Southeastern Lewis Hills (Bay of Islands Ophiolite): Geology of a deeply eroded, inside-corner, ridge-transform intersection

Citation
G. Suhr et Pa. Cawood, Southeastern Lewis Hills (Bay of Islands Ophiolite): Geology of a deeply eroded, inside-corner, ridge-transform intersection, GEOL S AM B, 113(8), 2001, pp. 1025-1038
Citations number
52
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
ISSN journal
0016-7606 → ACNP
Volume
113
Issue
8
Year of publication
2001
Pages
1025 - 1038
Database
ISI
SICI code
0016-7606(200108)113:8<1025:SLH(OI>2.0.ZU;2-5
Abstract
The Lewis Hills massif (Say of Islands Ophiolite, Newfoundland) preserves a deeply eroded transform fault. A major, low-angle, extensional mylonite zo ne is next to the transform assemblage and probably merges laterally into i t. The mylonite developed in a high-temperature environment and occurs at t he top of relatively rigid lithospheric mantle. The lithospheric mantle rep resents exhumed, older, arc-type basement of the Little Part Complex that i s also exposed across the transform in the western Lewis Hills. It differs dramatically from an asthenospheric mantle unit of the Bay of Islands Compl ex, exposed in the eastern Lewis Hills, that formed in a spreading ridge en vironment. The fossil ridge-transform segment and associated low-angle normal fault in the Lewis Hills formed at an inside-corner structural setting similar to r ecently discovered core complexes at oceanic ridge-transform intersections. However, the Lewis Hills segment developed in a setting where a spreading center propagated across a transform margin and rifted older arc-type litho sphere. Factors that contributed to formation of the low-angle detachment f ault are the lithospheric nature of the mantle basement, rheological weaken ing and strain focusing by intrusive sills, and weak lateral coupling reali zed by the extensional transform assemblage.