Testing Trace-Element Distribution and the Zr-Based Thermometry of Accessory Rutile from Chromitite

Federica Zaccarini, Giorgio Garuti, George Luvizzotto, Yuri De Melo Portella, Singh Athokapm

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung


Trace element distribution and Zr-in-rutile temperature have been investigated in accessory rutile from stratiform (UG2, Merensky Reef, Jacurici), podiform (Loma Peguera), and metamorphic chromitites in cratonic shields (Cedrolina, Nuasahi). Rutile from chromitite has typical finger-print of Cr-V-Nb-W-Zr, whose relative abundance distinguishes magmatic from metamorphic chromitite. In magmatic deposits, rutile precipitates as an intercumulus phase, or forms by exsolution from chromite, between 870 °C and 540 °C. The Cr-V in rutile reflects the composition of chromite, both Nb and Zr are moderately enriched, and W is depleted, except for in Jacurici, where moderate W excess was a result of crustal contamination of the mafic magma. In metamorphic deposits, rutile forms by removal of Ti-Cr-V from chromite during metamorphism between 650 °C and 400 °C, consistent with greenschist-amphibolite facies, and displays variable Cr-Nb, low V-Zr, and anomalous enrichment in W caused by reaction with felsic fluids emanating from granitoid intrusions. All deposits, except Cedrolina, contain Rutile+PGM composite grains (<10 µm) locked in chromite, possibly representing relics of orthomagmatic assemblages. The high Cr-V content and the distinctive W-Nb-Zr signature that typifies accessory rutile in chromitite provide a new pathfinder to trace the provenance of detrital rutile in placer deposits.

Seiten (von - bis)1-37
PublikationsstatusVeröffentlicht - 22 Juni 2021

Bibliographische Notiz

Funding Information:
The authors acknowledge the University Centrum for Applied Geosciences (UCAG) for the access to the E. F. Stumpfl electron microprobe laboratory. The author G.G. thanks the Ministero della Pubblica Istruzione and Consiglio Nazionale delle Ricerche (Rome, Italy) for having financed participation in the Third International Platinum Symposium, South Africa (1981), and field work in Brazil (1986?1989). The Ferbasa Company is gratefully acknowledged for the permission to visit the Jacurici mining sites (August 1988, September 1989). The authors G.G. and F.Z. acknowledge the 18va Conferencia Geologica del Caribe, Republica Dominicana, for having organized the field trip to the chromitite occurrences of Loma Peguera (March 2008). We are grateful to the academic editor and two anonymous referees for their fruitful comments. The editorial staff of Minerals is thanked for the help in editing the manuscript.

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© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

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