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Sample records for ma ar tuff

  1. 40Ar/39Ar dating of Pleistocene tuffs: an accurate age for the Matuyama-Brunhes geomagnetic reversal (MBGR)

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    Mark, D. F.; Renne, P. R.; Morgan, L. E.; Deino, A.; Smith, V. C.; Ellis, B. S.; Pearce, N. J.

    2012-12-01

    Recent recalibrations of the 40Ar/39Ar system [1,2] reveal inconsistencies with some previous ages inferred for the MBGR. An Ar/Ar age [3] for the Bishop Tuff (BT) (which post-dates the MBGR by at least 15.3 ± 2.2 ka [3]) recalculated [2] yields an age of 778.0 ± 3.8 ka (1σ, full systematic uncertainty). The age is c. 10 ka older than the BT zircon ID-TIMS U-Pb age [4] and places the MBGR at c. 793 ka, c. 13 and 20 ka older than astronomical ages for the MBGR of 780 ka [5] and 773 ka [6], respectively. To determine an accurate age for the MBGR, we have made a series of 40Ar/39Ar age determinations for Pleistocene tuffs from both Indonesia and North America that have direct relationships to the MBGR. Blind analyses were conducted at SUERC and BGC. We observed excellent inter-laboratory agreement and no systematic offset in data. Ar/Ar ages are reported relative to [2] (1σ, full systematic uncertainty). Drill cores from ODP Site 758 show the precise location of the MBGR. Below the MBGR are two distal tephra horizons that we have identified as products of two temporally distinct Old Toba Tuff (OTT) eruptions (layer d OTT1 and layer D OTT2). Continuous sedimentation between OTT1 (802.8 ± 0.7 ka, n = 100, MSWD 1.2) and OTT2 (796.2 ± 0.8 ka, n = 62, MSWD 1.3) allows for calculation of an accurate sedimentation rate and for extrapolation of an age from OTT2 to the MBGR. Data define an age for the MBGR of 795.2 ± 0.9 ka. Using tephra above the MBGR boundary, the Middle Toba Tuff (layer C) and Young Toba Tuff (layer A), extrapolation down core supports a MBGR age of c. 795 ka. Recent age data for BT sanidine reported relative to FCs at 28.172 Ma (767.4 ± 1.1 Ma) [7] oddly yielded an Ar/Ar age that was indistinguishable from the BT zircon U-Pb age [4], which is consistent with previous 40Ar/39Ar age measurements made relative to FCs at 28.02 Ma [3]. Thus we made a series of 40Ar/39Ar measurements on the exact same sample as used by Rivera et al. [7] and observed

  2. Using 40Ar/39Ar ages of intercalated silicic tuffs to date flood basalts: Precise ages for Steens Basalt Member of the Columbia River Basalt Group

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    Mahood, Gail A.; Benson, Thomas R.

    2017-02-01

    To establish causality between flood basalt eruptions and extinction events and global environmental effects recorded by isotopic excursions in marine sediments, highly accurate and precise ages for the flood basalts are required. But flood basalts are intrinsically difficult to date. We illustrate how 40Ar/39Ar feldspar ages for silicic tuffs intercalated with and overlying sections of Steens Basalt, the earliest lavas of the Middle Miocene Columbia River Basalt Group in the northwestern United States, provide high-precision ages that, for the first time, make it possible to resolve age differences with stratigraphic position within a section of these flood lavas. The stratigraphically lowest rhyolitic tuff, a fall deposit, yielded an age of 16.592 ± ± 0.028 Ma (FCs = 28.02 Ma), and the uppermost, the alkali rhyolite ignimbrite Tuff of Oregon Canyon, is 16.468 ± ± 0.014 Ma. The argon and stratigraphic data indicate that Steens Basalt eruptions occurred from ∼16.64 to 16.43 Ma in the southern end of its distribution. We estimate that the Steens Mountain geomagnetic reversal occurred at 16.496 ± ± 0.028 Ma (±0.18 Ma total error). Our estimates of the timing for initiation of volcanism and volumetric eruptive rates do not seem to support volcanic forcing by the initial stages of Columbia River Basalt Group eruptions as an explanation for the abrupt warming and carbonate dissolution at the beginning of the Miocene Climatic Optimum.

  3. Single-crystal 40Ar/39Ar incremental heating reveals bimodal sanidine ages in the Bishop Tuff

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    Andersen, N. L.; Jicha, B. R.; Singer, B. S.

    2015-12-01

    The 650 km3 Bishop Tuff (BT) is among the most studied volcanic deposits because it is an extensive marker bed deposited just after the Matuyama-Brunhes boundary. Reconstructions of the vast BT magma reservoir from which high-silica rhyolite erupted have long influenced thinking about how large silicic magma systems are assembled, crystallized, and mixed. Yet, the longevity of the high silica rhyolitic melt and exact timing of the eruption remain controversial due to recent conflicting 40Ar/39Ar sanidine vs. SIMS and ID-TIMS U-Pb zircon dates. We have undertaken 21 40Ar/39Ar incremental heating ages on 2 mm BT sanidine crystals from pumice in 3 widely separated outcrops of early-erupted fall and flow units. Plateau ages yield a bimodal distribution: a younger group has a mean of 766 ka and an older group gives a range between 772 and 782 ka. The younger population is concordant with the youngest ID-TIMS and SIMS U-Pb zircon ages recently published, as well as the astronomical age of BT in marine sediment. Of 21 crystals, 17 yield older, non-plateau, steps likely affected by excess Ar that would bias traditional 40Ar/39Ar total crystal fusion ages. The small spread in older sanidine ages, together with 25+ kyr of pre-eruptive zircon growth, suggest that the older sanidines are not partially outgassed xenocrysts. A bimodal 40Ar/39Ar age distribution implies that some fraction of rhyolitic melt cooled below the Ar closure temperature at least 10 ky prior to eruption. We propose that rapid "thawing" of a crystalline mush layer released older crystals into rhyolitic melt from which sanidine also nucleated and grew immediately prior to the eruption. High precision 40Ar/39Ar dating can thus provide essential information on thermo-physical processes at the millenial time scale that are critical to interpreting U-Pb zircon age distributions that are complicated by large uncertainties associated with zircon-melt U-Th systematics.

  4. Revised ages for tuffs of the Yellowstone Plateau volcanic field: Assignment of the Huckleberry Ridge Tuff to a new geomagnetic polarity event

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    Lanphere, M.A.; Champion, D.E.; Christiansen, R.L.; Izett, G.A.; Obradovich, J.D.

    2002-01-01

    40Ar/39Ar ages were determined on the three major ash-flow tuffs of the Yellowstone Plateau volcanic field in the region of Yellowstone National Park in order to improve the precision of previously determined ages. Total-fusion and incremental-heating ages of sanidine yielded the following mean ages: Huckleberry Ridge Tuff-2.059 ?? 0.004 Ma; Mesa Falls Tuff-1.285 ?? 0.004 Ma; and Lava Creek Tuff-0.639 ?? 0.002 Ma. The Huckleberry Ridge Tuff has a transitional magnetic direction and has previously been related to the Reunion Normal-Polarity Subchron. Dating of the Reunion event has been reviewed and its ages have been normalized to a common value for mineral standards. The age of the Huckleberry Ridge Tuff is significantly younger than lava flows of the Reunion event on Re??union Island, supporting other evidence for a normal-polarity event younger than the Reunion event.

  5. 40Ar/39Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy): Toward a new chronostratigraphic reconstruction of the Holocene volcanic activity

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    Fedele, L.; Insinga, D.D.; Calvert, A.T.; Morra, V.; Perrotta, A.; Scarpati, C.

    2011-01-01

    The Campi Flegrei hosts numerous monogenetic vents inferred to be younger than the 15 ka Neapolitan Yellow Tuff. Sanidine crystals from the three young Campi Flegrei vents of Fondi di Baia, Bacoli and Nisida were dated using 40Ar/39Ar geochronology. These vents, together with several other young edifices, occur roughly along the inner border of the Campi Flegrei caldera, suggesting that the volcanic conduits are controlled by caldera-bounding faults. Plateau ages of ∼9.6 ka (Fondi di Baia), ∼8.6 ka (Bacoli) and ∼3.9 ka (Nisida) indicate eruptive activity during intervals previously interpreted as quiescent. A critical revision, involving calendar age correction of literature 14C data and available 40Ar/39Ar age data, is presented. A new reference chronostratigraphic framework for Holocene Phlegrean activity, which significantly differs from the previously adopted ones, is proposed. This has important implications for understanding the Campi Flegrei eruptive history and, ultimately, for the evaluation of related volcanic risk and hazard, for which the inferred history of its recent activity is generally taken into account.

  6. Evidence for pre-Cretaceous history and partial Neogene (19-9 Ma) reequilibration in the Karakorum (NW Himalayan Syntaxis) from 40Ar- 39Ar amphibole dating

    Science.gov (United States)

    Rolland, Yann; Villa, Igor M.; Guillot, Stéphane; Mahéo, Gweltaz; Pêcher, Arnaud

    2006-09-01

    Amphiboles and a biotite from amphibolites and amphibolitic gneisses of the Karakorum Metamorphic Complex (KMC, NW Himalaya), were dated using the 40Ar/ 39Ar method. Isotope correlations were compared to electron-microprobe analyses. Both Al IV and Al VI contents of amphibole increase from the south near the Shyok Suture Zone to the Dassu-Askole Area in the north, with an increase in metamorphic grade (from anchizone to upper amphibolite facies). In the lower metamorphic zone, discordant age spectra were obtained. They are related to epidote-amphibolite overgrowth of amphibole rims on older (Precambrian to Mesozoic) magmatic cores. In the Shyok Suture Zone Ar/Ar ages of 38-62 Ma are contemporaneous with the emplacement of the Ladakh Batholith granodiorites, while middle Cretaceous magmatic Ar/Ar ages (˜ 120 Ma) are locally preserved in tschermakite relics. In the Southern Karakorum basement, a minimum Ar/Ar age of 651 Ma was preserved, while an age of 208.5±2 Ma was preserved in Panjal Trap-like diorites. At the margin of the domes zone, more recent metamorphism resulted in mineral growth at 20-5 Ma. In the domes zone, amphibole Ar/Ar ages of 17 Ma (Askole) and bimodal age spectra of 15-17 and 9-13 Ma (Dassu) extend towards the east the zone of Neogene amphibolite to granulite facies metamorphism known in the Nanga Parbat Syntaxis.

  7. Comparison of AcrySof MA30BA and Sensar AR40 acrylic intraocular lenses.

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    Casprini, Fabrizio; Tosi, Gian Marco; Quercioli, Pier Paolo; Caporossi, Aldo

    2002-07-01

    To compare differences in anterior (ACO) and posterior (PCO) capsule opacification and subjective glare between 2 acrylic intraocular lenses (IOLs): AcrySof MA30BA (Alcon) and Sensar AR40 (Allergan). Department of Ophthalmology and Neurosurgery, University of Siena, Siena, Italy. This retrospective study comprised 100 cataract patients who had phacoemulsification and IOL implantation. Fifty eyes of 50 patients received an MA30BA and 50 eyes of 50 patients, an AR40. The mean postoperative follow-up was 25 months (range 20 to 31 months) and 22 months (range 19 to 29 months), respectively. Examiners subjectively evaluated ACO, and a photographic image-analysis system was used to assess PCO. All patients received a questionnaire to evaluate the incidence of subjective photic phenomena. In the MA30BA group, 60% had no ACO, 19% had mild ACO, and 21% had anterior capsule fibrosis. In the AR40 group, 55% had no ACO, 27% had mild ACO, and 18% had anterior capsule fibrosis. In the MA30BA group, the mean PCO score measured by image-analysis was 0.043 (range 0.000 to 0.084) at 1 year and 0.125 (range 0.000 to 0.197) at 2 years and in the AR40 group, 0.071 (range 0.000 to 0.157) and 0.230 (range 0.091 to 0.628), respectively. Although the ACO percentages and the PCO scores at 1 year were not statistically different between the 2 groups (P >.05), the MA30BA group had statistically less PCO at 2 years (P .05). The findings indicate that the AcrySof MA30BA has a lower incidence of PCO than the Sensar AR40. The AR40 IOL induced less glare; however, the glare phenomena did not disturb those with an MA30BA lens and the symptoms decreased by 1 year after surgery. These results suggest that both optic design and haptic material influence postoperative clinical results.

  8. Further support for a Cretaceous age for the feathered-dinosaur beds of Liaoning,China:New 40Ar/39Ar dating of the Yixian and Tuchengzi Formations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We report new 40Ar/39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar/39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation.The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar/39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca/K ratios, excellent reproducibility and gave a mean age of 125.0 ± 0.18 (1SD) ±0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar/39Aranalyses of the Hengdaozi tuff gave a mean age of 125.0 +0.19 (1SD) ± 0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4 ± 0.19 (1SD) ± 0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous.``

  9. Eruption of the Continental Flood Basalts at ~259 Ma in the Emeishan Large Igneous Province, SW China: Evidence from Laser Microprobe 40Ar/39Ar Dating

    Institute of Scientific and Technical Information of China (English)

    HOU Zengqian; CHEN Wen; LU Jiren

    2006-01-01

    A suite of continental flood basalts sampled over a vast exposure and stratigraphic thickness in the Emeishan large igneous province (LLP), SW China was investigated for laser microprobe 40Ar/39Ar dating. There are two 40Ar/39Ar age groups for these basalts, corresponding to 259-246 Ma and 177-137 Ma, respectively. A well-defined isochron gives an eruption age of huge quantities of mafic magmas at 258.9±3.4 Ma, which is identical to previous dating and paleontological data. Much younger 40Ar/39Ar ages for some basalts with low-greenschist metamorphic facies probably recorded a late thermo-tectonic event caused by collision between the Yangtze and Qiangtang continental blocks during the Mesozoic, which resulted in the reset of argon isotope system. The 40Ar/39Ar age data, we present here, combined with previous dating and paleontological data, suggest relatively short duration (about 3 Ma) of mafic volcanism, which have important implication on mantle plume genesis of the Emeishan continental flood basalts in the LIP.

  10. Millennial-scale phase relationships between ice-core and Mediterranean marine records: insights from high-precision 40Ar/39Ar dating of the Green Tuff of Pantelleria, Sicily Strait

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    Scaillet, S.; Vita-Scaillet, G.; Rotolo, S. G.

    2013-10-01

    With the advent of annually-resolved polar ice records extending back to 70 ka, marine and continental paleoclimate studies have now matured into a discipline where high-quality age control is essential for putting on an equal pace layer-counted timescale models and Late Quaternary sedimentary records. High-resolution U-Th dating of speleothem records and 40Ar/39Ar dating of globally recorded geomagnetic excursions have recently improved the time calibration of Quaternary archives, reflecting the cross-disciplinary effort made to synchronize the geologic record at the millennial scale. Yet, tie-points with such an absolute age control remain scarce for paleoclimatic time-series extending beyond the radiocarbon timescale, most notably in the marine record. Far-travelled tephra layers recorded both onland and offshore provide an alternative in such instance to synchronize continental and marine archives via high-resolution 40Ar/39Ar dating of the parent volcanic eruption. High-resolution 40Ar/39Ar data are reported herein for one such volcanic marker, the Green Tuff of Pantelleria and its Y-6 tephra equivalent recorded throughout the Central and Eastern Mediterranean. Published radiochronometric and δ18O orbitally-tied ages for this marker horizon scatter widely from about 41 ka up to 56 ka. Our new 40Ar/39Ar age at 45.7 ± 1.0 ka (2σ) reveals that previous estimates are biased by more than their reported errors would suggest, including recent orbital tuning of marine records hosting the tephra bed that are reevaluated in the context of this study. This improved estimate enables potential phase lags and leads to be studied between deep-sea and terrestrial archives with unrivaled (near-millennial) 40Ar/39Ar precision in the marine record.

  11. Recurrent Early Cretaceous, Indo-Madagascar (89-86 Ma) and Deccan (66 Ma) alkaline magmatism in the Sarnu-Dandali complex, Rajasthan: 40Ar/39Ar age evidence and geodynamic significance

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    Sheth, Hetu; Pande, Kanchan; Vijayan, Anjali; Sharma, Kamal Kant; Cucciniello, Ciro

    2017-07-01

    The Sarnu-Dandali alkaline complex in Rajasthan, northwestern India, is considered to represent early, pre-flood basalt magmatism in the Deccan Traps province, based on a single 40Ar/39Ar age of 68.57 Ma. Rhyolites found in the complex are considered to be 750 Ma Malani basement. Our new 40Ar/39Ar ages of 88.9-86.8 Ma (for syenites, nephelinite, phonolite and rhyolite) and 66.3 ± 0.4 Ma (2σ, melanephelinite) provide clear evidence that whereas the complex has Deccan-age (66 Ma) components, it is dominantly an older (by 20 million years) alkaline complex, with rhyolites included. Basalt is also known to underlie the Early Cretaceous Sarnu Sandstone. Sarnu-Dandali is thus a periodically rejuvenated alkaline igneous centre, active twice in the Late Cretaceous and also earlier. Many such centres with recurrent continental alkaline magmatism (sometimes over hundreds of millions of years) are known worldwide. The 88.9-86.8 Ma 40Ar/39Ar ages for Sarnu-Dandali rocks fully overlap with those for the Indo-Madagascar flood basalt province formed during continental breakup between India (plus Seychelles) and Madagascar. Recent 40Ar/39Ar work on the Mundwara alkaline complex in Rajasthan, 120 km southeast of Sarnu-Dandali, has also shown polychronous emplacement (over ≥ 45 million years), and 84-80 Ma ages obtained from Mundwara also arguably represent post-breakup stages of the Indo-Madagascar flood basalt volcanism. Remnants of the Indo-Madagascar province are known from several localities in southern India but hitherto unknown from northwestern India 2000 km away. Additional equivalents buried under the vast Deccan Traps are highly likely.

  12. A method for intercalibration of U-Th-Pb and 40Ar- 39Ar ages in the Phanerozoic

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    Villeneuve, Mike; Sandeman, Hamish A.; Davis, William J.

    2000-12-01

    The increasing analytical precision of 40Ar- 39Ar geochronological data and its use in studies that combine U-Pb and 40Ar- 39Ar data has necessitated derivation of a means to intercalibrate ages between the two isotopic systems. The primary determinants inhibiting accurate cross calibration are uncertainty in decay constant values and uncertainty in 40Ar∗/ 40K (usually presented as apparent age) for 40Ar- 39Ar standards, notably those derived from the Fish Canyon Tuff. By utilizing a monazite- and biotite bearing Oligocene ash flow tuff (MAC-83) as the primary standard material, precise U-Th-Pb and 40Ar- 39Ar ages can be derived. Because both isotopic systems should reflect closure during the instantaneous eruption event, the 24.21 ± 0.10 Ma 207Pb/ 235U age should match the age resulting from 40Ar- 39Ar biotite analysis. This forced equivalence will partly offset the effects of decay constant uncertainty. Furthermore, by co-irradiating Fish Canyon Tuff sanidine with MAC-83 biotite, the apparent age for Fish Canyon Tuff sanidine is back-calculated to 27.98 ± 0.15 Ma, relative to the MAC-83 207Pb/ 235U age. Hence, intercalibration between the two isotopic systems in a relative sense can be accomplished, allowing for a direct and valid comparison of ages. It is also shown that forcing equivalence of the two isotopic systems minimizes the effect of decay constant uncertainty for samples of Phanerozoic age.

  13. Ma

    Directory of Open Access Journals (Sweden)

    Ingrid Berthon-Moine

    2012-01-01

    Full Text Available Ma (2009 is a single channel video of a mother and child walking together side by side, holding hands. The title is reminiscent of the affectionate nickname for a mother, 'Ma', but also a concealed way to convey maternal ambivalence. Maternal ambivalence is the result of the tension between the idealisation of motherhood and women’s lived experience of mothering. The maternal struggle finds its source in the difficulty of identifying with the ideological representation of the mother. This image still conveys an idealistic and nostalgic, patriarchal image of maternal love bounded by culture and history. http://podcast.ulcc.ac.uk/accounts/BirkbeckCollege/mamsie/MA.mov

  14. Magnetostratigraphy and 39Ar/40Ar studies of the Lana'i Long Volcanic Sequence (ca. 1.606+/-0.063 Ma), Hawaii, USA

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    Herrero-Bervera, E.; Jicha, B.; Valet, J.

    2013-12-01

    Previous published work on Lanai indicated that the volcano was formed mainly during the Matuyama Chron (Herrero-Bervera et al., 2000). In order to constrain further the timing of the active phases of the Lanai volcano, we conducted a paleomagnetic and rock magnetic study involving a ~500-m vertical thick sequence of lava flows that were erupted between 0.76+/-0.66 Ma and 1.6+/-0.09 Ma according to previous K/Ar and 40Ar/39Ar dating (Leonhardt et al., 2009). Low-field susceptibility versus temperature (k-T) and SIRM experiments performed on a dozen flows indicate that magnetite dominates the remanent magnetization (575°C). In a few cases, a low-temperature mineral phase (300-400°C) could reflect the presence of titanomagnetite with low Ti content, but the presence of maghemite or pyrrhotite cannot be completely excluded. Additional investigations are in progress on this matter. All specimens were step-wise demagnetized by alternating fields from 5 to 100 mT. Companion specimens from the same samples were demagnetized at 15 temperature steps. The demagnetization diagrams obtained with each technique showed a stable direction of remanence. In all cases, the characteristic (ChRM) component was clearly defined from at least seven successive directions isolated during step-wise demagnetization. The succession of the mean directions calculated for each lava flow reveals the existence of at least one polarity interval. Based on radiometric dates, they were assigned to the Gilsa, "excursion" (1.606+/-0.063 Ma). Thus, the present results, along with the radiometric ages of the lavas, indicate that the tholeiitic flows that formed the Lanai volcano were erupted over a short time period, and only during the Matuyama Chron (0.780-2.58 Ma). No eruptions have occurred during the Brunhes Chron (0.78 Ma) as previously indicated from K-Ar data on lavas in the Maunalei Gulch. The excursional VGPs from the onset of the Gilsa excursion recorded on Lanai are situated near the

  15. Vegetation during UMBI and deposition of Tuff IF at Olduvai Gorge, Tanzania (ca. 1.8 Ma) based on phytoliths and plant remains.

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    Albert, Rosa Maria; Bamford, Marion K

    2012-08-01

    As part of ongoing research at Olduvai Gorge, Tanzania, to determine the detailed paleoenvironmental setting during Bed I and Bed II times and occupation of the basin by early hominins, we present the results of phytolith analyses of Tuff IF which is the uppermost unit of Bed I. Phytoliths were identified in most of the levels and localities on the eastern paleolake margin, but there are not always sufficient numbers of identifiable morphologies to infer the specific type of vegetation due to dissolution. Some surge surfaces and reworked tuff surfaces were vegetated between successive ash falls, as indicated by root-markings and the presence of a variety of phytolith morphotypes. Dicotyledonous wood/bark types were dominant except at the FLK N site just above Tuff IF when monocots are dominant and for the palm-dominated sample from the reworked channel cutting down into Tuff IF at FLK N. The area between the two fault scarps bounding the HWK Compartment, approximately 1 km wide, was vegetated at various time intervals between some of the surges and during the reworking of the Tuff. By lowermost Bed II times the eastern margin was fully vegetated again. Climate and tectonic activity probably controlled the fluctuating lake levels but locally the paleorelief and drainage were probably the controlling factors for the vegetation changes. These data support a scenario of small groups of hominins making brief visits to the paleolake during uppermost Bed I times, followed by a more desirable vegetative environment during lowermost Bed II times. Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. 40Ar/(39)Ar dating of the Kapthurin Formation, Baringo, Kenya.

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    Deino, Alan L; McBrearty, Sally

    2002-01-01

    The(40)Ar/(39)Ar radiometric dating technique has been applied to tuffs and lavas of the Kapthurin Formation in the Tugen Hills, Kenya Rift Valley. Two variants of the(40)Ar/(39)Ar technique, single-crystal total fusion (SCTF) and laser incremental heating (LIH) have been employed to date five marker horizons within the formation: near the base, the Kasurein Basalt at 0.61+/-0.04 Ma; the Pumice Tuff at 0.543+/-0.004 Ma; the Upper Kasurein Basalt at 0.552+/-0.015 Ma; the Grey Tuff at 0.509+/-0.009 Ma; and within the upper part of the formation, the Bedded Tuff at 0.284+/-0.012 Ma. The new, precise radiometric age determination for the Pumice Tuff also provides an age for the widespread Lake Baringo Trachyte, since the Pumice Tuff is the early pyroclastic phase of this voluminous trachyte eruption. These results establish the age of fossil hominids KNM-BK 63-67 and KNM-BK 8518 at approximately 0.510-0.512 Ma, a significant finding given that few Middle Pleistocene hominids are radiometrically dated. The Kapthurin hominids are thus the near contemporaries of those from Bodo, Ethiopia and Tanzania. A flake and core industry from lacustrine sediments in the lower part of the formation is constrained by new dates of 0.55-0.52 Ma, a period during which the Acheulian industry, characterized by handaxes, is known throughout East Africa. Points, typical of the Middle Stone Age (MSA), are found in Kapthurin Formation sediments now shown to date to between 0.509+/-0.009 Ma and 0.284+/-0.012 Ma. This date exceeds previous estimates for the age of the MSA elsewhere in East Africa by 49 ka, and establishes the age of Acheulian to MSA transition for the region. Evidence of the use of the Levallois technique for the manufacture of both small flakes and biface preforms, the systematic production of blades, and the use and processing of red ochre also occurs in this interval. The presence of blades and red ochre at this depth is important as blades signify a high degree of technical

  17. Collision Event during 177-135 Ma on the Eastern Margin of the Qinghai-Tibet Plateau: Evidence from 40Ar/ 39Ar Dating for Basalts on the Western Margin of the Yangtze Platform

    Institute of Scientific and Technical Information of China (English)

    侯增谦; 陈文; 卢记仁

    2002-01-01

    Geochronology of continental flood basalts sampled from the Emei large igneous province (LIP) on the western margin of the Yangtze platform was investigated by the laser microprobe 40Ar/39Ar dating technique. These basalts yield a fairly wide range of 40Ar/39Ar ages, varying from 259 to 135 Ma. One basalt sample, at least altered, recorded the oldest 40Ar/39Ar age of about 259 Ma, corresponding to a peak eruption age of the Emei LIP continental flood basalts. Most of the samples yield much younger ages from 135 to 177 Ma, which are consistent with the K-Ar ages for the same samples (122.8-172.1 Ma). The dating data suggest that these Permian basalts had been widely affected by the regional tectonothermal event at 177-135 Ma. The event was probably caused by the convergence and collision among the Laurasia, Yangtze and Qiangtang-Qamdo continental blocks on the eastern margin of the Qinghai-Tibet plateau after the late Triassic. The age of the event reflects the timing of the peak collisional orogeny.

  18. 40Ar/39Ar dating of the Mumbai tholeiites and Panvel flexure: intense 62.5 Ma onshore-offshore Deccan magmatism during India-Laxmi Ridge-Seychelles breakup

    Science.gov (United States)

    Pande, Kanchan; Yatheesh, Vadakkeyakath; Sheth, Hetu

    2017-08-01

    Mumbai, located on the western Indian continental margin, exposes Danian-age Deccan magmatic units of diverse compositions, dipping seaward due to the Panvel flexure. The Ghatkopar-Powai tholeiitic sequence contains seaward-dipping (thus pre-flexure) flows and subvertical (thus post-flexure) dykes. We present new 40Ar/39Ar ages of 62.4 ± 0.7 and 62.4 ± 0.3 Ma (2σ) on two flows, and 62.2 ± 0.3, 62.8 ± 0.3 and 61.8 ± 0.2 Ma on three dykes, showing that this sequence is much younger than the main 66-65 Ma Deccan sequence in the Western Ghats escarpment. The mutually indistinguishable ages of the Ghatkopar-Powai tholeiites overlap with available 40Ar/39Ar ages of 62.6 ± 0.6 and 62.9 ± 0.2 Ma for the seaward-dipping Dongri rhyolite flow and 62.2 ± 0.6 Ma for the Saki Naka trachyte intrusion, both from the uppermost Mumbai stratigraphy. The weighted mean of these eight 40Ar/39Ar ages is 62.4 ± 0.1 Ma (2 SEM), relative to an MMhb-1 monitor age of 523.1 ± 2.6 Ma (2σ), and indicates essentially contemporaneous volcanism, intrusion and tectonic flexure. This age also coincides with the rift-to-drift transition of the Seychelles and Laxmi Ridge-India breakup and the emplacement of the Raman-Panikkar-Wadia seamount chain in the axial part of the Laxmi Basin. Pre-rift magmatism is seen in the 64.55 Ma Jogeshwari basalt in Mumbai and 63.5-63.0 Ma intrusions in the Seychelles. Post-rift magmatism is seen in the 60.8-60.9 Ma Manori trachyte and Gilbert Hill basalt intrusions in Mumbai and 60-61 Ma syenitic intrusions in the Seychelles. The Mumbai area thus preserves the pre-, syn- and post-rift onshore tectonomagmatic record of the breakup between the Seychelles and the Laxmi Ridge-India. Voluminous submarine volcanism forming the Raman, Panikkar and Wadia seamounts in the Laxmi Basin represents the offshore syn-rift magmatism.

  19. 40Ar/39Ar ages (600-570 Ma of the Serra do Azeite transtensional shear zone: evidence for syncontractional extension in the Cajati area, southern Ribeira belt

    Directory of Open Access Journals (Sweden)

    Rômulo Machado

    2007-12-01

    Full Text Available This paper presents 40Ar/39Ar ages of the rocks from the Serra do Azeite transtensional shear zone in the southern part of the Ribeira belt, between the States of São Paulo and Paraná, and also discusses the regional correlations and the tectonic implications for other parts of the belt. The geochronological data suggest that transtensional deformation was active between 600 and 580 Ma (hornblende and muscovite apparent ages, respectively. This time span is considerably older than previous proposals for the period of activity of these structures (520-480 Ma in the northern segment of this belt and in the Araçuaí belt. Kinematic analysis of the dated mylonites shows extensional structures with top-down movement to ESE compatible with structures found in other tectonic segments in the eastern portion of the Quadrilátero Ferrífero and in the Rio Doce Valley region. Our ages are situated in the same time interval defined for the alkaline magmatism of the Serra do Mar suite. We suggest that the regional tectonic framework was developed during continental-scale extension. This process has been coeval with convergent strain in the adjacent Neoproterozoic shear zones of the Apiaí/Ribeira and Araçuaí belts, which make up significant segments of these belts. The available data show that these structures may not be simply related to post-orogenic gravitational collapse, but must involve a more complex process probably related to dynamic balance between crustal thickening and thinning during tectonic convergence, basin formation and exhumation processes.Este trabalho apresenta idades 40Ar/39Ar de rochas da Zona de Cisalhamento Transtrativa Sinistral da Serra do Azeite, situada na parte sul do cinturão Ribeira, entre os Estados de São Paulo e Paraná, bem como discute a correlação regional e as implicações tectônicas com outras partes do cinturão. Os dados geocronológicos sugerem que a deformação extensional foi ativa entre 600 e 580 Ma

  20. Astronomical calibration of 40Ar/39Ar reference minerals using high-precision, multi-collector (ARGUSVI) mass spectrometry

    Science.gov (United States)

    Phillips, D.; Matchan, E. L.; Honda, M.; Kuiper, K. F.

    2017-01-01

    The new generation of multi-collector mass spectrometers (e.g. ARGUSVI) permit ultra-high precision (1%) in 40K decay constants and the ages of natural reference minerals that form the basis of the technique. For example, reported ages for widely used 40Ar/39Ar reference materials, such as the ca. 28 Ma Fish Canyon Tuff sanidine (FCTs) and the ca. 1.2 Ma Alder Creek Rhyolite sanidine (ACRs), vary by >1%. Recent attempts to independently calibrate these reference minerals have focused on K-Ar analyses of the same minerals and inter-comparisons with astronomically tuned tephras in sedimentary sequences and U-Pb zircon ages from volcanic rocks. Most of these studies used older generation (effectively single-collector) mass spectrometers that employed peak-jumping analytical methods to acquire 40Ar/39Ar data. In this study, we reassess the inter-calibration and ages of commonly used 40Ar/39Ar reference minerals Fish Canyon Tuff sanidine (FCTs), Alder Creek Rhyolite sanidine (ACRs) and Mount Dromedary biotite (MD2b; equivalent to GA-1550 biotite), relative to the astronomically tuned age of A1 Tephra sanidine (A1Ts), Faneromeni section, Crete (Rivera et al., 2011), using a multi-collector ARGUSVI mass spectrometer. These analyses confirm the exceptional precision capability (0.1% in the 40Ar/39Ar ages of reference minerals without consideration of recoil artefacts, thus limiting the benefits of high precision multi-collector analyses. Significant improvement to the accuracy of the 40Ar/39Ar method (<0.1%) will require further inter-laboratory 40Ar/39Ar studies utilizing multi-collector mass spectrometry, additional constraints on recoil 39ArK loss from reference minerals, further resolution of discrepancies between astronomically tuned sedimentary successions and refinement of the 238U/206Pb zircon age cross-calibration approach.

  1. Carpenter Ridge Tuff, CO

    Science.gov (United States)

    Bachmann, Olivier; Deering, Chad D.; Lipman, Peter W.; Plummer, Charles

    2014-06-01

    The ~1,000 km3 Carpenter Ridge Tuff (CRT), erupted at 27.55 Ma during the mid-tertiary ignimbrite flare-up in the western USA, is among the largest known strongly zoned ash-flow tuffs. It consists primarily of densely welded crystal-poor rhyolite with a pronounced, highly evolved chemical signature (high Rb/Sr, low Ba, Zr, Eu), but thickly ponded intracaldera CRT is capped by a more crystal-rich, less silicic facies. In the outflow ignimbrite, this upper zone is defined mainly by densely welded crystal-rich juvenile clasts of trachydacite composition, with higher Fe-Ti oxide temperatures, and is characterized by extremely high Ba (to 7,500 ppm), Zr, Sr, and positive Eu anomalies. Rare mafic clasts (51-53 wt% SiO2) with Ba contents to 4,000-5,000 ppm and positive Eu anomalies are also present. Much of the major and trace-element variations in the CRT juvenile clasts can be reproduced via in situ differentiation by interstitial melt extraction from a crystal-rich, upper-crustal mush zone, with the trachydacite, crystal-rich clasts representing the remobilized crystal cumulate left behind by the melt extraction process. Late recharge events, represented by the rare mafic clasts and high-Al amphiboles in some samples, mixed in with parts of the crystal cumulate and generated additional scatter in the whole-rock data. Recharge was important in thermally remobilizing the silicic crystal cumulate by partially melting the near-solidus phases, as supported by: (1) ubiquitous wormy/sieve textures and reverse zoning patterns in feldspars and biotites, (2) absence of quartz in this very silicic unit stored at depths of >4-5 km, and (3) heterogeneous melt compositions in the trachydacite fiamme and mafic clasts, particularly in Ba, indicating local enrichment of this element due mostly to sanidine and biotite melting. The injection of hot, juvenile magma into the upper-crustal cumulate also imparted the observed thermal gradient to the deposits and the mixing overprint that

  2. An Ediacaran–Cambrian thermal imprint in Rajasthan, western India: Evidence from 40Ar-39Ar geochronology of the Sindreth volcanics

    Indian Academy of Sciences (India)

    Archisman Sen; Kanchan Pande; Hetu C Sheth; Kamal Kant Sharma; Shraboni Sarkar; A M Dayal; Harish Mistry

    2013-12-01

    The Sindreth Group exposed near Sirohi in southern Rajasthan, western India, is a volcanosedimentary sequence. Zircons from Sindreth rhyolite lavas and tuffs have yielded U–Pb crystallization ages of ∼768–761 Ma, suggesting that the Sindreth Group is a part of the Malani magmatic event. Earlier 40Ar-39Ar studies of other Malani volcanic and plutonic rocks yielded disturbed argon release spectra, ascribed to a ∼550 Ma thermal event possibly related to the Pan-African orogeny. To test and confirm this possibility, we dated two whole-rock and three feldspar separate samples of the Sindreth volcanics by the 40Ar-39Ar method. All samples yield disturbed argon release spectra suggesting radiogenic argon loss and with plateau segments at 550 Ma or 490 Ma. We interpret these as events of argon loss at 550–490 Ma related to an Ediacaran–Cambrian thermal event, possibly related to the Malagasy orogeny. The combined older and new 40Ar-39Ar results are significant in showing that whereas Ediacaran–Cambrian magmatic and metamorphic events are well known from many parts of India, they left thermal imprints in much of Trans-Aravalli Rajasthan as well. The overall evidence is consistent with a model of multiphase assembly of Gondwanaland from separate continental landmasses.

  3. Rheomorphism of welded tuffs

    Science.gov (United States)

    Wolff, J. A.; Wright, J. V.

    1981-05-01

    Peralkaline welded tuffs from the islands of Gran Canaria, Canary Islands, and Pantelleria, Italy, show abundant evidence for post-depositional flow. It is demonstrated that rheomorphism, or secondary mass flowage, can occur in welded tuffs of ignimbrite and air-fall origin. The presence of a linear fabric is taken as the diagnostic criterion for the recognition of the process. Deposition on a slope is an essential condition for the development of rheomorphism after compaction and welding. Internal structures produced during rheomorphic flow can be studied by the methods of structural geology and show similar dispositions to comparable features in sedimentary slump sheets. It is shown that secondary flowage can occur in welded tuffs emplaced on gentle slopes, provided that the apparent viscosity of the magma is sufficiently low. Compositional factors favor the development of rheomorphism in densely welded tuffs of peralkaline type.

  4. Eruptive history and petrogenesis of the mid-Miocene McDermitt tuff, northern NV and southern OR

    Science.gov (United States)

    Starkel, W. A.; Henry, C. D.; Ellis, B. S.; Wolff, J. A.

    2010-12-01

    The mid-Miocene McDermitt caldera on the northern NV - southern OR border is commonly considered to mark initial silicic volcanism associated with the Yellowstone hotspot track, proposed by Pierce and Morgan (1992). It was initially interpreted to consist of five, partly overlapping calderas. Our new work substantially revises this picture to show that silicic magmatism began at ~16.5 Ma, after emplacement of Steens basalts likely erupted from vents to the north, but consisted of a mix of metaluminous and peralkaline rhyolite lavas, and that a single, 30 x 40 km caldera formed during eruption of a zoned rhyolite-dacite ignimbrite, the McDermitt tuff (MDT), at ~16.2 Ma. This tuff is spectacularly exposed along the west side of the caldera where Basin and Range faulting has revealed pre-caldera lavas overlain by a complete section of MDT and megabreccia, locally strongly rheomorphic and mega-rheomorphic (Hargrove and Sheridan, 1984), capped by post-collapse icelandite lava. The MDT varies from aphyric, high-SiO2, peralkaline rhyolite to abundantly porphyritic, metaluminous dacite. Detailed sections through the 600m - thick MDT have revealed significant variations in the lithologic characteristics of the tuff. These variations include 1) fiamme content (eutaxitic to fiamme-absent), 2) degree of rheomorphism, 3) phenocryst abundance and 4) lithic contents: lithic-rich tuff (clast sizes on mm- to cm-scale), single lithic mesobreccias (up to m-scale), and multi-lithic mega-breccia (up to 10’s of m-scale). Similar lithologic horizons within the MDT are found in different lateral and stratigraphic locations that cannot be easily correlated. These observations indicate that the MDT has a rather complex depositional history involving multiple eruptive events. High-precision single crystal 40Ar / 39Ar dates are all within analytical error (16.18 Ma +/- 0.03 Ma; n = 4), which indicates that all events probably occurred over much less than 100 ka. The interdigitation of

  5. 40Ar/(39)Ar dating of Chemeron Formation strata encompassing the site of hominid KNM-BC 1, Tugen Hills, Kenya.

    Science.gov (United States)

    Deino, Alan L; Hill, Andrew

    2002-01-01

    A fossil hominid temporal bone (KNM-BC 1) from surface exposures at Baringo Paleontological Research Project site BPRP#2 in the Chemeron Formation outcropping in a tributary drainage of the Kapthurin River west of Lake Baringo, Kenya has been attributed to Homo sp. indet. K-feldspar phenocrysts from lapilli tuffs bracketing the inferred fossiliferous horizon yield single-crystal(40)Ar/(39)Ar ages of 2.456+/-0.006 and 2.393+/-0.013 Ma. These age determinations are supported by stratigraphically consistent ages on higher tuff horizons and from nearby sections. In addition, new(40)Ar/(39)Ar ages on tuffaceous units near the base and top of the formation along the Kapthurin River yield 3.19+/-0.03 and 1.60+/-0.05 Ma respectively. The base of the formation along the Kapthurin River is thus approximately 0.5 Ma younger than the uppermost Chemeron Formation strata exposed at Tabarin, 23 km to the north-northwest. The upper half of the formation along the Kapthurin River was deposited at an average rate of approximately 11 cm/ka, compared to 21-23 cm/ka at Tabarin.

  6. Geochemical correlation and 40Ar/39Ar dating of the Kern River ash bed and related tephra layers: Implications for the stratigraphy of petroleum-bearing formations in the San Joaquin Valley, California

    Science.gov (United States)

    Baron, D.; Negrini, R.M.; Golob, E.M.; Miller, D.; Sarna-Wojcicki, A.; Fleck, R.J.; Hacker, B.; Erendi, A.

    2008-01-01

    The Kern River ash (KRA) bed is a prominent tephra layer separating the K and G sands in the upper part of the Kern River Formation, a major petroleum-bearing formation in the southern San Joaquin Valley (SSJV) of California. The minimum age of the Kern River Formation was based on the tentative major-element correlation with the Bishop Tuff, a 0.759??0.002 Ma volcanic tephra layer erupted from the Long Valley Caldera. We report a 6.12??0.05 Ma 40Ar/39Ar date for the KRA, updated major-element correlations, trace-element correlations of the KRA and geochemically similar tephra, and a 6.0??0.2 Ma 40Ar/39Ar age for a tephra layer from the Volcano Hills/Silver Peak eruptive center in Nevada. Both major and trace-element correlations show that despite the similarity to the Bishop Tuff, the KRA correlates most closely with tephra from the Volcano Hills/Silver Peak eruptive center. This geochemical correlation is supported by the radiometric dates which are consistent with a correlation of the KRA to the Volcano Hills/Silver Peak center but not to the Bishop Tuff. The 6.12??0.05 Ma age for the KRA and the 6.0??0.2 Ma age for the tephra layer from the Volcano Hills/Silver Peak eruptive center suggest that the upper age of the Kern River Formation is over 5 Ma older than previously thought. Re-interpreted stratigraphy of the SSJV based on the new, significantly older age for the Kern River Formation opens up new opportunities for petroleum exploration in the SSJV and places better constraints on the tectonostratigraphic development of the SSJV. ?? 2007 Elsevier Ltd and INQUA.

  7. Correlation of the Miocene Peach Spring Tuff with the geomagnetic polarity time scale and new constraints on tectonic rotations in the Mojave Desert, California

    Science.gov (United States)

    Hillhouse, John W.; Miller, David M.; Turrin, Brent D.; Reynolds, Robert E.; Miller, David M.

    2010-01-01

    We report new paleomagnetic results and 40Ar/39Ar ages from the Peach Spring Tuff (PST), a key marker bed that occurs in the desert region between Barstow, California, and Peach Springs, Arizona. The 40Ar/39Ar ages were determined using individual hand-picked sanidine crystals from ash-flow specimens used in previous paleomagnetic studies at eight sites correlated by mineralogy, stratigraphic position, and magnetic inclination. Site-mean ages, which range from 18.43 Ma to 18.78 Ma with analytical precision (1 s.d.) typically 0.04 Ma, were obtained from areas near Fort Rock, AZ; McCullough Mts, NV; Cima Dome, Parker Dam, Danby, Ludlow, Kane Walsh, and Stoddard Wash, CA. The regional mean age determination is 18.71 ± 0.13 Ma, after the data were selected for sanidine crystals that yielded greater than 90% radiogenic argon (N=40). This age determination is compatible with previous 40Ar/39Ar dating of the PST after taking various neutron-flux monitor calibrations into account. We report paleomagnetic results from eight new sites that bear on reconstructions of the Miocene basins associated with the Hector Formation, Barstow Formation, and similar fine-grained sedimentary deposits in the Barstow region. Key findings of the new paleomagnetic study pertain to age control of the Hector Formation and clockwise rotation of the Northeast Mojave Domain. Our study of a rhyolitic ash flow at Baxter Wash, northern Cady Mountains, confirms the correlation of the PST within the Hector Formation and prompts reinterpretation of the previously determined magnetostratigraphy. Our model correlates the PST to the normal-polarity zone just below the C6-C5E boundary (18.748 Ma) of the astronomically tuned Geomagnetic Polarity Time Scale. After emplacement of the Peach Spring Tuff at Alvord Mountain and the Cady Mountains, the southern part of the Northeast Mojave Domain (between Cady and Coyote Lake faults) underwent clockwise rotation of 30°–55°. Clockwise rotations increase with

  8. High northern geomagnetic field behavior and new constraints on the Gilsá event: Paleomagnetic and 40Ar/39Ar results of ∼0.5-3.1 Ma basalts from Jökuldalur, Iceland

    Science.gov (United States)

    Døssing, Arne; Muxworthy, Adrian R.; Supakulopas, Radchagrit; Riishuus, Morten S.; Mac Niocaill, Conall

    2016-12-01

    an investigation of the type sections of the so-called Gilsá normal polarity event around 1.62 Ma. Our revised model is based on 11 new 40Ar/39Ar ages. No evidence is found of the existence of the Gilsá event in Jökuldalur. Instead we find that the normal polarity intervals in the type sections can both be correlated to Olduvai subchron.

  9. Magnetic, structural and geochronologic evidence bearing on volcanic sources and Oligocene Deformation of Ash Flow Tuffs, northeast Nevada

    Science.gov (United States)

    Palmer, H. C.; MacDonald, W. D.; Hayatsu, A.

    1991-02-01

    Magnetic properties of mid-Tertiary volcanic rocks west of Jiggs in northeast Nevada were investigated for the purposes of interpreting igneous, structural, and tectonic processes in this part of the Basin and Range province. Anisotropy of magnetic susceptibility (AMS) patterns reflect flow fabrics and suggest previously unknown sources for these ash flow tuffs. Paleomagnetic and structural evidence suggest counterclockwise relative rotation of the southern part of the area with respect to the north. New stratigraphic, chemical and K-Ar isotopic data support these interpretations. Dacite to rhyolite ash flow tuffs of the Indian Well Formation were subdivided into two main units: the lower and predominant tuff of Jiggs (35.8-37.0 Ma) and the unconformably overlying but areally restricted tuff of Hackwood (30.8 Ma). The Jiggs unit has two polarities whereas the Hackwood has only a reversed polarity remanence. Together these units with tilt correction define a pole (92°E, 87°N, dp = 6°, dm = 8°) for approximately 30-37 Ma. This pole is concordant with coeval North American reference poles, indicating that this zone of approximately 30 km NS extent has not undergone significant vertical axis rotation relative to the North American reference. Andesite lavas of normal magnetic polarity and of 32.5-Ma age characterize the Diamond Hills immediately to the south. We interpret this region, from both structural evidence and discordant paleomagnetic direction, to have rotated approximately 25° counterclockwise relative to the Indian Well volcanic units to the north. The apparent rotation of the Diamond Hills is possibly the result of drag on the left-lateral Garcia fault which limits the Diamond Hills on the southwest. Analysis of AMS data suggests, by patterns of the K1 axes, two distinct sources for the Jiggs unit: a northern buried source and a central partially buried source. Lithologic evidence consistent with proximal vent facies is found near the latter source. An

  10. The Fish Canyon Tuff: A new look at an old low-temperature thermochronology standard

    Science.gov (United States)

    Gleadow, Andrew; Harrison, Mark; Kohn, Barry; Lugo-Zazueta, Rául; Phillips, David

    2015-08-01

    The Fish Canyon Tuff (FCT) has served as an important source for geochronology standards, particularly for fission track, K-Ar and (40Ar/39Ar) dating, even though efforts to establish precise ages for its constituent minerals have proved to be unexpectedly complex. To evaluate the suitability of FCT apatite as a standard for apatite (U-Th-Sm)/He (AHe) thermochronometry, and to test underlying assumptions about its suitability for apatite fission track (AFT) thermochronometry, we analysed samples from a series of sites throughout the vertical and lateral extent of the host ignimbrite sheet. Samples were collected from the relatively lithic-rich, classic sampling location in the lower part of the thick proximal ignimbrite and a ∼ 330 m vertical section of FCT immediately above it. Average weighted mean AHe ages from multiple analyses at five sites in this profile range from 20.8 ± 0.4 Ma from the classic site at the base, to an average of 28.4 ± 0.2 Ma (all ± 1 σ) in the upper part of the section. The AHe age at the classic site is substantially reduced at 20.8 ± 0.4 Ma relative to a reference age for ignimbrite emplacement of 28.2 Ma. Corresponding zircon (U-Th)/He (ZHe) ages for these samples are all concordant at 28.3 ± 0.4 Ma. By contrast, apatite fission track (AFT) ages from the same vertical section are all concordant at 27.4 ± 0.7 Ma with the central age of 28.8 ± 0.8 Ma at the classic site, except for the uppermost sample (23.2 ± 1.7 Ma) for which clear evidence for local, probably fire, disturbance is seen in the track length distribution. The AHe data at the classic site thus provide evidence for substantial post-eruptive Early Miocene cooling of the tuff consistent with its position at the bottom of a deeply incised valley with ∼ 800 m of local relief and probably > 1000 m of removed section above it. The AFT age of the classic sampling site, however, is indistinguishable from ignimbrite emplacement and thus continues to be a useful standard

  11. High-precision 40Ar/39Ar age for the Jehol Biota

    Science.gov (United States)

    Chang, S.; Zhang, H.; Renne, P. R.; Fang, Y.

    2008-12-01

    Abundant fossils of the terrestrial Jehol Biota, including plants, insects, dinosaurs, birds, mammals and freshwater invertebrates, were discovered from the Yixian Formation and the overlying Jiufotang Formation in Inner Mongolia, Hebei Province and Liaoning Province, northeastern China. Because of the exceptional preservation of fossils, the Jehol Biota is one of the most important Mesozoic fossil outcrops and referred to as a "Mesozoic Pompeii". The Jehol Biota has provided a rare opportunity to address questions about the origin of birds, the evolution of feathers and flight, the early diversification of angiosperms and the timing of the radiation of placental mammals. The Tuchengzi Formation, which lies unconformably just below the Yixian Formation and consists mainly of variegated sandstones, is less fossiliferous than the two overlying formations. However, dinosaur tracks, silicified wood and compressed plants are found in this formation. A systematic 40Ar/39Ar dating of the Yixian and the Jiufotang formations was undertaken to provide a framework for understanding the timing and duration of the Jehol Biota and evolutionary events represented within it. Furthermore, determining the absolute age of the Tuchengzi Formation provides information to interpret abundant dinosaur tracks within and provide better age constrains for the beginning of the Jehol Biota. Here we present robust high-precision 40Ar/39Ar data for six tuff samples and two basalt samples collected from the Tuchengzi, the Yixian and the Jiufotang formations near the classic outcrops in western Liaoning, NE China. We obtain an age of 139.5 ± 1.0 Ma for the uppermost Tuchengzi Formation, an age of 129.7 ± 0.5 Ma for a basaltic lava from the bottom of the Yixian Formation and an age of 122.1 ± 0.3 Ma for a tuff from the base of the overlying Jiufotang Formation. Our data indicate that the Yixian Formation was deposited during the Early Cretaceous, the Barremian to early Aptian, within a time span

  12. Melt-inclusion-hosted excess 40Ar in quartz crystals of the Bishop and Bandelier magma systems

    Science.gov (United States)

    Winick, J.A.; McIntosh, W.C.; Dunbar, N.W.

    2001-01-01

    40Ar/39Ar experiments on melt-inclusion-bearing quartz (MIBQ) from the Bishop and Bandelier Tuff Plinian deposits indicate high concentrations of excess 40Ar in melt inclusions. Two rhyolite glass melt inclusion populations are present in quartz; exposed melt inclusions and trapped melt inclusions. Air-abrasion mill grinding and hydrofluoric acid treatments progressively remove exposed melt inclusions while leaving trapped melt inclusions unaffected. Laser step-heating of MIBQ yields increasing apparent ages as a function of exposed melt inclusion removal, reflecting the higher nonatmospheric 40Ar concentrations hosted in trapped melt inclusions. Exposed melt inclusion-free MIBQ from the Bishop, Upper Bandelier, and Lower Bandelier Tufts yield total-gas ages of 3.70 ?? 1.00 Ma, 11.54 ?? 0.87 Ma, and 14.60 ?? 1.50 Ma, respectively. We interpret these old apparent ages as compelling evidence for the presence of excess 40Ar in MIBQ. Trapped melt inclusions in sanidine phenocrysts may contain excess 40Ar concentrations similar to those in MIBQ. This excess 40Ar has the potential to increase single-crystal laser-fusion ages of sanidine by tens of thousands of years, relative to the actual eruption age.

  13. Geohydrology of Bandelier Tuff

    Energy Technology Data Exchange (ETDEWEB)

    Abeele, M.V.; Wheeler, M.L.; Burton, B.W.

    1981-10-01

    The Los Alamos National Laboratory has been disposing of radioactive wastes since 1944. Environmental studies and monitoring for radioactive contamination started concurrently. In this report, only two mechanisms and rates by which the radionuclides can enter the environment are studied in detail: subsurface transport of radionuclides by migrating water, and diffusion of tritiated water (HTO) in the vapor phase. The report also includes a section concerning the influence of moisture on shear strength and possible resulting subsidences occurring in the pit overburdens. Because subsurface transport of radionuclides is influenced by the hydraulic conductivity and this in turn is regulated by the moisture content of any given material, a study was also undertaken involving precipitation, the most important climatic element influencing the geohydrology of any given area. Further work is in progress to correlate HTO emanation to atmospheric and pedological properties, especially including thermal characteristics of the tuff.

  14. Qualidade de maçãs ‘Gala’ armazenadas em atmosfera controlada dinâmica e estática com renovação do ar

    OpenAIRE

    2005-01-01

    Este experimento teve como objetivo avaliar o efeito da remoção periódica da atmosfera das câmaras de atmosfera controlada com ar e nova instalação, bem como o uso da atmosfera dinâmica, sobre a manutenção da qualidade da maçã 'Gala'. Os tratamentos utilizados foram: (1) controle (sem renovação); (2) renovação da atmosfera diariamente durante o resfriamento dos frutos; (3) renovação da atmosfera diariamente durante o resfriamento e mensalmente no período de armazenamento em atmosfera controla...

  15. New K-Ar ages from La Montagne massif, Réunion Island (Indian Ocean), supporting two geomagnetic events in the time period 2.2-2.0 Ma

    Science.gov (United States)

    Quidelleur, X.; Holt, J. W.; Salvany, T.; Bouquerel, H.

    2010-08-01

    We present new radiometric ages obtained at the type locality in La Réunion Island where palaeomagnetic records of the Réunion events have first been identified. Seven dated lava flows from the Rivière Saint Denis section, which recorded a reverse-to-normal transition, display ages from 2.12 +/- 0.03 to 2.17 +/- 0.03 Ma, with a mean age of 2.15 +/- 0.02 Ma. Two significantly younger flows from this section, interpreted here as valley fill flows from trace elements compositions and Pb isotopic data, have been dated at 2.06 +/- 0.03 and 2.08 +/- 0.03 Ma. Within the Grande Chaloupe section, where a normal-to-reverse transition is recorded, two coherent ages of 2.05 +/- 0.03 and 2.03 +/- 0.03 Ma have been obtained. When a direct comparison was possible, our new K-Ar ages performed on separated groundmass show a rather good coherence with previous ages from La Réunion Island. When considered with continuous palaeomagnetic sedimentary records in the 2.2-2.0 Ma interval, these new results suggest that two distinct events are recorded in La Montagne lava flows at La Réunion Island, with ages of 2.15 +/- 0.02 and 2.04 +/- 0.02 Ma. Following recent nomenclature, the former is the Réunion event s.s., while the latter can be related to the Huckleberry Ridge event. Globally distributed volcanic and sedimentary records show that the first (Réunion s.s.; RU-1) is associated with a large dipole intensity decrease at 2.15 +/- 0.02 Ma, and hence is recorded in many sequences. On the other hand, the dipole intensity decrease was not as pronounced at 2.04 +/- 0.02 Ma, when the Huckleberry Ridge (RU-2) palaeomagnetic event occurred. Consequently, it is not present as a full directional change in many sections worldwide, but rather appears as a geomagnetic excursion during an episode of increased secular variation. Finally, the use of the Réunion event for magnetostratigraphic studies is recommended, while the clear identification of the Huckleberry Ridge excursion might often

  16. An astronomical age for the Bishop Tuff and concordance with radioisotopic dates

    DEFF Research Database (Denmark)

    Rivera, Tiffany; Zeeden, Christian; Storey, Michael

    2014-01-01

    The Bishop Tuff forms a key stratigraphic horizon for synchronization of Quaternary sedimentary records in North America. The unit stratigraphically overlies the Matuyama-Brunhes geomagnetic polarity reversal by several thousand years; high-precision dating of this tuff may be valuable for regional...... and global correlation of records. The Quaternary time scale is anchored by 40Ar/39Ar ages on lava flows and ash layers where available, with stage boundaries and geomagnetic reversals including astronomically tuned records. However, astronomical dating has not yet validated the high-precision 238U/206Pb...... ages, including new single crystal 40Ar/39Ar sanidine fusion analyses presented here, which demonstrates that concordance through multiple dating techniques is achievable within the Quaternary...

  17. 40Ar/39Ar geochronology and geochemical reconnaissance of the Eocene Lowland Creek volcanic field, west-central Montana

    Science.gov (United States)

    Dudas, F.O.; Ispolatov, V.O.; Harlan, S.S.; Snee, L.W.

    2010-01-01

    We report geochronological and geochemical data for the calc-alkalic Lowland Creek volcanic field (LCVF) in westcentral Montana. 40Ar/ 39Ar age determinations show that the LCVF was active from 52.9 to 48.6 Ma, with tuff-forming eruptions at 52.9 ?? 0.14 and 51.8 ?? 0.14 Ma. These dates span the age range of vigorous Eocene igneous activity in the Kamloops-Absaroka-Challis belt. The LCVF evolved upward from basal rhyolites (SiO 2>71 wt%) to dacites and andesites (SiO 2 > 62 wt%). Compositional change parallels a transition from early explosive volcanism to late effusive activity. Four geochemical components can be detected in the rocks. A component with 206Pb/204Pb nd epsilon;Nd near-15 is predominant in anhydrous, two-pyroxene dacites; hydrous rhyolites, rhyodacites, and dacites with epsilon;Nd below-10 are dominated by a second component; hydrous rocks with 206Pb/ 204Pb > 18.3 and epsilon;Nd>-9 contain a third component; and an andesite with low Nd content and epsilon;Nd near-9 probably contains a fourth component. The first three components probably derive from the lower and middle crust, whereas the fourth is probably from the lithospheric mantle. ?? 2010 by The University of Chicago.

  18. Reconnaissance geochronology of tuffs in the Miocene Barstow Formation: implications for basin evolution and tectonics in the central Mojave Desert

    Science.gov (United States)

    Miller, D.M.; Leslie, S.R.; Hillhouse, J.W.; Wooden, J.L.; Vazquez, J.A.; Reynolds, R.E.

    2010-01-01

    Early to middle Miocene lacustrine strata of the Barstow Formation are well dated in just a few places, limiting our ability to infer basin evolution and regional tectonics. At the type section in the Mud Hills, previous studies have shown that the lacustrine interval of the Barstow Formation is between ~16.3 Ma and ~13.4 Ma. Elsewhere, lake beds of the Barstow Formation have yielded vertebrate fossils showing the Hemingfordian/Bartovian transition at ~16 Ma but are otherwise poorly dated. In an attempt to clarify the age and depositional environments of the lake deposits, we are mapping the Barstow Formation and dating zircons from interbedded tuffs, as well as testing ash-flow tuffs for the distinctive remanent magnetization direction of the widespread Peach Spring Tuff. Thus far, our new U-Pb zircon ages inficate that the Barstow lake beds contain tuff beds as old as 19.1 Ma and as young as 15.3 Ma. At Harvard Hill, Barstow lake beds contain a thick tuff dated at 18.7 Ma. On the basis of zircon ages, mineralogy, zircon chemistry, and paleomagnetic results, we consider the thick tuff to be a lacustrine facies of the Peach Spring Tuff. We have identified the Peach Spring Tuff by similar methods at eight localities over a broad area, providing a timeline for several fluvial and lacustrine sections. The new dates indicate that long-lived lacustrine systems originated before 19 Ma and persisted to at least 15 Ma. The onset of lacustrine conditions predates the Peach Spring Tuff in most Barstow Formation sections and may be older than 19.5 Ma in some places. The new data indicate that the central Mojave Desert contained narrow to broad lake basins during and after extension, and that Barstow lacustrine deposits did not exclusively postdate extensional tectonics. At present, it is unclear whether several separate, small lake basins coexisted during the early to middle Miocene, or if instead several small early Miocene basins gradually coalesced over about 6 millions

  19. Batman’da Yeni Bir Keşif: Deraser (Arık Mağara Resimleri A New Discovery In Batman Province: Prehistoric Cave Paintings Of Deraser (Arik

    Directory of Open Access Journals (Sweden)

    Ersoy SOYDAN

    2013-07-01

    kurulmuştur.Tarihi yerleşim birimlerinden biri de bugün Batman ilinin Gercüşilçesine bağlı Deraser (Arık mezrasıdır. Burada çok sayıda tarihi kalıntıbulunmaktadır. Gercüş ilçesine yaklaşık 20 kilometre uzaklıktabulunan ve Dicle nehrine hakim bir noktada kurulan Deraser (Arıkmezrasında çeşitli yapı kalıntıları, kayalara oyulmuş mezarlar vemağara duvarlarına çizilmiş tarihöncesi olduğu tahmin edilen resimlerbulunmaktadır. Anadolu’da kayalara çizilmiş tarihöncesi resimlerebirçok yerde rastlanmaktadır ancak kırmızı ve siyah boyayla freskotekniğiyle yapılmış resimler nadir olarak görülmektedir. Bu nedenleDeraser’deki (Arık Berha Nivisandi (Yazılı Mağara olarak adlandırılantoprak ya da kök boyayla yapılmış kırmızı ve siyah renkli resimlerinbulunması önemli bir gelişmedir. Buradaki mağara resimlerindegenellikle evcil hayvan tasvirleri, vahşi hayvan mücadeleleri ve kadınlıerkeklişenlik sahneleri bulunmaktadır. Dünyanın pek çok yerindebulunan tarihöncesi mağara resimleri ile tematik olarak benzeşmeklebirlikte çizim tekniği bakımından özgün bir biçime sahiptir.Çalışmamızda daha önce bölgede çalışan araştırmacılar tarafındançeşitli nedenlerle farkına varılamayan Deraser (Arık mağaralardanderlenmiş resimlere ve bu resimlerle ilgili olarak yapılan araştırmasonuçlarına yer verilecektir.

  20. Magnetic links among lava flows, tuffs and the underground plumbing system in a monogenetic volcano, derived from magnetics and paleomagnetic studies

    Science.gov (United States)

    Urrutia-Fucugauchi, Jaime; Trigo-Huesca, Alfonso; Pérez-Cruz, Ligia

    2012-12-01

    A combined study using magnetics and paleomagnetism of the Toluquilla monogenetic volcano and associated lavas and tuffs from Valsequillo basin in Central Mexico provides evidence on a 'magnetic' link between the lavas, ash tuffs and the underground volcanic conduit system. Paleomagnetic analyses show that the lava and ash tuff carry reverse polarity magnetizations, which correlate with the inversely polarized dipolar magnetic anomaly over the volcano. The magnetizations in the lava and tuff show similar southward declinations and upward inclinations, supporting petrological inferences that the tuff was emplaced while still hot and indicating a temporal correlation for lava and tuff emplacement. Modeling of the dipolar anomaly gives a reverse polarity source magnetization associated with a vertical prismatic body with southward declination and upward inclination, which correlates with the reverse polarity magnetizations in the lava and tuff. The study documents a direct correlation of the paleomagnetic records with the underground magmatic conduit system of the monogenetic volcano. Time scale for cooling of the volcanic plumbing system involves a longer period than the one for the tuff and lava, suggesting that magnetization for the source of dipolar anomaly may represent a long time average as compared to the spot readings in the lava and tuff. The reverse polarity magnetizations in lava and tuff and in the underground source body for the magnetic anomaly are interpreted in terms of eruptive activity of Toluquilla volcano at about 1.3 Ma during the Matuyama reverse polarity C1r.2r chron.

  1. Effect of moisture on tuff stone degradation

    NARCIS (Netherlands)

    Lubelli, B.A.; Nijland, T.G.

    2016-01-01

    Tuff stone elements with a large length/width ratio often suffer damage in the form of cracks parallel to the surface and spalling of the outer layer. The response of tuff to moisture might be a reason for this behaviour. This research aimed at verifying if differential dilation between parts with d

  2. Evolution Of An Upper Crustal Plutonic-Volcanic Plumbing System:Insights From High Precision U-Pb Zircon Geochronology Of Intracaldera Tuff And Intrusions In Silver Creek Caldera, Arizona, USA

    Science.gov (United States)

    Zhang, T.; Mundil, R.; Miller, C. F.; Miller, J. S.; Paterson, S. R.

    2010-12-01

    Study of both plutonic and volcanic regimes in one single magmatic system is a powerful approach towards obtaining a more complete view of the long-term evolution of magma systems. The recently discovered Silver Creek caldera is the source of the voluminous Peach Spring Tuff (PST) (Ferguson, 2008) and presents a unique opportunity to study a field laboratory of a linked plutonic-volcanic system. This relict west-facing half caldera is predominantly filled with trachytic intracaldera tuff with the caldera margin intruded by several petrologically distinct hypabyssal intrusions. These include porphyritic granite with granophyric texture, felsic leucogranite, porphyritic monzonite exposed on NE side of the caldera that is zoned from more felsic to more mafic, and quartz-phyric dikes that intrude the caldera fill. We present preliminary single zircon ages from 4 samples that have been analyzed using the CA-TIMS method after thermal annealing and chemical leaching (Mattinson 2005), including 1 sample from intracaldera tuff and 3 samples from caldera-related intrusions. 3-D total U/Pb isochron ages from all four samples fall within a range of 18.32-18.90 Ma with uncertainties between 0.09 and 0.39 Ma, although some of them lack precision and are compromised by elevated common Pb. For example, zircon from the dated porphyritic monzonite yields an age of 18.32±0.42 Ma (MSWD=2.7) where the excess scatter may result from real age dispersion and/or different compositions of the common Pb contribution. The PST had been dated to ~18.5 Ma by 40Ar/39Ar techniques (Nielson et al., 1990). In order to be compared to U/Pb ages the 40Ar/39Ar age must be adjusted for a revised age for the then used flux monitor (MMbh-1) and corrected for the now quantified systematic bias between 40Ar/39Ar and U/Pb ages (Renne et al., 2010), which results in a corrected age of 18.8 Ma. Thus, the ages for our samples match that of the PST within error. Based on current results, the age difference

  3. Feldspar dissolution rates in the Topopah Spring Tuff, Yucca Mountain, Nevada

    Science.gov (United States)

    Bryan, C.R.; Helean, K.B.; Marshall, B.D.; Brady, P.V.

    2009-01-01

    Two different field-based methods are used here to calculate feldspar dissolution rates in the Topopah Spring Tuff, the host rock for the proposed nuclear waste repository at Yucca Mountain, Nevada. The center of the tuff is a high silica rhyolite, consisting largely of alkali feldspar (???60 wt%) and quartz polymorphs (???35 wt%) that formed by devitrification of rhyolitic glass as the tuff cooled. First, the abundance of secondary aluminosilicates is used to estimate the cumulative amount of feldspar dissolution over the history of the tuff, and an ambient dissolution rate is calculated by using the estimated thermal history. Second, the feldspar dissolution rate is calculated by using measured Sr isotope compositions for the pore water and rock. Pore waters display systematic changes in Sr isotopic composition with depth that are caused by feldspar dissolution. The range in dissolution rates determined from secondary mineral abundances varies from 10-16 to 10-17 mol s-1 kg tuff-1 with the largest uncertainty being the effect of the early thermal history of the tuff. Dissolution rates based on pore water Sr isotopic data were calculated by treating percolation flux parametrically, and vary from 10-15 to 10-16 mol s-1 kg tuff-1 for percolation fluxes of 15 mm a-1 and 1 mm a-1, respectively. Reconciling the rates from the two methods requires that percolation fluxes at the sampled locations be a few mm a-1 or less. The calculated feldspar dissolution rates are low relative to other measured field-based feldspar dissolution rates, possibly due to the age (12.8 Ma) of the unsaturated system at Yucca Mountain; because oxidizing and organic-poor conditions limit biological activity; and/or because elevated silica concentrations in the pore waters (???50 mg L-1) may inhibit feldspar dissolution. ?? 2009 Elsevier Ltd. All rights reserved.

  4. Preliminary thermal expansion screening data for tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Lappin, A.R.

    1980-03-01

    A major variable in evaluating the potential of silicic tuffs for use in geologic disposal of heat-producing nuclear wastes is thermal expansion. Results of ambient-pressure linear expansion measurements on a group of tuffs that vary treatly in porosity and mineralogy are presente here. Thermal expansion of devitrified welded tuffs is generally linear with increasing temperature and independent of both porosity and heating rate. Mineralogic factors affecting behavior of these tuffs are limited to the presence or absence of cristobalite and altered biotite. The presence of cristobalite results in markedly nonlinear expansion above 200{sup 0}C. If biotite in biotite-hearing rocks alters even slightly to expandable clays, the behavior of these tuffs near the boiling point of water can be dominated by contraction of the expandable phase. Expansion of both high- and low-porosity tuffs containing hydrated silicic glass and/or expandable clays is complex. The behavior of these rocks appears to be completely dominated by dehydration of hydrous phases and, hence, should be critically dependent on fluid pressure. Valid extrapolation of the ambient-pressure results presented here to depths of interest for construction of a nuclear-waste repository will depend on a good understanding of the interaction of dehydration rates and fluid pressures, and of the effects of both micro- and macrofractures on the response of tuff masss.

  5. 2.8-Ma ash-flow caldera at Chegem River in the northern Caucasus Mountains (Russia), contemporaneous granites, and associated ore deposits

    Science.gov (United States)

    Lipman, P.W.; Bogatikov, O.A.; Tsvetkov, A.A.; Gazis, C.; Gurbanov, A.G.; Hon, K.; Koronovsky, N.V.; Kovalenko, V.I.; Marchev, P.

    1993-01-01

    Diverse latest Pliocene volcanic and plutonic rocks in the north-central Caucasus Mountains of southern Russia are newly interpreted as components of a large caldera system that erupted a compositionally zoned rhyolite-dacite ash-flow sheet at 2.83 ?? 0.02 Ma (sanidine and biotite 40Ar/39Ar). Despite its location within a cratonic collision zone, the Chegem system is structurally and petrologically similar to typical calderas of continental-margin volcanic arcs. Erosional remnants of the outflow Chegem Tuff sheet extend at least 50 km north from the source caldera in the upper Chegem River. These outflow remnants were previously interpreted by others as erupted from several local vents, but petrologic similarities indicate a common origin and correlation with thick intracaldera Chegem Tuff. The 11 ?? 15 km caldera and associated intrusions are superbly exposed over a vertical range of 2,300 m in deep canyons above treeline (elev. to 3,800 m). Densely welded intracaldera Chegem Tuff, previously described by others as a rhyolite lava plateau, forms a single cooling unit, is > 2 km thick, and contains large slide blocks from the caldera walls. Caldera subsidence was accommodated along several concentric ring fractures. No prevolcanic floor is exposed within the central core of the caldera. The caldera-filling tuff is overlain by andesitic lavas and cut by a 2.84 ?? 0.03-Ma porphyritic granodiorite intrusion that has a cooling age analytically indistinguishable from that of the tuffs. The Eldjurta Granite, a pluton exposed low in the next large canyon (Baksan River) 10 km to the northwest of the caldera, yields variable K-feldspar and biotite ages (2.8 to 1.0 Ma) through a 5-km vertical range in surface and drill-hole samples. These variable dates appear to record a prolonged complex cooling history within upper parts of another caldera-related pluton. Major W-Mo ore deposits at the Tirniauz mine are hosted in skarns and hornfels along the roof of the Eldjurta Granite

  6. Ars disyecta Ars disyecta

    Directory of Open Access Journals (Sweden)

    Alejandra Castillo

    2012-07-01

    Full Text Available Bajo la nominación Ars Disyecta se busca exponer el vínculo entre artes visuales, feminismo y metamorfosis. Las prácticas artísticas feministas aquí presentadas se proponen perturbar el espacio metafórico heredado de la diferencia sexual (pensemos, por ejemplo, en las palabras engendramiento, matriz, vida, compenetración o invaginamiento. En este sentido, la nominación Ars disyecta pone en escena un conjunto de prácticas e intervenciones que intentan interrumpir la matriz de la diferencia, desestabilizando lo femenino desde aquellas figuras que se resisten a la lógica de la totalidad y de un tiempo propio. Buscando seguir la huella de un arte disyecto es que interrogaré en este ensayo aquellas autorías feministas que en el arte contemporáneo trafican con las huellas del contagio, la mutación y la alteridad.This article aims to present the relation between visual arts, feminism I and metamorphosis. The feminist artistic practices portrayed in this article attempt to question categories inherited from the metaphor of sexual difference such as engendering, matrix and life. From this perspective, Ars disyecta will establish a set of artistic practices and interventions that intend to interrupt the proper idea of «feminine difference». Following this line of argument, I will discuss in this article a few contemporary feminist works of art that could be defined by words such as contagious, mutation and otherness.

  7. Mechanical excavator performance in Yucca Mountain tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Ozdemir, L. [Colorado School of Mines, Golden, CO (USA); Hansen, F.D. [Sandia National Labs., Albuquerque, NM (USA)

    1991-01-01

    A research effort of four phases is in progress at the Colorado School of Mines. The overall program will evaluate the cutability of welded tuff and other lithologies likely to be excavated at Yucca Mountain in the site characterization process. Several mechanical systems are considered with emphasis given to the tunnel boring machine. The research comprises laboratory testing, linear drag bit and disc cutter tests and potentially large-scale laboratory demonstrations to support potential use of a tunnel boring machine in welded tuff. Preliminary estimates of mechanical excavator performance in Yucca Mountain tuff are presented here. As phases of the research project are completed, well quantified estimates will be made of performance of mechanical excavators in the Yucca Mountain tuffs. 3 refs., 2 tabs.

  8. Development of waste packages for tuff

    Energy Technology Data Exchange (ETDEWEB)

    Rothman, A.J.

    1982-09-20

    The objective of this program is to develop nuclear waste packages that meet the Nuclear Regulatory Commission`s requirements for a licensed repository in tuff at the Nevada Test Site. Selected accomplishments for FY82 are: (1) Selection, collection of rock, and characterization of suitable outcrops (for lab experiments); (2) Rock-water interactions (Bullfrog Tuff); (3) Corrosion tests of ferrous metals; (4) Thermal modeling of waste package in host rock; (5) Preliminary fabrication tests of alternate backfills (crushed tuff); (6) Reviewed Westinghouse conceptual waste package designs for tuff and began modification for unsaturated zone; and (7) Waste Package Codes (BARIER and WAPPA) now running on our computer. Brief discussions are presented for rock-water interactions, corrosion tests of ferrous metals, and thermal and radionuclide migration modelling.

  9. Regional patterns of Mesozoic-Cenozoic magmatism in western Alaska revealed by new U-Pb and 40Ar/39Ar ages: Chapter D in Studies by the U.S. Geological Survey in Alaska, vol. 15

    Science.gov (United States)

    Bradley, Dwight C.; Miller, Marti L.; Friedman, Richard M.; Layer, Paul W.; Bleick, Heather A.; Jones, III, James V.; Box, Steven E.; Karl, Susan M.; Shew, Nora B.; White, Timothy S.; Till, Alison B.; Dumoulin, Julie A.; Bundtzen, Thomas K.; O'Sullivan, Paul B.; Ullrich, Thomas D.

