کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4716963 1638738 2009 18 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Devonian to Permian plate tectonic cycle of the Paleo-Tethys Orogen in southwest China (II): Insights from zircon ages of ophiolites, arc/back-arc assemblages and within-plate igneous rocks and generation of the Emeishan CFB province
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Devonian to Permian plate tectonic cycle of the Paleo-Tethys Orogen in southwest China (II): Insights from zircon ages of ophiolites, arc/back-arc assemblages and within-plate igneous rocks and generation of the Emeishan CFB province
چکیده انگلیسی

New SHRIMP zircon ages for ophiolites, arc/back-arc assemblages and within-plate igneous rocks constrain the evolution of the Paleo-Tethys Orogen of southwest China. Ophiolites represent remnants of the Paleo-Tethys ocean, which was divided by the Simao terrane into two tracts, the main ocean in the west (current position) and a branch in the east. The main ocean has been inferred to originate from Gondwana break-up in the Early Devonian, and the heritage is preserved as the Changning-Menglian ophiolite (SSZ-type). The oceanic branch is represented by the Ailaoshan (NMORB-type)–Jinshajinag (EMORB-type) ophiolites. Zircons from a diabase and a plagiogranite of the Ailaoshan ophiolite yielded 206Pb/238U ages of 382.9 ± 3.9 Ma and 375.9 ± 4.2 Ma. The age of a cumulate gabbro from the Jinshajiang ophiolite is 343.5 ± 2.7 Ma. A metagabbro of the Changning-Menglian ophiolite yielded a crystallization age of 267.1 ± 3.1 Ma. We interpret the ages of the Ailaoshan and Jinshajiang ophiolites to represent sea-floor spreading in the branch ocean, whereas the age of the Changning-Menglian ophiolite reflects closure of the main ocean. Arc/back-arc assemblages (zoned mafic–ultramafic complexes and arc volcanic rocks) are records of convergent plate boundary magmatic activity. Rocks of the Gicha complex (back-arc rift) yielded zircon ages of 306.2 ± 4.6 Ma for a tonalite, 301.0 ± 2.9 Ma for a microgabbro, 297.1 ± 2.0 Ma for a plagioclase hornblendite, and 281.3 ± 1.7 Ma for a diabase. A gabbro and a tonalite of the Banpo complex (plutonic arc) yielded identical ages of 285.6 ±1.7 Ma and 285.8 ± 2.0 Ma. A basalt of the Yaxianqiao volcanic arc was dated at 266.2 ± 2.2 Ma. Within-plate igneous rocks were also dated. Two amphbolite xenoliths in the Jinshajiang ophiolite mélange, derived from low-Ti continental flood basalts, have zircon ages of 439.3 ± 3.5 Ma and 403.7 ± 3.1 Ma, which we interpret to represent the inception of continental rifting prior to the opening of the branch ocean. The small Dalongkai differentiated mafic–ultramafic intrusion reflects post-orogenic extension and is characterized by superimposed arc and within-plate geochemical signatures. Zircons from a plagioclase pyroxenite of this intrusion yielded an age of 245.6 ± 1.4 Ma.These new results, combined with geological and geochemical data, allow the reconstruction of a Devonian to Permian plate tectonic cycle in which generation of the Emeishan CFB province correlates with Paleo-Tethys orogeny in time. This study provides evidence for cyclic continent–ocean–continent development via multiple orogenesis, as well as temporal constraints on the dynamic relationship between plate tectonics and generation of a large igneous province.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volume 113, Issues 3–4, December 2009, Pages 767–784
نویسندگان
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