Pleistocene to Holocene Growth of a Large Upper Crustal Rhyolitic Magma Reservoir beneath the Active Laguna del Maule Volcanic Field, Central Chile

Andersen, Nathan; Singer, Brad S.; Jicha, Brian R.; Beard, Brian L.; Johnson, Clark M.; Licciardi, Joseph M.

doi:10.1093/petrology/egx006

Cited by 58 publications

(180 citation statements)

References 131 publications

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“…Based on the postglacial eruption of andesite and rhyodacite almost exclusively outside the ring of rhyolite‐producing vents and the compositional continuity of the rhyolites, Hildreth et al () proposed that a large silicic magma reservoir resides beneath LdM and intercepts the ascent of mafic magma. A growing body of geologic, geochronologic, and geophysical evidence supports this hypothesis and indicates that the shallow magma system remains active to this day (Andersen, Singer, et al, , Andersen et al, ; Cordell et al, ; Feigl et al, ; Fierstein, ; Le Mével et al, , ; Miller, Williams‐Jones, et al, ; Miller, Le Mével, et al, ; Singer et al, ; Sruoga et al, ; Wespestad et al, ).…”

Section: Geologic Settingmentioning

confidence: 93%

“…LdM straddles the Chile‐Argentina border at 36° S in the southern Andes (Figure ). Volcanism since the last glacial retreat—locally completed by 22–19 ka based on 40 Ar/ 39 Ar dates of unglaciated lava flows (Andersen, Singer, et al, ; Singer et al, )—is dominated by effusive and explosive eruptions of crystal‐poor rhyolite issued from vents that ring the central lake basin (Figure ; Andersen, Singer, et al, ; Fierstein, ; Hildreth et al, ; Sruoga et al, ). The earliest known postglacial rhyolite is the 20 km 3 , plinian Rhyolite of Laguna del Maule ( rdm ), likely erupted from a vent beneath the modern lake (Fierstein, ).…”

Section: Geologic Settingmentioning

confidence: 99%

“…The subsequent rhyolite eruptions were each <3 km 3 and most widespread immediately following rdm during an early postglacial (EPG) period, 22.5–19 ka, and the middle to late Holocene. During the interim, silicic eruptions were limited to the southeastern lake basin (Figure ; Andersen, Singer, et al, ; Fierstein, ; Hildreth et al, ; Sruoga et al, ). Based on the postglacial eruption of andesite and rhyodacite almost exclusively outside the ring of rhyolite‐producing vents and the compositional continuity of the rhyolites, Hildreth et al () proposed that a large silicic magma reservoir resides beneath LdM and intercepts the ascent of mafic magma.…”

Section: Geologic Settingmentioning

confidence: 99%

“…The early postglacial (erupted 22.5–19 ka) and Holocene rhyolites are outlined in blue and red, respectively; the black‐outlined units were erupted during the interim. The units for which zircon data were obtained are highlighted with dark pink fill, thick outlines, and bold labels with the 40 Ar/ 39 Ar eruption age (Andersen, Singer, et al, ). The black stars are vents; the rdm vent location is approximated based on the mapping of tephra deposits by Fierstein ().…”

Section: Geologic Settingmentioning

confidence: 99%

“…Phenocrysts, when present, comprise plagioclase, biotite, Fe‐Ti oxide, quartz, apatite, and zircon; rdm also contains rare titanite. Although all the rhyolites possess similar whole‐rock, plagioclase, and magnetite compositions, detailed studies of their trace element compositions have revealed subtle differences between the EPG and Holocene units suggesting temporal or spatial heterogeneity within the magma reservoir (Andersen, Singer, et al, ; Andersen et al, ). Despite a narrow range of major element compositions, intracrystal trace element disequilibrium is pervasive in LdM rhyolite plagioclase crystals.…”

Section: Geologic Settingmentioning

confidence: 99%

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Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

2019

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Despite the hazard posed by explosive silicic eruptions, the magma storage conditions and dynamics that precede these events remain controversial. The Laguna del Maule volcanic field, central Chile, is an exceptional example of postglacial (younger than ca. 20,000 years) rhyolite volcanism and sustained unrest driven by a large, shallow, active silicic magma system. New zircon petrochronologic data reveal that compositionally distinct domains developed concurrently within the Laguna del Maule magma reservoir, which produced two episodes of concentrated rhyolitic eruptions at 23–19 and 8–2 ka. Zircon crystallization ages record 160 kyr of magma emplacement resulting in a several hundreds of cubic kilometers reservoir that has been imaged geophysically. The average magma emplacement rate inferred from the zircon geochronology and tomographically defined magma volume is consistent with those required by thermal models to maintain a shallow silicic system. Ti‐in‐zircon temperatures of crystal cores and rims and hiatuses in crystal growth indicates most of this volume persisted in a near‐solidus state. However, consistent patterns of trace element zoning in crystal interiors and crystallization rates derived from a model of diffusion‐limited zircon growth suggest the erupted rhyolite magma batches originated from long‐lived hot zones of extractable mush embedded within the larger, cool reservoir of rigid mush. These contrasting, coeval magma storage conditions obviate a simple hot versus cold storage dichotomy for large silicic magma systems.

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Section: Geologic Settingmentioning

confidence: 93%

Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

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Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

2019

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Microgravity changes at the Laguna del Maule volcanic field: Magma‐induced stress changes facilitate mass addition

et al. 2017

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Time‐dependent, or 4‐D, microgravity changes observed at the Laguna del Maule volcanic field, Chile, since 2013, indicate significant (1.5 × 1011 kg) ongoing mass injection. Mass injection is focused along the Troncoso fault, and subparallel structures beneath the lake at 1.5–2 km depth, and is best modeled by a vertical rectangular prism source. The low‐density change (156 to 307 kg/m3) and limited depth extent suggest a mechanism of hydrothermal fluid intrusion into existing voids, or voids created by the substantial uplift, rather than deeper‐sourced dike intrusion of rhyolite or basalt magma. Although the gravity changes are broadly spatially coincident with ongoing surface deformation, existing models that explain the deformation are deeper sourced and cannot explain the gravity changes. To account for this discrepancy and the correspondence in time of the deformation and gravity changes, we explore a coupled magmatectonic interaction mechanism that allows for shallow mass addition, facilitated by deeper magma injection. Computing the strain, and mean, normal, and Coulomb stress changes on northeast trending faults, caused by the opening of a sill at 5 km depth, shows an increase in strain and mean and normal stresses along these faults, coincident with the areas of mass addition. Seismic swarms in mid‐2012 to the west and southwest of the mass intrusion area may be responsible for dynamically increasing permeability on the Troncoso fault, promoting influx of hydrothermal fluids, which in turn causes larger gravity changes in the 2013 to 2014 interval, compared to the subsequent intervals.

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Deconstructing a complex obsidian “source‐scape”: A geoarchaeological and geochemical approach in northwestern Patagonia

et al. 2018

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Northwestern Patagonia is located in a tectonically active part of the southern Andes (Argentina), which has facilitated the formation of obsidian, including pyroclastic deposits that have been affected by geomorphic processes, resulting in a complex obsidian landscape. To date, the geomorphic relocation of obsidian in the landscape has not been a focus of systematic research, and this hampers our understanding of prehistoric human mobility. We present an updated assessment of the regional availability of different obsidian types based on results from our research program, which combines geoarchaeological survey and geochemical characterization to understand the properties and distribution of obsidian. This robust “source‐scape” provides the foundation for reconstructing patterns of lithic provisioning and discard. Our results suggest that interpretations of obsidian availability across the landscape should be more nuanced than is typically acknowledged. Based on our improved “source‐scape,” we discuss the patterns observed in an archaeological X‐ray fluorescence database. When compared with the geoarchaeological reconstruction of obsidian availability, the archaeological record conforms to a distance‐decay pattern. Contrary to previous interpretations, we suggest that the distribution of obsidian types is not isomorphic with human home ranges. This geoarchaeological research program provides a basis for integrating the archaeological record of different Andean regions.

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Pleistocene to Holocene Growth of a Large Upper Crustal Rhyolitic Magma Reservoir beneath the Active Laguna del Maule Volcanic Field, Central Chile

Cited by 58 publications

References 131 publications

Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

Microgravity changes at the Laguna del Maule volcanic field: Magma‐induced stress changes facilitate mass addition

Deconstructing a complex obsidian “source‐scape”: A geoarchaeological and geochemical approach in northwestern Patagonia

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