The Pacific Ocean evolved from the Panthalassic Ocean that was first formed ca 750 Ma with the rifting apart of Rodinia. By 160 Ma, the first ocean floor ascribed to the current Pacific plate was produced to the west of a spreading centre in the central Pacific, ultimately growing to become the largest oceanic plate on the Earth. The current Nazca, Cocos and Juan de Fuca (Gorda) plates were ini...

Dicussions 882 Despite the often divergent opinions regarding the evolution of the Teslin suture zone (TSZ), previous tectonic models broadly agree that the TSZ comprises a ductile shear zone that constitutes a fundamental crustal boundary (e.g., Tempelman-Kluit 1979; Erdmer 1985; Hansen 1989; Stevens and Erdmer 1996; Hansen and Dusel-Bacon 1998). In contrast, de Keijzer et al. (1999) offer a r...

Abstract In shallow-water limestones of the Plassen Formation in Tirolic nappe Northern Calcareous Alps, bauxite was formed on karstified and tilted platform margin grainstones to boundstones around ?Kimmeridgian/Tithonian boundary, or Early Tithonian as proven by Protopeneroplis striata Weynschenk, Labyrinthina mirabilis Salpingoporella pygmaea Gümbel. The established top obducted ophiolite st...

A common deviation from typical subduction models occurs when thrust sheets of oceanic crust and upper-mantle rocks are emplaced over more buoyant continental lithosphere. The archetypal example ophiolite obduction is the Semail in United Arab Emirates (UAE)-Oman orogenic belt, formed obducted onto Arabian margin during Late Cretaceous. Strait Hormuz syntaxis, northern extent UAE-Oman mountains...

Fluids circulate through the Earth's crust perhaps down to depths as great as 5^15 km, based on oxygen isotope systematics of exhumed metamorphic terrains, geothermal fields, mesozonal batholithic rocks and analysis of obducted ophiolites. Hydrothermal flows are driven by both thermal and chemical buoyancy; the former in response to the geothermal gradient and the latter due to differences in s...

Studies of the high-pressure (HP) As Sifah eclogites in NE Saih Hatat Window, Oman, have used different combinations radiometric dating results (Ar/Ar, Sm-Nd vs. U-Pb, Rb-Sr) to interpret disparate tectonic models for timing, geometry, and cause continental subduction—including its relationship Samail Ophiolite. To determine timing subduction, we coupled petrochronological analyses major (garne...

Abstract Ordovician and Silurian siliciclastic, volcanic, plutonic rocks in the southern Appalachian eastern Blue Ridge western Inner Piedmont, formerly interpreted as components of an obducted Taconic arc terrane, are recognized parts paired arc/back-arc system that formed on seaward edge Laurentian plate. New crystallization ages from metamorphosed plutonic-volcanic intruding intercalated wit...

S U M M A R Y We argue that subduction may be initiated at passive continental margins without shortening the lithosphere. Overcoming the lithosphere’s high compressive strength requires special circumstances, and these make it difficult to explain the nearly complete recycling of old sea-floor. Instead, we present a model that predicts tensile decoupling of the continental and oceanic lithosph...