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thesis entitled

The High Silica Rainier Mesa Magma Batches:
Implications on the Origin of Large Volume
Compositionally Zoned Magmatic Systems

presented by

Benjamin Woods Saltoun

has been accepted towards fulﬁllment
of the requirements for

Masters degree in Geological Sciences

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THE HIGH SILICA RAINIER MESA MAGMA BATCHES:
IMPLICATIONS ON THE ORIGIN OF LARGE VOLUME
COMPOSITIONALLY ZONED MAGMATIC SYSTEMS
By

Benjamin Woods Saltoun

A THESIS

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

MASTER OF SCIENCE

Department of Geological Sciences

1995

ABSTRACT
THE HIGH SILICA RAINIER MESA MAGMAS:
IMPLICATIONS ON THE ORIGIN OF LARGE VOLUME
COMPOSITIONALLY ZONED MAGMATIC SYSTEMS
By

Benjamin Woods Saltoun

Chemical heterogeneities occur in many large-volume ash-ﬂow sheets.
Most workers have assumed that the high-silica portions of these deposits
evolved largely by differentiation processes that occurred within the magma
chamber. However, the chemical heterogeneities of glassy pumice fragments
within the large volume, Rainier Mesa ash-ﬂow sheet are not consistent with
these processes. They occur in two primary chemical groups. A low and high
silica group. Additionally, the high-silica group contains two distinct
populations; a low-Th and a high-Th population. Geochemical, mineralogical
and geothermometry data on the high silica populations conﬁrms the
separate nature of these groups. All three magma types were resident in the
pre-eruptive Rainier Mesa magma chamber. Yet, major and trace element
variations of the high silica magma batches, especially La, Th and Zr, cannot
be modeled by differentiation processes that can occur within a single magma
body.

This abstract has been cut from its original form to ﬁt the space

requirements of the university.

ACKNOWLEDGMENTS

I guarantee that you would not be holding this thesis were it not for
the help of two pe0p1e: Tom Vogel and Kris Huysken. Firstly, I would like to
thank my advisor, Tom, for his unmitigated ﬁnancial, intellectual and moral
support throughout the duration of this project. Tom knew when to help me,
and he knew when to let me ﬁgure it out. I also thank Kris, ﬁrstly, for the
comradeship and, secondly, for answering my many geology questions.

I would also like to thank my committee members, Bill Cambray,
Duncan Sibley and Dave Matty for their willingness to assist in the

completion of this study.

iii

TABLE OF CONTENTS

List of Tables .................................................................................................. vi
List of Figures ................................................................................................ vii
Introduction ................................................................................................... 1
Geologic Setting ............................................................................................. 5
Sampling Procedure ...................................................................................... 7
Rainier Mesa Geochemistry .......................................................................... 8
Mineral Assemblage Chemistries of the High and Low-Th Magmas ....... 23
Ilmenite ........................................................................................... 23
Magnetite ........................................................................................ 25
Biotite .............................................................................................. 25
Feldspar ........................................................................................... 26
Geothermometry ............................................................................................ 30
Fe-Ti Oxide Geothermometry ......................................................... 30
Ternary-Feldspar Geothermometry ............................................... 32
Discussmn .................................................. 36
Background ..................................................................................... 36
Conﬁrmation of the High and Low-Th Magma Batches ............... 38
Geothermometric Considerations ................................................... 41
Conclusions .................................................................................................... 44
Appendix A: Analytical Techniques and Error Analysis ............................. 46
X-Ray Fluorescence ......................................................................... 46
INAA. ............................................................................................... 46
Electron Microprobe Analysis ........................................................ 47
Appendix B: Major and Trace Element Analyses ........................................ 49

iv

Appendix C: Electron Microprobe Analyses ................................................. 62

Bibliography .................................................................................................. 74

LIST OF TABLES

Table 1. Fe-Ti geothermometry data for the high and low magma
batches .......................................................................................... 3 1

Table 2. Mean compositions of coexisting feldspar pairs for the high
and low-Th magma batches. Ks denotes alkali-feldspar
compositions. Pl denotes plagioclase feldspar compositions ...... 34

Table 3. Error analysis of Instrumental Neutron Activation Analysis... 48

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

LIST OF FIGURES

Location Map of the Southwest Nevada Volcanic Field .......... 6

Total Alkali-Silica classiﬁcation diagram. The entire
Rainier Mesa Tuﬁ'is plotted. Includes data from

(Mills, 1991) ............................................................................... 9

Si02 versus Th/Nb. This diagram shows the two primary
magma groups of the Rainier Mesa Tuﬁ’. The high and low
magma groups are separated by a silica gap at approximately
70 wt% ........................................................................................ 10

Th versus Zr and La. The absence of diﬁ‘erentiation pathways
indicates that in situ diﬁerentiation cannot petrogenically
relate the three Rainier Mesa magma types ............................ 1 1

Th versus Nb for the high silica Rainier Mesa 'I‘uﬁ' ................ 13

Th/Nb versus selected major element oxides (after Cambray
et al., 1995) ...................................................... l ......................... l4

Th/Nb versus selected trace element ratios (after Cambray
et al., 1995) ................................................................................ 16

Th/Nb versus selected major element oxides; includes
symbols that depict new whole-pumice geochemistry
for the high and low-Th magma batches .................................. 19

Th/Nb versus selected trace element ratios; includes

symbols that depict new whole-pumice geochemistry
for the high and low-Th magma batches .................................. 2 1

vii

Figure 10.

Figure 11.

Figure 12.

Figure 13.

Figure 14.

Figure 15.

Figure 16.

Figure 17 .

a) FeO versus 'l‘iOz variation diagram for ilmenite
compositions of the high and low-Th magma batches.

b) MgO versus MnO variation diagram for ilmenite
compositions of the high and low-Th magma batches ............. 24

a) FeO versus TiOz variation diagram for magnetite
compositions of the high and low-Th magma batches.

b) MgO versus MnO variation diagram for magnetite
compositions of the high and low-Th magma batches ............. 27

a) Ti02 versus A1203 variation diagram for biotite

compositions of the high and low-Th magma batches.

b) Si02 versus MnO variation diagram for biotite

compositions of the high and low-Th magma batches ............. 28

Ternary feldspar diagram showing plagioclase
and alkali-feldspar compositions. The arrows indicate
inferred paths of magmatic evolution ....................................... 29

Fe-Ti oxide temperature distribution among the high
and low-Th magma batches ...................................................... 33

Ternary feldspar temperature distribution among the
high and low-Th magma batches.- ............................................. 33

Temperature versus Th/Nb. Both the Fe-Ti oxide and

ternary feldspar temperatures indicate that the high-Th
magma had signiﬁcantly higher temperatures than the

low-Th magma. Furthermore, the ternary feldspar
temperature data provides conﬁrmation of Fe-Ti ordde

data ............................................................................................ 40

Si02 versus temperature diagram showing the
discontinuous thermal gradient in the pre-eruptive Rainier
Mesa magma chamber ............................................................... 42

viii

Introduction

The origin of compositionally zoned magma chambers is currently one
of the most actively studied ﬁelds within igneous petrology. The common
occurrence of zoned magma chambers is well documented. de Silva and Wolﬁ'
(1995) maintain that in situ differentiation is almost entirely responsible for
any observed major and trace element variations that occur within a zoned
magma chamber. Their hypothesis is primarily based on: (1) the observation
that smaller volume zoned magmatic systems exhibit extreme compositional
zonation (Smith, 1979; Hildreth, 1981; de Silva, 1991), whereas, large
volume systems are commonly weakly zoned or homogenous (Whitney and
Stormer, 1985; de Silva, 1989a; Best et al., 1989; de Silva and Wolﬁ‘, 1995);
(2) the range of major and trace element variation in zoned magmas which is
consistent with crystal fractionation (Michael, 1983; Wolff and Storey, 1984;
W6rner and Schmincke, 1984a, b; Cameron and Cameron, 1986); (3) the
inference most isotopic variations are the result of magmatic contamination
by ﬂuids and/or assimilation of wall rock (Warner et al., 1985; Palacz and
Wolff, 1989; Tegtmeyer and Farmer, 1990) and (4) that calculated zoning
times are in general agreement with independent estimates.

Large-volume, compositionally zoned magmatic systems have been
observed by many workers (e.g., Dunbar and Hervig, 1992b; Stix and

Gordon, 1993; Cambray et al., 1995). However, reasonable in situ

2
diﬂerenﬁaﬁon models fail to characterize the chemistry of these systems.

Cambray et a1. (1995) have recently proposed that compositional zonation in
the large volume Rainier Mesa magma system was the result of batch
melting. They suggest that chemically distinct magma batches formed at the
source area by partial fusion of a protolith; either by heterogeneous melting
of a single protolith or simultaneous melting of multiple source areas
(Sawyer, 1994). These chemically distinct magma batches were extracted
from the source area either sequentially or simultaneously along faults. If
different magma batches simultaneously used the same fault conduit, they
would remain separate due to viscosity diﬁ‘erences (Carrigan and
Eichelberger, 1990; Carrigan, 1994). Over time, these chemically distinct
magma batches were stored within a dilatant releasing bend and became
density stratiﬁed to form a compositionally zoned magma chamber. Thus,
the chemical variations among the diﬁ‘erent magma batches are not
consistent with in situ diﬁ'erentiation mechanisms. However, the variations
within a single magma batch could have been the result of in situ
differentiation or continuous reaction melting (Cambray et al., 1995).
Considering its large compositional range (55 to 76 wt% Si02), the
Rainier Mesa ash-ﬂow sheet is ideal for the study of large volume zoned
magmatic systems. The Rainier Mesa ash-ﬂow sheet represents an 1 1.6 Ma
eruptive event that explosively erupted more than 1200 km3 of material.

Given the compositionally zoned nature of the Rainier Mesa ash-ﬂow sheet,

3

most workers have assumed that the pre-eruptive Rainier Mesa magma
chamber was chemically and thermally zoned. Furthermore, prior studies
have determined that the ash-ﬂow sheet is associated in time and place with
Basin and Range extension (Byers et al., 1976a; Christiansen et al., 197 7 ;
Eaton, 1984).

Mills (199 1) extensively studied the geochemistry of the Rainier Mesa
ash-ﬂow sheet. His detailed analysis indicated the presence of three
compositionally distinct magma batches. Mills (1991) observed that the
Rainier Mesa ash-ﬂow sheet is composed primarily of two main groups of
magma: a low silica batch (55 to 72 wt% Si02) and a high silica group (72 to
76 wt% Si02). The high silica group is, furthermore, composed of two
separate and distinct magma batches: high-Th/Nb ratio magma and a low-
Th/Nb ratio magma. Also, the high silica group comprises approximately
90% of the total volume of the Rainier Mesa ash-ﬂow sheet (~ 1080 ms)
(Mills, 1991).

The purpose of this study is, ﬁrstly, to conﬁrm the existence of the
high and low Tthb ratio magmas observed by Mills (1991). Secondly, to
determine if the high and low Th/Nb ratio magma batches are related by in
situ diﬁ'erentiation; and ﬁnally,at the same time, test the work of Cambray et
al. (1995) and de Silva and Wolff (1995).

In summary, de Silva and Wolff (1995) suggest that in situ

differentiation cannot produce the signiﬁcant chemical and thermal

4

zonations observed in many large volume systems. Consistent with this
suggestion is the Cambray et al. (1995) proposal that batch melting is the
mechanism by which the large volume compositionally zoned Rainier Mesa
system formed. The purpose of this research is to determine the petrogenic
relationship that exists between the high silica Rainier Mesa magma

batches.

Geologic Setting

The Rainier Mesa Tuﬁ‘ is part of the Southwest Nevada Volcanic Field
(SWNVF), and is located within the south-central Basin and Range Province
(Fig. 1). This area is characterized by extensive volcanism that occurred ﬁom
15.25 Ma to 7.5 Ma (Sawyer, 1994). Within the SWNVF are four large
volume compositionally zoned ash-ﬂow sheets, one of which is the Rainier
Mesa ash-ﬂow sheet. The eruption of both the Rainier Mesa (1200 ms) and
Ammonia Tanks (900km3) ash-ﬂow sheets resulted in the development of the
large Timber Mountain caldera complex. The Timber Mountain Caldera
complex was uplifted 1200 m after the eruption of the Ammonia Tank Tuﬁ'.
This uplift resulted in the formation of the present day Timber Mountain
(Christiansen, et al., 1977).

Structurally, the Timber Mountain Caldera complex is associated with
the Walker Lane Belt (Carr, 1990). The Walker Lane belt is a northwest
trending fault zone composed of right and left lateral detachment faults and
northwest trending structural blocks (Stewart, 1988; Scott, 1990).
Furthermore, geophysical evidence indicates that SWNVF overlies an
extensional pull-apart basin that coincides to a right-step in the Walker Lane

belt (Carr, 1990).

 

 
 
 
  
 

      
   

 
     

 

 

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(after Carr et al., 1984; Noble et al., 1984; and Vogel et al., 1987).

