Dyke complex of the East Pacific Rise exposed in the walls of Hess Deep and the structure of the upper oceanic crust

Francheteau, Jean; Armijo, Rolando; Cheminée, J. L.; Hékinian, Roger; Lonsdale, Peter; Blum, N.

doi:10.1016/0012-821x(92)90173-s

Cited by 92 publications

(90 citation statements)

References 22 publications

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“…Very low P 2 O 5 concentrations (<0.02 wt%) indicate low (<5%) proportions of trapped intercumulus liquids. Similar but less detailed observations are recorded from Hess Deep (Francheteau et al, 1992;Gillis, 1995).…”

Section: Rocks Expected With Deeper Drillingsupporting

confidence: 64%

“…Field mapping from the lower crust of the Oman ophiolite (e.g., Kelemen and Aha-ronov, 1998;MacLeod and Yaouancq, 2000;Nicolas and Boudier, 1991;Nicolas et al, 2000) and submersible studies and shallow drilling of EPR crust at Hess Deep (e.g., Francheteau et al, 1992;Gillis, 1995;Karson et al, 1992Karson et al, , 2002Natland and Dick, 1996) may be useful in this respect. However, because of the difficulties of detailed mapping and sampling using submersibles and remotely operated vehicles (ROVs) and the lack of deep drilling of the dike/gabbro boundary in Hess Deep, the well-exposed outcrops in Oman arguably provide the best available guide to the upper plutonic section of fast-spreading ocean crust (Fig.…”

Section: Rocks Expected With Deeper Drillingmentioning

confidence: 99%

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Scientists

Teagle

Ildefonse

et al. 2011

IODP Preliminary Report

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Section: Rocks Expected With Deeper Drillingsupporting

confidence: 64%

Section: Rocks Expected With Deeper Drillingmentioning

confidence: 99%

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Scientists

Teagle

Ildefonse

et al. 2011

IODP Preliminary Report

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“…Field mapping from the lower crust of the Oman ophiolite (e.g., Kelemen and Aharonov, 1998;MacLeod and Yaouancq, 2000;Nicolas and Boudier, 1991;Nicolas et al, 2000) and submersible studies and shallow drilling of EPR crust at Hess Deep (e.g., Francheteau et al, 1992;Gillis, 1995;Karson et al, 1992Karson et al, , 2002Natland and Dick, 1996) may be useful in this respect. However, because of the difficulties of detailed mapping and sampling using submersibles and remotely operated vehicles (ROVs) and the lack of deep drilling of the dike/gabbro boundary in Hess Deep, the well-exposed outcrops in Oman arguably provide the best available guide to the upper plutonic section of fast-spreading ocean crust (Fig.…”

Section: Rocks Expected With Deeper Drillingmentioning

confidence: 99%

Expedition 335 summary

Teagle¹,

Ildefonse²,

Blum³

et al. 2012

Proceedings of the IODP

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“…1;Lonsdale 1988;Francheteau et al 1990;Wiggins et al 1996;Gillis et al 2014b). The Ocean Drilling Project (ODP) Leg 147 took advantage of this tectonic window by drilling the exposures at the Hess Deep Rift.…”

Section: Geological Settingmentioning

confidence: 99%

“…A maximum pressure is provided from seismic data that reported a crustal thickness of 5-7 km with a water depth of ~3 km at the EPR spreading axis near the Galapagos microplate (Zonenshain et al 1980). Although the inferred pressure conditions have uncertainty because of the complex geologic structure of the Hess Deep Rift (e.g., Francheteau et al, 1990), the steep slope of reaction curves in the P-T diagram provides temperature conditions of 650-750 °C for spinel + pargasite formation (Fig. 9).…”

Section: Temperature Conditionsmentioning

confidence: 99%

Hydrothermal spinel, corundum and diaspore in lower oceanic crustal troctolites from the Hess Deep Rift

Nozaka

Meyer

Wintsch

et al. 2016

Contrib Mineral Petrol

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Aluminous spinel, corundum and diaspore are reported from intensely altered parts of primitive troctolites recovered from IODP Site U1415 at the Hess Deep Rift. The spinel is green-colored, has an irregular shape, has low Cr concentrations, and so distinct from primary igneous chromite. Corundum and diaspore occur mainly at the rims of green spinel grains with a texture suggesting a sequential replacement of spinel by corundum, and then corundum by diaspore. The green spinel is associated with anorthite and pargasite, which is overgrown by tremolite that forms coronitic aggregates with chlorite around olivine.These petrographic observations are supported by pressure-temperature pseudosections, which predict spinel + pargasite stability field, and tremolite/hornblende + chlorite field at lower temperature conditions. From these pseudosections and simplified system phase diagrams, estimated formation temperature conditions calculated at 2 kbar are 650-750 °C for spinel + pargasite, 410-690 °C for tremolite/hornblende + chlorite, 400-710 °C for corundum, and < 400 °C for diaspore. Because the aluminous spinel occurs in the domains that were previously occupied by magmatic plagioclase, and because spinel-bearing rocks characteristically have high Al 2 O 3 /CaO and Al 2 O 3 /SiO 2 ratios, it is likely that the stabilization of spinel was caused by the loss of Ca 2+ and SiO 2 (aq) in high-temperature hydrothermal fluids. The results of this study suggest that (1) the concentrations of aluminous phases in the lower oceanic crust are presently underestimated, and (2) chemical modification of the lower oceanic crust due to high-temperature hydrothermal metasomatic reactions could be common near spreading axes.

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Dyke complex of the East Pacific Rise exposed in the walls of Hess Deep and the structure of the upper oceanic crust

Cited by 92 publications

References 22 publications

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Expedition 335 summary

Hydrothermal spinel, corundum and diaspore in lower oceanic crustal troctolites from the Hess Deep Rift

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