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Biotite granodiorites belonging to the redwitzite suite of western part of the Bohemian Massif occur as small bodies in metasediments of the Horní Slavkov crystalline unit and/or as inclusions in biotite granites of the Krušné Hory/Erzgebirge Mts. batholith. Biotite granodiorites contain plagioclase, K-feldspar, biotite, quartz, and accessory minerals (apatite, zircon). Some of these granodiorites were hydrothermally altered and during breakdown of biotite originated chlorite, titanite, ilmenite, and REE-fluorocarbonates. The anhedral grains and irregular aggregates of REE-fluorocarbonates appear homogenous in composition in back-scattered electron images. However, the detailed microprobe analyses of individual REE-fluorocarbonate grains show relatively high compositional variability on thin section scale, particularly with respect to their contents of Ca and Y. The REE-fluorocarbonates are represented by parisite, bastnäsite and relatively rare synchysite. REE-fluorocarbonates are more widespread in the Variscan granites of the Krušné Hory/Erzgebirge Mts. and Slavkovský les Mts. than previously considered. The occurrence of these REE-fluorocarbonates demonstrates that during later post-magmatic alterations, primary accessory minerals (allanite, monazite, xenotime, zircon) became unstable with remobilization of REE, Th, and U into newly formed secondary minerals (REE-fluorocarbonates and coffinite).
Institute of Rock Structure and Mechanics, v.v.i., Czech Academy of Sciences, Prague, Czech Republic
Zdeněk Dolníček
Department of Mineralogy and Petrology, National Museum, Prague, Czech Republic
*Address all correspondence to: rene@irsm.cas.cz
1. Introduction
The bulk of the rare earth elements (REE) in granitic rocks is contained in primary accessory minerals, such as allanite, monazite, apatite, xenotime, and zircon. During post-magmatic hydrothermal alteration, biotite is usually altered to chlorite.
Hydrothermal alteration-related REE minerals can be used as useful tracers of fluid composition and crystallization conditions. Normalized REE patterns of hydrothermal minerals are only rarely directly reflecting those of source rocks due to usually strong crystallochemical control and chemical complexation of REEs. Because of changing the affinity of various REEs to complexing agents present in the fluid phase, various levels of fractionation of REEs are often observed in hydrothermal REE minerals, especially in rare-earth fluorocarbonates.
The original, magmatically crystallized accessories may be corroded, or even completely dissolved. Under the influence of fluorine- and CO2-bearing fluids, REE become preferentially redeposited as rare-earth fluorocarbonates, such as parasite, bastnäsite, and synchysite. These REE-fluorocarbonates occur in various geological environments, including carbonatites, alkaline magmatic rocks, weathering crusts, sedimentary rocks, as well as hydrothermal ore deposits [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21]. The most abundant REE-fluorocarbonate minerals are bastnäsite and synchysite, which have also economic importance as one of the major world supply sources of REE (Mountain Pass, California, USA; Bayan Obo, Inner Mongolia, China).
Parisite is a highly scarce representative of this mineral group and in the past, it was described from altered granites and acid volcanites [7, 11, 17, 18], carbonatite complexes [9, 11], and hydrothermal ore deposits [3, 4, 8, 18]. In altered granitic rocks of the Saxothuringian Zone, the most abundant REE-fluorocarbonates were bastnäsite and synchysite [3, 10, 12, 22].
The present paper describes the occurrence and detailed mineralogy of REE-fluorocarbonates (parisite, bastnäsite, and rare synchysite) in altered granodiorites (redwitzites) of the Krudum granite body that is an integral part of the Western Krušné Hory/Erzgebirge pluton [23, 24, 25].
Biotite granodiorites are part of the oldest redwitzite suite that occurred in the area of the Krudum granite body (KGB), which is a subsidiary intrusion of the Karlovy Vary pluton (KVP) (Figure 1) [25]. Redwitzite suite that was originally defined in NE Bavaria comprises a small group of mafic to intermediate magmatic rocks ranging from gabbros to granodiorites [26, 27, 28]. Later, rocks similar to redwitzites were described from other Variscan plutons of the north-western edge of the Bohemian Massif [29, 30].
Figure 1.
Geological map of the Krudum granite body (after [25] modified by authors).
