WORKSHOP ON

LUNAR VOLCANIC GLASSES:

SCIENTIFIC AND RESOURCE POTENTIAL

Edited by

John W. Delano and Grant H. Heiken

Held at

Lunar and Planetary Institute

Houston, Texas

October 10 - 11, 1989

Sponsored by

Lunar and Planetary Institute

Lunar and Planetary Sample Team

Lunar and Planetary Institute 3303 NASA Road 1 Houston, Texas 77058-4399

LPI Technical Report Number 90-02
Compiled in 1990 by the

LUNAR AND PLANETARY INSTITUTE

The Institute is operated by Universities Space Research Association under

Contract NASW-4066 with the National Aeronautics and Space Administration.

Material in this document may be copied without restraint for library, abstract

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acknowledgment of this publication.

This report may be cited as:

Delano J. W. and Heiken G. H., eds. (1990) Workshop on Lunar Volcanic Glasses:

Scientific and Resource Potential. LPI Tech. Rpt. 90-02. Lunar and Planetary

Institute, Houston. 74 pp.

Papers in this report may be cited as:

Author A. A. (1990) Title of paper. In Workshop on Lunar Volcanic Glasses:

Scientific and Resource Potential (J. W. Delano and G. H. Heiken, eds.), pp. xx-yy.

LPI Tech. Rpt. 90-02. Lunar and Planetary Institute, Houston.

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Contents

Preface

Program

Summary of Technical Sessions

Abstracts

Origin of Lunar Basalts: A Geophysical Interpretation

J. Arkani-Hamed

Lunar Pyroclastic Soils of the Apollo 17 Double Drive Tube 74001/2

A. Basu, D. S. McKay, and S. J. Wentworth

Lunar Explosive Volcanism: The Remote Sensing Perspective

C. R. Coombs and B. R. Hawke

The Optimal Lunar Resource: Ilmenite-rich Regional Pyroclastic Deposits

C. R. Coombs, B. R. Hawke, and B. Clark

Pyroclastic Volcanism in the Alphonsus Region

C. R. Coombs, B. R. Hawke, S. H. Zisk, and P. G. Lucey

Pristine Lunar Glasses: A "Window" into the Moon's Mantle

J. IV. Delano

Pristine Mare Glasses and Mare Basalts: Evidence for a General Dichotomy

of Source Regions

J. IV. Delano

Thermodynamic Models of Trace Metal and Volatile Element Transport

by Lunar Volcanism

B. Fegley Jr. and D. Kong

Remote Sensing and Geologic Studies of Lunar Dark Mantle Deposits: A ,. :view

B. R. Hawke

Impact and Volcanic Glasses of Mare Fecunditatis

Y. Jin and L. A. Taylor

Mapping Pyroclastic Deposits and Other Lunar Features for Solar Wind Implanted Helium

J. L. Jordan

Differentiates of the Picritic Glass Magmas: The Missing Mare Basalts

J. Longhi

1

3

7

13

15

20

22

24

26

28

30

32

34

41

43

46

iii
REE Distribution Coefficients for Pigeonite:

Mare Basalt Europium Anomaly

G. McKay, J. Wagstaff,, and L. Le

Constraints on the Origin of the

A Brief Literature Review of Observations Pertaining to Condensed Volatile

Coatings on Lunar Volcanic Glasses

C Meyer

Application of Remote-SIMS for Glass and Trace-Element Compositions of Lunar Soils

Y Miura

A 6-ram Sphere from the Apennine Front: An Exceptional Volcanic Glass (or Just

a Remarkable Impact Glass?)

G. Ryder

Apollo 17 Orange Soil: Interpretation of Geologic Setting

H. H. Schmitt

Secondary Ion Mass Spectrometric Analysis of Glasses, Trace Element Characteristics

of Lunar Picritic Glasses and Implications for the Mantle Sources of Lunar

Picritic Magmas

C. _ Shearer, J. J. Papike, K. C. Galbreath, H. Yurimoto, and N. Shimizu

Young Dark Mantle Deposits on the Moon

P. D. Spudis

Apollo 15 Green Glass I: New Compositional and Petrographic Insight

.4. M. Steele, R. L. Korotev, and L. A. Haskbt

Apollo 15 Green Glass II: Group Proportions and the Cluster Hypothesis

A. M. Steele, R. L. Korotev, and L. A. Haskin

Thermodynamic Calculations of Trace Species in Volcanic Gases: The Possible

Applications of New Computer Models to Lunar Volcanic Gases and Sublimates

R. B. Symonds and I4/.L Rose

Phenocryst Content of Mare Volcanics: Inferences for Magma Migration

Mechanisms on the Moon

G. J. Taylor

In Scarch of Ancient Lunar Pyroclastics

S. J. Wentworth, D. J. Lindstrom, D. S. McKay, and R. M. Martinez

List of Workshop Participants

48

50

52

54

56

58

60

62

64

66

68

70

73

iv
Preface

This report documents the "Workshop on Lunar Volcanic

Glasses: Scientific and Resource Potential" that was held at the

Lunar and Planetary Institute on October 10-11, 1989. This

workshop on lunar mare volcanism was the first since 1975 to deal

with the major scientific advances that have occurred in this

general subject, and the first ever to deal specifically with volcanic

glasses. Forty-five scientists attended and made 26 presentations.

Lunar volcanic glasses are increasingly being recognized as our

best geochemical and petrologic probes into the lunar mantle.

Lunar volcanic glasses, of which 25 compositional varieties are

presently known, appear to represent primary magmas that were

produced by partial melting of differentiated mantle source regions

at depths of perhaps 400-500 km. These high-magnesian picritic

magmas were erupted onto the lunar surface in fire fountains

associated with the release of indigenous lunar volatiles. The

cosmic significance of this volatile component, in an otherwise

depleted Moon, remains a lingering puzzle. The resource

potential, if any, of the surface-correlated volatile sublimates on

the volcanic glass spherules had not been systematically addressed

prior to this workshop.

The Organizing Committee consisted of Grant H. Heiken, Los

Alamos National Laboratory, and John W. Delano, State

University of New York at Albany, chairmen; B. Ray Hawke,

University of Hawaii; Chuck Meyer, NASA Johnson Space Center;

Paul Spudis, U.S. Geological Survey at Flagstaff; and G. Jeffrey

Taylor, University of New Mexico. Logistics and administrative

support were provided by the Program Development Office at the
2 _nar Volcanic Glasses

Lunar and Planetary Institute. Special recognition is due LeBecca

Simmons, Pam Jones, and the staff of the Publications Services

Department at the LPI, as well as Diana Paton at SUNY Albany,

for efficiency, professionalism, and good humor during the

organization of this important workshop.

John W. Delano and Grant H. Heiken
Technical Report 90-02 3

Program

Tuesday Morning, October 10

8:00 - 9:00 Registration

9:00 - 9:30 Lunar Volcanic Glasses: What Do We Know About Them

From Sample Studies?

J. W. Delano

9:30 - 10:00 Lunar Explosive Volcanism: The Remote Sensing Perspective

C. R. Coombs B. R. Hawke

10:00- 10:30

10:45 - 11:15

11:15 - 11:30

11:30 - 12:00

TOPIC 1 - GEOLOGIC SE'ITING

Chairman: Paul Spudis

Summarizer: A. Basu

Apollo 17 Orange Soil: Interpretation of Geologic Setting

H. 1t. Schrnitt

Pyroclastic Volcanism in the Alphonsus Region

C. R. Coombs B. R. Hawke S. Zisk P. Lucey

DISCUSSION AND WALK-ON CONTRIBUTIONS

TOPIC 2 - ERUPTION MECHANISMS

Chairman: B. Ray Hawke

Summarizer: Cassandra Coombs

Origin of Lunar Basaits: A Geophysical Interpretation

J. Arkani-Hamed

Tuesday Afternoon, October 10

TOPIC 2 - ERUPTION MECHANISMS, Continued

1:30 - 2:00 Phenocryst Content of Mare Volcanic.s: Inferences for Magma Migration

Mechanisms on the Moon

G. J. Taylor

DISCUSSION AND WALK-ON CONTRIBUTIONS 2:00 - 2:15
4 Lunar Volcanic Glasses

2:15 - 2:45

2:45 - 3:05

3:05 - 3:25

3:45 - 4:15

4:15 - 4:45

4:45 - 5:15

TOPIC 3 - PETROLOGY AND GEOCHEMISTRY

Chairman: Arch Reid

Summarizer:. John Jones

Lunar Pyroclastic Soils of the Apollo 17 Double Drive Tube 74001/2

A. Basu D. S. McKay S. I. Wentworth

Apollo 15 Green Glass I: New Compositional and Petrographic Insight

A. M. Steele R. L. Korotev L. A. Hasla'n

Apollo 15 Green Glass II: The Elusive Complete Database

A. M. Steele R. L. Korotev L. A. Haskin

In Search of Ancient Lunar Pyroclastics

S. Z Wentworth D. Z Lindstrom D. S. McKay R. M. Martinez

Pristine Glasses of Mare Fecunditatis

Y. Jin L. A. Taylor

DISCUSSION AND WALK-ON CONTRIBUTIONS

Wednesday Morning, October 11

9:00 - 9:15

TOPIC 4 - LUNAR VOLATILES

Chairman: Chuck Meyer

Summarizer:. Tammy Dickinson

Literature Review of Observations Pertaining to Condensed Volatile Coatings on

Lunar Volcanic Glasses

C Meyer

9:15 - 9:45

Thermodynamic Calculations of Trace Species in Volcanic Gases: The Possible

Applications of New Computer Models to Lunar Volcanic Gases and Sublimates

R. B. Symonds W. I. Rose

9:45- 10:15

Thermodynamic Models of Trace Metal and Volatile Element Transport by

Lunar Volcanism

B. Fegley D. Kong

10:15- 10:45 DISCUSSION AND WALK-ON CONTRIBUTIONS

11:00- 11:30

11:30- 12:00

TOPIC 5 - RESOURCE POTENTIAL

Chairman: Jack Schmitt

Summarizer: John Delano

The Optimal Lunar Resource: llmenite-Rich Regional Pyroclastic Deposits

C. R. Coombs B. R. Hawke B. Clark

Resource Potential of Lunar Sulfur

D. T. Vaniman G. H. Heiken
Technical Report 90-02 5

Wednesday Afternoon, October 11

TOPIC 6 - PETROLOGY AND GEOCHEMISTRY

Chairman: Jeff Taylor

Summarizer: John Jones

1:30 - 2:00 The Source of the Mare Basalt Europium Anomaly: REE Distribution

Coefficients for Pigeonite

G. McKay Z Wagstaff L. Le

2:00 - 2:30

2:45 - 3:15

Differentiates of the Picritic Glass Magmas: The Missing Mare Basalts

Z Longhi

Secondary Ion Mass Spectrometric Analysis of Glasses: Trace Element

Characteristics of Lunar Picritic Glasses and Implications for the Mantle Sources

of Lunar Picritic Magmas

C. K. Shearer J. J. Papike K. C. Galbreath H. Yurimoto N. Shimbu

3:15- 3:45 Pristine Lunar Glasses: A "Window" Into the Moon's Mantle

J. W. Delano

3:45 - 4:00 DISCUSSION AND WALK-ON CONTRIBUTIONS

4:00- 4:30

TOPIC 7 - RETURN TO THE MOON

Chairman: Jack Schmitt

Summarizer: B. Ray Hawke

Future Geologic Exploration of the Moon

G. J. Taylor P. D. Spudis

4:30 ADJOURN

Technical Report 90-02 7

PRECEDING PAGE BLANK NOT F;L,_ED

Summary of Technical Sessions

TOPIC 1:

GEOLOGIC SETTING

Summarized by Abhijit Basu

Three presentations were made dealing with the

geologic setting of lunar volcanic deposits. On a global

scale, P. Spudis proposed that some dark pyroclastic

materials associated with mare basaltic volcanism were

deposited on the Moon as recently as 109 years ago.

C. Coombs focused on localized dark mantle deposits,

which are associated with fractures on the floor of the

ll8-km-diameter Alphonsus Crater. H. (Jack) Schmitt

discussed a possible sorting mechanism that may have

caused separation of the orange glass spherules from

the denser crystal-laden black spherules on the rim of

the 80-m-diameter Shorty Crater at the Apollo 17

landing site.

Dark mantle deposits, which are generally believed to

have been produced by volcanic fire-fountaining, are not

only widespread on the Moon but also appear to span a

large age range. Since these unconsolidated deposits

cause craters to degrade rapidly, crater counting is not

reliable for estimating the ages of these deposits.

However, Spudis argued that superposition of dark

mantle deposits on datable mare basalt flows establishes

a minimum age. He used a calibration curve correlating

crater counts on basalt flows with absolute ages. He

showed that in Mare Smythii dark mantle deposits are

interbedded with basalts that are about 1.5 x 109 years

old. In addition, dark mantle deposits with associated

basalts occurring on the floor of the crater Taruntius

clearly postdate this -109-year-old crater. According

to Spudis, the geomorphologic similarity of all dark

mantle deposits, both young and old, suggests that the

styles of eruption on the Moon did not change

appreciably through time. In response to a question

from L. Taylor, Spudis said that Pb and Ar ages of

Apollo 12 breccias, as well as the landslide ages of

Apollo 17 regolith, constrained the absolute ages of

Copernicus (0.9 x 109 years) and Tycho (0.1 x 109

years) in the calibration curve. C. Wood observed that

crater counts on the floors of Copernicus and Tycho

agree with these a_c_.

Dark-halo craters and localized dark mantle deposits

inside the 1 18-km-diameter pre-Imbrian Alphonsus

Crater in south-central lunar highlands were examined

in detail by Coombs and coworkers. Weak echoes in

the 3.0-cm radar data indicate that the surfaces of these

localized dark mantle deposits are smooth. The

dominance of "red" in the UV-visible (0.3-1.1 _lm)

reflectance spectra suggests a basaltic composition.

Modelately deep (-6%) asymmetrical absorption bands

in the 1.0 _m region of the near-infrared (0.6-2.5 ;m)

reflectance spectra indicate dominance of olivine and

low-Ca pyroxene in these deposits. Individual deposits

are small (-450 km 2) and are associated with

prominent fractures and endogenic craters on the floor

of Alphonsus. Coombs and coworkers suggest that

magma emplacement at depth after crater formation

caused uplift of the crater floor and the ensuing violent

volcanism. In response to J. Longhi's question, Coombs

said that it is not yet possible to determine whether the

lava flows and pyroclastic deposits were petrogenetically

related.

Schmitt drew attention to the sharp contact between

the orange soil (mostly orange glass spherules and

clasts, -35 cm thick) and the black soil below (mostly

olivine- and ilmenite-rich spherules and clasts, >45 cm

thick) at the rim of the Shorty Crater (station 4, Apollo

17 site). Only the uppermost 10-15 cm show any

evidence of surface exposure. The glasses, which are

pyroclastic in origin and about 3.6 x 109 years old, must

have been buried almost immediately after eruption.

Schmitt assumed that the orange and black sphcrules,

and fragments thereof, were homogeneously mixed in

the original pyroclastic deposit, which was produced by

volcanic fire-fountaining associated with the release of

volatiles. He postulated that about 19 x 106 years ago,

the Shorty Crater event instantaneously released these

trapped volatiles causing fluidization of the buried pyroclastic deposits. Remobilization of these deposits

through impact-generated fractures was envisaged by

Schmitt as having led to an efficient sorting between the

less dense orange glass spherules and the denser crystalladen black spherules. This scenario might explain the

observed sharp contact between these two components

at station 4, Apollo 17 site.

TOPIC 2:

ERUPTION MECHANISMS

Summarized by Cassandra Coombs

Eruption mechanisms and conditions on the Moon

differ from those found on Earth. In addition, the

conditions under which an eruption occurs may be

locally variable. This session addressed some of these

differcnces and pointed out just how variable the

conditions and mechanisms for lunar pyroclastic

eruptions may be.

Three presentations were made in this session. The

first of these was an invited talk by J. Arkani-Hamcd in

which he discussed the geophysical state of the Moon

and what it implies for the origin and source rcgions of

mare basalts. He began by stating that the major

basaltic eruptions on the Moon were not triggered by

the impacts that formed the large basins; rather, the
8 Lunar Volcanic Gla_es

major flows occurred -100 m.y. after the formation of

the major basins.

Arkani-Hamed discussed the asymmetry between the

volume of basahs present on the near- and farsides of

the Moon and their absence on the southeast side.

From the discrepancy between the near- and farside

basalts, it was determined that the mare basalts were

partially melted at a depth greater than that of the base

of the crust and that the farside basalts should be much

more viscous than those found on the nearside. A

negative Bouguer gravity anomaly present below the

nearsidc highlands units indicates that no mascon is

present beneath them.

Electrical conductivity measurements, heat flow

experiments, seismic data, and magnetic field

measurements were used to model the temperature of

the lunar interior. From the model it was determined

that the temperature of the upper 300 km of the lunar

lithosphere is at present between 400o-800oc. From

models of thermal evolution, it appears that the upper

300 km cooled in the last 3 b.y. and that the heat was

transported by conduction. The magma was transported

through cracks created by global stress and local tension

in the viscous upper 400 km of the Moon. ArkaniHamed ended his presentation with a discussion of the

magma source and lateral magma migration.

Schmitt asked about the difference in formation

between most of the large basins, which are irregular in

shape, and Fecunditatis and Nectaris, which appear to

be almost circular. Arkani-Hamed responded that the

differences are most likely due to readjustments after

impact. Schmitt also mentioned that according to most

of the structural data he has seen, there is little or no

evidence for compression (or shearing) on the surface.

Arkani-Hamed said that many thrust faults have been

identified, and therefore compression did occur.

M. Cintala asked what Schmitt would call the LeeLincoln scarp. Schmitt responsed that he did not know.

J. Jones made the final observation that, if ArkaniHamed is correct, the young volcanic deposits described

by Spudis come from a deep source, and he asked

whether there is a need to sample these areas. ArkaniHamed replied that he thought there was a strong, thick

column of this "volcanic" material below the mantle.

The second talk was presented by J. Taylor who

observed that, in general, phenocrysts grow at depth;

however, there are few phenocrysts in lunar samples.

As an example, Taylor presented a slide of 14053 and

mentioned that it was hard to see large phenocrysts that

grew at depth. Why is there such a contrast between the

lunar basalts where virtually no phenocrysts are found,

and the terrestrial basalts where phenocrysts are

abundant? It appears that (1) mare basalt magmas had

quite different thermal histories than their terrestrial

counterparts; (2) lunar magmas spent less time in

magma chambers; and (3) lunar magmas traveled more

rapidly from their source regions and/or through hotter

rock.

The magma migration rate is 50% faster on the

Moon than on Earth due to the reduced gravitational

field and lower viscosity of the lunar magmas. Crack

propagation rates within the conduit are proportional to

one-third the gravity and inversely proportional to

magma viscosity. Lunar magma cooling rates also differ

from those on Earth. Wider conduits on the Moon

would lead to greater eruption rates and imply slower

cooling with more material flowing through the channels

and more heating of the surrounding wall rock, all of

which results in fewer phenocrysts and less fractionation. Fractional crystallization most likely occurred

in one or two places: (1) along the walls of the main

conduit or (2) in the flows.

Taylor concluded that (1) magraa recharge was less

effective on the Moon than on Earth due to the rarity of

magma chambers; (2) no ilmenite-rich cumulates of any

significance were produced in mare lava flows, except

possibly in lava lakes; (3) one should look for mantle

xenoliths near vents; and (4) perhaps Mg-suite rocks did

not form in magma chambers either.

Schmitt started the discussion following Taylor's

presentation with a question regarding crack propagation and magma migration rates on the Moon. Taylor

responded that since the viscosity of the magma is lower

on the Moon, the rates of migration would be faster.

Schmitt commented that one should not underestimate

the degree of differentiation among the Apollo 12 and

15 rock suites where there is a remarkable amount of

olivine present. Longhi noted that there is only one

mare basalt (74275) with true xenolith in it, a microdunite. J. Delano mentioned that the high-titanium

Apollo 17 station 4 sample, 74275, has a microdunite

fragment and olivine megacrysts. A high-resolution

microprobe analysis of these olivines by Delano showed

that the microdunite was a cognate xenolith that

appeared to preserve some information about the preeruptive history of the 74275 magma. Schmitt asked if

any petrogenetic relationship could be made between

the microdunite xenolith and the orange glass, such that

74275 may be from the flow that buried and protected

the orange glass. In reply, Delano said that the Fe and

Se in 74275 and 74220 are so different that they

appeared not to be petrogenetically related. Longhi

suggested that maybe 74275 started off as an orange

glass, to which Delano reiterated that the geochemical

data suggest 74275 is unrelated to the 74220 orange

glass. Spudis asked about the polygonal texture of the

olivines in the microdunite, and whether that texture

indicated metamorphism. J. Taylor responded that it is

possible to recrystallize crystals with strain and generate

the observed texture.

The rates and directions of propagation of dikes and

magma injection were then discussed. W. Phinney
"Fechnical f_cport 90-02 9

pointed out that in terrestrial examples dikes may

propagate laterally for hundreds of kilometers. Also,

evidence shows that (1) dikes radiate outward from the

center, and (2) whenever/wherever one finds phenocrysts, the dikes are offset. The phenocrysts tend to

pond on one side of the dike and are always on the same

side as the constrictions. Furthermore, trace element

abundances in samples collected from the chilled

margin over a 200-kin span are identical. Cintala commented that when one takes a megacryst and recrystallizes it in a strain field it will have the same

orientation as the strain field. L. Taylor asked what factors lead to low viscosity. J. Taylor replied that bulk

composition and liquidus temperature were the principal factors affecting viscosity. On average, terrestrial

basalts are 10 times more viscous than lunar mare

basalts. A. Basu then asked what criteria are used to

accept a megacryst as a phenocryst. J. Taylor said that

it is hard to tell which is which with some skeletal grains.

Schmitt questioned if it was worth doing a systematic

analysis of the vesicle assemblages in the samples.

J. Taylor said that the presence of the vesicles was noted

but as yet has not been studied in detail.

Schmitt presented a short walk-on discussion of some

of his original lantern slides of the Apollo 17 orange

glass deposit displaying the subtle color differences that

he had personally observed on the lunar surface at

station 4, Shorty Crater.

TOPICS 3 and 6

PETROLOGY AND GEOCHEMISTRY

Summarized by John Jones

A. Basu and coworkers presented new data on the

petrology and geochemistry of pyroelastic soils in the

double drive tube 74001/2 at station 4, Apollo 17. As

shown by earlier workers, a layer of pyroclastic orange

glass (74220) overlies, and is in sharp contact with, a

layer that is dominated by vesicular, black spherules.

These black pyroclastic spheres owe their opacity to tiny

crystals that nucleated during quenching of the melt.

Basu noted that many of the black spheres display crystallites that grow inward from the periphery, perhaps

due to a high amount of dust during the eruption that

stuck to the spherules' surfaces creating nucleation sites.

These observed differences in the petrologic nature of

the pyroclastic deposits were interpreted as being due to

variations in volatile abundances, dust content, and

plume geometry during the fire-fountaining event(s).

Observations by electron microprobe analysis showed

the compositional variation among these glasses to be

the result of olivine fractionation.

A. Steele and coworkers presented INAA data

collcctcd on more than 360 individual spheres of Apollo

15 green glass. In addition to confirming the existcnce

of several compositionally distinct groups of Apollo 15

green glass identified by earlier investigators, Stccle

discovered systematic geochemical trends (e.g., a strong

positive correlation between Co and Sm) for which no

interpretations were readily available. This work

provided compelling evidence that the petrogenesis of

these glasses was more complex than previously

appreciated and that much work and thought remained

to be done.

S. Wentworth and coworkers had been searching for

ancient mare pyroclastics that might occur in old Apollo

16 regolith breccias. Ultra Mg' compositions occur as a

rare suite of glasses in these breccias. Although these

unusual samples differ strongly from typical mare

glasses of volcanic origin, available criteria for distinguishing impact glasses from volcanic glasses are

presently inadequate for deciding the origin of these

Apollo 16 glasses.

Y. Jin and L. Taylor presented the results of a

laborious study that they have conducted on 116 glasses

from the Luna 16 landing site. Although most of these

glasses were concluded to be of impact origin, Jin and

Taylor proposed that a compositionally varied assortment of their glasses may be volcanic. This subset of

glasses was observed to be chemically unlike any of the

volcanic glasses identified at the Apollo landing sites.

As previously noted with respect to the study by

Wentworth and coworkers, it was concluded that as

more detailed searches are made for extremely rare

varieties of vo!ca.nic glass, additional criteria must be

developed to distinguish impact glasses from volcanic

glasses.

G. Ryder showed geochemical data that he had

recently collected on a large (i.e., 6-ram diameter) glass

spherule from the Apollo 15 Apennine Front. This

sample consists of chemically homogeneous orange/

brown glass with crystal and lithic fragments embedded

in its exterior surface. Based upon measured abundances of siderophile elements such as Ni, Ir, and Au,

there is no detectable chondritic contamination and

hence this glass may be volcanic. Ryder planned to

perform more analyses on this intriguing sample to

better constrain its origin.

G. McKay and coworkers presented new experimentally derived partition coefficients for rare earth

elements between low-Ca pyroxene and mafic melt. In

support of the concept recently advanced by C. Shearer

and J. Papike, McKay's results demonstrated that lowCa pyroxene can have a significant negative Eu anomaly.

This added further constraints to the hypothesis of

Shearer and Papike that the negative Eu anomaly

commonly observed among mare magmas (i.e., mare

basalts and volcanic glasses), which reflects Eu

depletion in the mantle source regions, may not be the

result of plagioclase flotation in the magma ocean

forming the highlands crust but rather is due to

pyroxenc accumulation during thc magma occan cvent

that formed the mantle source regions. Basu disagreed

with the Shearcr/Papike hypothesis by claiming that in
10 Lunar ['_)tcantc G/asses

order to explain both (1) the negative Eu anomaly and

(2) the high absolute abundance of Eu and the other

rare earth elements in mare magmas, extremely low

percentages of partial melting are required if plagioclase

played no role. In response, Shearer stated that low

degrees of partial melting to produce mare magmas was

feasible. L. Nyquist agreed with Shearer by noting that

the Apollo 1 7 high-Ti mare basalts appeared to be

products of low percentage partial melting. J. Taylor

countered that the mare volcanic glasses have high Mg's

that seem best explained by high percentages of partial

melting. The issue was left unresolved.

Longhi showed results of calculations that indicate

little, if any, petrogenetic link between the picritie volcanic glasses and the less magnesian mare basalts.

Specifically, the mare basalts do not, in general, appear

to have been produced by fractional crystallization at

low pressure of known picritic magmas. Although this

apparent absence of a petrogenetic link between these

two categories of mare magmas (i.e., basalts and picritic

volcanic glasses) may be due merely to incomplete

sampling of mare magmas, it might also indicate a real

dichotomy of source regions. In support of this latter

notion, Delano showed a plot of Sc vs. FeO illustrating

that the mare basalts and picritic volcanic glasses define

different trends that are suggestive of different mantle

reservoirs.

Shearer and coworkers provided a summary of their

latest geochemical data acquired on the mare volcanic

glasses by ion microprobe. Their trace-element data on

the Apollo 15 green glasses were in agreement with

those presented in an earlier talk by Steele. A large

dataset was also presented on about a dozen other

varieties of mare volcanic glass indicating, for example,

that the Apollo 14 glasses were derived from deep

mantle source regions where small quantities (< 1%) of

a KREEP-Iike component had been present. Solid-state

convection (i.e., mixing) of the differentiated lunar

mantle after the magma ocean event was suggested as a

possible mechanism for carrying KREEP into the deep

lunar interior.

Dclano presented experimental results intended to

constrain the oxidation state of the lunar mantle. The

strategy involved calibrating the abundance of Cr in

lunar melts at spinel saturation as a function of temperature and oxygen fugacity. As shown for terrestrial

basalt compositions by earlier investigators, and now for

lunar magmas, the abundance of Cr in the melt at spinel

saturation is systematically dependent upon T, fO 2.

These new data were used to argue that the high Cr

abundances observed in mare volcanic glasses could

best be explained if the lunar mantle had a low redox

state, in contrast to an earlier view by M. Sato that the

lunar mantle is relatively oxidized.

TOPIC 4:

LUNAR VOLATILES

Summarized by Tammy Dickinson

A review talk by C. Meyer addressed the following

questions: (1) What elements are enriched on the

surfaces of the glasses? (2) What was the condensate?

(3) Are these elements a possible lunar resource?

Numerous volatile elements are enriched on the glass

bead surfaces relative to local basalts and relative to the

interior of the glass beads. Elements Zn, Ge, Cd, TI,

Ag, and Br are enriched by a factor of about 100 over

local mare basalts; Ga, Pb, Sb, In, Au, Se, and Te are

enriched by factors of about 10. Fluorine and CI are

also enriched on the surfaces of the glass beads, but S is

not greatly enriched. These observations, along with

boiling point data, suggest that the surface-correlated

deposits on the volcanic glasses are mixed salts of metal

sulfides and halides.

Although the lunar volcanic glass beads are enriched

in volatile metals, the glass coatings are depleted relative to typical terrestrial basalts. Thus, it is unlikely that

the lunar glass deposits would provide a useful volatile

resource for a lunar base. However, the glass beads

themselves could be a potential source for ceramics and

fiberglass, among other things.

Several questions remain concerning the origin of the

volatiles on the lunar glass spheres. A mechanism is

needed for enriching some, but not all, volatile elements

in these glasses. For instance, why is Ni not enriched on

the surfaces of the lunar glasses? Also, the composition

of the condensate and the composition of the gas that

formed the condensate need to be determined.

The two contributed talks in this session investigated

thermodynamic modeling of possible lunar volcanic

gases and sublimates. R. Symonds reviewed the

modeling of metal transport in high-temperature, terrestrial volcanic fumaroles. The authors have successfully

predicted the compositional zoning of the sublimates

from the Merapi Volcano in Indonesia and Augustine

Volcano in Alaska using their SOLVGAS and

GASWORKS models. Their models were applicable to

a variety of lunar volcanologic problems: (1) the speciation of major and trace components in lunar volcanic

gases; (2) prediction of trace-element concentrations in

lunar volcanic gases; and (3) the speciation and origin of

lunar volcanic sublimates. However, in order to attack

these problems they need additional data that are not

yet available for the Moon. For instance, they would

like to know the composition of lunar volcanic gases, as

well as the composition and mineralogy of lunar

volcanic sublimates. They also need to know the

pressure and temperature of degassing and the oxygen

fugacity.
Technical Report 90-02 11

D. Kong described another thermodynamic model

that employed a similar approach to that of Symonds,

except that it did not consider fractional condensation.

The results showed that, for terrestrial volcanic systems,

halides are the most important species for the transport

of metals. Also, the calculations suggested that the

oxidation state of the assumed gas becomes more

reducing with decreasing temperature. Again, in order

to apply their model to lunar volcanic gases, more data

were needed on the composition of the lunar gas.

The discussion following this session centered on

possible ways to obtain the data required to apply these

thermodynamic models to lunar volcanic glasses. Some

felt that it may be possible to better measure the

composition of the sublimates. One might be able to

estimate the composition of the gas phase from sealed

vesicles within lunar volcanic glasses. It was pointed out

that the models would need to be improved to take into

account expansion of the gas phase into a vacuum.

Additional important questions include (1) What is the

source of the volatiles? and (2) Did the volatiles originate from the evolved lunar mantle, or from primitive

undifferentiated material deep within the lunar interior?

TOPIC 5:

RESOURCE POTENTIAL

Summarized by John Delano

B. R. Hawke and coworkers proposed that regional

dark mantle deposits (e.g., Sinus Aestuum), which

consist of high-Ti pyroclastic materials tens of meters

thick, may have resource potential. In addition to being

areally extensive and thick, these deposits are

(1) essentially uncontaminated with highlands and other

mare components, (2) generally devoid of blocks,

(3) well sorted, and (4) loose, unconsolidated material

that would allow relatively easy mining. In addition,

these thick, unconsolidated materials would be useful

for shielding habitation modules to the required depth

of about 5 m. Reduction of ilmenite crystals contained

in these high-Ti pyroclastics would yield oxygen, iron,

and titanium that would be valuable to operations on

the lunar surface and in low Earth orbit. Hawke further

hypothesized that He 3 and other volatiles might also be

present in these deposits in sufficient quantities for

utilization. G. Heiken pointed out that since the grain

size of the ilmenite crystals in these pyroclastic deposits

was probably on the order of only 1 _m, physically

concentrating these tiny crystals for an ilmenite

reduction process would be difficult.

Heiken and coworkers discussed the resource

potential of lunar sulfur, which is known to occur in

high-Ti mare regoliths at abundances of about 0.1 wt.%.

Since crushing of high-Ti mare basalt is energy

intensive, thermal extraction of S from regolith would be

preferable. Up to 90% of total S could be extracted by

heating to a temperature of ll00°C. The resource

potential of S derives largely from its special electrical,

chemical, and fluid properties. For example, a sulfur

concrete could be a valuable construction material.

Liquid SO 2 is a low-temperature, low-viscosity fluid

that might be feasible for use in hydraulic systems and

as a heat-exchange fluid, despite its extreme toxicity.

Batteries using a Na-S electrolyte might also prove to be

useful.

J. Jordan discussed the resource potential of He 3 as a

fuel for nuclear fusion. He concluded that lunar

pyroclastic glasses would, in general, be poor in He 3

due to their lack of exposure to solar wind. In order to

identify locations on the Moon having He 3 enrichments,

Jordan observed that an excellent correlation existed

between ppm He 4 and the product of %TIO2 and

ls/FeO. This indicated that areas consisting of old,

high-Ti regoliths that had been extensively exposed to

the solar wind would be promising areas of He 3

enrichments.

TOPIC 7:

RETURN TO THE MOON

Summarized by B. Ray Hawke

The final topic discussed at the workshop was one

close to the hearts of most, if not all, attendees. G. J.

Taylor and P. D. Spudis presented a well-received talk

concerning the future geologic exploration of the Moon.

They described a number of unanswered lunar questions and outlined a strategy for lunar geologic

exploration designed to resolve these issues. The plan

involved four kinds of geoscience research activities:

orbiting spacecraft, global geophysical networks,

reconnaissance missions with automated spacecraft that

return samples to Earth, and geological field investigations. Special emphasis was placed on the capabilities

of robotic field geologists.

The workshop participants agreed that detailed

sampling and analysis of lunar pryroclastic deposits

would almost certainly provide answers to a variety of

major questions concerning the volcanic history of the

Moon and the nature of the lunar interior. For example,

it should be possible to determine the source of the

volatile substances that are present on the surfaces of

lunar pyroclastic debris. In addition, many attendees

expressed the view that the pyroclastic deposits might

prove to be excellent sites for permanent lunar bases.

ABSTRACTS

PRECEDZNG PAGE BL*-.,,K, _O] _'_._._'_Eb

IMi_./__. 1NTENTIONAI_I I_J_l_

15

ORIGIN OF LUNAR BASALTS: A GEOPHYSICAL INTERPRETATION Jafar

Arkani-Hamed, Department of Geological sciences, McGill University,

Montreal, Quebec, Canada

Introduction:

Lunar basaltic lava covers about 17% of the Moon's surface

with an average thickness of about 1 km, constituting less than 1%

of the mass of the lunar crust. Nevertheless, initiation of

basaltic volcanism, its duration and spatial distribution, and

persistence of lunar mascons for over 3 G.y. provide strong

constraints on the thermal evolution of the lunar interior in the

last about 4 G.y. This paper reviews the main constraints of the

models proposed for the source of the basaltic magma.

Constraints:

Dating of lunar basaltic rocks [e.g. 1] and crater counts

[e.g. 2] indicate that basaltic flow on the moon was a very slow

process, taking from 300 to about 700 M.y. in a given mare.

Existence of flooded craters, such as Archimides, and lack of

ejecta of Imbrium and Orientale impacts on the older mare surfaces

imply that major mare fillings lagged the respective impact events

by about 100 to 200 M.y. The surface topography of mare

Tranquillitatis prior to its filling by basaltic lava is

satisfactorily explained by slow rising of the impact basin for

about a few hundred million years [3]. Detailed analysis of rills

and ridges of maria suggest that major basaltic flow was around

3.8-3.6 G.y. ago [4], though basaltic volcanism continued up to

about 2.5 G.y. ago These evidence suggest that basaltic magmatism

was not an instantaneous response of the lunar interior to large

impacts.

Surface distribution of mare basalts [5], positive gravity

a_omalies over circular basins [6] negative Bouguer anomalies of

highlands [7], negative gravity of unfilled basins [8], and lack

of shallow moonquake sources beneath the far-side and the SE nearside highlands [9] suggest a close correlation between basaltic

flow and large impacts, and lack of significant mascons beneath the

highlands. This indicates that basaltic sources in the lunar

mantle were activated by impact events and not by local

concentrations of radioactive heat sources. Local concentrations

of heat sources possibly created through initial differentiation

of the Moon and/or by impacts of large planetesimals during the

last stages of the lunar accretion [10] should in principle have

a random distribution which does not necessarily correlate with the

locations of the later event impacts which produced mare basins.

Basaltic magmatism generated by such concentrations would result

in randomly distributed intrusives and extrusives, and thus mass

concentrations which have not yet been observed. Also, localized

high concentrations of radioactive elements in the upper 400 km are

not supported by either magma ocean or completely molten moon

hypothesis both of which produce a spherically symmetric layered

moon more efficiently than a laterally heterogeneous one.

The power spectra of the lunar gravity field [7], the physical

J

PRECEDING PAGE BLANK NOT FI,..I_}.D
16

ORIGIN OF LUNAR BASALTS: Arkani-Hamed J.

liberation of the Moon [11] and the hypocenters of shallow

moonquakes [9] imply that major lateral variations of density occur

within the upper 400 km and produce shear stresses of about 50-100

bars at these depths [12]. To support lunar mascons and the

lateral density variations in the upper mantle for about 3.3 G.Y.,

the upper 400 km of the lunar mantle requires a minimum viscosity

of about 102_ poise [13]. Viscosities of about 1025-1026 poise were

cited for this region during mare filling [14], i.e. period between

4.1 to 3.3 G.y. ago. Bearing in mind the strong temperature

dependence of viscosity, these viscosity values provide essential

information about the thermal evolution of the Moon, the upper

about 400 km of the Moon beneath circular basins has been cold and

strong in the last 3.3 G.y.

Electrical conductivity and heat flow measurements [15]

indicate a cold lunar upper mantle with temperatures less than 0.75

times the melting temperature in the upper 400 km. Thermal

evolution models of the moon calculated on the basis of thermal

conduction [16], thermal convection [17] and thermal conduction

with simulated convection effects [18] also result in a cold lunar

upper mantle. The cold upper mantle prevents diapirism, basaltic

magma has reached to the surface through existing cracks or crack

propagation a transport which is mainly governed by the stresses

in the medium. The major basaltic flow around 3.7 G.y. is

interpreted in terms of global expansion of the Moon due to heating

of its deep interior [19]. This is based on the assumption that

the Moon was formed by accretion of cold planetesimals and that

heat transfer in the Moon was by the conduction mechanism.

However, a detailed study of global expansion due to thermal

evolution and phase changes [20] shows that the time of maximum

expansion is not well constrained, it depends on many parameters

such as the heat transfer mechanism, the chemical composition, and

phases of material constituting the Moon. Furthermore, an

initially molten moon model is always in contraction since it cools

monotonically [21]. It is therefore plausible to suggest that

local expansion induced by local partial melting in the upper 400

km provides a transport mechanism for basaltic volcanism.

Source of Basaltic Magma:

Any model suggested for the origin of basaltic volcanism

should satisfy the foregoing criteria. Geochemical analysis of

lunar rock samples suggests that basaltic magma was produced by

partial melting somewhere in the upper 400 km [22]. It requires

about 20-30% partial melting to account for major chemical

composition [23]. Such an extensive partial melting may not have

taken place in the upper mantle directly beneath circular maria

because it reduces the viscosity of this region drastically and the

mascons associated with these maria can not be supported for long

periods. For example, the mascon associated with mare Serenitatis

is due to about 3-4 km basaltic lava, say a cylinder of about 400

km diameter and 3-4 km thickness. Assuming that the extruded lava

was the access volume produced due to partial melting, a cylinder

of a similar diameter but about 30-40 km thick is needed in the
17

ORIGIN OF LUNAR BASALTS: Arkani-Hamed J.

upper mantle to become 30% partially molten. A gradual heating of

such a large region to its melting temperature tends to heat up the

surrounding area and thus reduce its viscosity by many orders of

magnitude. Furthermore, there is no obvious source of heat

generation directly beneath the basins. These regions tend to cool

faster than their surroundings [24].

Figure i shows a model for the generation of basaltic magma

triggered by a large impactor [25]. A large impactor producing

circular mare basins excavated the lunar crust down to a depth of

20-40 km and deposited the material on the surrounding area as a

loosely bound, highly porous ejecta blanket. The immediate rebound

of the upper mantle implaced a plug of about 10-30 km thickness

directly beneath the basin, upward displacing the radioactive-rich

upper-most part of the upper mantle. The heat produced by the

radioactive elements of the plug was conducted to the surface and

was lost more efficiently, resulting in a fast decrease of

temperature there. However, the loosely bound, porous ejecta

blanket with a low thermal conductivity [26] provided a thermal

blanket and hampered heat loss. The heat produced by radioactive

heat sources in the upper-most part of the upper mantle beneath the

ejecta blanket enhanced the temperature and partially melted this

region. The resulting basalts transported upward and filled the

basin. This simple model accounts for I) delay in basaltic

volcanism relative to impact event, 2) impact triggered lava flow,

3) support of the associated mascon by the cold and strong upper

mantle directly beneath the mascon, and 4) local expansion required

for magma transport.

RefeEences:

[i] Wasserburg, et al. (1977) Phil. Trans. R. Soc. Lond., Series

A, 285, 7-21; [2] Baldwin, R.B. (1987) Icarus, 71, 1-18; [3]

Solomon, S.C., et al. (1982) J. Geophys. Res., 8/7, 3975-3992; [4]

Solomon, S.C. and J. W. Head (1980) Rev. Geophys. Space Phys., 18,

107-141; [5] Head, J.W. (1976) Rev. Geophys. Space Phys., 14, 265-

300; [6] Muller, P.M. and W.L. Sjogren (1968) science, 161, 680-

684; [7] Bills, R.G., and A.J. Ferrari (1980) J. Geophys. Res., 85,

1013-1025; [8] Sjogren, W.L. (1977) Phil. Trans. R. Soc. Lond.

Series A, 285, 219-226; [9] Lammlein, D.R. (1977) Phil. Trans. R.

Soc. Lond., Series A, 28___5, 451-461; Goins, ".R. et al. (1981) J.

Geophys. Res., 86, 5061-5074; [i0] Taylor, J.R. (1982) Planetary

science: A Lunar Prespective; [Ii] Koziel, K. (1967) Icarus, 2, 1-

28; [12] Arkani-Hamed, J. (1973) The Moon, Z, 84-126; [13] ArkaniHamed, J. (1973) The Moon, _, i00-iii; [14] Baldwin, R.B. (1987)

Icarus, 71, 1-18; [15] Hood, L.L. et al. (1982) J. Geophys. Res.,

8_/7, AI09-AII6; Langseth, M.G. et al. (1972) Apollo 15 Prel. sci.

Rept., ii-i, 11-20; [16] Solomon, S.C., and M.N. Toksoz (1973)

Phys. Earth Planet. Inter., Z, 15-38; [17] Schubert, G. et al.

(1977) Phil. Trans. R. Soc. Lond., Series A, 28____5,523-536; ArkaniHamed, J. (1979) Geophys. J. R. Astron. Soc., 56, 63-80; [18]

Tokzos, M.N. et al. (1978) Moon Planets, 18, 281-320; [19]

Solomon, S.C. (1978) Geophys. Res. Letters, _, 461-464; [20] Kirk,

R.L., and D.J. Stevenson (1989) J. Geophys. Res., 94, 12,133-

12,144; [21] Binder, A.B., and J. Oberst (1985) Earth Planet. sci.
18

ORIGINOF LUNARBASALTS:Arkani-HamedJ.

Letters, 74, 149-154; [22] Taylor, S.R. (1987) American

Scientists, 75, 469-477; [23] Binder, A.B. (1982) J. Geophys.

Res., 87, A37-A53; [24] Arkani-Hamed, j. (1974) The Moon, _, 183-

209; [25] Arkani-Hamed, j. (1974) Proc. of the Fourth Lunar Sci.

Conf., 2673-2684; [26] Huang, J.H (1971) J Geophys Res 76, 6420-6427. " " - -, __
ORIGIN OF LUNAR BASALTS: Arkani-Hamed J.

19

ejecta blanket more

Bosolts

ejecta blanket

KREEP Crust

Px-PI

Partial

melt Px -IIm

Partial

melt

OI-Opx- Cpx

400km--
2O

LUNAR PYROCLASTIC SOILS OF THE APOLLO 17 DOUBLE DRIVE TUBE 74001/2

AbhlJit Basu, Indiana University, IN. 47405, D.S. McKay, NASA-JSC, and S.J.

Wentworth, Lockheed, Houston, TX. 77058

The soils of the double drive tube core 74001/2 below -5 cm do not

contain any agglutinate and are apparently devoid of any measurable surface

exposure; they must have erupted and then buried within a matter of hours

[i,2,3] and are unique samples of pure lunar pyroclastlc material. Only one

pair of initial petrologic study of this soil has been carried out [1,2].

The purpose of this note is to present some new data on this soil.

The soil 74001/2 consists of spheres and broken spheres of black,

brown, and yellow-orange crystal-laden and crystal-free glass. The black

spheres contain many crystallites of ilmenlte attached on the external

surfaces of euhedral, skeletal and dendritic crystals of olivine. The brown

spheres contain crystallites of olivine and most are free from ilmenite.

Crystal-free spheres are generally yellow-orange in color as are the glassy

parts of crystal-laden varieties. Intermediate varieties are common. Modal

analysis shows that the black variety is the most abundant (black: 74%;

brown: 20.3% and yellow-orange: 5.6%) and is also largest in size

incorporating larger phenocrysts (Table I). Many spheres contain vesicles

and many have crystallltes growing inward from the periphery. Such

inclusions are much less common in other lunar pyroclastlc glasses (Table

2). This suggests that more volatiles (to make gas bubbles) and dust (to

provide nucleation sites at the surfaces of droplets) were available during

the eruption of 74001/2 than during the eruption and emplacement of orange

glass soll (74220) or the green glass soils (15401, 15411, etc.).

Major variations in the chemical compositions of the yellow-orange

glass are controlled by olivine fractlonatlon. Glass spheres without

olivine crystals have higher Mg/(Mg+Fe) than those with olivine. A plot of

calculated Oi-An-Qz proportions shows an olivine fractionatlon trend (Fig.

I), which does not cross over into the pyroxene field although pyroxene

crystals are reported to have crystallized in these droplets. In addition,

a plot of TiO 2 vs. Mg/(Mg+Fe) does not show sufficient depletion of Fe

simultaneously with that of Ti suggesting that ilmenite fractionation has

not been significantly responsible for variations in glass compositions

(Fig. 2). This interpretation is compatible with the petrographic

observation mentioned above. If olivine were to have crystallized in

equilibrium with the liquids of the glass compositions, their Fo content

would have varied from about 82 to 59 percent (K D , 0.3 as an approximate

average; note that TiO 2 in glass does vary considerably [4]).

Interestingly, this is exactly the range of olivine composition reported

earlier [2].

Analysis of phenocrysts and skeletal crystals of olivine in the black

spheres show a variation of Fo content from about 83% to about 70% with an

average CaO content of about 0.3%. Although much of this variation is

related to crystal size, some of the phenocrysts show substantial zoning in

the Fe/Mg ratio. The zoning is not necessarily concentric in the euhedral

phenocrysts where "sector zoning" is more common. Large euhedral

phenocrysts (Fo=80) could be equilibrium crystallization products of the

more primitive glass compositions. We envisage that these phenocrysts

crystallized in the magma chamber before eruption and were caught, - both

intact and fractured, in the spray of a fire fountain event. The ilmenite

attached to these phenocrysts are dendritic in morphology and may have
SOILS OF 74001/2: Basu, A. et al.

crystallized, along with dendritic and feathery olivine, even during the

flight of the glass droplets [5].

In summary, we find evidence of probably the most volatile-rich and

dust-rlch eruption on the moon in this pyroclastlc soil. Eruption of a

mixture of early phenocrysts and the lava must have been rapid and the

pyroclasts were covered very quickly. This scenario is essentially

compatible with that proposed by Helken and McKay [6].

REFERENCES : [I] HcKay et al., PLSC 9, 1913-1932, 1978; [2] Heiken and

McKay, PLSC 9, 1933-1943, 1978; [3] Morris et al., PLSC 9, 2033-2048, 1978;

[4] Longhl et al., GCA, 42, 1545-1558, 1978; [5] Arndt and Engelhardt,

PLPSC 17, E372-E376, 1987; [6] Heiken and McKay, PLSC 8, 3243-3255, 1977.

Table I. Modal abundance of glasssphere-slzes in soil 74001,6038.

Micron Range Black Brown Yi-Orange

<4.7 0 0 0

4.7-9.3 0 3 1

9.3-18.6 0 i0 I0

18.6-37.2 I0 28 29

37.2-74.4 21 40 36

74.4-148.8 50 17 24

148.8-297.6 14 2 0

297.6-595.2 3 0 0

>595.2 2 0 0

_Z

+

E.

e4

CD o

m.

Fig. I. Recalculated compositions of

yellow-orange glass in 74001,6039

plotted in a Qz-Fo-An space; also

plotted are compositions of orange

glass (74220; ('0 ), and the bulk

compositions of top (_) and

bottom (A) soils of 74001/2•

Table 2. Glass spheres with and

without vesicles and crystals

growing from edge inward.

Crystals Vesicles

Present Absent Present Absent

A. 70 30 42 58

B. 3 39 1 41

C. 0 36 0 36

D. 4 13 0 17

E. 4 49 0 53

A. 74001,6038 (all size); B. 74220,6

(90-150_m); C. 15401,14+16 (250 -

500_m); D. 15411,42 (250-500_m);

Green Glass (C+D)

÷

++

+

÷÷

4-'I-

÷

4-

I I I I I

20.0 30.0 40.0 50.0 60.0 70.0

Hg/(Fe+Hg) x 100

Fig. 2. Plot to show that TiO 2 in

the yellow-orange glass in 74001,

6039 does not decrease significantly

with an increase in Mg/(Mg+Fe).

21
22

LUNAR EXPLOSIVE VOLCANISM: THE REMOTE SENSING

PERSPECTIVE Cassandra Runyon Coomb$, SN15, Johnson Space Center. Houston, TX,

77058, B. Ray Hawke, Planetary Geosclences Division, Hawaii Institute of Geophysics, 2525

Correa Rd., Honolulu, HI, 96822.

INTRODUCTION Prior to the Apollo nflsslons our knowledge of lunar pyroclastlc deposits was limited. The

recent aqulsltlon of remote sensing and geologlc data has helped increase our understanding of these deposits and the

role they played in resurfacing large portions of the Moon. Two geneUcally distinct types of pyroclast/c deposits have

been identified: reg/ona] and localized. Eruption mechanisms and emplacement styles for both the regional and

localized deposits have been inferred from their source vent morpholo_,, distribution, and the composition and

geometry of their mantling deposlts. Apollo and Lunar Orbfter photographs, UV-V]S, and near-IR reflectance spech-_

a]bedo maps, mu]t/spectral/mages, 3.0, 3.8, and 70-cm radar/n-rages, and compositional data from the returned lunar

samples have a/] been used to compile thls summary of what is known to date about the lunar pyroclastlc deposits.

REGIONAL PYROCLASTIC_ Reg/onal dark mantling deposlts (RDMD) are located in lunar highland areas

adjacent to many of the major maria. These extensive deposits are relatively flne textured w/th a smooth, velvety

appearance, 1"2'3 have a low albedo (0,079-0.096; 4}, and typlcalJy cover lO's of l,O00's of km 2. RDMD formed as

products of ftre-fountaining that occurred in assoc/ation with basaltic erupt/ons,e.g.. 5 and may have been associated

w/th some of the early mare-fiRing eplsodes.6.7 Depressions at the head of associated sinuous rules and/or irregular

depressions are the probable source vents for these deposlts.e_., 8,9 Depolarized 3.8-cm radar maps of these features

acquired by Z/sk eta/. 8 exhibit weak to nonexistent echoes. These low radar returns are believed to be due to a lack

of surface scatterers (i.e., rocks and boulders} in the 1-50 cm size range.e_, I l

Reflectance spectra {0.3 - I, I _ 0.6 - 2.5 Jan) and multispectra] imagery were obtained for a large number of

the RDMD. Ana]ysls and interpretation of the near-infrared spectra indicate that some of these mantling units (i.e.,

Mare Humorum and AHstarchus) contain a slgn/flcant Fe2*-bearing glass component. Other regiorud deposits [i.e.,

Taurus-L/ttrow and R/ma Bode) appear to be domLnated by a mixture of orange and black spheres sim/lar to those

returned from the Apollo 17 landing site. 9.10 The Apollo 17 orange glass and the/r "quench-crystalI/zed- equlvalent,

the black spheres, are thought to be relat/vely unfractiormted samples of the deep lunar interior(>300 kin) 5 These

spherules, collected from the distal portion of the Taurus-L/ttrow RDMD, have a volatile-rich coating. Presumably

condensed from gases involved in an explosive eruption, these glass coatings strongly suggest the ex/stence of a

volatile gas phase in their source magnms.

Studies have shown that the RDMD were most I/kely formed as a result of strombo]ian {continuous) eruption

activity rather than the coalescence of ]ocal/zed pyroc]asUc deposlts, l,12 and that the lunar equivalent of

stromboltan acttvlty is I/kely to sort and disperse the pyroclasts over a wide area. Hence, course material would be

concentrated in a zone peripheral to the vent while finer debris would be mere spread out.

LOC.AIJT_D PY]ROC/AST/_ Localized dark mantle deposits {LDMD} are relatively small {typically <250-550 krn2),

low albedo units that are also of pyroclastic origin. These deposits, too, are concentrated about the perimeters of the

major lunar maria and are commonly found in the floors of large Imbrlan and pre-lmbrlan aged impact

structures.e.g.,l 1.13.14 The LDMD are generally assocLated wlth small (< 3 krn) endogenic dark-halo craters that are
Lunar Explosive Volcanism Coombs and Hawke

23

aligned along crater floor-fractures and/or regional faults. These source craters typically are non-circular in shape

and lack obvious crater rays. Morphometric analyses of the LDMD "haloes" suggest a vulcania_-type eruption

mechanism, whereby gas accumulates in a capped magma chamber and eventually leads to an explosive eruption and

the emplacement of pymclastic material about the source vent. For these types of eruptions, the maximum range of

all pyroclasts much larger than 1 cm is up to 4 km. while the smaller clasts may be thrown up to 10's of kms. Spectral

reflectance studies have shown that the LDMD are spectrally distinct- e'g'' 13, 14,15 Three general compositional types

of LDMD have been identified on the basis of the depth, center and overall shape of the -1.0 pxn absorption features

and continuum slopes. Oroup I: Spectra in this group have a "checkmark-llke" shape, similar to those obtained for

typical lunar highlands areas. A strong feldspar-bearing maflc (orthopyroxene) assemblage is indicated. However, in

addition to the highlands spectral geometry of the 1.0 _tm band, these Group 1 spectra indicate an additional

component of volcanlc glass, olivlne, and/or clinopyroxene. Multispectral images of this group indicate the presence

of an exotic non-highlands component. The Group I pyroclastic deposits are most likely composed of a mixture of

highlands-rich wall rock and glass-rich Juvienfle material with lesser amounts of basaltic cap-rock. Group 2:

Spectra of the Group 2 pyroclastic deposits (i.e., from Rirna Fresnel, Vitruvius) are deeper and more symmetrical than

those in Group I. A Ca-rich clinopyroxene composition is inferred. These spectra most closely resemble spectra

obtained for mature mare areas. 16 Similarly, multispectral images obtained for the Group 2 deposits indicate that

they are composed predominately of fragmented basaltic plug rock with much lesser amounts of highlands debris and

Juvenile material. Group 3: Spectra from this group include the Alphonsus LDMD as well as J. Herschel and other

localities. These broad, asymmet_cal and moderately deep spectra are characteristic of a composite feature produced

by olivine and pyroxene, The olivine is thought to have been emplaced with the Juvenile material while the bulk of

the orthopyroxene was emplaced as a component in the highlands-rich wall rock. The basaltic plug rock may also

have contributed minor amounts of olivine and pyroxene.

Eruption mechanisms and emplacement styles for both the regional and localized lunar

pyroclasttc materials have shown that they are genetically different. A strombolian, or continuous, eruption origin

is consistent with the unfractionated, volatile-coated glass samples returned by Apollo 17 and the idea that these

originated deep in the lunar interior (> 300 kin). The lack of associated lava flows and the small radial extent of the

dark-halos around the localized dark mantle deposits suggests that they were formed during a short-lived (vulcanian)

explosive eruption. The explosive origin of these volatile-rich pyroclastic materials stands in striking contrast to

the massive outpouring of volatile-depleted low-viscosity magma which formed the lunar maria. Thus, lunar

pyroclastic mantling deposits are unique among lunar volcanic materials.

