![]() ![]() Tectonophys 15:219–231Ĭarmichael I, Turner F, Verhoogen J (1974) Igneous petrology. Geology 39:67–70Ĭaputo MG, Panza F, Postpischl D (1972) New evidences about the deep structure of the Lipari arc. J Petrol 45:1209–1235Ĭabrerra A, Weinberg RF, Wright HMN, Zlotnik S, Cas RAF (2011) Melt fracturing and healing: a mechanism for degassing and origin of silicic obsidian. Earth Planet Sci Lett 119:27–36īoorman S, Boudreau A, Kruger FJ (2004) The lower zone-critical zone transition of the Bushveld Complex: a quantitative textural study. In: Carroll MR, Holloway JR (eds) Volatiles in Magmas, Rev Miner vol 30, pp 157–182īlank JG, Stolper EM, Carroll MR (1993) Solubilities of carbon dioxide and water in rhyolite melt at 850 ☌ and 750 bars. Nature 242:322–323īlank JG, Brooker RA (1994) Experimental studies of carbon dioxide in silicate melts: solubility, speciation, and stable carbon isotope behaviour. Blackwell, Oxford, p 729īigazzi G, Bonadonna FP (1973) Fission track dating off the obsidian of Lipari Island (Italy). Earth Evol Sci 3:222–238īest MG (2003) Igneous and metamorphic petrology. J Geophys Res 78:5221–5232īeccaluva L, Rossi PL, Serri G (1982) Neogene to recent volcanism of the southern Tyrrhenian–Sicilian area: implications for the geodynamic evolution of the Calabrian Arc. Chem Geol 263:89–98īarberi F, Gasparini P, Innocenti F, Villari L (1973) Volcanism of the southern Tyrrhenian Sea and its geodynamic implications. Contrib Miner Petrol 123:335–344īalcone-Boissard H, Baker DR, Villemant B, Boudon G (2009) F and Cl diffusion in phonolitic melts: influence of the Na/K ratio. Eur J Miner 13:453–466īaker L, Rutherford MJ (1996) Sulfur diffusion in rhyolite melts. Phys Earth Planet Inter 159:225–233īaker DR, Freda C (2001) Eutectic crystallization in the undercooled orthoclase-quartz-H 2O system: experiments and simulations. Geology 34:517–520Īrrighi S, Tanguy J, Rosi M (2006) Eruptions of the last 2200 years at Vulcano and Vulcanello (Aeolian Islands, Italy) dated by high-accuracy archeomagnetism. Geophys J R Astron Soc 91:613–637Īnovitz LM, Riciputi LR, Cole DR, Fayek M, Elam JM (2006) Obsidian hydration: a new paleothermometer. Selective deformation of spherulites supports a down-temperature continuum of spherulite formation in the Rocche Rosse obsidian indeed, petrographic evidence suggests that high-strain zones may have catalyzed progressive nucleation and growth of further generations of spherulites during syn- and post-emplacement cooling.Īnderson HJ, Jackson JA (1987) The deep seismicity of the Tyrrhenian Sea. ![]() Based on the diffusion of H 2O across these temperature ranges (~800–300 ☌), timescales of spherulite crystallization occur on a timescale of ~4 days with further modification up to ~400 years (growth is prohibitively slow <400 ☌ and would become diffusion reliant). We propose that nucleation and growth rate are isothermally constant, but vary between differing stages of spherulite growth with continued cooling from magmatic temperatures, such that there is an evolution from a high to a low rate of crystallization and low to high crystal nucleation. Petrographic observation, CSD analysis, volatile and Ar data as well as diffusion modeling support continuous spherulite nucleation and growth starting at magmatic (emplacement) temperatures of ~790–825 ☌ and progressing through the glass transition temperature range ( T g ~ 750–620 ☌), being further modified in the solid state. Argon concentrations dissolved in the glass and spherulites differ by a factor of ~20, with Ar sequestered preferentially in the glass phase. These observations are consistent with diffusive expulsion of volatiles into melt, leaving a volatile-poor rim advancing ahead of anhydrous crystallite growth, which is envisaged to have had a pronounced effect on spherulite crystallization dynamics. Volatile concentrations across the spherulite boundary and within the spherulitic textures are highly variable. Numerous bulk volatile data in non-vesicular glass (spatially removed from spherulitic textures) reveal homogenous distributions of volatile concentrations: H 2O (0.089 ± 0.012 wt%), F (950 ± 40 ppm) and Cl (4,100 ± 330 ppm), with CO 2 and S consistently below detection limits suggesting either complete degassing of these volatiles or an originally volatile-poor melt. Bulk glass chemistry and spherulite chemistry analyzed along transects across the spherulite growth front/glass boundary reveal major-oxide and volatile (H 2O, CO 2, F, Cl and S) chemical variations and heterogeneities at a ≤5 μm scale. Spherulitic textures in the Rocche Rosse obsidian flow (Lipari, Aeolian Islands, Italy) have been characterized through petrographic, crystal size distribution (CSD) and in situ major and volatile elemental analyses to assess the mode, temperature and timescales of spherulite formation. ![]()
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