Eur. J. Mineral. 2006, 18, 369–377
Mineralogy and geochemistry of micas from the Pinilla de Fermoselle pegmatite (Zamora, Spain) ´ RODA-ROBLES1, *, ALFONSO PESQUERA1, PEDRO P. GIL-CRESPO1, JOSE´ TORRES-RUIZ2 ENCARNACION and PHILIPPE DE PARSEVAL3 1Departamento
de Mineralog´ıa y Petrolog´ıa, Universidad del Pa´ıs Vasco UPV/EHU, P.O. Box. 644, E-48080 Bilbao, Spain *Corresponding author, e-mail:
[email protected] 2Departamento de Mineralog´ıa y Petrolog´ıa, Universidad de Granada, Fuentenueva s/n, E-18002 Granada, Spain 3LMTG UMR 5563, Min´ eralogie, Observatoire Midi Pyr´en´ees, 14 Av. E. Belin, F-31400 Toulouse, France
Abstract: The highly fractionated, Li-F-Be-B-P-bearing Pinilla de Fermoselle (PF) pegmatite crops out in the westernmost part of the Zamora province (Spain). This body appears as a cupola over the PF leucogranite, displaying a non-symmetrical internal zonation with a complete sequence from a barren pegmatitic facies near the granite, to a highly evolved zone in the uppermost part of the body. Representative samples of micas from the different pegmatite zones have been studied. Based on textural and chemical criteria, the micas may be grouped into two assemblages: Al-rich micas and Fe-rich micas. In general, Al-rich micas show a continuous evolution from muscovitic to lepidolitic compositions from the leucogranite to the most evolved zone. Fe-rich micas range from Fe-biotite in the leucogranite and in the least evolved pegmatite zones, to an intermediate composition between zinnwaldite and trilithionite in the most evolved pegmatitic facies. The incorporation of Li into micas appears to be controlled by the substitutions Si2LiAl-3, and Li3Al-1䊐-2, AlLiR-2, SiLi2R-3, and SiLiAl-1R-1, where R = (Fe2+ + Mg + Mn). Paragenetic relationships and chemical variations in micas from different zones making up the PF pegmatite suggest that the pegmatitic system derived from a granitic melt and evolved upwards by fractionation processes. Evidence in support of this model comes from: (i) the gradual enrichment in Li, Rb, Cs and F, parallel to the decrease in Mg and Ti; (ii) the convergent evolutionary trends towards lepidolite showed by the Al- and Fe-micas; and (iii) the parallel decrease in the K/Rb ratio in micas. Key-words: micas, granitic pegmatites, mineral chemistry, Pinilla de Fermoselle, Spain.
Introduction The Pinilla de Fermoselle (PF) pegmatite (Zamora, Spain), located in the north-western part of the Tormes Dome (Central Iberian Zone), is the only known case in this region where a complete sequence from barren to highly evolved pegmatitic facies can be observed in a single body. The evolution develops gradually, from the PF leucogranite, at the bottom of the pegmatite, upwards; with the most evolved facies located in the upper part of the body, just below the hanging wall contact, close to the country rocks. The evolution is not only mineralogical, but also textural and compositional. In the PF pegmatitic body, all the pegmatite-forming minerals reflect clearly such evolution, which is even best evident for micas and tourmaline. Although there are numerous studies on the textural, structural, and chemical changes showed by micas associated to pegmatites with different evolution degrees (e.g. Cerny et al. 1970; Lentz, 1992; Foord et al., 1995; Roda et al., 1995; Wise, 1995; Kile & Foord, 1998; Brigatti et al., 2000), DOI: 10.1127/0935-1221/2006/0018-0369
studies on the evolution of micas inside individual bodies are much more scarce (e.g. Jolliff et al., 1987; Cerny et al., 1995; Kile & Foord, 1998). For this reason, the PF pegmatite is a good example to better understand the chemical, paragenetic and textural evolution of micas in pegmatitic environments. The purpose of this paper is to present data on the paragenesis and chemistry of micas from the PF pegmatite. We also discuss their significance in deciphering the internal evolution of this pegmatite.
Geology of the pegmatite The Li-F-Be-B-P bearing PF pegmatite crops out as a cupola in the apical part of a leucogranite body (Fig. 1). It shows a clear non-symmetrical vertical zoning from the contact with the leucogranite to the contact with the metamorphic country-rocks. The pegmatitic facies evolve gradually from the leucogranite upwards. The following sequence is observed from the contact with the leucogranite, upward to the 0935-1221/06/0018-0369 $ 4.05
ˇ 2006 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart
370
E. Roda-Robles, A. Pesquera, P. P. Gil-Crespo, J. Torres-Ruiz, Ph. de Parseval
K/Rb (micas)
Mica type
Habit
Grain size*
Texture
lepidolite
anhedral to subhedral
very fine to medium
UBZ
Lepidolite, albite, quartz, 9 to 35 muscovite, K-feldspar, pink elbaite, green elbaite, muscovite, zinnwaldite, Fe-lepidolite, beryl, cookeite, cassiterite, apatite, Fe-Mn phosphates
zinnwaldite muscovite
subhedral euhedral to subhedral
fine very fine to medium
Quartz, muscovite, plagioclase, Fe-Mn phosphates, Kfeldspar, zinnwaldite, biotite, schorl, green elbaite, apatite, beryl
muscovite
euhedral to subhedral
very fine to medium
IZ
Table 1. Mineralogy of the three units in the PF pegmatite, mica distribution and petrographic characteristics. ZONE Mineralogy
zinnwaldite
subhedral
fine to medium
pinkish small flakes or medium pseudobotroidal masses associated with albite and elbaite. Fine white pearly flakes in masses of greisen aspect masses of subhedral flakes graphic intergrowth with quartz, «book» text., associated with green elbaite and quartz graphic and radial intergrowth with quartz, «book» texture, small crystals wrap around other minerals masses of fine subhedral flakes, or «book» textures for the biggest crystals «book» textures
22 to 43
euhedral to subhedral K-Feldspar, quartz, musco27 to 87 muscovite euhedral to vite, biotite, plagioclase, subhedral schorl, apatite, Fe-Mn phosbiotite euhedral to phates subhedral *very fine < 6 mm; fine = 6 mm to 2.5 cm; medium = 2.5 cm to 10 cm.
LBZ
biotite
Fig. 1. Schematic geological map of the Pinilla de Fermoselle area; A) after L´opez-Plaza & Carnicero (1988); B) after Mart´ın-Izard et al. (1992).
fine to medium fine to medium fine to medium
«book» textures, graphic intergrowths with quartz «book» textures
hosting marbles (Table 1, Fig. 2) (for more information on the geology of the PF pegmatite see Roda et al. (2004, 2005): (1) The undifferentiated lower border zone (LBZ) appears just in contact with the leucogranite. The transition from the granitic to the pegmatitic facies is gradual, with an increase in the grain size. This way, the leucogranite evolves to a pegmatitic granite and finally to a barren pegmatitic facies. Two different subzones (a and b) are distinguished in the LBZ. The main difference between the subzones is the lack of tourmaline in a. In addition, the chemistry of micas from a and b subzones is different for some major elements. The main minerals are K-feldspar, quartz, muscovite, albite and biotite, with minor tourmaline in b. Fe-Mn phosphates and fluorapatite are accessory minerals. In this zone graphic intergrowths of quartz and K-feldspar are common. (2) The intermediate zone (IZ) is located just above LBZ. It is characterized by the occurrence of centimetric nodules of Fe-Mn phosphates (Roda et al., 1998). Besides these Fe-Mn phosphates, the main minerals are quartz and muscovite. Kfeldspar, albite, tourmaline and zinnwaldite are other common phases in this zone, with beryl as accessory mineral. (3) The highly evolved upper border zone (UBZ) is close to the metasedimentary host-rock. Quartz, micas from the muscovite-lepidolite series, albite and K-feldspar are their main minerals, with Li-tourmaline, zinnwaldite, and cookeite as minor constituents. Fe-Mn phosphates, apatite, montebrasite, cassiterite, beryl, and zircon appear as accessory minerals.
Mineralogy and geochemistry of micas from the Pinilla de Fermoselle pegmatite
371
Fig. 2. Idealized section on the PF pegmatite (RodaRobles et al, 2005).
Petrography Micas of the PF pegmatite may be grouped into two assemblages: Al-rich micas and Fe-rich micas. Muscovite, belonging to the first group, is the most abundant mica in the pegmatite, occurring in the three zones, and it is also a main constituent in the leucogranite. Its grain size changes from very fine (< 6 mm)(IZ, UBZ, and leucogranite) to coarse (up to 7 cm long) (LBZ, IZ, and UBZ). In the leucogranite, textural relationships suggest that muscovite was formed by the replacement of biotite, under subsolidus conditions. Booklike aggregates of muscovite are common in the pegmatitic body and it frequently constitutes graphic intergrowths with quartz in the three zones of the body, whereas in the IZ muscovite and quartz also exhibit a radial intergrowth. In this zone the smallest crystals of muscovite commonly surround other minerals as quartz, tourmaline or feldspar. In the UBZ, muscovite, commonly associated with small crystals of green elbaite (< 1.5 cm long), often exhibits a disequilibrium coronitic texture involving mantles of radial muscovite on subrounded cores. In the UBZ, together with muscovite, Li-muscovite and lepidolite are common. Li-micas commonly appear as pinkish, very fine- to medium-grained crystals (< 6 mm to 3 cm long), frequently associated with quartz, albite, and deep pink elbaite. The smallest grains of lepidolite appear as anhedral to subhedral flakes, growing together with finegrained anhedral quartz crystals, subhedral albite, and euhedral elbaite. The largest lepidolite crystals, commonly associated with muscovite, exhibit a pseudobotroidal habit. Less frequently, lepidolite appears as white, pearly, subhedral flakes, giving rise, together with anhedral quartz crystals, to rounded masses of up to 10 cm ø. These masses of white lepidolite are not associated with elbaite crystals, in contrast with the pinkish lepidolite. The Fe-rich micas are also common in the PF pegmatite as well as in the associated leucogranite, although they are not as abundant as the Al-rich micas. Biotite is a common constituent in the leucogranite and in the adjacent LBZ. It seems to be totally or partially replaced by later muscovite, and also, it is frequently chloritized, with numerous needles of rutile as a by-product. Inside the pegmatite, in the LBZ, biotite is also commonly related to muscovite as well as with
the quartz-K-feldspar graphic intergrowths. It appears as book-like, fine- to medium-grained crystals (from 6 mm up to 6 cm long). In the IZ and UBZ, zinnwaldite is dominant relative to biotite. In the IZ, fine- to medium-grained (from 6 mm up to 3 cm long) zinnwaldite crystals are found close to the Fe-Mn phosphate nodules. The smallest grains appear as centimetric masses of subhedral, very fine-grained flakes that under microscope exhibit a strong pleochroism ranging from reddish brown to beige. The biggest zinnwaldite crystals show book-like texture and an intense pleochroism from deep brown to reddish brown under microscope, like biotite in the LBZ. In the UBZ, only fine-grained zinnwaldite crystals are observed (from 6 mm to 1 cm long). In the Li-enriched UBZ, a Fe-enriched lepidolite is also found. It appears as medium-sized crystals ( » 3 cm long) intergrown with Fepoor lepidolite. The main petrographic features of these Aland Fe-bearing micas are summarized in Table 1.
