Mining Destinations: Panagyurishte’s Hidden Treasures

Panagyurishte has a picturesque location in the Sredna Gora mountains, near the mineral spas of Banya. As well as a thriving tourist industry, the region is known for its mining. The nearby copper processing facility at Asarel Medet extracts around 13 million tons of copper concentrate every year to feed the smelter at Pirdop. Various sites have been active since the 4th century BC, when exquisite Thracian ceremonial gold pieces were produced here.

The Thracian gold hoard was likely extracted and processed locally, with over 6.1kg being used to make the 8 famous pieces that make up the Panagyurishte treasures, found in the 1940s by local clay miners who were digging for a nearby tile factory.

The formation of the gold and copper deposits across the Panyagyurishte Metallurgical Belt is thought to be related to an upper cretaceous island arc system. Elatsite, Medet and Assarel are the three most notable deposits, thought to be related to regional scale monzodioritic and granodioritic intrusions. In the early phases of formation, rich NaCl fluids (430-530 C at 40-62% salinity) carried high concentrations of gold and platinum group elements from the depths to form breccia and vein systems in the Palaeozoic greenschist and granodiorite country rock. (Kehayov & Bogdanov, 2003)

Four major mineralisation events have been identified within the Elatsite deposit:

  • Magnetite-bornite-chalcopyrite (with merenskyite, moncheite, palladoarsenide PGEs)
  • quartz-chalcopyrite-pyrite
  • quartz-pyrite
  • quartz-galena-sphalerite.

The series shows an evolution of fluids along the Goldschmidt classification series from mid-depth to shallow and supports an island arc and crustal source for major metallic enrichments, with a semi-unrelated source for siderophile PGEs, which are thought to originate from re-melting of an earlier mantle melt, rather than the contemporaneous magmatic source of the porphyry systems (Augé, 2005).

Elatsite contains an academic 185 million tons with 0.4 wt-% Cu, 0.3 g/t Au, 0.68-1.9 g/t Ag, 0.07 g/t Pd and 0.02 g/t Pt. (Tarkian, 2003).

Just south of the Assarel and Chelopech mines, around 15km of propylitic and argillic (clay) alteration surrounds the historic Radka mine, which produced some 6.4 million tonnes at 1.06% Cu and 3 g/t Au. Radka sits inside the Elshitsa volcano-intrusive complex, formed by of the Elshitsa stratovolcano, within this island arc series.

Observed Au-Cu mineralisation here post-dates the stratovolcano, in-field relationships show mineralisation pervading faults within the Elshitsa pluton and tuff. This suggests a larger, long-lived source of fluids continued to circulate around the Panagyurishte zone long after the initial intrusion and magmatic event and throughout the Tethyan Belt’s formation in the Alpine-Himalayan orogeny.

In 2017, Mundoro were awarded government tenders for exploration around the mine. Their licence covers the entire area of alteration surrounding the Red Hill and Radka targets. Mundoro’s adjoining ‘Assarel’ exploration area is operated in JV with Freeport and together they hold a commanding position in the prolific region.

Mundoro’s Red Hill target seem to be part of a large stockwork system, proximal to a central sulphide (porphyry style) enrichment. It contains small vuggy silica-enargite bodies and quartz-breccias. The breccias host massive silica-barite replacement lenses up to 50 m x 15 m in size with reported grades up to 2.5 g/t Au and 59 g/t Ag from rock samples.

The Radka deposit hosts 2 major types of mineralisation, with porphyry sulphide enrichment overprinting the brecciation and stockwork systems, like those seen nearby at Red Hill.

We say this a lot in our blogs and writing, but if these proven Cu-Au deposits were in Canada or Australia, with paved road access, power, water and government support, they’d have been fought over for years and probably developed already. Despite years of exceptional academic and government work across the Bulgarian Tethyan Belt, the area is only now grabbing the interest of international investors and companies. Mundoro have an ‘early mover advantage’ from our international perspective (not to belittle the great work done by regional groups over the years!) and a skilled local team working between their Red hill, Radka, Zvezda and Byalo projects in Bulgaria.

We’ll have more on Mundoro’s other projects in the nearby Bulgarian Rhodopi mountains, and in Serbia, later in the week!