کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4691459 1636733 2015 14 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Paleotethyan subduction process revealed from Triassic blueschists in the Lancang tectonic belt of Southwest China
ترجمه فارسی عنوان
فرایند فرآیند پالئوتیتیان از بلوزچیستهای تریاس در کمربند تکتونیکی لانتاننگ جنوب غربی چین
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی


• The Suyi mafic blueschists were reported in the Lancang accretionary complex.
• The blueschist-facies metamorphism developed at ~ 0.5–0.9 GPa and 300–450 °C.
• The blueschist yields zircon age of 260 Ma and its protolith originated from seamount.
• The seamount was subducted easterly at 246 Ma and was transported upwardly at ~ 230 Ma.

The subduction of the Paleotethyan Ocean and subsequent continental collision along the Lancang tectonic belt of the southeastern Paleotethyan belt is a major tectonic event in Southwest China, but the event of the subduction preceding the final collision is still not well-constrained. The mafic blueschists exposed in the Lancang accretionary complex provide crucial records of the Paleotethyan subduction process. In this paper, we present a set of new petrologic, geochronological and geochemical data for the Suyi mafic blueschists in the Lancang metamorphic zone. The mineral assemblage of these blueschists consists of zoned sodic amphibole (25–30%), albite (15–20%), epidote (25–30%), phengite (5–10%), chlorite (~ 5–10%), and minor amounts of actinolite, apatite, sphene, zircon, ilmenite, quartz and secondary limonite. This suggests a prograde metamorphism from ~ 0.5 to ~ 0.9 GPa and retrograde metamorphic overprinting (back to ~ 0.6 GPa) within the temperature range of 300–450 °C. The Suyi blueschists give a zircon U–Pb age of 260 ± 4 Ma and glaucophane minerals formed during prograde metamorphism yield a 40Ar/39Ar plateau age of 242 ± 5 Ma (MSWD = 0.77; P = 0.54). The blueschists have geochemical compositions of subalkaline basalt and show typical OIB-type REE and multi-elemental patterns and εNd(t) values ranging from + 3.35 to + 4.85. Based on available data, it is inferred that the protolith formed at 260 Ma and originated from a basaltic seamount. The basaltic rocks subducted down to 30–35 km depths beneath the Lincang arc to form the epidote blueschists at ~ 242 Ma. The blueschists were subsequently transported to shallower crustal levels in response to the continuous underthrust of the subducted slab and the continent–continent collision in the middle–late Triassic. These results provide a systematic constraint on the tectonic evolution and temporal framework of the southeastern Paleotethyan belt in Southwest China.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tectonophysics - Volume 662, 1 November 2015, Pages 95–108
نویسندگان
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