GeolCarp_Vol60_No2_107

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Introduction

Migmatites  can  be  generated  by  four  major  processes:  a)  in-
jection  of  externally  derived  magmas  (Sederholm  1913),  b)
partial  melting  (Sederholm  1913;  Holmquist  1921;  Mehnert
1968),  c)  metasomatism  (Misch  1968)  and  d)  metamorphic
differentiation  (Robin  1979;  Ashworth  &  McLellan  1985).
Each of these processes can be responsible for generating mig-
matitic rocks in the particular metamorphic belt.

In the last fifty years, the migmatites and their relationships

to  granitic  intrusions  have  been  investigated  (e.g.  Mehnert
1968;  Ashworth  1985;  Brown  1994;  Sawyer  1996,  2001).
Petrogenesis  of  the  layer-parallel  leucosomes  and  the  impor-
tance of stress and deformation for the generation of migmati-
tic  rocks  were  considered  (e.g.  Sawyer  &  Barnez  1988,  and
Marchildon  &  Brown  2002).  Layer-parallel  leucosomes  can
be  formed  by  sub-solidus  processes  due  to  mobilization  of
quartz and feldspar by stress-induced mass-transfer of mobile
elements  (Sawyer  &  Barnez  1988)  or  by  anatectic  processes
(Marchildon & Brown 2002, 2003). In this paper, we present
evidence from the Hamedan region in Iran that layer-parallel
leucosomes may have originated by both sub-solidus and ana-
tectic  processes  during  progressive  high-grade  metamor-
phism.  In  the  outcrops,  the  various  stages  of  migmatization,
from initial sedimentary layers to sub-solidus leucosomes and
finally to anatectic leucosomes can be observed.

Field, petrographic and geochemical data on magmatism

and metamorphism in the Hamedan region have been present-
ed in some recent works (e.g. Irani 1993; Hadipour 1994;
Sadeghian 1994; Torkian 1995; Baharifar 1997, 2004; Sepahi
1999; Sepahi et al. 2004); however, the petrogenesis of mig-
matites has not been considered yet. In this paper, we provide

Low pressure migmatites from the Sanandaj-Sirjan

Metamorphic Belt in the Hamedan region (Iran)

ALI A. SEPAHI*, SEYEDEH R. JAFARI and SARA MANI-KASHANI

Department of Geology, Bu-Ali Sina University, Hamedan, Iran; *sepahi@basu.ac.ir

(Manuscript received February 23, 2008; accepted in revised form October 23, 2008)

Abstract: Migmatites with evidence for low pressure metamorphism and partial melting occur adjacent to the Alvand
Plutonic Complex in the Hamedan region of Iran. They show stromatic, schollen, diktyonitic and massive structure.
Sillimanite/andalusite/(kyanite)-garnet- and cordierite-K-feldspar-andalusite-spinel-bearing migmatites are the most
common rock types. Some of the granitic intrusions contain xenocrysts which resemble the porphyroblasts of nearby
migmatites (e.g. sillimanite, andalusite, cordierite and garnet). Although migmatitic rocks of the region are located near
the granitic intrusions, the degree of partial melting is not related to intrusions and is irregular. It appears that partial
melting and migmatization pre-date the intrusion of major granitic bodies in the region. Leucosomes in stromatic
migmatites are commonly parallel to bedding planes and are mostly formed by metamorphic segregation and/or in situ
partial melting (showing mafic selvedges, pinch and swell structures). The melt fraction and migmatite type depend on
the chemical composition of parent rocks and the distribution of high strain zones. The formation of thin leucosomes in
the stromatic migmatites was controlled by short-range melt movement along the grain boundaries. Melt-rich layers are
constrained by pre-existing compositional layering and foliation. Peak metamorphic conditions of ~ 650 °C and ~ 300 MPa
are consistent with the observed mineral assemblages and the presence of melt in the investigated migmatites.

Key words: Iran, Sanandaj-Sirjan, Hamedan, anatexis, granite, migmatite.

new data pertaining to the petrogenesis of migmatites (espe-
cially of stromatic migmatites) near to the Alvand Plutonic
Complex in the Hamedan region.

Geological setting

The study area is a part of the so-called Sanandaj-Sirjan

Zone or Zagros Imbricate Zone of the Zagros Orogen (accord-
ing to Alavi 1994, 2004). This zone comprises a metamorphic
belt  of  low-  to  high-grade  regional  and  contact  metamorphic
rocks that have been intruded by mafic, intermediate and fel-
sic plutonic bodies (Fig. 1). Major metamorphic and magmat-
ic  events  of  the  Sanandaj-Sirjan  Metamorphic  Belt  (SSMB)
occurred during the Mesozoic Era (e.g. Baharifar 1997, 2004;
Sepahi 1999; Rashidnejad-Omran et al. 2002; Sheikholeslami
et  al.  2003;  Sepahi  et  al.  2004;  Ahmadi-Khalaji  et  al.  2007).
Major granitic plutons of the SSMB have been atributed to the
Mesozoic-Tertiary magmatism ( ~ 200 to  ~ 40 Ma; e.g. Valiza-
deh & Cantagrel 1975; Masoudi 1997; Baharifar 2004; Ahma-
di-Khalaji  et  al.  2007;  Arvin  et  al.  2007).  These  events  have
been related to the subduction of the Neo-Tethys and later col-
lisional  events  (e.g.  Baharifar  1997,  2004;  Sepahi  1999  and
Sepahi et al. 2004).

Field

relations and petrography of the major plutonic

and metamorphic rocks

In the Hamedan region, low- to high-grade, regional and

contact metamorphic rocks occur adjacent to plutonic bodies
(Fig. 2). Metapelitic rocks are the most abundant, compris-

GEOLOGICA CARPATHICA, APRIL 2009, 60, 2, 107—119 doi: 10.2478/v10096-009-0007-2

108

SEPAHI, JAFARI and MANI-KASHANI

ing slates, phyllites, mica-schists, garnet-schists, garnet-an-
dalusite-(± sillimanite/ ± kyanite)-schists,

garnet-staurolite-

schists  and  garnet-sillimanite-(± kyanite)-schists.  They  are
inter-layered  with  minor  metabasic  rocks  (amphibole-bear-
ing schists and amphibolites), metacarbonates, and calc-sili-
cate  rocks.  Near  the  Alvand  Plutonic  Complex,  contact
cordierite  (Crd

)-K-feldspar-(± andalusite, fibrous silliman-

ite)-hornfelses, garnet-staurolite (± kyanite) hornfelses, and in
some places garnet-sillimanite-(± andalusite/ ± kyanite)-schists/
migmatites with inter-layers of cordierite (Crd

)-K-feldspar-

andalusite-spinel-migmatites occur. Mineral abbreviations are
used according to Kretz (1983).

In the eastern aureole of the Alvand Plutonic Complex, a

suite of migmatitic rocks occur, which were first reported by
Sepahi (1999). The contact of migmatites with nearby granitic
bodies is usually sharp. Despite high-grade metamorphism,
some bedding planes can be traced in the migmatitic rocks.

