Magma evolution in the upper part (Stage IV) of the Fongen-Hyllingen Layered Intrusion, central Norway

• EL-RUS Mohamed M. ABU

  Physics of Geological Processes, University of Oslo Present address: Geology Department, Assiut University

• WILSON J. Richard

  Department of Earth Sciences, Aarhus University

• SØRENSEN Henning S.

  Department of Earth Sciences, Aarhus University Present address: Danfoss A/S

抄録

The upper part (Stage IV) of the Fongen-Hyllingen intrusion, southeast of Trondheim, Norway, comprises a ∼ 1800 m thick sequence of cumulates showing a strong normal fractionation trend from olivine gabbros at the bottom through diorites to quartz-bearing syenites at the roof. Mineral compositions show extreme ranges: olivine Fo_74-0; Ca-rich pyroxene Mg#79-0; plagioclase An_60-0. The cumulate sequence has been divided into five intervals based on cumulus assemblages. The summation method has been used to calculate successive magma compositions for these intervals based on whole-rock major element chemical analyses of 49 samples. The most primitive calculated magma composition has 51.7% SiO₂, 5.0% MgO, 5.3% total alkalis and a Mg-number of 47.5; it lies near the base of the basaltic trachyandesite field in the Total Alkali Silica (TAS) diagram, very close to the dividing line between tholeiitic and alkaline suites. This magma evolved through the trachyandesite field into the trachyte field. The most evolved magma composition has ∼ 11.4% alkalies; alkali enrichment is not due to assimilation of metapelites. There was very little iron-enrichment during fractionation and magma density decreased continuously, enabling repeated influxes of new magma to pond and to elevate the resident melt, facilitating magma stratification. The parental magma may have resided in a lower crustal chamber where it differentiated before repeatedly supplying the overlying Fongen-Hyllingen chamber.

収録刊行物

• Journal of Mineralogical and Petrological Sciences

  Journal of Mineralogical and Petrological Sciences 102 (2), 93-114, 2007

  一般社団法人　日本鉱物科学会

キーワード

• Layered intrusion
• Summation method
• Parental magma
• Olivine hiatus
• Density evolution

詳細情報

• CRID: 1390001206545777152
• NII論文ID: 10018419071
• NII書誌ID: AA11460926
• DOI: 10.2465/jmps.060626
• ISSN: 13493825
• ISSN: 13456296
• 本文言語コード: en
• データソース種別:
  • JaLC
  • Crossref
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可