- Email: [email protected]
Distribution of manganese between coexisting biotite and hornblende in plutonic rocks
Distribution of manganese between coexisting biotite and hornblende in plutonic rocks* L. PAUL GREENLAND, DAVID GOTTFRIED and ROBERT I. TILLING U.S. Geological Survey, Washington, D.C. 20242 (Received
1 April
1968; accepted
in revised
form
12 July 1968)
Abstract-The distribution of manganese between coexisting biotite and hornblende for 80 mineral pairs from igneous rocks of diverse provenance (including Southern California, Sierra Nevada, Boulder, and Boulder Creek batholiths and the Jemez Mountains volcanics) has been determined by neutron activation analysis. Data on the distribution ratio (Kd = Mnhornblende/ Mn biotite) indicate that an equilibrium distribution of Mn is closely approached, though not completely attained, in most samples from plutonic environments. Comparison of K, values of mineral pairs with bulk chemica,l composition of host rocks reveals no correlation. Because initial crystallization temperatures vary with rock composition, the lack of correlation of composition with K, suggests that the equilibrium distribution of Mn between biotite and hornblende reflects exchange at, subsolidus temperatures rather than initial crystallization temperaturos. The highest K, values are for volcanic rocks, in which rapid quenching prevent’s subsolidus redistribution of Mn. For sample pairs from the Southern California and Sierra Nevada batholiths there is a Though the evidence is not compelling, positive correlation of Ii, with TiO, content of biotite. Kd may also correlate with t,ho r&e of cooling and/or the presence or absence of sphene in the rock.
GEOLOGIC applications of trace element distribution ratios between coexisting minerals have been thoroughly reviewed by MCINTIRE (1963). Recently, HXKLI and WRIGHT (1967) have shown that the distribution of Ni between olivine, clinopyroxene, and glass is temperature dependent, and HALL (1967) has shown that the distribution of Sr between plagioclase and alkali feldspar may be useful in geologic thermometry. MOXHA~~(1965) has reported the distribution of a number of elements between biotite and hornblende in a metamorphic suite and concluded that t’he distribution ratios of many of the elements studied vary with the metamorphic grade. Most existing data on distribution ratios relate to a single geologic unit or geographic region. In addition to the direct effects of temperature and pressure, distribution ratios may be indirectly influenced by water pressure, oxygen fugacity, and chemical potentials of other elements in the magma (or pore fluids) due to their effect on other aspects of mineral chemistry. Thus, for studies of distribution ratios to be generally useful, it is necessary to examine coexisting mineral pairs from rocks representing diverse geologic provinces, hence, diverse physico-chemical environments. Such a study has been made of the distribution of Mn between ilmenite and magnetite by BUDDINGTON (1964) who showed that this distribution is temperature dependent. The present study is essentially an extension of his work to biotite and hornblende. We present data on the distribution of Mn between coexisting biotitehornblende pairs from the Southern California, Sierra Nevada, Boulder (Montana)
THE
* Publication
authorized
hy the Director,
U.S. Geological 1149
Survey.
1150
L.
PAUL GREENLAND, DAVID GOTTFRIEDand ROBERTI. TILLING
and Boulder Creek (Colorado) batholiths. For comparison, biotite-hornblende pairs, from rocks of the Tatoosh pluton (Washington), the San Jacinto range (California) and the Jemez Mountains (New Mexico) also have been analyzed. Manganese was selected for this study because its ionic radius (0.80 A) is very close to that of the major elements Fez+ (0.74 A) and Mg (O-65 A) (radii from AHRENS, 1965), and because there are no complications from altervalent substitutions (MCI&TIRE, 1963) or from crystal field stabilization effects (SCHWARCZ, 1967). Thus, substitution of Mn in the lattice should be little affected by other elements in the mineral. Another advantage of Mn is the high precision with which it can be determined by activation analysis. The thermodynamic basis of trace element distribution ratios has been discussed extensively by KRETZ (1961) and MCINTIRE (1963) and will not be dealt with at length in this paper. In simple cases, the chemical potential of an element distributed between two phases IXand /? is pr = pa” + RT In a, ,LQ= ,u~’ + RT In a, where y” is the chemical potential in a standard state, R is the gas constant, T is the absolute temperature, and a is the activity of the component. At equilibrium, and thus
a/f - = a,
exp pu,” - 1%1° RT ’
For dilute solutions, Henry’s law states that the activity tional to its concentration, C, so that
%= ca
-
K
exp
of a component
is propor-
paocT@Po .
At a fixed temperature and pressure, the term on the right of the above expression is constant. Thus, we can define an equilibrium distribution coefficient of Mn between biotite and hornblende, K,, as K, =
concentration concentration
of Mn in hornblende of Mn in biotite
A more comprehensive appraisal of the factors affecting K, may be found in KRETZ (1961) and in MCINTIRE (1963). ANALYTICAL METHODS Pure biotite and hornblende were separated from crushed and sieved rock by magnetic and heavy liquid procedures. Optical counting of oil immersions indicated that the purity of all samples was 99 per cent or better. Small amounts of adhered quartz and/or feldspar constituted the predominant impurity in most samples; some of the samples were slightly chloritized. Trace amounts of opaque inclusions were observed in some samples. Although these inclusions (generally magnetite, more rarely ilmenite) could contain appreciable amounts of Mn, their paucity in the sample precludes their affecbing the observed K, to any significant extent.
Distribution
of manganese
between
coexisting
biotite
and hornblende
1151
Analysis was by a non-destructive neutron activation procedure similar to that described by STUEBER and GOLES (1967) and SCHMITT et al. (1965). Mineral samples were weighed (= 50 mg) into clean t dram polyethylene vials and irradiated in the reactor at the Naval Research Laboratory, Washington, D.C., at a thermal neutron flux of 7 x 1012 n-cm-2-set-1 for 1 min. After about 1 hr decay, the vials were opened in a fume hood and left for 2 more hours to permit escape of Ar41 formed from air in the vial. Manganese was then determined by counting the 0.84 MeV gamma radiation from Mn56 with a 2 by 2-in. NaI (Tl) crystal coupled to a 200channel analyzer. A natural silicate glass (tektite composite) of known Mn content was treated exactly like the mineral samples and used as a standard. For the purposes of this study it was essential to have an accurate estimate of the analytical precision. We analyzed 24 samples of the glass used as a standard, 16 samples of a biotite, and 14 samples of a hornblende from the Southern California batholith. The precision of the analyses, expressed as relative deviation was 52.8 per cent for the glass; +4.4 per cent for the biotite; h7.1 per cent for the hornblende. Analysis of nine samples of a hornblende and five of a biotite from the Boulder batholith resulted in deviations similar to those observed for the Southern California batholith samples. It was assumed that the discrepancy between the results for glass and for minerals was due to inhomogeneity of the minerals. This conclusion was supported by A. T. ANDERSON, U.S. Geological Survey (oral communication, 1967), who found a range of 0.34-0.41 per cent Mn in five hornblende grains and 0.19-0.23 per cent Mn in four biotite grains from our samples using the electron microprobe. Thus, the precision with which K, could be determined was limited by sample inhomogeneity rather than by the analytical technique. If the intra-sample variation found in the samples from the Southern California batholith is typical, the analytical reproducibility of K, is k8.3 per cent. Analytical accuracy was of lesser importance to this work. However, we checked the chemical analysis of the glass against a standard Mn solution and, further, analyzed G-l and W-l by this method. Good agreement with the chemical methods was obtained and it is probable that our analyses are accurate to at least 4 10 per cent. RESULTS
Southern California batholith The geology and petrology of the Southern California batholith have been described in detail by LARSEN (1948), who concluded that the batholithic rocks originated by magmatic differentiation. Subsequent mineralogic, trace element, and oxygen and lead isotope studies of rocks and minerals from the batholith (LARSEN and DRAISEN, 1950 ; NOCKOLDS and ALLEN, 1953 ; PATTERSON et al., 1956 ; SEN et al., 1959; ~YAYLOR and EPSTEIN, 1962a, b; TOWELL et al., 1965) have supported LARSEN’S original hypothesis of magmatic differentiation. A plot (Fig. 1) of Mn contents of the coexisting biotites and hornblendes (Table 1) shows a linear distribution, which closely approximates an equilibrium distribution at a single temperature. The distribution ratio (Kd) does vary, however, to a greater extent than can be accounted for as analytical error. Three possible explanations of this observation may be considered: (1) The minerals have equilibrated at different temperatures; (2) chemical variation of the minerals has affected the distribution coefficient; (3) complete equilibration has not been attained. The rocks from which these minerals have been separated range in composition from gabbroic to granitic and almost certainly have not all crystallized at the same temperature. If the equilibration temperature is the same as the igneous crystallization temperature one would expect some correlation between K, and rock type if Kd varies with temperature. However, plots of Kd vs. each of the major elements of the
1152
L. PAUL GREENLAND, DAVID GOTTFRIBD and ROBEETI. TILLIS~;
host rock (using the data from LARSEN, 1948, and from unpublished analyses) revealed no correlations. The failure of .K, to correlate with rock composition suggests that the variation of Kd is not related to the initial crystallization temperature and that equilibration of biotite and hornblende with respect to Mn was probably completed at subsolidus temperatures. Using the mineral analyses of LARSEN and DRAISEN (1950) and subsequent anpublished ana,lyses, we have attempted to relate X, with the major element
% Mn in biotite
Fig. 1. Distribution
of Mn between coexisting biotite Southern California batholith.
ant1 hornblende
in the
composition of the biotites and hornblendea. A positive correlation of K, with TiO, in both biotite and hornblende was observed, statist.ically signi~~ant at the 5 per cent level. The biotite correlation is shown in Fig. 2. The scatter of the data in Pig. 2, and the lack of other correlations imply that only a small fraction of the variation of K, can be attributed to minera* chemistry. The remainder can be ascribed only to incomplete equilibration. The rate of exchange of Mn between biotite and hornblende is in part dependent on the concentration gradient and the temperature and thus, at fixed temperature, decreases as equilibrium is approached. Because temperature was also decreasing, perfect equilibrium could not be expected. Lack of complete equilibration is suggested also by differences in Mn content of individual grains in a given sample (p. 1151). Nonetheless, the linear distribution of Mn between biotite and hornblende (Fig, 1) cannot be regarded as fortuitous and must indicate that equilibrium was closely apl)roached, even though not achieved.
