Primary Igneous Analcime: the Colima Minettes

American Mineralogist, Volume 74, pages216-223, 1989

Primary igneous analcime: The Colima minettes

Jlnrns F. Lurrn Department of Earth and Planetary Sciences,Washington University, St. Louis, Missouri 63 130, U.S.A. T. Kunrrs Kvsnn Department of Geological Sciences,University of Saskatchewan,Saskatoon, Saskatchewan S7N 0W0, Canada

Ansrnrcr Major-element compositions, cell constants, and oxygen- and hydrogen-isotopecompositions are presentedfor six analcimes from differing geologicenvironments, including proposed primary @-type) analcime microphenocrysts from a late Quaternary minette lava near Colima, Mexico. The Colima analcimehas X.,.,",: 0.684, ao: 13.712A, and one of the lowest D'sOvalues yet recorded for analcime (+9.28m).The major difficulty in identifuing primary @-type) igrreousanalcime is distinguishing it from analcime formed by ion-exchangeconversion of leucite (L-type analcime) or other precursor minerals. Pet- rographic criteria are shown to be unreliable in discriminating P and L analcimes,although the higher KrO and Rb contents and D'8Ovalues of L-type crystals may be diagnostic. P- and L-type analcimescan be distinguishedfrom classichydrothermal varieties (H-type) by the lower Fe contents of the latter. H-type analcimes,however, can have 6t8Ovalues as low as 8.9Vmand cannot be distinguished from P-type analcimes by this criterion. Analcimes formed from volcanic glass or zeolite precursorsin saline, alkaline lakes (S- type) or metamorphic sequences(M-type) can be distinguished from other varieties by their higher silica contents, smaller cell constants,and higher d'8O values of > + 17.7Vm. For all types of analcime, d'8O of the channel water does not correlate with 6180of the framework oxygen. With the exception of the P-type Colima sample, analcime channel watershave D'8Oand 6D valuesthat fall on the meteoric water line, but differ from modern meteoric water at the individual sample sites. The channel waters may reflect fluids that enteredthe analcime shortly after the mineral formed and have not been replacedby more modern waters. The Colima analcime has D'8Oslightly higher than expectedfor magmatic analcime, based on exchangepartitioning with mafic minerals in the Colima minettes. This enrichment in framework D18Oand the distinct isotopic composition of the channel water in the Colima analcime indicates that exchangebetween channel water and framework oxygen has occurred. In previous discussionsof primary igneous analcime, most attention has focused on blairmorites and analcimitescontaining centimeter-sizedeuhedral phenocrysts of analcime in the absenceof other primary hydrous minerals. We consider theserocks to be unlikely hosts for P-type analcime, which is far more likely to occur as microphenocrysts and groundmassmicrolites in mica- or hornblende-bearinglamprophyres, magmascharacter- ized by high water contents and silica undersaturation. The Quaternary minettes from Colima are the youngestand freshestlamprophyres yet describedand appear to represent the strongestcase for primary igneousanalcime.

INrnonucrron microscopic texture (Lonsdale, 1940). In the last few de- Historically, petrographershave interpreted euhedral cades,however, experimentalresults have turned the tide phenocrysts or microphenocrysts of analcime in mafic of opinion away from the concept of primary, magmatic alkalic igneousrocks as primary @-type) crystalsthat pre- analcime. Experiments have shown that leucite, nephe- cipitated directly from a silicate melt (Pirsson, 1896; line, albite, and other minerals can be rapidly converted Washington,l9l4; Tyrell, 1928;Larsen and Buie, 1938; to analcime by reaction with aqueous solutions at low Lonsdale,1940; Harker, 1954;Wilkinson, 1965, 19681 temperatures(Saha, l96l;Gupta and Fyfe, 1975).In ad- Pearce,1970; Williams et al., 1982).In this view, anal- dition, phase-equilibrium experiments in the synthetic cime is stable from late magmatic stagesthrough low- system NaAlSiOo-KAlSiOo-SiOr-HrO have demonstrat- temperature dueteric processes,and the different envi- ed that analcime and silicate melt cannot coexist above ronments of analcime formation can be distineuished bv 650 "C or below about 5-kbar pressureunder water-sat- 0003-004x/89 / 0 10242| 6s02.00 2t6 LUHR AND KYSER: PRIMARY IGNEOUS ANALCIME 2l'7

Fig. l. Photomicrographof proposedprimary @-type)analcime microphenocrysts(a) in Colima minette SAY-104. Also present are phlogopite (p), clinopyroxene (c), and titanomagnetite microlites in clear brown glass(g) with vesicles(v). Field ofview : 0.35 mm.

