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Brewsterite, Yellow Lake, British Columbia

Last Updated: 15th Oct 2018

By Richard Gunter

Brewsterite-Sr, Yellow Lake, British Columbia

Richard Gunter
5493 Cedarcreek Drive
Chilliwack, British Columbia
pamrichg@shaw.ca

Abstract:

Brewsterite-Sr is a relatively rare zeolite that occurs in different parageneses worldwide. In the Yellow Lake area of southern British Columbia brewsterite-Sr occurs with rare phases in veins and gas cavities within alkali basalt of the Eocene Marron Formation. The basalt is aphanitic with phenocrysts of clinopyroxene and plagioclase. The basalt’s gas cavities and veins are lined with abundant calcite and filled with the later-stage zeolites.

Metamorphism in the basalt is very low temperature (< 200O C for heulandite deposition) but alkaline (the deposition of wakefieldite-Ce requires a pH greater than 12.6). This allows the formation of a suite of zeolites and associated minerals that does not have any other worldwide analogues.

The chemistry of the brewsterite and other associated phases illustrates a mobility of CO3, Sr and Ce without the deposition of Sr or Ce carbonates. The alkalinity of the metamorphic fluid may also be responsible for the very low content of Ba in the brewsterite.

The chance exposure of the brewsterite suite in a series of roadcuts allows sufficient exposure for collecting of these unusual zeolites. There are no mineral deposits associated with them and there are no other excavations in the immediate vicinity. The possibility of more locations of brewsterite-Sr/wakefieldite-Ce in the area surrounding the roadcut is probably high but there is no data on other finds.

Table of Content:

Abstract:

Introduction:

Geology:

Minerals:

Halides:
Fluorite
Carbonates:
Calcite
Oxides:
Wakefieldite
Silicates:
Analcime
Brewsterite
Heulandite
Phillipsite
Scolecite-Mesolite-Natrolite
Thomsonite
Yugawaralite

Barium, Strontium and Phosphate content of Zeolite in Basalt:

Conclusions:

References:

Figures and Images:

Figures:

Figure 1: Tertiary and Quaternary Magmatic Rocks-British Columbia and Washington
Figure 2: Cross-section of the White Lake Basin
Figure 3: Strontium and Barium Distribution in the Marron Formation

Images:

Image 1: View of Lava Flows in Roadcut, Yellow Lake
Image 2: Flow Contacts between Lava Flows
Image 3: Porous Zone in Lava Flows
Image 4: Porous Lava lined with Zeolite Crystals
Image 5: Fluorite and Brewsterite
Image 6: Wakefieldite and Brewsterite
Image 7: Colourless, Prismatic Brewsterite-(Sr)
Image 8 Heulandite and Thomsonite
Image 9: Brewsterite and Heulandite
Image 10: Brewsterite and Heulandite
Image 11: Yugawaralite

Introduction:

Brewsterite-Sr (Sr1.70, Ba0.12)1.82Na0.48(Si11.68, Al4.34)16.02O32 (Tschernich (1992) from W. Wise (pers. comm.)) forms part of an unusual suite of zeolites and other phases in roadcuts and outcrops on the north shore of Yellow Lake on Highway 3A, approximately 30 kilometers southwest of Penticton, British Columbia.

The location has been briefly described by Tschernich (1992) in a number of his individual zeolite mineral descriptions. His description of heulandite from Yellow Lake is typical and says (p.254): Pointed, red, strontium-bearing heulandite crystals, up to 5 mm long with a few exceptional crystals up to 3 cm long, are covered by brewsterite, laumontite, calcite, goethite, and fluorite in veins crossing vesicular Eocene trachyte along Yellow Lake, near Olalla (RWT; Rudy Tschernich).

The complex crystallization history at this locality appears to represent shallow hot springs activity where the
zeolites, phillipsite> analcime> thomsonite > scolecite-mesolite-natrolite, crystallizing in vesicles, were invaded by fractures, followed by solutions depositing Sr-bearing heulandite >brewsterite-yugawaralite-fluorite La-bearing wakefieldite-(Ce) > laumontite, along with large amounts of calcite. At shallower depths, the same veins deposited only chabazite> calcite> stilbite > calcite> laumontite.

Heulandite-Sr is a rare species with only 9 worldwide occurrences listed in Mindat.org. Most occur with low-temperature barium mineralization, such as the Strontian, U.K. occurrence. Wakefieldite (Ce) is also a rare mineral with only 8 localities listed in Mindat.org with Yellow Lake being by far the best. In most other cases wakefieldite (Ce) occurs in pegmatites, vanadium-bearing rhyolites or as a minor phase in vanadium-bearing volcanic fumaroles.

Brewsterite-Sr is accompanied by a number of zeolite minerals, fluorite and wakefieldite-Ce. These are unusual zeolites for the Eocene volcanics of British Columbia and indicate an uncommon method of emplacement. Tschernich (1992) suggests that the paragenesis may have been the product of: shallow hot springs activity. (p. 83). There is no data on how hot the spring was postulated to be as: little is known about the range of temperature and/or pressures needed for crystallization. (p.82).

The Yellow Lake volcanics had an unusual alteration sequence due to the mobilization of Ce into wakefieldite; ((Ce0.60La0.26,Nd0.12,REE 0.02)(V0.96,Si0.04)O4; average of 10 analyses: another sample is (Ce0.49La0.40Nd0.11)1VO4; average of 10 analyses. Both samples are in the RRUFF database 2018)), Sr (brewsterite (Sr) and heulandite (Sr) (no detailed mineral analyses available)) and F (fluorite) into secondary cavity minerals.

The original characterization of wakefieldite-Y is from the Evans-Lou pegmatite and Miles et al suggests that it is formed from an alkaline solution at a pH greater than 12.6. The precipitation of wakefieldite moves to a lower pH with rising temperature. An alkaline hot spring might be responsible for the unusual suite of zeolites. A study of the crystallization of heulandite reported in Tschernich (1992) indicates that heulandite forms between 650 and 200oC, thus defining the upper limit of temperature for the hot spring. At Yellow Lake wakefieldite (Ce) is a very late phase implanted on the zeolites so it cannot have formed at a higher temperature than heulandite (Sr).

Geology:

The Yellow Lake area is part of the Early Tertiary magmatic Province in British Columbia. Figure 1illustrates the ages of the volcanic rocks in southern British Columbia and norther Washington State. The “Map Area” (center of the map) covers the White Lake Basin.

Figure 1:
Tertiary and Quaternary Magmatic Rocks; British Columbia and Washington; Church (1973)

The Yellow Lake occurrence was described by Hora and Church (1985) as: The Yellow Lake volcanics, lowest member of the (Eocene) Marron Formation, are visibly enriched in zeolites in fresh outcrops along Highway 3. These rocks are typically grey mafic phonolite lavas with dark pyroxene phenocrysts and light-coloured natrolite-fillcd amygdales. Calcite and analcite commonly accompany natrolite lining the gas cavities; thomsonite and mordenite are less common.

Pink laumontite-leonhardite occurs with calcite in veinlets along the main and satellitic fractures. The occurrence of primary analcite as phenocrysts and groundmass of the Yellow Lake lavas (Daly, 1912) is indicative: of silica undersaturation (Church. 1978). This characteristic is believed to have been an important factor favouring developments of zeolites in these host rocks.

The article did not mention the unusual zeolites at Yellow Lake, even though they were known at the time. Hora and Church were primarily interested in potentially commercial deposits of the zeolite clinoptilolite.

Figure 2:


Cross Section of the White Lake Basin, the “Map Area” of Figure 1; Yellow Lake occurs between Points “A” and “B” within the Marron Formation. (from Church , 1973)

Church (1973) in a description of the Yellow Lake Member of the Marron Formation in the regional geology of the Eocene volcanics says: Where the rocks are amygdaloidal, as near Yellow Lake, they contain much calcite, natrolite, some thomsonite, and rarely, brewsterite. Cracks and fissures contain calcite, laumontite-leonhardite and mordenite.

