کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
8911660 1638620 2018 54 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Timing and duration of Variscan high-pressure metamorphism in the French Massif Central: A multimethod geochronological study from the Najac Massif
ترجمه فارسی عنوان
زمان و مدت زمان دگرگونی فشار بالای واریسکان در مرکز ماسه فرانسوی: مطالعات ژئوشنگولوژی چند منظوره از ماسه نجاک
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
چکیده انگلیسی
Accurate dating of eclogite-facies metamorphism is of paramount importance in order to understand the tectonic evolution of an orogen. An eclogite sample from the Najac Massif (French Massif Central, Variscan belt) displays a zircon-bearing garnet-omphacite-amphibole-rutile-quartz peak assemblage. Pseudosection modeling suggests peak pressure conditions of 15-20 kbar, 560-630 °C. Eclogite-facies garnet displays Lu-enriched cores and Sm-rich rims and yields a Lu-Hf age of 382.8 ± 1.0 Ma and a Sm-Nd age of 376.7 ± 3.3 Ma. The ages are interpreted as marking the beginning of the prograde garnet growth during the initial stages of the eclogite-facies metamorphism, and the high-pressure (and temperature) peak reached by the rock, respectively. Zircon grains display chondrite-normalized REE spectra with variably negative, positive or no Eu anomalies and are characterized by either enriched or flat HREE patterns. However, they yield a well constrained in situ LA-ICP-MS U-Pb age of 385.5 ± 2.3 Ma, despite this REE pattern variability. Zr zonation in garnet, Y content in zircon and the diversity of zircon HREE spectra may suggest that zircon crystallized prior to and during incipient garnet growth on the prograde P-T path, recording the initial stages of the eclogite-facies conditions. Consequently, the zircon age of 385.5 ± 2.3 Ma, comparable within error with the Lu-Hf age obtained on garnet, is interpreted as dating the beginning of the eclogite-facies metamorphism. Accordingly, the duration of the prograde part of the eclogite-facies event is estimated at 6.1 ± 4.3 Myr. Subsequent exhumation is constrained by an apatite U-Pb age at 369 ± 13 Ma.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volumes 308–309, May 2018, Pages 381-394
نویسندگان
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