Open AccessThe Relation between Chemical Analysis and Mineralogy of Oxidized Titaniferous Magnetites in some Scottish Dolerites
Author(s) -
Unan C.
Publication year - 1971
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1971.tb03597.x
Subject(s) - magnetite , ilmenite , spinel , solvus , chemical composition , geology , mineralogy , magnetic mineralogy , mineral , mössbauer spectroscopy , magnetization , materials science , metallurgy , microstructure , chemistry , remanence , crystallography , magnetic field , superalloy , organic chemistry , quantum mechanics , physics
Summary The ore minerals consist of very heterogeneous phases probably produced during late stage oxidation of an original magnetite‐ulvöspinel solid solution. They usually contain a first generation of well‐formed ilmenite lamellae with a second generation intergrowth, composed of magnetite and ilmenite, between them. The second generation, fine intergrowth of magnetite and ilmenite was formed by the late oxidation of the original Mt‐Ulv 55 at temperatures below the magnetite‐ulvöspinel solvus. Due to incomplete oxidation some of the intrusions contain Fe‐Ti oxides with a small amount of Fe 2 TiO 4 still remaining in the magnetite phase. In other intrusions after complete oxidation of Fe 2 TiO 4 a transition to the oxidation of Fe 3 O 4 and FeTiO 3 has occasionally been observed. The late oxidation has produced very complex and heterogeneous phases and in order to recalculate the phases present from chemical analysis of the magnetic fraction it is shown that theoretical considerations of the oxidation process must be taken into account. Graphs for deducing the original and present mineralogical composition from the chemical composition are presented. Since all these specimens show reversed magnetization and contain a late generation of magnetite the reversal of the magnetization direction may be related to the CRM.