Crystallization History of Lunar 

F eldspa thic Basalt 14 310 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 841 

Prepared on behalf of the 

National Aeronautics and Space Administration 

Crystallization History of Lunar 

F eldspa thic Basalt 14 31 0 

By ODETTE B. JAMES 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 841 

Prepared on behalf of the 

National Aeronautics and Space Administration 

An account of the crystallization history 

of an unusual type of lunar basalt, 

deduced from detailed petrographic 

studies and microprobe mineral analyses 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress catalog-card No. 73-600177 

For sale by the Superintendent of Documents U.S. Government Printing Office 

Washington, D.C. 20402- Price 70 cents domestic postpaid or 50 cents GPO Bookstore 

Stock Number 2401-00361 
Abstract ----------------------------------------

Introduction -------------------------------------

Mineral assemblage and texture ------------------

General features -----------------------------

Locally developed fine-scale textures -----------

Orthopyroxene with preserved euhedral faces 

Composite grains with orthopyroxene cores 

and pigeonite rims --------------------

Coarse polysynthetically twinned pigeonite __ 

Ni-Fe, schreibersite, and troiHte ---------

Phase compositions -------------------------------

Plagioclase - __ --- __ ---- _ ---------------------

Subhedral laths -------------------------

Grains enclosing metal-schreibersite-troilite 

inclusions ________________ -- __ ---------

Laths adjacent to vugs -------------------

Laths in fine-grained clots ----------------

Orthopyroxene ------------------------------

Orthopyroxene with preserved euhedral crystal faces ------,------------------------

Orthopyroxene adjacent to vugs -----------

Orthopyroxene containing blebs and { 100} 

lamellae of augite ---------------------

Orthopyroxene formed by inversion of 

pigeonite ------------------------------

CONTENTS 

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Phase compositions-Continued 

Compositions of orthopyroxene and clinopyroxene 

at"their contacts ---------------------------

Pigeonite and ferropig,eonite ------------------

Augite _______ -------------------------------

Compositions of pigeonite and augite at their 

contacts -----------------------------------

Other pyroxenes -----------------------------

Compositions of intergrown and impinging plagioclase and pyroxene ------------------------

Other silicate and oxide phases ----------------

Fe-Ni metal and schreihersite -----------------

Phosphorus-bearing Ni-Fe and schreibersite 

Phosphorus-free Ni-Fe -------------------

Crystallization and cooling history ----------------

Silicate melt --------------------------------

Fe-Ni-P-8 melts and particles ---------------

Subsolidus effects ---------------------------- Crystallization conditions ________________________ _ 

Pressure ------------------------------------

Temperature --------------------------------

Oxygen fugacity -----------------------------

Volatiles ------------------------------------

Conditions of crystallization of fine-grained clots 

Genesis of the 14310 magma ----------------------

References cited ---------------------------------

ILLUSTRATIONS 

FIGURES 1-10. Photomicrographs showing: 

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1. General features of rock texture __ --------------------------------------------------- 2 

2. Fine-grained clots _ _ _ _ __ __ _ _ __ _ _ ___ __ _ _ _ _ _ _ ___ __ _ _ __ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 

3. Composite orthopyroxene-pigeonite-augite grain ----------------------------------------- 4 

~ Orthopyroxene grains ---------------------------------------------------------------- 4 

5. Composite orthopyroxene-pigeonite grains ---------------------------------------------- 5 

6. Composite orthopyroxene-pigeonite grain ----------------------------------------------- 5 

7. Composite orthopyroxene-pigeonite-augite grain ----------------------------------------- 6 

8. Coarse polysynthetically twinned grain of pigeonite ------------------------------------ 6 

9. Large composite, globules of Ni-Fe, schreibersite, and troilite ____ ----------------------- 7 

10. Globule of Ni-Fe + schreihersite included iri plagioclase ------------------------------- 8 

11. Diagrams showing variation in Ca, K, and Na along profiles within three large plagioclase laths ___ 10 

12. Plot of Wo:En:Fs contents of pyroxenes analyzed in this study-------------------------------- 11 

13. Diagrams showing variations in Mg, Ca, and Fe contents across a composite orthopyroxene-pigeoniteaugite grain ------------------------------------------------------------------------------- 12 

14. Plot of Wo:En:Fs contents of points on profiles shown on figure 13 ---------------------------- 12 

15. Diagrams showing variations in Mg, Ca, and Fe contents across orthopyroxene grains ------------ 13 

16. Plot of Wo: En: Fs contents of exsolution-free orthopyroxene, orthopyroxene with augite lamellae, 

and pigeonite at their contacts ------------------------------------------------------------- 14 

III 
IV 

FIGURE 

CONTENTS 

17. Diagrams showing variations in Mg, Ca, and Fe contents across orthopyroxene-pigeonite contacts __ 

18. Plot of Wo:En:Fs contents of coexisting augite and pigeonite ----------------------------------

19. Plot of Ni and Co contents of grains of phosphorous-bearing and phosphorous-free Ni-Fe _______ _ 

20. Diagrams showing variations in Ni and Co contents across large Fe--Ni-P-S globules ------------

21. Plots of Ni and Co contents of a Ni-Fe, 'Y Ni-Fe, and schreibersite in large Fe-Ni-P-S globules __ _ 

22. Plot of Ni and Co contents of a Ni-Fe, 'Y Ni-Fe, and schreibersite included in plagioclase --------

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CRYSTALLIZATION HISTORY OF LUNAR 

FELDSP ATHIC BASALT 14.'310 

By ODETTE B. JAMES 

ABSTRACT 

Lunar feldspathic basalt 14310 crystallized at or near 

the lunar surface from a melt of virtually the same bulk 

composition as the rock now has. This melt contained no 

silicate xenoliths or xenocrysts and probably no phenocrysts, 

but meteorite-derived Fe-Ni-P-S melt globules (and possibly also solid particles) were present. Plagioclase was the 

first silicate to form, at about 1310°-1320°C. After crystallization began there was no abrupt volatilization of alkalis 

from the melt. Orthopyroxene was the second major silicate 

to precipitate; some grains of this mineral show complex 

oscillatory and reverse zoning probably related to local 

variations in volatile content of the melt. As crystallization 

progressed in the silicate melt: ( 1) orthopyroxene reacted 

with liquid and pigeonite precipitated; (2) augite precipitated; (3) ilmenite precipitated; ( 4) augite crystallization 

ceased; and ( 5) mesostasis minerals crystallized and 

mesostasis glasses solidified. During crystallization of the 

silicate melt the globules of Fe-Ni- P-S melt it contained 

precipitated first Ni-Fe, then schreibersite, and then troilite. 

Characteristics of these particles indicate that the 14310 

melt was not quenched at any time during its crystallization, that final solidification of the rock took place at about 

950oC, and that subsolidus equilibration continued to below 

550°C, Oxygen fugacity throughout crystallization was about 

comparable to that in Apollo 12 basaltic melts. 

The 14310 melt could have been generated by: (1) partial 

or bulk melting of a feldspathic rock in the lunar crust; 

or (2) impact melting of feldspar-rich lunar surface materials. The latter alternative is favored here. 

INTRODUCTION 

Feldspathic basalt 14310 occupies a position of 

unique importance to lunar petrology, for this rock 

crystallized from a melt generated in a different geologic setting, and at an earlier time, than most lunar 

basalts brought back to earth. Most basalts brought 

back by the Apollo missions to date were collected 

from mare surfaces at the Apollo 11, 12, and 15 sites. 

Basalt fragments form a large percentage of the 

samples from these sites, and they were presumably 

derived from flows and sills that form local bedrock. 

Crystallization ages are in the range 3.15-3.70 b.y. 

(billion years). (See references on Rb/ Sr and 

40Ar/ 39Ar ages in Proceedings Volumes of the Apollo 

11, Second, and Third Lunar Science Conferences, 

and the volume of Apollo 15 short papers published 

by the Lunar Science Institute, Houston, Tex.). In 

contrast, basalt 14310 was collected at the Apollo 14 

site on the Fra Mauro formation, a geologic unit 

interpreted as an ejecta deposit from the impact 

event that formed the Imbrian basin (Swann and 

others, 1971). At this site the rocks on the moon's 

surface are apparently nearly all breccias ; only two 

specimens of basalt weighing more than 50 grams 

were returned, and 14310 is by far the larger of 

these. These basalts are probably not derived from 

local basaltic bedrock, but are instead fragments 

broken and transported far from their sites of crystallization by processes associated with impact 

events. Minimum age of crystallization of 14310 is 

about 3.91 b.y., and minimum age of crystallization 

of 14053, the other Apollo 14 basalt hand specimen, 

is about 3.95 b.y. (results of Rb/ Sr and 10Arj39Ar 

methods reported by Turner and others, 1971; Papanastassiou and Wasserburg, 1971; Murthy and 

others, 1972; Compston and others, 1972b; and York 

and others, 1972). 

Basalt 14310 is further of special interest because 

it appears to have crystallized from a parent melt 

much different in composition from the parent melts 

of the mare basalts, and of basalt 14053 as well. 

Mare basalts as a group, along with 14053, are typified by: dominance of pyroxene over plagioclase; 

presence of olivine as a common minor, sometimes 

major, constituent; virtual absence of orthopyroxene 

and dominance of calcic pyroxene over pigeonite; 

high content of FeO (16-23 percent) with attendant 

high ratio of FeO/ MgO; and very low contents of 

K, P, and Zr. In 14310, however, plagioclase is 

dominant over pyroxene, olivine is absent, orthopyroxene is an important constituent, pigeonite is 

dominant over augite, content of FeO is low and 

about equal to the content of MgO (Kushiro and 

others, 1972; Rose and others, 1972; Philpotts and 

others, 1972; Hubbard and others, 1972; Willis and 

1 
2 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

others, 1972; Compston and others, 1972a), and contents of K, P, and Zr are 11;2-2 times as high as in 

the mare basalts that are richest in these elements. 

This paper presents an account of the crystallization history of the parent magma of basalt 14310 

and its crystallization conditions, deduced from detailed petrographic and electron-microprobe studies 

of thin sections. Also included is a discussion of possible origins of the melt. The thin sections studied in 

detail were subsamples 25 and 9; supplementary 

microprobe analyses were made on grains in subsamples 4, 14, 30, 168, and 179, and 12 other thin 

sections were examined petrographically. 

Acknowledgments.-This work was done under 

NASA contract T-75412. I thank my colleagues 

E. C. T. Chao and R. T. Helz for discussion of many 

points in the paper and review of the manuscript. I 

am indebted to Judith B. Best for assistance in 

preparation of the illustrations and final assembly 

of the manuscript. 

MINERAL ASSEMBLAGE AND TEXTURE 

GENERAL F EATURES 

Major constituents of 14310 are plagioclase and 

pyroxene (orthopyroxene, pigeonite, augite); important minor constituents are ilmenite, metallic 

Ni-Fe, schreibersite, troilite, and mesostasis (a complex intergrowth of late-stage phases). PropO't'tions 

of these constituents, computed from a bulk-rock 

analysis (Rose and others, 1972) using the chemicalmode-calculation method described by Wright and 

Doherty (1970), are as follows (weight percent and 

volume percent calculated from weight percent, respectively) : plagioclase, 57.3, 62.0; pyroxene, 37.0, 

32.2; oxides (ilmenite + ulvospinel), 1.6, 1.0; and 

mesostasis (silica-rich glass + apatite + potassium 

feldspar), 4.1, 4.8. Proportions of major minerals 

indicated by this calculation correspond fairly 

closely with proportions derived from optical point 

counts (Melson and others, 1972). 

The rock texture ranges from fine-grained subophitic to fine-grained intergranular and is locally 

intersertal (fig. 1). Plagioclase forms a network of 

randomly oriented interlocking laths, most of which 

are subhedral. Feldspar grain-size distribution is 

roughly seriate rather than bimodal or porphyritic 

(Drever and others, 1972; Kushiro and others, 

1972) ; the laths are as much as 2 mm long and the 

average is about 0.2-0.3 mm long. Many large and 

intermediate-sized laths ( >0.1 mm) exhibit optically 

discernible normal progressive zoning and traces of 

oscillatory zoning that define euhedral crystal outlines throughout their interiors. Pigeonite, the most 

FIGURE !.-Photomicrograph of 14310,9. Seriate plagioclase 

forms a network of randomly oriented laths; interstices 

are filled with subophitic and intergranular pyroxene. The 

large plagioclase lath at upper left contains small Ni- Fe 

inclusions (black). A large part icle of Ni-Fe (black) and 

a small clot of fine-gr a ined plagioclase are at upper right. 

Pigeonite grain at lower left contains an equant core of 

ort hopyroxene (marked by arrow ). Width of field of 

view is 2.2 mm ; crossed polarizers. 

abundant of the pyroxene miner als, forms intergranular to subophitic grains in the int erstices of 

the plagioclase network. Most orthopyroxene forms 

cores within the pigeonite grains; where orthopyroxene is directly intergrown with plagioclase with 

no intervening pigeonite, the intergrowth tends to 

be graphic rather than subophitic. Most augite forms 

epitaxial overgrowths on, or zones within, pigeonite 

grains, but minute amounts of this mineral also 

occur as small blebs or stubby exsolved prisms 

within orthopyroxene grains. 

Textures of the minor constituents are as follows. 

