minerals in anatectic reactions by dissolving Hf-bearing major minerals into the anatectic melts. The significant Hf isotope variations in some anatectic and magmatic zircon domains from the migmatites and granites suggest not only the source heterogeneity but also the variable non-zircon Hf contributions. As such, the Hf isotope compositions of anatectic and magmatic zircons are substantially dictated by the mass balance between the non-zircon Hf from anatectic reactions and the zircon-Hf from the dissolution of protolith zircons into the anatectic melts. They are primarily controlled by P-T conditions and mechanism of crustal anatexis, and the magmatic processes during melt evolution. The present study highlights the important contribution of non-zircon Hf to the anatectic and magmatic zircon domains. In this regard, the greatly elevated 176Hf/177Hf ratios for newly grown zircon domains in the migmatites and granites cannot reflect

  10. Petrology of Zircon-Bearing Diogenite Northwest Africa 10666

    Science.gov (United States)

    Tanner, T. B.; Jeffcoat, C. R.; Righter, M.; Berger, E. L.; Lapen, T. J.; Irving, A. J.; Kuehner, S. M.; Fujihara, G.

    2017-01-01

    The howardite, eucrite, and diogenite (HED) meteorites are a group of achondrites thought to be derived from the asteroid 4 Vesta, though there is active debate as to whether all diogenites are part of the HED suite. Petrologic investigation of the HED meteorite group provides a means of understanding early planetary differentiation processes and early evolution of planets in our solar system. Diogenites are predominantly coarse grained ortho-pyroxenites with some samples containing appreciable amounts of clinopyroxene, olivine, chromite, and plagioclase. Accessory metal, troilite, and apatite are common. Many diogenites are brecciated, however, there are few poorly to unbrecciated samples. Diogenites are important because they may represent the lower crust of 4 Vesta. Although Mg isotope data indicates that the sources of diogenites are ancient, their crystallization ages are difficult to constrain due to their protracted thermal histories. The limited chronologic data for diogenites also limits the ability to test petrogenetic connections with eucrites and even parent body. A reliable and high closure-temperature isotope system, such as U-Pb in zircon, is needed to address the timing of diogenite igneous crystallization. Description of the textures and mineralogy of diogenites are essential to their classification and understanding their formation, in particular, whether all phases are petrogenetically related. Here, we present detailed petrographic data from a rare zircon-bearing feldspathic diogenite, Northwest Africa (NWA) 10666 and provide textural evidence for igneous crystallization of the zircon.

  11. Zircon Supported Copper Catalysts for the Steam Reforming of Methanol

    Science.gov (United States)

    Widiastri, M.; Fendy, Marsih, I. N.

    2008-03-01

    Steam reforming of methanol (SRM) is known as one of the most favorable catalytic processes for producing hydrogen. Current research on zirconia, ZrO2 supported copper catalyst revealed that CuO/ZrO2 as an active catalyst for the SRM. Zircon, ZrSiO4 is available from the by-product of tin mining. In the work presented here, the catalytic properties of CuO/ZrSiO4 with various copper oxide compositions ranging from 2.70% (catalyst I), 4.12% (catalyst II), and 7.12%-mass (catalyst III), synthesized by an incipient wetness impregnation technique, were investigated to methanol conversion, selectivity towards CO formation, and effect of ZnO addition (7.83%CuO/8.01%ZnO/ZrSiO4 = catalyst V). The catalytic activity was obtained using a fixed bed reactor and the zircon supported catalyst activity was compared to those of CuO/ZnO/Al2O3 catalyst (catalyst IV) and commercial Kujang LTSC catalyst. An X-ray powder diffraction (XRD) analysis was done to identify the abundant phases of the catalysts. The catalysts topography and particle diameter were measured with scanning electron microscopy (SEM) and composition of the catalysts was measured by SEM-EDX, scanning electron microscope-energy dispersive using X-ray analysis. The results of this research provide information on the possibility of using zircon (ZrSiO4) as solid support for SRM catalysts.

  12. Metasedimentary melting in the formation of charnockite: Petrological and zircon U-Pb-Hf-O isotope evidence from the Darongshan S-type granitic complex in southern China

    Science.gov (United States)

    Jiao, Shu-Juan; Li, Xian-Hua; Huang, Hui-Qing; Deng, Xi-Guang

    2015-12-01

    Charnockites are Opx-bearing igneous rocks commonly found in high-grade metamorphic terranes. Despite being volumetrically minor, they show a wide range in both bulk geochemistry and intensive parameters. They form a characteristic component of the AMCG (anorthosite-mangerite-charnockite-granite) suite, but their association with typical S-type granites is less well-known. The Darongshan S-type granitic complex (DSGC) in Guangxi Province, southern China, contains granites varying in mafic silicate mineral assemblages from Bt + Crd (Darongshan suite) to Opx + Grt + Bt + Crd (Jiuzhou suite) and Opx + Crd ± Bt (Taima suite), corresponding to a geochemical transition from magnesian calc-alkalic to ferroan calc-alkalic. However, its genesis, even the accurate age of intrusion, remains highly contentious despite intensive research. In order to understand the genesis of charnockite and its genetic relationship with S-type granite; here, we first determined zircon U-Pb ages of each suite using a SIMS on the basis of a detailed petrological study. Zircon U-Pb ages show that all suites of the complex were emplaced contemporaneously at ca. 249 Ma. Monazite apparent U-Pb ages are indistinguishable from zircon U-Pb ages within analytical error. Further in situ zircon Hf-O isotope analyses reveal that the granitic complex was dominantly derived from reduced melting metasedimentary rocks (δ18Ozircon = ca. 11‰; εHf(t)zircon = ca. - 10; Δlog FMQ ≤ 0; Mn in apatite oxybarometer) with rare material input from the mantle. The variation in δ18O (7.8‰-12.9‰) is more likely a result of hybridization, whereas that in εHf(t) (- 31.9 to - 1.8) is a result of both hybridization and disequilibrium melting. The variation in mineralogy and geochemistry may be interpreted as a result of entrainment of peritectic garnets from biotite-dehydration melting. Nevertheless, heat input from mantle through basaltic intrusion/underplating is considered to play a major role in high

  13. Effect of zircon on sintering, composition and microstructure of magnesia powders

    Directory of Open Access Journals (Sweden)

    Peng C.

    2009-01-01

    Full Text Available The effects of zircon on sintering, composition and microstructure of fused magnesia powders were studied by XRD, SEM and EDAX. With the increase of zircon content up to 6 wt%, the strength of sintered samples increased but the apparent porosity decreased. 6 wt% is an appropriate content of zircon to possess better properties of samples, and in this case the samples have a dense microstructure and lower content of glass phase. The presence of a liquid phase resulting from zircon addition is the main reason to improve sintering of magnesia powders.

  14. The Ordovician-Silurian tectonic evolution of the northeastern margin of the Tarim block, NW China: Constraints from detrital zircon geochronological records

    Science.gov (United States)

    Dong, Shunli; Li, Zhong; Jiang, Lei

    2016-05-01

    The northeastern margin of the Tarim block is a key tectonic-unit for understanding the evolution processes and geodynamic mechanisms of basin-range coupling between the Paleo-Asian tectonic realm to the north and the Tarim block to the south during the Paleozoic period. Four Upper Ordovician-Silurian sandstone samples were collected from the Tabei and Quruqtagh areas for measuring the detrital zircon U-Pb dating and Hf isotopic compositions, with an aim to decipher the provenances and elucidate the tectonic implications. The results show that all the sandstone samples yield evident detrital zircon U-Pb age groups of ca. 1100-720 Ma and ca. 2100-1700 Ma, demonstrating that the Tarim block was once a part of the Rodinia and Columbia supercontinents during the Neoproterozoic and the Paleoproterozoic, respectively. Remarkably, the Upper Ordovician sandstone sample from the Tabei area yields a higher proportion in age group of ca. 1100-900 Ma than that of ca. 860-720 Ma, whilst the Lower Silurian sample yields the opposite result. The former and the latter age groups aforementioned are consistent with the age patterns of the tectono-thermal events in the Central Tianshan microcontinent and the Tarim block, respectively. Combined with valuable igneous rock information, it is indicative that the Central Tianshan microcontinent drifted away from the proto Tarim block (with attachment of the Central Tianshan microcontinent) most likely at the Early Silurian. The Upper Silurian sandstone in the South Quruqtagh area yield massive detrital zircon U-Pb ages with a peak age of ca. 450 Ma, combining the Late Ordovician magmatic rocks reported from the Central Tianshan and northeastern Tarim margin, which suggests that there was a broad magmatic arc along the northeastern proto Tarim margin during the Late Ordovician. The opening of the South Tianshan Ocean began in the Early Silurian and continued in the Late Silurian, leaving a remanent magmatic arc along northeastern Tarim

  15. Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40Ar/39Ar and U-Pb dating of sanidine and zircon crystals

    Science.gov (United States)

    Vazquez, J. A.; Matthews, N. E.; Calvert, A. T.

    2015-12-01

    The last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff (LCT). Tephra from the eruption blanketed much of the western United States, and is a key Quaternary chronostratigraphic marker, in particular for dating deposition of mid-Pleistocene glacial and pluvial deposits in western North America. We performed 40Ar/39Ar dating of single sanidines to delimit eruption age, and ion microprobe U-Pb and trace-element analyses of crystal faces on single zircons to characterize magmatic evolution and date near-eruption crystallization, as well as analyses of crystal interiors to date the interval of zircon crystallization. Sanidines from the two LCT members A and B yield an 40Ar/39Ar isochron date of 631 ± 4 ka (2σ). Crystal faces on zircons from both members yield a weighted mean 206Pb/238U date of 627 ± 6 ka (2σ) and have trace element concentrations that vary with eruptive stratigraphy. Zircon interiors yield a weighted mean 206Pb/238U date of 660 ± 6 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high-U concentrations and dark cathodoluminescence (CL) cores. These crystals with high-U cores are possibly sourced from 'defrosting' of melt-impregnated margins of the growing subvolcanic reservoir. LCT sanidines mirror the variation of zircon composition within the eruptive stratigraphy, with crystals from upper LCT-A and basal LCT-B having bright-CL rims with high Ba concentrations, suggesting late crystallization after addition of less evolved silicic magma. The occurrence of distal LCT in stratigraphic sequences marking the Marine Isotope Stage 16-15 transition supports the apparent eruption age of ca. 631 ka. These results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up-temperature evolution for Yellowstone's subvolcanic reservoir in the 103-104 year interval

  16. From a long-lived upper-crustal magma chamber to rapid porphyry copper emplacement: Reading the geochemistry of zircon crystals at Bajo de la Alumbrera (NW Argentina)

    Science.gov (United States)

    Buret, Yannick; von Quadt, Albrecht; Heinrich, Christoph; Selby, David; Wälle, Markus; Peytcheva, Irena

    2016-09-01

    The formation of world class porphyry copper deposits reflect magmatic processes that take place in a deeper and much larger underlying magmatic system, which provides the source of porphyry magmas, as well as metal and sulphur-charged mineralising fluids. Reading the geochemical record of this large magmatic source region, as well as constraining the time-scales for creating a much smaller porphyry copper deposit, are critical in order to fully understand and quantify the processes that lead to metal concentration within these valuable mineral deposits. This study focuses on the Bajo de la Alumbrera porphyry copper deposit in Northwest Argentina. The deposit is centred on a dacitic porphyry intrusive stock that was mineralised by several pulses of porphyry magma emplacement and hydrothermal fluid injections. To constrain the duration of ore formation, we dated zircons from four porphyry intrusions, including pre-, syn- and post-mineralisation porphyries based on intersection relations between successive intrusion and vein generations, using high precision CA-ID-TIMS. Based on the youngest assemblages of zircon grains, which overlap within analytical error, all four intrusions were emplaced within 29 ka, which places an upper limit on the total duration of hydrothermal mineralisation. Re/Os dating of hydrothermal molybdenite fully overlaps with this high-precision age bracket. However, all four porphyries contain zircon antecrysts which record protracted zircon crystallisation during the ∼200 ka preceding the emplacement of the porphyries. Zircon trace element variations, Ti-in-zircon temperatures, and Hf isotopic compositions indicate that the four porphyry magmas record a common geochemical and thermal history, and that the four intrusions were derived from the same upper-crustal magma chamber. Trace element zoning within single zircon crystals confirms a fractional crystallisation trend dominated by titanite and apatite crystallisation. However, zircon

  17. U-Pb Dating of Unabraded Detrital Zircon Metamorphic Rims in the Nanaimo Basin, British Columbia

    Science.gov (United States)

    Boivin, M. P.; Guest, B.; Matthews, W.

    2016-12-01

    Thin metamorphic rims on detrital zircons from the Nanaimo Basin in SW British Columbia offer a unique opportunity to further constrain the source of these zircons, helping to resolve the long standing Baja BC controversy. Here we present an analytical approach for dating thin zircon rims and use it to show that zircons from the Nanaimo Basin are most likely derived from metamorphic rocks in southern California. Conventional in-situ laser ablation sample preparation typically requires mounting and polishing zircon grains to expose their core. However, in order to date these thin metamorphic zircon rims a depth-profiling approach on unabraded grains was employed. Zircon grains from the Upper Cretaceous Geoffrey, Spray, and Gabriola formations of the Nanaimo Group exposed on Denman and Hornby Islands (British Columbia) were sorted into five groups based on morphology. The zircons were then mounted on tape along with several grains of a well-characterised zircon reference material to validate the uncertainty of the method. The zircons were then imaged using a Zygo Zescope optical profilometer in order to correct for grain-to-grain variations in elevation relative to mounting medium and ensure consistent laser focus. Backscatter electron images (BSE) were used to further characterised the grains and optimize the location of laser ablation targets. Zircons were ablated using a Resonetics 193 nm excimer laser and uranium and lead isotopic ratios were measured using an Agilent 7700 quadrupole mass spectrometer. A low frequency laser repetition rate extended the data collection period on relatively thin zircon rims. Our results show that metamorphic zircon growth occurred in two main phases at 100 Ma and 77 Ma suggesting two sources of detrital zircons with differing metamorphic histories were present in the catchment area. The timing of metamorphism of the source area for the Nanaimo basin is inconsistent with derivation from sources in the Rocky Mountains (Lemhi sub

  18. Microstructural constraints on the mechanisms of the transformation to reidite in naturally shocked zircon

    Science.gov (United States)

    Erickson, Timmons M.; Pearce, Mark A.; Reddy, Steven M.; Timms, Nicholas E.; Cavosie, Aaron J.; Bourdet, Julien; Rickard, William D. A.; Nemchin, Alexander A.

    2017-01-01

    Zircon (ZrSiO4) is used to study impact structures because it responds to shock loading and unloading in unique, crystallographically controlled manners. One such phenomenon is the transformation of zircon to the high-pressure polymorph, reidite. This study quantifies the geometric and crystallographic orientation relationships between these two phases using naturally shocked zircon grains. Reidite has been characterized in 32 shocked zircon grains (shocked to stages II and III) using a combination of electron backscatter diffraction (EBSD) and focused ion beam cross-sectional imaging techniques. The zircon-bearing clasts were obtained from within suevite breccia from the Nördlingen 1973 borehole, close to the center of the 14.4 Ma Ries impact crater, in Bavaria, Germany. We have determined that multiple sets (up to 4) of reidite lamellae can form in a variety of non-rational habit planes within the parent zircon. However, EBSD mapping demonstrates that all occurrences of lamellar reidite have a consistent interphase misorientation relationship with the host zircon that is characterized by an approximate alignment of a {100}zircon with a {112}reidite and alignment of a {112}zircon with a conjugate {112}reidite. Given the tetragonal symmetry of zircon and reidite, we predict that there are eight possible variants of this interphase relationship for reidite transformation within a single zircon grain. Furthermore, laser Raman mapping of one reidite-bearing grain shows that moderate metamictization can inhibit reidite formation, thereby highlighting that the transformation is controlled by zircon crystallinity. In addition to lamellar reidite, submicrometer-scale granules of reidite were observed in one zircon. The majority of reidite granules have a topotaxial alignment that is similar to the lamellar reidite, with some additional orientation dispersion. We confirm that lamellar reidite likely forms via a deviatoric transformation mechanism in highly crystalline

  19. Empirical constraints on the effects of radiation damage on helium diffusion in zircon

    Science.gov (United States)

    Anderson, Alyssa J.; Hodges, Kip V.; van Soest, Matthijs C.

    2017-12-01

    In this study, we empirically evaluate the impact of radiation damage on zircon (U-Th)/He closure temperatures for a suite of zircon crystals from the slowly cooled McClure Mountain syenite of south-central Colorado, USA. We present new zircon, titanite, and apatite conventional (U-Th)/He dates, zircon laser ablation (U-Th)/He and U-Pb dates, and zircon Raman spectra for crystals from the syenite. Titanite and apatite (U-Th)/He dates range from 447 to 523 Ma and 88.0 to 138.9 Ma, respectively, and display no clear correlation between (U-Th)/He date and effective uranium concentration. Conventional zircon (U-Th)/He dates range from 230.3 to 474 Ma, while laser ablation zircon (U-Th)/He dates show even greater dispersion, ranging from 5.31 to 520 Ma. Dates from both zircon (U-Th)/He datasets decrease with increasing alpha dose, indicating that most of the dispersion can be attributed to radiation damage. Alpha dose values for the dated zircon crystals range from effectively zero to 2.15 × 1019 α /g, spanning the complete damage spectrum. We use an independently constrained thermal model to empirically assign a closure temperature to each dated zircon grain. If we assume that this thermal model is robust, the zircon radiation damage accumulation and annealing model of Guenthner et al. (2013) does not accurately predict closure temperatures for many of the analyzed zircon crystals. Raman maps of the zircons dated by laser ablation document complex radiation damage zoning, sometimes revealing crystalline zones in grains with alpha dose values suggestive of amorphous material. Such zoning likely resulted in heterogeneous intra-crystalline helium diffusion and may help explain some of the discrepancies between our empirical findings and the Guenthner et al. (2013) model predictions. Because U-Th zoning is a common feature in zircon, radiation damage zoning is likely to be a concern for most ancient, slowly cooled zircon (U-Th)/He datasets. Whenever possible, multiple

  20. Palaeoproterozoic continental arc magmatism, and Neoproterozoic metamorphism in the Aravalli-Delhi orogenic belt, NW India: New constraints from in situ zircon U-Pb-Hf isotope systematics, monazite dating and whole-rock geochemistry

    Science.gov (United States)

    Kaur, Parampreet; Zeh, Armin; Chaudhri, Naveen

    2017-04-01

    Presently, the extent, origin and petrogenesis of late Palaeoproterozoic (ca. 1.85 Ga) magmatism in the north-central Aravalli-Delhi orogenic belt, NW India and subsequent metamorphic overprints are poorly constrained. Results of new in situ zircon U-Pb-Hf isotope analyses in combination with whole-rock elemental and isotopic data provide the first hard evidence that granitoid magmatism occurred in a continental magmatic arc setting between 1.86 and 1.81 Ga. The Hf-Nd model ages of 3.0-2.6 Ga and inherited zircon grains of 3.3-2.5 Ga indicate abundant reworking of Archaean crust. Flat HREE patterns with negative Eu anomalies furthermore reveal that the granitoids were generated from garnet-free and plagioclase-rich sources at shallow depths. Significant isotope variation among granitoid samples (εHft = -3.7 to -9.0; εNdt = -4.8 to -7.9) indicate that the reworked Archaean crust was not completely homogenised during the Palaeoproterozoic. This is best reflected by zircon Hf-isotope variation of ca. 9.5 epsilon units within the oldest granitoid sample. Zircon grains from this sample define three discrete Hf-isotope groups at εHf1.86Ga = -8.9, -4.8 and -1.6. These are interpreted to result from mixing of zircon-saturated magmas derived from three distinct sources within the crust prior to solidification. A monazite U-Pb isochron age of 868 ± 4 Ma from one of the granitoid samples furthermore indicates that the Aravalli fold belt was affected by an important post-magmatic overprint, perhaps related to the widespread metasomatic, granulite metamorphic and/or magmatic events during the same time span.

  1. Genesis and Multi-Episodic Alteration of Zircon-Bearing Chromitites from the Ayios Stefanos Mine, Othris Massif, Greece: Assessment of an Unconventional Hypothesis on the Origin of Zircon in Ophiolitic Chromitites

    Directory of Open Access Journals (Sweden)

    Argyrios Kapsiotis

    2016-11-01

    source. Combined micro-textural and minerochemical data repeat the possibility of zircon derivation from limited volumes of high-T fluids emanating from the gabbroic intrusions. Once zircon is precipitated in cracks, it may be altered to Ca-rich Zr-bearing silicate phases (i.e., armstrongite, calciocatapleiite. Almost all zircons in these samples show evidence of gains in solvent compounds (CaO, Al2O3 and FeO possibly due to re-equilibration with late deuteric fluids.

  2. Cretaceous high-pressure metamorphism and low pressure overprint in the Sistan Suture Zone, eastern Iran: Additional temperature estimates for eclogites, geological significance of U-Pb zircon ages and Rb-Sr constraints on the timing of exhumation

    Science.gov (United States)

    Kurzawa, Timon; Bröcker, Michael; Fotoohi Rad, Gholamreza; Berndt, Jasper; Lisker, Frank

    2017-10-01

    The Sistan Suture Zone, eastern Iran, includes blocks and lenses of eclogite-, blueschist- and/or epidote amphibolite-facies rocks that provide an excellent opportunity to examine the exhumation history of oceanic HP/LT rocks and their retrograde derivatives. Zr-in-rutile thermometry of eclogites corroborates previous interpretations suggesting metamorphic temperatures of ca. 550-600 °C during the HP stage in the Sistan area. Flat HREE distribution patterns and Ti-in-zircon temperatures of ca. 500-600 °C document that zircon in eclogite is of metamorphic origin. REE patterns of zircon from felsic meta-igneous rocks do not allow to distinguish between a magmatic or metamorphic origin, but relatively low temperatures indicated by Ti-in-zircon thermometry (ca. 500-600 °C) and the close similarity of zircon (U-Pb) and white mica (Rb-Sr, Ar-Ar) ages favor a metamorphic zircon origin. Previously published isotopic ages of the felsic rocks cannot unambiguously be linked to the eclogite- and/or blueschist-facies P-T conditions due to the absence of unequivocal mineralogical and petrological evidence. Instead, these rocks may record contemporaneous metamorphic processes that took place at a different depth within the subduction complex, or may indicate active ridge subduction and/or melt formation in the subduction zone at relatively low pressures. Biotite-based internal Rb-Sr isochrons of newly dated epidote amphibolite and biotite-albite gneisses indicate ages of ca. 74-80 Ma, either dating fluid-infiltration-induced formation of biotite during relatively fast uplift, or the time of final passage through the effective biotite closure temperature. Rb-Sr ages of phengite from both an epidote amphibolite and a biotite-albite gneiss yield ages that correspond to the HP/LT stage. This outcome, combined with textural evidence for derivation from eclogitic precursors documents that white mica ages of some strongly overprinted Sistan rocks are compromised by inheritance and do

  3. Zircon petrochronology reveals the temporal link between porphyry systems and the magmatic evolution of their hidden plutonic roots (the Eocene Coroccohuayco deposit, Peru)

    Science.gov (United States)

    Chelle-Michou, Cyril; Chiaradia, Massimo; Ovtcharova, Maria; Ulianov, Alexey; Wotzlaw, Jörn-Frederik

    2014-06-01

    We present zircon geochronologic (LA-ICPMS and ID-TIMS), trace element and Hf isotopic evidence for a complex evolution of the plutonic roots of the Eocene Coroccohuayco porphyry system, southern Peru. LA-ICPMS U-Pb dating has initially been carried out to optimize grain selection for subsequent high-precision ID-TIMS dating and to characterize crustal assimilation (xenocrystic cores). This combined in-situ and whole-grain U-Pb dating of the same grains has been further exploited to derive a robust temporal interpretation of the complex magmatic system associated with the Coroccohuayco porphyry-skarn deposit. Our data reveal that a heterogeneous gabbrodioritic complex was emplaced at ca. 40.4 Ma and was followed by a nearly 5 Ma-long magmatic lull until the emplacement of dacitic porphyry stocks and dykes associated with the mineralizing event at ca. 35.6 Ma. However, at the sample scale, zircons from the porphyries provide insight into a 2 Ma-long lived “hidden” magmatism (probably at 4-9 km paleodepth) prior to porphyry intrusion and mineralization for which no other evidence can be found on the surface today. These dates together with zircon trace element analysis and Hf isotopes argue for the development of a long-lived magmatic system dominated by amphibole fractionation with an increasing amount of crustal assimilation and the development of a large and sustained thermal anomaly. The system was probably rejuvenated at an increasing rate from 37.5 to 35.6 Ma with injection of fresh and oxidized magma from the lower crust, which caused cannibalism and remelting of proto-plutons. The porphyry intrusions at Coroccohuayco were emplaced at the peak thermal conditions of this upper crustal magma chamber, which subsequently cooled and expelled ore fluids. Zircon xenocrysts and Hf isotopes in the porphyritic rocks suggest that this large upper crustal system evolved at stratigraphic levels corresponding to Triassic sediments similar to the Mitu group that may be

  4. Origins and evolution of rhyolitic magmas in the central Snake River Plain: insights from coupled high-precision geochronology, oxygen isotope, and hafnium isotope analyses of zircon

    Science.gov (United States)

    Colón, Dylan P.; Bindeman, Ilya N.; Wotzlaw, Jörn-Frederik; Christiansen, Eric H.; Stern, Richard A.

    2018-02-01

    We present new high-precision CA-ID-TIMS and in situ U-Pb ages together with Hf and O isotopic analyses (analyses performed all on the same grains) from four tuffs from the 15-10 Ma Bruneau-Jarbidge center of the Snake River Plain and from three rhyolitic units from the Kimberly borehole in the neighboring 10-6 Ma Twin Falls volcanic center. We find significant intrasample diversity in zircon ages (ranges of up to 3 Myr) and in δ18O (ranges of up to 6‰) and ɛHf (ranges of up to 24 ɛ units) values. Zircon rims are also more homogeneous than the associated cores, and we show that zircon rim growth occurs faster than the resolution of in situ dating techniques. CA-ID-TIMS dating of a subset of zircon grains from the Twin Falls samples reveals complex crystallization histories spanning 104-106 years prior to some eruptions, suggesting that magma genesis was characterized by the cyclic remelting of buried volcanic rocks and intrusions associated with previous magmatic episodes. Age-dependent trends in zircon isotopic compositions show that rhyolite production in the Yellowstone hotspot track is driven by the mixing of mantle-derived melts (normal δ18O and ɛHf) and a combination of Precambrian basement rock (normal δ18O and ɛHf down to - 60) and shallow Mesozoic and Cenozoic age rocks, some of which are hydrothermally altered (to low δ18O values) by earlier stages of Snake River Plain magmatism. These crustal melts hybridize with juvenile basalts and rhyolites to produce the erupted rhyolites. We also observe that the Precambrian basement rock is only an important component in the erupted magmas in the first eruption at each caldera center, suggesting that the accumulation of new intrusions quickly builds an upper crustal intrusive body which is isolated from the Precambrian basement and evolves towards more isotopically juvenile and lower-δ18O compositions over time.

  5. African/Amazonian Proterozoic correlations of Iberia: A detrital zircon U-Pb study of early Cambrian conglomerates from the Sierra de la Demanda (northern Spain)

    Science.gov (United States)

    ÁBalos, B.; Gil Ibarguchi, J. I.; SáNchez-Lorda, M. E.; Paquette, J. L.

    2012-06-01

    Unfoliated conglomerates define the base of an Early Cambrian transgressive system tract in the Sierra de la Demanda. Correlations allow us to bracket the corresponding sechron between 532 Ma and 520-521 Ma. These conglomerates contain sandstone and metamorphic quartzite pebbles carrying detrital tourmaline, rutile and zircon grains of plutonic or medium- to high-grade metamorphic derivation. Zircon detrital grains exhibit concordant or sub-concordant U/Pb ages clustered in various groups, including Neoarchean (2.52-2.56 Ga), Paleoproterozoic (1.71-2.02 Ga), and Mesoproterozoic (1.47 and ca. 1.1-1.0 Ga), the latter representative of orogenic magmatism related to Rodinia supercontinental assembly. The Neoproterozoic is represented by concordant ages in the range 750-880 Ma and by Cryogenian discordant ages. Ediacaran zircons cluster in two subsets ranging between 590 and 680 Ma and 560-585 Ma, both including several concordant ages. They reflect formation of juvenile crust in magmatic arc and back-arc basin settings. Zircon ages younger than 520-525 Ma postdate the depositional age of the conglomerate and may represent Hercynian overprinting. Bibliographic data overlooked in other provenance studies indicate that Mesoproterozoic relics as those presented here should no longer be considered of exotic origin with respect to a Gondwanan (West African) affinity of the Neoproterozoic to early Paleozoic of Iberia. The proposed source area, the "Ebro Massif" of central-north Iberia, currently is concealed under a kilometer-thick Paleozoic or younger cover. Its tectonic organization would compare to that of the North African or Amazonian cratons (including Mesoproterozoic components), rather than to the Neoproterozoic arc settings described in northwest and southwest Iberia.

  6. Precise Crystallization Age of the Bushveld Complex, South Africa: Direct Dating of the Platiniferous Merensky Reef Using the Zircon U-Pb Chemical Abrasion ID-TIMS Technique

    Science.gov (United States)

    Scoates, J. S.; Friedman, R. M.

    2006-12-01

    Determining the age of the Bushveld Complex, the world's largest layered intrusion and host to the majority of the known resources of platinum group elements, chromium and vanadium, has been difficult given the very low abundance of U-bearing minerals in the ultramafic-mafic cumulate rocks that comprise the body. This study provides a precise crystallization age for this giant layered intrusion and associated PGE mineralization, and allows for a re-evaluation of the duration and areal extent of Bushveld-related magmatic activity. Abundant, clear and colorless, anhedral zircon grains were separated from a sample of pegmatoidal feldspathic orthopyroxenite collected from the Merensky Reef in the West Mine (Townlands Shaft), Rustenburg Section. Low-U (21-105 ppm) zircon occurs with interstitial biotite and is locally directly in contact with sulfide. The zircon grains were subjected to different pre-treatment methods (no pre-treatment, air abrasion, and chemical abrasion [CA]) and isotope ratios for individual grains were analyzed by ID-TIMS. U-Pb data for the unabraded and air-abraded grains, and leachates from the CA procedure, are slightly discordant (0.1-1.6%) and yield overlapping 207Pb/206Pb dates ranging from 2052.5 to 2058.9 Ma. For the CA zircon grains (n=6), all data are concordant and give a Concordia age of 2054.3 ± 2.5 Ma (2sd, decay-constant errors included), which is interpreted as the age of crystallization of the Merensky Reef. This age is within error of published ages for the overlying, and locally cross-cutting, Bushveld or Lebowa granite suite, which implies that the entire Bushveld Complex was emplaced within a 2-3 myr interval. Comparison with ages from satellite intrusions (e.g. Moshaneng, Botswana; Uitkomst, South Africa) indicates that the Bushveld magmatic event at ca. 2054 Ma was regionally extensive across the northern Kaapvaal Craton and is consistent with relatively rapid emplacement of mantle-derived magmas along the Thabazimbi

  7. Positron annihilation lifetime study of radiation-damaged natural zircons

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, J. [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, The Australian National University, Canberra (Australia); Gaugliardo, P. [Centre for Antimatter-Matter Studies, School of Physics, University of Western Australia (Australia); Farnan, I.; Zhang, M. [Department of Earth Sciences, University of Cambridge (United Kingdom); Vance, E.R.; Davis, J.; Karatchevtseva, I.; Knott, R.B. [Australian Nuclear Science and Technology Organisation (Australia); Mudie, S. [The Australian Synchrotron, Victoria (Australia); Buckman, S.J. [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, The Australian National University, Canberra (Australia); Institute for Mathematical Sciences, University of Malaya, Kuala Lumpur (Malaysia); Sullivan, J.P., E-mail: james.sullivan@anu.edu.au [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, The Australian National University, Canberra (Australia)

    2016-04-01

    Zircons are a well-known candidate waste form for actinides and their radiation damage behaviour has been widely studied by a range of techniques. In this study, well-characterised natural single crystal zircons have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). In some, but not all, of the crystals that had incurred at least half of the alpha-event damage of ∼10{sup 19} α/g required to render them structurally amorphous, PALS spectra displayed long lifetimes corresponding to voids of ∼0.5 nm in diameter. The long lifetimes corresponded to expectations from published Small-Angle X-ray Scattering data on similar samples. However, the non-observation by PALS of such voids in some of the heavily damaged samples may reflect large size variations among the voids such that no singular size can be distinguished or. Characterisation of a range of samples was also performed using scanning electron microscopy, optical absorption spectroscopy, Raman scattering and X-ray scattering/diffraction, with the degree of alpha damage being inferred mainly from the Raman technique and X-ray diffraction. The observed void diameters and intensities of the long lifetime components were changed somewhat by annealing at 700 °C; annealing at 1200 °C removed the voids entirely. The voids themselves may derive from He gas bubbles or voids created by the inclusion of small quantities of organic and hydrous matter, notwithstanding the observation that no voidage was evidenced by PALS in two samples containing hydrous and organic matter. - Highlights: • Study of a range of naturally occurring zircons damaged by alpha radiation. • Characterised using a range of techniques, including PALS spectroscopy. • Effects on hydrous material appear important, rather than direct radiation damage. • Annealing is shown to remove the observed voids.

  8. Microwave-assisted hydrothermal synthesis of lead zirconate fine powders

    Directory of Open Access Journals (Sweden)

    Apinpus Rujiwatra

    2011-01-01

    Full Text Available A rapid synthesis of lead zirconate fine powders by microwave-assisted hydrothermal technique is reported. The influences of type of lead precursor, concentration of potassium hydroxide mineraliser, applied microwave power and irradiation time are described. The synthesised powders were characterised by powder X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopic microanalysis and light scattering technique. The merits of the microwave application in reducing reaction time and improving particle mono-dispersion and size uniformity as well as the drawbacks, viz. low purity of the desired phase and increasing demand of mineraliser, are discussed in relation to conventional heating method.

  9. Direct laser processing of bulk lead zirconate titanate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, Sheldon A.; Balla, Vamsi Krishna; Bose, Susmita [W.M. Keck Biomedical Materials Research Laboratory, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 (United States); Bandyopadhyay, Amit, E-mail: amitband@wsu.edu [W.M. Keck Biomedical Materials Research Laboratory, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 (United States)

    2010-08-15

    Laser Engineered Net Shaping (LENS{sup TM}) has been used to fabricate dense, net shape melt-cast structures of lead zirconate titanate (PZT), in a single step, directly on a metallic substrate by complete melting and resolidification of PZT powders. From our results, it appears that reasonable dielectric properties can be obtained in LENS{sup TM} processed PZT structures without post-fabrication heat treatments. Our results also demonstrate potential application of LENS{sup TM} towards direct fabrication of PZT based embedded sensors and transducers on structural components.

  10. Pb–Pb zircon ages of Archaean metasediments and gneisses from ...

    Indian Academy of Sciences (India)

    Zircons from orthogneisses from the two parts also yielded similar ages. Imprints of younger events have been discerned in the ages of overgrowths on older zircon cores in samples collected throughout the craton. Our data show that the evolution of the southwestern part of eastern Dharwar craton involved a significant ...

  11. Interpreting U-Pb data from primary and secondary features in lunar zircon

    Science.gov (United States)

    Grange, M. L.; Pidgeon, R. T.; Nemchin, A. A.; Timms, N. E.; Meyer, C.

    2013-01-01

    In this paper, we describe primary and secondary microstructures and textural characteristics found in lunar zircon and discuss the relationships between these features and the zircon U-Pb isotopic systems and the significance of these features for understanding lunar processes. Lunar zircons can be classified according to: (i) textural relationships between zircon and surrounding minerals in the host breccias, (ii) the internal microstructures of the zircon grains as identified by optical microscopy, cathodoluminescence (CL) imaging and electron backscattered diffraction (EBSD) mapping and (iii) results of in situ ion microprobe analyses of the Th-U-Pb isotopic systems. Primary zircon can occur as part of a cogenetic mineral assemblage (lithic clast) or as an individual mineral clast and is unzoned, or has sector and/or oscillatory zoning. The age of primary zircon is obtained when multiple ion microprobe analyses across the polished surface of the grain give reproducible and essentially concordant data. A secondary set of microstructures, superimposed on primary zircon, include localised recrystallised domains, localised amorphous domains, crystal-plastic deformation, planar deformation features and fractures, and are associated with impact processes. The first two secondary microstructures often yield internally consistent and close to concordant U-Pb ages that we interpret as dating impact events. Others secondary microstructures such as planar deformation features, crystal-plastic deformation and micro-fractures can provide channels for Pb diffusion and result in partial resetting of the U-Pb isotopic systems.

  12. Pb–Pb zircon ages of Archaean metasediments and gneisses from ...

    Indian Academy of Sciences (India)

    207Pb–206Pb ages of zircons in samples of metasediments as well as ortho- and para-gneisses from both the western and ... discerned in the ages of overgrowths on older zircon cores in samples collected throughout the craton. Our data show that ... ton and also examine the prevalent concepts on the tectonic evolution of ...

  13. Detrital and volcanic zircon U-Pb ages from southern Mendoza (Argentina): An insight on the source regions in the northern part of the Neuquén Basin

    Science.gov (United States)

    Naipauer, Maximiliano; Tapia, Felipe; Mescua, José; Farías, Marcelo; Pimentel, Marcio M.; Ramos, Victor A.

    2015-12-01

    The infill of the Neuquén Basin recorded the Meso-Cenozoic geological and tectonic evolution of the southern Central Andes being an excellent site to investigate how the pattern of detrital zircon ages varies trough time. In this work we analyze the U-Pb (LA-MC-ICP-MS) zircon ages from sedimentary and volcanic rocks related to synrift and retroarc stages of the northern part of the Neuquén Basin. These data define the crystallization age of the synrift volcanism at 223 ± 2 Ma (Cerro Negro Andesite) and the maximum depositional age of the original synrift sediments at ca. 204 Ma (El Freno Formation). Two different pulses of rifting could be recognized according to the absolute ages, the oldest developed during the Norian and the younger during the Rhaetian-Sinemurian. The source regions of the El Freno Formation show that the Choiyoi magmatic province was the main source rock of sediment supply. An important amount of detrital zircons with Triassic ages was identified and interpreted as a source area related to the synrift magmatism. The maximum depositional age calculated for the Tordillo Formation in the Atuel-La Valenciana depocenter is at ca. 149 Ma; as well as in other places of the Neuquén Basin, the U-Pb ages calculated in the Late Jurassic Tordillo Formation do not agree with the absolute age of the Kimmeridgian-Tithonian boundary (ca. 152 Ma). The main source region of sediment in the Tordillo Formation was the Andean magmatic arc. Basement regions were also present with age peaks at the Carboniferous, Neoproterozoic, and Mesoproterozoic; these regions were probably located to the east in the San Rafael Block. The pattern of zircon ages summarized for the Late Jurassic Tordillo and Lagunillas formations were interpreted as a record of the magmatic activity during the Triassic and Jurassic in the southern Central Andes. A waning of the magmatism is inferred to have happened during the Triassic. The evident lack of ages observed around ca. 200 Ma suggests

  14. Phase quantification of mullite-zirconia and zircon commercial powders using PAC and XRD techniques

    Energy Technology Data Exchange (ETDEWEB)

    Rendtorff, Nicolas M.; Conconi, Maria S.; Aglietti, Esteban F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC: CONICET-CIC) (Argentina); Chain, Cecilia Y.; Pasquevich, Alberto F. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina); Rivas, Patricia C. [CONICET (Argentina); Martinez, Jorge A., E-mail: toto@fisica.unlp.edu.ar; Caracoche, Maria C. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina)

    2010-06-15

    The short range technique of the Perturbed Angular Correlation (PAC) and x-ray diffraction (Rietveld) methods have been employed to determine the phase content in commercial mullite-zirconia and zircon raw materials that are ordinarily used to produce ceramic materials. The PAC technique, which probes zirconium-containing compounds at nanoscopic level, showed that zircon contains crystalline ZrSiO{sub 4} and an important amount of a structurally distorted zircon, which is also observed accompanying monoclinic zirconia in mullite-zirconia. This particular zircon phase was not detected by the long range x-ray diffraction-Rietveld technique. After an annealing treatment, important changes in crystalline contents of the powders allow confirming, by the x-ray diffraction-Rietveld method, the preexistence of this particular zircon phase. This fact must be taken into account when preparing multicomposites based on the present raw materials.

  15. Zircon reconnaissance dating of Proterozoic gneisses along the Kunene River of northwestern Namibia

    Science.gov (United States)

    Kröner, A.; Rojas-Agramonte, Y.; Wong, J.; Wilde, S. A.

    2015-11-01

    The northern margin of the Epupa Metamorphic Complex (EMC) along the Kunene River in NW Namibia is one of the geologically least known terranes in Africa because of its remoteness and difficult accessibility. We report field relationships and reconnaissance zircon ages for granitoid gneisses from a 120 km foot-traverse along the Kunene River between the Ruacana Falls in the east and Marienfluss in the west. Most rocks are late Palaeoproterozoic in age and correlate well with similar rocks of the EMC farther south in Kaokoland (1757-1835 Ma, one sample 1861 Ma) and with granitoid rocks in the Kamanjab Inlier, some 400 km SE of the Kunene River (1801-1836 Ma). All these rocks constitute a large magmatic province on the southwestern margin of the Congo Craton, whose protoliths are possibly related to arc magmatism during the Africa-wide so-called Eburnian event (ca. 2000 ± 200 Ma). However, there are also Mesoproterozoic granitoids, 1520-1530 Ma in age, whose tectonic significance remains uncertain but which seem to document a thermal event also seen in high-grade metamorphism and isotopic resetting in this part of SW Africa.

  16. Zircons reveal magma fluxes in the Earth's crust.

    Science.gov (United States)

    Caricchi, Luca; Simpson, Guy; Schaltegger, Urs

    2014-07-24

    Magma fluxes regulate the planetary thermal budget, the growth of continents and the frequency and magnitude of volcanic eruptions, and play a part in the genesis and size of magmatic ore deposits. However, because a large fraction of the magma produced on the Earth does not erupt at the surface, determinations of magma fluxes are rare and this compromises our ability to establish a link between global heat transfer and large-scale geological processes. Here we show that age distributions of zircons, a mineral often present in crustal magmatic rocks, in combination with thermal modelling, provide an accurate means of retrieving magma fluxes. The characteristics of zircon age populations vary significantly and systematically as a function of the flux and total volume of magma accumulated in the Earth's crust. Our approach produces results that are consistent with independent determinations of magma fluxes and volumes of magmatic systems. Analysis of existing age population data sets using our method suggests that porphyry-type deposits, plutons and large eruptions each require magma input over different timescales at different characteristic average fluxes. We anticipate that more extensive and complete magma flux data sets will serve to clarify the control that the global heat flux exerts on the frequency of geological events such as volcanic eruptions, and to determine the main factors controlling the distribution of resources on our planet.

  17. Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

    Directory of Open Access Journals (Sweden)

    Stopyra M.

    2016-06-01

    Full Text Available A2B2O7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho2Zr2O7 and praseodymium zirconate Pr2Zr2O7 via Polymerized-Complex Method (PCM. Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C fine-crystalline, single-phase material is obtained. Thermal diffusivity was measured in temperature range 25-200°C, Ho2Zr2O7 exhibits lower thermal diffusivity than Pr2Zr2O7. Additionally, PrHoZr2O7 was synthesized. The powder in as-calcined condition is single-phase, but during the sintering decomposition of solid solution took place and Ho-rich phase precipitated. This material exhibited the best insulating properties among the tested ones.

  18. Comparison of Zircon (Ti) Thermometry and Typology of the Cappadocian Ignimbrites

    Science.gov (United States)

    Akin, Lutfiye; Aydar, Erkan; Schmitt, Axel K.; Çubukçu, H. Evren

    2014-05-01

    The typological study of zircons is a valuable, convenient, reliable and economical tool since this mineral is highly resistant to alteration and post-magmatic heating. The zircon morphology yields information on temperature and the chemistry of magma hence can be a perfect indicator of the origin of material (e.g., crustal, hybrid or mantle). Zircon typology method has been applied to 8 different ignimbrite successions (Kavak-9.3 Ma, Zelve-9.2 Ma, Sarimadentepe-8.4 Ma, Sofular-8.2 Ma, Cemilkoy-7.2 Ma, Tahar-6.1 Ma, Gordeles-6.4 Ma, Kizilkaya-5.2 Ma) of Miocene-Pliocene in Central Anatolian Volcanic Province. The growth of the pyramidal and prismal faces of zircon crystals, extracted from pumices of each ignimbrite, has been examined and plot onto typology diagram. The temperature index (I.T.), which depends on the relative change of the (110) and (100) prismal faces and alkaline index (I.A.), which depends on the change of the (211) and (301) pyramidal faces, are determined. Typological Evolution Trend (T.E.T) which is used for granitoid classification, is drawn based on estimated I.T. and I.A.. Furthermore, Ti-thermometry of zircons has been applied in order to estimate the emplacement temperatures of the magmatic rocks. For that purpose, Ti concentrations of zircons and host rocks are determined. Zircon evolution temperatures and zircon saturation temperatures are calculated according to Ferry and Watson (2007) and Watson and Harrison (1983). Obtained zircon geothermometry data have been correlated with the zircon typology data. Zircon evolution temperature estimated from zircon crystals are 741oC ( Tmin=-30oC and Tmax=16oC) for Kavak, 749oC (Tmin=-31oC and Tmax=33oC) for Zelve, 811oC (Tmin=-37oC and Tmax=53 oC) for Sarimadentepe, 807oC (Tmin=-24oC and Tmax=61oC) for Sofular, 739oC (Tmin=-58oC and Tmax=42oC) for Cemilkoy, 768oC for Tahar, 806oC (Tmin=-37oC and Tmax=29oC) for Gordeles, 805oC (Tmin=-35oC and Tmax=69oC) for Gordeles-B, 765oC (Tmin=-25oC and Tmax=48

  19. Tectonic evolution of the NE section of the Pamir Plateau: New evidence from field observations and zircon U-Pb geochronology

    Science.gov (United States)

    Zhang, Chuan-Lin; Zou, Hai-Bo; Ye, Xian-Tao; Chen, Xiang-Yan

    2018-01-01

    The Pamir Plateau at the western end of the India-Asia collision zone underwent long-term terrane drifting, accretion and collision between early Paleozoic and Mesozoic. However, the detailed evolution of this plateau, in particular, the timing of the Proto- and Palaeo-Tethys ocean subduction and closure, remains enigmatic. Here we report new field observations and zircon U-Pb ages and Hf isotopic compositions of the representative rocks from the so-called Precambrian basement in the northeastern Pamir, i.e., the Bulunkuole Group. The rock associations of the Bulunkuole Group indicate volcano-sedimentary sequences with arc affinities. Geochronological data demonstrate that the deposition age of the Bulunkuole Group in the NE section of the Pamir was Middle to Late Cambrian (530-508 Ma) rather than Paleoproterozoic. The deposition age became progressively younger from south to north. The amphibolite- to granulite facies metamorphism of the Bulunkuole Group took place at ca. 200-180 Ma. Unlike the scenario in the Southern Kunlun terrane (SKT) in the eastern section of the West Kunlun Orogenic Belt (WKOB), early Paleozoic metamorphism (ca. 440 Ma) was absent in this area. Two phases of magmatic intrusions, composed of granites and minor gabbros with arc geochemical signatures, emplaced at 510-480 Ma and 240-200 Ma. The amphibolite (meta mafic sheet? 519 Ma) and the meta-rhyolite (508 Ma) have zircon εHf(t) values of 1.6 to 5.9 and - 1.5 to 1.4, respectively. The 511 Ma gneissic granite sheet and the 486 Ma gabbro have zircon εHf(t) values of - 0.1 to 2.4 and 1.3 to 3.6, respectively. Zircon εHf(t) of the 245 Ma augen gneissic granite sheet varies from - 2.2 to 2.0 whereas the metamorphic zircons from the amphibolite (193 Ma) and high-pressure mafic granulite sample (187 Ma) have negative εHf(t) values of - 5.3 to - 2 and - 15 to - 12, respectively. In line with rock association and the deposition age of the Bulunkuole Group and the Saitula Group in the eastern

  20. Testing the Existence of the South Gobi Microcontinent: U-Pb Zircon Dating of Tectonites within the East Gobi Fault Zone, Southeastern Mongolia

    Science.gov (United States)

    Taylor, J. P.; Webb, L. E.; Johnson, C. L.; Heumann, M. J.; Hagen-Peter, G. A.; Gehrels, G. E.

    2009-12-01

    The East Gobi Fault Zone (EGFZ) is a northeast trending structural corridor in southeastern Mongolia with a polyphase deformation history. Within the EGFZ, high grade and high strain metamorphic tectonites mapped as Precambrian have been interpreted to represent the South Gobi Microcontinent. Field and petrographic evidence, however, support an alternative hypothesis that the protoliths of the tectonites are Paleozoic arc and sedimentary sequences. Moreover, 40Ar/39Ar thermochronology indicates that fabrics in the metamorphic tectonites are the result of Mesozoic deformation. We present new LA-ICPMS, U-Pb zircon ages for rocks mapped as Precambrian within the EGFZ that serve to test the two hypotheses. Some zircons examined are small or exhibit complex zonation. In these cases, a small spot size of 10 μm was used, which excavates ~ 1 ng of material. The high spatial resolution capable with such a small spot size made dating these zircon grains and zones within grains possible. Two samples were dated from Tavan Har in the northern EGFZ. An augen gneiss (O7TH-10A) yielded zircons with dominantly Late Devonian-Early Permian ages. A granitic gneiss (07TH-12A), interpreted as a synkinematic intrusion in a Late Triassic sinistral shear zone based on field and 40Ar/39Ar data, yielded a weighted mean age of 219.4 ± 5.8 Ma. Within the southern EGFZ, samples from the lower plate of the Yagan-Onch Hayrhan metamorphic core complex were analyzed. Three samples (06OH-1-1, 06OH-1-2, 06OH-2-7) each yielded a large population of Late Devonian ages. Sample 06OH-2-7 also yielded a significant number of Early Devonian ages. Migmatite sample 08OH-4D yielded zircons with resorbed cores surrounded by high-U rims. These rims yielded highly discordant ages, however, multiple populations were resolved from analysis of the cores: The largest population consisted of Permian-Carboniferous ages with two additional smaller populations of Silurian-Cambrian ages and Precambrian ages, ca. 2500 Ma

  1. Zircon U-Pb Geochronology, Hf Isotopic Composition and Geological Implications of the Neoproterozoic Huashan Group in the Jingshan Area, Northern Yangtze Block, China

    Science.gov (United States)

    Yang, Z.; Yang, K.

    2015-12-01

    In the northern Yangtze Block, a clear angular unconformity between the Mesoproterozoic sequences (e.g. Dagushi Group) and the overlying Neoproterozoic strata (e.g. Huashan Group) marks the the Jinning orogeny. A combined study of Lu-Hf isotopes and U-Pb ages for detrital zircons from Huashan Group can provide information on the crustal evolution of sedimentary provenances and the timing of the Jinning orogeny. Detrital zircons from Huashan Group have two major U-Pb age populations of about 2.0Ga, 2.65Ga, and three subordinate age groups of about 0.82Ga, 2.5Ga, 2.9Ga with minor >3.0Ga ages. The youngest five analyses yield a weighted average age of 816±9Ma, which is consistent with that of interlayered basalt (824±9Ma, Deng et al., 2013) and roughly defines the minimum depositional age of Huashan Group. Detrital zircons of Huashan Group mostly have two stage Hf isotope model ages (TDM2) between 3.0 to 3.3Ga, indicating that the northern Yangtze Block experienced significant continental crustal growth during the Paleo- to Meso-archean. Similar U-Pb ages of detrital zircons have been obtained from Precambrian sedimentary rocks in the northern Yangtze Block from previous studies (Liu et al., 2008; Guo et al., 2014 and references therein). Recently, ca. 2.65Ga A-type granites had been reported from the Kongling and Huji area, which likely record the thermally stable lithosphere (Chen et al., 2013; Zhou et al., 2015). In combination with this study, it documents the widespread 2.6-2.7Ga magmatic rocks in the northern Yangtze Block. Zhao et al. (2013) demonstrated both the ca. 850Ma tonalite and trondhjemite of the Huangling igneous complex were formed in a continental arc setting. This suggests the Miaowan-Huashan oceanic basin proposed by Bader et al. (2013) has not been closed at ca. 850Ma. This evidence, together with the depositional age of the Huashan Group, indicates the Jinning orogeny took place at 850-820 Ma. [1] Bader et al., 2013 Tectonics [2] Deng et al

  2. Surface Characteristics and Bioactivity of a Novel Natural HA/Zircon Nanocomposite Coated on Dental Implants

    Directory of Open Access Journals (Sweden)

    Ebrahim Karamian

    2014-01-01

    Full Text Available The surface characteristics of implant which influence the speed and strength of osseointegration include surface chemistry, crystal structure and crystallinity, roughness, strain hardening, and presence of impurities. The aim of this study was to evaluate the bioactivity and roughness of a novel natural hydroxyapatite/zircon (NHA/zircon nanobiocomposite, coated on 316L stainless steel (SS soaked in simulated body fluid (SBF. NHA/zircon nanobiocomposite was fabricated with 0 wt.%, 5 wt.%, 10 wt.%, and 15 wt.% of zircon in NHA using ball mill for 20 minutes. The composite mixture was coated on 316L SS using plasma spray method. The results are estimated using the scanning electron microscopy (SEM observation to evaluate surface morphology, X-ray diffraction (XRD to analyze phase composition, and transmission electron microscopy (TEM technique to evaluate the shape and size of prepared NHA. Surfaces roughness tester was performed to characterize the coated nanocomposite samples. The maximum average Ra (14.54 μm was found in the NHA 10 wt.% of zircon coating. In addition, crystallinity (Xc was measured by XRD data, which indicated the minimum value (Xc = 41.1% for the sample containing 10 wt.% of zircon. Maximum bioactivity occurred in the sample containing 10 wt.% of zircon, which was due to two reasons: first, the maximum roughness and, second, the minimum crystallinity of nanobiocomposite coating.

  3. Modelling of optically stimulated luminescence of zircon: assessment of the suitability for dating

    Energy Technology Data Exchange (ETDEWEB)

    Turkin, A A [National Science Centre, Kharkov Institute of Physics and Technology, 1 Akademichna str., 61108 Kharkov (Ukraine); Vainshtein, D I [Solid State Physics Laboratory, University of Groningen, 4 Nijenborgh, 9747 AG Groningen (Netherlands); Hartog, H W den [Solid State Physics Laboratory, University of Groningen, 4 Nijenborgh, 9747 AG Groningen (Netherlands)

    2006-04-07

    The mineral zircon, ZrSiO{sub 4}, is a candidate material for optical dating because it exhibits luminescence after exposure to natural radioactivity. The kinetic model of zircon thermally stimulated luminescence proposed before has been modified and used to investigate optically stimulated luminescence (OSL) of zircon. The purpose is to explore what might be expected from zircon during real experiments because experimentally zircon OSL has not been studied systematically. Any luminescence dating method involves, as a necessary step, a laboratory irradiation at dose rates much higher than the dose rate of natural radioactivity. The model of zircon OSL predicts a significant and complicated dose rate and temperature effects. Our simulation results suggest that this problem may be solved by laboratory irradiation at elevated temperature followed by a preheat. Such a combined treatment allows one to reproduce the dose response expected from the naturally irradiated material (after the same preheat treatment). The shape of the theoretically calculated dose response curve reconstructed in this way exhibits a weak sensitivity to variation of laboratory irradiation temperature for ages younger than a few thousand years. This means that zircon OSL can probably be used successfully for dating of young samples.

  4. ;Inverted; zircon and apatite (U-Th)/He dates from the Front Range, Colorado: High-damage zircon as a low-temperature (<50 °C) thermochronometer

    Science.gov (United States)

    Johnson, Joshua E.; Flowers, Rebecca M.; Baird, Graham B.; Mahan, Kevin H.

    2017-05-01

    Zircon (U-Th)/He (ZHe) data were acquired for 23 Proterozoic basement samples from an E-W transect through the Colorado Front Range to evaluate whether metamict zircons yield sensible (U-Th)/He data patterns and useful thermal history information. The 112 ZHe dates vary from 147 to 7 Ma, define positive and negative date-eU correlations, and are younger than titanite (U-Th)/He dates that range from 976 to 614 Ma. At moderate to high alpha dose of 1018-1019 α /g, zircons from the range core yield Laramide (52.5 ± 9.6 Ma) dates, whereas those within ∼15 km of the range front yield Miocene (21.6 ± 7.7 Ma) results. The He dates for the high alpha dose zircons are reproducible within each sample suite despite their visibly metamict character. The ∼20 Ma range front ZHe dates are younger than apatite (U-Th)/He (AHe) dates (66.5 ± 9.6 Ma) and published apatite fission-track data (65-45 Ma) for the same and nearby samples. Thermal history simulations can reproduce the first-order range front date-eU patterns and ZHe-AHe date inversion, but the high-damage zircons are more He retentive than predicted by the zircon damage He kinetic model. The ∼20 Ma ZHe dates may be explained by reheating from hydrothermal fluids along range front faults. The results demonstrate the promise of using He data for high-damage zircons to detect low-temperature (<50 °C) events within and below the temperature sensitivity of the AHe system.

  5. Peculiar Feldspar And Quartz Inclusions Within Zircons From Anorthosites, North Eastern Desert, Egypt

    Science.gov (United States)

    Eliwa, H. A.; Dawoud, M. I.; Khalaf, I. M.; Negendank, J. F.; Itaya, T.

    2004-12-01

    Zircons from three anorthosite outcrops along Wadi Dib area, north Eastern Desert of Egypt contain abundant and conspicuous inclusions of quartz, feldspar, amphibole and apatite. These anorthosites, as (50-100m thick) layers, represent the top of mafic-ultramafic intrusions exhibiting rhythmic layering visible by reputation of melanocratic and leucocratic layers. Field and microscopic studies exhibit that these anorthosites were affected by the action of residual magmatic solutions associated with the late stage crystallization of the younger granites, which modified their mineralogical composition. They are composed totally of plagioclase with subordinate amount of clinoenstatite, augite, amphibole, biotite, K-feldspar, and quartz. Accessories are magnetite, ilmenite, apatite and zircon. The abundance and the mode of occurrence of K-feldspar, quartz, and biotite with apatite and zircon among the megacrysts suggest their formation is ascribed to the interaction with the residual solutions. The microprobe data exhibit difference between feldspar and amphiboles contained herein zircons and those as anorthosite mineral constituents. The genetic relationship between zircons and their inclusions suggests later growth of zircons than inclusions and most probably at the final stage of rock modification. Zircons are magmatic and found in the interstitial feldspar and quartz among plagioclase megacrysts in aggregates or as individual grains. The microscopic and SEM images investigation exhibit that most zircons are subhedral to euhedral equant and prismatic crystals. Most zircons have same range of crystal morphologies and internal growth structures with predominance of prism /{100/} and pyramid /{101/} and occasionally prism /{110/} and pyramid /{111/}. No evidences for poly-faceted grains, inherited cores or later overgrowths were detected. CL images distinguished zircons with visible core-rim structures and others with regular and continuous growth zones contained herein

  6. Annealing of natural metamict zircons: II high degree of radiation damage

    CERN Document Server

    Colombo, M

    1998-01-01

    In situ time-dependent high-temperature X-ray powder diffraction was used to study the amorphous to crystalline transition in natural zircons which are characterized by a high degree of radiation damage. It was possible to distinguish two stages of the annealing process: (i) the recovery of the heavily disturbed but still crystalline domains and (ii) the recrystallization of the amorphous regions. The first stage is very fast under the chosen experimental conditions and, at least apparently, is not thermally activated. The second stage is a diffusion-controlled process, whose products (zircon or zircon and zirconia phases) are strongly correlated to the annealing temperature.

  7. Strontium zirconate as silicon and aluminum scavenger in yttria stabilized zirconia

    DEFF Research Database (Denmark)

    Andersen, Thomas; Hansen, Karin Vels; Chorkendorff, Ib

    2011-01-01

    Here we report on strontium zirconate as a getter for silicon dioxide and aluminum oxide in yttria stabilized zirconia (YSZ) single crystals for cleaning purposes. YSZ single crystals were covered with strontium zirconate powder and heat treated at 1450°C in water vapor. After treatment the YSZ...... by transmission electron microscopy (TEM) the interface region between bump and YSZ single crystal bulk was examined. EDS showed a homogeneous distribution of silicon and aluminum through the cross section of a bump. The results suggest strontium zirconate as a good getter for silicon and aluminum from bulk...

