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The Moldanubian Batholith is the largest Variscan magmatic complex in the Bohemian Massif, which is part of the Central European Hercynian belt. In northern part of the Moldanubian Batholith occur relatively small bodies of granitoids which could be correlated with biotite granodiorites of the Mauthausen type which occur in the Austrian part of this batholithic complex. The first body is formed by biotite-muscovite granite of the Pavlov type. The second occurrence of granitoids of the Mauthausen type is formed by two, relatively small bodies of the biotite granodiorites of the Pohled type. The estimation of melting temperatures of granitic melts for granitic rocks from Pavlov and Pohled area, based on zircon and monazite saturation thermometers show that melting temperatures were partly higher than those of the Mauthausen granodiorites the Austrian part of the Moldanubian Batholith (732–817°C). Analysed apatites from both areas contain high F (3.05–4.00 wt.%) and little Cl (0.00–0.06 wt.%). The analysed zircons contain low Hf concentrations (0.93–1.65 wt.% HfO2, 0.008–0.013 apfu Hf). The analysed monazites form the Pavlov and Pohled granitoids plot close to the huttonite vector.
Institute of Rock Structure and Mechanics, v.v.i., Czech Academy of Sciences, Prague, Czech Republic
Zdeněk Dolníček
National Museum, Prague, Czech Republic
*Address all correspondence to: rene@irsm.cas.cz
1. Introduction
The biotite granodiorites of the Mauthausen type represent the youngest group of granitic rocks occurred in the Moldanubian Batholith, that are part of the Freistadt/Mauthausen suite (Figure 1) [1, 2, 3]. The granodiorites of the Mauthausen type occur predominantly in the Austrian part of the Moldanubian Batholith, especially along of the Danube River near of the Mauthausen town. Petrology and geochemistry of these granodiorites were in detail described by Vellmer and Wedepohl [4] and by Gerdes [5]. Smaller occurrences of this granodiorites exist also in the Austrian Mühlviertel. Later were found occurrences of granodiorites of the Mauthausen type also in northern part of the Moldanubian Batholith near Humpolec and Havlíčkův Brod in the Czech Republic (Figure 2) [6, 7, 8, 9]. However, in papers of Janoušek, Matějka and René, Matějka [7, 8] were these occurrences and their compositions described only very briefly. Therefore, the aim of presented chapter is detailed petrology, mineralogy and geochemistry of these granitoids, together with discussion of actually presented position of the Moldanubian Batholith in the Central European Variscan belt as whole [3, 10]. The similarity of granitoids of the Mauthausen type occurring in northern part of the Moldanubian Batholith with the Mauthausen granodiorites occurred in Austria is based on detailed geochemical study these granitoids and composition of selected accessory minerals, predominantly monazite.
Figure 1.
Geological map of the Moldanubian Batholith (after [1, 2], modified by authors).
Figure 2.
Geological map of the northern part of the Moldanubian Batholith (after [6], modified by authors).
The Moldanubian Batholith (and/or also South Bohemian Batholith) together with Fichtelgebirge/Erzgebirge Batholith on the basis of the synchronicity of geochronological data and the similarity of granite types belongs to one coherent and cogenetic plutonic megastructure, the Saxo-Danubian granite belt evolved in the Central European Variscides [10]. The granitoids of the Mauthausen type, together with the Freistadt granodiorites are part of the youngest magmatic group (318–316 Ma) of the Moldanubian Batholith [3, 10]. This magmatic group is recently interpreted as result of renewed decompression melting [3]. Dating of the Mauthausen granodiorites (316 ± 1 Ma, monazite, U-Pb dating by isotope dilution thermal ion mass spectrometry) is based on dating one sample from the Mauthausen quarry in Austria [10].