Ni-Fe, schreibersite, and troilite form single phase 

or composite particles that range from large globules 

(as much as 0.3 mm across) to minute irregular 

interstitial grains. Most particles of these phases are 

isolated and occur in interstices, but a few are also 

included in plagioclase and pyroxene. Ilmenite occurs 

as small subhedra that are restricted to marginal 

zones of pyroxene grains and interstices. Mesostasis 

fills interstices and consists of small crystals of 

ilmenite, ulvospinel, pyroxene, fayalite, potassium 

feldspar, baddeleyite, tranquillityite, apatite, and 

whitlockite and patches of silica-rich and devitrified 

iron-rich glasses. 

The rock shows appreciable textural heterogeneity. 

Locally, patches of the silicate intergrowth have 

grain size significantly coarser than in the rest of 

the rock; many of these patches are associated with 

open vugs. Patches where the silicate intergrowth is 
MINERAL ASSEMBLAGE AND TEXTURE 3 

FIGURE 2.-Photomicrographs of fine-grained clots. A, Large clot c,onsisting dominantly of minute plagioclase laths, subordinately of interstitial pyroxene in optical continuity. The basalt immediately surrounding the clot contains a concentration of interstitial mesostasis material (black). Width of field of view is 0.88 mm; plane-polarized light. B, Clot consisting of open framework of minute plagioclase laths with abundant interstitial silica-rich glass. Width of field of view 

is 0.58 mm; plane-polarized light. C, Minute plagioclase laths that nucleated on a larger plagioclase grain. Width o.f field of 

view is 0.41 mm; plane-polarized light. D, Ni-Fe particle within fine-grained clot. The Ni-Fe (white) is enclosed by a reaction rim of whitlockite ( w) and silica glass (g). The surrounding clot consists of plagioclase (dark-gray laths) and 

pyroxene (interstitial light-gray phase). Some of the pyroxene near the whitlockite reaction rim contains minute blebs 

of silica glass and appears partly resorbed. Width of field of view is 0.31 mm; reflected light. 

extremely fine grained are also present locally (fig. 

2). These range in size from clots 2 mm across to 

tiny clots of only a few grains. The larger clots consist dominantly of minute tightly intergrown plagioclase laths; pyroxene is greatly subordinate and 

forms interstitial grains that are commonly in optical continuity over large areas within single clots. 

Within most of these larger clots, phases other than 

plagioclase and pyroxene are absent; however, the 

network of plagioclase surrounding many of them 

contains a significantly greater proportion of interstitial mesostasis material than elsewhere in the 

rock (fig. 2A). Some of the smaller clots show h,xtures gradational into textures more typical of the 

rock as a whole: Some are open frameworks of 

minute plagioclase laths with abundant interstitial 

glass (fig. 2B) and others appear to have grown on 

or around larger plagioclase grains fig. 2C). 

LOCALLY DEVELOPED FINE-SCALE TEXTURES 

Several phases-most notably orthopyroxene, pigeonite, and intergrown Ni-Fe and schreibersitelocally show fine-scale textures whose origin has 

special bearing on interpretation of the crystallization history and origin of the rock. The textures are 

described below, and compositional variations shown 
4 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

by phases with these textures are presented in later 

sections. 

ORTHOPYROXENE WITH PRESERVED EUHEDRAL FACES 

Many orthopyroxene grains contain clouds of 

minute inclusions of a low-refractive-index phase 

that appears to be glass. In sparse grains, such inclusions are arranged along planes that mark the 

traces of euhedral growth surfaces within the crystals, and the orientations of these planes provide 

evidence as to the structure of the pyroxene that 

initially crystallized from the melt. Figures 3, 4A, 

and 5A illustrate three grains in which euhedral 

faces are preserved. The results of Universal-stage 

studies show that in such grains the best developed 

euhedral growth surface are parallel to {100}; 

faces parallel to {210} planes are less well developed, 

and faces parallel to {010} are rare. 

FIGURE 3.-Photomicrograph of composite orthopyroxenepigeonite-augite grain. The orthopyroxene (gray, center) 

has a core (center top) that is outlined by the traces of 

{210} faces marked by concentrations of glass inclusions. 

The outer part of the orthopyroxene grain contains abundant exsolution lamellae of augite parallel {100} of the 

host. The dot-dash line marks the contact of pigeonite 

and augite. Lines marked A- A and B- B indicate traces 

of microprobe profiles for which compositional data are 

presented on figures 13 and 14. Width of field of view is 

0.31 mm; crossed polarizers. 

CO:\!POS!TF. GRAI'."S WITH ORTHOPYROXENE 

CORES . .\'\D PIGEONITE RI.\15 

In nearly all the composite grains of these two 

pyroxenes, textures suggest that the orthopyroxene 

cores crystallized from melt as orthopyroxene. In a 

small proportion of the grains, the textures indicate 

the nature of the crystallization relationship between 

the orthopyroxene and surrounding pigeonite; the 

FIGURE 4.-Photomicrographs of orthopyroxene grains. A, 

Grain showing traces of euhedral growth surfaces. Orientations of the crystallographic planes are indicated on 

the photomicrograph. The line marked A-A indicates the 

trace of a microprobe profile for which compositional data 

are plotted on figure 15. Width of field of view is 0.28 mm; 

plane-polarized light. B, Grain bordering a vug. Orthopyroxene at the core (c) of the grain is graphically intergrown with plagioclase (pi). Along its right edge the 

orthopyroxene core is rimmed by orthopyroxene of slightly different extinction position (r), which is in turn 

rimmed by pigeonite (p) adjacent to the vug (black). The 

line labeled B-B indicates the trace of a microprobe profile plotted on figure 15. Width of field of view is 0.35 

mm; crossed polarizers. 

variations in these textures demonstrate that there 

were significant local variations in pyroxene crystallization history. In some grains the orthopyroxene 

core is clearly euhedral and did not react with surrounding melt before or during overgrowth by 

pigeonite (fig. 5A). In contrast, in other grains the 

orthopyroxene core is irregular and may have been 

partly resorbed (fig. 5B). In most composite grains, 

however, the presence or absence of reaction rela-
MINERAL ASSEMBLAGE AND TEXTURE 5 

FIGURE 5.-Photomicrographs of composite orthopyroxenepigeonite grains. A , Euhedral orthopyroxene core in 

pigeonite. Traces of euhedral growth surfaces within the 

orthopyroxene core are marked by planes rich in glass 

inclusions; crystallographic orientations of these planes 

are indicated on the photomicrograph. The line designated 

A- A indicates the position of a microprobe profile across 

the orlhopyroxene-pigeonite contact for which compositional data are presented on figure 17. Width of field of 

view is 0.35 mm; crossed polarizers. B, Irregular orthopyroxene core in pigeonite. The line designated B-B is 

the trace of a micr oprobe profile for which compositional 

data are plotted on figure 17. Width of field of view is 

0.35 mm; crossed polarizers. 

tionships is not clearly demonstrated. Most grains 

are similar to the one illustrated in figure 6. They 

have equant or prismatic cores of clear orthopyroxene free of visible exsolution lamellae; these cores 

either are overgrown directly by pigeonite, or are 

overgrown by orthopyroxene with abundant {100} 

augite exsolution lamellae that is in turn overgrown 

by pigeonite. Contacts of lamella-free and lamellarich orthopyroxene with each other and with pigeonFIGURE 6.-Photomicrograph of composite orthopyroxenepigeonite grain. Orthopyroxene forms a co-re (o), one end 

of which contains {100} exsolution lamellae of augite, encased in pigeonite (p). The orthopyroxene is inter grown 

near its center with the marginal zones of a plagioclase 

lath (pi) that contains a euhedral core. Width of field of 

view is 0.35 mm; crossed polarizers. 

ite are generally abrupt; commonly subhedral outlines are suggested by the shapes of the contacts, but 

just as commonly not. In a very small number of 

grains, the cores of orthopyroxene have textures that 

indicate they formed by direct nversion of surrounding pigeonite with no accompanying exsolution of 

augite (fig. 7) ; these grains are rare, however. 

Universal-stage data on crystallographic orientations of the two pyroxenes in single composite grains 

are consistent with inferences drawn from texture 

as to which orthopyroxenes are primary and which 

are inverted. In most composite grains, the corresponding crystallographic planes and axes of the 

orthopyroxene and pigeonite are only very roughly 

near coincidence. Generally the two pyroxenes have 

c axes about 10°-20° apart and their {010} planes 

range from nearly coincident to 45° apart. These departures from structural coincidence indicate that 

the cores cannot represent orthopyroxene that has 

inverted from enclosing pigeonite. In the grain with 

the inverted core illustrated in figure 7, however, c 

axes and {010} planes of the orthopyroxene and 

pigeonite are coincident within the error of measurement. 

COARSE POLYSYNTHETICALLY TWINNED PIGEONITE 

Locally, the rock contains large, polysynthetically 

twinned grains of pigeonite that envelop plagioclase 

grains rather than fill interstices between them (fig. 

8) ; the intergrowth with plagioclase tends to be 
6 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIG BASALT 14310 

FIGURE 7.-Photomicro.graph of composite orthopyroxenepigeonite-augite grain. The orthopyroxene core ( o) formed 

by inversion of enclosing pigeonite (p); it has a ragged 

spiked contact and shows elongations parallel to a {100} 

twin composition plane of the pigeonite (marked on photomicrograph). Rotation of the grain by Universal s'tage 

reveals that the core is actually a patch of thin laminae 

parallel to {100} of enclosing pigeonite; c axes and 

{010} planes in the orthopyroxene and pigeonite coincide 

within the error of measurement. Augite (a) forms an 

epitaxial overgrowth on the central pigeonite; contacts 

with the pigeonite are planar and parallel to {110} and 

{100} (marked on photomicrograph). The augite is in 

turn overgrown by ferriopigeonite (f). The line A-A' 

indicates the trace of a microprobe profile for which compositional data are plotted on figure 12. Width of field of 

view is 0.58 mm; crossed polarizers. 

FIGURE B.- Photomicrograph of coarse polysynthetically 

twinned grain of pigeonite. Traces of twin composition 

planes are dark lines trending east-west. The grain is 

graphically inter grown with plagioclase (pi), and borders 

a vug (black, lower right). Around its margin it contains 

elongate patches of orthopyroxene ( o) in optical continuity with one another, suggesting a possible inversion 

relationship between the two pyroxenes. The orthopyroxene 

patch at far right contains minute exsolved blebs of 

augite (white). Width of field of view is 0.88 mm; crossed 

polarizers. 

graphic, like typical orthopyroxene-plagioclase intergrowth, rather than subophitic. Most of these pigeonites also have cores of, or are intergrown with, 

orthopyroxene, and in some cases the texture of the 

intergrowth suggests a possible inversion relationship between the two pyroxenes (fig. 8). These 

coarse pigeonite grains commonly occur near vugs. 

Ni-Fe, SCHREIBERSITE, AND TROILITE 

The schreibersite-bearing particles in 14310 are 

of special interest because the presence of such 

particles has been cited as indicating an impact melting origin for the 14310 magma (Dence and others, 

1972). Most of the schreibersite in the rock occurs 

intergrown with Ni-Fe metal and troilite forming 

composite particles in interstices. The larger of 

these Fe-Ni-P-S particles (as much as 300 ,urn 

across) tend to have roughly spherical outlines. 

Some of the smaller ones, those less than 100 ,urn 

across, are also globular, but most tend to be less 

regular in outline and more molded against the 

edges of grains of adjacent silicate minerals. The 

particles are not uniformly distributed throughout 

the rock but tend to occur in scattered concentrations. 

Relative proportions of constituent minerals in 

schreibersite-bearing particles are highly variable. 

In particles greater than 100 ,urn across, Ni-Fe is 

dominant and troilite and schreibersite are subordinate; maximum proportions of the latter two minerals observed were 20 and 11 percent by volume, 

respectively. However, some particles less than 100 

,urn across contain much more schreibersite than this, 

and a few were observed in which schreibersite is 

more abundant than Ni-Fe. 

Figure 9 illustrates the textures of large schreibersite-bearing globules. Central areas of the globules are Ni-Fe that is generally free of inclusions 

of other phases fig. (9B). In a few particles, however, the metal contains stubby lamellae of schreibersite (fig. 9A) ; these lamellae typically show 

common orientations throughout a given particle, 

indicating that the Ni-Fe host is a single crystal. 

Most schreibersite, however, is concentrated at the 

edges of particles, forming thin discontinuous rinds. 

