Large heat and fluid fluxes driven through mid-plate outcrops on ocean crust

Hutnak, M.; Fisher, A. T.; Harris, Robert N.; Stein, Carol A.; Wang, Kelin; Spinelli, G. A.; Schindler, Marion; Villinger, H.; Silver, Eli A.

doi:10.1038/ngeo264

Cited by 114 publications

(169 citation statements)

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“…Low heat flow values averaging ~30 mW/m 2 exist in the EPR-generated crust offshore the Nicoya Peninsula (Langseth and Silver, 1996;Fisher et al, 2003;Hutnak et al, 2007Hutnak et al, , 2008. These values reflect <30% of the expected value from conductive lithospheric cooling models for 24 Ma crust (Stein and Stein, 1994) and indicate effective hydrothermal cooling of R.N.…”

Section: Volatiles and Fluidsmentioning

confidence: 99%

“…Dashed red line indicates the position of the thermal transition between areas of relatively low and high heat flow. East Pacific Rise (EPR)-generated crust to the north of the triple junction and fracture zone traces has heat flow suppressed by roughly 70%, whereas Cocos-Nazca spreading center (CNS)-generated crust to the south generally has heat flow that matches conductive lithospheric cooling models (Hutnak et al, 2007(Hutnak et al, , 2008. Figure F7.…”

Section: Better Understand the Impact Of Cocos Ridge Subduction The mentioning

confidence: 99%

“…The magnitude of the hydrological activity in a subducting oceanic plate setting is just beginning to be appreciated (Silver et al, 2000;Fisher et al, 2003;Hutnak et al, 2008;Spinelli and Wang, 2008;Solomon et al, 2009;Harris et al, 2010aHarris et al, , 2010b. Low heat flow values averaging ~30 mW/m 2 exist in the EPR-generated crust offshore the Nicoya Peninsula (Langseth and Silver, 1996;Fisher et al, 2003;Hutnak et al, 2007Hutnak et al, , 2008.…”

Section: Volatiles and Fluidsmentioning

confidence: 99%

“…F4). Regional heat flow measurements on the incoming Cocos plate reveal a large along-strike variation in heat flow (Von Herzen and Uyeda, 1963;Vacquier et al, 1967 In 2000 and 2001, heat flow studies specifically designed to investigate the nature of the thermal transition between cold EPR and warm CNS crust were undertaken (Fisher et al, 2003;Hutnak et al, 2007Hutnak et al, , 2008. Closely spaced heat flow values collocated with seismic reflection lines show a sharp transition (<5 km) between warm and cool seafloor seaward of the trench that generally corresponds to the area of the plate suture (Fig.…”

Section: Heat Flow Datamentioning

confidence: 99%

“…Collectively, the geochemical data in the décollement offshore Nicoya Peninsula indicate an active fluid flow system with a fraction of the flow derived from depths within the subduction zone where temperatures are ~80°-150°C (Chan and Kastner, 2000;Silver et al, 2000;Kastner et al, 2006;Solomon et al, 2009). The sharpness of the geochemical anomalies in the décollement and the estimated temperature of the fluid suggest updip flow from a source regioñ 38-55 km landward of the trench at ~9-14 km depth, near the updip limit of the seismogenic zone (Harris and Wang, 2002;Spinelli et al, 2006;Kastner et al, 2006;Harris et al, 2010b).The magnitude of the hydrological activity in a subducting oceanic plate setting is just beginning to be appreciated (Silver et al, 2000;Fisher et al, 2003;Hutnak et al, 2008;Spinelli and Wang, 2008;Solomon et al, 2009;Harris et al, 2010aHarris et al, , 2010b. Low heat flow values averaging ~30 mW/m 2 exist in the EPR-generated crust offshore the Nicoya Peninsula (Langseth and Silver, 1996;Fisher et al, 2003;Hutnak et al, 2007Hutnak et al, , 2008.…”

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Expedition 344 summary

Li¹,

Malinverno²,

Torres³

et al. 2013

Proceedings of the IODP

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Expedition 344 summaryProc. IODP | Volume 344 2 from velocity-strengthening to velocity-weakening friction, and shear becomes localized. The onset of seismogenic behavior is correlated with the intersection of the 100°-150°C isotherm and the subduction thrust (Hyndman et al., 1997;Oleskevich et al., 1999). With increasing depth down the subduction thrust, the frictional characteristics undergo a second transition either due to the juxtaposition with the forearc mantle or because the rocks are heated to 350°-450°C and can no longer store elastic stresses needed for rupture. Transitional regions between the three zones have conditional stability and can host rupture but are generally not thought to be regions where large earthquakes initiate.Although this three-zone two-dimensional view of the subduction thrust provides a reasonable framework, it is simplistic. Rupture models for large subduction earthquakes suggest significant fault plane heterogeneity in slip and moment release that in three dimensions is characterized as patchiness (Bilek and Lay, 2002). Additionally, we now know the transition zone from stable to unstable sliding is not simple but hosts a range of fault behaviors that includes creep events, strain transients, slow and silent earthquakes, and low-frequency earthquakes (Peng and Gomberg, 2010;Beroza and Ide, 2011;Ide, 2012).Fundamentally unknown are the processes that change fault behavior from stable sliding to stick-slip behavior. Understanding these processes is important for understanding earthquakes, the mechanics of slip, and rupture dynamics. For a fault to undergo unstable slip, fault rocks must have the ability to store elastic strain, be velocity weakening, and have sufficient stiffness. Hypotheses for mechanisms leading to the transition between stable and unstable slip invoke temperature, pressure, and strain-activated processes that lead to downdip changes in the mechanical properties of rocks. These transitions are also sensitive to fault zone composition, lithology, fabric, and fluid pressures.The composition of the material in the fault zone and its contrast with the surrounding wall rock play a key role in rock frictional behavior. The frictional state of the incoming sediment changes progressively with increasing temperature and pressure as it travels downdip. Important lithologic factors influencing friction are composition, fabric, texture, and cementation of rocks, as well as fluid pore pressure (Bernabé et al., 1992;Moore and Saffer, 2001;Beeler, 2007;Marone and Saffer, 2007;Collettini et al., 2009). For example, fault rocks with high phyllosilicate content are generally weaker than rocks with low phyllosilicate content (Ikari et al., 2011). Sediment properties including porosity, permeability, consolidation state, and alteration history also exert a strong influence on fault zone behavior. At erosive margins, where the plate boundary cuts into the overriding plate, the composition and strength of the upper plate is also important (McCaffrey, 1993).Field observations and la...