The granitoids of the Mauthausen type occurring in northern part of the Moldanubian Batholith are represented by three relatively small bodies of the biotite-muscovite granites of the Pavlov type and biotite granodiorites of the Pohled type (Figure 2). The fine-grained biotite-muscovite granites of the Pavlov type were firstly in detail mapped and recognised as individual granite variety in the northern part of the Moldanubian Batholith by Veselá et al. [11]. Its petrology and geochemistry were later described in detail by Matějka and Janoušek [7]. The biotite-muscovite granite of the Pavlov type occurs as NNE-SSW elongated body which was in the past opened by small quarries near Pavlov and Slavníč villages. During geological mapping two small biotite granodiorite bodies were recognised in quarries by villages Vysoká and Pohled, near Havlíčkův Brod [12]. The petrology and geochemistry of biotite granodiorite from the quarry Pohled was later briefly described by Mastíková [9] and Doleželová [13].
Representative rock samples weighting 2–5 kg, collected from quarries Pavlov and Slavníč were crushed in a jaw crusher and representative split of these samples were ground in an agate ball mill. Major and trace elements were determined by inductively coupled plasma mass spectrometry (ICP-MS) techniques at Activation Laboratories Ltd., Ancaster, Canada, using a Perkin Elmer Sciex ELAN 6100 ICP mass spectrometer, following standard lithium metaborate/tetraborate fusion and acid decomposition of the sample. Similar analytical techniques were used also for chemical analyses of four representative rock samples of biotite granodiorite from the Pohled quarry, which were performed in ACME laboratory in Vancouver, Canada. All analyses were calibrated against international reference materials. Geochemical data for the Mauthausen biotite granodiorite were taken from paper of Gerdes [5].
Approximately 140 quantitative electron microprobe analyses of apatite, zircon, monazite and selected rock-forming minerals (plagioclase, K-feldspar and biotite) were collected from representative samples of the Pavlov, Pohled and Mauthausen granitoids. All these minerals were analysed in polished thin sections. The back-scattered electron (BSE) images were acquired to study the internal structure of mineral aggregates and individual mineral grains. The abundances of all chemical elements were determined using a CAMECA SX 100 electron probe micro-analyser (EPMA) operated in wavelength-dispersive mode at the Department of Geological Sciences, Masaryk University in Brno and in National Museum, Prague. The accelerating voltage and beam currents were 15 kV and 20 nA or 40 nA, respectively, and the beam diameter was 1 to 5 μm. The peak count time was 20 s, and the background time was 10 s for major elements. For the minor elements, the counting times were 40–60 s on the peaks, and 20–30 s on each background position. The following standards, X-ray lines and crystals (in parentheses) were used: AlKα – sanidine (TAP), CaKα – fluorapatite (PET), CeLα – CePO4 (PET), ClKα – vanadinite (LPET), DyLα – DyPO4 (LLIF), ErLα – ErPO4 (PET), EuLβ – (LLIF), FKα – topaz (PC1), FeKα – almandine (LLIF), GdLβ – GdPO4 (LLIF), HfMα – Hf (TAP), KKα – sanidine (TAP), LaLα – LaPO4 (PET), MgKα –Mg2SiO4 (TAP), MnKα –spessartine (LLIF), NaKα – albite (PET), NbLα – columbite, Ivigtut (LPET), NdLβ – NdPO4 (LLIF), PKα – fluorapatite (PET), PbMα – vanadinite (PET), PrLβ – PrPO4 (LLIF), RbLα –RbCl (LTAP), SKα – SrSO4 (LPET), ScKα – ScP5O14 (PET), SiKα – sanidine (TAP), SmLβ – SmPO4 (LLIF), SrLα – SrSO4 (TAP), TaMα – CrTa2O6 (TAP), TbLα – TbPO4 (LLIF), ThMα – CaTh(PO4)2 (PET), TiKα – anatase (PET), UMβ –metallic U (PET), VKβ – vanadinite (LPET), YLα – YPO4 (PET), YbLα –YbPO4 (LLIF) and ZrLα – zircon (TAP). The raw data were corrected using the PAP matrix corrections [14]. The detection limits were approximately 400–500 ppm for Y, 600 ppm for Zr, 500–800 ppm for REE and 600–700 ppm for U and Th. Mineral formulae were recalculated using the MinPet 2.02 software [15]. The calculation of mineral formulae for end-member F-, Cl- and OH-apatites was performed according to Piccoli and Candela [16]. Mole fractions for components in monazite and xenotime were calculated according to Pyle et al. [17].
