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A lamproitic component in the high-K calc-alkaline volcanic rocks of the Capraia Island, Tuscan Magmatic Province: evidence from clinopyroxene crystal chemical data
| Content Provider | Semantic Scholar |
|---|---|
| Author | Chelazzi, Laura Bindi, Luca Olmi, Filippo Menchetti, Silvio Peccerillo, Angelo Conticelli, Sandro |
| Copyright Year | 2006 |
| Abstract | The Island of Capraia (Tuscan Archipelago) is the westernmost volcanic centre of the Tuscan Magmatic Province. It is made by the overlap of two volcanoes: the Capraia and the Zenobito ones. The Capraia Volcano is a large composite apparatus dominated by lava flows and lava domes with a high-K calc-alkalic affinity built up over the period between 7.5 and 6.9 Ma at its top. The Zenobito Volcano is a small monogenetic apparatus that produced a cinder cone associated to a very small plateau-like lava structure in a short time spanning at 4.6 Ma, overlapping the south-westernmost edge of the Capraia Volcano. Outcropping rocks of the older volcano are high-K calc-alkalic (HKCA) rocks ranging in composition from dominant andesite and dacite to rare rhyolite, straddling latite and trachyte fields. Volcanic rocks from the Zenobito Volcano are much more uniform in composition ranging from potassic trachybasalt to shoshonite, but some sub- alkalic samples falling within the andesite basaltic field have been also found. To explore the relationships between clinopyroxene structural and chemical parameters and the physico- chemical conditions of their crystallisation, selected clinopyroxene crystals from the older high-K calc- alkalic rocks (10 crystals) and from the younger shoshonitic rocks (2 crystals) of the Capraia and Zenobito Volcanoes, respectively, have been studied. Single-crystal X-ray diffraction measurements and microprobe analyses have been carried out. The clinopyroxene from Capraia Volcano has augitic composition whereas clinopyroxene from Zenobito Volcano is enriched in the diopsidic component. Structural parameters show significant variations, in particular in the V M1 and V cell . These volumes are larger for clinopyroxene crystals from Capraia volcanic rocks than those of clinopyroxene crystals from shoshonitic rocks of the Zenobito Volcano. It is unlikely that the increase of V M1 and V cell observed in |
| Starting Page | 75 |
| Ending Page | 94 |
| Page Count | 20 |
| File Format | PDF HTM / HTML |
| Volume Number | 75 |
| Alternate Webpage(s) | http://tetide.geo.uniroma1.it/riviste/permin/testi/V75/12.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
