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Madjarovo |
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Bulgaria |
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Au Pb Zn Cu Ag
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Super Porphyry Cu and Au
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The Madjarovo low sulphidation epithermal gold and base metal sulphide vein complex is located in south-eastern Bulgaria, some 200 km SE of Sofia.
The mineralisation at Madjarovo is within Oligocene (32 Ma) volcanics rocks of the Madjarovo shield volcano (basaltic to andesitic shoshonitic to high-K calc-alkaline rocks, dominantly latites, with numerous monzonitic stocks and other intrusives) and in the underlying high grade (amphibolite facies) Proterozoic and Palaeozoic metamorphics of the Rhodope Massif. The Rhodope Massif is part of the larger 500 km long and 130 to 180 km wide Macedonian-Rhodope-North Aegean magmatic belt that extends from western Turkey through Bulgaria into Serbia. Madjarovo occurs in a district characterised by abundant epithermal base (Pb-Zn-Cu) and precious (Au, Ag) metal deposits and sub-economic porphyry Cu-Mo mineralisation.
The central section of the Madjarovo volcano is extensively altered with several alteration styles and abundant veins with low sulphidation (adularia-sericite) epithermal mineralisation, defining the Madjarovo ore district. Alteration styles include advanced argillic (quartz-alunite-pyrophyllite-diaspore), pervasive quartz-sericite-pyrite and zones of silicification. These are surrounded by 'regional' propylitic alteration. Subjacent potassic alteration assemblages suggest a transition from an epithermal to porphyry setting, while skarns are spatially associated with monzonitic stocks in the same district.
The ore veins are distributed over an area of some 6x4 km and are hosted within a 700 to 800 m thick volcanic sequence and basement metamorphics (as described above), spatially associated with trachytic dykes. Mineralised bodies range from narrow brecciated zones a few hundred metres long containing quartz veins, to massive, brecciated veins up to 25 m wide and more than 3 km long occuring along significant splayed faults with displacement of as much as 200 m. The ore consists of variable amounts of sulphides (galena-sphalerite-chalcopyrite), Se-Bi-Pb-Ag-Sb sulphosalts and native gold and silver. The mineralised system exhibits a vertical zonation from base metals at depth, with precious metals at shallower levels.
Over the 45 years to 2002 some 10 Mt of base metal ore has been taken from the Madjarovo deposits, with 6.5 Mt remaining in reserves. The reserves were not being mined in 2002.
The gold resource in the upper part of the vein system contains 2 Mt @ 3.9 g/t Au, although this was regarded as sub-economic in 2002.
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2002.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Marchev P, Downes H, Thirlwall M F, Moritz R 2002 - Small-scale variations of 87Sr/86Sr isotope composition of barite in the Madjarovo low-sulphidation epithermal system, SE Bulgaria: implications for sources of Sr, fluid fluxes and pathways of the ore-forming fluids: in Mineralium Deposita v37 pp 669-677
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Rice C M, McCoyd R J, Boyce A J and Marchev P, 2007 - Stable isotope study of the mineralization and alteration in the Madjarovo Pb-Zn district, south-east Bulgaria : in Mineralium Deposita v42 pp 691-713
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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