Two migmatite types are present, namely Al

SiO

-bearing

and  cordierite-(± andalusite)-bearing  migmatites  (Fig. 3a—b).
Several structural varieties from stromatic to schollen, diktyon-
itic,  nebulitic  and  massive  can  be  seen  in  many  localities
(Fig. 3c—e). The progressive stages of partial melting can be ob-
served in the outcrops (Fig. 3f—h). Metatexites show stromatic
fabric  with  leucosomes  commonly  concordant  to  bedding
planes,  except  in  high  strain  zones,  such  as  faults  and  shear
zones.  The  foliation-parallel  leucosomes  are  usually  5—20 mm
thick. The distribution of most of the leucosomes is controlled
by the spatial distribution of pre-existing compositional layer-
ing  and  foliation  (Fig. 3i).  Some  boudin-like  structures  into
which leucocratic material has segregated are developed in the
inter-boudin partitions (Fig. 3j). Melts have also collected into

blasts  of  sillimanite/andalusite  (up  to  20 cm),  but  hornfelses
and  contact  migmatites  (injection  complex)  have  a  massive
structure and granoblastic texture without prismatic silliman-
ite (Fig. 5). In the injection complex, some of the leucocratic
veins can be observed adjacent to the plutonic bodies. In con-
trast  to  injection  migmatites,  regional  migmatites  show  vari-
ous  structures  and  occur  over  a  wider  area  (especially  to  the
south  of  Simin  village,  south  of  Hamedan  city  (sillimanite+
K-feldspar + Crd

zone on Fig. 2)).

Plutonic rocks

The Alvand Plutonic Complex (Fig. 2) is one of the major

plutonic complexes in the SSMB. It includes: 1) gabbro-dio-
rite-tonalite  (GDT)  association,  2)  granite-granodiorite  por-
phyric  rocks  and  3)  leucocratic  granitoids.  The  GDT
association  consists  of  olivine  gabbro,  gabbro,  gabbronorite,
diorite, and tonalite, which were metamorphosed by the intru-
sion of younger granitic bodies. The monzogranite-granodior-
ites (G

) contain feldspars (plagioclase, K-feldspar and minor

microcline), quartz and biotite (rarely muscovite) without any
hornblende. Xenocrysts of andalusite, sillimanite, garnet and
cordierite are common in these rocks. Leucocratic granitoids
(G

) comprise leucotonalites, leucogranodiorites and leucog-

ranites, forming small post-tectonic intrusions (Sepahi 1999).

In some of the granitic rocks, metamorphic (restitic) xenoc-

rysts of garnet, andalusite/sillimanite and cordierite are wide-
spread (Fig. 6a—c). These minerals were probably generated
during the mechanical dispersion of restitic enclaves or xeno-
liths of schists and migmatites. Xenocrystic andalusite crystals
show reaction microtextures, such as replacement of an-

Fig. 1. Distribution of major plutonic bodies in the Sanandaj-Sirjan Metamorphic
Belt,  Zagros  Orogen,  Iran  (tectonic  units  after  Alavi  1994,  2004  and  Mohajjel  &
Fergusson 2003; modified after Moazzen et al. 2004 and Sepahi & Athari 2006).
SQ – Saqqez,  SD – Sanandaj,  GH – Ghorveh,  AM – Almogholagh,  HD –
Hamedan (Alvand), AR – Arak, AS – Astaneh, BJ – Boroujerd, AG – Aligudarz,
AZ – Azna, MT – Muteh, KG – Kolah-Ghazi, SJ – Sirjan,  SK – Siah Kouh.

some small shear zones forming the discordant
leucosomes (Fig. 3k).

Aplitic-pegmatitic dykes are widespread in the

migmatitic zone and appear to be late to post-ana-
tectic  features.  They  contain  large  amounts  of
tourmaline.  Tourmaline  also  occurs  in  the  meta-
morphic rocks near the dykes. In the field, retro-
grade  reactions  are  visible  in  the  migmatites/
schists  adjacent  to  the  aplitic-pegmatitic  dykes.
The formation of muscovite and a second genera-
tion  of  staurolite  (St

), at the expense of an-

dalusite/sillimanite porphyroblasts (Fig. 4), is a
common feature near the dykes.

Except for a narrow zone (nearly 25 km long

and up to 5 km wide) in which migmatitic rocks
are in contact with intrusive bodies (i.e. gran-
ites), hornfelses with typical fine-grained grano-
blastic

(hornfelsic)

texture,

particularly

cordierite-hornfelses  occur  around  intrusive
bodies.  Minor  injection  complex  (migmatitic
hornfelses)  occurs  at  the  contacts  with  granites
(up to 50 meters from the contact zone). Migma-
titic  hornfelses  are  distinguished  from  the  re-
gional  migmatites  and  migmatitic  schists  by
their position close to the plutons, mineral assem-
blages  and  textures.  Regionally  metamorphosed
schists/migmatites have schistose (porphyro-lep-
idoblastic)  texture  containing  large  porphyro-

112

SEPAHI, JAFARI and MANI-KASHANI

maline and ilmenite. An AFM diagram for the typical mineral
assemblage of this zone is shown in Fig. 7d.

Kyanite-bearing schists and veins (not recognized in the

map): Kyanite-schists occur at scattered localities within the
other  zones  (especially  in  high-strain  zones  such  as  shear
zones).  In  these  rocks,  kyanite  frequently  occurs  as  pseudo-
morphs  after  andalusite/sillimanite.  The  typical  mineral  as-
semblage  of  these  rocks  is  biotite + plagioclase + quartz +
kyanite ± garnet.  The  garnets  of  these  rocks,  are  typically  al-
mandine-rich,  elongate,  and  irregularly  shaped.  Kyanite-
quartz  veins  cut  through  various  lithologies  especially  in  the
metamorphic  rocks  close  to  granitic  intrusions.  Retrograde
muscovite and chlorite are often present in these veins, as well
as minor diaspore.

High-grade schists and migmatites (sillimanite-K-feld-

spar  zone):  The  metamorphic  rocks  of  this  zone  are  com-
posed  of  high-grade  schists  and  migmatites  adjacent  to
granitic  bodies.  Migmatites  were  observed  within  the  15 km
of  the  ~ 120 km  long  contact  zones  in  which  sillimanite/an-
dalusite schists/migmatites alternate with minor inter-layers of
cordierite-bearing migmatites. The highest-grade schists in the
regional  metamorphic  sequence  contain  sillimanite + quartz +
biotite + muscovite + garnet + plagioclase + K-feldspar  (pethitic
K-feldspar)+ ilmenite ± andalusite ± kyanite ± staurolite.  With
increasing metamorphic grade these schists continue into mig-
matitic rocks, in which mesosome mineralogy is similar to the

mineral assemblages in the schists. These schists are cut by
abundant granitic pegmatites and sillimanite-quartz veins. The
inter-layers contain cordierite (Crd

), perthitic K-feldspar, mi-

nor biotite, plagioclase, spinel and opaque minerals. In these
rocks, symplectitic intergrowth of cordierite with spinel is vis-
ible around some andalusite porphyroblasts.

