GeolCarp_Vol61_No3_175

www.geologicacarpathica.sk

GEOLOGICA CARPATHICA, JUNE 2010, 61, 3, 175—191 doi: 10.2478/v10096-010-0009-0

Introduction

Gabbros and norites represent either products of middle stag-
es of fractionation of a basaltic magma in layered complexes
or differentiated sills. Gabbroic rocks in orogenic batholiths,
composed  of  members  of  the  gabbro—diorite—tonalite—
monzonite—granodiorite—granite  calc-alkaline  suite,  can
compose 7—14 vol. % of the whole (Pitcher 1978). They also
occur  in  intrusions  (partly  of  alkali  character)  in  extensional
settings with members of a granite—syenite trend or as mem-
bers of the gabbro—anorthosite—charnockite suite (2—10 vol. %
only – Vorma 1976). Phanerozoic gabbroic rocks also form
minor  components  of  alkalic  anorogenic  suites  related  to
crustal  doming  and  rifting  (e.g.  the  Oslo  Rift  –  Neumann
1978).

We present results on (ultra)mafic gabbroic bodies from:

1. the Monotonous Group of the Moldanubian Unit in close
spatial relationship with the Moldanubian pluton and 2. the
tectonic slice of the Vratěnín Varied Unit of the Moravian af-
finity, stacked in the Drosendorf window together with HP-
HT rocks of the Gföhl Unit and with MP-MT rocks of the

Constraints on the origin of gabbroic rocks from the

Moldanubian-Moravian units boundary (Bohemian Massif,

Czech Republic and Austria)

JAROMÍR ULRYCH

, LUKÁŠ ACKERMAN

, VÁCLAV KACHLÍK

, ERNST HEGNER

, KADOSA

BALOGH

, ANNA LANGROVÁ

, JAN LUNA

, FERRY FEDIUK

, MILOŠ LANG

and JIŘÍ FILIP

Institute of Geology v.v.i., Academy of Sciences of the Czech Republic, Rozvojová 269, 165 00 Praha 6, Czech Republic; ulrych@gli.cas.cz

Faculty of Science, Charles University, Albertov 6, 128 43 Praha 2, Czech Republic

Department of Geowissenschaften, Universität München, Theresiennstraße 41, D-80333 München, Germany

Institute of Nuclear Research, Hungarian Academy of Sciences, Bemtér 18/C, H-4026 Debrecen, Hungary

Jihlava, Březinova 41, 58 601 Jihlava, Czech Republic

Geohelp, Na Petřinách 1897, 162 00 Praha 6, Czech Republic

(Manuscript received May 29, 2009; accepted in revised form December 11, 2009)

Abstract: Gabbroic bodies from the Moldanubian Monotonous Group (Maříž) and the Moravian Vratěnín Unit (other
sites), often showing retrogressive recrystallization at their margins in the amphibolite-facies grade, have norite, gabbronorite,
gabbro and hornblendite compositions. Gabbros with preserved coronitic textures are limited to the Vratěnín Unit. The
estimated equilibration temperatures derived from plagioclase—amphibole pairs and orthopyroxene Ca contents calculated
for pressures 5—10 kbar overlap for coronitic (700—840 °C) and non-coronitic gabbroic rocks (680—850 °C). Although the
Moldanubian (Maříž) gabbroic rocks are more Mg-rich compared to the Moravian gabbroids, they show crust-like La/Nb
ratios of 2.1—6.6 characteristic of subduction-related magmatic rocks coupled with uniform low

values of + 0.6 to

+ 0.7. Apparent subduction-related features are probably caused by contamination by juvenile crust and/or by meta-
morphic fluid rich in incompatible elements during the Variscan metamorphism. Samples from Korolupy—Nonndorf
and Mešovice have La/Nb ratios < 1.7 and show negative correlations between La/Nb and

. Such decoupling between

La/Nb and

could be attributed to contamination of the subduction-related parent magma by crustal material with higher

La/Nb and lower

values. Samples from Uherčice show ambiguous geochemical patterns inherited from contamination

by very old recycled material. Gabbroic rocks from Maříž should represent an underplated, partly layered cumulate body
of continental tholeiite composition, strongly influenced by crustal contamination. In contrast, gabbroic bodies from the
Vratěnín Unit, having a close spatial relationship to the surrounding garnet amphibolites, were emplaced into a lithologi-
cally variable passive margin sequence probably during the Cadomian extension.

Key words: Bohemian Massif, Moldanubian Unit, Moravian Unit, Sr-Nd isotopes, K-Ar ages, geochemistry, gabbroic rocks.

Podhradí Unit (Jenček & Dudek 1971; Racek et al. 2006) ad-
jacent  to  the  major  thrust  boundary  with  the  underlying
Brunovistulian block. The Moldanubian pluton intruded the
paragneisses and migmatites of the Monotonous Unit in the
time span of ca. 330—280 Ma (Finger et al. 1997; Gerdes et
al. 2000). The main gabbroic and dioritic bodies occurring in
this  region  (Group II  of  Koller  1998)  occur  as  stockwork-
like  intrusions  or  lens-like  bodies,  less  than  1 km  in  size,
within both granites and gneisses. Additionally, small inclu-
sions  of  similar  composition  occur  within  the  granite
(Group I of Koller l.c.) from 5 cm to 2 m in diameter.

Geological settings

The Bohemian Massif represents a part of the Variscan oro-

genic belt formed during the collision of Gondwana, Laurus-
sia and associated microcontinents (e.g. Franke 2000; Matte
2001). It consists of four different crustal segments of the Peri-
Gondwanan affinity: (1) Moldanubian, (2) Saxothuringian,
(3) Teplá-Barrandian, and (4) Moravo-Silesian.

176

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

The studied gabbroic bodies occur in a complicated tectonic

stack  of  the  Moldanubian  and  Moravian  units  (called  the
Drosendorf stack – Tollman 1982) in close proximity to the
major  thrust  boundary  between  the  Moldanubian  high-grade
gneisses and Cadomian Brunovistulian foreland (cf. different
genetic  interpretations  –  see  discussion  in  Schulmann  et  al.
2005). The E—W profile trough the classical Drosendorf win-
dow with gabbros and retrogressed metagabbros illustrates the
pre-Variscan  geodynamic  setting  of  individual  crustal  slices.
From  the  top  to  the  bottom,  the  following  lithotectonic  units
(only those containing the studied gabbroic rocks) can be dis-
tinguished (see Fig. 1):

a) The Monotonous Unit formed by migmatitic paragneiss-

es with cordierite close to the contact with the Variscan grani-

toids. U-Pb dating of clastic zircons from paragneisses shows
a  maximum  Neoproterozoic  sedimentary  age  for  these  units
(Kröner et al. 1988). The layered gabbro from Maříž crops out
in  the  western  part  of  this  unit  near  the  contact  with  the
Moldanubian  pluton.  The  gabbroic  bodies  range  from  60  to
600 m in size and occur (in particular those near Maříž) along
the southern continuation of the Přibyslav Mylonite Zone.

b) The Vratěnín Varied Unit is composed of paragneisses

with  frequent  intercalation  of  marbles,  graphite  paragneisses
and garnet amphibolites with pyroxene relicts. Gabbroic rocks
form bodies X0 m in size in the surrounding paragneisses W
and SW of Korolupy and Nonndorf and between Uherčice and
Mešovice,  where  gabbros  are  spatially  associated  with  am-
phibolites,  calc-silicate  rocks  and  marbles.  Relatively  fresh

Fig. 1. A – Geological map of the Moldanubian/Moravian units boundary (modified after map 1 : 500,000 – Cháb et al. 2007); B – Sketch
map of the occurrences of the studied gabbroic rocks from the Moravia/Austria border, (B) The map of the Maříž gabbroic body 1 : 4,000 based
on new geological studies and geomagnetic measurements; C – Location of studied area in the frame of major zones of the Variscan orogen
(marked by a dark rectangle).

177

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

olivine and pyroxene gabbros and ultra-
mafic cumulates associated with gabbros
in  Korolupy  and  Mešovice  bodies  pass
to  amphibolitized  gabbros  and  fine-
grained  gabbroamphibolites  with  only
scarce relics of pyroxenes. This unit was
considered an equivalent of the Vranov-
Olešnice Unit of the Moravicum (Jenček
&  Dudek  1971)  or  correlated  with  the
Moldanubian Varied Unit (Schulmann et
al.  2005;  Racek  et  al.  2006).  Jenček  &
Dudek  (1971)  supposed  an  early
Variscan age for the gabbros, but without
any radiometric evidence.

Methods

Special attention was applied to the po-

sitions  and  shape  of  the  inhomogeneous
Maříž gabbroic body occurring at the im-
mediate  contact  with  the  Moldanubian
pluton.  Magnetometric  measurements
(57,000 m

with 7,500 of point measure-

ments) were performed using the method
of magnetometric gradiometry and the
Envi Scintrex proton magnetometer.

Whole-rock major element concentra-

tions were determined at the Charles Uni-
versity, Prague, using wet chemical
methods. Analyses of the reference stan-
dards (GM, TB, BN) and duplicate analy-
ses of the samples yield total errors of
± 5 % (1

σ). A quadrupole-based ICP-MS

(VG Elemental PQ3) was used for deter-
mination of REE and other trace elements
using the methods of Strnad et al. (2005).
The accuracy was tested against reference
rock  standard  BCR-2,  the  precision  was
monitored  by  replicate  analyses  of  the
same  reference  material  and  was  always
better than ± 5 % (1

σ).

Mineral analyses were carried out on a

Cameca  SX 100  electron  microprobe  us-
ing the wavelength-dispersive spectrome-
try  (WDS)  analyser  at  the  Institute  of
Geology,  Academy  of  Sciences  of  the
Czech  Republic.  Analytical  conditions
were as follows: 15 kV accelerating volt-
age, 10 nA beam current and 2 µm beam
diameter.  A  counting  time  of  10 s  was
used for all elements. Synthetic and natu-
ral minerals were used as standards. Data
reduction used the X-PHI Merlet correc-
tion (Merlet 1992).

The K-Ar isotope measurements were

carried out at the Institute of Nuclear Re-
search of the Hungarian Academy of Sci-
ences, Debrecen, according to the

Table 1:

List

samples

the

gabbroic

rocks

with

location

and

petrog

raphic

characteristics.

ple N

ati

tud

tude

and i

ogi

l c

har

ter

tic

Pet

rog

rap

hic ch

ogy

M-

.880

.564

nndo

o el

ptic

die

s (

0 m

90 m

)

bio

tite

old

anub

n U

t. The a

band

itu

in the

e ne

hbo

f t

liv

ine

rite

rnbl

-b

oop

ron

xtur

e a

round

oli

vin

Plg>

x~Ol>

row

n)>

(Ph

M-

.928

.626

pti

cal

(

0 m

) is

dde

d i

bio

tite

the

n U

t. A

ban

t qu

f t

ite

rnbl

-b

oop

ron

xtur

e m

tly

rou

ort

ho-

, par

y al

ine

>>H

row

n)>

(Ol,

M-

.923

.641

Uhe

rč

ice:

cto

niz

l is

(

)

ith m

e in

rcal

f t

n U

nit

. Bo

the

2 km

f the

nbl

ende

ela

l-gra

r t

ext

row

n)~Pl

g >

M-

.923

.641

Uhe

rč

ice:

e s

e loc

nbl

ende

ela

abbr

c f

ine

-g

ine

aic

bl (

le gr

een

)

>>P

Cpx

M-

.994

.614

eš

ice:

-S

– e

ate

d e

lli

(

0 m

)

bio

tite

d g

t am

ite

f t

n U

n t

E of th

e vi

lla

nbl

ende

bbr

phi

lite

c un

aine

d te

par

nte

ctu

l (b

row

n-gr

~ P

>>C

M-

.996

.316

říž:

o i

rregu

r N-S e

lon

d elli

ies

(150

y 1

d 150

) a

t the

t o

f t

e Mo

n U

t f

mig

ite

s a

mai

n te

e l

ocal

ity

. Bo

n a

d s

the

. F

log

ical

catio

n s

. 1.

nbl

ende

liv

ine

nori

c t

rooph

Plg~Hb

l (b

n)>

x~C

px>>

-f

M-

.995

.316

říž:

the

e l

ocal

ity

; m

ino

r r

ock

f the

ori

abbr

c te

Plg>

M-

.996

.316

říž:

the

e l

ocal

ity

; m

ino

r r

ock

f the

ioti

gab

rnbl

-b

l-gra

r t

ext

Bt>H

M-

.995

.316

říž:

the

e l

ocal

ity

; m

ino

r r

ock

f the

liv

ine

endi

nhe

-g

nul

ltr

amaf

ock f

e o

l (u

)

l>>O

mine

M-

.994

316

říž:

the

e l

ocal

ity

; m

ino

r r

ock

f the

nbl

ende

oti

-b

rin

abbr

c te

l (b

row

gre

)

>>Bt

M-

.060

.090

ím

ěř

gra

of th

ím

ěř

f the

ail

ing

tic

ock

s o

f the

old

n p

ton,

al a

ocia

h th

e ga

roi

c b

y of M

ař

íž

. T

arry

itu

of th

e vi

lla

mica g

rani

zogra

)

htl

y po

rphy

ritic

l-gra

r t

ext

-f (mi

croc

)

~Pl

g ~Q>

178

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

procedures described in Balogh (1985), results of an interlabo-
ratory calibration have been presented by Odin (Ed.) (1982).
Standards LP-6 and HD-B1 have been used to calibrate the
measurement of

Ar(rad) and K concentrations and atmo-

spheric argon for checking the determination of Ar isotopic ra-
tios. Atomic constants according to Steiger & Jäger (1977)
have been used for calculation of ages.

Apatite fission-track analysis (AFTA) was undertaken to

determine the age and the thermal history of gabbroic and spa-
tially-associated granite. The external detector method was
used for fission-track analysis.

The Sm-Nd isotopic work was carried out in the isotope lab-

oratory at the Universität München according to the proce-
dures outlined in Hegner et al. (1995). The isotopic
measurements were carried out on a MAT 261 in a dynamic
quadruple mass collection mode. The

143

Nd/

144

Nd ratios were

normalized to

146

Nd/

144

Nd= 0.7219. The external precision of

the

143

Nd/

144

Nd ratios is 1.2

×10

—5

as has been confirmed with

an Ames Nd standard solution yielding 0.512142±12 (N= 35),
corresponding to 0.511854 in the La Jolla Nd reference stan-
dard material. The

values were calculated with the parame-

ters of Jacobsen & Wasserburg (1980). Present-day values for
the chondrite uniform reservoir (CHUR):

147

Sm/

144

Nd=

0.1967,

143

Nd/

144

Nd= 0.512638 (Jacobsen & Wasserburg

1980;

143

Nd/

144

Nd re-normalized to

146

Nd/

144

Nd= 0.7219).

Sr/

Sr ratios were measured in a dynamic double cup mass

collection mode and normalized to

Sr/

Sr= 0.1194. The

NIST 987 reference material yielded

Sr/

Sr= 0.71022

(N= 22).

Sampled localities and petrography

The list of the rocks and their location is presented in Ta-

ble 1,  together  with  their  concise  petrographical  characteris-
tics. The rock names correspond to the modal classification of
Le Maitre (Ed.) (2002). Geographical coordinates of individual
rock samples are presented in Table 1 and quantitative modal
compositions  in  Table 2.  Prevailing  primary  magmatic  rock-
forming  mineral  assemblages  of  most  of  the  gabbroic  rocks

are  variably  overprinted  during  the  later  metamorphic  pro-
cesses.  Depending  on  fluid  activity,  coronitic  gabbros  from
the  Vratěnín  Unit  with  preserved  original  magmatic  ophitic
to  gabbroophitic  textures  were  variably  recrystallized  to
gabroamphibolites  where  pyroxene  is  mostly  replaced  by
different  amphibole  species.  Plagioclase  is  also  recrystal-
lized  and  variably  equilibrated  into  a  mosaic  of  newly
formed grains. Some samples from Maříž and Mešovice are
recrystallized  to  relatively  fine-grained  gabbroamphibolites,
where  only  several  relicts  of  uralitized  pyroxene  have  been
preserved. These microstructures show that recrystallization
occurred in the amphibolite facies grade.

Compositional layering on a centimeter scale of some

samples from Maříž show that cumulation of olivine- and/or
orthopyroxene-rich and feldspar-rich layers played an impor-
tant role in the differentiation of the parent magma.

Rock-forming minerals

Olivine is ubiquitous, in particular in the olivine norite

from Nonndorf, more rarely also Korolupy. It forms subhedral
grains (Fo

60—50

) concentrated in the centers of coronitic tex-

tures (Fig. 2A). Subhedral olivines in the matrix are less
magnesian (~ Fo

). More magnesian olivine (Fo

65—80

, cf.

data in Table 3) also occurs in substantial amounts in the oli-
vine gabbronorite (M-5-1) and olivine hornblendite (M-5-4)
from Maříž.

Orthopyroxene (En

70—60

) is common in the Korolupy and

Nonndorf norites, concentrated in the centers (Fig. 2B) or
forming the rims of olivine in coronitic textures (Fig. 2A). Its
rarer presence in the Nonndorf samples (En

70—60

, rare rims up

to En

) is compensated for by the substantial amount of oliv-

ine in the same structural position in the coronitic textures.
Maximum concentrations of orthopyroxene occur in the Maříž
gabbronorite (M-5-2) where compositions vary from enstatite
(En

80—70

) to rare rims of ferrosilite (En

) (cf. Fig. 3 and Ta-

ble 4). Uralitization of orthopyroxenes is common. Clinopy-
roxene occurs ubiquitously in the gabbroic rocks. It forms
over 40 vol. % in the Uherčice melanorites (M-3A) and sub-

Sample

No.

M-1b M-2 M-3A M-3B M-4 M-5-1 M-5-2 M-5-3 M-5-4 M-5-5 M-6

Olivine

20 2 0 0 0 8 0 0 30 0 0

Orthopyroxene

25 38 0 0 3 14 34 0 4 0 0

Clinopyroxene

0 0

43 8 0 12 11 8 0 0 0

Amphibole brown

5 7 35 0 51 28 2 13 0 47 0

Amphibole (light) green

0 0 0 62 0 0 0 0 61 5 0

Garnet

0 1 2 0 0 0 0 0 0 0 0

Dark mica

2 2 0 0 0 2 1 35 0 5 7

Muscovite

0 0 0 0 0 0 0 0 0 0 8

Plagioclase

45 47 20 29 38 31 49 40 0 41 25

K-feldspar

0 0 0 0 0 4 0 0 0 0

Quartz

0 0 0 0 0 0 0 0 0 0

Ore minerals

2 3

tr. 1 5 1 3 1 5 2

tr.

Titanite

0 0 0 0 2 0 0 1 0 0 0

Apatite

1 0 0 0 1 0 0 2 0 0

tr.

Total

100 100 100 100 100 100 100 100 100 100 100

Number of analytical points

950 1000 900 950 1000 1200 1000 1000 1100 1100 980

In samples Nos. M-5-1 and M-5-3 (both from Maříž), the presence of small amounts of cummingtonite has been microscopically stated; tr. — traces

Table 2: Modal composition of the gabbroic rocks (in vol. %).

179

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

Fig. 2. Back-scattered electron image (Cameca SX-100): A – Coronitic texture of olivine norite from Nonndorf. Olivine (Ol) in the centre of the
coronitic texture is rimmed by orthopyroxene (Opx) of enstatite and amphibole (Amp) of pargasite compositions. Chromium spinel (Sp) occurs
along the olivine-orthopyroxene boundary. Plagioclase (Plg) is of labradorite composition. B – Coronitic texture of norite from Korolupy. Ortho-
pyroxene (Opx) of enstatite composition in centres of coronite texture is rimmed by pargasite (Amp) with a marginal zone of intergrowths with
plagioclase (Plg) of labradorite composition. C – Younger biotite (Bt) laths penetrating along hypautomorph amphibole (magnesiohornblende)
grains (Amp) and plagioclase of andesite to labradorite composition (Plg) in the biotite gabbro M-5-3 from Maříž. Numerous apatite (Ap) grains
are present. D – An elongated hypautomorph laths of ilmenite (Ilm) with isometric titanite (Ttn) at the contact with pargasite (Amp) and plagio-
clase (Plg) of andesine to labradorite composition. Note the unusual parallel structure of the Mešovice hornblende norite.

