Abstract
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.
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.
| Originalsprog | Engelsk |
|---|---|
| Publikationsdato | 2011 |
| Antal sider | 1 |
| Status | Udgivet - 2011 |