Person: López Elorza, Maialen
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First Name
Maialen
Last Name
López Elorza
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
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Item Fabric and Fluid Inclusions Characterization of a Stalagmite from Eastern Spain: A Precondition for Noble Gas Analysis by Step-Crushing Methodology(Minerals, 2024) López Elorza, Maialen; Weißbach, Therese; Muñoz García, María Belén; Kluge, Tobias; Aeschbach, Werner; Martín Chivelet, JavierFluid inclusions in stalagmites are becoming increasingly important for paleoclimate research. Within this framework, noble gas thermometry, based on noble gases dissolved in water from fluid inclusions, provides quantitative estimations of cave air paleotemperature. Two major issues of Noble Gas Temperature (NGT) determination on speleothems are (1) the potential lack of enough water for the analysis and (2) the presence of trapped gas not dissolved in water that can be released during the analysis from biphasic or all-gas fluid inclusions, as its contribution to the bulk noble gas signal can hinder NGT results. Although the step-crushing method helps to reduce the second issue, it also decreases the amount of water available for the calculations. In order to obtain reliable NGT results with low uncertainties, a major challenge is still to reach a balance between sufficient water for analysis and a small amount of “atmospheric” gas. The difficulty is that the extraction process cannot be standardized since it strongly depends on the type of sample. The objective of this work is to investigate how the characteristics of the speleothem can determine the adequacy of the extraction process. For this purpose, we consider a stalagmite from a Mediterranean cave that consists of columnar elongated calcite and contains a significant quantity of fluid inclusions, which suggests good potential for NGT analysis. Results, however, were poorly satisfactory. Trying to understand the source of the problems, an integrated study of petrography and petrophysical features was performed. The samples were found to be different depending on the stage of coalescence of crystals and thus separated into “open” and “closed” fabrics. Classic petrographic analysis and non-destructive (nuclear magnetic resonance) techniques were used to characterize the type and amount of fluid inclusions present in both types of fabrics. The study indicates that the closed fabric (total coalescence of calcite crystals) has most water trapped in water-filled, small intracrystalline fluid inclusions that usually contain very little gas. This fabric is very suitable for NGT determination, but since the amount of water is quite small, the sample should be crushed in only one step with a large number of beats to break all the inclusions. In contrast, samples with open fabric (partial coalescence of calcite crystals) contain a higher amount of water and, also, gas-filled large intercrystalline fluid inclusions. For this fabric, step-crushing of the sample is necessary. However, the low amount of water left for the second and third crushings could lead to flawed NGT results. Thus, we suggest modifying the method to get rid of part of the gas in the first crushing while leaving enough water for the following steps. This work shows the importance of characterizing speleothems and fluid inclusions, including their petrography and petrophysical characteristics, before starting NGT analysis, allowing the selection of the most favorable samples and the customization of the step-crushing procedure.Item Fluid-inclusion petrography in calcite stalagmites: Implications for entrapment processes(Journal of sedimentary research, 2021) López Elorza, Maialen; Muñoz García, María Belén; González Acebrón, Laura; Martín Chivelet, JavierFluids trapped in speleothems have an enormous potential in frontier fields of paleoclimate and paleohydrological research. This potential is, however, hampered by diverse scientific and technical limitations, among which the lack of a systematic methodology for genetically characterizing fluid inclusions is a major one, as these can have different origins, and thus, the trapped fluid (usually water), different meanings. In this work, we propose a systematic petrological classification of fluid inclusions, based on: 1) the temporal relation between fluid inclusions and the host calcite, 2) the spatial relation between fluid inclusions and the “crystallites” and crystals aggregates, and 3) the phases (water, air) trapped inside fluid inclusions. The first criterion allows dividing fluid inclusions in two main categories: primary and secondary, whose identification is critical in any research based on trapped fluids. The other two criteria allow the definition of eight types of primary and four types of secondary fluid inclusions. Primary fluid inclusions contain the drip water that fed stalagmites at the time of crystal growth, and can be intercrystalline, i.e., located between adjacent crystallites, or intracrystalline, i.e., with the fluid trapped within crystallites. We differentiate six main types among the intercrystalline fluid inclusions (elongate, thorn-shaped, down-arrow, interbranch, macro-elongate, and bucket) and other two among intracrystalline inclusions (pyriform and boudin). In primary inclusions, water is the main phase, while gas is much less abundant. The presence of gas could be related to slow drip rates or degassing in the cave, but also to later leakage due to changes in temperature and humidity often occurring during inadequate handling of speleothem samples. Secondary fluid inclusions were clearly related to younger water inlet through stratigraphic disruptions