Sample M-1b

M-1b

M-2

M-5-1

Analysis COR/C

COR/C

COR/C C R

Location Nonndorf

Korolupy

Maříž

SiO

36.86

36.41

36.57

39.40

39.27

TiO

0.00

0.06

0.00

FeO

34.78

37.89

33.91

23.23

23.64

MnO

0.33

0.53

0.38

0.26

MgO

27.96

25.28

28.72

37.15 36.49

CaO

0.00

0.04

0.00

0.04

Total

99.93 100.17

99.62 100.04 99.70

1.018 1.020

1.011

1.024 1.027

0.000 0.001

0.000

0.000 0.000

0.804 0.888

0.784

0.505 0.517

0.008 0.013

0.009

0.006 0.006

1.151 1.056

1.184

1.439 1.422

0.000 0.000

0.001

0.000 0.001

Cations

2.981 2.978

2.989

2.974 2.989

Mg/(Fe+Mg)

0.59

0.54

0.60

0.74

0.73

C — core, R — rim, COR — coronite structure

Table 3: Representative microprobe analyses of olivine and empiri-
cal formulae based on 4 oxygens.

stantial amounts also occur in the Maříž olivine gabbronorite
(M-5-1),  gabbronorite  (M-5-2)  and  gabbro  (M-5-3).  Cli-
nopyroxene is present as euhedral to subhedral crystals while
smaller subhedral grains occur in the matrix. All the clinopy-
roxenes  have  the  composition  of  diopside  (Table 4  and
Fig. 3 – Morimoto 1988 classification), with compositions
in  the  range  of  En

45—37

15—07

53—46

. The clinopyroxene

crystals are largely homogeneous but with indistinct chemi-
cal and coloured zoning (light brown to light green).

Amhiboles are, together with orthopyroxenes the most

abundant ferromagnesian minerals of the gabbroic rocks.
They are either primary, represented by minor dark brown and
deep green subhedral crystals or secondary pale green acicular

180

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

Table 4:

Representative

microprobe

analyses

orthopyroxene

and

clinopy

roxene

and

empirical

formulae

ased

ations.

or  prismatic  crystals  pseudomorphing
primary  pyroxenes  and/or  amphiboles.
The  most  abundant  primary  amphibole
variety is pargasite to ferropargasite con-
centrated  in  rims  of  coronitic  textures
(Fig. 2A,B)  of  norites  from  Korolupy
and  Nonndorf.  However,  anhedral
grains  of  dark  brown  pargasite  some-
times  replace  orthopyroxene.  The  par-
gasite  to  ferropargasite  (Table 5  and
Fig. 4  –  Leake  (Ed.)  1997  classifica-
tion) are typical of the Mešovice samples
while  pargasite  to  edenite  characterize
the more strongly amphibolized Uherčice
and Maříž gabbroic rocks. Hornblendes of
the  tschermakite  to  magnesiohornblende
series,  transitional  to  the  secondary  am-
phiboles, are found in the Maříž rocks in
strongly retrogressed metagabbros to well
equilibrated gabbroamphibolites. The typ-
ical secondary amphiboles have actinolitic
compositions. Cummingtonite (mostly af-
ter  orthopyroxenes)  often  occurs  in  the
parallel growths with actinolite.

Dark

mica

typically

rare

(~ 1 vol. %)  as  anhedral  intercumulus
crystals in most of the gabbroic rocks but
forms up to 35 vol. % in the Maříž gab-
bro  (M-5-3).  It  penetrates  as  a  younger
mineral  along  the  grain  boundaries  (see
Fig. 2C).  An  Al

[6]

vs. Fe

tot

/(Fe

tot

+ Mg)

plot (Fig. 5; Fleet 2003) shows the
range from phlogopite (Maříž) to biotite
in the Korolupy and Nonndorf samples
(cf. in Table 6).

Plagioclase is the most abundant com-

ponent of the gabbroic rocks ranging from
subhedral laths to rare euhedral crystals.
Its composition varies from anorthite to
oligoclase in rims (An

20—90

05—07

10—80

)

(cf. Table 7 and Fig. 6). The most calcic
feldspars  occur  in  the  Uherčice  mela-
gabbro whereas oligoclase compositions
are  associated  with  samples  with  urali-
tized pyroxenes (cf. Koller 1998). Alkali
feldspar  occurs  as  subhedral  grains  in
some  gabbroic  samples  of  the  Maříž
body with a composition similar to that
in  the  Číměř  muscovite  biotite  granite
(cf. Table 7 and Fig. 6).

Hercynite is present in coronitic as-

semblages in the Korolupy and Nonndorf
norites. Inclusions in the Nonndorf oliv-
ines  are  Cr-spinels,  whereas  inclusions
in orthopyroxenes are of magnetite com-
position. Magnetite occurs as rare euhe-
dral  to  subhedral  corroded  crystals,
generally  in  association  with  the  mafic
minerals  and  their  secondary  products.

ple

-1b

-2

-5-

-3A

-3B M

-3B

-5-

Ana

COR/

R I

COR/

R I

COR/

C-R

nndo

říž U

her

či

ce M

ař

íž

TiO

FeO

MnO

Tot

T S

.003

T A

olas

ton

Ferr

ilit

13.

Jad

eit

— c

ore

, R

— rim

, Ph

—

cry

, IG

— inte

—

cor

oni

181

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

Fig. 3. Pyroxenes in quadrilateral diagram of Morimoto (1988).

Sample M-1b

M-1b

M-2

M-3B

M-4

M-5-2

M-5-4

M-5-5

Analysis

COR/C COR/R COR/C COR/R Ph/C Ph/R Ph/C Ph/R Ph/C C-R/Gr C/Br R/Gr

Location Nonndorf Korolupy Uherčice Mešovice

Maříž

SiO

41.12

41.08

41.58

40.12

45.41

41.76

42.32

39.65

51.36

45.64

50.88

54.87

TiO

0.04

0.07

0.04

0.19

0.68

1.45

1.60

0.94

1.30

0.12

0.14

17.51

18.39

16.72

18.60

12.49

14.54

11.31

14.19

7.48

13.06

7.99

3.97

0.05

0.08

0.00

0.64

0.00

0.83

0.61

0.03

0.00

FeO

10.58

11.06

11.92

12.97

8.62

10.26

18.15

18.44

5.88

5.21

9.28

7.99

MnO

0.18

0.03

0.20

0.12

0.30

0.20

0.14

0.11

0.23

0.26

MgO

12.52

12.23

11.95

11.17

14.45

12.34

9.50

8.21

18.93

17.07

17.09

18.71

CaO

11.50

11.44

11.16

10.90

11.68

11.94

11.75

11.54

11.87

11.85

10.81

11.60

2.59

2.77

2.36

2.54

2.16

2.52

1.89

2.30

1.13

2.01

1.05

0.51

0.59

0.73

0.58

0.72

0.29

0.73

0.76

0.91

0.24

0.39

0.20

0.05

Total

96.68

97.88

96.54

97.18

95.59

95.71

97.33

96.98

98.80

97.25

97.68

98.10

T Si

6.017 5.957 6.108 5.878

6.653

6.250

6.401

6.063

7.105

6.469

7.144

7.627

T Al

1.983 2.043 1.892 2.122

1.347

1.750

1.599

1.937

0.895

1.531

0.856

0.373

Sum_T

C Al

1.034

1.098

1.000 1.087

0.808

0.812

0.416

0.619

0.324

0.649

0.466

0.277

C Cr

0.006

0.009

0.000 0.000

0.000

0.076

0.000

0.091

0.068

0.003

0.000

C Fe

0.311

0.303

0.376 0.476

0.141

0.035

0.254

0.207

0.295

0.228

0.522

0.328

C Ti

0.004

0.008

0.008 0.004

0.021

0.077

0.165

0.184

0.098

0.139

0.013

0.015

C Mg

2.731

2.644

2.617 2.440

3.156

2.753

2.142

1.872

3.904

3.607

3.577

3.877

C Fe

0.903

0.936

0.987 0.985

0.856

1.228

2.010

2.110

0.281

0.303

0.406

0.489

C Mn

0.011

0.002

0.012 0.007

0.019

0.013

0.009

0.008

0.007

0.013

0.015

Sum_C

B Fe

0.081

0.102

0.128

0.059

0.021

0.032

0.042

0.104

0.087

0.162

0.112

B Mn

0.011

0.002

0.013

0.008

0.019

0.013

0.009

0.008

0.007

0.014

0.015

B Ca

1.803

1.778

1.756

1.711

1.833

1.915

1.904

1.891

1.759

1.800

1.683

1.805

B Na

0.105

0.118

0.129

0.153

0.089

0.046

0.051

0.058

0.128

0.107

0.141

0.068

Sum_B

A Na

0.630

0.661

0.543 0.568

0.525

0.686

0.503

0.624

0.175

0.446

0.088

0.000

A K

0.110

0.135

0.109 0.135

0.054

0.139

0.147

0.178

0.042

0.071

0.036

0.007

Sum_A

0.740

0.796

0.651 0.703

0.579

0.825

0.650

0.801

0.218

0.516

0.124

0.002

Sum_cat

15.740

15.796 15.651 15.703 15.579 15.825 15.650 15.801 15.218 15.516 15.124 15.002

Sum_oxy

23.006

23.030 23.011 23.000 23.067 23.053 23.000 23.000 23.050 23.050 23.043 23.059

C — core, R — rim, Ph — phenocryst, IG — intergrowth, COR — coronite structure, Br — brown, Gr — green

Table 5: Representative microprobe analyses of amphibole and em-
pirical formulae based on 15 cations.

Fig. 4. A,B – Amphiboles in classification diagram of Leake (Ed.)
(1997).

182

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

Table 6: Representative microprobe analyses of mica and empirical formulae based on
22 oxygens.

Fig. 5. Dark micas in 100 Fe

tot

/(Fe

tot

+Mg) vs. Al

diagram after

Fleet (2003).

The  highest  concentrations  are  in  the  Maříž  (M-5-4)  and
Mešovice  samples.  The  compositions  show  very  low  ulvö-
spinel contents (Usp 0—4 mol %). Ilmenite is present as a de-
composition  product  of  the  primary  titanium-rich  magnetite
from Korolupy, and Maříž (together with rare rutile) or pene-
trates as a younger mineral along grain boundaries (Mešovice,
MnO  ~ 10 wt. %,  Fig. 2D)  where  it  is  partly  “leucoxenized”
and transformed to titanite. Small crystals of titanite occur in
association with ilmenite in all gabbroic rocks. However, sub-
hedral grains of almandine, in symplectite association with
ilmenite occur in norite from Korolupy and as individual iso-
metric  grains  in  melanorite  from  Uherčice.  Pyrrhotite  has
been found at Maříž only. Fluorapatite occurs in all the gab-

broic rocks but zircon is known only as a
scarce accessory mineral in Maříž. Pyrite
is present in all the gabbroic rocks, particu-
larly at Mešovice where it occurs with
chalcopyrite.