Sampling and analytical methods The mica samples have been selected from the three different zones of the pegmatite body, as well as from the associated leucogranite. Some of the samples were prepared by hand picking, and later examined with a binocular microscope to remove impurities, and then, ground in an automatic agate pulverizer. Samples were analysed for Si, Ti, Al, Fe, Mn, Mg, Zn, Ca, Na, K, F, P, Rb, Cs, and Sr by electron microprobe (EMP) at the Universities of Granada and Toulouse. Both natural and synthetic standards were used: natural fluorite and topaz (F), natural sanidine (K), natural pollucite (Cs), synthetic MnTiO3 (Ti, Mn), sphalerite (Zn), natural wollastonite and diopside (Ca), synthetic BaSO4 (Ba), synthetic Fe2O3 (Fe), natural albite (Na), natural periclase (Mg), synthetic SiO2 (Si), natural apatite (P), synthetic Al2O3 (Al), and Si-aluminate glass with 2 wt % Rb and 2 wt % Cs. Trace elements, including Rb, Be, Sr, Ba, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Y, Nb, Ta, Zr, Hf, Mo, Sn, Tl, Pb, U, Th, W, and REE were analysed at the University of Granada using an inductively coupled plasma mass spectrometry (ICPMS) technique (Perkin Elmer SCIEX Elan-5000). Li con-
372
E. Roda-Robles, A. Pesquera, P. P. Gil-Crespo, J. Torres-Ruiz, Ph. de Parseval
tents were determined for some samples using atomic absorption (AA). Li and Rb were measured by laser ablation (LA-ICPMS) at the University of Granada on 60–70 µm thick polished sections of rock samples. Sections were studied first by optical and back-scattered scanning electron microscopy (BS-SEM) to determine inclusion-free areas with their major-element composition subsequently determined by EDAX. The LA-ICPMS system uses a torch-shielded quadrupolar Agilent-7500 spectrometer and a 213 nm NdYAG Mercantek laser unit. Ablation was done in a He atmosphere. The laser beam was set at a 95 µm-sided square section, with a repetition rate of 10 Hz. Spots were preablated for 60 s using a laser output energy of 50 %. Ablation was done for 60 s with a laser output energy of 75 % moving upwards the sample stage 5 µm every 20 s, to keep the laser focused and maximize the ablation efficiency. Si, previously determined by EDAX, was used as an internal standard. The glass NIST-610, which contains 464 ppm Li and 435 ppm Rb (Pearce et al., 1997), was used as an external standard. Every analytical session started and ended by analysing NIST-610, which was also measured every 6 to 8 spots. To improve detection limits, blanks (i.e. analyses with the laser energy set to zero) were recorded before each spot and subtracted from the analytical signal. Data reduction was carried out with a homemade software written in STATA® programming language. This software permits outliers to be identified and discarded, blank subtraction, drift correction, internal standard correction and conversion to concentration units. The precision, calculated as the coefficient of variation (100*standard deviation/average) on 10 replicates of NIST-610 measured in every session, was about ± 1 and 1.5 % for Li and Rb respectively. Based on the strong correlation between AA and laser ablation data of Li and EMP data of F, the rest of the Li contents has been estimated according to the equation: Li = 0.3112*F1.3414 (R2 = 0.92), obtained from our experimental data. This equation has been
modified from the one used in Roda-Robles et al. (2005) for micas from the same pegmatite, taking into account new AA, laser ablation and EPM data. Such correlation is consistent with the empirical relationships proposed by Henderson et al. (1989), Tindle & Webb (1990), Tischendorf et al. (1997) and Pesquera et al. (1999). Similar corrections have been experimentally demonstrated in trioctahedral and partly dioctahedral lithium micas by Monier & Robert (1986). Some representative samples of mica were also analysed with an X-ray diffractometer at the Department of Mineralogy and Petrology, University of the Basque Country, using Si as internal standard, by scanning from 5 to 70° (2 ’ ) using CuK [ radiation (step size = 0.02°, and time step = 4 s). Unitcell dimensions were obtained using the Fullprof software (Rodr´ıguez-Carvajal, 1998). The mica polytypes were identified from X-ray powder diffractograms, by comparison with the standard data in Bailey (1984).
Results and discussion Structural characteristics The polytypes and structural data of representative Al- and Fe-micas from the three zones of the PF pegmatite are reported in Table 2. The only polytype found among all the studied muscovites is 2M1. This polytype is also found, but in a very low proportion, according to the relative intensity of the diffraction peaks, in a lepidolite from the UBZ coexisting with 2M2 as main polytype, and with 1M also as a minor constituent. In the rest of the lepidolites, as well as in the intermediate mixed forms from the UBZ, 2M2 is the main polytype. It never appears as the only polytype but it coexists with the 1M, always present in low amounts. In the case of the Fe-rich micas, both biotites and zinnwaldites show the 1M polytype.
