Tectonic significance and geodynamic processes of large-scale early cretaceous granitoid magmatic events in the southern great Xing¡¦an range, north China
Journal
Tectonics
Journal Volume
36
Journal Issue
4
Pages
615-633
Date Issued
2017
Author(s)
Abstract
The origin and geodynamic evolution of peak Early Cretaceous magmatism in the southern Great Xing¡¦an Range, North China, have long been controversial. Here we report new U-Pb zircon ages (141¡V129Ma) of a suite of dioritic-granitic rocks from central InnerMongolia, far fromthe sutures or plate boundaries of the Paleo-Pacific and Mongol-Okhotsk oceans, thus delineating an Early Cretaceous intracontinentalmagmatic province,whichhadapeakactivityat130¡V120Ma.Dioriticsuiteincludingdiorite, tonalite,andgranodioriteshows variable zircon £`Hf(t) of +1.4 to+ 11.8 and £_18O values of +5.7 to +6.9?, while granitic suite consisting of monzogranite, syenogranite, and granite porphyry also records variable zircon £`Hf(t) of¡V0.9 to +15.0 and £_18O values of +6.3 to +8.1?, suggesting crustalmelting by preexisting crustal source with important recycled supracrustalcomponents includingfluids. Furthermore, these rocks showvariablewhole-rock £_7Livalues (¡V0.6 to +12.1?), indicating fluids played an important role inmagma source.We propose a deep-sourcedwater-fluxed melting scenario by ancient hydrous slabs inherited fromthe Paleo-Asian Ocean that were trapped in the deep interior, thus releasing aqueous fluids tomelt the lithosphericmantle and produce water-richmaficmagmas. Thesemaficmagmaswere underplated into crustwhere they promotedwater-fluxed partialmeltingto generate the large-scale Early Cretaceousmagmatismin the southern Great Xing¡¦an Range. Suchmelting due to fluxing of aqueous fluids was probably operating as a widespread process responsible for the Early Cretaceous dramatically tectonomagmatic events and evolution of continental crust in NE Asia. ? 2017. American Geophysical Union. All Rights Reserved.
Type
journal article