Abstract

Doleritic and gabbroic dike swarms cut the Pozanti-Karsanti ophiolite and basal metamorphic sole but do not extend into the underlying melange or platform carbonates. Dike emplacement therefore postdated formation of the ophiolite and metamorphic sole but predated final obduction onto the Tauride-Anatolide Platform. The dikes are compositionally similar to island-arc basalts and basaltic andesites and were affected by retrograde, static hydrothermal metamorphism over temperatures ranging from ∼900 C to below 450 C. Geochemical modeling of trace elements (including REEs) show that the dikes are possibly fractionated products of multiple, compositionally variable parental magmas. The range of parental magmas is interpreted to represent variably mixed melt increments generated through polybaric fractional or continuous melting within a column of rising mantle material. Melt increments extracted from shallower parts of the melting column at lower pressures are more refractory and apparently pooled less efficiently than melt fractions generated from deeper sources and higher pressures. Amphibolite and greenschist facies metabasalt from the subophiolitic sole represent metamorphosed alkalic basalt and MORB-like basalt, respectively. The Pozanti-Karsanti ophiolite probably constituted part of the fore-arc mantle wedge directly above an intra-oceanic subduction zone, whereas the metamorphic sole represents material progressively transferred and accreted to the base of the ophiolite from the downgoing oceanic plate during subduction. Since late-stage pre-obduction dike swarms transect the metamorphic sole, a probable subduction plane, melt generation must have occurred below the Wadati-Benioff Zone and not in the overlying mantle wedge. A probable source of parental liquids for the dikes may therefore be a subducting Neo-Tethyan spreading center.

First Page Preview

First page PDF preview
You do not currently have access to this article.