urated conditions (Peters et al., 1966; Morse, 1968; cubic cell constants, and oxygen- and hydrogen-isotope Boettcherand Wyllie, 1969;Kim and Burley, l97l; Liou, compositions. 197l; Roux and Hamilton, 1976).In hydrothermal experiments on a natural analcime-bearing from crinanite Slrr.rpr.Bs sruDIED AND TECHNIQUES the Dippin sill, analcimewas absentabove 400'C (Hen- mineral from derson and Gibb, 1977).Because the crystallization tem- Analcime characteristicallyforms asa secondary alteration of zeolites,volcanic glass,feldspathoids, or feldspars peratures of most analcime-bearing igneous rocks are in a broad rangeofgeologic and hydrologic environments.These much higher, thought to be euhedral analcime crystalsin include saline,alkaline lakes (S-type),hydrothermal veinlets (H- igneous rocks are now generally explained as low-tem- type), low-gradeburial metamorphic sequences(M-type), pelagic perature alteration products ofleucite, nepheline,or oth- sedimentaryrocks (Hay, 1966, 1978, 1986),and from precursors er precursor minerals (Rock, 1977; Wilkinson, 1977; of primary leucite and perhaps other feldspathoids in igneous Comin-Chiaramonti et al., 1979). rocks (L-type). In addition to the proposedP-type analcime from Although we concur with this interpretation for most Colima, five other analcimeswere investigated,representing L, analcime-phyric samples described in the literature, we S, and H varieties: argue that the most likely rock types to contain primary l. Colima minette SAY- 104 was chosento representthe pro- location is shown igneous analcime are lamprophyres. These are mafic al- posed primary @-type) analcime. The sample on the map of Luhr and Carmichael(1981). Whole-rock and kalic rocks containing phenocrysts of Mg-mica or am- glass analysesfor lava sample SAY-104 are given in Table 1. phibole groundmassfeldspars (Williams and et al., 1982), SAY-104 difers from other Colima minettes in its lack of feld- features consistent with high magmatic water contents. spars. In addition to olivine (5.1 volo/o)with spinel inclusions, Unfortunately, most lamprophyresoccur as dikes that are clinopyroxene(l6.6oh), phlogopite (0.40lo),and apatite, SAY-104 very old and substantially altered, thus rendering them contains more than 8.30/oeuhedral analcime microphenocrysts ill-suited to test for primary analcime. Luhr and Carmi- (up to 0.16 mm diameter) encasedin clear brown glass(Fig. 1). chael (1981) described Quaternary basanitesgradational These crystals are completely homogeneousand unaltered and to analcime-bearing minettes near Volcan Colima in may contain small clinopyroxene and titanomagnetite inclu- western Mexico. Minettes are the most common variety sions, identical to microlites in the surrounding glass.The lack in may of mica lamprophyre, with K./Na > 1 and characteristi- of feldspars and the large size of analcimes SAY-104 have resultedfrom the failure offeldspars to nucleateupon erup- cally high Ba and Sr contents. The Colima samples are tive quenching,a common development in experimental cool- the youngest freshestminettes yet reported, and and we ing-rate studies(Lofgen, 1980).A histogram of K,/Na ratios for consider them the best candidatesfor primary analcime. the various Colima alkaline samplesis shown in Figure 2. Sur- In this paper, the proposed primary P{ype) analcime prisingly, there is no systematicdifference in K,/Na betweenthe from Colima is comparedwith analcimesfrom other geo- basanites and minettes, although the three highest ratios are logic environments, using major-element compositions, clearly related to high abundancesof phenocrystic phlogopite. 2r8 LUHR AND KYSER:PRIMARY IGNEOUS ANALCIME

SAY 1O4 Trele 1. Colimaminette SAY-104: whole-rock and olass anal- WBG++ yses (wt%) -tr_'- _.La a 2% o.7% 11.8% (rililtilcretmtmmn nffi n SAY-104 Whole rock Glass o.5 1.O 1.5 sio, 50.20 53.91(0.6s) Tio, 1.80 1 83(0.10) K/N^ Alr03 13.05 18.03(0.26) FeO. 7.79 2.74(0.13}, Fig. 2. Whole-rock molar K,/Na ratios for 27 basanite-mi- MnO 0.14 0.11(0.01) nette samplesfrom Colima (Luhr and Carmichael, 1981; Luhr, Mgo 8.s8 1.2s(0.16) 1980). Open circlesare basanites,open squaresare minettes,and CaO 2.58(0.27]. Naro 379 5.s3(0.14) closed triangles show three leucite-bearingbasanites. The three KrO 3.72 6.76(0.24) minettes with the highest K,/Na values have the highest modal So. n.o. 0.19(0.04) phlogopitecontents as labeled(2 volo/o,0.7o/o, 11.8o/o). The whole- Total 10000 95.32 rock (WR) and glass(G : star) analysesof SAY 104 from Table LOI 2.94 n.o. K/Na(molar) 0.65 0.80 I are indicated. [The NarO and KrO values for Colima samples SAY-5A and SAY-6E were reversed in the above references: Nofe; Whole-rock analysis by xRF(normalized anhydrous) on pressed SAY-5A-2.55 wto/oNa,O, 3.850/oK,O; SAY-68-2.770loNa,O, powder with wet-chemicallyanalyzed minette standards used to define 4.160/oKrO.l workingcurves. Loss on ignition(LOl) determined at 950'C. Meananalysis (8 points)and 1 std dev (inparentheses) of brownglass in SAY-104(Fig. 1) determined by electronmicroprobe: 1s-kv accelerating potential,8-nA samplecurrent, with beam rasteredover 20 x 20 ttm arca. The three leucite-bearing, analcime-phlogopite-free basanites Na and K count rates were constantduring analysis.Glass total also have high K,iNa ratios of about l, whereasthe majority of bas- includes0.44 wt% BaO,0.69% SrO, 0.60 wt% P2Os,0.42h F, andO.24h cl. anites and minettes rangeto lower values.SAY-104 is typical of the latter group with K,/Na : 0.65. These lower values for the minettes might be argued to result from analcimization of leucite, but that argument cannot be applied to the analcimeJeu- analysesof the analcimesand the glassof SAY- 104 were deter- cite-free basanites.In addition, the glassof SAY-104 has K,/Na mined by electron microprobe at 15 kV-acceleratingpotential of only 0.80, demonstrating that values less than unity are in- and a sample current of 8 nA. With the beam rasteredover an deed magmatic. area of 20 x 20 pm, the Na count rates were constant during 2. Milk-white, L-type analcimeR-36 completely replacedcen- the 20-s analyses. timeter-sized leucite phenocrystsin a I Ma leucite tephrite lava Oxygenisotopes were measuredon dehydratedanalcime using flow from the Quaternary volcano Roccamonfinain western It- the BrF, procedure of Clayton and Mayeda (1963). The anal- aly (Giannetti, 1982).R-36 was collectednear the city Vologno. cimes were dehydratedby heatingthe samplesin vacuum at 100 Analcimization of leucite is a widespreadphenomenon among "C for 2 h to remove any surfacewater and then heating to 400 the potassicItalian volcanoes(Cundari and Graziani, I 964; Pas- 'C during which the channel water was releasedand collected. sagliaand Yezzaliri,1985; Luhr and Giannetti, 1987).Because The oxygen- and hydrogen-isotopecompositions of the channel ofgreat similarities in optical properties,analcime has beencon- water were measured using the micreCOr-HrO equilibration fused with either leucite (Washington, 1914) or glass (Pirsson, techniqueofKishima and Sakai(1980). 1896)in numerousigneous rocks. Isotopic compositions are reported in the familiar d notation 3. Vesicle-filling and veinlet-forming analcime BPF in Ter- in units of per mill relative to SMOW. Duplicate analysesin- tiary basalticlavas of the Bald PeakFormation in Tilden County dicate a reproducibility of DD and 6'80 of channel water of l0 Park, California (University of California, Berkeley, UCB no. and 2voorespectively, and 0.3V* for the 6t6Ovalue of the dehy- I6642), is typical ofthe earliest-recognizedtype ofanalcime, the drated analcime. The 6rEOvalue of NBS-28 qtartz standard is hydrothermal (H) variety (Mumpton, 1977 ; Hay, I 978). H-type 9.69* in the Saskatoonlaboratory. AI1 mineralogical, chemical, analcimespresumably precipitate from hydrothermal fluids and and isotopic results on analcime are given in Table 2. are not dependentupon a local precursor mineral or glass. 4. Veinlet-forming (H-type) analcime Kf1 is from rhe Kilpat- Rnsur,rs rick Hills, Scotland.(UCB no. 16658). Cell constantsand chemical compositions 5. Sample SZ is from the analcime diagenetic facies of the Miocene Skyline tuff(Sheppard and Gude, 1969),from the Bar- Saha(1959, 1961)synthesized solid solutionsofanal- stow Formation at Rainbow Gulch, near Barstow, California. cime under hydrothermal conditions from glassesranging This is typical of sedimentary analcime formed in saline, alka- across the binary system NaAlSiO" (nepheline)-NaAl- line lakes(S-type) (Surdam, 1977). SiO, (albite). He demonstrated a systematic decrease 6. Sample WMT (S-type)is from the analcime diageneticfa- in the cell constant ao with increasing silica, an effect cies of the upper JurassicWhite Mesa tuff (Brushy Basin Mem- causedby the shorter distanceofthe strongerSi4 bonds Morrison ber, Formation, near San Ysidro, New Mexico; Tur- versus the Al-O bonds. Recognizing the wide range of ner-Peterson,1985; Hay, 1986). conditions for analcime formation, attempts have been Each sample was crushed and sieved to 100-200 mesh, and made to use compositional parameters or the cubic cell the analcime was concentrated to >950/0using magnetic and particular density separation techniques.The cubic cell constant was de- constant to characterize environments. For ex- termined for each analcime by least-squaresrefinement of 15 ample, Fornaseri and Penta (1960) found high Rb in major reflectionsmeasured using a Guinier (Jago)powder cam- L-type analcimes in Italian volcanics; Hay (1966) and era with Si metal as a standard and FeKa, radiation. Only anal- Coombs and Whetten (1967) noted that S- and M-type cime reflectionswere observedfor each sample. Major-element analcimes are the most siliceous, reflecting their origins LUHR AND KYSER: PRIMARY IGNEOUS ANALCIME 2t9 from silica-rich volcanic glassprecursors; and Keith et al. (1983) found high concentrationsof Cs in H-type analcimes. Figure 3 is a plot of ao versus mole fraction tetrahedral Si (X.,) for the six analcimesfrom this study and 23 analysesfrom the literature, including S, M, H, and suggestedP types. As expected,the most siliceous analcimes are S and M types; S-type analcimes are also the most compositionally inhomogeneous,with the largest standard deviation values in Table 2. The Colima analcime falls near the canler of the range in Figure 3 (ao : 13.712A;, along with the L- and H-type analcimes and other possible primary analcimes from the Crowsnest 13.66 13.70 13.74 Formation, southeast Queensland(Wilkinson, 1977), northwest Iran (Comin-Chiaramonti et a1.,1979),and the uo (A) Highwoods Mountains, Montana (Wilkinson, 1968). Fig. 3. Mole fraction of Si in the tetrahedralsite (Xr,) of anal- Three analcimes from the SquareTop intrusion of New cime versus cubic cell constant ao. Solid symbols representthe South Wales (Wilkinson, 1965) have significantly lower six samplesfrom this study: dot : P-type analcime SAY-104; Si contentsand larger cell edges.From Figure 3, it is clear star : L-type analcime R-36; diamonds : S-type samples ST : that S- and M-type analcimes can generally be distin- and WMT; triangles H-type analcimes BPF and KH. Open guishedfrom other types by Si content and cell constant, symbols and letters are dala from the literature: open diamond : S-type analcime;open squares: M-type analcimes;and open but primary analcimecannot be distinguishedfrom either triangles: H-type analcimes(Coombs and Whetten, 1967).Sug- L H these or types by means. gestedP-type analcimesfrom the literature: C : CrowsnestFor- H-type analcimes can be distinguished from P and L mation (Wilkinson, 1968);X : Queenslandanalcimite (Wilkin- typesby the very low Fe contents(presumably tetrahedral son, 1977); vertically ruled field outlines analcimes from the Fet3) of the former (Fig. a). S- and M-type analcimesare Azerbaijan, Iran, tephrites,phonolites, and analcimites(Comin- also generallylow in Fe, with the exception of an S-type Chiaramonti et al., 1979);stippled field: analcimites and anal- samplenear Wikieup, Arizona, reportedby Ross (1928) cime phonolites from the Highwoods Mountains and analcime and Coombs and Whetten (1967). The Colima analcime tinguaite from the Otago Harbor (Wilkinson, 1968);horizontally : is high in FerO, (0.98 wto/o),as are feldsparsand leucites ruled field three analcimes from the Square Top Intrusion (Wilkinson, 1965). Enor bar indicates uncertainties from Ta- (0.48-1.71wto/o) from the high-temperatureColima bas- ble 2. anite-minettesuite (Luhr and Carmichael,l98l). Other

TABLE2. Electron-microprobeanalyses (wt%), formulae, cell constants(A), and 61sOand 6D valuesof analcimes

Samplenumber sAY-104 R-36 BP KH ST WMT Analcimetype: P - HHS a sio, 5s 28(028) 56.37(0.27) 54.06(0.37) 54.87(0.19) 57.10(0.91) 61.620.48) Alro3 21.04(0.16) 22.12(0.161 22.49(0.17) 22.21(0.17) 19.41(0.28) 19.50(0.83) Fe,O. 0.98(0.08) 0.27(0.03) 0.03(0.02) 0.02(0.02) 0.10(0.01) 0.20(0.07) CaO 0.26(004) 0 09(004) 0.18(0.07) 0.02(0.01) 0.02(002) 0.10(0.06) Naro 11.58(0 26) 1146(0 12) 13.20(0.12) 13.03(0.09) 11 .47(0.16) 11.02(0.63) K"O 0.38(0.05) 1.03(0.09) 0.05(0.02) 0.14(0.04) 0.15(0.06) 0.27(0.11) Total 89.52 91.34 90.01 90.29 8825 92.71 Onthe basisot sir oxygens Si 2 065(0.011) 2.062(0.010) 2 015(0.014) 2.035(0.007) 2.143(0.034) 2.189(0.053) AI 0.927(0.007) 0.954(0.007) 0 988(0.008) 0.971(0.007) 0.859(0.012) 0.817(0.035) Fe 0.028(0.002) 0.007(0.001) 0.001(0.001) 0.001(0.001) 0.003(0.001) 0.005(0.002) 0.010(0.002) 0.004(0.002) 0.007(0.003) 0.001(0.001) 0.001(0001) 0.004(0.002) Na 0.839(0.019) 0.813(0.009) 0.954(0.009) 0.937(0.007) 0.835(0.012) 0.759(0.043) K 0 018(0.002) 0.048(0004) 0.002(0.001) 0.007(0002) 0.007(0003) 0.012(0.005) Sum 3.886 3.888 3.968 J.YC I 3.847 3.786 X",,,", 0.684(0.009) 0.682(0.009) 0.671(0.011) 0.677(0.007) 0.713(0.028) 0.727(0.049) Cubiccell constant ao 13.712(0.001 ) 13710(0.001) 13.716(0.004) 13.720(0.001) 13.686(0.001) 13.693(0.002) lsotopic data 6160analcime (7@) +11_1 +13.9 +20.4 +21.O +17.7 Channel HrO (wto/.) 3.1 4.0 11 6.2 3.6 3.4 DDchannel HrO (7m) 119 - 136 - 155 -89 -112 -63 6'80 channel H2O(E*) -zo _20 _20 -12 -19 _Y d'80 modern meteoric watert (7m) A -10 -o -8 -10 -8 . Measureddirectly or estimatedfrom Dansgaard(1964) 220 LUHR AND KYSER: PRIMARY IGNEOUS ANALCIME

