The genesis of actively growing siliceous stromatolites: Evidence from Lake Specchio di Venere, Pantelleria Island, Italy

Geochemistry and mineralogy of a complex sedimentary deposit in the alkaline volcanic Lake Specchio di Venere (Pantelleria Island, south Mediterranean)

“…Lake waters are supersaturated with respect to aragonite, calcite, dolomite, huntite, hydromagnesite, magnesite, strontianite and witherite. Silica phases as tridymite, cristobalite, chalcedony and quartz are at equilibrium, whereas amorphous silica is slightly undersaturated (Cangemi et al, 2010;2016a).…”

“…1c), exhaling mainly CO 2 (98%) associated to minor amounts of N 2 , O 2 , Ar, CH 4 , H 2 and He (D' Alessandro et al, 1994;Parello et al, 2000;Aiuppa et al, 2007). Lake waters are characterized by the presence of Cl, Na, HCO 3 , SO 4 , CO 3 , K, Mg, Ca, Si, in order of abundance, strongly controlled by thermal waters feeding the lake and by a fractional evaporation process (Parello et al, 2000;Aiuppa et al, 2007, Cangemi et al, 2010Censi et al, 2015). Moreover, water-rock interaction processes contribute to the peculiar enrichment in alkaline elements (Duchi et al, 1994;Giannelli and Grassi, 2001;Di Figlia et al, 2007).…”

“…the carbonate bank running all around its shoreline (Cangemi et al, 2010;Madonia et al, 2013), has been poorly studied.…”

“…During the last decades, Lake Specchio di Venere, located in the northern sector of the volcanic island of Pantelleria (Italy), has attracted the interest of several researchers due to its peculiar characteristics: an ambient temperature, hydrothermal alkaline lake where siliceous stromatolites actively grow in a prevailing carbonate environment, despite the slight undersaturation of SiO 2 phases (Cangemi et al, 2010). Various authors studied different components of this geosite: lake water chemistry (Azzaro et al, 1983, Parello et al, 2000, Aiuppa et al, 2007, Cangemi et al, 20102016a;Censi et al, 2015), mineralogy and geochemistry of lake bottom sediments (Azzaro et al, 1983, Aiuppa et al, 2007, Cangemi et al, 2016b, and mineralogical, biogeochemical and isotopic characterisation of siliceous stromatolites and carbonate microbial mats (Cangemi et al, 2010;2016a;Censi et al, 2015).…”

“…Various authors studied different components of this geosite: lake water chemistry (Azzaro et al, 1983, Parello et al, 2000, Aiuppa et al, 2007, Cangemi et al, 20102016a;Censi et al, 2015), mineralogy and geochemistry of lake bottom sediments (Azzaro et al, 1983, Aiuppa et al, 2007, Cangemi et al, 2016b, and mineralogical, biogeochemical and isotopic characterisation of siliceous stromatolites and carbonate microbial mats (Cangemi et al, 2010;2016a;Censi et al, 2015). The lake is part of a nature reserve protecting a wide area of Pantelleria, with significant limitation of the permitted activities, including scientific researches.…”