Emplacement depths and radiometric ages of Paleozoic plutons of ...

Emplacement depths and radiometric ages of Paleozoic plutons of 

the Neukirchen–Kdyně massif: differential uplift and exhumation 

of Cadomian basement due to Carboniferous orogenic collapse 

(Bohemian Massif) 

Abstract 

Tectonophysics 352 (2002) 225–243 

Curd Bues a , Wolfgang Dörr b , Jirˇi Fiala c , Zdeněk Vejnar c , Gernold Zulauf d, * 

a Celtesstr. 14, D-85051 Ingolstadt, Germany 

b Institut für Geowissenschaften und Lithosphärenforschung, Universität Giessen, Senckenbergstr. 3, D-35390 Giessen, Germany 

c Geologicky´ ústav, AVČR, Rozvojová 135, CS-16500 Prague 6, Suchdol, Czech Republic 

d Institut für Geologie und Mineralogie, Universität Erlangen, Schloßgarten 5, D-91054 Erlangen, Germany 

Received 26 February 2001; accepted 12 December 2001 

The igneous complex of Neukirchen–Kdyně is located in the southwestern part of the Teplá–Barrandian unit (TBU) in the 

Bohemian Massif. The TBU forms the most extensive surface exposure of Cadomian basement in central Europe. Cambrian 

plutons show significant changes in composition, emplacement depth, isotopic cooling ages, and tectonometamorphic overprint 

from NE to SW. In the NE, the Vsˇepadly granodiorite and the Smrzˇovice diorite intruded at shallow crustal levels (< ca. 7 km 

depth) as was indicated by geobarometric data. K–Ar age data yield 547 F 7 and 549 F 7 for hornblende and 495 F 6 Ma for 

biotite of the Smrzˇovice diorite, suggesting that this pluton has remained at shallow crustal levels (T < ca. 350 jC) since its 

Cambrian emplacement. A similar history is indicated for the Vsˇepadly granodiorite and the Stod granite. In the SW, 

intermediate to mafic plutons of the Neukirchen–Kdyně massif (Vsˇeruby and Neukirchen gabbro, Hoher–Bogen metagabbro), 

which yield Cambrian ages, either intruded or were metamorphosed at considerably deeper structural levels (> 20 km). The 

Teufelsberg (Čertu˚v kámen) diorite, on the other hand, forms an unusual intrusion dated at 359 F 2 Ma (concordant U–Pb 

zircon age). K–Ar dating of biotite of the Teufelsberg diorite yields 342 F 4 Ma. These ages, together with published cooling 

ages of hornblende and mica in adjacent plutons, are compatible with widespread medium to high-grade metamorphism and 

strong deformation fabrics, suggesting a strong Variscan impact under elevated temperatures at deeper structural levels. The 

plutons of the Neukirchen area are cut by the steeply NE dipping Hoher–Bogen shear zone (HBSZ), which forms the boundary 

with the adjacent Moldanubian unit. The HBSZ is characterized by top-to-the-NE normal movements, which were particularly 

active during the Lower Carboniferous. A geodynamic model is presented that explains the lateral gradients in Cambrian pluton 

composition and emplacement depth by differential uplift and exhumation, the latter being probably related to long-lasting 

movements along the HBSZ as a consequence of Lower Carboniferous orogenic collapse. D 2002 Elsevier Science B.V. All 

rights reserved. 

Keywords: Cadomian orogeny; Variscan orogenic collapse; Corona gabbro; Teplá–Barrandian unit; Bohemian Massif 

* Corresponding author. Tel.: +49-9131-852-2617; fax: +49-9131-852-9295. 

E-mail address: zulauf@geol.uni-erlangen.de (G. Zulauf). 

0040-1951/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. 

PII: S0040-1951(02)00198-1 

www.elsevier.com/locate/tecto

226 

1. Introduction 

The southwestern Bohemian Massif has been subdivided 

into the Teplá–Barrandian unit (TBU) and the 

Moldanubian unit that differ from one another in their 

magmatic and tectonometamorphic evolution (e.g., 

Matte et al., 1990; Franke et al., 1995). Wide areas 

of the TBU consist of a Cadomian (Pan-African) lowgrade 

or very low-grade metamorphic basement that 

underwent deformation and metamorphism near the 

Proterozoic/Cambrian boundary. Electron microprobe 

dating of metamorphic monazite yielded 540–550 Ma 

(Zulauf et al., 1999). High-grade metamorphic rocks, 

on the other hand, prevail in the Moldanubian unit 

where the major tectonometamorphic imprint 

occurred during the Carboniferous (e.g., Kalt et al., 

2000). Cambrian plutons of mafic to felsic composition 

are characteristic for the TBU. Carboniferous 

granitoids, on the other hand, predominate in the 

Moldanubian unit and are related to the steeply dipping 

West Bohemian, Central Bohemian, and Hoher– 

Bogen shear zone (WBSZ, CBSZ, HBSZ), all of 

which form the boundary between the TBU and the 

Moldanubian unit (Fig. 1). 

In the southwestern TBU, plutons of the Neukirchen–Kdyně 

massif (NKM; Fig. 1) are time and 

depth markers that help to distinguish between Cadomian 

and Variscan tectonometamorphic imprints. In 

this study, we present new petrographic, geothermobarometric, 

U–Pb and K–Ar data derived from mafic 

to intermediate plutons of the NKM. These data yield 

constraints on (1) the protolith age, (2) the emplacement 

depth, and (3) the cooling history of the plutons. 

A clear relation between composition and emplacement 

depth will be shown by comparing and combining 

the new data with published emplacement and 

cooling ages of adjacent plutons. Finally, we present 

structural and kinematic data of the HBSZ, which 

suggest that the lateral gradients in composition, 

emplacement depth, and cooling ages of the plutons 

are related to Carboniferous orogenic collapse. 

C. Bues et al. / Tectonophysics 352 (2002) 225–243 

2. Geological setting 

The Neukirchen–Kdyně massif is the largest mafic 

to intermediate igneous complex in the Bohemian 

Massif. It consists of several intrusions that cover an 

area of about 300 km 2 (Fig. 1). Gabbro, olivine 

gabbro, gabbronorite, peridotite, and pyroxene diorite 

are dominant in the SW, whereas quartz diorite 

(F granodiorite) predominate in the NE. Cambrian 

intrusion ages were determined for the following 

plutons of the NKM and adjacent areas (see Fig. 1 

for locations and distribution of ages): Vsˇepadly 

granodiorite (524 F 3 Ma, U–Pb on zircon, Dörr et 

al., this volume), Smrzˇovice quartz diorite (504 F 30 

Ma, Rb–Sr whole rock, Miethig, 1995; 523 F 3 Ma, 

U–Pb on zircon, Dörr et al., this volume), Orlovice 

diorite (522 Ma, U–Pb on zircon, Dörr et al., this 

volume), Těsˇovice granite of the Stod pluton (522 F 2 

Ma, U–Pb on zircon, Zulauf et al., 1997), Mračnice 

trondhjemite of the Domazˇlice crystalline complex 

(523 + 4/ 5 Ma, U–Pb on zircon, Zulauf et al., 

1997). Cambrian magmatism is also indicated by a 

concordant U–Pb zircon age of an amphibolite within 

the HBSZ (511 F 3 Ma, Gebauer, 1993; Fig. 1). The 

country rocks of the plutons consist of mafic metavolcanics 

with intercalations of metagreywackes, 

metasiltstones, and metapelites (Vejnar, 1986, 1991). 

