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TITLE. Chemical t’ariahility of Zeolites at a Potential NuclearWaste Flepos ltorv, Yucca Mountain, Nevada

AUTHOR@): D. E. FJrO!(t OII, ESS- 1

SUBMITTED TO Proceeding!] of the International S}-rnposium on Management ofHazardous Chemical Waste Sites; October 7-11, !985:Winstcm-SaLem, NC

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CHEMICAL VARIAf31LITY OF ZEOLITES AT A POTENIIALNUCLEAR HASTE REPOSITORY, YUCCA MOIJNTAIN,NEVADA

D. E. Broxton

ABSTRACT

The compositions of clinoptilollte: and their host tuffs have been

examined by electron microprobe and x-ray fluorescence, respectively,

to determine their variability at a potential nuclear waste reposi-

tory, Yucca Mountain, Nevada. Because of their scrptive properties,

these zeolites could provide important geologic barriers to radionu-

clide migration. Variations in clinoptilolite composition can strong-

ly affect the mineral’s thermal and ion-exchange properties, thus

influencing its behavior in the repository environment.

Clinoptilolites and heulandites closest to the proposed repository

have calcium-rich compositions (60-90 mol.% Cd) and silica-to-aluminum

ratios that concentrate between 4.0 and 4.6. In contrast, clinopti lo-

lites and their host tuffs deeper in the volcanic sequence have highly

variable compositions that vary vertically and laterally. ikeper-

occur’ring clinoptilolltes in the eastern part of Yucca Mountain are

characterized by calcic-potassic compositions and tend to become more

calclum-rich with depth. Clinoptilolltes at equivalent stratigraphic

levels on the western side of Yucca Mountain trave sodic-potassic

compositions and tend to become more sodium-rich With depth, Oespite

their differences i~ exchangeable cation com~ositlorrs these two

deeper-occurring compositional suites have simil~r silica-to-aluminum

ratios, concentrating between 4.4 and S.0.

The chemical variability of cl inoptilolites and their host tuffs

ut Yucca Mountain suggest that their physical and chemical properties

will also vary. Compositional ly-dependant clinoptilolite properties

important for repository performance assessment include expansion/

contraction behavior, hydration/dehydration behavior, and ion-exchange

properties. Used in conjunction with experimental results, the data

presented here can be used to model tne behavior of these clinopti lo-

lite properties in the repository environment.

IN-fR~DUCTI()[{

Yucca Mountain is located along tne southwest border of the Nevada

Test Site, 28 km east of i3eatty, Nevada (F

tuffs at Yucca Mountain are being studied

Energy and its subcontractors to determine

g. 1), Ash-flow and bedded

by the U.S. Department of

their suitability to host a

potential underground high-level nljc~ear waste repository. These

studies are supported by the Nev?da Nuclear daste Storage Investiga-

tions (NNWSI) Project as part of the Civilian Radioactive Waste Man-

agement Program. The NNdSl Project i; managed by the Waste Management

Project Office of the U.S. Department of Energy (DOE), Nevada Opera-

tions Office. NNWSI Project work is sponsored by the Office of

Geologic Repositories of the DOE Office of Civ~iian Radioactive Waste

Management.

A major consideration for chousing Yucca Mountain as a potel’tial

repository site is the presence of abundant zeol!tes in the thicK

Tertiary tuffs, Tne principal zeulites at Yucca Mountain are clinop

tilolite, heulandite, mordenite, and analcime. These zeolites could

provide important geologic barriers to nuclear waste migration because

of their ability to exchange their constituent cat!ons with some im-

portant r~dionucl ides without & major change in structure and because

of their ability to gain and lose water reversibly, Factors affecting

-2-

the ability of these zeo!ites to selectively remove radioactive spe-

cies from solution include: (1) cation species (size, charge, hydra-

tion), (2) temperature, (3) concentration of species In solution, and

(4) zeolite structural characteristics (Breck, 1974). Several coun-

tries including the United States, Canada, Great Britain, Fr~nce,

Bulgaria, Hungary, Japan, West Germany, ~nd the Soviet Union have

capitalized on the ion-exchange properties of clinoptilolite to remove

radionucl ides, such as CS137, SrgO, T1204, AsllO, Ca45 from

waste solutions. Studies presently under way show that Yucca Mountain

zeolitic tuffs are selective for strontium, cesium, barium, neptunium,

uranium, and plutonium (Daniels et al., 1982; U.S. Department of

Energy, 1984).

This paper examines the c}lemical variability of clinoptilolites,

the most abundant zeolite at Yucca Mountain. Experimental studies

have shown that the chemical and physical properties cf clinoptilolite

can vary significantly with composition. Data from this study can be

used in conjunction with experimental studies to predict the Dehavior

of clinoptilolites under repository conditions.

GEOLOGIC 5ETTI14GOF THE NEPOSITURY

Yucca Mountain is an east-tilted Basin and Range uplift located on

the southern flank of tne Miocene-Pliocene Timber Mountain-Qesis Val-

ley caldera complex (Byers et al., 1976; Christianson et al., 1977),

Rhyolite and quartz latite ash-flow tuffs are tne dominant lithology

and range in aggregate thickness from 1,;? to over 1,8 km, Zeolites

are best developed in nonwelded tuffs and in the nonwelcied tops and

bottoms of ash flows th~t have denseiy welded, devitrificd inter~ors.

