Surinagite, taaffeite, and heryllian sapphirine from pegmatites in

Surinagite, taaffeite, and heryllian sapphirine from pegmatites in

American Mineralogist, Volume 66, pages 1022_1033, IggI
Surinagite, taaffeite, and heryllian sapphirinefrom pegmatitesin
granulite-faciesrocks of caJey Bay,Enderby Land, fntarctica
Eowano S. Gnew
Department of Earth and Space Sciences
Univ ersity of Caldo rni a
Los Angeles, Califurnia 90024
Abstrect
Surinamite,taaffeite,berylliaa sapphirine,niobian rutile, chrysoberyl,and wagnerite
occur
in sillimanite-rich,medium-grainedsegregationsin two pegmaiitesofprobable late
Archean
age which cut granulite-facies.rocksnear Mclntyre llaia-1erzz,s,4go05,E) in
casey Bay,
Antarctica. Antarctic surinamite contains 30.9-32.1wt.za sior, 33.7-37.3wt.vo
Alror,9.il3'4 wt.EoFeo, 0.01-0.2wt.voMro, and 16.4-1g.4wt.voMgo,0.5-r wt.voBe,
and 0.66+0.2
wt'VoH2O. Assuming water is absent,a constantBeO content of 3.5 wt.Vo,
and possibleFe3*
for Al substitution, surinamite analysesrecastto 32 oxygenscontain 22 cations.
Antarctic
taafeite conrains68.5-69.3,xt.voA12o3,9.7w.vo Feo, 10.6-11.0wr.% Mgo,
4.7-5.2 wt.vo
zno, and'0.5-l wt.% Be. cell parameterssre a :5.6g04 (2)A, c : +t.tC4-(zt1,
,"gg"r,;g
that this taaffeiteis the gR polyrype.sapphirine contains zo.i wt.cosio2, 5 l. l wt.vo
Airor ani
Be, indicating substitutionof Be for Al: Be + Si : 2Al. Associaredgarnet contains
9:-l Y.E"
33 to 42 mole vopyrope and associatedcordierite, I wt.7aNarO. Stablemineral
assemblages
in the segregationsat the time the pegrnatitescrystallized are quartz-sillimanite-surinamitebiotite-orthopyroxene-garnet, quartz-surinamite-taafeite, sillimanite-garnet-biotite-surinamite-taaffeite-sapphirine,and siltim4nite-garnet-biotite-chrysoberyl_surinamite.
Tem_
peraturesand pressuresat the time of pegmalils emplacement
are estimatedto have been
800-900"c and 7-8 kbar. The Archean beryllian pegmatitesare interpreted
to be of magmatic origin and may be related to charnockitic plutonic rocks such as the
body exposed&
Tange Promontory 70 km to the west.
Introduction
Surinamite, a rare Mg-Al-Fe silicate mineral re_
(Kozhevnikov et al., 1975). From the Musgrave
Rangesof central Australia, Hudson et at. (196i) de_
scribed a taaffeite nodule sheathed by spinel and
containing minor beryllian sapphirine (Wilson and
Hudson, 1967);the nodule occursin a phlogopite re_
placementzone in metapyroxenite.Teale (19g0) re_
ports taaffeiteand hdgbomiteenclosedin spinel por_
phyroblasts in a phlogopite rock from the Flinders
Ranges(South Australia). The type taaffeite is a cut
gemstoneof unknown provenance(Anderson el a/..
r95t).
I report here a new paragenesisfor surinamite and
taaffeite. These unusual minerals are present in sil_
Taaffeite,an oxide of Be, Al, Mg, and Fe, occursin limanite-rich segregations
in two pegmatitescutting
metasomatic rocks and in high-grade metamorphic granulite-faciesrocks;
associatedmineralsare garnet,
terrains. In China, taaffeite occurs with chrysoberyl beryllian sapphirine,
chrysoberyl, wagnerite, and so_
and spinel in lepidolite veins and in reaction skarns dian cordierite.
Prior to my finds, surinamite, taaf_
in linestone cut by these veins (Beus, 1966,p. 33) feite, chrysoberyl
and wagnerite had not been reand in eastern Siberia, in nica-fluorite metasomatite ported from Antarctica
(Grew, 1980a).I also present
000.3-oux/8| /09 I 0- I 022$02.00
to22
GREW: SITRINAMITE, TAAFFEITE, BERYLLIAN SAPPHIRINE
The granutite-faciesrocks of the Napier complex
are cut by two generations of pegmalilss. An early
generation includes pegmatitesdated radiometrically
at 2500 million years (m.y.) (Grew and Manton,
1979),some of which are shown in Figure l. These
pegmatites are found at many exposuresin the Napier complex, but are nowhere abundant (see also
Sheratonet al.,1980). Pegmatitesof the early generation form crosscuttingplanar veins up to I m across,
irregular masses,some of which are associatedwith
boudinage, or pods. The last are generally 0.5-2 m
thick and extend up to 4 m; they lie at a higb angle to
the compositonal layering. The early pegmatiteshave
a granulite-facies mineralogy. Accessoryminerals include orthopyroxene, garnet, biotite, apatite' perrierite, zircon, sillimanite, ilmenite, rutile, monazite,
and locally cordierite, hornblende, and the rare minerals to be described in more detail below' In a few
cases,the early pegmatites have an aureole of darkened country rock a few cm thick. An example of
new X-ray powder and microprobe analytical data
on taaffeite, surinamite, and on some of the associated minerals. The results of this study suggestthat
beryllium is an essential constituent of the Antarctic
surinamite; de Roever (personal communication,
1980) independently found significant beryllium in
surinamite from the type locality.
Geology of the pegmatltes
CaseyBay and neighboring parts of Enderby Land
(66"30'-67"45'5and 48-53oE,Fig. l) are underlain
by a late Archean (2500 m.y.) granulite-facies terrain, the Napier zone or complex (Ravich and Kamenev, 1975,p. 2; Grew and Manton,1979; Sheratonet
aL, 1980).The Napier complex consistslargely of orthopyroxene-quartz-feldspar gneisses ("charnockitic" and "enderbitic" gneisses),pyroxene granulite,
garnetiferous gneisses,and subordinate aluminous
and siliceous rocks, which are locally intruded by
anorthositicand charnockitic rocks (Fig. l).
+ 6605
50"E
Locolitiesfor BerylliumMinerols
( Indicoted
by Be)
In EnderbyLond,Antorctico
. ARCHEANPEGMATITES
t\
cz cnanNocKtlcRocKS
I
^ ANORTHOSITIC
ROCKS
-Fflvf
\||fvvf
rfv
.<+ar-7i
.'..:..
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v
,
fl--
):
{
{I
l. ;
":-Z
o^'
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lllngsv
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t.p
r,^.--.1.-._
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,-)/
(,) EXPosuRE
67"s
..- -.-.-.-.,
Y-+rt,
'a)
|
'fr
i
/\
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:r,'t
ffi'!if',,P.,ii;
:-)
(j
-$...
ecf
p,oro.io,v
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1.._€-cil--,' l'
t00\
ANTARCTICA
.