Sampling Procedure

Glassy pumice fragments from the high silica portion of the Rainier
Mesa ash-ﬂow sheet were analyzed for major and trace elements using XRF
and INAA techniques (see appendix A). Because glassy pumice fragments
represent pockets of solidiﬁed magma that were instantaneously erupted
from a single vent (Flood, 1989), they provide a better indication of processes
that may have occurred within the magma than whole ash-ﬂow tuﬁ' samples
(Hildreth and Mahood, 1985; Flood et al., 1989; Schuraytz et al., 1989; Vogel
et al., 1989; Mills, 1991; Huysken and Vogel, 1993). Conversely, whole ash-
ﬂow tuff samples represent an average composition of all material being
deposited over a given period of time at a given location. Hence, glassy
pumice fragments provides the most accurate representation of actual
magma compositions, minus lost volatiles, at the moment of eruption (Flood,

1987).

Rainier Mesa Geochemistry

Mills (1991) extensively evaluated the compositional and chemical
spectrum of the Rainier Mesa ash-ﬂow sheet. Glassy pumice sample
compositions were classiﬁed by Mills (1991) using the Total Alkali-Silica
(TAS) classiﬁcation system of Le Bas et al. (1986). The TAS diagram
indicates that the entire Rainier Mesa ash-ﬂow sheet compositionally ranges
from trachyandesite to rhyolite (Fig. 2) (Mills, 1991). It has been noted that
mobilization of alkalis can occur by secondary hydration of glass (Aramaki
and Lipman, 1965; Lipman, 1965; Noble, 1967). Hence, alkali mobilization
can skew classiﬁcation based on the TAS method (Le Bas et al., 1986; Irvine
and Barager, 1971). Mills (1991) observed that alkali mobilization within
the Rainier Mesa ash-ﬂow sheet is minimal based on the small variance of

the alkali data.

As observed by Mills (1991) and Cambray et a1. (1995) the most
remarkable characteristic of the Rainier Mesa ash-ﬂow sheet is a large silica
gap between 7 1 and 73 wt% Si02 (Fig. 3). This silica gap demarcates the
existence of the two main trends within the Rainier Mesa ash-ﬂow sheet.
The low silica trend occurs between 57 and 71 wt% Si02 and the high silica
trend occurs between 73 and 78 wt% Si02. The variation diagrams produced
by plotting Zr and La versus Th provide the best picture of the distinct

nature of these two trends (Fig. 4) (Mills, 1991). Furthermore, Figure 4

K,O + Na 20

16

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indicates that in situ diﬁ‘erentiation cannot petrogenically relate the
three Rainier Mesa magma types (after Cambray et al., 1995).

12 .
clearly shows that Zr and La versus Th variations between the low silica
trend and high silica trend cannot be produced by reasonable in situ
differentiation processes such as crystal fractionation or magma mixing.
This conclusion is based on the observation that there are no diﬁerenﬁaﬁon
pathways between the high silica and low silica trends for these elements

(Cambray et al., 1995).

Mills (1991) originally identiﬁed two separate high silica Rainier Mesa
magma types based on Th and Nb; a high Th/Nb ratio magma batch and a
low Th/Nb ratio magma batch (Fig. 5). These two high silica magma types are
also easily distinguished by the Zr and La versus Th, and Si02 versus Tthb
variation diagrams (Fig. 4). Additionally, Figure 4 also indicates that
reasonable in situ differentiation processes cannot petrogenically relate the
high and low Th/Nb magma types to one another. Cambray et a1. (1995) also
noted that there is no geochemical overlap between the high and low-Th
magmas; as exhibited by variation diagrams of major and trace elements
versus Th/Nb (Figs. 6 and 7). The chemically distinct nature of the high and
low-Th magmas in conjunction with the lack of reasonable diﬁerentiation
pathways suggest that these magmas are genetically unrelated (Cambray et
al., 1995). Furthermore, step-wise major element and trace element
modeling of the high and low-Th/Nb magmas was completed for this study.

This modeling quantitatively determined if realistic in situ differentiation

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14

Figure 6. W versus selected major element oxides
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18

models could petrogenically relate these magmas. All models for Raleigh
crystal fractionation, magma mixing and assimilation fractional
crystallization fail to accurately predict the observed geochemistry of the
high and low-Th/Nb magmas. For the remainder of this paper, the high and
low Th/Nb ratio magmas will be referred to simply as the high-Th magma or

the low-Th magma.

In an effort to conﬁrm the existence of high and low-Th magmas ﬁrst
observed by Mills (1991) and characterized by Cambray et a1. (1995),
additional analyses of new high silica glassy pumice fragments from the
Rainier Mesa ash-ﬂow sheet was completed. A primary goal of this research
was to determine if these distinct populations would be better deﬁned by
additional sampling of the high silica compositions. This analysis has
conﬁrmed the existence of the high and low-Th magmas. New geochemical
data of the high and low-Th magmas also exhibit no geochemical overlap, as
shown by variation diagrams of selected major and trace elements versus
Th/Nb (Figs. 8 and 9). Figures 8 and 9 demonstrate that the high and low-Th
magmas are distinct with respect to both major and trace elements. Note
that new geochemical analysis for the high and low-Th magmas are
consistent with Mills’ (1991) analysis. This data indicates that Mills’ (1991)

XRF and INAA whole-pumice analysis are reproducable.

19

Figure 8. Th/Nb versus selected major element oxides; includes
symbols that depict new whole-pumice geochemistry
for the high and low-Th magma batches.

 

 

 

 

 

 

 

 

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21

Figure 9. Th/Nb versus selected trace element ratios; includes
symbols that depict new whole-pumice geochemistry
for the high and low-Th magma batches.

22

 

 

 

 

 

 

 

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Mineral Assemblage Chemistries of the high and low-Th magmas

In order to determine the relationship between the high and low-Th
magmas, a complete electron microprobe study of the chemical compositions
of the mineral assemblage was completed. The two magma types contain
diﬁ'erent assemblages with distinct compositions. Both the high and low-Th
magmas contain biotite, ilmenite, magnetite, alkali feldspar and plagioclase
feldspar. However, pyroxene and amphibole occur only in the high-Th

magma.
Ilmenite

The chemistry of ilmenite for both the high and low-Th magmas are
different. Ilmenite grains from the high-Th magma have FeO compositiOns
which range from 49 to 55 wt%. TiOz compositions range from 36.4 to 40
wt%. Whereas, FeO compositions in ilmenite for the low-Th magma range
from 45 to 49 wt% and TiOz compositions range from 42 to 45 wt% (Fig. 10a).
Additionally, MgO and MnO concentrations in ilmenite are diﬂ'erent for the
high and low-Th magmas; the high-Th magma has higher MgO and lower

MnO than the low-Th magma (Fig. 10b).

23

24

 

 

 

 

46 I
_ A Q _.
A
A
44 —:
r A A £1.95
.. AA A _
A
42 ' ‘
'rio, - _
4o - D _
D
v— D —
_ El = High Th/Nb magma D '38 Cl _
A: Low Th/Nb magma D1 U D
36
40 50 60
FeO

Figure 10a. FeO versus ’I‘iO2 variation diagram for ilmenite
compositions of the high and low-Th magma batches.

 

 

 

 

7 I ID = High Th/Nb magma
6 A A A: Low Th/Nb magmad
AA
A
4 ” AAk '
MnO A A n

A _

3 r E D
A n D

2 _ DD (9 [a

U n LP D

D
o l l
0 1 2 3
MgO

Figure 10b. MgO versus MnO variation diagram for ilmenite
compositions of the high and low-Th magma batches

25

Magnetite

The composition of magnetite for the high and low-Th magmas are
different. The TiOz content of the magnetite from the low-Th magma range
from 4.5 to 5.5 wt% and FeO concentrations range from 83 to 85 wt%. In
contrast, the TiOz compositions of magnetite from the high-Th magma range
from 5.5 to 7.3 wt% and FeO compositions range from 77 to 84 wt% (Fig.

1 1a). The MgO and MnO content of the magnetite are diﬁ‘erent among the
high and low-Th magmas; this variation is similar to that of ilmenite. The
high-Th magnetite grains have higher MgO and smaller MnO concentrations

than the low-Th magnetite grains (Fig. 1 lb).
Biotite

Biotite is abundant in the high and low-Th magmas; and their
compositions are distinct in both the high and low-Th magmas. The A1203
compositions of the biotite grains in the low-Th magma range from 1 1.7 to
13.5 wt% and 'l‘iOz contents range from 3 to 3.7 wt%. The high-Th bioﬁtes
have a much larger chemical variation. The A1203 contents of biotite in the
high-Th magma range from 12 to 18.5 wt% and TiOz contents range from 4.1

to 6.1 wt% (Fig. 12a).

The Si02 and MnO contents in biotite are different between the high

and low-Th magmas. The Si02 content in biotite of the low-Th magmas

26 .
range from 35.5 to 40.7 wt%. Conversely the Si02 content in biotites of the
high-Th magmas range from 31 and 38.4 wt%. Additionally, the low-Th
biotites have higher MnO concentrations than the high-Th biotites. The
MnO contents in biotite of the low-Th magma range from 0.5 to 0.7 wt%,
while the MnO contents in biotites of the high-Th magma range from 0.3 to

0.6 wt% (Fig. 12b).
Feldspar

The plagioclase compositions are diﬂ'erent between the high and low—
Th magmas. The average plagioclase composition in the low-Th magma is
A1114, whereas the average plagioclase composition in the high-Th magma is
An21 (Fig. 13). Almost all plagioclase feldspars are compositionally
homogenous from the center of the grain to the edge, with very little
compositional variation among the plagioclase of each magma batch.
However, approximately 5% of the plagioclase grain are compositionally
zoned. These ubiquitous grains are clearly observable in Figure 13 and have
Ca-rich cores that gradationally evolve to Na-rich edges. Unlike the
compositions of magnetite, ilmenite, biotite and plagioclase, the composition
of the alkali feldspar grains for both the high and low-Th magmas are

indistinguishable from one another within error of analysis (Fig. 13).

27

 

TiO, 6 - '3 -

U = High Th/Nb magma

A: Low Th/Nb magma

4 l l l
70 75 80 85 90

FeO

Figure 1 1a. FeO versus TiOZ variation diagram for magnetite
compositions of the high and low-Th magma batches.

 

 

 

 

 

 

 

3 I
A A
A A
A
A
MnO Ag '3
1A & A D
5'
1 F E] D u ‘
D
D D = High 111le magma:
l A= Low 'l‘h/Nb magma
0
0 l 2
MgO

Figure 11b. MgO versus MnO variation diagram for magnetite
compositions of the high and low-Th magma batches.

28

 

19

17"

A1203 15 F

13

p—

 

Etc:
0 38° _
D gag _
D

.m

B D

A ﬁnned?
ED .4

k
#3 gas-n

l l

D = High Th/Nb magma-
A: [jaw 'I‘h/Nb magma

 

 

ll

4 5 c 7
Tio2

Figure 12a. 'l‘iO2 versus A1203 variation diagram for biotite
compositions of the high and low-Th magma batches.

 

 

 

 

1.0 l I l I I Al I 1 l I
U: HighTh/Nb magma A
A=Low Th/Nb magma
0.8 r- A W A -
A A
A AA 43 A
A
MnO 0.5 - [9% AAA 3 -
QC] [3
Cl 0 D '3 1::
0.3 _ '3 é] ‘3 D ‘5] u U E] g
0.0 l I l l l J L l l J
30 32 34 36 38 40
Sio2

Figure 12b. Si02 versus MnO variation diagram for biotite
compositions of the high and low-Th magma batches.

29

KAlSi308

 

NaAlSi3O8 CaAIZSiZOS
I]: High Th/Nb magma

A: Low Th/Nb magma

Figure 13. Ternary feldspar diagram showing plagioclase
and alkali-feldspar compositions. The arrows indicate
inferred paths of magmatic evolution.

Geothermometry

Fe-Ti Oxide Geothermometry

Electron microprobe analysis of ilmenite and magnetite allowed for the
calculation of pre-eruptive magma temperatures and oxygen fugacities.
Calculation of ulvospinel and hematite compositional parameters were
completed by the program OXPROJWT (Anderson et al., 1993) for all
magnetite grains. Ulvospinel and hematite compositions for all grains from a
single pumice fragment were statistically analyzed to determine population
distribution and mean composition. Mean compositional parameters for
magnetite and ilmenite pairs were then inputted into the Turbo Pascal
program QUIlF 4.1 (Anderson et al., 1993), which provided Fe-Ti oxide
geothermometry and oxygen fugacity data. Traditionally, Fe-Ti oxide
thermometry data is based only on equilibrium between Fe and Ti. QUIlF
4.1 is a versatile program that will calculate Fe-Ti oxide thermometry based .
on equilibrium between Fe, Mn, Mg, and Ti, which provides better
temperature resolution than Fe and Ti alone (Anderson et al., 1993). The low
Th magma has an average value of 716 °C and the high-Th magma has an

average value of 814 °C (Fig. 14) (Table 1).

Mills (1991) concluded that the high silica Rainier Mesa had an
average temperature of 755 °C. His Fe-Ti oxide thermometry data was

based only on Fe and Ti equilibrium. Furthermore, the 7 55 °C temperature

30

3]

Table 1. Fe-Ti oxide geothermometry data for the high

 

 

and low magma batches.

descrip. Si02 Th/Nb Temp°C

R18-15 73. 13 0.75 723
R180 75.00 0.79 708
R23-7 72.48 1.74 810
R26-14 74.67 1.79 818
R1 1-7 74.07 0.68 735
R18-2 72.70 1.65 787

R18-16 75.40 2.83 801

32

Mills (1991) calculated reﬂects his treatment of the high silica magma
batches as a single magma. Using QUIlF 4.1 (Anderson et al., 1993), Vogel
(1995, unpublished data) recalculated Fe-Ti oxide temperatures for the entire
Rainier Mesa based on Mills’ (1991) magnetite and ilmenite data. Vogel
(1995, unpublished data) determined that the high-Th magma had an
average temperature of 789 °C and the low-Th magma had a temperature of
7 35 °C. This recalculated thermometry data is based only on three samples;
one low-Th sample and two high-Th samples. This thermometry data is
presented because it indicates that the high-Th magma had a higher
temperature than the low-Th magma; and hence supports the ﬁndings of this

study.