Distribution
of manganese between coexisting biotito and hornblende
1153
Table 1. Manganese in coexisting hornblende and biotite from the Southern California batholith
“/;: Mn Hornblende
Biotitc
Gabbro __UL60-5 EL-230
0.237 0.408
0.109 0.149
2,17 2.74
Tonalite ~_ BCl-12 BCl-5 EL38-134 BL60-6 SLR-138 SLR-1016 BL60-2 LTS-3 BL60- 1
0.381 0.392 0.392 0.337 0.356 0.334 0.364 0.422 0.456
0.190 0.249 0.227 0.183 0.238 0.155 0.246 0.238 0.323
2.01 1.57 1.73 1.84 1.50 2.15 1.48 1.77 1.41
Granodiorito ~_____ .BL60-8 BL60-7 SLR-2242 s-2 s-13 s-14 S-8 s-11
0.376 0.931 0.604 0.692 0.756 1.02 0.875 0.686
0.246 0.570 0.332 0.469 0.474 0.563 0.520 0.461
1.53 1.63 1.82 1.48 1.59 1.81 1.68 1.49
0.477 0,565 0,614
0.270 0.314 0.294
1.77 1.80 2.09
0.291 0.355
0.160 0.231
1.54
Sa,mple
Quartz monzonitc EL38-167 LTS-2 EL38-265 Inclusions in tonalite ULBO-1B IJLBO-IA
1.82
Xierra Nevada batholith The geology of the Sierra Nevada has been summarized by BATEMANet al. (1963). The mineral samples used in the present work have been described previously in conjunction with K-Ar (KISTLER et al., 1965) and Rb-Sr (HURLEY et cd., 1965) studies. As with samples from the Southern California batholith, the variation of K, of Sierra Nevada samples (Table 2, Fig. 3) is greater than the experimental error; nevertheless, the data indicate a reasonable approximation to a constant Ir;, which we assume t’o be the equilibrium value. As with the Southern California samples, attempts to correlate K, with rock and mineral chemistry were unsuccessful except with TiO, in biotite and hornblende. Figure 2 demonstrates the correlation of Kd with TiO, in biotite in both the Sierra
1154
L. PAUL GREENLAND, DAVID GOTTFRIED and ROBERT I. TILLING
o SouthernCaliforniabatholith + SierraNevadabatholith
Fig. 2. Variation of K, with Ti content of the biotite in the Southern California and Sierra Nevada batholiths. Table 2. Manganese in coexisting hornblende and biotite in granodiorites from the Sierra Nevada batholith %Mn Sample
MT-2 BCc-13 BP-l MG-1 MG-3 BCa-20 SL-18
Hornblende
0.595 0.395 0.431 0.444 0.384 0.485 0.412
Riotite
K,
0.411 0.232 0.368 0.352 0.271 0.334 0.257
1.45 1.70 1.17 1.26 1.42 1.45 1.60
Nevada and Southern California batholiths. This figure also shows that both TiOz in biotite and K, are generally lower in the Sierra Nevada than in the Southern California batholith. Boulder batholith The geology of parts of the composite, Late Cretaceous Boulder batholith, Montana, has been described by KNOPF (1957), BECRAFT et al. (1963), and by SMEDES (1966). Rocks of the batholith range in composition from syenogabbro to alaskite; rocks of granodiorite-quartz monzonite composition predominate. Because
Distribution
of manganese
between
coexisting
biotite
and hornblende
1155
hornblende is extremely scarce or absent in the syenogabbroic and alaskitic rocks, it was possible to analyze hornblende-biotite pairs from granodiorites and quartz monzonites only. Most of the samples studied are from rocks of the Rader Creek pluton, a zoned body composed mainly of granodiorite (TILLING, 1964). The Mn values for mineral pairs from the Boulder batholith (Table 3) show less scatter when plotted (Fig. 4) than Mn values of the Southern California batholith (Fig. I), suggesting a closer approach to equilibrium. Possible deviation from Henry’s
06-
d 06E ii i .c i
0,4-
8
%
Fig.
3. Distribution
of Mn
Mn in biotite
between coexisting biotite Sierra Nevada batholith.
and
hornblende
in the
law at high Mn concentrations is suggested by Fig. 4 ; only three points are involved and thus the apparent deviation may not be real. The median K, (1.45) of these Boulder batholith samples is distinctly lower than the median K, (1.75) for the Southern California batholith but equal to that for the Sierra Nevada batholith (l-45). These differences in median Kd may be correlated qualitatively with the sphene content of the batholiths studied: the Sierra Nevada and Boulder batholiths, which are abundant in sphene, have the lower median Kd values (1*45), whereas the sphene-poor Southern California batholith has the markedly higher median Kd value of l-75. The correlation of Kd with TiO, in biotite noted for the Southern California and Sierra Nevada samples cannot be tested for the Boulder batholith biotites, because major element data are available for only four samples. Available analyses, however, indicate that the Boulder batholith biotites tend to be slightly higher in Ti relative to the Southern California biotites and are distinctly higher in Ti relative
L. PACL
1156
GREESLAND,
DAVID
GOTTFRIED
and ROBERT I. TILLISG:
to the Sierra Nevada biotites. Furthermore, the limited data for the Boulder batholith biotites suggest that, if a correlation between Kd and Ti in biotite can be demonstrated with additional data, the data would not plot on the same line as the Sierra Nevada and Southern California samples. Bo&ler
Creek batholith
The Precambrian Boulder Creek batholith, located in the Front Range, Colorado, is a body of talc-alkaline granodiorite and quartz monzonite which has undergone
% Fig. 4. Distribution
Mn in
biitite
of Mn between coexisting biotite Boulder batholith, Montana.
and hornblende
in the
regional metamorphism. The general geology of the batholith has been described by LOVERING and GODDARD (1950). Kd values for these rocks (Table 4, Fig. 5) show very little scatter and it is suggested that prolonged metamorphic heating provided more time for equilibration than the relatively short cooling histories of the other batholiths. The median K, of these samples (1.43) is the same as those of the Sierra Nevada and Boulder batholith samples, but lower than that of the Southern California batholith samples. This result correlates with the presence of abundant sphene in the Boulder Creek rocks; unfortunately, major element analyses of these mineral p&s are not available, so that the relationship of Kd to TiO, in biotite is not known. San Jacinto
Mountains
plutonic
rocks
Plutonic rocks from the San Jacinto Mountains are geographically near the Southern California batholith, but it is not yet certain whether they are derived from the same magmatic source. Although only three sample pairs are available the K,
Xstribution Table
of manganese
3. Manganese
coexisting
biotite
in coexisting hornblende and biotite batholith, Montana
%Mn
and hornblende
1157
from the Boulder
l3iotite
Kl?