    2017-03-02

    In support of regional geologic framework studies, we obtained 50 new argon-40/argon-39 (40Ar/39Ar) ages and 33 new uranium-lead (U-Pb) ages from igneous rocks of southwestern Alaska. Most of the samples are from the Sleetmute and Taylor Mountains quadrangles; smaller collections or individual samples are from the Bethel, Candle, Dillingham, Goodnews Bay, Holy Cross, Iditarod, Kantishna River, Lake Clark, Lime Hills, McGrath, Medfra, Talkeetna, and Tanana quadrangles.A U-Pb zircon age of 317.7±0.6 million years (Ma) reveals the presence of Pennsylvanian intermediate igneous (probably volcanic) rocks in the Tikchik terrane, Bethel quadrangle. A U-Pb zircon age of 229.5±0.2 Ma from gabbro intruding the Rampart Group of the Angayucham-Tozitna terrane, Tanana quadrangle, confirms and tightens a previously cited Triassic age for this intrusive suite. A fresh mafic dike in Goodnews Bay quadrangle yielded a 40Ar/39Ar whole rock age of 155.0±1.9 Ma; this establishes a Jurassic or older age for the previously unconstrained (Paleozoic? to Mesozoic?) sandstone unit that it intrudes. A thick felsic tuff in the Gemuk Group in Taylor Mountains quadrangle yielded a U-Pb zircon age of 153.0±2.0 Ma, extending the age of magmatism in this part of the Togiak terrane back into the Late Jurassic. We report three new U-Pb zircon ages between 120 and 110 Ma—112.0±0.9 Ma from syenite in the Candle quadrangle, 114.9±0.3 Ma from orthogneiss assigned to the Ruby terrane in Iditarod quadrangle, and 116.6±0.1 Ma from a gabbro of the Dishna River mafic-ultramafic complex in Iditarod quadrangle. The latter result requires a substantial age revision, from Triassic to Cretaceous, for at least some rocks that have been mapped as the Dishna River mafic-ultramafic complex. A tuff in the Upper Cretaceous Kuskokwim Group yielded a U-Pb zircon (sensitive high-resolution ion microprobe, SHRIMP) age of 88.3±1.0 Ma; we speculate that the eruptive source was an arc along the trend of the Pebble

  10. Voluminous lava-like precursor to a major ash-flow tuff: Low-column pyroclastic eruption of the Pagosa Peak Dacite, San Juan volcanic field, Colorado

    Science.gov (United States)

    Bachmann, Olivier; Dungan, M.A.; Lipman, P.W.

    2000-01-01

    The Pagosa Peak Dacite is an unusual pyroclastic deposit that immediately predated eruption of the enormous Fish Canyon Tuff (~5000 km3) from the La Garita caldera at 28 Ma. The Pagosa Peak Dacite is thick (to 1 km), voluminous (>200 km3), and has a high aspect ratio (1:50) similar to those of silicic lava flows. It contains a high proportion (40-60%) of juvenile clasts (to 3-4 m) emplaced as viscous magma that was less vesiculated than typical pumice. Accidental lithic fragments are absent above the basal 5-10% of the unit. Thick densely welded proximal deposits flowed rheomorphically due to gravitational spreading, despite the very high viscosity of the crystal-rich magma, resulting in a macroscopic appearance similar to flow-layered silicic lava. Although it is a separate depositional unit, the Pagosa Peak Dacite is indistinguishable from the overlying Fish Canyon Tuff in bulk-rock chemistry, phenocryst compositions, and 40Ar/39Ar age. The unusual characteristics of this deposit are interpreted as consequences of eruption by low-column pyroclastic fountaining and lateral transport as dense, poorly inflated pyroclastic flows. The inferred eruptive style may be in part related to synchronous disruption of the southern margin of the Fish Canyon magma chamber by block faulting. The Pagosa Peak eruptive sources are apparently buried in the southern La Garita caldera, where northerly extensions of observed syneruptive faults served as fissure vents. Cumulative vent cross-sections were large, leading to relatively low emission velocities for a given discharge rate. Many successive pyroclastic flows accumulated sufficiently rapidly to weld densely as a cooling unit up to 1000 m thick and to retain heat adequately to permit rheomorphic flow. Explosive potential of the magma may have been reduced by degassing during ascent through fissure conduits, leading to fracture-dominated magma fragmentation at low vesicularity. Subsequent collapse of the 75 x 35 km2 La Garita

  11. Efeito do 1-metilciclopropeno na conservação de maçãs 'Royal Gala' em ar refrigerado e atmosfera controlada Effects of 1-methylcyclopropene on 'Royal Gala' apples stored in refrigerated air and controlled atmosphere

    Directory of Open Access Journals (Sweden)

    Adriana Regina Corrent

    2004-08-01

    Full Text Available Maçãs 'Royal Gala', colhidas em dois estádios de maturação, foram tratadas com 1-MCP (1-metilciclopropeno nas concentrações de 0; 625 e 1250 nL.L-1, durante 48 horas, à temperatura de 20 ± 2 ºC. Após este tratamento, foram armazenadas em dois diferentes sistemas: em atmosfera controlada à temperatura de 0 ± 0,5 ºC, 2,1 a 2,3 kPa de CO2 , 1,8 a 2,0 kPa de O2 e umidade relativa de 95 ± 5 %, durante 9 meses. Em ar refrigerado a 0,5 ± 0,5 ºC e 95 ± 5 % de umidade relativa, durante 8 meses. As análises realizadas demonstraram a eficiência do 1-MCP em controlar a maturação das frutas durante o armazenamento em ambas as condições e pontos de colheita. A aplicação do 1-MCP reduziu drasticamente a produção de etileno, diminuiu a perda de firmeza, além de preservar a acidez total titulável.In the present work were evaluated the effects of 1-MCP on 'Royal Gala' apples stored in refrigerated air and controlled atmosphere. 'Royal Gala' apples were harvested at two ripeness stages and treated with 1-methylcyclopropene (1-MCP using two concentrations 625 and 1250 nL.L-1 which were applied during 48 hours at temperature of 20 ± 2 ºC. The control fruit was only kept in air. After the treatments the apples were stored in either controlled atmosphere 2,1 to 2,3 kPa CO2, 1,8 to 2,0 kPa O2 and 95 ± 0,5 % of relative humidity for 9 months at 0 ± 0,5 ºC or in refrigerated air storage at 0,5 ± 0,5 ºC and 95 ± 0,5 % of relative humidity, for 8 months. The 1-MCP applications on apples in both storages and ripening stages reduced dramatically the ethylene production. Pulp firmness losses and titratable acidity were also significanthy higher compared to control fruit.

  12. Combined K-Ar and 40Ar/39Ar dating of the upper Jaramillo reversal

    Science.gov (United States)

    Guillou, Herve; Carracedo, Juan Carlos; Kissel, Catherine; Laj, Carlo; Nomade, Sebastien; Perez Torrado, Francisco Jose; Rodriguez Gonzalez, Alejandro; Wandres, Camille

    2013-04-01

    The Jaramillo subchron was first evidenced in 1966 (Doell and Dalrymple) through the Rhyolotic domes of the Valles Caldera, New Mexico (USA). 40Ar/39Ar studies achieved by Spell et McDougall (1992), Spell et Harrison (1993), Izett and Obradovich (1994) and Singer et al. (1994) defined the base of this subchron at 1053±6 ka, and the ceiling at 986±5 ka. Channell et al. (2009) delimited the age of the Jaramillo subchron by astronomic calibration (base 1071 ka, top 990 ka). To provide additional absolute ages on this geomagnetic period, which is critical to improve our knowledge of the earth magnetic field behaviour, we have carried out a study combining paleomagnetism and isotopic dating of a lava sequence from Tenerife island. This sequence of basaltic lava flows is some 500 m thick. The first 400 m present, based on field magnetometer measurements, normal polarity lavas, with dykes of normal and reverse polarity, passing at the top to reverse polarity lavas. Preliminary K-Ar ages bracketed this sequence between 1018 ± 18 ka and 978 ± 17 ka. Therefore, the upper Jaramillo reversal at least appeared to be potentially recorded in this sequence. A more detailed paleomagnetic study was then carried out to more precisely delimit the reversal itself (see Laj et al., session EMRP3.4). We have undertaken 40Ar/39Ar incremental heating and unspiked K-Ar experiments on groundmass from four transitionally magnetized flows. The first transitional flow is K-Ar dated at 993 ± 18 ka and 40Ar/39Ar dated at 991 ± 13 ka, the second at 981 ± 17 ka (K-Ar) and 1000 ± 13 ka (40Ar/39Ar), the third at 950 ± 17 ka (K-Ar) and 1000 ± 8 ka (40Ar/39Ar) and the fourth at 984 ± 17 ka (K-Ar) and 977 ± 12 (40Ar/39Ar). 40Ar/39Ar ages and K-Ar ages (relative to FCT 28.02 Ma) are indistinguishable at 2σ. The age of the upper boundary of the Jaramillo event calculated combining 40Ar/39Ar ages and K-Ar ages is 992 ± 6 ka, in agreement with previous estimates.

  13. Inverse Dipolar Magnetic Anomaly Over the Volcanic Cone Linked to Reverse Polarity Magnetizations in Lavas and Tuffs - Implications for the Conduit System

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L. L.; Trigo-Huesca, A.

    2012-12-01

    A combined magnetics and paleomagnetic study of Toluquilla monogenetic volcano and associated lavas and tuffs from Valsequillo basin in Central Mexico provides evidence on a magnetic link between lavas, ash tuffs and the underground volcanic conduit system. Paleomagnetic analyses show that lavas and ash tuffs carry reverse polarity magnetizations, which correlate with the inversely polarized dipolar magnetic anomaly over the volcano. The magnetizations in the lava and tuff show similar southward declinations and upward inclinations, supporting petrological inferences that the tuff was emplaced while still hot and indicating a temporal correlation for lava and tuff emplacement. Conduit geometry is one of the important controlling factors in eruptive dynamics of basaltic volcanoes. However volcanic conduits are often not, or only partly, exposed. Modeling of the dipolar anomaly gives a reverse polarity source magnetization associated with a vertical prismatic body with southward declination and upward inclination, which correlates with the reverse polarity magnetizations in the lava and tuff. The study documents a direct correlation of the paleomagnetic records with the underground magmatic conduit system of the monogenetic volcano. Time scale for cooling of the volcanic plumbing system involves a longer period than the one for the tuff and lava, suggesting that magnetization for the source of dipolar anomaly may represent a long time average as compared to the spot readings in the lava and tuff. The reverse polarity magnetizations in lava and tuff and in the underground source body for the magnetic anomaly are interpreted in terms of eruptive activity of Toluquilla volcano at about 1.3 Ma during the Matuyama reverse polarity C1r.2r chron.

  14. The pre-Kos Plateau Tuff Volcanic Rocks on Kefalos Peninsula (Kos Island, Dodecanese, Greece): Crescendo to the Largest Eruption of the Modern Aegean Arc

    Science.gov (United States)

    Bachmann, O.; Schnyder, C.

    2006-12-01

    Young volcanic rocks (K-Ar ages of 3 to 0.5 Ma) from the Kefalos Peninsula (Kos Island, Dodecanese, Greece) erupted prior to the voluminous (>60 km\\ 3) Kos Plateau Tuff (KPT; Ar-Ar age of 0.16 Ma) were studied in order to better define the conditions that led to the paroxysmal eruption of the modern Aegean Arc. Two different whole-rock compositions were sampled on Kefalos peninsula; dacites (63-65 wt% SiO2) and rhyolites (75-77 wt% SiO2). Kefalos dacites are crystal-rich (>40% crystals), show high Sr-Ba contents compared to other continental arcs, and have "adakitic" Sr/Y ratios (>40). Kefalos rhyolites are typical high- SiO2 arc magmas, similar in composition and mineralogy to the KPT, but displaying lower crystallinities (30% in most of the KPT). The high Sr/Y ratios of the dacites is surprising in an area where the subducting slab is not particularly hot and the continental crust relatively thin (~30 km). If the low Y and high Sr-Ba contents result from the fact that magma formed deep enough to supress plagioclase and have garnet present, dacite magma generation must have occurred in the mantle. There is geochemical and mineralogical evidence for the Kefalos and KPT rhyolites being generated by fractional crystallization from magmas similar to the Kefalos dacites. However, the few distinctions between KPT and Kefalos rhyolites (KPT is more voluminous, contains more crystals, has lower whole-rock U and Th contents, and lower MgO-SiO2, but higher Al2O3-FeOtot in biotite) suggest slightly different conditions in the magma chambers. These observations, together with increasing explosivity of the volcanic products from ~3 Ma to 0.16 Ma, may indicate that the build-up to the large KPT eruption could be the result of an increase in magmatic water input in the system through time.

  15. Anisotropy of the Topopah Spring Member Tuff

    Energy Technology Data Exchange (ETDEWEB)

    Martin, R.J. III; Boyd, P.J.; Haupt, R.W. [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

    1992-07-01

    Mechanical properties of the tuffaceous rocks within Yucca Mountain are needed for near and far-field modeling of the potential nuclear waste repository. If the mechanical properties are significantly anisotropic (i.e., direction-dependent), a more complex model is required. Relevant data from tuffs tested in earlier studies indicate that elastic and strength properties are anisotropic. This scoping study confirms the elastic anisotropy and concludes some tuffs are transversely isotropic. An approach for sampling and testing the rock to determine the magnitude of the anisotropy is proposed.

  16. 40Ar/39Ar geochronology and exhumation of mylonitized metamorphic complex in Changle-Nanao ductile shear zone

    Institute of Scientific and Technical Information of China (English)

    王志洪; 卢华复

    1997-01-01

    New 40Ar/39Ar plateau ages from rocks of Changle-Nanao ductile shear zone are 107.9 Ma(Mus), 108.2 Ma(Bi), 107. 1 Ma(Bi), 109. 2 Ma(Hb) and 117. 9 Ma(Bi) respectively, which are concordant with their isochron ages and record the formation age of the ductile shear zone. The similarity and apparent overlap of the cooling ages with respective closure temperatures of 5 minerals document initial rapid uplift during 107-118 Ma following the collision between the Min-Tai microcontinent and the Min-Zhe Mesozoic volcanic arc. The 40Ar/39Ar plateau ages, K-Ar date of K-feldspar and other geochronologic information suggest that the exhumation rate of the ductile shear zone is about 0.18-1.12 mm/a in the range of 107-70 Ma, which is mainly influenced by tectonic extension.

  17. Properties of Tuffs, Grout and Other Materials.

    Science.gov (United States)

    1982-01-01

    Samples of tuff as-received have been wrapped in foil and sealed in beeswax in the field. Density and moisture content were determined from small pieces...received" density was deter- mined by weighing the chipped-off test specimen, coating it with wax, and measuring its volume using mercury displacement

  18. Evaluation of some Italian tuffs as compatible replacement stone for Römer tuff in the Netherlands

    NARCIS (Netherlands)

    Nijland, T.G.; Hees, R.P.J. van

    2007-01-01

    Rhenish tuffs from the volcanic Eifel region, Germany, are amongst the most prominent and voluminous natural stones in Dutch monuments. In particular, tuffs from the 11,900 bp Laacher See eruption have been used since Roman times, - hence the name Römer tuff-, and were widely used again in romanesqu

  19. Sorption of lanthanum ions by natural clinoptilolite tuff

    Science.gov (United States)

    Dampilova, B. V.; Zonkhoeva, E. L.

    2013-08-01

    The equilibrium and kinetics of sorption of lanthanum ions on natural clinoptilolite tuff are studied. It is demonstrated that sorption of lanthanum ions from diluted solutions occurs in micropores of clinoptilolite, and from concentrated solutions in the mesoporous structure of tuff. The main capacity of zeolite tuff is found in the secondary porous structure. The sorption of lanthanum ions is limited by diffusion in tuff grains. Lanthanum ions are regularly distributed in the tuff phase and interact with the Brønsted centers of large clinoptilolite cavities.

  20. The Tala Tuff, La Primavera caldera Mexico. Pre-eruptive conditions and magma processes before eruption

    Science.gov (United States)

    Sosa-Ceballos, G.

    2015-12-01

    La Primavera caldera, Jalisco Mexico, is a Pleistocenic volcanic structure formed by dome complexes and multiple pyroclastic flows and fall deposits. It is located at the intersection of the Chapala, Colima, and Tepic grabens in western Mexico. The first volcanic activity associated to La Primavera started ~0.1 Ma with the emission of pre-caldera lavas. The caldera collapse occurred 95 ka and is associated to the eruption of ~20 km3of pumice flows known as the Tala tuff (Mahood 1980). The border of the caldera was replaced by a series of domes dated in 75-30 ky, which partially filled the inner depression of the caldera with pyroclastic flows and falls. For more than a decade the Federal Commission of Electricity in Mexico (CFE) has prospected and evaluated the geothermal potential of the Cerritos Colorados project at La Primavera caldera. In order to better understand the plumbing system that tapped the Tala tuff and to investigate its relation with the potential geothermal field at La Primavera we performed a series of hydrothermal experiments and studied melt inclusions hosted in quartz phenocrysts by Fourier Infra red stectroscopy (FTIR). Although some post caldera products at La Primavera contain fayalite and quartz (suggesting QFM conditions) the Tala tuff does not contain fayalite and we ran experiments under NNO conditions. The absence of titanomagnetite does not allowed us to calculate pre-eruptive temperature. However, the stability of quartz and plagioclase, which are natural phases, suggest that temperature should be less than 750 °C at a pressure of 200 MPa. The analyses of H2O and CO2 dissolved in melt inclusions yielded concentrations of 2-5 wt.% and 50-100 ppm respectively. This data confirm that the pre-eruptive pressure of the Tala tuff is ~200 MPa and in addition to major elements compositions suggest that the Tala tuff is either, compositionally zoned or mixed with other magma just prior to eruption.

  1. ma a

    Directory of Open Access Journals (Sweden)

    Oscar del Barco, Trad. Davi Pessoa Carneiro

    2013-06-01

    Full Text Available Oscar del Barco escreveu o texto “ma a” para o catálogo ma a/Obra pictórica (Cór­doba, 2008, publicado na ocasião da exposição homônima, em que foram ex­postas 150 obras iné­ditas de distintos formatos e técnicas que del Barco vinha reali­zando há mais de 15 anos. Alguns escritores, artistas, ensaís­tas e pesquisadores, como Silvio Mattoni, Antonio Oviedo, Anamaría Ashwell, Gustavo Cosa­cov, Matías Lapezzata, entre outros, parti­ciparam da publi­cação. O texto foi posteriormente in­cluído em Alternativas de lo Posthumano (Buenos Aires: Caja Negra, 2010, com organização de Gabriel Livov e Pablo Gallardo. A tradução é do texto pu­blicado no mesmo livro (p. 279-283. [N.T.

  2. New palynology-based astronomical and revised 40Ar/39Ar ages for the Eocene maar lake of Messel (Germany)

    Science.gov (United States)

    Lenz, Olaf K.; Wilde, Volker; Mertz, Dieter F.; Riegel, Walter

    2015-04-01

    The annually laminated oil shale from the Eocene maar lake at Messel (Federal State of Hessen, Germany) provides unique paleoenvironmental data for a time interval of ~640 ka during the Paleogene greenhouse phase. As a consequence of orbitally controlled changes in the vegetation in the vicinity of the lake, the lacustrine laminites can now be astronomically tuned. Dating is based on the short eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical La2010a/La2010d solutions in combination with a revised 40Ar/39Ar age of a basalt fragment from a lapilli tuff section below the first lacustrine sediments. Depending on different newly suggested ages for the Fish Canyon sanidine used as monitor for neutron irradiation, the age for the eruption at Messel is between 48.27 ± 0.22 and 48.11 ± 0.22 Ma. This allows for the first time the exact correlation of a Paleogene lacustrine sequence to the marine record in Central Europe. The Messel oil shale becomes now slightly older than previously assumed and includes the Ypresian/Lutetian boundary that moves the base of the European Land Mammal Age Geiseltalian (MP 11) into the Lower Eocene. This opens a window for establishing an independent chronostratigraphic framework for Paleogene terrestrial records and their correlation to the marine realm. Furthermore, the study reveals that higher amounts of pollen from "wet" and thermophilous plants indicate less seasonal and more balanced precipitation and slightly higher temperatures during a well-expressed eccentricity minimum.

  3. Hydraulic characterization of hydrothermally altered Nopal tuff

    Energy Technology Data Exchange (ETDEWEB)

    Green, R.T.; Meyer-James, K.A. [Southwest Research Institute, San Antonio, TX (United States); Rice, G. [George Rice and Associates, San Antonio, TX (United States)

    1995-07-01

    Understanding the mechanics of variably saturated flow in fractured-porous media is of fundamental importance to evaluating the isolation performance of the proposed high-level radioactive waste repository for the Yucca Mountain site. Developing that understanding must be founded on the analysis and interpretation of laboratory and field data. This report presents an analysis of the unsaturated hydraulic properties of tuff cores from the Pena Blanca natural analog site in Mexico. The basic intent of the analysis was to examine possible trends and relationships between the hydraulic properties and the degree of hydrothermal alteration exhibited by the tuff samples. These data were used in flow simulations to evaluate the significance of a particular conceptual (composite) model and of distinct hydraulic properties on the rate and nature of water flow.

  4. Infiltration and Seepage Through Fractured Welded Tuff

    Energy Technology Data Exchange (ETDEWEB)

    T.A. Ghezzehei; P.F. Dobson; J.A. Rodriguez; P.J. Cook

    2006-06-20

    The Nopal I mine in Pena Blanca, Chihuahua, Mexico, contains a uranium ore deposit within fractured tuff. Previous mining activities exposed a level ground surface 8 m above an excavated mining adit. In this paper, we report results of ongoing research to understand and model percolation through the fractured tuff and seepage into a mined adit both of which are important processes for the performance of the proposed nuclear waste repository at Yucca Mountain. Travel of water plumes was modeled using one-dimensional numerical and analytical approaches. Most of the hydrologic properly estimates were calculated from mean fracture apertures and fracture density. Based on the modeling results, we presented constraints for the arrival time and temporal pattern of seepage at the adit.

  5. Structure of metal matrix composites with an addition of tuff

    Directory of Open Access Journals (Sweden)

    M. Łach

    2010-07-01

    Full Text Available The article presents preliminary results of tests of metal matrix composites structure which was modified by an addition of powderedvolcanic tuff. Distribution and shape of ceramic particles as well as the quality of the bonding along the tuff- metal matrix interface werestudied. Depth of tuff element diffusion in the matrix as well as diffusion in tuff particles were checked. Micro-hardness and porosity of the composites were also tested. The tuff from Filipowice near the town of Krzeszowice was used for the tests. Powder metallurgy wasapplied to obtain the composites and the matrix materials were copper and 316L steel powders. The tuff was introduced in 2, 5 and 10 %by weight. To remove water from the channels of aluminosilicates, the tuff was baked at 850 oC for 4 hours and then cooled together withthe oven. The tests revealed good quality of the bonding of the tuff particles and the matrix and their even distribution. The addition of tuff improved the hardness of the composites and reduced their porosity which has great significance because of possible applications of this kind of materials in general and copper composites in particular. This gives grounds for further studies on volcanic tuff use in metal composites

  6. 40Ar/39Ar dating of the Valsequillo volcanic deposits, Central Mexico: Resolution of an ongoing archaeological controversy and implications for the first human colonization of the 'New World'

    Science.gov (United States)

    Mark, Darren

    2010-05-01

    It is currently accepted that the Clovis culture was the first to migrate into the New World at 13.1 ka [1]. However, archeological evidence in the form of stone tools, linguistics, craniometrics and genetics suggest that the first Americans were ethnically diverse and a few sites dated to 15-16 ka BP challenge the 'Clovis First' model. Perhaps the biggest challenge to the 'Clovis First' model was the reported presence of human footprints within a basaltic ash (Xalnene Ash) dated to 38.04 ± 8.57 ka using optically stimulated luminescence (OSL) [2]. However, Renne et al. [3] challenged the validity of the footprints by dating lapilli from the Xalnene ash using 40Ar/39Ar and reported an age of 1.30 ± 0.03 Ma (2σ). They also reported a reversed palaeomagnetic polarity for the ash, consistent with deposition during chron C1r.2r. Such antiquity casts considerable doubt on the interpretation of the impressions as human footprints. Gonzalez et al. [4] questioned the validity of the 40Ar/39Ar age and highlighted the heterogeneous nature of the lapilli as a potential problem for 40Ar/39Ar geochronology. The lapilli contain abundant phenocrysts and xenocrysts. Olivine phenocrysts can be contaminated with excess Ar (40ArE) [5] and hence the dating of 40ArE-bearing lapilli and xenocrystic material may potentially produce anomalously old 40Ar/39Ar ages. Gonzalez et al. [4] also dismissed the significance of the reversed palaeomagnetic polarity as the proposed age of the ash (38.04 ± 8.57 ka) overlapped with the Laschamp Geomagnetic Excursion at 40.4 ± 1.1 ka. Subsequently there has been support for both sides of the debate. The OSL age presented was questioned [6] and reconfirmed by [7]. The OU 40Ar/39Ar laboratory showed the presence of 40ArE in the samples although they were unable to date the ash [2]. Palaeomagnetic data has both supported emplacement of the Xalnene Ash during the LGE [8,9] and at 1.3 Ma [10]. The age of the 'alleged' footprint-bearing Xalnene ash and

  7. Estimates of flow direction for calc-alkaline welded tuffs and paleomagnetic data reliability from anisotropy of magnetic susceptibility measurements: Central San Juan Mountains, southwest Colorado

    Science.gov (United States)

    Ellwood, Brooks B.

    1982-07-01

    Flow directions are estimated from the measurement of the magnetic fabric of 106 samples, collected at 18 sites in four welded tuff units in the central San Juan Mountains of southern Colorado. The estimates assume that the tuffs generally flowed directly away from the extrusive vents and that the lineations of magnetic grains within the tuffs represent the flow direction at individual sites. Errors in the estimation may arise from topographic variation, rheomorphism (post-emplacement mass flow) within the tuff, and other factors. Magnetic lineation is defined as the site mean anisotropy of magnetic susceptibility maximum azimuth. A test on the flow directions for individual units is based on the projection of lineation azimuths and their intersection within or near the known source caldera for the tuff. This test is positive for the four units examined. Paleomagnetic results for these tuffs are probably reliable indicators of the geomagnetic field direction in southwest Colorado, during the time (28.2-26.5 Ma) of emplacement.

  8. Batman’da Yeni Bir Keşif: Deraser (Arık) Mağara Resimleri
    A New Discovery In Batman Province: Prehistoric Cave Paintings Of Deraser (Arik)

    OpenAIRE

    SOYDAN, Ersoy; KORKMAZ, Ferhat

    2013-01-01

    Euphrates and Tigris rivers which are born from high and snowy mountains of Eastern and Anatolia and give life to a rid regions had a vital importance for early agricultural communities. Mesopotamian civilizations advanced between these two rivers in later centuries and lots of settlements had been established near Euphrates and Tigris. One of the historical settlements is Deraser (Arık) village which is in the district of today’s Batman city called Gercüş. A lot of historical remains exist t...

  9. Neogene fallout tuffs from the Yellowstone hotspot in the Columbia Plateau region, Oregon, Washington and Idaho, USA.

    Directory of Open Access Journals (Sweden)

    Barbara P Nash

    Full Text Available Sedimentary sequences in the Columbia Plateau region of the Pacific Northwest ranging in age from 16-4 Ma contain fallout tuffs whose origins lie in volcanic centers of the Yellowstone hotspot in northwestern Nevada, eastern Oregon and the Snake River Plain in Idaho. Silicic volcanism began in the region contemporaneously with early eruptions of the Columbia River Basalt Group (CRBG, and the abundance of widespread fallout tuffs provides the opportunity to establish a tephrostratigrahic framework for the region. Sedimentary basins with volcaniclastic deposits also contain diverse assemblages of fauna and flora that were preserved during the Mid-Miocene Climatic Optimum, including Sucker Creek, Mascall, Latah, Virgin Valley and Trout Creek. Correlation of ashfall units establish that the lower Bully Creek Formation in eastern Oregon is contemporaneous with the Virgin Valley Formation, the Sucker Creek Formation, Oregon and Idaho, Trout Creek Formation, Oregon, and the Latah Formation in the Clearwater Embayment in Washington and Idaho. In addition, it can be established that the Trout Creek flora are younger than the Mascall and Latah flora. A tentative correlation of a fallout tuff from the Clarkia fossil beds, Idaho, with a pumice bed in the Bully Creek Formation places the remarkably well preserved Clarkia flora assemblage between the Mascall and Trout Creek flora. Large-volume supereruptions that originated between 11.8 and 10.1 Ma from the Bruneau-Jarbidge and Twin Falls volcanic centers of the Yellowstone hotspot in the central Snake River Plain deposited voluminous fallout tuffs in the Ellensberg Formation which forms sedimentary interbeds in the CRBG. These occurrences extend the known distribution of these fallout tuffs 500 km to the northwest of their source in the Snake River Plain. Heretofore, the distal products of these large eruptions had only been recognized to the east of their sources in the High Plains of Nebraska and Kansas.

  10. Neogene fallout tuffs from the Yellowstone hotspot in the Columbia Plateau region, Oregon, Washington and Idaho, USA.

    Science.gov (United States)

    Nash, Barbara P; Perkins, Michael E

    2012-01-01

    Sedimentary sequences in the Columbia Plateau region of the Pacific Northwest ranging in age from 16-4 Ma contain fallout tuffs whose origins lie in volcanic centers of the Yellowstone hotspot in northwestern Nevada, eastern Oregon and the Snake River Plain in Idaho. Silicic volcanism began in the region contemporaneously with early eruptions of the Columbia River Basalt Group (CRBG), and the abundance of widespread fallout tuffs provides the opportunity to establish a tephrostratigrahic framework for the region. Sedimentary basins with volcaniclastic deposits also contain diverse assemblages of fauna and flora that were preserved during the Mid-Miocene Climatic Optimum, including Sucker Creek, Mascall, Latah, Virgin Valley and Trout Creek. Correlation of ashfall units establish that the lower Bully Creek Formation in eastern Oregon is contemporaneous with the Virgin Valley Formation, the Sucker Creek Formation, Oregon and Idaho, Trout Creek Formation, Oregon, and the Latah Formation in the Clearwater Embayment in Washington and Idaho. In addition, it can be established that the Trout Creek flora are younger than the Mascall and Latah flora. A tentative correlation of a fallout tuff from the Clarkia fossil beds, Idaho, with a pumice bed in the Bully Creek Formation places the remarkably well preserved Clarkia flora assemblage between the Mascall and Trout Creek flora. Large-volume supereruptions that originated between 11.8 and 10.1 Ma from the Bruneau-Jarbidge and Twin Falls volcanic centers of the Yellowstone hotspot in the central Snake River Plain deposited voluminous fallout tuffs in the Ellensberg Formation which forms sedimentary interbeds in the CRBG. These occurrences extend the known distribution of these fallout tuffs 500 km to the northwest of their source in the Snake River Plain. Heretofore, the distal products of these large eruptions had only been recognized to the east of their sources in the High Plains of Nebraska and Kansas.

  11. Ars Electronica

    DEFF Research Database (Denmark)

    Kristensen, Thomas Bjørnsten

    2009-01-01

    Anmeldelse af Ars Electronica festivalen 3. - 8. september, 2009 i Linz, Østrig, der fejrede 30 års jubilæum under temaet "Human Nature". Festivalen fokuserer på interaktion mellem menneske, teknologi, kunst og samfund med særlig vægt på udviklingen af computeren og det digitale. Udgivelsesdato: 15.12...

  12. Ars Electronica

    DEFF Research Database (Denmark)

    Kristensen, Thomas Bjørnsten

    2009-01-01

    Anmeldelse af Ars Electronica festivalen 3. - 8. september, 2009 i Linz, Østrig, der fejrede 30 års jubilæum under temaet "Human Nature". Festivalen fokuserer på interaktion mellem menneske, teknologi, kunst og samfund med særlig vægt på udviklingen af computeren og det digitale. Udgivelsesdato: 15.12...

  13. Ar-Ar and Rb-Sr Ages of the Tissint Olivine-phyric Martian Shergottite

    Science.gov (United States)

    Park, J.; Herzog, G. F.; Nyquist, L. E.; Shih, C.-Y.; Turin, B.; Lindsay, F. N.; Delaney, J. S.; Swisher, C. C., III; Agee, C.

    2013-01-01

    The fifth martian meteorite fall, Tissint, is an olivine-phyric shergottite that contains olivine macrocrysts (approximately 1.5 mm) [1]. [2] reported the Sm-Nd age of Tissint as 596 plus or minus 23 Ma along with Rb-Sr data that defined no isochron. [3] reported Lu-Hf and Sm-Nd ages of 583 plus or minus 86 Ma and 616 plus or minus 67 Ma, respectively. The cosmic-ray exposure ages of Tissint are 1.10 plus or minus 0.15 Ma based on 10Be [4], and 1.0-1.1 Ma, based on 3He, 21Ne, and 38Ar [5,6].We report Ar-Ar ages and Rb-Sr data.

  14. K/Ar chronologies of tephra units from the Middle Jurassic Sundance, and Late Early Cretaceous Mowry and Shell Creek Formations, Big Horn Basin, WY

    Science.gov (United States)

    Jiang, H.; Meyer, E. E.; Johnson, G. D.

    2013-12-01

    The Middle Jurassic Sundance and Late Early Cretaceous Shell Creek and Mowry Formations of the Big Horn Basin, Wyoming, contain an extensive record of altered tephra. These tephra are likely related to contemporary volcanic activity in the Sierra Nevada and various Coast Range terranes to the west and provide valuable chronometric control on the sedimentary record within a portion of the Sevier-aged and later Cordilleran foreland basin. In addition, several of these altered tephra (bentonites) provide a valuable economic resource. Despite the prominence of these strata across the basin, few isotopic ages have been reported to date. Here we present new K/Ar ages on biotite phenocrysts from those tephra occurrences as a chronometric check on samples that contained zircons with significant Pb loss, that preclude more precise U/Pb age determinations. A bulk biotite sample extracted from an altered tuff in the Lower Sundance Formation gives an age of 167.5 × 5 Ma. This tuff occurs just above a dinosaur track-bearing peritidal sequence. Bulk biotite ages from the lower Shell Creek Formation give an age of 100.3 × 3 Ma and are statistically indistinguishable from biotite grains dated at 103.1 × 3 Ma extracted from the economically important 'Clay Spur' bentonite found at the top of the Mowry Shale. This work provides important new chronometric constraints on a portion of the Medial Jurassic to Late Early Cretaceous stratigraphy of the Big Horn Basin, Wyoming, and may be useful in understanding the regional tectonics that helped shape the development of the Sevier foreland basin and Western Interior Seaway.

  15. From olivine nephelinite, basanite and basalt to peralkaline trachyphonolite and comendite in the Ankaratra volcanic complex, Madagascar: 40Ar/39Ar ages, phase compositions and bulk-rock geochemical and isotopic evolution

    Science.gov (United States)

    Cucciniello, Ciro; Melluso, Leone; le Roex, Anton P.; Jourdan, Fred; Morra, Vincenzo; de'Gennaro, Roberto; Grifa, Celestino

    2017-03-01

    The Ankaratra volcanic field covers an area of 3800 km2 in central Madagascar and comprises of lava flows, lava domes, scoria cones, tuff rings and maars emplaced at different ages (Miocene to Recent). The volcanic products include ultramafic-mafic (olivine-leucite nephelinite, basanite, alkali basalt, hawaiite and tholeiitic basalt), intermediate (mugearite and benmoreite) and felsic rocks (trachyphonolite, quartz trachyte and rhyolite), the latter often peralkaline. The 40Ar/39Ar determinations for mafic lavas yield ages of 17.45 ± 0.12 Ma, 16.63 ± 0.08 Ma and 8.62 ± 0.09 Ma, indicating a prolonged magmatic activity. The mineralogical and geochemical variations suggest that the magmatic evolution of the alkali basalt-hawaiite-mugearite-benmoreite-trachyte series can be accounted for by removal of olivine, feldspars, clinopyroxene, Fe-Ti oxides and accessory phases, producing residual trachytic and trachyphonolitic compositions mineralogically very similar to those of other volcanic areas and tectonic settings. The Ankaratra olivine leucite nephelinites, basanites and tholeiitic basalts do not seem to be associated with significant amounts of evolved comagmatic rocks. The 87Sr/86Sr (0.70504-0.71012), 143Nd/144Nd (0.51259-0.51244) and 206Pb/204Pb (17.705-18.563) isotopic ratios of trachytes and comendite are consistent with open-system processes. However, other trachyphonolites have 143Nd/144Nd (0.51280), 206Pb/204Pb (18.648), 207Pb/204Pb (15.582) and 208Pb/204Pb (38.795) similar to those of mafic rocks, suggesting differentiation processes without appreciable interaction with crustal materials. The Ankaratra volcanism is to be directly linked to a broadly E-W-trending intracontinental extension. A large-scale thermal anomaly, associated with an anomalously hot source region, is not required to explain the Cenozoic magmatism of Madagascar.

  16. Tracking fluid action in Little Sark Pluton (Channel Islands, UK): a UV laserprobe Ar/Ar study of excess 40Ar

    Science.gov (United States)

    Schwenzer, S. P.; Schwanethal, J.; Tindle, A. G.; Kelley, S. P.; Sherlock, S. C.

    2011-12-01

    Little Sark pluton (Channel Islands, UK) is a weakly to moderately deformed pluton of quartz diorite composition. Zircon from Little Sark has been dated as 611.4(+2.1/-1.3) Ma [Miller et al. 1991, Tectonophysics, 312], whereas titanite has an age of 606.2±0.6 Ma. Hornblende yields an Ar-Ar age of 606.4±3.4 Ma [Dallmeyer et al., 1991, J. Geol. Soc. London 148]. The rocks show evidence for post-magmatic hydrous alteration including chloritisation of biotite, and sericite formation in feldspar. We investigated the alteration in order to understand its influence on the Ar-Ar system. Detailed petrographic investigations of two samples indicate different deformation levels - S1, (less deformed), and S2 (more deformed). The feldspar is andesine to oligoclase in composition, but contains K-rich areas with patchy and sometimes cleavage guided sericitization. Mafic minerals include hornblende and biotite (the latter partially chloritized). Ar-Ar investigations were carried out using high spatial resolution UV laser ablation gas release in combination with a Nu instruments Noblesse gas mass spectrometer using spots of 80 to 140 μm diameter. Mafic minerals in S1 have highly variable 38Ar/39Ar and 37Ar/39Ar ratios and unusually high atmospheric contents for such old samples, possibly reflecting the presence of fluid inclusions associated with the sericite, particularly in the feldspar. The apparent ages in their entirety range from 429 to 668 Ma. Hornblende yields homogeneous apparent ages, whereas the younger and older ages are measured in both micas and feldspars, whose apparent ages range from 245-670 Ma. The modal age for feldspar is around 400-450 Ma, but this may not have geological meaning. Sample S2 shows many of the same features as S1. Mafic minerals span a slightly smaller age range and feldspars display apparent ages of ~245-645 Ma with a mode around 480 Ma. The alteration of both samples appears to have been accompanied by the introduction of 40Ar-rich fluids

  17. Preferential Flow in Fractured Welded Tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Salve, Rohit

    2004-08-15

    To better understand preferential flow in fractured rock, we carried out an in situ field experiment in the Exploratory Studies Facility at Yucca Mountain, Nevada. This experiment involved the release of {approx} 22 m3 of ponded water (at a pressure head of {approx} 0.04 m) over a period of 7 months, directly onto a 12 m2 infiltration plot located on a fractured welded tuff surface. As water was released, changes in moisture content were monitored along horizontal boreholes located in the formation {approx} 19-22 m below. Distinct flow zones, varying in flow velocity, wetted cross-sectional area, and extent of lateral movement, intercepted the monitoring boreholes. There was also evidence of water being diverted above the ceiling of a cavity in the immediate vicinity of the monitoring boreholes. Observations from this field experiment suggest that isolated conduits, each encompassing a large number of fractures, develop within the fractured rock formation to form preferential flow paths that persist if there is a continuous supply of water. In addition, in fractured welded tuffs the propensity for fracture-matrix interactions is significantly greater than that suggested by existing conceptual models,in which flow occurs along a section of fracture surfaces. An overriding conclusion is that field investigations at spatial scales of tens of meters provide data critical to the fundamental understanding of flow in fractured rock.

  18. Re-Evaluation of Ar-39 - Ar-40 Ages for Apollo Lunar Rocks 15415 and 60015

    Science.gov (United States)

    Park, J.; Nyquist, L. E.; Bogard, D. D.; Garrison, D. H.; Shih, C.-Y.

    2010-01-01

    We re-analyzed 39Ar-40Ar ages of Apollo lunar highland samples 15415 and 60015, two ferroan anorthosites analyzed previously in the 1970 s, with a more detailed approach and with revised decay constants. From these samples we carefully prepared 100-200 mesh mineral separates for analysis at the Noble Gas Laboratory at NASA-Johnson Space Center. The Ar-39-Ar-40 age spectra for 15415 yielded an age of 3851 +/- 38 Ma with 33-99% of Ar39 release, roughly in agreement with previously reported Ar-Ar ages. For 60015, we obtained an age of 3584 +/- 152 Ma in 23-98% of Ar39 release, also in agreement with previously reported Ar-Ar ages of approximately 3.5 Ga. Highland anorthosites like these are believed by many to be the original crust of the moon, formed by plagioclase floatation atop a magma ocean, however the Ar-Ar ages of 15415 and 60015 are considerably younger than lunar crust formation. By contrast, recently recovered lunar anorthosites such as Dhofar 489, Dhofar 908, and Yamato 86032 yield older Ar-Ar ages, up to 4.35 Ga, much closer to time of formation of the lunar crust. It follows that the Ar-Ar ages of the Apollo samples must have been reset by secondary heating, and that this heating affected highland anorthosites at both the Apollo 15 and Apollo 16 landing sites but did not affect lunar highland meteorites. One obvious consideration is that while the Apollo samples were collected from the near side of the moon, these lunar meteorites are thought to have originated from the lunar far side

  19. Comagmatic granophyric granite in the Fish Canyon Tuff, Colorado: Implications for magma-chamber processes during a large ash-flow eruption

    Science.gov (United States)

    Lipman, P.; Dungan, M.; Bachmann, Olivier

    1997-01-01

    The 27.8 Ma Fish Canyon Tuff, a vast ash-flow sheet (??5000 km3) of uniform phenocryst-rich dacite, is representative of "monotonous intermediate" eruptions from a magma chamber that lacked compositional gradients. Sparse small fragments of comagmatic granophyre in late-erupted tuff and postcaldera lava, having mineral compositions indistinguishable from phenocrysts in the tuff and precaldera lava-like rocks, record complex events in the Fish Canyon chamber just prior to eruption. Sanidine phenocrysts in the granophyre preserve zoning evidence of mingling with andesitic magma, then shattering by decompression and volatile loss accompanying early Fish Canyon eruptions before overgrowth by granophyre. The textural and chemical disequilibria indicate that the eruption resulted from batholith-scale remobilization of a shallow subvolcanic chamber, contrary to previous interpretations of magma storage and phenocryst growth in the lower crust.

  20. 40Ar/39Ar dating of Daqingshan thrust

    Institute of Scientific and Technical Information of China (English)

    LIU Zhenghong; XU Zhongyuan; YANG Zhensheng

    2003-01-01

    The Daqingshan thrust system, to the south of the Shiguai Mesozoic basin, is a complex system of top-to- the-north thrusting tectonic sheets. The thrust system has a complicated evolution due to multi-stage thrusting. In order to date the thrusting events, syntectonic muscovite and biotite grains are respectively analyzed with normal 40Ar/39Ar dating and laser 40Ar/39Ar dating, which yield 2 isochron ages, i.e. 193.74 ± 3.88 Ma and 121.6 ± 1.6 Ma. These ages suggest that faults within the Daqingshan thrust system formed during 2 stages of thrusting, one the early Indosinian and the other the late Yanshanian. The isotopic dating is consistent with field geological relations. Indosinan deformation is evidenced by top-to-the-north thrusting, with the occurrence of a series of large-scale east-west trending thrust faults and folds, while the Yanshanian thrusting is characterized by top-to-the-NNW thrusting. It is superposed on and modifies early Indosinian thrust faults.

  1. Degraded dryland rehabilitation: boosting seedling survival using zeolitic tuff

    Science.gov (United States)

    Alhamad, Mohammad Noor; Alrbabah, Mohammad; Athamneh, Hana

    2016-04-01

    More than 90% of Jordan is broadly defined as rangelands. Most rangelands are located within the arid zone of the country. Extensive grazing occurs across much of the natural pastures resulting in serious environmental degradation of natural resources in these rangelands. Several programs were carried out for rangeland conservation and rehabilitation in the country. However, these programs face a major challenge of the low survival rate of transplanted shrub seedlings. Seeking innovative approaches to assure healthy establishment of seedling is a big challenge to achieve successful rehabilitation programs. Drought is considered one of the major problems in rehabilitation. Promoting survival and growth, using zeolitic tuff added to planting holes is suggested to be a possible solution. The experiment was conducted on a factorial arrangement within RCBD design. Two shrub species (Atriplex halimus, Atriplex nummularia) were transplanted into holes prepared with three levels of tuff treatments (mulching, mixing and control) under rainfed condition. The result showed insignificant effect of tuff on seedling survival percentage, when mixing tuff with plantation soil or adding tuff as mulch. Also, the two species showed similar survival percentages over two measured dates. However, mixing tuff with soil during hole preparation significantly enhanced seedling heights. Furthers, The Australian atriplex (Atriplex nummularia) species significantly grow higher than Atriplex halimus. The study results suggested that mixing zeoltic tuff with soil during transplantation of seedling is promising in improving the success of rangeland rehabilitation in dry areas in Jordan.

  2. New high-precision 40Ar/39Ar ages on Oligocene volcanic rocks of northwestern Kenya

    Science.gov (United States)

    Brown, Francis H.; Jicha, Brian R.

    2016-02-01

    New, high-precision 40Ar/39Ar ages from volcanic rocks in northwestern Kenya are provided for some areas of exposure in this remote area. We report seven 40Ar/39Ar ages generated from single crystal total fusion experiments on alkali feldspar separated from volcanic rocks in the Mogila, Songot, and Lokwanamur Ranges and the Gatome valley. A rhyolite from the lower part of the sequence in the Mogila Range yielded ages of 32.31 ± 0.06 Ma and 32.33 ± 0.07 Ma, and a rhyolite near the top of that sequence yielded 31.67 ± 0.04 Ma. A single sample from the Songot Range yielded an age of 32.49 ± 0.07 Ma, slightly older than the rocks collected from Mogila. In both ranges the early Oligocene rhyolites are underlain by basalts, as is also the case in the Labur Range. Ages of 25.95 ± 0.03 Ma, 25.91 ± 0.04 Ma, and 27.15 ± 0.03 Ma were measured on alkali feldspar from rhyolites from the Lokwanamur Range, and the nearby Gatome valley. All of these rocks are part of an episode of widespread volcanism in northwestern Kenya in the mid-to late Oligocene that is not currently known from the Ethiopian Rift Valley.

  3. Permian plate margin volcanism and tuffs in adjacent basins of west Gondwana: Age constraints and common characteristics

    Science.gov (United States)

    López-Gamundí, Oscar

    2006-12-01

    Increasing evidence of Permian volcanic activity along the South American portion of the Gondwana proto-Pacific margin has directed attention to its potential presence in the stratigraphic record of adjacent basins. In recent years, tuffaceous horizons have been identified in late Early Permian-through Middle Permian (280-260 Ma) sections of the Paraná Basin (Brazil, Paraguay, and Uruguay). Farther south and closer to the magmatic tract developed along the continental margin, in the San Rafael and Sauce Grande basins of Argentina, tuffs are present in the Early to Middle Permian section. This tuff-rich interval can be correlated with the appearance of widespread tuffs in the Karoo Basin. Although magmatic activity along the proto-Pacific plate margin was continuous during the Late Paleozoic, Choiyoi silicic volcanism along the Andean Cordillera and its equivalent in Patagonia peaked between the late Early Permian and Middle Permian, when extensive rhyolitic ignimbrites and consanguineous airborne tuffaceous material erupted in the northern Patagonian region. The San Rafael orogenic phase (SROP) interrupted sedimentation along the southwestern segment of the Gondwana margin (i.e., Frontal Cordillera, San Rafael Basin), induced cratonward thrusting (i.e., Ventana and Cape foldbelts), and triggered accelerated subsidence in the adjacent basins (Sauce Grande and Karoo) located inboard of the deformation front. This accelerated subsidence favored the preservation of tuffaceous horizons in the syntectonic successions. The age constraints and similarities in composition between the volcanics along the continental margin and the tuffaceous horizons in the San Rafael, Sauce Grande, Paraná, and Karoo basins strongly suggest a genetic linkage between the two episodes. Radiometric ages from tuffs in the San Rafael, Paraná, and Karoo basins indicate an intensely tuffaceous interval between 280 and 260 Ma.

  4. 40Ar-39Ar age of carbonatite-alkaline magmatism in Sung Valley, Maghalaya, India

    Indian Academy of Sciences (India)

    Jyotiranjan S Ray; Kanchan Pande

    2001-09-01

    40Ar-39Ar analyses of one alkali pyroxenite whole rock and two phlogopite separates of calcite carbonatites from the Sung Valley carbonatite-alkaline complex, which is believed to be a part of the Rajmahal-Bengal-Sylhet (RBS) ood basalt province, yielded indistinguishable plateau ages of 108.8 ± 2.0 Ma, 106:4 ± 1.3 Ma and 107.5 ± 1.4 Ma, respectively. The weighted mean of these ages, 107.2 ± 0.8 Ma, is the time of emplacement of this complex. This implies that Sung Valley complex and probably other such complexes in the Assam-Meghalaya Plateau postdate the main ood basalt event (i.e., the eruption of tholeiites) in the RBS province by ∼10 Ma.

  5. Integrated stratigraphy and 40Ar/39Ar chronology of the early to middle Miocene Upper Freshwater Molasse in western Bavaria (Germany)

    Science.gov (United States)

    Aziz, Hayfaa Abdul; Böhme, Madelaine; Rocholl, Alexander; Prieto, Jerome; Wijbrans, Jan R.; Bachtadse, Valerian; Ulbig, Albert

    2010-12-01

    A detailed integrated stratigraphic study (biostratigraphy and magnetostratigraphy) was carried out on five sections from the western part of the Bavarian Upper Freshwater Molasse of the North Alpine Foreland Basin (NAFB), greatly improving the chronostratigraphy of these sediments. The sections belong to the lithostratigraphic units Limnische Untere Serie (UL) and Fluviatile Untere Serie (UF) and contain 19 (mostly new) small-mammal bearing levels, significantly refining the local biostratigraphy. Radiometric ages obtained from glass shards from tuff horizons are used together with the biostratigraphic information for constructing and confirming the magnetostratigraphic correlation of the studied sections to the Astronomical Tuned Time Scale (ANTS04; Lourens et al. in Geologic Time Scale 2004, Cambridge University Press, 2004). This correlation implies that the UL lithostratigraphic unit corresponds to the latest Ottnangian and the Early Karpatian, whereas the UF corresponds to the Karpatian and the Early Badenian. This indicates that the Brackish- to Freshwater Molasse transition already occurred during the late Ottnangian. The pre-Riesian hiatus occurred in the latest Karpatian and lower Early Badenian in Eastern Bavaria and Bohemia and in the Late Karpatian and earliest Badenian in Western Bavaria. The geochemical and Ar-Ar data of volcanic ashes suggest that highly evolved silicic magmas from a single volcano or volcanic center, characterized by a uniform Nd isotopic composition, erupted repetitively over the course of at least 1.6 Myr. Three phases of eruptive activity were identified at 16.1 ± 0.2 Ma (Zahling-2), 15.6 ± 0.4 Ma (Krumbad), and 14.5 ± 0.2 Ma (Heilsberg, Hegau). The correlation of the local biostratigraphic zonation to the ANTS04 enables further the characterization of both the Ottnangian-Karpatian and Karpatian-Badenian boundaries in the NAFB by small-mammal biostratigraphy. According to these results the Ottnangian-Karpatian boundary is

  6. K-Ar dating, whole-rock and Sr-Nd isotope geochemistry of calc-alkaline volcanic rocks around the Gümüşhane area: implications for post-collisional volcanism in the Eastern Pontides, Northeast Turkey

    Science.gov (United States)

    Aslan, Zafer; Arslan, Mehmet; Temizel, İrfan; Kaygusuz, Abdullah

    2014-04-01

    Volcanic rocks from the Gümüşhane area in the southern part of the Eastern Pontides (NE Turkey) consist mainly of andesitic lava flows associated with tuffs, and rare basaltic dykes. The K-Ar whole-rock dating of these rocks range from 37.62 ± 3.33 Ma (Middle Eocene) to 30.02 ± 2.84 Ma (Early Oligocene) for the andesitic lava flows, but are 15.80 ± 1.71 Ma (Middle Miocene) for the basaltic dykes. Petrochemically, the volcanic rocks are dominantly medium-K calc-alkaline in composition and show enrichment of large ion lithophile elements, as well as depletion of high field strength elements, thus revealing that volcanic rocks evolved from a parental magmas derived from an enriched mantle source. Chondrite-normalized rare-earth element patterns of the volcanic rocks are concave upwards with low- to-medium enrichment (LaCN/LuCN = 3.39 to 12.56), thereby revealing clinopyroxene- and hornblende-dominated fractionations for andesitic-basaltic rocks and tuffs, respectively. The volcanic rocks have low initial 87Sr/86Sr ratios (0.70464 to 0.70494) and ɛNd(i) values (+1.11 to +3.08), with Nd-model ages (TDM) of 0.68 to 1.02 Ga, suggesting an enriched lithospheric mantle source of Proterozoic age. Trace element and isotopic data, as well as the modelling results, show that fractional crystallization and minor assimilation played an important role in the evolution of the volcanic rocks studied. The Eocene to Miocene volcanism in the region has resulted from lithospheric delamination and the associated convective thinning of the mantle, which led to the partial melting of the subduction-metasomatized lithospheric mantle.

  7. 40Ar/39Ar ages of the older eruptive units of Somma-Vesuvius volcano, Italy

    Science.gov (United States)

    Lanphere, M. A.; Calvert, A. T.; Scarpati, C.; Melluso, L.; Morra, V.; Perrotta, A.; Thornber, C.; Cioni, R.; Champion, D. E.

    2008-12-01

    40Ar/ 39Ar ages have been measured on the older major explosive eruptions of Somma-Vesuvius volcano in Italy. These eruptions all have pumice fall, and pyroclastic surge and flow deposits. The eruptive history of Somma-Vesuvius volcano has previously been based on uncalibrated 14C ages, mostly on carbon from paleosols, reported by Delibrias and others (1979) and Sigurdsson and others (1985). These assigned ages, plus measured 14C ages, calibrated 14C ages (denoted as 14C*) and 40Ar/ 39Ar ages (all in years) are: Mercato Tuff ~8500 years 14C=8263±29, 14C*=9250±49, 40Ar/ 39Ar=9155±461, 9541±460 Verde Tuff ~15000 years 14C=14420±130, 14C*=17200±380, 40Ar/ 39Ar=18456±302 Pomici di Base ~17000 years 14C=17229±398, 14C*=20360±139, 40Ar/ 39Ar=21759±306, 21568±328 The assigned ages are from Delibrias (1979). The 14C ages (Aleisso and others, 1971, 1973, 1974, 1978) use 1σ counting errors reported by laboratories. The uncertainty in calibrated 14C ages (above) are these reported uncertainties plus 1σ uncertainties of the calibration curves in IntCal04 (Reimer and others, 2004). The uncertainties in 40Ar/ 39Ar ages are 1σ errors. Pomici di Base and Mercato samples were analyzed twice. The weighted mean of plateau ages for Pomici di Base fall unit is 21,670 ± 224 years, and the weighted mean of isochron ages is 21,313 ± 408 years. The weighted mean of plateau ages for Mercato Tuff is 9348 ± 326 years, and the weighted mean of isochron ages is 9577 ± 332 years. The period of time from 0-12.4 ka used in calibrating 14C ages is based on dendrochronologically-dated tree ring samples. The calibration older than 12.4 ka is based on marine samples, primarily corals, and the marine calibrations are in dispute. The calibrated 14C ages above are based on IntCal04. Chui and others (2007) have presented another calibration based on fossil corals. In the younger part of their record, less than 30,000 years, the age difference averages less than 100 years. Aleisso and

  8. Evaluation of three Italian tuffs (Neapolitan Yellow Tuf, Tufo Romano and Tufo Etrusco) as compatible replacement stone for Römer tuff in Dutch built cultural heritage

    NARCIS (Netherlands)

    Nijland, T.G.; Hees, R.P.J. van; Bolondi, L.

    2010-01-01

    Rhenish tuffs from the volcanic Eifel region in Germany, in particular the so-called Römer tuff, are among the most prominent and voluminous natural stones in Dutch monuments. The Römer tuff has been used since Roman times, and was widely used again in Romanesque (and to a lesser extent Romano-Gothi

  9. Evaluation of three Italian tuffs (Neapolitan Yellow Tuf, Tufo Romano and Tufo Etrusco) as compatible replacement stone for Römer tuff in Dutch built cultural heritage

    NARCIS (Netherlands)

    Nijland, T.G.; Hees, R.P.J. van; Bolondi, L.

    2010-01-01

    Rhenish tuffs from the volcanic Eifel region in Germany, in particular the so-called Römer tuff, are among the most prominent and voluminous natural stones in Dutch monuments. The Römer tuff has been used since Roman times, and was widely used again in Romanesque (and to a lesser extent

  10. Photon Shielding Features of Quarry Tuff

    Directory of Open Access Journals (Sweden)

    Vega-Carrillo Hector Rene

    2017-01-01

    Full Text Available Cantera is a quarry tuff widely used in the building industry; in this work the shielding features of cantera were determined. The shielding characteristics were calculated using XCOM and MCNP5 codes for 0.03, 0.07, 0.1, 0.3, 0.662, 1, 2, and 3 MeV photons. With XCOM the mass interaction coefficients, and the total mass attenuation coefficients, were calculated. With the MCNP5 code a transmission experiment was modelled using a point-like source located 42 cm apart from a point-like detector. Between the source and the detector, cantera pieces with different thickness, ranging from 0 to 40 cm were included. The collided and uncollided photon fluence, the Kerma in air and the Ambient dose equivalent were estimated. With the uncollided fluence the linear attenuation coefficients were determined and compared with those calculated with XCOM. The linear attenuation coefficient for 0.662 MeV photons was compared with the coefficient measured with a NaI(Tl-based γ-ray spectrometer and a 137Cs source.

  11. Photon Shielding Features of Quarry Tuff

    Science.gov (United States)

    Vega-Carrillo, Hector Rene; Hernandez-Adame, Luis; Guzman-Garcia, Karen Arlete; Ortiz-Hernandez, Arturo Agustin; Rodriguez-Rodriguez, Jose Antonio; Juarez-Alvarado, Cesar Antonio

    2017-09-01

    Cantera is a quarry tuff widely used in the building industry; in this work the shielding features of cantera were determined. The shielding characteristics were calculated using XCOM and MCNP5 codes for 0.03, 0.07, 0.1, 0.3, 0.662, 1, 2, and 3 MeV photons. With XCOM the mass interaction coefficients, and the total mass attenuation coefficients, were calculated. With the MCNP5 code a transmission experiment was modelled using a point-like source located 42 cm apart from a point-like detector. Between the source and the detector, cantera pieces with different thickness, ranging from 0 to 40 cm were included. The collided and uncollided photon fluence, the Kerma in air and the Ambient dose equivalent were estimated. With the uncollided fluence the linear attenuation coefficients were determined and compared with those calculated with XCOM. The linear attenuation coefficient for 0.662 MeV photons was compared with the coefficient measured with a NaI(Tl)-based γ-ray spectrometer and a 137Cs source.

  12. Transport properties of Topopah Spring tuff

    Energy Technology Data Exchange (ETDEWEB)

    Lin, W.; Daily, W.

    1984-10-01

    Electrical resistivity, ultrasonic P-waves velocity, and water permeability were measured simultaneously on both intact and fractured Topopah Spring tuff samples at a confining pressure of 5.0 MPa, pore pressures to 2.5 MPa, and temperatures to 140{sup 0}C. The tested samples were subjected to three dehydration and rehydration cycles. The dehydrations were accomplished at a temperature of 140{sup 0}C, and the rehydrations were accomplished at various combinations of temperature and pore pressures so that the wetting fluid was either liquid water, steam or both. The electrical resistivity measurements indicate that for the intact sample, the drying and resaturation took place fairly uniformly throughout the sample. On the other hand, for the fractured sample, the drying and resaturation was spatially quite nonuniform. When samples had been subjected to 5 MPa of confining pressure and 140{sup 0}C for several weeks, a gradual monotonic drift in resistivity was measured (decreasing resistivity when dry; increasing resistivity when wet). This may be the result of either minerological changes or grain boundary movement. In any case, the phenomenon may have important consequences on long term repository performance, and should be studied further. The permeability of the intact sample was independent of temperature, dehydration and rehydration cycles, and time. The permeability of the fractured sample, initially dominated by the fracture, decreased by about one order of magnitude after each dehydration and rehydration cycle. 11 references, 12 figures, 3 tables.

  13. 40Ar/39Ar and K/Ar dating of low grade metamorphism: examples on metabasites from Central Chile

    Science.gov (United States)

    Aguirre, L.; Feraud, G.; Fuentes, F.; Delbar, M.; Morata, D.

    2003-04-01

    Dating low to very low-grade burial metamorphic assemblages is often difficult because of (1) few mineral phases compositionally suitable to apply the 40Ar/39Ar and K-Ar methods, and (2) small amount in which these phases are commonly found. K-feldspar adularia, sericitic mica, and celadonite are the best known K-bearing secondary minerals. We present some successful attempts to analyse two distinct secondary phases from a same volcanic formation that allow to test the validity of the measured ages. These ages have been also compared with the crystallisation age of the volcanic rocks in which the secondary phases were lately developed. Adularia and sericite were selected from basic lava flows from a 3 to 13 km thick Cretaceous sequence from the Coastal Range of central Chile, at two different locations: the Bustamante Hill (west from Santiago), and the Cordón de Chacana, c. 80 km further north. Adularia came from a low-variance assemblage with pumpellyite, chlorite and low-albite contained in amygdules whereas sericite was present in milky-white strongly sericitized plagioclase crystals. While small clusters of rare fresh plagioclase grains from lava flows from Bustamante and Chacana displayed concordant plateau ages 119.4 ± 2.4 (2 sigma) and 118.7 ± 0.6 Ma, respectively, the adularia from the same formations gave sensibly younger ages around 94 Ma (high temperature steps), and 96.8 ± 0.2 Ma (plateau age) in Bustamante and Chacana, respectively. Sericite ages were measured in situ into single crystals of strongly transformed plagioclases. The relative proportion of sericite and plagioclase corresponding to each degasing step was monitored by measuring the Ca/K ratio (deduced from 37ArCa/39Ar_K). While intermediate ages were measured on some sericite of both sites (corresponding to a variable but permanent contribution of plagioclase on each step), a plateau age of 97.0 ± 1.6 Ma (concordant with adularia) could be obtained on a strongly sericitized plagioclase

  14. The Effects of Variable Welding and Devitrification on the Magnetic Fabric of Ash Flow Tuffs: An AMS and AARM Study of the Oligocene Carpenter Ridge Tuff, San Juan Mountains, Colorado

    Science.gov (United States)

    Mason, S. N.; Geissman, J. W.

    2011-12-01

    Anisotropy of magnetic susceptibility (AMS) data have been shown to be a powerful means of estimating the transport direction, and thus inferred source region, for several large volume, regionally extensive ash-flow tuffs (ignimbrites). Anisotropy of anhysteretic remanent magnetization (AARM) data have, on the other hand, corroborated inferred controls by different assemblages of magnetic particles on magnetic fabrics. For ash-flow tuffs, the effects of variable degrees of welding and subsequent devitrification on the magnetic fabric of these pyroclastic deposits are not well understood. We have collected magnetic fabric data from a continuously exposed sequence of outflow facies of the ca. 27.55 Ma Carpenter Ridge Tuff (CRT), one of the major large volume ash-flow tuffs of the Southern Rocky Mountain Volcanic Field, southwest Colorado, about 3 km east of Buffalo Pass on Colorado Highway 114. The CRT, a compound cooling unit, is of reverse polarity (although there is considerable internal variability in direction through the section) and was sourced from the Bachelor Caldera, southwest of the sample locality. Some 21 total independently oriented samples, as very large oriented blocks, were collected in traverse fashion through most of the lowermost cooling unit of the tuff, and an additional ten block samples were collected from the moderately welded and completely devitrified third cooling unit. At least ten and often 20 to 30 discrete specimens were prepared for analyses from each block. Orientation of AMS principal axes are internally consistent at the oriented sample level and, overall, throughout the section sampled, and imply a west to east transport orientation in this area, consistent with several other sampling sites in the CRT in the northeast part of the Southern Rocky Mountain Volcanic Field. AARM data at the block sample level are usually more dispersed. All of the samples have positive T values, implying strong foliations. The degree of anisotropy (P

  15. Testing the Consistency of Diffusion Modelling in Multiple Crystal Phases: A Case Study from the Bishop Tuff, California

    Science.gov (United States)

    Morgan, D. J.; Chamberlain, K. J.; Wilson, C. J. N.

    2014-12-01

    Diffusion modelling of elemental gradients across compositional zones within crystals is frequently used to investigate timescales of various magmatic processes. In most cases, however, only a single crystal phase is used for this modelling. The ~0.76 Ma Bishop Tuff (Long Valley, eastern California) in later parts of its eruptive sequence has zoned orthopyroxene, quartz and sanidine. It thus provides an unusual opportunity to compare the modelled timescales from each phase, and assess the limitations of single-phase diffusion modelling in lower-temperature, rhyolitic volcanic systems. The presence of a late-stage compositionally distinct melt (the 'bright-rim' melt) mixing into the lower parts of the Bishop magma chamber has been noted by many authors [e.g. Wark et al. 2007, Geology 35, 235; Roberge et al. 2013, CMP 165, 237; Chamberlain et al. 2014, J Petrol 55, 395] in later-erupted material discharged from vents along the northern ring fracture of the caldera. Here we present the results of 1D diffusion modelling of Ba and Sr in sanidine, Ti in quartz and Fe-Mg interdiffusion in orthopyroxene in samples from later-erupted ignimbrite packages in the tuff. Timescales from diffusion modelling of Fe-Mg interdiffusion in orthopyroxene are Bishop Tuff eruption. We highlight the importance of having a good understanding of the assumptions made and uncertainties in diffusion coefficients when undertaking such modelling, especially in examples where only one phase is available for diffusion modelling.

  16. Fossil Fumarolic Pipes in the Tshirege Member of the Bandelier Tuff

    Science.gov (United States)

    Caporuscio, F. A.; Gardner, J. N.; Schultz-Fellenz, E. S.; Lewis, C. J.; Kelley, R. E.; Greene, M. K.

    2008-12-01

    The geology exposed on the walls (3000 m2) of a large pit in the Bandelier Tuff gives unparalled 3-D exposures of many structures that develop in thick deposits of pyroclastic flows. Subunits of the Tshirege Member of the Bandelier Tuff, erupted at 1.25 Ma, exhibit distinct rubble-filled fissures, or pipes, that range in width from centimeters to meters. The fissures exhibit zones of fines depletion, indurated wall structures, upward flaring geometry to the top of the host unit, and fissure-filling blocks of the host unit as well as rubble derived from overlying pyroclastic units. In the units directly overlying the fissures are intensely fractured in- place rubble zones. Additionally, the fissures appear to be regularly spaced at about 4.5 or 7.5 meters apart. All these field characteristics are indicative of fumarolic activity. Petrographic, XRD, and XRF studies of distinct pipes were done to investigate the physical changes imparted to the tuff by the fumarolic activity. Petrography indicates that the pipe wall and pipe centers are enriched in tridymite and potassium feldspar. These minerals fill the void spaces in pumice and groundmass void spaces of the pipe wall rocks, imparting the indurated nature. Other mineralogic indicators of late stage fumarolic gas phase deposition are optically continuous, feathery overgrowths on sanidine phenocrysts and scapolite in pipe centers. Also, clinopyroxenes in the overlying rubble zones have oxidized rims indicative of highly oxidizing gases emanating from the fumarolic pipes below. XRD analyses of rubble zones above the pipes show decreased cristobalite (4 wt. %) and feldspar (9 wt. %), and increased clay contents (12 to 26 wt. %). This change from feldspar and cristobalite to clay suggests an acidic nature of fumarolic gases. XRF analyses show trends in bulk chemistry consistent with fumarolic data from other tuffs. The data indicate that there have been systematic changes in the geochemistry of the fissures readily

  17. Ar-Ar_Redux: rigorous error propagation of 40Ar/39Ar data, including covariances

    Science.gov (United States)

    Vermeesch, P.

    2015-12-01

    Rigorous data reduction and error propagation algorithms are needed to realise Earthtime's objective to improve the interlaboratory accuracy of 40Ar/39Ar dating to better than 1% and thereby facilitate the comparison and combination of the K-Ar and U-Pb chronometers. Ar-Ar_Redux is a new data reduction protocol and software program for 40Ar/39Ar geochronology which takes into account two previously underappreciated aspects of the method: 1. 40Ar/39Ar measurements are compositional dataIn its simplest form, the 40Ar/39Ar age equation can be written as: t = log(1+J [40Ar/39Ar-298.5636Ar/39Ar])/λ = log(1 + JR)/λ Where λ is the 40K decay constant and J is the irradiation parameter. The age t does not depend on the absolute abundances of the three argon isotopes but only on their relative ratios. Thus, the 36Ar, 39Ar and 40Ar abundances can be normalised to unity and plotted on a ternary diagram or 'simplex'. Argon isotopic data are therefore subject to the peculiar mathematics of 'compositional data', sensu Aitchison (1986, The Statistical Analysis of Compositional Data, Chapman & Hall). 2. Correlated errors are pervasive throughout the 40Ar/39Ar methodCurrent data reduction protocols for 40Ar/39Ar geochronology propagate the age uncertainty as follows: σ2(t) = [J2 σ2(R) + R2 σ2(J)] / [λ2 (1 + R J)], which implies zero covariance between R and J. In reality, however, significant error correlations are found in every step of the 40Ar/39Ar data acquisition and processing, in both single and multi collector instruments, during blank, interference and decay corrections, age calculation etc. Ar-Ar_Redux revisits every aspect of the 40Ar/39Ar method by casting the raw mass spectrometer data into a contingency table of logratios, which automatically keeps track of all covariances in a compositional context. Application of the method to real data reveals strong correlations (r2 of up to 0.9) between age measurements within a single irradiation batch. Propertly taking

  18. 40Ar-39Ar age of a lava flow from the Bhimashankar Formation, Giravali Ghat, Deccan Traps

    Indian Academy of Sciences (India)

    Kanchan Pande; S K Pattanayak; K V Subbarao; P Navaneethakrishnan; T R Venkatesan

    2004-12-01

    We report here a 40Ar-39Ar age of 66.0 ± 0.9Ma (2 ) for a reversely magnetised tholeiitic lava flow from the Bhimashankar Formation (Fm.), Giravali Ghat, western Deccan province, India. This age is consistent with the view that the 1.8–2km thick bottom part of the exposed basalt flow sequence in the Western Ghats was extruded very close to 67.4 Ma.

  19. Exhumation history of the NW Indian Himalaya revealed by fission track and 40Ar/39Ar ages

    Science.gov (United States)

    Schlup, M.; Steck, A.; Carter, A.; Cosca, M.; Epard, J.-L.; Hunziker, J.

    2011-01-01

    New fission track and Ar/Ar geochronological data provide time constraints on the exhumation history of the Himalayan nappes in the Mandi (Beas valley) - Tso Morari transect of the NW Indian Himalaya. Results from this and previous studies suggest that the SW-directed North Himalayan nappes were emplaced by detachment from the underthrusted upper Indian crust by 55. Ma and metamorphosed by ca. 48-40. Ma. The nappe stack was subsequently exhumed to shallow upper crustal depths (Elsevier Ltd.

  20. Exhumation history of the NW Indian Himalaya revealed by fission track and 40Ar/39Ar ages

    Science.gov (United States)

    Schlup, Micha; Steck, Albrecht; Carter, Andrew; Cosca, Michael; Epard, Jean-Luc; Hunziker, Johannes

    2011-01-01

    New fission track and Ar/Ar geochronological data provide time constraints on the exhumation history of the Himalayan nappes in the Mandi (Beas valley) — Tso Morari transect of the NW Indian Himalaya. Results from this and previous studies suggest that the SW-directed North Himalayan nappes were emplaced by detachment from the underthrusted upper Indian crust by 55 Ma and metamorphosed by ca. 48–40 Ma. The nappe stack was subsequently exhumed to shallow upper crustal depths (

  1. Compositional zoning of the bishop tuff

    Science.gov (United States)

    Hildreth, W.; Wilson, C.J.N.

    2007-01-01

    Compositional data for >400 pumice clasts, organized according to eruptive sequence, crystal content, and texture, provide new perspectives on eruption and pre-eruptive evolution of the >4600 km3 of zoned rhyolitic magma ejected as the BishopTuff during formation of Long Valley caldera. Proportions and compositions of different pumice types are given for each ignimbrite package and for the intercalated plinian pumice-fall layers that erupted synchronously. Although withdrawal of the zoned magma was less systematic than previously realized, the overall sequence displays trends toward greater proportions of less evolved pumice, more crystals (0-5 24 wt %), and higher FeTi-oxide temperatures (714-818??C). No significant hiatus took place during the 6 day eruption of the BishopTuff, nearly all of which issued from an integrated, zoned, unitary reservoir. Shortly before eruption, however, the zoned melt-dominant portion of the chamber was invaded by batches of disparate lower-silica rhyolite magma, poorer in crystals than most of the resident magma but slightly hotter and richer in Ba, Sr, andTi. Interaction with resident magma at the deepest levels tapped promoted growth ofTi-rich rims on quartz, Ba-rich rims on sanidine, and entrapment of near-rim melt inclusions relatively enriched in Ba and CO2.Varied amounts of mingling, even in higher parts of the chamber, led to the dark gray and swirly crystal-poor pumices sparsely present in all ashflow packages. As shown by FeTi-oxide geothermometry, the zoned rhyolitic chamber was hottest where crystal-richest, rendering any model of solidification fronts at the walls or roof unlikely.The main compositional gradient (75-195 ppm Rb; 0.8-2.2 ppm Ta; 71-154 ppm Zr; 0.40-1.73% FeO*) existed in the melt, prior to crystallization of the phenocryst suite observed, which included zircon as much as 100 kyr older than the eruption.The compositions of crystals, though themselves largely unzoned, generally reflect magma temperature and

  2. Correlation of the oldest Toba Tuff to sediments in the central Indian Ocean Basin

    Indian Academy of Sciences (India)

    J N Pattan; M Shyam Prasad; E V S S K Babu

    2010-08-01

    We have identified an ash layer in association with Australasian microtektites of ∼0.77Ma old in two sediment cores which are ∼450 km apart in the central Indian Ocean Basin (CIOB). Morphology and chemical composition of glass shards and associated microtektites have been used to trace their provenance. In ODP site 758 from Ninetyeast Ridge, ash layer-D (13 cm thick, 0.73–0.75 Ma) and layer-E (5 cm thick, 0.77–0.78 Ma) were previously correlated to the oldest Toba Tuff (OTT) eruptions of the Toba caldera, Sumatra. In this investigation, we found tephra ∼3100 km to the southwest of Toba caldera that is chemically identical to layer D of ODP site 758 and ash in the South China Sea correlated to the OTT. Layer E is not present in the CIOB or other ocean basins. The occurrence of tephra correlating to layer D suggests a widespread distribution of OTT tephra (∼3.6 × 107 km2), an ash volume of at least ∼1800 km3, a total OTT volume of 2300 km3, and classification of the OTT eruption as a super-eruption.

  3. Cooling age of Dabie orogen, China, determined by 40Ar-39Ar and fission track techniques

    Institute of Scientific and Technical Information of China (English)

    陈江峰; 谢智; 刘顺生; 李学明; K.A.Foland

    1995-01-01

    Based on 40Ar-39Ar results of hornblendes and biotites and fission track dating results of apatites separated from the same rock samples, cooling history of rocks from Dabie orogen is discussed. Rocks from both Southern Dabie Terrain (SDT) and Northern Dabie Terrain (NDT) have an early fast cooling followed by a more recent slow cooling. Rocks from SDT cooled to about 540℃ at about 190 Ma B.C., while rocks from NDT cooled to about 540℃ at 125 Ma B C. Until about 110-120 Ma B.C., rocks from both SDT and NDT cooled to about 100℃. This suggests that a relative movement among rocks from SDT, NDT and ul-Ira-high pressure metamorphic rocks exis-ts before 110-120 Ma B.C.

  4. 40Ar/ 39Ar systematics and argon diffusion in amber: implications for ancient earth atmospheres

    Science.gov (United States)

    Landis, G. P.; Snee, L. W.

    1991-12-01

    Argon isotope data indicate retained argon in bulk amber (matrix gas) is radiogenic [ 40Ar/ 39Ar ≃32o] than the much more abundant surface absorbed argon [ 40Ar/ 39Ar ≃295.5]. Neutron-induced 39Ar is retained in amber during heating experiments to 150° -250°C, with no evidence of recoiled 39Ar found after irradiation. A maximum permissible volume diffusion coefficient of argon in amber (at ambient temperature) D≤1.5 x 10 -17 cm 2S -1 is calculated from 39Ar retention. 40Ar/ 39Ar age calculations indicate Dominican Republic amber is ≃ 45 Ma and North Dakota amber is ≃ 89 Ma, both at least reasonable ages for the amber based upon stratigraphic and paleontological constraints and upon the small amount of radiogenic 40Ar. To date, over 300 gas analyses of ambers and resins of Cretaceous to Recent age that are geographically distributed among fifteen noted world locations identify mixtures of gases in different sites within amber (Berner and Landis, 1988). The presence of multiple mixing trends between compositionally distinct end-members gases within the same sample and evidence for retained radiogenic argon within the amber argue persuasivley against rapid exchange by diffusion of amber-contained gases with moder air. Only gas in primary bubbles entrapped between successive flows of tree resin has been interpreted as original "ancient air", which is an O 2-rich end-member gas with air-like N 2/Ar ratios. Gas analyses of these primary bubbles indicate atmospheric O 2 levels in the Late Cretaceous of ≃ 35%, and that atmospheric O 2 dropped by early Tertiary time to near a present atmospheric level of 21% O 2. A very low argon diffusion coefficient in amber persuasively argues for a gas in primary bubbles trapped in amber being ancient air (possibly modified only by O 2 reaction with amber).

  5. The Menengai Tuff: A 36 ka widespread tephra and its chronological relevance to Late Pleistocene human evolution in East Africa

    Science.gov (United States)

    Blegen, Nick; Brown, Francis H.; Jicha, Brian R.; Binetti, Katie M.; Faith, J. Tyler; Ferraro, Joseph V.; Gathogo, Patrick N.; Richardson, Jonathan L.; Tryon, Christian A.

    2016-11-01

    The East African Rift preserves the world's richest Middle and Late Pleistocene (∼780-12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40Ar/39Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution.

  6. Deciphering the Paleoproterozoic cooling history of the northeastern Trans-Hudson Orogen, Baffin Island (Canada), using 40Ar/39Ar step-heating and UV laser thermochronology

    Science.gov (United States)

    Skipton, D. R.; Schneider, D. A.; Kellett, D. A.; Joyce, N. L.

    2017-07-01

    The previously unstudied cooling and exhumation history of mid-crustal rocks exposed on southeastern Baffin Island (Canada) provides new insights into the post-orogenic evolution of the Paleoproterozoic Trans-Hudson Orogen (THO). New 40Ar/39Ar step-heat analyses of biotite, muscovite and phlogopite and core-to-rim intra-grain 40Ar/39Ar analyses of muscovite have a range of apparent ages compatible with slow regional cooling following peak metamorphism. Twenty-nine amphibolite- to granulite-facies rocks were dated using the 40Ar/39Ar step-heating laser (CO2) method. 40Ar/39Ar spot analyses were performed across muscovite grains from three samples using an ultraviolet (UV) laser to investigate intra-grain 40Ar/39Ar age variations. Step-heating apparent ages range from ca. 1788-1622 Ma for biotite, 1720-1630 Ma for phlogopite and 1729-1657 Ma for muscovite. UV spot 40Ar/39Ar analyses in the three muscovite grains range from ca. 1661-1640 Ma, 1675-1645 Ma and 1680-1652 Ma, with core-to-rim apparent age gradients of 20-30 Myr. Previous studies resolved peak metamorphism in this region to between ca. 1860 and 1820 Ma and identified late- to post-THO zircon and monazite populations at ca. 1800-1750 Ma. Numerical diffusion models for Ar in muscovite were conducted to test different Proterozoic cooling and exhumation scenarios. Comparisons with our 40Ar/39Ar ages attest to cooling rates of 1-2 °C/Myr following peak metamorphism and 1.5-2.5 °C/Myr after ca. 1740 Ma. Anomalously old apparent 40Ar/39Ar ages, in cases equivalent to U-Pb zircon rim and monazite ages, likely result from incorporation of excess Ar. The results suggest that mid-crustal rocks on southeastern Baffin Island remained hotter than 420-450 °C for 150-200 Myr after peak metamorphism, with subsequent slow cooling and denudation rates that are typical of Proterozoic orogens. The apparent absence of orogenic collapse implies that, despite high temperatures and estimated maximum crustal thicknesses

  7. Ar-Ar geochronology of Late Mesozoic volcanic rocks from the Yanji area,NE China and tectonic implications

    Institute of Scientific and Technical Information of China (English)

    LI ChaoWen; GUO Feng; FAN WeiMing; GAO XiaoFeng

    2007-01-01

    Ar-Ar dating results of late Mesozoic-Cenozoic volcanic rocks from the Yanji area, NE China provide a new volcano-sedimentary stratigraphic framework. The previously defined "Triassic-Jurassic" volcanic rocks(including those from Sanxianling, Tuntianying, Tianqiaoling and Jingouling Fms.)were erupted during 118-106Ma,corresponding to Early Cretaceous. The new eruption age span is slightly younger than the main stage(130-120 Ma)of the extensive magmatism in the eastern Central Asian Orogenic Belt and its adjacent regions. Subduction-related adakites occurring in the previously defined Quanshuicun Fm. Were extruded at ca.55 Ma. Based on these new Ar-Ar ages, the late Mesozoic to Palaeocene volcano-sedimentary sequences is rebuilt as:Tuopangou Fm., Sanxianling/Tuntianying Fm.(118-115 Ma),Malugou/Tianqiaoling Fm.(K1),Huoshanyan/Jingouling Fm.(108-106 Ma),Changcai Fm.(K2),Quanshuicun Fm.(~55 Ma)and Dalazi Fm. Our results suggest that subduction of the Palaeo-Pacific Ocean beneath the East Asian continental margin occurred during 106to 55 Ma. Consistent with the paleomagnetic observations and magmatic records which indicated that the Izanagi-Farallon ridge subduction beneath the southwestern Japan took place during 95-65 Ma.

  8. Ar-Ar geochronology of Late Mesozoic volcanic rocks from the Yanji area, NE China and tectonic implications

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ar-Ar dating results of late Mesozoic-Cenozoic volcanic rocks from the Yanji area, NE China provide a new volcano-sedimentary stratigraphic framework. The previously defined “Triassic-Jurassic” volcanic rocks (including those from Sanxianling, Tuntianying, Tianqiaoling and Jingouling Fms.) were erupted during 118―106 Ma, corresponding to Early Cretaceous. The new eruption age span is slightly younger than the main stage (130―120 Ma) of the extensive magmatism in the eastern Central Asian Orogenic Belt and its adjacent regions. Subduction-related adakites occurring in the previously defined Quanshuicun Fm. were extruded at ca. 55 Ma. Based on these new Ar-Ar ages, the late Mesozoic to Palaeocene volcano-sedimentary sequences is rebuilt as: Tuopangou Fm., Sanxianling/Tuntianying Fm. (118―115 Ma), Malugou/Tianqiaoling Fm. (K1), Huoshanyan/Jingouling Fm. (108―106 Ma), Changcai Fm. (K2), Quanshuicun Fm. (~55 Ma) and Dalazi Fm. Our results suggest that subduction of the Pa- laeo-Pacific Ocean beneath the East Asian continental margin occurred during 106 to 55 Ma, consistent with the paleomagnetic observations and magmatic records which indicated that the Izanagi-Farallon ridge subduction beneath the southwestern Japan took place during 95―65 Ma.

  9. Spatial evaluation of Ar-systematics in rocks from the British Channel Islands: a UV laserprobe Ar/Ar study of excess 40Ar

    Science.gov (United States)

    Schwenzer, S. P.; Sherlock, S.; Kelley, S. P.

    2010-12-01

    The Ar-Ar method is a powerful tool for constraining thermal histories of metamorphic and plutonic rocks, most commonly undertaken on potassium rich mineral separates rather than whole rocks. While this approach usually yields reasonable thermal histories, it is rarely as precise as dating volcanics, and such rocks are also frequently contaminated by excess argon, artificially elevating the Ar-Ar ages. Understanding the evolution of excess argon represents a challenge; whilst it is possible to discern the ‘sink’ as the host mineral now contaminated by excess argon, examining the ‘source’ and ‘transport’ mechanism is more challenging. The approach we have taken here is to combine measurements of potassium rich and potassium poor minerals to understand the argon reservoirs and argon transfer between minerals, grain boundaries and fluids. Considering the system as a whole provides a method for understanding the complete history of the rock and thus assessing any interactions which may impact on the interpretation of ages and thermal history [Kelley, 2002, Chem. Geol. 188]. Here we have studied a series of plutonic and metamorphic basement samples from the British Channel Islands with different ages and post-emplacement histories, namely Icart Gneiss, Perelle Quartz Diorite, L’Ancresse Granodiorite, and Bordeaux Diorite. The formation age of Icart Gneiss is ~2000 Ma [D’Lemos et al., 1990, Geol. Soc. Spec. Pub. 51]. Ar-Ar ages of hornblendes and biotites from quartz diorites on Guernsey and Sark range between 606 and 596 Ma [Dallmeyer et al. 1991, J. Geol. Soc. London 148], whilst U-Pb zircon ages are in the range 710 to 613 Ma [Dallmeyer et al. 1991; Samson & D’Lemos 1998, J. Geol. Soc. London 155; Miller et al. 1999, Tectonophysics 132]. Detailed petrograpic (microscope, electron microprobe) investigations established the crystallization and deformation history of the samples, and revealed that post-magmatic alteration is unevenly distributed. This

  10. Geochemistry and zircon U-Pb geochronology of the rhyolitic tuff on Port Island, Hong Kong: Implications for early Cretaceous tectonic setting

    Directory of Open Access Journals (Sweden)

    Longlong Zhao

    2017-05-01

    Full Text Available Early Cretaceous rhyolitic tuffs, widely distributed on Port Island, provide insights into the volcanism and tectonic setting of Hong Kong. In this paper we present petrological, geochronological and geochemical data of the rhyolitic tuff to constrain the diagenesis age and petrogenesis of the rocks, tectonic setting and early Cretaceous volcanism of Hong Kong. The first geochronological data show that the zircons in the volcanic rocks have U-Pb age of 141.1–139.5 Ma, which reveals that the rhyolitic tuff on Port Island was formed in the early Cretaceous (K1. Geochemically, these acid rocks, which are enriched in large ion lithophile elements (LILEs and light rare earth elements (LREEs, and depleted in high field strength elements (HFSEs, belong to the high K calc-alkaline to shoshonite series with strongly-peraluminous characteristic. The geochemical analyses suggest that the volcanic rocks were derived from deep melting in the continental crust caused by basaltic magma underplating. Based on the geochemical analysis and previous studies, we concluded that the rhyolitic tuffs on Port Island were formed in a back-arc extension setting in response to the subduction of the Paleo-Pacific Plate beneath the Eurasian Plate.

  11. Mobility of Metal Tracers in Unsaturated Tuffs of Busted Butte

    Science.gov (United States)

    Groffman, A. R.

    2001-12-01

    A complex tracer mixture was injected continuously for over two years into a 10 m x 10 m x 7 m block of unsaturated tuff as part of the Busted Butte unsaturated-zone tracer test at Yucca Mountain. The test was designed to measure tracer transport within the Topopah Springs and Calico Hills tuffs, units that occur between the potential high-level nuclear waste repository at Yucca Mountain and the water table below. The mixture included nonreactive (Br, I, and fluorinated benzoic acids (FBAs)) and reactive tracers (Li, Ce, Sm, Ni, Co, and Mn). Bromide, I, FBAs, and Li were detected during the test on absorbent pads emplaced in a series of solute collection boreholes located beneath the injectors but the more strongly sorbing metals did not reach the collection boreholes during this period. To determine the distribution and mobility of these metals, tracer constituents were extracted from tuff samples collected during overcoring and mineback of the test block. Tracers were extracted from the tuff samples by leaching with a 5% nitric acid solution for metals and a bicarbonate-carbonate buffer for anions. Results from the overcore sample suite show that metals have migrated through the tuff in the region adjacent to and immediately below the tracer injectors. Consistent with laboratory sorption measurements and observed breakthrough in the collection boreholes, rock analyses showed that Li is the most mobile of the metals. Co and Ni behave similarly, traveling tens of cm from the injection sites, while Sm and Ce moved far less, possibly due to precipitation reactions in addition to sorption. Determination of Mn transport is complicated by high background concentrations in the tuff; additional background samples are currently being evaluated. As expected, our rock analyses show that the nonreactive tracers Br and FBAs have moved beyond the overcore region, corroborating results from collection boreholes.

  12. Pyritic ash-flow tuff, Yucca Mountain, Nevada -- A discussion

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Larson, L.T.; Noble, D.C. [Univ. of Nevada, Reno, NV (United States)

    1994-12-31

    Textural and mineralogic evidence exists for at least one episode of widespread hydrothermal alteration of volcanic rocks deep in Yucca Mountain, Nevada. Despite this evidence, Castor et al. infer that most of the pyrite found in tuffs at Yucca Mountain was introduced as ejecta (lithic fragments) incorporated during the eruptions of the tuffs, rather than by in-situ hydrothermal activity. Their conclusions appear to be based on their observation that most of the pyrite resides in unaltered to variably altered and veined lithic fragments, whereas pyrite-bearing veins are absent in the tuff matrix, titanomagnetite and mafic phenocrysts in the matrix are generally not replaced by pyrite, and feldspar phenocrysts in the pyritic tuff matrix are generally unaltered. Castor et al. dismiss the much smaller quantities of pyrite disseminated in the tuff matrix, including relatively rare pyritized hornblende and biotite grains, as xenolithic as well. The pyritic tuffs belong to large-volume, subalkaline rhyolite ash-flow units (ca. > 150 to 250 km{sup 3} each). The interpretation of Castor et al. has broad implications for the temperature, fO{sub 2} and fS{sub 2} of major ash flow eruptions. Pyrite origin also bears on the nature of past fluid flow and water-rock reactions at Yucca Mountain, which in turn are important factors in assessing the potential for currently undiscovered mineral resources in the area of the proposed nuclear waste repository. We have studied core and cuttings from the same drill holes studied by Castor et al., as well as other drill holes. It is our contention that the inconsistent lateral and stratigraphic distribution of the pyrite, textural features of the pyrite, and phase stability considerations are incompatible with the {open_quotes}lithic{close_quotes} origin of Castor et al., and are more reasonably explained by in-situ formation from hydrothermal fluids containing low, but geochemically significant, concentrations of reduced sulfur.

  13. Biogas cleaning and upgrading with natural zeolites from tuffs.

    Science.gov (United States)

    Paolini, Valerio; Petracchini, Francesco; Guerriero, Ettore; Bencini, Alessandro; Drigo, Serena

    2016-01-01

    CO2 adsorption on synthetic zeolites has become a consolidated approach for biogas upgrading to biomethane. As an alternative to synthetic zeolites, tuff waste from building industry was investigated in this study: indeed, this material is available at a low price and contains a high fraction of natural zeolites. A selective adsorption of CO2 and H2S towards CH4 was confirmed, allowing to obtain a high-purity biomethane (CO2 zeolites from tuffs may successfully be used in a pressure/vacuum swing adsorption process.

  14. Uniaxial strength testing of Calico Hills tuff, Yucca Mountain: Preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qizhi; Schultz, R.A. [Univ. of Nevada, Reno, NV (United States)

    1994-12-31

    A detailed investigation of the strength properties of Calico Hills tuff was undertaken to further characterize the behavior of this unit. Uniaxial compression test on 47 samples of massive and reworked tuff show a dependence of peak strength and Young`s modulus on the total porosity, and thus on the geologic history of the Calico Hills tuff. Controlled deformation of test specimens documents axial splitting and faulting as failure mechanisms in the post-peak region of these brittle tuffs.

  15. Jurassic cooling ages in Paleozoic to early Mesozoic granitoids of northeastern Patagonia: 40Ar/39Ar, 40K-40Ar mica and U-Pb zircon evidence

    Science.gov (United States)

    Martínez Dopico, Carmen I.; Tohver, Eric; López de Luchi, Mónica G.; Wemmer, Klaus; Rapalini, Augusto E.; Cawood, Peter A.

    2016-12-01

    U-Pb SHRIMP zircon crystallization ages and Ar-Ar and K-Ar mica cooling ages for basement rocks of the Yaminué and Nahuel Niyeu areas in northeastern Patagonia are presented. Granitoids that cover the time span from Ordovician to Early Triassic constitute the main outcrops of the western sector of the Yaminué block. The southern Yaminué Metaigneous Complex comprises highly deformed Ordovician and Permian granitoids crosscut by undeformed leucogranite dikes (U-Pb SHRIMP zircon age of 254 ± 2 Ma). Mica separates from highly deformed granitoids from the southern sector yielded an Ar-Ar muscovite age of 182 ± 3 Ma and a K-Ar biotite age of 186 ± 2 Ma. Moderately to highly deformed Permian to Early Triassic granitoids made up the northern Yaminué Complex. The Late Permian to Early Triassic (U-Pb SHRIMP zircon age of 252 ± 6 Ma) Cabeza de Vaca Granite of the Yaminué block yielded Jurassic mica K-Ar cooling ages (198 ± 2, 191 ± 1, and 190 ± 2 Ma). At the boundary between the Yaminué and Nahuel Niyeu blocks, K-Ar muscovite ages of 188 ± 3 and 193 ± 5 Ma were calculated for the Flores Granite, whereas the Early Permian Navarrete granodiorite, located in the Nahuel Niyeu block, yielded a K-Ar biotite age of 274 ± 4 Ma. The Jurassic thermal history is not regionally uniform. In the supracrustal exposures of the Nahuel Niyeu block, the Early Permian granitoids of its western sector as well as other Permian plutons and Ordovician leucogranites located further east show no evidence of cooling age reset since mica ages suggest cooling in the wake of crystallization of these intrusive rocks. In contrast, deeper crustal levels are inferred for Permian-Early Triassic granitoids in the Yaminué block since cooling ages for these rocks are of Jurassic age (198-182 Ma). Jurassic resetting is contemporaneous with the massive Lower Jurassic Flores Granite, and the Marifil and Chon Aike volcanic provinces. This intraplate deformational pulse that affected northeastern

  16. Growth Rate Estimates of Supergene Manganese Nodule by 40Ar/39Ar Isotopic Dating

    Institute of Scientific and Technical Information of China (English)

    Li Jianwei; Vasconcelos P M

    2004-01-01

    Increasing world-class, high-grade, and metals-enriched supergene manganese ore deposits have been discovered in the last two decades, making them more and more economically important. However, data on the timing and duration of their formation are sparse, mainly due to the difficulties extracting datable minerals suited to traditional radiometric dating methods. Hollandite, cryptomelane, coronadite, todorokite, and manjiroite are common manganese oxide minerals in supergene environments. These minerals host potassium of variable amounts from 0.1 wt% to 5.0 wt% in their structural sites. This geochemical property provides possibility to date supergene manganese ores by using K-Ar and 40Ar/39Ar methods. In this study, we perform 40Ar/39Ar dating on a 7.1-cm-thick botryoidal manganese nodule from an ancient weathering profile at Mount Tabor, central Queensland, Australia. Laser microprobe incremental analyses of distinct growth bands, from the inner core through the intermediate bands to the outermost crusts of the nodule, have yielded high quality 40Ar/39Ar ages at 27.3 Ma, 20.9 Ma, 19.2 Ma, and 16.1 Ma, respectively. The age results permit preliminary estimates on the average growth rates of the nodule varying from 4.7×10-3 mm/ka to 7.6×10-3 mm/ka to 9.0×10-3 mm/ka, from the core to the rim. Results of this study are of significance in our understanding of the mode, mechanism, process, and climatic conditions in the formation of supergene manganese ore deposits.

  17. 40Ar/39Ar ages of lunar impact glasses: Relationships among Ar diffusivity, chemical composition, shape, and size

    CERN Document Server

    Zellner, N E B

    2015-01-01

    Lunar impact glasses, quenched melts produced during cratering events on the Moon, have the potential to provide not only compositional information about both the local and regional geology of the Moon but also information about the impact flux over time. We present in this paper the results of 73 new 40Ar/39Ar analyses of well-characterized, inclusion-free lunar impact glasses and demonstrate that size, shape, chemical composition, fraction of radiogenic 40Ar retained, and cosmic ray exposure (CRE) ages are important for 40Ar/39Ar investigations of these samples. Specifically, analyses of lunar impact glasses from the Apollo 14, 16, and 17 landing sites indicate that retention of radiogenic 40Ar is a strong function of post-formation thermal history in the lunar regolith, size, and chemical composition. Based on the relationships presented in this paper, lunar impact glasses with compositions and sizes sufficient to have retained 90% of their radiogenic Ar during 750 Ma of cosmic ray exposure at time-integra...

  18. Comparative 40Ar/39Ar and K-Ar dating of illite-type clay minerals: A tentative explanation for age identities and differences

    Science.gov (United States)

    Clauer, Norbert; Zwingmann, Horst; Liewig, Nicole; Wendling, Raymond

    2012-10-01

    The 40K/40Ar (K-Ar) and 40Ar/39Ar dating methods are applied here to the same, very small, micrometric illite-type particles that crystallized under low-temperature (samples with a total of fifteen size fractions from advantages, such as the plateaus obtained by incremental step heating of the various size fractions, even if not translatable straight as ages of the illite populations; they allow identification of two generations of authigenic illite that formed at about 200 and 175 Ma, and one detrital generation. However, 40Ar/39Ar dating of clay minerals remains challenging as technical factors, such as the non-standardized encapsulation, may have potential unexpected effects. Both dating methods have their limitations: (1) K-Ar dating requires relatively large samples (ca. 10-20 mg) incurring potential sample homogeneity problems, with two aliquots required for K and Ar analysis for an age determination, also inducing a higher analytical uncertainty; (2) an identified drawback of 40Ar/39Ar dating is Ar recoil and therefore potential loss that occurs during neutronic creation of 39Ar from 39K, mostly in the finer mineral particles. If all the recoiled 39Ar is redistributed into adjacent grains/minerals, the final 40Ar/39Ar age of the analyzed size fraction remains theoretically identical, but it is not systematic in clay-type material. The finest grain sizes (e.g., convenient and straightforward use supported by a standardized and well-controlled technical approach. The present comparison of the two Ar-dating methods as applied to clay material shows that neither method is presently outdated, and that they are even of reciprocal use. Both methods have distinct application fields in clay geochronology and complementary application fields in clay crystallography.

  19. Physical properties of ash flow tuff from Yucca Mountain, Nevada

    Science.gov (United States)

    Nelson, Philip H.; Anderson, Lennart A.

    1992-05-01

    The density and porosity of 198 samples of ash flow tuffs from three boreholes at Yucca Mountain, Nevada, are measured and determined. The electrical properties, velocity, and permeability of many of these samples are also determined. Zeolites and clays are found to reduce the grain density, increase the electrical conductivity, reduce the compressional velocity, and reduce the permeability.

  20. ArArCALC—software for 40Ar/ 39Ar age calculations

    Science.gov (United States)

    Koppers, Anthony A. P.

    2002-06-01

    ArArCALC is a Microsoft Excel ® 97-2000-XP application for performing calculations in 40Ar/ 39Ar geochronology. It is coded in Visual Basic for Applications and can be used under the Windows ® 95/98/NT/2000/ME/XP operating systems. ArArCALC provides an easy-to-use graphical interface for the calculation of age plateaus, total fusion ages and isochrons following the regression of 40Ar/ 39Ar mass spectrometry data. Results are stored in single Excel workbooks including nine different data tables and four different diagrams. Analytical, internal and external errors are calculated based on error propagation of all input parameters, analytical data and applied corrections. Finally, the age calculation results can be recalibrated with reference to the primary K-Ar standards (e.g. GA-1550, MMhb-1) in order to obtain more consistent absolute40Ar/ 39Ar age determinations. ArArCALC is distributed as freeware.

  1. Thermal History of the Felsite Unit, Geysers Geothermal Field, From Thermal Modeling of 40Ar/39Ar Incremental Heating Data

    Energy Technology Data Exchange (ETDEWEB)

    T. M. Harrison (U of California); G. B. Dalrymple (Oregon State U); J. B. Hulen (U of Utah); M. A. Lanphere; M. Grove; O. M. Lovera

    1999-08-19

    An Ar-40/Ar-39 and U-Pb study was performed of the Geysers plutonic complex of the Geysers Geothermal Field in California. Sixty-nine ion microprobe spot analyses of zircons from four granite samples from the plutonic complex that underlies the Geysers geothermal field yielded Pb-207/Pb-206 vs. U-238/Pb-206 concordia ages ranging from 1.13 {+-} 0.04 Ma to 1.25 {+-} 0.04 Ma. The U-Pb ages coincide closely with Ar-40/Ar-39 age spectrum plateau and ''terminal'' ages from coexisting K-feldspars and with the eruption ages of overlying volcanic rocks. The data indicate that the granite crystallized at 1.18 Ma and had cooled below 350 C by {approximately}0.9-1.0 Ma. Interpretation of the feldspar Ar-40/Ar-39 age data using multi-diffusion domain theory indicates that post-emplacement rapid cooling was succeeded either by slower cooling from 350-300 C between 1.0 and 0.4 Ma or transitory reheating to 300-350 C at about 0.4-0.6 Ma. Heat flow calculations constrained with K-feldspar thermal histories and the pre sent elevated regional heal flow anomaly demonstrate that appreciable heat input from sources external to the known Geysers plutonic complex is required to maintain the geothermal system. This requirement is satisfied by either a large, underlying, convecting magma chamber (now solidified) emplaced at 1.2 Ma or episodic intrusion of smaller bodies from 1.2-0.6 Ma.

  2. Comenditic and pantelleritic ash-flow tuffs from Volcan Las Navajas, Nayarit, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, S.A.; Hebre, J.A.

    1985-01-01

    Two distinctive ash-flow tuffs occur around the base of Volcan Las Navajas, a Pleistocene trachyte - peralkaline rhyolite center located in the northwestern segment of the Mexican Volcanic belt. The lower ash-flow unit is locally up to 65 m thick, is lithic rich and contains pumice blocks of comenditic rhyolite. The unit is not extensively exposed, and thus its areal extent and volume cannot be determined. Its chemical characteristics and stratigraphic relationship to other products erupted from Las Navajas suggest that it is related to the formation of the older of the two calderas which occur on Las Navajas. Unconformably overlying this unwelded ash-flow is a pantelleritic airfall pumice unit which is locally welded. This airfall unit is conformably overlain by a welded as-flow tuff that contains fiamme of pantelleritic composition (72 %SiO/sub 2/, 8% FeO*, 900 ppm Zr, agpaitic index of 1.7) as well as pumice blocks that show evidence of various degrees of mixing between pantellerite and trachyte. This suggests eruption from a chemically zoned magma chamber. This unit is locally up to 20 m thick, although its top has been removed by erosion. It is found on all sides of Las Navajas except on the south where it may be covered by Volcan Sanganguey, a Pleistocene to Recent calc-alkaline volcano. The welded ash-flow has been dated by K - Ar at 0.2+/-0.1 m.y. Stratigraphically and chemically this ash-flow appears to be related to the formation of younger of the two calderas.

  3. Eurekan deformation on Prins Karls Forland, Svalbard - new insights from Ar40/Ar39 muscovite dating

    Science.gov (United States)

    Faehnrich, Karol; Schneider, David; Manecki, Maciej; Czerny, Jerzy; Myhre, Per Inge; Majka, Jarosław; Kośmińska, Karolina; Barnes, Christopher; Maraszewska, Maria

    2017-04-01

    Eurekan deformation has been proven to be a complex sequence of tectonic episodes, dominated by compression in the Circum Arctic region. It was associated with early Cenozoic collision of Eurasia, North America and Greenland plates producing fold-thrust belt style of deformation. Timing of this enigmatic event has not yet been extensively resolved by radiometric dating (Piepjohn et al. 2016, Journal of the Geological Society, 173(6), 1007-1024). Reinhardt et al. (2013, Z. Dt. Ges. Geowiss., 164 (1), 131-147) dated syn-tectonic volcanic ashes at c. 60 Ma and 54 Ma on Ellesmere Island, Canada. Tagner et al. (2011, Earth and Planetary Science Letters, 303(3), 203-214) interpreted c. 49-47 Ma 40Ar/39Ar ages on trachyte flows in northern Greenland as peak compression during the Eurekan event. On Svalbard, Tessensohn et al. (2001, Geologisches Jahrbuch, B 91, 83-104) reported K/Ar whole rock ages ranging from c. 67 to 49 Ma for the slates from Svartfjella-Eidembukta-Daudmannsodden Lineament. Bentonite layers in the Central Tertiary Basin are as young as c. 56 Ma (Charles et al. 2011, Geochem. Geophys. Geosyst., 12, 1-19), predating latest deformation. Moreover, Barnes et al (2017, in prep.) applied (U-Th)/He thermochronology along the western margin of Svalbard and resolved Early to Middle Eocene heating, likely documenting burial related to thrusting. Here we present new results from 40Ar/39Ar muscovite dating of ductile to brittle shear zone on Prins Karls Forland, Svalbard, indicating Eurekan age of thrusting. Prins Karls Forland is dominated by Neoproterozoic siliciclastic metasediments (comprising Caledonian basement) regionally metamorphosed to greenschist facies conditions. A ˜1 km wide ductile to brittle shear zone (the Bouréefjellet shear zone) separates the amphibolite facies Pinkie Unit from the lower grade upper structural unit, the Grampianfjella Formation (Faehnrich et al. 2016, EGU 2016). The age of the amphibolite facies metamorphism (c. 370-355 Ma

  4. 40Ar/39Ar Ages for the Sentinel-Arlington Volcanic Field, Southwestern Arizona

    Science.gov (United States)

    Cave, S. R.; Greeley, R.; Champion, D. E.; Turrin, B. D.

    2007-12-01

    The Sentinel Plains lava field and proximate small (history as well as the timing of the ancient Gila River interactions that led to the development of the Painted Rock transverse drainage. The absolute timing was determined in order datermine causal relationships with local tectonism. The SAVF basal contact is ~30 m above the Holocene surface where exposed along the current river channel; and the lavas show similar amounts mantling by aeolian dust, development of pedogenic calcium carbonate, and subsequent incision by radial ephemeral drainages. Relative timing of eruptive events was determined by stratigraphic and embayment relationships. Continuity of distal flows exposed in cross-sections to their source vents could be established using field work, and confirmed using geomagnetic secular variation and geochemical analyses. Edifices generally corresponded to discreet geomagnetic inclination, declination, and paleointensity values. Older eruptive events exhibited normal polarity, while stratigraphically younger events exhibited reversed polarity. Most lavas were alkali olivine basalt with a range of unnormalized SiO2 weight percentages ranging from 47.16-51.48. Geochronology using 40Ar/39Ar method revealed an age of 1.94 +/- 0.85 Ma for Painted Rock Low Shield (New Mexico Geochronology Research Laboratory), 1.64 +/- 0.14 Ma for Theba Low Shield (Rutgers University) and 1.24 +/- 0.040 Ma for Wild Horse Low Shield (Rutgers University). Some ages were precise enough to correspond to the Matuyama reversed polarity epoch, with SAVF initiation possibly within the Olduvai normal polarity event. These dates represent an overall improvement in precision and accuracy over previous dates (values corresponding to 6.20 Ma to 1.28 Ma) collected in the late 1970s and early 1980s using K-Ar technique. The 40Ar/39Ar ages correspond to expected magnetic polarities and stratigraphic sequences.

  5. Qualidade de maçãs ‘Gala’ armazenadas em atmosfera controlada dinâmica e estática com renovação do ar Quality of ‘Gala’ apples stored in dynamic and static controlled atmosphere with air renovation

    Directory of Open Access Journals (Sweden)

    Auri Brackmann

    2005-04-01

    Full Text Available Este experimento teve como objetivo avaliar o efeito da remoção periódica da atmosfera das câmaras de atmosfera controlada com ar e nova instalação, bem como o uso da atmosfera dinâmica, sobre a manutenção da qualidade da maçã 'Gala'. Os tratamentos utilizados foram: (1 controle (sem renovação; (2 renovação da atmosfera diariamente durante o resfriamento dos frutos; (3 renovação da atmosfera diariamente durante o resfriamento e mensalmente no período de armazenamento em atmosfera controlada; (4 renovação da atmosfera mensalmente; (5 50µL L-1 de etileno no interior da câmara; e (6 atmosfera dinâmica (injeção diária de N2 para remoção do CO2. Após oito meses de armazenamento, o tratamento com renovação da atmosfera diariamente durante o resfriamento e mensalmente no período de armazenamento em atmosfera controlada proporcionou frutos com maior firmeza de polpa. Nenhuma das técnicas avaliadas permitiu manter os níveis de etileno nas câmaras de armazenamento abaixo de 5µL L-1. Provavelmente, a absorção do etileno proporciona um benefício igual ou maior com um menor custo, pois a renovação da atmosfera implica altos custos na aquisição de nitrogênio.This experiment was carried out aiming to evaluate the effect of periodical removal of the atmosphere of controlled atmosphere chambers with fresh air and the use of dynamic atmosphere on quality of 'Gala' apples. Evaluated treatments were: (1 control (without air renovation; (2 daily atmosphere renovation during fruit cooling; (3 daily atmosphere renovation during cooling and monthly during controlled atmosphere storage of fruits; (4 monthly atmosphere renovation; (5 50µL L-1 ethylene inside chamber; and (6 dynamic atmosphere (N2 injection to remove CO2. After eight months of storage, daily atmosphere renovation during cooling and monthly during controlled atmosphere storage maintained fruit firmness. None of the evaluated techniques allowed ethylene levels

  6. 40Ar* loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks

    Science.gov (United States)

    Cosca, M.; Stunitz, H.; Bourgeix, A.-L.; Lee, J.P.

    2011-01-01

    The effects of deformation on radiogenic argon (40Ar*) retentivity in mica are described from high pressure experiments performed on rock samples of peraluminous granite containing euhedral muscovite and biotite. Cylindrical cores, ???15mm in length and 6.25mm in diameter, were drilled from granite collected from the South Armorican Massif in northwestern France, loaded into gold capsules, and weld-sealed in the presence of excess water. The samples were deformed at a pressure of 10kb and a temperature of 600??C over a period 29 of hours within a solid medium assembly in a Griggs-type triaxial hydraulic deformation apparatus. Overall shortening in the experiments was approximately 10%. Transmitted light and secondary and backscattered electron imaging of the deformed granite samples reveals evidence of induced defects and for significant physical grain size reduction by kinking, cracking, and grain segmentation of the micas.Infrared (IR) laser (CO2) heating of individual 1.5-2.5mm diameter grains of muscovite and biotite separated from the undeformed granite yield well-defined 40Ar/39Ar plateau ages of 311??2Ma (2??). Identical experiments on single grains separated from the experimentally deformed granite yield results indicating 40Ar* loss of 0-35% in muscovite and 2-3% 40Ar* loss in biotite. Intragrain in situ ultraviolet (UV) laser ablation 40Ar/39Ar ages (??4-10%, 1??) of deformed muscovites range from 309??13 to 264??7Ma, consistent with 0-16% 40Ar* loss relative to the undeformed muscovite. The in situ UV laser ablation 40Ar/39Ar ages of deformed biotite vary from 301 to 217Ma, consistent with up to 32% 40Ar* loss. No spatial correlation is observed between in situ 40Ar/39Ar age and position within individual grains. Using available argon diffusion data for muscovite the observed 40Ar* loss in the experimentally treated muscovite can be utilized to predict average 40Ar* diffusion dimensions. Maximum 40Ar/39Ar ages obtained by UV laser ablation overlap those

  7. K/AR dating of clinoptilolite, mordenite, and associated clays from Yucca Mountains, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    WoldeGabriel, G.

    1993-07-01

    Zeolites are abundant in the geologic record in both continental and marine environments. The purpose of the present study is to evaluate the utility of K-bearing zeolites for dating by the K/Ar method to determine the time of zeolite diagenesis at Yucca Mountain, Nevada (Fig. 1). At Yucca Mountain, K-rich clinoptilolite and possibly mordenite are the only potentially K/Ar dateable secondary minerals present in the zeolite-rich tuffs except for some illite/smectites ({ge}10% illite layers) associated with these minerals. Direct dating of K-rich clinoptilolite, the most abundant zeolite in the altered tuffs, is important to delineate zeolite chronology as part of the site characterization of Yucca Mountain.

  8. 40Ar 39Ar Ages and tectonic setting of ophiolite from the Neyriz area, southeast Zagros Range, Iran

    Science.gov (United States)

    Lanphere, M.A.; Pamic, J.

    1983-01-01

    An ophiolite, considered to be an allochthonous fragment of Tethyan oceanic crust and mantle, crops out near Neyriz in the Zagros Range, Iran. 40Ar 39Ar ages ranging from 76.8 ?? 23.8 Ma to 105 ?? 23.3 Ma were measured on hornblende from five samples of plagiogranite and diabase from the ophiolite. The most precise ages are 85.9 ?? 3.8 Ma for a diabase and 83.6 ?? 8.4 Ma for a plagiogranite. The weighted mean age of hornblende from the five samples is 87.5 ?? 7.2 Ma which indicates that the igneous part of the Neyriz ophiolite formed during the early part of the Late Cretaceous. Pargasite from amphibolite below peridotite of the Neyriz ophiolite has a 40Ar 39Ar age of 94.9 ?? 7.6 Ma. The pargasite age agrees within analytical uncertainty with the ages measured on diabase and plagiogranite. Comparable ages have been measured on igneous rocks from the Samail ophiolite of Oman and on amphibolite below peridotite of the Samail ophiolite. ?? 1983.

  9. The Hydrogeologic Character of the Lower Tuff Confining Unit and the Oak Springs Butte Confining Unit in the Tuff Pile Area of Central Yucca Flat

    Energy Technology Data Exchange (ETDEWEB)

    Drellack, Jr., Sigmund L.; Prothro, Lance B.; Gonzales, Jose L.; Mercadante, Jennifer M.

    2010-07-30

    The lower tuff confining unit (LTCU) in the Yucca Flat Corrective Action Unit (CAU) consists of a monotonous sequence of pervasively zeolitized volcanic tuff (i.e., mostly bedded with lesser nonwelded to poorly welded tuff; not fractured) (Bechtel Nevada, 2006). The LTCU is an important confining unit beneath Yucca Flat because it separates the alluvial and volcanic aquifers, where many underground nuclear tests were conducted, from the regional lower carbonate aquifer. Recent sub-CAU-scale modeling by Los Alamos National Laboratory in the Tuff Pile area of Yucca Flat (Boryta, et al., in review) includes postulated low-porosity, high-permeability zones (i.e., fractured welded-tuff aquifers) within the LTCU. This scenario indicates that such postulated low-porosity, high-permeability zones could provide fast-path lateral conduits to faults, and eventually to the lower carbonate aquifer. A fractured and faulted lower carbonate aquifer is postulated to provide a flow path(s) for underground test-derived contaminants to potential offsite receptors. The ramifications of such a scenario are obvious for groundwater flow and contaminant migration beneath Yucca Flat. This paper describes the reasoning for not including postulated low-porosity, high-permeability zones within the LTCU in the Tuff Pile area or within the LTCU in the Yucca Flat CAU-scale model. Both observational and analytical data clearly indicate that the LTCU in the Tuff Pile area consists of pervasively zeolitic, nonwelded to poorly welded tuffs that are classified as tuff confining units (i.e., high-porosity, low-permeability). The position regarding the LTCU in the Tuff Pile area is summarized as follows: • The LTCU in the Tuff Pile area consists of a monotonous sequence of predominantly zeolitic nonwelded to poorly welded tuffs, and thus is accurately characterized hydrogeologically as a tuff confining unit (aquitard) in the Yucca Flat-Climax Mine hydrostratigraphic framework model (Bechtel Nevada

  10. The effects of retrograde reactions and of diffusion on 39Ar-40Ar ages of micas

    DEFF Research Database (Denmark)

    Allaz, Julien; Engi, Martin; Berger, Alfons

    2011-01-01

    Effects of metamorphic reactions occurring during decompression were explored to understand their influence on 39Ar-40Ar ages of micas. Monometamorphic metasediments from the Lepontine Alps (Switzerland) were studied. Collected samples reached lower amphibolite facies during the Barrovian....../K and Cl/K ratios) did not change and the resulting ages can be interpreted unambiguously. In mineral separates containing two white micas, Ca/K and Cl/K ratios were variable, reflecting non-simultaneous laboratory degassing of the two heterochemical Ar-reservoirs. These ratios were used to identify each...... Ar reservoir and to unravel the age. In a chlorite-margarite-biotite-calcschist equilibrated near 560 °C and 0.65 GPa, biotite, margarite, and muscovite all yield ages around 18 Ma. At slightly higher grade (560-580 °C, 0.8-0.9 GPa), the assemblage muscovite-paragonite-plagioclase is at equilibrium...

  11. Clinoptilolite zeolitized tuff from Central Alborz Range, North Iran

    Science.gov (United States)

    Taghipour, Batoul

    2010-05-01

    Zeolites are hydrated alumino-silicates of the alkaline and alkaline earth cations, principally sodium, potassium, calcium, and magnesium (Iijima 1980; Hay 1981). Zeolites occur principally in unmetamorphosed sedimentary rocks and are particularly widespread in volcani-clastic strata (Hay, 1978). Clinoptilolite is a natural zeolite of the heulandite group with the simplified formula of (Na, K)6 Si30 Al6 O72 .nH2. It is the most common natural zeolite found mainly in sedimentary rocks of volcanic origin. Alborz zone is one of the important geological divisions in Iran. This zone is restricted to Kopeh dagh zone in North & Central Iranian zone in South and is a region of active deformation within the broad Arabian-Eurasia collision zone (Allen et al. 2003). The zeolitized green tuff belt from Central Alborz which introduce here are made of volcanoclastic sequence of Karaj Formation. This belt is about 40 km long along Alborz Range and is Eocene in age. Zeolites and associated minerals of this altered vitric tuff studied. Zeolitization took place in some beds of Karaj Formations, with average range of 3 to 300 meters thickness. There are several gypsum lenses which interbed with a widespread green tuff succession in the studied area. On the basis of chemical composition these tuffs are in the range of acid to intermediate volcanic rocks. Also magmatic affinity is calc-alkaline and geological setting of the area belongs to volcanic arc granitoid. Petrographic data has shown that various shape and size of shard glass are the main component of tuffs. Based on the field studies, detail microscopy, XRD and electron microprobe analysis (EMPA), the following main minerals are determined: Clinoptilolite+montmorillonite+crystobalite. Clinoptilolite and smectite are predominant minerals in all altered samples. Concerning the Si/Al ratio of 40 point analyses of glass shards the Alborz tuff has clinoptilolite composition. Otherwise the chemical composition of altered shard glass

  12. MaXi Avisen

    DEFF Research Database (Denmark)

    Kanstrup, Anne Marie; Sørensen, Marianne; Bertelsen, Pernille

    2008-01-01

    maXi-projektets vision er at sprænge rammerne for sundhedsstøtte med it ved at sætte diabetikere og deres familier i centrum og ved at flytte fokus fra sygdom og hospitaler til samfund, hverdagsliv og services. maXi-projektet har til formål at afprøve og gennemføre brugerdreven innovation som...... eksperimenter i et 'living lab' - som etableres i Skagen. I 2009 udvælges nye brugere til deltagelse i projektet. maXi-projektet opbygges som et modelprojekt i samar-bejde mellem Aalborg Universitet, Fonden Skagen Helse, Teknologisk Institut og Edvantage Group. Se http://www.maxi-projektet.dk/ Projektet er...

  13. Repository site data report for unsaturated tuff, Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Tien, P.L.; Updegraff, C.D.; Siegel, M.D.; Wahi, K.K.; Guzowski, R.V.

    1985-11-01

    The US Department of Energy is currently considering the thick sequences of unsaturated, fractured tuff at Yucca Mountain, on the southwestern boundary of the Nevada Test Site, as a possible candidate host rock for a nuclear-waste repository. Yucca Mountain is in one of the most arid areas in the United States. The site is within the south-central part of the Great Basin section of the Basin and Range physiographic province and is located near a number of silicic calderas of Tertiary age. Although localized zones of seismic activity are common throughout the province, and faults are present at Yucca Mountain, the site itself is basically aseismic. No data are available on the composition of ground water in the unsaturated zone at Yucca Mountain. It has been suggested that the composition is bounded by the compositions of water from wells USW-H3, UE25p-1, J-13, and snow or rain. There are relatively few data available from Yucca Mountain on the moisture content and saturation, hydraulic conductivity, and characteristic curves of the unsaturated zone. The available literature on thermomechanical properties of tuff does not always distinguish between data from the saturated zone and data from the unsaturated zone. Geochemical, hydrologic, and thermomechanical data available on the unsaturated tuffs of Yucca Mountain are tabulated in this report. Where the data are very sparse, they have been supplemented by data from the saturated zone or from areas other than Yucca Mountain. 316 refs., 58 figs., 37 tabs.

  14. Hourglass inclusions: Theory and application to the Bishop rhyolitic tuff

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, A.T. Jr. (Univ. of Chicago, IL (United States))

    Hourglass inclusions are bodies of bubble-bearing glass in volcanic phenocrysts that extend to the crystal rim through a narrow neck. Compared to enclosed inclusions, hourglass inclusions are less devitrified, contain more gas, but contain less dissolved H{sub 2}O, CO{sub 2}, and Cl. A quantitative model of rhyolitic hourglass emptying is developed and applied to Bishop Tuff hourglass inclusions. Those in plinian pumice suggest rapid ascent at 10 m/s consistent with theoretical eruption models. Hourglass inclusions from the Mono ash-flow lobe of the Bishop Tuff suggest (1) initial crystallization of quartz, formation of some enclosed and some hourglass inclusions at approximately 2,400 bars; (2) magma decompression to approximately 1,100 bars for at least a week (duration of eruption for the Bishop Tuff ) while hourglass inclusions further evolved and bubbles of gas attained a 50{mu}m diameter; (3) magma ascent from 1,100 to approximately 700 bars at approximately 1 m/s, consistent with theory for ash-flow-producing (collapsing) eruption columns; (4) entrainment of some crystals that had decompressed to a pressure of 400 bars for several weeks; (5) thermal quenching of hourglass evolution as magmatic foam disrupted into fast-moving spray, erupted, and entrained cold air. Uncertainties are large but can be reduced by future studies of postdepositional cooling, hourglass volatile compositions, temperature, and viscosity to obtain estimates of eruptive and preeruptive magma movement and crystallization rate.

  15. Selenite transport in unsaturated tuff from Yucca Mountain

    Energy Technology Data Exchange (ETDEWEB)

    Conca, J.L. [WSU Tri-Cities, Richland, WA (United States); Triay, I.R. [Los Alamos National Lab., NM (United States)

    1994-12-31

    Direct measurements of unsaturated selenite retardation coefficients and unsaturated hydraulic conductivity were obtained on two tuff samples from Yucca Mountain using the UFA{trademark} technology. The retardation factor for the selenite species was only 2.5 in both Yucca Mountain vitric member at 62.6% saturation and zeolitized nonwelded tuff from G-tunnel at 52.8% saturation with respect to J-13 well water from the Nevada Test Site contaminated with selenium at 1.31 mg/l (ppm). In batch tests on the same material using 1.2 mg/l (ppm), the average K{sub d} was determined to be 13, giving retardation factors higher than the UFA column breakthrough tests by an order of magnitude. The difference could result from preferential flow paths in the UFA column as might occur in the field or differences in residence times between the two types of tests. The unsaturated hydraulic conductivities during the experiments were 2.49 {times} 10{sup {minus}8} cm/s for the Yucca Mountain vitric member and 1.16 {times} 10{sup {minus}8} cm/s for the zeolited nonwelded tuff.

  16. 40Ar-39Ar Dating of Quartz from Ore in the Baiyangping Cu-Co Polymetallic Ore-Concentrated Area, Lanping Basin, Yunnan

    Institute of Scientific and Technical Information of China (English)

    何明勤; 刘家军; 李朝阳; 李志明; 刘玉平; 杨爱平; 桑海清

    2004-01-01

    40Ar-39Ar fast neutron activation age spectrum of quartz in ore collected from the Baiyangping Cu-Co polymetallic ore-concentrated area, Lanping Basin, is saddle-shaped. The plateau age, minimum appearance age and isochron age shown on the spectra are 56.53±0.43 Ma, 55.52±1.78 Ma and 55.90±0.29 Ma respectively. The age data are consistent with each other within 1σ uncertainties. Because the given initial 40Ar/36Ar value of 294.7±1.14 is very close to Nier's value (295.5±5), both plateau and isochron ages may be considered as the forming time of quartz. So the age of 55.90-56.53 Ma represents the forming age of ore deposits. It is obvious that the ore deposits were formed during the Early Himalayan period.

  17. MaTeam-projektet

    DEFF Research Database (Denmark)

    Andreasen, Marikka; Damkjær, Helle Sejer; Højgaard, Tomas

    2011-01-01

    Projektet MaTeam beskrives med fokus på et toårigt forsøg hvor matematiklærerne på 4.-6. klassetrin på fire skoler i Silkeborg Kommune samarbejdede med forfatterne. Projektet handlede om udvikling af matematiklærerkompetencer med fokus på samarbejdet i de fire skolers matematiklærerfagteam...... matematiklærerfagteam og samarbejdsrelationer der indgår i projektet. Desuden beskriver vi forskellige typer af fagteam og lærere. Metodisk var MaTeam-projektet struktureret som en didaktisk modelleringsproces....

  18. The new 39Ar/40Ar dating facility of the LSCE, background and performances.

    Science.gov (United States)

    Scaillet, S.; Nomade, S.; Guillou, H.; Scaillet-Vita, G.

    2007-12-01

    Precise and accurate timescales are increasingly needed in most disciplines of the Earth sciences. To contribute to this challenging task, a new 39Ar/40Ar laboratory, specifically devoted to the dating of very recent (down to 1 ka) volcanic products, has been developed at the LSCE (CEA-IPSL-UVSQ, France). In this contribution, we present the first data obtained from this new facility. The laboratory comprises a VG 5400 mass spectrometer coupled with a high sensitivity and high dynamic range ion counting system. Gas extraction is achieved with a 25 watts C02 laser or a double vacuum furnace depending of the analyzed samples. The full metal vacuum and purification line feature a GP50 and a compact Ti flash getters which permit extremely low blank for all Argon isotopes (e.g. ~ 3.0 10e-19 Moles for 36Ar). Both analytical protocols and hardware were specifically developed and optimized to date extremely young samples. Analytical performances including protocols, flux monitoring as well mass spectrometer discrimination correction method will be presented in the light of data obtained over the last 10 months. All samples were irradiated, under cadmium, in the Β-1 position (~1.0 10e+13 fast n cm-2 s-1) of the 70MWh-1 OSIRIS reactor (Pierre Süe laboratory, CEA-Saclay, France). Irradiation package is composed of home-design Aluminium disks constituting a 4 cm stack (10 to 30 unknowns/irradiation). Analyzed neutrons flux standards indicate less than 1% variation along the 4cm stack and validate the use of this reactor for high-precision 39Ar/40Ar dating. The precision and accuracy of the facility has been checked from cross-comparison of international single grain standards including FCs (28.02Ma), ACR-2 (1.194Ma) and TCR (28.32Ma) using the most recent recommended values for these monitors. A total of 80 grains in two irradiations (10 and 120 minutes) will be presented in details. Results from single-grain analyses agree within errors with those proposed by Renne et al

  19. Additional 40Ar- 39Ar dating of the basement and the alkaline volcanism of Gorringe Bank (Atlantic Ocean)

    Science.gov (United States)

    Féraud, Gilbert; York, Derek; Mével, Catherine; Cornen, Guy; Hall, Chris M.; Auzende, Jean-Marie

    1986-09-01

    40Ar/ 39Ar step heating analyses are reported for a variety of samples from Gorringe Bank (Atlantic Ocean). Flat age spectra for two primary, igneous hornblendes of Gorringe (corresponding to an age of 143 Ma) show that the K-Ar ages obtained on these samples by Prichard and Mitchell [4] are evidently crystallization and not hybrid ages. This sustains the concept of an initiation age of 140 Ma [4] for Gorringe Bank. No support is found for Carpena's suggestion [7] that the formation of Gorringe Bank began 200 Ma ago. Secondary hornblendes from Ormonde seamount rocks appear to have formed shortly after the initiation of the Bank. Precise plateau ages on samples of two alkaline volcanics from Ormonde correspond to the older limit of the alkaline volcanism suggested by Féraud et al. [3,5].

  20. Sedimentary-volcanic tuffs formed during the early Middle Triassic volcanic event in Guizhou Province and their stratigraphic significance

    Institute of Scientific and Technical Information of China (English)

    XIAO Jiafei; HU Ruizhong

    2005-01-01

    The sedimentary-volcanic tuff (locally called "green-bean rock") formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements (REE), as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma.

  1. The Jaramillo Subchron: New Magnetostratigraphy and 40Ar/39Ar Dating in the Death Valley Region, California

    Science.gov (United States)

    Scott, G. R.; Deino, A. L.; Gibert, L.

    2014-12-01

    The Jaramillo subchron was the normal polarity period before the present Brunhes chron. However, the Jaramillo's duration was only 10% as long as the Brunhes. Lasting only about 70 ka, the Jaramillo has frequently been missed (or is missing) from many magnetostratigraphic studies of the Early Pleistocene. We have examined two internally-drained basins with high sediment accumulation rates, that also contain Sanidine-bearing tephras. At Kit Fox Hills, in the Death Valley Basin, we sampled across 50m of tilted (45°) fine-grained sandstone/siltstone. A normal polarity magnetozone was delineated over ~12m of section (sedimentation rate of ~15cm/ka). We also collected 8 tephra beds, 4 of which are within the normal magnetozone, and 2 below and 2 above. To the east is the Tecopa Basin, which until the middle Pleistocene was internally-drained. We sampled through 36m of mudstones between the Tecopa Tuff (1.25 Ma) and the Bishop Tuff (0.77 Ma). A normal magnetozone was delineated over a 9m interval, ending 12.5m below the Bishop Tuff. A Sanidine-bearing tephra (previously unidentified) was found 4m above the base of the Jaramillo zone. There were 2 beds of reverse polarity within the Jaramillo zone, at 4.5m and 8m above the base. At least the lower one has been reported from other continental deposits (China, Spain). These sections should provide precisely calibrated chronostratigraphic tie points (approximately every 10-30 ka), providing sub-precessional level, direct geochronological control through the Jaramillo subchron. These sections are also being examined for paleo-environmental indicators (and minerals) that can be used to determine wetter or drier conditions (expanding saline lakes or dry playas). With all these event horizons (ash falls and polarity shifts), the Jaramillo has the potential to be used for high resolution, paleo-climate reconstructions on a regional scale.

  2. 40Ar/39Ar Interlaboratory Calibration into the Holocene.

    Science.gov (United States)

    Heizler, M. T.; Jicha, B.; Koppers, A. A. P.; Miggins, D. P.

    2015-12-01

    Advances in 40Ar/39Ar analytical precision for very young rocks requires collaborative efforts amongst argon geochronology labs to demonstrate age reproducibility commensurate with high precision. NM Tech (NMT), the University of Wisconsin (UW) and Oregon State University (OSU) have each dated Quaternary flux monitor standard AC-2 sanidine (~1.185 Ma), a blind sanidine described as being 50-100 ka (BS) and sanidine from the Qixiangshan (QIX) flow (~10 ka), Changbaishan volcano, China. The samples were irradiated in a single package with FC-2 sanidine (28.201 Ma) as the flux monitor and the irradiated material was distributed amongst the labs. Heizler was present during analysis at both OSU and UW and Jicha attended OSU during analysis. Physical presence was key towards gaining understanding of individual protocols and prompted valuable discussions. Analyses were carried out on single crystals using total fusion and/or step heating approaches. Age agreement was achieved within 2s uncertainty that ranged between (0.03-0.3%, 0.13-0.37% and 1.8-2.6%) for AC-2, BS and QIX, respectively. Each lab found AC-2 to vary somewhat beyond a normal distribution and to yield an age relative to FC-2 of ~1.185 Ma that is ~1.3% (~5-10 sigma) lower than some published estimates. A key cause of the variation between this study and previous results may be variable gas pressure equilibration times between extraction line and mass spectrometer coupled with variable choices to estimate time zero by other laboratories. The majority of our efforts concentrated on the QIX sanidine where prior data obtained by our labs revealed a factor of two spread in age (~11 and 23 ka) based on experiments carried out by total fusion and bulk incremental heating. By conducting single crystal age spectrum analysis we were able to mitigate effects of melt inclusion hosted excess argon and xenocrystic contamination towards obtaining analytical agreement with apparent ages near 10 ka. However, philosophical

  3. MaXi Avisen

    DEFF Research Database (Denmark)

    Kanstrup, Anne Marie; Sørensen, Marianne

    2008-01-01

    eksperimenter i et 'living lab' - som etableres i Skagen. I 2009 udvælges nye brugere til deltagelse i projektet. maXi-projektet opbygges som et modelprojekt i samar-bejde mellem Aalborg Universitet, Fonden Skagen Helse, Teknologisk Institut og Edvantage Group. Se http://www.maxi-projektet.dk/ Projektet er...

  4. Woman Director Ma Yueying

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    Ma Yueying took office as director of the Jiaxing General Silk Mill, which had 200,000 yuan capital fund, in 1975. Since then, this mill has developed greatly. Now it has become an advanced enterprise with an annual output worth RMB¥30 million and fixed assets of RMB¥10 million.

  5. Isotopic Constraints (U, Th, Pb, Sr, Ar) on the Timing of Magma Generation, Storage and Eruption of a Late-Pleistocene Subvolcanic Granite, Alid Volcanic Center, Eritrea

    Science.gov (United States)

    Lowenstern, J. B.; Charlier, B. L.; Wooden, J. L.; Lanphere, M. A.; Clynne, M. A.; Bullen, T. D.

    2001-12-01

    Isotopic analyses demonstrate that a shallow granophyric intrusion from the Alid volcanic center (AVC) was generated, intruded and crystallized over a 20,000-year period in the latest Pleistocene. The granophyre is not exposed, but was ejected as unmelted blocks within a ~1 km3 pyroclastic flow deposit around 15 ka and is a subvolcanic equivalent of the erupted rhyolitic pumice (Lowenstern et al., 1997: J Petrol 12, p. 1707-1721). The rock contains 2.59) is 15.2+/- 5.8 ka (all errors are 2 σ ). Two other splits with lower density (thus higher in Na) yielded ages older than 24 ka, and may retain some excess Ar. Thus, the time between intrusion and complete crystallization for the granophyre was Danakil Depression and are found as unmelted lithic xenoliths in lavas and tuffs of the AVC. Pb isotopes also rule out significant assimilation of Precambrian basement during genesis of the young granophyre. Similarly zircon grains, analyzed with the Stanford-USGS SHRIMP-RG, show little evidence for inheritance, with only a single 760 Ma zircon (U-Pb age) that was also petrographically different from the 130 other zircons in the mount. The other zircons yielded SHRIMP 238U230Th disequilibrium ages of http://wrgis.wr.usgs.gov/docs/geologic/jlwnstrn/alid/ Alidpage.html

  6. Probing the volcanic-plutonic connection and the genesis of crystal-rich rhyolite in a deeply dissected supervolcano in the Nevada Great Basin: Source of the late Eocene Caetano Tuff

    Science.gov (United States)

    Watts, Kathryn E.; John, David A.; Colgan, Joseph P.; Henry, Christopher D.; Bindeman, Ilya N.; Schmitt, Axel K.

    2016-01-01

    Late Cenozoic faulting and large-magnitude extension in the Great Basin of the western USA has created locally deep windows into the upper crust, permitting direct study of volcanic and plutonic rocks within individual calderas. The Caetano caldera in north–central Nevada, formed during the mid-Tertiary ignimbrite flare-up, offers one of the best exposed and most complete records of caldera magmatism. Integrating whole-rock geochemistry, mineral chemistry, isotope geochemistry and geochronology with field studies and geologic mapping, we define the petrologic evolution of the magmatic system that sourced the >1100 km3Caetano Tuff. The intra-caldera Caetano Tuff is up to ∼5 km thick, composed of crystal-rich (30–45 vol. %), high-silica rhyolite, overlain by a smaller volume of comparably crystal-rich, low-silica rhyolite. It defies classification as either a monotonous intermediate or crystal-poor zoned rhyolite, as commonly ascribed to ignimbrite eruptions. Crystallization modeling based on the observed mineralogy and major and trace element geochemistry demonstrates that the compositional zonation can be explained by liquid–cumulate evolution in the Caetano Tuff magma chamber, with the more evolved lower Caetano Tuff consisting of extracted liquids that continued to crystallize and mix in the upper part of the chamber following segregation from a cumulate-rich, and more heterogeneous, source mush. The latter is represented in the caldera stratigraphy by the less evolved upper Caetano Tuff. Whole-rock major, trace and rare earth element geochemistry, modal mineralogy and mineral chemistry, O, Sr, Nd and Pb isotope geochemistry, sanidine Ar–Ar geochronology, and zircon U–Pb geochronology and trace element geochemistry provide robust evidence that the voluminous caldera intrusions (Carico Lake pluton and Redrock Canyon porphyry) are genetically equivalent to the least evolved Caetano Tuff and formed from magma that remained in the lower chamber after

  7. [MaRS Project

    Science.gov (United States)

    Aruljothi, Arunvenkatesh

    2016-01-01

    The Space Exploration Division of the Safety and Mission Assurances Directorate is responsible for reducing the risk to Human Space Flight Programs by providing system safety, reliability, and risk analysis. The Risk & Reliability Analysis branch plays a part in this by utilizing Probabilistic Risk Assessment (PRA) and Reliability and Maintainability (R&M) tools to identify possible types of failure and effective solutions. A continuous effort of this branch is MaRS, or Mass and Reliability System, a tool that was the focus of this internship. Future long duration space missions will have to find a balance between the mass and reliability of their spare parts. They will be unable take spares of everything and will have to determine what is most likely to require maintenance and spares. Currently there is no database that combines mass and reliability data of low level space-grade components. MaRS aims to be the first database to do this. The data in MaRS will be based on the hardware flown on the International Space Stations (ISS). The components on the ISS have a long history and are well documented, making them the perfect source. Currently, MaRS is a functioning excel workbook database; the backend is complete and only requires optimization. MaRS has been populated with all the assemblies and their components that are used on the ISS; the failures of these components are updated regularly. This project was a continuation on the efforts of previous intern groups. Once complete, R&M engineers working on future space flight missions will be able to quickly access failure and mass data on assemblies and components, allowing them to make important decisions and tradeoffs.

  8. The behaviour of consolidated volcanic tuffs: weathering mechanisms under simulated laboratory conditions

    OpenAIRE

    Stück, H.; Forgó, L. Z.; Rüdrich, J.; S. Siegesmund; Török, Á.

    2008-01-01

    Five volcanic tuffs ranging from dacitic tuffs of Hungary to rhyolite, phonolite and basaltic tuffs of Germany were consolidated under laboratory conditions. Prior to consolidation an anti-hygro, a hydrous consolidant, which reduces the swelling ability of clay minerals, was applied. The three consolidants, a silicic acid ester (SAE), an elastic silicic acid ester (eSAE) and an acrylate resin (PMMA) were applied on test specimens under vacuum. Petrographic characterisation (polarizing microsc...

  9. 40Ar/ 39Ar mineral ages from the Oki metamorphic complex, Oki-Dogo, southwest Japan: implications for regional correlations

    Science.gov (United States)

    Dallmeyer, R. D.; Takasu, A.

    1998-08-01

    The Oki metamorphic complex exposed in the Oki-Dogo islands consists predominantly of psammitic and pelitic gneisses with subordinate amphibolite and rare calcareous gneiss. The Oki gneisses were regionally metamorphosed to general amphibolite facies conditions, with local development of granulite facies assemblages. Peak metamorphic conditions of c. 800°C have been suggested. Hornblende concentrates from amphibolites collected within the Oki metamorphic complex record 40Ar/ 39Ar isotope correlation ages of 199-192 Ma. These are interpreted to date the post metamorphic cooling through temperatures required for intracrystalline retention of argon (c. 500°C). Muscovite concentrates record 40Ar/ 39Ar plateau ages of 167-168 Ma. These are interpreted to date post metamorphic cooling through appropriate closure temperature of muscovite (c. 400-375°C). Combined with the previously reported geochronological data, the Oki metamorphic complex appears to have experienced peak metamorphic conditions at c. 250 Ma. Subsequently, it cooled and was exhumed at the earth's surface at c. 90 Ma with cooling rate of c. 5°C/Ma. The Oki metamorphic complex records a similar prograde metamorphic event as the Hida metamorphic complex exposed in central Japan. The cooling and exhumation rates of the Hida metamorphic complex were significantly more rapid compared with the Oki metamorphic complex, and they were exhumed with extensively intruded Jurassic granites (Funatsu granites).

  10. Zircon crystallization and recycling in the magma chamber of the rhyolitic Kos Plateau Tuff (Aegean arc)

    Science.gov (United States)

    Bachman, O.; Charlier, B.L.A.; Lowenstern, J. B.

    2007-01-01

    In contrast to most large-volume silicic magmas in continental arcs, which are thought to evolve as open systems with significant assimilation of preexisting crust, the Kos Plateau Tuff magma formed dominantly by crystal fractionation of mafic parents. Deposits from this ~60 km3 pyroclastic eruption (the largest known in the Aegean arc) lack xenocrystic zircons [secondary ion mass spectrometry (SIMS) U-Pb ages on zircon cores never older than 500 ka] and display Sr-Nd whole-rock isotopic ratios within the range of European mantle in an area with exposed Paleozoic and Tertiary continental crust; this evidence implies a nearly closed-system chemical differentiation. Consequently, the age range provided by zircon SIMS U-Th-Pb dating is a reliable indicator of the duration of assembly and longevity of the silicic magma body above its solidus. The age distribution from 160 ka (age of eruption by sanidine 40Ar/39Ar dating; Smith et al., 1996) to ca. 500 ka combined with textural characteristics (high crystal content, corrosion of most anhydrous phenocrysts, but stability of hydrous phases) suggest (1) a protracted residence in the crust as a crystal mush and (2) rejuvenation (reduced crystallization and even partial resorption of minerals) prior to eruption probably induced by new influx of heat (and volatiles). This extended evolution chemically isolated from the surrounding crust is a likely consequence of the regional geodynamics because the thinned Aegean microplate acts as a refractory container for magmas in the dying Aegean subduction zone (continent-continent subduction).

  11. {sup 40}Ar-{sup 39}Ar dating of terrestrial and exterrestrial materials. Basalts from the Japan Sea floor, Deccan Plateau and meteorites from Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Kaneoka, Ichiro [Tokyo Univ. (Japan). Earthquake Research Inst.; Takigami, Yutaka

    1994-09-01

    Through a series of {sup 40}Ar-{sup 39}Ar dating for terrestrial and exterrestrial samples, the results for basalts from the Japan Sea floor, Deccan Plateau and for meteorites from Antarctica give significant information concerning their formation histories. {sup 40}Ar-{sup 39}Ar ages of basalts from the Japan Sea floor give a constraint that the Japan Sea floor was formed at least 20 Ma. {sup 40}Ar-{sup 39}Ar ages for dyke samples from the Deccan Plateau indicate a possibility for the occurrence of a little younger ages than that of the main plateau formations by a few million years. Meteorites collected from Antarctica show some variable {sup 40}Ar-{sup 39}Ar ages reflecting their different thermal histories. (author).

  12. Evaluation of Pleistocene groundwater flow through fractured tuffs using a U-series disequilibrium approach, Pahute Mesa, Nevada, USA

    Science.gov (United States)

    Paces, James B.; Nichols, Paul J.; Neymark, Leonid A.; Rajaram, Harihar

    2013-01-01

    Groundwater flow through fractured felsic tuffs and lavas at the Nevada National Security Site represents the most likely mechanism for transport of radionuclides away from underground nuclear tests at Pahute Mesa. To help evaluate fracture flow and matrix–water exchange, we have determined U-series isotopic compositions on more than 40 drill core samples from 5 boreholes that represent discrete fracture surfaces, breccia zones, and interiors of unfractured core. The U-series approach relies on the disruption of radioactive secular equilibrium between isotopes in the uranium-series decay chain due to preferential mobilization of 234U relative to 238U, and U relative to Th. Samples from discrete fractures were obtained by milling fracture surfaces containing thin secondary mineral coatings of clays, silica, Fe–Mn oxyhydroxides, and zeolite. Intact core interiors and breccia fragments were sampled in bulk. In addition, profiles of rock matrix extending 15 to 44 mm away from several fractures that show evidence of recent flow were analyzed to investigate the extent of fracture/matrix water exchange. Samples of rock matrix have 234U/238U and 230Th/238U activity ratios (AR) closest to radioactive secular equilibrium indicating only small amounts of groundwater penetrated unfractured matrix. Greater U mobility was observed in welded-tuff matrix with elevated porosity and in zeolitized bedded tuff. Samples of brecciated core were also in secular equilibrium implying a lack of long-range hydraulic connectivity in these cases. Samples of discrete fracture surfaces typically, but not always, were in radioactive disequilibrium. Many fractures had isotopic compositions plotting near the 230Th-234U 1:1 line indicating a steady-state balance between U input and removal along with radioactive decay. Numerical simulations of U-series isotope evolution indicate that 0.5 to 1 million years are required to reach steady-state compositions. Once attained, disequilibrium 234U/238U

  13. Stratigraphy, paleomagnetism, and magnetic fabric of the Toba Tuffs: Constraints on the sources and eruptive styles

    Science.gov (United States)

    Knight, Michael D.; Walker, George P. L.; Ellwood, Brooks B.; Diehl, Jimmy F.

    1986-09-01

    The Toba depression in north central Sumatra is a complex of several overlapping calderas resulting from three major ignimbrite-forming eruptions. Within the depression, the upland masses of Samosir and northern Uluan consist of welded ignimbrite capped by coarse breccia and lacustrine sediment, hitherto interpreted to be two parts of a single resurgent dome. This study has demonstrated that the welded tuffs of Samosir and Uluan have different magnetic polarities and therefore at least two different ignimbrites are present; the Samosir/Uluan massif may consist of parts of two resurgent domes. The first ignimbrite eruption occurred at 0.84 Ma and produced a very thick (>400 m), densely welded unit having a reversed polarity. Anisotropy of magnetic susceptibility (AMS) flow direction and lithic size data indicate that the source lies in the southern part of the Toba depression, and the thick deposit of Uluan is thought to have ponded in a 40-km-wide caldera. The second ignimbrite is normally magnetized. AMS flow direction data indicate two separate source vents, one to the north in the Haranggaol caldera, and another to the south. The thick deposit at Samosir is thought to have ponded in the southern caldera. Coarse sediments then accumulated over Samosir and northern Uluan and were capped by lacustrine deposits. A renewed episode of resurgence then uplifted Samosir Island and possibly the northern part of Uluan. At approximately 0.075 Ma the last and apparently largest ignimbrite eruption occurred from calderas in the north and south parts of the Toba depression. This ignimbrite is mostly nonwelded and normally magnetized. Part of the Uluan dome was destroyed by collapse of the Sibandung caldera and Latung graben and concomitant with renewed subsidence of the Haranggaol and Porsea calderas.

  14. Bond strength of cementitious borehole plugs in welded tuff

    Energy Technology Data Exchange (ETDEWEB)

    Akgun, H.; Daemen, J.J.K. [Arizona Univ., Tucson, AZ (USA). Dept. of Mining and Geological Engineering

    1991-02-01

    Axial loads on plugs or seals in an underground repository due to gas, water pressures and temperature changes induced subsequent to waste and plug emplacement lead to shear stresses at the plug/rock contact. Therefore, the bond between the plug and rock is a critical element for the design and effectiveness of plugs in boreholes, shafts or tunnels. This study includes a systematic investigation of the bond strength of cementitious borehole plugs in welded tuff. Analytical and numerical analysis of borehole plug-rock stress transfer mechanics is performed. The interface strength and deformation are studied as a function of Young`s modulus ratio of plug and rock, plug length and rock cylinder outside-to-inside radius ratio. The tensile stresses in and near an axially loaded plug are analyzed. The frictional interface strength of an axially loaded borehole plug, the effect of axial stress and lateral external stress, and thermal effects are also analyzed. Implications for plug design are discussed. The main conclusion is a strong recommendation to design friction plugs in shafts, drifts, tunnels or boreholes with a minimum length to diameter ratio of four. Such a geometrical design will reduce tensile stresses in the plug and in the host rock to a level which should minimize the risk of long-term deterioration caused by excessive tensile stresses. Push-out tests have been used to determine the bond strength by applying an axial load to cement plugs emplaced in boreholes in welded tuff cylinders. A total of 130 push-out tests have been performed as a function of borehole size, plug length, temperature, and degree of saturation of the host tuff. The use of four different borehole radii enables evaluation of size effects. 119 refs., 42 figs., 20 tabs.

  15. Chemical and physical erosion rhythms of the West African Cenozoic morphogenesis: The 39Ar-40Ar dating of supergene K-Mn oxides

    Science.gov (United States)

    Beauvais, Anicet; Ruffet, Gilles; HéNocque, Olivier; Colin, Fabrice

    2008-12-01

    Chemical weathering and mechanical erosion are first-order processes of long-term tropical morphogenesis, which is still poorly deciphered for lack of time constraints. We address this issue by laser probe 39Ar-40Ar dating of generations of cryptomelane [K1-2Mn8O16, nH2O] from the manganese ore deposit of Tambao in northern Burkina Faso. This Mn deposit results from the supergene weathering of carbonate and silicate Mn protores underneath lateritic palaeolandsurfaces. It consists of an upper cryptomelane-rich domain and a lower domain where pyrolusite (β-MnO2) is the dominant Mn oxide. The oldest 39Ar-40Ar ages (59-45 Ma) are obtained on surface outcrops while the youngest ones characterize deep oxidation fronts (3.4-2.9 Ma). Apparent correlations of 39Ar-40Ar age groups with δ18O and eustatic curves allow definition of the different stages of morphogenesis. Paleocene-Eocene ages (59-45 Ma) bracket a greenhouse period propitious to bauxitic weathering. The lack of significant ages between ˜45 and 29 Ma characterizes a period dominated by mechanical erosion, during which detrital sediments, including lateritic materials, were accumulated in intracratonic basins allowing the exhumation of a new lateritic landsurface. Two major weathering periods separated by a second erosion episode (24-18 Ma) are also depicted at the end of Oligocene (29-24 Ma) and lower to mid-Miocene (18-11.5 Ma) in the upper domain, during which newly shaped land surfaces conspicuously weathered. The shorter-weathering and erosion episodes recorded in the lower domain from ˜18 to ˜2.9 Ma led to the final geomorphic changes that were conducive to the formation of glacis. The preservation of old cryptomelane (59-45 Ma) in the upper part of the ore deposit indicates a Cenozoic denudation limited to the erosion of previous bauxites, and partly, of ferricretes.

  16. 40Ar/39Ar Dating of Deformation Events and Reconstruction of Exhumation of Ultrahigh-Pressure Metamorphic Rocks in Donghai,East China

    Institute of Scientific and Technical Information of China (English)

    LI Jinyi; YANG Tiannan; CHEN Wen; ZHANG Sihong

    2003-01-01

    Recent investigations reveal that the ultrahigh-pressure metamorphic (UHPM) rocks in the Donghai regionof East China underwent ductile and transitional ductile-brittle structural events during their exhumation. The earlierductile deformation took place under the condition of amphibolite facies and the later transitional ductile-brittledeformation under the condition of greenschist facies. The hanging walls moved southeastward during both of these twoevents. The 40Ar/39Ar dating of muscovites from muscovite-plagioclase schists in the Haizhou phosphorous mine, whichare structurally overlain by UHPM rocks, yields a plateau age of 218.0±2.9 Ma and isochron age of 219.8Ma, indicatingthat the earlier event of the ampibolite-facies deformation probably took place about 220 Ma ago. The 40Ar/39Ar dating oforiented amphiboles parallel to the movement direction of the hanging wall on a decollement plane yields a plateau age of213.1 ±0.3 Ma and isochron age of 213.4±4.1 Ma, probably representing the age of the later event. The dating of pegmatiticbiotites and K-feldspars near the decollement plane from the eastern Fangshan area yield plateau ages of 203.4±0.3 Ma,203.6±0.4 Ma and 204.8±2.2 Ma, and isochron ages of 204.0±2.0 Ma, 200.6±3.1 Ma and 204.0±5.0 Ma, respectively,implying that the rocks in the studied area had not been cooled down to closing temperature of the dated biotites and K-feldspars until the beginning of the Jurassic (about 204 Ma). The integration of these data with previous chronological ageson the ultrahigh-pressure metamorphism lead to a new inference on the exhumation of the UHPM rocks. The UHPM rocksin the area were exhumed at the rate of 3-4 km/Ma from the mantle (about 80-100 km below the earth's surface at about240 Ma) to the lower crust (at the depth of about 20-30km at 220 Ma), and at the rate of 1-2 km/Ma to the middle crust (atthe depth of about 15 km at 213 Ma), and then at the rate of less than 1 km/Ma to the upper crust about 10 km deep

  17. Ars Himera / Irina Lobanova

    Index Scriptorium Estoniae

    Lobanova, Irina

    2003-01-01

    Iseloomustatakse praegust aega ja moodsat kunsti: valitseb vastutustundetus ja ebainimlikkus. Näited - professor von Hageni "Korpwelten" ja uusim kunstinähtus Ars Chimaera - eksponeerimise eesmärgil surrogaatsete elusolendite saamise kunst

  18. The 40Ar/39Ar age record of formation and uplift of the blueschists and eclogites in the western Tianshan Mountains

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The 40Ar/39Ar ages indicate that the eclogite facies rocks of the Hasiate slice in the western Tianshan Mountains were formed at the early stage of Devonian (401 Ma) and had been uplifted to the greenschist facies tectonic level in the middle stage of Devonian (381 Ma). The formation and uplift of the blueschists of the Akesayi slice are constrained to the late stage of Devonian (370─364 Ma). The different tectonic slices in the high-pressure metamorphic belt have experienced the different uplift history.

  19. Laboratory determined suction potential of Topopah Spring tuff at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Daily, W.; Lin, Wunan

    1991-01-01

    The purpose of this work is to experimentally determine the capillary suction potential of Topopah Spring tuff from Yucca Mountain, Nye County, Nevada. This data can be used to help characterize the unsaturated hydraulic properties of the densely welded tuff at this site. 7 refs., 4 figs., 1 tab.

