Age of Mirny field kimberlites (Siberia) and application of rutile and titanite for U-Pb dating of kimberlite emplacement by LA-ICP-MS

抄録

This paper presents new data related to the emplacement ages of the Amakinskaya and Taezhnaya kimberlites of the Mirny field, Siberia, located in the southern part of the Yakutian diamondiferous province. This study analyzed rutile and titanite grains along with zircons for U-Pb isotope composition by laser ablation (LA)-inductively coupled plasma-mass spectrometry (ICP-MS) and evaluated the applicability of rutile and titanite for the dating of kimberlite emplacements. Both minerals contain substantial admixtures of common Pb in their Pb isotope composition. Therefore, the ²⁰⁷Pb method was applied for common Pb correction during age calculation. The obtained U-Pb ages of the Taezhnaya pipe were 363 ± 12 and 359 ± 12 Ma, respectively, for zircon and titanite. Ages of 366 ± 10 and 361 ± 16 Ma was obtained from Amakinskaya pipe titanite and rutile, respectively. All age estimates correspond to the main epoch of diamondiferous kimberlite activity in the Siberian platform and suggest the formation of the Mirny kimberlite field within a single event or two separate events occurring close together in time. Results obtained from this study indicate that rutile and titanite can be useful for the dating of kimberlite emplacements.