Table 2. Unit-cell parameters and polytypes of the different micas from the PF pegmatite.
LBZ
IZ
UBZ
ZONE
Biotite 1M a[Å] b[Å] c[Å] q [°] V[Å3] F[wt %] a[Å] b[Å] c[Å] q [°] V[Å3] F[wt %] a[Å] b[Å] c[Å] q [°] V[Å3] F[wt %]
5.3508(4) 9.2332(5) 10.2069(5) 100.106(5) 496.440(55) 1.59 5.3505(4) 9.2193(6) 10.2058(5) 100.173(6) 495.514(55) 0.96 Fe-micas
Zinnwaldite 1M 5.2704(4) 9.1086(8) 10.1305(9) 100.668(7) 477.918(73) 6.96 5.2946(4) 9.1775(6) 10.1463(5) 100.152(5) 485.298(51) 5.29
Muscovite 2M1 5.1899(4) 9.0068(7) 20.1018(9) 95.750(7) 934.919(117) 2.2 5.1989(7) 9.0189(9) 20.0607(14) 95.770(8) 937.855(165) 1.03 5.2022(3) 9.0212(5) 20.0737(12) 95.769(5) 937.286(90) 0.88 Al-micas
Lepidolite 2M2(1M) 9.0150(7) 5.1921(3) 20.3299(13) 99.792(5) 937.720(111) 9.03
Mineralogy and geochemistry of micas from the Pinilla de Fermoselle pegmatite
373
Fig. 4. A) Mg – Li vs. Fe + Mn + Ti – Al(IV) (Sid = siderophyllite, Zinn = zinnwaldite, Poly = polylithionite, Tri = trilithionite, Ms = muscovite).
Fig. 3. Plot of the F contents for lepidolites and zinnwaldites from the PF pegmatite vs. unit-cell parameters a and b (Å).
For the Li-rich trioctahedral micas, a clear negative correlation is found between a and b unit-cell parameters and F contents (correlation coefficient of 0.985) (Fig. 3). This means that with higher F contents, the a and b parameters of these micas decrease as it is discussed for synthetic OH-F tetrasilicic magnesium micas by Robert et al. (1993). In the case of these synthetic micas, the parameter b decreases for values of XF between 0 and 0.5, whereas around XF = 0.5 there is a break, and so, for 0.5 e XF e 1, the progressive replacement of OH- by F- has no significant effect on b. For the a unit-cell parameter, on the contrary, this break is not observed, and the decrease of a with increasing F content is continuous (Robert et al., 1993). In the case of the Li-bearing trioctahedral micas from the PF pegmatite, XF ranges between 0.60 for the zinnwaldites from the IZ to 0.98 for the lepidolites from the UBZ. For these micas there is a continuous decrease of the a and b unit-cell parameters parallel to the progressive replacement of OH- by F- (Fig. 3).