During exploration of the Sn-W mineralization in the Horní Slavkov-Krásno ore district the rocks of redwitzite suite were found as irregular magmatic bodies and sills in metamorphic rocks of the Slavkov crystalline unit (Figure 2) [31]. The granitic rocks of the Krudum granite body intrude the Slavkov crystalline unit composed of paragneisses, migmatites, and orthogneisses. The granitoid sequence of this body consists of a number of intrusive phases from the oldest redwitzite suite to the youngest F-rich, high-P2O5 Li-mica granites connected with Sn-W greisen mineralization occurred in greisen stocks (e.g., Hub stock) [32].
Figure 2.
Geological cross section of the redwitzite bodies from the Slavkovský les Mts. (after [31] modified by authors).
Two representative rock samples of biotite granodiorites (redwitzites) were taken from borehole HU-15, which was performed by SW of the Horní Slavkov town (Figure 2). The borehole encountered three granodiorite sills in paragneisses and migmatites of the Slavkov crystalline unit above hidden part of the F-rich, high-P2O5 Li-mica granites. Two representative rocks samples of redwitzites weighing 1 kg were crushed in a jaw crusher and representative splits of these samples were ground in an agate ball mill. The analyses of major elements were performed in the laboratory of Institute of Rock Structure and Mechanics of the Czech Academy of Sciences by conventional wet chemical methods. Trace elements were determined by ICP MS at Activation Laboratories Ltd., Lancaster, Canada on a Perkin Elmer Sciex ELAN 6100 ICP mass spectrometer. The decomposition of rock samples for ICP MS analyses involved lithium metaborate/tetraborate fusion.
Analyses of all REE-fluorocarbonates were performed using a CAMECA SX 100 electron microprobe working in WDX mode at the Institute of Geological Sciences, Masaryk University Brno. The accelerating voltage and beam currents were 15 kV and 10 nA, respectively, with beam diameters of 8 μm. The raw data were corrected using PAP matrix corrections [33]. The following standards, X-ray lines and crystals (in parentheses) were used: AlKα—almandine (TAP), AsLα—InAs (TAP), CaKα—brabantite (PET), BaLα—barite (LPET), CeLα—CeAl2 (PET), DyLα—DyPO4 (LLIF), ErLα—YErAG (LLIF), EuLβ—EuPO4 (LLIF), FKα—topaz (PC1), FeKα on andradite (LLIF), GdLβ—GdF3 (LLIF), LaLα—LaB6 (PET), MgKα—MgAl2O4 (TAP), MnKα—rhodonite (LLIF), NdLβ—NdF3 (LLIF), PKα—fluorapatite (PET), PrLβ—PrF3 (LLIF), SKα—barite (PET), SiKα—spessartine (TAP), SmLβ—SmF3 (LLIF), SrLα—SrSO4 (TAP), ThMα—brabantite (LPET), UMβ—metallic uranium (PET), YLα—YAG (PET), and ZrLα—zircon (TAP). Elements were measured for 20 s at the peak and for 10 s for each background. The detection limits were approximately 100 ppm for Y, 180–1700 ppm for REE, and 800–1100 ppm for U and Th.
The analyzed medium-grained biotite granodiorites consist of euhedral quartz (18–20 vol.%), anhedral to subhedral plagioclase (An27–37) (30–40 vol.%), andehral to subhedral K-feldspar (15–20 vol.%), and anhedral biotite (10–15 vol.%) (Figure 3). The unaltered biotite is characterized by distinctly higher content of TiO2 (3.8–4.6 wt.%) and usually lower concentrations of F (0.09–0.42 wt.% F). Biotite is represented by annite (Fe/(Fe + Mg) = 0.56–0.59, IVAl = 2.02–2.32 apfu and Ti = 0.47–0.59 apfu). Biotite often contains inclusions of accessories (apatite, zircon) and is partly altered to a mixture of chlorite, titanite, ilmenite, and REE-fluorocarbonates. Sericitization of both feldspars and chloritization of biotite are widespread, especially in sample R-1359.
Figure 3.
Microphotograph of the biotite granodiorite (redwitzite) (Bt—biotite, Kfs—K-feldspar, Pl—plagioclase, Qz—quartz), thin section, crossed polarizers.
The anhedral grains and irregular REE-fluorocarbonate aggregates appear homogenous in back-scattered electron images (Figures 4 and 5). However, the detailed microprobe analyses of individual REE-fluorocarbonate grains and aggregates show relatively high compositional variability on thin section scale, particularly with respect to their contents of Ca and Y (Table 1).
Figure 4.
Back-scattered electron (BSE) image of REE-fluorocarbonates from altered redwitzite (Ap—apatite, Prs—parisite).