This zone is associated with partial melting and develop-

ment  of  granitic  leucosomes  in  migmatites.  Plagioclase-rich
(trondjhemitic)  leucosomes  are  predominant,  but  some  con-
tain additional K-feldspar. Mesosomes of migmatites have por-
phyro-lepidoblastic  texture  and  contain  quartz,  biotite,  garnet
and  Al

SiO

polymorphs, especially sillimanite (but also an-

dalusite/kyanite)±staurolite±spinel±cordierite(Crd

)±graph-

ite.  Leucosomes  of  migmatites  have  granoblastic  texture  and
contain  quartz,  plagioclase  (in  some  places  K-feldspar)  and
muscovite (± garnet). Melanosomes are less developed and re-
semble  the  mesosomes  with  respect  to  their  mineralogy  and
texture,  except  for  greater  amounts  of  mafic  minerals  and
smaller amounts of felsic minerals.

SiO

-bearing migmatites are the most common rocks in

the migmatitic suite. Andalusite/sillimanite-bearing rocks
are predominant, but some kyanite-bearing rocks also occur,
especially in shear zones in which kyanite developed after
andalusite/sillimanite porphyroblasts. Garnet crystals of mil-
limeter to centimeter size (up to 2 cm) are common in these
rocks. There are two prograde and retrograde assemblages in

Fig. 6. a—c – Major types of enclaves and xenocrysts in the S-type granites of the APC: a – micaceous enclave and andalusite xenocryst,
b – pinitized cordierite (outcrop photo), and c – pinitized cordierite (photomicrograph). d – Conversion of andalusite xenocryst to silli-
manite in granites.

113

LOW PRESSURE MIGMATITES FROM THE SANANDAJ-SIRJAN METAMORPHIC BELT (IRAN)

SiO

-bearing migmatitic rocks; a prograde (sillimanite/

andalusite)-K-feldspar-biotite-(± garnet)-quartz assemblage
(Fig. 7e) and a retrograde staurolite (St

)-muscovite-(± gar-

net)-(± Ky) assemblage. Retrograde staurolite (St

) occurs

around and inside large porphyroblasts of Al

SiO

minerals

Fig. 7. AFM diagrams for typical mineral assemblages from various metamor-
phic zones. a – garnet zone, b – andalusite zone, c – staurolite zone, d – sil-
limanite zone, e – sillimanite-K-feldspar zone, f – cordierite(Crd

)-(an-

dalusite) zone, g – cordierite (Crd

)-K-feldspar zone and h – fibrolitic

sillimanite (Sil

)-K-feldspar zone. Zones a—e are regional metamorphic zones

and zones f—h are contact metamorphic zones. Quartz and muscovite (commonly
retrograde) are roughly present in each zone.

(especially  sillimanite  and  in  some  places,  an-
dalusite/kyanite, Fig. 4). Cordierite-rich layers also
occur  in  some  parts  of  the  migmatitic  sequence.
They  are  composed  of  quartz,  biotite,  cordierite
(Crd

), andalusite and K-feldspar, with minor

spinel and plagioclase. Symplectite texture gener-
ated by cordierite-spinel intergrowth occurs on the
rim of some andalusite porphyroblasts.

Contact metamorphic rocks

The protoliths of the contact metamorphic rocks

are similar to those in the regional metamorphic se-
quence  and  include  abundant  metapelitic  rocks.
Spotted  schists  containing  muscovite-staurolite-
chlorite  spots,  which  were  formed  due  to  intrusion
of plutonic bodies, are common in 1—2 km far from
the  contact  of  plutonic  bodies.  The  following  reac-
tion may be responsible for the appearance of these
spots:

Biotite + Andalusite + Quartz + H

O = Staurolite +

Muscovite + Chlorite.

Rocks with hornfelsic texture, but showing prima-

ry regional metamorphic assemblages, such as de-
formed andalusite, and kyanite (Ky

) are common in

the  contact  aureole.  In  some  of  the  kyanite-schists/
hornfelses  in  the  contact  zone,  two  distinct  genera-
tions of kyanite are observable. In these rocks, some
of the kyanite crystals are deformed, but other kyan-
ites  are  euhedral,  randomly  oriented  and  cross-cut
the  relict  foliation.  Sequential  development  of  the
Al

SiO

polymorphs during poly-metamorphic

events is observable in some of the hornfelsic rocks.
Andalusite-(kyanite

)-fibrolite sequential develop-

ment is predominant, but sequential development of
andalusite-(kyanite

)-fibrolite-kyanite

is also com-

mon in the hornfelsic rocks near to the quartz-kyan-
ite veins. Texturally-late cordierite (Crd

) also

occurs in some of the hornfelsed schists. The high-
est-grade hornfelsic rocks of the region are distin-
guished by development of cordierite

K-feldspar

and fibrolitic sillimanite (Sil

) adjacent to intrusive

bodies.  Rocks  in  the  inner  contact  zone  include
cordierite ± andalusite ± garnet-hornfels  (cordierite-
andalusite  zone),  cordierite-K-feldspar±garnet-horn-
fels  (cordierite-K-feldspar  zone),  and  sillimanite-
K-feldspar ± garnet-hornfels.

Two metamorphic zones are widespread around

plutonic bodies: contact cordierite (Crd

) ± fibrous

sillimanite (Sil

) ± andalusite and cordierite-K-feld-

spar zones. In addition, a narrow sillimanite
(fibrolite = Sil

)-K-feldspar zone is common around

the gabbro-dioritic intrusive bodies (Fig. 2).

Cordierite-(andalusite) zone: The major rock types in this

zone  are  cordierite-(andalusite)-hornfelses.  Cordierite-(an-
dalusite)-hornfelses  occur  all  around  the  Alvand  Plutonic
Complex,  except  for  some  localities  where  sillimanite-horn-
felses occur near the gabbroic rocks and also where regional

114

SEPAHI, JAFARI and MANI-KASHANI

migmatites occur at a sharp contact with plutons. The typical
mineral assemblage of this zone is quartz + biotite + contact
cordierite (Crd

) ± garnet ± fibrolite + plagioclase + opaque

minerals ± (relict andalusite). An AFM diagram for the typical
mineral assemblage of this zone is shown in Fig. 7f.

Cordierite-K-feldspar zone: Adjacent to the plutonic

rocks (contact zone) there is a narrow zone of cordierite-K-
feldspar. This metamorphic zone is common around the gra-
nitic part of the Alvand Plutonic Complex and is characterized
by coexisting cordierite and perthitic K-feldspar. The typical
mineral assemblage of these rocks is quartz + contact cordier-
ite (Crd

) + K-feldspar + biotite + minor plagioclase ± garnet

and opaque minerals. An AFM diagram for the typical mineral
assemblage of this zone is shown in Fig. 7g.