Biotite-muscovite granites of the Pavlov type are fine grained, usually equigranular rocks. Major components of this granite are quartz (29–35 vol.%), plagioclase (An22–37) (25–31 vol.%), K-feldspar (21–30 vol.%), biotite (5–9 vol.%) and muscovite (2–4 vol.%) (Figure 3). Biotite is represented by annite (Fe/Fe + Mg = 0.60–0.63, Al4+ = 2.22–2.23 apfu and Ti = 0.32–0.36 apfu (atoms per formula unit)). Accessory minerals are represented by apatite, zircon, ilmenite and monazite.
Biotite granodiorites of the Pohled type are fine to medium grained, usually equigranular rocks. Major components of this granodiorite are plagioclase (An16–45) (40–48 vol.%), quartz (24–37 vol.%), K-feldspar (12–15 vol.%) and biotite (10–13 vol.%) (Figure 4). Biotite is represented by annite (Fe/Fe + Mg = 0.51–0.54, Al4+ = 2.05–2.21 apfu and Ti = 0.45–0.55 apfu (atoms per formula unit)). Accessory minerals are represented by apatite, zircon, ilmenite and monazite. In places also hydrothermal allanite was found.
Figure 4.
Microphotograph of the Pohled biotite granodiorite (Bt – Biotite, Kfs – K-feldspar, Pl – Plagioclase, Qz – Quartz), thin section, crossed polarizers.
4.2 Geochemistry
Biotite-muscovite granites of the Pavlov type are weakly peraluminous granites with A/CNK [mol. Al2O3/(CaO + Na2O + K2O)] of 1.15–1.22 and contents of SiO2 68.5–69.9 wt.%, Na2O 3.3–3.8 wt.% and K2O 3.9–4.1 wt.%. These granites display relatively poorly fractionated REE pattern (LaN/YbN = 16.2–21.1) and negative Eu anomaly (Eu/Eu* = 0.33–0.54). In comparison with more fractionated two-mica granites of the Eisgarn type, the granites of the Pavlov type are enriched in CaO (1.9–2.1 wt.%), Ba (791–811 ppm), Sr. (505–535 ppm) and depleted in Rb (194–207 ppm).
Biotite granodiorites of the Pohled type are weakly peraluminous granites with A/CNK 1.05–1.15 and contents of SiO2 66.9–68.0 wt.%, Na2O 3.2–3.5 wt.% and K2O 3.7–4.3 wt.%, relatively poorly fractionated REE pattern (LaN/YbN = 12.3–23.5) and gently negative to missing Eu anomaly (Eu/Eu* = 0.73–1.05). In comparison with more fractionated two-mica granites of the Eisgarn type, the granodiorites of the Pohled type are distinctly enriched in CaO (2.0–2.9 wt.%), Ba (829–951 ppm), Sr. (603–668 ppm) and depleted in Rb (147–172 ppm) (Table 1).
Sample
R-1305
R-1306
Do-1
Do-3
Locality
Slavníč
Pavlov
Pohled
Pohled
Rock wt %
Biotite-muscovite granite
Biotite-muscovite granite
Biotite granodiorite
Biotite granodiorite
SiO2
68.51
69.85
67.48
68.02
TiO2
0.40
0.38
0.50
0.48
Al2O3
16.64
16.14
15.70
15.62
Fe2O3 tot.
2.29
2.14
3.40
3.21
MnO
0.03
0.03
0.06
0.05
MgO
0.65
0.68
1.30
1.22
CaO
2.12
1.92
2.59
2.32
Na2O
3.81
3.32
3.28
3.34
K2O
4.06
3.92
3.95
3.83
P2O5
0.18
0.16
0.15
0.15
CO2
0.04
0.04
0.04
0.08
S
0.01
0.01
0.05
0.04
L.O.I.