Chemistry of aluminium micas The Al-rich micas show a continuous compositional trend through the pegmatite body, from muscovitic to lepidolitic compositions (Fig. 4). In general, muscovite changes significantly in composition from the LBZ to the UBZ, whereas only slight differences in the major element contents are observed between muscovite from leucogranite and that from the LBZa (Table 3, Fig. 4, 5 and 6). The most significant chemical variations from the LBZ to the UBZ are for MnO (av. 0.02 to 0.11 wt %), Li2O (av. 0.03 to 0.50 wt %), F (av. 0.16 to 1.30 wt %), Cs (48 to 950 ppm), Rb (881 to 7010
ppm), Sn (85 to 632 ppm), and Nb (68 to 123 ppm). The contents in other elements decrease from the LBZ to the UBZ: Al2O3 (av. 35.65 to 35.08 wt %); TiO2 (av. 0.97 to 0.02 wt %); and MgO (av. 0.49 to 0.05 wt %) (Table 3, Fig. 5). On the average, the octahedral site occupancy for the muscovite from the leucogranite and from the LBZa varies from 4.025 to 4.050 apfu (Table 3), which is close to the ideal 4.0 apfu of the dioctahedral muscovite. These values increase upwards, with the highest values for the muscovites from the UBZ (av. 4.215 apfu). This kind of muscovite may be a mixed-layer form, involving both dioctahedral and trioctahedral structures, as documented by du Bray (1994) and Foord et al. (1995) for muscovites with similar octahedral sites occupancy. According to Foord et al. (1995), this mixed character of the muscovite could represent disequilibrium crystallization. Octahedral site occupancy for lepidolite from the UBZ is higher, with values between 4.944 and 5.788, that is, values belonging to a dioctahedral mica but very close to be trioctahedral (values < 5) or to a trioctahedral mica (values > 5). Thus, Al-rich micas evolve from the leucogranite upwards from di- to trioctahedral, through mixed forms in the UBZ. The K/Rb and K/Cs ratios for muscovite decrease from the LBZ upward (Table 1, Fig. 5) (from 27 to 87 in the LBZ, from 22 to 43 in the IZ, and from 9 to 35 in the UBZ); whereas K/Cs values vary from 562 to 3630 in the LBZ, from 158 to 1345 in the IZ, and from 500 to 1169 in the UBZ. The lowest K/Rb and K/Cs ratios for micas are found in lepidolites (from 9 to 12, and from 15 to 28, respectively). As the K/Rb ratio decreases, Al-rich micas are progressively enriched in Li from the LBZa to the UBZ (Table 3, Fig. 5). On average, the amounts of Li2O and F in lepidolite are 4.28 and 6.99 wt %, respectively, with the highest in the latest white lepidolites. Furthermore, they are characterized by relatively high contents in Mn (up to 0.48 wt % in MnO), Cs (975 to 7200 ppm); Rb (6943 to 9470 ppm); Nb (116 to 624 ppm); and, Ta (32 to 454 ppm).
Bt
Ms
0.02 (0.02)
4.40 (0.09)
98.54 (1.21)
O=F
Li2O (*)
H2O(*)
Total (*)
97.70 (1.14)
3.61 (0.09)
0.12 (0.07)
0.21 (0.09)
0.14 (0.11)
0.02 (0.02)
0.49 (0.21)
9.13 (0.27)
0.14 (0.05)
0.03 (0.03)
6.98 (0.23)
0.16 (0.04)
0.002 (0.004)
0.096 (0.024)
0.009 (0.120)
0.001 (0.001)
4.025 (0.033)
0.002 (0.002)
0.153 (0.021)
1.777 (0.053)
Fe2+
Mn
Mg
Li
Zn
(Y)
Ca
Na
K
0.041 (0.044)
3.959 (0.044)
F
OH
3.760 (0.103)
0.240 (0.103)
0.001 (0.001)
1.817 (0.044)
0.042 (0.015)
0.005 (0.005)
5.639 (0.057)
0.016 (0.013)
0.077 (0.041)
1.626 (0.046)
0.021 (0.005)
2.714 (0.079)
0.372 (0.023)
0.812 (0.059)
8.000
2.628 (0.082)
5.372 (0.082)
Numbers in parentheses are standard deviations (s) * Calculated
0.001 (0.001)
Cs
Rb
0.112 (0.022)
0.113 (0.018)
Ti
3.691 (0.028)
Al(VI)
8.000
Al(IV)
(Z)
6.107 (0.074)
1.893 (0.074)
Si
10
99.41 (2.72)
4.43 (0.08)
0.03 (0.02)
0.07 (0.05)
0.04 (0.11)
0.01 (0.02)
0.16 (0.11)
10.02 (1.64)
0.53 (0.11)
0.02 (0.04)
0.49 (0.15)
0.01 (0.02)
0.90 (0.18)
35.65 (0.92)
0.97 (0.32)
46.17 (0.55)
3.932 (0.045)
0.068 (0.045)
0.001 (0.001)
1.698 (0.268)
0.137 (0.028)
0.003 (0.005)
4.050 (0.082)
0.004 (0.010)
0.016 (0.011)
0.097 (0.029)
0.002 (0.002)
0.101 (0.019)
0.097 (0.031)
1.856 (0.079)
8.000
1.856 (0.079)
6.144 (0.079)
Structural formula on the basis of 24 (O, OH, F) atoms
0.01 (0.01)
0.04 (0.04)
ZnO
0.01 (0.02)
K2O
Cs2O
10.34 (0.40)
Na2O
0.10 (0.10)
0.58 (0.08)
CaO
F
0.48 (0.12)
0.01 (0.01)
MgO
0.02 (0.03)
MnO
20.78 (0.58)
18.69 (0.50)
35.16 (0.70)
Al2O3
1.00 (0.16)
3.17 (0.21)
1.11 (0.22)
FeO(tot)
34.40 (0.54)
45.32 (0.68)
TiO2
17
SiO2
Weight percent
8
3.638 (0.116)
0.362 (0.116)
0.001 (0.002)
1.803 (0.059)
0.038 (0.023)
0.003 (0.004)
5.675 (0.057)
0.010 (0.009)
0.132 (0.054)
1.573 (0.027)
0.020 (0.008)
2.770 (0.081)
0.344 (0.033)
0.826 (0.047)
8.000
2.582 (0.047)
5.418 (0.047)
98.07 (1.40)
3.50 (0.09)
0.21 (0.09)
0.31 (0.10)
0.09 (0.08)
0.02 (0.28)
0.74 (0.24)
9.08 (0.34)
0.13 (0.08)
0.02 (0.02)
6.78 (0.21)
0.15 (0.06)
21.28 (0.35)
18.59 (0.61)
2.94 (0.31)
34.81 (0.39)
11
Bt
Ms
Mica type
n°
a
granitic rocks
Subzone
Zone
3.648 (0.162)
0.352 (0.162)
0.001 (0.001)
1.679 (0.138)
0.187 (0.062)
0.002 (0.003)
4.158 (0.079)
0.002 (0.003)
0.138 (0.076)
0.068 (0.028)
0.003 (0.004)
0.173 (0.035)
0.011 (0.007)
3.764 (0.060)
8.000
1.840 (0.690)
6.160 (0.069)
99.42 (2.20)
4.10 (0.21)
0.26 (0.14)
0.35 (0.16)
0.02 (0.03)
0.02 (0.03)
0.84 (0.38)
9.86 (0.68)
0.72 (0.24)
0.01 (0.02)
0.34 (0.15)
0.03 (0.03)
1.55 (0.30)
35.68 (1.41)
0.11 (0.07)
46.20 (1.08)
20
Ms
3.204 (0.133)
0.796 (0.133)
0.002 (0.002)
1.713 (0.046)
0.029 (0.004)
0.008 (0.012)
5.776 (0.034)
0.029 (0.017)
0.371 (0.082)
0.636 (0.122)
0.073 (0.007)
3.169 (0.057)
0.136 (0.037)
1.361 (0.083)
8.000
2.582 (0.055)
5.418 (0.055)
97.15 (1.20)
3.03 (0.14)
0.58 (0.13)
0.67 (0.11)
0.25 (0.14)
0.03 (0.03)
1.59 (0.25)
8.48 (0.21)
0.09 (0.01)
0.05 (0.07)
2.70 (0.53)
0.55 (0.05)
23.93 (0.40)
21.13 (0.43)
1.14 (0.32)
34.22 (0.47)
8
Bt
b
LBZ
3.494 (0.144)
0.506 (0.144)
0.001 (0.001)
1.739 (0.053)
0.184 (0.039)
0.001 (0.002)
4.221 (0.065)
0.005 (0.005)
0.216 (0.084)
0.056 (0.043)
0.011 (0.009)
0.249 (0.065)
0.011 (0.019)
3.673 (0.057)
8.000
1.854 (0.057)
6.146 (0.057)
98.82 (2.36)
3.88 (0.18)
0.40 (0.15)
0.50 (0.14)
0.05 (0.05)
0.02 (0.02)
1.19 (0.34)
10.09 (0.36)
0.70 (0.16)
0.01 (0.01)
0.28 (0.22)
0.10 (0.08)
2.20 (0.56)
34.73 (1.22)
0.11 (0.20)
45.50 (1.08)
62
Ms
1.916 (0.316)
2.084 (0.316)
0.013 (0.007)
1.754 (0.074)
0.040 (0.014)
0.042 (0.219)
5.772 (0.164)
0.018 (0.013)
1.379 (0.280)
0.294 (0.260)
0.108 (0.062)
1.900 (0.237)
0.051 (0.091)
1.993 (0.279)
8.000
2.052 (0.165)
5.948 (0.165)
98.01 (1.99)
1.93 (0.29)
2.32 (0.50)
1.87 (0.31)
0.17 (0.11)
0.20 (0.10)
4.44 (0.74)
9.25 (0.49)
0.14 (0.05)
0.24 (1.25)
1.33 (1.17)
0.86 (0.49)
15.26 (1.64)
23.08 (1.60)
0.45 (0.82)
40.03 (2.00)
34
Zinn
Table 3. Chemical composition of representative micas from the PF granite and from the three units of the PF pegmatite.