Figure 5.
Back scattered electron (BSE) image of REE-fluorocarbonates from altered redwitzite (Ap—apatite, Bsn—bastnäsite, Chl-Bt—chloritized biotite, Ttn–titanite).
Sample wt.%
R-1359
R-1360
SiO2
57.10
57.41
TiO2
1.58
1.65
Al2O3
17.16
17.11
Fe2O3
1.88
1.73
FeO
5.02
5.04
MnO
0.09
0.09
MgO
2.61
2.57
CaO
4.13
4.59
Na2O
3.10
3.33
K2O
3.31
2.99
P2O5
0.55
0.48
H2O+
1.86
1.57
H2O−
0.43
0.31
Total
98.82
98.87
A/CNK
1.06
1.00
Ba ppm
2100
2110
Sr
734
764
Y
22
20
Zr
322
430
Table 1.
Representative compositions of the Horní Slavkov redwitzites.
4.2 Geochemistry
Analyzed biotite granodiorites are weakly peraluminous rocks, which show I-type signature with A/CNK (mol. Al2O3/(CaO + Na2O + K2O) of 1.00–1.06 and contents of SiO2 56.3–57.1 wt.%, TiO2 1.58–1.70 wt.% and MgO 2.60–2.61 wt.%. Potassium concentrations are higher (2.77–3.31 wt.% K2O) and K2O/Na2O ranges between 0.86 and 1.07, showing that these granodiorites belong to high-K magmas [34]. In addition, high content of Ba (1939–2000 ppm), Sr (680–715 ppm), and Zr (256–315 ppm) are significant (Table 2). The REE patterns of biotite granodiorites normalized to chondrite show the predominance of LREE over HREE (LaN/YbN = 40.17–52.20) and gently negative Eu anomaly (Eu/Eu* = 0.85–0.87) (Figure 6).
wt.%
1a
2a
3a
4
8a
10
10-1
SO3
b.d.l.
b.d.l.
b.d.l.
0.01
b.d.l.
b.d.l.
b.d.l.
P2O5
0.04
0.01
0.01
0.05
0.14
0.04
0.02
As2O5
0.07
0.07
b.d.l.
b.d.l.
b.d.l.
0.03
b.d.l.
CO2
22.72
21.98
22.07
21.35
20.93
22.24
25.34
SiO2
b.d.l.
0.21
0.15
b.d.l.
3.16
1.95
b.d.l.
ThO2
2.50
1.94
1.83
2.21
3.25
4.59
0.46
UO2
0.32
0.30
0.29
0.12
0.27
0.24
0.04
ZrO2
0.04
b.d.l.
b.d.l.
b.d.l.
b.d.l.
b.d.l.
b.d.l.
Al2O3
0.00
0.02
0.03
b.d.l.
1.61
0.97
b.d.l.
Y2O3
0.51
0.55
0.51
2.03
1.00
0.99
0.77
La2O3
16.78
17.62
17.76
13.53
15.06
15.07
11.75
Ce2O3
31.56
31.62
31.84
27.09
28.55
29.48
23.48
Pr2O3
3.04
2.99
3.07
2.79
2.96
2.81
2.53
Nd2O3
10.27
10.41
10.31
10.28
10.04
10.14
9.17
Sm2O3
1.19
1.27
1.25
1.52
1.37
1.29
1.27
Eu2O3
b.d.l.
b.d.l.
b.d.l.
0.01
b.d.l.
b.d.l.
b.d.l.
Gd2O3
0.37
0.41
0.41
0.94
0.52
0.62
0.50
Dy2O3
b.d.l.
0.12
0.09
0.46
0.28
0.03
0.09
Er2O3
b.d.l.
0.02
b.d.l.
0.20
0.06
0.13
0.04
FeO
1.04
0.51
0.33
0.29
0.22
0.18
1.52
MgO
0.05
0.05
0.03
0.18
0.13
0.10
0.45
CaO
5.43
4.73
4.86
5.84
6.21
6.80
13.28
SrO
0.60
0.62
0.63
0.28
0.29
0.37
0.25
PbO
0.02
0.03
b.d.l.
0.02
0.03
0.01
b.d.l.
