statistical test of reproducibility and operator variance .../67531/metadc... · petrography of...
TRANSCRIPT
LA-1U52-MS
UC-5WIssued: June 1989
LA— 11452-MS
DE89 015327
Statistical Test of Reproducibility andOperator Variance in Thin-Section ModalAnalysis of Textures and Phenocrysts in theTopopah Spring Member, Drill Hole USWVH-2, Crater Flat, Nye County, Nevada
L. M. MooreF.M.Byers,]r.D. E. Broxton
DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsi-bility for the accuracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, or service by trade name, trademark,manufacturer, or otherwise docs not necessarily constitute or imply its endorsement, recom-mendation, or favoring by the United States Government or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of theUnited States Government or any agency thereof.
W OF THiS DQCUMZK7
Los Alamos National Laboratory> Los Alamos.New Mexico 87545
STATISTICAL TEST OF REPRODUCIBILITY AND OPERATOR VARIANCE IN THIN-SECTION MODALANALYSIS OF TEXTURES AND PHENOCRYSTS IN THE TOPOPAH SPRING MEMBER,
DRILL HOLE USW VH-2, CRATER FLAT, NYE COUNTY, NEVADA
by
L. M. Moore, F. M. Byers, Jr., and D. E. Broxton
ABSTRACT
A thin-section operator-variance test was given to the 2 juniorauthors, petrographers, by the senior author, a statistician, using16 thin sections cut from core plugs drilled by the US GeologicalSurvey from drill hole USW VH-2 standard (HCQ) drill core. The thinsections are samples of Topopah Spring devitrified rhyolite tuff fromfour textural zones, in ascending order: 1) lower nonIithophysaI, 2)lower IithophysaI, 3) middle nonIithophysaI, and 4) upper Iitho-physa I. Drill hole USW VH-2 is near the center of Crater Flat, about6 miles WSW of the Yucca Mountain Exploration Block. The originalthin-section labels were opaqued out with removable enamel andrenumbered with alpha-numeric labels. The slides were then given tothe petrographer operators for quantitative thin-section modal(point-count) analysis of cryptocrysta11ine, spherulitic, grano-phyric, and void textures, as well as phenocryst minerals. Between-operator variance was tested by giving the two petrographers the sameslide, and within-operator variance was tested by giving the sameoperator the same slide to count in a second test set, administeredat least three months after the first set. Both operators wereunaware that they were receiving the same slide to recount.
The operator-variance test results presented in this reportindicate that operator differences, in addition to core variation,significantly affect the results of petrographic modal analysis ofthin-section slides. However, variability within operator asmeasured by multiple readings of a slide by the same operator doesnot appear to be a significant component of variation. Thus, it islikely that an individual operator would be able to reproduce point-count results within random error, but these results would probablybe significantly different from those of another operator.
One of the operators (Byers) visually estimated the majortextures and total phenocryst content of the entire 800-ft thicknessof devitrified rhyolite, using about 100 slides, including repli-cates. The estimated data agree qualitatively with the point-countdata. A significant discovery from this work is that, because of
burial below 2500 ft and below the static water level, the TopopahSpring is slightly hydrothermaIly altered with only quartz as thestable silica mineral and also sericitized plagioclase. The top ofthe Topopah Spring is faulted with only about 10 ft of quartz latiticcaprock remaining.
The operator-variance test results and the qualitative evalua-tion of all core available from USW VH-2 indicate, again, thatpetrography of thin sections varies in a consistent manner with zone.However, the results do not suggest the nature of any systematicstratigraphic variation or precisely how an operator's results mightbe used to determine the stratigraphic source of a sample. Signifi-cant variation with depth in zone and small-scale variation within asample may interfere with assessment of stratigraphic position aswell. Further study of petrographic variation with depth orstratigraphic position is suggested.
I. INTRODUCTIONPetrographic modal analysis of thin-section slides has been considered in
investigations of the potential nuclear waste repository site at Yucca
Mountain, Nevada, for the purpose of identifying the stratigraphic position or
zone from which a core sample was obtained (Byers 1985; Byers and Moore 1987).
As a result, investigation of the degree of consistency in modal point-count
results between different petrographic operators is of interest. Petrographic
thin-section categories may include fine or coarse textures, amount of
xenoliths (foreign rock fragments), phenocryst (crystal) assemblage, micro-
cavities characterized by different silica minerals (amygdules), and presence
or absence of granophyre or quartz veinlets. The classification of a point
count into texture or phenocryst categories depends on optical identification
by the operator reading the slide. The primary purpose of this report is to
present the design and initial analyses of an investigatory experiment to test
the consistency of point-count results on a series of slides read by two
operators, F. M. Byers, Jr., and D. E. Broxton, both of the Los Alamos National
Laboratory (LANL).
Although the primary purpose of the experiment was to evaluate differences
in point-count results between Byers and Broxton, it was hoped that additional
information on variation between multiple readings of a slide by the same
operator and variation between thin-section slides would be obtained. A suite
of core samples from drill hole USW VH-2, made available through the courtesy
of J. G. Rosenbaum of the US Geological Survey (USGS), provided a source of new
thin-section slides for analysis by the two operators. However, availability
of the operators during the course of these studies limited the number of
slides for which a complete modal analysis could be conducted. Thus, the
series of slides included in the operator-variance test were selected so that
some information about different potential sources of variability was obtain-
able while recognizing that only a limited number of slides could be point
counted by both operators. After both operators concluded the test series,
Byers qualitatively examined all slides produced from the core samples provided
from the devitrified zones of the Topopah Spring above the basal vitrophyre in
hole USW VH-2 in an attempt to obtain a stratigraphic perspective and a
generalized picture of the overall petrographic variation.
Part II of this report presents further background information on studies
of the potential waste repository at Yucca Mountain, Nevada, on the collection
of core samples used for the present studies and on the geologic setting of the
area involved. Part III provides information concerning slide preparation,
thin-section modal analysis, selection and modal analysis results on samples
used in the test series, and Byers' visual estimates. Statistical analyses of
the results on the test series, discussion of the overall variation in the core
hole on the basis of the visual and modal analyses, and conclusions are
presented in Part IV. This work was sponsered by the Yucca Mountain Project
Office as part of the Civilian Radioactive Waste Management Program. The
Project is managed by the US Department of Energy, Nevada Operations Office.
II. BACKGROUND AND PREVIOUS WORKA. The Potential Site for the Repository
Yucca Mountain, in the southwestern part of the Nevada Test Site and
adjacent area (Fig. 1), is being examined for a possible national underground
nuclear waste repository (Nuclear Waste Policy Act of 1982, Public Law 97-425,
January 7, 1983). The Yucca Mountain area is underlain by a lOOO-ft-thick
candidate host rock, the Topopah Spring Member of the Paintbrush Tuff, in the
lower part of the unsaturated zone, which is slightly less than 2000 ft thick
(US DOE 1986; US DOE 1988).
The Topopah Spring tuff within the Yucca Mountain Exploration Block (YMEB)
consists mainly of about 50 ft of basal vitrophyre (hydrated obsidian with
sparse crystals or phenocrysts) overlain by about 800 ft of devitrified high-
116°45' 116°30' 116° 37° 15
30 MILES 36°
10 15 20 25 30 KILOMETERS
Fig. 1.Index map of Nevada Test Site region, showing location of USW VH-2, otherdrill holes, and the Yucca Mountain exploration block.
silica rhyolite, which would contain the potential mine workings of the under-
ground nuclear waste repository. In outcrop and in drill core this devitrified
rhyolite can be subdivided according to the presence or absence of lithophysae
(small cavities, a few inches to 2 ft in long dimension, created by expanding
gas at time of formation) into four zones: 1) lower nonlithophysaI, 2) lower
lithophysal, 3) middle nonlithophysaI, and 4) upper IithophysaI (Scott and Bonk
1984; Scott and Castellanos 1984; Spengler and Chornack 1984). These zones are
overlain by a relatively thin crystalline zone of vapor-phase crystallization
in turn overlain by a crystal-rich quartz latitic caprock, which together total
about 150 ft in thickness. The four zones, especially the lower three, would
be difficult to identify in drill core or mine workings if the overall
stratigraphic position were unknown, such as when crossing a fault in a
horizontal drill hole or mine drift. Therefore, petrographic thin-section
categories, including fine or coarse textures, amount of xenoliths (foreign
rock fragments), phenocryst (crystal) assemblage, microcavities characterized
by different silica minerals (amygdules), and presence or absence of granophyre
or quartz veinlets, were applied not only to identify the devitrified rhyolitic
zone but also to estimate the stratigraphic position within the devitrified
zone (Byers 1985; Byers and Moore 1987).
B. Source of Core Samples for the Operator-Variance Tests
Early in 1987 a hierarchical variance test was planned to compare two
operators' modal analyses of thin sections (slides) taken from different
stratigraphic levels. The primary purpose of this test was to assess the
extent of agreement between different petrographers' optical identifications of
textures and minerals in thin section for Quality Level I work on samples from
Yucca Mountain. Because no access was permitted to outcrop and drill hole
samples, we obtained a suite of 89 1-in. core plugs of the Topopah Spring tuff
in USW VH-2 drill hole through the courtesy of J. G. Rosenbaum of the USGS.
These samples were collected for USGS paleomagnetic studies following
procedures described in NWM-USGS Technical Procedure GPP-06, R0 (Rock and
Paleomagnetic Investigations) and in Rosenbaum and Rivers (1985).
These 89 core plugs provided us with sufficient samples for the study and
were already shaped for thin sectioning, which not only saved time in drill
core sampling but also saved considerable time in thin-section preparation. An
excellent lithologic log of hole USW VH-2 (Carr and Parrish 1985) was avail-
able, and it was possible from Carr and Parrish's descriptions to infer
contacts between the nonlithophysaI and lithophysal zones. Table A-I in
Appendix A lists the sampling footages corresponding to the 89 core plugs and
indicates the zone that was assessed for each plug based on Carr and Parrish
(1985). Figure 1 indicates the far-field location of core hole USW VH-2
relative to the YMEB, suggesting a potential opportunity to study far-field
lateral petrographic variation of the Topopah Spring. Also, most of the 89
core plugs were collected at approximately 10- or 20-ft-depth intervals,
providing a much closer-spaced vertical sampling interval than that used in
Byers (1985) and Byers and Moore (1987). Study of as many as 89 samples of the
unit from VH-2 would reveal what changes occur within the Topopah Spring
5 miles WSW from the YMEB and in the unit between the unsaturated zone at the
YMEB and the saturated zone in VH-2. Therefore, the Topopah Spring core from
VH-2 was selected both for an operator-variance study and also for an
opportunity to learn more about lateral changes in the candidate host rock.
C. Geologic Sett i nq
The Topopah Spring tuff penetrated in USW VH-2 is deeper than that in any
other hole in the Yucca Mountain-Crater Flat region and is below the static
water level. Drill hole USW VH-2, which was cored to a depth of 4000 ft in the
center of Crater Flat (Fig. 1), is about 6 miles from the nearest core hole,
USW G-3/GU-3, in the YMEB. The original purpose of hole VH-2 was to explore
the possibility of Pleistocene, Pliocene, and latest Miocene silicic volcanic
rocks younger than about 10 million years and to find evidence regarding a
possible caldera under Crater Flat. No post-10-mi11 ion-year-old silicic rocks
were penetrated, only alluvium, minor basalt, and megabreccia that may have
come from Bare Mountain to the west (Carr and Parrish 1985).
