Crystal-chemistry of zirconolite and calzirtite from Jacupiranga, São Paulo (Brazil)
| Autor: | C. T. Williams, Fabio Bellatreccia, Gian Carlo Parodi, G. Della Ventura, E. Caprilli |
|---|---|
| Přispěvatelé: | Bellatreccia, Fabio, DELLA VENTURA, Giancarlo, Caprilli, E, WILLAMS T., C, Parodi, G. C. |
| Rok vydání: | 1999 |
| Předmět: |
Zirconolite
Mineral 010504 meteorology & atmospheric sciences Crystal chemistry Calzirtite Analytical chemistry Mineralogy Compositional zoning Actinide Mineral chemistry engineering.material 010502 geochemistry & geophysics 01 natural sciences Jacupiranga Metamictization Geochemistry and Petrology engineering Lamellar structure Brazil Geology 0105 earth and related environmental sciences Zirkelite |
| Zdroj: | Scopus-Elsevier |
| ISSN: | 1471-8022 0026-461X |
| DOI: | 10.1180/002646199548817 |
| Popis: | A specimen of zirconolite, collected from the type locality of the mineral originally described as zirkelite at Jacupiranga, São Paulo, Brazil has been re-examined and its mineral chemistry more completely characterized. All crystals studied are metamict and display very fine lamellar oscillatory zoning (1–3 µm in width) superimposed on a sector zonation. Such zoning, observed in backscattered electron images, is primarily related to differences in the concentration of Th.In comparison with other reported zirconolite samples from a variety of geological occurrences, Jacupiranga zirconolite has higher Ca, Th, (Nb + Ta) and lower Ti andREE, which is consistent with its occurrence in carbonatitic rocks. The compositional variation with respect to an ideal zirconolite is described by two main coupled substitutions:Calzirtite, Ca2Zr5Ti2O16, although intergrown with zirconolite and with identical major components, shows much less compositional variability with only minor amounts of Nb and Ta substituting for Ti. Unlike zirconolite, theREEand actinide elements are not easily accommodated in the calzirtite structure. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|