Geochemical characteristics of proterozoic post-orogenic magmatism in the Nagssugtoqidian Mobile Belt of southeast Greenland

摘要: The final event in the Nagssugtoqidian (NAG) Mobile Belt of East Greenland is represented by post-orogenic intrusion plutonic bodies into an Archaen-Proterozoic polymetamorphic basement. petrogenesis rocks and dykes, which make up Ikasaulak Intrusive Complex, interpreted on basis their major- trace-element geochemistry. The investigated intrusive complex consists a lower ultramafic-mafic sequence upper-intermediate felsic sequence. A compositional gap exists at 60–70% SiO2 range. Silica-rich rocks, corresponding to minimum-melt composition, are characterized strong LREE enrichment highly fractionated REE patterns, consistent with origin partial melting garnet-rich source, probably triggered mantle-derived melts. Most primitive mafic show large-ion lithophile elements depletion Nb Ta. Although these data suggestive magmas generated destructive plate margins, there no geological reason for assuming subduction-related melts. Thus compositions appear be feature mantle retaining geochemical signature crust-generating processes occurring during previous NAG ocean subduction (1920-1840 Ma). Petrogenetic modelling indicates that fractional crystallization can only partially account differences 60% other mechanisms, such as concurrent assimilation fluid activity, involved. The present suggest mobile belt was stabilization sub-continental mantle, occurred least 200–300 Ma after processes.