Fig. l. Map of a portion of thc Napicr complcx in Enderby Land showing localitics for surinamite, taaficitc, and beryllian sapphirinc
ncar trlclntyre IstanOin Caseylay (indicated by Bc), Archean pegmatitcs of possiblc plutonic origin (small circles) are planar veins and
podiform bodies, one of which was dated by Grew and Manton (1979). Sourccs of data: intrusive charnockitic rocks (7) on Tange
Promontory (Ravich and Kamcncv, 1975,p. 494 Sheraton el al., 1980),east end of CaseyBay (J. W' Sheraton, p€rsonal communication,
l9E0), and north of the Tula Mouatains (Ravich and Kamcnev, l9?5, p. 4%). Spccifc localitics of Soviet samplcs provided by Ye. N.
Kamenev (personal communication, l9?8) and of Shcraton et aL's (19E0)two anorthosites by J. W. Shcraton (pffsoml communication"
l9E0).
GREW: SURINAMITE, TAAFFEITE, BERYLLIAN
such an aureole was sampled along a sillimanitebearing pegmatitenear Mt. Pyhagoras (Fig. l). The
country rocks here are osumilite granulites.The aureole is darker in color than the country rock and appearsto be richer in biotite. In placesno increasein
biotite was noted in the aureole;the darker color is
due to darkening of orthopyroxeneas contact with
the pegmatiteis approached.Near the contact,orthopyroxene is partly replaced by garnet or a garnetquartz intergrowth. The mineralogical changessuggest an increasein Fe/Mg ratio as well as in water
content of the host rock; temperatureswere sufficiently high for osumilite to remain in some layers
within the aureole.
The later generationincludespegmatitesdated radiometrically at 520m.y. (Grew and Manton, lg79\.
The later pegmatitesare abundant in CaseyBay but
are rare elsewherein Enderby Land. They form (l)
cross-cuttingveins up to 4 m in width and up to at
least 350 m in extent, (2) subconcordantpods, or (3)
large massesseveralmetersand more across.Retrogressionof the country rock by the pegmatitesoccurred under amphibolite-faciesconditions in aureoles generally no more than a few meters thick.
Accessoryminerals include biotite, muscovite,hornblende, sphene, magnetite, allanite, beryl, kyanite,
sillimanite, garnet, staurolite,tourmaline, dumortierite, and, locally, sodian cordierite. Columbite-tantalite is present at Mount H6llingsworth (Fig. l),
which is the first reported locatty for this mineral
group in Antarctica (Grew, 1980a).
The later generationof pegmatitesappearsto be
spatially and temporally related to tectonic zones of
mylonitization and retrogressionunder amphibolitefacies conditions. These zones are more extensively
developed in the €astern part of Casey Bay than in
other parts of the Napier complex.
Description of the beryllim pegmatites
Surinamite and other rare minerals were found in
two podiform pegmatitesof the early generation (indicatedby Be on Figure l), one at "Christmas Point"
(informal name), at the south end of an unnamed island 5 km WSW of Mclntyre Island (67"22'5,
49o05'E),and the second at"Zirenn Point" (infonnal
name), a coastal exposure2 km soutl of Mclntyre Island.
The "Christmas Point" pegmatite is 1.5 m thick
and is one of a seriesof en echelonpods in a layer of
quartz granulite containing sapphirine, orthopyroxene, sillimadls, and garnet. This granulite is
part ofa block ofrelatively unalteredgranulite-facies
SAPPHIRINE
rocks within a tectoniczone of extensivedeformation
and retrogression.Pegmatitesof the later generation
are abundant.
The surinamite-bearing pegmatite consists of
coarse-grained(>l cm) quartz, microrcline,apatite,
biotite and sillimanite, and of medium-grained
(mostly 0.05-2 mm) dense segregationsrich in sillimanite, garnet, cordierite, biotite, apatite, and surinamite. In hand specimen,much of the microcline
is red. Sillimanite crystals(up to l0 cm long and 3 cm
across)are white or brown; brown sillimanite is chatoyant. The medium-grainedsegregationsform irregular veins,masses,and stringersup to 5 cm across.In
addition to the above listed minerals, some samples
of the medium-grained segregationscontain orthopyroxene, wagnerite, pynte, ilmeno-hematite,magnetite, or monazite(Table l). In generalthe minerals
exceptsillimanite lack preferredorientation. Sillimanite forms a few coarse prisms 0.5 to several cm in
length and bundlesof prisms (mostly 0.05 to 0.2 mm
acrossand up to 0.5 cm in length); someof the bundles appear as fans in thin section. Pleochroic haloes
are conspicuousin biotite, which is pale green to
brown, and in cordierite.Microveinlets(0.02-0.2mm
thick) of biotite or cordierite cut garnet, sillimanite,
and, rarely, surinamite. Cordierite typically forms
aggregatesengulfing surinamite, garnet, biotite and
finer-grainedsilliminals. In places,surinamite-quartz
grain contacts are preserved. Orthopyroxene grains
(0.07-0.4 mm across),a minor constituent, locally
have contacts with sillimanite and surinamite, or are
Table l. Mincralogy of the pegnatitic aggregates
Locality
Sanple No.
Section
No.
Quartz
s i IliMni
te
SurinaEi te
sapphirine
Taa f feite
(x)
(x)
(x)
(x)
chrysobe!yl
Garnet
Oathopy!oxene
Cordierite
Biotite
xx
x
(x)
(x )
x
xx
x
x
x
-x
-x
-
X = present;
sanples
2Incluales
x
x
x
Apatite
Wagnerite
Rutile
Magneti te
Mona zite
'Py!ite,
-x
(x)
(x)
= abaentt
(Xl
= probe
ilrenohenatite,
and K-feltlspar
pegmatite.
of this
several
rAs inclusion
qPlagioclase,
in
specirens
garnet
which
are
analysiE
are
present
contrDsitionally
ln
other
sihila!.
only.
present
kyanj-te,
and apatite
in quartz
enclosing the aggregate.
ssurinamite
in quartz
in smll
and taaffeite
offshoot
of main
present
No quartz
aggregate.
in the Min
aggregate.
K-feLtlspar
algo pregent
in quartz
encloging
the aggregate.
GREW: STJRINAMITE, TAAFFEITE, BERYLLIAN SAPPHIRINE
(Grew, 1978,
separatedfrom them by only a selvageof cordierite 1977-1978and 1979-1980field seasons
(quartz also present).Wagnerite, (Mg,Fe)'POoF,oc- 1980a).Two samples from the "Christmas Point"
curs in a yellow-brown aggregateI crn acrossand as pegmatite (22928,C) and three samples from the
scatteredgrains to I mm ecrossin oee eection; grrbs "Zircnn Point" pegmatite (2234L(2,3,4))were selected for electron microprobe analyses(Table l)
are in contact with quartz.
