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Dikes in the Koa'e fault system, and the Koa'e east rift zone structural grain at Kilauea Volcano, Hawai'i

Donald A. Swanson, Richard S. Fiske, Carl R. Thornber and Michael P. Poland
Dikes in the Koa'e fault system, and the Koa'e east rift zone structural grain at Kilauea Volcano, Hawai'i (in Field volcanology; a tribute to the distinguished career of Don Swanson, Michael P. Poland, Michael O. Garcia, Victor E. Camp and Anita L. Grunder)
Special Paper - Geological Society of America (February 2019) 538: 247-274

Abstract

Two small scoria vents were discovered in the Koa'e fault system, an extensional regime connecting the east and southwest rift zones of Kilauea that was previously considered to be noneruptive. The chemical composition of the scoria suggests an early to middle nineteenth-century age. The vents prove that magma can intrude several kilometers into the central part of the Koa'e fault system from the nearest rift zone, supporting previous seismic and geodetic inferences of intrusions into the Koa'e fault system in the twentieth century. Geodetic studies for the past 50 yr document widening of the Koa'e fault system at a time-averaged rate of approximately 4.5 cm/yr, involving mostly coseismic strains, but also creep and displacement related to dike intrusions. These rates are consistent with a longer-term widening rate for the past approximately 700 yr calculated from crack widths in a lava flow of about that age. The Koa'e fault system blends into, and is a structural continuation of, the east rift zone. We interpret the locus of intrusion in the east rift zone to have migrated approximately 6.5 km SE during the past 100,000-125,000 yr, as estimated from linear extrapolation of measured displacement rates across the Koa'e fault system and east rift zone. The inception of migration is consistent with the onset of the tholeiitic stage at Kilauea as interpreted by previous studies. As the rift zone moved away from the summit, a marked curvature in the transport pathway developed in order for the rift zone to maintain its connection to the summit magma reservoir. The migration resulted in development of the SE-trending east rift connector, a term we prefer instead of the upper east rift zone. The connector supplies magma to the ENE-trending rift zone from the summit storage complex but is not itself the site of significant magma storage or eruption. The Koa'e fault system merges into the southwest rift zone, which has been migrating southeastward for an uncertain period of time. Some magma that enters it passes from the summit reservoir complex through the southwest rift connector (seismic southwest rift zone), analogous to the east rift connector. Both connectors reflect the response of magma-transport pathways to asymmetric volcano spreading away from a relatively fixed summit magma reservoir. The ENE structural grain of the Koa'e fault system and east rift zone pervades Kilauea's entire edifice. Most eruptions take place along this trend. The major exception is the southwest rift zone, which may reflect the stresses of Mauna Loa spreading and the Ka'oiki fault system. The dominant ENE grain emphasizes the importance of SSE-directed volcano spreading in controlling most of Kilauea's tectonic and eruptive behavior.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 538
Title: Dikes in the Koa'e fault system, and the Koa'e east rift zone structural grain at Kilauea Volcano, Hawai'i
Title: Field volcanology; a tribute to the distinguished career of Don Swanson
Author(s): Swanson, Donald A.Fiske, Richard S.Thornber, Carl R.Poland, Michael P.
Author(s): Poland, Michael P.
Author(s): Garcia, Michael O.
Author(s): Camp, Victor E.
Author(s): Grunder, Anita L.
Affiliation: U. S. Geological Survey, Hawaiian Volcano Observatory, Hawaii National Park, HI, United States
Affiliation: U. S. Geological Survey, Cascades Volcano Observatory, Vancouver, WA, United States
Pages: 247-274
Published: 20190207
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 9780813795386
References: 80
Accession Number: 2020-016567
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch maps
N19°15'00" - N19°25'00", W155°19'60" - W155°04'60"
Secondary Affiliation: National Museum of Natural History, USA, United StatesCascades Volcano Observatory, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute.
Update Code: 2020
Program Name: USGSOPNon-USGS publications with USGS authors
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