Rocks of the southwestern NKM were strongly 

affected by Variscan medium-pressure metamorphism 

and deformation (Bues, 1992). The most deformed 

and metamorphosed rocks occur within the HBSZ, a 

sharply bent belt of mylonitic amphibolite, metaultrabasite, 

and garnet pyriclasite (Bues et al., 1998; 

Bues and Zulauf, 2000; Fig. 1). The HBSZ connects 

the WBSZ (Zulauf, 1994) with the CBSZ (Scheuvens 

and Zulauf, 2000), all of which are high-angle normal 

shear zones that dip towards the TBU. A minimum 

extensional throw of 10 km has been determined for 

both the WBSZ (Zulauf et al., 2002) and the CBSZ 

(Scheuvens and Zulauf, 2000). A similar minimum 

throw is inferred for the HBSZ. 

Fig. 1. Geological map of the Neukirchen–Kdyně massif (modified, according to Vejnar, 1986; Bues, 1992) with structural data of the Hoher– 

Bogen shear zone, sample locations described in the text (numbers 1 – 8) and geochronological data ((1) Vejnar (1962); (2) Fischer et al. (1968); 

(3) Kreuzer et al. (1989); (4) Kreuzer et al. (1990); (5) Kreuzer et al. (1992); (6) Gebauer (1993); (7) Dörr et al. (1996); (8) Dörr et al. (1997); (9) 

Zulauf et al. (1997); (10) Dallmeyer and Urban (1998); (11) Wemmer and Ahrendt (unpublished); (12) Dörr et al. (2002); (13) this study. HBSZ, 

NBSZ, WBSZ, CBSZ = Hoher–Bogen, North, West, Central Bohemian shear zone, respectively; AF = Andělice fault.

C. Bues et al. / Tectonophysics 352 (2002) 225–243 227

Table 1 

Composition of analysed minerals (average values) 

(A) Plagioclase (Pl) and potassium feldspar (Ksp) analyses (Pl_c = plagioclase core, Pl_r = plagioclase rim) 

No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 

Pl_c Pl_c Kfs Pl_c Pl_r Pl_c Pl_r Pl_c Pl_r Pl Pl Pl Pl Pl Pl Pl Pl Pl Pl 

SiO2 57.41 66.74 65.03 54.75 63.64 53.89 57.10 50.05 53.57 51.94 50.69 50.50 55.41 51.15 53.06 54.08 56.80 57.11 50.97 

TiO2 0.00 0.01 0.01 0.03 0.01 0.03 0.02 0.07 0.08 0.06 0.04 0.05 0.01 0.03 0.01 0.09 0.01 0.02 0.00 

Al2O3 26.55 20.52 17.89 28.64 22.96 29.56 27.36 32.44 30.01 30.36 31.06 31.48 28.53 30.69 29.67 28.96 26.98 26.92 32.02 

FeO * 0.06 0.20 0.02 0.26 0.07 0.07 0.11 0.13 0.09 0.20 0.08 0.05 0.13 0.04 0.07 0.14 0.05 0.09 0.05 

MnO 0.00 0.01 0.01 0.02 0.01 0.01 0.00 0.01 0.01 0.01 0.02 0.02 0.01 0.02 0.02 0.03 0.02 0.02 0.00 

MgO 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.05 0.00 0.04 0.01 0.01 0.00 0.01 0.00 0.06 0.01 0.01 0.00 

CaO 8.95 1.94 0.06 11.45 4.09 11.05 8.50 14.21 11.52 12.71 13.84 13.78 10.21 13.41 12.07 11.11 9.04 8.93 13.84 

Na2O 6.25 10.13 1.25 5.02 8.77 4.97 6.32 3.37 4.89 4.11 3.61 3.50 5.27 3.80 4.74 5.19 6.18 6.16 3.78 

K2O 0.13 0.16 14.77 0.19 0.19 0.20 0.23 0.02 0.01 0.09 0.03 0.04 0.15 0.04 0.04 0.04 0.17 0.26 0.01 

Total 99.35 99.71 99.04 100.37 99.74 99.78 99.64 100.35 100.18 99.52 99.38 99.43 99.72 99.19 99.68 99.70 99.26 99.52 100.67 

An 43.80 9.50 0.30 55.20 20.30 54.50 42.10 69.90 56.50 62.80 67.80 68.40 51.20 66.00 58.30 54.10 44.20 43.80 66.90 

Ab 55.40 89.60 11.40 43.70 78.60 44.40 56.60 30.00 43.40 36.70 32.00 31.40 47.80 33.80 41.50 45.70 54.70 54.70 33.00 

Or 0.80 0.90 88.30 1.10 1.10 1.10 1.30 0.10 0.10 0.50 0.20 0.20 0.90 0.20 0.20 0.20 1.00 1.50 0.10 

(B) Amphibole (Am) and biotite (Bt) analyses (Am_cor = corona amphibole) 

No. 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 

Am Am Am Am Am Am Am Am_cor Am Am_cor Am_cor Am_cor Am Am Am Bt Bt 

SiO2 44.04 45.40 47.91 48.38 52.09 44.30 41.86 42.95 49.30 43.37 41.56 40.84 44.47 46.53 43.53 35.40 35.48 

TiO2 1.48 1.11 0.95 0.86 0.09 1.21 2.91 0.03 0.99 0.05 0.31 0.06 1.32 1.27 1.64 3.15 4.08 

Al2O3 6.32 6.30 5.34 5.02 2.13 12.67 14.22 17.02 6.02 17.71 16.60 18.08 10.83 9.78 11.30 15.71 15.82 

FeO * 28.06 24.39 23.98 16.59 17.53 9.14 10.88 5.52 15.23 6.76 9.41 11.91 17.96 15.08 19.25 25.57 20.75 

MnO 0.51 0.87 0.92 0.28 0.39 0.22 0.14 0.13 0.20 0.10 0.14 0.23 0.18 0.23 0.20 0.37 0.07 

MgO 5.36 6.79 7.32 13.49 13.63 15.94 13.26 15.96 13.79 15.22 14.05 13.04 9.71 12.65 8.98 6.60 9.96 

CaO 9.71 10.93 10.81 11.05 10.97 10.90 11.95 11.90 11.04 11.71 11.86 10.29 11.12 10.94 10.63 0.08 0.01 

Na2O 1.60 1.02 0.77 0.53 0.11 2.39 2.22 2.51 0.61 2.56 2.85 3.27 1.28 1.04 1.19 0.06 0.19 

K2O 0.66 0.63 0.52 0.30 0.11 0.21 0.79 0.18 0.32 0.21 0.24 0.28 0.61 0.57 0.68 8.95 8.77 

Cr2O3 0.01 0.00 0.02 0.03 0.00 0.04 0.06 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.01 

NiO 0.01 0.01 0.00 0.01 0.03 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 

Total 97.76 97.45 98.54 96.54 97.08 97.02 98.30 96.20 97.53 97.69 97.02 98.00 97.48 98.09 97.40 95.92 95.14 

228 

C. Bues et al. / Tectonophysics 352 (2002) 225–243

(C) Orthopyroxene (Opx) and clinopyroxene (Cpx) analyses (Opx_cor = corona orthopyroxene, Cpx_cor = corona clinopyroxene) 

