40Ar/39Ar geochronology of magmatism and hydrothermal activity of the Madjarovo base–precious metal ore district, eastern Rhodopes, Bulgaria
Peter Marchev, Brad Singer, 2002. "40Ar/39Ar geochronology of magmatism and hydrothermal activity of the Madjarovo base–precious metal ore district, eastern Rhodopes, Bulgaria", The Timing and Location of Major Ore Deposits in an Evolving Orogen, D. J. Blundell, F. Neubauer, A. von Quadt
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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 40Ar/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 tephras comprising the complex and their relationship to the hydrothermal 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 compositionally 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.12–13 Ma 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.
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As an outcome of the European Science Foundation scientific programme, GEODE, on geodynamics and ore deposit evolution, this book examines the underlying geodynamic processes that lead to the formation of ore deposits in order to discover what controls the timing and location of major ore deposits in an evolving orogen.
A collection of 19 research papers examines various aspects of ore genesis in the context of the geodynamic processes occurring within an evolving orogen. Although the majority of papers relate to Europe, their findings have a global significance for metallogenesis.
The book will be of interest to all those involved in research or mineral exploration concerned with metallogenesis. In addition, ore deposits provide new evidence about magmatism associated with transient, rapid changes in plate motions and subduction processes in unusual tectonic settings, and are therefore of interest to those involved in both the magmatic and tectonic processes of orogenesis.