Hydrothermal alteration associated with beryllium deposits at Spor Mountain, Utah

Abstract

The beryllium deposits at Spor Mountain occur in waterlaid tuff that contains carbonate clasts. Vitric and zeolitic tuffs are present outside the mineralized area whereas argillic and feldspathic tuffs are present within the mineralized area. Early alteration of tuff was characterized by argillization and addition of Si, AI, Fe, Hp, F, Be, Li and many trace elements; advanced alteration was marked by feldspathization, fluorite-silica replacement of carbonate clasts, continued addition of many trace elements, and loss of water. As shown by potassium-feldspar and fluorite abundance, the alteration intensity at the Roadside beryllium deposit decreases with depth but shows a minor increase near the base of the tuff. The beryllium ore body and associated fluorite are near the top of the tuff and are underlain by a thick zone containing lithium-bearing trioctahedral montmorillonoid clay and associated calcite. Beryllium (as bertrandite), lithium, uranium, and other elements are concentrated in fluorite-rich nodules, and magnesium, lithium, and zinc are concentrated in trioctahedral montmorillonoid clay nodules. Most of the nodules are believed to be altered domomite clasts. Manganese oxide minerals occur as nodule coatings and fissure fillings.The elements concentrated at Spor Mountain are tentatively believed to have been derived from a buried granitic pluton by fluorine-rich hydrothermal solutions. These solutions ascended into the overlying tuff where they reacted with carbonate clasts, releasing carbonate ions whose hydrolysis turned the solutions alkaline. Decreasing temperature probably caused precipitation of silica minerals and fluorite, producing and accompanying decrease in fluorine concentration. Increasing pH triggered potassium fixation and resulted in widespread feldspathization of the tuffs. Increasing pH, decreasing temperature, and decreasing fluorine concentration were variously responsible for the breakdown of stable metal fluoride complex ions and for the precipitation of minerals of beryllium, uranium, and other elements.

Non-pegmatitic Deposits of Beryllium: Mineralogy, Geology, Phase Equilibria and Origin

“…24B and 25A). The tuff is extensively altered with a progression from regional diagenetic clays and Kfeldspar (Lindsey 1975) to intense Kfeldspathization with secondary sericite and smectite in the immediate vicinity of Spor Mountain (Lindsey et al 1973). Dolostone clasts in the tuff breccia show corresponding alteration from original dolomite to calcite to silica to fluorite (Fig.…”

“…These pipes lie along structures that also appear to control the Be orebodies. Lindsey et al (1973) speculated that a connection to deeper Be mineralization exists; however, the deposits could reflect shallow degassing of a magma without deeper mineralization, or they might have formed by leaching of the Be-rich Spor Mountain Rhyolite (cf. Wood 1992).…”

“…Warner et al 1959;Shawe 1966;Lindsey 1977;Burt and Sheridan 1986;Congdon and Nash 1991 Mainly western Utah Be belt, most occurrences in volcanic rocks, but also skarn (Hlv-Brl) and granite-hosted occurrences-dominant Be producer; magmas up to 80 ppm Be Spor Mountain, Utah, USA (see Fig. 24) rV (rpl), [rV (vn)] CenM (21) Shawe 1968;Lindsey et al 1973;Lindsey 1977;Ludwig et al 1980;Baker et al 1998;Johnson and Ripley 1998 21 Ma Brt in Fl-silica replacement of carbonate clasts in lithic tuff (7Mt @ 0.72% BeO), extensive Li-Zn-bearing Kfs and clay alteration; overlying 6-7 Ma topaz rhyolites have red Brl Wah-Wah, Utah, USA rV (vn) CenM (23) Keith et al 1994;Thompson et al 1996 Topaz Sainsbury 1968Sainsbury , 1969; Newberry 1998 Several Sn-W Bt granite centers with proximal Bebearing skarns and extensive distal Be-F-Al replacement deposits; similar in NE-most Siberia Lost River district, Alaska, USA (see Fig. 19) pG (rpl, sk, gr) MesL (CretL) Sainsbury 1968Sainsbury , 1969Sainsbury , 1988Dobson 1982 Extensive Ch-Dsp-Ms-Fl-replacement of carbonates other BASH minerals in Ms-Fl-Qtz veins (>3Mt @ 0.3-1.75% BeO) early and late relative to Sn-Ferich skarns (±Hlv) and greisen in Bt granite Northern Cordillera, Yukon & Alaska pG (sk, gr, vn) (E) MesL (Cret) Mulligan 1968Mulligan , 1971Dick and Hodgson 1982;Anderson 1988;Newberry et al 1990;Layne and Spooner 1991 Early Keith et al 1996;Olcott et al 1998 Emerald Hot-spot-related Monteregian-White Mountain alkaline province has minor occurrences (notably Dn) plus spectacular locality at Mt.…”

“…The tuff is also enriched in Li, Zn and other elements. (Alteration fromLindsey et al 1973. Be content fromGriffitts and Rader 1963.…”

Leaching characteristics of ash from the May 18, 1980, eruption of Mount St. Helens Volcano, Washington

“…It is interesting to note that Cu, Mo, and Li also show increased Teachability in the carbonatebicarbonate leach. These elements are also associated with sedimentary uranium deposits (Harshman, 1972;Lindsey et a!., 1973).…”