"Zircon Point" is composedof a well-layered se- from a total of l0 samplesthat I collectedfrom each
quenceof gneissesand granulitesshowingmuch less pegmatite.
The chemical compositions(except for BeO and
evidence of the retrograde metamorphism conspicuousat "Christmas Point." A few pegmatitesof HrO) are basedon electronmicroprobeanalysesof I
both generationsare present.The beryllian pegma- to 4 grains per section (automatedARL-EMXmicrotite, which has an indistinct contact aureole,consists probe). Minerals were analyzed in carbon-coated
largely of quartz and yellow microcline. The quartz polished thin sectionsand the data were reducedby
is cut by veinlets,stringers,and small masses(up to 6 the Bence-Albeemethod. The microprobe data on 3
cm across) rich in sillimanite. These segregations minerals (hand picked separates)were supplemented
contain taaffeite,sapphirine,surinamite,garnet, bio- by semi-quantitativeemissionspectrographicanalytite (in separategrains and in microveinlets),chry- sesprovided by Richard V. Gaines.Water was detersoberyl,apatite, rutile, and rare monazite (Table l). mined in surinamite (2292C)at the U.S. Geological
Nfost segregationshave a margin of biotite and gar- Survey (courtesyof J. R. O'Neill) by weighing hynet. Sillimanite, sapphirine,taaffeite,and surinamite drogen yield from a hand'picked 20 mg sample.
X-ray diffraction patternswere obtainedwith Mncommonly have a marked preferred orientation; this
foliation lies at a high angle to the contacts of the filtered iron radiation in a I14.6 cm diameterDebyesegregations.Sillimanite forms bundles of prisms Scherrercamera.
Duptcates of surinamite,sapphirine,and taaffeite
mostly 0.05 to 0.4 mm acrossand up to severalmm
long. Taaffeite forms plates 0.2 to about 2 cm in di- have been donated to the Smithsonian Institution.
ameter; some thicker plates appear to consist of la- National Museum of Natural History Catalog numminae differing in orientation. Sapphirine and su- bers are as follows: Surinamite 2292C-147434,saprinamite form irregular, tabular grains. Those of phirine 2282G-147435,and taaffeite 2234L-147436'
sapphirine appear to be nearly 3 cm in diameter;
those of surinamite, mostly 0.05 to 0.8 mm. ChryDescriptionand chemistryof the minerals
soberyl forms anhedral grains a few tenths to a few
mm acrossembeddedin sillimanite or, in one case,in
Surinamile
taaffeite. Microveinlets of biotite (mostly 0.02-0.2
The Antarctic surinamite in hand specimen is a
mm thick) commonly cut garnetand,locally, also sildark green-blue mineral resembling sapphirine. It
limanite, sapphirine,and taaffeite.
Quartz is absentfrom the sillimanite-rich segrega- forms tabular plates (flattened parallel to (010) actions. In section2234L(5)(Table l), surinamite,taaf- cording to de Roever et al., 1976) and appears to
feite, and biotite are in contact with quartz; these have (010)cleavage;cleavageat a high angleto (010)
minerals are in a microveinlet that appearsto be an is not conspicuousin most grains (cf. de Roever et
offshoot of a sillimanite-rich segregation.Surinamite al., 1976).The optical propertiesof the Antarctic suis in direct contact with quartz. Taaffeite is mantled rinamite are similar to thoseof the type material deby mica, but was probably in contact with quartz scribedby de Roeveret al. The optic plane is parallel
to (010).Pleochroismis spectacular:Z-gteentshblue,
prior to alteration.
In section 2234L(4\,kyanite, in prisms to 0.9 mm Y-purple, and X-pale yellow green. Dispersion of
long, and plagioclaseare presentin quartz near the the optic axesis marked.
In sample 2234L(3), surinamite tablets have a
sillimanite-rich segregation.The kyanite appearsto
fixed orientation relative to a large, irregular sapphibe secondary.
rine grain; the (010) planes of the two minerals are
Field and analyticalmethods
parallel and extinction is simultaneous.However, X
The two mineral occurrencesand geologicalobser- and Z in surinamite are not parallel to the correvationsreportedin this paper are basedon field work spondingaxesin sapphirine.The pleochroiccolorsof
which I undertook as a member of the Australian sapphirine in this sample appear to be less proNational Antarctic ResearchExpeditionsduring the nounced versionsof the surinamite colors: Z-green'
1026
GREW: SURINAMITE, TAAFFEITE. BERYLLIAN SAPPHIRINE
ish blue, I-blue, with a hint of purple, and X-very
pale yellow-brown.
Powder X-ray diffraction patterns of "Christmas
Point" (2292C) and of a "Zircon Point" (2234L(4))
surinamiteare identical, exceptthat a few high-angle
reflections are less sharp in the pattern for 2292C
(Table 2). All but two of the lines reporred by de
Roever et al. (1976)which are accessibleto Fe radiation are presentin the films of the Antarctic samples.
A large number of weak reflectionsare also present
in the Antarctic patterns. Many of these reflections
may also belong to surinamite and could have been
obscuredin the filn of de Roeveret al. (1976)by fluorescenoeofiron excited by Cu radiation.
The chemical composition of the Antarctic surinamite determined by electron microprobe analysesis
Table 2. X-ray powder diffraction data for surinamite
Intensityl
22g2cr
d
22i4Ll su!inah'?
q
C
r1 . 26
9.99
7.95
7 -O9
tr.30
10.03
1 -9a
7.I0
2292C
2
2
<l
2
2
4 -64
4.5r
4.35
3-71t
3.544
l*
I
<I
I
2
I
<l
6
r.5ll
1.496
I.467
1.428
1.510
1.495
1,465
1.445
t-421
3
3
6
2
2
| 420
1.4rO
r .395
1 .36r
r.348
I 4ta
r.4lO
1 394
I 360
r.347
r.420
2
I
2
1.3I5
I.3I3
1.316
or
Film
2Pron
3vi$al
3.166
3.O84
2.9IO
2-450
2.745
2-135
2 673
I
<t
<I
2.14
2 -615
2
2
2.635
2.515
2-424
2.635
2-51A
2.522
2.419
2-422
2 -64
2
2.364
2 324
2 -3r2
2 -264
2 .I99
2-364
2-333
2.309
2 -26I
2.199
2.37
2.064
I.997
1.9a8
1.915
1.841
2 063
1.99a
1.985
1.914
1.839
2-O4
r -99
1.96
r -92
l.aI7
1.789
1.76Id
r.72Id
1.596d
t.816
L?aa
l - 750d
t.7l9d
1.594d
1.816
I-544
l.5I
I.518
I 543
I.528
I.5ra
IO
present,
3 -341
J.255
l-166
3.OA7
sillimnit€
but
4.68
4.52
4-36
3.79
2 -9r
<1
rOtainea
4 -57
4.53
4.32
3 -170
3.6e4
2.9I0
2.453
2.743
2.735
2-610
I
<l
*Biotite
7.O5
<l
a
I
I
3
with
for
et
bever
estinate-
I.236
L.262
l -234
t-227
1.218
x
1.I47
r.170
I-225
1.216
r.20r
Ll85
1.r58
x
"Zlrcon
2234L
(3)
Point"
2234L
(4)
I
I
10l
lc2
Ar
lc2
Ar
1.0443
L 0442
1.0374
1.0378
1.o325
I O43t
2cr
lc2
2cr
L0208
I 02lo
I 0128
lo2
<lc r
l.oI23
-
I 02OO
1.0201
1.0115
l.ol14
1.0049
2-315
2 -27
2 -ta5
lcl
2d2
3Ct
2d2
2ct
r -762
r 122
1.596
<I02
I 534
1.518
2dr
-
d
diffuse
Fe radiation.