No. 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 

Cpx Opx Cpx Cpx Cpx Opx Opx_cor Cpx Opx Cpx Opx Cpx Opx_cor Cpx Opx_cor Cpx Opx Cpx Opx Cpx Opx Cpx Cpx_cor Opx_cor 

SiO2 51.38 50.99 51.20 50.97 52.04 54.23 55.91 52.15 54.64 51.57 50.83 51.94 55.26 50.29 53.34 50.97 53.04 50.70 49.32 50.35 48.90 51.91 52.08 54.57 

TiO2 0.27 0.19 0.76 1.04 0.73 0.27 0.00 0.63 0.21 0.28 0.17 0.54 0.02 1.20 0.04 0.82 0.01 0.14 0.07 0.19 0.35 0.47 0.36 0.04 

Al2O3 0.96 0.80 3.09 3.32 3.64 2.54 0.90 3.35 2.06 1.45 0.74 4.05 1.15 4.17 1.66 2.74 1.12 1.24 0.69 1.46 0.91 5.26 5.34 3.47 

FeO * 13.33 28.41 5.89 7.52 4.26 11.22 11.25 4.52 11.87 11.72 29.81 5.43 13.44 7.42 18.13 9.37 21.03 13.82 32.92 14.65 33.75 3.25 3.44 11.77 

MnO 0.36 0.56 0.18 0.24 0.12 0.19 0.30 0.12 0.23 0.30 0.65 0.15 0.32 0.22 0.39 0.28 0.47 0.34 0.81 0.34 0.71 0.25 0.09 0.26 

MgO 12.91 17.80 16.81 15.46 16.45 28.71 30.22 16.48 29.03 12.78 17.53 16.36 28.86 14.38 25.58 14.93 23.52 11.36 14.46 10.10 12.99 15.04 14.84 29.74 

CaO 20.23 1.31 20.51 21.08 21.37 1.17 0.12 20.91 1.27 21.06 0.92 20.25 0.16 21.09 0.32 20.02 0.24 21.40 0.91 21.74 1.65 23.31 23.25 0.29 

Na2O 0.19 0.03 0.39 0.45 0.49 0.04 0.01 0.44 0.02 0.23 0.01 0.55 0.02 0.61 0.01 0.42 0.01 0.28 0.02 0.31 0.04 0.70 0.77 0.00 

K2O 0.00 0.00 0.00 0.00 0.02 0.01 0.02 0.01 0.01 0.01 0.01 0.02 0.01 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 

Cr2O3 0.07 0.03 0.36 0.14 0.97 0.54 0.02 0.70 0.34 0.02 0.02 0.53 0.02 0.20 0.05 0.09 0.01 0.02 0.02 0.02 0.02 0.15 0.03 0.03 

NiO 0.02 0.04 0.01 0.01 0.04 0.09 0.06 0.03 0.02 0.01 0.00 0.03 0.04 0.05 0.02 0.03 0.01 0.03 0.03 0.01 0.02 0.00 0.00 0.00 

Total 99.72 100.16 99.20 100.23 100.13 99.01 98.81 99.34 99.70 99.43 100.69 99.85 99.30 99.65 99.55 99.68 99.47 99.34 99.26 99.18 99.35 100.35 100.21 100.17 

(D) Olivine analyses 

No. 61 62 63 64 65 66 67 68 

Ol Ol Ol Ol Ol Ol Ol Ol 

SiO2 36.80 37.19 32.62 39.39 38.55 36.53 35.18 38.92 

TiO2 0.00 0.00 0.02 0.01 0.00 0.01 0.00 0.01 

Al2O3 0.00 0.02 0.00 0.02 0.00 0.00 0.00 0.01 

FeO * 30.13 26.12 50.81 18.81 21.31 30.34 37.48 18.17 

MnO 0.49 0.41 0.88 0.23 0.29 0.43 0.50 0.22 

MgO 33.34 35.55 15.52 41.32 39.13 32.44 26.54 42.19 

CaO 0.02 0.03 0.03 0.01 0.02 0.02 0.01 0.03 

Cr2O3 0.01 0.01 0.01 0.02 0.03 0.01 0.02 0.01 

NiO 0.02 0.05 0.03 0.12 0.06 0.08 0.04 0.20 

Total 100.81 99.38 99.92 99.93 99.39 99.86 99.77 99.76 

Numbers of localities mentioned in the text and depicted in Fig. 1 (encircled) are listed in parentheses. Numbers without parentheses refer to the numbers of the columns of the tables: 

Vsˇepadly granodiorite (1) 1–3, 20; Smrzˇovice quartz diorite (2) 4 + 5, 21 + 22, 35; Smrzˇovice pyroxene diorite (2) 6 + 7, 23 + 24, 37 + 38; Smrzˇovice olivine gabbro (2) 8 + 9, 25, 39, 

61; Orlovice olivine gabbro (3) 10, 26, 40, 62; Orlovice hortonolite rock (3) 63; Vsˇeruby olivine gabbro (4) 11, 27, 41–43, 64; Vsˇeruby gabbronorite (4) 12, 44 + 45; Vsˇeruby 

pyroxene diorite (4) 13, 28, 46 + 47; Neukirchen olivine gabbro (5) 14, 29, 48 + 49, 65; Neukirchen olivine gabbro (5) 15, 30, 50 + 51, 66; Teufelsberg olivine gabbro (6) 16, 31, 

52 + 53, 67; Teufelsberg pyroxene diorite (6) 17, 32, 54 + 55; Teufelsberg pyroxene diorite (7) 18, 33 + 34, 36, 56 + 57; Hoher – Bogen olivine metagabbro (8) 19, 58–60, 68. 


230 

Several plutons, predominantly of granitic composition, 

intruded into or adjacent to the WBSZ and 

CBSZ, parts of them synkinematically (Scheuvens, 

1999; Zulauf et al., 2002). Lower Carboniferous 

emplacement ages, ranging from ca. 330 to 350 Ma, 

have been determined for these intrusions by U–Pb 

and Pb–Pb zircon dating (e.g., Bor pluton, Mutěnín 

pluton, Babylon granite, Drahotín gabbro, Klatovy 

pluton, Ny´rsko pluton; Dörr et al., 1997; Central 

Bohemian pluton; Holub et al., 1997). Only the 

Teufelsberg (Čertu˚v kámen) diorite yields an Upper 

Devonian age (see below). 

In contrast to the TBU, the Moldanubian unit is 

characterized by widespread Carboniferous granitoids 

and anatexis, the age of which has recently been 

determined at 322–326 Ma (U–Pb on zircon and 

titanite, 40 Ar– 39 Ar on hornblende, Kalt et al., 2000). 

Lower grade mica schists and gneisses are restricted to 

the Královsky Hvozd crystalline complex, a Moldanubian 

subunit situated SE of the NKM (Fig. 1). In 

this area, metapelitic rocks partly contain kyanite 

relics of an early medium pressure metamorphism 

(Vejnar, 1991; Babu˚rek, 1995), suggesting a multistage 

metamorphic evolution within parts of the 

Moldanubian unit. The age of this medium pressure 

metamorphism (i.e., Cadomian or Variscan) has yet 

not been determined. However, microspores preserved 

within low grade metamorphic mica schists near 

Rittsteig suggest a Paleozoic protolith for at least 

parts of the Královsky Hvozd metasediments (Reitz, 

1992). Apart from these mica schists, the Moldanubian 

unit adjacent to the study area consists of a 

prograde succession of andalusite-bearing mica 

schists, cordierite sillimanite gneisses, and cordierite 

K-feldspar anatexites (Blümel, 1990). 

