GeolCarp_Vol70_No3_261

GEOLOGICA CARPATHICA

, JUNE 2019, 70, 3, 261–276

doi: 10.2478/geoca-2019-0015

www.geologicacarpathica.com

The Upper Cretaceous intrusive rocks

with extensive crustal contribution in

Hacımahmutuşağı Area (Aksaray/Turkey)

SERHAT KÖKSAL

Middle East Technical University, Central Laboratory, R&D Research and Training Center, Radiogenic Isotope Laboratory, TR-06800,

Ankara, Turkey; skoksal@metu.edu.tr

(Manuscript received January 9, 2019; accepted in revised form April 23, 2019)

Abstract: The Hacımahmutuşağı area (Aksaray/Turkey) is located in the western part of the Central Anatolian Crystalline

Complex (CACC). Gneiss and marble compose the basement units, while intrusive rocks are gabbros and granitoids.

The pegmatitic hornblende gabbros contain pegmatitic to fine-grained hornblendes, plagioclase, clinopyroxene, and

accessory opaque minerals. The fine-grained gabbros, on the other hand, are composed of plagioclase, hornblende,

and biotite as major components whereas the apatite and opaque minerals are present in accessory content. Granitic–

granodioritic rocks are the common intrusive rock types in the area, and constitute quartz, orthoclase, plagioclase and

biotite, and accessory zircon and opaque minerals. Leucogranites, comprising quartz, orthoclase, plagioclase with minor

biotite, hornblende, and with accessory apatite and opaque minerals, are found as dykes intruding the marble and

the granitic–granodioritic rocks. Strontium–neodymium isotope data of gabbros and granitoids have high

Sr/

(i)

ratios

(0.7076 to 0.7117) and low ɛNd

(i)

values (−5.0 to −9.8) point out enriched source and pronounced crustal contribution

in their genesis. In the Hacımahmutuşağı area, it is plausible that the heat increase caused by the hot zone, which was

generated by underplating mafic magma along with the hydrous mafic sills in the lower crust, might have resulted in

partial melts from crystallized mafic sills and older crustal rocks. It can be suggested that these hybrid melts adiabatically

rose to the shallow crust, ponded and crystallized there and formed the magma source of the intrusive rocks within

the Hacımahmutuşağı area and the other hybrid granitic rocks with crustal signatures in the CACC. Geochemical data

indicate that granitoids and gabbros are collision to post-collision related sub-alkaline rocks derived from an enriched

source with extensive crustal inputs.

Key words: Hacımahmutuşağı, Central Anatolia, granitoids, gabbros, Sr–Nd isotopes.

Introduction

Intrusive igneous rocks are common rock types in the earth’s

crust and exist in various tectonic settings, ranging from sub-

duction and collision related regions to intra-continental areas

(e.g., Pitcher 1979; Pearce et al. 1984). They have particular

importance in complex tectonic regimes like Alpine Oroge-

nesis, which was effective in Central Anatolia (Turkey) during

the closure of the Neotethyan Ocean in the Late Cretaceous

(e.g., Moix et al. 2008; Göncüoğlu et al. 1997a, 2015). Traces

of this belt were recorded within the ophiolitic units over-

thrusting the basement units and the related igneous rocks

in the Central Anatolian Crystalline Complex (CACC) (e.g.,

Göncüoğlu et al. 1997a, 2010; Yalınız et al. 2000; Robertson

et al. 2009). In Central Anatolia, igneous rocks outcrop in

various places and their relationships with the other units

preserve evidence of the geodynamic evolution of the region

in spite of the extensive Eocene and post-Eocene tectonic/

magmatic activities (e.g., Boztuğ et al. 2009). Their petro-

logical characteristics are not only important in linking to

regional geodynamics but also in understanding the petro-

genesis and formation processes of similar igneous rocks in

the world.

Hacımahmutuşağı is a small town in West-Central Anatolia,

but it is one of the key areas for description of the common

igneous rocks and their petrogenetic characteristics in

the CACC (Fig. 1). Previous studies in the Hacımahmutuşağı

area focused on geological and petrographical studies with

limited geochemical and geochronological data (e.g., Köksal

1992; Köksal et al. 2001; Kadıoğlu et al. 2003). The aim of

this study is to investigate the petrology of the intrusive rocks

in the Hacımahmutuşağı area with new geochemical, inclu-

ding isotopic, data and to provide new insights into the geody-

namic approaches for the CACC.

Regional geology

Turkey covers a geologically noteworthy region since it is in

the junction between Eurasia and Gondwana (e.g., Göncüoğlu

et al. 1997a; Okay & Tüysüz 1999; Bozkurt & Mittwede 2001).

Alpine orogenesis related to the closure of the various branches

of Neotethys shaped the geology of the region especially

during the Late Cretaceous (e.g., Moix et al. 2008; Göncüoğlu

et al. 2015). Pontides in the northern part of the country repre-

sent the active south margin of Eurasia, which is bounded by

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GEOLOGICA CARPATHICA

, 2019, 70, 3, 261–276

HM-1

HM-2

HM-3

HM-4

HM-5

HM-6

HM-7

GRD

F.GAB

P.GAB

SiO

(wt. %)

69.78

74.27

71.06

74.27

68.07

51.80

52.44

TiO

(wt. %)

0.33

0.07

0.17

0.10

0.32

0.97

0.48

(wt. %)

13.95

11.53

14.93

12.85

16.06

17.95

9.26

tot

(wt. %)

3.10

0.77

1.92

1.19

4.00

11.01

8.44

MnO (wt. %)

0.058

0.089

0.083

0.059

0.062

0.235

0.146

MgO (wt. %)

1.14

0.14

0.46

0.21

0.95

4.48

13.10

CaO (wt. %)

2.83

0.69

1.80

0.97

4.52

6.46

13.99

O (wt. %)

2.72

3.71

3.64

3.26

3.64

3.37

1.28

O (wt. %)

4.34

5.26

4.58

4.82

1.73

2.53

0.96

(wt. %)

0.0008

0.0002

0.0004

0.0002

0.0015

0.0018

0.0008

LOI (wt. %)

1.4

1.3

1.1

1.3

0.8

SUM (wt. %)

99.64

97.82

99.75

98.83

100.65

100.10

100.90

Ba (mg/kg)

620

166

440

182

580

730

470

Cs (mg/kg)

9.1

8.2

6.5

27.8

1.23

3.1

0.74

Ga (mg/kg)

16.5

15.1

15.7

18.6

22.9

10.1

Hf (mg/kg)

2.31

2.91

2.38

2.48

0.82

1.24

0.92

Nb (mg/kg)

8.7

26.3

10.1

19.2

6.1

11.7

2.25

Rb (mg/kg)

180

431

254

331

106

26.8

Sr (mg/kg)

134

110

359

256

238

Ta (mg/kg)

0.94

3.94

1.15

3.33

0.41

0.72

0.17

Th (mg/kg)

17.8

24.2

9.1

5.69

3.73

U (mg/kg)

10.1

5.4

9.7

0.87

1.46

1.02

V (mg/kg)

5.51

25.6

9.9

276

230

Zr (mg/kg)

Y (mg/kg)

17.9

33.2

20.1

22.8

8.8

28.9

12.1

La (mg/kg)

26.4

13.9

18.2

29.2

8.05

10.6

Ce (mg/kg)

28.3

33.3

33.7

22.1

19.8

Pr (mg/kg)

5.69

3.17

3.16

3.5

5.29

3.41

2.33

Nd (mg/kg)

18.6

11.2

10.5

11.5

17.1

15.6

9.15

Sm (mg/kg)

3.71

3.44

2.36

2.52

2.76

4.62

2.43

Eu (mg/kg)

0.72

0.17

0.46

0.24

0.96

1.23

0.68

Gd (mg/kg)

3.27

4.04

2.41

2.62

2.18

4.79

2.45

Tb (mg/kg)

0.5

0.81

0.42

0.48

0.29

0.79

0.36

Dy (mg/kg)

2.96

5.31

2.64

3.17

1.58

5.02

2.14

Ho (mg/kg)

0.58

1.11

0.58

0.66

0.28

1.02

0.41

Er (mg/kg)

1.88

3.38

1.85

2.36

0.82

3.05

1.21

Tm (mg/kg)

0.28

0.51

0.31

0.37

0.12

0.42

0.16

Yb (mg/kg)

1.87

3.59

2.24

2.81

0.82

2.68

1.02

Lu (mg/kg)

0.27

0.52

0.36

0.45

0.13

0.4

0.15

Pb (mg/kg)

15.3

10.2

(Eu/Eu*)

0.63

0.14

0.59

0.28

1.19

0.80

0.85

(La/Yb)

9.59

2.63

5.16

4.40

24.19

2.04

7.06

A/CNK

0.97

0.80

1.01

0.96

1.15

1.03

0.42

Mg-no

Note: Fe

tot

= total Fe; LOI = loss on ignition; (Eu/Eu*)

=(Eu

) / √ (Sm

); Eu

, Sm

, Gd

and Yb

values are normalised to chondrite (McDonough & Sun 1995);

A/CNK = molar [Al

/(CaO+Na

O+K

O)]; Mg-no =100 × Mg /(Mg+Fe). GR: granite;

GRD: granodiorite; LG: leucogranite; F.GAB: fine-grained gabbro; P.GAB: pegmatitic gabbro.

Table 1: Whole-rock elemental geochemical data of the intrusive rocks from

the Hacımahmutuşağı area.

Paleocene cover units, Paleocene–Eocene volca-

nic, volcanoclastic and carbonate rocks, Oligocene–

Miocene evaporates, terrestrial clastics, vol

canoclastic and volcanic rocks (Göncüoğlu et al.

1993).

Analytical methods

Rocks were crushed and disintegrated into a pow-

der form by using jaw crusher and agate disc mill at

the Central Laboratory of Middle East Technical

University (METU). Furthermore, whole-rock

elemental and radiogenic isotope geochemical

analyses from seven samples were conducted at

the Central Laboratory of METU (Tables 1 and 2).

Major, trace and rare earth elements (REE) were

determined after LiBO

/Li

fusion by Perkin

Elmer Optima 4300DV ICP-OES and after dilute

nitric acid digestion (HNO

of 5 %) by Perkin

Elmer DRC II ICP-MS. Detection limits of these

analyses are 0.01 wt. % for SiO

, Al

, MgO,

CaO, Na

O, K

O, MnO, and TiO

, 0.04 wt. % for

, 0.001–0.002 wt. % for P

and Cr

and

0.10 wt. % for LOI. For trace and REE detection

limits are 8 ppm for V, 1 ppm for Ba, 0.5 ppm for

Sr, Gd and W, 0.3 ppm for Nd, 0.1 ppm for Cs, Hf,

Nb, Rb, Ta, U, Y, Zr, Th, La and Ce, 0.05 ppm for

Sm, Dy, Yb, 0.03 ppm for Er, 0.02 ppm for Pr, Eu

and Ho, 0.01 ppm for Tb, Tm, Lu. Standard errors

were 0.001–0.7 for major elements, 5×10

-8

– 4×10

-6

for trace elements and 1×10

-8

– 1×10

-6

for REE.