(1976,
I.226
Ll88
1.173
asfe
z).
Camra
I .0360
1.0360
1.03rt
0_99971
O.9999'
0.9887
O-9a79
0.9786d
0.9765
dimler
Surinanl
Strensavs
Ranlez-
-r2-
wetsht Per Cen!
s1o2
Tio2
3 2. 0 6
otzo3
ctzo3
3 7 .3 0
0.01
9 t0
Feo3
3r-97
33.1
0.04
0.02
36 58
0.01
35.20
33.8A
31.70
0
0.0r
0.02
0
-
9.55
r0.38
13.40
12.64
L2.25
10.64
0.16
0.18
0.20
r.05
18.40 16.37
16.57
16.45
0.02
0.01
M8o
r7 59
zno
Beo!
0 .1 9
3,5
1 7 .1 3
0.13
3.5
Caos
0 .1 8
0.24
00
-
0. 12
0.09
0
0,05
14.9
-
0.05
0
001
0,05
0
0.03
0.01
0
0
98.09
101.35
100.56
100.01
99.25
99.37
98.53
lons NorDlized
to 22
5 956
5-999
5.904
5.903
6.003
5.t52
0 004
0.006
A1
Cr.
8.167
0.001
8.tI3
0.001
Total
8.168
Pe2+
h
Ma
To taI
L.4t4
0.003
4.87L
6.2a8
Zn
0.025
0.018
-
Be
t.562
1.578
t,571
32 010
32-056
s1
Tt
Dash
-
not
analyzed.
0
18.50
0.lr
0 03
0.03
0
14.67
0.05
0.05
x-os
33.25
0.03
MnO
Na^o5
31.60 30,89 31.37
0
0
0.003
0,007
0
8.114
7.751 7.632 7.600
0
0.001 0.003
0.400 0.500 0,500
8.151 8.133 8,103
7 615
0
7-545
1 554
0.100
1.654
I 498
0.002
L.79I
5.291
r.22r t.642 1.523
0.025 0,029 0.032
5.r24 4.663 4-127
6.370 6.134 6.242
1.904
0,165
4.558
6.627
1.545
0
5,099
5.544
0.017
0,007
1.607 1.609
1.563
r.147
r.o55
I 0502
t.0OI3
l.OOI2
0.9956
O.sgSA
0.9891
reflection,
"christmesPolnt"
22C2C
22928
(1)
zero
-
31 984 3t.976
b€Iow
llmlt
of
't2.Os7
31.981
1.555
3r.974
detection.
tde
(1976).
Roere. et aI.
o.o5t
F also reoorted
2uoodford
(r976).
a;a wtl6on
3A1r
Fe as Feo.
rAs€med
Beo content.
sAnounts
in Antarctic
sampLee are belleved
Eeported
to
be
not signlflcant.
sEstlmtedl
see text.
Lr54
1.087
1.064
1.O5Il
2.435
shri*age
al.
l.4ll
t.391
r . z e a at | ' l l l u l r . z e s
_r ' -n- ^_r
O.9944r ^ ^^.
O.SSSO' "'""
0 9880
x
= r€ftection
be reasurd-
Un-fittered
@rlected
de
t-432
r.135
tupurity.
cdnot
Localtty
Sanple
No.
sectlon
No.
halysls
No.
AAA
1r .30
3.r0
3
Surinm
ddd
AA
<l
-<1'
<f
2
I
2234L
Intensity
Table 3. Chemical composition of surinamite
114.6
m.
similar to that of other surinamites,except that the
Antarctic mineral contains less SiO, and in some
cases,more ALO, (Table 3). Surinamite in sample
2292C contains 0.66*0.2 ,xl.VoH2O (J. R. O'Neill,
personalcommunication, 1980;the large error is attributed to the small amount of sample analyzed, 20
mg).
The sample analyzedfor HrO must contain an impurity of a few peroent biotite, for the most intense
biotite lines appear in the X-ray powder pattern
(Table 2); this biotite could contribute 0.I to 0.2 *.Vo
HrO to the analysis.Sample2292Calso contains 0.5
to I wt.VoBe (spectrographic analysis, Table 4),
equivalentto about 1.5to 3 wt.VoBeO.No other element analyzed spectroscopicallyis present in significant amounts.The small amount of zinc reported in
the microprobe analysesmay not be significant; less
was detectedspectroscopically.
than O.OlVo
GREW: SUNNAMITE,
Tablc 4. Emission sp€ctrographic analyses of sapphirine,
surinamite and taaffeite (F. Savino, Analyst). ln weigbt percent of
the element(major elementsnot includcd).
Sapphirine
2234L(3't
22A2c
BA
EE
B
Co
Cu
Ga
Ni
Zn
Li
Taaffeite
2234L
Surindite
2292C
<0.01
0.5-1.0
0.01-o.05
0.r-0.5
0.0r-0.05
<0.01
<0.0r
<0.01
<0.0r
<0.01
< 0. 0 1
0.5-r .o
<0.01
0 . 0 5 - 0. r
0.0t-0 .05
<0.01
0 -5 - r . 0
<0.0r
0.01-0.5
< 0. 0 1
<o.0r
0.1-o.5
<0.01
0.0r-0.05
< 0- 0 r
<o.01-0.05
0.01-0,05
<0.01
<0.0r
<0.01-0.05
0 . 0 1- 0 . 0 5
1-10
0 .or-0 .05
0.0r-0 .05
< o. 0 r
0 . 0 1 - 0. 0 5
o.0l-0 .r
o.01-0.05
< 0. 0 1
< 0- o r
<0.01
0.01-0.05
<0.01
<0.01-0.05
0.0r-0.05
<0-0r
< 0. 0 1
0.01-0.05
>10
0 . 0 1 - 0- 0 5
0.01-0.0s
----
lo27
TAAFFEITE, BERYLLIAN SAPPHIRINE
Notdetected
de Roever(personalcommunication,1980)reports
that a few wl.VoBeO (qualitative ion microprobe
analysis)is present and that significant amounts of
H* and OH- are not presentin surinamite from the
type locality.
