Introductory Chapter: Mineralogy, Geochemistry and Metallogeny of Granites

*Miloš René*

### **1. Introduction**

Granites are usually a medium- to coarse-grained magmatic rocks composed mostly of quartz, K-feldspar and plagioclase. The granites originated from magma with a higher content of silica and alkali metal oxides, which cool slowly and solidify in different levels of the continental crust. Granites in this continental crust form bodies of highly different size and form. The biggest bodies of granites form the batholiths, which could expose over more as hundreds of square kilometres. Granites are the most significant member of a larger family of granitic rocks and/or granitoids. The individual members of granitic rocks are classified according to their content of quartz, K-feldspar and plagioclase, based on international QAPF classification that was adopted by the International Union of Geological Sciences (IUGS) [1]. The granitic rocks and/or granites usually contain as minor mineral components such as micas (biotite, muscovite, Li-micas), amphiboles and pyroxenes. For granites, granitic rocks are also significant content of accessory minerals, as well as ilmenite, magnetite, apatite, zircon, monazite and xenotime. In some types of granites, which are associated with Sn-W mineralisation, are very significant accessory mineral topaz. Granites have significant highly different textures, from equigranular to porphyritic. Some cases have individual mineral grains, mostly grains of K-feldspars larger than the rock groundmass that form phenocrysts of different size (usually up to 2–5 centimetres) (**Figure 1**). Granites that occur in nature are usually lighter-coloured rocks with scattered darker minerals such as biotite, amphibole and/or relative scarce pyroxene.

### **2. Mineralogy**

Mineralogy of granites was all the time studied using polarisation microscopy. For this research are recently used highly sophisticated polarisation microscopes produced by the Carl Zeiss and Leica Microsystems companies from Germany and/or the Olympus company from Japan. All these polarisation microscopes use different number of oculars and objectives. For presentation of microphotographs, microscopes use highly sophisticated digital cameras having high resolution. For simple manipulation with these cameras, good software is provided, which could also

**Figure 1.** *Phenocryst of zoned K-feldspar in two-mica granite, Smrčiny pluton, Bohemian massif.*

analyse these pictures with different possibilities of qualitative and/or quantitative analyses of investigated granite samples.

Some other, also frequently used microscopic investigations of granites are using cathodoluminescence. Cathodoluminescence imaging is a very powerful tool to identify the intergrowth textures of different minerals, especially of quartz, K-feldspar and topaz (**Figures 2** and **3**). For the cathodoluminescence in mineralogy are used two different methods. By using of optical microscope cathodoluminescence (OM-CL), the CL spectra and colour images are obtained using a hot-cathode luminescence microscope. For the study of electron microscope cathodoluminescence (SEM-CL) are used electron microscopes and or electron microprobes equipped by different CL detectors [2–4]. The SEM-CL cathodoluminescence produced more detailed pictures of intergrowth textures, used also for detailed study of zoning of accessory minerals (zircon). For detailed microscopic study, different accessory minerals, especially zircon, are recently used through scanning electron microscopes.

### **3. Geochemistry**

The chemical analyses of granites and their rock-forming and accessory minerals are recently very useful methods, which are sometimes distinctly more used in comparison with microscopy-oriented investigations of these rocks. For chemical analysis, main rock-forming components are recently used, predominantly the X-rayfluorescence analysis (XRF), without decomposition of rock samples in solutions. For the analysis of rare elements, as well as for instance Ba, Sr., Rb, Zr, Y and REE

*Introductory Chapter: Mineralogy, Geochemistry and Metallogeny of Granites DOI: http://dx.doi.org/10.5772/intechopen.113106*

#### **Figure 2.**

*Growth structures of late-magmatic snowball quartz from highly fractionated lithium granite, Krásno-Horní Slavkov Sn-W ore deposit, Bohemian massif.*

#### **Figure 3.**

*Growth structures of topaz from highly fractionated lithium granite, Krásno-Horní Slavkov Sn-W ore deposit, Bohemian massif (Tpz—Topaz).*

are recently used two different analytical methods, instrumental neutron activation analysis (INAA) and/or inductive coupled plasma emission mass spectrometry (ICP-MS) [5]. The XRF analyses are produced usually by the majority of mineralogical and geochemical institutes and/or geological surveys in different countries in the whole world. The production of INNA analysis is more complicated and is coupled with the presence of nuclear reactors. The production of ICP-MS analysis is concentrated on relatively a small number of geochemical institutes. However, the INNA and ICP-MS analyses of different geological materials could be well obtained from two

geochemical laboratories in Canada (Act Labs and ACME). Both commercial laboratories are equipped with very sophisticated laboratory equipment and could produce very good chemical analyses, which are certified by a high number of international geochemical standards.