0.80
0.96
1.30
1.50
Total
99.54
99.55
99.80
99.86
A/CNK
1.15
1.22
1.09
1.13
ppm
Ba
811
791
951
829
Rb
194
207
158
147
Sr
535
505
628
603
Zr
160
162
139
141
U
3.5
3.3
8.5
5.5
Th
18.4
18.0
14.9
12.2
Table 1.
Representative compositions of the Pavlov and Pohled granitoids.
4.3 Accessory minerals association
The REE, Y and Zr bearing accessories in granites and granodiorites of the Pavlov and Pohled types are represented by primary magmatic apatite, zircon and monazite. In biotite granodiorites of the Pohled type also hydrothermal allanite was found. Apatite occurs usually in form of euhedral and subhedral grains (20–50 μm in size). Zircon usually occurs as small euhedral to subhedral grains (10–80 μm in size). Some zircon grains are oscillatory zoned (Figure 5). Monazite occurs as relatively rare, usually subhedral to anhedral grains (20–30 μm). The compositions of apatite, zircon and monazite were studied in detail.
Figure 5.
BSE picture of oscillatory zoned zircon from the Pohled biotite granodiorite.
4.3.1 Apatite composition
All analysed apatites contain high F (3.05–4.00 wt.%) and low Cl (0.00–0.06 wt.%). Their contents of Fe (0.14–0.49 wt.% FeO) and Mn (0.11–0.35 wt.% MnO) are low. Their contents of sulphur and natrium are low (0.00–0.05 wt.% SO3, 0.00–0.09 wt.% Na2O). The concentrations of Y are low (0.00–0.14 wt.% Y2O3) (Table 2).
Sample
1305–24
1305–25
1306–12
1306–13
Po-G1–97
Po-G2–91
Locality
Slavníč
Slavníč
Pavlov
Pavlov
Pohled
Pohled
P2O5
41.51
41.41
42.03
42.09
41.33
41.74
SiO2
0.00
0.14
0.12
0.11
0.00
0.16
Y2O3
b.d.l.
0.04
0.11
b.d.l.
b.d.l.
b.d.l.
CaO
55.04
54.31
54.76
55.06
55.04
55.08
FeO
0.20
0.38
0.32
0.47
0.10
0.06
MnO
0.11
0.27
0.28
0.12
0.14
0.09
Na2O
0.00
0.00
0.00
0.44
0.00
0.00
SO3
0.00
0.05
0.00
0.00
0.06
0.05
F
2.85
3.66
3.37
3.75
3.77
3.92
Cl
0.02
0.01
0.00
0.00
0.09
0.17
O=F,Cl
−1.20
−1.54
−1.42
−1.58
−1.61
−1.69
Total
98.53
98.73
99.57
100.46
98.92
99.58
XFap
0.757
0.972
0.895
0.995
0.987
0.977
XClap
0.003
0.001
0.000
0.000
0.013
0.023
XOHap
0.240
0.027
0.105
0.005
0.000
0.000
Table 2.
Representative microprobe analyses of apatite (wt. %).
b.d.l. below detection limit.
4.3.2 Zircon composition
The analysed zircons contain low Hf concentrations (0.93–1.65 wt.% HfO2, 0.008–0.013 apfu Hf, Table 3, Figure 6). The atomic ratio Hf/(Hf + Zr) varies from 0.008 to 0.014. The concentrations of Y in analysed zircons are relatively low (up to 1.08 wt.% Y2O3, 0.018 apfu Y). All analysed zircons display also low concentrations of U and Th, reached up to 0.52 wt.% UO2, 0.004 apfu U and up to 0.88 wt.% ThO2, 0.006 apfu Th in zircons from the Pohled biotite granodiorite. The concentrations of both elements in biotite-muscovite granites of the Pavlov type are partly lower (up to 0.28 wt.% UO2, 0.002 apfu U; up to 0.18 wt.% ThO2, 0.001 apfu Th).