In the absenceof a detailedcrystal structuredetermination of surinamite (crystal fragmentshave been
sent to P. B. Moore for study), a discussionof its
chemistry can at best be tentative. For the purposes
of the presentdiscussion,I assumethat water is not
an essential constituent of surinamite, and that the
deficiency in the microprobe analysesis made up by
3.5 wt. %BeO. This amount brings the analytical totals of the Antarctic samplesinto the 9$-lffiVo nnge
and results in a reasonablestoichiometry (Table 3).
However, the analytical total of the de Roever et a/.
(1976)surinamite exceedsl0l7o.
Cations total near 22 for analysesof the "Zircon
Point" and type surinamites recastto 32 oxygens,the
cell anion content proposed by Moore (1976). For
convenience, cation totals have been normalized to
22, and the number of oxygens for 22 cations compared (Table 3).
The number of oxygens for 22 cations in the "Zircon Point" and type surinamitesis close to 32, but
that for the "Christmas Point," and to a lesserextent,
the StrangwaysRange surinamites is less than 32.
Ferric iron substituting for aluminum may explain
this difference. Reasonable oxygen totals are obtained if one assumesthat Al * Fe3* is constant at
one value in the Antarctic samples and at another
value in the other two samples(Table 3). The differencesbetweenthe two setsof samplesmay be related
to the substitution(Mg + Fe2*+ Mn) + Si: 2(Al +
Fe'*).
The high Fe3* contentsof the "Christmas Point"
surinamite are consistent with compositions of associated minerals: sillimanite at "Christmas Point"
contains 0.9 to l.l wl.VoFerOt but that at "Zitcon
Point," oriy 0.4Vo.ffus highsr Mg/Fe2* and lower
Mn/Fe2* ratios of the "Zirc'on Point" surinamite relative to sample 2292C from "Christmas Point" are
consistentwith the differencesin Mg/Fe and Mn/Fe
ratios in associatedgarnet (Table 5). However, surinamite in sample 22928 has the highs5f Mg/Fe2*
ratio of the Antarctic surinamites, while associated
garnethas a lower MglFe ratio than the ratios of the
"Zireon Point" garnets.
Taafeite
Taaffeite in hand specimenforms dark-green platy
masses(flattened parallel to (001)) having a superficial resemblanceto chloritoid (seealso Hudson et a/,
1967).In thin section,taaffeiteis very pale green and
resemblescorundum.
The X-ray diffraction pattern of the Antarctic taaffeite is similar to that for the 9R rhombohedral polytype of Hudson et al. (1967) from the Musgrave
Ranges in Australia and reflections can be indexed
Tablc 5. Analysesofgarnet
Point"
2234L
"christms
22928
Point"
2292C
I
Locality
sample No.
Section No.
"Zircon
2234L
24
sio2
Tio2
39.70
weight Per Cent
39.43
39.62
38.98
AI2O3
0-0
22.75
2 3 .1 8
22.49
0.02
zz.>3
Cr2O3
Feo I
0
26.2L
0.01
28.01
0.r8
0.14
0
27.82
1.55
0,02
30.28
1.05
9.94
9.02
0.68
0.44
0.02
0.02
MnO
11
M9o
1l
1.18
q?
tn
L.27
ZnO
Na^O
0,01
Kzo
0.04
101.37
TotaI
0
0.03
0.0s
r02.70
102.15
cations per 12 oxygen
2.988
2.948
0
1.999
2.042
0
0.001
1,755
1.751
0.04
LOz.37
2.962
0.001
2.017
0.001
1.924
Ti
A1
Cr
Fe
2.98L
0
2.013
0
1.646
Mn
Mg
Ca
o.oll
L.265
0.095
0.009
L.172
0.102
0.099
1.rl8
0.055
0.068
1.021
0.036
Total
8.012
8.031
8.013
8.029
si
'AII
Fe as FeO.
r028
GREW: SURINAMITE, TAAFFEITE, BERYLLIAN SAPPHIRINE
on the basisof their pattern (Table 6). The calculated
unit cell parametemof the Antarctic taaffeite area:
5.6E04(2)Aand c - 4t.lO4(Z)A, which are larger
than those of the Musgrave Ranges taaffeite. This
site difference may be due to the substitution of Zn
and Fe for Mg (seebelow).
Q6mpositionally, the Antarctic taaffeite is richer in
iron and poorer in Mg than other analyzndtaaffeite
and is unique in its signifisancetenor of zinc (Table
7). Signifisantamountsof Be and Ga are also present
(Table 4). However,it is unlikely the gallium content
exceedsl%o,for large amounts were not noted in an
Table 6' X-ray powder data for taaffeitc from Cascy Bay, Endcrby Land, Antarctica (Sample
2234L). Fe radiation. Mn frltcr.
Il
d(obs)
hk12
5
I
13.70
5.846
4.565
4.222
0.0.3
0.0.5
r.0.I
0.0.9
0.1.5
3
3
I
3
<1
3
3
d (calc) 2
d (obs) 3
1 3 .7 0
6.851
4.885
4.567
4.22L
13.7
4.2L
2,976
2.835*
2.78L
2,556*
2.623
2.5L9
1.1.0
r.1.3
1.0.13
1.1.6
0.r. 14
2.840
2.78L
2.550
2.624
2.52L
2.836
2.776
2,658
2.443
2,4LO
2.388
2.355
2.269
2.0.2
1.1.9
0.2.4
2,0.5
0.2.7
2.442
2.4L2
2.392
2.356
2.269
2.438
2.408
2.390
2
6
L
3
I
2.108*
2.0535
1.9383*
1.8843
1.8560*
0.2.10
2.0.1r
0.2.l3
2.0.L4
2.L.L
2.r11
2.0545
L.94L4
I . 8855
r.6)/)
2.108
2.052
]. 9390
1.8843
L.2.2
0.2.15
1.2.8
I.0.22
2.O.t7
1.8518
L . 776 6
| .7 484
L,7466
r.8548
L . 7 75 8
r.7470
3
3
r.7756
1.7464
r.7239
I
I
2
2
5
r, 6788
r .6534
1.6390
L.5236
1.6020
0.1.23
I . 2 .1 1
0.3.0
0.2.L9
2.L.L3
r.6797
r.6647
I .6398
I.6244
1.6028
1.5697:t I.2.t4
1.5571 1.0.25
L.5424t 0.3.9
1.5218 0.0.27
1.5056 0.L.26
1.5708
]. 5594
1.5433
1.5224
r,5051
I .54t7
1. 5230
1.5044
1.4875
r.4878
L . 4 73 9
L.4458
I.4868
L.4742
| ,4447
3
<1
5
<1
2
5
4
L.4453
0.2.22
I.2.t7
2.0.23
r.4L97
r.3669
2.2.0
0 . 2. 2 s
J
t.3296
z.z.t
L. t . 2 7
2. 0 . 2 6
3
2
1.3188
1.2800
L.2527
L.2378
7
4.)t
I.0.7
0.1.8
0.0.12
I .0. l0
0. 1.11
10
I
5
6
hkt2
4.99
3.760!+
3.551
3.432
3.148't
2.970r,
6
2
5
I
5
d (obs)
t.ttL
3.553
3.425
3.55
J. I)C
3.15
2.975
I
1
2
2.520
2
I
<1
<1
I
z, i)J
2.271
L.2216
I.2t65
r.2042
r. r676
J.I.d
1 , 0 .3 1
1.3.13
3. 1 . 1 4
1 . 1. 3 0
4.0.1
4.0.4
0.4.5
I.2.26
0 . 4. 1 1
d (calc) 2
1.420r
r.3669
1 . 3561
1.3418
L.3299
r . 3187
r.2802
L.2527
1
tala
r.2340
1
"O?
