Applications of Isotope Geochemistry to the 

Reconstruction of Yucca Mountain, Nevada, 

Paleohydrology Status of Investigations: 

June 1996

Sy Joseph F. Whelan, Richard J. Moscati, Sarah B.M. Allerton, and 

Brian D. Marshall

U.S. GEOLOGICAL SURVEY 

Open-File Report 9&-8S

Prepared in cooperation with the 

NEVADA OPERATIONS OFFICE, 

U.S. DEPARTMENT OF ENERGY, under 

Interagency Agreement DE-AI08-97NV12033

Denver, Colorado 

1998
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Thomas J. Casadevall, Acting Director

The use of firm, trade, and brand names in this report is for identification purposes only and does 

not constitute endorsement by the U.S. Geological Survey.

For additional information write to:

District Chief 

U.S. Geological Survey 

Box 25046, Mail Stop 415 

Denver Federal Center 

Denver, CO 80225-0046

Copies of this report can be purchased 

from:

U.S. Geological Survey 

Information Services 

Box 25286 

Federal Center 

Denver, CO 80225
CONTENTS

Abstract.........................................................................................................._ 1

mtroduction................................................................................................_^ 1

Sample Distribution.............................................................................................................................................................^ 3

Sampling and analytical methods............................................................................................................................ 3

Paragenesis of Exploratory Studies Facility Occurrences..................................................................................................... 6

Most recent event: Calcite or opal? - Precipitation or dissolution?........................................................................ 8

Dissolution events within the unsaturated zone?..................................................................................................... 8

Isotopic Data.......................................................................................................................................................................... 13

Implications of new Exploratory Studies Facility data to previous interpretations................................................. 13

Carbon-13-enriched calcite from the Exploratory Studies Facility......................................................................... 13

Silica-phase oxygen isotope studies........................................................................................................................ 15

Radiocarbon geochronologic studies....................................................................................................................... 18

Conclusions............................................................................................................................................................................ 21

References Cited.................................................................................................................................................................... 21

Appendixes............................................................................................................................................................................ 23

FIGURES

1. Maps showing location of the Yucca Mountain region, Nevada, the potential repository site, 

the Bullfrog Mine, sampled boreholes, Trench 14, and the Exploratory Studies Facility..................................................... 4

2. Map showing location of the Exploratory Studies Facility, topographic features, prominent faults, 

and the locations of sampled secondary mineralization occurrences near Yucca Mountain, Nevada................................... 5

3. Schematic illustrations of the typical paragenetic sequences found (a) in lithophysal cavities and (b) on

fracture surfaces..................................................................................................................................................................... 7

4a.-4h. Photomicrographs showing: 

4a. Late botryoidal opal with rhombic overgrowths of calcite that are, in turn, locally pimpled with

tiny opaline spheres ........................................................................................................................_^ 9

4b. Late botryoidal opal grown on calcite and partially engulfed by a later stage of calcite............................................ 9

4c. Opal with overgrowths of a later opaline stage followed by calcite overgrowth coated with

botryoidal opal that is, in turn, partially buried by late calcite.............................................................................................. 10

4d. Bladed calcite crystals with scepter-like terminations................................................................................................ 10

4e. Pyramidal to spire-like calcite forms from the basal zone of lithophysal secondary calcite

mineralization........................................................................................................................................................................ 11

4f. Basal dissolution zone, with calcite microspeleothems or meniscus cements............................................................ 11

4g. Unetched surface of calcite crystal............................................................................................................................. 12

4h. Pitted surface of apparently etched calcite crystal face.............................................................................................. 12

5 7. Graphs showing:

5. Distribution of unsaturated-zone delta carbon-13 and delta oxygen-18 values of calcite 

plotted against depth.............................................................................................................................................................. 14

6. Distribution of delta carbon-13 and delta oxygen-18 values of Exploratory Studies Facility 

calcite samples plotted against distance from the portal........................................................................................................ 14

7. Preliminary radiogenic strontium isotopic compositions plotted against the stable carbon 

and oxygen isotopic compositions, and correlation of delta carbon-13 and delta oxygen-18 values 

of Exploratory Studies Facility calcite................................................................................................................................... 16

8-9. Histograms showing:

8. Yucca Mountainun unsaturated zone secondary silica delta oxygen-18 values.......................................................... 17

9. Distribution of carbon-14 ages from Exploratory Studies Facility calcite occurrences............................................. 20

CONTENTS III
TABLE

1. Major stratigraphic units in the Late Cenozoic volcanic rock sequence of the Yucca Mountian area, Nevada...... 3

Multiply By To obtain

centimeter (cm) 0.3937 inch

meter (m) 3.2808 foot

kilometer (km) 0.6214 mile

Degree Celsius (°C) may be converted to degree Fahrenheit (°F) by using 

the following equation:

°F = 9/5 (°C) + 32

Sea level: In this report "sea level" refers to the National Geodetic Vertical 

Datum of 1929 (NGVD of 1929)-a geodetic datum derived from a general 

adjustment of the first-order level nets of both the United States and Canada, 

formerly called Sea Level Datum of 1929.

The following terms also are used in this report:

Ma millions of years old

Ka thousands of years old

Ky thousands of years

Pz Paleozoic

ESF Exploratory Studies Facility

SMOW Standard Mean Ocean Water

PDB Pee Dee Belemnite

°C/km degrees Celsius per kilometer

AMS Accelerator Mass Spectrometer

pmc percent modern carbon

N normal

IV CONTENTS
Applications of Isotope Geochemistry to the 

Reconstruction of Yucca Mountain, Nevada, 

Paleohydrology Status of Investigations: 

June 1996

By Joseph R Whelan, Richard J. Moscati, Sarah B.M. Allerton, and Brian D. Marshall

Abstract

Tunneling of the Exploratory Studies 

Facility has offered the opportunity to sample and 

examine occurrences of secondary mineralization 

found in the unsaturated-zone tuffs of Yucca 

Mountain, Nevada. Petrographic and paragenetic 

analyses, calcite and silica-phase stable isotopic 

analyses, and preliminary strontium tracer isotope 

and radiocarbon age analyses of these samples 

indicate that (1) an early stage of secondary 

mineralization consisting largely of chalcedony 

and quartz, but possibly with or slightly preceded 

by calcite, probably formed at warmer than 

ambient temperatures; (2) later secondary mineralization consisting of calcite and opal appears 

completely consistent with formation from percolation of surface infiltration whose solute load and 

carbon isotopic compositions reflect passage 

through the overlying soils; (3) based on textural 

studies, all unsaturated-zone secondary mineral 

occurrences exposed within the Exploratory 

Studies Facility tunnel, with the exception of the 

vapor-phase assemblages that formed at high 

temperatures during cooling of the tuffs, probably 

formed in unsaturated settings; and (4) calcite 

radiocarbon ages, based on preliminary results, 

have not been compromised by post-depositional 

exchange with carbon-bearing water and gases in 

the unsaturated zone.

INTRODUCTION

Yucca Mountain, Nevada, is presently under 

evaluation as a potential national subsurface repository 

for high-level radioactive wastes. Current designs for 

the potential repository would emplace wastes within 

the sequence of welded and nonwelded tuffs in the 

thick unsaturated zone of the mountain, several 

hundred meters below ground surface but still well 

above the modem water table. Siting within the unsaturated zone is advantageous in that it isolates the 

wastes from regional ground water; unfortunately, it 

also introduces climate-driven infiltration and percolation through the unsaturated zone as site-evaluation 

variables. Although present climate is arid, past 

climates have ranged to much wetter (R.M. Forester, 

U.S. Geological Survey, oral commun., 1997), and 

future climates are likely to be wetter, as well. The 

effects of future climatic changes on site performance 

are critical issues for site suitability assessment.

Efforts to reconstruct the hydrologic response of 

Yucca Mountain to past climatic variations, especially 

within the unsalurated zone, have focused on textural 

and geochemical study of secondary minerals deposited from past percolation fluxes and ground water. 

This report discusses stable carbon and oxygen 

isotopic data and mineral parageneses determined 

from secondary calcite and silica mineralization and 

describes reconnaissance radiogenic strontium (Sr) 

isotopic and carbon-14 ( 14C) age data and their 

applicability to paleohydrologic and paleoclimatic 

studies. Most of the new data reported here were 

collected from samples of secondary mineral occurrences accessed during construction of the Exploratory 

Studies Facility (ESF) tunnel. Construction of the 

tunnel was a fundamental component of site-characterization studies of Yucca Mountain.

Abstract
Evolution of understanding of the origins of 

secondary minerals within the Yucca Mountain tuffs is 

reflected in several papers (Whelan and Stuckless, 

1990 and 1992; Whelan and others, 1994; and J.F. 

Whelan and R.J. Moscati, U.S. Geological Survey, 

written commun., 1997). The latter report summarized 

the evolution of studies of the secondary calcite and 

silica minerals within Yucca Mountain and updated 

understanding of the processes responsible for deposition of these minerals. It stated that:

"investigation of the secondary minerals within 

the mountain, spurred by the study of the surficial 

deposits, revealed that the calcite and opal commonly 

coating fractures and lining open cavities in the unsaturated zone were deposited during downward percolation of meteoric waters ... These fluids reflected the 

oxygen isotopic signature of precipitation ... and had 

acquired distinctive carbon and strontium isotopic 

signatures from the thin overlying soils during infiltration that were recorded by the secondary calcite and 

opal deposited by the fluids as they percolated through 

the tuffs." (Emphasis added.)

A stage of the secondary calcite, paragenetically 

early but volumetrically minor, is characterized by 

uncommonly carbon-13 ( 13C)-enriched isolopic 

compositions and by delta oxygen-18 (518O) values 

that decrease more rapidly with depth than succeeding 

calcite stages. That steeper 618O decrease may record 

a steeper geothermal gradient during formation of the 

paragenetically early calcite. Data collected from ESF 

occurrences during 1996 indicate that, at least locally, 

this paragenetically early calcite is volumetrically 

more abundant than drill hole studies had indicated.

Other studies of secondary mineralization in the 

ESF estimated Pleistocene percolation fluxes through 

the unsaturated zone by measuring secondary calcite 

and opal volumes and inferring rates of secondary 

calcite and opal formation from thorium-230/uranium 

(230Th/U) and 14C age determinations. If that early 

calcite stage were formed much earlier and under 

significantly different hydrologic conditions, as is 

suggested by its atypical 613C systematics, then its 

inclusion in the mineral record used to estimate past 

percolation fluxes might result in erroneous flux estimates.

This report describes efforts to map the parageneses of secondary mineral occurrences (appendix 1) 

within the ESF, discusses the stable carbon and 

oxygen isotopic compositions of calcite, the stable 

oxygen isotopic compositions of multiple stages of 

silica (chalcedony, quartz, and opal) deposition and

some provisional 87Sr/86Sr ratios of calcite, and evaluates the apparent timing of latest calcite formation in 

several occurrences from the ESF based on provisional 

14C age determinations. The purpose of this investigation is to use this isotopic characterization of 

secondary minerals to trace isotopic variations in the 

water that percolated through the sequence of volcanic 

rocks at Yucca Mountain and to reconstruct the hydrologic response of Yucca Mountain to past climatic 

variations. This study focuses mainly on samples 

obtained in excavations of the ESF and expands interpretations based on earlier studies. Sampling and 

examination of secondary mineralization within the 

ESF has increased our understanding of the distribution of secondary minerals and demonstrated a greater 

extent and thickness of secondary mineral occurrences, the very delicate nature of some of the calcite 

crystal forms, and a more widespread distribution of 

opal than had been observed from studies of drill-core 

occurrences.

Yucca Mountain is located near the western 

boundary of the Nevada Test Site in southwestern 

Nevada about 140 km northwest of Las Vegas and lies 

in the north-central part of the Basin and Range physiographic province. It consists of a series of rugged 

north-trending fault-block ridges composed of 

volcanic rocks with a general eastward tilt of 5° to 10° 

(Scott and Bonk, 1984). A thick section of Tertiary 

volcanic rocks (table 1) overlies Paleozoic sedimentary strata in the Yucca Mountain region (Byers and 

others, 1976) with units of the 12.8 to 12.7 Ma Paintbrush Group (Sawyer and others, 1994) forming most 

exposures (Christiansen and Lipman, 1965; Scott and 

Bonk, 1984). Two voluminous densely welded ashflow tuffs of the Paintbrush Group underlie Yucca 

Mountain (the Tiva Canyon and Topopah Spring 

Tuffs), separated by a much thinner interval of mostly 

nonwelded pyroclastic rocks (Buesch and others, 

1996); the tuffaceous rocks are greater than 3,000 m 

thick in some places (Snyder and Carr, 1984). Welding 

and consolidation of Uie thick tuffaceous units 

produced zones of abundant lithophysal cavities, 

where lithification around gas bubbles formed open 

cavities in the rock. High-angle faults locally exhibit 

displacements of several hundred meters (Carr, 1984; 

Scott and Bonk, 1984); numerous studies (summarized in Volume 1, Part A, of the Site Characterization 

Plan for Yucca Mountain; U.S. Department of Energy, 

1988, section 1.3) have shown that the tectonic setting 

of Yucca Mountain is complex, with the area situated 

at the intersection of contrasting structural zones.

Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
This document was originally a milestone report 

to the Department of Energy Yucca Mountain Project, 

submitted in June of 1996. This version has benefited 

from several thorough editorial reviews, but the 

content herein is consistent with the original 

1996 report.

SAMPLE DISTRIBUTION

Since tunneling began in 1995,145 occurrences 

of secondary mineralization within the ESF have been 

collected for the USGS, 88 by the Bureau of Reclamation during fiscal year (FY) 1995 as part of the

Table 1. Major stratigraphic units in the Late Cenozoic 

volcanic rock sequence of the Yucca Mountain area. Ages 

are given in millions of years (Ma). Modified from Sawyer 

and others 91994) and Buesch and others (1996).

Unit Age (Ma)1

Timber Mountain Group

Ammonia Tanks Tuff

Rainier Mesa Tuff

Post-Tiva Canyon pre-Rainier Mesa rhyolites2 

Paintbrush Group

Tiva Canyon Tuff 12.7

Yucca Mountain Tuff

Pah Canyon Tuff

Topopah Spring Tuff 12.8 

Calico Hills Formation 12.9 

Crater Flat Group

Prow Pass Tuff

Bullfrog Tuff 13.25

Tram Tuff 

Lithic Ridge Tuff 14.0

11.45

11.6

12.5

1 Ages have not been determined for all units.

2This informal grouping represents multiple rhyolites of small 

areal extent erupted from multiple sources at the margins of calderas 

such as the Timber Mountain caldera complex north of Yucca Mountain. Correlations are incompletely understood for all such identified 

rhyolites and calderas.

Consolidated Sampling Program and 57 during FY 

1996 by the USGS (Yucca Mountain Project) Isotope 

Hydrology Team. The location of the ESF and the 

locations of newly sampled boreholes (USW SD-7, 

USW SD-12, USW VH-1, USW VH-2, USW 

UZ-14, and UE-25 a #5) are shown on figure 1; the

approximate locations of those ESF occurrences that 

have been sampled are shown on figure 2.

Sampling and analytical methods

Secondary mineral occurrences were examined 

from drill cores UE-25 a #7, USW UZ-14, USW 

SD-7, USW SD-12, and USW VH-2 and from underground exposures in the ESF. These samples are 

tabulated in appendix 2 along with each sample's 

Hydrogenic Deposits (HD) sample tracking number. 

Individual occurrences from drill core are designated 

by borehole name and depth below surface. Position 

within the ESF is defined by station number (a station 

is located every 100 m beginning at the North Portal) 

and incremental distance from the previous station. 

For instance, an occurrence collected 1456.7 meters 

from the North Portal would be designated as 

station 14+56.7. Occurrences within the ESF are listed 

in appendix 2 by their distance from the North Portal.

Sample textures, morphology, and mineralogy 

were described from hand specimens and pctrographic 

thin sections. Hand specimens were examined under a 

stereomicroscope at magnifications up to 75x at 

visible and short-wave ultraviolet (UV) wavelengths. 

Minerals were identified by their habit, reaction to 

hydrochloric acid, hardness, and UV fluorescence. 

Thick (100- to 200-micrometers) polished sections 

were prepared from most samples for examination in 

plane-polarized light and observation of cathodoluminescence (CL) behavior. Scanning-electron microscopic (SEM) observations were made on gold-coated 

sections and specimen fragments on a Cambridge 

StereoScan 250 Mkll instrument at an accelerating 

voltage of 20 kV and a working distance of 

20 millimeters.

Calcite was sampled from hand specimens for 

stable isotope analysis by milling with dental burs. 

Sampling of individual mineralization stages, when 

such were distinct, was accomplished by milling under 

low-power magnification. Layers as thin as 

0.1 millimeter could be milled from calcite crystal 

faces and from channels as narrow as 0.5 millimeter 

within mineral sequences.

Silica minerals were sampled by chipping or 

gouging from hand specimens or by milling with a 

diamond-impregnated dental bit. Impurities were 

removed by hand-picking, and the separates were then 

digested at room temperature in 0.1 N HC1 to remove 

possible carbonate impurities.

SAMPLE DISTRIBUTION
116"

TIMBER MOUNTAIN 

CALDERA COMPLEX

X ^<v /

led area denotes exposed bedrock.

10 20 KILOMETERS 

II ii

}T. MILES

^\ &**

Potential Repertory 

f Site *^SBS>

^* f- . V«^

UatfsDJg' "^iS^^fer A^°"°ti»lR<*«ta' usr: s^J g - ^s-y&x ** it Sil? ^^

-; JI-* W B x "C:^<P?E«j>k»raiory Studies FaciEjy * 5"k

A- I /?^-,>ci* *t ^;;

^ i %gajg- r, -L^;-m»Qt jjT' Jj j^ a^M>fe ^fi **[&SS'* ""*

A 

 ^Sif|fe^p^"fe 

A , , «^"J5i^ «*?><»-, >Lcl* V£l *> l-¥--^*«fc JK~*.. 

4? ^^.,-« -VTWfc

Borehole location 

and name

Alluvium and colluvium 

Paintbrush Group 

Timber Mountain Group

Figure 1. Location of the Yucca Mountain region, Nevada, the potential repository site, the Bullfrog Mine, sampled 

boreholes, Trench 14, and the Exploratory Studies Facility.

4 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
N: 770000

N:765000

N: 760000

N: 755000

o 

o

ITi

tii Easting, in feet

o 

o 

o

iu

5000 ft. Base map grid based on Nevada State Coordinate System.

Contour Interval = 100 ft.

Tunnel distance indicated in meters x 100. measured from portal.

o

o 

o

o

- Fracture fill sample

- Lithophysal cavity sample

Exploratory Studies Facility

500 meters

I

Figure 2. Location of the Exploratory Studies Facility, topographic features, prominent faults, and the locations 

of sampled secondary mineralization occurrences, near Yucca Mountain, Nevada.

SAMPLE DISTRIBUTION
Procedures based on conventional techniques 

first described by McCrea (1950) were used to extract 

CO2 from carbonates. Oxygen was extracted from the 

silica separates by stepwise fluorination for more 

highly hydrated opaline separates according to procedures described by Haimson and Knauth (1983), or by 

reaction with BrF5 for less-hydrated separates 

according to procedures developed by Clayton and 

Mayeda (1963), and converted to CO2 by reaction 

with hot graphite. Stable carbon and oxygen isotopic 

compositions of the extracted CO2 were determined 

on Finnigan MAT 251 or 252 mass spectrometers. 

Stable isotope compositions are reported as the per 

mil deviations of the samples from the international 

standards PDB (for carbon) and SMOW (for oxygen). 

Delta (8) deviations are defined as

5 = ((Rsample ' Rstandard^slandard)) X 1000 (1)

where R is the ratio of the heavier isotope 

(13C or I8O) to the lighter isotope (I2C or 16O, respectively) in the sample or standard CO2 . One-sigma 

reproducibility of the 813C and 818O values is 

routinely less than or equal to 0.1 and 0.15 per mil, 

respectively.

Ninety-eight aliquots of laboratory standard 

NBS-19 (or its in-house equivalent, TS-1) analyzed 

during the course of data collection had average 813C 

and 5I8O values of 1.91±0.02 per mil and 

28.32 ± 0.15 per mil. respectively, compared to 

accepted values of 1.92 and 28.65 per mil. All 

<5 I8O values reported in appendix 2 have been adjusted 

by +0.30 per mil to correct the measured deviation 

from the accepted value for NBS-19.

Strontium isotopic compositions (87Sr/86Sr) 

were measured on samples of calcite from the ESF. 

Small (about 10-mg) subsamples of calcite were 

milled or chipped from natural or sawn surfaces. The 

subsamples were leached with hydrochloric acid to 

remove calcite from opal and wall rock, and any residues were dried and weighed to determine the actual 

amounts of calcite that was dissolved. Strontium was 

separated using standard ion-exchange methods, and 

isotopic compositions were determined on an automated multi-collector solid-source mass spectrometer. 

The reported 87Sr/86Sr ratios are within about 

± 0.005 per cent of the actual value.

PARAGENESIS OF EXPLORATORY 

STUDIES FACILITY OCCURRENCES

Paragenesis is defined as the order of mineral 

formation or a characteristic association or occurrence 

of minerals (Gary and others, 1974). A paragenesis 

may include a wide variety of minerals or only one or 

two; it may be simple, or it may be complex with 

numerous resolvable depositional events. Within a 

mineralization sequence, many textural relationships 

may be clear, some may seem clear but are not, and 

some will be ambiguous. Paragenetic descriptions 

always contain an element of subjectivity imparted by 

formulating a genetic framework from empirical 

observations they are, as such, interpretative. 

Appendix 1 lists preliminary descriptions of paragenetic sequences of about 70 samples collected in the 

ESF during FY 1996 by the USGS. That appendix also 

contains a brief glossary of some of the terminology 

used in the following discussion. The occurrences 

described in appendix 1 represent only about half of 

the occurrences collected to date (February 1996) 

from the ESF.

Within the brittle and fractured welded tuffs 

exposed in the ESF, post-vapor-phase secondary 

minerals are generally restricted to the footwalls of 

fractures or the floors of lithophysae. This relation 

indicates that the fluids that precipitated secondary 

minerals did not fill these open spaces; that is, those 

tuffs were not within the saturated zone at the time of 

secondary mineralization. Mineralizing fluids apparently filled only the smallest-aperture fractures and 

formed, at most, only shallow pools on the floors of 

lithophysae.

Lithophysal-cavity parageneses differ from 

those in steeply dipping fractures in that the cavities 

have thicker accumulations of secondary minerals, 

they contain larger free-growing crystals of calcite that 

commonly display unusual bladed habits, and they 

contain much more opal (figs. 3a and b). Lithophysalcavity paragenetic sequences begin with vapor-phase 

tridymite (± hematite), deposited while the tufs 

were still hot. Where lithophysae are connected to 

percolation-flux fracture pathways, those lithophysae 

may host later calcite and silica minerals.

The earliest secondary mineralization found in 

such lithophysae consists of massive silica (undiffcrentiated quartz and chalcedony, possibly with minor 

opal) with, locally, minor calcite that appears to 

underlie the massive silica. Calcite, with irregularly

Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
a.

early vapor-phase minerals 

quartz of massive silica stage

chalcedony/opal of massive 

silica stage

late bubbly or laminated opal

blocky calcite stage

bladed calcite and sceptor 

overgrowths

Figure 3. Schematic illustrations of the typical paragenetic sequences found (a) in lithophysal cavities and (b) 

on fracture surfaces. Descriptive terminology is defined in the glossary included in Appendix 1.

PARAGENESIS OF EXPLORATORY STUDIES FACILITY OCCURRENCES 7
distributed opal (both in time and space), generally 

completes the paragcnesis. Defined paragenelic stages 

are, therefore, early massive silica (± calcile) and later 

main-stage calcite (± opal). Main-stage calcite and 

opal, as defined here, are pertinent to model estimations of past flux.

Secondary mineral habits vary somewhat within 

the main stage of lilhophysae. Early main-stage calcite 

within the lithophysae is commonly blocky or tabular. 

Later main-stage calcite, however, commonly occurs 

as unusual bladed crystals, typically thin at the base 

and flaring outward at the top, a habit that results in a 

scepter-like cross section (figure 4d). Opal may be 

found throughout the main stage although it is typically more common in the later part. Opal most 

commonly occurs as scattered spheres or botryoidal to 

colloform masses (figures 4a-c) but locally forms thin 

laminated coatings. Thin-section observations indicate 

that opal deposition is commonly preceded or accompanied by dissolution of calcite substrates.

Secondary mineral parageneses in steeply 

dipping fractures differ in habit and mineral abundance from those in lithophysae. Steeply dipping fractures generally contain only blocky to tabular calcite, 

locally on patches of early-stage massive silica. The 

sceptered calcite blades and small-bubbled or laminated opal found in lilhophysal cavities are rare in 

steeply-dipping fractures. In the more horizontal fractures, however, the paragenetic sequences are similar 

to those found flooring lithophysae. This structural 

control indicates that spatial geometries that retard or 

halt flow, such as lithophysae or flat-lying fractures, 

promote formation of the coarse-bladed calcite as well 

as opal, perhaps because such settings allow solutions 

to pond and solutes to concentrate through 

evaporation.

Most Recent Event: Calcite or opal? - 

Precipitation or dissolution?

Dating the most recent record of percolation 

fluxes is important for correlation with regional 

climatic reconstructions and to provide bounds for 

assessment of performance of a potential repository. 

Observing the outer, free-growth surface of mineralization and identifying whether calcite or opal was the 

last-formed mineral seems straightforward, bearing in 

mind that the most recent evidence of percolation flux 

might be mineral dissolution. Scanning-electron 

microscope observations, however, have revealed

complex cycles of latest calcite/opal formation 

(figures 4a-c). These observations show that most 

calcite crystal faces appear fresh (figures 4b, d, and g). 

Some calcite crystal faces, however, appear pitted 

(figure 4h) which may indicate calcile dissolution 

(Vaniman and Chipera, 1996). Dating of materials 

from these outermost surfaces may, therefore, determine the age of most recent mineral deposition or, if 

the last event was mineral dissolution, the maximum 

age of the corrosion event. Either age constraint 

provides useful information, because correlating 

climatic states with percolation fluxes (and chemistries) that resulted in secondary mineral dissolution is 

as important as identifying those climates that 

produced mineralizing percolation.

Dissolution events within the unsaturated 

zone?

Many secondary mineral occurrences within the 

ESF, particularly those flooring lithophysae, appear to 

have been corroded around their basal attachment to 

the tuffaceous substrate (noted in appendix 1 as "basal 

dissolution"). This basal dissolution is local, 

commonly affecting only part of an occurrence that 

otherwise consists of firmly attached and tightly intergrown calcite crystals with pristine youngest crystal 

faces. Basal dissolution created voids several millimeters high by centimeters wide, a sort of small-scale 

cavernous porosity. Some of the calcite remnants in 

these "dissolution" zones are adorned with tiny, toothlike, calcite forms that appear to be overgrowths postdating dissolution (figures 4e and f). In fracture 

settings, basal dissolution is expressed as loosening of 

the attaching layer resulting in coatings that lie loosely 

on the fracture walls.

In many instances, the secondary mineral 

substrates are more permeable than the secondary 

mineralization coatings or growths they host, especially the bleached and altered margins associated 

with vapor-phase mineralization of lithophysae and 

fractured tuffs. In the laboratory, water dripped onto 

the bleached margin of a lithophysal cavity moved 

through the altered matrix and, within seconds, 

produced obvious wetting of the matrix 10 to 15 centimeters away. The high permeability of the altered rims 

of lithophysae provides a means for percolating water, 

perhaps at low flux rates, to contact and dissolve 

calcile from the base of a lilhophysal occurrence 

without corroding the later calcite in the occurrence.

8 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
IF

Figure 4a. Photomicrograph of late botryoidal opal with rhombic overgrowths of 

calcite that are, in turn, locally pimpled with tiny opaline spheres. Scale bar indicates 400 microns.

Figure 4b. Photomicrograph of late botryoidal opal on calcite (not shown) partially 

engulfed by a later stage of calcite. Note the clean uncorroded surfaces of the 

calcite and opal. Scale bar indicates 200 microns.

PARAGENESIS OF EXPLORATORY STUDIES FACILITY OCCURRENCES 9
Figure 4c. Photomicrograph of opal (lower left in left image) with overgrowths 

of a later opaline stage (white spheroids) followed by calcite overgrowth coated 

with botryoidal opal that is, in turn, partially buried by late calcite. Image on the 

right is an approximately 3X enlargement of the later mineralization stages. 

Scale bar indicates 100 microns.

Figure 4d. Photomicrograph of bladed calcite crystals with scepter-like terminations. Scale bar indicates 1 millimeter.

10 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paieohydrology Status of 

Investigations: June 1996
Figure 4e. Photomicrograph of pyramidal to spire-like calcite forms on the basal 

zone of lithophysal secondary calcite mineralization apparently corroded by later 

solutions; the relatively fresh faces of this calcite indicate that it may be 

neoformed and postdate the dissolution event. Scale bar indicates 100 microns.

Figure 4f. Photomicrograph of a basal dissolution zone, with delicate forms 

representing miniature speleothems or meniscus cements. Image on right is an 

approximately 3X enlargement. Scale bar indicates 100 microns.

PARAGENESIS OF EXPLORATORY STUDIES FACILITY OCCURRENCES 11
Figure 4g. Photomicrograph of an apparently unetched calcite crystal face. 

Calcite crystals present a variety of forms but typically appear fresh and unetched 

in these occurrences. Scale bar indicates 200 microns.

Figure 4h. Photomicrograph of pitted surface of apparently etched calcite 

crystal face. Image on right is any approximately 3X enlargement of the etched 

surface. Scale bar indicates 40 microns.

12 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
The generalizations discussed here and the 

specifics listed in appendix 1 are preliminary. Further 

petrographic and scanning-electron microscopic 

examination of samples collected during completion 

of the ESF might provide additional textural 

constraints that would clarify the hydrologic and 

geochemical histories of calcite and opal deposition.

ISOTOPIC DATA

Determinations of the 6 13C and 618O of 

310 secondary calcite samples from ESF occurrences 

and 123 determinations from drill-core occurrences 

were performed to obtain isotopic characterizations of 

the secondary calcite (appendix 2). These measurements supplement data from previously published 

reports (Whelan and Stuckless, 1992; Whelan and 

others, 1994; Whelan and Moscati, U.S. Geological 

Survey, written commun., 1997) and are merged with 

those data on figures 5 and 6. Isotopic data obtained 

from samples taken from ESF occurrences located 

between the northern portal and station 40 are listed in 

appendix 2. Calcite from those ESF occurrences has 

8 3C values ranging from -9 to +8.4 per mil and 8 18O 

values ranging from 10.5 to 20.6 per mil (fig. 6). 

Preliminary determinations of the 87Sr/86Sr ratio of 

ESF calcite from occurrences near stations 5, 14, 16, 

17,19, and 30 ranged from 0.70958 to 0.71250.

Implications of new Exploratory Studies 

Facility data to previous interpretations

Carbon isotopic compositions of unsaturatedzone calcite reflect exchange between infiltrating 

fluids and components of the overlying soils and are 

fundamentally controlled by variations in the proportions of C3 and C4 plants that comprise the surface 

plant community and which vary as a function of 

climate. Plants photosynthesize via two pathways, 

designated C3 and C4, which result in markedly 

different carbon isotopic compositions of about - 

26 and -13 per mil, respectively (see, for example, 

Quade and others, 1989). The C4 plants (such as many 

grasses) favor drier and hotter climates and are better 

suited to handle those climatic stresses, whereas 

wetter and milder climates promote growth of woody, 

herbaceous C3 plants. The isotopic compositions of 

soil organic matter and respired CC>2 in the soil are, 

therefore, closely related to climate, and the 6 13C

values of dissolved carbonate in unsaturated-zone 

percolation (and the calcite formed from it) are a 

reflection of the climate at the time of infiltration. 

Oxygen isotopic compositions of unsaturated-zone 

calcite record the 6 18O of contemporaneous meteoric 

waters. The newly obtained S I3C and 6 18O values 

shown in figures 5 and 6 and tabulated in appendix 2 

support the conclusions of Whelan and Stuckless 

(1992) that unsaturated-zone secondary mineralization 

formed in a vadose setting, largely from percolation of 

surface infiltration and at near present-day ambient 

temperatures. The new data reported here, however, 

demonstrate a much wider distribution of paragenetically early calcite than previous studies of drill-core 

occurrences had revealed. The early calcite has higher 

8 13C values that are incompatible with the carbon 

isotopic compositions of soil-exchanged percolation.

Carbon-13-enriched calcite from the 

Exploratory Studies Facility

Local occurrences of early calcite from drillcore samples display atypically heavy ( 13C-enriched) 

813C values (fig. 5). Those occurrences (Whelan and 

Moscati, U.S. Geological Survey, written commun., 

1997) also display 6 18O values that decrease more 

rapidly with depth, indicating that this early calcite 

was deposited at warmer temperatures and possibly 

was subject to a steeper geothermal gradient than 

prevailed during the formation of later, percolationdeposited calcite.

Exploratory Studies Facility calcite occurrences 

(fig. 6) more commonly display 8 13C values greater 

than 0 per mil than had been observed in drill-core 

occurrences (fig. 5). Most of that 13C-enriched calcite 

occurs within the upper half of the Topopah Spring 

Tuff. Because it is possible to examine and select the 

most paragenetically complete assemblages when 

sampling in the ESF, in contrast to the random set of 

occurrence intersections from drill core, the increased 

representation of 13C-enriched calcite in the ESF data 

set could reflect a sampling bias. However, it could as 

well indicate a real difference between the early 

hydrologic history of the Topopah Spring Tuff and the 

other unsaturated zone tuffs. The 13C-enriched calcite 

is much more common in the non-lithophysal zones 

than in the upper lithophysal zone of the Topopah 

Spring Tuff (fig. 6), although the cause of this apparent 

lithologic control is not clear.

ISOTOPIC DATA 13
100

CO

G) +rf

O

Q. 

LLJ

O

-600

-10 -5 10 15 20 25

513C (per mil, PDB) and 618O (per mil, SMOW)

Figure 5. Distribution of unsaturated-zone 613C (o symbol) and 618O 

(+ symbol) values of calcite plotted against depth (in meters). Occurrences 

of 13C-enriched paragenetically early calcite are designated by (613C) 

and (818O) symbols. The hatched line shows the predicted 618O of calcite 

precipitated along a hypothetical geothermal gradient of approximately 100° 

C/km from a fluid with a 618O of approximately -12.5 per mil.

o

O 

oo

(0

CD 

o 

o.

O

30.0

25.0-

20.0

15.0

10.0

5.0

0.0

-5.0

-10.0

Tiva Canyon Tuff

CO

3=

 o

0) o

 o

0)

.o

o 

o

upper

nonlithophysal 

zone "I

Topopah Spring Tuff

upper 

lithophysal zone

I.

middle 

non-lithophysal zone

0 200 600 1000 1400 1800 2200 2600 3000 3400 3800 4200

Position in ESF from portal, in meters

Figure 6. Graph showing 613C and 818O values of Exploratory StudiesFacility calcite samples plotted against distance from the 

portal (station 000). 518O values of all calcite are plotted as . 513C values of a calcite from lithophysal cavities and from fracture 

coatings are plotted as X and O, respectively.

14 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paieohydrology Status of 

Investigations: June 1996
Provisional measurements of the 87Sr/86Sr 

ratios of ESF calcite samples (20 analyses) provide 

further insight into the origin of the paragenetically 

early 13C-enriched calcite. Peterman and others (1992) 

and Marshall and others (1993) concluded that most of 

the secondary calcite in the unsaturated zone reflects 

pedogenic strontium sources which have an average 

87Sr/86Sr ratio of 0.71215. Unsaturated-zone calcite 

occurrences just above the water table, however, had 

strontium isotopic compositions (average 87Sr/86Sr 

value of 0.70909) indicating addition of less-radiogenic strontium, perhaps from the saturated zone. 

Saturated-zone calcite 87Sr/86Sr ratios are compatible 

with derivation of strontium either from the host tuffs 

of Yucca Mountain or from underlying Paleozoic 

marine carbonate rocks during an incursion of heated 

Paleozoic-aquifer water (Marshall and others, 1992), 

possibly during formation of the Timber Mountain 

caldera (Broxton and others, 1987; Bish and Aronson, 

1993).

Paragenetically early calcite has less-radiogenic 

87Sr/86Sr, higher 5 13C, and lower 5 18O, whereas 

paragenetically later calcite exhibits more-radiogenic 

87Sr/86Sr, lower 5 13C, and relatively higher 6 18O 

(figs. 7a and b). Whether these trends reflect a 

continuum of 87Sr/86Sr ratios, or mixtures of early 

and late calcite created mechanically during sampling, 

is not yet clear. It is clear, however, that the less-radiogenic 87Sr/86Sr ratios may indicate a tuffaceous strontium source for the early calcite as opposed to the 

more radiogenic pedogenic calcite that appears to 

provide strontium for the later unsaturated-zone 

calcite. Furthermore, the rapid decrease of early 

calcite 5 18O values with depth indicates a steeper 

geothennal gradient and warmer fluid temperatures 

(fig. 5). Both of the above observations are compatible 

with calcite deposition closely following eruptive 

activity, when geothennal gradients may have been 

higher and calcareous soils had not yet formed. 

Although these preliminary data indicate a distinctly 

different geochemical environment for the paragenetically early calcite, the distribution of that calcite is still 

spatially restricted to the footwalls of fractures and the 

floors of lithophysae. Therefore, other differences 

aside, the earliest and oldest calcite present in these 

samples still indicate formation under unsaturated 

conditions.

Silica-phase oxygen isotope studies

Silica minerals occur throughout the paragenesis. Tridymite formed as a vapor-phase mineral 

within lithophysal cavities and along cooling joints 

during initial cooling and outgassing of the tuffs. Chalcedony (cryptocrystalline quartz) and both drusy and 

coarse euhedral quartz appeared early and generally 

preceded calcite deposition, whereas opal occurs 

sporadically within and upon later calcite as laminated 

coats, botryoidal masses, or isolated hemispherical 

grains.

The fractionation of 18O between a silica 

mineral and the mineralizing fluid is determined by 

temperature; 5 18O values can be used, therefore, to 

infer the formation temperatures of such minerals. 

Histograms of the 5 18O values of the various silica 

phases sampled from Yucca Mountain drill cores and

1 0

outcroppings (appendix 3) display increasing 8 O 

with decreasing temperature (fig. 8). Tridymite 5 18O 

values record deposition at high, nearly syn-volcanic, 

temperatures and low water-to-rock ratios, with 

5 18O values in the range 9 to 17 per mil. Chalcedony, 

the earliest post-vapor-phase mineral in many occur1 ft

rences, has 8 O values ranging from 5.8 to 

17.3 per mil. Quartz, occurring both.as early drusy 

crusts within and upon the chalcedony and as sprays of 

clear, inclusion-free prismatic crystals as long as 1 cm, 

has 8 18O values ranging from 8.6 to nearly 24 per mil. 

Higher water temperatures are required by the lowest 

6 18O values of both the chalcedony and quartz, likely 

greater than 120°C 1 (Moscati and Whelan, 1996). 

Such temperatures are consistent with formation either

1 There are no independent constraints on the temperatures of 

any unsaturated-zone fluids except fluid inclusion studies of late 

calcite suggesting formation temperatures less than 100°C 

(Roedder and others, 1994). A fluid 5 18O of-12.5 per mil is 

assumed only to permit qualitative comparison of the 8 18O values 

of the different silica phases. At cooler temperatures, this is a 

reasonable assumption, although the 818O of percolation has 

likely varied by at least ± 2 per mil around this value. At higher 

temperatures, water exchanges 180 with the rocks that it passes 

through which results in increased water 818O values. The amount 

of the increase will be a function of the temperature and the waterto-rock ratio; assuming a value of-12.5 per mil for the heated 

water produces minimum calculated mineral-formation temperatures. Clayton and others (1972) and Kita and others (1985) are 

the respective sources of the quartz (and chalcedony)-H2O and 

opal-H2O fractionation factors used to determine formation 

temperatures.

ISOTOPIC DATA 15
A.

CD

co

oo

0.71300

0.71200-

0.71100-

0.71000-

0.70900

5.

 X

 X

 x

7 ' ' i ' ' ' i ' ' ' i ' ' ' i ' ' i ' ' ' i p ^ T 

-10 -5 0 5 10 15 20 25

13 18 

6 C (per mil, PDB) and 6 O (per mil, SMOW)

B. ^

^

O

i

 *

E

0)

^^

cT

oMi

19- 1 w

17-

-

15-

-

13-

11-

+ . . ;. ,

 

 : 

 * %

 .

; * 

-8-6-4-20 2 4 6 8 10

13 

5 C (per mil, PDB)

Figure 7. Preliminary radiogenic Sr isotopic compositions plotted against the 613C ( ) 

and 618O (X) isotopic compositions of the Exploratory Studies Facility (ESF) calcite (A), 

and the correlation between 613C and 818O values of the same ESF calcite 

( ), shown in (B). In general, larger 513C values correlate with older occurrences.

16 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
1

0

0

i i r 

4 8

Tridymite|

12 16 20 24 28 32

Early Chalcedony!

0 4

i i i r riii 

8 12 16 20 24 28 32

o

c

0) 3

C7 

<D 8 12 16 20 24 28 32

12T

8

0 \ i i i r

0 4 8 12 16 20 24 28 32

2\ 

0

Pedogenic Opal|

I I I I I T I I I I

0 4 8 12 16 20 24 28 32 

6 18O (per mil, SMOW)

Figure 8. Histograms of Yucca Mountain unsaturated zone secondary silica 818O (per mil, 

SMOW) values. Relative temperatures of formation and relative ages of silica phases 

decrease from top to bottom of the figure.

ISOTOPIC DATA 17
before the host tuff had cooled, or during a later 

thermal pulse, perhaps accompanying eruption of 

some of the younger units. Chalcedony and quartz 

8 18O values in the middle part of the observed range 

require either water temperatures slightly warmer 

(60 to 70°C) or water 818O values somewhat lower 

(about 2 per mil) than occur in the unsaturated zone

1 fi today, whereas the highest quartz 8 O values are 

compatible with present-day water 8 18O values and 

temperatures.

Silica mineralization records a wide range of 

depositional conditions and possibly long depositional 

history, as well. Whether silica phases also have 

recorded climatic variability is problematic. Silica 

phases might have been, occasionally, the dominant 

secondary minerals forming from percolation, perhaps 

during times or climates when overlying soils were 

thin or absent and percolating fluids were deprived of 

that important source of calcium and carbon for calcite 

formation.

Opal is the latest silica phase in the unsaturated 

zone, generally occurring only with calcite. Late opal 

has 8 O values ranging from 18.0 to 27.9 per mil and, 

assuming water of-12.5 per mil, formed at temperatures of 7 to 45°C (Moscati and Whelan, 1996). 

Temperatures in the lower part of this range are 

unlikely. Past variability in 8 18O values of meteoric 

water and (or) percolation probably contributed to the 

relatively large range of opal 8 18O values.

Pedogenic opal from the overlying soils has the 

highest 8 18O values, ranging from 22 to nearly 

32 per mil. Assumption of a water 8 18O value of 

-12.5 per mil produces estimates that the pedogenic 

opal formed at temperatures ranging from about 30°C 

down to an improbable -3°C. Such low estimated 

temperatures indicate that the opal with the highest 

8 18O values likely was formed from waters with 

818O values higher than -12.5 per mil. The 18Oenriched waters might reflect warmer and (or) 

wetter climates, or evaporative enrichment of the 

water precipitating pedogenic opal (Moscati and 

Whelan, 1996).

1 8

Silica-mineral 8 O values increase from early 

to late in the paragenetic sequence, implying an 

overall decrease of depositional temperatures with 

time. In addition, with the lowest calculated formation 

temperatures occurring within the overlying soils, opal

I o

8 O values conform to increasing temperatures with

depth in the unsaturated zone. Some of the early chalcedony and drusy quartz seem to have formed at somewhat elevated temperatures. Combined with their early 

position in the paragenesis, this indicates that they 

formed before the tuffs had completely cooled. Later 

quartz euhedra, however, appear seem to have formed 

at temperatures compatible with the modern geotherm 

and climate; their water-clear, inclusion-free crystalUnity and euhedral habit are consistent with slow 

growth from relatively cool fluids.

Radiocarbon geochronologic studies

The timing of latest calcite formation in ESF 

occurrences is being studied with 14C and 230Th/U 

geochronometers. Carbon-14 age determinations can 

be performed on far smaller amounts of calcite than 

can the 230Th/U method, an advantage that permits 

greater sampling resolution. Calcite 14C contents, 

however, may be susceptible to post-depositional 

contamination from modern carbon sources such as 

carbon-bearing fluids or gases in the unsaturated zone. 

Carbon-14 decays with a half-life of about 

5730 years. Although the analytical precision of accelerator mass spectrometry (AMS) is excellent, age 

determinations begin to lose credibility at ages about 

40 ka. At that age, over 99% of the initial 14C has 

decayed, and minimal contamination by modern 14C 

can seriously compromise age determinations, especially from small (10- to 30-mg) samples.

Past studies have demonstrated that percolating 

fluids in the unsaturated zone at Yucca Mountain 

obtain their 8 13C signature largely through interaction 

with carbonate and organic matter in the overlying 

soils (for example, Whelan and others, 1994). This 

interaction is characterized by the reaction

CaCO3 + CO2 + H2O (2)

in which, as CO2 is taken into solution, calcite 

is dissolved. The CO2, derived primarily from the 

oxidation of soil organic matter but secondarily from 

diffusion of atmospheric gases, is near 100 percent 

modern carbon (pmc). The calcite dissolved according 

to equation 2, however, may be old and have 0 pmc 

("dead" C), and the HCO3 ~ of the resulting solution 

could have a 14C content as low as 50 pmc; infiltrating

18 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
waters could, therefore, have an initial 14C age of one 

half-life, or about 5700 years. It is unlikely, therefore, 

that either percolating waters, or calcite precipitated 

from them in the unsaturated zone, ever record the 

correct timing of infiltration. Furthermore, the 14C 

clock for secondary calcite is not set until the calcite is 

precipitated, so estimates of the timing of infiltration 

must be adjusted for the travel time of the percolation 

to the site of deposition.

An ancillary undertaking is to evaluate the likelihood of exchange between the outer surfaces of 

secondary calcite crystals and later, 14C-bearing, gases 

and fluids in the unsaturated zone. Such exchange 

might create a 14C-enriched outer layer on the calcite 

crystals and, therefore, a young age bias in the 14C 

data. To test this possibility, the crystal faces of freegrowing calcite from several samples were etched 

briefly with dilute HC1 to remove the outer surface. 

Those etched surfaces were then sampled, as were 

comparable unetched free-growth calcite surfaces 

from the occurrence. A minimal difference between 

these paired 14C age determinations might indicate 

that post-depositional interaction with rock gases is 

not a concern. A large difference would be compatible 

with a thin surface layer of 14C-contaminated calcite 

on a 14C-"dead" substrate; such a relationship would 

also, however, be in accord with extremely low calcite 

depositional rates and most of the 14C-datable calcite 

record having been removed by the acid etching. This 

is a moot point, however, in that if calcite depositional 

rates are that low, then calculated 14C ages are 

probably unrealistic anyway.

In spite of the stated caveats, 14C dating of 

calcite still offers useful constraints on the history of 

percolation flux in the unsaturated zone, primarily 

because, in many of the occurrences, calcite was the 

last or only mineral formed. (This is especially true for 

the fracture occurrences.) Furthermore, because ages 

can be determined from calcite subsamples as small as 

10 mg, 14C permits finer-scale sampling and, therefore, better age resolution of calcite formation than 

can other dating techniques.

To date, subsamples submitted for 14C AMS age 

determination have come from (1) the latest surfaces 

of free-growth calcite crystals or (2) the basal zones of 

calcite dissolution present in many samples. All of the 

subsamples from zones of basal dissolution contain a 

mixture of the "late" overgrowths and the residual, 

possibly 14C-dead, calcite substrate. These subsamples 

should still provide an indication, however, of whether 

a given dissolution event occurred within the past 

40 ka, and the subsamples are therefore significant for 

reconstruction of hydrology/climate interactions in the 

recent past.

Provisional results of the 14C geochronometry 

indicate calculated 14C ages (radiocarbon years) in a 

range from greater than 16 ka to about 42 ka (fig. 9). A 

significant percentage of the samples showed calculated ages less than 32 ka, indicating a significant 

component of modem carbon. This relation implies 

that much of the secondary calcite sampled in the ESF 

contains at least thin layers deposited during or since 

the last glacial cycle, and that calcite 14C measurements provide at least a relative tool for spatial and 

temporal mapping of percolation pathways within the 

unsaturated zone at Yucca Mountain.

None of the data (shown in appendix 3 and 

fig. 8) discussed here tested the possibility of surfacelayer 14C contamination in ESF samples. Samples of 

thick mammillary calcite crusts, however, collected 

from the unsaturated zone of the Sterling Mine on 

Bare Mountain (fig. 1) west of Yucca Mountain, were 

tested. Opposite halves of a sawn specimen were 

ground and polished to reveal the growth banding. One 

half was briefly etched in dilute (0.2 N) HC1, then both 

were washed ultrasonically in deionized water, and the 

youngest band of calcite was milled from each half. 