Sample
1305–13
1305–16
1306–6
1306–7
Po-G124
Po-G1–25
Locality
Slavníč
Slavníč
Pavlov
Pavlov
Pohled
Pohled
SiO2
32.30
32.78
31.52
31.92
32.69
32.55
Al2O3
0.00
0.10
0.01
0.00
0.00
0.00
ZrO2
64.69
65.20
64.89
65.78
65.85
64.72
HfO2
1.06
1.04
1.04
1.00
1.25
1.17
CaO
0.00
0.08
0.01
0.01
0.03
0.02
FeO
0.44
0.01
0.53
0.72
0.01
0.01
P2O5
0.00
0.00
0.40
0.25
0.00
0.00
Sc2O3
0.08
0.05
0.10
0.05
0.00
0.06
Y2O3
0.26
0.03
0.35
0.00
0.00
0.07
Yb2O3
0.16
0.09
0.20
0.12
0.02
0.12
UO2
0.12
0.16
b.d.l.
b.d.l.
b.d.l.
b.d.l.
ThO2
0.13
0.08
0.15
0.11
b.d.l.
0.51
Total
99.24
99.62
99.20
99.96
99.85
99.23
apfu, O = 4
Si
0.999
1.005
0.976
0.981
1.002
1.004
Al
0.000
0.004
0.000
0.000
0.000
0.000
Zr
0.976
0.975
0.980
0.985
0.984
0.973
Hf
0.009
0.009
0.009
0.009
0.011
0.010
Ca
0.000
0.003
0.000
0.000
0.001
0.001
Fe
0.011
0.000
0.014
0.019
0.000
0.000
P
0.000
0.000
0.010
0.007
0.000
0.000
Sc
0.002
0.001
0.003
0.001
0.000
0.002
Y
0.004
0.000
0.006
0.000
0.000
0.001
Yb
0.002
0.001
0.002
0.004
0.000
0.001
U
0.001
0.001
0.000
0.000
0.000
0.003
Th
0.001
0.001
0.001
0.001
0.000
0.004
Table 3.
Representative microprobe analyses of zircon (wt. %).
b.d.l. – below detection limit.
Figure 6.
Chemical composition of zircon.
4.3.3 Monazite composition
In the Pavlov and Pohled granitoids, the sum of LREE (La + Ce + Pr + Nd + Sm) ranges between 3.27 and 3.87 apfu (calculation is based on 16 atoms of oxygen), being relatively higher in the Pohled biotite granodiorites. Cerium is in all cases the most abundant REE varying between 27.16 and 33.71 wt.% Ce2O3 (1.63–1.97 apfu Ce). The second most abundant REE is La 10.64–20.00 wt.% La2O3, 0.62–1.18 apfu La), followed by Nd (8.85–12.38 wt.% Nd2O3, 0.50–0.70 apfu Nd), Pr (2.54–3.42 wt.% Pr2O3, 0.15–0.20 apfu Pr) and Sm (0.76–2.41 wt.% Sm2O3, 0.04–0.13 apfu Sm). Thus, all analysed monazite grains form the Pavlov and Pohled granitoids should be termed monazite-(Ce) (Table 4). However, the ranges in atomic ratios amongst individual REEs vary broadly, the (La/Nd)cn ratio is between 1.65 and 4.35, the (La/Sm)cn ratio is between 3.06 and 14.57. The content of Y in analysed monazites from the Pavlov and Pohled granitoids ranges between 0.23 and 2.67 wt.% Y2O3 (0.02–0.22 apfu Y). The concentrations of Th vary between 0.14 and 9.54 wt.% ThO2 (0.01–0.35 apfu Th). The concentrations of U vary between below detection limit and 0.99 wt.% UO2 (0.00–0.04 apfu U). Two main coupled substitution mechanism have been proposed for monazite, namely the cheralite and huttonite substitutions [18]. The analysed monazites form the Pavlov and Pohled granitoids plot close to the huttonite vector (Figure 7).