0.866 0.849 0.652 0.669 0.762 0.590 0.519 0.563 0.650 0.592 0.490 0.587 0.583 0.583 0.577
0.811 0.606 0.465 0.461 0.507 0.422 0.340 0.384 0.510 0.361 0.328 0.391 0.405 0.392 0.415
1.07 1.40 1.40 1.45 1.50 1.40 1.53 1.47 1.27 1.64 1.49 1.50 1.44 1.49 1.39
0.463 0.393 0.419
0.373 0.250 0.242
1.24 1.57 1.73
0.412 0.553 0.415 0.742 0.620
0.250 0.428 0.286 0.518 0,450
1.65 1.29 1.45 1.27 1.38
0.973 1.39
0.765 1.10
1.27 1.26
0.516
0,357
1.45
Hornblende
Sample Rader
between
Creek pluton
Granodiorites 2T-1057 2T-1058 2T-1059 2T- 1060 2T-1061 2T-1062 2T-1063 2T-1064 2T-1065 2T-1066 2T-1067 2T-1070 2T-1071 2T-1080 lK-66 1 Quartz
monzonitcs
2T-1061 2T-1093 IK-647 Butte
quartz
monzonite
52C-10a Mafic quartz monzonite 6K-306 Quartz monzonite 52C-60 Quartz monzonit#e lK-241 Sihcio quartz monzonite 52C-45 Silicio quartz monzonite Leucocratic
rooks
27-797 Leucogranodiorite W-21 Leucogranodiorite Mafic inclusion
in Butte
53C 1601)
quartz
monzonim -
values (Table 5) are intermediate between the Southern California and the other batholiths. A statistical test (DIXON and MASSEY, 1951, p. 101) shows that the difference in mean Kd between the San Jacinto samples and the Boulder and the Southern California samples is not significant. The data for the sphene-rich San Jacinto tonalites neither confirm nor refute the qualitative correlation of K, with the presence of sphene. Tutoosh, pluton The Tatoosh pluton, a near-surface intrusive mass of middle Tertiary age in the (‘ascade Range of Washington State (Mount Rainier National Park), cooled rapidly
1158 Table
L. PAUL GREENLAND, 4. Manganese
-
DAVID GOTTFRIED and ROBERT I. TILLINC
in coexisting hornblende and biotite in granodiorites zonites from the Boulder Creek batholith, Colorado
Sample
%Mn
and quartzmon-
Biotite
K,
0.400 0.410 0.438 0.344 0.376
0250 0.301 0.302 0.244 0.254
1.43 1.36 1.45 1.41 1.48
0.343 0.335 0.335 0.337 0.310
0.220 0.235 0.226 0.236 0.225
1.56 1.43 1.48 1.43 1.38
Hornblende
Quartz monzonites GP-95 GP-15 GP-98 GP-52 GP-84 Granodiorites GP-1 GP-5 GP-40 GP-2 GP-17
Fig. 5. Distribution
of Mn between coexisting biotite Boulder Creek batholith, Colorado.
and hornblende
in the
as a result of explosive eruptions through its roof with concomitant sudden loss of volstiles and heat (FISKE et al., 1963). The I& values of the biotite-hornblende pairs analyzed here have a narrow range (Table 5), but are significantly higher than those observed for the other plutonic suites. These higher Kd values may reflect the temperature dependence of K,, because rapid cooling would serve to “freeze” the equilibrium distribution of Mn at a higher temperature. Alternatively, the high
Distribution of manganese between coexisting biotite and hornblende
1159
Table 5. Manganese in coexisting hornblende and biotite from various provinces
% Mn Sample
Rock type
Hornblende
Biotite
&i
0.337 0.347 0.307
0.216 0.214 0.209
1.56 1.62 1.47
0.312 0.300 0.366 0.350
0.155 0.160 0.170 0.165
2.01 1.88 2.15 2.12
0.165
0.161
1.02
0.935
0.501
1.87
0814 0.523
0.427 0.148
1.91 3.53
0.515
0.182
2.83
0.511 0.457
0.395 0.389
1.17 1.24
0.438
0.320
1.37
0.438
0.285
1.54
0,373 1.02
0.301 0.621
1.24 1.64
San Jacinto Mountains, California 66GSC-24 66GSC-18 G-3
Tonahte Tonalite Tonalite
Tatoosh pluton, Washington TLW-2 TLW-5 TP-34C TP-252
Granodiorite Granodiorite Granodiorite Granodiorite
Jemez Mountains, New Mexico 3149-7 3149.2 3149-10 3149-6 3149-5
Quartz latite, Santa Clara Rhyolite, South Mountain Rhyolite, San Antonio Rhyolite pumice, El Cajete Rhyolite flow, Banco Bonito
Lone Grove pluton, Texas ZL41 ZL3gr
Granite Granite
Harding, New Mexico 61GM-7
Sphene-rich granodiorite
Philipsburg batholith, Montana 530798
Granodiorite
New Hampshire granites NH/6-52 BNH-39
Lebanon Granite Conway Granite
Kd may be due to unique physico-chemical conditions placement of the hypabyssal Tatoosh pluton. Jem,ez Xountains
related to the shallow em-
volcanic rocks
The geology of the Jemez Mountains volcanic rocks has been outlined by Ross et al. (1061). The volcanic rocks studied (Table 5) are of particular interest in that they represent rapidly quenched materials and, hence, subsolidus equilibration of Mn between hornblende and biotite phenocrysts should be minimal. In fact, K, ranges from 1.0 to 3.5 (Table 5) virtually bracketing the range observed for all samples, both igneous and metamorphic (Fig. 6). If these are equilibrium values, something other than temperature is the principal factor which controls K,. In addition to differences in the rate of quenching, other
1160
L. PAUL GREENLAND,
DAVID GOTTFRIED and ROBERT
I. TILLIKG!
physico-chemical factors (e.g. zoning of phenocrysts, kinetic effects, oxidation, etc.) may also be partly responsible for the wide range in Kd. However, petrographic examination of the samples indicates that zoning of biotite and hornblende phenotrysts is feeble at best and probably cannot be a major contributive factor. On the other hand, four of these five mineral pairs and all the Tatoosh sample pairs have K,. > 1.8, strongly suggesting that these high K, values do indeed reflect the effect of rapid cooling from a high temperature. Arnph~bol~te fancies IKretz.
4
2
r!-
Epldote-amphibokte Ihloxhom. 1965)
642-
r-l
2-
r-l
Jemer
plvton
SanJaanto
Z’ {[
K
I
range
Boulder creek
i
batholith
--l
P IOB642-
I
rl Tatoosh
n
fancies
mountams
ri
-
2r
F
19591
111
-
r?-
Boulder
batholith
ri Swro
2
-
Nevada batholith
-
6 4 2
Southern
08
IO
12
14
16
I6
r-l 20
22
24
II--l 26 28
30
I,, 32
Californlo
bothohth
34
38
36
x,
Pig.
6. Distribution
of K, values of igneous samples (this paper) and comparison with published K, values of metamorphic samples.
Admittedly meager, the data nonetheless suggest a possible correlation of K, with the eruptive sequence or age of the Jemez Mountains samples. The mineral pairs with the highest Kd values (3.53 and 2.83) are from an explosively erupted pumice and a lava flow consisting chiefly of obsidian. These samples originated from the same volcanic center and are the youngest volcanic rocks in the region. The bwo rhyolites with K, values of l-87 and 1.91 are genetically related and were formed during a slightly earlier stage of rhyolitic eruptions. The sample with the unusually low R, of 1.0 is from an older quartz latite in the volcanic sequence. Thus, the correlation between K, and eruptive sequence may reflect differences in the eruptive and cooling history of the rocks, but due to the small number of samples, t,he possibility of spurious correlation cannot be precluded. CONCLUSIONS
With the exception of only three samples, our data clearly demonstrate that K, for igneous hornblende-biotite pairs varies within the relatively restricted range of 1.0-2-2, regardless of the composition and provenance of their host rocks (Table 6 and Fig. 6). Figure 6 also shows that Kd values for metamorphic samples of the epidote-amphibolit,e facies studied by MOXHAM (1965) have a median and range
Distribution Table
of manganese of K,
6. Distribution
Samples Southern
California
-~
biotite
and hornblende
and hornblende
Range
Ka
from
1161 igneous
rocks
Median
2 9 8 3 2
2.17-2.74 1.41-2.15 1.48-1.82 1.77-2.09 1.54-l .82
2.45 1.73 1.61 1.80 1.68
7
1.17-1.70
1.45
8 2
1.07-1.64 1.24-1.73 1.26-1.27
1.42 1.26
5 5
1.38-1.56 1.36-1.48
1.43 1.43
4 1
1.87-3.53 -
2.37 1.02
4
1.88-2.15
2.06
2
1.17-1.24
1.20
2
1.24-1.64
1.44
3
1.47-1.62
1.56
batholith
batholitb
Granodiorite Quartz monzonite Leucogranodiorite
Boulder
in coexisting
biotite
batholith
Granodiorite Boulder
coexisting
No. of pairs
Gabbro Tonalite Granodiorite Quartz monzonite Inclusions in tonalite Sierra Nevada
values
between
Creek batholith
Granodiorite Quartz monzonite .Jemez Mountains Rhyolite Quartz latite Tatoosh
pluton
Granodiorite Lone
Grove
pluton
New
Hampshire
Granite granites
Granite San Jacinto
Mounta,ins
Tonalite
practically identical to those of igneous samples we studied. In contrast, the wide variation of K, in amphibolite facies samples has been attributed by KRETZ (1959) to : (1) varying mineral composition ; and/or (2) dependence of Kd on Mn concentration ; and/or (3) lack of equilibrium. None of these explanations is in accord with MOXHAM’S or our data. Uniformity of Kd may be interpreted as indicating that: (1) the observed distribution of Mn between biotite and hornblende is an equilibrium distribution; (2) Henry’s law is obeyed at least to concentration levels of 1.0 % Mn in hornblende and of O*So/oin biotite ; and (3) the equilibrium temperature reflected by K, is either low (sub-solidus) or remarkably insensitive to temperature. Sub-solidus exchange of Mn is also supported by the generally higher K, values observed for rocks of the nearsurface Tatoosh pluton and the Jemez Mountains volcanic rocks; these rocks either are quenched products or have cooled relativelyrapidly, thus effectively “freezing” the equilibrium at a higher temperature and inhibiting the sub-solidus exchange of Mn which apparently is operative in rocks cooled under plutonic conditions. It is notable in this regard that the Boulder Creek samples, subjected to prolonged heating during 2
