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Title: The structural and metamorphic geology of the Tonale Pass area, Northern Italy
Author: Mendum, John Richard
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1976
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The area mapped lies astride the Tonale Line, a major, east-west, sub-vertical lineament marked by 10 to 70 m of brecoiated pseudotachylite. This zone of repeated movement divides the area into two major units, the Southern and Central Alps. Regional Alpine northward thrusting is restricted to the Central Alps which lie north of the Tonale Line. The Southern Alps consist of Greenschist grade metasediments which have been folded by the Heroynian and Alpine events. These rooks are intruded by the Adamello Massif, a composite calo-alkaline body of Oligocene age, which has a narrow metamorphic aureole. The tonalite and biotite-quartz-diorite within the area mapped are foliated adjacent to their northern margins, and strain values have been calculated from deformed xenoliths. The Central Alps consist of three distinct units: 1. The Stavel Gneiss, a 0.7 to 1 km wide zone of massive quartz-K-feldspar-phengite gneiss, lies adjacent to the Tonale Line. The gneiss formed from banded politic gneiss under high PH20 at moderate temperatures. Only Late Alpine folding is seen. Mineral compositions for phengites and co-existing feldspars are given and factors determining phengite composition and d spacing discussed. 2. The thrust sheets north of the Stavel Gneiss are composed of Caledonian Upper Amphibolite grade politic gneiss, marble and amphibolite. The rocks form a large 'backfold' which apparently 'roots' to the south. Heroynian, Early and Late Alpine folding and metamorphism have affected the gneisses although these events are localised in some areas. The mylonite zones which separate individual thrust sheets have been studied using available strain markers, microtestures, magnetic anisotropy and minor fold geometry. The mylonites formed by ductile flow under high shear stress along narrow wet zones, initiated as 'contact strain' areas. 3. North of the Peio Line, a Late Alpine mylonite zone, are a series of semipolitic schist showing evidence of Heroynian and Early Alpine deformation and metamorphism. These metasediments form the upper part of a larger thrust sheet.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available