Reactivation of Fault Systems by Compartmentalized Hydrothermal Fluids in the Southern Andes Revealed by Magnetotelluric and Seismic Data

Pearce, R.; Muela, Almudena Sánchez de la; Moorkamp, Max; Hammond, James; Mitchell, Thomas M.; Cembrano, José; Vargas, Jaime Araya; Meredith, P. G.; Iturrieta, Pablo; Pérez‐Estay, Nicolás; Marshall, Nicole R.; Smith, Jonathan D.; Yáñez, Gonzalo; Griffith, W. A.; Marquardt, Carlos; Stanton-Yonge, Ashley; Núñez, Rodolfo Masías

doi:10.1029/2019tc005997

Cited by 28 publications

(21 citation statements)

References 99 publications

(277 reference statements)

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“…5). Although characterization of the geothermal reservoir in the Aysén region has not yet been conducted, this estimate agrees with those for the Tinguiririca geothermal reservoir in central Chile (2-6 kmbsl) [40][41][42] and now provides a benchmark for future studies to test.…”

Section: Constraints On the Geothermal Groundwater Reservoir And Fluid Migrationsupporting

confidence: 76%

“…Despite considerable evidence for deep submarine discharge of meteorically altered geothermal groundwater at J1003, a fundamental question remains: How is this hydrogeologic connection established? Lateral migration of geothermal groundwater through the LOFZ controls the distribution of thermal springs in the Aysén region, which are often clustered near faults where buoyant hot water reaches the surface 40,42 . We now propose that this geothermal groundwater also migrates into the marine realm on the Chilean Margin.…”

Section: Constraints On the Geothermal Groundwater Reservoir And Fluid Migrationmentioning

confidence: 99%

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Deep submarine infiltration of altered geothermal groundwater on the south Chilean Margin

Clementi¹,

Rosenthal²,

Bova³

et al. 2022

Preprint

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Submarine groundwater discharge is increasingly recognized as an important component of the oceanic geochemical budget, but knowledge of the distribution of this phenomenon is limited. To date, reports of meteoric inputs to marine sediments are typically limited to shallow shelf and coastal environments, whereas contributions of freshwater along deeper sections of tectonically active margins like the Chilean Margin have generally been attributed to silicate diagenesis, mineral dehydration, or methane hydrate dissociation. Here we report that substantial pore water freshening on the south Chilean Margin reflects deep and focused contributions of meteorically modified geothermal groundwater, which has infiltrated marine sediments through regional fault systems. Geochemical fingerprinting of pore water data from Site J1003, recovered during D/V JOIDES Resolution Expedition 379T, highlights mixing between this fresh groundwater endmember and seawater, and provides the first constraints on the depth of geothermal groundwater reservoirs in the Aysén region of Patagonia. Collectively, our results identify an unappreciated locus of deep submarine groundwater and geothermal discharge along active margins, with potential implications for coastal biogeochemical processes and tectonic instability.

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Section: Constraints On the Geothermal Groundwater Reservoir And Fluid Migrationsupporting

confidence: 76%

Section: Constraints On the Geothermal Groundwater Reservoir And Fluid Migrationmentioning

confidence: 99%

Deep submarine infiltration of altered geothermal groundwater on the south Chilean Margin

Clementi¹,

Rosenthal²,

Bova³

et al. 2022

Preprint

View full text Add to dashboard Cite

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“…González ( 1999 ) estimated an emplacement depth of ∼13 km (400 MPa) for the Cerro Cristales Pluton, based on hornblende geobarometry and assuming a geothermal gradient of 30 °C/km. Instead, assuming a geothermal gradient of ∼50°C/km, typical of an active magmatic arc (e.g., the Southern Andes Volcanic Zone: Pearce et al., 2020 ; Sielfeld et al., 2019 ) and considering the estimated pressure (185 ± 150 MPa) for recrystallized matrix of the mafic tectonites, the emplacement depth of the pluton results at <10 km depth, as for plutons of similar age (140–155 Ma) emplaced along the El Salado segment of the AFS (Espinoza et al., 2014 ; Grocott & Taylor, 2002 ; Seymour et al., 2020 ). Moreover, the emplacement of several plutons in a short time span thermally weakens the crust facilitating pluton emplacement at shallow depths (Cao et al., 2016 ).…”

