Zircons from ultramafic-mafic intrusions at Noril'sk area (Russia): a compositional and U-Pb study

K. N. Malich, O. V. Petrov, I. Yu Badanina, Sergey L. Presnyakov

Research output: Contribution to journalMeeting abstractpeer-review

Abstract

World-class platinum-group-element (PGE)-Cu-Ni deposits closely linked to intracontinental paleorift-related ultramafic-mafic intrusions are located in the northwestern corner of the Siberian craton, Russia. In spite of its significant metallogenic potential, age constraints for majority of the orebearing
intrusions are poorly defined. Similarly, timing and duration of the ore concentration responsible to form an economic deposit has been rarely evaluated quantitatively. This study presents the results of trace element data and uranium-lead ages for about 550 grains of zircons, which were extracted using ppm-mineralogy technique (NATI Research JSC, St, Petersburg, http://www.natires.com) from drill core samples from the various types of igneous bodies. The latter include economic PGE-Cu-Ni deposits associated with the Noril’sk-1 (drill core MN-2), Talnakh (OUG-2) and Kharaelakh (KZ-844) intrusions, subeconomic deposits related to the Chernogorsk (MP-2), Zub-Marksheider (MP-27) and Vologochan (OV-29) intrusions and none economic the
Nizhny Talnakh (TG-31) intrusion. Isotope geochemical data (102 REE analyses and 616 U-Pb measurements) were determined with secondary ion mass spectrometer SHRIMP-II at All-Russia Geological Research Institute. Zircons are characterized by a fuzzy (smoky) cathode luminescence, with a virtual total absence of zoning. Petrographic inspection, however, revealed at least two generations of zircon that show distinct solid inclusion assemblage. In the binary Th-U diagram, the investigated zircons (Th/U = 0.8-7.5) are clearly different from zircons derived from various geological settings and only partly match zircons from MARID suite (Kinny and Dawson 1992). In REE discrimination diagrams (Sm/La)N – La and Ce/Ce* - (Sm/La)N zircons mainly plot in the field of “magmatic” zircon (after Hoskin, 2005), with a tale approaching the “hydrothermal” field.Four age groups of zircon were determined, with concordant U-Pb ages that vary in the range 220-260 Ma. Polyphase grains also preserve domains with U-Pb ages that cluster around 300 and 340 Ma. Rare detrital grains (around 1900 Ma) have been also observed. Our new findings are in a good agreement with assumption about the interaction of distinct magmas and a prolonged duration of component fractionation in the magmatic system. Consequently, these processes could lead to high degrees of separation and concentration of ore elements and formation of specific ore magma of unique scales and concentrations.
Original languageEnglish
Pages (from-to)A616-A616
Number of pages1
JournalGeochimica et Cosmochimica Acta
Volume71
Issue number15, Supplement
Publication statusPublished - Aug 2007
Externally publishedYes
EventGoldschmidt Conference (17th : 2007) - Cologne, Germany
Duration: 19 Aug 200724 Aug 2007
Conference number: 17

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