Ternary-Feldspar Thermometry

The coexistence of sanidine and plagioclase in many of the high and
low-Th pumice fragments allows for the determination of geothermometric
data. Ternary-feldspar temperatures are constrained by equilibrium among
the orthoclase, albite and anorthite components of these coexisting feldspars.
Initially, the orthoclase, albite and anorthite components were each
calculated from each feldspar grain edge analysis. Descriptive statistics then

determined the mean plagioclase and sanidine compositions for each sample

33

 

 

 

 

 

 

 

 

3 u
<C>=high-Th temperature b
0=low-Th temperature
2 " 7
<0 ‘3’ ‘3’
Th/Nb
1 '- d
o l l
700 g 750 800 860
Temp (°C)
Figure 14. Fe-Ti oxide temperature distribution
among the high and low-Th magma batches.
3 l j l I I l l l I l
A =high-Th temperature
A =low-Th temperature
2 >— ‘ .1
A
Th/Nb A ‘
1 - -
A AA
0 I l l I J l l I I l
710 730 760 770 790 810
Temp (°C)

Figure 15. Ternary-feldspar temperature distribution
among the high and low-Th magma batches.

34

Table 2. Mean compositions of coexisting feldspar pairs for the
high and low-Th magma batches. Ks denotes alkali-feldspar
compositions. Pl denotes plagioclase feldspar compositions.

 

 

Sample An Ab Or Cn

R23-7 ks 0.014 0.368 0.617 0.0003
R23-7 p1 0.189 0.716 0.095 0
R23-8 ks 0.014 0.377 0.609 0
R23-8 p1 0.206 0.714 0.080 7E-05
R23-4 ks 0.012 0.383 0.597 0.0002
R23-4 pl 0.310 0.630 0.059 0.0012
RIB-14 ks 0.011 0.350 0.639 0
R18-l4 pl 0.148 0.780 0.072 0.0009
R26-l9 ks 0.016 0.369 0.614 0.0017
R26-19 pl 0.212 0.715 0.073 0
R18-9 ks 0.008 0.366 0.623 0.0029
R18-9 pl 0.136 0.787 0.078 0
R18-l5 ks 0.007 0.360 0.633 0
R18-15 pl 0.129 0.794 0.076 0

35

(Table 2). Using the mean coexisting feldspar compositions, temperatures
were calculated by the Fuhrman and Lindsley (1988) feldspar thermometry

model in the SOLVCALC (Wen and Nekvasil, 1994) program.

The ternary-feldspar thermometer is pressure dependent. Typically,
this thermometer predicts an increase of 18 °C for every lkbar increase in
pressure (Stormer, 1975; Brown and Parson, 1981). However, ternary-
feldspar modeling of the high and low-Th magmas at various pressures did
not produce signiﬁcant temperature variations. Mills (1991) used the quartz-
amphibole geobarometry technique to determine that the best pressure
estimate for the Rainier Mesa magmatic system is 4.2 kbars. As such, a
pressure constant of 4.2 kbars for the feldspar thermometry calculations was
used for this study. The low-Th magma has feldspar temperatures which
range from 712 to 747 °C and has a mean temperature of 726 °C. The high-
Th magma has feldspar temperatures which range from 790 to 815 °C and

has a mean temperature of 799 °C (Fig. 15).

Discussion
Background

The occurrence of compositionally zoned magma chambers is not an
uncommon phenomena and, subsequently, has been the focus of much
research. Yet the physical processes controlling the development of these
features remain enigmatic. Many workers have regarded in situ
differentiation processes as the likely mechanism for the origin of
compositionally zoned magma chambers. For example, de Silva and Wolff
(1995) stipulate that eﬁiciency of any in situ differentiation mechanism

ultimately depends on convective fractionation at the vertical chamber wall.

Furthermore, de Silva and Wolﬁ‘ (1995) discuss the relationship
between zonation times, volume of magma and chamber shape. Thermal,
mechanical and volumetric restrictions require that small volume magma
chambers have a column-like chamber shape; whereas, larger volume
magmatic systems require a sill or coin-like chamber geometry (de Silva and
Wolﬂ‘, 1995). de Silva and Wolff (1995) suggest there is an inverse
relationship between volume of magma and the magnitude of compositional
zonation. This conclusion is based, partially, on the observations of Smith
(1979), Hildrith (1981) and de Silva (1991). Hence, they maintain that

signiﬁcant magmatic zonation due to in situ differentiation can only occur in

36

37

small to intermediate volume systems. In large volume magmatic systems,
in situ differentiation mechanisms cannot produce signiﬁcant compositional

zonation.

The pro-eruptive Rainier Mesa magma chamber was, without
question, a large volume compositionally zoned magmatic system. In
concordance with the observations of de Silva and Wolff (1995), Cambray et
al. (1995) have proposed that the compositional spectrum observed in the
Rainier Mesa Tuﬁ‘cannot be the result of in situ diﬂ'erentiation mechanisms.
This observation is best illustrated by the Zr and La versus Th variation
diagrams (Fig. 4). As previously mentioned, these diagrams illustrate that in
situ differentiation processes cannot relate the three distinct Rainier Mesa
magma types. There are no reasonable diﬂ'erentiation pathways among the
magma batches (Cambray et al., 1995). The variation diagrams led Cambray
et al. (1995) to propose that the chemistry of the three magma types was
controlled by batch melting processes at the source area(s).

The models of de Silva and Wolff (1995) and Cambray et a1. (1995) are
mutually supporting. Both models conclude that in situ diﬂ'erentiation
cannot produce large volume compositionally zoned magmas. The Batch
Emplacement model of Cambray et a1. (1995) was tested by: (1) determining
if the magma batches ﬁrst observed by Mills (1991) are real by better

deﬁning the chemistry of the system; and (2) characterizing the petrogenetic

38
relationship between the high and low-Th magma types. It has been

determined the compositionally distinct high and low-Th magma batches
observed by Mills (1991) are real. Additionally, it has been determined that
these magma batches are compositionally distinct and cannot be

petrogenically related by in situ differentiation.

Conﬁrmation of the existence of the high and low-7h magma batches

Using mineral and whole-pumice geochemistry in conjunction with
geothermometry, the existence of the high and low-Th magma batches has
been conﬁrmed. All geochemistry, both whole-pumice and mineral, indicates
separate and distinct compositions for the high and low-Th magma batches.

For whole-pumice geochemistry, Figures 8 and 9 clearly demonstrate,
ﬁrstly, that the high and low-Th magmas are distinct with respect to both
major and trace elements. Secondly, these ﬁgures indicate that Mills’ (1991)
XRF and INAA whole-pumice analysis are reproducable. Note that new
geochemical analysis for the high and low-Th magma batches are consistent
with Mills’ (1991) analysis.

Furthermore, mineral assemblage compositions for all phases are,
almost without exception, separate and distinct . Figures 10 through 13
demonstrate the compositional distinctness of all mineral phases present:
magnetite, ilmenite, biotite and plagioclase. Only alkali feldspar

compositions for both the high and low-Th magma batches are similar. If the

39
high and low-Th magmas were related by in situ differentiation, then it

would be reasonable to expect mineral compositions to overlap in a manner
that reﬂects progressive evolution of a single magma. The evidence of the
compositionally distinct mineral assemblages provides additional evidence
that the high and low-Th magma types are not petrogenically related by in
situ differentiation.

Mineral chemistry and composition can provide an understanding of
phase relationships, and also provide constraints on the physical conditions
present in the magma chamber prior to eruption. Fortunately, the mineral
assemblages for both the high and low-Th magmas were conductive to the
calculation of Fe-Ti oxide and ternary-feldspar geothermometry data. Both
the Fe-Ti oxide and ternary-feldspar thermometry data indicate that the
high-Th magma has a consistently higher temperature than low-Th magma
(Fig. 16).

The high and low-Th magma types have diﬂ'erent whole-pumice
geochemistry, different mineral compositions and different temperatures. On
the basis of these fundamental and consistent distinctions, the existence of
the compositionally distinct high and low-Th magma batches has been

conﬁrmed.

40

 

 

 

 

l l
0
‘ —
0
<0» ‘ ‘3’
‘ ‘
F 1
O A. . m
l l
700 750 Temp (0 C) 300 350

0 = Low-Th magma Fe-Ti oxide temperature
A = Low-Th magma feldspar temperature
‘3’ = High-Th magma Fe-Ti temperature

A = High-Th magma feldspar temperature

Figure 16. Temperature versus Th/Nb. Both the Fe-Ti oxide
and ternary-feldspar temperature indicate that the high-Th
magma had signiﬁcantly higher temperatures than the low-Th
magma. Furthermore, the ternary-feldspar temperature data
provides conﬁrmation of Fe-Ti oxide data.

41

Geothermometric Considerations

The geothermometry data establishes that the two magmas had
temperature diﬁ'erences that ranges from 74 to 98°C. This temperature
contrast implies that the surface area of contact between the high and low-Th
magmas must have been relative small to prevent thermal equilibrium.
Possibly, the magmas were vertically stratiﬁed in the pre-eruptive magma
chamber rather than commingling as unmixed blebs prior to eruption.
Vertically stratiﬁed magmas would have less contact surface area than
relatively spherical pockets of coexisting magma types.

Mills (199 1) evaluated the temperature distribution of the entire
Rainier Mesa Tuﬂ'. His thermometry data indicates the low silica Rainier
Mesa magma had temperatures which range from 875 to 900 °C. The
temperatures of the low silica magma are higher than the temperatures of
the high silica magmas. This observation is consistent with models of
stratigraphically zoned magma chambers. These models predict that maﬁc
magmas are overlain by cooler, less dense silicic magmas (e.g. Hildreth, 1981;
Smith, 1979).

However, it should be noted that typical models of stratigraphically
zoned magma chambers require in situ diﬂ’erentiation mechanisms to
produce cooler, silica rich, magmas. These models, furthermore, stipulate
that the temperature gradient continuously becomes cooler, higher in the

magma chamber (Hildreth, 1981; Smith, 1979). Contrary to the conclusions

Temp (°C)

900

850

800

750

700

42

 

 

 

 

l T l l I
+
+ + + +
+
.— ++ _
0 Q
_ ‘ ‘ 4;, _
0 A
0
0 A
l l l I Q
50 55 60 65 70 75 80
Sio2 ‘

0 = Low-Th magma Fe-Ti oxide temperature
A = Low-Th magma feldspar temperature
<C>= High-Th magma Fe-Ti temperature

L = High-Th magma feldspar temperature

‘1" = Low silica magma Fe-Ti oxide temperature
(Mills, 1991)

Figure 17. SiO2 versus temperature diagram showing the
discontinuous thermal gradient in the pre-eruptive Rainier
Mesa magma chamber.

43
of Mills (1991), the pre-eruptive Rainier Mesa magma chamber had a

discontinuous thermal gradient. All three of the Rainier Mesa magma types
had signiﬁcantly different temperatures (Fig. 17). However, it should be
noted that this geothermometic data cannot preclude the existence of
multiple high silica magma chambers.

In summary, geothermometric data are interpreted to indicate that the
magmas in the pre-eruptive Rainier Mesa magma chamber were
stratigraphically isolated rather than commingling as unmixed blebs prior to
eruption. Furthermore, the presence of a discontinuous thermal gradient
with sharp temperature interfaces additionally indicates that the high and

low-Th magmas cannot be petrogenically related by in situ differentiation.

Conclusions

The purpose of this investigation was to obtain whole-pumice
geochemistry and mineral assemblage chemistry to better characterize the
high and low-Th magma batches and, subsequently, test the batch
emplacement model of Cambray et a1. (1995). The signiﬁcant conclusions
that resulted from this study are:

l) The existence of the high and low-Th magma batches, ﬁrst observed
by Mills (1991), has been conﬁrmed. This conﬁrmation is based on a through
analysis of high and low-Th pumice geochemistry, mineral chemistry and
geothermometry data. The data indicates that the two high silica Rainier
Mesa magma types are chemically, mineralogically and physically distinct.

2) Fe-Ti oxide and ternary-feldspar thermometry data both indicate
that the high-Th magma is hotter ( 3:790 °C) than the low-Th magma
(~7 30°C). Therefore, the contact surface area between the two magma
batches must have been relatively small in order to inhibit thermal
equilibrium prior to eruption of the Rainier Mesa Tuﬂ’. To minimize contact
surface area, it is likely that the magmas were stratigraphically segregated
and did not commingle as unmixed pockets of distinct magma.

3) The batch emplacement model of Cambray et al. (1995) is
supported by this study. All step -wise multiple linear regression major

element and trace element models fail to relate the high and low-Th magmas ‘

45

by in situ diﬁ‘erentiation mechanisms. Additionally, there are no
differentiation pathways that relate the high and low-Th magmas within
variation diagrams of pumice geochemistry and mineral chemistry.

4) The models of Cambray et a1. (1995) and de Silva and Wolff (1995)
both stipulate that in situ differentiation cannot produce large volume zoned
magmatic systems. Because the work of Cambray et a1. (1995), and ‘
consequently de Silva and Wolff (1995), has been supported by this study, I

the origin of many large volume compositionally zoned magmatic systems

 

may be attributed to batch melting processes, not in situ diﬁ’erentiation.

APPENDICES

APPENDIX A

Analytical Techniques and Error Analysis

46
Appendix A' Analytical Techniques and Error Analysis

X—Ray Fluorescence

X-Ray Fluorescence analysis (XRF) of glassy pumice fragments provided
geochemical data on all major elements and the trace elements: Cr, Ni, Cu, Zn,
Rb, Sr, Y, Zr, Nb, La, and Ba. Samples were prepared for analysis by the XRF
methods outlined in Mills (1991). United States Geological Survey (U SGS)
standards were used as both known and unknowns to determine XRF analytical
error. All analytical errors for major elements are below 1%. Errors for Zn, Rb,
Sr, Y, Zr, Nb are all below 10 ppm. However, La and Ba errors are greater than
10 ppm. La and Ba concentrations were resolved with greater precision using
instrumental neutron activation analysis (IN AA). Cr, Ni and Cu concentrations

for these samples are generally below the detection limits of XRF analysis.

Instrumental Neutron Activation Analysis

All samples of the high and low-Th magma batches were analyzed by
Instrumental Neutron Activation Analysis (INAA). Each sample consisted of a
0.200g to 0.250g split of the XRF powder. All samples were heat sealed in a
high purity quartz tubing and sent to the Phoenix Laboratory/Ford Nuclear
Reactor at the University of Michigan for extended irradiation. Sc, Hf, Th, La,
Ce, Sm, Eu, Tb, Yb, and Lu concentrations were obtained by this analytical

technique. INAA analysis errors for all of these elements are reported in Table 3.

47
Appendix A: Continued

Electron Microprobe Analysis

Phenocryst compositions were obtained by automated electron microprobe
analysis on a Cameca microprobe at the University of Michigan. Phenocrysts
were separated from the glassy pumice ﬁ'agments using the methodology
described by Mills (1991). Typically, each grain was analyzed in three localities
(edge, middle and center) to determine compositional homogeneity. All minerals
were analyzed with a beam current of 9.4nA at l5kV. The beam was rastered
over an area of 100 umz. Oxide and silicate standards were analyzed
intermittently for calibration purposes. Furthermore, the software controlling
the automated electron miroprobe analysis used the Bence-Albee correction

procedure to resolve all quantitative analyses (Bence and Albee, 1968).

Appendix A: Continued 48
Table 3. Error analysis of Instrumental Neutron Activation Analysis. J G-3 is a

U.S.G.S. granodiorite geostandard, and JR-2 is a U.S.G.S. rhyolite geostandard.
Analytical uncertainty was calculated by determining the difference between the

known and INAA predicted elemental concentrations.

Sc Hf Th La Ce Sm Eu Tb Yb Lu

JG-3
Known (ppm) 8.93 4.29 8.0 20.7 41.1 8.41 0.91 0.46 1.86 0.27
Predicted (ppm) 8.40 4. 45 8.5 21.8 41.2 3.32 1.01 0.64 1.47 0.20

Uncertainty (ppm) 0.53 0.16 0.5 1.1 0.1. 0.09 0.10 0.22 0.39 0.07

JR-2
Known (ppm) 5.57 5.23 32.2 16.9 38.8 5.71 0.15 1.18 5.46 0.9
Predicted (ppm) 5.38 6.22 33.9 16.5 42.9 5.34 0. 20 1.21 5.40 0.9

Uncertainty (ppm) 0.19 0.99 0.7 0.4 3.9 0.37 0.05 0.03 0.06 0.0

APPENDIX B

Major and Trace Element Analyses

49

Appendix B: Major and Trace element analysis of the high

silica Rainier Mesa Tuﬂ‘. Includes data from Mills (1991).

The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
, R8-l R8-2 R8-3 R8-6 R8-7 R8-9
[ Weight Percent Oxide (wt%)
8102 76 75.99 ' 75.75 75.86 76.3 75.48
T102 0 0.11 0.1 0.11 0.11 0.1
.41203 12 12.03 11.89 12.09 12 12.09
FeO 0 0.52 0.55 0.44 0.58 0.52
MnO 0 0.07 0.06 0.07 0.06 0.07
MgO 0 0 0 0 0 0.01
CaO 0 0.4 0.48 0.42 0.48 0.43
NazO 3 2.91 2.52 3.08 2.52 2.69
K20 5 5.34 5.69 5.16 5.7 5.54
P205 0 0.01 0.01 0.01 0.01 0.01
Total 97 97.38 97.05 97.24 97.76 96.94
I X-Ray Fluorescence (ppm) 1
Cr 14 7.1 0.5 10.7 12.8 7.3
Ni 0 0 1.9 0 10 0
Cu 0 10.8 0 0 0 0
Zn 30 34.3 16.3 36.1 14.8 28.3
Rb 265 258.56 264.8 257.16 271.9 266.5
Sr 3 0 4.55 0.19 0 4.96
Y 30 33.38 31.32 31.28 26.01 32
Zr 69 89.26 73.64 78.21 80.16 70.78
Nb 29 25.72 26.26 29.57 23.85 30.25
La 35 20.14 41.66 48.36 28.14 22.19
Ba 132 100 190 86 169 87
L INAA (ppm) ]
Sc 4 4.25 4.17 4.14 3.34 4.59
Hf 4 3.9 3.44 2.62 2.31 2.9
Th 25 25.22 21.8 16.64 11.69 15.58
La 21 21.1 21.34 19.64 20.32 24.11
Ce 51 58.68 48.81 44.91 36.33 40.07
Sm 6 6.26 5.77 5.51 5.22 5.5
Eu 0 0.18 0.17 0.14 0.19 0.2
Tb 1 0.63 0.61 0.56 0.52 0.55
Yb 4 3.54 2.81 2.87 1.67 2.15
Lu 0 0.36 0.3 0.32 0.24 0.26

50

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuff. Includes data from Mills (1991).

The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
I R8-10 R8-ll R8-14 R8-15 R8-16 R8-32A |
I Weight Percent Oxide (wt%)
8102 74.69 73.93‘ 75.54 75.45 73.77 73.09
Tio2 0.09 0.09 0.1 0.1 0.12 0.21
A1203 12.2 12.48 12.21 12.16 12.86 12.84
FeO 0.42 0.39 0.42 0.46 0.74 0.86
MnO 0.07 0.07 0.07 0.07 0.08 0.05
MgO 0 0 0.04 0 0.52 0.12
CaO 0.4 0.44 0.41 0.43 0.41 0.79
NazO 3.48 3.54 2.73 2.52 2.51 2.82
K20 5.04 5.05 5.41 5.83 4.92 5.85
P20, 0.01 0.01 0.01 0.01 0.02 0.03
Total 96.4 96 96.94 97.03 95.95 96.66
F X-Ray Fluorescence (ppm) I
Cr 0 0 1.4 0 2.9 7.1
Ni 0 7.4 6.6 0 13 18.9
Cu 0 0 0 0 0 0
Zn 26.8 16.9 15.9 18.5 186.8 11.3
Rb 255.72 259.5 261.78 281.95 252.21 116.65
Sr 3.65 3.48 0 0 14.09 74.99
Y 32.1 29.77 31.56 28 45.77 16.95
Zr 59.8 62.01 71.89 72.43 107.22 168.08
Nb 27.96 26.77 27.61 24.32 26.24 14.09
La 44.95 16.44 15.24 9.33 35.86 82.39
Ba 88 229 203 88 268 485
L INAAgppm>
Sc 4.21 3.76 4.11 3.44 3.56 1.81
Hf 3.29 3.35 3.5 3.27 4.02 5.78
Th 22.14 21.81 22.83 22.74 24.43 35.23
La 18.72 18.91 18.62 16.91 16.34 80.23
Ce 44.2 45.19 47.79 48.97 61.18 129.64
Sm 5.22 5.6 5.25 5.29 5.83 5.69
Eu 0.12 0.14 0.17 0.17 0.28 0.73
Tb 0.62 0.61 0.62 0.61 0.63 0.68
Yb 4.08 3.79 3.84 3.65 3.99 1.81
Lu 0.42 0.41 0.35 0.36 0.49 0.19

51

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuff. Includes data from Mills (1991 ).
The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
R8-3ZB R8-35 R8-40 R8-41 R8-42 R1 1-3
Weight Percent Oxide (wt%) |
Si02 74.22 75.62 73.53 73.54 74.19 73.97
TiOz 0.25 0.2 0.2 0.22 0.27 0.11
A1203 12.35 11.72 12.83 12.95 12.59 12.53
FeO 1.01 0.87 0.81 0.88 1.02 0.5
MnO 0.06 0.04 0.04 0.05 0.05 0.05
M30 0.15 0.03 0.07 0.12 0.15 0.25
CaO 0.81 0.51 0.73 0.78 0.75 0.67
NaZO 2.67 2.18 2.83 2.61 2.86 2.41
K20 5.68 6.1 5.93 6.08 5.67 6.39
P205 0.03 0.02 0.03 0.03 0.03 0.02
Total 97.23 97.29 97 97.26 97.58 96.9
I X-Ray Fluorescence (ppm) J
Cr 5.4 0 5.7 6.3 0 0
Ni 0 0 0 1 0 1.4
Cu 0 6.7 0 0 0 0
Zn 33.3 32.6 26.8 16.1 20.9 16.3
Rb 117.04 141.98 112.09 125.06 121.2 247.68
Sr 58.69 34.59 62.92 72.58 68.19 0.23
Y 18.1 21.34 21.25 23.85 21.1 28.76
Zr 183.27 153.51 152.99 169.47 193.7 78.5
Nb 13.22 15.09 14.96 15.85 16.39 31.28
La 74.55 79.83 76.09 82.36 89.85 0
Ba 189 157 263 454 433 0
INAA (ppm) 1
Se 1.81 1.97 ‘ 1.62 1.73 1.95 3.66
Hf 5.78 4.71 4.4 4.87 5.42 3.27
Th 35.23 33.45 29.19 33.19 37.56 22.26
La 80.23 68.72 62.9 83.79 86.51 21.81
Ce 129.64 110.48 98.98 122.99 138.12 58.25
Sm 5.69 6.04 5.32 7.15 6.43 5.58
Eu 0.73 0.59 0.8 0.92 0.69 0.12
Tb 0.68 0.68 0.64 0.68 0.69 0.48
Yb 1.81 1.66 1.48 1.83 1.47 2.24
Lu 0.19 0.16 0.17 0.17 0.1 0.31

52

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬁ‘. Includes data from Mills (1991).

The " denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
R11-7 R11-20 R18-1 R18-2 R18-3 R18-4
| Weight Percent Oxide (wt%)
8102 74.08 72.16 76.12 72.72 74.98 75.58
Tio2 0.11 0.26 0.1 0.16 0.11 0.11
A1203 12.98 13.4 12.3 14.36 13.03 12.38
FeO 0.53 1.18 0.56 0.77 0.56 0.53
Mno 0.1 0.05 0.07 0.05 0.07 0.07
MgO 0.27 0.16 0.01 0.48 0.25 0
CaO 0.43 0.78 0.39 0.51 0.41 0.42
N820 2.59 2.39 3.51 2.56 3.05 3.58
K20 6.24 7.13 4.65 5.09 5.1 4.86
P205 0.02 0.05 0.01 0.02 0.01 0.01
Total 97.35 97.56 97.72 96.72 97.57 97.54
I X-Ray Fluorescence (ppm) I
Cr 0 0 0 0 0 0*
Ni 13 0 0 0 0 0
Cu 0 0 0 0 0 0
Zn 8 20.1 26.9 44.1 36.4 33.5
Rb 238.42 165.9 251 155.22 238.56 252.75
Sr 4.4 97.46 1.88 10.96 0 0.47
Y 32.17 16.3 29.94 22.56 31.77 31.04
Zr 78.68 210.82 67.21 112.18 80.92 73.46
Nb 31.16 16.21 27.26 20.42 27.54 26.43
La 36.8 85.6 27.4 33.6 10.3 36.2
Ba 0 407.6 0 0 0 0
I INAA (rpm) l
Sc 4.1 2.08 4.5 1.61 2.66 0.94
Hf 3.09 4.57 ‘ 3.26 4.53 1.96 3.79
Th 21.11 31.26 21.44 33.72 20.88 23.29
La 23.67 82.03 26.58 31.4 16.7 31.54
Ce 60.34 135.5 42.75 79.44 48.7 47.33
Sm 5.39 6.03 5.37 5.4 5.13 5.43
Eu 0.13 0.6 0.07 0.17 0.13 0.01
Tb 0.44 0.06 0.52 0.39 ' 0.49 0.49
Yb 2.21 1.18 2.94 2.13 1.83 2.75
Lu 0.28 0.09 0.44 0.33 0.37 0.47

 

53

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬁ’. Includes data ﬁom Mills (1991).

