Publication Date:
2017-04-04
Description:
Venere Lake, in the Pantelleria Island thermal system (Central Mediterranean Sea) consists of a mix of seawater
and hydrothermal volcanic fluids containing high levels of dissolved SiO2. Close to the lake's thermal springs,
siliceous stromatolites are deposed under high bacterial activity conditions whereas roughly interlaminated
Ca-carbonates and microbial mats are widely scattered in the lake. The dissolved REE speciation in lake waters
is dominated by [REE(CO3)2]−, [REE(CO3)]+ and [REE(H3SiO4)]2+ complexes. On the contrary the most
abundant Zr and Hf species are hydroxyl- and fluoride-complexes. The behavior of REE Zr and Hf in the Venere
lake waters is controlled by precipitation of amorphous silica, carbonates and bacterial activity. Chondritenormalized
REE patterns in stromatolites are characterized by positive La anomalies, superchondritic Y/Ho ratios
and negative Eu anomalies. The Eu depletion is also found in microbial mats where is associated to a “chondritic”
Y/Ho signature. Zr and Hf differently behave in dissolved phase and in newly-formed siliceous and carbonatic
material: Hf reacts easily into amorphous silica surfaces whereas Zr is preferentially partitioned onto phosphate
binding sites on microbial cell surfaces similar to the observed behavior of heavy REE (HREE).Wesuggest that the
Zr-Hf relationship reflect the interface processes between mineral phases and bacterial membranes or
compounds produced by bacterial activity.
Description:
Published
Description:
209-215
Description:
4V. Vulcani e ambiente
Description:
JCR Journal
Description:
restricted
Keywords:
Rare Earth Elements, Zr/Hf ratio, Silica-stromatolites, Pantelleria Island
;
04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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