Drill hole VH-2 penetrated the Topopah Spring Member of the Paintbrush
Tuff; although minor faults intersected the core, no significant amount appears
cut out by faults (Carr and Parrish 1985). The Topopah Spring was penetrated
from 2550 to 3794.5 ft, a total thickness of 1244.5 ft, with a basal vitrophyre
155 ft thick. These are probably minimum thicknesses, but they are still
greater than those of similar units penetrated in holes within or near the
YMEB. Despite the increases in thickness, one of the petrographers (Byers) was
able to recognize the nonlithophysal and lithophysal zones in the devitrified
rhyolite above the basal vitrophyre from the descriptions of Carr and Parrish
(1985). However, based on thin-section examination, the upper 264 ft of the
Topopah Spring above the upper lithophysal zone is almost all nonIithophysa1
devitrified rhyolite, except for 13.4 ft of crystal-rich caprock zone. This
caprock zone is somewhat less than its true thickness because the top is in
fault contact with the overlying bedded tuff (Carr and Parrish 1985).
III. METHODSA. Slide Preparation
The 1-in. cylindrical core plugs were cut perpendicular to the core plug
axis, and polished thin sections were prepared following LANL QA Procedure
TWS-ESS-DP-04, R4. If a core plug was of adequate length, a second (replicate)
slide was taken at least 5 mm from the first cut. This procedure was adopted
to ensure little or no overlap between samples front the same plug (the largest
texture diameters are about 5 mm for the lithics; most are smaller). The thin-
section slides were labeled with the customary drill hole and footage number,
and replicate slides were, additionally, designated A and B (e.g., VH2-2591.1A,
-2591.IB). The resulting slides are therefore circular and parallel. They are
oriented in a vertical plane, inasmuch as they are cut perpendicular to the
axis of the cylindrical 1-in. core plug, which in turn is horizontal with
respect to the vertical larger-diameter drill core (HCQ - 3.937 in.). (See
Rosenbaum and Rivers 1985, their Fig. 4.) The downward direction was marked on
the core plugs and is marked on the slides in the usual manner described in
Procedure TWS-ESS-DP-04, R4. However, in the statistical tests described
herein, no utilization was made of orientation involving the down arrow. Four
core plugs at -2632.4, -2717.3, -2819.6, and -3327.8 footages were considered
inadequate samples and were not thin sectioned, but the other 85 core plugs
provided 141 thin sections, including replicates. Twenty-nine cores provided
only one slide, owing to insufficient material to provide good replicate slides
of near-equal area, 5 mm or more apart. Table A-I indicates the number of
slides obtained from each of the core plugs.
Table A-II in Appendix A indicates the number of replicate slides and
single slides obtained from the set of core plugs by stratigraphic zone. The
location of the potential waste repository is within the devitrified rhyolite
between the basal vitrophyre and the caprock of the Topopah Spring Member of
the Paintbrush Tuff. Highlighted in caps in Table A-II are the four zones
contained within the devitrified rhyolite: upper lithophysal (UL), middle
nonlithophysal (MN), lower lithophysal (LL), and lower nonIithophysaI (LN).
Because the availability of the operators necessarily limited the number of
slides that could be point counted, it was decided that only slides from these
four relevant zones would be incorporated into the operator-variance test. As
indicated in Table A-II, there were 79 slides (31 with replicates and 17
without replicates) available in these 4 zones. Moore selected 16 slides (2
replicate pairs from each of the 4 zones) for the operator-variance test. It
was expected that the footage reference on a slide could influence an
operator's reading of a slide if he recognized having read the slide previously
or if he had some preconceived notion of the texture composition of a typical
slide from the same zone or near footage. To eliminate this problem, the
footage indications on slides presented to the operators for analysis were
obscured with a removable enamel and numbered with ink on the enamel surface
for reference purposes.
After the operator-variance test, Byers qualitatively examined the 101
slides of the devitrified Topopah Spring above the basal vitrophyre. Thin-
section labels showing depth, however, were visible so that these estimates, to
be discussed further below, are not truly "blind.11
B. Thin-Section Modal Analysis
The petrographic thin-section methods used in counting the different
textures and phenocrysts have been described in an earlier report (Byers 1985).
The methods are in accordance with LANL QA Procedure TWS-ESS-DP-102, R0, dated
February 6, 1987. Paragraph 4.5.2 under Point-Counting Procedures suggests
12 000 total points per slide on a rectangular 3.0- x 2.0-cm slide of the
Topopah Spring tuff in order to obtain 12C points in phenocrysts in a slide
with 1% phenocrysts. This number of points assumes a traverse spacing of 0.5
mm and a point spacing of 0.1 mm, which are the settings on Byers' mechanical
stage. The circular thin sections of the core plugs used for this report are
1 in. or 2.5 cm in diameter, and therefore Byers was able to count 9000 to 9500
points, depending on marginal attrition, based on the above traverse and point
spacing. Phenocrysts usually are one of the lower-percent texture constitu-
ents, so if a slide of the Topopah Spring cuts only 1% phenocrysts, then only
90 to 95 phenocryst point counts would be expected from Byers' point-count
results. Broxton's mechanical stage was set for a point spacing of 0.163 mm
and a traverse spacing of 0.398 mm so that Broxton was able to count 7000 to
7800 points per circular slide used in the operator-variance tests.
In general, two different operators will likely use slightly different
point-count spacings, and thereby the total points counted will vary between
operators. The texture and phenocryst point-count results are presented as
percents of the total number of points counted so as to establish a comparable
scale between operators. It is expected that the total number of points
8
counted is large enough that any effect due to a difference in number of points
counted will be negligible. If this is not the case, then an effect due to
totai points counted would probably constitute an operator effect and
subsequent analyses should detect this.
During the period of time that the operators were point counting the
operator-variance test slides, there was no discussion of the qualitative bases
for identifying texture or phenocryst points. After the conclusion of the test
series, a list of terminology used to describe textures and phenocrysts was
extracted from the operators' lab notebook tabulations of their results. In a
joint meeting between the authors, this terminology list was subdivided into
texture and phenocryst classifications similar to those used in Byers and Moore
(1987). Texture classifications are lithic fragments, granophyre, spherulites/
microlites, cryptocrystaI Iine, voids, veins, calcite, and phenocrysts. Pheno-
cryst classifications are quartz, sanidine, piagioclase, biotite, opaque
oxides, and other mafics and accessories.
Since the two petrographers are colleagues at LANL, it is expected that
through collaborations previous to this test they may have discussed and
established some common ideas for classifying points observed into the texture
and phenocryst categories. This indicates that the results of comparison tests
between these two operators will not necessarily extend to other operators. On
the other hand, Byers has considerable familiarity with textural components
within the Topopah Spring Member based on his early work (e.g., Byers 1985;
Byers and Moore 1987). Broxton has experience in point counting phenocryst
components but was unfamiliar with the classification and analysis of ground-
mass textures within the Topopah Spring Member before this test. Therefore,
this test includes data collected by one experienced operator (Byers) and one
inexperienced operator (Broxton); these differences in previous experience
should probably influence test results more than the previous collaborative
efforts between the two operators. It is emphasized that this operator-
variance test is investigating the potential for different point-count results
by different operators and provides inconclusive results when there is no
difference between operators.
C. Slide Selection for the Operator-Variance Test
In the initial planning stage of an experiment, judgments of potential
sources of effects or variation are made and incorporated into an assumed model
that forms a basis for development of an experimental plan. Consideration of
methods that may be used in the analysis stage is of interest in the design
stage since the experimenter wants to be somewhat assured that the results
provide a sufficient base for evaluating the significance of the model compo-
nents of prime interest. Often the experimenter does not have a clear idea of
what analyses may be of interest and obviously does not know what unforeseen
problems will appear in the experimental results to confound analyses. There-
fore, an experimental plan is usually developed on the basis of both an assumed
model with standard distributional assumptions and an assumed primary purpose
for initial analyses. In this section, the model assumptions, the approach to
obtaining the slides to be read by the operators, and the operators' results
are presented and discussed.
1. Model Assumptions. Given the goals of the operator-variance test,
the following model was assumed for a specified texture percent response, y, as
part of the basis for selecting a sampling plan:
y . . , , = u + o. + z. + P i / . \ + r ,.v + s, , • ,x + e . - , ,J i j k l m ^ i j K k ( j ) m ( i ) l ( j , k ) i j k l m
where
y..k|m represents the m response (from multiple readings) by
operator i on the I slide from plug k in zone j. The effects in the model on
the right side of this equation represent the following:
fi is the mean response;
o. is the effect due to operator i;
z. is the effect due to zone j;
Pk(--v is a component of error due to random plug variation within
zone j;
rm(.. is a component of error due to replicate readings of the same
slide by operator i;
s.,. ... is a component of error due to random slide variation1 (j >KJ
within plug k in zone j; andeijkim 's a component of error due to random variation not
accounted for by the previous effects or components of
error.
Since resources for the operator-variance test include a) the two
petrographers Byers and Broxton, b) two slides, at most, cut per core plug
available from USW VH-2, and c) the previously stated restriction to the four
10
devitrified rhyolite zones (UL, MN, LL, LN), the indices ranges for the above
model description are restricted as follows:
i = 1 (Broxton) or 2 (Byers);
j = 1 (UL), 2 (MN), 3 (LL), or 4 (LN);
k(j); variable with j, is limited to the number of plugs available
within zone j;
1 (j jk) = 1 or 2, variable with plug within zone; andm(i|jjk,l), variable with operator (i) and slide (j,k,l), is
the number of replicate readings of the same slide by operator i.
The classification of effects as either fixed or random implies different
interpretations in the model. A fixed effect is assumed to be a fixed value
component of the model such that whenever, for example, operator 1 reads a
slide, then the mean, fi, is affected by adding the value of ox, the fixed
effect parameter corresponding to the appropriate operator. A random effect is
assumed to be a random fluctuation added into the model generated from a
distribution (usually assumed to be normal) with zero mean and a variance of
a . A random effect on the result will differ from slide to slide with 90% of
the fluctuations in the result due to the random effect being between -(1.96)0"
and +(1.96)a if the fluctuations are normally distributed. All random effects,
including that due to random error, are usually assumed to be independent. A
model with some random effects as well as fixed effects is called a mixed
model. The mixed model analysis of variance problems is usually concerned with
estimating the fixed effects and the variance components of the random effects.
Sear Ie (1971, pp. 382-383) provides motivation for the classification of
the effects used in the operator-variance model as fixed effects or random
effects. The effects due to operator and zone are considered fixed effects
since inferences that may be made from the resulting experimental data will
only pertain to the additive effect due to the particular operator or zones
involved. However, the effects due to plug, slide, and multiple readings are
random effects since these plugs, slides, and readings are assumed to represent
random members of their corresponding populations of possible plugs, slides,
and readings, and inferences from the experimental results will concern varia-
tion in readings due to these components. The components of variance due to
plug, slide, and multiple readings are denoted as follows:
p k ( > ) are independent with mean 0 and variance a ;
s,.. k] are independent with mean 0 and variance a R; and
r ,.s are independent with mean 0 and variance a .
11
Although the operators might be considered representative of petrographers
in general, we did not assume this for two reasons. Since Byers and Broxton
are colleagues, as discussed in the previous section, they are likely not
random representatives of the population of petrographers. Also, the particu-
lar comparison of Byers and Broxton was of interest in that experimental
results concerning operators would provide estimates of differences between
these two particular operators.
Incorporation of the plug and slide components into the model suggests two
sources of variation in slide samples. The slide component suggests a small-
scale variation within a handsample, for example, whereas the plug component
suggests variation on a larger scale of more than 10 or 20 ft. Note that the
assumption of a random plug effect in the model above does not account for the
possibility of a trend with depth in zone. The more restricted model (not
accounting for depth in zone) was assumed since evaluation of a trend with
depth was not the primary purpose of this experiment, and limitations on the
number of slides that the operators could read necessitated limiting the amount
of information that could be modeled. It was expected that, by assuming a
random plug effect, any trend with depth would surface in a significant plug
component of variance and not interfere with assessing the influence of other
effects, such as the operator effect. ;
2. Sampling Plan Development. As noted previously, the number of plugs
and slides that may be read is variable with zone and the number of readings
may be variable with operator and slide. Standard analysis of a mixed effects
model, such as that indicated for the operator-variance test, usually assumes
balanced data are obtained. This required that the number of plugs and slides
read in each zone be the same, but multiple plugs and slides are needed from
some zones to evaluate variation with plug or slide. Thus, the choice of
slides from two plugs per zone was minimal to obtain balance with respect to
plugs and obtain some information about variation within zone on the scale of
more than 10 or 20 ft as represented by plugs. To maintain balance with regard
to slides and obtain some information on small-scale variation (within a
handsample), plugs -from which replicate slides were produced were selected.
Replicate slides from 2 plugs per zone suggested 16 slides (2 pairs of
replicate slides per the 4 zones) be included in the study, and this was the
most that were considered since operator availability required some limitations
to the number of slides to be read.
12
The 16 slides to be included in the operator-variance test were selected
by choosing, randomly, 2 plugs from each zone from among those plugs with
replicate slides. Table A-II indicates that 5 plugs in the UL zone, 10 in the
MN zcne, 6 in the LL zone, and 10 in the LN zone produced replicate slides.
Table A-III indicates the sampled footages from which slides for the operator-
variance test were taken.
In order to obtain information from which to assess the variability of an
individual operator on multiple readings of a slide as well as some information
for operator comparison, each operator needed to read some slides twice as well
as read some slides that the other operator had read. To maintain balanced
data would have required that each operator read each of the 16 slides twice.
Given the limitations on the availability of the operators, 32 readings per
operator seemed excessive, so the balanced design requirement was relaxed.
With four slides per zone, it was decided that each operator would read one
slide twice, two slides once, and one not at all. This meant that each
operator made 4 readings per zone, or 16 readings total. This design ensured
that fixed effects and components of variance could be estimated, although
standard inference capabilities were limited. This seemed to be reasonable
given the amount of time the operators had to conduct modal analyses and the
investigatory nature of this operator-variance test. This design plan does not
preclude the possibility of conducting a follow-up test in which a balanced
data set couId be obta i ned.
Assignment of slides to the operator was random within the constraints of
the design plan (each operator read at least one slide from each plug in the
test). Table A-III indicates the number of times each slide was read by the
operators. The slides were presented to the operators in two stages. In the
first stage, eight slides were presented to each operator with the slide
footages hidden and the reference labels identifying the slides in random
order. When both operators concluded modal analysis of their first eight
slides, the appropriate slides were switched and relabeled again in random
order for presentation to the operators for the final stage of the test.
3. Modal Analyses Results. The results of the modal point-count
analyses of textures and phenocrysts on the 16 slides included in the operator-
variance test are shown in Table A-IV (a) and (b), and the percent of total
counts for textures and phenocryst components are presented in Table A-V (a)
and (b). These tables in Appendix A associate the point counts with the
footage and replicate marks (A or B) of the slide read and in addition
13
identify the operator from which the results were obtained. Additionally, the
zone assignment based on the lithologic log of hole USW VH-2 (Carr and Parrish
1985) is identified in the "True Zone" columns of these tables. While the
footage of the slide, and thus the "True Zone," were hidden from the operators
during point counting, each operator assigned the slide to a zone on the basis
of his point-count results, his limited examination of the thin section, and
prior experience with core from the four devitrified rhyolite zones. These
zone assignments by the operators are listed in the columns labeled "Placed
Zone." The remaining column headings in these tables are self-explanatory.
P. Visual Estimates of Constituents in Thin Section
In order to view the variance tests in strati graphic perspective and to
obtain a generalized picture of the overall petrographic variation, Byers
qualitatively examined the 101 slides, including replicates, that sample the
devitrified zones of the Topopah Spring above the basal vitrophyre in hole USW
VH-2. This petrographic examination consisted of making estimates of the
constituents, following but without consulting the results of the operator-
variance test. Thin-section labels showing depth, however, were visible to the
operator, so these estimates are not truly "blind." The estimates of various
constituents normally counted in the mode were made by viewing the thin section
under the petrographic microscope at low magnifications; namely, 10X and 35X.
The percentages of different textures and total phenocrysts can be reasonably
estimated, but only ranking estimates are made among the different phenocrysts.
Constituents in a few slides of cores from the lower part of the upper litho-
physaI zone are not estimated at all, owing to the introduction of quartz and
recrystalIization.
IV. RESULTS
A. Analyses of Operator-Variance Test Results
Figures 2-14 are graphs of the percent point-count results for each
texture and phenocryst component against the footages of the samples analyzed.
Because each slide was analyzed two times and each footage has two associated
slides, there are four observations at each of eight footages. The observa-
tions at each footage are labeled "F" if Byers was the reader and "D" if
Broxton was the reader. Also, each observation is labeled by a slide number: 1
identifies the slide read once by both operators and 2 identifies the slide
read twice by the same operator.
14
ooo
CDO)CO
So
2.9
3.0
3.1-
3.2-
3.3-
3.4-
3.5
F1
(o D 1
*\D2
rolF?D1
F2
D OF1F2
F1O OD1
OD1
OD2
OjO OF1
F1O
OD2
D20 OD2
F2 F2O O
F2 F2O O
010 OD2
01o
F1O
OF1
O D 1
O D 2
0.0 0.2 0.4
Fig. 2.
0.6 0.8 1.0 1.2
percent lithics
1.4 1.6 1.8
OO
o0
Soo
2.8
2.9-
3.0
3.1- 08 02
0 0 OF1
3.2-
3.3-
3.4-
3.5.
F20 OF2
L/2
01000 OF2
210200 00 F10 2
D1
«>F1 OOF2F2
D1O Fo2
D10 0F1
D20OD2D1O
F2OOF1
01 02o oo
F1OD2
0.0 4.0 8.0 12.0 16.0 20.0 24.0
Fig. 3. percent granophyre
28.0 32.0
Plots of the individual texture and phenocryst content with depth in slidesfrom USW VH-2. Fl-Dl indicates count of same slide by two operators; F2-F2indicates count of same slide by F. Byers, D2-D2 indicates count of same slideby D. Broxton.
15
2.8
2.9
ooo0
BOo
3.0
3.1
3.2
3.3
3.4-
3.5.
F1O D1OOD2 OD2
OD2
OD2
OD1
Dl
D1O
F2O
0 F1OCPF2
D10DF2
D20
F2 F2
D1O (DOD1
D28DF1
D2F 1 O 0 OD2
F1 F 2 , F 2
DIOO cc
O F l
OF1
33.0 40.0 47.0 54.0 61.0 68.0 75.0 82.0 89.0 96.0
Fig. 4. percent spherulites/microlites
ooo
0
#O
o
2.8n
2.9-
3.0-
3.1-
F1 F20 0 OD1
F2
3.2-
3.3-
3.4-
3.5
F1 01O O OD2
F2 F2OOO OD1
Fl
F1OOD2
D2 D2
O <JDF
F2 F10 0 0 OD1
F2
F2 D1O OF2
F1OOD2
OD2
O D 2
O D 2 OD1
0.0 5.5 11.0 16.5 22.0 27.5 33.0 38.5 44.0 49.5 55.0 60.5
Fig. 5. percent cryptocrystalline
16
(100
0
CDO)
foot
*
2.9
3.0
3.1-
3.2-
3.3-
3.4-
3.5
FlO
DlO
OD1
020 OD2
Fl0
F2O OF2
F20OF2
F2O
FlO
OF2
O D 2
Fl Dl
O~ FS0D F2
F1CDD1
O D l
O D l
D20
DZO
D20OD?
D2O
Fl Dl
o o
DZ FT
o o <
0.35 0.55
Fig. 6.
0.75 0.95 1.15 1.35 1.55 1.75 1.95
O D l
2.15
percent phenocrysts
ooo
CDO)COoo
c.o-
2.9-
3.0-
3.1-<
3.2-
3.3-
3.4-
3.5
F2 Dl3 OF2 0 OF1
ID1/ (F l5 O OD2
D2
°2 F10 CfODl
D2
F2 F2000 ODlFl
(DlHF2 OF1
D2OOD2
1
F1O
02O OD2 OF1
F1O ODl
OF2
OD1
I 1
O F 2
1
O D l
1 )0.00 0.15
F ig . 7.
0.30 0.45 0.60 0.75 0.90 1.05 1.20 1.35
percent voids
17
2.8
ooo^,CDCDiSOO
2.9
3.0-
3.1-
3.2-
3.3-
3.4-(
\
\
IF1
I
F1D lF2F2
F l[DllD2
FlD1F2F2FlCO
F1D1F2F2
FlF2F2
F1D1D2D2
3.5.0.00
OD2
D10
Fig. 8.
°O OD1D2O
D1O
0.05 0.10 0.15 0.20 0.25
percent veins
ooo
CDO )CO+-»oo
£..O
2.9
3.0-
3.1-
3.2-
3.3-
3.4-
3.5
I F2
/Dl> OF2
IF1
/D2ID2
L IF1
\)D1)D2(D2i ni
NF1
]F2lF2
D1
| F 1
\°l1 D2
OF2
OF1
OD2 OD2
OF2 OF2
I J
0.00 0.05 0.10 0.15
Fig. 9. percent calcite
0.20 0.25
18
2.9
^ 3.0
ooo
CDO)CO
•i—<oo
3.1-
3.2-
3.3-
3.4-
3.5.
OFl
D2OO OD2
Fi
D10 OF2F2
O) F1
o o
F1o o
D2
F2 D1O OOOF1
F2
F2O OD1
OD1
O F l
O D 2
Or1
0.00 0.05
Fig. 10.
OD1
F10 OD2
0.10 0.15 0.20 0.25
quartz percent of total
0.30
ft)
(100
0
Q>D)frt
foot
.
<£.O
2.9-
3.0-
3.1-
3.2-
3.3-
3.4-
3.5
F1OODt
F1O D2®D2
D18DF1
1
F2 F2O O
OD1
01F1O O
D2 D2 F1O O D1OO
F2F2OO
D7F2OOF2 O O
Fl
1 I
F2 0DF2
D2O O D2
F1 010 O
D1 F1
D2O OOD2
0.0 0.2 0.4 0.6 0.8 1.0
Fig. i i . plagioclase percent of total
1.2
19
ft)
000
tage
oo
CO
2.9
3.0-
3.1-
3.2-
3.3-
3.4-
3.5
Fl F2 F2DlOO 0 O
F2OOF2 DlOOFI
O D1COF1
02 D202
D1OOF1 O 002
F20 OF2
F2 Dl
o a> OFIF2
02 O OD2
1 1
FlO O01
Dl FlO 0
D1OOF1
02O OD2
1 1 1
0.00 0.25 0.50 0.75 1.00 1.25
Fig. 12. sanidine percent of total
1.50 1.75
Ooo
O)CO
•«—>oo
C-.O
2.9-
3.0-
3.1-
3.2-
3.3-
3.4-
3.5
F2• o
F2O
FlOODl
FlO
0F2
002
Fl F2
X
OD2
D2OOD1
F1O
F20DF2
OF2
OFl
F1O
DlO
OD2
F1 Dl0 O
O D 2
1
Dl0
020
02O
010
1 1
02 Dlo o
01o
1 1
0.000 0.025 0.050 0.075 0.150 0.175
Fig. 13. opaques percent of total
20
+_,**~
ooo
0O)COOO
2.8
2.9
3.0
3.1
3.2-
3.3-
3.4-
3.5
F2 F2F 1O 0 OD1
D2D1O 0 OOF1
D2
D1 F2 F2F1O O O O
F1D2O 0 OD2 OD1
F1>D1 0 ©
D2 D2F2
D1OOF1 O OF2
F2 F2
FiO CD 0D1
D2Fit© OD2
J 1 I
O D 1
1 P
0.00 0.05 0.10 0.15 0.20
Fig. 14. biotite percent of total
0.25 0.30
Each texture and phenocryst component percent is analyzed individually by
fitting a mixed model analysis of variance to assess the significant components
of variance and estimate the fixed effects in the presence of the effects
corresponding to the significant variance components. Table A-VI (a) and (b) in
Appendix A lists the estimates of the significant fixed effects and variance
components for texture and phenocryst percents, respectively. Methods of
univariate analysis for a mixed model with unbalanced data are described in
Searle (1971), and the particular approach used in the following analyses is
referred to as the Fitting Constants Method or Henderson's Method 3 (Searle
1971). This method yields unbiased estimates of variance components, but since
the data are unbalanced, the standard distributional assumptions underlying
tests of significance are not valid. Usually a test of significance makes a
comparison between the estimate of the variance component and the error
variance estimate, so in the analyses conducted here a variance component was
judged significant if it was large relative to the error variance estimate. If
a variance component was not judged significant, it was dropped from the model
21
and the alternate model was fit and analyzed similarly. Since the data are
unbalanced, some estimates may change with the order of components in the model
or with exclusion of some components of the model. However, it is noted that
due to some aspects of balance in the data, the estimates of zone effects are
unchanged with model alteration. Since the operators did not read all slides
the same number of times, the estimates of operator effects wiI I change with
exclusion of r ..., or p.,.., or s.,. .., the multiple reading, or plug or sliderail / »UJ HJi")
components of variance. The components of variance estimates associated with
plug multiple readings and slides will be altered if their order is changed in
the model. These differences were taken into account in analyses, so several
model arrangements were considered to ensure that exclusion or inclusion of an
effect or component of variance did not change with these alterations in the
model. The final model contains those effects that wens judged significant,
and estimates are obtained on the basis of this model.
The operator effect is significant in the granophyre, spherulites/
microlites, cryptocrystalIine, phenocryst, and vein texture categories. In
Fig. 3, the graph of granophyre texture percents, it is noticed that Byers'
results on the slides read by both operators are consistently higher. Analysis
indicates an estimated expected difference in operators of about 2 percent
points with Byers' additive effect being higher. The estimated mean granophyre
percent count, across all slides, is 6.1%, with zones as a significant effect
and significant variation attributed to plug and slide as well. The estimated
expected difference between operators in spherulites/microlites texture
percents (graphed in Fig. 4) is about 12 percent points, Byers' percents being
typically higher, with an estimated mean, across slides, of about 835?. Zones
are the only other significant effects indicated by the spherulites/microlites
data. The dominant effect in the cryptocrystalIine results (graphed in Fig. 5)
is operator dependent with Broxton's expected results higher than Byers' by
about 12 percent points. This is significant when considering that the
estimated average percent cryptocrystalIine is about 9%, and no effect due to
zone is indicated. Figure 5, the graph of cryptocrystalIine percents, shows
that Broxton's results are noticeably higher than Byers'. The results for
phenocryst counts indicate significant variation due to plug and slide as well
as zone and operator differences. Figure 6 shows that slide 1 and slide 2
results are set apart one from the other for each plug. With the exception of
the operators' readings on the slide from footage 3137.3, Broxton's results
22
were typically greater than Byers' results with an estimated average difference
of 0.1 percent points relative to an estimated mean phenocryst percent of 1.1%.
In Fig. 8, the graph of the vein-percent results, it is immediately obvious
that Broxton has the only non-zero counts for veins. This is not merely an
artifact of slides read by Broxton since three of the seven non-zero vein
counts are on slides that Byers analyzed as well and two are replicate observa-
tions on slides that Broxton read once as having non-zero vein count. One
slide, from the plug at 3137.3 ft, Broxton analyzed twice with a non-zero vein
count. Since Broxton's counts on veins are low (<0.25%), it is hard to know
how much impact vein count might have on Broxton's strati graphic assessment of
a slide based on modal point counts. However, significant zone differences are
indicated for the vein-percent results with the UL zone having the lowest vein
counts and the LN zone having the highest vein counts. Also, vein-count
variation with plug is indicated as significant.
Plagioclase, sanidine, and opaque oxides are the phenocryst categories
with significant differences between operators. The plagioclase percents,
graphed in Fig. V , differed between operators with an estimated expected
difference of about 0.09%, Broxton's results typically being higher, relative
to an estimated average, across all slides, of about 0.55%. Sanidine percent
counts are graphed in Fig. 12. Byers' sanidine percents were typically higher
by an estimate of 0.06% on average relative to an estimated mean sanidine
percent of 0.40%. The opaque oxide percents, graphed in Fig. 13, differed
between operators with an estimated expected difference of about 0.04%,
Broxton's results being higher, relative to an estimated average, across all
slides, of about 0.05%.
The phenocryst counts are quite low relative to the total count. In the
case of the biotite (graph in Fig. 14) and the other mafics and accessories
categories (graph omitted due to low counts), the counts are not significantly
different from zero with random error variation. However, the other texture
categories do exhibit consistent variation with zone, and for these reasons the
phenocryst categories have been considered in past studies for use in
stratigraphic analysis (Byers 1985; Byers and Moore 1987).
The opaque oxides phenocryst category is the only one, among all texture
and phenocryst categories, in which the multiple reading component of variance
is significant. In this category, the multiple reading component of variance
is significant with an estimate of about 0.016% standard deviation relative to
23
an additional estimated random deviation of about 0.023%. This suggests that
either the operators are generally consistent in their evaluation of texture
and phenocryst categories or their inconsistencies are minor relative to other
sources of variation, sometimes including core variation with different plugs
and si ides.
The results of the plug and slide component of variance study suggest a
high level of variation in the core, possibly with respect to depth in zone but
also on a small scale. Plug and slide components of variation are significant
in granophyre, phenocryst, and calcite texture results and in plagioclase and
sanidine phenocryst results. Typically, in studying Figs. 2-14, one may look
for consistent discrepancies, such as one operator's results are always
somewhat higher than the other operator's or same slide results group away from
the results on the other slide at the same footage. For example, in Fig. 12,
the graph of sanidine percent results, the slide 2 results are typically offset
from the slide 1 results. In the statistical evaluation of the components of
variation for the sanidine texture results, the slide component of variation is
indicated as significant, in addition to the plug component of variation.
Additionally, the plug component of variation is indicated as significant in
the voids and veins texture results and the quartz and opaque oxides phenocryst
results. Further investigations of core variation with depth should probably be
pursued in future studies.
With the exception of cryptocrystalItne texture results and biotite and
other mafics and accessories phenocryst results, texture and phenocryst percent
results were significantly different according to zone. This is consistent
with previous studies (Byers 1985; Byers and Moore 1987), but a means of
determining zone or strati graphic position of a sample on the basis of the
petrographic point-count results is not immediately apparent from these
studies. However, it is noted that the lithic fragments, voids, and calcite
textural percents and the quartz phenocryst percent results (Figs. 2, 7, 9 and
10) do not indicate a significant operator effect. This suggests that operator
readings of these textures and quartz phenocrysts are fairly consistent, and
zone variation may be more clearly detected from these point-count results.
Further study of the nature of core variation with depth as well as a more
comprehensive approach to the use of petrographic point-count results for
strati graphic determination based on the compositional nature of these
multivariate observations should be pursued.
24
The analyses presented here are a first evaluation of the data obtained
from the operator-variance test. One assumption underlying these analyses is a
constant error variance independent of the magnitude of the expected result.
This assumption may be violated if the variation in texture percent increases
with an increase in texture percent. In previous studies such as Byers and
Moore (1985), a transformation of the data was employed to attain the property
of constant error variance. Analysis of transformed data yields estimates that
pertain to the transformed data. Relating these estimates back to differences
in the operators' percent results would then be difficult. Thus, in order to
obtain easily interpretable estimates of the differences in percent results
between the two operators and of the effects of the other factors on the
percent results, no transformations were considered. The impact of these
assumptions should be investigated in future analyses. In addition to
investigation of these arid other model assumptions, alternate methods to the
Fitting Constants Method for estimation of variance components and more
rigorous significance tests for unbalanced data might be considered.
The compositional nature of the results of modal analysis of a thin-
section slide was also not considered in these analyses. That is, since the
texture and phenocryst percents sum to 1OOJS, it may be of interest to consider
a comparison of the relative values of the percent results for the two opera-
tors and different slides. Research in and application of multivariate
techniques for compositional data analysis should be considered for evaluation
of modal analysis results.
B. Qualitative Petrographic Variation with Depth Above the Basal Vitrophyre
The petrographic modal analyses of the variance test and Byers' estimates
of the constituents are inserted at the proper strati graphic position in Table
B-I in Appendix B, which also shows strati graphic position of faults and
textural zones inferred from Carr and Parrish (1985). The graphical represen-
tation of five textural types selected from Table B-I is shown in Fig. 15 and
includes percentages of lithics, granophyre, cryptocrystalIine groundmass,
total phenocrysts, and quartz phenocrysts. These five textural categories were
chosen because they seemed to vary the most with depth of stratigraphic
position within the Topopah Spring.
Eight textural categories including the ones above were used to define
stratigraphic position within and near the YMEB (Byers and Moore 1987). The
three not used in Fig. 15 are spherulites, amygdules filled with Cristobalite
25
DEPTH (It)
2500-
2600-
2700-
2B00-
2900-
3000
3100
3200
3300-
3400-
3500
3600
3700
r
;;i--
~
-
rrrT
;Z.
Z_
:
-
-
;
:•
PRINCIPALZONES
Sampled tootayHS
TOP PAULTED
MIXED ZONE OF
RHYOLITE ANDOOatoQTZ LATITE
coniacl inferredirom petrography
RHYOLITIC ZONEOF VAPOR PHASECRYSTALLIZATIONLITHOPHYSAL INLOWEH PART
UPPER ,LITHOPHYSAL
ZONE ,
MIDDLE 'NONLITHOPHYSAL
ZONE
LOWERLITHOPHYSAL
ZONE
„ „ , LOWERNONUJHOPHYS^i
?ONE
BASALVfTROPHVRE
«-v-PAftTLY WELDE. . . . . . V/ITRIP
NONWELDED.
ZEOL'TJC
% LITHICS
0 5 10 15
O
O(none)
Q
Oa'fTlOBl
none)
. (net
O !ne>
o•oto *oo
«•-(+ Oto o
o 5
o ° o oI *o»: •
OO
o
(VITROPHYRE)
Thin SRCticins ininterval not estifnor counted
5.5-
(
10
3 -a
•
_?__
% GRANOPHYRE (LARGELY MICRO-
t?°°(Jo (
OD
offC£D»*
O
oV
S1
)»4
JTJ)
a>ooo
GRANULAR QUARTZ)
10
O
O
+
th snatea Q
•
+
B m i
20 30
o
me) • 4
(ne)
10
3 O
(3>*»o
y x «j
o • » +o
1
Sx .
3D
° °
8 8» >o • a
0
• f(VITROPHYRE)
Fault or brecciated zone (Carrand Parrish 1965).
Estimated percentage ptot (Byers)
orM Two-operator count ol5 J same thin section
Broxtcn count of same thin sectionat different limes
% CRYPTOCRYSTALLINE(INCLUDES CLAY IN PART)
20 30 40 50
CD
4- (ne)
(ne)
+O
o •
o
° 8n o p° 8 o
oo ° + 8
[VITROPHYRE)
EXPLANATION
x * Byers count of same thin sectionat different times
7 5 -J Estimaled percentage off diagram;i doubled arrow, both estimated off
diagram
(ne) Not estimated, owing to veining andrecrystallization
% PHENOCRYSTS
0.5
OD
o
o
8c
o
1.0
o
8• o
o
» » „o
0 o00
°<&Qb °
? *o
o o
8o
8OQ
8o
o
ocPft
° fi8oa%
1.5 2.0 2 5
8 S ° ^o * #
o °
o
o
o• -IB
(nelO
++
• •
HO+ • •
% QUARTZ PHENOCRYSTS(COUNTED MODES ONLY)
0,1 0.2
Sampled lootages ^
\
none) -
-
none)-
c(none)
-
(xx * :
(none)
' *f + -
»* :
» 4 x :
¥ 4 + :
(VITROPHYRE) (VITROPHYRE)
L1
, Vertical (strat graphic) position otsampled lootages. Most tootages have
1 two thin sections. -A and -B. whichcan only be identified as two similarplots per constituent per footage, butnot as A or -B (See Table B-1).
BASE 3723 It
Thin-section comparison of estimated modal percentages and counted modal percentages within and betweenpetrographers of selected constituents most likely to vary with depth (stratigraphic position) in theTopopah Spring Member, drill hole USW VH-2. The estimates were made on all thin sections above thevityrophyre. Selected petrographer-counted thin sections were estimated percentages made by onepetrographer (Byers) with knowledge of the footage but without access to the modal data.
or tridymite, and voids. The reasons for not showing these three categories on
Fig. 15, other than space, are as follows: 1) Percent of spherulites is
generally the residual or "waste basket" category in a thin-section modal count
and adds nothing that is not shown by variation of cryptocrystalIine and
granophyre textures. 2) Neither Cristobalite nor tridymite was seen in thin
section. Whatever Cristobalite or tridymite may have been present has all
probably converted to the stable phase quartz, and the amygdule fillings are
counted as granophyre. The absence of Cristobalite and tridymite may be
related to the deeper burial of the Topopah Spring approximately 2000 ft
beneath the static water level. 3) Finally, with few exceptions, any voids
that may have been present originally are now filled with quartz, calcite, or
other mineral, probably again owing to deep burial beneath the static water
level. It is approximately at 600-ft depth, based on a measurement in nearby
USW VH-1 (Fig. 1; Thordarson and Howells 1987).
The overview of the results of the operator-variance tests (Fig. 15)
illustrates the following by appropriate symbol: 1) Byers' percentage
estimates of the 101 slides as background; 2) 2 percentage estimates of
constituents in the same slide, one by Byers and the other by Broxton (between
operators); and 3) 2 percentage estimates of constituents in the same slide,
each by Byers and Broxton at different times (within operators). Figure 15
does not distinguish between thin section A and thin section B nor how close
percentage counts agree between A and B, but Table B-I does show these
comparisons. An examination of Fig. 15, however, indicates there are signifi-
cant differences in some petrographic constituents between many sampled
footages, but unfortunately it is not clear whether one could consistently
identify strati graphic position within most of the devitrified Topopah Spring
rhyolitic tuff.
The open circles representing Byers' estimates of thin-section parameters
in Fig. 15 are in general agreement with the "hard" data generated by thin-
section modal counts at 10 different strati graphic levels through the devitri-
fied rhyolite. The worst agreement both between and within operators occurs in
the lowest sample at 3428.6 ft just above the basal vitrophyre. Both A and B
replicates of this sample had significant granophyre and also significant clay
alteration, which overprinted cryptocrystalIine textures related to cooling of
the Topopah Spring tuff at the time of emplacement.
27
About the only criterion that most reliably might indicate strati graphic
position is the recognition of quartz I atitic pumice lenticles within the mixed
zone of rhyolite and minor quartz labite in the upper 100 ft of drill hole VH-2
(Fig. 15). At the bottom part of the devitrif led rhyoiste just above the basal
vitrophyre, proper evaluation of a combination of higher cryptocrystaMine
groundmass, higher quartz phenocryst content, arsd higher iithic content might-
indicate the lower non I ithophysa! zo.:ie (Fig. 15).
A finer-grained middle zone, possibly related to the middle nonIithophysaI
zone, is suggested by cryptocrystai 1i ne values, both counted and estimated,
ranging from 5 to 31% through the uppermost part of the lower IithophysaI zone
and the lower part of the middle noniithophysaI zone (Fig. 15). Within this
increased cryptocrystaJIine zone, however, are two low estimates of crypto-
crysta I i inity just below 3100-ft depth. The general increase in the crypto-
crystalline values in this interval is aiso accompanied by reduced granophyre
values, mostly less than 3%. If this interval is indeed the middle noniitho-
physa I zone, it wouSd be moved downward on the basis of the petrography by
about 50 ft, in comparison to the geologist's contacts (Carr and Parrish 1985,
their Table 2 ) . However, the reverse situation occurs with respect to driil
hole USW GU-3 between the geologists and the petrographer (Byers) in that the
petrographer (Byers and Moore 1987, pp. 28-29, their Fig. 12) picked the lower
contact of the middle noriIithophysa! zone about 50 ft higher than that based on
geology (Scott and CasteManos 1984, p. 99).
In general, both quartz phenocrysts and lithic fragments tend to decrease
upward (Fig. 15) but onfy to the extent that the upper fithophysa! zone and
higher zones might be recognized. A few of the specimens through the upper
part of the devitrified rhyoiite above the middle non!ithophysaI zone do not
fit this trend; this problem emphasizes the need to collect three or more
specimens at any one strati graphic level in order to determine approximate
stratigraphic position.
C. Conclusions and Summary
The operator-variance test results presented in this report indicate that
operator differences, in addition to core variation, significantly affect the
results of petrographic modal analysis of thin-section slides. However,,
variability within operator as measured by multiple readings of a slide by the
same operator does not appear to be a significant component of variation. Thus,
it is likely that an individual operator would be able to reproduce point-count
28
results within random error, bub these results would probably be significantly
different from those of another operator.
The operator-variance test results srsd the qualitative evaluation of a!i
core available from USW Vri-2 indicate, again, that; petrography of thin sections
varies in a consistent manner with zone. However,, the results do not suggest
the nature of any systematic stratigraphic variation or precisely how an
operator's results might bs used to determine the stratigraphic source of a
sample. Significant variation with depth in zone and suiaIi-sca!e variation
within a sample may interfere with assessment of stratigraphic position as
well. Further study of petrographic variation with depth or stratigraphic
position is suggested.
ACKNOWLEDGMENTSDavid A. Mann participated in discussions on how best to cut the thin
sections from the core piugs and provided excellent thin sections of the core.
Anthony T. Garcia and C. James Archuleta prepared the illustrations. Barbara
E. Hahn prepared the typescript and assembled the report following LANL
editoriai and QA procedures. Richard J. Beckman reviewed the manuscript, but
the authors accept fu i ! responsibility for the accuracy of the data and the
interpretations contained herein.
REFERENCES
Byers, F. M., Jr., "Petrochemical Variation of Topopah Spring Tuff Matrix withDepth (Stratigraphic Level), Drill Hole USW G~4, Yucca Mountain, Nevada,"Los Alamos National Laboratory report LA-1O56I-MS (December 1985),HQS.880517.1103
Syers, F. M., Jr., and L. M. Moore,. "Petrographic Variation of the TopopahSpring Tuff Matrix Within and Between Cored Drill Holes, Yucca Mountain,Nevada," Los Alamos National Laboratory report LA-10901-MS (February1987). HQS.880517.2630
Carr, W. J., and L. D. Parrish, RGeology of Drill Hole USW VH-2 and Structureof Crater Flat, Southwestern Nevada," US Geological Survey Open-FileReport 85-475, 41 pp. (1985). HQS.880517.1918
Rosenbaum, J. G., and W. C. Rivers, "Paleomagnetic Orientation of Core fromDrill Hole USW GU-3, Yucca Mountain, Nevada: Tiva Canyon Member of thePaintbrush Tuff,fi US Geological Survey Open-File Report 85-48, 116 pp.(1985). HQS.880517.2846
29
Scott, R. B., and J. Bonk, "Preliminary Geologic Map of Yucca Mountain, NyeCounty, Nevada, with Geologic Sections," US Geological Survey Open-FileReport 84-494 (1984). HQS.880517.1443
Scott, R. B., and M. Castellanos, "Preliminary Report on the GeologicCharacter of Drill Holes USW GU-3 and USW G-3, Yucca Mountain, NyeCounty, Nevada," US Geological Survey Open-File Report 84-491, 119 pp.(1984). HQS.880517.1444
Sear Ie, S. R., Linear Models (John Wiley ft Sons, Inc. New York, 1971).
Spengler, R. W., and M. P. Chornack, "Stratigraphic and StructuralCharacteristics of Volcanic Rocks in Core Hole USW G-4, Yucca Mountain,Nye County, Nevada," with a Section on "Geophysical Logs" by D. C. Mullerand J. E. Kibler, US Geological Survey Open-File Report 84-789, 77 pp.(1984). NNA.870519.0105
Thordarson, W., and L. Howells, "Hydraulic Tests and Chemical Quality of Waterat Well USW VH-1, Crater Flat, Nye County, Nevada," US Geological SurveyWater-Resources Investigations Report 86-4359, 20 pp. (1987).
US Department of Energy, "Environmental Assessment, Yucca Mountain Site,"Vol. I, DOE/RW-0073 (May 1986). NNA.890327.0062
US Department of Energy, "Exploratory Shaft Test Plan," Rev. 1, DOE/NVO-224(January 1988).
