Basalts from the Northern Part of the Mid-Atlantic Ridge

Muir, I. D.; Tilley, C. E.; Scoon, J. H.

doi:10.1093/petrology/7.2.193

Cited by 106 publications

(22 citation statements)

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“…Similar textures were also described and illustrated by Muir and Tilley (1966) in basalts dredged on the mid-Atlantic Ridge near 30°N, and they reached similar conclusions about the paragenesis of the major silicate minerals. Thus, the basalts at Sites 100 and 105 do not differ texturally in any important respect from samples dredged from surface outcrops along the Ridge, and could thus have been erupted and crystallized under conditions similar to those now prevailing in or near the median valley.…”

Section: Texturessupporting

confidence: 79%

Textural and Mineralogical Relations of Basalts from Sites 100 and 105

Bryan¹

1972

Initial Reports of the Deep Sea Drilling Project

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Section: Texturessupporting

confidence: 79%

Textural and Mineralogical Relations of Basalts from Sites 100 and 105

Bryan¹

1972

Initial Reports of the Deep Sea Drilling Project

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“…Here, an early survey of an arbitrarily chosen piece of ridge crest (Hill, 1960) recovered two dredge hauls; Muir andTilley (1964, 1966) studied the hauls, and showed that the basalts had a transitional character and incompatible-element concentrations several times greater than MORB. These results were confirmed by later surveys (Aumento et al, 1971).…”

Section: Previous Geochemical Workmentioning

confidence: 99%

Mantle Heterogeneity in the North Atlantic: Evidence from Leg 49 Geochemistry

Cann¹,

Tarney²,

Varet³

et al. 1979

Initial Reports of the Deep Sea Drilling Project

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“…Downes, 1973;Mäkipää, 1978), such crystals do seem to be common in basalts of all ages which have erupted onto the ocean floor (Pearce & Donaldson, 1974). They have been described in modern ocean-floor basalts (see Muir et al, 1966;Bryan, 1972;Hermes & Schilling, 1976), as well as in Proterozoic metalavas (see Baragar, 1960;Pearce & Donaldson, 1976) and younger, often spilitic, pillow lavas associated with ophiolites (Liou, 1974;Seguir & Laurent, 1975) and other Alpine formations (see Vuagnat, 1959;Batley, 1956). The pillow lavas of the Pahakangas Formation also contain quartz-filled gas cavities of the kind that are abundant in ocean-floor basalts (Wells et al, 1978), and which according to Anhaeusser (ref.…”

Section: Discussionmentioning

confidence: 98%

Komatiitic and tholeiitic metavolcanics of the Siivikkovaara area in the Archean Kuhmo greenstone belt, eastern Finland

Hanski¹

1980

Bull Geol Soc Finland

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HANSKI, EERO 1980: Komatiitic and tholeiitic metavolcanics of the Siivikkovaara area in the Archean Kuhmo greenstone belt, eastern Finland. Bull. Geol. Soc. Finland 52, Komatiitic metavolcanics are abundant and well-preserved in the Siivikkovaara area, which lies in the middle part of the Archean Kuhmo greenstone belt. Together with the underlying tholeiites, these form the Kellojärvi Group, which is divided into two formations, those of Pahakangas and Siivikkovaara. The Pahakangas Formation consists of pillowed and massive metalavas and intercalated banded iron formations. The metalavas are chemically typical Archean low-potassium tholeiites. The overlying Siivikkovaara Formation has three subunits, the Siivikko, Mäkinen and Raivio Members. The metavolcanics of the Siivikko Member, which are mainly peridotitic komatiites (MgO ^ 18 °/o), have many structures typical of extrusive rocks, including breccias, pillows, spinifex textures and polygonal jointing. The microspinifex-textured rocks richest in magnesium contain about 20 °/o MgO. The Mäkinen Member consists of basaltic and pyroxenitic komatiites (MgO < 18 °/o), which occur in the form of variolitic pillow lavas. The Raivio Member is composed of ultramafic to mafic metatuffs. The spinifex textures in the Siivikkovaara area were originally formed by clinopyroxene. Zones Ai, A-z, Bi and BL > can be distinguished in the spinifex-textured lava flows, and Ao has further subunits dominated by dendritic, platy or acicular hornblende pseudomorphs after clinopyroxene. The liquid composition of the spinifextextured flows is deduced to be in the range of pyroxenitic komatiite. These flows are differentiated mainly by olivine and minor pyroxene and chromite precipitation. Albite in the spinifex-textured rocks is formed through sodium metasomatism caused by sea-water. There are many indicators to support the notion of a deep-sea origin for the lavas of the Kellojärvi Group. Despite the relatively low MgO content of the komatiites in the Siivikkovaara Formation, two nickel-copper occurences have been found in the formation.

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Basalts from the Northern Part of the Mid-Atlantic Ridge

Cited by 106 publications

References 0 publications

Textural and Mineralogical Relations of Basalts from Sites 100 and 105

Textural and Mineralogical Relations of Basalts from Sites 100 and 105

Mantle Heterogeneity in the North Atlantic: Evidence from Leg 49 Geochemistry

Komatiitic and tholeiitic metavolcanics of the Siivikkovaara area in the Archean Kuhmo greenstone belt, eastern Finland

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