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This is to certify that the

thesis entitled

The Origin and Evolution of the
Burroughs Mountain Lava Flow,
Mount Rainier, Washington

presented by

Karen Renee Stockstill

has been accepted towards fulﬁllment
of the requirements for

Masters degree in Geological. Sciences

glam/aw

Major professor

 

 

Date 7’ / ’ 77

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINE return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE

DATE DUE

DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1/98 mimpesou

THE ORIGIN AND EVOLUTION OF THE BURROUGHS MOUNTAIN LAVA
FLOW, MOUNT RAINIER, WASHINGTON

By

Karen Renee Stockstill

A THESIS

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

MASTER OF SCIENCE
Department of Geological Sciences

1999

ABSTRACT

THE ORIGIN AND EVOLUTION OF THE BURROUGHS MOUNTAIN LAVA
FLOW, MOUNT RAINIER, WASHINGTON

By

Karen Renee Stockstill

The Burroughs Mountain lava ﬂow is a large volume andesitic lava ﬂow that
conformably overlies an andesitic block and ash-ﬂow deposit. A comparison between
the compositions of the lava ﬂow and the block and ash-ﬂow deposit is important in
determining if the eruptive styles of these deposits were chemically controlled.

A systematic sampling was conducted in order to reveal any spatial variation
within the lava ﬂow and to represent the full range of compositions in the block and
ash-ﬂow deposits. The data for this study includes chemical and mineralogical
analyses of these samples.

The chemical variation in the Burroughs Mountain lava ﬂow is consistent with
fractional crystallization. The spatial variation seen in the lava ﬂow suggests a two-
layered magma body, with a silicic, heterogeneous magma towards the top of the
magma body and a maﬁc, zoned magma towards the bottom of the magma body. The
zoning may have been present prior to eruption, produced by processes such as
fractional crystallization, or may have resulted from the eruption dynamics.

The block and ash-ﬂow deposits span the whole range of compositions
displayed by the lava ﬂow. Therefore, the eruption that produced the block and ash
ﬂow deposits tapped the entire magma chamber, but predominantly the upper to

middle portions. Therefore, the style of eruption was not chemically dependent.

For my Mom, Dad and brother Ray;

and for Faith, Paul and Graham.

iii

ACKNOWLEDGEMENTS

I would like to thank my Mom, Dad and brother Ray for their support
and encouragement. I could not have survived this adventure on my own! And thanks
to Dr. Faith Vilas, Dr. Paul Spudis, Dr. Graham Ryder and Dr. David Black, who ﬁrst
provided the opportunity of participating in Planetary Geology research.

Thanks to my committee members, Dr. Thomas A. Vogel, Dr. Lina Patino, Dr.
Michael Velbel, Dr. David Matty and Dr. Bill Cambray, for your guidance with this
project and with my academic career. Thanks to Dr. Thomas Sisson, who ﬁrst
introduced us to the Burroughs Mountain lava ﬂow two years ago and since then has
contributed a great deal to our understanding of this project. Thanks also to Ryan
Thomas who helped with ﬁeld work and sample preparation for this project, as well as
to J. P. Brandenburg and Jake Weaver who also helped with the sample preparation.

Thanks to the many ﬁ'iends that have shared the trials and tribulations of this
process, including (but not limited to!): Julie Cofﬁeld, Cari "Cori" Corrigan, Dave
"Pants" Szymanski, Ryan Thomas, Todd "T-O—D-D" Wallbom, Cheryl "Bibs"
Webster, Jonathan "Jon-E" Kolak, Rachel "Dr. Evil" Walker, Ed "That's-Not-A-
Freckle!" Wilson, Diane Baclawski, Matt Harold, Alexandra DeJong, the residents of
the 1996-1999 FOG House (long live the FOG house!), and my rockin' ofﬁce mates
(sorry 'bout the messy desk!). I have so many fond memories of our shared journey
and look forward to our paths crossing in the future. Rock on! A special thank you to
Chris Isaak, whose music got me through some rough spots and made my drives to

Ohio bearable.

TABLE OF CONTENTS

LIST OF TABLES ................................................................................. v
LIST OF FIGURES .............................................................................. vi
INTRODUCTION ................................................................................ 1
Purpose ........................................................................................ 1
Previous Work ................................................................................ 3
Regional Geology ............................................................................ 4
Methods ....................................................................................... 8
WHOLE ROCK CHEMISTRY ............................................................... 10
Maj or element variations .................................................................. 10
Trace element variations ................................................................... 12
Petrography .................................................................................. l 8
Mineral chemistry ........................................................................... 29
Spatial variations ........................................................................... 42
DISCUSSION ................................................................................... 45
Spatial variations ........................................................................... 47
Processes to produce systematic chemical variations .................................. 49
Testing Fractional Crystallization ........................................................ 51
Eruption of a zoned magma body ......................................................... 59
Model of Eruption Events .................................................................. 61
CONCLUSIONS ................................................................................ 62
APPENDIX ........................................................................................ 64

LIST OF TABLES

Table 1: Whole rock major element and selected trace element

chemical analyses .............................................................. 65
Table 2: Results of the t-test between lava ﬂow and block and ash-ﬂow

samples ......................................................................... 14
Table 3: Plagioclase phenocryst microprobe analyses of lava ﬂow and

block and ash-ﬂow samples .................................................. 34
Table 4: Pyroxene phenocryst microprobe analyses of lava ﬂow and

block and ash-ﬂow samples .................................................. 37
Table 5: Homblende and biotite phenocryst microprobe analyses of

lava ﬂow and block and ash-ﬂow samples ................................. 43
Table 6: Best results of the three steps of fractional crystallization as

well as from the most maﬁc (980820-30) to the least maﬁc

(970811-24) of the samples .................................................. 55
Table 7: Best results of the fractional crystallization modeling from

the most maﬁc to the least maﬁc samples for the upper

portion of the lava ﬂow. In addition, the failed results of the

fractional crystallization modeling for the lower portion of the

ﬂow .............................................................................. 58

vi

LIST OF FIGURES

Figure l: The Burroughs Mountain lava ﬂow as mapped by Dr. Tom
Sisson and colleagues. Map shows sample locations as well.
Left inset shows the 1998 vertical sequence of samples from
the second Burroughs Mountain. Right inset shows the more
distal vertical sampling location from ﬁrst Burroughs Mountain.

USGS Map ....................................................................... 2
Figure 2: Map of the Cascade Range, after Topinka (1997) .......................... 5
Figure 3: Plot of FezO3(tow) versus Si02 for samples of the Burroughs

Mountain lava ﬂow and block and ash-ﬂow deposits (open
region) relative to common lavas and pyroclastics found at
Mount Rainier (ﬁlled region) ................................................... 7

Figure 4: Some major element chemical compositions of the lava ﬂow
(ﬁlled squares), cognate cumulates (open squares), and crustal
xenoliths (open diamonds) .................................................. l 1

Figure 5: Some major element chemical compositions of the lava ﬂow
(ﬁlled squares) and the juvenile block and ash-ﬂow deposits
(open triangles) ................................................................. 13

Figure 6: Some major element chemical compositions of the block and
ash-ﬂow deposits (open triangles) and the associated inclusions
(ﬁlled triangles) ................................................................. 15

Figure 7: Some trace element chemical compositions for the lava ﬂow
(ﬁlled squares) .................................................................. 16

Figure 8: Rare earth element (REE) diagram showing relatively small
variation in rare earth elements for the lava ﬂow (left) and the
block and ash—ﬂow deposits (right). Bottom: REE diagrams
showing the variation from low-MgO (circles), middle-MgO
(asterisks) and high-MgO (stars) samples for both deposits.
(Chondrite values from Sun and McDonough, 1989) ..................... 17

Figure 9: Some trace element chemical compositions for the lava ﬂow
(ﬁlled squares), the cognate cumulates (open circles), and the
crustal xenoliths (open diamonds) .......................................... 19

vii

Figure 10: REE diagram of all the samples showing relatively small
variation in rare earth elements. Note the steeper slope of the
REE pattern of the crustal xenolith. (Chondrite values from
Sun and McDonough, 1989) ................................................. 20

Figure 11: Trace element chemical compositions for the block and
ash-ﬂow deposits (open triangles) and associated inclusions
(ﬁlled triangles) ................................................................ 21

Figure 12: Trace element chemical compositions for the lava ﬂow
(ﬁlled squares) and the juvenile block and ash-ﬂow deposits
(open triangles) ................................................................. 22

Figure 13: Photomicrograph of lava ﬂow sample 970812-47 in plane
polarized light (top) and cross polarized light (bottom). Note
the phenocrysts of plagioclase, orthopyroxene and clinopyroxene.
Photomicrographs are 4mm across .......................................... 24

Figure 14: Photomicrograph of block and ash-ﬂow sample 970809-6
(top). This plagioclase grain exhibits oscillatory zoning.
Photomicrograph of block and ash-ﬂow sample 970810-9
(bottom). This plagioclase grain exhibits both albite twinning
and oscillatory zoning. Both photomicrographs are
approximately 2 mm across .................................................. 25

Figure 15: Photomicrograph of quartz phenocryst in sample 970809-6
(top) and biotite phenocryst in sample 970810-9 (bottom).
Note that both phenocrysts have resorption rims. All photo-

micrographs are 2mm across .................................................. 26
Figure 16: Photomicrograph of a glomerophyric clot in lava sample

970812-47. Note that the clot has the same mineralogy as

the host lava. View is 4mm across .......................................... 27

Figure 17: Photomicrograph of block and ash-ﬂow sample 970810-10
in plane polarized light (top) and cross polarized light (bottom).
Note the disrupted nature of some plagioclase laths. Photo-
micrographs are 4 mm across ................................................. 28

Figure 18: Feldspar ternary showing all plagioclase phenocryst

compositions. These analyses include rim, middle and core
values ........................................................................... 3O

viii

Figure 19: F eldspar temaries showing plots of single plagioclase
phenocrysts for rim, middle, and core analyses ......................... 31

Figure 20: Pyroxene quadrilateral showing all pyroxene phenocryst
compositions. These analyses include rim, middle and core

analyses ........................................................................ 40
Figure 21: Pyroxene quadrilateral showing individual pyroxene phenocryst

compositions. Each quadrilateral shows analysis pairs with

like symbols .................................................................... 41

Figure 22: Major element plots of samples from the 1998 vertical sampling
of the lava ﬂow and a few selected samples from the 1997
ﬁeld season are represented by the squares. Filled symbols are
from the upper portion of the ﬂow and open symbols are from
the lower portion of the ﬂow. Samples taken from a different
location along the length of the lava ﬂow (1'. e. , further from
the summit) that also represent a vertical sampling are
represented by circles .......................................................... 44

Figure 23: Minor element plots of samples from the 1998 vertical sampling
of the lava ﬂow and a few selected samples from the 1997
ﬁeld season are represent by squares. Samples taken from a
different location along the length of the lava ﬂow (1'. e. , further
from the summit) that also represent a vertical sampling are
represented by circles ......................................................... 46

Figure 24: Possible pre-eruptive magma body, where the upper layer has
a heterogeneous, less maﬁc magma and the lower layer is a
more maﬁc magma with a chemically gradient ........................... 48

Figure 25: Linear trends of samples used in fractional crystallization

modeling (top) versus the linear trend of all lava samples
(bottom) ......................................................................... 53

ix

INTRODUCTION

The Burroughs Mountain lava ﬂow is a large volume (3.4 km3) andesitic lava
ﬂow, which is up to 350 m thick and extends 11 km in length (Figure 1, Sisson,
unpublished mapping), terminating where it abutted against glacier ice and formed
columnar joints (Lescinsky and Sisson, 1998). It erupted non-explosively 496,000 years
ago on the northeast side of Mount Rainier and conformably overlies an andesitic block
and ash-ﬂow deposit.

The lava ﬂow is a porphyritic andesite, containing medium- to coarse-grained
phenocrysts (plagioclase, orthopyroxene, clinopyroxene, and hornblende) in a ﬁne-
grained groundmass. Within the lava ﬂow are rare quenched magmatic inclusions and
crustal xenoliths as well as more common coarser-grained gabbroic to dioritic inclusions
of probable cumulate origin. The block and ash-ﬂow deposit consists of slightly- to non-
vesiculated andesitic blocks, some with radial prismatic jointing, in a brown to reddish-
brown ash matrix, which has been thermally oxidized. Glomerophyric clots are common

in both the lava ﬂow and the block and ash-ﬂow deposit.

