Origin of palaeofluids in a normal fault setting in the Aegean region
| Autor: | E. J. Hodge, Eddy Keppens, Griet Verhaert, D. A. Richards, Sara Vandycke, Ph. Muchez, Dominique Similox-Tohon, Manuel Sintubin |
|---|---|
| Rok vydání: | 2004 |
| Předmět: | |
| Zdroj: | Geofluids. 4:300-314 |
| ISSN: | 1468-8123 1468-8115 |
| Popis: | The province of Burdur (SW Turkey) is seismically an active region. A structural, geochronological, petrographical, geochemical and fluid inclusion study of extension veins and fault-related calcite precipitates has been undertaken to reconstruct the palaeofluid flow pattern in this normal fault setting in the Aegean region. A palaeostress analysis and U/Th dating of the precipitates reveals the neotectonic significance of the sampled calcites. Fluid inclusion microthermometry of calcites-filling extension veins shows final melting temperatures (Tm ice) of 0°C. This indicates pure water, most likely of meteoric origin. The oxygen isotope values (−9.8‰ to −6.5‰ VPDB) and the carbon isotopic composition (−10.4‰ to −2.9‰ VPDB) of these calcites also show a near-surface meteoric origin of the fluid responsible for precipitation. The microstructural characteristics of fault-related calcites indicate that calcite precipitation was linked with fault activity. Final melting temperature of fault-related calcites ranges between 0 and −1.9°C. The oxygen isotope values show a broad range between −15.0‰ and −2.2‰ VPDB. Several of these calcites have a δ18O composition that is higher or lower than the oxygen isotopic composition of meteoric calcites in the area (i.e. between −10‰ and −6‰ VPDB). The δ13C composition largely falls within the range of the host limestones and reflects a rock-buffered system. Microthermometry and stable isotopic study indicate a meteoric origin of the fluids with some degree of water–rock interaction or mixing with another fluid. Temperatures deduced from microthermometry and stable isotope analyses indicate precipitation temperatures around 50°C. These higher temperatures and the evidence for water–rock interaction indicate a flow path long enough to equilibrate with the host–rock limestone and to increase the temperature. The combined study of extension vein- and fault-related calcite precipitates enables determining the origin of the fluids responsible for precipitation in a normal fault setting. Meteoric water infiltrated in the limestones to a depth of at least 1 km and underwent water–rock interaction or mixing with a residual fluid. This fluid was, moreover, tapped during fault activity. The extension veins, on the contrary, were passively filled with calcites precipitating from the downwards-migrating meteoric water. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|