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Petrogenesis of Voluminous Silicic Magma in Northeast Iceland
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
2012 (Engelska)Konferensbidrag, Poster (med eller utan abstract) (Refereegranskat)
Abstract [en]

Neogene silicic volcanic complexes in the greater Borgarfjörður eystri area, NE-Iceland, are the focus of a petrological and geochemical investigation. The region contains the second-most voluminous occurrence of silicic rocks in Iceland, including caldera structures, inclined sheet swarms, extensive ignimbrite sheets, sub-volcanic rhyolites and silicic lava flows. Despite the relevance of these rocks to understand the generation of evolved magmas in Iceland, the area is geologically poorly studied [c.f. 1, 2, 3].

The voluminous occurrence of evolved rocks in Iceland (10-12 %) is very unusual for an ocean island or a mid-oceanic ridge, with a typical signal of magmatic bimodality, often called “Bunsen-Daly” compositional gap [e.g. 4, 5, 6]. The Bunsen-Daly Gap is a long-standing and fundamental issue in petrology and difficult to reconcile with continuous fractional crystallization as a dominant process in magmatic differentiation [7]. This implies that partial melting of hydrothermally altered crust may play a significant role. Our aim is to contribute to a solution to this issue by unravelling the origin, timing and evolution of voluminous evolved rhyolites in NE-Iceland.

We use a combined petrological, textural, experimental and in-situ isotope approach on a comprehensive sample suite of intrusive and extrusive rocks, ranging from basaltic to silicic compositions. We are performing major, trace element and Sr-Nd-Hf-Pb-He-O isotope geochemistry, as well as U-Pb geochronology and Ar/Ar geochronology on rocks and mineral separates. Zircon oxygen isotope analysis will be performed in conjuction with zircon U-Pb geochronology for further assessment of the role of processes such as partial melting of hydrated country rock and/or fractional crystallization in generating Icelandic rhyolites. In addition, high pressure-temperature partial melting experiments aim to reproduce and further constrain natural processes. Using the combined data set we intend to produce a comprehensive and quantitative analysis of rhyolite petrogenesis, and of the temporal, structural and geochemical evolution of silicic volcanism in NE-Iceland. The chosen field area serves as a good analogue for active central volcanoes in Iceland, such as Askja and Krafla, where interaction of basaltic and more evolved magma has led to explosive eruptions.

 

 

[1] Gústafsson (1992) PhD dissertation, Berlin University. [2] Martin & Sigmarsson (2010) Lithos 116, 129–144. [3] Burchardt, Tanner, Troll, Krumbholz & Gustafsson (2011) G3 12 (7), Q0AB09. [4] Bunsen (1851) Annalen der Physik und Chemie 159 (6), 197-272. [5] Daly (1925) Proceedings of the American Academy of Arts and Sciences 60 (1), 3-80. [6] Barth, Correns & Eskola (1939) Die Entstehung der Gesteine. Springer Verlag, Berlin. [7] Bowen (1928) The evolution of the igneous rocks. Princeton University Press.

 

Ort, förlag, år, upplaga, sidor
2012. s. 1475-
Nationell ämneskategori
Geovetenskap och miljövetenskap Geologi
Identifikatorer
URN: urn:nbn:se:uu:diva-191137OAI: oai:DiVA.org:uu-191137DiVA, id: diva2:584861
Konferens
22nd Annual V.M. Goldschmidt Conference in Montréal, Canada
Tillgänglig från: 2013-01-09 Skapad: 2013-01-09 Senast uppdaterad: 2017-01-25

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