Potassic rocks

Ernici -Roccamonfina (0.7 to 0.1 Ma) Ernici Pofi, Ceccano, Patrica, etc. (0.7-0.1) Roccamonfina (0.58-0.1) - Monogenetic pyroclastic and lava centres (Emici), and a stratovolcano (Roccamonfina) formed of mafic to felsic ultrapotassic and potassic rocks. 

Tyrrhenian Sea Floor (12 Ma to Present) Comacya (12), Magnaghi (3), Mar-sili (1.8-0), Vavilov, Aceste, Anchi-se, Lametini, Palinuro, older Ponza, etc. - Coexisting intraplate (oceanic tholeiites, Na-transitional and alkaline) and arc-type (arc-tholeiitic, calc-alkaline, potassic) rocks. 

Ultrapotassic rocks from Tuscany have a lamproitic composition (see Appendix for nomenclature of potassic rocks). Older lamproites (14 Ma) occur at Sisco, Corsica. Kamafugitic rocks make up a few monogenetic centres in the internal zones of northern-central Apennines (Umbria, Latium, Abruzzi), and have been found at Vulsini and as ejected blocks in pyroclastic deposits at Colli Albani (Federico et al. 1994). Roman-type potassic and ultrapotassic rocks (KS and HKS) form the bulk of magma-... 

Latium Province) defined here only includes Vulsini, Vico, Sabatini and Colli Albani volcanoes. Potassic rocks (KS) basically consist of trachyba-salts, latites and trachytes ultrapotassic rocks (HKS) are represented by... 

This province is characterised by the close association of KS and HKS rocks, showing diverse geochemical and isotopic signatures. Some low-potassium mafic rocks falling in the calc-alkaline compositional field have been also found. Potassic rocks display ratios of some incompatible trace elements such as Ba/La, and radiogenic isotope signatures that are close to those of the Neapolitan volcanoes (Vesuvio, Campi Flegrei, Ischia). On the contrary, ultrapotassic rocks resemble the Colle Albani and other Roman volcanoes. Therefore, the Ernici-Roccamonfina zone is characterised by the coexistence of Roman-type and Campanian-type rocks. 

Calc-alkaline, shoshonitic and potassic rocks Lamproiles... 

Petrologically, Roman Province volcanic rocks are mostly ultrapotassic and undersaturated in silica, but saturated to oversaturated potassic rocks... 

Roccamonfina 0.58 to 0.1 Potassic rocks generally younger than ultrapotassic rocks - Stravolcano with a main central caldera and eccentric cones, formed of alternating lava flows and pyroclastic products with a mafic to felsic subalkaline to alkaline potassic (KS) and ultrapotassic (HKS) composition. 

Pliocene buried volcanism 2 Ma - About 1300 m thick sequence of calc-alkaline basalt to andesite underlying Campi Flegrei potassic rocks. 

The volcanoes in the Campania Province, Pontine Islands and Vulture are composed of a wide variety of magma types. Silica undersaturated ultrapo-tassic volcanism is restricted to Somma-Vesuvio, whereas mildly undersaturated to oversaturated potassic rocks occur at Campi Flegrei, Ischia, Procida and Ventotene. In the latter two islands, low potassium compositions close to calc-alkaline basalts are found among lavas and lithic ejecta. Pliocene calc-alkaline rocks are found as rhyolites at Ponza and as basalts and basaltic andesites beneath the Campanian Plain. At Vulture, volcanism is highly enriched in both Na and K, a composition that is distinct from any other volcano in the Italian peninsula. 

De Astis et al. (2000) and Calanchi et al. (2002b) noticed that calc-alkaline and HKCA basalts at Vulcano and Panarea have distinct trace element ratios (e.g. La/U, Rb/Zr, Zr/Nb) compared to the associated sho-shonitic and KS mafic volcanics. However, the rocks of the Calabro-Peloritano basement underlying the Aeolian volcanoes show compositions that resemble the calc-alkaline rather than shoshonitic and KS rocks this was interpreted to exclude a derivation of potassic rocks from calc-alkaline parents via crustal assimilation. The same conclusion was drawn by Frez-zotti et al. (2004), who modelled magma contamination processes using melt inclusions entrapped in metamorphic xenoliths as contaminants. 

Gupta AK, Fyfe WS (2003) The young potassic rocks. Ane Books, New Delhi, 370 pp... 

Vollmer R, Hawkesworth CJ (1980) Lead isotopic composition of the potassic rocks from Roccamonfina (south Italy). Earth Planet Sci Lett 47 91-101 Voltaggio M, Barbieri M (1995) Geochronology. In Trigila R (ed) The volcano of the Alban Hills. University La Sapienza, Rome, pp 167-192... 

Waters F. G. (1987) A suggested origin of MARID xenoliths in kimberlites by high pressure crystallization of an ultra-potassic rock such as lamproite. Contrib. Mineral. Petrol 95, 523-533. 

Chung S.-L., Wang K.-L., Crawford A. J., Kamenetsky V. S., Chen C.-H., Lan C.-Y., and Chen C.-H. (2001) High-Mg potassic rocks from Taiwan implications for the genesis of erogenic potassic lavas. Lithos 59, 153-170. 

Nelson D. R. (1992) Isotopic characteristics of potassic rocks evidence for the involvement of subducted sediments in magma genesis. Lithos 28, 403-420. 

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