The zeolites formed by replacement of volcanic glass during diagenesis

-3-

of ~he tuffs. Uhere altered, the zeolitic tuffs form mappable inter-

vals that can be correlated laterally throughout most of Yucca Moun-

tain.

The potential repository is sited in the unsaturated zone in the

lowr half of the Topopah Spring Aember of the paintbrush Tuff

(Fig. 2). The repository host rock is densely welded and devitrifiad

to a thermally stable assemblage of alkali feldspar and silica miner-

als. Zeolitic tuffs occur in several stratigraphic intervals between

the repository and the watertable, providing probable barriers to

radionuclide migration in the unsaturated zone. Additional :aolitic

tuffs below the watertable provida potential barriers to radionuclide

migration through the saturated zone. Individual beds of zeolite-

bearing tuffs con’mnly range in thickness from 10 to 150 m and contain

50-75% clinoptilolite in the upper part of the volcanic sequence (Bish

and Vaniman, 1985).

MATERIALS AND METtKIDS

Except for a few outcrop samples, mineral and bulk-rock analyses

were performed on core and, to a lesser txtent, cuttings collected

from drill holes shown in Fig. 1. Mineral compositions were deter-

mined on an automated Cameca electron microprobe operated at 15 kev

with a 15 to 20 nanoamp beam current. Standards consisted of a set of

natural feldspars and other minerals, Uavelengtn-d ispersive x-ray

counts were collected for 10 to 20 s or 30,000 counts. Compositions

were corrected for differential mdtrix effects using the methods of

dence and Albee (1968).

Sodium was counted first in the analytical sequence because it

tend! to migraie from the region excited by the electron beam. The

-4-

beam was rastered to a aiameter of 15 to 25 microns to minimize sodium

migration. Oespite this precaution, sodium loss remained a signifi-

cant problem for tl]eanalysis of Clinoptilollte and the reported sodi-

um concentrations may be low by 5-20Z of the amount present. MOving

the sample Deneath the electron beam decreases sodium loss, but crys-

tals large enough to F!low sample Mvement during analysis are limited.

Bulk-rock major elements were analyzed with an automated Rigaku

wavelength-dispersive x-ray fluorescence (XRF) spectrophotometer.

Samples were crushed and homogenized (10 g), dried at 900°C, and a l-g

split was fused with 9 g of lithium tetraborate flux. A library of

x-ray intensities for standard rocks was used to calculate elemental

concentrations (Valentine, 19a3). Bulk-rock sodium was determined for

a separate sample split by atomic absorption spectrophotometry

plazma emission spectrometry because of sodium loss during the

procedure for XRF samples.

RESULTS AND DISCUSSION

and/or

drying

Representative compositions for clinopti lolite-group minerals are

giken in TdDlt? ]. Triangular diagrams showin~ variations in

exchangeable-cation compositions are presented in Figs. 3, 4, and 6.

Histograms of Si/Al ratios in these minerals are presented in Fig. 5.

Uased upon composition and mode of occurrence, these zeolites can be

dlvlded into (1) an upper group of cl inoptilolites and heulandites

that have limited distribution and uniform Calclum-rich compositions

(Fig. 3), and (2) a lower group of clinoptilolites that occur in

thick, widespread zones of alteration and have highly variable compo-

sitions (Fig.4). The upper group contains volumetrically small

amounts of zenlites but IS impo?tant because of the proximity of these

-5-

zeolites to the repository. The lower group includes thick zeolitic

tuffs both above and below the watertable.

Tne upper group of calcic clinoptilolites occurs below the reposi-

tory horizon in fractures (Carlos, 1985) and in a thin (0.2-1.0 m) but

nearly continuous zone of zeolite and smectite alteration concentrated

at the top of the basal vitrophyre in the Topopah Spring Member of the

Paintbrush Tuff (Levy, 1984). Oespite their scattered distribution in

local zones of alteration, the minerals in this group are invariably

ralcium-rich (Fig. 3) and have silica-to-alumina rdt!os ranging be-

tween 4.0 and 5,0 (Fig. 5). Magnesium contents of these zeolites are

relatively high, ranging from 0.6 to 1.5% MgO by weight. Some of

tnese zeolites have a thermal stability characteristic of heulandite

(i%mpton, 1960; Levy, 19b4), while others have a thermal stability in-

termediate bet~een heulandite and clinoptilolite (Group 2 of Boles,

1972).