The significant part of geochemical analyses recently represents chemical analyses of rock-forming and especially accessory minerals. For these purposes are used scanning electron microscopes equipped by energy-dispersive X-ray detectors (EDS) or more better electron microprobe analysers (EMPA), which are equipped with EDS detectors and wavelength-dispersive X-ray detectors (WDS), which are more suitable for quantitative analyses of rare elements, inclusive of REE. Recently are predominantly used microprobes produced by CAMECA in France and JEOL in Japan. The main interest is usually concentrated on detailed chemical analyses of different accessory minerals, predominantly on analyses of zircon, monazite and xenotime. By study of granites coupled with different ore mineralisation (Sn-W, U) the microprobe analyses are concentrated also on chemistry of Sn-W-Nb-Ta minerals and different uranium- and thorium-bearing minerals.

The important part of geochemistry represents interpretation and presentation of geochemical data. For these purposes are recently used predominantly two different software packages, the commercial software Minpet [6] and free available software GCDKit [7]. The software Minpet could be used only with Windows, version 7, whereas software GCDKit could be used under Windows versions 7-11. This software offers distinctly more possibilities for presentation and interpretation chemical analyses of granites, together with their statistical analyses, determination of granite melt temperatures based on analyses of Zr and REE and basic principles of geochemical modelling igneous processes.

The predominantly used geochemical classifications of granites are based on the determination of A/CNK ratio (mol. Al2O3/(CaO + Na2O + K2O). According this ratio are granites classified as peraluminous or metaluminous granites and/or as S- and I-type granites [8, 9]. Some other classifications of granites on I- and S-types are based on distribution of magnetite or ilmenite [10]. Similar classification of granitic rocks is based on modified alkali-lime index (Na2O + K2O – CaO) and content of SiO2. According to this classification, the granites could be distinguished on alkalic, alkali-calcic, calc-alkalic and calcic granitic rock [11]. Some other geochemical family of granites is A-type granites (anorogenic) which are in detail classified using the determinations of Al, Ga, Nb, Ta, Y and Zr [12, 13].

### **4. Metallogeny**

Granites are very often associated with different types of ore mineralisation, predominantly with U and Sn-W-Li bearing mineralisation. The mineralised granites are in these cases altered in different rock types, as well as aceites, episyenites and greisens. The basic internationally accepted terminology of these hydrothermally altered granitic rocks was adopted by the International Union of Geological Sciences (IUGS) [14].

The origin of aceites is coupled with uranium mineralisation originated in shear zones, which occurs in granitic rocks or in highly metamorphosed rocks (paragneisses). These rock series are usually altered in mixture of albite, chlorite and clay minerals, with different distributions of uranium minerals (uraninite, coffinite) (**Figure 4**). This low-temperature hydrothermal alteration is coupled with significant *Introductory Chapter: Mineralogy, Geochemistry and Metallogeny of Granites DOI: http://dx.doi.org/10.5772/intechopen.113106*

#### **Figure 4.**

*Back scattered electron (BSE) image of uraninite and coffinite from uranium deposit Okrouhlá Radouň, Bohemian massif (urn—Uraninite, Cfn—Coffinite).*

removal of original magmatic quartz. For describing of these altered rocks, evolved in disseminated uranium deposits in the Massif Central and Armorican Massif, France, were in the past used term episyenites [15, 16]. However, according to the recent IUGS classification for metasomatic rocks [14], the term episyenite could be abandoned. The term aceite was introduced to geosciences by Omel'yanenko [17].

The greisenisation is one of most significant hydrothermal alterations, which occurs in granite-related Sn-W ore deposits. Historically, the term 'greisen' has been used firstly by miners from the Krušné Hory/Erzgebirge Mts. to describe wall rocks consisting of quartz, Li-mica and topaz surrounding the Sn-W mineralisation, which occurs in this area [18]. This area hosts a number of Sn-W deposits (e.g. Cínovec/Zinnwald, Altenberg, Ehrenfriedersdorf, Krásno-Horní Slavkov) bound to greisenised granite stocks of the Variscan granite bodies. These granites represent highly fractionated, high-F, Li-mica granites of the Krušné Hory/Erzgebirge batholith [19].

### **5. Conclusions**

The chapter discussed the composition of granites, together with used mineralogical and geochemical methods, which are recently used for description and discussion of their composition and origin. The mineralogical and geochemical methods, together with study of relation of granites to uranium and tin-tungsten ore deposits, are recently the most significant research methods used in geoscience.

## **Acknowledgements**

The author would like to thanks to the support of the long-term conceptual development research organisation RVO: 67985891.

## **Conflict of interest**

There is no conflict of interest.

