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This is to certify that the
thesis entitled

A Method for Dating
Dating Quaternary Basalts from Hawaii

presented by

Susan C. Schock

has been accepted towards fulfillment
of the requirements for

MMegree in 590109;!

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Date May 5, 1981

 

0-7639

 

 

 

 

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OVERDUE FINES:
25¢ per day per item

 

RETURNING LIBRARY MATERIALS:

Place in book return to remove
charge fraa circulation records

 

A METHOD FOR DATING QUATERNARY BASALTS
FROM HAWAII

By

Susan C. Schock

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Geology

1981

ABSTRACT

A METHOD FOR DATING QUATERNARY BASALTS
FROM HAWAII

By

Susan C. Schock

Uranium-thorium disequilibrium systematics have been used to (k)
quaternary geochronology with speleothems, carbonates and ore bodies.
Presently available techniques for chronology, such as K-Ar, cannot give
ages for complicated stratigraphic sequences. The islands of Hawaii
offered a site where rocks of complicated stratigraphy were uncon-
taminated by continental rocks. These rocks were excellent candidates
upon which to test the application of the uranium-thorium method for
basaltic rocks.

In attempting to apply the principles of the method to basaltic
lavas, problems arose with incomplete silicate dissolution and iron
concentrations, which interfered with the isolation of the uranium and
thorium. Yields of both elements were low, which proved to be devastating
when dealing with rocks with very small initial concentrations of uranium
and thorium. More, complete dissolutions are necessary' and solvent

extractions to overcome the interferences to the method are suggested.

DEDICATION

TO MIKE

ACKNOWLEDGEDENTS

I would like to thank the members of my committee for their review
and advice, Dr. Thomas Vogel, Dr. John Wilband, Dr. William Cambray. I
acknowledge Dr. Russell Harmon whose grant funds partially supported this
project.

Special thanks go the other members of my research group, James
Baranowski and Richard Lively, for their constant help and encouragement
throughout the project. Further thanks to Dr. Carl Seyfert who introduced
me to the world of Geology and Dr. John Murtaugh whose interest,
friendship and advice kept me in graduate school when I wanted to give up.

Thank you to Debra Brock for typing, retyping, and retyping the
manuscript.

Last, but never least, my appreciation to my friends Art Hammonds,
Cynthia Sonich, Mona Zirkes, Lenore McNeal and to my husband, Michael, who

never let me quit and were always there when I needed them.

TABLE OF CONTENTS

INTRODUCTION .
U/TH SYSTEMATICS .

GEOLOGIC SETTING .

THE GEOCHEMISTRY OF URANIUM AND THORIUM IN IGNEOUS ROCKS .

SAMPLE COLLECTION AND PREPARATION.

URANIUM AND THORIUM ISOLATION.

ALPHA COUNTING PROCEDURE .

PROBLEMS OF DATA RESULTS AND CONSIDERATION .

REFERENCES .

APPENDICES

13

17

23

36

. 40

55

LIST OF TABLES

Table 1 - Location Data

Table 2 - Elemental Analyses of Samples Used for Dating by Weight
Percent

Table 3 - Regression Data for Rock 31-8 Phases

18

20

49

Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure

Figure

10

ll

12

13

14

15

16

17

18

19

LIST OF FIGURES

Decay Scheme of the Major Uranium IsotOpes

Typical Isochron Plot

Map of Collection Area

Classification of Volcanic Rocks

Ion Exchange Column Arrangement

Flow Chart of Analysis I

Uranium Procedure II

Thorium Procedure III

Plating Procedure IV

Schematic Diagram of<1 Spectrometer

Plot

Plot

Plot

Plot

Plot

Plot

Plot

Plot

Plot

of

of

of

of

of

of

of

of

of

Magnetite Point for Rock 31-8
Magnetite Points for Rock 31-8
Plagioclase Points for Rock 31-8
Pyroxene Point for Rock 31-8
Whole Rock Points for Rock 31-8
Phases for Aliquot 1

Phases for Aliquot 2

Phases for Aliquot 3

Phases for Aliquot 4

12

26

32

33

34

35

37

42

43

44

45

46

50

51

52

53

INTRODUCTION

In the study of young rock systems, such as Quaternary basalts,
available geochronologic techniques have been unable to help sort out
complicated stratigraphic sequences. The potassium-argon dating methods
for dating young rocks have been found to have large errors due to small
amounts of excess Argon (Damon, 1969; Dalrymple and Lanphere, 1969;
Funkhouser, Barnes, and Naughton, 1966). Also, problems of necessary
analytical accuracy due to the great length of the half-life of 40K and
low 4OAr (rad) factors can cause Quaternary rocks of widely varying ages
to appear contemporary (McDougall, 1961; Ku, 1976).

14C dates are limited to occurrences of carbonaceous materials such
as wood or charcoal, ashfall or tuff in rocks younger than 40,000 years.
The correlation of K-Ar dates with 14C dates have not helped with these
problems.

The purpose of this study, therefore, was to determine if uranium-
thoriuni disequilibrium systematics can be used to date Quaternary
basaltic rocks. The method has been used successfully for sediments,
speleothems, and ore bodies. It has been used for silicic, volcanic rocks
by Baranowski (1977) in Long Valley, California. The uranium-thorium
systematics method is useable for rocks up to 300,000 years old. Previous
work by Baranowski (1977) and Lively (1978) indicate that the most

reliable answers are obtained from those rocks which are between 10,000

and 200,000 years old. Basaltic rocks, especially those composed mainly
of ferromagnesiunlminerals, were expected to present greater problems due
to the fact that their initial content of uranium and thoriunlwould not be
as great as that of the silicic rocks. This proved to be true.

In order to test the validity of this idea, the youngest of the
Hawaiian islands, Hawaii itself, was chosen. The rocks of this island are
uncontaminated with continental rocks. Continental rock sequences would
be more complex in composition since they are accumulated, deposited and
accreted from a wide variety of sources. They tend to contain many more
silicic minerals. The partitioning of uranium into lighter, more silicic
rocks is preferable (Cherdyntsev and Senina, 1970; 1973; Nishimura,
1970). A small amount of contamination from uranium enriched continental
rock would therefore further complicate the chemical processing of the
rock samples. Since rocks which were not subject to this problem were
available in Hawaii, it was the logical choice. Furthermore, the rocks
fall into the chronologic range of the chosen method. Lastly, the flows
chosen for sampling were thick enough that we were able to sample deeply
enough to avoid extensive weathering.

The Kohala volcano, the oldest of the five volcanoes in Hawaii was
chosen for sampling since it has volcanic series which occur within the
range of the uranium-thorium method based on K-Ar dates. These series
have been sampled by Rodd May of the United States Geologic Survey (USGS),
who supplied us with explicit cite information for duplication and K-Ar

comparison dates.

CHAPTER I

U/Th SYSTEMATICS THEORY

For chronologic uses, there are three uranium-thorium decay series;
the 238U series, the 235U series, and the 232Th series. (See Figure 1).
The 238U series is mainly of interest for this study. In a closed
quaternary volcanic system, an initial disequilibrium exists between the
daughter 230Th and its parent 238U. The activity of the thorium gradually
returns to secular equilibrium with the activity of the parent uranium.

The activity change of 230Th relative to 238U is as follows:

 

230Thactivity = 230Thinitial (9XP(‘A 230Tht)) +
r
' 238U . .
238antivity [1 " (”MT 230mm (23 u acil‘flty -1) x
act1v1ty
A
230Th

 

,(1 - (exp(- ABOTh-k 23419:»

A _ A
230Th 234v

where A = decay constant

n
ll

age of the rock

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f.
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m =

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sevnN

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=NNN

 

mmaxmm aan~

Decay Scheme of the Major Uranium IsotOpes

Figurei

When little or no fractionation of 234U relative to 238U occurs, as
is the case in the closed magma system (Somayajulu, et a1, 1966), the
equation simplifies to:

230Th = 230Thinitia1 (eXp(- A230Tht + 238U (1 - (exp(-A23 Tht)))))

0

Dividing through by 232Th:

 

EEEEE = 230Th (exp(-A 230 t)) + 238U (1 - (exp(-X 230 t)))
232Th 232Th Th 232Th Th

Following the method of Allegre (1968, 1976; Condimines, 1976) these
(230Th/232Th and 238U/232Th) are the ratios used to plot the isochron line
to calculate the dates. The 230Th/232Th ratio is the y coordinate. The
y axis is essentially a range of the possible values of initial isotopes
of thorium found for this rock.

The 238U/232Th ratio is the x coordinate. The x axis is the range of
partitioning found for this rock. By plotting the ratios found for the
phases of this rock sample, an isochron line is determined. It's slope is
calculated and then substituted into the equation:

slope = 1 - exp(- A t)
230Th

The slope will vary from O to 1 as a function of time. (See Figure 2). The
line with a slope of 0, a horizontal line, represents the initial ratio of
230Th/232Th. The line with a slope of 1 represents equilibrium. The
isochron should fall somewhere between the initial and equilibrium. By

solving for t as shown above, the age of the rock is obtained.

Allllu

Ehmmmkdmmuv

 

-

q

 

To

 

1,

2b-. a 2.2m

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AthnN\£POmNV

Typical Isochron Plot

Figure 2

The major phases of the rocks were separated and the ratios found
each one. The assumption is made that the initial 230Th/232Th ratios for
the phases are the same since the phases are formed at relatively the same
time and the system has remained closed with respect to uranium and
thorium (Taddeuchi et a1, 1967). 'The 238U/232Thratio iseeffectively that
of the levels U/Th since neither isotOpe is produced by decay within the
range of the method, and therefore the ratio is set by the partitioning of

these elements in the original system (Hurley, 1957).

CHAPTER II

GEOLOGIC SETTING

The Hawaiian Islands are located in the central Pacific Ocean at the
southeastern end of a submarine ridge which begins near Midway Island to
the northwest and stretches in a relatively straight line to the
southeast. The ridge is an example of midplate volcanism, both submarine
and subareal, resulting from the movement of the Pacific Plate over a
stationary hot spot or mantle plume.

The Island of Hawaii, the focus of this study is the largest island
of the Hawaiian chain. It is comprised of five volcanoes, Kohala, Mauna
Kea, Hualalai, Mauna Loa, and Kilauea (See Figure 3).

These volcanoes, as well as the others of the chain, are typically
shieldvolcanoes with summit craters built (n1 fissure systems. The
volcanism here is generally mild eruptions of very fluid, hot basalt.
Such basalt is characteristically of low viscosity and flows easily,
allowing degassing t1) occur at 23 reasonably constant rate (Stearns,
1946).

