Start |Author Index | View Uploaded Presentations | Meeting Information

2002 Denver Annual Meeting (October 27-30, 2002)

Paper No. 6
Presentation Time: 1:30 PM-5:30 PM

MOLYBDENITE AGE FOR CANDELARIA IRON OXIDE CU-AU DEPOSIT, AND A COMPARISON OF THE RE-OS ISOTOPIC SIGNATURES OF ORE FROM THE CHILEAN IRON BELT


MATHUR, Ryan, Geology, Juniata College, 1700 Moore Street, Huntingdon, PA 16652, RUIZ, Joaquin, Department of Geosciences, Univ of Arizona, Gould-Simpson Bldg, Tucson, 85721, MARSCHIK, Robert, Institut für Mineralogie, TU Bergakademie Freiberg, Brennhausgasse 14, Freiberg, 09596, Germany and MUNIZAGA, Francisco, Departamento de Geología, Universidad de Chile, casilla 13518, Correo 21, Santiago, 6784537, Chile, Mathur@juniata.edu

Re-Os isotopes are used to determine the age of mineralization at Candelaria, Chile, and to explore possible genetic links with the batholithic intrusions in the area. Calculated Re-Os ages from molybdenite are 114.2 * 0.6 Ma and 115.2 * 0.6 Ma, and are interpreted to represent the age of mineralization. An isochron calculated by Re-Os ratios from hydrothermal magnetite and sulfides constrains an initial 187Os/188Os of 0.36 * 0.10. These values are broadly similar to the calculated initial 187Os/188Os for magmatic magnetite in nearby batholithic rocks that range from 0.20 to 0.41. The relatively radiogenic initial 187Os/188Os represents a mixture of mantle and crustal components in the ores and batholitic rocks. The similarity in initial 187Os/188Os of the ore and magmatic oxides suggest that the granitic plutons could be the source for metals in the Candelaria district. In order to establish a regional perspective, we analyzed ore minerals from other Chilean deposits of the iron oxide (Cu-U-Au-REE) class. Magnetite from the Manto Verde iron oxide Cu-Au deposit has Os and Re concentrations of 11 to 17 ppt and 4 to 6 ppb, respectively. The initial 187Os/188Os is approximately 0.20 and similar to that of ore minerals from Candelaria, and to the Early Cretaceous batholithic intrusions. These data indicate a similar metal source for the mineralization at Manto Verde and Candelaria. Magnetite from three magnetite-apatite deposits of the Chilean Iron Belt have Re concentrations between 0.8 and 3 ppb and Os concentrations between 11 and 76 ppt. Calculated initial 187Os/188Os of these magnetites range from 1.2 to 8.4, and are different from those of the iron oxide Cu-Au deposits. The cause of the comparatively high radiogenic signatures in the magnetite-apatite ores could be related to fluid interactions with the surrounding sedimentary rocks during their genesis. In contrast to the iron oxide Cu-Au systems, the Os in magnetite-apatite ores could be derived from sedimentary rocks.

Session No. 152--Booth# 6

Economic Geology (Posters)
Tuesday, 29 October 2002: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol. 34, No. 6, September 2002, p.337
© Copyright 2002 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
Back to: Economic Geology (Posters)
<< Previous Abstract | Next Abstract >>