Exhumation of eclogitized continental basement during Variscan lithospheric delamination and gravitational collapse, Sudety Mountains, Poland
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Abstract
A Variscan,deep-crustal-level (eclogite-facies),continental basement massif in western Poland, the Snieznik complex, was tectonically exhumed. Crustal-penetrating mylonite zones record three main kinematic events: early top-to-the-north-directed thrusting, right-slip transpression-tension, and late top-to-the-south and -east normal faulting. Thrusting resulted in extreme crustal thickening and associated eclogite-facies metamorphism. Right-slip movements produced retrogressive crystal-plastic simple-shear zones. Normal faults flank Carboniferous to Early Permian terrigenous sedimentary basins, documenting tectonic and erosional denudation of the Snieznik complex during lithospheric extension. Sm/Nd isotopic dates previously reported for the in situ eclogite-facies metamorphic mineral assemblages are 341, 337, and 329 Ma (Brueckner et al., 1991). 40Ar/39Ar isotopic dates for metamorphic hornblende (338, 333, and 332 Ma), muscovite (329 and 329 Ma), and biotite (328 Ma) reflect times of cooling through the ∼500, 350, and 300 °C isotherms, respectively. These nearly concordant mineral dates document rapid cooling from ∼850 °C (eclogue-facies temperatures) to ∼300 °C. Rapid denudation of these deep-crustal rocks (∼19-22 kbar pressures, >70 km depth) is attributed to processes, similar to those of metamorphic-core complexes, that operated during lithospheric delamination and gravitational collapse. The sequence of late Paleozoic (Alleghanian) crustal thickening followed by right-slip transpression-tension followed by normal faulting recognized in the U.S. Appalachians implies that this tectonic pattern may exist throughout the Afleghanian-Variscan belt.
Study Area
Publication type | Article |
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Publication Subtype | Journal Article |
Title | Exhumation of eclogitized continental basement during Variscan lithospheric delamination and gravitational collapse, Sudety Mountains, Poland |
Series title | Geology |
DOI | 10.1130/0091-7613(1993)021<1111:EOECBD>2.3.CO;2 |
Volume | 21 |
Issue | 12 |
Year Published | 1993 |
Language | English |
Publisher | GSA |
Contributing office(s) | Eastern Geology and Paleoclimate Science Center, Florence Bascom Geoscience Center |
Description | 4 p. |
First page | 1111 |
Last page | 1114 |
Country | Poland |
Other Geospatial | Sudety Mountains |
Google Analytic Metrics | Metrics page |