The lower group of clinoptilolites occurs in nonwelded tuffs in

which diagenetic alteration has completely replaced original volcanic

glass with zeolites. Tnese zeolite-rich tuffs occur at well-defined

stratigraphic intervals including: (1) the interval extending from

the base of the Topopah Spring Member, through the tuff of Calico

Hills, ~nd into the top of the Prow Pass Member, (2) the interval at

the b~se of the Prow Pass Member and top of the Bullfrog Member, and

(3) the Interval at the base of the Bullfrog Member and top of the

Tram Member (F!g, 2). Clinoptilolite compositions in this lower group

vary systematically both vertically and laterally (Fig. 4). On the

e~stern side of Yucca Mountain clinoptilolite compositions are calcic-

potassic and show a strong calcium enrichment trend with depth. In

contrast, clinoptilolite~ on the western side of Yucca Mountain are

-6-

sodic-pottissic and tend to become more sodium rich with depth. A

transition zone which separates the two suites has compositions simi-

lar to both suites. Silica-to-aluminum ratios are similar for both

compositional suites (Fig. 5) concentrating between 4.4 and 5.0. How-

ever, the silica-to-alumina ratios in the eastern clinoptilolite suite

are Dimodal with a small population of samples having ratios between

2.8 and 3.6. This smaller population of samples with low silica-to-

alumina ratios is associated with the most calcic clinoptilolites in

the deepest parts of the eastern suite.

Radionucl ide-transport models generally distinguish between trans-

port processes in the unsaturated and saturated zones. Figure 6 shows

only those clinoptilolite compositions (lower group) that are likely

to be encountered below the repository block in the unsaturated zone.

On the western side of th}erepository unsaturated-zone clinoptilolites

are potassic-sodic containing between 40 and 70 mol.% potassium as

exchangeable cations. The eastern side of the repository block coin-

cides with the transition zone for all clinoptilolites shown in Fig. 4

and has variaDle exchangeable cation composition. Part of the clinop-

tilolites illthe eastern part of the repository ~lock nave potassic-

sodic compositions similar to those to the west. However, others are

calcic-putassic, containing only 15-45 mol.% potassium.

Representative bulk-rock compositions for zeolitic tuffs from

Yucca Mountain are given in Table 11, For comparison, tuff composi-

tions from tt,e eastern part of Yucca Mountain are paired with tuff

compositions from the west. A triangular plot of alkalis and alkaline

earths shows that bulk-rock compositions vary from east to west in

manner similar to clinoptilolite compositions (Fig. 7). Zeolitic

tuffs from eastern Yucca Mountain are relatively calcium-rich and

-7-

deviate more from unaltered tuff compositions than tuffs to the west.

Groundwater c~positions in the saturated zone also vary ?aterally in

manner similar to clinoptilolite and bulk-rock compositions (Benson et

al., 1983; Ogard and I(errisk, 1984). These groundwaters become more

calcic and less sodic eastward. The more calcic groundwaters may be

partially derived from Paleozoic carbonate aquifers underlying the

volcanic rocks, or the groundwater may become more calcic after ion

exchange with calcium-rich zeolitic tuffs in the eastern part of Yucca

!buntain.

The physical and chemical pro~}erties of clinoptilolites and their

host tuffs at Yucca Mountain will probably vary with composition. For

example, experimental studies have shown that thermal and ion-exchange

properties of clinoptilolite, both of which are of particular interest

for repository performance assessment, are StrOtIgly influenced by com-

positional differences. Variations in physical and chemical propcr-

ti6S Of ClinOptllOliteS and ClinOptl lOlite-!)earing tIJffS IIIdy affect

their behavior in the repository setting.

The ~hermal properties of clinoptilolite are strongly affected by

exchangeable-cation compositions (Bish, 1984 and 1985).

Compositional ly-dependant thermal properties in clinoptilolite

include: (1) contraction and expansion behavior, (2) dehydration and

dehydration properties, and (3) mineral stability. Tnest? therlndl

properties are important because during the thermal pulse induced by

radioactive-waste decay clinoptllolites wI1l be heated to varying

degrees depending upon their proximity to the repository. Modelling

of the thermal pulse is not yet completed, but heating above ambient

temperatures will probably affect (1) clinoptilolite In fractures near

the repository, (2) cllnoPtilolite and hculandite associated with

-8-

alteration at the top of the Topopah Spring basal vitrophyre, and

(3) clinopti lolite-rich ltiffsat the base of the Topopah Spring Member

and in the tuff of Calico Hills.

In a changing thermal environment, unit-cell volumes of clinop-

tilolltes expand and contract in manner governed by the size, amount,

and charge of the exchangeable cations (bish, 1984). Significant

volume changes in zeolites could affect fluid flow paths by opening

fractures sealed by zeolites and by increasing permeabilities or open-

ing new fractures in tuffs containing large amounts of zeolites.

Sodium Clinoptilolites decrease in volume by about 8% when heated from

25°C to 300”C in unsaturated conditions (Fig. 8a). Calcic and potas-

sic clinoptilolites are reduced in volume 3.6% and 1.6%, respectively,

under the same conditions. Although Yucca Mountain cl”lfloptilolites

have mixed rather tnan pure end-member compositions, their contraction

and expansion behavior snould be governed by the dominant cations in

exchangeable sites. Tne clinoptilolites closest to the repository, in

fractures and at the top of the Topopah Spring basal vitrophyre, ars

calcium-rich and contain only subordinate sodium and potassium.