The acid-etched sample had an apparent C age of 

15.3 ± 0.12 ka, whereas the unetched sample gave an 

age of 14.7 ± 0.12 ka. The minimal difference between 

the two ages provides little support for post-depositional exchange between modern carbon and unsaturated-zone gases or fluids during the past 15 ky, at least 

at Bare Mountain.

ISOTOPIC DATA 19
o

c

CD

13 

CT

CDi_

LL

0

16 24 32

Apparent Radiocarbon Years (xlOOO)

40

100 50 25 10 5 2

Percent Modern Carbon

0.5

Figure 9. Histogram showing the distribution of 14C ages from the Exploratory Studies Facility calcite occurrences. Upper x-axis shows the apparent age calculated from measured percentages of modern carbon in the 

sample; no attempt was made to correct for incorporation of dead carbon or ground-water travel time. Lower 

x-axis displays the relationship between percent modern carbon and apparent age, and underscores the large 

error that trace amounts of 14C contamination cause in older materials. System blanks are the amounts of 1 C 

measured in samples of Paleozoic calcitic marble subjected to the entire extraction and Accelerator Mass 

Spectrometer analysis process.

20 Applications of isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paieohydroiogy Status of 

Investigations: June 1996
CONCLUSIONS

1. Post-vapor-phase secondary mineralization 

in the unsaturated zone consisted of an early stage 

dominated by silica deposition, locally with coeval or 

possibly precursor calcite, followed by main-stage 

calcite and opal. Main-stage mineralization, as defined 

herein, groups all early-stage calcite and opal deposition. This is probably a simplification, and further 

study might reveal a more complex depositional 

history.

2. Early calcite is characterized by heavy 8 13C 

values and 8 18O values that increase more rapidly with 

depth than those of main-stage calcite. Coupled with 

its association with formation of early chalcedony and 

quartz, this relation may indicate that the early calcite 

formed at somewhat higher temperatures than the 

main-stage calcite and that early calcite should not be 

included in estimates of past percolation fluxes based 

on the secondary mineral record.

3. Preliminary strontium isotope analyses indicate that the early calcite contains less- radiogenic 

strontium than does the main-stage calcite. Rather 

than a pedogenic strontium source as is the case for the 

main stage, the tuffs themselves may have been the 

source of strontium in the early calcite.

4. Delta- 18O values of the silica phases quartz, 

chalcedony, and opal indicate that some of the early 

massive-silica-stage phases must have formed from 

heated water, although parts of the massive-silica stage 

are compatible with modern or near-modem rock 

temperatures. Opal 8 18O values argue that evaporative

1 C

processes increased the 8 O of the precipitating water 

in the soil zone.

5. Preliminary radiocarbon age determinations 

argue that in situ interactions with later carbon-bearing 

water and gases have not significantly altered the 

14C ages of the calcite. Radiocarbon ages of the latest 

calcite in many of the occurrences may indicate relatively recent formation of the outermost calcite layers.

REFERENCES CITED

Bish, D.L. and Aronson, J.L., 1993, Paleogeothermal and 

paleohydrologic conditions in silicic tuff from Yucca 

Mountain, Nevada: Clays and Clay Minerals, v. 41, 

no. 2, p. 148-161.

Broxton, D.E., Bish, D.L., and Warren, R.G., 1987, Distribution and chemistry of diagenetic minerals at Yucca 

Mountain, Nye County, Nevada: Clays and Clay 

Minerals, v. 35, no. 2, p. 89-110.

Buesch, D.C., Spengler, R.W., Moyer, T.C., and Geslin, 

J.K., 1996, Revised stratigraphic nomenclature and 

macroscopic identification of lithostratigraphic units of 

the Paintbrush Group exposed at Yucca Mountain, 

Nevada: U.S. Geological Survey Open-File 

Report 94-469, 47 p.

Byers, P.M., Jr., Carr, W.J., Orkild, P.P., Quinlivan, W.D., 

and Sargent, K.A., 1976, Volcanic suites and related 

cauldrons of Timber Mountain-Oasis Valley caldera 

complex, southern Nevada: U.S. Geological Survey 

Professional Paper 919, 70 p.

Carr, W.J., 1984, Regional structural setting of Yucca 

Mountain, southwestern Nevada, and Late Cenozoic 

rates of tectonic activity in parts of the southwestern 

Great Basin, Nevada and California: U.S. Geological 

Survey Open-File Report 84-854, 109 p. 

Christiansen, R.L., and Lipman, P.W., 1965, Geologic 

map of the Topopah Spring NW quadrangle, Nye 

County, Nevada: U.S. Geological Survey Geological 

Quadrangle Map GQ-444, scale 1:24,000.

Clayton, R.N., and Mayeda, T.K., 1963, The use of bromine 

pentafluoride in the extraction of oxygen from oxides 

and silicates for isotopic analysis: Geochimica et 

Cosmochimica Acta, v. 27, no. 1, p. 43 52.

Clayton, R.N., O'Neil, J.R., and Mayeda, T.K., 1972, 

Oxygen isotope exchange between quartz and water: 

Journal of Geophysical Research, v. 77, 

p. 3057-3067.

Gary, M., McAfee, R., Jr., and Wolf, C.L., 1974, Glossary 

of Geology: American Geological Institute, Washington, D.C., 805 p.

Haimson, M., and Knauth, L.P., 1983, Stepwise fluorination 

 A useful approach for the isotopic analysis of 

hydrous minerals: Geochimica et Cosmochimica Acta, 

v. 47, no. 9, p. 1589-1595.

Kita, I., Taguchi, S., and Matsubaya, O., 1985, Oxygen 

isotope fractionation between amorphous silica and 

water at 34-93°C: Nature, v. 314, no. 6006, p. 63-64.

Marshall, B.D., Peteraian, Z.E., and Stuckless, J.S., 1993, 

Strontium isotopic evidence for a higher water table at 

Yucca Mountain, in High Level Radioactive Waste 

Management, Proceedings of the Fourth Annual International Conference, Las Vegas, Nevada, April 26-30, 

1993: LaGrange Park, Illinois, American Nuclear 

Society, v. 2, p. 1948-1952.

CONCLUSIONS 21
Marshall, B.D., Whelan, J.F., Peterman, Z.E., Futa, K.F., 

Mahan, S.A., and Stuckless, J.S., 1992, Isotopic 

studies of fracture coatings at Yucca Mountain, 

Nevada, in Kharaka, Y.K., and Maest, A.S., eds., 

Proceedings of the Seventh International Symposium 

on Water/Rock Interaction, Park City, Utah, 

p. 737-740.

McCrea, J.M., 1950, The isotopic chemistry of carbonates 

and a paleotemperature scale: Journal of Chemical 

Physics, v. 18, no. 8, p. 849-857.

Moscati, R.J., and Whelan, J.F., 1996, Origin of secondary 

silica within Yucca Mountain, Nye County, southwestern Nevada: U.S. Geological Survey Open-File 

Report 95-289, 14 p.

Peterman, Z.E., Stuckless, J.S., Marshall, B.D., Mahan, 

S.A., and Futa, K.A., 1992, Strontium isotope 

geochemistry of calcite fracture fillings in deep core, 

Yucca Mountain, Nevada a progress report, in High 

Level Radioactive Waste Management, Proceedings of 

the Third Annual International Conference, Las Vegas, 

Nevada, April 12-16, 1992: LaGrange Park, Illinois, 

American Nuclear Society, v. 2, p. 1582-1586.

Quade, Jay, Cerling, T.E., and Bowman, J.R., 1989, 

Systematic variations in the carbon and oxygen 

isotopic composition of pedogenic carbonate along 

elevation transects in the southern Great Basin, United 

States: Geological Society of America Bulletin, v. 101, 

no. 4, p. 464-475.

Roedder, Edwin, Whelan, J.F., and Vaniman, D.T., 1994, 

Fluid inclusion homogenization and crushing studies 

of calcite veins from Yucca Mountain, Nevada, tuffs: 

Environment of formation, in High-Level Radioactive 

Waste Management, Proceedings of the Fifth Annual 

International Conference, Las Vegas, Nevada, 

May 22-26, 1994: LaGrange Park, Illinois, American 

Nuclear Society, v. 4, p. 1854-1860.

Sawyer, D.A., Fleck, R.J., Lanphere, M.A., Warren, R.G., 

Broxton, D.E., and Hudson, M.R., 1994, Episodic 

caldera volcanism in the Miocene southwestern 

Nevada volcanic field revised stratigraphic framework, 40Ar/39Ar geochronology, and implications for 

magmatism and extension: Geological Society of 

America Bulletin, v. 106, p. 1304-1318.

Scott, R.B., and Bonk, Jerry, 1984, Preliminary geologic 

map of Yucca Mountain, Nye County, Nevada, with 

geologic sections: U.S. Geological Survey Open-File 

Report 84-494, scale 1:12,000.

Snyder, D.B., and Carr, W.J., 1984, Interpretation of gravity 

data in a complex volcano-tectonic setting, southwestern Nevada: Journal of Geophysical Research, 

v. 89, p. 10193-10206.

United States Department of Energy, 1988, Site characterization plan, Yucca Mountain site, Nevada Research 

and Development Area, Nevada: U.S. Department of 

Energy, Office of Civilian Radioactive Waste Management, document DOE/RW0199, 8 volumes.

Vaniman, D.T., and Chipera, S.J., 1996, Paleotransport of 

lanthanides and strontium recorded in calcite compositions from tuffs at Yucca Mountain, Nevada, USA: 

Geochimica et Cosmochimica Acta, v. 60, no. 22, 

p. 4417-4433.

Whelan, J.F., and Stuckless, J.S., 1990, Reconnaissance 

6 13C and 6 18O data from Trench 14, Busted Butte, and 

drill hole G-4, Yucca Mountain, Nevada Test Site, in 

High Level Radioactive Waste Management, Proceedings of the International Topical Meeting, Las Vegas, 

Nevada, April 8-12, 1990: LaGrange Park, Illinois, 

American Nuclear Society, v. 2, p. 930-934.

Whelan, J.F., and Stuckless, J.S., 1992, Paleohydrologic 

implications of the stable isotopic composition of 

secondary calcite within the Tertiary volcanic rocks of 

Yucca Mountain, Nevada, in High Level Radioactive 

Waste Management, Proceedings of the Third Annual 

International Conference, Las Vegas, Nevada, April 

12-16, 1992: LaGrange Park, Illinois, American 

Nuclear Society, v. 2, p. 1572-1581.

Whelan, J.F., Vaniman, D.T., Stuckless, J.S., and Moscati, 

R.J., 1994, Paleoclimatic and paleohydrologic records 

from secondary calcite: Yucca Mountain, Nevada, in 

High Level Radioactive Waste Management, Proceedings of the Fifth Annual International Conference, Las 

Vegas, Nevada, May 22-26, 1994: LaGrange Park, 

Illinois, American Nuclear Society, v. 4, p. 2738 2745.

