Evolution of the Cretaceous Magmatism from the Srednogorie Zone to the Rhodopes, Bulgaria

Workshop- 4th-8th September 2007, Bor, Serbia

Evolution of the Cretaceous magmatism from the Srednogorie zone to the Rhodopes: Constraints from isotope dating and tracing

Irena Peytcheva1,2*, Albrecht von Quadt1, Kalin Naydenov3,4, Stoyan Sarov4, Emilia Voinova4, Dimo Dimov3

1Institute of Isotope Geology and Mineral Resources, ETH-Zurich, Switzerland 2CLMC, Bulgarian Academy of Sciences, Sofia, Bulgaria 3Faculty of geology and geography, Sofia University, Bulgaria 4 “Geology and Geophysics” AD, Sofia; * now at Section des Sciences de la Terre, Université de Genève, Switzerland Regional position

Most major Cu-Mo-Au ore deposits in the Carpathian – Balkan orogen are related to a 1500 km long belt of Upper Cretaceous magmatism extending from Romania through Serbia to Bulgaria, with a continuation southeast of the Black Sea into Turkey, Caucasus and the Himalayas known as “Tethyan Eurasian Metallogenic Belt” (Jankovic, 1977)

⇒ related to the northward subduction of the Tethys ocean beneath the European continent. The European part – ABTSB (Popov et al., 2000) or Banatite MMB (Berza et al., 1997) Regional position

The Srednogorie and the Rhodopes are the main ore-bearing Alpine tectonic zones in Bulgaria.

Magmatism: Uper Cretaceous (Srednog.) mainly Pg in the Rhodopes.

Change of the deposit style from Cu-porphyry (Au-Mo) to mainly Pb-Zn epithermal Au.

Isotope geochrono- logical and geochemical studies in the border area from ⇒ In Eastern Serbia the Late Cretaceous magmatism is C Srednogorie to developed along two belts: the Timok Magmatic Complex in the E Rila-W Rhodopes and Ridanj-Krepoljin Zone in the W (Karamata et al., 1997); and further to South Geological background

(Ricou et al., 1998)

I phase – compression (110-90 Ma?) – southward trusting, High P (T) metam. II – extensional – Metametamorphic Core Complexes; syn- and post met. granitoids Maritsa fault; Srednogorie zone Geological map with sample localities

Sofia

a k

s Metamorphic complexes

Vakarel of Balkanide type (Pz12 -Pz ) Variscan intrusions Panagyurishte of the Central Srednogorie Ihtiman Rhodopean type metamorphic . complexes (Arda and Asenitsa Units) r Plana I ir Y V SZ i at Pz and Early Mz (T-J) rocks M Elshitsa constituting pre-K2 basement

r Vurshilo Elshitsa a Gutsal k L K2 volcanic and volcanoclastic

s u 2 3

I T d rocks (K22 - K ) r. op a Maritsa o lni Y tsa a 46 164 r. n K22 sediments (K - K2 ) a

r .

K2 intrusions of Srednogorie type 155 Pazardjik 159 . K2 intrusions of Rhodopean type 156 r a k s in Pg2 granitoids of the Rila- p 228 e WR batholith h c T Cap. Dimitrievo 4 2 Rila-West Rhodopes 230 Pg23 - Pg - sediments

Velingrad Ng - Q - sediments Yakoruda Strike-slip faults Belitsa Normal and Detachment faults M e s V3P ta Faults r . Babek-Grashevo dislocation zone IYSZ Iskar-Yavoritsa Shear Zone

Sample locality Timing of magmatism and metamorphism in the Western Rhodopes and Rila Mountain

Characteristic features of magmatism (subduction or collision/postcollision related?)

Problems Time-tectonic succession

• conventional ID-TIMS U-Pb single Timing zircon/monazite/xenotime method • in situ LA-ICP-MS U-Pb dating

Zircon tracing

SEM-CL images Hf-isotope data in situ (LA) ICP-MS analyses for dated zircons Methods Whole rock Sr, Nd, geochemical tracing

Field and structural data Discussions before sampling

Drawing of Sarov et al. AvQ 156

AvQ 155

Arda Unit

Sample AvQ 155: Metadiorite Sample AvQ 156: Metagranite

• „layering“ of amphibolite and gneiss • „gneisses“ are strongly plastic deformed • „gneisses“crosscutt theamphibolite Metadiorite AvQ-155 U-Pb zircon dating Metagranite AvQ-156

0.037 0.016 100 Amphibolite - Rila AvQ-155 Gneiss Rila 230 zircons and monazites 0.035 80 AvQ-156 314 Ma 0.012 156/4

220

U 60 U

0.033 238 zircon 210 0.008 Pb/ 156/1Mz 156/2Mz 156/3 lower intercept age: Pb/ 40 41.3 ± 4.1 Ma

206 156/7Mz 200 156/5 0.031 monazite Upper intercept age 0.004 207 235 253 ± 12 Ma 20 Pb/ U age: 41.02 ± 0.74 Ma 1900.205 0.215 0.225 0.235 0.245 0.255 0.265 207 0 0.029 0.000 0.00 0.02 0.04 0.06 0.08 0.10 Pb/ 235 U 207Pb/235U Where are we? Still in Arda Unit?