  20. The Ar-Ar age and petrology of Miller Range 05029: Evidence for a large impact in the very early solar system

    Science.gov (United States)

    Weirich, J. R.; Wittmann, A.; Isachsen, C. E.; Rumble, D.; Swindle, T. D.; Kring, D. A.

    2010-12-01

    Miller Range (MIL) 05029 is a slowly cooled melt rock with metal/sulfide depletion and an Ar-Ar age of 4517 ± 11 Ma. Oxygen isotopes and mineral composition indicate that it is an L chondrite impact melt, and a well-equilibrated igneous rock texture with a lack of clasts favors a melt pool over a melt dike as its probable depositional setting. A metallographic cooling rate of approximately 14 °C Ma-1 indicates that the impact occurred at least approximately 20 Ma before the Ar-Ar closure age of 4517 Ma, possibly even shortly after accretion of its parent body. A metal grain with a Widmanstätten-like pattern further substantiates slow cooling. The formation age of MIL 05029 is at least as old as the Ar-Ar age of unshocked L and H chondrites, indicating that endogenous metamorphism on the parent asteroid was still ongoing at the time of impact. Its metallographic cooling rate of approximately 14 °C Ma-1 is similar to that typical for L6 chondrites, suggesting a collisional event on the L chondrite asteroid that produced impact melt at a minimum depth of 5-12 km. The inferred minimum crater diameter of 25-60 km may have shattered the 100-200 km diameter L chondrite asteroid. Therefore, MIL 05029 could record the timing and petrogenetic setting for the observed lack of correlation of cooling rates with metamorphic grades in many L chondrites.

  1. The unsaturated hydraulic characteristics of the Bandelier Tuff

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, D.B.; Gallaher, B.M.

    1995-09-01

    This report summarizes the physical and, unsaturated hydraulic properties of the Bandelier Tuff determined from laboratory measurements made on core samples collected at Los Alamos National Laboratory. We fit new van Genuchten-type moisture retention curves to this data, which was categorized according to member of the Bandelier Tuff and subunit of the Tshirege Member. Reasonable consistency was observed for hydraulic properties and retention curves within lithologic units, while distinct differences were observed for those properties between units. With the moisture retention data, we constructed vertical profiles of in situ matric suction and hydraulic head. These profiles give an indication of the likely direction of liquid water movement within the unsaturated zone and allow comparison of core-scale and field-scale estimates of water flow and solute transport parameters. Our core-derived transport velocities are much smaller than values estimated from tritium, Cl, and NO{sub 3} contamination found recently in boreholes. The contaminant tracer-derived transport velocities from Los Alamos Canyon are greater than corederived values found for the Otowi Member, and for Mortandad Canyon, greater than core-derived values for that borehole. The significant difference found for Mortandad Canyon suggests that fracture or other fast-path transport may be important there. The relatively small difference between observed and predicted velocities at Los Alamos Canyon may mean that vadose zone transport there occurs by unsaturated matrix flow.

  2. Colloid Facilitated Transport of Plutonium in Fractured Volcanic Tuff

    Science.gov (United States)

    Kersting, A. B.; Zhao, P.; Walensky, J. R.; Roberts, S. K.; Johnson, M. R.; Zavarin, M.; Ramon, E. C.

    2004-12-01

    The transport of low-solubility radionuclides in a colloidal- or colloidal bound state is frequently suspected or observed. Groundwater contaminated with radionuclides associated with underground nuclear tests was collected from several different well locations at the Nevada Test Site (NTS). In each case, the low-levels of plutonium detected in the groundwater were overwhelmingly (>95percent) associated with the colloidal and not the dissolved fraction of the groundwater. The colloidal fractions consisted of secondary minerals such as clays and zeolites. To better understand the mechanisms controlling the potential colloidal transport of plutonium, colloid-facilitated fracture flow laboratory experiments are being conducted. Pseudocolloids consisting of Pu(IV) sorbed to clinoptilolite were combined with a radionuclide solution cocktail consisting of Np, U, Cs, Sr, Sm and 3H and Re (analog to Tc) tracers in NTS-type synthetic groundwater (4.5mM NaHCO3-). The cocktail was injected into a smooth fracture in a volcanic tuff rock core from the NTS and the effluent analyzed. Autoradiography and secondary ion mass spectrometry will be used to understand the mineral -colloid-radionuclide interactions in the fracture volcanic tuff.

  3. Computerized tomographic analysis of fluid flow in fractured tuff

    Energy Technology Data Exchange (ETDEWEB)

    Felice, C.W.; Sharer, J.C. (Terra Tek, Inc., Salt Lake City, UT (United States)); Springer, E.P. (Los Alamos National Lab., NM (United States))

    1992-01-01

    The purpose of this summary is to demonstrate the usefulness of X-ray computerized tomography to observe fluid flow down a fracture and rock matrix imbibition in a sample of Bandelier tuff. This was accomplished by using a tuff sample 152.4 mm long and 50.8 mm in diameter. A longitudinal fracture was created by cutting the core with a wire saw. The fractured piece was then coupled to its adjacent section to that the fracture was not expected. Water was injected into a dry sample at five flow rates and CT scanning performed at set intervals during the flow. Cross sectional images and longitudinal reconstructions were built and saturation profiles calculated for the sample at each time interval at each flow rate. The results showed that for the test conditions, the fracture was not a primary pathway of fluid flow down the sample. At a slow fluid injection rate into the dry sample, the fluid was imbibed into the rock uniformly down the length of the core. With increasing injection rates, the flow remained uniform over the core cross section through complete saturation.

  4. Environmental effects on corrosion in the Tuff repository

    Energy Technology Data Exchange (ETDEWEB)

    Beavers, J.A.; Thompson, N.G. [Cortest Columbus, Inc., OH (USA)

    1990-02-01

    Cortest Columbus is investigating the long-term performance of container materials used for high-level waste packages as part of the information needed by the Nuclear Regulatory Commission to assess the Department of Energy`s application to construct a geologic repository for high-level radioactive waste. The scope of work consists of employing short-term techniques, to examine a wide range of possible failure modes. Long-term tests are being used to verify and further examine specific failure modes identified as important by the short-term studies. The original focus of the program was on the salt repository but the emphasis was shifted to the Tuff repository. This report summarizes the results of a literature survey performed under Task 1 of the program. The survey focuses on the influence of environmental variables on the corrosion behavior of candidate container materials for the Tuff repository. Environmental variables considered include: radiation, thermal and microbial effects. 80 refs., 44 figs., 44 tabs.

  5. 40Ar-39Ar thermochronology of two ductile shear zones from Yiwulüshan, West Liaoning Region: Age constraints on the Mesozoic tectonic events

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Two ductile shear zones trending EW and NNE respectively not only controlled the tectonic framework of the northern North China, but also constrained the geodynamic background for gold mineralization in this region. Field observations and microstructural analyses reveal that the EW trending ductile shear zones are mainly contributed to dextral compressional deformation resulting from top-to- the-southeast oblique thrust shearing, whereas the NNE trending ones are genetically related to sinistral strike-slip and extensional faulting. One sample from the former yielded an 40Ar-39Ar plateau age of (219±4) Ma (Bi) and two samples from the latter gave 40Ar-39Ar plateau ages of (116±2) Ma (Bi) and (127±3) Ma (Bi). These ages provide constraints on the top-to-the-southeast oblique thrusting event occurring in Late Triassic and the sinistral extensional and strike-slip faulting event which occurred in Early Cretaceous.

  6. Investigation of Using Waste Welded Tuff Material as Mineral Filler in Asphalt Concrete

    Directory of Open Access Journals (Sweden)

    Sebnem KARAHANCER

    2016-08-01

    Full Text Available In this paper, the welded tuff waste- known as koyke in Isparta region - was used in the hot mix asphalt (HMA as mineral filler for reduction of the moisture susceptibility of HMA. Optimum binder content was assessed with Marshall Design Method. First of all, welded tuff was substituted as filler with limestone filler in proportion of 50% and 100%. After that Marshall Stability test was performed on specimens. The results showed that the 50% substitution was more effective than the 100% substitution. Therefore, welded tuff was substituted with limestone filler in proportion of 25%, 50%, 65% and 75%. Next, Indirect Tensile Strength test was practiced on the fabricated specimens and the results were assessed. According to the Indirect Tensile Strength results, welded tuff with 65% was given higher strength than the limestone filler. As a result, it has come up that welded tuff can be used as mineral filler in the hot mix asphalt.

  7. Age and petrology of the Late-Pleistocene brown tuffs on Lipari, Italy

    Science.gov (United States)

    Crisci, G. M.; Delibrias, G.; de Rosa, R.; Mazzuoli, R.; Sheridan, M. F.

    1983-12-01

    Late-Pleistocene volcanic products on Lipari consist mainly of pyroclastic surge deposits (Monte Guardia sequence) and fine-grained brown tuffs. Radiometric age determination on carbon from thin soils at the top of the tuffs indicate that they have several ages of emplacement ranging from more than 35,000 to 16,800 years ago. Chemical and microprobe data on glass and mineral fragments from these tuffs show that they belong to a shoshonite or high-K series. This composition is compatible with an origin related to the magma system of Vulcano, but not with the magma system on Lipari. These tuffs have a widespread distribution on several of the Aeolian islands as well as on the northern part of Sicily. They have features typical of ash-flow tuffs of hydromagmatic origin. We propose that they originated from submarine eruptions from the Vulcanello vent before this volcano emerged above sea level.

  8. SIMS U-Pb zircon age of a tuff layer in the Meishucun section, Yunnan, southwest China: Constraint on the age of the Precambrian-Cambrian boundary

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Determination of the age of the Precambrian-Cambrian boundary is critical in understanding early evolution of life on Earth. SIMS U-Pb zircon analyses of the Bed 5 tuff layer of the Meishucun section were carried out closely following the guidance of cathodoluminescence images, and the majority of analyses were conducted on the oscillatory zircon grains. Thirteen measurements yield a highly reliable Concordia U-Pb age of 536.7 ± 3.9 Ma for the Bed 5 horizon. A grand mean of 206Pb/238U age of 535.2± 1.7 Ma (MSWD = 0.53) is calculated based on 13 concordant SIMS measurements of this study and 4 nano-SIMS measurements of Sawaki et al., which is the best estimate of the deposition age of the tuff layer within Bed 5 in the Meishucun section. This age has provided a robust age constraint on the significant Precambrian-Cambrian boundary strata in southern China, which independently suggested the placement of the Precambrian-Cambrian boundary at the bottom of the Xiaowaitoushan Member (Marker A).

  9. Paleosol-based evidence for humid to semi-arid pre-10Ma climates in the Atacama Desert, Chile

    Science.gov (United States)

    Oerter, E.; Amundson, R.; Heimsath, A. M.; Jungers, M. C.; Chong, G.

    2011-12-01

    The Tertiary paleoclimate of the Atacama Desert is poorly known and widely debated. Post-10 Ma climate has at least one early period of hyperaridity (Resh et al., 2006, Geology, 34:761), and multiple lines of evidences for a strong and nearly-continuous post-Pliocene hyper-aridification largely coincident with changes in Pacific sea surface temperatures (Amundson et al., in press). In 2010, we examined a sequence of pre-10 Ma gravelly, continental sediments exposed at the El Tesoro Mine, near Calama Chile. The gravel underlies a 10 Ma ignimbrite, and the geomorphic surfaces above this layer consist of largely incised fluvial surfaces of Miocene (?) to recent age. Several tuff samples from nearby the mine have been identified and are being processed for 40Ar/39Ar geochronological analyses. Here, we focus on the ~300 m sequence of gravels we examined that contained a sequence of 22 or more paleosols (22° 57' S, 69° 5' W). The paleosols were developed on an aggrading alluvial fan system from streams largely to the east, and lie above the mineralized gravels that host the copper ore body. The soils are extremely well preserved due to minimal burial and little aqueous diagenesis. The remarkable feature of the paleosols is that they represent oscillating soil forming conditions between chemical weathering/clay production (humid: Alfisols) to environments that facilitated the accumulation of pedogenic carbonate (arid to semi-arid: Aridisols). All carbonate bearing samples are being analyzed for stable C and O isotopes. All bulk samples are being analyzed for total geochemical composition, to yield an examination of chemical alteration. Samples from the two oldest paleosols in the sequence (Calcids or Calciarids) average δ13C and δ18O values (VPDB) of ca. -3.1 and -4.2 respectively. Presently, the local region is a sulfate-, rather than carbonate-, forming soil environment. At elevations exceeding ~2500 m, carbonates begin to appear. Based on analyses of nearby sites

  10. 40Ar/39Ar geochronological constraints on syn-orogenic strike-slip movement of Tan-Lu fault zone

    Institute of Scientific and Technical Information of China (English)

    ZHU Guang; LIU Guosheng; W. J. Dunlap; C. Teyssier; WANG Yongsheng; NIU Manlan

    2004-01-01

    Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabie orogenic belt.A muscovite 40Ar/39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone. Three muscovite samples separated from mylonites of 3 localities in the earlier ductile shear belts yield 40Ar/39Ar plateau ages of 192.5±0.7 Ma, 189.7±0.6 Ma and 188.7±0.7 Ma, respectively. They are interpreted as cooling ages of the earlier sinistrai strike-slip deformation. It is suggested that left-lateral displacement of the Tan-Lu fault zone started in a late stage of the collision orogeny in the Dabie-Sulu orogenic belt between the North and South China plates. Therefore, the earlier Tan-Lu fault zone was syn-orogenic strike-slip tectonics.The fault zone was used again for sinistral displacement during tectonic activities of peri-Pacific regime in Early Cretaceous. It is proposed that the fault zone occurred as a transform fault during the orogenic process.

  11. 40Ar/ 39Ar ages for the alkaline volcanism and the basement of Gorringe Bank, North Atlantic ocean

    Science.gov (United States)

    Féraud, Gilbert; Gastaud, Janine; Auzende, Jean-Marie; Olivet, Jean-Louis; Cornen, Guy

    1982-01-01

    Gorringe Bank is situated on the Europe-Africa plate boundary at the eastern end of the Azores-Gibraltar fracture zone. It has two summits, Gettysburg Bank to the Southwest and Ormonde Bank to the northeast. We applied the 40Ar/ 39Ar stepwise heating method to date six samples of the alkaline volcanic rocks, two gabbros from the Ormonde Bank and a dolerite from the Gettysburg Bank. The results that the alkaline volcanism lasted probably for less than 6 Ma(66-60 Ma). Although the nature of this volcanism precludes any subduction feature during its setting, the alkaline volcanism of Ormonde is probably linked to Upper Cretaceous/Eocene compressive tectonic events. The basement rocks of Gorringe Bank reveal distrubed 40Ar/ 39Ar age spectra. One plagioclase and one biotite from a gabbro give evidence for a thermic event whose age is tentatively estimated at about 75 Ma, and related to a variation in the direction of the relative movement between Europe and Africa. The more probable age given by a plagioclase of another gabbro and by a dolerite (110 Ma) corresponds to tilting northeastward of the Gorringe massif.

  12. AR Alternative Splicing and Prostate Cancer Progression

    Science.gov (United States)

    2012-07-01

    evolutionary origin and sequence divergence, with relative ages (oldest to youngest) L1M1 > L1MA3 > L1PB2 > L1PREC2 > L1PA7 > L1PA5 (41, 42). Figure...variant of the human AR, which was originally identified via 5 0 rapid amplification of cDNA ends (RACE) with RNA isolated from human placenta tissue...prerequisite for tran- scriptional activation. However, this theory has not been rigor- ously tested. Therefore, we transfected cells with diverse trun

  13. Emplacement of Amba Dongar Carbonatite-alkaline Complex at Cretaceous/Tertiary Boundary: Evidence from 40Ar-39Ar Chronology

    Indian Academy of Sciences (India)

    Jyotiranjan S Ray; Kanchan Pande; T R Venkatesan

    2000-03-01

    40Ar-39Ar analyses of three fresh alkaline rock samples and a phlogopite separate from a carbonatite from Amba Dongar carbonatite-alkaline complex of the Deccan Flood Basalt Province, India, yield indistinguishable precise plateau ages of 64.8 ± 0.6, 64.7 ± 0.5, 65.5 ± 0.8 and 65.3 ± 0.6 Ma, giving a mean plateau age of 65.0 ± 0.3 Ma, which is the age of emplacement of this complex. This age implies contemporaneity of Amba Dongar with several other carbonatite-alkaline activities of Chhota Udaipur subprovince and is consistent with their Reunion-Deccan plume origin hypothesis. The emplacement of these complexes at 65 Ma makes them very significant in the ongoing debate on the K/T extinctions owing to their capacity to rapidly inject a substantial amount of CO2 and SO2 into the atmosphere.

  14. Magnetic fabric and welding processes in high-grade tuffs

    Science.gov (United States)

    Pioli, L.; Ort, M.; Lanza, R.; Rosi, M.

    2003-04-01

    The welding fabric of tuffs is generally quantified through two main parameters: porosity and fiamme aspect ratio. However, these parameters are not useful for high-grade ignimbrites that display features indicating extensive rheomorphic flow, partial to complete obliteration of primary vitroclastic textures, and syn-depositional welding rather than load-related compaction. In this case, a 3D-microstructural characterization of the rock fabric is a fundamental proxy for the assessment of the dynamics and duration of welding processes. We have investigated the relations between magnetic fabric and welding textures in a rhyolitic, high-grade ignimbrite from the Sulcis volcanic District (SW Sardinia, Italy). The ignimbrite is characterized by dense welding throughout its preserved thickness and by regular lateral and vertical variations of welding, devitrification and vesiculation facies. Field and structural data indicate that syn-depositional welding and non-particulate (NP) flow were extensive and continuous during the emplacement of the ignimbrite. Paleomagnetic measurements of AMS, NRM, and AIRM of samples from the tuff indicate that the magnetic fabric is strain-sensitive and it is not significantly affected by post-depositional, static processes such as devitrification and vapor-phase alteration; in particular, magnetic susceptibility of the rock and the welding texture correlate well in terms of shape and orientation of the anisotropy ellipsoid. The direction of the K1 axis is indicative of the flow direction in the site of measurement. The anisotropy degree (P) increases with increasing welding and foliation (F) and lineation (L) are directly related to the strain facies. Onset of welding increased the degree of anisotropy and foliation; a non particulate, laminar flow stage further deformed the fabric stretching it along the flow direction and thus increasing L. The intensity of L is strictly related to the duration and the effect of simple shear (laminar

  15. Arsenogoyazite in Cenozoic volcanic tuff at Tabalaopa Basin, Chihuahua, Mexico

    Science.gov (United States)

    Ren, M.; Rodriguez, A.; Goodell, P.

    2012-12-01

    Arsenogoyazite has been identified in Cenozoic volcanic tuff at Tabalaopa Basin, Chihuahua, Mexico. Tabalaopa Basin contains volcanic strata and the unconsolidated Quaternary deposit. Cenozoic volcanic tuff forms the low hill terrene in this area. It is a major reservoir for the City of Chihuahua groundwater. Arsenic anomaly (more than 20 ppb) has been observed at El Mimbre, northeast of the city. The exposed reddish color volcanic rocks are felsic welded tuff and rhyolite. Sanidine, quartz, and biotite phenocrysts show linear distribution within the fine grain matrix. The rocks contain large amount of vesicles which are lineated with the welding bends. White and colorless microsize crystals formed on the well of the cavities and the majority of them are K-feldspar. Quartz, Ti-magnetite, and arsenogoyazite are coexisting with feldspars. The sizes of the crystals in the cavities are 10 to several 10s of micrometers. The arsenic x-ray maps have been collected for the rock sections to locate the arsenic minerals. The crystals in cavities show euhedral shape. Most arsenic containing crystals have a near cubic form with triangle surfaces at some corners. The high resolution field-emission SEM images have been collected to study the symmetry of the crystals. EDS spectra for the high arsenic phases show three major elements As-Al-Sr and also minor amount of P-S-REE-Ca-Fe-Si. Since the arsenic minerals are growing on the wall of the vesicle, it is difficult to perform good electron microprobe analysis. Some primary microprobe data give following results in weight percent: SrO 11.8-13.1, CaO 0.2-0.3, FeO 0.3-0.5, Al2O3 28.6-30.9, La2O3 2.4-2.5, Ce2O3 2.3-.24, SiO2 1.1-3.6, As2O5 32.4-35.2, P2O5 1.7-1.9, SO3 0.8-1.4. This chemistry is similar to the reported arsenogoyazite chemical data. So this high arsenic phase is identified as arsenogoyazite. The arsenic anomaly in groundwater at El Mimbre, Chihuahua should be contributed from this arsenic mineral phase in the strata.

  16. 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

  17. Probing the volcanic-plutonic connection and the genesis of crystal-rich rhyolite in a deeply dissected supervolcano in the Nevada Great Basin: Source of the late Eocene Caetano Tuff

    Science.gov (United States)

    Watts, Kathryn E.; John, David A.; Colgan, Joseph P.; Henry, Christopher D.; Bindeman, Ilya N.; Schmitt, Axel K.

    2016-01-01

    Late Cenozoic faulting and large-magnitude extension in the Great Basin of the western USA has created locally deep windows into the upper crust, permitting direct study of volcanic and plutonic rocks within individual calderas. The Caetano caldera in north–central Nevada, formed during the mid-Tertiary ignimbrite flare-up, offers one of the best exposed and most complete records of caldera magmatism. Integrating whole-rock geochemistry, mineral chemistry, isotope geochemistry and geochronology with field studies and geologic mapping, we define the petrologic evolution of the magmatic system that sourced the >1100 km3Caetano Tuff. The intra-caldera Caetano Tuff is up to ∼5 km thick, composed of crystal-rich (30–45 vol. %), high-silica rhyolite, overlain by a smaller volume of comparably crystal-rich, low-silica rhyolite. It defies classification as either a monotonous intermediate or crystal-poor zoned rhyolite, as commonly ascribed to ignimbrite eruptions. Crystallization modeling based on the observed mineralogy and major and trace element geochemistry demonstrates that the compositional zonation can be explained by liquid–cumulate evolution in the Caetano Tuff magma chamber, with the more evolved lower Caetano Tuff consisting of extracted liquids that continued to crystallize and mix in the upper part of the chamber following segregation from a cumulate-rich, and more heterogeneous, source mush. The latter is represented in the caldera stratigraphy by the less evolved upper Caetano Tuff. Whole-rock major, trace and rare earth element geochemistry, modal mineralogy and mineral chemistry, O, Sr, Nd and Pb isotope geochemistry, sanidine Ar–Ar geochronology, and zircon U–Pb geochronology and trace element geochemistry provide robust evidence that the voluminous caldera intrusions (Carico Lake pluton and Redrock Canyon porphyry) are genetically equivalent to the least evolved Caetano Tuff and formed from magma that remained in the lower chamber after

  18. Ar-40/Ar-39 Ages for Maskelynites and K-Rich Melt from Olivine-Rich Lithology in (Kanagawa) Zagami

    Science.gov (United States)

    Park, J.; Herzog, G. F.; Nyquist, L. E.; Lindsay, F.; Turrin, B.; Swisher, C. C., III; Delaney, J. S.; Shih, C.-Y.; Niihara, T.; Misawa, K.

    2013-01-01

    We report Ar/Ar release patterns for small maskelynite grains and samples of a K-rich phase separated from the basaltic shergottite Zagami. The purpose of the work is to investigate the well-known discrepancy between published Ar/Ar ages of Zagami, >200 Ma, and its age of approx. 170 Ma as determined by other methods [1-6]. Niihara et al. [7] divide less abundant darker material present in Zagami into an olivine-rich lithology (ORL), from which most of our samples came, and a pyroxene-rich one (Dark Mottled-Lithology: DML) [8, 9]. ORL consists of vermicular fayalitic olivine, coarse-grained pyroxene, maskelynite, and a glassy phase exceptionally rich in K (up to 8.5 wt%), Al, and Si, but poor in Fe and Mg. The elemental composition suggests a late-stage melt, i.e., residual material that solidified late in a fractional crystallization sequence. Below we refer to it as "K-rich melt." The K-rich melt contains laths of captured olivine, Ca-rich pyroxene, plagioclase, and opaques. It seemed to offer an especially promising target for Ar-40/Ar-39 dating.

  19. Neutron and gamma (density) logging in welded tuff

    Energy Technology Data Exchange (ETDEWEB)

    Lin, W

    1998-09-12

    This Technical Implementation Procedure (TIP) describes the field operation, and the management of data records pertaining to neutron logging and density logging in welded tuff. This procedure applies to all borehole surveys performed in support of Engineered Barrier System Field Tests (EBSFT), including the Earge Block Tests (LBT) and Initial Engineered Barrier System Field Tests (IEBSFT) - WBS 1.2.3.12.4. The purpose of this TIP is to provide guidelines so that other equally trained and qualified personnel can understand how the work is performed or how to repeat the work if needed. The work will be documented by the use of Scientific Notebooks (SNs) as discussed in 033-YMP-QP 3.4. The TIP will provide a set of guidelines which the scientists will take into account in conducting the mea- surements. The use of this TIP does not imply that this is repetitive work that does not require profes- sional judgment.

  20. Neutron and gamma (density) logging in welded tuff

    Energy Technology Data Exchange (ETDEWEB)

    Lin, W

    1998-09-12

    This Technical Implementation Procedure (TIP) describes the field operation, and the management of data records pertaining to neutron logging and density logging in welded tuff. This procedure applies to all borehole surveys performed in support of Engineered Barrier System Field Tests (EBSFT), including the Earge Block Tests (LBT) and Initial Engineered Barrier System Field Tests (IEBSFT) - WBS 1.2.3.12.4. The purpose of this TIP is to provide guidelines so that other equally trained and qualified personnel can understand how the work is performed or how to repeat the work if needed. The work will be documented by the use of Scientific Notebooks (SNs) as discussed in 033-YMP-QP 3.4. The TIP will provide a set of guidelines which the scientists will take into account in conducting the mea- surements. The use of this TIP does not imply that this is repetitive work that does not require profes- sional judgment.

  1. Welded tuff infilling a volcanic vent at Weolseong, Republic of Korea

    Science.gov (United States)

    Reedman, Antony John; Park, Ki Hwa; Merriman, Richard James; Kim, Seon Eok

    1987-06-01

    A plug of parataxitically welded tuff, with an elliptical (700 × 400 m) cross section, crops out in Weolseong district, Republic of Korea. It intrudes late Cretaceous granodiorite and extrusive tuffs of the Chisulryoung Volcanic Formation and displays a steeply inclined welding foliation, concordant with the intrusive contacts, and a subvertical stretching lineation. These fabrics are interpreted as resulting from laminar shearing in a boundary layer during deposition of the tuff by agglutination along the walls of a vent which served as a feeder for extrusive ignimbrites.

  2. Anisotropy of magnetic susceptibility in welded tuffs: application to a welded-tuff dyke in the tertiary Trans-Pecos Texas volcanic province, USA

    Science.gov (United States)

    Wolff, John A.; Ellwood, Brooks B.; Sachs, Scott D.

    1989-06-01

    Consideration of published anisotropy of magnetic susceptibility (AMS) studies on welded ignimbrites suggests that AMS fabrics are controlled by groundmass microlites distributed within the existing tuff fabric, the sum result of directional fabrics imposed by primary flow lineation, welding, and (if relevant) rheomorphism. AMS is a more sensitive indicator of fabric elements within welded tuffs than conventional methods, and usually yields primary flow azimuth estimates. Detailed study of a single densely welded tuff sample demonstrates that the overall AMS fabric is insensitive to the relative abundances of fiamme, matrix and lithics within individual drilled cores. AMS determinations on a welded-tuff dyke occurring in a choked vent in the Trans-Pecos Texas volcanic field reveals a consistent fabric with a prolate element imbricated with respect to one wall of the dyke, while total magnetic susceptibility and density exhibit axially symmetric variations across the dyke width. The dyke is interpreted to have formed as a result of agglutination of the erupting mixture on a portion of the conduit wall as it failed and slid into the conduit, followed by residual squeezing between the failed block and in situ wallrock. Irrespective of the precise mechanism, widespread occurrence of both welded-tuff dykes and point-welded, aggregate pumices in pyroclastic deposits may imply that lining of conduit walls by agglutionation during explosive volcanic eruptions is a common process.

  3. Preliminary assessment of clinoptilolite K/Ar results from Yucca Mountain, Nevada, USA: A potential high-level radioactive waste repository site

    Energy Technology Data Exchange (ETDEWEB)

    WoldeGabriel, G.; Broxton, D.E.; Bish, D.L.; Chipera, S.J. [Los Alamos National Lab., NM (United States)

    1992-12-31

    At Yucca Mountain, evidence for at least three distinct temporal groups of clinoptilolites can be delineated from the preliminary K/Ar dates (2 - 3 Ma; 4 - 5 Ma; 7 - 11 Ma). The older K/Ar dates that are similar to published illite/smectite ages (9-12 Ma) may be crystallization ages, whereas the younger dates probably represent continued diagenetic reactions of older clinoptilolites with percolating fluids. The K/Ar dates increase with depth, suggesting minimal argon loss in the deeper samples. internal consistency of the clinoptilolite K/Ar results at different levels within the drill holes suggest that dating of K-rich zeolites may provide useful information for assessing the zeolitization at Yucca Mountain. Variations in the K/Ar dates are probably related to Ar loss during dissolution of older clinoptilolites and to contamination by finely crystalline feldspars. 18 refs., 1 tab.

  4. Preliminary assessment of clinoptilolite K/Ar results from Yucca Mountain, Nevada: A potential high-level radioactive waste repository site

    Energy Technology Data Exchange (ETDEWEB)

    WoldeGabriel, G.; Bish, D.L.; Broxton, D.E.; Chipera, S.J.

    1992-03-01

    At Yucca Mountain, evidence for at least three distinct temporal groups of clinoptilolites can be delineated from the preliminary K/Ar dates (2--3 Ma; 4--5 Ma; 7--11 Ma). The older K/Ar dates that are similar to published illite/smectite ages (9--12 Ma) may be crystallization ages, whereas the younger dates probably represent continued diagenetic reactions of older clinoptilolites with percolating fluids. The K/Ar dates increase with depth, suggesting minimal argon loss in the deeper samples. Internal consistency of the clinoptilolite K/Ar results at different levels within the drill holes suggest that dating of K-rich zeolites may provide useful information for assessing the zeolitization at Yucca Mountain. Variations in the K/Ar dates are probably related to Ar loss during dissolution of older clinoptilolites and to contamination by finely crystalline feldspars.

  5. Discovery and utilization of sorghum genes (Ma5/Ma6)

    Science.gov (United States)

    Mullet, John E; Rooney, William L; Klein, Patricia E; Morishige, Daryl; Murphy, Rebecca; Brady, Jeff A

    2012-11-13

    Methods and composition for the production of non-flowering or late flowering sorghum hybrid. For example, in certain aspects methods for use of molecular markers that constitute the Ma5/Ma6 pathway to modulate photoperiod sensitivity are described. The invention allows the production of plants having improved productivity and biomass generation.

  6. Discordant K-Ar and young exposure dates for the Windjana sandstone, Kimberley, Gale Crater, Mars

    Science.gov (United States)

    Vasconcelos, P. M.; Farley, K. A.; Malespin, C. A.; Mahaffy, P.; Ming, D.; McLennan, S. M.; Hurowitz, J. A.; Rice, Melissa S.

    2016-10-01

    K-Ar and noble gas surface exposure age measurements were carried out on the Windjana sandstone, Kimberley region, Gale Crater, Mars, by using the Sample Analysis at Mars instrument on the Curiosity rover. The sandstone is unusually rich in sanidine, as determined by CheMin X-ray diffraction, contributing to the high K2O concentration of 3.09 ± 0.20 wt % measured by Alpha-Particle X-ray Spectrometer analysis. A sandstone aliquot heated to 915°C yielded a K-Ar age of 627 ± 50 Ma. Reheating this aliquot yielded no additional Ar. A second aliquot heated in the same way yielded a much higher K-Ar age of 1710 ± 110 Ma. These data suggest incomplete Ar extraction from a rock with a K-Ar age older than 1710 Ma. Incomplete extraction at 900°C is not surprising for a rock with a large fraction of K carried by Ar-retentive K-feldspar. Likely, variability in the exact temperature achieved by the sample from run to run, uncertainties in sample mass estimation, and possible mineral fractionation during transport and storage prior to analysis may contribute to these discrepant data. Cosmic ray exposure ages from 3He and 21Ne in the two aliquots are minimum values given the possibility of incomplete extraction. However, the general similarity between the 3He (57 ± 49 and 18 ± 32 Ma, mean 30 Ma) and 21Ne (2 ± 32 and 83 ± 24 Ma, mean 54 Ma) exposure ages provides no evidence for underextraction. The implied erosion rate at the Kimberley location is similar to that reported at the nearby Yellowknife Bay outcrop.

  7. Geochemistry and 40Ar/39Ar age of Early Carboniferous dolerite sills in the southern Baltic Sea

    Directory of Open Access Journals (Sweden)

    Gediminas Motuza

    2015-08-01

    Full Text Available The Early Carboniferous magmatic event in the southern Baltic Sea is manifested by dolerite intrusions. The presumable area in which the dolerite intrusions occur ranges from 30 to 60 km in east–west direction, and is about 100 km in north–south direction. The dolerites were sampled in well D1-1 and investigated by applying chemical analysis and 40Ar/39Ar step-heating dating. Dolerites are classified as alkali and sodic, characterized by high TiO2 (3.92, 3.99 wt% and P2O5 (1.67, 1.77 wt% and low MgO (4.89, 4.91 wt% concentrations, enriched in light rare earth elements, originated from an enriched mantle magma source and emplaced in a continental rift tectonic setting. The 351 ± 11 Ma 40Ar/39Ar plateau age for groundmass plagioclase indicates a considerable age gap with the 310–250 Ma magmatism in southern Scandinavia and northern Germany. The magmatic rocks in the Baltic Sedimentary Basin are coeval with alkaline intrusions of NE Poland. Both magmatic provinces lie in the northwestward prolongation of the Pripyat–Dnieper–Donetsk Rift (370–359 Ma and may constitute a later phase of magmatic activity of this propagating rift system.

  8. Ramon Llull's Ars Magna

    DEFF Research Database (Denmark)

    Jensen, Thessa

    2017-01-01

    intelligence and knowledge representation, which seeks to formalise language and knowledge in a way which can be translated into a computer program. And as Fidora’s and Sierra’s [4] anthology Ramon Llull: From the Ars Magna to Artificial Intelligence shows, Llull’s influence and relevance is profound in today......’s work on topics ranging from conceptual graphs and logical analysis, social choice theory and adaptive reasoning to Llull’s influence on Peirce’s pragmatic thinking. Llull is important, even now, on a whole other level. His ethical considera-tions when he wanted to convince people of the one true faith...... Llull: From the Ars Magna to Artificial Intelligence. Barcelona: Artificial Intelligence Research Institute (2011)....

  9. Rapid pre-eruptive thermal rejuvenation in a large silicic magma body: the case of the Masonic Park Tuff, Southern Rocky Mountain volcanic field, CO, USA

    Science.gov (United States)

    Sliwinski, J. T.; Bachmann, O.; Dungan, M. A.; Huber, C.; Deering, C. D.; Lipman, P. W.; Martin, L. H. J.; Liebske, C.

    2017-05-01

    Determining the mechanisms involved in generating large-volume eruptions (>100 km3) of silicic magma with crystallinities approaching rheological lock-up ( 50 vol% crystals) remains a challenge for volcanologists. The Cenozoic Southern Rocky Mountain volcanic field, in Colorado and northernmost New Mexico, USA, produced ten such crystal-rich ignimbrites within 3 m.y. This work focuses on the 28.7 Ma Masonic Park Tuff, a dacitic ( 62-65 wt% SiO2) ignimbrite with an estimated erupted volume of 500 km3 and an average of 45 vol% crystals. Near-absence of quartz, titanite, and sanidine, pronounced An-rich spikes near the rims of plagioclase, and reverse zoning in clinopyroxene record the reheating (from 750 to >800 °C) of an upper crustal mush in response to hotter recharge from below. Zircon U-Pb ages suggest prolonged magmatic residence, while Yb/Dy vs temperature trends indicate co-crystallization with titanite which was later resorbed. High Sr, Ba, and Ti concentrations in plagioclase microlites and phenocryst rims require in-situ feldspar melting and concurrent, but limited, mass addition provided by the recharge, likely in the form of a melt-gas mixture. The larger Fish Canyon Tuff, which erupted from the same location 0.7 m.y. later, also underwent pre-eruptive reheating and partial melting of quartz, titanite, and feldspars in a long-lived upper crustal mush following the underplating of hotter magma. The Fish Canyon Tuff, however, records cooler pre-eruptive temperatures ( 710-760 °C) and a mineral assemblage indicative of higher magmatic water contents (abundant resorbed sanidine and quartz, euhedral amphibole and titanite, and absence of pyroxene). These similar pre-eruptive mush-reactivation histories, despite differing mineral assemblages and pre-eruptive temperatures, indicate that thermal rejuvenation is a key step in the eruption of crystal-rich silicic volcanics over a wide range of conditions.

  10. Additional /sup 40/Ar-/sup 39/Ar dating of the basement and the alkaline volcanism of Gorringe Bank (Atlantic Ocean)

    Energy Technology Data Exchange (ETDEWEB)

    Feraud, G.; York, D.; Mevel, C.; Cornen, G.; Hall, C.M.; Auzende, J.M.

    1986-09-01

    /sup 40/Ar//sup 39/Ar step heating analyses are reported for a variety of samples from Gorringe Bank (Atlantic Ocean). Flat age spectra for two primary, igneous hornblendes of Gorringe (corresponding to an age of 143 Ma) show that the K-Ar ages obtained on these samples by Prichard and Mitchell are evidently crystallization and not hybrid ages. This sustains the concept of an initiation age of 140 Ma for Gorringe Bank. No support is found for Carpena's suggestion that the formation of Gorringe Bank began 200 Ma ago. Secondary hornblendes from Ormonde seamount rocks appear to have formed shortly after the initiation of the Bank. Precise plateau ages on samples of two alkaline volcanics from Ormonde correspond to the older limit of the alkaline volcanism suggested by Feraud et al.

  11. Ars Electronica tulekul / Rael Artel

    Index Scriptorium Estoniae

    Artel, Rael, 1980-

    2003-01-01

    6.-11. IX toimub Austrias Linzis "Ars Electronica" festival, mille teema on "Code - The Language of Our Time". Festivali kavast, osalejatest, ava-performance'ist "Europe - A Symphonic Vision", näitusest "Cyberarts 2003. Prix Ars Electronica"

  12. Ars Electronica tulekul / Rael Artel

    Index Scriptorium Estoniae

    Artel, Rael, 1980-

    2003-01-01

    6.-11. IX toimub Austrias Linzis "Ars Electronica" festival, mille teema on "Code - The Language of Our Time". Festivali kavast, osalejatest, ava-performance'ist "Europe - A Symphonic Vision", näitusest "Cyberarts 2003. Prix Ars Electronica"

  13. Photoionization of Ar VIII

    Science.gov (United States)

    Liang, Liang; Jiang, Wen-xian; Zhou, Chao

    2017-01-01

    The photoionization cross section, energy levels and widths of 22 Rydberg series (in the autoionization region) for Na-like Ar VIII were investigated by using of R-matrix method. The relativistic distorted-wave method is used to calculate the radial functions, and QB method of Quigly-Berrington [Quigley et al. 1998] is employed to calculate the resonance levels and widths. We have identified the formant in the figure of the photoionization cross section.

  14. Laser fusion 40Ar/39Ar dating on young volcanic rocks.%(极)年轻火山岩激光熔蚀40Ar/39Ar定年

    Institute of Scientific and Technical Information of China (English)

    周晶; 季建清; Alan DEINO; 龚俊峰; 韩宝福; 涂继耀; 桑海清; 徐剑光

    2013-01-01

    It is extremely difficult to date young volcanic rocks.Accurate 40Ar/39Ar dating research and practice of young volcanic rocks in China put forward several notable and important points during the process of 40Ar/39 Ar dating for young volcanic rocks.Because of the low background level,small sample quantity,and high sensitivity of modem noble gas isotope mass spectrometry device,laser ablation 40Ar/39Ar dating technique has been used in depth application in volcanic rocks dating.With the laser in 40Ar/39Ar dating of young and modern volcanic rocks,the discrepancy of Nier value and initial argon isotope ratio in Quaternary samples may cause a remarkable deviation between K-Ar apparent age and 40 Ar/39 Ar apparent age.The deviation show exponential increase for samples younger than 0.2Ma,but it is not so notable for samples older than 2Ma.There out,the boundary of young and modern volcanic rocks,which is applied to 40 Ar/39 Ar system,is assigned at 0.2Ma:rocks aged 2 ~ 0.2Ma is defined as young volcanic rock,while rocks aged younger than 0.2Ma is defined as modem volcanic rock.The phenocrysts,which are from different argon isotope fractionation system,should be rejected from the sample during 40Ar/39 Ar dating.According to rock texture and grain size of mineral,the matrix should be picked with ideal grain size.In normal cases,about 0.2mm (or 60 ~ 80 mesh) is recommended; Cooling time after irradiation of fast neutron reactor should not be no more than three months,or else it may cause an error on 37 Ar measurement,and consequently on final results.As neutron-flux monitor,standards should be characteristic of high homogeneity during laser 40Ar/39Ar dating.In calibrating the international and domestic standards we have,we find that SB-778-Bi,Bern4M and BT-1 can be ideal standard samples with good homogeneity.We also find that the isochron age calculated from the laser 40Ar/39Ar data of the phenocryst and matrix,which were cooled and crystallized at the same time

  15. ARABIC LIGHT STEMMER (ARS

    Directory of Open Access Journals (Sweden)

    ASMA AL-OMARI

    2014-12-01

    Full Text Available Stemming is a main step used to process textual data. It is usually used in several types of applications such as: text mining, information retrieval (IR, and natural language processing (NLP. A major task in stemming is to standardize words; which can be achieved by reducing each word to its base (root or stem. Arabic stemming is not an easy task. Unlike other languages, Arabic language is a highly inflected language, since it uses many inflectional forms. Researchers are divided on the benefit of using stemming in fields of IR, NLP...etc., since in Arabic the morphological variants of a certain word are not always semantically related. The aim of this paper is to design and implement a new Arabic light stemmer (ARS which is not based on Arabic root patterns. Instead, it depends on well defined mathematical rules and several relations between letters. A series of tests were conducted on ARS stemmer to compare its effectiveness with the effectiveness of two other Arabic stemmers. Test shows clearly the effectiveness superiority of ARS compared to effectiveness of these two Arabic stemmers.

  16. Laboratory investigation of constitutive property up-scaling in volcanic tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Tidwell, V.C. [Sandia National Labs., Albuquerque, NM (United States). Geohydrology Dept.

    1996-08-01

    One of the critical issues facing the Yucca Mountain site characterization and performance assessment programs is the manner in which property up-scaling is addressed. Property up-scaling becomes an issue whenever heterogeneous media properties are measured at one scale but applied at another. A research program has been established to challenge current understanding of property up-scaling with the aim of developing and testing improved models that describe up-scaling behavior in a quantitative manner. Up-scaling of constitutive rock properties is investigated through physical experimentation involving the collection of suites of gas-permeability data measured over a range of discrete scales. To date, up-scaling studies have been performed on a series of tuff and sandstone (used as experimental controls) blocks. Samples include a welded, anisotropic tuff (Tiva Canyon Member of the Paintbrush Tuff, upper cliff microstratigraphic unit), and a moderately welded tuff (Tiva Canyon Member of the Paintbrush Tuff, Caprock microstratigraphic unit). A massive fluvial sandstone (Berea Sandstone) was also investigated as a means of evaluating the experimental program and to provide a point of comparison for the tuff data. Because unsaturated flow is of prime interest to the Yucca Mountain Program, scoping studies aimed at investigating the up-scaling of hydraulic properties under various saturated conditions were performed to compliment these studies of intrinsic permeability. These studies focused on matrix sorptivity, a constitutive property quantifying the capillarity of a porous medium. 113 refs.

  17. 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)

    Matthews, Naomi E.; Vazquez, Jorge A.; Calvert, Andrew T.

    2015-01-01

    The last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff. Tephra from the Lava Creek eruption is a key Quaternary chronostratigraphic marker, in particular for dating the deposition of mid Pleistocene glacial and pluvial deposits in western North America. To resolve the timing of eruption and crystallization history for the Lava Creek magma, we performed (1) 40Ar/39Ar dating of single sanidine crystals to delimit eruption age and (2) ion microprobe U-Pb and trace-element analyses of the crystal faces and interiors of single zircons to date the interval of zircon crystallization and characterize magmatic evolution. Sanidines from the two informal members composing Lava Creek Tuff yield a preferred 40Ar/39Ar isochron date of 631.3 ± 4.3 ka. Crystal faces on zircons from both members yield a weighted mean 206Pb/238U date of 626.5 ± 5.8 ka, and have trace element concentrations that vary with the eruptive stratigraphy. Zircon interiors yield a mean 206Pb/238U date of 659.8 ± 5.5 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high U concentration cores that likely grew from highly evolved melt. The occurrence of distal Lava Creek tephra in stratigraphic sequences marking the Marine Isotope Stage 16–15 transition supports the apparent eruption age of ∼631 ka. The combined 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 before eruption.

  18. Volátiles De Maíz {lea mays, cebada (Hordeum vulgare y café (Coffea arábica tostados. influencia de la adición de estos cereales en el aroma del café

    Directory of Open Access Journals (Sweden)

    Margoth Suárez

    2010-07-01

    Full Text Available Los volátiles de café a dos grados de torrefacción, como también los del maíz y los de cebada tostados, fueron extraídos por "Headspace" dinámico. La composición de los volátiles fue determinada por Cromatografía de Gases de Alta Resolución acoplada a Espectrometría de Masas (CGAREM. Los constituyentes mayoritarios del café torrefactado a 230 "C durante 8 minutos fueron el furfural 2-metil-3-dihidrofuranona y 2,3- pentadiona mientras que a230"Cy 10 minutos fueron el 2-furanmetanol, 3-metilpirazina, la 1,6-dimetilpirazina y acetato de 2-furanmetanol. Los constituyentes de mayor concentración en el maíz fueron el furfural y el 5-metilfurfuraI y en la cebada el 2-metilbutanal, el 3-metilbutanal y el furano. El análisis sensorial del café y mezclas de café con maiz y cebada permitió detectar adulteración a partir de 20% de cereal en un café torrefactado durante 8 min., pero cuando la torrefacción se realizó por 10 min. fue muy difícil percibir el aroma a cereal, principalmente cuando éste es cebada. Los resultados fueron utilizados como indicadores de la adulteración del café con cereales y como un criterio de evaluación para garantizar la pureza del café Colombiano.

  19. Tracking the timing of subduction and exhumation using 40Ar/39Ar phengite ages in blueschist- and eclogite-facies rocks (Sivrihisar, Turkey)

    Science.gov (United States)

    Fornash, Katherine F.; Cosca, Michael A.; Whitney, Donna L.

    2016-01-01

    Geochronologic studies of high-pressure/low-temperature rocks can be used to determine the timing and rates of burial and exhumation in subduction zones by dating different stages of the pressure–temperature history. In this study, we present new in situ UV laser ablation 40Ar/39Ar phengite ages from a suite of lawsonite blueschist- and eclogite-facies rocks representing different protoliths (metabasalt, metasediment), different structural levels (within and outside of a high-strain zone), and different textural positions (eclogite pod core vs. margin) to understand the timing of these events in an exhumed Neo-Tethyan subduction zone (Sivrihisar Massif, Tavşanlı Zone, Turkey). Weighted mean in situ 40Ar/39Ar ages of phengite from the cores of lawsonite eclogite pods (90–93 Ma) are distinctly older than phengite from retrogressed, epidote eclogite (82 ± 2 Ma). These ages are interpreted as the age of peak and retrograde metamorphism, respectively. Eclogite records the narrowest range of ages (10–14 m.y.) of any rock type analyzed. Transitional eclogite- and blueschist-facies assemblages and glaucophane-rimmed lawsonite + garnet + phengite veins from eclogite pod margins record a much wider age range of 40Ar/39Ar ages (~20 m.y.) with weighted mean ages of ~91 Ma. Blueschists and quartzites record more variable 40Ar/39Ar ages that may in part be related to structural position: samples within a high-strain zone at the tectonic contact of the HP rocks with a meta-ultramafic unit have in situ UV laser ablation 40Ar/39Ar ages of 84.0 ± 1.3–103.7 ± 3.1 Ma, whereas samples outside this zone range to older ages (84.6 ± 2.4–116.7 ± 2.7 Ma) and record a greater age range (22–38 m.y.). The phengite ages can be correlated with the preservation of HP mineral assemblages and fabrics as well as the effects of deformation. Collectively, these results show that high-spatial resolution UV laser ablation 40Ar/39Ar phengite data, when considered

  20. Tracking the timing of subduction and exhumation using 40Ar/39Ar phengite ages in blueschist- and eclogite-facies rocks (Sivrihisar, Turkey)

    Science.gov (United States)

    Fornash, Katherine F.; Cosca, Michael A.; Whitney, Donna L.

    2016-07-01

    Geochronologic studies of high-pressure/low-temperature rocks can be used to determine the timing and rates of burial and exhumation in subduction zones by dating different stages of the pressure-temperature history. In this study, we present new in situ UV laser ablation 40Ar/39Ar phengite ages from a suite of lawsonite blueschist- and eclogite-facies rocks representing different protoliths (metabasalt, metasediment), different structural levels (within and outside of a high-strain zone), and different textural positions (eclogite pod core vs. margin) to understand the timing of these events in an exhumed Neo-Tethyan subduction zone (Sivrihisar Massif, Tavşanlı Zone, Turkey). Weighted mean in situ 40Ar/39Ar ages of phengite from the cores of lawsonite eclogite pods (90-93 Ma) are distinctly older than phengite from retrogressed, epidote eclogite (82 ± 2 Ma). These ages are interpreted as the age of peak and retrograde metamorphism, respectively. Eclogite records the narrowest range of ages (10-14 m.y.) of any rock type analyzed. Transitional eclogite- and blueschist-facies assemblages and glaucophane-rimmed lawsonite + garnet + phengite veins from eclogite pod margins record a much wider age range of 40Ar/39Ar ages (~20 m.y.) with weighted mean ages of ~91 Ma. Blueschists and quartzites record more variable 40Ar/39Ar ages that may in part be related to structural position: samples within a high-strain zone at the tectonic contact of the HP rocks with a meta-ultramafic unit have in situ UV laser ablation 40Ar/39Ar ages of 84.0 ± 1.3-103.7 ± 3.1 Ma, whereas samples outside this zone range to older ages (84.6 ± 2.4-116.7 ± 2.7 Ma) and record a greater age range (22-38 m.y.). The phengite ages can be correlated with the preservation of HP mineral assemblages and fabrics as well as the effects of deformation. Collectively, these results show that high-spatial resolution UV laser ablation 40Ar/39Ar phengite data, when considered in a petrologic and structural

  1. Palaeomagnetism and K-Ar and 40Ar/39Ar ages in the Ali Sabieh area (Republic of Djibouti and Ethiopia): constraints on the mechanism of Aden ridge propagation into southeastern Afar during the last 10 Myr

    Science.gov (United States)

    Audin, L.; Quidelleur, X.; Coulié, E.; Courtillot, V.; Gilder, S.; Manighetti, I.; Gillot, P.-Y.; Tapponnier, P.; Kidane, T.

    2004-07-01

    A new detailed palaeomagnetic study of Tertiary volcanics, including extensive K-Ar and 40Ar/39Ar dating, helps constrain the deformation mechanisms related to the opening processes of the Afar depression (Ethiopia and Djibouti). Much of the Afar depression is bounded by 30 Myr old flood basalts and floored by the ca 2 Myr old Stratoid basalts, and evidence for pre-2 Ma deformation processes is accessible only on its borders. K-Ar and 40Ar/39Ar dating of several mineral phases from rhyolitic samples from the Ali Sabieh block shows indistinguishable ages around 20 Myr. These ages can be linked to separation of this block in relation to continental breakup. Different amounts of rotation are found to the north and south of the Holhol fault zone, which cuts across the northern part of the Ali Sabieh block. The southern domain did not record any rotation for the last 8 Myr, whereas the northern domain experienced approximately 12 +/- 9° of clockwise rotation. We propose to link this rotation to the counter-clockwise rotation observed in the Danakil block since 7 Ma. This provides new constraints on the early phases of rifting and opening of the southern Afar depression in connection with the propagation of the Aden ridge. A kinematic model of propagation and transfer of extension within southern Afar is proposed, with particular emphasis on the previously poorly-known period from 10 to 4 Ma.

  2. 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

    volcanic activity, zircon morphological zoning patterns coupled to strongly correlated changes in Ti-in-zircon thermometry and trace element indicators of progressive differentiation provide a proxy record for the evolution of the HRT member B magma body. Tandem in situ and isotope dilution U-Pb dating...

  3. Constraining the age of the Matuyama-Brunhes reversal using intercalibrated 40Ar/39Ar and astronomical ages of the Bishop Tuff and Australasian Tektite

    DEFF Research Database (Denmark)

    Rivera, Tiffany; Storey, Michael; Palike, Heiko

    Recent high-resolution δ18O records from North Atlantic (I)ODP cores, with reliable paleomagnetic signals, have placed the mean age of the Matuyama-Brunhes (MB) geomagnetic polarity reversal ca. 8 ka younger than previous estimates when correlated to ice-volume age models (Channell et al., 2010)....

  4. Geophysical tomography for imaging water movement in welded tuff

    Energy Technology Data Exchange (ETDEWEB)

    Daily, W.D.; Ramirez, A.L.

    1986-09-01

    Alterant tomography has been evaluated for its ability to delineate in-situ water flow paths in a fractured welded-tuff rock mass. The evaluation involved a field experiment in which tomographs of electromagnetic attenuation factor (or attenuation rate) at 300 MHz were made before, during, and after the introduction to the rock of two different water-based tracers: a plain water and dye solution, and salt water and dye. Alterant tomographs were constructed by subtracting, cell by cell, the attenuation factors derived from measurements before each tracer was added to the rock mass from the attenuation factors derived after each tracer was added. The alterant tomographs were compared with other evidence of water movement in the rock: borescope logs of fractures, and post experiment cores used to locate the dye tracer on the fractured surfaces. These comparisons indicate that alterant tomography is suitable for mapping water flow through fractures and that it may be useful in inferring which of the fractures are hydrologically connected in the image plane. The technique appears to be sensitive enough to delineate flow through a single fracture and to define fractures with a spatial resolution of about 10 cm on an imaging scale of a few meters. 9 refs., 3 figs.

  5. Surface complexation modeling of americium sorption onto volcanic tuff.

    Science.gov (United States)

    Ding, M; Kelkar, S; Meijer, A

    2014-10-01

    Results of a surface complexation model (SCM) for americium sorption on volcanic rocks (devitrified and zeolitic tuff) are presented. The model was developed using PHREEQC and based on laboratory data for americium sorption on quartz. Available data for sorption of americium on quartz as a function of pH in dilute groundwater can be modeled with two surface reactions involving an americium sulfate and an americium carbonate complex. It was assumed in applying the model to volcanic rocks from Yucca Mountain, that the surface properties of volcanic rocks can be represented by a quartz surface. Using groundwaters compositionally representative of Yucca Mountain, americium sorption distribution coefficient (Kd, L/Kg) values were calculated as function of pH. These Kd values are close to the experimentally determined Kd values for americium sorption on volcanic rocks, decreasing with increasing pH in the pH range from 7 to 9. The surface complexation constants, derived in this study, allow prediction of sorption of americium in a natural complex system, taking into account the inherent uncertainty associated with geochemical conditions that occur along transport pathways.

  6. 40Ar/39Ar dating of magmatic activities in the Donbas Foldbelt and the Scythian Platform (Eastern Europe) indicating a possible mantle plume source

    Science.gov (United States)

    Alexandre, P.; Saintot, A.; Wijbrans, J.; Stephenson, R.; Wilson, M.; Kitchka, A.; Chalot-Prat, F.

    2003-04-01

    The Donbas Foldbelt is the easternmost part of a large rift structure transecting the Precambrian Ukrainian Shield, the Devonian Pripyat-Dniepr-Donets Basin. It is bordered on the south by the Priazov Massif and to the north by the Voronezh Massif. To the east it connects with the deformed southern margin of the Russian Platform (Karpinsky Swell). The Scythian Platform is situated to the south of the Donbas Foldbelt, the Karpinsky Swell and to the north of the Caucasus. Several volcanic and intrusive rocks from these two units were dated by the 40Ar/39Ar method in order to obtain the ages of magmatic activity in these areas, and compare them. The plateau ages from the south margin of the Donbas Foldbelt vary from 151.4 ± 4.7 Ma to 278.1 ± 5.3 Ma, and form three age groups: Middle-Late Jurassic (153 ± 2 Ma), Middle-Late Triassic (219 ± 6 Ma), and Early Permian (278 ± 1 Ma). These ages are very similar to those obtained previously by the K-Ar method, but for some of them, they do not correspond to the stratigraphically derived ones. There are two possible ways to explain this discrepancy: (i) the relationships between the different sedimentary and igneous units are somehow problematic, which hampers their correct interpretation and the corresponding ages; (ii) the 40Ar/39Ar ages do not correspond to the emplacement ages of the igneous units as a result of subsequent perturbation and/or resetting of the isotopic systems of the dated minerals, possibly because of magmatic activity and its thermal effects. The age spectra obtained from the Scythian Platform samples are often disturbed as a result of limited alteration. The proposed ages (plateau and pseudoplateau) vary from 174.4 ± 2.1 Ma to 243.7 ± 1.4 Ma, with two major age groups, at 176 Ma and at 200 Ma. Here, as well as on the south Donbas margin, the ages obtained are interpreted as indicating magmatic activity. Comparison of the ages obtained in the two areas reveals a remarkable similarity: in both places

  7. Evaluating Complex Magma Mixing via Polytopic Vector Analysis (PVA in the Papagayo Tuff, Northern Costa Rica: Processes that Form Continental Crust

    Directory of Open Access Journals (Sweden)

    Guillermo E. Alvarado

    2013-08-01

    Full Text Available Over the last forty years, research has revealed the importance of magma mixing as a trigger for volcanic eruptions, as well as its role in creating the diversity of magma compositions in arcs. Sensitive isotopic and microchemical techniques can reveal subtle evidence of magma mixing in igneous rocks, but more robust statistical techniques for bulk chemical data can help evaluate complex mixing relationships. Polytopic vector analysis (PVA is a multivariate technique that can be used to evaluate suites of samples that are produced by mixing of two or more magma batches. The Papagayo Tuff of the Miocene-Pleistocene Bagaces Formation in northern Costa Rica is associated with a segment of the Central American Volcanic Arc. While this segment of the arc is located on oceanic plateau, recent (<8 Ma ignimbrites bear the chemical signatures of upper continental crust, marking the transition from oceanic to continental crust. The Papagayo Tuff contains banded pumice fragments consistent with one or more episodes of mixing/mingling to produce a single volcanic deposit. The PVA solution for the sample set is consistent with observations from bulk chemistry, microchemistry and petrographic data from the rocks. However, without PVA, the unequivocal identification of the three end-member solution would not have been possible.

  8. 祁漫塔格韧性剪切带中绢云母40Ar-39Ar定年及地质意义%40Ar-39Ar Dating of the Muscovite in the Sericite of the Qimantage Ductile Shear Zone and Its Geological Significance

    Institute of Scientific and Technical Information of China (English)

    郭通珍; 谈生祥; 常革红; 丁玉进; 张志青

    2012-01-01

    Qimantage ductile shear zone is the main tectonic boundary of Qimantage ophiolite belt and North Kunlun magmatic arc, we determine granitic mylonite in shear zone with sericite 40Ar-39 Ar meth-ods. Plateau age is 271. 1 ± 2. 2Ma,36 Ar/40 Ar-39 Ar/40 Ar reverse-isochron curve age is 270. 5 ± 3. 7 Ma (MSWD=2.7), and 39Ar/36Ar-40Ar/36Ar isochron age is 270.9±4.7Ma (MSWD = 0.22) . Plateau age 271. 1±2. 2Ma close to the age of mineral formation of sericite, it represents the formation age of Qiman-tage ductile shear zone. Through the ductile shear zone within the kinematic characteristics, dextral shear zone has the nature of Oblique filling. The formation of Qimantage ductile shear zone related Paleo-Tethys Ocean Subduction, is the remote effects of the process of Paleo-Tethys Ocean Northward subduction orog-eny.%祁漫塔格韧性剪切带是祁漫塔格蛇绿混杂岩带与北昆仑岩浆弧的区域主构造边界,对剪切带内花岗质糜棱岩中绢云母40Ar-39 Ar法年龄测定,获得了(271.1±2.2) Ma的坪年龄,相应的36Ar/40 Ar-39 Ar/40 Ar反等时线年龄为(270.5±3.7)Ma (MSWD=2.7),39Ar/36 Ar-40 Ar/35 Ar正等时线年龄为(270.9±4.7) Ma (MSWD=0.22);坪年龄(271.1±2.2) Ma接近于绢云母矿物的形成年龄,也代表了祁漫塔格韧性剪切带的形成年龄.通过韧性剪切变形带内运动学特征的研究,表明剪切带具有右旋斜冲的性质.祁漫塔格韧性剪切带的形成与古特提斯洋的俯冲作用有关,是古特提斯洋向北俯冲造山过程的远程效应.

  9. New U-Pb zircon and 40Ar/39Ar muscovite age constraints on the emplacement of the Lizio syn-tectonic granite (Armorican Massif, France)

    OpenAIRE

    Tartese, Romain; Poujol, Marc; Ruffet, Gilles; Boulvais, Philippe; Yamato, Philippe; Kosler, Jan

    2011-01-01

    International audience; LA-ICP-MS U-Pb analyses performed on zircon grains from the Lizio granite yielded an emplacement age of 316 6 Ma. Typical S-C structures show that the Lizio granite was emplaced contemporaneously with dextral shearing along the northern branch of the South Armorican Shear Zone and that it was therefore active at that time. 40Ar/39Ar analyses performed on muscovite grains yielded plateau dates ranging between 311.5 and 308.2 Ma. Muscovite chemistry is typical of primary...

  10. The behavior of biogenic silica-rich rocks and volcanic tuffs as pozzolanic additives in cement

    Science.gov (United States)

    Fragoulis, Dimitris; Stamatakis, Michael; Anastasatou, Marianthi

    2015-04-01

    Cements currently produced, include a variety of pozzolanic materials, aiming for lower clinker addition and utilization of vast deposits of certain raw materials and/or mining wastes and byproducts. The major naturally occurring pozzolanic materials include glassy tuffs, zeolitic tuffs, diatomites and volcanic lavas rich in glassy phase, such as perlites. Therefore, based on the available raw materials in different locations, the cement composition might vary according to the accessibility of efficient pozzolanic materials. In the present investigation, the behavior of pozzolanic cements produced with representative samples of the aforementioned materials was studied, following the characterization of the implemented pozzolanas with respect to their chemical and mineralogical characteristics. Laboratory cements were produced by co-grinding 75% clinker, 5% gypsum and 20% pozzolana, for the same period of time (45 min). Regarding pozzolanic materials, four different types of pozzolanas were utilized namely, diatomite, perlite, zeolite tuff and glassy tuff. More specifically, two diatomite samples originated from Australia and Greece, with high and low reactive silica content respectively, two perlite samples originated from Turkey and from Milos Island, Greece, with different reactive silica contents, a zeolite tuff sample originated from Turkey and a glassy tuff sample originated from Milos Island, Greece. The above pozzolana samples, which were ground in the laboratory ball mill for cement production performed differently during grinding and that was reflected upon the specific surface area (cm2/gr) values. The perlites and the glassy tuff were the hardest to grind, whereas, the zeolite tuff and the Australian diatomite were the easiest ones. However, the exceedingly high specific surface area of the Australian diatomite renders cement difficult to transport and tricky to use for concrete manufacturing, due to the high water demand of the cement mixture. Regarding

  11. Ar-Ar and U-Pb geochronology of Late Paleozoic basalts in western Guangxi and its constraints on the eruption age of Emeishan basalt magmatism

    Institute of Scientific and Technical Information of China (English)

    FAN Weiming; WANG Yuejun; PENG Touping; MIAO Laicheng; GUO Feng

    2004-01-01

    The Late Paleozoic layered or stratoid-layered basalts in western Guangxi have similar elemental and isotopic compositions to Emeishan high-Ti basalts. Whole-rock 40Ar/39Ar and SHRIMP zircon U-Pb dating were carried out for the representative basalt samples in three typical profiles in the area. Three basalts from the upper segment of Yangxu profile and lower segment of Yufeng and Min'an profiles yield the 40Ar/39Ar plateau ages of 253.6±0.4 Ma (20BS-71),255.4±0.4 Ma (20BS-99) and 256.2±0.8 Ma (20BS-119), respectively. Twenty-three analyses on 23 zircons of the basalt from the upper segment of Yangxu profile give a weighted mean 206pb/238U age of 253.7±6.1 Ma with an MSWD = 2.8.These new and published geochronological data for Emeishan large igneous province (LIP) indicate that the Emeishan LIP was initiated at ~260 Ma, voluminously erupted between 253 and 256 Ma, and possibly ended at ~251-253Ma' The age (251-260 Ma) is generally consistent with that of the associated environmental deterioration and mass extinction events at the end-Guadalupian and Permo-Triassic boundary. These precise geochronological data provide important constraints on the dominantly eruptive time of the Emeishan LIP and understanding of the distribution of Emeishan high-Ti basalts and its mantle plume dynamics.

  12. Eruption sequence of the Suwanoharu tuff ring in the Pliocene Oyano formation, western Kyushu, Japan

    Science.gov (United States)

    Kosugi, H.; Yokose, H.

    2005-12-01

    Volcanism in the Ariake sea region, west Kyushu, Japan, where is the northern extension of the Okinawa trough, have been active during the last 5 million years, from Pliocene to present Unzen volcano. The region has been subsided with development of the tectonic graben. Pliocene Oyano formation is predominated in shallow marine pyroclastic deposits including some base surge deposits. A series of stratified pyroclastic deposits, which were originated by phreatomagmatic eruption cycles is exposed on a sea cliff and is considered to be a remnant of tuff ring, which is called Suwanoharu tuff ring. Suwanoharu tuff ring is expected to preserve the complete eruption sequence. The sequence is basically alternation of massive white tuff layers and laminated gray coarse to lapilli tuff layers. We can identify seven eruption cycles bounded by the massive white air fall pyroclastic deposits (unit 1- 7). The gray pyroclastic deposits consist of massive dark gray medium tuff, crudely laminated medium to coarse-grained tuff, inversely graded lapilli tuff, cross-bedded lapilli tuff, and lapillistone and are considered to be a base surge deposit. Ascending to the eruption cycles, the thickness of massive white tuff layers is decreasing, but the gray layers are increasing. Representative samples were collected from 42 horizons of the tuff ring sequence and analyzed the bulk rock chemical compositions using XRF and the mineral assemblages using XRD. The bulk rock chemical compositions of the gray layers changes from andesite at the lower horizon to basalt at the upper horizon. On the other hand, massive white tuff layers have almost identical and are andesite. Because the compositions of basal layers are very similar to the silt of the basement rock, the beds in the unit 1 may have been deposited fragmented basement rocks by the first phreatomagmatic eruption. At the upper layers of the first eruption cycle (unit 1), chlorine contents are up to the maximum level (ca. 4%) and the

  13. Coeval 40Ar/39Ar Ages of 65.0 Million Years Ago from Chicxulub Crater Melt Rock and Cretaceous-Tertiary Boundary Tektites.

    Science.gov (United States)

    Swisher, C C; Grajales-Nishimura, J M; Montanari, A; Margolis, S V; Claeys, P; Alvarez, W; Renne, P; Cedillo-Pardoa, E; Maurrasse, F J; Curtis, G H; Smit, J; McWilliams, M O

    1992-08-14

    (40)Ar/(39)Ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180-kilometer subsurface Chicxulub crater in Yucatán, Mexico, has yielded well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from (40)Ar/(39)Ar ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The (40)Ar/(39)Ar ages, in conjunction with geochemical and petrological similarities, strengthen the recent suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.

  14. Coeval Ar-40/Ar-39 ages of 65.0 million years ago from Chicxulub crater melt rock and Cretaceous-Tertiary boundary tektites

    Science.gov (United States)

    Swisher, Carl C., III; Grajales-Nishimura, Jose M.; Montanari, Alessandro; Margolis, Stanley V.; Claeys, Philippe; Alvarez, Walter; Renne, Paul; Cedillo-Pardo, Esteban; Maurrasse, Florentin J.-M. R.; Curtis, Garniss H.

    1992-01-01

    Ar-40/Ar-39 dating of drill-core samples of a glassy melt rock recovered from beneath a massive impact breccia contained with the 180-kilometer subsurface Chicxulub crater yields well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from Ar-40/Ar-39 ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The Ar-40/Ar-39 ages, in conjunction with geochemical and petrological similarities, strengthen the suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.

  15. Zircon U–Pb geochronology and geochemistry of rhyolitic tuff, granite porphyry and syenogranite in the Lengshuikeng ore district, SE China: Implications for a continental arc to intra-arc rift setting

    Indian Academy of Sciences (India)

    Changming Wang; Da Zhang; Ganguo Wu; Yigan Xu; Emmanuel John M Carranza; Yaoyao Zhang; Huaikun Li; Jianzhen Geng

    2013-06-01

    SE China is well known for its Mesozoic large-scale granitoid plutons and associated ore deposits. Here, zircon U–Pb geochronological and geochemical data have been used to better constrain the petrogenesis of the igneous rocks associated with porphyry Ag–Pb–Zn deposits in the Lengshuikeng ore district, SE China. 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. The engshuikeng syenogranites are all alkali-rich and show A-type affinities. The syenogranites have high contents of high field strength elements such as Nb, Ta, Zr, Hf; with Zr + Nb + Ce + Y contents of < 350 ppm. Chondrite-normalized REE patterns show relative enrichment of LREEs and strong negative Eu anomalies. The Lengshuikeng granite porphyries, syenogranites and tuffs were probably derived from partial melting of underlying Proterozoic metasedimentary rocks with minor addition of mantle-derived magmas, accompanied by fractional crystallization. Detailed petrologic and geochemical data for the Jurassic igneous rocks from the Lengshuikeng ore district imply that during the Late Jurassic, SE China on the southeast of the Shi-Hang zone was a continental arc associated with the subduction of the Palaeo-Pacific plate and that since the beginning of the Early Cretaceous an intra-arc rift has been formed along the Shi-Hang zone.

  16. Promoting the Quality of Working Life: Sample of Archives of Public Institutions in Turkey Çalışma Yaşamının Kalitesinin Geliştirilmesi: Türkiye'deki Kamu Kurum Arşivleri Örneği

    Directory of Open Access Journals (Sweden)

    Dilek Bayır

    1999-09-01

    Full Text Available The quality of working life is a system targeting an increase of productivity in line with the benefits of the organization by considering the employers' expectations, attitudes and thoughts about the job. They are important components effecting communities' socio-cultural, economic, political etc. development. You must consider personal properties of employers, ergonomic conditions and, institutional properties when you prepare a program for promoting the quality of working life. In this study, conditions of the personnel and the institutions were determined in 7 public institutions archives within the frame of components effecting the quality of working life. The data were collected by means of questioners filled by the personnel of the archives and, interviews with the said personnel. Bu çalışma için bir pazarlama araştırması tekniği olan SERVQUAL yöntemi ile kütüphane kullanıcılarını? izlenimleri alınmıştır. Bir fakülte yönetiminin kaynaklarını çoğunlukla kütüphaneye yöneltmesi ile gelinen aşamada, öğretim elemanlarının hizmet kalitesi ile ilgili maddeleri nasıl derecelendirdikleri istatiksel olarak test edilmiş, alınan sonuçlar değerlendirilmiştir.

  17. 40Ar/39Ar dating of shear deformation of the Xianshuihe fault zone in west Sichuan and its tectonic significance

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Yueqiao; CHEN; Wen; YANG; Nong

    2004-01-01

    Based on field geological survey, structural measurements and classical 40Ar/39Ar dating of mica, biotite and K-feldspar, we obtain cooling ages for Miocene left-lateral shear along the Xianshuihe fault zone. The results document two thermal events during the sinistral shear.The early event (12-10 Ma) corresponds to rapid cooling of the Zheduoshan granitic massif from above 700℃ to below 350℃. The late event (5-3.5 Ma) corresponds to cooling of granites intruded along the eastern side of the fault zone. These dating results provide important thermochronological constraint on the timing of late Cenozoic eastward extrusion of the Chuan-Dian Block in the SE Tibetan margin.

  18. Geologic character of tuffs in the unsaturated zone at Yucca Mountain, southern Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Scott, R.B.; Spengler, R.W.; Diehl, S.; Lappin, A.R.; Chornack, M.P.

    1982-12-31

    At Yucca Mountain, a potential site for a high-level nuclear waste repository on the Nevada Test Site in southern Nevada, evaluation of the geologic setting and rock physical properties, along with previous regional hydrologic studies, has provided background that can be used for construction of a preliminary conceptual hydrologic model of the unsaturated zone. The 500-m-thick unsaturated portion of Yucca Mountain consists of alternating layers of two contrasting types of tuff. One type consists of highly fractured, densely welded, relatively nonporous but highly transmissive ash-flow tuffs. The other type consists of relatively unfractured, nonwelded, highly porous but relatively nontransmissive, argillic and zeolitic bedded tuffs and ash-flow tuffs. The contrast between these two sets of distinctive physical properties results in a stratified sequence best described as "physical-property stratigraphy" as opposed to traditional petrologic stratigraphy of volcanic rocks. The vast majority of recharge through the unsaturated zone is assumed to be vertical; the dominant migration may occur in fractures of densely welded tuffs and in the matrix of nonwelded tuff, but the mode of fluid flow in these unsaturated systems is undetermined. Limited lateral flow of recharge may occur at horizons where local perched water tables may exist above relatively nontransmissive zeolitized nonwelded tuffs. The pervasive north-northwest-striking fractures may control the direction of lateral flow of recharge, if any, in the unsaturated zone, and certainly that direction coincides closely with the observed southeasterly flow direction in the saturated zone under Yucca Mountain. Empirical evaluation of this conceptual hydrologic model has begun. 41 refs., 18 figs., 2 tabs.

  19. New data on the Volcanic Tuff from Petrestii de Jos (Cluj District

    Directory of Open Access Journals (Sweden)

    Bedelean Horea

    2001-04-01

    Full Text Available The present study was carried out on the cineritic interlayers from Petreştii de Jos (closed quarry from Indolului Valley, in order to present their detailed mineralogical-petrographical features. Previous work already noticed the similarity of this tuff level with Dej Tuff Complex in other areas. The studied outcrop consists of a compact volcanic tuff interlayered with marls and tuffaceous clays. The analytical investigations: chemical analyses, X-ray diffraction, IR spectroscopy and electron microscopy reveal the nature of the diagenetic transformations dominated by zeolitization. Besides clinoptilolite, which is the typical zeolite for Dej Tuff from the Transylvanian Depression, our investigation evidenced also the presence of phillipsite. The process was stepwise: during the primary, syngenetic stage K-clinoptilolite formed, while during the late epigenetic stage Ca-phillipsite crystallized; on behalf of the latter one, Ca-clinoptilolite was also generated. It is worth to mention that the highest amounts of zeolites are to be found in the basal horizon, while this amount decreases in the interlayers associated with the marly-clayey levels. From genetic point of view, the lower horizon in the outcrop represents a primary fall-out tuff. The thin interlayers within the upper horizons are resedimented tuffs. The tuff from Petreştii de Jos represents a cheap raw material located in the neighborhood of the industrial area of Turda town. For using it, only a more detailed research and the removal of the vegetal and soil layer on the top would be necessary.

  20. Geologic character of tuffs in the unsaturated zone at Yucca Mountain, southern Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Scott, R.B.; Spengler, R.W.; Diehl, S.; Lappin, A.R.; Chornack, M.P.

    1982-12-31

    At Yucca Mountain, a potential site for a high-level nuclear waste repository on the Nevada Test Site in southern Nevada, evaluation of the geologic setting and rock physical properties, along with previous regional hydrologic studies, has provided background that can be used for construction of a preliminary conceptual hydrologic model of the unsaturated zone. The 500-m-thick unsaturated portion of Yucca Mountain consists of alternating layers of two contrasting types of tuff. One type consists of highly fractured, densely welded, relatively nonporous but highly transmissive ash-flow tuffs. The other type consists of relatively unfractured, nonwelded, highly porous but relatively nontransmissive, argillic and zeolitic bedded tuffs and ash-flow tuffs. The contrast between these two sets of distinctive physical properties results in a stratified sequence best described as "physical-property stratigraphy" as opposed to traditional petrologic stratigraphy of volcanic rocks. The vast majority of recharge through the unsaturated zone is assumed to be vertical; the dominant migration may occur in fractures of densely welded tuffs and in the matrix of nonwelded tuff, but the mode of fluid flow in these unsaturated systems is undetermined. Limited lateral flow of recharge may occur at horizons where local perched water tables may exist above relatively nontransmissive zeolitized nonwelded tuffs. The pervasive north-northwest-striking fractures may control the direction of lateral flow of recharge, if any, in the unsaturated zone, and certainly that direction coincides closely with the observed southeasterly flow direction in the saturated zone under Yucca Mountain. Empirical evaluation of this conceptual hydrologic model has begun. 41 refs., 18 figs., 2 tabs.