Troilite is wholly restricted to the margins of the 

globules, where it forms highly irregular grains. In 

most of these particles, textures and bulk compositions are such that the schreibersite could have been 

entirely held in solid solution in the coexisting metal, 

but in a few of the large particles the textures and 

bulk compositions provide evidence for precipitation 

of phases from metal-rich melt (see fig. 9A). In 

smaller similar particles that are very rich in schrei-
MINERAL ASSEMBLAGE AND TEXTURE 7 

FIGURE 9.-Photomicrographs of large composite globules of Ni-Fe, schreibersite, and troilite. Schreibersite (intermediate 

gray) forms lamellae within, and marginal grains surrounding, Ni-Fe (light gray). Troilite (dark gray) forms irregular 

grains at the edges of the particles. A, Particle showing charcteristics of precipitation from metal-rich melt. Textural 

evidence for precipitation from melt is the presence of eutectoid blebs of Ni- Fe within marginal schreibersite (lower 

left). Compositional evidence is that the bulk particle contains about 2.3 percent by weight phosphorus (calculated using averaged microprobe analyses of phases and areal phase proportions conve·rted to volume proportions); this much 

phosphorus could not have been entirely held in solid solution in the associated metal (Doan and Goldstein, 1969). The 

lamellae of schreibersite within the Ni-Fe formed by exsolution, and the marginal schreibersite that precipitated from 

melt was probably also augmented by exsolution. The line marked A-A indicates the trace of a microprobe profile for 

which compositional data are plotted on figures 20 and 21. Short lines marked B-B', C- C', D-D', and E-E' indicate the 

positions of traverses for which compositional data are plotted on figure 21A. Width of field of view is 0.36 mm; reflected 

light, oil immersion. B, Large composite particle free of schreibersite exsolution lamellae. No textural evidence for precipitation from melt is apparent, and bulk composition is such that all phosphorus could have initially been held in 

solid solution in the metal. The line marked B-B indicates the trace of a microprobe profile for which compositional 

data are plotted on figure 20. Short lines marked A-A' and C- C' indicate the positions of traverses for which compositional data are plotted on figure 21B. Width of field of view is 0.44 mm; r·eflected light, oil immersion. 

bersite, textures are also suggestive of precipitation 

from metal-rich melt: these textures are very like 

those of the metal-troilite particles that crystallized 

from Fe-Ni-S melt immiscible in Apollo 11 basaltic 

magma (Skinner, 1970). 

Mesostasis immediately surrounding many of the 

large schreibersite-bearing particles contains more 

abundant grains of apatite and whitlockite than 

elsewhere in the rock. Typically the grains of phosphate minerals are clustered along the edges of the 

Fe-Ni-P-S particles and border metal with no intervening schreibersite. Phosphate minerals also form 

broad reaction rims bordering the few schreibersitebearing particles that occur within or near finegrained clots (fig. 2D). 

Particles in which Ni-Fe and troilite occur singly 

or together without schreibersite are more abundant 

than the schreibersite-bearing particles. They are, 

however, mostly less than about 20 p.m across, although a few are present that are as much as 120 

p.m across. Generally either troilite or Ni-Fe is 

strongly dominant in a given particle, and particl2s 

in the size range 20-120 ftm almost all have dominant Ni-Fe. Most commonly the particles are irregular and interstitial; less commonly they have spherical outlines, and very rarely they are euhedral. 

Ni-Fe, troilite, and schreibersite all occur as inclusions in plagioclase and pyroxene; individual inclusions may consist of any of these phases either 

singly or in combination. The inclusions in plagioclase were studied in detail in order to determine 

the approximate point in the crystallization sequence 

when a metal-bearing phase first appeared in the 

silicate melt. Most of these inclusions are rounded 

droplets about 5 p,m across, but a few are globules 

as large as 30 p.m across (fig. 10). The inclusions 

tend to be concentrated along twin composition 

planes in the host feldspar. 
8 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

FIGURE 10.-Photomicr·ographs of globule of Ni-Fe + schreibersite included in 

plagioclase. A, Fe-Ni-P globule (black) enclosed by ·euhedral feldspar. Width 

of field of view is 0.19 mm; plane-polarized light. B, Inclusion photographed with 

reflected light. Ni- Fe is white, schreibersite is gray. The line marked A-A' indicates the trace of a microprobe profile for which compositional data are plotted 

on figure 22. Width of field of view is 0.07 mm. 

PHASE COMPOSITIONS 

Average compositions of plagioclase and pyroxene in 14310 have been estimated from the results of 

chemical-mode calculations (method described by 

Wright and Doherty, 1970). The chemical modes 

were calculated using An9 ., and An,5 as end member plagioclases, and magnesian orthopyroxene, 

magnesian augite, and pyroxferroite as end member pyroxenes (with Al 2 0 3 and Ti02 contents in 

the latter three minerals assigned on the basis of 

electron microprobe analyses of typical grains). 

Rock analyses used were those reported by Kushiro 

and others (1972), Rose and others (1972), and 

Compston and others (1972a). The calculated average plagioclase composition is a calcic bytownite, 

Ori.2Ab,o.oAns8 .s, and the calculated average bulk 

pyroxene composition is a pigeonite, Wo, o uEnss.oFS:l t.l· 

Electron-microprobe analyses were made in order 

to determine the nature of compositional variations 

in important phases throughout the crystallization 

sequence. Most of the analyses were not complete. 

Plagioclase was analyzed only for Ca, K, and N a, 

and potassi urn feldspar for Ca, K, N a, and Ba; 

standards were chosen sufficiently close in composition to the unknowns that only background corrections were necessary. Pyroxenes were analyzed only 

for Ca, Mg and Fe, and the raw data were corrected using the correction program of Boyd and 

others (1969), with contents of minor elements and 

Si assigned on the basis of a few complete analyses 

performed on typical grains. (For data on Alz03, 

Ti02 , and Cr2 0 3 contents of pyroxenes, the reader 

is referred to papers by Kushiro and others, 1972, 

Ridley and others, 1972, Brown and others, 1972, 

Bence and Pap ike, 1972, and Hollister, 1972.) Ni-Fe 

and schreibersite were analyzed for Ni, Co, and P. 

The Ni and Co intensity values, corrected for background, were assumed to vary linearly with content 

of these elements in both unknowns and standards. 

Phosphorus was determined only semiquantitatively. 

PLAGIOCLASE 

Subhedral laths of all sizes were analyzed and the 

zoning variations in the larger laths were studied in 

detail in order to determine the pattern of overall 

compositional variation during the crystallization 

history. The results of these analyses, presented 

below, show an orderly progressive change of compositions that provide a rough scale against which 

it is possible to calibrate points of appearance of, 

and compositional changes within, coprecipitating 

phases. To determine points of first precipitation of 

orthopyroxene and coarse polysynthetically twinned 

pigeonite, analyses were made of plagioclase included within and graphically intergrown with these 

pyroxenes. Plagioclase enveloping particles of Ni- Fe 

± schreibersite ± troilite was analyzed to determine 

points of appearance of these phases. Edges of laths 

bordering vugs were analyzed to determine at what 
PHASE COMPOSITIONS 9 

approximate point in the crystallization sequence 

open vugs formed, and laths in fine-grained clots 

were analyzed to determine their compositional relationships to feldspar elsewhere in the rock. 

SUBHEDRAL LATHS 

Compositions within laths analyzed in this study 

range from An97 to An62· Cores of grains tend to be 

at the more calcic end of this range, and rims tend 

to be at the more sodic end, but the extent of zoning 

varies considerably from grain to grain. Other investigators have reported similar values, and all data 

fall within an overall range of An98 to An58 (Dence 

and others, 1972; Kushiro and others, 1972; Walter 

and others, 1972; Brown and Peckett, 1971; Longhi 

and others, 1972; Trzcienski and Kulick, 1972; Ridley and others, 1972). Trace element contents were 

reported by Trzcienski and Kulick (1972). 

Large ( >300 pm) subhedral laths analyzed here 

have cores that are about An94-95 and edges adjacent 

to mesostasis glass that are about An65_71 • The overall compositional change is normal progressive zoning with superimposed minor oscillatory zoning. 

Figure 11 presents microprobe profiles across three 

large subhedral laths. In these grains the compositional oscillations represent about 2 percent An content at a maximum. No major reversals in zoning 

are observed, but the grains analyzed all show a consistent dip in N a20 content at about one-quarter the 

distance from center to edge. 

Zoning in intermediate-sized (75-300 pm) subhedrallaths is much like in larger laths. The grains 

analyzed in this study have cores as calcic as An93 -'' 

and rims adjacent mesostasis as rich in K and N a 

as Or5.oAb32.5An62.5· Slight oscillatory zoning is present, and again there is no significant reverse zoning. 

Only a few small ( <75 pm) laths in mesostasis 

glass were analyzed here, and their compositions 

cover virtually the entire range of An content observed in larger grains-An94 to An62· Most, however, are in the range An62 to An,s, and one tiny 

core of plagioclase within a potassium feldspar grain 

has the composition Or5.oAb2,.9An67.1• 

Brown and Peckett (1971) and Ridley and others 

(1972) analyzed large and intermediate-sized zoned 

laths similar to those studied here and found similar 

ranges of composition, cores of An95-94 and rims of 

An,2-5s· Ridley and others further reported analyses 

of laths that were unzoned or asymmetrically zoned; 

unfortunately these authors did not describe the 

phases bordering such grains, so crystallization histories cannot be evaluated. Kushiro and others 

(1972) and Ridley and others (1972), respectively, 

reported that compositions of small laths associated 

with mesostasis are Ans4-<4 and An94-sl· Brown and 

Peckett ( 1971) analyzed microlaths of An94.5-91 in 

their samples, but whether or not these grains bordered glass was not specified. 

GRAINS ENCLOSING MET AL-SCHREIBERSITETROILITE INCLUSIONS 

Ten grains of plagioclase enclosing particles of 

Ni-Fe metal ± schreibersite -+-- troilite were analyzed in this study. Plagioclase directly impinging 

on the inclusions ranges from Anss.o to An95. 7 and 

averages An93 .5. (Plagioclase enveloping the globule 

shown in fig. 10 is Ann3.7·) Microprobe traverses 

from core to edge of two feldspar laths that contain 

Ni-Fe inclusions show that the plagioclase at the 

same "stratigraphic" horizon as the inclusions is 

about An94· 

LATHS ADJACENT TO VUGS 

The plagioclase at the extreme edges of two laths 

bordering vugs is Anso.l and An,4.4• 

LATHS IN FINE-GRAINED CLOTS 

Plagioclase grains in clots in which mesostasis 

minerals are absent have quite calcic compositions. 

In the three clots studied, all grains analyzed average about An95-96; the most sodic plagioclase found 

is An86, at the extreme edge of one lath. (Walter and 

others, 1972, found an identical compositional range 

for plagioclase in a clot they studied, An96-s"' and 

Kushiro and others, 1972, reported An92 in a clot 

they studied.) 

ORTHOPYROXENE 

Most orthopyroxene grains analyzed in this study 

have compositions in the range W o-1En,9Fs17 to 

W o5En65Fs3o and are zoned from more magnesian 

at their centers to more iron rich at their edges. In 

a few grains, thin marginal zones less than 10 pm 

wide show stronger iron enrichment, with Fs content as much as 40 percent (see profile B-B', fig. 12). 

Other workers (Ridley and others, 1972; Brown and 

Peckett, 1971; Ringwood and others, 1972; Hollister 

and others, 1972; Kushiro, 1972; and Takeda and 

Ridley, 1972) reported similar ranges or analyses 

within this range. Compositional variations associated with specific textures are presented in detail 

below. 

OR THO PYROXENE WITH PRESERVED EUHEDRAL 

CRYSTAL FACES 

Grains that retain traces of euhedral growth surfaces were studied in detail because their textures 
10 

>-

t: 

V) 

z 

w 

1-

z 

0 

-100 

-300 

-400 

Co 

-500 

-600 

K 100 

0 

1000 

900 

800 

700 

600 

No 

200 

100 

CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASAL·T 14310 

Profile A 

~ 75fLm ____.. Center Edge 

Profile B 

14---- 80 fL m -------..4 

Center Edge 

DISTANCE 

Profile C 

Center 

160 }A-m 

Edge 
PHASE COMPOSITIONS 11 

<1111 FIGURE 11.-Variations in Ga, K, and Na contents along profiles from centers to edges bordering mesostasis of three different large plagioclase laths. Points were analyzed at 2-p.m intervals. Ordinates :represent intensity of X-rays generated 

by electron bombardment in an electron microprobe; units are counts per constant increment of beam current, and the 

scale is relative to pure anorthite for Ca and to background for K and Na. For reference, a point with 0 Ca and 0 Na 

would be pure anorthite, and a point with -800 Ca and + 800 N a would be about An11. Abscissas represent linear distance. All grains show zones slightly depleted in Na20 at about one-quarter the distance from center to edge, minor 

oscillations throughout their interiors, and margins abruptly enriched in K and Na. 

* Calculated compo"toon of bulk pyroxene 

• Augote bleb and surroundmg orthopyroxene !Holloster and others. 19721 

• Small groom on mesmtmos 

h. Subcolcic ougote 

A Augote and pogeonote ontergrown woth subcobc ougote 

Grains 1n fone-grooned clots 

• lnterslitool. unreacted 

0 Border~ng reoctoon r~m of phosphate 

monerol on No-Fe 

Augite formon\l overgrowth nms and 

interstotiol groons 

/-Pogeonite on graphic. subophitic, and 

mtergronulor groons 

• 

• 

FIGURE 12.-Wo: En: Fs contents of pyroxenes analyz,ed in this study. For comparison the composition of bulk pyroxoene calculated from chemical mode computations is also plotted. Heavy solid lines outline fi·elds of compositions of pyroxenes of 

specific textural types. Long-dashed lines connect compositions of augite blebs with compositions of orthopyroxene that 

encloses them. Light solid lines connect points analyz·ed at 2-p.m intervals along profiles across two grains. A-A' is a 

profile across the composite orthopyroxene-pigeonite-augite grain illustrated in figure 7, beginning just within the core 

of inverted orthopyroxene, crossing the inner pigeonite zone, the augite epitaxially overgrown on the pigeonite, and the 

outer rim of ferropigeonite, and ending at the grain margin. B-B' is a profile across a 12-,um-wide marginal zone of an 

orthopyroxene grain that shows strong iron enrichment at its extreme edge (B'). Short-dashed lines connect compositions of adjacent points in intergranular grains that consist of complexly intergrown augite, ferropigeonite, and subcalcic augite. 

suggest that they might represent the earliest crystallized mafic minerals in the rock ; furthermore, the 

observation that these grains contain glassy inclusions that were trapped periodically during their 

crystallization suggests that the pyroxene compositions might show the effects of periodic fluctuations 

in volatile content or temperature in the melt. Four 

such pyroxene grains were analyzed. They have 

average compositions about WouEn,3_7 sFsls-22' in the 

more magnesian part of the orthopyroxene range. 

The zoning patterns are indeed unusual: All grains 

show complex oscillatory variations of Fe/Mg ratio, 

and some show reverse zoning as well, small cores 

being as iron rich as Fs29· 

In two of the grains, euhedral cores are outlined 

by inclusion-rich planes but are themselves relatively 

inclusion free. Figure 3 illustrates one of these 

grains, and figures 13 and 14 show the compositional 

variations it exhibits. The euhedral core contains 

one band about 15 ftm wide with about 1 percent 

greater Fs cont·~nt than the rest of the core (see profile A, figs. 13 and 14). In the other similar grain 

analyzed, adjacent bands in the core differed by as 

much as 11 percent in Fs content. 

The other two grains analyzed show traces of 

euhedral outlines throughout their interiors, and 

these lines clearly define the nuclei of the grains and 

their growth directions. Figures 4A and 5A illustrate these grains, and figure 15 (profile A) shows 

the compositional variations across the first of them. 

The nucleus of the grain is about Wo:.En6,Fs2~ and 

shows reverse zoning to W o.1En,6Fs2o· The remainder 
12 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

Profile A Profile B 

OPX. joPX.+lAMELLAE I PIG ~ OPX.+ I LAMEllAE I PIG. ~ 

DIRECTION OF GROWTH DIRECTION OF GROWTH 

18000 

l 16000 

Mg 

14000 

12000 

10000 

600 

500 

> 

1-

v; 400 

z 

w Co 1- 300 z 

1 

~¥!6- ~~ 

200 

100 

j 

Fe 

L 

DISTANCE 

of the grain averages about this latter composition 

but shows pronounced oscillatory zoning, with alternating bands several micrometers thick differing by 

about 1.5 percent in Fs content. 

ORTHOPYROXE~E ADJACE~T TO VUGS 

A grain of orthopyroxene bordering a vug was 

analyzed to determine whether or not its composition was affected by local variations in volatile con-

<111111 FIGURE 13.-Variations in Mg, Ca, and Fe contents along 

profiles across the composite orthopyroxene-pigeoniteaugite grain pictured in figure 3. Profiles A and B correspond to profiles A-A and B-B marked on figure 3. Ordinates represent intensity of X-rays generated by electron 

bombardment in an electron microprobe; units are absolute 

numbers of counts per constant increment of beam current. Abscissas represent linear distanc,e. Growth directions in the grain and positions of boundaries between 

phases are indica ted above profiles; vertical lines on 

abscissas mark the positions of inclusion-rich planes. 

Wo: En: Fs contents of circled points are plotted on figure 14. The orthopyroxene core (profile A) shows oscillatory and normal progressive zoning. For the surrounding 

zone where the orthopyroxene contains abundant exsolved 

augite lamellae, compositions of the two phases are best 

resolved in data obtained in profile A, whereas composition 

of the primary pyroxene is approximated in data obtained 

in profile B. 

... 

Wo 

FIGURE 14.-Wo:En:Fs contents of points on the profiles 

plotted on figure 13. Op~en circles are points on profile A; 

solid circles are points on profile B. Light solid lines connect consecutive points on the profiles. For comparison, 

the heavy dashed line outlines the boundary of the field 

of compositions of pigeonite in graphic, subophitic, and 

intergranular grains fr~om figure 12. 

tent associated with vug formation. The grain is 

illustrated in figure 4B, and the compositional variations it shows in a profile from its center to its edge 

are plotted in figure 15 (profile B) . The grain shows 

alternating reverse and normal zoning that combine 

to produce broad oscillatory variations in Fe/Mg 

ratio in bands parallel to the vug edge. At its core, 

the orthopyroxene is W o5Eni1Fs24 ; in the direction 

of the vug the grain shows reverse zoning to 

Wo4En.,Fs 19 and then normal progressive zoning to 

Wo 1En,:,Fsn. Orthopyroxene of this composition is 

rimmed by orthopyroxene of similar composition but 

different extinction position; the rim orthopyroxene 

shows reverse zoning to Wo~En,i';Fsts followed by 

normal zoning to W o.,Eni1Fs 2 .

1• Orthopyroxene of this 

latter composition is in turn overgrown by pigeonite, 

which forms a 10-1lm-thick rim directly bordering 

the vug and is normally zoned from W o,En6,Fs;t6 to 

WoroEn.;oFSw. 
PHASE COMPOSITIONS 13 

>-

..... 

18000 

17000 

Mg 

16000 

Profile A 

DIRECTION OF GROWTHProfile B 

OPX. I OPX. IPIG. 

CORE RIM RIM VUG 

DIRECTION OF GROWTH 

v; 15000 

z 

w 

..... 

z 

Co 

Fe 

200~ 

100 

4000 

3000 

t----- 92)-l- m ~ 

FIGURE 15.-Variations in Mg, Ca, and Fe contents along 

profiles across orthopyroxene grains. Ordinate, abscissa, 

and designations of textural relations are the same as described in the caption to figure 13, except that, in addition 

to inclusion-rich planes, inclusion-rich zones are marked 

on abscissas by patterned boxes. Profile A crosses a grain 

that shows traces of euhedral growth surfaces throughout 

its interior (fig. 4A). This grain shows pronounced reverse and oscillatory zoning in Fe-Mg contents. Profile B 

crosses a grain that borders a vug (fig. 4B). The grain 

shows reverse and normal zoning that combine to produce 

bands of oscillating Fe/Mg ratio parallel to the vug edge. 

ORTHOPYROXENE CONT AINI~G BLEBS AND 

{100} LAMELLAE OF AUGITE 

From their textures, these blebs and lamellae all 

appear to have been exsolved from the enclosing 

orthopyroxene (see figs. 3, 6, and 8) , and the mineral 

pairs were analyzed to investigate the compositional 

range in which this exsolution occurred. All such 

grains of orthopyroxene analyzed in this study are 

in the more iron-rich part of the compositional 

range, Fs>25, but Hollister and others (1972) reported finding blebs in a more magnesian orthopyroxene, Wo1Eni4Fszz· (Hollister and others interpreted the blebs they analyzed as inclusions rather 

than exsolution products. The compositions, however, are reasonable extrapolations of the compositional range of the exsolved blebs analyzed here, and 

it is likely that all such blebs have the same origin.) 

The field of compositions of the grains analyzed 

here, and the analysis reported by Hollister and 

others, are indicated on figure 12. 

Figures 13 and 14 give the compositional data for 

the grain containing abundant augite lamellae pictured in figure 3. The present composition of the host 

orthopyroxene is about W o5En,oFsz5 to W o6En61FS33 

(best resolved in profile A, fig. 13), and the primary 

pyroxene prior to exsolution appears to have ranged 

from about Wo0En71Fszs to about Wo9En62FS29 (profile B, fig. 13) . 

ORTHOPYROXENE FORMED BY INVERSION 

OF PIGEONITE 

Two orthopyroxene cores that formed by inversion 

of surrounding pigeonite with no visible exsolution 

of augite (one is illustrated in fig. 7) were analyzed 

in order to determine whether or not a compositional change accompanied the inversion. The field 

of compositions for these cores, and a trace from 

within one of them across the contact with surrounding pigeonite (profile A-A') are plotted on 

figure 12. There is no compositional discontinuity 

at the contact; the orthopyroxene averages about 

Wou.En7.1.fiFS21, and immediately adjacent pigeonite 

is of similar composition. 

COMPOSITION OF ORTHOPYROXENE AND 

CLINOPYROXENE AT THEIR CONTACTS 

Microprobe traverses were made across contacts 

of exsolution-free orthopyroxene with pigeonite, and 

with orthopyroxene that contains abundant exsolution, in order to determine whether or not the textural variations observed are correlated with specific 

compositional ranges. The data for the 16 composite 

grains analyzed are shown on figure 16. There do 

appear to be several consistent correlations of composition with texture. Orthopyroxene grains that 

have euhedral outlines (fig. 5A), contain preserved 

traces of euhedral outlines (fig. 4A), or have inverted from pigeonite (fig. 7) are generally more 

magnesian than Fsz 3 at their edges. In these grains 

the pigeonite at the contact is typically close in com-
14 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

Wo • 

FlGURE 16.-Wo: En: Fs contents of exsolution-free orthopyroxene, orthopyroxene with augite lamellae, and pigeonite at their contacts. Solid circles are orthopyroxene, solid 

triangles are orthopyroxene containing abundant augite 

lamellae, and open circles are pigeonite. Solid lines connect compositions across the contacts, and the points are 

separated by no more than 6 p.m. 

position to the orthopyroxene, and in many grains 

there is virtually no compositional discontinuity (fig. 

17, profile A). Orthopyroxene cores that are overgrown by orthopyroxene with abundant augite lamellae are around Fs25 at the contact of the two 

orthopyroxenes ; the primary pyroxene in the overgrowth appears to have been appreciably more calcic 

than the orthopyroxene in the core (figs. 13, 14, and 

16). Orthopyroxene cores for which textures do not 

indicate whether or not they reacted with melt prior 

to pigeonite precipitation tend to be more iron-rich 

than Fs25 at their edges, and the compositional transitions across the contacts range from continuous to 

strongly discontinuous. The one grain analyzed that 

shows a possible resorbed margin (fig. 5B) is Fs26 

at its edge, and the compositional change across the 

contact is sharply discontinuous with the adjacent 

pigeonite much depleted in Mg and enriched in Ca 

and Fe (fig. 17, profile B). 

None of the orthopyroxene grains analyzed here 

are directly rimmed by augite; all have intervening zones at least a few micrometers thick of 

pigeonite. However, Hollister and others (1972) reported an analysis of an unusually calcic hypersthene, Wo11En58Fs 3 1, directly overgrown by augite, 

W Os1En42FS21· 

PIGEONITE AND FERROPIGEONITE 

The pigeonites that form the bulk of the pyroxene 

grains in the rock have an extremely wide range of 

Fe/Mg ratios but are fairly restricted in Ca contents. The compositional field of such pigeonites 

analyzed in this study is outlined on figure 12 (pigeonites in graphic, subophitic, and intergranular 

grains) ; other authors report pigeonite compositions within the overall range observed here (Kushiro and others, 1972; Gancarz and others, 1971; 

Brown and others, 1972). Single grains are in gen18000 

17000 

Mg 

16000 

15000 

>- 1-

v; 

z 14000 w 

1-

z 500 

400 

Co 300 

200 

100 

5000 

Fe 

Profile A 

~~6;E(IG~~ITE 

DIRECTION OF 

GROWTH 

Profile B 

OPX. PIGEONITE 

CORE RIM 

DIRECTION OF GROWTH 

18000 

16000 

14000 

12000 

10000 

8000 

500 

7000 

6000 

DISTANCE 

FIGURE 17.-Variations in Mg, Ca, and Fe contents along 

profiles across orthopyroxene-pigeonite contacts. Ordinate, 

abscissa, and designations of textural relations are as described in caption to figure 13. A is a profile across the 

contact in the composite grain illustrated in figure 5A. 

B is a profile from center to edge of the composite grain 

illustrated in figure 5B. In profile A there is virtually no 

compG-sitional discontinuity at the eontact, but in profile 

B there is a strong discontinuity. 
PHASE COMPOSITIONS 15 

eral strongly zoned with progressive iron enrichment 

toward their margins. The extent of zoning and the 

average Fe/Mg ratio vary considerably from grain 

to grain. Variation of about 20 percent Fs content 

was the maximum observed in continuously zoned 

grains analyzed here, and none of the grains contains the complete range of Fe/Mg ratios shown by 

all pigeonites as a group. As an illustration of 

typical zoning variation, a microprobe profile across 

the composite orthopyroxene-pigeonite-augite grain 

pictured in figure 7 is plotted on figure 12 (A-A'). 

The coarse twinned pigeonite grains that are 

graphically intergrown with plagioclase are unusual 

in composition as well as texture. Points in such 

grains are Wo-1En,9Fs1, to Wo6En69Fs2,, a compositional range nearly identical to that of the magnesian orthopyroxenes in the rock. In single grains of 

these pigeonites Ca contents are fairly constant, 

whereas Fe and Mg contents vary irregularly over 

the range given above; the grains increase abruptly 

in Ca and Fe at their extreme edges. 

Ferropigeonites with Fs contents between 40 and 

55 percent have highly variable Ca contents in comparison with pigeonites that have Fs less than 40 

percent. This variability apparently indicates that 

many such grains consist of exsolution intergrowths 

of ferropigeonite and iron-rich augite, as demonstrated by data presented by Ridley and others 

(1972) and Takeda and Ridley (1972). 

