The Central-Sudetic ophiolites (SW Poland): Petrogenetic issues, geochronology and palaeotectonic implications
101
Citation
52
Reference
10
Related Paper
Citation Trend
Keywords:
Massif
Geochronology
Baddeleyite
Reconstructing the tempo and emplacement mechanisms of large igneous provinces (LIPs) and establishing potential links to environmental change and biological crises requires detailed and targeted high-precision geochronology. Contact metamorphism during LIP intrusive magmatism can release large volumes of thermogenic gas, so determining the timing of these events relative to global climate change is crucial. The most reliable age information comes from U-Pb geochronology; however, LIP mafic igneous rocks do not commonly crystallize U-bearing minerals, such as zircon or baddeleyite. Recent work has shown that U-rich minerals can crystallize in fractionated melt pockets in intrusive components of LIPs after contamination of the melt by sedimentary rocks at emplacement level. Zircon and baddeleyite from these pockets make high-precision U-Pb geochronology of LIPs possible, but these unique mechanisms add other complexities.
Geochronology
Baddeleyite
Cite
Citations (3)
CONNECTION OF THE ŚLĘŻA OPHIOLITE WITH THE VARISCAN STRUCTURE OF THE SOWIE MEIAMORPHIC ROCKS
Summary
The structural analysis made in the area of about 100 sq km of the Sowie Mountains metamorphic segments (the Middle Sudety Mountains - the lower Silesia) shows that the main fold macrostructures developed in the second deformation phase (D2). The basic influence on geometry, size and orientation of microfolds (F2) had thrust sheets of basic rocks - mainly amphibolites. The most basic and ultrabasic rocks developed from segments of the former ocean crust (the Śleza ophiolite).
As a results of long standing tectonic processes (beginning in the Cadomian tectogenesis and lasted to lower Carboniferous) on the margins of the Bohemian Massif (in the Saxo-Turonian zone), mutual displacements of various segments of continental (Cadomides) and ocean crusts (e.g. the Śleza ophiolites) took place.
From the ocean crust undergoing subduction beneath the Bohemian Massif a large segment (the Śleza ophiolite) was tectonically detached. This ophiolite thrust sheet impressed in existing structural discontuities of the Cadomides.
Concomitance of subduction and obduction processes resulted in decreasing the rate of overthrust of this segment of the Bohemian Massif on the ocean crust. The rate of overthrust of the whole Bohemian Massif was not decreased.
Originated in that way the disagreement in displacement rates caused detachment and overthrust the Sowie Mountains sheets (northward) on the overthrusting (southward) the Śleza ophiolite. As the result of this process the thickness and weight increased in this marginal part of the Bohemian Massif. It caused submerging the whole zone (much more in the eastern part) and development among others migmatites and locally granitoids during the third deformation phase (D3). The Sowie Mountains structure is characterized by the tectonic macromelange pattern.
Thrust sheets, thrust slices, boundins, lens of ophiolite segments, numerous in the lower part of the Sowie Mountains slab characterize this type of pattern.
These macrostructural features originated in the Variscan tectogenesis (the Acadian phase?).
Massif
Obduction
Ultramafic rock
Island arc
Cite
Citations (4)
Massif
Outcrop
Section (typography)
Cite
Citations (35)
Synthetic seismograms for the Samail ophiolite, computed using the full reflectivity technique, are used to test the hypothesis that this ophiolite complex can serve as a prototype for young oceanic crust. If so, then this ophiolite complex can be compared with the older (45 m.y.) Bay of Islands (BOI) ophiolite to develop an aging model for oceanic crust. Synthetics for this young emplacement age (5–8 m.y.) ophiolite are compared with ocean bottom hydrophone data from 0.5‐ and 4.5‐m.y.‐age crust obtained during the Rivera Ocean Seismic Experiment. Second‐arrival phases from reflected refractions from one ophiolite velocity‐depth model and data from 4.5‐m.y.‐age crust are in excellent agreement; this agreement suggests that the Samail ophiolite is a good working model for young oceanic crust. Earlier work has shown that the BOI ophiolite is a good prototype for mature oceanic crust. The BOI ophiolite data also suggest that alteration of the lower oceanic crust and upper mantle is limited. We use the petrologic and geochemical properties of the Samail and BOI ophiolites to develop a two‐stage model for crustal aging that directly limits alteration of the lower crust and upper mantle materials.
Seismogram
Cite
Citations (24)
Massif
Cite
Citations (0)
Massif
Cite
Citations (11)
Massif
Ultramafic rock
Riphean
Cite
Citations (3)
Baddeleyite
Geochronology
Cite
Citations (17)
Obduction
Cite
Citations (119)
Complete developmental ophiolitic suites have a sight of typical four layered textures, which shows similarities to nowadays oceanic crust. They are formed in an extend environment by the mid oceanic ridge. Because of tectogenesis make for ophiolitic suites dismember and tectonic emplacement in to the Continental suture zone. Along the faults zones ophiolitic mass occurred in the form of tectonic shect and tectonic melange. Ophiolite give main evidence for the oceanic crust formation and break. Ophiolite belt or paleo suture line has a direct mark, which defined paleo oceanic basin in the orogenic belt and defined block of continet block
Oceanic basin
Cite
Citations (0)