Hawaiian volcanism generally follows a four stage pattern. Not all
of the volcanoes of the chain have gone through the complete patterns The
first step is the extrusion of highly fluid picritic basalt to form a
shield. All of the volcanoes of Hawaii seem to have gone through this

8

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HUALALN KOHALA MAUNA KEA MAUNA LOA KILAUEA
VOLCANO MOUNTAIN VOLCANO .VOLCANO VOLCANO

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Map of the Collection Area

Figure 3

9

10

stage. Second, a caldera is formed and grabens and cliffs develop along
the rift zones. These cliffs and grabens usually form during a rapid
succession of flows. The Kilauea and.Mauna Loa volcanoes are presently in
this stage. iBoth are still visibly active volcanoes. Third, the calderas
and grabens are filled by a succession of less frequent flows of a similar
basalt. The older volcanoes, Mauna Kea and Kohala, have gone through
this phase and are now dormant or extinct. Hualalai had entered this
phase before its apparent extinctionwwithin.historic time. 'Last, there is
a long period of erosion when the activity ceases and then is replaced by
an onset of more nephelinic flow (Macdonald and Katsura, 1964). No
volcanoes on Hawaii have yet reached this terminal stage of development.

Initially it was the intent of this study to process a suite of
basalts encompassing the major rock types found on Hawaii. These samples
were collected on. two ‘visits in 1977, but analytical. difficulties
precluded work on all but the Kohala samples. Kohala Mountain is the
oldest of the five volcanoes on Hawaii, comprising the northernmost part
of the island. Its surface is dotted with a large number of cinder cones
from its last period of activity. The rocks of Kohala occur in two
volcanic series, both olivine basalts. The oldest series is the Pololu
which is composed of basaltic flows, each from five to twenty feet thick.
They range in composition from tholeiitic basalt to alkalic basalt
(Turner and Verhoogan, 1960). These occur in thinly bedded, highly
vesicular flows which weather to a rusty, reddish-brown (Stearns and
Macdonald, 1948). This series extends from the floor of the sea to as much

as 2000 feet above sea level in some places. There is very little ash

11

found within this series. The Hawi volcanic series is separated from
older underlying Pololu series by an erosional unconformity representing
a period of little or no volcanic activity. It is more massive than the
Pololu series and weathers to greyish soils (Stearns and Macdonald,
1948). Compositionally, the Hawi series is mainly mugearite, an alkali
olivine basalt, and a small amount of trachyte (Turner and Verhoogan,
1960). See Figure 4 for a graphic representation of these rock types.
There is more ash found in this series than in the Pololu which helps to
differentiate them in the field and correlate them stratigraphically. The
last flows of the Hawi are interfingered with and overflown by the
volcanics of Mauna Kea to the southeast. This interfingering is one of
the stratigraphic problems which could be later addressed if the uranium-
thorium disequilibrium dating method shows itself to be viable for
basalts.

The older Pololu series is considered to be of Pliocene age, which
probably began to build up about 0.7 million years ago. The Hawi is
considered to be Pleistocene in age. It probably ceased erupting about
0.06 million years ago (Turner and Verhoogan, 1960). These estimates are

based mainly on K-Ar dates and stratigraphy.

SUBALKALINE ROCKS ALKALINE ROCKS

THOLEIITIC BASALT SERIES ALKALI OLIVINE BASALT SERIES NEPHELINIC.LEUC|TIC
and ANALCITIC ROCKS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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after the Canadian Journal of Earth Science

General Classification of Volcanic Rocks

Figure 4

12

CHAPTER III

THE GEOCHEMISTRY OF URANIUM AND THORIUM IN IGNEOUS ROCKS

Uranium and thorium are radioactive elements of the actinide series
which have isotopes with long enough half lives that they are still
abundant in nature. 238Uranium, the parent of one of the series of
interest in this study, has a half-life of 4.51 x 109 years (Attree et a1,
1962). 232Thorium has a half-life of 1.4 x 1010 years. 235Uranium, which
is not of Special relevance in this study, has a half—life of 7.13 x 108
years (Friedlander, Kennedy, Miller, 1955).

Uranium and thorium exhibit very similar geochemical behavior. The
similarities are due to their outer electron shell configuations. The
ions are similar in size and in the tetravalent form have the same co-
ordination with oxygen. Unfilled second shells in the configurations of
hexavalent uranium, called uranyl ion, and tetravalent thorium allow
their easy participation in chemical reactions. These reactions are
commonly oxidation reactions. The shape of the hexavalent uranyl ion
(U022+) changes to elongate from the spherical tetravalent form. This
ellipsoid with oxygens on the ends is a more soluble fornn The properties
of uranium which differ from those of thorium are due to its inner
unfilled electron shell which can act as valence electrons along with
those the outer shell. This situation in uranium allows it to attain the

hexavalent state by oxidation (Seaborg and Katz, 1954).

13

l4

Thorium occurs naturally as 232Th. This major radioisotope has an
extremely long half life. It is the parent isotope in the decay series
whose final product is 208Pb (see Figure 1). This series undergoes decay
so slowly that for the purposes of Pleistocene chronology, we often
consider 232Th as constant.

230Th, also known as ionium, is a daughter product of the 238U series
whose end member is 206Pb (see Figure 1). It results from the decay of
234U which is in turn a decay product of 238D. 234U can fractionate from
238U during weathering (Cherdyntsev, 1967) due to the easy mobilization
of the easily oxidized hexavalent form of uranium. 230Th has a short
half-life (7.52 x 104 years) making it useful for the uranium-thorium
disequilibrium chronology method.

As described above, the thorium isotOpes are tetravalent and
relatively insoluble ions. 'This prOperty makes it possible to assume that
the abundance of thorium found in igneous rocks is nearly that of the
initial rock (Cherdyntsev, 1968).

The geochemistry of thorium is similar to that of potassium and
frequently thoriunl occurs in. association ‘with potassium. in silicic
igneous rocks (Holland, 1954). The compounds formed in such rocks can
more easily migrate towards the surface during crystallization, taking
the thorium with them. Therefore magmas held in high chambers in the
upper mantle may be enriched upward with respect to thorium (Tatsumoto et
a1, 1965).

Uranium occurs naturally as three isotOpes, 238U with a half-size of

4.49 x 109 years. 235U with a half-life of 7.1 x 109 years, and 234U with

15

a half-life of 2.48 x 105 years (see Figure l).

238U is the most common radioisotOpe and along with 235U accounts for
more than ninety-nine percent of all naturally occuring uranium. The
third, much shorter half—lived isotOpe, 234U, is an intermediate decay
product in the 238U series (Ku, 1976).

Uranium occurs in both tetravelent and hexavalent ion forms. The
tetravalent ion easily oxidizes to hexavalent form is very soluble and
therefore very mobile. This transition from +4 to +6 state occurs easily
under the conditions of the geologic surface or near surface environment
(Kaufman et a1, 1964). Due to the mobility of the hexavalent uranium, it
is difficult to determine the original abundance of uranium in heavily
weathered rocks or those which have been acted upon for long periods of
time by solutions. The uranyl ions are very large and will accumulate
during weathering rather than combining quickly into compounds (Tieh et
a1, 1980). These accumulations are often found as ore bodies.

Uranium and thorium occur in all three major rock types. Their
abundance increases as the rocks become more silicic. The range of
variations of uranium abundances is very large. The average abundance in
continental rocks is approximately 2 ppm. Thorium abundances for
granitic continental rocks can be as high as 10-20 ppm, but decreases in
the intermediate rocks to 2-5 ppm and is only about 0.05 to 2.2 ppm in the
very basic continental rocks (Whitfield, 1958).

The average thorium to uranium ratio for igneous rocks is 3.5
(Rankama, 1954). This is the average of a very large range. Oceanic

rocks, basic rocks, have a low thorium to uranium ratio as stated above.

 

 

ar

th

16

Continental, acidic, rocks can have abundances as great as 8 ppm thorium
and 2 ppm uranium (Cherdyntsev, 1968).

Oceanic crust is usually assumed to be primitive material which
approximates the upper mantle. Its thorium to uranium ratio is about 2.
This ratio results from the fractional melting of basaltic lava in the
upper mantle without fractionating uranium and thorium between the solid
and liquid phases (Rogers and Adams, 1957). This means that abundances of
uranium and thorium do not represent radiogenic components and are true
initial abundances before weathering (Nishamura, 1970).

Accessory 'minerals such as zircon and sphene are ‘usually the
carriers of uranium and thorium. The early forming accessories seldom
have a ratio of 3.5. Their ratio is often about 1. However, in magmas
where accessory minerals have not crystallized, the ratio is found to be
about 3.5, which indicates that the process of formation of accessory
minerals allows for this change in distribution (Adams, Osmond and
Rogers, 1969) to this study that rocks without accessory minerals be used
to determine chronology. The formation of olivine is not a problem with
respect to this situation, since olivine incorporates almost no thorium
and uranium. There is no evidence that any mineral forms from a basic
magma which draws significantly from the original concentrations of
thorium and uranium so that we find a relatively uniform distribution of
these minerals in all the constituent members of the resultant rocks in
intrusive suites. In extrusive rocks, the rapid cooling of the lava

allows the major phases to contain the uranium and thorium.

CHAPTER IV

SAMPLE COLLECTION AND PREPARATION

Samples were collected from the Hawi and Pololu series of the Kohala
mountain volcano. Specific locations are described in Table 1. As often
as possible, an effort was made to correlate samples with those previously
collected by Dr. Rodd May of the USGS Geochemical Division, presently at
Menlo Park, California. His samples were collected for thermolum-
inescence work and K-Ar dating two to three years before the collections
for this study. For several reasons, many more samples were collected
than were used, primarily to ensure that weathering-free samples were
collected at each site. The weathering could be more clearly discerned
after thin sections were made. Also, samples from the four other
volcanoes on the island were collected in case further studies on the
"younger" volcanoes became desirable. At each site collections were made
of fresh 10-15 kg. samples, as free of weathering as possible in order
that the loss of uranium to the weathering process be minimized. Since
uranium is easily oxidized to the +6 Estate and mobilized during
weathering, this problem was avoided as much as possible. Relatively
unweathered samples are needed for processing to obtain.minera1 phases so
that phase isolation will yield as true a representative of the original

as can be obtained. Thin sections were again used to determine what

17

Table 1

LOCATION DATA

Details of locations are noted here in the event that someone
wishes to resample at a duplicated site. I was very grateful to Dr.

Rodd May, USGS for this kind of information.

 

 

 

Sample Number Series and Rock Type Field Location
761231-8 Pololu series Mahukona Quadrangle
tholeiitic basalt 1 mile north of

Mahukona point on
old highway 27 on the
right roadcut going

north
761231-10 Hawi Mahukona Quadrangle
Mugearite in a roadcut 3.8

miles north of Mahukona
point on old highway
27 on right side going

north
761231-12 Hawi Mahukona Quadrangle
Mugearite in a road at 6.7 miles

north of Mahukona point
on the right side of
old highway 27 going
north. This member
appears as a sill about
3 feet above the road

level
761231-13 Hawi Kamuela Quadrangle on
Mugearite highway 27 in the first

roadcut north of Waiaka

l8

l9

phases were present and if any weathering products might interfere with
their isolation.

