Cymrite as an indicator of high barium activity in the formation of hydrothermal rocks related to carbonatites of the Kola Peninsula

Abstract

Cymrite, BaAl 2 Si 2 O 8 · n H 2 O, is a rare mineral formed during low-grade dynamothermal metamorphism ( T = 250-300 ° C, P = 1-3 kbar). Cymrite has been described from many metasedimentary ores and hydrothermal rocks. In carbonatites, it has been found for the first time. Cymrite has been identified in the Kovdor and Seblyavr massifs, Kola Peninsula. In Kovdor, this mineral has been described from one of the hydrothermal veins cutting the pyroxenite-melilitite-ijolite complex at the Phlogopite deposit; cymrite is associated with thomsonite, calcite, and stivensite. In the Seblyavr pluton, cymrite occurs in thin veins of calcite carbonatite that cut pyroxenite contacting with ijolite. Cymrite from the Seblyavr pluton is associated with calcite, natrolite, pyrite, and chalcopyrite. The mineral is optically negative and uniaxial, with extinction parallel to elongation; ω ~ 1.607(1). According to X-ray diffraction data, cymrite from Seblyavr is monoclinic, space group P 1 m 1; unit-cell dimensions are: a = 5.33, b = 36.96, c = 7.66 Å, β = 90 ° , V = 1510.55 Å 3 . According to the results of IR spectroscopy, in the series of samples from different massifs (in the running order KovdorVoishor-Seblyavr), the double-layer deformation is enhanced and accompanied by a decrease in the Si-O-Si angle and weakening of hydrogen bonds of interlayer water. The empirical formulas of cymrite calculated from electron microprobe analyses are Ba 0.(H 2 O) at Seblyavr and Kovdor, respectively. Cymrite from the carbonatite massifs of the Kola Peninsula was formed under hydrothermal conditions at low temperature (200-300 ° C), high activity of Ba and Si, and high water pressure. At Kovdor, the mineral crystallized directly from the residual solution enriched in Ba. The sequence of mineral deposition is as follows: thomsonite-cymrite-calcite-stevensite. Cymrite from the Seblyavr pluton is a product of hydrothermal alteration of primary Na-K-Ba silicates of ijolite: nepheline, feldspar, and probably celsian. Natrolite replaces cymrite indicating high alkalinity of late hydrothermal fluids.

Mineralogy of the P-12 K-Ti-richterite diopside olivine lamproite from Wajrakarur, Andhra Pradesh, India: implications for subduction-related magmatism in eastern India

“…The groundmass and the carbonate clasts host prismatic cymrite crystals which are interpreted to be pseudomorphs after potassium feldsparcelsian and/or barite (Essene 1967;Hsu 1994;Moro et al 2001). Cymrites in association with carbonates have been reported only from the Kovdor carbonatite (Sorokhtina et al 2008). Cymrite crystals are commonly completely pseudomorphed by hydrogarnet-like material.…”

“…Gittinsite and cymrite have been previously recognized from carbonatites (Ansell et al 1980;Birkett et al 1992;Chakhmouradian and Zaitsev 2002;Sorokhtina et al 2008). Gittinsite and SrZrSi 2 O 7 occur in P-12 in association with calcite, chlorite, pyroxene, and barite in the groundmass.…”

“…Cymrites have been reported to form under diverse pressure-temperature conditions in many geological environments (Runnells 1964;Essene 1967;Reinecke 1982;Moles 1985;Stankova et al 1989;Jacobsen 1990;Hsu 1994;Moro et al 2001;Sorokhtina et al 2008;Raith et al 2014). Reports of cymrite forming from celsian by hydration are documented for barite-bearing siliceous and carbonate rocks (Moro et al 2001).…”

New insights into the origin of the Evate apatite-iron oxide-carbonate deposit, Northeastern Mozambique, constrained by mineralogy, textures, thermochronometry, and fluid inclusions

“…), strongly alkaline carbo-hydrothermal fluids (Zaitsev 1996, Wall and Zaitsev 2004, Sorokhtina et al 2008. Hence, we interpret the sandwich veinlets and stringers in pyrrhotite from Evate (Fig.…”

The association of oxygen-bearing minerals of chalcophile elements in the orogenetic zone related to the “mixed series” complex near Nežilovo, Republic of Macedonia

“…The very complex mineral parageneses of higher temperature stages are often metasomatically replaced with hydrothermal mineral assemblages in which barite quantitatively predominates over all other minerals showing very high barium potential. The presence of cymrite in the rocks underlying dolomitic marbles also indicates a high activity of barium and moderate (250-300 ºC) temperatures of crystallization (see [28]). As a result, almost all sulfur becomes fixed in barite that is characterized by a very low solubility and mobility under hydrothermal conditions up to 300 ºC and 1400 bars [29].…”