Fibrolite-K-feldspar zone: A narrow fibrolite-K-feldspar

zone can be observed around gabbro-dioritic bodies, in some
places. In these rocks, some of the garnet crystals are relicts
from the previous regional metamorphic event, which are
partly converted to fibrolitic sillimanite and biotite. In the leu-
cocratic veins which cross cut through these rocks, preferred
crystallization of some other garnet crystals also occurs along-
side the veins. Therefore, two regional and contact metamor-
phic assemblages can be distinguished in these rocks: 1 – an
older regional metamorphic assemblage of quartz-biotite

-gar-

net

-andalusite, 2 – a younger contact metamorphic assemblage

of quartz-fibrolite-biotite

-(± garnet

, ± K-feldspar, ± mus-

covite). An AFM diagram for the typical mineral assemblage
(assemblage 2) of this zone is shown in Fig. 7h.

Mineral chemistry

The major metamorphic rocks (and protoliths of the mig-

matites) include semipelitic and psammitic rocks but pelitic
lithologies  are  rather  widespread  (Table 1,  Fig. 9);  they  are
inter-layered with some metabasic rocks. The chemical com-
position  of  metamorphic  minerals  (chlorite,  biotite,  musco-
vite,  garnet,  andalusite,  kyanite,  sillimanite,  staurolite,
cordierite and feldspars) have been described in some recent
publications (e.g. Sepahi et al. 2004 and Baharifar 2004). The
mineral  compositions  presented  in  this  paper,  were  obtained
using a JEOL JXA-8900 electron microprobe at the University

Fig. 8. Outcrops of two major regional metamorphic rock units of the region: (a) andalusite- and (b) staurolite-schists.

of Minnesota, USA. Operating conditions for quantitive anal-
ysis (WSD) were 15 kV accelerating voltage, 15—25 nA beam
current and a range of 5—20 µm beam diameters.

The chemical compositions of minerals in the metamorphic

and  migmatitic  rocks  are  presented  in  the  Tables 2—3.  The
range of XMg in biotite in the metamorphic rocks is between
0.3  and  0.6,  but  biotite  in  the  higher-grade  rocks  has  larger
XMg in contrast to lower-grade ones (Table 2). In the musco-
vite  of  migmatitic  rocks  (samples  MM1—MM3  in  Table 3),
which come from the sillimanite-K-feldspar zone (Fig. 2), the
Na/(Na+K)  ratios  are  mostly  lower  than  0.3.  These  are  also
lower than the ratios for mica-schists (samples MS1—MS5 in
Table 3),  from  the  biotite  zone  (Fig. 2)  and  hornfelses  (sam-
ples MH1—MH2 in Table 3), from the cordierite zone. Stauro-
lite is commonly Fe-rich (Sepahi et al. 2004). Garnet is mostly
almandine-rich  both  in  low-grade  and  medium—high-grade
rocks, with considerable amounts of MnO and CaO (Sepahi et
al.  2004).  It  is  worth  noting  that  the  stability  of  garnet  in
metapelites  expands  to  the  lower  temperature  and  pressure
with  the  addition  of  Mn,  hence  garnet  appears  as  a  stable
phase at low pressures (Mahar et al. 1997). Plagioclase in the
mesosome of migmatites (An

at core to An

at rim) is more

calcic than in the surrounding lower-grade metamorphic rocks
(e.g. in nearby staurolite schists; An

at core to An

at rim).

Fig. 9. A simplified ACFK diagram (modified after Winkler 1976)
representing chemical compositions of the metamorphic rocks of
the Hamedan region (circled field). P – Pelitic rocks, A – Arkose,
Gw – Greywackes.

115

LOW PRESSURE MIGMATITES FROM THE SANANDAJ-SIRJAN METAMORPHIC BELT (IRAN)

Table 1: Representative chemical analyses for some of the metamorphic rocks of the region (data from Baharifar 1997 and Sepahi 1999).
Four samples are hornfelses (marked *) and the other ones are regional metamorphic rocks.

Samples BS

SiO

(wt. %) 33.41 34.48 34.30 34.80 35.94 35.11 35.39 35.79 35.62 35.49

35.28 35.32 35.50 34.94

TiO

53 1.81 1.68 1.88 1.68 1.63 1.50 1.58 1.73 1.69 1.68 1.71 1.79 1.68

20.25 20.53 20.14 20.51 20.69 19.67 20.02 19.91 20.20 20.24 20.15 19.90 20.25 19.66

FeO

20.91 20.47 20.37 20.40 20.03 21.03 20.91 20.77 20.31 19.73 19.31 20.03 19.84 20.61

MnO

32 0.32 0.31 0.28 0.06 0.04 0.08 0.08 0.04 0.01 0.04 0.03 0.03 0.07

MgO

92 9.85 10.08 9.83 9.29 9.54 9.68 9.91 9.91 9.92 9.85 9.92 9.84 9.71

CaO

28 0.18 0.17 0.16 0.07 0.02 0.02 0.06 0.04 0.05 0.33 0.09 0.00 0.04

21 0.43 0.30 0.36 0.27 0.28 0.27 0.26 0.13 0.19 0.05 0.19 0.23 0.20

33 8.82 8.89 9.10 8.05 9.25 8.98 8.88 8.79 8.73 6.99 8.62 8.90 8.63

Total

94.16 96.88 96.23 97.33 96.08 96.58 96.85 97.24 96.76 96.04 93.68 95.81 96.37 95.51

Number of cations on the basis of 24 Oxygens

5.15 5.19 5.20 5.21 5.38 5.31 5.32 5.34 5.33 5.33 5.37 5.33 5.33 5.31

0.18 0.20 0.19 0.21 0.19 0.18 0.17 0.18 0.19 0.19 0.19 0.19 0.20 0.19

tot

3.68 3.64 3.60 3.62 3.65 3.51 3.55 3.50 3.56 3.58 3.62 3.54 3.58 3.52

4.32 4.36 4.40 4.38 4.35 4.49 4.45 4.50 4.44 4.42 4.38 4.46 4.42 4.48

2.70 2.58 2.58 2.55 2.51 2.66 2.63 2.59 2.54 2.48 2.46 2.53 2.49 2.62

2.28 2.21 2.28 2.19 2.07 2.15 2.17 2.21 2.21 2.22 2.24 2.23 2.20 2.20

0.06 0.13 0.09 0.11 0.08 0.08 0.08 0.07 0.04 0.05 0.02 0.05 0.07 0.06

1.44 1.69 1.72 1.74 1.54 1.79 1.72 1.69 1.68 1.67 1.36 1.36 1.70 1.67

XFe

0.53 0.53 0.52 0.53 0.55 0.55 0.55 0.54 0.53 0.53 0.52 0.53 0.53 0.54

XMg

0.46 0.44 0.45 0.44 0.43 0.43 0.44 0.44 0.45 0.45 0.45 0.45 0.45 0.44

Table 2: Electron microprobe representative analyses (wt. %) of biotite in staurolite-schists (BS

—BS

), cordierite-hornfelses (BH

—BH

)

and in melanosome of migmatites (BM

—BM

) of the region.