30
APPENDIX A
STATISTICAL DATA ON REPRODUCIBILITY AND OPERATOR VARIANCE INTHIN-SECTION MODAL ANALYSIS OF SELECTED SLIDES FROM DRILL CORE OF
TOPOPAH SPRING DEVITRIFIED RHYOLITE, DRILL HOLE USW VH-2
TABLE A-I
SAMPLING FOOTAGES, ASSIGNED ZONES, AND NUMBER OF THIN-SECTION SLIDESCUT FROM USW VH-2 1-in. CORE PLUGS
Samp 1edFootage
25S9.22571.02581.12591.12601 . 82612.42632.426542668.22707.12717.32766.42776.32809.92819.62829.82849.02868 .72879.52889.62899.32909 .52919.22929 .82949.42959.12968.72978.82988.82998.83007.53020.23035.23046.23058.23068.83078.53088.33103.43115.33125.23137.33146.83175.83185.2
Zone*
CR'CR]'CR];CR]CRCR"CRgCRCR'CR'CR:
CRCRCR
L,O
D
kUL "ULULULULULULULULULULULULMNMNMNMNMNMNMNMNMNMNMNLLLLLLLLLLLLLL
SI idesCut
221222012202220112112221112222122222222122121
Samp 1edFootage
3213.43224.23246.23256.53266.83227.03287.13297.53307.53317.53327.83336.13346.43356.73378.43397.23408.03418.53428.13438.73458.63468.73496.73508.83518.83528.73538.83559.23569.63579.63590.53600.53610.5362O.53630.53640.23650.63660.63670.63680.63690.53700.63710.63720.6
Zone"
LLLLLLLLLLLNLNLNLNLN .LN b
LNLNLNLNLNLNLNLNBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBVBV
S1i desCut
21112221202222112211121121122221211222222222
Zone indicators (based on Carr and Parrish 1985):CR: cap rock. Those in brackets proved to be phenocryst poor,
devitrified rhyol ite, based on thin-section examination (Tab IB-I, Appendi x B) .upper Iithophysal.UL:
MN:LL:LN:BV: basal vitrophyre.
Insufficient material prohibited preparing slides from some plugs.
m i ddIe nonI i thophysaI .lower I ithophysal.lower nonIithophysal.
33
TABLE A-II
NUMBER OF REPLICATE AND SINGLE SLIDES PREPARED FROMTHE 89 CORE PLUGS AVAILABLE FROM USW VH-2 BY ZONE
Zone
[CR]ULMNLLLNBV
* [CR]:UL:MN:LL:LN:BV:
Plugs
141311121425
caprockupper 1m i dd1e1ower 1
Two s1i des
105
106
1015
(see footnote,ithophysa1.non1i thophysa1.ithophysa1.
lower noniithophysa1.basa1 v itrophyre.
One siide
2*7b16.3b
10
Table A-I).
Insufficient material or severe fracturing pro-hibited preparation of slides from some plugs.
Zone*
UL
MN
LL
LN
TABLE A-III
OPERATOR-VARIANCE TEST
Samp 1edFootage/SIide
2868.7/AB
2919.2/AB
2998.8/AB
3058.2/AB
3137.3/AB
3213.4/AB
3317.5/AB
3428.6/AB
TimesBroxton Read
0112101212011021
PLAN
TimesByers Read
2110121010211201
UL: upper IithophysaI.MN: middle noniithophysaILL: Iower Ii thophysaI.LN: lower noniithophysa!.
34
Samp 1edFootage
2868.7A2868.7A2868.7B2868.7B2919.2A2919.2A2919.2B2919.2B2998.8A2998.8A2998.8B2998.8B3058.2A3058.2A3058.2B30S8.2B3137.3A3137.3A3137.3B3137.3B3213.4A3213.4A3213.4B3213.4B3317.SA3317.0A3317. SB3317.bP3428.6A3428.6A3428.SB3428.SB
TrueZone
ULULULULULULULULMNMNMNMNMNMNMNMNLLLLLLLLLLLLLLLLLNLNLNLNLNLNLNLN
Operator
22121211122212111211221212221112
PlacedZone
LLLLLLLLLLULULULLNLLLLMNLLLLLNLNLNLLLNLNLLLLLNLNULLLLLLNLNLNLLLN
TotalCount
93009227759692337307938770477114737095119196897075469500735974557223914173437489936688067501930572359074949992517801718174649213
TABLE A-IV(a)
RESULTS: TEXTURE COUNTS
LithicFragments
01212000219021282963203845623848791641143170615512348100
Grano-phyre
531418698937170931117857831372323832363464592852631172147203152564273288804816681575317203460
Spherulites/Microlites
84338343638382144659551345435262668889478550832562168739676352214797848170027032878882286806863961938128815575676866335226368332
Crypto-crystal1ine
1623013770
7836131541890437208146303889198226
1866224436115426111721042636155619386964168
32824480115
Voids
957110045555836281218600063441063740800563129
Pheno-crysts
7993363699921351387597107103779660382843118111726114116466796859132101166177
Calcite
00000071100510000000000000514190000
Veins
000000020000600213016130000180000000
Operator 1 is Broxton; operator 2 is Byers.
00en
SampledFootage
2868.7A2868.7A2868.7B2868.7B2919.2A2919.2A2919.2B2919.2B2998.8A2998.8A2998.8B2998.8B3058.2A3058.2A3058.2B3068.2B3137.3A3137.3A3137.3B3137.3B3213.4A3213.4A3213.4B3213.4B3317.6A3317.6A3317.5B3317.5B3428.6A3428.6A3428.6B3428.6B
TrueZone
ULULULULULULULULMNMNMNMNMNMNMNMNLLLLLLLLLLLLLLLLLNLNLNLNLNLNLNLN
Operator
22121211122212111211221212221112
PlacedZone
LLLLLLLLLLULULULLNLLLLMNLLLLLNLNLNLLLNLNLLLLLNLNULLLLLLNLNLNLLLN
TotalCount
93009227759692337307938770477114737095119196897075469500735974657223914173437489936688067501930572359074949992517801718174649213
TABLE A-IV(b)
RESULTS:
TotalPhenocrystCount
7993363699921351387697107103779660382843118111726114116466796859132101166177
PHENOCRYST COUNTS
Quartz
0001612108213600044621233731116201016
Sanidine
383215204869104110263646202766111732271813467282010633225672
Plagio-clase
376610103081414414985834559352814187373404083824343363468646479
Biotite
3242374532107844202227623634454195
OpaqueOxides
13731271185212116232736184663361115
Other Maficsand Accessories
00000000005400000000000000220060
Operator 1 is Broxton; operator 2 is Byers.
O O O O IO O O O I
I O O (O O I> O O O O (
IOOC0OOC0C0OCMI>»OOOOUJOOOOOOOi o o o r "" "lOOOriONHOOOONOOOOOOO
oooooooooooooodoodoodoooooddoodd
OOOOOOOLOOOUJr-IOOOOOOOOOOOOOCOlOrHOOOOOOOOOO-liHOOOOOOOOOOOOOOOOOOrHCMOOOO
oooooooooooooooooooooooooooooooo
Or-IOOrHOi-lr-lr-li-l<-liHr-l«HOOOOrHWOOf-<r-tOOOO<-<rHCMf-l
tOVHOOIOO)VOO)OOOOOG4r(IOOOOOOOOOOOOOO^TCO
id^-idddddddddddddoooddooodooooooo
TOTA
L
u.o
2 y? S< 0.
(•>
ID
Spt
1o
>o
M
:ro
l i
•
CM <0
tnOVNMMrirlOlCOOVNOia
d<onHHriN<<)Hri
I-111.
35o oI - VJ
IIIa. rsil
C 01
ddddd^
I I I I t I I5li§§I§IIIdddddddd53535335
33S3S300 00 00 00 3v 3) 3 #) 00 00 00 00 00 00 00 00<Dtt)CD(DHHHHQtO)OtOtU}U)U)U) - _ . _ - _ . _ .00 00 00 00 (A 0) Oft Ok Ok Ob Ok Ok 3 O 3 0 H «H <*4 C"J OJ C4 OJ CO CO CO CO * * t" CMCMCMCMCMCMCMCMCMCMCMCMCOCOCOCOn>C9<a<OtOCOCO(0«>CQCOCQ<0(OCOCO
CM
t .
I&o
2.o
37
«m —o
— o<t- «m in3 •
U
OOOOOOMOOOOOOOOOOOOOOIo o oooooooooooooOOOOOOr»(NOOOOOOOOOOOOO_ _oncoogooggogggooooowOOOOOOOOOOVTOOOOOOOOOOOOOI
OOOOOOOOOOUJ^-OOOOOOOOOOOOOOCMCMOOOOOoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
a. x
o o
<o
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xi a:s-t UJ> o.I
< I -(0
UJ >-CO U< OI- Z
UJI0.
is
o uo >-C 0
^•CDC)^COU3^U>< .
OOOOtHOtHi-IOOOOOOOOOOOOOOt-IOOOOOOOt-IO
dodddddddddddddddddddddddddododd
(^* ») ^ ^ f U) 00 J 00 ZJ oi C? 3 00 ^ ^ r 4 ) 9 tr 7* ^ v r 00 ^ ^
^A ^ ^ o^ c ) ^^j a oo ^ ^ oo ^ ) f C J ji v*4 ^ oo M! QO G V ) oo oo ^ ^ ^
OOOOOOOOOOtHoSoOOOOOOOOOOOOOOOOCMO
odododdooododdooooddoooooooodooo
00000000>U>0)CP^-U3<-<'oianoooicioiiDfHNiCO CD *"4 tH f O *H tH US 14} Ok Ok I f l CO CO i
doddddddddddddddddddddi-iddddddddd
ddddddrHiHododdddddoododo'dddodoooo
oooMON«aooNioorioooooia«««oii)Ns««atn
O C3 O >H 00 tH C4 tH C3 00 J T4 CO US 3 O O ^ IA 00 C*l **i M CO CO 4 Ok CO OOOOOOOOOOOOOOOOOOOOOOOOOOOt-!t-ICMtHfH
oooooooooooooooooooooooooooooooo
«o«nnaio)aiooriHoc)«ionY««N«ctr>a>oD««e?NaidHdoH'driHriHiHriririddddrtHddHriddddrirtNri
•P 3o o
SI
«a.ocoP
3 c1- oI— Ml
E oIf) U.I
o•P
o
38
TABLE A-VI(a)
ESTIMATES OF SIGNIFICANT FIXED EFFECTS AND VARIANCE COMPONENTSFOR TEXTURE PERCENTS
Effects/VarianceComponents
V-
°i
°2
Zl
Z2
Z3
Z4
%
ft
a
LithicFragments
0.4847
-
-
-0.4747
-0.2509
0.2766
0.4491
-
-
0.3605
Grano-phyre
6.1034
-1.2263
1.2263
7.4291
-2.6147
-4.6109
-0.2034
3.4195
2.9799
1.7888
Spheru1i tes/Microlites
82.5647
-6.1928
6.1928
-5.6872
5.7978
7.2128
-7.3234
-
_
12.9143
Textures
Crypto-crysta11i ne
9.
6.