## **Author details**

Miloš René Institute of Rock Structure and Mechanics, v.v.i., Czech Academy of Sciences, Prague, Czech Republic

\*Address all correspondence to: rene@irsm.cas.cz

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Introductory Chapter: Mineralogy, Geochemistry and Metallogeny of Granites DOI: http://dx.doi.org/10.5772/intechopen.113106*

### **References**

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[3] Slaby E, Götze J, Wörner G, Simon K, Wrzalik R, Smigielski M. K-feldspar phenocrysts in microgranular magmatic enclaves: A cathodoluminescence and geochemical study of crystal growth as a marker of magma mingling dynamics. Lithos. 2008;**105**:85-97. DOI: 10.1016/j. lithos.2008.02.006

[4] Kempe U, Götze J. Cathodoluminescence (CL) behaviour and crystal chemistry of apatite from rare-metal deposits. Mineralogical Magazine. 2002;**66**:151-172. DOI: 10.1180/0026461026610019

[5] Rollinson HR. Using geochemical data: Evaluation, presentation, interpretation. Essex: Longham; 1993. p. 352

[6] Richard LR. MinPet: Mineralogica and Petrological Data Processing System, Version 2.02. Québec, Canada: MinPet Geological Software; 1988-1995

[7] Janoušek V, Moyen JF, Hervé M, Erban V, Farrow C. Geochemical Modelling of Igneous Processes – Principles and Recipes in R Language. Heidelberg: Springer. p. 346. DOI: 10.1007/978-3-662-46791-6

[8] Shand SJ. Eruptive Rocks. London: Thomas Murby& Co.; 1927. p. 360

[9] Chappell BW, White AJR. Two contrasting granite types. Pacific Geology. 1974;**8**:173-174

[10] Ishihara S. The magnetite-series and ilmenite-series granitic rocks. Mining Geology. 1977;**27**:293-305

[11] Frost BR, Frost CD. A geochemical classification for feldspathic igneous rocks. Journal of Petrology. 2008;**49**:1955-1969. DOI: 10.1093/ petrology/cgn054

[12] Whalen JB, Currie KI, Chappell BW. A-type granites: Geochemical characteristics, discrimination and petrogenesis. Contribution to Mineralogy and Petrology. 1987;**95**:407-419. DOI: 10.1007/BF00462202

[13] Eby GN. Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications. Geology. 1992;**20**:641-644. DOI: 10.1130/0091-7613(1992)020˂0637

[14] Fettes D, Desmons J, editors. Metamorphic Rocks. A Classification and Glossary of Terms. Cambridge: Cambridge University Press; 2007. p. 244

[15] Cathelineau M. The hydrothermal alkali metasomatism effects on granitic rocks. Quartz dissolution and related subsolidus changes. Journal of Petrology. 1986;**27**:945-965. DOI: 10.1093/petrology 127.4.945

[16] Leroy J. The Margnac and Fanay uranium deposits of the Le Crouzille district (western massif central, France): Geologic and fluid inclusion studies. Economic Geology. 1978;**73**:1611-1634. DOI: 10.2113/gsecongeo.73.8.1811

[17] Omelýanenko BI. Wall-Rock Hydrothermal Alterations. Moscow: Nedra Publishing House; 1978. p. 215 (in Russian)

[18] Lempe JF. Beschreibung des Bergbaues aus dem Sächsiscen Zinnwalde. Magazin für die Bergbaukunde. 1785;**1**:100-142

[19] Förster HJ, Tischendorf G, Trumbull RB, Gottesmann B. Latecollisional granites in the Variscan Erzgebirge, Germany. Journal of Petrology. 1999;**40**:1613-1645. DOI: 10.1093/petroj/40.11.1613

### **Chapter 2**

## Granitoids of the Mauthausen Type in the Czech Part of the Moldanubian Batholith

*Miloš René and Zdeněk Dolníček*

### **Abstract**

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.

**Keywords:** granite, Moldanubian batholith, bohemian massif, petrology, geochemistry

### **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**) [1–3]. 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

### **Figure 1.**

*Geological map of the Moldanubian Batholith (after [1, 2], modified by authors).*

Czech Republic (**Figure 2**) [6–9]. 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.

### **2. Geological setting**

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

*Granitoids of the Mauthausen Type in the Czech Part of the Moldanubian Batholith DOI: http://dx.doi.org/10.5772/intechopen.113101*

#### **Figure 2.**

*Geological map of the northern part of the Moldanubian Batholith (after [6], modified by authors).*

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].

