Regional Geological Setting

Source: Sillitoe et al. (2020), Tzankova (2023), Bogdanov (1987).

Tectonic framework

The Rosen ore field lies in the East Srednogorie segment of the Carpathian-Balkan calc-alkaline volcano-plutonic arc. This arc formed during the Late Cretaceous as a result of subduction and extreme slab rollback along the closing Tethys margin. The mineralization at Rosen formed during an end-stage interval of extreme slab rollback and intra-arc rifting, which farther east gave rise to seafloor spreading in the Western Black Sea basin (Sillitoe et al. 2020).

The resulting submarine volcano-sedimentary rift basin is dominated by intermediate to mafic shoshonitic to ultrapotassic volcanism, with subsidiary gabbro to syenite intrusion.

The Burgas ore region — four ore fields

Copper ore deposits in SE Bulgaria are associated with four Late Cretaceous volcano-plutonic centers, grouped into four ore fields (Tzankova 2023, after Bogdanov 1987):

The Zidarovo and Bakadzhik fields do not carry the molybdenum and cobalt-bearing pyrite mineralization typical of Rosen.

Host rocks

The main pluton rock varieties are syenites and monzonites, which intruded into trachyandesite and andesite volcanic rocks. Numerous dykes of the same composition cut across these rocks. The ore veins are of hydrothermal hypabyssal origin (Bogdanov 1987; Popov et al. 1993).

The Rosen ore field

• Located ~20 km SE of Burgas.
• Covers the hills of Medni Rid and Rosen Bair (Alatepe).
• Ore-bearing faults are mainly developed in volcanic rocks; almost all ore veins are embedded in them, with ore accumulations generally in the deep parts of the faults (Bogdanov 1987; Popov et al. 1993).
• The ore veins formed deposits in a NW–SE occurrence (see deposits-and-mines.md).

Geochemical context

Geochemical maps of the Burgas ore region show the highest zinc anomalies repeating lead anomalies in the southern part. Copper anomalies have a smaller areal presence but a distribution almost identical to Pb and Zn, located around separate volcanic-plutonic centers. Nickel anomalies in the SE part are less frequent but more contrasting. Tin anomalies are spatially correlated with the ore fields (Boyadzhiev et al. 2012).

Key references for this section

• Bogdanov, B. (1987) — Copper Deposits in Bulgaria. Sofia, Tehnika, 388 pp. (in Bulgarian). [The foundational monograph.]
• Popov, P. et al. (1993) — Geology and metallogeny of the Burgas ore region. Annual of the University of Mining and Geology 1, 93 pp. (in Bulgarian).
• Vasileva-Stanisheva, G., Vasilev, L. (1981) — The Rosen ore field – a possible model for a central type volcanic structure and its metallogenic significance. Rudodobiv 36(2): 1–6 (in Bulgarian).
• Sillitoe et al. (2020) — see 07-references/.

Rosen Ore Field — IOCG Deposit Model

Source: Sillitoe et al. (2020), Economic Geology 115(3): 481–488 (the definitive deposit-model paper), supplemented by Tzankova (2023) and Bogdanov (1987).

Classification

The Rosen copper veins are recognized for the first time as an iron oxide-copper-gold (IOCG) district (Sillitoe et al. 2020). The mineralogical and compositional features are:

• comparable to well-known IOCG deposits worldwide, and
• geometrically similar to the vertically extensive IOCG veins in the Coastal Cordillera province of northern Chile.

A subsidiary granitophile signature accompanies the characteristic siderophile IOCG suite — a feature also recognized recently at the giant Olympic Dam deposit (South Australia) and elsewhere.

The Rosen pluton and vein geometry

• The E- to NE-striking veins define a NW-striking alignment along the western contact of the syenite-dominated Rosen pluton.
• The Rosen pluton is inferred to be part of a large ring dike.
• More than 40 veins; the most important were formerly mined to depths as great as 1,000 m.
• Although no exposed intrusion is definitively implicated in genesis, coexisting gabbro and syenite fluid sources may be hypothesized at depth in or beneath the coeval ring dike.

Paragenesis (mineralization sequence)

Two successive stages of endogenous mineral formation (Bogdanov 1987; Sillitoe et al. 2020):

1. Early pegmatoidal, calcic-potassic assemblage.
2. Predominant magnetite (including the mushketovite variety), chlorite, and carbonates — plus quartz, chalcopyrite, pyrite, and numerous other metallic minerals.

The detailed mineral associations of the single pulsating ore-forming process (Bogdanov 1987, p. 276):

1. apatite-feldspar
2. magnetite-scheelite
3. cobalt-bearing quartz-pyrite
4. hematite
5. quartz-molybdenite
6. chalcopyrite-pyrite
7. quartz-magnetite
8. quartz-specularite
9. ankerite-dolomite
10. calcite
11. quartz-chalcedony

Fluid conditions

Vein-type deposits formed by relatively high-temperature fluids: 320–365 °C. Only one pulsating ore-forming process has been recognized (Bogdanov 1987).

Geochemical signature

An unusual Fe-Cu-Au-Mo-Co-Ni-U-light rare earth element (LREE)-W-Bi-Zn-Pb association. The close correlation between Fe, Cu, U, and LREEs is evident even in the flotation tailings (Sillitoe et al. 2020).

REE note: Tzankova (2023) reported microinclusions with high P, La, Ce, Sr, Y, and U in malachite from the Propadnala Voda deposit, raising the question of possible REE mineralization in that area. Florencite-(Ce) (first find in Bulgaria; Kunov et al. 1992) and the APS minerals (svanbergite, woodhouseite, alunite) reflect the LREE-bearing nature of the system.