During the thermal pulse, these calcium-rich clinoptilolites will

probably change volume by less than 4g. The potassic-sodic and

calcic-potassic clinoptilolites in unsaturated zeolite-rich tuffs at

the base of the Topopah Spring Member and in the tuff of Calico Hills

(Fig. 6) wi 11 probably undergo considerably less volume change because

of their potassium-rich compositions and because of tneir greater

distance from the repository.

The dehydration properties of clinoptilolites also are strongly

affected by the nature of their exchangeable cations. Dehydration

effects should be greatest in Cl inoptilolites near the repository

-Y-

during the heating and cooling cycle associated

pulse. Bish (1985) demonstrated that water loss in

rapid between 50°C and 130°C and slower a: higher

with the thermal

clinoptilolites is

temperatures (Fig.

8b). Calcic clinoptilolites give up about 27% of their original water

upon heating to 100°t, whereas sodic and potassic clinoPtilolit= lose

29A and 35%, respectively.

may be a significant source

environment if temperatures

Partially-dehydrated zeolites

These data suggest that clinoptilolites

cf water in the repository near-field

approach 100°C (Bish, 1985). These

could also act as significant sinks for

water durinq the cooling portion of the thermal pulse.

Ion exchange capacities in zeolites are largely controlled by tne

silica-to-aluminum ratios of their structural framework .(Sherry, 1969;

Breck, 1974). Substitution of A13+ for Si4+ causes a charge

deficiency in the mineral framework that requires a greater number of

exchangeable cations to maintain electrical Dalance. Therzfore,

zeolites with low silica-to-alumina ratios nave the high ion-excF1ange

capacities. For example, heulandite witn a silica-to-alumina ratio of

3.5 has a theoretical ion-exchange capacity 15% ~reater than clinop-

tilolite with a silica-to-alumina ratio of 5.0 (Mumpton,

Table 1). Yucca Mountain cl inoptilolites and heulandites have

19!31;

vari-

able silica-to-alumina ratios ranging from 2.3 to 6.0 (Fig. 5). Tne

calcic clinoptilolites and heulandites in fractures near the reposi-

tory and in the thin zone of zeolites at the top of tne Topopah Spring

vitrophyre tend to have slightly lower silica-to-alumina ratios thatl

cl inoptilolites deeper in the volcanic pile and, therefore, should

halve slightly higher iOn-exCllange CapaCit~eS. The deeper clinopti lo-

lites have similar silica-to-aluminum ratios despite their large

variations in exchangeable cation compositions (Fig. 5) and probab!y

-1o-

have similar ion-exchange capacities. The calcic clinoptilolites or

heulandites in the deepest clinoptilolite-bearing rocks in the eastern

part of Yucca Mountain are unusual in that they have very low silica-

te-alumina ratios (2.8 to 3.6) compared to other clinoptilolites found

at similar depths. These unusual zeolites should have relatively high

ion-exchange capacities but would only be effective in sorbing radio-

n~cl ides being transported deep within the sarurated zone on the east-

ern side of Yucca Wuntain.

The ion-exchange selectivity of zeolites for radionuclides can be

strongly affected by cations already in the exchangeable cation posi-

tions (Breck, 1974). Ames (1060) determined that the cation selectiv-

ity for clinoptiicilte is C. RbKBaSr Na Ca FeAl Mg Li. This

selectivity seq~ence is only qualitatively correct because selectivity

can varj with degree of exchange and the nature of cation speciation

in solution (il~cck, 1!]74). However. it does demonstrate that cl!nop-

tilolites in contact with groundwater solutions wili tend to selec-

tively sorb and retain radionuclides with large ionic radii. Also,

clinoptilolites already occupied by relatively large exchangeable

cations (e.g., potassium) may be less likely to exchange with radio-

nucl ides with smaller ionic radii (e.g., Sr), effectively reducing the

ion-exchange capacity of the zeolites for these elements.

In the unsaturated zone, the calcic cl~noptilolites nearest to the

repository (upper group) should be highly selective for many important

r~dionuclides including cesium, rubidium, barium, and strontium. The

selectivity of heulandite for radionuclides is less well-known, but it

and other sorptive minerals such as smectttes and manganese oxides are

conmnly associated with the cdlclc clinoptilolites and should provide

additional sorptive barriers near the repository, In the lower part

-11-

of the unsaturated zone, potasslc-sodlc and potassic-calcic clinop-

tilolites (Fig. 6) occur in thick zones containing 50-75% clinoptilo-

lite, forming major sorptive barriers between the repository and the

watertable. Between 40 and 70% of exchangeable cation sites in these

clinoptilolites are occupied by potassium in the western p~-t of the

repository. Some clinoptilolites in the eastern part of the reposi-

tory contain only 15-40% potassium as exchangeable cations. The

potdssium in these cl inoptilolites may exchange readily with cesium or

rubidium but may exchmge poorly with cat!ons of small ionic radius

such as strontium and barium. Simple exchange w+thin these clinop-

tilolites may be further complicated by cation-sieving effects in

which large cdions such as potassium may oe locked into certain

structural positions during crystallization of the mineral (Breck,

1974). Nevertheless, these clinoptilolites, particularly thos~ on the

east side of the repository, also contain significant concentra~ions

of sodium and ca?cium which should exchange more readily with a wider

variety of radionucl ides. 3atch-sorption experiments nave shown that

Yucca Mountain zeolitic tuffs are highly sorptive of cati~nic radio-

nucl ides (Janiels et al., 1982; U.S. Ikpartment of Energy, 19U4)

despite their potassium-rich clinoptilolite compositions. Ultimately,

variations in ion-exchange selectivity with clinoptilolite composition

may be relatively unimportant given the large volumes of zeolites that

gwundwaters must pass through along transport pathways, tlowgver,

this remains to be demonstrated.

