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208 results on '"Koepke, Juergen"'

8. Drilling to Gabbro in Intact Ocean Crust

Author

Wilson, Douglas S., Alt, Jeffrey C., Banerjee, Neil R., Umino, Susumu, Miyashita, Sumio, Acton, Gary D., Anma, Ryo, Barr, Samantha R., Belghoul, Akram, Carlut, Julie, Christie, David M., Coggon, Rosalind M., Cooper, Kari M., Cordier, Carole, Crispini, Laura, Durand, Sedelia Rodriguez, Einaudi, Florence, Galli, Laura, Gao, Yongjun, Geldmacher, Jörg, Gilbert, Lisa A., Hayman, Nicholas W., Herrero-Bervera, Emilio, Hirano, Nobuo, Holter, Sara, Ingle, Stephanie, Jiang, Shijun, Kalberkamp, Ulrich, Kerneklian, Marcie, Koepke, Jürgen, Laverne, Christine, Maclennan, John, Morgan, Sally, Neo, Natsuki, Nichols, Holly J., Park, Sung-Hyun, Reichow, Marc K., Sakuyama, Tetsuya, Sano, Takashi, Sandwell, Rachel, Scheibner, Birgit, Smith-Duque, Chris E., Swift, Stephen A., Tartarotti, Paola, Tikku, Anahita A., Tominaga, Masako, Veloso, Eugenio A., Yamasaki, Toru, Yamazaki, Shusaku, and Ziegler, Christa

Published
2006

10. Gabbro

Author

Koepke, Jürgen, Harff, Jan, editor, Meschede, Martin, editor, Petersen, Sven, editor, and Thiede, JÖrn, editor

Published
2016
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16. Mantle rock exposures at oceanic core complexes along mid-ocean ridges

Author

Ciazela Jakub, Koepke Juergen, Dick Henry J.B., and Muszynski Andrzej

Subjects
peridotite, occ, detachment fault, megamullion, slow-spreading ridge, Geology, QE1-996.5
Abstract

The mantle is the most voluminous part of the Earth. However, mantle petrologists usually have to rely on indirect geophysical methods or on material found ex situ. In this review paper, we point out the in-situ existence of oceanic core complexes (OCCs), which provide large exposures of mantle and lower crustal rocks on the seafloor on detachment fault footwalls at slow-spreading ridges. OCCs are a common structure in oceanic crust architecture of slow-spreading ridges. At least 172 OCCs have been identified so far and we can expect to discover hundreds of new OCCs as more detailed mapping takes place. Thirty-two of the thirty-nine OCCs that have been sampled to date contain peridotites. Moreover, peridotites dominate in the plutonic footwall of 77% of OCCs. Massive OCC peridotites come from the very top of the melting column beneath ocean ridges. They are typically spinel harzburgites and show 11.3–18.3% partial melting, generally representing a maximum degree of melting along a segment. Another key feature is the lower frequency of plagioclase-bearing peridotites in the mantle rocks and the lower abundance of plagioclase in the plagioclase-bearing peridotites in comparison to transform peridotites. The presence of plagioclase is usually linked to impregnation with late-stage melt. Based on the above, OCC peridotites away from segment ends and transforms can be treated as a new class of abyssal peridotites that differ from transform peridotites by a higher degree of partial melting and lower interaction with subsequent transient melt.

Published
2015
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23. Cumulates

Author

Koepke, Jürgen, Harff, Jan, editor, Meschede, Martin, editor, Petersen, Sven, editor, and Thiede, JÖrn, editor

Published
2016
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26. Metal migration through an oceanic crust-mantle transition zone (ICDP OmanDP holes CM1A and CM2B)

Author

Marciniak, Dariusz, primary, Ciążela, Jakub, additional, Pieterek, Bartosz, additional, Jesus, Ana, additional, Koepke, Juergen, additional, Strauss, Harald, additional, Lazarov, Marina, additional, Panczyk, Magdalena, additional, Kuhn, Thomas, additional, Horn, Ingo, additional, Slaby, Ewa, additional, Prell, Marta, additional, and Czupyt, Zbigniew, additional

Published
2022
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32. Quantifying the Axial Magma Lens Dynamics at the Roof of Oceanic Magma Reservoirs (Dike/Gabbro Transition): Oman Drilling Project GT3 Site Survey

Author

France, Lydéric, Lombard, Maéva, Nicollet, Christian, Berthod, Carole, Debret, Baptiste, Koepke, Juergen, Ildefonse, Benoit, and Toussaint, Aurore

