Triassic emplacement age of the Kalkfeld complex

Authors: U Kramm T Körner M Kittel H Baier S Sindern

Publish Date: 2017/03/18

Volume: 106, Issue: 8, Pages: 2797-2813

PDF Link

Abstract

Rb–Sr wholerock and mineral isotope data from nepheline syenite tinguaite and carbonatite samples of the Kalkfeld Complex within the Damaraland Alkaline Province NW Namibia indicate a date of 242 ± 65 Ma This is interpreted as the age of final magmatic crystallization in the complex The geological position of the complex and the spatially close relationship to the Lower Cretaceous Etaneno Alkaline Complex document a repeated channeling of smallscale alkaline to carbonatite melt fractions along crustal fractures that served as pathways for the mantlederived melts This is in line with Triassic extensional tectonic activity described for the nearby Omaruru Lineament–Waterberg Fault system The emplacement of the Kalkfeld Complex more than 100 Ma prior to the ParanáEtendeka event and the emplacement of the Early Cretaceous Damaraland intrusive complexes excludes a genetic relationship to the Tristan Plume The initial εSr–εNd pairs of the Kalkfeld rocks are typical of younger African carbonatites and suggest a melt source in which EM I and HIMU represent dominant componentsWe are very grateful to A Stracke Münster and K Mezger now Bern for the chance to perform the isotope measurements at the lab of the Institute of Mineralogy University of Münster R B Trumbull Potsdam kindly provided the two critical samples KF 201 und KF 203 of Bühn and Trumbull 2003 The careful chemical work of J Jakobi and help during preparation of figures by MA Voß both RWTH Aachen University as well as stylistic corrections by N Jordan Leicester are greatly appreciated Constructive criticism of the reviewers B Trumbull Potsdam and RE Harmer Grahamstown which significantly improved the manuscript is gratefully acknowledged

Keywords: