The Structural Characteristics of Palagonite from Dsdp Site 335 Zhihong Zhoui and William S. Fyfe Kazue Tazaki

Canadion Mineralogist Vol. 30, pp. 75-81(1992)

THE STRUCTURALCHARACTERISTICS OF PALAGONITEFROM DSDP SITE 335

ZHIHONG ZHOUI ANDWILLIAM S. FYFE Department of Geology, University of Western Ontario, London, Ontario N6A 587

KAZUE TAZAKI Departmentof Geologt, ShimaneUniversity, Matsue, Shimane 690, Japan

SJIERK J. VAN DER GAAST NetherlandsInstitute for SeaResearch, P.O. Box 59, 1790AB Den Burg, Texel,The Netherlands

ABSTRACT smectitesdi- et tri-octa6driquede compositionet degr6 de cristallinit6variables, ainsi que leurs pr6curseurs.

The palagonite from the FAMOUS area of the (Traduitpar la Rddaction) Mid-Atlantic Ridge at 36'N, DSDP Site 335, is mainly composedof smectite-likeparticles and their spheroidal Mots-clds:palagonite, smectite, structure cristalline, precursors.The crystallinity of the smectitelike particles alt6ration,diffraction X, microscopie6lectronique par is good along the a and D axes,but poor along the c axis. transmission,ride m6dio-atlantique. Although they show structural similarities to stevensite and nontronite, the smectitelike minerals are composi- tionally different from the two minerals.Their spheroidal INTRODUCTION precursorshave very poor crystallinity, and are rich in Al and Fe. Neither oxide phasesof Fe, Mn, and Ti, nor The palagonitization of sideromelanehas been zeoliteswere found in the palagonite.The palagonite is the subject of many studiessince 1846,when von considereda composite material that contains di- and Waltershausenintroduced the term palagonite to trioctahedral smectite of variable composition and describealtered basaltic glass of hyaloclastitesfrom crystallinity, and their precursors. Palagonia in the Hyblean Mounts, Sicily. Despite Keywords: palagonite, smectite, mineral structure, altera- an impressive number of publications on the tion, X-ray diffraction, transmissionelectron micros- subject(e.9. , Byerset ol. I 987, Crovisieret al. 1987, copy, Mid-Atlantic Ridge. Furnes 1978, 1980, Honnorez 1978, 1981, Jakobsson (1978), Jakobsson & Moore 1986, Jercinovicet al. 1990,Staudigel & Hart 1983),the SoMMAIRE nature of palagonite is still not well defined. Honnorez (1981) suggestedthat palagonite is a La palagonite du site DSDP 335 de la rdgion mixture, in variable proportions, of altered, FAMOUS, le long de la ride mddio-atlantique(36"N), hydrated, and oxidized glass with authigenic contient surtout desparticules ressemblant ir la smectite, minerals such as clays and zeolites,and proposed et sespr6curseurs sph6roides. Le degr6de cristallinit6 des to abandon the term. However, studies by X-ray particulesi aspectsmectitique est 6levele long des axes diffraction of carefully separatedpalagonite show a et b, mais faible le long de c. Tout en ayant des poorly resolvedlayer silicate(Andrews 1978, caractdristiques structurales semblablesi la stevensiteet only a la nontronite, la composition des particules i aspect Bonatti 1965,Hay & Iijima 1968a,b, Singer1974, smectitiquediff&re de celle de ces deux min6raux. Les Stokesl97l). Eggleton& Keller (1982)noted the pr6curseurssphdroides ont un degr€ de cristallinit6 tr0s similarity of averagepalagonite to smectitewhen faible, et sont enrichisen Al et Fe. Nous n'avons trouvd recalculated to a cation charge of +22, and ni oxyde de Fe, Mn et Ti, ni de zdolitedans la palagonite. concluded lhat palagonite is composed of a La palagonite serait un matdriau composite contenant dioctahedral smectite with significant Mg in the sheet of octahedra. In a previous paper (Zhou & lPresentaddress: Oil Sandsand Hydrocarbon Recovery Fyfe 1989),we discussedthe chemicalcomposition Department,Alberta ResearchCouncil, P.O. Box 8330, and mechanism of formation of the palagonite Station F, Edmonton, Alberta T6H 5X2. from the Mid-Atlantic Ridge. The present com- 75

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munication focuseson the structural characteristics RESULTS of the palagonite. An XRD pattern of the parent glass from Site Sauplrs lNn ExpruusNtaL MEtHops 335shows a hump from 4.95to 2.43 A, with peak position at 3.26 A (fie. 1A), The hump is typical The samples studied are from the FAMOUS of glassand other amorphousmaterials, although area,at 36oN of the Mid-Atlantic Ridge, and were its peak position shifts dependingon the composi- recoveredduring Leg 37 of the Deep Sea Drilling tion of the glass.^The glass also shows a broad Project (DSDP) at Site 335. The sampledportion hump at about 12 A with low-angleXRD (Fig. lB). of acousticbasement at Site 335 underliesa 454'm A change in relative humidity shows no shift or thick sequenceof foram-bearingnannofossil ooze increasein intensity at low angles.The glassshows and consistsof a very uniform sequenceof pillow a smooth surfaceunder TEM, and its electron-dif- basaltswith numerousglass rinds and intercalations fraction pattern showsno diffraction rings or spots. of nannofossilchalk (Aumento et ol. 1977).A best This further confirms its amorphous nature. estimate of the basement age for this site is Therefore, clay mineralsor clay mineral precursors approximately 13 Ma (Miles & Howe 1977).The are not presentin the parent glass. samples were collected from the glass rinds of An XRD study of palagonile from Site 335 pillow basalts(see Zhou & Fyfe 1989).The glassis showstwo strong peaksat 4.53 A 4nd 2.60 A and primarily dark brown to black sideromelane,with a moderate-intensitypeak at 1.52 A (Fig. 2A). An a yellowishorange palagonite rind on surfacesand "amorphous" hump similar to that of the glasscan along fractures. still be seen.The basal reflection of palagoniteis In order to characterize the nature of the weak and variable from 12 to l5 A, and becomes palagonite, glass and associatedpalagonite were more diffuse after treatment with ethyleneglycol. mechanically separated and then hand-picked With the low-angle XRD method, one can see a under a binocular microscope.Both the glassand peak that shifts with changinghumidity (Fie. 2B). palagoniteseparates were ultrasonically cleanedin The peak is located at 16.2 A at 10090RH, 15.8 an acetonebath and ground into powder. Suspen- sions of the powders were made, and deposited onto glass slides for X-ray diffraction (XRD) or deposited onto 3 mm holey carbon grids for analysis by transmission electron microscopy (TEM). Thin sectionswith a thicknessof about 600 A also were prepared for TEM analysis. The ultramicrotomy followed proceduresdescribed by Lee et al. (1975). XRD analyses were first carried out with a Rigaku X-ray diffractometer system(CuKa radiation). A low-angleX-ray powder-diffraction study (CoKo radiation) was further performed on 35 31 27 23 19 15 selectedsamples according to the method described by van der Gaast et al. (1986).The glasssamples 20 CuKcr for low-angle XRD were milled in dried cyclohexanebecause dry-milling causesdestruction of structures and milling in water results in clay formation (Kiihnel & Van der Gaast 1989). The 0n! palagonite sampleswere Ca-exchangedin water. Structural characteristicsof palagonite were observed using a JEOL JEM 100C TEM, with an acceleratingvoltage of 100 kV. High-resolution TEM studies were carried out with a Philips 400 STEM system equipped with EDX detector, operatedat 100 kV. Electron-diffraction patterns wererecorded wherever possible, but the crystalline structurewas generallydestroyed by the high-ener- 1815't29630 gy electron beam. From the electron-diffraction 2g 00Ko patterns,d valueswere calculatedthrough calibra- Frc. l. X-ray-diffraction (XRD) patterns of the glass. A. tion with a pulverizedgold standard. Normal XRD, B. Low-angle XRD.

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o< o

q or< q

?0 CuKo

.s - /, l0f/oHH ?"l! 5A6RH------f/oFH......

MoS2 (lnt SEndad) /r,

181512963 ?0 CoKo

Frc. 2. X-ray-diffraction patterns of palagonite. A. Normal XRD. B. Low-angleXRD.

A at 50VoRH, and L2.g L at 090 RH. This kind of peak shift with changing RH is normal for smectite minerals (Van der Gaast el al. 1986). However, the scaleof peak shift for the palagonite is smaller than most of the smectite minerals reported by van der Gaast et al. (1986). In addition to the shifting peak, there is a low-anglehump at 20 A that can best be seenat 090 RH (Fig.2B); this feature points to the presenceof curved or (A) folded layers (seealso Van der Gaast et al. 1986). Frc. 3. Transmissionelectron micrograph andlattice image(B) of the smectite-likeparticles in palagonite. The TEM study indicates that most of the palagonite is composedof fibrous to lathlike or strongly folded layered particles similar to smectite minerals(Fig. 3A). Lattice image^sof the palagonite conditions applied in TEM, all interlayer water is particlesshow a d value of l0 A @ig. 3B), which lost. Electron-diffraction patternsof the palagonite corresponds to the low-angle X-ray diffraction showdiffryction rings or diffuse spotsat 4.55,2.61, maximum at 12.9 A at ltlo RH. This difference in and 1.52 A (Fig. 4A), which agreeswith the XRD d value reflects the change in the degree of results very well. This indicates that degree of dehydration of the material in the two techniques. dehydrationhas little or no effect on thesed values, In low-angle XRD at OVo RH, Ca-exchanged and thus thesediffraction maxima must belong to smectite still keeps one layer of absorbed water the [001] zone. In fact, the electron-diffraction (Ktihnel& Van der Gaast1989), whereas at vacuum pattern is consistentwith [CIl] diffraction pattern

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,:,:l:

.33 20

Frc. 5. Spheroidalparticles in palagonite(A) and their . .11.13 replacementby randomlyoriented short line-structures(arrows) (B). a O .o2 .06 a of palagonitealong a and D axesalso was observed by Singer (1974). a Associated with the smectite-likeparticles are clusters of small, spheroidal particles, a few aa hundred angstrdmsin diameter(Fig. 5A). They are Frc. 4. Electron-diffraction pattems of the smectitelike very poorly crystallineand similar to the "cell-like particles in palagonite.A. Diffuse diffraction-spots. structures" described by Banfield & Eggleton B, Indexeddiffraction pattern A. (1990).These spheroidal particles may representthe precursorsof smectite-likeclays. Figure 5B shows the progressivereplacement of these spheroidal particles by small, randomly oriented line-structures, which lead to formation of smectite-like of smectiteminerals and can be indexedas (02) and clays. (ll), (13)and (20),and (06) and (33) (Ftg. 4B). The chemical composition of palagonite is We also noted that the particlesof smectite-like known to be variable (Honnorez 1981). The palagonite usually have well-organized crystallinity compositional changesduring palagonitization at alongthe a and D axes.Along the c axis,the number Site 335has beendiscussed by Zhou & Fyfe (1989). of stacked layers is usually less than 7. The Using a scanningtransmission electron microscope crystallinity along c axis of the smectite-like equippedwith an EDX detector, we were able to particlesmay be poor in general,as their (000peaks aralyze palagonite particles having different mor- on XRD are weak. A high degree of crystallinity phology. Compositionalvariations are quite large,

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TABLE I. CIIEMICAL OMFOSIIION OF SBIJCTED PARTICLES change capacity and small swelling ability of IN THE PAI.AGOMTE FROM DSDP SITE 335, stevensite(Brindley 1955). However, the chemical composition Srmti$[ke fbrdcLs Sph@tdal of the 1234 56 palagonite from Site 335 is variable and can be (Table sio, 5L2 53.0 52.3 532 47.4 49.9 significantlydifferent from that of stevensite Arp' 18.7 r7.r 5.9 u.8 r9.0 l). The structural formula of stevensite was FqOr. 15.2 74.O 7S 9.8 15.3 19.5 rfrq (1953) 1.6 r.4 l.E 0.9 3.2 suggested by Faust & Murata to be: Mgo 10.3 llJ 31.7 353 2,1 7.1 [Mgr.rrMn6.62Feo.er3+]SiaOre[OH]2,which differs CaO - 1.8 r3 0.2 Kp 2.r 2.9 0.9 7.6 I.t from saponite in lacking essential aluminum. Torsl tm.l lm.l lm.r 100.1 99J 100.0 Stevensite found in experimental alteration of basaltic glass (Trichet 1969) is a nearly pure ' Dffihd bt @irsio elffi@ niouoopy ei& @E-dispqsi@ Mg-silicate hydrate. The Mg-rich smectite-like X-E' sp€dr8i Epqed s fl% of qid€ @ ehld@s bssi& z Tdsl h@s&Oj. particles in the palagonite invariably contain significant amount of Fe or Al (or both). Thus, they are compositionallyincompatible with stevens- evenwithin eachindividual sample(Table l). The ite. In chemical composition, the smectite-like major oxidespresent are SiO2,Al2O3, Fe2O3, MgO, palagoniteparticles are similar to saponite,but th^e TiO2 and K2O. The spherical particles (Table l, 060 peak of the p-alagonitehas a d of 1,52 A analyses 5 and 6) are rich in Al and Fe, whereas comparedto 1.53 A for saponite (Table 2). the smectite-likeparticles (Table l, analysesl-4) The XRD data could also be accounted by are Mg- and Fe-rich silicares. nontronite, although the fit is not as good as with stevensite.However, those nontronite peaks that DIScUSSIoN are absentin the palagoniteare of the 00/ type. As discussedabove, the crystallinity of palagonite is The structural characteristicsof smectiteJike poor along the c axis, and the discrepancycould poor minerals describedabove are similar to those of result from this crystallinity. stevensiteand nontronite. Table 2 comparesthe However, nontronite alone cannot account for XRD data of palagonite and those of stevensite, the observed chemical composition of the saponite, and nontronite. The match betweenthe palagoniteeither. Its structural formula (Brindley palagonite and stevensitedata is very good. Nor & Brown 1980) is [M*".nHzO][Fd*2j[Si4-* only the positions of the diffraction peaks of the AlxOr0l[OH]2, i.e., it should contain little or no palagonite but also their relative intensities are Mg. In contrast, the smectitelike particles in the similar to those of stevensite. Stevensite was palagoniteusually contain more than l0 wt.9o MgO establishedas a memberof smectitegroup by Faust (Table l, analysesl-4). & Murata (1953).This wasconfirmed in subsequent We suggesthere that the discrepancyis due to studies(Brindley 1955,Faust et al. 1959),although the composite nature of the palagonite. Both the detailedstructural characteristicsof the mineral dioctahedralnontronite and trioctahedralstevensite remainto be defined (Brindley & Brown 1980).The (or saponite)may be present.The closeassociation smallershift of the 001 peak position of palagonite of the smectiteminerals of variable compositionat with changingRH (ascompared with most smectite a submicrometerscale leads to a variable chemical minerals)also is consistentwith the low cation-ex- compositionthat cannot be accountedfor by either mineral alone. The chemical analysis of the palagonite also is complicated by the spherical TABLE Z X-RAY-DIFFRACIToI.I DATA FOR STEVENSIIE SAPOMTI. particles N(I{TRONTTq AND PAI.AGOMTB FROM DSDP SIIE 335 that are closely associated with the smectite-likeparticles. In this respect,it should be Siereld&' Samolte! No!lrodte' Pdeni!e noted that the areacovered by electronbeam during EDX analysiswas about 0.05 pm in diameter.This AtAr ArA IA size is much greater than that of the smectitelike ?ATlZOs- particlesin the palagonite.Therefore 14.6 v - the chemical rZ4 lm U.2 l0O 14.6 100 13.0 r2.U w composition determinedas such may be that of a 7Al0716l0_ 5.0 m 4.96 4 4.98 10 _ composite material. In fact, diffuse diffraction 4J4 lm 4.57 50 4.53 lm 4.53 vs 4J3 v8 spots and diffraction rings observed for the 3J0 50 3.67 & 3.67 m 3.60 e 3.49 s palagonite 3.0 - 2-g l0 3.01 30 3.Ot e - (Fig. a) provide direct evidencethat the 2.62 N 2J8 m 2.il 50 2.fi w 2.60 w material is both polycrystallineand poorly crystal- 2.X 4 2.n m 2.n l0 2.28 w 1.73 & 1.73 2n L72 m rJs , line. It is also interesting to note that the basal lJ2 90 1.53 90 1.52 80 1.52 s 1.52 s reflection of the palagonitevaries between12 and 15 A, and may be split (Fig. 2A). This again 'AsrM bAsrM s 7-357; $t3-86: "ASTM$34{42 suggeststhat the palagoniteis compositein nature.

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Thus the observed structural and compositional muscovite, and K-feldspar weathering. Cloys CIay characteristicsof the palagonite from DSDP Site Minerals 38, 77-89. 335 can explainedby the microscaleassociation of (1965): hyaloclastites and dioctahedralnontronite and trioctahedralstevensite BoNanrr, E. Palagonite, alteration of volcanic glass in the ocean, Bull. (or with the saponite). This finding contrasts Volcanol. 28, 257-269. observationof Eggleton& Keller (1982)that their palagoniteis composedof a dioctahedralsmectite BnnorEv, C.W. (1955): Stevensite,a montmorillonite- with significant Mg in the octahedral sites. type mineral showing mixed-layer characleristics. Dioctahedral (nontronile) and trioctahedral Am. Mineral. 40, 239-247. (saponite)clays also were suggestedto occur in the palagonite of Contrada Acqua Amara, neuu & BnowN,G. (1980):Crystal Structures of Clay Palagonia(Crovisier et al, 1987). Minerals and their X-ray ldentification (3rd ed.). The sphericalparticles are probably the precur- Mineralogical Society, London. sorsof the smectiteJikeminerals. Eggleton & Keller (1987): (1982) Bvsns,C.D,, JrnctNovtc,M.J. & EwrNc,R.C. noted the formation of smectite from A study of natural glass analogues as applied to spherical particles during palagonitization. Our alteration of nuclear waste glass.Argonne National observation indicates that spherical particles are laD., NUREG / CR4842, ABK-86-46. first replaced by short-range crystalline domains that eventuallydevelop into smectite-likeminerals. Cnovrsrcn, J.L., HoNNonez, I. & Enrnuanr, J.P. The presenceof sphericalparticles may accountfor (1987): Dissolution of basaltic glass in seawater: the "amorphous" hump seenin XRD pattern of mechanism and rate. Geochim. Cosmochim. Acto the palagonite(Fig. 2A). 51,2977-2990. It should be noted that oxide phasesof Fe, Mn KrtLrn, J. (1982): The and Ti and zeoliteswere not found in the palagonite Ecomrou, R.A. & palagonitization of limburgite glass- a TEM study. itself, although they are closely associatedwith it Neues Jahrb. Mineral. Monatsh., 321-336. (Zhou & Fyfe 1989). Therefore, it may be inappropriate to consider this palagonite as a Fausr, G.T., HanHewAY,J,C. & Mu-ror, G. (1959): mixture of altered glass with clays, oxides and A restudy of stevensite and allied minerals, Am. zeolite.Rather, the palagonitefrom DSDP Site 335 Mineral. U,342-370. can be consideredas a composite material that containssmectile minerals (of variablecomposition & Munnra, K.J. (1953):Stevensite, redefined and crystallinity) and their precursors. as a member of the montmorillonite group. Am, Mineral. 38,973-987. AcrNowl.gocEMENTS FuRNes, H. (1978): Element mobility during palagonitization of a subglacial hyaloclastite in We are grateful to Dr. P.T. Robinson, Depart- Iceland. Chem. Geol. 22,249-26/., ment of Geology, Dalhousie University, for providing the DSDP..samples. We thank R. ( I 980): Chemical changes during palagonitiza- Humphery of the University of Guelph for his tion ofan alkali olivine basaltic hyaloclastite, Santa assistancewith the STEM analysis.The technical Maria, Azores. Neues Jahrb. Mineral. Abh. 13E, and editorial comments from refereesand editor l4-30. are appreciated.The financial support of this study (1968a): came from an operating grant from the Natural H,cv, R.L. & Ittur,n, A. Nature and origin of palagonite of the Honolulu. Group on Oahu, Engineering Research Council of tuffs Sciencesand Hawaii. Geol. Soc. Am., Mem. l\6' 331-376. Canadato W.S. Fyfe. " - & - (1968b): Petrology of palagonite REFERENcES tuffs of Koko Craters, Oahu, Hawaii. Contrib. Mineral. Petrol. 17, l4l-154. ANonrws,A.J. (1978):Petrology and Geochemistry of Alteration in Layer 2 Basahs.Ph.D. disserta- HoNuorcz,J. (1978):Generation of phillipsitesby tion, Univ. WesternOntario, London, Ontario. palagonitizationof basalticglass in seawater and the origin of K-rich deep-seasediments. .Iz Natural Aurrcrro, F. & MrmoN, W.G. el al. (1977):Initial Zeolites- Occurrence,Properties, Use (L.B. Sand Reportsof the DeepSea Drilling Project37, U.S. & F.A. Mumpton,eds.). Pergamon Press, Oxford' GovernmentPrinting Office, Washineton(1008- u.K. (24s-2s8). 1024). (1981): The aging of the oceanic litlosphere. BaNrmlo, J.F. & Eccrrrou, R.A. (1990):Analf,tical ,In The Oceanic Lithosphere (C. Emiliani, ed.), The transmissionmicroscope studies of plagioclase, jea 7, 525-587.