3. Methods 

The composition, emplacement depth, cooling history, 

and tectonometamorphic overprints of granodiorite, 

diorite, and gabbro of the Vsˇepadly, Smrzˇovice, 

Orlovice, Vsˇeruby, Neukirchen, Teufelsberg, and 

Hoher–Bogen–Rittsteig areas have been investigated 

(for localities, see encircled numbers 1–8 in Fig. 1). 

In the case of the Teufelsberg pluton, we also determined 

the protolith age. Geobarometric and geothermometric 

data were derived from the chemical 


compositions of olivine, pyroxene, amphibole, biotite, 

and feldspar, which were analysed at the Technische 

Universität Darmstadt and the Universität Würzburg 

using a Cameca SX-50 electron microprobe. The 

operating conditions were similar to those reported 

in Bues and Zulauf (2000). Summaries of representative 

mineral analyses are listed in Table 1. The mineral 

abbreviations used throughout the text are according 

to Kretz (1983). 

We applied the geothermometer of Blundy and 

Holland (1990) and Holland and Blundy (1994) to 

calculate equilibration temperatures of hornblende and 

plagioclase for the Vsˇepadly granodiorite and Smrzˇovice 

quartz diorite. These rocks also contain the 

appropriate buffer assemblage required for the Al-in- 

Hbl barometry according to Schmidt (1991) and 

Anderson and Smith (1995). Equilibration temperatures 

of orthopyroxene and clinopyroxene were calculated 

for the Smrzˇovice, Vsˇeruby, and Teufelsberg 

pyroxene diorite using the TWQ program of Berman 

(1991) together with the revised thermodynamic database 

of Berman et al. (1995) and Berman and Aranovich 

(1996). This method was also applied to the 

Opx–Cpx–Spl corona of the olivine metagabbro of 

the eastern Hoher–Bogen area. For the Vsˇeruby 

olivine gabbro and gabbronorite, we additionally used 

the Opx–Cpx geothermometer of Wells (1977). 

To carry out K–Ar analyses of hornblende and 

biotite, mineral separation was performed in the 

laboratory of the geological institute of the AVČR 

(Prague) using standard techniques, such as crushing, 

sieving, flotation, Frantz magnetic separation, and 

hand picking. K–Ar analyses were carried out in the 

laboratory of the Bundesanstalt für Geowissenschaften 

und Rohstoffe (BGR, Hannover) using flame 

photometry and noble-gas mass spectrometry for 

K–Ar determination. Details of sample processing 

are given by Kreuzer et al. (1989). All errors quoted 

were calculated on the 95% (2r) confidence level. 

Zircons of the Teufelsberg pluton (locality 

‘Hoher–Stein’) have been separated and abraded 

(for the separation and analytical techniques, see also 

Dörr et al., this volume). Dissolution and separation of 

U and Pb were carried out after Krogh (1973). Each 

single zircon was placed in a Teflon vessel within an 

autoclave and digested over 6 days at 180 jC with 24 

N HF. After cooling, a mixed 235 U– 208 Pb spike was 

added to one-third of the solution of the zircon to

determine the concentrations of U and Pb. The 

remainder of the solution was used to determine the 

natural Pb isotope composition of the zircon. The 

isotopic analyses were carried out with a Finnigan 

MAT261 solid-source mass spectrometer in multicollector 

static mode with ion-counting system for 

204 Pb. The measured lead isotopic ratios were corrected 

for mass fractionation (1.12 F 0.18x per 

amu), blank, and initial lead. Lead blanks are about 

3–5 pg. The calculation and correlation of errors for 

the 206 Pb/ 238 U and 207 Pb/ 235 U ratios were carried out 

after Ludwig (1980). Regression lines and concordia 

diagram were processed using the program Geodate 

2.2 (Eglington and Harmer, 1991). 

4. Composition and structure 

In the NE part of the NKM, igneous rocks mostly 

consist of quartz diorite that contain small, lensshaped 

bodies (maximum 1–2 km long) of olivine 

gabbro, pyroxene diorite, and granodiorite. The Vsˇepadly 

granodiorite (Location 1, Fig. 1) is composed 

of quartz, plagioclase, K-feldspar, hornblende, biotite, 

titanium oxide, and few amounts of cummingtonite. 

Apart from weak sericitization of plagioclase cores, 

alteration of hornblende and/or biotite margins to 

chlorite and weak undulose extinction of anhedral 

quartz, the magmatic fabric does not indicate a major 

post-plutonic overprint. Euhedral to subhedral plagioclase 

is strongly zoned, with core-to-rim compositions 

ranging from An 43 – 44 to An 3–19 (Table 1A). Ferrohornblende 

forms anhedral to subhedral crystals, 

which are almost homogeneous in composition. Biotite 

is locally intergrown with cummingtonite that 

probably results from the breakdown of orthopyroxene. 

The Smrzˇovice quartz diorite (Location 2, Fig. 1) 

consists of plagioclase, quartz, hornblende, biotite, 

titanium oxide, and few amounts of K-feldspar. 

Locally, plagioclase, hornblende, and biotite are 

weakly altered to sericite ( F epidote) and chlorite, 

respectively. Slightly deformed parts of the rock indicate 

undulose extinction, subgrains, and partial recrystallization 

of quartz, as well as deformation twins with 

tapering edges in plagioclase. The compositional zoning 

of subhedral plagioclase is characterized by relatively 

homogeneous Ca-rich cores (An 49 – 60) and 

C. Bues et al. / Tectonophysics 352 (2002) 225–243 231 

narrow Na-rich rims (An 17 – 22; Table 1A). K-feldspar 

occurs as antiperthitic exsolutions within the Na-rich 

rims or as small anhedral grains at the boundary of 

plagioclase. The composition of subhedral to anhedral 

ferro-hornblende ranges from Si = 7.0 to 7.2 pfu (Table 

1B; Fig. 2). 

The Smrzˇovice pyroxene diorite consists of plagioclase, 

orthopyroxene, clinopyroxene, hornblende, biotite, 

titanium oxide, and few amounts of quartz. The 

composition of zoned, subhedral plagioclase ranges 

from An52 – 58 (core) to An40 – 45 (rim; Table 1A). 

Anhedral Ca-amphibole ranges from magnesio-horn- 

Fig. 2. Classification of investigated Ca-amphiboles (according to 

Leake and CNMMN, 1997). Location (1) = Vsˇepadly, (2) = Smrzˇovice, 

(3) = Orlovice, (4) = Vsˇeruby, (5) = Neukirchen, (6 and 7) = Teufelsberg 

(Čertu˚v kámen). Fields: Ca-amphiboles of (A) gabbroic, 

(B) dioritic–granodioritic rocks, and (C) secondary formed Caamphiboles 

from the localities listed above according to Vejnar 

(1984, 1986), (D) metamorphic amphiboles of dioritic rocks from 

the Teufelsberg intrusion according to Bues (1992).

