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RESEARCH PRODUCT

Volcanic products of Lipari (Aeolian islands, Italy): Multivariate analysis of petrographic and radiometric data

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Abstract A petrographic and radiometric study, along with statistical multivariate analysis of volcanic products of the island of Lipari (Aeolian islands, Italy) was carried out. The volcanological history of Lipari was reconstructed defining two stages (pre- and post-erosive stages) further on subdivided in four volcanic phases, each of which characterized by products with a particular chemical composition and separated by stratigraphic unconformities. The correlations between petrographic features, determined by X-ray fluorescence, and volcanological history of the island highlight a gradual differentiation with younger rocks showing a more acid chemical composition than the older ones. Radiometric features, and in particular the content of primordial radionuclides 238 U, 232 Th and 40 K, have been measured through gamma-ray spectrometry with hyper-pure germanium detector. The different volcanic lithologies, such as basalts, andesites and rhyolites, have been characterized by petrographic diagrams. The calculated dose rate has also been used as an additional classification parameter. Older products show low alkali content than the younger ones. This is related with the increasing of incompatible elements, such as uranium and thorium, in the younger products. Principal components and hierarchical clustering statistical analyses have provided additional information on sample differentiation and similarities.