in the saturated zone, the ~otassium contents of clinoptilolites

decrease systematically with depth, Calcium and sodium become pro-

gressively enriched with depth on the eastern and western sides of

Yuccd Mountain, respectively. Because of their low potassium con-

-12-

tents, these clinoptilolites should have generally similar selectivity

properties and better Ion-exchange capacities for some small-radii

radionuclides than zeolites in the unsaturated zone.

CONCLUSIONS

The compositions of Yucca 140untain clinoptilolites and their host

tuffs are highly variable. Clinoptllolltes and heulandites in frac-

tures near the repository and in a thin, altered zone at the top of

the Topopah Spring basal vitrophyre have consistent calcium-rich com-

positions, Below this level, cl inoptilolites in thick zones of dia-

genetlc alteration on the east side of Yucca Mountain have calcic-

potassic compositions and become more calcium rich with depth.

Clinoptllol~tes in stratigraphically equivalent tuffs to the west have

sodic-potasslc compositions and become more sodic with depth.

Clinoptilolite properties important for repository performance

ass~ssment include thermal expansion/contraction behavior, hydration/

dehydration behavior, and ion-exchange properties. These properties

can be significantly affected by clinoptilollte compositions. Tne

compositional variations for clinoptllolites found by this study sug-

gest that the properties will vary vertically and laterally at Yucca

thuntain. Used in conjunction with experimental data, the cllnoptllo-

lite compositions presented here can be used to model the behavior of

clinoptllolltes in the repository environment and along transport

pdthways.

-13-

ACKNOWLEDGMENTS

I want to thank Roland Hagan and Gary Luedemann for analysis of

the bulk-rock samples by XRF. Lois Tilden typed the manuscript, and

Anthony Garcia and Sharon Mikkelson prepared the illustrations. I

also thank David 1...Bish, Kimberly W. Thomas, and David T. Vaniman for

their critical review of the manuscript.

REFERENCES

Nnes, L.L., Jr., 1960, The Cation Sieve Properties of Clinoptilolite:Amer. Mineralogist, Vol 45, 689-700.

Bence, A.E.; and Albee, A.L., 1968, Empirical Correction Factors forElectron Microanalysis ~f Silicates and Oxides: J. Geol., Vol 76,382-4d3.

Bens~n, L,V.; Robison, J.H.; Blankennagel, R.K.; and Ogard, A.E.,1983, Chemical Composition of Ground ‘Water and the Locations ofPermeable Zones in the Yucca blountain Area, Nevada: U.S. Geol, SurveyOpen-File Report, 83-854, 19P.

Bish, D.L., 1984, Effects of Exchangeable Cation Composition on theThermal Expansion/Contraction of Clinoptilolite:Minerals, Vol 32, No. 6, 444-~6Z.—.

Clay and Clay

Bish, D.L,, 1985, Effects of Composition on the Dehydration Behaviorof Clinoptilolite md Heulandite: Proceedings for the InternationalConference on the Occurrence, Properties, and Ilization of datural’

Leolites, Budapest, Hunqary,

tlish, D,L.; and Vaniman, O.T., 1985, i~ineralogic Summary of YuccaMountain, Nevada: Los Alamos National Laboratory Report, LA-10543-MS,

Breck, D.d., 1974, Zeolite Molecular Sieves: Structure, Chemistry, andUse, John Wiley and Sons, NY, 771P,

Byers, F,M., Jr,; Carr, X,J,; Orkild, P.P.; Quinl ivan, W,D,; andSargent, K.A., 1976, Volcanic Suites and Related Cauldrons of TimberMountain-Oasis Valley Caldera Complex, Southern Nevada: u.S. Geol,Survey Prof, Paper, 919, 70p,

——

Christianson, R,L.; Lipman, P,W,; Carr, W,J,; Byers, F.M., Jr.;Lrkild, P,P,; Sargent, K,A., 1977, Timber Mountain-Oasis ValleyCaldera Complex ot Southern Nevada: Geul. Sot, Americ~ Bull,, Vol !38,943-959.

Daniels, WOR, et al, 1982, Summary Report on the Geochemistry of Yuccabbuntain and Environs: Los Alamos National Laboratory Report,LA-9328-MS, 364P,

-14-

.

‘. ~vy, S.S., lq84, Petrology of Samples from Dri11 Holes USW H-3, H-4,and H-5, Yucca Mountain Nevada: Los Alamos National Laboratory Report,LA-9706-MS, 77P.

