Secondary Minerals in Basalt from the Costa Rica Rift, Holes 501 and 504B, Deep Sea Drilling Project Legs 68, 69, and 70

Kurnosov, Victor B; Kholodkevich, I.V.; Чубаров, В. М.; Shevchenko, A.Ya.

doi:10.2973/dsdp.proc.69.130.1983

Cited by 13 publications

(3 citation statements)

References 10 publications

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“…Calculated Mn0 2 contents vary up to 86% by weight. Similar manganese-rich analyses have been reported by Kurnosov et al (1983) from DSDP Hole 501, by Bohlke et al (1980) from DSDP Leg 46, and by Adamson (1984) from DSDP Hole 504B. The high silica and iron contents of analyses 3 through 5 suggest they represent dispersed manganese oxides associated with clay minerals or iron oxyhydroxides.…”

Section: Trend 3 (Iron-rich Analyses)supporting

confidence: 78%

Low-Temperature Alteration of Very Young Basalts from ODP Hole 648B: Serocki Volcano, Mid-Atlantic Ridge

Adamson¹,

Richards²

1990

Proceedings of the Ocean Drilling Program

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Basalts in Hole 648B, located in the rift valley of the Mid-Atlantic Ridge at 23°N in crust estimated to be less than 100,000 years old, are mainly fresh, but small amounts of secondary phases are found on fracture surfaces and in alteration halos within the rocks. The halos are defined by dark bands 1-4 mm thick that have developed parallel to fracture surfaces or pillow margins and which in some cases have migrated some centimeters into the rock. The dark bands are the principal locus of secondary phases. The secondary phases are olive-green and yellow protoceladonites, of composition and structure intermediate between celadonite and iron-rich saponite, red (Mn-poor) to opaque (Mn-rich) iron oxyhydroxides, mixtures of protoceladonite and iron oxyhydroxide, and rare manganese oxides. These phases occur mainly as linings or fillings of open spaces in the basalt within the dark bands. Sulfides and intersertal glass are the only primary phases that can be seen to have been altered. Where dark bands have migrated into the rock, the rock behind the advancing band is almost devoid of secondary phases, implying redissolution. The potassium and magnesium in the secondary phases could have been supplied from ambient seawater. The aluminum in the protoceladonites must have been derived from local reaction of intergranular glass. The source of iron and silica could have been intergranular glass or low temperature mineralizing solutions of the type responsible for the formation of deposits of manganese oxides and iron oxyhydroxides and silicates on the seafioor.

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Section: Trend 3 (Iron-rich Analyses)supporting

confidence: 78%

Low-Temperature Alteration of Very Young Basalts from ODP Hole 648B: Serocki Volcano, Mid-Atlantic Ridge

Adamson¹,

Richards²

1990

Proceedings of the Ocean Drilling Program

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“…The assemblage of secondary minerals is similar with a predominance of smectite in both suites, and minor or trace amounts of chlorite, illite, glauconite/celadonite, talc, phillipsite, analcime, quartz, carbonate, and aragonite. A similar secondary mineral assemblage was deter- mined in the upper part of the basalt sequence of the Costa Rica Rift in Hole 504B (Kurnosov et al, 1983). Possibly the superimposed accretionary process weakly influenced the alteration of the uppermost ophiolitic effusives with the formation of partial smectites and particularly mixed-layer minerals among primary smectites.…”

Section: Discussionmentioning

confidence: 63%

Comparison of the Alteration and Petrology of the Taitao Ridge to the Taitao Ophiolite

