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  • 1
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    Geochronology : Linking the Isotopic Record with Petrology and Textures (2003)
    London : The Geological Society
    Details
    Description / Table of Contents: Isotope geochemistry has produced many technical developments in the past decade or so that have revolutionized the potential information available on the tectonics of metamorphic belts from geochronology. These include the ability to date minerals and rocks on small spatial scales, scales that at last approach those from which other types of information — structural and petrological — are obtained. However, interpreting the new data, and their integration with the other datasets available, is not straightforward and requires careful chemical and textural observations that go hand-inhand with the geochronology. The increasing realization of the importance of this approach has led to a number of symposia at international conferences devoted to this topic in recent years. The set of papers in this book emanates from one such symposium and describes recent progress in integrating this new information with other datasets from metamorphic petrology on a mineral and sub-mineral scale.
    Pages: Online-Ressource (VII, 266 Seiten)
    ISBN: 186239146 7
    URL: http://sp.lyellcollection.org/content/220/1.toc
    Language: English
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    E-BOOK
  • 2
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    Age of the Corsica–Sardinia rotation and Liguro–Provençal Basin spreading: new paleomagnetic and Ar/Ar evidence (2008)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The age of spreading of the Liguro–Provençal Basin is still poorly constrained due to the lack of boreholes penetrating the whole sedimentary sequence above the oceanic crust and the lack of a clear magnetic anomaly pattern. In the past, a consensus developed over a fast (20.5–19 Ma) spreading event, relying on old paleomagnetic data from Oligo–Miocene Sardinian volcanics showing a drift-related 30° counterclockwise (CCW) rotation. Here we report new paleomagnetic data from a 10-mthick lower–middle Miocene marine sedimentary sequence from southwestern Sardinia. Ar/Ar dating of two volcanoclastic levels in the lower part of the sequence yields ages of 18.94±0.13 and 19.20±0.12 Ma (lower–mid Burdigalian). Sedimentary strata below the upper volcanic level document a 23.3±4.6° CCW rotation with respect to Europe, while younger strata rapidly evolve to null rotation values. A recent magnetic overprint can be excluded by several lines of evidence, particularly by the significant difference between the in situ paleomagnetic and geocentric axial dipole (GAD) field directions. In both the rotated and unrotated part of the section, only normal polarity directions were obtained. As the global magnetic polarity time scale (MPTS) documents several geomagnetic reversals in the Burdigalian, a continuous sedimentary record would imply that (unrealistically) the whole documented rotation occurred in few thousands years only. We conclude that the section contains one (or more) hiatus(es), and that the minimum age of the unrotated sediments above the volcanic levels is unconstrained. Typical back-arc basin spreading rates translate to a duration ≥3 Ma for the opening of the Liguro–Provençal Basin. Thus, spreading and rotation of Corsica–Sardinia ended no earlier than 16 Ma (early Langhian). A 16–19 Ma, spreading is corroborated by other evidences, such as the age of the breakup unconformity in Sardinia, the age of igneous rocks dredged west of Corsica, the heat flow in the Liguro–Provençal Basin, and recent paleomagnetic data from Sardinian sediments and volcanics. Since Corsica was still rotating/drifting eastward at 16 Ma, it presumably induced significant shortening to the east, in the Apennine belt. Therefore, the lower Miocene extensional basins in the northern Tyrrhenian Sea and margins can be interpreted as synorogenic "intra-wedge" basins due to the thickening and collapse of the northern Apennine wedge.
    Description: Published
    Description: 231-251
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Paleomagnetism ; Corsica-Sardinia ; Liguro-Provençal Basin ; Back-arc spreading ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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    PAPER (OA)
  • 3
    Electronic Resource
    Electronic Resource
    Eel calcitonin binding site distribution and antinociceptive activity in rats
    Amsterdam : Elsevier
    Peptides 7 (1986), S. 315-322 
    Details
    ISSN: 0196-9781
    Keywords: Antinociceptive activity ; Autoradiography ; Binding site distribution ; Eel calcitonin ; Salmon calcitonin
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(86)90230-5
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  • 4
    Electronic Resource
    Electronic Resource
    Treatment with pertussis toxin does not prevent central effects of eel calcitonin
    Amsterdam : Elsevier
    Peptides 12 (1991), S. 549-553 
    Details
    ISSN: 0196-9781
    Keywords: Adenylyl cyclase ; Antinociceptive activity ; Eel calcitonin ; Gastric acid secretion ; Morphine ; Pertussis toxin
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(91)90099-B
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  • 5
    Electronic Resource
    Electronic Resource
    Osteocyte-Bone Lining Cell System at the Origin of Steady Ionic Current in Damaged Amphibian Bone (1998)
    Springer
