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Production of multi‐décollement folding by pressure release in the formation of a microbreccia at Lough Doon, Donegal, eire
Author(s) -
Holder M. T.
Publication year - 1984
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350190405
Subject(s) - breccia , geology , dalradian , décollement , deformation (meteorology) , geochemistry , folding (dsp implementation) , petrology , metamorphism , oceanography , engineering , electrical engineering , sedimentary rock
An unusual matrix‐supported microbreccia of Caledonian age is described from the Dalradian rocks of Donegal. Field and textural relationships indicate that the breccia formed ‘in situ’ by a non‐dilational mechanism during regional deformation. The presence of breccia veins of low competancy during this deformation caused multi‐décollement folds to be formed adjacent to the breccias. A cyclical mechanism of formation of these breccias is proposed in which fluctuations in the overpressuring of pore fluids escaping from an adjacent crystallizing appinite mass caused periodic excursions from ductile to brittle deformation during the regional folding.