For radiogenic isotope analyses, Sr was enriched

through 2 ml volume BioRad AG50 W-X8 (100–

200 mesh) resin by using 2.5 N HCl. REE were

collected with 6 N HCl after Sr chromatography,

and Nd was separated from other REE in 2 ml

HDEHP (bis-ethyexyl phosphate) coated biobeads

(BioRad) resin with 0.22 N HCl. Strontium was

loaded on single Re filament with Ta-activator and

dilute H

. Neodymium, on the other hand, was

loaded on double filaments with dilute H

Sr/

Sr ratios were normalized to

Sr/

Sr = 0.1194,

and NIST SRM 987 standard was measured as

Sr/

Sr = 0.710244 ± 8 (n = 2).

143

Nd/

144

Nd ratios

were normalized with

143

Nd/

144

Nd = 0.7219 and La

Jolla Nd standard was measured as

143

Nd/

144

Nd =

0.511847 ± 5 (n = 2). Isotopic ratios were measured with

a Thermo-Fisher Triton TIMS. No bias correction was applied

for Sr and Nd analyses. Quality control of the isotope analyses

was checked by applying the same procedures to

the USGS rock standards. During the period of analyses,

the BCR-1 USGS standard gave

Sr/

Sr = 0.705027 ± 12 (n = 3)

and AGV-2 USGS standard gave

143

Nd/

144

Nd = 0.512776 ± 10

(n = 5). Details of the radiogenic isotope methods are described

by Köksal et al. (2017).

Field characteristics

Metamorphic rocks form the basement units of the Hacı-

mahmutuşağı area (Fig. 2) (e.g., Göncüoğlu et al. 1993), and

these units are contemporary with the Kalkanlıdağ and

Tamadağ formations (e.g., Seymen 1981) or Gümüşler and

Aşıgediği formations (e.g., Göncüoğlu 1986; Göncüoğlu et al.

1993) in the other parts of Central Anatolia. Gneisses, oldest

rock units of the CACC (i.e., Kalkanlıdağ or Gümüşler

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, 2019, 70, 3, 261–276

formations), crop out in the middle-north

part of the Hacımahmutuşağı area. Mar-

bles (i.e., Tamadağ or Aşıgediği forma-

tions) transitionally overlay gneisses and

generally dip to the southeast. Well

defined contact metamorphism between

the basement rocks and the intrusive

rocks are observed in the study area.

Gabbroic rocks in the study area are

dark coloured and represented by two

types as pegmatitic gabbros, including

large amphibole crystals, and fine-crystal-

line gabbros occupying larger areas than

the pegmatitic ones. The contact zones

of gabbros and the metamorphic rocks

are concealed by recent cover units in

the study area, but in the north-eastern

part of the study area some gabbro blocks

have fallen over the marbles. Thus, these

gabbros were initially suggested by

Köksal (1992) and Köksal et al. (2001) as

rocks belonging to the allochthonous

ophiolitic units observed in various parts

of the CACC (e.g., Sarıkaraman: Yalınız

et al. 2000; Ekecikdağ: Göncüoğlu & Türeli

1994; Köksal et al. 2017). However,

the geochemical findings presented in this

study show that the gabbros and the grani-

toids have similar petrological features.

Therefore, the field relations of gabbros

and marble should be resulted from the sub-

sequent tectonic events. Similar gabbroic

rocks observed in the Hacımahmutuşağı

area were initially documented in the NW

of the study area in the Ağaçören (e.g.,

Güleç et al. 1996; Kadıoğlu et al. 1998a,

2003) and SE of the study area in the

Eke cikdağ (e.g., Göncüoğlu & Türeli

1994) areas. Kadıoğlu et al. (2003) indi-

cated that the granitoids and the gabbros

in the Ağaçören area are coeval and

gabbro blocks in the area belong to the

large intrusive bodies emplaced 1.55 km

deep based on the magnetic modelling

studies.

The granitoids in the Hacımahmutuşağı

area are differentiated into two groups:

granite–granodiorite and leucogranite

(Fig. 3). Granite–granodiorite is the main

intrusive phase in the area (Figs. 2, 3a, b, c).

Granite–granodiorite is characterized by large feldspar crys-

tals and visible quartz and mafic mineral content (Fig. 3c).

Leucogranite, on the other hand, is a relatively younger phase

with white colour and very little mafic mineral content

(Fig. 3d). Leuco granite cuts both granite–granodiorite and

host rock marble (Fig. 2).

Granitoids in the nearby areas were investigated in detail in

previous works; Ağaçören granitoids (e.g., Kadıoğlu et al.

2003; Köksal et al. 2012) and Ekecikdağ granitoids (e.g.,

Göncüoğlu & Türeli 1994; Toksoy-Köksal, 2016). Granite–

granodiorite in the study, considering the geological and

pet rological features, resembles amphibole-biotite granite in

Sr/

(i)

143

Nd/

144

143

Nd/

144

(i)

εNd

(i)

HM-1

0.716092±15

0.711672

0.512096±4

0.512033

−9.8

HM-2

0.749279±15

0.707566

0.512326±4

0.512229

−6.0

HM-3

0.716779±12

0.709181

0.512285±3

0.512214

−6.3

HM-4

0.734712±18

0.710508

0.512263±3

0.512194

−6.7

HM-5

GRD

0.710307±7

0.709803

0.512202±2

0.512151

−7.5

HM-6

F.GAB

0.710504±6

0.709141

0.512302±2

0.512208

−6.4

HM-7

P. GAB

0.708530±8

0.708159

0.512364±3

0.512280

−5.0

Note: Rb, Sr, Nd and Sm concentrations are taken from Table 1. Initial isotopic ratios are calculated for t=80

Ma. GR: granite, GRD: granodiorite, LG: leucogranite, F.GAB: fine-grained gabbro, P.GAB: pegmatitic

gabbro.