Ingelson (1984) mentions the occurrence of unusual zeolites at Yellow Lake in one of the chapters in his article. The rare zeolites are described, focusing on the brewsterite and thomsonite, but not the geological setting. Ingelson does not mention the presence of Wakefieldite in the zeolite suite; it was described from Yellow Lake by Howard, Tschernich and Klein (1995). The zeolite suite was described many years before that time.

In the road cuts along the north shore of Yellow Lake the lava flows are well exposed. Image 1: View of lava flows in roadcut, Yellow Lake

They contain multiple flows separated by red paleosol
Detail of paleosol and flow contact at Yellow Lake

Yellow Lake, Olalla, Osoyoos Mining Division, British Columbia, Canada
Image 2: Flow contacts between the lava flows (Norman King photo)

and contain areas of high porosity Image 3: Porous zone in the lava flows.

The images illustrate the shallow dip of the lava flows and the large amount of calcite veining and porosity that occurs within them. The veining is generally vertical, perpendicular to the surface of the lava flow. The porous zones are also vertically oriented but the individual cavities within the zone are elongated subhorizontally.

Zeolites occur lining every pore space and coating the walls of the calcite veins. The heulandite-(Sr) sample Image 4: Porous lava lined with zeolite crystals

is an example of the calcite-zeolite lined pores. The fluids that crystallized the zeolites altered the immediate wall rock of the veins and porous zones but the alteration is not pervasive. The Eocene volcanics of British Columbia are distinctly different in chemistry, mineralogy and occurrence to the Columbia River flood basalts of Washington and Oregon States. The Eocene basalts are bound to localized basins and do not form large, laterally extensive, lava flows.

Minerals:

If possible the head formula is taken from actual analyses reported in Zeolites of the World (Tschernich 1992); if not they are from Fleischer’s Glossary. Many of the zeolite species here are strontium-rich if they are not strontium-dominant. It appears that the later the deposition in the paragenetic sequence the phase is the higher the strontium content. The plot of the temperature decline in the paragenetic sequence is not a descending line as the late stage wakefieldite-brewsterite sequence is higher temperature than the earlier sequence zeolites.

Halides:

Fluorite (CaF2):
Colourless 1 to 2 mm octahedrons of fluorite occur on the crystal faces of brewsterite in some of the cavities. It is a late-stage mineral that occurs after the crystallization of the zeolites. Fluorite is not a normal phase associated with zeolites in a basaltic paragenesis and none of the analyzed zeolites contain F in their formula.

Image 5: Fluorite and Brewsterite, Yellow Lake; Karl Volkmann photograph.

Carbonates:

Calcite CaCO3:

Coarse-grained white to light pink anhedral calcite forms as the filling in the zeolite veins at Yellow Lake. It is present in almost all parageneses except the porous sequence where zeolite line cavities with an early stage of 1 mm prismatic light brown non-fluorescent calcite but no calcite vug filling. There is no evidence of Sr contamination in the calcite (strong white SW fluorescence is normally characteristic) or the presence of strontianite in the carbonate veins.

Oxides:

Wakefieldite (Ce) ((Ce0.60La0.26,Nd0.12,REE 0.02)(V0.96,Si0.04)O4):

Wakefieldite is a late-stage oxide phase that crystallizes after the zeolite minerals. It often occurs as small crystals on a brewsterite or analcime matrix. The mobilization of cerium, lanthanum and vanadium within the Marron Formation phonolite and the crystallization of a late-stage phase have an approximate equivalent in the post-zeolite cavansite/pentagonite vanadium silicate mineralization in altered basalt in India and Oregon. Vanadate and arsenate minerals occur as late-stage phases in cavities and joints in Mn-rich deposits such as Franklin, New Jersey, Falotta, Switzerland and Val Graveglia, Italy. Normally these are Mn-dominant (sarkinite, palenzonaite etc.) but some phases have other cations dominant (tilasite etc.). Vanadium and arsenic often form arseno- or vanado-silicates in these environments but there are no vanadium silicates at Yellow Lake so the fSi must have been very low.

There are 6 photographs of wakefieldite-(Ce) in the Mindat.org directory. One of the photos is Image 6: Wakefieldite and Brewsterite, Yellow Lake; Robert Meyer Photograph. This image illustrates the euhedral wakefieldite crystallizing on brewsterite.

