气候变化领域集成服务门户(CCPortal): Emplacement of unusual rhyolitic to basaltic ignimbrites during collapse of a basalt-dominated caldera: The Halarau{eth}ur eruption, Krafla (Iceland)

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DOI	10.1130/B35450.1
	Emplacement of unusual rhyolitic to basaltic ignimbrites during collapse of a basalt-dominated caldera: The Halarau{eth}ur eruption, Krafla (Iceland)
	Rooyakkers S.M.; Stix J.; Berlo K.; Barker S.J.
发表日期	2020
ISSN	167606
起始页码	1881
结束页码	1902
卷号	132 期号:2021-09-10
英文摘要	Deposits of the ca. 110 ka Halarau{eth}ur eruption of Krafla caldera (reconstructed volume = 7 ± 6 km3 dense rock equivalent) include the only spatter-rich ignimbrite known in Iceland, and an exceptionally rare lava-like basaltic ignimbrite. We present a revised stratigraphy and new whole-rock major-element data set for products of this unusual event, one of only three Quaternary ignimbrite eruptions identified in Iceland. Compositions of Halarau{eth}ur products span a broad range (50.0-74.6 wt% SiO2), reflecting mixing of rhyolite with underplating basalt. Small-volume, valley-ponded, basal pumice- and spatter-bearing lithic breccias and ignimbrite (rhyolite to andesite) reflect rapid column collapse during early opening of ring-fault vents. A transition to voluminous, regionally dispersed spatter agglomerates (dacite to basaltic andesite) marks an abrupt eruptive intensification, as gas-poor magma was squeezed into a developing ring-fault system by the subsiding chamber roof. Spatial heterogeneities in ascent rates and outgassing through this variably dilated fault system caused coeval formation of collapsing plumes and spatter fountains at separate vents. Spatter was entrained into flows from the more explosive vents, which deposited proximal spatter agglomerates and more distal spatter- bearing ignimbrite. Overlying lava-like ignimbrite deposits (basaltic andesite to basalt) reflect a final opening of vents, as mafic magma from deep levels of the chamber was squeezed through a dilated ring-fault system by the subsiding roof block and erupted at uncharacteristically high mass flux. Development of a mature ring-fault conduit system during early tapping of silicic magma appears to be a prerequisite for the emplacement of welded basaltic ignimbrites, and it should be considered as a possible eruption scenario in basalt-dominated systems where silicic magma has been known to also accumulate. Poor preservation of the Halarau{eth}ur deposits exemplifies the challenges of studying ignimbrite eruptions in frequently glaciated regions like Iceland, where they may be more common than the geological record suggests. © 2019 Geological Society of America.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184726
作者单位	Department of Earth and Planetary Sciences, McGill University, Montreal, QC H3A 0E8, Canada; School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, 6012, New Zealand
推荐引用方式 GB/T 7714	Rooyakkers S.M.,Stix J.,Berlo K.,et al. Emplacement of unusual rhyolitic to basaltic ignimbrites during collapse of a basalt-dominated caldera: The Halarau{eth}ur eruption, Krafla (Iceland)[J],2020,132(2021-09-10).
APA	Rooyakkers S.M.,Stix J.,Berlo K.,&Barker S.J..(2020).Emplacement of unusual rhyolitic to basaltic ignimbrites during collapse of a basalt-dominated caldera: The Halarau{eth}ur eruption, Krafla (Iceland).Bulletin of the Geological Society of America,132(2021-09-10).
MLA	Rooyakkers S.M.,et al."Emplacement of unusual rhyolitic to basaltic ignimbrites during collapse of a basalt-dominated caldera: The Halarau{eth}ur eruption, Krafla (Iceland)".Bulletin of the Geological Society of America 132.2021-09-10(2020).