Ultramafic-carbonate breccias from the equatorial Mid Atlantic Ridge

Bonatti, Enrico; Emiliani, Cesare; Ferrara, G.; Honnorez, J.; Rydell, H.

doi:10.1016/0025-3227(74)90057-7

Cited by 103 publications

(65 citation statements)

References 14 publications

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“…Both the strong alkalinity of the solution, resulting from the hydrolysis of basalt, and the increase of the calcium concentration would tend to promote precipitation of calcium carbonate cements. Such a mechanism has been invoked by several authors to explain the submarine cementation of ultramafic and basaltic breccias (Bonatti et al, 1974;Bernoulli, Garrison, and McKenzie, 1978). Our oxygen isotope data are in agreement with such a low-temperature origin of both calcite and zeolite cements.…”

Section: Calcite Cementssupporting

confidence: 79%

“…The alkaline environment favorable for the precipitation of late diagenetic calcite cements and of zeolites in a low-temperature regime may be directly related to the alteration of basaltic material, which leads to increased pH and calcium concentration of pore waters (Thompson, 1972;Bonatti et al, 1974). Both would tend to promote the precipitation of CaCO 3 , especially in the presence of preexisting carbonates.…”

Section: Origin Of Zeolite Cementsmentioning

confidence: 99%

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Shallow-Water Carbonate Sediments from the Emperor Seamounts: Their Diagenesis and Paleogeographic Significance

McKenzie¹,

Bernoulli²,

Schlanger³

1980

Initial Reports of the Deep Sea Drilling Project

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Deep sea drilling on four seamounts in the Emperor Seamount chain revealed that Paleogene shallow-water carbonate sediments of the "bryozoan-algal" facies crown the basalt edifices. According to the biofacies model of Schlanger and Konishi (1966, 1975), this bryozoan-algal assemblage suggests that the seamounts formed in cooler, more northerly waters than those presently occupied by the island of Hawaii; i.e., the paleolatitudes of formation were greater than 20 °N. Moving southward toward the youngest member of the seamount chain, a facies gradient indicative of warmer waters was observed. This gradient is interpreted as a reflection of a northward shift in isotherms during the time span in which the seamounts were progressively formed (Savin et al., 1975). On all seamounts, sedimentation at the drilling sites occurred in a high-energy environment with water depths of approximately 20 meters. Early-stage carbonate diagenesis began in the phreatic zone in the presence of meteoric water, but proceeded after subsidence of the seamounts into intermediate sea waters, where the bulk, stable isotopic composition was determined. The subsidence into intermediate waters was rapid, and permitted establishment of an isotopic equilibrium which, like the facies gradient, reflects the northward shift in isotherms during the Paleogene. Calcite and zeolite cements comprise the later-stage diagenesis, and originated from solutions arising from the hydrolysis of the underlying basalt.In conclusion, the results of this study of the shallow-water carbonate sediments are not inconsistent with a paleolatitude of formation for Suiko Seamount (Site 433) of 26.9 ±3.5 °N, as determined by paleomagnetic measurements (Kono, this volume).

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Section: Calcite Cementssupporting

confidence: 79%

Section: Origin Of Zeolite Cementsmentioning

confidence: 99%

Shallow-Water Carbonate Sediments from the Emperor Seamounts: Their Diagenesis and Paleogeographic Significance

McKenzie¹,

Bernoulli²,

Schlanger³

1980

Initial Reports of the Deep Sea Drilling Project

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“…It is highly possible that zincian chromite was originally formed as a low -temperature, low -pressure product in peridotitic rocks, transported by subduction into the deeper mantle, and trapped in diamonds before it attained equilibrium with the hightemperature, high -pressure Mg -rich mantle rocks. Serpentinites commonly contain carbonates (e.g., Bonatti et al, 1974;Kerrick and Connolly, 1998), and zincian chromites enclosed by CaCO 3 are a good candidate for the inclusions in diamonds. Subducted CaCO 3 can be a source of carbon (diamond) in the lower mantle (e.g., Seto et al, 2008), and it is possible that it prevents the zincian chromite from being enriched with Mg from the surrounding Mg -rich mantle minerals.…”

Section: Discussionmentioning

confidence: 99%

Zincian chromite inclusions in diamonds: Possibility of deep recycling origin

Arai

Ishimaru

2011

Journal of Mineralogical and Petrological Sciences

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It was reported by Meyer and Boyd (1972) that zincian chromite, having 2 wt% to 3 wt% ZnO and high (>0.9) Cr# (= Cr/(Cr + Al) atomic ratio), appears as inclusions in diamonds obtained from kimberlite. Zincian chromite is characterized by a low (<0.03) Mg# [= Mg/(Mg + ferrous Fe + Zn + Mn + Ni + Co) atomic ratio] and an appreciable amount of MnO (0.4 -0.5 wt%). The chemistry of zincian chromite is very different from commonly found chromite inclusions (magnesiochromite) in diamonds, which contain low amounts of ZnO (<0.1 wt%) and MnO (<0.1 wt%). Zincian and manganoan chromites are also commonly found in meteorites and in altered/ metamorphosed peridotites and related rocks. The chromites found in meteorites mostly have an intermediate Mg# (0.2 -0.5) and a high Cr# (mostly >0.8); moreover, the major -element chemistry of these chromites is similar to that of the magnesiochromite inclusions in diamonds. Spinels obtained from altered rocks show a chemical range that comprises the zincian chromite inclusions found in diamonds. The origin of these inclusions possibly lies in deep recycling. They were initially formed at the Earth's surface in altered/metamorphosed peridotites; they then sank deep down into the mantle and were entrained to the surface again by kimberlite magmatism.

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“…Details were discussed in Warren et al (2008). (例えば，Miyashiro, 1973(例えば，Miyashiro, , 1975a(例えば，Miyashiro, , 1975bGass et al, 1975;Hynes, 1975;Moores, 1975 Barnes et al, 1967Barnes et al, , 1978Frost, 1985;O'Hanrey, 1996) (Evans, 2004(Evans, , 2008Frost and Beard, 2007)。海洋底の蛇紋岩やオフィオライトのマントル部において，炭酸塩鉱物を伴うことが多いことから (Bonatti et al, 1974(Bonatti et al, , 1980Ohnmacht, 1974;TrommsdorŠ and Evans, 1977 …”

Section: マントル科学研究の最近の動向-特に再肥沃化，レオロジー，オフィオライト問題：第５回国際レルゾライト会議報告unclassified