Silicates:

Analcime (Na1.84K0.05Ca0.04[Al1.96Si4.05O12].xH2O

One of the earlier zeolites, analcime is found with characteristic colourless 2 mm crystals. It often occurs as a matrix for the later phases. There is no strontium in the analcime chemistry so it may have crystallized earlier in the paragenesis that the introduction of Sr-bearing fluids.

Brewsterite-Sr (Sr1.70, Ba0.12)1.82Na0.48 (Si11.68, Al4.34)16.02O32):

One of the more abundant zeolites at Yellow Lake, brewsterite occurs a vein and vug filling within fractures and pores of the Marron Formation phonolites. The crystals are colourless, white or light pink. All of the analyses of Brewsterite-Sr from Yellow Lake have approximately the same chemistry so the late-stage fluids must have had much higher Sr than Ba.

Brewsterite is a rare zeolite that the Handbook of Mineralogy (1990) indicates is: Hydrothermally deposited in druses lining cavities in basalt and schists; more rarely in ore deposits. The high strontium in the Yellow Lake brewsterite appears to be characteristic and all brewsterite from Yellow Lake are brewsterite-(Sr). It forms as coatings on cavity walls Image 7: Colourless prismatic Brewsterite-(Sr), Yellow Lake. There are 40 photographs of brewsterite-(Sr) in Mindat and all appear to have approximately the same size and shape of brewsterite-(Sr) crystals; thus there is probably a single phase of brewsterite crystallization.

Heulandite-Sr (Sr0.5, Ca0.5, Na, K) 9[Al9Si27O72].24H2O no analyses in Tschernich (1992) only “strontium-bearing heulandite):

A second late-stage, strontium-bearing, zeolite phase at Yellow Lake is heulandite-(Sr). It occurs as 2 to 5 mm colourless prismatic crystals of a characteristic “coffin” shape. Heulandite-(Sr) is contemporaneous with brewsterite-(Sr) and thomsonite and is one of the last phases to form in a particular vug.

Heulandite and thomsonite occur together Image 8: Heulandite and Thomsonite, Yellow Lake Heulandite can also occur with brewsterite Image 9: Brewsterite and Heulandite, Yellow Lake; John Sobolewski photograph and Image 10: Brewsterite and Heulandite, Yellow Lake; Rick Dalrymple photograph

Phillipsite (K, Ca0.5Na, Mg0.5, Sr0.5)9[Al9Si27O72].24H2O no analyses in Tschernich (1992):

Phillipsite occurs as an early stage zeolite that often forms a small, 1 mm colourless cavity lining crystals with characteristic twins. There is no phillipsite analysis in Tschernich (1992) so there is no data on the Sr or Ba content of the Yellow Lake crystals.

Scolecite-Mesolite-Natrolite (Ca8.54Na0.33[Al16.12Si23.56O80].xH2O:

The scolecite-mesolite-natrolite group is a series of long prismatic zeolite minerals whose members form early in the paragenesis at Yellow Lake. The analysis from Tschernich (1992) is high calcium scolecite; there are no analyses for mesolite or natrolite from Yellow Lake. The scolecite-mesolite-natrolite aggregates occur as 2 mm hemispheres of colourless needles associated with colourless crystals of Heulandite-(Sr) and coralloid aggregates of thomsonite on light brown calcite.

Tschernich (1992) says: Colorless, pink, salmon-orange to dark red mesolite needles (colored from hematite inclusions) form flattened crystals, in groups up to 15 mm long, extending from scolecite or Sr-bearing thomsonite in vesicular trachyte OQY,'S along Yellow Lake, near Olalla (RWT). The complex crystallization history at this locality appears to represent shallow hot springs activity where the zeolites, phillipsite> analcime> thomsonite > scolecite-mesolite-natrolite, crystallizing in vesicles, were invaded by fractures followed by solutions depositing Sr-bearing heulandite > brewsterite-yugawaralite-fluorite, La-bearing wakefieldite-(ce) > laumontite, along with large amounts of calcite.

