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| Titel |
Recrystallization history and P-T-time-isotopic evolution of coesite-bearing eclogites: implications for exhumation processes (SW Tianshan, China) |
| VerfasserIn |
Zhou Tan, Philippe Agard, Jun Gao, Timm John, Ji-Lei Li, Tuo Jiang, Léa Bayet, Xin-Shui Wang, Xi Zhang |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148565
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| Publikation (Nr.) |
 EGU/EGU2017-12831.pdf |
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| Zusammenfassung |
| The Chinese Southwestern Tianshan high- to ultra-high pressure low temperature
(HP-UHP/LT) metamorphic belt exhibits well-preserved mafic layers, tectonic
blocks/slices and boudins of different sizes and lithology embedded within dominant
meta-volcanosedimentary rocks. Despite a wealth of previous studies on UHP relicts, P-T
paths estimates and age constraints for metamorphism, controversies still exist on
P-T-t assessments and regional exhumation patterns (i.e., tectonic mélange versus
internally coherent “sub-belt” model). Our study focuses on a group of coesite-bearing
eclogite samples from a thick (∼ 5 meters) layered metabasalt outcrop in order to
unravel its detailed tectono-metamorphic evolution through space and time (both
prograde, peak and exhumation). Using SIMS zircon U-Pb and oxygen isotope
analyses, TIMS Sm-Nd multi-point isochron dating, in situ laser-ICP-MS trace-element
analyses, classical thermobarometry and thermodynamic modeling, we link the
multistage zircon growth to garnet growth and reconstruct a detailed P-T-time-isotopic
evolution history for this UHP tectonic slice: from UHP peak burial ∼ 2.95 ± 0.2
GPa, 510 ± 20 ∘ around 318.0 ± 2.3 Ma to HP peak metamorphism ∼ 2.45 ±
0.2 GPa, 540 ± 20 ∘ at 316.8 ± 0.8 Ma, then, with eclogite-facies deformation ∼
2.0 ± 0.15 GPa, 525 ± 25 ∘ at 312 ± 2.5 Ma, exhumed to near surface within
ca. 303 to ca. 280 Ma. Our P-T-time-isotopic results combined to the exhaustive
compilation of regional radiometric data and P-T estimates notably point to the existence
of a short-lived period of rock detachment and exhumation (< 10 Ma, i.e. at ca.
315 ± 5 Ma) with respect to “long-term” subduction duration (> 50-100 Ma). |
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