Sch-Kh

Ph-Hs

Gj-Absd

Ph-Meh

Zg-ash

Zg-Msh

Samples/Oxides (wt. %)

61.34

67.96

64.26

61.56

60.67

60.00

59.94

SiO

0.98

0.80

0.92

0.95

1.04

0.93

0.90

TiO

19.08

15.93

17.77

20.00

20.63

20.14

18.14

1.49

1.34

7.44

7.30

8.91

10.40

7.51

5.14

3.87

–

FeO

–

0.13

0.09

0.13

0.14

0.11

MnO

2.22

1.71

2.52

2.24

2.72

2.35

2.76

MgO

0.74

0.70

0.42

0.56

0.60

0.52

3.02

CaO

4.30

3.39

4.63

5.18

3.81

4.72

4.70

0.75

0.71

1.42

1.54

0.82

0.30

2.33

–

0.16

0.18

0.09

0.25

0.19

96.04

96.41

99.67

99.60

99.42

99.75

99.60

Total

Sch-Ab

Sch-Chp

Sch-Az

Sch-Nj

Hfs-Dn*

Sch-Zg

Hfs-Jh*

Samples/Oxides (wt. %)

65.53

60.79

65.79

60.53

63.52

57.61

64.98

SiO

0.80

0.70

0.75

0.84

0.80

0.83

0.79

TiO

18.16

23.92

17.05

19.35

18.82

20.44

17.66

0.58

2.34

2.44

1.57

0.48

3.48

0.03

5.39

3.35

3.13

4.66

6.00

3.93

6.56

FeO

3.14

1.89

2.04

3.22

2.29

2.48

3.15

MgO

0.58

0.71

1.01

3.41

0.72

0.83

0.75

CaO

3.22

3.65

3.16

3.54

3.98

5.33

3.41

1.83

0.54

1.41

3.20

1.80

1.34

3.41

99.03

97.89

96.78

100.32

98.41

96.27

100.74

Total

The P-T conditions of metamorphism

Baharifar (1997) estimated a temperature of 570 °C and a

pressure  of  430 ± 50 MPa  for  sillimanite-schists  and  garnet-
staurolite-schists  340 ± 5 MPa  for  staurolite-schists  of  the
study area. Sepahi et al. (2004) have estimated a temperature
range of 520—560 °C for the sillimanite±kyanite-schists using
garnet-biotite  thermometer.  For  this  temperature  range,  they
calculated  a  pressure  of  270—350 MPa  using  garnet-silliman-
ite-plagioclase-quartz  barometry.  Garnet-biotite-plagioclase-
muscovite-quartz  and  garnet-plagioclase-muscovite-quartz

barometry have yielded consistent results for the same sam-
ples  ( ~ 300 MPa). On the basis of field observations, meta-
morphic  reactions,  and  thermobarometric  calculations,
maximum conditions of 250—350 MPa and 550—600 °C were
suggested  for  the  highest-grade  contact  metamorphic  rocks
(Baharifar  1997;  Sepahi  1999).  The  peak  temperature  for
metamorphic rocks in the migmatitic zone is estimated to be
about 650—670 °C (Baharifar 2004). This estimation is in ac-
cordance  with  vapor-present  melting  at  P = 300 MPa  and
T = 640 °C which has been suggested for Mt Stafford, Central
Australia (Greenfield et al. 1998), and solidus temperature of

116

SEPAHI, JAFARI and MANI-KASHANI

640 °C at P = 500 MPa for the stromatic migmatites of Ne-
laug, Southern Norway (Gupta & Johannes 1982).

We have calculated some new P-T values using the garnet-

biotite  thermometry  (Ferry  &  Spear  1978)  for  3  samples
from the low-grade (garnet-mica-schist from the garnet zone
on  Fig. 2),  low—medium-grade  (garnet-andalusite-schist  from
the andalusite zone on Fig. 2) and medium-grade rocks (gar-
net-sillimanite-schist  from  the  sillimanite  zone  on  Fig. 2).
The  calculated  temperatures  are  432,  517  and  532 °C  at  a
pressure of 300 MPa which are consistent with field and pet-
rographic observations.

The typical assemblage of inter-layers of cordierite-migma-

tites  (quartz-cordierite-andalusite-biotite-K-feldspar-spinel)
can be stable at a temperature higher than  ~ 600 °C, at maxi-
mum pressure of  ~ 300 MPa (Tinkham et al. 2001). Consider-
ing the rapid decrease in the volume of biotite in these rocks
and partial replacement of andalusite porphyroblasts by cordi-
erite-spinel symplectites in these rocks, the temperature could
be higher than 650 °C but andalusite persisted metastably into
the sillimanite + melt field. This is presented in the phase dia-
gram  according  to  White  et  al.  (2003),  with  a  few  changes
(Fig. 10) (see also Johnson et al. 2004). Sepahi (1999) consid-
ered a diapiric rise as a possible mechanism for the ascent and
emplacement of the migmatites and associated S-type granites
into the upper levels of crust in the region, similar to the dia-
piric rise of the country rocks near the Bushveld Complex in
South Africa (Johnson et al. 2004).

The formation of retrograde muscovite and the second gen-

eration of staurolite (St

) at the expense of andalusite/silliman-

ite porphyroblasts yields have given rise to the assemblage
staurolite ± garnet

+ muscovite + quartz, observed only in-

side and around the andalusite/sillimanite porphyroblasts
close to the aplitic-pegmatitic dykes (Fig. 4). This assemblage
is not stable at a pressure lower than 300 MPa and indicates

Table 3: Electron microprobe representative analyses (wt. %) of muscovite in migmatites (MM

—MM

), schists (MS

—MS

) and hornfelses

(MH

—MH

) of the region.

Samples MM

SiO

(wt. %)

45.77 45.73 45.51 44.41 44.18 44.94 43.65 43.41 46.10 46.17

TiO

0.51 0.34 0.25 0.62 0.50 0.48 0.49 0.46 0.46 0.48

35.99 35.54 35.56 37.05 37.34 37.75 36.94 35.59 37.21 37.21

FeO

1.00 1.11 1.11 1.34 1.28 1.20 3.39 4.82 1.07 1.21

MnO

0.00 0.00 0.00 0.19 0.24 0.21 0.24 0.22 0.00 0.00

MgO

0.61 0.79 0.73 0.65 0.56 0.61 0.59 0.71 0.44 0.43

CaO

0.00 0.00 0.00 0.14 0.14 0.15 0.57 0.27 0.00 0.00

0.98 0.77 0.82 1.44 1.49 1.42 1.20 1.02 1.26 1.41

9.68 9.76 9.80 9.26 9.13 9.01 7.77 7.64 8.84 9.12

Total

94.54 94.04 93.78 95.09 94.86 95.76 94.84 94.13 95.39 96.02

Number of cations on the basis of 24 Oxygens

6.11 6.14 6.13 5.92 5.90 5.93 5.86 5.90 6.07 6.06

0.05 0.03 0.03 0.06 0.05 0.05 0.05 0.05 0.05 0.05

tot

5.66 5.62 5.64 5.82 5.88 5.87 5.84 5.70 5.77 5.75

2.34 2.38 2.36 2.18 2.12 2.13 2.16 2.30 2.23 2.25

3.32 3.25 3.29

3.65

3.76

–

3.55 3.51

0.11 0.12 0.13 0.15 0.14 0.13 0.38 0.55 0.12 0.13

0.12 0.16 0.15 0.13 0.11 0.12 0.12 0.14 0.09 0.08

0.25 0.20 0.21 0.37 0.39 0.36 0.31 0.27 0.32 0.36

1.65 1.67 1.68 1.58 1.56 1.52 1.33 1.33 1.49 1.53

XFe

0.48 0.44 0.46 0.47 0.47 0.45 0.63 0.73 0.58 0.61

XMg

0.03 0.04 0.04 0.03 0.03 0.35 0.18 0.18 0.02 0.02

XAl

0.92 0.91 0.92

0.91

0.91 –

–

0.93 0.93

higher pressure, post-migmatization conditions in the region.
The following reaction could have occurred near the dykes
(just incompletely) to generate such a mineral assemblage:

