Experimental evidence for the exsolution of ilmenite from titaniferous spinel

Other| October 01, 1995 Experimental evidence for the exsolution of ilmenite from titaniferous spinel Dominique Lattard Dominique Lattard Technische Universitaet Berlin, Fachgebiet, Petrologie, Technische, Berlin, Federal Republic of Germany Search for other works by this author on: GSW Google Scholar American Mineralogist (1995) 80 (9-10): 968–981. https://doi.org/10.2138/am-1995-9-1013 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Dominique Lattard; Experimental evidence for the exsolution of ilmenite from titaniferous spinel. American Mineralogist 1995;; 80 (9-10): 968–981. doi: https://doi.org/10.2138/am-1995-9-1013 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Microintergrowths of titaniferous spinel and ilmenite have been experimentally produced in the system Fe-Ti-Cr-0 by annealing in vacuo at constant temperatures in the range 700–1100 °C of spinel + ilmenite assemblages previously synthesized at 1300 °C under controlled low fO2. Depending on the original fO2 of synthesis at 1300 °C, annealing produces three types of microintergrowths: Type I (lowest fO2: 10−11) has rims and trellislike lamellae of ilmenite as well as small blebs of metallic iron; type II (fO2: 10−10−10−9) shows spinel with rims and a few lamellae of ilmenite; type III (highest fO2: 10−8.5) displays both spinel with rims and lamellae of ilmenite and ilmenite with rims and lamellae of spinel.On the basis of microprobe analysis, including precise determination of the O contents, it is shown that the synthetic microintergrowths did not form by a redox process. Rather, the textures represent exsolution caused by vacancy relaxation in spinel (and, for the most reduced samples, in ilmenite), according to the substitution schemeFe22+Ti−14+☐−1.(1)The presence of metallic iron in the most reduced samples (type I) results from the shift of the iron saturation surface toward more Fe-rich compositions with decreasing temperature. The rims and lamellae of spinel around and within ilmenite in the type-III samples result from the combination of Exchange 1 and the well-known substitution Fe2+ + Ti4+ = 2Fe3+.These experimental results show that natural spinel + ilmenite microintergrowths do not always result from either an oxidation or a reduction process. In particular, textures similar to those of type I, which were observed in lunar basalts, may simply record cooling under O2-conserving conditions. In most terrestrial rocks, however, spinel + ilmenite intergrowths are certainly best interpreted as resulting from oxidation of at least a subsystem of the rock. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.