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Title: Mass transfer during wall-rock alteration: An example from a quartz-graphite vein, Black Hills, South Dakota

Abstract

Mass transfer and fluid-rock interaction have been evaluated along two sample traverses in low-sillimanite grade quartz-mica schist adjacent to a synmetamorphic quartz-graphite vein in the southern Black Hills, South Dakota. In an {approximately}17 cm halo between apparently unaltered schist and the vein contact is an outer zone of cryptic alteration and three inner zones of visible alteration. The cryptic zone consists of the original prograde metamorphic mineral assemblage plus anomalously high amounts of tourmaline. The outermost visible zone contains abundant graphite. The second visible zone is defined by intensive bleaching of the schist. The innermost visible zone, immediately adjacent to the vein, is tourmaline + quartz + plagioclase + limonite + graphite. The vein is composed almost entirely of quartz, but also contains trace amounts of graphite. Mass balance calculations indicate that Al was essentially inert. The predominant chemical changes during wall-rock alteration were addition of B and C from the vein-forming fluid along with loss of K from the wall rocks, corresponding to precipitation of tourmaline and graphite, and the progressive destruction of microcline, biotite, and muscovite toward the vein. In addition, the elements V, Cr, Cu, Zn, Pb, As, Sb, W, and Au were introduced into the countrymore » rock, whereas Si, Rb, Ba, and Cs were removed. Fluid-rock interaction modeling suggests that between one and four equivalent masses of fluid interacted chemically with the most altered mineral assemblages. In addition, greater than one equivalent mass of reactive fluid penetrated to distances of at least 5 cm from the vein contact.« less

Authors:
; ;  [1];  [2]
  1. (South Dakota School of Mines and Technology, Rapid City, SD (USA))
  2. (Pacific Northwest Laboratories, Richland, WA (USA))
Publication Date:
OSTI Identifier:
5181330
DOE Contract Number:
FG01-84ER13259; AC06-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; (USA); Journal Volume: 52:7
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; SCHISTS; CHEMICAL COMPOSITION; HYDROTHERMAL ALTERATION; MINERALOGY; SOUTH DAKOTA; GEOCHEMISTRY; GEOLOGIC HISTORY; GRAPHITE; MASS BALANCE; MASS TRANSFER; PETROGENESIS; QUARTZ; ROCK-FLUID INTERACTIONS; CARBON; CHALCOGENIDES; CHEMISTRY; ELEMENTAL MINERALS; ELEMENTS; FEDERAL REGION VIII; METAMORPHIC ROCKS; MINERALS; NONMETALS; NORTH AMERICA; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; ROCKS; SILICON COMPOUNDS; SILICON OXIDES; USA; 580000* - Geosciences

