⁴⁰ Ar/ ³⁹ Ar geochronology of magmatism and hydrothermal activity of the Madjarovo base-precious metal ore district, eastern Rhodopes, Bulgaria

Abstract

The Madjarovo volcanic complex and ore district comprise alteration styles from potassium silicate, advanced argillic and sericite alteration to adularia-sericite alteration/ mineralization with a close and unambiguous spatial relationship to specific magmatic events. New 4°Ar/39Ar laser fusion and incremental heating experiments on nine sanidine, biotite, adularia, K-feldspar, and alunite samples constrain the ages and time span of lavas and tepluas comprising the complex and their relationship to the hydrothennal activity. These results demonstrate that high-K calc-alkaline to shoshonitic volcanic activity began c.32.7 Ma and terminated c.500 ka later with the extrusion of quartz latite lavas at 32.2 Ma. The final stage of volcanism was accompanied by intrusion of cornpositionally similar monzonite stocks and trachytic dykes (c.32.2-32.1 Ma) and associated barren advanced argillic and sericite alteration (lithocap) and adularia-sericite base/precious metal vein mineralization. A probable thermal event at c. 12-13Ma disturbed the ages of alunite and sericite-bearing alteration at low stratigraphic levels. However, field relations combined with a plateau age of 32.1 ± 0.2 Ma from adularia in low-sulphidation veins that cross-cut lithocap indicate that hydrothermal activity, including base-and precious-metal vein deposition, was coeval with the youngest magmatic activity.

40Ar/39Ar geochronology constraints on the Middle Tertiary basement extensional exhumation, and its relation to ore-forming and magmatic processes in the Eastern Rhodope (Bulgaria)

“…The ages of the magmatic rocks are younger than alteration and coincide with the timing of main phase volcanic activity as recorded elsewhere in the eastern Rhodope [40][41][42][43].…”

“…Xanthi, Leptokaria, Simvolon) intruded the metamorphic units between 32-23 Ma [11,22,39]. The whole time span of volcanic activity in the eastern Rhodope region, including intrusion of subvolcanic bodies and dyke swarms, is bracketed between 37-21 Ma [25,[40][41][42][43] with the alkali basalts being emplaced in the Bulgarian side of the Kesebir-Kardamos and Biala reka-Kechros domes between 28-26 Ma [34].…”

40Ar/39Ar and U-Pb geochronology of the Iran Tepe volcanic complex, Eastern Rhodopes

“…Additional data on the age of Iran Tepe and the nearby Ada Tepe ore deposit is published in a companion paper (Márton et al, 2010). The reported 40 Ar/ 39 Ar ages have similar precisions to 40 Ar/ 39 Ar ages acquired from other major volcanic areas in the Eastern Rhodopes (Singer and Marchev, 2000;Marchev and Singer, 2002;Moskovski et al, 2004;Georgiev and Marchev, 2005), which collectively provide a more accurate and precise geochronological framework for interpreting the timing and duration of volcanism in the Rhodope massif.…”

“…Clasts of volcanic rocks in the uppermost part of the marl-limestone formation mark the onset of volcanism in the area. Volcanic rocks of the complex are covered by a regional tephro-stratigraphic marker, which is composed of rhyodacitic ashfall and pumice-flow tuff of an unknown source, named the Reseda Tuff (Ivanov and Kopp 1969), dated at 32.44 ±0.23 Ma (Marchev and Singer, 2002).…”

The Karavansalija Mineralized Center at the Rogozna Mountains in SW Serbia: Magma Evolution and Time Relationship of Intrusive Events and Skarn Au ± Cu–Pb–Zn Mineralization

“…Furthermore, there are a few major economic high-sulfidation epithermal deposits directly associated with porphyry deposits in the Cenozoic. The Cenozoic Au ± Cu deposits span greater ranges in age, distribution, and style than the Cretaceous deposits (Baker, 2019;Marchev and Singer 2002;Marchev et al, 2010). In a very simplistic view, the age variation of the Cenozoic deposits show several clusters at 35-31 Ma, 28-24 Ma, 15-12 Ma, and <9 Ma (Baker, 2019) in comparison to the Cretaceous age cluster with its Cu-Au deposits between 92 and 80 Ma (von Quadt et al, 2005;Jelenković et al, 2016;Banješević et al, 2019).…”