Thomsonite Ca1.44Na0.15Sr0.53[Al5.05Si4.93O20].xH2O; Tschernich (1992) mentions 10% strontium in the thomsonite:

Microcrystals of complex Sr-0bearing thomsonite occur in the vesicles at Yellow Lake. Tschernich (1992) contains 12 crystal drawings of thomsonite and 4 microphotos of the complex thomsonite crystals. Thomsonite also occurs in 2 mm colourless coralloid aggregates in light brown calcite.

Tschernich (1992) says: Pink, white, and colorless thomsonite crystals (containing 10% strontium) are found in flattened vesicles, 2to 8 cm long, in Eocene trachyte along Yellow Lake, near Ollala (Wise and Tschernich, 1978b; Tealdi and Tschernich, 1985). Thomsonite forms simple, flat blades; thick, chisel-shaped blades; stout to elongated pseudotetragonal prisms; and needlelike prisms with complex terminations. The thomsonite crystals that range (rom 0.5 to 8 mm long in a few instances were interrupted by the crystallization of calcite that preserved the early simple generations of thomsonite. The earliest generation of thomsonite formed white to pink, radiating, thin blades with the forms {100}, {010}, {110}, {801}, {502} , and {001} (Figs. 551,555,562). In some cavities, the blades are overgrown by bloc.ky pseudohexagonal appearing colorless thomsonite with smooth {100}, {010}, {110}, and {001} (Figs. 571,574). Continued growth of the thomsonite (not covered by calcite) developed the complex additional forms {101}, {410}, {301}, and (801} on chisel-shaped crystals (Figs. 552,554,557-559,561,563,586). Other cavities developed blocky, prismatic crystals (square in cross section) with dominant {100}, {010}, and {001}, with small {010}, {502}, {110}, and frosted {021} (Figs. 566,568,575,576,583-585). Other crystals possess all the forms seen on the chisel and blocky crystals, along with small {30t} and {021} (Figs. 565,570). The complex crystallization history at this locality appears to represent shallow hot springs activity where the zeolites phillipsite> analcime> thomsonite > scolecite-mesolite-natrolite, crystallizing in vesicles, were invaded by fractures, followed by solutions depositing Sr·bearing heulandite > brewsterite-yugawaralite-fluorite La-bearing
wakefieldite-(Ce) > laumontite along with large amounts of calcite (RWT).

Yugawaralite Ca0.95Sr0.06Na0.01[Al2.01Si5.99O16].xH2O (analysis W. Wise pers. comm.in Tschernich (1992))

Tschernich (1992) says: Yugawaralite has been found in only one pocket in vesicular Eocene porphyritic trachyte at
Yellow Lake, near Olalla, in southern British Columbia (Wise and Tschernich, 1978b; Tealdi and Tschernich, 1985). It forms stout, tabular, light pink to colorless, glassy crystals, up to 1em long, heavily striated parallel to the c-axis with the dominant forms {010}, {100}, {001}, {011}, {111}, {120} and tiny {032}, {110}, {140}, {344}, {301}, {012},and {102} (RWT). Yugawaralite occurs in the crystallization sequence: analcime> Sr-bearing thomsonite > bladed calcite > yugawaralite. The complex crystallization history at this locality appears to represent shallow hot spring activity where zeolites (crystallizing in vesicles) in the order: phillipsite> analcime> thomsonite > scolecite-mesolite-natrolite were invaded by fractures followed by solutions depositing Sr-bearing heulandite > brewsterite-yugawaralite-fluorite, La-bearing wakefieldite (Ce) > laumontite, along with large amounts of calcite (RWT).

Image 11: Yugawaralite, Yellow Lake; Rock Currier Photograph.

Yugawaralite is currently noted as a very rare component of the Yellow Lake paragenesis but has sufficient Sr in the chemistry to indicate it is one of the later phases. It may be more common as small crystals associated with the brewsterite-fluorite paragenesis than is currently noted. The presence of Yugawaralite is unusual as it is a relatively rare zeolite.

