Arfvedsonite-phlogopite minettes with high strontian apatite within the Mountain Crimea

Spiridonov E. M.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2021. V. 150. N 2. P. 1-17

https://doi.org/10.31857/S0869605521020106

Full text is available on eLIBRARY.RU

Language: Russian

Abstract

Small-scale Epicimmerian post-Jurassic dikes of arfvedsonite-phlogopite minettes crosscut Early Bajocian gabbroids and quartz diorites of Kushnaryov and Petropavlovsk intrusives and the products of their low-grade metamorphism of the late Jurassic age, namely, prehnite, pumpellyite, and lomontite aggregates (Bodrak fault zone within the Lozovskaya zone of Mountain Crimean cimmerides). Fluorine-free phlogopite with minor Cr₂O₃ (2.1 wt %) and TiO₂ (6.8 wt %), which is a probable mantle crystallization product, composes cores of large phenocrysts in minettes. An outer zone of phenocrysts is composed of fluoro-hydroxyl phlogopite with 1.8–2.7 wt % of F, for which Fe/(Fe + Mg) increases from 7.8 to 22.6 from cores to rims, whereas titanium content increases from 1.4 to 3.1 wt %, chromium content decreases from 0.5–0.7 wt % to traces. Single olivine and augite phenocrysts are replaced by phlogopite. Minettes are extremely rich in phosphorus and contain 2.6 wt % of Р₂О₅ in average. Orientation of phlogopite and apatite phenocrysts emphasizes the flow textures which is parallel to dike contacts or has wavy boundaries. Fluorapatite-I contains 1.9–6.6 wt % of SrO. Fluorapatite-II with 16–21.6 wt % of SrO replaces fluorapatite-I. Prisms of sanidine, arfvedsonite, and augite, xenomorphic calcite and quartz, rare pyrite with barite inclusions, small crystals of zircon, titanite, galena, monazite and xenotime compose the matrix of minettes. Low fluorous alumina-free arfvedsonite is enriched with Ti (TiO₂ 4.2–5.2 wt %),Mg and K. Zircon contains (wt %): HfO₂ 2.8, REE₂O₃ 5.2, Y₂O₃ 2.7, Nb₂O₅ 1.3, ThO₂ 1.2; its ZrO₂/HfO₂ is equal 19; rare earth elements and yttrium form ordered sequence with their contents Y Ce > Nd Gd = Sm > Dy, La.

Keywords: Epicimmerian minette, phlogopite, high strontium fluorapatite, titanian potassic alumina-free arfvedsonite, Fe-bearing sanidine, Mountain Crimea