Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.476580
Title: Structural, metamorphic and geochronological studies in the south-east Tauern
Author: Waters, David John
ISNI:       0000 0001 2446 2865
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1976
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Abstract:
An area of c. 50 km2 within the Altkristallin Sheet (Upper East Alpine Sheet sensu lato) south of the Tauern Window has been mapped at a scale of 1:10,000. The rocks have been tilted southwards by uplift of the Hohe Tauern area, and the mapped area represents a section from deep tectonic levels characterised by early Alpine (80 my) K-Ar mineral ages, through to higher levels with Hercynian (220-300 My) ages. The rocks are mainly metasediments with minor amounts of metamorphosed igneous material. Three principal schist types are distinguished. (i) in the south: phyllitic garnet-muscovite and quartzose schists. (Kreuzeck Schists). (ii) in the north: medium- to coarse-grained mica-schists and para-gneisses (Polinik Schists). (iii) in a central zone: schists intermediate in character between the above (intermediate Schists). The tectonic sequence in the map area has been determined by structural analysis and correlation, and the K-Ar mineral age provinces correlated with episodes of mineral growth. The area underwent a major Hercynian deformation and metamorphic event (F1 and M1) of amphibolite facies, with pelitic assemblages dominated by muscovite and garnet, now preserved in the Kreuzeck Schists. Mineral textures indicate syntectonic growth. Relict eclogites in the Polinik Schists are also assigned to this phase. An F2 deformation increases northwards (i.e. downwards in the Altkristallin Sheet) in both intensity and ductile nature. F2 structure has been synthesised across the map area largely by minor fold correlation. Early Alpine metamorphic recrystallisation also increases downwards, obliterating M1 textures and defining a new foliation, axial-planar to F2 folds. Although mineral growth is post-tectonic, it is suggested that M2 and F2 are part of the same tectonic event. An F3 deformation, involving microfolding, flexuring and local chevron-folding, was followed by late Alpine retrogression (M3) which is patchily distributed over most of the area, but more uniformly developed in greenschist facies in the basal kilometer of the Altkristallin Sheet. The Altkristallin Sheet is broken up into blocks by shear zones of (at least) two generations, distinguished on lithological grounds. Strain in quartz fabrics is related to late structures, probably to late arching of the Altkristallin Sheet (F4), and locally to the development of shear zones. Petrograhic mapping revealed the progressive overprint of M1 by M2 assemblages in the Kreuzeck and Intermediate Schists, with the following features in approximate order of appearance, south to north: (i) growth of biotite and plagioclase porphyroblasts; (ii) gradual increase in muscovite fabric recrystallisation; (iii) growth of staurolite and breakdown of old garnet; (iv) breakdown of M2 staurolite and growth of Al-silicates (sillimanite, andalusite and kyanite). Three isograds may be constructed in the Intermediate Schists: (i) an isograd marking the first appearance of M2 staurolite; (ii) an andalusite-sillimanite isograd; (iii) a garnet-Al silicate-biotite isograd. Isograds (ii) and (iii) have been mapped over an outcrop length of 8 km and a vertical relief of c. 1 km, and are approximately parallel to the M2 regional foliation and the compositional banding. The Polinik schists lie within the stability field of staurolite + quartz, but entirely within the kyanite field, indicating that there are two distinct areas of differing thermal gradient during M2.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.476580  DOI: Not available
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