Metasomatic reactions between archean dunite and trondhjemite at the seqi olivine mine in greenland

Laura Whyatt, Stefan Peters, Andreas Pack, Christopher L. Kirkland, Tonci Balic-Zunic, Kristoffer Szilas*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

A metasomatic zone formed between the contact of a 2940 ± 5 Ma intrusive trondhjemite sheet in the Archean dunite of the Seqi Ultramafic Complex, SW Greenland, consists of three distinct mineral zones dominated by (1) talc, (2) anthophyllite, and (3) phlogopite. These zones supposedly resulted from a process of dissolution of olivine by silica rich fluid residual from the trondhjemite magma, with crystallization of secondary minerals along a compositional gradient in the fluid phase. A zircon crystal inclusion in a large (4 cm) olivine porphyroblast was dated in situ via LA-ICP-MS U–Pb isotope analysis, yielding a weighted mean207 Pb/206 Pb age of 2963 ± 1 Ma, which coincides with granulite facies metamorphism and potential dehydration. Considering phase relations appropriate for the dunite composition, we deduced the talc forming conditions to be at temperatures of 600–650 C and at a pressure below 1 GPa. This is supported by oxygen isotope data for talc, anthophyllite and phlogopite in the metasomatic zone, which suggests formation in the temperature range of 600–700 C from fluids that had a δ18 O of ~8%o and a ∆’17 O0.528 of about −40 ppm, i.e., from fluids that could have been derived from the late stage trondhjemite sheet.

Original languageEnglish
Article number85
JournalMinerals
Volume10
Issue number1
DOIs
Publication statusPublished - Jan 2020

Bibliographical note

Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Other keywords

  • Anthophyllite
  • Archaean
  • Greenland
  • Metasomatism
  • Phlogopite
  • Talc
  • Ultramafic rocks

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