1,.22tL
L.ZlOJ
L.2044
L.1682
d(obs)3
I .4189
1.3682
I . 3559
L. 5442
r.3289
t.2788
r.2539
r.2360
r.2322
L.2292
L.2202
t.2L54
L.2039
1.1670
r.1419
1.1343*
1.1180*
1.1097*
I .1019
0 . 0 .3 5
0.4.L4
2. 3 . 5
4 . 0 .1 6
0 . 4. 1 7
L.0962
2. L . 3 L
I .0796
I .0790
lcl
lat
1.0961
1.0797]
r . 0 79 9 '
| . 0 73 6
1. 0 6 2 8
1.4.0
3 . 2. t 3
1.0735
1.0629
L.072L
r .0525
2at
Lcz
1cl
Laz
r.0597I
I .0591',
1.05341
1.0533',
1.1.35
1.0594
1.0587
2,3.r4
1.0534
4cr
h2
3cr
2u2
.lct
1.0450]
1.0450'
1.03841
1.0384'
1.0332
t.4.9
I .0450
1.0440
2.2.7
I .0384
I .0378
3.2.16
r.0333
4ot
3oz
3c1
2ez
L . 0 2 73 . 1
1,0273'
1 0131]
1.0132'
4.O.22
L . 0 2 73
2et
Lcz
1
1
1'
1.1418
1.1344
1.11811.1093
I .1019
I.
I4I4
1.1330
t.tzzg)
1.6380
L.6230
I .6011
1.5690
lat
4ct
3tz
2el
0 . 9 93 0
0. 9848]
0.9849'
o.9707
*Not
lncluded
ln cell
reflnement.
rVlsual
egtLmates.'
2Based on hexagonal (rhonbohedral)
rlludaon
a1. (1957)
!!
{lludson g'1q
(1957) lndexed thl6
al,
FiIn corrected
for shrlnkage.
- 114.6 ro.
Canera dlaneter
cell
of e = 5.6804(2)
reflection
as 0.2.17.
i,
c = af.f0a(2)
i,.
o.4.23
1.0131
o . 2. 3 7
t.ot24
L.2.35
0.9929
c.v.z)
0.9848
0 . 4. 2 6
0.9707
L.0265
1.0120
0.9842
ro29
GREW: SURINAMITE, TAAFFEITE, BERYLLIAN SAPPHIRINE
Tablc 7. Composition of taaffcite from "Zircon Point"
Sample No.
No.
Section
2234L
3
2234L
weight
Per cent
0.05
0
sio 2
TiO2
0
AI2O3
58.45
Cr2O3
Feo r
0.01
69.3r
0.0r
9.69
9.10
MnO
0.0r
0.01
Mgo
10.64
r0.99
ZnO
f.ro
4.55
CaO
0.09
0.11
Kzo
0.04
0.05
99 -62
r00 . 35
Gage Ridge Qocated l0 km northwest of Mount
$rthagoras, Fig. l) containing garnet' sillimanite,
and minor sapphirine, spinel, and corundum, is comparable (Table 8). Spectrographicanalysesshow that
ihe sapphirine n 2234L(3) contains 0.5 to l%oBe
(Table 4).
The anomalous composition and low microprobe
analytical totals can be explained as a result of beryllium substitution of Al such that Be * Si - 2Al'
Reasonablestoichiometries and analytical totals are
Tablc 8. Composition of sapphirine
Beo2
Total
3
Cationa
si
AI
FE
per
8 oxygen
0.002
3.99r
0
0. 396
0
3.983
0
0.400
Z1
Be
0
0.783
0.189
o.652
0
0.800
0.158
0.645
Total
6.008
6.002
Mn
rAII Fe as Feo
2Assumed content
3GaIIium
content
of Beo, from
not included.
Hudson et
aI.
(1967)
Point"'
2234L
(2)
sio2
20,26
19.15
Tio2
-
o.0r
o.06
dzog
5 1. 1 4
50.71
54.43
cr203
o.o2
0.0
Feo2
I0.05
16.94
o.o2
9.90
LZ. J'
"Christmas
Point"
1 ?
15
61 .34
0
9.52
MnO
o.o1
0.03
o.20
o.03
MgO
15.48
15.45
13.s2
L6.49
ZnO
0.17
o .03
Nio
0.09
0
1.0
o
0.10
0 .10
0.o5
0.01
Beo3
2.5
2.2
Cao
o.l5
0.o5
*zo
o
00
Na2O
element scan with the energy dispersive system on
the electron microprobe. Analysesrecastto 8 oxygens
assuming the BeO content of the Musgrave Ranges
taaffeite (5.5 ,nl.Vo)and neglecting Ga'O' result in
reasonableanalytical totals and stoichiometry (Table
?). Significant amounts of FerO, are not required, for
there are nearly 4 Al per 8 oxygens.Taafieite oomposition varies from one part of the pegmatite to another (Table 7), and some grains appear to be compositionally zoned.
Gage
RJ.dge
2045A
"zitcon
2234L
(3)
Lcality
Sample No.
section No.
o.o3
0.o4
0.0r
BaO
Total.
99.74
cations
qi
Ti
99.25
9?.55
for
100-87
20 oxygens
2.404
2.327
2.06'?
-
o.ool
0.006
l-592
A-620
7.154
7.262
7.827
o.oo2
0
0.002
0
Fe3+2
0.037
o.Osl
0.026
0.196
F"2+'
0.960
0.925
L.234
0.753
Sapphirine
wl
o.ool
0.003
0.o20
0.oo3
Sapphirine is a major constituent of sample
2234L(3) and occurs as a single inclusion in garnet in
sample 2234L(2) from "Zircon Point" (Table l).
Compositionally, sapphirine of this locality is anomalous; it contains more SiO, and less AlrO, (Table 8)
than any of the sapphirines in the compilations of
Deer et al. (1978,Table 64) 6d [liggins et al. (1979),
and of sapphirines from Enderby Laod (Ellis et al.,
1980;Grew, 1980b)of which sample2282Gis representative. Only one other Enderby Land sapphirine,
sample 2O45A, a quartzofeldspathic gneiss from
M9
2.739
2.799
-
2.514
2.93L
0.015
0.003
A1
Zn
o.oo9
o .009
Ni.
Be
Total
lsapphirine
0.642
0.293
14.018 14.04r
14.ol3
o.713
0
14 .098
comPonent of the
in 2234L(3) is a mjor
rockr in 2234L(21 it is found only as a sml]
in garnet.
inclusion
?r
2+
2all re as Feo.
