کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5781186 1635740 2017 70 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Syn-convergence extension in the southern Lhasa terrane: Evidence from late Cretaceous adakitic granodiorite and coeval gabbroic-dioritic dykes
ترجمه فارسی عنوان
فرورفتگی همگرا در جنوب لهاسا تررین: شواهد از قرنطینه اواخر کرتاسه آداکیتی و دایکهای گابرویی-دیوریتی کوبه ای
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی
Late Cretaceous (∼100-80 Ma) magmatism in the Gangdese magmatic belt plays a pivotal role in understanding the evolutionary history and tectonic regime of the southern Lhasa terrane. The geodynamic process for the formation of the early Late Cretaceous magmatism has long been an issue of hot debates. Here, petrology, geochronology and geochemistry of early Late Cretaceous granodiorite and coeval gabbroic-dioritic dykes in the Caina region, southern Lhasa, were investigated in an effort to ascertain their petrogenesis, age of intrusion, magma mixing and tectonic setting. Zircon U-Pb dating of granodiorite yields 206Pb/238U ages of 85.8 ± 1.7 and 86.4 ± 1.1 Ma, whilst that of the E-W trending dykes yields ages of 82.7 ± 2.6 and 83.5 ± 3.5 Ma. Within error, the crystallization ages of the dykes and the granodiorite are indistinguishable. Field observations and mineralogical microstructures are suggestive of a magma mixing process during the formation of the dykes and the granodiorite. The granodiorite exhibits geochemical features that are in agreement with those of subduction-related high-SiO2 adakites. The granodiorite and dykes have relatively constant εNd(t) values of +2.2 to +4.9 and initial 87Sr/86Sr ratios (0.7045-0.7047). These similar characteristics are herein interpreted as an evolutionary series from the dykes to granodiorite, consistent with magma mixing process. Ti-in-zircon thermometer and Al-in-hornblende barometer indicate that the granodiorite and the dioritic dyke crystallized at temperatures of ca. 750 and 800 °C, depths of ca. 6-10 and 5-9 km, respectively. Taking into account the synchronous magmatic rocks in the Gangdese Belt and the coeval rifted basin within the Lhasa terrane, the granodiorite and dykes reveal an early Late Cretaceous syn-convergence extensional regime in the southern Lhasa terrane, triggered by slab rollback of the Neotethyan oceanic lithosphere.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Geodynamics - Volume 110, October 2017, Pages 12-30
نویسندگان
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