or unconformities. They are formed after water infiltration, but sealed before the renewed crystal growth. We differentiate four main types of secondary inclusions: interconnected, rounded, triangular, and vertical fluid inclusions. The identification of primary and secondary fluid inclusions in speleothems is a key for interpretation in paleoclimate studies. Integration of petrological results allow establishment of three different genetic scenarios for the formation of fluid inclusions, whose identification can be relevant because of their predictive character.Item El contaje de puntos como método de estimación de la cantidad de agua de las inclusiones fluidas en espeleotemas(Geotemas, 2021) López Elorza, Maialen; Muñoz García, María Belén; Martín Chivelet, JavierLas inclusiones fluidas albergan el agua que originó el crecimiento del mineral huésped, y su estudio proporciona información relevante sobre las condiciones de crecimiento del propio mineral. En el caso de los espeleotemas, las inclusiones fluidas primarias atrapan el agua de goteo que originó el crecimiento del espeleotema. Esta agua proviene del agua meteórica que se infiltró desde el epikarst hasta la cueva, lo que supone que las inclusiones fluidas albergan el agua fósil derivada de la que precipitó en los alrededores de la cueva durante el periodo de crecimiento del espeleotema. Estas inclusiones de agua presentan una estrecha relación genética con la fábrica calcítica, y su distribución o la cantidad de agua que contienen dependen de las condiciones de crecimiento del cristal colindante. Para poder analizar todo ello, en este trabajo presentamos un nuevo método de estimación de la cantidad de agua de las inclusiones fluidas de los espeleotemas basada en el contaje de puntos petrográfico. Esta técnica permite 1) caracterizar la fábrica de calcita; 2) determinar la relación espacial entre inclusión-calcita; y por último, 3) cuantificar la cantidad de agua y aire que contienen las inclusiones. La técnica pretende ser una herramienta de gran utilidad previa a los diferentes estudios geoquímicos que se llevan a cabo en las inclusiones fluidas de los espeleotemas.Item Comparison of speleothem fabrics and microstratigraphic stacking patterns in calcite stalagmites as indicators of paleoenvironmental change(Quaternary International, 2016) Muñoz García, María Belén; Cruz, J.; Martín Chivelet, Javier; Ortega, Ana Isabel; Turrero, M.J.; López Elorza, MaialenIn the necessary task of obtaining high-resolution paleoclimate series from speleothems, the characterization of their internal microstratigraphy is a useful tool for: a) improving geochronology, and b) reaching a more complete knowledge of the speleothem formation and evolution through time and thus obtaining additional paleoenvironmental information. However, the development of standardized methodologies for microstratigraphic characterization is a pending task. In this paper, two different approaches allow construction of microstratigraphic logs for three stalagmites retrieved from two different caves. The logs correspond to vertical variations in speleothem fabrics and in microstratigraphic stacking patterns. The “fabrics logs” essentially provide information about the drip rate (sometimes used as a precipitation proxy) and the regularity or irregularity of each drip in the short-term. The “microstratigraphic stacking patterns logs” can be interpreted to obtain information about the changes in drip rates in the mid- and long-term. The results show a broad correlation between both kinds of logs that supports their validity as paleoenvironmental proxies. Fabrics formed under relatively constant and regular drips (columnar compact, open and elongated) usually constitute aggradational or progradational microstratigraphic stacking patterns. On the other hand, retractional stacking patterns are usually related with fabrics precipitated under more irregular drips (dendritic and columnar microcrystalline).However, this relation is not rigid and the information obtained from the logs is not equivalent, but complementary. The combination of both logs allows reconstruction of the hydrological history for each drip site. As all the obtained information derives directly from the drip conditions, drip effects result to be very important and can, in some cases, overwhelm the paleoclimate information recorded in each stalagmite.Item Petrografía de inclusiones fluidas en espeleotemas: comparación con calcitas no espeleotémicas(Geotemas, 2016) López Elorza, Maialen; Muñoz García, María Belén; González Acebrón, Laura; Martín Chivelet, JavierLos espeleotemas presentan inclusiones fluidas que pueden utilizarse como proxy paleoclimático ya que sus características dependen de las condiciones físicoquímicas y ambientales bajo las que se generaron. En esta línea, su caracterización petrográfica aparece como una tarea fundamental, previa a cualquier otro tipo de análisis. En este trabajo se presenta el estudio petrográfico de las inclusiones fluidas de dos coladas de Cueva del Cobre (Palencia), que ha permitido clasificarlas en siete tipos en función de su morfología (thorn shaped, boudin shaped, elongate, amorphous, oval shaped, pyriform y round shaped). Todas ellas son monofásicas líquidas. Dependiendo del tipo de morfología de las inclusiones, su posición en relación al cristal encajante es variable, siendo las elongated y thorn shaped exclusivamente intercristalinas, y todas las demás intracristalinas. Un análisis comparativo con inclusiones descritas en calcitas no espeleotémicas revela que las inclusiones fluidas elongated, amorphous y oval shaped son también comunes en esas calcitas, mientras que las pyriform y las boudin shaped no han sido descritas hasta ahora.