Table 2: Whole-rock Sr–Nd isotopic data of the intrusive rocks from the Hacı mahmutuşağı

area.

Fig. 2. Geological map and cross section of the study area (GPS coordinates of samples are:

HM-1: 38°43’57.38” N, 33°55’43.02” E; HM-2: 38°43’51.37” N, 33°55’25.08” E;

HM-3: 38°44’4.18” N, 33°56’0.68” E; HM-4: 38°43’42.46” N, 33°55’10.78” E;

HM-5: 38°44’7.65” N, 33°56’31.87” E; HM-6: 38°44’11.25” N, 33°56’28.89” E;

HM-7: 38°44’14.90” N, 33°56’18.04” E).

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the Ağaçören area (Kadıoğlu et al.

2003) and/or Borucu granitoid in

the Ekecikdağ area, leucogranite

on the other hand is similar to

the Kalebalta leucogranite in the

Eke cikdağ area (Göncüoğlu &

Türeli 1994). Moreover, there are

widespread aplitic micro-granite

dykes reaching up to hundreds of

metres long, cutting the gneisses

and granitoids and representing

the youngest intrusive phase in

the study area. In this area, meta-

morphic rocks are found as roof-

pendants on the granitoids (Fig. 2).

There are dykes of granite–grano-

diorite and leucogranite along

the contacts and inside the marble

units. The wollastonite hornfelses

observed along the granitoid–mar-

ble contact indicate intrusive fea-

tures of the granitoids in the stu died

area. Gabbros, mafic microgra-

nular enclaves and granitoids have

generally sinuous contacts in the

study area (Fig. 3b). Neogene cover units, represented by

fluvial and lacustrine deposits, unconformably overlay older

units in the area (Fig. 2).

Results

Petrography

Gneisses have intermediate to highly developed gneissic

texture with quartz, feldspar and garnet crystals in between

biotite, sillimanite and cordierite rich bands. The main contact

metamorphic phase is cordierite and related to the intrusion of

the aplitic micro-granite. Marbles with granoblastic and mas-

sive texture show large calcite crystals along the contacts of

the intrusive rocks.

Pegmatitic gabbros are represented by abundant large horn-

blend crystals. The main minerals are hornblend, plagioclase

(andesine and/or labradorite), clinopyroxene (diopside) and

opaque minerals; secondary minerals are chlorite and epidote

(Fig. 4a, b). Fine-grained gabbros are composed of plagioclase,

hornblend, biotite as main mineral phases and chlorite as

secondary, opaque minerals and apatite as accessory minerals

(Fig. 4c, d, e). In both gabbro types, there are extensive uraliti-

zations, where hornblendes are partly preserved along the rims

of the clinopyroxenes (e.g., Fig. 4a). These gabbros can be

interpreted as uralitic gabbros although this is not the case for

the whole gabbroic intrusions. Moreover, along the granitoid–

gabbro contact, primary hornblend in the gabbroic part was

generally replaced by actinolite and chlorite due to the heat

transfer and chemical interaction between gabbro and

semi-solid granitoid (Fig. 4d, e, f). Chilled margins along these

contacts are also observed in the study area (Fig. 4f).

Granite–granodiorites are characterized by phaneritic tex-

ture and greyish colour with 15–25 % mafic mineral content

and widespread argillitization and sericitization. Quartz,

orthoclase, plagioclase, hornblend and biotite are the major

mine rals, with minor amounts of opaque minerals, zircon and

secondary muscovite (Fig. 4g). Leucogranites have white

colour, medium grained texture and scarce mafic content

(ca. 5–10 %) with quartz, orthoclase and albitic plagioclase as

the main mineral phases, and chloritized biotite, hornblend,

epidote, apatite and opaque minerals as accessory minerals

(Fig. 4h). Micrographic and myrmekitic textures are also

well-developed in the studied leucogranites. Aplitic micro-

granite dykes on the other hand are light coloured rocks with

fine grained, holocrystalline and microgranular texture. These

dykes have quartz and orthoclase — extensively argillitized

and sericitized — as major, plagioclase as minor, and garnet,

tourmaline and opaque minerals as accessory minerals.

Wollastonite hornfelses with wollastonite, diopside and epi-

dote minerals are the contact metamorphism products observed

in the study area.

Major and trace element geochemistry

Geochemical data from the whole-rock elemental analyses

studied are given in Table 1. In the Kadıoğlu et al. (2003)

study covering the Hacımahmutuşağı area five gabbro sam-

ples fall into the boundaries of the study area of the present

research. The data from these five gabbro samples, which

were documented by Kadıoğlu et al. (2003), are specified as

Fig. 3. Field views of the studied intrusives and their contact relationships: a — granite–granodiorite

(Gr) and marble (Mar); b — photograph showing granite-granodiorite (Gr) and large mafic micro-

granular enclave (MME); c — granite–granodiorite close-up view; d — leucogranite close-up view.

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gabbro (2) in the geochemical diagrams and are evaluated

along with the new geochemical data presented in Table 1 for

better assessment.

