Tectonic evolution of the Cocos-Nazca spreading center

Hey, R. N.

doi:10.1130/0016-7606(1977)88<i:teotcs>2.0.co;2

Cited by 140 publications

(214 citation statements)

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“…Our findings do not support either of these interpretations and rather point to a tectonic mélange that was accreted prior to the arrival of the Cocos Ridge during subduction, underthrusting and tectonic burial of seamounts and seamounts chains. The evidence for active, recent tectonic erosion of the forearc is compelling , and Osa Mélange does not reflect accretion from the currently subducting plate, given the southeastward migration of the Cocos-Nazca-Caribbean triple junction over the last 5 Myr [Hey, 1977;Gardner et al, 1992;MacMillan et al, 2004], possible transform jumps [Lonsdale and Klitgord, 1978;Lowrie et al, 1979], and the subduction of the Cocos Ridge .…”

Section: Introductionmentioning

confidence: 99%

From seamount accretion to tectonic erosion: Formation of Osa Mélange and the effects of Cocos Ridge subduction in southern Costa Rica

Vannucchi¹,

et al. 2006

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The Costa Rica portion of the Middle America Trench (MAT) is characterized by active tectonic erosion, a process that causes the removal of material from the base of the upper plate as the plate boundary migrates upward. Offshore studies demonstrate accelerated subduction erosion starting at the Miocene‐Pliocene boundary, as the result of subduction of thickened Galapagos related crust, as presently represented by the Cocos Ridge. The subduction of the Cocos Ridge also caused uplift and exposure of the outer forearc on the Osa Peninsula, which offers a window to explore the tectonic evolution of the area. The rocks outcropping on Osa Peninsula are a middle Eocene–middle Miocene mélange dominated by basalt, chert, and limestone resulting from accretion of seamounts. The accretion‐dominated period of the MAT evolution ended at the Miocene‐Pliocene boundary, when thickened crust, a paleo‐Cocos Ridge, produced at the Galapagos hot spot arrived at the trench. The thick crust caused uplift and severe tectonic erosion of the accretionary edifice allowing exhumation of the Osa Mélange. The change from accretion to erosion caused the outer forearc to be offset along subvertical faults that define small (kilometer to tens of kilometers size) blocks that are going through differential vertical movements in response to the morphology of the subducting ridge. Subduction accretion and erosion are two processes that can alternate in time and space or coexist along the same margin, so that mass removal can develop on a previously growing margin and completely remove an accretionary prism.

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Section: Introductionmentioning

confidence: 99%

From seamount accretion to tectonic erosion: Formation of Osa Mélange and the effects of Cocos Ridge subduction in southern Costa Rica

Vannucchi¹,

et al. 2006

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“…Estimates range between ~1 Ma (Hey, 1977;Lonsdale and Klitgord, 1978), ~5 Ma (Sutter, 1985), and ~20-22 Ma (Lonsdale and Klit gord, 1978; van Andel et al, 1971 the current phase of subduction erosion (Fig. F2).…”

Section: Upper Plate and Subaerial Geologymentioning

confidence: 99%

“…Estimates range between ~1 Ma (Hey, 1977;Lonsdale and Klitgord, 1978), ~5 Ma (Sutter, 1985), and ~20-22 Ma (Lonsdale and Klitgord, 1978;van Andel et al, 1971). The 5 Ma age is based on the emplacement of adakitic arc rocks between 5.8 and 2.0 Ma (Abratis and Wörner, 2001) and thermochronological information on the uplift of the Talamanca Cordillera (Gräfe et al, 2002).…”

Section: Upper Plate and Subaerial Geologymentioning

confidence: 99%

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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“…The half spreading rate over the last 8 m.y. for the southern flank of the Rift has been 3.3 cm/yr (Hey, 1975). This is intermediate between the half spreading rates of ridges such as the MidAtlantic Ridge and Gorda Ridge (0.7-1.5 cm/yr; Needham and Francheteau, 1974) and the East Pacific Rise (~8 cm/yr at 31 °S; Rea, 1977).…”

Section: Discussionmentioning

confidence: 94%

Strontium- and Lead-Isotope Composition of Some Basalts from Deep Sea Drilling Project Hole 504B, Costa Rica Rift, Legs 69 and 70

Barrett¹

1983

Initial Reports of the Deep Sea Drilling Project

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Seventeen whole-rock samples, generally taken at 25-to 50-meter intervals from 5 to 560 meters sub-basement in Deep Sea Drilling Project Hole 504B, were analyzed for 87 Sr/ 86 Sr ratios, and rubidium and strontium concentrations. Ten of these samples also were analyzed for Pb-isotope composition. Strontium-isotope ratios for eight samples from the upper 260 meters of the hole range from 0.70287 to 0.70377, with a mean of 0.70320. In the interval 330 to 560 meters, five samples have a restricted range of 0.70259 to 0.70279, with a mean of 0.70266, almost identical to the average value of fresh mid-ocean-ridge basalts. In the interval 260 to 330 meters, approximately intermediate strontium-isotope ratios are found.The higher 87 Sr/ 86 Sr ratios in the upper part of the hole can be interpreted in terms of strontium-isotope alteration during basalt-sea-water interaction. Relative to average fresh mid-ocean ridge basalts, the upper 260 meters of basalts are enriched by an average of about 9% in sea-water strontium ^7Sr/ 86 Sr = 0.7091). This Sr presumably is located in the smectites, which, as the main secondary minerals throughout the hole, replace olivine and matrix glass and locally fill vesicles (analyzed samples contained no veins).The strontium-isotope data strongly suggest that the integrated flux of sea water through the upper part of the Hole 504B crust has been greater than through the lower part. This is also suggested by (1) the common occurrence of Feoxide-hydroxide minerals as alteration products above 270 meters, but their near absence below 320 meters, (2) the presence of vein calcite above 320 meters, but its near absence below this level, and (3) the occurrence of vein pyrite only below a depth of 270 meters. Sea-water circulation in the lower basalts may have been partly restricted by the greater number of relatively impermeable massive lava flows below 230 meters sub-basement. Although sufficient sea water was present within the lower part of the hole to produce smectitic alteration products, the overall water /rock ratio was low enough to prevent significant modification of strontium-isotope ratios.Lead There is no trend in Hole 5O4B lead-isotope ratios with vertical position in the basement. The arrays indicate that the lead-isotope composition of the upper mantle from which the Hole 504B basaltic melts were derived was inhomogeneous.

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Tectonic evolution of the Cocos-Nazca spreading center

Cited by 140 publications

References 0 publications

From seamount accretion to tectonic erosion: Formation of Osa Mélange and the effects of Cocos Ridge subduction in southern Costa Rica

From seamount accretion to tectonic erosion: Formation of Osa Mélange and the effects of Cocos Ridge subduction in southern Costa Rica

Expedition 344 summary

Strontium- and Lead-Isotope Composition of Some Basalts from Deep Sea Drilling Project Hole 504B, Costa Rica Rift, Legs 69 and 70

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