scholarly journals MAGNETIC FABRICS OF THE TERTIARY VRONDOU PLUTONIC COMPLEX, NORTHERN GREECE.

2004 ◽  
Vol 36 (3) ◽  
pp. 1316 ◽  
Author(s):  
I. Zananiri ◽  
S. Dimitriadis ◽  
D. Kondopoulou ◽  
A. Kilias
Keyword(s):  
Plastic Deformation ◽  
Magnetic Susceptibility ◽  
Tectonic Evolution ◽  
Early Miocene ◽  
Northern Greece ◽  
The West ◽  
Rock Types ◽  
Saturated Rock ◽  
Magnetic Fabrics ◽  
Plutonic Complex

The emplacement and tectonic evolution of the Tertiary Vrondou granitoid in the Greek Rhodope has been studied by a combination of field tectonic, microtextural and anisotropy of magnetic susceptibility (AMS) methods. The Vrondou pluton is composed of at least two intrusions, a Mid-Oligocene one at its eastern and an Early Miocene at its western parts. Room for the emplacement in both cases was provided by the opening of an extensional ramp space within a several km thick, mid-crustal subhorizontal shear zone, with a top to the SW sense, active during the Mid-Oligocene to Early Miocene period. The older eastern part of the pluton is much less deformed than the younger western part. Magmatic textures are well preserved in the older intrusion whereas they are scarcely present in the younger one. They indicate a NW-SE direction of magmatic flow in both cases. Sub-solidus plastic deformation affected mostly the younger western part of the pluton and only locally the older eastern one. In both cases mineral lineations trending NE-SW were developed. An increase in the shear rate by the Early Miocene or a localization of shear mainly in the west, in combination with the more silica saturated rock types present there, are probably the reasons for the different deformational behaviour of the two parts of the pluton.

Tectonic evolution of the west Spitsbergen fold belt

1985 ◽  
Vol 114 (1-4) ◽  
pp. 193-211 ◽  
Author(s):  
C. Craddock ◽  
E.C. Hauser ◽  
H.D. Maher ◽  
A.Y. Sun ◽  
Zhu Guo-Qiang
Keyword(s):  
Tectonic Evolution ◽  
Fold Belt ◽  
The West ◽  
West Spitsbergen

ESTIMATION OF SOURCE PARAMETERS IN IBADAN, SOUTH – WESTERN NIGERIA USING DIGITIZED AEROMAGNETIC DATA

2018 ◽  
Vol 14 (2) ◽  
pp. 15-28
Author(s):  
A A ALABI ◽  
O OLOWOFELA
Keyword(s):  
Magnetic Susceptibility ◽  
Source Parameters ◽  
Granite Gneiss ◽  
Geological Structure ◽  
Magnetic Data ◽  
Susceptibility Map ◽  
Rock Types ◽  
Upward Continuation ◽  
Magnetic Basement ◽  
Local Wavenumber

Airborne magnetic data covering geographical latitudes of 7000‟N to 7030‟N and longitudes of 3 30′E to 4 00′E within Ibadan area were obtained from Nigeria Geology Survey Agency. The data were ana-lyzed to map the sub surface structure and the source parameters were deduced from the quantitative and qualitative interpretation of magnetic data. The upward continuation technique was used to de-emphasize short – wavelength anomaly while the depth to magnetic sources in the area was deter-mined using local wavenumber technique, the analytic signal was also employed to obtain the depths of the magnetic basement. Analysis involving the local wavenumber, upward continuation and appar-ent magnetic susceptibility techniques significantly improves the interpretation of magnetic data in terms of delineating the geological structure, source parameter and magnetic susceptibility within Iba-dan area.. These depth ranges from 0.607km to 2.48km. The apparent susceptibility map at the cut-off wavelength of 50 m ranges from -0.00012 to 0.00079 which agree with the susceptibility value of some rock types; granite gneiss, migmatite biotite gneiss, biotite muscovite granite, hornblende granite, quartz and schists. The result of the local wavenumber suggests variation along the profiles in the surface of magnetic basement across the study area.

Meliatic blueschists and their detritus in Cretaceous sediments: new data constraining tectonic evolution of the West Carpathians

2018 ◽  
Vol 112 (1) ◽  
pp. 55-81 ◽  
Author(s):  
Dušan Plašienka ◽  
Štefan Méres ◽  
Peter Ivan ◽  
Milan Sýkora ◽  
Ján Soták ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
The West ◽  
West Carpathians

scholarly journals Different Tectonic Evolution of Fast Cooling Ophiolite Mantles Recorded by Olivine-Spinel Geothermometry: Case Studies from Iballe (Albania) and Nea Roda (Greece)

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 64
Author(s):  
Micol Bussolesi ◽  
Giovanni Grieco ◽  
Alessandro Cavallo ◽  
Federica Zaccarini
Keyword(s):  
Tectonic Evolution ◽  
Early Stage ◽  
Mineral Chemistry ◽  
Northern Greece ◽  
Present Contribution ◽  
Cooling Rates ◽  
History Of ◽  
Ferrian Chromite ◽  
Fast Cooling ◽  
Subduction Setting

Mg-Fe2+ diffusion patterns in olivine and chromite are useful tools for the study of the thermal history of ultramafic massifs. In the present contribution, we applied the exponential modeling of diffusion patterns to geothermometry and geospeedometry of chromitite ores from two different ophiolite contexts. The Iballe ophiolite (Northern Albania) hosts several chromitite pods within dunites. Primary and re-equilibrated Mg#, estimated by using an exponential function, provided re-equilibration and primary temperatures ranging between 677 and 996 °C for chromitites and between 527 and 806 °C for dunites. Cooling rates for chromitites are higher than for dunites, suggesting a different genesis for the two lithologies, confirmed also by spinel mineral chemistry. Chromitites with MORB affinity formed in a SSZ setting at a proto-forearc early stage, explaining the higher cooling rates, while dunites, with boninitic affinity, were formed deeper in the mantle in a more mature subduction setting. At the Nea Roda ophiolite (Northern Greece) olivine in chromitites do not show Mg-Fe variations, and transformation into ferrian chromite produced “fake” diffusion patterns within chromite. The absence of diffusion patterns and the low estimated temperatures (550–656 °C) suggest that Nea Roda chromitites were completely re-equilibrated during an amphibolite-facies metamorphic event that obliterated all primary features.

Anisotropy of magnetic susceptibility (AMS) of impact melt breccia and target rocks from the Dhala impact structure, India

2021 ◽  
Author(s):  
Anuj Kumar Singh ◽  
Jayanta Kumar Pati ◽  
Shiva Kumar Patil ◽  
Wolf Uwe Reimold ◽  
Arun Kumar Rao ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Anisotropy Of Magnetic Susceptibility ◽  
Impact Structure ◽  
Magnetic Phases ◽  
Impact Melt ◽  
Rock Samples ◽  
Average Value ◽  
Magnetic Fabrics ◽  
Target Rock ◽  
The Impact

ABSTRACT The ~11-km-wide, Paleoproterozoic Dhala impact structure in north-central India comprises voluminous exposures of impact melt breccia. These outcrops are discontinuously spread over a length of ~6 km in a semicircular pattern along the northern, inner limit of the monomict breccia ring around the central elevated area. This study of the magnetic fabrics of impact breccias and target rocks from the Dhala impact structure identified a weak preferred magnetic orientation for pre-impact crystalline target rocks. The pre- and synimpact rocks from Dhala have magnetite and ilmenite as common magnetic phases. The distributions of magnetic vectors are random for most impact melt breccia samples, but some do indicate a preferred orientation. Our anisotropy of magnetic susceptibility (AMS) data demonstrate that the shape of susceptibility ellipsoids for the target rocks varies from prolate to oblate, and most impact melt breccia samples display both shapes, with a slight bias toward the oblate geometry. The average value for the corrected degree of anisotropy of impact melt rock (P′ = 1.009) is lower than that for the target rocks (P′ = 1.091). The present study also shows that both impact melt breccia and target rock samples of the Dhala structure have undergone minor postimpact alteration, and have similar compositions in terms of magnetic phases and high viscosity. Fine-grained iron oxide or hydroxide is the main alteration phase in impact melt rocks. Impact melt rocks gave a narrow range of mean magnetic susceptibility (Km) and P′ values, in contrast to the target rock samples, which gave Km = 0.05–12.9 × 10−3 standard international units (SI) and P′ = 1.036–1.283. This suggests similar viscosity of the source magma, and limited difference in the degrees of recorded deformation. Between Pagra and Maniar villages, the Km value of impact melt breccias gradually decreases in a clockwise direction, with a maximum value observed near Pagra (Km = 1.67 × 10−3 SI). The poor grouping of magnetic fabrics for most impact melt rock samples implies local turbulence in rapidly cooled impact melt at the front of the melt flow immediately after the impact. The mean K1 for most impact melt samples suggests subhorizontal (<5°) flow in various directions. The average value of Km for the target rocks (4.41 × 10−3 SI) is much higher compared to the value for melt breccias (1.09 × 10−3 SI). The results of this study suggest that the melt breccias were likely part of a sheet-like body of sizeable extent. Our magnetic fabric data are also supported by earlier core drilling information from ~70 locations, with coring depths reaching to −500 m. Our extensive field observations combined with available widespread subsurface data imply that the impact melt sheet could have covered as much as 12 km2 in the Dhala structure, with an estimated minimum melt volume of ~2.4 km3.

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