On the Na

O+K

O vs. SiO

diagram of Cox et al. (1979),

HM-7 (pegmatitic gabbro) and the gabbro samples from

Kadıoğlu et al. (2003), plot into

the sub-alkaline area while HM-6

(fine-grained gabbro) falls in the

alkaline area (Fig. 5a). In the same

diagram, the studied granitic rocks,

namely granodiorite/granite, show

transition from granodiorite to

alkali granite, and these samples

which cannot be exactly distin-

guished based on field and petro-

graphic observations, are identi fied

by using this classification (Fig. 5a).

Excess silica contents of the gab-

bro samples concerned in this study

(Table 1; Fig. 5a) infer their

geochemical compositions are

akin to diorites. However, based

on the nomenclature revealed by

O+K

O vs. SiO

diagram

(Fig. 5a) and to be consistent with

the existing literature (e.g.,

Kadıoğlu et al., 2003, 2006;

Kadıoğlu and Güleç, 1998, 2001;

Güleç and Kadıoğlu, 1998) the

mafic intrusive rocks in the pre-

sent research are named and eva-

luated as “gabbro”.

Granite and leucogranite show

transition from calc–alkalic to

alkali–calcic field, while grano-

diorite is in the calcic part on the

O+K

O−CaO vs. SiO

diagram

(Frost et al. 2001) (Fig. 5b). LOI

values of the rock samples (Table 1)

show less than 1.5 % inferring

secondary events like argillitiza-

tion and sericitizion are not very

effective in evaluating geochemis-

try. However, it is plausible to

describe the samples as sub-alka-

line by using trace elements,

which are less affected by altera-

tion (Fig. 5c).

On the AFM diagram (Irvine &

Baragar 1971), granitoids and fine-

grained gabbro (HM-6) display

calc–alkaline character, whereas

pegmatitic gabbro and gabbro (2)

show transition from calc–alka-

line to tholeiitic (Fig. 5d). Based

on the A/CNK values granitoids in

the area can be described as metaluminous except a granodio-

rite sample showing weak peraluminous character (Table 1).

In addition, regarding the magnesium numbers, leucogranite

have the lowest, and pegmatitic gabbro has the highest Mg-no

(Table 1) among the rock samples analysed.

Fig. 4. Photomicrographs of the gabbros and granitoids: a, b — pegmatitic gabbro, plane polarized

light (a), crossed polars (b); c, d, e — fine crystalline gabbro, plane polarized light (c, d), crossed

polars (e); f — microscopic view from the contact of granitoid and gabbro, plane polarized light.

g — granite–granodiorite, crossed polars; h — leucogranite, crossed polars. qt: quartz, orth: ortho-

clase, bio: biotite, pl: plagioclase, hb: hornblend, mus: muscovite, op: opaque minerals, chl: chlorite,

di: diopside, act: actinolite.

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When Harker diagrams plotted against SiO

are evaluated it

is difficult to mention a genetic relationship between grani-

toids and gabbros. The scatter of the gabbro samples and a gap

between the gabbros and granitoids, also considering the few-

ness of the analysed samples, there are not enough findings to

suppose a trend inferring fractionation from mafic to felsic

rocks in the area (Fig. 6). Although it is possible to deduce that

leucogranite has similar but less evolved/enriched source than

granite, granodiorite exhibits the most depleted source among

the granitoids (Fig. 6). The similar situation stands out in

the trace elements vs. SiO

diagrams (Fig. 7). Variation in

the genetic characteristics within the granitic rocks, especially

for Rb, Ba, Sr, Nb, U, Y and V elements, is remarkable (Fig. 7).

Granodiorite displays depletion in Nb, Rb, Th, U, Zr, and Pb

with respect to granite and leucogranite. In contrast, gabbro

samples exhibit less crustal contribution (e.g., U, Pb, and Rb)

than granitoids and cluster in different areas than the grani-

toids in trace element vs. SiO

diagrams (Fig. 7).

On the multi-element diagram normalized to primitive man-

tle (Sun & McDonough 1989) granitoids and gabbros show

similar trends, where gabbros illustrate relatively lower Th,

La, Ce, Pb and higher Ti contents. Furthermore, depletion of

Rb, Nb and Ta is significant in pegmatitic gabbro. Leuco-

granites presenting Ba, P, Eu and Ti depletion with Pb, K, U

and Th enrichment differ from other rocks with their higher

crustal contribution/effect in their source (Fig. 8a). Nb–Ta

depletion observed in the Figure 8a may be related with

the earlier subduction component inherited in the source

region, but it is also characteristic for the continental crust

(Kelemen et al. 1993). Chondrite-normalized REE patterns

(Sun & McDonough 1989) infer LREE are more enriched than

HREE in all samples, while gabbros have lower LREE con-

tents than granitoids (Fig. 8b). La/Yb fractionation is the hig-

hest in granodiorite ( [La/Yb]

= 24.19), moderate to high in

granite ( [La/Yb]

= 5.16 – 9.59), and lower and limited in

leucogranite ( [La/Yb]

= 2,63 – 4,40). Data from gabbros, on

the other hand, are fairly scattered ( [La/Yb]

= 2.04 – 7.06).

Negative Eu anomalies of granite ( [Eu/Eu*]

= 0.59 – 0.63)

and leucogranite ( [Eu/Eu*]

= 0.14 – 0.28) put forward pla-

gioclase fractionation. Conversely positive Eu anomaly of

granodiorite ( [Eu/Eu*]

= 1.19) suggests plagioclase fractio-

nation is not pronounced, but amphibole fractionation should

Fig. 5. Intrusive rocks in the study area: a — nomenclature based on the Na

O+K

O vs. SiO

diagram (Cox et al. 1979); b — classification

based on the Na

O+K

O−CaO vs. SiO

diagram (Frost et al. 2001); c — Zr/Ti – Nb/Y diagram (Pearce 1996); d — A–F–M diagram (Irvine &

Baragar 1971).