Fe-' and Fe-'
In recast analyses.
(Higgins et a1',
fron stoichioretry
are calculated
1979) .
3estisted
(excePt
22a2G) .
from stoichioretry
GREIA: S URI NAM ITE, TAAFFEITE, BERYLLIAN SAPPHI RI N E
obtained by assuming BeO contents of 2.2 to 2.5
wt.Vofor the "Zircon point" sapphirines and l%ofor
the Gage Ridge sapphirine (Table g). By contrasr,
the sapphirine in sample 2282G, a qaartz granulite
from 'Christmas Point," contains insignificant Be
(Table 4) and its chemistry is similar to other En_
derbVLand sapphirines.Wilson and Hudson's(1967)
beryllian sapphirine (0.65 wt.VoBeO) difiers from the
Antarctic sapphirines in that there is no evidence of
increasedsilica content; they report 14.42\ft.qo SlO2
or 1.709Si per 20 oxygens.
An X-ray diflraction pattern of the ..Zircon point"
sapphirine (2234L(3)) is very simitar to, though not
identical with, one taken of a ..normal" ,"pphirio.,
sample 2M4H (see Grew, 1980b,Table 4). If there
are any crystallographic differences between these
sapphirines, single crystal techniques will be needed
to resolvethem.
Cordierit e and sillimanite
Cordierite associatedwith surinamite at ,.Christ-
N on2282E) suggestftaf signifigantamountsof BeO
Table 9. Analyses of cordierite from ..Christmas point',
SanpIe
22928
22828
sio2
47.77
47.62
TiO2
0.0t
A1203
30.91
29.92
Cr2O3
0
0.01
Feo I
3.55
6.62
MnO
0.05
0.76
u9o
ll. 23
ZrLO
8.79
0. 13
BeO2
0.75
1.3
CaO
0.11
0.20
Na2O
0.98
1.68
K20
0.06
0.05
95. /t3
97.08
Total
Cations
per
18 Oxygen
Si
Ti
A1
Cr
4.974
0.001
3.793
0
FE
lln
M9
Zn
0. 310
0.005
L . 74 4
o.577
0.057
1.366
0.010
BE
ca
Na
K
0.188
0.012
0.197
0.008
0.32s
0.022
0.339
0.007
LL.232
11.362
Total
4.963
3.675
0. 001
Fe as FeO
-: A
B leI O
content estimated
fron Na2O content using
cordierite
analyses
of eernf ind povondra
(1966) and Schreyer et al. (fSZS).
FerO, contents in sillimanite are 0.4 wt.Vofor sam_
ples2234L,0.9Vorn 22928, and l.lVo rn 2292C.CrrO,
contents are negtgible.
ciency in the analnical totals, then this rutile contains
about 90 mole VoTiO2 and l0 mole Voof Fe2*Other minerals
Nb oxide having Fe:Nb ratios of roughly l:2 to.3:4,
Chrysoberyl (identification confirmed by X_ray somewhat higher than other
niobian rutiles (palache
diffraction in one sample) is pale yellow in hand et al.,1944,p. 558).
sample and mostly colorless in thin section. It conOptical identifcation of wagnerite,(Mg,Fe).pOoF,
tains 1.5 wt.VoFeO and less than 0.lVo CrrO, and was confirmed
by the near identity of its X-ray powTior.
der pattern with that of Colorado wagnerite (SheriRutile is found only at ,,Zirconpoint" and some is dan et al.,1976, Fig.
l7A), in particular, the presence
of reflectionsnear 5.65A and S.S2A.
Parageneses
The main stablesilicatemineral assemblagein the
medium-grained segregationsat "Christmas Point"
Elements scanswith energy dispersive detector re- at the time the pegmatites
crystailized appears
veal the presenceof significant niobium and minor have been quartz-sillimanite-garnet-surinamite-to
tungsten, the latter probably not exceeding I wt.Voin biotite + orthopyroxene.
In the segregationsat .Ziramount. If NbrO, is assumedto make up the defi_ con Point,n'assemblages
include sillimsnils-garnet-
GREW: SURINAMITE, TAAFFEITE, BERYLLIAN SAPPHIRINE
l03l
sapphirine-surinamite-taaffeite+ rutile-biotite and sillimanite. [n addition, orthopyroxeneis not found
sillimanite-garnet-chrysoberyl-biotite-surinamiteor in the later pegmatitesor in the amphibolite-facies
taaffeite.Quartz was absentin the "Zircon Point" as- rocks of the tectoniczones(seealso Kamenev, 1979).
semblagesexcept in sample 2234L(5), in which a Consequently,the restriction of the surinamite and
quartz-surinamite-taaffeite assemblageis present. taaffeite paragenesesto Casey Bay where the later
Biotite appears to have been part of the "Zircon pegmatitesare most abundant is interpreted not to
cordierite was absent.The dif- indicate a causal relation between these beryllium
Point" assemblages,
ferencesin the assemblagesfrom the two localities minerals and the younger pegmatites.
of beryllium minerals in
The unusual assemblages
may be due to compositionalfactors,e.g.,Fe/Mgra'
tio, as indicated by garnet compositions,and Fe3* thesepegmatitesmay be due not only to high temcontents, as implied by sillimanite FerO' contents peraturesof crystallizationrelative to thosefor other
Compositional varia- beryllian pegmatites,but also to the relatively high
and Fe-Ti oxide assemblages.
tions within the pegmatite at each locality are re- MglFe ratio in the bulk corrposition of the Antarctic
flected in variable compositionsof the minerals as pegmatites.Possibleequivalentsto the associations
well as in differing mineralogy from one part of the describedhere are the AlrSiO'-garnet (rich in almandine and spessartine)-chrysoberyl-quartz assempegmatiteto another.
The textures involving cordierite, kyanite, and blages reported from aluminous pegmatitesformed
some biotite imply that theseninerals formed after at lower temperatures(Jacobsonand Webb, 1946,p.
the crystallization of the assemblagesinvolving su- 27; Beus, 1966,p. 32; Okrusch,1972).However,the
rinamite and taaffeite.They may be related to retro- garnetsin the Antarctic pegmatitesare richer in pygrade metamorphism associatedwith the tectonic rope and poorer in spessartinethan most pegnatitic
zones and later pegmatites,although the cordierite garnets, and are associatedwith minerals having
and biotite microveinletscould have formed during a greaterMg/Fe ratios than garnet.
Another possible indication of the unusual Mglate, water-rich stage in the crystallization of the
rich bulk compositionis wagnerite,(Mg,Fe)rPOnF,a
early pegmatites.
