Inversion of magnetic anomalies and sea-floor spreading in the Cayman Trough

Macdonald, Ken C.; Holcombe, Troy L.

doi:10.1016/0012-821x(78)90163-2

Cited by 117 publications

(52 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The former is a fast-spreading ridge with a full spreading rate of 13 cm/y 4) and the latter, a slow-spreading ridge with a full spreading rate of 1.5 to 2 cm/y. 5) I further discuss the role of dunite for the genesis of primitive MORB. Sample descriptions.…”

mentioning

confidence: 96%

Role of dunite in genesis of primitive MORB

Arai

2005

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

View full text Add to dashboard Cite

Both Hess Deep and the dredging sites of MCT are not associated with transform faults, 10),11) and the transform effect on the rocks discussed here will be minimized. Abstract: Dunite and related rocks from the Moho transition zone of the East Pacific Rise (EPR) and the Mid-Cayman Trough (MCT) are examined to know the spreading-rate dependence of their compositions. The rocks from both ridges are basically a reaction product between peridotite and primitive MORB. Despite the large difference of prevalent peridotite chemistry, depleted harzburgite for EPR and lherzolite for MCT, the dunite has less different compositional ranges. The Al 2 O 3 content of spinel differs only by 5 wt%, which may be equivalent to the difference of about 1 wt% of Al 2 O 3 in the melt. This is almost equal to the possible spreading-rate dependent compositional difference of observed Mg-rich MORB. The relatively unfractionated MORBs erupted are in equilibrium with the oceanic dunite of which composition is independent of or only slightly dependent on spreading rate. Dunite is calculated to be about half of the total oceanic mafic crust by weight. The dunite is concentrated as the Moho transition zone, and is sparsely distributed as small lenses within the uppermost mantle peridotite. Petrology and origin of the dunite-troctolite-

show abstract

mentioning

confidence: 96%

Role of dunite in genesis of primitive MORB

Arai

2005

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

View full text Add to dashboard Cite

show abstract

“…For the several studies where a direct inversion for magnetization was made Ofacdonald, 1977;Macdonald and Holcombe, 1978;McGregor et al, n In Paper 1, the directions of plate motion implied by earthquake focal mechanisms were. estimated by projecting the slip vectors gAtp a horizontal plane.…”

Section: Introductionmentioning

confidence: 99%

“…The most important datum (0.95) is the rate across the Mid-Cayman Rise (Macdonald and Holcombe, 1978); alone, it essentiallY determines the relative speed of NORM-CARE. When the entire data set is considered, 501-4 of the cumulative importance is associated with a the 49 most important data, and only 10% with the 151 least important data.…”

Section: Introductionmentioning

confidence: 99%

Present‐day plate motions

Minster¹,

Jordan²

1978

J. Geophys. Res.

2,098

793

View full text Add to dashboard Cite

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.

show abstract

“…The best evidence on this dilemma may be that reconstruction of Cayman Fracture Zone slippage of 2 to 4 cm/y. (MacDonald and Holcomb, 1978) places the Guatemala-Honduras corner of the Caribbean Plate near the Leg 66 area 12.5 to 25 Ma, or during the time of plate reorganization suggested by Pacific magnetic anomalies and in the time gap between end of subsidence and onset of accretion. Central American rocks south of the Motagua-Polochic faults, which separate the Caribbean and North American plates, contain granodiorite intrusives of Cretaceous and Tertiary ages (Seely, 1979;Fig.…”

Section: Tectonic Historymentioning

confidence: 96%

Tectonic Synthesis, Leg 66: Transect and Vicinity

Watkins¹,

McMillen²,

Bachman³

et al. 1982

Initial Reports of the Deep Sea Drilling Project

View full text Add to dashboard Cite

Cores recovered from eight sites drilled along a transect across the Middle America Trench off southwestern Mexico show that accretion and offscraping of trench turbidites and the pelagic-hemipelagic blanket covering the ocean crust has been active for approximately 10 m.y. Active offscraping and imbricate underthrusting have been limited to the lower slope, whereas middle and upper slopes show uplift due to underplating by subducted sediments and younging of ocean crust. Offscraped trench sands of Pleistocene to Miocene age have been uplifted as much as 2 to 3 km above the present-day trench floor by combined accretion and underplating.Sediment input into the subduction zone is partitioned, with roughly equal amounts being offscraped, underplated, and subducted. The offscraped component appears to consist primarily of trench turbidites, whereas the subducted component is thought to consist primarily of pelagic-hemipelagic sediments. The trench turbidite component probably dominates the underplated component.Partitioning values based on mass balance budget and on theoretical lithospheric bending were comparable. This comparability lends confidence to our theory of flux partitioning.Although we find no direct evidence of tectonic erosion, there is indirect evidence to support the feasibility of the mechanism, and although there is no present forearc basin, differential uplift rates suggest incipient development.Thus we infer the following history of the region: 23-20 Ma-reorganization of plate motion: relative movement of Pacific and North American plate changes from oblique normal (subduction) to parallel (sinistral strike-slip) with margin subsidence and marine transgression.19-17 Ma-margin sinks rapidly to, or just below, CCD, then begins slow rise. Sinistral strike-slip motion continues.10 m.y.-plate motion changes from strike-slip to normal-oblique; accretion begins and continues to present.

show abstract

Inversion of magnetic anomalies and sea-floor spreading in the Cayman Trough

Cited by 117 publications

References 23 publications

Role of dunite in genesis of primitive MORB

Role of dunite in genesis of primitive MORB

Present‐day plate motions

Tectonic Synthesis, Leg 66: Transect and Vicinity

Contact Info

Product

Resources

About