Purpose

The purpose of this study is to document and evaluate the origin of the chemical
and mineralogical variations within the Burroughs Mountain lava ﬂow and the
underlying block and ash-ﬂow deposit. An additional objective is to determine if the
explosive and non-explosive behavior of the magmas is chemically controlled. The data

for this study are chemical and mineralogical analyses of samples of the lava ﬂow and

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block and ash-ﬂow deposit along with associated inclusions. Samples of the lava ﬂow
were collected to evaluate spatial variations in chemistry within the lava ﬂow. Samples
of the block and ash-ﬂow deposits were collected only to represent the range of chemical
variation within the block and ash-ﬂow deposit. An analysis of the spatial variation
within the lava ﬂow will lead to a better understanding of the evolution of the magma
and the eruption dynamics (Blake, 1981; Carrigan et al., 1992).

Similar to many other orogenic andesites, the Burroughs Mountain lava ﬂow
contains hornblende, which requires at least 3 wt. % water to crystallize (Eggler, 1972a;
Rutherford et al., 1985). A major question is why this relatively large-volume, water-
rich lava ﬂow erupted non-explosively, whereas the associated block and ash-ﬂow
erupted explosively. A comparison between the compositions of the block and ash-ﬂow
and the lava ﬂow is important in determining if magmas with such drastically different
eruptive styles are chemically different. A chemical comparison of the two types of
ﬂows may hold the key to understanding how large volume, water-rich andesitic magmas
can erupt nonexplosively. The study will evaluate the processes that may have led to the

chemical variations in this system.

Previous Work

Previous work on the Burroughs Mountain lava ﬂow is limited. Dr. Thomas
Sisson and colleagues mapped and dated the Burroughs Mountain lava ﬂow (Sisson,
unpublished mapping, 1997) and the underlying block and ash-ﬂow deposit. Mapping is

shown in Figure 1.

Regional Geology

The Cascade Range trends north-south from Mt. Lassen in northern California to
Meager Mountain in British Columbia (Figure 2). The Cascade volcanic province is
subdivided into three parts, the Western Cascades, the High Cascades and the North
Cascades. The Western Cascades is a broad belt of basaltic and andesitic volcanic vents
that were active from the Eocene through the Miocene epochs and form the base of the
High Cascades (Smith and Carmichael, 1968; Orr and Orr, 1996). The younger
Cascades (intermittently erupted since Pliocene time) consist of the High and North
Cascades. The High Cascades range from the southernmost Mount Lassen through
Mount Rainier. The North Cascades are the northern extension of the High Cascades
and range from Glacier Peak to the northernmost Meager Mountain (Orr and Orr, 1996).

Formation of the Western Cascades was initiated during the Eocene epoch when
the angle of subduction of the Farallon plate changed, causing continental volcanic arc
magrnatism along the North American coastline. Subsequent erosion occurred when the
Cascade Range was uplifted during the Pliocene epoch, forming the folded, faulted and
metamorphosed base for the contemporary range. Formation of the High Cascades
began during the Pliocene epoch with continental arc magrnatism related to the
subduction of the Explorer, Juan de Fuca and Gordo plates beneath the North American
plate and continued with intermittent volcanism throughout the Pliocene and Holocene
epochs (Orr and Orr, 1996).

The entire range of orogenic lavas, from basalt to rhyolite, exists within the
Cascade Range; however, andesite is by far the most common lava type. The origin of

andesites in the Cascade Range is still problematic. Processes, such as fractional

 

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crystallization of basaltic magmas, hydrous partial melting of a basalt, magma
contamination or mixing and melting of quartz eclogite, have been used to explain the
origin of the andesites (Eggler, 1972b; Eichelberger, 1975; Baker et al. , 1994).

Mount Rainier is primarily composed of andesite and dacite lava ﬂows, with
minor amounts of pyroclastic ﬂow deposit. The compositions of lava ﬂows range from
54.9 to 67.1 wt. % $02, with an average SiOz content of 61.2 wt. %. Pyroclastic ﬂows
are not compositionally distinct from lavas (Sisson and Lanphere, 1999). The Burroughs
Mountain lava ﬂow ranges from 56.6 to 64.3 wt. % $02, with an average SiOz content
of 60.5 wt %. Figure 3 displays data for the Burroughs Mountain lava ﬂow and block
and ash-ﬂow deposits compared to data for a large number of Mount Rainier lava and
pyroclastic deposits. Dr. Tom Sisson proved the Mount Rainier data.

Mount Rainier had two recent periods of increased volcanic activity, the ﬁrst
between 500,000 and 420,000 years ago (including the Burroughs Mountain lava ﬂow)
and the second between 280,000 and 190,000 years ago. These periods marked the
emplacement of a generally east-west radial dike system, large volume ﬂank vent
eruptions, and possibly the formation of most ﬂank hydrothermal alteration. Between
40,000 and 60,000 years ago, lavas were erupted and conﬁned to the upper, southern
portion of Mount Rainier. Volume estimates of lavas indicate an integrated eruptive rate
of 0.4 km3/ka (:l:0.1) for these southern ﬂank eruptions (Sisson and Lanphere, 1999).
Approximately 5,600 years ago, the ENE ﬂank of Mount Rainier collapsed, forming the
Osceola mudﬂows and a large amphitheater shaped collapse feature that included Willis

Wall. Subsequent eruptions have nearly ﬁlled in this crater and volume estimates for

 

15 ,

 

 

 

 

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Figure 3: Plot of F 0203(tom1) vs. SiOz for samples of the Burroughs Mountain
lava ﬂow and block and ash-ﬂow deposits (ﬁlled region) relative to common lavas
and pyroclastics found at Mount Rainier (open region).

these lavas indicate a similar integrated eruption rate of 0.35 km3/ka ($0.1) (Sisson and

Lanphere, 1999).

Methods

During the summers of 1997 and 1998, a systematic sampling of the Burroughs
Mountain lava ﬂow was conducted in order to reveal any chemical variations in the ﬂow.
Sampling of the underlying block and ash-ﬂow deposit was conducted for comparison to
the lava ﬂow. Approximately 100 ﬁst-sized samples were collected from both deposits.
Sampling was designed to include cognate cumulates, crustal xenoliths, and other
inclusions. Spatially-controlled samples were collected from the entire length of the lava
ﬂow in order to reveal any lateral variation. In one location, a complete vertical series of
samples were collected from the top to the bottom of the ﬂow (~200 m vertically) in
order to reveal any vertical variation. Samples of the block and ash-ﬂow deposit were
collected from three locations. In total, 84 lava ﬂow samples were analyzed, including
60 ﬂow samples, 22 cognate cumulates, one crustal xenolith and one maﬁc inclusion. In
addition, 40 samples from the block and ash-ﬂow deposit were analyzed, which included
36 block and ash-ﬂow samples and 4 inclusions.

Several analytical techniques were used for this study. The mineralogy and
textures of the lava ﬂow and block samples were determined through petrographic
analysis of thin sections. Whole rock major-element and selected trace-element
concentrations were determined by X-ray ﬂuorescence spectrometry (XRF) for all
samples. Additional whole rock trace element and rare earth element concentrations

were determined for selected samples, using laser ablation Inductively Coupled Plasma

Mass Spectrometer (Cetac LSX200 and Micromass Platform ICP-MS). The major-
element chemical compositions of phenocrysts were determined by electron microprobe
anlaysis (EMPA) at Central Michigan University for selected samples, using an Applied
Research Laboratories Scanning Electron Microprobe Quantizer (ARL-SEMQ).

Fused glass disks were used for both XRF and LA-ICP-MS analyses. These
disks were made by diluting 3.0 g of ﬁnely ground rock powder with 9.0 g of lithium
tetraborate and 0.5 g of ammonium nitrate as an oxidizer. These materials were then
mixed and fused in a platinum crucible for at least 30 minutes and then poured into
platinum molds. Glass disks were then analyzed by XRF and LA-ICP-MS methods.

XRF maj or-element analyses were reduced using the ftmdamental parameter data
reduction (Criss, 1980). XRF trace-element analyses were reduced by standard linear
regression techniques. For LA-ICP-MS results, calcium was used as the internal
standard. Prior to any calculation the background signal was subtracted from standards
and samples. The concentration of the REE in the samples was calculated based on
linear regression techniques using BHVO-l, W-2, JB-2, JA-3, BIR-l standards. The
data reduction was done using MassLynx, the instrument software.

Preparation for electron microprobe analyses involved choosing thin sections
representing a range in compositions for both the lava ﬂow and the block and ash-ﬂow
deposit. Three samples were chosen to represent the least silicic, intermediate, and most
silicic samples of both deposits. In addition, a lava ﬂow sample containing the crustal
xenolith was also chosen. Two to three analyses of each of the selected phenocrysts as
well as minerals forming the glomerophyric clots were obtained per sample. When

possible, these analyses included a core, middle and rim analyses points. The minerals

analyzed included plagioclase, hornblende, clinopyroxene, orthopyroxene and Opaques.
The microprobe was equipped with three wavelength spectrometers with LiF, PET, and
TAP crystals. Operating conditions included a 15 kV accelerating potential, an 80 A
ﬁlament current, and 15 nA sample current. Counting times for individual elements

ranged from 10 to 20 seconds.

WHOLE ROCK CHEMISTRY

Major element variation

The lava ﬂow ranges from 56.6 to 64.3 wt. % SiOz and 2.66 to 4.88 wt. % MgO.
The major elements of the lava ﬂow vary systematically with linear decreases in
FezO3(tom1), CaO and TiOz and linear increases in SiOz with respect to decreases in MgO
(Figure 4). The alkalis (i.e., NaZO and K20) are more scattered, but also exhibit a
general increase with respect to decreases in MgO. Whole rock major element and
selected trace element chemical analyses are presented in Table 1 in the Appendix.

The inclusions associated with the lava ﬂow consist of cognate cumulates and
crustal xenoliths. The cognate cumulates are generally more maﬁc than the lava ﬂow,
ranging from 52.6 to 63.2 wt. % Si02 and 2.99 to 7.51 wt. % MgO. The crustal
xenoliths are generally less maﬁc than the lava ﬂow, ranging from 59.4 to 66.4 wt. %
SiOz and 2.2 to 2.96 wt. % MgO. Plots of major element oxides versus MgO display

fairly linear trends for the lava ﬂow and associated inclusions (Figure 4).

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The block and ash-ﬂow deposit ranges from 56.4 to 64.1 wt. % SiOz and 2.43 to
4.47 wt. % MgO. Plots of major element oxides versus MgO display large amounts of
overlap between the lava ﬂow and block and ash-ﬂow deposit (Figure 5). A student T-
test was performed element—by-element to statistically demonstrate the correlation of the
element means of the two data sets (Table 2). The critical value of t falls between 1.671
and 1.658 for this data set (Davis, 1986). The results must be greater than the critical
value of t to disprove the null hypothesis. The results for all the elements are much
smaller than the critical value of t, hence there is no evidence to suggest that the two
samples came from populations having different means. In addition, the plots of major
element oxides versus MgO demonstrate fairly linear trends for the block and ash-ﬂow
deposits as well. Rare inclusions occur within the block and ash-ﬂow deposit. Most of
these inclusions are chemically indistinguishable from the block and ash-ﬂow deposit,

except for one inclusion that strongly differs from the juvenile blocks in its MgO content

(Figure 6).

Trace element variations

The variation in trace elements shows some scatter for the lava ﬂow. However,
with respect to variations in major elements, the main body of the data displays slight
increases of incompatible trace elements and slight decreases in compatible trace
elements. Plots of trace elements versus MgO for the lava ﬂow are shown in Figure 7.
The lava ﬂow displays little variation in the trace elements on the rare earth element

(REE) diagrams shown in Figure 8.

12

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Similarly, the cognate cumulates displays slight variations of trace elements with
respect to decreasing MgO content. Plots of incompatible trace elements versus MgO
for the cognate cumulates are shown in Figure 9. This ﬁgure also displays the relative
enrichment in incompatible trace elements for the crustal xenoliths. The crustal xenolith
also displays a steeper slope on the REE diagram than lava ﬂow and block and ash-ﬂow
deposits (Figure 10).

Similarly, the variation in trace elements for the block and ash-ﬂow deposit
displays slight variations with respect to decreasing MgO content. Plots of incompatible
trace elements versus MgO for the block and ash-ﬂow deposits are shown in Figure 11.
As with major element oxides, large amounts of overlap exist between the lava ﬂow and
block and ash-ﬂow deposits for the trace elements as well (Figure 12). The block and
ash-ﬂow deposit also displays little variation of the trace elements on the REE diagrams

in Figure 8.