Barium, Strontium and Phosphate Content of Zeolites in Basalts:

The strontium content of the Yellow Lake zeolites is related to their position in the paragenetic sequence. This is a rare type of paragenesis with few other examples. Most other Ba-Sr bearing zeolites, for example the type localities for brewsterite and harmotome and the Ice River, British Columbia locality for edingtonite do not have other non Ba-Sr zeolites associated with them. There is thomsonite that occurs with edingtonite at its Scottish type locality but there is no chemistry for it in Tschernich (1992).

Most of the Ba-Sr bearing zeolite phases occur in the gangue minerals of Pb-Zn-Ag veins or as a late phase in nepheline syenite. Most basalt does not have mobile Ba or Sr which generally occurs as minor elements in the primary basaltic feldspars. For example the Indian basalt sequence has locally mobile V (cavansite and pentagonite), Fe (julgoldite and babingtonite) and Mo (powellite). No Sr or Ba minerals have been reported from the Indian basalt quarries in the literature. The Columbia River basalt province has more mineralogical data with local mobile V (the type locality of cavansite and pentagonite are in Oregon) and Fe (sphaerosiderite occurs in basalt cavities in Washington and Oregon).

The Siberian plateau basalt province probably has a similar suite of secondary minerals to the Indian basalt province but the poor weather and low population density means that the density of reported basalt mineralogy is a fraction of the Indian basalt province. Barite is noted in some of the amethyst geodes in the Parana Province in Rio Grande Do Sul Province, Brazil (Jurchem (2011)).

Barite is present as a late-stage, post zeolite mineral in the Nova Scotia paragenesis at Wasson’s Bluff and Five Islands (Pe-Piper and Miller (2002)). Chemical analyses of the zeolite phases recorded Sr and Ba as a minor elements in the Wasson’s Bluff heulandite with Ba being less abundant. No other zeolite phase recorded the presence of Ba or Sr. Heulandite is the earliest zeolite phase in the parageneses where it contained Sr and Ba.

Figure 3:
Barium and Strontium Distribution, Marron Formation

Yellow Lake, Olalla, Osoyoos Mining Division, British Columbia, Canada
Strontium and Barium Distribution in the Marron Formation Volcanics (Church, 1973); the Yellow Lake brewsterite locality is within Series C.

The andesite in the Marron Formation has locally elevated Ba and Sr contents. Figure 3 illustrates the geochemical makeup of Ba and Sr in the various series in the White Lake basin. The mineralogy of the andesite in series A, B and C does not vary so the individual plagioclase phenocrysts must contain significantly more Sr and Ba in the series C strata. The amount of background Ba is almost twice the amount of background Sr; however this is not reflected in the chemistry of the enclosed zeolites which are Sr dominant. This probably reflects the lesser solubility of Ba over Sr in the low-temperature environment.

In the low-temperature environments of zeolite crystallization Ba and Sr are relatively immobile. In similar Pb-Zn deposits in limestone the occurrences of low-temperature witherite and strontianite are often direct reactions from the pre-existing sulphates barite and celestine (Baldasari and Speer 1979). Thus once Ba and Sr enter the paragenesis they tend to stay put. The reaction producing brewsterite and heulandite-(Sr) at Yellow Lake will not be higher in temperature than the barite/witherite reactions. Thus the brewsterite occurrence would be a direct reaction to Sr and Ba in the host rock. Church (1973) indicated that the plagioclase in the Marron Formation has increased Ba and Sr. Alteration of the plagioclase at zeolite grade would produce locally mobile Sr and Ba ions.

The reactions within the basalt at Yellow Lake occur in gas cavities and vertical veins so they are open-space fillings rather than reactions with the basalt. The edges of the gas cavities and veins are sharp with little visible alteration of the basalt a few millimeters inward from the vein edge. This minimal alteration is not uncommon in other zeolite localities where the edges of the gas cavities can be knife-sharp and macroscopically unaltered.