22 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
APPENDIX

23
Appendix 1. Paragenetic sequences of secondary mineral occurrences within the Exploratory Studies Facility (ESF), Yucca Mou

APPENDIX

M

Sample #

2021

2022

2023

2001

2025

2026

2027

2028

2029

2030

2002

2003

2004

2032

2005

2006(1)

2006 (2)

2075

2007-1

2007-2

2008

2020 (2)

2020(1)

2020 (3)

2009

2010

2011

2012(1)

2012(2)

2012(3)

2013 

2014 

2015 

2016

2017

ESF Location*

12+21.83

12+44.25

14+06.0

14+20

14+55

14+72.53

14+79.55

15+05.25

15+33.25

15+68.58

15+99.95

16+12.38

16+46.6

16+70.1

17+10.95

19+00.0

19+00.0

19+75

22+13.0

22+13.0

22+72

24+37.6

24+39.58

24+41.6

24+43.50

24+68.2

25+68.0

25+76.7

25+76.7

25+76.7

26+78.58 

26+88 

26+95.00 

27+18.38

27+24

Type

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

fracture

litho cavy

fracture

litho cavy

fracture

litho cavy

litho cavy

litho cavy

litho cavy

litho cavy

litho cavy

fracture

fracture

fracture

int. frac+litho

litho cavy

fracture 

fracture 

fracture 

litho cavy

litho cavy

Basal 

Dissolution

calcite

calcite

(calcite)

(calcite)

calcite

calcite

calcite

calcite

calcite

calcite

calcite

calcite

calcite

calcite 

calcite

(calcite)

msv silica - cal & opal

msv silica - (bubbly opal)

blocky to bladed cal - bubbly opal

(anhedral cal) - msv silica - flourite - bladed cal - bubbly opal

msv silica + cal - blocky cal - (opal)

msv silica - bladed cal

msv silica - blocky cal - fluorite - bladed cal

msv silica - blocky cal - fluorite - bladed cal

anhedral cal - msv silica - blocky cal - fluorite - (opal) - cal o'gth

(anhedral cal) - msv silica - bladed cal

(anhedral cal) - flourite - msv silica - blocky cal & flourite - bladed cal

anhedral cal ± fluorite ± msv silica (paragenesis unclear) - late bladed 

(calcite) -msv silica - (blocky cal) - bladed cal

wall-to-wall cal vein - cal + (opal)

cal (breccia cement) - (blocky cal) -bladed cal

vapor phase - blocky cal - bubbly opal - (zeolite) - bladed cal - bubbly 

blocky cal - bladed cal

vapor phase -blocky cal - bladed cal - bubbly opal - blocky cal -bladed 

blocky cal - msv silica - bladed cal - bubbly opal - cal o'gths - (late opa

vapor phase - blocky cal - bladed cal - bubbly opal

vapor phase - blocky cal - (opal) - blocky cal - bubbly opal - cal o'gths 

vapor phase - blocky cal - bubbly opal

vapor phase - blocky cal

vapor phase - blocky cal - bubbly opal

vapor phase - blocky cal - bubbly opal - (cal o'gths)

blocky cal - bladed cal

blocky cal - bladed cal - scepter o'gths

blocky cal

vapor phase - blocky cal

vapor phase - blocky cal - sparse opal - blocky cal - bladed cal

blocky cal - bubbly opal - blocky cal 

blocky cal - bladed cal - opal coat -cal o'gths 

blocky cal - opal - blocky to bladed cal 

blocky cal - msv sislica - blocky cal - bladed cal - bubbly opal - (scept

vapor phase - blocky cal - bubbly opal - bladed cal - (scepter o'gths) - 
1

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blocky cal -botry'l bladed opal scepter - bladedlocky silica calopl coat msvs<- 

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u

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26 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations: June 1996
Appendix 1. Paragenetic sequences of secondary mineral occurrences within the Exploratory Studies Facility (ESF), Yucca Mou

Sample #

2077 (B)

2078

2079 (A)

2079 (B)

2079 (C)

2081

2083

2082

2084 (A)

2084 (B)

2085

2086

2087

2088

2089 (A)

2089 (B)

ESF Location*

37+62.9

37+67

38+17.2

38+17.2

38+17.2

38+61

38+64.0

38+68.8

38+87.8

38+87.8

39+38.7

39+44.0

39+50.7

39+61

39+91.4

39+91.4

Type

fracture

litho cavy

litho cavy

litho cavy

litho cavy

litho cavy

fracture

litho cavy

litho cavy

fracture

litho cavy

fracture

gouge

litho cavy

fracture

litho cavy

litho cavy

Basal 

Dissolution

calcite

calcite

calcite

calcite

calcite

calcite

calcite

calcite

blocky cal - msv silica - biaded cal - scepter cal o'gth - bubbly opal - c

vapor phase - blocky cal - msv silica - biaded cal - bubbly opal - scept

opal

msv silica - vapor phase - blocky cal

msv silica - vapor phase - blocky cal - biaded cal - scepter cal o'gth

vapor phase - blocky cal w/ scattered msv silica - biaded cal - scepter c

opal coat - bubbly opal - cal o'gth

vapor phase - blocky cal - coarser blocky cal + fluorite - bubbly opal - 

cal o'gth

blocky cal - biaded cai

vapor phase + msv silica - blocky cal - coarser blocky cal + fluorite - c

vapor phase - blocky cal - biaded cal - scepter cal o'gth - coat to bubbl

blocky to biaded cal - msv silica

vapor phase + msv silica - flourite - blocky cal - biaded cal - scepter ca

multi-stage blocky cal

vapor phase - blocky cal - biaded cal - bubbly opal - biaded cal ± cal o

blocky cal - msv silica - blocky cal

vapor phase + msv silica - blocky cal - biaded cal - scepter cal o'gth - 

vapor phase + msv silica - blocky cal - biaded cal - scepter cal o'gths - 

TJ 

TJ

m

o

X
<§ -o

" 7 

§ 3

* 2.

c. 

II

w 1

1

*

1

o

1

8

o

a

I 

§

0

80

O

i

3

?

i

0 

~3

8

Basal Dissolution:

Paragenesis:

litho cavy:

fracture:

vapor phase:

msv silica:

freegrowth: 

calcite (cal):

- anhedral:

- blocky:

- bladed:

- scepter o'gth: 

- o'gth:

opal:

- coat: 

- bubbly:

- botry'l:

fluorite:

GLOSSARY OF TERMS AND ABBREVIATIONS USED IN APPENDIX AND TEXT

"calcite" or "silica" in this column indicates possible later corrosion at the tuff-mineralization contact

the interpreted sequence of mineral deposition from first to last

lithophysal cavity (identified by presence of vapor-phase minerals)

secondary mineralization on fracture surface (does not preclude presence of vapor-phase minerals)

refers to minerals, most commonly tridymite and hematite, precipitated during post-eruption cooling

massive silica - typically preceding calcite/late opal; a mixture of chalcedony, quartz, and possibly opal

a mineralization stage in which the mineral form or crystal faces indicate growth into open space; may be co

rare early stage of tightly intergrown calcite grains

a freegrowth stage of equant to thick tabular calcite crystals

a freegrowth stage of tabular calcite, typically tall and broad, but very thin

calcite overgrowth on blades resulting in blade tops much thicker than their bases 

minor deposition of later calcite on earlier calcite crystals

thin, laminar coating of opal, typically on crystal faces of calcite 

scattered grains or aggregates of grains of opal with a soap-bubble-like form

botryoidal denotes a thick occurrence of laminar opal with a hummocky, rounded surface

a calcium-fluoride mineral that occurs locally as an accessory phase

zeolite: any zeolite mineral within the mineralization sequence, except as the earliest fracture coating 

( ): indicates some uncertainty in either paragenetic position, mineral identification, or feature identification 

* - Tunnel distance indicated in meters x 1 00, measured from portal

«< 

ex
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESP) and drill holes near Yucca Mountain, Nevada

Sample #

HD-1837b

HD-1837d

HD-1837c

HD-1837d

HD-1837a

HD-1836Aa

HD-1836Ba

HD-1850a

HD-1850b

HD-1850c

HD-1838a

HD-1838b

HD-1838b

HD-1852a

HD-1852b

HD-1852a

HD-1849a

HD-1919sa

HD-1927sa

HD-1933sa

HD-1933sb

HD-1839a

HD-1841 a

HD-1840a

HD-1840b

HD-1948sa

HD-1848b

HD-1844a

HD-1843a

HD-1847a

HD-1847b

HD-1875a

HD-1880a

HD-1937sa

HD-1879a

HD-1881 a

HD-1881 a

HD-1877b

HD-1877a

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

Depth/Distance: m*

98.80

98.80

98.80

98.80

98.90

109.05

109.05

111.17

111.17

111.17

111.55

111.55

111.55

149.47

149.47

149.47

161.90

168.20

168.20

168.20

168.20

288.90

301.80

324.49

324.49

336.79

358.95

360.20

371.00

375.19

375.19

382.82

412.40

444.60

454.04

465.45

465.45

473.40

473.40

513-C PDB

-4.0

-4. 1

-5.2

-4. 1

-3.4

-4.4

-5.9

-5.7

-3.3

-1.4

-6.7

-3.1

-3.2

-6.2

-3.0

-6.2

-1.1

-4.5

-6.1

-5.0

-6.3

-6.6

-2.6

-5.2

-5.3

-5.5

-5.2

-5.3

-5.5

-5.5

-5.2

-5.2

-5.1

-5.9

-5.3

-5.9

-6.0

-4.3

2.5

518-O SMOW

19.1

1 9.9

19.1

20.0

19.7

19.7

18.9

19.1

19.7

19.3

19.0

19.5

19.6

19.5

17.6

19.2

12.8

18.4

19.4

18.4

19.5

18.8

20.6

20.5

20.1

19.4

20.2

20.0

19.6

19.9

20.5

20.3

19.9

19.9

20.5

20.2

20.1

19.4

11.6

APPENDIX 29
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-1882b

HD-1883b

HD-1878a

HD-1878b

HD-1940sa

HD-1940sb

HD-1945 sa

HD-1945 sb

HD-1873a

HD-1873b

HD-1941 sa

HD-1865a

HD-1934sa

HD-1934sb

HD-1866a

HD-1944sa

HD-1869a

HD-1876a

HD-1868a

HD-1868b

HD-1867a

HD-1870a

HD-1870b

HD-1872a

HD-1942 sa

HD-1942 sb

HD-1935 sa

HD-1952 sa

HD-1939sa

HD-1939sa

HD-1922 sb

HD-1918sa

HD-1923sa

HD-1932 sc

HD-1931 sa

HD-1929sa

HD-1938sa

HD-2021 sa

HD-2023 sa

HD-2001 sa

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

Depth/Distance: m*

473.40

473.40

483.05

483.05

509.09

509.09

513.20

513.20

529.40

529.40

529.40

531.25

532.49

532.49

556.95

556.95

557.09

577.03

579.15

579.15

584.75

588.15

588.15

640.20

652.70

652.70

658.75

803.80

818.20

818.20

822.68

988.97

1008.00

1090.30

1114.75

1147.00

1212.05

1221.83

1406.00

1420.00

513-C PDB

-5.6

-0.2

-6. 1

-5.4

-5.7

-5.9

-4.8

-5.0

-6.0

-5.8

-2.1

-3.5

-4.5

-4.9

-6.5

-6.2

-6.2

-6.4

-6.4

-6.2

-5.5

-5.5

-6.6

-6.2

-3.4

-6.7

-6.1

-6.2

-6.8

-6.8

-6.5

-6.8

-9.0

-0.2

-4.6

-5.9

-0.2

-6.2

-0.6

-2.5

518-OSMOW

19.9

16.4

20.0

19.9

20.0

20.2

19.7

20.1

20.3

20.1

20.3

20.2

19.3

19.9

19.9

19.0

19.6

19.4

18.8

19.4

18.6

18.2

19.0

18.6

18.8

18.8

18.7

18.4

18.7

18.6

18.8

18.3

18.6

14.3

18.1

18.2

18.2

17.7

14.8

17.3

30 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations June 1996
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample*

HD-2001 sb

HD-2025 sa

HD-2025 sb

HD-2026 sa

HD-2027 sa

HD-2028 sb

HD-2028 sa

HD-2029 sa

HD-2029 sb

HD-2030 sa

HD-2030 sb

HD-2002 sb

HD-2002 sc

HD-2002 sa

HD-2003 sa

HD-2003 sb

HD-2003 sc

HD-2004 sc

HD-2004 sb

HD-2004 sa

HD-2004 sb

HD-2032 sa

HD-2032 sb

HD-2032 sc

HD-2005 sa

HD-2005 sa

HD-2006 sa

HD-2006 sb

HD-2006 sc

HD-2075 sa

HD-2075 sb

HD-2075 sc

HD-2007 Isb

HD-2007 Isc

HD-2007 2sa

HD-2007 Isb

HD-2007 2sb

HD-2007 Isa

HD-2007 2sa

HD-2008 sa

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

Depth/Distance: m*

1420.00

1455.00

1455.00

1472.53

1479.55

1505.25

1505.25

1533.25

1533.25

1568.58

1568.58

1599.95

1599.95

1599.95

1612.38

1612.38

1612.38

1646.60

1646.60

1646.60

1646.60

1670.10

1670.10

1670.10

1710.95

1710.95

1900.00

1900.00

1900.00

1975.00

1975.00

1975.00

2213.00

2213.00

2213.00

2213.00

2213.00

2213.00

2213.00

2272.00

613-C PDB

6.3

6.9

-3.7

-6.0

-2.0

-4.7

2.9

4.6

-4.6

0.2

3.6

4.8

-5.7

4.1

6.2

7.6

-6.2

1.9

8.4

4.5

8.3

5.4

5.8

2.4

-6.3

-6.3

-0.6

0.0

-6.2

-5.4

-4.6

-6.5

-5.8

-6.1

-7.0

-5.6

-7.2

-6.1

-7.1

-4.2

618-OSMOW

12.4

13.0

18.2

19.2

18.1

18.2

14.4

12.6

18.3

16.2

15.1

14.6

17.7

14.7

11.5

13.5

17.5

15.6

13.0

13.3

12.9

10.5

12.3

16.1

17.8

17.7

15.0

13.9

17.7

17.5

13.6

17.1

16.9

15.9

15.9

17.1

16.6

16.0

16.0

17.2

APPENDIX 31
Appendix 2. Caicite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-2008 sb

