Epithermal gold-bearing sulfide ore deposit Tulallar: Structure, structural geology and mineralization patterns

Abstract

In the latest decades, the characteristic of geology and mineralization in Somkhito–Karabakh island–arc paleosystem undergoes cardinal rethinking. This article describes epithermal gold-bearing sulfide ore deposit Tulallar in the Lesser Caucasus in Azerbaijan. The deposit adjoins a partly eroded volcano-tectonic depression and localizes in the east–westward striking Upper Jurassic andesite-dacitic and andesite strata more than 500 m thick. In the center, the Tulallar Fault splits the structure into three blocks — Western, Central and Eastern, which hold the same-name zone of gold-bearing ore lodes and veins. The main concentrators of finely dispersed and free gold are chalcopyrite and pyrite. The essential tectonic structures which govern distribution of the mineralization are the bordering branches of the Tulallar–Chiragdar–Toganaly fault. The test deposit is the volcanic epithermal shallow and medium-depth cluster within the structurally isolated wedge-like junction of the regional northwestern and northeastern faults. Based on the revealed localization patterns of the mineralization, the prognostic estimation procedure is developed for different-scale ore potentials. The direct and indirect signs of a mineralization are identified. The type, spatial location and intensity of these signs are assumed as the estimation criteria. Regarding the lithological criterion, these are the volcano-clastic facies and the same-age sub-volcanic Kimmeridgian bodies. The types of folds are considered as different values of folding structures. The same principle is used to differentiate between two types of faulting (strike-slip faults and thrustfaults). The information content of the criteria was assessed by the relative weights found empirically during filed operations, and by the method of analogy.