Xenocrystic zircon in Central New York State Kimberlites record Neoproterozoic disturbance of Grenville Basement rocks

• Published in: Lithos 2023-11, Vol.456-457, p.107303, Article 107303
• Main Authors: Lupulescu, M.V., Chiarenzelli, J.R., Fisher, C.M., Hanchar, J.M., Bailey, D.G.
• Format: Article
• Language: English
• Subjects: Central New York State; Kimberlite; Late Neoproterozoic rifting; Lu-Hf isotopes; Middle Devonian sedimentary rocks; U-Th-Pb dates; Zircon xenocrysts
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2023.107303

Zircon grains from two central New York State (USA) Mesozoic kimberlite dikes intruding Middle and Upper Devonian sedimentary rocks were analyzed for UPb and LuHf isotopes, and trace elements, and were derived from different parts of the continental crust and/or upper mantle. Zircon from the Six Mile Creek (SMC) kimberlite has variable physical properties and “felsic” chondrite normalized REE patterns, and yields dates (321–1732 Ma) compatible with entrainment of sedimentary xenoliths during accent through the upper crust. In contrast, zircon from the Taughannock Creek (TAG) kimberlite have near concordant UPb dates that are distributed between intercept ages of 572 ± 25 and 960 ± 20 (2σ) Ma (MSWD = 0.61) with homogeneous LuHf systematics and 176Lu/177Hf ratios 900 °C) during the final assemblage of the supercontinent Rodinia, followed by subsequent Pb-loss, resulting in a discordant array and decoupling of the UPb and LuHf isotopic systems prior to entrainment. Concordant zircon UPb dates, anchoring the lower intercept, yield an age of 596 ± 7 (2σ) Ma for the timing of Pb-loss. This most likely occurred in a zone of rifting and mafic magmatism beneath Central New York and Pennsylvania during the opening of the Iapetian Ocean. •Xenocrystic zircons were recovered from kimberlite dikes in central New York, USA.•One sample yielded detrital zircons derived from the local Paleozoic section.•The other sample yielded zircon from underlying lower crust or mantle sources.•Granulite facies zircons of Grenville age show Neoproterozoic (∼ 597 Ma) lead loss.•The study area is hypothesized to overlie a rift basin of the Iapetus Ocean.