Petrography

Fifty-four thin section billets were prepared of the lava ﬂow and the block and
ash-ﬂow deposit and billets were cut in order to include any inclusions or glomerophyric
clots present in the sample. Phenocrysts, in general, were obvious because of the
bimodal size distribution. Occasionally, if distinctions were difﬁcult, grains smaller than
0.5 mm were considered groundmass and any grains larger were considered phenocrysts.
The amount of phenocrysts in the lava ﬂow ranged from 30% to 40%.

The lava flow is a porphyritic andesite with phenocrysts of plagioclase,

orthopyroxene, clinopyroxene, hornblende and Opaques. The groundmass is dominated

18

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20

Nd Sm Gd Dy Er Yb

Ce

Note the steeper slope of the REE pattern of the crustal xenolith. (Chondrite values from Sun and

Figure 10: REE diagram of the all samples showing relatively small variation in rare earth elements.
McDonough, 1989)

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22

by very f'me-grained, euhedral to subhedral plagioclase laths (Figure 13). Plagioclase
phenocrysts occur as medium- to coarse-grained, euhedral to subhedral laths, which may
exhibit albite twinning, normal oscillatory zoning or both (Figure 14). Orthopyroxene
and clinopyroxene are the next most abundant phenocrysts within the samples.
Orthopyroxene phenocrysts occur as medium-grained, subhedral grains. Clinopyroxene
phenocrysts occur as to medium-grained, subhedral grains. Phenocrysts of hornblende
are less abundant than the pyroxenes, occurring as medium- to coarse-grained, euhedral
to subhedral grains. Homblende and pyroxene occasionally contain opaques as
inclusions. The opaques consist of very ﬁne-grained, anhedral magnetite and ilrnenite
grains.

In rare instances, subhedral biotites and anhedral quartz grains occur in lava ﬂow
samples (Figure 15). Both biotite and quartz are always partially resorbed, and thus
represent disequilibrium phenocrysts.

Glomerophyric clots and cognate cumulates in the lava ﬂow, as well as in the
block and ash-ﬂow deposit, have the same mineralogy as the phenocrysts that occur in
the host (plagioclase, clinopyroxene, orthopyroxene, hornblende, and opaques). Figure
16 shows a typical glomerophyric clot found in a lava ﬂow sample. The crustal
xenoliths are more coarse-grained than the cognate cumulates and contain phenocrysts of
plagioclase, pyroxenes and hornblende.

The block and ash-ﬂow deposit contains porphyritic, poorly to non-vesiculated
andesite blocks in a brown to reddish-brown ash matrix. The groundmass of the juvenile
blocks is dominated by very ﬁne-grained plagioclase laths with minor amounts of

opaques as well (Figure 17). The mineralogy of the block and ash-ﬂow deposit is very

23

 

Figure 13: Photomicrographs of lava ﬂow sample 970812-47 in plane
polarized light (top) and cross polarized light (bottom). Note the
phenocrysts of plagioclase, orthopyroxene and clinopyroxene. Photo-
micrographs are 4mm across.

24

 

Figure 14: Photomicrograph of block and ash—ﬂow sample 970809-6
(top). This plagioclase grain exhibits oscillatory zoning. Photo-
micrograph of block and ash-ﬂow sample 970810-9 (bottom). This
plagioclase grain exhibits both albite twinning and oscillatory zoning.
Both photomicrographs are 2mm across.

25

 

Figure 15: Photomicrographs of quartz phenocryst in sample 970809-6
(top) and biotite phenocryst in sample 970810-9 (bottom). Note that
both quartz and biotite phenocrysts have resorption rims. All photo-
micrographs are 2mm across.

26

‘ .
.uu‘ \'
._.

‘2. _ ”wre‘ﬂ‘l i

 

Figure 16: Photomicrograph of a glomerophyric clot in lava sample
970812-47. Note that the clot has the same mineralogy as the host
lava. View is 4 mm across. Top is plain polarized light and bottom
is crossed polarized light.

27

 

Figure 17: Photomicrographs of block and ash-ﬂow sample 970810-10
in plane polarized light (top) and cross polarized light (bottom). Note
the disrupted nature of some plagioclase laths. Photomicrographs are
4mm across.

28

similar to the lava ﬂow samples. However, large phenocrysts are occasionally fractured
and disrupted, likely due to the violent nature of their eruption. Disequilibrium

phenocrysts are slightly more common in this deposit.

Mineral Chemistry

Microprobe analyses were done on all major phases present in the thin sections,
including both phenocrysts and minerals associated with glomerophyric clots. Three
analyses were obtained of each phase to represent a rim, middle and core composition.
The middle analysis points were usually located halfway between the rim analysis points
and the core analysis points.

For phenocrysts in general, the plagioclase rim compositions range from An“) to
Anso, whereas the core compositions range from Ann to AD49. The complete range of
plagioclase phenocrysts for all analyses is shown in Figure 18, whereas single phenocryst
variations are shown in Figure 19. There is a mix of normally-zoned and reversely
zoned plagioclase phenocrysts within the lava ﬂow and the block and ash-ﬂow deposit.
The largest compositional variation (from core to rim) for a phenocryst in a lava ﬂow
sample is for reversely-zoned phenocrysts, such as in sample 970811-32 where the
composition varies from An46 at the core to Anso at the rim (Figure 19b). Larger
compositional variations from rim to core occur for normally-zoned phenocrysts of
inclusions (e.g. inclusion within 970809-6, from Am; at the rim to An7o at the core) and
for phenocrysts of glomerophyric clots (e.g. glomerophyric clot within 970810-9, from
Amy, at the rim to My at the core) (Figure 19a). Plagioclase compositions are presented

in Table 3.

29

 

 

Figure 18: F eldspar ternary showing all plagioclase phenocryst
compositions. These analyses include rim, middle and core values.

30

 
  

   
  
   

Block and ash-ﬂow sample 970809—06

Inclusion within sample 970809-06

MV‘IV‘LMMV

Ab Or Ab Or

Block and ash-ﬂow sample 970810-09 Glomerophyric clot within 970810-09

0r Ab 0r

Figure 19a: Feldspar temaries showing plots of single plagioclase
phenocrysts for rim, middle and core analyses.

31

Lava flow sample 970810-12 Glomerophyric clot within 970810-14

PlagO1-middle
PlagOl -eore

 

Or Ab Or
Block and ash-ﬂow sample 970810-14

 

Ab 0r
Lava ﬂow sample 970811-32 Glomerophyric clot within 970811-32

 

Figure 19b: Feldspar temaries showing plots of single plagioclase
phenocrysts for rim, middle and core analyses.

32

Lava ﬂow sample 970812-41 Glomerophyric clot within 970812-41

Plague-middle

 

Ab Or

Figure 19c: Feldspar temaries showing plots of single plagioclase
phenocrysts for rim, middle and core analyses.

33

 

 

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35

 

 

 

I‘.‘

Some middle analyses (between the cores and the rims of the phenocrysts) have
very different anorthite contents from their rims and/or cores. A large compositional
variation from rim to middle position exists for the oscillatory-zoned phenocryst in
sample 970809-6, from An.“ at the rim to A1163 at the middle position (Figure 19a). The
glomerophyric clot phenocryst in sample 970811-32 also has a relatively large
compositional variation from the rim to the middle position, from My at the rim to My
at the middle position (Figure 19c). The plagioclase phenocrysts in the lava ﬂow
samples tend to be reverse-zoned, whereas the plagioclase phenocrysts in the block and
ash-ﬂow deposit tend to be normally-zoned.

For the same sample, the mineral compositions in glomerophyric clots are, in
general, slightly less evolved than the phenocryst compositions. For example, in lava
sample 970812-41, the plagioclase phenocryst ranges from A1149 to An55, whereas the
glomerophyric clot plagioclase range from My; to My (Figure 19c).

Both the orthopyroxene and the clinopyroxene phenocrysts are MgO rich and
show relatively small variations in composition. These compositions are presented in
Table 4 and are plotted in Figure 20. Individual phenocryst variations are plotted in
Figure 21.

For orthopyroxene phenocrysts, the rim compositions range from EnsoFsso to
En62F536. The maximum change in composition (from core to rim) of an orthopyroxene
phenocryst is from En51F843 to Ensts46 for sample 970810-09 (Figure 21). The
variation within a phenocryst is small relative to the varition of composition between

phenocrysts.

36

 

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38

 

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39

 

 

 

Figure 20: Pyroxene quadrilateral showing all pyroxene phenocryst
compositions. These analyses includes rim, middle and core analyses.

40

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41

For clinopyroxene phenocrysts, the rim compositions range from Di41Hd16Wo43
to Di49HdloWo4o. The core compositions range ﬁ'om Di39Hd17W044 to Di46Hd12Wo42.
The maximum change in composition (from core to rim) of a clinopyroxene phenocryst
is from Di49Hd10Wo41 to Di46Hd|2Wo42for sample 970810-12. The inclusion
phenocrysts of sample 970809-06 also show slightly larger variation than the
clinopyroxene phenocrysts of the lava ﬂow (Figure 21).

Homblende compositions do not vary greatly from rim to core. The most
variation within the amphibole analyses is within $02, which varies from 41.2 wt. % to
42.3 wt. %. Only one analysis point was obtainable from the biotite grain due to its
small size and resorption near the rim. Homblende and biotite compositions are
presented in Table 5. Opaques were identiﬁed using the electron microprobe, but no
analyses were obtained. Magnetite was the dominant opaque mineral, with minor
amounts of ilmenite. In some cases, the magnetite grain had granule exsolution of

ilmenite along the rim.

Spatial variation

In order to detect any vertical variations in composition within the lava ﬂow,
samples were collected at different elevations on the north side of the second Burroughs
Mountain (see inset of Figure 1). Major element oxide variations with respect to their
elevation above the base of the lava ﬂow are shown in Figure 22. The samples of the
upper portion of the lava ﬂow are distinct from the samples of the lower portion.

Samples of the upper portion have an average F e203 (ml) content of 6.4 wt. %, whereas

42

 

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44

the samples of the lower portion have an average FezOgmm) content of 5.9 wt. %. In
general, samples from the upper portion of the lava ﬂow are slightly more maﬁc than
samples from the lower portion. However, trace elements cannot be used to discriminate
between the upper and lower portions of the ﬂow (Figure 23).

In addition, a systematic zoning is present in the upper portion of the ﬂow, which
is absent in the lower portion of the ﬂow. In the upper portion of the lava ﬂow, the lava
samples are least maﬁc towards the top and increasely more maﬁc towards the bottom
(Figure 22). For example, sample 970811-34 is from the top of the upper portion and
has an Fe203(ml) content of 6.21 wt. %, whereas sample 980820-31 is from the bottom
of the upper portion and has an F6203(mm1) content of 6.78 wt. %.

In order to detect lateral variations, samples were taken over the length of the
lava ﬂow. Samples collected at different elevations on the northeast side of the ﬁrst
Burroughs Mountain (see inset of Figure 1) are also shown in Figure 22. Again, the
samples of the upper portion of the lava ﬂow are, in general, more maﬁc than the
samples of the lower portion of the lava ﬂow. Additional sampling of this area is

necessary to comment on any systematic zoning in this location.

DISCUSSION

The Burroughs Mountain lava ﬂow has compositionally-distinct layers with
systematic chemical zoning present in the upper portion of the lava ﬂow. These zoning
patterns can be produced prior to eruption by such processes as assimilation and

fractional crystallization. The major element oxides display linear relationships with

45

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46

respect to MgO. In addition, trace elements also display small variations with respect to
changes in MgO wt. %. These chemical variations can be explained entirely by

fractional crystallization, so additional processes are not necessary. Eruption dynamics
may also produce the observed spatial variation. A model of the eruption event can be
constructed based on the distribution of the block and ash-ﬂow deposits and the lava
ﬂow. Because the compositional variation of the block and ash-ﬂow deposit spans the
full range of compositional variation of the lava ﬂow, this eruption tapped both layers of

magma that produced the lava ﬂow.

Spatial variations

The Burroughs Mountain lava ﬂow has two layers, which are chemically distinct.
The lower portion of the lava ﬂow is, in general, less maﬁc than the upper portion of the
lava ﬂow. In addition, there is no systematic chemical zoning in samples from the lower
portion of the lava ﬂow, whereas there is a systematic zoning in samples from the upper
portion of the lava ﬂow. In the upper portion of the lava ﬂow, the chemical zoning is
more maﬁc at the bottom and less maﬁc towards the top.

