Pegmatite-wallrock interaction: holmquistite-bearing amphibolite, Edison pegmatite, Black Hills, South Dakota

Journal Article · · Am. Mineral.; (United States)

OSTI ID:6894581

Shearer, C K; Papike, J J

The fluid transport of relatively incompatible elements (Li, Rb, Cs) out of the rare-element pegmatite system and the subsequent interaction between that fluid and amphibolite result in the stabilization of holmquistite-bearing assemblages. In the amphibolite adjacent to the Edison pegmatite, Black Hills, South Dakota, three amphibolite assemblages resulting from fluid-country rock interaction can be distinguished: (1) biotite alteration assemblage, (2) hornblende-holmquistite alteration assemblage, and (3) hornblende-plagioclase assemblage. Holmquistite occurs only in assemblages 1 and 2 in which it coexists with and partially replaces hornblende. In coexisting holmquistite-hornblende pairs, the (Al + Fe/sup 3 +/ + 2Ti/sup 4 +/) value is greater, and the (Fe/sup 2 +/ + Mn)/(Fe/sup 2 +/ + Mn + Mg) ratio is less in holmquistite than in coexisting hornblende. By analogy to calcic and Fe-Mg amphiboles, a wide compositional gap exists between calcic and Li-rich amphiboles at temperatures of alteration-zone formation. The alteration of the amphibolite appears to be the result of (1) Li and K metasomatic alteration by alkali-rich, pegmatite-derived aqueous fluids and (2) retrograde metamorphism by the aqueous fluids resulting in the instability of plagioclase and ilmenite and the formation of epidote and sphene. The fluid has low B and F concentrations relative to fluids derived from lepidolite-bearing pegmatites in the same region. The conditions at which the alteration occurred were between 510 and 350/sup 0/C at 3-4 kbar. Field and textural evidence cannot discriminate between a single fluid-amphibolite interaction model and a multiple fluid-amphibolite interaction model. 51 references.

• Research Organization: South Dakota School of Mines and Technology, Rapid City (USA)
• DOE Contract Number: FG01-84ER13259
• OSTI ID: 6894581
• Journal Information: Am. Mineral.; (United States), Journal Name: Am. Mineral.; (United States) Vol. 73:3-4; ISSN AMMIA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
ALKALI METALS
AMPHIBOLE
AMPHIBOLITES
BIOTITE
CESIUM
CHEMICAL COMPOSITION
ELEMENTS
FEDERAL REGION VIII
FLUIDS
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GRANITES
HORNBLENDE
HYDRAULIC TRANSPORT
IGNEOUS ROCKS
LITHIUM
METALS
METAMORPHIC ROCKS
MICA
MINERALOGY
MINERALS
MOUNTAINS
NORTH AMERICA
PEGMATITES
PLUTONIC ROCKS
PRESSURIZING
RESERVOIR FLUIDS
ROCK-FLUID INTERACTIONS
ROCKS
RUBIDIUM
SILICATE MINERALS
SOUTH DAKOTA
TRANSPORT
USA