232 

blende to actinolite (Si = 7.2 to 7.7 pfu; Table 1B; Fig. 

2). The latter is attributed to local uralitization of 

pyroxene. 

Olivine gabbro of the Smrzˇovice complex consists 

of plagioclase, clinopyroxene, olivine, titanium oxide, 

and pargasite. Although anhedral olivine (Fo64 – 67; 

Table 1D, Fig. 3) and clinopyroxene are unzoned, 

euhedral to subhedral plagioclase have core-to-rim 

compositions ranging from An 67 – 72 to An 51 – 62 (Table 

1A). Unzoned pargasite is restricted to small anhedral 

grains within the ophitic fabric. Boundaries between 

olivine and plagioclase are free from reaction rims 

except in altered parts where olivine, pyroxene, and 

plagioclase are replaced by amphibole and sericite, 

respectively. 

Sub-ophitic Orlovice olivine gabbro (Location 3, 

Fig. 1) contains anhedral or roundish olivine (Fo 70 – 71, 

Table 1D), anhedral clinopyroxene, and subhedral 

Fig. 3. Chemical composition of olivine and pyroxene. For 

localities, see Figs. 1 and 2. En–Fs–Di–Hd quadrilateral according 

to Morimoto et al. (1988). Fields: pyroxene compositions according 

to Vejnar (1984, 1986). 


plagioclase (An 60 – 65, Table 1A). Small amounts of 

anhedral pargasite may also occur in the matrix. 

Locally, the Orlovice intrusion is affected by secondary 

alteration especially in its marginal parts. In 

weakly altered olivine gabbros, coronas of amphibole 

(F orthopyroxene) are developed around olivine at the 

contact to plagioclase. In case of strong alteration, 

olivine, orthopyroxene, clinopyroxene, and plagioclase 

are replaced by serpentine, cummingtonite, 

actinolite, and sericite (F epidote). Deformed plagioclase 

is characterized by deformation twins, undulose 

extinction, subgrains, and incipient bulging of grain 

boundaries, the latter suggesting the onset of recrystallization 

driven by grain–boundary migration. 

Gabbroic and dioritic rocks of the Vsˇeruby intrusion 

(Location 4, Fig. 1) underwent intensive retrograde 

overprint (uralitization, serizitisation, Fsaussuritization). 

Rare relics of wherlite, olivine gabbro, 

and gabbronorite consist of olivine, orthopyroxene, 

clinopyroxene, plagioclase, and opaque phases in 

varied modal amounts. Orthopyroxene (En77 – 80, Table 

1C) and olivine (Fo79–80, Table 1D) mostly form 

euhedral to subhedral cumulate phases, whereas plagioclase 

(An 65 – 71) and clinopyroxene occur as anhedral 

intercumulate minerals. In contrast to the 

Smrzˇovice and Orlovice intrusions, olivine of the 

Vsˇeruby gabbro is surrounded by double reaction rims 

at the contact with plagioclase that consist of orthopyroxene 

(En82 – 83) and pargasite–spinel symplectite 

(Fig. 4). 

As indicated by discrete shear zones and pervasive 

foliations, the post-intrusive strain and metamorphism 

increased considerably towards the SW. Details about 

the increase in postmagmatic strain from NE to SW are 

given in Köhler et al. (1993). Wide areas of the 

Neukirchen and Teufelsberg intrusion were transformed 

into amphibolite or orthogneiss. Relics of 

olivine gabbro are restricted to low-strain domains of 

these intrusions. Similar to the Vsˇeruby olivine gabbro, 

coronitic reaction rims of orthopyroxene (En 78 – 79) and 

pargasite–spinel symplectite are developed around 

olivine (Fo75 – 77) at the contact to plagioclase (An65 – 

67) of the sub-ophitic Neukirchen olivine gabbro (Location 

5, Fig. 1). Further relics of olivine gabbro of the 

Neukirchen intrusion consist of olivine (Fo65 – 66) and 

plagioclase (An57 – 60) with a reaction rim of orthopyroxene 

(En70 – 71) towards olivine and pargasite–spinel 

intergrowth towards plagioclase. In deformed meta-

gabbros, olivine and pyroxene are entirely replaced by 

polycrystalline aggregates of amphibole (mostly magnesio-hornblende). 

Relics of large magmatic plagioclase 

show undulose extinction and deformation twins. 

These grains frequently pass into domains of small 

dynamically recrystallized grains. Additionally, plagioclase 

is replaced by epidote + clinozoisite and less 

common by sericite. 

The fabric and mineral assemblage of the Teufelsberg 

olivine gabbro (Locations 6 and 7, Fig. 1) is 

similar to that of the Orlovice area. However, olivine 

of the Teufelsberg intrusion (Fo54 – 57) is surrounded 

by a large corona of orthopyroxene (En65 – 66) and 

pargasite–spinel symplectite at the contact to plagioclase 

(An50 – 57), similar to that of the Vsˇeruby and 

Neukirchen olivine gabbro. 

Apart from a stronger overprint, the mineral assemblage 

of the Teufelsberg pyroxene (meta)diorite is 


Fig. 4. Coronitic microfabrics of olivine gabbros. (a and b): double reaction rims of orthopyroxene (close to olivine) and intergrowths of 

pargasite + spinel (close to plagiaclase) surrounding olivine (Location 5). (c and d): Large reaction rims of orthopyroxene and intergrowths of 

clinopyroxene + spinel around olivine (Location 8). All photomicrographs with parallel polarizers. 

similar to that of the Smrzˇovice area. Plagioclase 

(An37–48) is characterized by undulose extinction, 

subgrains, and recrystallization, whereas the subhedral 

habit of orthopyroxene (En39 – 54) indicates a magmatic 

origin. The southern part of the Teufelsberg intrusion 

consists of more strongly deformed metadiorite and 

orthogneiss, where pyroxene is entirely transformed 

into amphibole, and plagioclase shows pervasive 

grain-size reduction by dynamic recrystallization. 

The Hoher–Bogen metabasite belt forms the most 

deformed and metamorphosed part of the NKM, 

affected by ductile shearing along the HBSZ (Bues 

et al., 1998). Highly deformed domains consist of 

mylonitic epidote amphibolite with porphyroclasts of 

hornblende embedded in a matrix of recrystallized 

plagioclase. Domains that did not suffer pervasive 

deformation contain relics of granoblastic pyroxene 

amphibolite, garnet pyriclasite, garnet hornblendite,

234 

Fig. 5. Lower-hemisphere equal-area plots of D2 extensional structures of the Hoher–Bogen shear zone (HBSZ). Poles to mylonitic shear planes 

(S 2) with traces of displacement vector are depicted (arrow indicates movement direction of hanging wall); (a) western part of HBSZ; (b) eastern 

part of HBSZ; (c) southern part of HBSZ. 

garnet amphibolite, and small amounts of metagabbro 

(Bues and Zulauf, 2000). More or less, mylonitized 

and serpentinized spinel metaperidotite also occur 

within the HBSZ. Relics of (granulitic?) olivine 

metagabbro, located ca. 2 km W of Rittsteig (Number 

8, Fig. 1), differ from that described above. In this 

rock, large coronas around olivine (Fo80 – 81) occur 

with an inner rim of orthopyroxene (En80 – 82) and an 

outer rim of clinopyroxene–spinel symplectite at the 

contact to plagioclase (An64 – 69) (Fig. 4). The com- 


position of matrix clinopyroxene is similar to that of 

corona clinopyroxene (Table 1C). 

