Geochemical features of the drusite massifs,the central part of the Belomorian mobile belt: I. Distribution of major and trace elements in the rocks |
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Authors: | N A Krivolutskaya V F Smol’kin N M Svirskaya V P Mamontov A S Fanygin B V Belyatskii I A Roshchina |
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Institution: | 1.Vernadsky Institute of Geochemistry and Analytical Chemistry,Russian Academy of Sciences,Moscow,Russia;2.Vernadsky State Geological Museum,Moscow,Russia;3.OAO Murmanskaya GRE,Apatity,Russia;4.All-Russia Research Institute of Geology and Mineral Resources of the World Ocean (VNIIOkeanologiya),St. Petersburg,Russia |
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Abstract: | The comparative-geochemical study was first conducted for the ultrabasic-basic massifs of the central part of the Belomorian
mobile belt, which were previously ascribed to the drusite complex on the basis of the presence of coronal textures. The studied
magmatic bodies are geochemically heterogeneous and can be subdivided into three groups: (1) high-Mg rocks (MgO > 20 wt %)
with elevated Cr content, enriched trace element patterns, and deep negative Ta-Nb anomaly (Sorkajoki Massif). Intrusions
of this group are geochemically close to the layered plutons of Northern and Eastern Karelia (Kivakka, Burakovsky) and to
the intrusions of the Kola Peninsula (Monchepluton and others); (2) low-Mg intrusions (MgO < 10 wt %) with elevated contents
of Fe, Ti, and P (403-m Height Massif). The rocks composing these intrusions are characterized by subhorizontal trace element
patterns and weak Ta-Nb anomaly; (3) intrusions with intermediate MgO contents (10–20 wt %), flat, occasionally depleted REE
patterns, and lack of Ta-Nb anomaly (Mt. Grob Tundra). The identified geochemical differences do not depend on the degree
of metamorphic transformations, but were presumably caused by differences in phase and chemical composition of parental magmas,
as well as by conditions of their crystallization. It was substantiated that ultrabasic-basic massifs presently united into
the drusite complex are genetically diverse and acquired similar textural appearance due to regional metamorphism. Thus, the
presence of coronal textures is insufficient to ascribe the intrusions to the drusite complex, their mineralogical and geochemical
composition should be taken into account. |
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