Petrogenesis of synorogenic high-temperature leucogranites (Damara orogen, Namibia): Constraints from U-Pb monazite ages and Nd, Sr and Pb isotopes

A. Paul*, Stefan Jung, R. L. Romer, A. Stracke, F. Hauff

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Two suites of leucogranites were emplaced at 508 +/- 5.9 Ma in the Okombahe District of the Damara belt (Namibia) synchronous with the peak of regional high-temperature metamorphism. The Sr (Sr-87/Sr-86(init): 0.707 to 0.711), Nd (epsilon Nd-init: -4.5 to -6.6), and Pb isotopic (Pb-206/Pb-204: 18.51-19.13; Pb-207/Pb-204: 15.63-15.69; Pb-208/Pb-204: 38.08-38.66) compositions indicate that these peraluminous S-type granites were derived from mid- to lower-crustal rocks, which are slightly different to the metapelitic rocks into which they intruded. Since the leucogranites are unfractionated and show no evidence for assimilation or contamination, they constrain the temperature and pressure conditions of their formation. Calculated Zr and LREE saturation temperatures of ca. 850 degrees C indicate high-temperature crustal melts. High Rb/Sr and low Sr/Ba ratios are consistent with biotite dehydration melting of pelitic source rocks. Qz-Ab-Or systematics reveal that melting and segregation for the least fractionated samples occurred at ca. 7 kbar corresponding to a mid-crustal level of ca. 26 km. However, there is no evidence for a mantle component that could have served as a local heat source for crustal melting. Therefore, the hot felsic magmas that formed close to the time of peak metamorphism are the result of long-lasting high temperature regional metamorphic conditions and intra-crustal collision. (C) 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)1614-1626
Number of pages13
JournalGondwana Research
Volume25
Issue number4
DOIs
Publication statusPublished - May 2014

Keywords

  • Leucogranites
  • Crustal melts
  • Biotite dehydration melting
  • U-Pb monazite
  • Sr Nd Pb isotopes
  • TRACE-ELEMENT
  • PAN-AFRICAN
  • SM-ND
  • FRACTIONAL CRYSTALLIZATION
  • PERALUMINOUS GRANITOIDS
  • METASEDIMENTARY ROCKS
  • CRUSTAL EVOLUTION
  • PELITIC SYSTEM
  • KAOKO BELT

Fingerprint

Dive into the research topics of 'Petrogenesis of synorogenic high-temperature leucogranites (Damara orogen, Namibia): Constraints from U-Pb monazite ages and Nd, Sr and Pb isotopes'. Together they form a unique fingerprint.

Cite this