After the collected rocks were returned to the laboratory, hand
specimens were taken of the samples, and thin sections were made. Most of
the remaining rock was then crushed and pulverized with a Chipmunk Crusher
Pulverizer at McMaster University, Ontario, Canada, then milled to less
than 200 mesh size with a ball mill.

Five grams of whole rock powder in each case were sent to Dr. Robert
McNutt of McMaster University to be analyzed for major elements by x-ray
fluorescence (XRF). This was done both to demonstrate the similarity to
Dr. Mays' samples, and to check the Optical analyses.

Thirty grams of each sample powder were sent to Dr. Hugh Millard of
the USGS, Denver for total uranium and thorium abundance analysis by XRF.
The results of these analyses appear in Table 2. The results were used to
help estimate the amount of sample needed to be processed to get
reasonable counts, and to loosely check the components of the rocks as
determined by thin section analysis.

About 200 grams of whole rock.materia1 were set aside for whole rock
analysis. A portion of the remaining powder was cleansed of clay-size
particles by gravity settling after washing it with water, allowing the
clay particles to remain in suspension and the larger particles to settle
out. Centrifuging was not necessary with these rocks because the phases
were reasonably discreet and of varied enough densities as to allow them
to be separable without it. The clay-size particles were then decanted.

The removal of the clay-size particles was necessary since they inter-

Table 2

ELEMENTAL ANALYSES OF SAMPLES USED FOR DATING BY WEIGHT Z

#761231—8 #761231-10 #761231—12 #761231-13
Sioz 49.01 44.75 49.49 53.94
A1203 13.96 8.88 16.65 17.14
Fe203 14.63 17.45 11.85 10.54
MgO 5.21 17.23 4.40 3.48
CaO 10.00 7.31 10.42 6.38
NaZO 2.74 1.54 3.09 4.24
K20 0.80 0.54 0.95 1.85
Ti02 3.40 1.87 2.92 2.13
MnO 0.20 0.20 0.18 0.20
p205 0.04 0.22 0.05 0.10

analyses by Dr. Robert McNutt, McMaster University, Canada

pmeh 0.58 0.00 1.64 3.79
pme 0.68 0.41 0.59 2.00
Th/U 0.85 0.00 2.62 1.89

analyses by Dr. High Millard, USGS, Denver, Colorado

20

21

ferred with mineral phase separation by clogging the Frantz Isodynamic
Separator and rendering it useless. The large particle fraction was dried
in a drying oven.

Magnetite was separated from the large particles by repeated hand
magnet removal” The product of this removal was washed, settled and dried
again for further purification.

The rest of the large particle fraction was run through the Frantz
Isodynamic Separator several times to isolate the pyroxene, and then the
plagioclase. The pyroxene was magnetic and the plagioclase, which was
virtually non-magnetic, dropped out. The Frantz settings used are listed
in Appendix B.

The separated pyroxene and plagioclase were washed, settled and
dried several more times to remove impurities. The resulting products
were examined optically to insure eighty percent purity or greater. The
only exception to the purity was possibly the plagioclase, whidh was
frequently so finely grained that it retained microscopic particles of
other mineral phases. Other phases were much freer of contamination. The
mineral separates were then dried and weighed. It was decided that ten
gram splits would be analyzed for uranium and thorium. This was decided
because the trial runs of up to 100 grams required prohibitively large
volumes of residue to form during dissolution. Since the mathematics of
the method deal with the isotope ratios within each phase, it is not
necessary to be strictly quantitative with the separations. The
optimization of yields is therefore more important than large volumes of

total.material processed, as long as accurate weighing;of the final amount

22

was done. The yield is the percent of the actual amount of isotope which
is extracted from a given phase by the chemical processing. The way in
which the yield is determined is through the use of a spike of a known
amount of an isotope which is not contained in the sample. The spike is
discussed in Appendix A. After their determination by counting, yields

were normalized to one hundred percent.

CHAPTER V

URANIUM AND THORIUM ISOLATION

The final chemical processing of the prepared powders to isolate
uranium and thoriunlevolved through trials and adjustments. The original
method was patterned after that of Peter Thompson (1973a, 1973b). As the
work proceeded and problems arose, alternatives were sought. .A flow chart
of the final process appears in Figures 6-9 at the end of this section.

The magnetite phase was taken into solution with about 100 mL of
hydrochloric acid (HCl) on a stirrer overnight. The result was complete
dissolution. The solution was then taken to dryness on a hotplate and
then redissolved in concentrated nitric acid (HNO3) and diluted with
enough deionized water to make a 4N solution.

Ten to fifteen grams of whole rock sample or silicate mineral
separate was digested with 50 mL of concentrated hydrofluoric acid (HF).
Sample and acid were fumed on a hot plate in a covered 250 mL teflon beaker
for twelve hours. Due to the residues which formed about the lip of the
beaker and the rim of the cover plate, it was feared that uranium was being
lost as a volatile fluoride compound. The probability was confirmed by
discussions with members of the Chemistry faculty.

Consequently, a fusion with sodium carbonate flux was done. The
sample powder was ground to less than 200 mesh, mixed with ten parts flux

to one part sample, and then divided into ten gram splits and placed in

23

24

platinum crucibles in a muffle oven at 850°C for eight to twelve hours.

The fusions should have produced an easily dissolved product. This
was not the case, however, and insoluble residues recurred over the course
of two to three refusions. These residues were finally subjected to
hydrofluoric acid fuming. After the dissolution had been achieved, the
solution was taken to dryness on the hotplate while still in the teflon
beaker. The resulting product was taken into solution with 4N nitric
acid. If residues were left behind, as they often were, they were
filtered or centrifuged off, dried and fused once again” The solution.was
then added to the original dissolution volume in a 4000 mL pyrex beaker.

After the sample was totally in solution, 2 mLs of a dilute spike of
known uranium and thorium isotopic content was added. The spike is
discussed in Appendix A. “The volume of dissolved sample at this point was
usually slightly less than 2000 mL. The volume was raised to 2000 mL with
4N nitric acid. Also added at this point were forty mL of a solution of
250 mg lanthanum oxide, 5 mL HClO4 and 5 mL HNO3, whose purpose it was to
carry the thorium with it through a later step, preventing it from
combining into insoluble products.

The spike and lanthanum oxide were stirred into the sample solution
and allowed to equilibrate for at least 24 hours. The use of magnetic
stirring equipment shortened the time rmmessary for equilibration to
about twelve hours.

After equilibration was achieved, concentrated ammonium hydroxide

(NH4OH) was added, slowly, through a glass funnel while stirring

25

with a magnetic stirrer. This caused the precipitation of iron hydroxide
at precisely the point when a pH of 7 was reached. This reaction was
extremely exothermic, and the addition of the NH4OH had to be done slowly
or spattering and even breakage of the container could take place. The
precipitated iron hydroxide carried the uranium and thorium with it.
Unfortunately aluminum and manganese were also carried along. These
elements complicated later steps.

In an attempt to remove the aluminum, a hot sodium hydroxide wash was
done (Kaufman, 1964). Uranium loss caused the abandonment of this step.

In a later ion exchange stepito overcome the aluminum problem, longer
columns of greater diameter, and therefore greater resin capacity were
used. The individual columns available were not long enough to allow the
alumnimum to be taken up by the resin and still to have sites left for the
uranium. To overcome this problem, two columns were mounted, one above
the other, and the solution not taken up by the first was allowed to pass
directly into the second below it. (See Figure 5).

After the iron hydroxide precipitation step, the precipitate was
next dissolved in 9N hydrochloric acid (HCl) (after Thompson, 1973) and
the resulting solution purged of iron by extraction with isoprOpyl ether.
This was done by putting 75-100 mL of sample solution and an equal volume
of isopropyl ether into a 250 mL separatory funnel and vigorously shaking
them for several.minutes being careful to aspirate the pressure created by
agitating the mixture, at 30-60 second intervals. The iron was reduced
and taken in the ether, which was then allowed to stand for several

seconds to gravity separate from the solution. The ether and iron were

7 4”, stopper

4,...— ion exchange resin

 

. 4.... glass wool
‘<—— Parafilm wrap

 

 

 

 

 

 

é— ceilectlon beaker

 

 

 

 

 

J O

 

L

 

Ion Exchange Column Arrangement

Figure 5

26

27

then discarded. This procedure was repeated until the ether no longer
took on a yellow color after agitation or until no further change of color
to the sample indicated that no more iron.was being extracted. 2H:did not
mean, however, that there was no more iron in the sample solution. In
basic rocks, like the Hawaiian basalts, later steps yielded enough iron to
interfere with the alpha counting process. Since this iron was not
available for reduction in the ether extraction step, it must not have
been existing as free ion in solution, and therefore could not be reduced
and extracted.

After ether extraction, the sample was gently heated.on.almotplate to
drive off the remaining ether. Then the solution was fed onto an anion
exchange column of Dowex AGl-X8 Resin which had already been conditioned
to the chloride form with 9N HCl. The column was then rinsed with about
30 mL of 9N HCl. The uranium remained on the resin column at that time.
The fluid that passed through the column contained the thorium and was,
therefore, retained in a vycor beaker. Vycor was used for this part of the
procedure since it is made of a high silica glass and the uranium and
thorium were less likely to be lost to adsorption on the beaker.

At this point it was important to note the time when the uranium was
separated from the thorium. Thorium228 is produced in both the decay of
uranium232 and thorium232. Therefore, it is necessary to include a
correction for the change in the thorium228 contributing factors after
separation when doing subsequent calculations.

Uranium was eluted from the ion exchange column with 100 mL of 0.1N

'HCl into a separate vycor beaker.

28

The thorium bearing fluid was fed onto an anion exchange column which
had been conditioned to the nitrate form with 8N HNO3. The thorium was
taken onto the resin column. After rinsing with 30 mL of 8N HN03, the
waste was discarded and the thorium eluted with 100 mL of 0.1 N HNO3 into
a vycor beaker. There was discoloration of the resin and loss of flow
through the column.

An anion exchange column, conditioned with a solution of 5 mL of 5N
HNO3 and 45 mL of methanol was used to isolate the thorium after Tera et
a1. (1961). The fluid left behind after the separation of the uranium*was
evaporated to dryness on a hotplate and then brought back up in 5 mL of 5N
HNO3. It was added to 45 mL of methanol. This solution was immediately
fed onto the HNO3-methanol column. After rinsing with another 30 mL of
90% methanol solution and discarding the passed fluid, the thorium was
eluted with 100 mL of 0.1 N HNO3. The resultant thorium yields were not
high, but were better than those previously obtained. The interference
from elements or complexes not removed in earlier steps caused the resin
sites to be occupied before the thorium was taken up completely. Pro—
hibitively large amounts of resin would have been needed to correct this
problem, if indeed it could be corrected. The use of consecutive columns,
as used before, still did not alleviate the situation.

