Transition metal rutiles and titanates from the Deadhorse Creek diatreme complex, northwestern Ontario, Canada

Abstract

AbstractThe main mineralized zone of the West subcomplex of the Deadhorse Creek diatreme complex, northwestern Ontario possesses an exotic mineralogy. Mineralization involves the first-order transition metals (principally Sc, Ti, V, Cr, Mn, and Fe), the second-order transition metals (principally Zr and Nb), the lanthanides, the actinides (principally Th and U), Be, Ba and Sr. Minerals include phenacite, zircon, uraninite, thorite, monazite-(Ce), xenotime-(Y), barylite, thortveitiite, hollandite, tyuyamunite, a number of unknown and as yet undescribed species, and those minerals more specifically described in this paper. These are Cr-V-Nb rutile, V-rich members of the crichtonite series, and a titanate of general composition (Cr,V3+,Fe3+)2(Ti,V4+,Nb)O5.Similar to rutiles reported from alkaline rocks in general, the Deadhorse Creek rutiles are enriched in Cr and Nb, with the latter element attaining some of the highest recorded values. V contents are also unusually high and this element is thought to exist in both the tri- and tetravalent states.The V-rich crichtonites are essentially vanadium analogues of crichtonite and lindsleyite. M-site Nb and V are the highest yet recorded. A-site cations are dominated by Ba and Sr with an inverse relationship together with lesser but significant amounts of Ca and Pb. Although not of upper mantle origin, they plot in the upper mantle LIMA quadrant of TiO2vs. FeO + Fe2O3 + MgO (Haggerty, 1991).(Cr,V3+,Fe3+)2(Ti,V4+,Nb)O5 is thought to be a member of an homologous series of type (Cr,V3+,Fe3+)2p(Ti,V4+,Nb)2p+qO5p+4q with p = 1 and q = 0 and a V3O5-type structure. Whether this structure is ultimately derived from that of rutile or from α-PbO2 by crystallographic shear is not known.The rutiles and titanates discussed here are thought to have formed from hydrous alkaline solutions which have scavenged the necessary elements from a mafic/ultramafic source. The origin of the solutions is not specifically known although the magmatic activity associated with the spatially related Coldwell alkaline complex and/or the Prairie Lake complex are both potential sources. Both complexes contain the necessary mafic/ultramafic rocks.