Subjects
Dewey Decimal Classification::500 | Naturwissenschaften::550 | Geowissenschaften, magma chamber, granoblastic dikes, ddc:550, heat flux, fast-spreading oceanic centers, gabbros
Abstract

At oceanic spreading centers, the interactions between the igneous system that builds the crust, and the hydrothermal system that cools it govern the plumbing system architecture and its thermokinetic evolution. At fast-spreading centers, most of those interactions occur around the axial magma lens (AML) that feeds the upper crust, and possibly part of the underlying mushy igneous reservoir. Heat extracted from crystallizing AML is transferred through a conductive boundary layer to the overlying hydrothermal system. Quantifying the AML physical and thermal evolutions and its interactions with hydrothermal system is therefore essential to understand oceanic accretion. Those general issues were the rationale of drilling ICDP OmanDP Hole GT3A, and we present herein the geological, structural, and petrological data that were used as a site survey to select its location. GT3 area enables observations in three dimensions of fossilized AMLs and overlying dikes. The new field data and corresponding mineral compositions are used together with thermokinetic and thermodynamic models to deliver an integrated dynamic model for the AML/hydrothermal system interactions. Results attest that the isotropic gabbro interval is composite, with gabbro bodies intruding and reheating both gabbros and dikes (up to 1,040°C). We show that AMLs should be considered as transient igneous bodies that likely crystallize from primitive MORBs in decades, releasing heat to the intruded hosts, and feeding high temperature vents on the seafloor. We show for the first time that the thermal gradient recorded in AML roof is consistent with the heat fluxes reported at active hydrothermal vents.

Published
2021

37. Primitive layered gabbros from fast-spreading lower oceanic crust

Author

Gillis, Kathryn M., Snow, Jonathan E., Klaus, Adam, Abe, Natsue, Adrião, Álden B., Akizawa, Norikatsu, Ceuleneer, Georges, Cheadle, Michael J., Faak, Kathrin, Falloon, Trevor J., Friedman, Sarah A., Godard, Marguerite, Guerin, Gilles, Harigane, Yumiko, Horst, Andrew J., Hoshide, Takashi, Ildefonse, Benoit, Jean, Marlon M., John, Barbara E., Koepke, Juergen, Machi, Sumiaki, Maeda, Jinichiro, Marks, Naomi E., McCaig, Andrew M., Meyer, Romain, Morris, Antony, Nozaka, Toshio, Python, Marie, Saha, Abhishek, and Wintsch, Robert P.

Published
2014
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39. Evidence for delocalized anticooperative flash induced proton binding as revealed by mutants at the M266His iron ligand in bacterial reaction centers

Author

Cheap, Helene, Tandori, Julia, Derrien, Valerie, Benoit, Mireille, de Oliveira, Pedro, Koepke, Juergen, Lavergne, Jerome, Maroit, Peter, and Sebban, Pierre

Subjects
Hemoproteins -- Electric properties, Hemoproteins -- Structure, Bacterial proteins -- Electric properties, Bacterial proteins -- Structure, Iron compounds -- Electric properties, Iron compounds -- Structure, Biological sciences, Chemistry
Abstract

Two bacterial reaction centers (RCs) mutants with a modified ligand of the non-heme iron are studied by flash-induced absorbance change spectroscopy. No important changes are observed for the rate constants of the first and second electron transfers between the first quinoc electron acceptor [Q.sub.A] and [Q.sub.B].