Personal communication with Dr. Allegre and Dr. Condomines from
Paris, France led to another change which is described here and was
incorporated into the final process. The early steps of the adapted
Thompson method remain the same until the filtering of the iron hydroxide

precipitate. At that time a plastic funnel was substituted for the glass

29

one for filtration. The precipitate was then dissolved with 100 mL of
concentrated hydrofluoric acid into a teflon beaker. This solution
contained the uranium and iron. The white residue left behind in the
filter paper contained the thorium and lanthanunn Again, the time of the
separation of the uranium and thorium was noted in order to correct the
thorium228 value.

The uranium bearing hydrofluoric acid solution in a covered teflon
beaker was evaporated to half its original volume. About a teaspoon of
boric acid powder was added and the solution raised to 100 mL with
concentrated nitric acid, thereby yielding soluble nitrates rather than
insoluble fluorides. This solution was evaporated to dryness on a
hotplate. The residues that were left were wetted with a few dr0ps of
concentrated nitric acid and once again evaporated to dryness. This step
was repeated twice more to insure that all the residues were in a soluble
form.

Next, the residue was taken into solution with 9N HCl and this
solution extracted for iron as previously described. Once the iron had
been removed and the ether driven off, the uranium bearing solution was
run on a 9N HCl anion exchange column and eluted as described before. The
final uranium bearing solution was evaporated to dryness in a vycor
beaker, covered and set aside until the final steps were performed. The
amount of occurring uranium isotopes were not changed with respect.to each
other over the time they were held. The thorium on the other hand, was

subject to change, making it important to process it first.

30

The thorium bearing residue left behind in the filter paper in the
plastic funnel was treated with concentrated nitric acid to liberate the
thorium. After this acid drained into a teflon beaker, the residue was
rinsed again with 5N HNO3 into the same beaker to free any remaining
thorium. Tflngel remaining in the filter paper was discarded after it was
found to be mainly aluminum by XRF analysis. The acid containing the
thorium was evaporated to dryness, then the residue brought up in 5 mL of
5N HN03, and added to 45 mL of methanol. This solution was processed on
a 90% methanol column as described before. The resulting elutate was
evaporated to dryness in a vycor beaker.

The thorium was brought back up in a small amount of 8N HNO3 and
reevaporated. Then about 2 mL of 0.1N HNO3 acid were added. The pH of
this solution was checked to determine if it was 1.2. ‘If not, it was
adjusted using more 0.1N HNO3 or dilute NH4OH as needed. The method
available for this check.was pH paper, which was a source of gross error.
The acid was then transferred to a test tube and 2 mL of triethylene-
tetraamine (TTA) and benzene solution added to it. These liquids were
mixed on a test tube mixer for several minutes to extract the thorium into
the organic phase. The tube was centrifuged briefly to separate the acid
and organic phases. Then the organic upper layer was carefully drawn off
with a disposable pipette, being careful not to take up any of the acid
phase. The organic phase was placed in a 10 mL beaker. This extraction
step was repeated several times to assure complete extracthma. The
organic phase was then evaporated to a small volume (about 1 mL) and drawn

up into a warmed, clean disposable pipette and evaporated a drop at a time

31

onto the center of a stainless steel planchette. The planchette was then
heated to a dull red over a Bunsen burner flame to drive off the organics
and any interferring 0235 which may have been present. .After'it was cool,
the disc was counted as described in the next section” Thorium discs were
counted first beginning as few minutes as possible after separation from
uranium to minimize the Th228 correction needed. The uranium residue was
raised in 0.1N HNO3, as was the thorium, but the pH was adjusted with
dilute NH4OH to 3.4. The acid was then transferred to a test tube and 2
ad“ of TTA.and benzene added. The same procedure used before was followed
here except at the higher pH with several extractions, evaporation and
transferral to the stainless steel planchete.

Anywhere along the way in the process after the first ether
extraction, if there appeared to be a great deal of iron in the sample, it
was possible to take the solution to dryness, raise it in 9N HCl and ether
extract again, then pick.up the procedure at the point it had reached when
the iron had become apparent.

All evaporations, precipitations and platings were done in fume
hoods to prevent the inhalation of fumes.

A flow chart of the procedure appears in Figures 6-9.

FLGii CHART 0F AllALYS IS I

 

IWEIGHED SAMPLE]

L

IFLUXADDED]

 

 

FUSION

 

, l
[RESIDUES]

IDISSOLUTION I-—--'
I

ISPIKE ADDITION ANDI

 

 

LANTHANUM OXIDE
l ,
lEQUILIBRATIONI

_ I ,
lPRECIPIlTATIONI

 

 

WITH NHQOH

 

 

SETTLIING OF
PRECIPITATE

 

IFILTER PRECIPITATEI

[Ti
DISSOLUTION WITH HFJ

 

 
 

 

III

, THORIUM 3
(IN RESIDUE)

II

 

 

URANIUM
(IN SOLUTION)

 

 

Figure 6

32

URANIUM PROCEDURE II

 

[URANIUM SOLUTION]
. r 2 *
IEVAPORATIONI

|80RIC ACID]

1

[ADDITION OF HN03|

[EVAPORATIONI

[ADDITION OF HCLI

[EVAPORATION]

 

 

 

 

 

 

I 9NHCLI

l

[ANION EXCHANGE C0LUMN|

l

IELUTION]

L

[EVAPORATIONI

|(IR0N) ETHER EXTRACTION |

lEVAPORATIONI

L
IPLATIN6(IV)]

 

 

Figure 7

33

THORIUM PROCEDURE III

ITHORIUM BEARING RESIDUEI-

I ,
DISSOLUTION]
_ I -

IWASHING]
j

[EVAPORATION]

. I
[HN03 AND METHANOL ADDITION]

l .
[ANION EXCHANGE COLUMN]

I
[ ELUTION]

I .
[EVAPORATION]
I ,

[(IRON) ETHER EXTRACTION]
LI _
[EVAPORATION]
l ,
[HN03 DISSOLUTION]

- I -
[EVAPORATION]

. l -
[PLATING(IV)]

 

 

 

 

 

 

 

 

 

 

 

 

Figure 8

34

PLATING PROCEDURE IV

 

[DISSOLUTION]

lpH ADJUSTMENT]

I -
[TIA ADDITION]...

 

 

 

 

 

[ CENTRIFUOE] REPEAT

l _
[DRAW OFF ACID

.1

I EVAPORATI ON I

PLATING ONTO
PLANCHETTE

[ COUNTING]

 

Figure 9

35

CHAPTER VI

ALPHA COUNTING PROCEDURE

Once the stainless steel planchettes ‘were prepared, they' were
counted on an.ORTEC Ca-070-950-100 Spectrometer. (See Figure 10). This
is a surface-barrier semi-conductor detector which is a solid state
instrument which affords high resolution” The spectrometer provides a 0-
10 volt linear signal which is sent to the vacuum chamber containing the
sample. The sample planchette is mounted on a holder inside the detector.
It is important that the area of the planchette containing the sample be
centered as well as possible on the holder to optimize the geometry. The
detection chamber is cooled with dry ice to maintain low backgrounds which
are due to buildup of contaminants from alpha recoil nucleii. As was
mentioned before, background was measured throughout the data acquisition
period by counting blank planchettes over the same channels as had been
determined for the isotopes of interest.

The signal from the detector is passed through a pre-amplifier and an
amplifier and then onto a multichannel analyzer (MCA). After at least
twenty four hours, the spectrum gathered for a planchette was counted over
the channels corresponding to the various isotOpes of interest. The raw
counts, time and correlated background values were then entered into data

sheets to be used with the computer program in Appendix E.

36

Figure 10

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j

nth—1033.“.

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- ammzazu
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maoum_33_umo
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_\ _ _. _ - az<nmma
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szz<zou_eoaz_. — omm<_m hi _ m<mz~5 ,
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l

 

7
3

38

Thorium planchettes which contained the much shorter half life
isotOpes, were counted as soon as possible after their plating. The
corresponding uranium - that is, the one from the same aliquot of sample
was counted after the thorium.

The data sheets for each sample appear in Appendix F. The count
rates for the isotopes are very low in most cases. This occurs for several
reasons. First, the content of total uranium and total thorium in these
samples was extremely low. Even if a high yield of the elements had been
obtained, it would have been necessary to count the samples for much
longer periods of time in order to achieve the high counts (approximately
1000) which yield good counting statistics. The unfortunate situation
was that the work load and schedule of the research group allowed only a
short time for the completion of the counting before the removal of the
equipment took place. iFor this reason, every time a planchette was put in
the detector, the spectrum acquisition was viewed for several minutes to
half'an.hour. Iftu3decays appeared during that time, the final steps of
the plating were repeated on the undisturbed containers and the new
planchettes counted. The chemical interferences discussed in the
previous chapter attenuated the decays almost completely in some cases.
The procedure should have been SUSpended and redone from the beginning at
this point, but time constraints made this option hnpossible so the counts
were done on the samples at hand.in hopes that some data might be obtained.

The intention of this thesis was to determine whether this method

could be applied to basic volcanic rocks to obtain chronology informa-

39

tion. Under the conditions of this work, the answer to that question
seems to be that it cannot. However, I feel that complete fusions and
solvent extraction could provide good data.

Fusions with an alternate flux, potassium flouride (KF), have been
used (Sill, 1977) in processing thorium for alpha spectrometry. This may

be a viable alternative.

CHAPTER VII

PROBLEMS OF DATA RESULTS AND CONSIDERATIONS

After counting samples for at least twenty—four hours, the data were
entered into a computer program and run on an IBM 370 computer to
calculate the 238U/232Th ratio, the 230Th/232Th ratio, and the errors in
each of these ratios. The computer program, as used, appears in Appendix
E.

The calculations take the following general pattern” The raw counts
for the isotope of interest are divided by the counting time for that
isotope. Background counts for the corresponding channels, divided by
its count time are substracted from the raw counts per minute. If
correction factors are to be applied to the particular isotope, they are
done at this point. Finally, the corrected amount is divided through by
the yield for the element being treated.

Ratios of yield corrected values are determined next and the errors
for each value calculated in double precision. The exact equations used
to do each of these steps are laid out in the program in Appendix E.