AUGITE 

Compositional fields for the major textural types 

of augite are outlined on figure 12. Analyses reported by Ridley and others (1972) indicate that the 

field of overgrowth and interstitial augites extends 

to more iron-rich compositions than found in this 

study, as iron-rich as W0:32En2"'Fs 10 • The augites that 

form exsolution lamellae in orthopyroxene are too 

fine for accurate analysis, but the data suggest they 

are similar in composition to the augites that form 

exsolved blebs and prisms in this mineral. 

COMPOSITIONS OF PIGEONITE AND AUGITE 

AT THEIR CONTACTS 

In order to compare the compositions of coexisting pigeonite-augite pairs in 14310 with compositions of coexisting pyroxene pairs formed during 

equilibrium crystallization experiments, microprobe 

traverses were made across 24 pigeonite-augite contacts. Such comparisons yield information on 

whether or not the natural pyroxenes crystallized 

metastably or under equilibrium conditions. The 

W o: En: Fs contents of the coexisting pyroxenes are 

plotted on figure 18. 

OTHER PYROXENES 

The compositions of small grains of highrefractive-index pyroxene in mesostasis are indiFIGURE 18.:-W~:E~:Fs contents of coexisting augite and pigeonite. Solid circles are compositions of pyroxenes in contact 

where p1geomte IS overgrown by augite; open cirdes are compositions of pyroxenes in contact where augite h:; ()Vergrown by ferropigeonite. Solid lines connect compositions across the contacts, and the points are separated by no more 

than 6 ,urn. 
16 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

cated on figure 12. Most of these grains are very 

iron-rich ferropigeonites with Fs content ranging 

from 62 to 80, but a few are more magnesian with 

Fs content as low as 40. 

Compositions of pyroxenes in fine-grained clots 

are plotted on figure 12. These pyroxenes have Fe/ 

Mg ratios about like average pigeonites elsewhere in 

the rock, but in Ca content they are intermediate 

between augite and pigeonite. Pyroxene that is within a fine-grained clot, but borders a reaction rim of 

whitlockite surrounding a Ni-Fe particle (fig. 2D), 

appears to be depleted in Fe and Ca relative to unreacted pyroxene within clots (see fig. 12). 

The edges of four grains of pigeonite and one 

grain of augite immediately bordering vugs were 

analyzed. The pigeonites are "\\'.,. olo-uEn,..o-5;;FS:;.,_40 

and the augite is Wo3zEn35Fs33• 

Some intergranular grains of augite and ferropigeonite contain small patches of subcalcic augites 

whose compositions are fairly uniform and intermediate between pigeonite and augite. Analyses of 

points in several such patches of subcalcic augite, 

and the compositions of the adjacent augites and 

pigeonites, are plotted on figure 12. 

COMPOSITIONS OF INTERGROWN AND 

IMPINGING PLAGIOCLASE AND PYROXENE 

Intergrown and impinging grains of plagioclase 

and pyroxene were analyzed in order to obtain a 

rough calibration of compositional changes in the 

different pyroxenes relative to the crystallization 

history of the plagioclase. As would be expected, the 

more magnesian pyroxenes are intergrown with the 

more calcic plagioclase, and relatively iron-rich pyroxenes with relatively sodic plagioclase. Moreover, 

there are several consistent correlations of types of 

intergrowth textures with certain compositional 

ranges. 

Most orthopyroxene grains that occur in intimate 

intergrowth with plagioclase are in the more magnesian part of the compositional range, W o4En,oFs17 

to W o4En,2FS24· Coarse twinned pigeonites intergrown with plagioclase are of similar compositions. 

Cores of plagioclase grains included in, and centers 

of plagioclase grains graphically intergrown with, 

magnesian orthopyroxene range from An91 to Ans2.4 

and average Ans7.2; centers of grains graphically 

inte:rgrown with coarse twinned pigeonite range 

from Ans,.6 to Ans2.7· The few plagioclase grains 

intergrown with more iron-rich orthopyroxene tend 

to be more sodic, ranging from Anss.5 to Anso.l and 

averaging Ans3.1· Within a few micrometers of contacts, the plagioclase grains are commonly slightly 

enriched in sodi urn and the pyroxene grains in iron. 

The maximum sodium enrichment in plagioclase 

near contacts corresponds to an increase of about 

10 percent in Ab content, and the maximum iron 

enrichment in pyroxene corresponds to an increase 

of about 5 percent in Fs content. Plagioclase bordering very iron rich orthopyroxene, Wo~,r.En.-.~ .. lFs,o.:;, is 

more sodic, Or::.:-.Ab~.-..~~An~o.n· Plagioclase bordering a 

contact of augite and pigeonite (Wo:; En10 Fs~:: rimming WoloEn.-.:!FS::~) is Or:l,zAb~~.-~An,~.l· Plagioclases 

bordering more iron-rich augites are still more 

sodic: OruAb19.nAn"'·'' adjacent tc "\Vo::j_nEn:;s_-.Fszu, 

and Or.>uAbz~.~Anui.ll adjacent to Wo:Jt.oEn:;:;_,Fs32.!J· 

OTHER SILICATE AND OXIDE PHASES 

Fayalite, potassium feldspar, and silica-rich glass 

are the only mesostasis phases analyzed in this study. 

The fayalite is Fo2o-21 ; a complete analysis was given 

by Gancarz and others (1971). The potassium feldspar grains are all Ba rich and are somewhat variable in N a contents: In grains analyzed here, molecular percent of celsian ranges from 5.9 to 9.0, of albite 

from 6.4 to 10.4, and of anorthite from 3.2 to 4.2. 

Silica-rich glass is also rich in K but is poor in Ba; 

Dence and Plant (1972), Kushiro and others (1972), 

Longhi and others (1972), and Roedder and Weiblen 

(1972) report that such glass contains 5-8 percent 

KzO and 75-77 percent Si02 • Other phases for which 

analyses have been reported are: ilmenite (Gancarz 

and others, 1971, and El Goresy and others, 1971) ; 

ulvospinel (Haggerty, 1972, and El Goresy and 

others, 1972) ; baddeleyite (El Goresy and others, 

1971) ; whitlockite (Brown and others, 1972, Gancarz and others, 1971, Griffin and others, 1972) ; 

tranquillityite (Brown and others, 1972, and El 

Goresy and others, 1972) ; a new Zr-rich mineral 

(Brown and others, 1972) ; and devitrified iron-rich 

glass (Roedder and Weiblen, 1972). 

Fe-Ni ME'T AL AND SCHREIBERSITE . Schreibersite and Ni-Fe were analyzed to determine whether or not these phases show any compositional characteristics that are: (1) diagnostic of 

either meteoritic or indigenous origin; or (2) diagnostic of either crystallization from metal-rich melt 

or precipitation by reduction in silicate melt. Detailed studies were also made of compositions of 

coexisting metal and schreibersite in single particles, 

for under suitable conditions this mineral pair is an 

excellent recorder of subsolidus temperature history. 

The analyses of Ni-Fe reveal that there are two 

distinct compositional populations of metal in the 

rock: phosphorus-bearing and phosphorus-free. Mineral associations, and thus textures as well, are cor-
PHASE COMPOSITIONS 17 

related with this compositional grouping. Phosphorus-bearing metal grains consist of: all grains 

associated with schreibersite; a minor number of the 

small irregular particles that have no associated 

schreibersite; and about half the metal-bearing particles included in plagioclase. Phosphorus-free metal 

grains consist of: most of the irregular particles that 

have no associated schreibersite; about half the 

metal-bearing particles included in plagioclase; and 

most globules and small euhedra in troilite or mesostasis. 

Compositions of the phosphorus-bearing metal 

grains cluster, with Ni ranging from 12 to 17.5 percent and Co from 0.6 to 1.2 percent (fig. 19A). The 

phosphorus-free grains, in contrast, vary widely in 

Ni and Co, and contents of these elements are 

roughly linearly correlated (fig. 19B) ; variation is 

from. near 0 to 42.4 percent Ni and 0 to 2.52 percent 

Co. (Error in the Co analyses may be relatively 

large, perhaps as great as ±0.1 percent absolute, and 

some of the scatter in Co values may be due to analytical error.) Other workers who analyzed Ni-Fe 

in 14310 did not report P values; their reported 

ranges for Ni and Co are within the ranges reported 

here (El Goresy and others, 1971; Gancarz and 

others, 1971; Ridley and others, 1972). 

The schreibersites analyzed in this study have Ni 

contents from 11.2 to 29.8 percent and Co contents 

from 0.25 to 1.14 percent; within single grains these 

elements show large variations on a very fine scale 

produced by subsolidus equilibration. (El Goresy 

and others, 1971, reported an analysis of schreibersite with Ni and Co contents in the range found 

here; schreibersites analyzed by Axon and Goldstein, 1972, have slightly lower Ni but similar Co. 

No schreibersite with Ni<11 percent was found in 

this study, but El Goresy and others, 1971, report 

finding pure Fe3P in their sample.) 

PHOSPHORUS-BEARING Ni-Fe AND SCHREIBERSITE 

Volumetrically, large composite particles like 

those illustrated in figure 9 contain most of the 

phosphorus-bearing Ni-Fe and schreibersite in 

14310. The y Ni-Fe 1 that is the major constituent 

of these particles ranges in Ni from about 13 to 16 

percent. Co contents are more variable, from 0.6 to 

1.1 percent, and this element may be heterogeneously 

distributed even within single grains (uncertain because of possible analytical error). The y Ni-Fe 

1 It is likely that this phase actually coru;ists of a very fine exsolution 

intergrowth of a and 'Y Ni-Fe that developed from ')' Ni-Fe during low 

temperature subsolidus equilibration; as the original phase was 'Y Ni-Fe 

and the exsolution is too fine to resolve with methods used here, the 

designation 'Y will be used in this paper for all Ni-Fe of suitable composition. 

ISOLATED PARTICLES 

w.th ~chre•ber~lle 

12 ..., 60 ,u m 

<60,-u.m 

No o~soc•oted schre1ber~•te 

>IOO,tLm 

10 w1th trod1te 0 < !OO,.u.m 

no a~~octoted 

trod1le o 

0 8 

Co INCLusioNs IN PLAGIOCJ.t..~ + 

Co 

0 6 

04 

0 2 

A 

I50LATED IRREGULAR PA~ 

>85,u..m 

<85 .ILm 

ISOLATED GLOBULES AND EUHEDRA 

W1thon trod•!~ 

>30 ""'m 0 <30 J.Lm o 

W,th•n me~O\Iasos gloss 

:~g ::~ 0 IB~~ 

4. 

0. 

. "• 

~ . .. +0 . 

0 

0 

0 

B 

.. 

0 

+ 

Ni 

-: .. 

0 

cNi = 42.4 

Ni 

FIGURE 19.-Ni and Co contents, in weight percent, of grains 

of phosphorus-bearing (A) and phosphorus-free (B) NiFe. Solid lines connect compositions of points in the same 

grain. Particles designated as "isolated" are those not 

included in plagioclase or pyroxene. 

grains commonly have rims a few micrometers thick, 

formed during subsolidus equilibration, of a Ni-Fe 

that contains about 7 percent Ni. Ni content in 

schreibersite in any given composite particle varies 

widely; a common range observed is from about 2 

percent less than, to about 10 percent greater than 

the Ni content in associated y Ni-Fe. However, Co 

content in schreibersite is always less than the Co 

content in associated a or y Ni-Fe. To illustrate 

these compositional variations, the compositional 

data for the two globules pictured in figure 9 are 

presented in detail below. 

The compositional data for Ni-Fe and schreibersite in the particle illustrated in figure 9A are 

plotted on figures 20 (profile A) and 21A. As is 

evident in figure 20, the large grain of y Ni-Fe that 

forms the bulk of the particle is zoned: Ni content 
18 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

Prolole A Prolole B 

DISTANCE 

FIGURE 20.-Variations in Ni and Co contents along profiles 

across large Fe-Ni-P-S globules. Ordinate, abscissa, and 

designations of textural relations are the same as described 

for figure 13. Profiles A and B correspond to profiles indicated on figure 9. On profile B, the counts for Ni in the 

a Ni-Fe phase are not plotted because they are· below 

the indicated scale. 

I 0 

08 

0 6 

Co 

04 

0 2 

0 

0 

A 

I 6 

I 0 

08 

Co 

06 

04 

02 

B 

t!ci<. Average near center ot porliCie £ 

Pomt~ on trover~~ e futecto•d bleb 

Bordertng trod.te 

Ave:ch~:.:e~:~,:''~ mello 

Schretber~•le 

Potnh on traver'e~ 

Average •n lamella 

1!!1 

~ 

Ill 

Pomt~ on traverse~ e v.~tble 'lnd of C( pho~e Ill 

Schr~ttber5tle 

Pomt\ on traver~e\ X 

Center., of random porltde\ 0 

c 

10 

Ni 15 20 25 

Ni 

FIGURE 21.-Ni and Co contents (in weight percent) of a 

Ni-Fe, 'Y Ni-Fe, and schreibersite in large Fe-Ni-P-S 

globules. Solid lines connect cons,ecutive (but not always 

adjacent) points on traverses across phases at edges of 

globules; arrows indicate traverse direction and point 

from the extreme edge toward the interior of the particle. 

