The Krumovgrad region is located within the Eastern Rhodopes Massif which comprises the eastern portion of a large metamorphic terrain. The massif underwent Late Cretaceous–Miocene extension leading to exhumation of the lower crust rocks, exposed in metamorphic core complexes, including the formation of the Kesebir-Kardamos metamorphic dome in the Krumovgrad area. This event was accompanied by low-angle detachment faulting, graben development, and the formation of sedimentary basins.
Basement rocks in the Krumovgrad area consist of Precambrian and Paleozoic metasediments, gneisses, and amphibolites of the Kessebir metamorphic core complex. The basement is unconformably overlain by Tertiary (Paleocene-Oligocene) conglomerates, sandstones, siltstones and limestones of the Krumovgrad Group. The basal Shavar Formation, the primary host to gold-silver mineralization within the Krumovgrad License area, consists of a chaotic accumulation of coarse to fine sedimentary breccia and conglomerates typically sourced from the adjacent basement, and regarded to have been deposited during rapid exhumation of the Kesebir-Kardamos metamorphic dome.
Felsic to intermediate volcanism began in the Late Eocene and progressed episodically until the Late Oligocene. Several lead-zinc (gold-silver) epithermal vein deposits are related to volcanoes formed during this period including Zvezdel and Madjarovo, which are situated 15 km west and 25 km northeast of Krumovgrad respectively. More recent Neogene-Quaternary sedimentary cover occurs throughout the region.
Gold and silver mineralization in the Krumovgrad Project area is predominantly hosted within the Shavar Formation proximal to the unconformable fault contact or detachment with the underlying basement rocks of the Kesebir-Kardamos metamorphic dome. Sedimentary rocks within the Shavar Formation typically form laterally discontinuous units ranging from coarse breccia to conglomerate to inter-bedded pebbly sandstone, siltstone and marl to marl-argillite and capping tectonic breccia with overlying marl and limestone. Upward variations in the stratigraphy of the Krumovgrad Group reflect progression from a high-energy environment, breccia-conglomerates and coarse sandstones through to the lower energy siltstones and limestones characteristic of increasing basin maturity.
The dominant structure at the Ada Tepe deposit is the detachment structure that separates the metamorphic rocks of the Kesebir-Kardamos dome from the overlying sedimentary rocks, and forms a 10° to 15° northeast dipping lower structural bounding surface to the deposit. The deposit is bound to the northwest and southeast by approximately NE-SW striking, steep dipping faults.
The Ada Tepe deposit is a high level epithermal gold-silver deposit, formed during the Early Oligocene within the East Rhodopes depression. It is characterized as a low-sulphidation epithermal gold silver deposit. These deposit types are common throughout the world and form in association with volcanic arcs along subduction zones on plate boundaries.
The gold and silver mineralization at Ada Tepe has been subdivided into two types, based on the mineralized zone geometry and style, as follows:
The initial stage Wall Zone mineralization is interpreted to be associated with early silica flooding, replacements and relatively low gold grades. However regions of the Wall Zone through which well-developed Upper Zone vein mineralization passes are typically thicker more intensely brecciated and contain epithermal vein and hydraulic breccia infill textures and associated high gold grades not present in regions where Upper Zone vein mineralization is absent. These thick strongly continuous regions of high grade Wall Zone mineralization are generally thin and diminish in grade away from and between regions of well-developed Upper Zone vein mineralization.
The textural style and grade of mineralization at Ada Tepe, which contain high grades in association with open-space fill textures, such as bladed silica replacement after carbonate (i.e. evidence of boiling), crustiform-colloform quartz-adularia-sulphide veins, hydrothermal breccias and also the presence of sinter material, suggests proximity to the paleosurface and a low-sulphidation nature of mineralization.
In 2014, ground gravity and magnetic surveys were carried out over the licence areas. The data was integrated with geological and geochemical data to define both near surface and covered target areas. Three holes totaling 602 meters were drilled on the Podrumche target. Anomalous levels of gold associated with silicified sedimentary rocks were encountered in two of the holes.
In 2015, approximately 100 line kilometers of Induced Polarization was surveyed and 15 holes totaling 3,394 meters were drilled in nine target areas. At the Kupel North target, located about two kilometers east of Ada Tepe, an 8 meter interval grading 12.8 g/t Au and 4.9 g/t silver was intersected at a depth of 273 meters. Three follow up diamond drill holes were completed at the Kupel North including drill hole KPDD012, located 170 meters south of KPDD009 which intersected 5.0 meters with an average grade of 17.35 g/t gold and 7.0 g/t silver (true width is estimated to be between 2-3 meters) and drill hole KPDD011, located 350 meters south of KPDD009, which intersected one meter with a grade of 14.79 g/t gold and 2.6 g/t silver. Interpretation is ongoing and further follow up drilling is planned for later in the year.
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Dundee Precious Metals Inc. is a Canadian based, international gold mining company engaged in the acquisition, exploration, development, mining and processing of precious metals.