Isotopic age determinations of crystalline rocks of the Upper Harz Mountains, Germany

Baumann, A.; Grauert, B.; Mecklenburg, Sabine; Vinx, Roland

doi:10.1007/bf01803694

Cited by 49 publications

(24 citation statements)

References 29 publications

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“…The emplacement age of the microgranodiorite dykes and their Sr and Nd isotopic compositions are comparable to those of the products of late-stage magmatic activity in the Variscan orogen (2951 Ma, U±Pb zircon; Baumann et al 1991;Finger et al 1997). However, the late-stage magmatism is mostly localized in the external parts of the orogen and the rocks are typically A-type peraluminous to metaluminous leukogranites with high Y, Th, K, and Rb contents.…”

Section: Magma Originmentioning

confidence: 89%

40Ar/39Ar hornblende dating of a microgranodiorite dyke: implications for early Permian extension in the Moldanubian Zone of the Bohemian Massif

2001

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Laser fusion 40 Ar/ 39 Ar ages of titanian pargasite from a microgranodiorite dyke swarm in the southern Bohemian Massif effectively date the early Permian (late Autunian) emplacement of dykes into a cool Moldanubian crust. This intrusion represents the youngest magmatic phase recorded in this part of the Moldanubian Zone. Strontium and neodymium isotopic ratios of microgranodiorites point to magma derivation from re-melting the lower crustal rocks with a possible component of upper mantle composition. Spatial and temporal association of the dykes with movements on a major N±S (NNE±SSW) tectonic discontinuity (Blanice±Kaplice±Rödl fault zone) suggests that their emplacement corresponds to the maximum age of fault movements associated with the E/Woriented extension in this part of the Bohemian Massif.

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Section: Magma Originmentioning

confidence: 89%

40Ar/39Ar hornblende dating of a microgranodiorite dyke: implications for early Permian extension in the Moldanubian Zone of the Bohemian Massif

2001

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“…350 Ma (e.g. Balintoni et al 2007 (Baumann et al 1991) and Iberian Massif (Dias et al 1998;Bea et al 1999;Fernándes-Suárez et al 2000;Azevedo et al 2003). Table 3).…”

Section: Discussionmentioning

confidence: 99%

The emplacement age of the Muntele Mare Variscan granite (Apuseni Mountains, Romania)

Balintoni¹,

Balica²,

Cliveţi³

et al. 2009

Geologica Carpathica

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Like the Alps and Western Carpathians, the Apuseni Mountains represent a fragment of the Variscan orogen involved in the Alpine crustal shortenings. Thus the more extensive Alpine tectonic unit in the Apuseni Mountains, the Bihor Autochthonous Unit is overlain by several nappe systems. During the Variscan orogeny, the Bihor Unit was a part of the Some terrane involved as the upper plate in subduction, continental collision and finally in the orogen collapse and exhumation. The Variscan thermotectonic events were marked in the future Bihor Unit by the large Muntele Mare granitoid intrusion, an S-type anatectic body. Zircon U-Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating yielded a weighted mean age of 290.9 ± 3.0 Ma and a concordia age of 291.1 ± 1.1 Ma. U-Pb isotope dilution zircon analyses yielded a lower intercept crystallization age of 296.6 + 5.7/-6.2 Ma. These two ages coincide in the error limits. Thus, the Muntele Mare granitoid pluton is a sign of the last stage in the Variscan history of the Apuseni Mountains. Many zircon grains show inheritance and/or Pb loss, typical for anatectic granitoid, overprinted by later thermotectonic events.

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“…Granitoid and gabbroic plutonic rocks form ca. 295-Ma old (Baumann et al 1991), high-level intrusions within Devonian and Lower Carboniferous country rocks. Significant metamorphic imprint is confined to thermal aureoles around these intrusions.…”

Section: Regional Setting and Basic Petrographical Featuresmentioning

confidence: 99%

“…Bankwitz (1995) suggested that the EGC represents a CadomianCaledonian tectonic flake formed during the collision of Gondwana with East Avalonia. Other authors favored a model that explains the EGC as being uplifted upon the intrusive ascent of the magmas of the adjacent Brocken Granite and the Harzburg Gabbronorite (Baumann et al 1991;Franz et al 1997). Based on the ''Cadomian'' (Pan-African) age Franz et al (1997) further speculated that the EGC belongs to the East Avalonian terrane.…”

Section: Introductionmentioning

confidence: 96%

Ion microprobe (SHRIMP) dating of detrital zircon grains from quartzites of the Eckergneiss Complex, Harz Mountains (Germany): implications for the provenance and the geological history

Geisler

Vinx

Martin-Gombojav

et al. 2005

Int J Earth Sci (Geol Rundsch)

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The Eckergneiss Complex (EGC) is a geologically unique medium-to high-grade metamorphic unit within the Rhenohercynian domain of the Mid-European Variscides. A previously, poorly defined conventional lower U-Pb intercept age of about 560 Ma from detrital zircons of metasedimentary rocks has led to speculations about an East Avalonian affinity of the EGC. In order to unravel the provenance and to constrain the age of the sediment protolith, we carried out sensitive high-resolution ion microprobe U-Pb analyses on detrital zircons from five different EGC quartzite occurrences. The obtained age spectrum indicates a SW Baltica provenance of the detritus. Sveconorwegian ages between 0.9-1.2 Ga are particularly well represented by analyses from metamorphic recrystallization/alteration zones penetrating into igneous zircon. Cadomian (PanAfrican) ages, which might reflect a metamorphic event, could not be substantiated. Instead, zircons of igneous origin yielded concordant Lower Devonian and Silurian ages of 410±10, 419±10, and 436±6 Ma (1r), implying that sedimentation of the EG protolith must have taken place after 410±10 Ma. The lower age limit of the EGC metamorphism is constrained by 295 Ma intrusion ages of the adjacent, nonmetamorphosed Harzburg Gabbronorite and Brocken Granite. Sedimentation and metamorphism must thus have taken place between about 410 Ma and 295 Ma. Given that this time span coincides with most of the sedimentation within the virtually nonmetamorphosed (lowest grade) Rhenohercynian in the Harz Mountains, including the direct vicinity of the EGC, along with the high-grade metamorphism, the EGC can hardly be seen as uplifted local basement. A possible candidate for the root region is an easterly, concealed marginal segment of the Rhenohercynian domain of the Variscides, which is tectonically overridden and suppressed by the Mid-German Crystalline Rise during continent collision. However, based on the concept of strike-slip movement of Variscan terranes with different P-T-t histories as a result of postaccretion intraplate deformation, the EGC could also represent a fault-bounded complex with an origin located far east or south east of the present location.

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Isotopic age determinations of crystalline rocks of the Upper Harz Mountains, Germany

Cited by 49 publications

References 29 publications

40Ar/39Ar hornblende dating of a microgranodiorite dyke: implications for early Permian extension in the Moldanubian Zone of the Bohemian Massif

40Ar/39Ar hornblende dating of a microgranodiorite dyke: implications for early Permian extension in the Moldanubian Zone of the Bohemian Massif

The emplacement age of the Muntele Mare Variscan granite (Apuseni Mountains, Romania)

Ion microprobe (SHRIMP) dating of detrital zircon grains from quartzites of the Eckergneiss Complex, Harz Mountains (Germany): implications for the provenance and the geological history

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