  8. U-Pb (LA-ICPMS) zircon ages and Nd isotopes for granitoids of the Tamboril-Santa Quiteria Complex, Ceara Central Domain: implication for neoproterozoic syncollisional magmatism in north Borborema Province, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Felipe Grandjean da; Araujo, Carlos Eduardo Ganade de; Vasconcelos, Antonio Maurilio, E-mail: felipe.costa@cprm.gov.br, E-mail: caegeo@gmail.com, E-mail: maurilio.vasconcelos@cprm.gov.br [Servico Geologico do Brasil (CPRM), Fortaleza, CE (Brazil); Amaral, Wagner da Silva, E-mail: wamaral@ufc.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Geologia; Rodrigues, Joseneusa Brilhante, E-mail: joseneusa.rodrigues@cprm.gov.br [Servico Geologico do Brasil (CPRM), Brasilia, DF (Brazil)

    2013-06-15

    The Tamboril-Santa Quiteria Complex (TSQC) is one of the largest Neoproterozoic plutonic manifestations in the north Borborema Province (NE Brazil). It represents an anatectic/igneous association characterized by a number of magmatic pulses that occurred in the 650-610 Ma interval. In this paper, we present U-Pb (LA-MC-ICP-MS) zircon ages and Nd isotopes for quartz monzonite and quartz diorites of the southern part of TSQC. The quartz monzonite belong to a hybrid granitoid association, including monzonite, syenites and quartz syenites, all with abundant mafic magmatic enclaves. A quartz monzonite sample yielded a U-Pb zircon age of 634 {+-} 10 Ma and a TDM age of 2.69 Ga. The quartz diorites are much more homogeneous in composition and yielded a U-Pb zircon age of 618 {+-} 23 Ma and a TDM age of 2.19 Ga. The presence of coeval mantle-derived magmatism and diatexites (crustal anatexis) post-dating high-pressure metamorphism (ca. 650 Ma), and together with high-temperature metamorphism (ca. 630-610 Ma), suggests that this large magmatic manifestation evolved in a collisional setting, probably related to slab break off during the Western Gondwana amalgamation. (author)

  9. Zircon U-Pb ages and Hf isotope compositions of the Mayuan migmatite complex, NW Fujian Province, Southeast China: Constraints on the timing and nature of a regional tectonothermal event associated with the Caledonian orogeny

    Science.gov (United States)

    Liu, Rui; Zhou, Hanwen; Zhang, Li; Zhong, Zengqiu; Zeng, Wen; Xiang, Hua; Jin, Song; Lu, Xinqian; Li, Chunzhong

    2010-10-01

    U-Pb ages, trace elements, and Hf isotope compositions of zircons from the Mayuan migmatite complex in NW Fujian province have been determined to provide constraints on the source and genesis of anatexis and tectonothermal evolution related to the Caledonian orogeny in South China. The migmatites investigated consist of various amounts of mesosome, leucosome, and melansome. Zircons extracted from mesosome, leucosome, and granite samples are characterized by oscillatory overgrowths enclosing inherited cores or occur as newly grown grains. The ages of the inherited zircons from the leucosome and granite samples are consistent with those of adjacent basement paragneiss in the study area, suggesting that both leucosome and granite were generated by partial melting of the latter. A comparison of Hf isotopes between the newly-formed zircons and inherited cores indicates that the former resulted from the breakdown of preexisting inherited zircons and/or less Hf-rich minerals other than zircons at the source. One mesosome sample contains typical metamorphic zircons that yielded a weighted mean 206Pb/ 238U age of 453 ± 3 Ma. They show enrichments in heavy REEs (Lu N/La N up to 22,709), indicating their growth prior to garnet crystallization. The other mesosome sample, in contrast, contains both newly-formed metamorphic rims and grains that gave a weighted mean 206Pb/ 238U age of 442 ± 8 Ma. They are characterized by relatively low Th/U ratios, depletions in heavy REEs (Lu N/La N = 117-396), and low 176Lu/ 177Hf ratios, suggesting their growth synchronous with garnet crystallization. The U-Pb ages of the mesosome samples are interpreted as recording the time of early (ca. 453 Ma) to peak (442 Ma) stages of a regional metamorphic event. Two leucosome and two granite samples yield consistent U-Pb ages of 438 ± 5 Ma to 442 ± 4 Ma, which provide constraints on the timing of subsequent anatexis and magmatism. The geochronological data reported here reveal a consecutive

  10. Radiation-induced disorder in compressed lanthanide zirconates.

    Science.gov (United States)

    Park, Sulgiye; Tracy, Cameron L; Zhang, Fuxiang; Park, Changyong; Trautmann, Christina; Tkachev, Sergey N; Lang, Maik; Mao, Wendy L; Ewing, Rodney C

    2018-02-28

    The effects of swift heavy ion irradiation-induced disordering on the behavior of lanthanide zirconate compounds (Ln 2 Zr 2 O 7 where Ln = Sm, Er, or Nd) at high pressures are investigated. After irradiation with 2.2 GeV 197 Au ions, the initial ordered pyrochlore structure (Fd3[combining macron]m) transformed to a defect-fluorite structure (Fm3[combining macron]m) in Sm 2 Zr 2 O 7 and Nd 2 Zr 2 O 7 . For irradiated Er 2 Zr 2 O 7 , which has a defect-fluorite structure, ion irradiation induces local disordering by introducing Frenkel defects despite retention of the initial structure. When subjected to high pressures (>29 GPa) in the absence of irradiation, all of these compounds transform to a cotunnite-like (Pnma) phase, followed by sluggish amorphization with further compression. However, if these compounds are irradiated prior to compression, the high pressure cotunnite-like phase is not formed. Rather, they transform directly from their post-irradiation defect-fluorite structure to an amorphous structure upon compression (>25 GPa). Defects and disordering induced by swift heavy ion irradiation alter the transformation pathways by raising the energetic barriers for the transformation to the high pressure cotunnite-like phase, rendering it inaccessible. As a result, the high pressure stability field of the amorphous phase is expanded to lower pressures when irradiation is coupled with compression. The responses of materials in the lanthanide zirconate system to irradiation and compression, both individually and in tandem, are strongly influenced by the specific lanthanide composition, which governs the defect energetics at extreme conditions.

  11. Stages of late Paleozoic to early Mesozoic magmatism in the Song Ma belt, NW Vietnam: evidence from zircon U-Pb geochronology and Hf isotope composition

    Science.gov (United States)

    Hieu, Pham Trung; Li, Shuang-Qing; Yu, Yang; Thanh, Ngo Xuan; Dung, Le Tien; Tu, Vu Le; Siebel, Wolfgang; Chen, Fukun

    2017-04-01

    The Song Ma zone in NW Vietnam bears important tectonic implications as a potential subduction corridor between the Indochina and South China blocks. On the basis of U-Pb ages, the Hf isotopic characteristics of zircons and the geochemical composition of granitoids, a two-stage magmatic evolution process of the Song Ma zone at 290-260 and 245-230 Ma can be proposed. Isotopic analyses indicate magmatic contributions from Neoproterozoic oceanic island basalt, Proterozoic continental crust, and depleted mantle or juvenile lithosphere. By combining geochronological and geochemical data from the granitoid rocks, we suggest that the staged magmatic processes of Song Ma zone may be related to a long-lasting period of ocean subduction (ca. 290-260 Ma) and subsequent syn-/post-collisional evolution (ca. 245-230 Ma).

  12. Zircon from historic eruptions in Iceland: Reconstructing storage and evolution of silicic magmas

    Science.gov (United States)

    Carley, T.L.; Miller, C.F.; Wooden, J.L.; Bindeman, I.N.; Barth, A.P.

    2011-01-01

    Zoning patterns, U-Th disequilibria ages, and elemental compositions of zircon from eruptions of Askja (1875 AD), Hekla (1158 AD), ??r??faj??kull (1362 AD) and Torfaj??kull (1477 AD, 871 AD, 3100 BP, 7500 BP) provide insights into the complex, extended, histories of silicic magmatic systems in Iceland. Zircon compositions, which are correlated with proximity to the main axial rift, are distinct from those of mid-ocean ridge environments and fall at the low-Hf edge of the range of continental zircon. Morphology, zoning patterns, compositions, and U-Th ages all indicate growth and storage in subvolcanic silicic mushes or recently solidified rock at temperatures above the solidus but lower than that of the erupting magma. The eruptive products were likely ascending magmas that entrained a zircon "cargo" that formed thousands to tens of thousands of years prior to the eruptions. ?? 2011 Springer-Verlag.

  13. Crystallographically controlled crystal-plastic deformation of zircon in shear zones

    Science.gov (United States)

    Kovaleva, Elizaveta; Klötzli, Urs

    2014-05-01

    Plastically-deformed zircons from various types of strained natural metamorphic rocks have been investigated in-situ by electron backscatter diffraction analysis (EBSD), allowing crystallographic orientation mapping at high spatial resolution. Plastic deformation often forms under the control of grain-internal heterogeneities. At the crystal structure scale deformation is controlled by the physical anisotropy of the lattice. Three most common slip systems in zircon are [100]{010}, [010]{001} and [001]{010} (Leroux et. al., 1999; Reddy et. al., 2007). They are genetically connected with the main zircon crystallographic directions: [001] (c-axis), [100] and [010] (a and b axes). Atomic models show weak planes normal to these directions that preferably evolve to glide planes in the deforming crystal. The visualization of seismic (elastic) properties of zircon with the MATLAB toolbox MTEX shows a similar pattern. The slowest S-wave velocities are observed in directions parallel to [100], [010] and [001] crystallographic directions. The highest Young's modulus values lie in the same directions. In natural zircon grains, the common slip systems are preferably activated when zircon is hosted by rheologically comparatively weaker phases or a fine-grained matrix. In these cases zircon behaves as a rigid clast. During progressive deformation high deviatoric stresses together with high strain rates concentrate at crystal tips, as shown by numerical modeling. Softer host phases allow more degrees of freedom for zircon to be deformed according to its crystallographic and internal properties. These conclusions are supported by the misorientation axes density distribution maps, derived with MTEX. Deformed zircon hosted by a relatively soft phase (mostly biotite) develops a crystallographic preferred orientation (CPO), which has not been documented for zircon before. At the same time deformation of zircon hosted by a rheologically stronger matrix causes the activation of less

  14. Real-Time Salmonella Detection Using Lead Zirconate Titanate-Titanium Microcantilevers

    National Research Council Canada - National Science Library

    McGovern, John-Paul; Shih, Wan Y; Shih, Wei-Heng; Sergi, Mauro; Chaiken, Irwin

    2005-01-01

    .... We have developed and investigated the use of a lead zirconate titanate - titanium (PZT-Ti) microcantilever for in situ detection of the common food- and water-born pathogen, Salmonella typhimurium...

  15. Accurate Hf isotope determinations of complex zircons using the "laser ablation split stream" method

    National Research Council Canada - National Science Library

    Christopher M Fisher; Jeffery D Vervoort; S Andrew DuFrane

    2014-01-01

      The "laser ablation split stream" (LASS) technique is a powerful tool for mineral-scale isotope analyses and in particular, for concurrent determination of age and Hf isotope composition of zircon...

  16. Provenance of zircon of the lowermost sedimentary cover, Estonia, East-European Craton

    Directory of Open Access Journals (Sweden)

    Konsa, M.

    1999-12-01

    Full Text Available Bulk and accessory mineral composition of fresh and weathered crystalline rocks, and sedimentary deposits overlying the crystalline-sedimentary unconformity have been examined in core samples from 28 drill holes in Estonia. Before the Late Vendian to Early Cambrian regional subsidence and sedimentation, the region represented a flat plateau within the Svecofennian Domain. Palaeo-and Mesoproterozoic crystalline rocks, regardless their different initial mineral composition, subcrop under the Upper Vendian/Lower Cambrian sedimentary cover as usually intensely weathered rocks (saprolites composed of residual quartz, altered micas and prevailing clay minerals mainly of the kaolinite group. Thus, the bulk mineral composition of any basement crystalline rocks imparts no specific inherited rock-forming minerals into the covering sedimentary rocks. From the variety of accessory and opaque minerals of crystalline rocks, only zircon populations survived in saprolites. Crystalline rocks of different origin yield different zircons. Relationships between the zircon typology of the basement rocks having specific areas of distribution and the sedimentary rocks immediately overlying those crystalline rocks were the main subject of this study. The result is that siliciclastic sedimentary rocks covering weathered crystalline rocks only in places inherited zircons with typological features characteristic of specific basement areas. In northeastern Estonia, local lenses of the Oru Member (the earliest Upper Vendian sedimentary rocks in Estonia resembling the debris of weathered crystalline rocks yield accessory zircon which in a 1-2 m thick layer above the basement surface is similar to the zircons of the underlying weathering mantle of certain crystalline rocks. In the next unit, the Moldova Member, up to 43 m above the basement surface, a mixture of zircons resembling those of various local basement rocks has been found. Further upwards, in the Vendian and Lower

  17. Detrital Zircons U-Pb Age and Hf Isotope from the Western Side of the Taiwan Strait: Implications for Sediment Provenance and Crustal Evolution of the Northeast Cathaysia Block

    Directory of Open Access Journals (Sweden)

    Yonghang Xu

    2014-01-01

    Full Text Available In situ detrital zircons U-Pb and Hf isotope analyses from the Min and Jiulong River of Southeast China were carried out to identify sediment provenance and crustal evolution of the northeast Cathaysia Block. Detrital zircons from both rivers displayed similar spectrum peaks at 236, 155, and 110 Ma, but samples from the Min River displayed a distinct Caledonian peak (ca. 460 Ma and contained more Precambrian particles (ca. 1.8 Ga, which likely stemmed from the upstream area of the Wuyishan terrain. Interestingly, because Taiwan Island cannot supply Caledonian and Paleoproterozoic detrital materials and because the Ou and Jiulong River also lack components from these two populations, it is highly likely that the sediment in the western Taiwan coast partially originates from the Min River. The sediments from the Min River in Fujian are also considered the most likely source of the beach sands of western Taiwan (Chen et al. 2006. However, we stress that the ~1.8 Ga age source in the western Taiwan sediments was found and recognized. Combining U-Pb dating and Hf-isotope suggests that the northeast Cathaysia Block contains some Neoarchean detrital zircons, which derived from the incorporation of juvenile mantle materials and re-melting of ancient crustal substances. The wide ranges of εHf(t value in the Paleoproterozoic and Neoproterozoic demonstrate the re-melting of ancient crustal materials with minor juvenile mantle materials. Phanerozoic zircons stemmed from re-melting and recycling of Proterozoic crustal materials with or without the invasion of juvenile mantle-derived magmas.

  18. Geochronological study of zircons from continental crust rocks in the Frido Unit (southern Apennines)

    Science.gov (United States)

    Laurita, Salvatore; Prosser, Giacomo; Rizzo, Giovanna; Langone, Antonio; Tiepolo, Massimo; Laurita, Alessandro

    2015-01-01

    Zircon crystals have been separated from gneisses and metagranitoids of the Pollino area (southern Apennines) in order to unravel the origin of these crustal slices within the ophiolite-bearing Frido Unit. The morphology of the zircon has been investigated by SEM, and the internal structure was revealed by cathodoluminescence. Data obtained by U/Pb dating have been used to deduce the age and significance of the different crystallization stages of zircon, connected to the evolutionary stages of the continental crust (Late Paleozoic-Early Mesozoic). Zircons in gneisses are characterized by inherited cores of magmatic origin, bordered by metamorphic rims. Inherited zircons generally show Paleoproterozoic to Ordovician ages, indicating the provenance of the sedimentary protolith from different sources. The exclusive presence of Late Neoproterozoic zircon cores in leucocratic gneisses may suggest a different magmatic source possibly connected to Pan-African events. Late Carboniferous-Early Permian ages are found mainly in zircon rims of metamorphic origin. These are similar to the emplacement ages of protolith of the metagranites in the middle crust portion. Late Carboniferous-Early Permian metamorphism and magmatism testify the extensional collapse of the Hercynian belt, recorded in European, particularly, in the Corsica-Sardinia block and in Calabria. Late Permian-Triassic ages have been detected in zircon rims from gneisses and metagranitoids. These younger ages appear related to deformation and emplacement of albite-quartz veins in both lithologies, and are related to an extensional episode predating the Middle Triassic to Middle Jurassic rifting in the Tethyan domain, followed by Middle to Late Jurassic spreading.

  19. Structural Characterization of Natural and Processed Zircons with X-Rays and Nuclear Techniques

    OpenAIRE

    Laura C. Damonte; Patricia C. Rivas; Pasquevich, Alberto F.; Fernanda Andreola; Federica Bondioli; Anna M. Ferrari; Laura Tositti; Giorgia Cinelli

    2017-01-01

    In ceramic industry, zircon sand is widely used in different applications because zirconia plays a role as common opacifying constituent. In particular, it is used as a basic component of glazes applied to ceramic tiles and sanitary ware as well as an opacifier in unglazed bulk porcelain stoneware. Natural zircon sands are the major source of zirconium minerals for industrial applications. In this paper, long, medium, and short range studies were conducted on zirconium minerals originated fro...

  20. Electron-beam-induced annealing of natural zircon: a Raman spectroscopic study

    Science.gov (United States)

    Váczi, Tamás; Nasdala, Lutz

    2017-06-01

    The annealing of radiation damage in zircon by low-energy electron irradiation was explored systematically. Natural zircon samples spanning a wide range of self-irradiation damage were irradiated with the focused electron beam of an electron probe microanalyser. The effects of beam current and irradiation time were tested systematically, and the changes in zircon were measured using Raman spectroscopy. Our results confirm the damage-annealing effect of an accelerated electron beam. We demonstrate that non-thermal annealing occurs through electron-enhanced defect reactions and that the extent of the annealing is a function of both the irradiation time and the beam current. The complete annealing of radiation damage in zircon by an accelerated electron beam was not possible under the conditions of our experiments. Our results indicate that Raman band broadening in ion-irradiated zircon can possibly be explained through phonon confinement, as the estimated domain sizes of the crystalline volume amid recoil clusters decrease with increasing α dose. The results underlay the importance of doing Raman spectroscopy before electron-beam and ion-beam analysis. To avoid unwanted beam-induced annealing of damage in zircon during EPMA analysis, the electron energy transferred per volume unit of sample should be minimised, for instance by keeping the integrated charge low and/or by defocusing the electron beam.

  1. Structural Characterization of Natural and Processed Zircons with X-Rays and Nuclear Techniques

    Directory of Open Access Journals (Sweden)

    Laura C. Damonte

    2017-01-01

    Full Text Available In ceramic industry, zircon sand is widely used in different applications because zirconia plays a role as common opacifying constituent. In particular, it is used as a basic component of glazes applied to ceramic tiles and sanitary ware as well as an opacifier in unglazed bulk porcelain stoneware. Natural zircon sands are the major source of zirconium minerals for industrial applications. In this paper, long, medium, and short range studies were conducted on zirconium minerals originated from Australia, South Africa, and United States of America using conventional and less conventional techniques (i.e., X-Ray Diffraction (XRD, Positron Annihilation Lifetime Spectroscopy (PALS, and Perturbed Angular Correlations (PAC in order to reveal the type and the extension of the regions that constitute the metamict state of zircon sands and the modifications therein produced as a consequence of the industrial milling process and the thermal treatment in the production line. Additionally, HPGe gamma-ray spectroscopy confirms the occurrence of significant levels of natural radioactivity responsible for metamictization in the investigated zircon samples. Results from XRD, PALS, and PAC analysis confirm that the metamict state of zircon is a dispersion of submicron disordered domains in a crystalline matrix of zircon.

  2. U-Pb ages and geochemistry of zircon from Proterozoic plutons of the Sawatch and Mosquito ranges, Colorado, U.S.A.: Implications for crustal growth of the central Colorado province

    Science.gov (United States)

    Moscati, Richard J.; Premo, Wayne R.; Dewitt, Ed; Wooden, Joseph L.

    2017-01-01

    southern portion of the Sawatch and Mosquito ranges.(2) Calc-alkalic to alkali-calcic magmas intruded this region approximately 55 m.y. after the Roosevelt Granite with emplacement of pre-deformational plutons at ca. 1,710 Ma (e.g., Henry Mountain Granite and diorite of Denny Creek), and this continued for at least 30 m.y., ending with emplacement of post-deformational plutons at ca. 1,680 Ma (e.g., Kroenke Granodiorite, granite of Fairview Peak, and syenite of Mount Yale). The timing of deformation can be constrained to sometime after intrusion of the diorite of Denny Creek and likely before the emplacement of the undeformed granite of Fairview Peak. Geochemistry of both whole-rock and zircon indicates that the older group of ca. 1,710-Ma plutons formed at shallower depths, and then they intruded the younger group of more deeply generated, commonly peraluminous and sodic plutons. Although absent in the Sawatch and Mosquito ranges, Mazatzal-age (ca. 1,680–1,620 Ma) plutonic rocks are present regionally. Inherited zircon components of Mazatzal-age were found as cores in some 1.4-Ga Sawatch and Mosquito Range zircons, indicating the likelihood of a relatively local source. These combined data suggest the possibility that all were produced within a continental-margin magmatic arc created as a result of southward-migrating (slab rollback?), north-dipping subduction to the south of the region.(3) Widespread Mesoproterozoic plutonism—with emplacement at various depths and exhibiting bimodal geochemistry—is recognized in 16 different samples. An older group of predominantly peraluminous, yet magnesian granitoids (e.g., granodiorite of Sayers, granite of Taylor River, and the St. Kevin Granite) were emplaced between ca. 1,450 and 1,425 Ma. These geochemical parameters suggest moderate degrees of partial melting in a low-pressure environment. Three younger metaluminous, but ferroan plutons (diorite of Grottos, diorite of Mount Elbert, and granodiorite of Mount Harvard

  3. Geochronology of the Archaean Kolmozero-Voron'ya Greenstone Belt: U-Pb dating of zircon, titanite, tourmaline and tantalite (Kola Region, North-Eastern BAltic Shield)

    Science.gov (United States)

    Kudryashov, N.; Gavrilenko, B.; Apanasevich, E.

    2003-04-01

    The Archaean Kolmozero-Voron’ya greenstone belt is one of the most ancient geological structures of the Kola Peninsula. It is located between Upper Archaean terrains: Murmansk, Central Kola and Keivy. Within the Kolmozero-Voron'ya greenstone belt there are rare metal (Li, Cs with accessory Nb, Ta, and Be), Cu, Mo, and Au deposits. All rocks were metamorphosed under amphibolite facies conditions and intruded by granodiorites, plagiomicrocline and tourmaline granites and pegmatite veins. Four suites are distinguished within the belt: lower terrigenous formation, komatiite-tholeite, basalt-andesite-dacite and upper terrigenous formation. The U-Pb age of 2925±6 Ma on magmatic zircon was obtained for leucogabbro of differentiated gabbro-anorthosite massif Patchemvarak, situated at the boundary between volcanic-sedimentary units and granitoids of the Murmansk block. This age is the oldest for gabbro-anorthosites of the Kola Peninsula. Sm-Nd age of komatiites is ca. 2.87 Ga (Vrevsky, 1996). U-Pb age of zircon from biotite schist, which belongs to acid volcanites is 2865+/-5 Ma. Quartz porphyries, which are considered to be an intrusive vein analogous of acid volcanites has an age of 2828+/-8 Ma, that marks the final stage of the belt development. Dating of titanite from ovoid plagioamphibolites yielded an U-Pb age of 2595+/-20 Ma that probably is connected with the closure of the U-Pb isotopic titanite system during the regional metamorphism. The Porosozero granodioritic complex with an age of 2733+/-6 Ma is located between granites of the Murmansk domain, migmatites and gneisses of the Central Kola terrain and the Keivy alkaline granites. Tourmaline granites are found all over the Kolmozero-Voron’ya belt occurring among volcanogenic-sedimentary rocks of the belt. Their Pb-Pb age of 2520+/-70 Ma appears to denote the tourmaline crystallization at a post-magmatic stage of the complex formation. U-Pb zircon age from rare metal pegmatites is 1.9-1.8 Ga. Zircons from

  4. Timing of anatexis and melt crystallization in the Socorro-Guaxupé Nappe, SE Brazil: Insights from trace element composition of zircon, monazite and garnet coupled to Usbnd Pb geochronology

    Science.gov (United States)

    Rocha, B. C.; Moraes, R.; Möller, A.; Cioffi, C. R.; Jercinovic, M. J.

    2017-04-01

    The timing of partial melting and melt crystallization in granulite facies rocks of the Socorro-Guaxupé Nappe (SGN), Brazil is constrained using a combination of imaging techniques, LA-ICP-MS and EPMA dating, trace element geochemistry and thermobarometry. (Orthopyroxene)-garnet-bearing migmatite that records extensive biotite dehydration melting shows evidence for a clockwise P-T-t path. UHT peak conditions were attained at 1030 ± 110 °C, 11.7 ± 1.4 kbar, with post-peak cooling to 865 ± 38 °C, 8.9 ± 0.8 kbar. Cryogenian igneous inheritance of ca. 720-640 Ma is identified in oscillatory zoned zircon cores (n = 167) with steep HREE patterns. Resorbed, Y-rich monazite cores preserve a prograde growth stage at 631 ± 4 Ma prior to the partial melting event, providing an upper age limit for the granulite facies metamorphism in the SGN. REE-rich, Th-depleted monazite related to apatite records the initial stages of decompression at 628 ± 4 Ma. Multiple monazite growth episodes record melt crystallization events at 624 ± 3 Ma, 612 ± 5 Ma and 608 ± 6 Ma. Stubby, equant ;soccer ball; zircon provide evidence for melt crystallization at 613 ± 2 Ma and 607 ± 4 Ma. The excess scatter in zircon and monazite age populations between 629 ± 4 and 601 ± 3 Ma is interpreted as discontinuous and episodic growth within this age range, characterizing a prolonged metamorphic event in the SGN lasting ca. 30 m.y. The development of Y + HREE-rich monazite rims at ca. 600 Ma documents retrograde garnet breakdown, extensive biotite growth and the final stages of melt crystallization. Th-rich, Y + HREE-poor monazite rims at ca. 590 Ma record monazite recrystallization.

  5. Zircon geochronology reveals polyphase magmatism and crustal anatexis in the Buchan Block, NE Scotland: Implications for the Grampian Orogeny

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    T.E. Johnson

    2017-11-01

    Full Text Available The type locality for high-temperature, low-pressure regional metamorphism, the Buchan Block in NE Scotland, exhibits profound differences to the rest of the Grampian Terrane. These differences have led some to regard the Buchan Block as an exotic crustal fragment comprising Precambrian basement gneisses and cover rocks thrust into their current position during Grampian orogenesis. Although rocks of the Buchan Block are now generally correlated with Dalradian strata elsewhere, the origin of the gneisses and the cause of the high heat flow and associated magmatism is debated. We report SIMS U–Pb and LA-ICPMS Hf isotopic data in zircon from high-grade rocks from the northeast (Inzie Head Gneiss and northwest (Portsoy corners of the Buchan Block. Around Inzie Head, upper amphibolite to granulite facies metasedimentary gneisses coexist with diorite sheets that were emplaced contemporaneously with partial melting of their host rocks, at least locally. U–Pb geochronology indicates a crystallisation age for the diorite of 486 ± 9 Ma. Highly-deformed diorites within the Portsoy Gabbro have a crystallisation age of 493 ± 8 Ma. Ages of ca. 490 Ma for magmatism and high-grade metamorphism, which are broadly contemporaneous with ophiolite obduction and the onset of orogenesis, are significantly older than the established peak of Grampian metamorphism (ca. 470 Ma. We propose a new model for the Grampian Orogeny involving punctuated tectonothermal activity due to tectonic switching during accretionary orogenesis. Rollback of a NW-dipping subduction zone at ca. 490 Ma produced a back-arc environment (the Buchan Block with associated arc magmatism and high dT/dP metamorphism. Arrival of an outboard arc resulted in shortening (the initial phase of the Grampian Orogeny at ca. 488 Ma. Rollback of a NW-dipping subduction zone to the SE of the ca. 488 Ma suture began at 473 Ma and led to lithospheric-scale extension, decompression melting and

  6. Alteration and chemical U-Th-total Pb dating of heterogeneous high-uranium zircon from a pegmatite from the Aduiskii massif, middle Urals, Russia

    Science.gov (United States)

    Zamyatin, Dmitry A.; Shchapova, Yuliya V.; Votyakov, Sergey L.; Nasdala, Lutz; Lenz, Christoph

    2017-09-01

    The U-Th-Pb isotope system in the accessory mineral zircon may be disturbed, as for instance by the secondary loss of radiogenic lead. The recognition of such alteration is crucial for the sound interpretation of geochronology results, in particular for chemical dating by means of an electron probe micro-analyser (EPMA). Here we present the example of high-U zircon samples from a granite pegmatite from the Aduiskii Massif, Middle Urals, Russia. The structural and chemical heterogeneity of samples was characterised by EPMA, including joint probability distribution (JPD) analysis of back-scattered electrons (BSE), cathodoluminescence (CL) and U M β images, and by Raman and photoluminescence (PL) spectroscopy. We found a high-U interior region (U up to 11.4 wt%) without any obvious indication of alteration. This domain has stoichiometric composition, and its Raman spectrum is similar to that of amorphous ZrSiO4. In addition, altered lower-U regions are present that are non-stoichiometric and contain non-formula elements such as Ca, Al, Fe, and water up to several wt%. Their Raman spectra yielded a band near 760-810 cm-1 which is not related to any ZrSiO4 vibration; we assign it tentatively to the symmetric stretching of (UO2)2+ groups. This assignment is supported by the observation of a fairly intense PL phenomenon whose spectral position and vibrational-coupling structure strongly indicates a uranyl-related emission. Altered zones were formed by both fluid-driven diffusion reaction and coupled dissolution-reprecipitation processes. The variation of BSE and CL intensities in amorphous high-U zircon is controlled by its chemical composition and the presence of water and uranyl groups. We have determined a weighted mean EPMA age of 246 ± 2 Ma, which agrees reasonably well with previous dating results for the Aduiskii Massif.

  7. Precambrian-Cambrian provenance of Matinde Formation, Karoo Supergroup, northwestern Mozambique, constrained from detrital zircon U-Pb age and Lu-Hf isotope data

    Science.gov (United States)

    Bicca, Marcos Müller; Jelinek, Andrea Ritter; Philipp, Ruy Paulo; de Carvalho Lana, Cristiano; Alkmim, Ana Ramalho

    2018-02-01

    The Permian-Triassic time interval was a period of high sedimentation rates in the intracontinental Karoo rift basin of northwestern Mozambique, reflecting high exhumation rates in the surrounding high ground Precambrian-Cambrian basement and juxtaposed nappes. U-Pb LA-MC-ICPMS dating and Lu-Hf isotopic analysis of detrital zircons from the Late Permian-Early Triassic Matinde Formation of the Karoo Supergroup is used as a reliable proxy to map denudation patterns of source regions. Data allow discrimination of U-Pb age populations of ca. 1250-900 Ma, a secondary population between ca. 900-700 and a major contribution of ages around ca. 700-490 Ma. Zircon grains of the Mesoproterozoic age population present Mesoproterozoic (1000-1500 Ma) to Paleoproterozoic (1800-2300 Ma) Hf TDM ages, with positive (0 to +11) and negative εHf values (-3 to -15), respectively. The younger U-Pb age population also presents two different groups of zircon grains according to Lu-Hf isotopes. The first group comprise Paleoproterozoic (1800-2300 Ma) ages, with highly negative εHf values, between -10 and -22, and the second group exhibits Mesoproterozoic ages (1200-1500 Ma), with increased juvenile εHf values (ca. 0 to -5). These Hf isotopes reinforce the presence of unexposed ancient crust in this region. The oldest U-Pb age population resembles the late stages of Grenville Orogeny and the Rodinia Supercontinent geotectonic activity mostly represented by magmatic rocks, which are widely present in the basement of northern Mozambique. The juvenile Hf-isotope signature with an older age component is associated to rocks generated from subduction processes with crust assimilation by continental arcs, which we correlate to rocks of the Nampula Complex, south and east of the Moatize-Minjova Basin. The U-Pb ages between 900 and 700 Ma were correlated to the calc-alkaline magmatism registered in the Guro Suite, related to the breakup phase of Rodinia, and mark the western limit of the Moatize

  8. Major zircon megacryst suites of the Indo-Pacific lithospheric margin (ZIP) and their petrogenetic and regional implications

    Science.gov (United States)

    Sutherland, Lin; Graham, Ian; Yaxley, Gregory; Armstrong, Richard; Giuliani, Gaston; Hoskin, Paul; Nechaev, Victor; Woodhead, Jon

    2016-04-01

    Zircon megacrysts (± gem corundum) appear in basalt fields of Indo-Pacific origin over a 12,000 km zone (ZIP) along West Pacific continental margins. Age-dating, trace element, oxygen and hafnium isotope studies on representative zircons (East Australia-Asia) indicate diverse magmatic sources. The U-Pb (249 to 1 Ma) and zircon fission track (ZFT) ages (65 to 1 Ma) suggest thermal annealing during later basalt transport, with slab subduction.

  9. Ce and Eu anomalies in zircon as proxies for the oxidation state of magmas

    Science.gov (United States)

    Trail, Dustin; Bruce Watson, E.; Tailby, Nicholas D.

    2012-11-01

    Chondrite normalized rare earth element (REE) patterns of zircons generally have enriched Ce values relative to La and Pr, and depleted Eu values relative to Sm and Gd. High Ce contents in zircon may imply oxidizing conditions (Ce4+ is more compatible than Ce3+), whereas depleted Eu contents may imply reducing conditions (Eu2+ does not substitute into the zircon lattice). We report 41 experiments in which temperature, melt composition, and oxygen fugacity (fO2) were varied in order to explore the details of Ce and Eu incorporation into zircon. Crystals were synthesized in hydrous silicate melts at 10 kbar and 800-1300 °C. Synthetic rock mixes were doped with La + Ce + Pr (±P) or Sm + Eu + Gd and buffered at oxygen fugacities ranging from ∼IW (iron-wüstite) to >MH (magnetite-hematite); the run products were analyzed by electron microprobe to obtain crystal/melt partition coefficients. Cerium anomalies increase with higher oxygen fugacities and lower crystallization temperatures. In agreement with other experimental studies, peralkaline melts yield the largest zircon grains but show only modest Ce anomalies even at fO2s > MH. The same reason that zircons grown in peralkaline melts are easy to synthesize in the laboratory (these melts are capable of dissolving wt.% levels of Zr before zircon saturation due to high alkali content) makes the melt structure/composition atypical and not representative of most natural magmas. With this in mind, we synthesized zircons in a granitic melt with more modest alkali contents that require geologically plausible Zr contents for saturation. We obtained the following empirical relationship: ln Ce/CeD=(0.1156±0.0050)×ln(fO2)+13,860±708T/(K)-6.125±0.484 where (Ce/Ce∗)D is the Ce anomaly in zircon calculated from partition coefficients, and T is the zircon crystallization temperature in K. Europium anomalies from the same melt composition are more negative at lower oxygen fugacities, but with no resolvable temperature

  10. Raman spectra of impact zircons in the Jarva-varaka layered massif (the Monchegorsk ore region, the Kola Peninsula

    Directory of Open Access Journals (Sweden)

    Kaulina T. V.

    2017-03-01

    Full Text Available Zircon crystals from granophyre norites of the Jarva-varaka massif of the Monchegorsk ore region (the Kola Peninsula have been studied by means of back-scattered electron (BSE imaging and Raman spectroscopy. The Jarva-varaka massif according to geological and geochemical data has been compared with the Sudbury structure, for which an impact origin is assumed. Zircon study is stipulated by zircon ability to keep signs of shock metamorphism even under granulite-facies conditions, thus it can be used for identification of ancient impact structures. BSE images reveal complicated internal texture – darker central domains (cores and light rims without texture. Mineral inclusions in zircon are represented by sillimanite and plagioclase which indicates that the studied zircon grains were inherited from the host aluminous gneisses. Zircon crystals show variation of Raman spectra from the core of crystals with typical zircon Raman pattern to complete absence of spectral bands in the marginal parts and rims. Mineral inclusions in zircon rims also have no Raman spectra. Such patterns may be associated with the transformation of crystalline zircon (and mineral inclusions in it to diaplectic glass under the influence of shock metamorphism, core domains were screened by rims and thus preserved their structure. The received data suggest the participation of the meteorite impact in the formation of the Jarva-varaka massif that requires further investigation.

  11. Zircon (U-Th)/He evidence for pre-Eocene orogenic exhumation of eastern North Pyrenean massifs, France

    Science.gov (United States)

    Ternois, Sébastien; Vacherat, Arnaud; Pik, Raphaël; Ford, Mary; Tibari, Bouchaïb

    2017-04-01

    Orogens and their associated foreland basins are considered as part of a single dynamic system evolving from an early, non equilibrated, growth stage to a late, mature, steady-state stage. Most of our understanding in foreland basins, in particular early convergence-stage deposition, comes from the subducting plate, so that the classic paradigm for foreland basins is the pro-wedge. Models that clearly depict the relationship between erosion of the orogenic wedge and sedimentation into its associated foreland basin only focus on the late post-orogenic phase. Relatively little is known and understood about the very long phase of initiation of orogenesis. In the doubly wedged Pyrenean orogen, where we know and understand relatively little about how the early retro-wedge developed, the record of the onset of orogenic denudation from massifs is quite limited, not only in time but also in space. As part of the OROGEN project funded by TOTAL and the BRGM, this study presents first single-grain zircon (U-Th)/He data from two Palaeozoic massifs of the external Northern Pyrenean Zone, the Agly and Salvezines massifs. It aims at constraining the exhumation history of eastern Pyrenean massifs and understanding what is their significance for early orogenic wedge growth. The Pyrenean orogeny was generated from end Santonian (84 Ma) to Oligocene-Miocene due to convergence of the Iberian and European plates. Aquitaine foreland basin history (Ariège region) indicates that convergence took place in two phases, Campanian to Maastrichian and Eocene, separated by a quiet Paleocene phase. Yet, only Eocene cooling events are recorded by low-temperature thermochronometers in the central Pyrenean massifs (Arize and Trois-Seigneurs). Nine bedrock samples were collected along a WNW-ESE traverse (Salvezines and Saint-Arnac granites, Belesta-Caramany gneisses) and analysed for ZHe dating. Zircon (U-Th)/He data for the Agly and Salvezines massifs, together with forward modelling of data for

  12. Phase equilibria modelling and zircon dating for Precambrian metapelites from Xinghuadukou Group in Lvlin Forest of Erguna Massif, NE China

    Science.gov (United States)

    Xu, Jiulei; Zheng, Changqing; Tajcmanova, Lucie; Zhong, Xin; Xu, Xuechun; Han, Xiaomeng; Wang, Zhaoyuan

    2017-04-01

    Xinghuadukou Group, the basement metamorphic complex of Erguna Massif in NE China, is considered to be Mesoproterozoic with Sm-Nd age of 1157±32 Ma. However, the new zircon data from these metamorphic supracrustal rocks in Lvlin Forest show that they formed in Neoproterozoic with the age of 800 Ma. Old zircon age with 2.5 Ga, 2.0 Ga and 1.8 Ga, indicate that the Erguna Massif had an affinity to both Columbia and Rodinia continents. Furthermore, we also present 500 Ma metamorphic age in micashists and 500 Ma age of adjacent granitoids that might have thermally influenced its surrounding. No detailed studies have been undertaken on the metamorphic evolution of the Xinghuadukou Complex. The typical paragneissic mineral assemblage of garnet sillimanite mica schist is Grt+Sil+Bt+Mus+Qtz±Kfs. (Zhou et al., 2011) proposed that the Xinghuadukou Complex appears to have undergone similar granulite facies metamorphic conditions based on the similarity of mineral assemblages to the Mashan Complex in the Jiamusi Massif, NE China. However, the new phase equilibria modelling result shows that these rocks are high amphibolite facies product with 650℃. We can easily find K-feldspar formed by partial melting due to the consuming of muscovite. Also the remaining muscovite is directly connected with a fluid channel in thin sections which indicate that the remaining muscovite formed from retrograde with the existence of fluid. The zoned garnet has low MgO and high CaO content in rims and high MgO and low CaO content in core. It seems that this garnet has high pressure and low temperature (HP-LT) in rims and low pressure and high temperature (LP-HT) in core which would point to an anti-clockwise metamorphic evolution. Zhou, J.B., Wilde, S.A., Zhang, X.Z., Zhao, G.C., Liu, F.L., Qiao, D.W., Ren, S.M. and Liu, J.H., 2011b. A> 1300km late Pan-African metamorphic belt in NE China: new evidence from the Xing'an block and its tectonic implications. Tectonophysics, 509(3): 280-292.

  13. Synthesis and characterization of nanostructured CaZrO{sub 3} and BaZrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Ibiapino, Amanda Laura; Figueiredo, Laysa Pires de [Departamento de Quimica, Instituto de Ciencias Exatas e da Terra, Universidade Federal do Mato Grosso, MT (Brazil); Lascalea, Gustavo E. [LISAMEN/CONICET, Ciudad de Mendoza (Argentina); Prado, Rogerio Junqueira, E-mail: rjprado@ufmt.br [Instituto de Fisica, Universidade Federal do Mato Grosso, Cuiaba - MT (Brazil)

    2013-09-01

    In this work, nanostructured samples of barium zirconate (BaZrO{sub 3}) and calcium zirconate (CaZrO{sub 3}) were synthesized by the gel-combustion method, using glycine as fuel. The ceramic powders were calcined at 550 Degree-Sign C for 2 h and subsequently heat treated at 1350 Degree-Sign C for 10 min (fast-firing). The X-ray diffraction technique was employed to identify and characterize the crystalline phases present in the synthesized powders, using the Rietveld method. Monophasic nanostructured samples of BaZrO{sub 3} and CaZrO{sub 3} presenting average crystallite sizes of around 8.5 and 10.3 nm, respectively, were found after fast-firing. (author)

  14. Zircon-Based Ceramic Coatings Formed by a New Multi-Chamber Gas-Dynamic Accelerator

    Directory of Open Access Journals (Sweden)

    Marina Kovaleva

    2017-09-01

    Full Text Available In this work, dense zircon-based ceramic coatings were obtained from inexpensive zircon powder on a steel substrate by using a new multi-chamber gas-dynamic accelerator. The microstructure and phase composition of the coating were characterized by scanning electron microscopy, optical microscopy, and X-ray diffraction. The mechanical properties of the coatings were evaluated using microindentation, wear tests and bonding strength tests. The results showed that the obtained zircon-based ceramic coatings were continuous without cracks and bonded well with substrate without a sublayer. The zircon-based ceramic coatings consisted of c-ZrO2 (major phase, m-ZrO2 and SiO2. The zircon-based ceramic coatings had a porosity of 0.1%, hardness of 526 ± 65 HV0.2, and a fracture toughness of 2.5 ± 0.6 (МPа∙m1/2. The coatings showed the low specific wear rate and average erosion rate. The failure mode occurring in the tested coatings was cohesive.

  15. Research on the response improvement of optical actuation based on lead lanthanum zirconate titanate ceramics

    Directory of Open Access Journals (Sweden)

    Xinjie Wang

    2015-12-01

    Full Text Available Lead lanthanum zirconate titanate actuators taken as one type of photo-deformable actuators have been widely applied for micro-driven systems and active vibration control of photostrictive laminated flexible structures. However, the slow response of photodeformation of single patch lead lanthanum zirconate titanate actuator greatly affects its application. In this article, the main factors for the slow response of the lead lanthanum zirconate titanate actuator are investigated using experimental method. The increasing temperature during light on state and the residual photovoltage and photodeformation during light off state are considered as dominant factors causing the slow response of the lead lanthanum zirconate titanate actuator. To gain a better driving capability of lead lanthanum zirconate titanate actuator, some effective solutions through weakening the effect of increasing temperature and eliminating residual photovoltage and photodeformation are proposed and experimentally validated in this article. Considering the effective solutions proposed in this article, a novel optical driving mechanism based on multi-patches combination is proposed.

  16. A short and long range study of mullite-zirconia-zircon composites

    Energy Technology Data Exchange (ETDEWEB)

    Rendtorff, Nicolas M.; Conconi, Maria S.; Aglietti, Esteban F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC: CONICET-CIC) (Argentina); Chain, Cecilia Y.; Pasquevich, Alberto F. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina); Rivas, Patricia C. [CONICET (Argentina); Martinez, Jorge A., E-mail: toto@fisica.unlp.edu.ar; Caracoche, Maria C. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina)

    2010-06-15

    In the field of refractory materials, ceramics containing mullite-zirconia are the basis of those most used in the industry of glass and steel. It is known that the addition of zircon improves the behavior of the refractory used in service. Knowing that some mullite-zirconia composites properties as fracture strength and the elastic modulus E are associated with the material microstructure integrity, the eventual thermal decomposition of zircon into zirconia and silica could seriously alter the material elastic properties. In this paper the phase content of a series of mullite-zirconia-zircon (3Al{sub 2}O{sub 3}.2SiO{sub 2}-ZrO{sub 2}-ZrSiO{sub 4}) composites is determined at atomic level via perturbed angular correlations (PAC) and compared with that derived from the long range X-ray diffraction technique. PAC results on the as-prepared materials indicate that all nominal zircon is present and that it involves two types of nanoconfigurations, one of them describing aperiodic regions. The thermomechanical properties already reported for these materials could be related to the crystalline to aperiodic zircon concentrations ratio they exhibit.

  17. U-Pb dating by zircon dissolution method using chemical abrasion

    Energy Technology Data Exchange (ETDEWEB)

    Takehara, Lucy, E-mail: lucytakehara@gmail.com.br [Servico Geologico do Brasil (CPRM), Brasilia, DF (Brazil); Chemale Junior, Farid [Universidade de Brasilia (UnB), Brasilia, DF (Brazil). Inst. de Geociencias. Lab. de Geocronologia; Hartmann, Leo A. [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Inst. de Geociencias; Dussin, Ivo A.; Kawashita, Koji [Universidade de Sao Paulo (USP), SP, (Brazil). Centro de Pesquisa Geocronologicas

    2012-06-15

    Chemical abrasion was carried out on zircons grains of the Temora II standard for U-Pb dating prior to analyses using in situ Laser Ablation-Multi Collector Ion Coupled Plasma Mass Spectrometer (LA-ICPMS) followed by the Isotope Dissolution Thermal Ionization Mass Spectrometer (ID-TIMS) method. The proposed methodology was herein applied in order to reduce primarily the effects of secondary Pb loss, the presence of common lead and/or silicate impurities. Nine Temora II zircon grains were analyzed by the laser ablation method yielding an age of 418.3 +- 4.3 Ma. Zircon grains of a same population were separated for chemical abrasion before dissolution and mass spectrometry analyses. Six fractions of them were separated for isotope dissolution using {sup 235}U-{sup 205}Pb mixed spike after we have checked and assured the laboratory conditions of low blank values for total Pb of less than 2 pg/g. The obtained U-Pb zircon age by the ID-TIMS method was 415.7 +- 1.8 Ma (error 0.43 %) based on four successful determinations. The results are consistent with the published ages for the Temora diorite (Temora I - 416.75 +- 1.3 Ma; Temora II - 416.78 +- 0.33 Ma) and established as 416 +- 0.33 Ma. The technique is thus recommended for high precision U-Pb zircon analyses (error < 1 %), mainly for high resolution stratigraphic studies of Phanerozoic sequences. (author)

  18. Piezoelectric lead zirconate titanate ceramic fiber/polymer composites

    Energy Technology Data Exchange (ETDEWEB)

    Waller, D.J.; Safari, P. (Dept. of Ceramic Engineering, Rutgers-State Univ. of New Jersey, Piscataway, NJ (US))

    1992-06-01

    This papers on piezoelectric lead zirconate titanate (PZT) ceramic fiber/polymer composite were fabricated by a novel technique referred to as relic processing. Basically, this involved impregnating a woven carbon-fiber template material with PZT precursor by soaking the template in a PZT stock solution. Careful heat treatment pyrolized the carbon, resulting in a PZT ceramic relic that retained the fibrous template form. After sintering, the densified relic was backfilled with polymer to form a composite. Optimized relic processing consisted of soaking activated carbon-fiber fabric twice in an intermediate concentration (405-mg PZT/(1-g solution)) alkoxide PZT solution and sintering at 1285{degrees}C for 2 h. A series of piezoelectric composites encompassing a wide range of dielectric and piezoelectric properties was prepared by varying the PZT-fiber orientation and polymer-matrix material. In PZT/Eccogel polymer composites with PZT fibers orientated parallel to the electrodes, K = 75, d{sub 33} = 145 pC/N, d{sub h} = 45 {plus minus} 5 pC/N, and d{sub h}g{sub h} = 3150 {times} 10{sup {minus}15} m{sup 2}/N were measured. Furthermore, in composites with a number of PZT fibers arranged perpendicular to the electroded surfaces, K = 190, d{sub 33} = 250 pC/N, d{sub h} = 65 {plus minus} 2 pC/N, and d{sub h}g{sub h} = 2600 {times} 10{sup {minus}15} m{sub 2}/N.

  19. Study of nanoconfigurations in Zircon-Mullite composites using perturbed angular correlations

    Energy Technology Data Exchange (ETDEWEB)

    Chain, Cecilia Y., E-mail: yamil@fisica.unlp.edu.ar; Pasquevich, Alberto F. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina); Rivas, Patricia C. [CONICET (Argentina); Martinez, Jorge A.; Caracoche, Maria C. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina); Rendtorff, Nicolas M. [CONICET (Argentina); Conconi, Maria S. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC: CONICET-CIC) (Argentina); Aglietti, Esteban F. [CONICET (Argentina)

    2010-06-15

    It has been already published that, at nanoscopic level, zircon exhibits wide regions of aperiodic material not detected by the ordinary techniques used to analyse the obtained product in the production of ceramic materials. In this paper it is reported how the Perturbed Angular Correlations (PAC) technique has assisted the interpretation of a mismatch between experiment and theoretical estimation of a mechanical property in some zircon-mullite composites. In fact, it has been proved that the difference observed between the calculated and the experimental value of the elastic modulus in composites of the form (1-x) ZrSiO{sub 4} - x 3Al{sub 2}O{sub 3}.2SiO{sub 2} (with x = 15, 25, 35 and 45 wt.%) behaves very similarly as the relative amount of aperiodic zircon determined by PAC. This result allows to re-interpret the mullite role during the materials preparation.

  20. Refined Proterozoic evolution of the Gawler Craton, South Australia, through U-Pb zircon geochronology

    Science.gov (United States)

    Fanning, C.M.; Flint, R.B.; Parker, A.J.; Ludwig, K. R.; Blissett, A.H.

    1988-01-01

    Through the application of both conventional U-Pb zircon analyses and small-sample U-Pb isotopic analyses, the nature and timing of tectonic events leading to the formation of the Gawler Craton have been defined more precisely. Constraints on deposition of Early Proterozoic iron formation-bearing sediments have been narrowed down to the period 1960-1847 Ma. Deformed acid volcanics, including the economically important Moonta Porphyry, have zircon ages of ??? 1790 and 1740 Ma. The voluminous acid Gawler Range Volcanics and correlatives to the east were erupted over a short interval at 1592 ?? 2 Ma, and were intruded by anorogenic granites at ??? 1575 Ma. Small-sample zircon analyses proved to be an extremely valuable adjunct to conventional analyses, generally yielding more-concordant data which forced a curved discordia through an upper intercept slightly younger than from a conventional straight-line discordia. ?? 1988.

  1. Theoretical modeling of zircon's crystal morphology according to data of atomistic calculations

    Science.gov (United States)

    Gromalova, Natalia; Nikishaeva, Nadezhda; Eremin, Nikolay

    2017-04-01

    Zircon is an essential mineral that is used in the U-Pb dating. Moreover, zircon is highly resistant to radioactive exposure. It is of great interest in solving both fundamental and applied problems associated with the isolation of high-level radioactive waste. There is significant progress in forecasting of the most energetically favorable crystal structures at the present time. Unfortunately, the theoretical forecast of crystal morphology at high technological level is under-explored nowadays, though the estimation of crystal equilibrium habit is extremely important in studying the physical and chemical properties of new materials. For the first time, the thesis about relation of the equilibrium shape of a crystal with its crystal structure was put forward in the works by O.Brave. According to it, the idealized habit is determined in the simplest case by a correspondence with the reticular densities Rhkl of individual faces. This approach, along with all subsequent corrections, does not take into account the nature of atoms and the specific features of the chemical bond in crystals. The atomistic calculations of crystal surfaces are commonly performed using the energetic characteristics of faces, namely, the surface energy (Esurf), which is a measure of the thermodynamic stability of the crystal face. The stable crystal faces are characterized by small positive values of Esurf. As we know from our previous research (Gromalova et al.,2015) one of the constitutive factors affecting the value of the surface energy in calculations is a choice of potentials model. In this regard, we studied several sets of parameters of atomistic interatomic potentials optimized previously. As the first test model («Zircon 1») were used sets of interatomic potentials of interaction Zr-O, Si-O and O-O in the form of Buckingham potentials. To improve playback properties of zircon additionally used Morse potential for a couple of Zr-Si, as well as the three-particle angular harmonic

  2. Age and compositional data of zircon from sepiolite drilling mud to identify contamination of ocean drilling samples

    Science.gov (United States)

    Andrews, Graham D. M.; Schmitt, Axel K.; Busby, Cathy J.; Brown, Sarah R.; Blum, Peter; Harvey, Janet. C.

    2016-08-01

    Zircon extracted from drilled oceanic rocks is increasingly used to answer geologic questions related to igneous and sedimentary sequences. Recent zircon studies using samples obtained from marine drill cores revealed that drilling muds used in the coring process may contaminate the samples. The JOIDES Resolution Science Operator of the International Ocean Discovery Program has been using two types of clays, sepiolite and attapulgite, which both have salt water viscosifier properties able to create a gel-like slurry that carries drill cuttings out of the holes several hundred meters deep. The dominantly used drilling mud is sepiolite originating from southwestern Nevada, USA. This sepiolite contains abundant zircon crystals with U-Pb ages ranging from 1.89 to 2889 Ma and continental trace element, δ18O, and ɛHf isotopic compositions. A dominant population of 11-16 Ma zircons in sepiolite drilling mud makes identification of contamination in drilled Neogene successions particularly challenging. Interpretation of zircon analyses related to ocean drilling should be cautious of zircon ages in violation of independently constrained age models and that have age populations overlapping those in the sepiolite. Because individual geochronologic and geochemical characteristics lack absolute discriminatory power, it is recommended to comprehensively analyze all dated zircon crystals from cores exposed to drill mud for trace element, δ18O, and ɛHf isotopic compositions. Zircon analyzed in situ (i.e., in petrographic sections) are assumed to be trustworthy.

  3. Isotope U-Pb age on single zircon and REE distribution in rocks and zircon from paleoproterozoic Kandalaksha-Kolvitsa complex Baltic shield

    Science.gov (United States)

    Steshenko, Ekaterina; Bayanova, Tamara; Drogobuzhskaya, Svetlana; Lyalina, Ludmila; Serov, Pavel; Chashchin, Viktor; Elizarov, Dmitriy

    2017-04-01

    Kandalaksha-Kolvitsa paleoproterozoic complex located in the N-E part of Baltic shield and consists of three zones. Marginal zone (mesocratic metanorite) lies at the base of the massif. Main zone is composed of leucocratic metagabbro. The upper zone is alteration of mataanorthosite and leucocratic metagabbro. All rocks were subjected to granulate and anorthositic metamorphism. Age of magmatic crystallization of the massif was determined for the first time, using the U-Pb isotope method for single zircon grains. Three fractions of single zircons from anorthosite of the Kandalaksha massif gave precise U-Pb age of 2435.5 ± 4.8 Ma. For the first time REE concentration (WR) was determined using a quadrupole mass spectrometer (Agilent 7500 ce ICP-MS) in the main varieties of rocks of the Kandalaksha-Kolvitsa paleoproterozoic complex. Anorthosite and leucocratic metagabbros (main zone) are characterized by a flat spectrum distribution of HREE, which were normalized by [1]. The REE pattern is characterized by significant positive anomalies of Eu ((Eu / Eu *)n = 3.72-3.91) in anorthosite and leucogabbros and 7.26 - in ortoamfibolitah. General content of individual elements that are common for this type of rocks: Cen = 5.82-8.54, Ybn = 1.54-1.58, which indicates that the process of crystallization of the rock occurred with predominant accumulation of plagioclase. According to geochemical and Nd-Sr isotopic data (ISr=0.702 - 0.706, ɛNd(T) = +1 - (-3)) Kandalaksha Kolvitsa complex, appear to have a general plume source with Paleoproterozoic layered intrusions of the Baltic Shield [2] Distribution of REE (ELAN-9000 ICP-MS) in zircon have a typical magmatic species: a positive Ce, negative Eu anomaly and HREE flat spectrum. Titanium content in zircons were measured for the calculation of their crystallization temperature with 8350C. These data are evidence of magmatic origin of zircon [3]. The scientific researches are supported by RFBR (projects № 15-35-20501, № 16

  4. New U-Pb SHRIMP zircon ages for pre-variscan orthogneisses from Portugal and their bearing on the evolution of the Ossa-Morena tectonic zone

    Directory of Open Access Journals (Sweden)

    Cordani Umberto G.

    2006-01-01

    Full Text Available New SHRIMP U-Pb zircon ages for the Portalegre and Alcáçovas orthogneisses document a complex pre- Variscan history for the Iberian basement in Portugal. The available geochemical and geochronological data for the Alcáçovas orthogneiss (ca. 540 Ma tend to favor its involvement in a Cadomian orogenic event. This is consistent with the development of an active continental margin setting at the end of the Proterozoic and supports a Gondwanan provenance for the Iberian crust. On the other hand, the Ordovician emplacement age obtained for the magmatic precursors of the Portalegre orthogneisses (497?10 Ma provides additional evidence for the occurrence of rift-related magmatic activity during the Lower Paleozoic.

  5. Detrital zircons from the Hronicum Carboniferous-Permian sandstones (Western Carpathians, Slovakia): depositional age and provenance

    Science.gov (United States)

    Vozárová, Anna; Larionov, Alexander; Šarinová, Katarína; Vďačný, Marek; Lepekhina, Elena; Vozár, Jozef; Lvov, Pavel

    2017-11-01

    For the assessment of depositional age and provenance of the Hronicum Unit Pennsylvanian to Permian siliciclastic sediments, SIMS (SHRIMP) U-Pb analyses have been carried out on detrital zircons. To constrain the presumed provenance of the Hronicum Unit sediments five samples have been taken from two lithostratigraphic units, the Nižná Boca and the Malužiná formations. The detrital-zircon age spectrum demonstrates two prominent populations, the first, Late Pennsylvanian-Early Cisuralian (288-309 Ma) and the second, Famennian—Tournaisian (345-371 Ma). The probability density age peak at 297 Ma permits to estimate the maximum sedimentation age of the Nižná Boca Fm. to younger than Asselian and the beginning of the Malužiná Formation sedimentation has been assessed at least in Sakmarian. The sedimentation persisted, with the exception of a short break in the Wordian/Capitanian, through the Lopingian. Smaller zircon age clusters range within 446-541 Ma, with a dominance of the Cambrian detrital zircons (491-541 Ma). The Precambrian time-span is dominated by the two groups of detrital zircons; Ediacaran in the range of 545-612 Ma and Paleoproterozoic-Neoarchean ranging from 1.8 to 2.8 Ga. The documented zircon ages reflect derivation of the Hronicum sediments from the Variscan Western Carpathian crystalline basement, the Late Devonian/Early Mississippian magmatic arc. These data support close relations of the presumed Hronicum basement with the Armorican terranes and derivation from the Cadomian Belt, associated with the West African Craton during Neoproterozoic and Cambrian time.

  6. Nanogeochronology of discordant zircon measured by atom probe microscopy of Pb-enriched dislocation loops

    Science.gov (United States)

    Peterman, Emily M.; Reddy, Steven M.; Saxey, David W.; Snoeyenbos, David R.; Rickard, William D. A.; Fougerouse, Denis; Kylander-Clark, Andrew R. C.

    2016-01-01

    Isotopic discordance is a common feature in zircon that can lead to an erroneous age determination, and it is attributed to the mobilization and escape of radiogenic Pb during its post-crystallization geological evolution. The degree of isotopic discordance measured at analytical scales of ~10 μm often differs among adjacent analysis locations, indicating heterogeneous distributions of Pb at shorter length scales. We use atom probe microscopy to establish the nature of these sites and the mechanisms by which they form. We show that the nanoscale distribution of Pb in a ~2.1 billion year old discordant zircon that was metamorphosed c. 150 million years ago is defined by two distinct Pb reservoirs. Despite overall Pb loss during peak metamorphic conditions, the atom probe data indicate that a component of radiogenic Pb was trapped in 10-nm dislocation loops that formed during the annealing of radiation damage associated with the metamorphic event. A second Pb component, found outside the dislocation loops, represents homogeneous accumulation of radiogenic Pb in the zircon matrix after metamorphism. The 207Pb/206Pb ratios measured from eight dislocation loops are equivalent within uncertainty and yield an age consistent with the original crystallization age of the zircon, as determined by laser ablation spot analysis. Our results provide a specific mechanism for the trapping and retention of radiogenic Pb during metamorphism and confirm that isotopic discordance in this zircon is characterized by discrete nanoscale reservoirs of Pb that record different isotopic compositions and yield age data consistent with distinct geological events. These data may provide a framework for interpreting discordance in zircon as the heterogeneous distribution of discrete radiogenic Pb populations, each yielding geologically meaningful ages. PMID:27617295

  7. Late Cretaceous volcanic arc system in Southwest Korea: Occurrence, lithological characteristics, SHRIMP zircon U-Pb age, and tectonic implications

    Science.gov (United States)

    Koh, Hee Jae; Kwon, Chang Woo

    2017-04-01

    In the southwest region of the Korean Peninsula, four large volcanoes, the Buan, Seonunsan, Wido, and Beopseongpo, with a maximum diameter of ca 20 km, form a distinct topographic undulation along the NE-SW-trending Hamyeol Fault. These volcanics comprise various types of pyroclastic, sedimentary, and lava/intrusive rocks, and are interpreted as remnants of calderas resulting from various volcanic eruptions, indicating that Hamyeol Fault, together with crustal extension, played an important role in volcano formation in this region. SHRIMP U-Pb ages of zircon isolated from each volcanics are as follows. For Buan Volcanics, Cheonmasan Tuff 87.23 ±0.92 Ma, Udongje Tuff 86.79 ±0.71 Ma, Seokpo Tuff 87.30 ±0.99 Ma and Yujeongje Tuff 86.66 ±0.93 Ma. For Seonunsan Volcanics, Gyeongsusan Tuff 84.9 ±1.1 Ma and Yeongije Tuff 86.61 ±0.67 Ma. These ages indicate that the four volcanics were formed in the Late Cretaceous. The ages are comparable to those of the volcanic rocks of the Aioi and Arima groups in Southwestern Japan, suggesting that the Late Cretaceous volcanic arc systems developed in a NE-SW direction from the Japanese Islands to the southwestern part of the Korean Peninsula caused by regional magmatism together with crustal deformation as reflected by occurrence of the volcanic rocks along the Hamyeol Fault.