This layered and zoned lava ﬂow requires a pre-eruptive magma body that was
also layered and possibly zoned in the lower layer. Figure 24 illustrates a simple
explanation for this magma body, where a less maﬁc upper layer overlies a chemically-
zoned, more maﬁc layer. This layered system would have been gravitationally stable.

The magma layer that produced the systematic zoning observed in the upper
portion of the lava ﬂow must have been gravitationally stable also. If the chemical

gradient exited prior to eruption, this requires either a "reverse" relationship between

47

Buoyant rise

 

 

Heterogeneous,
less matic magma °f.°".°"’°d
llqmds?
higher content
of plagioclase
phenocrysts
Higher M90 or volatiles
Possible
Observed causes of
gradient gradient
lower content
Lower M90 of plagioclase
phenocrysts
Convection? or volatiles

Chemically-zoned.
more matic magma

Figure 24: Possible pro-eruptive magma body, where the upper layer has a
heterogeneous, less maﬁc magma and the lower layer is a more maﬁc magma
with a chemical gradient Sidewall (fractional) crystallization may produce
evolved liquids, which rise buoyantly to form the upper, less maﬁc magma.
The fractional crystallization may also produce a chemical gradient. Finally,
the buoyant rise may also result in convection within the lower magma body.

48

density and F e-content. This "reverse" relationship has been explained in picritic
tholeiites and mid-ocean ridge basalts (MORBs) by the liquid line of descent (Stolper
and Walker, 1980). The liquid density originally decreases with increasing
Fe/(Fe+Mg)molar when olivine is the only crystallizing phase. However, the density
will then increase with increasing Fe/(Fe+Mg)molar when pyroxene and plagioclase join
in crystallization. This is primarily due to the FeO enrichment and removal of low-
density plagioclase components from the liquid (Stolper and Walker, 1980). Thus, in a
MORB system, a more Fe-rich magma may actually have a lower density than a less Fe-
rich magma. However, this phenomenon has not been documented in andesitic
subduction zone magmas. An increase in the content of H20 and/or of plagioclase
phenocryst could also decrease in density towards the top of this layer (Bottinga and
Weill, 1970).

The reversely-zoned plagioclase phenocrysts observed in the lava ﬂow samples
require disequilibrium in the system, such as new batches of magma entering the magma
chamber. Convection of the magma body would also bring phenocrysts into contact with
less evolved liquids and create reversely-zoned phenocrysts.

Any model of the evolution and eruptive events must explain the lack of
systematic zoning in the upper layer of the magma body and the presence of reverse

systematic zoning in the lower layer of the magma body.

Processes to produce systematic chemical variations
Fractional crystallization and sidewall crystallization have been recognized as

mechanisms that may cause density gradients in a magma body. Miller and Mittlefehldt

49

(1983) suggested that crystal-liquid separation during crystallization and subsequent
eruption could yield an extremely fractionated, crystal-poor magma. However, this
model requires extensive crystal fractionation (50 to 90%). Loss of heat through the roof
causes crystallization in the upper part of the magma chamber, forming a depleted
horizontal layer in the upper part of the magma chamber. Sidewall crystallization results
in a boundary of fractionated liquid (parallel to the walls) that may rise buoyantly, also
forming a depleted cap. These buoyant, fractionated liquids are erupted ﬁrst followed by
denser less felsic magmas (Miller and Mittlefehldt, 1983).

McBimey et al. (1984) proposed liquid fractionation for producing zoned magma
bodies. Liquid fractionation is the process by which differentiated liquids segregate
gravitationally to form a compositionally-graded magma body (McBimey et al., 1984).
The composition grades from a low density, silicic magma near the top to a denser, maﬁc
magma near the bottom of the magma body.

Trial and Spera (1990) grouped proposed mechanisms that produce systematic
variations in pyroclastic deposits. Compositional zoning may develop during the
formation of the magma body (ab initio) or by differentiation of an initially
homogeneous magma body (in situ) (Trial and Spera, 1990). Ab initio processes include
pseudo-invariant anatexis or melting of the magma chamber roof. However, assimilation
of country rock is not important for all systems (Trial and Spera, 1990), including the
Burroughs Mountain lava ﬂow.

In situ processes include volatile transfer and boundary layer mechanisms. The
low solubility of major elements in water vapor would require magma chambers to be

highly supersaturated with respect to water for volatile transfer to be the sole mechanism.

50

Major elements also have relatively small chemical diffusivities in magmas, so Trial and
Spera (1990) argue that boundary layer mechanisms may be insufﬁcient to explain the
differentiation of the magma body on geologically reasonable time scales. However,
McBimey et al. (1986) previously argued that enrichment of a component that has a low
chemical diffusivity (for example, $02) is not necessarily the result of addition of that
component. Rather, enrichment may result from removing other components and

concentrating that component in the decreasing mass of liquid.

Testing Fractional Crystallization

The linear decreases in major element oxides with respect to decreases in MgO
are consistent with fractional crystallization (Cox et al., 1979). Furthermore, the
ﬂattened heavy rare earth element (HREE) pattern is consistent with fractional
crystallization of pyroxene (Figure 8). In situ processes, including fractional
crystallization, may be responsible for the chemically-distinct upper and lower portions
of the lava ﬂow as well as the systematic chemical variations in the upper portion of the
lava ﬂow.

Fractional crystallization was modeled using multiple linear regression
techniques (Bryan et al., 1969). Mineral compositions were chosen from compositions
obtained by electron microprobe analyses and represent the full range of compositions.
For example, the plagioclase compositions used in modeling represent a range of
compositions from low Na-content to high Na—content analysis points. For the ﬁrst

attempt at modeling, the mid-range mineral compositions were used (for example, the

51

mid-Na plagioclase). For subsequent runs, the choice of mineral compositions was
adjusted accordingly to improve the results of modeling.

The whole rock compositions of the most maﬁc lava ﬂow sample (970820-30)
was chosen as parent magmas to model fractional crystallization to a slightly less maﬁc
lava ﬂow sample (970812-45). Then, modeling was also done from the most maﬁc lava
ﬂow sample to the least maﬁc lava ﬂow sample (970811-24). Figure 25 illustrates the
linear relationship between these samples relative to the entire lava data set.

The model that produced the best result (i.e. smallest sum of the square of the
residuals and non-negative values for liquid remaining and percent of phases
crystallized) was chosen to represent that step in the fractional crystallization trend. This
process was repeated, using the sample that was daughter in the most recent modeling as
the parent and choosing a more silicic lava sample as a daughter. These steps allowed the
fractional crystallization to be modeled from the most maﬁc to the more silicic lava
samples.

The chemical variations seen in the Burroughs Mountain lava ﬂow can be
accounted for by fractional crystallization of plagioclase, orthopyroxene, clinopyroxene,
hornblende and magnetite. The largest sum of the square of the residuals for any
fractional crystallization step is 0.026. Table 6 illustrates the best results of the stepped
fractional crystallization tests as well as the best result of the overall fractional
crystallization test. The fraction of liquid remaining and the fraction of crystallizing
phases are listed in Table 6 also.

In the stepped fractional crystallization tests, the fraction of liquid remaining after

all three steps is 0.82. In the overall fractional crystallization test, the fraction of liquid

52

 

F6203 (total) 6 '-

 

 

 

 

 

Fe203 (total) 6 "

 

 

 

 

Figure 25: Linear trend of samples used in fractional crystallization
modeling (top) versus the linear trend of all lava samples (bottom)

53

 

CaO

 

 

 

 

2.5 3.0 3.5 4.0

 

R2=.67 I
65 — R’=.80 I -

CaO

 

 

 

 

2.5 3.0 3.5 4.0

Figure 25 (continued): Linear trends of samples used in fractional
crystallization modeling (top) versus the linear trend of all lava
samples (bottom)

54

Table 6: Best results from the three steps of fractional crystallization as well as
from the most maﬁc (980820-30) to least maﬁc (970811-24) samples.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Step 1: Parent = 980820-30 Daugter = 97081245
Mineral Fraction % Cumulate
BO9-medfe-opx 0.014 30.9
B 14-medca-cpx 0.002 3 .9
BO6-medfe-hb 0.009 19
BO6-lmNa-pl 0.021 46.2
Liquid remaining 0.956

Si02 TiOz A1203 FeO MnO MgO CaO NaZO K20 P20,
‘Dau ter 60.47 0.94 17.07 5.71 0.1 3.59 6.05 4.16 1.6 0.31
Parent
[Observed 60.18 0.97 17.05 5.9 0.1 3.87 6.14 4.02 1.52 0.26
[Calculated 60.14 0.93 17.05 5.91 0.1 3.87 6.14 4.08 1.53 0.3
[Difference 0.02 0.04 0.00 -0.01 0.00 0.00 -0.0l -0.06 -0.02 -0.04
[Sum of the squares of the residuals = 0.008
Step 2: Parent = 970812-45 Dau hter = 970810-16
Mineral Fraction % Cumulate
B14-medca-cpx 0.01 l 12. l
BO6—medfe—hb 0.041 47.4
BO6-loNa-pl 0.029 33.5
Cn-avg—mt 0.006 6.9
Liquid remaining 0.911

Si02 TiOz A1203 FeO MnO MgO CaO NaZO K20 P205
Dau ter 62.16 0.86 17.06 5.12 0.09 3.06 5.5 4.28 1.68 0.19
Parent
Qbserved 60.47 0.94 17.07 5.71 0.1 3.59 6.05 4.16 1.6 0.31
Ealculated 60.52 0.98 17.07 5.71 0.1 3.58 6.04 4.11 1.54 0.17
[Difference -0.02 -0.04 0.00 0.01 0.00 0.00 0.01 0.05 0.06 0.14
ISum of the squares of the residuals = 0.026
Step 3: Parent = 970810-16 DauLhter = 970811-24
Mineral Fraction % Cumulate
B14-lofe-opx 0.018 35.5
BO6-loca-cpx 0.001 2.1
B06-loNa—pl 0.03 1 61.7
Cn—avg-mt 0 0.7
Liquid remaining 0.951

SiOz TiOz A1203 FeO MnO MgO CaO N320 K20 P205
Dau ter 62.53 0.87 16.96 4.99 0.09 2.78 5.27 4.43 1.89 0.2
Parent
Observed 62.16 0.86 17.06 5.12 0.09 3.06 5.5 4.28 1.68 0.19
ICalculated 62.1 0.84 17.1 5.12 0.1 3.08 5.5 4.32 1.8 0.19
IDifference 0.03 0.03 -0.02 0.00 -0.01 -0.02 -0.01 -0.04 ~0.12 0.00
[Sum of the squares of the residuals = 0.018
Total of liquid remaining: 0.82
Total degree of fractional crystallization: 0.18

55

 

 

 

Table 6: continued.

Fractional crystallization from most mafic to least mafic

Parent = 980820-30 Dalgihtcr = 970811-24

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mineral Fraction % Cumulate
B09-medfe-opx 0.03 1 l 8. 1
B l4-medca-cpx 0.01 1 6.5
B06-medfe-hb 0.05 1 30.2
B06-loNa-pl 0.073 42.9
Cn-avg—mt 0.004 2.4
Liquid remaining 0.83

SiOz TiOz A1203 FeO MnO MgO CaO NaZO K20 P20,
Dau ter 62.53 0.87 16.96 4.99 0.09 2.78 5.27 4.43 1.89 0.2
Parent
Observed 60.18 0.97 17.05 5.9 0.1 3.87 6.14 4.02 1.52 0.26
Calculated 60.14 0.92 17.06 5.91 0.1 3.87 6.14 4.05 1.59 0.17
Difference 0.01 0.05 -0.01 -0.01 0.00 -0.01 -0.01 -0.04 -0.07 0.09
Sum of the squares of the residuals=0.018
Degree of fractional crystallization: 0.17

56

 

remaining is 0.83. Thus, the observed chemical variations in the Burroughs Mountain
lava ﬂow require 17 to 18% fractional crystallization.

Fractional crystallization was also modeled within the upper portion of the lava
ﬂow and within the lower portion of the lava ﬂow separately to evaluate the origin of the
layers and zoning. For both portions of the lava ﬂow, fractional crystallization was
modeled only from the most maﬁc sample to the least maﬁc sample of that portion. The
variation seen within the upper portion of the lava ﬂow is consistent with fractional
crystallization. In fact, the result was as successful as the results of the previous
modeling (where modeling was done in steps) with a sum of the squares of the residuals
of 0.016 (Table 7).