_(I) Cernan E.A. et al. (1972) MSC.07629. (2) Lucchlta B.K. (1972)U.S.G.S. Map 1-725. (3) Luechlta B.K. and Schmltt

H.H. {1974) PI..PSC 5th.pp. 223-234. (4) Pohn H.A. and Wlldey R.L. (1970)U.S.G.S. Prof Pap, 599-E. Plate I. (5) Heike_ G.H. et al.

(1974) C,eo. Costa. Act_ 38, 1703-1718. (6) Howard K.A. et al. (1973}NASA SP-330, pp. 29-1 to 29-12. (7) Head J.W. (1974}PLPSC 5th,

pp. 207-222. (8) Z_sk S.H. (1974]The Moon, 17, 59-99. (9) Gaddls L.R. et al. (1985)Icarus, 6], 461-489. (lO) Picters C.M. et al. (1973)

J.G.R., 78, 5867-5875. (11) Head J.W. and Wilson L. (1979}PLPSC IOth, pp. 2861-2897. (12) Wl]s_n L. _ Head J.W. (1981J.G.R.,

782971-300. (13) Coombs C.R. et _d. (19871-U Sym. on How Vole. Work. (14) Coombs C.R. and Hawke B.R. (1989) Proc. Kagoshtrna

In_l. Conf. on Vole, 416-419. (15)Hawke B.R. eta]. (1989] PLPSC 191h,pp. 255-268. (16) McCord T.B. et al. (1981)J.G.R., 86, ]0883-

10892.
24

THE OPTIMAL LUNAR RESOURCE: ILMENITE-RICH REGIONAL

PYROCLASTIC DEPOSITS Cassandra Runyon Coombs, SN 15, Johnson Space Center,

Houston, TX, 77058; Bernard Ray Hawke and Beth Clark, Planetary Geosciences Division,

Hawaii Institute of C,eophysics. 2525 Correa Rd., Honolulu, HI, 96822.

INTRODUCTION

With the onset of a new space era for the U.S. and a commlttment to establish a lunar

base, the need for lunar resources has increased dramatically. It has been suggested that

titanium production might be a profitable activity for a lunar base, and that lunar material

would be useful for shielding space habitats and military facilities in orbit. Recently,

attention has focused on the production of oxygen propellant and He-3 as nuclear fusion fuel

(e.g., 1). Ilmenite-rlch material is the preferred source of these substances. Efforts to locate

ilmenite-rlch deposits thus far have focused on the high-titanlum mare basalts present on the

lunar nearslde. Instead. we suggest that large, ilmenite-rich pyroclastic deposits would make

an excellent source. Not only would these deposits provide useful by-products, but they would

be easy to mine as they are relatively thick and unconsolidated and have a block-free surface.

DISCUSSION

Direct sampling and remote sensing studies have indicated that major deposits of

high-Ti mare-basalt exist on the Moon. Spectral reflectance and orbital geochemical data

indicate that Mare Tranquflltatis contains the largest expanse of high-Ti basalt on the

eastern nearside (e.g., 2,3). The orange glasses and black spheres sampled at Shorty Crater

and elsewhere at the Apollo 17 site are fine grained droplets. Their chemical compositions are

indistinguishable; the only difference being that the black spheres are largely crystallized.

The black quench-crystallized spheres are rich in TiO 2 (9 - 10 %) and llmenite and are similar

in composition to the Apollo 17 mare basalts. Nearly all flmenites identified in the Apollo 17

orange glass spheres are fine-grained and have dendritic shapes (4). One of the most unique

features of the these and other lunar pyroclastics are the sublimates that coat the individual

grain surfaces. These consist of sulfur compounds and include elements such as Zn, K, CI, Na,

Ga, Ni, Cu, and Pb (5). These sublimates most likely were emplaced on the pyroclast surfaces

during lava fire-fountaining. A large deposit of these pyroclastic spheres exists 50 krn west of

the Apollo 17 site at Taurus Littrow. This deposit extends over 4000 km 2 and is 10's of meters

thick. Other large flmenlte-bearing regional pyroclastlc deposits also occur at Rima Bode, S.

Sinus Aestuum, and S. Mare Vaporum.

Another lunar product wlth a potentially large market that would require minimal

processing is 0 2 for use as spacecraft propellant (6). Lunar oxygen may also prove to be a

viable export for sustaining operations in low-Earth orbit (LEO) and elsewhere in near-Earth

space. A variety of methods for producing oxygen from lunar rocks and softs have been

investigated. After extensive research, however, the reduction of flmenite seems to be the

preferred method (e.g., 6). In addition, potentially useful by-products such as Fe and Ti are

produced by the reduction of ilmenite. Lunar He-3 supplies originate from solar wind
Lunar Resources: Coombs C.R. et al.

materials that are embedded in near-surface regions of fine grained regolith particles.The

utilization of lunar He-3 as a nuclear fusion fuel would dramatically improve our energy

future (7). Helium and other solar wind gases can easily be extracted from the lunar regolith by

the relatively simple procedure of heating the soft to temperatures of 700C or higher.

Cameron (8,9) noted that mare regoliths rich in titianium, hence ilmenite, exhibit high

helium contents. During the course of operations to extract He-3 from the regolith, other

valuable volatiles implanted by the solar wlnd such as H 2, N 2, CO2, CH4, and the noble gases,

could be collected with relatively small mass and power penalties (10,11).

25

CONCLUSION

Numerous flmenite-rich regional pyroclastic deposits have been identified on the lunar

surface (i.e., Taurus Littrow, Rima Bode). The large areal extent of these deposits as weU as their

relatively great thicknesses (10's m's) make them excellent sites for mining operations. In

addition to the production of oxygen and He-3, the pyroclastic deposits could provide byproducts such as Fe and Ti in addition to S, Cu, Ni, Pb, Zn, and Cd which are present on the

surface of the pyroclastic spheres. Also, other volatile elements implanted by the solar wind,

such as H 2, N 2, and CO 2, may be recovered. In addition to the above mentioned elements, the

unconsolidated, thick pyroclastic deposits would provide a ready source of shielding material

against meteorite impact and space radiation. In short, the resource potential of the lunar

RDMD should not be taken lightly when deciding where to locate a permanent lunar base.

REFERENCES

(1) Kulcinski G.L. ed. (1988) Astrofuel for the 21st Century. College of Engineering,

University of Wisconsin, Madison. 20 pp. (2) Pieters C.M. (1978) Proc. Lunar and Planet. Sci.

Conf. 9th, pp. 2825-2849. (3} Johnson T.V., Mosher J.A. and Matson D.L. (1977) Proc, Lunar

Planet. ScL Conf. 8th, pp. 1013-1028. (4) Heiken G.H. and McKay D.S. (1977) Proc. Lunar

Planet. Scl. Conf. 8th, pp. 3243-3255. (5) Meyers C., Jr., McKay D.S., Anderson D.H. and Butler

P. (1975) Proc. Lunar Scl. Conf. 4th, pp. 1625-1634. (6) Mendell W.W., ed., (1985) Lunar Bases

and Space Acttvities of the 21st Century. Lunar and Planetary Institute, Houston, TX, 866 pp.

(7) Wittenberg L.J., Santarius J.F., and Kulcinski G.L. (198C "uslon Technology, 10, 167-178.

(8) Cameron E.N. (1987) WCSAR-TR-AR3-8708, Wisconsin Center for Space Automation and

Robotics (WCSAR), Madison, WI. (9) Cameron, E.N. (1988) In Papers Presented to the

Symposium on Lunar Bases and Space Activities of the 21st Century, p. 47. Lunar and

Planetary Institute, Houston. (10) Crabb T.M. and Jacobs M.K. (1988) In Papers Presented to

the Symposium on Lunar Bases and Space Activities of the 21st Century, p. 62. Lunar and

Planetary Institute, Houston. (11) Haskin L.A. (1989) In Lunar and Planetary Science XX, pp.

387-388. Lunar and Planetary Institute, Houston.
26

PYROCLASTIC VOLCANISM IN THE ALPHONSUS REGION Cassandra

Runyon Coombs. SNI5 Johnson Space Center, Houston, TX 77058; B. Ray Hawke, Stan H.

Zisk, and Paul G. Lucey. Planetary Geosciences Division, Hawaii Institute of Geophysics.

Honolulu, HI. 96822.

INTRODUCTION

AIphonsus, a slightly elongate. 118-kin, pre-lmbrian crater located in the southcentral lunar highlands, has long been of interest to lunar scientists. Floor fractures, dark

halo craters (DHC's) and a north-south trending central ridge within Alphonsus distinguish it

from other highland craters of similar size. The majority of the work done on AIphonsus has

centered around the dark halo craters scattered about the periphery of Its floor. Suggested

origins for these deposits have varied from tephra deposits due to rnaars (1) to pyroclastic

deposits from a central vent (2). Vulcanian eruption models developed by (3) and (4) support

the pyroclastic nature of the localized dark mantle deposits (LDMD). as do recent spectral and

geologic investigations (e.g.. 5. 6, 7, 8). This study, in particular, takes a closer look at the

spectral signatures of the AIphonsus DHC's and their adjacent features in an effort to address

some outstanding questions: (1) What is the composition of the dark mantling material

surrounding the endogenic craters? (2) What Is the origin of the light plains material on the

crater floor? (3) How was the central ridge formed and is it related to the formation of the

central peak and DHC's? (4) What caused the crater floor uplift and is It related in any way to

the deposition of the dark mantling material?

METHOD

Spacecraft and Earth-based photographs, topographic maps. UV-visible (0.3 - I. 1 _rn)

and near-infrared (0.6 - 2.5 _rn) reflectance spectra as well as newly obtained 3.0-cm radar

data were used in this study. Spectra were collected for three of the localized dark mantle

deposits within Alphonsus. the central peak. the light plains mantling the floor, and a variety

of other features associated with Alphonsus.

ICESUL T_ AND DISCUSSION

The radar. UV-vlslble and near-IR reflectance data collected for this study have helped

greatly in unravelling the geologic and stratigraphic history of the Alphonsus region. Weak

echoes in the new 3.0 cm radar indicate that the surfaces of the A]phonsus LDMD are smooth.

The UV-VIS spectra for the Alphonsus features vary somewhat. Spectra collected for a portion

of the northeast floor (light plains material) indicate a highlands composition sirnflar to that

of the Apollo 16 site. In contrast, the spectra taken of the western LDMD are "red". indicating

a basaltic composition. One group of spectra collected and analyzed for another LDMD.

AIphonsus R. in southeast AIphonsus. suggest that it may have a different compostion than

the western LDMD.

The near-infrared reflectance spectra collected of these Alphonsus features, on the

other hand, are more consistent. The spectra of the LDMD indicate a basaltic composition
A1phonsus Pyroclastics: Coombs C,R, et al,

rich in olivine and have been classified as being typical of the Group 3 spectral class of Hawke

et al. (7,9). These spectra exhibit broad, moderately deep (5 - 7 %) asymmetrical absorption

bands in the 1.0 _tm region. The broad nature and asymmetrical shape are indicative of

composite features with band centers in the 1.0 pln region. Most often, this type of band

indicates the presence of both olivine and orthopyroxene (10,11). While in theory this band

could be produced by the combination of clinopyroxene, orthopyroxene, and Fe2+-bearing '

glass, the analyses presented by McCord et al. (10) and Hawke et al. (7) indicate that this is

unlikely.

Some of the olivine may have come from the basaltic rock, however, it is thought that

the majority was emplaced with the Juvenile material brought up from depth. Also, it seems

likely that the bulk of the orthopyroxene in the Alphonsus DHC deposits was present as a

component in the highlands-rich wall rock and that it was eroded and emplaced during the

explosive eruptions which produced the LDMD. Spectra of the light plains deposits on the

crater floor exhibit a noritic composition, different from the other locally derived Alphonsus

features. The origin of this deposit is still uncertain, however, these deposits are thought to be

related to the Imbrium impact event that resurfaced the Alphonsus region. Spectra collected

of the central ridge and peak of Alphonsus indicate that they are non-basaltic in composition.

Rather, the central ridge appears to be composed of Imbrium-related material and the central

peak is composed of pure anorthosite.

27

Vulcanian-type eruptions deposited several localized dark mantle deposits on the

floor of Alphonsus. Associated with prominent floor fractures and endogenlc source craters,

the individual deposits cover areas less than 450 km 2, while the largest coalesced deposit is

nearly 800 km 2. The reflectance spectra collected for the LDMD indicate that the Alphonsus

pyroclastics are rich in olivine and pyroxene and contain lesser amounts of fragmented

basaltic plug-rock and highlands-rich wall rock. The central ridge appears to have an origin

related to the Imbrium impact event and is not related to the formation of the DHC's or the

central peak. The central peak is composed solely of anorthosite, suggesting that a lens of the

material must have been present at depth below the target site Floor uplift within Alphonsus

most likely is the result of magma emplacement at depth well a. __.r the crater had formed.

(I) Howard K.A. and Masursky H. (1968) U.S.G.S. Map 1-566. (2) Car;" M.H. (1969) U.S.G.S. Map

1-599. (3) Head J.W. andWilson L (1979) P_ JOth, pp. 2861-2897. (4) Wilson L. and Head J.W. (1981)

J.G.R., 78, 2971-3001. (5) Gaddls L.R., Pieters C.M., and Hawke B.R. (1985) Icarus, 81, 461-489. (6)

Coombs C.R., Hawke B.R. and Gaddls LR (1987)LPSC XVIII, pp. 197-198. Lunar and Planetary Institute.

Houston, TX. (7) Hawke B.R. Coombs C.R., Gaddis L.R., Lucey P.G. Owensby P.D. {1989) P_ 19th, pp.

255-268. (8) Coombs C.R., Hawke B.R-, Lucey P.G., Head J.W. (1989) _ XX, pp. 185-186. (9) Hawke B.R.

• Lucey P.G., BelIJ.F., Owensby P.D. (1985) _XV/, pp. 329-330. (10) McCord T.B., Clark R.N., Hawke

B.R. McFadden L.A., Owensby P.D. (1981) J. G.R., 86, 10883-10892. (I l) Singer R.B. (1981) J.G.R., 86,

7987-7982.
28

PRISTINE LUNAR GLASSES: A 'WINDOW' INTO THE MOON'S MANTLE. J.W. Delano,

Dept. of Geological Sciences, State University of New York, Albany, NY 12222

Pristine lunar glasses are a suite of twenty-five, high-Mg magmatic compositions that were erupted onto the Moon's surface in fire fountains [e.g.

1-3]. Since these magmas appear to be geochemically less evolved than the

crystalline mare basalts [e.g. 4-7_, they provide our best 'window' into the

Moon's mantle. Specific constraints are furnished on the followin E topics:

(a) oxidation state of the Moon's mantle [e.g. 8]; (b) compositional heterogeneity of the Moon's differentiated mantle [e.g. 6]; (c) depths of mare

source-regions [e.g. I0,Ii]; (d) residual mineralogy in mantle source-regions

[6,10,11]; (e) composition of the Moon [12]; and (f) the possible role of

melt/solid density-crossovers in the Moon's geochemical evolution [9].

Oxidation State of the Moon's Mantle

Although the lunar science community appears to implicitly believe that

the oxidation state of the Moon's mantle is strongly reducing, the most

careful study conducted thus far on pristine lunar glasses by M. Sato [8]

concluded something quite different. Sato [8] proposed that the oxidation

state of the lunar mantle may be controlled by the so-called 'graphite

surface' involving chemical equilibrium with C (graphite) + CO + CO 2 + 02 .

If correct, owing to the large pressure-dependence on this redox reaction

[e.g. 13-15|, the oxidation state prevailing in the source-regions of the

mare magmas at a pressure of about 20-25 kilobars [I0,II] would be near the

fayalite + magnetite + quartz (FMQ) buffer (highly oxidizing). Although

this hypothesis [8] has had major implications for the petrogenesis of mare

magmas, it has gone unchallenged.

The low abundance of Cr (<700 ppm) in terrestrial basalts (e.g. MORB's)

is known to be caused in part by the elevated redox states (~FMQ) in the

mantle source-regions. The Cr abundance of the melt is controlled by spinel

saturation [16]. Importantly, the Cr abundance in a mafic melt at spinel

saturation is known to be a function of temperature and oxygen fugacity.

For example, with decreasing oxidation state (at constant temperature), the

abundance of Cr in the melt required for spinel saturation increases sharply

[e.g. 17,18,19]. This raises a decisive question: If, as proposed by [8],

the lunar mantle at 20-25 kilobars is relatively oxidizing (~FMQ), why do

mare basalts and pristine glasses contain high abundances (~_000 ppm) of

Cr compared to terrestrial basalts? (Figure I) Experiments designed to

measure the Cr abundance in the melt at spinel saturation as a function of

temperature and oxygen fugacity in a pristine glass composition should

clarify this question bearing on the oxidation state of the lunar interior.

Isothermal (1260"C) subliquidus experiments have been perfor_ned on a

synthetic Apollo 15 yellow/brown volcanic glass composition [6,7] for a

range of oxygen fugacities. One hundred milligram pellets were suspended on

Pt-wire loops [e.g. 20] in a Deltech furnace where the oxygen fugacity was

controlled by CO + CO 2 gas mixtures and continuously monitored with a yttriadoped zirconia sensor. Equilibrium was verified based on reversibility of

the results plotted in Figure 2. Note that at constant temperature (1260°C),

the abundance of Cr in the melt at spinel saturation decreases by a factor

of 4 in the redox range between the iron/wustite (IW) and nickel/nickel

oxide (NNO) buffers. This is a manifestation of the marked change in

valence state of Cr occurring within that interval of oxygen fugacity [e.g.

21] from about 30% Cr (III) at IW to about 90% Cr (III) at NNO [e.g. 17].

The partitioning behavior of Cr between spinel and melt is therefore strongly

dependent on the valence state. These preliminary data from a lunar composi-
PRISTINE LUNAR GLASSES: Delano J. W.

tion (Figure 2) imply that mare magmas having Cr abundances of -4000 ppm

were derived from mantle source-regions having a low redox state, rather

than the high redox state proposed by Sato [8].

Compositional Heterogeneity of the Moon's Mantle

Petrologists have constrained the composition of a primary picritic MORB

(mid-ocean ridge basalt) that helps to better define the composition and

mineralogy of the Earth's upper mantle beneath mid-ocean ridges [e.g. 18,19].

This notion of one primary magma has proven successful largely due to the

limited compositional (major elements) variability in fertile regions of the

Earth's upper mantle. In stark contrast, the Moon's mantle appears to be so

heterogeneous that no one primary magmatic composition is universally applicable. Instead, the twenty-five pristine glasses, which span a remarkable

range from 0.4 to 16.4 weight % TiO2, are all primary magmas [6]. Continued

discovery of additional varieties of pristine lunar glass [e.g. 5] will

provide further constraints on the nature and causes of this extraordinary

variability in the lunar mantle.

REFERENCES: [I] Heiken et al. (1974) Geochim. Cosmochim. Acta, 38, p.

1703-1718; [2] Wilson and Head (1981) J. Geophys. Res., 86, p. 2971-3001;

[3] Gaddis et al. (1985) Icarus, 61, p. 461-489; [4] Longhi (1987) PLPSC 17,

p. E349-E360; [5] Shearer et al. (1989) Geochim. Cosmochim. Acta, in press;

[6] Delano (1986) PLPSC 16, p. D20I-D213; [7] Hughes et al. (1988) Geochim.

Cosmochim. Acta, 52, p. 2379-2391; [8] Sato (1979) PLPSC I0, p. 311-325;

[9] Delano (1989) PLPSC 20, in press; [i0] Green et al. (1975) PLPSC 6, p.

871-893; [ii] Delano (1980) PLPSC ii, p. 251-288; [12] Jones and Delano

(1989) Geochim. Cosmochim. Acta, 53, p. 513-527; [13] Brett and Sato (1984)

Geochim. Cosmochim. Acta, 48, p. 111-120; [14] French and Eugster (1965) J.

Geophys. Res., 70, p. 1529-1539; [15] Woermann et al. (1978) EOS, 59, p. 813;

[16] Langmuir et al. (1977) Earth Planet. Sci. Left., 36, p. 133-156; [17]

Barnes (1986) Geochim. Cosmochim. Acta, 50, p. 1889-1909; [18] Murck and

Campbell (1986) Geochim. Cosmochim. Acta, 50, p. 1871-1887; [19] Hill and

Roder (1974) J. Geol., 82, p. 709-729; [20] Donaldson et al. (1975) Amer.

Mineral., 60, p. 324-326; [21] Schreiber (1977) PLSC 8, p. 1785-1807; [22]

Green et al. (1979) The Earth: Its Origin, Structure, and Evolution (M.W.

McElhinny, ed.), p. 265-290. Academic Press, London; [23] Stolper (1980)

Contrib. Mineral. Petrol., 74, p. 13-27.

29

Cr'50

atomic

Ti ,10 Mg

3000

2500

2000

1500

1000

Jog f_(Iw)

40 30 20 I0

i I I

+

+

÷#

O0

500;, 0 ' I , I _ 1 , I

8O, 90 IO0 riO...,

NNO wu Iw

-log fOz at t260"C

Figure I Figure 2
3O

PRISTINE MARE GLASSES AND MARE BASALTS: EVIDENCE FOR A GENERAL

DICHOTOMY OF SOURCE REGIONS. $.W. Delano, Department of Geological Sciences

State University of New York, Albany, NY 12222

Mare volcanic (i.e. pristine) glasses are generally regarded as being

better candidates for primary, mantle-derived magmas than most, if not all,

of the crystalline mare basalts rl]. Although this might be taken to imply

that the crystalline mare baslats are fractional differentiates from high-MgO

parental magmas represented by the pristine glasses, such does not appear to

be the case [2-4]. Despite general similarities between calculated differentiates from pristine glasses and mare basalts [5, 6], no mare basalts can

yet be attributed to any of the pristine glasses via low-pressure crystal/

liquid fractionation [2-4]. While this may only indicate that mare basalts

have been subjected to fractionation processes that were more complex than

the low-pressure crytal/liquid differentiation that has been modelled, other

possibilities exist. For example, the picritic magmas represented by the

pristine glasses may have been derived from different regions of the lunar

mantle than those magmas represented by the majority of mare basalts in the

present sample-collection. This hypothesis seems to be supported by the

relationships illustrated in Figure I. Mare basalts (open circles) define

two main trends on this diagram of Sc vs FeO. Most mare basalts (Apollo 14

groups 1-5; Apollo 17 VLT; Apollo II high-Ti basalts A, El, B2, B3, D;

Apollo 17 high-Ti basalts A, B, C; and Apollo 12 hiEh-Al mare basalt) plot

alone a high-Sc trend in Figure I. The other group of mare basalts (Apollo

12, 15, and Luna 24 low-Ti) have a FeO/Sc ratio close to a value of 5400.

Note that all of the pristine mare glasses (black boxes) analyzed thus far

[4-7] also occur in the same grouping as the Apollo 12, 15 and Luna 24 low-Ti

magmas. Each of the two groupings of mare magmas in Figure 1 contain lowand high-Ti compositions. Since experimental pertrology suggests that

olivine ± clinopyroxene were the sole residual phases in most, if not all, of

the mantle source-region s for mare magmas, the bulk partition coefficients

for FeO and Sc during partial melting may have been near unity. If so, the

dichotomy apparent in Figure 1 was inherited from the mantle sources, in

which the majority of mare basalts came from different reservoirs than the

pristine glasses. Hubbard and Rhodes [8] were the first to suspect this

relationship by noting that the Apollo 17 orange, high-Ti pristine glass

(74220) had a closer compositional resemblance to the Apollo 12 ilmenite

basalts than to the Apollo ii, 17 high-Ti mare basalts.

In summary, the picritic magmas represented by the pristine mare glasses

may have been derived from different mantle source-regions than the majority

of sampled mare baslats.

REFERENCES: [I] Delano J. W. (1986) PLPSC 16, p. D201-D213; [2] Longhi

(1987) PLPSC 17, p. E349-E360; [3] Longhi (1989), this volume; [4] Shearer

et al. (1989) Geochim. Cosmochim. Acta, in press; [5] Hughes et al. (1988)

Geochim. Cosmochim. Acta, 52, p. 2379-2391; [6] Hughes et al. (1989) PLPSC

19, p. 175-188; [7] Hughes et al. (1990) PLPSC 20, in press; [8] Hubbard and

Rhodes (1976) Lunar Sci-VII, p. 390-392.
3]

DICHOTOMY OF SOURCE REGIONS: Delano J. W.

E

c=.

(3

co

I00

8O

6O

4O

2O

0

O0

0

0

0 0

0

°o @

0 o

oo o

o

;2o7_;;oo •

0

i _lliil I-- 0 •

15 2O

FeO (wt. %)

25

PRISTINE GLASSES •

MARE BASALTS 0
32

THERMODYNAMIC MODELS OF TRACE METAL AND VOLATILE ELEMENT TRANSPORT

BY LUNAR VOLCANISM Bruce Fegley Jr. and Derrick Kong, Department of Earth, Atmospheric and

Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139

Introduction. In this abstract, we present preliminary results of the first set of comprehensive chemical

equilibrium calculations on the gas phase chemistry of trace metals and volatile elements (e.g., B, C, F,

Na, S, CI, Cu, Zn, Ga, Ge, Br, Ag, Cd, In, Sb, Te, I, Au, Hg, TI, Pb, Bi, etc.) associated with lunar

glasses (1). These results are important for identifying the major gas phase species of these elements and

for modelling the transport mechanisms for trace metals and volatile elements in lunar volcanic gases.

Calculations. A revised and expanded version of the TOP20 code was used for the ideal gas chemical

equilibrium calculations. This code uses the dual constraints of mass balance and chemical equilibrium

to solve the molecular composition (at a specified temperature, pressure, and set of elemental atomic

abundances) of a gas phase containing over 1000 gases of over 70 elements. The thermodynamic data used

in the calculations come from standard compilations such as the JANAF Tables (2,3). The computational

method used in the TOP20 code has been schematically described by Barshay and Lewis (4).

Results. A preliminary subset of our results for the gas phase chemistry of sulfur, copper, sodium, and

potassium is illustrated by the figures on the next page. These calculations were done at a total pressure

of 1 bar and with an "average" terrestrial fumarolic gas composition having the following normalized

elemental atomic abundances: N=l.0, F=6.8, S=21.8, C1=36.1, C=163, O-3982, and H'-7417. The Br

and I elemental abundances were determined by assuming C]/Br and Cl/I atomic ratios appropriate for

seawater (5). The abundances of other elements such as copper, sodium, and potassium were deliberately

set at 1 part per billion. By doing this, their chemistry can be calculated without affecting the overall mass

balance of the gas phase.

Discussion. An important result of the calculations is that halides are important species for the

transport of metals such as copper, sodium, and potassium. This is also true for several other metals

including Fe, Mg, Ca, Ni, Ti, Cr, Mn, and Co. For copper, sodium, and potassium, a chloride is tile

dominant gas over a wide temperature range. The elemental abundances of the other halogens (F, Br, I)

will be an important factor for determining the relative importance of gaseous bromides, fluorides, and

iodides. A second important result is that more complex species such as dimers and trimers become

important at low temperatures (e.g., see the graphs for copper and potassium). If no A1 remains in the gas

at: low temperatures, dimeric halides will also be the dominant sodium-bearing gases. Third, the oxidation

state of this assumed gas composition becomes more reducing at lower temperatures. This is reflected by

the decreased abundances of oxidized sulfer gases and by the increased abundances of reduced sulfur gases

at low temperatures.

Summary. Preliminary idea] gas chemical equilibrium calculations illustrated here show that even in

water-rich gases, ha]ides are an important species for the transport of metals including Cu, Na, and K.

Calculations done with drier assumed volcanic gas compositions reinforce this conclusion.

Acknowledgements. This work was supported by grants from the NASA Planetary Materials and

Geochemistry Program and the Planetary Atmospheres Program to MIT. The MIT UROP Program also

provided partial support for DK.

References. (1) J.W. Delano 1986 Proc. lath LPSC d. Geophys. Res. 91, D201-D213, (2) JANAF

Tables 3rd. edition, (3) Thermodynamic Properties of Individual Substances, 4 vols., High Temperature Institute, Moscow, USSR, (4) S.S. Barshay and J.S. Lewis 1978 Icarus 33 593-607, (5) Handbook of Chemisfr v

and Physics, 55th ed., p. F190.
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34

REMOTE SENSING AND GEOLOGIC STUDIES OF LUNAR DARK MANTLE DEPOSITS: A

REVIEW. B. R. Hawke, Planetary Geosciences Division, Hawaii Institute of Geophysics, University of Hawaii, Honolulu, I-fl 96822.

