CaltechAUTHORS
  A Caltech Library Service

Ilmenite (high Mg,Mn,Nb) in the carbonatites from the Jacupiranga Complex, Brazil

Gaspar, José C. and Wyllie, Peter J. (1983) Ilmenite (high Mg,Mn,Nb) in the carbonatites from the Jacupiranga Complex, Brazil. American Mineralogist, 68 (9-10). pp. 960-971. ISSN 0003-004X. https://resolver.caltech.edu/CaltechAUTHORS:20160203-085338860

Full text is not posted in this repository.

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20160203-085338860

Abstract

Ilmenite occurs rarely in the carbonatite plug (five separate intrusions) of the Jacupiranga Complex, in the jacupirangite near the contacts, and in the banded reaction zones between carbonatite and jacupirangite. Electron microprobe analyses reveal a wider range of ilmenite compositions than previously reported from carbonatites, as solid solutions in FeTiO_3-MgTiO_3-MnTiO_3-Fe2O_3, with high-Nb ilmenites containing up to 3.68 wt.% (Nb_2O_5 + Ta_2O_5). A group of discrete primary ilmenites from one carbonatite is distinguished by unusually high MnTiO_3 (MnO 15.1-19.6%); ilmenite inclusions in magnetites of the carbonatite intrusions are similar in composition to magnesian ilmenites previously reported; other ilmenites (a few discrete grains, but mainly lamellae with some granules associated with magnetite), have compositions that vary almost completely from FeTiO_3 to MgTiO_3, with less than 10% Fe_2O_3. Titanomagnetites (with Nb_2O_5 below detection limits) in jacupirangite have ilmenite lamellae near and within the reaction zones, with Nb_2O_5 increasing (Nb_2O_5 + Ta_2O_5 up to 0.95%) and Fe_2O_3 decreasing in ilmenite as carbonatite is approached. Pentavalent Nb and Ta replace Ti in ilmenite, causing cation deficiency. In coexisting magnetite and ilmenite, MgO and MnO partition preferentially into ilmenite; MgO shows a regular pattern of distribution between ilmenite and magnetite, whereas MnO is distributed irregularly. Coexisting magnetite and ilmenite (with low MgO and MnO) from the reaction rocks give equilibration temperatures of 570-595°C and oxygen fugacities of 10^(-18.5) to 10^(-19.5) atmospheres. The ilmenites are distinguished from ilmenites in kimberlites by high MnO, very low Cr_2O_3, and high (Nb_2O_5 + Ta_2O_5).


Item Type:Article
Additional Information:© 1983 Mineralogical Society of America. Manuscript received, June 18, 1982; accepted for publication, March 18, 1983. We thank Serrana S/A de Mineração, G. C. Melcher, and V. A. V. Girardi for making possible the field work of JCG, I. M. Steele for invaluable assistance with microprobe analyses, and J. V. Smith for assistance with the microprobe. Financial support was provided by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) PROC 201.158/80 and PROC 40.1410/81, Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP) PROC 80/470 and PROC 81/0168-8, and the Earth Science Division of the National Science Foundation Grants EAR 76-20410, and EAR 81-08599.
Funders:
Funding AgencyGrant Number
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PROC 201.158/80
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PROC 40.1410/81
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PROC 80/470
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PROC 81/0168-8
NSFEAR 76-20410
NSFEAR 81-08599
Issue or Number:9-10
Record Number:CaltechAUTHORS:20160203-085338860
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160203-085338860
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64182
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:03 Feb 2016 23:17
Last Modified:03 Oct 2019 09:35

Repository Staff Only: item control page