HD-2008 sa

HD-2020 subl sa

HD-2020 sub2 sb

HD-2020 sub2 sc

HD-2020 sub3 sd

HD-2020 subl sa

HD-2009 sa

HD-2009 sb

HD-2010sa

HD-2010sb

HD-2011 sa

HD-201 1 sb

HD-2012sa

HD-201 2 sb

HD-201 2 sc

HD-201 3 sa

HD-201 3 sb

HD-201 4 sa

HD-201 5 sb

HD-201 6 sa

HD-201 6 sb

HD-201 6 sc

HD-201 7 sa

HD-201 7 sb

HD-201 7 sc

HD-201 7 sd

HD-201 7 sb

HD-201 8 sa

HD-201 8 sb

HD-201 9 sc

HD-201 9 sd

HD-201 9 sb

HD-201 9 se

HD-201 9 sf

HD-201 9 sa

HD-201 9 sg

HD-201 9 sh

HD-2054 sc

HD-2054 sd

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

Depth/Distance: m*

2272.00

2272.00

2439.58

2439.58

2439.58

2439.58

2439.58

2443.50

2443.50

2468.20

2468.20

2568.00

2568.00

2576.70

2576.70

2576.70

2678.58

2678.58

2688.00

2695.00

2718.38

2718.38

2718.38

2724.00

2724.00

2724.00

2724.00

2724.00

2750.65

2750.65

2880.00

2880.00

2880.00

2880.00

2880.00

2881.00

2881.00

2881.00

2881.60

2881.60

813-C PDB

-6.7

-4.7

-0.7

-1.9

-1.8

-2.7

-0.9

-3.8

-6.7

-6.9

-5.7

-1. 2

-5.7

-4. 1

-6.3

-5.8

4.8

-4. 1

-2. 1

-5.7

-2.4

-2.3

-5.8

4.2

-2.0

0.6

-7.4

0.7

4.2

-7.3

1.8

-2.6

6.7

-3.4

-7.2

-5.3

4.9

-6.9

4.2

1.6

518-OSMOW

17.3

15.4

16.8

16.3

17.1

16.5

16.7

17.0

18.0

18.0

18.4

16.7

18.1

17.4

18.4

17.4

14.5

16.7

16.3

16.8

16.1

15.9

16.7

14.1

15.3

15.8

17.2

15.6

13.5

16.9

15.1

13.8

13.5

15.3

17.2

16.6

13.2

16.6

14.7

15.2

32 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations June 1996
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility {ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-2054 se

HD-2054 sa

HD-2054 sb

HD-2055 sb

HD-2055 sc

HD-2055 se

HD-2055 sa

HD-2055 sd

HD-2056 sa

HD-2056 sc

HD-2056 sb

HD-2056 sd

HD-2056 se

HD-2057 sa

HD-2057 sa

HD-2057 sa

HD-2057 sc

HD-2057 se

HD-2057 sb

HD-2057 sg

HD-2057 sd

HD-2057 sf

HD-2058 sc

HD-2058 sa

HD-2058 sb

HD-2058 sd

HD-2059 sc

HD-2059 se

HD-2059 sa

HD-2059 sb

HD-2059 sf

HD-2059 sk

HD-2059 si

HD-2059 sj

HD-2059 si

HD-2059 sj

HD-2059 si

HD-2060 sb

HD-2060 sc

HD-2060 sa

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

Depth/Distance: m*

2881.60

2881.60

2881.60

2911.20

2911.20

2911.20

2911.20

2911.20

2922.90

2922.90

2922.90

2922.90

2922.90

2962.20

2962.20

2962.20

2962.20

2962.20

2962.20

2962.20

2962.20

2962.20

2979.98

2979.98

2979.98

2979.98

3017.78

3017.78

3017.78

3017.78

3017.78

3017.78

3017.78

3017.78

3017.78

3017.78

3017.78

3026.58

3026.58

3026.58

513-C PDB

-6.9

4.9

4.2

-2.0

-5.6

-6.7

7.7

-6.9

-6.2

-1.5

-3.1

-2.5

-6.8

-7.3

-7.3

-7.4

5.0

-7.3

6.8

0.4

0.8

-7.8

-6.8

0.4

-0.4

-7.7

-7.2

-7.3

-8.0

-8.1

3.5

-6.0

-7.2

-0.6

1.7

-0.5

-7.2

-5.1

-7.1

4.4

518-0 SMOW

1 6.7

1 4.2

13.7

15.7

16.9

17.8

14.0

17.6

17.0

16.4

16.8

16.4

17.4

17.3

17.3

17.4

15.6

17.5

14.0

16.7

17.4

17.2

17.5

16.5

16.9

16.8

16.7

16.8

16.9

16.7

14.9

16.6

16.9

15.8

15.1

15.6

16.8

16.3

16.8

14.1

APPENDIX 33
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-2074 sb

HD-2074 sc

HD-2074 sd

HD-2074 se

HD-2061 sc

HD-2061 sd

HD-2061 se

HD-2061 sf

HD-2061 sg

HD-2061 sb

HD-2061 sb

HD-2073 sb

HD-2073 sc

HD-2073 sd

HD-2073 se

HD-2073 sa

HD-2073 se

HD-2073 sc

HD-2062 sa

HD-2062 sb

HD-2062 sc

HD-2062 sd

HD-2063 sa

HD-2063 sb

HD-2064 sa

HD-2065 sa

HD-2065 sb

HD-2065 sc

HD-2065 sd

HD-2065 sf

HD-2065 sg

HD-2065 sh

HD-2065 si

HD-2065 sj

HD-2065 sk

HD-2065 si

HD-2065 sn

HD-2065 sc

HD-2065 se

HD-2066 sa

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

Depth/Distance: m*

3050.70

3050.70

3050.70

3050.70

3057.68

3057.68

3057.68

3057.68

3057.68

3057.68

3057.68

3103.00

3103.00

3103.00

3103.00

3103.00

3103.00

3103.00

3107.40

3107.40

3107.40

3107.40

3116.10

3116.10

3195.70

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3316.20

3395.78

513-CPDB

5.9

0.8

-3.2

-7.3

6.5

-3. 1

-1.2

-6.4

-7.2

2.0

2.5

-2.2

-6.6

-7.5

-7.5

6.2

-7.6

-6.8

-7.1

-0.3

-6.8

-7.6

0.0

-5.8

1.9

7.4

4.9

6.3

6.7

7.4

7.2

6.3

5.0

6.8

6.6

4.1

-6.5

6.4

6.8

-1.6

618-OSMOW

1 4.6

14.6

14.5

17.0

14.6

15.7

14.8

16.9

16.9

14.9

14.8

14.8

17.5

17.3

16.9

14.6

16.9

17.1

17.5

16.1

17.3

17.2

16.7

17.2

15.5

15.0

15.2

14.7

14.5

14.7

14.7

14.8

15.4

14.6

14.3

15.2

17.5

14.5

14.4

17.4

34 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations June 1996
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-2066 sb

HD-2066 sc

HD-2066 sd

HD-2066 se

HD-2067 sb

HD-2067 sc

HD-2067 sd

HD-2067 sa

HD-2068 sa

HD-2068 sb

HD-2069 sb

HD-2069 sc

HD-2069 sc

HD-2069 sa

HD-2070 sa

HD-2070 sb

HD-2071 sa

HD-2071 sb

HD-2071 sc

HD-2071 sd

HD-2071 se

HD-2072 sa

HD-2076 sa

HD-2076 sb

HD-2076 sc

HD-2077 Asa

HD-2077 Asb

HD-2077 Bsc

HD-2077 Bsd

HD-2077 Bse

HD-2078 sb

HD-2078 sc

HD-2078 sd

HD-2078 sa

HD-2079 Asa

HD-2079 Bsb

HD-2079 Bsc

HD-2079 Bsd

HD-2079 Cse

HD-2079 Csf

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

Depth/Distance: m*

3395.78

3395.78

3395.78

3395.78

3428.18

3428.18

3428.18

3428.18

3486.48

3486.48

3503.78

3503.78

3503.78

3503.78

3523.63

3523.63

3545.40

3545.40

3545.40

3545.40

3545.40

3557.20

3697.50

3697.50

3697.50

3762.90

3762.90

3762.90

3762.90

3762.90

3767.00

3767.00

3767.00

3767.00

3817.20

3817.20

3817.20

3817.20

3817.20

3817.20

513-C PDB

-2. 1

-5.7

-7.0

-6.4

-0.9

-5.3

l.O

-0.6

O.I

-5.8

-3.3

-6.5

-6.4

2.3

-1.5

-6.4

1.5

5.3

-6.4

-5.5

2.0

3.4

-1.4

-2.5

-6. 1

1. 8

-6.4

4.3

-1.5

-7.7

-0.6

-0.8

-6.5

2.4

-1.2

3.2

-3.3

-6.0

1.5

-O.I

518-O SMOW

1 7.5

1 8.3

1 7.7

1 8.5

1 6.5

I7.l

15.9

16.9

16.0

17.3

16.1

16.9

17.1

15.3

15.8

17.1

15.1

14.8

17.2

17.3

15.0

14.7

15.7

15.5

16.5

15.4

17.6

14.5

15.9

17.5

15.6

15.5

17.6

15.6

16.4

15.7

17.0

17.6

16.2

16.4

APPENDIX 35
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-2079 Csg

HD-2079 Csh

HD-2081 sc

HD-2081 sa

HD-2081 sb

HD-2083 sa

HD-2083 sb

HD-2083 sc

HD-2083 sd

HD-2082 sb

HD-2084 Asa

HD-2084 Asb

HD-2084 Asb

HD-2084 Bsa

HD-2084 Bsb

HD-2085 sa

HD-2085 sb

HD-2086 sa

HD-2086 sb

HD-2086 sc

HD-2086 sc

HD-2087 sb

HD-2087 sa

HD-2088 sa

HD-2088 sb

HD-2088 sc

HD-2089 Asa

HD-2089 Asa

HD-2089 Asb

HD-2089 Bsa

HD-2089 Bsb

HD-769 a

HD-776 a

HD-777 a

HD-778 a

HD-779 a

HD-780 a

HD-780 c

HD-780 b

HD-781 a

Locality

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

ESF

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

Depth/Distance: m*

3817.20

3817.20

3861.00

3861.00

3861.00

3864.00

3864.00

3864.00

3864.00

3868.80

3887.80

3887.80

3887.80

3887.80

3887.80

3938.70

3938.70

3944.00

3944.00

3944.00

3944.00

3950.70

3950.70

3961.00

3961.00

3961.00

3991.40

3991.40

3991.40

3991.40

3991.40

47.70

92.90

94.80

95.80

97.80

102.90

102.90

102.90

105.90

513-C FOB

-7.0

-7.2

-7.0

2.8

-0.5

-0.6

2.8

3.6

-5.4

2.0

0.3

-7.0

-7.1

1.8

-3.3

1.2

0.9

5.1

-3.1

-5.8

-6.0

-5.8

-2.4

4.4

3.4

4.7

-0.1

-0.5

-5.5

-3.5

-5.8

-7.0

-5.1

6.2

-6.1

-6.7

-6.2

-5.6

-5.2

-4.1

518-0 SMOW

1 8.0

1 8.0

17.5

16.4

16.9

16.5

15.7

15.3

16.9

15.3

15.5

17.0

17.0

15.9

17.6

15.7

15.7

14.7

17.2

17.5

17.4

17.5

16.9

14.6

14.9

14.5

15.7

15.9

17.3

16.5

17.3

18.6

17.7

14.8

17.7

17.8

17.8

16.9

16.0

16.5

36 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations June 1996
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-781 a

