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  Dating fluid-mineral interaction in exhumed (U)HP rocks (Dabie Shan, China and Rhodope, Greece): processes and implications

Wawrzenitz [Hoymann], N., Romer, R. L., Grasemann, B., Kylander-Clark, A. R. C., Krohe, A., Mposkos, E. (2013): Dating fluid-mineral interaction in exhumed (U)HP rocks (Dabie Shan, China and Rhodope, Greece): processes and implications - Abstract Volume, 10th International Eclogite Conference (Courmayeur, Italy 2013), 122-122.

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Wawrzenitz [Hoymann], N.1, Autor              
Romer, R. L.1, Autor              
Grasemann, B.2, Autor
Kylander-Clark, A. R. C.2, Autor
Krohe, A.2, Autor
Mposkos, E.2, Autor
Affiliations:
13.1 Inorganic and Isotope Geochemistry, 3.0 Geochemistry, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum, ou_146040              
2External Organizations (TEMPORARY!), ou_persistent22              

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 Zusammenfassung: In rocks exhumed from depth corresponding to (U)HP conditions, fluid-induced dissolution– precipitation processes have significant bearing on element and isotope transport, on mineral reactions and hence on rheology. The U-Th-Pb system in geochronometers of such rocks — in this case, titanite and monazite — responds to fluid-mineral interaction; this response is dependent on the composition of the interacting fluid and on the deformation mechanism activated in the hosting rock. Tracking and dating the fluid-mineral-deformation histories using simultaneously measured in-situ U-Th-Pb and trace element data (Laser Ablation Split Stream ICPMS; LASS) and also Sr isotope data, is exemplified by the study of (A) pre- and post-UHP titanite from calc-silicates (Dabie UHP unit) and (B) monazite from relict granulites (Rhodope UHP domain). A) A pre-UHP titanite megacryst (XAl 0.18-0.19) has been partly replaced in a series of reactions that gave chemically and/or Sr-isotopically distinct product minerals. During stage I (subduction associated with rock deformation), rutile formed at the rim of the titanite. Following stage I, rutile back-reacted to form titanite by dissolution-precipitation reactions (stage II). The new titanite has relatively high XAl (0.21-0.27) and low HFSE contents. It is in turn replaced during stage III by titanite, showing low XAl (0.09-0.15) and relative HFSE enrichment. Channelized fluid infiltration (stage IV) resulted in titanite replacement by allanite. These four stages record in a single titanite the mineral-fluid reaction history from deep subduction to exhumation. Variable Sr isotopic composition demonstrates that fluids from different sources were present during the various stages of fluid-rock interaction. In rim portions completely replaced during the dissolution precipitation reaction stages, U-Th-Pb dating yield ages of c. 224 Ma (stage II) and c. 214 Ma (stage III). In the calc-silicate host rock pervasive fluid infiltration during exhumation has not been accompanied by ductile deformation. B) A HP granulite with the pre-deformative granulite mineral assemblage garnet, rutile, kyanite, K-feldspar, plagioclase, quartz has been pervasively deformed at high dislocation creep strain at high temperature and pressure conditions. The granulite is a relict within migmatitic rocks, migmatized in the presence of fluid during decompression at c. 42 Ma (Liati et al., 2011). Rutile and biotite yield U-Pb and Rb-Sr ages of 39–36 Ma, probably reflecting cooling following the migmatitization. Monazite in the HP granulite reacted with fluid by fluid-induced dissolution– precipitation reactions, resulting in resetting of U-Th-Pb ages at c. 54 Ma. Trace-element data are used to link the ages to the fluid-mineral-reaction-history and to identify monazite domains that have been completely reset during deformation.

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 Datum: 2013
 Publikationsstatus: Final veröffentlicht
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 Identifikatoren: GFZPOF: PT2 Earth System Dynamics: Coupled Processes and Regional Impact
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Veranstaltung

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Titel: 10th International Eclogite Conference
Veranstaltungsort: Courmayeur, Italy
Start-/Enddatum: 2013-09-02 - 2013-09-10

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Titel: Abstract Volume
Genre der Quelle: Konferenzband
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Seiten: - Band / Heft: - Artikelnummer: - Start- / Endseite: 122 - 122 Identifikator: -