  1. The mineralogical and physicochemical properties of clinoptilolite tuff: A comparative study and an outlook for its potential use

    Energy Technology Data Exchange (ETDEWEB)

    Nistratova, I.E.; Novikova, V.A.; Marsii, I.M.; Sokolova, A.L. [Institute of Geology of Ore Deposits, Moscow (Russian Federation)

    1995-09-01

    Mineral and chemical composition, petrographical characteristics, mechanical strength, and ion exchange selectivity of clinoptilolite tuff were studied with the aim of estimating its potential use in water treatment.

  2. Ramon Llull's Ars Magna

    DEFF Research Database (Denmark)

    Jensen, Thessa

    ; conceived and written in the late 13th century by a lay-monk whose life alone would be worth a Hollywood movie. In this paper I will take a brief look at Llull’s life and work, before explaining the four main parts of his Ars Magna. Finally, I will try to give a new perspec-tive on how the Ars Magna still...... might be a viable and valuable approach to understand some of the challenges and possibilities found in computer science and ethics. Vita Llull was born in 1232 in Palma de Mallorca, a melting pot for different cul-tures and religions at the time. Being educated at the king’s court, Llull learned...... the trade of the troubadour as well as reading and writing in Catalan. He became a devout Christian later in life only after he had married. Jesus showed himself to Llull on several occasions, and eventually Llull resumed his rather debauched life and decided to dedicate the rest of his life to three...

  3. Cadomian vs. Variscan evolution of the Ossa-Morena zone (SW Iberia): field and 40Ar/ 39Ar mineral age constraints

    Science.gov (United States)

    Dallmeyer, R. D.; Quesada, C.

    1992-12-01

    Six hornblende and ten muscovite concentrates have been dated from three contrasting tectonic units exposed within the Ossa-Morena zone of the Iberian Massif. These include: (1) the Obejo-Valsequillo domain (north of the Badajoz-Córdoba shear zone); (2) the Sierra Albarrana structural unit (immediately south of the Badajoz-Córdoba shear zone); and (3) the thermal some exposed within the Olivenza-Monesterio antiform (Zafra-Monesterio domain). Hornblende from foliated amphibolite in the Obejo-Valsequillo domain (Siera Negra unit) displays internally discordant 40Ar/ 39Ar age spectra as a result of both intracrystalline contamination with extraneous argon and slight rejuvenation. 36Ar/ 40Ar vs. 39Ar/ 40Ar isotope-correlations are generally well-defined and yield ages of c. 550-560 Ma. These are interpreted to date cooling following late Precambrian-early Paleozoic (Cadomian) tectonothermal activity. This was followed by slight Variscan rejuvenation at c. 375-400 Ma. Muscovite from this unit displays internally discordant age spectra which reflect more extensive Variscan rejuvenation of intracrystalline argon systems which had initially cooled below appropriate blocking temperatures at c. 560 Ma. Hornblende and muscovite from the Sierra Albarrana domain (Sierra Albarrana Group) record 40Ar/ 39Ar plateau and isotope-correlation ages which range between c. 392 Ma and 351 Ma. These results indicate that complete Variscan rejuvenation was followed by relatively rapid post-metamorphic cooling. Hornblende separated from various lithologie elements exposed in the Olivenza-Monesterio Antiform yield variable results. Hornblende within a mafic xenolith in the Monesterio Granodiorite records an isotope-correlation age of c. 553 Ma which is interpreted to date the last cooling through appropriate argon retention temperatures. Hornblende within amphibolite of the Montemolin Series (lower Serie Negra) records internally discordant age spectra which reflect extensive Variscan (c

  4. Detailed 40Ar/39Ar dating of geologic events associated with the Mantos Blancos copper deposit, northern Chile

    Science.gov (United States)

    Oliveros, Verónica; Féraud, Gilbert; Aguirre, Luis; Ramírez, Luis; Fornari, Michel; Palacios, Carlos; Parada, Miguel

    2008-03-01

    The 40Ar/39Ar geochronological method was applied to date magmatic and hydrothermal alteration events in the Mantos Blancos mining district in the Coastal Cordillera of northern Chile, allowing the distinction of two separate mineralization events. The Late Jurassic Mantos Blancos orebody, hosted in Jurassic volcanic rocks, is a magmatic-hydrothermal breccia-style Cu deposit. Two superimposed mineralization events have been recently proposed. The first event is accompanied by a phyllic hydrothermal alteration affecting a rhyolitic dome. The second mineralization event is related to the intrusion of bimodal stocks and sills inside the deposit. Because of the superposition of several magmatic and hydrothermal events, the obtained 40Ar/39Ar age data are complex; however, with a careful interpretation of the age spectra, it is possible to detect complex histories of successive emplacement, alteration, mineralization, and thermal resetting. The extrusion of Jurassic basic to intermediate volcanic rocks of the La Negra Formation is dated at 156.3 ± 1.4 Ma (2 σ) using plagioclase from an andesitic lava flow. The first mineralization event and associated phyllic alteration affecting the rhyolitic dome occurred around 155-156 Ma. A younger bimodal intrusive event, supposed to be equivalent to the bimodal stock and sill system inside the deposit, is probably responsible for the second mineralization event dated at ca. 142 Ma. Other low-temperature alteration events have been dated on sericitized plagioclase at ca. 145-146, 125, and 101 Ma. This is the first time that two distinct mineralization events have been documented from radiometric data for a copper deposit in the metallogenic belt of the Coastal Cordillera of northern Chile.

  5. MA-verpakking : oude techniek, nieuwe toepassing

    NARCIS (Netherlands)

    Stijger, H.; Boogaard, van den G.J.P.M.

    2004-01-01

    Toepassing van MA-verpakking (Modified Atmosphere) bij houtig kleinfruit. Bij MA-verpakking wordt het product in een speciale MA-folie ingepakt, het zogenoemde flowpacken, en al dan niet begast, zodat kwetsbare producten langer in goede conditie blijven

  6. Preliminary survey of tuff distribution in Esmeralda, Nye, and Lincoln Counties, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Smith, G.V.; Pink, T.S.; Lawrence, J.R.; Woodward, L.A.; Keil, K.; Lappin, A.R.

    1981-02-01

    This report inventories the surface distribution of silicic tuffs in Nye, Esmeralda, and Lincoln Counties, NV, based on a review of available literature. The inventory was taken to provide a data base in evaluating tuff sites for the disposal of high-level nuclear waste. Silicic ash-flow tuffs that are about 11 to 34 million years (my) old are widespread in these counties. These rocks are locally deformed by right-lateral movement along Walker Lane and the Las Vegas Shear Zone, and left-lateral movement along a zone from near the Nevada Test Site (NTS) to the Utah border, and are commonly offset by steeply dipping normal faults. The normal faults that bound horsts, grabens, and tilted-fault blocks of the Basin-and-Range Province began to form 30 my ago; some are still active. Tuff distribution is discussed on a regional basis. Tuff thicknesses and alterations, structural complexity, and proximity to recent faulting, recent volcanism, and mineral resources are discussed for each area. Although the literature on which it is based is often incomplete and sketchy, this report is intended to serve as a basis for future, more detailed work that includes initial field inspection, detailed field and laboratory studies, and extrapolations to the subsurface.

  7. A model for the formation of vesiculated tuff by the coalescence of accretionary lapilli

    Science.gov (United States)

    Rosi, Mauro

    1992-07-01

    Observations on phreatomagmatic ash deposits of Phlegraean Fields and Vesuvius supply evidence for the origin of vesiculated tuff in a cool environment. Early deposition by fallout of a matrix-free bed of damp accretionary lapilli is followed by deposition of cohesive mud or a mud rain. The lapilli bed becomes partly or completely transformed into a vesiculated tuff by mud percolation and eventual coalescence of accretionary lapilli with consequent trapping of air originally contained in the interstices. The proposed mechanism accounts for vesiculated tuff formation in distal deposits beyond limits commonly attained by pyroclastic surges. This same mechanism may, nevertheless, also operate in proximal tuff-ring and cone deposits during fallout of phreatomagmatic ash separating bed sets in surge-dominated successions. The sequence of events in the proposed model fits well with the evolution of a cooling phreatomagmatic ash cloud in which early ash aggregation (accretionary lapilli fallout) is followed closely by steam condensation (mud or muddy rainfall). This new model invoking a cool-temperature origin is intended to be complementary to previously proposed theories. Although difficult to assess because of the often complete obliteration of original lapilli, the process is believed to be relatively common in the generasion of vesiculated tuffs within phreatomagmatic deposits.

  8. Geochemistry and Mineralogy of Tuff in Zhongliangshan Mine, Chongqing, Southwestern China

    Directory of Open Access Journals (Sweden)

    Jianhua Zou

    2016-05-01

    Full Text Available Coal-bearing strata that host rare metal deposits are currently a hot issue in the field of coal geology. The purpose of this paper is to illustrate the mineralogy, geochemistry, and potential economic significance of rare metals in the late Permian tuff in Zhongliangshan mine, Chongqing, southwestern China. The methods applied in this study are X-ray fluorescence spectrometry (XRF, inductively coupled mass spectrometry (ICP-MS, X-ray diffraction analysis (XRD plus Siroquant, and scanning electron microscopy in conjunction with an energy-dispersive X-ray spectrometry (SEM-EDX. The results indicate that some trace elements including Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Zr, Nb, Cd, Sb, REE, Hf, Ta, Re, Th, and U are enriched in the tuff from Zhongliangshan mine. The minerals in the tuff mainly include kaolinite, illite, pyrite, anatase, calcite, gypsum, quartz, and traces of minerals such as zircon, florencite, jarosite, and barite. The tuff is of mafic volcanic origin with features of alkali basalt. Some minerals including florencite, gypsum, barite and a portion of anatase and zircon have been derived from hydrothermal solutions. It is suggested that Zhongliangshan tuff is a potential polymetallic ore and the recovery of these valuable elements needs to be further investigated.

  9. Paleoclimate change in the Nakuru basin, Kenya, at 119 - 109 ka derived from δ18Odiatom and diatom assemblages and 40Ar/39Ar geochronology

    Science.gov (United States)

    Bergner, Andreas; Deino, Alan; Leng, Melanie; Gasse, Francoise

    2016-04-01

    A 4.5m-thick diatomite bed deposited during the cold interval of the penultimate interglacial at ~119 - 109 ka documents a period in which a deep freshwater lake filled the Nakuru basin in the Central Kenya Rift (CKR), East Africa. Palaeohydrological conditions of the basin are reconstructed for the paleolake highstand using δ18Odiatom and characterization of diatom assemblages. The age of the diatomite deposit is established by precise 40Ar/39Ar-dating of intercalated pumice tuffs. The paleolake experienced multiple hydrological fluctuations on sub-orbital (~1,500 to 2,000 years) time scales. The magnitude of the δ18Odiatom change (+/- 3‰) and significant changes in the plankton-littoral ratio of the diatom assemblage (+/- 25%) suggest that the paleolake record can be interpreted in the context of long-term climatic change in East Africa. Using 40Ar/39Ar age control and nominal diatomite-sedimentation rates we establish a simplified age model of paleohydrological vs. climatic change, from which we conclude that more humid conditions prevailed in equatorial East Africa during the late Pleistocene over a relatively long time interval of several thousands years. Then, extreme insolation at eccentricity maximum and weakened zonal air-pressure gradients in the tropics favored intensified ITCZ-like convection over East Africa and deep-freshwater lake conditions.

  10. K-Ar Geochronology of Mesozoic Mafic Dikes in Shandong Province, Eastern China:Implications for Crustal Extension

    Institute of Scientific and Technical Information of China (English)

    LIU Shen; HU Ruizhong; ZHAO Junhong; FENG Caixia

    2004-01-01

    Based on K-Ar isotope analyses, Mesozoic mafic (and alkali ultramafic) dikes from western and eastern Shandong Province, China, are dated at 88.2±1.70 Ma to 169.5±3.7 Ma with the majority of ages ranging from 90 Ma to 140 Ma. The emplacement of the dikes suggests a major Yanshanian (Cretaceous) crustal extension in Shandong province.Together with other available age data, this study suggests four periods of crustal extension at about 80 Ma, 100 Ma, 120 Ma and 140 Ma, respectively. Besides the effect of collapse of the Yanshanian orogenic belt on the emplacement of the mafic dikes in Shandong in the Cretaceous, the mantle plume and the extensive left-lateral advection and extension of the Tanlu fault also have controlled the crustal extension and the emplacement of the mafic dikes in eastern Shandong and western Shandong, respectively.

  11. Ar-Ar Analysis of Chelyabinsk: Evidence for a Recent Impact

    Science.gov (United States)

    Beard, S. P.; Kring, D. A.; Isachsen, C. E.; Lapen, T. J.; Zolensky, M. E.; Swindle, T. D.

    2014-01-01

    The Chelyabinsk meteorite is an LL5 ordinary chondrite that fell as a spectacular fireball on February 15th, 2013, over the Ural region in Russia. The meteoroid exploded at an altitude of 25-30 km, producing shockwaves that broke windowpanes in Chelyabinsk and surrounding areas, injuring some 1500 people. Analyses of the samples show that the meteorite underwent moderate shock metamorphism (stage S4; 25-35 GPa) [1]. Most of the samples have a fusion crust ranging from 0.1-1mm thick, and roughly a third of the samples were composed of a dark fine-grained impact melt with chondrule fragments which were targeted for chronometry. A Pb-Pb age obtained by [2] of a shock-darkened and potentially melted sample of Chelyabinsk is reported as 4538.3 +/- 2.1 Ma, while a U-Pb study [3] gave an upper concordia intercept of 4454 +/- 67 Ma and a lower intercept of 585 +/- 390. Galimov et al. 2013 [1] suggest the Sm-Nd system records a recent impact event [290 Ma] that may represent separation from the parent body, while the Rb-Sr isotopic system is disturbed and does not give any definitive isochron. In order to better understand its history, we have performed 40Ar-39Ar analysis on multiple splits of two Chelyabinsk samples; clast- rich MB020f,2 and melt-rich MB020f,5. The term "clast-rich" lithology is meant to indicate a mechanical mixture of highly shock-darkened and less shocked components, both with some shock melt veining.

  12. 40Ar/39Ar age calibration against counted annuallayers

    DEFF Research Database (Denmark)

    Storey, Michael; Stecher, Ole

    2008-01-01

    worth exploring for an improved absolute age basis for the 40Ar/39Ar system is through cross-calibration with counted annual layers (e.g. tree rings, varves and ice cores). North Atlantic Ash Zone (NAAZ) II is found within the dated part of the annual Greenland ice core record. NAAZ II has been...

  13. The 40Ar/39Ar dating of magmatic activity in the Donbas Fold Belt and the Scythian Platform (Eastern European Craton)

    Science.gov (United States)

    Alexandre, P.; Chalot-Prat, F.; Saintot, A.; Wijbrans, J.; Stephenson, R.; Wilson, M.; Kitchka, A.; Stovba, S.

    2004-09-01

    The Donbas Fold Belt is the compressionally deformed southeasternmost part of the intracratonic late Paleozoic Dniepr-Donets rift basin. It is situated in an intracratonic setting but close to the southern margin of the East European Craton, south of which lies the Scythian Platform. A range of igneous rocks from the Donbas Fold Belt and the Scythian Platform were dated by the 40Ar/39Ar method in order to constrain the ages of magmatic activity in these areas, and compare them. The plateau ages from the south margin of the Donbas Fold Belt vary from 151.4 +/- 4.7 Ma to 278.1 +/- 5.3 Ma, and define three main age groups: Middle-Late Jurassic, Middle-Late Triassic, and Early Permian. The age spectra obtained from the Scythian Platform samples are often disturbed as a result of limited alteration. The proposed ages (plateau and pseudoplateau) vary from 174.4 +/- 2.1 Ma to 243.7 +/- 1.4 Ma, and two major age groups are defined, in Early Carboniferous and Triassic/Jurassic times. The Early Permian (285-270 Ma) and Early Triassic (245-250 Ma) ages of magmatic activity are the same in both areas; in the Late Triassic, the ages of magmatic activity are slightly different (220 and 205 Ma), and they are entirely different thereafter. These data can be interpreted as indicating a mantle plume as common deep magmatic source.

  14. Was there a super-eruption on the Gondwanan coast 477 Ma ago?

    Science.gov (United States)

    Gutiérrez-Alonso, G.; Gutiérrez-Marco, J. C.; Fernández-Suárez, J.; Bernárdez, E.; Corfu, F.

    2016-06-01

    Precise zircon and monazite ID-TIMS U-Pb dating of three Lower Ordovician altered ash-fall tuff beds (K-bentonites) in the Cantabrian Zone of NW Iberia yielded coeval ages together with an equivalent previously studied sample (477.5 ± 1 (Gutierrez-Alonso et al., 2007)), of 477 ± 1.3 Ma, 477.2 ± 1.1 Ma and 477.3 ± 1 Ma, with a pooled concordia age (all analyses in the four samples) of 477.2 ± 0.74 Ma. A conservative estimation of the volume and mass of the studied K-bentonite beds (using exclusively the CZ data) yields a volume for the preserved deposits of ca. 37.5 km3 (Volcanic Explosivity Index - VEI = 6, Colossal). When considering other putative equivalent beds in Iberia and neighboring realms (i.e. Armorica, Sardinia) the volume of ejecta associated to this event would make it reach the Supervolcanic-Apocalyptic status (VEI = 8, > 1000 km3). At variance with most known cases of this kind of gigantic eruption events, geological observations indicate that the studied magmatic event was related to continental margin extension and thinning and not to plate convergence. We speculate that a geochronologically equivalent large caldera event recognized in the geological record of NW Iberia could be ground zero of this super-eruption.

  15. Scaling of X pinches from 1 MA to 6 MA.

    Energy Technology Data Exchange (ETDEWEB)

    Bland, Simon Nicholas (Imperial College, London, United Kingdom); McBride, Ryan D.; Wenger, David Franklin; Sinars, Daniel Brian; Chittenden, Jeremy Paul (imperial College, London, United Kingdom); Pikuz, Sergei A. (Cornell University, Ithaca, NY); Harding, Eric; Jennings, Christopher A.; Ampleford, David J.; Yu, Edmund P.; Cuneo, Michael Edward; Shelkovenko, Tatiana A. (Cornell University, Ithaca, NY); Hansen, Stephanie B.

    2010-09-01

    This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parameters at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).

  16. Mo and Ni Removal from Drinking Water Using Zeolitic Tuff from Jordan

    Directory of Open Access Journals (Sweden)

    Khalil M. Ibrahim

    2016-11-01

    Full Text Available Mo and Ni metals could be hazardous in natural waters. The initial Mo and Ni concentration in the sampled domestic drinking water of north Jordan is 550 and 110 μg/L, respectively. The efficiency of using natural faujasite–phillipsite and phillipsite–chabazite tuffs in removing Mo and Ni from contaminated drinking water was tested. Batch experiments using different weights of the adsorbent were conducted at different contact times to determine the optimum conditions. The maximal uptake capacity of Mo from drinking water was equivalent to 440–420 μg/g adsorbent. The maximum removal efficiency of Mo by faujasite–phillipsite, phillipsite–chabazite, and the modified surfactant phillipsite–chabazite tuffs were 80%, 76%, and 78%, respectively. The proportional relationship between contact time and removal efficiency of Ni from water samples was observed. The maximum removal efficiency of Ni by the zeolitic tuffs is up to 90% compared to the original groundwater sample.

  17. Ar-Ar and U-Pb ages of marble-hosted ruby deposits from Central and South-east Asia

    Science.gov (United States)

    Garnier, V.; Giuliani, G.; Maluski, H.; Ohnenstetter, D.; Deloule, E.

    2003-04-01

    Marble-hosted ruby deposits represent the first source of gemstones in Asia. The deposits from Jegdalek (Afghanistan), Hunza Valley (Pakistan), Nangimali (Azad-Kashmir), Chumar, Ruyil (Nepal), Mogok (Myanmar), Luc Yen, Yen Bai and Quy Chau (Vietnam) were dated using the 40Ar-39Ar laser stepwise heating technique on syngenetic micas. The following ages were obtained : 24.7 ± 0.3 Ma at Jegdalek ; 10.8 ± 0.3 to 5.4 ± 0.3 Ma at Hunza ; 17.2 ± 0.2 to 15.3 ± 0.1 Ma at Nangimali ; 4.6 ± 0.1 Ma at Ruyil ; 5.6 ± 0.4 Ma at Chumar ; 18.7 ± 0.2 to 17.1 ± 0.2 Ma at Mogok ; 33.8 ± 0.4 to 30.8 ± 0.8 Ma at Luc Yen ; 24.4 ± 0.4 to 23.2 ± 0.6 Ma at Yen Bai, 22.1 ± 0.6 to 21.6 ± 0.7 Ma at Quy Chau. These ages represent cooling ages and thus minimum ages for ruby formation. The ages obtained for Nangimali are close to the Ar-Ar cooling age of 19 Ma recorded in the Chichi granite, North to the ruby deposit. However, (C,O)-isotopic studies of the ruby-bearing marbles show no genetic relation between granite emplacement and ruby deposition in this area. The age found at Jegdalek is similar to the K-Ar ages obtained on the Sairobi pegmatitic dykes (20-26 Ma) and of the Jalalabad pluton (25 Ma), located close to the ruby deposit. At Mogok, the ruby deposits yield ages close to those obtained on high grade metamorphic and foliated intrusive regional rocks (15.8 ± 0.7 - 19.5 ± 1.0 Ma). The ages obtained at Chumar and Ruyil agree with those of the Lesser Himalaya Formation (12 - 6 Ma). Those found at Quy Chau agree with those found for the shear zone activity. Furthermore, U-Pb dating was done on zircons included in a ruby from Luc Yen and spinels in marble from Luc Yen and Hunza. The wide range of 238U-206Pb ages obtained for Luc Yen (266 - 45 Ma) evidences a complex metamorphic history. Ruby crystallised at 45 Ma during ductile activity of the Red River shear zone. At Hunza, an 238U-206Pb age of 94.0 ± 2.1 Ma obtained on inherited zircons confirms the U-Pb age obtained on

  18. Hydraulic Characterization of Overpressured Tuffs in Central Yucca Flat, Nevada Test Site, Nye County, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    K.J. Halford; R.J. Laczniak; D.L. Galloway

    2005-10-07

    A sequence of buried, bedded, air-fall tuffs has been used extensively as a host medium for underground nuclear tests detonated in the central part of Yucca Flat at the Nevada Test Site. Water levels within these bedded tuffs have been elevated hundreds of meters in areas where underground nuclear tests were detonated below the water table. Changes in the ground-water levels within these tuffs and changes in the rate and distribution of land-surface subsidence above these tuffs indicate that pore-fluid pressures have been slowly depressurizing since the cessation of nuclear testing in 1992. Declines in ground-water levels concurrent with regional land subsidence are explained by poroelastic deformation accompanying ground-water flow as fluids pressurized by underground nuclear detonations drain from the host tuffs into the overlying water table and underlying regional carbonate aquifer. A hydraulic conductivity of about 3 x 10-6 m/d and a specific storage of 9 x 10-6 m-1 are estimated using ground-water flow models. Cross-sectional and three-dimensional ground-water flow models were calibrated to measured water levels and to land-subsidence rates measured using Interferometric Synthetic Aperture Radar. Model results are consistent and indicate that about 2 million m3 of ground water flowed from the tuffs to the carbonate rock as a result of pressurization caused by underground nuclear testing. The annual rate of inflow into the carbonate rock averaged about 0.008 m/yr between 1962 and 2005, and declined from 0.005 m/yr in 2005 to 0.0005 m/yr by 2300.

  19. Hydraulic characterization of overpressured tuffs in central Yucca Flat, Nevada Test Site, Nye County, Nevada

    Science.gov (United States)

    Halford, Keith J.; Laczniak, Randell J.; Galloway, Devin L.

    2005-01-01

    A sequence of buried, bedded, air-fall tuffs has been used extensively as a host medium for underground nuclear tests detonated in the central part of Yucca Flat at the Nevada Test Site. Water levels within these bedded tuffs have been elevated hundreds of meters in areas where underground nuclear tests were detonated below the water table. Changes in the ground-water levels within these tuffs and changes in the rate and distribution of land-surface subsidence above these tuffs indicate that pore-fluid pressures have been slowly depressurizing since the cessation of nuclear testing in 1992. Declines in ground-water levels concurrent with regional land subsidence are explained by poroelastic deformation accompanying ground-water flow as fluids pressurized by underground nuclear detonations drain from the host tuffs into the overlying water table and underlying regional carbonate aquifer. A hydraulic conductivity of about 3 x 10-6 m/d and a specific storage of 9 x 10-6 m-1 are estimated using ground-water flow models. Cross-sectional and three-dimensional ground-water flow models were calibrated to measured water levels and to land-subsidence rates measured using Interferometric Synthetic Aperture Radar. Model results are consistent and indicate that about 2 million m3 of ground water flowed from the tuffs to the carbonate rock as a result of pressurization caused by underground nuclear testing. The annual rate of inflow into the carbonate rock averaged about 0.008 m/yr between 1962 and 2005, and declined from 0.005 m/yr in 2005 to 0.0005 m/yr by 2300.

  20. Emplacement age for the mafic-ultramafic plutons in the northern Dabie Mts. (Hubei): Zircon U-Pb, Sm-Nd and 40Ar/39Ar dating

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The protoliths of mafic-ultramafic plutons in the northern Dabie Mts. (NDM) (Hubei) include pyroxenite and gabbro. The zircon U-Pb dating for a gabbro suggests that emplacement of mafic magma took place in the post-collisional setting at the age of 122.9(0.6 Ma. It is difficult to obtain a reliable Sm-Nd isochron age, due to disequilibrium of the Sm-Nd isotopic system. Two hornblende 40Ar/39Ar ages of 116.1(1.1 Ma and 106.6(0.8 Ma may record cooling of metamorphism in the mafic-ultramafic plutons in Hubei below 500(C. The hornblende 40Ar/39Ar ages for the mafic-ultramafic rocks in Hubei are evidently 15-25 Ma younger than those for the same rocks in Anhui, indicating that there is a diversity of the cooling rates for the mafic-ultramafic rocks in Hubei and Anhui. The difference in their cooling rates may be controlled by the north-dipping normal faults in the NDM. The intense metamorphism occurring in the mafic-ultramafic rocks in Hubei may result from the Yanshanian magmatic reheating and thermal fluid action induced by the Cretaceous migmatization. The geochemical similarity of these mafic-ultramafic rocks wherever in Hubei and Anhui may be attributed to the same tectonic setting via an identical genetic mechanism.

  1. Lithostratigraphy of the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Moyer, T.C.; Geslin, J.K. [Science Applications International Corp., Las Vegas, NV (United States)

    1995-07-01

    Lithostratigraphic relations within the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) were reconstructed from analysis of core samples and observation of outcrop exposures. The Calico Hills Formation is composed of five nonwelded pyroclastic units (each formed of one or more pyroclastic-flow deposits) that overlie an interval of bedded tuff and a basal volcaniclastic sandstone unit. The Prow Pass Tuff is divided into four pyroclastic units and an underlying interval of bedded tuff. The pyroclastic units of the Prow Pass Tuff are distinguished by the sizes and amounts of their pumice and lithic clasts and their degree of welding. Pyroclastic units of the Prow Pass Tuff are distinguished from those of the Calico Hills Formation by their phenocryst assemblage, chemical composition, and ubiquitous siltstone lithic clasts. Downhole resistivity tends to mirror the content of authigenic minerals, primarily zeolites, in both for-mations and may be useful for recognizing the vitric-zeolite boundary in the study area. Maps of zeolite distribution illustrate that the bedded tuff and basal sandstone units of the Calico Hills Formation are altered over a wider area than the pyroclastic units of both the Calico Hills Formation and the upper Prow Pass Tuff.

  2. Decay of Rhenish Tuffs in Dutch Monuments. Part 2: Laboratory Experiments as a Basis for the Choice of Restoration Stone

    NARCIS (Netherlands)

    Van Hees, R.P.J.; Brendle, S.; Nijland, T.G.; De Haas, G.J.L.M.; Tolboom, H.J.

    2003-01-01

    Rhenish tuffs (Eifel, Germany), have been used as building material in the Netherlands since Roman times. They were the most important natural building stone in the Netherlands in early medieval times. In addition, tuff was used as raw material for production of trass, that served as a pozzolanic ad

  3. Decay of Rhenish Tuff in Dutch monuments. Part 2 : Laboratory experiments as a basis for the choice of restoration stone

    NARCIS (Netherlands)

    Hees, R.P.J. van; Brendle, S.; Nijland, T.G.; Haas, G.J.L.M. de; Tolboom, H.J.

    2003-01-01

    Rhenish tuffs (Eifel, Getmany), have been used as building material in the Netherlands since Roman times. They were the most important natural building stone in the Netherlands in early medieval times. In addition, tuff was used as raw material for production of trass, that served as a pozzolanic ad

  4. The 40Ar/39Ar age record and geodynamic significance of Indo-Madagascar and Deccan flood basalt volcanism in the Sarnu-Dandali alkaline complex, Rajasthan, northwestern India

    Science.gov (United States)

    Vijayan, Anjali; Pande, Kanchan; Sheth, Hetu; Kant Sharma, Kamal

    2017-04-01

    The Sarnu-Dandali alkaline complex in Rajasthan, northwestern India, is considered to represent early, pre-tholeiite magmatism in the Deccan Traps continental flood basalt (CFB) province, based on a single 40Ar/39Ar age of 68.57 Ma. Rhyolites found in the complex are considered to be 750 Ma Malani basement. Our new 40Ar/39Ar ages of 88.9-86.8 Ma (for syenites, nephelinite, phonolite and rhyolite) and 66.3 ± 0.4 Ma (2σ, melanephelinite) provide clear evidence that whereas the Sarnu-Dandali complex has Deccan-age components, it is dominantly an older (by ˜20 million years) alkaline complex, with rhyolites included. Sarnu-Dandali is thus an alkaline igneous center active at least twice in the Late Cretaceous, and also much before as suggested by a basalt flow underlying the Early Cretaceous Sarnu Sandstone. The 89-86 Ma 40Ar/39Ar ages fully overlap with those for the Indo-Madagascar CFB province formed during continental break-up between India (plus Seychelles) and Madagascar. Recent 40Ar/39Ar work has shown polychronous emplacement (over ≥ 45 million years) of the Mundwara alkaline complex in Rajasthan, 100 km from Sarnu-Dandali, and 84-80 Ma ages obtained from Mundwara also arguably represent late stages of the Indo-Madagascar CFB volcanism. Remnants of the Indo-Madagascar CFB province are known from several localities in southern India but hitherto unknown from northwestern India 2000 km away. Additional equivalents buried under the vast Deccan Traps are highly likely. We relate the Sarnu-Dandali and Mundwara complexes to decompression melting of ancient, subduction-fluxed, enriched mantle lithosphere due to periodic lithospheric extension during much of the Cretaceous, and hundreds of kilometers inland from the India-Madagascar and India-Seychelles rifted margins.

  5. Some geochemical considerations for a potential repository site in tuff at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Erdal, B.R.; Bish, D.L.; Crowe, B.M.; Daniels, W.R.; Ogard, A.E.; Rundberg, R.S.; Vaniman, D.T.; Wolfsberg, K.

    1982-12-31

    The Nevada Nuclear Waste Storage Investigations, which is evaluating potential locations for a high-level waste repository at the Nevada Test Site and environs, is currently focusing its investigations on tuff, principally in Yucca Mountain, as a host rock. This paper discusses some of the geochemical investigations. Particular emphasis is placed on definition of some basic elements and necessary technical approaches for the geochemistry data acquisition and modeling program. Some site-specific tuff geochemical information that is important for site selection and repository performance will be identified and the current status of knowledge will then be discussed.

  6. Hydrothermal convection and mordenite precipitation in the cooling Bishop Tuff, California, USA

    Science.gov (United States)

    Randolph-Flagg, N. G.; Breen, S. J.; Hernandez, A.; Self, S.; Manga, M.

    2014-12-01

    We present field observations of erosional columns in the Bishop Tuff and then use laboratory results and numerical models to argue that these columns are evidence of relict convection in a cooling ignimbrite. Many square kilometers of the Bishop Tuff have evenly-spaced, vertical to semi-vertical erosional columns, a result of hydrothermal alteration. These altered regions are more competent than the surrounding tuff, are 0.1-0.7 m in diameter, are separated by ~ 1 m, and in some cases are more than 8 m in height. JE Bailey (U. of Hawaii, dissertation, 2005) suggested that similar columns in the Bandelier Tuff were formed when slumping allowed water to pool at the surface of the still-cooling ignimbrite. As water percolated downward it boiled generating evenly spaced convection cells similar to heat pipes. We quantify this conceptual model and apply it the Bishop Tuff to understand the physics within ignimbrite-borne hydrothermal systems. We use thin sections to measure changing porosity and use scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses to show that pore spaces in the columns are cemented by the mineral mordenite, a low temperature zeolite that precipitates between 120-200 oC (Bish et al., 1982), also found in the Bandelier Tuff example. We then use scaling to show 1) that water percolating into the cooling Bishop Tuff would convect and 2) that the geometry and spacing of the columns is predicted by the ignimbrite temperature and permeability. We use the computer program HYDROTHERM (Hayba and Ingebritsen, 1994; Kipp et al., 2008) to model 2-phase convection in the Bishop Tuff. By systematically changing permeability, initial temperature, and topography we can identify the pattern of flows that develop when the ignimbrite is cooled by water from above. Hydrothermally altered columns in ignimbrite are the natural product of coupled heat, mass, and chemical transport and have similarities to other geothermal systems, economic ore deposits

  7. Late Triassic tuff intervals in the Ordos basin, Central China: Their depositional, petrographic, geochemical characteristics and regional implications

    Science.gov (United States)

    Qiu, Xinwei; Liu, Chiyang; Mao, Guangzhou; Deng, Yu; Wang, Feifei; Wang, Jianqiang

    2014-02-01

    Tuff intervals of Upper Triassic Yanchang Formation are laterally widespread in the Ordos basin, Central China. This paper focuses on magmatic origins and potential source regions of these tuff intervals through detail depositional, petrographic and geochemical analyses. Most of the tuff intervals are well-documented at the bottom of the Chang7 oil reservoir unit and can be correlated laterally, and certain tuff beds are reworked by turbidity current or seismic activity. Petrographic studies of the Chang7 tuffs indicate that they are composed of crystal shards, lithic shards and altered glass shards, and the crystal shards include plagioclase, quartz and biotite. Alteration of the Chang7 tuffs is ubiquitous, thus, most of these tuffs transformed into illite/smectite (I/S) mixed-layers which are identified by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Less common minerals are also detected in the Chang7 tuffs such as zircon, hematite, siderite, anatase. Major elements are determined by the X-ray fluorescence (XRF) analysis, the results indicate that the Chang7 tuffs are enriched in K2O (average 4.21%), the ratio of SiO2/Al2O3 ranges from 1.73 to 2.85 (average 2.17), and the ratio of TiO2/Al2O3 varies between 0.006 and 0.032 (average 0.017), which imply that the Chang7 tuffs originated from a felsic parental magma. Trace elements are determined by inductively coupled plasma mass spectrometry (ICP-MS), indicating the total rare earth element (∑REE) concentrations are variable, and range from 117.46 to 466.83 ppm (average 251.88 ppm). REE distribution pattern of the Chang7 tuffs presents a LREE rightward incline with flat HREE curve. The value of δEu ranges from 0.151 to 0.837 (average 0.492), suggesting a strong to weak negative Eu anomaly. The Chang7 tuffs show positive anomalies in Rb, Th and U and negative anomalies in Nb, Sr and Eu on a primitive mantle normalized spidergram. A preliminary analysis of the geochemical composition of the

  8. 40Ar/39Ar geochronology of the Faku tectonites: Implications for the tectonothermal evolution of the Faku block, northern Liaoning

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Xiaohui; WANG; Hui; LI; Tiesheng

    2005-01-01

    For lack of reliable isotopic chronological data, the metamorphic rock series in the Faku region of northern Liaoning has long been regarded as the platform basement. Recent studies reveal that these deformed and metamorphosed rocks, with a variety of protoliths of plutonic intrusions and supracrustal volcanic and sedimentary rocks, were genetically related to later ductile shearing events, and they, together with the syntectonic intrusions, constituted the large-scale Faku tectonites. In this paper, we report new 40Ar/39Ar data on hornblende, biotite, and K-feldspar from typical granitic mylonites in this suite of tectonites. The plateau age 256 Ma of FK53 hornblende and the high-temperature plateau age 262 Ma of Fk51-1 biotite should represent the cooling ages when the granites, formed as a result of Paleozoic oceanic crustal subduction beneath the continental crust or collision of multiple micro-continental blocks, were exhumed into shallow crustal levels. The plateau age 231 Ma of FK51-1 boitite and the apparent age 227 Ma of Fk51-2 K-feldspar are interpreted to record the time of ductile deformation occurring under greenschist facies conditions, i.e. the formation age of the Faku tectonites, while the age gradient from 197 Ma to 220 Ma of Fk51-2 K-feldspar probably record the subsequent stable uplift-cooling process. The tectonic exhumation event indicated by the plateau age 180 Ma of Fk51-2 K-feldspar may be associated with the onset of paleo-Pacific subduction beneath the North China plate. In addition, the U-Pb dating of FK54 zircon from later-intruded granite yields the age of crystallization of this super-unit intrusion at 159 Ma, thus establishing an upper limit for the formation age of the Faku tectonites, while the plateau age 125 Ma of Fk54 K-feldspar most likely corresponds to the rapid cooling and tectonic denudation event associated with the final collision between the Siberian plate and the North China plate. These isotopic ages provide important

  9. 40Ar-39Ar ages of the Louzidian-Dachengzi ductile shear zone near Chifeng,Inner Mongolia and their tectonic significance

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Louzidian normal fault occurs as the eastern detachment fault of the Kalaqin metamorphic core complex. Field observations and microstructural analyses reveal that the Louzidian-Dachengzi ductile shear zone developed in its lower-plate was genetically related to sinistral strike-slips and extensional faulting. Two samples from this ductile shear zone yield 40Ar-39Ar plateau ages of 133 Ma (Bi) and 126 Ma (Kp), which are concordant with their isochron ages. The plateau age of 133 Ma (Bi) records the formation age of the ductile shear zone. The inconsistent relationship between the earlier strike-slip ductile shear zone and the later normal fault makes the Kalaqin Quasi-metamorphic core complex distinctive from Cordilleran metamorphic core complex. These ages provide important geochronological data for putting constraints on the formation age and genesis of such ductile shear zones.

  10. Presencia de arsénico en pozos y en cultivos en Oaxaca, México

    OpenAIRE

    Pablo Ubaldo Caballero-Guti\\u00E9rrez; Jos\\u00E9 Cruz Carrillo-Rodriguez; Rosa Mar\\u00EDa Gomez-Ugalde; Martha Patricia Jerez-Salas

    2009-01-01

    Presencia de arsénico en pozos y en cultivos en Oaxaca, México. El objetivo de este trabajo fue determinar la presencia de arsénico en agua de pozos y en cultivos. Se muestrearon pozos noria y semip rofundos, y diferentes cultivos (tomate, lechuga, frijol y maíz), pertenecie ntes al paraje "Flor de Guayabal", en Tlacolula, Oaxaca, México, durante un periodo de 10 meses (julio 2006 a abril 2007).Hubo dos fases: la primera fue el diagnóstico que se obtuvo de la determinación mensual del arsénic...

  11. New 40Ar/ 39Ar dating results from the Shanwang Basin, eastern China: Constraints on the age of the Shanwang Formation and associated biota

    Science.gov (United States)

    He, Huaiyu; Deng, Chenglong; Pan, Yongxin; Deng, Tao; Luo, Zhaohua; Sun, Jimin; Zhu, Rixiang

    2011-07-01

    The fluvio-lacustrine sequence of the Shanwang Basin, eastern China, preserves a rich and important terrestrial fossil fauna and flora; the exceptional preservation of these fossils reveals the dynamics of ancient mammalian ecosystems and plant biology. However, the timing of this sedimentary sequence has been the subject of debate for decades. Here we contribute to this debate by presenting the detailed results of 40Ar/ 39Ar analysis of the basalts above, below, and within the Shanwang Formation. These dates place stringent constraints on the age of Shanwang Formation and associated biota. 40Ar/ 39Ar ages obtained from basalts of the Niushan and Yaoshan Formations, which underlie and overlie the Shanwang Formation, are 21.0 ± 2.5 Ma (2σ, full external error) and 17.3 ± 1.5 Ma (2σ, full external error), respectively. The 40Ar/ 39Ar age of the basalt in the Shanwang Formation is 17-18 Ma. Given the age constraints of the basalts of the Yaoshan and Shanwang Formations, the age of the Shanwang biota is estimated to be ca. 17 Ma, late Burdigalian of the Early Miocene, indicating that the deposition of this fauna coincided with the onset of the mid-Miocene Climatic Optimum. The results provide new age constraints on the Shanwang mammal fauna, and independently support interpretations that this fauna can be assigned to chronozone MN4, and correlated with middle Orleanian of the European Land Mammal Age, and to late Hemingfordian of the North American Land Mammal Age. Biological diversity of the Shanwang Formation could reflect the global-scale mid-Miocene Climatic Optimum.

  12. 40Ar/39Ar geochronology, paleomagnetism, and evolution of the Boring volcanic field, Oregon and Washington, USA

    Science.gov (United States)

    Fleck, Robert J.; Hagstrum, Jonathan T.; Calvert, Andrew T.; Evarts, Russell C.; Conrey, Richard M.

    2014-01-01

    The 40Ar/39Ar investigations of a large suite of fine-grained basaltic rocks of the Boring volcanic field (BVF), Oregon and Washington (USA), yielded two primary results. (1) Using age control from paleomagnetic polarity, stratigraphy, and available plateau ages, 40Ar/39Ar recoil model ages are defined that provide reliable age results in the absence of an age plateau, even in cases of significant Ar redistribution. (2) Grouping of eruptive ages either by period of activity or by composition defines a broadly northward progression of BVF volcanism during latest Pliocene and Pleistocene time that reflects rates consistent with regional plate movements. Based on the frequency distribution of measured ages, periods of greatest volcanic activity within the BVF occurred 2.7–2.2 Ma, 1.7–0.5 Ma, and 350–50 ka. Grouped by eruptive episode, geographic distributions of samples define a series of northeast-southwest–trending strips whose centers migrate from south-southeast to north-northwest at an average rate of 9.3 ± 1.6 mm/yr. Volcanic activity in the western part of the BVF migrated more rapidly than that to the east, causing trends of eruptive episodes to progress in an irregular, clockwise sense. The K2O and CaO values of dated samples exhibit well-defined temporal trends, decreasing and increasing, respectively, with age of eruption. Divided into two groups by K2O, the centers of these two distributions define a northward migration rate similar to that determined from eruptive age groups. This age and compositional migration rate of Boring volcanism is similar to the clockwise rotation rate of the Oregon Coast Range with respect to North America, and might reflect localized extension on the trailing edge of that rotating crustal block.

  13. Estimation of engineering properties of selected tuffs by using grain/matrix ratio

    Science.gov (United States)

    Korkanç, Mustafa; Solak, Burak

    2016-08-01

    Petrographic properties of rocks substantially affect their physical and mechanical properties. In the present study, for the purpose of examining the relationship between the petrographic and geomechanical properties of pyroclastic rocks, fresh samples were taken from tuffs of different textural properties that have wide distribution in Cappadocia region. Experimental studies were conducted on 20 fresh samples to determine their engineering properties through petrographic examinations. Dry and saturated unit weights, water absorption by weight, effective porosity, capillary water absorption, slake durability index, P-wave velocity, point load index, uniaxial compressive strength and nail penetration index of the samples were determined. Higher geomechanical values were obtained from the samples of Kavak tuffs affected by hydromechanical alteration and by tuffs with high welded rates. On thin sections prepared with the fresh samples, petrographic studies were carried out by using a point counter with a polarizing microscope, and mineral composition, texture, void ratio, volcanic glass presence and state of these fragments within the rock, secondary mineral formation and opaque mineral presence were determined. Grain/matrix ratio (GMR) was calculated by using the ratios of phenocrysts, microlites, volcanic glass, voids and opaque minerals after point counting on thin sections. A potential relationship between the petrographic and geomechanical properties of fresh samples was tried to determine by counting correlation analysis. Such a relationship can be significantly and extensively suggestible for engineering applications. For this purpose, we used the poorly-welded Kavak and densely-welded Kızılkaya tuff samples in our study.

  14. Corrosion testing of type 304L stainless steel in tuff groundwater environments

    Energy Technology Data Exchange (ETDEWEB)

    Westerman, R.E.; Pitman, S.G.; Haberman, J.H.

    1987-11-01

    The stress-corrosion cracking (SCC) resistance of Type 304L stainless steel (SS) to elevated temperatures in tuff rock and tuff groundwater environments was determined under irradiated and nonirradiated conditions using U-bend specimens and slow-strain-rate tests. The steel was tested both in the solution-annealed condition and after sensitization heat treatments. The material was found to be susceptible to SCC in both the solution-annealed and solution-annealed-and-sensitized conditions when exposed to an irradiated crushed tuff rock environment containing air and water vapor at 90{sup 0}C. A similar exposure at 50{sup 0}C did not result in failure after a 25-month test duration. Specimens of sensitized 304 SS conditioned with a variety of sensitization heat treatments resisted failure during a test of 1-year duration in which a nonirradiated environment of tuff rock and groundwater held at 200{sup 0}C was allowed to boil to dryness on a cyclical basis. All specimens of sensitized 304 SS exposed to this environment failed. Slow-strain-rate studies were performed on 304L, 304, and 316L SS specimens. The 304L SS was tested in J-13 well water at 150{sup 0}C, and the 316L SS at 95{sup 0}C. Neither material showed evidence of SCC in these tests. Sensitized 304 SS did exhibit SCC in J-13 well water in tests conducted at 150{sup 0}C. 12 refs., 27 figs., 13 tabs.

  15. Cerro Xalapaxco: An Unusual Tuff Cone with Multiple Explosion Craters, in Central Mexico (Puebla)

    Science.gov (United States)

    Abrams, M. J.; Siebe, C.

    1994-01-01

    The Xalapaxco tuff cone is located on the northeast flank of La Malinche stratovolcano in central Mexico. An unusually large number (10) of explosion craters, concentrated on the central and on the uphill side of the cone, expose alternating beds of stratified surge deposits and massive fall deposits.

  16. Maximum likelihood Bayesian averaging of airflow models in unsaturated fractured tuff using Occam and variance windows

    NARCIS (Netherlands)

    Morales-Casique, E.; Neuman, S.P.; Vesselinov, V.V.

    2010-01-01

    We use log permeability and porosity data obtained from single-hole pneumatic packer tests in six boreholes drilled into unsaturated fractured tuff near Superior, Arizona, to postulate, calibrate and compare five alternative variogram models (exponential, exponential with linear drift, power, trunca

  17. Variability of the physical properties of tuff at Yucca Mountain, NV

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, P.J.; Martin, R.J. III [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

    1994-12-31

    Lateral and vertical variabilities in the bulk and mechanical properties of silicic volcanic tuff at the potential nuclear waste repository site in Yucca Mountain, NV have been evaluated. Laboratory measurements have been performed on tuff specimens recovered from boreholes located to support the design of the Exploratory Studies Facility/North Ramp. The data include dry and saturated bulk densities, average grain density, porosity, compressional and shear wave velocities, elastic moduli, and compressional and tensional fracture strengths. Data from eight boreholes aligned in a northwest-southeast direction have been collected under the required quality assurance program. Three boreholes have penetrated the potential repository horizon. The information collected provides for an accurate appraisal of the variability of rock properties in the vicinity of the boreholes. As expected, there is substantial variability in the bulk and mechanical properties of the tuff with depth (lithology). This is due to variations in gross characteristics of the tuffs (e.g., cooling units, mode of deposition, etc.), as well as smaller scale features (welding, porosity, and internal structures) that have developed as a result of depositional and post-depositional mechanisms. An evaluation of the lateral variability in bulk and mechanical properties is somewhat limited, at this time, due to a lack of borehole control to the north and south (parallel to the depositional flow direction). Initial observations indicate that there is minimal lateral variability within lithologic units. There are observable differences however, that can be related to variability in specific properties (e.g., porosity, and internal structures).

  18. Cerro Xalapaxco: An Unusual Tuff Cone with Multiple Explosion Craters, in Central Mexico (Puebla)

    Science.gov (United States)

    Abrams, M. J.; Siebe, C.

    1994-01-01

    The Xalapaxco tuff cone is located on the northeast flank of La Malinche stratovolcano in central Mexico. An unusually large number (10) of explosion craters, concentrated on the central and on the uphill side of the cone, expose alternating beds of stratified surge deposits and massive fall deposits.

  19. Occurrence of rhyolytic tuffs at deep sea drilling project site 219 on the Laccadive Ridge

    Digital Repository Service at National Institute of Oceanography (India)

    Siddiquie, H.N.; Sukheswala, R.N.

    A study of thin sections from the lower and middle parts of Unit 5 (Paleocene) from Site 219 shows that these largely consist of acidic or rhyolitic tuffs. The overlying limestones in Unit 5 (Paleocene) and Unit 4 (Lower Eocene) also contain...

  20. Experimental study on the Neapolitan Yellow Tuff: Salt weathering and consolidation

    Science.gov (United States)

    La Russa, Mauro Francesco; Ruffolo, Silvestro Antonio; Alvarez de Buergo, Monica; Ricca, Michela; Belfiore, Cristina Maria; Pezzino, Antonino; Mirocle Crisci, Gino

    2016-04-01

    Salt crystallization is one of the major weathering agents in porous building materials due to the crystallization pressure exerted by salt crystals growing in confined pores. The consolidation of such degraded stone materials is a crucial issue in the field of Cultural Heritage restoration.
 This contribution deals with laboratory experimentation carried out on the Neapolitan Tuff, a pyroclastic rock largely used in the Campanian architecture. Several specimens, collected from a historical quarry nearby the city of Naples, were treated with two different consolidating products: a suspension of nanosilica in water (Syton X30®) and ethyl silicate (Estel 1000®) dispersed in organic solvent (TEOS). Then, in order to assess the effectiveness of consolidation treatments, both treated and untreated samples underwent accelerated degradation through salt crystallization tests. A multi-analytical approach, including mercury intrusion porosimetry, peeling tests and point load test, was employed to evaluate the correlation between the salt crystallization and the micro-structural features of the examined tuff specimens. In addition, the calculation of the crystallization pressures was also performed in order to make a correlation between the porous structure of the tuff and its susceptivity to salt crystallization. Obtained results show that both the tested products increase the resistance of tuff to salt crystallization, although inducing an increase of crystallization pressure. Ethyl silicate, however, shows a better behaviour in terms of superficial cohesion, even after several degradation cycles.

  1. Cinéma / Canada

    OpenAIRE

    Berthomé, Jean-Pierre; Coulombe, Michel; Dvorak, Marta; Garel, Sylvain; Noguez, Dominique; Suchet, Simone; Vimenet, Pascal

    2013-01-01

    Longtemps connue en France par le biais de cinéastes québécois tels que Claude Jutra, Gilles Carle, ou Pierre Perrault, l'industrie cinématographique du Canada a dû se développer dans l'ombre d'Hollywood. Elle s'est forgée une réputation internationale d'excellence dans les domaines qui ne concurrençaient pas les studios américains : le documentaire, le court-métrage, et les films d'animation. Nous sommes en présence d'un cinéma fortement subventionné (et même d'un cinéma d'État) qui repose s...

  2. BaMa / Raivo Juurak

    Index Scriptorium Estoniae

    Juurak, Raivo, 1949-

    2002-01-01

    Eesti ülikoolide üleminekust 3+2 süsteemile. Lühend BaMa on tulnud kasutusele seoses Euroopa ülikoolide õppekavade reformimisega ning tähistab õppekava, kus esimese astme läbimise järel omandatakse bakalaureuse- ja teise järel magistrikraad. Õppekavade tüüpidest Eesti ja Euroopa Liidu kõrgkoolides ning Bologna deklaratsioonist

  3. XRD-based 40Ar/39Ar age correction for fine-grained illite, with application to folded carbonates in the Monterrey Salient (northern Mexico)

    Science.gov (United States)

    Fitz-Díaz, Elisa; Hall, Chris M.; van der Pluijm, Ben A.

    2016-05-01

    Due to their minute size, 40Ar/39Ar analysis of illite faces significant analytical challenges, including mineral characterization and, especially, effects of grain size and crystallography on 39Ar recoil. Quantifying the effects of 39Ar recoil requires the use of sample vacuum encapsulation during irradiation, which permits the measurement of the fraction of recoiled 39Ar as well as the 39Ar and 40Ar∗ retained within illite crystals that are released during step heating. Total-Gas Ages (TGA) are calculated by using both recoiled and retained argon, which is functionally equivalent to K-Ar ages, while Retention Ages (RA) only involve retained Ar in the crystal. Natural applications have shown that TGA fits stratigraphic constraints of geological processes when the average illite crystallite thickness (ICT) is smaller than 10 nm, and that RA matches these constraints for ICTs larger than 50 nm. We propose a new age correction method that takes into account the average ICT and corresponding recoiled 39Ar for a sample, with X-ray Corrected Ages (XCA) lying between Total-Gas and Retention Ages depending on ICT. This correction is particularly useful in samples containing authigenic illite formed in the anchizone, with typical ICT values between 10 and 50 nm. In three samples containing authigenic illite from Cretaceous carbonates in the Monterrey Salient in northern Mexico, there is a range in TGAs among the different size-fractions of 46-49, 36-43 and 40-52 Ma, while RAs range from 54-64, 47-52 and 53-54 Ma, respectively. XCA calculations produce tighter age ranges for these samples of 52.5-56, 45.5-48.5 and 49-52.5 Ma, respectively. In an apparent age vs ICT or %2M 1illite plot, authigenic illite grains show a slope that is in general slightly positive for TGA, slightly negative for RA, but close to zero for XCA, with thinner crystallites showing more dispersion than thicker ones. In order to test if dispersion is due to a different formation history or the result

  4. In-situ tuff water migration/heater experiment: experimental plan

    Energy Technology Data Exchange (ETDEWEB)

    Johnstone, J.K.

    1980-08-01

    Tuffs on the Nevada Test Site (NTS) are currently under investigation as a potential isolation medium for heat-producing nuclear wastes. The National Academy of Sciences has concurred in our identification of the potentially large water content ({le}40 vol %) of tuffs as one of the important issues affecting their suitability for a repository. This Experimental Plan describes an in-situ experiment intended as an initial assessment of water generation/migration in response to a thermal input. The experiment will be conducted in the Grouse Canyon Welded Tuff in Tunnel U12g (G-Tunnel) located in the north-central region of the NTS. While the Grouse Canyon Welded Tuff is not a potential repository medium, it has physical, thermal, and mechanical properties very similar to those tuffs currently under consideration and is accessible at depth (400 m below the surface) in an existing facility. Other goals of the experiment are to support computer-code and instrumentation development, and to measure in-situ thermal properties. The experimental array consists of a central electrical heater, 1.2 m long x 10.2 cm diameter, surrounded by three holes for measuring water-migration behavior, two holes for measuring temperature profiles, one hole for measuring thermally induced stress in the rock, and one hole perpendicular to the heater to measure displacement with a laser. This Experimental Plan describes the experimental objectives, the technical issues, the site, the experimental array, thermal and thermomechanical modeling results, the instrumentation, the data-acquisition system, posttest characterization, and the organizational details.

  5. Origin, Age, and Geochemistry of the Tuff of Saguache Creek, Southwestern Colorado

    Science.gov (United States)

    Turner, K. J.; Young, M. D.; Wendlandt, R. F.

    2003-12-01

    A crystal-poor, rhyolitic, ash-flow tuff in the Eastern San Juan Volcanic Field currently known as the tuff of Saguache Creek (TSC) was reinterpreted by Simon and Wendlandt (1999) as not being distal Sapinero Mesa Tuff. Currently there is no source caldera established for this tuff thereby leaving uncertainties in the volcanic history. Regional mapping of the TSC has subsequently been completed to constrain a possible source caldera. Petrographic studies, and EPMA and LA-ICPMS analyses of the mineral assemblage have been performed to characterize further the tuff, enable correlation of mapped TSC, and constrain petrogenetic models. Petrographic and chemical identification of the TSC builds on characteristics set forth by Simon (2000). These characteristics include abundant feldspar clusters, alkali feldspar mantled plagioclase, no modal quartz, Fe-Ti oxides (often with apatites and zircons), and sparse biotite and pyroxene. Pyroxenes show curiously high MnO (avg 2.70 wt%) and Mg# (avg 79.2) and might be xenocrystic. In comparison, biotites have much lower MnO (avg 0.82 wt%). Average sanidine (Or50) and plagioclase (Ab71) compositions fall within the documented range (Simon, 2000) and show little trace element substitution including Eu Conejos age volcanic deposits. Similarly, an andesitic topographic high just west of Trickle Mtn has TSC vitrophyre on the east-facing slope suggesting strong north-south channeling of the flow unit by paleo-topographic lows. Outcrop elevations also decrease from north to south supporting a possible source caldera to the north. This source could be explained by a distinct circular gravity low on the southeastern slope of the Continental Divide. The low is bordered to the north by a circular arrangement of peaks as well as debris breccias, andesitic flow breccias, and lahars.

  6. Heulandite and mordenite-rich tuffs from Greece: a potential source for pozzolanic materials

    Science.gov (United States)

    Kitsopoulos, K. P.; Dunham, A. C.

    1996-09-01

    The microcystalline mass of the Pliocene tuffs of Santorini and Polyegos islands, in the South Aegean Volcanic Arc, Greece, is very rich in zeolite minerals, more specifically heulandite type 3, i.e. clinoptilolite, and mordenite. In Santorini, clinoptilolite is the dominant authigenic phase and it was formed in a semi-closed system, by the activity of interstitial water within the volcaniclastic sequence. In Polyegos, mordenite dominates and it was formed by hydrothermal alteration of pyroclastics. Experiments described in this work show that the presence of the zeolite minerals has created materials with excellent pozzolanic properties. Tuffs from the two areas were calcined at 760 °C and for 12 h and then mixed with lime in a constant ratio of 1 part lime to 3 parts calcined tuff. As a result, the free lime content of the lime-calcined tuff mixtures was reduced from 25% to 2.05% (Santorini) and 1.31% (Polyegos). Compressive strength tests were carried out on concrete cubes made with 100% Portland cement as the cementitious agent, to be used as reference cubes, and concrete cubes in which the Portland cement has been replaced in 4% and 7% proportions by the calcined tuff as pozzolans. The free lime estimation and the compressive strength tests were all carried out in accordance with the British Standards Institution (BS 4550 and BS 1881) guidelines. Early stage measurements of the compressive strength showed that pozzolan-bearing concrete cubes reached values as high as 140% of the reference cubes. The pozzolan-bearing concrete cubes maintained this superior strength throughout the entire one year period of the experiments. After 360 days, they finally maintained 107% of the compressive strength of the reference cubes.

  7. Evenly-spaced columns in the Bishop Tuff as relicts of hydrothermal convection

    Science.gov (United States)

    Randolph-Flagg, N. G.; Breen, S. J.; Hernandez, A.; Self, S.; Manga, M.

    2015-12-01

    A few square km of the Bishop Tuff in eastern California, USA have evenly spaced erosional columns. These columns are more resistant to erosion due to the precipitation of the low-temperature zeolite (120-200 ºC), mordenite, which is not found in the surrounding tuff. Similar features observed in the Bandelier Tuff were hypothesized to form when cold water from above infiltrated into the still-hot tuff interior. This water would become gravitationally unstable and produced convection with steam upwellings and liquid water downwellings. These downwellings became cemented with mordenite while the upwellings were too dry for chemical reactions. We use two methods to quantitatively assess this hypothesis. First, scaling that ignores the effects of latent heat and mineral precipitation suggests the Rayleigh number (Ra, a measure of convective vigor) for this system is ~103 well above the critical Ra of 4π2. Second, to account for the effect of multiphase flow and latent heat, we use two-dimensional numerical models in the finite difference code HYDROTHERM. We find that the geometry of flow is consistent with field observations and confirm that geometry is sensitive to permeability and topography. These tests suggest a few things about low-pressure hydrothermal systems. 1) The geometry of at least some convection appears to be broadly captured by linear stability theory that ignores reactive transport, heterogeneity of host rock, and the effects of latent heat. 2) Topographic flow sets the wavelength of convection meaning that these columns formed somewhere without topography—probably a lake. Finally, these observations imply a wet paleoclimate in the Eastern Sierra namely that, in the aftermath of the Long Valley eruption, either rain or snow was able to pool in the caldera before the tuff cooled on the order of a hundred years after the eruption.

  8. In-situ tuff water migration/heater experiment: experimental plan

    Energy Technology Data Exchange (ETDEWEB)

    Johnstone, J.K.

    1980-08-01

    Tuffs on the Nevada Test Site (NTS) are currently under investigation as a potential isolation medium for heat-producing nuclear wastes. The National Academy of Sciences has concurred in our identification of the potentially large water content ({le}40 vol %) of tuffs as one of the important issues affecting their suitability for a repository. This Experimental Plan describes an in-situ experiment intended as an initial assessment of water generation/migration in response to a thermal input. The experiment will be conducted in the Grouse Canyon Welded Tuff in Tunnel U12g (G-Tunnel) located in the north-central region of the NTS. While the Grouse Canyon Welded Tuff is not a potential repository medium, it has physical, thermal, and mechanical properties very similar to those tuffs currently under consideration and is accessible at depth (400 m below the surface) in an existing facility. Other goals of the experiment are to support computer-code and instrumentation development, and to measure in-situ thermal properties. The experimental array consists of a central electrical heater, 1.2 m long x 10.2 cm diameter, surrounded by three holes for measuring water-migration behavior, two holes for measuring temperature profiles, one hole for measuring thermally induced stress in the rock, and one hole perpendicular to the heater to measure displacement with a laser. This Experimental Plan describes the experimental objectives, the technical issues, the site, the experimental array, thermal and thermomechanical modeling results, the instrumentation, the data-acquisition system, posttest characterization, and the organizational details.

  9. Neutron-hole states in 45Ar from p(46Ar,d)45Ar reactions

    CERN Document Server

    Lu, F; Tsang, M B; Bazin, D; Coupland, D; Henzl, V; Henzlova, D; Kilburn, M; Lynch, W G; Rogers, A M; Sanetullaev, A; Sun, Z Y; Youngs, M; Charity, R J; Sobotka, L G; Famiano, M; Hudan, S; Horoi, M; Ye, Y L

    2013-01-01

    To improve the effective interactions in the pf shell, it is important to measure the single particle- and hole- states near the N=28 shell gap. In this paper, the neutron spectroscopic factors of hole-states from the unstable neutron-rich 45Ar (Z=18, N=27) nucleus have been studied using 1H(46Ar, 2H)45Ar transfer reaction in inverse kinematics. Comparison of our results with the particle-states of 45Ar produced in 2H(44Ar, H)45Ar reaction shows that the two reactions populate states with different angular momentum. Using the angular distributions, we are able to confirm the spin assignments of four low-lying states of 45Ar. These are the ground state (f7/2), the first-excited (p3/2), the s1/2 and the d3/2 states. While large basis shell model predictions describe spectroscopic properties of the ground and p3/2 states very well, they fail to describe the s1/2 and d3/2 hole-states.

  10. Ars Poetica : [luuletused] / Mats Traat

    Index Scriptorium Estoniae

    Traat, Mats, 1936-

    2008-01-01

    Sisu: Ars poetica ; Veepeegel ; Kontrollõed ; Mandariiniriik ; Nikolai Siamashvili (1888-1911) ; Kolmekümne kolmas aasta ; Kiri linast 1966 ; Italmaz Nuriyev ; Rudolf Rimmelile mõeldes ; Gennadi Aigi

  11. Ars Poetica : [luuletused] / Mats Traat

    Index Scriptorium Estoniae

    Traat, Mats, 1936-

    2008-01-01

    Sisu: Ars poetica ; Veepeegel ; Kontrollõed ; Mandariiniriik ; Nikolai Siamashvili (1888-1911) ; Kolmekümne kolmas aasta ; Kiri linast 1966 ; Italmaz Nuriyev ; Rudolf Rimmelile mõeldes ; Gennadi Aigi

  12. Pulsed discharge production Ar* metastables

    Science.gov (United States)

    Han, Jiande; Heaven, Michael C.; Emmons, Daniel; Perram, Glen P.; Weeks, David E.; Bailey, William F.

    2016-03-01

    The production of relatively high densities of Ar* metastables (>1012 cm-3) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel plate pulsed discharge. With discharge pulses of 1 μs duration we find that metastable production is dominated by processes occurring within the first 100 ns of the gas break-down. Application of multiple, closely spaced discharge pulses yields insights concerning conditions that favor metastable production. This information has been combined with time-resolved measurements of voltage and current. The experimental results and preliminary modeling of the discharge kinetics are presented.

  13. 40Ar-39Ar Age and Geological Significance of the Sawur Gold Belt in Northern Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    SHEN Ping; SHEN Yuanchao; ZENG Qingdong; LIU Tiebing; LI Guangming

    2005-01-01

    The 40Ar-39Ar age method is employed in this work to analyze fluid inclusions of quartz in the ore bodies from the Kuo'erzhenkuola and Bu'erkesidai gold deposits in the Sawur gold belt, northern Xinjiang. The results show that the main mineralization occurred in 332.05±2.02-332.59±0.51 Ma and 335.53±0.32 Ma-336.78±0.50 Ma for the Kuo'erzhenkuola and Bu'erkesidai gold deposits respectively, indicating that the two deposits are formed almost at the same time, and the metallogenic time of the two deposits are close to those of the hosting rocks formed by volcanic activity of the Sawur gold belt. This geochronological study supplies new evidence for determining the timing of gold mineralization, the geneses of gold deposits, and identifies that in the Hercynian period, the Altay area developed a tectonic-magmatic-hydrothermal mineralization of the Early Carboniferous period, except the two known mineralization periods including the tectonic-magmatic-hydrothermal mineralization of the Devonian period and Late CarboniferousPermian period.

  14. K-Ar age of young volcanic rocks and excess argon--Binary mixing model and quantitative study of excess argon effect

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A binary mixing model for excess argon is suggested in the note. According to this model and the data of excess argon component obtained in our experiment , a quantitative study of the effect of excess argon on real K-Ar age of young volcanic rocks is done. The result indicates that the effect of 5% excess argon component in samples on K-Ar age of the samples more than 2 Ma is less than 7.36% and can lead K-Ar age of 0.5 Ma samples to increase by 32.4%, while 1% excess argon component leads K-Ar age of 0.5 Ma samples to increase by 6.26%. Therefore, when pre-processed excess argon component is ≤1%, K-Ar age of the samples more than 0.5 Ma should be credible. On this basis we suggest a principal opinion for evaluation of previous K-Ar dating results and propose that the matrix is used to determine K-Ar age of young volcanic rocks. For the samples less than 0.2 Ma, in the case of high excess argon content, even if only 1% excess argon component exists in their matrix, it can also greatly affect their K-A age. Thus it must be careful to treat the dating result.

  15. The effect of thermal resetting and recrystallisation on white mica 40Ar/39Ar ages during retrograde metamorphism on Syros, Greece

    Science.gov (United States)

    Uunk, Bertram; Wijbrans, Jan; Brouwer, Fraukje

    2015-04-01

    White mica 40Ar/39Ar dating is a proven powerful tool for constraining timing of metamorphism, deformation and exhumation. However, in high-pressure metamorphic rocks, dating often results in wide age ranges which are not in agreement with constraints from other isotopic systems, indicating that geological and chemical processes complicate straightforward 40Ar/39Ar dating. In this research project, white mica ages from rocks of the Cycladic Blueschist Unit on Syros, Greece with contrasting rheology and strain mechanisms are compared, in order to better understand the role of deformation, recrystallization and fluid flow on 40Ar/39Ar ages of white mica during retrograde metamorphism. Resulting ages vary along different sections on the island, inconsistent with other isotopic constraints on eclogite-blueschist metamorphism (55-50 Ma) and greenschist overprinting (41-30 Ma). Two end-member models are possible: 1) Results represent continuous crystallization of white mica while moving from blueschist to greenschist conditions in the metamorphic P-T loop, or 2) white mica equilibrated in eclogite-blueschist conditions and their diffusion systematics were progressively perturbed during greenschist overprinting. The single grain fusion analyses yielded contrasting age distributions, which indicate contrasts in degree of re-equilibration during retrograde metamorphism. Step wise heating of larger grain populations resulted in flat plateau shapes, providing no evidence for partial resetting. Electron microprobe measurements of Si per formula unit, as a proxy for pressure during crystallisation, do not explain age variation within sections or on the island scale. The previously unreported north-south age trend and age ranges per sample, as shown only in the 40Ar/39Ar system of the metapelitic and marble lithologies, contains key information that will allow us to test between different scenarios for age formation. Excess argon infiltration at this stage seems to have been of

  16. Pre-Himalayan tectono-magmatic imprints in the Darjeeling-Sikkim Himalaya (DSH) constrained by 40Ar/39Ar dating of muscovite

    Science.gov (United States)

    Acharyya, Subhrangsu K.; Ghosh, Subhajit; Mandal, Nibir; Bose, Santanu; Pande, Kanchan

    2017-09-01

    The Lower Lesser Himalayan Sequence (L-LHS) in Darjeeling-Sikkim Himalaya (DSH) displays intensely deformed, low-grade meta-sedimentary rocks, frequently intervened by granite intrusives of varied scales. The principal motivation of our present study is to constrain the timing of this granitic event. Using 40Ar/39Ar geochronology, we dated muscovite from pegmatites emplaced along the earliest fabric in the low grade Daling phyllite, and obtained ∼1850 Ma Ar-Ar muscovite cooling age, which is broadly coeval with crystallization ages of Lingtse granite protolith (e.g., 1800-1850 Ma U-Pb zircon ages) reported from the L-LHS. We present here field observations to show the imprints (tectonic fabrics) of multiple ductile deformation episodes in the LHS terrain. The earliest penetrative fabric, axial planar to N-S trending reclined folds, suggest a regional tectonic event in the DSH prior to the active phase of Indo-Asia collision. Based on the age of granitic bodies and their structural correlation with the earliest fabric, we propose that the L-LHS as a distinct convergent tectono-magmatic belt, delineating the northern margin of Indian craton in the framework of the ∼1850 Ma Columbia supercontinent assembly.

  17. Ar-40 to Ar-39 ages of the large impact structures Kara and Manicouagan and their relevance to the Cretaceous-Tertiary and the Triassic-Jurassic boundary

    Science.gov (United States)

    Trieloff, M.; Jessberger, E. K.

    Since the discovery of the Ir enrichment in Cretaceous-Tertiary boundary clays in 1980, the effects of a 10-km asteroid impacting on the Earth 65 Ma ago have been discussed as the possible reason for the mass extinction--including the extinction of the dinosaurs--at the end of the Cretaceous. But up to now no crater of this age that is large enough (ca. 200 km in diameter) has been found. One candidate is the Kara Crater in northern Siberia. Kolesnikov et al. determined a K-Ar isochron of 65.6 +/- 0.5 Ma, indistinguishable from the age of the K-T boundary and interpreted this as confirmation of earlier proposals that the Kara bolide would have been at least one of the K-T impactors. Koeberl et al. determined Ar-40 to Ar-39 ages ranging from 70 to 82 Ma and suggested an association to the Campanian-Maastrichtian boundary, another important extinction horizon 73 Ma ago. We dated four impact melts, KA2-306, KA2-305, SA1-302, and AN9-182. Results from the investigation are discussed.

  18. Laser probe 40Ar/39Ar dating for quartz from auriferous quartz veins in the Shihu gold deposit, western Hebei Province, North China

    Institute of Scientific and Technical Information of China (English)

    CAO Ye; LI Shengrong; ZHANG Huafeng; AO Chong; LI Zhenzhen; LIU Xiaobin

    2010-01-01

    The Shihu gold deposit is situated in the central shear zone of the Meso-Cenozoic Fuping metamorphic core complex in the middle-northern part of the Taihang Mountains. This kind of gold deposits named after 'Shihu type' widely occurs in this region. Gold-bearing quartz veins are their most important industrial orebodies. Detailed laser 40Ar/39Ar geochronology of the mineralized quartz veins in the study area reveals details of its tectono-magmatic history. The 40Ar/39Ar ages for the quartz are between 134.4 Ma and 155.9 Ma with a mean age of 141±4 Ma on the isochron line and 139±7 Ma on the inverse isochron line, respectively, which is interpreted to be the best estimate of the crystalline age of the quartz veins. The gold mineralization was most likely related to an underplating event that took place in the northern part of the Taihang Mountain at ca. 140 Ma. The timing of gold mineralization in the area is similar to those observed in other major gold-producing provinces in the NCC. This episode is simultaneous with those in the eastern NCC, indicative of a widespread late Yanshanian metallogenic event that was a response either to the subduction of the Izanagi-Pacific plate beneath eastern China or to the removal of the Early Cretaceous lithosphere in the eastern NCC. The ore-forming material sources may be the Early Precambrian metamorphic basement, instead of intermediate-acid rock bodies and dykes.

  19. Runas darbības aktivizēšana bērniem ar cerebrālo trieku un dizartriju rehabilitācijas centrā

    OpenAIRE

    2011-01-01

    Zilgalve I., maģistra darba tēma: „Runas darbības aktivizēšana bērniem ar cerebrālo trieku un dizartriju rehabilitācijas centrā.” Maģistra darba mērķis Teorētiski izzināt un praktiski pārbaudīt runas darbības aktivizāciju bērniem ar cerebrālo trieku un dizartriju rehabilitācijas centrā. Izvirzot maģistra darba uzdevumus autore ir ņēmusi vērā logopēdiskā darba pamatnosacījumus, kas jāievēro strādājot ar bērniem ar cerebrālo trieku un dizartriju. Maģistra darba uzdevumi 1.Izzin...

  20. Diatreme evolution during the phreatomagmatic eruption of the Songaksan tuff ring, Jeju Island, Korea

    Science.gov (United States)

    Go, S. Y.; Kim, G. B.; Jeong, J. O.; Sohn, Y. K.

    2017-03-01

    The Songaksan tuff ring, Jeju Island, Korea, which erupted ca. 3.7 ka BP in a coastal setting, provides an unusual opportunity to study the processes of phreatomagmatic eruption and the formation of a diatreme because of the exceptionally well-preserved ejecta beds and well-known subsurface geology. The tuff sequence can be divided into four units (A to D), which have distinctly different accidental componentry (quartz-rich vs. quartz-poor), grain surface features (abraded and ash-coated vs. unabraded and uncoated), and chemical compositions of juvenile particles. The basal tephra bed of unit A, which probably erupted after the removal of the relatively hard shallow-level (120 m deep) accidental grains, suggesting that the early erupted tephra had not yet experienced recycling and pre-eruption mixing in the diatreme. On the other hand, the overlying tephra beds of units A, B, and D contain an abundance of abraded and ash-coated juvenile/accidental grains, suggesting that the tephra comprised significant proportions of "recycled" or "premixed" materials from previous eruptions or subsurface explosions, which participated in the explosion-driven mixing in the diatreme before eventual ejection from the diatreme. Unit C is unusual in that it comprises extremely rare accidental grains and ash-coated juvenile/accidental grains. We interpret that the supply of solid materials, either accidental or juvenile, to the diatreme was greatly reduced because of temporary stabilization of the diatreme and the reduction in magma flux to the diatreme. The diatreme is therefore envisaged to have been filled with a water-saturated slurry, in which particle abrasion and adhesion were inhibited. We also infer that the diatreme fill was temporarily removed by a powerful explosion before eruption of unit C on the basis of the near absence of the tephra grains from earlier eruptions throughout the tephra beds of unit C. The ratio of tachylite to sideromelane grains generally increases up

  1. High Spatial Resolution 40Ar/39Ar Geochronology of Impact Melt Breccias from Apollo 17 Boulders at Stations 2, 6, and 7

    Science.gov (United States)

    Mercer, C. M.; Hodges, K. V.; Jolliff, B. L.; Van Soest, M. C.; Wartho, J. A.; Weirich, J. R.