The results of the first runs of the data showed very clearly that
there were significant problems. These were mainly that the data points
plotted far from the region of the diagram where they were expected to

plot. Figure 11 is a plot of the data points found for repeated analyses

40

41

of each of the four phases of rock number 31-8. The points cluster along
the y axis in all but 3 cases. A more pronounced pattern emerged when each
phase is plotted separately, as in Figures 12, 13, 14 and 15. Figure 12
shows that the magnetite points are reasonably distributed closer to the
45 degree 'equiline' and the x-axis closer to where they should fall» The
plagioclase points, on Figure 13, cluster close to the y axis, as do the
pyroxene (Figure 14) and whole rock points (Figure 15). Each phase can.be
found in an area of the graph progressively higher on the y axis and each
may be related to a similarly progressively worse problem in the
dissolution chemistry.

The magnetite (Fe304), a simple iron oxide rather than a silicate,
was easier to take into solution than the other phases. It was possible
to take each aliquot of this phase into solution in hydrochloric acid
overnight. However, the predominance of the iron in the solution, once
attained, was so overwhelming that repeated iSOpropyl ether extractions
throughout the procedure could not remove it. Enough excess iron came off
onto the ion exchange columns in the later steps of the process after
several extractions to 'clog' the columns. This demonstrated that not all
of the iron had been extractable into the ether and remained as an iron
complex rather than .as free, extractable iron. ion. .At the final
planchette plating step, the iron remaining was once more ether extracted
and when absolutely no more could be removed, plating was done. An iron
residue formed during the evaporation of the final drOps of solution.

This residue was thick enough to attenuate the alpha counts severely.

xeom-muo:= 4 . mzmxoaLa a

 

mw<moon<4m ¢ whHhmzw<z a mm<z¢ "QZMGML
:rwmw\:mmw
m. 4. m_ N. __ a. m w A o m v m N _ a
L L _ L _ _ _ _ L L L _ L _ _ L
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a a m.
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Nmaf—I\N®Nl—'I

Plot of All Data Points for Rock 3178

Figure 11

42

 

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15.83me
.3122 :26. w L o. m
L _ _ L _ _ . _ _ _ _ _
Ts
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OJCGISDb-IIZ‘\<\IU>CUi—']:

Figure 12

43

uwjoogjm o uwfit "ozmom:
1533me

m_:m_w_:a_m w m o m w

 

L. _ _ _ _ h _ b — _ P L I?
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Figure 13

44

mzmxomt < mwsi "02mm”:
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L__L__,___L__L_

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GJODCSI—'3E‘\JRJG)CVi—'I:

Figure 14

45

m—
L

v.
L

m—
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N—
L

xoomnmmozz * mw<zm "ozmomm

 

IPNMN\:me
L. 5. MW m N“ o, Mm v
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Figure 15

46

47

This problem of excess iron was not a problem in the work done on
speleothems or light rocks since the iron content of those materials is
preportionally so much lower than that of magnetite that the problem had
not been seen in this magnitude before during the work of this research
group. In fact, iron.was added in processing those kinds of rock.in.order
to facillitate the iron hydroxide precipitation step.

The other phases of the rock; plagioclase, pyroxene and whole rock,
in addition to their iron content are silicates. This fact is the other
of the two most serious problems faced in the chemistry which produced
this data. After the initial attempt to take each phase into solution
with hydrofluoric acid and perchloric acid followed by nitric acid, the
residue which was left behind clearly required more intensive treatment.
To this end, a fusion with sodium bicarbonate was attempted. The other
available flux material was lithium metaborate. In discussions with the
head of the research.tean1it was decided that the lithium in the flux would
interfere ‘with the carriage of the thorium through the procedure.
Therefore, the fusions were done with the sodium bicarbonate. According
to the texts on fusions, the optimum temperature for fusion of these
phases was 850°C. The recommended flux-to-phase prOportions ranged from
4:1 to 10:1. Experimental trials with whole rock were run since whole
rock was the one phase which needed the least processing and virtually
unlimited amounts were available. Successive trials with different
combinations of flux, time, and temperature were run. When any
combination which involved a temperature greater the 850°C was tried, a

black, pastey looking, insoluble coating, probably iron, formed around

48

the edge of the crucible and on the underside of the cover. [Itemperature
of lower than 850°C produced no noticeable change in the powder at all,
even if left for longer than 10 to 12 hours.

Flux proportions lower than 8:1 produced little if any noticeable
change in the powder and no improvement in the total amount of residue
left behind after the dissolution. The final combination was the one
which produced the best results with the fewest problems. That
combination was 10:1 flux to sample heated to 850°C for 4 hours for phases
like plagioclase and pyroxene and for six hours for whole rock.

The results of the fusions never reached the glass bead stage about
which I had read, but all attempts to better them with the materials
available resulted in no better products. Never was it possible to reduce
the residues appreciably. The clustering of the silicate phases along the
y-axis, may possibly be explained by their compositions. 'The inability to
breakdown the phases, coupled with the loss of uranium in the fuming
hydrofluoric acid step could account for the extreme vertical displace-
ment of the points. The thorium loss, as well as additional uranium loss,
during the many times solutions were taken to dryness and redissolved
could. account for the horizontal diSplacement and further vertical
displacement of the points on the graph. Since attempts to mathematically
correct the values back to 100 percent yields were relatively unsuccess-
ful and the use of weighted linear regression techniques only increased
the problem, (Table 3 and Figures 16-19) chemical interferences were the

reasonable causes.

Table 3

REGRESSION DATA FOR 31-8 PHASES

 

 

 

Phase Y Intercept SloEe R Square
Magnetite 2.935590 -0.49 0.07487
Plagioclase 5.072947 16.58 0.98920
Whole Rock 4.52390 -0.13 0.00530
Pyroxene 8.39158 0.60 0.10582

PHASE DATA
Lab Number Th/Th Ratio Error U/Th Ratio
M80251 1.1897 0.371 2.8435 0.451
M80252 1.5590 0.688 3.9705 1.034
M80253 5.2106 0.162 0.2597 0.034
MS0256 2.4733 0.133 13.0218 0.658
M80255 11.6556 0.422 1.1170 0.061
M80292 5.4999 0.056 0.1355 0.011
M80293 5.3464 0.025 0.0610 0.003
M80294 5.6379 0.017 0.0224 0.002
M80261 6.0872 0.046 0.0775 0.006
M80267 0.7885 0.006 0.0063 0.003
M80268 6.8489 0.021 0.0112 0.001
M80269 4.1110 0.320 0.5970 0.099
M80257 13.5426 0.153 0.092 0.009
M80258 3.1521 0.013 0.0197 0.002
M80259 11.6146 0.040 0.8095 0.005
M80295 5.5927 0.104 0.1042 0.021

49

 

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50

 

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51

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Figure 19

53

54

In the general sense, it seems unreasonable to take a rock into
solution, even given that dissolution is complete, and then to remove
everything except a minute portion, in order to analyze that portion. It
would seem to be much more reasonable to remove the trace elements of
interest by some method, such as solvent extraction, early in the
processing, leaving all the rest behind.

A type of solvent extraction was tried at one point in this work.
Several telephone conversations with the chemists at one of Atlantic
Richfield's Research and DevelOpment Laboratories yielded samples of four
quaternary amines which are commonly used in industrial uranium solvent
extraction” .Attempts to facilitate solvent extractions in the laboratory
were failures. The equipment necessary could not by synthesized and the
technique was too cumbersome to miniaturize with no real understanding of
the procedure and no guidance aside from phone conversations with some
very well meaning scientists. llzremains my conviction that the technique
of solvent extraction is the way to proceed if this approach to basic
volcanic rocks is to be used. Work by Gunyon, 1975; Jenkins 1969, and
others seem to show the viability of this approach.

Whatever method is used, however, primary dissolution is necessary.
Fusions or pressure bombs to break down the silicates must be successfully
carried out in order to assure the release of the extremely small

fractions or uranium and thorium from the rock or phase.

References

Adams,J.A.S., J.F.Osmond, J.J.W.Rogers, 1969 The Natural Radiation Environ-
ment Wiley and Sons, New York.

 

A11egre,C.J., and M. Condimines, 1976 Fine chronology of volcanic processes
using 2380 - 230Th systematics. Earth & Planet. Sci. Lett. v.28, p.395.

Allegre,C.J., 1968 230Th date of volcanic rocks: a comment. Earth & Plant.
Sci. Letter. v.5, p.209.

Attree,R.W., M.J.Cabe11, R.L. Cushing3 and J.J.Pieron, 1962 A colorimetric
determination of the half-life of OTh and consequent revision of its
neutron capture cross section. Can.J.Phys., v. 40, p.194.

Baranowski, James 1977 2380/230Th isotope systematics of rhyolites from
Long Valley California. unpublished MS thesis, Michigan State University.

Cherdyntsev,V.V., G.I.Kislitsina, V.L.Zverev, 1967 Isotopic composition of
uranium and thorium in rocks and products of active volcanism. Akad.
Nauk SSSR Doklady, V.l72, p.177.

Cherdyntsev,V.V., G.I.Kislitsina, V.M.Kuptsov, E.A.Kuzina, V.L.Zverev, 1967
Radioactivity and absolute age of young volcanic rocks. Geochim. Int.
v.4, p.639.

Cherdyntsev,V.V., V.M.Kuptsov, E.A.Kuzima, V.L.Zverev, 1968 Radioisotope
and proctactinium age of neovolcanic rocks of the Caucasus. Geochim.
Int. v.5, p.56.

Cherdyntsev,V.V., and N.A.Senina, 1970 Radioactivity of young volcanic rocks
of three Pacific Islands. Geochim. Int. v.8, p.652.

Cherdyntsev,V.V. and N.A.Senina, 1973 On the behavior of uranium-234 in
volcanic processes. Geochim. Int., v.10, p.18.

Condimines,M., M.Bernat, and C.J.A11egre 1976 Evidence for contamination
of recent Hawaiian lavas from 230Th - 1380 data. Earth & Plant. Sci.
Lett. v.33, p.122.

Dalrymple,G.G., and M.A.Lanphere, 1969 K-Ar Dating W.H.Freeman, New York.

 

Damon,P.E., A.W.Laug1in, J.K.Percious, 1969 Problem of excess argon-40 in
volcanic rocks, in Proceedings of a symposium on radioactive dating and
methods of low level counting. IAEA, March 1969, p.463.

Freidlander, Gerhart, J.W.Kennedy, and J.M.Miller, 1955 Nuclear and Radio-
chemistry John Wiley and Sons, New York.

 

55

Funkhouser,J.G., I.L.Barnes, and J.J.Naughton, 1966 Probelms in the dating
of volcanic rocks by the potassiumrargon method. Bull Volcan, v.29, p.709.

Guyon,J.C., and B.Madison, 1975 Studies on the solvent extraction of thorium,
Mikrochim. Acta v.1, p.133.

Holland,H.D., and L.Kulp, 1954 The transport and deposition of uranium,
ionium, and radium in rivers, oceans, and ocean sediments. Geochim.
Cosmo. Acta, v.5, p.197. ’

Hurley,J., and R.Fairbairn, 1957 Partioning of uranium and thorium.