Mumpton, F.A., 1960, Clinoptilolite Redefined: Amer. Mineral., Vol 45,351-369.

14impton, F.A., 1981, Natural Zeolites, in F.A. Mumpton, Ed.,Mineralogy and Geology of Natural Zeolites: Mineral Sot. AnericaReviews ;nMineraloqy, Vol 4, 1-17.

Ogard, A.E.; and Kerrisk, J.F., 1984, Groundwater Chemistry Along F1OWPaths 8etween a Proposed Repository Site and the A&cessibleEnvironment: Los Alamos Nationdl Laboratory Report-, LA-10188-MS.

Sherry, H.S., 1969, The Ion-exchange Properties of Zeolites, inJ.A. Maririsky, Ed., Ion Exchange, A Series of Advances, Vol 2, MarcelDekker, Inc., NY, 89-133,

U.S. Department of Energy, 1984, Draft Environmental Assessment, Yuccahbuntain Site, Nevada Research and Development Area, Nevada: Office ofCivilian Radioactive Haste Management Report, 00E/RW-0012.

Valentine, G., 1983, Procedures for Analysis of Silicate Rocks andMinerals at Los Alamos National Laboratory by X-ray Fluorescence: LosAlanms National Laboratory Report, LA-9663-MS, 33p.

Zielinski, R.A,, 1983, Evaluation of Ash-flow Tuffs as Hosts forRadioactive Waste: Criteria Based on Selective Leaching of YlanganeseOxides: U.S. Geol. Survey Open-Fi le Report, 83-480, 21p.

-15-

LIST OF FIGURES

1.

2.

3.

4.

5.

6.

7.

8.

Map showing location of Yucca Mountain, Nevada.

Schematic cross-section of Yucca Mountain, Nevada, showingposition of potential repository and principal zeol itic tuffs.

Exchangeab’s-cation compositions in Calcic Clinoptilolites andheulandites (upper group), Yucca Mountain, Nevada.

Summary of exchangeable-cation compositions in the lower group ofclinoptilolltes, Yucca Mountain, Nevada.

Silica-to-alumina ratios in clinoptilolites, Yucca Mountain,Nevada.

Clinoptilolite exchangeable-cation compositions (lower group )below the repository block in the unsaturated zone, YuccaMountain, Nevada,

Exchangeable-cation compositions in bulk rocks, Yucca Mountain.

Effect of composition on clinoptilolite thermal properties.

-16-

Tale 1. REWRESEKTATIVE CLIKWTILOLITE CWOSITIONS, TUCCA MAIN. WVAOA

kuk ihit—.—

~le rn.a

Si02

Ti02

“203 ~

‘=203

w

cdl

hi)

~o

K,(J.

TOTM

Si

TI

Al

Fe”’

*

Ca

ea

M

K

K

Ra

[~*Pq

.---------------------------ibsatmated Zone---------------------------- ------------Saturated Zme------------

Prm Pass *..

10wWI Spring -., Tuff of Calico Hilh, luff of cdifC~ Hills, crater Flat Tuff,

Paintbrmh luff. East sf&of Ust Sitiof CastSi& ofTopof Basal Vitmph~e Repository Block i?e!wsitw~lodt— —— Repository Bled.——. ——

J-13-1335 LE25a#I-132- Usu 6-1-1774 UE i?5afl-2oE7

66.0

0.02

13.1

0.47

o.~1

4.49

O.in

1.07

1.05

m.7

72.6

0.02

17.0

0.39

0.84

5.39

0.922.28i-413

66.1

0.03

11.6

0.02

0.38

4.01

0.15!

0.67

1.78

84.7

74.0

0.03

i5.j

0.02

O.M4.07

0.07

1.47

2.57

68.1

0.00

12.2

0.00

0.09

Ill

0.03

2.84

4.20

80.5

CATiON PERCENT—-----—71.9

0.00

15.2

0.00

0.14

1.26

0.015.82

5.66

SilAl

64.1

o.m

12.0

O.(M3

0.71

3.78

0.05

n.47

I .54

82.7

74.3

O.al

16.4

O.(YJ

1.23

4.70

0.02

1.06

2.28

4.3 4.8 4.7 4.5

*1.X EXCHAWEA8LE CATIOHS.--.—15 27 — 44 25

23 15 45 11

62 58 11 64

PraPlss Pbr.,C-alterFlat luff,

tkst SideiifRepository 810ck

Usu 6-1-2083

67.3

O.m

11.7

0.00

0.07

0.78

0.08

3.13

3.34

IM.4

72.8

0.0014.9

0.00

0.11

0.91

0.03

6.574.61

4.9

38548

——.- __

a~le ndmr cm,sists of drill hole d@5ivatfm followed by depth of saqle in feet beneath the surface.