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Section: Volatiles and Fluidsmentioning

confidence: 99%

Section: Better Understand the Impact Of Cocos Ridge Subduction The mentioning

confidence: 99%

Section: Volatiles and Fluidsmentioning

confidence: 99%

Section: Heat Flow Datamentioning

confidence: 99%

mentioning

confidence: 99%

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Expedition 344 summary

Li¹,

Malinverno²,

Torres³

et al. 2013

Proceedings of the IODP

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Seafloor basalt alteration and chemical change in the ultra thinly sedimented South Pacific

Zhang

Smith-Duque

2014

Geochem Geophys Geosyst

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Determining the relationship between ocean floor basalt alteration and sedimentation is fundamental to understanding how oceanic crust evolves with time. Ocean floor basalts recovered at IODP Sites U1365 (100 Ma) and U1368 (13.5 Ma) in the South Pacific have been subjected to remarkably low sedimentation rates (0.71 and 1.1 m/Myr 21 , respectively). We report detailed petrographic and geochemical analysis of basalt cores from these sites in order to investigate what impact sediment insulation has on seafloor alteration beyond 10-15 Myr of ocean crust formation. Both sites exhibit low-temperature (<150 C) alteration (e.g., iron-hydroxides, carbonate, and quartz) within a predominantly oxidative regime, albeit with markedly different alteration styles and intensity. Alteration at Site U1365, which is predominantly composed of sheet flows, occurs mainly near sheet flow boundaries and fractures. In contrast, Site U1368 comprises interlayered pillows and thin sheet flows that have been subjected to relatively even levels of alteration. Variation of alteration style and intensity between Sites U1365 and U1368 appear closely tied to lithology and crustal structure. Although alteration-induced elemental changes at both sites are similar in, e.g., increasing K, Rb, U, Ba, and Fe 31 and decreasing Fe 21 , Ca, and Ni, they show distinct differences in Th, which is significantly decreased at Site U1365 but relatively constant at Site U1368. At both sites enrichment of LREEs relative to HREEs is ascribed to alteration. The greater vein abundance and notably higher Fe 31 /TiO 2 , K 2 O/TiO 2 , LOI/TiO 2 , and Rb/TiO 2 ratios of representative samples at Site U1365 compared to Site U1368 are attributed to increased alteration intensity. This is mirrored by greater overall chemical change (Fe 2 O 3 , FeO, CaO, K 2 O, Li, Rb, Pb, and U) observed at Site U1365 than those of Site U1368 and other DSDP/ODP sites between 6 and 46 Ma. Since both Sites U1365 and U1368 endured only minimal sedimentation, we attribute the differences in overall chemical change across the two sites to duration of exposure to seawater.

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Remarkably consistent thermal state of the south central Chile subduction zone from 36°S to 45°S

Rotman

Spinelli

2014

JGR Solid Earth

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Delineating rupture areas of subduction zone earthquakes is necessary for understanding the controls on seismic and aseismic slip. For the largest recorded earthquake, the 1960 Chile event with moment magnitude 9.5, the rupture area is only loosely defined due to limitations in the global seismic network at the time. The rupture extends~900 km along strike. Coastal deformation is consistent with either a constant rupture width of~180-200 km along the entire length or a narrower (~115 km) rupture in the southern half. A southward narrowing of the seismogenic zone has been hypothesized to result from warming of the subduction zone to the south, where the subducting plate is younger. We present results of thermal models at 36°S, 38°S, 43°S, and 45°S to examine potential along-strike changes in thermal state. Models most consistent with observed surface heat flux include fluid circulation in the oceanic crust that advects heat to the ocean. This ventilated hydrothermal circulation preferentially cools transects with young subducting lithosphere; frictional heating preferentially warms transects with older subducting lithosphere. The combined effects of frictional heating and hydrothermal circulation increase décollement temperatures in the 36°S and 38°S transects by up to~155°C and decrease temperatures in the 45°S transect by up to~150°C. In our preferred models, décollement temperatures 200 km landward of the trench in all four transects arẽ 350-400°C. This is consistent with a constant~200 km wide seismogenic zone for the 1960 M w 9.5 rupture, with decreasing slip magnitude in the southern half of the rupture.

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Large heat and fluid fluxes driven through mid-plate outcrops on ocean crust

Cited by 114 publications

References 25 publications

Expedition 344 summary

Expedition 344 summary

Seafloor basalt alteration and chemical change in the ultra thinly sedimented South Pacific

Remarkably consistent thermal state of the south central Chile subduction zone from 36°S to 45°S

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