Tectonic position of the sandstone Cenozoic Uranium Deposit of Bulgaria

Size: px

Start display at page:

Download "Tectonic position of the sandstone Cenozoic Uranium Deposit of Bulgaria"

Gilbert Newman
6 years ago
Views:

Tectonic position of the sandstone Cenozoic Uranium Deposit of Bulgaria Radoslav Nakov Geological Institute, Bulgarian Academy of Sciences Pirin Mountain

1 Tectonic position of the sandstone Cenozoic Uranium Deposit of Bulgaria Radoslav Nakov Geological Institute, Bulgarian Academy of Sciences Pirin Mountain view from Eleshnitsa Mine 2915 m Technical meeting on Uranium Deposits associated with sedimentary environments 10/5/ Vienna, September 29 October 1, 2015

2 Objectives: 1. Brief overview of the tectonic position of Bulgaria in the Balkan-Eastern Mediterranean tectonic system 2. Tectonic position and some structural features of the Cenozoic sandstone uranium deposits on Bulgarian territory 10/5/2015 2

3 Balkan - Eastern Mediterranean Tectonic Belts resulting from collision in Alpine time (from ~ 250m.y. to present) Alps Pannonian Basin Moesian Platform Balkanides Black Sea Aegean Sea Eastern Mediterranean 10/5/2015 3

metamorphic rocks with ages starting from over 540 m.y. to present.

4 Geology and tectonic units of Bulgaria Moesian Platform Balkan Fold-thrust Belt The territory of Bulgaria ( km 2 ) encloses various sedimentary, magmatic and metamorphic rocks with ages starting from over 540 m.y. to present. They witness for the presence of extinct volcanic arcs, closed marine basins and exhumed terrains from the Earth s depth. 10/5/2015 4

5 Cenozoic Uranium Sandstone Deposits in Bulgaria all hosted in grabens. Therefore, understanding Cenozoic extensional tectonics is very important Romania Serbia Moesian plain Black Sea Kosovo Balkan Range FYR Macedonia Rhodopes Mtn Turkey Greece 10/5/2015 5

Bulgaria and the Cenozoic East Mediterranean Tectonics In Cenozoic time three extensional domains developed in the Eastern Mediterranean: the Pannonian Basin, the Tyrrhenian Sea and the Aegean Sea.

6 Bulgaria and the Cenozoic East Mediterranean Tectonics In Cenozoic time three extensional domains developed in the Eastern Mediterranean: the Pannonian Basin, the Tyrrhenian Sea and the Aegean Sea. Most of the territory of Bulgaria belongs to the northern part of the Aegean extensional domain, defined as South Balkan Extensional Region/System. Extension within this region began in Paleogene time during thefinal closure of the Vardar Ocean and subsequent post-collisional deformation. Subsequently the region was directly part of the more regional Aegean extensional realm before the formation of the North Anatolian fault zone in late Miocene/Pliocene time. 10/5/2015 6

Cenozoic extensional basins in the South Balkan Extensional Region. The Cenozoic history and evolution of the SBES is largely recorded in the abundant sedimentary basins developed in the region.

7 Cenozoic extensional basins in the South Balkan Extensional Region. The Cenozoic history and evolution of the SBES is largely recorded in the abundant sedimentary basins developed in the region. SERBIA B a l k a n R a n g e Since Late Eocene extension is the main form of deformation. The extension is spread between the Aegean subduction system to the south and the Moesian Platform (the southern edge of the Balkan Range) to the north. Extension has created numerous extensional continental basins (grabens) to the south of the Balkan Range. They occurred in several well distinguished consecutive stages of extension. 10/5/2015 7

Earlier Paleogene extension In latest Cretaceous and earliest Cenozoic time the region of the SBES lay on the European plate separated from continental areas to the west and south by the Vardar Ocean.

This suggests thatat least the earliest part of the Paleogene extension occurred within an overall compressional environment during final closure along thevardar suture zone.

8 Earlier Paleogene extension In latest Cretaceous and earliest Cenozoic time the region of the SBES lay on the European plate separated from continental areas to the west and south by the Vardar Ocean. During at least the earliest part of this Paleogene extension, the Balkanthrust belt was active in northern Bulgaria. This suggests thatat least the earliest part of the Paleogene extension occurred within an overall compressional environment during final closure along thevardar suture zone. In the western Rhodope Mountains a WSW-dipping extensional detachment fault along the eastern side of the Mesta half-graben is established, which marks the beginning of the Aegean extension (Upper (Middle?) Eocene)in age. The Paleogene extension lies within zone of magmatic activity that extends NW-SE. 10/5/2015 8

9 Short period of local compression Late Oligocene Early Miocene There was a short-lived and welldatedperiod of shortening during latest Oligocene/Early Miocene time. This shortening event is interpreted to be related to shortlived collision of the Kruja continental fragmentat the north Hellenic trench in Albania causing a temporarychange in the stress regime east of the trench before normal subduction rollback was reestablished.there was also a period of shortening that occurs within the Thrace basin in northwest Turkey, but its age is not well documented. 10/5/2015 9

10 Neogene stage of extension Sandanski Graben By earlymiddle Miocene time (~15 Ma, Badanian) extension on the westdipping StrymonValley detachment fault began in northern Greece and SW Bulgaria. The Strymon Valley detachment parallels the Mesta detachment and has a geometry, kinematics and timing that couldbe interpreted to be the temporal westward stepping of the Mesta detachment, a pattern of migration of faulting well known in regionally extensional terrains 10/5/

