The Role of Cooling Cracks Formed at High Temperatures and of Released Gas in the Formation of Chilled Basic Margins in Net-veined Intrusions

Windley, Brian F.

doi:10.1017/s0016756800000224

Cited by 4 publications

(2 citation statements)

References 20 publications

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“…However the granite around the Sarqa-Amitsoq plutons could have been less mobile at the time of their intrusion than was the Sydprøven granite at the time when its associated gabbros were formed. Moreover, mixing of semicontemporaneous acid and basic magmas is not bound to occur, as can be shown by studies on net-veined intrusions (WINDLEY, 1965a(WINDLEY, , 1965b. V.PETROLOGY…”

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confidence: 92%

The geology of two small layered hornblende peridotite (picrite) plutons in South Greenland

Berrangé¹

1970

bullggu

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Two ultramafic dykes, which pinch and swell both vertically and horizontally and have a form similar to some kimberlite bodies, were intruded 1700 to 1335 m.y. ago during the 2nd episode of Ketilidian plutonism. Contact metamorphism of the adjacent granite was slight -albite-epidote hornfels facies. Petrological, mineralogical and chemical evidence indicates that the parent magma was picritic in composition, that it underwent flowage differentiation as a result of rapid intrusion, and then magmatic differentiation with gravity settling. The internal picritic (chemical classification) layered group crystallised first and includes hornblende peridotites, hornblende-hypersthene peridotites and rare harzburgite. The border group which crystallised later is formed of hypersthene-olivine hornblendites that chemically are picrites, and mica hornblendites that chemically are monzonites with affinities to kentallenite. Hornblende gabbro is a minor late differentiate. Steeply dipping banding cuts the earlier rhythmic layering and is thought to have formed by diffusion of material into cooling cracks developed prior to complete solidification. There are local concentrations of sulphides and platinoids. Three complete silicate analyses and a number of analyses for the platinoids, Au, Cr, Co, Cu, Ni, Ag, Pb and Zn are presented.

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confidence: 92%

The geology of two small layered hornblende peridotite (picrite) plutons in South Greenland

Berrangé¹

1970

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“…The author is indebted to the board of GGU and to its director K. ELLITSGAARD-RASMUSSEN for excellent facilities in the field and in the laboratory and for permission to publish this paper. The study at hand formed part of a doctorate thesis in the University of Exeter, England (WINDLEY, 1963). The author is grateful to Dr. K. COE for supervision and to Professor S. SIMPSON for use of the facilities at Exeter.…”

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The composite net-veined diorite intrusives of the Julianehåb district, South Greenland

Windley¹

1965

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Net-veined diorite intrusive are described from a plutonic environment of Precambrian granites in the Julianehåb district of S. Greenland. They are composite, minor intrusions consisting of a central diorite flanked by margins of aplitic granodiorite and they are characterised by the presence of pillow-shaped diorite blocks formed by granitic net-veins penetrating from the margins into the central diorite. The net-veins have not chilled the diorite, but along a few there are coarser grained margins in the diorite in which biotite, sphene and orthite have recrystallised. A contraction crack - shear plane theory is proposed to explain the formation of the net-veins. The granite material was introduced along the walls of the bodies from where it penetrated inwards through a network of contraction cracks. It was also introduced through the central parts of bodies along a set of parallel sheet fractures formed by shearing and compression of the diorite. The granitic material was produced by rheomorphism-at-depth from the recently reactivated granites of the Julianehåb district; it followed its basic parent to higher levels, where it penetrated the diorite at least partly by a process of recrystallisation and replacement.

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Theory of Some Local Features

Scheidegger¹

1982

Principles of Geodynamics

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The Role of Cooling Cracks Formed at High Temperatures and of Released Gas in the Formation of Chilled Basic Margins in Net-veined Intrusions

Cited by 4 publications

References 20 publications

The geology of two small layered hornblende peridotite (picrite) plutons in South Greenland

The geology of two small layered hornblende peridotite (picrite) plutons in South Greenland

The composite net-veined diorite intrusives of the Julianehåb district, South Greenland

Theory of Some Local Features

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