Barium Minerals Barite and Chlorinedominant Ferrokinoshitalite \({\mathbf{BaFe}}{{_{3}^{{2 + }}}^{{}}}[{\mathbf{C}}{{{\mathbf{l}}}_{{\mathbf{2}}}}/{\mathbf{A}}{{{\mathbf{l}}}_{{\mathbf{2}}}}{\mathbf{S}}{{{\mathbf{i}}}_{{\mathbf{2}}}}{{{\mathbf{O}}}_{{{\mathbf{10}}}}}]\) in Plagioperidotites of the Yoko-Dovyren Intrusion, Northern Baikal Area: Products of Epigenetic Low-Grade Metamorphism

The plagioperidotites of the Yoko-Dovyren ultramafic–mafic intrusion, which were affected by low-grade metamorphism (LGM) to the prehnite–pumpellyite facies (PPF), show evidence of Ba, Cl, and Sr mobilization. The background Ba and Sr contents in the plagioperidotites are 36–313 ppm (at an average of 130 ppm) and 25–169 ppm (average 86 ppm), respectively, at Ba/Sr = 0.5–4 (average 1.5). The Ba-bearing minerals are phlogopite and plagioclase, and the Cl-bearing ones are chloroferrisadanagite in alumochromite-hosted inclusions, late magmatic phlogopite, K–Cl ferropargassite and Cl-apatite in the margins of sulfide pockets. In the course of the low-grade metamorphism, these minerals were replaced by chlorites, tremolite, and diopside, which contain very little Ba and Cl. In plagioperidotite domains containing Ba‑bearing minerals, these rocks contain 348–518 ppm Ba and 4–6 ppm Sr, which indicates that Ba was redistributed and Sr was removed. The metamorphic Ba minerals are Sr-free barite and Ba–Fe–Cl mica: Cl-dominant ferrokinochitalite. They coexist with minerals of the rodingite association: hydrogarnet, tremolite, diopside, chlorite, antigorite, magnetite, and hydroxylapatite. The ferrokinoshitalite replaces phlogopite, plagioclase, and sulfides, contains up to 21 wt % BaO, 31% FeO, and 11% Cl, and has a Fe mole fraction f = 75.8–90.5. The composition of a ferrokinochitalite individual riches in Cl corresponds to the formula \({{{\text{(B}}{{{\text{a}}}_{{{\text{0}}{\text{.83}}}}}{{{\text{K}}}_{{{\text{0}}{\text{.16}}}}}{\text{)}}}_{{{\text{0}}{\text{.99}}}}}{{{\text{(Fe}}_{{2.63}}^{{2 + }}{\text{M}}{{{\text{g}}}_{{{\text{0}}{\text{.28}}}}}{\text{Fe}}_{{0.04}}^{{3 + }}{\text{A}}{{{\text{l}}}_{{{\text{0}}{\text{.02}}}}}{\text{C}}{{{\text{r}}}_{{{\text{0}}{\text{.01}}}}}{\text{M}}{{{\text{n}}}_{{{\text{0}}{\text{.01}}}}}{\text{)}}}_{{\text{3}}}}{\text{[(C}}{{{\text{l}}}_{{{\text{1}}{\text{.86}}}}}{\text{O}}{{{\text{H}}}_{{{\text{0}}{\text{.12}}}}}{{{\text{S}}}_{{{\text{0}}{\text{.02}}}}}{{{\text{)}}}_{{\text{2}}}}{\text{/A}}{{{\text{l}}}_{{{\text{1}}{\text{.86}}}}}{\text{S}}{{{\text{i}}}_{{{\text{2}}{\text{.14}}}}}{{{\text{O}}}_{{{\text{10}}}}}{\text{]}}\). Because ferrokinochitalite from the Yoko-Dovyren Massif is Cl-dominated, it is a new mineral species.