Abstract
Here, we present in situ U–Pb laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) ages of andradite-grossular garnet from four magmatic-hydrothermal polymetallic skarn prospects in the Schwarzenberg District, Erzgebirge (Germany), located in the internal zone of the Variscan Orogenic Belt. Within the geochronological framework of igneous rocks and hydrothermal mineralization in the Erzgebirge, the obtained garnet ages define three distinct episodes of Variscan skarn formation: (I) early late-collisional mineralization (338–331 Ma) recording the onset of magmatic-hydrothermal fluid flow shortly after the peak metamorphic event, (II) late-collisional mineralization (~ 327–310 Ma) related to the emplacement of large peraluminous granites following large-scale extension caused by orogenic collapse and (III) post-collisional mineralization (~ 310–295 Ma) contemporaneous with widespread volcanism associated with Permian crustal reorganization. Our results demonstrate that the formation of skarns in the Schwarzenberg District occurred episodically in all sub-stages of the Variscan orogenic cycle over a time range of at least 40 Ma. This observation is consistent with the age range of available geochronological data related to magmatic-hydrothermal ore deposits from other internal zones of the Variscan Orogenic Belt in central and western Europe. In analogy to the time–space relationship of major porphyry-Cu belts in South America, the congruent magmatic-hydrothermal evolution in the internal zones and the distinctly later (by ~ 30 Ma) occurrence of magmatic-hydrothermal ore deposits in the external zones of the Variscan Orogenic Belt may be interpreted as a function of their tectonic position relative to the Variscan collisional front.
Highlights
Tin and W deposits are commonly associated with highly evolved ilmenite-series granitoid rocks in collisional zones (Lehmann 2020); they occur in a number1 3 Vol.:(0123456789)Mineralium Deposita of mineralization styles, including vein-type, skarn, carbonate replacement, and greisen deposits
We present in situ U–Pb LA-ICPMS geochronological data of andradite-grossular garnet from four major skarn prospects in the Schwarzenberg District, Erzgebirge (Germany)
Uranium-Pb garnet age data was subsequently collected on a ThermoFisher Element 2 sector field ICP-MS coupled with a Resonetics RESOLution S-155 193 nm ArF Excimer laser equipped with a two-volume Laurin Technic ablation cell at the Frankfurt Isotope & Element Research Center (FIERCE) of Goethe-Universität Frankfurt following the methodology described in Burisch et al (2019b)
Summary
Tin and W deposits are commonly associated with highly evolved ilmenite-series (peraluminous) granitoid rocks in collisional zones (Lehmann 2020); they occur in a number1 3 Vol.:(0123456789)Mineralium Deposita of mineralization styles, including vein-type, skarn, carbonate replacement, and greisen deposits. It has been widely assumed that formation of magmatic-hydrothermal ore deposits in these provinces is constrained to a narrow interval of ≤ 15 Ma (e.g., Bouchot et al 2005; Cuney et al 2002; Lefebvre et al 2019; Romer et al 2007; Zhang et al 2017) coinciding with intense magmatism during post-collisional extension (Förster et al 1999) This is in contrast to several recent studies suggesting that magmatic-hydrothermal Sn-W-polymetallic mineralization formed episodically over a time span of more than 40 Ma (Burisch et al 2019b; Harlaux et al 2018; Moscati and Neymark 2020; Romer and Kroner 2015, 2016; TimónSánchez et al 2019; Zhang et al 2019)
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