2.977 (0.153)
1.023 (0.153)
0.009 (0.010)
1.719 (0.183)
0.027 (0.014)
0.011 (0.020)
5.696 (0.057)
0.033 (0.010)
0.518 (0.109)
0.293 (0.026)
0.089 (0.009)
3.030 (0.230)
0.047 (0.016)
1.685 (0.177)
8.000
2.446 (0.080)
5.554 (0.080)
95.57 (1.54)
2.79 (0.11)
0.81 (0.18)
0.85 (0.14)
0.28 (0.08)
0.13 (0.15)
2.03 (0.34)
8.43 (0.89)
0.09 (0.04)
0.07 (0.12)
1.23 (0.01)
0.66 (0.07)
22.66 (1.56)
21.94 (0.84)
0.39 (0.13)
34.76 (0.82)
6
Bt
IZ
3.446 (0.460)
0.554 (0.460)
0.002 (0.002)
1.808 (0.060)
0.104 (0.048)
0.001 (0.002)
4.215 (0.203)
0.009 (0.012)
0.274 (0.290)
0.010 (0.022)
0.013 (0.013)
0.159 (0.135)
0.002 (0.006)
3.748 (0.221)
8.000
1.837 (0.133)
6.133 (0.133)
98.46 (1.42)
3.82 (0.52)
0.50 (0.54)
0.55 (0.46)
0.09 (0.12)
0.04 (0.03)
1.30 (1.08)
10.48 (0.33)
0.40 (0.18)
0.01 (0.01)
0.05 (0.11)
0.11 (0.12)
1.40 (1.18)
35.08 (2.45)
0.02 (0.05)
45.60 (1.05)
30
Ms
0.940 (0.311)
3.060 (0.311)
0.018 (0.003)
1.757 (0.042)
0.040 (0.008)
0.008 (0.017)
6.014 (0.106)
0.016 (0.004)
2.335 (0.325)
0.145 (0.027)
0.115 (0.027)
1.361 (0.192)
0.016 (0.007)
2.024 (0.360)
8.000
1.585 (0.179)
6.415 (0.179)
99.07 (1.06)
0.98 (0.31)
4.09 (0.63)
2.87 (0.34)
0.15 (0.04)
0.30 (0.05)
6.80 (0.80)
9.67 (0.33)
0.14 (0.03)
0.05 (0.11)
0.69 (0.13)
0.95 (0.20)
11.40 (1.39)
21.47 (0.82)
0.15 (0.06)
45.05 (2.09)
34
Zinn
2.823 (0.379)
8.000
1.245 (0.360)
6.755 (0.336)
100.21 (2.31)
1.13 (0.98)
4.45 (1.79)
3.01 (0.95)
0.20 (0.18)
0.16 (0.07)
7.16 (2.24)
10.44 (0.23)
0.35 (0.20)
0.02 (0.03)
0.02 (0.05)
0.49 (0.09)
1.68 (0.51)
25.97 (4.25)