Andalusite/Sillimanite + Biotite + Garnet

+ H

O = Stauro-

lite + Muscovite + Garnet

+ Quartz.

A temperature of ~ 570 °C at ~ 300 MPa has been proposed

for  the  equilibrium  conditions  of  such  a  reaction  (Thompson
&  Norton  1968;  Carmichael  1970;  Winkler  1974).  Field  ob-
servations confirm that such retrograde conditions occurred si-
multaneously with the intrusion of younger aplitic-pegmatitic
dykes  into  the  high-grade  schists/migmatites  (Fig. 5c).  Ac-
cording to Garcia-Casco et al. (2003), staurolite in migmatites
could  be  generated  from  retrograde  reactions  during  subse-
quent cooling or a distinct thermal pulse. This can be support-
ed  by  the  occurrence  of  staurolite  in  the  region  around  the
pegmatitic-aplitic  dykes  cutting  through  the  schists/migma-
tites of the area. This is in accordance to the latter idea.

Discussion

Possible origin(s) of the leucosome layers

Although migmatitic rocks in the Hamedan region are locat-

ed near the younger porphyric granites, the degree of partial
melting is not controlled by distance from the pluton contacts
and is very irregular. Instead, it seems that melt fraction and
migmatite type were determined by the chemical composition
of parent rocks and/or by the presence of deformation/fluids
in high strain zones. In the adjacent layers within an outcrop
the degree of partial melting is variable, due to changes in par-
ent rock compositions and the existence of high strain zones
which enabled the movement of fluids.

117

LOW PRESSURE MIGMATITES FROM THE SANANDAJ-SIRJAN METAMORPHIC BELT (IRAN)

Fig. 10.  A  modified  pseudo-section  dia-
gram (after White et al. 2003) for estima-
tion of possible P-T condition of the for-
mation  of  the  migmatitic  rocks  of  the
Hamedan  region.  The  dashed  field  best
fits with the observed mineral assemblage
in  the  cordierite-K-feldspar-andalusite-
(sillimanite)-spinel-migmatites.

The formation of thin leucosomes, in the migmatites of the

region,  was  possibly  controlled  by  short-range  melt  move-
ment  along  grain  boundaries  to  form  melt-rich  layers  con-
strained by pre-existing compositional layering (Marchildon
& Brown 2003). Leucosomes in stromatic migmatites of the
region  are  parallel  to  bedding  planes  in  some  parts.  These
layer-parallel leucosomes can be formed by sub-solidus pro-
cesses and/or in situ melting in a closed system. Melt trans-
fer  from  grain-scale  sites  where  melting  occurred  to
layer-parallel  leucosomes  was  controlled  by  the  spatial  dis-
tribution of pre-existing compositional layering and foliation
formed  by  metamorphic  segregation,  but  some  times  by  in
situ  partial  melting  (showing  pinch  and  swell  structures;
Fig. 3i).  Some  of  the  leucosomes  were  generated  by  meta-
morphic  differentiation  or  in  situ  partial  melting  showing
mafic selvedges.

Accumulation of melt in the fault zones, shear zones,

hinge zone of folds and boudin necks is common in the mig-
matitic zone of the region. Bedding and schistosity planes
have also been important for the movement of melts/fluids
in the parent rocks.

Partial melting occurred at a temperature near to andalusite-

sillimanite  univariant  curve  so  that  andalusite-,  sillimanite-
and andalusite-sillimanite-bearing migmatites alternate in the
adjacent  layers.  The  existence  of  tourmaline-rich  aplites  and
pegmatites,  and  tourmalinites  cutting  through  the  medium—
high-grade metamorphic rocks, and occurrence of tourmaline
in  the  country  rocks  confirm  a  possible  boron-rich  environ-
ment during and after partial melting processes (e.g. Wolf &
London  1997).  In  the  boron-rich  environments,  the  stability
field  of  andalusite  can  be  expanded  to  higher  temperatures
(Greenfield et al. 1998).

In the sillimanite-(andalusite)-migmatites, the size and

abundance of the K-feldspar and garnet crystals commonly
increase with the abundance of the leucosome portions in the

migmatites. Therefore, the following reactions could have
occurred simultaneously during partial melting in these
rocks:

Andalusite = Sillimanite;
Biotite + Sillimanite/Andalusite + Quartz = Garnet + K-feld-
spar + Melt.

The higher content of garnet and K-feldspar in the migmati-

tic  rocks  (especially  in  leucosomes)  in  contrast  to  the  lower
amount  of  these  minerals  in  the  lower-grade  equivalents  of
migmatites,  preferred  accumulation  of  garnet  crystals  in  the
leucosomes, univariant change of the andalusite to sillimanite
in the migmatitic rocks and the absence of white mica in the
medium-grade  rocks  of  the  region  (except  retrograde  white-
mica  formed  at  the  expense  of  some  of  the  andalusite/silli-
manite porphyroblasts), are good indicators for such reactions.

In the cordierite-migmatites the volume of leucosomes is

rather higher than that in the Al

SiO

-bearing migmatites.

There is an obvious increase in the amount of cordierite and
K-feldspar in the cordierite-migmatites in contrast to the low-
er-grade rocks. At the same time as the increase in the abun-
dance of cordierite and K-feldspar, the amount of biotite (and
Al

SiO

minerals) decreases rapidly; therefore, the following

reaction may be possible during the partial melting of these
rocks:

Biotite + Sillimanite/Andalusite + Quartz = Cordierite + K-feld-
spar + Melt.

Considering the absence of muscovite in the medium-grade

rocks  adjacent  to  the  migmatites,  this  reaction  can  be  more
possible  than  a  dehydration-melting  reaction  of  muscovite.
However, considering a low decrease in the amount of biotite
in  the  Al

SiO

-bearing migmatites in contrast to the cordier-

ite-bearing migmatites, an input of some fluids from the exter-
nal source(s), especially in high strain zones such as shear

118

SEPAHI, JAFARI and MANI-KASHANI

zones, may be necessary for the partial melting. Therefore, a
complex model involving sub-solidus segregation and in situ
partial melting assisted by H

O (fluids) resulting from the bi-

otite dehydration reaction may explain the observed features
of migmatitic rocks in some localities. Instead, a model involv-
ing partial melting in the presence of some external fluids may
better explain the features of migmatites in the shear zones.