bTotdl irm calculated as Fe203

TAUE 1[. RE~ESC~ATIVC R4AK-R(XK C~OSITIONS FM 91 AIXNETICALLY ALTERED TuFFS, YKCA MOUNTAIN, WVAEIA

Rock Unit—. .-— ToPp.M SpricgMm,

Paintbrush Tuff .--------Tuff Of c~lico H~lls.--------Pr* Pass Mder,

----------c~ater Flat TUff--.---.-.---Ehllfrog -m,

-..--.-.-.-cr~ter Flat TUff -----------

A.Nonuelded Zeolitfcluff, East Si@ of

Repository Ellock

B.Ncmeldd Ztolit{cTuff, Uest Side ofRepositoryBlocc.—

Zeollu- and

Clay-Rich Zme●t Top of

Basal Vitroptlyre

A.naMel(M ZmlltlcTuff, East Side of

Repository Elock

tE75&#l-1667

72.1

O.oa

11.3

1.00

0.05

O.lz

2.67

1.47

3.47

0.02

7.68

99.9

B.Ncwmelded Zeol~tlcTuff. Mest Side of

Reposlt~y Block

Usu 6-1-1771

A.kmwelded ZeollticTuff, East Side of

Reposltmy 810ck

B.Ibuelded ZeolitlcTuff, Wst Side of

Reps itcwy Block

U5M G-4-1314 UW G-4-2226

66.4

0.14

13.2

1.45

0.05

0.25

2.43

2.15

3.70

0.01

Usw 6U3-19C166

67.9

0.10

12.4

1.23

0.07

0.11

0.87

3.44

3.72

0.02

10.2

Km.]

N25b/lH-2879A

67.3

o.~5

11.2

1.82

0.04

:.30

3.13

1.18

3.75

0.09

7.24

USU G-3-2577

Si02 m.?

0-1/

16.7

1 .U

71.8

0.10

11.8

1.40

O(n

0.24

1.20

2.79

3.76

0.00

5.64

%.8

72.7

0.08

14.1

I .07

0.03

0.36

1.30

5.48

4.s

0.00

66.3

0.12

12.9

Ti02

Al$3~ ~

Fe703 1.32

0.10ho

wCdo

Na70

0.09

0.90

3.51

1-m

0.27

2.34

2.43

3.61

0.02

K2i

W5CLOI

0.72

0.02

5.91 9.40 9.83

TOTAL 101.5 99.2 99.2 99.3

CATION PERCENT--——--

69.8

0.1116.31.15

0.040.392.744.3.85.070.01

Si

Ti

Al

69.6

0.10

19.5

1.07

o-m

1.33

3.73

3.65

0.91

0.02

74.7

0.06

13.7

0.78

0.04

0.19

2.%

2.95

4 59

0.02

70.7

0.08

15.2

0.97

0.05

0.17

0.97

6.54

4.94

0.02

69.5

0.19

16.0

1.42

0.03

2.00

3.46

2.36

4.94

0.08

69.8

0.10

16.1

1.05

0.07

0.42

2.64

4.%

4.85

0.02

Fe+l

m

--———-●~le rider cwsists

Zielinskl (1983).

of drill hole desfgndtion folloued by depth of sqle In feet beneath the surface. Sample analfiis USU 6-1-1771 from

blotal irm as Fe20>

Vw?H

al1-Z H I

sTATi~Iy$TE~TABLE

- -. , ,-----.-..” .. .. .. ..+m$.’..m.....

h-’

\p

‘ ‘ ● *... +,.!.!.:,:,:.....0..:,;.,,;’$@j:q~; :

5E?ULLFROG MEMBER

:1

.,....,,.....,..’>,,$’.“!”,’.,.%?,4,,,,,,,,, ,,

I& ,,.. >,,,:’:::::,y~,’ .............,~t.,!,.,.,#,,,.,..,.,!...,,..,.,.,<,..’4.,,,,,,,....Abk&....6..~~*.*:s,. t,...,.:.;,;.;,;,l<.,,4.:’:.;,,..,’..,.,’,4:<..~,...,.:.,,,,,,,,,!,,!,>...$

..’*., .~.,.+4’’..,..,..’.,’,.,.,.,,,,,,..,,.!..,,,,t.,....,~...t.,,.,.,’..,’.,.,..’~,...’.,...‘,,,,$>,.,.,,,,,,.,’..., ,.,.,..>.,‘ ,,..,,,,!,.,!,,,..!.,.,.,.$.,.,,,.,,,$..,! .,,$,.$, ,,,,....,,,,.,,....,,,,...,..,,.,.,,:.:.:.:,.,.a?,.>;,~,.,<,.m.,,,,,,~,.,!,t,.,.,,..............,.~,.’,>,,.,.,,,.,J’~AM ?vIEMOE~--J?W?WA%9X.’,,, ...%’,.,...,.,, ....,,.,.,.,.,...,.,,.,,,,...!,..,,. .,, ,, --+’.+.’.,,.,.,,’.’~,.’+’$........,+,.,,,<...,.,.,,.............,,,,.,..~,...,,.!.,.,,,..!,,..,.,,,,...,,!,.,.,,.,.:.,,.,.,.,.:,:..,...>.,i4..i4.,,,,.,’,,,...,.,.,.,.,.,~,~,.,!,.,.,,,,,..t.,.,,,,..$,$:,.;,.,!..:tyf’,.<....4...,..,... ..............$....4......,,,,..,,.,.,,,..,..,.4.‘..,,..................,,!,,,.....‘ .,., .,.,...,,,,,,,,.,,’,..,.,,........,,,>$,.......’........,’,:,:,.,,,.,.;.:,::...,......,“.+,..,..,,.,,,,,,,,..,,,,,,,,’.4,+,:,::.:4;.:,:.;

