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Title: Petrogenetic relationships between pegmatite and granite based on geochemistry of muscovite in pegmatite wall zones, Black Hills, South Dakota, USA

Abstract

The compositions of large samples of granitic pegmatite wall zones have been determined for a suite of ten pegmatites of diverse geochemical character and degree of compositional evolution in the Keystone area of the Black Hills. Whole-rock compositions are strongly peraluminous, and they deviate substantially from the granite minimum composition in quartz-albite-orthoclase normalized components, showing considerably more scatter than Harney Peak Granite whole rocks. Wall-zone minerals are commonly coarsely segregated, leading to large modal variability among whole rocks. These features make whole-rock samples of wall zones unsuitable for the determination of initial pegmatite bulk compositions. Trace and minor element compositions of muscovite separates from the wall zones were thus determined to eliminate the effects of modal variability on trace element concentrations so that geochemical differences between pegmatites could be modeled. Estimates of initial pegmatite melt trace element concentrations range from 800-4,000 ppm Rb, 100-1,000 ppm Cs, 200-2,000 ppm Li, and 1-50 ppm Ba. Trace element concentrations of muscovite from a given pegmatite generally cluster together, although several show considerable intra-pegmatite scatter, and there are large overlaps among different pegmatites. The geochemical characteristics of samples from the Etta pegmatite indicate mixing with and assimilation of country rocks. Exceptionally low Rb/Cs ratiosmore » of muscovite from the Etta pegmatite and similar to those of muscovite from K-feldspar-rich assemblages of other pegmatites where the Rb concentration of melt may have been buffered by crystallizing assemblages that had bulk Rb distribution coefficients close to 1.« less

Authors:
 [1]; ;  [2]
  1. Washington Univ., St. Louis, MO (United States)
  2. Univ. of New Mexico, Albuquerque (United States)
Publication Date:
OSTI Identifier:
7206245
DOE Contract Number:  
FG01-84ER13259
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta; (United States)
Additional Journal Information:
Journal Volume: 56:5; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; GEOLOGIC FORMATIONS; GEOCHEMISTRY; GRANITES; MUSCOVITE; PEGMATITES; SOUTH DAKOTA; ABSORPTION SPECTROSCOPY; ALBITE; BARIUM; CALCIUM; CESIUM; CHEMICAL COMPOSITION; CRYSTALLIZATION; DATA ANALYSIS; ELECTRON MICROPROBE ANALYSIS; EXPERIMENTAL DATA; FLUORINE; GEOLOGIC HISTORY; GEOLOGY; IRON; LITHIUM; MANGANESE; MAPS; MINERALOGY; MINERALS; NIOBIUM; ORTHOCLASE; POTASSIUM; QUARTZ; RUBIDIUM; SAMPLING; STRONTIUM; TANTALUM; TRACE AMOUNTS; VARIATIONS; X-RAY DIFFRACTION; ZINC; ALKALI METAL COMPOUNDS; ALKALI METALS; ALKALINE EARTH METALS; ALUMINIUM COMPOUNDS; ALUMINIUM SILICATES; CHEMICAL ANALYSIS; CHEMISTRY; COHERENT SCATTERING; DATA; DEVELOPED COUNTRIES; DIFFRACTION; ELEMENTS; FEDERAL REGION VIII; FELDSPARS; HALOGENS; IGNEOUS ROCKS; INFORMATION; METALS; MICA; MICROANALYSIS; NONDESTRUCTIVE ANALYSIS; NONMETALS; NORTH AMERICA; NUMERICAL DATA; OXIDE MINERALS; OXYGEN COMPOUNDS; PHASE TRANSFORMATIONS; PLUTONIC ROCKS; POTASSIUM COMPOUNDS; POTASSIUM SILICATES; ROCKS; SCATTERING; SILICATE MINERALS; SILICATES; SILICON COMPOUNDS; SPECTROSCOPY; TRANSITION ELEMENTS; USA; 580000* - Geosciences

Citation Formats

Jolliff, B L, Papike, J J, and Shearer, C K. Petrogenetic relationships between pegmatite and granite based on geochemistry of muscovite in pegmatite wall zones, Black Hills, South Dakota, USA. United States: N. p., 1992. Web. doi:10.1016/0016-7037(92)90320-I.
Jolliff, B L, Papike, J J, & Shearer, C K. Petrogenetic relationships between pegmatite and granite based on geochemistry of muscovite in pegmatite wall zones, Black Hills, South Dakota, USA. United States. https://doi.org/10.1016/0016-7037(92)90320-I
Jolliff, B L, Papike, J J, and Shearer, C K. 1992. "Petrogenetic relationships between pegmatite and granite based on geochemistry of muscovite in pegmatite wall zones, Black Hills, South Dakota, USA". United States. https://doi.org/10.1016/0016-7037(92)90320-I.
@article{osti_7206245,
title = {Petrogenetic relationships between pegmatite and granite based on geochemistry of muscovite in pegmatite wall zones, Black Hills, South Dakota, USA},
author = {Jolliff, B L and Papike, J J and Shearer, C K},
abstractNote = {The compositions of large samples of granitic pegmatite wall zones have been determined for a suite of ten pegmatites of diverse geochemical character and degree of compositional evolution in the Keystone area of the Black Hills. Whole-rock compositions are strongly peraluminous, and they deviate substantially from the granite minimum composition in quartz-albite-orthoclase normalized components, showing considerably more scatter than Harney Peak Granite whole rocks. Wall-zone minerals are commonly coarsely segregated, leading to large modal variability among whole rocks. These features make whole-rock samples of wall zones unsuitable for the determination of initial pegmatite bulk compositions. Trace and minor element compositions of muscovite separates from the wall zones were thus determined to eliminate the effects of modal variability on trace element concentrations so that geochemical differences between pegmatites could be modeled. Estimates of initial pegmatite melt trace element concentrations range from 800-4,000 ppm Rb, 100-1,000 ppm Cs, 200-2,000 ppm Li, and 1-50 ppm Ba. Trace element concentrations of muscovite from a given pegmatite generally cluster together, although several show considerable intra-pegmatite scatter, and there are large overlaps among different pegmatites. The geochemical characteristics of samples from the Etta pegmatite indicate mixing with and assimilation of country rocks. Exceptionally low Rb/Cs ratios of muscovite from the Etta pegmatite and similar to those of muscovite from K-feldspar-rich assemblages of other pegmatites where the Rb concentration of melt may have been buffered by crystallizing assemblages that had bulk Rb distribution coefficients close to 1.},
doi = {10.1016/0016-7037(92)90320-I},
url = {https://www.osti.gov/biblio/7206245}, journal = {Geochimica et Cosmochimica Acta; (United States)},
issn = {0016-7037},
number = ,
volume = 56:5,
place = {United States},
year = {Fri May 01 00:00:00 EDT 1992},
month = {Fri May 01 00:00:00 EDT 1992}
}