Chemistry of Primary and Secondary Phases in Intraplate Basalts and Volcaniclastic Sediments, Deep Sea Drilling Project Leg 89

Floyd, P. A.; Rowbotham, G.

doi:10.2973/dsdp.proc.89.116.1986

Cited by 13 publications

(5 citation statements)

References 23 publications

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“…Ti abundances are low (0.01 cfu) with Ti/Al ratios of approximately 1:10, although with the exception of Sample 802A-62R-2, 53-59 cm, within-sample variation is limited. The Ti and Cr contents are similar to those of the Nauru Basin clinopyroxenes (Floyd and Rowbotham, 1986) and generally reflect the low Ti and Cr contents of the bulk rocks.…”

Section: Pyroxenesmentioning

confidence: 55%

“…Many primitive mid-ocean ridge basalts (MORB) containing highly calcic plagioclase may display increasing Mg abundances with decreasing An content (Bence et al, 1975), whereas Nauru Basin plagioclases from evolved tholeiites show a positive correlation between Mg and An (Floyd and Rowbotham, 1986). On the other hand, Kempton et al (1985) noted a positive correlation of Mg with An content for phenocrysts, xenocrysts, and groundmass feldspar only when the compositions were below An 79 and had a complex relationship in compositions more An-rich than this figure.…”

Section: Plagioclasesmentioning

confidence: 87%

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Mineral Chemistry of Primary and Secondary Phases in Basaltic Rocks, Leg 129

Rowbotham¹,

Floyd²

1992

Proceedings of the Ocean Drilling Program

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Primary magmatic phases (spinel, olivine, plagioclase, clinopyroxene, amphibole, and biotite) and secondary Phyllosilicates (smectite, chlorite-smectite, and celadonite) were analyzed by electron microprobe in alkalic and tholeiitic dolerites and basalts from Ocean Drilling Program Sites 800, 801, and 802. Aphyric alkalic dolerite sills (Hole 800A) and basalt flows (Holes 80IB and 801C) share common mineralogical features: matrix feldspars are strongly zoned from labradorite cores to discrete sodic rims of alkali feldspar with a high Or component, which overlaps that of quench microlites in glassy mesostasis; little fractionated clinopyroxenes are Ti-rich diopsides and augites (with marked aegirine-augite rims at Site 801); rare, brown, Fe 3+ -rich amphibole is winchite; and late biotites exhibit variable Ti contents. Alkalic rims to feldspars probably developed at the same time as quenched mesostasis feldspars and late-stage magmatic biotite, and represent the buildup of K-rich hydrous fluids during crystallization. Phenocryst phases in primitive mid-ocean ridge tholeiites from Hole 801C (Mg numbers about 70) have extreme compositions with chrome spinel (Cr/Cr + Al ratios about 0.2-0.4), Ni-rich olivine (Fo 90 ), and highly calcic plagioclase (An 90 ). Later glomerophyric clumps of plagioclase (An 75 _ 80 ) and clinopyroxene (diopside-augite) are strongly zoned and probably reflect rapidly changing melt conditions during upward transport, prior to seafloor quenching. In contrast, phenocryst phases (olivine, plagioclase, and clinopyroxene) in the Hole 802A tholeiites show limited variation and do not have such primitive compositions, reflecting the uniform and different chemical composition of all the bulk rocks.Replacive Phyllosilicates in both alkalic and tholeiitic basalts include various colored smectites (Fe-, Mg-, and Al-saponites), chlorite-smectite and celadonite. Smectite compositions typically reflect the replaced host composition; glass is replaced by brown Fe-saponites (variable Fe/Mg ratios) and olivine by greenish Mg-saponites (or Al-rich chlorite-smectite).

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Section: Pyroxenesmentioning

confidence: 55%

Section: Plagioclasesmentioning

confidence: 87%

Mineral Chemistry of Primary and Secondary Phases in Basaltic Rocks, Leg 129

Rowbotham¹,

Floyd²

1992

Proceedings of the Ocean Drilling Program

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“…content for saponite, celadonite, and saponite–celadonite mixtures ± Fe‐oxyhydroxides. Fields for celadonite, saponite, and saponite‐celadonite mixtures are based on data from other DSDP and ODP drill holes (Hole 896A [ Laverne et al , 1996]; Holes 801C and 1149D [ Talbi and Honnorez , 2003]; Leg 168 [ Marescotti et al , 2000; Porter et al , 2000]; Holes 585 and 585A [ Viereck et al , 1984]; Hole 585 [ Floyd and Rowbotham , 1984]; Hole 896A [ Teagle et al , 1996]; Site 417 [ Alt and Honnorez , 1984] and the Troodos ophiolite [ Gillis and Robinson , 1990]).…”

