Tectonic evolution of the Betic-Rif orogen constrained by 3-D microstructural analysis and Sm-Nd dating of garnet porphyroblasts

Abstract. The Late Cretaceous Asteroussia event as recorded in the Cyclades is a potential key to the tectonic evolution of Western Tethys. Microstructural analysis and 40Ar/39Ar geochronology on garnet–mica schists and the underlying granitoid basement terrane on the island of Ios demonstrates evidence of a Late Cretaceous high-pressure, medium-temperature (HP–MT) metamorphic event. This suggests that the Asteroussia crystalline nappe on Crete extended northward to include these Gondwanan tectonic slices. In this case, the northern part of the Asteroussia nappe (on Ios) is overlain by the terrane stack defined by the individual slices of the Cycladic Eclogite–Blueschist Unit, whereas in the south (in Crete) the Asteroussia slices are near the top of a nappe stack defined by the individual tectonic units of the external Hellenides. This geometry implies that accretion of the Ios basement terrane involved a significant leap of the subduction megathrust (250–300 km) southward. Accretion needs to have commenced at or about ∼38 Ma, when the already partially exhumed slices of the Cycladic Eclogite–Blueschist Unit began to thrust over the Ios basement. By ∼35–34 Ma, the subduction jump had been accomplished, and renewed rollback began the extreme extension that led to the exhumation of the Ios metamorphic core complex.

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Microstructural analysis of the classical spiral garnet porphyroblasts of south-east Vermont: evidence for non-rotation

Journal of Metamorphic Geology ◽

10.1111/j.1525-1314.1992.tb00106.x ◽

1992 ◽

Vol 10 (4) ◽

pp. 567-587 ◽

Cited By ~ 59

Author(s):

N. HAYWARD

Keyword(s):

Microstructural Analysis ◽

Garnet Porphyroblasts

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Microstructural analysis and tectonic evolution in thrust systems: examples from the Assynt region of the Moine Thrust Zone, Scotland

Deformation Processes in Minerals, Ceramics and Rocks ◽

10.1007/978-94-011-6827-4_10 ◽

1990 ◽

pp. 228-261 ◽

Cited By ~ 9

Author(s):

Robert J. Knipe

Keyword(s):

Tectonic Evolution ◽

Microstructural Analysis ◽

Thrust Zone ◽

Moine Thrust Zone

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Microstructural Analysis of SiO2-Al2O3 Glasses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055059 ◽

1982 ◽

Vol 40 ◽

pp. 562-563

Author(s):

C. M. Jantzen ◽

D. G. Howitt

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Microstructural Analysis ◽

Liquid Immiscibility ◽

Metastable Region ◽

Transmission Electron ◽

Liquidus Temperatures

The mullite-SiO2 liquidus has been extensively studied, and it has been shown that the flattening of the liquidus is related to the existence of a metastable region of liquid immiscibility at sub-liquidus temperatures which is detectable by transmission electron microscopy (TEM) (Fig. 1).

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Applications of ultramicrotomy for materials characterization

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100147004 ◽

1993 ◽

Vol 51 ◽

pp. 232-233

Author(s):

R.T. Blackham ◽

J.J. Haugh ◽

C.W. Hughes ◽

M.G. Burke

Keyword(s):

Materials Science ◽

Microstructural Analysis ◽

Analytical Electron Microscopy ◽

Austenitic Stainless Steels ◽

Specimen Preparation ◽

Preparation Technique ◽

Thermally Induced ◽

Radiation Induced ◽

Characterization Of Materials

Essential to the characterization of materials using analytical electron microscopy (AEM) techniques is the specimen itself. Without suitable samples, detailed microstructural analysis is not possible. Ultramicrotomy, or diamond knife sectioning, is a well-known mechanical specimen preparation technique which has been gaining attention in the materials science area. Malis and co-workers and Glanvill have demonstrated the usefulness and applicability of this technique to the study of a wide variety of materials including Al alloys, composites, and semiconductors. Ultramicrotomed specimens have uniform thickness with relatively large electron-transparent areas which are suitable for AEM anaysis.Interface Analysis in Type 316 Austenitic Stainless Steel: STEM-EDS microanalysis of grain boundaries in austenitic stainless steels provides important information concerning the development of Cr-depleted zones which accompany M23C6 precipitation, and documentation of radiation induced segregation (RIS). Conventional methods of TEM sample preparation are suitable for the evaluation of thermally induced segregation, but neutron irradiated samples present a variety of problems in both the preparation and in the AEM analysis, in addition to the handling hazard.

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