Geothermobarometry

Temperature and pressure estimates are

difficult to obtain as a result of composi-
tional  variability  in  the  minerals  arising
from recrystallization and partial re-equil-
ibration  during  cooling  and  decompres-
sion. Estimates of the highest temperature
and  pressure  equilibration  conditions  of
the  rocks  are  therefore  based  on  the  core
compositions  of  minerals  judged,  on  tex-
tural grounds, to represent the earliest as-
semblages.

Temperatures were calculated using the

plagioclase-amphibole  thermometer  of
Holland & Blundy (1994). Additionally, in
samples  with  coronitic  texture  (Korolupy
and Nonndorf), the temperature of coronas
was  calculated  using  “Ca-in-orthopyrox-
ene  thermometer”  of  Brey  &  Köhler

Sample

M-1b M-1b M-2 M-2 M-5-1 M-5-3 M-5-5

Analysis

R R C R C

(cpx)

Ph/C

Location Nonndorf

Korolupy

Maříž

SiO

35.08

35.49

34.84

35.35

38.74

37.45

37.53

TiO

5.90 4.02 5.03 5.65 3.16 3.43 3.15

14.31

15.89

14.22

13.71

16.37

15.24

15.82

0.03 0.06 0.00 0.00 0.50 0.18 0.20

FeO

24.12

19.83

24.45

24.25

8.06

14.11

13.12

MnO

0.02 0.09 0.00 0.00 0.00 0.21 0.11

MgO

7.39

11.18

7.08

6.47

18.41

14.26

15.26

BaO

0.06 0.00 0.00 0.03 0.25 0.77 0.29

0.15 0.35 0.01 0.00 0.65 0.09 0.13

9.44 8.88 9.26 9.31 8.37 9.64 8.99

Total

96.50

95.79

94.89

94.77

94.51

95.38

94.60

5.444

5.402

5.502

5.581

5.605

5.603

5.586

2.556 2.598 2.498 2.419 2.395 2.397 2.414

0.059 0.250 0.147 0.130 0.394 0.288 0.359

0.689 0.460 0.598 0.671 0.344 0.386 0.353

3.130 2.524 3.229 3.202 0.975 1.765 1.633

0.004 0.007 0.000 0.000 0.057 0.021 0.024

0.003 0.012 0.000 0.000 0.000 0.027 0.014

1.710 2.537 1.667 1.523 3.971 3.180 3.386

0.004 0.000 0.000 0.002 0.014 0.045 0.017

0.045 0.103 0.003 0.000 0.182 0.026 0.038

1.869 1.725 1.866 1.875 1.545 1.840 1.707

Cations

15.513 15.618 15.510 15.403 15.482 15.578

15.531

Mg/(Fe+Mg)

0.35 0.50 0.34 0.32 0.80 0.64 0.67

C — core, R — rim, IG — intergrowth, Ph — phenocryst

(1990).  Because  of  the  lack  of  a  precise  barometer  for  cli-
nopyroxene-free  gabbroic  rocks,  pressures  were  calculated
only  for  clinopyroxene-bearing  gabbros  using  the  clinopy-
roxene geobarometer (Nimis 1999). The BH model of Nimis
(1999)  was  selected  as  the  most  reliable,  because  it  is  cali-
brated for a composition similar to that of the gabbros under
consideration.

Equilibrium temperature and pressure estimates are given in

Table 8. The temperatures calculated for pressures 5—10 kbar
are  similar  for  coronitic  (700—840 °C)  and  non-coronitic
gabbroic  rocks  (680—850 °C).  The  pressures  calculated  for
the  Uherčice  melanorite  and  Maříž  gabbro  (M-5-3)  range
from 7 to 13 kbar. This large uncertainty reflects the strong
dependence of the clinopyroxene barometer on the estimated
temperature. The two-pyroxene thermometry (1000—700 °C)
and  clinopyroxene—plagioclase  barometry  (8—5 kbar)  per-
formed by Koller (1998) also show a wide scatter of data for
these rocks.

Geochemical characteristics of the gabbroic rocks

Major element and trace element data of ten gabbroic rock

samples from one locality in the Moldanubian Monotonous
Unit and four localities from the Vratěnín Unit of the Mora-
vian affinity, and one granite sample from the Moldanubian
pluton are presented in Table 9.

Major and minor elements

The gabbroic rocks show large variation of Mg# from 61

(49) to 83 [Mg#= 100Mg/(Mg+ Fe

) for Fe

/Fe= 0.15]. The

183

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

Sample M-1b

M-1b

M-2 M-2

M-3B

M-3B M-4 M-4

M-5-3

M-5-5

Analysis COR/C

COR/R Ph/C Ph/R Ph/C Ph/R INC/C INC/R Ph/C Ph/R Ph/R Ph

Location Nonndorf Korolupy

Uherčice

Mešovice

Maříž

SiO

53.14 57.79 53.15 54.81 45.24 60.85 46.00

60.52 50.45 55.62

64.00

64.61

TiO

0.00 0.06 0.03 0.00 0.00 0.04 0.00

0.00 0.00 0.03

0.00

30.57 26.85 29.68 29.37 34.88 24.70 35.02

25.35 31.83 28.58

23.31

18.51

FeO

0.14 0.19 0.29 0.19 0.10 0.13 0.37 0.27 0.02 0.07 0.00 0.02

MnO

0.02 0.03 0.03 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.00 0.00

MgO

0.01 0.01 0.26 0.12 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00

BaO

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.03 0.03 0.19

CaO

12.26 8.08 12.37 11.01 18.38 6.19 17.48

6.14 14.56 10.04

4.14

0.00

4.70 7.34 4.45 5.21 0.94 8.15 1.43 8.16 3.37 5.52 9.42

0.20

0.04 0.06 0.05 0.05 0.00 0.03 0.00 0.10 0.05 0.15 0.13

16.50

Total

100.88 100.41 100.31 100.76 99.54 100.09 100.33

100.54 100.28 100.04

101.03 100.03

9.541 10.322

9.605

9.809 8.375 10.812 8.441

10.721 9.168 9.994 11.199 11.968

6.464

5.648

6.316

6.190 7.605

5.168

7.568

5.288

6.812

6.048

4.803

4.038

0.000

0.008

0.004

0.003 0.000

0.005

0.000

0.004

0.000

0.021

0.028

0.044

0.028 0.015

0.019

0.057

0.040

0.003

0.011

0.000

0.003

0.005

0.000 0.000

0.000

0.003

0.000

0.003

0.070

0.032 0.000

0.000

0.003

0.000

0.000 0.000

0.000

0.002

0.014

2.358

1.546

2.395

2.111 3.646

1.178

3.437

1.165

2.835

1.933

0.776

0.000

1.636

2.542

1.559

1.808 0.337

2.808

0.509

2.803

1.187

1.923

3.196

0.072

0.009

0.014

0.012

0.011 0.000

0.007

0.000

0.023

0.012

0.034

0.029

3.899

16.005 15.978 15.925 16.000 15.980 15.985 16.009

16.009 15.980 16.046 16.002 16.006

4.030 4.138 4.085 3.990 3.998 4.012 4.009

4.031 4.037 3.903 4.003 3.988

Albite

40.9

62.0

39.3

46.0

8.5

70.3

12.9

70.2

29.4

49.4

79.8

1.8

Anorthite 58.9

37.7

60.4

53.7

91.5

29.5

87.1

29.2

70.3

49.7

19.4

0.0

Orthoclase 0.2

0.3

0.1

0.2

0.1

0.6

0.3

0.9

0.7

97.8

Celsian

0.0

0.1

0.4

C — core, R — rim, Ph — phenocryst, INC — inclusion, COR — coronite structure

Table 7: Representative microprobe analyses of feldspars and empirical formulae based on 32 oxygens.

Fig. 6. Feldspars in Ab—Or—An diagram after Smith (1974).

lower  Mg#  (61—64)  are  typical  for  coronitic  norites  from
Korolupy  and  Nonndorf.  Only  the  Mešovice  norite  has  a
lower  Mg#  of  49  coupled  with  high  TiO

contents

(3.4 wt. %), higher contents of Fe

, P

together with

Zr,

and very low contents of compatible elements (Cr, Co), show-
ing a more fractionated nature of the rocks after earlier accu-
mulation of Mg-bearing phases. The relationship between the
SiO

and alkalies of the studied rocks is illustrated on TAS di-

agram (Fig. 7; Cox et al. 1979). In spite of their similar petrog-
raphy, the two samples from Maříž (M-5-2 and M-5-4)
straddle the gabbro field boundary towards the lower alkali
contents. No significant correlations were found between SiO

and selected oxides (Al

, MgO, TiO

, P

, see Fig. 8). The

wide variability of compatible element contents, for example
Ni (53—1076 ppm), Co (16—140 ppm), Cr (22—1867 ppm),
V (159— 521ppm), and Sc (22—40 ppm) and Sr-Nd isotopes
illustrates the heterogeneity of the gabbroic rocks even from
a single locality, such as Maříž.

Table 8: Estimated equilibration temperatures and pressures of the gabbroic rocks.

Temperature (°C)

Pressure (kbar)

Locality/No. Rock

type

Plg–Amp

Ca-in-opx*

Cpx (BH model)

Nonndorf (M-1b)

Olivine norite (coronitic)

700–840

670–800

Korolupy (M-2)

Norite (coronitic)

710–810

640–770

Uherčice (M-3A)

Amphibole melanorite

780–850

7–12

Mešovice (M-4)

Hornblende norite

740–850

Maříž (M-5-1)

Hornblende ol. gabbronorite

810–860

Maříž (M-5-3)

Biotite gabbro

680–720

8–13

*temperature estimates for olivine–ortopyroxene–amphibole coronas. Plg–Amp–plagioclase — amphibole thermometer of Holland & Blundy (1994) calculated for
pressures from 5 to 10 kbar; Ca-in-opx — orthopyroxene thermometer of Brey & Köhler (1990) calculated for pressures 5–10 kbar; Cpx (BH model) — clinopyroxene
barometer (BH model) of Nimis (1999) calculated for temperatures obtained from Plg–Amp thermometer.

184

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

Trace elements

The chondrite-normalized REE patterns reveal similar

trends (cf. Fig. 9A) with characteristic LREE enrichment in
most of the samples. Nonetheless, the degree of LREE en-
richment is high (La

/Yb

= 2.2—49.1), with the highest de-

gree of REE fractionation observed in the Maříž
gabbronorite sample M-5-2. A distinct positive Eu anomaly
present in all the studied samples (Eu/Eu*= 1.1 to 1.6) is in
agreement with plagioclase accumulations in the studied
rocks.