INTRODUCTION: In recent years, interest in lunar dark mantle deposits of pyroclastic origin has

dramatically increased. Dark mantle deposits are low-albedo surface units that mantle and subdue subjacent

terrain. They vary in area from a few square kilometers for those surrounding endogenic clark halo craters to tens

of thousands of square kilometers for the extensive regional deposits. In the pre-Apollo era, opinions differed

concerning the nature and origin of dark mantle deposits. Some correctly suggested that the dark haloes

surrounding certain small, irregular craters were produced by explosive volcanism. However, the regional dark

mantle units were often interpreted as dark facies of basin ejecta or as dark volcanic constructs. A variety of

pyroclastic debris was returned from the Apollo landing sites. Intensive study of these samples, e.g., 1, 2, 3, as

well as remote sensing and geologic studies of dark mantle deposits during the post-Apollo era e.g., 4, 5, 6, 7

have resulted in a greatly improved understanding of explosive volcanism on the Moon. In the past decade,

almost all lunar scientists have accepted the pyroclastic origin of dark mantle deposits 7, 8, 9.

Two genetically distinct types of pyroclastic deposits have been recognized on the lunar surface: regional and

localized 8. Compositions, eruption mechanisms, and emplacement styles for both regional and localized dark

mantle deposits have been determined, based on their distribution, geometry, and source vent morphology as

well as a variety of remote sensing data 7,8,9. These remote sensing data included near-infrared reflectance

spectra, multispectral images, albedo maps, 3.8- and 70- cm radar images, and Apollo orbital geochemistry data.

The purpose of this paper is to summarize the results of remote sensing and geologic studies of lunar dark

mantle deposits and to present an overall picture of explosive volcanism on the Moon.

REGIONAL DARK MANTLE DEPOSITS: Regional dark mantle deposits ('RDMD) cover many thousands of

square kilometers and are generally considered to be the products of ftre-fountaining that occurred in association

with basaltic eruptions e.g., 1,8,9. These regional pyroclastic deposits commonly occur in lunar highlands areas

adjacent to many of the major maria; their emplacement may have been associated with some of the early

mare-filling volcanic episodes 10,11. Depressions at the heads of associated sinuous rilles and other related

irregular depressions are the probable source vents for the RDMD e.g., 9,12. Characteristically, the regional

pyroclastic deposits are low-albedo (0.079 - 0.096 13) units that appear to cover and subdue the features of the

underlying terrain. Visual observations as well as photographs obtained during the Apollo missions indicated

that the surfaces of lunar pyroclastic deposits are very fine-textured and exhibit an extremely smooth, velvety

appearance 14,15,16. All of the RDMD exhibit very weak to nonexistent echoes on the depolarized 3.8- cm

radar maps ofZisk et al. 17. A lack of surface scatterers (rocks, blocks, etc.; 1-50 cm in size) is believed to be

responsible for the low radar returns 4,9,12.

The material which comprised a major regional pyroclastic deposit was sampled at the Apollo 17 landing

site. One of the major objectives of the Apollo 17 mission was to characterize the "dark mantle" unit at the

site; premission analysis had indicated that this was a relatively young deposit of pyroclastic origin 5,6,9,15.

After the mission, it was considered surprising that no obvious evidence was found of a young dark mantling

material component in the returned samples 6. The regolith samples collected from the Iow-albedo unit on the

valley floor are composed largely of ancient (-3.76 b.y.) high-titanium mare basalt 18. However, subsequent

research identified the orange glass droplets and the chemically - equivalent, partially crystallized black spheres as

pyroclastic components in the Apollo 17 soil 1,5,6. The chemical compositions of the orange and black

spheres are indistinguishable, the only difference being that the black spheres are largely crystallized. The

quench-crystallized black spheres are rich in TiO2 (9 - 10%) and ilmenite and they are similar, though not

identical, in composition to the Apollo 17 mare basalts. The pyroclastic debris is slightly younger (-3.6 b.y.)

than the mare basalts at the site (-3.7 - 3.8 b.y.) 18.

Although the orange and black pyroclastic spheres are not abundant at the Apollo 17 site, there is a

major regional pyroclastic deposit (Taurus-Littrow dark mantle deposit) just over 50 km west of the site. A

comparison of reflectance spectra obtained for the Taurus-Littrow dark mantling deposit (DMD) with laboratory

and telescopic reflectance measurements have demonstrated that the Apollo 17 black spheres are the characteristic

ingredient of the Taurus-Littrow pyroclastic mantling deposit 4,5,6,9,19. The thickest part of the

Taurus-Littrow DMD has an areal extent of just over 4000 km2. However, the thinner portions of the deposit

blanket a much larger area. Both geological and radar studies of the Taurus-Littrow DMD indicate that the core
Lunar Dark Mantle Deposits

Hawke, B.R.

35

portion of the deposit has a thickness of many tens of meters. The deposit exhibits very weak to nonexistent

echoes on the depolarized 3.8-cm radar maps produced by Zisk et al. 17. These very low depolarized radar returns

are generally attributed to the lack of scatterers (1-50 cm) on the smooth surface of the pyroclastic mantling

deposits 4,9,17. A very low degree of small-scale surface roughness and a relatively block-free surface are

indicated. Areas of enhanced-return, high-albedo material exposed by small impact craters which have penetrated

this pyroclastic mantling unit are very rare. The 70-cm radar data obtained by Thompson 20 shows that the

Taurus-Littrow DMD is deficient in large (-1-2 m) blocks.

Several other major occurrences of regional pyroclastic mantling deposits have been documented 9,21

including those at the following locations: Rima Bode, Aristarchus Plateau, Sulpicius Gallus, Montes

Harbinger, southern Sinus Aestuum, southwestern Mare Humorum, and southern Mare Vaporum. These units

have been characterized as extensive deposits of low-albedo (0.079-0.096) material which appear to subdue and

mantle underlying terrain, are relatively fine-textured, and exhibit a smooth, velvety appearance. The low

returns on Earth-based 3.8-cm depolarized radar back scatter maps conf'trrn these observations of mantled areas

and indicate an absence of surface scatters in the 1 to 50-cm size range. The surfaces of the regional pyroclastic

deposits are rock-free.

Spectral reflectance studies have provided important information concerning the composition of regional

pyroclastic (DMD) deposits 8,9,10,22. Near-infrared spectra for a large number of regional pyroclastic deposits

were obtained at the 2.2-m University of Hawaii telescope facility on Mauna Kea, Hawaii. As discussed above,

the Taurus-Littrow DMD is dominated by ilmenite-rich black spheres. The spectra obtained for the Rima Bode

pyroclastic deposits are almost identical to those collected for various positions of the Taurua-Littrow deposit.

A similar composition is indicated. The reflectance and continuum-removed spectra obtained for the DMD on

the Aristarchus Plateau and southwest of Mare Humorum exhibit broader, longer-wavelength absorption bands

than those which can be attributed to pyroxenes alone in highland and mare soils. As noted by Gaddis et al.9

and Lucey et al. 22, there must be additional Fe-bearing soil components which have both modified the "1

band" and maintained the low albedo of the materials observed. The presence of Fe2+-bearing volcanic glasses

in the mantling deposits from which the spectra were obtained is most consistent with the available spectral

evidence 9,19,22. The A_ristasrchus Plateau and Mare Humorum pyroclastics appear "red" (low 0.40/0.56 _rn

values) in multispectral images 12,22,24.

The UV-VIS spectra (0.3-1.11am) presented by Pieters et al.4, 6 and Adams et al.5 have demonstrated that

several DMD on the lunar nearside contain a significant component of ilmenite-rich spheres of pyroclastic

origin. These include the following deposits; 1) Taurus-Littrow, 2) Rima Bode, 3) Southern Mare Vaporum,

and 4) Southern Sinus Aestuum. The spectra (0.3-1.1 l.tm) for all of these deposits exhibit similar

characteristics. For example, they exhibit very high 0.40/0.56 lain values and the deposits appear "blue" in

0.40/0.56 lain multispectral ratio images presented by Pieters et al.6 and McCord et al. 23.

As mentioned previously, all of the regional pyroclastic deposits exhibit very low values on depolarized

3.8-cm radar images 4,9,12,17. Low values are also commonly seen on 70-cm radar images 20. 3.8-cm and

70-cm radar demonstrate that the regional pyroclastic debris is apparently unweided or annealed. Otherwise,

small craters in these dark mantle deposits would have excavated welded blocks. The deposits cover very large

areas (up to 30,000 km2) and both geologic and radar data indicate that the '._ve thicknesses of tens of meters.

Most of the regional pyroclastic deposits overlie highlands terrain but _ /ew (e.g., Taurus-Littrow) were

emplaced on a mare substrate.

The results of studies conducted by Head and Wilson 12,26 indicated that RDMD are likely to have been

produced by eruption conditions such as those characteristic of strombolian or continuous eruptions, and that it

is unlikely that these extensive dark mantle units are the results of coalescing deposits of localized pyroclastics

(i.e. Alphonsus-Type dark halo craters). The results of their calculations indicate that the lunar equivalent of

strombolian activity is likely to lead to the dispersal of pyroclasts over a wide area, with extreme sorting of

particles. More specifically, clasts greater than a few centimeters in diameter would remain within several tens

of meters of the vent, while clasts much smaller than 1 mm may be projected for many tens to hundreds of

kilometers.

LOCALIZED DARK MANTLE DEPOSITS: Localized lunar dark mantle deposits _LDMD) are small (typically

<250-550 kin2), low-albedo units of pyroclastic origin that are commonly located in the floors of large Imbrian

to pre-Imbrian-aged (i.e., >3.4 b.y.) impact structures and are concentrated around the perimeters of the major

lunar maria 8, 9, 25, 26, 27, 28, 29. These deposits, typified by the Alphonsus dark halo craters, are generally
36 Lunar Dark Mantle Deposits

Hawke, B.R.

associated with endogenic dark halo craters within large highland impact craters. Characteristically, these dark

halo craters are small in size (>3 km), aligned along crater floor fractures, have a noncircular shape, and lack

obvious rays. The source craters are surrounded by peripheral deposits of smooth, block-free, low-albedo

material that composes the dark halo. Though endogenic dark halo crater deposits are by far the most common

mode of occurrence of LDMD, other types of localized deposits have also been identified. These include deposits

found (1) as isolated patches in the highlands _ith no obvious source vents, (2) as isolated patches on the

maria, and (3) as isolated patches in the highlands adjacent to the mare deposits. The source vents for these

deposits may have been obscured by pyroclastic debris or by flooding with mare basalt. Sizes of the LDMD

vary. Individual (i.e., from one source vent) LDMD typically are <100km2, while larger coalesced LDMD are

in general <1000 km2 (most fall between 250-550 kin2). A few exceptional deposits are as large as 2100 kin2.

This variation in size is in pan a result of the number of coalesced deposits at each locality.

Morphometric analyses of these "haloes" and their associated source vents have led investigators to

suggest an eruption mechanism for the LDMD analogous to that of terrestrial vulcanian explosive eruptions 25

In this style of eruption, the accumulation of gas in a capped magma body leads to explosive decompressionl

and the subsequent emplacement of a pyroclastic deposit around an endogenic source crater. It has been shown

that for these types of eruptions, the maximum range of all pyroclasts much larger than 1 cm is up to 4 km,

while smaller clasts may be thrown up to tens of kilometers, leaving a well-defined division between the

localized deposits of coarse clasts and the widely dispersed deposits of small clasts 25, 26.

Although LDMD may be genetically related and they exhibit many morphologic similarities, spectral

reflectance studies have shown that they are spectrally, thus compositionally distinct 7,8,27,30. Three general

compositional types of LDMD have been identified on the basis of the depth, center and overall shape of their

~l.0-I.tm absorption features as well as their continuum slopes. The spectral characteristics of the various

groups are discussed in detail below.

Group I

Spectra. This group includes spectra from the Grimaldi pyroclastics, the Franklin dark floor deposits,

the Atlas dark halo craters, the dark Archimedes south rim deposits, and the pyroclastics on the eastern edge of

Mare Nectar'is. Spectra for these deposits exhibit 1.0-l.tm absorption band centers near 0.93-0.95 lain and the

depths are approximately 4-5%. These bands are asymmetrical and have been described as "checkmark-like,"

with a straight, steep short-wavelength edge followed by a shallower straight long-wavelength edge 7. Some

spectra in this group exhibit relatively steep continuum slopes. These Group I spectra are similar in many

ways to those obtained for typical lunar highlands areas. The Group 1 band parameters indicate the presence of

feldspar-bearing rocks with mafic assemblages that are dominated by orthopyroxene. Although major amounts

of highland material are present in Group 1 LDMD, the relatively broad, asymmetric, and shallow "l.0-1am"

bands indicate the presence of one or more additional components such as volcanic glass, olivine, or

clinopyroxene.

Additional information about these deposits is provided by multispectral and albedo images of Group 1

deposits. The 0.40/0.56 lain images indicate that both the Atlas and the Franklin pyroclastic deposits are "blue"

(high 0.40/0.56 l.tm values) relative to the surrounding highlands. In addition, these pyroclastic deposits have

very low visible albedoes. This evidence indicates the presence of an exotic, nonhighlands component in these

deposits. Based on all the available information, it seems likely that Group I pyroclastic deposits are composed

of a mixture of highlands-rich wall rock and glass-rich juvenile material with lesser amounts of basaltic caprock

material. The available spectral evidence indicates that the deposit composition does vary from place to place on

the lunar surface. In fact, some Group 1 deposits (e.g., Archimedes south rim) exhibit low ("red")

0.40/0.56-1am values in the multispectral data set 31. It is clear that this group is very complex and that

additional research will be required to fu/ly understand the composition and origin of all members.

Geology. The geology of two Group 1 members is very similar to the other deposits included in this

group. Both Atlas and Franklin floor pyroclastic deposits are associated with vents that occur along fractures on

the floor of the craters. The Franklin floor deposit appears to be associated with a series of aligned elongate

craters on the eastern side of the crater floor 7. The dark mantle material covers a horseshoe-shaped area

approximately 20-40 km wide by 45 km long. This post-lmbrium deposit was emplaced during a late stage of

volcanic activity in the Geminus region of the Moon. Pyroclastic deposits also cover a portion of the floor of

Atlas, another Imbrian-aged impact crater. These deposits also occur around vents that are associated with a

series of floor fractures in the interior of the crater. Two separate deposits were formed in the crater, one in the
Lunar Dark Mantle Deposits

Hawke, B.R.

south and one in the north. Both of the deposits are roughly 25 km in diameter. The southern dark mantle

deposit is the more pronounced of the two and is associated with an elongate vent (7 km by 5 km) near the

intersection of three major floor rille systems. Dark mantling material extends up to 14 km away from the

southern vent.

Group 2

Spectra. The group comprises spectra from LDMD east of Aristoteles 1 and 2, Rima Fresnel

pyroclastics, and Vitruvius floor. As apparent in the spectra of the LDMD east of Aristoteles 1 and 2, these

"l.0-i.tm" bands are centered at or beyond 0.96 lain. These bands are deeper (7%) and more symmetrical than

those in Group 1. These absorption bands indicate the presence of Ca-rich clinopyroxene. Group 2 spectra

closely resemble those obtained for mature mare areas (e.g., McCord et al32), and the deposits in this group

contain very large amounts of mare basalt.

Multispectral ratio maps show that most of the Group 2 deposits exhibit low (red 0.40/0.56-lam values

and relatively high 0.95/0.56-1am ratios. These deposits appear to be dominated by fragmented basaltic plug

rock material with much lesser amounts of highlands debris and juvenile material present. In at least one

instance (east of Aritoteles 2) basaltic wall rock may be a major component in the deposit because one of the

two major vents is located in the mare.

Geology. The Rima Fresnel LDMD mantles portions of the Apennine Bench formation and adjacent

highlands north of the Apollo 15 landing site. The irregularly shaped deposit covers an area of more than 2120

km2. The distribution pattern, irregular shape, and relatively large extent of this deposit suggest that several

source vents may have been responsible for its formation. One source for this deposit is probably an irregularly

shaped volcanic crater situated at the junction of Rima Fresnel II, another smaller rille, and a lineament (28 °

252q, 3o 55'E). However, if this feature is the sole source vent, it is not clear why the dark mantle is

asymmetrically distributed around the crater, with the vast bulk of the material occurring to the east. This

asymmetry could be due to partial vent blockage31. Alternatively, some of the deposit may have been erupted

from fissure vents associated with faults along Rima Fresnel 1. The mare-type signature of this deposit is

probably due to the explosive eruption of basaltic plug rock in association with the mare-filling episode of

Imbrium basin.

Two separate localized dark mantle deposits were identified and described in the region east of

Aristoteles21,28,33. The westernmost deposit (east of Aristoteles 1) is roughly circular and covers a highland

area about 45 km in diameter. This LDMD is centered around a northwest-southeast trending chain of endogenic

craters; several of these craters appear to have been the source vents for the pyroclastic material. The major vent

in this chain measures 4x7 kin. The easternmost LDMD (east of Aristoteles 2) is more complex and irregular

in shape. This deposit is elongate (-20x40 km) and is superposed on both mare and highlands terrain. Three

distinct endogenic crater chains are located in the dark-mantled area. Based on deposit geometry, two large

irregular craters appear to have been the primary source vents for the bulk of the pyroclastic debris 7. One is

located in Mare Frigoris and the other is in the adjacent highland terrain. It should be noted that the source vent

in the mare would have ejected basaltic wall rock during the explosive er_'gdon that emplaced a portion of the

LDMD.

Group 3

Spectra. A typical spectrum for Group 3 is that obtained of the J. Herschel pyroclastics. Other spectra

included in this group are from four separate pyroclastic deposits: three on the floor of Alphonsus crater 34 and

one on the south flank of Cruger crater35. These spectra have moderately deep (5-7%), broad, and asymmetrical

absorption bands in the "l.0-_m" region. These bands are clearly composite features with centers at or beyond

1.0 lain. A quantitative analysis of the "l.0-1am band in the J. Herschel deposit spectrum presented by McCord

et al32 indicated that this feature could best be explained by a mixture of olivine and orthopyroxene. While in

theory this band could be produced by the combination of clinopyroxene, orthopyroxene, and Fe2+-bearing

glass, additional band analyses have indicated that this is unlikely. The other members of Group 3 may also

contain material rich in olivine and pyroxene. While the basaltic plug rock could be the source of some of the

olivine, the very high olivine abundance indicated by the spectral data requires another source. The bulk of this

olivine was almost certainly emplaced with the juvenile material. It also seems likely that the bulk of the

orthopyroxene in the J. Herschel deposits was present as a component in the highlands-rich wall rock and that it

37
38 Lunar Dark Mantle Deposits

_awke, B.R.

was eroded and emplaced during the J. Herschel eruption. Spectral data obtained for adjacent highland deposits

indicate that the dominant mafic mineral present is orthopyroxene. No evidence for olivine was found in the spectra of these highlands units.

In summary, the J. Herschel pyroclastic deposit is dominated by olivine and pyroxene. The olivine was

emplaced with the juvenile material and the bt:lk of the orthopyroxene was emplaced as a component in the

highlands-rich wall rock. The basaltic plug rock could have contributed minor amounts of olivine and pyroxene. Some pyroclastic glass may be present.

Geology. A major deposit of dark mantling material is located on the eastern side of the floor of J.

Herschel crater. This deposit was f'trst identified by Ulrich36. Here, low-albedo material drapes and subdues

subjacent highland terrain. Like certain others, this deposit is associated with a major rille system on the floor

of the crater. The rille itself appears to be composed, at least in part, of coalesced craters of endogenic origin.

Four of these craters appear to have been the major sources of the dark mantling material now spread over the

eastern floor of the crater. Vent diameters range in size from 4-8 km with the dark mantling deposit covering an

area approximately 60 km by 35 km. The other endogenic craters associated with this rille complex may have

been formed by the drainage of debris into the subsurface along fauhs7.

The 118-km-diameter crater Alphonsus is located in the highlands of the central nearside. Scattered about

the perimeter of the floor are 11 endogenic dark halo craters, each of which is associated with a floor fracture or

series of fractttres34. Several pyroclastic deposits exist in the Cruger region35. The largest of these units is

located on the southern rim of Cruger crater. This deposit covers an area of roughly 760 kin2. The major

portion of the deposit is a tongue-shaped feature that extends straight south from the crater rim. A narrow finger

of dark mantle material extends eastward of the main deposit No source vents have been positively identified

for shapedthis deposit. deposit, but it is possible that several vents were responsible for emplacing such a large, irregularly

Different depths for the location of the plug rocks may be at least in part responsible for the

compositional differences among the various LDMD groups7. For example, the highlands-rich deposits of

Group I suggest that a thin plug rock formed under a thick overburden of highlands material. Likewise, the

mare-like composition of the Group 2 deposits suggests the presence of a thicker plug rock at a shallower depth,

or that lesser amounts of highlands overburden existed above the conduit prior to the eruption. The mare-like

deposits of Group 2 may also have been formed by the eruption of an excessive amount of mare-type material.

In addition, in those instances where the source vent formed in preexisting mare terrain (e.g., east of Aristoteles

2), the wall rock emplaced in the pyroclastic deposits would be expected to be composed largely of mare basalt

The abundant olivine component in the Group 3 deposits might be explained in several ways. These include the

following (1) the olivine may have existed in the form of phenocrysts in the magma and been emplaced with the

juvenile material upon eruption, (2) the olivine now exists as devitrified glass in the localized pyroclastic

deposits, (3) olive-rich mantle inclusions might have been present in the melt and now could be found as

plug xenoliths in the pyroclastic deposits, and/or (4) a small amount of olivine could be derived from the basaltic rock.

SUMMARY: Regional deposits are the products of s_'ombolian or continuous eruptions while localized

deposits are the result of vulcanian eruptions. Some regional deposits contain large amounts of Fe2+-bearing

glass while others are dominated by mixtures of black and orange spheres similar to those returned from the

Apollo 17 landing site. Localized pyroclastic deposits exhibit three distinct compositions. The f'trst group is

dominated by highlands debris and a dark juvenile component The second group is composed largely of basaltic

caprock material with much lesser amounts of highlands-rich wall rock and juvenile material. The f'mal group is

dominated by a mixture of olivine and pyroxene. Based upon their compositions, it is very unlikely that

regional pyroclastic deposits are the result of coalesced localized dark mantle deposits. Both regional and

localized deposits exhibit low-radar returns (3.8-cm), have smooth surfaces and low albedoes. A strombolian or

continuous eruption origin of lunar regional pyroclastic deposits is consistent with the characteristics of the

volatile-coated spheres returned from the Apollo 17 landing site. The lack of associated lava flows and the small

radial extent of the dark-haolos (3-5 kin) around the localized dark mantle deposits suggests that they were

formed during a short-lived (vulcanian) explosive eruption.
Lunar Dark _L_ntle Deposits

Hawke, B.R.

39

REFERENCES

1. Heiken G. H., McKay D. S., and Brown P. W. (1974) Lunar deposits of possible pyroclastic origin.

Geochim. Cosmochim. Acta, 38, 1703-1718.

2. Delano J. W. (1979) Apollo 15 green glass: Chemistry and possible origin. Proc. Lunar Planet. Sci.

Conf. lOth, pp. 275-300.

3. Delano, J. W. (1986) Pristine lunar glasses: Criteria, data, and implications. Proc. Lunar Planet. Sci.

Conf. 16th, in J. Geophys. Res., 91, D201-D213.

4. Pieters C. M., McCord T. B., Zisk S. H., and Adams J. B. (1973) Lunar black spots and the nature of the

Apollo 17 landing area. J. Geophys. Res., 78, 5867-5875.

5. Adams, J. B., Pieters C. M., and McCord T. B. (1974) Orange glass: Evidence for regional deposits of

pyroclastic origin on the Moon. Proc. Lunar Sci. Conf., 5th, pp. 171-186.

6. Pieters C. M., McCord T. B., Charette M. P., and Adams J. B. (1974) Lunar surface: Identification of the

dark mantling material in the Apollo 17 soil samples. Science, 183, 1191-11194.

7. I-Iawke B.R., Coombs C.R., Gaddis L.R., Lucey P.G., and Owensby P.D. (1989b) Remote sensing and

geologic studies of localized dark mantle deposits on the Moon. Proc. Lunar Planet. Sci. Conf. 19th,

pp. 255-268.

8. Coombs C.R. and Hawke B.R. (1989) Explosive volcanism on the Moon: A review. Proc. Kagoshima

Int'i Conf. on Volcanoes, Kagoshima, Japan, pp. 416-419.

9. Gaddis L.R., Pieters C.M., and Hawke B.R. (1985) Remote sensing of lunar pyroclastic mantling

deposits. Icarus, 61,461-489.

10. Howard K.A., Cart M.H., and Muelberger W.R. (1973) Basalt stratigraphy of southern Mare Serenitatis.

Apollo 17 Preliminary Science Report, NASA SP-330, pp. 29-1 to 29-12.

11. Head J.W. (1974) Lunar dark-mantle deposits: Possible clues to the distribution of early mare deposits.

Proc. Lunar Sci. Conf. 5th, pp. 207-222.

12. Zisk S.H., Hodges C.A., Moore H.J., Shorthill R.W., Thompson T.W., Whitaker E.A., and Wilhelms

D.E. (1977) The Aristarchus-I-Iarbinger region of the Moon: Surface geology and history from recent

remote-sensing observations. The Moon, 17, 59-99.

13. Pohn H.A. and Wildey R.L. (1970) A photoelectric-photographic study of the normal albedo of the Moon.

U.S. Geol. Surv. Prof. Pap. 599-E, Plate 1.

14. Cernan E.A., Evans R.E., and Schmitt H. (1972) Apollo 17 technical air-to-ground voice transcription.

MSC-07629.

15. Lucchitta B. K. (1973) Photogeology of the dark material in the Taurus-Littrow region of the Moon. Proc.

Lunar Sci. Conf. 4th, pp. 149-162.

16. Lucchitta B.K. and Schmitt H.H. (1974) Orange material in the Sulpicius Gallus formation at the

southwestern edge of Mare Serenitatis. Proc. Lunar Sci. Conf. 5th, pp. 223-234.

17. Zisk S.H., Pettengill G.H., Catuna G.W. (1974) High-resolution radar map of the lunar surface at 3.8-cm

wavelength. The Moon, 10, 17-50.

18. Taylor S.R. (1982) Planetary Science: A Lunar Perspective. Lunar and Planetary Institute Houston. pp.

481.

19. Hawke B. R., Coombs C. R., and Clark B. (1990) Ilmenite-rich pyroclastic deposits: An ideal lunar

resource. Proc. Lunar Planet. Sci. Conf. 20th, in press.

20. Thompson T.W. (1979) A review of Earth-based radar mapping of the Moon. Moon Planets, 20, 179-198.

Wilhelms D.E. and McCauley J.F. (1971) Geologic map of the nearside of the Moon. U.S. Geol.

Surv. Misc. Map 1-703.

21. Wilhelms D.E. and McCauley J.F. (1971) Geologic map of the nearside of the Moon. U.S. Geol. Surv.

Misc. Map 1-703.

22. Lucey P.G., Hawke B.R., Pieters C.M., Head J.W., and McCord T.B. (1986) A compositional study of the

Aristarchus region of the Moon using near-infrared reflectance spectroscopy. Proc. Lunar Planet. Sci.

Conf. 16th, in J. Geophys. Res., 91, D344-D354.

23. McCord T.B., Pieters C.M., and Feierberg M.A. (1976) Multispectral mapping of the lunar surface using

ground-based telescopes. Icarus 29, 1-34.

24. Pieters C., Head J. W., McCord T. B., Adams J. B., and Zisk S. (1975) Geochemical and geological units

of Mare Humorum: Defmition using remote sensing and lunar sample information. Proc. Lunar Sci.
40 Lunar Dark Mantle Deposits

Hawke, B.R.

Con:.6th,pp. 2689-2710.

25. Head LW. and Wilson L. (1979)Alphonsus-typedin'k-halocraters"Morphology, morphomelry and 25.

eruptionconditions.Proc.Lunar Planet.Sci.Co_. lOth,pp.2861-2897.

26. Wilson L.,and Head J.W. (1981) Ascent and eruptionof basalticmagma on the Earth and Moon. J. Geophys. Res.,78, 2971-3001.

27. Coombs C.R., Hawke B.R., and Owensby P.D. (1988) A recent survey of localized lunar dark mantle

deposits (abstract). In Lunar and Planetary Science X/X, pp. 209-210. Lunar and Planetary Institute, Houston.

