Fast sea-floor spreading on the Chile Ridge

Klitgord, Kim D.; Mudie, John D.; Larson, Peggy A.; Grow, John A.

doi:10.1016/0012-821x(73)90144-1

Cited by 69 publications

(12 citation statements)

References 17 publications

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“…The slower opening rate along the NAZC-PCFC boundary also affects the motion along the Chile Rise. In particular, the RM2 rate is considerably less than the 7.6 cm/yr estimate derived from the profile of Klitgord et al (1973), which we consider to be the best rate observation along this boundary and is the only value included in the data set. However, the RM2 rate i:-.…”

Section: 'mentioning

confidence: 88%

Present‐day plate motions

Minster¹,

Jordan²

1978

J. Geophys. Res.

2,106

793

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A data set comprising 110 spreading rates, 78 transform fault azimuths, and 142 earthquake slip vectors has been inverted to yield a new instantaneous plate motion model, designated Relative Motion 2 (RM2). The model represents a considerable improvement over our previous estimate, RM1 [Minster et al., 1974]. The mean averaging interval for the spreading rate data has been reduced to less than 3 m.y. A detailed comparison of RM2 with angular velocity vectors which best fit the data along individual plate boundaries indicates that RM2 performs close to optimally in most regions, with several notable exceptions. The model systematically misfits data along the India‐Antarctica and Pacific‐India plate boundaries. We hypothesize that these discrepancies are manifestations of internal deformation within the Indian plate; the data are compatible with northwest‐southeast compression across the Ninetyeast Ridge at a rate of about 1 cm/yr. RM2 also fails to satisfy the east‐west trending transform fault azimuths observed in the French‐American Mid‐Ocean Undersea Study area, which is shown to be a consequence of closure constraints about the Azores triple junction. Slow movement between North and South America is required by the data set, although the angular velocity vector describing this motion remains poorly constrained. The existence of a Bering plate, postulated in our previous study, is not necessary if we accept the proposal of Engdahl and others that the Aleutian slip vector data are biased by slab effects. Absolute motion models are derived from several kinematical hypotheses and compared with the data from hot spot traces younger than 10 m.y. Although some of the models are inconsistent with the Wilson‐Morgan hypothesis, the overall resolving power of the hot spot data is poor, and the directions of absolute motion for the several slower‐moving plates are not usefully constrained.

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Section: 'mentioning

confidence: 88%

Present‐day plate motions

Minster¹,

Jordan²

1978

J. Geophys. Res.

2,106

793

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“…Serpentinization of the slab mantle lithosphere is common in subduction zones [e.g., Peacock , 2001; Hacker et al , 2003b] and is believed to occur at spreading centers, at the outer rise of subduction zones, and along fracture zones. Within this region, the Nazca plate is formed at the fast spreading East Pacific Rise (∼15 cm/yr) and Chile Rise (∼5 cm/year) [ Klitgord et al , 1973; DeMets et al , 2010]. Little serpentinization of the mantle lithosphere is believed to occur at fast spreading centers, making spreading center hydration unlikely for the Nazca Plate in this region.…”

Section: Discussionmentioning

confidence: 99%

Shear wave velocities in the Pampean flat‐slab region from Rayleigh wave tomography: Implications for slab and upper mantle hydration

et al. 2012

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[1] The Pampean flat-slab region, located in central Argentina and Chile between 29 and 34 S, is considered a modern analog for Laramide flat-slab subduction within western North America. Regionally, flat-slab subduction is characterized by the Nazca slab descending to $100 km depth, flattening out for $300 km laterally before resuming a more "normal" angle of subduction. Flat-slab subduction correlates spatially with the track of the Juan Fernandez Ridge, and is associated with the inboard migration of deformation and the cessation of volcanism within the region. To better understand flat-slab subduction we combine ambient-noise tomography and earthquake-generated surface wave measurements to calculate a regional 3D shear velocity model for the region. Shear wave velocity variations largely relate to changes in lithology within the crust, with basins and bedrock exposures clearly defined as low-and high-velocity regions, respectively. We argue that subduction-related hydration plays a significant role in controlling shear wave velocities within the upper mantle. In the southern part of the study area, where normal-angle subduction is occurring, the slab is visible as a high-velocity body with a low-velocity mantle wedge above it, extending eastward from the active arc. Where flat-slab subduction is occurring, slab velocities increase to the east while velocities in the overlying lithosphere decrease, consistent with the slab dewatering and gradually hydrating the overlying mantle. The hydration of the slab may be contributing to the excess buoyancy of the subducting oceanic lithosphere, helping to drive flat-slab subduction.

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“…6a is derived from published data, and essentially follows Cande and Leslie (1986), who summarised and reviewed earlier work (e.g. Klitgord et al 1973;Chase 1978; Minster and Jor- Herron et al 1981;Cande 1983;Forsythe et al 1986). Although lateral movements are part of the assembly process at ocean margins (e.g.…”

Section: Basin Models and Reconstructed Sedimentary Inputmentioning

confidence: 99%

Balance of tectonically accreted and subducted sediment at the Chile Triple Junction

Behrmann

Kopf²

2001

International Journal of Earth Sciences

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An active oceanic spreading ridge is being subducted beneath the South American continent at the Chile Triple Junction. Mass balance estimations to characterize temporal and spatial variations in the frontal accretion, or underplating and subduction of sediments since the Late Miocene, were made using seismic and drill-hole data. At 200 km north of the triple junction, almost 80% of the sediment on the downgoing Nazca plate are subducted. Sediment subduction rate decreases towards the triple junction because of a low in sedimentation rates as the flank of the spreading ridge approaches the trench. At the triple junction, the forearc is almost completely destroyed by spreading ridge collision and subduction erosion. Less than 12% of the available sedimentary input is accreted. South of the triple junction, where the spreading ridge passed 6 Ma ago, a large fraction (>60%) of the sediment on the incoming Antarctic plate has been scraped off and was frontally accreted to the Chile forearc. Spreading ridge subduction leaves a distinctive geological fingerprint, and has a large impact on the mass balance of the subduction zone. However, the high rates of change in the process may make this fingerprint hard to detect in fossil convergent orogens. In the ridge collision zone the sediment supplied to the trench, and the amount of sediment subducted, show strong and distinctive variations on a 1-to 5-million-year time scale. On a 10-million-year time scale, sediment subduction to the Earth's mantle is reduced by spreading ridge collision, caused by the need of the overriding forearc to regain a low angle of taper by frontal accretion.

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Fast sea-floor spreading on the Chile Ridge

Cited by 69 publications

References 17 publications

Present‐day plate motions

Present‐day plate motions

Shear wave velocities in the Pampean flat‐slab region from Rayleigh wave tomography: Implications for slab and upper mantle hydration

Balance of tectonically accreted and subducted sediment at the Chile Triple Junction

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