Novel applications of fluid inclusions and isotope geochemistry in unravelling the genesis of fossil travertine systems

Abstract

The Denizli Basin is a fault-bounded Neogene-Quaternary depression located in the Western Anatolian Extensional Province, Western Turkey. The basin is a unique geological site with abundant active and fossil (Quaternary) travertine and tufa deposits. Fluid inclusion microthermometry and isotopic analysis were applied to study the genesis of the Ballk fossil travertine deposits, located in the south-eastern part of the basin. Microthermometry on fluid inclusions indicates that the main travertine precipitating and cementing fluids are characterized by low salinity (<07wt% NaCl equivalent) and variable temperatures that cluster at <50 degrees C and ca 100 degrees C. Fluids of meteoric origin have been heated by migration to the deeper subsurface, possibly in a local high geothermal gradient setting. A later uncommon cementation phase is related to a fluid with a significantly higher salinity (255 to 260wt% bulk). The fluid obtained its salinity by interaction with Late Triassic evaporite layers. Strontium isotopes indicate that the parent carbonate source rock of the different travertine precipitates is very likely to be the Triassic limestone of the Lycian Nappes. Carbon isotopes suggest that the parent CO2 gas originated from thermal decarbonation of the Lycian limestones with minor contributions of magmatic degassing and organic soil CO2. Oxygen isotopes confirm the meteoric origin of the fluids and indicate disequilibrium precipitation because of evaporation and degassing. Results were integrated within the available geological data of the Denizli Basin in a generalized travertine precipitation model, which enhanced the understanding of fossil travertine systems. The study highlights the novel application of fluid inclusion research in unravelling the genesis of continental carbonates and provides several recommendations for hydrocarbon exploration in travertine-bearing sedimentary basins. The findings suggest that travertine bodies and their parent carbonate source rocks have the potential to constitute interesting subsurface hydrocarbon reservoirs

Geobody architecture, genesis and petrophysical characteristics of the Budakalász travertines, Buda Hills (Hungary)

“…The lime mudstones of the marsh-pool facies can be considered an exception, with a higher occurrence of 'primary' micrite. directly reflects the Sr isotopic composition of their precipitating fluids (Minissale et al, 2002;El Desouky et al, 2015). Based on the reported geological setting, the travertine bearing fluids could have interacted with Late Triassic, Eocene and/or to limited extent with Miocene carbonate sequences within the TR (Fig.…”

Investigating fossil hydrothermal systems by means of fluid inclusions and stable isotopes in banded travertine: an example from Castelnuovo dell’Abate (southern Tuscany, Italy)

“…However, the application of this technique to travertine deposits is rather new (Słowakiewicz 2003;Gibert et al 2009;El Desouky et al 2015) and has not been attempted before on Italian deposits. Fluid inclusions investigation in travertine is potentially complicated by: (1) the generally small size of the fluid inclusions (Pentecost 2005); (2) their metastability, which prevents the nucleation of the bubble upon cooling from the trapping conditions to room temperature (Shepherd et al 1985;Diamond 2003); (3) the intrinsic difficulties in performing microthermometric analysis in calcite, which is often subjected to anelastic stretching phenomena (Roedder 1984;Shepherd et al 1985), that may lead to misinterpretation of the results.…”

Comparative study of the Pleistocene Cakmak quarry (Denizli Basin, Turkey) and modern Mammoth Hot Springs deposits (Yellowstone National Park, USA)

“…These values have been interpreted as original nondiagenetic differences that reflect changes in spring fluid sources spatially or through time . Oxygen stable isotopes and radiogenic Sr-isotopes indicate that carbonates and evaporites of the thrusted, Triassic Lycian nappes were flushed by and interacted with infiltrating meteoric waters, providing the Ca 2þ and HCO 3 À source El Desouky et al, 2015).…”

“…The slope Facies C2, consisting of alternating beds of encrusted, hanging macrophyte branches (phyto fabric) and crust fabrics, is recurrent in the deposits of the Ballık area, but has no equivalent in the MHS Complex. Preliminary, initial estimates of the water temperature during travertine precipitation, based on d 18 O travertine and fluid inclusion temperature data El Desouky et al, 2015), suggest overall temperatures in a broad range between 18 and possibly 46 C in the Ballık area. The phyto fabric of hanging, encrusted macrophyte branches, furthermore resembles those of some cooler spring carbonate deposits (Pedley and Rogerson, 2010;Camuera et al, 2014), called 'barrages'.…”

“…Often, a distinction has been made between cool water 'tufa' and warm or hot water 'travertine' deposits (Ford and Pedley, 1996;Pedley, 2009). Such classification, however, proves difficult when mapping ancient travertine in the field (Brasier, 2011;Capezzuoli et al, 2014;Cantonati et al, 2016).…”