1162
L. PAUL GREENLAND, DAVID GOTT~RIEOand ROBERTI. TILLING
regional metamorp~sm, demonstrate the least variation in 6_-, of the batholiths studied. Although &In appears to be distributed nearly ideally between biotite and hornblende, continued exchange at sub-solidus temperatures renders .I& useless as a geothermometer. In spite of the general uniformity of Kd,there are small but significant differences in K, between batholiths and between samples from a single batholith. Some of this variation can be attributed in part to chemical effects. l?or example, in the Southern California and Sierra Nevada samples, for which major element data are available, K,, shows a positive correlation with Ti content of biotite. In addition, the differences between the Southern California and Boulder bathoiith is statistically significant at the 5 per cent level; this difference can be qnaIitatively correlated with the virtual
absence of sphene in the Southern California batho~th and the relative abundance of sphene in the Boulder, Sierra Nevada, and Boulder Creek batholiths. If valid, this apparent correlation would suggest a -very complex chemical effect on Kd indeed, because, theoretically, the presence of another phase cannot directly affect the distribution of an element between two other phases. It is possible, however, that the physico-chemical conditions governing the crystallization of sphene from a magma could also modify the crystal st~ructuresof hornblende and/or biotite such that it could indirectly alter the equilibrium distribution of Mn. are indebted to F. C. W. DODGE and T. L. WRIGHT,U.S. Geological R. A. BAILEY,F. G. LESURE,and T. P. Survey for samples. We &rograteful to A. T. ANDERSON, THAYER,U.S. Geological Survey, for critically reading the manuscript and making helpful comments. Note added ilz proof: Since submission of this manuscript for publication, two papers relevant Acknowledgments-We
to this work have uome to our attention. HASLAM (J. Petrol. 9, 84, 1968) described the Ben lysvis igneous complex, emplaced in a near surface environment, and reported analyses of ten coexisting biotite-hornblende mineral pairs. If, values for these samples have a range of 1.50-3.35 and a median of 1.87. The shallow Ben Nevis complex presumably cooled relatively rapidly; thus, K, data for this body are in accord with our data and interpretation of the Tatoosh pluton. SAXENA(Neues Jahrb. Mineral. Monatsh. 67, 1966) studied the distribution of Mm, and other elements, between coexisting biotite and hornblende in metamorphic rocks of the Caledonides. In four of his five samples, K, ranges from l-31 to 1.49; the fifth has an apparently anomalous K, of 2.56. It is apparent that these data are in good agreement with our results on samples from slowly-oooled plutons and thus support our suggestion of sub-solidus exchange of Mn between biotite and hornblende.
REFERE~~~~ AHRENSL. H. (X965) ~~~~~b~~~onof the ~~erne~ts in our PEaset, p. 40. ~~cGraw-Hill. BATEMANP. C., CLARKL. C., HE-BERN. K., MOOREJ. G. and RINEHARTC. D. (1963) The Sierra Nevada batholith-a syuthesis of recent work across the central part. U.S. Geol.Surv. Prof. Paper 414D, 46 pp. BECRAFTG. F., PINCKNEY D. M. and ROSENBLUM~ 8. (1963) Geology and mineral deposits of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana. U.S. Geol. Survey Prof. Paper 428, 101 pp. BUDDINGTON A. F. (1964), Distribution of MnO between coexisting ilmenite and magnetite. l’n Advancing Frontiers in Geology and Geophysics, (editor A. P. Subramaniam), pp. 233-248. Indian Geophysical Union, Hyderabad.
DIXONW. J. and MASSEYF. J. (1951) I&-odwtion to Sta~isticaZAnalysis. McGraw-Hill. FISKER. S., HOPSONC. A. and WATERSA. C. (1963) Geology of Mount Rainier National Pwk, U.S. CeoE.Surv. Prof. Paper 444, 93 pp. W~hin~on. H&KLIT. A. and WRIGHT T. L. (1967) The fractionation of nickel between ofivine and augite as a geothermometer.
Geochim. ~o~~o~~l~rn.Acta 31, S77-884.
Distribution
of manganese
between
coexisting
biotite
and hornblende
1163
HALL A. (1967) The distribution of some major and trace elements in feldspars from the Rosscs and Ardara granite complexes, Donegal, Ireland. Geochim. Cosmocliim. Acta 31, 835-847. HURLEY P. M., BATEMAN P. C., FAIRBAIRN H. W. and PINSON W. H., JR. (1965) Investigations Bull. Geol. Sot. -4mer. 76, of initial Srs7/SrS6 ratios in the Sierra Nevada plutonic province. 165-174. KISTLER R. W., BATEXAN P. C. and BRANNOCK IV. IV. (1965) Isotopic ages of minerals from granitic rocks of the contra1 Sierra Nevada and Inyo Mountains, California. Bill. Beol. Sot. Amer. 76, 155-164. KNOPF A. (1957) The Boulder Batholith of Montana. Amer. J. Sci. 255, 81-103. KRETZ R. (1959) Chemical study of garnot, biotite, and hornblende from gneisses of southwestern Quebec with emphasis on distribution of elements in coexisting minerals. J. Geol. 67, 37 l-402. KIZETZ It. (1961) Some applications of thermodynamics to coexisting minerals of varying Examples: orthopyroxeno-clinopyroxeno and orthopyroxeno-garnat. J. composition. Geol. 69, 361-386. LARSEN .E. S., JR. (1948) Batholith and associated rocks of the Corona, Elsinore, and San Luis Rey quadrangles, southern California. .&1em. Geol. Sot. Amer. 29, LARSEN E. S., JR. and DRAISEN W. M. (1950) Composition of the minerals in tho rocks of southern California batholith. Rept. 18th Int. Geol. Congress, 1948. Part II, Proc. Sect. A, 66-79. LOVERING T. S. and GODDARD E. N. (1950) G-eology and ore doposits of the Front Range, Colorado. U.S. Cool. Surv. Prof. Paper 223, 319 pp. MCINTII~E 11’. L. (1963) Trace element partition coefficients-a review of theory and applications to geology. Geochim. Cosmochim. Acta 27, 1209-1264. MOXHA~~ R. L. (1965) Distribution of minor elomcnts in coexisting hornblcndes and biotitcs. Can. ivl&eral. 8, 204-240. NOCKOLDS S. R. and ALLEN R. (1953) The geochemistry of some igneous rock series. Geoc%~~. Cosmochim. Acta 4, 105-142. PATTERSOX C., SILVER I,. and MCKINNEY C. (1956) Lead isotopes and magmatic differentiation (abs). Rosumenes de las trabajos presentadas, 20” Congrcsso Geologico International, Mexico City, pp. 221-222. Ross C. S., SMITH R. L. and BAILEY R. A. (1961) Outline of geology of the Jemey Mountains, New Mexico. Guideboolc Sczo Mexico Geol. Sot. Twelfth Pield Cont., Albcrquerque, N.M., 1961, PP. 13HL143. SCHMITT R. A., SMITH R. II. and GOLES G. G. (1965) Abundances of Sa, SC, Cr, Mn, Fe, Co and Cu in 218 individual meteorite chondrulos via activation analysis, 1. J. Goophys. Res. 70, 2419-2444. SCIfwAltCZ H. P. (1967) The offect of crystal field stabilization on the distribution of transition metals between metamorphic minerals. Geochim. Cosmochim. Acta 31, 503-517. SEX N., NOCKOLDS S. R. and ALLEN R. (1959) Trace elements in minerals from rocks of tho S. California batholith. Geochim. Cosmochim. Acta 16, 58-78. SMEDES H. W. (1966) Geology and igneous petrology of the Northern Elkhorn Mountains, Jefferson and Broadwater Counties, Montana. U.S. Geol. Surv. Paper 510, 115 pp. STU~BER A. M. and GOLES G. G. (1967), Abundances of Na, Mn, Cr, SC and Co in ultramafic rocks. Geochim. Cosmochim. Acta 31, 75-93. TAYLOR II. P., JR. and EPSTEIN S. (1962a) Relationship between 01s/Or6 ratios in coexisting minerals of igneous and metamorphic rocks, 1. Principles and experimental results. Bull. Geol. Sot. Amer. 73, 461-480. TAYLOR II. P., JR. and EPSTEIN S. (196213) Relationship between 01s/(Y6 ratios in coexisting minerals of igneous and metamorphic rocks, 2, Application to petrologic problems. Bull. Geol. Sot. Amer. 73, 675-694. TILLING R. I. (1964) Variation in modes and norms of an “homogeneous” pluton of the Boulder batholith, Montana. U.S. Geol.Surv. Prof. Paper, 501-D, D8-D13. TO~ELL D. G., WINCHESTER J. W. and SPIRN R. V. (1965) Rare earth distributions in some rocks and associated minerals of the batholith of Southern California. J. Geoph,ys. Res. 70, 3485 3496.
