Evolution of the Acipayam (Denizli,Turkey) Rodingites |
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| Abstract: | Numerous diabase and gabbro dikes intrude the Lycian peridotite thrust sheet of southwestern Turkey. Some of the dikes are rodingitized and the host harzburgite is serpentinized. The present study demonstrates that the major episodes of serpentinization (of harzburgite) and rodingitization (of dikes) predated the obduction of the Lycian peridotite thrust sheet. Hydrogrossular veins, which represent the major event of calcium metasomatism in the dikes, are locally fractured, fragmented, and offset. High-field-strength-element concentrations and Ta/Yb-Th/Yb ratios in the mafic rocks suggest that the dikes were originally emplaced in an island-arc environment; thus, they must have been transported to their current location. Fluid-inclusion microthermometry obtained on primary fluid inclusions in hydrogrossulars indicates that the fluid involved in rodingitization and contemporaneous serpentinization was moderately saline (8 equiv. wt% NaCl) and within the range of 250°-450°C. The above salinity and temperature are consistent with microthermometric measurements obtained from rodingite minerals worldwide. It is apparent from our study that rodingite geochemistry and mineralogy provide valuable information on the tectonic and metamorphic evolution of a region. Trace-element and REE geochemistry can define the tectonic setting of dikes, detailed mineralogy of the dikes and host serpentinite provides information on the relative timing of serpentinization and contemporaneous rodingitization, and fluid-inclusion microthermometry provides information on the temperature and composition of the Ca-rich metamorphic fluids. |
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