AvQ-229

AvQ-228 Metagranodiorite AvQ-229

0.0114 0.0120 73 AvQ229 - метагранодиорит AvQ229 - metagranodiorite 76 абрадирани и неабрадирани циркони concordant zircons 0.0118 AvQ229/2 72 0.0112 0.0116 74

U 71 0.0114 U 238 238 0.0110

72 Pb/ Pb/ 0.0112 70 206 206 AvQ229/4 AvQ229/7 0.0110 AvQ229/1 AvQ229/6 0.0108 70 69 AvQ229/3 AvQ229/6 Concordia Age = 70.770 ±0.087 Ma 0.0108 (2σ, decay-const. errs included) MSWD (of concordance) = 7.3 68 0.0106 68 0.0106 0.068 0.070 0.072 0.074 0.076 0.078 0.080 0.069 0.070 0.071 0.072 0.073 0.074 0.075 207Pb/235U 207Pb/235U Metagranite AvQ-228

data-point error ellipses are 2σ 50

0.0075 AvQ228 - metagranite zircons and monazites 46 Av Q228/6

42 AvQ228/2 0.0065 U Av Q228/5 38 238 Av Q228/1 abraded zircons

Pb/ 0.0055 34 206

30 0.0045 228/4Mz

26 228/3Mz

0.0035 0.020 0.024 0.028 0.032 0.036 0.040 0.044 0.048 0.052 207Pb/235U Sample AvQ 159: Rila Granodiorite (Unit 1) Belmeken body Sample V3P – Grancharitsa body U-Pb dating Belmeken and Gruntcharitsa bodies (unit 1) – AvQ 159 – V3P 0.0112

Rila-West Rhodopes batholith 72 AvQ 159 and V3P (unit 1) 0.0108

AvQ 159: concordia age 70 69.26 ± 0.26 Ma

U V3P: concordia age 68 0.0104 66.79 ± 0.27 Ma 238

Pb/ 66 206 0.0100 64 206 Pb/ 238 U mean age 0.062 0.064 0.066 0.068 0.070 0.072 0.074all points 207 68.5 ± 1.5 Ma 62 0.0096

Pb/ 235 U Sample AvQ 164: Rila Granite (Unit 2), S of Dolna Banya Highly milonitic Milonitic Rila granite

AvQ 164 0.008 Rila granite 50 Mylonite zone south of Dolna Banja village 45 0.007

40 U 0.006 238 zircon analyses: 35

Pb/ inherited components -one grain concordant 206 0.005 at 37.47 Ma

0.004 25 monazites: overconcordant different 207Pb/235U lead loss - deformation (?)

0.003 0.02 0.03 0.04 0.05 207Pb/235U Conclusion 1

~39 (24?) • Upper Cretaceous (meta) magmatic rocks in the Rila- WRhodopes Batholith and ~250 ~69 in the “high-metamorphic ~42 (28) 70 Arda Unit • Real protoliths of Arda 39 (24) ~39 Unit – Pz-T • All intruded by Late Alpine granitoid rocks (syn- metamorphic ~ 42 Ma and postmetamorphic ~ 39 Ma) ~68 Conclusion 2

• Perspectives with meta- morphosed K2 intermediate rocks? ε - Nd values and 0.706 increasing 0.705 – Sr Tracing: (Elatsite) 0.705 decreasing -10 -8 -6 -4 -2

0 2 4 6 inital

0.709 North ‐ ‐ 0.708 0.706

(Vitosha); ratios

(CRD) to

from

0.704 (Rila)

Panagyurishte

87 86 Sr/ Sr initial 0.703 0.704 0.705 0.706 0.708 0.712 0.716 0.720 0.724 Assarel Chelopech Elatsite Arda unit Arda Rila granite Vurshilo basement Variscan Vitosha Dimitrievo Capitan Elshitsa Vetren-Velichkovo North 87 at: intercept Sr/ 86 Sr: 0.70499 Sr: South -10 -8 -6 -4 -2 0 2 4 6 South Variscan intrusions Variscan Vitosha Dimitrievo Capitan Vruh Vlaykov Elshitsa Vurshilo Velichkovo Assarel Medet Chelopech Elatsite CRD unit Arda granite Rila Conclusion 3 ¾ All isotope data show higher input of astenospheric material in the Panagyurishte district from North to South; ¾ In the Rhodopes an assimilation of (mixing with) continental crust material play an important role for the magma source.

North South After 15 15 Richards, 2005

10 10

5 5 values

Hf 0 0

-5 -5 Elatsite

initial Chelopech Assarel -10 Medet -10 Vetren Elshitsa Cap. Dimitrievo Vitosha Arda unit CRD granitoids 70 Ma granitoids 40 Ma Nu-1 ICPMS-MC - Eximer Laser 193 nm at IGMR ETH Zurich

videocamera

Microscope ICPMS-MC videocamera

Multi-collector system

November/December 2006 Von Quadt, IGMR – ETH Zurich, [email protected] 20 TiO2 1000

0 AvQ155 100 AvQ156 10 90 AvQ159 20 100 Unit I 80 Unit II Unit I 30 Unit III Unit II 70 Unit III 40 new data 60 MORB 50 OIT 10 50

60 40 IAT 70 30 sample / chondrite 1 80 OIA Bon 20

90 10 Rb/30 100 CAB 0 0 102030405060708090100P O * 10 0.1 MnO * 10 0 2 5 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 100 1000 10 90 Unit I 20 Unit II WPG 80 Unit IIIo 30 new data 70 Unit I Unit II 40 syn-COLG 100 Unit III 60 new data 50 50

60 VAG + syn-COLG 40

70 late - post-COLG Nb (ppm) 30 VAG 10 80 20 ORG 90 WPG 10

100 0 Hf 0 102030405060708090100Ta * 1 1 10 100 1000 Y (ppm) All data plot define island arc and calc-alkaline signatures