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be the case concerning the bowl shape pattern of HREE

(Fig. 8b). Moreover for the gabbro samples showing weak

Eu anomaly ( [Eu/Eu*]

= 0.80 – 0.85) plagioclase fractionation

does not seem prevalent.

Tectonic discrimination diagrams (Fig. 9a, b) indicate that

granitoids show syn-collisional character. However, a grano-

diorite sample plotted in volcanic arc field in Rb vs. Yb +Ta

diagram (Pearce et al. 1984) (Fig. 9a) shows transition from

syn-collisional to late and post-collisional stage granitoids in

Rb/30 – Hf – Tax3 diagram (Harris et al. 1986) (Fig. 9b).

Nb/Yb vs. Th/Yb diagram (Fig. 9c) points to enriched source

for all intrusive rocks investigated with a large recycled crustal

component (Pearce 2008).

Considering the geochemical data along with the petro-

graphic examinations (mafic mineral contents of granite/

grano diorite and leucogranite) we can suggest that granitoids

among themselves were subjected to different levels of frac-

tionation and/or crustal contamination processes. Since there

are no age data from each granitoid type available exact

description of the genetic relationships is not possible.

However, in the nearby area (Ekecikdağ) similar leucogranites

are reported to be younger than the granite/granodiorites based

on geochronological data (Toksoy-Köksal 2019). Thus, grano-

diorite may represent the first and leucogranite is the last

granitic phase in the Hacımahmutuşağı area.

Sr–Nd isotope geochemistry

Initial Sr and Nd isotope ratios are calculated for 80 Ma

(Köksal et al. 2012) (Table 2; Fig. 10). Kadıoğlu et al. (2003)

reported apparent

Ar/

Ar ages for gabbro samples in

the Hacımahmutuşağı area as 78.0 ± 0.3 Ma to 78.8 ±1.0 Ma;

and 77.7 ± 0.3 Ma for a granite sample close to southeast of

the study area. However similar granitoids in the Ağaçören

region near the Hacımahmutuşağı area yield older U–Pb

zircon ages (Köksal et al. 2012), therefore these Ar–Ar ages

are assumed to be the cooling age and 80 Ma is suggested for

the intrusive rocks in the study area.

Initial strontium isotope data for granitoids are in the

Sr/

(i)

= 0.707566 – 0.711672 interval, but there is no sig-

nificant variation in between leucogranite, granite and grano-

diorite samples considering the initial Sr isotope ratios (Table 2).

Güleç (1994) also reported

Sr/

(i)

= 0.708616 (n = 3) data

from the Ağaçören granitoid on the NW of the study area.

A similar case is valid for the gabbros where fine-grained gab-

bro yields

Sr/

(i)

= 0.709141 and pegmatitic gabbro gives

Sr/

(i)

= 0.708159 values; and these data are comparable

to those of the granitoids (Table 2; Fig. 10). Furthermore

granite-granodiorite shows a larger range of initial Nd isotope

data (

143

Nd/

144

(i)

= 0.512033 – 0.512214; ɛNd

(i)

= −6.3 to −9.8),

than leucogranite displaying

143

Nd/

144

(i)

= 0.512194 – 0.512229;

ɛNd

(i)

= −6.0 to −6.7 values (Table 2). Initial

143

Nd/

144

Nd iso-

tope ratios for fine-grained gabbro and pegmatitic gabbro are

0.512208 (ɛNd

(i)

= −6.4) and 0.512280 (ɛNd

(i)

= −5.0), respec-

tively (Table 2). Neodymium isotope data of gabbros also

reflect that they are comparable to the granitoids isotopically.

This situation is rather different from the expected isotopic

ratios where gabbros display higher

143

Nd/

144

Nd and lower

Sr/

ratios than granitoids elsewhere (e.g., Miller et al.

2011). While the HM-1 granite sample has the most crustal

contribution among the intrusive samples, the HM-7 pegma-

titic gabbro sample has the least initial Nd isotope data.

Collectively Sr and Nd isotope data yielding high

Sr/

(i)

ratios, 0.7076 to 0.7117, and low ɛNd

(i)

values, −5.0 to −9.8,

indicate that the intrusive rocks concerned have the enriched

source with high crustal input instead of depleted mantle

source (Fig. 10).

Discussion

CACC intrusive rocks have been the subject of various

stu dies, but their petrology is not sufficiently clear because of

their complex geodynamic environment. In this manner inves-

tigation of the Cretaceous intrusive rocks of the CACC is

important for understanding the Alpine orogenesis. The Hacı-

mahmutuşağı area in this way is one of the unique areas in

Central Anatolia for studying the petrogenesis of these rocks

and their relationships. The geochemical data presented in this

study infer that both rock types are formed in similar tectonic

environments. The cutting relationship between granitoid and

gabbro is revealed by geological and petrographical

Fig. 8. a — Primitive mantle-normalized (Sun & McDonough 1989)

multi-element spider diagram; b — chondrite-normalized (Sun &

McDonough 1989) REE diagram.

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quartz syenite, syenite, and nepheline- and pseudoleucite-

bearing alkali rocks. Kadıoğlu et al. (2006) thought that

the derivation of these granitoids is related to subduction

instead of collision, yielding a subduction-modified and

metasomatized mantle source for granite and monzonite

supersuites, and enriched mantle source with considerable

crustal contribution for the syenite supersuite magmas. Güleç

& Kadıoğlu (1998) suggested the involvement of upper crustal

and subduction-modified upper mantle-derived sources with

an isotope signature of MORB in the petrogenesis of I-type

Ağaçören granitoids to the NW of the study area by using

Sr-isotopic data. Mafic microgranular enclaves found in

the granitoids provide evidence for magma mingling (Güleç &

Kadıoğlu 1998). Moreover, Kadıoğlu et al. (2003) suggested

that the evolution of the granitoids and gabbros in a region,

covering Hacımahmutuşağı area, are related to the Andean-

style magmatic arc, inferring the existence of Inner-Tauride

Ocean between the CACC and the Tauride carbonate platform.

