The concealed granite massif of Eichigt−Schönbrunn (Vogtland, Germany): Petrography, mineralogy, geochemistry and age of the Eichigt apical intrusion

The Eichigt granite is one of two apical intrusions forming the concealed massif of Eichigt−Schönbrunn in the Erzgebirge−Vogtland metallogenic province of Germany. It represents a peraluminuous, medium-grained, Si-rich biotite monzo- to syenogranite of aluminuous A-type affinity and post-collisional (-orogenic) tectonic setting, which belongs to the group of medium-F, low-P Variscan granites of the Erzgebirge. Mineralogically and geochemically, the Eichigt granite shows the closest affinity to the Gottesberg subvolcanic microgranite/rhyolite complex some 25 km north-east of the massif. The granites contain phenocrysts of quartz and K-feldspar and sporadically accessory topaz and andalusite. A special feature is the presence of accessory primary fergusonite-(Y) and secondary synchysite-(Ce). Minor amounts of quartz, K-feldspar, and siderophyllite likely represent antecrysts, i.e., crystallized from a lesser silicic forerunner magma. These observations attest to the operation of magma mingling during the formation of the Eichigt granite. Calculation of Th−U−total Pb uraninite ages proves that the Eichigt and Schönbrunn granites are coeval and emplaced at about 306 ± 3 Ma (2σ), i.e., were formed during the same magmatic episode as the northwesterly Henneberg granite in Thuringia und the microgranite/rhyolith suite at Gottesberg and the Seiffen granite in the Erzgebirge−Vogtland. Geochemical data and mineralogical features do not lend support a genetical relation between the Eichigt−Schönbrunn granites and the spatially associated Sn-polymetallic veins