Loveringite

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Formula: (Ca,Ce,La)(Zr,Fe)(Mg,Fe)₂(Ti,Fe,Cr,Al)₁₈O₃₈
Valence: (Ca,Ce³⁺,La)(Zr⁴⁺,Fe³⁺)(Mg,Fe³⁺)₂(Ti⁴⁺,Fe³⁺,Cr³⁺,Al)₁₈O₃₈
Anhydrous oxide, crichtonite group, cerium-, lanthanum-, titanium- and chromium- bearing mineral
Crystal system: Trigonal
Specific gravity: 4.42 calculated
Hardness: 5
Streak: Iron-grey
Colour: Black
Environments

Plutonic igneous environments

Loveringite is a late-stage mineral from residual magma in the pyroxene, olivine-chromite or plagioclase-rich layers of mafic intrusions (HOM).

Localities

At the Laouni West intrusion, Laouni, In Guezzam District, In Guezzam Province, Algeria, loveringite is an accessory mineral in layered complexes. It occurs in cumulate rocks (igneous rocks formed by the accumulation of crystals from a magma either by settling or floating), mainly in two distinct settings, namely olivine-chromite cumulates and anorthosite cumulates. In the lowermost cumulates, loveringite is closely associated with chromium-bearing spinel, and coexists with titanium-rich pargasite, (Na, K)-phlogopite, picroilmenite, rutile and magnesium-bearing pseudobrookite.
In the anorthosite cumulates, at the top of the lower banded zone, the loveringite crystallised away from the chromium-bearing spinel; it coexists with zirconolite, zircon and a minor amount of ilmenite and rutile. As a result, it is strongly depleted in Ti and enriched in Zr and rare earth elements. It may be fully enclosed in the cumulus plagioclase and is free of late magmatic minerals (CM 25.4.683–693).

The type locality, the Jimberlana Intrusion, Norseman, Dundas Shire, Western Australia, Australia, consists of a repeated sequence of olivine and bronzite cumulate layers overlain by a thick plagioclase - augite - hypersthene cumulate layer. Loveringite is most abundant in bronzite cumulates, but even in these layers it rarely exceeds 5 grains per thin section. The mineral is also found in trace amounts in the lower half of the plagioclase - augite - hypersthene cumulate layer, but has not been recorded in the olivine cumulates. It is closely associated with quartz-K-feldspar intergrowths or phlogopite and is thought to be amongst the last phases to crystallise from the residual intercumulus liquid (CM 17.635-638).
Other uranium- and rare earth- bearing accessory minerals in the cumulate layers include baddeleyite, apatite, zircon, titanite and rutile. Ilmenite and chromite are also common (AM 63.28-36).
The rare-earth elements belong to the incompatible group of elements, that is, they show little tendency to enter into the structures of common igneous minerals. They concentrate in the residual liquid of a fractionating magma and finally crystallise in certain late-stage accessory minerals such as loveringite (MM 42.187-193).

At the Bracco Unit, Genoa, Liguria, Italy, loveringite and baddeleyite are found within layers of chromium-bearing spinel in gabbroic cumulates from the ophiolitic Unit. Altered plagioclase or olivine represent the major phases interstitial to the chromium-bearing spinel; loveringite and baddeleyite, together with magnesium- or manganese- bearing ilmenite, aspidolite, Ti-rich pargasite, rutile, Zr-rich titanite, apatite and Cu and Ni sulphides, are accessory phases. An origin involving a liquid enriched in incompatible elements introduced by metasomatic infiltration during fractionation of chromium-bearing spinel seems likely (CM 35.4.899–908).

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