caa a22 4500 445839376 CHVBK 20180317145339.0 cr unu---uuuuu 170323e20111201xx s 000 0 eng 10.1007/s00015-011-0074-0 doi (NATIONALLICENCE)springer-10.1007/s00015-011-0074-0 Tremolite-calcite veins in the footwall of the Simplon Fault, Antigorio Valley, Lepontine Alps (Italy) [Elektronische Daten] [Vito Meggiolaro, Michele Sapigni, Anna Fioretti] The lowermost units of the nappe pile of the Lepontine Alps crop out in the Antigorio valley in the footwall of the Simplon Fault. The whole orthogneiss section of the Antigorio Unit is exposed on both sides of the valley, sandwiched between the Mesozoic metasedimentary sequences of the Baceno unit below and the Tèggiolo unit above. The petrography and mineral composition of tremolite-calcite veins occurring in dolomite marble in both metasedimentary sequences were investigated. Tremolite-calcite (with lesser talc and minor phlogopite) veins have rhythmic banded texture. Banding is due to cyclic differences in modal abundances and fabric of tremolite and calcite. These veins are very similar to those occurring in dolomite rafts within the Bergell granite and it is inferred that they formed by the same "fracture-reaction-seal” mechanism. Veins formed by reaction of a silica-rich aqueous fluid with the host dolomite marble along fractures. According to thermo-barometric calculations, based on electron microprobe analyses, reaction occurred at temperatures between 450 and 490°C and minimum pressure of 2-3kbar. Such temperature conditions occurred in this footwall region of the Simplon Fault Zone around 15Ma, during exhumation and cooling of the nappe pile and a transition to brittle behaviour. Aqueous, silica-rich fluids concentrated along fractures, forming tremolite-calcite veins in the dolomite marbles and quartz veins in the orthogneiss. Swiss Geological Society, 2011 Tremolite nationallicence Vein nationallicence Simplon nationallicence Antigorio valley nationallicence Meggiolaro Vito Via Botticelli 3, Ponte San Nicolò, 35020, Padova, Italy aut Sapigni Michele Engineering Department, ENEL SpA, Via Torino 16, 30172, Venezia-Mestre, Italy aut Fioretti Anna CNR-Istituto Geoscienze e Georisorse, Unità Operativa di Padova, Via Gradenigo 6, 35131, Padova, Italy aut Swiss Journal of Geosciences SP Birkhäuser Verlag Basel 104/3(2011-12-01), 355-365 1661-8726 104:3<355 2011 104 15 https://doi.org/10.1007/s00015-011-0074-0 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00015-011-0074-0 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Meggiolaro Vito Via Botticelli 3, Ponte San Nicolò, 35020, Padova, Italy aut NATIONALLICENCE 700 1- Sapigni Michele Engineering Department, ENEL SpA, Via Torino 16, 30172, Venezia-Mestre, Italy aut NATIONALLICENCE 700 1- Fioretti Anna CNR-Istituto Geoscienze e Georisorse, Unità Operativa di Padova, Via Gradenigo 6, 35131, Padova, Italy aut NATIONALLICENCE 773 0- Swiss Journal of Geosciences SP Birkhäuser Verlag Basel 104/3(2011-12-01), 355-365 1661-8726 104:3<355 2011 104 15 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer