Earth-prints repository, logo   DSpace

About DSpace Software
|earth-prints home page | roma library | bologna library | catania library | milano library | napoli library | palermo library
Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/10288

Authors: Di Piazza, A.*
Rizzo, A. L*
Barberi, F.*
Carapezza, M. L.*
De Astis, G.*
Romano, C.*
Sortino, F.*
Title: Geochemistry of the mantle source and magma feeding system beneath Turrialba volcano, Costa Rica
Title of journal: Lithos
Series/Report no.: /232 (2015)
Publisher: Elsevier Science Limited
Issue Date: 31-Jul-2015
DOI: 10.1016/j.lithos.2015.07.012
Keywords: Turrialba
3He/4He ratio
Fluid inclusions
Adakite
MORB mantle
OIB mantle
Abstract: Turrialba volcano lies in the southern sector of the Central American Volcanic Front (CAVF) in Costa Rica. The geochemistry of major and trace elements, and Sr and Nd isotopes of a selected suite of volcanic rocks ranging in composition from basaltic andesite to dacite and belonging to the last 10 ka of activity of Turrialba volcano is described, together with the He-, Ne-, and Ar-isotope compositions of fluid inclusions hosted in olivine and pyroxene crystals. Most of the variability in the rock chemistry is consistentwith typical trends of fractional crystallization, but there is an outlying group of andesites that displays an adakite-like composition (with a consistent depletion in high-field-strength elements and a marked enrichment in Sr) and low 3He/4He ratios (7.0–7.2 Ra). The trace-element composition of these rocks is typical of subduction-related magmas influenced by an OIB-like component at the source associated with the subduction of the Galapagos seamounts. The 87Sr/86Sr (0.703612–0.703678) and 143Nd/144Nd (0.512960–0.512984) ratios of the bulk rocks vary within narrowranges, and are among the least-radiogenic isotope signatures of the CAVF volcanoes. The 3He/4He ratios measured in fluid inclusions hosted in olivine crystals (up to 8.1 Ra) are among the highest for the CAVF, and indicate that radiogenic 4He from fluids derived fromthe subducting slab contribute negligibly to the mantle wedge. The difference in He isotopes between most of studied rocks and those showing adakite-like features reasonably reflects two distinct components in the local mantle: (1) a MORB-like component, characterized by the highest He-isotope ratios (7.8–8.1 Ra), and (2) an OIB-like component, characterized by lower He-isotope ratios (7.0–7.2 Ra), coming from the subduction of the Galapagos seamounts. An overview at the regional scale indicates that high He-isotope ratios are peculiar to the two extreme sectors of the CAVF (Costa Rica to the south and Guatemala to the north), whereas in the central sector (Nicaragua) the magma source is probably contaminated by slab fluids. For the past few years Turrialba volcano has been in a volcanic unrest phase that has included a series of explosions, the most recent of which occurred between October 2014 and May 2015. The volcano is subject to an ongoing safety alert due to the possibility of a magmatic eruption. One of the crucial questions to be addressed is the kind of eruption that can be expected, and hence what type of magma is likely to be involved. The high 3He/4He ratios (7.8–8.0 Ra) measured during 2011 at high-temperature fumaroles of Turrialba craters are comparable to those measured in fluid inclusions of basaltic andesites that erupted in 1864–1866, suggesting that the magma currently feeding the shallow plumbing system has similar geochemical characteristics to the most recently erupted magma.
Appears in Collections:04.04.07. Rock geochemistry
04.08.01. Gases
04.08.05. Volcanic rocks
04.04.05. Mineralogy and petrology
04.04.12. Fluid Geochemistry
Papers Published / Papers in press

Files in This Item:

File SizeFormatVisibility
Di Piazza et al., 2015.pdf2.76 MBAdobe PDFonly authorized users View/Open

This item is licensed under a Creative Commons License
Creative Commons


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.


Share this record
Del.icio.us

Citeulike

Connotea

Facebook

Stumble it!

reddit


 

Valid XHTML 1.0! ICT Support, development & maintenance are provided by CINECA. Powered on DSpace Software. CINECA