-6
10
.4347
.4247
.4247
-
-
-
-
-
-
.6973
Phenocrysts
1.1188
0.0525
-0.0525
-0.005
-0.1725
0.0125
0.165
0.3356
0.3378
0.1041
Voids
0.2406
-
-
0.4931
-0.1731
-0.1994
-0.1206
0.0817
_
0.1551
Veins
0.03
0.0304
-0.0304
-0.0263
-0.0163
0.0413
0.0013
0.0333
_
0.0503
Ca1c i tes
0.0228
-
-
0.0084
-0.0153
-0.0228
0.0297
0.0301
0.0336
0.0188
TABLE A-VI(b)
ESTIMATES OF SIGNIFICANT FIXED EFFECTS AND VARIANCE COMPONENTS FOR PHENOCRYST PERCENTS
Effects/VarianceComponents
/»
°i
°2
zi
Z2
Z3
Z4
^P
ar
°*a _
Quartz
0.0523
-
-
-0.0341
-0.0261
-0.0185
0.0787
0.0298
-
-
0.0350
Plagioclase
0.5470
0.0442
-0.0442
-0.2801
0.0767
0.1065
0.0969
0.1172
-
0.1991
0.0775
Phenocrysts
Sanidine
0.3984
-0.0300
0.0300
0.2996
-0.2042
-0.0408
-0.0547
0.2234
-
0.2063
0.0414
OpaqueOxides
0.0504
0.0176
-0.0176
0.0270
-0.0272
-0.0056
0.0058
0.0161
0.0155
-
0.0234
Other MaficsBiotite and Accessories
0.0548 0.0069
0 .0186
APPENDIX B
PETROGRAPHIC MODAL DATA FOR ALL THIN SECTIONS OF DEVITRIFIED RHYOLITEAND QUARTZ LATITE, TOPOPAH SPRING MEMBER, DRILL HOLE USW VH-2
41
TABLE B-I
ESTIMATED MODES (BY BYERS) OF ALL THIN SECTIONS OF CORES OF TOPOPAH SPRING DEVITRIFIED TUFF ABOVE VITROPHYRE, HOLE USW VH-2,COMPARED WITH COUNTED MODES BY OPERATORS (BROXTON, BYERS) OF UNKNOWN VH-2 THIN SECTIONS SELECTED BY STATISTICIAN (MOORE)
(Footage A and B are replicate thin sections cut at least 5 mm apart from same core plug. Welding zones: pmwt, partially tomoderately welded; mwt, moderately welded; mdwt, moderately to densely welded; dwt, densely welded. Microlitic/spheruliticestimates by difference from 100% Phenocryst estimates qualitative; Plag, plagioclase; San, sanidine; Q, quartz; B, Biotite; Maf,mafic pseudomorph; Cpx, clinopyroxene; Opx, orthopyroxene; A, allanite; opaque oxides not estimated; ne, not estimated)
FootageA & B Welding
Crypto- Microlitic/ TotalLithics Granophyre crystalline Spherulitic Phenocr. Phenocryst* (as percent of whole rock where counted)/
(X) (X) (X) (X) (X) Remarks (e.g., quartz vein lets)
Quartz latitic caprock: (Top of Topopah Spring Tuff, 2E50-ft depth, at fault, 10° dip, Carr and Parrish, 1985.)2659.2A pmwt 0.3 0.0 40 60 7 San>Plag>B>Cpx=: Perrierite. Mixture, rhy. A qtz lat.2559.2B pmwt 0.0 0.0 40 SO 8 San>Plag>B>Cpx=; Perrierite. Mix, rhyolite k qtz lat.
Rhyolitic vapor-phase crystallization zone, with less than 10X lenticles of quartz latite pumice:2571.0A2571.0B
pmwtmwt
2581.1 pmwt
2691.1A2591.IB
2601.8A2001.8A2601.8B2601.8B
2612.4A2612.4B
2654
2668.2A2668.2B
mwtmwt
0.00.1
0.1
0.50.0
53
1.6
1.01.0
0.00.0
0.0
1.01.0
9095
95
9595
2 San>Plag>B. Plag gone. Irregular quartz veinlet.
2.5 San>Plag>=: B>Cpx(?). Plag A Cpx altered k gone.
1.5 San>Plag- B. Plag altered; may exceed biotite.
2.0 San>Plag>B. Plag altered. Flattened vesicles ~2X.1.5 San>Plag2 B>Q. Plag alt. Flattened vesicles ~1X.(2595-2601 ft, several high-angle faults, clay and breccia; Carr and Parrish, 1985.)
mwt 0.0 6 1.0 90 1.0 San^ Plag>B. Quartz latite pumice ~3X.mwt 0.04 7.73 0.94 89.28 1.76 San, 0.96; Plag, 0.61; B, 0.12. (BYERS mode).mwt 0.0 3 3 95 1.0 San=s Plag>8. Quartz latite pumice ~8X.mwt 0.00 0.46 4.43 92.6 2.38 San, 0.76; Plag, 1.31; B, 0.20. (BROXTON mode).
pmwt 0.0 3 3 95 1.0 San=£ Plag>B>alt. mafic. Qtz. latite pumice ~5X.
mwt 0.0 2.6 3.6 90 1.5 San>Plag>B>Q. Quartz latite pumice ~6X.
mwt 0.0 0.6 1.0 96 2.0 San>Plag>B. Quartz latite pumice ~7X.
mwt 0.0 0.5 6 90 1.7 San>Plag>B>Q. Quartz latite pumice ~55t.pmwt 0.1 1.0 1.0 95 0.7 San^ Plag>B>alt mafic. Lithic(?), quartz latite.
Rhyolitic vapor-phase zone: (No quartz latite pumice below 2707-ft depth.)2707.1A2707.IB
2766.4A2766-4B
2776.3A2776.3B
dwtdwt
dwtdwt
mdwtmdwt
0.00.0
0.00.0
0.30.0
2010
106
44
0.00.0
0.0<0.6
<0.5<0.S
8090
9095
9695
0.2 Pfag>San- B. Granophyre veinlets, mostly Q.0.3 San>Plag>B. Granophyre veinlets, mostly Q.
1.0 San- Plag>B. Granophyre veinlets, mostly Q.1.5 San- Plag>B>Q. Smectite-Iined fractures.
0.6 Plag>Sans B>Q. Granophyre veinlet.1.0 San>Plag>B- Q. Granophyre veinlet.
TABLE B-I (cont)
FootageA * B Welding
Lithics
COGranophyre
Crypto-crystalIine
(*)
Microlitic/Spherulitic
TotalPhenocr.
(X)Phenocrysts (as percent of whole rock where counted)/Remarks (e.g., quartz vein lets)
2809.9A mdwt2809.9A mdwt2809.9B mdwt2809.OB dwt
0.20.010.20.00
2.04.972.03.45
1.02.521.03.97
9090.989091.54
1.5 S»n>Plag>B>Q. Clay aggregate ~5X.1.51 San, 0.97; Plag, 0.47; B, 0.01; 0, 0.0 (BYERS).1.2 San>Plag>8 >A(incl. w. Cpx below). Clay agg. ~6%.0.93 San, 0.47; Plag, 0.32; B, 0.01; Cpx, 0.05 (BROXTON).
Upper lithophysal zone: (Byers' interpretation of Cam and Parrish, 1985, drill log.)2829.8 dwt 0.2 1.0 1.0 90 1.2 San>Plag>B>Q. Clay aggregate ~5%.
2849.0 dwt 0.0 2.0 <0.E 90
2868.7A2868.7A2868.7A2868.7B2868.7B2868.7B
2879.5
2889.6
2899.3A2899.3B
2909.6A2909.5B
2919.2A2919.2A2919.2A2919.2B2919.2B2919.2B
2929.8
2949.4
2959.1
2968.7A2968.7B
dwtdwtdwtdwtdwtdwt
mdwt
mdwt
dwtdwt
dwtdwt
dwt?dwtdwtdwt?mdwtdwt
dwt
dwt
dwt
dwtmdwt
0.00.000.010.10.030.01
0.0
0.1
0.00.0
0.06
n*0.030.00ne0.000.00
3
0.0
ne
2.00.3
6.05.714.536.09.1910.15
3
3
65
103
ne23.3933.14ne11.1411.01
<0.S
5
ne
1.01.0
1.01.743.26<0.S4.960.00
1.0
<0.5
0.00.0
0.00.0
ne10.726.63ne21.8712.51
3
10
ne
<0.S<0.S
9090.6890.429084.0388.96
95
95
9090
8590
ne63.7658.73ne
64.4773.97
90
85
ne
9595
1.00.851.010.60.470.39
1.2
2.0
1.01.0
1.01.0
1.0?1.350.982.0?1.921.94
0.8
1.0
ne
0.70.8
2.0 San>Plag>B. Clay aggregate ~5X.
San>Plag>B. Clay aggregate, present.San, 0.41; Plag, 0.40; B, 0.03 (BYERS I mode).San, 0.35; Plag, 0.61; B, 0.02 (BYERS II mode).San>Plag= B. Clay agg. ~5X. Granophyre veinlet.San, 0.20; Plag, 0.13; B, 0.05 (BROXTON mode).
San, 0.22; Plag, 0.11; B, 0.02; Q, 0.01(BYERS mode).
San£Plag>B=; Q. Est. <2X clay agg. Granoph. veinlet.
San>Plag>B>Maf, possibly Cpx.
San>Q(l large)>Plag>B.San>Plag>B- Q. Clay more diffuse ft not in patches.San>Plag>B. Clay agg. Granophyre gash veinets.San>Plag>B>Q. Clay agg. Cognate lithic (Tpt?).
Tuff, fractured, recrystalIized, fcsilicified.San, 0.65; Plag, 0.41; Q, 0.08; B, 0.04 (BROXTON).San, 0.74; Plag, 0.09; Q, 0.01; B, 0.07 (BYERS).Tuff, fractured, recrystalIized, Asilicified.San, 1.48; Plag, 0.20; B, 0.06; Q, 0.03 (BROXTON I).
San, 1.65; Plag, 0.20; B, 0.07; q, 0.01(BROXTON II).
San>Plag>B- Q. Extreme welding like flow banding.
San>Plag>B>Maf. RecrystalIized quartz near fault?
Fractured, silicified; 2mm-wide quartz veinlet.
Sans: Plag>B>Q. Clay agg. ~5X. Cognate I ithic(Tpt?) .Plag>San>B>Maf(Cpx?). Clay aggregate ~3X.
TABLE B-I (cont)
FootageA * B Welding
Lithics
(X)Granophyre
(X)
Crypto-crystal1ine
(X)
Microlitic/Spherulitic
(X)
TotalPhenocr.
(X)Phenocrysts (as percent of whole rock where counted)/Remarks (e.g., quartz vein lets)
Middle nonIithophysal zone:2978.8A dwt 0.12978.8B dwt 0.0
(Byers' interpretation of Carr and Parrish, 1985, drill log.)3 <0.5 95 0.5 Plag>San=* B>Maf(Cpx?). Clay aggregate ~4%.3 <0.B 95 1.5 Plag>San>B. Clay aggregate ~4%.
2988.2988.
2998.2998.2998.2998.2998.2998.
3007.
3020.3020.
3035.3035.
3046,3046,
305830583058305830583058
30683068
30783078
30883088
8A8B
9A9A9A9B9B9B
6
,2A,2B
2A.2B
,2A.2B
.2A
.2A
.2A
.2B
.2B
.2B
.8A
.8B
.5A
.SB
-3A.3B
dwtmdwt
dwtdwtdwtdwtdwtmdwt
dwt
mdwtmdwt
mdwtmdwt
mdwtmdwt
mdwtdwtmdwtmdwtmdwtmdwt
dwtdwt
mdwtmdwt
mdwtmdwt
0.0.
0.0.0.0.0.0.
10
2.0.
0.0.
0,0,
000100
0<0
00
0<0
20
0280900002
.0,0
.0
.2
.0
.0
.5
.16
.08
.0
.39
.85
.0
.5
.0
.0
.0
.5
1.4
2.1.2.2.4.2.
<1.
1.1.
1.4
33
444433
33
11
11
0
0864401663
0
.0
.0
.0
.59
.83
.87
.53
.5
.0
.0
.0
2.<o.<o.5.2.<0.1.3.
<0.
1.2.
<l.<1.
