Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Franchini, M. B. Articles by Vallés, J. M. Search for Related Content GeoRef GeoRef Citation

First Occurrence of Ilvaite in a Gold Skarn Deposit

Marta B. Franchini

CONICET-CIMAR, Facultad de Ingenería, Universidad Nacional del Comahue, Avenida Buenos Aires 1400, 8300 Neuquén, Argentina

Lawrence D. Meinert

Department of Geology, Washington State University, Pullman, Washington 99164-2812

Jorge M. Vallés

CONICET-CIMAR, Facultad de Ingenería, Universidad Nacional del Comahue, Avenida Buenos Aires 1400, 8300 Neuquén, Argentina

Corresponding author: email, franchini{at}infovia.com.ar

Ilvaite occurs in the Fortitude Au skarn deposit, Nevada, the first reported occurrence in a Au skarn deposit. Ilvaite is a mixed-valence calcium and iron silicate known previously as a relatively rare mineral in some Zn(Pb), Fe, and Sn skarns. At Fortitude, ilvaite is present as resinous, black grains with quartz, ferroactinolite, and sulfides (pyrrhotite-arsenopyrite-bismuthinite). It also occurs as a late-phase replacing prograde pyroxene (Hd_91–96 Jo_3–5) in magnetite-rich exoskarn near the skarn-marble contact and replacing calcite grains at the marble front.

Electron microprobe analyses show that the ilvaite from the Fortitude Au-skarn is similar in composition to ilvaite from Fe skarns. Both have high iron and low manganese relative to Zn skarns. The high iron content in ilvaite from Fe and Au skarns is consistent with the high-Fe activities and low-f_O2 conditions that characterize both skarn types and their associated intrusions. Similarly, the ilvaite from Zn skarns reflects the Mn-rich mineralogy of these deposits. Ilvaite from one Sn skarn occurrence has higher Al₂O₃ and TiO₂ and lower MnO and Fe⁺³ than ilvaite from the other skarn types and FeO totals intermediate between ilvaite from Zn and Fe-Au skarns. The Al₂O₃ and TiO₂ content of ilvaite appears to be inversely proportional to that of the associated intrusions. Although it is a rare mineral in most skarns, these observations suggest that the occurrence and composition of ilvaite can be used to discriminate among different skarn deposit types and to provide information about the geological and geochemical environment of formation.

This article has been cited by other articles:

				I. K. Bonev, R. D. Vassileva, N. Zotov, and K. Kouzmanov MANGANILVAITE, CaFe2+Fe3+(Mn, Fe2+)(Si2O7)O(OH), A NEW MINERAL OF THE ILVAITE GROUP FROM Pb Zn SKARN DEPOSITS IN THE RHODOPE MOUNTAINS, BULGARIA Can Mineral, June 1, 2005; 43(3): 1027 - 1042. [Abstract] [Full Text] [PDF]