skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Fluid inclusion and stable isotope data for the Pea Ridge Fe-REE orebody, Missouri

Abstract

New fluid-inclusion and stable-isotope data define the character of the mineralizing fluids that formed the iron and rare-earth-element ore deposit at the Pea Ridge Mine, southeast Missouri. These fluids were very hot and highly saline brines that may have been magmatically derived. Early, pre-magnetite ore skarn alteration of the host rhyolitic tuff took place at temperatures greater than 420 C and possibly as high as 680 C based upon calculated temperatures of quartz-magnetite pairs. Halite homogenization of three- or more phase (liquid + vapor + salts) fluid inclusions in quartz indicates that the skarn-forming fluid had a temperature of about 460 C to > 530 C and a salinity of about 45 to 57 equivalent weight percent NaCl. Analyses of [delta][sup 18]O in quartz from the skarn zone average about 14.5[per thousand], compared to a value of about 13.0[per thousand] for quartz in the host rhyolite. Average [delta][sup 34]S values for pyrite of about 2.3[per thousand] in the skarn zone may reflect a magmatic source. Magnetite ore was deposited at temperatures between about 340 C and 530 C from a fluid with a salinity between about 54 and 60 equivalent weight percent NaCl. The large apparent range of temperatures indicatedmore » by both fluid-inclusion and stable-isotope data within each zone may be due to contamination by quartz from multiple stages of quartz deposition. Also, the assumed isotopic equilibrium between some mineral pairs may be incorrect. Moreover, fluid inclusions are relatively rare in all ore and alteration zones except the silicified zone, and only a few inclusions are clearly primary in origin. Nonetheless, the predominance of high temperatures and high salinities in all of the mineralized and altered zones supports the interpretation that Pea ridge is a magmatic hydrothermal deposit. This magmatic hydrothermal model is also supported by paragenetic relations defined by geologic mapping and geochemical modeling of major-, minor-, and trace-element data.« less

Authors:
; ;  [1]
  1. Geological Survey, Denver, CO (United States)
Publication Date:
OSTI Identifier:
7281342
Report Number(s):
CONF-9303210-
Journal ID: ISSN 0016-7592; CODEN: GAAPBC
Resource Type:
Conference
Journal Name:
Geological Society of America, Abstracts with Programs; (United States)
Additional Journal Information:
Journal Volume: 25:3; Conference: 27. annual Geological Society of America (GSA) North-Central Section meeting, Rolla, MO (United States), 29-30 Mar 1993; Journal ID: ISSN 0016-7592
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 15 GEOTHERMAL ENERGY; GEOLOGIC DEPOSITS; HYDROTHERMAL ALTERATION; MINERALIZATION; MAGNETITE; HYDROTHERMAL SYNTHESIS; MISSOURI; RARE EARTH COMPOUNDS; RHYOLITES; ISOTOPE RATIO; GEOCHEMISTRY; GEOTHERMOMETRY; INCLUSIONS; ROCK-FLUID INTERACTIONS; CHEMISTRY; DEVELOPED COUNTRIES; IGNEOUS ROCKS; IRON ORES; MINERALS; NORTH AMERICA; ORES; OXIDE MINERALS; ROCKS; SYNTHESIS; USA; VOLCANIC ROCKS; 580000* - Geosciences; 152002 - Geothermal Data & Theory- Properties of Minerals & Rocks; 152004 - Geothermal Data & Theory- Isotope & Trace Element Studies

Citation Formats

Sidder, G B, Day, W C, and Rye, R O. Fluid inclusion and stable isotope data for the Pea Ridge Fe-REE orebody, Missouri. United States: N. p., 1993. Web.
Sidder, G B, Day, W C, & Rye, R O. Fluid inclusion and stable isotope data for the Pea Ridge Fe-REE orebody, Missouri. United States.
Sidder, G B, Day, W C, and Rye, R O. 1993. "Fluid inclusion and stable isotope data for the Pea Ridge Fe-REE orebody, Missouri". United States.
@article{osti_7281342,
title = {Fluid inclusion and stable isotope data for the Pea Ridge Fe-REE orebody, Missouri},
author = {Sidder, G B and Day, W C and Rye, R O},
abstractNote = {New fluid-inclusion and stable-isotope data define the character of the mineralizing fluids that formed the iron and rare-earth-element ore deposit at the Pea Ridge Mine, southeast Missouri. These fluids were very hot and highly saline brines that may have been magmatically derived. Early, pre-magnetite ore skarn alteration of the host rhyolitic tuff took place at temperatures greater than 420 C and possibly as high as 680 C based upon calculated temperatures of quartz-magnetite pairs. Halite homogenization of three- or more phase (liquid + vapor + salts) fluid inclusions in quartz indicates that the skarn-forming fluid had a temperature of about 460 C to > 530 C and a salinity of about 45 to 57 equivalent weight percent NaCl. Analyses of [delta][sup 18]O in quartz from the skarn zone average about 14.5[per thousand], compared to a value of about 13.0[per thousand] for quartz in the host rhyolite. Average [delta][sup 34]S values for pyrite of about 2.3[per thousand] in the skarn zone may reflect a magmatic source. Magnetite ore was deposited at temperatures between about 340 C and 530 C from a fluid with a salinity between about 54 and 60 equivalent weight percent NaCl. The large apparent range of temperatures indicated by both fluid-inclusion and stable-isotope data within each zone may be due to contamination by quartz from multiple stages of quartz deposition. Also, the assumed isotopic equilibrium between some mineral pairs may be incorrect. Moreover, fluid inclusions are relatively rare in all ore and alteration zones except the silicified zone, and only a few inclusions are clearly primary in origin. Nonetheless, the predominance of high temperatures and high salinities in all of the mineralized and altered zones supports the interpretation that Pea ridge is a magmatic hydrothermal deposit. This magmatic hydrothermal model is also supported by paragenetic relations defined by geologic mapping and geochemical modeling of major-, minor-, and trace-element data.},
doi = {},
url = {https://www.osti.gov/biblio/7281342}, journal = {Geological Society of America, Abstracts with Programs; (United States)},
issn = {0016-7592},
number = ,
volume = 25:3,
place = {United States},
year = {Mon Mar 01 00:00:00 EST 1993},
month = {Mon Mar 01 00:00:00 EST 1993}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share: