“Granite tectonics” revisited: insights from comparison of K-feldspar shape-fabric,anisotropy of magnetic susceptibility (AMS), and brittle fractures in the Jizera granite,Bohemian Massif |
| |
Authors: | Ji?í ?ák Kry?tof Verner Josef Klomínský Marta Chlupá?ová |
| |
Institution: | (1) Institute of Geology and Paleontology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic;(2) Czech Geological Survey, Klárov 3, Prague, 11821, Czech Republic;(3) Institute of Petrology and Structural Geology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic;(4) Boháčova 866, Prague, 14900, Czech Republic |
| |
Abstract: | In the Jizera granite of the Krkonoše–Jizera Plutonic Complex, northern Bohemian Massif, contrasting patterns of magmatic
K-feldspar fabrics and brittle fractures characterize different structural levels of the pluton. The uppermost exposed level
at ∼800–1,100 m above sea level is dominated by flat foliation that overprints two steep foliations. In contrast, K-feldspar
shape-fabric in an underground tunnel (∼660 m above sea level) shows complex variations in orientation and intensity. Magnetic
fabric carried by coaxial contributions of biotite, magnetite, and maghemite is homogeneous along the examined section of
the tunnel, and is decoupled from the K-feldspar fabric. The Jizera granite is crosscut by two regional sets of subvertical
fractures (∼NE–SW and ∼NW–SE) and by near-surface exfoliation joints. The multiple fabrics are inferred to reflect a complex
magmatic strain history at different structural levels of the pluton, bearing little or no relationship to the fracture network.
In contrast to the original concept of Hans Cloos (“granite tectonics”), we conclude that no simple genetic relationship exists
between fabrics and fractures in plutons. An alternative classification of fractures in plutons thus should avoid relationships
to magmatic fabrics and should instead consist of cooling, syntectonic, uplift, and post-uplift fractures. |
| |
Keywords: | Bohemian Massif Fracture Granite Fabric Pluton |
本文献已被 SpringerLink 等数据库收录! |
|