A, Points in the particle illustrated in figure 9A. Dashed 

line connects the average composition of a schreibersite 

lamella on traverse A-A with the composition of ''l Ni-Fe 

progressively increases from about 14.1 percent at 

its center to about 15.2 percent at its edge. The 

schreibersite lamella analyzed is about 1.75 percent 

lower in Ni than bordering y Ni-Fe (A-A, fig. 

21A). Traverses B-B' and C-C' plotted on figure 

21A show clearly that schreibersite immediately adjacent to a Ni-Fe is enriched in Ni and depleted in 

Co relative to schreibersite at the center of the marginal grains of this mineral. 

The compositional data for phases in the globule 

illustrated in figure 9B are· shown on figures 20 (profile B) and 21B. The y Ni-Fe in this globule shows 

zoning similar to that in the globule described above, 

with Ni increasing progressively toward the edges 

of the grain. Ni enrichment of schreibersite immediately adjacent to a Ni-Fe is evident in the two 

traverses plotted on figure 21B. Unlike in the globule pictured in figure 9A, the a Ni-Fe analyzed here 

is appreciably enriched in Co relative to y Ni-Fe as 

well as to schreibersite. Inhomogeneities in Co distribution are suggested by the data, but their magnitude is close to the estimated uncertainty in the 

analyses. 

Ni and Co contents in all analyzed metal and 

schreibersite grains included in plagioclase are 

plotted on figure 22. The compositional variations in 

the large schreibersite-bearing inclusion illustrated 

in figure 10 (traverse A-A' on fig. 22) are like those 

shown by the large globules pictured in figure 9 

immediately bordering it. Trav:erses B-B' and C-C' show 

the compositions of, consecutively: schreibersite at the 

extreme edge of the particle; schreibersite at the c·enter 

of a marginal grain; schreibersite immediately bordering 

a Ni-Fe; a Ni-Fe (resolvable and plotted only in B-B'); 

and the edge of the 'Y Ni-Fe grain bordering a Ni-Fe. 

Points on the D~D' travers1e show the compositions of, 

consecutively: sch~eibersite at the ·extreme edge of the 

particle; a small bleb of a Ni-Fe with eutectoid texture 

in marginal schreihersite; schreibersite (two points) 

bordering the central 'Y Ni-Fe grain; and the edge of 

the 'Y Ni-Fe grain. The E-E' traverse shows the composi·tion of a Ni-Fe in contact with troilite and the composition of 'Y Ni-Fe bordering the a phase. B, Points in 

the particle illustrated in figure 9B. Travers.e A-A' is 

similar to the trav·erses B-B' and C-C' described in A 

above. The C-C' traverse shows compositions of, consecutively: a small bleb of 'Y Ni-Fe (two points) enclosed in 

a patch of schreibersite at the margin of the particle; 

schreibersite (two points) forming a narrow band that 

intervenes between the Ni-Fe bleb and the central Ni-Fe 

grain; a Ni-Fe forming a thin rind between schreibersite 

and 'Y Ni-Fe; and 'Y Ni-Fe at the edge of the central 

metal grain. Also plotted are compositions of the centers 

of several randomly chosen grains of schreibersite along 

the margins of the particle, and compositions of a Ni-Fe 

at points where this phase forms a rind thick enough to 

be optically dfse.el'nible~ 
CRYSTALLIZATION AND COOLING HISTORY 19 

Co 

SCHREIBER51TE -llfARING INCLUSIONS 

N1-Fe • 

5chretber<..tte 

SCHREIBER5!!~- FREE INCLUSIONS 

' ~ P-beonng N,-Fe e ' ---~--........_____ P- free Nt- Fe 0 

' 0, 

,, -~----- '-----~ 

"~ X 

A 

Ni 

FIGURE 22.-Ni and Co contents (in weight percent) of a 

Ni-Fe, 'Y Ni-Fe, and schreibersite included in plagioclase. 

Data for both phosphorus-bearing and phosphorus-free 

particles are plotted. Where two points in single inclusions 

were analyzed, dashed lines connect compositions of these 

points. Phase assemblages are: 'Y Ni-Fe; schreibersite; 'Y 

Ni-Fe + troilite; schreibersite + troilite; 'Y Ni-Fe + 

schreibersi.te + troilite; and a Ni-Fe + 'Y Ni-Fe + schreibersite. The inclusion containing the last of these assemblages is the one pictured in figure 10. Tra:verse A-A' shows 

the compositions of points in the inclusion pictured in 

figure 10; solid lines connect consecuti:ve points on this 

tra:v·erse, and arrows indicate the direction o.f the center 

of the inclusion. 

(traverses B-B' and C-C' on fig. 21A, traverse A-A' 

on fig. 21B). 

PHOSPHORUS-F'REE Ni-Fe 

Large isolated irregular particles of phosphorusfree Ni-Fe all have fairly similar compositions, Ni 

ranging from 10 to 13 percent and Co from 0.75 to 

0.9 percent (fig. 19B) ; unlike the phosphorusbearing particles, they are unzoned and are either 

homogeneous or their compositions vary irregularly. 

Small isolated irregular particles have compositions 

that cover the entire range plotted on figure 19B. 

Small particles with spherical or euhedral outlines 

show some consistent correlations of composition 

with occurrence. Such particles in mesostasis glass 

have less than 12 percent Ni and less than 1.1 percent Co, and content of these elements seems roughly 

proportional to size. Globules of metal in troilite 

show a very wide range of Ni contents (2 to 42.4 

percent) but much more restricted Co (nearly all 

are in the range 0.24 to 0.77 percent). (El Goresy 

and others, 1971, also pointed out that the grains 

they analyzed with highest Ni contents tend to he 

associated with troilite.) 

CRYSTALLIZATION AND COOLING HISTORY 

The data presented in this paper indicate that 

feldspathic basalt 14310 crystallized from a melt of 

the same, or nearly the same, bulk composition as 

the rock now has. Globules of Fe-Ni-P-S melt that 

were immiscible in the silicate melt, and possibly 

also particles of crystalline Ni-Fe, were present in 

the magma very early in its crystallization sequence. 

Evidence for this latter inference is that: ( 1) plagioclase typical of the earliest part of the silicate 

crystallization sequence, An94' envelops metal particles; and (2) some Fe-N i-P-S particles are as much 

as 300 ~-tiD across and their outlines are not greatly 

interfered with by adjacent plagioclase grains. As 

the silicate and metal-rich melts crystallized as. separate systems, the sequence of events in each is described separately below. 

SILICATE MELT 

The first crystals of a silicate mineral present in 

the 14310 magma were of plagioclase, An94-95· These 

crystals formed in the melt and were not xenocrysts, 

for their cores preserve traces of euhedral outlines 

and their zoning patterns and textures show no evidence of an episode of reheating. (The irregular 

zoning cited by Ridley and others, 1972, as evidence 

for broken crystals probably resulted from growth 

of impinging grains during the middle part of the 

crystallization sequence.) Grain-sh~e distribution is 

roughly seriate, and few, if any, true phenocrysts 

are present. Cores of the larger grains might represent early formed cumulus crystals, but these make 

up only 3-4 percent by volume of the total rock 

(results of point count on 14310,9). The texture 

(seriate grain sizes, random orientation of laths) 

indicates that virtually all of the rock must have 

crystallized in situ. 

The overall pattern of compositional change in 

plagioclase is one of orderly normal progressive 

zoning with superimposed minor reversals and oscillations. Cores of the large plagioclase laths analyzed 

in this study are outlined by sodium-depleted zones 

that represent an increase in anorthite content of 

about 2 percent. This zoning reversal may be a reflection of melt-wide loss of alkalis by volatilization 

early in the crystallization sequence. The grains 

show no evidence of consistent melt-wide reverse 

zoning formed later in the sequence. Minor oscillations and reversals in composition occur, but these 

vary from grain to grain and probably reflect local 

changes in growth environment of single crystals. 

Compositions and zoning are similar in large and 

intermediate-size laths, and most plagioclase adjacent to mesostasis glass-whether small laths in 

interstices or edges of larger laths-is relatively 

sodic, An62-78· The simplest explanation for these 

observations is that abundant nuclei of calcic plagioclase formed early in the crystallization sequence 
20 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

and cores of intermediate-size laths crystallized 

simultaneously with cores and intermediate zones of 

larger laths (also suggested by Ridley and others, 

1972, and Longhi and others, 1972). The evidence 

presented here indicates that, although there may 

have been minor volatilization of alkalis shortly after 

crystallization began, profound alkali volatilization 

(proposed by Brown and Peckett, 1971) did not 

occur at any point in the crystallization sequence. 

In crystallization experiments by Ford and others 

(1972), chrome spinel was the next phase to precipitate from the melt. There is no trace of this mineral in the natural rock. If chrome spinel formed in 

the natural crystallization sequence, it was later 

completely resorbed. Moreover, the crystallization 

experiments (Ford and others, 1972; Kushiro and 

others, 1972; Green and others, 1972; Walker and 

others, 1972) show olivine as the first, or one of the 

first, of the mafic silicates to form. In the experiments the olivine reacted with melt and was resorbed 

on precipitation of pigeonite. No evidence of olivine 

crystallization is preserved in the natural rock, but 

if only a small proportion of this mineral formed it 

could have been completely resorbed without leaving 

a trace. 

Orthopyroxene was the second silicate mineral to 

precipitate from the melt for which evidence is recorded in the natural rock. None of the crystals of 

this mineral are xenocrysts. Hollister and others 

(1972) cite presence of reverse zoning as evidence 

that cores of some grains are exotic, but the results 

of this study indicate that the reverse zoning formed 

during in situ magmatic crystallization. The evidence is as follows: ( 1) some reverse-zoned grains 

are graphically intergrown with plagioclase and 

must have grown in situ; and (2) in many or most 

grains with reverse zoning, such zoning is not a 

single simple reversal but is associated with complex 

oscillatory zoning related to preserved traces of 

euhedral growth surfaces. The reverse and associated oscillatory zoning in pyroxene are probably the 

results of fluctuations in conditions such as oxygen 

and (or) sulfur fugacity during crystallization. 

Most orthopyroxene probably crystallized from the 

melt as orthopyroxene. The cores of most composite 

orthopyroxene-pigeonite grains did not form by inversion from enclosing pigeonite, for c axes and 

{010} planes of the two minerals do not generally 

coincide. The preferential developments of {100} 

relative to {210} and {010} crystal faces, where 

traces of such planes are preserved, suggests that the 

crystals grew from the melt as orthopyroxene and 

not pigeonite. A small proportion of the orthopyroxene did form by inversion of. calcium-poor, magnesium-rich pigeonite, but textures of such grains 

generally indicate their origin. 

The magnesian orthopyroxene grains that show 

complex combinations of reverse, oscillatory, and 

normal progressive zoning, and in some cases small 

iron-rich nuclei, may have been among the first 

crystallized. If so, precise composition of the earliest 

orthopyroxene is difficult to determine. Composition 

of plagioclase crystallizing from the melt when such 

orthopyroxene :formed appears to have been about 

Anss-s9 (estimated from analyses of plagioclase included by or intergrown with orthopyroxene). This 

estimate is supported by the results of 1-atmosphere 

experimental crystallization studies by Ford and 

others (1972), in which Anss is the plagioclase precipitating at temperatures slightly above first precipitation of pyroxene. 

Rock texture suggests that during coprecipitation 

of orthopyroxene and plagioclase local concentrations of volatiles developed in the melt. (Unfortunately, compositions of these volatile constituents 

cannot be specified on the basis of the data now 

available.) At the sites of these concentrations, 

graphic intergrowths developed relatively coarse 

grain size, and later in the crystallization sequence 

open vugs formed. Variations in volatiles likely produced the reverse and oscillatory zoning observed in 

pyroxene formed during this period, and the abundant minute glass inclusions in some grains may 

represent trapped droplets of a volatile-rich phase. 

The precise sequence of events during the period 

when pigeonites first precipitated appears to have 

varied from place to place in the rock, probably 

reflecting local variations in compositions and conditions in the crystallizing melt. The observed relationships could be interpreted in several different 

ways, but one of the more likely of these interpretations follows. Temperature and bulk composition of 

the melt were such that crystallization of the early 

pyroxenes occurred very close to the orthopyroxenepigeonite transition curve. Local variations in volatile and minor-element contents, and possibly also 

in temperature, produced conditions such that orthopyroxene and pigeonite were alternately stable at 

the same point in the melt, or simultaneously stable 

at different points. Rims of magnesium-rich, calcium-poor pigeonite that overgrew orthopyroxene of 

identical composition formed as a result of such 

conditions. Furthermore, it is likely that the coarse 

polysynthetically twinned grains of magnesi urn-rich, 

calcium-poor pigeonite formed by inversion of pyroxene that initially crystallized as orthopyroxene. 

The textures of some of these grains definitely suggest a pigeonite-orthopyroxene inversion relation-
CRYSTALLIZATION AND COOLING HISTORY 21 

ship (fig. 8), and the X-ray patterns of the pigeonites indicate inversion from orthopyroxene (Malcolm 

Ross, oral commun., 1972). The compositions of the 

orthopyroxenes and pigeonites are in many cases 

identical, however, whereas the compositions of the 

two pyroxenes should differ by about 4 percent in 

W o content if the transition took place under equilibrium conditions (Malcolm Ross, oral commun., 

1972). Thus it is likely that the inversion was not 

an equilibrium process. Cores of some of the magnesium-rich pigeonites subsequently inverted to orthopyroxene with little or no exsolution of augite. 