They further advocated that a subduction zone dipping away

from the Tauride platform consumed the ﬂoor of the Inner-

Tauride ocean basin and resulted in the emplacement of its

remnant oceanic crust onto the platform edge, and this subduc-

tion zone within the Inner-Tauride ocean basin that produced

a magmatic arc along the western margin of the CACC.

The second group, on the other hand, think that during

the closure of the northern branch of the Alpine Neotethyan

Ocean, ophiolitic rocks overthrusting the CACC basement

rocks resulted in crustal thickening

followed by thermal relaxation in

Central Anatolia. The results of

the present study favour the colli-

sional to post-collisional nature for

the intrusive rocks in the Hacımah-

mutuşağı area instead of Andean-

style magmatic arc origin.

The collision and subsequent

periods caused evolution of colli-

sional to post-collisional granitoids

in the region (e.g., Göncüoğlu et

al. 1993, 1997b; Yalınız et al.

1999; Boztuğ et al. 2007, 2009;

İlbeyli et al. 2004; Köksal et al.

2012, 2013). The second assess-

ment fundamentally disagrees

with the existence of the Inner

Tauride Ocean, because the pro-

posed place for the Inner Tauride

Suture is buried under the Ulukışla

Basin (e.g., Robertson et al. 2009),

one of the large sedimentary basins

in Central Anatolia like Kızılırmak

and Sivas, which were formed by

thermal relaxation and extensional

regime in Upper Maastrichtian–

Paleocene (Göncüoğlu et al. 1993;

Dirik et al. 1999; Alpaslan et al.

2004; van Hinsbergen et al. 2016). A similar scenario was

reported from the Variscan Belt of Europe where evolution of

the granitoids are explained as related to the post-collisional

restoration and re-equilibration of a thickened continental

lithosphere, through delamination and/or erosion of its mantle

root and erosion combined with exhumation in a following

extensional regime (e.g., Bussy et al. 2000).

Köksal & Göncüoğlu (2008) and Köksal et al. (2004, 2012)

suggested that the evolution of the Cretaceous CACC grani-

toids can be subdivided into three main phases: namely colli-

sional crustal S- and I-type granites-granodiorites of 85–80 Ma,

post-collisional A-type syenites and the I-type granitoids,

mainly monzonites, formed ca. 75 Ma, and later (i.e. 74 Ma

and/or younger) alkaline intrusives, mainly syenites and

foid-syenites, and volcanic rocks related to the post-collisional

extension in the CACC.

Examples of first group are the Üçkapılı Granitoid

(Göncüoğlu 1986), Behrekdağ batholite (İlbeyli et al. 2004)

and Danacıobası Granitoid (Boztuğ et al. 2007) (Fig. 1). These

granitoids are calc–alkaline rocks associated with thermal influx

related to the crustal thickening and coeval with the regio nal

metamorphism (e.g., Göncüoğlu 1986; Whitney et al. 2003).

This crustal thickening is claimed to be caused by collision of

an ensimatic island arc in the İzmir–Ankara–Erzincan Ocean

and the CACC basement rocks in Turonian–Coniacian (e.g.,

Göncüoğlu 1986). The granitoids in the Hacımah mutuşağı

area are probably members of this group of rocks.

Fig. 10. Initial ɛNd vs.

Sr/

(i)

diagram of the intrusive rocks in the Hacımahmutuşağı area.

Areas for comparison: Ekecikdağ ophiolitic rocks (Köksal et al. 2017); S-, I- and A-type Central

Anatolian granitoids (Köksal & Göncüoğlu 2008 and references therein); Ulukışla alkaline volcanic

rocks (Alpaslan et al. 2004); Ulukışla ultrapotassic volcanic rocks (Alpaslan et al. 2006). Mantle

components: EM (enriched mantle) and oceanic basalts are from Zindler & Hart (1986) and Hart

(1988).

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Second period granitoids are characterized by Cefalıkdağ

quartz-monzonite (Kadıoğlu et al. 2006), Baranadağ quartz-

monzonite (Köksal et al. 2004; İlbeyli et al. 2004; Boztuğ et al.

2007), Terlemez quartz-monzonite (Yalınız et al. 1999) and

other monzonitic rocks exposed in different parts of the CACC

(Fig. 1). These Campanian monzonitic rocks are described as

sub-alkaline-transitional (e.g., İlbeyli et al. 2004) and assumed

to be connected to the partial melting of lithospheric mantle

with lower and middle crust due to the heat transfer from

underplating mafic magma during post-collisional uplifting

and extension regime combined with lithospheric delamina-

tion, lithospheric thinning and crustal contamination processes

(e.g., Köksal et al. 2004, 2012; İlbeyli et al. 2004; Boztuğ et al.

