The Surdulica Molybdenum Porphyry System of Southeast Serbia
The Surdulica molybdenum porphyry system of SE Serbia lies within the SE portion of the Alpine-Balkan-Carpathian-Dinaride (ABCD) orogenic belt of the Western Tethyan Belt and is the largest, potentially open pittable, molybdenum porphyry system within Europe. Systematic resource definition drilling by a previous operator during 2007/2008 has defined an Indicated Mineral Resource of 22Mt @ 0.05% Mo and an Inferred Mineral Resource 125Mt @ 0.05% (0.03% Mo cut-off grade). Exploration has outlined a large lozenge-shaped porphyry system extending across an area of 4.3km x 2.5km with a current vertically defined extent in excess of 600m. Primary molybdenum mineralization is associated with multiple phases of stockwork and sheeted quartz-molybdenite veining. Hydraulic fracturing and veining has occurred in rigid silicified zones within the dacite and metamorphic basement rocks on the outer carapace of irregular-shaped intrusive dacite stocks, in association with intense potassic and phyllic alteration.
It has been proposed that the ascent and emplacement of the Surdulica porphyry system was dominantly a fault- and fracture-controlled phenomenon associated with a granitoid-related, structurally complex, metallogenic event. This event was related with Oligocene to early Miocene, N-NNE directed oblique convergence, high-K calc-alkaline continental arc granitoid magmatism, transpressive stress partitioning into arc-parallel translithospheric structures with predominantly dextral strike-slip movement and other related structures associated with the closure of the Vardar Ocean.
Granitoid and porphyry emplacement were localized within a N-S trending flexure in the magmatic arc, coincident with a broad intersection zone between SW-NE, NW-SE and NNE-SSW trending regional-scale faults. The geometry of this junction may have been conducive to the formation of transtensional structures that represented the site of maximum crustal permeability that, in turn, could have guided the ascent of magma in the upper crust.
Post-collisional orogenic collapse may have caused relaxation and subsequent release of stored compressive stress by faulting and fracturing, possibly during uplift. This imposed strain partitioning resulted in E-W to WNW-ESE trending, inclined to steep, linear zones of intense hydraulic fracturing, pervasive silicification, veining and molybdenum mineralization. Late syn- to post-mineralization dacite dykes have intruded the porphyry system along a similar fracture network and overprint the mineralization. Higher grade molybdenum mineralization occurs in sites where E-W to WNW-ESE trending linear structures are superimposed on lithological contacts.
The interpreted controls to mineralization at the Surdulica porphyry system provide predictive tools for porphyry exploration in arc settings throughout the ABCD orogenic belt.
