The komatiite nickel sulfide association at Scotia; a petrochemical investigation of the ore environment

Stolz, G.W.; Nesbitt, R.W.

doi:10.2113/gsecongeo.76.6.1480

Cited by 17 publications

(6 citation statements)

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“…A and B). However, it can be seen that certain interelement ratios in the altered rocks are not only relatively constant, but lie within the range of ratios reported from unaltered aluminiumundepleted komatiites (Nesbitt et al 1979;Stolz 1981;Stolz & Nesbitt 1981;McQueen 1981aMcQueen , 1981b. Some of these ratios are independent of the MgO content of the original rock, as long as it was in the range 11-50% (i.e.…”

Section: Textural and Chemical Evidence Of Original Rock Typessupporting

confidence: 72%

“…There is no textural evidence that any of these rocks were sediments. The spinifex textures allow the rocks to be characterized as komatiites (Nesbitt 1971;Stolz & Nesbitt 1981). The pyroclastic textures are also similar to those found in komatiitic sequences (Stolz & Nesbitt 1981), but not necessarily diagnostic of komatiites.…”

Section: Textural and Chemical Evidence Of Original Rock Typesmentioning

confidence: 74%

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Metamorphosed altered komatiites at Mount Martin, Western Australia — Archaean weathering products metamorphosed at the aluminosilicate triple point

Purvis

1984

Australian Journal of Earth Sciences

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Section: Textural and Chemical Evidence Of Original Rock Typessupporting

confidence: 72%

Section: Textural and Chemical Evidence Of Original Rock Typesmentioning

confidence: 74%

Metamorphosed altered komatiites at Mount Martin, Western Australia — Archaean weathering products metamorphosed at the aluminosilicate triple point

Purvis

1984

Australian Journal of Earth Sciences

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“…3) is unique in the Komati Formation, somewhat similar komatiites are described from sections hosting Ni deposits in Scotia, Australia (Stolz and Nesbitt 1981). Their type-C komatiites share the following features: (1) lensoid shape, (2) threepart zoning with vesicles in the upper zone, harrisitic olivine growth in the interior zone, and dunites at the base, (3) thickness (>15 m), and (4) position low in the spinifex horizon and lateral to more persistent, thinner spinifex units.…”

Section: Comparison With Other Vesicular Komatiitesmentioning

confidence: 72%

Vesicular komatiites, 3.5-Ga Komati Formation, Barberton Greenstone Belt, South Africa: inflation of submarine lavas and origin of spinifex zones

Dann

2001

Bulletin of Volcanology

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Komatiites of the 3.5-Ga Komati Formation are ultramafic lavas (>23% MgO) erupted in a submarine, lava plain environment. Newly discovered vesicular komatiites have vesicular upper crusts disrupted by synvolcanic structures that are similar to inflation-related structures of modern lava flows. Detailed outcrop maps reveal flows with upper vesicular zones, 2-15 m thick, which were (1) rotated by differential inflation, (2) intruded by dikes from the interior of the flow, (3) extended, forming a flooded graben, and/or (4) entirely engulfed. The largest inflated structure is a tumulus with 20 m of surface relief, which was covered by a compound flow unit of spinifex flow lobes. The lava that inflated and rotated the upper vesicular crust did not vesiculate, but crystallized as a thick spinifex zone with fist-size skeletal olivine. Instead of representing rapidly cooled lava, the spinifex zone cooled slowly beneath an insulating upper crust during inflation. Overpressure of the inflating lava may have inhibited vesiculation. This work describes the oldest vesicular komatiites known, illustrates the first field evidence for inflated structures in komatiite flows, proposes a new factor in the development of spinifex zones, and concludes that the inflation model is useful for understanding the evolution of komatiite submarine flow fields.

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“…Tephra Types I and II of Wohletz (1983), which predominate throughout K2v-b, are also suggestive of mafic liquids. Overall, pyroclasts in the Kromberg Formation are similar in shape and texture to basaltic and ultramafic pyroclasts described by Heiken (1972), Stolz and Nesbitt (1981), and Echeverria and Aitken (1986). Absent from the Kromberg Formation in the study area are coarse fragmental breccias characteristic of felsic volcanic sequences, such as H6 at the top of the Hooggenoeg Formation (Viljoen, R. P., and Viljoen, 1969a).…”

Section: Composition Of the Original Magmamentioning

confidence: 65%

Subaqueous to subaerial Archean ultramafic phreatomagmatic volcanism, Kromberg Formation, Barberton Greenstone Belt, South Africa

Ransom¹,

Byerly²,

Lowe³

1999

Geologic Evolution of the Barberton Greenstone Belt, South Africa

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Thick mafic and ultramafic volcanic sequences that characterize Archean greenstone belts are made up largely of massive and pillowed flow rocks; corresponding pyroclastic rocks are less common. Widespread mafic volcaniclastic deposits of the middle member of the Kromberg Formation (K2) in the Barberton Greenstone Belt are an exception. Their outcrops in the Onverwacht anticline and the adjoining Kromberg syncline expose a well-preserved tephra blanket more than 30 km in extent and as much as 1 km thick. On the west limb of the Onverwacht anticline, where the tephra sheet is thickest, it includes from base upward: 0-100 m of fine-grained tuff (division K2v-a); 300-1,000 m of massive to current-structured lapillistone and lapilli tuff (K2v-b); and a thin capping chert composed of silicified, commonly currentworked ash and dust (K2c). The mineralogy and composition of all rocks have been changed by early low-temperature alteration and later metamorphism. However, relict mineralogy, pyroclast textures, and trace-element chemistry suggest that the pyroclastic debris of K2v-b were derived from mafic to ultramafic magmas.The thickest section of pyroclastic debris on the west limb of the Onverwacht anticline represents the fill of a phreatomagmatic explosion crater formed by the removal of as much as 300 m of the underlying Buck Reef Chert. The lower part of the 1,000-m-thick fill consists largely of coarse lapillistone containing accidental blocks of Buck Reef Chert. This debris was deposited mainly by coarse subaqueous sediment flows but may include pyroclastic fall deposits, both deriving material from a subaqueous eruption column. Initial water depth is estimated to have been 700 m or less. Shoaling of the vent and the eventual transition to subaerial eruptions are suggested by upward transitions in the volcaniclastic pile into shallow-water, currentstructured lapilli tuff deposits in the upper part of the sequence. The chert cap, K2c, is composed of fine-grained silicified ash and accretionary lapilli deposited under very shallow water to subaerial conditions.

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The komatiite nickel sulfide association at Scotia; a petrochemical investigation of the ore environment

Cited by 17 publications

References 0 publications

Metamorphosed altered komatiites at Mount Martin, Western Australia — Archaean weathering products metamorphosed at the aluminosilicate triple point

Metamorphosed altered komatiites at Mount Martin, Western Australia — Archaean weathering products metamorphosed at the aluminosilicate triple point

Vesicular komatiites, 3.5-Ga Komati Formation, Barberton Greenstone Belt, South Africa: inflation of submarine lavas and origin of spinifex zones

Subaqueous to subaerial Archean ultramafic phreatomagmatic volcanism, Kromberg Formation, Barberton Greenstone Belt, South Africa

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