The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number

R18-5“ R18-6“ R18-8 R18-9* R18-10* R18-11“ 7

Weight Percent Oxide (wt%) I

Si02 74.77 75 75.07 76.16 75.48 75.7
TiOz 0.1 0.12 0.18 0.1 0.14 0.1
A1203 13.08 12.73 12.92 12.81 12.61 13
FeO 0.58 0.68 0.81 0.51 0.63 0.51
MnO 0.07 0.07 0.05 0.07 0.06 0.07
MgO 0.29 0.08 0.37 0.14 0.25 0.33
C80 0.38 0.39 0.58 0.41 0.48 0.4
Nazo 2.94 3.48 2.53 2.8 2.51' 2.87
K20 5.28 4.9 5.22 5.56 5.67 5.35
P205 0.01 0.02 0.23 0.01 0.02 0.01
Total 97.5 97.47 97.96 98.57 97.85 98.34

X-Ray Fluorescence (ﬁlm) I

Cr 46.19 50.37 0 54.04 44.58 50.687
Ni 0 0 0 0 0 0
Cu 0 0 0 0 0 0
Zn 40.94 33.47 49.6 29.83 54.15 29.71
Rb 245.06 252.29 151.73 253.55 195.36 251.54
Sr 2.03 4.73 23.87 2.69 13.65 2.93
Y 30.28 31.56 20.07 30.23 21.7 27.69
Zr 77.78 73.44 112.39 78.23 97.31 82.97
Nb 27.6 28.8 17.56 31.4 22.6 30.4
La 59.26 17.51 22 12.62 19.7 0
Ba 138.02 6.23 0 158.42 113.98 23.54

INAA (ppm) 1

Se 4.04 3.95 3.63 4 2.67 3.89
Hf 3.91 3.79 4.15 3.81 3.91 3.6
Th 24.57 22.64 34.49 23.58 29.35 23.02
La 22.55 21.15 38.23 22.03 36.43 22
Ce 51.45 50.58 88.54 51.53 72.12 48.97
Sm 4.32 4.32 5.12 4.37 5.13 4.46
Eu 0.09 0.167 0.25 0.17 0.178 0.172
Tb 0.84 0.672 0.37 0.86 0.728 0.726
Yb 3.06 3.17 2.03 3.37 2.24 3
Lu 0.513 0.527 0.26 0.52 0.337 0.495

54

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬁ’. Includes data from Mills (1991).
The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
7 R18-12 R18-14* RIB-15* Rl8-l6 R18-l8 R18-19 7
I Weight Percent Oxide (wt%) I
S102 75.11 76.1 73.13 75.42 76.22 75.41
1102 0.12 0.11 0.1 0.16 0.12 0.11
A1203 12.49 12.42 12.55 12.39 12.02 12.48
FeO 0.63 0.58 0.56 0.72 0.6 0.48
MnO 0.06 0.07 0.08 0.05 0.05 0.07
MgO 0.04 0.01 0.56 0.18 0 0
CaO 0.46 0.4 1.23 0.58 0.49 0.43
Na20 3.41 3.47 2.75 2.93 3.36 3.53
K20 5.2 4.94 5.64 5.54 4.93 4.94
P205 0.01 0.01 0.01 0.02 0.01 0.01
Total 97.53 98.11 96.61 97.99 97.8 97.46
I X-Ray Fluorescence (ppm) I
Cr 0 42.54 39.04 0 0 2
Ni 0 0 0 0 ' 0 0
Cu 0 0 0 0 0 0
Zn 30.7 29.35 36.68 28 24.6 30.3
Rb 222.31 236.45 265.82 144.77 177.93 251.26
Sr 0 1.81 53.36 21.61 6.97 0
Y 25.65 33.28 26.43 18.17 19.92 27.99
Zr 83.07 70.94 87.04 109.77 87.2 71.32
Nb 21282 33.6 29.9 11.12 15.01 23.96
La 40.9 4.86 21.74 39.6 51 22.3
Ba 0 144.94 6.5 12.8 0.9 0
L INAA (_ppm) 1
Sc 3.5 3.59 3.83 3 3.17 3.04
Hf 3.93 3.54 3.98 3.5 3.42 3.87
Th 25.06 21.03 22.5 31.47 25.72 22.34
La 27.96 20.48 21.22 36.68 30.19 29.06
Ce 57.59 46.74 47.15 85.23 61.88 46.64
Sm 5.51 4.16 4.22 4.97 5.06 5.05
Eu 0.16 0.102 0.166 0.32 0.08 0.05
Tb 0.4 1.04 0.811 0.5 0.23 0.53
Yb 2.41 3.09 3.14 2.01 2.36 3.16
Lu 0.41 0.5 0.535 0.25 0.41 0.53

55

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬂ‘. Includes data from Mills (1991).

The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
R18-20 R18-22 R18-23 R21-5 R21-6 R21-9
L Weight Percent Oxide (wt%)
Sio2 73.97 75' 75.35 73.48 74.2 74.91
Tio2 0.23 0.12 0.1 0.27 0.24 0.2
A1203 12.64 12.37 12.35 12.72 12.74 12.34
FeO 0.93 0.56 0.48 1.18 0.98 0.79
MnO 0.05 0.06 0.07 0.07 0.06 0.06
MgO 0.17 0 0.04 0.61 0.09 0.08
C80 0.65 0.5 0.42 0.82 0.67 0.61
N820 3.37 3.52 3.59 2.89 2.98 2.81
K20 5.23 5.04 5.03 5.38 5.45 5.55
P20, 0.03 0.01 0.01 0.05 0.03 0.02
Total 97.27 97.18 97.44 97.47 97.44 97.37
I X-Ray Fluorescence (_ppm) J
Cr 0.3 0 0 1 0.4 0
N1 0 0 0 0 0 0
Cu 0 0 0 5.4 1.1 3.5
Zn 49.3 29.7 26.9 55.9 37.8 34.6
Rb 127.58 206 253.88 99.18 111.49 122.2
Sr 45.52 6.65 5.27 66.79 59.29 31.54
Y 14.28 23.99 28.15 14.96 14.86 14.51
Zr 169.42 81.61 72.21 205.05 187.38 150.12
Nb 15.94 25.75 27.45 14.76 13.78 13.01
La 56.2 30.1 15.8 103.94 76.27 74.03
Ba 94.2 0 0 277 263 35
I INAA (ppm)
Sc 1.86 3.6 3.1 1.7 1.87 2.45
Hf 5.1 3.62 3.82 5.28 5.43 4.35
Th 33.3 26.16 21.93 32.2 34.69 31.54
La 56.73 33.34 28.81 76.52 78.5 69.46
Ce 122.61 62.65 45.59 130.81 135.81 111.06
Sm 5.99 5.17 5.26 6.63 5.76 5.38
Eu 0.54 0.03 0.03 0.59 0.6 0.4
Tb 0.3 0.37 0.42 0.74 0.74 0.75
Yb 2.16 2.64 2.98 1.84 1.85 1.86
Lu 0.32 0.42 0.55 0.18 0.25 0.24

56

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬂ‘. Includes data from Mills (1991 ).

The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
7 R21-12 R21-18 R21-19 R21-23 R21-26 R21-40
I Weight Percent Oxide (wt%) I
8102 74.52 75.11 74.52 74.57 75.49 7613
T10; 0.21 0.14 0.13 O. 13 0.13 0.13
A1203 12.21 12.13 12.63 12.41 12.09 11.99
FeO 0.85 0.72 0.72 0.69 0.71 0.61
MnO 0.05 0.08 0.08 0.08 0.08 0.05
MgO 0.34 0 0.32 0.01 0 0
CaO 0.59 0.41 0.35 0.37 0.37 0.51
Na20 2.54 3.55 2.99 3.75 3.6 2.88
K20 5.48 5.07 5.3 4.7 4.99 5.29
P205 0.03 0.01 0.01 0.01 0 0.01
Total 96.82 97.22 97.05 96.72 97.46 97.6
I X—Ray Fluorescence (ppm) I
Cr 0 0 0 O 0 0
Ni 0 0 0 0 0 0
Cu 0.3 1 0 1.6 0 0
Zn 32.7 53.3 55.9 55.3 54.2 75.6
Rb 133.75 218.76 208.97 217.9 222.23 163.87
Sr 26.96 3.8 0 4.79 2.42 22.03
Y 13.94 30.06 27.64 27.16 34 15.31
Zr 166.75 131.3 128.13 120.08 125.52 95.8
Nb 12.81 28.38 28.3 31.03 31.15 18.69
La 92.15 50.51 51.7 44.27 34.22 48.65
Ba 55 0 25 128 104 134
I INAA (ppm) 1
Sc 1.79 1.34 1.54 1.58 1.69 2.66
Hf 5.05 5.22 3.92 5.31 5.58 2.66
Th 32.43 29.95 24.19 31.96 32.76 20.96
La 72.62 34.67 28.48 33.06 32.04 ' 40.47
Ce 118.15 64.01 49.65 57.84 69.9 55.41
Sm 5.92 5.8 5.51 5.24 6.13 5.18
Eu 0.4 0.09 0.12 0.17 0.16 0.16
Tb 0.75 0.76 0.47 0.75 0.74 0.33
Yb 1.93 3.11 1.3 2.76 2.98 0.99
Lu 0.28 0.55 0.22 0.5 0.55 0.11

57

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬂ‘. Includes data from Mills (1991).
The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number 7
R21-44 R21-5 R21-6 R21-9 R21-12 R21-18 |
Weight Percent Oxide (wt%) I
$10; 74.4 73.48 74.2 74.91 74.52 75.11
TiOz 0.24 0.27 0.24 0.2 0.21 0.14
A1203 12.83 12.72 12.74 12.34 12.21 12.13
FeO 1.06 1.18 0.98 0.79 0.85 0.72
MnO 0.05 0.07 0.06 0.06 0.05 0.08 7
MgO 0.13 0.61 0.09 0.08 0.34 0
C80 0.75 0.82 0.67 0.61 0.59 0.41
NaZO 3.03 2.89 2.98 2.81 2.54 3.55
K20 5.47 5.38 5.45 5.55 5.48 5.07
P205 0.03 0.05 0.03 0.02 0.03 0.01
Total 97.99 97.47 97.44 97.37 96.82 97.22
X-Ray Fluorescence (ppm) j
Cr 11.8 1 0.4 0 0 0
N1 0 0 0 0 0 0
Cu 0 5.4 1.1 3.5 0.3 1
Zn 45.5 55.9 37.8 34.6 32.7 53.3
Rb 116.25 99.18 111.49 122.2 133.75 218.76
Sr 69.91 66.79 59.29 31.54 26.96 3.8
Y 14.52 14.96 14.86 14.51 13.94 30.06
Zr 186.51 205.05 187.38 150.12 166.75 131.3
Nb 9.71 14.76 13.78 13.01 12.81 28.38
La 82.9 103.94 76.27 74.03 92.15 50.51
7Ba 258 277 263 35 55 0
INAAme)
Sc 1.73 1.7 1.87 2.45 1.79 1.34
Hf 3.66 5.28 5.43 4.35 5.05 5.22
Th 24.06 32.2 34.69 31.54 32.43 29.95
La 73.02 76.52 78.5 69.46 72.62 34.67
Ce 87.38 130.81 135.81 111.06 118.15 64.01
Sm 5.25 6.63 5.76 5.38 5.92 5.8
Eu 0.55 0.59 0.6 0.4 0.4 0.09
Tb 0.33 0.74 0.74 0.75 0.75 0.76
Yb 0.66 1.84 1.85 1.86 1.93 3.11
Lu 0.07 0.18 0.25 0.24 0.28 0.55

58

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬂ‘. Includes data from Mills (1991).

The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
7 R21-19 R21-23 R21-26 R21-40 R21-44 R23-7* 7
| Weight Percent Oxide (wt%) |
SiO2 74.52 74.57t 75.49 76.13 74.4 72.48
TiO2 0.13 0.13 0.13 0.13 0.24 0.29
.41203 12.63 12.41 12.09 11.99 12.83 13.65
FeO 0.72 0.69 0.71 0.61 1.06 1.36
MnO 0.08 0.08 0.08 0.05 0.05 0.06
MgO 0.32 0.01 0 0 0.13 0.44
CaO 0.35 0.37 0.37 0.51 0.75 0.85
NaZO 2.99 3.75 3.6 2.88 3.03 2.94
K20 5.3 4.7 4.99 5.29 5.47 5.64
P205 0.01 0.01 0 0.01 0.03 0.05
Total 97.05 96.72 97.46 97.6 97.99 97.76
I X-Ray Fluorescence (m) I
Cr 0 0 0 0 11.8 55.92
Ni 0 0 0 0 0 0
Cu 0 1.6 0 0 0 0
Zn 55.9 55.3 54.2 75.6 45.5 35.82
Rb 208.97 217.9 222.23 163.87 116.25 131.19
Sr 0 4.79 2.42 22.03 69.91 122.08
Y 27.64 27.16 34 15.31 14.52 26.53
Zr 128.13 120.08 125.52 95.8 186.51 250.45
Nb 28.3 31.03 31.15 18.69 9.71 20.2
La 51.7 44.27 34.22 48.65 82.9 69.63
Ba 25 128 104 134 258 485.13
1 INAA (9pm) I
Sc 1.54 1.58 1.69 2.66 1.73 2.13
Hf 3.92 5.31 5.58 2.66 3.66 8.04
Th 24.19 31.96 32.76 20.96 24.06 35.07
La 28.48 33.06 32.04 40.47 73.02 100.65
Ce 49.65 57.84 69.9 55.41 87.38 168.28
Sm 5.51 5.24 6.13 5.18 5.25 6.6
Eu 0.12 0.17 0.16 0.16 0.55 0.781
Tb 0.47 0.75 0.74 0.33 0.33 0.741
Yb 1.3 2.76 2.98 0.99 0.66 1.63
Lu 0.22 0.5 0.55 0.11 0.07 0.223

59

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬁ‘. Includes data from Mills (1991).

The * denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
R23-9* R23-8* R25-1 R25-11 R25-12 R25-14
Weight Percent Oxide (wt%) |
SiO2 76.02 7505' 75.97 72.32 75.27 73.86
TiO2 0.18 0.24 0.13 0.29 0.11 0.24
A1203 12.2 12.69 11.64 13.82 12.45 12.9
FeO 0.81 0.91 0.74 1.15 0.42 0.86
MnO 0.04 0.05 0.1 0.06 0.05 0.05
MgO 0.34 0.23 0.18 0.31 0.03 0.28
C80 0.53 0.66 0.5 0.81 0.38 0.56
NazO 2.67 3.06 2.84 3.22 2.78 3.05
K20 5.41 5.46 5.76 5.26 5.55 5.3
P205 0.02 0.03 0.1 0.06 0.01 0.03
Total 98.22 98.38 97.96 97.3 97.05 97.13
I X-Ray Fluorescence (ppm) I
Cr 39.51 48.02 0 0 1.4 0
Ni 0 0 12.4 0 0 1.7
Cu 0 0 0 0 0 0
Zn 29.38 58.07 32.8 156.8 95 108
Rb 143.44 118.85 240.85 161.35 272.61 272.23
Sr 37.31 56.71 7.45 84.66 0 47.1
Y 18.62 16.98 40.46 18.99 30.88 14.72
Zr 135.09 193.55 127.96 239.99 82.73 186.98
Nb 20.6 21.9 35 16.28 27.09 15.8
La 71.95 45.44 19.8 82.6 12.4 76.7
Ba 111.46 140.15 1.7 288 0 153.6
INAA(_ppm) I
So 1.67 1.85 1.93 2.44 3.47 2
Hf 4.99 6.51 4.48 5.18 3.16 4.41
Th 28.14 32.02 31.12 31.59 21.75 31.22
La 48.71 75.13 33.51 93.86 23.06 70.44
Ce 94.06 129.53 79.59 156.19 57.22 125.41
Sm 4.57 5.53 6.13 6.37 5.07 5.43
Eu 0.352 0.577 0.26 0.72 0.13 0.49
Tb 0.525 0.412 0.4 0.38 0.43 0.24
Yb 1.5 1.44 2.33 1.64 2.14 1.4
Lu 0.183 0.285 0.3 0.17 0.28 0.13

60

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuff. Includes data from Mills (1991).
The "' denotes new chemical analyses.

 

 

 

 

 

 

 

Sample Number
7 R25-16 R25-20 R26-12* R26-14* R26-19* R26-20* 7
| Weight Percent Oxide (wt%) |
SiO2 75.68 76.07 74.98 74.67 75.67 75.1
TiO2 0.15 0.1 0.18 0.19 0.19 0.15
4.1203 12.19 12.48 12.92 12.58 12.8 12.98
FeO 0.56 0.35 0.89 0.76 0.93 0.82
MnO 0.04 0.05 0.04 0.04 0.05 0.06
MgO 0.08 0.01 0.24 0.14 0.18 0.26
CaO 0.5 0.36 0.51 0.5 0.54 0.37
NaZO 2.77 2.94 2.38 2.77 2.45 3.16
K20 5.54 5.5 6 6.01 6.09 5.03
P205 0.01 0.01 0.01 0.01 0.02 0.01
Total 97.52 97.87 98.15 97.67 98.92 97.94
X-Ray Fluorescence (ppm) I
Cr 0 0 41.87 44.53 51.84 40.59
Ni 0 7 0 0 0 0
Cu 0 0 0 o 0 0
Zn 32.7 59.9 27.03 65.46 28.01 62.33
Rb 220.07 337.53 160.05 131.05 140.36 215.54
Sr 9.22 0 25.78 27.81 32.18 0
Y 25.63 28.26 19.12 19.59 20.49 34.95
Zr 104.17 68.25 131.3 144.79 150.8 95.96
Nb 17.07 28.5 22.6 17.6 21.6 29.9
La 40.9 11.4 26.42 47.88 68.18 0
Ba 0 30.8 67.07 152.27 165.88 0
INAA (ppm) l
Sc 2.47 3.88 2 1.75 1.92 4.18
Hf 3.25 2.9 4.88 5.15 5.23 4.37
Th 28.46 19.28 30.13 31.57 30 23.42
La 42.3 22.27 51.18 63.93 66.13 25.5
Ce 81.96 49.76 94.41 111.84 105.84 60.18
Sm 5.35 4.98 5.41 5.51 6.06 4.6
Eu 0.17 0.06 0.399 0.507 0.618 0.183
Tb 0.21 0.43 0.482 0.682 0.746 0.755
Yb 1.33 1.92 1.83 1.54 1.73 3.31
Lu 0.14 0.26 0.281 0.205 0.326 0.518

61

Appendix B: Major and Trace element analysis of the high
silica Rainier Mesa Tuﬂ‘. Includes data from Mills (1991).
The * denotes new chemical analyses.
Sample Number

 

 

 

 

 

 

 

R26-21* R26-23*
Weight Percent Oxide (wt%)
8102 76.04 76.78
TiOz 0.1 0.16
A1203 12.77 12.35
FeO 0.56 0.81
MnO 0.06 0.04
MgO 0.04 0.07
CaO 0.38 0.51
NaZO 2.56 2.51
K20 6.03 5.94
P205 0.01 0.01
Total 98.55 99.18
X-Ray Fluorescence (ppm)
iCr 42.92 37.12
Ni 0 0
Cu 0 0
Zn 18.63 23.79
Rb 260.8 150.23
Sr 0 20.3
Y 32.39 19.38
Zr 72.78 123.18
Nb 32.4 21.8
La 13.14 44.9
Ba 74.07 18.89
INAA (gm)
Sc 3.77 1.87
Hf 3.41 4.26
Th 22 30.45
La 22 49.59
Ce 51.12 89.52
Sm 4.57 5.25
Eu 0.153 0.361
Tb 0.766 0.536
Yb 3.65 1.65
Lu 0.568 0.312

APPENDIX C

Electron Microprobe Analyses

62
Appendix C: Electron Microprobe Analyses
I Biotite Analysis I
|descn'pt. F N820 MgO .41203 SiO2 c1 K20 CaO TiO2 Cr203 M110 FeO TotalJ

 

 

R23-14-1 edge 0.69 0.58 13.57 18.10 33.07 0.05 8.24 0.02 5.79 0.02 0.29 15.01 95.43
R23-14-1 mid 0.56 0.65 13.52 18.34 32.92 0.05 8.06 0.01 6.01 0.00 0.27 15.24 95.63
R23-14-1 ctr 0.32 0.47 13.81 18.54 32.90 0.05 8.36 0.01 5.94 0.00 0.25 15.27 95.90
1123-14-2 edge 0.63 0.68 13.61 17.84 30.99 0.02 8.23 0.02 5.98 0.00 0.27 14.93 93.21
R23-14-2 mid 0.81 0.72 14.13 18.34 36.38 0.05 8.67 0.03 5.83 0.00 0.30 15.53 100.81
R23-14o2 mid2 0.70 0.69 13.75 18.32 36.20 0.04 8.52 0.06 6.08 0.00 0.33 15.48 100.16
R23-l4-3 edge 0.93 0.62 14.20 17.46 31.74 0.04 8.38 0.06 5.70 0.00 0.30 14.34 93.78
R23-14-3 mid 0.59 0.58 13.72 17.73 33.56 0.04 8.60 0.02 5.71 0.00 0.34 15.17 96.05
1123-14-3 ctr 0.77 0.64 13.93 17.67 33.74 0.03 8.44 0.02 5.71 0.00 0.28 14.85 96.08
1126-19-1 edge 1.06 0.54 13.88 16.52 36.60 0.06 8.47 0.02 4.21 0.03 0.33 15.71 97.43
R26-19-1 mid 0.97 0.55 13.88 17.73 36.96 0.08 8.38 0.02 4.12 0.01 0.35 15.68 98.74
1126-19-1 ctr 2.42 0.38 13.62 17.31 38.00 0.10 8.40 0.03 4.15 0.00 0.40 14.45 99.25
R26-19-2 edge 0.77 0.64 15.55 17.32 37.13 0.04 8.64 0.00 4.61 0.03 0.33 14.43 99.49
R26-l9-2 mid 0.78 0.64 15.28 17.08 36.99 0.05 8.55 0.01 4.71 0.00 0.28 14.17 98.52
R26—19-3 edge 1.31 0.48 14.60 16.86 36.59 0.06 8.45 0.04 4.62 0.00 0.33 14.63 97.97
R26-19-3 mid 0.99 0.56 15.22 17.06 36.21 0.08 8.59 0.01 4.92 0.00 0.30 14.31 98.23
R26-19-3 ctr 0.94 0.53 14.83 17.10 35.96 0.05 8.31 0.03 4.73 0.00 0.26 14.01 96.75
R18olS-l edge 2.38 0.44 14.19 13.01 37.82 0.10 9.07 0.02 3.52 0.04 0.67 16.19 97.45
R18-15-l mid 2.25 0.40 13.82 12.94 37.52 0.09 8.66 0.04 3.51 0.04 0.62 16.04 95.94
R18-15-1 ctr 2.02 0.40 13.77 12.95 38.29 0.09 8.72 0.06 3.62 0.06 0.63 16.42 97.02
Rl8-15-2 edge2 2.50 0.51 14.21 13.05 37.54 0.07 9.35 0.02 3.61 0.06 0.77 16.73 98.41
R18«15-2 mid 1.74 0.52 13.81 12.71 35.97 0.09 9.12 0.00 3.59 0.02 0.60 16.41 94.59
R18—15-2 ctr 1.78 0.52 13.94 12.81 36.88 0.06 9.29 0.01 3.71 0.03 0.63 16.26 95.92

R18-15—3 mid 2.20 0.42 13.93 12.83 37.05 0.11 8.82 0.11 3.43 0.03 0.63 16.53 96.11

R18—6—1 edge 1.81 0.51 14.24 12.05 38.62 0.10 9.15 0.00 3.56 0.08 0.73 16.89 97.74

Appendix C: Electron Microprobe Analyses

63

 

 

 

I Biotite Analysis I
klescript. F N820 MgO A1203 8102 C1 K20 CaO TiO2 Cr203 MnO FeO Total]
R18-6-1 mid 1.49 0.51 14.20 11.89 38.25 0.11 9.11 0.00 3.64 0.02 0.73 16.50 96.43
R18-6-1 ctr 1.44 0.57 14.68 12.19 39.39 0.09 9.30 0.00 3.53 0.08 0.76 16.43 98.46
R18-6-2edge 1.84 0.51 13.81 12.08 38.60 0.09 9.16 0.06 3.58 0.00 0.76 16.94 97.42
R18-6-2mid 1.67 0.52 14.54 12.60 39.94 0.09 9.17 0.00 3.65 0.05 0.78 16.33 99.33
R18-6-2 ctr 1.64 0.54 14.12 12.46 39.32 0.09 8.99 0.05 3.53 0.04 0.75 16.23 97.77
R18—6-3edge 1.58 0.54 13.80 11.91 39.08 0.06 9.30 0.00 3.58 0.07 0.77 16.44 97.13
R18-6-3mid 1.28 0.49 14.10 12.01 38.33 0.07 9.17 0.01 3.61 0.03 0.74 16.15 96.00
R18-6-3 ctr 1.89 0.49 14.24 12.15 38.29 0.07 9.15 0.00 3.58 0.01 0.77 15.80 96.45
R26-14-1 ctr 1.25 0.57 15.65 12.46 36.14 0.04 8.94 0.00 4.63 0.06 0.37 14.57 94.68
R26-14-2 edge 1.85 0.57 15.47 12.33 35.80 0.07 9.27 0.01 4.61 0.00 0.32 14.71 95.02
R26-14-2 mid 1.09 0.59 15.44 12.56 36.77 0.07 9.12 0.01 4.68 0.06 0.36 14.46 95.21
R26-14-2ctr 1.15 0.49 15.54 12.44 36.75 0.05 9.11 0.01 4.84 0.00 0.41 14.21 94.98
R26-14-3 edge 1.29 0.42 14.98 12.61 36.52 0.08 9.08 0.02 4.44 0.02 0.44 15.50 95.40
R26-14-3ctr 1.43 0.50 15.06 12.69 36.68 0.06 9.17 0.01 4.54 0.01 0.38 15.58 96.11
R18—15-1 edge 2.38 0.44 14.19 13.01 37.82 0.10 9.07 0.02 3.52 0.04 0.67 16.19 97.45
R18-15-1 mid 2.25 0.40 13.82 12.94 37.52 0.09 8.66 0.04 3.51 0.04 0.62 16.04 95.94
R18-15-1 ctr 2.02 0.40 13.77 12.95 38.29 0.09 8.72 0.06 3.62 0.06 0.63 16.42 97.02
R18-15.26dg62 2.50 0.51 14.21 13.05 37.54 0.07 9.35 0.02 3.61 0.06 0.77 16.73 98.41
R18-15-2mid 1.74 0.52 13.81 12.71 35.97 0.09 9.12 0.00 3.59 0.02 0.60 16.41 94.59
Rl8-15-2ctr 1.78 0.52 13.94 12.81 36.88 0.06 9.29 0.01 3.71 0.03 0.63 16.26 95.92
R18-15-3 mid 2.20 0.42 13.93 12.83 37.05 0.11 8.82 0.11 3.43 0.03 0.63 16.53 96.11
R18-11-1 edge 1.80 0.66 12.31 12.68 40.66 0.08 7.19 0.28 3.16 0.04 0.61 15.64 95.10
R18-11-1 mid 1.71 0.68 12.53 13.03 39.79 0.10 7.55 0.28 3.25 0.01 0.54 14.98 94.43
R18-11-lctr 1.90 0.55 12.94 12.33 39.45 0.12 7.62 0.35 3.23 0.03 0.55 14.87 93.95
R18-ll-2 edge 1.95 0.44 13.53 12.54 36.93 0.08 8.62 0.22 3.42 0.03 0.62 15.48 93.85