20 6180 15

+5 1368 13.70 13.72 13.66 13.70 13.74 (A) "" (A) Fig. 5. 6tEOvalues ofanalcime versus cubic cell constant for "o the six samplesof this study.Symbols as in Fig. 3. Fig. 4. FerO, contentof analcime(wto/o) versus cubic cell constantao. Symbols as in Fig. 3. The S- and H-type analcimeshave much higher 6'80 values(+ 13.9to -l2l.lVu), as expectedif they equilibrated suggestedprimary analcimes are also rich in FerO, (Fig. with surfacewaters at relatively low temperatures.Karls- 4:0.2-1.560/o).The L-type analcimefrom Roccamonfina son et al. (1985)reported similar d'8Ovalues for S-type falls at the low end of this range(0.27o/o), a value presum- analcimes,but their values for H-type analcimesranged ably inherited from the precursor leucite. Thus, Fe con- from * l2.3%mdown to +8.9Vm,below our value for the tent may be effectivein distinguishingP- and L-type anal- Colima analcime.Staudigel et al. (1981) and Alt et al. cimes from S, M, and H varieties. The L-type analcime (1986)measured D'8O values of + l8 to -l24%ufor H- or has significantly higher KrO content than the Colima M-type analcime from veinlets in altered oceanic crust. analcime, consistentwith the high Rb contents of L-type These results are broadly consistent with the negative crystalsdescribed by Fornaseri and Penta (1960). K and correlation between D'8Oof framework oxygen in anal- Rb abundancesmay prove effective in discriminating cime and temperatureof formation as suggestedby Karls- P- and L-type analcimes,although analcime formed from son et al. (1985),although this relationshipis somewhat nepheline or other precursor minerals would probably confused by the overlap between H-type and proposed show different inherited enrichments. P-typeanalcimes. Karlsson et al. (1985)also reported in- termediatevalues (+ 13.6to +14.3E@)for analcimefrom 6180of framework oxygen the Crowsnest Formation (Pearce, 1970), clearly dem- Oxygen-isotopevalues are plotted versuscell constants onstrating the nonprimary nature of theseanalcime phe- in Figure 5 for the six analcimesof this study. The lowest nocrysts in which framework oxygens have apparently d'8Ovalue is for the Colima specimen(+9.28ffi). Karlsson been partially exchangedwith fluids. In summary, based et al. (1985)dehydrated this samesample and measured on available results, oxygen-isotopecompositions appear a value of +8.87mon the framework oxygen. This small to be usable for distingishing P-type analcime from discrepancy is related to the ditrerent methods used in L- and S-typesand can be used to deny primary statusto calculating Dt8Ovalues of silicatesrelative to the SMOW most analcimes.Overlap exists,however, for 6'80 values standard. We assumethat the D'8Ovalue of framework of P-type and some H-type analcimes. oxygen in primary igneous analcime should be similar to the feldspard'SO values. Kyser et al. (1981)measured 6180and 6D in channel water 6'80 of *6Vu in clinopyroxene phenocrysts from other The water extractedfrom analcime channelsbelow 400 Colima basanitesand minettes. Basedon oxygen-isotope "C could originate from either (l) the fluid from which partitioning between clinopyroxene and plagioclase,we the analcime originally crystallizedor (2) a later fluid that expect primary Colima analcime to have d18Oof about has replaced the channel water but not substantially af- tTVu-The highervalue ofthe Colima analcime(+9.28m), fectedthe framework oxygen.Karlsson et al. (1985) re- therefore, is inconsistent with simple magmatic equili- ported that the 6'80 values of channel water in analcimes bration. The L-type analcime from Roccamonfina is from a variety ofenvironments do not correlatewith those somewhatmorer8O rich at -lll.l%m and is not in the of the framework oxygen, a result that is confirmed by rangeof freshleucites (+7.6 to +9.0E@)at Roccamonfina the data of this study (Table 2). For example,S-type anal- (Taylor et al., 1979). This indicates that simple ion-ex- cime WMT has a D'sOvalue of -9V* fot the channel change conversion of leucite to analcime was accom- water and a D'8Ovalue of +17.7Vmfor the framework panied by partial disruption of the Si-Al-O framework. oxygen. H-t1pe analcime KH presumably formed at a LUHR AND KYSER: PRIMARY IGNEOUS ANALCIME 221

