Lipari obsidian is of excellent quality, black in colour, very shiny and sometimes perlitic
It is generally subaphyric and contains clinopyroxene micro-phenocrysts (10–50 m), almost always durante synneusis with magnetite and olivine micro-phenocrysts (Acquafredda et al., 1999).
3.2. Sardinia: Montagna Arci
30 km 2 and located per the comprensorio of the gulf of Oristano. The volcanic activity developed during two distinct cycles durante the Pliocene and Pleistocene, and therefore it belongs to the latest volcanism con Sardinia. The magmatic products erupted during the second cycle, can be divided into four phases. The lavas erupted in the first phase were very rich sopra silica, and consisted mainly of rhyolites, either massive or perlitic-obsidianaceous. Dacites and andesites, trachytes and trachyrhyolites followed durante chronological succession, until the last stages of volcanic activity, which were characterized by quiet eruptions of basaltic lava flows (Piras, 2002; Bigazzi et al., 2005).
The obsidian outcrops were described for the first time con the 19 th century by De La Marmora (1839–40). Subsequently, mediante the 1980s, several independent studies contributed puro the characterization of the multiple Monte Arci obsidian outcrops. Unfortunately, the results of these studies are available only mediante brief conference papers (Francaviglia, 1986; Mackey and Warren 1983) or sopra an unpublished dissertation (Herold, 1986).
More recently, considering the geochemical features the obsidian of Monte Arci, Tykot (2002) subdivided them into four groups, SA, SC, SB1 and SB2. The obsidian sampled near Depressione Cannas and Uras are clustered within the SA group; those sampled near Pau, Perdas Urias and Sonnixeddu belong to the SC group; those sampled at Santa Maria Zuarbara and Marrubiu are sopra the SB1 and SB2 groups, respectively (Tykot, 2002; Nave et al., 2007; De Francesco et al., 2008). Paio sicuro their geochemical similarity, SB1 and SB2 have been grouped under the name SB con the present study.
Ammasso Arci obsidian populations are characterized by large biotite micro-phenocrysts (50–200 ?m), abundant crystals of feldspar (plagioclase and alkali feldspar) 50 ?m in size, orthopyroxene, magnetite, monazite and ilmenite (Acquafredda et al., 1999).
3.3. Palmarola
Geochronological datazione, obtained by fission-track analyses, indicate an age of 1.7±0.3 Ma for obsidian from Mucchio Settentrione (Bigazzi et al., 1971; Bigazzi and Radi, 1981). Con verso recent sistema Tykot et al. (2005) provided per detailed geochemical study of 80 samples, and were able esatto distinguish three source localities: Lingua Vardella, the northern end of Pezzo Vardella and Montagna Settentrione. However, given the small size of the island, this distinction can be considered irrelevant from an archaeological point of view.
Palmarola obsidian contains micro-phenocrysts of clinopyroxene (5–20 ?m) and biotite. It is generally black per colour, glassy, poorly shiny and semi-opaque (Acquafredda et al., 1999). However, per small amount of highly transparent obsidian was found at Lingua Vardella by Tykot et al. (2005).
3.4 Pantelleria
90 km https://datingranking.net/it/minichat-review/ east of Cape Bon, Tunisia. Pantelleria is famous for its peralkaline rocks, and especially for its greenish obsidian enriched con sodium and iron, known as Pantellerite (Fraschetta et al., 1998; Acquafredda et al., 1999). Pantelleria has per bimodal distribution of magmatic products. Mafic lavas, exposed in the NW corner of the island, include transitional basalt and hawaiite (from
62 to 72 wt.% SiO2), prevail in the SE sector (White et al., 2009). K–Ar determinations of mafic lavas done on different basaltic units give ages of 118 ± 9, 83 ± 5 and
29 ka BP (Civetta et al., 1984). Ages determined on felsic volcanic rocks range from 324 ka BP esatto 4 ka BP (Civetta et al., 1984, 1988, 1998; Mahood and Hildreth, 1986). The volcanic history of the island is characterized by large explosive eruptions, some of which produced caldera collapses, alternating with periods dominated by less energetic eruptions (Civetta et al., 1998). The oldest caldera, named La Nonna, is dated at 114 ka BP (Mahood and Hildreth, 1986); the youngest caldera, named the Chiesa caldera by Cornette et al. (1983) and the Cinque Sporgenze caldera by Mahood and Hildreth (1983), is related preciso the eruption of the Green Tuff (50 ka BP; Orsi and Sheridan, 1984). The more recent (post-50 ka) history of the island has been subdivided by Civetta et al. (1998) into six sialic eruptive cycles, intercalated with basaltic eruptions. The Green Tuff is considered the first of these six cycles. All the others are dated at around 35–29, 22, 20–15, 14–12 and 10–4 ka BP, respectively (Civetta et al., 1998).
