1. Evolution of the Lower Crust in the Point of View of Fluid-Rock Interaction Under the Bakony-Balaton Highland Volcanic Field
Bianca Németh 1,2*
1Lithosphere Fluid Research Lab (LRG), Department of Petrology and Geochemistry, Institute of Geography and Earth Sciences, Eötvös University, Budapest, Hungary
2Eötvös Loránd Geophysical Institute of Hungary (ELGI) *
ISZA
Békéscsaba
5. April, 2013.

2. Outline Introduction Geological settings Results of earlier studies
Petrography
Electronmicroprobe analyses
Raman- and IR analyses
Fluid Evolution
Summary
Acknowledgements

3. Introduction
Studied rock: lower crustal mafic garnet granulite xenoliths from pyroclastics from the Bakony—Balaton Highland Volcanic Field (BBHVF)
Aims: Study the fluid-rock interactions in the lower crust: petrography (reactions, reaction textures)
study fluid and melt inclusions  melt inclusion and fluid compositions, possible sources of melts and types of fluid-rock interactions in the lower crust

4. Geological Settings

5. Mindszentkálla
(Káptalantóti) Sabar-hegy

6. Metamorphic Evolution of the Granulite

7. Petrography Unique samples  SMIs Mineral assemblage Texture
Dry: Grt – Cpx – Pl ± Opx ± Ttn ± Ilm ± Qtz
Wet: ± Bt ± Amp
Grt – Cpx – Pl ± Opx ± Ttn ± Ilm ± Qtz
+SMIs
granoblastic,
equilibrium with reaction texture domains
reaction textures with equilibrium domains

8. The silicate melt inclusions

9. TAS-diagram of the glass phases of silicate melt inclusions

10. IR Analyses on Rock Forming Minerals, and on Host Minerals
57 ±17 ppm
122±37 ppm
600±200 ppm
182±55 ppm
12±4 ppm
137±41 ppm
36±10 ppm
113±34 ppm

11. Water Content – Partial Melting
large scale partial melting
Amp: 2 weight% of structurally bound OH- in their lattice (from the mineral formula) 20000 ppm
The average modal component of the original rock: 15% Amp + 35% garnet + 30% Cpx + 20% Pl.
By estimating the average total water content for the original rock, using the previously mentioned modal components with 0 ppm of water content in the NAMs (Pl; Cpx; Grt): ppm.
vs ~70 ppm

12. Raman Analyses on FI and SMI
CO2+H2O
CO2+H2O
± N2, CH4
CO2+CO+H2S

13. Reconstructed Fluid Evolution
1. Wall-rock part of Sab38 xenolith CO2-dominated ± CO, H2S fluid inclusions Crystallization of Cpx in the vein CO2 + H2O fluid
3. Crystallization of Pl in vein
boiling system
CO2 + H2O fluid became more complex with addition of N2 and CH4.
4. Local reaction: sphene+meltIlm+Cpx±Pl±Opx.
This reaction extracts silica from the originally acidic melt leaving behind a rather mafic melt, trapped in SMIs of Ilm.
5. Interaction with the rising basalt producing secondary FI planes in the xenoliths.

14. Summary
Lower-crustal mafic garnet granulites from Bakony—Balaton Highland Volcanic Field
SMI: Mindszentkálla and Káptalantóti
Difference in microtextures compared to the previously studied samples
The studied SMIs generated by the melting of different parent rocks – e.g. metasediments and metabasalts – in the presence of CO2 and H2O.
Significant partial melting probably related to the extension of the Pannonian Basin when the temperature of the lower crust is significantly increased or remain constant parallel with a continuous decrease of pressure (isotherm decompression).

15. Thank You for your attention!
My supervisors: Kálmán Török and Csaba Szabó
Prof. Rainer Abart (University of Vienna, EMPA)
István Kovács (IR)
the financial support of OTKA NN and for the REG_KM_INFRA_09 Gábor Baross Programme