H2O*
0.47
1.81
1.83
0.17
0.28
0.43
0.14
F
5.56
5.76
5.73
5.80
6.13
5.91
5.18
O=F
−2.34
−2.56
−2.77
−2.44
−2.58
−2.49
−2.56
Total
100.24
100.47
100.26
92.71
99.91
102.18
93.72
S6+
0.000
0.000
0.000
0.000
0.000
0.000
0.000
P5+
0.004
0.000
0.000
0.004
0.011
0.001
0.001
As5+
0.003
0.001
0.000
0.000
0.000
0.000
0.000
C4+
2.993
0.992
0.995
2.996
2.691
1.999
1.999
Si4+
0.000
0.007
0.005
0.000
0.298
0.000
0.000
Subtotal
3.000
1.000
1.000
3.000
3.000
2.000
2.000
Th4+
0.055
0.015
0.014
0.052
0.070
0.006
0.006
U4+
0.007
0.002
0.002
0.003
0.006
0.001
0.001
Zr4+
0.002
0.000
0.000
0.000
0.000
0.000
0.000
Al3+
0.000
0.001
0.001
0.000
0.178
0.000
0.000
Y3+
0.026
0.010
0.009
0.111
0.050
0.024
0.024
La3+
0.597
0.215
0.216
0.513
0.523
0.250
0.250
Ce3+
1.115
0.383
0.385
1.019
0.984
0.497
0.497
Pr3+
0.107
0.036
0.037
0.104
0.102
0.053
0.053
Nd3+
0.354
0.123
0.122
0.377
0.338
0.189
0.189
Sm3+
0.040
0.014
0.014
0.054
0.044
0.025
0.025
Eu3+
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Gd3+
0.012
0.004
0.004
0.032
0.016
0.010
0.010
Dy3+
0.000
0.001
0.001
0.015
0.009
0.002
0.002
Er3+
0.000
0.000
0.000
0.006
0.002
0.001
0.001
Fe2+
0.084
0.014
0.009
0.025
0.017
0.074
0.074
Mg2+
0.007
0.003
0.002
0.027
0.019
0.039
0.039
Ca2+
0.561
0.168
0.172
0.644
0.627
0.822
0.822
Sr2+
0.034
0.012
0.012
0.017
0.016
0.008
0.008
Pb2+
0.000
0.000
0.000
0.000
0.001
0.000
0.000
Na+
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Subtotal
3.001
1.000
1.000
3.000
3.000
2.000
2.000
OH−*
0.302
0.399
0.403
0.117
0.176
0.054
0.054
F−
1.697
0.602
0.598
1.885
1.826
0.946
0.946
Subtotal
2.000
1.001
1.001
2.002
2.002
1.000
1.000
O2−
10.344
3.610
3.612
10.232
10.292
10.324
6.559
La/Ce
0.53
0.56
0.56
0.50
0.53
0.51
0.51
La/Nd
1.63
1.69
1.72
1.62
1.50
1.49
149
Mineral
Parisite
bastnäsite
bastnäsite
parisite
parisite
parisite
Synchysite
Table 2.
Representative analyses of fluorocarbonates from the altered redwitzites of the Krudum granite body.
b.d.l.—below detection limit.
Figure 6.
Chondrite normalized REE diagram of redwitzites from the Krudum granite body (this work) and Bavaria (data from [34]) by [35].
4.3 Fluorocarbonate composition
The REE-fluorocarbonates have Ce as the dominant REE cation, and should be named as parisite-(Ce), bastnäsite-(Ce), and/or synchysite-(Ce). The concentration of the most abundant LREE oxide, Ce2O3, decreases from 28.2 to 26.5 wt.%. The thorium is present in concentrations between 2.0 and 4.2 wt.% of ThO2. The content of yttrium is considerably low (0.8–1.1 wt.% Y2O3) (Figure 7). Relatively low in all analyzed REE fluorocarbonates are also concentrations of neodymium (2.6–10.7 wt.% Nd2O3) (Figure 8).
Figure 7.
Distribution of La, Ce and Y in REE-fluorocarbonates from redwitzites of the Krudum granite body (this work) and from Li-mica granites of the Krušné Hory/Erzgebirge Mts. (data taken from [3, 22]).
Figure 8.
Distribution of La, Ce and Nd in REE-fluorocarbonates from redwitzites of the Krudum granite body (this work) and from Li-mica granites of the Krušné Hory/Erzgebirge Mts. (data taken from [3, 22]).