28. Hawke B.R. and Head J.W. (1980) Small dark mantle deposits of possible pyroclastic origin: Geologic

setting, composition, and relation of regional stratigraphy (abstract). In Lunar and Planetary Science

XI, pp. 426-428. Lunar and Planetary Institute, Houston.

29. Hawke B.R., McCord T.B., and Head J.W. (1980) Small lunar dark mantle deposits of probable pyroclastic

origin. NASA TM-82385, pp. 155-157.

30. Lucey P.G., Gaddis L.R., Bell J.E., and Hawke B.R. (1984) Near-infrared spectral reflectance studies of

localized dark mantle deposits (abstract). In Lunar and Planetary Science XV, pp. 495-496. Lunar and

Planetary Institute, Houston.

31. Hawke B. R., MacLaskey D., McCord T. B., Adams J. B., Head J. W., Pieters C. M., and Zisk S. H.

(1979) Multispectral mapping of the Apollo 15-Apennine region: The identification and distribution of

regional pyroclastics. Proc. Lunar Planet. Sci. Conf. lOth, pp. 2995-2934.

32. MeCord T. B., Clark R. N., Hawke B. R., McFadden L. A., Owensby P. D., Pieters C. M., and Adams J.

B. (1981) moon: Near-infrared spectral reflectance, a first good look. J. Geophys. Res., 86, 10883-10,892.

33. Lucchitta B. K. (1972) Geologic map of the Aristoteles quadrangle of the Moon. U.S. Geol. Surv. Misc.

Map 1-725.

34. Coombs C. R. and Hawke B. R., Lucey P. G., Owensby P. D., and Zisk S.H. (1989) The Aiphonsus

region: A geologic and remote sensing perspective. Proc. Lunar Planet. Sci. Conf. 20th, in press.

35. I-Iawke B. R., Coombs C. R., and Lucey P. G. (1989) A remote-sensing and geologic investigation of the

Cruger region of the moon. Proc. Lunar Planet. Sci. Conf. 19th, pp. 127-135.

36. Ulrich G. E. (1969) Geologic map of the J. Herschel quadrangle of the Moon. U.S. Geol. Surv. Misc. Map 1-604.
41

IMPACT AND VOLCANIC GLASSES OF HARE FECONDITATIS. Yuequn JTN and

Lawrence A. TAYLOR, Dept. of Geological Sciences, Univ. of Tennessee,

Knoxville, TN 37996.

• " f lasses within the lunar soils have yielded significant

Investlgat1°ns-°--g_^*h the imnactin_ processes on the moon and the

informatlon regarulng u u# .... =r-n +he_r studies of thousanos o_ glasbu=

_etrogeneses. or mare Dasalts. oa_UrU s have nronosed 25 different types of

In lunar soils, uelanoran_1 _u_wu.[_=_ _o4_ _tu_ies were restricted to the

lunar volcanlc magmas t ,_J. ,.uw=_.=_, _ ....

sites visited b the A_ollo mlsslons. In an attempt to expand the global

coverage of studies on _unar samples and to search for possible new prlstine

m the moon etroKraphic examination and microprobe analyses of

magma types fro!_^les have Pbeen-performed in a Luna 16 sample fromsMc%rre

_lu g l.ass.pa_1_0_36 15 These analyses were undertaken in otter _o u_

recuno1_a_1_, -'_--" Mare Fecundltatis and to examine the impact glasses as

the arenKal magmas _uL -- -_- _;_ _.nn_nts. _our types O£ glabb

hes p might relate_ to provenance for >jtu ._b _ _'r._._ 7 thosit'-c noritetere identified [3]_: 1_ basaltic [33._7_o)b4z._%_.la_n_n_5 HASP t4] (0.9%).

troctolite) suite _b>.z_); _) masKe_ynt_e x

. none of the Luna 16 _lasses plots within the field of the Apollo Notice that • _- --_^ o_==es are more orimitive.

pristine glass types [F£g. I]; _,e _Fu_ s .... The'ANT suite glasses

_POLLOP'RISTINE .... plot well away from the

O 40

,e3o

_" 20

01o

o

_u_ss _VPES Fig. 1

".._ EE "r " ......,"" L_ \ 1_

...... -_-_"..... , LUNA --

,'_lJ • ^ J_. BULK SOIL

"" ......... L<:;;,.... -_ ",

;,_ _ ",,

_,A'_ A: HASP

AI_I I "_. L_ v_L_.. _ ._ _.:

..__..,,,...

LUNA 16 GLASSES _._" .... -_"_._

• PRISTINE :_.._ __._.._.._J

A IMPACT MASI'_I.YNITE

average bulk composition

of the soil, which has a

composition within the

b_saltic glass field [Fig

lJ. It is possible that

the ANT suite glass is

foreign to the Luna 16

landin_ site and could be

from t_e nearby highlands

i00 km to the East and to

the North, such as t2h_t

sampled by Luna

Alternatively, they could

be derived from the

highland materials excavated from beneath the

relatively thin mare lava

flows by meteorite bomcanic origin of the . _

If Ni is a contaminant from meteorzte

impact, the compositions should follow

the arrow in F_gure 2 (i.e., sidero- %

bile component). In fact; the Luna 16

;lass with the highest N_ content (97 _; _0 IMPACT

_pm) could be interprete_ as De_ng or

xmpact origin usinK this criterion.

The _rzstine g'iasses have similar ..... , , '

compositional ranges of FeO, TiO 2, CaO, 20 so _0o _o

and AI20o to those of Luna 16 b_saltic Ni (PPM)

fragment_ [5]. However, the majority

, , , , , bardment • Various criteria have

0 20 40 60 been applied in order to AI + CaO identi_¥ the prist_nl Y _ . of_the I16 glass parti-

• no and Livi [I] and Delano [2], pristine glasses cles. Accordlng to Dela __ . " A1 ratios but contain no

ntra sam le homogenelty and hl h M / ' " 0 A1 O ossess i - P • • • t_ose lasses w_th Ca / 3

P xotlc incluslons. 0n_y g

schlier, en and/or e ........ ;;=_od to have mare parentage [_] :

(weight) ratlo rea_er than 0.75 are uu ........

• . "teria for volcanic glass, fourteen particles ot

Applying the co_lect._ve_cr_:^_ +_ be _ristine. These pristine glass gr.a_n_

basaltlc glass were._geus_=_,kX _r_ ....._-_ _mes. AS nas been o_u_rrwere analy_ed forNl_bYiln°_%e_"_unSeCm%g_a"usu%ll_y behaves, as a llt_o%%_lae

b Delano [z_ _-= ,._ • • • • In _i ure z, _,e

e_ement and w_ll have a positive correlation w_th }{gO. g ,

16 ristine glasses occup_ a scattereO ',,ou_m,_,, ..... _"" _)

are p but generally tall algng ._ne _renc _ _,. _.._'" [3 /"

defined by the Apollo prlsr_.ne glass _ • o_ou,, f'"_ c_ _/

nd seem to extend, the _reno _ • o_ou_, ._ /"

types a o 1_w-M_O end. Ibis treno lS _ _..,-"_ _ _ /

LUW_._._ _,'_ T _ o 0 l-- O_' _"_'" _" cited as evidence to support the v /_--_ e [] /

Iour_een glasses. .- _" _"

S" _ [] .._..s"

•_ _ , i'" Fig. 2

• _ l../"/'

I_ • s..s "_""_

160
42

LUNA 16 IMPACT AND VOLCANIC GLASSES

JIN & TAYLOR

24 I t , I , I ' I • _ of _" " *

• ' one Prmqtlne glasses have hi_her M

_.3(a) contents. (7-12 wt._) a-A u__ .... gO

ratzos (0.4-0.7) th._"_'Z_/_Pg÷_e)

equiva ent °- one Izthic

20 /_'x So_I feb .)_Fi s (2-9. wt.% and 0.2-0.4,

"" Be\ " -r_sti g. 3(b)J. Inspection of the

O la • "_ . . . ne. glass cneml •

e "--.,-..;:.t s

"= Is _....--m.i........ __J_..*ne_broup A glass is char_c_'=_

"_'m/ "" " "....J wt.%). This ro . e ._I._.5-Y6._

"-'" F ........ g up_ zs szmtlar to _2 ecuno_catls Ty_Pe A Basalr;e c.1 ....

. ' oaKes et al. f61 _- ;-._r _-y_.- uf

, _ , I . I , i , i , i the GrA,,D A _-_ "" ._._urelat.lonsbl of

F-_ • =_.... _.--_ - _,_sses -_th the has P "

,4 • /mi th,. Ql_zlcult .to Olscern. Although alts is

• -.--.. - .." _-, enem cou,o .... _m= u_

12 .'_ e"_._\ ! ! _..-.''";, basaZts b- b e..p.arental to t_e. Luna 16

i i B !i - im ( ..--"_- m/" 3b]. otho-_ ...... ct_onatzon IFiR.

_ 1oj t \ A....=m_.....-"" . CaO'or Fe() vs_.'=_Acl'e(_emen_.PZPtS (e.gT,

n I " : "x _ -" oossibil;_ .... 2 3 / elzmznate this

s I I. "x... "'1_' _ [on-hi [_.__nowever., as poznted out by

• "'-.. o #, mOSE O¢ [ne A o11 • ,I Iglass t_'pes do not appearPto _)eV_°alrc2nntlc

4 I__ "- ...._..A AA """"x, ] G;o_; e A_°;lalstacSoaulltdS':uThiefref_re', "'C_e

A _'- from an J ably come

] _7,1 _. A x i_la . . unusual source wztl_ high

2 _ _ _ I .__ L__...... A_/ P, _gzoc.zase content. Without fur -

/ s_ I =_a.$ "'-'.--J'_ oata, this -ues _- ..... --_-ther

| , , , I, ' ' ' " ' ' l The Gr_'ou c_UUla%nn°r be resolved.

' ' P g ses are lower zn 1o 12 14 16 18 _ CaO and AI,Oo conr_-*_ (o o= ,^ . _

AI_ "_ and 8.64-I#0.o8 .._'_Y_ :_..÷--_u.? wt._

_'2v3 cpntent (17.3__0:_+" fu_,nl_ner. _n. FeO

similar om o " " the Grou A 1 -_.._ nan tnar oz

__ . __.P sztzons to those o _ F ....._._ _. P g asses (Fzg. 3_. They h ....

ec a_. [bJ. Ba_ __ .. _..=_-uuuzCaElS lvne B Ba=_+-^ ,_, _a ....

related to tho t_-_-_ uP _zgure O_b), it would an_ar +_,-_°2L%_- u _1⁄4ass ot Jak.es

as seen in the Ti0^-M.nsalts O szmple fract_onation of oi" g ses can be rra .... -._ _ut (FI . 4 " " . iv.lne. However

ctlonatlon Is required to ex-I _g- .2_' l..Imen_te or llmenlte + oliv{n_'

_rou_ _ glasses mav re-r ...... _ o__- _-u ,,_gn-zZ members. Th --_ oasalts in Mayo _i..-_-_.="_,-_."- u j_arental ma_mas _f _ .... .erefore, the

_L_ _ _ t_ -=_uuuxcauls _bl_b-Ti. Inw-T4 OLj _,_*._,,= v,rlo s t es of Lpe _,roup _ glasses nrobakl ..... _o.... . ---*, auu alumlnous eEC P the C r _.-_ _= _eueuc [wo or , ._. {ndeed,

..... roup A glass populatlon, t_ere arm -_+ _.more.magma types. Here, as with

uuuc±us_ons. - .... ouff_clent data to draw absolute

SUI_Ry: 1. More. than half of the glasses (AN suite) in the Luna 16 soil

sample under considerationd are foreign

to the Mare Fecunditatis and are im act

products of highland components; an_ 2.

It would appear that Mare Fecunditatis s

_en_C_:: _I_ata_ d

po_o samples. These

new ma_mas are unusual, cpmpared Delano s -rist; ....... to

_-__ • ='._ _,,_ _ass [zJ, bein

_>_gner zn AI20 _ (8:64-19.6 wt.% V g

4.6-9.6 wt.%) add C=O (9.2 _ ,= _ .s:,

vs. 6.27-9.40 wt.%) and lower in M 0 0

(8.51-14.4 wt.% vs. 12.1-19.5 wt.%_.

There is an obvious higher plagioclase

component to the Luna 16 magmas.

i i i i i i i i i i i i i i

Fig. 4 G_BGI. _ I_

,..,..

....

I ._ "" _ -'.%._.x \

Gr_Jp A

[ i i A i i l 1 , i i • I l i •

2 6 10 14

MgO

REFERENCES: [i] Delano J.W. & Livi K. (1981) Geochim Cosmochim Acta. 45, .

2137-2149: [2] Delano J.W. (1986) PLPSC 16th, JGR, 91 p. D201-213; [3] Jin

& Taylor £.A. (1989) LPS XX. p. 466-467. [4J Naney M._., Crowl D M & Pa ike

J.J. (1976) PLSC 7th P. 15_-184- [5 _urat G. et al. (1976 " " P

_-_; .[_. et al. (_972_ _ . ) eEOC 7th .

_yo>). £n worKsbo on Lunar v^1---3- _[_L' 13, [. 257-271; [7] Lon_h#

rotentlal Pp. xx-yy, -_._au_c _lasses: Scientific and Re_oJr_
43

MAPPING PYROCLASTIC DEPOSITS AND OTHER LUNAR FEATURES

FOR SOLAR WIND IMPLANTED HELIUM, J.L. Jordan, Office of Lunar Base Research,

Department of Geology, P.O. Box 10031, Lamar University, Beaumont, TX 77710

In addition to the ubiquitous presence of oxygen in lunar materials, the large amounts of

hydrogen and helium of solar wind origin found in returned lunar samples have led to suggestions that the lunar regolith may provide a valuable source of energy for future space exploration

as well as assisting in meeting the terresmal energy demands of the future [1,4,14].

Studies of mineral separates from lunar soils have revealed that the mineral ilmenite

(FeTiO3) is the most retentive phase for these solar wind implanted gases [3,12]. Concentrations

of solar wind H and He in lunar ilmenites may be more than an order of magnitude greater than

in other soil constituents [3,12]. Thus knowledge of the distribution of ilmenite - rich materials

can provide insight as to the location of potential H and He reservoirs. In addition, at least one

process for extraction of oxygen from the lunar regolith involves the use of an ilmenite separate

as a feedstock [4].

There has been the suggestion made in this workshop that regional deposits of ilmenite -

rich lunar volcanic glasses could be a valuable lunar resource [2]. The existence of these large

scale deposits has been suggested from remote sensing observations [8,13]. Unfortunately the

only returned samples that contain lunar volcanic glasses (the Apollo 15 green glass soil, 15426;

and the orange soil 74220) were apparently severely outgassed and may have been shielded from

further solar wind exposure after their formation [5,7,9]. In regions where soils have been

effectively gardened through meteoritic bombardment over a period of a few billion years the

exposure of surfaces of grains that originated from depths of several meters is assumed. A

quantitative measure of this regolith maturing process is desired since it is a fraction of the solar

wind fluence that is ultimately retained.

The "maturity index" that has proven to be very reliable for measuring the degree of

solar wind exposure that a soil has experienced is the ratio Is/FeO, which is the fraction of fine

metal produced in the surfaces of the grains by solar wind reduction to the total FeO [10,11].

This ratio ranges from 0 to greater than 100 in lunar soils, and if there were no large differences

in the trapping efficiency of the mineral phases one may expect the He contents of the soil would

correlate with this ratio. Mineralogical differences between and within sites make this correlation generally poor.

Maturity and ilmenite contents can compensate for one another in the role they play in

the H and He contents of lunar soils. Thus a correlation between He and the product

(Is/FeO)(TiO2 wt %) should be expected to be global. This correlation is illustrated in Fig. 1 for

greater than 60 returned Apollo soils for which data on all three parameters exists (references for

measurements given in [7]). The linear fit of the trend allows curves of equal He concentration

(helium isocons) to be constructed in a plot of Is/FeO versus TiO2 (wt %) shown in Fig.2. Thus

the H and He distribution at the lunar surface may be within the grasp of quantitative assessment

if both soil maturity and TiO2 content of the soil are known.

The suggestion that regional pyroclastic deposits may be enriched in lunar resources

could be followed by quantitative assessment if remote means of determining Is/FeO in addition

to TiO2 could be established. Spectral reflectance data on samples for which the Is/FeO has

been determined may provide this important link. If there exists a well defined correlation
44

]_tAPPING FOR SOLAR WIND IMPLANTED HELIUH: J. L. Jordan

between theseobservations,then supcrpositionof thisdata with remote TiO2 data allows the

predictionof H and Hc - rich zones with a reasonabledcgrcc of certainty.These depositsshould

have (Is/FcO)CTiO2 wt %) products greaterthan 350 ifthey arc expected tocontain greaterthan

average (8 wppb) amounts of 3He.

Fig. 1

BO

4 He vs. (Is/FeO)(Ti02 wt %)

4 He wt ppm

5O

40

30

2O

10

0

0

Linear ApDroximation

Z • 0.0?6 XY * 3.9

1 I 1 I I

'_oo _oo 300 400 soo

(IslFeO)(Ti02 wt %)

80_

Fig. 2

120

100

80

eO

40

20

Predicted 4 He Content in Lunar Soils

Is/FIO

_____ 'socons in W, ppm

S 4 8 B 7 a e lO 11 12 13 14 18

Ti02 (wt %)
45

MAPPING FOR SOLAR WIND IMPLANTED HELIUM: J. L. Jordan

Acknowledgments

This work is supported by a Johnson Space Center Regional Universities Grant NAG9-376.

References

1. Carter, J.L. (1985) Lunar Regolith fines:A Source of Hydrogen,In Symposium on Lunar Bases

and Space Activities of the 21st Century (W.W. Mendell, ed.), p.571-581. Lunar and Planetary

Institute, Houston.

2. Coombs, C.R., Hawke, B.R., Clark, B. (1989) The Optimal Lunar Resource: Ilmenite-Rich

Regional Pyroclastic Deposits, In abstracts for this workshop, Lunar Planet. Inst., Houston.

3. Eberhardt, P., Geiss, J., Graf, H., Grogler, N., Mendia, M.D., Morgeli, M., Schwaller, H., and

Stettler, A. (1972) Trapped Solar Wind Noble Gases in Apollo 12 Lunar Sci. Conf. Vol. 2, p.

1821.

4. Gibson, M.A. and Knudsen, C.W.(1985) Lunar Oxygen Production from Ilmenite, In Symposium for Lunar Bases and Space Activities of the 21st Century (W.W. Mendell, ed.),p.543-550,

Lunar and Planetary Institute, Houston.

5. Hintenberger, H., Schultz, L., and Weber, H.W. (1975) A Comparison of Noble Gases in

Lunar Fines and Soil Breccias: Implications for the Origin of Soil Breccias, Proc. Sixth Lunar

Sci. Conf. Conf., Vol. 2, p.2261-2270.

6. Jordan, J.L. (1975) Inert Gas Investigations of the Apollo 15 and 17 Landing Sites, PhJ).

Thesis, Rice University.

7. Jordan, J.L. (1989) Prediction of the He Distribution at the Lunar Surface, In papers submitted

to the First Ann. Symposium for Space Mining and Manufacturing, UA/NASA SERC, Tucson.

8. Johnson, T.V., Mosher, J.A. and Matson, D.L. (1977) Proc. Lunar Planet. Sci. Conf. 8th,

p.3243-3255.

9. Lakatos, S., Heymann, D., and Yaniv, A. (1973) Green Spherules from Apollo 15: Inferences

about their Origin from Rare Gas Measurements, The Moon, Vol. 7, p.132.

10. Morris, R. V. (1976) Surface Exposure Indices of Lunar Soils: A Comparative FMR Study,

Proc. Seventh Lunar Sci. Conf., Vol. 1, p.315-335.

11. Morris, R.V. (1978) The Surface Exposure (Maturity) of Lunar Soils: Some Concepts and Is/

FeO Compilation, Proc. Ninth Lunar and Planet. Sci. Conf., Vol. 2, p.2287-2298.

12. Mueller, H.W., Jordan, J.L., Kalbitzer, S., Kiko, J., and Kirsten, T. (1976) Rare Gas Ion

Probe Analysis of Helium Profiles in Individual Lunar Soil Particles, Proc. Seventh Lunar Sci.

Conf.,Vol. 2, p.937-951.

13. Pieters, C.M. (1978) Proc. Lunar and Planet. Sci. Conf. 9th, p.2825-2849.

14. Wittenberg, L.J., Santarius, J.F., and Kulcinski, G.L. (1986) Lunar Source of 3He for

Commercial Fusion Power, Fusion Technology, Vol. 10, No. 2, p.167.
46

DIFFERENTIATES OF THE PICRITIC GLASS MAGMAS: THE MISSING MARE BASALTS; j.

Longhi, Lamont-Doherty Geological Observatory, Palisades, NY 10964

One prediction of the hypothesis that mare basslts are differentiates of more primitive magmas similar in

composition to the picritic volcanic glasses (1,2,3) is that there should be mare basalts with compositions

spanning the range expected of differentiates of the known picritic compositions. Figure 1 demonstrates that this

predicition has not yet been conFu'med. Figure 1 shows the TiO 2 and MgO concentrations of fine-grained mare

bs,slts and pieritic glasses (2); also plotted are calculated differentiation trends of a few of the picritc glass

compositions. It is clear that there ire no basalt compositions near the kinked portions of the red mad black glass

trends. There is also a dearth of basalt compositions corresponding to differentiates of the yellow glasses. Basalts

with intermediate end very high TiO 2 concentrations may thus be thought of as "missing", at least from the

sample collections. Remote sensing studies (4,5) indicate abundant unsampled flows with intermediate TiO2, so

the non-primary basalt hypothesis is at least consistent with the data in this portion of the composition range

and the dearth of the mare basalts with intermediate TiO 2 is apparently a sarnpling problem. The missing veryhigh-Ti basalts are more problematical. The sarne remote sensing studies also describe extensive areas of an

unsampled high-Ti basalt type (HDSA) that is similar to Apollo 11 and 17 basalts in TiO 2 concentration, but is

apparently more marie. Taken at face value, the reflectance spectra of these bass.Its (actually soils) do not

correspond the differentiates of the red and black glasses, which should have TiO 2 concentrations in the range of

ll(evolved) to 17 (primitive) wt%. So it is not clear whether the very-high-Ti basalts are simply missing from our collections or are simply not present on the Moon.

Given the possibility that a few rare fragments of these intermediate-Ti and very-high-Ti basalts may be

present in our collections, it should be useful to describe some the petrographic and chemical characteristics

predicted for differentiates of yellow, red, and black glass compositions that might help in their discovery.

Accordingly, I have calculated near-perfect fractional crystallization sequences for the Apollo 14 and 15 Yellow.

the Apollo 15 Red. and the Apollo 14 Black glass compositions tabulated by (2). Partial results are listed in Table

1 in terms of temperature, volume (approximate) percent crystallized, order of mineral appearance, and silicate

mineral composition. The calculations were arbitrarily stopped at 80 mole% crystallization.

Intermediate-Ti Basalts: Calculations show that all picritic glass compositions crystallize olivine and

chromite early. The result in fine-grained differentiates should be olivine phenocrysts with chromite inclusions.

After olivine and chromite, differentiates of the Apollo 14 and 17 yellow glass magmas should differ only slightly

in crystallization sequence. Augite will crystallize next in the Apollol4 magma followed soon after by nearly

simultaneous crystallization of plagioclase and ilmenite. The result in fine- to intermediate-grained rocks should be

a sub-ophitic texture with ilmenite having the sarne textural position as plagioclase. Although plagioclase should

be the second major phase to crystallize from the Apollo 17 magma (assuming no nucleation delays), plagioclase.

augite, and ilmenite should begin to crystallize nearly simultaneously and produce an ophitic groundmass. In

general appearance, differentiates of the Apollo 14 and 17 yellow glass magmas will resemble Apollo 12 ilmenite basalts (6), but with 1 to 3 % more ilmenite in the mode.

Very-high.Ti Basalts. Mineralogically, differentiates of the Apollo 15 Red and 14 Black glass magmas

should be generally similar to some of the Apollo 11 and 17 basalts: phenocrysts of olivine with chromite

inclusions and phenocrysts of ilmenite with cores of armalcolite in groundmasses of intergrown augite,

plagioclase, and ilmenite. It is possible that very fine-grained or vitrophyric basalts might have phenocrysts of

only olivine (with chromite) and armalcolite. Chemically, these bass.Its would be readily distinguishable from

known mare basalts by their concentrations of TiO2: up to 15 wt% (Red) or 17 wt% (Black). Petrographically, the

total mode of opaques (>25%) would be diagnostic in medium- to coarse-grained rocks, and in fine-grained rocks the amount of armalcolite might approach 10%.

An interesting feature of these calculations is that pigeonite does not appear to crystallize from any of

the four magmas modeled. Although pigeonite is the dominant pyroxene in low-Ti mare basalts, it is not a

ubiquitous phase in the Apollo 12 ilmenite basalts (6) and in the high-Ti basalts (e.g.,7). Its absence in these

latter rocks and in the calculations can be explained in terms of the extent of fraetionation which is a reflection of

cooling rate. Melting experiments on lunar compositions have shown that pigeonite is unstable with respect to

olivine plus silica in highly ferroan (Ms' < 0.15) liquids (8). If Ms" in s magma drops below this value before the

magma reaches saturation with pigeonite, then no pigeonite will crystallize. This situation is most favorable in

magmas undergoing near perfect fractional crystallization that are saturated with augite because augite

crystallization will cause M E" to decrease with minimal increase in SiO 2. The same magma undergoing inefficient

fractionation will crystallize pigeonite because Ms' decreases much more slowly per unit of crystallization and the

magma is able to reach a sufficiently high SiO 2 content to stablize pigeonlte while M 8' is still above 0.15. Thus

it is observed that pigeonite is stable predominantly in the more coarsely grained and hence more slowly cooled

members of the Apollo 12 ilmenite basalt suite (6) and Apollo 17 high-Ti basalts (7). A related feature of the

calculations is the continuous stability of olivine (Table 1). Once augite begins to crystallize the proportion of

olivine crystallizing falls almost to zero and then increases once silica begins to crystallize. If pigeonite were to

crystallize, then olivine would quickly disappear only to reappear in the latest stages of crystallization when pigeonite became unstable.
47

MISSING BASALTS: Longhi J.

REFERENCES

(1) Taylor S.R. (1982) Planetary Science: A Lunar Perspective, The Lunar & Planetary Institute. (2) Delano J.W.

(1986) J. Geophys. Res., 91, D201-D213. (3) Longhi J. (1987) ]. Geophys. Res., 92, E349-E360. (4) BVSP

(1981) Basaltic Volcanism on the Terrestrial Planets, The Lunar & Planetary Institute. (5) Pieters C.M., Head J.W.,

Adams J.B., McCord T.B., Zisk S., and Whitford-Stark J.L. (1980) J. Geophys. Res., 85, 3913-3938. (6) Dungan

M.A. and Brown R. W. (1977) Proc. Lunar Sci. Conf. 8th, p. 1339-1381. (7) Longhi J. (1974) Proc. Lunar Sci.

Conf. 5th, p. 447-469. (8) Longhi J. and Pan V. (1988) J. Petrol., 29, 115-147.

TABLE 1. Fractional Crystallization of Picritic Magmas

Apollo 14 Yellow

T(*C) VFX

1350 0 fo7 8

1346 1 fo78, crrnt

1126 39 fo54, (ermt), Wo35En39

1091 46 fo48, Wo34En35, An88

1084 50 fo46, Wo34En33 , An87, ilm

1043 83 fol6, Wo35En14 , An80' ilm

Apollo 17 Yellow

T(*C) VFX

1292 0 fo7 8

1287 1 fo78, crmt

1126 28 fo62, (crmt), An92

1123 31 fo61, An92,Wo34En43

1119 37 fo59, An91,Wo33En42 ,ilm

1069 76 fo32, An86,W°34 En26,ilm' sil

1064 84 fo21, An83,Wo33En19 .ilm' sil

Apollo 15 Red

T(*C) VFX

1254

1248

1207

1136

1132

1115

1049

0 foB0

1 fo80, ermt

10 fo77, crrnt, arm

30 fo67, (arm), ilm

31 fo66, ilm, Wo33En46

37 fo63, ilm, Wo33En44,An88

84 fo28, ilm, Wo36En22,An78

Apollo 14 Black

T(*C) VFX

1273 0 fob 0

1268 1 foB0, crmt

1244 8 fo78, crmt, arm

1172 36 fo67, (arm), ilm

1129 43 fo61, ilm, Wo34En42

1092 56 fo52, ilm, Wo35En36,An90

1060 78 fo33, ilm, Wo39En25,An87, sil

1047 84 f°25, ilm, Wo39En20,An86, sil

¢q

O

I--

20

10

plcrltlc glasses O

Ap11 •

."_'-o 14 Bk

Ap12 • ,'/ 0

Ap14 • : ,,..

Ap15 • I"/,, ''"(3 15 R

Ap17 Luna a _ a 0 • _'

&_a A O

---o 17 Y

e• _,I_ .... ol4 Y

eee o

n•m m@l 0

ll

f ....... _*..... o°o

0 20

0 10

MgO wt%

Figure 1. TiO2 versus MgO in

mare basalts and picritic

glasses. Dashed lines are

partial liquid lines of descent

calculated by the method of

(3). For green and yellow

glasses, liquids are saturated

only with olivine and

chromite; for red and black

glasses, negative slope

represents liquids saturated

with olivine and chromite,

positive slope indicates

olivine, chromite, and

armalcolite.
48

REE DISTRIBUTION COEFFICIENTS FOR PIGEONITE: CONSTRAINTS ON TIlE ORIGIN OF THE

MARE BASALT EUROPIUM ANOMALY. G. McKay (SN4, NASA-JSC, Houston, TX,77058) J. Wagstaff, and

L. Le (Lockheed ESCO, 2400 NASA Rd. 1, Houston, TX 77058)

Introduction. A long-held paradigm of lunar science is that the complementary REE patterns and Eu

anomalies of the lunar crust and mare basalt source regions reflect an early differentiation event of global

scale resulting from the crystallization of a lunar magma ocean (MO) [e.g. 1,2]. The positive Eu anomaly of

the crust is generally thought to result from plagioclase enrichment, while the negative Eu anomaly in mare

basalts is thought to be inherited by the source region from an evolved MO in which prior plagioclase removal

had produced a negative Eu anomaly [e.g. 2,3].

Several workers [e.g. 4,5] have called into question the need for prior plagioclase removal, suggesting that

the mare basalt Eu anomaly was instead a result of Eu anomalies in the distribution coefficient patterns of the

ferromagnesian cumulate minerals in the source regions. However, even some of these workers have recanted

their heresy [6], and called for a Eu anomaly in the MO prior to formation of the cumulate source regions.

This issue has again been raised by Brophy and Basu [7] and Shearer and Papike [8]. These authors

explicitly addressed the question of whether prior plagioclase removal is required to produce Eu anomalies of

the magnitude observed in mare basalts. However, using slightly different approaches, and more importantly,

using different values for mineral/melt distribution coefficients for Eu and trivalent REE, these authors

arrived at opposite conclusions: Brophy and Basu concluded that prior plagioclase removal is required, while

Shearer and Papike concluded that it is not.

Part of the uncertainty in this issue is a result of inadequate mineral/melt partition coefficient data,

especially for Eu at lunar oxygen fugacities. The situation is most critical for low-Ca pyroxene (a major carrier

of REE among MO crystallization products throughout much of the MO crystallization sequence), but less so

for olivine and high-Ca pyroxene. Olivine distribution coefficients are so low [9] that even a small proportion

of pyroxene in the source region will dominate REE abundances in both cumulates and their partial melts.

High-Ca pyroxene distribution coefficients have been studied by several workers [e.g. 10,11,12] under nearlunar oxygen fugacities, and indicate a significant Eu anomaly (Fig. 1).

The magnitude of the Eu 1

anomaly for Low-Ca PX is less

well constrained. OPX distribution coefficients [13] indicate

only a very minor anomaly (Fig.

1). However, those results were

obtained before the difficulty of

measuring very low distribution

coefficients on small crystals was _ 0.1

appreciated [9], so the magnitude

of the anomaly is likely to be un- r_

reliable. The goal of this study is

to provide reliable values for the

partitioning of REE between

low-ca pyroxene and melt under

near-lunar fOzso that the origin 0.01

of the mare basalt Eu anomaly

can be better constrained.

.Experiments. McKay [14]

reported distribution coefficients

o

t j t I I I I I l

Ce Nd Sm Eu Gd

J I I I i

Yb

for trivalent REE between pigeonite and a melt produced by 15-20% crystallization of a synthetic basalt

resembling 12015, but did not study partitioning of Eu. For the present study, we prepared a similar starting

composition containing about I wt% each of Gd and Eu. Pellets (125mg) of this starting material were

suspended on wire loops in a controlled atmosphere (CO/CO2) furnace at oxygen fugacities near IW, held at

1300°C for four hours, cooled to 1200" in 2 hours, then to 1175° at 0.3°/hr, held for 24 hours, and then air

quenched. This multi-stage cooling history permitted growth of large (>200 p.m wide) pigeonite a3_tais for

which even very low partition coefficients could be measured without interference from adjacent glass [9].
REE DISTRIBUTION COEFFICIENTS FOR PIGEONITE

McKay, O. et al.

49

Resulting charges were sectioned, polished and analyzed with the JSC Cameca Table 1.

microprobe, with no analyzed spot being closer than l00 p.m from the nearest glass, t° Xtl D_ D_ DE,_d

ensure absence of analytical interference. A .0070 .022.5 .321

Results. Resulting Eu and Gd partition coefficients for each crystal are given in B .0077 .0218 .361

Table 1, and average compositions of crystals and glass for the current experiments C .0065 .0230 .283

and our earlier experiments [14] are given in Table 2. The partition coefficients

showed slight differences among the three charges (Table 1), but values for Eu/Gd are Avg .0071 .0224 .321

quite consistent. Values for Dod from the present study differ from our earlier values

[14] by nearly 80%, despite the similarity in melt and pyroxene composition and experimental procedures and

conditions.

Discussion. The major difference between the two sets of experiments

is the presence of 0.4 wt% alkalies in the earlier glass, and the slightly

more calcic nature of the earlier pyroxene (Table 2). McKay et aL [15]

noted the strong dependence of CPX distribution coefficients on Ca

content, and we suspect that this is at least partially responsible for the

difference between our present and earlier results for Gd. We speculate

that the presence of alkalies in the earlier melt increased the activity of Ca

in that melt, resulting in growth of more calcic pyroxene. Experiments

using the new starting composition to which Na has been added are in

progress to test this hypothesis.

Because of the absence of alkalies in the present starting composition

and the apparent resulting effect on distribution coefficients, for this

abstract we rely on the current experiments only to define the magnitude

of the Eu anomaly in the pigeonite partition coefficient pattern. We take

the absolute values for the trivalent REE from our earlier study, and use

the DE,_C,_ratio from the current study to compute a value for DE, which is

consistent with the earlier trivalent values.

Results are shown in Figure 2, along with the OPX values of [13] for

comparison. It is clear from these results that low-Ca pyroxene has a much

Table 2.

McKav(1981_ This Study

LJq Px Liq Px

SiO 2 46.1 53.2 45.9 53.1

TiO 2 3.43 0.47 3.70 0.48

Ai20 3 10.5 1.43 10.9 1.43

Cr20 3 0.24 0.73 0.23 1.07

F¢O 16.6 15.8 16.4 14.4

MgO 7.43 24.5 7.48 25.8

CaO 11.0 3.41 11.7 2.58

Na20 0.28 0,00

0.11 0.00

Eu20 3 1.22 0.0085

Crd20 3 2.05 0.096 1.25 0.028

mg 0.444 0.734 0.449 0.762

wo 0.068 0.052

D(Gd) 0.036 0.022

D(Eu) 0.0071

larger capacity to develop a Eu anomaly than the earlier data suggest. These results are in qualitative

agreement with partition coefficients derived by [16] from ion probe analyses of Wo w pyroxenes from lunar

mare basalt, but suggest an even larger Eu anomaly for pyroxenes with lower Ca content, in agreement with

arguments based on crystal chemistry [8]. Whether the Eu anomaly in low-Ca pffoxene partition coefficients

is large enough to explain the Eu

anomaly in mare basalt without prior

plagioclase crystallization awaits

detailed modelling studies which are

beyond the scope of this abstract.

References..: [ l ] Walker _ _ (1975) P_

6th, 1103. [21Taylor (1982) rbmet_'

Science: A Lna_r pe_pecUve. [3] Wood

(1975) PI.,SC 6th, 1087. [4] Shih ind Schonfeld

(1976) PLSC 7th, 1757. [51Nyqu_ a at

(1977) PLSC 8th, 1383. [6] Nyquht! aa/.,

(1981) EPSL $5, 335. [7] Brophy and Basu

(1989) LPSC XX, 115. [8] Shearer and Papike

(1989) LPSC XX,994. [9] McKay(1986) GCA

$0, 69. [10] Grutzeck a a/. (1974) GcophyL

Res. Left. l, 273. [l 1 ] McKay a a/. (1988)

Mtk, orllkl 23, 289. [12] McKay a a/. (1989)

LIPS(: XX, 677. [13] Weill and McKay (1975)

PLSC 6th, 1143. [14] McKay (1981) F.,OS,

Trans. AGU 62, 1070. [15] McKay eta/. (1986)

GCA $0, 927. [16] Shearer a a/. (1989) GCA

$3,1041

ft.

v

rs

0.1

0.01

o.D

i 1 t l I I I I I I 1 I i

C,e Nd Sm Eu Gd Yb
5O

A BRIEF LITERATURE REVIEW OF OBSERVATIONS PERTAINING

TO CONDENSED VOLATILE COATINGS ON LUNAR VOLCANIC GLASSES.

C. Meyer, NASA Johnson Space Center, Houston TX 77058

Many studies have been made of the condensed volatile coatings on the Apollo 15 green

and Apollo 17 orange glass beads. Lunar samples 15426 and 74220 and adjacent samples

contain enrichments in a large number of volatile trace elements when compared to local mare

basalts at the same slte (see table). Zn, Ge. Cd, 2o4pb, Tl, Ag, Au, h', Re and Br are enriched by

a factor ofabout I00 and Ga, Cu, Sb, Bi, In, As. Hg?, Se and Te are enriched by a factor of

about I0. However, lunar basalts are so very depleted in these elements when compared to

terrestrial rocks that these lunar deposits are probably not a significant resource for planning a

]unar base.

Leaching experiments (Reed et al 1977, Tatusumoto et al 1987}, selective volatilization

(Silver 1975, Cirlin et al 1978) and grain-slze studies (Wasson et al 1976. Thode and Rees

1976, Krahenbuhl et al 1974, Morgan and Wandless 1984) showed that these volatfles were

located on the surfaces of the particles in these glass samples. Depth profiling measurements

by Auger electron (Grant et al 1974), ion microprobe (jovanovlc and Reed 1974, Meyer et al

1975) and a resonant nuclear proton.19F experiment {Goldberg et al 1976} directly showed that

these were surface deposits. Although there is less sulfur in these glass samples than in the

local basalt, the surface deposits appear to be mixed salts of metal sulfides and halldes (Meyer

et al 1975). Buffer and Meyer 1976 found S to be present on the primary surfaces of nearly all

spheres. They reported surface concentrations of Zn, K, Cl, Cu, Ni and P. SEM studies by

Butler and Meyer 1976, Buffer 1978 and Clanton et al 1978 showed that these deposits had a

characteristic "mlcromound" texture. The size of the micromounds is about 30 to 50

angstroms and this would appear to be the thickness of the coating. However, mild leaching

does not completely remove the coating so that reaction with the glass surface is probable

(Goldberg et al 1976}.

Metal halide (Wasson et al 1976) and metal carbonyl |Sato 1979) have been discussed

as the volatile species in the volcanic vapor that produced these deposlts of glass beads.

However, the major component of the volcanic vapor has not been identified.

The presence of trace siderophfle elements in these samples Is not understood. Some

authors (Morgan and Wandless 1984) think these elements came from an added meteorite

component. However, the close association with volatile metal hal/des in these very immature

soll samples indicates that the siderophile elements in these samples may have a lunar

volcanic origin I

References: Buffer P. 1978 PLPSC 9. 1459-1471; Buffer P. and Meyer C. 1976 PLSC 7.

1561-1581; Chou C-L. et al 1975 PLSC 6. 1701-1727; Ctrlin E.H. et al 1978 PLPSC 9, 2049-

2063; Clanton et al 1978 PLPSC 9, 1945-1957; Ganapathy R. et al 1973 PLSC 4. 1239-1261;

Gibson E.K. and Moore G.W. 1974 PLSC 5, 1823; Goldberg R.H. et al 1976 PLSC 7, 1597-

1613; Grant R.W. et al 1974 PLSC 5, 2423-2439; Jovanovlc S. and Reed G. 1974 PLSC 5,

1685-1701; Krahenbuhl U. et al 1977 PLSC 8, 3901-3916; Krahenbuhl U. 1980 PLPSC I I,

1551-1564; Meyer C. et al 1975 PLSC 6, 1673-1699; Morgan J.W. et al. 1974 PLSC 5, 1703-

1736; Morgan J.W. and Wandless G.A. 1984 {abs.} Lunar Science XV, 562-563; Reed G. et al

1977 PLSC 8, 3917-3930; Rhodes j.M. et al 1974 PLSC 5, 1097-1117; Sato M. 1979 PLPSC

I0, 311-325; SilvEr L.T. 1975 Lunar Science Vl, 738-740; Tatsumoto M. et al 1987 PLPSC 17.

E361-371; Taylor S.R. et al 1973 PLSC 4, 1445-1459; Thode H.G. and Rees C.E. 1976 PLSC

7, 459-468; Wanke H. et al 1973 PLSC 4. 1461-1481; Wanke H. et al 1974 PLSC 5, 1307-

1335; Wasson J.T. 1976 PLSC 7, 1583-1595.
51

Condensed Volatile Coatings; Meyer C.

Volatile Enrichment Ratio

Green A15 Orange A17

Glass Basalt RATIO Glass Basalt

15426 74220

RATIO

Plm 80 1 80 300 2

Ga 6 3 2 16 4

Ni 96 70 -3 75 3

Cu 3.5 26 2

S 700 450 2000

F -100

CI -100 1-15

150

4

25

10

0.2

PGPeb 196 3 60 250 1.2 200

Cd 181 1 180 320 2 160

TI 7 0.2 35 20 0.2 100

Sb 1.6 0.1 16 .6 0.1 6

Bi 2.4 0.12 20 1.4 0.05 30

In 9 0.6 15 29

Br 136 8 20 520 8 70

Se 174 100 2 640 160 4

Te 16 6 3 62 2 30

As 15 4 4

Hg 6 -3 -2

Sn .12

Ag 39 1 40 111 1 100

Au 1.2 0.01 100 1 0.01 100

Ir 0.4 .005 80 0.4 .003 100

Re .05 .001 50 .05 .001 50

Data are from: Zn Duncan, Rhodes, WankeP4 P5, MorganP5, Wasson, Chou; Ga

Wasson, Taylor, WankeP4; N! WankeP4. Morgan; Cu Duncan, Taylor. WankeP4; S

Gibson, Thode; F,CI jovanovic, Wanke P4; C_ Chou. Wasson. Ganapathy. WankeP4.

MorganP5; _ MorganP5 P 15, Wasson, Ganapathy; TI Ganapathy, MorganP5; Sb

MorgartP5 P15, Ganapathy; BI MorganP5, Ganapathy; In MorganP5. Wasson; Br

MorganP5, Ganapathy; Se.Te MorganP5. Ganapathy; As WankeP4 and P5; llg

jovanovlc, Krahenbuhl; Sn Taylor; Ag.Au._.Re MorganP5 P15. Chou. Wasson.

Ganapathy.
52

APPLICATION OF REMOTE-SIMS FOR GLASS AND TRACE-ELEMENT COMPOSITIONS OF

LUNAR SOILS;

Y. Miura. Faculty of Science, Yamaguchi University, Yoshida, Yamaguchi 753

Japan. ' ,

The lunar soils can be analyzed by the mass spectral attern of r

secondary ion mass spectroscopy (i.e. remo_o (Tu_ r_ _ _P .... emote

_-_,,J L_,_,oJJ. Inls type o?

examination can be applied to lunar glasses and trace-element compositions of

lunar soils. As a preliminary step at calibrating of this technique, various

samples were measured and compared; tektite from Moldau; terrestrial volcanic

glass (obsidian); artificial "thin-section" glass; and three simulants of 74220

and portions of 60025 and 14305 lunar rocks.

2,3,4]:The main characteristics of the remote-SIMS are summarized as follows [I,

(I) Complete compositional data from light (H,He,C etc.) to heavy elements;

(2) Distinction of glassy states and fine-grained textures from crystalline

and coarse-grained rocks;

(3) In-situdetection on the lunar surface by reducing the working-distance

from 50 m (about 40 cm used in this study);

(4) Investigation of implantation degree of the solar-wind and sedimentation

process of the impact-related planetary process.

Ion spectral patterns of the remote-SIMS suggest that glasses and small

aggregates (e.g., agglutinates) show comparatively higher peak intensity of the

remote-SIMS data than hard crystalline rocks. The glass typically gives a

more complex pattern than a given rock.

The following results from this study are summarized and shown in Fig. I:

(I) Lunar volcanic glass of the 74220-type simulant shows different remoteSIMS pattern when compared with the obsidian, tektite (of higher Na peak

intensity) and slide glass plate (of lower peak intensity);

(2) Even in lunar simulant samples, the 74220 glass reveals higher peak intensity

than the other simulants (60025 and 14305);

(3) Characteristic remote-SIMS spectral pattern of the 74220-type simulant glass

can be applied as remote sensing for the lunar glass;

(4) A data base of real lunar glass, rocks and soils is required for application

of the remote-SIMS to the lunar surface.

The research is in part supported by the Grant-in-Aid for Scientific research

on Priority Areas (Origin of the Solar System) of the Japanese Ministry of

Education, Science and Culture (01611005) of the author.
REMOTE-SIMS

53

Miura, Y.

References:

[I] Miura, Y. (1989): Lunar and Planetary Science, XX, 705-706.

[2] Sasaki, S., Yamori, A., Ka_ashima, K., Miura, Y., Ohta, M. and Yokoi

R. (1989): 1988 Res. Report of "Origin of the So]dr Systen" (by the

Monbusho), 451-461.

[3] Hiura, Y., Sasaki, S., Ka_ashima, N., Yamori, A. and Ohta, M.

(1989): ISAS Research Note, 410_ 1-30.

[4] Sagdeev, R.Z., Managadze, G.G., Shutyaev, I. Yu., Szege, K., and

Timofeev, P.P. (1985), Adv. Space Res., 5, 111-120.

Fig. 1. RemoteSIMS patterns of _. 30.0

synthetic lunar "

20.0

simulant 74220,

60025,and 14305,

iO.O

tektite from 1.o

Moldau, terres- =

2 o.1 trial volcanic

o.m

glass of Yatsugatake obsidian _ o.ooi

and slide glass

plate.

2 3Na+

/)_ -----0 S74220-type ...... Q S60025-type

- - • S14305-type

2 + / _ --8 Tektlte(Moldau)

H2 16 + /." [_ - w Slide glass

02/ Li27 + 39K+ -- -II Obsidian

_ ." ] AZ ._.40 Ca+

t .

.-V '-W

• " 24 28 .

"23 "{2 {6 2_' 17"h _ _ _ "

I_ss
54

A 6oMM SPHERE FROM THE APENNINE FRONT: AN EXCEPTIONAL

VOLCANIC GLASS (OR JUST A REMARKABLE IMPACT GLASS?) Graham Ryder,

Lunar and Planetary Institute, 3303 NASA Road One, Houston, TX 77058

15434,28 is a 0.39 g, 6 mm sphere collected in the regolith at Station 7 on the

Apennine Front, Apollo 15. It was described by Powell [1] as a spherule with a knobby

surface, and included with a group of 26 glass and glass-rich particles (15434,1). The

sphere is a yellow/orange glass of intermediate-Ti mare composition (TiO2 3.2%). The

interior is homogeneous and crystal-free, but the exterior is a thin diffuse rind (less

than 200 microns) containing debris of mare basalt materials. Major and trace element

chemistry suggest that the glass sphere is volcanic, with adhering material.

Petrography: The interior of the broken sphere is shiny black (orange/brown in thin

flakes). It is homogenous, with conchoidal fracture. The outer 150 to 200 microns is

duller, as if devitrified. The exterior surface is dark gray and slightly bumpy or

blistered, and scattered mineral and lithic fragments are embedded in it. One 2 mm

fragment is a coarse mare basalt; the mineral fragments are mainly pyroxene and

olivine. These embedded fragments have clean surfaces, lacking adhering glass or dust. A

chip was taken for two serial thin sections. One (,130) has a yellow/orange glass core

with devitrified glass containing some fragmental lithic and mineral debris forming a

rind. Towards the interior of the rim tiny crystallites of skeletal olivine are prominent.

The embedded fragments coarse enough for identification appear to be solely of mare

derivation, and mainly olivines and pyroxenes, though plagioclase, chromite, and ilmenite

are present. The largest mineral fragment is about 700 microns across. The second thin

section (,131) is almost entirely homogeneous yellow/orange glass, with few fragments

(mainly pyroxene) at one edge, and is obviously a more interior portion of the sphere.

None of the fragments in either thin section contain any shock features. The thin

sections sample only the outer 1/2 mm of the glass sphere, and the rind is grossly

over-represented.

Chemistry: Microprobe analyses of the yellow glass were made by Phinney et al. [2] and

Vaniman (pers. comm). (The analysis in [2] is reported as ,48 because of a sample

misnumbering during thin section making). These analyses are very similar and show

that the glass is of mare basalt composition with 21% FeO, 3.5% TiO2, and 9.3%

Al203. I acquired 144 mg as two chips for chemical analysis. One fragment of 66 mg

lacking conspicuous fragments was ground into a homogeneous powder for microprobe

fused bead and INAA analyses; the other is preserved for future studies. The analysis is

reported in the table and the figure, with other compositions for comparison.

The major element analysis is similar to those previously reported for the yellow/orange

glass, and within the realm of other intermediate-TiO2 compositions glasses from the

Apollo 15 site, including the yellow volcanic glass and the yellow impact glasses [3-5,

and others]. It differs from the volcanic glass mainly in being lower in MgO and

Cr203, and higher in alkalis. It differs from most of the impact glasses in having lower

Ti02 and SiO2, and higher FeO.

The trace elements show that 15434,28 is an exceptional glass. For a mare basalt

composition it has high rare earth elements, although not as high as Apollo II high-K

basalts. Most of the incompatible elements are 3 to 4 x those in the Apollo 15 olivine

basalts and 2 x those in the A15 yellow volcanic glass. 15434,28 is a little more

enriched in the lighter rare earths than the heavier ones compared to those two groups,

but the pattern is certainly not KREEP-Iike (Fig. I). The incompatible elements are

less than half as abundant as those in the 15010 yellow impact glass, which has a

much more KREEP-Iike slope of rare earths. U and Th are less than 1/5 as abundant

as in the yellow impact glass. Sr, Sc, Co, Ni, and Ni/Co are similar to those in the

volcanic glass. Ir and Au abundances do not exceed the INAA detectability limits of

about 4 ppb.
SPHERE FROM APENNINE FRONT: G, Ryder

55

Origin of the _lass: The glass is exceptional in both structure and chemistry. Most

impact glasses are more heterogeneous, with at least flow-banding if not schlieren. In

impact glasses, fragments are not confined to the outermost few hundred microns, but

occur throughout; they generally include shocked varieties. Many impact glasses are

vesicular or hollow, but 15434,28 is neither. The chemistry gives no indication of

meteoritic contamination, whereas most impact glasses are formed from contaminated

regolith (yellow impact glass 15010 for instance contains 26 ppb Au). The unusual bulk

composition cannot be manufactured by mixing materials known among lunar samples.

Any hypothetical mixture contains a high proportion of a mare basalt with an unusual

composition; the elevated rare earths are not a result of KREEP contamination, but are

inherent in the mare material (as was concluded for the 15010 impact glass [4]).

15434,28 differs from lunar volcanic glass beads in its large size and its adhering

material. Accepted lunar volcanic beads are smaller, no larger than 1 mm and most are

less than 300 microns. Although lunar volcanic beads include composites, none have so

far been described that have rinds similar to 15434,28, which is more llke some

terrestrial volcanic beads in size and structure. However, if 15434,28 were broken up

and its fragments analyzed, it would form a cluster that would certainly be identii%d

as a volcanic glass group. It would be mildly unusual; its Ms/AS would be the lowest

of any volcanic group, although not much lower than A15 yellow volcanic glass. On

most element-element plots it would plot at the edge of or within volcanic glass

compositions. It lacks vesicles, schlleren, banding, and meteoritic contamination.

Conclusions: I find no evidence that 15434,28 was produced in an impact, and its

features are entirely compatible with those of a fire fountain product. Therefore I

conclude that 15434,28 is an exceptional (size,rind, composition) volcanic glass. It

remains possible that it is a remarkable impact glass. Isotopic and more detailed

siderophile data for the glass are desirable, and the ramiScations of intermediate Ti

glasses in the evolution of the Imbrium area remain to be explored. If the sphere is

volcanic, why is it so large? and whatever its origin, why does it have adhering

crystals? The adhering mare materials are of petrologic and geologic interest.

Table. Composition of 1_434,28 (this study;

NA_"X_, MFB) and other Apollo lb yellow

glass+" IS-S]-

_. Trace elements in 164$4,2S and

comparitive materials, normalized to bulk

Moon composition.

100 , , , , , , , , , " "

I "_t I" .............. :

1K B8 Th, U, L8 &.Sen Eu Yb Lu Hf S¢ l i

111 Powell B. (1972) NASA MSC O$278,

91pp. 12] Phinne¥ W. et &l. (1072) Apollo 1S

Lunar Samples, LPI, p.149 /31 Delano J.

(1985) PLPSC 16th, p. D201. [4] Delano J.

.t al. (1982) PLPSC lath, p. Alb9. lsl

Hulhu S. et al. (19S8) Geochim.

Cosmochim. Aeta &2, :Z$'/9.

2O

,w

_#

uJ

.J

0-

lS434 A15 Yell 15010

,211,202 vole implct

SiO 2 4 3.6 42.9 (47)

TiO 2 3, I 9 3.48 4.2

Al203 9. ! II .3 9.5

Cr203 1.45 0.59 0.31

FeO 2 1.3 22. I 18.9

l_mO 0.2 $ 0.27 0 24

MgO I0.'7 12.1 9.3

9.0 9.0 9.5

Ns20 I. $ 9 0.45 0.32

K20 e. 13 0.08 0.22

P205 0.37 0.22

Sc 3 II 42 39

Co 5'7 69 4]

Ni '7 I 85

Sr 174 165

7..r 323 460

Hf 8.1 5.3 12.6

Ba 16'7 410

Th 1.39 8.3

U (.3) 0.3 3.0

La 21.6 8.5'_ 48.2

Ce 6 2 24.6 106

Sm 13. O 6.4 20.3

Eu 2. ! i .47 1.61

Tb 2. $ 1.4 4. l

Yb 6.4 4.3 15.6

Lu 0.90 0.48 2.4
56

APOLLO 17 ORANGE SOIL: INTERPRETATION OF GEOLOGIC

SETTING; H.H. Schmitt, Consultant, Albuquerque, NM, 87191

The discovery of the orange soil in the rim of Shorty

Crater during the Apollo 17 Mission to the Valley of TaurusLittrow (I), and subsequent recognition of orange materials

as a major component of mantling deposits at the southwestern

edge of Mare Serenitatis (2), added excitement, puzzles, and

critical new information to our studies of the moon. The

excitement came from the discovery of what, at the time,

appeared to be volcanic material the science team had

speculated might be found at Shorty. The puzzles came when,

after the soil had be examined carefully on Earth, we had to

conclude that somehow 3.6 aeons old (3) orange glass beads of

pyroclastic origin, underlain by their black devitrified

equivalent, had been emplaced in the rim and ejecta blanket

of an 80 m. diameter impact crater with only minor

contamination by other material (4). The critical new

information came when it became clear that the source region

for the orange soil magma must be the deep interior of the

moon, (5). below the region included in the original melted shell

An explanation of the geologic setting of the orange and

black soils comes from the writer's personal observations of

the effects of the explosion of 500 tons of ammonium nitrate

(1971 DIAL PACK event) near Medicine Hat, Alberta. This

explosion caused the pressurization of underlying water

saturated sand strata and the eruption of the water-sand

mixture along conduits in radial and circumferential

fractures cutting the rim and ejecta blanket of the explosion

crater. By analogy and further logic, the following sequence

Crater: of events may have taken place in the vicinity of Shorty

i. Eruption of the mare basalt flows that partially

filled the Valley (3.7 aeons (3)).

2. Pyroclastic eruption (4) of orange glass beads and

black devitrified glass beads (3.6 aeons (3)).

3. Immediate covering of the pyroclastic deposits by a

basalt flow of sufficient thickness to protect the orange and

black glass from significant contamination by regolith materials.

4. Avalanche from the north side of the South Massif

(1) to form the Light Mantle.