1 April
1968; accepted
in revised
form
12 July 1968)
Abstract-The distribution of manganese between coexisting biotite and hornblende for 80 mineral pairs from igneous rocks of diverse provenance (including Southern California, Sierra Nevada, Boulder, and Boulder Creek batholiths and the Jemez Mountains volcanics) has been determined by neutron activation analysis. Data on the distribution ratio (Kd = Mnhornblende/ Mn biotite) indicate that an equilibrium distribution of Mn is closely approached, though not completely attained, in most samples from plutonic environments. Comparison of K, values of mineral pairs with bulk chemica,l composition of host rocks reveals no correlation. Because initial crystallization temperatures vary with rock composition, the lack of correlation of composition with K, suggests that the equilibrium distribution of Mn between biotite and hornblende reflects exchange at, subsolidus temperatures rather than initial crystallization temperaturos. The highest K, values are for volcanic rocks, in which rapid quenching prevent’s subsolidus redistribution of Mn. For sample pairs from the Southern California and Sierra Nevada batholiths there is a Though the evidence is not compelling, positive correlation of Ii, with TiO, content of biotite. Kd may also correlate with t,ho r&e of cooling and/or the presence or absence of sphene in the rock.
GEOLOGIC applications of trace element distribution ratios between coexisting minerals have been thoroughly reviewed by MCINTIRE (1963). Recently, HXKLI and WRIGHT (1967) have shown that the distribution of Ni between olivine, clinopyroxene, and glass is temperature dependent, and HALL (1967) has shown that the distribution of Sr between plagioclase and alkali feldspar may be useful in geologic thermometry. MOXHA~~(1965) has reported the distribution of a number of elements between biotite and hornblende in a metamorphic suite and concluded that t’he distribution ratios of many of the elements studied vary with the metamorphic grade. Most existing data on distribution ratios relate to a single geologic unit or geographic region. In addition to the direct effects of temperature and pressure, distribution ratios may be indirectly influenced by water pressure, oxygen fugacity, and chemical potentials of other elements in the magma (or pore fluids) due to their effect on other aspects of mineral chemistry. Thus, for studies of distribution ratios to be generally useful, it is necessary to examine coexisting mineral pairs from rocks representing diverse geologic provinces, hence, diverse physico-chemical environments. Such a study has been made of the distribution of Mn between ilmenite and magnetite by BUDDINGTON (1964) who showed that this distribution is temperature dependent. The present study is essentially an extension of his work to biotite and hornblende. We present data on the distribution of Mn between coexisting biotitehornblende pairs from the Southern California, Sierra Nevada, Boulder (Montana)
THE
* Publication
authorized
hy the Director,
U.S. Geological 1149
Survey.
1150
L.
PAUL GREENLAND, DAVID GOTTFRIEDand ROBERTI. TILLING
and Boulder Creek (Colorado) batholiths. For comparison, biotite-hornblende pairs, from rocks of the Tatoosh pluton (Washington), the San Jacinto range (California) and the Jemez Mountains (New Mexico) also have been analyzed. Manganese was selected for this study because its ionic radius (0.80 A) is very close to that of the major elements Fez+ (0.74 A) and Mg (O-65 A) (radii from AHRENS, 1965), and because there are no complications from altervalent substitutions (MCI&TIRE, 1963) or from crystal field stabilization effects (SCHWARCZ, 1967). Thus, substitution of Mn in the lattice should be little affected by other elements in the mineral. Another advantage of Mn is the high precision with which it can be determined by activation analysis. The thermodynamic basis of trace element distribution ratios has been discussed extensively by KRETZ (1961) and MCINTIRE (1963) and will not be dealt with at length in this paper. In simple cases, the chemical potential of an element distributed between two phases IXand /? is pr = pa” + RT In a, ,LQ= ,u~’ + RT In a, where y” is the chemical potential in a standard state, R is the gas constant, T is the absolute temperature, and a is the activity of the component. At equilibrium, and thus
a/f - = a,
exp pu,” - 1%1° RT ’
For dilute solutions, Henry’s law states that the activity tional to its concentration, C, so that
%= ca
-
K
exp
of a component
is propor-
paocT@Po .
At a fixed temperature and pressure, the term on the right of the above expression is constant. Thus, we can define an equilibrium distribution coefficient of Mn between biotite and hornblende, K,, as K, =
concentration concentration
of Mn in hornblende of Mn in biotite
A more comprehensive appraisal of the factors affecting K, may be found in KRETZ (1961) and in MCINTIRE (1963). ANALYTICAL METHODS Pure biotite and hornblende were separated from crushed and sieved rock by magnetic and heavy liquid procedures. Optical counting of oil immersions indicated that the purity of all samples was 99 per cent or better. Small amounts of adhered quartz and/or feldspar constituted the predominant impurity in most samples; some of the samples were slightly chloritized. Trace amounts of opaque inclusions were observed in some samples. Although these inclusions (generally magnetite, more rarely ilmenite) could contain appreciable amounts of Mn, their paucity in the sample precludes their affecbing the observed K, to any significant extent.
Distribution
of manganese
between
coexisting
biotite
and hornblende
1151
Analysis was by a non-destructive neutron activation procedure similar to that described by STUEBER and GOLES (1967) and SCHMITT et al. (1965). Mineral samples were weighed (= 50 mg) into clean t dram polyethylene vials and irradiated in the reactor at the Naval Research Laboratory, Washington, D.C., at a thermal neutron flux of 7 x 1012 n-cm-2-set-1 for 1 min. After about 1 hr decay, the vials were opened in a fume hood and left for 2 more hours to permit escape of Ar41 formed from air in the vial. Manganese was then determined by counting the 0.84 MeV gamma radiation from Mn56 with a 2 by 2-in. NaI (Tl) crystal coupled to a 200channel analyzer. A natural silicate glass (tektite composite) of known Mn content was treated exactly like the mineral samples and used as a standard. For the purposes of this study it was essential to have an accurate estimate of the analytical precision. We analyzed 24 samples of the glass used as a standard, 16 samples of a biotite, and 14 samples of a hornblende from the Southern California batholith. The precision of the analyses, expressed as relative deviation was 52.8 per cent for the glass; +4.4 per cent for the biotite; h7.1 per cent for the hornblende. Analysis of nine samples of a hornblende and five of a biotite from the Boulder batholith resulted in deviations similar to those observed for the Southern California batholith samples. It was assumed that the discrepancy between the results for glass and for minerals was due to inhomogeneity of the minerals. This conclusion was supported by A. T. ANDERSON, U.S. Geological Survey (oral communication, 1967), who found a range of 0.34-0.41 per cent Mn in five hornblende grains and 0.19-0.23 per cent Mn in four biotite grains from our samples using the electron microprobe. Thus, the precision with which K, could be determined was limited by sample inhomogeneity rather than by the analytical technique. If the intra-sample variation found in the samples from the Southern California batholith is typical, the analytical reproducibility of K, is k8.3 per cent. Analytical accuracy was of lesser importance to this work. However, we checked the chemical analysis of the glass against a standard Mn solution and, further, analyzed G-l and W-l by this method. Good agreement with the chemical methods was obtained and it is probable that our analyses are accurate to at least 4 10 per cent. RESULTS
Southern California batholith The geology and petrology of the Southern California batholith have been described in detail by LARSEN (1948), who concluded that the batholithic rocks originated by magmatic differentiation. Subsequent mineralogic, trace element, and oxygen and lead isotope studies of rocks and minerals from the batholith (LARSEN and DRAISEN, 1950 ; NOCKOLDS and ALLEN, 1953 ; PATTERSON et al., 1956 ; SEN et al., 1959; ~YAYLOR and EPSTEIN, 1962a, b; TOWELL et al., 1965) have supported LARSEN’S original hypothesis of magmatic differentiation. A plot (Fig. 1) of Mn contents of the coexisting biotites and hornblendes (Table 1) shows a linear distribution, which closely approximates an equilibrium distribution at a single temperature. The distribution ratio (Kd) does vary, however, to a greater extent than can be accounted for as analytical error. Three possible explanations of this observation may be considered: (1) The minerals have equilibrated at different temperatures; (2) chemical variation of the minerals has affected the distribution coefficient; (3) complete equilibration has not been attained. The rocks from which these minerals have been separated range in composition from gabbroic to granitic and almost certainly have not all crystallized at the same temperature. If the equilibration temperature is the same as the igneous crystallization temperature one would expect some correlation between K, and rock type if Kd varies with temperature. However, plots of Kd vs. each of the major elements of the
1152
L. PAUL GREENLAND, DAVID GOTTFRIBD and ROBEETI. TILLIS~;
host rock (using the data from LARSEN, 1948, and from unpublished analyses) revealed no correlations. The failure of .K, to correlate with rock composition suggests that the variation of Kd is not related to the initial crystallization temperature and that equilibration of biotite and hornblende with respect to Mn was probably completed at subsolidus temperatures. Using the mineral analyses of LARSEN and DRAISEN (1950) and subsequent anpublished ana,lyses, we have attempted to relate X, with the major element
% Mn in biotite
Fig. 1. Distribution
of Mn between coexisting biotite Southern California batholith.
ant1 hornblende
in the
composition of the biotites and hornblendea. A positive correlation of K, with TiO, in both biotite and hornblende was observed, statist.ically signi~~ant at the 5 per cent level. The biotite correlation is shown in Fig. 2. The scatter of the data in Pig. 2, and the lack of other correlations imply that only a small fraction of the variation of K, can be attributed to minera* chemistry. The remainder can be ascribed only to incomplete equilibration. The rate of exchange of Mn between biotite and hornblende is in part dependent on the concentration gradient and the temperature and thus, at fixed temperature, decreases as equilibrium is approached. Because temperature was also decreasing, perfect equilibrium could not be expected. Lack of complete equilibration is suggested also by differences in Mn content of individual grains in a given sample (p. 1151). Nonetheless, the linear distribution of Mn between biotite and hornblende (Fig, 1) cannot be regarded as fortuitous and must indicate that equilibrium was closely apl)roached, even though not achieved.
Distribution
of manganese between coexisting biotito and hornblende
1153
Table 1. Manganese in coexisting hornblende and biotite from the Southern California batholith
“/;: Mn Hornblende
Biotitc
Gabbro __UL60-5 EL-230
0.237 0.408
0.109 0.149
2,17 2.74
Tonalite ~_ BCl-12 BCl-5 EL38-134 BL60-6 SLR-138 SLR-1016 BL60-2 LTS-3 BL60- 1
0.381 0.392 0.392 0.337 0.356 0.334 0.364 0.422 0.456
0.190 0.249 0.227 0.183 0.238 0.155 0.246 0.238 0.323
2.01 1.57 1.73 1.84 1.50 2.15 1.48 1.77 1.41
Granodiorito ~_____ .BL60-8 BL60-7 SLR-2242 s-2 s-13 s-14 S-8 s-11
0.376 0.931 0.604 0.692 0.756 1.02 0.875 0.686
0.246 0.570 0.332 0.469 0.474 0.563 0.520 0.461
1.53 1.63 1.82 1.48 1.59 1.81 1.68 1.49
0.477 0,565 0,614
0.270 0.314 0.294
1.77 1.80 2.09
0.291 0.355
0.160 0.231
1.54
Sa,mple
Quartz monzonitc EL38-167 LTS-2 EL38-265 Inclusions in tonalite ULBO-1B IJLBO-IA
1.82
Xierra Nevada batholith The geology of the Sierra Nevada has been summarized by BATEMANet al. (1963). The mineral samples used in the present work have been described previously in conjunction with K-Ar (KISTLER et al., 1965) and Rb-Sr (HURLEY et cd., 1965) studies. As with samples from the Southern California batholith, the variation of K, of Sierra Nevada samples (Table 2, Fig. 3) is greater than the experimental error; nevertheless, the data indicate a reasonable approximation to a constant Ir;, which we assume t’o be the equilibrium value. As with the Southern California samples, attempts to correlate K, with rock and mineral chemistry were unsuccessful except with TiO, in biotite and hornblende. Figure 2 demonstrates the correlation of Kd with TiO, in biotite in both the Sierra
1154
L. PAUL GREENLAND, DAVID GOTTFRIED and ROBERT I. TILLING
o SouthernCaliforniabatholith + SierraNevadabatholith
Fig. 2. Variation of K, with Ti content of the biotite in the Southern California and Sierra Nevada batholiths. Table 2. Manganese in coexisting hornblende and biotite in granodiorites from the Sierra Nevada batholith %Mn Sample
MT-2 BCc-13 BP-l MG-1 MG-3 BCa-20 SL-18
Hornblende
0.595 0.395 0.431 0.444 0.384 0.485 0.412
Riotite
K,
0.411 0.232 0.368 0.352 0.271 0.334 0.257
1.45 1.70 1.17 1.26 1.42 1.45 1.60
Nevada and Southern California batholiths. This figure also shows that both TiOz in biotite and K, are generally lower in the Sierra Nevada than in the Southern California batholith. Boulder batholith The geology of parts of the composite, Late Cretaceous Boulder batholith, Montana, has been described by KNOPF (1957), BECRAFT et al. (1963), and by SMEDES (1966). Rocks of the batholith range in composition from syenogabbro to alaskite; rocks of granodiorite-quartz monzonite composition predominate. Because
Distribution
of manganese
between
coexisting
biotite
and hornblende
1155
hornblende is extremely scarce or absent in the syenogabbroic and alaskitic rocks, it was possible to analyze hornblende-biotite pairs from granodiorites and quartz monzonites only. Most of the samples studied are from rocks of the Rader Creek pluton, a zoned body composed mainly of granodiorite (TILLING, 1964). The Mn values for mineral pairs from the Boulder batholith (Table 3) show less scatter when plotted (Fig. 4) than Mn values of the Southern California batholith (Fig. I), suggesting a closer approach to equilibrium. Possible deviation from Henry’s
06-
d 06E ii i .c i
0,4-
8
%
Fig.
3. Distribution
of Mn
Mn in biotite
between coexisting biotite Sierra Nevada batholith.
and
hornblende
in the
law at high Mn concentrations is suggested by Fig. 4 ; only three points are involved and thus the apparent deviation may not be real. The median K, (1.45) of these Boulder batholith samples is distinctly lower than the median K, (1.75) for the Southern California batholith but equal to that for the Sierra Nevada batholith (l-45). These differences in median Kd may be correlated qualitatively with the sphene content of the batholiths studied: the Sierra Nevada and Boulder batholiths, which are abundant in sphene, have the lower median Kd values (1*45), whereas the sphene-poor Southern California batholith has the markedly higher median Kd value of l-75. The correlation of Kd with TiO, in biotite noted for the Southern California and Sierra Nevada samples cannot be tested for the Boulder batholith biotites, because major element data are available for only four samples. Available analyses, however, indicate that the Boulder batholith biotites tend to be slightly higher in Ti relative to the Southern California biotites and are distinctly higher in Ti relative
L. PACL
1156
GREESLAND,
DAVID
GOTTFRIED
and ROBERT I. TILLISG:
to the Sierra Nevada biotites. Furthermore, the limited data for the Boulder batholith biotites suggest that, if a correlation between Kd and Ti in biotite can be demonstrated with additional data, the data would not plot on the same line as the Sierra Nevada and Southern California samples. Bo&ler
Creek batholith
The Precambrian Boulder Creek batholith, located in the Front Range, Colorado, is a body of talc-alkaline granodiorite and quartz monzonite which has undergone
% Fig. 4. Distribution
Mn in
biitite
of Mn between coexisting biotite Boulder batholith, Montana.
and hornblende
in the
regional metamorphism. The general geology of the batholith has been described by LOVERING and GODDARD (1950). Kd values for these rocks (Table 4, Fig. 5) show very little scatter and it is suggested that prolonged metamorphic heating provided more time for equilibration than the relatively short cooling histories of the other batholiths. The median K, of these samples (1.43) is the same as those of the Sierra Nevada and Boulder batholith samples, but lower than that of the Southern California batholith samples. This result correlates with the presence of abundant sphene in the Boulder Creek rocks; unfortunately, major element analyses of these mineral p&s are not available, so that the relationship of Kd to TiO, in biotite is not known. San Jacinto
Mountains
plutonic
rocks
Plutonic rocks from the San Jacinto Mountains are geographically near the Southern California batholith, but it is not yet certain whether they are derived from the same magmatic source. Although only three sample pairs are available the K,
Xstribution Table
of manganese
3. Manganese
coexisting
biotite
in coexisting hornblende and biotite batholith, Montana
%Mn
and hornblende
1157
from the Boulder
l3iotite
Kl?
0.866 0.849 0.652 0.669 0.762 0.590 0.519 0.563 0.650 0.592 0.490 0.587 0.583 0.583 0.577
0.811 0.606 0.465 0.461 0.507 0.422 0.340 0.384 0.510 0.361 0.328 0.391 0.405 0.392 0.415
1.07 1.40 1.40 1.45 1.50 1.40 1.53 1.47 1.27 1.64 1.49 1.50 1.44 1.49 1.39
0.463 0.393 0.419
0.373 0.250 0.242
1.24 1.57 1.73
0.412 0.553 0.415 0.742 0.620
0.250 0.428 0.286 0.518 0,450
1.65 1.29 1.45 1.27 1.38
0.973 1.39
0.765 1.10
1.27 1.26
0.516
0,357
1.45
Hornblende
Sample Rader
between
Creek pluton
Granodiorites 2T-1057 2T-1058 2T-1059 2T- 1060 2T-1061 2T-1062 2T-1063 2T-1064 2T-1065 2T-1066 2T-1067 2T-1070 2T-1071 2T-1080 lK-66 1 Quartz
monzonitcs
2T-1061 2T-1093 IK-647 Butte
quartz
monzonite
52C-10a Mafic quartz monzonite 6K-306 Quartz monzonite 52C-60 Quartz monzonit#e lK-241 Sihcio quartz monzonite 52C-45 Silicio quartz monzonite Leucocratic
rooks
27-797 Leucogranodiorite W-21 Leucogranodiorite Mafic inclusion
in Butte
53C 1601)
quartz
monzonim -
values (Table 5) are intermediate between the Southern California and the other batholiths. A statistical test (DIXON and MASSEY, 1951, p. 101) shows that the difference in mean Kd between the San Jacinto samples and the Boulder and the Southern California samples is not significant. The data for the sphene-rich San Jacinto tonalites neither confirm nor refute the qualitative correlation of K, with the presence of sphene. Tutoosh, pluton The Tatoosh pluton, a near-surface intrusive mass of middle Tertiary age in the (‘ascade Range of Washington State (Mount Rainier National Park), cooled rapidly
1158 Table
L. PAUL GREENLAND, 4. Manganese
-
DAVID GOTTFRIED and ROBERT I. TILLINC
in coexisting hornblende and biotite in granodiorites zonites from the Boulder Creek batholith, Colorado
Sample
%Mn
and quartzmon-
Biotite
K,
0.400 0.410 0.438 0.344 0.376
0250 0.301 0.302 0.244 0.254
1.43 1.36 1.45 1.41 1.48
0.343 0.335 0.335 0.337 0.310
0.220 0.235 0.226 0.236 0.225
1.56 1.43 1.48 1.43 1.38
Hornblende
Quartz monzonites GP-95 GP-15 GP-98 GP-52 GP-84 Granodiorites GP-1 GP-5 GP-40 GP-2 GP-17
Fig. 5. Distribution
of Mn between coexisting biotite Boulder Creek batholith, Colorado.
and hornblende
in the
as a result of explosive eruptions through its roof with concomitant sudden loss of volstiles and heat (FISKE et al., 1963). The I& values of the biotite-hornblende pairs analyzed here have a narrow range (Table 5), but are significantly higher than those observed for the other plutonic suites. These higher Kd values may reflect the temperature dependence of K,, because rapid cooling would serve to “freeze” the equilibrium distribution of Mn at a higher temperature. Alternatively, the high
Distribution of manganese between coexisting biotite and hornblende
1159
Table 5. Manganese in coexisting hornblende and biotite from various provinces
% Mn Sample
Rock type
Hornblende
Biotite
&i
0.337 0.347 0.307
0.216 0.214 0.209
1.56 1.62 1.47
0.312 0.300 0.366 0.350
0.155 0.160 0.170 0.165
2.01 1.88 2.15 2.12
0.165
0.161
1.02
0.935
0.501
1.87
0814 0.523
0.427 0.148
1.91 3.53
0.515
0.182
2.83
0.511 0.457
0.395 0.389
1.17 1.24
0.438
0.320
1.37
0.438
0.285
1.54
0,373 1.02
0.301 0.621
1.24 1.64
San Jacinto Mountains, California 66GSC-24 66GSC-18 G-3
Tonahte Tonalite Tonalite
Tatoosh pluton, Washington TLW-2 TLW-5 TP-34C TP-252
Granodiorite Granodiorite Granodiorite Granodiorite
Jemez Mountains, New Mexico 3149-7 3149.2 3149-10 3149-6 3149-5
Quartz latite, Santa Clara Rhyolite, South Mountain Rhyolite, San Antonio Rhyolite pumice, El Cajete Rhyolite flow, Banco Bonito
Lone Grove pluton, Texas ZL41 ZL3gr
Granite Granite
Harding, New Mexico 61GM-7
Sphene-rich granodiorite
Philipsburg batholith, Montana 530798
Granodiorite
New Hampshire granites NH/6-52 BNH-39
Lebanon Granite Conway Granite
Kd may be due to unique physico-chemical conditions placement of the hypabyssal Tatoosh pluton. Jem,ez Xountains
related to the shallow em-
volcanic rocks
The geology of the Jemez Mountains volcanic rocks has been outlined by Ross et al. (1061). The volcanic rocks studied (Table 5) are of particular interest in that they represent rapidly quenched materials and, hence, subsolidus equilibration of Mn between hornblende and biotite phenocrysts should be minimal. In fact, K, ranges from 1.0 to 3.5 (Table 5) virtually bracketing the range observed for all samples, both igneous and metamorphic (Fig. 6). If these are equilibrium values, something other than temperature is the principal factor which controls K,. In addition to differences in the rate of quenching, other
1160
L. PAUL GREENLAND,
DAVID GOTTFRIED and ROBERT
I. TILLIKG!
physico-chemical factors (e.g. zoning of phenocrysts, kinetic effects, oxidation, etc.) may also be partly responsible for the wide range in Kd. However, petrographic examination of the samples indicates that zoning of biotite and hornblende phenotrysts is feeble at best and probably cannot be a major contributive factor. On the other hand, four of these five mineral pairs and all the Tatoosh sample pairs have K,. > 1.8, strongly suggesting that these high K, values do indeed reflect the effect of rapid cooling from a high temperature. Arnph~bol~te fancies IKretz.
4
2
r!-
Epldote-amphibokte Ihloxhom. 1965)
642-
r-l
2-
r-l
Jemer
plvton
SanJaanto
Z’ {[
K
I
range
Boulder creek
i
batholith
--l
P IOB642-
I
rl Tatoosh
n
fancies
mountams
ri
-
2r
F
19591
111
-
r?-
Boulder
batholith
ri Swro
2
-
Nevada batholith
-
6 4 2
Southern
08
IO
12
14
16
I6
r-l 20
22
24
II--l 26 28
30
I,, 32
Californlo
bothohth
34
38
36
x,
Pig.
6. Distribution
of K, values of igneous samples (this paper) and comparison with published K, values of metamorphic samples.
Admittedly meager, the data nonetheless suggest a possible correlation of K, with the eruptive sequence or age of the Jemez Mountains samples. The mineral pairs with the highest Kd values (3.53 and 2.83) are from an explosively erupted pumice and a lava flow consisting chiefly of obsidian. These samples originated from the same volcanic center and are the youngest volcanic rocks in the region. The bwo rhyolites with K, values of l-87 and 1.91 are genetically related and were formed during a slightly earlier stage of rhyolitic eruptions. The sample with the unusually low R, of 1.0 is from an older quartz latite in the volcanic sequence. Thus, the correlation between K, and eruptive sequence may reflect differences in the eruptive and cooling history of the rocks, but due to the small number of samples, t,he possibility of spurious correlation cannot be precluded. CONCLUSIONS
With the exception of only three samples, our data clearly demonstrate that K, for igneous hornblende-biotite pairs varies within the relatively restricted range of 1.0-2-2, regardless of the composition and provenance of their host rocks (Table 6 and Fig. 6). Figure 6 also shows that Kd values for metamorphic samples of the epidote-amphibolit,e facies studied by MOXHAM (1965) have a median and range
Distribution Table
of manganese of K,
6. Distribution
Samples Southern
California
-~
biotite
and hornblende
and hornblende
Range
Ka
from
1161 igneous
rocks
Median
2 9 8 3 2
2.17-2.74 1.41-2.15 1.48-1.82 1.77-2.09 1.54-l .82
2.45 1.73 1.61 1.80 1.68
7
1.17-1.70
1.45
8 2
1.07-1.64 1.24-1.73 1.26-1.27
1.42 1.26
5 5
1.38-1.56 1.36-1.48
1.43 1.43
4 1
1.87-3.53 -
2.37 1.02
4
1.88-2.15
2.06
2
1.17-1.24
1.20
2
1.24-1.64
1.44
3
1.47-1.62
1.56
batholith
batholitb
Granodiorite Quartz monzonite Leucogranodiorite
Boulder
in coexisting
biotite
batholith
Granodiorite Boulder
coexisting
No. of pairs
Gabbro Tonalite Granodiorite Quartz monzonite Inclusions in tonalite Sierra Nevada
values
between
Creek batholith
Granodiorite Quartz monzonite .Jemez Mountains Rhyolite Quartz latite Tatoosh
pluton
Granodiorite Lone
Grove
pluton
New
Hampshire
Granite granites
Granite San Jacinto
Mounta,ins
Tonalite
practically identical to those of igneous samples we studied. In contrast, the wide variation of K, in amphibolite facies samples has been attributed by KRETZ (1959) to : (1) varying mineral composition ; and/or (2) dependence of Kd on Mn concentration ; and/or (3) lack of equilibrium. None of these explanations is in accord with MOXHAM’S or our data. Uniformity of Kd may be interpreted as indicating that: (1) the observed distribution of Mn between biotite and hornblende is an equilibrium distribution; (2) Henry’s law is obeyed at least to concentration levels of 1.0 % Mn in hornblende and of O*So/oin biotite ; and (3) the equilibrium temperature reflected by K, is either low (sub-solidus) or remarkably insensitive to temperature. Sub-solidus exchange of Mn is also supported by the generally higher K, values observed for rocks of the nearsurface Tatoosh pluton and the Jemez Mountains volcanic rocks; these rocks either are quenched products or have cooled relativelyrapidly, thus effectively “freezing” the equilibrium at a higher temperature and inhibiting the sub-solidus exchange of Mn which apparently is operative in rocks cooled under plutonic conditions. It is notable in this regard that the Boulder Creek samples, subjected to prolonged heating during 2