Section: Resultsmentioning

confidence: 99%

“…and K values >1.3 a.p.f.u. ; Holes 801C and 1149D [Talbi and Honnorez, 2003]; Leg 168 [Marescotti et al, 2000;Porter et al, 2000]; Holes 585 and 585A [Viereck et al, 1984]; Hole 585 [Floyd and Rowbotham, 1984]; Hole 896A ; Site 417 [Alt and Honnorez, 1984] and the Troodos ophiolite [Gillis and Robinson, 1990]). [20] Saponite is Mg-rich ( Figure 5) with magnesium numbers (Mg# = Mg/(Fe T + Mg)) ranging from 0.48 to 0.96 (Table S2).…”

Section: Phyllosilicatesmentioning

confidence: 99%

ODP Site 1224: A missing link in the investigation of seafloor weathering

Paul

Gillis

Coggon

et al. 2006

Geochem Geophys Geosyst

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[1] A section of Eocene (46 Ma) upper oceanic crust was recovered at Ocean Drilling Program (ODP) Site 1224 in the northeast Pacific basin. The secondary mineralogy and geochemistry of altered basalts and isotopic composition of Ca-carbonate were studied to determine the extent and nature of alteration at this site. Most basalts are <5% altered to secondary mineral assemblages of Fe-oxyhydroxides, celadonite, saponite, Ca-carbonate, trace pyrite, and rare phillipsite and quartz. Alteration is concentrated within brown and dark gray haloes, which formed adjacent to veins and fractures. Haloes comprise 10% of the core (9% dark gray; 1% brown); veins comprise <1% of the core, with an average of 18 veins per meter of recovered cores. Calculated chemical fluxes, which account for groundmass alteration and the composition and abundance of secondary minerals associated with veins, vesicles, and haloes, indicate significant additions of Si, Fe T , Mg, Ca, and CO 2 and minor additions of Al, Mn, and Na to the crust. The magnitude of these fluxes is low relative to other drilled volcanic sections such as Sites 504, 896, 417, and 418. 87 Sr/ 86 Sr ratios (0.70776 to 0.70824) and trace element ratios (Mg/Ca) of calcite imply that Ca-carbonate formed within 20 Ma of crustal formation from relatively unaltered seawater. Oxygen isotope data yield Ca-carbonate formation temperatures of 4 to 11°C. The relative freshness of the Site 1224 lavas is attributed to the capping of the volcanic section by massive flows.

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“…Studies of the alteration of basaltic glass in pillow lavas under low temperature conditions abound, but less so for hyaloclastites (for example, Floyd and Rowbotham, 1986;Schmincke, 1983a;Viereck et al, 1982Viereck et al, ,1986.…”

Section: Alteration Of Glass Shardsmentioning

confidence: 99%

Petrography and Geochemistry of Graded Volcaniclastic Sediments and Their Clasts, Leg 129

Lees¹,

Rowbotham²,

Floyd³

1992

Proceedings of the Ocean Drilling Program

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Samples collected from the coarse basal portions of mid-Cretaceous volcaniclastic turbidites from the Mariana and Pigafetta basins are remarkably similar in terms of the petrographic and chemical features of their igneous clasts and bulk rock composition. Clasts of magmatic origin are dominated by glassy vesicular shards, variably phyric, holocrystalline basalts, and crystal fragments (olivine, clinopyroxene, plagioclase, amphibole, and biotite). The composition of the pyroxenes and amphiboles are typical of those found in differentiated hydrous alkali basalts. The bulk chemical composition of the volcaniclastites (based on stable incompatible elements and their ratios in highly vitric samples) is characteristic of alkali basalts found in within-plate oceanic eruptive environments. Miocene volcaniclastites from Site 802 are broadly similar to the Cretaceous samples in terms of clast type and bulk composition, and have also been derived from an oceanic alkali basalt source. The chemistry of the Miocene volcaniclastites differ, however, in having distinctive Zr/Y and Zr/Nb ratios and a more restricted chemical composition. The magmatic products of nearly emergent seamounts within the western Pacific basins appears to have been dominated by alkali basalt volcanism during the mid-Cretaceous and also the Miocene.The highly vitric nature of the Cretaceous and Miocene volcaniclastites, together with the morphology and vesicularity of their shards, suggests that they are the reworked (via mass flow) products of hyaloclastite accumulations produced in a shallow-water eruptive environment, such as that adjacent to nearly emergent seamounts or ocean islands. The association of ooids, reefal debris, and, in rare cases, woody material with the volcaniclastites supports their shallow-water derivation.

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Chemistry of Primary and Secondary Phases in Intraplate Basalts and Volcaniclastic Sediments, Deep Sea Drilling Project Leg 89

Cited by 13 publications

References 23 publications

Mineral Chemistry of Primary and Secondary Phases in Basaltic Rocks, Leg 129

Mineral Chemistry of Primary and Secondary Phases in Basaltic Rocks, Leg 129

ODP Site 1224: A missing link in the investigation of seafloor weathering

Petrography and Geochemistry of Graded Volcaniclastic Sediments and Their Clasts, Leg 129

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