Redwitzites were originally found in the NW part of the Bohemian massif in NE Bavaria (Germany) [26, 27] and comprise mafic to intermediate Variscan igneous rocks ranging from gabbros to granodiorites. These rocks represent very specific rock type which represent the oldest rock variety that evolved during the Variscan magmatic phase in the north-west part of the Bohemian Massif [28, 34]. Later were similar rocks found and described also from the area of the Krudum granite body [23, 24, 29]. In area of the Krudum granite body occur monzodiorites, quartz diorites and granodiorites composed of plagioclase (An24–52) (30–50 vol.%), K-feldspar (5–20 vol.%), quartz (5–20 vol.%), biotite (10–30 vol.%), hornblende (0–24 vol.%), and rare pyroxene (0–5 vol.%). Composition of biotite range from phlogopite to annite. For biotite from the Bavarian redwitzites the presence of phlogopite is significant (Fe/(Fe + Mg) = 0.46–0.51, IVAl = 2.30–2.40 apfu and Ti = 0.32–0.53 apfu). Accessory minerals are apatite, zircon, ilmenite, titanite, allanite, rutile, magnetite, and pyrrhotite [23, 24].
The SiO2 contents in the Bavarian redwitzites fluctuates over a wide range (49–63 wt.%). The TiO2 content in the Bavarian redwitzites is partly lower as its content in redwitzites from the Krudum granite body (0.69–1.88 wt.%). Potassium concentrations in the Bavarian redwitzites are partly higher than the concentrations in redwitzites from the Slavkov granite body (1.40–4.37 wt.% K2O) and K2O/Na2O ranges between 0.53 and 1.49. The analyzed Bavarian redwitzites display lower contents of Ba (513–1656 ppm), Sr (278–591 ppm), and Zr (157–371 ppm) than the similar rocks from the Krudum granite body. The REE pattern of biotite granodiorites normalized to chondrite shows the predominance of LREE over HREE (LaN/YbN = 8.27–24.48) and partly negative Eu anomaly (Eu/Eu* = 0.47–0.95) (Figure 6) [34].
5.2 Occurrence of REE-fluorocarbonates in the Krušné Hory Mts./Erzgebirge granitic rocks
Rare-earth fluorocarbonates are relatively widespread in some hydrothermally altered Variscan granites of the Krušné Hory/Erzgebirge Mts. and Slavkovský les Mts. Occurrence of these REE-fluorocarbonates demonstrates that during later post-magmatic alterations primary accessory minerals (allanite, monazite, xenotime, zircon) became unstable with the remobilization of REE, Th, and U into newly formed secondary minerals (REE-fluorocarbonates, highly rare REE-arsenates and coffinite). In addition to newly founded REE-fluorocarbonates from the Krudum granite body, REE-fluorocarbonates and rare REE-arsenates were noted from the Niederbobritzsch granite (cerite-(Ce), synchysite-(Ce) [10], Kirchberg granite (bastnäsite-(Ce), Altenberg granite (fluorocerite-(Ce), bastnäsite-(Ce) [36], Cínovec granite (bastnäsite-(Ce), synchysite-(Ce), synchysite-(Y), chernovite-(Y) [3], Hora Svaté Kateřiny granite (bastnäsite-(Ce), bastnäsite-(Y), chernovite-(Y) [22], Gottesberg microgranite (synchysite-(Ce) [37] and Markersbach granite (synchysite-(Ce), synchysite-(Y) [12]. For all these occurrences is significant the predominance of bastnäsite-(Ce) and synchysite-(Ce). The La/Ce ratio for bastnäsite-(Ce) from hydrothermally altered, low-P2O5, high-F, Li-mica granites from the Krušné Hory/Erzgebirge batholith (Cínovec, Markersbach, Hora Svaté Kateřiny [3, 12, 22] is 0.26–0.83 and La/Nd ratio for bastnäsite-(Ce) from these rocks is 0.45–1.67. For synchysite-(Ce) from these rocks, the La/Ce ratio is 0.13–0.46 and the La/Nd ratio is 0.53–1.23. In REE-fluorocarbonates from redwitzites of the Krudum granite body are in comparison with REE-fluorocarbonates from above mentioned Li-mica granites distinctly lower concentrations of yttrium and also partly lower the concentrations of neodymium (Figures 7 and 8).
5.3 Chemical composition and origin of REE-fluorocarbonates
Although REE-fluorocarbonates have been described from several carbonatite complexes and hydrothermally altered granitic rocks, detailed compositional data are relatively rare. Identification of these minerals is commonly based on microprobe chemical analyses.