    2015-12-01

    Several boulders located at the bases of the North and South Massifs were among the primary field targets of the Apollo 17 mission to the Taurus-Littrow Valley on the Moon [1]. Some boulders are polylithologic, including Boulder 1 at Station 2 and the boulders at Stations 6 and 7. These boulders were the subjects of consortium studies [2, 3] that included 40Ar/39Ar geochronology to determine the ages of distinct lithologies within each boulder [e.g., 4-6]. We report new 40Ar/39Ar data for the impact melt breccias 72255, 76315, 77075, and 77135 obtained using the UV laser ablation microprobe (UVLAMP) methods of [7]. For 72255, we obtained a preliminary isochron date ca. 3814 Ma from 22 melt analyses, which is younger than published plateau dates (e.g., 3951-3835 Ma [4, 8]). Fifteen melt analyses of 76315 yield a preliminary isochron date ca. 3850 Ma, younger than the 3900 ± 16 Ma date reported by [8]. Melt analyses of 77075 yield preliminary dates between ca. 3797-3584 Ma, possibly reflecting partial loss of 40Ar. In this case, the oldest date may provide a minimum age for the formation of melt in 77075. Finally, the UVLAMP dates for the 77135 melt range from 3810-3361 Ma and corresponding Ca/K ratios range from ca. 100-6. Electron microprobe analyses of small (ca. 10s of microns wide) pockets of K-rich materials show that both K-rich glass and K-feldspar are present. The UVLAMP dates for 77135 likely reflect spatially variable 40Ar loss, consistent with published step heating results [e.g., 6]. References: [1] Schmitt (1973) Science, 182, 681-690. [2] Ryder (1993). Catalog of Apollo 17 Rocks: Volume 1 - Stations 2 and 3 (South Massif). LPI. [3] Ryder (1993). Catalog of Apollo 17 Rocks: Volume 4 - North Massif. LPI. [4] Leich et al. (1975) The Moon, 14, 407-444. [5] Cadogan & Turner (1976). LPSC, 7, 2267-2285. [6] Stettler et al. (1978). LPSC, 9, 1113-1115. [7] Mercer et al. (2015) Sci. Adv., 1, e1400050. [8] Dalrymple & Ryder (1996). JGR, 101, 26069-26084.

  2. Integrated single crystal laser ablation U/Pb and (U-Th)/He dating of detrital accessory minerals - Proof-of-concept studies of titanites and zircons from the Fish Canyon tuff

    Science.gov (United States)

    Horne, Alexandra M.; van Soest, Matthijs C.; Hodges, Kip V.; Tripathy-Lang, Alka; Hourigan, Jeremy K.

    2016-04-01

    Excimer laser technologies enable a rapid and effective approach to simultaneous U/Pb geochronology and (U-Th)/He thermochronology of a wide range of detrital accessory minerals. Here we describe the 'laser ablation double dating' (LADD) method and demonstrate its viability by applying it to zircon and titanite crystals from the well-characterized Fish Canyon tuff. We found that LADD dates for Fish Canyon zircon (206Pb/238U - 28.63 ± 0.11 Ma; (U-Th)/He - 28.38 ± 0.73 Ma) are statistically indistinguishable from those obtained through established, traditional methods of single-crystal dating. The same is true for Fish Canyon titanite LADD dates: 206Pb/238U - 28.08 ± 0.90 Ma; (U-Th)/He - 27.98 ± 0.86 Ma. As anticipated, given that LADD involves the analysis of smaller amounts of material than traditional methods, it yields dates with higher analytical uncertainty. However, this does not substantially reduce the utility of the results for most applications to detrital datasets. An important characteristic of LADD is that it encourages the chemical characterization of crystals by backscattered electron, cathodoluminescence, and/or Raman mapping prior to dating. In addition, by permitting the rapid and robust dating of crystals regardless of the degree of their abrasion during sedimentary transport, the method theoretically should yield dates that are more broadly representative of those of the entire population of detrital crystals in a natural sample.

  3. Polychronous (Early Cretaceous to Palaeogene) emplacement of the Mundwara alkaline complex, Rajasthan, India: 40Ar/39Ar geochronology, petrochemistry and geodynamics

    Science.gov (United States)

    Pande, Kanchan; Cucciniello, Ciro; Sheth, Hetu; Vijayan, Anjali; Sharma, Kamal Kant; Purohit, Ritesh; Jagadeesan, K. C.; Shinde, Sapna

    2016-07-01

    The Mundwara alkaline plutonic complex (Rajasthan, north-western India) is considered a part of the Late Cretaceous-Palaeogene Deccan Traps flood basalt province, based on geochronological data (mainly 40Ar/39Ar, on whole rocks, biotite and hornblende). We have studied the petrology and mineral chemistry of some Mundwara mafic rocks containing mica and amphibole. Geothermobarometry indicates emplacement of the complex at middle to upper crustal levels. We have obtained new 40Ar/39Ar ages of 80-84 Ma on biotite separates from mafic rocks and 102-110 Ma on whole-rock nepheline syenites. There is no evidence for excess 40Ar. The combined results show that some of the constituent intrusions of the Mundwara complex are of Deccan age, but others are older and unrelated to the Deccan Traps. The Mundwara alkaline complex is thus polychronous and similar to many alkaline complexes around the world that show recurrent magmatism, sometimes over hundreds of millions of years. The primary biotite and amphibole in Mundwara mafic rocks indicate hydrous parental magmas, derived from hydrated mantle peridotite at relatively low temperatures, thus ruling out a mantle plume. This hydration and metasomatism of the Rajasthan lithospheric mantle may have occurred during Jurassic subduction under Gondwanaland, or Precambrian subduction events. Low-degree decompression melting of this old, enriched lithospheric mantle, due to periodic diffuse lithospheric extension, gradually built the Mundwara complex from the Early Cretaceous to Palaeogene time.

  4. ISEA reversed event in the Cretaceous Normal Superchron (CNS):40Ar/39Ar dating and paleomagnetic results

    Institute of Scientific and Technical Information of China (English)

    SHI Ruiping; HE Huaiyu; ZHU Rixiang; PAN Yongxin

    2004-01-01

    In order to provide the age for the ISEA (one reversed event in the CNS) a combined rock magnetic, paleomagnetic and geochronologic study has been conducted on two Cretaceous andesitic basalt lava flows from Sanbaoying, Liaoning Province of northeastern China. Rock magnetic investigations show that pseudo-single domain (PSD) titanomagnetite with poor-Ti content is the dominant magnetic mineral in Sanbaoying lava flows. Detailed systematic thermal demagnetization allowed us to isolate two remanence components after removing a low temperature component at 100℃/150℃; an intermediate temperature component with normal polarity at 150℃/200℃-380℃/400℃ and the characteristic remanence component (ChRM) with reversed polarity above 400℃/450℃. 40Ar/39Ar dating results show that Sanbaoying rocks were erupted at 116.0±0.3 Ma. Combination of paleomagnetic results and 40Ar/39Ar dating indicates that the reversed event recorded in Sanbaoying lavas corresponds to the ISEA event in the CNS. Our age determination for ISEA reversed event provides chronological evidence to study the relevance between global geological events that occurred in the CNS and geodynamo processes.

  5. 40 Ar/39 Ar Ages of Auriferous Quartz Veins from the Fengyang and Zhangbaling Regions and Their Geological Significance

    Institute of Scientific and Technical Information of China (English)

    应汉龙; 赵利清

    2003-01-01

    Geotectonically the Fengyang and Zhangbaling regions belong to the North China craton and the Dabie-Sulu orogene, respectively. Neo-Archean gneiss and amphibolite and metamor-phosed sea-facies sodic volcanic rocks are the main outcrops in the two regions, respectively. The Zhangbaling terrane strike-skipped along the Tancheng-Lujiang fault zone in Mesozoic and Cenozo-ic eras and got close to the Fengyang terrane. Mesozoic Yanshanian intrusions occur broadly in the two regions. Gold-bearing quartz veins occur in the metamorphic rocks in the Fengyang region and in the granodiorite and metamorphosed sea-facies sodic volcanic rocks in the Zhangbaling region.Generally, the formation of the auriferous quartz veins involved three stages. At the first stage, gold-poor sulfide quartz veins were formed; at the second stage gold-rich quartz sulfide veins were formed; and at the third stage gold-poor barite and/or carbonate veins were formed. The 40Ar/39Ar step-heating plateau ages of the first-stage and the second-stage quartz aggregates from the Zhuding, Maoshan and Shangcheng gold deposits range between 116.1 + 0.6 Ma and 118.3 + 0.5 Ma and are pretty close to their least apparent ages and isochronal ages, respectively. All plat-eau, least apparent and isochronal ages range between 113.4 ± 0.4 Ma and 118.3 ± 0.5 Ma,which are considered as the formation age range of the quartz. It is reasonable and reliable to take the 40Ar/39Ar age range of the quartz as the formation age range of gold-bearing quartz veins on the basis of spatial relationship between gold-bearing quartz veins and their country rocks. The gold deposits in the two regions were formed in Aptian, Cretaceous, when the Tancheng-Lujiang fault zone moved as a normal fault with slightly right-lateral strike-skip, was extensional and expe-rienced very strong magmatic process. It is shown that the magmatic hydrothermal fluid is a very important part of the gold ore-forming hydrothermal fluid in the Fengyang and

  6. Monazite and allanite U-Th-Pb vs mica 39Ar-40Ar ages in equilibrated metasediments: closure behavior and closure temperatures

    Science.gov (United States)

    Allaz, J.; Engi, M.; Berger, A.; Janots, E.; Villa, I. M.

    2009-12-01

    The art of geochronology implies identification of processes, so as to correctly interpret an isotopic age as (1) crystallization, (2) cooling, or (3) meaningless owing to inheritance and/or late mineral recrystallization. We address here a field calibration of 39Ar-40Ar ages against U-Th-Pb ages. We demonstrate that detailed petrological, micro-textural and micro-chemical investigations are a necessary prerequisite for meaningful geochronology. The Barrovian metamorphism in the Alps results from the collision of Europe and Apulia and reaches its thermal maximum (upper amphibolite facies) in the Central Alps. Age estimates for the Alpine orogeny have long been controversial, despite a multitude of studies. Based on the resetting of Rb-Sr and K-Ar ages in muscovite from polymetamorphic gneisses, Jäger [1] had proposed an age of 38±2 Ma for the Barrovian metamorphism, corresponding to a “closure temperature TC” (following [2]) of 350 °C for K-Ar in muscovite. However, a uniform Eocene age for the metamorphism in the Central Alps was in conflict already with early monazite and xenotime U-Pb ages from the same area, namely 30 Ma in the southern, and ~20 Ma in the northern part (e.g. [3]). A recent study [4] both confirmed the young monazite ages in the north (SHRIMP U-Pb of 18-19 Ma near Tmax = 570 °C), and demonstrated that ca. 30 Ma ago this part of the belt was still heating up, as allanite grew prograde near 440 °C. These results once more prove isotopic inheritance, and therefore underestimation of mica K-Ar TC, in Jäger’s [1] samples. To avoid isotopic inheritance problems we selected only Mesozoic metasediments from the northern Central Alps. We screened all samples by PTAX: many had undergone a variety of retrogression reactions and calculations show petrological disequilibrium; we favored those in near-ideal petrological equilibrium. 39Ar-40Ar ages for mica separates from equilibrium samples yield ages between 18.93±0.83 and 15.79±0.11 Ma for

  7. Analysis list: Ar [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Ar Gonad,Kidney,Prostate + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/targe...t/Ar.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Ar.5.tsv http://dbarchive.biosciencedbc.jp/...kyushu-u/mm9/target/Ar.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Ar.Gonad.tsv,http://dbarchive.bioscience...dbc.jp/kyushu-u/mm9/colo/Ar.Kidney.tsv,http://dbarchive.bioscienced...bc.jp/kyushu-u/mm9/colo/Ar.Prostate.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Gonad.gml,http://dbarchive.bioscience

  8. Analysis list: AR [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available AR Blood,Breast,Prostate + hg19 http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/target/AR.1.tsv http:...//dbarchive.biosciencedbc.jp/kyushu-u/hg19/target/AR.5.tsv http://dbarchive.biosciencedbc....jp/kyushu-u/hg19/target/AR.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/colo/AR.Blood.tsv,http://d...barchive.biosciencedbc.jp/kyushu-u/hg19/colo/AR.Breast.tsv,http://dbarchive.biosc...iencedbc.jp/kyushu-u/hg19/colo/AR.Prostate.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/colo/Blood.gml,http:

  9. U-Pb and Ar-Ar geochronology of the Fujiawu porphyry Cu-Mo deposit, Dexing district, Southeast China: Implications for magmatism, hydrothermal alteration, and mineralization

    Science.gov (United States)

    Li, Xiaofeng; Hu, Ruizhong; Rusk, Brian; Xiao, Rong; Wang, Cuiyun; Yang, Feng

    2013-09-01

    The Fujiawu porphyry Cu-Mo deposit is one of several porphyry Cu-Mo deposits in the Dexing district, Jiangxi Province, Southeast China. New zircon SHRIMP U-Pb data yield a weighted mean 206Pb/238U age of 172.0 ± 2.1 and 168.5 ± 1.4 Ma from weakly altered granodiorite porphyry and quartz diorite porphyry, respectively. Two hydrothermal biotites from granodiorite porphyry give an Ar-Ar step-heating plateau age of 169.9 ± 1.8 and 168.7 ± 1.8 Ma. Hydrothermal apatite exsolved from altered biotite yields an isotope dilution thermal ionization mass spectrometry isochron age of 164.4 ± 0.9 Ma. The apatite age is similar to the ages obtained from hydrothermal rutile (165.0 ± 1.1 and 164.8 ± 1.6 Ma) and indicates that the magmatism and hydrothermal activity in the Fujiawu deposit occurred in the Middle Jurassic. Hydrothermal fluid circulation related to multiple stages of magma emplacement resulted in Cu-Mo mineralization in the Fujiawu porphyry deposit. The zircon SHRIMP U-Pb ages and the published molybdenite Re-Os age (170.9 ± 1.5 Ma) represent the timing of magma crystallization and Mo mineralization, whereas the rutile and apatite U-Pb ages reflect the timing of Cu mineralization following quartz diorite emplacement. The data suggest slow cooling after emplacement of the quartz diorite porphyry.

  10. Tectono-thermal evolution of the India-Asia collision zone based on 40Ar-39Ar thermochronology in Ladakh, India

    Indian Academy of Sciences (India)

    Rajneesh Bhutani; Kanchan Pande; T R Venkatesan

    2004-12-01

    New 40Ar-39Ar thermochronological results from the Ladakh region in the India-Asia collision zone provide a tectono-thermal evolutionary scenario. The characteristic granodiorite of the Ladakh batholith near Leh yielded a plateau age of 46.3 ± 0.6Ma (2 ). Biotite from the same rock yielded a plateau age of 44.6 ± 0.3Ma (2 ). The youngest phase of the Ladakh batholith, the leucogranite near Himya, yielded a cooling pattern with a plateau-like age of ∼36 Ma. The plateau age of muscovite from the same rock is 29.8 ± 0.2Ma (2 ). These ages indicate post-collision tectonothermal activity, which may have been responsible for partial melting within the Ladakh batholith. Two basalt samples from Sumdo Nala have also recorded the post-collision tectono-thermal event, which lasted at least for 8MY in the suture zone since the collision, whereas in the western part of the Indus Suture, pillow lava of Chiktan showed no effect of this event and yielded an age of emplacement of 128.2 ± 2.6Ma (2 ). The available data indicate that post-collision deformation led to the crustal thickening causing an increase in temperature, which may have caused partial melting at the base of the thickened crust. The high thermal regime propagated away from the suture with time.

  11. Cenozoic tectonics in the Buruanga Peninsula, Panay Island, Central Philippines, as constrained by U-Pb, 40Ar/39Ar and fission track thermochronometers

    Science.gov (United States)

    Walia, M.; Yang, T. F.; Knittel, U.; Liu, T.-K.; Lo, C.-H.; Chung, S.-L.; Teng, L. S.; Dimalanta, C. B.; Yumul, G. P.; Yuan, W. M.

    2013-01-01

    Buruanga Peninsula forms the westernmost part of Panay Island, Central Philippines and is a part of the Palawan Continental Terrane (PCT), which was formerly attached to south-eastern China. It acted as the leading edge of the continental fragment and collided with the Philippine Mobile Belt (PMB) followed by convergence beneath the latter. Dating of the collision is crucial for understanding the evolution of the archipelago. Samples collected from Buruanga Peninsula were dated using U-Pb, 40Ar/39Ar and fission track dating (FTD) techniques to constrain the timing of the tectonic events related to the collision of the PMB with the PCT. These techniques have enabled us to obtain ages over a range of closure temperatures from about 700 °C to about 110 °C. Paleoproterozoic and Permian zircon U-Pb ages from Saboncogon Formation emphasize derivation of the western part of Buruanga Peninsula from SE China; zircon and apatite fission track ages of 51 Ma and 16 Ma, respectively, constrain the exhumation of this formation. The age data suggest tectonic events at ~ 14 Ma, ~ 11-12 Ma and about 7-8 Ma following intrusive activity at about 18 Ma. Uplift and exhumation at ~ 14 Ma are thought to be the result of subduction of low-density crustal rocks, at 11 Ma to be the result of isostatic uplift as a consequence of crustal thickening and at ~ 8 Ma to be due to the isostatic re-equilibration of the sediments overlying the former suture. Hence, collision is constrained to have started at about 14-15 Ma and to have ended before 8 Ma. Multi-element patterns of the 18 Ma Patria-Diorite from Buruanga Peninsula show enrichment in LILE (Rb, Sr, and K) and LREE and depletion in HFSE elements (Ti, Nb, and Ta) similar to those from Luzon volcanics and the volcanic rocks of Negros Island. These arc-signatures indicate a subduction related environment for the emplacement of this intrusive body and show that the diorite belongs to the PMB. The age constraints of the present study neither

  12. Studies of the mobility of uranium and thorium in Nevada Test Site tuff

    Energy Technology Data Exchange (ETDEWEB)

    Wollenberg, H.A.; Flexser, S.; Smith, A.R. [Lawrence Berkeley Lab., CA (United States)

    1991-06-01

    Hydro-geochemical processes must be understood if the movement of radionuclides away from a breached radioactive waste canister is to be modeled and predicted. In this respect, occurrences of uranium and thorium in hydrothermal systems are under investigation in tuff and in rhyolitic tuff that was heated to simulate the effects of introduction of radioactive waste. In these studies, high-resolution gamma spectrometry and fission-track radiography are coupled with observations of alteration mineralogy and thermal history to deduce the evidence of, or potential for movement of, U and Th in response to the thermal environment. Observations to date suggest that U was mobile in the vicinity of the heater but that localized reducing environments provided by Fe-Ti-Mn-oxide minerals concentrated U and thus attenuated its migration.

  13. Diffusion of sodium, potassium, calcium, manganese, and radon in tuff and clinoptilolite under leaching

    Science.gov (United States)

    Dikii, N. P.; Dovbnya, A. N.; Lyashko, Yu. V.; Medvedev, D. V.; Medvedeva, E. P.; Uvarov, V. L.; Achkasov, K. V.

    2011-07-01

    Nuclear physics methods are used to determine the diffusion coefficients of Na, Ca, Mn, K, and 222Rn in clinoptilolite (Sokirnitsa occurrence, Ukraine) and in natural tuff (Yucca Mountain, Nevada, United States) and in tuff irradiated by γ-quanta ( E max = 23 MeV) to a dose of 107 Gy at a leaching temperature of 37°C. The diffusion coefficients of sodium and potassium in clinoptilolite are found to differ considerably: 4 × 10-17 and 2 × 10-20 m2/s, respectively. This indicates the influence of aquacomplexes on the cation transfer. The diffusion coefficient of radon in these materials is determined: in clinoptilolite it equals 2.5 × 10-12 m2/s.

  14. Sorption and desorption of remazol yellow by a Fe-zeolitic tuff

    Energy Technology Data Exchange (ETDEWEB)

    Solache R, M. J. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Villalva C, R.; Diaz N, M. C., E-mail: marcos.solache@inin.gob.m [Instituto Tecnologico de Toluca, Division de Estudios del Posgrado, Av. Tecnologico s/n, Ex-Rancho La Virgen, 52140 Metepec, Estado de Mexico (Mexico)

    2010-07-01

    The adsorption of remazol yellow from aqueous solution was evaluated using a Fe-zeolitic tuff. The adsorbent was characterized by scanning electron microscopy, IR spectroscopy and X-ray diffraction. Sorption kinetic and isotherms were determined and the adsorption behavior was analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results, indicating chemisorption on a heterogeneous material. The regeneration of the material was best accomplished by using a H{sub 2}O{sub 2} solution. The sorption capacity of the Fe-zeolitic tuff increased when the saturated samples were treated with a H{sub 2O2} or FeCl{sub 3} solution. (Author)

  15. 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...

  16. 33 CFR 80.125 - Marblehead Neck, MA to Nahant, MA.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Marblehead Neck, MA to Nahant, MA... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Atlantic Coast § 80.125 Marblehead Neck, MA to Nahant, MA. The 72 COLREGS apply on the harbors, bays, and inlets on the east coast of Massachusetts...

  17. 33 CFR 80.135 - Hull, MA to Race Point, MA.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Hull, MA to Race Point, MA. 80.135 Section 80.135 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Atlantic Coast § 80.135 Hull, MA to Race Point, MA....

  18. Zeolitic volcanic tuffs from Macicas (Cluj County, natural raw materials used for NH4+ removal from wastewaters

    Directory of Open Access Journals (Sweden)

    Horea Bedelean

    2006-04-01

    Full Text Available Volcanic tuffs out cropping in Măcicaş area (Cluj County have been investigated and tested for their ammonium removal capacity. The zeolitic volcanic tuffs from Măcicaş are mainly represented by vitric and vitric crystal tuffs. In this region, significant amounts of volcanic glass in the pyroclastic sequence have been replaced by zeolites (between 50-80 %. The main zeolite species identified in volcanic tuffs from Măcicaş is clinoptilolite and subordinately mordenite. The zeolitic tuff samples considered in zeolitic sodium form (labeled M1-Na and M2-Na are tested in ammonium removal experiments. The ammonium ions were completely removed from 0.0716g/dm3 NH4+ solution onto 10g of zeolitic material in static regime. In dynamic regime, the ammonium ions were completely removed after 250 ml and 500 ml solution passed on M1-Na and M2-Na sample respectively. Also the zeolite exhaustion takes place after more than 1500 ml solution is processed in both cases. The ionic exchange properties suggest that the zeolitic tuff of the Măcicaş region can be used as a final stage (following the biological process in wastewater treatment plants in order to assure compliance with environmental standards.

  19. Alteration history of Mount Epomeo Green Tuff and a related polymictic breccia, Ischia Island, Italy: evidence for debris avalanche

    Science.gov (United States)

    Altaner, S.; Demosthenous, C.; Pozzuoli, A.; Rolandi, G.

    2013-05-01

    This paper presents mineralogical, chemical, and textural data for the Mount Epomeo Green Tuff and an associated polymictic breccia on Ischia Island, Italy with the purpose of defining the alteration history of the two units and the emplacement origin of the polymictic breccia. Our results indicate that the Green Tuff trachytic ignimbrite experienced three alteration events that produced the following mineral assemblages: (1) phillipsite, randomly interstratified (R0) illite/smectite (I/S), Fe-illite, and smectite (in situ Green Tuff); (2) chabazite, phillipsite, R0 I/S, and Fe-illite (proximal facies Green Tuff at Scarrupata di Barano); and (3) analcime, authigenic K-feldspar, Fe-illite, R0 I/S, and smectite (clasts of Green Tuff in polymictic breccia). Phillipsite, chabazite, and R0 I/S within the in situ and proximal facies Green Tuff indicate low-temperature alteration ( T 70 °C) alteration within a mostly closed chemical system. These data suggest that the polymictic breccia represents a debris avalanche deposit created by a catastrophic volcanic collapse, which was associated with low-temperature hydrothermal alteration and thus structural weakening of the volcano. The debris avalanche that produced the polymictic breccia on Ischia may be related to nearby massive debris avalanche deposits recently discovered offshore of southern Ischia. The young age of the polymictic breccia (5.7-8.6 ka) and the possibility of its catastrophic emplacement indicate an additional volcanic hazard for Ischia Island.

  20. On the physics of unstable infiltration, seepage, and gravity drainage in partially saturated tuffs.

    Science.gov (United States)

    Faybishenko, B; Bodvarsson, G S; Salve, R

    2003-01-01

    To improve understanding of the physics of dynamic instabilities in unsaturated flow processes within the Paintbrush nonwelded unit (PTn) and the middle nonlithophysal portion of the Topopah Spring welded tuff unit (TSw) of Yucca Mountain, we analyzed data from a series of infiltration tests carried out at two sites (Alcove 4 and Alcove 6) in the Exploratory Studies Facility (ESF), using analytical and empirical functions. The analysis of infiltration rates measured at both sites showed three temporal scales of infiltration rate: (1) a macro-scale trend of overall decreasing flow, (2) a meso-scale trend of fast and slow motion exhibiting three-stage variations of the flow rate (decreasing, increasing, and [again] decreasing flow rate, as observed in soils in the presence of entrapped air), and (3) micro-scale (high frequency) fluctuations. Infiltration tests in the nonwelded unit at Alcove 4 indicate that this unit may effectively dampen episodic fast infiltration events; however, well-known Kostyakov, Horton, and Philip equations do not satisfactorily describe the observed trends of the infiltration rate. Instead, a Weibull distribution model can most accurately describe experimentally determined time trends of the infiltration rate. Infiltration tests in highly permeable, fractured, welded tuff at Alcove 6 indicate that the infiltration rate exhibits pulsation, which may have been caused by multiple threshold effects and water-air redistribution between fractures and matrix. The empirical relationships between the extrinsic seepage from fractures, matrix imbibition, and gravity drainage versus the infiltration rate, as well as scaling and self-similarity for the leading edge of the water front are the hallmark of the nonlinear dynamic processes in water flow under episodic infiltration through fractured tuff. Based on the analysis of experimental data, we propose a conceptual model of a dynamic fracture flow and fracture-matrix interaction in fractured tuff

  1. Bench-scale experimental determination of the thermal diffusivity of crushed tuff

    Energy Technology Data Exchange (ETDEWEB)

    Ryder, E.E.; Finley, R.E.; George, J.T.; Ho, C.K.; Longenbaugh, R.S. [Sandia National Labs., Albuquerque, NM (United States); Connolly, J.R. [New Mexico Univ., Albuquerque, NM (United States)

    1996-06-01

    A bench-scale experiment was designed and constructed to determine the effective thermal diffusivity of crushed tuff. Crushed tuff particles ranging from 12.5 mm to 37.5 mm (0.5 in. to 1.5 in.) were used to fill a cylindrical volume of 1.58 m{sup 3} at an effective porosity of 0.48. Two iterations of the experiment were completed; the first spanning approximately 502 hours and the second 237 hours. Temperatures near the axial heater reached 700 degrees C, with a significant volume of the test bed exceeding 100 degrees C. Three post-test analysis techniques were used to estimate the thermal diffusivity of the crushed tuff. The first approach used nonlinear parameter estimation linked to a one dimensional radial conduction model to estimate thermal diffusivity from the first 6 hours of test data. The second method used the multiphase TOUGH2 code in conjunction with the first 20 hours of test data not only to estimate the crushed tuffs thermal diffusivity, but also to explore convective behavior within the test bed. Finally, the nonlinear conduction code COYOTE-II was used to determine thermal properties based on 111 hours of cool-down data. The post-test thermal diffusivity estimates of 5.0 x 10-7 m{sup 2}/s to 6.6 x 10-7 m{sup 2}/s were converted to effective thermal conductivities and compared to estimates obtained from published porosity-based relationships. No obvious match between the experimental data and published relationships was found to exist; however, additional data for other particle sizes and porosities are needed.

  2. Reaction of the Topopah Spring Tuff with J-13 water at 120{sup 0}C

    Energy Technology Data Exchange (ETDEWEB)

    Oversby, V.M.

    1984-07-18

    This report describes a series of hydrothermal experiments using crushed tuff from the Topopah Spring Member and natural ground water from well J-13. The purpose of these experiments is to define the changes in water chemistry that would result from temperature changes caused by emplacing high-level nuclear waste in a repository in the Topopah Spring tuff. Experiments were conducted at 120{sup 0}C in Teflon-lined reaction vessels at four separate rock-to-water ratios and for reaction times up to 72 days. The composition of evaporite deposits contained in the pores of the surface-outcrop rock material used in these experiments is determined from solution compositions resulting from treatment of the rock before the start of the experiments. Results from the experiments at 120{sup 0}C are compared with previous experimental results from hydrothermal reaction of the Topopah Spring tuff with J-13 water at 90 and 150{sup 0}C. The main conclusion that can be drawn from this work is that changes in the water chemistry due to heating of the rock-water system can be expected to be very minor. There is no significant source of anions (F{sup -}, Cl{sup -}, NO{sub 3}{sup -}, or SO{sub 4}{sup 2-}) in the rock; solution anion compositions after reaction of pretreated rock with J-13 water differ very little from the starting compositions. The major changes in cations are an increase in silica to approximately the level of cristobalite solubility, supersaturation of aluminum followed by slow precipitation, and fairly rapid precipitation of calcium and magnesium due to the retrograde solubility of calcite. These results are in good agreement with those previously reported for reaction of the tuff with J-13 water at 90 and 150{sup 0}C. 7 references, 7 figures, 28 tables.

  3. On the physics of unstable infiltration, seepage, and gravity drainage in partially saturated tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, B.; Bodvarsson, G.S.; Salve, R.

    2002-04-01

    To improve understanding of the physics of dynamic instabilities in unsaturated flow processes within the Paintbrush nonwelded unit (PTn) and the middle nonlithophysal portion of the Tonopah Spring welded tuff unit (TSw) of Yucca Mountain, we analyzed data from a series of infiltration tests carried out at two sites (Alcove 4 and Alcove 6) in the Exploratory Studies Facility, using analytical and empirical functions. The analysis of infiltration rates measured at both sites showed three temporal scales of infiltration rate: (1) a macro-scale trend of overall decreasing flow, (2) a meso-scale trend of fast and slow motion exhibiting three-stage variations of the flow rate (decreasing, increasing, and [again] decreasing flow rate, as observed in soils in the presence of entrapped air), and (3) micro-scale (high frequency) fluctuations. Infiltration tests in the nonwelded unit at Alcove 4 indicate that this unit may effectively dampen episodic fast infiltration events; however, well-known Kostyakov, Horton, and Philip equations do not satisfactorily describe the observed trends of the infiltration rate. Instead, a Weibull distribution model can most accurately describe experimentally determined time trends of the infiltration rate. Infiltration tests in highly permeable, fractured, welded tuff at Alcove 6 indicate that the infiltration rate exhibits pulsation, which may have been caused by multiple threshold effects and water-air redistribution between fractures and matrix. The empirical relationships between the extrinsic seepage from fractures, matrix imbibition, and gravity drainage versus the infiltration rate, as well as scaling and self-similarity for the leading edge of the water front are the hallmark of the nonlinear dynamic processes in water flow under episodic infiltration through fractured tuff. Based on the analysis of experimental data, we propose a conceptual model of a dynamic fracture flow and fracture-matrix interaction in fractured tuff

  4. Creep in Topopah Spring Member welded tuff. Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Martin, R.J. III; Boyd, P.J.; Noel, J.S. [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

    1995-06-01

    A laboratory investigation has been carried out to determine the effects of elevated temperature and stress on the creep deformation of welded tuffs recovered from Busted Butte in the vicinity of Yucca Mountain, Nevada. Water saturated specimens of tuff from thermal/mechanical unit TSw2 were tested in creep at a confining pressure of 5.0 MPa, a pore pressure of 4.5 MPa, and temperatures of 25 and 250 C. At each stress level the load was held constant for a minimum of 2.5 {times} 10{sup 5} seconds and for as long as 1.8 {times} 10{sup 6} seconds. One specimen was tested at a single stress of 80 MPa and a temperature of 250 C. The sample failed after a short time. Subsequent experiments were initiated with an initial differential stress of 50 or 60 MPa; the stress was then increased in 10 MPa increments until failure. The data showed that creep deformation occurred in the form of time-dependent axial and radial strains, particularly beyond 90% of the unconfined, quasi-static fracture strength. There was little dilatancy associated with the deformation of the welded tuff at stresses below 90% of the fracture strength. Insufficient data have been collected in this preliminary study to determine the relationship between temperature, stress, creep deformation to failure, and total failure time at a fixed creep stress.

  5. Micromorphology of pedogenically derived fracture fills in Bandelier Tuff, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Davenport, D.W.; Wilcox, B.P. [Los Alamos National Lab., NM (United States); Allen, B.L. [Texas Tech Univ., Lubbock, TX (United States)

    1995-11-01

    Fractures in the Bandelier Tuff are potential paths for water movement and transport of contaminants from waste disposal sites and other contaminated areas at Los Alamos National Laboratory, Los Alamos, NM. Contaminants transported in this way could ultimately be found in Los Alamos drinking water or in the Rio Grande, which flows through heavily populated areas in both the USA and Mexico. We conducted this study to determine (i) the morphology and origin of soil-like material in the fractures, and (ii) the likelihood of significant water movement through the fractures. We examined thin sections of fracture fills, soils, and tuffs to obtain fabric and mineralogical data, and collected field data on soil horizons, color, texture, structure, clay films, and root abundance. Fracture fills consist of clay, CaCO{sub 3}, or combinations of the two with minor inclusions of tuff and sand grains. Clay consists of thick, highly oriented argillans aligned parallel to fracture walls, and of discrete books in fracture interiors. Carbonate consists of massive microcrystalline calcite, which completely fills some fractures, and laminae or infillings between clay laminae or books in clay-dominated fractures. The potential creation of new macropores by a variety of processes, however, including seismic activity and biological disturbance, could allow rapid water movement and contaminant transport. 44 refs., 8 figs., 4 tabs.

  6. Studies of ancient concrete as analogs of cementitious sealing materials for a repository in tuff

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; Langton, C.A.

    1989-03-01

    The durability of ancient cementitious materials has been investigated to provide data applicable to determining the resistance to weathering of concrete materials for sealing a repository for storage of high-level radioactive waste. Because tuff and volcanic ash are used in the concretes in the vicinity of Rome, the results are especially applicable to a waste repository in tuff. Ancient mortars, plasters, and concretes collected from Rome, Ostia, and Cosa dating to the third century BC show remarkable durability. The aggregates used in the mortars, plasters, and concretes included basic volcanic and pyroclastic rocks (including tuff), terra-cotta, carbonates, sands, and volcanic ash. The matrices of ancient cementitious materials have been characterized and classified into four categories: (1) hydraulic hydrated lime and hydrated lime cements, (2) hydraulic aluminous and ferruginous hydrated lime cements ({plus_minus} siliceous components), (3) pozzolana/hydrated lime cements, and (4) gypsum cements. Most of the materials investigated are in category (3). The materials were characterized to elucidate aspects of the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical, mineralogical, and microstructural factors. Their durability was found to be affected by the matrix mineralogy, particle size, and porosity; aggregate type, grading and proportioning; and the methodology of placement. 30 refs.

  7. Studies of ancient concrete as analogs of cementitious sealing materials for a repository in tuff

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; Langton, C.A.

    1989-03-01

    The durability of ancient cementitious materials has been investigated to provide data applicable to determining the resistance to weathering of concrete materials for sealing a repository for storage of high-level radioactive waste. Because tuff and volcanic ash are used in the concretes in the vicinity of Rome, the results are especially applicable to a waste repository in tuff. Ancient mortars, plasters, and concretes collected from Rome, Ostia, and Cosa dating to the third century BC show remarkable durability. The aggregates used in the mortars, plasters, and concretes included basic volcanic and pyroclastic rocks (including tuff), terra-cotta, carbonates, sands, and volcanic ash. The matrices of ancient cementitious materials have been characterized and classified into four categories: (1) hydraulic hydrated lime and hydrated lime cements, (2) hydraulic aluminous and ferruginous hydrated lime cements ({plus_minus} siliceous components), (3) pozzolana/hydrated lime cements, and (4) gypsum cements. Most of the materials investigated are in category (3). The materials were characterized to elucidate aspects of the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical, mineralogical, and microstructural factors. Their durability was found to be affected by the matrix mineralogy, particle size, and porosity; aggregate type, grading and proportioning; and the methodology of placement. 30 refs.

  8. Effects of Sabalan Tuff as a Natural Pozzolan on Properties of Plastic Concrete

    Science.gov (United States)

    Doodaran, R. Sadeghi; Khiavi, M. Pasbani

    One of the most common methods for watertighting in dams is to use cutoff or watertight walls. These types of walls should have high plasticity and low permeability [1]. Developing these walls with such qualities requires using plastic concrete with paneling method. In most cases, adding these materials to concrete improves some of its qualities such as consistency, viscosity of fresh concrete, decrease in permeability, increase in plasticity, long term increase in compressive strength, durability against sulphats and decrease in price. The main purpose of this project is using Sabalan natural tuff in plastic concrete for an access to a desirable modulus of elasticity without a decrease in compressive strength. In this paper, in addition to the impact of Sabalan natural pozzolan tuff on plastic concrete qualities, the impacts of pozzolan cement made of this kind of tuff (Ardebil pozzolan cement) on it has been considered. The results showed improvement on the qualities of plastic concrete such as decrease in permeability, decrease in modulus of elasticity and increase in durability against destructive factors with retaining compressive strength.

  9. Formation of a Hydrothermal Kaolinite Deposit from Rhyolitic Tuff in Jiangxi, China

    Institute of Scientific and Technical Information of China (English)

    Ye Yuan; Guanghai Shi; Mengchu Yang; Yinuo Wu; Zhaochong Zhang; Anjie Huang; Jiajing Zhang

    2014-01-01

    The Longmen kaolinite deposit is one of the largest hydrothermal clay deposits of Ganxi volcanic basin (northern Wuyi Mountain area, China). The pristine host rocks are rhyolitic crystal-vitric tuff and minor lapilli tuff from the Late Jurassic Ehuling Formation. The ore consists of kaolin-group minerals (kaolinite, dickite), pyrophyllite with minor quartz, sericite, pyrite, etc.. From the host rocks to the transition zones (altered rocks) then to the vein ores, contents of SiO2 and TFe2O3 decrease, whereas Al2O3 and LOI increase, consistent with the contents increase of kaolin minerals and pyrophyllite in the samples. The total REE abundances of the ores are much lower than that of the host and altered rocks, Rb, Nb, Nd, Zr, Ti and Y are significantly depleted. Apparent zoning features of bulk geochemistry and mineral component reflect that the kaolinite deposit occurred at the expense of the host rock by ascending hydrothermal fluids with distinct removal of SiO2, TFe2O3, Na2O, K2O. According to the mineral assemblage, the formation temperature of this deposit falls within the range of 270-350 ℃. With regard to the industrial applications, the kaolinized ores are suitable for use in ceramics and gemologic materials crafted for seal stones. Moreover, in mineralogical terms, this deposit is also proved to be an excellent example for studying channeled hydrothermal alterations of rhyolitic tuff.

  10. Magnetic fabric, welding texture and strain fabric in the Nuraxi Tuff, Sardinia, Italy

    Science.gov (United States)

    Pioli, L.; Lanza, R.; Ort, M.; Rosi, M.

    2008-09-01

    Anisotropy of magnetic susceptibility (AMS) has been used to interpret flow directions in ignimbrites, but no study has demonstrated that the AMS fabric corresponds to the flow fabric. In this paper, we show that the AMS and strain fabric coincide in a high-grade ignimbrite, the Nuraxi Tuff, a Miocene rhyolitic ignimbrite displaying a wide variability of rheomorphic features and a well-defined magnetic fabric. Natural remanent magnetization (NRM) data indicate that the magnetization of the tuff is homogeneous and was acquired at high temperatures by Ti-magnetite crystals. Comparison between the magnetic fabric and the deformation features along a representative section shows that AMS and anisotropy of isothermal remanent magnetization (AIRM) fabric are coaxial with and reproduce the shape of the strain ellipsoid. Magnetic tests and scanning electron microscopy observations indicate that the fabric is due to trails of micrometer-size, pseudo-single domain, magnetically interacting magnetite crystals. Microlites formed along discontinuities such as shard rims and vesicle walls mimicking the petrofabric of the tuff. The fabric was thus acquired after deposition, before late rheomorphic processes, and accurately mimics homogeneous deformation features of the shards during welding processes and mass flow.

  11. Leaching of solutes from ion-exchange resins buried in Bandelier Tuff

    Energy Technology Data Exchange (ETDEWEB)

    Essington, E.H.; Fuentes, H.R.; Polzer, W.L.; Lopez, E.A.; Stallings, E.A.

    1986-10-01

    Prediction of solute transport at shallow land burial facilities requires a knowledge of the rates of release of solutes (source term) from the buried wastes and of those processes affecting transport through the surrounding media. The leaching (removal) of lithium, strontium, and cesium from a resin/tuff mixture (Bandelier Tuff) was conducted under unsaturated steady and unsteady (drainage) flow conditions in both laboratory columns and large-scale field caissons to approximate the conditions of buried contaminated-waste resins. Lithium was leached most rapidly and strontium least rapidly. Stopping the flow for a period of 40 to 60 days to create drainage (unsteady flow) conditions had very little effect on the concentrations of solutes leached from the resin/tuff layer. Leaching of these solutes in laboratory columns simulated the large-scale (caisson) leaching very well. Thus, laboratory studies may be reasonable predictors of leaching under certain large-scale field conditions. Also, leaching appears to be a kinetics-controlled process that, for the experimental conditions of this study, may be represented by simple first-order kinetics. Further work should concentrate on understanding the effect of environmental factors such as solute mixtures, concentrations, and temperature, as well as those mechanisms that control leaching of solutes. Also, the evaluation and development of alternative mathematical models for describing the source term are needed.

  12. High-temperature, large-volume, lavalike ash-flow tuffs without calderas in southwestern Idaho

    Science.gov (United States)

    Ekren, E.B.; McIntyre, David H.; Bennett, Earl H.

    1984-01-01

    Rhyolitic rocks were erupted from vents in and adjacent to the Owyhee Mountains and Owyhee Plateau of southwestern Idaho from 16 m.y. ago to about 10 m.y. ago. They were deposited on a highly irregular surface developed on a variety of basement rocks that include granitic rocks of Cretaceous age, quartz latite and rhyodacite tuffs and lava flows of Eocene age, andesitic and basaltic lava flows of Oligocene age, and latitic and basaltic lava flows of early Miocene age. The rhyolitic rocks are principally welded tuffs that, regardless of their source, have one feature in common-namely internal characteristics indicating en-masse, viscous lavalike flowage. The flowage features commonly include considerable thicknesses of flow breccia at the bases of various cooling units. On the basis of the tabular nature of the rhyolitic deposits, their broad areal extents, and the local preservation of pyroclastic textures at the bases, tops, and distal ends of some of the deposits, we have concluded that the rocks were emplaced as ash flows at extremely high temperatures and that they coalesced to liquids before final emplacement and cooling. Temperatures of l090?C and higher are indicated by iron-titanium oxide compositions. Rhyolites that are about 16 m.y. old are preserved mostly in the downdropped eastern and western flanks of the Silver City Range and they are inferred to have been erupted from the Silver City Range. They rarely contain more than about 2 percent phenocrysts that consist of quartz and subequal amounts of plagioclase and alkali feldspar; commonly, they contain biotite, and they are the only rhyolitic rocks in the area to do so. The several rhyolitic units that are 14 m.y. to about 10 m.y. old contain only pyroxene-principally ferriferous and intermediate pigeonites-as mafic constituents. The rhyolites of the Silver City Range comprise many cooling units, none of which can be traced for great distances. Rocks erupted from the Owyhee Plateau include two sequences

  13. Volcaniclastic facies architecture of a long-lived, nested silicic tuff ring: the Los Loros volcano, Mendoza, Argentina

    Science.gov (United States)

    Németh, Károly; Risso, Corina; Nullo, Francisco

    2010-05-01

    Los Loros is a small, well-preserved volcanic depression. New K/Ar age dating revealed that the volcano is least 1 million years old. The circular morphology of the ~50 m deep and ~ 1 km broad crater of Los Loros was initially inferred to be of phreatomagmatic origin. Recent work, however, concluded that Los Loros is a far more complex volcano than originally thought; with multiple eruptive phases produced by magmatic and minor phreatomagmatic explosive fragmentation-dominated eruptive processes that consequently formed a low aspect ratio volcano. Previous work also suggested that volcanic rocks of Los Loros were entirely basaltic in composition (Puente Formation) and their age was mid-upper Pleistocene. Newly obtained geochemical data, alongside a new age determination, underlies the fact that the volcano is far older than had been expected from its morphology, and its composition shows no signs of basalt, instead it is trachytic. The volcanic succession forms a ~100 m thick pile sitting directly on Cretaceous continental red beds. The base of the volcanic succession is a polymict volcaniclastic conglomerate with variable bed thickness and occasional cross stratification, indicating a channel-filling nature and an origin from a braided river system. The diversity of the clasts suggests that they likely have been transported from a nearby Miocene back-arc volcanic complex, the Sierra Cachahuén (~40 km), which is a lava dome dominated multiple volcano with thick silicic pyroclastic successions. The volcaniclastic conglomerate is covered by a trachytic pumiceous unit thickening toward the SSE. They are composed of loosely packed rounded pumice lapilli. These beds have a well-sorted texture with no characteristic internal stratification, indicating that they are fall in origin and the bed thickness variation is inferred to reflect the paleo-wind direction. A thick pile of pumiceous tuff (up to 20 m) overlies the basal pumice fall unit. It is stratified, cross

  14. "Ars Electronica 2009" / Raivo Kelomees

    Index Scriptorium Estoniae

    Kelomees, Raivo, 1960-

    2009-01-01

    30. "Ars Electronica" festival "Human Nature" ("Inimese loomus") Linzis. Osaka ülikooli professori Hiroshi Ishiguro mehaanilis-digitaalsest nukust. Hübriidkunsti kategoorias peapreemia saanud Eduardo Kaci inimtaimest. Konverentsidest. Näitusest "See this Sound", mis oli pühendatud helile kujutavas kunstis

  15. "Ars Electronica 2009" / Raivo Kelomees

    Index Scriptorium Estoniae

    Kelomees, Raivo, 1960-

    2009-01-01

    30. "Ars Electronica" festival "Human Nature" ("Inimese loomus") Linzis. Osaka ülikooli professori Hiroshi Ishiguro mehaanilis-digitaalsest nukust. Hübriidkunsti kategoorias peapreemia saanud Eduardo Kaci inimtaimest. Konverentsidest. Näitusest "See this Sound", mis oli pühendatud helile kujutavas kunstis

  16. AR DOC: Augmented reality documentaries

    DEFF Research Database (Denmark)

    Vistisen, Peter

    2014-01-01

    Augmented Reality Documentaries (AR DOC) er et ’lille’ Shareplay projekt (ansøgte midler augmented reality cross media løsninger, til at skabe engagerende publikumsformidling...... indenfor oplevelsesindustrien. Projektet har genereret ny viden omkring, hvordan fysisk og digital formidling kan understøttes via Augmented Reality som formidlingsformat....

  17. USDA-ARS Quartlerly News

    Science.gov (United States)

    This quarterly article is an update of research going on at The USDA-ARS Thad Cochran Southern Horticultural Laboratory in Poplarville, MS to be published in the Louisiana Nursery and Landscape Associations (LANLA) quarterly newsletter. This is one of three publications that I am sending out to the ...

  18. 40Ar/39Ar Age and Geological Significance of Lamprophyres in Pishan on the SW Margin of the Tarim Terrane, NW China

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The dike swarm of lamprophyres at Pishan on the SW margin of the Tarim terrane is composed of ultra-potassic lamprophyres that have intruded into the Proterozoic hornblende schists. 40Ar/39Ar dating data suggest that the isochron ages for phlogopite and whole rock separates of the lamprophyres are 231.7±0.3 Ma and 228.5±0.3 Ma, respectively. Geochemical data indicate that the dikes were derived from a subduction-related or metasomatized mantle. During the Middle-Late Triassic the western Kunlun area entered the post-orogeny period, and thus the occurrence of the dike swarm in the study area may have been controlled by underplating.

  19. Mineralogy and clinoptilolite K/Ar results from Yucca Mountain, Nevada, USA: A potential high-level radioactive waste repository site

    Energy Technology Data Exchange (ETDEWEB)

    WoldeGabriel, G.; Broxton, D.E.; Bish, D.L.; Chipera, S.J.

    1993-11-01

    The Yucca Mountain Site Characterization Project is investigating Yucca Mountain, Nevada, as a potential site for a high-level nuclear waste repository. An important aspect of this evaluation is to understand the geologic history of the site including the diagenetic processes that are largely responsible for the present-day chemical and physical properties of the altered tuffs. This study evaluates the use of K/Ar geochronology in determining the alteration history of the zeolitized portions of Miocene tuffs at Yucca Mountain. Clinoptilolite is not generally regarded as suitable for dating because of its open structure and large ion-exchange capacity. However, it is the most abundant zeolite at Yucca Mountain and was selected for this study to assess the feasibility of dating the zeolitization process and/or subsequent processes that may have affected the zeolites. In this study we examine the ability of this mineral to retain all or part of its K and radiogenic Ar during diagenesis and evaluate the usefulness of the clinoptilolite K/Ar dates for determining the history of alteration.

  20. Book review: Advances in 40Ar/39Ar dating: From archaeology to planetary sciences

    Science.gov (United States)

    Cosca, Michael A.

    2015-01-01

    The recently published book Advances in 40Ar/39Ar Dating: From Archaeology to Planetary Sciences is a collection of 24 chapters authored by international scientists on topics ranging from decay constants to 40Ar/39Ar dating of extraterrestrial objects. As stated by the editors in their introduction, these chapters were assembled with the goal of providing technique-specific examples highlighting recent advances in the field of 40Ar/39Ar dating. As this is the first book truly dedicated to 40Ar/39Ar dating since the second edition printing of the argon geochronologist’s handbook Geochronology and Thermochronology by the 40Ar/39Ar Method (McDougall and Harrison 1999), a new collection of chapters highlighting recent advances in 40Ar/39Ar geochronology offers much to the interested reader.

  1. Armenian Astronomical Society (ArAS) activities

    Science.gov (United States)

    Mickaelian, A. M.

    2016-09-01

    A review on the activities and achievements of Armenian Astronomical Society (ArAS) and Armenian astronomy in general during the last years is given. ArAS membership, ArAS electronic newsletters (ArASNews), ArAS webpage, Annual Meetings, Annual Prize for Young Astronomers (Yervant Terzian Prize) and other awards, international relations, presence in international organizations, local and international summer schools, science camps, astronomical Olympiads and other events, matters related to astronomical education, astronomical heritage, amateur astronomy, astronomy outreach and ArAS further projects are described and discussed.

  2. Episodes of Cenozoic Gold Mineralization on the Eastern Margin of the Qinghai-Tibet Plateau: 40Ar/39Ar Dating and Implication for Geodynamic Events

    Institute of Scientific and Technical Information of China (English)

    WANG Denghong; MAO Jingwen; YAN Shenghao; YANG Jianmin; XU Jue; CHEN Yuchuan; XUE Chunji

    2005-01-01

    A lot of new gold deposits have been found on the eastern margin of the Qinghai-Tibet Plateau during the past two decades. Among them, three main types of gold deposits have been recognized, including quartz-vein-type, shearzone-type and porphyry-type. The former two types of gold deposits are mainly hosted within metamorphic rocks, while the latter is related to Cenozoic magmatism. Although all of these gold deposits are believed to have been formed during the uplift process of the Qinghai-Tibet Plateau in the Cenozoic era (Wang et al., 2002b), precise isotopic age constraints have still been lacking until quite recently. This paper presents new 40Ar/39Ar data of some gold deposits on the eastern margin of the Qinghai-Tibet Plateau, which indicate that gold mineralization in the region occurred in response to the episodic stages of the orogenies.Recently obtained 40Ar/39Ar data on quartz and feldspars from several gold deposits, such as the Sandiao deposit, the Baijintaizi deposit, the Pusagang deposits, provide new constraints on gold mineralization on the eastern margin of the Qinghai-Tibet Plateau. Geochronological studies of gold deposits along the Daduhe River indicate that there are three stages of gold mineralization. The early two stages occurred as early as 65.1 Ma in the Shuibaiyang deposit and 58.95 Ma in the Ruoji deposit, while the latter stage occurred as late as 25.35 Ma in Baijintaizi and 24.70 Ma in Sandiao. Isotopic dating of three plagioclases from the Beiya deposit, Zhifanggou deposit and Luobodi deposit and a K-feldspar from the Jinchangqing deposit in Yunnan Province indicates that these deposits were formed at two stages. The Zhifanggou and Jinchangqing deposits have early stage records as old as 58.82 Ma in Zhifanggou and 55.49 Ma in Jinchangqing, but all of the above four deposits in Yunnan have late stage records of 23.18 Ma in Jinchangqing, 24.54 Ma in Zhifanggou, 24.60 Ma in Luobodi and 24.56 Ma in Hongnitang. The above results suggest

  3. Ma Ying-jeou’s Presidential Discourse

    OpenAIRE

    2012-01-01

    "Despite the substantial advances made in cross-Strait relations during Ma Ying-jeou's (Ma Yingjiu) first term, the ROC president's rhetoric varied considerably as he grappled with the difficult reality of implementing campaign and inauguration pledges to establish better relations with China while striving to maintain national respect and sovereignty. In this article, the authors put forward a framework for measuring, analyzing and explaining this variation in President Ma's first-term disco...

  4. Potash-rich volcanic rocks and lamprophyres in western Shandong Province: 40Ar39Ar dating and source tracing

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Highly precise 40Ar39Ar dating results demonstrate that the ages of potash-rich volcanic rocks in western Shandong Province are 114.7-124.3 Ma, and that of the lamprophyres is 119.6 Ma. The potash-rich volcanic rocks have relatively high (87Sr/86Sr)i ratios ( 0.708715-0.711418)and distinctly negative εNd values ( -11.47 - -17.54), and are enriched in radiogenic lead (206Pb/204pb=17.341-17.622,207pb/204Pb=15.525-15.538, 208Pb/204pb = 37.563-37.684).Similarly, the lamprophyres also have quite low εNd values ( -11.57 - -19.64). Based on the fact that the Sr, Nd and Pb isotopic compositions of potash-rich volcanic rocks are very consistent with that of the clinopyroxene separates, and by integrating comprehensive analyses of their tectonic settings,and extensive comparisons of the Sr, Nd isotopic compositions with that of the related simultaneous rocks, it is concluded that the potash-rich volcanic rocks and lamprophyres in western Shandong Province were most possibly derived from the partial melting of enriched mantle which was caused by source contamination and metasomatism of subducted continental crustal materials.``

  5. Carbon isotope stratigraphy, magnetostratigraphy, and 40Ar/39Ar age of the Cretaceous South Atlantic coast, Namibe Basin, Angola

    Science.gov (United States)

    Strganac, Christopher; Salminen, Johanna; Jacobs, Louis L.; Polcyn, Michael J.; Ferguson, Kurt M.; Mateus, Octávio; Schulp, Anne S.; Morais, Maria Luísa; Tavares, Tatiana da Silva; Gonçalves, António Olímpio

    2014-11-01

    We present the δ13C and paleomagnetic stratigraphy for marine strata at the coast of southern Angola, anchored by an intercalated basalt with a whole rock 40Ar/39Ar radiometric age of 84.6 ± 1.5 Ma, being consistent with both invertebrate and vertebrate biostratigraphy. This is the first African stable carbon isotope record correlated to significant events in the global carbon record spanning the Late Cenomanian to Early Maastrichtian. A positive ∼3‰ excursion seen in bivalve shells below the basalt indicates the Cenomanian-Turonian Boundary Event at 93.9 Ma, during Oceanic Anoxic Event 2. Additional excursions above the basalt are correlated to patterns globally, including a negative ∼3‰ excursion near the top of the section interpreted as part of the Campanian-Maastrichtian Boundary Events. The age of the basalt ties the studied Bentiaba section to a pulse of Late Cretaceous magmatic activity around the South Atlantic and significant tectonic activity, including rotation, of the African continent.

  6. Time relationships between volcanism-plutonism-alteration-mineralization in Cu-stratabound ore deposits from the Michilla mining district, northern Chile: a 40Ar/39Ar geochronological approach

    Science.gov (United States)

    Oliveros, Verónica; Tristá-Aguilera, Dania; Féraud, Gilbert; Morata, Diego; Aguirre, Luis; Kojima, Shoji; Ferraris, Fernando

    2008-01-01

    The Michilla mining district comprises one of the most important stratabound and breccia-style copper deposits of the Coastal Cordillera of northern Chile, hosted by the Middle Jurassic volcanic rocks of the La Negra Formation. 40Ar/39Ar analyses carried out on igneous and alteration minerals from volcanic and plutonic rocks in the district allow a chronological sequence of several magmatic and alteration events of the district to be established. The first event was the extrusion of a thick lava series of the La Negra Formation, dated at 159.9 ± 1.0 Ma (2 σ) from the upper part of the series. A contemporaneous intrusion is dated at 159.6 ± 1.1 Ma, and later intrusive events are dated at 145.5 ± 2.8 and 137.4 ± 1.1 Ma, respectively. Analyzed alteration minerals such as adularia, sericite, and actinolite apparently give valid 40Ar/39Ar plateau and miniplateau ages. They indicate the occurrence of several alteration events at ca. 160-163, 154-157, 143-148, and 135-137 Ma. The first alteration event, being partly contemporaneous with volcanic and plutonic rocks, was probably produced in a high thermal gradient environment. The later events may be related either to a regional low-grade hydrothermal alteration/metamorphism process or to plutonic intrusions. The Cu mineralization of the Michilla district is robustly bracketed between 163.6 ± 1.9 and 137.4 ± 1.1 Ma, corresponding to dating of actinolite coexisting with early-stage chalcocite and a postmineralization barren dyke, respectively. More precisely, the association of small intrusives (a dated stock from the Michilla district) with Cu mineralization in the region strongly suggests that the main Michilla ore deposit is related to a magmatic/hydrothermal event that occurred between 157.4 ± 3.6 and 163.5 ± 1.9 Ma, contemporaneous or shortly after the extrusion of the volcanic sequence. This age is in agreement with the Re-Os age of 159 ± 16 Ma obtained from the mineralization itself (Tristá-Aguilera et al

  7. The U-Th-Pb systematics of zircon from the Bishop Tuff: A case study in challenges to high-precision Pb/U geochronology at the millennial scale

    Science.gov (United States)

    Ickert, Ryan B.; Mundil, Roland; Magee, Charles W.; Mulcahy, Sean R.

    2015-11-01

    Dating zircon by U-Pb in the Pleistocene Bishop Tuff is challenging because the concentration of radiogenic Pb is low and the correction required for disequilibrium in the intermediate daughter products is large. The dates can be difficult to interpret, because their absolute precision is similar in magnitude to purported timescales of crystallization. Previous estimates of the duration of zircon crystallization span two orders of magnitude and appear to depend on the analytical approach. To reconcile the differing interpretations, we present new SIMS and ID-TIMS zircon Pb/U dates, including some crystals that are dated by both techniques. Both the SIMS and ID-TIMS dates have similar distributions as previous results. Normalized to a Th/Umelt = 2.81, SIMS spot dates from interior regions of sectioned grains range from 769 ± 31 ka to 845 ± 28 ka (2σ) and ID-TIMS dates have a range from 760 ± 7 ka to 793 ± 6 ka. Individual crystals dated by both methods have an average difference of 31 ka, with the SIMS dates being consistently older than the bulk crystal dates. This level of variability precludes the assignment of a geological significance to a mean (or weighted-mean) zircon date. A previous ID-TIMS investigation of single BT zircon that showed apparent statistically significant clustering of zircon ages was compromised by an incorrect treatment of the covariance structure of 230Th-corrected Pb/U data. We show approximate and exact methods for the correct treatment and demonstrate substantially more scatter in that data than previously recognized. Close scrutiny of available partition coefficient data show that they are not adequately precise for Bishop Tuff to <775 ka, which conflicts with some estimates of the 40Ar-39Ar sanidine age of eruption.

  8. Molecular Mechanism of Isocupressic Acid Supresses MA-10 Cell Steroidogenesis

    Directory of Open Access Journals (Sweden)

    Kuan-Hao Tsui

    2012-01-01

    Full Text Available Consumption of ponderosa pine needles causes late-term abortions in cattle and is a serious poisonous plant problem in foothill and mountain rangelands. Isocupressic acid (IA is the component of pine needles responsible for the abortifacient effect, its abortifacient effect may be due to inhibition of steroidogenesis. To investigate the more detail molecular mechanism, we used MA-10 cell, which is wild used to investigate molecular mechanism of steroidogenesis, to characterize the molecular mechanisms underlying the actions of IA in more detail. In this report, we focus on the function of IA on important steroidogenic genes, including steroidogenic acute regulatory protein (StAR, cytochrome P450 cholesterol side-chain cleavage (P450scc, and 3β-hydroxysteroid dehydrogenase (3β-HSD. We found that IA does not affect enzyme activities of these genes but inhibits transcription of P450scc and translation of StAR and P450scc through attenuating cAMP-PKA signaling. Thus, steroid productions of cells were suppressed.

  9. ar

    Directory of Open Access Journals (Sweden)

    P. Fanlo

    Full Text Available A pesar de que el pulmón es el órgano diana por excelencia de la tuberculosis, cualquier otro órgano y sistema puede verse afectado. En este trabajo se revisan las formas de tuberculosis extrapulmonar a excepción de la pleural que requieren del facultativo, en ocasiones, su más valiosa pericia diagnóstica. Desde la temida meningitis tuberculosa, pasando por la afectación insidiosa de la espondilodiscitis, la llamativa afectación ganglionar, la afectación genitourinaria, la pericarditis, para terminar las formas menos frecuentes como la ocular o la cutánea. En cada apartado indicaremos lo más característico con la finalidad de que pueda servir de orientación diagnóstica y terapéutica.

  10. LA-ICPMS U-Pb Dating of Zircons from Tuffs of the Upper Permian-Middle Triassic in Youjiang Basin,Guangxi Province and Its Geological Significance%右江盆地上二叠统—中三叠统凝灰岩年龄及其地质意义

    Institute of Scientific and Technical Information of China (English)

    黄虎; 杨江海; 杜远生; 黄宏伟; 黄志强; 谢春霞; 胡丽沙

    2012-01-01

    Upper Permian-Middle Triassic sections in Youjiang basin contain many volcanic tuff horizons. Zircon LA-ICP-MS U-Pb dating of 4 volcanic tuff samples from the bottom of the Luolou and Baifeng formations in the Jiuxu and Lizhou areas, Guangxi Province, yield the depositional ages of 252. 8 + 1. 8, 253. 0 + 2. 4, 247. 2+1. 5 and 239. 3±2. 7 Ma, respectively, which, together with the inherited or xenocrystal zircon ages (with peak values of 264 and 267 Ma), indicate that episodical volcanism occurred during Middle Permian Gudalupian and Middle Triassic Bithynian in southwestern China The appearance of the inherited zircon ages (260-270 Ma) from the volcanic tuffs around the Permian-Triassic boundary (PTB) indicate the volcanic events in South China may have caused the End-Permian extinction. The depositional age of 247. 2 + 1. 5 Ma from the volcanic tuff at the bottom of the Middle Triassic Baifeng Formation indicates it is more appropriate to place the Early to Middle Trissic boundary at 247. 2 Ma. The petrographical study of the volcanic tuffs indicates the Youjiang basin expierenced the tectonic transition from extension to compression after Middle Triassic, and especially after Bithynian, which resulted in the great tectonic subsidence of the basin.%右江盆地上二叠统—中三叠统地层中常含有多层凝灰岩,对采自广西河池九圩及田林利周罗楼组和百逢组底部的4件凝灰岩样品进行锆石原位LA-ICPMS方法U-Pb同位素定年,结果显示凝灰岩的形成年龄分别为252.8±1.8Ma、253.0±2.4 Ma、247.2±1.5Ma和239.3±2.7Ma,指示晚二叠世末期到中三叠世Bithynian期华南地块西南缘存在多期火山活动,其可能与华南西南缘陆块的裂解与汇聚有关.凝灰岩中继承或捕虏锆石年龄(260~270Ma)记录了中晚二叠世峨眉山大火成岩省岩浆活动或华南西南缘岛弧火山活动事件.凝灰岩的岩相学研究表明,中三叠世特别是Bithynian期之后右江盆地由伸展

  11. 40Ar/39Ar ages of seamount trachytes from the South China Sea and implications for the evolution of the northwestern sub-basin

    Institute of Scientific and Technical Information of China (English)

    Xiaohu Li; Jiabiao Li; Xing Yu; Chunsheng Wang; Fred Jourdan

    2015-01-01

    A chronological study of seamount rocks in the South China Sea basin provides a great opportunity to understand the expansion and evolution history of the sea basin. In this paper, we analyzed the 40Ar/39Ar age of trachytic samples collected from the Shuangfeng seamounts in the northwestern sub-basin of the South China Sea. The two samples yielded plateau ages of 23.80 ? 0.18 and 23.29 ? 0.22 Ma, respectively, which indicate magmatic activity in late Oligocene which helpful constraints the expansion time of the northwest sub-basin. Previous studies suggested that the northwestern sub-basin and southwestern sub-basin have experienced a relatively consistent expansion in the NWeSE direction followed by a late expansion of the eastern sub-basin. We concluded that the expansion of the northwestern sub-basin began prior to ca. 24 Ma, which also implicated magmatic events of a late or stop expansion of the northwestern sub-basin combined with our results of 40Ar/39Ar age data and previous geophysical data.

  12. 40Ar/39Ar ages of seamount trachytes from the South China Sea and implications for the evolution of the northwestern sub-basin

    Directory of Open Access Journals (Sweden)

    Xiaohu Li

    2015-07-01

    Full Text Available A chronological study of seamount rocks in the South China Sea basin provides a great opportunity to understand the expansion and evolution history of the sea basin. In this paper, we analyzed the 40Ar/39Ar age of trachytic samples collected from the Shuangfeng seamounts in the northwestern sub-basin of the South China Sea. The two samples yielded plateau ages of 23.80 ± 0.18 and 23.29 ± 0.22 Ma, respectively, which indicate magmatic activity in late Oligocene which helpful constraints the expansion time of the northwest sub-basin. Previous studies suggested that the northwestern sub-basin and southwestern sub-basin have experienced a relatively consistent expansion in the NW–SE direction followed by a late expansion of the eastern sub-basin. We concluded that the expansion of the northwestern sub-basin began prior to ca. 24 Ma, which also implicated magmatic events of a late or stop expansion of the northwestern sub-basin combined with our results of 40Ar/39Ar age data and previous geophysical data.

  13. 40Ar-39Ar dating and tectonic implications of volcanic rocks recovered at IODP Hole U1342A and D on Bowers Ridge, Bering Sea

    Science.gov (United States)

    Sato, Keiko; Kawabata, Hiroshi; W. Scholl, David; Hyodo, Hironobu; Takahashi, Kozo; Suzuki, Katsuhiko; Kumagai, Hidenori

    2016-03-01

    During the Integrated Ocean Drilling Program (IODP), a total of 41.54 m of basement rock, consolidated volcaniclastic sediment, was recovered beneath a thin sediment cover. The drilled site is at the eastern end of the crestal area of Bowers Ridge, a north and westward sweeping offshoot of the Aleutian Arc into the Bering Sea. The volcanic sequence recovered from Holes U1342A and U1342D was divided into six major lithologic units. We used the single grain 40Ar-39Ar dating method performed by step-wise heated laser fusion technique to date andesites of Unit 1. Thereby two ages of Oligocene volcanism (34-32 Ma, 28-26 Ma) were distinguished each other according to our 40Ar-39Ar data. These ages refute a hypothesized Cretaceous origin in the North Pacific as an exotic arc massif or sector of the Hawaiian-Emperor chain and indicate that the Bowers Ridge is a Bering-Sea formed arc or remnant arc that ceased forming in the latest Oligocene to the earliest Miocene time.

  14. ARS - Helsinki - 2006 / Galina Balashova

    Index Scriptorium Estoniae

    Balashova, Galina

    2006-01-01

    Steven Holli projekteeritud Kiasma muuseumihoonest Helsingis. Kontseptuaalkunsti näitusest ARS 06 "Reaalsustunne" Kiasmas. Eestlastest esineb Mark Raidpere. Vene kunstnikegrupi AEC+F ja vene kunstnike Juri Vassiljevi ning Aleksandr Ponomarjovi töödest näitusel. Ka Gerda Steineri & Jörg Lenzlingeri (Šveits), Martin & Munoz'i (USA, Hispaania), arvutigraafik Charles Sandisoni (SB), videokunstnik Bill Viola (USA) jt. töödest

  15. ARS - Helsinki - 2006 / Galina Balashova

    Index Scriptorium Estoniae

    Balashova, Galina

    2006-01-01

    Steven Holli projekteeritud Kiasma muuseumihoonest Helsingis. Kontseptuaalkunsti näitusest ARS 06 "Reaalsustunne" Kiasmas. Eestlastest esineb Mark Raidpere. Vene kunstnikegrupi AEC+F ja vene kunstnike Juri Vassiljevi ning Aleksandr Ponomarjovi töödest näitusel. Ka Gerda Steineri & Jörg Lenzlingeri (Šveits), Martin & Munoz'i (USA, Hispaania), arvutigraafik Charles Sandisoni (SB), videokunstnik Bill Viola (USA) jt. töödest

  16. Ars Industrialis, arsindustrialis.org

    Directory of Open Access Journals (Sweden)

    Frédérique Mingant

    2012-03-01

    Full Text Available The arsindustrialis.org website was created in 2005, when the association Ars Industrialis came into being. The association was founded by a group of philosophers and jurists, on the initiative of philosopher Bernard Stiegler, the former director of the IRCAM (Institut de Recherche et Coordination Acoustique/Musique–Institute of Research and Coordination on Acoustic/Music and the current director of the Department of cultural development at the Centre Georges Pompidou (French National Arts C...

  17. Ars Industrialis, arsindustrialis.org

    OpenAIRE

    Frédérique Mingant

    2012-01-01

    The arsindustrialis.org website was created in 2005, when the association Ars Industrialis came into being. The association was founded by a group of philosophers and jurists, on the initiative of philosopher Bernard Stiegler, the former director of the IRCAM (Institut de Recherche et Coordination Acoustique/Musique–Institute of Research and Coordination on Acoustic/Music) and the current director of the Department of cultural development at the Centre Georges Pompidou (French National Arts C...

  18. Hormonal activation of a kinase cascade localized at the mitochondria is required for StAR protein activity.

    Science.gov (United States)

    Poderoso, Cecilia; Maloberti, Paula; Duarte, Alejandra; Neuman, Isabel; Paz, Cristina; Cornejo Maciel, Fabiana; Podesta, Ernesto J

    2009-03-01

    It is known that ERK1/2 and MEK1/2 participate in the regulation of Star gene transcription. However, their role in StAR protein post-transcriptional regulation is not described yet. In this study we analyzed the relationship between the MAPK cascade and StAR protein phosphorylation and function. We have demonstrated that (a) steroidogenesis in MA-10 Leydig cells depends on the specific of ERK1/2 activation at the mitochondria; (b) ERK1/2 phosphorylation is driven by mitochondrial PKA and constitutive MEK1/2 in this organelle; (c) active ERK1/2 interacts with StAR protein, leads to StAR protein phosphorylation at Ser(232) only in the presence of cholesterol; (d) directed mutagenesis of Ser(232) (S232A) inhibited in vitro StAR protein phosphorylation by ERK1; (e) transient transfection of MA-10 cells with StAR S232A cDNA markedly reduced the yield of progesterone production. We show that StAR protein is a substrate of ERK1/2, and that mitochondrial ERK1/2 is part of a multimeric complex that regulates cholesterol transport.

  19. Constraints on the thermal history of the Blue Ridge in northernmost Virginia: [sup 40]Ar/[sup 39]Ar age dating results

    Energy Technology Data Exchange (ETDEWEB)

    Kunk, M.J.; Lyttle, P.T.; Schindler, S.J.; Burton, W.C. (Geological Survey, Reston, VA (United States))

    1993-03-01

    [sup 40]Ar/[sup 39]Ar age dating techniques have been used to analyze hornblende, phlogopite, white mica, biotite, and K-feldspar mineral separates from Middle and Late Proterozoic crystalline basement and from Late Proterozoic-Early Cambrian cover rocks in the Blue Ridge anticlinorium. Regionally, both cover and basement rocks contain a variably developed overprint fabric, the Blue Ridge-South Mountain cleavage, commonly defined by white mica. Petrographic analysis indicates a maximum metamorphic overprint of lower greenschist facies that locally produces biotite. [sup 40]Ar/[sup 39]Ar age spectra of hornblende from crystalline basement units suggest ages ranging from about 1 Ga to about 920 Ma. [sup 40]Ar/[sup 39]Ar age spectra of most cleavage-defining white mica are sigmoidal in shape suggesting the presence of multiple generations of white mica, the last of which probably grew below the blocking temperature for retention of argon in muscovite ([approximately]350 C). Interpretation of these complex spectra suggest that most of the cleavage-defining white mica may have formed below [approximately]350 C during the Late Paleozoic Alleghanian orogeny. However, these complex age spectra, together with age spectra from cleavage-defining phlogopite from a marble in the Fauquier Formation and biotite in the Late Proterozoic Robertson River Igneous Suite suggest the existence of an earlier episode of white mica growth of Middle Paleozoic age that has not been thermally reset or totally recrystallized. High temperature release steps can be interpreted to represent times of cooling through closure during the Middle Paleozoic. Low-temperature steps of these same age spectra suggest final closure or partial resetting of the samples at about 200 Ma or less and are interpreted to represent the effects of Mesozoic rifting.

  20. Messinian events: new constraints from sedimentological investigations and new 40Ar/ 39Ar ages in the Melilla-Nador Basin (Morocco)

    Science.gov (United States)

    Cornée, J. J.; Roger, S.; Münch, P.; Saint Martin, J. P.; Féraud, G.; Conesa, G.; Pestrea-Saint Martin, S.

    2002-07-01

    New 40Ar/ 39Ar ages obtained both from within a platform and from the adjacent basin allow, through the extension of a previous argon dataset, the establishment of a chronological framework for the Messinian carbonate complex of Melilla (Morocco). In the platform, prograding bioclastic deposits began around 6.87±0.02 Ma, whereas the youngest preserved deposits are 5.77±0.04 Ma old. The southern part of the basin was uplifted and emergent prior to 6.23±0.03 Ma. The Tortonian/Messinian and the Messinian/Pliocene boundaries have not yet been identified in the Melilla region. Durations of the prograding bioclastic deposits (ca. 410 ka), the prograding Porites reefs (ca. 360 ka) and the preserved part of the terminal carbonate complex (TCC) (ca. 330 ka) can be estimated. Sedimentological and geochronological investigations do not indicate any major subaerial unconformity nor any major time gap. If a major sea level fall did exist during Messinian times, it developed after 5.77±0.04 Ma. Chronological correlations show that the onset of the Sorbas gypsum deposition (Southern Spain), considered as the marker of the Messinian Salinity Crisis onset, is contemporaneous with aggrading Porites reef building of the terminal carbonate complex of Melilla. A major paleoceanographic change in the marginal areas of the Mediterranean, with the cessation of upwelling systems, could be partly coeval with the onset of the Messinian Salinity Crisis.

  1. {sup 40}Ar/{sup 39}Ar thermo-chronology and lithospheric mechanisms. Methodological and applied approach: the Kunlun range (Asia) and the Afar triple junction area (East Africa); Thermochronologie {sup 40}Ar/{sup 39}Ar et mecanismes lithospheriques. Approche methodologique et appliquee: exemples de la chaine du Kunlun (Asie) et de la jonction triple de l'Afar (Afrique de l'Est)

    Energy Technology Data Exchange (ETDEWEB)

    Mock, C

    1998-12-04

    A {sup 40}Ar/{sup 39}Ar thermo-chronological study has been carried out for two contrasted geodynamic settings: - the Eastern Kunlun range (Northern Tibet), in order to characterize the lithospheric deformation mechanisms related to the India-Asia collision; - the Afar triple junction area (East Africa), in order to constrain the timing of mantle plume-related basement uplift in Ethiopia and Yemen, which will indicate whether rifting was active or passive. In the Kunlun, the cooling event (9-15 deg.C/Ma) outlined at 30 Ma for the granitoids (Bt = 128-138 Ma; Kf = 102-147 Ma) reflects a denudation event (0.2-0.3 km/Ma), related to ramp stacking and normal faulting with associated uplift. This unroofing period is coeval with the great Asian strike-slip faults. This suggests that 30 Ma ago, the India-Asia collision was accommodated by lateral extrusion along great strike-slip faults, which might have led to local crustal thickening because of the formation of anticlines from major thrusts 'branching' from the Kunlun fault. In the Afar area the Panafrican basement (granitoids = 462-678 Ma;metamorphic rocks 505-750 Ma) has undergone a reheating event during the Cenozoic; its temperature is estimated around 138-177 deg.C over the last 50 Ma for a depth of 2 km, implying a thermal gradient of 69-88 deg./km. This reheating event results from both heat conduction, related to the mantle plume. and heat advection. because of magma transfer. However, it was not possible to define the timing of the mantle plume-related basement uplift. This study outlines the important thermal effect of continental flood basalts on the crust and suggests that the {sup 40}Ar/{sup 39}Ar thermo-chronology does not allow to characterize the denudation of the lithosphere for an extension-type geodynamic setting. Finally, some of the results suggest that diffusion in the laboratory and in nature may be different. {sup 40}Ar/{sup 39}Ar thermo-chronological analysis thus might be tricky

  2. U-Pb SHRIMP and {sup 40}Ar/{sup 39}Ar constraints on the timing of mineralization in the Paleoproterozoic Caxias orogenic gold deposit, Sao Luis cratonic fragment, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Evandro Luiz, E-mail: evandro.klein@cprm.gov.br [Servico Geologico do Brasil (CPRM), Belem, PA (Brazil); Tassinari, Colombo Celso Gaeta, E-mail: ccgtassi@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Geociencias. Centro de Pesquisas Geocronologicas; Vasconcelos, Paulo Marcos, E-mail: paulo@earth.uq.edu.au [University of Queensland, School of Earth Sciences, Brisbane (Australia)

    2014-07-01

    Caxias is an orogenic gold deposit in the Sao Luis cratonic fragment, which is correlated with the Rhyacian terranes of the West-African Craton. The deposit postdates peak metamorphism (estimated at 2100 ± 15 Ma) and is hosted in a shear zone that cuts across schists of the Aurizona Group (2240 ± 5 Ma) and the Caxias Microtonalite. The emplacement age of the microtonalite, as determined in this work by SHRIMP U-Pb zircon dating, is 2009 ± 11 Ma and represents a latest age magmatic event in the Sao Luis cratonic fragment. Older zircon age of 2139 ± 10 Ma is interpreted as due to inheritance from the older granitoid or volcanic suites (magmatic sources?) or to contamination during emplacement. Lead isotope compositions indicate that the Pb incorporated in ore-related pyrite was probably sourced from regional, orogenic calc-alkaline granitoids of ca. 2160 Ma. Hydrothermal sericite from Caxias yielded a {sup 40}Ar/{sup 39}Ar plateau age of 1990 ± 30 Ma, which combined with the emplacement age of the Caxias Microtonalite brackets the age of gold mineralization between 2009 ± 11 and 1990 ± 30 Ma. (author)

  3. M&A Negotiations and Lawyer Expertise

    NARCIS (Netherlands)

    Karsten, C.; Malmendier, U.; Sautner, Z.