The Eocene basalts were not able to mobilize PO4 easily. The native asphalt-collinsite-hydroxyapatite occurrence at Francois Lake, British Columbia occurs between two Eocene Age lava flows and the PO4 minerals have not been mobilized beyond their original layers. It appears that some of the phosphate layers were not solid when the volcanic strata overrode them; yet the phosphate-bearing strata was not disrupted and brecciated. The only secondary mineral deposited within cavities in the basalt underlying the phosphate layer was ferrierite. There was no evidence for phosphate veining or widespread fluid flow; thus no secondary phosphates are noted associated with the zeolites.

Conclusions:

Rare Sr-Ba bearing zeolites occur at Yellow Lake, British Columbia within Eocene Age basalt of the Marron Formation. Brewsterite in 1 to 2 cm crystals occurs in vugs and veinlets within the basalt in and around roadcuts along Highway 3A. Brewsterite-(Sr) crystals are only noted from two localities; Yellow Lake, British Columbia and Strontian, Scotland. Variability in temperature and pH/Eh within the Marron Formation is probably responsible for the mobilization of the necessary Ba and Sr to form the zeolite species at Yellow Lake.

The temperature and alkalinity of formation of brewsterite and wakefieldite require the local spring to have been alkaline (pH > 12.6) and hot (less than approximately 200 O C). These two conditions are rarely met in hot springs, which explains the rarity of the brewsterite-wakefieldite-heulandite-Sr paragenesis.

The suite of unusual zeolites at Yellow Lake is in contrast to the many occurrences of more common zeolites (ferrierite, levyne, analcime etc.) in the Eocene Age volcanic strata of British Columbia (Tschernich 1992). Ferrierite is not a common mineral from zeolite localities elsewhere in the world but is not rare in the British Columbia Eocene basalts. The alkalinity of most of the Eocene Age flows contributed to the mobility of magnesium for the ferrierite.

At the Strontian locality brewsterite occurs in the gangue of a lead-zinc deposit in gneissic rocks so the chemistry is significantly different than the alkali basalt at Yellow Lake. There are no sulphides or sources of sulphur in the immediate area of Yellow Lake so the formation of galena/sphalerite as occur in Strontian was not possible; nor is the deposition of Ba in the form of baryte. Carbonate ions are common at the locality; calcite is ubiquitous as a late-stage vein filling, but no one has identified strontianite or witherite. This differs from the Strontian occurrence where strontianite is a common phase. Harmotome has not been identified at Yellow Lake yet is common at Strontian. The presence of wakefieldite in the Yellow Lake paragenesis indicates REE and V mobilization, possibly from the basaltic magnetite.

References:

Baldasari A. and Speer A. (1979) Witherite composition, physical properties and genesis; American Mineralogist, v. 64, p. 742-747

Church B.N. (1973) Geology of the White Lake Basin; British Columbia Department of Mines, Bulletin 61, 120 p.

Church B.N. (1978) Shackanite and related Analcite-bearing rocks in British Columbia; Canadian Journal of Earth Sciences, v. 15, no. 10, pp. 1669-1672

Daly R.A. (1912) Geology of the North American Cordillera at the 49th Parallel; Geological Survey of Canada Memoir 38, 857p.

Hora Z.D. and Church B.N. (1985) Zeolites in Eocene Rocks of the Penticton Group, Okanagan-Boundary Region, South-Central British Columbia; British Columbia Geological Survey, Geological Fieldwork 1985, p. 51-56

Howard D.G., Tschernich R.W. and Klein G.L. (1995) Occurrence of Wakefieldite-(Ce) with Zeolites at Yellow Lake, British Columbia, Canada; N.Jb.Miner. Mh 1995, H.3, p. 127-132

Ingelson A. (1984) Mineral Occurrences in Western Canada; Mineralogical Record, v. 15 no. 2, pp. 89-94

Jurchem P.J. (2011) Gem Materials in Rio Grande Do Sul State, Brazil-A Field Trip Guide; 11 GIA International Gemological Symposium , Carlsbad , California, 14 p.

Pe-Piper G. and Miller L. (2002) Zeolites minerals from the North Shore of the Minas Basin, Nova Scotia; Atlantic Geology v. 38 p. 11-28

Tschernich R.W. (1992) Zeolites of the World; Geoscience Press, Phoenix, Arizona, 563 p.




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