Jenkins,I.L., Dallas E.Lidington, and A.G.Wain3 1969 Separation of small
amounts of 229Tb from large quantities of 23 U. J.App1.Chem. v.19, p.213.

Kaufman,A., 1964 23[*0/230'I‘h dating of carbonates from Lakes Lahontan and
Bonneville. Ph.D. Dissertation, Columbia University, New York.

Ku,T.L., 1976 The u-series methods of age determination. Ann. Rev. of Earth
and Planet. Sci., v.4, p.347.

Lively, Richard, 1978 Uranium Series Disequilibrium: Investigations of three
surficial uranium deposits. unpublished thesis. Michigan State University.

MacDonald,G.A., 1949 Hawaiian petrographic province. Geol. Soc. Amer. Bull
Soc. 60.

MacDonald,G.A., and T.Katsura, 1964. Chemical composition of Hawaiian Lavas:
J.Pet., v.5, p.82.

McDougall,I., 1961 Potassium-argon ages from lavas of the Hawaiian Islands
Geol. Soc. Am. Bull. 75, p.107.

Nishamura,S., 1970 Disequilibrium of the 2380 series in recent volcanic
rocks. Earth Planet. Sci. Letters, v.8, p.239.

Rankama,K., 1954 Isotope Geology Pergamon Press, London.

 

Rogers,J.J.W., and J.A.S.Adams, 1957 Autoradiography of volcanic rocks of
Mount Lassen, Science v.125, 1150.

Seaborg,G.T., and J.J.Katz, 1954 The Actinide Elements National Nuclear
Energy Series, McGraw-Hill, New York.

 

8i11,C.W., 1977 Determination of thorium and uranium isotopes in ores and
mill tailings by alpha spectrometry. Anal. Chem. v.49, p.618.

Stearns,H.T., 1946 Geology of the Hawaiian Islands. Hawaii Div. Hydrog.
Bull. 8.

Stearns,H.T., and G.A.MacDonald, 1948 Geology and groundwater resources of
the Island of Hawaii. Hawaii Div. of Hydrog. Bull. 9.

56

Somayajulu,B.L.K., M.Tatsumoto, J.N.Rosholt, and R.J.Knight, 1966 Dis-
equilibrium of the 2380 Series in basalt. Earth & Planet. Sci. Lett.
v.1, p.387.

Taddeuchi,A., W.S.Broecher, D.L.Thurber, 1967 230Th dating of volcanic
rocks. Earth & Planet. Sci. Lett. v.3, p.338.

Tatsumoto,M., C.E.Hedge, and A.E.Enge1, 1965 230Th dating of volcanic rocks.
Earth & Planet. Sci. Lett. v.3, p.338. '

TatsumotoéM., C.E.Hedge, and A.E.Enge1, 1965 K, Rb, Sr, Th, 0, and the
SR87/SR 6 ratio in oceanic tholeiitic basalt. Science. v.150, p.886.

Tera,F., J.Korkisch, and F.Hecht, 1961 The distribution of thorium between
alcohol-nitric acid solutions and the strongly basic anion exchanger
Dowex-1. Separation of thorium from uranium. J.Inorg. ch. Chem., v.16,

p.345.

Tieh,T.T., E.B.Ledger, and M.W.Rowe, 1980 Release of uranium from granitic
rocks during in situ weathering and initial erosion (central Texas).
Chem. Geol., v.29, p.227.

Thompson,P., 1973a A method of analysis of uranium and thorium for paleo-
climatology. unpublished thesis. McMaster University.

Thompson,P., 1973b Extraction and isotopic analysis of tract amounts of
uranium and thorium from speleothems. McMaster Univ. Tech. Memo. 73.

Turner,F., and J.Verhoogan, 1960 Igneous and Metamorphic Petrology McGraw
Hill Book Company, New York.

 

Whitfield,J.M., 1958 Uranium and thorium content of some granitic rocks.
Unpublished Ph.D. Thesis The Rice Institute.

57

APPENDICE S

APPENDIX A

228Th/23ZU SPIKE

228Th/2320 SPIKE

In order to quantitatively evaluate the yields of the uranium and
thorium, a spike of 228Th and 2320 in known quantity was added to the
dissolved samples. ‘These isotopes 'were best used since they' were
relatively non-existent in the system considered. Small corrections were
made for the presence of both in the calculation of the age.

228Th is a short lived daughter product of 232Hand therefore the two
are reasonably considered to be at equilibrium in a closed system such as
this.

It was also advantageous to use these isotopes because their
energies fall into an easily used part of the spectrum for counting
purposes.

Since known quantities of spike were used, the percent yield could be
determined from the samples. Therefore, a normalized value would give the
abundance of uranium and thorium in the original rocks.

The concentrated spike was diluted with 6N HCl to prevent it from
adsorbing into the glass of the storage recepticle. Exactly 10.0 mL of
concentrated spike was pipetted into a solution composed of 10 mL of
concentrated HCl and 500 mL of concentrated HN03 contained in a l-liter
volumetric flask. This solution was then brought to volume with distilled
water. A 5.0 mL aliquot of this solution at a time was then diluted to one

liter with distilled water in a pyrex beaker. This was called the "dilute

Spike" and was stored in a dark brown pyrex glass bottle, refrigerated.
When using a spike of 228Th, it becomes necessary to correct for the
unsupported 228Th decay with a half-life of 1.90 years. This correction

is made by the following equation:
223mm” = cpm 223% - (2320 x .055) exp( x 228m x DECT)

where:

228Thcorr - activity corrected for unsupported decay

228Thmeas = measured activity

A. = decay constant for 228Th (9.927 x 10'4) yrs

DECT = the time which elapses between the chemical separa-
tion of uranium from thorium and when the actual
counting beings

cpm = counts per minute corrected for background

The spike was periodically analyzed to determine the change of

isotOpic ratios in it and its activity.

APPENDIX B

USE OF FRANTZ ISODYNAMIC SEPARATOR

USE OF FRANTZ ISODYNAMIC SEPARATOR

Whole rock samples, crushed to less than 200 mesh size and cleansed
of clay size particles, were dried and then passed through the Frantz

Isodynamic Separator at the following settings:

Range: always set on low for mafic rocks
Side-side angle: approximately 18 degrees

Front-back angle: approximately 27 degrees

 

Mineral Amps Vibrator Setting
Magnetite .025 4-6
Pyroxene .08-1.0 6-7
Plagioclase two runs at 1.0 5-6

two runs at 1.5 5-6

If the rock was relatively free of altered minerals, several runs at
each setting removed the discreet grains of more magnetically susceptible
minerals. Then a setting of 1.5 amps cleared the remaining plagioclase of
grains which were amalgams of mafic and non-mafic minerals. Glass, if
present, could be removed by heavy liquids or water-gravity settling. For
the Hawaiian basalts, water washes were at least as successful as heavy
liquids separations. For obvious reasons, water separations were

preferred.

APPENDIX C

REAGENTS

II.

III.

REAGENTS

Water was distilled and deionized.

Prepared reagents:

 

Reagent Strength Ingredients
A. Nitric Acid 8N 510 mL conc. to l L w/ H20
0.1N 6.4 mL conc. l L w/ H20
5N 320 mL conc. 1 L w/ H20

measured with graduated cylinders or class A pipettes

B. Hydrochloric Acid 9N 710 mL conc.
0.1N 8.6 mL conc.

C. Ammonium Hydroxide 0.3N 20 mL conc.

D. TTA Solution 25 gms + 500 mL

all stocks were reagent grade

Spike:
from: Radiochemical Centre

Amersham, England

1 L W/ H20
1 L w/ H20
1 L W/ H20

benzene

APPENDIX D

CLEANING 0F GLASSWARE

CLEANING 0F GLAS SWARE

All glassware was scrubbed with phOSphate free detergent and hot
water; Next it was rinsed with tap water, then scrubbed with 8N HN03. It
was then rinsed with tap and finally with distilled water.

Centrifuge tubes, test tubes, and 10 mL beakers were rinsed with
acetone, detergent scrubbed and tap water rinsed. Next they were scrubbed
with 8N HNO3, rinsed with tap water and then rinsed with distilled water.
An acetone rinse and final distilled water rinse followed.

Vycor beakers and teflon beakers were soaked overnight in 2:1

HNO3:H20 before washing.

APPENDIX E

COMPUTER PROGRAMS USED TO PROCESS THE DATA AND TO

CALCULATE THE ERRORS

OOOOOOOOOOOOOOOOOOOOOO00000000

COMPUTER PROGRAMS USED TO PROCESS THE DATA AND TO
CALCULATE THE ERRORS

THIS PROGRAM CORRECTS RAW COUNT RATE DATA AND COMPUTES U-238/TH-232,
U-234/U-238 AND TH-230/TH-232 ISOTOPE RATIOS. YIELDS OF U AND TH ARE
CALCULATED AND THE ERRORS IN THE RATIOS CALCULATED.
N1=U-238 COUNT RATE
N2=U-234 COUNT RATE
N3=U-232 COUNT RATE
N4=TH-232 COUNT RATE
N5=TH—230 COUNT RATE
N6=TH-228 COUNT RATE
N7=RA-224 COUNT RATE
CN1=CORRECTED U-238 COUNT RATE YIELD CORRECTED
CN2=CORRECTED U-234 COUNT RATE YIELD CORRECTED
CN3=CORRECTED U-232 COUNT RATE YIELD CORRECTED
CN4=CORRECTED TH-232 COUNT RATE YIELD CORRECTED
CN5=CORRECTED TH-230 COUNT RATE YIELD CORRECTED
CN6=CORRECTED TH-228 COUNT RATE YIELD CORRECTED
CNTU ACCUMULATION TIME FOR U SPECTRUM (MINS)
CNTT ACCUMULATION TIME FOR TH SPECTRUM (MINS)
CNBD = ACCUMULATION TIME FOR BLANK DISC (MIN)
SAR=ACTIVITY OF 1.0 ML U-232/TH-232 SPIKE
WT=WEIGHT OF SAMPLE USED
SPIKE=TH-228/U-232 ACTIVITY RATIO IN SPIKE
THALF8=THE DECAY CONSTANT FOR TH-228=9.94E-04
DECT=DELAY BETWEEN COUNTING TH228 AND SEPARATION FROM U
B1=COUNTER BACKGROUND CORRECTION FOR U-238
Bz=COUNTER BACKGROUND CORRECTION FOR U-234
B3=COUNTER BACKGROUND CORRECTION FOR U-232
B4=COUNTER BACKGROUND CORRECTION FOR TH-232
B5=COUNTER BACKGROUND CORRECTION FOR TH-230
B6=COUNTER BACKGROUND CORRECTION FOR TH—228
DOUBLE PRECISION N1,N2,N3,N4,N5,N6,N7,CN1,CN2,CN3,CN4,CN5,CN6,
2 CNTU,CNTT,CNBD,SAR,SAU,SAT,B1,B2,B3,B4,B5,B6,DECT,ML,WT,YU,
3 YT,R21,Rl4,R54,YUP,YTP,PPMU,ER1,ER2,ER4,ER5,ER14,ER54,ER21,YI,
4 YII,THALF8,Y2,Y3,Y4,Y5,Y6,Y7
DIMENSION TITLE(10)

