U–Pb geochronology of calcite carbonatites and jacupirangite from the Guli alkaline complex, Polar Siberia, Russia
- 9 June 2021
- journal article
- research article
- Published by Mineralogical Society in Mineralogical Magazine
- Vol. 85 (4), 469-483
- https://doi.org/10.1180/mgm.2021.53
Abstract
This work is the first in situ U–Pb geochronological study of perovskite and calcic garnet (andradite) from the Guli complex in the Maimecha–Kotuy alkaline province (Polar Siberia, Russia). The U–Pb isotopic compositions of perovskite from contact zones of the two carbonatite stocks (Southern and Northern) and from jacupirangite separating the stocks were determined by laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICPMS) and isotope-dilution thermal-ionisation mass-spectrometry (ID-TIMS). The LA-ICPMS and ID-TIMS data for perovskite from the Northern carbonatite stock are in good agreement, yielding 206Pb/238U ages of 250.4 ± 1.1 Ma and 249 ± 2 Ma, respectively. These ages are also within the analytical uncertainty from the ID-TIMS results for perovskite from jacupirangites (250 ± 1 Ma). The LA-ICPMS results for perovskite from the Southern carbonatite stock indicate its somewhat older age (255.3 ± 2.4 Ma), implying the possibility of small-volume mantle magmatism predating the eruption of the Siberian flood basalts at ca. 252–251 Ma. This interpretation is supported by reports of pre-flood magmatism elsewhere in eastern Siberia. Andradite crystals from the contact between the Southern stock and metasomatised melilitolite were analysed by ID-TIMS. These measurements are inconclusive (247 ± 6 Ma) and could not be used to constrain further the timing of carbonatitic magmatism in the southern part of the complex. The present contribution also presents a refined methodology for LA-ICPMS geochronological studies of perovskite with elevated levels of common lead, and addresses some of the problems with previously proposed calibration standards.Keywords
This publication has 65 references indexed in Scilit:
- U–Pb ages, Sr–Nd- isotope geochemistry, and petrogenesis of kimberlites, kamafugites and phlogopite-picrites of the Alto Paranaíba Igneous Province, BrazilChemical Geology, 2013
- Trace-element partitioning in perovskite: Implications for the geochemistry of kimberlites and other mantle-derived undersaturated rocksChemical Geology, 2013
- The origin of Triassic/Jurassic kimberlite magmatism, Canada: Two mantle sources revealed from the Sr-Nd isotopic composition of groundmass perovskiteGeochemistry, Geophysics, Geosystems, 2011
- Iolite: Freeware for the visualisation and processing of mass spectrometric dataJournal of Analytical Atomic Spectrometry, 2011
- Trace-element study and uranium-lead dating of perovskite from the Afrikanda plutonic complex, Kola Peninsula (Russia) using LA-ICP-MSTschermaks Mineralogische und Petrographische Mitteilungen, 2010
- A Pb isotope investigation of the Guli massif, Maymecha-Kotuy alkaline-ultramafic complex, Siberian flood basalt province, Polar SiberiaTschermaks Mineralogische und Petrographische Mitteilungen, 2006
- Emplacement age and isotope geochemistry of Sung Valley alkaline–carbonatite complex, Shillong Plateau, northeastern India: implications for primary carbonate melt and genesis of the associated silicate rocksLithos, 2005
- First report of early Triassic A-type granite and syenite intrusions from Taimyr: product of the northern Eurasian superplume?Lithos, 2003
- Three compositional varieties of perovskite from kimberlites of the Lac de Gras field (Northwest Territories, Canada)Mineralogical Magazine, 2001
- Separation and preconcentration of uranium from acidic media by extraction chromatographyAnalytica Chimica Acta, 1992