    2013-01-01

    We use proprietary data to look into the "black box" of M&A negotiations and to shed light on the effects of lawyer expertise on M&A contract design, the bargaining process, and acquisition pricing. Measuring the effects of buyer relative to seller lawyer expertise, we document that more expertise i

  4. Magnesium oxide-impregnated tuff soil-derived ceramic: a novel cadmium(II) adsorbing media

    Science.gov (United States)

    Salim, Md; Bhakta, Jatindra N.; Maneesh, Namburath; Munekage, Yukihiro; Motomura, Kevin

    2017-07-01

    The contamination of cadmium (Cd) in the aquatic environment is one of the serious environmental and human health's risks. The present study attempted to develop the potential magnesium oxide (MgO)-impregnated tuff soil-derived ceramic (MITDC)-based novel adsorbent media for adsorbing higher rate of cadmium [Cd(II)] from water phase. A potential MITDC adsorbent media was developed using volcanic raw tuff soil and its Cd(II) adsorption capacity from water phase was evaluated comparing with the raw tuff soil. A series of studies were carried out in an agitated batch method at 20 ± 2 °C to characterize the adsorption capacity of MITDC under different conditions of factors, such as contact time (0-360 min), initial pH (3-11) of solution, dose of MITDC (2, 5, 7.5 and 10 g/L), and initial concentration of Cd(II) (5, 10, 20, 30, and 40 mg/L), influencing the adsorption mechanism. MITDC exhibited the equilibrium state of maximum Cd(II) adsorption at the contact time 120 min and pH 4.7 (removed 98.2 % Cd) when initial Cd(II) concentration was 10 mg/L in the present study. The dose of 7.5 g MITDC/L showed maximum removal of Cd(II) from water. Experimental data were described by the Freundlich and the Langmuir isotherms and equilibrium data fitted well with the Langmuir model ( R 2 = 0.996). The Cd(II) adsorption capacity of MITDC was 31.25 mg/g. The high Cd(II) adsorption capacity indicated that novel MITDC could be used as a potential ceramic adsorbent media to remove high rate of Cd(II) from aqueous phase.

  5. Estimation of possibilities of making euro pallets from reclaimed polyolefin’s with tuff

    Directory of Open Access Journals (Sweden)

    S. Kuciel

    2010-07-01

    Full Text Available Possibilities of reusing and developing of waste plastics are one of the main problems of waste management for municipal governmentespecially in the context of adapting Polish law to standards of EC [1]. During the last 10 years total amount of plastics waste increasedtwice, especially in communal agglomerations. Among communal waste plastics make up 7 to 14% of whole their mass and 30% of theirvolume [1,2]. Plastic products have been recycled to be used in a number of different products often different from their original use.Reclaimed plastics can’t be used as products which have contact with food or as high demands esthetic and hygienic products, they alsoshouldn’t be applied as short-time used products because they quickly come back to plastics store-place. Reclaimed plastics have lowerproperties than virgin plastics – mainly the strength falls with the simultaneous fall of modules and increase fragile especially for PP, PE,PS and PET [1]. One of the possibilities of reinforcement of polyolefines is adding diverse fillers like glass or carbon fibers (but they arerather expensive and natural fillers like mineral, wood and others [3]. It’s especially important for wasted of low density polyethylenewhich has low modulus. For the tests it was used waste polyethylene (LDPE and HDPE from industrial with 15% mineral fillers – tuff.For the tests it was prepared two kinds of composites materials with 15% of tuff powder. Besides for comparison it was tested recycledpolyethylene (HDPE and LDPE and next was tested specimens cut out from produced europallets (with 15% of tuff. It was testedmechanical properties all prepared composite materials like tensile strength, stress and bending e-modulus and processing properties likemelt flow, Vicat point and photos on SEM microscope.

  6. Magnesium oxide-impregnated tuff soil-derived ceramic: a novel cadmium(II) adsorbing media

    Science.gov (United States)

    Salim, Md; Bhakta, Jatindra N.; Maneesh, Namburath; Munekage, Yukihiro; Motomura, Kevin

    2015-07-01

    The contamination of cadmium (Cd) in the aquatic environment is one of the serious environmental and human health's risks. The present study attempted to develop the potential magnesium oxide (MgO)-impregnated tuff soil-derived ceramic (MITDC)-based novel adsorbent media for adsorbing higher rate of cadmium [Cd(II)] from water phase. A potential MITDC adsorbent media was developed using volcanic raw tuff soil and its Cd(II) adsorption capacity from water phase was evaluated comparing with the raw tuff soil. A series of studies were carried out in an agitated batch method at 20 ± 2 °C to characterize the adsorption capacity of MITDC under different conditions of factors, such as contact time (0-360 min), initial pH (3-11) of solution, dose of MITDC (2, 5, 7.5 and 10 g/L), and initial concentration of Cd(II) (5, 10, 20, 30, and 40 mg/L), influencing the adsorption mechanism. MITDC exhibited the equilibrium state of maximum Cd(II) adsorption at the contact time 120 min and pH 4.7 (removed 98.2 % Cd) when initial Cd(II) concentration was 10 mg/L in the present study. The dose of 7.5 g MITDC/L showed maximum removal of Cd(II) from water. Experimental data were described by the Freundlich and the Langmuir isotherms and equilibrium data fitted well with the Langmuir model (R 2 = 0.996). The Cd(II) adsorption capacity of MITDC was 31.25 mg/g. The high Cd(II) adsorption capacity indicated that novel MITDC could be used as a potential ceramic adsorbent media to remove high rate of Cd(II) from aqueous phase.

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

    Science.gov (United States)

    Fu, Roger R.; Weiss, Benjamin P.; 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.

    2017-01-01

    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 history of the earliest geodynamo, which would hold broad implications for the early Earth's interior and atmosphere. However, the ability of zircons to record accurately the geomagnetic field has not been demonstrated. Here we conduct thermal and 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 eleven zircons measured using a superconducting quantum interference device (SQUID) microscope yield a mean paleointensity of 54.1 ± 6.8μT (1σ; 42.6 ± 5.3μT after excluding possible maghemite-bearing zircons), which is consistent with high-precision results from Bishop Tuff whole rock (43.0 ± 3.2μT). High-resolution quantum diamond magnetic (QDM) mapping, electron microscopy, and X-ray tomography indicate that the bulk of the remanent magnetization in Bishop Tuff zircons is carried by Fe oxides associated with apatite inclusions, which may be susceptible to destruction via metamorphism and aqueous alteration in older zircons. As such, while zircons can reliably record the geomagnetic field, robust zircon-derived paleomagnetic results require careful characterization of the ferromagnetic carrier and demonstration of their occurrence in primary inclusions. We further conclude that a combination of quantum diamond magnetometry and high-resolution imaging can provide detailed, direct characterization of the ferromagnetic mineralogy of geological samples.

  8. Radionuclide Transport in Tuff and Carbonate Fractures from Yucca Flat, Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    Zavarin, M; Johnson, M R; Roberts, S K; Pletcher, R; Rose, T P; Kersting, A B; Eaton, G; Hu, Q; Ramon, E; Walensky, J; Zhao, P

    2006-02-01

    In the Yucca Flat basin of the Nevada Test Site (NTS), 747 shaft and tunnel nuclear detonations were conducted primarily within the tuff confining unit (TCU) or the overlying alluvium. The TCU in the Yucca Flat basin is hypothesized to reduce radionuclide migration to the regional carbonate aquifer (lower carbonate aquifer) due to its wide-spread aerial extent and chemical reactivity. However, shortcuts through the TCU by way of fractures may provide a migration path for radionuclides to the lower carbonate aquifer (LCA). It is, therefore, imperative to understand how radionuclides migrate or are retarded in TCU fractures. Furthermore, understanding the migration behavior of radionuclides once they reach the fractured LCA is important for predicting contaminant transport within the regional aquifer. The work presented in this report includes: (1) information on the radionuclide reactive transport through Yucca Flat TCU fractures (likely to be the primary conduit to the LCA), (2) information on the reactive transport of radionuclides through LCA fractures and (3) data needed to calibrate the fracture flow conceptualization of predictive models. The predictive models are used to define the extent of contamination for the Underground Test Area (UGTA) project. Because of the complex nature of reactive transport in fractures, a stepwise approach to identifying mechanisms controlling radionuclide transport was used. In the first set of TCU experiments, radionuclide transport through simple synthetic parallel-plate fractured tuff cores was examined. In the second, naturally fractured TCU cores were used. For the fractured LCA experiments, both parallel-plate and rough-walled fracture transport experiments were conducted to evaluate how fracture topography affects radionuclide transport. Tuff cores were prepared from archived UE-7az and UE-7ba core obtained from the USGS core library, Mercury, Nevada. Carbonate cores were prepared from archived ER-6-1 core, also obtained

  9. Occurrences of Excess 40Ar in Hydrothermal Tourmaline:Interpretations from 40Ar-39Ar Dating Results by Stepwise Heating

    Institute of Scientific and Technical Information of China (English)

    QIU Huaning; PU Zhiping; DAI Tongmo

    2007-01-01

    The occurrences of excess 40Ar within a hydrothermal tourmaline is discussed in term of the analysis data of syngenetic muscovite and tourmaline from the Lushui hydrothermal tin-tungsten deposit in western Yunnan, China, using the 40Ar-39Ar stepwise heating technique. About 80% excess 40Ar was released in the last step when the tourmaline was fused, corresponding to a release of only ~3% 39Ar (K), which indicates that most excess 40Ar was held in the mineral lattice rather than in the channels parallel to the Z-axis. This suggests that the excess 40Ar was incorporated during crystallization and not diffused into the tourmaline during the post-crystallization history.

  10. 33 CFR 80.120 - Cape Ann, MA to Marblehead Neck, MA.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Cape Ann, MA to Marblehead Neck, MA. 80.120 Section 80.120 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Atlantic Coast § 80.120 Cape Ann, MA...

  11. Experimental research on sealing of boreholes, shafts and ramps in welded tuff

    Energy Technology Data Exchange (ETDEWEB)

    Fuenkajorn, K. [Rock Engineering International, Tucson, AZ (United States)

    1996-04-01

    Laboratory and in-situ experiments have been conducted to determine the mechanical and hydraulic performance of cement borehole seals in densely welded Apache Leap tuff. Test results indicate that under saturated conditions, commercial expansive cement can provide good bond strength and adequate hydraulic performance for borehole seal under changing stress conditions. The cement seal should be installed at the intact portion of the opening, and should have a length-to-diameter ratio greater than four. Drying increases borehole plug permeability and decreases mechanical and hydraulic bonds at the plug-rock interface. In-situ testing indicates that installation procedure may significantly affect the cement plug performance.

  12. 40Ar-39Ar and U-Pb ages of metadiorite from the East Kunlun Orogenic Belt: Evidence for Early-Paleozoic magmatic zone and excess argon in amphibole minerals

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Single-grain zircon U-Pb and amphibole 40Ar-39Ar dating have beenconducted on a deformed and metamorphosed diorite in the East Kunlun Orogenic Belt, which intruded into the middle Proterozoic Kuhai Group exposed in the south of Xiangride region, Dulan County, NW Qinghai Province. The zircon gives a concordant U-Pb age of (446.5±9.1) Ma. The amphibole yields Ar plateau age of (488.0±1.2) Ma and an isochronal age of (488.9±5.6) Ma. Age results of both stepwise released Ar and conventional K-Ar analysis are remarkably higher than that of zircon U-Pb, suggesting that the amphibole contains excess argon and the amphibole plateau age cannot be taken as the timing of metamorphism or deformation. The zircon age is interpreted to be crystallization age of the diorite pluton, which suggests that an Early-Paleozoic magmatic zone indeed existed in the East Kunlun Orogenic Belt stretching along the region south to the Golmud, Normuhong and Xiangride.

  13. Tephrochronology of the Mont-Dore volcanic Massif (Massif Central, France): new 40Ar/39Ar constraints on the Late Pliocene and Early Pleistocene activity

    Science.gov (United States)

    Nomade, Sébastien; Pastre, Jean-François; Nehlig, Pierre; Guillou, Hervé; Scao, Vincent; Scaillet, Stéphane

    2014-03-01

    The Mont-Dore Massif (500 km2), the youngest stratovolcano of the French Massif Central, consists of two volcanic edifices: the Guéry and the Sancy. To improve our knowledge of the oldest explosive stages of the Mont-Dore Massif, we studied 40Ar/39Ar-dated (through single-grain laser and step-heating experiments) 11 pyroclastic units from the Guéry stratovolcano. We demonstrate that the explosive history of the Guéry can be divided into four cycles of explosive eruption activity between 3.09 and 1.46 Ma (G.I to G.IV). We have also ascertained that deposits associated with the 3.1-3.0-Ma rhyolitic activity, which includes the 5-km3 "Grande Nappe" ignimbrite, are not recorded in the central part of the Mont-Dore Massif. All the pyroclastites found in the left bank of the Dordogne River belong to a later explosive phase (2.86-2.58 Ma, G.II) and were channelled down into valleys or topographic lows where they are currently nested. This later activity also gave rise to most of the volcanic products in the Perrier Plateau (30 km east of the Mont-Dore Massif); three quarters of the volcano-sedimentary sequence (up to 100 m thick) was emplaced within less than 20 ky, associated with several flank collapses in the northeastern part of the Guéry. The age of the "Fournet flora" (2.69 ± 0.01 Ma) found within an ash bed belonging to G.II suggests that temperate forests already existed in the French Massif Central before the Pliocene/Pleistocene boundary. The Guéry's third explosive eruption activity cycle (G.III) lasted between 2.36 and 1.91 Ma. It encompassed the Guéry Lake and Morangie pumice and ash deposits, as well as seven other important events recorded as centimetric ash beds some 60 to 100 km southeast of the Massif in the Velay region. We propose a general tephrochronology for the Mont-Dore stratovolcano covering the last 3.1 My. This chronology is based on 44 40Ar/39Ar-dated events belonging to eight explosive eruption cycles each lasting between 100 and 200

  14. Excess Ar in biotites from the Broderick Falls (Webuye) area, western Kenya: implications for the tectonothermal history of the Mozambique Belt and its Archaean foreland

    Science.gov (United States)

    Shibata, K.; Suwa, K.; Uchiumi, S.; Agata, T.

    1996-10-01

    RbSr whole rock and KAr mineral age determinations were made on rocks from the Broderick Falls (Webuye) area, western Kenya. Granitic rocks yielded a RbSr whole rock isochron age of 2555 ± 101 Ma with an initial {87Sr}/{86Sr} ratio of 0.70121 ± 0.00038. This age represents the time of granitoid emplacement. KAr mineral ages range from 574 to 3420 Ma, which is very variable with respect to mineral type and locality. Mylonitic granodiorite very close to the Nandi Escarpment gave a KAr age of 916 Ma from biotite, suggesting the time of the activity of the Nandi Fault, which may be an earlier phase of the Pan-African Orogeny. Ages of biotites in a zone between 4 and 6 km northeast of the Nandi Fault are anomalously high compared to those of coexisting hornblende and the RbSr isochron age, confirming the existence of excess 40Ar in biotite. Excess 40Ar was probably introduced into biotite under the appropriate temperature conditions prevailing near the Nandi Fault. Taramite, a rare sodic-calcic amphibole, was found in a cordierite-biotite gneiss of the Kavirondian Supergroup and gave a typical Pan-African KAr age of 574 Ma. The last Pan-African metamorphism occurred in the terrane east of the Surongai Thrust.

  15. 40Ar/39Ar Dating of Zn-Pb-Ag Mineralization in the Northern Brooks Range, Alaska

    Science.gov (United States)

    Werdon, Melanie B.; Layer, Paul W.; Newberry, Rainer J.

    2004-01-01

    The 40Ar/39Ar laser step-heating method potentially can be used to provide absolute ages for a number of formerly undatable, low-temperature ore deposits. This study demonstrates the use of this method by determining absolute ages for Zn-Pb-Ag sediment-hosted massive sulfide deposits and vein-breccia occurrences found throughout a 300-km-long, east-west-trending belt in the northern Brooks Range, Alaska. Massive sulfide deposits are hosted by Mississippian to Pennsylvanian(?) black carbonaceous shale, siliceous mudstone, and lesser chert and carbonate turbidites of the Kuna Formation (e.g., Red Dog, Anarraaq, Lik (Su), and Drenchwater). The vein-breccia occurrences (e.g., Husky, Story Creek, West Kivliktort Mountain, Vidlee, and Kady) are hosted by a deformed but only weakly metamorphosed package of Upper Devonian to Lower Mississippian mixed continental and marine clastic rocks (the Endicott Group) that stratigraphically underlie the Kuna Formation. The vein-breccias are mineralogically similar to, but not spatially associated with, known massive sulfide deposits. The region's largest shale-hosted massive sulfide deposit is Red Dog; it has reserves of 148 Mt grading 16.6 percent zinc, 4.5 percent lead, and 77 g of silver per tonne. Hydrothermally produced white mica in a whole-rock sample from a sulfide-bearing igneous sill within the Red Dog deposit yielded a plateau age of 314.5 Ma. The plateau age of this whole-rock sample records the time at which temperatures cooled below the argon closure temperature of the white mica and is interpreted to represent the minimum age limit for massive sulfide-related hydrothermal activity in the Red Dog deposit. Sulfide-bearing quartz veins at Drenchwater crosscut a hypabyssal intrusion with a maximum biotite age of 337.0 Ma. Despite relatively low sulfide deposition temperatures in the vein-breccia occurrences (162°-251°C), detrital white mica in sandstone immediately adjacent to large vein-breccia zones was partially to

  16. Pore-water extraction from unsaturated tuff by triaxial and one-dimensional compression methods, Nevada Test Site, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Mower, T.E. [PRC Environmental Management, Inc., Denver, CO (United States); Higgins, J.D. [Colorado School of Mines, Golden, CO (United States); Yang, In C.; Peters, C.A. [Geological Survey, Denver, CO (United States)

    1994-07-01

    The hydrologic system in the unsaturated tuff at Yucca Mountain, Nevada, is being evaluated for the US Department of Energy by the Yucca Mountain Project Branch of the US Geological Survey as a potential site for a high-level radioactive-waste repository. Part of this investigation includes a hydrochemical study that is being made to assess characteristics of the hydrologic system such as: traveltime, direction of flow, recharge and source relations, and types and magnitudes of chemical reactions in the unsaturated tuff. In addition, this hydrochemical information will be used in the study of the dispersive and corrosive effects of unsaturated-zone water on the radioactive-waste storage canisters. This report describes the design and validation of laboratory experimental procedures for extracting representative samples of uncontaminated pore water from welded and nonwelded, unsaturated tuffs from the Nevada Test Site.

  17. Petrographic and geochemical characteristics of a section through the Tiva Canyon Tuff at Antler Ridge, Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Singer, F.R.; Widmann, B.L.; Dickerson, R.P. [Science Applications International Corp., Golden, CO (United States); Byers, F.M. Jr. [Geological Survey, Denver, CO (United States)

    1994-12-31

    The Tiva Canyon Tuff of the Paintbrush Group of Miocene age caps much of Yucca Mountain, Nevada and is a compositionally zoned, compound cooling, pyroclastic flow that ranges from a dominantly high-silica rhyolitic base to a quartz-latitic caprock. Petrographic and geochemical studies have focused on rigorously defining the internal stratigraphy of this unit to support the detailed mapping of the Ghost Dance fault and other structures in the central fault block of Yucca Mountain. This study shows that devitrification textures and vapor phase mineralogy, in addition to other physical attributes such as pumice variability (flattening) and crystal content, can be used as distinguishing criteria to better define lithologic zones within the Tiva Canyon Tuff. In addition, the study also shows that the petrographic textures and chemistry of the groundmass vary systematically within recognizable lithologic zones and may be used to characterize and vertically divide litho-stratigraphic zones within the Tiva Canyon Tuff.

  18. Ars Memorativa, Ars Oblivionis in Middle English Religious Plays

    Directory of Open Access Journals (Sweden)

    Ciobanu Estella Antoaneta

    2015-12-01

    Full Text Available This paper investigates the multi-layered violence of religious representation in the late medieval York biblical plays, with a focus on the Supper at Emmaus. I read Emmaus (Y40, a play which commemorates the Crucifixion and openly encourages strong anti-Judaism, alongside scenes in an early predecessor pageant, The Crucifixion (Y35, within their contemporary devotional and mnemonic practices, i.e. the confessional Book of Margery Kempe and Thomas Bradwardine’s tract on ars memorativa. Emmaus in particular demonstrates how a fundamentally violent ars memorativa, the legacy of ancient rhetoric to the Middle Ages, also underpins the instruction of the laity in the basics of Christian faith, here with the aid of highly musical prosody and repetition, and thereby hones a biased, intolerant and violence-inured Christian collective memory. To study the York play’s position relative to late medieval mnemonic practices, I frame my analysis within memory studies, enriched with the more specific insights offered by social-psychological, neurobiological and cognitivist studies of memory.

  19. Distinct brief major events in the Karoo large igneous province clarified by new 40Ar/ 39Ar ages on the Lesotho basalts

    Science.gov (United States)

    Jourdan, F.; Féraud, G.; Bertrand, H.; Watkeys, M. K.; Renne, P. R.

    2007-10-01

    Recent mineral separate ages obtained on the Karoo large igneous province (southern Africa) suggest that the province was built by several distinct magmatic pulses over a rather long period on the order of 5-6 Ma concerning the main erupted volume [Jourdan, F., Féraud, G., Bertrand, H., Kampunzu, A.B., Tshoso, G., Watkeys, M.K., Le Gall., B., 2005. The Karoo large igneous province: Brevity, origin, and relation with mass extinction questioned by new 40Ar/ 39Ar age data, Geology 33, 745-748]. Although this apparently atypical province is dated in more detail compared to many other large igneous provinces, volumetrically important areas still lack sufficient high-quality data. The timing of the Karoo province is crucial as this event is correlated with the breakup activity of the Gondwana supercontinent. The Lesotho basalts represent a major lava sequence of the province, but have not yet been precisely dated by systematic analysis of mineral separates. We analyzed plagioclase separates from five lava flows encompassing the complete 1.4-km-thick Lesotho sequence from top to bottom using the 40Ar/ 39Ar method. We obtained five plateau and mini-plateau ages statistically indistinguishable and ranging from 182.3 ± 1.6 to 181.0 ± 2.0 Ma (2 σ). We derived an apparent maximum duration for this event of ˜ 0.8 Ma by neglecting correlated errors embedded in the age uncertainties. A critical review of previous ages obtained on the Lesotho sequence [Duncan R.A., Hooper, P.R., Rehacek, J., Marsh, J.S., Duncan, A.R., 1997. The timing and duration of the Karoo igneous event, southern Gondwana. Journal of Geophysical Research 102, 18127-18138] shows that groundmass analyses are unreliable for high-resolution geochronology, due to alteration and 39Ar recoil effects. Discrepancy between our ages and a previous plagioclase age at ˜ 184 Ma obtained by the later workers is tentatively attributed to the heterogeneity of the monitor used and/or cryptic excess 40Ar *. The current age

  20. Weathering and denudation history of the western continental margin of India constrained by combined Ar-Ar dating and paleomagnetism

    Science.gov (United States)

    Jean, Amandine; Mathé, Pierre-Etienne; Beauvais, Anicet; Chardon, Dominique; Demory, François; Janwari, Shazia

    2017-04-01

    The western continental passive margin of Peninsular India is fringed by an escarpment, the Western Ghats escarpment (WGE), which separates a narrow coastal lowland plain drained to the west from a highland plateau drained to the east. Since Deccan Traps emplacement, the combined effects of chemical alteration and mechanical erosion led to the formation and dissection of lateritic landscapes whose relicts are preserved both sides of the WGE. Ar-Ar ages of K-rich manganese oxides (cryptomelane) sampled in the lateritic profile of each paleolandscape element have documented the weathering history and put constraints on the paleoclimatic and denudation history of Peninsular India [1,2]. The results have documented intense lateritic weathering during the Eocene (ca. 53-45 Ma) on either sides of the escarpment. Here, we present new independent constraints on the age of that weathering based on paleomagnetism of ferricretes included in thick lateritic weathering mantles of the coastal lowland plain. Our method is based on the paleomagnetic properties of Fe-oxy-hydroxides crystallized in situ in the lateritic weathering profile. The major magnetic minerals, hematite and goethite, have been analyzed by combining hysteresis and remanent magnetizations together with magnetic susceptibility measurements including thermomagnetic curves (KT curves). The main carrier of Natural Remanent Magnetization (NRM) at low temperature is a well-crystallized goethite of first generation characterized by sharp Neel temperature, Tn, at 85°C on KT curves; late goethite generations with distributed Tn below diurnal temperatures (primary and neoformed hematite mimics the primary goethite component. The derived paleopole fits the APWP of India at paleolatitude of 62.3° (with alpha95=5.2°) suggesting an age of ca. 52 Ma [3]. The reverse polarity systematically observed may be ascribed to Chron 23 [4] that refines the paleomagnetic age of the primary goethite to 51.9 - 52.2 Ma. This new age is

  1. PF-AR upgrading project

    CERN Document Server

    Kasuga, T

    2002-01-01

    The upgrading project of the dedicated pulse X-ray source PF-AR has been completed by the end of the 2001 fiscal year. Machine commissioning exclusively using the injector linac was successfully accomplished in the beginning of January 2002. After fine tuning of the machine and cleaning of the vacuum system with the beams from the middle of January to the middle of March, routine operation for users has begun in April. The historical details, commissioning and results of the project are reported. (author)

  2. Yolcu Gemisi Pis Su Arıtım Standartları ve Arıtma Sistemleri

    Directory of Open Access Journals (Sweden)

    Volkan Şahin

    2015-06-01

    Full Text Available Yolcu gemisi sektörü, dünya turizminde payı en yüksek olan sektörlerden bir tanesidir. Hızla büyüyen bu sektör, yolcu gemilerini yüzer şehirler haline dönüştürmüştür. Dev yolcu gemileri gerek binlerce yolcusunun ürettiği gerekse de operasyonu sırasında oluşturduğu atıklar bakımından denizlerimiz için ciddi bir tehdit haline gelmiştir. 3000 – 4000 yolcu kapasiteli bu yüzer şehirlerin diğer yük gemileriyle karşılaştırıldıklarında önemli miktarda pis su boşaltımı yaptıkları görülmektedir. Oluşan pis suyun arıtım ve boşaltım prosedürleri MARPOL ve EPA gibi önemli kuruluşlar tarafından düzenlenmekte ve denetlenmektedir. Bu çalışmada pis su arıtım sistemlerinin tipleri, çalışma prensipleri, arıtılmış atığın ulusal ve uluslararası kuruluşlar tarafından belirlenen standartlara uygunluğu ve denetim kuruluşlarının boşaltım standartları incelenerek karşılaştırılmıştır. Pis su arıtımında özellikle yolcu gemilerinde kullanılan MSDs (Klasik Arıtma Sistemleri ve AWTs (Gelişmiş Atık Su Arıtma Sistemleri sistemlerinin pis su içeriğinde bulunan patojen, nütrient, kimyasal bileşenler ve ağır metal gibi zararlı bileşenleri arıtma yöntemleri hakkında bilgiler verilmiştir. Bu sistemlerin verimleri birbirleriyle karşılaştırılarak, uluslararası pis su boşaltım kurallarına uygunluğu incelenmiştir. MSD ve AWT sistemleri, arıtım prosedürleri ve arıttıkları atık suyun konsantrasyonları açısından karşılaştırıldıklarında, AWT sistemlerinin, MSD sistemlerine göre daha yüksek ve kaliteli şekilde arıtım yaptığı görülmüştür. Özellikle Alaska sularına yapılan boşaltımları denetleyen EPA’nın, diğer uluslararası kurallara göre daha sıkı olan standartları, özellikle yolcu gemilerinde MSD sisteminden, AWT sistemine geçişi kaçınılmaz hale getirmiştir.

  3. Dating slate belts using 40Ar/39Ar geochronology and zircon ages from crosscutting plutons: A case study from east-central Maine, USA

    Science.gov (United States)

    Ghanem, Hind; Kunk, Michael J.; Ludman, Allan; Bish, David L.; Wintsch, Robert P.

    2016-12-01

    We report the ages of cleavage development in a normally intractable lower greenschist facies slate belt, the Central Maine-Aroostook-Matapedia belt in east-central Maine. We have attacked this problem by identifying the minimum ages of muscovite in a regional Acadian cleavage (S1) and in a local ductile fault zone cleavage (S2) using 40Ar/39Ar geochronology and the ages of crosscutting plutons. Our success stems from the regional low-grade metamorphism of the rocks in which each crystallization event preserves a40Ar/39Ar crystallization age and not a cooling age. Evidence for recrystallization via a pressure solution mechanism comes from truncations of detrital, authigenic, and in some rocks S1 muscovite and chlorite grains by new cleavage-forming muscovite and chlorite grains. Low-blank furnace age spectra from meta-arkosic and slaty rocks climb from moderate temperature Devonian age-steps dominated by cleavage-forming muscovite to Ordovician age-steps dominated by a detrital muscovite component. S1- and S2-cleaved rocks were hornfelsed by granitoids of ∼407 and 377 Ma, respectively. The combination of these minimum ages with the maximum metamorphic crystallization ages establishes narrow constraints on the timing of these two cleavage-forming events, ∼410 Ma (S1) and ∼380 Ma (S2). These two events coincide in time with a change in the plate convergence kinematics from the arrival of the Avalon terrane (Acadian orogeny), to a right-lateral transpression arrival of the Meguma terrane in the Neoacadian orogeny.

  4. WA1ms: A ∼2.61 Ga muscovite standard for 40Ar/39Ar dating

    Science.gov (United States)

    Jourdan, Fred; Frew, Adam; Joly, Aurore; Mayers, Celia; Evans, Noreen J.

    2014-09-01

    by Renne et al. (2011) yield a weighted mean age of 2614.2 ± 1.5 Ma (±0.055%; P = 0.8; 1σ) for WA1ms against the three standards. When calibrated solely against FCs in order to minimize correlated errors between FCs vs. GA1550 and Hb3gr, we calculate a preferred age of 2613.0 ± 2.4 Ma (±0.09%) which is recommended when using this standard. Additionally, this corresponds to a 40Ar∗/40K value of (0.3375 ± 0.0057) × 10-1 for WA1ms, which is independent of the value of the decay constant used for calculation and allows recalculation of the age of WA1ms for any preferred set of decay constants and standard ages. Using the constants proposed by Steiger and Jäger (1977) directly calculated from the three R-values, yields an age of 2598.2 ± 3.5 Ma corresponding to an identical, although less precise 40Ar∗/40K value of (0.3375 ± 0.0086) × 10-1. Benefits of this standard include: (1) an increased relative precision per crystal analyzed relative to other standards for Proterozoic and Archaean samples, (2) no post-irradiation waiting time due to the absence of Ca (no need to wait for 37ArCa decay), and (3) loading of standard grains that are optically different from the unknown (e.g., pyroxene or hornblende) to avoid standard-unknown mixing. WA1ms is freely available to the 40Ar/39Ar community.

  5. Uranium(VI adsorption on surfactant modified heulandite/clinoptilolite rich tuff

    Directory of Open Access Journals (Sweden)

    SRDJAN MATIJASEVIC

    2006-12-01

    Full Text Available The adsorption of uranium(VI on heulandite/clinoptilolite rich zeolitic tuff modified with diferent amounts (2, 5 and 10 meq/100 g of hexadecyltrimethyl ammonium (HDTMA ion was investigated. The organozeolites were prepared by ion exchange of inorganic cations at the zeolite surface with HDTMA ions, and the three prepared samples were denoted as OA-2, OA-5 and OA-10. The maximal amount of HDTMAin the organozeolite OA-10 (10 meq/100 g was equal to the external cation exchange capacity of the starting material. The results showed that uranium( VI adsorption on unmodified zeolitic tuff was low (0.34 mg uranium(VI/g adsorbent, while for the organozeolites, the adsorption increased with increasing amount of HDTMA at the zeolitic surface. The highest adsorption indexes were achieved for the organozeolite OA-10, in which all the surface inorganic cations had been replaced with HDTMA. An investigation of the adsorption of uranium(VI ions onto organozeolite OA-10 at different pH values (3, 6 and 8 showed that the adsorption index increased with increasing amount of adsorbent in the suspension. Since uranium(VI speciation is highly dependent on pH, from the adsorption isotherms, it can be seen that uranium(VI adsorption on organozeolite OA-10 at pH 6 and 8 is well described by a Langmuir type of isotherm, while at pH 3, it corresponds to a Type III isotherm.

  6. Clinoptilolite compositions in diagenetically-altered tuffs at a potential nuclear waste repository, Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Broxton, D.E.

    1987-12-31

    The compositions of Yucca Mountain clinoptilolites and their host tuffs are highly variable. Clinoptilolites and heulandites in fractures near the repository and in a thin, altered zone at the top of the Topopah Spring basal vitrophyre have consistent calcium-rich compositions. Below this level, clinoptilolites in thick zones of diagenetic alteration on the east side of Yucca Mountain have calcic-potassic compositions and become more calcium rich with depth. Clinoptilolites in stratigraphically equivalent tuffs to the west have sodic-potassic compositions and become more sodic with depth. Clinoptilolite properties important for repository performance assessment include thermal expansion/contraction behavior, hydration/dehydration behavior, and ion-exchange properties. These properties can be significantly affected by clinoptilolite compositions. The compositional variations for clinoptilolites found by this study suggest that the properties will vary vertically and laterally at Yucca Mountain. Used in conjunction with experimental data, the clinoptilolite compositions presented here can be used to model the behavior of clinoptilolites in the repository environment and along transport pathways.

  7. Biofilms on tuff stones at historical sites: identification and removal by nonthermal effects of radiofrequencies.

    Science.gov (United States)

    Cennamo, P; Caputo, P; Giorgio, A; Moretti, A; Pasquino, N

    2013-10-01

    A methodology aiming at identifying and removing biofilms from cultural heritage was applied to stones from tuff walls in historical sites. Identification of phototrophic encrusting microorganisms was carried out by optical and electron microscopy, as well as by molecular techniques (DNA analyses and denaturing gradient gel electrophoresis (DGGE)). In all sites, the examination of microbial components of biofilms resulted in the identification of 17 species belonging to Cyanobacteria, Rhodophyta, Bacillariophyta and Chlorophyta, with Cyanobacteria being the dominant components in all biofilms. In order to remove the biofilms, an innovative technique based on the use of nonthermal effects of radiofrequencies was adopted. The source of the electromagnetic fields was a signal generator connected to a horn antenna through an amplifier to provide the power boost required to generate the target field amplitude. Seven days after exposure to radiofrequency electromagnetic field, about 50 % reduction of biofilm was observed; after 14 days, biofilm extension was reduced by about 90 %. DGGE analyses performed after 14 days confirmed these visual inspections. Also, DGGE analyses carried out before and 14 days after treatments showed that 12 out of 17 identified species disappeared. A complete visual disappearance of biofilms was observed a month after the beginning of treatments. DGGE repeated at this time confirmed the total disappearance of biofilm-forming species. Treated stones, when transferred back to their original sites, did not show any microorganism re-growing after 6 months. No alteration in the color and structural consistency of tuff substrata was observed after radiofrequency treatments.

  8. Ash-flow tuffs of the Galiuro Volcanics in the northern Galiuro Mountains, Pinal County, Arizona

    Science.gov (United States)

    Krieger, Medora Louise Hooper

    1979-01-01

    The upper Oligocene and lower Miocene Galiuro Volcanics in the northern part of the Galiuro Mountains contains two distinctive major ash-flow tuff sheets, the Holy Joe and Aravaipa Members. These major ash-flows illustrate many features of ash-flow geology not generally exposed so completely. The Holy Joe Member, composed of a series of densely welded flows of quartz latite composition that make up a simple cooling unit. is a rare example of a cooling unit that has a vitrophyre at the top as well as at the base. The upper vitrophyre does not represent a cooling break. The Aravaipa Member. a rhyolite, is completely exposed in Aravaipa and other canyons and on Table Mountain. Remarkable exposures along Whitewash Canyon exhibit the complete change from a typical stacked-up interior zonation of an ash flow to a non welded distal margin. Vertical and horizontal changes in welding, crystallization, specific gravity, and lithology are exposed. The ash flow can be divided into six lithologic zones. The Holy Joe and Aravaipa Members of the Galiuro Volcanics are so well exposed and so clearly show characteristic features of ash-flow tuffs that they could be a valuable teaching aid and a source of theses for geology students.

  9. Wireline-rotary air coring of the Bandelier Tuff, Los Alamos, New Mexico

    Science.gov (United States)

    Teasdale, W.E.; Pemberton, R.R.

    1984-01-01

    This paper describes experiments using wireline-rotary air-coring techniques conducted in the Bandelier Tuff using a modified standard wireline core-barrel system. The modified equipment was used to collect uncontaminated cores of unconsolidated ash and indurated tuff at Los Alamos, New Mexico. Core recovery obtained from the 210-foot deep test hole was about 92 percent. A standard HQ-size, triple-tube wireline core barrel (designed for the passage of liquid drilling fluids) was modified for air coring as follows: (1) Air passages were milled in the latch body part of the head assembly; (2) the inside dimension of the outer core barrel tube was machined and honed to provide greater clearance between the inner and outer barrels; (3) oversized reaming devices were added to the outer core barrel and the coring bit to allow more clearance for air and cuttings return; (4) the eight discharge ports in the coring bit were enlarged. To control airborne-dust pollution, a dust-and-cuttings discharge subassembly, designed and built by project personnel, was used. (USGS)

  10. Analysis of Fracture in Cores from the Tuff Confining Unit beneath Yucca Flat, Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    Lance Prothro

    2008-03-01

    The role fractures play in the movement of groundwater through zeolitic tuffs that form the tuff confining unit (TCU) beneath Yucca Flat, Nevada Test Site, is poorly known. This is an important uncertainty, because beneath most of Yucca Flat the TCU lies between the sources of radionuclide contaminants produced by historic underground nuclear testing and the regional carbonate aquifer. To gain a better understanding of the role fractures play in the movement of groundwater and radionuclides through the TCU beneath Yucca Flat, a fracture analysis focusing on hydraulic properties was performed on conventional cores from four vertical exploratory holes in Area 7 of Yucca Flat that fully penetrate the TCU. The results of this study indicate that the TCU is poorly fractured. Fracture density for all fractures is 0.27 fractures per vertical meter of core. For open fractures, or those observed to have some aperture, the density is only 0.06 fractures per vertical meter of core. Open fractures are characterized by apertures ranging from 0.1 to 10 millimeter, and averaging 1.1 millimeter. Aperture typically occurs as small isolated openings along the fracture, accounting for only 10 percent of the fracture volume, the rest being completely healed by secondary minerals. Zeolite is the most common secondary mineral occurring in 48 percent of the fractures observed.

  11. Stable isotopes of authigenic minerals in variably-saturated fractured tuff

    Energy Technology Data Exchange (ETDEWEB)

    Weber, D.S.; Evans, D.D.

    1988-11-01

    Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ({sup 18}O/{sup 16}O) and carbon ({sup 13}C/{sup 12}C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to result from near-surface isotopic enrichment due to evaporation rather than the effects of rock-water interaction. Oxygen isotope ratios of rock matrix opal samples exhibited an isotopic gradient believed to result from, leaching and reprecipitation of silica at depth. Methods and results can be used to further define primary flowpaths and the movement of water in variably-saturated fractured rock. 71 refs., 23 figs., 3 tabs.

  12. U-Pb zircon and 40Ar/39Ar geochronology of sericite from hydrothermal alteration zones: new constraints for the timing of Ediacaran gold mineralization in the Sukhaybarat area, western Afif terrane, Saudi Arabia

    Science.gov (United States)

    Harbi, Hesham M.; Ali, Kamal A.; McNaughton, Neal J.; Andresen, Arild

    2017-07-01

    The Sukhaybarat East and Red Hill deposits, in the northeastern part of the Arabian Shield, are mesothermal vein-type gold deposits hosted by late Cryogenian-Ediacaran intrusive rocks of the Idah suites (diorite, tonalite, granodiorite) and, at Sukhaybarat East, also by Ediacaran metasedimentary rocks. Gold mineralization comprises quartz-arsenopyrite veins (Sukhaybarat East), quartz-carbonate-pyrite veins (Red Hill), and subordinate gold-base metal sulfide veins. In the Red Hill deposit, alteration is complicated due to multiple overprinting hydrothermal events and is characteristically affected by pervasive, pink quartz-K-feldspar-hematite alteration which is overprinted by potassic alteration characterized by a quartz-biotite-carbonate-muscovite/sericite-rutile-apatite assemblage. This assemblage is associated with molybdenite veins which appear to form late in the paragenetic sequence and may represent either evolution of the ore fluid composition, or a later, unrelated mineralized fluids. Hydrothermal alteration at the Sukhaybarat East deposit is dominated by quartz-carbonate-sericite-arsenopyrite assemblages. Zircon from ore-hosting tonalite at Sukhaybarat East yields a U-Pb age of 629 ± 6 Ma, and biotite from the same rock gives an 40Ar/39Ar age of 622 ± 23 Ma. The 40Ar/39Ar age is within the uncertainty range for the U-Pb age of the host intrusion and is interpreted as a minimally disturbed cooling age for the tonalite. In the Red Hill area, granodiorite was emplaced at 615 ± 5 Ma, whereas muscovite/sericite separated from a mineralized sample of a quartz-carbonate-pyrite vein, that was overprinted by molybdenite-bearing veinlets, yields an 40Ar/39Ar age of 597 ± 8 Ma. We interpreted this age to represent the maximum age of the molybdenite mineralization and the probable minimum age of gold mineralization in the Red Hill deposit.

  13. Subduction of the South Chile active spreading ridge: A 17 Ma to 3 Ma magmatic record in central Patagonia (western edge of Meseta del Lago Buenos Aires, Argentina)

    Science.gov (United States)

    Boutonnet, E.; Arnaud, N.; Guivel, C.; Lagabrielle, Y.; Scalabrino, B.; Espinoza, F.

    2010-01-01

    The Chile Triple Junction is a natural laboratory to study the interactions between magmatism and tectonics during the subduction of an active spreading ridge beneath a continent. The MLBA plateau (Meseta del Lago Buenos Aires) is one of the Neogene alkali basaltic plateaus located in the back-arc region of the Andean Cordillera at the latitude of the current Chile Triple Junction. The genesis of MLBA can be related with successive opening of slabs windows beneath Patagonia: within the subducting Nazca Plate itself and between the Nazca and Antarctic plates. Detailed 40Ar/ 39Ar dating and geochemical analysis of bimodal magmatism from the western flank of the MLBA show major changes in the back-arc magmatism which occurred between 14.5 Ma and 12.5 Ma with the transition from calc-alkaline lavas (Cerro Plomo) to alkaline lavas (MLBA) in relation with slab window opening. In a second step, at 4-3 Ma, alkaline felsic intrusions were emplaced in the western flank of the MLBA coevally with the MLBA basalts with which they are genetically related. These late OIB-like alkaline to transitional basalts were generated by partial melting of the subslab asthenosphere of the subducting Nazca plate during the opening of the South Chile spreading ridge-related slab window. These basalts differentiated with small amounts of assimilation in shallow magma chambers emplaced along transtensional to extensional zones. The close association of bimodal magmatism with extensional tectonic features in the western MLBA is a strong support to the model of Patagonian collapse event proposed to have taken place between 5 and 3 Ma as a consequence of the presence of the asthenospheric window (SCR-1 segment of South Chile Ridge) below the MLBA area.

  14. Mineralogy, petrology and whole-rock chemistry data compilation for selected samples of Yucca Mountain tuffs; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Connolly, J.R. [New Mexico Univ., Albuquerque, NM (United States)

    1991-12-01

    Petrologic, bulk chemical, and mineralogic data are presented for 49 samples of tuffaceous rocks from core holes USW G-1 and UE-25a{number_sign}1 at Yucca Mountain, Nevada. Included, in descending stratigraphic order, are 11 samples from the Topopah Spring Member of the Paintbrush Tuff, 12 samples from the Tuffaceous Beds of Calico Hills, 3 samples from the Prow Pass Member of the Crater Flat Tuff, 20 samples from the Bullfrog Member of the Crater Flat Tuff and 3 samples from the Tram Member of the Crater Flat Tuff. The suite of samples contains a wide variety of petrologic types, including zeolitized, glassy, and devitrified tuffs. Data vary considerably between groups of samples, and include thin section descriptions (some with modal analyses for which uncertainties are estimated), electron microprobe analyses of mineral phases and matrix, mineral identifications by X-ray diffraction, and major element analyses with uncertainty estimates.

  15. Ma olin Saddami poeg / Latif Jahija

    Index Scriptorium Estoniae

    Jahija, Latif

    1995-01-01

    Järg Jan/21.,28. lk. 7,5. L. Jahija sensatsiooniline raamat "Ma olin Saddami poeg", milles ta pajatab kuidas ta a. 1987-1991 oli Iraagi presidendi vanema poja teisik. Lühikokkuvõte sellest jutustusest

  16. LA-ICP-MS zircon U-Pb geochronology of the tuffs on the uppermost of the Emeishan basalt succession in Panxian County, Guizhou Province: Constraints on genetic link between Emeishan large igneous province and the mass extinction%贵州盘县峨眉山玄武岩系顶部凝灰岩LA-ICP-MS锆石U-Pb年龄:对峨眉山大火成岩省与生物大规模灭绝关系的约束

    Institute of Scientific and Technical Information of China (English)

    朱江; 张招崇; 侯通; 康健丽

    2011-01-01

    在20世纪90年代,有学者认为峨眉山大火成岩省(Emeishan Large Igneous Province,ELIP)大规模火山活动与二叠-三叠系之交(Permian-Triassic Boundary,P-TB)的生物大灭绝事件在时间上有耦合关系,随后的40Ar/39Ar同位素测年结果也显示峨眉山大火成岩省是晚二叠世形成的.但是,近些年大量的SHRIMP U-Pb测年结果表明,ELIP大规模火山喷发约在~260Ma;因此有研究认为,ELIP火山活动与中二叠世瓜德卢普期末(end-Guadalupian)的生物灭绝事件在时间上联系更加紧密.至于P-T界线生物大灭绝,现在多数学者认为是,由于西伯利亚大火成岩省火山强烈活动释放大量气体和火山灰所造成环境变化引起的.最近,我们在ELIP东部的贵州盘县峨眉山玄武岩系剖面中发现顶部发育厚度达近百米的凝灰岩层,其LA-ICP-MS U-Pb法测年结果为251.0±1.0Ma,与浙江煤山剖面中二叠系-三叠系边界处黏土层或火山灰层的锆石U-Pb年龄接近.因此,峨眉山玄武岩喷发结束的时间应该在P-T边界,与西伯利亚大火成岩省的主体喷发时间一致.新的测年结果暗示了ELIP火山活动与地球历史上最大的一次生物灭绝事件(P-T边界)可能存在着成因联系.%In 1990s, some researchers suggested a temporal link between volcanism of the Emeishan Large Igneous Province(ELIP) and the mass extinction at the Permian-Triassic Boundary (P-TB) , and were supported by the 40Ar/39 Ar isotopic dating showing that the ELIP formed in the Late Permian. However, in recent years, a quantity of SHRIMP U-Pb datings suggested that the large-scale volcanism erupted at ~ 260Ma. Hence, the ELIP volcanism has been attributed to be the cause of the end-Guadalupian mass extinction in the Middle Permian. In contrast, the intense volcanism in Siberian traps has been considered to be the main cause of the P-T boundary great mass extinction which has been ascribed to a global environmental change due to

  17. Interpretation of discordant 40Ar/39Ar age-spectra of mesozoic tholeiites from antarctica

    Science.gov (United States)

    Fleck, R.J.; Sutter, J.F.; Elliot, D.H.

    1977-01-01

    Conventional K-Ar ages of tholeiitic basalts of the Ferrar Group in the central Transantarctic Mountains indicate significant loss of radiogenic 40Ar from this unit over much of its outcrop area. Argon loss varies inversely with amount of devitrified matrix in the basalts, which have not been thermally or tectonically disturbed since extrusion. 40Ar/19Ar age-spectra of these tholeiites are generally discordant and indicate significant inhomogeneity in the distribution of radiogenic 40Ar with respect to 39Ar, but are distinctly different from release patterns of thermally disturbed samples. Amounts of argon redistribution vary directly with amounts of devitrification and are reflected in progressive modification of the age spectra. A model of redistribution of radiogenic 40Ar by devitrification of originally glassy matrix is suggested that is consistent with disturbance of the conventional K-Ar systematics as well as the 40Ar/39Ar age-spectra. Samples with substantial redistribution but minor loss of radiogenic argon yield age spectra whose apparent ages decrease from low-temperature to high-temperature steps, similar to those reported for some lunar basalts, breccias, and soils. Modification of all the age spectra is attributed to redistribution of radiogenic 40Ar during progressive devitrification, although 39Ar-recoil effects suggested by Turner and Cadogan (1974) may be a factor in some cases. Where devitrification involves most potassium sites within the basalt, 40Ar/39Ar age-plateaux may be formed that have no geologic significance. ?? 1977.

  18. EFFECT OF Ar PRESSURE ON STRUCTURAL AND ELECTRICAL PROPERTIES OF Cu FILMS DEPOSITED ON GLASS BY DC MAGNETRON SPUTTERING

    Institute of Scientific and Technical Information of China (English)

    P.Wu; F.P.Wang; L.Q.Pan; Y.Tian; H.Qiu

    2002-01-01

    Cu films with thickness of 630-1300nm were deposited on glass substrates withoutheating by DC magnetron sputtering in pure Ar gas. Ar pressure was controlled to0.5, 1.0 and 1.5Pa respectively. The target voltage was fixed at 500V but the targetcurrent increased from 200 to 1150mA with Ar pressure increasing. X-ray diffrac-tion, scanning electron microscopy and atomic force microscopy were used to observethe structural characterization of the films. The resistivity of the films was measuredusing four-point probe technique. At all the Ar pressures, the Cu films have mixturecrystalline orientations of [111], [200] and [220] in the direction of the film growth.The film deposited at lower pressure shows more [111] orientation while that depositedat higher pressure has more [220] orientation. The amount of larger grains in the filmprepared at 0.5Pa Ar pressure is slightly less than that prepared at 1. 0Pa and 1.5PaAr pressures. The resistivities of the films prepared at three different Ar pressures rep-resent few differences, about 3-4 times of that of bulk material. Besides the depositionrate increases with Ar pressure because of the increase in target current. The contri-bution of the bombardment of energetic reflected Argon atoms to these phenomena isdiscussed.

  19. The Early Andean Magmatic Province (EAMP): 40Ar/ 39Ar dating on Mesozoic volcanic and plutonic rocks from the Coastal Cordillera, northern Chile

    Science.gov (United States)

    Oliveros, Verónica; Féraud, Gilbert; Aguirre, Luis; Fornari, Michel; Morata, Diego

    2006-10-01

    The Early Andean Magmatic Province (EAMP), consists of about 150 000 km 3 of volcanic and plutonic units in the Coastal Cordillera of northern Chile and southern Peru and represents a major magmatic Mesozoic event in the world, for which the precise age of the thick volcanic series was unknown. Thirty 40Ar/ 39Ar analyses were carried out on primary mineral phases of volcanic and plutonic rocks from northern Chile (18°30'-24°S). Reliable plateau and "mini plateau" ages were obtained on plagioclase, amphibole and biotite from volcanic and plutonic rocks, despite widespread strong alteration degree. In the Arica, Tocopilla and Antofagasta (700 km apart) regions, the ages obtained on lava flows constrain the volcanic activity between 164 and 150 Ma and no N-S migration of volcanism is observed. The uppermost lava flows of the volcanic sequence at the type locality of the La Negra Formation extruded at ca. 153-150 Ma, suggesting the end of the volcanic activity of the arc at that time. The oldest volcanic activity occurred probably at ca. 175-170 Ma in the Iquique area, although no plateau age could be obtained. The plutonic bodies of the same regions were dated between ca. 160 and 142 Ma, indicating that they were partly contemporaneous with the volcanic activity. At least one volcanic pulse around 160 Ma is evidenced over the entire investigated reach of the EAMP, according to the ages found in Arica, Tocopilla, Michilla and Mantos Blancos regions. The episodic emplacement of huge amounts of subduction related volcanism is observed throughout the whole Andean history and particularly during the Jurassic (southern Peru, northern Chile and southern Argentina). These events probably correspond to periodic extensional geodynamic episodes, as a consequence of particular subduction conditions, such as change of obliquity of the convergence, change in the subduction angle, slab roll back effect or lower convergence rate, that remain to be precisely defined.

  20. Preliminary K/Ar geochronology of the Crater Basalt volcanic field (CBVF, northern Patagonia

    Directory of Open Access Journals (Sweden)

    Z. Pécskay

    2007-03-01

    Full Text Available The Crater Basalt volcanic field is one of the Quaternary intraplate basaltic fields in northern Patagonia. A systematic geological, volcanological and geochronological study of CBVF indicates a multistage history of eruptions of basaltic volcanoes. K/Ar dating, using whole rock samples shows that the measured analytical ages are fully consistent with the available stratigraphic control. The radiometric ages fall into three distinct, internally consistent age groups, which give evidence that there were at least three major episodes of volcanic activity, at about 1.0 Ma, 0.6 Ma and 0.3 Ma ago. The age differences appear to be just significant, even although less than 10 % radiogenic argon was found in the isotope analysis of whole rock samples.

  1. Ars grammatica de Dionisio Tracio

    Directory of Open Access Journals (Sweden)

    Beltrán Jorge Enrique

    2003-06-01

    Full Text Available

    Ars Grammatica de Dionisio Tracio (170-90 a. C fue la primera gramática griega que se escribió. Su contenido y método fueron modelos que siguieron las gramáticas escolares posteriores. La versión española que se presenta ahora responde a la necesidad que se tenía en nuestro medio de una traducción completa de este texto. Finalmente, se acompaña la traducción de una introducción y de abundantes notas, en un intento por hacerla comprensible para el hablante del español, no necesariamente conocedor de la lengua griega.

  2. Studying the sorption properties of a clinoptilolite-containing tuff with respect to europium(III) ions

    Science.gov (United States)

    Kozhevnikova, N. M.

    2014-03-01

    The kinetic laws of sorption of europium(III) ions from sulfate solutions by a clinoptilolite-containing tuff are studied. The kinetic parameters of sorption process are determined and absorption isotherms are constructed for europium ions. It is found that both external and internal diffusion are rate-limiting steps, and europium is completely extracted from dilute solutions (<0.0025 m).

  3. Zeolitic alteration and fracture fillings in silicic tuffs at a potential nuclear waste repository, Yucca Mountain, Nevada, USA

    Energy Technology Data Exchange (ETDEWEB)

    Broxton, D.E.; Carlos, B.A.

    1986-12-31

    This paper describes the distribution and chemistry of zeolites in tuffs and in fractures at Yucca Mountain. Samples used in this study were collected from continuously-cored exploratory drill holes. A variety of analytical techniques, including optical petrography, x-ray powder diffraction, electron microanalysis, and x-ray fluorescence, were used to characterize the distribution and chemistry of zeolites in these samples.

  4. Structure, stratigraphy, and eruption dynamics of a young tuff ring: Hanauma Bay, O'ahu, Hawai'i

    Science.gov (United States)

    Rottas, K. M.; Houghton, B. F.

    2012-09-01

    The Hanauma Bay-Koko Head complex is one of several young volcanic landforms along the Koko fissure, in southeastern O'ahu. The Hanauma Bay region of the complex comprises two nested tuff rings, inner and outer Hanauma Bay, and multiple smaller vents. The internal structure of the inner tuff ring, well exposed due to subsequent breaching by the ocean and wave erosion, indicates that it formed during a minimum of five distinct phases of deposition that produced five mappable units. Significant inward collapses generated major unconformities that separate the units exposed in the inner wall. The planes of failure are cut by narrow steep-walled, locally overhung channels and gullies, suggesting that the collapse events were each followed by short time breaks during which the deposits were eroded by rainfall runoff. Within each pyroclastic unit, there are many local slump scars and unconformities, suggesting that minor instability of the inner wall was a near-constant feature. From bedding sags and surge bed forms, it is apparent that the vent shifted at least twice during tuff ring growth. Ballistic blocks in the youngest unit indicate that the eruption overlapped in time with a separate eruption to the north, most likely to be that of the Kahauloa tuff ring 880 m away.

  5. Characterization of liquid-water percolation in tuffs in the unsaturated zone, Yucca Mountain, Nye County, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Kume, J.; Rousseau, J.P.

    1989-12-31

    A surface-based borehole investigation currently (1989) is being done to characterize liquid-water percolation in tuffs of Miocene age in the unsaturated zone beneath Yucca Mountain, Nye County, Nevada Active in-situ testing and passive in-situ monitoring will be used in this investigation to estimate the present-day liquid-water percolation (flux). The unsaturated zone consists of a gently dipping sequence of fine-grained, densely fractured, and mostly welded ash-flow tuffs that are interbedded with fine-grained, slightly fractured, non-welded ash-flow and ash-fall tuffs that are partly vitric and zeolitized near the water table. Primary study objectives are to define the water potential field within the unsaturated zone and to determine the in-situ bulk permeability and bulk hydrologic properties of the unsaturated tuffs. Borehole testing will be done to determine the magnitude and spatial distribution of physical and hydrologic properties of the geohydrologic units, and of their water potential fields. The study area of this investigation is restricted to that part of Yucca Mountain that immediately overlies and is within the boundaries of the perimeter drift of a US Department of Energy proposed mined, geologic, high-level radioactive-waste repository. Vertically, the study area extends from near the surface of Yucca Mountain to the underlying water table, about 500 to 750 meters below the ground surface. The average distance between the proposed repository and the underlying water table is about 205 meters.

  6. Spectral Differences Between Palagonite Tuffs Formed in Sub-Glacial Versus Liquid Water Environments: Relevance to Mars

    Science.gov (United States)

    Farrand, W. H.; Lane, M. D.

    2002-01-01

    The reflectance and emissivity spectra of palagonite tuffs formed in sub-glacial environments are compared with those formed in liquid water environments. The relevance to palagonites produced by water-magma interactions on Mars is discussed. Additional information is contained in the original extended abstract.

  7. GPS-Based AR Games Development Potential

    Directory of Open Access Journals (Sweden)

    Gregorius Alvin Raditya Santoso

    2014-11-01

    Full Text Available The application of new technologies in a game is not a new thing. One example is the application of Augmented Reality (AR technology in game. Many people do not know the application of AR technology in game, although the application of this technology is able to produce a game with unique gameplay. In addition, since AR game is GPS-based, it offers new gaming experience, that is, playing outdoors in which the real world becomes the game arena. This advantage gives the AR technology a huge potential to be developed into a game

  8. K-Ar ages for the Yahazudake volcanic rocks from southwest Kyushu, Japan; Kyushu nanseibu yahazudake kazanganrui no K-Ar nendai

    Energy Technology Data Exchange (ETDEWEB)

    Yokose, H.; Kikuchi, W. [Kumamoto Univ. (Japan)] Nagao, K. [Okayama Univ. (Japan)264000] Kodama, K. [Kochi Univ. (Japan)

    1998-05-05

    Many volcanic rocks, seemed to be erupted during the period from the Pliocene epoch to the Pleistocene epoch, are distributed abounding in Kyushu, Japan. In this study, K-Ar ages determination about the 4 samples which represents the Hisatsu volcanic rocks distributed around Yahazudake and rhyolite distributed in Gesujima placed in the southernmost extremity of Amakusa Shimojima, was conducted. And consideration of time/space distribution of the Hisatsu volcanic rocks upon collecting the data which were reported until now and the data obtained by the present K-Ar age determination, was done. In the result of the present measurement, the absolute age of the Hisatsu volcanic rocks distributed around Minamata-shi became clear. I was clarified that Yahazudake volcanic rocks consisted of andesite, which is comparatively lacking in potassium, were formed during about 100 thousand years from 1.98 to 2.08 Ma, and Ontake volcanic rocks which exists for the bottom erupted at about 2.15 Ma. And, the age value of 2.89 Ma was obtained from Ushibuka rhyolite distributed in Gesujima. 35 refs., 4 figs., 3 tabs.

  9. 40Ar/39Ar ages and Sr-Nd-Pb isotopic compositions of alkaline and tholeiitic rocks from the northern Deccan Traps

    Science.gov (United States)

    Marzoli, A.; Parisio, L.; Jourdan, F.; Melluso, L.; Sethna, S. F.; Bellieni, G.

    2015-12-01

    The Deccan large igneous province in India was emplaced close to the Cretaceous-Paleogene boundary (K-Pg; 66.0 Ma) and is formed by tholeiitic and alkaline rocks. Definition of the origin of Deccan magmatism and of its environmental impact relies on precise and accurate geochronological analyses. We present new 40Ar/39Ar ages from the northern sector of the province. In this area, tholeiitic and alkaline rocks were contemporaneously emplaced at 66.60±0.35 to 65.25±0.29 Ma in the Phenai Mata area, while rocks from Rajpipla and Mt. Pavagadh yielded ages ranging from 66.40±2.80 to 64.90±0.80 Ma. Indistinguishable ages for alkaline and tholeiitic magmatism, coupled with distinct major and trace element and Sr-Nd-Pb isotopic compositions suggest that distinct mantle sources, necessary for the two magmatic series were synchronously active. The new ages are compared with previous ages, which were carefully screened and filtered and then recalculated in order to be comparable. The entire data set of geochronological data does not support a time-related migration of the magmatism related to the northward Indian Plate movement relative to the Reunion mantle plume. The main phase of magmatism, including the newly dated rocks from the Northern Deccan occurred across the K-Pg boundary, confirming a causal link between the emplacement of the province and the K-Pg mass extinction.

  10. Preliminary K/Ar geochronology of the Crater Basalt volcanic field (CBVF, northern Patagonia

    Directory of Open Access Journals (Sweden)

    Z. Pécskay

    2007-11-01

    Full Text Available The Crater Basalt volcanic field is one of the Quaternary intraplate basaltic fields in northern Patagonia. A systematic geological, volcanological and geochronological study of CBVF indicates a multistage history of eruptions of basaltic volcanoes. K/Ar dating, using whole rock samples shows that the measured analytical ages are fully consistent with the available stratigraphic control. The radiometric ages fall into three distinct, internally consistent age groups, which give evidence that there were at least three major episodes of volcanic activity, at about 1.0 Ma, 0.6 Ma and 0.3 Ma ago. The age differences appear to be just significant, even although less than 10 % radiogenic argon was found in the isotope analysis of whole rock samples.El campo volcánico del Basalto Cráter (CVBC constituye uno de los campos basálticos cuaternarios de intraplaca de la Patagonia septentrional. El estudio sistemático de la geología, volcanología y geocronología del CVBC muestra una historia eruptiva multiepisódica de volcanes basálticos. Las dataciones K-Ar realizadas sobre roca total son coherentes con el control estratigráfico. Las edades obtenidas para el Basalto Cráter permiten distinguir tres episodios diferentes, pero individualmente coherentes, de actividad volcánica, ocurridos hace ~1,0 Ma; 0,6 Ma y 0,3 Ma. Las diferencias de edad parecen ser significativas, aún cuando el contenido de argón radiogénico determinado en los análisis de roca total resultó menor al 10 %.

  11. Progreso y retos de la geocronología 40Ar/39Ar en Costa Rica y Nicaragua Progress and Challenges Using 40Ar/39Ar Geochronology in Costa Rica and Nicaragua

    Directory of Open Access Journals (Sweden)

    Ian Saginor¹

    2011-12-01

    Full Text Available Con el principal objetivo de realizar mejores cálculos de la producción volcánica, en el Arco Volcánico de América Central, realizamos 61 dataciones 40Ar/39Ar en tefras y lavas en localidades de frente volcánico de Costa Rica y Nicaragua por medio de varias campañas de campo y análisis de laboratorio (preparación de muestras, envió al reactor nuclear, espectroscopía de masas de las muestras radiactivas, al laboratorio de gases nobles del Departamento de Ciencias de la Tierra y Planetarias de la Universidad Rutgers del 2002-2008. En este artículo presentamos diferentes observaciones que resultaron de este estudio donde se describe la precisión, exactitud y la confiabilidad de las edades 40Ar/39Ar. El primer resultado muestra las limitaciones de esta técnica en muestras baja en K2O con edades To better estimate the extrusive flux of the Central American Arc, from 2002-2008, we obtained sixty one high precision 40Ar/39Ar ages on geographically well-situated lavas and tephra from Costa Rica and Nicaragua. Here, we describe a number of observations encountered during this study using four examples that well document the precision, accuracy and general reliability of the 40Ar/39Ar ages. First, low K2O values, particularly in samples from Nicaragua, is a major limitation in or attempts to obtain reliable dates on samples under 1 My. Second, extensive weathering of samples due to the tropical climate of Central America has resulted in various levels of argon loss even when the hand sample appeared unaltered. Third, our field and geochronological data lead us to conclude that eruptive rates have not been constant over the past 15 to 20 My, but rather appears punctuated by gaps of up to several million years. We attempted to address the temporal gaps in several ways. First, geochemical analyses were used to identify samples that may have erupted during time periods without known volcanism. For example, U/Th values in the active Central

  12. 40Ar/39Ar dating of the Honghuaqiao Formation in SE China

    Science.gov (United States)

    Chang, S.; Zhang, H.; Hemming, S. R.; Mesko, G. T.; Fang, Y.

    2010-12-01

    The Jehol Biota, defined as the characteristic Eosestheria-Ephemeropsis-Lycoptera assemblage (Grabau, 1923, Bulletin of the Geological Survey of China), is widely distributed in eastern and central Asia (Li et al., 1982, Acta Geologica Sinica; Chen, 1988, Acta Palaeontologica Sinica). Abundant and varied fossils of the terrestrial Jehol Biota, including plants, insects, dinosaurs, birds, mammals, and freshwater invertebrates, have been discovered from the Dabeigou, the Yixian and the Jiufotang Formations (or their correlative strata) in northeast China from the Liaoning and Hebei Provinces and Inner Mongolia (Chen and Jin, 1999, Acta Palaeontologica Sinica). In addition, strata that may be correlative with the classic Jehol fossil-bearing formations have been identified extensively in central and eastern China, the Korean Peninsula, Mongolia, and Siberia. In the past three decades mollusk, conchostracan, ostracod, insect, fish, and plant fossils from localities in southeastern China, interpreted as related to the Jehol biota of the northeast, have been found (Mateer and Chen, 1986, Cretaceous Research; Li, 2003, Chinese Science Bulletin; Chen, Li and Batten, 2007, Geological Journal). However, a detailed correlation between the classic Jehol outcrops and the more recently found localities to the South and West has yet to emerge. Volcanic rocks from the Honghuaqiao fossil-bearing Formation in Tuzhou City of eastern Anhui Province, southeastern China provide an excellent opportunity to rectify this situation. Preliminary results of a pilot study suggest that the Honghuaqiao Formation is equivalent to the Longwanshan Formation of Anhui Province, southeastern China and the Yixian Formation, northeastern China (Chang et al., 2009, AGU abstract). Initial 40Ar/39Ar results indicate that conchostracans from the upper Honghuaqiao Formation are approximately 130 Ma. Our ongoing work aims to establish a high-resolution chronostratigraphy for Tuzhou City in Anhui Province

  13. In defense of Magnetite-Ilmenite Thermometry in the Bishop Tuff and its implication for gradients in silicic magma reservoirs

    Science.gov (United States)

    Evans, Bernard W; Hildreth, Edward; Bachmann, Olivier; Scaillet, Bruno

    2016-01-01

    Despite claims to the contrary, the compositions of magnetite and ilmenite in the Bishop Tuff correctly record the changing conditions of T and fO2 in the magma reservoir. In relatively reduced (∆NNO 1, e.g., Fish Canyon Tuff, Pinatubo), and the d(aTiO2)/dT slope can be negative. Biotite, FeTi-oxides, liquid, and possibly plagioclase largely maintained equilibrium in the Bishop Tuff magma (unlike the pyroxenes, and cores of quartz, sanidine, and zircon) prior ro and during a mixing event triggered by a deeper recharge, which, based on elemental diffusion profiles in minerals, took place at least several decades before eruption. Equilibrating phases and pumice compositions show evolving chemical variations that correlate well with mutually consistent temperatures based on the FeTi-oxides, sanidine-plagioclase, and ∆18O quartz-magnetite pairs. Early Bishop Tuff (EBT) temperatures are lower (700 to ~780‎°C) than temperatures (780 to >820°C) registered in Late Bishop Tuff (LBT), the latter defined here not strictly stratigraphically, but by the presence of orthopyroxene and reverse-zoned rims on quartz and sanidine. The claimed similarity in compositions, Zr-saturation temperatures and thermodynamically calculated temperatures (730-740°C) between EBT and less evolved LBT reflect the use of glass inclusions in quartz cores in LBT that were inherited from the low temperature rhyolitic part of the reservoir characteristic of the EBT. LBT temperatures as high as 820°C, the preservation of orthopyroxene, and the presence of reverse-zoned minerals (quartz, sanidine, zircons) are consistent with magma recharge at the base of the zoned reservoir, heating the cooler rhyolitic melt, partly remelting cumulate mush, and introducing enough CO2 (0.4-1.4 wt%, mostly contained in the exsolved fluid phase) to significantly lower H2O-activity in the system.

  14. Stratigraphy, correlation, depositional setting, and geophysical characteristics of the Oligocene Snowshoe Mountain Tuff and Creede Formation in two cored boreholes

    Science.gov (United States)

    Larsen, Daniel; Nelson, Philip H.

    2000-01-01

    Core descriptions and geophysical logs from two boreholes (CCM-1 and CCM-2) in the Oligocene Snowshoe Mountain Tuff and Creede Formation, south-central Colorado, are used to interpret sedimentary and volcanic facies associations and their physical properties. The seven facies association include a mixed sequence of intracaldera ash-flow tuffs and breccias, alluvial and lake margin deposits, and tuffaceous lake beds. These deposits represent volcanic units related to caldera collapse and emplacement of the Snowshoe Mountain Tuff, and sediments and pyroclastic material deposited in the newly formed caldera basin, Early sedimentation is interpreted to have been rapid, and to have occurred in volcaniclastic fan environments at CCM-1 and in a variery of volcaniclastic fan, braided stream shallow lacustrine, and mudflat environments at CCM-2. After an initial period of lake-level rise, suspension settling, turbidite, and debris-flow sedimentation occurred in lacustrine slope and basin environments below wave base. Carbonate sedimentation was initially sporadic, but more continuous in the latter part of the recorded lake history (after the H fallout tuff). Sublacustrine-fan deposition occurred at CCM-1 after a pronounced lake-level fall and subsequent rise that preceded the H tuff. Variations in density, neutron, gamma-ray, sonic, and electrical properties of deposits penetrated oin the two holes reflect variations in lithology, porosity, and alteration. Trends in the geophysical properties of the lacustrine strata are linked to downhole changes in authigenic mineralology and a decrease in porosity interpreted to have resulted primarily from diagenesis. Lithological and geophysical characteristics provide a basis for correlation of the cores; however, mineralogical methods of correlation are hampered by the degree of diagenesis and alteration.

  15. Performance predictions for mechanical excavators in Yucca Mountain tuffs; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Ozdemir, L.; Gertsch, L.; Neil, D.; Friant, J. [Colorado School of Mines, Golden, CO (United States). Earth Mechanics Inst.

    1992-09-01

    The performances of several mechanical excavators are predicted for use in the tuffs at Yucca Mountain: Tunnel boring machines, the Mobile Miner, a roadheader, a blind shaft borer, a vertical wheel shaft boring machine, raise drills, and V-Moles. Work summarized is comprised of three parts: Initial prediction using existing rock physical property information; Measurement of additional rock physical properties; and Revision of the initial predictions using the enhanced database. The performance predictions are based on theoretical and empirical relationships between rock properties and the forces-experienced by rock cutters and bits during excavation. Machine backup systems and excavation design aspects, such as curves and grades, are considered in determining excavator utilization factors. Instanteous penetration rate, advance rate, and cutter costs are the fundamental performance indicators.

  16. Long-term desorption behavior of uranium and neptunium in heterogeneous volcanic tuff materials /

    Energy Technology Data Exchange (ETDEWEB)

    Dean, Cynthia A.

    2010-05-01

    Uranium and neptunium desorption were studied in long-term laboratory experiments using four well-characterized volcanic tuff cores collected from southeast of Yucca Mountain, Nevada. The objectives of the experiments were to 1. Demonstrate a methodology aimed at characterizing distributions of sorption parameters (attributes of multiple sorption sites) that can be applied to moderately-sorbing species in heterogeneous systems to provide more realistic reactive transport parameters and a more realistic approach to modeling transport in heterogeneous systems. 2. Focus on uranium and neptunium because of their high solubility, relatively weak sorption, and high contributions to predicted dose in Yucca Mountain performance assessments. Also, uranium is a contaminant of concern at many DOE legacy sites and uranium mining sites.

  17. Hydration of tricalcium silicate in blended Cements manufactured with cuban tuffs

    Directory of Open Access Journals (Sweden)

    Duque Fernández, Gabriel Luis

    1989-03-01

    Full Text Available The tricalcium silicate (alite hydration velocity in cements with and without additives is studied in the presence of "Las Carolinas" quarry tuffs from Cienfuegos province, Cuba, the alite hydration velocity is enhanced reaching velocity constants 1.5 higher than in the standard cement.

    Se estudia la velocidad de hidratación del silicato tricálcico (alita presente en el cemento con y sin adiciones, demostrándose que en presencia de tobas del yacimiento "Las Carolinas" en la provincia de Cienfuegos, Cuba, se acelera la velocidad de hidratación de este componente, obteniéndose constantes de velocidad de reacción aproximadamente 1,5 veces mayores que en el cemento patrón.

  18. Stratigraphic relations and hydrologic properties of the Paintbrush Tuff (PTn) hydrologic unit, Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Moyer, T.C.; Geslin, J.K. [Science Applications International Corp., Golden, CO (United States); Flint, L.E. [U.S. Geological Survey, Yucca Mountain Project, Mercury, NV (United States)

    1996-08-01

    Yucca Mountain is being investigated as a potential site for a high- level nuclear waste repository. The intent of this study was to clarify stratigraphic relations within the Paintbrush Tuff (PTn) unit at Yucca Mountain in order to better understand vertical and lateral variations in hydrologic properties as they relate to the lithologic character of these rocks. This report defines informal stratigraphic units within the PTn interval, demonstrates their lateral continuity in the Yucca Mountain region, describes later and vertical variations within them, and characterizes their hydrologic properties and importance to numerical flow and transport models. We present tables summarizing the depth to stratigraphic contacts in cored borehole studies, and unit descriptions and correlations in 10 measured sections.

  19. Stratigraphy, sedimentology and eruptive mechanisms in the tuff cone of El Golfo (Lanzarote, Canary Islands)

    Science.gov (United States)

    Pedrazzi, Dario; Martí, Joan; Geyer, Adelina

    2013-07-01

    The tuff cone of El Golfo on the western coast of Lanzarote (Canary Islands) is a typical hydrovolcanic edifice. Along with other edifices of the same age, it was constructed along a fracture oriented NEE-SWW that coincides with the main structural trend of recent volcanism in this part of the island. We conducted a detailed stratigraphic study of the succession of deposits present in this tuff cone and here interpret them in light of the depositional processes and eruptive dynamics that we were able to infer. The eruptive sequence is represented by a succession of pyroclastic deposits, most of which were emplaced by flow, plus a number of air-fall deposits and ballistic blocks and bombs. We distinguished five different eruptive/depositional stages on the basis of differences in inferred current flow regimes and fragmentation efficiencies represented by the resulting deposits; the different stages may be related to variations in the explosive energy. Eight lithofacies were identified based on sedimentary discontinuities, grain size, components, variations in primary laminations and bedforms. The volcanic edifice was constructed very rapidly around the vent, and this is inferred to have controlled the amount of water that was able to enter the eruption conduit. The sedimentological characteristics of the deposits and the nature and distribution of palagonitic alteration suggest that most of the pyroclastic succession in El Golfo was deposited in a subaerial environment. This type of hydrovolcanic explosive activity is common in the coastal zones of Lanzarote and the other Canary Islands and is one of the main potential hazards that could threaten the human population of this archipelago. Detailed studies of these hydrovolcanic eruptions such as the one we present here can help volcanologists understand the hazards that this type of eruption can generate and provide essential information for undertaking risk assessment in similar volcanic environments.

