The Genesis and Development of the Guli Dunite Core Complex of the Guli Massif, Northern Siberia, Russia. A Multi - Disciplinary Study

Janine Pink

Research output: ThesisDoctoral Thesis

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Abstract

The Guli Massif, located in the Meimecha Kotui province of northern Siberia, Russia, represents the worlds largest Alaskan-Uralian-type complex, oval in shape, and with an extension of 35 x 45 km, occupying an area of 1500 to 1600 km2. It is composed of a giant dunite core complex with occasional uneconomic chromite disseminations and clinopyroxenite dykes, an alkaline suite surrounding the core complex, and carbonatite intrusions. Geological field work was primarily focused on logging and sampling of selected drill cores from the Guli core complex (G17, G13) and from the ultramafic-mafic alkaline sequence forming the envelope around the core complex (G1). The aims of this study were i) to characterise the formation and genesis of the dunite core complex, ii) investigate possible links between the dunite core complex, its surrounding ultramafics and the meimechites, and iii) investigate a possible source for the PGE placers that occur within the Massif. The detailed mineralogical, textural, petrological and geochemical investigations of this study revealed the following results: The Guli dunite core complex represents a restitic mantle material with a metasomatic overprint. This becomes obvious on the basis of textural, mineralogical (e.g. Fo of olivine 91-93) geochemical evidences and by modelling data. The Guli core dunite composition is achieved after 9 episodes of continuous partial melting of primitive mantle material under wet conditions, equivalent to a total partial melting of 52% and an extraction of approximately 95% of each melt batch. Clinopyroxenite dykes and plugs, intruding the dunite restite and found in the Guli core complex surrounding alkaline suite, represent early melt batches. Very minor melt portions of similar composition can be found in interstitial spaces within the restitic dunites of the core complex and are interpreted as not having escaped from the residue. Two distinct olivine cumulates (i.e. from G1 and G13), occurring at the periphery of the core complex, represent late melt batches, after approximately 40% of partial melting. The meimechites show a clear genetic link to the more primitive, less fractionated type of olivine cumulates (G1). Mineralogical and geochemical evidences indicate a common parental magma for the G1 olivine cumulates and the meimechites, the residuum of which is represented by the Guli core dunites. All rock types investigated show a variable enrichment of LREE, which has been characterised by addition of 0.03 to 0.05% of carbonatitic material to the dunite residuum and the melt batches.
Translated title of the contributionGenese und magmatische Entwicklung des Guli Dunit Komplexes des Guli Massivs, Nordsibirien, Russland. Eine multidisziplinäre Studie.
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Thalhammer, Oskar, Assessor A (internal)
  • Ebner, Fritz, Assessor B (internal)
Publication statusPublished - 2008

Bibliographical note

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Keywords

  • Guli Massif
  • mantle
  • metasomatism
  • dunite
  • olivine cumulate
  • LREE enrichment

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