Cnudde, Veerle

Dewanckele, Jan

Fernández-Valle, ME

Fort, R

López-Arce, P

Martín-Chivelet, J

Muñoz-García, MB

English

Ghent University Academic Bibliography

Geophysical Research AbstractsVol. 14, EGU2012-9016, 2012EGU General Assembly 2012© Author(s) 2012Weathering of speleothems: study of diagenesis with non-destructivetechniquesM.B. Muñoz-García (1), P. López-Arce (2), M.E. Fernández-Valle (3), J. Dewanckele, J. (4), J. Martín-Chivelet(1,2), R. Fort (2), and V. Cnudde (4)(1) Dpto. Estratigrafía, Universidad Complutense de Madrid, Madrid, Spain (mbmunoz@geo.ucm.es), (2) Instituto deGeociencias IGEO - Geosciences Institute IGEO (CSIC-UCM), Spanish Research Council CSIC – Complutense University ofMadrid UCM, Madrid, Spain, (3) Resonancia Magnética Nuclear (Instituto Pluridisciplinar), UCM, Madrid, Spain, (4)Department of Geology and soil science, Ghent University, Krijgslaan 281/ Centre for X-ray tomography B-9000 Gent,BelgiumNon-destructive techniques (NDT): X-Ray Microtomography (CT scan) and Nuclear Magnetic Relaxometry andMagnetic Resonance Imaging (NMR-MRI) have been used to obtain a three dimensional reconstruction of theinner part of a speleothem, since one of the main concerns when working with speleothems is the common needof using destructive techniques for their study, from the first collection inside the cave to the last microscopic orgeochemical analysis.Common calcite microfabrics have been studied, resulting in different porosities and hydric behaviors and, as aconsequence, also different sensibility to diagenetic processes related to the influx of waters.The NMR-MRI technique is sensitive to the magnetization and relaxation times of protons, which allows obtainingan estimation of the amount of water in the sample. In the CT tomography, the diminution of the energy of X-rayspassing through the stalagmite is a function of its density and atomic number. The results of both techniquesshow the porosity distribution, and also the inner textures formed during the growth of the stalagmite and laterdiagenesis. A complete map of fluid inclusions as well as the open porosity fully saturated with water wasobtained, together with relaxometry data related to size, shape and surface-to-volume ratio of the pores.The analyses show that stalagmites can behave as complex, small-scale hydrological systems, and that circu-lation of waters through them following complex nets of interconnected pores might be a common process.As circulation of waters favours diagenetic transformations which involve geochemical and isotopic changes,characterization of flow patterns appears as a key task for outlining areas susceptible of such modifications. Thisis critical in paleoclimate studies based in speleothems, when geochemical and stable isotopic data are used aspaleoenvironmental proxies and absolute ages are obtained by means of radioactive isotope ratios. It has alsoobvious implications for studies based in fluid inclusions in speleothems.These NDT allow determining the diagenetic transformations when substantial changes in drip waters occurin the cave environment, showing a high potential for characterization of any kind of speleothems as well asother continental carbonates. CT scan and NMR-MRI could be very useful tools for helping to select the mostappropriate microfacies for further palaeoclimatic studies.

Weathering of speleothems : study of diagenesis with non-destructive techniques

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Weathering of speleothems : study of diagenesis with non-destructive techniques

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