  20. Fitful and protracted magma assembly leading to a giant eruption, Youngest Toba Tuff, Indonesia

    Science.gov (United States)

    Reid, Mary R; Vazquez, Jorge A.

    2017-01-01

    The paroxysmal eruption of the 74 ka Youngest Toba Tuff (YTT) of northern Sumatra produced an extraordinary 2800 km3 of non-welded to densely welded ignimbrite and co-ignimbrite ash-fall. We report insights into the duration of YTT magma assembly obtained from ion microprobe U-Th and U-Pb dates, including continuous age spectra over >50% of final zircon growth, for pumices and a welded tuff spanning the compositional range of the YTT. A relatively large subpopulation of zircon crystals nucleated before the penultimate caldera-related eruption at 501 ka, but most zircons yielded interior dates 100-300 ka thereafter. Zircon nucleation and growth was likely episodic and from diverse conditions over protracted time intervals of >100 to >500 ka. Final zircon growth is evident as thin rim plateaus that are in Th/U chemical equilibrium with hosts, and that give crystallization ages within tens of ka of eruption. The longevity and chemical characteristics of the YTT zircons, as well as evidence for intermittent zircon isolation and remobilization associated with magma recharge, is especially favored at the cool and wet eutectoid conditions that characterize at least half of the YTT, wherein heat fluxes could dissolve major phases but have only a minor effect on larger zircon crystals. Repeated magma recharge may have contributed to the development of compositional zoning in the YTT but, considered together with limited allanite, quartz, and other mineral dating and geospeedometry, regular perturbations to the magma reservoir over >400 ka did not lead to eruption until 74 ka ago.

  1. Geology, geochemistry and Ar Ar geochronology of the Nangimali ruby deposit, Nanga Parbat Himalaya (Azad Kashmir, Pakistan)

    Science.gov (United States)

    Pêcher, A.; Giuliani, G.; Garnier, V.; Maluski, H.; Kausar, A. B.; Malik, R. H.; Muntaz, H. R.

    2002-12-01

    The Nangimali ruby deposit in the southern part of the Nanga Parbat Himalaya, has been investigated through field work, geochemistry, stable and radiogenic isotopes. It outcrops in the Shontar valley in a large north-vergent syncline consisting of high-grade metamorphic gneisses capped by a metasedimentary series dominated by marbles and amphibolites. The ore-body is stratiform. Ruby is found within 0.1-2 cm thick shear-veinlets and gash veins cutting dolomitic marbles and carbonate-bearing bands. The marbles of the Nangimali Formation display restricted ranges in δ18O (from 23.6 to 27.6‰ relative to SMOW) and in δ13C (from -1.9 to 2.6‰ relative to PDB). Fluid infiltration along the shear-zone in the marble has no effect on the isotopic signatures of the carbonates. Fluids are metamorphic and CO 2 is derived from the decarbonation of marbles. Mass-balance and geochemical analyses suggest that the mobilisation by the fluids of aluminium and chromium in the marbles is sufficient to enable the formation of ruby in the shear-zone. Rubies have been indirectly dated using a stepwise 40Ar- 39Ar laser heating technique on syngenetic phlogopites. The Miocene age records a Neogene cooling in the South of the Nanga Parbat massif and a minimum formation age for ruby of 16 Ma.

  2. 40Ar-39Ar Age Constraints on Volcanism and Tectonism in the Terror Rift of the Ross Sea, Antarctica

    Science.gov (United States)

    2007-01-01

    Volcanic sills and dikes inferred from seismic reflection profiles and geophysical studies of the Ross Sea are thought to be related to the rift basins in the region, and their emplacement to be coeval with extension. However, lack of precise geochronology in the Terror Rift of the Ross Sea region has left these inferred relationships poorly constrained and has hindered neotectonic studies, because of the large temporal gaps between seismic reflectors of known ages. New 40Ar/39Ar geochronology presented here for submarine volcanic rocks provides better age constraints for neotectonic interpretations within the Terror Rift. Several samples from seamounts yielded young ages between 156 ± 21 and 122 ± 26 Ka. These ages support interpretations that extension within the Terror Rift was active at least through the Pleistocene. Three evenly spaced samples from the lowermost 100 m of Franklin Island range in age from 3.28 ± 0.04 to 3.73 ± 0.05 Ma. These age determinations demonstrate that construction of a small volcanic edifice such as Franklin Island took at least several hundred thousand years, and therefore that much larger ones in the Erebus Volcanic Province are likely to have taken considerably longer than previously inferred. This warrants caution in applying a limited number of age determinations to define the absolute ages of events in the Ross Sea region

  3. Modification of stearic acid in Ar and Ar-O2 pulsed DC discharge

    Directory of Open Access Journals (Sweden)

    Euclides Alexandre Bernardelli

    2011-12-01

    Full Text Available Stearic acid (CH3(CH216COOH was treated with Ar and Ar-O2 (10% pulsed DC discharges created by a cathode-anode confined system to elucidate the role of oxygen in plasma cleaning. The treatment time (5 to 120 minutes and plasma gas mixture (Ar and Ar-O2 were varied, and the results showed that the mass variation of stearic acid after Ar-O2 plasma exposure was greater than that of pure Ar plasma treatment. Thus, compared to Ar*, active oxygen species (O and O2, in all states enhance the etching process, regardless of their concentration. During the treatments, a liquid phase developed at the melting temperature of stearic acid, and differential thermal analyses showed that the formation of a liquid phase was associated with the breakage of bonds due to treatment with an Ar or Ar-O2 plasma. After treatment with Ar and Ar-O2 plasmas, the sample surface was significantly modified, especially when Ar-O2 was utilized. The role of oxygen in the treatment process is to break carbonaceous chains by forming oxidized products and/or to act as a barrier again ramification, which accelerates the etching of stearic acid.

  4. Study of the symbiotic star AR Pavonis

    Directory of Open Access Journals (Sweden)

    C. Quiroga

    2001-01-01

    Full Text Available We present a study of the optical spectra and linear polarization of the eclipsing binary AR Pavonis. The optical spectra were obtained between 1990 and 1998, and polarimetric data between 1995 and 1998. From spectroscopic variations along the orbital motion we analized the nature of the system. Polarimetric studies indicate that AR Pav has intrinsic polarization.

  5. Latvijas sakari ar Lietuvu un Igauniju mākslas jomā. 1918-1940

    OpenAIRE

    2016-01-01

    Maģistra darba „Latvijas sakari ar Lietuvu un Igauniju mākslas jomā. 1918-1940” mērķis ir izpētīt Latvijas mākslas sakarus ar Lietuvu un Igauniju laikā no 1918. līdz 1940. gadam, iezīmējot to veidošanos, norisi, kā arī galvenās attīstības tendences. Darbā aplūkota valsts iestāžu un sabiedrisko organizāciju loma Latvijas mākslas sakaru ar Lietuvu un Igauniju veidošanā, kā arī sakari tādās jomās kā literatūra, skatuves māksla, mūzika un tēlotāja māksla. Apskatāmajā laika periodā Latvijas māksla...

  6. MaRIE Undulator & XFEL Systems

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Dinh Cong [Los Alamos National Laboratory; Marksteiner, Quinn R. [Los Alamos National Laboratory; Anisimov, Petr Mikhaylovich [Los Alamos National Laboratory; Buechler, Cynthia Eileen [Los Alamos National Laboratory

    2015-03-23

    The 22 slides in this presentation treat the subject under the following headings: MaRIE XFEL Performance Parameters, Input Electron Beam Parameters, Undulator Design, Genesis Simulations, Risks, and Summary It is concluded that time-dependent Genesis simulations show the MaRIE XFEL can deliver the number of photons within the required bandwidth, provided a number of assumptions are met; the highest risks are associated with the electron beam driving the XFEL undulator; and risks associated with the undulator and/or distributed seeding technique may be evaluated or retired by performing early validation experiments.

  7. M&A Takeover Fever Heats Up

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ China's M&A activity is in turbo-drive. Outward investment is soaring, as many more Chinese companies need and are able to pursue opportunities overseas. Inward investment is accelerating, as foreign firms seek a foothold in the potentially lucrative Chinese market. And domestic consolidation is heating up among the country's fragmented industries due to overcapacity. Now that the Chinese government plans to address policy hurdles affecting M&A and relax foreign currency controls, activity levels should rise across most sectors. But while this may improve market positions and increase synergies for local and foreign investors, credit risks could intensify.

  8. Operation and maintenance in ST-MA

    CERN Document Server

    Nunes, R

    2003-01-01

    This paper will review the Operation & Maintenance (O&M) activities in the ST-MA group, giving an overview of the services provided by the Group as well as the contract activities. As an introduction, a conceptual framework for O&M is proposed in order to better situate the domains of Operation and Maintenance respectively. The ST-MA activities shall be looked at through the three main service axes and special emphasis will be given to the contractual implementation, supervision and follow-up methodology.

  9. M&A information technology best practices

    CERN Document Server

    Roehl-Anderson, Janice M

    2013-01-01

    Add value to your organization via the mergers & acquisitions IT function  As part of Deloitte Consulting, one of the largest mergers and acquisitions (M&A) consulting practice in the world, author Janice Roehl-Anderson reveals in M&A Information Technology Best Practices how companies can effectively and efficiently address the IT aspects of mergers, acquisitions, and divestitures. Filled with best practices for implementing and maintaining systems, this book helps financial and technology executives in every field to add value to their mergers, acquisitions, and/or divestitures via the IT

  10. The Coronae of AR Lac

    CERN Document Server

    Huenemoerder, D P; Drake, J J; Sanz-Forcada, J; Canizares, Claude R.; Drake, Jeremy J.; Huenemoerder, David P.; Sanz-Forcada, Jorge

    2003-01-01

    We observed the coronally active eclipsing binary, AR Lac, with the High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV spectra and photometry were also obtained with the Extreme Ultraviolet Explorer. Significant variability in both X-ray and EUV fluxes were observed, dominated by at least one X-ray flare and one EUV flare. We saw no evidence of primary or secondary eclipses. X-ray flux modulation was largest at high temperature, indicative of flare heating of coronal plasma. Line widths interpreted in terms of Doppler broadening suggest that both binary stellar components are active. From line fluxes obtained from total integrated spectra, we have modeled the emission measure and abundance distributions. A strong maximum was found in the differential emission measure, characterized by peaks at log T = 6.9 and 7.4, together with a weak but significant cooler maximum near log T=6.2, and a moderately str...

  11. U-Pb-Hf zircon study of two mylonitic granite complexes in the Talas-Fergana fault zone, Kyrgyzstan, and Ar-Ar age of deformations along the fault

    Science.gov (United States)

    Konopelko, D.; Seltmann, R.; Apayarov, F.; Belousova, E.; Izokh, A.; Lepekhina, E.

    2013-09-01

    A 2000 km long dextral Talas-Fergana strike-slip fault separates eastern terranes in the Kyrgyz Tien Shan from western terranes. The aim of this study was to constrain an age of dextral shearing in the central part of the fault utilizing Ar-Ar dating of micas. We also carried out a U-Pb-Hf zircon study of two different deformed granitoid complexes in the fault zone from which the micas for Ar dating were separated. Two samples of the oldest deformed Neoproterozoic granitoids in the area of study yielded U-Pb zircon SHRIMP ages 728 ± 11 Ma and 778 ± 11 Ma, characteristic for the Cryogenian Bolshoi Naryn Formation, and zircon grains analyzed for their Lu-Hf isotopic compositions yielded εHf(t) values from -11.43 to -16.73, and their calculated tHfc ages varied from 2.42 to 2.71 Ga. Thus varying Cryogenian ages and noticeable heterogeneity of Meso- to Paleoproterozoic crustal sources was established for mylonitic granites of the Bolshoi Naryn Formation. Two samples of mylonitized pegmatoidal granites of the Kyrgysh Complex yielded identical 206Pb/238U ages of 279 ± 5 Ma corresponding to the main peak of Late-Paleozoic post-collisional magmatism in the Tien Shan (Seltmann et al., 2011), and zircon grains analyzed for their Lu-Hf isotopic compositions yielded εHf(t) values from -11.43 to -16.73, and calculated tHfc ages from 2.42 to 2.71 Ga indicating derivation from a Paleoproterozoic crustal source. Microstructural studies showed that ductile/brittle deformation of pegmatoidal granites of the Kyrgysh Complex occurred at temperatures of 300-400 °C and caused resetting of the K-Ar isotope system of primary muscovite. Deformation of mylonitized granites of the Bolshoi Naryn Formation occurred under high temperature conditions and resulted in protracted growth and recrystallization of micas. The oldest Ar-Ar muscovite age of 241 Ma with a well defined plateau from a pegmatoidal granite of the Kyrgysh Complex is considered as a “minimum” age of dextral motions

  12. Revised error propagation of 40Ar/39Ar data, including covariances

    Science.gov (United States)

    Vermeesch, Pieter

    2015-12-01

    The main advantage of the 40Ar/39Ar method over conventional K-Ar dating is that it does not depend on any absolute abundance or concentration measurements, but only uses the relative ratios between five isotopes of the same element -argon- which can be measured with great precision on a noble gas mass spectrometer. The relative abundances of the argon isotopes are subject to a constant sum constraint, which imposes a covariant structure on the data: the relative amount of any of the five isotopes can always be obtained from that of the other four. Thus, the 40Ar/39Ar method is a classic example of a 'compositional data problem'. In addition to the constant sum constraint, covariances are introduced by a host of other processes, including data acquisition, blank correction, detector calibration, mass fractionation, decay correction, interference correction, atmospheric argon correction, interpolation of the irradiation parameter, and age calculation. The myriad of correlated errors arising during the data reduction are best handled by casting the 40Ar/39Ar data reduction protocol in a matrix form. The completely revised workflow presented in this paper is implemented in a new software platform, Ar-Ar_Redux, which takes raw mass spectrometer data as input and generates accurate 40Ar/39Ar ages and their (co-)variances as output. Ar-Ar_Redux accounts for all sources of analytical uncertainty, including those associated with decay constants and the air ratio. Knowing the covariance matrix of the ages removes the need to consider 'internal' and 'external' uncertainties separately when calculating (weighted) mean ages. Ar-Ar_Redux is built on the same principles as its sibling program in the U-Pb community (U-Pb_Redux), thus improving the intercomparability of the two methods with tangible benefits to the accuracy of the geologic time scale. The program can be downloaded free of charge from

  13. U-Pb, Re-Os and Ar-Ar dating of the Linghou polymetallic deposit, Southeastern China: Implications for metallogenesis of the Qingzhou-Hangzhou metallogenic belt

    Science.gov (United States)

    Tang, Yanwen; Xie, Yuling; Liu, Liang; Lan, Tingguan; Yang, Jianling; Sebastien, Meffre; Yin, Rongchao; Liang, Songsong; Zhou, Limin

    2017-04-01

    The Qingzhou-Hangzhou metallogenic belt (QHMB) in Southeastern China has gained increasingly attention in recent years. However, due to the lack of reliable ages on intrusions and associated deposits in this belt, the tectonic setting and metallogenesis of the QHMB have not been well understood. The Linghou polymetallic deposit in northwestern Zhejiang Province is one of the typical deposits of the QHMB. According to the field relationships, this deposit consists of the early Cu-Au-Ag and the late Pb-Zn-Cu mineralization stages. Molybdenite samples with a mineral assemblage of molybdenite-chalcopyrite-pyrite ± quartz are collected from the copper mining tunnel near the Cu-Au-Ag ore bodies. Six molybdenite samples give the Re-Os model ages varying from 160.3 to 164.1 Ma and yield a mean age of 162.2 ± 1.4 Ma for the Cu-Au-Ag mineralization. Hydrothermal muscovite gives a well-defined Ar-Ar isochron age of 160.2 ± 1.1 Ma for the Pb-Zn-Cu mineralization. Three phases of granodioritic porphyry have been distinguished in this deposit, and LA-ICP-MS zircon U-Pb dating shows that they have formed at 158.8 ± 2.4 Ma, 158.3 ± 1.9 Ma and 160.6 ± 2.1 Ma, comparable to the obtained ages of the Cu-Au-Ag and Pb-Zn-Cu mineralization. Therefore, these intrusive rocks have a close temporal and spatial relationship with the Cu-Au-Ag and Pb-Zn-Cu ore bodies. The presences of skarn minerals (e.g., garnet) and vein-type ores, together with the previous fluid inclusion and H-O-C-S-Pb isotopic data, clearly indicate that the Cu-Au-Ag and Pb-Zn-Cu mineralization are genetically related to these granodiorite porphyries. This conclusion excludes the possibility that this deposit is of ;SEDEX; type and formed in a sag basin of continental rifts setting as previously proposed. Instead, it is proposed that the Linghou polymetallic and other similar deposits in the QHMB, such as the 150-160 Ma Yongping porphyry-skarn Cu-Mo, Dongxiang porphyry? Cu, Shuikoushan/Kangjiawang skarn Pb

  14. Mineralogy, origin and commercial value of the zeolite-rich tuffs in the Petrota-Pentalofos area, Evros County, Greece

    Directory of Open Access Journals (Sweden)

    Walsh, J. N.

    1998-04-01

    Full Text Available The zeolite-rich tuffs of the Petrota-Pentalofos area were deposited in the Arrestees Basin during the Eocene. They are up to 100 m thick and extend more than 15 Km in a long axis. Most of the outcrops consist of frequent alternations of very fine grained tuff with pumice and lapel tuffs, the latter containing detrital fragments of the Mesozoic substrate of the basin. X-ray Diffraction, Scanning Electron Microscopy and light microscopy analysis on quarry and borehole samples has shown that the tuffs are composed mainly of clinoptilolite and minor cristobalite, with a small proportion of detrital constituents (quartz, mica-schist and pyrogenic crystals (feldspars, quartz, biotite. Minor amounts of mordenite randomly occur in some of the northern outcrops, closer to the occurrences of lava. ICP-AES chemical analysis of the tuffs gives evidence that the original magmas were of quartz-latite composition. The tuffs rest on pre-Cenozoic metamorphic basement and pass gradationally upwards into sandstone and limestone. Evidence is given for deposition of the tuffs in a supra to infra-littoral environment. The zeolitic tuffs originated as epiclastic volcanic sediments, transported by water from the source of the eruption. The transformation of the volcanic glass of the tuffs to zeolite and cristobalite has taken place by meteoric waters in an open hydrological system existed during the Tertiary. The zeolitic rocks are currently being exploited as an animal feed supplement.Las tobas ricas en cebollitas del área de Petrota-Pentalofos se depositaron en la cuenca de Orejitas durante el Doceno. Alcanzan 100 m de potencia y superan los 15 km de extensión longitudinal. La mayoría de los afloramientos consisten en alternancias de toba de grano muy fino y toba de pómez y lapilli con fragmentos detritos del sustrato Mesozoico de la cuenca. Análisis por difamación de rayos X, microscopía electrónica de barrido y microscopía óptica en muestras de mano y de

  15. Morphological modifications of the Kerguelen Islands (South Indian Ocean) in response to Neogene climate change: evidence from 40Ar/39Ar and (U-Th)/He thermochronology

    Science.gov (United States)

    Ahadi, Floriane; Delpech, Guillaume; Gautheron, Cécile; Nomade, Sébastien; Pinna-jamme, Rosella; Ponthus, Léandre; Guillaume, Damien

    2016-04-01

    The processes driving erosion in geodynamic contexts in which regional tectonics is of minor importance, such as in oceanic islands, can be seen as a combination of positive/negative retroactions between climate change, isostasy or dynamic topography. The Kerguelen Islands (48-50° S, 68.5-70.5° E) are of particular interest to understand the impact of Cenozoïc climatic variations on the long-term geomorphological evolution of emerged reliefs at mid-latitudes. The Kerguelen Islands (6700 km2) are the emerged part of the vast Kerguelen oceanic plateau and reach a maximum height of 1852m asl. The archipelago is mostly made up of Oligocene basaltic traps (≈25 Ma) up to 1000m asl that are cross-cut by a dense network of large and deep valleys. The impact of glacial erosion during the last Quaternary glaciations on the landscape morphology is attested by the occurrence of U-shaped valleys, abundant moraines, erratic blocs and glacial lakes, as well as remnants of glaciers. Numerous plutonic complexes of various age (25-4.5 Ma) locally intrude theses traps and cover about 15% of the main island's surface; the largest being located in the Rallier du Baty peninsula (800 km2). This plutonic complex is mainly constituted of syenites with minor occurrence of gabbros and monzonites. The southern part of this complex has a laccolith structure with satellites plutons and formed between 13.7 and 8.0 Ma. The cooling history of syenites from the Rallier du Baty plutonic complex was investigated in order to identify one or several denudation periods and to understand the potential role of climate change on the geomorphological evolution of the islands since the Oligocene. We conducted the first thermochronological study on the Kerguelen Islands using the biotite 40Ar/39Ar thermochronometer and the apatite (U-Th)/He thermochronometer (AHe). The 40Ar/39Ar ages range from 9.44 ± 0.13 Ma to 13.84 ± 0.07 Ma for the various parts of the southern complex. These ages are identical to

  16. [sup 40]Ar/[sup 39]Ar analysis of supergene jarosite and alunite: Implications to the paleoweathering history of the western USA and West Africa

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcelos, P.M.; Brimhall, G.H. (Univ. of California, Berkeley, CA (United States)); Becker, T.A.; Renne, P.R. (Institute of Human Origins, Berkeley, CA (United States))

    1994-01-01

    Supergene alunite (KAl[sub 3](SO[sub 4])[sub 2](OH)[sub 6]) and jarosite (KFe[sub 3](SO[sub 4])[sub 2](OH)[sub 6]) are often precipitated during the oxidation of sulfide-bearing rocks by meteoric solutions. Dating of these phases by the [sup 40]Ar/[sup 39]Ar method allows timing of the progression of the oxidation front during chemical weathering. Fine-scale laser-heating [sup 40]Ar/[sup 39]Ar dating of hypogene alunite and supergene jarosites allows to precisely and accurately time hydrothermal alteration and subsequent supergene oxidation in Goldfield, Nevada. The results indicate that pervasive weathering occurred in the western USA during the Late Miocene ([approximately] 10 Ma ago). Similar application of this technique to the study of weathering and laterite formation in West Africa indicates that the last pervasive oxidation event recorded in the weathering profile in this area also occurred in the Miocene ([approximately] 13 Ma ago). The occurrence of a pervasive Mid to Late Miocene oxidation event recorded in these weathering profiles in the western USA and Africa, and also previously measured in Brazil and Chile, indicates that climatic conditions at that time were conducive to worldwide development of deep weathering sequences. Subsequent weathering processes have not been as pervasive as the late Miocene event, indicating a general climatic transition to cooler, drier climates in most of the areas studied. The results indicate that deep weathering profiles reflect past climatic conditions and may not be directly linked to the present climates.

  17. 40Ar/39Ar Ages of Carbonaceous Xenoliths in 2 HED Meteorites

    Science.gov (United States)

    Turrin, B.; Lindsay, F. N.; Park, J.; Herzog, G. F.; Delaney, J. S.; Swisher, C. C., III; Johnson, J.; Zolensky, M.

    2016-01-01

    The generally young K/Ar and 40Ar/39Ar ages of CM chondrites made us wonder whether carbonaceous xenoliths (CMX) entombed in Howardite–Eucrite–Diogenite (HED) meteorites might retain more radiogenic 40Ar than do ‘free-range’ CM-chondrites. To find out, we selected two HED breccias with carbonaceous inclusions in order to compare the 40Ar/39Ar release patterns and ages of the inclusions with those of nearby HED material. Carbonaceous inclusions (CMXs) in two HED meteorites lost a greater fraction of radiogenic 40Ar than did surrounding host material, but a smaller fraction of it than did free-range CM-chondrites such as Murchison or more heavily altered ones. Importantly, however, the siting of the CMXs in HED matrix did not prevent the 40Ar loss of about 40 percent of the radiogenic 40Ar, even from phases that degas at high laboratory temperatures. We infer that carbonaceous asteroids with perihelia of 1 astronomical unit probably experience losses of at least this size. The usefulness of 40Ar/39Ar dating for samples returned from C-type asteroids may hinge, therefore, on identifying and analyzing separately small quantities of the most retentive phases of carbonaceous chondrites.

  18. Flow direction indicators in lithic-rich, basal ground layers in western exposures of the Miocene Peach Spring Tuff, California

    Science.gov (United States)

    Buesch, D.

    2012-12-01

    Lithic-rich, basal ground layer (BGL) deposits occur in three western exposures of the 18.7 Ma Peach Spring Tuff (PST), and structures indicate directions of transport in the pyroclastic flow. Locations include (1) Kane Wash (Newberry Mountains), (2) "West Gem" (Daggett Ridge), and (3) Alvord Mountain area. These locations are 190-225 km from the PST source in the Silver Creek Caldera, southwest Black Mountain, Arizona (Pearthree and others, 2009); however, ~50 km is from extension across the Lower Colorado River Extensional Corridor. In each location, many lithic clasts were locally derived. Lithic-rich horizons in Kane Wash exposures of the PST were described by Buesch (1991). Total thickness of valley-filling ignimbrite ranges from stream sandstone. Thickness of 8 individual lithic-rich horizons (a type of BGL) range from 4-300 cm with lithic clasts 2-472 cm. Clast size-grading, imbrication, and elongation indicate directions of flow. Each horizon was attributed to (1) incorporation and concentration of local clasts into a boundary layer of the pyroclastic flow as it traversed topography, (2) decoupling of a lithic-rich layer from the over riding flow, (3) independent movement of a lithic-rich flow along local topography (180°±30°) with the ash-rich pyroclastic flow direction probably independent of local topography, but along the main paleovalley (245°±20°), and (4) introduction and westward deflection of lithic-rich flows into the main, valley-filling, pyroclastic flow. Multiple lithic-rich horizons indicate repeated, locally developed boundary layers from the body of the pyroclastic flow throughout the flow history. In the West Gem exposure, the PST is 5.3 m thick and was deposited on alluvial sandstone. The 60-cm thick, lithic-rich, BGL contains lithic clasts rip-up flap from the BGL folded into the lower part of the ignimbrite, indicate a general flow toward the west-southwest. In the Alvord Mountain area, 13 PST exposures occur for 9 km around the

  19. K—Ar Geochronology and Evolution of Cenozoic Volcanic Rocks in Eastrn China

    Institute of Scientific and Technical Information of China (English)

    王慧芬; 杨学昌; 等

    1989-01-01

    Cenozoic volcanic rocks widespread in eastern China constitute an important part of the circum-Pacific volcanic belt.This paper presents more than 150K-Ar dates and a great deal of petrochemical analysis data from the Cenozoic volcanic rocks distributed in Tengchong,China's southeast coast,Shandong,Hebei,Nei Monggol and Northeast China.An integrated study shows that ubiquitous but uneven volcanic activities prevailed from the Eogene to the Holocene,characterized as being multi-eqisodic and multicycled.For example,in the Paleocene(67-58Ma),Eocene(57-37.5Ma),Miocene(22-18,16-19Ma),Pliocene(8-3Ma),and Early Pleistocene-Middle Pleistocene(1.2-0.5Ma) there were upsurges of volcanism,while in the Oligocene there was a repose period.In space,the older Eogene volcanic rocks are distributed within the region or in the central part of the NE-NNE-striking fault depression,while the younger Neogene and Quaternary volcanic rocks are distributed in the eastern and western parts.Petrologically,they belong essentially to tholeiite-series and alkali-series basalts,with alkalinity in the rocks increasing from old to youg.The above regularities are controlled by both global plate movement and regional inherent tectonic pattern.

  20. Salatoimikud : ma tahan uskuda / Mart Rummo

    Index Scriptorium Estoniae

    Rummo, Mart

    2008-01-01

    USA sarjale "The X-Files" põhinev teine järjefilm "Salatoimikud: Ma tahan uskuda" ("The X-Files: I Want to Believe") : režissöör Chris Carter : peaosades David Duchovny, Gillian Anderson : Ameerika Ühendriigid - Kanada 2008

  1. Maíz I (Zea mays)

    OpenAIRE

    Sánchez Ortega, Iván; Pérez-Urria Carril, Elena

    2014-01-01

    El maíz es uno de los cultivos básicos más importantes y extendidos en todo el mundo. Constituye una de las fuentes principales de alimento de millones depersonas, sobre todo en América y Asia. Se trata de una de las primeras plantas que se domesticaron y se difundieron por todo el mundo.

  2. 76 FR 36953 - Massachusetts Disaster #MA-00036

    Science.gov (United States)

    2011-06-23

    ... From the Federal Register Online via the Government Publishing Office ] SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00036 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for the State...

  3. 77 FR 76585 - Massachusetts Disaster # MA-00052

    Science.gov (United States)

    2012-12-28

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00052 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth...

  4. 77 FR 66214 - Massachusetts Disaster # MA-00049

    Science.gov (United States)

    2012-11-02

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00049 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth...

  5. 76 FR 56859 - Massachusetts Disaster #MA-00039

    Science.gov (United States)

    2011-09-14

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00039 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for the Commonwealth...

  6. 75 FR 45681 - Massachusetts Disaster #MA-00028.

    Science.gov (United States)

    2010-08-03

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00028. AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth...

  7. 75 FR 22874 - Massachusetts Disaster # MA-00027

    Science.gov (United States)

    2010-04-30

    ... From the Federal Register Online via the Government Publishing Office ] SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00027 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance...

  8. 76 FR 56853 - Massachusetts Disaster #MA-00040

    Science.gov (United States)

    2011-09-14

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00040 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance...

  9. Teacher MA Attainment Rates, 1970-2000

    Science.gov (United States)

    Larsen, S. Eric

    2010-01-01

    The share of female teachers in the U.S. with an MA more than doubled between 1970 and 2000. This increase is puzzling, as it is much larger than that of other college-educated women, and it occurred over a period of declining teacher aptitude. I estimate the contribution of changes in teacher demographic characteristics, increases in the returns…

  10. 76 FR 65557 - Massachusetts Disaster #MA-00043

    Science.gov (United States)

    2011-10-21

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00043 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth...

  11. 75 FR 17177 - Massachusetts Disaster #MA-00025

    Science.gov (United States)

    2010-04-05

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00025 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for the State...

  12. 76 FR 36952 - Massachusetts Disaster #MA-00037

    Science.gov (United States)

    2011-06-23

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00037 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance...

  13. 77 FR 76584 - Massachusetts Disaster # MA-00051

    Science.gov (United States)

    2012-12-28

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00051 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth...

  14. 77 FR 2600 - Massachusetts Disaster #MA-00046

    Science.gov (United States)

    2012-01-18

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00046 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance...

  15. 76 FR 13697 - Massachusetts Disaster #MA-00032

    Science.gov (United States)

    2011-03-14

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Massachusetts Disaster MA-00032 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance...

  16. 78 FR 2708 - Massachusetts Disaster # MA-00050

    Science.gov (United States)

    2013-01-14

    ... ADMINISTRATION Massachusetts Disaster MA-00050 AGENCY: U.S. Small Business Administration. ACTION: Notice... completed loan applications to: U.S. Small Business Administration, Processing and Disbursement Center... Disaster Assistance, U.S. Small Business Administration, 409 3rd Street SW., Suite 6050, Washington,...

  17. 78 FR 25336 - Massachusetts Disaster #MA-00054

    Science.gov (United States)

    2013-04-30

    ... ADMINISTRATION Massachusetts Disaster MA-00054 AGENCY: U.S. Small Business Administration. ACTION: Notice...: 01/21/2014. ADDRESSES: Submit completed loan applications to: U.S. Small Business Administration... CONTACT: A. Escobar, Office of Disaster Assistance, U.S. Small Business Administration, 409 3rd Street...

  18. Fabrication technology for ODS Alloy MA957

    Energy Technology Data Exchange (ETDEWEB)

    ML Hamilton; DS Gelles; RJ Lobsinger; MM Paxton; WF Brown

    2000-03-16

    A successful fabrication schedule has been developed at Carpenter Technology Corporation for the production of MA957 fuel and blanket cladding. Difficulties with gun drilling, plug drawing and recrystallization were overcome to produce a pilot lot of tubing. This report documents the fabrication efforts of two qualified vendors and the support studies performed at WHC to develop the fabrication-schedule.

  19. Vaccines against stimulants: cocaine and MA.

    Science.gov (United States)

    Kosten, Thomas; Domingo, Coreen; Orson, Frank; Kinsey, Berma

    2014-02-01

    While the worldwide prevalence of cocaine use remains significant, medications, or small molecule approaches, to treat drug addictions have met with limited success. Anti-addiction vaccines, on the other hand, have demonstrated great potential for treating drug abuse using a distinctly different mechanism of eliciting an antibody response that blocks the pharmacological effects of drugs. We provide a review of vaccine-based approaches to treating stimulant addictions; specifically and cocaine addictions. This selective review article focuses on the one cocaine vaccine that has been into clinical trials and presents new data related to pre-clinical development of a methamphetamine (MA) vaccine. We also review the mechanism of action for vaccine induced antibodies to abused drugs, which involves kinetic slowing of brain entry as well as simple blocking properties. We present pre-clinical innovations for MA vaccines including hapten design, linkage to carrier proteins and new adjuvants beyond alum. We provide some new information on hapten structures and linkers and variations in protein carriers. We consider a carrier, outer membrance polysaccharide coat protein (OMPC), that provides some self-adjuvant through lipopolysaccharide components and provide new results with a monophosopholipid adjuvant for the more standard carrier proteins with cocaine and MA. The review then covers the clinical trials with the cocaine vaccine TA-CD. The clinical prospects for advances in this field over the next few years include a multi-site cocaine vaccine clinical trial to be reported in 2013 and phase 1 clinical trials of a MA vaccine in 2014.

  20. Salatoimikud : ma tahan uskuda / Mart Rummo

    Index Scriptorium Estoniae

    Rummo, Mart

    2008-01-01

    USA sarjale "The X-Files" põhinev teine järjefilm "Salatoimikud: Ma tahan uskuda" ("The X-Files: I Want to Believe") : režissöör Chris Carter : peaosades David Duchovny, Gillian Anderson : Ameerika Ühendriigid - Kanada 2008

  1. Global Plate Driving Forces at 50Ma

    Science.gov (United States)

    Butterworth, N. P.; Quevedo, L. E.; Müller, R. D.

    2011-12-01

    We apply a novel workflow utilising the BEM-Earth geodynamic software to analyse the global coupled plate-mantle dynamics at 50 Ma. A subduction history model based on kinematic data going as far back as 80 Ma was developed using the GPlates software. Advection of the plates into the mantle takes into account the absolute plate motions and lithospheric thickness derived from its age to produce an estimated density heterogeneity initial model condition in the upper mantle. The resulting global model consists of regions of a mantle viscosity and density structure that is post-processed to ensure smooth non-overlapping 3D surfaces. BEM-Earth is then free to evolve the model toward the 50 Ma solution. The evolution of the model is driven by self-consistent buoyancy driven mantle dynamics. We use the model velocity output to quantify changes in forces driving the plates before and after 50 Ma. We analyse the rapid change in plate motion of India, Africa and plates in the Pacific Ocean basin by considering slab-pull, ridge-push and mantle drag/suction forces that naturally result from such top-down driven mantle flow. We compare the results with plate kinematic reconstructions and other geological observations.

  2. 77 FR 33263 - Massachusetts Disaster #MA-00048

    Science.gov (United States)

    2012-06-05

    ... ADMINISTRATION Massachusetts Disaster MA-00048 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth of Massachusetts dated 05/29/2012. Incident: Lake Williams Condominium Complex Fire. Incident Period:...

  3. 76 FR 30748 - Massachusetts Disaster #MA-00033

    Science.gov (United States)

    2011-05-26

    ... ADMINISTRATION Massachusetts Disaster MA-00033 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth of Massachusetts dated 05/19/2011. Incident: Apartment Building Fire. Incident Period: 04/30/2011. Effective...

  4. 75 FR 79064 - Massachusetts Disaster #MA-00030

    Science.gov (United States)

    2010-12-17

    ... ADMINISTRATION Massachusetts Disaster MA-00030 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth of Massachusetts dated 12/07/2010. Incident: Apartment complex fire. Incident Period: 11/21/2010. Effective...

  5. 76 FR 40766 - Massachusetts Disaster #MA-00035

    Science.gov (United States)

    2011-07-11

    ... ADMINISTRATION Massachusetts Disaster MA-00035 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth of Massachusetts dated 06/29/2011. Incident: Johnsonia Apartment Building Fire Incident Period:...

  6. 77 FR 12350 - Massachusetts Disaster #MA-00047

    Science.gov (United States)

    2012-02-29

    ... ADMINISTRATION Massachusetts Disaster MA-00047 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth of Massachusetts dated 02/21/2012. Incident: Brookline Apartment Building Fire. Incident Period:...

  7. 75 FR 3764 - Massachusetts Disaster # MA-00024

    Science.gov (United States)

    2010-01-22

    ... ADMINISTRATION Massachusetts Disaster MA-00024 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the Commonwealth of Massachusetts dated 01/15/2010. Incident: Mystic Side Estates Apartment Building Fire. Incident Period:...

  8. Paleomagnetic secular variation study of Ar-Ar dated lavas flows from Tacambaro area (Central Mexico): Possible evidence of Intra-Jaramillo geomagnetic excursion in volcanic rocks

    Science.gov (United States)

    Peña, Rafael Maciel; Goguitchaichvili, Avto; Guilbaud, Marie-Noëlle; Martínez, Vicente Carlos Ruiz; Rathert, Manuel Calvo; Siebe, Claus; Reyes, Bertha Aguilar; Morales, Juan

    2014-04-01

    More than 350 oriented paleomagnetic cores were obtained for rock-magnetic and paleomagnetic analysis from radiometrically dated (40Ar-39Ar) magmatic rocks occurring in the southern segment (Jorullo and Tacámbaro areas) of the Michoacán-Guanajuato Volcanic Field in the Trans-Mexican Volcanic Belt. Most of the lavas (37) stem from monogenetic volcanoes dated at less than 4 Ma. Two additional sites were sampled from the plutonic basement dated at 33-30 Ma. Primary remanences carried by low-Ti titanomagnetites allowed to determining 34 reliable site-mean directions of mostly normal (27) but also reversed (7) polarities. The mean directions of these two populations are antipodal, and suggest neither major vertical-axis rotations with respect to the North America craton nor tilting in the region for the last 4 Ma (rotation and flattening of the inclination parameters being less than -5.9 ± 3.8 and 0.1 ± 3.9, respectively). The corresponding paleomagnetic pole obtained for Pliocene-Pleistocene times is PLAT = 83.4°, PLON = 2.4° (N = 32, A95 = 2.7°). Virtual geomagnetic poles also contribute to the time averaged field global database and to the paleosecular variation (PSV) investigations at low latitudes from lavas for the last 5 Ma, showing a geomagnetic dispersion value that is in agreement with available PSV models. When comparing the magnetic polarities and corresponding radiometric ages of the studied sites with the Cenozoic geomagnetic polarity time scale (GPTS), a good correlation is observable. This finding underscores the suitability of data obtained on lavas in Central Mexico for contributing to the GPTS. Furthermore, the detection of short-lived geomagnetic features seems possible, since the possible evidence of Intra-Jaramillo geomagnetic excursion could be documented for the first time in these volcanic rocks.

  9. The L3-6 chondritic regolith breccia Northwest Africa (NWA) 869: (I) Petrology, chemistry, oxygen isotopes, and Ar-Ar age determinations

    Science.gov (United States)

    Metzler, Knut; Bischoff, Addi; Greenwood, Richard C.; Palme, Herbert; Gellissen, Marko; Hopp, Jens; Franchi, Ian A.; Trieloff, Mario

    2011-05-01

    Northwest Africa (NWA) 869 consists of thousands of individual stones with an estimated total weight of about 7 metric tons. It is an L3-6 chondrite and probably represents the largest sample of the rare regolith breccias from the L-chondrite asteroid. It contains unequilibrated and equilibrated chondrite clasts, some of which display shock-darkening. Impact melt rocks (IMRs), both clast-free and clast-poor, are strongly depleted in Fe,Ni metal, and sulfides. An unequilibrated microbreccia, two different light inclusions and two different SiO2-bearing objects were found. Although the matrix of this breccia appears partly clastic, it is not a simple mixture of fine-grained debris formed from the above lithologies, but mainly represents an additional specific lithology of low petrologic type. We speculate that this material stems from a region of the parent body that was only weakly consolidated. One IMR clast and one SiO2-bearing object show Δ17O values similar to bulk NWA 869, suggesting that both are related to the host rock. In contrast, one light inclusion and one IMR clast appear to be unrelated to NWA 869, suggesting that the IMR clast is contaminated with impactor material. 40Ar-39Ar analyses of a type 4 chondrite clast yield a plateau age of 4402 ± 7 Ma, which is interpreted to be the result of impact heating. Other impact events are recorded by an IMR clast at 1790 ± 36 Ma and a shock-darkened clast at 2216 ± 40 Ma, demonstrating that NWA 869 escaped major reset in the course of the event at approximately 470 Ma that affected many L-chondrites.

  10. 40Ar/39Ar dating, geochemistry, and isotopic analyses of the quaternary Chichinautzin volcanic field, south of Mexico City: implications for timing, eruption rate, and distribution of volcanism

    Science.gov (United States)

    Arce, J. L.; Layer, P. W.; Lassiter, J. C.; Benowitz, J. A.; Macías, J. L.; Ramírez-Espinosa, J.

    2013-12-01

    Monogenetic structures located at the southern and western ends of the Chichinautzin volcanic field (Trans-Mexican Volcanic Belt, Central Mexico) yield 40Ar/39Ar ages ranging from 1.2 Ma in the western portion of the field to 1.0-0.09 Ma in the southern portion, all of which are older than the volcanic field. These new ages indicate: (1) an eruption rate of 0.47 km3/kyr, which is much lower than the 11.7 km3/kyr previously estimated; (2) that the Chichinautzin magmatism coexisted with the Zempoala (0.7 Ma) and La Corona (1.0 Ma) polygenetic volcanoes on the southern edge of Las Cruces Volcanic Range (Trans-Mexican Volcanic Belt); and confirm (3) that the drainage system between the Mexico and Cuernavaca basins was closed during early Pleistocene forming the Texcoco Lake. Whole-rock chemistry and Sr, Nd, and Pb isotopic data indicate heterogeneous magmatism throughout the history of Chichinautzin activity that likely reflects variable degrees of slab and sediment contributions to the mantle wedge, fractional crystallization, and crustal assimilation. Even with the revised duration of volcanism within the Chichinautzin Volcanic Field, its eruption rate is higher than most other volcanic fields of the Trans-Mexican Volcanic Belt and is comparable only to the Tacámbaro-Puruaran area in the Michoacán-Guanajuato Volcanic Field to the west. These variations in eruption rates among different volcanic fields may reflect a combination of variable subduction rates of the Rivera and Cocos plates along the Middle America Trench, as well as different distances from the trench, variations in the depth with respect to the subducted slab, or the upper plate characteristics.

  11. 46 CFR 308.550 - Certificate, Form MA-320.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 8 2010-10-01 2010-10-01 false Certificate, Form MA-320. 308.550 Section 308.550... Risk Cargo Insurance Iv-General § 308.550 Certificate, Form MA-320. Wherever any provision of this... execute a certificate on Form MA-320-A for an individual, on Form MA-320-B for a partnership, or on...

  12. 42 CFR 422.4 - Types of MA plans.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Types of MA plans. 422.4 Section 422.4 Public...) MEDICARE PROGRAM MEDICARE ADVANTAGE PROGRAM General Provisions § 422.4 Types of MA plans. (a) General rule. An MA plan may be a coordinated care plan, a combination of an MA MSA plan and a contribution into...

  13. 用于早前寒武纪岩石Ar-Ar法定年的K-Ar法年龄国家二级标准物质——ZMT04白云母的定值结果%The certified results of ZMT04 muscovite reference material utilized for 40Ar/39Ar isotopic geochronological research on Early precambrian rocks in China.

    Institute of Scientific and Technical Information of China (English)

    桑海清; 王非; 龚俊峰; 周晶

    2013-01-01

    为了满足Ar-Ar快中子活化法定年的需要,经过十几年的连续测定与检验,一个用于早前寒武纪矿物定年的K-Ar法年龄标准物质—ZMT04白云母已被研制成功.它采自内蒙古自治区卓资县天皮山.40Ar-39 Ar定年结果表明,40Ar*在矿物晶格中保存均匀稳定,年龄谱平坦,39 Ar析出量为99.1%,40Ar/39 Ar坪年龄为1823±15Ma,说明该白云母结晶以来未受热扰动,40K-40Ar*同位素计时体系封闭良好.40Ar/39Ar等时年龄为1824±15Ma,与坪年龄一致,代表了伟晶岩中白云母的结晶时间.(40Ar/36Ar)0初始值为288±16,此值与(40Ar/36Ar)a大气氩丰度比(295.5±0.5)处于同一范围,表明该白云母不含过剩氩.根据国家一级标准物质技术规范(JJG 1006-1994)的有关规定,对ZMT04白云母进行了一系列分析检验.均匀性检验结果表明,在0.05显著性水平下,K和40Ar*的F分布值小于F临界值,证明该白云母是均匀的.t检验法和稳定性检验与分析表明,ZMT04白云母完全满足国家一级标准物质技术规范对稳定性的要求.国内8个实验室参加了ZMT04白云母K和40 Ar*含量的定值分析,正态性和等精度检验结果显示,全部定值分析数据服从正态分布并具等精度.当置信概率为0.95时,该白云母40Ar*和K含量的相对标准偏差都小于1%.经过严格计算最后获得40 Ar*和K含量及年龄的认定值和不确定度分别为:40Ar*=4.449±0.060×10-8mol/g(2σ),K=8.28±0.04%(2σ),K-Ar年龄=1804±21Ma(2σ).此标准物质纯度达100%,总重量为1080g,缩分为196瓶,每瓶5.51g.可供我国K-Ar和Ar-Ar法年代学实验室至少使用54年.此标准物质于2009年3月4日被国家质量监督检验检疫总局审核批准为国家二级标准物质(见国质检量函[2009] 89号文),国家质检总局认定的ZMT04白云母制造计量器具许可证编号为GBW (E) 040019.%In the 40Ar-39Ar dating technique,the irradiation with a high integrated neutron dose is very

  14. Reassessment and new chronological data (Ar/Ar, Rb/Sr and Sm/Nd) from the Pelotas batholith, Rio Grande do Sul state: petrogenesis implications and reactivation age of the shear zones; Reavaliacao e novos dados geocronologicos (Ar/Ar, Rb/Sr e Sm/Nd) do batolito Pelotas, no Rio Grande do Sul: implicacoes petrogeneticas e idade de reativacao das zonas de cisalhamento

    Energy Technology Data Exchange (ETDEWEB)

    Philipp, Ruy Paulo; Chemale Junior, Farid [Rio Grande do Sul Univ., Porto Alegre (Brazil). Inst. de Geociencias. Centro de Estudos em Petrologia e Geoquimica]. E-mail: ruy.philipp@ufrgs.br; Machado, Romulo [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica

    2003-08-15

    SHRIMP and conventional U-Pb and Pb/Pb evaporation dating of zircon from the Pelotas batholith indicates one group of ages between 625 and 633 Ma for the Pinheiro Machado suite, and another group between 575 and 599 Ma for the Viamao, Encruzilhada do Sul and Dom Feliciano suites. Sr 87/Sr 86 isotopic ratios of 0.7060-0.7016, epsilon{sub Nd} values of -5 and -10, and Nd T{sub DM} model ages between 2200 and 1600 Ma suggest that the suites were mainly derived by melting of Paleoproterozoic crust formed during the Tranzamazonic Cycle. Basic magmatism and heterogeneous magma mixing in the Pinheiro Machado, Viamao, Encruzilhada do Sul and Dom Feliciano suite and the Piquiri alkaline magmatism, with Pb/Pb zircon evaporation ages between 610 and 615 Ma, suggest that a mantle component also contributed to the formation of the Pelotas batholith. 39 Ar/40 Ar determinations in micas from mylonitic rocks of high- and low-dip shear zones showed ages between 540 and 530 Ma, which show that important tectonic events occurred after the emplacement of the batholith. This event developed in a transpressive regime, was responsible for the reactivation of older shear zones, and was probably contemporaneous with the development of the Camaqua basin. (author)

  15. Ielu sociālais darbs ar bezpajumtniekiem Rīgā

    OpenAIRE

    Vintiša, Inese

    2017-01-01

    Maģistra darbs “Ielu sociālais darbs ar bezpajumtniekiem Rīgā “ veltīts ielu sociālā darba aktualitātei Rīgā, jo bezpajumtnieku skaits nemazinās pēc sociāli ekonomiskās krīzes. Maģistra darba mērķis ir izpētīt ielu sociālo darbu ar bezpajumtniekiem Rīgā un izstrādāt priekšlikumus ielu sociālā darba pilnveidei. Autore veica teorētisko un empīrisko izpēti par ielu sociālo darbu ar bezpajumtniekiem Rīgā. Teorētiskajā ietvarā tika izmantota sociālā darba ekoloģiskā pieeja, bezpajumtnieku sociāl...

  16. Mañana remisión de V. crepúsculo de la mañana.

    OpenAIRE

    2011-01-01

    [ES] Definición del término Mañana remisión de V. crepúsculo de la mañana. en el diccionario Dicter. [EN] Definition of the word Mañana remisión de V. crepúsculo de la mañana. in the dictionary Dicter.

  17. Green-tuff landslide areas are beneficial for rice nutrition in Japan

    Directory of Open Access Journals (Sweden)

    Kazue Tazaki

    2006-12-01

    Full Text Available Japanese Islands are covered with weathered volcanic rocks and soils. Terraced rice field are located in green-tuff areas which are very fertile but where landslides occur associated to strong earthquakes. The Xray diffraction and X-ray fluorescence analyses of the soils in landslide area identified predominant smectite and Mg, Al, Si, K, Ti, Mn and Fe are main components. The rice leaf showed that S, Cl, K and Ca play important roles for nutrients in the area. Drainpipe systems have set up in the green- tuff areas to reduce the risks of landslides. Reddish brown microbial mats inhabited bacteria and diatom in the drainpipe outlets. The microbial mats are rich in Fe and PO4(3-. The iron bacteria in the ground water have a high metabolic rate suggesting that the weathering materials were produced by not only physical and chemical influence but also by microorganism. Many microorganisms attach to mineral surfaces and show their high impact in the water mineral chemistry in the landslide area. Bacteria in the green-tuff over landslide area play important roles for sustainable agriculture including rice nutrition.As Ilhas Japonesas são cobertas de rochas e solos vulcânicos intemperizados. Terraços de campos de arroz estão comumente localizados em áreas de tufos verdes, as quais são férteis, mas estão geralmente sujeitas a trágicos deslizamentos de terra associados a grandes terremotos. As análises dos solos por difração e fluorescência de raios-X em áreas de deslizamento identificam a predominância de esmectitas, cujos componentes principais são Mg, Al, Si, K, Ca, Ti, Mn, e Fe como principais componentes. A palha de arroz mostrou que S, Cl, K, e Ca têm importantes papéis para a nutrição dos solos dessa área. Sistemas de tubos de deslizamento foram instalados nestas áreas detufos verdes de forma a reduzir os riscos de deslizamentos. Nas saídas dos tubos de descarga se formou uma esteira de algas microbianas marrom avermelhadas

  18. Confort 15 model of conduit dynamics: applications to Pantelleria Green Tuff and Etna 122 BC eruptions

    Science.gov (United States)

    Campagnola, S.; Romano, C.; Mastin, L. G.; Vona, A.

    2016-06-01

    Numerical simulations are useful tools to illustrate how flow parameters and physical processes may affect eruption dynamics of volcanoes. In this paper, we present an updated version of the Conflow model, an open-source numerical model for flow in eruptive conduits during steady-state pyroclastic eruptions (Mastin and Ghiorso in A numerical program for steady-state flow of magma-gas mixtures through vertical eruptive conduits. U.S. Geological Survey Open File Report 00-209, 2000). In the modified version, called Confort 15, the rheological constraints are improved, incorporating the most recent constitutive equations of both the liquid viscosity and crystal-bearing rheology. This allows all natural magma compositions, including the peralkaline melts excluded in the original version, to be investigated. The crystal-bearing rheology is improved by computing the effect of strain rate and crystal shape on the rheology of natural magmatic suspensions and expanding the crystal content range in which rheology can be modeled compared to the original version ( Conflow is applicable to magmatic mixtures with up to 30 vol% crystal content). Moreover, volcanological studies of the juvenile products (crystal and vesicle size distribution) of the investigated eruption are directly incorporated into the modeling procedure. Vesicle number densities derived from textural analyses are used to calculate, through Toramaru equations, maximum decompression rates experienced during ascent. Finally, both degassing under equilibrium and disequilibrium conditions are considered. This allows considerations on the effect of different fragmentation criteria on the conduit flow analyses, the maximum volume fraction criterion ("porosity criterion"), the brittle fragmentation criterion and the overpressure fragmentation criterion. Simulations of the pantelleritic and trachytic phases of the Green Tuff (Pantelleria) and of the Plinian Etna 122 BC eruptions are performed to test the upgrades in

  19. Refinement of the time-space evolution of the giant Mio-Pliocene Río Blanco-Los Bronces porphyry Cu-Mo cluster, Central Chile: new U-Pb (SHRIMP II) and Re-Os geochronology and 40Ar/39Ar thermochronology data

    Science.gov (United States)

    Deckart, Katja; Clark, Alan H.; Cuadra, Patricio; Fanning, Mark

    2013-01-01

    Representing one of the largest known (estimated >5 Gt at 1 % Cu and 0.02 % Mo) porphyry system, the Río Blanco-Los Bronces deposit incorporates at least five hypabyssal intrusive and hydrothermal centres, extending for about 5 km from the Río Blanco and Los Bronces mines in the north, through the Don Luis mine, to the Sur Sur mine, La Americana and Los Sulfatos in the south. The new geochronology data, which now include data on different molybdenite vein types, confirm the U-Pb ages of the pre-mineralisation intrusions but slightly increase their age range from 8.8 to 8.2 Ma. The distinct magmatic pulses of the mineralisation-associated porphyritic intrusives (Late Porphyries) indicate an age interval instead of the previously suggested individual ages: the quartz monzonite porphyry ranges from 7.7 to 6.1 Ma (Sur Sur 5.74 ± 0.13 Ma), the feldspar porphyry shows an interval from 5.8 to 5.2 Ma and the Don Luis porphyry from 5.2 to 5.0 Ma. The new Re-Os data on distinct molybdenite vein types confirm the protracted history of Cu(-Mo) mineralisation, inferred previously. The vein development occurred at least from 5.94 to 4.50 Ma, indicating a time-span of 1.5 Ma for the hydrothermal activity. Hydrothermal minerals dated by the 40Ar/39Ar method are generally too young to record the age of early, high-temperature mineralisation. The majority of the 40Ar/39Ar data in the Río Blanco porphyry cluster record reheating by either the youngest member of the Late Porphyry suite or the post-mineralisation dacite or rhyolite plug formations at around 4.9-4.7 Ma.

  20. Instrumentation development for In Situ 40Ar/39Ar planetary geochronology

    Science.gov (United States)

    Morgan, Leah; Munk, Madicken; Davidheiser-Kroll, Brett; Warner, Nicholas H.; Gupta, Sanjeev; Slaybaugh, Rachel; Harkness, Patrick; Mark, Darren

    2017-01-01

    The chronology of the Solar System, particularly the timing of formation of extra-terrestrial bodies and their features, is an outstanding problem in planetary science. Although various chronological methods for in situ geochronology have been proposed (e.g., Rb-Sr, K-Ar), and even applied (K-Ar), the reliability, accuracy, and applicability of the 40Ar/39Ar method makes it by far the most desirable chronometer for dating extra-terrestrial bodies. The method however relies on the neutron irradiation of samples, and thus a neutron source. Herein, we discuss the challenges and feasibility of deploying a passive neutron source to planetary surfaces for the in situ application of the 40Ar/39Ar chronometer. Requirements in generating and shielding neutrons, as well as analysing samples are described, along with an exploration of limitations such as mass, power and cost. Two potential solutions for the in situ extra-terrestrial deployment of the 40Ar/39Ar method are presented. Although this represents a challenging task, developing the technology to apply the 40Ar/39Ar method on planetary surfaces would represent a major advance towards constraining the timescale of solar system formation and evolution.

  1. Ars Baltica-verkoston puheenjohtajuus Suomeen Risto Ruohoselle

    Index Scriptorium Estoniae

    1999-01-01

    1990. a. loodud võrgustiku Ars Baltica sekretariaat (Ars Baltica Contact Point & Communication Center) tuleb Kielist Tallinnasse Eesti kultuuriministeeriumi kuni aastani 2002 (Suur-Karja 23). Ars Baltica (ühendus)

  2. Ars Baltica-verkoston puheenjohtajuus Suomeen Risto Ruohoselle

    Index Scriptorium Estoniae

    1999-01-01

    1990. a. loodud võrgustiku Ars Baltica sekretariaat (Ars Baltica Contact Point & Communication Center) tuleb Kielist Tallinnasse Eesti kultuuriministeeriumi kuni aastani 2002 (Suur-Karja 23). Ars Baltica (ühendus)

  3. Influence of temperature on the adsorption of α-tocopherol from ethanol solutions on acid-activated clinoptilolite tuff

    Science.gov (United States)

    Kotova, D. L.; Vasilyeva, S. Yu.; Krysanova, T. A.

    2014-08-01

    Patterns in the adsorption of α-tocopherol on acid-activated clinoptilolite tuff at 283, 295, 305, and 333 K are established and explained. It is found that the selectivity of the sorbent toward the vitamin rises as the temperature of the process falls. The adsorption of α-tocopherol from dilute solutions is described in terms of the Langmuir adsorption theory. It is shown that the fixing of vitamin E monolayers in the structural matrix of clinoptilolite tuff is due to the formation of hydrogen bonds between isolated silanol groups of the adsorbent and oxygen atoms of the chromane ring and the phenol residue of α-tocopherol. The thermodynamic functions of monolayer adsorption of the vitamin are estimated. It is concluded that the formation of polymolecular layers in the form of associates is due to hydrophobic interactions between side substituents of α-tocopherol.

  4. MaJAZ1 Attenuates the MaLBD5-Mediated Transcriptional Activation of Jasmonate Biosynthesis Gene MaAOC2 in Regulating Cold Tolerance of Banana Fruit.

    Science.gov (United States)

    Ba, Liang-jie; Kuang, Jian-fei; Chen, Jian-ye; Lu, Wang-jin

    2016-02-01

    Previous studies indicated that methyl jasmonate (MeJA) treatment could effectively reduce the chilling injury of many fruits, including banana, but the underlying mechanism is poorly understood. In this study, one lateral organ boundaries (LOB) domain (LBD) gene, designated as MaLBD5, was isolated and characterized from banana fruit. Expression analysis revealed that accumulation of MaLBD5 was induced by cold temperature and MeJA treatment. Subcellular localization and transactivation assays showed that MaLBD5 was localized to the nucleus and possessed transcriptional activation activity. Protein-protein interaction analysis demonstrated that MaLBD5 physically interacted with MaJAZ1, a potential repressor of jasmonate signaling. Furthermore, transient expression assays indicated that MaLBD5 transactivated a jasmonate biosynthesis gene, termed MaAOC2, which was also induced by cold and MeJA. More interestingly, MaJAZ1 attenuated the MaLBD5-mediated transactivation of MaAOC2. These results suggest that MaLBD5 and MaJAZ1 might act antagonistically in relation to MeJA-induced cold tolerance of banana fruit, at least partially via affecting jasmonate biosynthesis. Collectively, our findings expand the knowledge of the transcriptional regulatory network of MeJA-mediated cold tolerance of banana fruit.

  5. In situ zircon Hf isotopic, U-Pb age and trace element study of monzonite xenoliths from Pingquan and Fuxin basalts: Tracking the thermal events of 169 Ma and 107 Ma in Yanliao area

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Jianping; ZHANG; Ruisheng; YU; Chunmei; TANG; Huay

    2004-01-01

    K-Ar ages of the Mesozoic (92-100 Ma) Fuxin alkalic basalts (western Liaoning Province) and the Tertiary (23-45 Ma) Pingquan alkalic basalts (eastern Hebei Province), and the results of in situ zircon U-Pb dating, Hf isotope and the trace elements from three monzonite xenoliths carried in the alkalic basalts are reported. The crust-mantle interaction occurring in the Yanshan intracontinental orogenic belt is also discussed. Fuxin zircons show highly uniform U-Pb age ((169±3) Ma). More than 95% Pingquan zircons display the age of (107±10) Ma except two are 2491 Ma and 513 Ma respectively. Zircons with the ages of (169±3) Ma have εHf close to zero. εHf of the zircons with the ages of (107±10) Ma are mainly at -11.5--16.3, showing the crustal derivation. Fuxin zircons contain low Nb, Ta, Sr, Th, U contents, low and narrow Hf model ages (0.87-1.00 Ga), which reflect that the source materials of the monzonite xenoliths are young to Pingquan (focus at (1.28±0.08) Ga). High contents of the incompatible elements, and wide range of Hf model ages (0.89-2.56 Ga) in Pingquan zircons suggest a more complex source and the highly crustal maturity in their petrogenesis. Comprehensive information including the published data indicates that J3-K1 is the key period of the deep processes and shallow tectonic reverse in the Yanliao area. However, the processes were highly heterogeneous in spatial and in temporal.

  6. In situ zircon Hf isotopic, U-Pb age and trace element study of monzonite xenoliths from Pingquan and Fuxin basalts:Tracking the thermal events of 169 Ma and 107 Ma in Yanliao area

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jianping; ZHANG Ruisheng; YU Chunmei; TANG Huayun; ZHANG Pei

    2004-01-01

    K-Ar ages of the Mesozoic (92-100 Ma) Fuxin alkalic basalts (western Liaoning Province) and the Tertiary (23-45 Ma) Pingquan alkalic basalts (eastern Hebei Province), and the results of in situ zircon U-Pb dating, Hf isotope and the trace elements from three monzonite xenoliths carried in the alkalic basalts are reported. The crust-mantle interaction occurring in the Yanshan intracontinental orogenic belt is also discussed. Fuxin zircons show highly uniform U-Pb age ((169±3) Ma). More than 95% Pingquan zircons display the age of (107±10) Ma except two are 2491 Ma and 513 Ma respectively. Zircons with the ages of (169±3) Ma have εHf close to zero. εHf of the zircons with the ages of (107±10) Ma are mainly at -11.5--16.3, showing the crustal derivation. Fuxin zircons contain low Nb, Ta, Sr, Th, U contents, low and narrow Hf model ages (0.87-1.00 Ga), which reflect that the source materials of the monzonite xenoliths are young to Pingquan (focus at (1.28±0.08) Ga). High contents of the incompatible elements, and wide range of Hf model ages (0.89-2.56 Ga) in Pingquan zircons suggest a more complex source and the highly crustal maturity in their petrogenesis. Comprehensive information including the published data indicates that J3-K1 is the key period of the deep processes and shallow tectonic reverse in the Yanliao area. However, the processes were highly heterogeneous in spatial and in temporal.

  7. Mass and Reliability System (MaRS)

    Science.gov (United States)

    Barnes, Sarah

    2016-01-01

    The Safety and Mission Assurance (S&MA) Directorate is responsible for mitigating risk, providing system safety, and lowering risk for space programs from ground to space. The S&MA is divided into 4 divisions: The Space Exploration Division (NC), the International Space Station Division (NE), the Safety & Test Operations Division (NS), and the Quality and Flight Equipment Division (NT). The interns, myself and Arun Aruljothi, will be working with the Risk & Reliability Analysis Branch under the NC Division's. The mission of this division is to identify, characterize, diminish, and communicate risk by implementing an efficient and effective assurance model. The team utilizes Reliability and Maintainability (R&M) and Probabilistic Risk Assessment (PRA) to ensure decisions concerning risks are informed, vehicles are safe and reliable, and program/project requirements are realistic and realized. This project pertains to the Orion mission, so it is geared toward a long duration Human Space Flight Program(s). For space missions, payload is a critical concept; balancing what hardware can be replaced by components verse by Orbital Replacement Units (ORU) or subassemblies is key. For this effort a database was created that combines mass and reliability data, called Mass and Reliability System or MaRS. The U.S. International Space Station (ISS) components are used as reference parts in the MaRS database. Using ISS components as a platform is beneficial because of the historical context and the environment similarities to a space flight mission. MaRS uses a combination of systems: International Space Station PART for failure data, Vehicle Master Database (VMDB) for ORU & components, Maintenance & Analysis Data Set (MADS) for operation hours and other pertinent data, & Hardware History Retrieval System (HHRS) for unit weights. MaRS is populated using a Visual Basic Application. Once populated, the excel spreadsheet is comprised of information on ISS components including

  8. 40Ar-39Ar laser dating of ductile shear zones from central Corsica (France): Evidence of Alpine (middle to late Eocene) syn-burial shearing in Variscan granitoids

    Science.gov (United States)

    Di Vincenzo, Gianfranco; Grande, Antonietta; Prosser, Giacomo; Cavazza, William; DeCelles, Peter G.

    2016-10-01

    The island of Corsica (France) plays a central role in any reconstruction of Western Mediterranean geodynamics and paleogeography but several key aspects of its geological evolution are still uncertain. The most debated topics include the interpretation of the Corsican orogen as the result of an east- or west-directed subduction, and the actual involvement of the Variscan basement of Corsica in the Alpine orogenic cycle. This study integrates 40Ar-39Ar laserprobe, mesostructural, microtextural, and microchemical analyses and places relevant constraints on the style, P-T conditions, and timing of Alpine-age, pervasive ductile shear zones which affected the Variscan basement complex of central Corsica, a few kilometers to the west of the present-day front of the Alpine nappes. Shear zones strike ~ NNE-SSW, dip at a high angle, and are characterized by a dominant sinistral strike-slip component. Two of the three investigated shear zones contain two texturally and chemically resolvable generations of white mica, recording a prograde (burial) evolution: (1) deformed celadonite-poor relicts are finely overgrown by (2) a celadonite-rich white mica aligned along the main foliation. White mica from a third sample of another shear zone, characterized by a significantly lower porphyroclast/matrix ratio, exhibits a nearly uniform high-celadonite content, compositionally matching the texturally younger phengite from the nearby shear zones. Mineral-textural analysis, electron microprobe data, and pseudosection modeling constrain P-T conditions attained during shearing at ~ 300 °C and minimum pressures of ~ 0.6 GPa. In-situ 40Ar-39Ar analyses of coexisting low- and high-celadonite white micas from both shear zones yielded a relatively wide range of ages, ~ 45-36 Ma. Laser step-heating experiments gave sigmoidal-shaped age profiles, with step ages in line with in-situ spot dates. By contrast, the apparently chemically homogenous high-celadonite white mica yielded concordant in

  9. The one-dimensional compression method for extraction of pore water from unsaturated tuff and effects on pore-water chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Higgins, J.D.; Burger, P.A. [Colorado School of Mines, Golden, CO (United States); Yang, L.C. [Geological Survey, Denver, CO (United States)

    1997-12-31

    Study of the hydrologic system at Yucca Mountain, Nevada, requires extraction of pore-water samples from unsaturated tuff bedrock. Two generations of compression cells have been designed and tested for extracting representative, unaltered pore-water samples from unsaturated tuff cores. The one-dimensional compression cell has a maximum compressive stress rating of 552 MPa. Results from 86 tests show that the minimum degree of saturation for successful extraction of pore water was about 14% for non welded tuff and about 61% for densely welded tuff. The high-pressure, one-dimensional compression cell has a maximum compressive stress rating of 827 MPa. Results from 109 tests show that the minimum degree of saturation for successful extraction of pore water was about 7.5% for non welded tuff and about 34% for densely welded tuff. Geochemical analyses show that, in general, there is a decrease in ion concentration of pore waters as extraction pressures increase. Only small changes in pore-water composition occur during the one-dimensional extraction test.

  10. Ars ornata / Kadri Mälk

    Index Scriptorium Estoniae

    Mälk, Kadri, 1958-

    1998-01-01

    V rahvusvaheline ehtekunsti konverents 'Ars ornata Europeana' juuni lõpus Stockholmis. New Yorgis elava kuraatori Charon Kranseni ja prantsuse ehtekunstniku Christophe Burger' juhitud vestlusringidest. 1997. a. Pariisis loodud International Craft Design Association'ist (ICDA).

  11. Differential AR algorithm for packet delay prediction

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Different delay prediction algorithms have been applied in multimedia communication, among which linear prediction is attractive because of its low complexity. AR (auto regressive) algorithm is a traditional one with low computation cost, while NLMS (normalize least mean square) algorithm is more precise. In this paper, referring to ARIMA (auto regression integrated with moving averages) model, a differential AR algorithm (DIAR) is proposed based on the analyses of both AR and NLMS algorithms. The prediction precision of the new algorithm is about 5-10 db higher than that of the AR algorithm without increasing the computation complexity.Compared with NLMS algorithm, its precision slightly improves by 0.1 db on average, but the algorithm complexity reduces more than 90%. Our simulation and tests also demonstrate that this method improves the performance of the average end-to-end delay and packet loss ratio significantly.

  12. "Ars Ornata" Mediterrania / Kadri Mälk

    Index Scriptorium Estoniae

    Mälk, Kadri, 1958-

    1999-01-01

    VI rahvusvaheline ehtekunstinäitus "Ars Ornata" juuni lõpus Barcelonas. Konverentsist, peanäitusest (osalejad Eestist), ehtekunstiõpetust andvast kõrgkoolist Escola Massana'st Barcelonas, õppejõude. Eesti ehtekunsti tulevikust.

  13. ARS 01 Helsingi Kiasmas / Tarmo Virki

    Index Scriptorium Estoniae

    Virki, Tarmo

    2001-01-01

    Helsingis Kiasmas avatud rahvusvahelisest kunstinäitusest ARS 01 alapealkirjaga "Avanevaid perspektiive", kus esines oma töödega ka Marko Mäetamm. Näituse raames toimuvast Santiago Sierra kunstiprojektist kodututega

  14. ARS 01 Helsingi Kiasmas / Tarmo Virki

    Index Scriptorium Estoniae

    Virki, Tarmo

    2001-01-01

    Helsingis Kiasmas avatud rahvusvahelisest kunstinäitusest ARS 01 alapealkirjaga "Avanevaid perspektiive", kus esines oma töödega ka Marko Mäetamm. Näituse raames toimuvast Santiago Sierra kunstiprojektist kodututega

  15. Ars ornata / Kadri Mälk

    Index Scriptorium Estoniae

    Mälk, Kadri, 1958-

    1998-01-01

    V rahvusvaheline ehtekunsti konverents 'Ars ornata Europeana' juuni lõpus Stockholmis. New Yorgis elava kuraatori Charon Kranseni ja prantsuse ehtekunstniku Christophe Burger' juhitud vestlusringidest. 1997. a. Pariisis loodud International Craft Design Association'ist (ICDA).

  16. Cassiterite LA-MC-ICP-MS U/Pb and muscovite 40Ar/39Ar dating of tin deposits in the Tengchong-Lianghe tin district, NW Yunnan, China

    Science.gov (United States)

    Chen, Xiao-Cui; Hu, Rui-Zhong; Bi, Xian-Wu; Li, Hui-Min; Lan, Jiang-Bo; Zhao, Cheng-Hai; Zhu, Jing-Jing

    2014-10-01

    The Tengchong-Lianghe tin district in northwestern Yunnan, China, is an important tin mineralization area in the Sanjiang Tethyan Metallogenic Domain. There are three N-S trending granite belts in the Tengchong-Lianghe area, with emplacement ages ranging from Early Cretaceous to Late Cretaceous and Early Cenozoic. Tin mineralization is spatially associated with these granitic rocks. However, the petrogenetic link between the tin deposits and the host granites is not clear because of the lack of age data for the tin mineralization. We investigate the possibility of direct dating of cassiterite from three typical tin deposits in the Tengchong-Lianghe tin district, using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). In situ LA-MC-ICP-MS dating of seven cassiterite samples from the Lailishan (LLS-1 and LLS-2), Xiaolonghe (XLH, WDS, DSP, and HJS), and Tieyaoshan (TYS) tin deposits yielded well-defined 206Pb/207Pb-238U/207Pb isochron ages. To assess the accuracy of the in situ U/Pb dating of cassiterite, 40Ar/39Ar dating of coexisting muscovite (in samples LLS-1, DSP, and TYS) was also performed. The cassiterite in situ U/Pb ages (47.4 ± 2.0, 71.9 ± 2.3, and 119.3 ± 1.7 Ma, respectively) are in excellent agreement with the coexisting muscovite 40Ar/39Ar ages (48.4 ± 0.3, 71.9 ± 1.4, and 122.4 ± 0.7 Ma, respectively). The U/Pb ages of cassiterite combined with the 40Ar/39Ar ages of muscovite indicate that there are three tin mineralization events in this district: the Lailishan tin deposit at 47.4 ± 2.0 to 52 ± 2.7 Ma, the Xiaolonghe tin deposit at 71.6 ± 2.4 to 3.9 ± 2.0 Ma, and the Tieyaoshan tin deposit at 119.3 ± 1.7 to 122.5 ± 0.7 Ma. These ages are highly consistent with the zircon U/Pb ages of the host granites. It is su.ggested that the Cretaceous tin mineralization might have taken place in a subduction environment, while the Early Tertiary tin metallogenesis was in a postcollisional geodynamic setting.

  17. Report on static hydrothermal alteration studies of Topopah Spring tuff waters in J-13 water at 150{sup 0}C

    Energy Technology Data Exchange (ETDEWEB)

    Knauss, K.G.; Beiriger, W.B.

    1984-08-31

    This report presents the results of preliminary experimental work done to define the package environment in a potential nuclear waste repository in the Topopah Spring Member of the Paintbrush Tuff. The work is supported by the Nevada Nuclear Waste Storage Investigations (NNWSI) Project as a part of the Waste Package task to design a package suitable for waste storage within volcanic units at the Nevada Test Site. Static hydrothermal alteration experiments were run for 4 months using polished wafers either fully submerged in an appropriate natural ground water or exposed to water-saturated air with enough excess water to allow refluxing. The aqueous results agreed favorably with similar experiments run using crushed tuff, and the use of solid polished wafers allowed us to directly evaluate the effects of reaction on the tuff. The results are preliminary in the sense that these experiments were run in Teflon-lined, static autoclaves, whereas subsequent experiments have been run in Dickson-type gold-cell rocking autoclaves. The results predict relatively minor changes in water chemistry, very minor alteration of the host rock, and the production of slight amounts of secondary minerals, when liquid water could return to the rock pores following the temperature maximum during the thermal period. 7 references, 16 figures, 10 tables.

  18. Stochastic Model of Fracture Frequency Heterogeneity in a Welded Tuff EGS reservoir, Snake River Plain, Idaho, USA

    Science.gov (United States)

    Moody, A.; Fairley, J. P., Jr.

    2014-12-01

    In light of recent advancements in reservoir enhancement and injection tests at active geothermal fields, there is interest in investigating the geothermal potential of widespread subsurface welded tuffs related to caldera collapse on the Snake River Plain (SRP). Before considering stimulation strategies, simulating heat extraction from the reservoir under in-situ fracture geometries will give a first-order estimation of extractable heat. With only limited deep boreholes drilled on the SRP, few analyses of the bulk hydrologic properties of the tuffs exist. Acknowledging the importance of the spatial heterogeneity of fractures to the permeability and injectivity of reservoirs hosted in impermeable volcanic units, we present fracture distributions from ICDP hole 5036-2A drilled as a part of Project HOTSPOT. The core documents more than 1200 m of largely homogeneous densely welded tuff hosting an isothermal warm-water reservoir at ~60˚ C. Multiple realizations of a hypothetical reservoir are created using sequential indicator algorithms that honor the observed vertical fracture frequency statistics. Results help form criteria for producing geothermal energy from the SRP.

  19. Adsorption kinetic of arsenates as water pollutant on iron, manganese and iron-manganese-modified clinoptilolite-rich tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Cedillo, M.J. [Instituto Nacional de Investigaciones Nucleares, Departamento de Quimica, A.P. 18-1027, Col, Escandon, Del, Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico); Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Paseo Colon y Paseo Tollocan s/n, Toluca (Mexico); Olguin, M.T. [Instituto Nacional de Investigaciones Nucleares, Departamento de Quimica, A.P. 18-1027, Col, Escandon, Del, Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)], E-mail: mog@nuclear.inin.mx; Fall, Ch. [Centro Interamericano de Recursos del Agua, CIRA, km 14.5 de la Carretera Toluca - Ixtlahuaca, Unidad San Cayetano, Estado de Mexico (Mexico)

    2009-04-30

    Arsenate adsorption from aqueous solutions onto clinoptilolite-heulandite rich tuffs modified with iron or manganese or a mixture of both iron and manganese in this work was investigated. A kinetic model was considered to describe the arsenates adsorption on each zeolitic material. The modified clinoptilolite-heulandite rich tuffs were characterized by scanning electron microscopy and X-ray diffraction analysis. The elemental composition and the specific surface area of the zeolitic material were also determined. The arsenate adsorption by the modified zeolites was carried on in a batch system considering a contact time from 5 min to 24 h for the kinetic experimentation. The arsenic was detected by atomic absorption spectrometer using a hydride generator. The kinetics of the arsenate adsorp