Orthopyroxene that contains abundant exsolved 

lamellae of augite probably also initially crystallized 

as pigeonite, for the primary pyroxene in such 

grains appears to have had a calcium content appropriate for pigeonite (fig. 14). This pigeonite inverted 

to orthopyroxene and then exsolved augite, as is indicated by the crystallographic orientation of the lamellae (Huebner and Ross, 1972). At some point in 

the crystallization sequence, however, orthopyroxene 

became generally unstable and began to be resorbed, 

and pigeonite became the stable pyroxene phase precipitating throughout most of the melt. Most orthopyroxene grains in the rock appear to have continued precipitation until this point in the crystallization sequence was reached. Their margins have 

compositions of Fs>25 and they were overgrown by 

pigeonite appreciably enriched in Ca and (or) Fe 

(see fig. 16). Comparison with phase relations experimentally determined by Huebner and Ross 

(1972) suggests that this type of pigeonite crystallization was an equilibrium process. Locally, however, crystallization of orthopyroxenes progressively 

enriched in iron continued well beyond the point at 

which this pyroxene had ceased to form in the rest 

of the melt, and crystallization of the most iron-rich 

orthopyroxenes overlapped with crystallization of 

ilmenite. 

The above sequence of events in pyroxene crystallization is supported by data on compositions of coexisting plagioclase and pyroxene. Magnesian orthopyroxene (Fs<25) is graphically intergrown with 

plagioclase averaging An87 and iron-rich orthopyroxene (Fs>25) with plagioclase averaging An8 3. 

Analyses of pyroxenes and plagioclases where they 

impinge upon each other show that orthopyroxenes 

and coarse twinned pigeonites of identical compositions, about Fs21, border plagioclases also of identical compositions, about An85 • Orthopyroxene extremely enriched in iron, Fs.10, impinges on more 

sodic plagioclase, Ann. 

Shortly after the initiation of pigeonite crystallization throughout the melt and resorption of orthopyroxene, augite also began to precipitate. Both 

augite and pigeonite continued to crystallize simultaneously, with local compositional variations in the 

melt determining which pyroxene was precipitating 

at any given place (similar to crystallization patterns in composite pigeonite-augite phenocrysts in 

Apollo 12 basalts described by Boyd and Smith, 

1971). The pattern of crystallization is that which 

would be predicted for stable cotectic crystallization 

of augite and pigeonite (Ridley and others, 1972; 

experimental phase data reported by Ross and 

others, 1973). Plagioclase that formed during this 

period of cotectic crystallization is more sodic than 

that bordering the earlier formed orthopyroxene or 

magnesian pigeonite. An, 8 borders an augite-pigeonite contact where the pyroxenes have Fe/Mg ratios 

about in the middle of the compositional range 

shown on figure 18, and still more sodic plagioclase, 

An68 , is in contact with more iron-rich augite. 

During coprecipitation of augite, pigeonite, and 

plagioclase, vugs were forming in areas of volatile 

concentrations. Ilmenite probably began precipitating during this same period, for most ilmenite is 

enveloped by ferropigeonite, augite, or mesostasis, 

and none was observed in orthopyroxene (except in 

anomalously iron-rich grains) 0r in magnesian pigeonite. 

When the magma had almost entirely crystallized, 

augite precipitation ceased and ferropigeonite was 

the only pyroxene to continue crystallizing. Just 

prior to and just after cessation of augite crystallization, subcalcic augites with compositions intermediate between augite and pigeonite precipitated 

locally. These subcalcic augites and calcium-rich 

ferropigeonites that now consist of exsolution intergrowths of ferropigeonite and augite likely crystallized as metastable pyroxenes (compare fig. 12 in 

this paper with fig. 10 in Ross and others, 1973). 

Final events in crystallization of the silicate melt 

were: precipitation in interstices of very iron-rich 

ferropigeonite, fayalite, barium-rich potassium feldspar, tranquillityite, and baddeleyite; and quenching 

of silica-rich and iron-rich immiscible melts to form 

glasses. Plagioclase bordering these late-stage mesostasis materials is the most sodic in the rock, as 

sodic as Ane2· 

Fine-grained clots.-Origin of the fine-grained 

clots is a problem of special significance to the question of origin of the 14310 melt. Previous investigators have interpreted these clots as possible cognate 

inclusions (LSPET, 1971; Gancarz and others, 1971; 

Walter and others, 1972) or as possible products of 

in situ crystallization (Brown and Peckett, 1971; 

Ridley and others, 1972). Textural evidence strongly 
22 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIC BASALT 14310 

favors the latter interpretation: Textures of the 

clots grade into textures typical of the rest of the 

rock, and the clots are commonly surrounded by 

zones enriched in mesostasis. Compositions of minerals in the clots, however, do not follow the same 

consistent patterns shown by coexisting minerals 

elsewhere in the rock. The plagioclases are of the 

very calcic compositions typical of the early part of 

the crystallization sequence, but the pyroxenes have 

Fe/Mg ratios characteristic of pyroxenes crystallizing during coprecipitation of augite, pigeonite, and 

plagioclase. Furthermore, Ca contents of the pyroxenes are intermediate between those of augite and 

pigeonite and suggest that they may have crystallized 

metastably. 

Fe-Ni-P-S MELTS AND PARTICLES 

While the silicate melt was crystallizing, the globules of Fe-Ni-P-S melt it contained were precipitating Ni-Fe metal, schreibersite, and troilite. In one 

of the large Fe-Ni-P-S melt globules described in 

detail here (illustrated in fig. 9A), the textural and 

compositional variations are a particularly good 

illustration of its crystallization history. In this globule the first phase to form was y Ni-Fe, which precipitated as a single grain. The grain is progressively 

enriched in Ni toward its margins, a zoning pattern 

far more likely to be developed in a grain crystallizing from a metal-rich melt than in a crystal precipitated directly by reduction in a silicate melt. When 

crystallization was nearly complete, schreibersite, 

and then troilite, began to precipitate along with the 

metal from melt concentrated at the edges of the 

globule. Crystallization of schreibersite and troilite 

did not begin until surrounding silicate melt was almost entirely solidified, for these two minerals are 

molded on adjacent grains of silicate minerals. In the 

end stages of crystallization, phosphorus derived 

from the metal-rich particle combined with calcium 

from the surrounding silicate melt to precipitate 

apatite and whitlockite grains in mesostasis bordering the globule. 

In other large particles less rich in total phosphorus there appears to have been little or no primary precipitation of schreibersite, and all grains 

of this mineral apparently exsolved from coexisting 

metal. In these particles, texture alone does not indicate whether or not the metal crystallized from 

metal-rich melt or precipitated by reduction of silicate melt. Only one such particle has been studied in 

detail (fig. 9B) ; here the presence of Ni enrichment 

toward margins of the metal grain suggests growth 

in metal-rich melt. 

In contrast, it is likely that most of the phosphorus-free Ni-Fe particles precipitated directly by 

reduction of the silicate melt during the crystallization sequence. Characteristics consistent with this 

interpretation are: ( 1) The particles fill irregular 

interstices, most quite small; and (2) zoning is generally absent and the grains are either homogeneous 

or their compositions vary irregularly. Particles. that 

contain appreciable proportions of both Ni-Fe and 

troilite probably crystallized from late-stage FeNi-S melts immiscible in the silicate melt, for their 

textures are like those of the Apollo 11 metal + 

troilite particles that formed from such immiscible 

melts (Skinner, 1970). 

SUBSOLIDUS EFFECTS 

Changes in texture and composition of phases continued to take place during cooling below the solidus. 

Such changes were substantial in coexisting Ni-Fe 

and schreibersite and their results are obvious in 

the petrographic and microprobe data. Subsolidus 

equilibration was also extensive in the pyroxenes, 

producing exsolution and cation ordering (Gibb and 

others, 1972; Finger and others, 1972; Schlirmann 

and Hafner, 1972; Ghose and others, 1972; Takeda 

and Ridley, 1972), but these effects are for the most 

part not on a scale easily investigated by the methods used here. 

The effects of subsolidus equilibration in coexisting metal and schreibersite are those that would be 

predicted from experimental phase relations (Doan 

and Goldstein, 1969, 1970). In particles relatively 

rich in phosphorus, such as the one illustrated in 

figure 9A, y Ni-Fe began to exsolve lamellae and 

marginal grains of schreibersite immediately after 

crystallization ceased. In other particles with less 

phosphorus, such as the one shown in figure 9B, 

schreibersite may not have begun to exsolve until the 

temperature had dropped appreciably below the 

solidus. Schreibersite that formed at or close to the 

solidus was slightly poorer in Ni than coexisting y 

Ni-Fe. As temperature dropped and more schreibersite formed, this mineral was progressively enriched 

in Ni and depleted in Co relative to adjacent metal. 

As te1nperature dropped still further, thin rinds of 

a Ni-Fe, much depleted in Ni relative to adjacent y 

Ni-Fe and schreibersite, fonned at interfaces. Within a few micrometers of contacts with metal, schreibersite continued to be progressively enriched in Ni 
CRYSTALLIZATION CONDITIONS 23 

and depleted in Co until equilibration ceased. 

CRYSTALLIZATION CONDITIONS 

PRESSURE 

Crystallization of the 14310 melt probably took 

place entirely at or very near the lunar surface. The 

large metal particles that were present early in the 

course of crystallization were not removed by settling, and the first-formed pyroxenes are graphically 

intergrown with plagioclase, indicating crystallization of the bulk of the rock at a single site. The fine 

grain size of the rock and the presence of vugs indicate that this site was near or at the lunar surface. 

Cores within large plagioclase grains ( <3-4 percent 

by volume of total rock) are the only fraction that 

could conceivably have formed prior to surface crystallization. 

TEMPERATURE 

As basalt 14310 represents a melt crystallized at 

low pressures, the approximate temperature history 

of crystallization can be derived from the results of 

experimental crystallization studies at 1 atmosphere. 

Liquidus temperature for the silicate minerals is 

about 1310°-1320°C (Ford and others, 1972; Walker 

and others, 1972; Green and others, 1972), but~ liquidus temperatures for the immiscible Fe-Ni-P-S 

melts may have been appreciably higher. The approximate bulk composition of the Fe-Ni-P-S globule pictured in figure 9A is, in weight percent, 81.2 

Fe, 14.0 Ni, 1.1 Co, 2.3 P, and 1.4 S (derived from 

averaged microprobe analyses of phases and point 

counts of phase proportions converted to volume percent and corrected for the effects of sphericity). No 

experimental data are available for the liquidus temperature of such a mix, but estimates based on data 

for the binary systems Fe-Ni, Fe-S, and Fe-P 

(Hansen and Anderko, 1958) suggest a liquidus temperature around 1375°C. If, however, these metalrich melts contained appreciable initial P or S, or 

both, that was lost during crystallization, their 

liquidus temperatures could have initially been much 

lower. The presence of concentrations of phosphate 

minerals bordering the particles indicates that initial P content was indeed greater than at present, 

but the magnitude of P loss is nearly impossible to 

estimate. In order to lower the liquidus temperature 

of the globule pictured in figure 9A to near that of 

the silicate minerals, the initial content of P + S 

would have to have been about double that now present. Most other composite Fe-Ni-P-S particles, such . 

as the one pictured in figure 9B, have still less Sand 

P and would have required even greater losses of 

these constituents to lower their liquidus temperatures to that of the silicate melt. Rock texture yields 

no definitive evidence on whether or not such large 

proportional losses of P and (or) S are reasonable. 

The natural crystallization sequence at the point 

of entry of the mafic silicates does not appear to 

have been reproduced experimentally by any group 

of investigators. In experiments reported by Ford 

and others (1972) and Green and others (1972), 

olivine precipitated at about 1230°C and no orthopyroxene formed. In experiments by Walker and 

others (1972), orthopyroxene was the first major 

mafic mineral to crystallize, but during their experiments it appears that there was significant loss of 

FeO from the, silicate melt. However, all groups 

found that the second major mafic mineral was 

pigeonite and that this pyroxene formed by reaction 

of the first major mafic silicate with melt between 

1200°-1180°C. The near-solidus temperature indicated by the data of Green and others (1972), Ford 

and others (1972), and Walker and others (1972) is 

about 1100°C, by which temperature nearly all the 

silicate melt had crystallized. 

The experimental data on phase relations in the 

system Fe-Ni-P (Doan and Goldstein, 1970) suggest that the Fe-Ni-P-S melt globules probably 

would not have been entirely solidified until temperatures L950°C. Textures of silicate minerals surrounding the globules suggest that final solidification of mesostasis in the silicate melt took place at 

about the same temperature. 

Textures of the Fe-Ni-P-S particles indicate that 

the magma was at no time quenched during its crystallization. In the particle shown in figure 9A, the 

bulk composition indicates that y Ni-Fe would have 

been the only phase crystallizing at temperatures 

above about 975°C (Doan and Goldstein, 1969, 

1970), encompassing the range of crystallization of 

nearly all the surrounding silicate melt. They Ni-Fe 

in this particle shows no evidence of any sudden 

temperature drop or abrupt loss of volatile P or S 

during its crystallization. It is smoothly zoned and 

grew slowly enough that it formed a single crystal. 