A surprising result from this modeling is that fractional crystallization is not
consistent with the chemical variation within the lower portion of the lava ﬂow. From
fractional crystallization modeling of the entire lava ﬂow, the three most maﬁc samples
group compositionally with the upper portion of the lava flow, whereas the least maﬁc
sample groups compositionally with the lower portion of the lava ﬂow. Thus, fractional
crystallization of the upper portion of the lava ﬂow can be successfully modeled to
produce the lower portion of the lava ﬂow. Therefore, the lower portion of the lava ﬂow
may represent evolved liquids formed by sidewall crystallization of the magma that
formed the upper portion of the lava ﬂow.

Fractional crystallization can fully account for the chemical and spatial variations
in the lava ﬂow. Additional processes are not necessary to explain these variations.

Because subduction zone magmatism has existed in the Cascade Range since Eocene

57

Table 7: Best results of the fractional crystallization modeling from the
most maﬁc to the least maﬁc samples for upper protion of the ﬂow.

In addition, failed results of thefractional crystallization modeling for

the lower portion of the ﬂow.

For upper portion of the lava ﬂow:

Parent = 980820-31

Daughter = 980820-25

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mineral Fraction %Cumulate
B09-medfe-opx 0.025 63.4
B12-lofe-hb 0.002 6
B06-loNa-pl 0.01 1 27.6
Cn-avg-mt 0.001 3
Liquid remaining 0.961

SiOz TiOz A1203 FeO MnO MgO CaO Na20 K20 P205
Daughter 60.95 0.91 17.02 5.57 0.09 3.51 6.04 4.09 1.57 0.25
Parent
Observed 60.62 0.97 16.66 6.08 0.11 3.92 6.02 3.88 1.5 0.25
Calculated 60.56 0.9 16.73 6.09 0.09 3.94 6 3.97 1.51 0.24
Difference 0.03 0.06 -0.03 -0.01 0.02 -0.02 0.02 -0.09 -0.02 0.01
Sum of the squares of the residuals = 0.016 V
For lower portion of the lava ﬂow:
Parent = 980820-37 Daughter = 980820-35
Mineral Fraction %Cumulate
Bl4-lofe-opx 0.015 7.5 *
B06-loca-cpx -0.03 -14.6
B12-1ofe-hb 0.07 34.3
B09-hiNa-pl 0.132 64.2
Cn-avg-mt 0.018 8.6
Liquid remaining 0.793

SiOz TiOz A1203 FeO MnO MgO CaO NaZO [(20 P20,
Daughter 63.97 0.83 16.62 4.95 0.08 2.68 5.22 3.82 1.6 0.21
Parent
Qbserved 60.89 0.93 17.05 6.11 0.1 3.33 5.5 4.3 1.58 0.2
[Calculated 60.94 1.03 17.26 6.09 0.09 3.32 5.48 4.06 1.36 0.17
IDiﬁ‘erence -0.02 -0.10 -0.11 0.02 0.01 0.01 0.02 0.24 0.23 0.04

 

 

 

 

 

 

 

 

 

 

 

ISum of the squares of the residuals = 0.132
MIXTURE OF ASSIMILATION AND FRACTIONATION

 

58

 

 

epoch, any potential assimilants have geochemical characteristics that are very similar to
the host magma. In addition, the erupted lavas are far removed in chemical composition
from melts of the mantle. No convincing conclusions can be drawn concerning
petrogenetic processes in the mantle based on the chemical variation in these samples.

In situ processes (for example, fractional crystallization) are consistent with the
chemical variations seen in the Burroughs Mountain lava ﬂow. However, ab initio
processes (for example, assimilation of country rock) were not important in the evolution
of the Burroughs Mountain lava ﬂow. Therefore, in situ processes are responsible for

the spatial variation observed in the lava ﬂow.

Eruption of a zoned magma body

Compositional zoning is commonly observed in many high-silica, pyroclastic
deposits (Smith, 1979; Hildreth, 1981) and is less commonly found in lava ﬂows
(Wilcox, 1954; Carrigan and Eichelberger, 1990). Whereas the pyroclastic deposits
typically exhibit a maﬁc-over-silicic zonation, lava ﬂows usually exhibit a silicic-over-
maﬁc zonation (Carrigan and Eichelberger, 1990). This difference in deposition may
result from the eruption dynamics of the magma body.

Carrigan et al., (1992) investigated the role of two-phase ﬂow in dikes and the
inﬂuence of viscosity on eruption dynamics. They looked at chemical variation across a
33-m-wide conduit that feeds the Obsidian Dome volcano in Long Valley, California.
Based on drill core, the lower viscosity (more maﬁc) magma is found near the conduit
walls, whereas the higher viscosity (more silicic) magma is found near the center of the

conduit. Similarly, the lava ﬂow has the more maﬁc lava at the base of the ﬂow. The

59

lack of a chill margin between the two magma types in the conduit requires that these
magmas ﬂowed contemporaneously through the conduit. Carrigan et al., (1992)
suggested that during ﬂow through the conduit, the magmas are sorted so that the more
maﬁc magma is found near the conduit walls. Furthermore, the more maﬁc magma
actually lubricates the passage of the less maﬁc magma through the conduit. When the
magma reaches the surface, the more maﬁc magma is erupted ﬁrst. Thus, the eruption
results in a systematically zoned lava with the most maﬁc lava at the base of the ﬂow.
The systematic variation in composition seen in the upper portion of the Burroughs
Mountain lava ﬂow is consistent with this model.

The shift ﬁom a heterogeneous lava in the lower portion of the ﬂow to zoned
lava in the upper portion of the ﬂow might be explained by a hiatus in the eruption. This
hiatus would have allowed the lower portion of the magma body (the upper part of the
ﬂow) to become more gravitationally stratiﬁed (Spera et al., 1986). However, because
there are no discrete ﬂow units or cooling breaks, this lava ﬂow is thought to be one
continuous ﬂow. There are two possible explanations for the spatial variation observed
in the lava ﬂow.

The ﬁrst is that a single magma body occupied the chamber and underwent
fractional crystallization (sidewall crystallization). The upper, less maﬁc magma was
formed by the crystal-liquid separation mechanisms of Miller and Mittlefehldt (1983).
This resulted in a lower density, less maﬁc magma layer towards the top of the magma
chamber. No chemical zoning is observed in this portion of the lava, perhaps because
none was present in the magma chamber or the zoning was destroyed during eruption.

Regardless, the upper layer of magma body erupted ﬁrst. As the upper layer of the

60

magma was derived from the lower layer, this lower layer became chemically zoned.
The lower layer was "reversely" zoned, similar to that observed in MORBs (Stolper and
Walker, 1980). This "reverse" zoning must have been gravitationally stable, perhaps
aided by increasing volatile and plagioclase phenocryst content towards the top of the
layer. The zoning is consistent with crystal fractionation. This model is consistent with
the magma body shown in Figure 24.

The second explanation is similar to the ﬁrst explanation. A layered magma
body existed within the magma chamber, with the less maﬁc layer near the top and a
more maﬁc layer beneath. However, a chemical gradient does not exist within the lower
part of the magma body prior to eruption. Instead, the magma body is heterogeneous and
the zoning results from eruption dynamics as described by Carrigan et al., (1992) rather
than eruption from a layer with apparent reverse chemical zoning.

In this model, the upper layer of the magma body erupted forming the lower
portion of the lava ﬂow. The lower layer of the magma body reached the conduit and,
during ﬂow through the conduit, became sorted so that the most maﬁc magma lubricated
the conduit walls. When this magma reached the surface, the most maﬁc magma erupted

ﬁrst, forming the lowermost part of the upper portion of the ﬂow.

Model of Eruption Events

Despite their differing textures and eruptive styles, the lava ﬂow and the block
and ash-ﬂow deposit are compositionally indistinguishable. Thus, their differing
eruptive styles must result from some aspect of their ascent and degassing. The

distribution of the units indicates that the pyroclastic ﬂows erupted through the summit,

61

whereas the large lava ﬂows erupted from ﬂank vents. For the Burroughs Mountain lava
ﬂow, the ﬂank vent was probably in the vicinity of St. Elmo Pass (Sisson, personal
communication, 1999).

A model of eruption events can be constructed based on the distribution of the
block and ash-ﬂow and lava ﬂow units. Initially, the magma, accompanied by its full
compliment of magmatic gases, erupted through the summit producing the block and
ash-ﬂow deposits. This process opened the summit conduit system, allowing the
magmatic gases to vent. An increase in magmatic ﬂux opened a radial dike in the
present area of St. Elmo Pass. Ascending magma was diverted through this opening
while magmatic gases continued to vent through the summit conduit system, allowing
the remaining magma to become degassed. The degassed magma erupted effusively to

form the lava ﬂow.

CONCLUSIONS

The purpose of this study was to document and evaluate the origin of the
chemical and mineralogical variations within the Burroughs Mountain lava ﬂow and the
underlying block and ash-ﬂow deposits and to determine if the explosive and non-
explosive behavior of the magmas is chemically controlled. The chemical variations in
the Burroughs Mountain lava ﬂow are consistent with fractional crystallization from the
most maﬁc sample to the least maﬁc sample being the dominant process. However, the
scatter of incompatible trace elements requires additional processes.

A spatial variation in composition is present in the Burroughs Mountain lava

ﬂow. This spatial variation represents a two-layered magma body, where the lower layer

62

of the magma body was a relatively maﬁc magma and the upper layer of the magma was
a relatively silicic magma. The variation seen in the zoned, upper portion of the lava
ﬂow (lower part of the magma body) is consistent with fractional crystallization from the
most maﬁc to the least maﬁc sample. One simple explanation is eruption from a
“reversely-zoned” magma body, possibly stabilized by volatile gradients. However, an
alternative explanation is eruption from a heterogeneous magma body that was sorted by
viscosity during eruption. The chemical variation within the lower portion of the lava
ﬂow (upper part of the magma body) is not consistent with fractional crystallization from
the most maﬁc sample to the least maﬁc sample. Instead, this magma probably
represents evolved liquids produced by fractional crystallization of the more maﬁc,
zoned magma.

The underlying block and ash-ﬂow deposits span the full range of compositions
displayed by Burroughs Mountain lava ﬂow. Hence, the composition does not control
the nature of the eruption. Instead, the control must be some aspect of the ascent and

degassing, allowing for transition from an explosive to a non-explosive eruption.

63

APPENDIX

64

Table 1: Whole rock major element and selected trace element
chemical analyses.

970809-1 970809-2H 970809-2C 970809-3I-I 970809-3C 970809-5

 

8102 61.11 61.15 56.27 61.76 54.92 56.39
rio2 0.87 0.87 0.98 0.84 1.19 0.96
4.1203 17.3 17.61 17.07 17.42 17.2 17.85
F8203 5.87 5.72 7.12 5.55 7.06 7.24
MnO 0.09 0.09 0.12 0.09 0.1 0.11

MgO 3.13 2.94 4.56 2.89 5.29 4.47
CaO 5.61 5.62 8.02 5.61 7.87 6.99
NaZO 4.17 4.36 3.96 4.21 3.58 4.03
K20 1.53 1.58 0.96 1.56 1.09 1.3

820, 0.2 0.22 0.22 0.2 0.12 0.18
Total 99.88 100.16 99.28 100.13 98.42 99.52
Cr 22.9 5.9 51 20.1 67.8 139.2
Ni 24.8 10.1 24.5 9.6 33 55.9
Cu 39.7 28.9 91.5 36.7 118.4 34.8
Zn 70.7 64.8 77.8 67.6 66.7 83.4
Rb 37.1 35.2 22 37.4 26.5 29

Sr 542.1 575.9 584.9 545.1 430.3 601.4
Y 17.8 17 17.8 17.7 18.5 15.2
Zr 158.3 160.3 100.6 158.6 111.9 127.6
Nb 9.3 5.9 5.9 8.2 6.9 6.6

Ba 365.3 452.4 280.5 419 218.9 326.9
La 17.4 15.94
Ce 37.34 34.02
Pr 4.62 4.45

Nd 19.98 18.53
Sm 4.08 3.84
Eu 1.25 1.31

Gd 3.66 3.7

Tb 0.55 0.57
Dy 2.84 2.99
Ho 0.52 0.58
Er 1.54 1.67
Tm 0.23 0.27
Yb 1.34 1.56
Lu 0.21 0.27

65

Table 1: (continued)

