Geochemical features of lithospheric mantle beneath Wilcza Góra (Eger Rift, SW Poland): inferences from noble gases and CO2 in fluid inclusions of peridotite xenoliths
Abstract
The investigation of mantle-derived products coming from the subcontinental lithospheric mantle (SCLM) is crucial for constraining its geochemical features and evolution. This work investigates a selection of mantle xenoliths from Wilcza Góra (SW Poland), integrating the petrography and geochemistry of minerals with the chemical and isotope composition of fluid inclusions. These xenoliths were brought to the surface by intraplate alkaline basalts, intensely outpoured a few tens of kilometres outside the northern part of the Eger Rift, a NE branch of the Rhine-Eifel Rift. Nodules are mostly harzburgites with occurrence of amphibole. Olivine crystals are classified in two groups based on forsterite content: 1) Fo88.9-91.5, which account for a fertile to depleted mantle; 2) Fo85.5-88.1, which testify for a large interaction with circulating (basic) melts. Analogously orthopyroxene and clinopyroxene show two ranges of mg{#} (molar Mg/Mg+Fe) and clear evidences of recrystallization due to interaction with metasomatic melt/s (Matusiak-Malek et al., 2017). Fluid inclusions hosted in minerals are dominated by CO2, as independently observed in a previous study (Ladenberger et al., 2009), with N2 as second major species. The carbon isotope composition of CO2 (δ13C V-PDB) ranges between -4.7‰ and -3.1‰ and is not related to the CO2 concentration excluding any influence of magmatic degassing. Olivine crystals have a slightly less negative ratios (-3.8± 0.4‰ compared to orthopyroxene (-4.1±0.4‰, falling within typical MORB range (-8‰)
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2018
- Bibcode:
- 2018EGUGA..2018539R