  8. U Pb zircon and monazite geochronology of Variscan magmatism related to syn-convergence extension in Central Northern Portugal

    Science.gov (United States)

    Valle Aguado, B.; Azevedo, M. R.; Schaltegger, U.; Martínez Catalán, J. R.; Nolan, J.

    2005-05-01

    The Viseu area is located in the Central Iberian Zone of the Iberian Variscan Belt and hosts numerous post-thickening, collision-related granitoids intruded into upper and middle crustal levels. The present paper reports high precision U-Pb zircon and monazite ages for four plutons of the Viseu area: the syn-kinematic granitoids of Maceira (314±5 Ma), Casal Vasco (311±1 Ma) and Junqueira (307.8±0.7 Ma) and the late-kinematic biotite monzogranites of Cota (306±9 Ma). This points to a synchronous emplacement of the different syn-kinematic plutons shortly followed by the intrusion of the late-kinematic granites and shows that the Upper Carboniferous plutonism occurred within a short time span of ca. 10 million years. The ascent of granite magmas took place after an extensional tectonic event (D 2) and is coeval with dextral and sinistral crustal-scale transcurrent shearing (D 3). Field and petrographical evidence suggest a narrow time-span between peak T metamorphic conditions and the intrusion of granitic melts which implies very fast uplift rates accommodated through active tectonic exhumation. Magma compositions evolve through time, reflecting an increasing involvement of mid-crustal sources and the underplating effect of an upwelling asthenospheric mantle at the base of a thinning and stretching continental crust.

  9. Detrital zircon geochronology of pre- and syncollisional strata, Acadian orogen, Maine Appalachians

    Science.gov (United States)

    Bradley, Dwight C.; O'Sullivan, Paul B.

    2017-01-01

    The Central Maine Basin is the largest expanse of deep-marine, Upper Ordovician to Devonian metasedimentary rocks in the New England Appalachians, and is a key to the tectonics of the Acadian Orogeny. Detrital zircon ages are reported from two groups of strata: (1) the Quimby, Rangeley, Perry Mountain and Smalls Falls Formations, which were derived from inboard, northwesterly sources and are supposedly older; and (2) the Madrid, Carrabassett and Littleton Formations, which were derived from outboard, easterly sources and are supposedly younger. Deep-water deposition prevailed throughout, with the provenance shift inferred to mark the onset of foredeep deposition and orogeny. The detrital zircon age distribution of a composite of the inboard-derived units shows maxima at 988 and 429 Ma; a composite from the outboard-derived units shows maxima at 1324, 1141, 957, 628, and 437 Ma. The inboard-derived units have a greater proportion of zircons between 450 and 400 Ma. Three samples from the inboard-derived group have youngest age maxima that are significantly younger than the nominal depositional ages. The outboard-derived group does not share this problem. These results are consistent with the hypothesised provenance shift, but they signal potential problems with the established stratigraphy, structure, and (or) regional mapping. Shallow-marine deposits of the Silurian to Devonian Ripogenus Formation, from northwest of the Central Maine Basin, yielded detrital zircons featuring a single age maximum at 441 Ma. These zircons were likely derived from a nearby magmatic arc now concealed by younger strata. Detrital zircons from the Tarratine Formation, part of the Acadian foreland-basin succession in this strike belt, shows age maxima at 1615, 980 and 429 Ma. These results are consistent with three episodes of zircon recycling beginning with the deposition of inboard-derived strata of the Central Maine Basin, which were shed from post-Taconic highlands located to the

  10. Detrital zircon (U-Th)/He and fision track data of natural deep borehole samples and its geological significance

    Science.gov (United States)

    Qiu, Nansheng; Cai, Change

    2017-04-01

    The zircon (U-Th)/He and fission track (FT) thermochronometry has been used as a thermal indicator to study thermal history of the deep sedimentary basin at high temperature. The closure temperature of helium and annealing temperature of FT are important parameters for the zircon (U-Th)/He thermochronometry. In this paper, the zircon He closure temperature and FT annealing temperature were studied by establishing the evolutionary pattern between zircon He and FT ages and zircon burial depth based on the data of natural borehole samples obtained from the Cenozoic strara in the Bohai Bay and Tarim basins, which have different thermal settings. The results show that the zircon He closure temperature of natural samples in the sedimentary basin is approcimately 195°C, higher than the temperature obtain from the thermal simulation experiments (183°C). The high He closure temperature resulted from long term radiation damage accumulation and sufficient grain radius. In addition, two zircon FT age profiles from different thermal background show that there exist different annealing temperatures. The ZFT annealing temperature is about 160°C in the deep borehole of Tarim basin with low thermal background. However, the ZFT annealing temperature is about 210°C in the deep borehole of the Bohai Bay basin with high thermal background. We also point out that effective uranium concentration and radiogenic 4He concentration have apparent influence on the zircon He and FT ages. This study is a revaluation of the conventional zircon He closure temperature and annealing temperature. Thus, properly understanding the ZHe/ZFT ages, closure /annealing temperatures, and their influence factors, ZHe/ZFT dating can provide the true explanation of the testing zircon He/FT ages, and has a great guiding significance in the studying of the evolution of source rocks and the process of hydrocarbon accumulation in the deep sedimentary basin.

  11. Concordant ages for the Lava Creek Tuff from high-spatial-resolution U-Pb dating of zircon rim faces and single-crystal sanidine 40Ar/39Ar dating

    Science.gov (United States)

    Matthews, N. E.; Vazquez, J. A.; Calvert, A. T.

    2013-12-01

    The last great explosive supereruption from the Yellowstone Plateau formed present-day Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff (LCT). The LCT eruption blanketed much of the western United States in ash, and consequently is a key chronostratigraphic marker bed for delimiting Quaternary uplift rates, the age of middle Pleistocene glacial and pluvial deposits, and tephra correlation in North America. Previous 40Ar/39Ar dating of the two mineralogically distinct LCT members (A & B) yield ages ranging from ca. 600 ka (Gansecki et al., 1998) to ca. 640 ka (Lanphere et al., 2002). To resolve the timing of eruption and crystallization timescale for the LCT magma, we dated both LCT members using a dual-method approach as follows: (1) ion microprobe (SHRIMP-RG) U-Pb dating and trace-element characterization of the final few micrometers of zircon crystallization by analysis of unpolished rims on indium-mounted crystals, and dating of the onset of zircon crystallization by traditional analysis of sectioned crystal interiors, and (2) laser-fusion 40Ar/39Ar dating of single sanidine crystals from bulk LCT ignimbrite and pumice. The unpolished rims of zircon from LCT members A & B yield indistinguishable ages, with a mean age of 621.8 × 2.5 ka (1σ) after correction for initial 230Th disequilibrium as constrained by ion-probe analyses of LCT melt inclusions. Single sanidine crystals from LCT-B yield a mean age of 624.9 × 2.6 ka (FCT=28.17 Ma) that is indistinguishable from the zircon rim ages for both members. These results indicate that LCT members A & B erupted over a geologically brief interval, which is supported by the direct and gradational contact of their equivalent fallout in distal lacustrine deposits and a lack of field evidence for a significant time-break between the LCT A & B in proximal deposits (Christiansen, 2001), but contrasts with older Yellowstone ignimbrite (e.g., Huckleberry Ridge) that may have erupted

  12. U-Pb age and genetic significance of heterogeneous zircon populations in rocks from the Favourable Lake area, Northwestern Ontario

    Science.gov (United States)

    Corfu, F.; Ayres, L. D.

    1984-11-01

    The study evaluates the relationships between measured U-Pb ages and zircon characteristics of five morphologically, texturally, and isotopically complex zircon populations and compares the zircon development stages to the orogenic evolution of the Favourable Lake area. Two distinct zircon types from a hornblendite xenolith in a granitoid batholith of the Sachigo subprovince of the Superior Province yield U-Pb ages of 2729.0±6.8 Ma and 2714.8{-6.4/+7.4}Ma, which date specific metamorphic phases coinciding with major plutonic pulses in the batholith. Zircons from a metamorphosed felsic dike, crosscutting the hornblendite, consist of an old zircon component with a minimum age of 2788 Ma possibly reflecting igneous crystallization ≧ 2950 Ma ago, and a younger component with an inferred age of 2725±15 Ma, probably reflecting metamorphism during batholith emplacement. In the Berens River subprovince to the south, granodiorite forms both a late tectonic phase in a large batholith and a post-tectonic pluton intruded into the batholith, yet zircons from these granodiorites have identical ages of 2697.3±1.7 Ma and 2696.2±1.2 Ma, respectively. The late tectonic granodiorite also contains inherited zircons with a minimum age of 2767 Ma which are indirect evidence for the presence of old sialic crust in this subprovince. Zircons from a sheared monzonite near the boundary fault between the two subprovinces yield an upper intercept age of 2769{-26/+63}Ma, which we interpret as the intrusion age of the monzonite. This rock is older than most dated units in the surrounding batholiths and suggests that the boundary is a long-lived Archean structure. A lower intercept age of about 1750 Ma for zircons of the hornblendite is the result of chemical alteration of the zircons. This, and a similar lower intercept age shown by the sheared monzonite zircons, are thought to reflect increased fluid activity and possibly shearing during the Early Proterozoic Hudsonian orogeny which

  13. Silica–calcium zirconate nanocomposite, studying its thermal and ...

    Indian Academy of Sciences (India)

    in the ZrO2–CaO quasi-binary systems and has received great attention due to its unique characteristics.1 ... for refractory ceramic applications.9–12 Bin et al13 reported that the dielectric properties of BaTiO3 can be ... sion which make it suitable for numerous applications. For example, low dielectric constant of silica ...

  14. Zircon ages, geochemistry and Nd isotopic systematics for the Palaeoproterozoic 2.3-1.8 Ga Kuilyu Complex, East Kyrgyzstan - The oldest continental basement fragment in the Tianshan orogenic belt

    Science.gov (United States)

    Kröner, A.; Alexeiev, D. V.; Kovach, V. P.; Rojas-Agramonte, Y.; Tretyakov, A. A.; Mikolaichuk, A. V.; Xie, H.; Sobel, E. R.

    2017-03-01

    Precambrian microcontinents represent key tectonic units in the accretionary collages of the western Central Asian Orogenic Belt (CAOB), and their geological history is reasonably well established since the Mesoproterozoic but remains weakly constrained for older epochs due to a scarcity of exposed Palaeoproterozoic and Archaean rocks. Early Precambrian rocks were previously reported from several metamorphic complexes in the Kyrgyz Tianshan orogenic belt, mainly based on multigrain conventional zircon dating, but the present study only confirmed such rocks at one site, namely in the Kuilyu Complex of eastern Kyrgyzstan. New single grain SHRIMP II zircon ages, geochemical data, and whole-rock Nd isotopic compositions for granitoid gneisses of the Kuilyu Complex elucidate the age, origin and tectonic settings of this oldest continental fragment in the Tianshan. The Kuilyu Complex is part of the basement in the Ishim - Middle Tianshan microcontinent. It consist of a strongly deformed and metamorphosed supracrustal assemblage of paragneisses and schists which are tectonically interlayered with amphibolites, migmatites and granitoid gneisses. Our zircon dating indicates that the Kuilyu Complex contains two suites of Palaeoproterozoic granitoid gneisses with magmatic protolith ages of ca. 2.32-2.33 Ga and 1.85 Ga. Granitoid magmatism at 1.85 Ga was almost immediately followed by amphibolite-facies metamorphism at ca 1.83 Ga, evidenced by growth of metamorphic zircon rims. The older, ca 2.3 Ga granitoid gneisses chemically correspond to calc-alkaline, metaluminous, I-type magnesian quartz diorite and granodiorite. The protolith of the younger, ca. 1.85 Ga granite-gneiss is an alkalic-calcic, metaluminous to peraluminous, ferroan medium-grained porphyric granite with chemical features resembling A-type granites. The 2.3 Ga and 1.85 Ga granitoid gneisses have slightly to distinctly negative initial εNd values of -1.2 and -6.6, and similar depleted mantle Nd model ages of 2

  15. Petrogenesis, zircon U–Pb age, and geochemistry of the A-type ...

    Indian Academy of Sciences (India)

    Keywords. Zircon U–Pb dating; Syn-collision; post-collision; syenite; Mogou; Qinling orogen ... Eu anomalies are positive for the medium- to coarse-grained syenite and weakly negative for the fine-grained quartz syenite. In addition, the syenites are enriched in large-ion lithophile elements (Ba, K, Sr, and Pb) but depleted ...

  16. Detrital zircon and apatite fission track data in the Liaoxi basins ...

    Indian Academy of Sciences (India)

    vation events in the northern margin of the North. China Craton (figure 1a). In this paper, detrital zircon and apatite fission track (AFT and ZFT) ages of the sedimentary rocks from the Liaoxi basins are presented. The purposes of this study are: • to study the geothermal status of the basins to understand lithosphere evolution;.

  17. On the valency state of radiogenic lead in zircon and its consequences

    DEFF Research Database (Denmark)

    Kramers, J.; Frei, Robert; Newville, M.

    2009-01-01

    at this temperature, show age effects that should have been observed in SIMS dating. Further, in zircon evaporation as well as in leaching experiments, common Pb is generally released preferentially to radiogenic Pb. After removal of less radiogenic Pb, the evaporation record generally shows pure radiogenic Pb during...

  18. Dating of zircon from high-grade rocks: Which is the most reliable method?

    Directory of Open Access Journals (Sweden)

    Alfred Kröner

    2014-07-01

    Full Text Available Magmatic zircon in high-grade metamorphic rocks is often characterized by complex textures as revealed by cathodoluminenscence (CL that result from multiple episodes of recrystallization, overgrowth, Pb-loss and modifications through fluid-induced disturbances of the crystal structure and the original U-Th-Pb isotopic systematics. Many of these features can be recognized in 2-dimensional CL images, and isotopic analysis of such domains using a high resolution ion-microprobe with only shallow penetration of the zircon surface may be able to reconstruct much of the magmatic and complex post-magmatic history of such grains. In particular it is generally possible to find original magmatic domains yielding concordant ages. In contrast, destructive techniques such as LA-ICP-MS consume a large volume, leave a deep crater in the target grain, and often sample heterogeneous domains that are not visible and thus often yield discordant results which are difficult to interpret. We provide examples of complex magmatic zircon from a southern Indian granulite terrane where SHRIMP II and LA-ICP-MS analyses are compared. The SHRIMP data are shown to be more precise and reliable, and we caution against the use of LA-ICP-MS in deciphering the chronology of complex zircons from high-grade terranes.

  19. Petrogenesis, zircon U–Pb age, and geochemistry of the A-type ...

    Indian Academy of Sciences (India)

    4Centre for Exploration Targeting, Australian Research Council Centre of Excellence for Core to Crust Fluid. Systems (CCFS), School .... Petrogenesis, zircon U–Pb age, and geochemistry of A-type Mogou syenite, Henan Province 587 were trondhjemite ...... destructive plate boundaries; In: Andesites (ed.) Thorpe. R S; John ...

  20. Demonstrating the potential of yttrium-doped barium zirconate electrolyte for high-performance fuel cells.

    Science.gov (United States)

    Bae, Kiho; Jang, Dong Young; Choi, Hyung Jong; Kim, Donghwan; Hong, Jongsup; Kim, Byung-Kook; Lee, Jong-Ho; Son, Ji-Won; Shim, Joon Hyung

    2017-02-23

    In reducing the high operating temperatures (≥800 °C) of solid-oxide fuel cells, use of protonic ceramics as an alternative electrolyte material is attractive due to their high conductivity and low activation energy in a low-temperature regime (≤600 °C). Among many protonic ceramics, yttrium-doped barium zirconate has attracted attention due to its excellent chemical stability, which is the main issue in protonic-ceramic fuel cells. However, poor sinterability of yttrium-doped barium zirconate discourages its fabrication as a thin-film electrolyte and integration on porous anode supports, both of which are essential to achieve high performance. Here we fabricate a protonic-ceramic fuel cell using a thin-film-deposited yttrium-doped barium zirconate electrolyte with no impeding grain boundaries owing to the columnar structure tightly integrated with nanogranular cathode and nanoporous anode supports, which to the best of our knowledge exhibits a record high-power output of up to an order of magnitude higher than those of other reported barium zirconate-based fuel cells.

  1. Energy conversion with Zr-rich lead zirconate/titanate ceramics

    NARCIS (Netherlands)

    Duan, Ning; Cereceda, Noé; Noheda, Beatriz; Fernandez-del-Castillo, José Raúl; Gonzalo, Julio A.

    1997-01-01

    The conversion efficiency and power output to convert thermal energy to electrical energy by means of a ferroelectric–ferroelectric phase transition has been investigated. The material used was the ceramic mixed system lead zirconate/titanate (PZT) with a very Zr-enriched composition (Zr/Ti=97/3%).

  2. The zircon evidence of temporally changing sediment transport—the NW Gondwana margin during Cambrian to Devonian time (Aoucert and Smara areas, Moroccan Sahara)

    Science.gov (United States)

    Gärtner, Andreas; Youbi, Nasrrddine; Villeneuve, Michel; Sagawe, Anja; Hofmann, Mandy; Mahmoudi, Abdelkader; Boumehdi, Moulay Ahmed; Linnemann, Ulf

    2017-03-01

    Detrital zircon provenance studies are an established tool to develop palaeogeographic models, mostly based on zircon of siliciclastic rocks and isotope data. But zircon is more than just istopes and features well definable morphological characteristics. The latter may indicate single grain transport histories independent of the individual grade of concordance. This additional tool for palaeogeoraphic reconstructions was tested on zircon from siliciclastic and carbonate sedimentary rocks of Palaeozoic age from the Aoucert and Smara areas of the Souttoufides, while findings of zircon in limestone generally open new archives for sedimentary provenance analysis. The morphologies—length, width, roundness, grain surfaces—of 834 detrital zircons from sediments of allochthonous Cambrian, and (par-)autochthonous Ordovician, and Devonian units were studied, while 772 of them were analysed for their U-Th-Pb isotopes by LA-ICP-MS. Mesoproterozoic zircon contents of more than 10% in the Cambrian sediments exclude the West African Craton (WAC) as exclusive source area. Thus, at least one additional external source is suggested. This is likely the western Adrar Souttouf Massif with its significant Mesoproterozoic zircon inheritance, or comparable, yet unknown sources. Decreasing Mesoproterozoic zircon age populations in Ordovician sediments are thought to be linked to the rifting of the terranes in the course of the Rheic Ocean opening and a predominant supply of WAC detritus. The Devonian sediments likely contain reworked material from the Cambrian siliciclastics, which is shown by the zircon age distribution pattern and the zircon morphologies. Therefore, multiple shifts in the direction of sedimentary transport are indicated.

  3. U-Pb ages and Hf isotope compositions of zircons in plutonic rocks from the central Famatinian arc, Argentina

    Science.gov (United States)

    Otamendi, Juan E.; Ducea, Mihai N.; Cristofolini, Eber A.; Tibaldi, Alina M.; Camilletti, Giuliano C.; Bergantz, George W.

    2017-07-01

    The Famatinian arc formed around the South Iapetus rim during the Ordovician, when oceanic lithosphere subducted beneath the West Gondwana margin. We present combined in situ U-Th-Pb and Lu-Hf isotope analyses for zircon to gain insights into the origin and evolution of Famatinian magmatism. Zircon crystals sampled from four intermediate and silicic plutonic rocks confirm previous observations showing that voluminous magmatism took place during a relatively short pulse between the Early and Middle Ordovician (472-465 Ma). The entire zircon population for the four plutonic rocks yields coherent εHf negative values and spreads over several ranges of initial εHf(t) units (-0.3 to -8.0). The range of εHf units in detrital zircons of Famatinian metasedimentary rocks reflects a prolonged history of the cratonic sources during the Proterozoic to the earliest Phanerozoic. Typical tonalites and granodiorites that contain zircons with evolved Hf isotopic compositions formed upon incorporating (meta)sedimentary materials into calc-alkaline metaluminous magmas. The evolved Hf isotope ratios of zircons in the subduction related plutonic rocks strongly reflect the Hf isotopic character of the metasedimentary contaminant, even though the linked differentiation and growth of the Famatinian arc crust was driven by ascending and evolving mantle magmas. Geochronology and Hf isotope systematics in plutonic zircons allow us understanding the petrogenesis of igneous series and the provenance of magma sources. However, these data could be inadequate for computing model ages and supporting models of crustal evolution.

  4. Effect of pressure on Zircon's (ZrSiO4) Raman active modes: a first-principles study

    Science.gov (United States)

    Sheremetyeva, Natalya; Cherniak, Daniele; Watson, Bruce; Meunier, Vincent

    Zircon is a mineral commonly found in the Earth crust. Its remarkable properties have given rise to considerable attention. This includes possible inclusion of radioactive elements in natural samples, which allows for geochronological investigations. Subsequently, Zircon was proposed as possible host material for radioactive waste management. Internal radiation damage in zircon leads to the destruction of its crystal structure (an effect known as metamictization) which is subject to ongoing research. Recently, the effect of pressure and temperature on synthetic zircon has been analyzed experimentally using Raman spectroscopy which led to the calibration of zircon as a pressure sensor in diamond-anvil cell experiments. While there have been a number of theoretical studies, the effect of pressure on the Raman active modes of zircon has not been investigated theoretically. Here we present a first-principles pressure calibration of the Raman active modes in Zircon employing density-functional theory (DFT). We find excellent quantitative agreement of the slopes ∂ω / ∂P with the experimental ones and are able to rationalize the ω vs. P behavior based on the details of the vibrational modes.

  5. Geochemistry and U-Pb geochronology of detrital zircons in the Brujas beach sands, Campeche, Southwestern Gulf of Mexico, Mexico

    Science.gov (United States)

    Tapia-Fernandez, Hector J.; Armstrong-Altrin, John S.; Selvaraj, Kandasamy

    2017-07-01

    This study investigated the bulk sediment geochemistry, U-Pb ages and rare earth element (REE) geochemistry of one hundred detrital zircons recovered from the Brujas beach sands in southwestern Gulf of Mexico to understand the provenance and age spectra. The bulk sediments are high in Zr and Hf contents (∼1400-3773 ppm and ∼33-90 ppm, respectively) suggested the abundance of resistant mineral zircon. The chondrite normalized REE patterns of the bulk sediments are less fractionated with enriched low REE (LREE; LaCN/SmCN = ∼491-693), depleted heavy REE (HREE; GdCN/YbCN = ∼44-69) and a negative Eu anomaly (Eu/Eu∗ = ∼0.44-0.67) suggested that the source rock is felsic type. The results of this study revealed highly varied contents of Th (∼4.2-321 ppm), U (∼20.7-1680 ppm), and Hf (∼6970-14,200 ppm) in detrital zircons compared to bulk sands. The total REE content (∼75 and 1600 ppm) and its chondrite-normalized pattern with positive Ce and negative Eu anomalies as well as low Th/U ratio of zircon grains indicated that they were dominantly of magmatic origin. U-Pb data of zircons indicated two age populations, with predominance of Permian-Triassic (∼216-286 Ma) and Neoproterozoic (∼551-996 Ma). The Permian-Triassic zircons were contributed by the granitoids and recycled metasedimentary rocks of the Chiapas Massif Complex. The major contribution of Neoproterozoic zircons was from the Chaucus, Oaxacan, and Chiapas Massif Complexes in Grenville Province, southern Mexico. U-Pb ages of zircons from the Brujas beach are consistent to the reported zircon ages from the drainage basins of Usumacinta, Coatzacoalcos, and Grijalva Rivers in southern Mexico, suggesting that the sediments delivered by the rivers to the beach area are vital in defining the provenance of placers.

  6. Interpretation of zircon coronae textures from metapelitic granulites of the Ivrea–Verbano Zone, northern Italy: two-stage decomposition of Fe–Ti oxides

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    E. Kovaleva

    2017-07-01

    Full Text Available In this study, we report the occurrence of zircon coronae textures in metapelitic granulites of the Ivrea–Verbano Zone. Unusual zircon textures are spatially associated with Fe–Ti oxides and occur as (1 vermicular-shaped aggregates 50–200 µm long and 5–20 µm thick and as (2 zircon coronae and fine-grained chains, hundreds of micrometers long and ≤ 1 µm thick, spatially associated with the larger zircon grains. Formation of such textures is a result of zircon precipitation during cooling after peak metamorphic conditions, which involved: (1 decomposition of Zr-rich ilmenite to Zr-bearing rutile, and formation of the vermicular-shaped zircon during retrograde metamorphism and hydration; and (2 recrystallization of Zr-bearing rutile to Zr-depleted rutile intergrown with quartz, and precipitation of the submicron-thick zircon coronae during further exhumation and cooling. We also observed hat-shaped grains that are composed of preexisting zircon overgrown by zircon coronae during stage (2. Formation of vermicular zircon (1 preceded ductile and brittle deformation of the host rock, as vermicular zircon is found both plastically and cataclastically deformed. Formation of thin zircon coronae (2 was coeval with, or immediately after, brittle deformation as coronae are found to fill fractures in the host rock. The latter is evidence of local, fluid-aided mobility of Zr. This study demonstrates that metamorphic zircon can nucleate and grow as a result of hydration reactions and mineral breakdown during cooling after granulite-facies metamorphism. Zircon coronae textures indicate metamorphic reactions in the host rock and establish the direction of the reaction front.

  7. Denudation of SW Iberia during Pangeá s break-up: geochemical and detrital zircon geochronology characterization of Triassic basins

    Science.gov (United States)

    Pereira, Manuel F.; Ribeiro, Carlos; Vilallonga, Filipa; Chichorro, Martim; Drost, Kerstin

    2010-05-01

    subduction of the Paleotethys and, the birth of the Neotethys sea. In SW Iberia, the late Carboniferous greywackes are characterized by an increase of the maturity towards the top of the succession demonstrated by the decrease of Al2O3/SiO2 and Al2O3/(CaO+Na2O) ratios and Fe2O3(T)+MgO. These variations reflect the quartz enrichment and the decomposition of feldspar, biotite, amphibole and pyroxene. These chemical differences are also imprinted on the late Triassic sandstones. The chondrite-normalized REE-patterns show a strong enrichment of the LREE relative to the HREE, and have a characteristic negative Eu-anomaly typical of the erosional products of felsic igneous rocks. Late Carboniferous greywackes and late Triassic sandstones show a continental arc signature and a felsic provenance. The only exception is the oldest greywacke with high Ni content indicative of a mafic provenance. Cathodoluminescence imaging of the zircons show euhedral to subhedral simple grains with oscillatory growth zoning consistent with a precipitation from the melt phase of felsic to intermediate magmas, and also simple, needle-shaped, acicular, medium to large zircons that can derived from mafic and/or peralkaline magmas.The younger siliciclastic sediments also include a significant amount of complex zircons, composed of a core surrounded by generally concentric zoned or unzoned (low or high luminescent) overgrowths. The results indicate that weathering and sorting of the reworked siliciclastic sediments were more intense in the late Carboniferous sediments and less efficient in late Triassic. The continental arc signature of these greywackes and sandstones is probably inherited from the sedimentary sources that include continental arc igneous rocks, dominated by felsic magmas, and related recycled sediments. The significant presence of complex zircons in the younger sediments and their scarcity in the older sediments suggest that the cratonic sources were mainly uplifted and underwent intense

  8. INTRACELLULAR Ca2+ HOMEOSTASIS

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    Shahdevi Nandar Kurniawan

    2015-01-01

    Full Text Available Ca2+ signaling functions to regulate many cellular processes. Dynamics of Ca2+ signaling or homeostasis is regulated by the interaction between ON and OFF reactions that control Ca2+ flux in both the plasma membrane and internal organelles such as the endoplasmic reticulum (ER and mitochondria. External stimuli activate the ON reactions, which include Ca2+ into the cytoplasm either through channels in the plasma membrane or from internal storage like in ER. Most of the cells utilize both channels/sources, butthere area few cells using an external or internal source to control certain processes. Most of the Ca2+ entering the cytoplasm adsorbed to the buffer, while a smaller part activate effect or to stimulate cellular processes. Reaction OFF is pumping of cytoplasmic Ca2+ using a combination mechanism of mitochondrial and others. Changes in Ca2+ signal has been detected in various tissues isolated from animals induced into diabetes as well as patients with diabetes. Ca2+ signal interference is also found in sensory neurons of experimental animals with diabetes. Ca2+ signaling is one of the main signaling systems in the cell.

  9. Late Paleoproterozoic charnockite suite within post-collisional setting from the North China Craton: Petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

    Science.gov (United States)

    Yang, Qiong-Yan; Santosh, M.; Rajesh, H. M.; Tsunogae, T.

    2014-11-01

    Charnockites (pyroxene-bearing granitoids) of magmatic origin in diverse tectonic settings and ranging in age from Mesoarchean to Cretaceous constitute important components of the continental crust. Here we report charnockites displaying both magnesian and ferroan compositions associated with gabbros from an AMCG (anorthosite-mangerite-charnockite-granite) suite in the North China Craton. The orthopyroxene in the magnesian charnockite is characterized by moderate XMg of 0.63-0.65 (Wo1-2En62-63Fs35-36), and low Al2O3 content of 0.59-0.71 wt.%. The magnesian charnockites show medium- to high-K contents, and high Mg# (~ 47-69) similar to that of gabbros, whereas the Mg# of the ferroan charnockites is low (~ 6-28). The ferroan charnockites are alkali-calcic to alkalic, and weakly peralkaline to metaluminous, whereas the magnesian charnockites are calcic to calc-alkalic, and metaluminous. Although magnesian charnockites are in general considered to have formed in subduction setting, the medium- to high-K contents, high Mg# values with a wide range, and the highly negative εHf values of the zircons in these rocks (- 8. 4 to - 13.6), suggest inheritance of the arc signature from the melting of ancient arc-related crustal material. The ferroan charnockites show tholeiitic affinity and define a common differentiation trend with the gabbroic anorthosites and likely represent fractionated end-members with or without crustal interaction in a post-collisional rift setting. We present U-Pb age data from zircon grains on seven samples including two ferroan charnockites, three magnesian charnockites, one gabbroic enclave in magnesian charnockite and one gabbroic anorthosite which show emplacement ages of 1748.8 ± 6.4 Ma, 1747.1 ± 9.5 Ma, 1756.4 ± 7.3 Ma, 1756.7 ± 9.2 Ma, 1731 ± 17 Ma, 1731.6 ± 8.2 Ma and 1746.5 ± 7.3 Ma respectively. The negative εHf values (- 1.2 to - 13.6) of zircon grains from these rocks and the older crustal model ages ranging from Mesoarchean to

  10. U-Pb zircon geochronology and phase equilibria modelling of a mafic eclogite from the Sumdo complex of south-east Tibet: Insights into prograde zircon growth and the assembly of the Tibetan plateau

    Science.gov (United States)

    Weller, O. M.; St-Onge, M. R.; Rayner, N.; Waters, D. J.; Searle, M. P.; Palin, R. M.

    2016-10-01

    The Sumdo complex is a Permian-Triassic eclogitic metamorphic belt in south-east Tibet, which marks the location of a suture zone that separates the northern and southern Lhasa terranes. An integrated geochronological and petrological study of a mafic eclogite from the complex has constrained its tectonometamorphic history and provides a case study of zircon growth in eclogite as a product of prograde dissolution-precipitation. In situ U-Pb geochronology indicates that the eclogite contains a single population of zircon with a crystallisation age of 273.6 ± 2.8 Ma. The morphology and chemistry of the zircon grains are consistent with growth by dissolution-precipitation of protolith magmatic zircon. The presence of zircon grains as inclusions in the cores of peak phases indicates that zircon dissolution-precipitation occurred during prograde metamorphism, and calculated pressure and temperature conditions over which mineral inclusions in zircon are stable suggest that the zircon most likely precipitated at 15.5-16.5 kbar and 500-560 °C. Subsequent peak metamorphism is calculated to have reached pressure-temperature conditions of 27 ± 1 kbar and 670 ± 50 °C. Previous studies, which have documented a range of peak metamorphic conditions from high- to ultrahigh-pressure at c. 266-230 Ma, indicate that the Sumdo complex is a composite belt that experienced protracted eclogite exhumation. The results of this study are consistent with this interpretation, and extend the age range of high-pressure metamorphism in the complex to over 40 Myr. Analysis of published pressure-temperature-time data indicates two systematic behaviours within this spread. First, peak metamorphic temperatures declined over time. Second, eclogite exhumation occurred in two discrete intervals: soon after formation, and during the demise of the subduction zone. The latter behaviour serves as a reminder that eclogite exhumation is the exception rather than the rule.

  11. Detrital zircon study of the Dezful Embayment in the central Zagros, southern Iran

    Science.gov (United States)

    Hsieh, Hao Cheng; Chung, Sun Lin; Talebian, Morteza; Chen, Ling; Zarrinkoub, Mohammad H.; Lee, Hao Yang

    2016-04-01

    The Dezful Embayment of the Zagros Simply Folded Belt (ZFTB) in southern Iran is a foreland basin that formed as a flexural basin during the Miocene by the Zagros orogeny. This study reports a LA-ICPMS analysis of zircon U-Pb geochronology of 13 sedimentary rock samples from the Dezful Embayment, and five others from the Urumieh-Dokhtar magmatic arc (UDMA) and the Sanandaj-Sirjan zone (SSZ). In the northern and central parts of the Dezful Embayment, samples were collected from four principal sedimentary sequences including, from bottom to top, the Gachsaran Formation, Mishan Formation, Agha Jari Formation and Bakhtyari Formation. Our new zircon ages, together with published geochronological data from the UDMA and SSZ, can be used to better constrain the source provenance and tectonic implication of the Dezful Embayment related to the Arabia-Eurasia collision following the closure of Neo-Tethys. Samples of the UDMA and SSZ are characterized by abundant zircon ages of Eocene to Oligocene (55-25 Ma) and Jurassic (176-144 Ma), respectively. In the Dezful Embayment, detrital zircon age populations show significant variations. The age spectra of the northern Embayment show major peaks at the Precambrian (950-550 Ma), Late Carboniferous (323-299 Ma), Jurassic (176-144 Ma) and Eocene to Oligocene (55-25 Ma), with the last two age peaks suggesting an important source provenance from Eurasia, involving the SSZ and UDMA. By contrast, in the central Embayment, detrital zircons are dominated by Precambrian ages (2500 Ma, 1850 Ma, and 950-550 Ma), with rare Jurassic and Cenozoic ages. This suggests a different sedimentary source that we interpret to be the Arabian continent from the south. Moreover, gradual changes in the detrital zircon age spectra and thus in the source provenances are observed in different parts of the Dezful Embayment. The change in the northern Embayment occurred in the Agha Jari Formation, earlier than that in the central Embayment occurring between the

  12. What Hf isotopes in zircon tell us about crust-mantle evolution

    Science.gov (United States)

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Itano, Keita; Hibiya, Yuki; Suzuki, Kazue

    2017-03-01

    The 176Lu-176Hf radioactive decay system has been widely used to study planetary crust-mantle differentiation. Of considerable utility in this regard is zircon, a resistant mineral that can be precisely dated by the U-Pb chronometer and record its initial Hf isotope composition due to having low Lu/Hf. Here we review zircon U-Pb age and Hf isotopic data mainly obtained over the last two decades and discuss their contributions to our current understanding of crust-mantle evolution, with emphasis on the Lu-Hf isotope composition of the bulk silicate Earth (BSE), early differentiation of the silicate Earth, and the evolution of the continental crust over geologic history. Meteorite zircon encapsulates the most primitive Hf isotope composition of our solar system, which was used to identify chondritic meteorites best representative of the BSE (176Hf/177Hf = 0.282793 ± 0.000011; 176Lu/177Hf = 0.0338 ± 0.0001). Hadean-Eoarchean detrital zircons yield highly unradiogenic Hf isotope compositions relative to the BSE, providing evidence for the development of a geochemically enriched silicate reservoir as early as 4.5 Ga. By combining the Hf and O isotope systematics, we propose that the early enriched silicate reservoir has resided at depth within the Earth rather than near the surface and may represent a fractionated residuum of a magma ocean underlying the proto-crust, like urKREEP beneath the anorthositic crust on the Moon. Detrital zircons from world major rivers potentially provide the most robust Hf isotope record of the preserved granitoid crust on a continental scale, whereas mafic rocks with various emplacement ages offer an opportunity to trace the Hf isotope evolution of juvenile continental crust (from εHf[4.5 Ga] = 0 to εHf[present] = + 13). The river zircon data as compared to the juvenile crust composition highlight that the supercontinent cycle has controlled the evolution of the continental crust by regulating the rates of crustal generation and intra

  13. 1.8 Billion Years of Detrital Zircon Recycling Calibrates a Refractory Part of Earth's Sedimentary Cycle.

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    Thomas Hadlari

    Full Text Available Detrital zircon studies are providing new insights on the evolution of sedimentary basins but the role of sedimentary recycling remains largely undefined. In a broad region of northwestern North America, this contribution traces the pathway of detrital zircon sand grains from Proterozoic sandstones through Phanerozoic strata and argues for multi-stage sedimentary recycling over more than a billion years. As a test of our hypothesis, integrated palynology and detrital zircon provenance provides clear evidence for erosion of Carboniferous strata in the northern Cordillera as a sediment source for Upper Cretaceous strata. Our results help to calibrate Earth's sedimentary cycle by showing that recycling dominates sedimentary provenance for the refractory mineral zircon.

  14. Differing responses of zircon, chevkinite-(Ce), monazite-(Ce) and fergusonite-(Y) to hydrothermal alteration: Evidence from the Keivy alkaline province, Kola Peninsula, Russia

    Science.gov (United States)

    Macdonald, Ray; Bagiński, Bogusław; Zozulya, Dmitry

    2017-09-01

    A quartzolite from the Rova occurrence, Keivy alkali granite province, Kola Peninsula, Russia, is used to examine the differing responses of certain rare-metal minerals during interaction with hydrothermal fluids. The minerals are two silicates [chevkinite-(Ce) and zircon], a phosphate [monazite-(Ce)] and an oxide [fergusonite-(Y)]. Textural evidence is taken to show that the dominant alteration mechanism was interface-coupled dissolution-reprecipitation. Zircon was the most pervasively altered, possibly by broadening of cleavage planes or fractures; the other minerals were altered mainly on their rims and along cracks. The importance of cracks in promoting fluid access is stressed. The compositional effects of the alteration of each phase are documented. The hydrothermal fluids carried few ligands capable of transporting significant amounts of rare-earth elements (REE), high field strength elements (HFSE) and actinides; alteration is inferred to have been promoted by mildly alkaline, Ca-bearing fluids. Expansion cracks emanating from fergusonite-(Y) are filled with unidentified material containing up to 35 wt% UO2 and 25 wt% REE2O3, indicating late-stage, short-distance mobility of these elements. Electron microprobe chemical dating of monazite yielded an age of 1665 ± 22 Ma, much younger than the formation age of the Keivy province (2.65-2.67 Ga) but comparable to that of the Svecofennian metamorphic event which affected the area (1.9-1.7 Ga) or during fluid-thermal activation of the region during rapakivi granite magmatism (1.66-1.56 Ga). Dates for altered monazite range from 2592 ± 244 Ma to 773 ± 88 Ma and reflect disturbance of the U-Th-Pb system during alteration.

  15. The elusive snowball earth: U-Pb zircon ages from the upper diamictite of the Gifberg Group, South Africa

    Science.gov (United States)

    Naidoo, Thanusha; Zimmermann, Udo; Vervoort, Jeff; Tait, Jenny

    2017-05-01

    U-Pb dating of detrital zircons was undertaken in the matrix component of the Swartleikrans Bed (Bloupoort Formation, Gifberg Group), located in the Vredendal Outlier of western South Africa. Results from this study indicate detrital zircons were derived from both local and regional (or distal) sources. The deposit is reportedly Neoproterozoic in age, but convincing age constraints are absent. These meta-diamictitic rocks were interpreted as glacial and are correlated with other diamictites in SW Gondwana, in the wake of the snowball Earth hypothesis. While sedimentological data is interpreted as glacial, geochemical proxies (Mo, Cr, U/Th, Ce*, V) point to an oxygenated depositional environment. Thus, if the deposit was related to a snowball Earth glacial event, then deposition must have been distal to the ice sheets. Nearly 50% of the dated detrital zircons (n = 68) have crystallization ages that cannot be correlated with known sources in the locally exposed basement. These predominantly Mesoproterozoic grains were either derived from distal sources or are reworked from unknown, now eroded, sedimentary rocks. Only 14% of all concordant zircon have an Early Mesoproterozoic to Late Palaeoproterozoic age, and a single grain relates to an older Paleoproterozoic event. Results are similar to other glacial deposits in the region (further north, in Namibia). In total, sedimentological observations and detrital zircon age populations point to a large catchment area, characteristic of glacial events of regional significance. However, direct regional correlation is still not possible using maximum depositional ages indicated by detrital zircons.

  16. An in vitro evaluation of novel NHA/zircon plasma coating on 316L stainless steel dental implant

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    Ebrahim Karamian

    2014-04-01

    Full Text Available The surface characteristics of an implant that influence the speed and strength of osseointegration include crystal structure and bioactivity. The aim of this study was to evaluate the bioactivity of a novel natural hydroxyapatite/zircon (NHA/zircon nanobiocomposite coating on 316L stainless steel (SS dental implants soaking in simulated body fluid. A novel NHA/zircon nanobiocomposite was fabricated with 0 (control, 5, 10, and 15 wt% of zircon in NHA using ball mill for 1 h. The composite mixture was coated on SS implants using a plasma spray method. Scanning electron microscopy (SEM was used to evaluate surface morphology, and X-ray diffraction (XRD was used to analyze phase composition and crystallinity (Xc. Further, calcium ion release was measured to evaluate the coated nanobiocomposite samples. The prepared NHA/zircon coating had a nanoscale morphological structure with a mean crystallite size of 30–40 nm in diameter and a bone-like composition, which is similar to that of the biological apatite of a bone. For the prepared NHA powder, high bioactivity was observed owing to the formation of apatite crystals on its surface. Both minimum crystallinity (Xc=41.1% and maximum bioactivity occurred in the sample containing 10 wt% of zircon because of minimum Xc and maximum biodegradation of the coating sample.

  17. Residual stress development and effect on the piezoelectric performance of sol-gel derived lead zirconate titanate (PZT) thin films

    Science.gov (United States)

    Berfield, Thomas A.

    Ferroelectric thin films have higher energy densities, larger strain capabilities and more rapid response times than their bulk counterparts. Typical applications include micro-actuators, micro-sensors and ultrasonic motors for MEMs applications, as well as, nonvolatile computer memories and switching capacitors for integrated circuitry. The electro-mechanical performance of ceramic thin films is greatly influenced by many factors, including grain size, orientation, film thickness, and residual stress level. Residual stresses which arise during the various processing phases of thin film manufacturing can be quite high due to substantial mismatches in substrate-film thermal properties, intrinsic sources (such as grain boundary interactions, etc.), and other external factors. This dissertation examines the relationship between field-induced displacement response and residual stress level for lead zirconate-titanate (PZT) thin films. The film piezoelectric properties are characterized via interferometric measurements for two different loading cases, while the residual stress is determined experimentally from wafer curvature measurements. Additionally two patterning methods, traditional chemical wet-etching and a novel soft lithographic technique, are explored as a means to reduce residual stress within film features. For the soft lithographic technique, film features are created by selective film cracking, a result of poor substrate adhesion promoted by a mediated, self-assembled monolayer. Wafer curvature stress measurements and DIC-based strain measurements of mediated monolayer patterned features reveal that the in-plane stress/strain development is reduced compared to the blanket film case. Critical in-plane strains at crack initiation are also measured using a new digital image correlation technique, in which fluorescent nanoparticles (c.a. 140 nm) provide the speckle pattern. A corresponding increase in the field induced displacements is observed for the film

  18. Magnesia-zircon brick: Evolution of microstructure, properties and performance with increasing sintering temperature

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    Gao J.

    2013-01-01

    Full Text Available Depending on phase components and densification, Magnesia-Zircon brick varies in appearance from white to veined and then brown with increasing sintering temperature. Properties including bulk density, apparent porosity and hot modulus of rupture as well as performance embodied with creep resistance and refractoriness continue to improve with sustaining enhancement of sintering temperature. Exceptionally, cold crushing strength first increases then decreases with rising sintering temperature and a peak exists at 1550oC. Microstructural evolution suffers zircon decomposition companying by silica escape, forsterite formation, matrix solidification and zirconia coagulation, until a zirconia/forsterite composites belt tightly coating on magnesia aggregates. Excessive coagulation of zirconia caused by oversintering probably results in microcracks formation and defects enlargement thereby degrades cold crushing strength.

  19. Precise U-Pb Zircon Dating of the Syenite Phase from the Ditrau Alkaline Igneous Complex

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    Pană Dinu

    2000-04-01

    Full Text Available The Ditrău igneous complex represents the largest alkaline intrusion in the Carpathian-Pannonian region consisting of a plethora of rock types formed by complicated magmatic and metasomatic processes. A detailed U-Pb zircon age study is currently underway and the results for the syenite intrusion phase is reported herein. The U-Pb zircon emplacement age of the syenite of 229.6 +1.7/-1.2 Ma documents the quasi-contemporaneous production and emplacement of the gabbro and syenite magmas. We suggest that the syenite and associated granite formed by crustal melting during the emplacement of the mantle derived gabbroic magma around 230 Ma. The thermal contact aureole produced by the Ditrău alkaline igneous complex constrains the main tectonism recorded by surrounding metamorphic lithotectonic assemblages to be pre-Ladinian.

  20. Investigation of zircon/zirconia ceramics doped with {sup 239}Pu and {sup 238}Pu

    Energy Technology Data Exchange (ETDEWEB)

    Burakov, B.E.; Anderson, E.B.; Zamoryanskaya, M.V.; Nikolaeva, E.V.; Strykanova, E.E.; Yagovkina, M.A. [V.G. Khlopin Radium Institute, Saint Petersburg (Russian Federation)

    2001-07-01

    Several samples of crystalline double-phase ceramics based on zircon, (Zr,Pu)SiO{sub 4} and zirconia, (Zr,Pu)O{sub 2}, were synthesized by sintering in air, precursors containing approximately 5-6 and 10 wt% {sup 239}Pu, respectively. One sample doped with 5-6 wt% {sup 238-39-40}Pu was also obtained under the same conditions. All ceramic samples were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and MCC-1 leach test in deionized water at 90 C. Results indicate that even radiation damaged zircon/zirconia ceramics retain high chemical resistance and mechanical durability. (author)

  1. Localized rejuvenation of a crystallizing pluton recorded in zircon from the Lassen Volcanic Center, southern Cascade Range, California

    Science.gov (United States)

    Klemetti, E. W.; Clynne, M. A.; Ring, M.; Bertolett, E. M.

    2013-12-01

    The Lassen Volcanic Center (LVC) in northern California produced the only eruption in the Cascades other than Mount St. Helens over the past century with its activity in 1914-17. The LVC dates back to ~825 ka and has produced ~215 km3 of dominantly andesite to rhyodacite (with minor basaltic andesite and rhyolite) lava and tephra over that period with activity since 90 ka divided into the Twin Lakes (~90 to 0.01 ka) and Eagle Peak sequences (~66 to 1.1 ka). The Twin Lakes sequences has a higher proportion of basaltic input relative to the Eagle Peak sequence, however both sequence show extensive evidence of magma mixing and mingling. Examining the age spectra and composition of zircon from representative eruptions in the LVC can illuminate the petrologic conditions of the underlying magmatic system. We collected (via SHRIMP-RG) the first 238U-230Th model ages and trace-element compositions of zircon from one Twin Lakes sequence eruption (1915 dacite of Lassen Peak) and three Eagle Peak sequence eruptions (the rhyodacite of Chaos Crags, the 27 ka dacite of Lassen Peak and the 66 ka rhyodacite of Eagle Peak). Zircon age spectra from the rhyodacite of Chaos Crags and 1915 and 27 ka dacites of Lassen Peak (62 zircon analyses) are similar, with a range of 25 ka to secular equilibrium (~350 ka) with no crystals within error of their host eruption age. The dominant period of zircon crystallization falls between 190-90 ka. This is a period of volcanic quiescence in the LVC and this zircon bloom represents the crystallization of a proto-pluton following the end of the Bumpass Sequence (350-193 ka). Surface analyses of zircons from the analyzed eruptions range from 25 ka to 74 ka; none of which is within error of the eruption age of the host lava. This suggests that zircon crystallization effectively ended at ~25-30 ka. The host lavas, when erupted, were zircon undersaturated, so zircon preservation is likely due to inclusion in other phases. Overall, the zircon from these

  2. Lead zirconate titanate nanowire textile nanogenerator for wearable energy-harvesting and self-powered devices.

    Science.gov (United States)

    Wu, Weiwei; Bai, Suo; Yuan, Miaomiao; Qin, Yong; Wang, Zhong Lin; Jing, Tao

    2012-07-24

    Wearable nanogenerators are of vital importance to portable energy-harvesting and personal electronics. Here we report a method to synthesize a lead zirconate titanate textile in which nanowires are parallel with each other and a procedure to make it into flexible and wearable nanogenerators. The nanogenerator can generate 6 V output voltage and 45 nA output current, which are large enough to power a liquid crystal display and a UV sensor.

  3. Strontium Zirconate TBC Sprayed by a High Feed-Rate Water-Stabilized Plasma Torch.

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Nevrlá, Barbara; Čížek, Jan; Lukáč, František

    2017-01-01

    Roč. 26, č. 8 (2017), s. 1804-1809 ISSN 1059-9630 R&D Projects: GA TA ČR(CZ) TE02000011 Institutional support: RVO:61389021 Keywords : adhesion * plasma spraying * strontium zirconate * thermal insulator Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.488, year: 2016 https://link.springer.com/article/10.1007/s11666-017-0641-7

  4. Late Triassic uplift of southern Norway revealed by detrital zircons in the Norwegian-Danish Basin

    Science.gov (United States)

    Olivarius, Mette; Nielsen, Lars H.; Weibel, Rikke; Kristensen, Lars; Thomsen, Tonny B.

    2016-04-01

    Zircon U/Pb geochronometry is used to identify the sediment source areas of the Upper Triassic to Lower Jurassic shallow marine to paralic Gassum Formation in the Norwegian-Danish Basin. The analyses of zircon grains from geographically and stratigraphically widely distributed cores take advantage of the detailed sequence stratigraphic framework existing for the succession. The zircon ages indicate that the sediment in the lower part of the Gassum Formation in the northern and central parts of the basin was supplied solely from the Telemarkia Terrane in the southern part of southern Norway. However, age signatures from other basement terranes were added during periods of transgression presumably as a result of longshore reworking. The sediment in the eastern part of the basin has a different provenance signature that reflects supply from various sources of which some or all seemingly include older sediments. The basinwide fluvial incision that occurred during a relative sea-level fall in the Rhaetian is interpreted to be related to uplift of southern Norway since a pronounced content of zircon grains with U/Pb ages of 1.65 Ga were introduced in the Norwegian-Danish Basin at the time. This age is dominant in the upper part of the Gassum Formation and is present in all studied younger sediments in the Norwegian-Danish Basin, whereas it is missing in older sediments in the basin. Rocks with corresponding ages are presently exposed in the Jotun Nappe Complex and the Western Gneiss Complex in the central and northern parts of southern Norway. Thus, major faulting activity must have occurred in southern Norway during the Late Triassic that made such rocks available for erosion with permanent southeastwards drainage.

  5. Production Technology of Lead Zirconate Titanate Type-4 Spherical Elements for Underwater Transducers

    OpenAIRE

    M.P.S. Namboodiri; S. B. Ekbote; G. S. Dhami

    1991-01-01

    The paper describes the production technology evolved for the fabrication of 60 mm hollow spherical elements from lead zirconate titanate type-4 material, suitable for use in the manufacture of underwater omnidirectional transducers. It covers the characteristics of the starting powder, techniques of isostatic pressing, precision spherical machining, sintering to produce dielectrically sound, distortion-free hemispheres to the required physical dimensions, electroding, poling to achiev...

  6. Determination of strontium and lanthanum zirconates in YPSZ-LSM mixtures for SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Cortes-Escobedo, Claudia Alicia [Centro de Investigacion e Innovacion Tecnologica del IPN, Cda. Cecati s/n, Col. Sta. Catarina, CP 02250, Azcapotzalco, D.F. (Mexico); Munoz-Saldana, Juan [Centro de Investigacion y Estudios Avanzados del IPN, Unidad Queretaro, pdo. Postal 1-798, 76001 Queretaro, Qro. (Mexico); Bolarin-Miro, Ana Maria; Sanchez-de Jesus, Felix [Centro de Investigaciones en Materiales y Metalurgia, Universidad Autonoma del Estado de Hidalgo, CU, Carr. Pachuca-Tulancingo Km. 4.5, Mineral de la Reforma, CP 42184, Hidalgo (Mexico)

    2008-05-15

    Mixtures of 3% yttria- and partially-stabilized zirconia with LSM{sub x} (strontium-doped lanthanum manganite, x = 0, 0.15 and 0.2) were prepared and heat treated at temperatures between 1000 and 1300 C to recreate the cathode-electrolyte interface interactions taking place during preparation and operation of solid oxide fuel cells (SOFC). Such interactions include the formation of La{sub 2}Zr{sub 2}O{sub 7} and SrZrO{sub 3}, which are undesirable for SOFC. The effect of the manganese oxidation number on the mechanosynthesis of LSM during zirconate formation is also discussed. A quantitative analysis of zirconate formation by X-ray diffraction and Rietveld refinement was undertaken. Formation of lanthanum and strontium zirconates was completely avoided at temperatures as high as 1300 C by synthesizing lanthanum manganites from MnO{sub 2} doped with 15 at.% of Sr. Finally, in the presence of LSM, monoclinic phase content was diminished to less than 1.5 mol% after heat treatment at 1300 C. (author)

  7. Zircon U-Pb dating using LA-ICP-MS: Quaternary tephras in Yakushima Island, Japan

    Science.gov (United States)

    Ito, Hisatoshi; Uesawa, Shimpei; Nanayama, Futoshi; Nakagawa, Shojiro

    2017-05-01

    Zircon U-Pb dating using LA-ICP-MS was applied to three Quaternary tephras in Yakushima Island, southern Japan: the Anbo Tephra, the Koseda pyroclastic flow deposit (Ksd), and the Kikai-Tozurahara (K-Tz) Tephra. The obtained U-Pb ages were 0.73 ± 0.04 Ma (error shown as 95% confidence level) for the Anbo, 0.63 ± 0.04 Ma for the Ksd, and 0.17 ± 0.05 Ma for the K-Tz. These ages are consistent with or slightly older than those reported previously, which demonstrates the applicability of the U-Pb method to date zircons as young as 0.1 Ma. The K-Tz contains 0.7-0.6 Ma zircons, assumed to be derived from the Anbo and Ksd tephras. Because the K-Tz was originated from the Kikai Caldera, 30 km north of Yakushima Island, both the Anbo and Ksd were likely also derived from the same caldera system. Therefore our data and interpretation will contribute to elucidate the magmatic history of the Kikai Caldera whose latest eruption devastated prehistoric human settlements of southern Kyushu, Japan, and provide an improved chronostratigraphic constraint for Japan.

  8. Zirconate Pyrochlore Frustrated Magnets: Crystal Growth by the Floating Zone Technique

    Directory of Open Access Journals (Sweden)

    Monica Ciomaga Hatnean

    2016-07-01

    Full Text Available This article reviews recent achievements on the crystal growth of a new series of pyrochlore oxides—lanthanide zirconates, which are frustrated magnets with exotic magnetic properties. Oxides of the type A 2 B 2 O 7 (where A = Rare Earth, B = Ti, Mo have been successfully synthesised in single crystal form using the floating zone method. The main difficulty of employing this technique for the growth of rare earth zirconium oxides A 2 Zr 2 O 7 arises from the high melting point of these materials. This drawback has been recently overcome by the use of a high power Xenon arc lamp furnace for the growth of single crystals of Pr 2 Zr 2 O 7 . Subsequently, large, high quality single crystals of several members of the zirconate family of pyrochlore oxides A 2 Zr 2 O 7 (with A = La → Gd have been grown by the floating zone technique. In this work, the authors give an overview of the crystal growth of lanthanide zirconates. The optimum conditions used for the floating zone growth of A 2 Zr 2 O 7 crystals are reported. The characterisation of the crystal boules and their crystal quality is also presented.

  9. Laser-Assisted Atom Probe Tomography of Deformed Minerals: A Zircon Case Study.

    Science.gov (United States)

    La Fontaine, Alexandre; Piazolo, Sandra; Trimby, Patrick; Yang, Limei; Cairney, Julie M

    2017-04-01

    The application of atom probe tomography to the study of minerals is a rapidly growing area. Picosecond-pulsed, ultraviolet laser (UV-355 nm) assisted atom probe tomography has been used to analyze trace element mobility within dislocations and low-angle boundaries in plastically deformed specimens of the nonconductive mineral zircon (ZrSiO4), a key material to date the earth's geological events. Here we discuss important experimental aspects inherent in the atom probe tomography investigation of this important mineral, providing insights into the challenges in atom probe tomography characterization of minerals as a whole. We studied the influence of atom probe tomography analysis parameters on features of the mass spectra, such as the thermal tail, as well as the overall data quality. Three zircon samples with different uranium and lead content were analyzed, and particular attention was paid to ion identification in the mass spectra and detection limits of the key trace elements, lead and uranium. We also discuss the correlative use of electron backscattered diffraction in a scanning electron microscope to map the deformation in the zircon grains, and the combined use of transmission Kikuchi diffraction and focused ion beam sample preparation to assist preparation of the final atom probe tip.

  10. Simulation of the effects of the dose rate and temperature on zircon thermoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Turkin, A A [National Science Centre Kharkov Institute of Physics and Technology, 61108 Kharkov (Ukraine); Es, H J van [Solid State Physics Laboratory, University of Groningen, 4 Nijenborgh, NL-9747 AG Groningen (Netherlands); Vainshtein, D I [Solid State Physics Laboratory, University of Groningen, 4 Nijenborgh, NL-9747 AG Groningen (Netherlands); Hartog, H W den [Solid State Physics Laboratory, University of Groningen, 4 Nijenborgh, NL-9747 AG Groningen (Netherlands)

    2005-01-07

    After exposure to ionizing irradiation, mineral zircon exhibits thermoluminescence (TL), which can be used to calculate the irradiation dose and the age of natural samples. Different aspects of the dating procedure based on zircon TL, including laboratory added irradiation at room and elevated temperatures, fading and preheat processes, have been considered within the framework of the kinetic model developed by our group earlier. It is shown that dose rate effects arising due to the difference between natural and laboratory irradiation can be removed by a suitable preheat treatment of the laboratory irradiated samples prior to the TL measurements. We demonstrate that the TL behaviour of zircon which has been irradiated under natural conditions can be reproduced by means of laboratory irradiation at some elevated temperature. This opens a promising possibility of (i) getting rid of dose rate effects and anomalous fading and (ii) reconstructing the dose dependence of the total TL signal emitted by samples irradiated under natural conditions. The model has been checked by simulating the dating procedures used for our coastal dune sand samples from Ameland (NL), the age of which is known from historical records; the results agree well with the available experimental data. The results of this investigation demonstrate the utility of the kinetic model for planning dating experiments and for development of new and innovative TL dating methods.

  11. Lead zirconate (PbZrO3 embedded in natural rubber as electroactive elastomer composites

    Directory of Open Access Journals (Sweden)

    Anuvat Sirivat

    2014-11-01

    Full Text Available Perovskite lead zirconate (PbZrO3 was synthesized in an orthorhombic form at a temperature below the Curie temperature, TC. The orthorhombic form is a noncentrosymmetric structure which is capable of spontaneous polarization. Fourier transform infrared (FTIR spectra and X-ray diffraction (XRD patterns confirm the successful synthesis of the lead zirconate; and scanning electron microscopy (SEM micrographs indicate that PbZrO3 particles are moderately dispersed in the natural rubber (NR matrix. Without an electrical field, the particles merely act as a ferroelectric filler, which can absorb and store additional stress. Under an electrical field, particle-induced dipole moments are generated, leading to interparticle interaction and a substantial increase in the storage modulus. At a small amount of lead zirconate particulates present in the natural rubber matrix, at a volume fraction of 0.007306, the electrical conductivity increases dramatically by nearly two orders of magnitude at the electrical frequency of 500 kHz.

  12. Zircon LA-ICPMS geochronology of the Cornubian Batholith, SW England

    Science.gov (United States)

    Neace, Erika R.; Nance, R. Damian; Murphy, J. Brendan; Lancaster, Penelope J.; Shail, Robin K.

    2016-06-01

    Available Usbnd Pb age data for the Cornubian Batholith of SW England is based almost entirely on monazite and xenotime, and very little zircon Usbnd Pb age data has been published. As a result, no zircon inheritance data is available for the batholith, by which the nature of the unexposed basement of the Rhenohercynian Zone in SW England might be constrained. Zircon LA-ICPMS data for the Cornubian Batholith provides Concordia ages (Bodmin Moor granite: 316 ± 4 Ma, Carnmenellis granite: 313 ± 3 Ma, Dartmoor granite: ~ 310 Ma, St. Austell granite: 305 ± 5 Ma, and Land's End granite: 300 ± 5 Ma) that are consistently 20-30 Ma older than previously published emplacement ages for the batholith and unrealistic in terms of geologic relative age relationships with respect to the country rock. This discrepancy is likely as a consequence of minor pre-granitic Pb inheritance. Several of the batholith's granite plutons contain a component of late-Devonian inheritance that may record rift-related, lower crustal melting or arc-related magmatism associated with subduction of the Rheic Ocean. In addition, the older granites likely contain Mesoproterozoic inheritance, although the highly discordant nature of the Mesoproterozoic ages precludes their use in assigning an affinity to the Rhenohercynian basement in SW England.

  13. Desulfurizing Ability of the CaOsatd.-CaCl2-CaF2 Slags

    Science.gov (United States)

    Liu, Jiazhan; Kobayashi, Yoshinao

    2017-04-01

    Desulfurizing ability of the CaO-CaCl2-CaF2 slags saturated with CaO has been investigated from the viewpoint of the sulfide capacity and CaO solubility. The CaO-CaCl2-CaF2 slags containing small amounts of Cu2O and CaS were inserted in a CaO crucible with metallic copper. The CaO crucible was sealed in a nickel holder to prevent the evaporation of CaCl2, then heated up and kept at temperatures from 1573 K (1300 °C) to 1673 K (1400 °C) for 24 hours, which enabled the system inside the CaO crucible to reach the equilibrium. As expected, the sulfide capacity derived from the data obtained as well as CaO solubility of the slag increase with an increase in temperature at a constant ratio of CaCl2/CaF2. The solubility of CaO increases by the replacement of CaF2 with CaCl2, whereas the sulfide capacity slightly decreases and the activity coefficient of CaS ( γ CaS) increases. This suggests that CaF2 has stronger interaction with CaS than CaCl2. The sulfur distribution ratio between carbon-saturated iron melts and the CaO-CaCl2 slag has been calculated to be about 10 000 at 1573 K (1300 °C) using the sulfide capacity obtained, which value is still large enough even with the replacement of CaF2 by CaCl2.

  14. Zircons from a metasomatic alteration profile: block-matrix interaction in high-pressure rocks from Syros (Greece)

    Science.gov (United States)

    Keasling, A.; Bröcker, M.

    2003-04-01

    On Syros (Cyclades, Greece), a mélange sequence was affected by low-temperature eclogite-facies metamorphism. Fluid-enhanced exchange processes between blocks and the ultramafic matrix are recorded by reaction rinds which formed during HP-metamorphism. Some blocks and their metasomatic rims are characterized by remarkably high modal amounts of zircon (tens to hundreds of grains on thin-section scale). The geological significance of Cretaceous U-Pb zircon ages (c. 75-80 Ma) reported for these rocks is controversial. Zircon growth was either related to metamorphic or magmatic processes. In order to provide further arguments for this debate, we have studied zircons from a metasomatic alteration profile which developed around a jadeitite block. Towards the serpentinite matrix, three zones (c. 5-30 cm in thickness) can be distinguished, which predominantly consist either of omphacite, glaucophane or actinolite- chlorite. Zircon is present in the jadeitite and all reaction rims, but not in the serpentinite. Using SEM, CL-imaging and LA-ICP-MS, we have systematically documented morphological and compositional characteristics of zircons from this alteration profile. In the jadeitite and omphacitite short-prismatic grains are more abundant than in the outer zones which contain a higher amount of long-prismatic grains. Trace element patterns of all zircons are very similar. However, the total abundance of these elements decreases from the center of the block towards the peripheral parts, with the exception of Hf and Ti concentrations which remain constant. In most cases, no significant differences between core and rim compositions were recognized within individual zones. A notable exception are some zircons from the jadeitite and omphacitite which are characterized by U- and Th-rich cores (complex cauliflower-like CL images). For the rims (broad oscillatory CL patterns) significantly lower concentrations of these elements were obtained. The Th/U ratio of zircons

  15. Teale CA. Counties

    Data.gov (United States)

    California Department of Resources — California Spatial Information System (CaSIL) is a project designed to improve access to geo-spatial and geo-spatial related data information throughout the state of...

  16. Detrital zircon constraints and implications for the magmatic evolution and Cimmerian orogeny in Georgian Caucasus

    Science.gov (United States)

    Lee, H. Y.; Chung, S. L.; Chang, Y. H.; Chiu, H. Y.; Javakhishvili, Z.

    2016-12-01

    We present U-Pb ages and Hf isotopic results of the detrital zircons obtained from the sedimentary rocks representative of the Jurassic to Miocene formations in Georgia or so-called Georgian Caucasus. Georgian Caucasus, covering parts of the area of Greater, Trans- and Lesser Caucasus, is located in the most northern Caucasus-Iran-Anatolia (CIA) region elevated by the collision of Arabia with Eurasia. Here several significant magmatic episodes are exhibited in the Phanerozoic including (1) a major one from 500 to 420 Ma, (2) a major one at 320 Ma, (3) minor ones at 220 and 170 Ma, (4) a major one from 110 to 90 Ma and (5) a major one at 45 Ma. The Hf isotopes, furthermore, show large variation of the compositions in the former two stages of 500 to 420 Ma and 320 Ma, and mainly positive-dominant values since 220 Ma. This scenario could be better to correlate with that from the magmatic zircons of the igneous rocks in central and south Georgian Caucasus, NE Turkey and NW Iran. It displays the multi-stage magmatism at 320, 220, 90 and 45 Ma along with abundant inherited zircons from 700 to 480 Ma, and shows the similar Hf isotopic features as those of the detrital zircons. These data strongly suggest that the detrital zircons might come from the erosion of igneous successions in Georgian Caucasus. This infers injection of the juvenile Arabian-Nubian Shield (ANS) crust into the relict old crust from the Cambrian to Silurian, and the existence of a juvenile crust all over Georgian Caucasus since the Carboniferous, representing the extensively growth of the continental crust during the Phanerozoic. It is notable that the Carboniferous episode ( 320 Ma) was possibly caused by the remelting of the old ANS-derived ribbon continents and represented as the timing of the Neo-Tethys opening and Cimmerian orogeny. Therefore, the results in this study could be well applicable to the distinctly magmatic events related to the Gondwana separation, opening and closure of the Paleo

  17. Cretaceous crust beneath SW Borneo: U-Pb dating of zircons from metamorphic and granitic rocks

    Science.gov (United States)

    Davies, L.; Hall, R.; Armstrong, R.

    2012-12-01

    Metamorphic basement rocks from SW Borneo are undated but have been suggested to be Palaeozoic. This study shows they record low pressure 'Buchan-type' metamorphism and U-Pb SHRIMP dating of zircons indicates a mid-Cretaceous (volcaniclastic) protolith. SW Borneo is the southeast promontory of Sundaland, the continental core of SE Asia. It has no sedimentary cover and the exposed basement has been widely assumed to be a crustal fragment from the Indochina-China margin. Metamorphic rocks of the Pinoh Group in Kalimantan (Indonesian Borneo) are intruded by granitoid rocks of Jurassic-Cretaceous age, based on K-Ar dating, suggesting emplacement mainly between 130 and 80 Ma. The Pinoh metamorphic rocks have been described as a suite of pelitic schists, slates, phyllites, and hornfelses, and have not been dated, although they have been correlated with rocks elsewhere in Borneo of supposed Palaeozoic age. Pelitic schists contain biotite, chlorite, cordierite, andalusite, quartz, plagioclase and in some cases high-Mn almandine-rich garnet. Many have a shear fabric associated with biotite and fibrolite intergrowth. Contact metamorphism due to intrusion of the granitoid rocks produced hornfelses with abundant andalusite and cordierite porphyroblasts. Granitoids range from alkali-granite to tonalite and contain abundant hornblende and biotite, with rare white mica. Zircons from granitoid rocks exhibit sector- and concentric- zoning; some have xenocrystic cores mantled by magmatic zircon. There are four important age populations at c. 112, 98, 84 and 84 Ma broadly confirming earlier dating studies. There is a single granite body with a Jurassic age (186 ± 2.3 Ma). Zircons from pelitic metamorphic rocks are typically euhedral, with no evidence of rounding or resorbing of grains; a few preserve volcanic textures. They record older ages than those from igneous rocks; U-Pb ages are Cretaceous with a major population between 134 and 110 Ma. A single sample contains Proterozoic

  18. Solubility of manganotantalite, zircon and hafnon in highly fluxed peralkaline to peraluminous pegmatitic melts

    Science.gov (United States)

    van Lichtervelde, Marieke; Holtz, Francois; Hanchar, John M.

    2010-07-01

    The behavior of tantalum and zirconium in pegmatitic systems has been investigated through the determination of Ta and Zr solubilities at manganotantalite and zircon saturation from dissolution and crystallization experiments in hydrous, Li-, F-, P- and B-bearing pegmatitic melts. The pegmatitic melts are synthetic and enriched in flux elements: 0.7-1.3 wt% Li2O, 2-5.5 wt% F, 2.8-4 wt% P2O5 and 0-2.8 wt% B2O3, and their aluminum saturation index ranges from peralkaline to peraluminous (ASILi = Al/[Na + K + Li] = 0.8 to 1.3) with various K/Na ratios. Dissolution and crystallization experiments were conducted at temperatures varying between 700 and 1,150°C, at 200 MPa and nearly water-saturated conditions. For dissolution experiments, pure synthetic, end member manganotantalite and zircon were used in order to avoid problems with slow solid-state kinetics, but additional experiments using natural manganotantalite and zircon of relatively pure composition (i.e., close to end member composition) displayed similar solubility results. Zircon and manganotantalite solubilities considerably increase from peraluminous to peralkaline compositions, and are more sensitive to changes in temperature or ASI of the melt than to flux content. A model relating the enthalpy of dissolution of manganotantalite to the ASILi of the melt is proposed: ∆ H diss (kJ/mol) = 304 × ASILi - 176 in the peralkaline field, and ∆ H diss (kJ/mol) = -111 × ASILi + 245 in the peraluminous field. The solubility data reveal a small but detectable competitivity between Zr and Ta in the melt, i.e., lower amounts of Zr are incorporated in a Ta-bearing melt compared to a Ta-free melt under the same conditions. A similar behavior is observed for Hf and Ta. The competitivity between Zr (or Hf) and Ta increases from peraluminous to peralkaline compositions, and suggests that Ta is preferentially bonded to non-bridging oxygens (NBOs) with Al as first-neighbors, whereas Zr is preferentially bonded to NBOs

  19. Quantifying Volcanic Stresses from Residual Stress Preserved in Magnetite and Zircon

    Science.gov (United States)

    Leonhardi, T. C.; Befus, K.; Manga, M.; Stan, C. V.; Tamura, N.

    2016-12-01

    Stresses active in volcanic systems are intimately linked with the processes driving magma chamber evolution and volcanic eruptions. These processes are difficult to quantify directly. Instead, insights come from a combination of modeling, geophysical observations, petrology and geochemistry. To directly quantify the forces and stresses associated with volcanic systems (such as chamber over-pressure) we need to develop techniques that provide new insights into volcanic processes. Here we quantified volcanic stresses in crystals from two units erupted from Yellowstone caldera. We used the Laue x-ray microdiffraction technique to measure preserved elastic lattice strain and the equivalent stress required to produce the strain. We analyzed zircon and magnetite crystals from pumice clasts in the pyroclastic fall deposit from the Tuff of Bluff Point and a flow front sample of the effusive Summit Lake lava flow. Analyses were performed using the x-ray microdiffraction beamline (12.3.2) at the Advanced Light Source, Lawrence Berkeley National Lab. Zircon preserved residual stress values in the range of 290-430 MPa for both units. Magnetite from the Tuff of Bluff Point preserves stress values of 310-370 MPa, whereas Summit Lake magnetite preserved values of 210-280 MPa. These values are greater that the estimates for lithostatic pressure in the final shallow storage chamber. If the values do represent the minerals' formation depth, then this indicates magnetite and zircon formed early in the magmatic system at greater depth. If true, residual stress in zircon and magnetite may be used as a crystallization geobarometer. Alternatively, if these values did not result from storage depth, they could reflect other processes in the chamber and conduit (such as fragmentation and thermal quenching). The observed differences in magnetite values suggest a change in the storage depth and/or volcanic stresses active in eruptions of the two deposits. For zircon, recoil damage and trace

  20. Selective zircon accumulation in a new benthic foraminifer, Psammophaga zirconia, sp. nov.

    Science.gov (United States)

    Sabbatini, Anna; Negri, Alessandra; Bartolini, Annachiara; Morigi, Caterina; Boudouma, Omar; Dinelli, Enrico; Florindo, Fabio; Galeazzi, Roberta; Holzmann, Maria; Lurcock, Pontus C.; Massaccesi, Luca; Pawlowski, Jan W.; Rocchi, Sergio

    2017-04-01

    Benthic foraminifera are single-celled eukaryotes that make a protective organic, agglutinated or calcareous test. Some agglutinated, single-chambered taxa, including Psammophaga Arnold, 1982, retain mineral particles in their cytoplasm, but the selective mechanism of accumulation is not clear. Here, we report the ability of a foraminiferal species to select and accumulate zircons and other heavy minerals in their cytoplasm. In particular, the use of Scanning Electron Microscope coupled with an Energy Dispersive X-ray microanalysis system (SEM-EDS) enabled a representative overview of the mineral diversity and showed that the analysed Psammophaga zirconia sp. nov. individuals contained dominantly crystals of zircon (51%), titanium oxides (27%), and ilmenite (11%) along with minor magnetite and other minerals. The studied specimens occur in the shallow central Adriatic Sea where the sediment has a content of zircon below 1% and of other heavy minerals below 4%. For that reason, we suggest that: (i) P. zirconia may be able to chemically select minerals, specifically zircon and rutile; (ii) the chemical mechanism allowing the selection is based on electrostatic interaction, and it could work also for agglutinated foraminifera. In particular, this aptitude for high preferential uptake and differential ingestion or retention of zircon is reported here for the first time, together with the selection of other heavy minerals already described in members of the genus Psammophaga. They are generally counted among early foraminifera, constructing a morphologically simple test with a single chamber. Our molecular phylogenetic study confirms that P. zirconia is a new species, genetically distinctive from other Psammophaga, and occurs in the Adriatic as well as in the Black Sea. Finally, the presence of eukaryotic soft-walled monothalamous microfossils, capable of building a fine aluminosilicate case, in the Precambrian geological record, makes them useful as a valuable record

  1. Oxygen fugacity and porphyry mineralization: A zircon perspective of Dexing porphyry Cu deposit, China

    Science.gov (United States)

    Zhang, Chan-chan; Sun, Wei-dong; Wang, Jin-tuan; Zhang, Li-peng; Sun, Sai-jun; Wu, Kai

    2017-06-01

    Oxygen fugacity (fO2) is a key factor that controls the formation of porphyry Cu deposits. Porphyry Cu deposits are typically oxidized, but when and how porphyry magmas gain their high oxygen fugacity signatures, and how oxygen fugacity controls porphyry mineralization, remains obscure. To trace the origin of the high oxygen fugacity in porphyry Cu deposits, we determined trace element compositions and U-Pb ages of magmatic and inherited zircon from Dexing porphyry Cu deposit, calculated Ce4+/Ce3+ of zircons and estimated the oxygen fugacity of their parental magmas. The Ce4+/Ce3+ ratios of Middle Jurassic (∼170 Ma) magmatic zircons are high (550 on average), whereas the Ce4+/Ce3+ ratios of inherited zircons (200-880 Ma) are much lower (263 on average). The relationship suggests that the Dexing porphyry magma was highly oxidized when the Jurassic magmatic zircons crystallized (estimated fO2: ΔFMQ + 0.7 (±1.3) - ΔFMQ + 1.9 (±1.3)), which cannot be attributed to partial melting of the Neoproterozoic arc crust (estimated fO2: ΔFMQ - 2.4 (±1.1) - ΔFMQ + 0.7 (±1.2)) as proposed previously. Instead, the high fO2 (ΔFMQ + 1.5) of these magmas is a primary feature of the latest magmatism. Sulfate rather than sulfide is the dominant species at fO2 > ΔFMQ + 1.5. In general, the behavior of Cu and other chalcophile elements is controlled by sulfide, while the sulfur speciation is controlled by oxygen fugacity. Previous modeling results show that partial melting of mantle peridotite under high oxygen fugacity (even at >ΔFMQ + 1.5) cannot form Cu-rich magmas, which plausibly explains the lack of porphyry Cu deposits in normal arc rocks. This is because mantle peridotite has low Cu and S contents. Our modeling shows that partial melting of subducted oceanic crust, under oxygen fugacities higher than ΔFMQ + 1.5, is favorable for producing primary magmas with Cu contents sufficiently high for porphyry mineralization, which plausibly explains the close relationship

  2. Geochemistry and Temperatures Recorded by Zircon During the Final Stages of the Youngest Toba Tuff Magma Chamber, Sumatra, Indonesia

    Science.gov (United States)

    Gaither, T.; Reid, M. R.; Vazquez, J. A.

    2009-12-01

    The ~74 ka eruption of the Youngest Toba Tuff (YTT) in Sumatra, Indonesia, was one of the largest single volcanic eruptions in geologic history, on par with other voluminous silicic eruptions such as the Huckleberry Ridge Tuff of Yellowstone and the Bishop Tuff of Long Valley, California. We are exploring how zircon and other accessory mineral phases record compositional and thermal changes that occurred in the YTT magma, and the important clues these crystal scale records hold for magma chamber dynamics and processes that lead up to supervolcano eruptions. In this study, we report trace element (REE, U, Th, Ti, and Hf) characteristics, Ti-in-zircon crystallization temperatures, and apparent REE partition coefficients obtained for YTT zircon rims. Twenty-nine zircons from pumices with a compositional range of 70-76 wt% SiO2 were analyzed on the UCLA Cameca ims 1270 ion microprobe. The grains were mounted so that only the outermost ~1.5 microns of the crystals were analyzed. Median Zr/Hf ratios of 34 to 38 characterize zircons from the pumices; the high silica rhyolite grains have lower Zr/Hf. Chondrite-normalized REE patterns are strongly LREE-depleted. Positive Ce anomalies are large (Ce/Ce* ranges up to 88) and Eu/Eu* varies by a factor of four (0.05 to 0.21). Eu/Eu*, Nd/Yb, and Th/U decrease with decreasing Zr/Hf, showing that the variation in zircon rim compositions may be related by co-precipitation of feldspar and allanite along with zircon. Titanium contents also decrease with decreasing Zr/Hf, suggesting that the chemical differences could be related to temperature changes. REE partition coefficients calculated from zircon rim compositions and pumice glass compositions give a good fit to a lattice strain model. They are also quite similar to the partition coefficients of Sano et al. (2002) which have been shown to be successful at reproducing melt compositions in other settings. Temperatures of crystallization calculated using the Ti-in-zircon

  3. Provenance and age delimitation of Quadrilátero Ferrífero sandstones based on zircon U Pb isotopes

    Science.gov (United States)

    Hartmann, Léo A.; Endo, Issamu; Suita, Marcos Tadeu F.; Santos, João Orestes S.; Frantz, José Carlos; Carneiro, Maurício A.; McNaughton, Neal J.; Barley, Mark E.

    2006-03-01

    The Quadrilátero Ferrífero has some of the largest iron and gold deposits in the world and is a major geotectonic unit of the São Francisco Craton in Brazil. U-Pb zircon SHRIMP geochronology of six detrital sedimentary and metasedimentary rocks (114 zircon crystals, 118 spot analyses) has improved the understanding of the sedimentary processes and provenance ages of both rocks and the associated iron formation. The age of deposition of the iron formation is constrained between 2.58 and 2.42 Ga. The presence of an old Paleoarchean crust is dated in detrital zircon crystals, including the oldest zircon in South America (3809±3 Ma). Only high-Th/U, magmatic zircon crystals are present in the dated sedimentary rocks, and these indicate that the crust of the region was formed mostly during the Jequié cycle (six age peaks between 3055 and 2635 Ma). This time span of ˜420 m.y. is similar to the duration of a long-lived Wilson cycle. Most of the Rio das Velhas Basin was filled during approximately 30 m.y. between 2746 and 2717 Ma, though volcanism probably started earlier. The youngest detrital zircon age from the Minas Supergroup indicates that the intracratonic basin fill, including the iron formation, was deposited after 2580 Ma. Therefore, the crust was cratonized shortly after the intrusion of minor granitic bodies at around 2.62-2.58 Ga. A large gap in orogenic activity is indicated by the absence of zircon ages of 2580-2182 Ma.

  4. Localized rejuvenation of a crystal mush recorded in zircon temporal and compositional variation at the Lassen Volcanic Center, northern California.

    Directory of Open Access Journals (Sweden)

    Erik W Klemetti

    Full Text Available Zircon ages and trace element compositions from recent silicic eruptions in the Lassen Volcanic Center (LVC allow for an evaluation of the timing and conditions of rejuvenation (reheating and mobilization of crystals within the LVC magmatic system. The LVC is the southernmost active Cascade volcano and, prior to the 1980 eruption of Mount St. Helens, was the site of the only eruption in the Cascade arc during the last century. The three most recent silicic eruptions from the LVC were very small to moderate-sized lava flows and domes of dacite (1915 and 27 ka eruptions of Lassen Peak and rhyodacite (1.1 ka eruption of Chaos Crags. These eruptions produced mixed and mingled lavas that contain a diverse crystal cargo, including zircon. 238U-230Th model ages from interior and surface analyses of zircon reveal ages from ∼17 ka to secular equilibrium (>350 ka, with most zircon crystallizing during a period between ∼60-200 ka. These data support a model for localized rejuvenation of crystal mush beneath the LVC. This crystal mush evidently is the remnant of magmatism that ended ∼190 ka. Most zircon are thought to have been captured from "cold storage" in the crystal mush (670-725°C, Hf >10,000 ppm, Eu/Eu* 0.25-0.4 locally remobilized by intrusion of mafic magma. A smaller population of zircon (>730°C, Hf 0.4 grew in, and are captured from, rejuvenation zones. These data suggest the dominant method to produce eruptible melt within the LVC is small-scale, local rejuvenation of the crystal mush accompanied by magma mixing and mingling. Based on zircon stability, the time required to heat, erupt and then cool to background conditions is relatively short, lasting a maximum of 10 s-1000 s years. Rejuvenation events in the LVC are ephemeral and permit eruption within an otherwise waning and cooling magmatic body.

  5. Zircon Geochronology (U-Pb, Petrography, Geochemistry and Radioisotopes of Bornaward Metarhyolites (Central Taknar Zone-Northwest of Bardaskan

    Directory of Open Access Journals (Sweden)

    Reza Monazzami Bagherzadeh

    2016-07-01

    Full Text Available Introduction The Bornaward area is located in the Northeastern Iran (in the Khorasan Razavi province 28 km northwest of the city of Bardaskan at 57˚ 46΄ to 57˚ 52΄ N latitude and 35˚ 21΄ to 35˚ 24΄E longitude. The Taknar structural zone, situated in the North central Iranian micro continent, is part of the Lut block (Forster, 1978. The Taknar zone is an allochthonous block bounded by the Darouneh and Taknar major faults. Much of this zone consists of metarhyolite-rhyodacite volcanic rocks, and rhyolitic tuff with interlayers of sandstone and dolomite (Taknar Formation. Analytical Results ICP-MS analysis of REE and minor elements of samples of the Bornaward metarhyolites was carried out at the ACME Laboratory in Vancouver, Canada. U-Pb dating of the metarhyolites was performed on isolated zircons in Crohn's Laser Lab, in Arizona (Gehrels et al., 2008. Measurement of Rb, Sr, Sm and Nd isotopes and (143Nd/144Ndi and (87Sr/86Sri ratios took place in the radioisotope laboratory of the University of Aveiro in Portugal. Petrography The volcanic rocks are porphyritic, commonly containing phenocrysts of orthoclase and rarely sanidine, quartz and intermediate plagioclase in a groundmass of fine-grained quartz and feldspar. An alteration has produced oriented needles of sericite and clay minerals, clusters of fine-grained green biotite and clots of epidote and chlorite. Geochemistry The compositions of the volcanic rocks are calc alkaline and high K- calc alkaline. The obtained Shand index (Al2O3/( CaO+Na2O+K2O is above 1.1, in the peraluminous S-type granite field (Chappell and White, 2001. Plotted on the TAS diagram (Middlemost, 1994, all the metarhyolite-rhyodacite samples are located in the sub-alkaline field and the majority fall into the rhyolite group. The metarhyolite-rhyodacites show enrichment of LREE with a moderately ascending pattern ((La/YbN=2.51-10.11 and La=46.45-145.48. Europium shows a negative anomaly (Eu/Eu*=0.23-0.71. U

  6. Petrology and zircon U-Pb geochronology of metamorphic massifs around the middle segment of the Tan-Lu fault to define the boundary between the North and South China blocks

    Science.gov (United States)

    Shi, Yonghong

    2017-06-01

    The Tan-Lu fault (TLF) is a significant linear structure of eastern China. The middle segment of the TLF in the northern Anhui Province separates the North China Block (NCB) and South China Block (SCB). Lack of geological work makes the plate boundary here ambiguous. Detailed field survey and laboratory analyses have been conducted to constrain the formation and evolution of the TLF. To the west of the TLF, the Wuhe massif underwent a granulite facies metamorphism with T = 778-836 °C, P = 1.0-1.2 GPa during 2.41-2.43 Ga according to LA-ICP-MS U-Pb zircon dating. On the contrary, to the east of the TLF, the Zhangbaling massif suffered a greenschist to lower amphibolite facies metamorphism with the average metamorphic temperature at around 340-440 °C, with the protolith igneous ages of ca. 750 Ma. These differences indicate that the two massifs belong to the different blocks. Furthermore, the granitic gneiss in the central part of TLF gives three populations of zircon U-Pb age at 667-504 Ma, 228 ± 2 Ma and 211 ± 2 Ma, respectively. The later two groups of spectra correspond to the periods of subduction and exhumation of the Dabie massif (245-200 Ma). Combined with previous study, the precise plate boundary between NCB and SCB has been delineated as the Zhuding-Shimenshan fault, and the initial time of the motion for the TLF is also discussed.

  7. Stratigraphy, tectonics and detrital zircon U-Pb (LA-ICP-MS) geochronology of the Rio Preto Belt and northern Paramirim corridor, NE, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Alcantara, Davi da Costa Bezerra Gobira de; Uhlein, Alexandre; Caxito, Fabricio de Andrade; Pedrosa-Soares, Antonio Carlos, E-mail: davibgobira@hotmail.com, E-mail: auhlein@gmail.com, E-mail: facaxito@yahoo.com.br, E-mail: pedrosasoares@gmail.com [Universidade Federal de Minas Gerais (CPMTC/UFMG), Belo Horizonte, MG (Brazil). Instituto de Geociencias. Centro de Pesquisa Professor Manoel Teixeira da Costa; Dussin, Ivo, E-mail: ivodusin@yahoo.com.br [Universidade Estadual do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Faculdade de Geologia

    2017-04-15

    Two important Proterozoic metasedimentary sequences, the Rio Preto and Santo Onofre Groups, crop out along the northwestern margin of the Sao Francisco craton and in northern Paramirim corridor, respectively. The Rio Preto Group, involved in the eponymous fold-thrust belt along the northwestern cratonic boundary, comprises the Formosa (garnet schist, quartz schist, quartzite, chlorite-sericite schist and ferriferrous quartz schist) and Canabravinha (quartzite, micaceous quartzite, metarhytmite, phylite, schist and metaturbidite) formations. The Santo Onofre Group occurs exclusively in the Paramirim corridor, and is composed of quartzite and minor carbonaceous or Mn-rich phylite. These units record sedimentation in shallow to deep-water marine settings related to rift basins, and were deformed and metamorphosed under green schist facies conditions during the Brasiliano orogeny. Here we present 427 new detrital zircon U-Pb ages, which constrain the maximum depositional ages of ca. 971 Ma for the Santo Onofre Group, ca. 912 Ma for the Canabravinha Formation, and ca. 65 Ma for the Formosa Formation of the Rio Preto Group. Our data suggests that the Santo Onofre and the Rio Preto Groups accumulated in two distinct basin settings. The latter, composed mostly of sandy rocks, would represent a relatively stable, shallow-marine shelf environment. The Rio Preto Group, with metadiamictite, quartzite, pelitic and rhythmitic rocks, represents a shallow to deep marine environment influenced by gravity flows. Both groups were probably deposited in the Late Tonian, and are potential correlatives of the lower (pre-glacial) units of the Macaubas Group of the Aracuai belt. (author)

  8. Protoliths of enigmatic Archaean gneisses established from zircon inclusion studies: Case study of the Caozhuang quartzite, E. Hebei, China

    Directory of Open Access Journals (Sweden)

    Allen P. Nutman

    2014-07-01

    Full Text Available A diverse suite of Archaean gneisses at Huangbaiyu village in the North China Craton, includes rare fuchsite-bearing (Cr-muscovite siliceous rocks – known as the Caozhuang quartzite. The Caozhuang quartzite is strongly deformed and locally mylonitic, with silica penetration and pegmatite veining common. It contains abundant 3880–3600 Ma and some Palaeoarchaean zircons. Because of its siliceous nature, the presence of fuchsite and its complex zircon age distribution, it has until now been accepted as a (mature quartzite. However, the Caozhuang quartzite sample studied here is feldspathic. The shape and cathodoluminescence petrography of the Caozhuang quartzite zircons show they resemble those found in immature detrital sedimentary rocks of local provenance or in Eoarchaean polyphase orthogneisses, and not those in mature quartzites. The Caozhuang quartzite intra-zircon mineral inclusions are dominated by quartz, with lesser biotite, apatite (7% and alkali-feldspar, and most inclusions are morphologically simple. A Neoarchaean orthogneiss from near Huangbaiyu displays morphologically simple inclusions with much more apatite (73%, as is typical for fresh calc-alkaline granitoids elsewhere. Zircons were also examined from a mature conglomerate quartzite clast and an immature feldspathic sandstone of the overlying weakly metamorphosed Mesoproterozoic Changcheng System. These zircons have oscillatory zoning, showing they were sourced from igneous rocks. The quartzite clast zircons contain only rare apatite inclusions (<1%, with domains with apatite habit now occupied by intergrowths of muscovite + quartz ± Fe-oxides ± baddeleyite. We interpret that these were once voids after apatite inclusions that had dissolved during Mesoproterozoic weathering, which were then filled with clays ± silica and then weakly metamorphosed. Zircons in the immature feldspathic sandstone show a greater amount of preserved apatite (11%, but with petrographic

  9. Sources and assembly of diverse rhyolitic magmas in a hotspot environment inferred from microanalysis of zircon isotopes

    Science.gov (United States)

    Colon, D.; Bindeman, I. N.; Christiansen, E. H.; Stern, R. A.; Wotzlaw, J. F.

    2016-12-01

    We present new, extremely diverse O and Hf isotope measurements from zircons from four rhyolitic tuffs from the Bruneau-Jarbidge center and one tuff and three lavas from the Kimberly drill core in the Twin Falls center on the Yellowstone hotspot track. O isotopes were measured in zircon cores and rims by SIMS, Hf isotopes were measured in nearby spots by LA-ICP-MS, and U-Pb ages were also measured via ICP-MS to eliminate inherited grains. We found considerable inter- and intra-crystal diversity in both O and Hf isotopes in all eruptive units. Zircon δ18O values range from -2.4‰ to 4.7‰ among the Bruneau-Jarbidge tuffs, and range from -1.3‰ to 4.9‰ in the Kimberly rhyolites. Similar variations in ɛHf values were found, ranging from -13 to 0 at Bruneau Jarbidge, and from -24 to +7 at Kimberly. Intra-grain variability was similarly extreme, with core-rim differences of up to 5.7‰ in δ18O and 14 ɛHf units at Bruneau-Jarbidge and Twin Falls, respectively. In some of the studied eruptive units, most notably Cougar Point Tuff V from Bruneau-Jarbidge, zircon cores are significantly more diverse in both δ18O and ɛhf than the rims, suggesting that the eruption of the final magma was preceded by a batch assembly process that was followed by overgrowth of zircon rims which reflect the final melt composition. This final homogenized composition matches δ18O inferred from major phenocrysts. The zircon cores, therefore, provide a unique opportunity to infer the sources of the crust and mantle-derived melts that contributed to the final erupted rhyolite. At both volcanic centers, the oldest studied rhyolite, including a newly-discovered 14.8 Ma old unit underlying the Cougar Point Tuff sequence, has zircons with the most diverse ɛHf values, and contains the only very low-ɛHf­ zircons in the case of Twin Falls. This suggests evolution of the magma bodies over time, becoming diluted by continued mixing and input of mantle-derived melts. Additionally, there is a

  10. The provenance and internal structure of the Cycladic Blueschist Unit revealed by detrital zircon geochronology, Western Cyclades, Greece

    Science.gov (United States)

    Seman, S.; Stockli, D. F.; Soukis, K.

    2017-07-01

    This study presents detrital zircon U-Pb analyses of 23 samples of the Cycladic Blueschist Unit (CBU) from Kea, Kythnos, and Serifos islands, as well as the Lavrion Peninsula of SE Attica. The maximum depositional ages (MDA) and age distributions of detrital zircon U-Pb dates are used to correlate metasediments between the islands considered herein and infer their provenance. Two distinct detrital zircon U-Pb age distributions are found in CBU metasediments: "Proterozoic," comprised of >40% Neoproterozoic zircons with Triassic-Early Jurassic maximum depositional ages and "Paleozoic," containing >30% Paleozoic zircons and yielding Late Jurassic-Cretaceous MDAs. Proterozoic affinity metasediments are rift margin deposits derived from the northern Gondwanan margin. Paleozoic metasediments are flysch sediments most probably sourced from the Internal Hellenides. This metamorphosed flysch forms a distinct marker horizon found in a similar structural position in Lavrion, Kythnos, and Serifos. Based on lithologic correlation, sediment provenance, and MDA estimates, the CBU of Kythnos is correlative to the Lavrion Schists of Attica. On the islands of Serifos and Kythnos and within the Lavrion Schists only young-on-old relationships exist between rocks based on MDA estimates.

  11. Characteristics of zircons from volcanic ash-derived tonsteins in Late Permian coal fields of eastern Yunnan, China

    Science.gov (United States)

    Zhou, Y.; Ren, Y.; Tang, D.; Bohor, B.

    1994-01-01

    Kaolinitic tonsteins of altered synsedimentary volcanic ash-fall origin are well developed in the Late Permian coal-bearing formations of eastern Yunnan Province. Because of their unique origin, wide lateral extent, relatively constant thickness and sharp contacts with enclosing strata, great importance has been attached to these isochronous petrographic markers. In order to compare tonsteins with co-existing, non-cineritic claystones and characterize the individuality of tonsteins from different horizons for coal bed correlation, a semi-quantitative method was developed that is based on statistical analyses of the concentration and morphology of zircons and their spatial distribution patterns. This zircon-based analytical method also serves as a means for reconstructing volcanic ash-fall dispersal patterns. The results demonstrate that zircons from claystones of two different origins (i.e., tonstein and non-cineritic claystone) differ greatly in their relative abundances, crystal morphologies and spatial distribution patterns. Tonsteins from the same area but from different horizons are characterized by their own unique statistical patterns in terms of zircon concentration values and morphologic parameters (crystal length, width and the ratio of these values), thus facilitating stratigraphic correlation. Zircons from the same tonstein horizon also show continuous variation in these statistical patterns as a function of areal distribution, making it possible to identify the main path and direction in which the volcanic source materials were transported by prevailing winds. ?? 1994.

  12. Seeing is believing: Visualization of He distribution in zircon and implications for thermal history reconstruction on single crystals.

    Science.gov (United States)

    Danišík, Martin; McInnes, Brent I A; Kirkland, Christopher L; McDonald, Brad J; Evans, Noreen J; Becker, Thomas

    2017-02-01

    Zircon (U-Th)/He thermochronometry is an established radiometric dating technique used to place temporal constraints on a range of thermally sensitive geological events, such as crustal exhumation, volcanism, meteorite impact, and ore genesis. Isotopic, crystallographic, and/or mineralogical heterogeneities within analyzed grains can result in dispersed or anomalous (U-Th)/He ages. Understanding the effect of these grain-scale phenomena on the distribution of He in analyzed minerals should lead to improvements in data interpretation. We combine laser ablation microsampling and noble gas and trace element mass spectrometry to provide the first two-dimensional, grain-scale zircon He "maps" and quantify intragrain He distribution. These maps illustrate the complexity of intracrystalline He distribution in natural zircon and, combined with a correlated quantification of parent nuclide (U and Th) distribution, provide an opportunity to assess a number of crystal chemistry processes that can generate anomalous zircon (U-Th)/He ages. The technique provides new insights into fluid inclusions as potential traps of radiogenic He and confirms the effect of heterogeneity in parent-daughter isotope abundances and metamictization on (U-Th)/He systematics. Finally, we present a new inversion method where the He, U, and Th mapping data can be used to constrain the high- and low-temperature history of a single zircon crystal.

  13. Biomarker CA125

    DEFF Research Database (Denmark)

    Kargo, Anette Stolberg

    Background: The majority of patients with ovarian cancer (OC) are diagnosed with advanced disease (70-80 %) and will experience disease relapse with only limited curative potential. Early initiation of relapse treatment based on rising CA125 alone does not improve survival. Increasing CA125 can...... be detected months before symptoms arise and recurrence is visible on imaging. Therefore, biochemical detection of potential relapse by CA125 assessment can cause significant distress. A decision aid (DA) is a tool that provides information and describes advantages and disadvantages of a specific intervention...... patient organisations and cancer societies. First, a focus group of seven former OC patients was performed followed by a quantitative rating of the DA pilot version. The DA was adapted accordingly and then tested in 14 OC patients with recurrence using a structured interview guide (alpha testing). A final...

  14. Chemical characterisation of zircon-cadmium sulfoselenide ceramic pigments; Caracterizacion quimica de pigmentos ceramicos a base de sulfoseleniuro de cadmio

    Energy Technology Data Exchange (ETDEWEB)

    Gazulla Barreda, M. F.; Rodrigo Edo, M.; Blasco Roca, E.; Orduna Cordero, M.

    2013-07-01

    The present paper addresses the development of a methodology that allows the complete chemical characterisation of zircon cadmium sulfoselenide ceramic pigments including minor and major elements. To develop the methodology, five zircon-cadmium sulfoselenide pigments with different hues were selected, studying the different measurement process steps, from sample preparation to the optimisation of the measurement of the different components of the pigments by spectroscopic techniques (WD-XRF and elemental analysis by combustion and IR detection). The chemical characterisation method developed was validated with synthetic standards prepared from the mixture of certified reference materials and pure oxides because no certified referenced materials of this type of pigments were commercially available. The developed method can be used for a complete chemical characterization of zircon-cadmium sulfoselenide ceramic pigments with a very low uncertainty for all the elements analysed. (Author)

  15. EFFECT OF FLUORINE AND CHLORINE IONS ON THE REACTION SINTERING OF MECHANICALLY ACTIVATED ZIRCON-ALUMINA MIXTURE

    Directory of Open Access Journals (Sweden)

    R. Zamani Foroshani

    2015-09-01

    Full Text Available The aim of this work was to study the effect of fluorine and chlorine ions on the formation of mullite during the reaction sintering of mechanically activated zircon-alumina powder mixture. The results showed that mechanical activation of zirconalumina powder mixture for 20 h led to grain refinement and partial amorphization. In the presence of fluorine and chlorine ions, complete formation of mullite in the mechanically activated sample occurred after 2 h of reaction sintering at 1300oC and 1400oC, respectively. In the sample lacking fluorine and chlorine ions, mullitization was not completed even after 2 h of reaction sintering at 1400oC. It was concluded that presence of fluorine and chlorine ions enhance the dissociation of zircon and formation of mullite during the reaction sintering of mechanically activated zircon-alumina mixture.

  16. Cenozoic foreland basins of Central Andes: a preliminary provenance U-Pb zircon analysis of sedimentary sequences of Calchaqui Valley

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Alisson Lopes; Hauser, Natalia; Pimentel, Marcio Martins; Matteini, Massimo, E-mail: alisson_oliveira@hotmail.com [Universidade de Brasilia (UnB), DF (Brazil). Laboratorio de Geocronologia; Galli, Claudia Ines [Faculdad de Ingenieria, Universidad Nacional de Jujuy (Argentina); Coira, Beatriz [CIT Jujuy, CONICET. Instituto de Geologia y Mineria (Argentina); Alonso, Ricardo; Barrientos, Andrea [Instituto CEGA, CONICET. Universidad Nacional de Salta (Argentina)

    2015-07-01

    The Eocene of northwestern Argentina records complex basin and structural evolution, including continental sedimentation of the post-rift Salta Basin and the beginning of the Andean uplift and foreland system evolution. This illuminates a significant period of evolutionary history of this and surrounding basins in northwestern Argentina. U-Pb zircon analyses by LA-ICP-MS for three formations representing post-rift to foreland stages allowed interpretation about provenance terrains. The Lumbrera Formation, representing the post-rift stage, shows bimodal sources with a main zircon population around 462 Ma, and a second population around 1023 Ma. The Los Colorados and Angastaco Formations representing the sedimentation in a foreland basin, show a unimodal source around 490 Ma, and 517 Ma respectively. Zircons younger than 50 Ma were not identified during this study. (author)

  17. Chemical homogeneity effects on the nonlinear dielectric response of lead zirconate titanate thin films

    Science.gov (United States)

    Ihlefeld, Jon F.; Shelton, Christopher T.

    2012-07-01

    Rayleigh analysis has been used to investigate dielectric nonlinearity in polycrystalline lead zirconate titanate thin films that possess a chemically homogeneous B-site and those with titanium/zirconium gradients through the film thickness. Chemically homogeneous films possess greater irreversible and reversible contributions and greater ratios of irreversible to reversible contributions to dielectric nonlinearity than chemically heterogeneous films. These measurements demonstrate that the ferroelectric performance improvements observed in chemically homogeneous Pb(Zr,Ti)O3 thin films, with compositions near the morphotropic phase boundary, are associated with enhanced extrinsic contributions owing to improved domain wall mobility.

  18. Ferroelectric response from lead zirconate titanate thin films prepared directly on low-resistivity copper substrates

    Science.gov (United States)

    Losego, Mark D.; Jimison, Leslie H.; Ihlefeld, Jon F.; Maria, Jon-Paul

    2005-04-01

    We demonstrate films of the well-known ferroelectric lead zirconate titanate (PZT) prepared directly on copper foils by chemical solution deposition (CSD). The films exhibit saturating polarization hysteresis, remanent polarization values of 26μC/cm2, and permittivities of 800; these properties are comparable to those achieved using semiconductor-grade substrates. The preparation methodology is founded upon an understanding of solution chemistry as opposed to conventional gas-phase / condensed-phase equilibrium approaches. By adopting this technique, base-metal compatibility can be achieved using much lower temperatures, and a broader set of devices can be prepared offering intimate contact with high conductivity, easily patternable, or ferromagnetic metals.

  19. The pre-orogenic detrital zircon record of the Variscan orogeny: Preliminary results

    Science.gov (United States)

    Stephan, Tobias; Kroner, Uwe

    2017-04-01

    To test plate-tectonic constellations in consideration of the long-term development of sedimentary transport paths, temporally and spatially highly resolved records of provenance analysis are mandatory. The interpretation of existing studies focus on small-scale areas within an orogen thereby neglecting the differing distribution of provenance data in the entire orogenic system. This study reviews a large data set of compiled geochronological data to document the development of pre-orogenic tectonic units on the example of the Variscan orogeny. Constrained by tectonic and geological models, the temporal distribution of U-Pb detrital zircon ages, used as a proxy for sedimentary provenance, shows that some minima and maxima of zircon abundance are nearly synchronous for thousands of kilometres along the orogeny. Age spectra of Precambrian to Lower Palaeozoic samples were constructed on the basis of 38729 U-Pb ages from 685 samples that were compiled from 102 publications. The age compilation combines thermal ionization mass spectrometry (TIMS), laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS), sensitive high-resolution ion microprobe (SHRIMP), and secondary ion mass spectrometry (SIMS) analyses. The data was re-processed using a common age calculation and concordance filter to ensure comparability. The concordance of each zircon grain was calculated from 206Pb/238U and 207Pb/235U ages to guarantee that only concordant grains, i.e., with 3) is used for the maximum age of deposition. In addition to the location of >600 samples, the precise depositional ages result in a spatially and temporally high resolution. To avoid the different levels of analytical precision of the compiled TIMS, LA-ICP-MS, SHRIMP, and SIMS data, detrital zircon ages are plotted as kernel density estimates. Spatial and temporal distribution of the kernel density estimates, as well as further statistical techniques (e.g. multidimensional scaling) are used to discriminate

  20. Tracing the depositional history of Kalimantan diamonds by zircon provenance and diamond morphology studies

    Science.gov (United States)

    Kueter, Nico; Soesilo, Joko; Fedortchouk, Yana; Nestola, Fabrizio; Belluco, Lorenzo; Troch, Juliana; Wälle, Markus; Guillong, Marcel; Von Quadt, Albrecht; Driesner, Thomas

    2016-11-01

    Diamonds in alluvial deposits in Southeast Asia are not accompanied by indicator minerals suggesting primary kimberlite or lamproite sources. The Meratus Mountains in Southeast Borneo (Province Kalimantan Selatan, Indonesia) provide the largest known deposit of these so-called ;headless; diamond deposits. Proposals for the origin of Kalimantan diamonds include the adjacent Meratus ophiolite complex, ultra-high pressure (UHP) metamorphic terranes, obducted subcontinental lithospheric mantle and undiscovered kimberlite-type sources. Here we report results from detailed sediment provenance analysis of diamond-bearing Quaternary river channel material and from representative outcrops of the oldest known formations within the Alino Group, including the diamond-bearing Campanian-Maastrichtian Manunggul Formation. Optical examination of surfaces of diamonds collected from artisanal miners in the Meratus area (247 stones) and in West Borneo (Sanggau Area, Province Kalimantan Barat; 85 stones) points toward a classical kimberlite-type source for the majority of these diamonds. Some of the diamonds host mineral inclusions suitable for deep single-crystal X-ray diffraction investigation. We determined the depth of formation of two olivines, one coesite and one peridotitic garnet inclusion. Pressure of formation estimates for the peridotitic garnet at independently derived temperatures of 930-1250 °C are between 4.8 and 6.0 GPa. Sediment provenance analysis includes petrography coupled to analyses of detrital garnet and glaucophane. The compositions of these key minerals do not indicate kimberlite-derived material. By analyzing almost 1400 zircons for trace element concentrations with laser ablation ICP-MS (LA-ICP-MS) we tested the mineral's potential as an alternative kimberlite indicator. The screening ultimately resulted in a small subset of ten zircons with a kimberlitic affinity. Subsequent U-Pb dating resulting in Cretaceous ages plus a detailed chemical reflection make

  1. The formation of Luoboling porphyry Cu-Mo deposit: Constraints from zircon and apatite

    Science.gov (United States)

    Li, Cong-ying; Hao, Xi-luo; Liu, Ji-qiang; Ling, Ming-xing; Ding, Xing; Zhang, Hong; Sun, Wei-dong

    2017-02-01

    The Luobuling porphyry Cu-Mo deposit belongs to the Late Cretaceous Zijinshan Cu-Au-Mo mineralization field in southeastern China. Due to intensive hydrothermal alteration and weathering, it is very difficult to collect fresh whole rock samples for geochemical and isotopic studies in Luobuling. Zircon and apatite are accessory minerals that are resistant to hydrothermal alterations. In this study, we compared the trace element and isotope compositions of zircon and apatite from ore-bearing and barren samples to understand the formation of the Luoboling Cu-Mo deposit. Zircon U-Pb LA-ICP-MS dating shows that the Luoboling porphyries formed at 100 Ma (100.3 ± 1.2 Ma, 100.6 ± 1.5 Ma and 98.6 ± 1.2 Ma), which belongs to the late stage mineralization of the Zijinshan mineralization field. Zhongliao porphyritic granodiorite has the same age as the deposit (99.5 ± 1.6 Ma). The age of barren Sifang granodiorite is slightly older (109.7 ± 0.8 Ma). All these zircon grains have high Ce4+/Ce3+ ratios, indicating high oxygen fugacities. The ore-bearing samples show variable εHf(t) of - 7.3 to 0.2, suggesting either heterogeneous sources or mixing of two different magmas. Interestingly, the Hf isotope composition of barren samples is systematically higher (εHf(t) of - 3.6 to 5.5), implying a lower contribution of crustal materials. The OH mole percent of apatite grains from barren samples (LBL22-03 and SF09-05) is 0.5, which is higher than that of apatite from the ore-bearing samples (LBL20-01 LBL20-02 and LBL22-02), indicating lower F, Cl contents or higher water contents in the magma. In apatite from the ore-bearing samples, Sr is high, indicating the absence of plagioclase crystallization. In contrast, barren samples have varied and lower Sr, indicating that apatite crystallization was accompanied by plagioclase. These patterns were controlled by water contents because the crystallization of plagioclase is suppressed by high water contents in magmas. It also suggests

  2. Stability of Zircon U-Pb Systematics in a Greenschist-Grade Mylonite: An Example from the Rockfish Valley Fault Zone, Central Virginia, USA

    National Research Council Canada - National Science Library

    David M. Wayne; A. Krishna Sinha

    1992-01-01

    ... (with alternating U-Hf-rich and U-Hf-poor bands), and contain numerous radial microcracks. Zircons from the RVFZ mylonite are unzoned, fragmented, show no internal microfractures, and have low U and Hf concentrations relative to the PRCS zircons...

  3. Stability of zircon U-Pb systematics in a greenschist-grade mylonite: An example from the Rockfish Valley Fault Zone, central Virginia, USA

    National Research Council Canada - National Science Library

    Wayne, D.M; Sinha, A.K. (Virginia Tech, Blacksburg

    1992-01-01

    ... (with alternating U-Hf-rich and U-Hf-poor bands), and contain numerous radial microcracks. Zircons from the RVFZ mylonite are unzoned, fragmented, show no internal microfractures, and have low U and Hf concentrations relative to the PRCS zircons...

  4. Synthesis, microstructural and mechanical properties of ex situ zircon particles (ZrSiO4 reinforced Metal Matrix Composites (MMCs: a review

    Directory of Open Access Journals (Sweden)

    Satish Kumar Thandalam

    2015-07-01

    This review article details the current development on the synthesis, microstructure and mechanical properties of zircon reinforced MMCs, with specific attention on the abrasive wear behavior of the composites. This review also summarizes the work done by various research groups on zircon reinforced MMCs in achieving higher hardness and wear resistance in these composites.

  5. Topological organization of CA3-to-CA1 excitation.

    Science.gov (United States)

    Hongo, Yoshie; Ogawa, Koichi; Takahara, Yuji; Takasu, Keiko; Royer, Sebastien; Hasegawa, Minoru; Sakaguchi, Gaku; Ikegaya, Yuji

    2015-09-01

    The CA1-projecting axons of CA3 pyramidal cells, called Schaffer collaterals, constitute one of the major information flow routes in the hippocampal formation. Recent anatomical studies have revealed the non-random structural connectivity between CA3 and CA1, but little is known regarding the functional connectivity (i.e. how CA3 network activity is functionally transmitted downstream to the CA1 network). Using functional multi-neuron calcium imaging of rat hippocampal slices, we monitored the spatiotemporal patterns of spontaneous CA3 and CA1 burst activity under pharmacological GABAergic blockade. We found that spatially clustered CA3 activity patterns were transformed into layered CA1 activity sequences. Specifically, synchronized bursts initiated from multiple hot spots in CA3 ensembles, and CA1 neurons located deeper in the pyramidal cell layer were recruited during earlier phases of the burst events. The order of these sequential activations was maintained across the bursts, but the sequence velocity varied depending on the inter-burst intervals. Thus, CA3 axons innervate CA1 neurons in a highly topographical fashion. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  6. Trace element features of hydrothermal and inherited igneous zircon grains in mantle wedge environment: A case study from the Myanmar jadeitite

    Science.gov (United States)

    Lei, Weiyan; Shi, Guanghai; Santosh, M.; Ng, Yinok; Liu, Yingxin; Wang, Jing; Xie, Gen; Ju, Yan

    2016-12-01

    Jadeitites are considered to crystallise in ultramafic rocks in the subduction channel presumably from the overlying mantle wedge, and therefore zircons from these rocks provide important insights into mantle wedge processes. Here we investigate hydrothermal zircon (Group II) formed within a subduction zone and compare these with the igneous zircon cores (Group I) from the Myanmar jadeitite. Previous U-Pb studies reported ages of Groups I and II zircons as 163 Ma, and 147 Ma respectively, and both show isotope signature of the depleted mantle. Group I zircons have much higher total concentrations of rare earth elements (REEs) (500-1945 ppm) than those of Group II zircon (112-307 ppm), and contains relatively higher abundance of Y, Nb, Ta, Ti, Th and U with higher (Sm/La)N ratios (25.3-501) and Ce-anomalies (8.04-140) but lower (Yb/Gd)N ratios (9.76-57.0) than those of the Group II ((Sm/La)N ratios = 2.12-32.2, Ce-anomalies = 1.63-19.6, (Yb/Gd)N ratios = 44.8-142). Hf concentrations are broadly similar in both Groups. The Group I zircons are considered to be magmatic and crystallised from H2O-rich basaltic melt at relatively high pressure in the mantle wedge, whereas the Group II zircon overgrowth took place through recrystallisation and precipitation with distinct dissolution of the Group I zircons. Variation in the concentration of trace elements in zircons from Groups I to II in the mantle wedge is related to an intra-oceanic subduction system in the presence of Na-rich hydrothermal fluids under high-pressure and low-temperature. The Ti-in-zircon thermometer yield a mean crystallisation temperature of 742 ± 141 °C for Group I zircons, whereas the Group II zircons yield 339 ± 33 °C. The two groups of zircons also provide insights into the probable protolith involved in formation of the Myanmar jadeitite.

  7. High-precision U-Pb zircon age from the Anfiteatro de Ticó Formation: Implications for the timing of the early angiosperm diversification in Patagonia

    Science.gov (United States)

    Perez Loinaze, Valeria S.; Vera, Ezequiel I.; Passalia, Mauro G.; Llorens, Magdalena; Friedman, Richard; Limarino, Carlos O.; Césari, Silvia N.

    2013-12-01

    The Baqueró Group is one of the most relevant units regarding the study of the early diversification of angiosperms in South America. Whereas the age of the upper part of the Group, namely the Punta del Barco Formation, has been recently dated at 114.67 ± 0.18 Ma, the rest of the unit still lacks precise dating. In this contribution a CA-TIMS U-Pb zircon age of 118.23 ± 0.09 Ma for a tuff interlayered with fossiliferous rocks of the Anfiteatro de Ticó Formation (lower part of the Baqueró Group) is reported. This age constrains the duration of deposition of the Baqueró Group to approximately 4 Ma and provides new evidence for the age interpretation of the previously described angiosperm flora and associated pollen assemblages from this unit, until now interpreted as early Aptian or possibly Barremian in age. The Aptian age of the Baqueró Group allows a better comparison between the paleofloras from this southernmost region.

  8. Geochemistry and zircon ages of mafic dikes in the South Qinling, central China: evidence for late Neoproterozoic continental rifting in the northern Yangtze block

    Science.gov (United States)

    Zhu, Xiyan; Chen, Fukun; Liu, Bingxiang; Zhang, He; Zhai, Mingguo

    2015-01-01

    Neoproterozoic volcanic-sedimentary sequences of the southern Qinling belt, central China, were intruded by voluminous mafic dikes. secondary ion mass spectrometry zircon U-Pb dating indicates that these dikes were emplaced at 650.8 ± 5.2 Ma, coeval with mafic rocks occurring at the northern margin of the Yangtze block. The dikes are characterized by enrichment of large ion lithophile elements, high Ti contents (up to 3.73 wt%) and Nb/Ta ratios between 14.5 and 19.6, suggesting a mantle source of oceanic island basalt affinity. Initial 87Sr/86Sr ratios show positive correlation with SiO2 contents and negative correlation with Zr/Nb ratios, implying that these rocks were affected by crustal contamination during the magma ascend and emplacement process. The dikes have initial ɛ Nd values of +0.2 to +3.3, low 206Pb/204Pb ratios of 16.96-17.45, and moderate 87Sr/86Sr ratios of 0.7043-0.7076, likely pointing to the involvement of an enriched mantle source. The mafic dikes and coeval mafic volcanic equivalents in the South Qinling and the northern Yangtze are hypothesized to be related with the prolonged breakup of the supercontinent Rodinia, suggesting that continental rifting lasted until ca. 650 Ma.

  9. On the longevity of silicic magma based on multi-isotope investigation of zircons and modeling their survivals destinies

    Science.gov (United States)

    Bindeman, I. N.; Wotzlaw, J. F.; Melnik, O. E.

    2015-12-01

    Large volumes of crystal poor, near-liquidus rhyolites are erupted worldwide as tuffs and lavas in rift and hot spots more common previously on early earth, creating temporally very high magma production rates. In this contribution we combine results of IDTIMS dating of zircons with numerical modeling of zircon crystallization. New investigation of zircons in major Yellowstone tuffs: Huckleberry Ridge (Members A,B,C), Mesa Falls, and Lava Creek (A,B) tuffs was done by a combination of in situ measurements of oxygen isotopes followed by ID-TIMS U-Pb dating, Hf isotopes and trace elemental investigation of single crystals. We discover that nearly all zircons are of eruption age, but display significant isotope (O,Hf) diversity and often show decoupled O and Hf isotope systematics. This record rapid (~103yrs) double or triple remelting and sequestration from diverse Archean crust and hydrothermally altered shallow-crustal rocks from previous eruptive cycles, followed by effective mixing of co-existing magma reservoirs with diverse zircons prior to eruptions. Similar results characterize other studied Snake River Plain rhyolites in pre-Yellowstone Heise complex. These results collectively suggest that zircons crystallize after reheating above saturation rejuvenation in isotopically-diverse areas of the crust in the magma plumbing system. Modeling of zircon and quartz dissolution and crystallization trajectories outline conditions of survival (inheritance) vs complete dissolution on conductive timescales, and when combined with a phase diagram, magma T-t paths can be computed. Zircon rejuvenation requires hot, >770-800°C peak temperatures lasting 10-102yrs. We speculate that near liquidus hot and dry Yellowstone rhyolites are kept alive in a multi-batch state by a series of interconnected pods and sills that can rapidly get thermomechanically assembled into large, shallow and eruptable supervolcanoic magma bodies. We suggest that overpressure and roof dynamics and

  10. New zircon (U-Th)/He and U/Pb eruption age for the Rockland tephra, western USA

    Science.gov (United States)

    Coble, Matthew A.; Burgess, Seth; Klemetti, Erik W.

    2017-01-01

    Eruption ages of a number of prominent Quaternary volcanic deposits remain inaccurately and/or imprecisely constrained, despite their importance as regional stratigraphic markers in paleo-environment reconstruction and as evidence of climate-altering eruptions. Accurately dating volcanic deposits presents challenging analytical considerations, including poor radiogenic yield, scarcity of datable minerals, and contamination of crystal populations by magma, eruption, and transport processes. One prominent example is the Rockland tephra, which erupted from the Lassen Volcanic Center in the southern Cascade arc. Despite a range in published eruption ages from 0.40 to 0.63 Ma, the Rockland tephra is extensively used as a marker bed across the western United States. To more accurately and precisely constrain the age of the Rockland tephra-producing eruption, we report U/Pb crystallization dates from the outermost ∼2 μm of zircon crystal faces (surfaces) using secondary ion mass spectrometry (SIMS). Our new weighted mean 238U/206Pb age for Rockland tephra zircon surfaces is 0.598 ± 0.013 Ma (2σ) and MSWD = 1.11 (mean square weighted deviation). As an independent test of the accuracy of this age, we obtained new (U-Th)/He dates from individual zircon grains from the Rockland tephra, which yielded a weighted mean age of 0.599 ± 0.012 Ma (2σ, MSWD = 5.13). We also obtained a (U-Th)/He age of 0.628 ± 0.014 Ma (MSWD = 1.19) for the Lava Creek Tuff member B, which was analyzed as a secondary standard to test the accuracy of the (U-Th)/He technique for Quaternary tephras, and to evaluate assumptions made in the model-age calculation. Concordance of new U/Pb and (U-Th)/He zircon ages reinforces the accuracy of our preferred Rockland tephra eruption age, and confirms that zircon surface dates sample zircon growth up to the time of eruption. We demonstrate the broad applicability of coupled U/Pb zircon-surface and single-grain zircon (U-Th)/He geochronology to

  11. New zircon (U-Th)/He and U/Pb eruption age for the Rockland tephra, western USA

    Science.gov (United States)

    Coble, Matthew A.; Burgess, Seth D.; Klemetti, Erik W.