970809-56 970809-6G 970809-6 970809-7 970809-8 970810-9

 

3102 56.74 61.37 57.31 59.23 62.18 60.63
T102 0.82 0.76 0.92 0.72 0.84 0.8

111203 17.51 17.43 17.87 16.68 16.7 18.31
F6203 5.98 5.56 6.73 6.03 5.56 5.56
MnO 0.1 0.09 0.11 0.1 0.09 0.09
MgO 3.4 3.16 4.25 3.95 2.93 3.06
CaO 6 5.65 6.63 6.04 5.14 5.48
NaZO 4.34 4.25 4 4.13 4.33 4.25
[(20 1.37 1.43 1.28 1.38 1.84 1.51

920, 0.16 0.17 0.17 0.16 0.2 0.22
Total 96.42 99.87 99.27 98.42 99.81 99.91
ct 767.5 69.2 101 849 26.6 34.1

Ni 102.7 33.3 51.8 115.8 14.1 23.4
Cu 35.9 30.4 36 52.4 23 22

Zn 72.8 66.8 75.3 65.7 66.5 71.5
Rb 31.4 27.2 29.4 35.8 43.1 27.3
31’ 582 537.3 596.6 519 489.6 609.5
Y 12.1 13.5 13.2 16.3 19.5 13.9
Zr 135.5 136.4 127.6 129.6 181.2 146.8
Nb 5.6 5.9 4.7 4.5 6.2 6.8

Ba 369.1 394.5 288.4 366.5 486.5 503.5
La 15.08 14.58 13.18 20.37
Ce 33.59 34.97 31.53 43.4
Pr 3.98 3.89 3.73 5.01

Nd 16.42 15.81 15.8 18.92
Sm 3.25 3.17 3.25 3.78
Eu 1.08 1.06 1.14 1.16
Gd 2.73 2.62 2.87 3.35
Tb 0.44 0.43 0.45 0.48
Dy 2.19 2.12 2.37 2.64
116 0.4 0.41 0.43 0.47
Er 1.23 1.21 1.32 1.63
Tm 0.19 0.2 0.21 0.24
Yb 1.29 1.21 1.32 1.34
Lu 0.18 0.18 0.21 0.2

66

Table 1: (continued)

 

970810-10 970810-11 970810—12 970810—13H 970810-13C 970810—14
8102 58.81 60.96 60.57 56.86 56.42 60.81
T102 0.85 0.81 0.88 0.88 0.96 0.91
A1203 17.56 17.27 17.77 17.15 16.71 17.21
F8203 5.8 5.8 6.14 6.28 6.93 5.75
MnO 0.09 0.09 0.1 0.09 0.1 1 0.09
MgO 3.13 3.11 3.54 4.88 5.39 3.06
CaO 5.79 5.84 6.18 6.89 6.83 5.4
NaZO 4.62 4.16 4.18 3.83 3.5 4.57
K20 1.45 1.48 1.39 1.62 1.55 1.65
P205 0.21 0.21 0.24 0.15 0.17 0.21
Total 98.31 99.73 100.99 98.63 98.57 99.66
Cr 39.3 28.9 54.3 141.6 155.7 32.5
Ni 24.7 21.3 26.5 87.6 89.3 16.9
Cu 23.2 27.4 21.7 119.3 68.5 18.5
Zn 71.8 74.9 70.9 96 104.3 66.1
Rb 23.5 33.7 28.1 40.9 36 34.5
Sr 633.1 585 662.1 589.3 570.7 500.6
Y 13 17.1 17.2 16.6 15.4 17.4
Zr 148.7 153 146.9 147 155.3 166.2
Nb 6.2 6.3 4.1 6.4 6.3 9.6
Ba 418.4 412.1 458.3 499.2 487.3 388.6
La 16.44 16.17

Ce 41.88 37.97

Pr 4.59 4.4

Nd 17.98 18.2

Sm 3.33 3.77

Eu 1.12 1.34

Gd 2.71 3.37

Tb 0.43 0.49

Dy 2.17 2.73

Ho 0.39 0.51

Er 1.21 1.47

Tm 0.19 0.22

Yb 1.28 1.41

Lu 0.19 0.23

67

Table 1: (continued)

 

970810-15 970810-16 970810-17 970810-17G 970810-19C 970810-20H
$102 60.9 61.88 60.74 61.43 59.74 59.02
T102 0.91 0.86 0.93 0.91 0.81 0.77
A1203 16.99 16.98 17.24 16.67 17.15 15.89
F8203 5.97 5.66 6.05 6.05 6.07 5.91
MnO 0.1 0.09 0.1 0.09 0.1 0.09
MgO 3.44 3.05 3.33 3.48 3.27 3.24
CaO 5.53 5.47 5.59 5.59 5.98 5.82
NazO 4.23 4.26 4.29 4.1 4.17 3.97
K20 1.62 1.67 1.58 1.62 1.47 1.54
9,0, 0.21 0.19 0.2 0.19 0.19 0.19
Total 99.9 100.11 100.05 100.13 98.95 96.44
Cr 38.1 24 34.7 34.6 42.2 53.7
Ni 21.3 15.5 17.8 14.9 29.3 28.2
Cu 30.8 27.9 67 51.8 52.9 51.4
Zn 69.8 66.5 85.6 74 95.2 78.5
Rb 33.2 41.5 31.8 40.7 31.6 35.9
st 493.9 482.7 517.7 467.3 596.1 576.6
Y 16.6 19.4 16 17.9 15.8 15.8
Zr 161.2 173 159.7 165.9 146 146.5
Nb 10.3 8.8 8.9 9.3 5.2 8.2
Ba 359.5 374.4 457.1 414.6 401.4 361.3
La 16.32 18.01
Ce 38.98 42.55
Pr 4.26 4.78
Nd 16.75 19.09
Sm 3.31 3.63
Eu 1.09 1.19
Gd 2.67 2.92
Tb 0.47 0.47
Dy 2.27 2.35
Ho 0.41 0.44
Er 1.22 1.27
Tm 0.21 0.21
Yb 1.28 1.24
Lu 0.19 0.19

68

Table 1: (continued)

97081 l-21C 97081 l-21H_ 97081 l-22C 9708114? 97081 1-24 97081 1-25

 

8102 61.17 62.74 62.54 62.71 61.95 61.05
Tlo2 0.86 0.84 ‘ 0.85 0.82 0.86 0.85
A1203 16.82 16.14 17 16.58 16.8 16.82
Fe203 5.8 5.75 5.82 5.45 5.5 5.77
MnO 0.09 0.09 0.09 0.08 0.09 0.09
MgO 3.15 3.03 3.22 2.78 2.75 3.15
CaO 5.55 5.31 5.59 5.43 5.22 5.62
NaZO 4.07 4.01 4.21 4.11 4.39 4.05
K20 1.75 1.93 1.83 1.89 1.87 1.72
P205 0.18 0.18 0.19 0.18 0.2 0.18
Total 99.44 100.02 101.34 100.03 99.63 99.3
Cr 40.8 35.8 35.6 23 28.4 50.2
Ni 18.1 19 18.2 19.8 13.5 17.5
Cu 31.9 40.3 46.5 33.7 27.4 28.9
Zn 75.8 73 73.2 76.8 71.3 74.9
Rb 40.4 45.7 43.4 45.8 41 40.5
Sr 520.4 476.2 518.9 497.6 528.9 513
Y 19.2 20.7 19.9 19.9 18.2 21.1
Zr 169.9 180.9 175.6 176.2 179 175.3
Nb 7.7 7.7 8 9.5 8.8 10.3
Ba 417 448.2 407.8 422.8 458.5 435.7
La 21.32 20.4 19.65 19.29
Ce 50.45 48.87 46.84 47.74
Pr 6 5.42 5.1 1 5.26
Nd 22.75 21.78 20.79 20.47
Sm 4.45 4.02 3.98 3.87
Eu 1.33 1.21 1.19 1.21
Gd 3.96 3.55 3.48 3.32
Tb 0.63 0.59 0.54 0.49
Dy 3.37 2.97 2.97 2.58
Ho 0.6 0.54 0.54 0.51
Er 1.9 1.58 1.66 1.48
Tm 0.3 0.26 0.25 0.25
Yb 1.76 1.73 1.61 1.55
Lu 0.29 0.25 0.25 0.22

69

Table 1: (continued)

97081 1-26 97081 1-27 97081 l-28H 97081 l-28C 97081 1-29 97081 l-29I

 

SiOz 61.88 61.61 62.02 59.19 60.26 56.15
TiOz 0.82 0.85 0.86 1.1 1 0.89 0.96
A1203 16.79 17.04 16.44 16.39 17.38 18.13
Fe203 5.56 5.53 5.68 6.23 6.15 7.41
MnO 0.09 0.09 0.09 0.09 0.1 0.12
MgO 3.14 2.95 3.17 4.12 3.32 4.55
CaO 5.43 5.33 5.18 5.86 5.75 7.05
NaZO 4.21 4.48 4.2 3.91 4.2 3.66
K20 1.67 1.69 1.74 1.33 1.5 1.11
P20, 0.18 0.21 0.19 0.28 0.2 0.17
Total 99.77 99.78 99.57 98.51 99.75 99.31
Cr 40.7 26 44.4 78.8 19.3 40.3
Ni 22.4 18.4 26.4 63.7 10.9 30.7
Cu 32.4 34.7 49 49.5 24.6 73.9
Zn 74.4 65.2 73.2 77 .8 68.4 75.2
Rb 39.1 34.6 38.2 27.5 35.6 25
Sr 538 592.7 541.1 518.4 525.8 511.7
Y 16.9 14.1 17.9 17.4 15.4 14.8
Zr 159.6 160.2 170.2 177.4 134.4 107.5
Nb 6.4 8.7 6.8 15.2 8.4 6.2
Ba 382.9 383.6 342 295.5 387.9 287.3
La 21.49

Ce 46.76

Pr 5.22

Nd 21.35

Sm 4.25

Eu 1.39

Gd 3.56

Tb 0.56

Dy 2.77

Ho 0.52

Er 1.51

Tm 0.23

Yb 1.46

Lu 0.22

70

Table 1: (continued)

970811-30 970811-31 970811-32 970811-33 970811-34 970811-35

 

s102 59.01 60 62.06 60.38 59.73 59.62
Tio2 0.92 0.9 0.79 0.9 0.92 0.96
A1203 16.21 17.45 17.33 17.06 16.93 16.82
F8203 6.27 6.16 5.22 6.09 6.21 6.34
MnO 0.1 0.1 0.09 0.1 0.1 0.1
MgO 4.51 3.29 2.66 3.48 3.61 3.7
C80 6.42 5.99 5.36 5.96 5.93 5.9
NaZO 3.69 3.74 4.08 3.9 4.25 3.89
K20 1.75 1.45 1.64 1.52 1.61 1.59
920, 0.29 0.2 0.2 0.25 0.26 0.25
Total 99.17 99.28 99.43 99.64 99.55 99.17
Cr 121.4 25.6 19 59.8 50.6 55.6
Ni 20 29.3 13.1 21.2 20.9 25.4
Cu 40.5 23.8 31 42.3 23.5 24.3
Zn 70 69.9 64.2 72.5 72 74.1
Rb 45 31.6 38.1 35.7 34 39.5
Sr 650.9 549.9 571 626 626.3 580.2
Y 17.5 16.1 15.3 17.2 17 15.8
Zr 177.1 146.2 163.9 165.2 167.9 171.9
Nb 8.7 6.6 7 4.7 8.5 8
Ba 568.7 385.9 375.6 354.6 403.5 466.8
La 19.9 20.6

Ce 44.53 48.23

Pr 4.9 5.48

Nd 19.27 21.73

Sm 3.86 4.09

Eu 1.22 1.27

Gd 3.24 3.26

Tb 0.5 0.51

Dy 2.96 2.52

Ho 0.52 0.46

Er 1.69 1.34

Tm 0.25 0.21

Yb 1.43 1.31

Lu 0.26 0.2

71

Table 1: (continued)

970811-36_ 970812-37H 970812-37C 970812-381-1 970812-38C 970812-39_

 

 