2007, 2009). The latest phase of the Late-Cretaceous CACC

intrusives are presumed to be alkaline rocks formed in

advanced stages of the crustal extension with significant man-

tle component and exemplified by Bayındır–Akpınar (Kaman)

alkaline rocks (e.g., Kadıoğlu et al. 2006), Buzlukdağ syeni-

toid (Deniz & Kadıoğlu 2016), İdiş Dağı quartz-syenitoid

(Göncüoğlu et al. 1997b) and Çamsarı quartz syenitoid

(Köksal et al. 2004) (Fig. 1). Some of these syenitic intrusives

(e.g., Hamit: İlbeyli et al. 2004; Çamsarı: Köksal et al. 2004)

coexist with the monzonitic rocks, which is attributed to

the heterogeneity in the pre-collisional mantle source featured

by intraplate component and pre-subduction component and/or

variable involvement of continental materials (e.g., İlbeyli et

al. 2004; Köksal et al. 2004). This magmatism is accompanied

by Late Cretaceous volcanic rocks in some places in the com-

plex (e.g., Karahıdır volcanic rocks; Göncüoğlu et al. 1997b)

or followed by Lower Tertiary volcanism characterized by

alkaline basalts, trachytes and trachy-andesites (e.g., Gökten

& Floyd 1987; Çevikbaş & Öztunalı 1992; Alpaslan et al.

2004, 2006).

All these interpretations above commonly put forward

the presence of granitic (granite to granodiorite), monzonitic

and syenitic rocks in Central Anatolia, with different proposed

sources such as subduction-modified mantle, lithospheric

mantle, lower and middle crust, and several processes effec-

tive in their petrogenesis, including lithospheric delamination,

slab-break-off, lithospheric thinning, crustal contamination,

assimilation–fractional crystallization and mixing–mingling

mechanisms.

However, these explanations do not explain the prominent

crustal source, revealed mainly by isotopic data, of granitoids

and gabbros in the Hacımahmutuşağı area. Köksal et al. (2013)

studied the monzonitic rocks in the Satansarı area (Fig. 1)

and expressed their crustal source mostly based on zircon Hf

isotope data and multiple resorption zones of zircons. Köksal

et al. (2013) suggested an evolution scheme for these crustal

sourced-granitoids based on the Annen et al. (2006)’s petro-

logical model, which shows similar aspects to the MASH-type

models (e.g., Hildreth & Moorbath 1988; Petford & Gallagher

2001). In this model, a so called “hot zone” is formed in

the deep crust due to the heat transfer from the underplated

mafic magma

in the course of lithospheric thinning and

delamination (i.e., fig. 9 in Köksal et al. 2013). This “hot zone”

serves as a host for the water-rich magmas, which are pro-

duced by residual melts

from basalt crystallization

and partial

melts of pre-existing crustal rocks (e.g., Paleozoic–Mesozoic–

Cretaceous metamorphic and igneous rocks in the CACC)

within the lower crust (Annen et al. 2006; Köksal et al. 2013).

Episodic injections of these mixed melts by adiabatic ascent

and crystallization in the shallow crust (e.g., Köksal et al. 2013)

may give rise to the evolution of intrusives in the Hacımah-

mutuşağı area. Chemical and isotopic exchange probably

occur during these intermittent injections and genetic charac-

ter may be modified and lead to the formation of hybrid

magma (e.g., Petford & Gallagher 2001). Compositional dif-

ference of these intrusive rocks (i.e., granitic and gabbroic)

may point out a heterogeneity of the source of coeval rocks or

subsequent gabbro intrusion with less fertile restite compo-

nents (e.g., Meade et al. 2014). This kind of magma reservoir

within the crust can be prolonged for a million years (e.g.,

Deering et al. 2016). Jackson et al. (2018) propose that reac-

tive melt flow is a criticial mechanism in controlling magma

storage, accumulation and differentiation in these long-lived

mid- to lower-crustal mush reservoirs rather than fractional

crystallization in magma chambers. Coeval evolution of mafic

and felsic magmatic rocks is supposed to exist by differentia-

tion of reactive melt flow in such mush reservoirs (Jackson et

al. 2018). Partial melting of previously formed crustal compo-

nents triggered by mafic underplating magma is possibly

a phenomenon valid for the other intrusive rocks, displaying

hybrid nature with a significant crustal signature, in Central

Anatolia and also for the similar intrusive rocks in the world

(e.g., Annen et al. 2006; Kemp et al. 2007; Barnes et al. 2012;

Wang et al. 2018).

Conclusions

The findings of this study infer collisional/post-collisional

character for the granitoids in the Hacımahmutuşağı area,

where granite–granodiorite represents the first magmatic phase

with formation of leucogranite, more crustal contamination

and fractionation, following up. Both granitoids and gabbros

are conceivably formed from an enriched source with a note-

worthy crustal component. The coeval granitic and gabbroic

rocks observed in the Hacımahmutuşağı area are likely to have

been formed in shallow crust due to fractionation and episodic

magmatic injections from a hot zone previously formed within

the crust.

Acknowledgements: I gratefully thank Prof. Dr. Cemal

Göncüoğlu for help in all stages of this study. I thank to

Dr. Fatma Toksoy-Köksal for contributions in evaluation of

petrographical and geochemical data, and comparison with

the other gabbroic rocks in Central Anatolia. I am indebted to

Prof. Dr. Mehmet Arslan for his reviews of the earlier version

the manuscript. I acknowledge the Central Laboratory of Mid-

dle East Technical University for geochemical and radiogenic

isotope analyses. I would like to thank Serap Tekin Kaya and

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, 2019, 70, 3, 261–276

Sezen Yıldırım for geochemical analyses and Dr. Selin Süer

and Sultan Atalay for their assistance in isotope analyses.

Prof. Dr. Orhan Karslı, Prof. Dr. Sabah Yılmaz Şahin and

Prof. Dr. Semih Gürsu are acknowledged for their constructive

reviews and comments, which significantly helped to modify

the manuscript.

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