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JaronssoN, S.P. (1978): Environmental factors con- material from the Golan Heights, Israel. Clays Clay trolling the palagonitization of the Sufisey tephra, Minerols 22,231-240. Iceland. Bull. Geol. Soc, Denmark n.9l-105. SrauorcrL, H. & Henr, S.R. (1983): Alteration of & Moonr, J.c. (1986):Hydrothermal minerals basaltic glass: mechanismsand significance for the and alterationrates at SurtseyVolcano, Iceland. oceanic crust - sea water budget, Geochim, Geol. Soc.Am. Bull. 97, tu8-659. Cosmochim. Acta 41, 337-350.

Jencnovrc,M.J., KEn, K., Surru,M.R. & Scuvrrr, Srorrs, K.R. (1971): Further investigations into the R.A. (1990):Alteration of basalticglasses from nature of the materials chlorophaeite and north-cenhalBritish Columbia, Canada. Geochim. palagonite. Mineral. Mag. 38, 205-214. Cosmochim.Acto 54, 2679-2696. TRrcnEr, J. (1969): Contribution d l'4tude de KUuNrr, R.A & VaN Dsn Geesr, S.J. (1989): I'altdration expdrimentale des verres volcaniques. Formation of clay mineralsby mechanochemical Th&se de doctorat, Ecole Normale Supdrieure, reactionsduring grinding of basalt under water. Paris, France. Appl. Cloy Sci,4,295-305. J.H.F. Len, S.Y., JacrsoN,M.L. & BnowN,J.L. (1975): VeN Drn Gaasr, S.J., MlzotA, C. & JeNsrr, (1986): Curved smectite in soils from volcanic ash Micaceousinclusions in kaolinite observedby powder and high resolution electron in Kenya and Tanzania: a low-angle X-ray ultramicrotomy 34,665-67-. microscopy.Clays Clay Minerols23, 125-129. diffraction sttdy. Clays Clay Minerals Mrles, G.A. & Howr, R.C. (1977):Biostratigraphic Znou, ZuruoNc & Fvrr, W.S. (1989): Palagonitization summary,Deep Sea Drilling Project Leg 37. In of basaltic glass from DSDP Site 335, Leg 37: Initial Reportsof DSDP 37 (F. Aumento, W.G. textures, chemical composition, and mechanism of Melson, et al., eds.).U.S. GovernmentPrinting formation. Am. Mineral. 74, lM5-1053. Office, Washington(968-977). Received February 6, 1991, revised manuscript ac- SrrcEn, R.A. (1974): Mineralogy of palagonitic cepted August 6, 1991.

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