Table 9: Chemical composition of the gabbroic rocks.

Sample

M/1b M-2 M-3A M-3B M-4 M-5-1 M-5-2 M-5-3 M-5-4 M-5-5 M-6

SiO

49.12 50.48 46.14 46.52 41.68 49.86 51.72 45.26 47.22 49.96 73.08

TiO

0.98 0.95 0.91 0.56 3.38 0.44 0.37 1.68 0.28 1.00 0.23

15.75 15.86 14.88 12.84 14.21 15.32 10.26 14.78 4.15 18.47 14.33

1.95 1.91 1.30 1.95 4.70 0.89 1.40 1.67 3.05 1.69 0.44

FeO

8.86 8.18 4.30 5.41 11.53 6.55 7.01 7.22 9.48 4.14 0.99

MnO

0.15 0.14 0.19 0.21 0.16 0.12 0.15 0.12 0.18 0.13 0.02

MgO

8.98 7.38 9.77 11.13 7.29 13.77 18.46 10.95 27.62 8.18 0.36

CaO

9.06 9.92 16.69 16.82 11.60 8.97 7.68 9.58 2.41 8.75 0.79

2.66 2.87 1.04 1.08 1.95 1.51 0.95 1.16 0.25 2.25 2.91

0.38 0.40 1.54 1.05 0.73 0.36 0.26 3.48 0.09 1.97 5.32

0.15 0.15 0.13 0.09 0.25 0.08 0.07 1.06 0.10 0.10 0.25

–

0.10 0.14 0.20 0.18 0.16 0.18 0.18 0.14 0.10 0.24 0.04

0.83 0.76 1.98 1.44 1.89 0.67 0.77 2.09 4.00 2.50 0.66

0.48 0.47 0.41 0.30 0.16 0.70 0.35 0.24 0.58 0.24 0.15

Total

99.45 99.61 99.48 99.58 99.69 99.42 99.63 99.43 99.51 99.62 99.57

Rb (ppm)

9.56

8.75

48.99

29.46

15.64

12.18

6.60

151.80

2.71 130.6

310.0

0.52 0.39 2.30 1.68 0.45 3.73 1.46 13.66 1.62 8.86

17.78

203

240

231

212

498

415

207

1273

584

149

412

233

215

150

3961

622

253

1.92

0.90

25.58

5.59

7.62

2.61

7.03

1.83 14.32 29.43

21.4

22.0

31.0

32.4

35.1

28.6

39.8

33.8

28.2

26.0

2.7

12.2

11.4

14.3

9.1

15.6

7.2

6.7

14.9

4.2

19.1

8.1

5.02 5.01 11.26 4.83 14.16 4.04 2.53 69.15 2.10 9.24 23.63

11.54 11.53 25.52 11.01 31.94 8.84 5.72 153.10 4.72 20.98 52.90

1.64

1.62 3.44

1.53

4.34

1.17

0.79 20.27 0.62 2.72 6.68

7.15

7.74 13.45

6.47 18.47

5.12

3.50 79.27 2.65 11.56 24.45

2.10

2.24

3.12

1.73

4.55

1.20

0.93 10.97 0.58 2.89 5.40

0.91 0.99 1.09 0.72 1.64 0.65 0.40 3.51 0.21 1.23 0.51

2.37 2.44 2.81 1.77 4.10 1.26 1.00 6.12 0.59 3.24 3.73

0.40 0.41 0.48 0.29 0.63 0.20 0.18 0.81 0.11 0.54 0.51

2.40 2.27 2.85 1.85 3.43 1.34 1.21 3.40 0.72 3.33 1.98

0.48 0.43 0.53 0.35 0.64 0.28 0.25 0.58 0.16 0.68 0.28

1.29 1.19 1.49 0.96 1.61 0.81 0.73 1.49 0.48 1.99 0.67

0.17 0.15 0.21 0.14 0.20 0.11 0.12 0.17 0.08 0.28 0.08

1.09 0.92 1.25 0.85 1.16 0.76 0.78 0.95 0.52 1.71 0.48

0.15 0.14 0.18 0.12 0.16 0.11 0.11 0.14 0.09 0.26 0.06

1.23

0.72

4.55

1.02

1.49

0.59

0.54 2.65 0.36 2.48 17.23

0.18

0.19

2.23

0.33

0.36

0.15

0.15 0.64 0.11 0.58 8.76

22.90

18.00 31.6

21.9

32.1

25.6

14.3

15.2

13.2

36.0

85.2

0.79 0.60 1.33 0.80 1.52 0.75 0.52 0.88 0.40 1.14 2.83

182

165

193

192

521

186

245

230

159

139

10.4

5.06

4.68

7.10

2.93 21.28

1.92

0.85 10.50

0.99

4.00 15.84

1.58

0.86

0.68

0.58 1.34

0.48

0.27 0.49

0.26

0.51 1.58

340

224

337

515

1242

1867

149

1842

528

140

1.7

167

133

129

141

149

157

1076

211

2.0

#Mg

64.0

61.0

78.9

76.5

49.3

79.7

82.4

72.5

82.6

75.2

35.3

ΣREE

36.7

37.1

67.7

32.6

87.0

25.9

18.2

349.9

13.6

60.7

121.4

/Yb

3.30

3.92

6.44

4.10

8.75

3.80

2.33 52.42

2.90

3.88 35.45

Eu/Eu*

1.24 1.29 1.10 1.24 1.14 1.61 1.26 1.19 1.09 1.22 0.33

La/Nb

0.99 1.07 1.59 1.65 0.67 2.11 2.98 6.59 2.13 2.31 1.49

/Th

0.49 0.77 0.19 0.34 1.71 0.38 0.19 0.47 0.33 0.19 0.11

/Sm

0.43 0.32 0.40 0.50 0.28 0.84 0.61 0.06 0.90 0.49 0.62

The primitive mantle-normalized incompatible trace ele-

ment patterns of the gabbroic rocks show differences between
both absolute and relative trace element abundances (cf.
Fig. 9B). Nevertheless, most of the samples show similar dis-
tinctively fractionated patterns with common positive peaks at
K and Sr, but negative anomalies for Nb and Zr (Nb

= 0.2—0.8, Zr

/Sm

= 0.1—0.9). The only exception is in a

sample of norite from Mešovice, which is very rich in TiO

and Nb (3.4 wt. % and 21.3 ppm, respectively) due to the high
modal contents of titanian magnetite, ilmenite (0.1—0.3 wt. %
Nb

), and titanite (0.3—0.9 wt. % Nb

). The trace element

185

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

Fig. 8. Harker’s diagrams of indicative major and trace element variation of the gabbroic rocks.

Fig. 7. Total alkali-silica diagram of Cox et al. (1979) showing the
composition of the gabbroic rocks.

pattern of the Číměř granite from the Moldanubian pluton dif-
fers from those of the gabbroic rocks in its higher Th, K

O and

REE concentrations (Fig. 9A,B) and the presence of the char-
acteristic negative Eu anomaly (Eu/Eu*= 0.3).

Sr/

Sr and

143

Nd/

144

Nd isotopic systematics

The Nd-Sr isotopic compositions of the gabbroic samples

and  a  single  sample  of  Variscan-age  granite  associated  with
the Maříž gabbros are listed in Table 10 and plotted in Fig. 10.
As  outlined  below,  K-Ar  ages  of  570  to  550 Ma  for  horn-
blende relics, interpreted to be of magmatic origin, suggest a
Cadomian age for these suites. Regression of the Sm-Nd data
for all samples, with the exception of the isotopically distinct
Uherčice melagabbros, yielded an age of 290 Ma and a large
error of ~ 700 Ma. Rb-Sr isotopic data for these samples yield-
ed 660 Ma and an error of 370 Ma. The Sm-Nd isotopic data
from  two  gabbroic  samples  from  the  Uherčice  Complex  plot
on a line corresponding to 1.3 Ga. Clearly the Rb-Sr and Sm-
Nd  isotopic  systems  do  not  help  to  constrain  geologically
meaningful ages for these rocks. In the following we accept a
crystallization  age  of  560 Ma  for  them  and  outline  some
source  characteristics  for  these  mafic  lithologies  of  the

186

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

Fig. 9. A – Chondrite-normalized REE patterns for the gabbroic rocks.
B – Primitive mantle-normalized incompatible trace element patterns.
Normalizing values from Sun & McDonough (1989).

Table 10:

Rb-Sr

and

Sm-Nd

isotopic

data

for

the

gabbroic

rocks.

Fig. 10. Initial

Sr/

Sr vs.

isotopic ratios for the gabbroic rocks.

e Ro

(Ma

)

Rb/

)

(t)

147

144

143

Nd/

144

Nd(m

)

143

Nd/

144

Nd(t)

d(t)

M-1

liv

e no

rite

7063

7052

1744

5123

5117

–3

M-2

ite ~

7 24

7052

7043

1757

5125

5118

–0

M-3

. m

ano

rite

–8

M-3

l. m

ela

.5 21

7059

7027

1507

5121

5115

–6

M-4

nde

-5-

l. ol

. ga

ron

ori

.2 41

7057

7051

1415

5124

5119

-5-

abbr

ono

rite

7037

7030

1538

5124

5118

–0

-5-

ioti

gab

12 0.

09 0.

-5-

Horn

7097

7046

778

1472

5124

5118

–0

M-6

a gra

nit

.100

7768

7104

1349

5121

–6

— m

d ra

tio,

— init

l ra

tio;

Sr/

ized t

119

Deter

inat

n o

e acc

y a

nd e

xte

r NI

ded.

710237 ± 11 (

143

144

Nd r

ios ar

e n

ized

146

Nd/

144

Nd =

7219.

147

144

2% (

2σ

es Nd st

dar

d so

repar

ed at

uni

ded

143

Nd/

144

Nd =

512095 ± 12

σ,

N =

);

wer

e cor

rected

hin

e b

ias

y add

ing

000040 s

o t

giv

a r

io o

512135 eq

uiv

ale

511850 in

a J

la Nd s

ndar

d Nd deter

ed wer

e deter

y i

tope dilut

b and Sr

y I

-M

187

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

Moldanubian basement. Because all samples, except those
from Nonndorf, have low Sm/Nd ratios, age uncertainties up
to 20 Ma will have only negligible effects on the calculated
initial

values.