Sample
1305–11
1305–14
1306–22
1306–25
Po-G1–22
Po-G1–27
Locality
Slavníč
Slavníč
Pavlov
Pavlov
Pohled
Pohled
P2O5
28.54
28.06
27.91
29.25
29.68
28.28
SiO2
1.19
1.08
1.32
0.78
0.44
0.94
ThO2
7.18
6.44
5.74
4.30
2.98
3.67
UO2
0.22
0.16
0.15
0.09
0.09
0.00
Y2O3
0.46
0.50
0.23
0.42
2.67
0.59
La2O3
13.89
14.53
16.84
16.10
13.59
16.88
Ce2O3
30.02
30.60
31.27
31.84
28.85
30.90
Pr2O3
3.12
2.99
2.93
3.16
3.25
3.00
Nd2O3
10.89
11.04
10.37
11.06
11.77
9.69
Sm2O3
1.48
1.41
0.99
1.45
2.13
1.37
Gd2O3
0.60
0.68
0.41
0.80
1.29
0.56
Dy2O3
0.20
0.14
b.d.l.
0.12
0.70
0.27
Er2O3
b.d.l.
b.d.l.
b.d.l.
b.d.l.
0.28
0.16
Yb2O3
b.d.l.
b.d.l.
b.d.l.
b.d.l.
0.12
0.08
CaO
0.78
0.63
0.75
0.54
0.59
0.69
PbO
0.09
0.09
0.10
0.06
0.03
0.10
Total
98.66
98.35
99.01
99.97
98.46
97.18
apfu, O = 16
P
3.849
3.821
3.780
3.892
3.953
3.864
Si
0.190
0.174
0.211
0.123
0.069
0.152
Th
0.260
0.236
0.209
0.154
0.107
0.135
U
0.008
0.006
0.005
0.003
0.003
0.000
Y
0.039
0.043
0.020
0.035
0.223
0.051
La
0.815
0.861
0.993
0.932
0.788
1.004
Ce
1.749
1.800
1.829
1.830
1.660
1.824
Pr
0.181
0.175
0.171
0.181
0.186
0.176
Nd
0.619
0.634
0.592
0.620
0.661
0.558
Sm
0.081
0.078
0.055
0.078
0.115
0.076
Gd
0.032
0.036
0.022
0.042
0.067
0.030
Dy
0.010
0.007
0.000
0.006
0.035
0.014
Er
0.000
0.000
0.000
0.000
0.014
0.008
Yb
0.000
0.000
0.000
0.000
0.006
0.004
Ca
0.133
0.109
0.129
0.091
0.099
0.119
Pb
0.004
0.004
0.004
0.003
0.001
0.004
Mole fractions:
LREEPO4
0.8759
0.8892
0.9014
0.9153
0.8585
0.9084
HREEPO4
0.0112
0.0110
0.0077
0.0128
0.0325
0.0145
CaTh(PO4)2
0.0676
0.0546
0.0639
0.0458
0.0498
0.0594
ThSiO4
0.0353
0.0343
0.0220
0.0173
0.0030
0.0050
YPO4
0.0099
0.0108
0.0050
0.0088
0.0561
0.0127
Table 4.
Representative microprobe analyses of monazite (wt. %).
In the past, the origin and fractionation of granitic rocks of the Moldanubian Batholith was discussed by geochemical modelling based on trace-element fractionation. According to these studies, granitic rocks of the Moldanubian Batholith could originate by LP-HT partial melting of various metasediments and/or by melting of a mixture of metasediments and amphibolites [7, 19, 20, 21]. According to majority of these studies, the granitic rocks of the individual magmatic suites occurred in the Moldanubian Batholith were also variably fractionated [7, 21]. The fractionation of these magmatic suites could be well documented by distribution of some trace elements (e.g., Ba, Sr., Th, Zr, REE) (Figures 8 and 9).
Figure 8.
Distribution of Ba an Sr in analysed rocks.
Figure 9.
Distribution of Th and Zr in analysed rocks.