    2017-09-01

    Eruption ages of a number of prominent Quaternary volcanic deposits remain inaccurately and/or imprecisely constrained, despite their importance as regional stratigraphic markers in paleo-environment reconstruction and as evidence of climate-altering eruptions. Accurately dating volcanic deposits presents challenging analytical considerations, including poor radiogenic yield, scarcity of datable minerals, and contamination of crystal populations by magma, eruption, and transport processes. One prominent example is the Rockland tephra, which erupted from the Lassen Volcanic Center in the southern Cascade arc. Despite a range in published eruption ages from 0.40 to 0.63 Ma, the Rockland tephra is extensively used as a marker bed across the western United States. To more accurately and precisely constrain the age of the Rockland tephra-producing eruption, we report U/Pb crystallization dates from the outermost ∼2 μm of zircon crystal faces (surfaces) using secondary ion mass spectrometry (SIMS). Our new weighted mean 238U/206Pb age for Rockland tephra zircon surfaces is 0.598 ± 0.013 Ma (2σ) and MSWD = 1.11 (mean square weighted deviation). As an independent test of the accuracy of this age, we obtained new (U-Th)/He dates from individual zircon grains from the Rockland tephra, which yielded a weighted mean age of 0.599 ± 0.012 Ma (2σ, MSWD = 5.13). We also obtained a (U-Th)/He age of 0.628 ± 0.014 Ma (MSWD = 1.19) for the Lava Creek Tuff member B, which was analyzed as a secondary standard to test the accuracy of the (U-Th)/He technique for Quaternary tephras, and to evaluate assumptions made in the model-age calculation. Concordance of new U/Pb and (U-Th)/He zircon ages reinforces the accuracy of our preferred Rockland tephra eruption age, and confirms that zircon surface dates sample zircon growth up to the time of eruption. We demonstrate the broad applicability of coupled U/Pb zircon-surface and single-grain zircon (U-Th)/He geochronology to accurate

  12. "Taconic" arc magmatism in the central Brooks Range, Alaska: New U-Pb zircon geochronology and Hf isotopic data from the lower Paleozoic Apoon assemblage of the Doonerak fenster

    Science.gov (United States)

    Strauss, J. V.; Hoiland, C. W.; Ward, W.; Johnson, B.; McClelland, W.

    2015-12-01

    The Doonerak fenster in the central Brooks Range, AK, exposes an important package of early Paleozoic volcanic and sedimentary rocks called the Apoon assemblage, which are generally interpreted as para-autochthonous basement to the Mesozoic-Cenozoic Brookian fold-thrust belt. Recognition in the 1970's of a major pre-Mississippian unconformity within the window led to correlations between Doonerak and the North Slope (sub-) terrane of the Arctic Alaska Chukotka microplate (AACM); however, the presence of arc-affinity volcanism and the apparent lack of pre-Mississippian deformation in the Apoon assemblage makes this link tenuous and complicates Paleozoic tectonic reconstructions of the AACM. Previous age constraints on the Apoon assemblage are limited to a handful of Middle Cambrian-Silurian paleontological collections and five K-Ar and 40Ar/39Ar hornblende ages from mafic dikes ranging from ~380-520 Ma. We conducted U-Pb geochronologic and Hf isotopic analyses on igneous and sedimentary zircon from the Apoon assemblage to test Paleozoic links with the North Slope and to assess the tectonic and paleogeographic setting of the Doonerak region. U-Pb analyses on detrital zircon from Apoon rocks yield a spectrum of unimodal and polymodal age populations, including prominent age groups of ca. 420-490, 960-1250, 1380­-1500, 1750-1945, and 2650-2830 Ma. Hf isotopic data from the ca. 410-490 Ma age population are generally juvenile (~7-10 ɛHf), implying a distinct lack of crustal assimilation during Ordovician-Silurian Doonerak arc magmatism despite its proximity to a cratonic source terrane as indicated by an abundance of Archean and Proterozoic zircon in the interbedded siliciclastic strata. These data are in stark contrast to geochronological data from the non-Laurentian portions of the AACM, highlighting a prominent tectonic boundary between Laurentian- and Baltic-affinity rocks at the Doonerak window and implying a link to "Taconic"-age arc magmatism documented along

  13. Zircon U-Pb and Lu-Hf isotopic and geochemical constraints on the origin of the paragneisses from the Jiaobei terrane, North China Craton

    Science.gov (United States)

    Shan, Houxiang; Zhai, Mingguo; Zhu, Xiyan; Santosh, M.; Hong, Tao; Ge, Songsheng

    2016-01-01

    Clastic sedimentary rocks are important tracers to understand the evolution of the continental crust. Whole-rock major and trace element data, zircon U-Pb dating and Hf isotopic data for the paragneisses from the Jiaobei terrane are presented in this study in order to constrain their protoliths, provenance and tectonic setting. The paragneisses are characterized by enrichment in Al2O3 and TiO2, negative DF (DF = 10.44 - 0.21SiO2 - 0.32Fe2O3T - 0.98MgO + 0.55CaO + 1.46Na2O + 0.54K2O) values and the presence of aluminum-rich metamorphic minerals (e.g., garnet and sillimanite). Together with the mineral assemblages and zircon features, it can be inferred that the protoliths of these rocks are of sedimentary origin. The K-A (A = Al2O3/(Al2O3 + CaO + Na2O + K2O), K = K2O/(Na2O + K2O)) and log(Fe2O3/K2O)-log(SiO2/Al2O3) diagrams indicate that they belong principally to clay-silty rocks with some contributions from graywacke. A series of geochemical indexes, such as the widely employed CIA (CIA = [Al2O3/(Al2O3 + CaO∗ + Na2O + K2O)] × 100; molar proportions) and ICV (ICV = (Fe2O3 + MnO + MgO + CaO + Na2O + K2O + TiO2)/Al2O3) values, and the A-CN-K diagram for the paragneisses indicate relatively weak weathering in the source rocks and negligible post-depositional K-metasomatism. In addition, their REE patterns, low Cr/Zr (0.61-1.99), high Zr/Y (4.81-23.59) and Th/U (3.21-40.67) ratios, the low to moderate contents of Cr (197-362 ppm) and Ni (6.68-233 ppm), and source rock discrimination diagrams collectively suggest that the sediments of the protoliths of the paragneisses in the Jiaobei terrane were derived from the source with intermediate-acidic composition, probably granitic-to-tonalitic rocks. In combination with geochronological and isotopic studies on the paragneisses and the basement rocks in the Jiaobei terrane, it is suggested that the Archean-early Paleoproterozoic granitic rocks in the Jiaobei terrane possibly provided the most important source materials. In

  14. Timing of Crystallisation of the Lunar Magma Ocean Constrained by the Oldest Zircon

    Science.gov (United States)

    Nemchin, A.; Timms, N.; Pidgeon, R.; Geisler, T.; Reddy, S.; Meyer, C.

    2009-01-01

    The presently favoured concept for the early evolution of the Moon involves consolidation of debris from a giant impact of a Mars sized body with Earth forming a primitive Moon with a thick global layer of melt referred to as the Lunar Magma Ocean1 . It is widely accepted that many significant features observed on the Moon today are the result of crystallisation of this magma ocean. However, controversy exists over the precise timing and duration of the crystallisation process. Resolution of this problem depends on the establishment of precise and robust key crystallisation time points. We report a 4417 6 Myr old zircon in lunar breccia sample 72215,195, which provides a precisely determined younger limit for the solidification of the Lunar Magma Ocean. A model based on these data, together with the age of the Moon forming giant impact, defines an exponential time frame for crystallisation and suggests formation of anorthositic crust after about 80-85% of the magma ocean was solidified. In combination with other zircon ages the 4417 +/- 6 Myr age also suggests that the very small (less than a few per cent) residual portion of the magma ocean continued to solidify during the following 300-500 m.y.

  15. Oxidation state of uranium in metamict and annealed zircon: near-infrared spectroscopic quantitative analysis

    CERN Document Server

    Zhang Ming; Ewing, R C

    2003-01-01

    Radiation and thermally induced changes in the oxidation state of uranium in metamict zircon have been systematically analysed, for the first time, using polarized near-infrared spectroscopy. The results showed that in damaged zircon U ions in crystalline domains exhibited relatively sharp, anisotropic signals from tetravalent and pentavalent U ions in crystalline domains (U sub c sub r sub y sub s sub t sub a sub l sup 4 sup + and U sub c sub r sub y sub s sub t sub a sub l sup 5 sup +). The linewidths and peak positions of the 4834 cm sup - sup 1 band (U sub c sub r sub y sub s sub t sub a sub l sup 4 sup + , E || c) and the 6668 cm sup - sup 1 band (U sub c sub r sub y sub s sub t sub a sub l sup 5 sup + , E perp. c) are a non-linear function of the self-radiation dose. They reach nearly constant values at doses greater than approx 3.5 x 10 sup 1 sup 8 alpha-events g sup - sup 1. Quantitative analysis of U sub c sub r sub y sub s sub t sub a sub l sup 4 sup + and U sub c sub r sub y sub s sub t sub a sub l...

  16. Atmosphere-ocean-lithosphere interactions during the Great Oxidation Event: insights from zircon δ18O

    Science.gov (United States)

    Spencer, C. J.; Partin, C. A.; Kirkland, C.; Shiels, C.; Raub, T. D.; Kinny, P.

    2016-12-01

    The Great Oxidation Event (GOE) records a precipitous atmospheric oxygen rise, perhaps by as much as three to four orders of magnitude within a few million years. The timescale of the GOE is primarily constrained by the rapid loss of mass-independently fractionated sulfur isotopes. The drastic surface changes associated with the GOE are reflected by the appearance of marine sulfate and manganese deposits, as well as increased redox-sensitive trace metal abundances in banded iron formations and shale. Each of these manifestations is recorded at the atmosphere-lithosphere or atmosphere-ocean interface. However, how the GOE affected the lithosphere beyond the atmosphere interface has received little attention to date. We present zircon δ18O data from Paleoproterozoic sedimentary successions in Western Australia and Canada that display a step-change from the isotopically distinct reservoir with high δ18O that was incorporated into subduction zone magmas. One likely candidate is marine sulfate evaporite deposits, which appear with the GOE. The incorporation of this enriched δ18O reservoir would have facilitated the step change seen in the zircon δ18O record. This signal may also be present to a much lower degree associated with the "whiffs" of atmospheric oxygen prior to the GOE.

  17. Estimating the formation age distribution of continental crust by unmixing zircon ages

    Science.gov (United States)

    Korenaga, Jun

    2018-01-01

    Continental crust provides first-order control on Earth's surface environment, enabling the presence of stable dry landmasses surrounded by deep oceans. The evolution of continental crust is important for atmospheric evolution, because continental crust is an essential component of deep carbon cycle and is likely to have played a critical role in the oxygenation of the atmosphere. Geochemical information stored in the mineral zircon, known for its resilience to diagenesis and metamorphism, has been central to ongoing debates on the genesis and evolution of continental crust. However, correction for crustal reworking, which is the most critical step when estimating original formation ages, has been incorrectly formulated, undermining the significance of previous estimates. Here I suggest a simple yet promising approach for reworking correction using the global compilation of zircon data. The present-day distribution of crustal formation age estimated by the new "unmixing" method serves as the lower bound to the true crustal growth, and large deviations from growth models based on mantle depletion imply the important role of crustal recycling through the Earth history.

  18. Effect of rheological properties of zircon-alumina suspensions on density of green casts

    Directory of Open Access Journals (Sweden)

    Garrido L.B.

    2001-01-01

    Full Text Available Rheological properties of aqueous suspensions (48 vol% of zircon-alumina mixtures containing different amounts of polyelectrolyte as dispersant were studied. Slip casting in a plaster mold and pressure filtration at 8 MPa experiments were performed to correlate the rheological properties of the suspensions with the relative density of green casts. Flow curves fitted satisfactorily to the Casson model. The Casson viscosity values remained nearly constant whereas Casson yield stress parameter decreased to a minimum and then increased with increasing the amount of dispersant added. The influence of particle size distribution (PSD of the powder mixtures on Casson yield stress parameter and on the minimum viscosity was also examined. Green densities increased as yield stress Casson parameter decreased. The mixture of alumina and zircon as fine and coarse powders produced bimodal PSD which maximized the green density of the compacts. Some weakly flocculated suspensions having low apparent viscosity and small yield stress produced casts with relatively high densification. This is attributed to a slight higher viscosity at low shear rates of these suspensions in which settling of particles and /or segregation of components can not occur.

  19. Climatic and anthropogenic influences on sediment mixing in the Mississippi source-to-sink system using detrital zircons: Late Pleistocene to recent

    Science.gov (United States)

    Mason, Cody C.; Fildani, Andrea; Gerber, Thomas; Blum, Michael D.; Clark, Julian D.; Dykstra, Mason

    2017-05-01

    U-Pb geochronology of detrital zircons (DZ) is a robust tool used to elucidate linkages between tectonics, climate, and drainage configurations. However, timescales of sedimentary system response to modulation of up-system boundary conditions are rarely investigated using detrital geochronology. Here we present results of mixture modeling using modern and Late Pleistocene DZ samples from each of the Mississippi system segments, and show that high-frequency changes in up-system boundary conditions-anthropogenic sediment impoundment and late Pleistocene ice sheet dynamics-have measurable effects on detrital compositions. Results of DZ mixing models show a high positive correlation to measured suspended sediment loads for each major tributary (ca. 1970s-2000s). Differences between model results and historical records are explained by recent anthropogenic sediment impoundment. Results of DZ mixing models using late Wisconsin deep-sea samples indicate major increases from the Missouri and Upper Mississippi rivers. Boundary conditions responsible for increased sediment loads from these catchments include ice stream activity, increased transport capacity during deglacial melt-water floods, and an increased gradient of a glacial lower Mississippi Valley. These results suggest sediment mixtures in large rivers respond to icehouse climate change at timescales of 103-4 yrs, in contrast to calculated equilibrium response times of ca. 250-25 ka for the Mississippi system, and indications that anthropogenic river modifications alter relative sediment loads instantaneously. Adjustments in detrital mixtures occur at timescales an order-of-magnitude less than Milankovitch-timescale climate change, indicating rapid environmental signal propagation and preservation within transcontinental source-to-sink systems influenced by continental ice sheets.

  20. Ab initio calculation of thermodynamic functions for crystals; Calcul des fonctions thermodynamiques du zircon, de la fluorapatite et de l'iodoapatite

    Energy Technology Data Exchange (ETDEWEB)

    Fleche, J.L. [CEA Saclay, Dept. des Procedes d' Enrichissement (DCC/DPE/SPCP), 91 - Gif-sur-Yvette (France)

    2000-07-01

    The knowledge of thermodynamic functions is essential to investigate crystal stability and chemical reactivity. These functions are not always experimentally known, as for some crystalline host phases for radioactive waste. Fortunately, it is possible to calculate them. Although possible, the full ab initio calculation is not realistic because the calculation time rapidly becomes too long. These functions are obtained using an analytical model containing physical quantities determined by ab initio calculations. This enabled us to estimate the main thermodynamic functions of zircon ZrSiO{sub 4}, fluor-apatite Ca{sub 10}(PO{sub 4}){sub 6}F{sub 2} and stoichiometric iodo-apatite Pb{sub 10}(VO{sub 4}){sub 6}I{sub 2} from the variation of cohesive energy with volume and the harmonic vibration frequencies at the center of the first Brillouin zone for the unit cell corresponding to maximum cohesive energy. These ab initio quantities are calculated with the DMOL{sup 3} code that solves the electronic Schroedinger equation using the electronic density functional theory (DFT) in local density approximation, corrected (NLDA) or not (LDA) with its gradient. To limit calculation time, we made additional approximations: - acoustic and optical vibrations beyond the first Brillouin zone center are described by the Debye and Einstein models respectively; - to allow thermal expansion of the crystal we used the quasi-harmonic approximation which assumes that frequency variations are proportional to volume variations. The proportionality coefficients known as Gruneisen coefficients are derived in this study, with specific approximations; - we used the spherical cellular approximation and considered the crystal as isotropic. The thermodynamic functions calculated with this model are the following measurable quantities : enthalpy and free enthalpy, heat capacity at constant pressure, bulk modulus and thermal expansion coefficient. For zircon and fluor-apatite, for which the main

  1. Ground-state correlations in 40Ca and 48Ca

    Science.gov (United States)

    Takayanagi, K.; Lipparini, E.

    1992-01-01

    Second-order perturbation theory with a G-matrix is adopted to examine from a unified point of view the effects of two-particle-two-hole correlations on the matter and momentum distributions and the occupation numbers in 40Ca and 48Ca. Polarization effects induced by the neutron excess in 48Ca are investigated in detail.

  2. Source to sink zircon grain shape: Constraints on selective preservation and significance for Western Australian Proterozoic basin provenance

    Directory of Open Access Journals (Sweden)

    V. Markwitz

    2018-03-01

    Calculations of the proportions of source material in sedimentary rocks relative to the proportions of source material in the overall catchment area (erosion parameter ‘K’ calculated based on age spectra produced values typical for mature river systems, with K = 6 for the Yilgarn-Capricorn and K = 5.5 for the Musgrave-Amadeus source-sink system. For the Yilgarn-Capricorn system, we also calculated ‘K’ based on Minor Axis, to determine whether grain width can be linked to age populations. Results of the shape-based K of 5.3 suggest a similarity between age-based and shape-based ‘K’ values, demonstrating that zircon grain width may be a useful discriminator of provenance. Contrary to commonly applied qualitative shape classifications, we found no consistent correlations between shape descriptors of magmatic zircons and the composition of their host rock. While metamict zircons were preferentially removed during transport, the similarities in grain shape and age distribution of magmatic and detrital populations suggest that hydraulic sorting did not have a significant effect. We conclude that transport of zircon grains from magmatic source to sedimentary sink affects their width less than their length.

  3. An Early Proterozoic U-Pb zircon age from an Eskolabreen Formation gneiss in southern Ny Friesland, Spitsbergen

    Energy Technology Data Exchange (ETDEWEB)

    Balashov, Y.A.; Larionov, A.N.; Gannibal, L.F.; Sirotkin, A.N.; Tebenkov, A.M.; Ryungenen, G.I.; Ohta, Y. (Kola Science Centre, Russian Acadamy of Sciences, Apatity (Russian Federation))

    1993-12-01

    A preliminary U/Pb zircon age determination has been carried out on a grey gneiss of the Eskolabreen Formation, the lowest observable lithostratigraphic unit of Precambrian metamorphic rocks in southern Ny Friesland, NE Spitsbergen. The obtained age, appr. 2,400 Ma, is considered to be a metamorphic age and suggests and Early Proterozoic tectonothermal event. 25 refs., 3 figs., 2 tabs.

  4. Chronological constraints on tectonic evolution of the Chinese Tianshan Orogen through detrital zircons from modern and paleo-river sands

    Science.gov (United States)

    Ren, Rong; Guan, Shuwei; Han, Baofu

    2017-04-01

    The Chinese Tianshan Orogen marked the prolonged, complicated interactions between the southwestern Paleo-Asian Ocean and surrounding blocks. Massive new and previous detrital zircon U-Pb chronological data from modern and paleo-river sands (more than 7000 ages from 102 samples) were compiled to constrain its tectonic evolution. The Chinese Tianshan Orogen is characterized by predominant Paleozoic and minor Mesozoic and Precambrian detrital zircon ages that show multimodal characteristic. The oldest Phanerozoic zircon population (peak at 475 Ma) results from subduction and closure of the Early Paleozoic Terskey Ocean. But the absence of this peak in Chinese North and southern South Tianshan suggests that the subductions of the North and South Tianshan oceans may not initiate until Late Ordovician, with subsequent 460-390 Ma and 360-320 Ma arc magmatism. Similar to magmatic suite in classic collisional orogens, the youngest massive 320-270 Ma magmatism is supposed to be post-collisional. The North and South Tianshan oceans therefore probably had their closure to form the Chinese Tianshan Orogen during Late Carboniferous. The weak Mesozoic intra-plate magmatism further argues against a Late Permian-Triassic Tianshan Orogen for the lack of extensive syn- and post-collisional magmatism. Moreover, the diverse Precambrian detrital zircon age patterns indicate that the surrounding blocks have distinct tectonic evolution and short-term amalgamation during the Neoproterozoic.

  5. Detrital zircons - the unique source of information on tectonics, paleogeography and denudation processes of East Antarctica (subglacial challenge)

    Science.gov (United States)

    Belyatsky, Boris; Leitchenkov, German; Rodionov, Nickolay; Antonov, Anton; Sergeev, Sergey; Savva, Helen

    2010-05-01

    Vast (about 7 billions km2) almost wholly (98%) covered with ice continental mass of East Antarctica is the central fragment of ancient supercontinents of Rodinia and Gondwana. Any information on its geologic structure is of the greatest importance for solving the problems of formation and amalgamation of lithosphere of ancient continents, processes of intraplate activity, denudation and peneplanation of the earth crust and for geodynamic reconstruction. Geologic structure of central part of the East Antarctica is still absolutely unknown due to the thick (up to 4000 m) ice cover, which is the obstacle even for modern drilling technology to sample directly the underlying rocks. The main goal of the study has been to make an attempt in fill up the hiatus in geologic knowledge on the origin of subglacial continental crust of the Antarctica. We studied detrital zircons from sedimentary and metasedimentary rocks outcropped in Prince-Charles Mts (PCM, East Antarctica). Rock specimens were sampled from the Permian-Triassic sedimentary succession outcropped along the Beaver Lake coast (sandstones and siltstones) and from moraine of the Fisher Massive (metasandstone) and Meridith Massive (sandstone). A lump of zircons which are characterized by different grain morphology from well-rounded to poorly-rounded has been extracted from rock specimens for isotopic studies and dating. The age determinations of 302 zircons from 6 specimens were conducted using secondary ion-microprobe SHRIMP-II and laser-ablation ICP-MS. The age of zircons ranges from 500 to 3200 Ma. Isotopic analysis and probability distribution diagrams for zircon populations show heterogeneity of provenance. Zircons of 500 Ma old are proposed to come from the eastern flank of Lambert Glacier and/or from central Antarctica; 900-1100 Ma old - from Proterozoic Mobile Belt (central-northern PCM); while 2400-3200 Ma old - from granite-greenstone terrain (southern PCM). Additionally, 21 trace elements and isotopic

  6. U-Pb zircon in situ dating with LA-MC-ICP-MS using a mixed detector configuration

    Energy Technology Data Exchange (ETDEWEB)

    Chemale Junior, Farid, E-mail: fchemale@unb.br [Universidade de Brasilia (UnB), DF (Brazil). Inst. de Geociencias; Kawashita, Koji; Dussin, Ivo A. [Universidade de Sao Paulo (USP), SP (Brazil). Centro de Pesquisas Geocronologicas; Avila, Janaina N. [Australian National University, Canberra, (Australia). Research School of Earth Sciences; Justino, Dayvisson; Bertotti, Anelise [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Curso de Pos-Graduacao em Geociencias

    2012-06-15

    The LA-MC-ICP-MS method applied to U-Pb in situ dating is still rapidly evolving due to improvements in both lasers and ICP-MS. To test the validity and reproducibility of the method, 5 different zircon samples, including the standard Temora-2, ranging in age between 2.2 Ga and 246 Ma, were dated using both LA-MC-ICP-MS and SHRIMP. The selected zircons were dated by SHRIMP and, after gentle polishing, the laser spot was driven to the same site or on the same zircon phase with a 213 nm laser microprobe coupled to a multi-collector mixed system. The data were collected with a routine spot size of 25 {mu}m and, in some cases, of 15 and 40 {mu}m. A careful cross-calibration using a diluted U-Th-Pb solution to calculate the Faraday reading to counting rate conversion factors and the highly suitable GJ-1 standard zircon for external calibrations were of paramount importance for obtaining reliable results. All age results were concordant within the experimental errors. The assigned age errors using the LA-MC-ICP-MS technique were, in most cases, higher than those obtained by SHRIMP, but if we are not faced with a high resolution stratigraphy, the laser technique has certain advantages. (author)

  7. Electrochemical characterization of praseodymia doped zircon. Catalytic effect on the electrochemical reduction of molecular oxygen in polar organic solvents

    Energy Technology Data Exchange (ETDEWEB)

    Domenech, Antonio, E-mail: antonio.domenech@uv.es [Departament de Quimica Analitica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain); Montoya, Noemi; Alarcon, Javier [Departament de Quimica Inorganica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain)

    2011-08-01

    Highlights: > Electrochemical characterization of Pr centers in praseodymia-doped zircon. > Study of the catalytic effect on the reduction of peroxide radical anion in nonaqueous solvents. > Assessment of non-uniform distribution of Pr centers in the zircon grains. - Abstract: The voltammetry of microparticles and scanning electrochemical microscopy methodologies are applied to characterize praseodymium centers in praseodymia-doped zircon (Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4}; y + z = x; 0.02 < x < 0.10) specimens prepared via sol-gel synthetic routes. In contact with aqueous electrolytes, two overlapping Pr-centered cathodic processes, attributable to the Pr (IV) to Pr (III) reduction of Pr centers in different sites are obtained. In water-containing, air-saturated acetone and DMSO solutions as solvent, Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} materials produce a significant catalytic effect on the electrochemical reduction of peroxide radical anion electrochemically generated. These electrochemical features denote that most of the Pr centers are originally in its 4+ oxidation state in the parent Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} specimens. The variation of the catalytic performance of such specimens with potential scan rate, water concentration and Pr loading suggests that Pr is not uniformly distributed within the zircon grains, being concentrated in the outer region of such grains.

  8. effect of post-precipitation treatment on the pore-structure stability of sol-gel derived lanthanum zirconate

    NARCIS (Netherlands)

    Nair, Jalajakumari; Kumar, K.N.P.; Nair, P.; van Ommen, J.G.; Ross, J.R.H.; Ross, Julian R.H.; Burggraaf, Anthonie J.; Burggraaf, Anthonie

    1998-01-01

    The importance of post-precipitation treatments (pore-fluid exchange and its removal) on the evolution of the texture of coprecipitated lanthanum zirconate has been investigated. The nature of the pore fluid and the type of fluid-removal (drying) process have shown a profound effect on the aggregate

  9. Analysis of the state of poling of lead zirconate titanate (PZT) particles in a Zn-ionomer composite

    NARCIS (Netherlands)

    James, N.K.; Comyn, T.; Hall, D.; Daniel, L.; Kleppe, A.; Zwaag, S. van der; Groen, W.A.

    2016-01-01

    The poling behaviour of tetragonal lead zirconate titanate (PZT) piezoelectric ceramic particles in a weakly conductive ionomer polymer matrix is investigated using high energy synchrotron X-ray diffraction analysis. The poling efficiency, crystallographic texture and lattice strain of the PZT

  10. Mineral inclusions in placer zircon from the Ohře (Eger) Graben: New data on „strontiopyrochlore“

    Czech Academy of Sciences Publication Activity Database

    Seifert, W.; Förster, H.-J.; Rhede, D.; Tietz, O.; Ulrych, Jaromír

    2012-01-01

    Roč. 92, 1/2 (2012), s. 39-53 ISSN 0930-0708 R&D Projects: GA ČR(CZ) GA205/09/1170 Institutional support: RVO:67985831 Keywords : Eger Graben * zircon * "strontiopyrochlore" Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.681, year: 2012

  11. Zircon U-Pb SHRIMP Ages From Eastern Ghats Belt, India and Their Implication on the Indo-Antarctic Correlation

    Science.gov (United States)

    Bose, S.; Dunkley, D. J.; Arima, M.

    2008-12-01

    We analyze zircon using U-Pb SHRIMP method to constrain the timing of important thermal events in the Eastern Ghats Belt (EGB) which shows a comparable geological history with the Precambrian rocks of east Antarctica. Zircon grains show contrasting morphological and chemical characters depending on the rock types and locality. Zircon from UHT aluminous granulites from the central part show detrital (c. 1820 Ma) and igneous cores (c. 1760 Ma) occasionally surrounded by oscillatory-zoned mantle (c. 1650 Ma). Thick metamorphic rim (U-rich) over detrital core is and simple concentric zoned zircon grains show well-grouped concordant age of c. 950 Ma. This event is correlated with the Rayner structural event (980-930 Ma) strengthening the fact that the Eastern Ghats-Rayner Complex evolved as a composite orogen during Meso- Neoproterozoic time. The c. 1650 Ma event possibly suggests the timing of UHT metamorphism and anatexis. Absence of Pan-African ages (550-500 Ma) in all of these samples suggests thermal input was not strong enough to cause zircon growth during this event. Zircon grains from leptynite from the southern part shows well-grouped concordant age of c. 1760 Ma with partial resetting at c. 1690 Ma due to UHT metamorphism. The c. 950 Ma event was unseen by rocks of this area. Rocks of the northern part bear distinct geochronological signatures. Zircon grains in the HT/UHT aluminous granulites are sector zoned, cloudy homogeneous metamorphic grains with nearly concordant age of c. 780 Ma. Few metamorphic grains show c. 520 Ma age which possibly is responsible for partial modification and recrystallization of the c. 780 Ma grains. Our data suggest that the northern part of Eastern Ghats is exotic in origin and was possibly amalgamated to the rest of the Eastern Ghats during the Neoproterozoic-Phanerozoic time. The immediate counterpart of this segment is not properly known, but Prydz Bay area of east Antarctica shows a comparable evolutionary history. The

  12. Zircon Lu-Hf systematics and the evolution of the Archean crust in the southern Superior Province, Canada

    Science.gov (United States)

    Smith, P.E.; Tatsumoto, M.; Farquhar, R.M.

    1987-01-01

    A combined Lu-Hf and U-Th-Pb isotopic study was made of 25 zircons and 2 whole rocks from the late Archean crust (2,888-2,668 Ma) in the southern Superior Province, Canada. The relative abundances of U, Th, Lu and Hf in zircons from the low grade Michipicoten and Gamitagama greenstone belts show variable patterns which in part reflect the bulk compositional differences of their parent rocks. Zircons from the high grade lower crustal regions adjacent to these belts (Kapuskasing Structural Zone) are distinguished from the low grade zircons by their strong depletions of Lu and Hf. The low Hf contents imply that the growth of metamorphic zircon involves a significant fractionation of the Zr/Hf ratio. Initial Hf isotope ratios for Hf in zircons from the low grade rocks are correlated with silica enrichment of their host rocks. eHf varies from +9.2 to -1.3 and data from similar rock types exhibit correlations of eHf with time. Whole rock basalt analyses yield eHf values of +8.7 and +11.3 suggesting their derivation from a depleted mantle. The basalt data fall on an evolution trend which implies that differentiation from a chondritic mantle occurred at 3,100-2,900 Ma. Low eHf values (-1.3 to +1.4) for rhyolites and granites are consistent with a derivation involving remelting of old crust similar to a 2,888 Ma granite with eHF of +0.5. Significantly higher values (+1.4 to +3.9) are found in zircons from 2,748-2,682 Ma dacites and tonalites suggesting that their parent rocks had higher Lu/Hf ratios. This may indicate that their parent rocks were mafic. However, there is some evidence that the possible lower crustal source reservoirs of these rocks may have undergone processes early in their histories which increased their Lu/ Hf ratios. This would give rise to the higher eHf values observed in their derivatives. ?? 1987 Springer-Verlag.

  13. Heavy Isotope Composition of Oxygen in Zircon from Soil Sample 14163: Lunar Perspective of an Early Ocean on the Earth

    Science.gov (United States)

    Nemchin, A. A.; Whitehouse, M. J.; Pidgeon, R. T.; Meyer, C.

    2006-01-01

    Thirty oxygen analyses of a large (sub-millimetre) zircon grain from the lunar soil sample 14163 have been determined using CAMECA 1270 ion microprobe. The sample 14163 was returned form the Fra Mauro region by Apollo 14 mission. Zircon grain of 0.6-0.8 mm in size extracted from the sample was imaged using CL detector fitted to the Philips Electron Microscope in order to reveal internal structure. Oxygen isotopes have been analysed during two sessions. The first set of data was collected using the original mount where the grain was set in the resin attached to the glass slide. This resulted in the two complications: (i) standard zircon has to be analysed from the separate mount and (ii) the lunar zircon grain was rased in the holder compared to the standard. In order to investigate, if the elevated oxygen compositions observed during this session could have resulted from this difference in geometric configuration during the standard and sample analyses, the lunar zircon was extracted from the original mount, remounted with the standard chip in the new resin disk and reanalysed during the second session. All analyses made during the first session show delta O-18 values heavier than 6.0%. The second set of data has a wider spread of delta O-18 values with some values as low as 5.6%. Nevertheless, a half of observed delta O-18 values in this set is also higher than 6.0%. Slightly lighter oxygen compositions observed during the second session indicate possible dependence of measured delta O-18 values on the geometry of analysed samples. Presence of zircons with similar heavy oxygen isotope compositions on the Moon, which neither had liquid water or felic crust similar to that on the Earth nor ever developed regime similar to plate tectonics, suggests that other mechanisms can be responsible for elevated delta O-18 values in zircons. This implies that there is no support for the presence of an ocean on the surface of the early Earth and as the ocean appears to be an

  14. Tracing magma sources of three different S-type peraluminous granitoid series by in situ U-Pb geochronology and Hf isotope zircon composition: The Variscan Montes de Toledo batholith (central Spain)

    Science.gov (United States)

    Merino Martínez, E.; Villaseca, C.; Orejana, D.; Pérez-Soba, C.; Belousova, E.; Andersen, T.

    2014-07-01

    Zone. Nevertheless, the highly negative initial Nd isotopic signature measured in some type-1 granitoids (ƐNd300 up to - 9.4) also suggests a contribution of more mature metasedimentary sequences, such as those described in the northern Central Iberian Zone. On the contrary, the high Ca, Na and Sr bulk-rock contents in type-3 granitoids, together with the presence of Ordovician magmatic inherited zircons, and the absence of inheritances older than Cryogenian ages, suggest the involvement of a metaigneous protolith. This conclusion is also supported by the similar mean whole-rock ƐNd300 isotopic values, TDM ages, ƐHf isotope zircon composition and trace-element modelling of type-3 granitoids when compared to data from outcropping augen orthogneisses from Central Spain. The estimated crystallisation temperatures for the granitoids from the Montes de Toledo batholith (750°-880 °C) suggest that the partial melting of the crustal protoliths could be induced by the own heat generated by the thickening of a highly radiogenic crust, such is that from central Spain. Our results not only indicate that the implication of metasedimentary and/or metaigneous sources contributes to enhance geochemical and isotopic differences in S-type peraluminous granitoid series in intracontinental orogenic settings, but also fractional crystallisation processes are responsible for the geochemical variability through the evolution of these felsic magmas.

  15. Provenance and drainage system of the Early Cretaceous volcanic detritus in the Himalaya as constrained by detrital zircon geochronology

    Directory of Open Access Journals (Sweden)

    Xiu-Mian Hu

    2015-01-01

    Full Text Available The age range of the major intra-plate volcanic event that affected the northern Indian margin in the Early Cretaceous is here defined precisely by detrital zircon geochronology. U–Pb ages of Early Cretaceous detrital zircons found in the Cretaceous to the Paleocene sandstones cluster mainly between 142 Ma and 123 Ma in the northern Tethys Himalayan unit, and between 140 Ma and 116 Ma in the southern Tethys Himalayan unit. The youngest and oldest detrital zircons within this group indicate that volcanism in the source areas started in the latest Jurassic and ended by the early Albian. Stratigraphic data indicate that volcaniclastic sedimentation began significantly earlier in southern Tibet (Tithonian than in Nepal (Valanginian, and considerably later in Spiti and Zanskar (Aptian/Albian to the west. This apparent westward migration of magmatism was explained with progressive westward propagation of extensional/transtensional tectonic activity and development of fractures cutting deeply across the Indian continental margin crust. However, detrital zircon geochronology provides no indication of heterochroneity in magmatic activity in the source areas from east to west, and thus lends little support to such a scenario. Westward migration of volcaniclastic sedimentation may thus reflect instead the westward progradation of major drainage systems supplying volcanic detritus sourced from the same volcanic centers in the east. Development of multiple radial drainage away from the domal surface uplift associated with magmatic upwelling, as observed for most large igneous provinces around the world, may also explain why U–Pb ages of detrital zircons tend to cluster around 133–132 Ma (the age of the Comei igneous province in Tethys Himalayan units, but around 118–117 Ma (the age of the Rajmahal igneous province in Lesser Himalayan units.

  16. Resolving arc processes through detrital zircon U-Pb geochronology and geochemistry: a case study from the southern California Mesozoic convergent margin

    Science.gov (United States)

    Johnston, S. M.; Kylander-Clark, A. R.

    2015-12-01

    Detrital zircon geochronology has been widely exploited to establish temporal characteristics in sedimentary source terranes. Detrital zircon geochemistry, however, has been largely overlooked given results from continentally derived igneous zircon that show subtle intersample variation in trace-element concentrations, and which make correlation between detrital zircon and their host terrane difficult. Nevertheless, recent studies suggest systematically variable geochemistry in McCoy Mountain detrital zircons derived from the southern California Mesozoic arc, and our preliminary data from the Peninsular Ranges batholith indicates strong correlations between whole-rock and zircon geochemistry. Here, we present coupled U-Pb geochronology and geochemistry measured by laser ablation split stream ICPMS on detrital zircons from Nacimiento block forearc sediments in Central California to characterize temporal and geochemical trends in the adjacent Mesozoic arc terrane. 1098 grains of Mesozoic age analyzed from 22 samples in the Nacimiento block define three periods of high magmatic flux in the Permian (270-250 Ma), Jurassic (170-140 Ma), and late Cretaceous (115-90 Ma). Zircon from the Permian arc is the least abundant of the three magmatic pulses, although they consistently display elevated Yb/Gd and U/Yb. Jurassic zircons display consistently low U/Yb, variably elevated Yb/Gd, abruptly higher Th/U and LREE from 155-145, and abruptly lower REE concentrations from 145-140 Ma. Zircon from the Cretaceous arc displays gradually increasing U/Yb, Th/U and LREE, with abruptly decreasing Yb/Gd at 95 Ma. The geochemical trends observed in the Nacimiento block detrital zircons of Cretaceous age are strikingly similar to temporal changes in geochemistry known from Cretaceous arc rocks of the Mojave and Peninsular Ranges, and strongly suggest a southern California provenance for Nacimiento block sediments. Furthermore, the similarity of geochemical trends between Cretaceous detrital

  17. Rare earth element selenochemistry of immiscible liquids and zircon at Apollo 14 - An ion probe study of evolved rocks on the moon

    Science.gov (United States)

    Snyder, Gregory A.; Taylor, Lawrence A.; Crozaz, Ghislaine

    1993-01-01

    Results are presented of trace-element analyses of three lunar zircons. The major-element and REE compositions were determined using electron microprobes, and a correction was made for zircon for Zr-Si-O molecular interferences in the La to Pr mass region. The three zircons were found to exhibit similar REE abundances and patterns. Results of the analyses confirm earlier studies (Hess et al., 1975; Watson, 1976; Neal and Taylor, 1989) on the partitioning behavior of trace elements in immiscible liquid-liquid pairs. The results also support the postulated importance of silicate liquid immiscibility in the differentiation of the upper mantle and crust of the moon.

  18. Research on output signal of piezoelectric lead zirconate titanate detector using Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    Takechi, Seiji, E-mail: takechi@elec.eng.osaka-cu.ac.jp [Graduate School of Engineering, Osaka City University, Osaka 558-8585 (Japan); Mitsuhashi, Tomoaki; Miura, Yoshinori [Graduate School of Engineering, Osaka City University, Osaka 558-8585 (Japan); Miyachi, Takashi; Kobayashi, Masanori; Okudaira, Osamu [Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba 275-0016 (Japan); Shibata, Hiromi [The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Fujii, Masayuki [Famscience Co., Ltd., Tsukubamirai, Ibaraki 300-2435 (Japan); Okada, Nagaya [Honda Electronics Co., Ltd., Toyohashi, Aichi 441-3193 (Japan); Murakami, Takeshi; Uchihori, Yukio [National Institute of Radiological Sciences, Chiba 263-8555 (Japan)

    2017-06-21

    The response of a radiation detector fabricated from piezoelectric lead zirconate titanate (PZT) was studied. The response signal due to a single 400 MeV/n xenon (Xe) ion was assumed to have a simple form that was composed of two variables, the amplitude and time constant. These variables were estimated by comparing two output waveforms obtained from a computer simulation and an experiment on Xe beam irradiation. Their values appeared to be dependent on the beam intensity. - Highlights: • The performance of PZT detector was studied by irradiation of a 400 MeV/n Xe beam. • Monte Carlo simulation was used to examine the formation process of the output. • The response signal due to a single Xe ion was assumed to have a simple form. • The form was composed of two variables, the amplitude and time constant. • These variables appeared to be dependent on the beam intensity.

  19. Occupational exposure to natural radioactivity in a zircon sand milling plant

    Energy Technology Data Exchange (ETDEWEB)

    Ballesteros, Luisa [Laboratorio de Radioactividad Ambiental, Universidad Politecnica de Valencia, Apartado 22012, E-46071 Valencia (Spain)], E-mail: lballest@upvnet.upv.es; Zarza, Isidoro [Laboratorio de Radioactividad Ambiental, Universidad Politecnica de Valencia, Apartado 22012, E-46071 Valencia (Spain)], E-mail: iszarpe@upvnet.upv.es; Ortiz, Josefina [Laboratorio de Radioactividad Ambiental, Universidad Politecnica de Valencia, Apartado 22012, E-46071 Valencia (Spain)], E-mail: jortiz@iqn.upv.es; Serradell, Vicente [Laboratorio de Radioactividad Ambiental, Universidad Politecnica de Valencia, Apartado 22012, E-46071 Valencia (Spain)], E-mail: vserradell@iqn.upv.es

    2008-10-15

    Raw zirconium sand is one of the substances (naturally occurring radioactive material, NORM) which is widely used in the ceramic industry. This sand contains varying concentrations of natural radionuclides: mostly U-238 but also Th-232 and U-235, together with their daughters, and therefore may need to be regulated by Directive 96/29/EURATOM. This paper describes the method used to perform the radiological study on a zircon sand milling plant and presents the results obtained. Internal and external doses were evaluated using radioactivity readings from sand, airborne dust, intermediate materials and end products. The results on total effective dose show the need for this type of industry to be carefully controlled, since values near to 1 mSv were obtained.

  20. Magnetoelectric effect of polymer electrolyte composites with Terfenol-D and lead zirconate titanate inclusions

    Science.gov (United States)

    Chau, K. H.; Wong, Y. W.; Shin, F. G.

    2009-05-01

    The magnetoelectric effects of three-phase composites in 0-0-3 connectivity were investigated. The composites consist of particulate Terfenol-D and lead zirconate titanate blended in different polymer matrices. The magnetoelectric coefficient αq, which is the charge density change in response to a change in the applied magnetic field, of the samples was measured under short circuit condition. The results show that the αq of the samples with an electrolytic polymer matrix is larger than that of the samples with an insulating matrix, while samples with an ion-doped electrolytic polymer matrix exhibit the largest αq. These results conform with the expectation that higher matrix conductivity has an effect of enhancing the magnetoelectric signals.

  1. Preparation of Lanthanum Zirconate Coatings by the Solution Precursor Plasma Spray

    Science.gov (United States)

    Wang, W. Z.; Coyle, T.; Zhao, D.

    2014-06-01

    Solution precursor plasma spray (SPPS) can synthesize powders and deposit the coatings synchronously. The lanthanum zirconate coatings are deposited by SPPS in the present study, and the dense coating can be obtained through changing the precursor solution. The addition of urea can change the heat exchange process for some precursor mixtures. However, almost no effect can be found on the microstructure of powder and coating by the addition of urea. The extra heat energy caused by the addition of urea is so small, as compared with the heat input by the present plasma jet, so that the heating effect can be ignored. The porosity of coatings increase when the LaCl3·7H2O instead of La(NO3)3·6H2O reacts with Zr(CH3CO2)4.

  2. A zircon vs titanite geochronometres by SHRIMP IIe as a tool in multistage magmatic intrusion problems

    Science.gov (United States)

    Wiszniewska, Janina; Krzemińska, Ewa

    2017-04-01

    Most of crystalline basement area of NE Poland is represented by late Svecofennian (1.84-1.80 Ga) orogenic granitoids and supracrustal succession. These early rock assemblages were intruded by plutons of the Mezoproterozoic AMCG suite, which occupies most of W-E trending belt of the so called Mazury Complex. This suite is dominated by A-type granitoids of rapakivi-like texture. The subsequent important components are gabbro-norite, anorthosite and locally mangerite and charnockite rock variations. Anorthosite occurs at three autonomic massifs Sejny, Suwałki(SAM) and Ketrzyn. The basic geochronological investigation was carried out previously using mainly the U-Pb-Th system of zircon and monazite geochronometers. The AMCG suite yielded ages mainly in the range between 1548 to 1500 Ma. The isotopic work also reveals sporadic ages recorded on titanite (1526±11 Ma), considered as the crystallization age of the titanites under subsolidus conditions (Dörr et al.,2002). The geochemical and isotopic whole rock investigation suggests that formation of the AMCG suite was a complex process with multiple magma batches sequentially differentiating, and probably undergoing mixing and crustal assimilation. In this study, we report sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon and titanite single grain age data from upper part of drill section (Krasnopol 6, depth 1003m) located within easternmost vicinity of the SAM. Both of mineral phases have been selected from the contact between A-type granitoid with Pb-Pb TIMS age of 1525±5 Ma (op cit) and mafic chilled margin interpreted as next magma input. Dating of 20 single zircons from the contact zone yielded concordia ages of 1510±10 Ma for most of grains defined as emplacement age with inheritance at 1850±10 Ma. It evidenced a younger dose of the melt on the top of plutonic body and some input of older crustal material, detected also by whole rock isotopic signatures. Single titanite grains from the same zone

  3. Putting zircon surface geochronology and geochemistry in textural context using 3D Xray tomography: Probing the magmatic history of Mount St. Helens

    Science.gov (United States)

    Claiborne, L. L.; Wooden, J. L.; Miller, C. F.; Gualda, G. A.; Clynne, M. A.; Flanagan, D. M.

    2010-12-01

    Zircon U-Series and U-Pb geochronology from 25 samples spanning the eruptive history of Mount St. Helens volcano (MSH) reveal complex and wide-ranging age populations, suggesting that some magmas intruded beneath MSH are stored for up to a few 100 kyr before being rejuvenated, recycled into younger hot magmas, and erupted (Claiborne et al., 2010). The compositions of these zircons record thermal and chemical transitions in the magmatic system independent of the eruptive behavior. An apparent paucity of eruption-age zircon precluded assessment of near-eruption magmatic conditions and suggested that zircon was undersaturated in all magmas just prior to eruption or that zircons were not cognate to the erupted magmas. However, this could be an artifact of traditional SHRIMP methods that use a 15 to 40 micron ion beam to analyze interiors of polished grains and therefore cannot access micrometer-scale outer rims that may represent final growth. To address these possibilities, we analyzed the outermost rims of zircon from 6 of the 25 eruptive units by pressing grains into indium and analyzing their surfaces. In 3 samples, zircon growth within error of or less than the previously estimated eruption age was identified. In 3 samples, the surface ages and chemistry were similar to the older zircon interiors. Each sample exhibited variation in surface ages and compositions among grains, including some surface ages more than 10 kyr older than eruption. This variation within samples indicates that the zircon in an erupted magma experienced different conditions prior to eruption, a conclusion also supported by the varied external morphology and grain size within individual samples (rounded vs. euhedral, glass-covered vs. clean). In order to determine the source of these variations in surface composition and age, it was necessary to place the zircons in textural context. Since zircons are scarce in MSH rocks and rarely visible in thin section, we used differential absorption x

  4. Divergence of Ca(2+) selectivity and equilibrium Ca(2+) blockade in a Ca(2+) release-activated Ca(2+) channel.

    Science.gov (United States)

    Yamashita, Megumi; Prakriya, Murali

    2014-03-01

    Prevailing models postulate that high Ca(2+) selectivity of Ca(2+) release-activated Ca(2+) (CRAC) channels arises from tight Ca(2+) binding to a high affinity site within the pore, thereby blocking monovalent ion flux. Here, we examined the contribution of high affinity Ca(2+) binding for Ca(2+) selectivity in recombinant Orai3 channels, which function as highly Ca(2+)-selective channels when gated by the endoplasmic reticulum Ca(2+) sensor STIM1 or as poorly Ca(2+)-selective channels when activated by the small molecule 2-aminoethoxydiphenyl borate (2-APB). Extracellular Ca(2+) blocked Na(+) currents in both gating modes with a similar inhibition constant (Ki; ~25 µM). Thus, equilibrium binding as set by the Ki of Ca(2+) blockade cannot explain the differing Ca(2+) selectivity of the two gating modes. Unlike STIM1-gated channels, Ca(2+) blockade in 2-APB-gated channels depended on the extracellular Na(+) concentration and exhibited an anomalously steep voltage dependence, consistent with enhanced Na(+) pore occupancy. Moreover, the second-order rate constants of Ca(2+) blockade were eightfold faster in 2-APB-gated channels than in STIM1-gated channels. A four-barrier, three-binding site Eyring model indicated that lowering the entry and exit energy barriers for Ca(2+) and Na(+) to simulate the faster rate constants of 2-APB-gated channels qualitatively reproduces their low Ca(2+) selectivity, suggesting that ion entry and exit rates strongly affect Ca(2+) selectivity. Noise analysis indicated that the unitary Na(+) conductance of 2-APB-gated channels is fourfold larger than that of STIM1-gated channels, but both modes of gating show a high open probability (Po; ~0.7). The increase in current noise during channel activation was consistent with stepwise recruitment of closed channels to a high Po state in both cases, suggesting that the underlying gating mechanisms are operationally similar in the two gating modes. These results suggest that both high affinity Ca

  5. SHRIMP U-Pb zircon dating of Pedras Grandes Suite, southern Santa Catarina State, Brazil

    Directory of Open Access Journals (Sweden)

    Andréa R. Jelinek

    2005-03-01

    Full Text Available Two major magmatic pulses of the granitic Florianópolis Batholith in Santa Catarina State, southern Brazil, occurred between 613±5Ma and 595±5 Ma, during the Neoproterozoic Brasiliano Cycle. These ages were obtained by U-Pb isotopic determinations with the sensitive high mass-resolution ion microprobe on igneous zircons from Pedras Grandes Suite in Santa Catarina State. Euhedral zircons remained unaltered close to a fluorite vein deposited at 180?C or more. These ages suggest a northern limit for the Pedras Grandes Suite, explaining the spatial relationship between the fluorite veins and the source rock.Dois dos principais pulsos da atividade granítica no Batólito Florianópolis em Santa Catarina ocorreram entre 613 ±5 Ma e 595 ±5 Ma, durante o Neoproterozóico do Ciclo Brasiliano. Estas idades foram obtidas a partir dedeterminações isotópicas U-Pb em cristais de zircão da Suite Pedras Grandes por "Sensitive high-resolution íon microprobe" - SHRIMP II. Os cristais de zircão permaneceram inalterados mesmo mediante condições hidrotermais com temperaturas iguais e, até mesmo, superiores a 180ºC. Estas idades sugerem a delimitação norte do Maciço Pedras Grandes, explicando a relação espacial existente entre os filões de fluorita e a rocha fonte destas mineralizações.

  6. Detrital zircon geochronology of lower to mid-crustal rocks associated with a microplate-continent collision, NW Argentina

    Science.gov (United States)

    Austin, L. J.; Roeske, S.; Garber, J. M.; Wimpenny, J.; Yin, Q.

    2011-12-01

    New LA-ICPMS U-Pb detrital zircon data give insight into the age and origin of complexly deformed metaigneous and metasedimentary rocks in an ancient collision zone, and help clarify the structural relationships of lower to mid-crustal structural packages in the Sierra de Pie de Palo, northwest Argentina. The Pie de Palo range contains complexly deformed Precambrian crystalline rocks that have experienced single- or multi-phase metamorphism, the latest of which is associated with convergence and collision of the Precordillera microplate with the Famatina arc of Gondwana. The two main metamorphic events occurred at ~1070 Ma and ~470 Ma, based on isotopic ages from several samples. The regional extent of both events, and thus the geometry of the collisional system, is not well defined. West-vergent shear zones separate two Precambrian basement complexes, the Pie de Palo Complex and Central Complex, from the Caucete Group, a suite of intensely deformed, medium grade Cambrian quartzite and marble. Detrital zircons from the hanging wall of the ductile Duraznos shear zone within the Pie de Palo range constrain the timing of cessation of Precambrian deformation and reflect no significant regional metamorphism between 1070 Ma and 470 Ma. Garnets with one clear phase of growth in the hanging wall are juxtaposed with two-phase garnets in the footwall. ~25% of the detrital zircon grains analyzed from the immediate hanging wall are younger than 1050 Ma, precluding the existence of the hanging wall package and the Duraznos shear zone in the 1070 Ma event. Detrital zircon ages also constrain the geometry of the Las Pirquitas Thrust, and support the interpretation of a structural window within the Pie de Palo Complex into the younger Caucete Group. Age distribution peaks correspond to previous detrital zircon analyses of Caucete Group metasediments. The presence of a window into Caucete Group rocks amidst the Pie de Palo Complex implies a very low-angle thrust and a thin thrust

  7. An ion microprobe study of individual zircon phenocrysts from voluminous post-caldera rhyolites of the Yellowstone caldera

    Science.gov (United States)

    Watts, K. E.; Bindeman, I. N.; Schmitt, A. K.

    2010-12-01

    Following the formation of the Yellowstone caldera from the 640 ka supereruption of the Lava Creek Tuff (LCT), a voluminous episode of post-caldera volcanism filled the caldera with >600 km3 of low-δ18O rhyolite. Such low-δ18O signatures require remelting of 100s of km3 of hydrothermally altered (18O-depleted) rock in the shallow crust. We present a high resolution oxygen isotope and geochronology (U-Th and U-Pb) study of individual zircon crystals from seven of these voluminous post-caldera rhyolites in order to elucidate their genesis. Oxygen isotope and geochronology analyses of zircon were performed with an ion microprobe that enabled us to doubly fingerprint 25-30 µm diameter spots. Host groundmass glasses and coexisting quartz were analyzed in bulk for oxygen isotopes by laser fluorination. We find that zircons from the youngest (200-80 ka) post-caldera rhyolites have oxygen isotopic compositions that are in equilibrium with low-δ18O host groundmass glasses and quartz and are unzoned in oxygen and U-Th age. This finding is in contrast to prior work on older (500-250 ka) post-caldera rhyolites, which exhibit isotopic disequilibria and age zoning, including the presence of clearly inherited zircon cores. Average U-Th crystallization ages and δ18O zircon values for Pitchstone Plateau flow (81±7 ka, 2.8±0.2‰), West Yellowstone flow (118±8 ka, 2.8±0.1‰), Elephant Back flow (175±22 ka, 2.7±0.2‰) and Tuff of Bluff Point (176±20 ka, 2.7±0.1‰) are overlapping or nearly overlapping in age and identical in oxygen isotope composition within uncertainty (2 SE). New U-Pb geochronology and oxygen isotope data for the North Biscuit Basin flow establish that it has an age (188±33 ka) and δ18O signature (2.8±0.2‰) that is distinctive of the youngest post-caldera rhyolites. Conversely, the South Biscuit Basin flow has a heterogeneous zircon population with ages that range from 550-250 ka. In this unit, older and larger (200-400 µm) zircons have more

  8. The enigmatic Gula Complex of the central Norwegian Caledonides: new constraints on age and origin from zircon dating and geochemistry

    Science.gov (United States)

    Gasser, Deta; Grenne, Tor; Eivind Augland, Lars

    2017-04-01

    Reconstructing the closure of the Iapetus Ocean is a major task in order to understand the evolution of the Caledonian orogeny in space and time. Major questions remain regarding the timing of formation, closure and accretion of oceanic basins as well as the age and origin of continental fragments caught and incorporated into these oceanic domains during closure. One of the largest, yet least constrained in terms of age and setting, of these continent-derived units is the Gula Complex, which is juxtaposed with Iapetus-derived oceanic units within the Trondheim Nappe Complex of the central Norwegian Caledonides. The Gula Complex consists of metamorphosed siliciclastic rocks with subordinate ribbon-chert, black schist and volcanic rocks of mainly mafic composition. In this contribution we present new geochemical data from volcanic rocks, U-Pb TIMS zircon ages from metavolcanites and dykes, and U-Pb LA-ICP-MS detrital zircon age spectra from metasedimentary rocks. A basaltic andesite with an earliest Neoproterozoic zircon age was apparently associated with a brief volcanic interval represented by laterally extensive, MORB- to within plate-type rift-related basalts. Nearby metapsammites have maximum ages also consistent with deposition in the early Neoproterozoic. By contrast, detrital zircon spectra in other metapsammites indicate that parts of the Gula Complex were deposited in Cambro-Silurian times. Prominent latest Neoproterozoic and Cambrian detrital zircons (660-610, 530-490 Ma) reflect a source region atypical for both Laurentia and Baltica. Basaltic units with a back-arc type geochemical signature are tentatively thought to have formed within this time span. An intermediate dyke yielding Middle Ordovician zircons is possibly related to the back-arc basin type volcanism, indicating at least one magmatic pulse prior to the widespread Mid-Silurian trondhjemitic to dioritic magmatism well known from the Gula Complex. Our new data demonstrate that the Gula Complex

  9. Petrological and zircon evidence for the Early Cretaceous granulite-facies metamorphism in the Dabie orogen, China

    Science.gov (United States)

    Gao, Xiao-Ying; Zhang, Qiang-Qiang; Zheng, Yong-Fei; Chen, Yi-Xiang

    2017-07-01

    An integrated study of petrology, mineralogy, geochemistry, and geochronology was carried out for contemporaneous mafic granulite and diorite from the Dabie orogen. The results provide evidence for granulite-facies reworking of the ultrahigh-pressure (UHP) metamorphic rock in the collisional orogen. Most zircons from the granulite are new growth, and their U-Pb ages are clearly categorized into two groups at 122-127 Ma and 188 ± 2 Ma. Although these two groups of zircons show similarly steep HREE patterns and variably negative Eu anomalies, the younger group has much higher U, Th and REE contents and Th/U ratios, much lower εHf(t) values than the older group. This suggests their growth is associated with different types of dehydration reactions. The older zircon domains contain mineral inclusions of garnet + clinopyroxene ± quartz, indicating their growth through metamorphic reactions at high pressures. In contrast, the young zircon domains only contain a few quartz inclusions and the garnet-clinopyroxene-plagioclase-quartz barometry yields pressures of 4.9 to 12.5 kb. In addition, the clinopyroxene-garnet Fe-Mg exchange thermometry gives temperatures of 738-951 °C. Therefore, the young zircon domains would have grown through peritectic reaction at low to medium pressures. The younger granulite-facies metamorphic age is in agreement not only with the adjacent diorite at 125 ± 1 Ma in this study but also the voluminous emplacement of coeval mafic and felsic magmas in the Dabie orogen. Mineral separates from both mafic granulite and its adjacent diorite show uniformly lower δ18O values than normal mantle, similar to those for UHP eclogite-facies metaigneous rocks in the Dabie orogen. In combination with major-trace elements and zircon Lu-Hf isotope compositions, it is inferred that the protolith of mafic granulites shares with the source rock of diorites, both being a kind of mafic metasomatites at the slab-mantle interface in the continental subduction channel

  10. Evolution of the Yunkai Terrane, South China: Evidence from SHRIMP zircon U-Pb dating, geochemistry and Nd isotope

    Science.gov (United States)

    Wan, Yusheng; Liu, Dunyi; Wilde, Simon A.; Cao, Jianjin; Chen, Bin; Dong, Chunyan; Song, Biao; Du, Lilin

    2010-01-01

    The Yunkai Terrane is one of the most important pre-Devonian areas of metamorphosed supracrustal and granitic basement rocks in the Cathaysia Block of South China. The supracrustal rocks are mainly schist, slate and phyllite, with local paragneiss, granulite, amphibolite and marble, with metamorphic grades ranging from greenschist to granulite facies. Largely on the basis of metamorphic grade, they were previously divided into the Palaeo- to Mesoproterozoic Gaozhou Complex, the early Neoproterozoic Yunkai 'Group' and early Palaeozoic sediments. Granitic rocks were considered to be Meso- and Neoproterozoic, or early Palaeozoic in age. In this study, four meta-sedimentary rock samples, two each from the Yunkai 'Group' and Gaozhou Complex, together with three granite samples, record metamorphic and magmatic zircon ages of 443-430 Ma (Silurian), with many inherited and detrital zircons with the ages mainly ranging from 1.1 to 0.8 Ga, although zircons with Archaean and Palaeoproterozoic ages have also been identified in several of the samples. A high-grade sillimanite-garnet-cordierite gneiss contains ˜242 Ma metamorphic zircons, as well as ˜440 Ma ones. Three of the meta-sedimentary rocks show large variations in major element compositions, but have similar REE patterns, and have tDM model ages of 2.17-1.91 Ga and ɛNd (440 Ma) values of -13.4 to -10.0. Granites range in composition from monzogranite to syenogranite and record tDM model ages of 2.13-1.42 Ga and ɛNd (440 Ma) values of -8.4 to -1.2. It is concluded that the Yunkai 'Group' and Gaozhou Complex formed coevally in the late Neoproterozoic to early Palaeozoic, probably at the same time as weakly to un-metamorphosed early Palaeozoic sediments in the area. Based on the detrital zircon population, the source area contained Meso- to Neoproterozoic rocks, with some Archaean material. Palaeozoic tectonothermal events and zircon growth in the Yunkai Terrane can be correlated with events of similar age and

  11. Zircon Geochemistry of Granitic Rocks from Ong Valley and Moraine Canyon in the Central Transantarctic Mountains, Antarctica

    Science.gov (United States)

    Liu, J.; Morgan, D. J.; Claiborne, L. L.; Padilla, A. J.; Edwards, K. L.; Putkonen, J.; Bibby, T.; Cribb, J. W.

    2015-12-01

    A number of granitic rocks exposed throughout the Central Transantarctic Mountains (CTAM) are thought to have been generated during and following the Ross Orogeny (late Cambrian to early Ordovician). Understanding the origin of these rocks can help improve our understanding of the tectonic events responsible for the suturing of Gondwana. In this study, we use zircon as a tool to investigate the magmatic origins and evolution of CTAM granites. Zircon has a low solubility in almost all melt and fluid compositions, is stable and resistant to alteration at Earth's surface, and is physically durable during transport. These features enable it to survive many crustal processes during which most other minerals are destroyed, thus preserving an important geochemical record of its crystallizing environments. We collected granitic samples from two sites in the CTAM: Ong Valley (157.5°E, 83.25°S), where the Hope Granite is exposed intruded into pre-Cambrian gneisses, and Moraine Canyon (157.55°W, 86.1°S), where bedrock exposure is dominated by a silicic porphyry of the Wyatt Formation. Our zircon U-Pb data, collected in-situ by laser ablation (LA) ICP-MS, suggests that the Hope Granite has a mean weighted crystallization age of 582 ± 23 Ma (2σ; n=26), older than the published age (510 ± 9 Ma, 1σ; whole-rock Rb-Sr isochrons; Faure & Mensing, 2010). The spread in individual zircon ages is consistent with previous estimates for the duration of intrusion (~20 Myr) of the Hope Granite. Published ages for Wyatt Fm rocks range from ~525 to ~800 Ma, but their origin is uncertain. We will analyze zircons from the Wyatt porphyry for U-Pb isotopes (by LA-ICP-MS) to better constrain its age. In addition, we will obtain trace element compositions of zircons from both intrusions to investigate their magmatic origins. This will allow us to explore potential geochemical connections between the intrusions, and may yield additional insight into the tectonic events involved in the Ross

  12. Contrasting zircon morphology and UPb systematics in peralkaline and metaluminous post-orogenic granite complexes of the Arabian Shield, Kingdom of Saudi Arabia

    Science.gov (United States)

    Aleinikof, J.N.; Stoeser, D.B.

    1989-01-01

    Uzircon ages are reported for seven metaluminous-to-peralkaline post-orogenic granites from the Late Proterozoic Arabian Shield of Saudi Arabia. Zircons from the metaluminous rocks are prismatic, with length-to-width ratios of ??? 2-4: 1 and small pyramidal terminations. In contrast, zircons from three of the four peralkaline complexes either lack well-developed prismatic faces (are pseudo-octahedral) or are anhedral. Some zircons from the peralkaline granites contain inherited radiogenic Pb and have very high common Pb contents (206Pb/204Pb Zircons in the metaluminous granites do not contain inheritance and yield well-defined concordia intercepts. The span of ages of the seven complexes (670-470 Ma) indicates that post-orogenic granitic magmatism was not a singular event in the Arabian Shield but rather occurred as multiple intrusive episodes from the Late Proterozoic to the Middle Ordovician. ?? 1989.

  13. U‐Pb zircon ages from the Indian plate in northwest Pakistan and their significance to Himalayan and pre‐Himalayan geologic history

    National Research Council Canada - National Science Library

    DiPietro, Joseph A; Isachsen, Clark E

    2001-01-01

    U‐Pb zircon isotopic ages of seven rock samples are combined with field data to provide constraints on deposition, intrusion, and metamorphism in the northwestern part of the Indian plate (Pakistani...

  14. The Eocene Thermal Maximum 2 (ETM-2) in a terrestrial section of the High Arctic: identification by U-Pb zircon ages of volcanic ashes and carbon isotope records of coal and amber (Stenkul Fiord, Ellesmere Island, Canada)

    Science.gov (United States)

    Reinhardt, Lutz; von Gosen, Werner; Piepjohn, Karsten; Lückge, Andreas; Schmitz, Mark

    2017-04-01

    The Stenkul Fiord section on southern Ellesmere Island reveals largely fluvial clastic sediments with intercalated coal seams of the Margaret Formation of Late Paleocene/Early Eocene age according to palynology and vertebrate remains. Field studies in recent years and interpretative mapping of a high-resolution satellite image of the area southeast of Stenkul Fiord revealed that the clastic deposits consist of at least four sedimentary units (Units 1 to 4) separated by unconformities. Several centimeter-thin volcanic ash layers, recognized within coal layers and preserved as crandallite group minerals (Ca-bearing goyazite), suggest an intense volcanic ash fall activity. Based on new U-Pb zircon ages (ID-TIMS) of three ash layers, the volcanic ash fall took place at 53.7 Ma in the Early Eocene, i.e. within the Eocene Thermal Maximum 2 (ETM-2) hyperthermal. The ETM-2 is bracketed further by discrete negative excursions of carbon isotope records of both bulk coal and amber droplets collected from individual coal layers of the section. The identification of the ETM-2 hyperthermal provides a stratigraphic tie-point in the terrestrial Margaret Formation sediments enabling assignment of the lowermost sedimentary Unit 1 to the Late Paleocene-earliest Eocene, Unit 2 to the Early Eocene, whereas Unit 3 and 4 might be Early to Middle Eocene in age. Thus the timing of syn-sedimentary movements of the Eurekan deformation causal for the observed unconformities in the section can be studied and the positions of further hyperthermals like the PETM or the ETM-3 in the section can be identified in the future. The integration of structural studies, new U-Pb zircon ages, and different carbon isotope records provides a new stratigraphic framework for further examination of the unique Early Eocene flora and fauna preserved in this high-latitude outcrop.

  15. Complicated secondary textures in zircon record evolution of the host granitic rocks: Studies from Western Tauern Window and Ötztal-Stubai Crystalline Complex (Eastern Alps, Western Austria)

    Science.gov (United States)

    Kovaleva, Elizaveta; Harlov, Daniel; Klötzli, Urs

    2017-07-01

    Samples of metamorphosed and deformed granitic rocks were collected from two Alpine complexes with well-constrained metamorphic history: Western Tauern Window and Ötztal-Stubai Crystalline Complex. Zircon grains from these samples were investigated in situ by a combination of scanning electron microscope techniques, cathodoluminescence (CL) imaging and Raman spectroscopy. The aims were: to describe and interpret complicated secondary textures and microstructures in zircon; based on cross-cutting relationships between secondary microstructures, reconstruct the sequence of processes, affecting zircon crystals; link the evolution of zircon with the history of the host rocks. The results indicate that zircon in the sampled granitic rocks forms growth twins and multi-grain aggregates, which are unusual for this mineral. Moreover, various secondary textures have been found in the sampled zircon, often cross-cutting each other in a single crystal. These include: distorted oscillatory CL zoning with inner zones forming inward-penetrating, CL-bright embayments, which are the evidence of dry recrystallization via annealing/lattice recovery; CL mosaicism with no preservation of growth zoning, but abundant nano- and micro-scale pores and mineral inclusions, which are the evidence of recrystallization by coupled dissolution-reprecipitation and/or leaching; embayed zircon boundaries filled with apatite, monazite, epidote and mylonitic matrix, indicating mineral-fluid reactions resulting in zircon dissolution and fragmentation; overgrowth CL-dark rims, which contain nano-pores and point to transport and precipitation of dissolved zircon matter. We conclude that zircon in our meta-granites is sensitive to metamorphism/deformation events, and was reactive with metamorphic fluids. Additionally, we have found evidence of crystal-plastic deformation in the form of low angle boundaries and bent grain tips, which is a result of shearing and ductile deformation of the host rock. We

  16. Trace element composition and U-Pb age of zircons from Estherville: Constraints on the timing of the metal-silicate mixing event on the mesosiderite parent body

    Science.gov (United States)

    Haba, Makiko K.; Yamaguchi, Akira; Kagi, Hiroyuki; Nagao, Keisuke; Hidaka, Hiroshi

    2017-10-01

    Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2

  17. Zircon U-Pb ages and geochemistry of newly discovered Neoproterozoic orthogneisses in the Mishan region, NE China: Constraints on the high-grade metamorphism and tectonic affinity of the Jiamusi-Khanka Block

    Science.gov (United States)

    Yang, Hao; Ge, Wen-chun; Zhao, Guo-chun; Bi, Jun-hui; Wang, Zhi-hui; Dong, Yu; Xu, Wen-liang

    2017-01-01

    The Jiamusi-Khanka Block, located in the easternmost segment of the Central Asian Orogenic Belt (CAOB), is one of the least understood blocks in northeastern China. The age of its basement, the timing of the high-grade metamorphism, and the tectonic affinity of this block have all been subjects of controversy. Here we describe newly discovered Neoproterozoic orthogneisses from the Mishan region in the central Jiamusi-Khanka Block. SIMS and LA-ICP-MS U-Pb dating of the magmatic cores of zircons from three of these high-grade orthogneisses yielded weighted mean ages that range from 898 ± 4 to 891 ± 13 Ma, indicating that early Neoproterozoic magmatism did occur in the Jiamusi-Khanka Block. Twenty-two analyses of metamorphic zircons (rims as well as some grains) gave two groups of concordant ages, one at ca. 563 Ma, interpreted as the timing of the high-grade metamorphism, and the other around 518-496 Ma, interpreted as representing a subsequent retrograde metamorphism. The orthogneisses represent metamorphosed peraluminous syn-collisional syenogranites with SiO2 = 71.29-78.08 wt%, A/CNK = 1.06-1.99, and Na2O/K2O = 0.03-1.49, and they belong chemically to the high-potassium calc-alkaline series. They have low Sr (32-134 ppm) contents and Sr/Y ratios (1.6-16.9), and display strongly fractionated to nearly flat REE patterns with negative Eu anomalies (δEu = 0.22-0.95) and depletions in Nb-Ta. These geochemical characteristics suggest that the syenogranitic rocks were derived under low pressures from a crustal source with a high proportion of sedimentary rocks, perhaps in a subduction-related setting that was undergoing transition from compression to extension. In the context of the reconstruction of Gondwana, the ca. 898-891 Ma magmatic activity and the ca. 563 Ma high-grade metamorphism in the Mishan region provide constraints on the possible linkages between the Jiamusi-Khanka Block and East Gondwana during the Neoproterozoic to early Paleozoic.

  18. Tectono-magmatic evolution of the Chihuahua-Sinaloa border region in northern Mexico: Insights from zircon-apatite U-Pb geochronology, zircon Hf isotope composition and geochemistry of granodiorite intrusions

    Science.gov (United States)

    Mahar, Munazzam Ali; Goodell, Philip C.; Feinstein, Michael Nicholas

    2016-11-01

    We present the whole-rock geochemistry, LA-ICP-MS zircon-apatite U-Pb ages and zircon Hf isotope composition of the granodioritic plutons at the southwestern boundary of Chihuahua with the states of Sinaloa and Sonora. These granodiorites are exposed in the north and south of the Rio El Fuerte in southwest Chihuahua and northern Sinaloa. The magmatism spans over a time period of 37 Ma from 90 to 53 Ma. Zircons are exclusively magmatic with strong oscillatory zoning. No inheritance of any age has been observed. Our new U-Pb dating ( 250 analyses) does not support the involvement of older basement lithologies in the generation of the granitic magmas. The U-Pb apatite ages from granodiorites in southwest Chihuahua vary from 52 to 70 Ma. These apatite ages are 1 to 20 Ma younger than the corresponding zircon U-Pb crystallization ages, suggesting variable cooling rates from very fast to 15 °C/Ma ( 800 °C to 500 °C) and shallow to moderate emplacement depths. In contrast, U-Pb apatite ages from the Sinaloa batholith are restricted from 64 to 61 Ma and are indistinguishable from the zircon U-Pb ages range from 67 to 60 Ma within the error, indicating rapid cooling and very shallow emplacement. However, one sample from El Realito showed a larger difference of 20 Ma in zircon-apatite age pair: zircon 80 ± 0.8 Ma and apatite 60.6 ± 4 Ma, suggesting a slower cooling rate of 15 °C/Ma. The weighted mean initial εHf (t) isotope composition (2σ) of granodiorites varies from + 1.8 to + 5.2. The radiogenic Hf isotope composition coupled with previous Sr-Nd isotope data demonstrates a significant shift from multiple crustal sources in the Sonoran batholithic belt to the predominant contribution of the mantle-derived magmas in the southwest Chihuahua and northern Sinaloa. Based on U-Pb ages, the absence of inheritance, typical high Th/U ratio and radiogenic Hf isotope composition, we suggest that the Late Cretaceous-Paleogene magmatic rocks in this region are not derived from

  19. Provenance of Oligo-Miocene Strata from the Adriatic Foredeep of the Alps-Apennines System Determined through Detrital-Zircon U-Pb Geochronology

    Science.gov (United States)

    Dafov, L. N.; Anfinson, O. A.; Malusa', M. G.; Stockli, D. F.

    2014-12-01

    U-Pb geochronology of detrital zircon is an effective method for evaluating exhumation history, provenance, and depositional age constraints of sedimentary deposits. Over 1400 grains evaluated from thirteen samples collected from distal and proximal Oligo-Miocene strata of Adriatic turbidites are consistent with modern characterization of the proposed source region. Studies indicate that the principal source area of Oligo-Miocene strata from Adriatic deposits is the Lepontine Dome of the Central Alps. Our data reveals a significant shift in detrital zircon U-Pb age populations during the Oligocene-Miocene boundary which, when compared with data from modern sands, closely correlates to the westward shift of the erosional foci within the Lepontine Dome, from the Ticino to the Toce subdome, due to progressive indentation of Adria. This is coeval with progressive unroofing of Periadriatic magmatic rocks of Tertiary age along the Insubric Fault. The lowermost Upper Oligocene proximal samples collected from the Como and Villa Olmo Conglomerates are dominated by Caledonian and Cadomian detrital zircon U-Pb age populations. The uppermost Oligocene and lower Miocene proximal samples collected from the Como Conglomerate are dominated instead by Periadriatic detrital zircon. Distal samples collected from the Lower Oligocene Aveto Formation have a dominant Periadriatic age peak with lesser amounts of late Cretaceous, Variscan, Caledonian and Cadomian detrital zircon. The lowermost Upper Oligocene distal samples collected from the Macigno Formation contain populations of Periadriatic, Variscan, Caledonian, and Cadomian detrital zircon, with major shifts in relative abundance from the lower to upper strata. The most dramatic shift in provenance in the distal units is between two samples located relatively proximally to one another in the Modino unit: Upper Oligocene marls contains primarily Variscan and Caledonian zircon grains with no individuals yielding Periadriatic ages

  20. Stability of zircon u-pb systematics in a greenschist-grade mylonite - an example from the rockfish valley fault zone, central Virginia, USA

    OpenAIRE

    Wayne, D. M.; Sinha, A. K.

    1992-01-01

    The mid-Paleozoic, greenschist-grade Rockfish Valley Fault Zone (RVFZ) of central Virginia cuts the Grenville-aged Pedlar River Charnockite Suite (PRCS) and contains zircons that underwent brittle failure during ductile deformation. Electron microprobe analyses and scanning electron microscope (SEM) backscattered electron (BSE) imaging show that zircons from the protolith PRCS are concentrically zoned (with alternating U-Hf-rich and U-Hf-poor bands), and contain numerous radial microcracks. Z...

  1. U-Pb-Hf-REE-Ti zircon and REE garnet geochemistry of the Cambrian Attunga eclogite, New England Orogen, Australia: Implications for continental growth along eastern Gondwana

    Science.gov (United States)

    Manton, Ryan J.; Buckman, Solomon; Nutman, Allen P.; Bennett, Vickie C.; Belousova, Elena A.

    2017-08-01

    The timing and location of eclogite metamorphism is central to understanding subduction events responsible for the assembly of eastern Gondwana. The Attunga eclogite is one of only six eclogites in Australia and occurs as small blocks within a schistose serpentinite mélange known as the Weraerai terrane, along the Peel Fault of the southern New England Orogen. Our zircon data reveal the presence of high Th/U oscillatory zoned magmatic zircon with a weighted mean 206Pb/238U age of 534 ± 14 Ma and recrystallized metamorphic domains with an age of 490 ± 14 Ma. The latter have lower Th/U ratios, mostly no Eu anomalies and heavy rare earth element (HREE)-depleted patterns. Garnet rims demonstrate that the final stages of garnet growth occurred in a HREE-depleted environment, due to coeval formation with metamorphic zircon. Direct application of the Ti-in-zircon thermometer to metamorphic zircon yields temperatures of 770-610°C. Hf isotopic analyses of the zircons have an average ɛHf(t) of +13, indicating a juvenile crustal signature. We interpret the Attunga eclogite to be an indicator of Late Cambrian subduction beneath an oceanic suprasubduction zone prior to accretion against eastern Gondwanan in the latest Devonian. Phillips et al. () suggest two metamorphic age populations within the Attunga eclogite, based on U-Pb zircon and 40Ar/39Ar phengite data. These are 515 Ma and 480 Ma. We confirm these data, but our zircon trace element chemistry data indicate that the Early Cambrian age (530 Ma) represents igneous protolith formation rather than eclogite metamorphism.

  2. Zircon record of fractionation, hydrous partial melting and thermal gradients at different depths in oceanic crust (ODP Site 735B, South-West Indian Ocean)

    Science.gov (United States)

    Pietranik, A.; Storey, C.; Koepke, J.; Lasalle, S.

    2017-03-01

    Felsic veins (plagiogranites) are distributed throughout the whole oceanic crust section and offer insight into late-magmatic/high temperature hydrothermal processes within the oceanic crust. Despite constituting only 0.5% of the oceanic crust section drilled in IODP Site 735B, they carry a significant budget of incompatible elements, which they redistribute within the crust. Such melts are saturated in accessory minerals, such as zircon, titanite and apatite, and often zircon is the only remaining phase that preserves magmatic composition and records processes of felsic melt formation and evolution. In this study, we analysed zircon from four depths in IODP Site 735B; they come from the oxide gabbro (depth approximately 250 m below sea floor) and plagiogranite (depths c. 500, 860, 940 m below sea floor). All zircons have similar ɛHf composition of c. 15 units indicating an isotopically homogenous source for the mafic magmas forming IODP Site 735B gabbro. Zircons from oxide gabbro are scarce and variable in composition consistent with their crystallization from melts formed by both fractionation of mafic magmas and hydrous remelting of gabbro cumulate. On the other hand, zircon from plagiogranite is abundant and each sample is characterized by compositional trends consistent with crystallization of zircon in an evolving melt. However, the trends are different between the plagiogranite at 500 m bsf and the deeper sections, which are interpreted as the record of plagiogranite formation by two processes: remelting of gabbro cumulate at 500 m bsf and fractionation at deeper sections. Zircon from both oxide gabbro and plagiogranite has δ18O from 3.5 to 6.0‰. Values of δ18O are best explained by redistribution of δ18O in a thermal gradient and not by remelting of hydrothermally altered crust. Tentatively, it is suggested that fractionation could be an older episode contemporaneous with gabbro crystallization and remelting could be a younger one, triggered by

  3. /sup 40/Ca-/sup 48/Ca isotope shift

    Energy Technology Data Exchange (ETDEWEB)

    Khodel, V.A.; Platonov, A.P.; Saperstein, E.E. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Atomnoj Ehnergii)

    1982-07-01

    Contributions of the virtual low-lying collective excitations to the nuclear density are calculated within the framework of the theory of self-consistent finite Fermi systems. It is shown that this effect is responsible for the /sup 40/Ca-/sup 48/Ca isotope shift.

  4. Gamma-rays attenuation of zircons from Cambodia and South Africa at different energies: A new technique for identifying the origin of gemstone

    Science.gov (United States)

    Limkitjaroenporn, P.; Kaewkhao, J.

    2014-10-01

    In this work, the gamma-rays interaction properties of zircons from Cambodia and South Africa have been studied. The densities of Cambodian and South African's zircons are 4.6716±0.0040 g/cm3 and 4.5505±0.0018 g/cm3, respectively. The mass attenuation coefficient and the effective atomic number of gemstones were measured with the gamma-ray in energies range 223-662 keV using the Compton scattering technique. The mass attenuation coefficients of both zircons decreased with the increasing of gamma-rays energies. The different mass attenuation coefficients between the two zircons observed at gamma-ray energies below 400 keV are attributed to the differences in the photoelectric interaction. The effective atomic number of zircons was decreased with the increasing of gamma-ray energies and showed totally different values between the Cambodia and South Africa sources. The origins of the two zircons could be successfully identified by the method based on gamma-rays interaction with matter with advantage of being a non-destructive testing.

  5. Neoproterozoic granitic magmatism along the Ailao Shan-Red River belt: U-Pb zircon geochronology, Lu-Hf isotopes and tectonic implications

    Science.gov (United States)

    Chen, Xiaoyu; Liu, Junlai; Qi, Yinchuan; Fan, Wenkui; Burg, Jean-Pierre

    2017-04-01

    The Neoproterozoic tectonic characteristics of the high grade metamorphic massifs along the Ailao Shan-Red River belt are debated. Controversies are on 1) whether the massifs were parts of the Yangtze block to the northeast or 2) parts of the Indochina block to the southwest and 3) the magmatic rocks represent arc magmatism or rifting linked to break-up of the Rodinia supercontinent. This study presents new and precise LA-ICP-MS U-Pb age dating and geochemical and Hf isotopic analyses of granitic intrusions along the Ailao Shan-Red River belt in an attempt to elucidate the Neoproterozoic magmatic evolution of this belt. In general, zircon U-Pb ages of the studied granitic rocks are between 804 and 724Ma, with a weighted mean of ca. 770 Ma, thus confirming Neoproterozoic magmatism. All samples plot into the peraluminous domain, indicating a major crustal resource. In consistency with these conclusions, most of the Neoproterozoic granitoids show negative ɛHf (t) values near the chondrite line. A few samples possess low positiveɛ Hf (t) values, being signatures of mantle sources. It is therefore concluded that the Neoproterozoic magmatism along the ASRR belt originated from mantle sources with important contributions through anatexis of ancient lower crust. Discrimination diagrams of tectonic settings suggest continental arc magmatism. Neoproterozoic magmatism is widely reported along the margins of the Yangtze block, especially in the northern margin. However, there are fewer reports about Neoproterozoic magmatic activity along the southern and southwestern margins. The geochronology spectrum and geochemisty of the studied Neoproterozoic granitic rocks are similar to those along the western margin of the Yangtze block. The present study, combined with previous results, suggests that oceanic subduction contributed to the generation of the arc magmatisms along the western and southwestern margin of the Yangtze plate and along the ASRR belt (as part of the

  6. Zircon U-Pb dating of Maherabad porphyry copper-gold prospect area: evidence for a late Eocene porphyry-related metallogenic epoch in east of Iran

    Directory of Open Access Journals (Sweden)

    Azadeh Malekzadeh Shafaroudi

    2011-04-01

    Full Text Available Eastern Iran has great potential for porphyry copper deposits, as a result of its past subduction zone tectonic setting that lead to extensive alkaline to calc-alkaline magmatic activity in Tertiary time. Maherabad is the first porphyry Cu-Au prospecting area which is discovered in eastern Iran. This is related to a succession o f monzonitic to dioritic porphyries stocks that were emplaced within volcanic rocks. Monzonitic porphyries have basic role in mineralization. Hydrothermal alteration zones are well developed including potassic, sericitic-potassic, quartz-sericite-carbonate-pyrite, quartz-carbonate-pyrite, silicified-propylitic, propylitic, carbonate and silicified zones. Mineralization occurs as Disseminated, stockwork and hydrothermal breccia. Based on early stage of exploration, Cu is between 179- 6830 ppm (ave. 3200 ppm and Au is up to 1000 ppb (ave. 570 ppb. This prospect is gold- rich porphyry copper deposit. Laser-ablation U-Pb dating of two samples from ore-related intrusive rocks indicate that these two monzonitic porphyries crystallized at 39.0 ± 0.8 Ma to 38.2 ± 0.8 Ma, within a short time span of less than ca. 1 Ma during the middle Eocene. This provides the first precise ages for metallogenic episode of porphyry-type mineralization. Also, the initial 87Sr/86Sr and (143Nd/144Ndi was recalculated to an age of 39 Ma. Initial 87Sr/86Sr ratios for monzonitic rocks are 0.7047-0.7048. The (143Nd/144Ndi isotope composition are 0.512694-0.512713. Initial ε Nd isotope values 1.45-1.81. Based on isotopic data the magma had originated beyond the continental crust. The study will be used for tectonic-magmatic setting and evolution of eastern Iran. Keywords: Lut block, Middle Eocene, Zircon, Geochronology, Laser ablation ICP-MS,

  7. Mitochondrial Ca2+ homeostasis during Ca2+ influx and Ca2+ release in gastric myocytes from Bufo marinus

    Science.gov (United States)

    Drummond, Robert M; Mix, T Christian H; Tuft, Richard A; Walsh, John V; Fay, Fredric S

    2000-01-01

    The Ca2+-sensitive fluorescent indicator rhod-2 was used to monitor mitochondrial Ca2+ concentration ([Ca2+]m) in gastric smooth muscle cells from Bufo marinus. In some studies, fura-2 was used in combination with rhod-2, allowing simultaneous measurement of cytoplasmic Ca2+ concentration ([Ca2+]i) and [Ca2+]m, respectively. During a short train of depolarizations, which causes Ca2+ influx from the extracellular medium, there was an increase in both [Ca2+]i and [Ca2+]m. The half-time (t½) to peak for the increase in [Ca2+]m was considerably longer than the t½ to peak for the increase in [Ca2+]i. [Ca2+]m remained elevated for tens of seconds after [Ca2+]i had returned to its resting value. Stimulation with caffeine, which causes release of Ca2+ from the sarcoplasmic reticulum (SR), also produced increases in both [Ca2+]i and [Ca2+]m. The values of t½ to peak for the increase in [Ca2+] in both cytoplasm and mitochondria were similar; however, [Ca2+]i returned to baseline values much faster than [Ca2+]m. Using a wide-field digital imaging microscope, changes in [Ca2+]m were monitored within individual mitochondria in situ, during stimulation of Ca2+ influx or Ca2+ release from the SR. Mitochondrial Ca2+ uptake during depolarizing stimulation caused depolarization of the mitochondrial membrane potential. The mitochondrial membrane potential recovered considerably faster than the recovery of [Ca2+]m. This study shows that Ca2+ influx from the extracellular medium and Ca2+ release from the SR are capable of increasing [Ca2+]m in smooth muscle cells. The efflux of Ca2+ from the mitochondria is a slow process and appears to be dependent upon the amount of Ca2+ in the SR. PMID:10713963

  8. U-Pb zircon ages from the southwestern Karoo Basin, South Africa - Implications for the Permian-Triassic boundary

    Science.gov (United States)

    Fildani, A.; Weislogel, A.; Drinkwater, N.J.; McHargue, T.; Tankard, A.; Wooden, J.; Hodgson, D.; Flint, S.

    2009-01-01

    U-Pb ages determined using sensitive high-resolution ion microprobe-reverse geometry on 205 single-grain zircons from 16 ash beds within submarine fan deposits of the Ecca Group provide the first evidence of a marine Permian-Triassic (P-T) boundary in the Karoo Basin of South Africa. These U-Pb ages provide an objective basis for correlating the deep-marine sediments of the southwest Karoo Basin with fluvial-deltaic deposits in the central and eastern parts of the basin where the P-T boundary is recorded in a diverse macrofauna. Furthermore, these new zircon ages and their correlation imply asymmetric subsidence and variable sedimentation rates across the basin. ?? 2009 Geological Society of America.

  9. Fifty Shades of Grey: Zircon Perspectives on the Timing and Chemistry of Magma Interactions Reflected in the Bishop Tuff

    Science.gov (United States)

    Chamberlain, K. J.; Wilson, C. J.; Wooden, J. L.; Baker, J. A.; Charlier, B. L.

    2012-12-01

    The ~0.76 Ma Bishop Tuff eruption in eastern California is an archetypal example of the products of a compositionally stratified magma chamber. Key issues regarding the melt-dominant magma body that have arisen from recent studies include the role of horizontal variability versus vertical stratification, and the nature and timing of a late-stage ingress of compositionally contrasting melt. The latter is reflected in, for example, CL-bright rims on quartz, and Sr- and Ba-rich rims on sanidines, both of which are reported in samples from ignimbrite erupted from vents along the northern caldera rim. Various studies have placed contrasting temporal constraints on assembly and evacuation of the Bishop Tuff magma body and the processes occurring within it from one or two mineral phases. Although the overall crystal specific record is more complex, it has the potential to distinguish between mixing, in-situ crystallisation and other magmatic processes, and resolve the associated timings of these events. Zircon has been widely utilised in the Bishop Tuff and other silicic systems because of its unique records of information about the ages and P-T-X environments of growth. Here we present SHRIMP-RG ion probe data from Bishop Tuff zircons, collected from samples spanning the full eruptive sequence. A combination of age data, textural analysis and trace element analysis is used to yield insights into magma chamber development and the pre-eruptive state of the melt-dominant magma body, as evidenced in material erupted from different vent areas around what became the Long Valley caldera. U-Pb dating of 307 spots from all zones in crystals from all samples yields a strongly unimodal age spectrum, with a mean age of 794+/-3 ka (10 spots rejected, MSWD = 2.0). CL images of the dated zircon suites show the appearance of bright-rimmed zircons in later-erupted ignimbrite packages (accompanied generally by bright-rimmed sanidine and quartz crystals), but with diversity in the

  10. Zircon from Mount St. Helens Reveals Residence Times of Tens to Hundreds of Thousands of Years at Low Magmatic Temperatures Prior to Eruption

    Science.gov (United States)

    Claiborne, L. L.; Miller, C. F.; Clynne, M. A.; Wooden, J. L.; Pallister, J. S.; Lowenstern, J. B.; Mazdab, F. K.

    2007-12-01

    U-series and U-Pb geochronology of zircons from four samples that span the 300,000 year eruptive history of Mount St. Helens, combined with zircon trace element geochemistry and application of the Ti-in-zircon thermometer, provide critical constraints on the time-temperature-compositional history of the sub-volcanic magmatic system. Preliminary results indicate that prior to and throughout its eruptive history, one or more relatively cool, crystal-rich reservoirs have been accumulating beneath the volcano. SHRIMP-RG U-Pb ages of the oldest sample, a dacite erupted ~300 ka, reveal that zircons grew between ~320 and 520 ka, suggesting magmatic activity may have begun 200 ka before eruption. 238U-230Th age spectra in the three youngest samples indicate multiple ages of growth for each sample. The oldest of these three young samples (eruption constrained to ~35-50 ka) contains zircons ranging from ~50 to ~200 ka, with the main concentration of ages ~100 ka. Zircons from a 35 ka dacite range from ~65 to ~230 ka in age, with a dominant episode of growth ~130 ka. Dacite from the current eruption, sampled from the dome in 2005, contains zircons from ~40 to ~170 ka in age, with distinct populations at ~130 and ~170 ka. Taken together, these ages of tens to hundreds of thousands of years prior to eruption and the distinct episodes of growth suggest repeated injection and accumulation of one or more crystal-rich reservoirs beneath the volcanic edifice, a scenario that is further supported by Ti-in-zircon geothermometry (Watson et al. 2006). Ti concentrations indicate zircons grew at temperatures from ~840 to ~640 C, with 90% of analyzed spots recording temperatures between ~770 and ~670 C (T's carry uncertainties of tens of degrees, mostly from uncertainty in a(TiO2)). These temperatures are significantly lower than the eruption temperatures of their host magmas, which range from ~950-800 C. The rounded, resorbed surface morphology of many of the grains attests to the

  11. Differentiation and thermal history of the post-collapse magma reservoir at Yellowstone caldera as revealed by combining the temperature-age-compositional history of zircons

    Science.gov (United States)

    Vazquez, J. A.; Reid, M. R.; Kyriazis, S. F.

    2006-12-01

    Coupling the age and compositional history recorded between and within single accessory minerals, such as zircon or allanite, may provide a high-resolution perspective on the thermochemical evolution of voluminous magma reservoirs in the prelude to eruption. At Yellowstone caldera, USA, more than 900km3 of high- silica rhyolite erupted sequentially in the aftermath of caldera collapse from an evolving magma reservoir. At least 21 lavas and tuffs comprise the voluminous Central Plateau Member (CPM) of the Plateau Rhyolite which erupted between 160 ka and 70 ka. 238U-230Th disequilibrium and U-Pb dating reveal that CPM zircons crystallized approximately 0 to 60 thousand years prior to their respective K-Ar eruption ages, and contain little inheritance from the caldera-forming magma. To obtain a temperature-time-compositional history for CPM zircons and evaluate the applicability of the zircon thermometry to high-silica rhyolites, we performed ion microprobe analyses of trace element concentrations in >65 of the dated zircons from four lavas representing early, middle, and late tapping of the CPM reservoir. Most CPM zircons contain typical REE patterns with chondrite-normalized Lu/La of up to 30,000, and with Eu/Eu* as low as 0.03. A subset of the results (~45%) yield elevated light REE, Ti, and Fe concentrations where sampled zircon domains included small inclusions of Fe-Ti oxides, chevkinite, and/or monazite. Application of Ti-in-zircon thermometry to dated zircons that are unaffected by inclusions yield temperatures that have a range of approximately 70 degrees. Calculated temperatures would largely fall within the range of 800°-840°C for CPM magmas obtained by Zr-glass, zircon saturation, and QUILF thermometry if an essentially fixed melt aTiO2 of 0.3 due to ilmenite saturation is assumed. Where analyzed, the rims of single zircons yield temperatures that are 10°-20° lower than their cores. Our combination of zircon thermometry, age, and composition reveals

  12. Denudation of SW Iberia during Pangea's break-up: geochemical and detrital zircon geochronology characterization of Triassic basins

    OpenAIRE

    Pereira, M. francisco; Ribeiro, Carlos; Vilallonga, Filipa; Chichorro, Martim; Drost, Kerstin

    2010-01-01

    This provenance study is mainly based on new whole-rock geochemistry data but also involves detrital zircon geochronology. More specifically, this study investigates the Early Mesozoic denudation of a Late Paleozoic mountain range and the coeval development of basins during Pangea break-up in SW Iberia. The relations with past dynamic Earth events in Western Europe also include the amalgamation of Pangea and the development of the Carboniferous basins. U-Pb LA-ICP-MS geochronology on ...

  13. Effect of dopants on ferroelectric and piezoelectric properties of lead zirconate titanate thin films on Si substrates

    NARCIS (Netherlands)

    Nguyen, Duc Minh; Trinh, Thong Q.; Dekkers, Jan M.; Houwman, Evert Pieter; Vu, Hung Ngoc; Rijnders, Augustinus J.H.M.

    2014-01-01

    Lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (undoped PZT) and doped PZT thin films with thickness of about 500 nm were grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition (PLD). In this study, 1.0 mol% Nb-doping (at Zr/Ti site) as donor, 1.0 mol% Fe-doping (at Zr/Ti) as acceptor and 10 mol%

  14. Archean U-Pb isotope age of zircon from dunite of the Nizhny Tagil massif (the Uralian Platinum Belt)

    Science.gov (United States)

    Malitch, K. N.; Efimov, A. A.; Ronkin, Yu. L.

    2009-07-01

    Material identity of dunite from zoned-type massifs of the Aldan shield (Kondyor, Chad and others) and dunite “cores” from the Uralian Platinum Belt (i.e., UPB) allows considering them as blocks of ancient material, which have the platform nature, integrated into complex structure of the UPB. In order to provide more clarity in the proposed hypothesis, grains of zircon from dunite of the Nizhny Tagil massif, an undisputable example of a zoned Uralian-type clinopyroxenite-dunite complex, genetically not connected to gabbro, have been studied by methods of isotope geology. Grains of zircon are represented by crystals and their fragments in the size range from 70 up to 170 microns long with length to width ratios from 1.3 up to 1.6. Parameters of U-Th-Pb isotope system were measured using sensitive high-resolution ion microprobe SHRIMP-II at 11 local areas of 8 crystals. Results for studied zircons in concordia diagram 207Pb/235U-206Pb/238U define three statistically different age clusters, i.e., 585 ± 29, 1608 ± 56 and about 2655 million years, accordingly. We presume that the Late Archean age cluster characterize time of dunite generation in a subcontinental mantle. Presence of three discrete age clusters, along with morphological variety of zircons and 232Th/238U values in an interval 0.071-1.692, together with already existing geological facts, reflect prolonged evolution of the dunite in complex geochemical and geodynamic conditions, supporting the conclusion about autonomy of the dunite “cores” in the structure of the UPB.

  15. Zircon dating and mineralogy of the Mokong Pan-African magmatic epidote-bearing granite (North Cameroon)

    Science.gov (United States)

    Tchameni, R.; Sun, F.; Dawaï, D.; Danra, G.; Tékoum, L.; Nomo Negue, E.; Vanderhaeghe, O.; Nzolang, C.; Dagwaï, Nguihdama

    2016-09-01

    We present the mineralogy and age of the magmatic epidote-bearing granite composing most of the Mokong pluton, in the Central Africa orogenic belt (North Cameroon). This pluton intrudes Neoproterozoic (~830 to 700 Ma) low- to high-grade schists and gneisses (Poli-Maroua group), and is crosscut or interleaved with bodies of biotite granite of various sizes. The pluton is weakly deformed in its interior, but solid-state deformation increases toward its margins marked by narrow mylonitic bands trending NNE-SSW. The magmatic epidote granitic rocks are classified as quartz monzodiorite, granodiorite, monzogranite, and syenogranite. They are medium- to coarse-grained and composed of K-feldspar + plagioclase + biotite + amphibole + epidote + magnetite + titanite + zircon + apatite. In these granites, the pistacite component [atomic Fe+3/(Fe3+ + Al)] in epidote ranges from 16 to 29 %. High oxygen fugacity (log ƒO2 - 14 to -11) and the preservation of epidote suggest that the magma was oxidized. Al-in hornblende barometry and hornblende-plagioclase thermometry indicate hornblende crystallization between 0.53 and 0.78 GPa at a temperature ranging from 633 to 779 °C. Zircon saturation thermometry gives temperature estimates ranging from 504 to 916 °C, the latter being obtained on samples containing inherited zircons. U/Pb geochronology by LA-ICP-MS on zircon grains characterized by magmatic zoning yields a concordia age of 668 ± 11 Ma (2 σ). The Mokong granite is the only known occurrence magmatic epidote in Cameroon, and is an important milestone for the comparison of the Central Africa orogenic belt with the Brasiliano Fold Belt, where such granites are much more abundant.

  16. Detrital U-Pb Zircon Dating of the Cenozoic Metamorphic Terrane in Taiwan Orogenic Belt and its Tectonic Implication

    Science.gov (United States)

    Tsai, W.; Lee, Y.

    2011-12-01

    The Taiwan orogen resulted from the collision between the Philippine Sea plate and Eurasia plate since 6.5 Ma and comprises four geologic provinces. From east to west, they are the Coastal Range, the Backbone Range, the Hsuehshan Range, and the Western Foothills. The Coastal Range belongs to Philippine Sea plate. The Backbone Range and Hsuehshan Range are metamorphic terrane are composed of Cenozoic metamorphic terrane and pre-Tertianay metamorphic basement. The Cenozoic metamorphic terrane are lack of fossil and cut by several major faults that results in hard to obtain deposition age and stratigraphic correlation relationship. Here we analysis of more than 3000 grains of detrital U-Pb zircon ages to obtain the age spectrum from Eocene to Miocene metamorphic terrane. The major ages of the Eocene strata are less than 500 Ma; on the contrast the Miocene strata have high percentage of 1800 Ma. Instead of older ages (>100Ma) we found several groups of young U-Pb zircon age, ~39 Ma, ~ 44Ma, ~50 Ma in Eocene strata and 22~25 Ma in Miocene strata which are related with Cenozoic magmatism events in continental margin of Eurasia Plate. This young U-Pb zircon ages indicates the strata age should be younger or similar with these ages. The Eocene strata have been cut by several thrust faults and separated into different blocks. The metamorphic grade increases from west to east of the blocks. The U-Pb Zircon ages indicate the deposition age of the Eocene strata are similar (40Ma) but with different metamorphic grade across the major thrust fault that infers that those thrust faults are preexisting normal faults and are reactive as thrust fault during recently deformation. We also found that the major tectonic boundary "Lishan fault" is unconformity rather than faulting relationship.

  17. In vitro evaluation of the fracture resistance of anterior endodontically treated teeth restored with glass fiber and zircon posts.

    Science.gov (United States)

    Qing, Hai; Zhu, ZhiMin; Chao, YongLie; Zhang, WeiQun

    2007-02-01

    The published information is equivocal regarding the fracture resistance of endodontically treated teeth restored with fiber posts. Additionally, little is known about the biomechanical performance of glass fiber and zircon posts. This in vitro study investigated the fracture resistance of anterior endodontically treated teeth prepared with a 2-mm ferrule, restored with glass fiber and zircon posts and composite resin cores or cast posts and cores. Twelve matched pairs of teeth were obtained from 4 cadavers, and all were endodontically treated and prepared with a standardized 2-mm ferrule. According to a random number table, the 2 teeth from each matched pair were randomly divided into 2 groups. The test group consisted of 12 specimens restored with a glass fiber and zircon post (Fibio) and composite resin (Durafil) core. Twelve matching specimens restored with a nickel-chromium (NiCr) cast post and core served as the control. Specimens in both groups were cemented with resin cement (Panavia F). After cementation of cast NiCr complete crowns with zinc polycarboxylate cement (ShangChi), the specimens were loaded with an incremental static force at an angle of 135 degrees to the long axis of the root until failure occurred. A paired sample t test was used to compare the fracture resistance (N) of teeth restored with the 2 post-and-core systems (alpha=.05). The mean failure load of paired differences between the 2 groups was -261.3+/-237.3 N. The test group exhibited significantly lower failure loads than the control group (P=.004). All specimens displayed root fractures, most of which were oblique, with cracks initiating from the palatal cervical margin and propagating in a labial-apical direction. Within the limitations of this study, the teeth restored with glass fiber and zircon posts demonstrated significantly lower failure loads than those with cast NiCr post and cores. All specimens failed via root fractures.

  18. Provenance evolution of the Jurassic northern Qaidam Basin (West China) and its geological implications: evidence from detrital zircon geochronology

    Science.gov (United States)

    Yu, Long; Xiao, Ancheng; Wu, Lei; Tian, Yuntao; Rittner, Martin; Lou, Qianqian; Pan, Xiaotian

    2017-03-01

    The Jurassic system is the major hydrocarbon source rock and of crucial importance for understanding the Mesozoic intra-continental tectonics in West China. This paper presents systematic detrital zircon geochronology of the Jurassic outcropping at the Dameigou locality in the northern Qaidam Basin, and reports 1000 single-grain U-Pb zircon ages that have implications for the provenance, the corresponding basin property as well as the tectonic setting of West China during Jurassic. Zircon ages exhibit two major clusters at 250 and 2400 Ma whereas two minor clusters at 450 and 850 Ma, suggesting primary sources from the East Kunlun Shan and Oulongbuluke Block, secondary sources from the North Qaidam UHP belt and South Qilian Shan. Combined with observation of lithology and sedimentary facies, two rifting periods were inferred in the earliest Jurassic and the early stage of the Middle Jurassic, respectively, accompanied by further extension throughout the Jurassic. Our results do not support a foreland basin related to the Jurassic southward thrusting of the South Qilian Shan, but favor that the Mesozoic intra-continental tectonics in West China were characterised by pulsed responses to specific collisions rather than a persisting contractional setting during Jurassic period.

  19. Detrital zircon ages and provenance of Neogene foreland basin sediments of the Karnali River section, Western Nepal Himalaya

    Science.gov (United States)

    Baral, Upendra; Ding, Lin; Chamlagain, Deepak

    2017-05-01

    This paper deals with the possible provenance of the middle Miocene to early Pleistocene fluvial sediments of the Siwalik Group along with the Karnali River section (Western Nepal) and adds new insights into the formation and evolution of the Himalayan orogeny by means of detrital zircon U-Pb dating by LA-ICP-MS supplemented with sandstone petrography. The modal composition of the dated sandstone samples shows a 'recycled orogen' field in QFL diagram, indicating significant reworking and recycling of the detrital sediments during the mountain building process. The detrital zircon U-Pb ages from the Lower Siwalik cluster around ∼490-600 Ma and ∼750-1300 Ma with major peaks at 560 Ma, 927 Ma, and 983 Ma. The result shows that the Tethys Himalaya, Higher Himalaya and possibly the Lesser Himalaya were the predominant sources during the deposition of the Lower Siwalik Group. Contrarily, the detrital zircon U-Pb ages in the Middle Siwalik rocks contains clusters around ∼299-727 Ma, ∼750-1200 Ma, ∼1650-1900 Ma with major peaks at 469 Ma and 905 Ma. However, the increased input of mid-Proterozoic detritus (∼1600 Ma) points to the possibility of denudation of the lower Lesser Himalaya following the deposition of the lower part of Middle Siwalik (i.e. since ∼10 Ma).

  20. Detrital zircons from the Nanaimo basin, Vancouver Island, British Columbia: An independent test of Late Cretaceous to Cenozoic northward translation

    Science.gov (United States)

    Matthews, W. A.; Guest, B.; Coutts, D.; Bain, H.; Hubbard, S.

    2017-05-01

    The development of the Cordilleran orogen of western North American is disputed despite a century of study. Paleomagnetic observations require large-scale dextral displacements of crustal fragments along the western margin of North America, from low latitudes to moderate latitudes during the Cretaceous-Paleogene. A lack of corroborating geological evidence for large-scale (>1500 km) displacements has prevented the widespread integration of paleomagnetic data into most contemporary tectonic models for the margin. Here we use detrital zircons from the Nanaimo basin, southwestern British Columbia, Canada as an independent test of its Late Cretaceous paleogeographic position. We compare 4310 detrital zircon U/Pb dates from 16 samples to potential source areas in western North America to test hypothesized northern and southern Late Cretaceous paleogeographic positions. Our detrital zircon data suggest that sediment in the Nanaimo basin derives from either a geographically restricted portion of the Belt-Purcell basin or the Mojave-Sonoran region of southwestern North America. A paleogeographic position for the basin adjacent to the Mojave-Sonoran region is preferred as it is consistent with the paleomagnetic results, but further geological, isotopic, or geophysical data are required to rule out a Belt-Purcell source.

  1. Eruption and magma crystallization ages of Las Tres Vírgenes (Baja California) constrained by combined 230Th/ 238U and (U-Th)/He dating of zircon

    Science.gov (United States)

    Schmitt, Axel K.; Stockli, Daniel F.; Hausback, Brian P.

    2006-11-01

    Las Tres Vírgenes volcano is a calc-alkaline composite cone located near the main Gulf of California escarpment on the E coast of the Baja California peninsula. High-sensitivity ion microprobe U-series ( 230Th/ 238U) ages for zircon from La Vírgen tephra average 121 - 10 + 12 ka (1σ; MSWD = 2.7), with discrete age peaks at ˜ 100 and 160 ka. The noble gas mass spectrometric (U-Th)/He zircon age, corrected for disequilibrium and pre-eruptive storage, is 36 ± 3 ka. This result for the eruption age of La Vírgen tephra is significantly older than previously postulated historic or Holocene ages that were based on an 18th century map reference and 14C dating of accidental charcoal, respectively. The new (U-Th)/He zircon age is consistent with a > 26 ± 4 ka age derived from cosmogenic He exposure dating of an overlying basaltic lava flow [Hausback, B.P. and Abrams, M.J., 1996. Plinian eruption of La Virgen Tephra, Volcán Las Tres Virgenes, Baja California Sur, Mexico. Eos, Transactions, American Geophysical Union, 77(46, Suppl.): 813-814.]. U-Pb zircon analysis of ignimbrites erupted from the adjacent Early Pleistocene La Reforma and El Aguajito calderas yielded ages of 1.38 ± 0.03 Ma ( n = 12; MSWD = 1.0) and 1.17 ± 0.07 Ma ( n = 23; MSWD = 1.3), respectively. No evidence for these ages is found among La Vírgen zircons, whereas pre-Quaternary zircon xenocrysts are common. The La Vírgen magma, therefore, evolved unrelated to Early Pleistocene magmatism in adjacent calderas, but assimilated local basement rocks. A gap between average Th-U and (U-Th)/He zircon ages suggests that zircon crystallization was discontinuous in the La Vírgen magma chamber. In addition, partial resorption of zircon suggests episodic thermal rejuvenation, most likely by basaltic recharge. Based on the zircon record, the > 100 ka lifetime of the thermal anomaly that sustained repeated intrusive pulses significantly exceeds the age of the last eruption. This strengthens the view that Tres

  2. Origin and assembly of Eastern Himalayan crust: constraints from field mapping and U-Pb zircon geochronology

    Science.gov (United States)

    Webb, A. G.; Yin, A.; Dubey, C.

    2012-12-01

    The eastern 1/5th of the Himalayan orogen has received little study, but is a pivotal region for questions of along-strike variations in timing of collision, total shortening, and mountain-building processes. We present field mapping and U-Pb dating of igneous and detrital zircons that establish the lithostratigraphic architecture of the eastern Himalaya, including the first detrital zircon data set to span the range east of Bhutan. Results include: (1) that Late Triassic and Early Cretaceous sedimentary samples from the northern Indian margin show a similar age range of detrital zircons from ~3500 Ma to ~200 Ma, but the Late Triassic rocks are distinguished by a significant age cluster between ~280 and ~220 Ma and a well-defined age peak at ~570 Ma; (2) that the South Tibet detachment along Bhutan-China border is a top-north ductile shear zone; (3) a Cambro-Ordovician crystallization age of an augen gneiss in the South Tibet Detachment shear zone in southeast Tibet; (4) that Main Central thrust hanging-wall paragneiss and footwall quartzites from the far western Arunachal Himalaya share similar provenance and Late Proterozoic maximum depositional ages; and (5) that Main Central thrust footwall metagreywacke from the central western Arunachal Himalaya has a Paleoproterozoic maximum depositional age indicated by a single prominent age peak of ~1780 Ma. The ~280 - 220 Ma detrital zircons of the Late Triassic strata are derived from an arc developed along the northern margin of the Lhasa terrane. Detritus from this arc were deposited on the northern margin of India during India - Lhasa rifting. Along-strike heterogeneity in Main Central thrust footwall chronostratigraphy is indicated by detrital-zircon-age spectrum differences from central western to far-western Arunachal. Nonetheless, the Late Proterozoic rocks in the Main Central thrust hanging wall and footwall in far western Arunachal can be correlated to each other, and to previously analyzed rocks in the South

  3. The Origin of the Chinese Central Tianshan Block in the Southern Central Asian Orogenic Belt: Evidence from Detrital Zircon Study

    Science.gov (United States)

    Huang, Z.; Long, X.; Yuan, C.

    2016-12-01

    The Chinese Central Tianshan Block (CTB) is one of the oldest continental fragments in the southern Central Asian Orogenic Belt (CAOB). Although it is vital for understanding the evolution of the CAOB, its origin has been poorly studied. The CTB was previously suggested to have been originated from the North China, the South China, the Tarim cratons or the East European Craton (Baltica). A total of 165 concordant U-Pb and Hf isotopic analyses of detrital zircon are obtained from three meta-sediments in the CTB, including one meta-sandstone from Xingxingxia formation and one meta-sandstone as well as one quartzite from Kawabulake formation. Detrital zircon grains from the Xingxingxia and Kawabulake formations are dominated by respective youngest age populations at 1002 Ma and 930-960 Ma, providing constraints on the maximum depositional ages for these two formations. Zircon grains from the meta-sediments have very similar age distributions, with two dominant peaks at 0.93-1.0 Ga and 1.0-1.6 Ga and a minor peak at 2.3-2.7 Ga. They have similar Hf isotopic signatures, suggesting that the meta-sediments in the CTB share similar sedimentary provenance. The early Neoproterozoic detrital zircon grains are mainly local-derived, whereas the Paleo-Mesoproterozoic grains are both autochthonous and allochthonous. The occurrence of these Mesoproterozoic and Neoproterozoic zircon grains are coincident with the Nuna breakup and the Rodinia assembly. This suggests that the CTB might experience the tectonic switching of the Nuna to the Rodinia. The distinct Meso-Neoproterozoic age patterns and Hf isotopic compositions of these detrital grains from the CTB and the surrounding blocks indicate that the CTB was not located close to the North China, the South China or the Tarim cratons in Precambrian. Our new data suggest that the CTB was most likely once a part of the East European Craton before the Neoproterozoic. This study was supported by National Basic Research Program of China

  4. Fatigue of extracted lead zirconate titanate multilayer actuators under unipolar high field electric cycling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hong, E-mail: wangh@ornl.gov; Lee, Sung-Min; Wang, James L. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Lin, Hua-Tay [School of Mechanical and Electronic Engineering, Guangdong University of Technology, Guangzhou, 510006 (China)

    2014-12-21

    Testing of large prototype lead zirconate titanate (PZT) stacks presents substantial technical challenges to electronic testing systems, so an alternative approach that uses subunits extracted from prototypes has been pursued. Extracted 10-layer and 20-layer plate specimens were subjected to an electric cycle test under an electric field of 3.0/0.0 kV/mm, 100 Hz to 10{sup 8} cycles. The effects of measurement field level and stack size (number of PZT layers) on the fatigue responses of piezoelectric and dielectric coefficients were observed. On-line monitoring permitted examination of the fatigue response of the PZT stacks. The fatigue rate (based on on-line monitoring) and the fatigue index (based on the conductance spectrum from impedance measurement or small signal measurement) were developed to quantify the fatigue status of the PZT stacks. The controlling fatigue mechanism was analyzed against the fatigue observations. The data presented can serve as input to design optimization of PZT stacks and to operation optimization in critical applications, such as piezoelectric fuel injectors in heavy-duty diesel engines.

  5. MECHANICAL STRENGTH RESPONSES OF POLED LEAD ZIRCONATE TITANATE UNDER EXTREME ELECTRIC FIELD AND VARIOUS TEMPERATURE CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hong [ORNL; Matsunaga, Tadashi [ORNL; Zhang, Kewei [ORNL; Lin, Hua-Tay [ORNL; Wereszczak, Andrew A [ORNL

    2016-01-01

    PZT (lead zirconate titanate), particularly PZT-5A, is used in a variety of critical actuation and sensing systems because of its high Curie temperature and large piezoelectric coefficients. However, PZT is susceptible to mechanical failure. The evaluation of the mechanical strength of the material under the target working conditions is very important. This study presents part of the recent experimental developments in mechanical testing and evaluation of PZT materials at Oak Ridge National Laboratory. Ball-on-ring and four-point bending testing setups were used, with modifications made to account for testing requirements from high-level electric field and elevated temperature. The poled PZT-5A or equivalent material was tested under various specimen and testing conditions. The parameters of the distribution of strengths (characteristic strength and Weibull modulus) are discussed in relation to the testing conditions. Fractographic results based on scanning electron microscopy are also presented and discussed. The related data can serve as input for the design of piezoceramic devices, not only those used in energy systems like fuel injectors in heavy-duty diesel engines, but also those used in structural health monitoring, energy harvesting, and other critical systems in aerospace and civil engineering.

  6. Lead zirconate titanate fiber/polymer composites prepared by a replication process

    Energy Technology Data Exchange (ETDEWEB)

    Waller, D.J.; Safari, A. (Dept. of Ceramic Engineering, Rutgers, State Univ. of New Jersey, Piscataway, NJ (US)); Card, R.J.; O' Toole, M.P. (Chemical Research Div., American Cyanamid Co., Stamford, CT (US))

    1990-11-01

    The woven replication process was used to fabricate lead zirconate titanate (PZT)/polymer composites with 1-3, 2-3, and 3-3 connectivities by starting with novoloid-derived carbon fiber, woven fabric, and nonwoven felt templates, respectively. Activated carbon-fiber template material was impregnated with PZT by soaking it in a solution containing stoichiometric amounts of dissolved lead, zirconium, titanium, and niobium ions. Heat treatment burned out the carbon, leaving a PZT replica with the same form as the template material. Replicas were sintered in a controlled atmosphere and back-filled with an epoxy polymer to form final composites. This method, which is believed to be adaptable for mass production, is capable of producing composites and extremely fine microstructures. Woven composite samples have fiber tow diameters of 200 to 250 {mu}m and spacings between tows of about 150 to 250 {mu}m. Average d{sub 33} = 90 pC/N, g{sub 33} = 211 mV {center dot} m/N, and d{sub h}g{sub h} hydrophone figure of merit of 2100 {times} 10{sup {minus}15} m{sup 2}/N values are reported for woven PZT/polymer composites.

  7. Non-aqueous electrochemical deposition of lead zirconate titanate films for flexible sensor applications

    Science.gov (United States)

    Joseph, Sherin; Kumar, A. V. Ramesh; John, Reji

    2017-11-01

    Lead zirconate titanate (PZT) is one of the most important piezoelectric materials widely used for underwater sensors. However, PZTs are hard and non-compliant and hence there is an overwhelming attention devoted toward making it flexible by preparing films on flexible substrates by different routes. In this work, the electrochemical deposition of composition controlled PZT films over flexible stainless steel (SS) foil substrates using non-aqueous electrolyte dimethyl sulphoxide (DMSO) was carried out. Effects of various key parameters involved in electrochemical deposition process such as current density and time of deposition were studied. It was found that a current density of 25 mA/cm2 for 5 min gave a good film. The morphology and topography evaluation of the films was carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively, which showed a uniform morphology with a surface roughness of 2 nm. The PZT phase formation was studied using X-ray diffraction (XRD) and corroborated with Raman spectroscopic studies. The dielectric constant, dielectric loss, hysteresis and I-V characteristics of the film was evaluated.

  8. A Piezoelectric Plethysmograph Sensor Based on a Pt Wire Implanted Lead Lanthanum Zirconate Titanate Bulk Ceramic

    Directory of Open Access Journals (Sweden)

    Ernesto Suaste-Gómez

    2010-07-01

    Full Text Available This work reports on the development of a Lead Lanthanum Zirconate Titanate (PLZT bulk ferroelectric poled ceramic structure as a Piezoelectric Plethysmograph (PZPG sensor. The ceramic was implanted during its fabrication with a platinum (Pt wire which works as an internal electrode. The ceramic was then submitted to an experimental setup in order to validate and determine the Pt-wire mechanical effects. This PZPG sensor was also mounted on a finger splint in order to measure the blood flow that results from the pulsations of blood occurring with each heartbeat. Fingertip pulses were recorded jointly with an ECG signal from a 25 year old male to compare the time shift; the PZPG sensor guarantees the electrical isolation of the patient. The proposed PZPG has several advantages: it can be adjusted for fingertip measurements, but it can easily be extended by means of spare bands, therefore making possible PZPG measurements from different body locations, e.g., forehead, forearm, knee, neck, etc.

  9. Neutron irradiation effects on domain wall mobility and reversibility in lead zirconate titanate thin films

    Science.gov (United States)

    Graham, Joseph T.; Brennecka, Geoff L.; Ferreira, Paulo; Small, Leo; Duquette, David; Apblett, Christopher; Landsberger, Sheldon; Ihlefeld, Jon F.

    2013-03-01

    The effects of neutron-induced damage on the ferroelectric properties of thin film lead zirconate titanate (PZT) were investigated. Two sets of PbZr0.52Ti0.48O3 films of varying initial quality were irradiated in a research nuclear reactor up to a maximum 1 MeV equivalent neutron fluence of (5.16 ± 0.03) × 1015 cm-2. Changes in domain wall mobility and reversibility were characterized by polarization-electric field measurements, Rayleigh analysis, and analysis of first order reversal curves (FORC). With increasing fluence, extrinsic contributions to the small-signal permittivity diminished. Additionally, redistribution of irreversible hysterons towards higher coercive fields was observed accompanied by the formation of a secondary hysteron peak following exposure to high fluence levels. The changes are attributed to the radiation-induced formation of defect dipoles and other charged defects, which serve as effective domain wall pinning sites. Differences in damage accumulation rates with initial film quality were observed between the film sets suggesting a dominance of pre-irradiation microstructure on changes in macroscopic switching behavior.

