Chemical transport through continental crust: (Annual) progress report, 1988
The main objective of these studies is to understand the extent and mechanisms of chemical migration over a range of temperatures and in diverse geologic media. During 1988--1989 we continued to attack these problems through studies in the granite-pegmatite systems of the Black Hills, South Dakota. Mineral chemistry, major element chemistry and trace element modeling of the Harney Peak Granite (Black Hills, South Dakota) suggest that 75% to 80% fractional crystallization was the dominant mechanism in producing evolved tourmaline-bearing granite (high B, Li, Rb, Cs, Be, Nb) from a biotite-muscovite granite. To evaluate the petrogenetic-evolutionary relations between the granite and the surrounding rare-element pegmatite field, over 500 K-feldspars (Kf) were analyzed from 60 unzoned to complexly zoned pegmatites. Pegmatites with Kf relatively high in Ba (>140 ppM) and relatively low in Rb (<1000 ppM) and Cs (<30 ppM) are distributed in regions of high pegmatite density (>200 pegmatites/sq. mile), whereas highly evolved pegmatites with Kf enriched in Rb (>4000 ppM) and Cs (>500 ppM) are distributed in regions of low pegmatite density (<100 pegmatites/sq. mile). The extent of pegmatite evolution as reflected in the Kf documents the relation between the degree of fractionation and internal zoning characteristics. Modeling of these data is a major task for the next grant year to provide new insights into chemical and thermal transport in the midcrust.
- Research Organization:
- South Dakota School of Mines and Technology, Rapid City (USA)
- DOE Contract Number:
- FG02-88ER13982
- OSTI ID:
- 6453866
- Report Number(s):
- DOE/ER/13982-1; ON: DE89008763
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
Similar Records
Relations of zoned pegmatites to other pegmatites, granite, and metamorphic rocks in the southern Black Hills, South Dakota
Mineral recorders of pegmatite internal evolution: REE contents of tourmaline from the Bob Ingersoll pegmatite, South Dakota