11 Early Late Miocene extension change from E-W to N S extension The eastern part of the South Balkan extensional region in Bulgaria is characterized by N S extension that began by Late Miocene time. However, Middle Miocenestrata that could be related to xtensional faulting are rare in this region, but by Late Miocene time (Late Sarmatian-Early Meotian (11 8 Ma) strata related to E Wtrending normal faults are present along the north and southsides of the Upper Thracian basin(utb), the Sub- Balkan Graben System (SBGS) and along the Sofia basin (SG) to the west. Sedimentation continues in Sandanski Graben (SG). 10/5/

Latest Miocene Pliocene - Pleistocene N S extensionalfaults and related strata become more abundant in latest Miocene to early Pliocenetime (to 3.

12 Latest Miocene Pliocene - Pleistocene N S extensionalfaults and related strata become more abundant in latest Miocene to early Pliocenetime (to 3.5 Ma) This pattern of faulting and fault migration continued into the Pleistocenewhen all of central and southern Bulgaria and characterizedby N S extension. The Strymon Valley detachment continued activity into until perhaps Pliocene time ~3.5 Ma). In Latest Miocene to early Pliocene time the North Anatolian fault zone became well developed in the northern Aegean Sea and N S extension was active in the UpperThrace basin (UTB). 10/5/

Presently: The Aegean Extensional System is interesting due to the complexity of its structure and being still active. Extension (The velocities and tectonic units are adopted from McClusky et al.

13 Presently: The Aegean Extensional System is interesting due to the complexity of its structure and being still active. Extension (The velocities and tectonic units are adopted from McClusky et al., 2000) The ongoing tectonics is driven by complex forces,where the back-arc extension above the northern deepening Hellenic Subduction Zone, trench roll-backand the protrusion of Anatolia along the North Anatolian Fault System are dominating. 10/5/

14 10/5/

mountains and topography in Bulgaria and the Balkans Rila

15 Active faulting and relief building the neotectonic and active faults are responsible for the origin of the highest mountains and topography in Bulgaria and the Balkans Rila Mountain 2925 m Fault Pirin Mountain The active Predela Fault 10/5/

16 Deposits from SW Bulgaria some examples 10/5/

17 Eleshnitsa Deposit located just under Eleshnitsa Town 10/5/

18 Mesta half-graben Ore bodies Eleshnitsa deposit: The deposit is hosted in the Mesta Eocene-Oligocene half-graben, formed along the Mesta Detachment. The Detachment is exposed at different structural levels. The mineralization is formed in the northern part of the graben, probably related to fine lacustrine sediments. Here, the detachment is exposed at higher structural level, suggesting that the sedimentary section is better preserved. 10/5/

19 Sedimentary infilling of the Mesta Graben Various sediments: from very coarse conglomerates to very fine shales, interfingering with tuffs and volcanics 10/5/

20 Remediation of the mining site The former tailing pond Old shafts 10/5/

related the strongest earthquake in Europe for the 20th century

21 The Simitli Deposit: hosted in Middle-Upper Miocene Simitli Graben Bordered to the south by the active Kroupnik fault, to which is related the strongest earthquake in Europe for the 20th century magnitude ~7 April 04, 1904 N SW -NE Kroupnik Fault Simitli Graben S 10/5/

22 Melnik and Zlatolist deposits hosted in Middle Upper Miocene rocks of Sandanski Graben forming erosional landforms with significant esthetic value Melnik rock pinnacles 10/5/

23 Deposits in the Upper Thracian Basin (Upper Thracian Complex Graben) Some examples 10/5/

24 Momino deposit strongly faulted; horizontal beds and ore bodies adopted from unpublished data of the National geofund 10/5/

25 Maritsa, Navusen and Troyan deposits hosted in Middle-Upper Paleogene rocks. adopted from unpublished data of the National geofund 10/5/

26 Debur deposit usual landscape for the Upper Thracian Basin 10/5/

27 Ahmatovo Formation (latest Miocene (?)- Pliocene (?) Pleistocene host rock for the Neogene deposits in the Upper Thracian Basin. Outcrop in a quarry. 10/5/

28 Conclusions: The territory of Bulgaria has a diverse geology and significant Cenozoic tectonic activity. Cenozoic extension is responsible for the forming of extensional basins and relief building. The basins have accumulated the uranium leached from the uplifted and fast eroding surrounding blocks, thus tectonics was a very important factor for the forming of the deposits. Understanding Cenozoic tectonics is an important tool in exploration of mineral deposits in Bulgaria and on the Balkans. P.S. Bulgaria has numerous diverse uranium deposits and opportunities for new discoveries. Unfortunately, during the last 23 years they are not subject of research, exploration and mining due to the total ban on any activities related to exploration and production of uranium. The numerous geological data acquired in the past remain almost unknown for the broad geological society. 10/5/

29 Thank you for your attention! Stara Planina Mt. (Balkan Range) View from the south on part of Sofia Graben with the first uranium deposit of Bulgaria - Buhovo Sofia Graben 10/5/

Aegeis deep structure & slab rollback in the Mediterranean

Aegeis deep structure & slab rollback in the Mediterranean A paper for the Naxos field trip with Prof. Dr. Janos Urai, Summer Term 2014 Caspar Sinn, Martin Schlemmer August 31st, 2014 RWTH Aachen University,