100
101

1000
102
103

104
105

140

6000

6001

00000

125
126

READ(5,101,END=999)TITLE,CNTU,CNTT,SPIKE,DECT,ML,WT
FORMAT(10A1,6E10.4)
WRITE(6,1000)TITLE,CNTU,CNTT,DECT,ML,WT
FORMAT(1x,1OA1,2x,2(1PE20.10),/,13x,3(1PE20.1O))
READ(5,103)N1,N2,N3,N4,N5,N6,N7
FORMAT(7F10.4)
WRITE(6,103)N1,N2,N3,N4,N5,N6,N7
READ(5,105)B1,B2,B3,B4,B5,B6,CNBD
FORMAT(7F10.4)
WRITE(6,105)B1,BZ,B3,B4,BS,B6,CNBD
THALF8=9.94E-O4
SAU=25.39
SAT=22.62
SAR=SAU/ SAT
WRITE(6,140)SAR
FORMAT(2X,’SAR=’,1PE20.10)
CORRECT FOR BACKGROUND, CALCULATE COUNTS PER MINUTE AND NORMALIZE
YU=(((N3/CNTU)-(B3/CNBD))/(SAU*.2))
Y2=N6/CNTT
Y3=B6/CNBD
Y4=Y2-Y3
Y5=N7/CNTT
Y6=B6/CNBD
Y7=(Y5-Y6)*.055
YI=(Y4-Y7)
YII=YI*(YI*DEXP(THALF8*DECT))
YT=(YII/(SAT*.2))
WRITE(6,6000)YI
FORMAT(2X,’YI=’,1PE20.10)
WRITE(6,6001)YII
FORMAT(2X,’YII=’,lPE20.10)
CORRECT COUNTS FOR BACKGROUND AND PEAK TAILING AND YIELD CORRECT
CN1= ((Nl/CNTU)-(B1/CNBD))/YU
CN2=(((N2/CNTU)-(B2/CNBD))/YU)-(CN1/21.7)
CN3=((N3/CNTU)-(B3/CNBD))/YU
CN4=((N4/CNTT)-(B4/CNBD))/YT
CN5=((N5/CNTT)-(B5/CNBD))/YT
CN6=(YII)/YT
CALCULATION OF ISOTOPE RATIOS AND ERRORS IN THESE RATIOS
DUE TO STATISTICAL ERRORS IN THE COUNT RATE
R21=0234/0238
R14=0238ITH232
R54=TH230/TH232
R21=CN2/CN1
R14=(CN1/CN4)
R54=CN5/CN4
CORRECTED COUNTS IN ORDER 1-6
WRITE(6,126)CN1,CN2,CN3,CN4,CN5,CN6
FORMAT(2X,’CN1=’,1PE20.10,2X,’CN2=',1PE20.10,2X,'CN3=',1PE20.10,/,
2X,’CN4=’,lPE20.10,2X,’CN5=’,1PE20.10,2X,’CN6=',lPE20.lO)

117
118

251

000

5000

5001

5002

5003

119
120
106
131
108
133
107
109
110
135
111
132
134
136

7000

999

YUP=YU*100
WRITE(6,118)YUP
FORMAT(10X,’YU= ',1PE10.2,’PERCENT’)
PPMU=((.2)*(CN1)*(304.93))/(CN3*WT)
WRITE(6,251)PPMU
FORMAT(’ PPMU= ',1PE10.2)
CALCULATION OF THE ERROR IN THE RATIOS
ER = TOTAL ERROR IN U-TH COUNT RATES DERIVED FROM U-TH COUNT RATES
, BLANK DISC COUNT RATE FOR U-TH COUNT TIMES
, BLANK DISC COUNT RATE FOR BLANK DISC COUNT TIMES
ER1=DSQRT((CNl/CNTU)+(Bl/CNBD)+(Bl/CNTU))
WRITE(6,5000)ER1
FORMAT(2X,’ERROR IN CN1=’,1PE20.10)
ER2=DSQRT((CN2/CNTU)+(B2/CNBD)+(B2/CNTU))
WRITE(6,5001)ER2
FORMAT(2X,'ERROR IN CN2=’,1PE20.10)
ER4=DSQRT((CN4/CNTT)+(B4/CNBD)+(B4/CNTT))
WRITE(6,5002)ER4
FORMAT(2X,’ERROR IN CN4=’,1PE20.10)
ER5=DSQRT((CN5/CNTT)+(B5/CNBD)+(B5/CNTT))
ER14=(CN1/CN4)*DSQRT(ER1*ER1/(CN1*CN1)+ER4*ER4/(CN4*CN4))
WRITE(6,5003)ER5
FORMAT(2X,'ERROR IN CN5=',1PE20.1O)
ER21=(CN2/CN1)*DSQRT(ER2*ER2/(CN2*CN2)+ER1*ER1/(CN1*CN1))
ER54=(CNS/CN4)*DSQRT(ER5*ER5/(CN5*CN5)+ER4*ER4/(CN4*CN4))
YTP=YT*100
WRITE(6,120)YTP
FORMAT(10X,’YT= ’,1PE10.2,’PERCENT’)
WRITE(6,107)R14
WRITE(6,132)ER14
WRITE(6,109)R54
WRITE(6,134)ER54
FORMAT(10X,’0238/TH232=’,lPE20.10)
FORMAT(10x,'TH230/TH232=’,1PE20.1O)
WRITE(6,111)R21
WRITE(6,136)ER21
FORMAT(10X,’0234/0238=’,1PE20.10)
FORMAT(2X,’ERROR UZ38/TH232= ’,1PE20.10)
FORMAT(2X,’ERROR TH230/TH232= ’,1PE20.10)
FORMAT(2X,’ERROR 0234/0238=’,1PE20.10,//)
WRITE(6,7000)TITLE,R54,ER54,R41,ER41
FORMAT(2X,2A4,2X,4(1PE20.10,2X,//)
GO TO 100
STOP
END

M80251
235.0
9.0
M80252
48.0
9.0
M80253
183.0
23.0
M80255
128.0
11.0
M80256
1121.0
11.0
M80257
267.0
11.0
M80258
105.0
11.0
M80259
336.0
11.0
M80261
28.0
11.0
M80267
25.0
11.0
M80268
79.0
11.0
M80269
160.0
11.0
M80292
55.0
11.0
M80293
43.0
11.0
M80295
128.0
11.0
M80294
16.0
11.0

1328.8
226.0
31.0
1494.95
94.0
31.0
2456.43
305.0
61.0
1336.0
159.0
23.0
1516.12
1565.0
23.0
2685.05
319.0
23.0
1585.2
139.0
23.0
1315.93
432.0
23.0
1275.93
61.0
23.0
1205.03
232.0
23.0
1473.0
109.0
23.0
1553.83
210.0
23.0
1431.18
102.0
23.0
2819.3
107.0
23.0
1393.1
204.0
23.0
1342.68
62.0
23.0

1382.53
493.0
6.0
1534.63
92.0
6.0
3104.0
658.0
21.0
1577.8
236.0
16.0
2899.33
326.0
16.0
1809.02
1548.0
16.0
1430.18
465.0
16.0
2607.35
54.0
16.0
1594.0
92.0
16.0
1262.0
500.0
16.0
1393.3
391.0
16.0
1427.35
1166.0
16.0
2439.0
208.0
16.0
2957.48
128.0
16.0
1880.88
1223.0
16.0
3007.88
64.0
16.0

6.0
0.99
163.0
6.0
0.99
41.0
18.0
0.99
60.0
7.0
0.99
110.0
7.0
0.99
12.0
7.0
0.99
24.0
7.0
0.99
20.0
7.0
0.99
27.0
7.0
0.99
275.0
7.0
0.99
24.0
7.0
0.99
36.0
7.0
0.99
27.0
7.0
0.99
66.0
7.0
0.99
36.0
7.0
0.99
20.0
7.0

3.977
644.0
32.0
1.826
305.0
32.0
4.388-
153.0
62.0
31.038
670.0
6.0
3.216
264.0
6.0
38.213
123.0
6.0
8.994
70.0
6.0
11.01
184.0
6.0
5.001
150.0
6.0
14.111
217.0
6.0
40.01
150.0
6.0
19.021
140.0
6.0
19.078
129.0
6.0
27.949
330.0
6.0
9.360
186.0
6.0
26.08
88.0
6.0

00.2
1990.0
20.0
00.2
1558.0
20.0
00.2
220.0
40.0
00.2
420.0
23.0
00.2
1032.0
23.0
00.2
98.0
23.0
00.2
59.0
23.0
00.2
82.0
23.0
00.2
108.0
23.0
00.2
244.0
23.0.
00.2
48.0
23.0
00.2
444.0
23.0
00.2
177.0
23.0
00.2
198.0
23.0
00.2
249.0
23.0
00.2
82.0
23.0

10.0
236.0
682.97

15.0
235.0
682.97

10.0
109.0
1627.43

10.0
170.0
4065.65

10.0
220.0
4065.65

10.0
31.0
4065.65

10.0
36.03
4065.65

10.0
54.0
4065.65

10.0
45.0
4065.65

10.0
515.0
4065.65

10.0
36.0
4065.65

10.0
92.0
4065.65

10.0
45.0
4065.65

10.0
87.0
4065.65

2.5
60.0
4065.65

10.0
33.0
4065.65

APPENDIX F

DATA SHEETS FROM THE LABORATORY RESULTS

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA:

Laboratory Number 252 Sample Number 31-8 Mag. Sample Weight 15 8E3-

Sample Identification Magnetite from Pololu Basalt

.Date Preparation Began 9111/77 Date & Time of U/Th Separation 9116/77

 

Amount of Tracer 2 m1.

