CASETTA, Federico

COLTORTI, Massimo

FACCINI, Barbara

Italiano, Francesco

Ntaflos, Theodoros

RIZZO, ANDREA LUCA

English

Andrea Luca Rizzo

Massimo Coltorti

Barbara Faccini

Federico Casetta

Theodoros Ntaflos

Francesco Italiano

Archivio istituzionale della ricerca - Università di Ferrara

EGU2020-14005, updated on 22 Jun 2021https://doi.org/10.5194/egusphere-egu2020-14005EGU General Assembly 2020© Author(s) 2021. This work is distributed underthe Creative Commons Attribution 4.0 License.Geochemistry of noble gas and CO2 in fluid inclusions fromlithospheric mantle beneath Eifel and Siebengebirge (Germany)Andrea Luca Rizzo1,2, Massimo Coltorti2, Barbara Faccini2, Federico Casetta2, Theodoros Ntaflos3,and Francesco Italiano11Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Palermo, Italy (andrea.rizzo@ingv.it)2Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Ferrara, Italy3Department of Lithospheric Research, University of Vienna, Vienna, AustriaThe study of fluid inclusions (FI) composition (He, Ne, Ar, CO2) integrated with the petrography andmineral chemistry of mantle xenoliths representative of the Sub Continental Lithospheric Mantle(SCLM) is a unique opportunity for constraining its geochemical features and evaluating theprocesses and the evolution that modified its original composition. An additional benefit of thistype of studies is the possibility of better constraining the composition of fluids rising through thecrust and used for volcanic or seismic monitoring.  In this respect, the volcanic areas of Eifel and Siebengebirge in Germany represent a greatopportunity to test this scientific approach for three main reasons. First, these volcanic centersdeveloped in the core of the Central European Volcanic Province where it is debated whether thecontinental rift was triggered by a plume (Ritter, 2007 and references therein). Second, Eifel andSiebengebirge formed in Quaternary (0.5-0.01 Ma) and Tertiary (30-6 Ma), respectively, thusspanning a wide range of age. Third, Eifel is characterized by the presence of CO2-dominated gasemissions and weak earthquakes that testify that local magmatic activity is nowadays dormant,but not ended (e.g., Bräuer et al., 2013). It is thus important to better constrain the noble gassignature expected in surface gases in case of magmatic unrest.This work focuses on the petrological and geochemical study of mantle xenoliths sampled in theWest Eifel and Siebengebirge volcanic areas (Germany) and aims at enlarging the knowledge of thelocal SCLM. Gautheron et al. (2005) carried out the first characterization of noble gases in FI ofcrystals analyzed by crushing technique (as in our study) but limited to olivines and to West Eifeleruptive centers. Here, we integrate that study by analyzing olivines, orthopyroxenes andclinopyroxenes from a new suite of samples and by including two eruptive centers fromSiebengebirge volcanic field (Siebengebirge and Eulenberg quarries).Xenoliths from the Siebengebirge localities are characterized by the highest Mg# for olivine,clinopyroxene and Cr# for spinel, together with the lowest Al2O3contents for both pyroxenes,suggesting that the mantle beneath Siebengebirge experienced high degree of melt extraction (upto 30%) while metasomatic/refertilization events were more efficient in the mantle beneath WestEifel.In terms of CO2and noble gas concentration, clinopyroxene and most of the orthopyroxene showthe highest gas content, while olivine are gas-poor. The3He/4He varies between 5.5 and 6.9 Ra.These values are comparable to previous measurements in West Eifel, mostly within the rangeproposed for European SCLM (6.3±0.4 Ra), and slightly below that of MORB (Mid-Ocean RidgeBasalts; 8±1Ra). The Ne and Ar isotope ratios fall along a binary mixing trend between air andMORB-like mantle. He/Ar* in FI and Mg# and Al2O3content in minerals confirm that the mantlebeneath Siebengebirge experienced the highest degree of melting, while themetasomatic/refertilization events largely affected the Eifel area.ReferencesBräuer, K., et al. 2013. Chem. Geol. 356, 193–208.Gautheron, C., et al. 2005. Chem. Geol. 217, 97–112.Ritter, J.R.R., 2007. In: Ritter, J.R.R., Christensen, U.R. (Eds.), Mantle Plumes: A MultidisciplinaryApproach. Springer-Verlag, Berlin Heidelberg, pp. 379–404.Powered by TCPDF (www.tcpdf.org)

Geochemistry of noble gas and CO2 in fluid inclusions from lithospheric mantle beneath Eifel and Siebengebirge (Germany)

https://iris.unife.it/bitstream/11392/2419400/2/EGU2020-14005-print.pdf

Geochemistry of noble gas and CO2 in fluid inclusions from lithospheric mantle beneath Eifel and Siebengebirge (Germany)

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Archivio istituzionale della ricerca - Università di Ferrara