Punctuated, episodic magmatism and mineralization of the Rogozna skarn-hosted Au-Zn-Pb-Cu deposits revealed through high-precision U-Pb zircon geochronology

Abstract

The subvolcanic regions of magmatic centers are commonly associated with alteration, mineralization, and economic ore deposits, however the duration and frequency of mineralizing pulses within the overall lifespan of these centers can be poorly defined. Therefore, models for the formation of mineral systems require more high-precision geochronology data to refine their evolutionary models. Rogozna Mountain and its eponymous magmatic complex, located in SW Serbia, hosts multiple base metal deposits associated with variable rock types and structural expressions and serves as a natural laboratory to test the span and periodicity of mineralizing events. Unlike many deposits within the Rogozna magmatic complex (RMC) and elsewhere within the broader Serbo-Macedonian magmatic and metallogenic belt represented by Pb-dominated base metal sulfides, the Rogozna mining project (composed of the Gradina, Medenovac, Copper Canyon and Šanac deposits) also hosts Au-Cu mineralization. Based on previous isotope geochemistry, a single magmatic source was responsible for the sulfide crystallization associated with Au-Cu mineralization at the Copper Canyon deposit. Therefore, a detailed determination of igneous events and their temporal relationship remains crucial for understanding the formation of the Rogozna mineralized system and its multiple deposits.High-precision chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon geochronology of six representative samples revealed the first phase of oxidized Au-Zn mineralization at the Medenovac deposit occurred prior to 28.833 ± 0.154 Ma, based on the inclusion of mineralized skarn clasts in breccia supported by an igneous-matrix. This age indicates that mineralization and skarn formation began over 1 Myr prior to reduced Au-Cu mineralization at the Copper Canyon deposit, which occurred over a period from approximately 27.76–27.61 Ma associated with a series of texturally diverse but compositionally similar quartz latite intrusions. Trachyandesitic dykes emplaced at 25.384 ± 0.068 Ma represent the youngest igneous event in the RMC. Previous models of the formation of the Rogozna mineralized system are likely flawed by inaccurate unit classification and incomplete sampling of intrusions associated with the deposits, resulting in an unrealistically simplistic evolutionary model for mineralization, rather than a protracted history of episodic alteration and mineralization. Therefore, a reinterpreted temporal hierarchy of the RMC is proposed based on new compositional and geochronological data, defining multiple mineralization events. This work highlights the necessity of combining a robust suite of textural analyses, field relationships, and high-precision geochronology to make accurate interpretations of deposit formation.