Possibletemperaturesand pressuresof crystalliza- mineral which would be expectedin magnesianbulk
tion of thesepegmatitesare constrainedby the ab- compositionswith an excessof phosphorusover calsenceof primary cordierite and kyanite and by the cium (Sheridan et al., 1976).In some parageneses'
presenceof sillimanite-orthopyroxene-quartz;they wagneriteappearswith minerals rich in magnesium,
are estimated to be be 800-9000c and 7-8 kbar e.g., ferroan magnesite in quartz-carbonate veins
(Grew, 1980b,Fig. 5). Partial pressureof water must near Werfen, Austria (Hegemann and Steinmetz,
have been sufficientlylow for the associationsillima- 1927), and phlogopite-enstatite near Kragery'
nite-orthopyroxene to be stable (Newton, 1972). (Bamble),Norway (Brlgger and Reusch,1875;NeuComparable physical conditions are indicated for marrn et al., 1960), while in others, it is associated
sapphirine-bearingquartz granulites, which are with magnetiteor ilmenit/ €.9.tnear Kragerf (816g'
found in the country rocks of the pegmatitesat both ger and Reusch, 1875) and in Bavaria (Propach,
localities.Sapphirinein the granulites at "Christmas 1976).Possibly low calcium and high fluorine concoronasof tents are more i.mportantthan high Mg contentsfor
Point" (e.g.,sample2282G)has successive
sillinanite (containing minor corundum) and ortho- wagneritestability. In any case,the diversity of wagimplies that this mineral is stable
pyroxene.Thesetextural relationshipsimply that an nerite parageneses
early-formed sapphirine-quartz associationreacted over a wide range of pressure-temperaturecondito form sillimanite + orthopyroxene + corundum. tions, and that its scarcity is more likely related to
Theserelationshipsare similar to thosein the Wilson compositionalfactors or failure of identification.
Lake, Labrador, sapphirine-quartz rocks illustrated
Origin of the berYllium
by Chatterjeeand Schreyer(1972,Fig.6) exceptfor
Beryllium mineralization in granulite facies terthe presenceof corundum. The high temperaturesof
formation and absenceof beryl, kyanite, and mus- rains is rare. To my knowledge, the only other recovite imply that the beryllium mineralization in the ports of such mineralization are the two taaffeite ocearly pegmatitesis unrelatedto the later pegmatites. currences in Australia and the three surinamite
In the later pegmatites,beryl and rare beryllian so- occurrences,a5suming these surinamites, like the
dian cordierite (e.9.,22828) are the only beryllium Antarctic surinamite, contain significant beryllium'
minerals present; kyanite and muscovite accompany The field and mineralogical evidence relating to the
1032
GRE}I: SURINAMITE, TAAFFEITE, BERYLLIAN SAPPHIRINE
origin of the beryllium minerals and their host pegmatitesin Antarctica is thereforeof interest.
The petrologic considerationsdiscussedabove,UPb isotopic data on the early pegmatites(Grew and
Manton, 1979),and U-Pb isotopic data on the metamorphic country rocks (W. I. Manton, personalcommunication, 1980)indicate that pegmatite emplacement and the granulite-faciesmetamorphismof the
Napier complex were roughly coeval.
Sheratonet al. (1980,p. 6) suggestthat the early
pegmatiteswere "probably derived by local mobilisation" of the country rock. Some of the early pegmatites,such as the irregular massesassociatedwith
boudinage (Grew and Manton, 1979),may have a
non-magmaticorigin. On the other hand, the crosscutting planar veins and podiform pegmatites are
more likely of magmaticorigin; theseare indicatedin
Figure l. Evidencefor this origin is found in the contact aureoles,which di_fferfrom the contact effects
around non-magmaticpegmatitesdescribedby Ramberg (1956,p. 199),and the presenceof the beryllium
minerals. It could be argued that the beryllium in
these minerals originated in the country rocks, but
concentrationsof beryllium in sedimentaryor metamorphic rocks (other than in the contact aureolesof
pegmatites) are exceptional. Moreover, were rocks
with above average Be contents (of which sample
2045A may be an example)abundant in the Napier
complex, there is no obvious mechanismfor transporting and concentratingberyllium under granulitefacies conditions. Aqueous fluids are generally believed to provide such a mechanism,but it is doubtful that aqueousfluids were presentin the host rocks
at the time of the granulite-faciesmetamorphism.
Fluid inclusion studiesin other granulite-faciesterrains suggestCOr-rich compositionsfor such fluids
(e.9.,Weisbrodet al.,1926),and the mineral assemblagesof the Napier complex granulite-faciesrocks
imply P",o ( P,o,.r(Sheraton et al., 1980: Grew,
1980b). Consequently,a non-magmatic source for
beryllium in the two pegmatitesappearsunliksly.
A possiblesouroeof someof the early pegmatites
is a charnockitic plutonic rock related to the orthopyroxene-bearing granodiorite and granite reported
by Ravich and Kamenev (1975,p. a9e and Sheraton
et al. (1980)from Tange Promontory 00 km west of
"Christmas Point") and other parts of the Napier
complex(Figure l). In the MusgraveRangesof Australia, a plutonic rock of charnockitic affinities, the
Ernabella Adamellite, is believed to be the source of
beryllium in taafeite at this locality (Hudson e/ a/.,
re67).
The partial pressureof water (and fluorine?)in residual fluids from a charnockitic pluton may have
been sufficient to transport beryllium, but not to
hydrate the sillimanite-orthopyroxene assemblageto
cordierite at the high ambient temperatures during
emplacement.Only after pegmatiteemplacement,as
temperaturesdecreased,did the high-temperaturesillimanite-orthopyroxene-surinamiteassemblage
react
to form beryllian cordierite, and the fractures in the
rock flll with biotite.
The CaseyBay beryllium parageneses
indicate the
possibility of beryllium mineralization associated
with charnockitic plutonism in granulite-faciesterrains. Such mineralization may have been overlooked in most studiesof granulite-faciesterrains,for
the more coillmon and easily recognized beryllium
minerals such as beryl may not be present.Taaffeite
and surinamite, which may be the principal beryllium minerals in these deposits,could be confused
with chloritoid or sapphirinein the field. More anention should be devoted to the pegmatitesassociated
with charnockitic plutons; these may reveal previously unknown geochemical features of the
charnockitic suite.
Acknowledgments
I thank the Antarctic Division of the Department of Scienceand
the Environrnent,Australia, for enabling me to participate in thc
Australian National Antarctic ResearchExpeditions during the
197'l-78and 1979-80field seasons,and for providing logistic support for my field work. I alsothank M. Sandifordand C. J. L. Wilson of the Departmentof Gcology, University of Melbourne, for
providing me with scveral samplesof the latcr p€gmatitesand for
inviting mc to join them in field work on "Christmas point." an
invitation which led to my discoveryof the mincrals describedin
this report.
I thank J. W. Sheratonfor providing unpublished information
on localities of chamockitic and anorthositic rocks in Endcrby
Land, and E.W.F. de Roever,for unpublisheddata on surfuramite.
I thank J. S. White and R. V. Gaina for arrangingthc emission
spectrographic analyscsand J. R. O'Neill, the water analysis.
Commentsby W. A. Dollase,P. C. Grew, P. B. Moore, and G.
R. Rossmanon an earlier version of this manuscript are much appreciated.
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