Abstract
This thesis provides new constraints for the origin and structural evolution of ophiolite nappes. These constraints involve new data from detailed and integrated field studies of the Brooks Range ophiolite and Timor, Indonesia, where similar tectonic processes can be sampled and studied in various deformational stages and structural levels. Comparative studies were also conducted in similar belts in Oman and Taiwan.
The Middle Jurassic Brooks Range ophiolite is emblematic of Tethyan-type ophiolite associations. It formed by multiple intrusions above a zone of intense partial melting of depleted mantle - a feature alcin to intra-oceanic arc environs. Sub-ophiolite metamorphic rocks document that the Brooks Range ophiolite was formed near, and was immediately emplaced onto, T-type Mid-oceanic ridge basalts (MORB) lavas of the Copter Peak allochthon, which may represent lavas and sediments of the Ellesmerian passive continental margin. Emplacement involved passive roof thrusting and later phases of extensional attenuation along down-to the-north detachment faults which 1) dip away from basement culminations; 2) cut down section in the direction of transport; 3) truncate, rotate and re-activate contractional structures; 4) omit structural section; and 5) juxtapose the BRa with thermally immature and structurally lowest allochthons.
Timor is part of the Neogene Banda orogenic arc which represents a modern, immature analogue of the Brooks Range. The allochthons in Timor document the progressive collision between that part of the Banda allochthon, represented by the forearc basement, Banda intra-oceanic volcanic are, and the Jurassic-Pliocene passive continental margin of NW Australia. Three major deformational phases of the collision are recognized: 1) frontal accretion, 2) allochthon emplacement. and 3) culmination development. The continental basement and arc-type cover sequences
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