The mylonitic S2-foliation of the HBSZ results 

from a second deformation (D2, Bues et al., 1998). 

D 1-deformation fabrics occur only as relicts that do 

not permit assessment of the D 1-kinematics. The S 2foliation 

is moderately to steeply dipping (50j to 80j) 

and its strike changes gradually from NW–SE (in the 

W, towards the WBSZ) to NE–SW (in the E, towards 

the CBSZ; Figs. 1 and 5). The mylonitic lineation is a 

Fig. 6. Temperature and pressure calculations for granodiorite, quartz diorite, pyroxene diorite, olivine gabbro, and gabbronorite. Localities are 

depicted like in Figs. 1 and 2. Applied geothermometer and barometer: AS95 = Anderson and Smith (1995); BH90 = Blundy and Holland 

(1990); BF94 = Bucher and Frey (1994); G84 = Gasparik (1984); HB94 = Holland and Blundy (1994); S91 = Schmidt (1991); TWQ = Berman 

(1991), Berman et al. (1995) and Berman and Aranovich (1996); W77 = Wells (1977); solidus according to Bucher and Frey (1994); Al2SiO5 

triple point according to Bohlen et al. (1991).


236 

Table 2 

Analytical data of K–Ar age determinations on biotite and hornblende. Argon concentrations in nanoliter per gram at standard conditions (nl/g 

STP); potassium concentrations in weight percentage (wt.%) 

Sample Locality Mineral Fraction (Am) K (wt.%) Radiogenic Ar Date (Ma) 

(nl/g STP) (%) 

PAM27F Hoher–Stein biotite 125–63 6.75 98.89 99.1 342 F 4 

113 quarry Smrzˇovice biotite 250–125 6.94 153.80 98.8 495 F 6 

SK4 quarry Smrzˇovice hornblende 125–63 

(magnetic fraction) 

0.26 6.49 91.7 547 F 7 

SK4 quarry Smrzˇovice hornblende 125–63 

(unmagnetic fraction) 

0.27 6.81 91.9 549 F 7 

Mean standard deviation (2r) of radiogenic argon is about 0.3% and of potassium about 1% for high-K and low-K materials, respectively. The 

error in the K –Ar apparent age is given at the 95% confidence level. Note that our K–Ar date for the standard glauconite GL-O is about 1% 

younger than the mean value of the compilation of Odin (1982). 

dip–slip or slightly oblique-slip lineation portrayed 

by stretched plagioclase or by the long axes of 

amphibole. Non-coaxial top–down-to-the-NE normal 

movements are indicated by asymmetric amphibole 

porphyroclasts (j- and y-clasts) and by shear band 

fabrics (see Table 1A in Bues et al., 1998). 

5. Depth of pluton emplacement 

Using the geothermometers and geobarometers 

mentioned above and shown in Fig. 6, we calculated 

the following temperatures and pressures. For granodiorite 

and quartz diorite of the Vsˇepadly and 

Smrzˇovice intrusion, the equilibration temperatures 

of hornblende and plagioclase are in the range of 

Fig. 7. Cathodoluminescence image of a zircon separated from the 

Teufelsberg diorite (for further explanation, see text). 


620–680 jC (Fig. 6A and B). Low crystallization 

pressures of hornblende (1.5–3 kbar; Fig. 6A and B) 

indicate emplacement at shallow crustal levels. Higher 

equilibration temperatures of 830–920 jC were calculated 

for pyroxene diorite of the Smrzˇovice, Vsˇeruby, 

and Teufelsberg intrusion (Fig. 6C and E) that do 

not show the appropriate mineral assemblage for 

using the Al-in-Hbl barometry. For the Smrzˇovice 

pyroxene diorite, the pressure should be similar to 

that of the quartz diorite from the same locality. For 

the Vsˇeruby and Teufelsberg pyroxene diorite, we 

have inferred the pressure from the corona microfabrics 

that occur in the associated olivine gabbros 

(see below). Ortho- and clinopyroxene equilibration 

temperatures up to 980–1080 jC have been derived 

from olivine gabbro and gabbronorite of the Vsˇeruby 

intrusion (Fig. 6D). Equilibration temperatures of 

reaction rims between olivine and plagioclase are 

Fig. 8. Concordia diagram for zircons from the Teufelsberg diorite 

(locality Hoher–Stein).

Table 3 

U–Pb analytical results for zircons of the Teufelsberg diorite 

Sample Weight 

(Ag) 

U 

(ppm) 

Pb r. 

(ppm) 

Pb i. 

(ppm) 

206 Pb/ 

204 Pb F 2r* 

207 Pb/ 

206 Pb F 2r* 

208 Pb/ 

206 Pb F 2r* 

207 Pb/ 

235 U F 2r 

206 Pb/ 

238 U F 2r 

207 Pb/ 

206 Pb F 2r 

Cor. Appara. 

206 Pb/ 

238 U F 2r 

Ages 

207 Pb/ 

235 U F 2r 

(Ma) 

207 Pb/ 

206 Pb F 2r 

(1) 38 242.9 13.27 0.22 1304 F 6 0.06498 F 6 0.08609 F 24 0.4240 F 18 0.05716 F 22 0.05379 F 24 0.88 358 F 1 359 F 2 362 F 10 

(2) 37 336.7 17.58 0.45 1313 F 13 0.06475 F 9 0.08409 F 37 0.4047 F 21 0.05472 F 23 0.05364 F 28 0.83 343 F 1 345 F 2 356 F 12 

(3) 40 268.7 14.01 0.05 2178 F 54 0.06022 F 13 0.07163 F 48 0.4038 F 24 0.05472 F 22 0.05353 F 32 0.71 343 F 1 344 F 2 352 F 13 

(4) 36 356.1 18.38 0.01 1991 F 30 0.06114 F 9 0.07678 F 49 0.4005 F 29 0.05397 F 35 0.05382 F 29 0.92 339 F 2 342 F 3 363 F 13 

(5) 41 652.9 24.14 0.20 2562 F 13 0.05928 F 7 0.06370 F 10 0.2880 F 24 0.03898 F 31 0.05359 F 25 0.98 247 F 2 257 F 2 354 F 10 

Errors are 2r. Asterisk means corrected for mass fractionation and blank. Pb r. radiogenic lead; Pb i. initial common lead. 


238 

ranging from 890 to 940 jC for Opx–Prg–Spl 

assemblages (Vsˇeruby and Neukirchen olivine gabbro; 

Fig. 6D) and 810 to 920 jC for Opx–Cpx–Spl 

coronas (Hoher–Bogen olivine metagabbro; Fig. 6F). 

For these rocks, a pressure estimate is possible based 

on the reaction: Ol + Pl F H2O ! Opx + Am or Cpx + 

Spl. Such coronitic microfabrics are typical features in 

olivine gabbros that underwent magmatic cooling or 

high-grade metamorphism at P =6.5–8 kbar (e.g., 

Grantham et al., 1993; Jan and Karim, 1995). According 

to Bucher and Frey (1994), such microfabrics are 

diagnostic for pressures >6 kbar. In Fig. 6D and F, the 

spinel-in reaction in the system CaO–MgO–Al2O3– 

SiO2 is illustrated according to Gasparik (1984). In 

natural systems containing iron (XMg = ca. 0.9), spinel 

may occur at some lower pressures (Bucher and Frey, 

1994). 