2.1,
1,112<1325
11
65
1030
05
5931955838
5
00
0.0
.0
.0
.0
.58
.08
.0
.07
.02
.0
.0
9595
9590.7594.079592.9892.81
90
9590
9090
9090
9082.3791.999091.9070.03
9090
8585
8565
1.0 Plag=* San>B. Quartz-caIcite veinlets.0.7 Plag>San>B. Clay aggregate present.
1.0 Plag- San>B>Q. Sparse calcite in vert, fracture.1.02 Plag,0.56; San,0.35; B,0.04; Q,0.00 (BROXTON mode).1.02 Plag,0.52; San,0.38; B.0.02; Q.,0.08 (BYERS mode).1.0 Plag>San2 B>Maf (Opx?). Open fract. with calcite.1.18 Plag,0.92;San,0.04;B,0.11;M»f,0.05;Q,0.02 (BYERS I).1.15 Plag,0.93;San,0.07;B,0.08;Maf,0.04;Q,0.01(BYERS II).
0.5 Ptag>San>B>Q. Calcite veinlet, 1 mm wide. Cognate I.
0.5 Plag>San>B=: Q. Calcite veinlet, 0.1 mm wide.0.8 Plag>San=: Q>B. Clay aggregate ~5X.
0.6 PI»g>S»n>B. Clay aggregate present. -1.0 Plag>- San>B. Clay aggregate present.
0.7 Plag>San>B>Q. Clay aggregate present.0.5 Plag>San>B. Clay agg. pros.
0.5 Plag>San>B. Granophyre veinlets. Clay aggregate.1.02 Plag, 0.60; San, 0.27; B, 0.11; Q, 0.04 (BROXTON).1.01 Plag, 0.62; San, 0.28; B, 0.04; Q, 0.05(BYERS mode).0.5 Plag>San>B. Granophyre veinlets. Clay aggregate.0.68 Plag, 0.48; San, 0.08; B, 0.05 (BROXTON mode I).0.51 Plag, 0.38; San, 0.08; B, 0.03 (BROXTON mode II).
0.4 Plag- San>B. Granophyre veinlets. Clay aggregate.0.5 Plag^ San- Q>B- Maf. Granoph. veinlets. Clay agg.
0.5 Plag>San>B. Granophyre veinlets. Minor clay agg.0.5 Plag- San>B>Q. Granoph. veinlets. Minor clay agg.
0.5 PlagK San>B>Q. CryptocrystalIine incl. clay agg.1.2 Plag>San>B>Q. Cryptocrys. includes clay aggregate.
Cn
TABLE B-I (cont)
FootageA A 8 Welding
Lithics
<*)Granophyre
(*)
Crypto-crystal1ine
(X)
Microlitic/Spherulitic
(X)
TotalPhenocr.
(X)Phenocrysts (as percent of whole rock where counted)/Remarks (e.g., quartz veinlets)
Lower lithophysal zone: (Byers' interpretation of Carr and Parrish, 1985, drill log; fault at 3091 ft.)3103.4A mdwt 3 <1.0 <1.0 95 0.8 Plag=^ San>B. Shard walls fuzzy and indistinct.3103.4B mdwt 0.0 1.0 <1.0 95 1.0 Plag>San= B=i Q. Shard walls indistinct as in .4A.
311E.3 mdwt 0.0 2.0 95
3125.2A3125.2B
3137.3A3137.3A3137.3A3137.3B3137.3B3137.3B
3146.8
3175.8A3176.8B
3185.2
3213.4A3213.4A3213.4A3213.4B3213.4B3213.4B
mdwtdwt
dwtdwtdwtdwtdwtdwt
dwt
mdwtmdwt
mdwt
mdwtdwtmdwtmdwtdwtmdwt
<0.5<0.5
1.00.280.420.30.610.69
0.0
0.00.1
1.0
0.50.730.551.01.051.76
<1.1.
1.1.2.<1.0.0.
4
64
5
332<000
00
062340.1027
.36
.91
.5
.56
.78
5.0<1.0
1031.073.95102.103.49
20
<0.6<0.S
2.0
1.01.252.382.05.683.88
9095
8566.92.9095.93.
75
9596
90
959393959091
4178
3690
.83
.44
.73
.77
1.0.
0.0.0.1.1.1,
0,
00
0
000111
08
439470.61.48
.5
.8
.5
.5
.5
.77
.69
.2
.88
.76
3224.2 mdwt <0.6 1.0 3.0 95
0.6 Plag>San>B>Q. Shard walls indist. Clay aggregate.
Plag>S»n>B>Q. Shard walls indist. Clay aggregate.Plag>S»n>B- Q. Granophyre veinlet.
Plag>San>B- Q. Cryptocr. incl. clay agg. Gr. veinlet.Plag, 0.20; San, 0.15; B, 0.00; Q, 0.00 (BR0XT0N).Plag, 0.20; San, 0.19; B, 0.02; Q, 0.04 (BYERS mode).Plag- San>Q>B. Cryptocr. incl. clay agg. Gr. veinlet.Plag, 1.00; San, 0.44; 0,, 0.05; B, 0.03 (BROXTON I).Plag, 0.97; San, 0.36; Q, 0.08; B, 0.03 (BROXTON II).
Plags: San>B>Q. Shard walls distinct. Granoph. vein I.
Plag- San>B. Shard walls not identifiable.Plag- San>B. As above. Typical lower lithophysal.
Plag>S»n>B= Q. As above. Typical lower lithophysal.
Plag>S»n>B>Q. Discontinuous granophyre veinlet.Plag, 0.43; San, 0.19; B, 0.07; Q, 0.02 (BYERS I).Plag, 0.46; San, 0.15; B, 0.07; Q, 0.01 (BYERS II).Plag- SirOBs; Q. Granophyre veinlet.Plag, 1.11; San, 0.61; B, 0.03; Q, 0.03 (BROXTON).Plag, 0.88; San, 0.77; 6, 0.03; Q, 0.03 (BYERS mode).
1.0 Plag- San>Q>B. CryptocrystalIine largely clay.
3246.2
3256.5
(Many fractures from 3223 to 3235 ft, C»rr and Parrish, 1985.)dwt 3 2.0 IS 80 1.2
dwt
3266.8A dwt3266.8B dwt
1.02.0
1.0
36
10
65
85
9085
0.5
0.50.8
Plag>San>B. Cryptocryst. incl. ~l/2 clay.
Plag- San>Q>B. Crypto, incl. clay. Granoph. veinlet.
Plag- San>Q>B. Granoph. v. No clay in cryptocrys.Plag- San>Qs Maf>B. Granophyre veinlets. No clay.
Lower nonlithophysal zone: (Byers' interpretation of Carr and Parrish, 1985; also fault at 3272 ft.)3277.OA dwt 10 3 5 80 0.7 Plag>San>R>B. No clay in cryptocrystalIine.3277.0B dwt 0.5 2.0 10 85 0.5 Plag>San^ Q>B. Granoph. v., 0.1 mm wide, mostly Q.
San>Plag- Q>B. Granophyre v. No clay, see above.Plag- San>B>Q. Granophyre veinlets. No clay.
3287.1A3287.IB
dwtdwt
1.0<0.5
2.04
105
8590
0.80.7
GO
VE
RN
ME
NT
PB
INT
II IG O
FFICE
:
!<bu
t
FootageA * B
3297.6A3297.5B
3307.5
3317.5A3317.6A3317.5A3317.5B3317.6B3317.6B
3336.1A3336.IB
3346.4A3346.4B
3356.7A3356.7B
3378.4A3378.4B
Welding
dwtdwt
dwt
dwtdwtmdwtdwtmdwtmdwt
dwtdwt
Lithics(X)
1.6Z
1.0
1.680.340.00.740.66
1.06
Granophyre(X)
33
6
53.988.8668.596.28
33
Crypto-crystal1ine
(X)
2016
20
57.680.21104.0610.42
2530
(3336-3340 ft, fault zone, Carr and Parrishdwt 1.0 3 20dwt 2.0 3 30
dwtdwt
dwtdwt
2.07
2.6
43
63
630
6060
TABLE B-I
Micro!itic/Spherulitic
(X)
7580
75
9085.6089.578585.8581.80
7060
, 1985.)7566
9060
4636
(cont)
TotalPhenocr.
(X)
1.01.0
0.5
0.7C.910.870.60.610.64
0.71.0
1.00.6
0.61.0
0.51.0
Phenocrysts (as percent of whole rock where counted)/Remarks (e.g., quartz vein lets)
Plag- San>B)Q. Granophyre veinlets up to 0.1 mm wide.San>Plag>Q— B. Granophyre veinlets up to 0.1 mm wide.
Plag— San>B— Q. Granophyre v. No clay, see above.
g^ San>Q=? B. Granoph. v. No clay, see above.Plag, 0.59; San, 0.11, Q, 0.04, B, 0.08 (BROXTON).Plag, 0.47; San, 0.22, Q, 0.08, B, 0.03 (BYERS mode).Plag>San>Q- B. Granophyre A calcite veinlets. Clay.Plag, 0.38; San, 0.10; Q, 0.03; B, 0.04 (BYERS I).Plag, 0.37; San, 0.05; Q, 0.12; B, 0.04 (BYERS II).
Plag=! San>Q>B. Granoph. veinlets. Little or no clay.Plag= San>Q>B. Granoph. veinlets. Little or no clay.
Plag= San>q>B. Granophyre veinlets. No clay,l San>Q^ B. Granophyre veinlets. No clay.
g= San>B. No Q. No clay in cryptocrystalIine.San>Plag>Q>B. Granophyre veinlets. No clay see above.
Plag— San>Q- B. Granoph. veinlets. No clay see above.Plag>San= 0,>B. Granoph. v. No clay in cryptocryst.
(3387-3391 ft, highly fractured, calcite and MnO coated, some breccia, Carr and Parrish, 1985.)3397.2 dwt 3 2 75 20 1.0 Plag>San>Q= B. Granoph. veinlets. No clay, see above.
(3401-3403 ft, highly fractured, calcite and MnO coated, some breccia, Carr and Parrish, 1985.)3408.0 mdwt 4 6 40 60 1.0 PlagK San>q=! B. One granoph. v. No visible clay.
San>Plag^ Q>B. Granoph. veinlets. No visible clay.Plag>San>Q>B. Granoph. veinlets. No visible clay.
Plag^ San>0.~ B. No granoph. veinlets or visible clay.Plag, 0.87; San, 0.42; Q, 0.19; B, 0.06 (BROXTON I).Plag, 0.76; San, 0.31; Q, 0.28; B, 0.06 (BROXTON II).San>Plag>Qs B. No granoph. veinlets or visible clay.Plag, 0.86; San, 0.75; Q, 0.13; B, 0.26 (BROXTON).Plag, 0.85; San, 0.78; Q, 0.13; B, 0.05 (BYERS mode).
(3436-3437 ft, highly fractured and brecciatod, calcite and MnO coated, Carr and Parrish, 1986.)Top of basal vitrophyre, 155 ft thick, at 3438-ft depth (Carr and Parrish, 1985.)
3418.5A3418.SB
3428.6A3428.6A3428.6A3428.6B3428.6B3428.6B
mdwtmdwt
mwtdwtdwtmdwtmwtmdwt
616
60.711.711.00.641.09
31.0
37.374.412.02.724.99
6030
602.1646.702060.021.25
4065
4088.0146.687633.9890.44
1.01.0
1.01.691.411.52.221.92
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