higher temperaturethan the S-type samples,and isotopic ur.r*nrrrt fractionations between analcime and water should be f smaller.KH hasa D'8Ovalue of -l2V* for channelwater, higher value +20.47rc framework but a D'8O of for the -40 oxygen. These results suggestthat the channel water in many analcimesdoes not representthe fluid from which -80 the analcime originally formed. The mobility of water in zeolites is slowest for analcime (Dyer and Molyneux, 1968),but the analcimechan- -120 nels provide a pathway for fasterexchange between water and the framework oxygen than does lattice diffusion. If -160 channel-water diffusion and exchange with framework -30 -2O -1O O +1O oxygen is fast at relatively low temperatures,the isotopic sl8o composition of the channel water should correlate with Fig. 6. dD and 6'80 values ofchannel water extracted from both local meteoric water and framework oxygen.As dis- various types of analcime (Table 2). Symbols as in Fig. 3. All cussedabove, however, neither parameter is well corre- channel waters except that of P-type analcime from the Colima lated with D'8Oof the channel water, suggestingthat ex- minette (SAY-104) have isotopic compositions similar to mod- changebetween local water, channel water, and framework ern meteoric waters (MWL : meteoric water line from Craig, oxygenis slow at low temperatures,and that the channel 1961), but typically ditrerent from modern water in the local water has not equilibrated with local meteoric water. area. Open diamond indicates standard mean ocean water Inasmuchas the isotopic compositionsof channelwater (sMow. in most samples plot on the meteoric line (Fig. 6) but differ from modern meteoric water in the area from which tephrites(Comin-Chiaramonti et al., 1979)in which anal- the sampleswere collected, the channel water must rep- cime forms large euhedral phenocrysts up to 3 cm in resent an ancient meteoric water that has neither been diameter and (2) minettes, monchiquites, and other lam- replaced by modern water nor appreciably exchangedwith prophyres in which analcime occurs as discrete micro- the framework oxygen.As such,the isotopic composition phenocrystsor groundmasscrystals (Jahns, 1938; Rock, of channel water probably reflects a paleoclimate, al- 1977,1984; Williams et al., 1982) as well as a diffuse though the age of this paleoclimate would be difficult to groundmassphase, apparently a replacementof original determine. The only channel water that falls off the me- glass. teoric line is from the Colima analcime, which plots to Without exception, the blairmorites and other igneous the left. Becausemeteoric water can be affected in this rocks with phenocrystic analcime are lavas that are as- way by a limited number of processes(e.g., Welhan, 1987), sociatedwith only minor pyroclastic material. They lack the most likely explanation for the isotopic composition mica, hornblende, or other hydrous minerals and can be of the channel water from the Colima analcime is that construed to have formed from relatively anhydrous the water has become r8O-depletedbecause of either low- magmas.These magmasprobably crystallized in the sta- temperature precipitation or exchange with a silicate bility field of leucite or other feldspathoids, and their phase,such as the analcime itself. This would result in a analcime (L-type) formed from these primary minerals slight '8O enrichment in analcime and perhaps raise the by low-temperature ion exchange.The very low silica 6'80 value of the Colima analcime from the presumed contents and large cell constantsfor analcimes from the magmatic value of about -t77n to the observedvalue of SquareTop intrusion (Fig. 3) may reflect formation from +9.2Vm. a low-silica precursor such as nepheline or kalsilite in- steadofleucite. DrscussroN The petrography oflamprophyres, on the other hand, Petrographershave traditionally relied on the fresh ap- requires very hydrous magmatic conditions. High water pearanceof certain euhedral analcime crystalsin igneous contentsstabilize mica or amphibole and couple with rel- rocks to argue for a primary origin (Washington, l9l4). atively low magmatic Al contentsto contract the stability The Colima analcime of Figure l, however, is petro- fields for feldsparsand leucite. We suggestthat primary graphically indistinguishable from many L-type anal- analcime can become stableinstead of leucite in hydrous cimes. A photomicrograph of virtually identical L-type magmas of appropriate mafic alkalic composition. The analcime from the 0.38 Ma Brown Leucitic Tuf of Roc- upper temperaturelimit of analcime stability in synthetic camonfinais given in Luhr and Giannetti (1987). Tex- systems(650 'C) might be enhancedin natural lampro- tural argumentsin favor of primary analcime, therefore, phyric magmas by the presenceof Ca, Fe, Ti, and other are not definitive. elementsand by slightly water-undersaturatedconditions Igneous rocks in which analcime has been considered that are known to increasethe thermal stability of horn- as a primary mineral can be divided into the broad groups: blende and other hydrous minerals (Allen and Boettcher, (l) blairmorites(Pearce, 1970; Woolley and Symes,1976), 1978).The Colima basanitesand minettes have high con- analcimites (Wilkinson, 1968, 1977), phonolites, and tents of Mg, Cr, and Ni, with olivine (Foro-no)and Cr-rich 222 LUHR AND KYSER: PRIMARY IGNEOUS ANALCIME