6. Radiometric dating 

For carrying out K–Ar age dating, biotite and 

hornblende have been separated from samples of the 

Smrzˇovice and Teufelsberg intrusions. Light brown to 

greenish magnesio-hornblende sampled from finegrained 

hornblende–biotite diorite of the large Smrzˇovice 

quarry (sample SK 4, Location 2 in Fig. 1) shows 

weak alteration along the cleavage planes. Magnetic 

and unmagnetic fractions yield 547 F 7 and 549 F 7 

Ma, respectively (Table 2). Dark brown to reddish 

brown biotite separated from biotite–hornblende 

quartz diorite of the Smrzˇovice quarry (sample 113) 

shows few inclusions of plagioclase, ilmenite 

F hornblende. The degree of biotite alteration is 

very weak. In a few places, biotite is moderately 

altered to clinozoisite (along the cleavage planes) 

and/or chlorite at the margins. K–Ar dating of this 

biotite yields 495 F 6 Ma (Table 2). 

K–Ar dating of biotite of the Teufelsberg pyroxene 

diorite (Location 7 in Fig. 1) yields 342 F 4 Ma. 

Similar to the Smrzˇovice samples, the Teufelsberg 

biotite is relatively fresh. Rare alteration in form of 

weak chloritization is restricted to the marginal parts. 

The separated zircons of the Teufelsberg diorite 

(Location 7 in Fig. 1) are colourless and yellow 

belonging to the subtypes S20 to S25 and J1 to J5 

according to the classification of Pupin (1980). The 

internal structure of the zircons is perceptible in 


cathodoluminescence (CL) images oriented parallel 

to the zircon c-axis. The different light–dark contrasts 

and bright color display different amounts of trace 

element content. The bright color represents more or 

less pure zircon phase, whereas the different dark 

colors reflect variable amount of U and Y contents. 

The internal structure of all zircons is complex (e.g., 

Fig. 7). A rounded heterogeneous core is surrounded 

by a thin discordant bright zone (A in Fig. 7), the 

latter suggesting a first stage of dissolution. A narrowspaced 

oscillatory zoning follows combined with 

compositional sector zoning between dark prisms 

and light–dark 101-pyramides until a second stage 

of dissolution is indicated by a thin discordant bright 

zone (B in Fig. 7). Towards the margin, a similar 

combination follows including small light–dark 211pyramids 

ceasing with a third stage of dissolution 

indicated by a thick discordant bright zone (C in Fig. 

7). The margin of the zircon consists of dark prisms 

and pyramids. 

The single zircons have a weight of 37–41 Ag and 

thus, a total lead from 513 to 998 pg, resulting in high 

beam intensities and allowing static-mode measurements 

in all cases. The concordant single zircon 1 and 

four discordant single zircons 2 to 5 define a discordia 

with an upper intercept at 361 F 4 Ma and a lower 

intercept at 16 F 12 Ma (Fig. 8F, Table 3). These data, 

together with the age of a concordant zircon at 

359 F 2 Ma, are interpreted to reflect the age of the 

zircon crystallization and thus, the magmatic emplacement 

age of the Teufelsberg diorite. Although the CL 

images show a complex core pattern in the zircons, no 

inherited lead could be detected (Table 3). 

7. Discussion and conclusions 

The Vsˇepadly granodiorite and the Smrzˇovice 

diorite of the NE part of the NKM intruded at shallow 

crustal levels (< 7 km depth) as is indicated by Al-in- 

Hbl barometry. Similar emplacement depths have 

been determined for the Těsovice granite of the 

adjacent Stod pluton (Zulauf et al., 1997). A supracrustal 

emplacement level is also indicated by the 

small differences between U–Pb zircon ages (that 

reflect the time of pluton emplacement) and K–Ar 

and Ar–Ar ages of hornblende and mica (that reflect 

cooling of the pluton through particular isotherms).

The new K–Ar ages of hornblende of the Smrzˇovice 

diorite (547 F 7 and 549 F 7 Ma) are unambiguously 

higher than the concordant U–Pb zircon age of the 

same rock (523 F 3 Ma, Dörr et al., this volume). One 

possibility to explain these apparently high K–Ar 

ages is that excess argon may have been incorporated 

into hornblende during younger post-magmatic thermal 

events. Relics of pyroxene, locally intergrown 

with hornblende, are further candidates that may 

explain the high K–Ar ages of hornblende. Despite 

careful hornblende separation, some of these pyroxenes 

could have occurred in the fraction, a possibility 

that is compatible with the difference in the potassium 

content determined from single hornblende using the 

electron microprobe (K2O = 0.52–0.63 wt.%, Table 

1B) and from hornblende separates using flame photometry 

(K 2O = 0.31–0.33 wt.%). The potassium content 

of biotite of the Smrzˇovice quartz diorite is also 

relatively low, probably because of local chloritization 

that may have caused some loss of radiogenic argon. 

Thus, the K–Ar age of biotite (495 F 6 Ma) is 

interpreted as minimum cooling age that is compatible 

with the U–Pb zircon age, which reflects the time of 

crystallization. Similar to the ages of the Smrzˇovice 

quartz diorite, the Cambrian K–Ar and Ar–Ar ages of 

the Stod granite (biotite, 491–513 Ma, S ˇ mejkal and 

Vejnar, 1967; 518 F 5 Ma, Kreuzer et al., 1990) and 

the Vsˇepadly granodiorite (hornblende, 516 F 1.3 Ma, 

Dallmeyer and Urban, 1998) suggest no significant 

burial and metamorphic reheating above the closure 

temperatures for the K–Ar isotopic system of hornblende 

and biotite. Closure to diffusional loss of 

radiogenic 40 Ar in hornblende and biotite, although 

primarily a function of temperature, is also influenced 

by the cooling rate and perhaps more importantly, by 

the composition and crystalline structure of the mineral. 

Using models for argon diffusion in biotite of 

intermediate composition and assuming geologically 

reasonable cooling rates yield closure temperatures 

between 280 and 350 jC (Harrison et al., 1985; Grove 

and Harrison, 1996 and references therein). The 

closure temperature for the Ar diffusion in hornblende 

has been constrained between ca. 490 and 550 jC 

(Harrison, 1981; Baldwin et al., 1991). 

In the SW part of the NKM, a strong post-intrusive 

Variscan thermal event is obvious from: (1) Carboniferous 

(321–329 Ma) K–Ar cooling ages of mica of 

metapelitic wall rocks in the Neukirchen area (Kreuzer 


et al., 1992; Fig. 1), (2) various K–Ar cooling ages 

(330–460 Ma) of hornblende of the Hoher–Bogen 

amphibolites (Fischer et al., 1968; Kreuzer et al., 

1992), (3) Upper Devonian (359 F 2 Ma) intrusion 

of the Teufelsberg pyroxene diorite (see above). The 

potassium content of biotite of the Teufelsberg diorite 

is relatively low, probably because of local chloritization 

that may have caused some loss of radiogenic 

argon. Thus, similar to the Smrzˇovice quartz diorite, 

the newly determined K–Ar age of biotite of the 

Teufelsberg pluton (342 F 4 Ma) is interpreted as 

minimum cooling age that is compatible with the U– 

Pb zircon age. 