Published
2007

40. The formation of SiO.sub.2-rich melts within the deep oceanic crust by hydrous partial melting of gabbros

Author

Koepke, Juergen, Berndt, Jasper, Feig, Sandrin T., and Holtz, Francois

Subjects
Silica, Earth sciences
Abstract

Byline: Juergen Koepke (1), Jasper Berndt (2), Sandrin T. Feig (1), Francois Holtz (1) Keywords: Oceanic plagiogranite; Gabbro; Oceanic crust; Partial melting; Plagioclase Abstract: Small amounts of felsic, evolved plutonic rocks, often called oceanic plagiogranites, always occur as veins or small stocks within the gabbroic section of the oceanic crust. Four major models are under debate to explain the formation of these rocks: (1) late-stage differentiation of a parental MORB melt, (2) partial melting of gabbroic rocks, (3) immiscibility in an evolved tholeiitic liquid, and (4) assimilation and partial melting of previously altered dikes. Recent experimental data in hydrous MORB-type systems are used to evaluate the petrogenesis of oceanic plagiogranites within the deep oceanic crust. Experiments show that TiO.sub.2 is a key parameter for the discrimination between different processes: TiO.sub.2 is relatively low in melts generated by anatexis of gabbros which is a consequence of the low TiO.sub.2 contents of the protolith, due to the depleted nature of typical cumulate gabbros formed in the oceanic crust. On the other hand, TiO.sub.2 is relatively high in those melts generated by MORB differentiation or liquid immiscibility. Since the TiO.sub.2 content of many oceanic plagiogranites is far below that expected in case of a generation by simple MORB differentiation or immiscibility, these rocks may be regarded as products of anatexis. This may indicate that partial melting processes triggered by water-rich fluids are more common in the deep oceanic crust than believed up to now. At slow-spreading ridges, seawater may be transported via high-temperature shear zones deeply into the crust and thus made available for melting processes. Author Affiliation: (1) Institut fuer Mineralogie, Leibniz Universitaet Hannover, Callinstrasse 3, 30167, Hannover, Germany (2) Institut fuer Mineralogie, Westfaelische Wilhelms-Universitaet, Corrensstrasse 24, 48149, Muenster, Germany Article History: Registration Date: 16/08/2006 Received Date: 01/04/2006 Accepted Date: 15/08/2006 Online Date: 16/09/2006 Article note: Communicated by J. Hoefs.

Published
2007

46. Uphill electron transfer in the tetraheme cytochrome subunit of the Rhodopseudomonas viridis photosynthetic reaction center: evidence from site-directed mutagenesis

Author

Chen, I-Peng, Mathis, Paul, Koepke, Juergen, and Michel, Hartmut

Subjects
Biochemistry -- Research, Cytochromes -- Research, Mutagenesis -- Research, X-ray crystallography -- Analysis, Biological sciences, Chemistry
Abstract

Research has been conducted on the cytochrome subunit of the Rhodopseudomonas viridis photosynthetic reaction center (RC). The mutant RC structure has been determined via X-ray crystallography.

Published
2000

48. Rapid Cooling History Of A Neotethyan Ophiolite: Evidence For Contemporaneous Subduction Initiation And Metamorphic Sole Formation

Author

Parlak, Osman, Dunkl, Istvan, Karaoglan, Fatih, Kusky, Timothy M., Zhang, Chao, Wang, Lu, Koepke, Juergen, Billor, Zeki, Hames, Willis E., Simsek, Emrah, Simsek, Gokce, Simsek, Tugce, and Ozturk, Selena Ezgi

Abstract

The Beywhir-Hoyran Nappes, including Mesozoic carbonate platform rocks, deepsea sediments, and ophiolite-related units, crop out extensively on the western limb of the Isparta Angle in the Central Taurides, Turkey. The ophiolite-related rocks are represented by variably serpentinized harzburgitic mantle tectonites, tectonically underlain by a subophiolitic metamorphic sole and melange. The harzburgitic mantle tectonites and metamorphic sole are intruded by undeformed isolated dikes. Protoliths of the metamorphic sole are similar to within-plate alkali basalts and associated sediments. The isolated dikes were geochemically derived mainly from tholeiitic magma and, to a lesser extent, from alkaline magma. Five isolated dike samples yielded U-Pb ages ranging from 90.8 +/- 1.6 Ma to 87.6 +/- 2.1 Ma (zircon) and from 102.3 +/- 7.4 Ma to 87.5 +/- 7.9 Ma (titanite). Seven amphibolite samples yielded U-Pb age ranges of 91.1 +/- 2.1-88.85 +/- 1.0 Ma (zircon) and 94.0 +/- 4.8-90.0 +/- 9.4 Ma (titanite) and a Ar-40-Ar-39 age range of 93.7 +/- 0.3-91.4 +/- 0.4 Ma (hornblende). U-Pb and Ar-40-Ar-39 ages of mineral phases with different closure temperatures (similar to 900-500 degrees C) from the isolated dikes and metamorphic sole rocks are almost identical and overlapping within 1 sigma, suggesting that both the magmatic growth of oceanic crust and formation of metamor- phic sole were contemporaneous and cooled very rapidly. Hence, all the data should be interpreted as the crystallization ages of the ophiolite and metamorphic sole pair. Genesis of suprasubduction zone-type oceanic crust, genesis and exhumation of the metamorphic sole, and postmetamorphic dike emplacement within the Inner Tauride Ocean can be best explained by subduction initiation and rollback processes during the Late Cretaceous based on petrological and geochronological data obtained from the ophiolitic rocks of the Beywhir-Hoyran Nappes.

Published
2019

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