The initial

values calculated for 560 Ma show a very

large variation of + 5 to —8 (Fig. 10; Table 10). They docu-
ment a magmatic history of these gabbroic complexes charac-
terized by involvement of juvenile mantle-derived material as
seen in the norite sample from Mešovice, and major recycling
of ancient crustal components as documented in the Uherčice
gabbroic rocks with

values of ca. —6 to —8.

Interpretation of K-Ar ages and fission-track data

The first K-Ar ages on gabbroic rocks from the Moldanubi-

an and Moravian units of W Moravia and N Austria are sum-
marized  in  Table 11.  The  majority,  measured  on  amphibole,
clinopyroxene,  plagioclase  and  biotite,  range  from  389  to
254 Ma, confirming the importance of Variscan metamorphic
processes  on  Ar  behaviour.  However,  older  ages  (1302 Ma
and  550 Ma)  have  been  obtained  from  plagioclase  and  am-
phibole at Korolupy, 796 Ma, from plagioclase, from the simi-
lar gabbroic body at Nonndorf, and 568 Ma from amphibole at
Maříž. It is generally accepted that the closure temperature of
amphibole  is  significantly  higher  than  for  plagioclase  (Har-
land et al. 1990), suggesting that the older age of plagioclase
is  due  to  excess  Ar.  This  assumption  is  confirmed  by  the
Variscan  age  (344 Ma)  measured  on  the  plagioclase  M-2  at
Maříž,  after  treatment  with  diluted  HF.  The  plagioclase  ages
from the gabbronorites (M-5-1 and M-5-2) at Maříž are close-
ly similar (389 Ma and 388 Ma), despite the difference in their
K contents. This provides an argument against the presence of
excess Ar at this locality. K-Ar ages for amphibole and plagio-
clase from sample M-5-1 correspond to their closure tempera-
tures:  the  amphibole  is  significantly  older  (568 Ma)  and  is
very  similar  to  the  age  of  amphibole  from  Korolupy  sample
M-2 (550 Ma), where the excess Ar is indicated by the age of
plagioclase. Regarding the importance of Variscan events, the

individual  minerals  in  sample  M-2,  such  as  plagioclase  (pri-
mary  and  leached),  biotite  and  amphibole  of  various  density
fractions,  were  tested  for  overprinting,  at  least  partly,  during
the Variscan events. A separated lower density fraction (partly
actinolitized pargasite) yielded a significantly younger age of
449 Ma, while an older age of 573 Ma has been measured on
the higher density fraction (pargasite) from M-2.

Since there is no indication from plagioclase of any excess

Ar at Maříž, excess Ar is also not inferred for the amphibole.
The similarity of amphibole ages at Korolupy (573 Ma) and at
Maříž (568 Ma) suggests that Cadomian ages may have been
retained during the Variscan tectonometamorphic processes.
In units strongly overprinted by the Variscan metamorphism,
however, only zircon ages can solve the real age of gabbros.

Apatite fission-track analysis of two gabbroic samples

from Korolupy and Maříž (M-5-1) and the Číměř granite in-
dicate very similar ages of 150.2± 18.0 Ma (standard devia-
tion ±1

σ). Furthermore the samples show comparable track

length distribution and shortening of initial fission-track
lengths (mean length 11.5 µm) implying a slow and continu-
ous cooling from total annealing zone (i.e. > 120 °C) from
the Late Jurassic to the present.

Discussion

Rock associations and their relationship

The gabbroic rocks under consideration occur either in the

Moldanubian  Monotonous  Group  at  contact  with  the  Molda-
nubian pluton or in the Vratěnín Unit of the Moravian affinity
(sensu  Jenček  &  Dudek  1971).  However,  the  latter  unit  was
often  correlated  with  the  Moldanubian  Varied  Unit  (e.g.
Schulmann  et  al.  2005  and  references  therein).  We  prefer  to
correlate  the  Vratěnín  Group  with  the  Moravian  Unit  of  the
Brunovistulian margin for the following reasons:

a) apparent lithological similarity with the Vranov-Olešnice

Unit, which is intercalated with ca. 600 Ma old Cadomian
orthogneisses (Bíteš gneisses – Friedl et al. 2004);

Sample Rock

Dated mineral

K (%)

Ar(rad) 10

–6

ccSTP/g*

Ar(rad) %

Age ±1σ (Ma)

M-1b

Olivine norite

Plg

0.224

8.706

77.7

796 ± 32

M-2

Norite

Plg

0.215

15.960

77.6

1302 ± 50

M-2

Plg HF treated

0.274

4.037

20.1

344 ± 25

M-2

2.687

35.950

91.4

315 ± 12

M-2

Amp

0.323

8.023

86.9

550 ± 18

M-2

Amp>3.15

g·cm

–3

0.495

9.800

82.5

449 ± 17

M-2

Amp>3.20

g·cm

–3

0.244

6.399

72.4

573 ± 22

M-3A

Hornblende melagabbro

Amp

0.530

7.864

79.8

346 ± 13

M-4

Hornblende norite

Amp

0.591

8.773

90.7

346 ± 13

M-5-1

Hornblende ol. gabbronorite

Plg

0.171

2.889

60.1

389 ± 23

M-5-1

Amp

0.346

8.989

89.1

568 ± 21

M-5-2

Gabbronorite

Plg

0.115

1.935

71.3

388 ± 22

M-5-2

Cpx

0.411

4.365

81.2

254 ± 10

M-5-3

Biotite gabbro

6.492

87.460

95.5

320 ± 12

M-5-3

Amp+Cpx

0.332

4.846

71.6

342 ± 13

M-5-3

Amp~3.15

g·cm

–3

0.527

6.572

65.3

296 ± 12

M-5-3

Plg

1.246

13.990

73.4

268 ± 10

M-6

Two-mica granite

5.853

80.895

96.7

324 ± 12

*1 cm

of gas at standard temperature and pressure

Table 11: K-Ar ages of the gabbroic rocks.

188

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

b) the coronitic gabbro from Olešnice (Weiss 1985) in the

Svratka window shows the same pattern of corona develop-
ment and is spatially associated with marbles and garnet am-
phibolites as coronitic gabbros in the Vratěnín Unit.

The studied gabbroic rocks mostly form small rounded

bodies  X0  to  X00 m  in  size,  strongly  differentiated  by  pro-
cesses  of  crystal  accumulation,  liquid  fractionation  and  as-
similation  of  country  rocks.  This  implies  that  most  bodies
represent  cumulates  of  (ultra)mafic  composition.  Gabbroic
cumulates from the Moldanubian Monotonous Unit and the
Vratěnín Unit differ in: a) preserved magmatic layering ob-
served  only  in  the  Maříž  locality,  b)  their  composition:  the
Maříž  samples  are  Mg-rich,  while  those  from  the  Vratěnín
Unit are Fe-rich (cf. Koller 1998; Matějka & Holub 2003), c)
their mineralogy: the Maříž samples mostly contain only or-
thopyroxene,  while  those  of  the  Vratěnín  Unit  are  mostly
two  pyroxene-bearing,  d)  their  textures:  coronitic  textures
are developed only in the Vratěnín Unit.

Ultramafic to mafic cumulate gabbroic complexes with

coronitic textures typically occur in medium- to high-pressure
amphibolite-granulite  facies  metamorphic  terrains  (e.g.  de
Haas  2002),  but  olivine-plagioclase  coronas  were  described
from low-pressure (up to 1 kbar) domains (Turner & Stuewe
1992). They may be formed either by late magmatic processes
during  reaction  of  cumulus  phases  with  hydrous  interstitial
liquids, or in the solid state due to the activities of fluid-assist-
ed metamorphic processes (Claeson 1998; de Haas et al. 2002;
Ikeda et al. 2007; Helmy et al. 2008).

Their tectonomagmatic and metamorphic histories are

postdated  by  the  Variscan  high-grade  metamorphic  event
(ca.  350—340 Ma)  recorded  in  the  Moldanubian  Unit  and
somewhat  later  also  in  the  underlying  Moravian  complexes
(Fritz & Neubauer 1993; Kotková et al. 2007). Unfortunate-
ly,  the  Sm-Nd  isochrone  ages  fail  to  give  real  geological
ages,  most  likely  due  to  variable  contamination  of  gabbros
by host rocks. The results of K-Ar dating of different miner-
als  from  the  coronitic  and  non-coronitic  gabbros  show  a
relict  of  ca.  570—550 Ma  Cadomian  ages,  but  also  a  strong
Variscan imprint, which disturbed the K-Ar isotopic system.
Three possible scenarios exist:

1. The gabbroic complexes represent pre-Variscan intru-

sions involved in the Variscan high-grade metamorphic pro-
cesses. The presence of coronitic textures only in the Vratěnín
Unit reflects different conditions during the Cadomian late
magmatic processes – the presence of H

O-rich late magmat-

ic fluids, rapid exhumation and cooling in the case of coronitic
gabbros from the Vratěnín Unit. Mafic to ultramafic complex-
es with coronitic textures of ca. 570—550 Ma and very similar
geochemical and Sm-Nd isotopic characteristics were reported
by Cottin et al. (1998) from the Panafrican Belt in Hoggar and
the  Panafrican  Eastern  Desert  terrane  in  Egypt  (Helmy  et  al.
2008).  Both  regions  are  possible  candidates  for  areas  from
which  the  Armorican  and  Brunovistulian  crustal  fragments
could be derived.

2. The gabbros are pre-Variscan intrusives, possibly Cado-

mian in age, but coronitic textures originated during the
Variscan metamorphic processes connected with underthrust-
ing of the Brunovistulian margin beneath the Moldanubian
root. Such processes, in which the intrusive age is much high-

er than that of the coronas, have been reported from the Gren-
villian orogen in Canada, Norway, but also from Variscan ter-
rains  of  the  Massif  Central,  France  and  Bohemian  Massif
(Štědrá  et  al.  2002).  This  interpretation  is  supported  by  the
presence  of  a  garnet  corona  around  plagioclase  in  a  solitary
sample  from  Korolupy  and  replacement  of  ilmenite  with  de-
veloped amphibole coronas by titanite.

3. Olivine—orthopyroxene coronas could have originated in

the magmatic stage in pre-Variscan times because olivine is in
textural equilibrium with the magmatic pargasite, which also
replaces orthopyroxenes. Fine-grained symplectitic amphibole
with  spinel  grains  and  scarcely  preserved  garnet  coronas
around  plagioclase  are  products  of  solid-state  fluid-assisted
metamorphic  reactions,  which  accompanied  the  dehydration
in the host metasediments.

