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Article

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

1
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry Russian Academy of Sciences (IGEM RAS), 119017 Moscow, Russia
2
Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKhI), 119334 Moscow, Russia
3
Geology Department, Lomonosov Moscow State University, 119991 Moscow, Russia
4
Vilyui GRE AC ALROSA, 163000 Arkhangelsk, Russia
*
Author to whom correspondence should be addressed.
Academic Editor: Paolo Nimis
Received: 17 April 2021 / Revised: 15 May 2021 / Accepted: 16 May 2021 / Published: 19 May 2021
(This article belongs to the Special Issue Petrogenesis and Geochemistry in Alkaline Ultramafic Rocks)
To provide new insights into the evolution of kimberlitic magmas, we have undertaken a detailed petrographic and mineralogical investigation of highly evolved carbonate–phlogopite-bearing kimberlites of the Kepino cluster, Arkhangelsk kimberlite province, Russia. The Kepino kimberlites are represented by volcanoclastic breccias and massive macrocrystic units within pipes as well as coherent porphyritic kimberlites within sills. The volcanoclastic units from pipes are similar in petrography and mineral composition to archetypal (Group 1) kimberlite, whereas the sills represent evolved kimberlites that exhibit a wide variation in amounts of carbonate and phlogopite. The late-stage evolution of kimberlitic melts involves increasing oxygen fugacity and fluid-phase evolution (forming carbonate segregations by exsolution, etc.). These processes are accompanied by the transformation of primary Al- and Ti-bearing phlogopite toward tetraferriphlogopite and the transition of spinel compositions from magmatic chromite to magnesian ulvöspinel and titanomagnetite. Similar primary kimberlitic melts emplaced as sills and pipes may be transitional to carbonatite melts in the shallow crust. The kimberlitic pipes are characterised by low carbonate amounts that may reflect the fluid degassing process during an explosive emplacement of the pipes. The Kepino kimberlite age, determined as 397.3 ± 1.2 Ma, indicates two episodes of ultramafic alkaline magmatism in the Arkhangelsk province, the first producing non-economic evolved kimberlites of the Kepino cluster and the second producing economic-grade diamondiferous kimberlites. View Full-Text
Keywords: Arkhangelsk diamond province; kimberlite; kimberlitic sills; phlogopite; spinel; melt evolution Arkhangelsk diamond province; kimberlite; kimberlitic sills; phlogopite; spinel; melt evolution
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MDPI and ACS Style

Kargin, A.V.; Nosova, A.A.; Sazonova, L.V.; Tretyachenko, V.V.; Larionova, Y.O.; Kovalchuk, E.V. Ultramafic Alkaline Rocks of Kepino Cluster, Arkhangelsk, Russia: Different Evolution of Kimberlite Melts in Sills and Pipes. Minerals 2021, 11, 540. https://0-doi-org.brum.beds.ac.uk/10.3390/min11050540

AMA Style

Kargin AV, Nosova AA, Sazonova LV, Tretyachenko VV, Larionova YO, Kovalchuk EV. Ultramafic Alkaline Rocks of Kepino Cluster, Arkhangelsk, Russia: Different Evolution of Kimberlite Melts in Sills and Pipes. Minerals. 2021; 11(5):540. https://0-doi-org.brum.beds.ac.uk/10.3390/min11050540

Chicago/Turabian Style

Kargin, Alexey V., Anna A. Nosova, Ludmila V. Sazonova, Vladimir V. Tretyachenko, Yulia O. Larionova, and Elena V. Kovalchuk 2021. "Ultramafic Alkaline Rocks of Kepino Cluster, Arkhangelsk, Russia: Different Evolution of Kimberlite Melts in Sills and Pipes" Minerals 11, no. 5: 540. https://0-doi-org.brum.beds.ac.uk/10.3390/min11050540

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