 

Date 8 Time of Completion 9/18/77

DECT 1.8799

1525

Method of Dissolution HG]

 

ASSAY:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

U Th
Date & Time of Chemical Extraction 10/21/77 1150 9118177 1136
Begin Count Time 10/21/77 1250 9718/77 1232
End Count Time 10/22/77 1350 9/19/77 1412
Actual Count Time (min) 1494,95 1534463
Channels Eggggg QEEEEEAE ngggg
2380 123-223 48 232Th 92-193 163
235D . 23°Th 194-316 305
2340 224-324 94 228Th 317-446 1558
232v 325-435 92 224Ra 451-494 235

 

 

 

 

 

COMMENTS:

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA :

Laboratory Number 292 Sample Number 31-8 iplag Sample Weight 10 gms

Sample Identification alagjgglggg EEQE £9191” Bagalt (1)
Date-8 Time of U/Th Separation 19221222

Date Preparation Began 1_0115/77

 

Amount of Tracer 2 ml

 

Date 8 Time of Completion 10/27L77

 

DECT 19.078

 

1155

fusion

Method of Dissolutiong‘ BNO;

 

ASSAY:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 Th
Date & Time of Chemical Extraction 1123/77 1155 1126227 ZQQQ
Begin Count Time 1123/77 L348 1122222 219§
End Count Time 11/4211 1343 1129222 1392
Actual Count Time (min) 12,3ng 1439.0
Channe 1 s M Channe 1 s m
2330 124-224 :5 232'“: 70-188 22
2350 2 230Th 439-307 429
2340 225_32§ 402 228% 393-935 177
2320 322-525 208 224118 437-493 45

 

 

 

 

COMMENTS :

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA: _
Laboratory Number 259 Sample Number 31—8 pyroxl Sample Weight 10 gms.

Sample Identification pyroxene 2]) from 2Q191" 3333];
Date Preparation Began gjlgjjzi Date & Time of U/Th Separation 9228222

 

 

 

 

 

 

Amount of Tracer 2Lm14 1530

Date & Time of Completion 1019271

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fusion
DECT 12,2333 Method of Dissolution & END;
ASSAY: 0 Th
Date & Time of Chemical Extraction 11112177 1430 10110122 1995
Begin Count Time 11214277 1559 lflllfllll___lfléé__
End Count Time 11415177 1400 10,112,177 1625
Actual Count Time (min) 1315 91, 2607 35
Channels Counts Channels Counts
2381’ 197-297 135 2321311 Zn-IBL 20
235u g 230Th 190-3117 184
234” 228—293 ma 228'“ Ins-4.4.1 87
232” 229—429 SA 224118 442—490 54

 

 

 

 

COMMENTS:

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA: _
Laboratory Number 261 Sample Number 31-8 WRl Sample Weight 10 gms.

 

 

 

Sample Identification E0912 309k Pololu Basalt

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Date Preparation Began 9/22/7L Date.& Time of U/Th Separation 9/29/77
Amount of Tracer 2 mL 1345
Date 8 Time of Completion 1013/7]
fusion
DECT 36_Qo1 Method of Dissolution 5. £1103
ASSAY: . U Th
Date & Time of Chemical Extraction 11/4/77 1250 11/4/77 1250
Begin Count Time 1115/77 1626 _1_1 13 7
End Count Time 1116/77 1342 11/5/77 1621
Actual Count Time (min) 1215 193 1594,0
Channe l 5 Ms Channe 1 s 932112
2380 121-221 28 2321311 69-189 27
235“ . 230% 190-307 150
2340 222-324 51 228% 308-448 108
232!) 325-425 92 224118 439-490 45

 

 

 

 

 

COMMENTS :

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA:

Laboratory Number 253 Sample Number 3]-§9mag2 Sample Weighth gms.
Sample Identification Magnetite (2) firm 2910111 Basalt

Date Preparation Began 9/15/77

 

Amount of Tracer 421ml-

 

Date & Time of Completion 9221/77

 

DECT 6-202

 

 

Date & Time of U/Th Separation 9223/77

 

1105

 

Method of Dissolution HCl

 

ASSAY:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

U Th
Date & Time of Chemical Extraction 10126177 1358 9/28177 1638
Begin Count Time 10126177 1455 9129177 1556
End Count Time 10128177 937 9130/77 2112
Actual Count Time (min) _2545443 3104.0
Channels £23253 Channels Eggggg
238” 191:2?) 183 232Th 1172-193 31
235U . 2301:}. 194-316 153
2340 ”3:292. 205 228Th 517-442 220
2320 325-431 658 224Ra 443-496 109
COMMENTS: Thorium was re-extracted and replated for counting due to a

problem in the electronics of the counter which caused the element to

need changing; and the count to be restarted.

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA:

Laboratory Number 223 Sample Number 31—8 plégZ

 

Sample Identification Elagicclase $2) from Pololu Bgsalt
Date Preparation Began 19115122 Date & Time of U/Th Separation 10/21[77

Amount of Tracer 2 m]

Date & Time of Completion 10/25/77

 

DECT 27.012

Sample Weight 10 gms.

 

 

1300

fusion

Method of Dissolution.& HNO3

 

ASSAY:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

U Th
Date & Time of Chemical Extraction lll23/77 1145 11/18/77 1045
Begin Count Time 11123177 1446 11118177 1147
End Count Time 2819.3 2957.48
Actual Count Time (min) 2319‘3 2957,48
Channels 922255 Channels £22253
2380 124-224 . 43 232Th 270-188 66
23511 . 230% 189-3117 330
2340 225,324 107 228Tb 308:436, 198
2320 295-425 123 224Ra 431-495 _87

 

 

 

 

COMMENTS:

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA: .
Laboratory Number 257 Sample Number 31.8 pyroxz Sample Weight 10_gms.

 

 

Sample Identification Pyroxene (2) from Pololu Basalt

Date Preparation Began 9115/77 Date & Time of U/Th Separation.9/23L]7

 

 

Amount of Tracer 2 m1. 1115

 

Date & Time of Completion 10/1/77

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DECT 38,213 Method of Dissolution HF & HNO3
ASSAY: U Th
Date & Time of Chemical Extraction 10/22/77 1256 10/31/77 1532
Begin Count Time 10/22/77 1358 10/31/77 1622
End Count Time 10123/77 1055 11/1177 1325
Actual Count Time (min) 2685,05 1809.02
Channels 922233 Channels £23253
2380 128-228 267 232% 75-193 12
235” . 23011: 194—315 123
23411 229-329 319 228% 316-440 98
2321, 3304.29 1548 2248a 441—495 31

 

 

 

 

 

COMMENTS:

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA: _
Laboratory Number 268 Sample Number 31-8WR2 Sample Weight 10 gms.

 

 

Sample Identification Whole Rock (2) Pololu Basalt

Date Preparation Began 9/18/77 Date& Time of U/Th Separation 10/9/77

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Amount of Tracer 2 m1. 1130
Date & Time of Completion 10/16fl7 '
fusion
DECT 30.101 Method of Dissolution & HN03
ASSAY: ‘ U Th
Date & Time of Chemical Extraction 11/15/77 1325 11/8/77 1130
Begin Count Time 11/17/77 1102 11/8/77 1355
End Count Time 11/18/77 1133 11/9/77 1308
Actual Count Time (min) 1473.27 1393.93
Channe l s M Channe 1 s _C_o_u_n_t_s
2380 123-223 79 232Th 72-186 24
2350 , 2301311 187-308 150
2340 294-325 109, 228Th 309-441_ 48
23211 396-1131 391 2241“! 2142-494 36

 

 

 

 

 

COMMENTS :

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DATA: ' _
Laboratory Number _21Q_ Sample Number 31-3 mag} Sample Weight 10 gag;
Sample Identification. Magnetite Replicate (3) fIQm £9101” §a§a1t
Date Preparation Began 9/15777 Date.& Time of U/Th Separation. 2723122
Amount of Tracer 22ml- 1110
Date 8 Time of Completion 9125/17
DECT 32216 Method of Dissolution HG]
ASSAY: U Th
Date & Time of Chemical Extraction 10/28/77 1330 9/26/77 1545
Begin Count Time 10/30/77 1445 9/26/77 1621
End Count Time 10/31/77 1605 9/28/77 1658
Actual Count Time (min) 1516.12 2899.33
Channels Counts Channels Counts
2380 121-221 1121 232'!!! 75-193 110
2350 2 2301b 19k315 264
2340 222-325 1565 228% 316-445 1032
2320 326-426 326 22““ _446-493 220

 

 

 

 

 

COMMENTS:

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA: . .
Laboratory Number 2251 Sample Number 31-8 p1ag3 Sample Weight ngms.

 

 

Sample Identification Plagioclase (3) from Pololu Basalt

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Date Preparation Began 10L15£77 Date & Time of U/Th Separation 10/25/77
Amount of Tracer z m] 1130
Date & Time of Completion 10/28177
fusion
DECngfiyog Method of Dissolution & “N03
ASSAY: . U Th
Date & Time of Chemical Extraction 11/23/77 1130 11120/77 1215
Begin Count Time 11/28/77 1310 11120177 1325
End Count Time 11128177 1337 11122177 1541
Actual Count Time (min) 1342.68 3007.88
Channels £22255 Channels Counts
2380 124-224 16 232% 72-186 20
2350 . 23011: 187-308 88
2340 225-325 62 2281‘}! 309-440 82
2320 326-426 64 224118 441-494 33

 

 

 

 

 

COMMENTS:

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA: .
Laboratory Number 258 Sample Number 31-8‘pntnx3 Sample Weight 10 gms

Sample Identification _EyLaxene_L31_£xnm_Bnlnln_BasaJt
Date Preparation Began 9115/77 Date & Time of U/Th Separation 9/23/77

 

 

 

Amount of Tracer 2 m1. 1330

 

 

Date & Time of Completion 10/1/77

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DECT 8.994 Method of Dissolution HF & HNO3
ASSAY: U Th
Date & Time of Chemical Extraction 10[27/77 1530 10/2/77 1230
Begin Count Time 10[28/77 945 10[2[77 1321
End Count Time lQ[29/77 1226 10/3/77 1551
Actual Count Time (min) 1585.2 1430.18
Channels £22253 Channels 922253
2330 125-225 105 232Th 71-190 24
2350 : 230Th 191-308 70
2340 226-324 139 223% 309-438 59
2320 3254,25 465 2248a 439-490 36

 

 

 

 

 

COMMENTS:

Michigan State University

RADIOACTIVE DATING DATA SHEET

 

DATA: 7
Laboratory Number 262 Sample Number 31-8WR3 Sample Weight loggms.

 

 

Sample Identification Whole Rock (3) Pololu Basalt

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Date Preparation Began 9/18/77 Date & Time of U/Th Separation 10/4/77
Amount of Tracer 24E1, 1530
Date 8 Time of Completion 10/15117
fusion
DECT 19.816 Method of Dissolution & HNO3
ASSAY: U Th
Date & Time of Chemical Extraction 11[2j77 1030 10/23/77 1630
Begin Count Time 11/2/77 1135 10/24/77 1100
End Count Time 1113/77 1343‘ 10/25177 1105
Actual Count Time (min) 1553,83 1427.35
Channels 922253 Channels £22253
2380 122-223 160 232Th 70-189 36
2350 . 230Th 190-307 140
2340 224-325 210 228Th 308-441 444
2320 326-428 1166 22411:: 442-491 92

 

 

 

 

 

COMMENTS:

 

- «sua- n—o--—“~ .. . _._-. . .-_ ,,