We performed a noble gases investigation of fluid inclusions hosted in olivines and pyroxenes from mafic enclaves contained in the 1570 and 1925 A.D. dacitic magmas erupted at Nea Kameni. These enclaves are a portion of mafic magma batches that replenished the shallow chamber of the plumbing system hosting cooler and more silicic melts. Their Sr-Nd isotope ratios are quite similar to those measured in the host dacitic rocks, implying a common parental magma. Therefore, the analysed enclaves may be considered representative of the historic magma erupted at Nea Kameni which could be still present in the volcano plumbing system feeding the crater fumaroles. Gases extracted from fluid inclusions are affected by an appreciable air contamination, as their 4He/20Ne and 40Ar/36Ar ratios are near to the typical atmospheric signature. The 3He/4He ratios of olivines, once corrected for air contamination (3.1-3.6 Ra), show higher and more reliable values than the cogenetic pyroxenes. These values partially overlap those of the gases (3.5-4.0 Ra) collected from Nea Kameni fumarolic field and from bubbling springs at Palea Kameni. The range of 3He/4He ratios (3.1-4.0 Ra) is appreciably lower than typical arc volcanoes (R/Ra ~7-8), implying that a contamination by 4He-rich fluids occurred either directly in the mantle and/or in the plumbing system. Comparison of 3He/4He and 4He/40Ar* ratios measured in enclaves with those of fumarolic gases, as well as long-term monitoring of R/Ra in the latters, coherently indicate that magma involved in the 2011-2012 unrest is likely more primitive and 3He-rich than the mafic enclaves. This would imply that the Santorini magma presently available for eruption has a lower explosive potential than in the recent historic eruption of Nea Kameni.

Noble gases geochemistry of magma degassing at Santorini (Greece): inferences on 2011-2012 unrest / A. RIZZO; F. BARBERI; M.L. CARAPEZZA; L. FRANCALANCI; W. D’ALESSANDRO; A. DI PIAZZA; F. SORTINO. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - ELETTRONICO. - 77:(2013), pp. 2067-2067. (Intervento presentato al convegno Goldschmidt 2013 Conference tenutosi a Firenze (Italia) nel 25-30 agosto 2013).

Noble gases geochemistry of magma degassing at Santorini (Greece): inferences on 2011-2012 unrest

FRANCALANCI, LORELLA;
2013

Abstract

We performed a noble gases investigation of fluid inclusions hosted in olivines and pyroxenes from mafic enclaves contained in the 1570 and 1925 A.D. dacitic magmas erupted at Nea Kameni. These enclaves are a portion of mafic magma batches that replenished the shallow chamber of the plumbing system hosting cooler and more silicic melts. Their Sr-Nd isotope ratios are quite similar to those measured in the host dacitic rocks, implying a common parental magma. Therefore, the analysed enclaves may be considered representative of the historic magma erupted at Nea Kameni which could be still present in the volcano plumbing system feeding the crater fumaroles. Gases extracted from fluid inclusions are affected by an appreciable air contamination, as their 4He/20Ne and 40Ar/36Ar ratios are near to the typical atmospheric signature. The 3He/4He ratios of olivines, once corrected for air contamination (3.1-3.6 Ra), show higher and more reliable values than the cogenetic pyroxenes. These values partially overlap those of the gases (3.5-4.0 Ra) collected from Nea Kameni fumarolic field and from bubbling springs at Palea Kameni. The range of 3He/4He ratios (3.1-4.0 Ra) is appreciably lower than typical arc volcanoes (R/Ra ~7-8), implying that a contamination by 4He-rich fluids occurred either directly in the mantle and/or in the plumbing system. Comparison of 3He/4He and 4He/40Ar* ratios measured in enclaves with those of fumarolic gases, as well as long-term monitoring of R/Ra in the latters, coherently indicate that magma involved in the 2011-2012 unrest is likely more primitive and 3He-rich than the mafic enclaves. This would imply that the Santorini magma presently available for eruption has a lower explosive potential than in the recent historic eruption of Nea Kameni.
2013
Goldschmidt2013 Conference Abstract
Goldschmidt 2013 Conference
Firenze (Italia)
A. RIZZO; F. BARBERI; M.L. CARAPEZZA; L. FRANCALANCI; W. D’ALESSANDRO; A. DI PIAZZA; F. SORTINO
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/960502
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