### **3. Materials and methods**

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 backscattered 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, Xray lines and crystals (in parentheses) were used: AlK<sup>α</sup> – sanidine (TAP), CaK<sup>α</sup> – fluorapatite (PET), CeL<sup>α</sup> – CePO4 (PET), ClK<sup>α</sup> – vanadinite (LPET), DyL<sup>α</sup> – DyPO4 (LLIF), ErL<sup>α</sup> – ErPO4 (PET), EuL<sup>β</sup> – (LLIF), FK<sup>α</sup> – topaz (PC1), FeK<sup>α</sup> – almandine (LLIF), GdL<sup>β</sup> – GdPO4 (LLIF), HfM<sup>α</sup> – Hf (TAP), KK<sup>α</sup> – sanidine (TAP), LaL<sup>α</sup> – LaPO4 (PET), MgK<sup>α</sup> –Mg2SiO4 (TAP), MnK<sup>α</sup> –spessartine (LLIF), NaK<sup>α</sup> – albite (PET), NbL<sup>α</sup> – columbite, Ivigtut (LPET), NdL<sup>β</sup> – NdPO4 (LLIF), PK<sup>α</sup> – fluorapatite (PET), PbM<sup>α</sup> – vanadinite (PET), PrL<sup>β</sup> – PrPO4 (LLIF), RbL<sup>α</sup> –RbCl (LTAP), SK<sup>α</sup> – SrSO4 (LPET), ScKα – ScP5O14 (PET), SiK<sup>α</sup> – sanidine (TAP), SmL<sup>β</sup> – SmPO4 (LLIF), SrL<sup>α</sup> – SrSO4 (TAP), TaM<sup>α</sup> – CrTa2O6 (TAP), TbL<sup>α</sup> – TbPO4 (LLIF), ThM<sup>α</sup> – CaTh (PO4)2 (PET), TiK<sup>α</sup> – anatase (PET), UM<sup>β</sup> –metallic U (PET), VK<sup>β</sup> – vanadinite (LPET), YL<sup>α</sup> – YPO4 (PET), YbL<sup>α</sup> –YbPO4 (LLIF) and ZrL<sup>α</sup> – 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– *Granitoids of the Mauthausen Type in the Czech Part of the Moldanubian Batholith DOI: http://dx.doi.org/10.5772/intechopen.113101*

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 OHapatites was performed according to Piccoli and Candela [16]. Mole fractions for components in monazite and xenotime were calculated according to Pyle et al. [17].

### **4. Results**

### **4.1 Petrology**

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 3.**

*Microphotograph of the Pavlov biotite-muscovite granite (Bt – Biotite, Kfs – K-feldspar, Ms. – Muscovite, Pl – Plagioclase, Qz – Quartz), thin section, crossed polarizers.*

**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**).

### **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).


*Granitoids of the Mauthausen Type in the Czech Part of the Moldanubian Batholith DOI: http://dx.doi.org/10.5772/intechopen.113101*

#### **Table 1.**

*Representative compositions of the Pavlov and Pohled granitoids.*

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.

### *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**).

#### **Figure 5.**



#### **Table 2.**

*Representative microprobe analyses of apatite (wt. %).*

### *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


#### **Table 3.**

*Representative microprobe analyses of zircon (wt. %).*

#### **Figure 6.** *Chemical composition of zircon.*

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).

### *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,


*Granitoids of the Mauthausen Type in the Czech Part of the Moldanubian Batholith DOI: http://dx.doi.org/10.5772/intechopen.113101*


#### **Table 4.**

*Representative microprobe analyses of monazite (wt. %).*

#### **Figure 7.** *Chemical composition of 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**).

### **5. Discussion**

In the past, the origin and fractionation of granitic rocks of the Moldanubian Batholith was discussed by geochemical modelling based on trace-element

*Granitoids of the Mauthausen Type in the Czech Part of the Moldanubian Batholith DOI: http://dx.doi.org/10.5772/intechopen.113101*

**Figure 8.** *Distribution of Ba an Sr in analysed rocks.*

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, 19–21]. 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**).

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 [23–25]. 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

**Figure 9.** *Distribution of Th and Zr in analysed rocks.*

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 Stype 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].

### **6. Conclusions**

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 metagreywackemetabasalt 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.

### **Acknowledgements**

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.

### **Conflict of interest**

The authors declare no conflict of interests.

*Recent Advances in Mineralogy*

### **Author details**

Miloš René<sup>1</sup> \* and Zdeněk Dolníček2

1 Institute of Rock Structure and Mechanics, v.v.i., Czech Academy of Sciences, Prague, Czech Republic

2 National Museum, Prague, Czech Republic

\*Address all correspondence to: rene@irsm.cas.cz

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Granitoids of the Mauthausen Type in the Czech Part of the Moldanubian Batholith DOI: http://dx.doi.org/10.5772/intechopen.113101*

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### **Chapter 3**
