Melt compositions and processes in the kimberlite provience of southern West Greenland
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Melt compositions and processes in the kimberlite provience of southern West Greenland. / Pilbeam, Llewellyn; Nielsen, Troels; Waight, Tod Earle.
2011.Publikation: Konferencebidrag › Konferenceabstrakt til konference › Forskning
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T1 - Melt compositions and processes in the kimberlite provience of southern West Greenland
AU - Pilbeam, Llewellyn
AU - Nielsen, Troels
AU - Waight, Tod Earle
N1 - Goldschmidt, Vienna, Austria, 14-19 August 2011. Mineralogical Magazine 75, p. 1643.
PY - 2011
Y1 - 2011
N2 - The kimberlite province of southern West Greenland (600- 560Ma) comprises kimberlite sensu stricto on the Archean craton and aillikites on the paleoproterzoic sheild to the North. Carbonatite melt and xenocrystic olivine dominate the kimberlite sensu stricto occurrences of the Manitsoq region [1] whilst the silica content and H2O/CO2 ratio of the bulk rocks increases towards Sisimuit [2, 3]. A common carbonatite rich end-member is implicated [2]. This is in contrast to the prevailing dogma of a continuum from carbonatite though aillikite to kimberlite with increasing melting degree [4]. The authors have demonstrated that a process of DFC (digestion fractional crystallisation) whereby the cognate olivine crystallisation is coupled to entrained xenocrystic orthopyroxene assimilation is a key process during the formation of the Majugaa occurrence of the Manitsoq region [5]. Mass balance considerations are here applied to the Majuagaa bulk rock in term of the DFC mechanism obtaining an estimate of parental melt and magma composition for the Majuagaa kimberlite. We use bulk rock major and trace element geochemistry together with mineral chemistry to investigate the range of melt compositions involved in the region. Melting models involving introduction of a carbonatite melt are applied to inferred lithospheric mantle compositions based upon nodule assemblages. Compositional variations across the southern West Greenland province are explained by interaction of an aesthenospheric carbonatite melt with lithospheric mantle. The major and trace element budgets are understood as a combination of melting regime together with mixing and reaction between the primary melts and the dispersed xenocryst assemblages. Variations of the mineral assemblages of the cognate groundmass are similarly explained.
AB - The kimberlite province of southern West Greenland (600- 560Ma) comprises kimberlite sensu stricto on the Archean craton and aillikites on the paleoproterzoic sheild to the North. Carbonatite melt and xenocrystic olivine dominate the kimberlite sensu stricto occurrences of the Manitsoq region [1] whilst the silica content and H2O/CO2 ratio of the bulk rocks increases towards Sisimuit [2, 3]. A common carbonatite rich end-member is implicated [2]. This is in contrast to the prevailing dogma of a continuum from carbonatite though aillikite to kimberlite with increasing melting degree [4]. The authors have demonstrated that a process of DFC (digestion fractional crystallisation) whereby the cognate olivine crystallisation is coupled to entrained xenocrystic orthopyroxene assimilation is a key process during the formation of the Majugaa occurrence of the Manitsoq region [5]. Mass balance considerations are here applied to the Majuagaa bulk rock in term of the DFC mechanism obtaining an estimate of parental melt and magma composition for the Majuagaa kimberlite. We use bulk rock major and trace element geochemistry together with mineral chemistry to investigate the range of melt compositions involved in the region. Melting models involving introduction of a carbonatite melt are applied to inferred lithospheric mantle compositions based upon nodule assemblages. Compositional variations across the southern West Greenland province are explained by interaction of an aesthenospheric carbonatite melt with lithospheric mantle. The major and trace element budgets are understood as a combination of melting regime together with mixing and reaction between the primary melts and the dispersed xenocryst assemblages. Variations of the mineral assemblages of the cognate groundmass are similarly explained.
M3 - Conference abstract for conference
ER -
ID: 33811867