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Abstract

Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics,as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensionaltectonic regimes, Archean/Proterozoic carbonatites provide important constraints on the timing of thebreakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, inpart because of the difficulty in recognizing Archean/Proterozoic carbonatites, which are characterized by strongfoliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies.Here,we report the recognition of a ~1.85 Ga carbonatite in Chaihulanzi area of Chifeng in north China basedon systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. Thecarbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation.Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals alongwith minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo N 98), phlogopite, diopside,and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silicacontent together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantleplume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might betriggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent,the Proterozoic tectonic evolution of the North China Craton (NCC) provides important insights into thegeodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoicboundary is the key point of tectonic transition from compressional to extensional settings in the NCC. Thenewly identified ~1.85 Ga carbonatite provides a direct link between the long-lasting supercontinental breakupand plume activity, which might be sourced from the “slab graveyard,” continental crustal slabs subducted intoasthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation ofthe continental breakup at ~1.85 Ga.

Item Type:	Article
Authors/Creators:	Xie, Y and Qu, Y and Zhong, R and Verplanck, PL and Meffre, S and Xu, D
Keywords:	carbonatite, North China Craton, mantle plume, Columbia supercontinent breakup
Journal or Publication Title:	Gondwana Research
Publisher:	Int Assoc Gondwana Research
ISSN:	1342-937X
DOI / ID Number:	https://doi.org/10.1016/j.gr.2018.10.001
Copyright Information:	Copyright 2018 International Association for Gondwana Research
Related URLs:	Google Scholar: Meffre, S UTAS Profile: Meffre, S
Item Statistics:	View statistics for this item

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