  10. Neutron irradiation effects on domain wall mobility and reversibility in lead zirconate titanate thin films

    Energy Technology Data Exchange (ETDEWEB)

    Graham, Joseph T. [Nuclear Engineering Teaching Laboratory, University of Texas at Austin, Austin, Texas 78758 (United States); Electronic, Optic and Nano Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Brennecka, Geoff L.; Ihlefeld, Jon F. [Electronic, Optic and Nano Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Ferreira, Paulo [Materials Science and Engineering Program, University of Texas at Austin, Austin, Texas 78751 (United States); Small, Leo [Electronic, Optic and Nano Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Duquette, David [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Apblett, Christopher [Advanced Power Sources R and D Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Landsberger, Sheldon [Nuclear Engineering Teaching Laboratory, University of Texas at Austin, Austin, Texas 78758 (United States)

    2013-03-28

    The effects of neutron-induced damage on the ferroelectric properties of thin film lead zirconate titanate (PZT) were investigated. Two sets of PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} films of varying initial quality were irradiated in a research nuclear reactor up to a maximum 1 MeV equivalent neutron fluence of (5.16 {+-} 0.03) Multiplication-Sign 10{sup 15} cm{sup -2}. Changes in domain wall mobility and reversibility were characterized by polarization-electric field measurements, Rayleigh analysis, and analysis of first order reversal curves (FORC). With increasing fluence, extrinsic contributions to the small-signal permittivity diminished. Additionally, redistribution of irreversible hysterons towards higher coercive fields was observed accompanied by the formation of a secondary hysteron peak following exposure to high fluence levels. The changes are attributed to the radiation-induced formation of defect dipoles and other charged defects, which serve as effective domain wall pinning sites. Differences in damage accumulation rates with initial film quality were observed between the film sets suggesting a dominance of pre-irradiation microstructure on changes in macroscopic switching behavior.

  11. Synthesis, characterization, and catalytic activity of Rh-based lanthanum zirconate pyrochlores for higher alcohol synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Abdelsayed, Victor; Shekhawat, Dushyant; Poston, James A.; Spivey, James J.

    2013-05-01

    Two lanthanum zirconate pyrochlores (La{sub 2}Zr{sub 2}O{sub 7}; LZ) were prepared by Pechini method and tested for higher alcohols selectivity. In one, Rh was substituted into the pyrochlore lattice (LRZ, 1.7 wt%) while for the second, Rh was supported on an unsubstituted La{sub 2}Zr{sub 2}O{sub 7} (R/LZ, 1.8 wt%). X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR) results show that the surface reducibility depends on whether the Rh is in (or supported on) the LZ pyrochlore. Rhodium in the LRZ is more reducible than rhodium supported on the R/LZ pyrochlore, likely due to the presence of a perovskite phase (LaRhO{sub 3}; identified by XRD), in which rhodium is more reducible. The formation of the perovskite accompanies that of the pyrochlore. CO hydrogenation results show higher ethanol selectivity for R/LZ than LRZ, possibly due to the strong interaction between Rh and LZ on the R/LZ, forming atomically close Rh{sup +}/Rh{sup 0} sites, which have been suggested to favor ethanol production.

  12. Enhancement of piezoelectric properties for [poly (vinylidene fluoride)/barium zirconate titanate] nanocomposites

    Science.gov (United States)

    Hemeda, O. M.; Tawfik, A.; El-Shahawy, M. M.; Darwish, K. A.

    2017-08-01

    Poly (vinylidene fluoride) / barium zirconate titanate nanocomposite samples with the formula [ x (PVDF) / (1 - x) BZT] (where x = zero, 0.2, 0.4, 0.6, 0.8 and 1) are prepared using the hot pressing method. The BZT is prepared using the tartrate precursor method. The properties of these nanocomposites are characterized by X-ray diffraction (XRD), scan electron microscope (SEM), transmission electron microscope (TEM) and Fourier transformed infrared (FTIR) at room temperature. The XRD patterns indicate that the average crystallite size ranges from 7.5 to 23.8nm. The grain size is estimated from SEM micrograph and lies between 263 and 186nm, whereas the average crystallite size has a distribution between 14 and 70nm from TEM images. The FTIR spectra illustrate the absence of any absorption band related to the (γ) phase, but the absorption bands characteristic for (α), and (β) phases of PVDF are observed. The fraction of the (β) phase of PVDF increases by increasing the BZT content, which is very useful in industrial applications, such as sensors, actuators and transducers. The high value of the piezoelectric coefficient d_{33} is measured for the PVDF/BZT nanocomposites.

  13. Thermoluminescence and optically stimulated luminescence of gamma-irradiated mineral zircon

    Energy Technology Data Exchange (ETDEWEB)

    Secu, M. [National Institute of Materials Physics, Bucharest-Magurele (Romania); Vainshtein, D.; Hartog, H.W. den [University of Groningen (Netherlands); Turkin, A.A. [National Science Centre, Kharkov Institute of Physics and Technology (Ukraine)

    2007-03-15

    Thermoluminescence (TL) manifested by gamma-irradiated mineral zircon has shown a strong TL peak at about 165 C which is due to recombination of electrons and Dy{sup 3+} related shallow hole traps. After they have been removed by a short preheat we have observed two TL peaks at 300-320 C and {approx}420 C, which are mainly due to recombination of electrons and Tb{sup 3+} related hole traps centres yielding its characteristic luminescence. The experimental results indicate that optically stimulated luminescence (OSL) is due to luminescent emission of Tb{sup 3+}ions and [SiO {sub 4}] {sup 4-} groups. The deep traps related to the 420 C TL peak contribute to the Tb {sup 3+} related OSL. The deep traps related to the 300-320 C TL peak contribute to OSL associated with the luminescent emission of [SiO {sub 4}] {sup 4-} groups. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Elution of lead from lead zirconate titanate ceramics to acid rain

    Science.gov (United States)

    Tsurumi, Takaaki; Takezawa, Shuhei; Hoshina, Takuya; Takeda, Hiroaki

    2017-10-01

    The amount of lead that eluted from lead zirconate titanate (PZT) ceramics to artificial acid rain was evaluated. Four kinds of PZT ceramics, namely, pure PZT at MPB composition, CuO-added PZT, PZT with 10 mol % substitution of Ba for Pb, and CuO-added PZT with 10 mol % substitution of Ba for Pb, were used as samples of the elution test. These PZT ceramics of 8 mm2 and 1.1-1.2 mm thickness were suspended in 300 ml of H2SO4 solution of pH 4.0. The concentration of lead eluted from PZT was in the range from 0.2 to 0.8 ppm. It was found that both liquid phase formation by the addition of CuO and the substitution of Ba for Pb were effective to reduce the amount of lead that eluted. By fitting the leaching out curve with a classical equation, a master curve assuming no sampling effect was obtained. The lead concentration evaluated from the amount of lead that eluted from a commercial PZT plate to H2SO4 solution of pH 5.3 was almost the same as the limit in city water. It is concluded that PZT is not harmful to health and the environment and the amount of lead that eluted from PZT can be controlled by modifying PZT composition.

  15. Fatigue of extracted lead zirconate titanate multilayer actuators under unipolar high field electric cycling

    Science.gov (United States)

    Wang, Hong; Lee, Sung-Min; Wang, James L.; Lin, Hua-Tay

    2014-12-01

    Testing of large prototype lead zirconate titanate (PZT) stacks presents substantial technical challenges to electronic testing systems, so an alternative approach that uses subunits extracted from prototypes has been pursued. Extracted 10-layer and 20-layer plate specimens were subjected to an electric cycle test under an electric field of 3.0/0.0 kV/mm, 100 Hz to 108 cycles. The effects of measurement field level and stack size (number of PZT layers) on the fatigue responses of piezoelectric and dielectric coefficients were observed. On-line monitoring permitted examination of the fatigue response of the PZT stacks. The fatigue rate (based on on-line monitoring) and the fatigue index (based on the conductance spectrum from impedance measurement or small signal measurement) were developed to quantify the fatigue status of the PZT stacks. The controlling fatigue mechanism was analyzed against the fatigue observations. The data presented can serve as input to design optimization of PZT stacks and to operation optimization in critical applications, such as piezoelectric fuel injectors in heavy-duty diesel engines.

  16. Characterization methodology for lead zirconate titanate thin films with interdigitated electrode structures

    Science.gov (United States)

    Nigon, R.; Raeder, T. M.; Muralt, P.

    2017-05-01

    The accurate evaluation of ferroelectric thin films operated with interdigitated electrodes is quite a complex task. In this article, we show how to correct the electric field and the capacitance in order to obtain identical polarization and CV loops for all geometrical variants. The simplest model is compared with corrections derived from Schwartz-Christoffel transformations, and with finite element simulations. The correction procedure is experimentally verified, giving almost identical curves for a variety of gaps and electrode widths. It is shown that the measured polarization change corresponds to the average polarization change in the center plane between the electrode fingers, thus at the position where the electric field is most homogeneous with respect to the direction and size. The question of maximal achievable polarization in the various possible textures, and compositional types of polycrystalline lead zirconate titanate thin films is revisited. In the best case, a soft (110) textured thin film with the morphotropic phase boundary composition should yield a value of 0.95Ps, and in the worst case, a rhombohedral (100) textured thin film should deliver a polarization of 0.74Ps.

  17. The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT

    Directory of Open Access Journals (Sweden)

    Christoph Slouka

    2016-11-01

    Full Text Available The different properties of acceptor-doped (hard and donor-doped (soft lead zirconate titanate (PZT ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

  18. Zircon U-Pb age, Lu-Hf isotope, mineral chemistry and geochemistry of Sundamalai peralkaline pluton from the Salem Block, southern India: Implications for Cryogenian adakite-like magmatism in an aborted-rift

    Science.gov (United States)

    Renjith, M. L.; Santosh, M.; Li, Tang; Satyanarayanan, M.; Korakoppa, M. M.; Tsunogae, T.; Subba Rao, D. V.; Kesav Krishna, A.; Nirmal Charan, S.

    2016-01-01

    The Sundamalai peralkaline pluton is one among the Cryogenian alkaline plutons occurring in the Dharmapuri Rift Zone (DRZ) of the Salem Block in the Southern Granulite Terrane (SGT) of India. Here we present zircon U-Pb age and Lu-Hf isotopic composition, mineral chemistry and geochemistry of the pluton to explore the petrogenesis and geodynamic implications. Systematic modal variation of orthoclase, Na-plagioclase, Ca-amphibole (ferro-edenite and hastingsite) and quartz developed quartz-monzonite and granite litho units in the Sundamalai pluton. Thermometry based on amphibole-plagioclase pair suggests that the pluton was emplaced and solidified at around 4.6 kbar pressure with crystallization of the major phases between 748 and 661 °C. Estimated saturation temperature of zircon (712-698 °C) is also well within this range. However, apatite saturation occurred at higher temperatures between 835 and 870 °C, in contrast with monazite saturation (718-613 °C) that continued up to the late stage of crystallization. Estimated oxygen fugacity values (log fO2: -14 to -17) indicate high oxidation state for the magma that stabilized titanite and magnetite. The magmatic zircons from Sundamalai pluton yielded a weighted mean 206Pb/238U age of 832.6 ± 3.2 Ma. Geochemically, the Sundamalai rocks are high-K to shoshonitic, persodic (Na2O/K2O ratio > 1), silica-saturated (SiO2:65-72 wt.%), and peralkaline in composition (aluminum saturation index, ASI peralkaline as result of fractional crystallization (plagioclase effect) controlled differentiation between quartz-monzonite and granite. Both rock types have high content of Na2O (5.1-6.3 wt.%), Ba (350-2589 ppm) and Sr (264-1036 ppm); low content of Y (8.7-17 ppm) and Yb (0.96-1.69 ppm); elevated ratios of La/Yb (11-46) and Sr/Y (46-69) and are depleted in Ti, with a positive Sr anomaly suggesting an adakite-like composition and garnet controlled melting of a plagioclase-poor source. The low content of MgO (zircon ε

  19. CA125 in ovarian cancer

    DEFF Research Database (Denmark)

    Duffy, M J; Bonfrer, J M; Kulpa, J

    2005-01-01

    CA125 is currently the most widely used tumor marker for ovarian epithelial cancer. The aim of this article is to provide guidelines for the routine clinical use of CA125 in patients with ovarian cancer. Due to lack of sensitivity for stage I disease and lack of specificity, CA125 is of little...... value in the detection of early ovarian cancer. At present, therefore, CA125, either alone or in combination with other modalities, cannot be recommended for screening for ovarian cancer in asymptomatic women outside the context of a randomized controlled trial. Preoperative levels in postmenopausal...... women, however, may aid the differentiation of benign and malignant pelvic masses. Serial levels during chemotherapy for ovarian cancer are useful for assessing response to treatment. Although serial monitoring following initial chemotherapy can lead to the early detection of recurrent disease...

  20. Sonoma County, CA, 2013 Lidar

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sonoma County Vegetation Mapping and LiDAR Consortium retained WSI to provide lidar and Orthophoto data and derived products in Sonoma County, CA. A classified LAS...

  1. Detrital zircon provenance from three turbidite depocenters of the Middle-Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production

    Science.gov (United States)

    Weislogel, A.L.; Graham, S.A.; Chang, E.Z.; Wooden, J.L.; Gehrels, G.E.

    2010-01-01

    To test the idea that the voluminous upper Middle to Upper Triassic turbidite strata in the Songpan-Ganzi complex of central China archive a detrital record of Dabie ultrahigh-pressure (UHP) terrane unroofing, we report 2080 single detrital U-Pb zircon ages by sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis from 29 eastern Songpan-Ganzi complex sandstone samples. Low (Paleozoic and bimodally distributed Precambrian zircon populations, which, together with south-to southeast-directed paleocurrent data, indicate derivation from the retro-side of the Qinling-Dabie (Q-D) collisional orogen wedge. In the central depocenter, the dominantly Paleozoic detrital zircon signature and south-to southwest-oriented paleocurrent indicators reflect a profusion of Paleozoic zircon grains. These data are interpreted to reflect an influx of material derived from erosion of Paleozoic supra-UHP rocks of the Dabie terrane in the eastern Qinling-Dabie orogen, which we speculate may have been enhanced by development of a monsoonal climate. This suggests that erosional unroofing played a significant role in the initial phase of UHP exhumation and likely influenced the petrotectonic and structural evolution of the Qinling-Dabie orogen, as evidenced by compressed Triassic isotherms/grads reported in the Huwan shear zone that bounds the Dabie terrane to the north. The central depocenter deposits reflect a later influx of bimodally distributed Precambrian zircon, signifying either a decrease in the influx of Paleozoic zircon grains due to stalled UHP exhumation and/or dilution of the same influx of Paleozoic zircons by spilling of Precambrian zircon from the northeastern depocenter into the central depocenter basin, perhaps due to infilling and bypass of sediment from the northern depocenter or due to initial collapse and constriction of the eastern Songpan-Ganzi complex basin. The

  2. Impact of volcanism on the evolution of Lake Van (eastern Anatolia) III: Periodic (Nemrut) vs. episodic (Süphan) explosive eruptions and climate forcing reflected in a tephra gap between ca. 14 ka and ca. 30 ka

    Science.gov (United States)

    Schmincke, Hans-Ulrich; Sumita, Mari

    2014-09-01

    Fifteen Lateglacial to Holocene rhyolitic, dominantly primary tephra layers piston-cored and drilled (ICDP Paleovan drilling project) in western Lake Van (eastern Anatolia, Turkey) were precisely correlated to either of the two adjacent and active large volcanoes Nemrut and Süphan based on shard textures, mineralogy and mineral and glass compositions. The young peralkaline (comenditic to pantelleritic) primary rhyolitic Nemrut tephras are characterized by anorthoclase, hedenbergitic to augitic clinopyroxene, fayalitic olivine, minor quartz, and rare accessory chevkinite and zircon. Phenocrysts in subalkaline primary rhyolitic Süphan tephras are chiefly oligoclase-labradorite, with minor K-rich sanidine in some, biotite, amphibole, hypersthene, rare augitic clinopyroxene, relatively common allanite and rare zircon. Two contrasting explosive eruptive modes are distinguished from each other: episodic (Süphan) and periodic (Nemrut). The Lateglacial Süphan tephra swarm covers a short time interval of ca. 338 years between ca. 13,078 vy BP and 12,740 vy BP, eruptions having occurred statistically every ca. 42 years with especially short intervals between V-11 (reworked) and V-14. Causes for the strongly episodic Süphan explosive behavior might include seismic triggering of a volcano-magma system unable to erupt explosively without the benefit of external triggering, as reflected in pervasive faulting preceding the Süphan tephra swarm. Seismic triggering may have caused the rise of more mafic ("trachyandesitic") parent magma, heating near-surface pockets of highly evolved magma - that might have formed silicic domes during this stage of volcano evolution - resulting in ascent and finally explosive fragmentation of magma essentially by external factors, probably significantly enhanced by magma-water/ice interaction. Explosive eruptions of the Nemrut volcano system, interpreted to be underlain by a large fractionating magma reservoir, follow a more periodic mode of (a

  3. New zircon ages on the Cambrian-Ordovician volcanism of the Southern Gemericum basement (Western Carpathians, Slovakia): SHRIMP dating, geochemistry and provenance

    Science.gov (United States)

    Vozárová, Anna; Rodionov, Nickolay; Šarinová, Katarína; Presnyakov, Sergey

    2017-09-01

    The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-sedimentary rock complexes, constitutes a record of the polyphase Cambrian-Ordovician continental volcanic arc volcanism. These metavolcanic rocks are characterized by the enrichment in K, Rb, Ba, Th and Ce and Sm relative to Ta, Nb, Hf, Zr, Y and Yb that are the characteristic features for volcanic arc magmatites. The new SHRIMP U-Pb zircon data and compilation of previously published and re-evaluated zircon ages, contribute to a new constrain of the timing of the Cambrian-Ordovician volcanism that occurred between 496 and 447 Ma. The following peaks of the volcanic activity of the Southern Gemericum basement have been recognized: (a) mid-late Furongian at 492 Ma; (b) Tremadocian at 481 Ma; (c) Darriwilian at 464 Ma prolonged to 453 Ma within the early Upper Ordovician. The metavolcanic rocks are characterized by a high zircon inheritance, composed of Ediacaran (650-550 Ma), Tonian-Stenian (1.1-0.9 Ma), and, to a lesser extent, Mesoproterozoic (1.3 Ga), Paleoproterozoic (1.9 Ga) and Archaean assemblages (2.6 Ga). Based on the acquired zircon populations, it could be deduced that Cambrian-Ordovician arc crust was generated by a partial melting of Ediacaran basement in the subduction-related setting, into which old crustal fragments were incorporated. The ascertained zircon inheritances with Meso-, Paleoproterozoic and Archaean cores indicate the similarities with the Saharan Metacraton provenance.

  4. Zircon morphology and U-Pb geochronology of seven metaluminous and peralkaline post-orogenic granite complexes of the Arabian Shield, Kingdom of Saudi Arabia

    Science.gov (United States)

    Aleinikoff, John Nicholas; Stoeser, D.B.

    1988-01-01

    The U-Pb zircon method was used to determine the ages of seven metaluminous-to-peralkaline post-orogenic granites located throughout the Late Proterozoic Arabian Shield of Saudi Arabia. Zircons from the metaluminous rocks are prismatic, with length-to-width ratios of about 2-4:1 and small pyramidal terminations. In contrast, zircons from three of the four peralkaline complexes either lack well developed prismatic faces (are pseudo-octahedral) or are anhedral. Some of the zircons from the peralkaline granites contain inherited radiogenic lead. This complicates interpretation of the isotopic data and. in many cases, may make the U-Pb method unsuitable for determining the age of a peralkaline granite. Zircons in the metaluminous granites do not contain inheritance and thus, best-fit chords calculated through the data have upper concordia intercepts that indicate the age of intrusion, and lower intercepts that indicate simple episodic lead loss. The results show that these granites were emplaced during multiple intrusive episodes from 670 to 510 Ma (Late Proterozoic to Cambrian).

  5. Zircon geochronology of the Mashak volcanic rocks and the problem of the age of the lower-middle Riphean boundary (Southern Urals)

    Science.gov (United States)

    Krasnobaev, A. A.; Kozlov, V. I.; Puchkov, V. N.; Busharina, S. V.; Sergeeva, N. D.; Paderin, I. P.

    2013-09-01

    In the type sections of the Riphean within the Bashkirian mega-anticlinorium (Southern Urals), the Mashak Formation represents a basal unit of the Middle Riphean erathem. The formation comprises throughout its area of distribution the alternation of volcanic, volcano-sedimentary, and sedimentary sequences and is divided into the lower, middle, and upper subformations. The volcanic rocks containing zircons (four samples, rhyodacite and rhyolite collected at Mashak, Berezyak, and Bolshoi Shatak ranges) are largely confined to the lower subformation. Analyses were performed using a SHRIMP II methodology, with special attention to the mineralogical characteristics of zircons, including their habit, morphology, preservation, and inclusions. All zircons show similarities in their mineral chemistry and geochemistry, which are indicative of the geochemical affinity of the volcanic rocks. At the same time, all zircon grains are characterized by specific typological parameters, which may equally reflect the parameters involved in the development of such volcanic rocks under different conditions. The integrated U-Pb age of zircons (SHRIMP II, VSEGEI, St. Petersbrug) from the four samples is 1383 ± 3 Ma. On the basis of the age of the Berdyaush gabbro-granitoid intrusion (up to 1410 Ma), the most likely age of this boundary is 1400 Ma, which is equated to the Calymmian and Ectasian of the International Stratigraphic Scale.

  6. Crystal chemical infrared and Raman study of new rare earth fluorophosphates with zircon structure. Etude cristallographique, infra-rouge et Raman de nouveaux fluorophosphates de terres rares de structure zircon

    Energy Technology Data Exchange (ETDEWEB)

    Zambon, D.; El-Ghozzi, M.; Avignant, D. (Clermont-Ferrand-2 Univ., 63 - Aubiere (FR)); Ben Said, N.; Mansouri, I. (Universite Hassan II, Casablanca (MA))

    1991-10-01

    Single-phase compositions of general formula Li{sub x}Ln{sub x}Y{sub 1-x} (PO{sub 4}){sub 1-x}F{sub 4x} where Ln = Gd to Lu, Y and 0 {<=} x {<=} 0.45 with the zircon like structure were characterized during the study of LiLnF{sub 4} - YPO{sub 4} pseudo-binary systems. Their crystal chemical characteristics have been determined from polycrystalline samples using X-ray diffraction. The infra-red and Raman spectra of members of them have been recorded for the x = 0.40 composition and analyzed.

  7. Magnetic structural effect (MSE in epitaxial films of cerium oxide and lanthanum zirconate

    Directory of Open Access Journals (Sweden)

    Fatima Kh. Chibirova

    2015-06-01

    Full Text Available Increasing the critical current density in the second generation high-temperature superconducting wires (2G HTS is the major challenge for researchers and manufacturers of 2G HTS wires all over the world. We proposed a new approach to increase the number of percolation paths for supercurrent, i.e. increasing the number of low angle grain boundaries (<5° in the epitaxial superconducting YBCO layer by magnetic structural processing (MSP of buffer layers. New experimental results have been presented on the application of MSP for improving the structure and increasing the texture sharpness of buffer in electrical conducting element of 2G HTS wire. The influence of MCO on the structural and textural properties has been investigated in a buffer consisting of epitaxial films of cerium oxide CeO2 and lanthanum zirconate La2Zr2O7 in the CeO2/4La2Zr2O7 architecture. The influence of the magnetic processing of the epitaxial La2Zr2O7 buffer film on the shape of grains has been found. An atomic force microscopical study has shown that after magnetic processing the shape of grains improved significantly. A multilayer CeO2/4La2Zr2O7 buffer each layer of which was processed in a magnetic field has a high degree of orientation: only one diffraction peak with (200 indexes is observed in the X-ray spectrum. The X-ray settings of the (200 diffraction peak indicate a well developed epitaxial structure of CeO2 and La2Zr2O7 layers. The texture of the buffer is by more than 2° sharper than that of the Ni–5 at% W substrate.

  8. Effect of off-center ion substitution in morphotropic lead zirconate titanate composition

    Science.gov (United States)

    Bhattarai, Mohan K.; Pavunny, Shojan P.; Instan, Alvaro A.; Scott, James F.; Katiyar, Ram S.

    2017-05-01

    A detailed study of the effect of off-center donor ion (Sc3+) substitution on structural, microstructural, optical, dielectric, electrical, and ferroelectric properties of morphotropic composition of lead zirconate titanate electroceramics with the stoichiometric formula Pb0.85Sc0.10Zr0.53Ti0.47O3 (PSZT) and synthesized using a high energy solid-state reaction technique was carried out. Powder x-ray diffractometry was used to identify the stabilized tetragonal phase (space group P 4 m m ) with considerably reduced tetragonal strain, c /a = 1.005. An analysis of the thermal dependence of the Raman results indicated a smooth displacive (ferroelectric-paraelectric) phase transition as revealed by the observed disappearance of the soft modes A1 (1TO) and A1 (2TO) above 460 K. The dielectric response of Pt/PSZT/Pt metal-ferroelectric-metal capacitors was probed over a wide range of thermal excursions (85-600 K) and ac signal frequencies (102-106 Hz). Thermally activated dynamic and static conduction processes indicate hopping conduction mechanism ( Ea c t ≤ 0.015 eV) and the formation of small polarons caused by the electron and/or hole-lattice (phonon) interaction ( Ea c t ≥ 0.1 eV) at low (100-300 K) and high temperatures (300-600 K), respectively. The reduction in remnant polarization obtained is in good agreement with the largely reduced tetragonal strain observed in this sample, ( Pr ∝ √{c /a -1 } ). DC conduction is dominated by Poole-Frenkel mechanism that assumes a Coulombic attraction between detrapped electrons and positively charged stationary defect species in the polycrystalline matrix.

  9. Transverse piezoelectric coefficient measurement of flexible lead zirconate titanate thin films

    Energy Technology Data Exchange (ETDEWEB)

    Dufay, T.; Guiffard, B.; Seveno, R. [LUNAM Université, Université de Nantes, IETR (Institut d' Électronique et de Télécommunications de Rennes), UMR CNRS 6164, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3 (France); Thomas, J.-C. [LUNAM Université, Université de Nantes-École Centrale Nantes, GeM (Institut de Recherche en Génie Civil et Ingénierie Mécanique), UMR CNRS 6183, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3 (France)

    2015-05-28

    Highly flexible lead zirconate titanate, Pb(Zr,Ti)O{sub 3} (PZT), thin films have been realized by modified sol-gel process. The transverse piezoelectric coefficient d{sub 31} was determined from the tip displacement of bending-mode actuators made of PZT cantilever deposited onto bare or RuO{sub 2} coated aluminium substrate (16 μm thick). The influence of the thickness of ruthenium dioxide RuO{sub 2} and PZT layers was investigated for Pb(Zr{sub 0.57}Ti{sub 0.43})O{sub 3}. The modification of Zr/Ti ratio from 40/60 to 60/40 was done for 3 μm thick PZT thin films onto aluminium (Al) and Al/RuO{sub 2} substrates. A laser vibrometer was used to measure the beam displacement under controlled electric field. The experimental results were fitted in order to find the piezoelectric coefficient. Very large tip deflections of about 1 mm under low voltage (∼8 V) were measured for every cantilevers at the resonance frequency (∼180 Hz). For a given Zr/Ti ratio of 58/42, it was found that the addition of a 40 nm thick RuO{sub 2} interfacial layer between the aluminium substrate and the PZT layer induces a remarkable increase of the d{sub 31} coefficient by a factor of 2.7, thus corresponding to a maximal d{sub 31} value of 33 pC/N. These results make the recently developed PZT/Al thin films very attractive for both low frequency bending mode actuating applications and vibrating energy harvesting.

  10. Transverse piezoelectric coefficient measurement of flexible lead zirconate titanate thin films

    Science.gov (United States)

    Dufay, T.; Guiffard, B.; Thomas, J.-C.; Seveno, R.

    2015-05-01

    Highly flexible lead zirconate titanate, Pb(Zr,Ti)O3 (PZT), thin films have been realized by modified sol-gel process. The transverse piezoelectric coefficient d31 was determined from the tip displacement of bending-mode actuators made of PZT cantilever deposited onto bare or RuO2 coated aluminium substrate (16 μm thick). The influence of the thickness of ruthenium dioxide RuO2 and PZT layers was investigated for Pb(Zr0.57Ti0.43)O3. The modification of Zr/Ti ratio from 40/60 to 60/40 was done for 3 μm thick PZT thin films onto aluminium (Al) and Al/RuO2 substrates. A laser vibrometer was used to measure the beam displacement under controlled electric field. The experimental results were fitted in order to find the piezoelectric coefficient. Very large tip deflections of about 1 mm under low voltage (˜8 V) were measured for every cantilevers at the resonance frequency (˜180 Hz). For a given Zr/Ti ratio of 58/42, it was found that the addition of a 40 nm thick RuO2 interfacial layer between the aluminium substrate and the PZT layer induces a remarkable increase of the d31 coefficient by a factor of 2.7, thus corresponding to a maximal d31 value of 33 pC/N. These results make the recently developed PZT/Al thin films very attractive for both low frequency bending mode actuating applications and vibrating energy harvesting.

  11. Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray

    Science.gov (United States)

    Mahade, Satyapal; Curry, Nicholas; Björklund, Stefan; Markocsan, Nicolaie; Nylén, Per; Vaßen, Robert

    2017-01-01

    7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 °C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 °C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures (>1200 °C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triple-layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM.

  12. The ca. 1380 Ma Mashak igneous event of the Southern Urals

    Science.gov (United States)

    Puchkov, Victor N.; Bogdanova, Svetlana V.; Ernst, Richard E.; Kozlov, Vjacheslav I.; Krasnobaev, Arthur A.; Söderlund, Ulf; Wingate, Michael T. D.; Postnikov, Alexander V.; Sergeeva, Nina D.

    2013-08-01

    A review of the geochronology, geochemistry and distribution of the 1380 Ma Mashak Large Igneous Province (LIP) of the eastern margin of the East European craton indicates a potential link to a major breakup stage of the Mesoproterozoic supercontinent Columbia (Nuna), link to a major stratigraphic boundary (Lowe-Middle Riphean), and economic significance for hydrocarbons and metallogeny. Specifically, the Mashak event likely has much greater extent than previously realized. Two U-Pb baddeleyite (ID TIMS) age determinations on dolerite sills obtained from borehole (Menzelinsk-Aktanysh-183) confirm the western extent of the Mashak event into the crystalline basement of the East European Craton (1382 ± 2 Ma) and into the overlying Lower Riphean sediments (1391 ± 2 Ma), and the imprecise ages reported elsewhere indicate the possible extension into the Timan region, with an overall areal extent of more than 500,000 km2 (LIP scale). It has tholeiitic compositions and is associated with breakup on the eastern margin of the craton - in addition, precise SHRIMP zircon ages of 1386 ± 5 Ma and 1386 ± 6 Ma (this paper) provide confirmation of previous approximate 1380-1383 Ma zircon age determination of the same formation, and suggest an age of ca. 1.4 Ga for the Lower/Middle Riphean boundary which was formerly considered to be 1350 ± 10 Ma. Contemporaneous magmatic rocks in the northeastern Greenland part of Laurentia (Zig-Zag Dal and Midsommerso formations) and Siberia (Chieress dykes and other dolerites) together with the Mashak event are suggested to be fragments of a single huge LIP and to correspond to breakup stage of the Columbia (Nuna) supercontinent. The Mashak LIP also has some significance, at least in Volgo-Uralia, for hydrocarbons and metallogeny.

  13. Trace-Element Mobility in Eclogite-Facies Subducted Crust: Garnet, Zircon, and Rutile Petrochronology of As Sifah, Oman

    Science.gov (United States)

    Garber, Joshua M.; Rioux, Matthew; Kylander-Clark, Andrew R.; Vervoort, Jeff D.; Wilford, Diane; Hacker, Bradley R.; Searle, Michael P.; Waters, David J.; Warren, Clare

    2017-04-01

    Trace element flux in subduction zones is strongly affected by the chemistry and availability of an accompanying fluid, in addition to mineral partitioning behavior. These factors may be exacerbated in certain lithologies, suggesting a role for lithology-specific rock permeability, fluid fugacity, and/or trace-element partitioning during subduction. To assess lithological controls on elemental transport in subducted mafic crust and sediment, we obtained dates (Sm-Nd, Lu-Hf, and U-Pb) and major- and trace-element concentrations for garnet, zircon, and rutile in end-member mafic and metapelitic rocks from the ultrahigh-pressure As Sifah unit of Oman. The three phases record similar isotopic dates among all lithologies, but trace-element records for each phase are distinct for each rock type. For example, i) mafic rocks show expected garnet/zircon rare-earth element (REE) partitioning, but metapelitic garnet and zircon do not, and ii) mafic rutiles record lower intergranular solubilities for high-field-strength elements (HFSEs) than pelitic rutiles. Together, these data suggest that REE and HFSE equilibrium length-scales varied significantly between adjacent lithologies, implicating crucial differences in fluid flux during subduction. Further, Lu-Hf isotopic data are scattered and non-isochronous for all rocks - even in metapelites that exhibit cm- to outcrop-scale HFSE equilibrium length-scales - suggesting that achievement of elemental equilibrium does not imply isotopic equilibrium, even at the same scale. Our approach illustrates the power of multi-phase petrochronology in determining the behavior of distinct trace-element groups during metamorphism.

  14. Meteorite zircon constraints on the bulk Lu−Hf isotope composition and early differentiation of the Earth

    Science.gov (United States)

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

    2015-01-01

    Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The 176Lu−176Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day 176Hf/177Hf and 176Lu/177Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess 176Hf due to the accelerated decay of 176Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu−Hf system. Herein we report the first, to our knowledge, high-precision Lu−Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial 176Hf/177Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess 176Hf and accurately represent the Lu−Hf system of the bulk Earth (176Hf/177Hf = 0.282793 ± 0.000011; 176Lu/177Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago. PMID:25870298

  15. Meteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth.

    Science.gov (United States)

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

    2015-04-28

    Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The (176)Lu-(176)Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day (176)Hf/(177)Hf and (176)Lu/(177)Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess (176)Hf due to the accelerated decay of (176)Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu-Hf system. Herein we report the first, to our knowledge, high-precision Lu-Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial (176)Hf/(177)Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess (176)Hf and accurately represent the Lu-Hf system of the bulk Earth ((176)Hf/(177)Hf = 0.282793 ± 0.000011; (176)Lu/(177)Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago.

  16. Constraints on the Timing and Style of Paleogene Extension in the Basin and Range from Apatite and Zircon Double Dating

    Science.gov (United States)

    Canada, A.; Cassel, E. J.; Stockli, D. F.; Smith, M. E.; Jicha, B. R.; Singer, B. S.

    2016-12-01

    In the Paleogene hinterland of the Sevier orogenic belt, from eastern Nevada to western Utah, high-elevation intermontane basins record widespread accommodation and early-onset extension within the Basin and Range. Detrital zircon U-Pb-He double dating of siliciclastic sediments deposited across the width of the Cordilleran hinterland shows that early and middle Eocene sediments are predominantly multi-cycle and consistent with gradual erosional exhumation of the hinterland. During the middle Eocene and into the early Oligocene, volcanic glass hydration waters indicate that Copper Basin formed at an elevation of 3 km in northeastern Nevada. The basin contains a 1.5 km-thick sequence of fluvial, lacustrine, and volcanic rocks that accumulated on the footwall of the Copper Creek normal fault and conformably above Paleozoic sediments. Detrital zircon and apatite double dating of Paleogene sediments from Copper Basin enables comparison of sedimentary lag times at various phases of basin evolution. We interpret sedimentary lag times within a chronostratigraphic framework developed from 6 new single crystal sanidine 40Ar/39Ar ages for Copper Basin tuff beds. Fluvial sedimentology and detrital zircon U-Pb age populations indicate that proximal volcanic sources were the dominate source of detritus to Copper Basin until a Cretaceous back-arc pluton, the Coffeepot Stock, unroofed along the Copper Creek normal fault during the middle Eocene. Laser Ablation Split Stream-ICPMS U-Pb dating of detrital apatite from Copper Basin sediments corroborates derivation from the 109 Ma Coffeepot Stock. Double dating of zircon grains derived from the Coffeepot Stock shows moderate lag times of 25-50 Myr whereas apatite grains imply lag times of cooling along the Copper Creek normal fault, which continued through the early Oligocene, was likely triggered by the onset of proximal 45 Ma volcanism in the Northern Bull Run Caldera of northeastern Nevada. Rapid early-onset extension in this

  17. Detrital Zircon Record of a Dammed River in Texas - Implications for Modern River Provenance Stories and Sediment Budgets

    Science.gov (United States)

    Dafov, L. N.; Stockli, D. F.; Mohrig, D. C.; Olariu, C.

    2016-12-01

    The Colorado River in Texas is a meandering river that is bisected by a chain of highland lakes and dams that were completed by 1951. Intuitively, dams trap sediment, but how does that disruption of sediment flow affect overall sediment flux and river morphology downstream of the dams? Observations from aerial photographs were combined with detrital zircon (DZ) U-Pb geochronology to quantify the anthropogenic effect of dams on sand generation. DZ U-Pb were collected from modern river channel sands, modern point bar sands, and modern delta sand sample. The U-Pb age data were evaluated in the context of bedrock U-Pb age data from the Llano Uplift Grenville basement above the dams and DZ U-Pb age data from the 30-40 km wide outcrop belt of Paleocene Wilcox Fm., dominated by Mesozoic Western US zircons, below the dams to evaluate possible entrenchment and sediment generation below the dams. While the modern river sediment collected upstream of the dams are dominated by Grenville DZ U-Pb ages, point bars below the dams show an abrupt increase of Wilcox derived zircons with only 1/3 of zircons derived from above the dams. This appears to be at least in part due to significant re-incision and erosion downstream of the dams out of the Paleocene Wilcox Formation. The lack of significant sand bars for 33 river kilometers below the dams and the progressive increase in sand bar size further downstream, combined with new DZ U-Pb data suggest that the modern river is incising into the Paleocene Wilcox below the dams and generating new sand. This is corroborated by the presence of 35 Ma DZ farther downstream, incorporated from Oligocene units. This progressive entrenchment of the river below the dams and incorporation of DZ from stratigraphic units encountered downstream illustrates the short-term response of the river geomorphology and sediment generation in light of anthropogenic perturbations of the river. These data also have interesting implications for sediment budget of

  18. Acoustic response of piezoelectric lead-zirconate-titanate to a 400MeV/n xenon beam

    CERN Document Server

    Miyachi, T; Ito, H

    2003-01-01

    Characteristics of lead-zirconate-titanate (PZT) elements were studied by directly irradiating them with a 400 MeV/n Xe beam. The elements were sensitive to 10 sup 4 Xe ions and their output amplitudes were proportional to the beam intensity. An ensemble of those output amplitudes displayed a Bragg-curve-like response towards the range of 400 MeV/n Xe ion. We discuss the potential of PZT elements as a radiation detector and their application to high-intensity and high-energy detectors. (author)

  19. Magma generation at a large, hyperactive silicic volcano (Taupo, New Zealand) revealed by U-Th and U-Pb systematics in zircons

    Science.gov (United States)

    Charlier, B.L.A.; Wilson, C.J.N.; Lowenstern, J. B.; Blake, S.; van Calsteren, P.W.; Davidson, J.P.

    2005-01-01

    Young (New Zealand, has involved the development and evacuation of several crustal magmatic systems. Up to and including the 26??5 ka 530 km 3 Oruanui eruption, magmatic systems were contemporaneous but geographically separated. Subsequently they have been separated in time and have vented from geographically overlapping areas. Single-crystal (secondary ionization mass spectrometry) and multiple-crystal (thermal ionization mass spectrometry) zircon model-age data are presented from nine representative eruption deposits from ??? 45 to ???3??5 ka. Zircon yields vary by three orders of magnitude, correlating with the degrees of zircon saturation in the magmas, and influencing the spectra of model ages. Two adjacent magma systems active up to 26??5 ka show wholly contrasting model-age spectra. The smaller system shows a simple unimodal distribution. The larger system, using data from three eruptions, shows bimodal model-age spectra. An older ???100 ka peak is interpreted to represent zircons (antecrysts) derived from older silicic mush or plutonic rocks, and a younger peak to represent zircons (phenocrysts) that grew in the magma body immediately prior to eruption. Post-26??5 ka magma batches show contrasting age spectra, consistent with a mixture of antecrysts, phenocrysts and, in two examples, xenocrysts from Quaternary plutonic and Mesozoic-Palaeozoic metasedimentary rocks. The model-age spectra, coupled with zircon-dissolution modelling, highlight contrasts between short-term silicic magma generation at Taupo, by bulk remobilization of crystal mush and assimilation of metasediment and/or silicic plutonic basement rocks, and the longer-term processes of fractionation from crustally contaminated mafic melts. Contrasts between adjacent or successive magma systems are attributed to differences in positions of the source and root zones within contrasting domains in the quartzo-feldspathic (<15 km deep) crust below the volcano. ?? Oxford University Press, 2004; all

  20. Zircon Hf isotopic constraints on the mantle source of felsic magmatic rocks in the Phan Si Pan uplift and Tu Le basin, northern Vietnam

    Science.gov (United States)

    Usuki, T.; Lan, C.; Tran, T.; Pham, T.; Wang, K.

    2013-12-01

    Permian plume-related rocks, such as picrites, flood basalts and silicic volcanic rocks occur in northern Vietnam. This area was displaced 600 km southeastward along the Ailao Shan-Red River fault during mid-Tertiary in response to the India-Eurasia collision. The original location of the area was situated at the central Emeishan Large Igneous Province (ELIP) in SW China before Tertiary. The picrites and flood basalts in northern Vietnam have been investigated by many authors and are comparable with the ELIP. While, felsic magmatisms in northern Vietnam has been poorly studied. Zircon U-Pb age and Hf isotopic data are useful to compare the felsic magmatism in northern Vietnam with that in the ELIP, because the magmatisms of the ELIP had a characteristic time period (260-250 Ma) and the Hf isotopes show a remarkable mantle signature. Therefore, this study carried out in-situ U-Pb ages and Hf isotopic compositions for 300 zircon grains in eighteen granitoids and rhyolites in Phan Si Pan uplift and Tu Le basin in northern Vietnam. Zircons from the granitoids and rhyolites occasionally show development of {101} pyramid and {100} prism crystal facies, suggesting typical zircons crystallized from high temperature alkaline granite. 206Pb/238U ages of granitoid and rhyolite yield consistently in a narrow range of 260 to 250 Ma, which coincides with those from peralkaline to metaluminous granites in the ELIP. ɛHf(t) values of zircons in rhyolites and granites of this study dominate in the range of +5 to +10, which is consistent with those from the ELIP. U-Pb ages and Hf isotopic compositions of zircons indicate that felsic magmatic rocks in the Phan Si Pan uplift and Tu La basin have been derived from the same mantle source with the ELIP.

  1. U-Pb zircon dating of the Gruf Complex: disclosing the late Variscan granulitic lower crust of Europe stranded in the Central Alps

    Science.gov (United States)

    Galli, A.; Le Bayon, B.; Schmidt, M. W.; Burg, J.-P.; Reusser, E.; Sergeev, S. A.; Larionov, A.

    2012-02-01

    Permian granulites associated with noritic intrusions and websterites are a common feature of the post-Variscan European crust. Such granulites are common in the Southern Alps (e.g. Ivrea Zone), but occur only in the Gruf Complex in the Central Alps. To understand the geotectonic significance of these granulites, in particular in the context of Alpine migmatisation, zircons from 15 high-grade samples have been U-Pb dated by SHRIMP II analysis. Oscillatory zoned zircons from charnockite sheets, interpreted as melts generated through granulite facies fluid-absent biotite melting at 920-940°C, yield ages of 282-260 Ma. Some of these zircons contain inclusions of opx, unequivocally attributable to the granulite facies, thus confirming a Permian age for the charnockites and associated granulites. Two samples from an enclave-rich orthogneiss sheet yield Cambrian and Ordovician zircon cores. Two deformed leucogranites and six ortho- and augengneisses, which compose two-thirds of the Gruf Complex, give zircon ages of 290-260 Ma. Most zircons have milky rims with ages of 34-29 Ma. These rims date the Alpine amphibolite facies migmatisation, an interpretation confirmed by directly dating a leucosome pocket from upper amphibolite facies metapelites. The Gruf charnockites associated with metre-scale schlieren and boudins of opx-sapphirine-garnet-granulites, websterites and gabbronorites can thus be identified as part of the post-Variscan European lower crust. A geotectonic reconstruction reveals that this piece of lower crust stranded in the (European) North upon rifting of the Neotethys, such contrasting the widespread granulite units in the Southern Alps. Emplacement of the Gruf lower crust into its present-day position occurred during migmatisation and formation of the Bergell Pluton in the aftermath of the breakoff of the European slab.

  2. Petrogenesis and tectonic implications of the Early Paleozoic intermediate and mafic intrusions in the South Qinling Belt, Central China: Constraints from geochemistry, zircon U-Pb geochronology and Hf isotopes

    Science.gov (United States)

    Wang, Ruirui; Xu, Zhiqin; Santosh, M.; Liang, Fenghua; Fu, Xuehai

    2017-08-01

    The characteristics and tectonic implications of the Early Paleozoic alkaline magmatic belt in the South Qinling Belt, which was originally part of the northern Yangtze Block prior the Devonian, have remained elusive. Whether this magmatic belt is related to rifting of the passive continental margin, to back-arc extension in the active continental margin, or to mantle plume activity is debated. Understanding the origin and geodynamic significance of this magmatic belt can provide new constraints on the Early Paleozoic tectonic evolution of the northern Yangtze Block. Here we present zircon U-Pb data from a suite of nepheline syenite, quartz syenite, diabase, and gabbro from the northern margin of the Yangtze Block which show an age range of ca. 435-440 Ma. The εHf(t) values of the intermediate rocks up to 16.59 suggest magma generation from depleted mantle sources and new crustal growth. Geochemically, the syenites showing high total alkali contents and are enriched in LREE, LILE (Rb, Ba, and K), and HFSE (Th, U, Nb, Ta, Zr, and Hf), with depletion in Sr, P, and Ti. The intermediate and mafic magmatic rocks were generated through magmas sourced from the subcontinental lithospheric mantle metasomatized by asthenospheric mantle and underwent fractional crystallization without significant crustal contamination. The magmatic suite represents a significant phase of crustal extension in the northern margin of the Yangtze Block.

  3. Rapid magma evolution constrained by zircon petrochronology and 40Ar/39Ar sanidine ages for the Huckleberry Ridge Tuff, Yellowstone, USA

    DEFF Research Database (Denmark)

    Rivera, Tiffany; Storey, Michael; Schmitz, Mark

    2014-01-01

    Understanding the time scales of magmatic differentiation, storage, and eruption of large volume silicic magmas is a primary goal of igneous petrology. Within the Huckleberry Ridge Tuff (HRT; Idaho, USA), representing the earliest and largest caldera-forming eruption associated with Yellowstone...... of single zircon crystals demonstrates an absence of pre-Pleistocene xenocrysts, but reveals the presence of antecrysts recycled from pre-caldera rhyolites in the HRT magma. The petrochronologic interpretation of autocrystic zircon thermal, chemical, and temporal characteristics suggests that HRT member B...

  4. Direct Comparison of Detrital Garnet, Monazite, and Zircon Ages from a Southern Appalachian Tributary System for the French Broad River, North Carolina, USA

    Science.gov (United States)

    Maneiro, K. A.; Baxter, E. F.; Samson, S. D.; Marschall, H.

    2016-12-01

    Nineteen detrital garnet ages from a tributary draining into the French Broad River of North Carolina represent the first full-scale deployment of a new detrital garnet geochronometer. Under the new geochronometer, inclusions within the garnet serve as a proxy for the original source rock and eliminate required assumption of a single source for detritus. Additionally, method development has advanced techniques for small sample Nd and Sm analysis by thermal ionization mass spectrometry (TIMS), allowing for Sm-Nd analysis of single detrital garnet grains for the first time. This is also the first dataset allowing direct comparison of detrital garnet, monazite, and zircon. The three proximate tributaries sampled drain a limited source lithology, and prior studies provide detrital monazite and zircon ages (e.g. Hietpas et al., 2010, Geology; Moecher et al., 2011, Geosphere). The weighted average age for tributary detrital monazite is 460.9 ± 2.5 Ma (95% confidence). Zircon cores failed to record Paleozoic metamorphism, while zircon rims gave a weighted average age of 443.5 ± 8.7 Ma (95% confidence). The tributary system is garnet-bearing, with garnet grains exceeding the current minimum volume required for single grain analysis (≥ 0.4 mm max. diameter). Previously reported initial ages from the garnet grains (Maneiro-Eccles, 2015, Goldschmidt) have been updated to include blank correction accounting for extremely small Nd loads; clean garnet analyses contain 17-445 pg Nd and repeat blanks indicate contribution of 4.31 ± 0.59 pg Nd. The resulting weighted average age for garnet is 438.8 ± 8.1 Ma (95% confidence). The weighted average ages for zircon rims and garnet overlap within error, while the monazite age is older (22.1 ± 8.5 Myr older than garnet, 17.4 ± 9.1 Myr older than zircon). Age variance between minerals could be attributed to monazite sampling bias, limited sample size, and either influence by a secondary tectonic event (e.g. the Cherokee Orogeny

  5. SIMS U-Pb, Sm-Nd isotope and geochemical study of an arkosite-amphibolite suite, Peräpohja Schist Belt: evidence for ca. 1.98 Ga A-type felsic magmatism in northern Finland

    Directory of Open Access Journals (Sweden)

    Eero Hanski

    2005-01-01

    Full Text Available In the northern and north-eastern part of the Peräpohja Schist Belt, northern Finland, an extensive supracrustal rock unit has been identified which is composed of alternating amphibolitic and arkositic components. The amphibolites form layers whose thickness varies from one millimeter to some tens of meters, being most often a few tens of centimeters. They represent mafic tuff beds deposited concurrently with more abundant arkositic rocks. Most of the arkosites have a modal and major and trace element compositionsimilar to that of A2-type granites. For example, they exhibit high LREE/HREE, negative Eu anomalies, and flat HREE and are moderately enriched in Nb, Zr, and Y. The genesis of the arkosites is enigmatic as they show features supporting either a volcaniclastic or an epiclastic origin. In the latter case, they were derived via erosion of a source dominated by A2-type granitic rocks. Previous conventional ID-TIMS and new SIMS U-Pb dating of zircons from two arkosite samples and one mica schist sample, all three picked from the northern part of the schist belt, indicate that these rocks contain a single population of zircons with an age of ca. 1975 Ma suggesting that they are among the youngest supracrustal rocks in the schist belt. In contrast, one mica schist sample from the western part of the belt revealed only the presence of Archean zircons. The samples do not differ markedly in terms of their Nd isotopecomposition as they all have a moderately negative εNd(1900 Ma. Regardless of the genesis of the arkosites, their isotopic and geochemical data suggest a previously unknown occurrence of extensive A-type felsic magmatism at ca. 1.98 Ga, contemporaneously withsome continental flood basalts. However, concrete evidence for this felsic A-type magmatism in the form of ca. 1.98 Ga felsic plutonic rocks is virtually absent in the presently exposed Fennoscandian Shield.

  6. Geochemical and zircon U-Pb geochronological study of the Yangshan A-type granite: Insights into the geological evolution in south Anhui, eastern Jiangnan Orogen

    Science.gov (United States)

    Gu, Huangling; Yang, Xiaoyong; Deng, Jianghong; Duan, Liuan; Liu, Lei

    2017-07-01

    The Early Cretaceous Yangshan granite is an A-type granitic intrusion that was emplaced along the eastern Jiangnan Orogen in southern Anhui Province, South China. The Yangshan intrusion mainly consists of syenite porphyry (127.0 ± 0.6 Ma) and alkali-feldspar granite porphyry (126.0 ± 1.0 Ma). As a part of Qingyang-Jiuhuashan complex intrusion, the Yangshan A-type granites have lower MgO, CaO, Co, Sr, and higher Rb, Nb, Th and HREE contents, with enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE), and slightly negative Eu anomalies. However, the syenite porphyry and the alkali-feldspar granite porphyry differ in terms of zircon εHf(t) values: small variations in the syenite porphyry from - 5.5 to - 3.7, corresponding to Hf model ages (tDMC) between 1.42 Ga and 1.53 Ga, and large variations in the alkali-feldspar granite porphyry from - 6.4 to + 4.4, yielding tDMC of 0.90-1.59 Ga. While both rocks also have similar εNd(t) values ranging from - 7.02 to - 5.47, corresponding Nd model ages (TDMC) are 1.37-1.49 Ga, falling within the Hf model ages. We take these features to indicate that the Qingyang I-type granites, which are isotopically similar, and Yangshan A-type granites were originated from partial melting of Mesoproterozoic-Neoproterozoic crust, with minor juvenile crust input for the alkali-feldspar granite porphyry, followed by fractional crystallization. In combination with previous studies, we propose that the Cretaceous A-type granitic rocks formed between 135 Ma and 122 Ma, implying an important Mesozoic extensional event in eastern Jiangnan Orogen, which facilitated underplating of mantle-derived magma and crustal heating. This may have occurred in a back-arc extension in response to the drift of subduction direction of the Paleo-Pacific plate, which started as early as 135 Ma ago.

  7. Clinical Significance of Serum HE4, CA125, CA724, and CA19-9 in Patients With Endometrial Cancer.

    Science.gov (United States)

    Bian, Jing; Sun, Xiaoxu; Li, Bo; Ming, Liang

    2017-08-01

    Serum markers with increased sensitivity and specificity for endometrial cancer are required. To date, no good marker has met this standard. The aims of our study were to evaluate the utility of tumor markers HE4, CA125, CA724, and CA19-9 as potential markers in patients diagnosed with endometrial cancer. Blood samples from 105 patients with endometrial cancer and 87 healthy women were analyzed by Roche electrochemiluminescent immunoassay, and serum values were measured for the following biomarkers: HE4, CA125, CA724, and CA19-9. Serum HE4, CA125, CA724, and CA19-9 concentrations were significantly higher in patients with endometrial cancer, compared with controls ( P endometrial cancer, HE4 had higher sensitivity (58%), positive predictive value (60%), and negative predictive value (67%) than any other single tumor marker, and in the combination of HE4, CA125, CA724, and CA19-9, the sensitivity and positive predictive values reached 59.1% and 88%, respectively. Meanwhile, the receiver operating characteristic area under the curve of the combination of the 4 markers was significantly increased than any other group, either in stage I or in stage II to IV cases. HE4 and CA125 both correlate with advanced age; in addition, HE4 was related to pathology subtypes and positive adnexal involvement, CA125 was related to International Federation of Gynecology and Obstetrics stage, CA19-9 was related to International Federation of Gynecology and Obstetrics stage, and CA724 was correlated with positive lymph node. Combination of HE4, CA125, CA724, and CA19-9 has the highest value in diagnosing endometrial cancer, and they can be a useful tissue immune marker for patients with endometrial cancer.

  8. Effects of the poling process on dielectric, piezoelectric, and ferroelectric properties of lead zirconate titanate

    Science.gov (United States)

    Prewitt, Anderson D.

    Smart materials are widely used in many of today's relevant technologies such as nano and micro electromechanical systems (NEMS and MEMS), sensors, actuators, nonvolatile memory, and solid state devices. Many of these systems rely heavily on the electromechanical properties of certain smart materials, such as piezoelectricity and ferroelectricity. By definition, piezoelectricity is a mechanical stress in a material that produces an electric displacement (known as the direct piezoelectric effect) or electrical charge in a material which produces a mechanical strain (known as the converse piezoelectric effect). Ferroelectricity is a sub-class of piezoelectricity in which the polarization occurs spontaneously and the dipoles can be reoriented. Domain walls are the nanoscale regions separating two finite distinctively polarized areas in a ferroelectric. The reorientation of polarization in a material is called the poling process and many factors can influence the effectiveness of this process. A more fundamental understanding of how electrical and mechanical loading changes the domain structure of these materials could lead to enhanced properties such as increased energy transduction and decreased nonlinear behavior. This research demonstrates the influence of mechanical pressure and electrical field during and after the poling process on domain walls. The effects of strong mechanical forces on large-scale domain switching and weak cyclic forces on small-scale domain wall motion are investigated to show how they affect the macroscopic behavior of these materials. Commercial lead zirconate titanate ceramics were studied under various poling conditions and the effect of domain wall motion on the piezoelectric, dielectric, and ferroelectric properties was investigated. Polarization and strain measurements from samples poled at specific conditions and converse piezoelectric coefficient and dielectric permittivity data was extracted and interpreted in the context of

  9. U-Pb (SIMS) Zircon Ages of Granitoids from the Basement of Pechora Basin

    Science.gov (United States)

    Soboleva, A. A.; Andreichev, V. L.; Dovzhikova, E. G.; Coble, M. A.; Sergeev, S. A.; Miller, E. L.; Ronkin, Y. L.

    2015-12-01

    SIMS dating (SHRIMP-RG, SHRIMP-II) of zircons from granitoids penetrated by boreholes in the basement of Pechora Basin yield mostly ages of 544-565 Ma similar to Pb-Pb ages by Gee et al. (2000). Intrusive rocks studied in 8 boreholes are subduction-related mainly I-type granitoids within the Pripechora-Ilych-Chikshino fault zone, an assumed Neoproterozoic suture (Olovyanishnikov et al., 1995, Kostiuchenko, 1994). Older granites and plagiogranites in the 1-Prilukskaya borehole (595 ± 14 Ma) and 1-Nizhnyaya Omra borehole (602 ± 2 Ma) also have geochemical characteristics of subduction-related rocks. Their origin is probably related to the long-term development of active margin magmatism within the Arctida paleocontinent. The most ancient of the granitoids studied are sub-alkaline A-type granites from the 50-West Hilchuyu borehole (625 ± 25 Ma) and granosyenites and granodiorites of the 2-Veyak borehole (607 ± 6 Ma). Their within plate geochemical characteristics (high alkalinity, relatively high content of HREE, HFSE, and crustal ISr = 0.70622 (2-Veyak borehole) indicate that granite melts were generated in thick continental crust and indirectly support the hypothesis of existence of Pre-Neoproterozoic blocks of continental crust in the basement of the NE part of the Pechora Basin. These granites were formed prior to the proposed Timanide collision or accretion. They are comparable to 613-617 Ma syenites and subalkaline granites which intruded the NE passive margin of Baltica and are exposed at the surface in the Northern Timan (Larionov et al., 2004). This magmatic stage marks Late Neoproterozoic rifting on the NE edge of Baltica during which rifting apart of continental crustal blocks could have occurred. As suggested by geophysical data, one of these, the Khoreyver microcontinent (Olovyanishnikov et al., 1995) currently lies at a depth of more than 4 km beneath the Pechora Basin. At the end of Vendian to the beginning of Cambrian time, these terranes, which

  10. Thermochemical properties of some alkaline-earth silicates and zirconates. Fission product behaviour during molten core-concrete interactions

    Energy Technology Data Exchange (ETDEWEB)

    Huntelaar, M.E.

    1996-06-19

    This thesis aims to make a contribution to a better understanding of the chemical processes occurring during an ex-vessel MCCI accident with a western-type of nuclear reactor. Chosen is for a detailed thermochemical study of the silicates and zirconates of barium and strontium. In Chapter one a short introduction in the history of (research in) nuclear safety is given, followed by the state-of-the-art of molten core-concrete interactions in Chapter two. In both Chapters the role of chemical thermodynamics on this particular subject is dealt with. The experimental work on the silicates and zirconates of barium and strontium performed for this thesis, is described in the Chapters three, four, five, six, and parts of eight. In Chapter three the basis for all thermochemical measurements, the sample preparation is given. Because the sample preparation effects the accuracy of the thermodynamic measurements, a great deal of effort is spent in optimizing the synthesis of the silicates which resulted in the TEOS-method widely employed here. In the next Chapters the different thermochemical techniques used, are described: The low-temperature heat capacity measurements and the enthalpy increment measurements in Chapter four, the enthalpy-of-solution measurements in Chapter five, and measurements to determine the crystal structures in Chapter six. (orig.).

  11. Zircon-quartz-calcite segregations in carbonate-alkaline metasomatic rocks of the western Baikal region and their petrogenetic implications

    Science.gov (United States)

    Savelyeva, V. B.; Bazarova, E. P.; Sharygin, V. V.; Karmanov, N. S.

    2015-12-01

    Fine-grained segregations up to 5 mm in size composed of graphic intergrowths of zircon, quartz, calcite and containing up to 0.8 wt % SrO have been found in albite-riebeckite and dolomite-biotite metasomatic rocks formed after alaskite granite. They contain magnetite, titanomagnetite (25.4 wt % TiO2), cerite-(Ce,Nd), rutile (up to 1.2 wt % Nb2O5), as well as rare micrograins of monazite-(Ce), bastnaesite-(Ce), and barite (up to 5.7 wt % SrO). The fine-grained structure of mineral aggregates suggests a metacolloidal nature. It is assumed that the zircon-quartz-calcite assemblage was formed due to exchange decomposition reaction between the salt phase of hydrothermal solution with predominant Na2CO3, elevated Zr and, to a lesser extent, Fe, Ti, LREE, Nb contents and dissolved calcium and silica compounds of a Na2SiO3 type.