Si02 58.78 59.2 55.72 59.34 55.88 58.53
TiOz 0.98 0.95 0.82 0.91 0.9 0.91
A1203 17.24 16.95 14.74 16.95 16.99 17.1
Fe203 6.48 6.42 9.18 6.24 8.53 6.51
MnO 0.1 0.1 0.13 0.1 0.13 0.1
MgO 3.76 3.56 6.89 3.39 4.92 3.88
CaO 6.05 5.91 7.42 6.04 6.85 5.98
NaZO 4.17 3.93 2.88 3.88 3.88 4.11
K20 1.57 1.58 1.17 1.51 0.85 1.58
P205 0.26 0.25 0.18 0.24 0.21 0.24
Total 99.39 98.85 99.13 98.6 99.14 98.94
Cr 46.3 42.4 330.6 67.7 147.6 54
Ni 16.8 22.2 120.4 21.4 56.2 20.7
Cu 22.5 39.2 306.2 46.4 213.1 45.4
Zn 75.8 71.5 104.2 70.5 94.9 74.3
Rb 31.7 36.4 22.7 38.1 20.6 33
Sr 595.5 591.1 433.6 598.1 566.6 604.7
Y 17.1 16 15.3 14.7 12.1 16.1
Zr 175 168.9 129.7 166.7 75.1 162
Nb 9.4 7.5 7.2 5.7 4.6 4.8
Ba 379 409.2 303.7 416.4 310.5 417.1
La 14.97 22.28
Ce 32.33 49.47
Pr 3.86 5.99
Nd 17.01 23.54
Sm 3.72 4.42
Eu 1 1.4
Gd 3.46 4.01
Tb 0.58 0.64
Dy 2.95 3.26
Ho 0.56 0.61
Er 1.63 1.99
Tm 0.25 0.3
Yb 1.61 1.81
Lu 0.25 0.29

72

Table 1: (continued)

970812-401-1 970812-40X 970812-411-1 970812-41C 970812-42H 970812-42C

 

 

s102 59.55 59.4 56.63 55.11 58.99 55.73
Tio2 0.92 0.69 0.99 0.77 0.97 0.84
111203 17.3 17.83 16.79 15.17 17.31 15.63
F8203 6.23 6.04 7.09 9.12 6.41 8.91
MnO 0.1 0.06 0.12 0.14 0.1 0.16
MgO 3.51 2.2 4.24 7.51 3.66 6.6
CaO 5.97 4.29 6.04 7.91 5.9 7.44
NaZO 4.1 4.77 4.18 2.89 4.15 3.32
K20 1.58 1.61 1.58 0.88 1.54 0.8
P20, 0.24 0.1 1 0.24 0.15 0.23 0.08
Total 99.5 97 97.9 99.65 99.26 99.51
Cr 47 11.8 838.3 380.3 49.3 234.2
Ni 20.3 0.5 105.3 103.1 18 51.2
Cu 43.5 214.4 54.2 233.5 45.7 99.9
Zn 76.2 48.2 81.4 88.4 81.2 108.2
Rb 31.9 34.7 36.2 16.2 32.4 11.8
Sr 632.8 491.7 610.5 497.3 595 527.8
Y 18.5 12.6 16.2 14.2 18.2 13.1
Zr 164.3 199 164.5 103.2 163.2 97.6
Nb 4.3 5.8 2.2 1.9 5.2 2.3
Ba 480.1 412.6 416.9 207.8 467.3 292.7
La 23.69 13.45

Ce 49.07 29.74

Pr 6.34 3.67

Nd 25.21 15.38

Sm 4.97 3.3

Eu 1.5 0.92

Gd 4.67 2.95

Tb 0.71 0.48

Dy 3.83 2.43

Ho 0.73 0.46

Er 2.14 1.43

Tm 0.32 0.22

Yb 1.95 1.44

Lu 0.33 0.23

73

Table 1: (continued)

970812-43 970812-44 970812-45 970812-46H 970811-46C 970811-47

 

S102 58.1 58.63 60.21 58.27 56.44 59.54
TiOz 0.95 0.96 0.94 0.93 0.93 0.97
A1203 17.39 17.25 17 17.57 16.4 17.23
F e203 6.37 6.32 6.32 6.4 8.43 6.43
MnO 0.1 0.1 0.1 0.1 0.14 0.1
MgO 3.85 3.76 3.57 3.74 5.54 3.57
CaO 6.4 6.2 6.02 6.48 7.61 6
NaZO 4.24 4.22 4.14 4.18 3.34 3.88
K20 1.69 1.76 1.59 1.47 0.92 1.52
P205 0.26 0.27 0.31 0.26 0.21 0.26
Total 99.35 99.47 100.2 99.4 99.96 99.5
Cr 58.7 56.1 43.4 62 197.2 42.3
Ni 31.3 27.6 18.3 14.3 50.5 22.5
Cu 37.8 42.9 27.2 37.3 84.2 39.6
Zn 72.3 72.1 71.8 73.3 90.8 74.4
Rb 36.3 34.6 34.5 31.4 19.9 34.5
Sr 706.9 693 .9 593 640.9 571.4 627.1
Y 17.4 16 19 16.2 16.8 17.2
Zr 165 176.2 166.6 155.7 104.6 162.5
Nb 4.5 6.2 8.4 4.7 8.4 8.7
Ba 411.5 461.9 430.3 338.2 285 431.5
La 20.95 21.56 13.12

Ce 49.76 48.4 31.22

Pr 5.59 5.63 3.85

Nd 22.39 23.08 16.76

Sm 4.29 4.28 3.79

Eu 1.29 1.37 1.24

Gd 3.31 3.71 3.44

Tb 0.54 0.56 0.54

Dy 2.71 2.94 2.86

Ho 0.51 0.55 0.55

Er 1.41 1.6 1.69

Tm 0.24 0.25 0.25

Yb 1.49 1.58 1.55

Lu 0.21 0.24 0.25

74

Table 1: (continued)

 

i 970813-48 970813-49 #970813-50 970813-51 970816-52 970816-53
8102 61.52 61.65 61.91 58.85 58.7 59.21
Tio2 0.89 0.86 0.79 0.95 0.95 0.95
A1203 17.31 16.95 17.17 17.23 17.66 17.33
F6203 5.63 5.67 5.11 6.41 6.51 6.28
MnO 0.09 0.1 0.08 0.1 0.1 0.1
MgO 3.14 3.17 2.77 3.84 3.45 3.65
C80 5.29 5.46 5.38 6.4 6.61 6.2
NaZO 4.17 3.99 4.13 4.24 4.29 4.22
K20 1.74 1.55 1.65 1.58 1.18 1.55
920, 0.23 0.2 0.19 0.26 0.24 0.26
Total 100.01 99.6 99.18 99.86 99.69 99.75
Cr 38.2 38.7 23.1 52.4 43.2 44.8
Ni 19.8 14.3 16.1 23 7.9 22.9
Cu 31.6 9.6 28.6 48 36.3 31.9
Zn 66.1 76.3 62.9 71 70.1 76.4
Rb 38.4 38.5 37.9 31.6 21.6 34.2
Sr 561.8 595.2 589.5 667.1 673.4 613.5
Y 21.4 16.9 16.7 16.3 14.1 15.4
Zr 174.7 157.9 163.8 164 143 156.9
Nb 8.5 6.5 6.6 6.2 4.3 8.4
Ba 409.2 402 419.8 441.6 338.1 405.9
La 18.02 21.13
Ce 44.81 48.96
Pr 4.99 5.7
Nd 19.13 23.1
Sm 3.84 4.19
Eu 1.24 1.37
Gd 3.33 3.43
Tb 0.54 0.54
Dy 2.96 2.7
Ho 0.59 0.5
Er 1.59 1.45
Tm 0.26 0.22
Yb 1.51 1.4
Lu 0.26 0.22

75

 

Table 1: (continued)

Si02
T102
A1203
Fe203

MgO
CaO
NaZO
K20
P205
Total

Cr
Ni
Cu
Zn
Rb
Sr

Zr

Ba
La
Ce
Pr

Nd
Sm
Eu
Gd

Ho
Er
Tm

Lu

58.25
1.03
17.05
6.77
0.1 1
4.02
6.34
4.96
1.52
0.28
100.33

51.3
28.4
31.5
81.6
30.3
638.3
15.9
154.9
8.3
386.4

58.18
0.92
17.57
6.65
0.12
4.35
6.58
3.97
1.38
0.21

99.93

56.7
28.5
39.3
75.4
28.2
61 1.6
14.8
135.3
2.9
382.1
15.77
36.99
4.06
16.45
3.34
1.21
2.75
0.45
2.38
0.42
1.26
0.19
1.25
0.19

970816-54 970816-546 980817-01

60.07
0.93
16.38
6.44
0.1
3.67
6.03
3.9
1.59
0.25
99.36

69.6
18.5
30.1
67.8
33.4
559.9
17.9
170.9
7.3
503.4

76

59.68
0.96
16.17
6.56
0.1
3.76
5.95
3.91
1.56
0.26

98.91

70.6
22.7
48.7
70.7
35.3
585.9
18.3
182
5.6
458.1

52.63
1.31
16.83
9.41
0.14
5.4
8.95
3.72
0.42
0.23
99.04

84.3
67.9
256.8
86.9
7.2
607.4
16.4
71.1
6.6
252.8
12.57
28.63
3.6
17.75
3.84
1.32
3.58
0.54
3.1
0.54
1.63
0.24
1.66
0.24

980817-02H 980817-02C 980817-03

63.76
0.81
16.34
5.64
0.09
2.96
5.45
4.03
1.81

0.2
101.09

47.3
16.2
51.5
64
45.2
486.6
16.5
157.2
8.6
500.3

Table 1: (continued)

980818-04 980818-05 980818-06 980818-07 980819-08 980819-09

 

8102 59.55 59.79 62.66 62.357 64.14 59.14
Tlo2 0.9 0.96 0.86 0.93 0.73 0.7
A1203 16.65 17.13 16.39 16.19 17.22 17.06
Fe203 6.35 6.49 5.96 6.1 4.83 5.25
MnO 0.1 0.1 0.09 0.09 0.08 0.08
MgO 3.14 3.65 3.11 3.27 2.45 2.44
CaO 6 6.47 5.58 5.52 5.42 5.07
NaZO 4.03 3.66 4.09 4.03 4.19 4.29
K20 1.67 1.52 1.75 1.78 1.76 1.63
P20, 0.29 0.15 0.23 0.24 0.19 0.19
Total 98.68 99.92 100.72 100.5 101.01 95.85
Cr 22.7 52.2 51.6 46.3 22.7 1430
Ni 4.5 27.2 23 19 -3.7 153.9
Cu 36.5 59 43.2 62.8 43.1 52.6
Zn 72.3 64.1 68.2 64.8 67.3 68.7
Rb 32.8 37.3 49.9 46.7 44.6 43.5
st 821.9 526.1 507.8 508.9 612.3 646.8
Y 19.1 16.7 15.7 17 15.5 15
Zr 184.9 143.2 158.9 165 145.3 146.6
Nb 2.2 6.7 9.6 8.6 4.7 3.2
Ba 51 1.1 421.3 461.6 459.6 497.5 536
La 16.74

Ce 35.13

Pr 3.8

Nd 16.4

Sm 3.23

Eu 1.15

Gd 2.94

Tb 0.44

Dy 2.59

Ho 0.45

Er 1.44

Tm 0.22

Yb 1.3

Lu 0.21

77

Table 1: (continued)

980819-10 980819-11 980819-12 980819-13 980819-14 980819-15

 

SiOz 62.13 63.82 63.31 63.34 62.9 61.2
TiOz 0.74 0.73 0.74 0.72 0.73 0.89
A1203 17.2 17.03 17.03 17.3 17.5 17.5
Fe203 5.13 4.79 4.95 4.91 4.88 5.76
MnO 0.09 0.08 0.08 0.08 0.08 0.1
MgO 2.48 2.67 2.53 2.43 2.58 3.3
CaO 5.49 5.33 5.28 5.35 5.54 6.01
NazO 3.94 4.28 4.07 4.09 4.04 3.94
K20 1.73 1.61 1.76 1.81 1.76 1.39
P205 0.19 0.18 0.2 0.19 0.19 0.21
Total 99.12 100.52 99.95 100.22 100.2 100.3
Cr 29.4 29.3 27.3 19.6 24.4 33.6
Ni -4 -4.2 -7.5 -5.6 0.4 -4.5
Cu 25.1 12.2 25.9 24.7 19.9 27.5
Zn 61.6 70.9 63 60.9 62.9 74.5
Rb 46 35.5 41.5 45.8 47.3 26.9
Sr 595.6 606.1 617.1 620.5 647 620.5
Y 15.7 18.2 17 15.8 15.5 19.6
Zr 144.9 140 147 144.7 141.2 150
Nb 6 5 5.8 3.6 3.8 4.3
Ba 490.5 411.5 446.6 433.3 436.7 422.3
La 18.3