Appendix C: Electron Microprobe Analyses

64

 

 

 

I Biotite Analysis I
Idescript. F N820 MgO 74.1203 SiO2 C1 K20 CaO TiO2 Cr203 MnO FeO Total|
R18-11-2mid 1.68 0.46 13.63 12.51 37.93 0.08 8.01 0.24 3.26 0.04 0.53 14.95 93.33
R18-11-2ctr 1.76 0.36 13.74 12.59 38.35 0.10 8.20 0.17 3.50 0.00 0.53 15.14 94.44
R18-11-3 edge 2.59 0.48 13.88 13.05 38.05 0.06 8.72 0.22 3.45 0.00 2.36 15.60 98.46
R18—11-3mid 1.65 0.58 13.17 12.78 38.79 0.07 8.01 0.24 3.18 0.04 0.65 15.72 94.89
R23-7-1edge2 0.45 0.71 14.46 13.77 34.71 0.00 8.41 0.00 5.60 0.00 0.27 13.93 93.67
R23-7-1edge3 0.74 0.49 14.73 13.87 35.38 0.02 8.45 0.00 5.23 0.02 0.30 14.20 94.69
R23-7-1 mid 0.36 0.53 14.66 13.67 35.28 0.02 8.40 0.00 5.21 0.00 0.28 14.14 93.75
R23-7-1 mid 1.72 0.60 14.57 13.95 35.51 0.09 8.71 0.13 5.63 0.13 0.40 14.48 97.72
R23-7-1ctr 0.57 0.61 15.09 14.08 35.82 0.06 8.59 0.13 5.45 0.12 0.40 14.10 96.74
R23-7-1edge4 0.86 0.79 15.24 14.46 35.81 0.09 8.46 0.16 5.85 0.15 0.46 13.91 98.15
R23-7-2 edge 0.76 0.67 14.65 13.47 36.14 0.10 8.86 0.21 5.73 0.14 0.51 14.83 97.12
R23-7-2mid 0.66 0.69 14.53 13.62 35.96 0.09 9.01 0.19 5.79 0.11 0.49 14.83 97.14
R23-7-2ctr 0.84 0.52 14.95 13.91 36.45 0.08 8.97 0.20 5.47 0.14 0.50 15.26 98.47
R23-7-3edge 1.46 0.60 15.13 13.52 36.54 0.10 8.90 0.14 5.49 0.12 0.53 14.39 97.77
R23-7-3mid 0.65 0.57 15.17 13.15 36.06 0.10 9.07 0.14 5.34 0.13 0.48 14.73 96.36
R23-7-3ctr 1.45 0.58 14.96 13.14 36.43 0.08 8.96 0.15 5.42 0.14 0.55 14.74 97.41
R23-8-1 edge 1.21 0.57 15.52 12.65 36.61 0.06 9.23 0.00 4.73 0.00 0.28 14.19 95.21
R23-8-1ctr 0.85 0.63 15.62 12.69 36.52 0.05 8.71 0.09 4.62 0.01 0.31 13.76 93.99
R23-8-2 edge 1.52 0.49 14.61 12.32 36.56 0.07 8.82 0.01 4.41 0.00 0.32 13.82 93.02
R23-8.2etr 1.39 0.44 14.72 13.58 35.04 0.07 8.46 0.08 5.27 0.00 0.35 14.75 95.98
R23-8—2mid 0.85 0.49 14.98 13.51 35.45 0.07 8.76 0.01 5.34 0.00 0.38 15.36 96.71
R23-8-3 edge 1.01 0.66 16.54 13.14 38.25 0.06 9.03 0.00 4.52 0.00 0.30 13.97 97.58
R2383 mid 1.12 0.40 15.84 12.76 37.75 0.07 9.26 0.00 4.44 0.00 0.27 14.53 96.50
R18—14-1 edge 2.11 0.49 14.36 13.63 37.99 0.07 8.65 0.03 3.58 0.00 0.71 16.84 98.55
R18-14-1ctr3 1.70 0.38 12.83 13.22 38.68 0.09 7.65 0.22 3.07 0.00 0.52 14.75 93.20

Appendix C: Electron Microprobe Analyses

65

 

 

 

I Biotite Analysis I
Idescript. r N820 MgO A1203 sro2 c1 K20 CaO TiO2 Cr203 MnO FeO TotalI
Rl8-14-2edge 1.79 0.42 14.79 12.74 37.73 0.10 9.27 0.03 3.13 0.00 0.68 16.14 96.81
R18-14-201I' 1.96 0.47 14.88 13.42 38.10 0.09 9.18 0.02 3.53 0.00 0.65 16.25 98.61
R18-l4-3edge 1.52 0.30 12.45 13.41 39.76 0.07 7.50 0.26 3.05 0.00 0.51 14.19 93.04
R18-14-4edge 1.86 0.57 14.35 13.34 38.02 0.14 8.78 0.02 3.33 0.12 0.75 15.88 97.70
R18-l4-4ctr 2.08 0.58 14.60 13.17 37.33 0.13 9.29 0.00 3.44 0.13 0.90 16.39 98.60
R18-14-5edge 1.86 0.52 13.73 12.45 35.67 0.15 9.22 0.00 3.59 0.14 0.95 16.30 95.10
R18-14-5ctr 1.88 0.66 13.55 12.88 38.76 0.10 8.08 0.19 3.44 0.17 0.68 15.08 95.97
R18-14-5mid 1.93 0.40 13.40 12.52 38.92 0.15 8.16 0.22 3.21 0.10 0.73 15.59 95.88

Appendix C: Electron Microgobe Analyses

66

 

 

 

I Fcldspar Analysis I
Idescript. NazO $102 ,4le3 MgO K20 CaO BaO FeO F6303 Total |
R23-7-l ctr 4.08 67.48 19.08 0.01 10.64 0.26 0.00 0.09 0.10 101.66
R23-7-1 edge 4.16 67.56 19.14 0.00 10.58 0.27 0.00 0.06 0.06 101.83
R23-7-1 mid 3.91 65.67 18.76 0.00 10.62 0.31 0.03 0.06 0.06 99.42
R23-7-2 edge 8.19 63.95 22.39 0.00 1.65 3.92 0.00 0.23 0.26 100.35
R23-7-2 mid 8.35 63.48 22.30 0.01 1.66 3.95 0.00 0.25 0.28 100.05
R23-7-2 ctr 8.16 63.58 22.64 0.00 1.52 4.36 0.00 0.18 0.20 100.46
R23-7-3 edge 4.05 65.80 18.68 0.01 10.34 0.30 0.03 0.13 0.15 99.41
R23-7-3 mid 4.11 66.76 18.92 0.01 10.41 0.28 0.08 0.03 0.04 100.64
R23-7-3 ctr 4.15 66.49 18.76 0.01 10.43 0.27 0.06 0.09 0.10 100.34
R23-8-l edge 4.48 63.31 18.03 0.00 10.20 0.28 0.00 0.05 0.06 96.46
R23-8-1 edge 4.19 66.12 18.65 0.02 10.30 0.29 0.00 0.10 0.11 99.69
R23-8-1 mid 4.21 65.77 18.61 0.01 10.40 0.29 0.00 0.13 0.15 99.48
R23-8-l ctr 4.10 65.87 18.50 0.00 10.57 0.30 0.00 0.05 0.06 99.46
R23-8-2 ntid 8.34 62.94 22.54 0.01 1.50 4.10 0.01 0.22 0.25 99.67
R23-8-2 ctr 8.51 63.86 . 22.17 0.01 1.60 3.89 0.00 0.21 0.23 100.29
R23-8-3 edge 8.41 62.78 22.79 0.02 1.41 4.46 0.00 0.24 0.26 100.10
R23-8-3 mid 8.17 62.52 22.70 0.03 1.39 4.43 0.00 0.27 0.30 99.52
R23-8-3 ctr 8.27 62.25 22.58 0.01 1.40 4.57 0.00 0.30 0.34 99.39
R23-8-3 edge2 8.27 62.44 22.78 0.01 1.33 4.52 0.00 0.29 0.32 99.67
R23-4-1 mid 3.95 64.25 18.44 0.00 10.78 0.23 0.10 0.11 0.12 98.02
R2341 edge 3.98 64.68 18.41 0.00 9.97 0.21 0.10 0.09 0.10 97.44
R23-4-1 edge2 4.28 65.16 18.11 0.00 9.60 0.48 0.10 0.07 0.08 97.80
R23-4-1 ctr 3.97 65.22 18.50 0.00 10.21 0.26 0.14 0.11 0.12 98.43

Appendix C: Electron Microprobe Analyses

67

 

 

 

I Feldspar Analysis

[descript Na20 8102 .41203 MgO K20 CaO BaO FeO Fe203 Total]
R2342 edge2 7.23 58.48 23.60 0.01 1.03 6.45 0.07 0.30 0.34 97.20
R23-4-2 mid 6.96 57.75 24.61 0.02 0.79 7.25 0.22 0.29 0.32 97.91
R2342 edge 8.19 62.52 22.38 0.00 1.49 4.07 0.00 0.23 0.26 98.92
R2343 mid 8.08 62.63 22.61 0.00 1.33 4.42 0.00 0.21 0.23 99.29
R2343 ctr 8.25 62.60 22.32 0.00 1.42 4.23 0.01 0.28 0.32 99.14
R2344 edge 6.56 56.80 26.61 0.01 0.53 8.10 0.25 0.28 0.31 99.16
R2344 ctr 6.27 56.88 26.27 0.01 0.47 8.46 0.07 0.32 0.35 98.78
R18-14-1 edge 8.90 63.46 21.19 0.01 1.24 3.05 0.05 0.13 0.15 98.05
R18-14—1 mid 9.33 62.49 21.01 0.02 1.42 2.74 0.00 0.17 0.18 97.20
R18-14-l ctr 9.42 62.91 21.17 0.00 1.27 2.95 0.00 0.16 0.17 97.89
R18-14-2 edge 3.86 63.19 17.80 0.00 10.76 0.21 0.00 0.11 0.12 95.95
R18-14-2 ctr 4.13 63.12 18.20 0.00 10.80 0.25 0.00 0.04 0.04 96.53
R18-14-2 mid 4.09 65.70 18.34 0.00 10.78 0.17 0.00 0.09 0.10 99.19
R18-14-3 edge 3.91 65.85 17.70 0.00 10.80 0.23 0.00 0.12 0.13 98.62
R18-14-3 ctr 4.06 66.08 18.43 0.00 10.81 0.17 0.00 0.11 0.12 99.65
R26-14-1 ctr 4.35 65.68 18.51 0.01 10.07 0.51 0.01 0.14 0.15 99.30
R26-14-1 mid 4.14 65.29 18.47 0.00 10.61 0.30 0.07 0.16 0.17 99.06
R26-14-2 mid 3.82 64.23 17.94 0.02 10.76 0.30 0.00 0.14 0.16 97.24
R26-14-2 ctr 3.98 64.83 17.97 0.00 10.56 0.23 0.00 0.21 0.23 97.80
R18-11-1 ctr 3.93 64.51 17.92 0.01 11.06 0.20 0.00 0.12 0.13 97.75
R18-11-2 mid 3.91 63.95 18.19 0.00 10.96 0.18 0.00 0.14 0.15 97.35
R18-11-2 ctr 4.01 64.68 18.24 0.01 10.69 0.14 0.00 0.09 0.10 97.87
R18-11-3 mid2 3.79 63.27 17.82 0.01 10.74 0.20 0.00 0.07 0.08 95.89

Appendix C: Electron Microprobe Analyses

68

 

 

