Formation and transformation of mixed-layer minerals by tertiary intrusives in cretaceous mudstones, West Greenland

Victor A. Drits, Holger Lindgreen, Boris A. Sakharov, Hans Jørgen Jakobsen, Anthony E. Fallick, Alfred L. Salyn, Lidia G. Dainyak, Bella B. Zviagina, Dan N. Barfod

Research output: Contribution to journalArticleResearchpeer-review

21 Citations (Scopus)


In the Nuussuaq Basin, West Greenland, a thick succession of Tertiary dolerites has penetrated Upper Cretaceous mudstone. The mixed-layer minerals of mudstone core samples have been analyzed by X-ray diffraction, solid-state 29Si and 27Al magic-angle spinning nuclear magnetic resonance, Mössbauer and infrared spectroscopies, thermal analysis, chemical analysis, stable isotopes ( 18O/ 16O), and K/Ar dating. The mixed-layer minerals include for each sample two mixed-layer phases consisting of pyrophyllite, margarite, paragonite, tobelite, illite, smectite and vermiculite layers. The main, 80 m thick intrusion resulted in the formation of pyrophyllite, margarite, paragonite and tobelite layers. However, the tobelite layers are absent in samples <21 m from this intrusion. Furthermore, chlorite was formed and kaolinite destroyed in samples adjacent to minor intrusions and at distances <60 m from the large intrusion. For the first time, the detailed, complex mixed-layer structures formed during contact metamorphism of kaolinitic, oil-forming mudstones have been investigated accurately. The formation of tobelite layers reveals that oil formation has taken place during contact metamorphism. Furthermore, K/Ar dating of mixed-layer minerals from shale indicates that the intrusives are of early Eocene age. The 80 m thick intrusive is responsible for the main mixed-layer transformations, whereas two thin (3 m and 0.5 m thick) intrusions contribute little. Thus, the detailed mixed-layer investigation has contributed significantly to the understanding of the regional geology and the contact metamorphic processes.

Original languageEnglish
Pages (from-to)260-283
Number of pages24
JournalClays and Clay Minerals
Issue number3
Publication statusPublished - Jun 2007


  • Burial diagenesis
  • Greenland
  • Illite-smectite
  • Oil-source rocks
  • Tobelite

Programme Area

  • Programme Area 4: Mineral Resources


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