Ce 41.97

Pr 4.42

Nd 18.28

Sm 3.34

Eu 1.05

Gd 2.75

Tb 0.42

Dy 2.2

Ho 0.39

Er 1.26

Tm 0.19

Yb 1.38

Lu 0.18

78

Table 1: (continued)

 

 

980819-13 980819—17 980819-1811 980819-18C 980819-19 980819-20

Si02 62.86 60.67 62.59 58.26 61.97 62.4
TiOz 0.7 0.88 0.86 0.79 0.85 0.84
A1203 17.21 17.5 17.77 14.91 17.51 17.55
FezO3 4.98 5.74 5.2 6.78 5.4 5.31
MnO 0.08 0.1 1 0.07 0.1 0.07 0.07
MgO 2.5 3.31 2.75 6.83 2.93 2.96
CaO 5.44 6.15 6.22 7.57 5.92 5.96
NaZO 4.01 3.65 4.18 3 4.18 4.19
K20 1.7 1.52 1.29 1.32 1.34 1.34
P205 0.19 0.22 0.2 0.07 0.19 0.19
Total 99.67 99.75 101.13 99.63 100.36 100.81
Cr 15.4 31.7 91.9 486.2 86.9 89.7
Ni -1.7 -6.4 19.1 73.9 22.6 17.2
Cu 28.9 20.2 39.9 66.4 34.7 38.4
Zn 64.2 73.9 51.8 65.8 55.8 55.1
Rb 43.5 34.1 28 33.6 33.6 35.7
Sr 630.6 621.9 537.4 355 524.5 523.9
Y 16.6 17.7 15.7 17.6 15.5 16.2
Zr 147.3 151.1 134.6 117.4 140.4 143.1
Nb 6.4 5.1 4.9 5.4 5 3.5
Ba 402.6 414.7 332.7 280.2 347.5 339.3
La 18.4

Ce 40.55

Pr 4.74

Nd 21 . 13

Sm 3.97

Eu 1.25

Gd 3.33

Tb 0.52

Dy 2.76

Ho 0.49

Er 1.54

Tm 0.23

Yb 1.52

Lu 0.22

79

Table 1: (continued)

 

090819-21 980820-22 980820-23 980820-24 980820-25 980820-26
S102 57.18 63.54 63.06 61.57 60.78 61.5
TiOz 0.8 0.84 0.88 0.93 0.91 0.91
A1203 17.35 16.23 16.11 16.46 16.97 16.5
Fe203 5.96 5.74 5.81 6.3 6.17 6.27
MnO 0.08 0.09 0.09 0.1 0.09 0.1
MgO 3.33 2.94 3 3.63 3.5 3.6
C30 5.87 5.35 5.08 5.95 6.02 5.85
NaZO 4.27 4.1 4.1 3.76 4.08 4.04
K20 1.22 1.85 1.91 1.48 1.57 1.65
P20, 0.17 0.2 0.21 0.25 0.25 0.25
Total 96.23 100.88 100.25 100.43 100.34 100.67
Cr 1465.5 53.2 54.4 75.7 68.6 70.4
Ni 209.4 16.1 15.8 24.8 17.2 20.1
Cu 49.3 33.7 30 41.6 31.9 39.9
Zn 63 .6 66.4 68.9 75 69.1 69.4
Rb 33.9 46 46.5 31.3 31.9 37.7
Sr 554.8 510.1 493.4 606.3 631.2 590.8
Y 11.6 18.7 18.1 18.3 17.3 18.9
Zr 137.3 181.3 186.8 172.3 174.7 178.6
Nb 4.2 6.9 9.3 9.3 6.3 8
Ba 376.9 467.1 490.3 451.3 456 448.1
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu

80

Table 1: (continued)

 

980820-27 980820-28H 980820-28X 980820-29 980820-30 980820-31
SiOz 61.27 60.28 66.44 61.75 59.93 60.81
Ti02 0.94 0.92 0.66 0.96 0.97 0.97
A1203 16.43 16.53 17.48 16.43 16.98 16.71
Fe203 6.44 6.59 2.77 6.47 6.53 6.78
MnO 0.1 0.1 0.03 0.1 0.1 0.11
MgO 3.79 3.97 2.96 3.58 3.85 3.93
CaO 5.91 6.1 4.59 5.91 6.11 6.04
NaZO 3.99 4 3.83 3.98 4 3.89
K20 1.63 1.46 1.15 1.65 1.51 1.5
P205 0.27 0.26 0.2 0.26 0.26 0.25
Total 100.77 100.21 100.11 101.09 100.24 100.99
Cr 73.1 78.7 50.2 69.6 69.7 74.3
Ni 24.5 23.3 14.5 21.2 21.9 22.9
Cu 34.6 47.1 76.9 28.8 33.1 28.3
Zn 71.5 76.4 43.8 73.6 76.6 77
Rb 38.6 33.3 41.9 35.6 33.7 27
Sr 581.8 602.1 419.7 586.8 608.3 575.6
Y 17.8 17.2 16.6 16.4 14.8 15.2
Zr 180 175.9 139 176.3 173.2 176.8
Nb 7.3 8.5 8.3 4 6.2 6.3
Ba 463.6 430.1 440.9 386.5 369.2 380.9
La 20.75
Ce 45.46
Pr 5.27
Nd 23.54
Sm 4.3
Eu 1.31
Gd 3.51
Tb 0.54
Dy 2.78
Ho 0.47
Er 1.51
Tm 0.24
Yb 1.45
Lu 0.22

81

Table 1: (continued)

980820—32C 980820—33C 980820-34 980820-351—1 980820-35C 980820-36H_

 

8102 63.2 61.69 58.24 63.43 55.36 64.32
Tio2 0.9 0.86 0.66 0.82 0.46 0.87
A1203 16.42 16.83 15.32 16.48 15.74 16.06
F6203 6.02 5.91 7.25 5.46 8.85 5.89
MnO 0.09 0.09 0.1 1 0.08 0.16 0.09
MgO 2.99 3.26 6.95 2.66 6.83 2.86
CaO 4.98 5.78 6.66 5.18 7.94 4.98
NazO 4.09 4.09 2.99 3.79 3.41 4.07
[(20 1.74 1.53 0.98 1.59 0.77 1.84
P20, 0.2 0.19 0.12 0.21 0.14 0.19
Total 100.63 100.23 99.28 99.7 99.66 101.17
Cr 52.7 57.1 221.7 41.8 289.9 46.9
Ni 14.2 18.6 96 10.1 51.7 13.2
Cu 16.6 37 44.9 24.7 77.3 20.3
Zn 67.6 65.7 67.9 62.7 99.2 65.8
Rb 37.2 28.9 21 32.4 16.2 41
Sr 517 556.2 487 522.5 566.4 493
Y 16.5 16.5 14.7 14.9 15 16.8
Zr 177.7 163.5 129.6 173.1 88.4 182.2
Nb 7.3 4.9 2.9 6.4 1 4.6
Ba 386 350.1 287.5 361 197.6 340.8
La 19.01 13.03 18.78

Ce 39.68 28.1 40.95

Pr 4.77 3.26 4.62

Nd 20.77 14.81 20

Sm 3.8 3.01 3.71

Eu 1.12 0.98 1.18

Gd 3.05 2.56 3.11

Tb 0.48 0.39 0.47

Dy 2.57 2.19 2.66

Ho 0.45 0.39 0.43

Er 1.44 1.26 1.39

Tm 0.22 0.19 0.21

Yb 1.36 1.28 1.34

Lu 0.21 0.18 0.21

82

Table 1: (continued)

 

980820-36C 980820-37 980821-38 980821-39 980821-40 980821-41
8102 60.31 59.61 61.46 61.61 61.19 60.96
T102 0.88 0.91 0.83 0.83 0.86 0.87
A1203 17.86 16.69 17.21 17.46 17.44 17.26
Fe203 5.92 6.65 5.85 5.78 6 6.15
MnO 0.1 0.1 0.09 0.09 0.09 0.1
MgO 3.06 3.26 3.16 3.03 3.09 3.37
CaO 5.81 5.38 5.85 5.67 5.77 5.84
NaZO 4.14 4.21 4.14 4.2 4.19 4.12
K20 1.28 1.55 1.5 1.55 1.57 1.45
P205 0.21 0.2 0.22 0.21 0.22 0.21
Total 99.57 98.56 100.31 100.43 100.42 100.33
Cr 49.6 1397.5 58.8 54.3 56.7 57.9
Ni 13.6 165.4 23.3 20.7 23.7 22.9
Cu 41.5 42.5 25.4 35.2 33.5 34.8
Zn 69 65.8 66.3 66.5 68.4 70.3
Rb 16.1 37.6 36.3 37.2 36.3 31.6
Sr 585.3 522 624.2 605.3 607 610.1
Y 15 17 16.1 14.1 16.4 15.9
Zr 171.7 168.2 152.6 152.4 156.2 158.6
Nb 3.8 7.4 7.5 5.5 7.3 8
Ba 383.7 424.9 472.7 448.2 412.8 418.8
La 19.26
Ce 40.1
Pr 4.35
Nd 18.61
Sm 3.39
Eu 1.17
Gd 2.86
Tb 0.43
Dy 2.34
Ho 0.39
Er 1.3
Tm 0.18
Yb 1.31
Lu 0.17

83

Table 1: (continued)

980821-42 980821-43 980821-44 980821-45 980821-46

980821-47

 

$102 61.8 61.57 61.05 60.46 60.95
T102 0.86 0.8 0.83 0.85 0.85
A1203 17.52 17.32 17.57 17.7 17.6
Fe203 6.05 5.68 5.71 5.99 6.06
MnO 0.09 0.09 0.09 0.09 0.09
MgO 3.02 3.1 1 3.25 3.29 3.2
CaO 5.6 5.73 5.99 5.89 5.71
NaZO 4.09 4.15 4.19 4.21 4.2
K20 1.56 1.52 1.38 1.46 1.51
P205 0.21 0.22 0.21 0.21 0.22
Total 100.8 100.19 100.27 100.15 100.39
Cr 56.1 51.4 65.7 53 52.8
Ni 22.2 19.9 23.6 23 24.1
Cu 25.6 33.4 28.3 33.1 43
Zn 69.6 65.5 67.2 72.8 68.3
Rb 32.9 33.9 21.5 27.2 32.9
Sr 616 633.4 643.4 624 597.7
Y 17.7 16.5 17.2 16.5 16.5
Zr 148.8 153.4 147.7 153.8 154.7
Nb 8.3 7 7 5.8 5.5
Ba 497.5 391 417.2 479.9 361
La 18.73

Ce 43.02

Pr 4.83

Nd 21.24

Sm 3.73

Eu 1.2

Gd 3.06

Tb 0.44

Dy 2.48

Ho 0.44

Er 1.29

Tm 0.21

Yb 1.21

Lu 0.19

84

60.16
0.86
17.77
6.06
0.1
3.38
6.11
4.19
1.35
0.22
100.2

58.8
27
46.3
69.7
19.6
648.6
15.1
148.6
3.4
377.4

Table 1: (continued)

980821-48 980821-49C 980821-4911

 

8102 61.24 55.34 59.78
Tio2 0.82 0.93 0.89
4.1203 17.64 17.86 18.13
F6203 5.89 8.24 6.23
MnO 0.09 0.13 0.1
MgO 3.08 5.01 3.48
CaO 5.76 7.35 5.96
Nazo 4.13 3.81 4.04
K20 1.48 0.46 1.22
920, 0.23 0.18 0.21
Total 100.36 99.31 100.04
Cr 50.6 1 17.6 65.9
Ni 20.7 25.7 26.3
Cu 48.1 60.5 41.4
Zn 68.1 109 69.4
Rb 25.5 7 16.7
Sr 638.3 589 710.9
Y 14.2 17.4 14.9
Zr 157.5 92.7 154.1
Nb 3.6 4.5 2.4
Ba 415.7 247.1 414.7
La 14.07 19.28
Ce 36.45 43.35
Pr 4.56 4.85
Nd 22.09 21.35
Sm 4.89 3.77
Eu 1.44 1.19
Gd 4.24 2.83
Tb 0.72 0.43
Dy 3.68 2.47
Ho 0.63 0.42
Er 1.94 1.26
Tm 0.29 0.19
Yb 1.63 1.2
Lu 0.26 0.18

85

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88

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