Behaviour of geochronometers and timing of metamorphic reactions during deformation at lower crustal conditions: phase equilibrium modelling and U–Pb dating of zircon,monazite, rutile and titanite from the Kalak Nappe Complex,northern Norway          下载免费PDF全文

D. Gasser  P. Jeřábek  C. Faber  H. Stünitz  L. Menegon  F. Corfu  M. Erambert  M. J. Whitehouse 《Journal of Metamorphic Geology》2015,33(5):513-534

This study investigates the behaviour of the geochronometers zircon, monazite, rutile and titanite in polyphase lower crustal rocks of the Kalak Nappe Complex, northern Norway. A pressure–temperature–time–deformation path is constructed by combining microstructural observations with P–T conditions derived from phase equilibrium modelling and U–Pb dating. The following tectonometamorphic evolution is deduced: A subvertical S1 fabric formed at ~730–775 °C and ~6.3–9.8 kbar, above the wet solidus in the sillimanite and kyanite stability fields. The event is dated at 702 ± 5 Ma by high‐U zircon in a leucosome. Monazite grains that grew in the S1 fabric show surprisingly little variation in chemical composition compared to a large spread in (concordant) U–Pb dates from c. 800 to 600 Ma. This age spread could either represent protracted growth of monazite during high‐grade metamorphism, or represent partially reset ages due to high‐T diffusion. Both cases imply that elevated temperatures of >600 °C persisted for over c. 200 Ma, indicating relatively static conditions at lower crustal levels for most of the Neoproterozoic. The S1 fabric was overprinted by a subhorizontal S2 fabric, which formed at ~600–660 °C and ~10–12 kbar. Rutile that originally grew during the S1‐forming event lost its Zr‐in‐rutile and U–Pb signatures during the S2‐forming event. It records Zr‐in‐rutile temperatures of 550–660 °C and Caledonian ages of 440–420 Ma. Titanite grew at the expense of rutile at slightly lower temperatures of ~550 °C during ongoing S2 deformation; U–Pb ages of c. 440–430 Ma date its crystallization, giving a minimum estimate for the age of Caledonian metamorphism and the duration of Caledonian shearing. This study shows that (i) monazite can have a large spread in U–Pb dates despite a homogeneous composition; (ii) rutile may lose its Zr‐in‐rutile and U–Pb signature during an amphibolite facies overprint; and (iii) titanite may record crystallization ages during retrograde shearing. Therefore, in order to correctly interpret U–Pb ages from different geochronometers in a polyphase deformation and reaction history, they are ideally combined with microstructural observations and phase equilibrium modelling to derive a complete P–T–t–d path.  相似文献   

The DEEP2 Galaxy Redshift Survey: the relationship between galaxy properties and environment at z∼ 1     

Michael C. Cooper  Jeffrey A. Newman †  Darren J. Croton  Benjamin J. Weiner  Christopher N. A. Willmer  Brian F. Gerke  Darren S. Madgwick †  S. M. Faber  Marc Davis  Alison L. Coil †  Douglas P. Finkbeiner  Puragra Guhathakurta  David C. Koo 《Monthly notices of the Royal Astronomical Society》2006,370(1):198-212

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Molecular Gas in the Abell 262 Cluster Galaxy Ugc 1347     

Thomas Bertram  Andreas Eckart  Melanie Krips  Johannes Staguhn 《Astrophysics and Space Science》2005,295(1-2):303-308

We present the results of ¹²CO(1-0) and ¹²CO(2-1) observations on UGC 1347 obtained with BIMA and the IRAM 30 m telescope. UGC 1347 is a member of the Abell 262 cluster. In Abell 262, a nearby spiral rich cluster, the signs of galaxy interaction and therefore the mechanisms which play an important role in galaxy evolution within clusters can be studied with high spatial resolution. Aside from its bright central region, UGC 1347 features a second prominent source at the southern tip of the bar, which has been identified as region with recent enhanced star formation. The CO observations prove the existence of reservoirs of cold molecular gas at the positions of both bright regions.  相似文献   

Stellar orbits near Sagittarius A*     

A.Eckart  R.Genzel  T.Ott  R.Schödel 《Monthly notices of the Royal Astronomical Society》2002,331(4):917-934

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Early Miocene carbonate ramp development in a warm ocean,North West Shelf,Australia     

Rosine Riera  Julien Bourget  Tony Allan  Eckart Hkansson  Moyra E. J. Wilson 《Sedimentology》2022,69(1):219-253