%a\ 4I0 II

‘—’——————

il,’, fWiOPOSED 13EP0SlT0HY‘*4 ~REAK~UT HORIZO~i

GALGiC CLl@PTILOLITES AND MEULANDITES AT lC?PD of yOp&AH SPFlft@8A$$ALVITffOPti’@C{lJPPE~GFiOUP)

,* 2@’4E= (?FABUNOANT GLU’JQPTILQLITEIN131AGENETICALLYSa ALT~!?E~rJ@WELDEO TUFFS (LCIWERGHOUP}

I

..●

EXCHANGEABLE-CATIONS IN Ca-CLINOPTILOLITEAND HEULANDITE (UPPER GROUP), YUCCA

MOUNTAIN, NEVADA

K

●

✼

Na Ca + Mg

,- !:..’ .

.

WESTERNALKALIC GROUP

EASTERNTRANSITIONAL CALCIC GROUP

~....... . . L&_.-d_... . . . . . \ t--- —------- .

0

c1

A

●

Cm+Mg Na Ca. Mg N8 C, + Mg

NONWELOED BASE OF TOPOPAH SPRING MBR TUFF OF CALICO HILLS, AND TOP

OF Pi-iOW PASS MBR

NONWELDED BASE OF PROW PASS MBR AND TOP OF BULLFROG MBR

NONWELDED TOP OF BULLFROG MBR, AND TRAM MBR

PRE. TRAM VOLCANIC ROCKS

NOTE, SMALL ARROWS WITHIN PLOTS INDICATE CHEMICAL rRENDS WITH INCREASINGOEPTH

SCALE

o ! mile— ——

●

301

UPPER GROUP OF CALCIC CLINOP-TILOLITES AND HEULANDITES

LOWER GROUP OF CLINOPTILOLITESON EASTERN SIDE OF YUCCA MTN.

LOWER GROUP OF CLINOPTILOLITESON WESTERN SIDE OF YUCCA MTN.

IL20 :,’...’.’

. .. . . .

, (-j :;:.}::;

, :.....,.. ,.,,, :,.., ,,.,,..,. ,: ..,!.;,,’..,..”, .,, ,, ..,.. ,,,. ..,.

4.0 5.0

701

3:0 4:0 5.0 6,CJ

SilAl

40- ,,t’.,’::”:’,,:;;’.,..:..,:.”.:,,.,,.,!,’:.‘,.,,,

30-.................,..,., :,,’.....,;.“.,:,.,,’$,,,,,,

20-,:,’,,,,,,,,:,”.,,.;,;,,:”‘:,,,,,’:.,.,,,,,

lo-,,,’,,,,.,.,‘.,,,,:.,.,,,,,.:,,,,.,,,.,,,

,,,,., ,, :,A-kL I I 1 1 ! I --r*~—ll—r—,!

r-; l

3:0 4:0 5.’0 6s0

Si/Al

. .

CLINOPTILOLITE EXCHANGEABLE-CATION COMPOSITIONS BELOWTHE REPOSITORY BLOCK IN THE UNSATURATED ZONE

K

o

WESTERN PARTREPOSITORY BLOCK

EASTERN PART OFREPOSITORY BLOCKI

%\

/0

0-0

00%

~~oQ9 Om

QoO.O 0 00 0

0 Cp 000

0

[ 1 1 I 1

Na Ca+Mg

EXCHANGEABLE-CATION COMPOSTIONS IN BULK ROCKS,YUCCA MOUNTAIN, NEVADA

K

Po&

00 ●

FIELD OF UNALTERED o dTUFF COMPOSITIONS 00 ~ ●0

Oodo

\

\

o WESTERN YUCCAMOUNTAIN

● EASTERN YUCCAMOUNTAIN

/!!1 ~s

1 1

Na Ca + Mg

!

h>CLINOPTILOLITE UNITCELL VOLUMES AS A FUNCTION OFCOMPOSITION AND TEMPERATURE

em<

1>,

Na+XCHANt3ED ‘t1DSG CLINOPTILCILITE ‘*,

h. . ..--------------------------

~

J--A~o--4c4cFROM 81SH, 1944

RT. ROOM.tEMPERATUREVAC = VACUUM

!)DEHYDRATION PROPERTIES OF CLINOPTILOLITE AS AFUNCTION OF COMPOSITION AND TEMPERATURE

UJ

duNSATURATED CONDITIONS

z96 -

Al.<1 ‘,\gg 92 . ‘. \

V.EXCHANOEO CLINOPTILOLITE

(?JLu-3

‘,, \

!5

sODIUM.EXcHANOEO” ‘ “ ‘~1= kuu+. _,: .::, ... ,.,,,

CLINOPTILOLITE ——.

$ I 1 1 1 1 I 1

200 a Soa 800

TEMPERATURE (*C)