The Chailag-Khem fluorite-barium-strontium rare earth carbonatite occurrence, the Western Sayan Range, Russia

Abstract

The geological and mineralogical data on the Chailag-Khem F-Ba-Sr-REE occurrence in the Western Sayan Range, Russia, are discussed. The chemical compositions of rocks, ores, and minerals (ICP-MS, Link) are reported. The occurrence is localized in a tectonic crush zone composed of Cambrian quartz-sericite slates intruded by quartz syenite porphyry. Ore mineralization occurs as veins, cement of tectonic breccia, and metasomatic disseminations in host rocks. Massive ore consists of calcite, strontianite, and quartz; impregnations of euhedral fluorite, ankerite, and bastnaesite crystals; and fine-grained barite aggregate. Accessory minerals include parisite, synchysite, barytocelestine, sulfides, rutile, and uraninite. Late metasomatic calcite and strontianite segregations and veinlets are abundant. In genetic, mineralogical, and geochemical features, the Chailag-Khem occurrence is similar to the Late Mesozoic carbonatite deposits of Central Tuva, of which the Karasug Fe-F-Ba-Sr-REE deposit is the largest and best known. All carbonatite deposits and occurrences are located within a longitudinal zone transverse to the major tectonic elements of the region.

Origin of REE-rich ferrocarbonatites in southern Siberia (Russia): implications based on melt and fluid inclusions

“…In the majority of cases, the siderite carbonatite breccia matrix contains fragments of previously formed rocks such as ankerite-calcite carbonatites, magmatic rocks, and host country rocks. These geological characteristics unambiguously indicate that the sequence of formation of magmatic rocks in this region was alkaline-mafic magmatism (120-150 Ma, Ontonev 1984, Bolonin et al 2009) followed by ankerite-calcite carbonatites (118 ± 9 Ma, Nikiforov et al 2006), and then followed by siderite carbonatites (117.2 ± 1.3 Ma).…”

“…Earlier K-Ar age data from the spatially associated altered magmatic rocks from the Karasug ore field yielded an age interval of about 150-120 Ma (Ontonev 1984). The zircon U-Pb age of granosyenites at the Karasug deposit is 119 ± 2 Ma (Bolonin et al 2009). …”

Uranium in Fluorite, a Case Study: The La Azul Fluorspar Deposit, Taxco, Guerrero, Mexico

“…This explains the close relationship of uranium-rich fluorite with highly differentiated alkaline volcanic rocks, e.g., [17,18]. This association has also been widely connected to recent volcanic activity (tertiary to present) and extensional tectonism [17][18][19][20][21][22][23]. It is worth mentioning that fluorite deposits are commonly related to this type of magma in areas of thickened crust, e.g., [20][21][22][23][24], possibly due to crustal contamination processes.…”

“…The association of uranium and other lithophile trace elements (e.g., Th, Mo, Be, Zn, V, and As) in fluorite ore deposits appears to be frequently related to the alkalinity of the source rocks [12][13][14][15][16]. This explains the close relationship of uranium-rich fluorite with highly differentiated alkaline volcanic rocks, e.g., [17,18]. This association has also been widely connected to recent volcanic activity (tertiary to present) and extensional tectonism [17][18][19][20][21][22][23].…”