The Chemical Evolution from Older (323–318 Ma) towards Younger Highly Evolved Tin Granites (315–314 Ma)—Sources and Metal Enrichment in Variscan Granites of the Western Erzgebirge (Central European Variscides, Germany)

Abstract

The sources and critical enrichment processes for granite related tin ores are still not well understood. The Erzgebirge represents one of the classical regions for tin mineralization. We investigated the four largest plutons from the Western Erzgebirge (Germany) for the geochemistry of bulk rocks and autocrystic zircons and relate this information to their intrusion ages. The source rocks of the Variscan granites were identified as high-grade metamorphic rocks based on the comparison of Hf-O isotope data on zircons, the abundance of xenocrystic zircon ages as well as Nd and Hf model ages. Among these rocks, restite is the most likely candidate for later Variscan melts. Based on the evolution with time, we could reconstruct enrichment factors for tin and tungsten starting from the protoliths (575 Ma) that were later converted to high-grade metamorphic rocks (340 Ma) and served as sources for the older biotite granites (323–318 Ma) and the tin granites (315–314 Ma). This evolution involved a continuous enrichment of both tin and tungsten with an enrichment factor of ~15 for tin and ~7 for tungsten compared to the upper continental crust (UCC). Ore level concentrations (>10–100 times enrichment) were achieved only in the greisen bodies and dykes by subsequent hydrothermal processes.

Relative Abundance and Compositional Variation of Silicates, Oxides and Phosphates in the W-Sn-Rich Lodes of the Panasqueira Mine (Portugal): Implications for the Ore-Forming Process

“…These ore systems comprise varied styles of W and Sn mineralization, often coexisting with rare element (e.g., Li, Cs, Ta, Be) pegmatites, which are associated with different voluminous suites of peraluminous granites mostly generated and emplaced during the 320-290 Ma time window [23][24][25][26][27][28][29][30][31][32][33][34]. Recent reassessments of critical factors determining the development of this belt and its metal endowment [35][36][37][38][39][40][41][42][43][44][45][46] provided many innovative insights, showing that ore-forming processes are synchronous of the main exhumation stages of the European Variscan cordillera and that conventional genetic models should be reviewed [47][48][49][50][51][52]. In fact, these ore-forming processes can no longer be interpreted simply as a result of the emplacement of single intrusions that generate large amounts of fluids at the summit of the granite cupola during its fractionated crystallization, and also promote the growth of divergent fracture sets above the cupola, depending on the confining pressure.…”

Two-phase late Paleozoic magmatism (~ 313–312 and ~ 299–298 Ma) in the Lusatian Block and its relation to large scale NW striking fault zones: evidence from zircon U–Pb CA–ID–TIMS geochronology, bulk rock- and zircon chemistry

“…In comparison to other basement rocks of Saxothuringia (Pietranik et al 2013;Linnemann et al, 2014;Słodczyk et al 2018;Tichomirowa et al 2018Tichomirowa et al , 2019b; Fig. 10b), the Hf-and Nd-isotope compositions are higher and Hf and Nd model ages are younger indicating a larger mantle contribution (Fig.…”

“…Isotope data on zircon are particularly suitable to determine sources of rocks, because these data are not affected by fractional crystallization or hydrothermal overprint and thus represent the composition of the melt (Chen and Zheng 2017;Tichomirowa et al 2019b). The zircon Hf data from sample BGK1 (biotite-bearing granite of Koenigshain, Table 6) vary from εHf (t) = − 4.1 to nearly chondritic ratios (εHf (t) = − 0.6).…”

“…Late Paleozoic late-to post-Variscan igneous rocks (combined here under the term Variscan) of the Bohemian Massif are in many cases bound to strike-slip faults (Oberc-Dziedzic et al 2015) and their radiometric dating may give information about the temporal evolution of the tectonic activity on these structures. Most of the Variscan igneous rocks have been dated repeatedly by different geochronological methods (summarized by, e.g., Förster and Romer 2010;von Seckendorff 2012) and extensively analysed geochemically (e.g., Hammer 1996;Förster et al 1999;Hammer et al 1999;Słaby and Martin 2008;Tichomirowa et al 2019b). Recently, first high-precision zircon U-Pb CA-ID-TIMS data of Variscan granitic rocks allow to reliably differentiate single magmatic pulses of the post-Variscan period indicating distinct short (1-2 Myr) magmatic periods (Kryza et al 2014a;Tichomirowa et al 2019a).…”

Complex Characteristic of Zircon from Granitoids of the Verkhneurmiysky Massif (Amur Region)

“…The studied zircon from the Verkhneurmiysky granites (both biotite leucogranites and zinnwaldite granites) demonstrates the most similar composition with zircon from Chukotka granites (Severny massif), as well as with zircon from rare-metal topaz-bearing granites of the Mole massif (Australia) [41], Zinnwald Massif (Germany) [40], and Erzgebirge (Germany) [44] where REE concentrations almost reach the level of hydrothermal mineralization [41,45].…”