5. Meteor impact that created Shorty Crater (5) which

penetrated below the Light Mantle and into the basalt flow

overlying the pyroclastic deposits (19 My (7)).

6. Instantaneous release and pressurization of adsorbed

gases and the fluidization of pyroclastic deposits

immediately beneath Shorty Crater.

7. Eruption of gas/bead mixtures along conduits in the

radial and circumferential fractures around Shorty Crater.
57

APOLLO 17 ORANGE SOIL: Schmitt, H.H.

8. Continuous sorting of the less dense orange glass

beads toward the top of the gas column to give the sharp

separation of orange and black beads observed in and on the

core tube (i).

9. Development of thin regolith on the exposed top of

each orange and black bead deposit.

The primitive nature of the gases adsorbed on the

surfaces of the orange and black beads (8) indicate a source

region in the deep interior of the moon, below the zones

affected by the degasing of the magma ocean (9). This in

turn suggests that these deep source materials remained

relatively cool during the processes that formed the moon and

had not been subject to significant earlier differentiation.

The existence of a necessary density reversal below 200-300

km., the probable depth of differentiated crust and mantle,

to maintain the average density of the moon supports this

conclusion. Both these constraints on lunar composition and

structure severely limit possible mechanisms for the

formation of the moon and suggest formation as a

contemporaneous partner to Earth rather than derivation from

the early, already differentiated Earth as suggested by

others (i0).

References:

(i) Schmitt, H.H. (1973) Apollo 17 report on the Valley of

Taurus-Littrow. Science, 182, 680-690.

(2) Lucchitta, B.K., and Schmitt, H.H. (1974) Orange material

in the Sulpicius Gallus Formation at the southwestern edge of

Mare Serenitatis. LSCP 5, i, 223-234.

(3) Wilhelms, D.E. (1987) The geologic history of the moon.

USGS Prof. Paper 1348, 237.

(4) Heiken, G.H., and others (1974) Lunar deposition of

possible pyroclastic origin. Geochim. Cosmochim. Acta 38, Ii,

1703-1718.

(5) Schmitt, H.H. (1975) Evolution of the moon: The 1974

model. Space Sci. Rev., 18, 259-279.

(6) Wolfe, E.W., and others (1981) The geologic investigation

of the Taurus-Littrow valley: Apollo 17 landing site. USGS

Prof. Paper 1080, 280p.

(7) Eugster, O. (1977) The cosmic ray exposure history of

Shorty Crater samples: The age of Shorty Crater. LSCP 8, 3,

3059-3082.

(8) Taylor, S.R. (1982) Planetary science: The lunar

perspective. LPI, Houston, 298-299.

(9)Warren, P. (1985) The magma ocean concept and lunar

evolution. Ann. Rev. Earth Planet. Sci., 13, 201-240.

(10) Hartmann, W.H., and others (1986) Origin of the Moon.

LPI, Houston, TX.
5_

SECOHDAR! 1OH MASS SPECTROHETRIC _qALTSIS OF GLASsEs. TRACE ELEHENT CHARACTERISTICS OF

LUNAR PICRITIC GLASSES _ IMPLICATIONS FOi THE H/urI'LE SOURCES OF LUNAR PICRITIC MAGHAS; C.K.

Shearer, J.J. Paplke, K.C. Galbraath, H. Yurlmoto (SDSM&T, Rapid City, SD 57701) end H. Shlmlzu

(HIT, Cambridge, IdA 0213g).

Introduction. Trace element analysis of microvolumea of geologic materials ualn& secondary

ion mass spectrometry (SIMS) has a wide range of applications to terrestrial and lunar

petrogenetic problems. SIMS involves bombardment of the mlcrovolume by energetic ions (0"),

ejection of material by a process known as sputtering and analysis of ionized sputtered material

by mass spectrometry. Complexities in the secondary ion mass spectra of geologic materials

greatly slowed the quantitative application of SIMS. These complexities involved the generation

of molecular ions during sputtering resulting in isobaric interferences, unknown effects caused

by matrix variations, lack of quantification of secondary-ion intensities and lack of numerous,

well-documented standards. However, within the last ten years moat of these problems have been

resolved. Molecular ionic interference may be largely removed by kinetic energy filtering

(1,2) and isobaric corrections (2,3). Matrix effects are commonly resolved by comparing

unknowns with standards of the same major element chemistry (4) or empirical relationships

between ion yield and matrix (5). Empirical relationships between concentration and relative

intensity in a variety of silicate matrices have been documented (3,4,6).

_xperlmental technl_e. Our current work on lunar glass beads (volcanic. impact) involves

establishing working curves for appropriate silicate glass compositions and trace element

analysis of lunar glasses. Trace element analyses (RBE, Be. Sc, St, Co, V, Zr, Cr*, Zn*, Cu*,

and Rb*) are being conducted with Cameca IMS 3f ion probes located at kIT and the University of

Tsukuba (*). A primary beam of 0" ions is focused to s spot of 15-25 _ in diameter for REE and

8-15 #m in diameter for the other set of trace elements. Molecular ion interferences are

virtually eliminated from the mass spectra by reducing the secondary ion accelerating voltage

(1,2,5). Secondary positive ions are analyzed with combined electrostatic and magneti c analyzer

sectors. Secondary ions are detected by an electron multiplier in pulse counting mode.

Interference of BaO ions on Eu(151Eu-135BaI60 and 153Eu - 137Ba160) is corrected by empirical

relations among 151Eu/153Eu, 135Ba/137Ba and BaO/Ba ratio observed in silicate glasses ('0.I).

Similar empirical relations were used to correct other interferences (i.e. 151EulSo on 167Er).

For our studies, three sets of well-documented glass standards were used to investigate

matrix effects on ion yield in calculating working curves; synthetic glasses produced from GSJ

standards, A-15 Green Glass and A-17 Orange Glass. Secondary intensities (I) of REE were

normalized to 30Si to produce I(REE)/I(30Si ) vs. REE (concentration) working curves. Working

curves for other trace elements were normalized to a constant Si content. Concentrations were

then recalculated based on giG 2 content of the individual glass beads. Using these working

curves, A-17 Orange, A-15 Green and A-15 Yellow glasses were analyzed as secondary standards.

These standards were analyzed at the beglnnin8 and during each analytical session. To monitor

both reproducibility and drift over a single analytical session (8-24 hours), a single glass

bead is used as an "internal standard". Every 3 to 5 analyses, the operator returns to the

"internal standard".

Based on the major element classification scheme of Delano (7), the glass beads thus far

analyzed in this study are: A-lh Green B, Green A, VLT, Yellow, Orange, Red/Black; A-17 Orange

I (preliminary), Orange I/ (preliminary), Orange 74220-type; A-15 Green A, B, C (preliminary),

D, E, Red (preliminary) and All Orange (preliminary). In addition, A-16 Ultra Mg 81asses (8)

and the A-14 LAP glass (9) have been analyzed. REE patterns and selected trace element

characteristics of the various glass types show wide to subtle variation among glasses of

similar composition from different sites (i.e. A-14 VLT va A-17 VLT), wide variation among glass

types (i.e. high-Ti vs. low-Ti glasses) and wide (A-14 Red/Black) to subtle (A-15 Green)

variations within a glass type.

Variations among glasses of similar composition from dlffer_t ait_ . REE patterns for the

low-Ti glasses from A-14 (Green A, Green B. VLT) are commonly llght-REE enriched with (Ca - 14-

70 x chondrite) Sm/Eu - 6-14, Be/St • 1.4 and Zr content between 66-508 ppm. In contrast, the
59

SIMS ANALYSIS OF GLASSES: Shearer st •l.

low-Ti glasses at the A-17 site (VLT) have flat REE patterns, lower REE •bund•nces (Ca - 6-9 x

chondrite), slight (-) to No Eu anomaly, Ba/Sr < 0.5 and Zr-20-50 ppm. Relative to the A-17

low-Ti glass, th• A-14 glasses have • trace element signature which suggests • KREEP component.

Regardless of possible models, the glass compositions indicate that mantle characteristics at

the two sites •re intrinsically different.

Tzace elan[mr differences among al•sses of oontr•sting ma_or element chemistry

Comparisons of glasses from individual sites (A-14, A-17) indicate that th• low-Ti glasses

(Green, VLT) •re depl•ted in incompatible elem•nts (REE, B•, St, Zr, Zn, Cu) and enriched in

compatible elements (Co, Hi (7)] rel•tlv• to the high-Ti glasses (Red/Black, Orange). These

d•t• •re g•nerally consistent with various lunar mantle cumulate and hybridization models (i.e.

7,10,11,12) which predict that high-Ti basalts r•pr•sent • more evolved source. However, the

evolved cumulate mantle source appears to he composltlonelly variable (A-17 Orange 74220 and

Type I; A-17 Orange Type II; A-14 Red/Black; A-14 Orange).

Composltional variations within individual Klmes Rroups. Trace element variations within

individual glass groups (i.e. Red/Black, A-15 Green) confirm their compositional heterogeneity

observed by major element studies (i.e. 7). The Red/Black glasses display a large range of Be,

Rb, Na20, K20 whereas REE and Zr show limited enrichment. These variations may be attributed to

selective assimilation or volatile exchange during eruption. More subtle are the compositional

variations observed in A-15 Green Glass. Cluster analyses of the trace element data delineates

five groups (A-E), equivalent to those previously defined (7). Two trends are defined on trace

element variation diagrams (Zr, Ba, REE vs. Co); a high-Co trend composed of groups A and D and

a low-Co trend composed of groups B, C, and E. REE abundances of groups A, B, D and E overlap

(Ca 3.3 to 8.5 x chondrlte), whereas abundances in the more MgO-rich group C are slightly lower

(Ca - 2.7 - 3.1 x chondrite). Trace element variation trends (e.g. positive correlations of Zr,

Be, Sr and REE with Co) •re difficult to reconcile in terms of fractionatlon or partial melting

processes involving • single, chemically distinct mantle source. Magma mixing and very subtle

compositional differences in mantle source are being evaluates to explain the complex chemical

trends.

Trace element oharscterlstice of Ultra M_ Klaaeea. Wentworth and McKay (8) identified a

suite of minute Ultra Mg glasses in A-16 regolith braccias. The wide major element

compositional range and Ultra-Mg character (atomic Mg/Mg+Fe _ .g0) of the glasses suggest a

variety of possible origins from complex impact processes to complex volcanic processes

involving rather exotic and primitive magmatism. Trace element data show a wide range of

concentrations (La N " 25-290, Yh N " 16-120, Be " 80-1000, Zr - 182-800 and Sr = 70-230) but with

distinct trace element characteristics Ba/Sr > I, (La/Yb)H - 1.5-2.5, (Eu/Sm) H - 0.1-0.3, and

low slderophile element concentrations (Co - 2-10 ppm). Low Co and high incompatible element

concentrations eliminate the possibility that these glasses are a product of lunar komatiitlc

volcanism. The low siderophile concentrations suggest • complex, impact melt process.

ContinuinR studies. These initial SIMS generated trace element data indicate that picritic

glasses represent partial melts derived from numerous compositional distinct sources. In

addition, the data are useful in distinguishing volcanic process from impact related phenomena.

Continuing SIMS studies on lunar glass beads will emphasize further work on A-17 (additional

VLT, Orange I and II, Green), A-I4 (further studies of chemical variations within glass groups)

and A-15 (Yellow and Red), end new studies involving A-If, A-12 and A-16, new volcanic types,

calibration of • new trace element package and SIMS analyses of surface coatings.

References: 1) Shlmlzu, M. (1978) EPS____LL 39, 395-405. 2) _eke et el. (1983) OC___AA47, 1635-

1640. 3) Jolllff et el. (1969) GC._._AA53, 429-441. 4) Rd_ and Hart (1982) Int. J. Mass. Spec. Io_

Phys. 44, 231-255. 5) Shimlsn (1985) Int. J. Mass. Spec. Ion Phys. 44, 231-255. 6) Shimizu et

el. (1978) GC____AA42, 1321-1334. 7) Delamo (1986) PLS___C 16, D201-D213. 8) Wentworth and McKay

(1988) PLS____C 18, 67-77. 9) Papike at el. (1968) LP____SXX, 818-819. i0) Bu&hes et •l. (1988) GC___6A

52, 2379-2392. Ii) Rlngwood and Kesson (1976) PLS.___CC7, 1597-1722. 12) Taylor and Jake• (1974)

PLS.____qCC 5, 1287-1305.
6O

YOUNG DARK MANTLE DEPOSITS ON THE MOON; Paul D. Spudis, U.S.

Geological Survey, Flagstaff, AZ 86001

Dark mantling deposits were recognized and postulated to be of volcanic origin during

the geologic mapping of the Moon (e.g, [1]). Based on a general belief that "dark" -

'young" (see [1,2]), they were considered to be the youngest products of lunar volcanism.

The Apollo 17 mission was sent to the Taurus-Littrow Valley to sample the extensive dark

mantle deposits in this region that were inferred to be young [3-5]. Samples returned from

that mission showed that the Taurus-Littrow dark mantle was the product of pyroclastic

volcanism that occurred over 3.7 billion years ago [6]. Since then, it has been widely

assumed that lunar pyroclastic volcanism was confined to the "main phase" of mare

volcanism, i.e., from around 3.8 to 3 billion years ago. Subsequent reinterpretations of

other lunar dark mantle deposits [7], the stratigraphy of Mare Serenitatis [8], and crater

densities in the Apollo 17 region [9] all concluded that lunar pyroclastic deposits are old

(> 3 Ga) and that "young" dark mantling deposits probably do not exist.

Estimating the age of dark mantle deposits on the Moon is difficult. Because these

units are fine-grained, unconsolidated debris in which craters are eroded very rapidly, crater

densities are of little value [9]. The only way to estimate the age of unvisited dark mantle

deposits is to bracket them stratigraphically with units that can be dated by crater densities.

I here discuss two dark mantle deposits on the eastern limb of the Moon that occur in

different geological settings and attempt to determine their ages. Although of small extent,

their presence suggests that explosive volcanism on the Moon continued to as recently as

about 1 billion years ago.

Dark mantle deposits of Mare Smythii. Mare Smythii is a circular mare on the equatorial

eastern limb of the Moon [10, 11]. Several dark deposits are evident on high-sun

illumination photographs of the region. In particular, dark mantle deposits occur around

the margins of the inner basin ring (370 km dia.) near the craters Haldane, Kiess, and

McAdie. These deposits are closely associated with the mare fill of the Smythii basin.

Within the basin, the dark mantle material underlies the mare in some places (e.g., western

rim of McAdie at 3 N, 93 E) while it overlies mare basalt elsewhere (e.g., near a volcanic

vent north of Haldane at 0, 83 E). It thus appears that eruption of mare basalt in the

Smythii basin was accompanied by eruptions of dark mantling material; such a relation is

similar to that found at the Apollo 17 site, where dark mantle pyroclastics are of similar age

(and composition) to the local mare basalts.

Dark mantle deposits within Taruntius crater. The crater Taruntius (5.6 N, 46.5 E; 55 km

dia.) is a floor fractured impact crater [12] of Copernican age. A low albedo deposit is

associated with irregularly shaped craters and fractures on the floor of Taruntius; these

deposits are similar to localized dark mantle deposits [13] that occur within crater floors

elsewhere on the Moon. They probably represent deposits from vulcanian eruptions [13]

associated with the injection of magma beneath the crater floor, floor uplift, and fracturing

[12]. The Taruntius dark mantle deposits are also associated with minor mare basalt

flooding of portions of the crater floor. All of these volcanic events post-date the formation

of the crater Taruntius, which appears to be about the same age as Copernicus.

Ages of the Smythii and Taruntius dark mantle deposits. I have attempted to determine

the ages of these two deposits by measuring the crater densities on units that have a clear

stratigraphic relation to the dark mantle (Figure 1; after [14]). The Smythii mare basalts

(point "Mare Smythii" in Fig. 1) are among the youngest on the Moon; an estimate based

on known ages of the Apollo mare sites and inferred ages of Copernicus and Tycho (850

Ma and 100 Ma respectively; [15]) suggest an age of about 1.2 +_. 0.3 Ga for the basalts of
61

YOUNG DARK MANTLE DEPOSITS; Paul D. Spudis

Mare Smythii. Because the dark mantle deposits of the Smythii basin are contemporaneous

with the basalts, a similar age for the dark mantle is inferred, i.e., from about 1.5 Ga to less

than 1 Ga. Similarly, the crater density and inferred absolute age of Taruntius suggests that

it is about the same age as the crater Copernicus (about 1 Ga; [15]). The dark mantle on

the floor of Taruntius post-dates the crater; thus, these volcanic deposits must be younger

than 1 Ga. The dark mantle deposit within Taruntius is the youngest recognized volcanic

unit on the Moon, possibly younger than the mare flow that embays Lichtenberg crater [14].

While these dark mantle deposits are not extensive, their existence indicates that very

late volcanism on the Moon exhibited the same styles of eruption and emplacement

operative during earlier epochs of mare volcanism. Both of the two major types of

occurrence determined for explosive volcanic deposits on the Moon [13] are displayed by

these two pyroclastic deposits.

References. [1] Wilhelms D.E. and McCauley J.F. (1971) USGS Map 1-703. [2] Mutch T.A.

(1970) Geolom, of the Moon. Princeton Univ. Press, 324 pp. [3] Carr M.H. (1966) USGS

Map 1-489. [4] Scott D.H. et al (1972) USGS Map 1-800. [5] Greeley R. and Gault D.E.

(1973) _ 18, 102. [6] Taylor S.R. (1982) Planetary_ Sci¢nc¢, LPI Press, 481 pp. [7] Head

J.W. (1974) P,L,$_Q5th, 207. [8] Howard K.A. et al. (1973) Apollo 17 PSR. NASA SP-330,

p. 29-1. [9] Lucchitta B.K. and Sanchez A. (1975) _ 6th, 2427. [10] Wilhelms D.E and

EI-Baz F. (1977) USGS Map 1-948. [11] Spudis P.D. and Hood LL (in press)

[12] Schultz P.H. (1976) _ 15, 241. [13] Hawke B.R. et al. (1989) _ 19, 255.

_I1"4]Schultz P.H. and Spudis P.D. (1983) _ 302, 233. [15] BVSP (1981)

Y_0.l.ga.Uil_ Pergamon Press, Ch. 8.

10

!

0

4.0

vii -

Imlxian

_ii_ -J

7_ -w

Eratosthenian Copernican

APOLLO T

15 T+APOLLO 12

MARE SMYTHII

__._ \_ TARUNTIUS

IMBRIUM FLOW 'k _ TYCHO

COPERNICUS _ I

I I |

3.0 2D 1.0 0

ABSOLUTE AGE IGal

Figure 1. Crater densities and absolute ages for sampled units (open circles) and inferred

ages for unsampled units (solid circles) on the Moon. Dark mantle deposit ages (above

curve) are inferred from stratigraphic evidence. Lunar stratigraphic divisions shown at top.

After [14].
62

APOLLO 15 GREEN GLASS I: NEW COMPOSITIONAL AND PETROGRAPHIC

Washington INSIGHT. Alison University, M. Steele, St. Louis, RandyMO L.63130. Korotev, and Larry A. Haskin, Dept. of Earth and Planetary Sciences,

Introduction: Because the petrogenesis of the Apollo IS green glasses is still enigmatic, we are currently

examining a suite of them using a variety of techniques, which include determining both ma'or and trace

element abundances for individual spherules, assessing both green glass vitrophyres and vitric s_ies together,

and utilizing petrographic observations. We hope that b,/ characterizing individual particles at this level of detail we will provide additional constraints on their formaUon.

Materials and Procedu_: Green glass particles were handpicked from splits 15426,9012 and 15426,154. The

matrix (unconsolidated material < 1 /ag) of 15426,9012 is light green in color and is composed mainly of

pulverized green glass. It is also relatively rich in larger (>50lag) green glass particles. In contrast, 15426,154 is free grained and brown/grey with sparse large

green glasses and contains a variety of litholog/es. Glasses were

chosen from these two diverse splits of 15426 so that we could evaluate whether green glass compositional spread was related to host material or split.

Three hundred six,y-five glass particles were analyzed by INAA. Following radioassasy, petrographic

examinations were made of each, with the following features noted: crystallinity (vitric/vitrophyric); droplet

shape where determinable (sphere/spheroid/elongate); presence or absence of surface coating; contamination

(i.e. adhering regolith); and, in the case of broken spherules, the approximate percentage of the original droplet

remaining, where determinable. Although continua exist among some of these criteria, each particle was

described as objectively as possible so that physical features could be compared with compositions.

Vmally, 41 of the 365 particles were analyzed byllect[on .m.!.c/oprobe. These 41 spanned the entire

compositional range indicated by INAA, and all were me. in anamon to several weB-characterized probe

standards, one of our own green glasses was used as an "internal standard" for all probing sessions.

_Result_ and Discussicn: Relative elemental abundances determined by INAA are precise for the elements

plotted in Figures 1-3 and limited only by "counting statistics." However, the accuracy of the absolute

abundances is limited by the accuracy with which the sample masses can be determined, and this is the largest

source of uncertainty for these small samples (range: 36-3800 _ug; mean: 120 ,ug). Errors in mass determination

lead to correlated errors in element concentrations along diagonal lines intersectin the

plots such as Figs 1-3 To corn .... ,. r^..._:_,_. . . _ , . g origin on 2-element

• • t,,-,-,_-_,,. ,_,J wv_gnmg errors {ana other correlated err r "

for the 41 glasses we have probed to date have been normalized to m: .... ..a.. ..... ,_o ._ ff pr,esenl), INAA data

,,.,,.,p,uv_ ,gamts using Pet) coocentraU_on,

which is determined by both techniques. Figures la and lb compare data for Sc and Fen before and after

normalization and show that the two positive trends in the unnormalized INAA data are artifacts induced by

weighing errors, and that the samples in the trends actually form tight compositional clusters (Figure lb).

Furthermore, the suite having the greatest range in Fen (squares; Figure la), rather than being of variable Sc

concentration, actually exhibits nearly constant Sc concentration (Figure lb).

Major element data for 41 glasses indicate that the Sc-FeO divide we observe (Figure la, lb)

corresponds to the major compositional hiatus described by Delano [1]. In general, we agree with the group

divisions suggested by Delano [1] and will thus retain the established names of A though E for the green glass

groups, although we will not presently separate E from D or C from B, and we will elaborate on A.

Figure 2 illustrates that there is a split in Group A and that glasses on either side of this split show

significant petrographic _and morphologi'cal d!f.ferences.. These suggest that Group A actually consists of two

subgroups that formed unuer amerem eruptive conoations. On plots involving compatible elements (e.g.,

Figure lb) these subgroups, which we will call High-Sm Group A and Low-Sm Group A, are not entirely

resolved although the amount of overlap is minor. The compositions of individual spherules within each of

these clusters appear to be nearly identical within analytical uncertainty for Fen and Sc Fi ur lb), but trends

are still present lot Na and probably for REE (F'_,ure 2). ( g e

Figure 3 illustrates how Group B-C differs from the other green glass groups. On all plots we have

examined to date, Group B-C forms apparent trends rather than dusters as the other groups do. In addition,

although it is often ambiguous on major-element plots whether or not Groups A, B, and C form a

compositional continuum (e.g., [1, Figure 2-8]), trace element data indicate that they do not. There is a definite

compositional break between A and B-C on Figure 3, and this is evident on other plots as well (e.g. Sm vs.

Na20 for Group B-C, not shown). Furthermore, Figure 3 suggests that Group B-C itself might consist of three

clusters aligned to resemble a single trend. We offer the sulggestion that all Apollo 15 green glasses may

belong only to discrete, tight compositional groups, of approxa_ately the extent of compositional variability

exhibited by the High- and Low-Sin Group A clusters, but that some are sufficiently similar in composition to

overlap or in some cases produce apparent compositional trends. This hypothesis is essentially an extension of

previous suggestions that, like many other kinds of lunar glass such as the Apollo 17 orange glass [2]. Apollo 15

green glass occurs as compositional clusters [1; 31. Individual clusters could represent material from "

eruptive events or phases, each from a slightly different sour ....... ,.... ,_......... dis_ete

•, ., ,.,. u, ,,_m, out now mose sources might be relatetl

still has to be explained. We cannot be certain, however, whether the B-C group consists of obvious discrete

clusters or a single, continuous trend because we have not yet analyzed enough samples from this group.
APOLLO 15 GREEN GLASS h Steele A. M. et all.

_. Combined major and trace element data reinforce previous indications [1] that the Apollo 15

green glasses belong to several distinct compositional groups. Furthermore, incompatible trace element data

indicate that one additional division (High-Sin vs. Low-Sm Group A) not evident on plots involving compatible

elements is present, and that other analogous divisions may also exist within Group B-C. Not only are the longignored green glass vitrophyres members of these previously defined groups, their distribution, along with other

petrographic criteria, help to distinguish such clusters having only slight compositional differences.

REFERENCES: [1] Delano, J.W. 1979. PLPSC 10: 275-300. [2] Hughes, S.S., Delano, J.W. and Schmitt, R.A. 1988. PLPSC XIX: 517-518.

[3] Delano, J.W. 1986. PLPSC XVI: D201-D213.

63

40

38

E 36

Q.

o34

09

32

30

15

Figure la.

INAA (n=365)

n

o

o• o

o ° _

°

O O

/

17

FeO

O

o

t3 ° '_'

d' * * w'_f

O 4, V V

n Group B-C [1]

o

a GroupA [1]

v Group D-E [1]

1'9 ;_1 23

(wt.%)

40

38

E

36

Q.

v

o

0934

32

30

Figure lb.

Microprobe-normalized (n=41)

o _ _"

O o O OOO O O 0 ?

v

D

15 17

FeO (wt. %)

o B-C

o High-Sin/_

Low-Sin A

v D-E

21 23

1.1

0.9

E

Q.

ca. 0.7

E

03

0.5

Figure 2.

INAA Htoh-Srn Group A (o):

Group A alone. 44_ ofsamples are vitropnyres

29*/. of vitric samples .

e oo appear tO have a coa_

ot o o_°_¢ 8o_ oo oo 37% of vitflC samples

o_._ 3o0 are elongated

Aa ,_ Low-Sin Group A (_): 10% of _11samples

a _a A %,= ,L are vttrophytes

13% of vitr_csamples

appear 1o havea c,oa'

10% of vitnc samples

are elongated

0.9

E

Q.

""0.7

E

03

o o

0

8 o

1.1

Figure 3.

INAA

o

0.5 oe_

0

5O

o o

0

o _oO

• o

ooo

_°°

at,

o/

0.3 0.3 _ 76 '

0.1 0.i2 0.i4 o.ie o.ie 0.2

Na20 (wt. %) Co (ppm)

I_ B-C

* High-Sin A

a Low-Sm A

90

Notes on Figures 1-3. Small c_ represent one sigma uncertainties in the relative abundances of the elements in question. The larger

diagonal bars emanating from the small cro_cs on the INAA plots (Figure la, 2, 3) represent our estimate of the correlated random

uncertainties in absolute concentration if we add (1) an estimate of a correlated random uncertainty from INAA, and, (2) a weighing

error of *-4%, which is what we have observed for replicate weighings. When one corrects for correlated errors by normalizing to

microprobe FeO values, the only serious remaining correlated error is that for FeO by microprobe, which is what is represented by the

much smaller diagonal bar on Figure lb.
64

APOLLO 15 GREEN GLASS lh GROUP PROPORTIONS AND THE CLUSTER HYPOTHESIS.

Alison M. Steele, Randy L. Korotev, and Larry A. Haskin, Dept. of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130.

Despite the exceedingly small sizes of the Apollo 15 green glasses and the corresponding difficulty in

obtaining precise analyses of individual spherules, several studies have successfully illustrated and confirmed

their compositional variability [1, 2, 3, 4]. However, most workers have approached the green glass problem by

using a database limited to either major elements [1, 3] or minor and trace elements [2]; only one study [4] has

combined both types of compositional data with petrographic information. The development of petrogenetic

explanations for green glass has previously been influenced by data that do not illustrate complete green glass compositional characteristics.

Ma et 02. [2] used INAA procedures similar to ours to analyze green glasses from an unspecified split of

15426. Figure 1 superimposes Sc-FeO data for the spherules they analyzed on the compositional range we

found [4]; the difference in distribution is striking. Some compositions (e.g. Group B-C; E) are relatively rare.