Petrogenesis of the gabbros: mantle and crustal contribution

The geochemical data help to define the petrogenesis of

the gabbroic rocks. SiO

vs. alkali contents show their subal-

kaline character (Fig. 7), with the exception of the Mešovice
norite and the Maříž (M-5-5) gabbros. The chemical compo-
sition  of  the  primary  gabbroic  rocks  should  suggest  deriva-
tion  of  the  primary  gabbroic  magmas  from  mantle-sources.
The high Mg# numbers and MgO concentrations in most of
the samples (Table 9) most likely point to their cumulate ori-
gin produced by fractional crystallization, probably in crust-
al  magma  chambers.  The  positive  Eu  anomalies  (Fig. 9A)
suggest  that  plagioclase  is  a  major  cumulus  phase  in  these
rocks. The evolution of basaltic magmas in the crust is typi-
cally  accompanied  by  variable  degrees  of  contamination,
namely by the assimilation-fractional crystallization processes
outlined by Hildreth & Moorbath (1988). High trace element
contents (e.g. light rare earth elements – LREE, large ion li-
thophile elements – LILE), well developed negative Nb anom-
alies and distinctly variable Sr-Nd isotopic composition (e.g.
ε

—8.0 to +5.0) of the samples (see Table 10) may suggest

either significant contribution by crustal (subduction-related)
material in the magma source or (more probably) incorpora-
tion of felsic crustal material to the parent magma during its
ascent or emplacement.

In order to account for the observed geochemical charac-

teristics we consider two possibilities for their petrogenesis:
(1) the magma was derived from enriched upper mantle sourc-
es with subduction-related characteristics or (2) primary mag-
ma of mantle origin was contaminated during emplacement
(underplating) by crustal material and acquired its geochemi-
cal characteristics as a result of the assimilation-fractional
crystallization process.

In spite of their similar petrography and their present geotec-

tonic position, the Maříž gabbroic rocks are distinctly different
from those at Korolupy—Nonndorf and Mešovice. For example,
all the Maříž gabbroic rocks have high crust-like La/Nb ra-
tios of 2.1—6.6 (bulk continental crust has La/Nb ratio of 2.5;
Rudnick & Gao 2003), coupled with uniform low

values

from —0.6 to + 0.7 whereas gabbroic rocks from other locali-
ties have La/Nb ratios < 1.7 and show negative correlations
between La/Nb and

(Fig. 11). Such decoupling between

La/Nb (and also

Sr/

Sr) and

may be attributed to crustal

189

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

contamination by material with high La/Nb (Rudnick & Gao
2003) and/or derivation of the magma from the source with
already fractionated La/Nb  ratios  and  decoupled  Sr-Nd  iso-
topic  composition.  This  phenomenon  is  also  shown  by  the
differentiated  Maříž  intrusion.  The  degree  of  enrichment  of
mobile elements (Cs, Ba, Rb, K, Sr etc.) in the Maříž sam-
ples  is  strongly  correlated  with  the  radiogenic  Sr  isotopic
compositions. Such geochemical signatures commonly char-
acterize  the  mantle  wedge  affected  by  subduction-related
metasomatism (e.g. Keppler 1986; Hawkesworth et al. 1991;
Hermann et al. 2006).

Compared to the other samples, the Mešovice norite is dis-

tinct in having a positive Nb-anomaly (Nb

/Th

= 1.7) cou-

pled with a very high TiO

content (3.4 wt. %; Table 9), an

alkaline composition as signified in the TAS (Fig. 7) and a ra-
diogenic

value of +5.0. Positive Nb-anomalies as well as

high TiO

contents are characteristic of OIB or rift-related ba-

salts free of any subduction component (e.g. Lustrino & Wil-
son 2007 and references therein). The fact that the Mešovice
norite also has a character indicative of a highly incompatible
element-depleted mantle source, with highly radiogenic

(+ 5.0), strongly supports mantle-derived magma emplace-
ment during the continued crustal extension.

The Korolupy—Nonndorf norites have smaller negative

Nb-anomalies (Nb

/Th

= 0.5—0.8) than those from Maříž

(Nb

/Th

< 0.5). In spite of having La/Nb ratios and Sr con-

tents similar to those of the Uherčice gabbros, they are signifi-
cantly poorer in large lithophile elements than the Uherčice
gabbros. This suggests that they were only slightly contami-
nated by crustal material. In contrast, in spite of their similar
moderately negative Nb-anomalies and much lower

values

(—6 to —8), the Uherčice gabbros show two distinct geochemi-
cal patterns: (1) low Rb coupled with a highly non-radiogenic
Sr isotopic composition of 0.70275 (Uherčice, M-3B) and
(2) large lithophile element enrichment associated with high-
ly radiogenic Sr isotopic composition of 0.71909 (Uherčice,
M-3A). This can be interpreted as inherited from assimila-
tion of different crustal materials or more probably, old (e.g.

Nd model ages of 2.5 to 3.0 Ga; Liew & Hofmann 1988),
extensively recycled material.

Apparent trends (negative correlations between La/Nb and

and a possible mixing line in the Sr-Nd isotopic diagram)

for the Mešovice—Korolupy—Nonndorf—Uherčice rocks sug-
gest that these rocks originated from a single parent magma
that was affected by varying degrees of assimilation-fractional
crystallization process.

Conclusions

Petrological, geochemical, Sr-Nd isotopic and K-Ar studies

of gabbroic cumulates from the Moldanubian Monotonous
Unit and the Moravian Vratěnín Unit provide the following
constraints on the sources, evolution and age of these rocks:

(1) Both complexes represent pre-Variscan, partly differen-

tiated ultramafic—mafic intrusions of probably Cadomian age
(ca. 550—570 Ma), with very similar geochemical and isotopic
characteristics. They were emplaced into units of different mi-
crocontinent  fragments  derived  from  the  African  part  of  the
Neoproterozoic  Avalonian—Cadomian  orogen.  They  were
heterogeneously  involved  in  the  Variscan  collision  of  the
Moldanubian  and  the  Brunovistulian  microcontinents.  The
two-pyroxene  thermometry  (1000—700 °C)  and  clinopyrox-
ene-plagioclase  barometry  (8—5 kbar)  performed  by  Koller
(1998) also show a wide scatter of data for these rocks.

(2) Coronitic texture, present in the gabbroic rocks of the

Vratěnín  Unit,  could  have  originated  more  probably  during
both magmatic (orthopyroxene coronas) and/or the solid-state
fluid-enhanced  metamorphic  reactions.  Amphibole-  and
spinel-bearing, scarcely also garnet coronas were produced at
contact  between  symplectitized  orthopyroxene  and  plagio-
clase.  According  to  the  strong  amphibolite-facies  imprint  in
some gabbroic samples passing to garnet amphibolites, we as-
sume  that  amphibole—garnet  coronas  could  have  originated
during  underthrusting  of  the  Brunovistulian  margin  below
the  Moldanubian  Unit.  Later,  they  were  equilibrated  in  the
amphibolite-facies  conditions,  during  exhumation  and  final
imbrication of the Drosendorf stack.

(3) The studied gabbroic rocks crystallized from magma

which was derived from moderately depleted mantle sources
but  enriched  by  subduction-related  fluids  before  their  em-
placement.  More  probably  they  were  differentially  contami-
nated  by  heterogeneous  crustal  material  in  two  lithologically
distinct crustal units during the emplacement in pre-Variscan
times. This would explain the wide range of obtained

val-

ues  (+ 5  to  —8).  Close  spatial  relation  of  the  gabbroic  cumu-
lates  to  garnet  amphibolites  and  marbles  suggest  that  their
emplacement was connected with fragmentation and rifting of
a  passive  margin  sequence  in  the  case  of  the  Vratěnín  Unit
suite. This is supported by the presence of gabbros of alkaline
character  and  positive

values of ca. + 5, which suggest a

lower contamination by slab fluids or a continental crust assimi-
lation. Their original geochemical characteristics were strongly
influenced by the assimilation-fractional crystallization process.
The cumulate gabbro complexes are relatively heterogeneous;
their example, the Maříž suite, was contaminated by a larger
volume of continental crust compared to the Vratěnín Unit.

Fig. 11. La/Nb vs.

for the gabbroic rocks.

190

ULRYCH, ACKERMAN, KACHLÍK, HEGNER, BALOGH, LANGROVÁ, LUNA, FEDIUK, LANG and FILIP

Acknowledgments:  This  research  was  supported  by  the
Grant Agency of the Academy of Sciences CR IAA3013403
within the Research Programme of the Institute of Geology,
v.v.i.,  CEZ:  AV0Z30130516  and  Research  Plan  No.
MSM0021620855 supported by Ministry of Education, Youth
and  Sports  of  the  Czech  Republic  (V.  Kachlík).  K-Ar  dating
was supported by OTKA Projects No. T060965 and M41434
to  K.  Balogh  and  fission-track  studies  by  IAA300130902
Project  to  R.  Skála.  We  are  indebt  to  V.  Vonásková  for
whole-rock  analyses  and  L.  Strnad  for  ICP-MS  analyses  of
trace  elements,  both  from  Charles  University,  Prague.  The
manuscript benefited from comments and criticism by B.G.J.
Upton, University of Edinburgh. We are indebted to J. Pavková
and V. Sedláček for technical assistance, both of the Institute
of Geology AS CR, v.v.i., Prague and reviewers I. Petrík and
P.  Uher  from  Bratislava  for  their  comments  and  improve-
ment of the manuscript.

References

Balogh K. 1985: K/Ar dating of Neogene volcanic activity in Hunga-

ry. Experimental technique, experience and methods of chrono-
logical studies. ATOMKI Report D/1, Debrecen, 277—278.

Brey G.P. & Köhler T. 1990: Geotermometry in four-phase lherzo-

lites: II. New thermobarometers, and practical assessment of ex-
isting thermobarometers. J. Petrology 31, 1352—1378.

Cháb J., Stráník Z. & Eliáš M. 2007: Geological Map of Czech Re-

public 1: 500,000. Czech Geol. Surv., Prague.

Claeson D.T. 1998: Coronas, reaction rims, symplectites and em-

placement depth of the Rymmen gabbro, Transscandinavian Ig-
neous Belt, southern Sweden. Mineral. Mag. 62, 743—757.

Cottin J.Y., Lorand J.P., Agrinier P., Bodinier J.L. & Liégeois J.P.

1998: Isotopic (O, Sr, Nd) and trace element geochemistry of
the Laouni layered intrusions (Pan-African belt, Hoggar, Alge-
ria): evidence for post-collisional continental tholeiitic mag-
mas variably contamined by continental crust. Lithos 45,
197—222.

