Journal of African Earth Sciences 197 (2023) 104750 Available online 7 October 2022 1464-343X/© 2022 Elsevier Ltd. All rights reserved. The timing and tectonic context of Pan-African gem bearing pegmatites in Malawi: Evidence from Rb–Sr and U–Pb geochronology Tuhin Chakraborty a, * , Charles F. Kankuzi a, b , Johannes Glodny c , Dirk Frei d , Steffen H. Büttner a a Department of Geology, Rhodes University, Grahamstown, 6140, Eastern Cape, South Africa b Geology and Earth Sciences Department, University of Malawi, Zomba, Malawi c GFZ German Research Centre for Geosciences, Potsdam, Germany d Department of Earth Science, University of Western Cape, South Africa A R T I C L E INFO Keywords: Malawi Pegmatite Gondwana East Africa orogen Kuunga Rb–Sr U–Pb zircon ABSTRACT The Pan-African belts of Malawi contain a largely unexplored endowment of gem bearing pegmatites. We present U–Pb in zircon (LA-ICPMS) and Rb–Sr mineral isochron geochronological and isotope data from pegmatites across Malawi. The pegmatites contain tourmaline, beryl, aquamarine, zircon, amethyst and sunstone as gemstone species. Two zircon bearing pegmatites in southern Malawi intruded early in the Pan-African orogenic cycle at 719 ± 5 Ma and 729 ± 4 Ma and are associated with the emplacement of alkaline rocks that formed during an intra-continental rifting episode in the eastern part of former Rodinia. One further zircon pegmatite containing inherited zircon of a similar age (746 ± 44 Ma) was emplaced at 598 ± 15 Ma, after the assembly of Western and Eastern Gondwana and the formation of the East African Orogen (EAO). The majority of the ana- lysed pegmatites, however, are signifcantly younger. The ~550 Ma pegmatites were emplaced during the Kuunga Orogeny, correlating with the collision of northern and southern Gondwana cratonic entities. During a prolonged post-collisional period, possibly related to crustal collapse and extension, further gem-mineralised pegmatites formed at ~520 ± 6 Ma and ~500–485 Ma. The youngest pegmatite intruded in the southern Malawian Ntcheu area in the Middle Ordovician at ~460 Ma. A large spread in 87 Sr/ 86 Sr initial isotopic ratios between 0.70556 and 0.79018 suggests a variety of magma sources for the Kuunga-related pegmatites with a variably strong crustal affnity. 1. Introduction The Pan-African belts in eastern and southeastern Africa formed over a prolonged period of contractional, transcurrent and collisional tec- tonics in the late Neoproterozoic and early Paleozoic. Two major orogenic belts formed during this time, the East African Orogen (EAO), stretching from today’s Arabic Peninsula to Malawi and Mozambique, and the slightly younger Kuunga Orogen, transecting southern Africa from east to west, from northern Mozambique through Malawi, Zambia, Botswana and Namibia (e.g., Stern, 1994; Grantham et al., 2003, 2008, 2019; Meert, 2003; Oriolo et al., 2017, Fig. 1). In present-day southern and eastern Africa, the amalgamation of Gondwana during the East African and Kuunga orogenies followed the subduction of the Mozambique Ocean and its western extension, the Khomas Ocean, that formed an oceanic connection to the Adamastor Ocean (Meert, 2003; Oriolo et al., 2017, 2021, Fig. 1). These oceans had existed since the early stages of Rodinia break-up in the Neoproterozoic (~850–800 Ma; Meert, 2003; Li et al., 2008), forming complex marginal basins and intra-oceanic magmatic arcs that were active between ~800 and 700 Ma (e.g. Stern, 1994; Meert, 2003; Grantham et al., 2003; Collins and Pisarevsky, 2005; Fitzsimons and Hulscher, 2005; J¨ ons and Schenk, 2008). From about 700 Ma onwards the oceanic basins closed, leading to the collisional assembly of Gondwana between ~650 and 520 Ma, with an extended post-collisional and possibly post-Pan-African period of deformation, metamorphism and magmatic activity in the EAO and the Kuunga Orogen, lasting to the end of the Ordovician (e.g. Grantham et al., 2003, 2008; Meert, 2003; Oriolo et al., 2017, 2021). In this paper we refer to the evolution of related lithospheric entities from the break-up of Rodinia, through the stages of oceanic growth and consumption to the collisional assembly of Gondwana during the East African and Kuunga orogenies as the Pan-African orogenic cycle. The region of Malawi and parts of the neighbouring Mozambique, * Corresponding author. E-mail address: t.chakraborty@ru.ac.za (T. Chakraborty). Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci https://doi.org/10.1016/j.jafrearsci.2022.104750 Received 9 March 2022; Received in revised form 4 October 2022; Accepted 4 October 2022