Kurnosov¹,

Forsythe²,

Lindsley‐Griffin³

et al. 1995

Proceedings of the Ocean Drilling Program, 141 Scientific Results

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Samples from the Taitao Ridge collected at Site 862, Leg 141, consist of a bimodal suite of subalkalic basalts and dacites to rhyolites. Effusives and sheeted dikes from the Taitao Ophiolite consist of basalts, andesites, and dacites to rhyolites. The ophiolitic basalts are more vesicular than basalts from the Taitao Ridge and are dominated by plagiophyric and pyroxene-plagiophyric textures. Basalts from the Taitao Ridge are dominated by plagioclase-clinopyroxene (±olivine) vitrophyric textures. Geochemically, basalts of both suites fall within the alkaline olivine series, but samples from the Taitao Ridge exhibit more tholeiitic characteristics. The degree of alteration of basalts from Site 862 on the Taitao Ridge is low (to rarely moderate) with smectite as the main secondary mineral. In contrast, the degree of alteration in the effusives and sheeted-dike complex of the Taitao Ophiolite is moderate to strong, resulting in the development of greenschist facies minerals. The basalts and silicic volcanic rocks in each suite are comagmatic and may have been derived from a subalkaline primary melt that shared some features with mid-oceanic ridge tholeiite basalts (MORB) and with intraplate-rise alkaline basalts. The subalkaline basalts and silicic volcanic rocks comprising the Taitao Ridge and the Taitao Ophiolite may have formed synchronously with Pliocene-Pleistocene arrival of the Chile Rise and Taitao Fracture Zone at the continental slope and shelf. During the complicated interval of trench-transform-trench to trench-ridge-trench triple junction evolution, the ophiolite originally generated from melts within the Taitao Fracture/Transform's collision zone was uplifted and faulted against latest Miocene and Pliocene near-trench plutons and the preLate Jurassic metamorphic rocks of the Taitao Peninsula. The uppermost effusives of the ophiolite sequence may have been altered about as much as the Taitao Ridge basalts while in an oceanic setting, and then subjected to additional alteration at the time of emplacement on the continental margin. Alternatively, the higher state of alteration seen in the onshore ophiolitic samples may merely represent differences in the original magmatic/hydrothermal setting, such as the degree of sediment burial, the rates and durations of volcanism, or the age of the samples.

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“…Since the hole was begun in 1979, secondary alteration has been studied by many researchers (Adamson, 1983;Alt et al, 1983Alt et al, , 1985Alt et al, , 1986Honnorez et al, 1983;Kurnosov et al, 1983;Noack et al, 1983;Boronikhin, 1983a, 1983b;Ishizuka, 1989;Bohlke, 1980;Hart, 1973;Mével, 1980). Their data were used, along with data from other deep-penetration holes in the oceanic basement (Bass, 1976;Pertsev and Rusinov, 1980;etc.…”

Section: Introductionmentioning

confidence: 99%

Metasomatic and Metamorphic Peculiarities of the Diabase Dike Alteration in Hole 504B, Leg 140

Pertsev¹,

Kurdyukov²

1996

Proceedings of the Ocean Drilling Program, 148 Scientific Results

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The diabase dikes recovered during Leg 140 display four types of mineralogical alteration: (1) chlorite + amphibole + titanite; (2) chlorite + amphibole + ilmenite; (3) epidote + prehnite + anhydrite; (4) zeolites + smectite. The first two types represent both background and vein alteration. The third and fourth types are locally overprinted on the previous types. The third type exhibits oxidative features, whereas the fourth formed with cooling of the dike complex. Some veins and patches of strong alteration are surrounded by infiltrate-metasomatic halos, which suggest a difference in fluid pressure in pores and fractures. The temperature of the main alteration types ranged between 350° and 400°C. Noticeable temperature fluctuations in space and time were caused by alternating heating and cooling resulting from intrusions of younger dikes within short time intervals.

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Secondary Minerals in Basalt from the Costa Rica Rift, Holes 501 and 504B, Deep Sea Drilling Project Legs 68, 69, and 70

Cited by 13 publications

References 10 publications

Low-Temperature Alteration of Very Young Basalts from ODP Hole 648B: Serocki Volcano, Mid-Atlantic Ridge

Low-Temperature Alteration of Very Young Basalts from ODP Hole 648B: Serocki Volcano, Mid-Atlantic Ridge

Comparison of the Alteration and Petrology of the Taitao Ridge to the Taitao Ophiolite

Metasomatic and Metamorphic Peculiarities of the Diabase Dike Alteration in Hole 504B, Leg 140

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