HD-783 a

HD-784 c

HD-785 a

HD-786 a

HD-787 a

HD-788 a

HD-790 a

HD-790 a

HD-791 a

HD-791 b

HD-1833a

HD-1834a

HD-1835a

HD-1835a

HD-1644a

HD-1650a

HD-1651 a

HD-1652a

HD-1653a

HD-1654b

HD-1654a

HD-1655a

HD-1655b

HD-1655c

HD-1655a

HD-1656a

HD-1656b

HD-1657a

HD-1658a

HD-1659a

HD-1660a

HD-1661 a

HD-1662a

HD-1663a

HD-1664a

HD-1665a

HD-1666a

HD-1667a

HD-1667b

Locality

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 A-7

UE-25 UZ-14

UE-25 UZ- 14

UE-25 UZ-14

UE-25 UZ-14

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

USWSD-12

Depth/Distance: m*

105.90

108.10

113.00

117.30

124.40

128.80

131.00

140.60

140.60

143.50

143.50

94.10

179.20

246.90

246.90

2.40

22.10

25.80

26.50

28.10

30.20

30.20

32.90

32.90

32.90

32.90

37.90

37.90

42.40

46.60

48.20

48.70

51.40

54.20

57.10

63.70

75.40

77.20

100.90

100.90

513-C PDB

-4. 1

-6.5

-4.5

-4.5

-6.4

-6.9

-5.5

-5.5

-5.5

-6.3

1.0

-4.8

-6.0

6.2

6.8

-7.1

-6.0

-6.2

-5.1

-6.1

-4.3

-3.6

-7.3

-4.5

-6.4

-7.3

-5.4

-6.3

-5.8

-8.0

-7.4

-5.6

-5.0

-5.4

-2.4

-3.9

-7.3

-7.0

-5.2

-5.3

518-O SMOW

16.6

17.8

16.8

17.8

17.6

17.8

17.9

14.8

14.8

17.9

14.0

15.2

16.2

13.2

13.0

20.0

19.7

19.8

19.5

19.8

19.4

19.3

20.0

19.6

19.3

19.9

20.0

19.1

19.1

19.0

19.4

19.0

19.9

19.5

18.7

19.1

18.9

19.3

18.7

18.6

APPENDIX 37
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample #

HD-1668a

HD-1669a

HD-1669a

HD-1670a

HD-1671 a

HD-1672a

HD-1675 a

HD-1675a

HD-1676a

HD-1677a

HD-1677b

HD-1887a

HD-1887b

HD-1888a

HD-1890a

HD-1891 a

HD-1892a

HD-1896b

HD-747 b

HD-1250a

HD-1250a

HD-1251 a

HD-1251 b

HD-1252 a

HD-1252b

HD-728 b

HD-728 a

HD-729 b

HD-730 a

HD-730 b

HD-731 c

HD-731a

HD-731 b

HD-732 b

HD-732 d

HD-732 c

HD-732 a

HD-733 a

HD-733 a

HD-734 b

Locality

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-12

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW VH-1

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

Depth/Distance: m*

132.60

141.80

141.80

146.70

149.30

160.60

223.30

223.30

223.50

282.50

282.50

17.40

17.40

34.00

49.80

94.40

95.20

301.90

563.80

301.90

301.90

346.80

346.80

349.20

349.20

354.10

354.10

356.30

364.40

364.40

370.40

370.40

370.40

372.30

372.30

372.30

372.30

375.80

375.80

379.00

513-C PDB

-3.9

-5.2

-5.2

-4.5

-6.3

-3.6

-4.5

-4.2

-1.7

-0.5

-1.4

-6.9

-6.8

-7.5

-7.3

-7.3

-7.3

-6.7

-0.5

-1.2

-1.2

-1.1

-1.6

0.4

-1.0

-0.7

1.0

-1.3

-2.9

-0.7

-1.5

-4.3

-4.3

-4.5

-2.1

-0.6

-8.0

-0.6

-0.5

-1.8

818-O SMOW

18.3

18.5

18.5

18.3

18.8

17.8

17.3

17.2

16.6

15.9

16.1

20.6

20.6

19.5

20.2

19.1

19.7

17.6

25.5

17.9

18.2

16.3

16.0

15.2

16.0

17.0

13.8

25.1

14.8

15.3

15.3

16.3

17.0

16.9

14.5

15.7

16.6

15.1

15.1

14.8

38 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations June 1996
Appendix 2. Calcite delta carbon-13 and delta oxygen-18 values from secondary mineral occurences within 

the Exploratory Studies Facility (ESF) and drill holes near Yucca Mountain, Nevada (Continued)

Sample*

HD-734 c

HD-734 a

HD-735 a

HD-736 a

HD-736 b

HD-742 a

HD-742 b

HD-743 b

HD-743 a

HD-743 c

HD-744 b

HD-745 b

HD-745 a

HD-747 a

HD-748 b

HD-748 a

HD-748 c

HD-749 b

HD-749 a

HD-749 c

HD-749 c

HD-750 b

HD-750 a

HD-750 d

HD-759 a

HD-759 b

HD-760 a

HD-760 b

HD-761 b

HD-761 a

HD-761 b

HD-763 a

HD-763 b

HD-764 a

Locality

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

USW VH-2

Depth/Distance: m*

379.00

379.00

385.80

388.90

388.90

490.60

490.60

535.10

535.10

535.10

538.30

550.50

550.50

563.80

571.40

571.40

571.40

581.00

581.00

581.00

581.00

595.20

595.20

595.20

854.30

854.30

865.30

865.30

871.50

871.50

871.50

874.60

874.60

897.50

513-C PDB

-1.9

-3.9

-0.8

-4.0

-0.9

-4.1

-2.0

0.8

-0.2

0.4

0.3

-0.1

0.1

0.0

2.5

3.1

1.3

2.8

2.6

0.9

0.9

0.9

1.4

0.0

1.5

-1.9

1.4

-0.6

0.9

-1.9

0.9

-2.2

0.3

0.5

518-O SMOW

14.5

16.4

14.9

16.4

15.0

14.8

13.5

25.7

23.6

24.8

20.4

26.8

24.2

14.2

12.9

12.8

19.2

12.5

12.9

18.8

18.7

12.7

15.5

20.5

4.4

13.0

5.7

9.5

7.2

11.6

7.2

13.0

7.6

8.3

"-Depth in borehole or distance from ESF portal (in meters)

PDB-Pee Dee Belemnite standard

SMOW-Standard Mean Ocean Water standard

APPENDIX 39
Appendix 3. Secondary silica and calcite delta oxygen-18 values from the Exploratory Studies Facility (ESP), drill holes, 

and outcrop samples obtained near Yucca Mountain, Nevada, and from the Bullfrog Mine.

Sample

HD-306c opal

HD-3515 opal

HD-355a opal

HD-356a opal

HD-358a opal

HD-362a opal

HD-929a opal

HD-926a opal

HD-700a opal

349,P2 Cut 1

349,P2 Cut 2*

T- 14 grab, Cut 1

T-l 4 grab, Cut 2*

7, P3, Cut 1

7,P3, Cut 2*

LANL49, PI, Cut 2*

LANL49, PI, Cut 1

HD-577b qtz

HD-590b chal

HD-406b tridy

HD-304c qtz

HD-307b qtz

HD-308a tridy

HD-1497bqtz

HD-1500aqtz

HD-939-l-cqtz

HD-940c opal

HD-941fqtz

HD-941gopal

HD-1184cqtz

HD-1189cqtz

HD-1189dqtz

HD-1191bqtz

HD-1191cchal

HD-270b qtz

HD-1186fqtz

HD-1186gchal

HD-1186hqtz

Lab

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

ASU

uses

uses

uses

uses

uses

uses

uses

uses

uses

uses

USGS

uses

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

Locality

UE-25 a#l

USW G-2

USW G-2

USW G-2

USW G-2

USW G-2

UE-25 a#5

UE-25 a#5

USWG-4

Trench 14

Trench 14

Trench 14

Trench 14

Trench 14

Trench 14

Trench 14

Trench 14

USW G-2

USW G-2

USW GU-3

UE-25 a#l

UE-25 a#l

UE-25 a#l

UE-25 NRG#2

UE-25 NRG#2

Bullfrog Mine

Bullfrog Mine

Bullfrog Mine

Bullfrog Mine

ESF

ESF-6

ESF-6

ESF-8, bag 3

ESF-8, bag 3

USW G-3

ESF-3

ESF-3

ESF-3

Depth (ft)

253

92.2

236.7

240.7

257.8

280.2

92.2

85.2

74.2

4116.4

5635.8

630

780.6

845.6

898.1

187

210.5

958 bench

1024 bench

1042 bench

1042 bench

4803

Tuff Member

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Yucca Mtn

Yucca Mtn

Tiva Canyon

Tiva Canyon

Tiva Canyon

pedogenic

pedogenic

pedogenic

pedogenic

pedogenic

pedogenic

pedogenic

pedogenic

un-named lava

un-named lava

Topopah Spg

Topopah Spg

Topopah Spg

818-OSMOW 

for silica

18.6

26.6

20.5

21.7

24.1

21.2

23.3

21.9

24.1

22.6

27.6

26.1

24.0

22.8

30.9

22.5

31.3

5.9

10.2

11.5

11.3

17.9

12.5

20.8

8.6

5.6

24.8

8.5

21.5

19.4

16.8

14.1

20.7

14.6

6.9

19.0

7.9

20.2

818-OSMOW 

for calcite

16.9

20.7

17.9

19.0

17.4

18.7

17.9

17.7

nocal

20.0

20.0

20.0

20.0

20.0

20.0

20.0

20.0

15.8

5.8

20.1

17.2

16.4

nocal

19.8

nocal

5.8

19.2

5.0

5.0

19.5

19.4

19.4

19.3

19.3

7.5

17.1

17.1

17.1

40 Applications of Isotope Geochemistry to the Reconstruction of Yucca Mountain, Nevada, Paleohydrology Status of 

Investigations June 1996
Appendix 3. Secondary silica and calcite delta oxygen-18 values from the Exploratory Studies Facility (ESF), drill holes, 

and outcrop samples obtained near Yucca Mountain, Nevada, and from the Bullfrog Mine. (Continued)

Sample

HD-1563bopal

HD-1566bopal

HD-1568bopal

HD-1573btridy

HD-1584achal

HD-1667copal

HD- 1678 opal

HD-1679a late opal

HD-1679bmsvchal

HD-1679cmsvchal

HD-1679d milky opal

HD-1679e milky opal

HD-1679f early chal

HD-1680copal

HD-803a tridy

HD-1837e early chal

HD-1 83 8c young opal

H D-l 83 8d late opal

HD-1839b surface opal

HD-1848c surface opal

HD-1848dLNopal

HD-1865b opal bubbles

HD-1865cqtz

HD-1865dLN opal rose

HD-1 865e LN young opal

HD-1870c tridy

HD-1875bopal

HD-1875cqtz

HD-1882a lithophysal qtz

HD-1883achoq

HD-1889a tridy

HD-1893a tridy

HD-1894a early tridy

HD-1894b late qtz

HD-1895a early tridy

HD-1895b late qtz

HD-1896a early qtz

HD-1897aqtz

HD-1 92 la early chal

HD-1922aopal

Lab

USGS

USGS

uses

uses

uses

uses

uses

uses

USGS

uses

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

Locality

USWUZ-14

USWUZ-14

USW UZ-14

USWUZ-14

UE-25 NRG#3

USWSD-12

YM-2-SSL P2

YF-4-SSL

YF-4-SSL

YF-4-SSL

YF-4-SSL

YF-4-SSL

YF-4-SSL

NRST-1-SSL

UE25a #7

ESF 98.8

ESF 11 1.55

ESF 111. 55

ESF 2+88. 19

ESF 358.95

ESF 358.95

ESF 5+3 1.25

ESF 5+3 1.25

ESF 5+3 1.25

ESF 5+3 1.25

ESF 5+88. 15

ESF 382.82

ESF 382.82

ESF 4+73 .4

ESF 4+73.4

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW SD-7

USW SD-7

ESF 10+28.05

ESF 8+22.68

Depth (ft)

29} A

310.1

319.4

1043.6

253.1

331.1

728.5

132

919.8

955.3

955.3

969.6

969.6

990.4

1069.3

Tuff Member

Tiva Canyon

Topopah Spg

Topopah Spg

Topopah Spg

Topopah Spg

Topopah Spg

Topopah Spg

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

TuffX

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

Tiva Canyon

pre Pah Canyon

Tiva Canyon

518-OSMOW 

for silica

20.1

23.4

22.8

14.2

8.4

24.0

27.9

25.7

17.3

10.3

18.5

18.3

11.4

20.3

15.1

13.9

22.5

23.0

26.6

22.3

18.0

23.0

21.2

22.4

19.9

13.5

22.8

21.5

22.8

13.0

8.8

19.7

17.8

19.6

18.7

19.9

20.3

19.0

15.0

23.3

518-OSMOW 

for calcite

16.7

17.2

17.9

14.8

nocal

18.7

nocal

nocal

nocal

nocal

nocal

nocal

nocal

nocal

nocal

19.1

19.5

19.0

18.8

20.2

20.2

20.2

20.2

20.2

20.2

18.6

20.3

20.3

19.9

16.4

nocal

nocal

nocal

nocal

nocal

nocal

17.6

nocal

nocal

18.8

APPENDIX 41