spinel as the earliest-formed minerals. Oxygen-isotope AcxNowr,oocMENTS partitioning among phenocrystsin these samples yields .C Samplesofanalcime were kindly provided by Tom Bell, PeggyGenaro, equilibration temperaturesof 1000 to 1200 (Kyser et and Bernardino Giannetti We thank Ian S E. Carmichael, Richard L. al., l98l). The water-saturatedsolidus temperaturesof Hay, and Hal Karlsson for discussionson the question of igneousanal- basaltsat crustal pressuresare as low as 700 to 800 .C cime, H Rudy Wenk for help with the cell-constantmeasurements, and (Yoder and Tilley, 1962;Holloway and Burnham, 1972; David Pezdericand Geofry Koehler for their expertise,assistance, and patiencein the isotopic analyses The manuscript was carefully reviewed Stern et al., 1975).Thus, the Colima minettes may have by Robert N Clayton and Richard A. Sheppard.Clayton provided valu- encountered the stability field of primary analcime on able advice on the thorough dehydration ofanalcime approaching solidus temperatures near the Earth's sur- face. RrrnnnNcns crrnn Allen,J.C., and Boettcher,A.L ( I 978)Amphiboles in andesiteand basalt: CoNcr,usroNs II Stability as a function of P-T-fn,o-fo,. American Mineralogist, 63, l The proposed P-type analcime from Colima can be 1074-t087 . distinguished from most S- and M-types by the lower Si Alt, J.C.,Muehlenbachs, K , and Honnorez,J. (1986)An oxygenisotopic profile content through the upper kilometer of the oceaniccrust, DSDP Hole and larger unit cell of the former. 5048. Eafth and PlanetaryScience Letters, 80,217-219 2. P-type analcime can be distinguished from H-type Boettcher,A.L., and Wyllie P J. (1969)Phase relationships in the sysrem analcime by the much higher Fe content of the former, NaAlSiOn-SiOr-HrOto 35 kilobars pressure.American Journal of Sci- althoughd'8O values may overlap. ence.26'7^ 875-909. Clayton,R N and Mayeda,T.K. (1963)The pentafluo- 3. P-typeanalcime should have low D'8Ovalues similar , useof bromine lde in the extraclion of oxygen from oxides and silicatesfor isotopic to magmatic feldspars(+6 to +&Em).The Colima anal- analysis.Geochimica et CosmochimicaActa,27, 43-52. cime,which hasa d'8Ovalue of +9.2E@,mayhaveformed Comin-Chiaramonti,P, Meriani, S., Mosca,R, and Sinigoi,S. (1979) as a magmaticphase, but has undergonea limited amount On the occurrenceofanalcime in the northeastemAzerbaijan volcanics of low-temperature exchangewith its channel water re- (northwestemIran) Lithos, 12, 187-198. Coombs,D.S., and Whetten, (1967)Composition sulting in a slight J.T. of analcimefrom D'8Oenrichment. sedimentary and burial metamorphic rocks. Geological Society of 4. We investigateda single sample of L-type analcime, America Bulletin, 78, 269-282. derived from leucite. It has higher dr8O than both the Craig, H. (1961) Isotopic variationsin meteoricwaters Science,133, presumed precursor leucite and the P-type Colima anal- t702-t103 Cundari, A, (1964) cime, although P- and L-type varieties are identical in and Graziani, G. Prodotti di alterazionedella leucite nellevulcaniti vicane. Periodico Mineralogia (Rome), 33, 35-43. cell constant and in petrographic appearance.As a cor- Dansgaard,W (1964)Stable isotopes in precipitation Tellus, 16, 436- ollary, textural arguments in favor of primary analcime 468 cannot be definitive. In addition to higher d'8O values, Dyer, A , and Molyneux,A ( 1968)The mobility of water in zeolites.I. KrO and Rb contents appear to be systematicallyhigher Self-ditrusionof water in analcime. Journal of Inorganic and Nuclear in L-type parameters Chemistry,30, 829-837. analcimes.These three may prove Fornaseri,M., and Penta, A. (1960) Elementi alcalini minori negli anal- the only reliable discriminators of P- and L-type anal- cimi e loro compartamentonel processod,i analcimizzazionedella leu- clmes. cite PeriodicoMineralogia, 29, 85-101. 5. Primary analcime is most likely to occur in lampro- Giannetti,B. (1982)Roccamonfina Volcano, Italy. Volcano News, 12, phyres, alkali-rich, silica-undersaturatedmagmas whose t-3. Gupta, A.K., and Fyfe, W.S. (1975)Leucite survival: The alterationto high water contents are essentialfor the stability ofanal- analcime CanadianMineralogist, 13, 361-363 cime and other hydrous minerals. The Quaternary Co- Harker, A. (1954)Petrology for students,283 p CambridgeUniversity lima minettes seemto be the best candidatesfor primary Press,Cambridge, England. analcime. Hay, R.L. (1966) Zeolites and zeolitic reactions in sedimentary rocks. GeologicalSociety ofAmerica Paper p. 6. Analcimites, blairmorites, Special 85, 130 and related lavas contain- -(1978) Geologicoccurrence of zeolites In L.B. Sand and F.A ing analcime phenocrystsin the absenceof other hydrous Mumpton, Eds., Natural zeolites,occurrence, properties, use, p. 135- minerals are unlikely hosts for primary analcime. With 143 Pergamon,Oxford increasingtemperature of alteration,these analcimes range -(1986) Geologic occurrenceof zeolites and some associatedmin- from strict L-types to H and M varieties having heavier erals Pure and Applied Chemistry, 58, 1339-1342. Henderson,C.M.B , and Gibb, F G.F. (1977)Formation of analcimein oxygen-isotopecompositions. the Dippin sill, Isle of Arran. Mineralogical Magazine, 41, 534-537. 7. The hydrogen-and oxygen-isotopecompositions of Holloway, J.R., and Burnham,C W (1972)Melting relationsof basalt channel water in all but P-type analcime fall on the me- with equilibrium water pressureless than total pressure.Journal of teoric water line and may record the composition of me- Petrology,13, l-29. R.H. (1938)Analcite-bearing intrusives teoric water at the time Jahns, from South Park, Colo- of analcime formation. The D'sO rado. American Journal of Science.36, 8-26 values of the channel water do not generally correlate Karlsson,H.R., Clayton,R.N, and Mayeda,T.K. (1985)Analcime-A with either the values of modern meteoric water in the potential geothermometer?Geological Society of America Abstracts environs of each sample or with the 6'80 value of the with Programs,11, 622-623. framework oxygen, suggestingthat exchange between Keith, T.E C , Thompson,J.M., and Mays,R E (1983)Selective concen- tration in groundwater, of cesium analcime during hydrothermal alteration, Yellow- channel water, and framework oxygen is stone National Park, Wyoming Geochimica et Cosmochimica Acta, slow. 4'7,795-804 LUHR AND KYSER: PRIMARY IGNEOUS ANALCIME 223

