**2. Geological setting**

The Moldanubian batholith forms one of the plutonic complexes within the Central European Variscan belt, covering 10,000 km2 [5] (**Figure 1**). In detail, the Moldanubian batholith is built by multiple plutons, predominantly composed of granitic to granodioritic rocks with either S- or transitional I/S-type character [5–7]. All these granitic rocks can be classified into three main suites. These three suites are represented as (1) coarse-grained, porphyritic I- to I/S-type biotite granites to

**23**

electron microprobe analyzed allanite.

*Allanite from Granitic Rocks of the Moldanubian Batholith (Central European Variscan Belt)*

granodiorites of the Weinsberg suite, (2) medium grained, partly porphyritic twomica S-type granites of the Eisgarn suite, and (3) fine- to medium-grained I/S-type

A significant part of the Weinsberg suite is in situ evolved Schlieren granite, which occurs in the Upper Mühlviertel area (Austria) and attached area of the Bavaria (Germany). Diffuse and irregular contacts, transitional rock varieties, and intrusion of one granite to the other indicate that the Schlieren and Weinsberg granites coexisted as magmas; thus, they are of the same age [9]. However, in the past, the Schlieren granite was originally mapped and described as "coarse grained gneiss" [10]. With intrusion of the Weinsberg granite suite in the Bavarian and Austrian part of the Moldanubian batholith are also connected intrusions of diorite

Two petrographic varieties were identified in the main body of the Freistadt suite in the Austrian Mühlviertel, the coarse-grained "marginal variety", and medium-grained "central variety" [12]. Allanite, however, occurs only in granodio-

The granitic rocks of the Moldanubian batholith are in some cases intruded by dykes of microdiorites, microgranodiorites, granite and melasyenite porphyries, and stock of highly fractionated two-mica and muscovite granites [11, 13–19].

Allanite was more commonly found in the Schlieren granite of the Weinsberg suite. As a relatively rare accessory mineral, allanite occurs also in diorites connected with granodiorites of the Weinsberg suite, in granodiorites of the Freistadt/ Mauthausen suite and in microgranodiorites occurring on the eastern margin of the

Allanite together with selected rock-forming minerals (plagioclase, biotite) was analyzed in polished thin sections. The back-scattered electron (BSE) images were acquired to study the internal structure of individual allanite grains. Element abundances of Al, Ca, Ce, Dy, Er, Eu, F, Fe, Gd, Ho, La, Lu, Mg, Mn, Na, Nd, P, Pb, Pr, Sc, Si, Sm, Sr, Tb, Th, Ti, Tm, U, Y, and Yb were determined using a CAMECA SX-100 electron microprobe operated in wavelength-dispersive mode. The concentrations of these elements were determined using an accelerating voltage and a beam current of 15 kV and 20 nA, respectively, with a beam diameter of 2–5 μm. The following standards, X-ray lines, and crystals (in parentheses) were used: AlKα—sanidine (TAP), CaKα—fluorapatite (PET), CeLα—CePO4 (PET), DyLα— DyPO4 (LiF), ErLα—ErPO4 (PET), EuLβ—EuPO4 (LIF), FeKα—almandine (LiF), GdLβ—GdPO4 (LiF), HoLβ—HoPO4 LiF), LaLα—LaPO4 (PET), LuMβ—LuAg (TAP), MgKα—spessartine (LIF), NdLβ—NdPO4 (LIF), PKα—fluorapatite (PET), PbMα—vanadinite (PET), PrLα—PrPO4 (LIF), SrLα—SrSO4 (TAP), ScKα—ScP5O14 (PET), SiKα—sanidine (TAP), SmLβ—SmPO4 (LIF), TbLα—TbPO4 (LIF), ThMβ— CaTh(PO4)2 (PET), TiKα—anatas (PET), TmLα—TmPO4 (LiF), UMβ—metallic U (PET), and YLα—YPO4 (PET). Intra-REE overlaps were partially resolved using Lα and Lβ lines. Empirically determined coincidences were applied after analysis: ThMα on the PbMα line and ThMγ on the UMβ line. The raw data were converted into concentrations using appropriate PAP-matrix corrections [20]. The detection limits were approximately 400 pm for Y, 180–1700 ppm for REE, and 800–1000 ppm for U and Th. The plot (REE + Y + Th + Mn + Sr) vs. Al proposed by Petrík et al. [21] was used for estimation of the Feox = Fe3+/(Fe3+ + Fe2+) ratio by

biotite granites to granodiorites of the Freistadt/Mauthausen suite [5, 6, 8].

*DOI: http://dx.doi.org/10.5772/intechopen.86356*

stocks (diorite 1) [11].

rites of the "marginal variety".

**3. Sampling and methods**

Klenov pluton.

### **Figure 1.**

*Geological map of the Moldanubian batholith (after [5], modified by the author).*

### *Allanite from Granitic Rocks of the Moldanubian Batholith (Central European Variscan Belt) DOI: http://dx.doi.org/10.5772/intechopen.86356*

granodiorites of the Weinsberg suite, (2) medium grained, partly porphyritic twomica S-type granites of the Eisgarn suite, and (3) fine- to medium-grained I/S-type biotite granites to granodiorites of the Freistadt/Mauthausen suite [5, 6, 8].

A significant part of the Weinsberg suite is in situ evolved Schlieren granite, which occurs in the Upper Mühlviertel area (Austria) and attached area of the Bavaria (Germany). Diffuse and irregular contacts, transitional rock varieties, and intrusion of one granite to the other indicate that the Schlieren and Weinsberg granites coexisted as magmas; thus, they are of the same age [9]. However, in the past, the Schlieren granite was originally mapped and described as "coarse grained gneiss" [10]. With intrusion of the Weinsberg granite suite in the Bavarian and Austrian part of the Moldanubian batholith are also connected intrusions of diorite stocks (diorite 1) [11].

Two petrographic varieties were identified in the main body of the Freistadt suite in the Austrian Mühlviertel, the coarse-grained "marginal variety", and medium-grained "central variety" [12]. Allanite, however, occurs only in granodiorites of the "marginal variety".

The granitic rocks of the Moldanubian batholith are in some cases intruded by dykes of microdiorites, microgranodiorites, granite and melasyenite porphyries, and stock of highly fractionated two-mica and muscovite granites [11, 13–19].
