Formation ages and source regions of the Palaeoproterozoic Gaofan, Hutuo and Dongjiao groups in the Wutai and Dongjiao areas of the North China Craton from SHRIMP U-Pb dating of detrital zircons: Resolution of debates over their stratigraphic relationships

Abstract

This paper reports detrital zircon age distributions of meta-sedimentary rocks of the Gaofan, Hutuo and Dongjiao groups in the Wutai and Dongjiao areas of the North China Craton. Detrital zircons of a quartzite from the Gaofan Group are mainly ∼2.5 Ga in age, with some ∼2.7 Ga and older. A quartzite pebble from the basal conglomerate of the Hutuo Group is similar in detrital zircon age distribution to the quartzite of the Gaofan Group. For a meta-feldspar-quartz sandstone from the Dongjiao Group, the age of detrital zircons is mainly concentrated at ∼2.5 Ga. No zircons older than 2.6 Ga have been identified, but with some being 1.84 Ga and 2.2–2.0 Ga in age. Combined with earlier studies, the following conclusions can be drawn: (1) The Gaofan Group is early Palaeoproterozoic in age and is much younger and unrelated to the late Neoarchaean Wutai granite-greenstone terrane, which it unconformably overlies. As such, the Gaofan Group is one of the oldest Palaeoproterozoic meta-sedimentary units in the North China Craton. (2) The Hutuo Group was deposited in the middle Palaeoproterozoic (2.14-2.09 Ga) on a continental basement, after the early Palaeoproterozoic Gaofan Group. (3) The Dongjiao Group was formed after 1.84 Ga, and probably belongs to the lower portion of the Changcheng System. (4) The detrital zircons from all the three groups show an obvious age peak of ∼2.5 Ga, being sourced from the igneous rocks formed in the intense tectono-magma-thermal events at the end of Archaean in the North China Craton.