 

r Feldspar Analysis

Idescript. NagO SiO2 A1203 MgO K20 CaO BaO FeO Fe203 Tori]
R18-6-1 edge 8.93 65.34 20.34 0.00 1.68 2.37 0.00 0.06 0.07 98.73
R18-6-1 ctr 9.00 64.72 21.66 0.00 1.25 3.09 0.00 0.08 0.09 99.82
R18-6-1 mid 9.00 62.86 21.44 0.00 1.28 3.07 0.00 0.10 0.11 97.77
R18-6-2 mid 9.08 63.80 21.36 0.00 1.18 2.89 0.07 0.07 0.08 98.46
R18-6-2 ctr 9.31 64.37 21.15 0.00 1.28 2.82 0.01 0.11 0.12 99.08
R18-6-3 edge 7.55 59.43 23.14 0.00 0.63 5.65 0.02 0.06 0.07 96.50
R18-6-3 ctr 8.46 62.86 22.08 0.00 0.98 3.98 0.05 0.16 0.18 98.59
R18-6-3 edge2 7.80 59.06 24.65 0.00 0.52 6.40 0.00 0.13 0.14 98.57
Rl8-6-4 ctr 9.25 63.90 21.34 0.00 1.32 2.88 0.00 0.08 0.09 98.79
R18-6-4 edge 9.14 63.90 21.59 0.00 1.29 3.03 0.00 0.09 0.10 99.06
R26-19-1 edge2 4.13 65.37 18.21 0.00 10.52 0.31 0.09 0.17 0.19 98.82
R26-19-1 mid 4.06 65.12 18.12 0.00 10.53 0.30 0.18 0.15 0.17 98.47
R26-19-1 ctr 4.03 65.12 18.27 0.00 10.57 0.32 0.16 0.20 0.23 98.68
R26-19-2 edge 8.44 62.76 22.90 0.01 1.31 4.54 0.00 0.25 0.28 100.24
R26-19-2 mid 8.41 62.70 22.63 0.00 1.38 4.28 0.00 0.21 0.23 99.65
R26-19-2 ctr 8.17 60.87 21.93 0.00 1.44 4.06 0.04 0.24 0.27 96.77
R26-19-3 edge 4.21 64.95 18.59 0.00 10.58 0.33 0.10 0.14 0.16 98.91
R26-19-3 mid 4.10 64.89 18.36 0.00 10.54 0.34 0.10 0.13 0.15 98.48
R26-19-3 ctr 4.17 64.87 18.45 0.00 10.59 0.30 0.11 0.15 0.17 98.66
R18-9-1 mid2 4.04 65.22 18.26 0.00 10.75 0.16 0.11 0.05 0.06 98.60
R18-9-1 ctr 4.14 65.44 18.17 0.00 10.62 0.16 0.04 0.12 0.13 98.71
R18-9-1 edge 4.03 65.43 18.00 0.01 10.60 0.16 0.16 0.10 0.12 98.50
R18-9-2 edge 4.04 66.44 18.16 0.02 10.46 0.16 0.16 0.11 0.12 99.57

Appendix C: Electron Microprobe Analyses

69

 

 

 

I Feldspar Analysis

Idescript. N820 sro2 A1303 MgO K20 CaO BaO FeO F6303 Total I
R18-9-2 ctr 4.18 65.34 18.52 0.00 10.56 0.13 0.09 0.10 0.11 98.94
111853 edge 8.82 62.57 20.92 0.00 1.33 2.75 0.00 0.19 0.21 96.59
R18-9-3 ctr 9.21 63.50 21.23 0.00 1.27 2.77 0.00 0.13 0.15 98.13
R18-9-3 mid 9.13 63.62 20.75 0.01 1.29 2.75 0.00 0.16 0.17 97.73
Rl8-15-1 edge 4.02 65.45 18.40 0.01 10.86 0.15 0.00 0.06 0.07 98.96
Rl8-15-l mid 4.10 65.89 18.46 0.00 10.93 0.14 0.06 0.12 0.14 99.72
Rl8-15-l ctr 4.02 66.19 18.37 0.00 10.74 0.15 0.00 0.10 0.11 99.59
R18-15-2 edge 4.12 66.47 18.52 0.00 10.76 0.14 0.00 0.04 0.05 100.06
R18-15-2 mid 4.04 66.41 18.58 0.00 10.85 0.12 0.01 0.04 0.05 100.07
Rl8-15-2 ctr 4.11 65.81 18.60 0.00 10.77 0.15 0.00 0.01 0.01 99.46
R18-15-3 edge 9.17 65.71 21.03 0.00 1.34 2.70 0.00 0.11 0.12 100.08
R18-15-3 mid 9.29 65.59 21.17 0.00 1.35 2.80 0.00 0.13 0.14 100.34
R18-15-4 edge 3.95 63.59 18.13 0.00 10.69 0.14 0.00 0.05 0.06 96.56
R18-15-4 mid 4.11 65.72 18.43 0.00 10.78 0.13 0.06 0.08 0.09 99.32
R18-15-5 edge 4.07 66.18 18.54 0.00 10.81 0.12 0.01 0.07 0.08 99.80
R18-15-5 ctr 4.02 66.31 18.49 0.01 10.85 0.17 0.00 0.04 0.05 99.89

Appendix C: Electron Microprobe Analyses

70

 

 

 

 

| Maggtite Analysis

[descrip. MgO A1208 T102 Cr203 MnO FeO Total
R18- 15-2 mid 0. 57 0.99 4.71 0.04 2.06 84.78 93.18
R18-15-2 ctr 0.58 0.97 4.68 0.01 2.13 84.77 93.20
R18-l5-3 edge 0.22 l. 12 4.84 0.00 1.24 82.69 90.18
R18-15-3 ctr 0.46 0.89 4.81 0.00 2.15 84.48 92.86
R23-7-1 edge 0.84 1.23 6.67 0.01 0. 98 82. 39 92. 32
R23-7-1 ctr 0.22 0.95 7.25 0. l l 0. 31 79.43 88.80
R23-7-2 edge 1.03 2. 11 4.99 0.05 0.91 65.79 80.21
R23-7-2 edge2 1.54 2. 19 5.46 0.06 1.36 81.52 92.39
R23-7-2 ctr 1.13 1.83 7.19 0.03 0.95 81.33 92.67
Rl8-6-l mid 0.26 1.30 5.33 0.16 1.54 83.22 91.99
R 18-6-1 mid2 0.16 0.95 5.03 0. 11 1.37 84.28 92.02
R 18-6-1 ctr 0.16 1.11 5.08 0.14 1. 33 83.82 93.49
R18-6-2 edge 0.30 1.08 5.08 0.13 1.50 84.56 92.77
R 18-6-2 mid 0. 41 0. 8 1 4.98 0. l3 2. 39 84. 74 93.65
R 18-6-2 ctr 0.51 1.05 4.94 0.14 2.57 84.59 93.97
R 18-6-3 edge 0. 39 0.88 4. 79 0.1 1 2. 52 84.63 93.44
R18-6-3 ctr 0.34 1.11 5.07 0.15 1.74 83.79 92.31
R26- 14-1 edge 0.93 1.06 6.05 0.04 1.08 80.99 90.38
R26- 14-1 mid 0.94 0.95 5.61 0.00 l. 12 83. 75 92.44
R26-14-2 edge 0. 41 2. l4 6. 59 0.07 0. 78 76.86 90. 56
R26- 14-2 mid 1.09 1.32 5.34 0.09 1.53 83.30 92.82
R18-15o2 mid 0.57 0.99 4.71 0.04 2.06 84.78 93.18
R18-15—2 ctr 0. 58 0. 97 4.68 0.01 2. 13 84.77 93. 20
R18-15-3 edge 0.22 1.12 4.84 0.00 1.24 82.69 90.18
Rl8- 15-3 ctr 0.46 0.89 4.81 0.00 2.15 84.48 92.86

. R23-7-1 edge 0.84 1.23 6.67 0.01 0.98 82.39 92.32
R23-7-1 ctr 0.22 0.95 7.25 0. 1 1 0. 31 79. 43 88.80
R23-7-2 edge 1.03 2. 11 4.99 0.05 0. 91 65. 79 80.21

71
Appendix C: Electron Microprobe Analyses

 

 

 

 

[ ﬁagnetite Analysis

[descrip. M 50 A1203 T102 C1903 MnO FeO Total
R23-7-2 edge2 1.54 2.19 5.46 0.06 1.36 31.52 92.39
R23-7-2 ctr 1.13 1.83 7.19 0.03 0.95 81.33 92.67
Rl8-ll-1 mid 0.54 0.94 4.84 0.11 2.31 84.16 93.00
R18-11-1 ctr 0.31 1.11 4.96 0.00 1.60 83.26 91.35
1118-15-1 mid 0.02 0.17 0.00 0.02 1.26 87.17 89.53
R18- 15- ledge 0.00 0.38 0.00 0.00 1.11 87.72 90.00

Appendix C: Electron Micgonobe Analysis

72

 

 

 

| 11mgn1te Analysis
Hescript. MgO A1203 T102 Cr203 MnO F 90 - Total
R23-14-1 edge 1.22 0.11 39.80 0.07 1.54 49.50 92.56
R23-14-1 mid 2.65 0.17 36.53 0.04 3.47 49.77 92.86
R23-14-1 ctr 1.31 0.18 36.48 0.06 1.67 53.06 93.06
1123-14-2 edge 1.21 0.19 42.69 0.10 3.11 44.73 92.22
R23-14-2 mid 1.20 0.09 43.43 0.06 3.49 43.69 92.19
R26-19-1 edge 1.13 0.08 38.60 0.10 1.40 53.44 94.85
R26-19-1 ctr 1.57 0.14 39.48 0.07 1.81 51.58 94.79
R26-19-2 edge 2.56 0.28 36.60 0.04 2.16 51.32 93.82
R26-19-2 mid 1.75 0.18 38.00 0.16 1.41 53.83 95.41
R26-19-2 ctr 0. 93 0.22 37.54 0.08 0. 85 53.81 93.54
R26- 19-3 edge 1.64 0.16 38.32 0. 10 1.72 53.41 95.41
1126-19-3 ctr 1.46 0. 13 38.05 0. 13 1.65 53.92 95.38
R23-7-1 edge 1.36 0.17 37.96 0.00 1.10 52.60 93.34
R23-7-1mid 2. 32 0. 15 36. 75 0.05 2.00 53.82 95. 14
R23-7- lctr 2. l6 0. 16 36.83 0.01 1.75 53.96 94.88
R23-7-2 edge 1.76 0.15 37.40 0.00 1.55 53.68 94.58
R23-7-2 mid 2.41 0.18 36.85 0.00 1.86 53.54 94.88
R23-7-2 ctr 2.18 0.17 37.01 0.02 1.94 53.93 95.29
R23-8-1 edge2 1. 17 0. 1 1 38.56 0.09 0.84 52.89 93.77
R23-8-l mid 1.57 O. 18 37.78 0.04 1.23 53.34 94.21
R23-8—1 ctr 2.07 0. 1 1 37.45 0.02 1.39 52.57 93.77
R23-8-2 edge 0. 76 0.16 38.37 0.02 0.67 52.07 92.24
R23-8-2 mid 0. 87 0.18 36.80 0.00 0.61 55.08 93.69
R23-8-2 ctr 1.15 0.12 38.33 0.01 0. 89 52.80 93.47
R23-8-3 edge 1.53 0.15 38.45 0.00 1.14 52.05 93.42
R23-8-3 mid 1.98 0.14 38.98 0.04 1.60 51.30 94.26
R23-8-3ctr 0.62 0.21 38.03 0.00 0.40 53.73 93. 20
R18-6-l edge 0.61 0.00 44.86 0.11 2.71 47.82 96.25

Appendix C: Electron Microprobe Analysis

73

 

 

 

| Ilmenite Analysis I
[descript MgO A1203 T102 Cr203 MnO Fe0 Totﬂ
R18-6-1 mid 1.09 0.00 44.41 0.10 4.75 48.40 98.85
R 18-6-1 ctr 1.28 0.01 43.77 0.09 4.87 47.65 97.81
R18-6-2 edge 0.49 0.03 45.01 0.14 2.26 47.59 95.64
R 18-6-2 mid 1.16 0.01 43.89 0.09 4.68 48.12 98.07
R18-6-2 ctr 1.20 0.00 43.95 0.12 4.91 47.84 98.13
R18-6-3 edge 0.63 0.00 45.08 0.07 2.89 46.61 95.43
R18-6-3 mid 1.10 0.00 43.93 0.10 6.10 45.49 96.86
R26-14-l edge 2.33 0.08 38.51 0.08 2.49 51.67 95.32
R26-14-1 mid 2.30 0.06 38.72 0.10 2.22 52.39 95.90
R26-14-2 edge 1.20 0.09 38.66 0.13 1.20 52.77 94.12
R26-14-2 ctr 2.08 0.09 38.07 0.04 2.23 53.26 95.94
R23-7- ledge 1.36 0. 17 37.96 0.00 1.10 52.60 93. 34
R23-7-1m1d 2.32 O. 15 36. 75 0.05 2.00 53.82 95. 14
R23-7- lctr 2. 16 0. 16 36.83 0.01 1.75 53.96 94.88
R23-7-2 edge 1.76 0.15 37.40 0.00 1.55 53.68 94.58
R23-7-2 mid 2.41 0.18 36.85 0.00 1.86 53.54 94.88
R23-7-2 ctr 2.18 0.17 37.01 0.02 1.94 53.93 95.29
R18-11-1 mid 1.14 0.09 43.22 0.00 4.25 47.11 95.89
R18-ll-1 edge 1.20 10.07 42.95 0.00 4.69 47.15 96.14
R18-1 1-2 mid 0. 98 0.10 43.47 0.00 3.83 47.33 95.77
R18-15-1 mid 1.50 0.05 43.47 0.00 5.35 45.07 95.53
R18-15-l ctr 1.42 0.04 42.82 0.00 6.19 45.16 95.68
R18-l5-1 edge 1.06 0.04 42.77 0.00 3.82 48.19 95.92
R18-15-2 mid 1.12 0.08 42.34 0.00 4.08 47.22 94.97
R18-15-2 ctr 1.01 0.07 42.80 0.01 4.36 47.98 96.34
R18-15-3 edge 1.08 0.07 44.10 0.01 3.55 46.04 94.97
R18- 15-3 ctr 1.56 0.09 43.86 0.00 5. 47 45.09 96.09

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