Contact metamorphic and metasomatic processes at the Kharaelakh intrusion, Oktyabrsk deposit, Norilsk-Talnakh ore district: Application of LA-ICP-MS dating of perovskite, apatite, garnet, and titanite

• Published in: Economic Geology
• Main Authors: Marfin, AE, Ivanov, AV, Kamenetsky, VS, Abersteiner, A, Yakich, TY, Dudkin, TV
• Format: Article in Journal/Newspaper
• Language: English
• Published: Economic Geology Publ Co 2020
• Subjects: Earth Sciences; Geology; Geochronology; Norilsk; Talnakh; norilsk
• Online Access: https://doi.org/10.5382/ECONGEO.4744; http://ecite.utas.edu.au/143719

The Norilsk-Talnakh ore district in the northwestern Siberian platform contains globally unique reserves of Cu-Ni-sulfides with Pt and, especially, Pd. The Oktyabrsk deposit, which is one of the largest in the district, is spatially and genetically associated with the Kharaelakh mafic-ultramafic intrusion and its exceptionally large metamorphic and metasomatic aureoles. In this study, we employed in situ laser ablation-inductively coupled plasma-mass spectrometry U-Pb isotope dating of apatite, titanite, garnet, and perovskite that cocrystallize with disseminated sulfides within the aureole of metasomatic and contact metamorphic rocks. The calculated isotopic ages for apatite (257.3 4.5 and 248.9 5.1 Ma), titanite (248.6 6.8 and 249.1 2.9 Ma), garnet (260.0 11.0 Ma), and perovskite (247.3 8.2 Ma), though with large uncertainties, indicate that sulfide mineralization within metasomatic and contact-metamorphic rocks is coeval with the emplacement of the Kharaelakh intrusion. These isotopic dates are in complete agreement with the published isotope dilution-thermal ionization mass spectrometry U-Pb zircon ages for the Norilsk intrusions and, at the same time, notably older than available Re-Os isochron ages of sulfides. The latter ages have been long interpreted as evidence for a prolonged duration of magmatic ore-forming processes; however, our data narrow their life span. Trace elements in titanite and garnet allow distinguishing late- and postmagmatic grains, which show indistinguishable U-Pb isotope ages.