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The Dovyren intrusive complex (northern Baikal region, Russia); isotope-geochemical markers of contamination of parental magmas and extreme enrichment of the source

A. A. Ariskin, L. V. Danyushevsky, E. G. Konnikov, R. Maas, Yu. A. Kostitsyn, A. McNeill, S. Meffre, G. S. Nikolaev and E. V. Kislov
The Dovyren intrusive complex (northern Baikal region, Russia); isotope-geochemical markers of contamination of parental magmas and extreme enrichment of the source
Russian Geology and Geophysics (March 2015) 56 (3): 411-434

Abstract

The Dovyren intrusive complex includes the ore-bearing (Cu-Ni-PGE) Yoko-Dovyren layered pluton (728 Ma, up to 3.4 km in thickness), underlying ultramafic sills, and comagmatic leuconorite and gabbro-diabase dikes. Studies of Sr-Nd-Pb isotope systems were carried out for 24 intrusive rocks and five associated low- and high-Ti basalts. The high-Ti basalts show 0.7028 < or = ( (super 87) Sr/ (super 86) Sr) (sub T) < or = 0.7048 and 4.6 < or = epsilon (sub Nd) (T) < or = 5.8, similar to the values in MORB. The intrusive basic and ultrabasic rocks are geochemically similar to the low-Ti formation, making a compact cluster of compositions with extremely high ratios of radiogenic Sr and Pb isotopes and low epsilon (sub Nd) values. The maximum enrichment in radiogenic Sr is shown by the rocks near the pluton bottom (( (super 87) Sr/ (super 86) Sr) (sub T) = 0.71387 + or - 0.00010 (2sigma ); epsilon (sub Nd) (T) = -16.09+ or -0.06), which are the products of crystallization of the most primitive high-Mg magmas. The above-located dunites, troctolites, and gabbro show lower enrichment, probably because of the contamination of the host rocks during the filling of the magma chamber and/or because of the slight heterogeneity of the source. Calculations of the proportions of mixing of the parental melt with carbonate terrigenous material have shown that the variations in the Sr and Nd isotope ratios are due to the incredibly high contamination of the sediments, up to 40-50%. This contradicts the succession of the main rock types in the Yoko-Dovyren pluton in accordance with the crystallization of picrite-basaltic magma. The contribution of 5-10% high-Ti component seems more likely and suggests interaction between two isotopically contrasting magmas in this province in the Late Riphean. In general, the minor variations in epsilon (sub Nd) (T) of the intrusive rocks and metavolcanics (-14.3+ or -1.1) testify to the isotopically anomalous source of the low-Ti magmas. The time variation trend of epsilon (sub Nd) and geochemical features of the Dovyren rocks indicate that the products of melting of 2.7-2.8 Ga suprasubduction mantle might have been the massif protolith. Thus, the Dovyren parental magmas formed from a much older (sub)lithospheric source in the Late Riphean. The source was initially enriched in a mafic component with a low Sm/Nd ratio and was isolated from the convecting mantle and mantle melting processes for approximately 2 Gyr. The existence of such a long-living and at least twice reactivated lithospheric substratum is confirmed by the fact that the Nd isotope evolution trend of the initially nonanomalous mantle protolith includes not only the Dovyren rocks but also the Paleoproterozoic gabbro of the Chinei pluton and the Archean enderbites of the Baikal region.


ISSN: 1068-7971
Serial Title: Russian Geology and Geophysics
Serial Volume: 56
Serial Issue: 3
Title: The Dovyren intrusive complex (northern Baikal region, Russia); isotope-geochemical markers of contamination of parental magmas and extreme enrichment of the source
Affiliation: Moscow State University, Faculty of Geology, Moscow, Russian Federation
Pages: 411-434
Published: 201503
Text Language: English
Publisher: Allerton Press, New York, NY, United States
References: 41
Accession Number: 2021-062609
Categories: Igneous and metamorphic petrologyEconomic geology, geology of ore depositsIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch map
N54°00'00" - N58°00'00", E108°00'00" - E114°00'00"
Secondary Affiliation: Russian Academy of Sciences, V. Vernadskiy Institute of Geochemistry and Analytical Chemistry, RUS, Russian FederationUniversity of Tasmania, Hobart, Tasmania, AUS, AustraliaRussian Academy of Sciences, Institute of Experimental Mineralogy, Moscow, RUS, Russian FederationUniversity of Melbourne, Parkville, Victoria, AUS, AustraliaBuryat State University, Ulan-Ude, RUS, Russian Federation
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2021
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