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| Titel |
Title: Sorption of the Rare Earth Elements and Yttrium (REE-Y) in calcite: the mechanism of a new effective tool in identifying paleoearthquakes on carbonate faults |
| VerfasserIn |
Daniel Moraetis, Vasiliki Mouslopoulou, Alexandros Pratikakis |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104017
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| Publikation (Nr.) |
 EGU/EGU2015-3437.pdf |
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| Zusammenfassung |
| A new tool for identifying paleoearthquakes on carbonate faults has been successfully
tested on two carbonate faults in southern Europe (the Magnola Fault in Italy and
the Spili Fault in Greece): the Rare Earth Element and Yttrium (REE-Y) method
(Manighetti et al., 2010; Mouslopoulou et al., 2011). The method is based on the
property of the calcite in limestone scarps to absorb the REE and Y from the soil
during its residence beneath the ground surface (e.g. before its exhumation due to
earthquakes). Although the method is established, the details of the enrichment
mechanism are poorly investigated. Here we use published data together with new
information from pot-experiments to shed light on the sorption mechanism and the time
effectiveness of the REE-Y method. Data from the Magnola and Spili faults show that the
average chemical enrichment is ~45%, in REE-Y while the denudation rate of the
enriched zones is ~1% higher every 400 years due to exposure of the fault scarp in
weathering. They also show that the chemical enrichment is significant even for short
periods of residence time (e.g., ~100 years). To better understand the enrichment
mechanism, we performed a series of pot experiments, where carbonate tiles extracted
from the Spili Fault were buried into soil collected from the hanging-wall of the
same fault. We irrigated the pots with artificial rain that equals 5 years of rainfall in
Crete and at temperatures of 15oC and 25oC. Following, we performed sorption
isotherm, kinetic and pH-edge tests for the europium (Eu), the cerium (Ce) and the
ytterbium (Yt) that occur in the calcite minerals. The processes of adsorption and
precipitation in the batch experiments are simulated by the Mineql software. The
pot experiments indicate incorporation of the REE and Y into the surface of the
carbonate tile which is in contact with the soil. The pH of the leached solution during
the rain application range from 7.6 to 8.3. Nutrient release like Ca is higher in the
leached solution at lower temperature (15oC) probably due to higher calcite solubility
(higher dissolved CO2(g) content) and to less adsorption capability of the soil in
elevated temperatures. The isotherm sorption modeling showed that REE-(CO3)2
precipitation is the dominant mechanism in the incorporation of REE into calcite, while the
kinetic tests showed instant REE sorption (within few hours). Our experiments show
that pH>7.5 and temperatures ~25Ë C favor REE-Y sorption on calcite surface.
Hence, due to the REE-Y fast interaction with carbonate scarp face and the low
denudation rate due to later weathering, the REE-Y method is considered a reliable
method for tracing paleoearthquakes along carbonate fault scarps when the scarp is
in contact with soil at temperate climates. The resolution of identifying frequent
paleoearthquakes with low residence time in contact with soil is also considered
high.
References
Mouslopoulou, V., Moraetis, D., Fassoulas, C., 2011. Earth Planet. Sci. Lett. 309,
45-55.
Manighetti, I., Boucher, E., Chauvel, A., Schlagenhauf, A., Benedetti, L., 2010.
Terra Nova 22, 477-482. |
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