Isotopic-Geochemical Systematics (Sm–Nd, Lu–Hf) of Neoarchean Subalkaline and Alkaline Rocks of the Keivy Structure (Kola Peninsula): Their Age and Genetic Relations

The Neoarchean subalkaline magmatism of the Keivy structure is expressed in the formation of the volcanoplutonic latite–monzonite–granite association (LMGA). The formation of LMGA magmas is assumed to occur due to melting of metasomatically altered mafic rocks during intrusion into the lower crust o...

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Bibliographic Details
Published in:Geology of ore deposits 2019-12, Vol.61 (7), p.581-588
Main Author: Vetrin, V. R.
Format: Article
Language:English
Subjects:
Age composition
Alkalies
Alkalis
Aluminum oxide
Earth and Environmental Science
Earth Sciences
Gabbro
Geological data
Intrusion
Iron
Magma
Massifs
Melts
Mineral Resources
Radiometric dating
Rock
Rocks
Silica
Silicon dioxide
Systematics
Titanium dioxide
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Summary:The Neoarchean subalkaline magmatism of the Keivy structure is expressed in the formation of the volcanoplutonic latite–monzonite–granite association (LMGA). The formation of LMGA magmas is assumed to occur due to melting of metasomatically altered mafic rocks during intrusion into the lower crust of basaltic melts initial for rocks of the dike complex and gabbro–labradorite massifs. The alkaline granites associated with LMGA have a close U–Pb age but a later formation time based on the geological data. With respect to LMGA, alkali granites have increased concentrations of SiO 2 , alkalis (K 2 O/Na 2 O = 1.1–1.4), iron (F# = 84–98%), a high agpaitic index ( K agp = 0.86–1.2), and lower quantities of TiO 2 , MgO, Fe tot , and Al 2 O 3 , which probably resulted from the higher degree of differentiation of their initial melts compared to LMGA.
ISSN:1075-7015
1555-6476
DOI:10.1134/S1075701519070146