    Calcified tissue international 63 (1998), S. 331-339 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Ionic current — Amphibian bone — Osteocytes — Bone lining cells.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. A wound-generated steady electric current was measured by a two-dimensional vibrating probe system in the metatarsal bones of 22 adult frogs (Xenopus laevis) placed in amphibian Ringer. Inward currents were recorded entering a micrometric hole drilled through the cortex at middiaphyseal level. These steady state currents (mean ± SD 8.50 ± 2.77 μA/cm2) last approximately 2 hours, were dependent on the presence of sodium in the incubation medium, were no more detectable after fixation, and were reduced to background level when the cell membranes were solubilized. These results agree with previous recordings of metatarsal bones of weanling mice, under identical conditions. Both results suggest that the measured ionic currents have a cellular origin. Metatarsal bones of adult amphibian were purposely selected for this study because, unlike mammalian bones, their shafts are avascular and only contain an osteocyte-bone lining cell system, as documented by scanning and transmission electron observations. Thus, unlike the data from previous investigations on mammals, the results succeeded in giving the first convincing evidence that the osteocyte-bone lining cell system is the origin of damage-generated ionic currents. As damage exposes bone ionic compartment to plasma, damage-generated ionic currents are representative of ion fluxes at bone plasma interface, and cells at the origin of the current generate the driving force of such fluxes. By demonstrating that osteocytes and bone lining cells are at the origin of the current, this study suggests that the osteocyte-bone lining cell system, though operating as a cellular membrane partition, regulates ionic flow between bone and plasma. Since strain-related adaptive remodeling could also depend on ionic characteristics and flow of the bone fluid through the osteocyte lacuno-canalicular network, the results reported here support the view that osteocyte and bone lining cells may constitute a functional syncytium involved in mineral homeostasis as well as in bone adaptation to mechanical loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900536
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  • 6
    Electronic Resource
    Electronic Resource
    Assessing Ar transport paths and mechanisms in the McClure Mountains hornblende (1996)
    Springer
    Contributions to mineralogy and petrology 126 (1996), S. 67-80 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We have investigated the mechanisms and pathways by which Ar diffuses through the McClure Mountains hornblende (ferroan pargasite), selected as a good example of material normally dated during Ar-Ar studies. A coarse-grained hornblende separated from the same hand specimen as the MMhb-1 age standard was subjected to a hydrothermal cold-seal bomb experiment and characterized by TEM. Heated and unheated crystals were subjected to four different 39Ar/40Ar dating extraction techniques: conventional stepwise heating, infra-red laser spot, ultra-violet laser depth profiling, and closed-system stepwise etching. The stepwise heating age spectrum reproduces the features often interpreted as resulting from a concentric diffusive zonation, but the other three techniques yield results that are not compatible with such a simple picture. The IR laser data indicate that the dependence of laboratory Ar loss on grain size, predicted by Fickian diffusion, is at best poor and instead is related mainly to mineralogical variations. The depth profiles show the importance of planar zones (spaced between 〈1 and 〉150 μm from TEM evidence) in providing fast pathways for inward diffusion of atmospheric Ar from the capsule, but showed no evidence of diffusive profiles in the bulk of the hornblende lattice. The data from closed system stepwise etching underscore the role of zones rich in planar defects both for Ar loss and for nucleation of etching. The age spectra obtained by stepwise heating suffer from the differential breakdown of impurity phases, whose presence can be diagnosed with several isotope correlation plots; particularly revealing are Cl-Ca-K trends. In addition to the problems of mineral decomposition during in-vacuo laboratory degassing, an equally important decomposition occurs during many hydrothermal experiments which, combined with problems of mineral purity, have led to an overestimation of the rate of argon diffusion in hornblende. The response of hornblende to thermal disturbance in a hydrothermal environment can be every bit as complex as breakdown in vacuo. Laboratory experiments on bulk samples have not succeeded in quantitatively constraining volume diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050236
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  • 7
    Electronic Resource
    Electronic Resource
    Time calibration of a PT-path from the Western Tauern Window, Eastern Alps: the problem of closure temperatures (1989)
    Springer
    Contributions to mineralogy and petrology 101 (1989), S. 1-11 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract New Hornblende K-Ar and 39Ar-40Ar and mica Rb-Sr and K-Ar ages are used to place specific timemarks on a well-constrained pressure-temperature path for the late Alpine metamorphism in the Western Tauern Window. After identification of excess 40Ar, the closure behavior of Ar in hornblende is compared with that of Sr and Ar in phengite and biotite. Samples were collected in three locations, whose maximum temperatures were 570° C (Zemmgrund), 550° C (Pfitscher Joch), and 500–540° C (Landshuter Hütte). The average undisturbed age sequence found is: Phengite Rb-Sr (20 Ma)〉hornblende K-Ar (18 Ma)〉phengite K-Ar (15 Ma)〉biotite Rb-Sr, K-Ar (13.3 Ma)〉apatite FT (7 Ma). Except for the phengite Rb-Sr age, the significance of which is debatable, all ages are cooling ages. No compositional effects are seen for closure in biotite. Additionally, Rb-Sr phengite ages from shearzones possibly indicate continuous shearing from 20 to 15 Ma, with reservations regarding the validity of the initial Sr correction and possible variations of the closure temperatures. The obviously lower closure temperature (T c) for Ar in these hornblendes than for Sr in the