The Romanian territory contains numerous ore deposits mined since pre-Roman times. An assessment of historical gold production of the Gold Quadri-lateral (GQ) yielded a total estimate of 55.7 Moz of gold throughout an area of 2400 km2. Interpreted in terms of mineralization density this is 23,208 oz of gold/ km2. The geological setting of the GQ is represented mainly by Tertiary (14.7 My to 7.4 My) calc-alkaline volcano-plutonic complexes of intermediate character in sedimentary basins of molasse type. These basins are tectonically controlled by NW-SE lineation across early Alpine magmatic products, i.e. subduction related Jurassic-Lower Cretaceous igneous association (island arc ophiolites and granitoids) and Upper Cretaceous igneous association (banatites). The Tertiary magmatism is associated with extensional tectonics caused by NE escape of the Pannonian region during Upper Oligocene-Lower Miocene times. As a result of tectono-magmatic and mineralization-alteration characteristics, two metallogenetical types were separated in the GQ, i.e. calc-alkaline andesitic (CAM) and sub-alkaline rhyodacitic (SRM). Both develop almost entirely low-sulfidation type of Au epithermal mineralization. However, two subtypes, -rich in sulfide (2-7%) and -poor in sulfide (7-20%) were delineated and correlated with CAM type and SRM type respectively. Furthermore, CAM is connected at deeper levels with Cu-Au+/-Mo porphyry systems in contrast with SRM, which is a non-porphyry environment. The Brad-Săcărâmb district contains mainly CAM type andesitic structures. It is a porphyry environment with epithermal low-sulfidation-rich sulfide vein halo (Barza, Troiţa-Bolcana deposits). However, a few SRM type patterns, such as Măgura Ţebii, Băiţa-Crăciuneşti and Săcărâmb, deposits exhibit Au-Ag-Te low-sulfidation-poor sulfide epithermal vein halo. The Zlatna-Stănija district exhibits similar characteristics, with Au-Ag+/-Pb, Zn veins in Cu-Au subvolcanic-porphyry environment (CAM type). An exception is the Faţa Băii Au-Ag-Te vein system that corresponds to SRM type. Rosia Montana-Bucium district is more elaborated in terms of a porphyry-epithermal relationship. Both CAM type (Roşia Poieni, Bucium Tarniţa deposits) and SRM type (Roşia Montană deposit) exist. The Baia de Arieş district is definitely the non-porphyry environment of SRM type, with Au-Ag-Te veins and breccia pipes hosted in sub-alkaline andesitic rocks.
Vlad, Șerban-Nicolae and Orlandea, Eugen
Metallogeny of the Gold Quadrilateral: style and characteristics of epithermal - subvolcanic mineralized structures, South Apuseni Mts., Romania,
Studia UBB Geologia
Available at: http://scholarcommons.usf.edu/geologia/vol49/iss1/art2