Hydrothermal magnetite from the Starra iron oxide‑copper gold (IOCG) deposit in northwest Queensland, Australia, records a gradual decrease in V, Ni, Cr, and Mn that correlates with the transition from early, amphibole-biotite-magnetite dominant alteration to late, chlorite-quartz-hematite-dominated alteration assemblages. The observed systematic change in multivariate elements in magnetite is interpreted to indicate an increase in fO2 during the main Cu(Au) mineralization. We suggest that variations in the V, Ni, and Cr contents of magnetite at Starra indicate either a primary magmatic fluid source or the leaching of mafic rocks by fluids during early albitization. Late silician magnetite contained in ankerite veins that crosscut the preexisting alteration assemblages in the hanging wall to the Starra 222 ore body is likely the result of a second mineralization phase, which contributed additional metals to the Starra ore bodies.

Existing data on magnetite chemistry from several IOA, IOCG, Fe, and FeW skarn deposits show that the ratio of V to Ga discriminates the various ore types effectively. Skarn deposits are separated from IOA and IOCG by lower concentrations of V, Ni, and Cr, suggesting a more primitive fluid source or the precipitation of magnetite at distinct physicochemical conditions than IOA and IOCG deposits. Magnetite from IOA deposits exhibits a consistently elevated V concentration whereas magnetite from Fe(W) skarn records an increase in V concentration with the evolution of the system. A pronounced decrease in the V contents of magnetite associated with CuAu mineralization at Starra is interpreted as a change in redox conditions from reduced to oxidized at the time of mineralization. Such variations are also observed in other IOCG deposits. We propose that systematic decreases in V concentration in magnetite during the paragenetic evolution of the host mineral system is a diagnostic indicator for Cu(Au) mineralization in IOCG deposits, and as such, it may be used as a proxy for CuAu exploration, if the paragenetic context of magnetite is well constrained.

澳大利亚昆士兰州西北部斯塔拉氧化铁-铜金 (IOCG) 矿床的热液磁铁矿记录了 V、Ni、Cr 和 Mn 的逐渐减少，这与从早期角闪石-黑云母-磁铁矿主导蚀变到晚期的转变相关。 ，以绿泥石-石英-赤铁矿为主的蚀变组合。观察到的磁铁矿中多元元素的系统变化被解释为表明主要 Cu(Au) 矿化过程中f O2的增加。我们认为，斯塔拉磁铁矿中 V、Ni 和 Cr 含量的变化表明，要么是原生岩浆流体来源，要么是早期钠长石化过程中流体对基性岩的浸滤。铁白云石矿脉中所含的晚硅石磁铁矿将上盘中先前存在的蚀变组合横切至 Starra 222矿体，这可能是第二个矿化阶段的结果，该阶段为 Starra 矿体贡献了额外的金属。

来自多个 IOA、IOCG、Fe 和 Fe W 矽卡岩矿床的磁铁矿化学的现有数据表明，V 与 Ga 的比率可以有效地区分各种矿石类型。矽卡岩矿床通过较低浓度的 V、Ni 和 Cr 与 IOA 和 IOCG 分开，这表明与 IOA 和 IOCG 矿床相比，存在更原始的流体来源或在不同的物理化学条件下磁铁矿的沉淀。来自 IOA 矿床的磁铁矿表现出持续升高的 V 浓度，而来自 Fe( W) 矽卡岩的磁铁矿记录了 V 浓度随着系统的演化而增加。与 Starra 铜金矿化相关的磁铁矿 V 含量显着下降被解释为矿化时氧化还原条件从还原状态变为氧化状态。在其他 IOCG 矿床中也观察到了这种变化。我们认为，在宿主矿物系统的共生演化过程中，磁铁矿中 V 浓度的系统性降低是IOCG 矿床中铜（金）矿化的诊断指标，因此，它可以用作铜金勘探的代理，如果磁铁矿的共生背景受到很好的限制。