Details

Autor(en) / Beteiligte

• Mormone, A.
• Troise, C.
• Piochi, M.
• Balassone, G.
• Joachimski, M.
• De Natale, G.

Titel

Mineralogical, geochemical and isotopic features of tuffs from the CFDDP drill hole: Hydrothermal activity in the eastern side of the Campi Flegrei volcano (southern Italy)

Ist Teil von

• Journal of volcanology and geothermal research, 2015-01, Vol.290, p.39-52

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2015

Quelle

ScienceDirect

Beschreibungen/Notizen

• A 506m drill-hole has been recently drilled in the framework of the Campi Flegrei Deep Drilling Project (CFDDP) and the International Continental Scientific Drilling Program (ICDP) with the intention of coring the subsurface in the eastern sector of the Campi Flegrei caldera. The borehole, located in the western district of the Neapolitan city (Bagnoli Plain) 3km to the east of the most active volcanic area and about 5m above sea level, is now targeted for monitoring purposes. This paper reports the results obtained from the analysis of two short cores collected at depths of −443 and −506m below the ground level. The cores sampled two pre-caldera tuffs. Observations performed by optical and scanning electron microscopy, energy dispersive spectroscopy and powder X-ray diffraction were used to achieve data on the primary lithology, both primary and secondary mineralogical assemblages, and the relationship between texture and secondary mineralization. Sr isotope ratios were determined on selected primary feldspars, whereas δ13C and δ18O analyses were performed on carbonates from veins and filled-voids in tuffs. Our results provide information on the hydrothermal system in the eastern sector of the caldera that was not among the goals in the previous drilling programs. Secondary mineralization suggests a saline hydrothermal environment characterized by fluids that progressively evolved from boiling toward more alkaline and cooler conditions. A paleo-temperature of ca. 160°C has been inferred from authigenic mineral occurrences and calculated on the basis of equilibria between cored calcites and fluids presently emitted at the surface, by using carbon and oxygen isotope data. The temperature measured at the bottom of the drilling is about 80°C. •The 443–506m subsurface in the eastern sector of the Campi Flegrei caldera has been cored during the CFDDP drilling.•The neogenic assemblages record the past hydrothermal state and support boiling conditions.•δ13C and δ18O of calcite have been determined and compared with data available on the present day fluid emissions.•A difference of up to 100°C has been detected between present temperature and the fossil one registered in neogenic minerals.