For distinguishing source rock series (greywackes vs. pelites) could be used some major elements, especially CaO/Na2O and Al2O3/TiO2 ratios [22]. According to these studies, in detail discussed by René [19], the granitic rocks of the Eisgarn suite originated by partial melting of metapelites, whereas granites and granodiorites of the Weinsberg and Freistadt/Mauthausen suites originated by partial melting of a metagreywackes-metabasalt mixture.
The estimation of melting temperatures of granitic melts is usually based on saturation thermometers based on melting of zircon and monazite [23, 24, 25]. According to zircon saturation thermometry granitic rocks are usually divided on the hot and cold [26]. The most detailed study of all problems connected with using of zircon thermometry was published by Siégel et al. [27] and Clemens et al. [28]. For all granitic rocks from the Moldanubian Batholith the TZrnsat was calculated according to revisited formula published by Boehnke et al. [24] and TMnzsat according to model of Montel [25]. The saturation temperatures from both models for the Mauthausen granodiorite from the Austrian part of the Moldanubian Batholith varied between 693 and 803°C. However, in recent study of thermometry of the Moldanubian Batholith granitoids [3], based on older zircon saturation thermometry [23], the melting temperatures for the Mauthausen granites from occurrences in Austria are estimated in distinctly higher range (790–840°C). However, the new data of Ti-zircon thermometry for biotite granodiorite from the Mauthausen quarry give temperature data partly similar to our data presented in this study (736–844°C). The saturation temperatures for biotite-muscovite granites of the Pavlov type are partly higher (745–817°C). The saturation temperatures for the Pohled biotite granodiorite are similar (732–802°C). It is also interesting that in all these cases the TMnzsat is usually partly higher than the TZrnsat temperatures. These differences could be partly explained by restitic (inherited) monazite crystals from original metasediments.
The distribution of Fe, Mn, F and Cl in analysed apatites is similar to those of the S-type granites [15]. The low content of Hf in analysed zircon (0.93–1.65 wt.% HfO2) is partly lower as its content in two-mica granites of the Eisgarn suite (1.0–2.5 wt.% HfO2) [29]. The composition of analysed monazite is similar to those of the Freistadt biotite granodiorites, but distinctly different as its composition from two-mica granites of the Eisgarn suite. For monazites from the Freistadt granodiorites is similar huttonite substitution significant, whereas monazites from two-mica granites of the Eisgarn suite display cheralite substitution [30].
Granitic rocks of the Mauthausen type from northern part of the Moldanubian Batholith occurring between Pavlov and Pohled are according to their mineralogical and geochemical composition similar to the Mauthausen type occurrences in the Austrian part of the Moldanubian Batholith. These biotite-muscovite granites and biotite granodiorites are weakly peraluminous rocks, enriched especially in Ba and Sr. Their fractionation is documented by distribution of the Ba, Sr., Th and Zr. These granites and granodiorites originated by partial melting of a metagreywacke-metabasalt mixture. The estimation of melting temperatures of granitic melts for granitic rocks from Pavlov and Pohled area, based on zircon and monazite saturation thermometers, show that melting temperatures were partly higher as the melting temperatures for the Mauthausen granodiorites from the Austrian part of the Moldanubian Batholith (732–817°C). Analysed apatites from both areas contain high F (3.05–4.00 wt.%) and negligible Cl (0.0–0.06 wt.%). The analysed zircons contain low Hf concentrations (0.9–1.65 wt.% HfO2, 0.00–0.013 apfu Hf). The composition of monazites form the Pavlov and Pohled granitoids plot close to the huttonite vector.
The support of the Long-Term Conceptual Development Research Organisation RVO 67985891 is thanked, Z.D. acknowledge 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 grateful to R. Škoda and J. Haifler for their technical assistance by using electron microprobe analyses of selected minerals (plagioclase, biotite, zircon, monazite). We are also grateful for constructive comments of an anonymous reviewer and to F. Finger for new, unpublished data of Ti-zircon thermometry of the Mauthausen granite.
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Written By
Miloš René and Zdeněk Dolníček
Submitted: 16 January 2023Reviewed: 28 February 2023Published: 28 March 2023
Open access peer-reviewed chapter
