Summary:
The Çöpler district deposits (Çöpler, Greater Çakmaktepe, and Bayramdere) are best classified as epithermal, disseminated, and skarn deposits related to porphyry copper-gold systems. Mineralizing fluids, derived from the intrusions, were primarily controlled by structural fluid pathways and lithology, including traps controlled by lithological contacts, resulting in replacement, vein and stockwork mineralization.
Çöpler
Economic Çöpler mineralization occurs predominantly between elevations 1,590 m and 740 m and across a 3,000 m by 1,300 m wide surface area.
The Çöpler Deposit gold, silver, and copper mineralization is exposed in four adjacent open pits from east to west: Manganese Pit, Marble Pit, Main Pit, and West Pit. The mineralization is considered to be related to fluids associated with diorite intrusions at depth; mineralization is generally controlled by structural fluid pathways, intrusion contacts, and traps associated with lithological contacts. More specifically, there are three primary controls on mineralization: the hornfels-marble contact, the diorite geometry, and 2nd or 3rd order fault structures and their confluence.
Most of the Çöpler mineralization is controlled by the physical trap/seal that the hornfels formed for the diorite-derived fluids and associated with typical replacement-style processes (e.g.jasperoid).
Mineralization generally manifests as three closely related styles:
• Iron skarn and carbonate replacement mineralization.
• Intermediate sulfidation epithermal mineralization.
• Low-grade porphyry vein mineralization.
Manganese skarn mineralization is primarily observed in the Manganese Pit. The geometries of mineralization in the Manganese pit are typically consistent with those of the diorite intrusion; manganese skarns wrap around the contact and display internal porphyry-style mineralization.
Intermediate sulfidation epithermal mineralization is primarily observed in the Manganese Pit as clusters of bright pink, banded, colloform, rhodochrosite base metal sulfide veins and breccia lodes. Carbonate base metal veins contain base metal sulfides sphalerite±galena±chalcopyrite in a gangue of calcite, ferroan dolomite, and/or rhodochrosite and realgar.
In the Main Pit, the base metal carbonate veins are coarsely crystalline whereas veins in the Manganese Pit display brecciation, colloform banding, and locally quartz pseudomorphs of bladed calcite. The change in vein style suggests the Manganese Pit represents a higher level position with respect to the mineralising system.
Epithermal veins and mineralized faults are mostly thin and hosted in the hornfels within the Main Pit.
Greater Çakmaktepe
Greater Çakmaktepe mineralization occurs approximately between elevations 1,020 m and 1,615 m, is approximately 2,500 m long (northwest–southeast) by 950 m wide (northeast–southwest), and ranges in thickness from 10 m to 200 m.
The Greater Çakmaktepe (Çakmaktepe and Çakmaktepe Ext) deposit is a structurally controlled gold– silver–copper deposit, displaying typical replacement mineralization styles. Mineralization is primarily associated with jasperoid and listwanite.
As with the Çöpler deposit, Çakmaktepe is thought to be the result of intrusive activity that generated suitable conditions for mineralization of ophiolite, limestone, and hornfels lithologies. The mineralization is controlled by a complex system of structural fluid pathways and traps controlled by lithological contacts, in typical replacement-style processes, rather than being constrained by relatively discrete fault or shear zones characteristic of epithermal-style mineralization.
The mineralization at Çakmaktepe Ext is also considered to be related to fluids associated with diorite intrusions at depth, much like those observed at the Çöpler and Çakmaktepe deposits. However, diorite dykes are less common at Çakmaktepe Ext, unlike the adjacent Çakmaktepe deposit and nearby Çöpler deposit where diorite is a dominant lithology.
Mineralization is strongly structurally controlled. Two steep faults are intruded by diorites and played a role as conduits for mineralization at Greater Çakmaktepe.
Relatively shallowly dipping thrust-related mineralization is characterised at Çakmaktepe East, Çakmaktepe South-East, Çakmaktepe Central, and Çakmaktepe North. This is interpreted as a ramp-flat stacked thrust system that has resulted in rollover/stack geometries. Key to each structurally associated style of mineralization is the juxtaposition of ophiolites against limestone and hornfels. Contacts between ophiolite and limestone, limestone and hornfels, and all lithologies in contact with intrusive diorite sills and dykes are generally mineralized. The listwanite horizon is the most favourable host rock for gold mineralization. Diorite intrusions show evidence of hydrothermal activity that either takes the form of massive iron-dominated replacement (magnetite, specular hematite, or pyrite) or sheeted crystalline quartz vein bearing jasperoid closer to diorite contacts.
Other mineralized zones within the Çakmaktepe deposit are referred to as ‘contact’ styles of mineralization where iron, sulfur, gold, copper, and silver have been emplaced along thrust surfaces where ophiolite is next to limestone and metasediment. Epithermal veining and replacement alteration and textures are prevalent. Skarn and metasomatic mineralization occur in contact with intrusive diorite dykes, sills, and stocks.
Oxide mineralization at Çakmaktepe is predominantly characterised by silica–iron–carbonate rich jasperoid, less-siliceous iron-rich gossan, and epithermal veined and brecciated limestone. The mineralization at Çakmaktepe Ext is related to crystalline and chalcedonic quartz veins within the brecciated and silicified listwanite and dolomite zones. The mineralization is predominantly in the form of oxide, with sulfide mineralization confined to limited pyrite-rich jasperoid zones. Clay/gossan in jasperoid or limestone karstic boundaries also contain highgrade gold across Çakmaktepe Ext.
Gold grades increase at dolomite/listwanite contacts and within silica-rich listwanite that acts as horizontal traps for higher-grade gold-bearing mineralization. Increases in gold grade can be seen along the lithological contacts. Elevated grades can exist within either contact lithology. Several drill holes show a very rapid downhole change in gold grade from mineralized to unmineralized material, indicating that mineralization is tightly constrained instead of disseminated across the deposit.
Bayramdere
Bayramdere mineralization occurs approximately between elevations 1,290 m and 1,370 m, is approximately 370 m long (east–west) by 50 m to 110 m wide (north–south), and ranges in thickness from 5 m to 20 m.
The Bayramdere mineralization is localized within three stacked, shallow-dipping zones that formed at the contact of limestone and ophiolite, with mineralization having replaced limestone along the contacts. The limestone / ophiolite contacts are low-angle thrusts, typified by limestone wedges within a dominantly ophiolite stratigraphy. Mineralization occurs within shallow iron-rich gossan horizons.