Pegmatite-wallrock interactions, Black Hills, South Dakota: interaction between pegmatite-derived fluids and quartz-mica schist wallrock

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

OSTI ID:6913764

Shearer, C K; Papike, J J; Simon, S B; Laul, J C

The modification of mineral compositions through mineral-fluid exchange reactions (e.g., biotite Rb/K, F/OH) results in the formation of extensive exomorphic halos around the pegmatites. The compositional characteristics of the dispersion halos are related to pegmatite mineralogy. The dispersion halo associated with the Etta pegmatite (spodumene-bearing) is enriched in alkali elements (Li, Rb, Cs), As, and U, whereas the dispersion halos associated with the Bob Ingersoll No. 1 and Peerless pegmatites (lepidolite- or lithia mica-bearing, spodumene-absent) are enriched in alkali elements (Li, Rb, Cs), As, U, B, and F. The dispersion halos extend 21 to 90 m from the pegmatite contact along sampling traverses. The relative mobilities suggested from the enrichment of the quartz-mica schist and its mineral components are As = U < B = F < Rb less than or equal to Cs < Li. The extent of fluid infiltration into the country rock surrounding the pegmatites and fluid composition can be approximated through trace-element modeling. At the pegmatite contact, less than one equivalent mass of fluid equilibrated with the schist. The pegmatite-derived fluids have relatively high solute concentrations (> 1000 ppm) and exhibit compositional differences between pegmatites.

• Research Organization: South Dakota School of Mines and Technology, Rapid City
• OSTI ID: 6913764
• Journal Information: Am. Mineral.; (United States), Journal Name: Am. Mineral.; (United States) Vol. 71:3-4; ISSN AMMIA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
&amp; Rock Mechanics-- (-1989)
ACTINIDES
ALKALI METALS
ARSENIC
BORON
CESIUM
CHALCOGENIDES
CHEMICAL COMPOSITION
CRYSTALLIZATION
ELEMENTS
ENRICHMENT
FEDERAL REGION VIII
GEOLOGIC HISTORY
GRANITES
IGNEOUS ROCKS
LITHIUM
METALS
MICA
MINERALOGY
MINERALS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEGMATITES
PHASE TRANSFORMATIONS
PLUTONIC ROCKS
QUARTZ
ROCKS
RUBIDIUM
SEMIMETALS
SILICON COMPOUNDS
SILICON OXIDES
SOUTH DAKOTA
TRANSITION ELEMENTS
URANIUM
USA
VANADIUM