Iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of Fe, Cu, and Au. Magnetite is the modally dominant and commodity mineral in IOA deposits, whereas magnetite and hematite are predominant in IOCG deposits, with copper sulfides being the primary commodity minerals. It is generally accepted that IOCG deposits formed by hydrothermal processes, but there is a lack of consensus for the source of the ore fluid(s). There are multiple competing hypotheses for the formation of IOA deposits, with models that range from purely magmatic to purely hydrothermal. In the Chilean iron belt, the spatial and temporal association of IOCG and IOA deposits has led to the hypothesis that IOA and IOCG deposits are genetically connected, where S-Cu-Au–poor magnetite-dominated IOA deposits represent the stratigraphically deeper levels of S-Cu-Au–rich magnetite- and hematite-dominated IOCG deposits. Here we report minor element and Fe and O stable isotope abundances for magnetite and H stable isotope abundances for actinolite from the Candelaria IOCG deposit and Quince IOA prospect in the Chilean iron belt. Backscattered electron imaging reveals textures of igneous and magmatic-hydrothermal affinities and the exsolution of Mn-rich ilmenite from magnetite in Quince and deep levels of Candelaria (>500 m below the bottom of the open pit). Trace element concentrations in magnetite systematically increase with depth in both deposits and decrease from core to rim within magnetite grains in shallow samples from Candelaria. These results are consistent with a cooling trend for magnetite growth from deep to shallow levels in both systems. Iron isotope compositions of magnetite range from δ⁵⁶Fe values of 0.11 ± 0.07 to 0.16 ± 0.05‰ for Quince and between 0.16 ± 0.03 and 0.42 ± 0.04‰ for Candelaria. Oxygen isotope compositions of magnetite range from δ¹⁸O values of 2.65 ± 0.07 to 3.33 ± 0.07‰ for Quince and between 1.16 ± 0.07 and 7.80 ± 0.07‰ for Candelaria. For cogenetic actinolite, δD values range from –41.7 ± 2.10 to –39.0 ± 2.10‰ for Quince and from –93.9 ± 2.10 to –54.0 ± 2.10‰ for Candelaria, and δ¹⁸O values range between 5.89 ± 0.23 and 6.02 ± 0.23‰ for Quince and between 7.50 ± 0.23 and 7.69 ± 0.23‰ for Candelaria. The paired Fe and O isotope compositions of magnetite and the H isotope signature of actinolite fingerprint a magmatic source reservoir for ore fluids at Candelaria and Quince. Temperature estimates from O isotope thermometry and Fe# of actinolite (Fe# = [molar Fe]/([molar Fe] + [molar Mg])) are consistent with high-temperature mineralization (600°–860°C). The reintegrated composition of primary Ti-rich magnetite is consistent with igneous magnetite and supports magmatic conditions for the formation of magnetite in the Quince prospect and the deep portion of the Candelaria deposit. The trace element variations and zonation in magnetite from shallower levels of Candelaria are consistent with magnetite growth from a cooling magmatic-hydrothermal fluid. The combined chemical and textural data are consistent with a combined igneous and magmatic-hydrothermal origin for Quince and Candelaria, where the deeper portion of Candelaria corresponds to a transitional phase between the shallower IOCG deposit and a deeper IOA system analogous to the Quince IOA prospect, providing evidence for a continuum between both deposit types.

中文翻译：

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从氧化铁铜金到氧化铁磷灰石矿床的连续体：铁和氧稳定同位素和磁铁矿微量元素化学的证据

氧化铁铜金（IOCG）和氧化铁磷灰石（IOA）沉积物是铁，铜和金的主要来源。磁铁矿是IOA矿床中的主要优势矿物和商品矿物，而磁铁矿和赤铁矿则是IOCG矿床的主要矿物，硫化铜是主要的商品矿产。人们普遍认为，IOCG沉积物是由水热过程形成的，但是对于矿液的来源缺乏共识。对于IOA矿床的形成有多种相互竞争的假设，其模型范围从纯岩浆到纯热液。在智利的铁矿带中，IOCG和IOA矿床的时空关联导致了以下假设：IOA和IOCG矿床是遗传相关的，其中贫S-Cu-Au的磁铁矿为主的IOA矿床代表了地层较深的富S-Cu-Au的磁铁矿和赤铁矿为主的IOCG矿床。在这里，我们从智利铁矿床的坎德拉里亚IOCG矿床和Quince IOA矿床报告了磁铁矿的微量元素以及Fe和O的稳定同位素丰度，以及阳起石的H稳定同位素丰度。反向散射电子成像显示了火成岩和岩浆热液亲和力的质地，以及木瓜中的磁铁矿和坎德拉里亚深层（露天矿底部以下> 500 m）中富含锰的钛铁矿的溶解。在坎德拉里亚的浅层样品中，磁铁矿中的痕量元素浓度随着沉积物深度的增加而系统地增加，而从铁心到边缘的磁铁矿颗粒中的痕量元素浓度逐渐降低。这些结果与两个系统中磁铁矿从深部到浅部生长的冷却趋势一致。磁铁矿的铁同位素组成为δ^木瓜的56 Fe值为0.11±0.07至0.16±0.05‰，坎德拉里亚的Fe值为0.16±0.03至0.42±0.04‰。的磁铁矿范围氧同位素组成从δ ^18个2.65±0.07 O值3.33±0.07‰，木瓜和坎德拉里亚1.16和7.80之间±0.07±0.07‰。对于同源的阳起石，δD值的范围从-41.7±2.10到±-39.0‰2.10对木瓜和从-93.9±2.10 -54.0至±2.10‰，坎德拉里亚，Δ ¹⁸Quince的O值范围为5.89±0.23至6.02±0.23‰，坎德拉里亚的O值范围为7.50±0.23至7.69±0.23‰。磁铁矿的成对的Fe和O同位素组成以及阳起石指纹图的H同位素特征是坎德拉里亚和昆斯的矿石流体的岩浆源储层。通过O同位素测温法和阳起石的Fe＃（Fe＃= [摩尔Fe] /（[摩尔Fe] + [摩尔Mg]）估算的温度与高温矿化（600°–860°C）一致。富钛原生磁铁矿的重新整合成分与火成岩磁铁矿一致，并支持了在昆西矿床和坎德拉里亚沉积深部形成磁铁矿的岩浆条件。坎德拉里亚较浅水平的磁铁矿中的微量元素变化和分区与冷却岩浆-热液流体中的磁铁矿生长一致。结合的化学和组织学数据与昆斯和坎德拉里亚的火成岩和岩浆热液联合成因相一致，其中坎德拉里亚的较深部分对应于较浅的IOCG沉积物和较深的IOA系统（类似于昆斯IOA前景）之间的过渡阶段，为两种存款类型之间的连续性提供证据。