Citation Formats

Galbreath, K.C., Duke, E.F., Papike, J.J., and Laul, J.C. Mass transfer during wall-rock alteration: An example from a quartz-graphite vein, Black Hills, South Dakota. United States: N. p., 1988. Web. doi:10.1016/0016-7037(88)90014-2.
Galbreath, K.C., Duke, E.F., Papike, J.J., & Laul, J.C. Mass transfer during wall-rock alteration: An example from a quartz-graphite vein, Black Hills, South Dakota. United States. doi:10.1016/0016-7037(88)90014-2.
Galbreath, K.C., Duke, E.F., Papike, J.J., and Laul, J.C. 1988. "Mass transfer during wall-rock alteration: An example from a quartz-graphite vein, Black Hills, South Dakota". United States. doi:10.1016/0016-7037(88)90014-2.
@article{osti_5181330,
title = {Mass transfer during wall-rock alteration: An example from a quartz-graphite vein, Black Hills, South Dakota},
author = {Galbreath, K.C. and Duke, E.F. and Papike, J.J. and Laul, J.C.},
abstractNote = {Mass transfer and fluid-rock interaction have been evaluated along two sample traverses in low-sillimanite grade quartz-mica schist adjacent to a synmetamorphic quartz-graphite vein in the southern Black Hills, South Dakota. In an {approximately}17 cm halo between apparently unaltered schist and the vein contact is an outer zone of cryptic alteration and three inner zones of visible alteration. The cryptic zone consists of the original prograde metamorphic mineral assemblage plus anomalously high amounts of tourmaline. The outermost visible zone contains abundant graphite. The second visible zone is defined by intensive bleaching of the schist. The innermost visible zone, immediately adjacent to the vein, is tourmaline + quartz + plagioclase + limonite + graphite. The vein is composed almost entirely of quartz, but also contains trace amounts of graphite. Mass balance calculations indicate that Al was essentially inert. The predominant chemical changes during wall-rock alteration were addition of B and C from the vein-forming fluid along with loss of K from the wall rocks, corresponding to precipitation of tourmaline and graphite, and the progressive destruction of microcline, biotite, and muscovite toward the vein. In addition, the elements V, Cr, Cu, Zn, Pb, As, Sb, W, and Au were introduced into the country rock, whereas Si, Rb, Ba, and Cs were removed. Fluid-rock interaction modeling suggests that between one and four equivalent masses of fluid interacted chemically with the most altered mineral assemblages. In addition, greater than one equivalent mass of reactive fluid penetrated to distances of at least 5 cm from the vein contact.},
doi = {10.1016/0016-7037(88)90014-2},
journal = {Geochimica et Cosmochimica Acta; (USA)},
number = ,
volume = 52:7,
place = {United States},
year = 1988,
month = 7
}
  • Green structures, 0.5 to 1.5 in. across, occur in a Tertiary rhyolite pipe in the northern Black Hills, South Dakota. The structures are of two types: angular to ellipsoidal masses and stretched or smeared structures. Thin section analysis revealed that those of the first type are massive, with no internal structure, and those of the second type are cellular and have classic flame structure characteristics. XRD indicated the composition to be a mixture of secondary mordenite (a zeolite) and montmorillonite. The first type is interpreted to be deuterically altered vitrophyre clasts and the second type to be altered vesicular structuresmore » produced by degassing of the magma in the pipe. Chemical analysis of the alteration material indicates a loss of alkalies and silica, with an increase in water, CaO, MgO and ferric iron when compared to the composition of fresh vitrophyre from the same pipe. The changes are in agreement with experimental work on the alteration of rhyolitic glass by a number of researchers. This is the first occurrence of mordenite reported for the Black Hills.« less
  • Several uraniurn deposits are present in the Fall River sandstone of Early Cretaceous age on the northeast flank of the Black Hills, Butte County, South Dakota. The deposits are within a fine-grained, well-sorted, persistent basal sandstone unit that ranges in thickness from 2 to 18 feet and dips about 4 deg NE. Detailed mapping of about 2 square miles surrounding the deposits has shown that all the uranium occurrences and most of the areas of high radioactivity are where the color changes in the basal sandstone from reddish on the up-dip side of the occurrences to yellowish-gray or buff down-dip.more » Radioactivity measurements show that uraniurn is distributed almost continuously along the sinuous red-buff contact for more than 5 miles. Laboratory work indicates that the red color is caused by hematlte resulting from the alteration of ferrous iron minerals and hydrous ferric oxides. The close association of the red-buff contact and the uraniurn deposits suggests that the two were formed by the same solutions. The uranium was probably deposited originally from ground water that moved down-dip and gradually changed from an oxidizing solution near the surface to a mildly reducing solution at depth. Concentrations of uranium have resulted from the localization of reducing conditions caused perhaps by structures superimposed on the regional dip, local thinning or decrease in permeability of the sandstone, or concentrations of pyritiferous carbonaceous material. The red alteration is probably the result of pre-Oligocene weathering that has extended downward in the more permeable beds about 200 feet below the ancient erosion surface. Oxidation of the primary uranium during the present weathering cycle has resulted in the formation of carnotite and possibly other secondary uranium minerals. (auth)« less
  • 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 contactmore » 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.« less
  • 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 compositionsmore » 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.« less
  • The focus of this research was to determine if abandoned mines constitute a major environmental hazard in the Black Hills. Many abandoned gold mines in the Black Hills contribute acid and heavy metals to streams. In some areas of sulfide mineralization local impacts are severe, but in most areas the impacts are small because most ore deposits consist of small quartz veins with few sulfides. Pegmatite mines appear to have negligible effects on water due to the insoluble nature of pegmatite minerals. Uranium mines in the southern Black Hills contribute some radioactivity to surface water, but he impact is limitedmore » because of the dry climate and lack of runoff in that area. 26 refs.« less