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Isotope geochemistry (Sr–Nd–Pb) and petrogenesis of leucite-bearing volcanic rocks from “Colli Albani” volcano, Roman Magmatic Province, Central Italy: inferences on volcano evolution and magma genesis |
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| Authors: | Elena Boari Riccardo Avanzinelli Leone Melluso Guido Giordano Massimo Mattei Arnaldo A De Benedetti Vincenzo Morra Sandro Conticelli |
| Institution: | 1. Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira, 4, 50121, Florence, Italy 5. Department of Earth Sciences, University of Bristol, Wills Memorial Building, BS8 1RJ, Bristol, UK 2. Dipartimento di Scienze della Terra, Università degli Studi di Napoli Federico II, Via Mezzocannone, 8, 80134, Naples, Italy 3. Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre, Largo San Leonardo Murialdo, 1, 00146, Rome, Italy 4. Sezione di Firenze, Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via G. La Pira, 4, 50121, Florence, Italy |
| Abstract: | The “Colli Albani” composite volcano is made up of strongly silica-undersaturated leucite-bearing rocks. Magmas were erupted during three main periods, but a complex plumbing system dominated by regional tectonics channelled magmas into different reservoirs. The most alkali-rich magmas, restricted to the caldera-forming period (pre-caldera), are extremely enriched in incompatible trace elements and display more radiogenic Sr (87Sr/86Sr?=?0.71057–0.71067), with slightly less radiogenic Pb with respect to those of the post-caldera period. Post-caldera volcanic activity was concentrated in three different volcanic environments: external to the caldera, along the caldera edge and within the caldera. The post-caldera magmas produced melilite- to leucitite-bearing, plagioclase-free leucitites. In contrast to the pre-caldera lavas, they are characterised by lower incompatible trace element abundances and less radiogenic Sr (87Sr/86Sr?=?0.71006–0.71039). Magmas evolved through crystal fractionation plus minor crustal assimilation in a large magma chamber during the pre-caldera period. The multiple caldera collapses dissected and partially obliterated the early magma chamber. During the post-caldera stage, magmas were channelled through several pathways and multiple shallow-level magma reservoirs were established. A lithospheric mantle wedge previously depleted in the basaltic component and subsequently enriched by metasomatic slab-derived component is suggested as the mantle source of Colli Albani parental magmas. Two different parental magmas are recognised for the pre- and post-caldera stages. The differences may be related to the interplay between smaller degrees of melting for the pre-caldera magmas and more carbonate-rich recycled subducted lithologies in the post-caldera magmas. |
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