Zones of massive to semi-massive Fe-Ti oxide mineralization are present in the Northwest River Anorthosite, a ca. 1625-Ma Paleoproterozoic massif-type anorthosite located in the Grenville Province of south-central Labrador. The oxide mineralization is predominantly composed of coarse to very-coarse grained V-rich magnetite with less abundant coarse granular ilmenite and pleonaste that formed by exsolution from the primary, chemically impure magnetite; all observed oxide minerals have complex and abundant subsolidus reequilibration and exsolution textures. Using petrography, oxide mineral chemistry, whole-rock geochemistry, and oxide-anorthosite field relationships, a three-process model is proposed for the formation of the oxide mineralization: (1) late-stage magmatic crystallization of impure magnetite; (2) concentration of Fe-Ti oxides via solid-state remobilization; and (3) reequilibration during subsequent post-emplacement cooling and Grenvillian metamorphism. These subsolidus processes significantly modified the primary magmatic composition of the magnetite through exsolution and reequilibration. Results from in-situ magnetite EPMA and LA-ICPMS analyses were plotted on magnetite mineral chemical discrimination diagrams. The data display a wide spread and typically do not plot exclusively in the expected anorthosite-hosted Fe-Ti-V magnetite fields. This is most likely due to modification of magnetite chemistry during subsolidus cooling and reequilibration. As such, care must be taken when using magnetite discrimination diagrams for Fe-Ti-V deposits given the complex petrogenetic histories that magnetite within these types of deposits experience.

中文翻译：

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富钒磁铁矿为主的Fe-Ti氧化物成矿的起源与演化；加拿大拉布拉多中南部西北河斜长岩

西北河斜长岩中存在块状至半块状 Fe-Ti 氧化物矿化带。位于拉布拉多中南部格伦维尔省的 1625-Ma 古元古代地块型斜长岩。氧化物矿化主要由粗粒到非常粗粒的富钒磁铁矿和较少量的粗粒钛铁矿和由原生、化学不纯磁铁矿出溶形成的pleonaste组成；所有观察到的氧化物矿物都具有复杂而丰富的亚固相线再平衡和出溶结构。利用岩石学、氧化物矿物化学、全岩地球化学和氧化物-斜长岩场关系，提出了氧化物成矿的三过程模型：（1）不纯磁铁矿后期岩浆结晶；(2) 通过固相再活化来浓缩 Fe-Ti 氧化物；(3) 在随后的入位后冷却和格伦维尔变质作用过程中的再平衡。这些亚固相线过程通过出溶和再平衡显着改变了磁铁矿的主要岩浆成分。将原位磁铁矿 EPMA 和 LA-ICPMS 分析的结果绘制在磁铁矿矿物化学鉴别图上。数据显示范围很广，通常不会专门绘制在预期的斜长岩承载的 Fe-Ti-V 磁铁矿场中。这很可能是由于亚固相线冷却和再平衡过程中磁铁矿化学性质的改变。因此，