1162
L. PAUL GREENLAND, DAVID GOTT~RIEOand ROBERTI. TILLING
regional metamorp~sm, demonstrate the least variation in 6_-, of the batholiths studied. Although &In appears to be distributed nearly ideally between biotite and hornblende, continued exchange at sub-solidus temperatures renders .I& useless as a geothermometer. In spite of the general uniformity of Kd,there are small but significant differences in K, between batholiths and between samples from a single batholith. Some of this variation can be attributed in part to chemical effects. l?or example, in the Southern California and Sierra Nevada samples, for which major element data are available, K,, shows a positive correlation with Ti content of biotite. In addition, the differences between the Southern California and Boulder bathoiith is statistically significant at the 5 per cent level; this difference can be qnaIitatively correlated with the virtual
absence of sphene in the Southern California batho~th and the relative abundance of sphene in the Boulder, Sierra Nevada, and Boulder Creek batholiths. If valid, this apparent correlation would suggest a -very complex chemical effect on Kd indeed, because, theoretically, the presence of another phase cannot directly affect the distribution of an element between two other phases. It is possible, however, that the physico-chemical conditions governing the crystallization of sphene from a magma could also modify the crystal st~ructuresof hornblende and/or biotite such that it could indirectly alter the equilibrium distribution of Mn. are indebted to F. C. W. DODGE and T. L. WRIGHT,U.S. Geological R. A. BAILEY,F. G. LESURE,and T. P. Survey for samples. We &rograteful to A. T. ANDERSON, THAYER,U.S. Geological Survey, for critically reading the manuscript and making helpful comments. Note added ilz proof: Since submission of this manuscript for publication, two papers relevant Acknowledgments-We
to this work have uome to our attention. HASLAM (J. Petrol. 9, 84, 1968) described the Ben lysvis igneous complex, emplaced in a near surface environment, and reported analyses of ten coexisting biotite-hornblende mineral pairs. If, values for these samples have a range of 1.50-3.35 and a median of 1.87. The shallow Ben Nevis complex presumably cooled relatively rapidly; thus, K, data for this body are in accord with our data and interpretation of the Tatoosh pluton. SAXENA(Neues Jahrb. Mineral. Monatsh. 67, 1966) studied the distribution of Mm, and other elements, between coexisting biotite and hornblende in metamorphic rocks of the Caledonides. In four of his five samples, K, ranges from l-31 to 1.49; the fifth has an apparently anomalous K, of 2.56. It is apparent that these data are in good agreement with our results on samples from slowly-oooled plutons and thus support our suggestion of sub-solidus exchange of Mn between biotite and hornblende.
REFERE~~~~ AHRENSL. H. (X965) ~~~~~b~~~onof the ~~erne~ts in our PEaset, p. 40. ~~cGraw-Hill. BATEMANP. C., CLARKL. C., HE-BERN. K., MOOREJ. G. and RINEHARTC. D. (1963) The Sierra Nevada batholith-a syuthesis of recent work across the central part. U.S. Geol.Surv. Prof. Paper 414D, 46 pp. BECRAFTG. F., PINCKNEY D. M. and ROSENBLUM~ 8. (1963) Geology and mineral deposits of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana. U.S. Geol. Survey Prof. Paper 428, 101 pp. BUDDINGTON A. F. (1964), Distribution of MnO between coexisting ilmenite and magnetite. l’n Advancing Frontiers in Geology and Geophysics, (editor A. P. Subramaniam), pp. 233-248. Indian Geophysical Union, Hyderabad.
DIXONW. J. and MASSEYF. J. (1951) I&-odwtion to Sta~isticaZAnalysis. McGraw-Hill. FISKER. S., HOPSONC. A. and WATERSA. C. (1963) Geology of Mount Rainier National Pwk, U.S. CeoE.Surv. Prof. Paper 444, 93 pp. W~hin~on. H&KLIT. A. and WRIGHT T. L. (1967) The fractionation of nickel between ofivine and augite as a geothermometer.
Geochim. ~o~~o~~l~rn.Acta 31, S77-884.
Distribution
of manganese
between
coexisting
biotite
and hornblende
1163
HALL A. (1967) The distribution of some major and trace elements in feldspars from the Rosscs and Ardara granite complexes, Donegal, Ireland. Geochim. Cosmocliim. Acta 31, 835-847. HURLEY P. M., BATEMAN P. C., FAIRBAIRN H. W. and PINSON W. H., JR. (1965) Investigations Bull. Geol. Sot. -4mer. 76, of initial Srs7/SrS6 ratios in the Sierra Nevada plutonic province. 165-174. KISTLER R. W., BATEXAN P. C. and BRANNOCK IV. IV. (1965) Isotopic ages of minerals from granitic rocks of the contra1 Sierra Nevada and Inyo Mountains, California. Bill. Beol. Sot. Amer. 76, 155-164. KNOPF A. (1957) The Boulder Batholith of Montana. Amer. J. Sci. 255, 81-103. KRETZ R. (1959) Chemical study of garnot, biotite, and hornblende from gneisses of southwestern Quebec with emphasis on distribution of elements in coexisting minerals. J. Geol. 67, 37 l-402. KIZETZ It. (1961) Some applications of thermodynamics to coexisting minerals of varying Examples: orthopyroxeno-clinopyroxeno and orthopyroxeno-garnat. J. composition. Geol. 69, 361-386. LARSEN .E. S., JR. (1948) Batholith and associated rocks of the Corona, Elsinore, and San Luis Rey quadrangles, southern California. .&1em. Geol. Sot. Amer. 29, LARSEN E. S., JR. and DRAISEN W. M. (1950) Composition of the minerals in tho rocks of southern California batholith. Rept. 18th Int. Geol. Congress, 1948. Part II, Proc. Sect. A, 66-79. LOVERING T. S. and GODDARD E. N. (1950) G-eology and ore doposits of the Front Range, Colorado. U.S. Cool. Surv. Prof. Paper 223, 319 pp. MCINTII~E 11’. L. (1963) Trace element partition coefficients-a review of theory and applications to geology. Geochim. Cosmochim. Acta 27, 1209-1264. MOXHA~~ R. L. (1965) Distribution of minor elomcnts in coexisting hornblcndes and biotitcs. Can. ivl&eral. 8, 204-240. NOCKOLDS S. R. and ALLEN R. (1953) The geochemistry of some igneous rock series. Geoc%~~. Cosmochim. Acta 4, 105-142. PATTERSOX C., SILVER I,. and MCKINNEY C. (1956) Lead isotopes and magmatic differentiation (abs). Rosumenes de las trabajos presentadas, 20” Congrcsso Geologico International, Mexico City, pp. 221-222. Ross C. S., SMITH R. L. and BAILEY R. A. (1961) Outline of geology of the Jemey Mountains, New Mexico. Guideboolc Sczo Mexico Geol. Sot. Twelfth Pield Cont., Albcrquerque, N.M., 1961, PP. 13HL143. SCHMITT R. A., SMITH R. II. and GOLES G. G. (1965) Abundances of Sa, SC, Cr, Mn, Fe, Co and Cu in 218 individual meteorite chondrulos via activation analysis, 1. J. Goophys. Res. 70, 2419-2444. SCIfwAltCZ H. P. (1967) The offect of crystal field stabilization on the distribution of transition metals between metamorphic minerals. Geochim. Cosmochim. Acta 31, 503-517. SEX N., NOCKOLDS S. R. and ALLEN R. (1959) Trace elements in minerals from rocks of tho S. California batholith. Geochim. Cosmochim. Acta 16, 58-78. SMEDES H. W. (1966) Geology and igneous petrology of the Northern Elkhorn Mountains, Jefferson and Broadwater Counties, Montana. U.S. Geol. Surv. Paper 510, 115 pp. STU~BER A. M. and GOLES G. G. (1967), Abundances of Na, Mn, Cr, SC and Co in ultramafic rocks. Geochim. Cosmochim. Acta 31, 75-93. TAYLOR II. P., JR. and EPSTEIN S. (1962a) Relationship between 01s/Or6 ratios in coexisting minerals of igneous and metamorphic rocks, 1. Principles and experimental results. Bull. Geol. Sot. Amer. 73, 461-480. TAYLOR II. P., JR. and EPSTEIN S. (196213) Relationship between 01s/(Y6 ratios in coexisting minerals of igneous and metamorphic rocks, 2, Application to petrologic problems. Bull. Geol. Sot. Amer. 73, 675-694. TILLING R. I. (1964) Variation in modes and norms of an “homogeneous” pluton of the Boulder batholith, Montana. U.S. Geol.Surv. Prof. Paper, 501-D, D8-D13. TO~ELL D. G., WINCHESTER J. W. and SPIRN R. V. (1965) Rare earth distributions in some rocks and associated minerals of the batholith of Southern California. J. Geoph,ys. Res. 70, 3485 3496.