Section: Discussionmentioning

confidence: 99%

Structural Evolution of a Crustal‐Scale Seismogenic Fault in a Magmatic Arc: The Bolfin Fault Zone (Atacama Fault System)

et al. 2021

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How major crustal‐scale seismogenic faults nucleate and evolve in crystalline basements represents a long‐standing, but poorly understood, issue in structural geology and fault mechanics. Here, we address the spatio‐temporal evolution of the Bolfin Fault Zone (BFZ), a >40‐km‐long exhumed seismogenic splay fault of the 1000‐km‐long strike‐slip Atacama Fault System. The BFZ has a sinuous fault trace across the Mesozoic magmatic arc of the Coastal Cordillera (Northern Chile) and formed during the oblique subduction of the Aluk plate beneath the South American plate. Seismic faulting occurred at 5–7 km depth and ≤ 300°C in a fluid‐rich environment as recorded by extensive propylitic alteration and epidote‐chlorite veining. Ancient (125–118 Ma) seismicity is attested by the widespread occurrence of pseudotachylytes. Field geologic surveys indicate nucleation of the BFZ on precursory geometrical anisotropies represented by magmatic foliation of plutons (northern and central segments) and andesitic dyke swarms (southern segment) within the heterogeneous crystalline basement. Seismic faulting exploited the segments of precursory anisotropies that were optimal to favorably oriented with respect to the long‐term far‐stress field associated with the oblique ancient subduction. The large‐scale sinuous geometry of the BFZ resulted from the hard linkage of these anisotropy‐pinned segments during fault growth.

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“…This is in contrast to the Indonesian volcanic arc, where the Sumatra Fault has limited control on volcanic processes, distribution and size (Acocella et al, 2018). These crustal fault intersections represent highly permeable zones for fluid circulation and magmatic intrusion (Piquer et al, 2019;Norini et al, 2020;Pearce et al, 2020), but also transfer structural instabilities to the overlying edifice. The role of the regional tectonic regime and the collapse of stratovolcanoes has been studied for decades (Moriya, 1980;Francis and Wells, 1988;Tibaldi, 1995;Lagmay et al, 2000;Wooller et al, 2009;Mathieu et al, 2011;Paguican et al, 2012), and as is illustrated by the examples above, is a potentially significant control on both the construction and failure of mafic edifices, just as in edifices dominated by broader or more evolved compositional ranges.…”

Section: External Factorsmentioning

confidence: 96%

Volcanic Lateral Collapse Processes in Mafic Arc Edifices: A Review of Their Driving Processes, Types and Consequences

et al. 2021

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Volcanic cones are frequently near their gravitational stability limit, which can lead to lateral collapse of the edifice, causing extensive environmental impact, property damage, and loss of life. Here, we examine lateral collapses in mafic arc volcanoes, which are relatively structurally simple edifices dominated by a narrow compositional range from basalts to basaltic andesites. This still encompasses a broad range of volcano dimensions, but the magma types erupted in these systems represent the most abundant type of volcanism on Earth and rocky planets. Their often high magma output rates can result in rapid construction of gravitationally unstable edifices susceptible both to small landslides but also to much larger-scale catastrophic lateral collapses. Although recent studies of basaltic shield volcanoes provide insights on the largest subaerial lateral collapses on Earth, the occurrence of lateral collapses in mafic arc volcanoes lacks a systematic description, and the features that make such structures susceptible to failure has not been treated in depth. In this review, we address whether distinct characteristics lead to the failure of mafic arc volcanoes, or whether their propensity to collapse is no different to failures in volcanoes dominated by intermediate (i.e., andesitic-dacitic) or silicic (i.e., rhyolitic) compositions? We provide a general overview on the stability of mafic arc edifices, their potential for lateral collapse, and the overall impact of large-scale sector collapse processes on the development of mafic magmatic systems, eruptive style and the surrounding landscape. Both historical accounts and geological evidence provide convincing proofs of recurrent (and even repetitive) large-scale (>0.5 km3) lateral failure of mafic arc volcanoes. The main factors contributing to edifice instability in these volcanoes are: (1) frequent sheet-like intrusions accompanied by intense deformation and seismicity; (2) shallow hydrothermal systems weakening basaltic rocks and reducing their overall strength; (3) large edifices with slopes near the critical angle; (4) distribution along fault systems, especially in transtensional settings, and; (5) susceptibility to other external forces such as climate change. These factors are not exclusive of mafic volcanoes, but probably enhanced by the rapid building of such edifices.

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Reactivation of Fault Systems by Compartmentalized Hydrothermal Fluids in the Southern Andes Revealed by Magnetotelluric and Seismic Data

Cited by 28 publications

References 99 publications

Deep submarine infiltration of altered geothermal groundwater on the south Chilean Margin

Deep submarine infiltration of altered geothermal groundwater on the south Chilean Margin

Structural Evolution of a Crustal‐Scale Seismogenic Fault in a Magmatic Arc: The Bolfin Fault Zone (Atacama Fault System)

Volcanic Lateral Collapse Processes in Mafic Arc Edifices: A Review of Their Driving Processes, Types and Consequences

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