Kim, K-T, and Burley, B.J (1971)Phase equilibria in the systemNa- - ( l96l) The systemNaAlSiOr (nephelinelNaAlSiO, (albitefH,O AlSi.OgNaAlSi04-HrO with specialemphasis on the stability of anal- AmericanMineralogist, 46, 859-884 cite CanadianJournal of Earth Sciences.8. 3 I l-337. Sheppard,R A., and Gude,A.J (1969)Diagenesis oftuffs in the Barstow Krshima,N, and Sakai,H. (1980)Oxygen-18 and deuteriumdetermi- Formation, Mud Hills, San Bemadino County, California. U.S. Geo- nation of a singlewater sampleof a few milligrams. Analytical Chem- logicalSurvey Professional Paper 634, 35 p. istry,52,356-358. Staudigel,H., Muehlenbachs,K., Richardson,S.H., and Hart S.R.(1981) Kyser,T K, O'Neil, J.R, and Carmichael,I S.E.(1981) Oxygen isotope Agents of low temperature ocean crust alteration. Contributions to '7'7, thermometry of basiclavas and mantle nodules Contributions to Min- Mineralogyand Petrology, 150-157 eralogyand Petrology,71, ll-23 Stem,C R., Huang,W-L., and Wyllie, P J. (1975)Basalt-andesite-rhyo- Larsen,ES., and Buie, B.F. (1938)Potash analcime and pseudoleucite lite-H,O: Crystallization intervals with excessH'O and HrO-undersat- from the Harwood Mountains of Montana American Mineralogist,23, urated liquidus surfacesto 35 kilobars, with implications for magma 83 7-849 genesisEarth and PlanetaryScience Letters, 28, 189-196 Liou, J.G (1971)Analcime equilibria Lithos,4, 389402. Surdam, R.C. (1917)Zeoliles in closedhydrologic systems Mineralogical Lofgren,G (1980)Experimental studies on the dynamic crystallization SocietyofAmerica Short CourseNotes, 4,65-91 of silicatemelts. In R.B Hargraves,Ed , Physicsof magmatic process- Taylor, H.P., Jr,, Giannetti,B, and Tun, B (1979)Oxygen isotope geo- es,p 487-551 PrincetonUniversity Press, Princeton, New Jersey chemistry of the potassicigneous rocks from the RoccamonfinaVol- Lonsdale,J.T. (1940)Igneous rocks ofthe Terlingua-Solitarioregion, Tex- cano, Roman Comagmatic region, Italy Earth and Planetary Science as GeologicalSociety ofAmerica Bulletin, 51,1539-1626 Letters.46. 81-1 06. Luhr, J F (1980)The Colima volcaniccomplex. Ph D dissertation,146 Turner-Pelerson,C E (1985)Lacustrine-humate model for primary ura- p. University California, Berkeley,California nium ore deposits, Grants uranium region, New Mexico Amencan Luhr, J.F, and Carmichael,I.S E. (1981)The Colima volcaniccomplex, Associationof Petroleum GeologistsBulletin, 69, 1999-2020 Mexico: Part II Late-Quaternarycinder cones Contributions to Min- Tyrrell, G W. (1928) On some dolerite-sillscontaining analcite-syenitein '76, eralogyand Petrology, 121-147. cenlral Ayrshire Quarterly Journal ofthe GeologicalSociety, 84, 540- Luhr, J.F, and Giannetti,B. (1987)The Brown LeuciticTuffof Rocca- 569 monfina Volcano (Roman region, Italy). Contnbutions to Mineralogy Washington,H S (1914)The analcitebasalts of Sardima.Joumal of Ge- and Petrology,95, 420-436 ology, 22, 142-'7 53. Morse, S.A (1968)Syenite. Camegie Institution of WashingtonYear Book Welhan,J A. (1987)Stable isotope hydrology. Mineralogical Association 68, I 12-120. ofCanadaShor't Course, 13, 129-16l Mumpton,F A ( 1977)Natural zeolites Mineralogical Socrety of America Wilkinson,J.F.G (1965)Some feldspars, nephelines and analcimesfrom ShortCourse Notes, 4, l-l 7. the SquareTop Intrusion, Nundle, N.S.W Joumal of Petrology,6, Passaglia,E., and Vezzalini,G. (1985)Crystal chemistryof diagenetic 420-444. zeolitesin volcanoclasticdeposits ofltaly. Contributions to Mineralogy -(1968) Analcimesfrom somepotassic igneous rocks and aspects and Petrology,90, 190-198. of analcime-richigneous assemblages Contributions to Mineralogy and Pearce,T H. ( I 970) The analcite-bearingvolcanic rocks of the Crowsnest Petrology18,252-269. Formation, Alberta. CanadianJournal of Earth Sciences,7 , 46-66 -(1977) Analcime phenocrystsin a vitrophyric analcimite-Pri- Peters,T J , Luth, W C, and Tuttle, O.F. (1966)The meltingofanalcite mary or secondary?Contributions to Mineralogy and Petrology,64, l- solid solutions in the system NaAlSiOo-NaAlSirO8-HrO.American l0 Mineralogist,3 I,'136-1 53 Williams, H, Turner, FJ., and Gilbeft, CM. (1982)Petrography: An Pirsson,L.V (1896)On the monchiquitesor analcitegroup of igneous introductionto the sludyofrocks in thin sections(2nd edition)626 p. rocks. Journal of Geology, 4, 619-690 W.H Freeman.San Francisco. Rock, N.M.S (1977)The natureand origin of lamprophyres:Some def- Woolley,A.R., and Symes,R F (1976)The analcime-phyricphonolites initions, distinctions,and derivatives Earth-ScienceReviews, 13, 123- (blairmorites) and associatedanalcime kenytes of the Lupata Gorge, 169. Mocambique Lithos, 9. 9-15 -(1984) Natureand origin of calc-alkalinelamprophyres: Minettes, Yoder,H S-,and Tilley C.E (1962)Origin of basaltmagmas: Experimen- vogesiles,kersantites, and spessartitesTransactions of the Royal So- tal study of natural and synthetic rock systems.Journal of Petrology, ciety of Edinburgh-Earth Sciences,'74, 193-227 3.342-s32. Ross,C.S. (1928) Sedimentary analcite American Mineralogist, i3, 195- 197. Roux, J, and Hamilton D.L. (19i6) Primary igneousanalcite-An ex- perimentalstudy. Joumal of Petrology,11, 244-257. Saha,P (1959)Geochemical and X-ray investigationofnatural and syn- M.muscnrpr RECETvEDMav 18, 1987 theticanalcites. American Mineralogist, 44, 300-313. MeNuscnrpr AccEprED Septeusen 27, 1988