The metamorphic overprint of the Teufelsberg metadiorite, 

constrained at T>600 jC and P = 6–7 kbar 

(Bues, 1992), is consistent with the metamorphic conditions 

determined for the mylonitic shearing of epidote 

amphibolite along the HBSZ (T = 540–610 jC, 

P = 3–6 kbar, Artmann et al., 2002; Bues and Zulauf, 

2000). As most of these mylonites result from retrograde 

shearing of high-grade amphibolites and granulites, 

the P–T data mentioned above are minimum 

values for the Variscan metamorphism in the southernmost 

NKM. In low-strain domains of the HBSZ, relics 

of garnet pyriclasite indicate equilibration at infracrustal 

levels (T>750–840 jC, P < 10–13 kbar) prior to the 

retrograde transformation to epidote amphibolite (Bues 

and Zulauf, 2000). With the exceptions of the slices of 

mantle-derived metaperidotite, these garnet pyriclasites 

represent the deepest buried rocks of the NKM 

(ca. 35 km). 

The presence of coronitic microfabrics in olivine 

(meta)gabbros SW of the Orlovice intrusion (Vsˇeruby, 

Neukirchen, Teufelsberg, Hoher–Bogen–Rittsteig 

areas) reflects cooling from magmatic conditions 

and/or reheating due to renewed burying and related 

granulite facies metamorphism at deep structural levels 

(ca. 20–25 km). As there is no systematic change 

in the Mg content of olivine in the investigated 

gabbros and metagabbros (Fig. 3), the spatial restriction 

of corona microstructures to the southwestern 

NKM probably reflects higher pressure ( P>6–7 kbar) 

during their post-intrusive evolution. The occurrence 

of Opx–Cpx–Spl coronas in the Hoher–Bogen olivine 

metagabbro that equilibrated at T = 840–920 jC 

emphasizes the existence of former medium-pressure 

granulite facies conditions for parts of the southernmost 

NKM.

240 

C. Bues et al. / Tectonophysics 352 (2002) 225–243

The changes in composition, emplacement level, 

isotopic cooling ages, and degree of post-intrusive 

tectonometamorphic overprint of the Cambrian plutons 

suggest that deeper structural levels are encountered 

when moving from the Stod pluton to the HBSZ. 

A major break in the crustal profile occurs along the 

NNW–SSE trending Andělice fault (AF in Fig. 1; see 

also Scheuvens, 1999). Rocks to the NE of this fault 

mostly include intermediate to felsic plutons that have 

not been deeply buried since their supracrustal 

emplacement (T < ca. 300 jC since the Cambrian). 

The plutons SW of the Andělice fault are intermediate 

to mafic in composition and show evidence for 

emplacement at infracrustal levels and/or subsequent 

deep burying, particularly when approaching the 

HBSZ. The HBSZ contains lower crustal mafic granulites 

and metaperidotites, the latter being probably 

derived from the upper mantle. Thus, a more or less 

complete oblique crustal section is exposed between 

Stod and the HBSZ to the SW. 

We suggest that extensional movements along the 

steeply NE dipping HBSZ and probably along the 

Andělice fault caused differential uplift and exhumation 

in the NKM. Due to large displacement along the 

HBSZ, the infrastructural granulites and metaperidotites 

were juxtaposed against Moldanubian mica 

schists and gneisses. These interpretations and published 

data from surrounding areas are incorporated 

into the following model, which accounts for the 

present distribution of Cambrian and younger plutons 

in the SW part of the TBU. 

In Cambrian times, felsic to intermediate melts 

were emplaced at upper crustal levels (Stod, Vsˇepadly 

and Smrzˇovice area), whereas intermediate to mafic 

plutons intruded at deeper structural levels (Vsˇeruby, 

Neukirchen, Hoher–Bogen areas, Fig. 9A). Although 

strong evidence for syntectonic emplacement has not 

been found so far in the NKM, it is possible that some 

of the melts were emplaced along transtensional, 

ENE–WSW trending shear zones. Such types of 

shear zones have facilitated the emplacement of the 

Cambrian Mračnice trondhjemite of the Domazˇlice 


crystalline complex (Zulauf et al., 1997; for location 

of the Mračnice trondhjemite, see Fig. 1). 

To explain the presence of slices of lower crust and 

mantle material within the HBSZ, we assume that 

during the Upper Devonian collision, the entire crust 

of the TBU was thrust towards the SE over the 

Moldanubian unit including the lower crustal mafic 

granulite and parts of the Teplá–Barrandian mantle 

(Fig. 9B). This type of stacking led to overthickened 

crust that became gravitationally unstable. Intrusion of 

the mantle-derived Teufelsberg diorite at 359 F 2Ma 

was simultaneous to the exhumation and cooling of the 

Domazˇlice crystalline complex below the K–Ar closure 

temperature of white mica (ca. 350 jC; cf. cooling 

ages depicted in Fig. 1). The Teufelsberg pluton 

intruded into this thickened, collapsing crustal wedge. 

Its geodynamic significance, however, is difficult to 

interpret. Cooling and exhumation of the Teufelsberg 

pluton from deep structural levels (>20 km at T>600 

jC) to upper crustal levels, where T < ca. 300 jC, 

occurred between 359 F 2 and 342 F 4 Ma. We suggest 

that this Upper Devonian to Lower Carboniferous 

phase of pluton exhumation was related to the persistent 

activity of the HBSZ. Thus, the recent distribution 

of felsic to mafic plutons of the NKM and Stod area, as 

well as their difference in emplacement level and 

metamorphic imprints may result from differential 

uplift that was largely controlled by the normal movements 

along the HBSZ and related shear zones that cut 

through the southeastern part of the NKM. The fact that 

the composition of the Cambrian plutons changes from 

felsic to mafic towards deeper structural levels is 

compatible with a Cambrian layered intrusion, as has 

been suggested by Vejnar (1986). 

Acknowledgements 

We thank S. Weinbruch, T. Thybusch (Technical 

University Darmstadt), and U. Schüssler (University 

Würzburg) for their help at the electron microprobe. 

We further acknowledge the help of the BGR isotopic 

Fig. 9. Geodynamic evolution of the SW part of the Teplá–Barrandian unit. (A) Cambrian emplacement of mafic to felsic plutons at different 

crustal levels during dextral transtension. Pluton emplacement postdates tilting of Cadomian metamorphic isograds. (B) Continent–continent 

collision of the Saxothuringian, Teplá –Barrandian, and Moldanubian unit during the Upper Devonian. The Teplá–Barrandian unit was thrust 

over the Moldanubian unit as an entire crustal block including mantle slices from its base. (C) During the orogenic collapse, the infracrustal 

Hoher–Bogen metabasites were exhumed and the southern NKM was tilted to the NE along the HBSZ, forced by rising domes of anatexites 

and granites within the adjacent Moldanubian unit during the Lower Carboniferous. For further explanations, see text.

242 

laboratory (Hannover) when carrying out K–Ar 

analyses of biotite and hornblende. We would also 

like to thank A. Castro, B. Murphy, and I. Vigneresse 

for their helpful comments. This study was supported 

by grants of the Deutsche Forschungsgemeinschaft 

(Zu 73/1-5, BL 191/12). 

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