unsheared phengites indicates that the T c sequence in the Western Tauern Window is different from those observed in other terrains. In spite of this discrepancy, valuable geological conclusions can be drawn if the application of closure temperatures is limited to this restricted area with similar T, P and $$P_{H_2 O}$$ : (1) All ages of samples located on equal metamorphic isotherms decrease from east to west by about 1 Ma which is the result of a westward tilting of the Tauern Window during uplift. (2) In a PT-path, the undisturbed cooling ages yield constantly decreasing uplift rates from 3.6 mm/a to 0.1 mm/a. (3) Use of recently published diffusion data for Ar in hornblende (T c=520° C) and biotite (T c=320° C) suggests an extrapolated phengite closure temperature for Sr at 550° C. This suggests that the prograde thermal metamorphism at this tectonic level of the Tauern Window lasted until some 20 Ma ago.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387196
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  • 8
    Electronic Resource
    Electronic Resource
    Argon retentivity and argon excess in amphiboles from the garbenschists of the Western Tauern Window, Eastern Alps (1988)
    Springer
    Contributions to mineralogy and petrology 100 (1988), S. 1-11 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract 22 hornblende K-Ar ages and 10 39Ar-40Ar spectra were obtained for hornblende garbenschists from the Western Tauern Window. The post-kinematic amphiboles were produced during the late Alpine prograde metamorphism (6–10 kb and 500–570° C). Two nearly potassiumfree cummingtonites rimming hornblende yield K-Ar ages of 120 Ma, while the 20 tschermakitic hornblendes scatter between 17 and 37 Ma. The reason for this scatter is excess Ar, possibly incorporated into amphiboles during healing of fractures, now traceable by trails of fluid inclusions. Excess Ar is semiquantitatively corrected for by combining cogenetic hornblende and cummingtonite with K-Ar isochrons. It can be quantified in 4 out of 10 hornblendes by 39Ar-40Ar stepwise heating experiments. Ages of 18–20 Ma result for corrected hornblendes. The retentivity of 40Ar, after correction for excess, shows no correlation with chemistry within the narrow compositional range observed; rather, it shows intriguing correlations with irregularities in Ca/K spectra, pointing to a microstructurally controlled mechanism for Ar loss. This observation leads to a critical evaluation of the closure temperature “constant”, which apparently depends on an incompletely known number of mineralogical and environmental parameters. In particular those 39Ar-40Ar release spectra which yield low temperature steps with younger ages than the plateaus are not interpretable in terms of a synchronous closure. This gives evidence that loss of radiogenic isotopes proceeds by a more complex mechanism than simple volume diffusion through isotropic media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399435
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  • 9
    Electronic Resource
    Electronic Resource
    Rb-Sr and K-Ar ages on minerals at temperatures of 300°–400° C from deep wells in the Larderello geothermal field (Italy) (1982)
    Springer
    Contributions to mineralogy and petrology 81 (1982), S. 340-349 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Rb-Sr and K-Ar ages have been obtained on six biotites, two muscovites and one hornblende from samples of micaschist, gneiss and amphibolite of Lower Paleozoic to Precambrian age at a depth exceeding 2,000 m in basement rocks of the Larderello-Travale geothermal region. Most of the data cluster in the range 2.5–3.7 Ma, revealing the existence of a Pliocene thermal event to which the origin of the field may be attributed. The resulting duration of the Larderello geothermal field is unexpectedly long. In the basement levels of the two wells examined, unstabilized minimum temperatures of 290° and 380° C were measured. All the biotites show almost complete 40Ar and 87Sr retention at the measured well temperatures. Petrologic evidence (stilpnomelane stability) and experimental data (activation energies and diffusion coefficients) also favour a closure temperature above 400° C for Rb-Sr and K-Ar in biotites, in agreement with recent direct experimental determinations. For the last 3 Ma mean geothermal gradients of 120°–150° C/km have been evaluated in the first 2–3 km, and 60°–65° C/km in the underlying 2 km. A rough estimate of total cooling in the last 3 Ma gives a value of 120° C at 2,500 m depth and 50° C at 4,000 m depth in Sasso 22 well. A mean uplift rate of about 0.2 mm/year is calculated independently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371688
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  • 10
    Electronic Resource
    Electronic Resource
    The evolution of latera caldera (central Italy) in the light of subsurface data (1984)
    Springer
    Bulletin of volcanology 47 (1984), S. 125-141 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Subsurface geothermal exploration has considerably added to our knowledge of the Latera volcanic complex. A syenitic body is located about 2 km below the present-day surface; K-Ar data point a 0.9 Ma age. The primary magma was a silica-saturated trachyte; undersaturated, hauyne-bearing products are found near the carbonatic wall-rocks and have been interpreted as reaction products. Subsurface data from deep drilling and geophysical surveys suggest that the Latera caldera resulted from three main successive collapse phases: (i) formation of an old caldera, now buried, related to the eruption of ignimbrites from the syenitic magma chamber; (ii) sinking of the eastern sector as a consequence of the formation of the nearby Bolsena caldera (∼0.3 Ma); (iii) multistage formation of the present Latera caldera (∼0.16 Ma).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01960544
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