Regional and tectonic implications

The mineral assemblages of the investigated metamorphic

rocks indicate that multiple metamorphic events occurred in the
Hamedan region. Some minerals such as staurolite and cordier-
ite  crystallized  during  two  different  stages  of  metamorphism.
The  mineral  assemblages  of  migmatites  comprise  metastable
andalusite and locally development of retrograde staurolite and
muscovite  (± garnet

) at the expense of Al

SiO

minerals and

biotite (especially near aplitic-pegmatitic dykes and post-meta-
morphic intrusions). The higher pressure condition of the retro-
grade  assemblage  are  at  odds  with  the  isobaric  conditions  or
decompression  reactions.  It  is  possible  that  aplitic-pegmatitic
dykes were intruded into the environment during a higher-pres-
sure  event  (collisional  tectonic  regime).  The  development  of
widespread late-stage quartz-kyanite veins in the region (cutting
through regional and contact metamorphic rocks as well as old-
er intrusive rocks; see also Sepahi et al. 2004) may be consid-
ered as complementary evidence for this argument.

Only in some places, migmatites occur adjacent to younger

granitic bodies and they are not always common around these
granitic intrusions. In many other places, they are absent in the
contact zone of younger granitic intrusions, and instead horn-
felsic rocks occur there. So, the major parts of the migmatites
of the region are not contact migmatites. Retrograde reactions
in the migmatites, adjacent to granitic bodies and aplitic-peg-
matitic  dykes,  indicate  that  the  intrusion  of  these  dykes  and
younger granitic bodies post-date the migmatization phenom-
enon. This means that anatexis was not facilitated by heating
from the younger granitic plutons but intrusion of older gab-
broic-dioritic bodies. The occurrence of xenocrystic andalusite
(partially  replaced  by  sillimanite),  in  gabbro-dioritic  rocks,
suggests  that  the  conditions  of  the  regional  metamorphism
reached  the  andalusite  stability  field  prior  to  the  intrusion  of
granitic bodies into the metamorphic rocks. Contemporaneous
with the gabbro-dioritic intusions, the temperature conditions
reached the univariant curve between andalusite and silliman-
ite, and the stability field of sillimanite.

According to the evidence presented here and in the previ-

ous works, the metamorphic-magmatic history of the region
can be summarized in the following stages:

1) A LP-HT arc-type metamorphism (in Jurassic-Creta-

ceous)  involving  sequential  development  of  various  index
minerals  including  chlorite,  biotite,  andalusite  (chiastolite),
garnet  (almandine-rich),  staroulite  (St

), prismatic sillimanite

(Sil

), cordierite (Crd

) and K-feldspar, development of syn-

metamorphic quartz-Al

SiO

-bearing veins (e.g. quartz-an-

dalusite veins and quartz-sillimanite veins (Sepahi et al. 2004;
Sepahi & Cavosie 2005)) as well as the emplacement of the
mafic to felsic plutonic rocks of an arc system and regional
migmatization.

2) Intrusion of younger post-tectonic granitoids (i.e. the

small intrusions of leucocratic granitoids). These granitic bod-
ies generated very limited (on a meter to decimeter scale) low-
grade contact metamorphism and alteration zones in the
previously metamorphosed rocks and older plutonic rocks.

Acknowledgment: We are grateful of A. Berger and P. Ná-
belek for their review and comments on an older version of
the manuscript.

References

Ahmadi-Khalaji A., Esmaeily D., Valizadeh M.V. & Rahimpour-

Bonab H. 2007: Petrology and geochemistry of the granitoid
complex of Boroujerd, Sanandaj-Sirjan Zone, Western Iran. J.
Asian Earth Sci. 29, 5—6, 859—877.

Alavi M. 1994: Tectonics of Zagros orogenic belt of Iran: new data

and interpretation. Tectonophysics 229, 211—238.

Alavi M. 2004: Regional stratigraphy of the Zagros fold-thrust belt of

Iran and its proforeland evolution. Amer. J. Sci. 304, 1—20.

Arvin M., Pan Y., Dargahi S., Malekizadeh A. & Babaei A. 2007:

Petrochemistry of the Siah-Kuh granitoid stock southwest of
Kerman, Iran: Implications for initiation of Neo-Tethys subduc-
tion. J. Asian Earth Sci. 30, 474—479.

Ashworth J.D. 1985: Introduction. In: Ashworth J.D. (Ed.): Migma-

tites. Blackie and Son, Glasgow, 1—35.

Ashworth J.D. & McLellan E.L. 1985: Textures. In: Ashworth J.D.

(Ed.): Migmatites. Blackie and Son, Glasgow, 180—203.

Baharifar A.A. 1997: New perspective on petrogenesis of regional

metamorphic rocks of Hamedan area. M.Sc. Thesis, Tarbiat
Moallem University, Tehran, Iran (in Farsi).

Baharifar A.A. 2004: Petrology of metamorphic rocks in the Hamed-

an area. Ph.D. Thesis, Tarbiat Moallem University, Tehran, Iran
(in Farsi).

Braud J. 1987: La suture du Zagros au niveau de Kermanshah (Kurdis-

tan Iranian): Reconstitution paleogeographique, evolution geody-
namique, magmatique et structurale. Ph.D. Thesis, Geodiffusion
editeur, Paris, France.

Brown M. 1994: The generation, segregation, ascent and emplacement

of granite magma: the migmatite-to-crustally-derived granite con-
nection in thickened orogens. Earth Sci. Rev. 36, 83—130.

Carmichael D.M. 1970: Intersecting isograds in the Whetstone Lake

Area, Ontario. J. Petrology 11, 147—181.

Clarke D.B. et al. (35 co-authors) 2005: Occurrence and origin of An-

dalusite in peraluminous felsic igneous rocks. J. Petrology 46, 3,
441—472.

Ferry J.M. & Spear F.S. 1978: Experimental calibration of the parti-

tioning of Fe and Mg between biotite and garnet. Contr. Miner.
Petrology 66, 113—117.

Garcia-Casco A., Haissen F., Castro A., El-Hmidi H., Torres-Roldan

R.F. & Millan G. 2003: Synthesis of staurolite in melting exper-
iments of a natural metapelite: consequences for the phase rela-
tions in low-temperature pelitic migmatites. J. Petrology 44, 10,
1727—1757.

Greenfield J.E., Clarke G.L. & White R.W. 1998: A sequence of par-

tial melting reactions at Mt Stafford, Central Australia. J. Meta-
morph. Geol. 16, 3, 363—378.

Gupta L.N. & Johannes W. 1982: Petrogenesis of a stromatic migma-

tite (Nelaug, Southern Norway). J. Petrology 23, 4, 548—567.

Hadipour M. 1994: Metamorphism and magmatism of Hamedan-Ma-

layer-Teuyserkan region. M.Sc. Thesis, Tarbiat Moallem Uni-
versity, Tehran, Iran (in Farsi).