Ma et 02. [2] attempted to sample the entire compositional range of green glasses by choosing 55 particles that

covered the full range of Mn and Na20 concentrations, which they determined first for a larger number of

particles. While not exactly random, this procedure should not cause gross discrimination between Groups A

and D-E, since both groups have comparable ranges in Mn and Na20. However, most of their samples belong

to Group A (Figure 1), suggesting that the split of 15426 they were allocated did not have the same ratio of

Groups A to D-E as either of ours; based on our results, we would have expected a preponderance of Group DE (Table 1). As only four of their glasses plot in the D-E field, these authors were not able to distinguish D-E

as a separate group, and their interpretations reflect this. In addition, we presume that since their INAA data

span a slightly larger range in Sc and FeO than ours and lie along the same correlated error line (Figure 1) the

trends in their data probably result largely from correlated errors, as ours do [4]. Thus, we find it difficult to

support their suggested petrogenetic explanation of fractional crystallization lines lying orthogonal to a general mixing trend (e.g. [2, Figure 3b, 4b]).

Similarly, workers who examined only major element data [1, 3] could not observe that Group A should

be subdivided into the two discrete clusters that are fully evident on plots of incompatible trace elements [4,

Figure 2]. That this division is fully evident only in incompatible trace elements illustrates how compositionally

similar some green glass groups can be. It seems reasonable, then, that other clusters with compositions that

differ only slightly from one another might exist and are as yet unidentified, such as within Group B-C [4].

Furthermore, some clusters could overlap in composition with respect to all elements, so they would be visually

inseparable on any given 2-element plot. This might be the case for Group D-E, because it forms a noticeably

larger, looser cluster than Group A [4, Figure 2], and thus might be composed of several overlapping or

s_perimposed clusters (we will subject Group D-E to statistical analyses to test this possibility).

Differences among subsplits of 15426 in the proportions of the different compositional groups, such as

those between our study and that of Ma et 02. [2], have been reported previously (e.g. [3]). A compilation of

studies done since the groups were first designated as A-E [1] is presented in Table 1. Group proportions we

find [4] contrast with Delano's [1] initial f'mdings, and those of both Ryder [3] and Ma et 02. [2] differ even more

in having a predominance of Group A. Curiously, even though we deliberately chose our samples from two

dissimilar splits of 15426, one very green-glass rich (,9012) and the other ix)or (,154), our splits show essentially

the same percentages of the various groups. We take the results presented in Table 1 at face value. These

differences suggest that green glass of all compositions was not deposited simultaneously. At the very least,

emplacement of the two groups on either side of the Sc-FeO hiatus (Figure 1) appears to require a number of

discrete events. The differences shown in Table 1 also support the extended clustering hypothesis [4] in which

each identified cluster would represent a single pyroclastic event. It would follow that, since different portions

of a clod contain different proportions of the various compositional clusters, the green glass clods may retain

some of the stratigraphy of a volcanic field where multiple pyroclastic events occurred. At one extreme, there

may have been a single vent emitting different material at different times, at the other extreme, a series of

different vents each emitting materials of a single group. We plan to investigate mechanisms to see how the

compositions of the various clusters might relate to one or a few sources.

REFERENCES: Ill Delano, J.W. 1979.PLPSC 10: 275-300. [2] Ma, M-S., Liu, Y.-G. andSchmitt, ILA. 1981.PLPSC 12B: 915-933.

[3] Ryder, G. 1986.LPS XVII:738-739. [4] Steele, A.M., Korotev,R_L.and Haskin, L.A. 1989:.this volume.
APOLLO15 GREEN GLASS !I: Steele A.M. et al.

65

E

O.

Q.

O

¢/)

4O

38

36

34

32

30

Figure 1. o

o O

INAA Studies ° °_ o_,d'JL, % o_

° • o =,,_311dr o'_-'_>o

o • == o°o°_--_@°_

o o %° o°_°

15

o o ° I ¢ Our study (n=365)

• Me et al. (1981)

(n:55)

Data not normalized

17 19 21

FeO (wt. %)

23

Figure 1. See [4] for explanation of error expressions for our data. Error estimates for the data of Ma et al. [2] are taken from their

Appendix.

Table 1.

Comparison of Apollo 15 Green Glass Studies

Author

Delano

(1979)

Ma et aL

('981_____L_)

Ryder

(1986)

Steele et al.

(1989)

Steele et al.

(1989)

Spl_(s)

15425,15

15426,72

15427,26

15426,?

15426,26

15426,154

15426,9012

# % samples analytical

analyses group D-E meth_m__h___

416 probe

55

113

142

223

% samples

group A-C

65%

93%

83%

39%

33%

35%

7%

17%

61%

67%

INAA

probe

INAA+ probe

INAA+probe

Table 1. Comparison of the green glass group proportions found by different workers. Our percentages [4] have been recalculated on a

vitrophyre-free basis for the comparison, since the other workers examined only vitric particles.
THERMODYNAMIC CALCULATIONS OF TRACE SPECIES IN VOLCANIC GASES:

THE POSSIBLE APPLICATIONS OF NEW COMPUTER MODELS TO LUNAR

VOLCANIC GASES AND SUBLIMATES; R. B. Symonds and W. I. Rose,

Dept. of Geological Engineering, Geology, and Geophysics,

Michigan Technological University, Houghton MI 49931 (906-487-

2714)

Over the past several years, we have studied metal transport in

volcanic gases sampled from volcanoes on Earth. Our approach has

consisted of using a variety of field sampling techniques at

high-temperature volcanic fumaroles followed by thermochemical

modeling of the resulting data. We have found the thermochemical

modeling to be particularly useful in understanding chemical

processes in terrestrial volcanic fumaroles. Here we will

present some of our results of the thermodynamic calculations for

terrestrial volcanic gases. We are now looking for new

applications of our programs and propose to apply the models to

lunar volcanic gases. Several possible applications will be

discussed as well as the necessary inputs to our programs to

complete the modeling. A major purpose of this presentation is

to obtain feedback on the best possible input parameters for our

computer models.

SOLVGAS and GASWORKS (our thermochemical models) are computer

programs for calculating homogeneous and heterogeneous (GASWORKS)

equilibrium in gaseous systems. They accommodate minor and trace

components (e.g. Na, As, Cu, Zn, Pb, Mo) and species in addition

to the major ones (those in the C-O-H-S-CI-F system), and provide

for strict oxygen mass balance, allowing calculation of the

oxygen fugacity at any P and T. The programs calculate the

distribution of hundreds of gas and solid (GASWORKS) species in a

system of 30-40 components as a function of temperature and

pressure using the basic formulations of equilibrium calculations

for aqueous systems (i) modified for gases. The calculations

consist of solving simultaneously a series of mass balance and

mass action equations using a Newton-Raphson method.

By calculating the most stable gas species out of the hundreds

possible, SOLVGAS and GASWORKS determine the molecular form in

which elements are actually transported in the gas phase. The

programs have been applied to trace element transport studies at

terrestrial volcanoes. Examples of applications to Merapi

Volcano, Indonesia (2) and Augustine Volcano, Alaska will be

discussed. In both cases, the calculations show that (on Earth):

i) the concentration of most elements in high-temperature

volcanic gases can be explained by equilibrium volatilization

from magma, 2) most metals are transported as chloride gas

species, and 3) sublimates at these fumaroles form in an order

predicted by their equilibrium saturation temperatures.

SOLVGAS and GASWORKS are potentially applicable to a variety of

lunar volcanological problems: I) the speciation of major and

trace components in lunar volcanic gases, 2) prediction of the

concentration of trace elements in a lunar volcanic gas, and 3)

the speciation and origin of lunar volcanic sublimates.
67

THERMODYNAMIC CALCULATIONS OF TRACE SPECIES IN VOLCANIC GASES:

THE POSSIBLE APPLICATIONS OF NEW COMPUTER MODELS TO LUNAR

VOLCANIC GASES AND SUBLIMATES; R. B. Symonds and W. I. Rose

To attack these problems, we need help to obtain (or derive a

best estimate of)

1) the elemental composition of the lunar volcanic gases (C, O,

H, S, Cl, F, Br),

2) the pressure and temperature conditions during degassing,

3) the range of compositions and mineralogy of the lunar

basalts, and

4) the composition and mineralogy of the lunar volcanic

sublimates.

This proposed study would improve on previous work (3-5) on

lunar volcanic gases and sublimates by 1) considering more

possible gas species than was done by (3), 2) providing a

theoretical model for the origin of sublimates on the moon, and

3) predicting possible sublimate phases not described by (3-5).

(1) Reed M. H. (1982) Geochimica et Cosmochimica Act_, 48, p.

513-528.

(2) Symonds R. B., Rose W. I., Reed M. H., Lichte F. E., Finnegan

D. L. (1987) Geochimica et Cosmochimica Acta, 51, p.

2083-2101.

(3) Naughton J. J., Hammond D. A., Margolis S. V. and Muenow D.

W. (1972) Proceedings of the Third Lunar Science Conference,

p. 2015-2024.

(4) Meyer C. Jr., McKay D. S., Anderson D. H., and Butler P. Jr.

(1975) Proceedinqs of the Sixth Lunar science Conference, P.

1673-1699.

(5) Chou C. L., Boynton W. V., Sundberg L. L., and Wasson J. T.

(1975) Proceedings of the sixth Lunar Science Conference, p.

1701-1727.
PHENOCRYST CONTENT OF MARE VOLCANICS: INFERENCES FOR MAGMA

MIGRATION MECHANISMS ON THE MOON G. Jeffrev Taylor, Institute of Meteori "

and Department of Geology, University of New Mexico, Albuquerque, NM 87131 tics

A striking feature of lunar volcanic deposits is the rarity of phenoc sts rown

depth. Mare basalts have no more than a few "er"°-', ..c _1. ....... ry; .g , at

have less than one percent Observed nhenocrve_t_"_]'.._".._."_"- °cr)'sls; p_o¢lastlc glasses

• • ,- -..,_._, _u_., _ts those in ApOllO 13 pyroxenephync basalts, formed when the basalts erupted(I,2). Even in Apollo- 15 olivine basalts.

among the basalts richest in phenocrysts, the phenocrysts seem to have rown in thicl_

flows on the surface (3)• This is in sharp contrast to terrestrial basalts, w_ich are rarely

free of phenocrysts (4); most basalts from the Aleutians, for example, contain 25 to 55%

phenocrysts. Basalts associated with rifts, such as MORBs, contain fewer henoc sts.

_(typically < 10%), but few are comnletel,, a,-,h,-,,ic "^ "" v-__,_ _ , p ry .-

I ar"ue ,.ol ..... 1._..,_._ j.,.,. _. .., r. ,J _.--,. ,,,,. _.uuu, personal communication.

• b . o_Low.tnett this Ul_terence mpnenocryst content between t ical terrestrial an)d

mnar oasalts is caused mostly by differences in migration rates dY_u_to differences in

magma viscosities, and by the rarity of magma chambers on the Moon•

Magma migration

As Marsh (4) points out, it is imorobable to observe terrestrial mam'nas near th

liquidi, so they contain phenocrvsts Thus it _.... ,i- ...... ,-- ,- ,., . . eir

J'r*" - -1 ..... a.. " , ._._.,Jlla tLlat llli:llC oasalt mazmas nao ouit

alrIerent thermal nlstorles titan did terrestrial basalts This imolies that th'_v _n,,,,,_ _,,._e

rapmly Irom meir source re_sions or traveled th ..... ,. ;......... t . -;---.Td .... ; ..... '-'-_.

• _ e_ _,au_j _Juttct rOCK, or ooln. I hey also coul0

not nave spent significant time in subsurface holding chambers•

Transit time. The velocity of a magma moving by porous flow is directly proportional to the gravitational acceleration (g) and inversely proportional to viscosity (5).

Lunar gravity is one-sixth of that on Earth; mare basaltic v_scosities are about ten times

less than those of terrestrial basalts. Thus, lunar magmas will flow from their source

regions about 50% faster than terrestrial basaltic magmas• Once they reach the colder,

more solid lithosphere (and perhaps even before), magmas cease migrating by porous flow

and probably move by fluid fracture (5), essentially making their own dik'e-like con uits.

As shown by Turcotte (e.g., 5) for laminar flow the velocity lsoroportional to g and h _ (the

conduit width), and inverselv proportional to the viscosity l_ecause the c " "

proportional to g-1/3, the ve[oci ,, ,-,_".... 1. ........ .__ ,.... ondult w!dth !s

. . t: ,.,, ,.,a,.,., l.,_upagatlon tano nence ma_ma ml ra 1

directly proportional to gl/3 and inversely nronortional t" v; .... :-- "_'2--"- g t on) IS

• .- . - ,- _ ._ r r v la,,,uaity. _neretore, magmas

W_ll move a rector ot ten _aster on the Moon because of the lower viscosities of lunar

basaltic magmas and the weak dependence on gravity. It appears that there was less time

available for cooling lunar magmas, so there would be fewer phenocrysts in magmas reaching the lunar surface. In addition, regional stress fields are proportional to gravity, leading

to wider conduit widths and greater eruption rates on the Moon than on Earth (6)• '

Cooling rates during migration. A consequence of the larger conduit size is a slower

cooling rate, leading to a greater time spent near the liquidus. The greater volume of

magma coursing through a given conduit also would have led to greater heating of the

surrounding wall rocks, thus limiting cooling of magmas in the channels• This, of course.

would have led to fewer phenocrysts and less fractionation.

Magma chambers. Magma chambers are crystal factories. In them, magma ceases

to migrate through the crust and cools by conduction, mainly through the top and bottom•

Crystals form and sink or float. Although most are captured by the solidification front (7),
Taylor, G. J.

Phenocrystcontent 69

some escape and are mixed by convection or dissolved. If the fluid portion of the ma[gma

erupts, it will containphenocrysts, their abundance increasing as the chamber crystalhzes.

Frequent eruption andreplenishment might lead to a substantial amount of basalt erupted

with low phenocryst contents, but eventually the system would produce some lavas laded

with phenocrysts. The lack of phenocrysts in mare basalts indicates that magma chambers

were rare on the Moon. This Is supported by the absence of collapse structures in lunar

volcanic regions (8), evidence for the absence of near-surface magma chambers. The

eneral intensely brecciated nature of the upper lunar crust is consistent with the rarity of

rge magma chambers. It also suggests that mare basalt magmas might form extensive

networks of dikes.

Where did mare basalt fractionation take place?

Suites of mare basalts show clear evidence for low-pressure fractional crystallization (e.g., 9); for example, calculations indicate that up to 25 wt.% of olivine and Fe-Ti

oxides fractmnated from Apollo 17 high-Ti basalts. If the basalts erup.ted without phenocrysts, where did this fractionation take place? There are two possibdities: First, it could

have occurred in conduits as the magmas migrated through the crust. Some crystallization

would have occurred alon_ the walls, especially early in a magmatic cycle when the walls

were cold. The crystals m_ght nucleate on the walls, thus removing them from the flowing

magma. Continued build up of such crystals would increase the viscosity of a zone near

the walls, eventually reaching a point where the viscosity increases so much that the material behaves as a solid, i.e., a rheological locking point (4). Alternatively, much of the

differentiation could have occurred in flows. Some thin mare basalt flows traveled for

hundreds of kilometers (8), during which substantial amounts of differentiation could have

taken place. As Walker et al. (3) showed, thick flows can also differentiate. Fractionation

processes in thick, flowing, low viscosity lavas ought to be studied.

Implications

The unique rheological properties of lunar magmas and the tectonic env!ronment

in which they operated have several consequences. the rarity oI magma cnamoers suggests that magma recharge was less effectwe on the Moon than it might be on Earth,

although it could occur to some extent in a complex system of dikes. It seems unlikely that

vast layers of ilmenite-rich cumulates were produced from mare basalt magmas, though

such cumulates might have formed in lava lakes. For example, ilmenite-rich cumulates

could exist in the bottom of the crater Jansen in Mare Tranquillitatis. If magma chambers

were rare for mare volcanism, perhaps the magmas thatproduced highland rocks also

rarely occupied them. If so, most pristine highland rocks formed in dikes, not large l?lutons. The presence of large exsolution lamellae in the pyroxenes in some of them m_ght

simply be a record of the depth of their emplacement, not the size of the magma bodies in

which they formed.

References: 1) Dowty, E. et al. (1974) J. Petrol. 15, 419-453. 2) Lofgren, G. et al. (1974) PLSC 5th, 549-567. 3)

Walker, D. (1976) PLSC 7th, 1365-1389. 4) Marsh, B.D. (1981) Contrib. Mineral. Petrol. 78, 85-98. 5) Turcotte, D. (1987) In Magmatic Processes: Physicochernical Processes, 69-74. 6) Wilson, L. and Head, J.W.

(1988) LPSC XIX, 1283-1284. 7) Marsh, B.D. (1988) Geol. Soc. Am. Bull. 100, 1720-1737. 8) Head, J.W.

(1976) Rev. Geophys. Space Phys. 14, 265-300. 8) Papike, JJ. et al. (1976) Rev. Geophys. Space Phys. 14, 475-

540.
70

IN S_ARCH OF ANCIENT LUNAR PYRO_CL_STICS. S. J. Wentworth I, D. J.

Lindstro4"n , D. S. McKay , and R. M. Martinez . Lockheed, 2400 NASA Rd. 1, Houston, TX

77058; "NASA Johnson Space Center, Houston, TX 77058.

Background During previous studies of glass clasts in Apollo 16 regolith breccias, we

found traces of mare and ultra Mg' (atomic Mg/MB + Fe..>0.90) glasses in the ancient (-4 Gy)

regolith breccias [1,2]. Some of the ultra Mg' glasses have compositions similar to that of the

hypothetical lunar komatiite proposed by [3], suggesting a pyroclastic origin for the ultra Mg'

glasses. Trace element data for ancient mare glasses would be very important in understanding

the systematics of the earliest mare volcanism, and the identification and characterization of

lunar komatiitic glasses would be of great benefit in deciphering the history of the moon as a

whole. Therefore, we have undertaken a search for individual mare and ultra Mg' glass

spherules in ancient regolith breccias in order to characterize their major and trace element

compositions.

Methods Samples included ancient regolith breccias 60016,165 and 66075,16. Splits of

these samples had previously been disaggregated by both freeze-thaw (FT) and ultrasonic (S)

techniques and sieved into standard lunar soil size fractions [2]. For this study, spherules were

picked from the 150-250, 90-150, and 45-90 micrometer fractions of 60016,165FT, 60016,165S,

66075,16FT, and 66075,16S, and the 20-45 micrometer fraction of 60016,165S. Scanning

electron microscopy and energy dispersive X-ray analysis (SEM/EDS) were used to identify

possible mare or ultra Mg' glasses. Spherules of interest were analyzed by INAA according to

methods similar to those previously tested for individual highland impact glasses from Apollo 16

regolith breccias [4]. The final step is electron microprobe major element analysis of flat

polished surfaces of the glasses in order to obtain more accurate leO contents than those

determined by EDS; these numbers can be compared with INAA Fe data so that absolute

abundances can be calculated for the INAA data (the spheres were not weighed because of their

small sizes).

Result£ A total of 282 spherules was picked from 60016,165 and 66075,16 and analyzed

by SEM/EDS. Most of the spherules are heterogeneous (recrystallized or devitrified) rather than

homogeneous glass. This predominance of heterogeneous glass is consistent with our earlier

results for the Apollo 16 ancient regolith breccia glasses [2]. Most of the spherules seem to have

compositions typical of common highlands glasses. Quantitative EDS indicated that only two

spherules, both from 60016,165S, had unusual compositions. Based on the EDS data, one

sphere, 208A (from 60016,165S 20-45 _um), had a high FeO content, which is characteristic of

mare glasses; the other unusual spherule, A-8 (from 60016,165S 150-250 tam), had a high Mg'

value (0.89 by EDS).

The two unusual spheres and four typical highlands-type spheres were analyzed by

INAA. Trace element data (Table 1) indicate that all of the spherules, with the possible

exception of high Mg' glass A-8, are probably highlands impact glasses. The REE patterns

(Fig. 1) for all but A-8 are typical of highlands impact melts, including the pattern for 208A,

which had high FeO according to EDS. High Mg' glass A-8 has a similar pattern but lower

abundances; most other trace element abundances in the high Mg' glass are also very low (Table

1). Electron microprobe major element data for high Mg' glass A-8 are given in Table 2.

Spherule A-8 is not an ultra Mg' glass (microprobe Mg' ,, 0.86) but it has a major element

composition similar to that of troctolitic-noritic ultra Mg' glass (Table 2). Both glasses have

norms that consist mostly of olivine, orthopyroxene, and plagioclase (Table 2).

Several possible origins have been proposed for the ultra Mg' glasses. Possibilities

include preferential removal of Fe (by impact volatilization or reduction of FeO to Fe during

impact), mixing of lunar materials with very high MB' meteoritic material, and derivation from

high Mg' lunar material by impact or volcanic processes [1]. Of the different compositional

types of high and ultra Mg' glass, troctolitic-noritic glasses 60016 A-8 and 65715,5-4 (Table 2)

are the most likely candidates for a volcanic origin because of their similarities to the

composition proposed by [3] for a lunar komatiite (Table 2). The trace elements in high Mg'

glass A-8 do not clearly indicate a volcanic origin for the glass, however; e.g., a pristine

volcanic glass would be expected to have much higher Ni and Co abundances.

sTumrnarl_ One of the most significant results of this study is that none of the 282

glasses analyzed by EDS have a definite mare composition, illustrating the extreme rarity of

mare glasses in the ancient regolith breccias. High Mg' bead 60016,165S 150-250 lain A-8 is not

an ultra Mg' glass as defined in [1], but it seems to be closely related to troctolitic-noritic ultra

Mg' glass. The origins of these troctolitic-noritic glasses are still uncertain.
71

IN SEARCHOF ANCIENT LUNAR PYROCLASTICS; Wentworth S. J. et al.

Re[¢rcnces: [1] Wentworth and McKay (1988) Proc. LPSC 18th, 67-77. [2] McKay et

al. (1986) Proc. LPSC 161h, D277-D303. [3] Ringwood et al. (1987) EPSL 81, 105-117. [4]

Wentworth et al. (1989) LPS XX, i195-1196.

TABLE I: INAA trace element abundances for Apollo 16 spheres. For A-8, absolute abundances

are scaled to microprobe FeO. For other spherules, absolute abundances are based on masses

(estimated from sizes).

60016 A-0 60016 A-2 60015 201U_ 66075 C-1 66075 <7-10 66075 I)-12

22.0 _g, 42.0 nq, 17.0 nq. 540. nq. 750. nq. 250. nq,

Nil20 0.200 ,__0.004 l.. 0";3 ÷_ 0.024 0.149___ 0.007 1.00503")-_*_0.0150.09 0.01t1__±00016 0.053059 +-_.0.0130_09

K20 0.055 +_ 0.006 _ 10.0 2 2.3 1.6 *_ t.4 5.2 *_ 2.0

C80 6.0 t 0,4 _ (10. 4.49 0.08 4,49 0.O "t

FOO 8.94 _ 0*10 5.89:2 0,16 10.]4 t" 0.24 4.53 *. 0.08

SC

Ct

Co

WI

Rb

C|

Sr

Be

L4

Co

Nd

Sm

¢u

Yb

LU

Zr

Hf

To

U

5b

W

It

Br

5.96 :2 0.06 14.74 :2 0.25 21.9 .+ 0.4 15.53 *__ 0.18 1].22 __* 0.15 9.53 __* 0.12

1965. :l: 24. 1440. :2 30. 1770. :2 40, 1470. ± :10, 1426. ¢ 19. 1114. *_ 16.

20.46:2 0,23 10.7 ¢ 0.9 40.3 t 1.9 23,5 2 0.4 12,41:2 0.24 30.0 t 0.5

71. 2 4. 340. :1: 100- 610. 2 110. 460, t 40. 1O]. 2 20. 400. *_ 40.

<1.2 t80. <SO, _41, 5.7 2 2.2 13. 2 "/"

(0.0") (1.S (2.9 0.64 I" 0.21 (0.31 1.35) :2 0.17

"il. 1" 0, (SO0. (1100. 110. _' 40. 110. :2 40. 240. 1" 40.

92. _ 5, 430. :It 190. (1600. S00. :2 SO. 390. _ 30, 410. 1" 60.

11,26 t: 0.13 4i.i :2 2.9 26.1 1" 1.? 69.'I ___ 1.0 3).8 :2 O.S 33.? _" 0.6

30.2 2 0,5 ++19. 1" 8, 55. 1" g, 107, 2 3. 106.3 _: 1.9 90,1 _: 2,5

19.73: 1.4 (110.

4.46 _: 0.17 15.72 0.0

0.721" 0.03 <3.6

0.966 t: 0.020 3.2 _P 0.5

2.94 ¢ 0.06 12. _ 3.

0.359 t 0.010 4.? _ 1.1

103. 2 13. (1100.

4.00 i 0.07 14.1 _: 1.]

(120. 137. 1" 14. 72. :2 0. 52, 2 t].

9.2 t 0.7 25.0 t 1,0 11.5 2 0.5 11,6 _* 0.5

(5. 1.97:2 0.22 1.60:2 0.15 2.01 __ 023

(2.4 5.91:2 0.14 ].93 t 0.11 2.41 1" 0.10

<27. 19,0 1" 0.9 11.2 2 0.S 9,1 _ 0.$

(2.6 2.$1 t 0.10 1,$2:2 0.09 1.95:2 0.15

_1400. 970. _ 120. $50. :2 ?0, 350. t 100.

0.7 :2 1.7 2].1 1" 0.S 10,1 :2 0.3 9.9 _ 0.4

0.58 _ 0.04 2.6:2 1.4 (4, 2.0 1" 0.3 1.31:2 0.16 1.23 ¢ 0.27

0.624 t 0.024 _10. (19. 2.0:2 0.4 1.11:2 0.10 1.0 1" 0.4

1.00 1" 0.03 4.4 :2 0.t 4.3 2 1.0 10.44 1" 0.$0 6,11 1" 0.10 4.8i +_ 0.24

0.056:2 0.024 <10. _2]. (1.] (0.4

1,2 t 0.0 (31. <SO, <7. <6. (0. _0.09 <0.]0

<0.007 (1.7 (]" _0.21

0.09 2 0,0S 3460. t 50. 30?00. t S00. 141.7 2 2.6 _1.6 2 1.1 36.1 :2 1.3

_0.00| (0.15 <0,]9 (0.06 (0.029 _0.020

0.OOZl :20,000& 3.3:2 0.3 1.1:2 0.4 <0.091 (0.019 0.00 _ 0.04 (3.1 (S.

(0.7 <24. <40. (6. 29, :2 _.

$.9 t 0._ 71, 2 24. 110. _ _0. 24. 2 6. 9- :2 4, (0.7 <3.1

0.41 2 0.07 (11. (15, (S.

TABLE 2: Major element compositions.

(l) (2) (3)

SiO 2 45.2 47.4 45.4

TiP 2 0.54 1.33 0.86

Al20 3 6.61 12.6 9.56

Ce_)O3 14.8 0.40 0.24 3.15 0.28 9.05

MnO 0.19 0.03 0.11

MgO 26.9 28.7 30.4

CaO 5.31 5.86 5.25

Na20 0. l 0 0.08 0.23

K20 n.d. 0.20 0.02

p_)OI_AL 100.0 n.d. 99.60.07 100.0 0.17

Mg' 0.76 0.90 0.86

Major normative minerals (wt%):

Feldspar i 8.4 30.6 27.1

Olivine 43.4 25.0 47.3

Diopside 7.0 0.0 0.0

Hypersthene 29.5 39.3 24.6

(1) Proposed komatiite [3].

(2) Ultra Mg' glass 65715,5-4 [1].

(3) High Mg' glass 60016,1655 150-250 lain A-8.

ORIGINAL PAGE IS

OF POOR QUALITY

::a,.,u'_. . ' ' ' ' '

I FIGURE I

¢- 50. °

e_

|

_0.

,]

5.1, , d , '

La Ce Srn Eu Tb YI;) Lu

PRECEDING PAGE BLANK NOT FILMED

73

List of Workshop Participants

Judy Allton

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Lockheed ESCO

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Robert Andres

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Michigan Technological Institute

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McGiU University

Montreal, Quebec

Canada

Abhijit Basu

Department of Geology

Indiana University

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Univev'sity of Houston

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Mark J. Cintala

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Cassandra Coombs

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Shah DeSilva

Lunar and Planetary Institute

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John Delano

Department of Geological Sciences

State University of New York

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Tammy Dickinson

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John Dietrich

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B. Ray Hawke

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Hawaii Institute of Geophysics

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Grant I leikcn

Geology Group, D462

Los Alamos National Laboratory

Los Alamos, NM 87545

Odette James

U. S. Geological Survey

959 National Center

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Yuequn Jin

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Un_ersity of Tennessee

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John Jones

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Jim Jordan

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Lamar University

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Massachusetts Institute of Technology

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David J. Lindstrom

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Marilyn Lindst tom

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Gary I.ofgren

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74 Lunar Volcanic Glasses

John Longhi

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David McKay

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Gordon A. McKay

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Charles Meyer

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Lunar and Planetary Institute

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South Dakota School of Mines and Technology

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