Internal structures and dating of complex zircons from Meissen Massif monzonites, Saxony

摘要: Abstract U–Pb zircon ages were determined for accessory zircons from two monzonites the Meissen Massif (Northern Bohemian Massif, Germany) by SHRIMP ion microprobe. BSE and CL imaging revealed that monzonite zircons, showing oscillatory growth zoning, often contain inherited cores. Raman microprobe measurements showed zoned rims (U 277–1426 ppm, Th 144–910 ppm) are slightly disordered to moderately metamict whereas cores have a wide spectrum of structural states, well-crystallized highly metamict. The radionuclide (U+Th) content varies few hundred more than 20,000 ppm. probe on rims, interpreted as during crystallization magma, gave concordant Carboniferous 206 Pb / 238 U 326±6 Ma (monzonite Leuben) 330±5 Heidenschanze; 95% confidence), respectively. These consistent with recently published 40 Ar 39 329.1±2.8 330.4±2.8 (2σ) amphiboles same rocks. In contrast, range (slightly discordant) Proterozoic relic in low discordant data most Previously obtained 207 (single evaporation technique) 340±16 357±16 (1σ) probably mixed-ages between magmatic components. postdate Upper Devonian/Lower subduction collision events area about 20 Ma. Due their shoshonitic chemical signature which is typical rocks destructive plate boundary settings, might be originating these ≈350 events, earlier appeared confirm this interpretation. However, both our current results show only enrichment lithospheric mantle source, but not intrusion itself, was directly related events. itself took place ≈330 ago, framework strike-slip tectonics Elbe Valley zone. Widely occurring indicative crustal contamination causing considerable modification signatures (trace element content) monzonites.