Cox K.G., Bell J.D. & Pankhurst J. 1979: The interpretation of igne-

ous rocks. Allen and Uwin, London, 1—450.

de Haas G.J.L.M., Nijland T.G., Valbracht P.J., Maijer C., Verschure

R. & Andersen T. 2002: Magmatic versus metamorphic origin
of olivine-plagioclase coronas. Contr. Mineral. Petrology 143,
537—550.

Finger F., Roberts M.P., Hauenschmidt B., Schermaier A. & Steyer

H.P. 1997: Variscan granitoids of central Europe: their typology,
potential sources and tectonothermal relations. Miner. Petrology
61, 67—96.

Fleet M.E. 2003: Micas. In: Deer W.A., Howie R.A. & Zussman J.

(Eds.): Rock-forming minerals. 2

. Geol. Soc., London, 354—369.

Franke W. 2000: The mid-European segment of the Variscides: tec-

tonostratigraphic units, terrane boundaries and plate tectonic
evolution. In: Franke W., Haak V., Oncken O. & Tanner D.
(Eds.): Orogenic processes: Quantification and modeling in the
Variscan Belt. Geol. Soc. London, Spec. Publ. 179, 337—354.

Friedl G., Finger F., Paquette J.-L., Quadt A.V., McNaughton N.J. &

Fletcher I.R. 2004: Pre-Variscan geological events in the Austri-
an part of the Bohemian Massif deduced from U-Pb zircon ages.
Int. J. Earth Sci. 93, 802—823.

Fritz H. & Neubauer F. 1993: Kinematics of crustal stacking and dis-

persion in the south-eastern Bohemian Massif. Geol. Rdsch. 82,
556—565.

Gerdes A., Worner G. & Henk A. 2000: Post-collisional granite

generation and HT-LP metamorphism by radiogenic heating:
the Variscan South Bohemian Batholith. J. Geol. Soc. 157,
577—587.

Harland W.B., Armstrong R.L., Cox A.V., Craig L.E., Smith A.G. &

Smith D.G. 1990: A geologic time scale 1989. Cambridge Univ.
Press., Cambridge, N.Y., Port Chester, 1—263.

Hawkesworth C.J., Hergt J.M., McDermott F. & Ellam R.M. 1991:

Destructive margin magmatism and the contributions from the
mantle wedge and subducted crust. Austr. J. Earth Sci. 38,
577—594.

Hegner E., Walter H.J. & Satir M. 1995: Pb-Sr-Nd isotopic composi-

tion and trace element geochemistry of megacrysts and melili-
tites from the Tertiary Urach volcanic field: source composition
of small volume melts under SW Germany. Contr. Mineral. Pe-
trology 122, 322—335.

Helmy H.M., Yoshikawa M., Shibata T., Arai S. & Tamura A. 2008:

Corona structure from arc mafic-ultramafic cumulates: The role
and chemical characteristics of late-magmatic hydrous liquids.
J. Miner. Petrol. Sci. 103, 333—344.

Hermann J., Spandler C., Hack A. & Korsakov A.V. 2006: Aqueous

fluids and hydrous melts in high-pressure and ultra-high pres-
sure rocks: Implications for element transfer in subduction
zones. Lithos 92, 399—417.

Hildreth W. & Moorbath S. 1988: Crustal contributions to arc mag-

matism in the Andes of central Chile. Contr. Mineral. Petrology
98, 455—489.

Holland T. & Blundy J. 1994: Non-ideal interactions in calcic am-

phiboles and their bearing on amphibole-plagioclase thermome-
try. Contr. Mineral. Petrology 116, 433—447.

Ikeda T., Nishiyama T., Yamada S. & Yanagi T. 2007: Microstructures

of olivine-plagioclase corona in meta-ultramafic rocks from Sefu-
ri Mountains, NW Kyushu, Japan. Lithos 97, 289—306.

Jacobsen S.B. & Wasserburg G.J. 1980: Sm-Nd isotopic evolution of

chondrites. Earth Planet. Sci. Lett. 50, 139—155.

Jenček V. & Dudek A. 1971: Beziehungen zwischen dem Moravikum

und Moldanubikum am Westrand der Thaya-Kuppel. Věst. Ústř.
Úst. Geol. 46, 331—338.

Keppler H. 1986: Constraints from partitioning experiments on the

composition of subduction-zone fluids. Nature 380, 237—240.

Koller F. 1998: Gabbros and diorites related to the “South Bohemian

Pluton”. Acta Univ. Carol., Geol. 2, 50.

Kotkova J., Gerdes A., Parrish R.R. & Novak M. 2007: Clasts of

Variscan high-grade rocks within Upper Visean conglomerates
– constraints on exhumation history from petrology and U-Pb
chronology. J. Metamorph. Geology 25, 781—801.

Kröner A., Wendt I., Liew T.C., Compston W., Todt W., Fiala J.,

Vaňková V. & Vaněk J. 1988: U-Pb zircon and Sm-Nd model
ages of high-grade Moldanubian metasediments. Bohemian Mas-
sif, Czechoslovakia. Contr. Mineral. Petrology 99, 257—266.

Leake B.E. (Ed.) 1997: Nomenclature of amphiboles: Report of the

Subcommission on Amphiboles of the International Mineralogi-
cal Association, Commission on New Minerals and Mineral
Names. Amer. Mineralogist 82, 1019—1037.

Le Maitre R.W. (Ed.) 2002: Igneous rocks. A classification and glos-

sary of terms. 2

Ed. Int. Union Geol. Sci., Cambridge Univ.

Press, Cambridge, 1—236.

Liew T.C. & Hofmann A.W. 1988: Precambrian crustal components,

plutonic associations, plate environment of the Hercynian Fold
Belt of central Europe: Indications from a Nd and Sr isotopic
study. Contr. Mineral. Petrology 98, 129—138.

Lustrino M. & Wilson M. 2007: The circum-Mediterranean anoro-

genic Cenozoic igneous province. Earth Sci. Rev. 81, 1—65.

Matějka D. & Holub F. 2003: Olivine-bearing gabbroic rocks of the

South Bohemian (Moldanubian) Batholit. Zpr. Geol. Výzk. 2002,
171—172 (in Czech).

Matte P. 2001: The Variscan collage and orogeny (480—290 Ma) and

191

ORIGIN OF GABBROIC ROCKS FROM THE MOLDANUBIAN—MORAVIAN UNITS (BOHEMIAN MASSIF)

the tectonic definition of the Armorica microplate: a review.
Terra Nova 13, 122—128.

Merlet C. 1992: Quantitative electron probe microanalysis: new accu-

rate

Φ(pz) description. Mikrochim. Acta 12, 107—115.

Morimoto N. 1988: Nomenclature of pyroxenes. Mineral. Mag. 52,

535—550.

Neumann E.-R. 1978: Petrology of the plutonic rocks. In: Dons J.A.

& Larsen B.T. (Eds.): The Oslo Paleorift. Universitetsforlaget,
Trondheim etc., 25—35.

Nimis P. 1999: Clinopyroxene geobarometry of magmatic rocks.

Part 2. Structural geobarometers for basic to acid, tholeiitic and
mildly alkaline magmatic systems. Contr. Mineral. Petrology
135, 62—74.

Odin G.S. (Ed.) 1982: Interlaboratory standards for dating purposes.

In: Odin G.S. (Ed.): Numerical dating in stratigraphy. Wiley &
Sons, Chichester etc., 123—149.

Pitcher W.S. 1978: The anatomy of a batholith. J. Geol. Soc. London

135, 157—182.

Racek M., Stipska P., Pitra P., Schulmann K. & Lexa O. 2006: Metamor-

phic record of burial and exhumation of orogenic lower and middle
crust: a new tectonothermal model for the Drosendorf window (Bo-
hemian Massif, Austria). Miner. Petrology 86, 221—251.

Rudnick R.L. & Gao S. 2003: Composition of continentral crust. In:

Rudnick R.L. (Ed.): Treatise in geochemistry. The Crust. Elsevier
Pergamon, Amsterdam, 3, 1—64.

Schulmann K., Kroner A., Hegner E., Wendt I., Konopasek J., Lexa

O. & Stipska P. 2005: Chronological constraints on the pre-oro-
genic history, burial and exhumation of deep-seated rocks along
the eastern margin of the Variscan Orogen, Bohemian Massif,
Czech Republic. Amer. J. Sci. 305, 407—448.

Smith J.V. 1974: Feldspar minerals. 1. Crystal structure and physical

properties. Springer, Berlin etc., 1—627.

Steiger R.H. & Jäger E. 1977: Subcommission on geochronology:

convention on the use of decay constants in geo- and cosmo-
chronology. Earth Planet. Sci. Lett. 12, 359—362.

Strnad L., Mihaljevič M. & Šebek O. 2005: Laser ablation and solu-

tion ICP-MS determination of rare earth elements in USGS
BIR-1G, BHVO-2G and BCR-2G glass reference material. Geo-
stand. Geoanal. Res. 29, 303—314.

Sun S.S. & Mc Donough W.F. 1989: Chemical and isotopic system-

atics of oceanic basalts. Implication for mantle composition and
processes. In: Sounders A.D. & Norry M.J. (Eds.): Magmatism
in the Ocean basins. Geol. Soc., Spec. Publ. 42, 313—345.

Štědrá V., Kachlík V. & Kryza R. 2002: Coronitic metagabbros of the

Mariánské Lázně Complex and Teplá Crystalline Unit: inferenc-
es for the tectonometamorphic evolution of the western margin
of the Teplá Barrandian Unit, Bohemian Massif. In: Winchester
J., Pharaoh T. & Verniers J. (Eds.): Palaeozoic amalgamation of
Central Europe. Geol. Soc. London, Spec. Publ. 201, 217—236.

Tollmann A. 1982: Großräumiger variszischer Deckenbau im Mold-

anubikum und neue Gedanken zum Variszikum Europas.
Geotekt. Forsch. 64, 1—91.

Turner S.P. & Stuewe K. 1992: Low-pressure corona textures be-

tween olivine and plagioclase in unmetamorphosed gabbros
from Black Hill, south Australia. Mineral. Mag. 56, 503—509.

Vorma A. 1976: On the petrochemistry of rapakivi granite, with spe-

cial reference to the Laitila massif, southwestern Finland. Bull.
Geol. Surv. Finland 285, 125—140.

Weiss J. 1986: Petrography of basic rocks west of Olešnice at Mora-

via. Sbor. Úst. Úst. Geol. Odd. Geol. 23, 29—58 (in Czech).