Research Article Origin of rare-element-mineralized Damara Belt pegmatites: A geochemical and light stable isotope study L. Ashworth a,b, ⁎, J.A. Kinnaird a , P.A.M. Nex a , C. Harris c , A.B. Müller d,e a School of Geosciences, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa b School of Geography, Environment and Earth Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6012, New Zealand c Department of Geological Sciences, University of Cape Town, Rondebosch 7700, South Africa d Natural History Museum, University of Oslo, P.O. Box 1172 Blindern, N-0318 Oslo, Norway e Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom abstract article info Article history: Received 12 December 2019 Received in revised form 8 June 2020 Accepted 20 June 2020 Available online 05 July 2020 Neoproterozoic Li–Cs–Ta (LCT) pegmatites and pegmatitic sheeted leucogranites (SLGs) of the Damara Belt, Namibia, although coeval, are variably mineralized and have intruded multiple tectono-stratigraphic units. Major and trace element data together with oxygen and hydrogen isotopes were used to identify possible sources for these pegmatite melts. Two groups of pegmatites can be identified on the basis of O-isotopes. Group A peg- matites, which include U-enriched pegmatitic SLGs with a Nb–Y–F (NYF) pegmatite affinity (Kinnaird and Nex, 2007), and Li–Be-rich LCT pegmatites, with δ 18 O = 11.2–12.9‰, are metaluminous to peraluminous, suggesting that they evolved from a partial melt of a mixed metasedimentary and igneous source. Group B pegmatites, which contain Sn, Li–Sn and tourmaline mineralization, have higher δ 18 O values (14–16‰), consistent with their derivation from a purely S-type source, with possible incorporation of, or exchange with, carbonates. Crys- tallization temperatures calculated using Ti-in-quartz and O-isotope thermometry are in agreement with each other, and range from 420 to 575 °C for LCT pegmatites and 650 °C for pegmatitic SLGs. The juxtaposition of co- eval, post-tectonic LCT pegmatites and pegmatitic SLGs with an NYF affinity in the Damara Belt precludes tectonic setting as the only source of compositional variability in LCT and NYF pegmatite melts. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Granitic pegmatites are among the most highly-evolved, fraction- ated magmatic components of the Earth's crust. They have been a sub- ject of interest due to their mineralogical and textural complexity, as well as their economic importance as sources of Li, Nb, Ta, Sn and indus- trial minerals, with extensive studies having been conducted on their internal zonation, mineralogy, textural characteristics, emplacement, and composition; however, these have focused on highly evolved, volatile- and rare metal-enriched bodies (see reviews in London, 2008). A number of studies have used O- and H-isotopes to understand the origins and internal evolution of LCT and NYF pegmatites (e.g. Kontak and Kyser, 2009; Taylor et al., 1979). The Damara Belt of Namibia provides an ideal setting in which to study mineralized LCT pegmatites and coeval pegmatitic sheeted leucogranites (SLGs) due to their abundance, compositional diversity, and favourable field exposure. Here, post-orogenic pegmatite dikes have been emplaced in metasedimentary and igneous rocks of the Damara Supergroup (Borg and Gauert, 2018). Whereas they have been studied in isolation or on a local scale (e.g. Diehl, 1993; Keller et al., 1999; Kinnaird and Nex, 2007; Marais, 2019; Roering and Gevers, 1964; Schneider and Seeger, 1992; Singh, 2009), this contribution aims to compare ten coeval, yet mineralogically diverse, Damaran pegmatites on a regional scale. This was done using geochemical and O- and H-isotope studies to identify the source of pegmatite magmas, as a source of mineralogical heteroge- neity, during the late stages of continental collision. 2. Regional geology The northeast-trending Damara Belt in Namibia forms part of the Neoproterozoic Damara Orogen, one of several orogenic belts which led to the amalgamation of Gondwana (see reviews in Miller, 2008; Borg and Gauert, 2018). It intersects the north-trending Kaoko and south-trending Gariep Belts in Swakopmund, Namibia, which to- gether record successive phases of rifting and spreading, subduction, and continental collision between the Kalahari, Congo, and Rio de la Plata plates between 900 and 460 Ma (Borg and Gauert, 2018; Frimmel et al., 2011; Gray et al., 2008; Milani et al., 2015; Miller, 2008; Stanistreet et al., 1991). The Damara Belt is composed of metasedimentary sequences which unconformably overlie the Pre- Lithos 372–373 (2020) 105655 ⁎ Corresponding author at: School of Geography, Environment and Earth Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6012, New Zealand. E-mail address: luisa.ashworth@vuw.ac.nz (L. Ashworth). https://doi.org/10.1016/j.lithos.2020.105655 0024-4937/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos