Depositional age, provenance and tectonic setting of the Proterozoic Ruyang Group, southern margin of the North China Craton

Late Paleoproterozoic rifting and accompanying magmatism and sedimentation, which occurred widely in the North China Craton, are interpreted to be related to the breakup of the supercontinent Columbia. The Ruyang Group, overlying the Xiong'er Group in the southern margin of the craton, is a typical fluvial-marine sedimentary sequence mainly composed of sandstone with minor shale and dolostone. Sandstones from the Ruyang Group exhibit high contents of SiO2 (86.8-98.7 wt.%) but relatively low contents of Al2O3, K2O, Na2O, TiO2 and MgO, typical of mature siliceous clastic rocks. Trace elements of these rocks indicate that the sequence was deposited in a passive continental margin environment and that the sedimentary detritus was derived from a Paleoproterozoic silicic-intermediate source, similar to other Paleo-Mesoproterozoic sedimentary sequences in the region. Detrital zircons from three sandstone samples of the Ruyang Group yield (207)pb/Pb-206 ages ranging from 1.70 Ga to 2.70 Ga with two pronounced peaks at ca. 2.10 Ga and 1.86 Ga. A weighted mean age at 1744 +/- 22 Ma from nine young zircon ages between 1.80 Ga and 1.70 Ga can constrain the maximum depositional age of the Ruyang Group. Most detrital zircons exhibit negative epsilon(Hf)(t) values ranging from -15.6 to 0 and old T-DM(C) ages ranging from 2.50 Ga to 3.60 Ga, implying reworking of Archean crust. A close match between the U-Pb ages and T-DM(C)(Hf) ages, as well as the positive epsilon(Hf)(t) values for some detrital zircons, indicate a contribution of juvenile materials. The detrital zircon grains have T-DM(C)(Hf) ages clustering between 3.00 Ga and 2.60 Ga with a peak at around 2.80-2.70 Ga, indicating a major period of crustal growth at this time. (C) 2014 Elsevier B.V. All rights reserved.