Holmquist P.J. 1921: Typen and nomenkaltur der adergesteine. GFF

43, 613—631.

119

LOW PRESSURE MIGMATITES FROM THE SANANDAJ-SIRJAN METAMORPHIC BELT (IRAN)

Irani M. 1993: The study of the Alvand granitic body and its meta-

morphic aureole. M.Sc. Thesis, Shahid Beheshti University, Te-
hran, Iran (in Farsi).

Johnson T., Brown M., Gibson R. & Wing B. 2004: Spinel-cordierite

symplectites replacing andalusite: evidence for melt-assisted di-
apirism in the Bushveld Complex, South Africa. J. Metamorphic
Geology 22, 6, 529—545.

Kretz R. 1983: Symbols for rock-forming minerals. Amer. Mineralo-

gist 69, 277—279.

Mahar E.M., Baker J.M., Powell R., Holland T.J.B. & Howell N.

1997: The effect of Mn on mineral stability in metapelites. J.
Metamorphic Geology 15, 2, 223—238.

Marchildon N. & Brown M. 2002: Grain-scale melt distribution in two

contact aureole rocks: implications for controls on melt localiza-
tion and deformation. J. Metamorphic Geology 20, 4, 381—396.

Marchildon N. & Brown M. 2003: Spatial distribution of melt-bear-

ing structures in anatectic rocks from Southern Britany, France:
implications for melt transfer at grain to orogen-scale. Tectono-
physics 364, 215—235.

Masoudi F. 1997: Contact metamorphism and pegmatite development

in the region SW of Arak, Iran. Ph.D. Thesis, Dept. Earth Sci.,
Univ. Leeds, UK.

Mehnert K.R. 1968: Migmatites and the origin of granitic rocks.

Elsevier, Amsterdam, 1—393.

Misch P. 1968: Plagioclase compositions and non-anatectic origin of

migmatitic gneisses in Northern Cascade mountains of Wash-
ington State. Contr. Mineral. Petrology 17, 1—70.

Rashidnejad-Omran N., Emami M.H., Sabzehei M., Rastad E. & Bel-

lon H. 2002: Lithostratigraphy and Paleozoic to Paleocene histo-
ry of some metamorphic complexes from Muteh area,
Sanandaj-Sirjan zone (southern Iran). C. R. Geoscience 334, 16,
1185—1191.

Robin Y.F. 1979: Theory of metamorphic segregation and related

processes. Geochim. Cosmochim. Acta 43, 1587—1600.

Sadeghian M. 1994: The study of petrology of igneous and metamor-

phic rocks of Cheshme-Ghassaban, Hamedan. M.Sc. Thesis,
University of Tehran, Iran (in Farsi).

Sawyer E.W. 1996: Melt segregation and magma flow in migmatites:

implications for the generation of granite magmas. Trans. Roy.
Soc. Edinburgh, Earth Sci. 87, 1—2, 85—94.

Sawyer E.W. 2001: Melt segregation in continental crust: distribution

and movement of melt in anatectic rocks. J. Metamorphic Geol-
ogy 19, 3, 291—309.

Sawyer E.W. & Barnez S.-J. 1988: Temporal and compositional dif-

ferences between sub-solidus and anatectic migmatite leuco-
somes from the Quetio metasedimentary belt, Canada. J.
Metamorphic Geology 6, 4, 437—450.

Sederholm J.J. 1913: Die entstehung der migmatitischen gesteine.

Geol. Rdsch. 4, 174—185.

Sepahi A.A. 1999: Petrology of the Alvand plutonic complex with

special reference on granitoids. Ph.D. Thesis, Tarbiat Moallem
Univ., Tehran, Iran (in Farsi).

Sepahi A.A. & Athari S.F. 2006: Petrology of major granitic plutons of

the northwestern part of the Sanandaj-Sirjan Metamorphic Belt,
Zagros Orogen, Iran: with emphasis on A-type granitoids from
the SE Saqqez area. Neu. Jb. Mineral. Abh. 183, 1, 93—106 (14).

Sepahi A.A. & Cavosie A. 2005: Constraints on isotope thermometry

of quartz-aluminosilicate veins in the Hamedan region using
Oxygen stable isotopes. Iranian J. Crystallography and Miner-
alogy 13, 2, 245—258 (in Farsi with English abstract).

Sepahi A.A., Whitey D.L. & Baharifar A.A. 2004: Petrogenesis of

Andalusite-Kyanite-Sillimanite veins and host rocks, Sanandaj-
Sirjan metamorphic belt, Hamedan, Iran. J. Metamorphic Geol-
ogy 22, 2, 119—134.

Sergi A. 1997: Mafic micro-granular enclaves from the Xanthi pluton

(Northern Greece): an example of mafic-felsic magma interac-
tion. Miner. Petrology 61, 1—4, 97—117.

Sheikholeslami R., Bullen H., Emami M.H., Sabzehei M. & Pique A.

2003: New structural and K

-Ar

data for the metamorphic

rocks in Neyriz area (Sanandaj-Sirjan zone, southern Iran):
Their interest for an overview of the Neo-Tethyan domain in the
Middle East. C. R. Geoscience 335, 13, 981—991.

Thomson J.B. & Norton S.A. 1968: Paleozoic regional metamor-

phism in New England and adjacent areas. In: Zen, E-An, et al.
(Eds.): Studies of Appalachian geology: Northern and Mari-
time. Inter-Science Publ. John Wiley, New York, 319—327.

Tinkham D.K., Zuluaga C.A. & Stowell H.H. 2001: Metapelite phase

equilibria in MnNCKFMASH: The effect of variable Al

and

MgO/(MgO + FeO) on mineral stability. Geol. Material Res.,
Mineral. Soc. Amer. 3, 1, 1—42.

Torkian A. 1995: The study of petrography and petrology of Alvand

pegmatites (Hamedan). M.Sc. Thesis, Univ. Tehran, Iran (in
Farsi).

Valizade M.V. & Cantagral J.M. 1975: Premieres donnees radi-

ometriques (K-Ar et Rb-Sr) sur les micas du complexe magma-
tique du Mont Alvand pres Hamadan (Iran Occidental). C. R.
Hebd. Séanc. Acad. Sci., Sér. D. Sci. Natur. 281, 1083—1086.

White R.W., Powell R. & Clarke G.L. 2003: Prograde metamorphic

assemblage evolution during partial melting of metasedimentary
rocks at low pressures: Migmatites from Mt Stafford, Central
Australia. J. Petrology 44, 1937—1960.

Winkler H.G.F. 1974: Petrogenesis of metamorphic rocks. 3

Ed.

Springer, Berlin, 1—334.

Winkler H.G.F. 1976: Petrogenesis of metamorphic rocks. 4

Ed.

Springer, Berlin, 1—334.

Wolf M.B. & London D. 1997: Boron in granitic magmas: stability of

tourmaline in equilibrium with biotite and cordierite. Contr.
Mineral. Petrology 130, 12—30.