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A cost–benefit analysis of mitigation options for optimal management of risks posed by flow-like phenomena     

Narasimhan  Harikrishna  Ferlisi  Settimio  Cascini  Leonardo  De Chiara  Giovanna  Faber  Michael Havbro 《Natural Hazards》2015,77(1):117-125

We analyzed the fractal and multifractal properties of the earthquake time series occurred around the Enguri dam in West Georgia by applying the methods of detrended fluctuation analysis and multifractal detrended fluctuation analysis. We examined the interevent time series in two periods: (1) 1960–1980, in which the investigated area was characterized by the natural seismicity; and (2) 1981–2012, in which the quasi-periodic change of the reservoir water level affected the earthquake generation. Our findings show that the water level variation may influence the fractal properties of earthquake temporal distribution in the local area around the Enguri dam. In particular, it is observed that the time distribution features of seismicity occurred in the second period are more persistent than the natural seismicity occurred in the first period. Furthermore, the seismic process of the second period shows a lower multifractal degree than that of the first period, indicating that the influence of quasi-periodic fluctuation of water level features the seismicity as more regular compared to the natural seismicity.  相似文献   

Preface     

Jörg Büchner  Ian Axford  Eckart Marsch  Vytenis Vasyliūnas 《Astrophysics and Space Science》1998,261(1-4):9-10

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A deep Chandra survey of the Groth Strip – II. Optical identification of the X-ray sources     

A. Georgakakis †  K. Nandra  E. S. Laird  S. Gwyn  C. C. Steidel  V. L. Sarajedini  P. Barmby  S. M. Faber  A. L. Coil  M. C. Cooper  M. Davis  J. A. Newman ‡ 《Monthly notices of the Royal Astronomical Society》2006,371(1):221-234

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Isotopic and molecular composition of coal-bed gas in the Amasra region (Zonguldak basin—western Black Sea)     

Hakan Hogrmez  M Nam&#x;k Yal&#x;n  Bernhard Cramer  Peter Gerling  Eckhard Faber  Rainer G Schaefer  Ulrich Mann 《Organic Geochemistry》2002,33(12)

Previous studies on the coal-bed methane potential of the Zonguldak basin have indicated that the gases are thermogenic and sourced by the coal-bearing Carboniferous units. In this earlier work, the origin of coal-bed gas was only defined according to the molecular composition of gases and to organic geochemical properties of the respective source rocks, since data on isotopic composition of gases were not available. Furthermore, in the western Black Sea region there also exist other source rocks, which may have contributed to the coal-bed gas accumulations. The aim of this study is to determine the origin of coal-bed gas and to try a gas-source rock correlation. For this purpose, the molecular and isotopic compositions of 13 headspace gases from coals and adjacent sediments of two wells in the Amasra region have been analyzed. Total organic carbon (TOC) measurements and Rock-Eval pyrolysis were performed in order to characterize the respective source rocks. Coals and sediments are bearing humic type organic matter, which have hydrogen indices (HI) of up to 300 mgHC/gTOC, indicating a certain content of liptinitic material. The stable carbon isotope ratios (δ¹³C) of the kerogen vary from −23.1 to −27.7‰. Air-free calculated gases contain hydrocarbons up to C₅, carbon dioxide (<1%) and a considerable amount of nitrogen (up to 38%). The gaseous hydrocarbons are dominated by methane (>98%). The stable carbon isotope ratios of methane, ethane and propane are defined as δ¹³C₁: −51.1 to −48.3‰, δ¹³C₂: −37.9 to −25.3‰, δ¹³C₃: −26.0 to −19.2 ‰, respectively. The δD₁ values of methane range from −190 to −178‰. According to its isotopic composition, methane is a mixture, partly generated bacterially, partly thermogenic. Molecular and isotopic composition of the gases and organic geochemical properties of possible source rocks indicate that the thermogenic gas generation took place in coals and organic rich shales of the Westphalian-A Kozlu formation. The bacterial input can be related to a primary bacterial methane generation during Carboniferous and/or to a recent secondary bacterial methane generation. However, some peculiarities of respective isotope values of headspace gases can also be related to the desorption process, which took place by sampling.  相似文献   

天然气中氮的地球化学特征   总被引：23，自引：0，他引：23  

杜建国 Faber  E 《沉积学报》1996,14(1):143-148

本文研究了天然气中氮的地球化学特征，并讨论了氮的成因。  相似文献