Geochemical consequences of the metasomatic conversion of an Early Archean komatiite sequence into chert

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6593069

Hanor, J S; Duchac, K C

Duchac and Hanor (1985) have demonstrated from field and petrographic evidence that the stratiform, muscovite-bearing cherts of Skokhola Ridge, Barberton Mountain Land, South Africa, represent a pervasively silicified sequence of komatiites and komatiitic basalts of Early Archean age. Most alteration took place early, prior to any significant tectonic deformation. The isovolumetric nature of the alteration, as confirmed by excellent preservation of igneous textures, and the immobility of Al make it possible to quantify elemental gains and losses during metasomatism. The sequence was strongly depleted in Na, Mg, Ca, Sr, Fe, and Mn, and enriched in K, Rb, and Ba, Al, Y, Zr, Ti, and P were immobile. It is most likely that the sequence was altered by large volumes of ascending hydrothermal solutions, with the decrease in T upward favoring precipitation of silica and muscovite. The net effect was to convert an ultramafic igneous rock into a rock having a composition approaching that of the average sandstone. Such alteration, if regionally extensive, undoubtedly affected the geochemical evolution of both the Early Archean crust and hydrosphere in the Barberton greenstone belt.

• Research Organization: Louisiana State Univ., Baton Rouge (USA)
• OSTI ID: 6593069
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
AFRICA
BASALT
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
CHERT
GEOCHEMISTRY
HYDROTHERMAL ALTERATION
HYDROTHERMAL SYNTHESIS
IGNEOUS ROCKS
PETROGENESIS
PETROGRAPHY
ROCK-FLUID INTERACTIONS
ROCKS
SEDIMENTARY ROCKS
SOUTH AFRICA
SYNTHESIS
VOLCANIC ROCKS