Age

• Vein molybdenite dated at 80.6 ± 0.4 Ma (Sillitoe et al. 2020) — Late Cretaceous (Campanian).
• This is similar to a U-Pb zircon age for monzosyenite from the Rosen pluton, confirming a coeval magmatic-hydrothermal relationship.

Mineral count

More than 60 hypogene and 20 supergene minerals have been discovered and described in the Rosen ore field (Bogdanov 1987; Tzankova 2023). See 04-minerals/mineral-list.md.

Oxidation & supergene zone

Minerals from the oxidation zone and secondary sulfide enrichment are distributed in the subsurface parts of the ore veins down to 15–20 m depth (Bogdanov 1987):

• hydrogoethite, hydrohematite
• malachite, azurite, chrysocolla
• native copper
• chalcocite, covellite
• rare minerals: ilsemannite, γ-kertschenite, vivianite, powellite

Key references for this section

• Sillitoe, R.H., Magaranov, G., Mladenov, V., Creaser, R.A. (2020) — Rosen, Bulgaria: a newly recognized iron oxide-copper-gold district. Economic Geology 115(3): 481–488. https://doi.org/10.5382/econgeo.4731
• Bogdanov, B. (1987) — Copper Deposits in Bulgaria. Sofia, Tehnika, 388 pp.
• Todorov, T. (1971) — Mineralization at depth in the copper-molybdenum deposits of Rossen. Spisanie na Bulgarskoto Geologichesko Druzhestvo 32(1): 11–20.
• Strashimirov, S., Kovachev, V. (1992) — Temperatures of ore formation of copper deposits from the Srednogorie zone based on fluid inclusion studies. Spisanie na Bulgarskoto Geologichesko Druzhestvo 53(2): 1–12 (in Bulgarian).

Deposits & Mines of the Rosen Ore Field

The five named deposits of the Rosen ore field, in NW–SE occurrence (Tzankova 2023, after Bogdanov 1987). Alternate names from mindat and the literature are reconciled here.

Mindat locality record

Mindat URL: https://www.mindat.org/loc-25109.html

The five deposits (NW → SE)

1. Propadnala Voda (a.k.a. Cherveno Zname / “Red Flag”)

• Bulgarian: Пропаднала вода (“Collapsed Water”); the mine Cherveno Zname = “Red Flag”.
• mindat lists Propadnala Woda mine and Cherveno zname mine as separate entries; Tzankova (2023) treats Propadnala Voda and Červeno Zname as one deposit. The literature sometimes equates them.
• Notable: native copper and pseudomalachite recorded here by mindat; Tzankova (2023) found the most variable impurity profile in malachite (absent tin, elevated Se and As), plus REE-bearing inclusions (P, La, Ce, Sr, Y, U) suggesting possible REE mineralization. Elevated radiation levels reported (Kunze & Pernicka 2020b).
• Photo caption on mindat: “Pseudomalachite — Propadnala Woda mine”.

2. Sarneshko Kladenche (Surneshko Kladenche)

• Bulgarian: Сърнешко кладенче (“Surneshko well” / deer well).
• mindat spells it “Surneshko Kladenche”.
• Malachite here carries the highest silver (up to 187.38 ppm) and high magnesium (368–612 ppm) among the studied deposits (Tzankova 2023). Records: apatite, calcite, muscovite, quartz, tenorite, pyrite.

3. Meden Rid (Bakarlak / Bakarlaka)

• The deposit underlying the ridge itself, beneath Mount Bakarlaka.
• mindat also lists “Medni Rid” as a child locality.
• Malachite here shows the highest zinc (563–2340 ppm) and lowest cobalt of the studied deposits (Tzankova 2023).
• This is the deposit tied to the geographic Medni Rid ridge and the Bakarlaka Thracian fortress.

4. Korucheshme (Kyumyurlaka / Stahanov)

• Bulgarian: Коручешме (Turkish-derived, “blind well”); also called Kyumyurlaka or Stahanov.
• mindat does not list it separately under loc-25109 (its list is not exhaustive), but Tzankova (2023) includes it as one of the five.
• Malachite here is depleted in almost all impurities (low Zn, Co, Mg, As, Ag, Se).

5. Rosen (at Atia)

• The main mine of the field, located at/near the village of Atia on the eastern foothills.
• mindat sub-locality: “Rosen mine, Atia”.
• This is the last copper mine in the district, closed in 1995 (Wikipedia).
• Malachite here carries the highest cobalt (250–484 ppm) and lowest zinc of the studied deposits (Tzankova 2023).
• Records on mindat: bornite, chalcocite, chalcopyrite, malachite, pyrite, calcite (30 cm scalenohedral crystals).

Other sub-localities listed by mindat

• Atia — village on the eastern foothills; site of the Rosen mine.
• Medni Rid — listed as a child locality (the ridge deposit above).

Naming caveat

The mindat mineral list notes it “does not claim to be a complete list.” Spellings vary across Bulgarian, Turkish-derived, and transliterated forms (e.g. Rossen/Rosen, Surneshko/Sarneshko, Červeno Zname/Cherveno zname, Propadnala Voda/Woda). Where sources disagree, the Bulgarian standard form is preferred and alternates noted.

See also

• rosen-ore-field-deposit-model.md — the IOCG model and paragenesis.
• ../04-minerals/mineral-list.md — which minerals come from which deposit.

See the pluton & veins on the 3D map