Origin of palaeofluids in a normal fault setting in the Aegean region

Abstract

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 (T m 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 d 18 O 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 d 13 C 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.

Different styles of faulting deformation along the Dead Sea Transform and possible consequences for the recurrence of major earthquakes

“…The different CL-patterns are best interpreted in terms of changing redox conditions (Meyers, 1978). The older brightly luminescent cement could be precipitated under meteoric phreatic to deep burial conditions, while the younger blue or non-luminescent cement is thought to have precipitated under near surface oxidizing conditions (Verhaert et al, 2004).…”

Travertine occurrences along major strike-slip fault zones: structural, depositional and geochemical constraints from the Eastern Anatolian Fault System (EAFS), Turkey

“…In contrast, the other vein set (e.g. nonhydrothermal veins), with low Sr and negative δ 13 C values (Sr: 52-83 ppm, δ 13 C: −11.0 to −2.7‰ V-PDB) ( Figure 15, Table 2), has been precipitated from shallow circulated surface waters, as in speleothems (Fairchild et al, 2006;Uysal et al, 2011;Verhaert et al, 2004).…”

“…In tectonically active regions, vein formation is widespread and are associated with fluid circulation and fault reactivation (De Filippis et al, 2012;Özkul et al, 2013;Uysal et al, 2009Uysal et al, , 2011Verhaert et al, 2004).…”

“…Some of them, such as those in southwest Turkey, have been named as 'non-hydrothermal vein' (Uysal et al, 2011) and/or 'extension vein' similar to speleothems (e.g. stalagmite, stalagtite and flowstone) that resulted from shallow-seated surface waters circulating within the fracture network (Verhaert et al, 2004). It is known that speleothems grow mostly during warm/wet periods (Baker, Smart, & Edwards, 1995;Baykara, 2014;Fairchild et al, 2006;Wang et al, 2004).…”

“…Mineralogical composition of travertines and associated veins, which are precipitated by hydrothermal or nonhydrothermal fluids circulating in damage zones in tectonically active regions Uysal et al, 2007Uysal et al, , 2011Verhaert et al, 2004), was controlled by a complex set of interrelated parameters (Jones & Renaut, 2010).…”