ΠΜΣ με ειδίκευση στη Στρωματογραφία - Παλαιοντολογία
Library of the School of Science

2015-03-06

2015

Υψηλάντη Ελένη

Φ. Πομόνη-Παπαϊωάννου Καθηγήτρια (Επιβλέπουσα), Μ. Σταματάκης Καθηγητής, Β. Καρακίτσιος Καθηγητής

Ιζηματολογική Μελέτη των Τριαδικών Ουρανιούχων Φωσφορούχων Ανθρακικών Σχηματισμών του Όρους Κιθαιρώνα

Greek

Sedimentological Study of the Triassic Uraniferous Phosphatic Carbonate Rocks of Mountain Kitheron

The study focuses on a formation that belongs to the Middle-Upper Triassic of
the Sub-Pelagonian zone and is characterized as phosphatic dolomitic
limestone/dolostone, situated in the area of NW Attica region, at Mt Kitheron.
The radioactivity of the carbonate rocks of the afore-mentioned formation was
checked with a Geiger counter that revealed high anomalies for common
carbonates.
Apatite occurs as angular and in rare cases prismatic grains hosted in the
groundmass of the dolostone or dolomitic limestone. In some cases the analysis
of these grains revealed the presence of Uranium, confirming the fact that
apatite acts as a bearer incorporating Uranium into its crystal lattice, while
Sr, V, S and Fe enrichments were detected either associated with the apatite or
not.
Microfacies analysis of the studied formation showed deposition in a peritidal
environment and more specifically in a shallow intertidal to
supratidal-pedogenic environment. Regarding dolomitization, two phases were
recognized: the first one that resulted in microcrystalline dolomite formation
is considered that happened penecontemporaneously and/ or during the early
diagenesis in a mixing zone of meteoric and seawater rather than a sabkha type
(absence of evaporitic minerals and low Sr values) and the second phase that
resulted in larger dolomite crystals, characterized by irregular edges and
disruption of the original tissue elements and texture that took place during
late/burial diagenesis. Phosphorus content of the dolomitic limestones and or
dolostones reaching max. 8190ppm (attributed to 5% of hydroxylapatite content)
is not sufficient, in order for these rocks to be characterized as
phosphorites, while a low U-enrichment (max 92ppm) cannot justify the presence
of U-metallogeny. On the other hand P and U are strongly correlated (R=0,96),
suggesting substitution of Ca cations by U respectively. Based on the fact that
V was not observed in the microanalysis of the apatite grains, and is found
with other elements like Fe, Al, Si, we could assume that its presence is
attributed to basic/ultrabasic surrounding formations. The presence of higher
amounts of Uranium in joins and fissures of the rock during dry periods, judge
for its secondary migration by meteoric waters towards the surface where it was
concentrated by evaporation.

Kitheron, Dolomitization, Phosphatic Carbonate Rocks, Uranium, Triassic Carbonate Rocks

No

0

Yes

100

138

File access is restricted only to the intranet of UoA.

https://pergamos.lib.uoa.gr/uoa/dl/object/1318007