TY - JOUR
T1 - Monogenetic volcanoes fed by interconnected dikes and sills in the Hopi Buttes volcanic field, Navajo Nation, USA
AU - Muirhead, James D.
AU - Van Eaton, Alexa R.
AU - Re, Giuseppe
AU - White, James D.L.
AU - Ort, Michael H.
N1 - Funding Information:
We thank the local Navajo people and the Prosser family for kindly allowing us access to the field areas described in this study. Support for JDM was provided by the New Zealand Fulbright-Ministry of Science and Innovation Award. Ramon Arrowsmith and Amanda Clarke are thanked for hosting JDM at Arizona State University during field work. Nicolas Le Corvec kindly provided his MATLAB script and statistical data on monogenetic cone fields. AVE acknowledges NSF Postdoctoral Fellowship EAR1250029 and a U.S. Geological Survey Mendenhall Fellowship. We thank reviewers Mike Poland, Steffi Burchardt, and Nicolas Le Corvec, and editor Valerio Acocella, who provided insightful comments that improved the manuscript. Field work in the Navajo Nation was conducted under a permit from the Navajo Nation Minerals Department. Any persons wishing to conduct geological investigations on the Navajo Nation must first apply for and receive a permit from the Navajo Nation Minerals Department, P.O. Box 1910, Window Rock, Arizona 86515, and telephone number (928) 871–6587.
Publisher Copyright:
© 2016, Springer-Verlag Berlin Heidelberg.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - Although monogenetic volcanic fields pose hazards to major cities worldwide, their shallow magma feeders (<500 m depth) are rarely exposed and, therefore, poorly understood. Here, we investigate exposures of dikes and sills in the Hopi Buttes volcanic field, Arizona, to shed light on the nature of its magma feeder system. Shallow exposures reveal a transition zone between intrusion and eruption within 350 m of the syn-eruptive surface. Using a combination of field- and satellite-based observations, we have identified three types of shallow magma systems: (1) dike-dominated, (2) sill-dominated, and (3) interconnected dike-sill networks. Analysis of vent alignments using the pyroclastic massifs and other eruptive centers (e.g., maar-diatremes) shows a NW-SE trend, parallel to that of dikes in the region. We therefore infer that dikes fed many of the eruptions. Dikes are also observed in places transforming to transgressive (ramping) sills. Estimates of the observable volume of dikes (maximum volume of 1.90 × 106 m3) and sills (minimum volume of 8.47 × 105 m3) in this study reveal that sills at Hopi Buttes make up at least 30 % of the shallow intruded volume (∼2.75 × 106 m3 total) within 350 m of the paeosurface. We have also identified saucer-shaped sills, which are not traditionally associated with monogenetic volcanic fields. Our study demonstrates that shallow feeders in monogenetic fields can form geometrically complex networks, particularly those intruding poorly consolidated sedimentary rocks. We conclude that the Hopi Buttes eruptions were primarily fed by NW-SE-striking dikes. However, saucer-shaped sills also played an important role in modulating eruptions by transporting magma toward and away from eruptive conduits. Sill development could have been accompanied by surface uplifts on the order of decimeters. We infer that the characteristic feeder systems described here for the Hopi Buttes may underlie monogenetic fields elsewhere, particularly where magma intersects shallow, and often weak, sedimentary rocks. Results from this study support growing evidence of the important role of shallow sills in active monogenetic fields.
AB - Although monogenetic volcanic fields pose hazards to major cities worldwide, their shallow magma feeders (<500 m depth) are rarely exposed and, therefore, poorly understood. Here, we investigate exposures of dikes and sills in the Hopi Buttes volcanic field, Arizona, to shed light on the nature of its magma feeder system. Shallow exposures reveal a transition zone between intrusion and eruption within 350 m of the syn-eruptive surface. Using a combination of field- and satellite-based observations, we have identified three types of shallow magma systems: (1) dike-dominated, (2) sill-dominated, and (3) interconnected dike-sill networks. Analysis of vent alignments using the pyroclastic massifs and other eruptive centers (e.g., maar-diatremes) shows a NW-SE trend, parallel to that of dikes in the region. We therefore infer that dikes fed many of the eruptions. Dikes are also observed in places transforming to transgressive (ramping) sills. Estimates of the observable volume of dikes (maximum volume of 1.90 × 106 m3) and sills (minimum volume of 8.47 × 105 m3) in this study reveal that sills at Hopi Buttes make up at least 30 % of the shallow intruded volume (∼2.75 × 106 m3 total) within 350 m of the paeosurface. We have also identified saucer-shaped sills, which are not traditionally associated with monogenetic volcanic fields. Our study demonstrates that shallow feeders in monogenetic fields can form geometrically complex networks, particularly those intruding poorly consolidated sedimentary rocks. We conclude that the Hopi Buttes eruptions were primarily fed by NW-SE-striking dikes. However, saucer-shaped sills also played an important role in modulating eruptions by transporting magma toward and away from eruptive conduits. Sill development could have been accompanied by surface uplifts on the order of decimeters. We infer that the characteristic feeder systems described here for the Hopi Buttes may underlie monogenetic fields elsewhere, particularly where magma intersects shallow, and often weak, sedimentary rocks. Results from this study support growing evidence of the important role of shallow sills in active monogenetic fields.
KW - Conduit
KW - Dike
KW - Intrusive complex
KW - Monogenetic volcanic field
KW - Saucer-shaped sill
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U2 - 10.1007/s00445-016-1005-8
DO - 10.1007/s00445-016-1005-8
M3 - Article
AN - SCOPUS:84958044072
SN - 0258-8900
VL - 78
SP - 1
EP - 16
JO - Bulletin of Volcanology
JF - Bulletin of Volcanology
IS - 2
M1 - 11
ER -