  12. SHRIMP zircon U-Pb ages and tectonic implications of igneous events in the Ereendavaa metamorphic terrane in NE Mongolia

    Science.gov (United States)

    Miao, Laicheng; Zhang, Fochin; Baatar, Munkhtsengel; Zhu, Mingshuai; Anaad, Chimedtseren

    2017-08-01

    The Ereendavaa metamorphic terrane in NE Mongolia has long been considered as a Pre-Altaid block or a Precambrian cratonic terrane with a Paleoproterozoic basement overlain by Neoproterozoic-Cambrian rocks, but the idea has not been supported by any isotopic dating. Sensitive high resolution ion microprobe (SHRIMP) zircon U-Pb dating on gneisses, amphibolite and schists (mylonites) of the Ereendavaa terrane suggests that the terrane mainly formed during Early Paleozoic (495-464 Ma) and Late Paleozoic-Early Mesozoic (295-172 Ma). A minor amount of Precambrian rocks might have been involved in the formation of the protoliths of these rocks, as shown by Precambrian inherited zircons (1796-794 Ma). The new age data also suggest that the Ereendavaa terrane experienced at least two periods of magmatism: (1) Early Paleozoic (495-464 Ma) and (2) Late Paleozoic-Early Mesozoic (295-172 Ma), which are probably produced by the subduction of the Paleo Asian Ocean in the south and the subduction of the Mongol-Okhotsk Ocean in the north, respectively. The mylonitized granite (172 Ma) and undeformed pegmatite (163 Ma) are interpreted to be syn- and post-kinematic products. The new age data constrain the closure of the Mongol-Okhotsk Ocean at mid-Jurassic.

  13. U-Pb ages of detrital zircon and provenances of Red Clay in the Chinese Loess Plateau

    Science.gov (United States)

    Gong, Hujun; Xie, Wenbin; Zhang, Rui; Zhang, Yunxiang

    2017-05-01

    The Chinese Loess Plateau (CLP), which is located in the central part of China, mainly contains two sequences: the Quaternary loess-paleosol sequence and the late Miocene-Pliocene Red Clay sequence. U-Pb ages of detrital zircon from the Quaternary loess-paleosol sequences indicate that the current spatial pattern of central Asian aridification was largely established during the early Quaternary. U-Pb ages of detrital zircon from the underlying Red Clay sequences demonstrate that the northern source regions were important contributors for the dust since the late Miocene, except for the periods of ∼8 Ma and ∼5.5 to ∼4 Ma. These two periods correspond to increased and decreased dust deposition in the North Pacific, respectively, ascribed to the late Miocene aridification of the Qaidam Basin (in the west of the CLP) and the early Pliocene aridification of the Tarim Basin (in the west of the CLP). We attribute the increase of the Qaidam Basin-derived North Pacific dust fluxes to the uplift of the NE Tibetan Plateau. Such uplift also controlled the climatic and environmental changes in central Asian during the late Miocene. This study highlights the dynamical process of the central Asian aridification during the late Miocene-Pliocene.

  14. Tracking the Cretaceous transcontinental Ceduna River through Australia: The hafnium isotope record of detrital zircons from offshore southern Australia

    Directory of Open Access Journals (Sweden)

    Jarred Lloyd

    2016-03-01

    Full Text Available The middle–upper Cretaceous Ceduna River system traversed continental Australia from the NE coast to the centre of the southern coast. At its mouth, it formed a vast delta system that is similar in scale to the Niger delta of West Africa. The delta system is composed of two main lobes that represent different phases of delta construction. A recent hypothesis has challenged the traditional idea that both lobes of the delta were derived from a transcontinental river system by suggesting that the upper lobe (Santonian–Maastrichtian is instead derived from a restricted catchment within southern Australia. Hf isotopic data presented here fingerprint the original source of the upper delta lobe zircons to NE Australia, with data comparing well with similar U-Pb and Lu-Hf isotopic data from the Lachlan Orogen, the New England Orogen, the eastern Musgraves Province and the northern Flinders Ranges. These data do not preclude a model where the lobe is derived from recycled Eromanga Basin sediments during a phase of late Cretaceous inland Australian uplift, but when coupled with reconnaissance low-temperature thermochronometry from the region of the Ceduna River course indicating widespread Triassic–Jurassic exhumation, and comparisons with detrital zircon data from the Winton Formation upstream of any proposed uplift, we suggest that both lobes of the Ceduna Delta are likely to be derived from a transcontinental Ceduna River.

  15. U-Pb zircon constraints on the age and provenance of the Rocas Verdes basin fill, Tierra del Fuego, Argentina

    Science.gov (United States)

    Barbeau, David L.; Gombosi, David J.; Zahid, Khandaker M.; Bizimis, Michael; Swanson-Hysell, Nicholas; Valencia, Victor; Gehrels, George E.

    2009-12-01

    The Late Jurassic to Early Cretaceous Rocas Verdes basin constitutes one of the most poorly understood components of the southernmost Andes. As a result, accurate reconstructions and interpretations of deformation associated with the Andean orogeny and the kinematics of Scotia arc development also remain poorly constrained. In this data brief, we report U-Pb zircon ages from sandstones of the Rocas Verdes basin fill and from a crosscutting pluton in the southernmost Andes of Argentine Tierra del Fuego. Detrital samples contain predominant Early to early Middle Cretaceous (circa 130-105 Ma) U-Pb zircon age populations, with very small or single-grain middle Mesozoic and Proterozoic subpopulations. A very small subpopulation of Late Cretaceous ages in one sample raises the unlikely possibility that parts of the Rocas Verdes basin are younger than perceived. A sample from a crosscutting syenitic pegmatite yields a crystallization age of 74.7 +2.2/-2.0 Ma. The data presented herein encourage further geochronologic evaluation of the Rocas Verdes basin in order to better constrain the depositional ages and provenance of its contents.

  16. The crystal structure and morphology of NiO-YSZ composite that prepared from local zircon concentrate of Bangka Island

    Energy Technology Data Exchange (ETDEWEB)

    Rahmawati, F., E-mail: fitria@mipa.uns.ac.id; Apriyani, K.; Heraldy, E. [Research Group of Solid State Chemistry & Catalysis, Department of Chemistry, Sebelas Maret University, Jl. Ir. Sutami 36A Kentingan Surakarta (Indonesia); Soepriyanto, S. [Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132 (Indonesia)

    2016-03-29

    In order to increase the economic value of local zircon concentrate from Bangka Island, NiO-YSZ was synthesized from Zirconia, ZrO{sub 2} that was prepared from local zircon concentrate. The NiO-YSZ composite was synthesized by solid state reaction method. XRD analysis equipped with Le Bail refinement was carried out to analyze the crystal structure and cell parameters of the prepared materials. The result showed that zirconia was crystallized in tetragonal structure with a space group of P42/NMC. Yttria-Stabilized-Zirconia (YSZ) was prepared by doping 8% mol yttrium oxide into zirconia and then sintered at 1250°C for 3 hours. Doping of 8% mol Yttria allowed phase transformation of zirconia from tetragonal into the cubic structure. Meanwhile, the composite of NiO-YSZ consists of two crystalline phases, i.e. the NiO with cubic structure and the YSZ with cubic structure. SEM analysis of the prepared materials shows that the addition of NiO into YSZ allows the morphology to become more roughness with larger grain size.

  17. Geochemical and zircon U-Pb dating analysis of metamagmatic rocks from the Yuli belt in Taiwan

    Science.gov (United States)

    Hung, Chia-Chia

    2016-04-01

    The Tananao Schist Complex of the oldest rocks in Taiwan is exposed at the eastern limb of Backbone Range. Based on the lithologic and metamorphic characteristics, the complex can be divided into the Tailuko and Yuli belts. The Tailuko belt consists of marble, gneiss, and subordinate scattered metabasite; the Yuli belt is composed of greenschist, serpentinite, meta-tuff, meta-gabbro, metabasite, and glaucophane-schist blocks which enclosed by spotted schist of the host rocks. The metamorphic belts were inferred as a Mesozoic mélange. It's still controversial due to the difficulty of analyzing metamorphic rocks. In this study, we focus on the zircon U-Pb dating, geochemistry, and petrographic analysis of spotted schist, metabasite, meta-gabbro, and meta-tuff in order to constrain the formation and crystallization ages and interpret its tectonic setting. Based on zircon U-Pb dating, the host rocks of spotted schist and the exotic blocks of meta-tuff, meta-gabbro (the peak age of 14.4, 15.8, and 16.7 Ma), and metabasite occurred at Miocene. Geochemical characteristics for metabasite and meta-gabbro blocks show Ta-Nd-Ti depletion and LREE depletion in spidergram occurring volcanic arc and N-MORB type affinities, respectively. Results as above mentioned, we suggest that the metamagmatic rocks in the Yuli belt occur within a mélange during the Eurasia continental margin subduction at the Middle-Late Miocene.

  18. Achaean TTG and high alimunia gneisses on Baltic Shield: Precise U-Pb (ID-TIMS) and SHRIMP-II ages on single zircon

    Science.gov (United States)

    Bayanova, Tamara; Morozova, Ludmila; Mitrofanov, Felix; Serov, Pavel; Nitkina, Elena; Fedotov, Dzorzh; Larionov, Alexander

    2014-05-01

    New U-Pb (ID-TIMS) data on single zircon from high alimunia gneisses near Murmansk in the Central-Kola domain gave 3.17 Ga. Core from these zircon population has the age 3695±5 Ma by SHRIMP-II. Time of amphibolites metamorphism was dated with 2753±3 Ma. Achaean gneisses in Monchegorsk ore region were firstly dated in the Central-Kola domain. Single zircon from gneisses in Monchegorsk region which are the basement for Paleoproterozoic PGE layered intrusions with U-Pb ages on zircon and baddeleyite from 2.4-to 2.5 Ga (Bayanova et all, 2009) has 3.16 Ga. Single zircon from gnneisses gave 2776±3 Ma and is considered as amphibolites metamorphism. Voche-Lambina international polygon lies on the boundary between Belomorian mobile block and Central -Kola domain (Morozova et al, 2011). New neoarhaean U-Pb data on single zircon from TTG of polygon yielded 3158.2±8.2. Zircon are characterized by low concentration U and Pb, low U/Th ratio with 0.2. REE diagrams of grey gneisses reflect high fractionation La/Yb>30,encriched by light REE and depleted by heavy Yb<0.6 ppm. Model Sm-Ng ages on the rocks have protolith from with the ages 3.4 to 3.2 Ga, positive ɛNd from +1.29 to +3.3, ISr equals 0.702. Precise (ID-TIMS) age of amphibolites metamorphism has been dated on single zircon with 2704.3±5.9 Ma. In the frame of the Central-Kola domain there is an Ingosersky TTG complex. Firstly U-Pb dating on single zircon from Bt-gneisses reflects 3149±49 Ma. Metamorphic alterations were in 2725.2±2.5 Ma and connected with origin of Amf-Bt gneisses and 2733.6±6.6 with Bt-Amf gneisses. (NItkina et al., 2012). Therefore based on the new data on single zircon from TTG and high alimunia gneisses from Central-Kola domain leads to the long history of continental crust origin in the Baltic or Fennoscandian Shield from 3.16 to 3.7 Ga. We thank to G. Wasserburg for 205 Pb artificial spike, J. Ludden for 91500 and Temora standards, F. Corfu, V. Todt and U. Poller for assistance in the

  19. Erosional history of the Appalachians as recordeed in detrital zircon fission-track ages and lithic detritus in Atlantic Coastal Plain sediments

    Science.gov (United States)

    Naeser, C.W.; Naeser, N.D.; Edwards, Lucy E.; Weems, Robert E.; Southworth, C. Scott; Newell, Wayne

    2016-01-01

    Comparison of fission-track (FT) ages of detrital zircons recovered from Atlantic Coastal Plain sediments to FT ages of zircons from bedrock in source terranes in the Appalachians provides a key to understanding the provenance of the sediments and, in turn, the erosional and depositional history of the Atlantic passive margin.In Appalachian source terranes, the oldest zircon fission-track (ZFT) ages from bedrock in the western Appalachians (defined for this paper as the Appalachian Plateau, Valley and Ridge, and far western Blue Ridge) are notably older than the oldest ages from bedrock in the eastern Appalachians (Piedmont and main part of the Blue Ridge). The age difference is seen both in ZFT sample ages and in individual zircon grain ages and reflects differences in the thermotectonic history of the rocks. In the east, ZFT data indicate that the rocks cooled from temperatures high enough to partially or totally reset ZFT ages during the Paleozoic and (or) Mesozoic. The majority of the rocks are interpreted to have cooled through the ZFT closure temperature (∼235 °C) at various times during the late Paleozoic Alleghanian orogeny. In contrast, most of the rocks sampled in the western Appalachians have never been heated to temperatures high enough to totally reset their ZFT ages. Reflecting their contrasting thermotectonic histories, nearly 80 percent of the sampled western rocks yield one or more zircon grains with very old FT ages, in excess of 800 Ma; zircon grains yielding FT ages this old have not been found in rocks in the Piedmont and main part of the Blue Ridge. The ZFT data suggest that the asymmetry of zircon ages of exposed bedrock in the eastern and western Appalachians was in evidence by no later than the Early Cretaceous and probably by the Late Triassic.Detrital zircon suites from sands collected in the Atlantic Coastal Plain provide a record of detritus eroded from source terranes in the Appalachians during the Mesozoic and Cenozoic. In Virginia

  20. Provenancial correlation between Kanmon Group and Tetori Group, SW Japan and Gyeongsan Supergroup, Korea by age distributions of detrital zircon

    Science.gov (United States)

    Katsube, A.; Hayasaka, Y.

    2009-12-01

    The Japanese Island Arc System was located along the eastern margin of Asian Continent before opening of the Sea of Japan at around 15 Ma, and abundant clasts from Asian Continent. Now a question arises as to how the Japanese Archipelago was connected to the continent of Asia? Marine to non-marine sediments of Lower Cretaceous Gyeongsang Basin are widely spread over southeastern Korean Peninsula facing the Japan Sea. On the other side of the sea, in the Southwest Japan, the Lower Cretaceous Kanmon Group distributed from Northeastern Kyushu to the western edge of Honshu, and the Tetori Group distributed in the Hida Mountains, also exist. Gyeongsang Supergroup in the Gyeongsang Basin and the Kanmono Group demonstrate good correlation based on their sedimentary phases and whole rock REE composition. Paleomagnetic studies moreover, have shown that the Kanmon Group distributed in close to the Gyeongsang Basin before opening of the Japan Sea. Some geologists, however, suggest that the Gyeongsang Supergroup and the Tetori group are correlated. This idea rests on a paleogeographic model, which in turn is based on Pre-Cretaceous basement of Japan, being correlated with southern Primorye of Russia (Yamakita and Otoh, 2000). In this study, we compare the provenance of their sediments using detrital zircon or monazite age, and discuss the immediacy of their depositional site. We separated zircon and monazite from sandstone, and dated single grain U-Th total Pb age using EPMA. Sandstone was sampled from the early Cretaceous Gyeongsang Supergroup in South Korea, and the early Cretaceous Kanmon Group, the late Jurassic to early Cretaceous Toyonishi Group, the middle Jurassic Toyora Group in Shimonoseki area of Yamaguchi Prefecture, and the late Jurassic to early Cretaceous Tetori Group. As a result of EPMA analysis and statistical processing, zircons and monazites from sandstones in the Lower Cretaceous Gyeongsang Supergroup yield a wide range of ages and, according to their

  1. Solid State compatibilities in CaO-CaO∙Al2O3-CaF2 system

    Directory of Open Access Journals (Sweden)

    Jiménez Molina, S.

    1998-03-01

    Full Text Available In open atmosphere the two phases containing fluorine, C11A7∙CaF2 and 3CA∙CaF2, laying in the CaO-CaO∙Al2O3-CaF2 were synthesized. The synthesis of the 3CA∙CaF2 at 1.100°C was possible without loss of F, when the stoichiometric mixture of CA and CaF2 was pressed into tablets and was applied vacuum, avoiding in such a way the presence of moisture. According to TGA studies, the vapour pressure of phases containing fluorine, at 1.100°C is very low and follows this sequence: CaF2 2 11A7∙CaF2. At 1.000°C the system behaves as condensated. Verification of some compatibilities in solid state in the system CaO-CaO∙Al2O3-CaF2 at 1000°C has been done. Compatibility triangles found are the same described by Chaterjee, and different from the compatibilities given by Brisi and Rolando.Se han sintetizado en atmósfera abierta las dos fases fluoradas del sistema CaO-CaO∙Al2O3-CaF2: C11A7∙CaF2 y 3CA∙CaF2. La síntesis del 3CACaF2 a 1.100°C ha sido posible sin pérdida de F, cuando la mezcla estequiométrica de CA y CaF2 se empastilló a presión y aplicando vacío, como modo de evitar la presencia de humedad. De acuerdo con los resultados de Análisis Termogravimétrico, la presión de vapor de las fases fluoradas, a 1.100°C, es muy baja y sigue el orden: CaF2 2 11A7∙CaF2. A 1.000°C, el sistema se comporta como condensado. Se han verificado algunas relaciones de fases compatibles en estado sólido, en el sistema CaO-CaO∙Al2O3-CaF2, a 1.000°C. Las relaciones de fases compatibles que se han encontrado coinciden con aquéllas descritas por Chaterjee, y son diferentes a las encontradas por Brisi y Rolando.

  2. Zircon U-Pb geochronology and petrogenesis of metabasites from the western Beihuaiyang zone in the Hong'an orogen, central China: Implications for detachment within subducting continental crust at shallow depths

    Science.gov (United States)

    Liu, Yi-Can; Liu, Li-Xiang; Li, Yuan; Gu, Xiao-Feng; Song, Biao

    2017-09-01

    Deformed low-grade metabasites from the western segment of the Beihuaiyang zone in the Hong'an orogen, central China can be divided into two types, i.e. meta-gabbro and meta-basalt. These lithologies have been studied by using whole-rock elemental and Sr-Nd-Pb isotopic analyses, and zircon SHRIMP U-Pb dating. Concordant zircon U-Pb ages of 631 ± 5 Ma and 623 ± 14 Ma are obtained for the meta-gabbros, consistent with a previously reported U-Pb age of 635 ± 5 Ma. The meta-basalt was dated to have a protolith age of middle Neoproterozoic (∼750 Ma) and a metamorphic age at ca. 240 Ma. The all studied metabasites occur as block or slice within a metamorphosed Ordovician volcanic zone (originally named as the Dingyuan Formation) and are in tectonic contact to each other. The gabbro and basalt emplaced at ∼630 Ma and ∼750 Ma, respectively in a continental rifting setting, whereas their present country rocks were erupted at ∼465 Ma in an arc setting. The Pb-isotope compositions of the low-grade meta-gabbros and meta-basalts are similar to those from the Dabie ultrahigh-pressure (UHP) meta-igneous rocks with an upper continental crust affinity. The protolith ages of the studied relatively low-grade meta-basic rocks are in good agreement not only with ages for two episodes of middle and late Neoproterozoic mafic and felsic magmatism in the Suizhou to Zaoyang areas at the northern margin of the South China Block, but are also in agreement with the protolith ages of UHP meta-igneous rocks in the Dabie-Sulu orogenic belt. Therefore, these Neoproterozoic low-grade metabasites are considered to be exotic and they may have been detached and offscraped from the subducting upper crust of the South China Block at shallow depths during continental collision in the Triassic. They were subsequently exhumed in the initial stage of continental subduction, and thrusted over the Paleozoic metamorphosed rocks in the southern margin of the North China Block or as foreign slices

  3. Geochronology of diamond-bearing zircons from garnet peridotite in the North Qaidam UHPM belt, Northern Tibetan Plateau: A record of complex histories from oceanic lithosphere subduction to continental collision [rapid communication

    Science.gov (United States)

    Song, Shuguang; Zhang, Lifei; Niu, Yaoling; Su, Li; Jian, Ping; Liu, Dunyi

    2005-05-01

    We report the results of a comprehensive study of zircons separated from the Lüliangshan peridotite massif within the 400-km-long North Qaidam UHPM belt, northern Tibetan Plateau, NW China. The peridotite massif is dominated by garnet lherzolite with minor amounts of interlayered garnet-bearing dunite and cross-cutting garnet pyroxenite dikes. Most zircons from the garnet lherzolite show rather complex zoning. One diamond and a few graphite inclusions are identified in some zircons by Raman spectroscopy. SHRIMP dating on these zircons show four major age groups: (a) 484-444 Ma (weighted mean age, 457 ± 22 Ma) for cores of most crystals, whose morphology and rare earth element (REE) systematics (i.e., very high [Lu / Sm] CN = 88-230) suggest a magmatic origin, consistent with the protolith being magmatic cumulate; (b) 435-414 Ma with a mean of 423 ± 5 Ma, which, given by mantle portions of zircon crystals, is interpreted to record the event of ultrahigh-pressure metamorphism (UHPM) at depths greater than 200 km in an Andean-type subduction zone; (c) 402-384 Ma (mean age 397 ± 6 Ma) for near-rim portions of zircon crystals; and (d) 368-349 Ma for outermost rims, which is interpreted as representing some post-orogenic thermal events. Inherited cores in two zircon crystals were identified using CL and found to be Proterozoic. Morphology and CL images show that zircons from dunite and garnet pyroxenite are of metamorphic origin. The mean age of dunite zircons is 420 ± 5 Ma, which overlaps the mantle age of the garnet lherzolite zircon (see (b) above). The mean age of garnet pyroxenite zircons is 399 ± 8 Ma, which overlaps ages of near-rim domains in garnet lherzolite zircons (see (c) above). Some garnet pyroxenite zircons also recorded a retrograde event at 358 ± 7 Ma. All these data suggest that the Lüliangshan garnet peridotite massif is not a fragment of ancient lithospheric mantle, but a peridotite body with long and complex histories from Early Ordovician

  4. KWU-werkersklasdramas in Afrikaans (ca. 1930 - ca. 1950

    Directory of Open Access Journals (Sweden)

    J. L. Coetser

    1999-05-01

    Full Text Available GWU working class theatre in Afrikaans (ca. 1930 - ca. 1950In 1984 Elsabé Brink drew attention to plays, prose and poetry written between 1930 and 1950 in Afrikaans by members of the Garment Workers’ Union (GWU. Scholars such as Stander and Willemse (1992, Van Niekerk (1996 and Van Wyk (1995, 1997 have also referred to GWU plays. Apart from these overviews, GWU plays as such have not yet received the attention they deserve. This article presents a revaluation, initially by providing an overview of their contents, followed by an examination of cultural, economic and political influences. It is argued that - retrospectively - the GWU plays reflected a unique cultural specificity from the framework established by Sitas (1986 for more contemporary working class theatre.

  5. Effect of the temperature and oxalic acid in the uranyl sorption in zircon; Efecto de la temperatura y acido oxalico en la sorcion de uranilo en circon

    Energy Technology Data Exchange (ETDEWEB)

    Ordonez R, E.; Almazan T, M. G.; Garcia G, N. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Hernandez O, R., E-mail: eduardo.ordonez@inin.gob.mx [Instituto Tecnologico de Veracruz, Ingenieria Quimica, Miguel Angel de Quevedo No. 2779, 91860 Veracruz (Mexico)

    2012-10-15

    In this work the results of the temperature effect study are presented on uranyl solutions adsorbed on zirconium silicate (ZrSiO{sub 4}) and also on the compounds formed in surface with oxalic acid. The adsorption isotherms of uranyl on hydrated zircon with NaClO{sub 4} 0.5 M, show an increase of the uranyl sorption efficiency when increasing the temperature from 20 to 4 C with a sudden descent in this efficiency when changing the temperature at 60 C. The uranyl sorption efficiency increases to hydrate the zircon with a solution of oxalic acid 0.1 M, maintaining the same tendency regarding to the temperatures of the sorption in medium NaClO{sub 4} 0.5 M. The complex formation in the zircon surface with organic acids of low molecular weight increases the fixation of the uranyl in solution due to the formation of ternary systems, in the order Zircon/A. Organic/Uranyl, without altering their response to the temperature. (Author)

  6. Proterozoic basement and Palaeozoic sediments in the Ringkøbing–Fyn High characterized by zircon U–Pb ages and heavy minerals from Danish onshore wells

    DEFF Research Database (Denmark)

    Olivarius, Mette; Friis, Henrik; Kokfelt, Thomas F.

    2015-01-01

    New data from the Proterozoic basement and scattered Palaeozoic sediments in the Ringkøbing–Fyn High including zircon U–Pb geochronometry, heavy mineral compositions and whole rock geochemistry is presented here to provide a frame of reference for detrital provenance studies. The Ringkøbing...

  7. U–Pb zircon and biostratigraphic data of high‐pressure/ low‐temperature metamorphic rocks of the Talea Ori : tracking the Paleotethys suture in central Crete, Greece

    NARCIS (Netherlands)

    Zulauf, G.; Dörr, W.; Krahl, J.; Lahaye, Y.; Chatzaras, V.|info:eu-repo/dai/nl/374329249; Xypolias, P.

    2016-01-01

    Inherited deformation microfabrics of detrital quartz grains and U–Pb (Laser ablation (LA)-ICPMS and ID TIMS) ages of detrital zircons separated from the Phyllite–Quartzite Unit s.l. of the Talea Ori, central Crete, suggest strikingly different source rocks. Albite gneiss of the lower Rogdia Beds

  8. Zircon ages delimit the provenance of a sand extrudite from the Botucatu Formation in the Paraná volcanic province, Iraí, Brazil

    Directory of Open Access Journals (Sweden)

    VITER M. PINTO

    2015-09-01

    Full Text Available Ion microprobe age determinations of 102 detrital zircon crystals from a sand extrudite, Cretaceous Paraná volcanic province, set limits on the origin of the numerous sand layers present in this major flood basalt province. The zircon U-Pb ages reflect four main orogenic cycles: Mesoproterozoic (1155-962 Ma, latest Proterozoic-early Cambrian (808-500 Ma and two Palaeozoic (Ordovician- 480 to 450 Ma, and Permian to Lower Triassic- 296 to 250 Ma. Two additional small concentrations are present in the Neoarchean (2.8 to 2.6 Ga and Paleoproterozoic (2.0 to 1.7 Ga. Zircon age peaks closely match the several pulses of igneous activity in the Precambrian Brazilian Shield and active orogeny in Argentina. A main delimitation of the origin of the sand is the absence of zircon ages from the underlying Cretaceous basalts, thus supporting an injectite origin of the sand as an extrudite that emanated from the paleoerg that constitutes the Botucatu Formation.

  9. Zircon ages delimit the provenance of a sand extrudite from the Botucatu Formation in the Paraná volcanic province, Iraí, Brazil.

    Science.gov (United States)

    Pinto, Viter M; Hartmann, Léo A; Santos, João O S; McNaughton, Neal J

    2015-09-01

    Ion microprobe age determinations of 102 detrital zircon crystals from a sand extrudite, Cretaceous Paraná volcanic province, set limits on the origin of the numerous sand layers present in this major flood basalt province. The zircon U-Pb ages reflect four main orogenic cycles: Mesoproterozoic (1155-962 Ma), latest Proterozoic-early Cambrian (808-500 Ma) and two Palaeozoic (Ordovician- 480 to 450 Ma, and Permian to Lower Triassic- 296 to 250 Ma). Two additional small concentrations are present in the Neoarchean (2.8 to 2.6 Ga) and Paleoproterozoic (2.0 to 1.7 Ga). Zircon age peaks closely match the several pulses of igneous activity in the Precambrian Brazilian Shield and active orogeny in Argentina. A main delimitation of the origin of the sand is the absence of zircon ages from the underlying Cretaceous basalts, thus supporting an injectite origin of the sand as an extrudite that emanated from the paleoerg that constitutes the Botucatu Formation.

  10. Cadomian basement and Paleozoic to Triassic siliciclastics of the Taurides (Karacahisar dome, south-central Turkey): Paleogeographic constraints from U-Pb-Hf in zircons

    Science.gov (United States)

    Abbo, Avishai; Avigad, Dov; Gerdes, Axel; Güngör, Talip

    2015-06-01

    The Tauride block in Turkey is a peri-Gondwana, Cadomian-type terrane that rifted from the Afro-Arabian margin of Gondwana in the Permo-Triassic and re-accreted to Arabia in the Neogene. In the Karacahisar dome in the southern-central Taurides, Neoproterozoic basement metasediments and intrusive rocks are overlain by Cambro-Ordovician, Carboniferous and Triassic sediments. We studied U-Pb-Hf in zircons from major rock units exposed in Karacahisar in order to constrain the Cadomian crustal evolution of the Taurides, to evaluate the provenance of the Neoproterozoic and overlying sediments, to constrain the paleogeography of the Taurides, and to assess their linkage to Gondwana. The Neoproterozoic metasediments are low-grade metamorphic wacke-type turbidites that evolved in a broad back-arc basin peripheral to Afro-Arabia. Their detrital zircon U-Pb signal comprises a preponderance (40-68%) of Neoproterozoic-aged zircons (peak ages defined at 635 and 830 Ma), indicating that the sedimentary pile was built mainly from the erosion of Pan-African terranes from Afro-Arabia. The εHf values of the younger population (635 Ma) are mostly positive, indicating derivation from a juvenile arc, whereas Cryogenian-Tonian detrital zircons spread vertically (- 25 Neo-Tethys rifting was incipient at that time, allowing Afro-Arabian detritals to reach the Taurides.

  11. Effect of zircon-based tricolor pigments on the color, microstructure, flexural strength and translucency of a novel dental lithium disilicate glass-ceramic.

    Science.gov (United States)

    Yuan, Kun; Wang, Fu; Gao, Jing; Sun, Xiang; Deng, Zai-Xi; Wang, Hui; Jin, Lei; Chen, Ji-Hua

    2014-01-01

    The purpose of this study was to investigate the effect of zircon-based tricolor pigments (praseodymium zircon yellow, ferrum zircon red, and vanadium zircon blue) on the color, thermal property, crystalline phase composition, microstructure, flexural strength, and translucency of a novel dental lithium disilicate glass-ceramic. The pigments were added to the glass frit, milled, pressed, and sintered. Ninety monochrome samples were prepared and the colors were analyzed. The effect of the pigments on thermal property, crystalline phase composition, and microstructure were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Addition of the pigments resulted in the acquisition of subtractive primary colors as well as tooth-like colors, and did not demonstrate significant effects on the thermal property, crystalline phase composition, microstructure, and flexural strength of the experimental glass-ceramic. Although significant differences (p glass-ceramic to produce abundant and predictable tooth-like colors without significant adverse effects, if mixed in the right proportions. Copyright © 2013 Wiley Periodicals, Inc.

  12. The effect of titanite crystallisation on Eu and Ce anomalies in zircon and its implications for the assessment of porphyry Cu deposit fertility

    Science.gov (United States)

    Loader, Matthew A.; Wilkinson, Jamie J.; Armstrong, Robin N.

    2017-08-01

    The redox sensitivity of Ce and Eu anomalies in zircon has been clearly demonstrated by experimental studies, and these may represent an important tool in the exploration for porphyry Cu deposits which are thought to be derived from oxidised magmas. These deposits are significant because they are the source of much of the world's copper and almost all of the molybdenum and rhenium, key elements in many modern technologies. However, Ce and Eu anomalies in zircon are also affected by the co-crystallisation of REE bearing phases, such as titanite. Here, we report the trace element chemistry of zircons from titanite-bearing intrusions associated with mineralisation at the world class Oyu Tolgoi porphyry Cu-Au deposit (Mongolia). Based on these data, we suggest that neither zircon Eu/Eu*, nor Ce4+/Ce3+ are robust proxies for melt redox conditions, because they are both too strongly dependent on melt REE concentrations, which are usually poorly constrained and controlled by the crystallisation of titanite and other REE-bearing phases. In spite of this, Eu/Eu* can broadly distinguish between fertile and barren systems, so may still be an indicator of porphyry magma fertility, and a useful tool for exploration.

  13. The determination of major and some minor constituents in lead zirconate-titanate compositions by x-ray fluorescence and atomic absorption spectrometry

    NARCIS (Netherlands)

    van Willigen, J.H.H.G.; Kruidhof, H.; Dahmen, E.A.M.F.

    1972-01-01

    An accurate X-ray fluorescence spectrometric method is described for the determination of lead, zirconium and titanium in lead zirconate-titanate ceramics. Careful matching of samples and standards by a borax fusion method resulted in a relative standard deviation of about 0.2% for the major

  14. Chronology of early Archaean granite-greenstone evolution in the Barberton Mountain Land, South Africa, based on precise dating by single zircon evaporation

    Science.gov (United States)

    Kruener, Alfred; Byerly, Gary R.; Lowe, Donald R.

    1991-01-01

    Precise Pb-207/Pb-206 single zircon evaporating ages are reported for low-grade felsic metavolcanic rocks within the Onverwacht and Fig Tree Groups of the Barberton Greenstone Belt (BGB), South Africa, as well as for granitoid plutons bordering the belt. Dacitic tuffs of the Hooggenoeg Formation in the upper part of the Onverwacht Group are shown to yield ages between 3445 + or - 3 and 3416 + or - 5 Ma and to contain older crustal components represented by a 3504 + or - 4 Ma old zircon xenocryst. Fig Tree dacitic tuffs and agglomerates have euhedral zircons between 3259 + or - 3 Ma in age which are interpreted to reflect the time of crystallization. The comagmatic relationships between greenstone felsic volcanic units and the surrounding plutonic suites are keynoted. The data adduced show that the Onverwacht and Fig Tree felsic units have distinctly different ages and thus do not constitute a single, tectonically repeated unit as proposed by others. It is argued that conventional multigrain zircon dating may not accurately identify the time of felsic volcanic activity in ancient greenstones, and that the BGB in the Kaapval craton of southern Africa and greenstones in the Pilbara Block of Western Australia may have been part of a larger crustal unit in early Archaean times.

  15. SHRIMP U-Pb zircon dating of anatexis in high-grade migmatite complexes of Central Spain: implications in the Hercynian evolution of Central Iberia

    Science.gov (United States)

    Castiñeiras, Pedro; Villaseca, Carlos; Barbero, Luis; Martín Romera, Cristina

    2008-02-01

    U-Pb SHRIMP ages obtained in zircons from the Sotosalbos and Toledo anatectic complexes in Central Spain give new constraints to the evolution of the inner part of the Hercynian Iberian belt. Pre-Hercynian ages in zircons from the Sotosalbos complex (˜464 Ma) are well preserved and reveal that an age diversity of the Lower Paleozoic magmatism in the area exists, as previous data on westernmost orthogneisses yield significant older ages. Zircon ages in the pelite-derived granites from the Toledo complex also show an important Neoproterozoic age component which points to a metasedimentary protolith deposited maximally 560 Ma ago. Younger zircon populations in both complexes at ˜330 Ma in the Sotosalbos region and ˜317 Ma in the Toledo complex indicate an important diachronism between the anatectic processes in both areas but also that these processes are mainly unrelated to the generation of the later Hercynian granite batholith of Central Spain, which could be of deeper crustal derivation. In addition, as migmatization occurred late in the metamorphic cycle, after peak conditions were attained, the age of anatexis is younger than the age of the main Hercynian metamorphic event, which still is not well constrained.

  16. U-Pb detrital zircon geochronology from the basement of the Central Qilian Terrane: implications for tectonic evolution of northeastern Tibetan Plateau

    Science.gov (United States)

    Liu, Changfeng; Wu, Chen; Zhou, Zhiguang; Yan, Zhu; Jiang, Tian; Song, Zhijie; Liu, Wencan; Yang, Xin; Zhang, Hongyuan

    2017-08-01

    The Tuolai Group dominates the Central Qilian Terrane, and there are different opinions on the age and tectonic attribute of the Tuolai Group. Based on large-scale geologic mapping and zircon dating, the Tuolai Group is divided into four parts: metamorphic supracrustal rocks, Neoproterozoic acid intrusive rocks, early-middle Ordovician acid intrusive rocks and middle Ordovician basic intrusive rocks. The metamorphic supracrustal rocks are the redefined Tuolai complex-group and include gneiss and schist assemblage by faulting contact. Zircon U-Pb LA-MC-ICP-MS dating was conducted on these samples of gneiss and migmatite from the gneiss assemblage, quartzite, two-mica schist and slate from the schist assemblage. The five detrital samples possess similar age spectra; have detrital zircon U-Pb main peak ages of 1.7 Ga with youngest U-Pb ages of 1150 Ma. They are intruded by Neoproterozoic acid intrusive rocks. Therefore, the Tuolai Group belonging to late Mesoproterozoic and early Neoproterozoic. With this caveat in mind, we believe that U-Pb detrital zircon dating, together with the geologic constraints obtained from this study and early work in the neighboring regions. We suggest that the formation age of the entire crystalline basement rocks of metasedimentary sequence from the Central Qilian Terrane should be constrained between the Late Mesoproterozoic and the Late Neoproterozoic, but not the previous Paleoproterozoic. The basement of the Central Qilian Terrane contains the typical Grenville ages, which indicates the Centre Qilian Terrane have been experienced the Grenville orogeny event.

  17. Detrital Zircon U-Pb and Hf-isotope Constrains on Basement Ages, Granitic Magmatism, and Sediment Provenance in the Malay Peninsula

    Science.gov (United States)

    Sevastjanova, Inga; Clements, Benjamin; Hall, Robert; Belousova, Elena; Pearson, Norman; Griffin, William

    2010-05-01

    The Malay Peninsula forms the western part of central Sundaland in SE Asia. Sundaland comprises Indochina, the Thai-Malay Peninsula, Sumatra, Java, Borneo, and the shallow shelf between these landmasses. It is a composite region of continental crustal fragments that are separated by sutures that represent remnant ocean basins and volcanic arcs. The Malay Peninsula includes two of these fragments - East Malaya and Sibumasu - separated by the Bentong-Raub Suture Zone. The latter is a Palaeo-Tethyan ocean remnant. Granitoids of the Malay Peninsula are the major sources of detrital zircon in Sundaland. East Malaya is intruded by Permian-Triassic Eastern Province granitoids interpreted as products of Palaeozoic subduction of oceanic crust beneath the East Malaya Volcanic Arc. Sibumasu is intruded by Triassic Main Range Province granitoids interpreted as syn- to post-collisional magmatism following suturing to East Malaya. Locally, there are minor Late Cretaceous plutons. Basements of Sibumasu and East Malaya are not exposed and their ages are poorly constrained. The exact timing of the collision between these fragments is also contentious. In order to resolve these uncertainties, 752 U-Pb analyses from 9 samples were carried out on detrital zircons from modern rivers draining the Malay Peninsula and, of these, 243 grains from 6 samples were selected for Hf-isotope analyses. U-Pb zircon ages show that small numbers of Neoarchean-Proterozoic grains are consistently present in all samples, but do not form prominent populations. Permian-Triassic populations are dominant. Only one sample contains a small Jurassic population probably sourced from the area of Thailand and most likely recycled from fluvial-alluvial Mesozoic 'red-beds'. Late Cretaceous populations are locally abundant. Hf-isotope crustal model ages suggest that basement beneath the Malay Peninsula is heterogeneous. Some basement may be Neoarchean but there is no evidence for basement older than 2.8 Ga beneath

  18. Molecular dynamics simulation of lattice structure, radiation damage, and vibrational spectra of zircon (ZrSiO{sub 4}).

    Energy Technology Data Exchange (ETDEWEB)

    Liu, G. K.; Zhuang, H.-Z.; Beitz, J. V.

    2000-11-03

    The lattice structure, phonon density of states, and infrared spectrum for crystalline zircon, ZrSiO{sub 4}, have been studied using a molecular dynamics (MD) simulation method that utilizes the Born-Mayer-Huggins and Coulomb pair potentials and the Stillinger-Weber three-body potential. A lattice block of ZrSiO{sub 4}, which contains 343 unit cells with dimensions of 4.6249 x 4.6249 x 4.1874 nm{sub 3} and containing 8232 ions, was considered in our calculations. The simulated lattice structure agreed with that determined from x-ray and neutron diffraction experiments. The vibrational modes and absorption spectrum were calculated based on the simulated lattice and compared with infrared absorption spectra. Characteristic lines in infrared spectra obtained from previous experiments on natural and synthetic zircon were assigned to specific bond structures by interactive MD simulations with variation of selected potential parameters. It is shown that the O-Si-O three-body correlations in the SiO{sub 4} tetrahedron significantly influence the spectrum. It is demonstrated that the oxygen ions that are parallel and perpendicular to the c-axis in the SiO{sub 4} tetrahedron are inequivalent and make different contributions to the vibration spectrum. The energy distribution among 24 atoms in a unit cell in the 1011-cm{sup {minus}1} vibrational mode is shown in Fig. 1. Comparison between the simulated infrared absorption spectrum and that from experiments on synthetic zircon is shown in Fig. 2. The interactive method of fitting simulated results to those determined from experiments may be used as a tool for studying nanostructure and thermodynamics properties of materials. The model potentials for the ZrSiO{sub 4} lattice are refined and further applied to MD simulation of lattice disordering and line broadening that are induced by radiation damage processes and amorphization. We have further simulated alpha-decay-induced damage and dynamical recovery in the lattice of Zr

  19. U-Pb ages of detrital zircons from deep-water Well LS33A at Lingnan Low Uplift of the Qiongdongnan Basin and their geological significances

    Science.gov (United States)

    Xiu, C.; Sun, Z. P.; Zhai, S. K.; Liu, X. Y.; Liu, X. F.; Chen, K.

    2017-12-01

    U-Pb ages of detrital zircons from Well LS33A at Lingnan Low Uplift of the Qiongdongnan Basin (QDNB) are measured with LA-ICP-MS technique. Th/U ratios of detrital zircons mostly with oscillatory zoning are higher than 0.1, indicating a magmatic origin. Zircon U-Pb data of the Yacheng Formation yield an age range from 95.8 to 387.9 Ma, with two major clusters of 95-106 Ma and 214-237 Ma, representing Yanshanian and Indosinian, respectively. U-Pb age range of the Yinggehai-Ledong Formations varies widely from 87 to 2 490 Ma, exhibiting four remarkable age peaks of 88 Ma, 146 Ma, 208 Ma and 386 Ma on age spectrum. The variation in zircon age assemblage reveals that in provenance. Based on synthesizing seismic data, heavy mineral assemblages, geochemical data and zircon U-Pb ages, the main conclusions are as follows. There existed frequent fault-block activities in study area during the Yacheng deposition of Early Oligocene, which controlled the wedge-shaped disorderly fillings, and sediments chiefly came from the southern exposed tectonic uplift area of the QDNB. As it entered post-rifting stage and transgression continued, the provenance from the Pliocene to the Quaternary expanded to far- and multi-source realm, with Hainan Island, Red River and Indo-China Peninsula being source areas. The Proterozoic metamorphic basement, which supplied main material sources for the Yacheng Formation of Well LS33A, existed in the southern tectonic uplift area. Two large-scale magmatic activities, occurring in the southern uplift area in the Indosinian (214-237 Ma) and Yanshanian (95-106 Ma), not only destroyed the original metamorphic basement, but also provided an acidic magmatic provenance to study area.

  20. Detrital zircon age patterns from turbidites of the Balagne and Piedmont nappes of Alpine Corsica (France): Evidence for an European margin source

    Science.gov (United States)

    Lin, Wei; Rossi, Philippe; Faure, Michel; Li, Xian-Hua; Ji, Wenbin; Chu, Yang

    2018-01-01

    At the front of metamorphic Cenozoic Alpine nappe of Schistes Lustrés, Western Alpine Corsica (France) exposes non- to very low grade metamorphic nappes, such as the Piedmont nappes, Upper nappes, and the Balagne nappe. The provenance of the Balagne nappe remains still opened: an origin close to the Corsican continental margin; or an origin far East from the Corsican margin toward the "Apenninic" oceanic domain. This would constrain that the Balagne ophiolite be derived from the opposite OCT (Ocean - Continent transition), close to a microcontinent located to the East of the Mesozoic Corsican margin. A systematic U-Pb dating of 586 detrital zircon grains collected from the turbidites in the Balagne and Piedmont nappes has been performed to constrain the source of sediments. The zircon grains yield U-Pb age spectra ranging from Neoarchean to Late Paleozoic with age peaks at 2600 Ma, 2080 Ma, 1830 Ma, 910 Ma, 600 Ma, 560 Ma, 450 Ma, 330 Ma and 280 Ma with different continental model ages (TDM2) from 3.5 Ga to 1.0 Ga. The variety of composition of the Corsican batholith, unique in its present Mediterranean environment, and in spite of Alpine transcurrent movements, provide a key to analyze the detrital zircon age distribution patterns of sedimentary rocks. These new results i) confirm the lack of any Cretaceous zircon that validates absence of a magmatic arc of this age, at least in the surroundings of the turbiditic formations from the Balagne and the Piedmont nappes; ii) fully support an European provenance of detritus of the Balagne nappe, iii) put forward evidence that no ophiolitic zircon was contained neither in the Cretaceous nor in the Eocene turbidites samples, and iv) question both the deposition of the Piedmont Narbinco flysch within the ocean continent transition and its possible relationships with the Late Cretaceous Pyrenean basins.

  1. SHRIMP zircon dating and LA-ICPMS Hf analysis of early Precambrian rocks from drill holes into the basement beneath the Central Hebei Basin, North China Craton

    Directory of Open Access Journals (Sweden)

    Yusheng Wan

    2014-07-01

    Full Text Available The Central Hebei Basin (CHB is one of the largest sedimentary basins in the North China Craton, extending in a northeast–southwest direction with an area of >350 km2. We carried out SHRIMP zircon dating, Hf-in-zircon isotopic analysis and a whole-rock geochemical study on igneous and metasedimentary rocks recovered from drill holes that penetrated into the basement of the CHB. Two samples of gneissic granodiorite (XG1-1 and gneissic quartz diorite (J48-1 have magmatic ages of 2500 and 2496 Ma, respectively. Their zircons also record metamorphic ages of 2.41–2.51 and ∼2.5 Ga, respectively. Compared with the gneissic granodiorite, the gneissic quartz diorite has higher ΣREE contents and lower Eu/Eu* and (La/Ybn values. Two metasedimentary samples (MG1, H5 mainly contain ∼2.5 Ga detrital zircons as well as late Paleoproterozoic metamorphic grains. The zircons of different origins have εHf (2.5 Ga values and Hf crustal model ages ranging from 0 to 5 and 2.7 to 2.9 Ga, respectively. Therefore, ∼2.5 Ga magmatic and Paleoproterozoic metasedimentary rocks and late Neoarchean to early Paleoproterozoic and late Paleoproterozoic tectono-thermal events have been identified in the basement beneath the CHB. Based on regional comparisons, we conclude that the early Precambrian basement beneath the CHB is part of the North China Craton.

  2. Paleo-Pacific subduction-accretion: Evidence from Geochemical and U-Pb zircon dating of the Nadanhada accretionary complex, NE China

    Science.gov (United States)

    Zhou, Jian-Bo; Cao, Jia-Lin; Wilde, Simon A.; Zhao, Guo-Chun; Zhang, Jin-Jiang; Wang, Bin

    2014-12-01

    The Nadanhada Terrane, located along the eastern margin of Eurasia, contains a typical accretionary complex related to paleo-Pacific plate subduction-accretion. The Yuejinshan Complex is the first stage accretion complex that consists of meta-clastic rocks and metamafic-ultramafic rocks, whereas the Raohe Complex forms the main parts of the terrane and consists of limestone, bedded chert, and mafic-ultramafic rocks embedded as olistolith blocks in a weakly sheared matrix of clastic meta-sedimentary rocks. Geochemical data indicate that the Yuejinshan metabasalts have normal mid-ocean ridge basalt (N-MORB) affinity, whereas the Raohe basaltic pillow lavas have an affinity to ocean island basalts (OIB). Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon analyses of gabbro in the Raohe Complex yield a weighted mean 206Pb/238U zircon age of 216 ± 5 Ma, whereas two samples of granite intruded into the complex yield weighted mean 206Pb/238U zircon ages of 128 ± 2 and 129 ± 2 Ma. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb zircon analyses of basaltic pillow lava in the Raohe Complex define a weighted mean age of 167 ± 1 Ma. Two sandstone samples in the Raohe Complex record younger concordant zircon weighted mean ages of 167 ± 17 and 137 ± 3 Ma. These new data support the view that accretion of the Raohe Complex was between 170 and 137 Ma, and that final emplacement of the Raohe Complex took place at 137-130 Ma. The accretion of the Yuejinshan Complex probably occurred between the 210 and 180 Ma, suggesting that paleo-Pacific plate subduction was initiated in the Late Triassic to Early Jurassic.

  3. Laser Ablation Split Stream (LASS) U-Pb & Lu-Hf Isotope Analysis of Detrital Zircons from the Old Red Sandstone, NW Svalbard: Implications for Northern Caledonian Paleogeography

    Science.gov (United States)

    Beranek, L. P.; Gee, D. G.; Fisher, C. M.

    2015-12-01

    The Svalbard archipelago consists of three Caledonian provinces that were assembled by thrusting and transcurrent faulting during the Silurian and Devonian in a location directly northeast of the Greenland Caledonides. Syn- to post-orogenic alluvial strata, referred to as the Old Red Sandstones, filled pull-apart basins adjacent to the transcurrent faults and comprise cover assemblages that help constrain the timing of the Caledonian orogeny. To further investigate the tectonic history and paleogeography of the Raudfjorden-Liefdefjorden-Woodfjorden area of Spitsbergen, NW Svalbard, we analyzed rock samples of the Old Red Sandstones and underlying Precambrian basement complexes for detrital zircon analysis. Laboratory studies of the Old Red Sandstones include the novel Laser Ablation Split Stream (LASS) technique, which allows for simultaneous U-Pb & Lu-Hf isotope analysis of zircon crystals. Lower Devonian Red Bay Group strata contain a range of early Neoproterozoic to Neoarchean detrital zircons with prominent age peaks c. 960, 1050, 1370, 1450, 1650, and 2700 Ma; subordinate Ordovician (c. 460-490 Ma) and Cryogenian (c. 650 Ma) detrital zircons occur in a subset of the samples. Underlying Precambrian metasedimentary rocks are composed of similar earliest Neoproterozoic to Neoarchean age populations, which argues for much of the Red Bay Group to be derived from local basement rocks during thrusting and other faulting. The U-Pb ages and Hf isotope compositions of Paleozoic to Neoarchean detrital zircons are consistent with Arctic crustal evolution, and support the hypothesis that northwestern and northeastern provinces of the Svalbard Caledonides are extruded fragments of the northeast Greenland allochthons. The new Hf isotope results further allow paleogeographic and stratigraphic comparisons with rock assemblages proximal to the North Atlantic Caledonides during the Silurian-Devonian, including the Pearya terrane of Ellesmere Island, Alexander terrane of NW

  4. Synthesis, characterization and electric evaluation of barium zirconate doped with trivalent lanthanides; Sintesis, caracterizacion y evaluacion electrica de circonatos de bario dopados con lantanidos trivalentes

    Energy Technology Data Exchange (ETDEWEB)

    Gerena, O. A.; Carda, J. B.; Beltran, H.; Cordoncillo, E.; Valencia, J. S.

    2014-04-01

    Barium zirconate is an oxidic material having perovskite structure that exhibits high chemical stability in both oxidizing and reducing environments, such as in the presence of water and carbon dioxide, its conductivity has led to consider it as a electrolyte for solid oxide fuel cell finding good results, with the limitation of operating at temperatures above 800 degree centigrade. Several researchers have proposed that it is possible to improve their electrical conductivity by changes in chemical composition, particularly for doping with trivalent cations that replace the zirconium in B site of perovskite. In this study, barium zirconate was synthesized by the amorphous citrate method to examine the possibility of obtaining in more favorable conditions than those made by the conventional method of synthesis (ceramic method or solid state reaction) conditions are synthesized. Barium zirconate doped with europium, gadolinium, holmium, lanthanum, neodymium and praseodymium was prepared, the present phase identified cation was verified by X-ray diffraction (XRD), the electrical properties were examined by impedance spectroscopy (IS) at temperatures between 480 and 680 degree centigrade in order to evaluate its potential use as a fuel cell electrolyte in solid oxide. The contributions of this research has focused on the synthesis method, in the production of ceramic powders of barium zirconate at temperatures lower than those required by the ceramic method, in obtaining chemical, structural, morphological and electrical information of material synthesized. The desired phase synthesis conditions set found, also, a significant increase is seen in the solid conductivity of doped lanthanum, holmium and europium zirconate of barium in relation to the material without doping. (Author)

  5. Exhumation of the Source Area of the Cameros Basin revealed by detrital zircon fission track analysis

    Science.gov (United States)

    Del Rio, Pedro; Barbero, Luis; Casas-Sainz, Antonio

    2010-05-01

    The Cameros Basin (NW of the Iberian Range, NE of the Iberian Peninsula) was an intracontinental basin during Mesozoic times, which was inverted during Alpine compression. Its formation was due to a main rifting stage during Thithonian-Albian times related with an extensional period due to the opening of the Bay of Biscay. This extensional period is characterized by high subsidence and the filling of the basin with up to 8 km of continental sediments. A very low-grade metamorphic event is recorded during Albian times reaching maximum temperatures of ~350°C. Although the Cameros Basin has been studied for several decades from different geological points of view, the source area for the Cameros Basin still remains unknown. Previous studies have given some information about the possible location and nature of the source area: (1) Paleocurrent data indicate that the main source area was located SW of the basin (Salas et al., 2001); (2) Calculated chemical alteration indices show no intense chemical weathering of the source area and no significant variations along the stratigraphic section (Mata et al., 2000); (3) mineralogical studies trace elements ratios indicate that the material source should be acid igneous rock or any rock derived from them (Mata et al., 2000). In this work we present new detrital zircon fission track (ZFT) data from samples collected in different stratigraphic units of the Cameros Basin. Five samples were not reset for ZFT during burial and the metamorphic episode that occurred during Albian times. Those samples have a thermal signal previous to their deposition in the Cameros Basin and reveal the cooling history of the source area. Youngest peak ages for ZFT are in a range of 149 to 214 Ma. Lag-time values for those samples show a break-in-slope at ~130 Ma. Older samples show a decrease in lag-time values (from 55 myr to 20 myr) which implies an increase in exhumation rate between 145 and 135 Ma coinciding with the beginning of the rifting

  6. Continuously Tunable Ca2+ Regulation of RNA-Edited CaV1.3 Channels

    Directory of Open Access Journals (Sweden)

    Hojjat Bazzazi

    2013-10-01

    Full Text Available CaV1.3 ion channels are dominant Ca2+ portals into pacemaking neurons, residing at the epicenter of brain rhythmicity and neurodegeneration. Negative Ca2+ feedback regulation of CaV1.3 channels (CDI is therefore critical for Ca2+ homeostasis. Intriguingly, nearly half the CaV1.3 transcripts in the brain are RNA edited to reduce CDI and influence oscillatory activity. It is then mechanistically remarkable that this editing occurs precisely within an IQ domain, whose interaction with Ca2+-bound calmodulin (Ca2+/CaM is believed to induce CDI. Here, we sought the mechanism underlying the altered CDI of edited channels. Unexpectedly, editing failed to attenuate Ca2+/CaM binding. Instead, editing weakened the prebinding of Ca2+-free CaM (apoCaM to channels, which proves essential for CDI. Thus, editing might render CDI continuously tunable by fluctuations in ambient CaM, a prominent effect we substantiate in substantia nigral neurons. This adjustability of Ca2+ regulation by CaM now looms as a key element of CNS Ca2+ homeostasis.

  7. New data on the U-Pb (SHRIMP II) age of zircons from aluminous gneisses of the Archean Kola Group of the Baltic shield and the problem of their interpretation

    Science.gov (United States)

    Myskova, T. A.; Mil'kevich, R. I.; Glebovitskii, V. A.; L'vov, P. A.; Berezhnaya, N. G.

    2015-07-01

    New data on the U-Pb (SHRIMP II) age are obtained for aluminous gneisses of the Kola Group of the Baltic shield. Gneisses are typically ascribed to metasedimentary rocks with detrital zircons. Our work interprets the isotopic data based on the magmatic (tonalite) origin of gneisses and zircon that was established from study of the morphology and geochemistry of zircons. The age of crystallization of the protolith is 2.9 Ga. The existence of two stages of Archean granulite metamorphism is confirmed: an early stage (2.9 Ga) and later granulite metamorphism (2707-2656 Ma).

  8. Thickness effect on the structure, grain size, and local piezoresponse of self-polarized lead lanthanum zirconate titanate thin films

    Energy Technology Data Exchange (ETDEWEB)

    Melo, M.; Araújo, E. B., E-mail: eudes@dfq.feis.unesp.br [Departamento de Física e Química, Faculdade de Engenharia de Ilha Solteira, UNESP—Univ. Estadual Paulista, 15385-000 Ilha Solteira, SP (Brazil); Shvartsman, V. V. [Institute for Materials Science, University Duisburg-Essen, 45141 Essen (Germany); Shur, V. Ya. [Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation); Kholkin, A. L. [Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation); Department of Physics and CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro (Portugal)

    2016-08-07

    Polycrystalline lanthanum lead zirconate titanate (PLZT) thin films were deposited on Pt/TiO{sub 2}/SiO{sub 2}/Si substrates to study the effects of the thickness and grain size on their structural and piezoresponse properties at nanoscale. Thinner PLZT films show a slight (100)-orientation tendency that tends to random orientation for the thicker film, while microstrain and crystallite size increases almost linearly with increasing thickness. Piezoresponse force microscopy and autocorrelation function technique were used to demonstrate the existence of local self-polarization effect and to study the thickness dependence of correlation length. The obtained results ruled out the bulk mechanisms and suggest that Schottky barriers near the film-substrate are likely responsible for a build-in electric field in the films. Larger correlation length evidence that this build-in field increases the number of coexisting polarization directions in larger grains leading to an alignment of macrodomains in thinner films.

  9. Generation of electrical energy using lead zirconate titanate (PZT-5A) piezoelectric material: Analytical, numerical and experimental verifications

    Energy Technology Data Exchange (ETDEWEB)

    Butt, Zubair; Ahmad, Nasir [Dept. of Mechanical, Mechatronics and Manufacturing Engineering, UET Lahore, Faisalabad Campus, Lahore (Pakistan); Pasha, Riffat Asim; Qayyum, Faisal; Anjum, Zeeshan [Dept. of Mechanical Engineering, University of Engineering and Technology, Taxila (Pakistan); Elahi, Hassan [Northwestern Polytechnical University, Xian (China)

    2016-08-15

    Energy harvesting is the process of attaining energy from the external sources and transforming it into usable electrical energy. An analytical model of piezoelectric energy harvester has been developed to determine the output voltage across an electrical circuit when it is forced to undergo a base excitation. This model gives an easy approach to design and investigate the behavior of piezoelectric material. Numerical simulations have been carried out to determine the effect of frequency and loading on a Lead zirconate titanate (PZT-5A) piezoelectric material. It has been observed that the output voltage from the harvester increases when loading increases whereas its resonance frequency decreases. The analytical results were found to be in good agreement with the experimental and numerical simulation results.

  10. In situ neutron diffraction studies of a commercial, soft lead zirconate titanate ceramic: Response to electric fields and mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

    Pramanick, Abhijit [University of Florida; Prewitt, Anderson [University of Florida; Cottrell, Michelle [University of Florida; Lee, Wayne [ITT Corporation Acoustic Sensors; Studer, Andrew J. [Bragg Institute, ANSTO; An, Ke [ORNL; Hubbard, Camden R [ORNL; Jones, Jacob [University of Florida

    2010-01-01

    Structural changes in commercial lead zirconate titanate (PZT) ceramics (EC-65) under the application of electric fields and mechanical stress were measured using neutron diffraction instruments at the Australian Nuclear Science and Technology Organisation (ANSTO) and the Oak Ridge National Laboratory (ORNL). The structural changes during electric-field application were measured on the WOMBAT beamline at ANSTO and include non-180{sup o} domain switching, lattice strains and field-induced phase transformations. Using time-resolved data acquisition capabilities, lattice strains were measured under cyclic electric fields at times as short as 30 {mu}s. Structural changes including the (002) and (200) lattice strains and non-180{sup o} domain switching were measured during uniaxial mechanical compression on the NRSF2 instrument at ORNL. Contraction of the crystallographic polarization axis, (002), and reorientation of non-180{sup o} domains occur at lowest stresses, followed by (200) elastic strains at higher stresses.

  11. Cenozoic and Precambrian Accessory Zircons in Gabbroids of the 3rd layer of Oceanic Crust in Axial Part of the Mid-Atlantic Ridge, 6oN: U-Pb SIMS SHRIMP Data

    Science.gov (United States)

    Bortnikov, N. S.; Zinger, T. F.; Sharkov, E. V.; Lepekhina, E. N.; Antonov, A. V.; Sergeev, S. A.

    2008-12-01

    We studied ages of 150 grains of zircon from 8 gabbroid samples, dragged at 4 sites in axial part of the MAR, Sierra-Leone area, 6oN, during 10th cruise of R/V "Academic Ioffe" (2001-2002) and 22nd cruise of R/V "Professor Logachev" (2003) by regular procedure (Williams, 1998; Ludwig, 2000; Baldwin, Ireland, 1995) using SIMS technique on SHRIMP-II. Zircon grains from cataclased and altered leucogabbronorites and fresh non-cataclased troctolite were examined. Typical zircons were mounted in epoxy, ground to half of their thickness and polished before cathodeluminescence imaging