Calcic Garnets as a Source of Information on the Age of Ultramafic Alkaline Intrusions in the Kola Magmatic Province

Ultramafic Alkaline Rocks of Kepino Cluster, Arkhangelsk, Russia: Different Evolution of Kimberlite Melts in Sills and Pipes

“…A recent study of Rb-Sr-isotopic ages of phlogopite from kimberlites in ADP has shown that pipes in the Zolotica and Chernoozero clusters, as well as the Tersky Coast kimberlite, were emplaced within an age range of 380 ± 2 Ma to 375 ± 2 Ma [34]. These ages match the main episode of ultramafic alkaline magmatism with carbonatite formation in the KACP massifs (e.g., [43,80]). In contrast, Kepino cluster kimberlites were emplaced earlier (397.3 ± 1.2 Ma), prior to the majority of the ADP kimberlites and the KACP massifs.…”

Timing of Carbonatite Ultramafic Complexes of the Eastern Sayan Alkaline Province, Siberia: U–Pb (ID–TIMS) Geochronology of Ca–Fe Garnets

“…Calcic garnet is a widespread mineral of rocks of the foidolite series, and is therefore a promising source of reliable information about the age of alkaline ultramafic intrusions. The results of a U-Pb (ID-TIMS) geochronological study of calcic garnet from alkaline ultramafic complexes of the Kola Alkaline province (Vuoriyarvi, Sallanlatva, Salmagorsky, and Afrikanda) enable an evaluation of a narrower time span of the main pulse of alkaline ultramafic magmatic activity in Kola province than was previously estimated [14]. This study is an example of attempt to solve the problem of the duration of the Eastern Sayan alkaline magmatic province using a U-Pb system of calcic garnet from ultramaficalkaline series intrusive rock complexes.…”

Emplacement ages of diamondiferous kimberlites in the Wafangdian District, North China Craton: New evidence from LA-ICP-MS U-Pb geochronology of andradite-rich garnet

“…Andradite-rich garnets are widespread in crustal metamorphic rocks and skarns, which can also be generated (but comparatively rare) in some mantle-related rocks including serpentinized peridotites from ophiolites (Ghosh et al, 2017) and silicaundersaturated alkaline ultramafic complexes (Barrie, 1990;Müntener and Hermann, 1994;Vuorinen et al, 2005;Tappe et al, 2006Tappe et al, , 2009Marks et al, 2008;Dongre et al, 2016;Salnikova et al, 2019;Choudhary et al, 2020;Millonig et al, 2020;Stifeeva et al, 2020). Here, the Wafangdian kimberlites containing abundant andradites pose an interesting problem regarding the nature of these calcic garnets.…”

“…In comparison with perovskite, andradite-rich garnet is frequently found in the heavy-mineral concentrates of cratonic kimberlites and also more easily separated from crushed materials owing to its relatively large grain size. Although direct dating of calcic garnet varieties from kimberlite pipes has rarely been attempted, such Ti-andradites have been proven to faithfully record the emplacement ages of compositionally diverse magmas (e.g., ultramafic-alkaline and/or carbonatitic intrusive rocks: Salnikova et al, 2018aSalnikova et al, , 2018bSalnikova et al, , 2019Yang et al, 2018;Stifeeva et al, 2020) as its U-Pb isotopic clock would be triggered during magmatic ascent. Moreover, the chemical composition and textural features of different garnet generations can provide some key information about multiple stages of magmatic crystallization or metasomatic alteration associated with kimberlite formation (e.g., Dongre et al, 2016;Zhu et al, 2019b;Choudhary et al, 2020).…”