DOI: 10.1016/j.epsl.2018.01.007
Scopus记录号: 2-s2.0-85042656105
论文题名: Imaging the Laguna del Maule Volcanic Field, central Chile using magnetotellurics: Evidence for crustal melt regions laterally-offset from surface vents and lava flows
作者: Cordell D. ; Unsworth M.J. ; Díaz D.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 488 起始页码: 168
结束页码: 180
语种: 英语
英文关键词: hydrothermal reservoir
; magma reservoir
; magnetotellurics
; southern volcanic zone
; volcanism
Scopus关键词: Hot springs
; Lakes
; Location
; Magnetotellurics
; Temperature
; Volcanoes
; Ground deformations
; Hydrothermal fluids
; Low temperatures
; Low-frequency signals
; Magma reservoirs
; Volcanic hazards
; Volcanic zone
; volcanism
; Reservoirs (water)
; conductivity
; crustal structure
; electrical resistivity
; hydrothermal vent
; lava flow
; magma chamber
; magnetotelluric method
; Pleistocene-Holocene boundary
; volcanism
; Laguna del Maule Volcanic Field
; Southern Volcanic Zone
英文摘要: Magnetotelluric (MT) data were collected at the Laguna del Maule volcanic field (LdMVF), located in central Chile (36°S, 70.5°W), which has been experiencing unprecedented upward ground deformation since 2007. These data were used to create the first detailed three-dimensional electrical resistivity model of the LdMVF and surrounding area. The resulting model was spatially complex with several major conductive features imaged at different depths and locations around Laguna del Maule (LdM). A near-surface conductor (C1; 0.5 Ωm) approximately 100 m beneath the lake is interpreted as a conductive smectite clay cap related to a shallow hydrothermal reservoir. At 4 km depth, a strong conductor (C3; 0.3 Ωm) is located beneath the western edge of LdM. The proximity of C3 to the recent Pleistocene-to-Holocene vents in the northwest LdMVF and nearby hot springs suggests that C3 is a hydrous (>5 wt% H2O), rhyolitic partial melt with melt fraction >35% and a free-water hydrothermal component. C3 dips towards, and is connected to, a deeper conductor (C4; 1 Ωm). C4 is located to the north of LdM at >8 km depth below surface and is interpreted as a long-lived, rhyolitic-to-andesitic magma reservoir with melt fractions less than 35%. It is hypothesized that the deeper magma reservoir (C4) is providing melt and hydrothermal fluids to the shallower magma reservoir (C3). A large conductor directly beneath the LdMVF is not imaged with MT suggesting that any mush volume beneath LdM must be anhydrous (<2 wt% H2O), low temperature and low melt fraction (<25%) in order to go undetected. The presence of large conductors to the north has important implications for magma dynamics as it suggests that material may have a significant lateral component (>10 km) as it moves from the deep magma reservoir (C4) to create small, ephemeral volumes of eruptible melt (C3). It is hypothesized that there may be a north–south contrast in physical processes affecting the growth of melt-rich zones since major conductors are imaged in the northern LdMVF while no major conductors are detected beneath the southern vents. The analysis and interpretation of features directly beneath the lake is complicated by the surface conductor C1 which attenuates low-frequency signals. The attenuation from C1 does not affect C3 or C4. At 1 km depth directly beneath LdM, a weak conductor (C2; <10 Ωm) is imaged but is not required by the data. Forward modeling tests show that a relatively large (30 km3), high melt fraction (>50%), silicic reservoir with 5 wt% H2O at 2 to 5 km depth beneath the inflation center is not supported by the MT data. However, a smaller (10 km3) eruptible volume could go undetected even with relatively high melt fraction (>50%). The location of large melt regions to the north has important implications for long-term volcanic hazards at LdMVF as well as other volcanoes as it raises the possibility that the vent distribution is not always indicative of the location of deeper source regions of melt. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109980
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Department of Physics, University of Alberta, Edmonton, T6E 2E1, Canada; Departamento de Geofísica, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile; Centro de Excelencia en Geotermia de Los Andes, Plaza Ercilla 803, Santiago, Chile
Recommended Citation:
Cordell D.,Unsworth M.J.,Díaz D.. Imaging the Laguna del Maule Volcanic Field, central Chile using magnetotellurics: Evidence for crustal melt regions laterally-offset from surface vents and lava flows[J]. Earth and Planetary Science Letters,2018-01-01,488