Our contribution is concentrated on occurrences REE-fluorocarbonates in hydrothermal altered redwitzites, which represent a highly rare occurrence of these minerals in granitic and related rock types, not yet published from other parts of the world. In previous contributions concentrated on occurrence of REE-fluorocarbonates in hydrothermal altered rocks, the older studies were concentrated on hydrothermal altered rocks coupled with uranium mineralization [4, 18] and on hydrothermal alteration of highly fractionated granitic rocks [3, 10, 12, 20, 22].
The majority of previously examined parisites-(Ce) contain Th concentrations below 1 wt.%. The Th-enriched parisite-(Ce) was found in carbonatites from Malawi and Brazil [15, 16]. The occurrence of REE-fluorocarbonates requires the presence of fluorine- and carbon dioxide-bearing fluids. The crystallization of parisite instead of bastnäsite indicates that the activity of Ca2+ in that fluid was distinctly higher. The primary magmatic plagioclase has a sufficient amount of calcium, which could be liberated during its sericitization. Potential source of fluorine is biotite, however, its content in biotite from examined granodiorites is relatively low (0.09–0.18 wt.% F). At the Horní Slavkov-Krásno Sn-W ore district carbonate country rocks are absent. On the other hand, CO2 has been proven in the residual melt fractions of Li-mica granites [38]. Moreover, the CO2-enriched fluid inclusions were recently found in quartz from Sn-W mineralization of the Horní Slavkov-Krásno ore district [39].
According to Fleischer [40] the average La/Nd ratio for REE-fluorocarbonates from hydrothermally altered granitic rocks is 0.89–1.83. Similar value gives for synchysite from hydrothermally altered granitic rocks also Schmandt et al. [18]. These values well correspond with La/Nd ratios which were found for parisite (1.33–1.63) and bastnäsite (1.56–1.72) from examined hydrothermally altered redwitzites of the Krudum granite body. The evolution of La/Ce ratio in bastnäsite from different geological environments was studied by Schmandt et al. [18] and for bastnäsite from hydrothermally altered granitic rocks, they give a value of 0.45–0.50. These data could very good correlate with our data for bastnäsite (0.49–0.56) and parisite (0.47–0.53).
The analyzed medium-grained biotite granodiorites from the Krudum granite body consist of quartz, plagioclase (An27–37), K-feldspar, and biotite. The unaltered biotite is characterized by the distinctly higher content of TiO2. Biotite is represented by annite (Fe/(Fe + Mg) = 0.56–0.59). Biotite often contains inclusions of accessories (apatite, zircon) and is partly hydrothermally altered to a mixture of chlorite, titanite, ilmenite, and REE-fluorocarbonates. Analyzed unaltered biotite granodiorites are weakly peraluminous rocks, which show an I-type signature.
The anhedral grains and irregular aggregates of REE-fluorocarbonates appear homogenous in back-scattered electron images. However, the detailed microprobe analyses of individual REE-fluorocarbonate grains and aggregates show relatively high compositional variability on a thin section scale, particularly with respect to their contents of Ca and Y. The REE-fluorocarbonates have Ce as the dominant REE cation, and should be named as parisite-(Ce), bastnäsite-(Ce), and/or very rare synchysite-(Ce). However, for analyzed REE-fluorocarbonates from biotite granodiorites (redwitzites) are considerably low concentrations of yttrium (0.8–1.1 wt.% Y2O3).
The La/Nd ratios which were found for parisite (1.33–1.63) and bastnäsite (1.56–1.72), occurred in redwitzites from the Krudum granite body are characteristic of REE-fluorocarbonates from hydrothermally altered granitic rocks. Also, the La/Ce ratios in analyzed bastnäsite (0.49–0.56) and parisite (0.47–0.53) are similar to these ratios which were found in REE-fluorocarbonates from hydrothermally altered granitic rocks.
The support of the Long-Term Conceptual Development Research Organization RVO 67985891 is thanked, Z.D. acknowledges the financial support of the Ministry of Culture of the Czech Republic (long-term project DKRVO 2019–2023/1.i.e; National Museum, 00023272). We are also grateful to Š. Benedová and R. Škoda for their technical assistance in using electron microprobe analyses of REE-fluorocarbonates, plagioclase, and biotite. We are also grateful for the constructive comments of an anonymous reviewer.
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Written By
Miloš René and Zdeněk Dolníček
Submitted: 23 May 2023Reviewed: 24 July 2023Published: 03 October 2023
Open access peer-reviewed chapter