Comparisons with experimental data on subsolidus phase relations in the Fe-Ni-P system (Doan 

and Goldstein, 1970) indicate that the Fe-Ni-P-S 

particles record the effects of equilibration to final 

temperatures between 800° and <550°C. In the particle shown in figure 9A, an exsolved schreibersite 

lamella has a Ni content 1. 75 percent lower than 
24 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIG BASALT 14310 

adjacent y Ni-Fe, suggesting a final equilibration of 

the bulk lamella with surrounding metal at about 

800°C. In other similar particles, compositional differences between lamellae and host metal record 

temperatures as low as 650°C. Comparisons of the 

average Ni contents of metal and of marginal schreibersite in individual composite particles yield equilibration temperatures for different bulk particles 

ranging from 800° to 650°C. For a particle of the 

bulk composition of the one in figure 9A., temperature of formation of a Ni-Fe should have been about 

600°C; the observed Ni contents of the a and y 

phases are consistent with this estimate. The lowest 

temperatures of equilibration are recorded at contacts between a Ni-Fe and schreibersite, where locally the latter mineral was highly enriched in Ni. 

The most nickel-rich schreibersites analyzed contain 

25.0 and 26.3 percent Ni; Ni in adjacent a Ni-Fe is 

8.7 and 7.4 percent, respectively. Equilibration temperatures indicated by the compositions of these two 

mineral pairs are less than 550°C, possibly on the 

order of 500°C. Axon and Goldstein (1972) estimated an even lower final equilibration temperature, 

about 450°C, for one particle analyzed by El Goresy 

and others (1971) in their sample of 14310. 

Data on subsolidus equilibration in pyroxenes indicate that final equilibration temperatures for these 

minerals were similar to those for metal and schreibersite. Studies of cation distribution in pyroxenes 

reported by Gibb and others (1972), Finger and 

others (1972) and Ghose and others (1972) yielded 

equilibration temperatures of about 625°, 550°, and 

700°C, respectively. 

Several authors have also discussed subsolidus 

cooling rates in 14310. Based on their studies of 

cation ordering in pyroxenes, Finger and others 

(1972) and Ghose and others (1972) found that the 

cooling rate was comparable to that of the coarsegrained Apollo 12 pigeonite basalt 12021. Ghose and 

others (1972), Lally and others (1972), and Takeda 

and Ridley (1972) variously stated that the rock 

cooled slowly relative to basalt 14053, to Apollo 11 

and 12 basalts, and to mare basalts in general. On 

the basis of their studies of particles of metal + 

schreibersite, Axon and Goldstein (1972) gave a 

quantitative estimate of cooling rate: from solidus 

to 700°C in 1 month. 

OXYGEN FUGACITY 

Oxygen fugacity in the 14310 melt throughout its 

crystallization appears to have been roughly comparable to that in the melts that crystallized to form 

the Apollo 12 basalts. Metal particles or metal-rich 

molten globules were present in both the 14310 and 

Apollo 12 melts during the earliest parts of their 

crystallization sequences, and both types of basalt 

show similar reduction of ulvospinel to ilmenite + 

Fe in the latest stages of crystallization. Comparisons of the observed natural mineral assemblages 

with experimental data permit some semiquantitative estimates of !02 values at different points during crystallization. Experiments reported by Ford 

and others (1972) suggest that at the point of precipitation of the first mafic silicates, about 1200°C, 

log !02 was between -11.6 and -14 and may have 

been closer to the latter value. Experimental data on 

log !02 for the late-stage reduction of ulvospinel 

(Taylor and others, 1972) indicate that when the 

silicate melt had cooled about to its solidus 

( __, 1000°C) log /02 was probably less than -15.3. 

VOLATILES 

The presence of volatiles in the melt and escape 

of volatiles during crystallization is attested to by 

the presence of vugs in the rock. Additional evidence 

for the escape of volatiles is the presence of reverse 

and oscillatory zoning in pyroxenes; such zoning is 

most likely the product of periodic degassing, for it 

is in some cases clearly associated with vugs. Crystals that grew near vugs are commonly coarser than 

elsewhere in the rock; therefore the volatiles that 

concentrated at these sites favored diffusion to existing crystal nuclei over nucleation of new grains, and 

possibly also favored relatively rapid grain growth. 

Composition of the volatile species is problematical. 

Wellman (1970) proposed that the major volatile 

species in Apollo 11 melts were H2, H20, N2, CH4, 

CO, and C02, and Motoaki Sato and R. T. Helz 

(oral commun., 1972) have suggested that S2, F2, 

and Cl2 might have been important volatiles in these 

and other lunar melts. In the 14310 melt it is possible that P2 as well was a major volatile species. 

CONDITIONS OF CRYSTALLIZATION OF 

FINE-GRAINED CLOTS 

Conditions at the sites of crystallization of the 

fine-grained clots favored both formation of abundant nuclei of plagioclase and extensive growth of 

this mineral. Ridley and others (1972) have proposed that the clots may represent sites that differed 

from the rest of the melt in content of volatile species (from the data presented here, presumably different volatile species from those that formed vugs). 

There is some evidence that favors such an interpretation. Large composite particles of metal + schreibersite + troilite in and near clots commonly are 

enveloped by reaction rims of phosphate minerals 
GENESIS OF THE 14310 MAGMA 25 

(fig. 2D), suggesting possible higher fOz at these 

sites than elsewhere in the melt. Analyses were 

made of the products and reactants involved in 

formation of one such reaction rim in an attempt 

to define the form of the reaction in order to be able 

to calculate its equilibrium !Oz. The analyses, the 

derived reaction, and the calculated equilibrium !02 

values are presented below, but the results are not 

definitive. The calculated fOz values are slightly 

higher than those estimated for the rock as a whole 

in the last stages of its crystallization, but the differences are well within the uncertainties in the 

calculation. 

The area studied in detail is pictured in figure 2D. 

Textures indicate that the reactants were schreibersite (or phosphorus dissolved in metal) and pyroxene and products were whitlockite, silica glass, and 

probably also native Fe. The whitlockite is fairly 

uniform in composition and contains Ca, Mg, and Fe 

in molar proportions 88:3: 9 ; metal and schreibersite 

contain about 0.86 mole fraction Fe. Reacted pyroxene appears to be depleted inCa relative to unreacted 

pyroxene, but Ca contents in both pyroxenes are 

quite variable (fig. 12). It appears that the reaction had the general form 3 (Ca,Mg) Si03+2Fe3P 

+%02= (Ca,Mg) 3 (Po-t) 2+3Si0z+6Fe. Oxygen fugacity at equilibrium at 1000°C was calculated 

for the related reaction: 3CaSi03+2Fe3P+%02 

=Ca3 (PO-t) 2+3Si0z+6Fe. For this calculation, thermodynamic data were taken from Latimer (1952), 

Kelly (1960), Kelley and King (1961), and Kubaschewski and Evans (1958) ; activities were assumed 

to be equal to mole fractions. Because the pyroxenes 

show appreciable variability in Ca contents, two calculations were made, one with mole fraction of wollastonite set at 0.13, the other at 0.19. The values of 

log !Oz derived from these two calculations are -14.7 

and -14.9, respectively. These values represent minimum values, because in the actual reaction the presence of Ni in the schreibersite and metal would have 

raised the equilibrium /02 somewhat. Uncertainty 

in the thermodynamic data introduces considerable 

uncertainty into the results, however-on the order 

of at least ±0.5. Moreover, if the reaction involved 

P dissolved in metal rather than Fe'lP, the !02 

could have differed by more than an order of magnitude from that calculated here (Olsen and Fuchs, 

1967). 

GENESIS OF THE 14310 MAGMA 

From data presented here and by others, it appears that the large Fe-Ni-P-S globules in basalt 

14310 represent meteoritic contaminant material. 

The very appearance of these particles suggests an 

exotic origin: Many are much larger than the rest 

of the metal-bearing grains, and they tend to occur 

in local concentrations. Their bulk compositions are 

appropriate for meteorite-derived particles (Axon 

and Goldstein, 1972), and the metal they contain has 

Ni-Co-P contents clearly distinct from the rest of 

the metal grains in the rock. Data on siderophile 

trace elements Ir, Re, and Au-elements carried 

virtually entirely by the metal particles-provide 

further support for a meteoritic origin. Absolute 

abundances of these elements are unlike those in 

other lunar basalts, but are similar to those in lunar 

soil (Morgan and others, 1972). Moreover, ratios of 

Re/ Au and Ir I Au in 14310 are close to those in 

lunar soils and in some classes of chondrites and 

appreciably different from those in mare basalts and 

other Apollo 14 basalts. 

Thus it appears that the parent melt of 14310 

began its crystallization at or near the lunar surface 

containing no more than 3-4 percent plagioclase 

crystals, perhaps none, and scattered globules of 

Fe-Ni-P-S immiscible melt (and possibly also crystalline metallic particles). The magma probably 

contained no silicate xenoliths or xenocrysts, and the 

metal-rich material was entirely melted or equilibrated with surrounding silicate melt prior to crystallization. 

The presence of meteoritic contaminant suggests 

that the 14310 melt was generated at the lunar surface or in the _upper levels of the lunar crust. Similarly, the results of experimental crystallization 

studies have indicated that derivation of the 14310 

melt by partial melting deep within the moon is unlikely. These studies show that 14310 could not represent a direct anhydrous partial melt of likely 

lunar mantle material (Ford and others, 1972; Kushiro and others, 1972; Green and others, 1972; 

Walker and others, 1972). Kushiro (1972) and Ford 

and others (1972) suggested that if additional alkalis, or alkalis and water, were present in parent 

mantle during melting, a partial melt of 14310 composition could have been generated. However, the 

presence of alkalis and (or) water during highpressure melting would have appreciably reduced the 

liquidus temperature of the melt, and it should have 

begun to crystallize on the lunar surface at a temperature below that of its anhydrous liquidus; this 

was not the case. Hypotheses that invoke crystal 

accumulation into a mantle-generated melt to explain the high plagioclase content of the rock are not 

admissible because the texture indicates that no such 

accumulation has occurred. Moreover, it is improbable that 14310 represents a mantle-generated melt 
26 CRYSTALLIZATION HISTORY OF LUNAR FELDSPATHIG BASALT 14310 

that incorporated feldspathic and meteoritic debris 

from the regolith upon extrusion, because it would 

have been necessary for such a melt to possess an 

unreasonable degree of superheat in order to retain 

a temperature > 1310°C after melting all incorporated material. 

From the above lines of evidence it appears that 

there are two possible ways in which the 14310 melt 

could have been generated: (1) by partial or bulk 

melting of a feldspathic rock in the lunar crust 

(Kushiro, 1972; Walker and others, 1972) ; or (2) 

by impact melting of feldspar-rich lunar surface 

materials (Dence and others, 1972; Axon and Goldstein, 1972; Ehmann and others, 1972; Green and 

others, 1972; Schnetzler and others, 1972; Hollister 

and others, 1972). In either case, the parental material must have been feldspar rich and probably 

was derived from rocks of a preexisting feldspathic 

lunar crust. 

In the first hypothesis, that of partial melting in 

the lunar crust, the parent material necessarily 

would have contained meteoritic metal and might 

most likely have been consolidated or unconsolidated 

impact debris. This hypothesis, however, requires 

that very high temperatures be generated by processes other than direct shock melting very near the 

lunar surface-temperatures of at least 1310°C and 

possibly considerably higher if the apparent liquidus 

temperatures of the Fe-Ni-P-S melt globules represent their true liquidus temperatures. Such high 

temperatures of partial melting so close to the lunar 

surface would not be expected on the basis of terrestrial experience, but the evidence that some lunar 

breccias have been recrystallized at tempera;tures on 

the order of 1000°-1100°C (Williams, 1972; Grieve 

and others, 1972; Anderson and others, 1972) indicates that it might have been possible for even 

higher temperatures to be generated locally in nearsurface rocks. 

In the second hypothesis, that of impact melting, 

the problem of finding a plausible heat source is removed. Generation of melts that have very high 

temperatures indeed is possible by shock. For this 

reason I favor the interpretation that impact melting in some form was important in generation of 

the 14310 melt; however, the possible schemes of 

genesis involving impact are numerous, and a probable parent material is not easily specified. For example, the 14310 melt could represent: an impact 

melt of lunar rock, with addition only of Fe-Ni-P-S 

particles from the impacting body; an impact melt 

of regolith or micro breccia; a contaminated melt 

consisting of a mixture of impact melt with impact 

debris; or a hybrid melt consisting of a mixture of 

impact melt with magma derived from the lunar 

interior. 

If indeed basalt 14310 crystallized from an impact 

melt, its crystallization history demonstrates that on 

the surface of the moon in its early history impact 

melts were formed that were not rapidly quenched. 

They instead followed crystallization paths like those 

of mare basalts, or were incorporated into melts that 

followed such paths. Distinction of such melts from 

magmas formed in the lunar interior adds yet another dimension of complexity to studies of lunar 

petrology, but such distinction is necessary before 

questions of the genesis, evolution, and thermal history of the lunar mantle and crust can be considered 

in the light of petrologic evidence. 

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11 u.s. GOVERNMENT PRINTING OFFICE: 1973-515-659/67