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| Titel |
A high-resolution geochronological and geochemical study on Aegean carbonate deposits, SW Turkey |
| VerfasserIn |
Ezgi Ünal-İmer, I. Tonguç Uysal, Veysel Işık, Jian-xin Zhao, James Shulmeister |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100333
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| Publikation (Nr.) |
 EGU/EGU2014-16265.pdf |
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| Zusammenfassung |
| Vein and breccia carbonates precipitated in highly fractured/faulted carbonate bedrock
were investigated using high-resolution U-series geochronology, as well as through
microstructural and geochemical studies including Sr-O-C isotope and REE element
analyses.
The study area (Kumlubük and Amos vein systems), located south of the town of
Marmaris in SW Turkey, is a part of an active large-scale extensional system. Field studies
show that the calcite veins generally occur sub-vertically and strike mostly NW and EW, in
agreement with the regional N-S extensional stress regime. Microscopic observations indicate
that the calcite veins formed through crack-seal mechanism, typically accompanied/initiated
by intensive hydraulic fracturing of wall-rock evidenced by the presence of widespread
breccia deposits. Vein textures are dominated by elongated, fibrous, and blocky
calcites. Successive fracturing and layering of calcite with sharp contacts are traceable
along the fluid inclusion bands occurring parallel to the wall rock boundary. In
particular, inclusion trails aligned perpendicular to the wall-rock and calcite crystal
elongation give information about the vein dilation (crack opening) vector and growth
direction.
High-resolution U-series dating (11-272 ka BP) and geochemical compositions of the
vein and breccia samples were used to investigate the long-term behaviour as well as the
general identity of the CO2-bearing fluids within deformed crust. The seismic nature of
calcite veining is further assessed by stable isotopic ratio (δ18O and δ13C) plots against vein
depths (distance from the wall-rock). The average δ18OPDBvalue for Kumlubük veins is
-3.79o, while Amos has an average value of -4.05o. Similarly, average carbon isotope ratio
(-8.30o) of the Kumlubük veins is slightly higher than that is observed for the Amos veins
(-9.66o). Isotopic compositions are interpreted to reflect cyclic (or episodic) CO2 variations.
This suggests the presence of several fluid sources and mechanisms (e.g. luid-rock
interaction) indicating the significance of pressure and temperature controls on the evolution
of the CO2-bearing fluid system. Sr-isotope ratios (87Sr/86Sr: 0.7082-0.7085) in
combination with REE compositions are used to trace fluid sources. REE data of the veins
from both regions show typical seawater signatures with distinct negative Ce and
positive Y anomalies, which corresponds well with the REE composition of the host
limestone. While majority of the samples show similar PAAS-normalised REE
variations, some of the veins further display positive Eu anomalies, which could be
indicative of contribution from a deeply derived, hot, and reduced fluid component. |
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