Magmatic evolution and volatile inventory of the Lonquimay Volcano, South Central Chile.

Gilbert, David, Freundt, Armin, Kutterolf, Steffen, Burkert, Cosima and Garbe-Schönberg, Dieter (2012) Magmatic evolution and volatile inventory of the Lonquimay Volcano, South Central Chile. [Poster] In: The Lübeck Retreat, Collaborative Research SFB 574 Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanisms for Natural Disasters. , 23.05-25.05.2012, Lübeck . The Lübeck Retreat: final colloquium of SFB 574; May 23-25, 2012: program & abstracts. ; p. 7 .

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Abstract

The Lonquimay Volcanic Complex (LVC) in South Central Chile (38.38°S, 71.58°W) is part of the
Southern Volcanic Zone of the Andes, which formed in response to the subduction of the Nazca Plate beneath the South American Plate. During the last 10200+-70 years of its magmatic evolution, the LVC produced 23 explosive eruptions documented in the succession of widespread tephra deposits. We investigated this stratigraphic sequence for matrix glass, mineral and bulk rock compositions of the juvenile components. Furthermore, melt inclusions were analyzed for their major element and volatile contents. The tephra succession reflects six mafic replenishments of the LVC magma reservoir followed by progressive magmatic differentiation. Each cycle has been successively tapped by several eruptions. Compositionally zoned tephras were typically deposited early in a cycle, whereas late eruptions discharged more evolved magmas. Intermediate compositions typically contain mixed disequilibrium mineral assemblages. The maximum degree of fractionation reached during a cycle increases with younger ages. Our investigations of melt inclusions, in order to
reconstruct the pre-eruptive volatile inventories of the LVC magma chamber, reveal the exsolution of two separate fluid phases. One S-rich fluid phase released from mafic melts in the middle crust and one Cl-rich aqueous phase, released from more ifferentiated melts that resided in the upper part of LVC´s plumbing system. The pre-eruptive saturation state of the LVC melts indicates that felsic
eruptions may have been triggered by H2O-supersaturation whereas mafic melts seem to have
experienced a complex replenishment history potentially exciting LVC´s mafic eruptions.

Document Type: Conference or Workshop Item (Poster)
Keywords: Geodynamics
Research affiliation: OceanRep > SFB 574 > C4
OceanRep > SFB 574 > B6
OceanRep > SFB 574 > C2
Kiel University
OceanRep > SFB 574
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Date Deposited: 10 Sep 2012 10:33
Last Modified: 24 Oct 2012 09:49
URI: http://oceanrep.geomar.de/id/eprint/15168

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