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- Title
Zircon geochronology, elemental and Sr-Nd isotope geochemistry of two Variscan granitoids from the Odenwald-Spessart crystalline complex (mid-German crystalline rise).
- Authors
Siebel, W.; Eroğlu, S.; Shang, C.; Rohrmüller, J.
- Abstract
The crystalline parts of the Bergsträsser (western) Odenwald and the southern Spessart expose Variscan I-type granitoids of the mid-German crystalline rise that formed during subduction of the Rheic ocean and collision of Avalonia and Armorica about 365 and 330 Ma ago. We present geochemical, Sr-Nd isotopic, single zircon Pb/Pb evaporation and conventional U -Pb data from a diorite-granodiorite complex of the southern Spessart and from a flasergranitoid of the Bergsträsser Odenwald unit II. Both intrusions provide almost identical zircon ages (332.4 ± 1.6 Ma for Odenwald and 330.4 ± 2.0 Ma for Spessart). Lack of inherited or pre-magmatic zircon components connotes magma genesis in deep crustal hot zones despite low temperature estimates (758-786 °C) derived from zircon saturation thermometry. Investigated rock samples display normal- to high-K calc -alkaline metaluminous (Spessart) and weakly peraluminous (Odenwald) geochemical characteristics. The Spessart pluton has lower εNd values (−2.3 to −3.0) and higher Sr/Sr ratios (0.7060 to 0.7066) compared to Odenwald flasergranitoid (εNd = −0.8 and Sr/Sr = 0.7048). In terms of the tectonic setting, the diorite-granodiorite complex of the southern Spessart forms the continuation of the north Armorican arc segment exposed in the Bergsträsser Odenwald. Taking into account previously reported geochemical and isotopic results, it is concluded that the Spessart pluton does not match compositions of Odenwald unit II granitoids but likely represents the north-eastward extension of unit III.
- Subjects
ODENWALD (Germany); SPESSART (Germany); GERMANY; GEOLOGICAL time scales; ZIRCON; GEOCHEMISTRY; SUBDUCTION; MAGMAS; RHEIC Ocean
- Publication
Mineralogy & Petrology, 2012, Vol 105, Issue 3/4, p187
- ISSN
0930-0708
- Publication type
Article
- DOI
10.1007/s00710-012-0200-3