The Mina Justa Iron Oxide Copper-Gold (IOCG) Deposit, Peru: Constraints on Metal and Ore Fluid Sources
The Mina Justa Iron Oxide Copper-Gold (IOCG) Deposit, Peru: Constraints on Metal and Ore Fluid Sources
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DOI：
10.5382/econgeo.4875
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发表时间：
2021-10
期刊：
影响因子：
5.8
通讯作者：
M. Rodríguez-Mustafa;A. Simon;L. Bilenker;I. Bindeman;R. Mathur;Edson L. B. Machado
中科院分区：
文献类型：
--
作者：
M. Rodríguez-Mustafa;A. Simon;L. Bilenker;I. Bindeman;R. Mathur;Edson L. B. Machado
铁氧化物铜金(IOCG)矿床是铜的主要来源，含有丰富的铁氧化物，在某些矿床中可能含有Au、Ag、Co、稀土元素(REES)、U等金属作为重要的经济副产品。它们是由热液作用形成的，但金属和矿液的来源(S)仍有争议。研究了秘鲁Mina Justa IOCG矿床热液单元和曼托矿体中的磁铁矿的地球化学特征，以评价铁氧化物的来源及其与经济铜矿化的关系。我们鉴定了三种类型的磁铁矿：有包裹体的磁铁矿(类型I)只在芒果中发现，是微量元素最丰富的，结晶温度在459°C到707°C之间；暗型(D)没有可见的包裹体，形成温度在543°C左右；明亮类型(B)没有包裹体，铁含量最高，形成于443°C左右。Mina Justa磁铁矿样品的δ56Fe±2σ为0.28±0.05‰(n=9)，δ18O±2σ为2.19±0.45‰(n=9)，Δ‘17O为-0.075~-0.047‰。硫化物分离得到δ65Cu值，范围为-0.32至-0.09‰。磁铁矿的微量元素组成和结构，以及磁铁矿结晶温度的估算，与属于铁氧化物-磷灰石(IOA)式矿化的地幔磁铁矿一致，该矿化被更年轻的构造控制的IOCG事件叠加，形成了热液单元矿体。总之，稳定的同位素数据确定了米纳朱斯塔携带铁和铜的成矿流体的岩浆热液来源，排除了大气降水和盆地卤水的重大输入。
Iron oxide copper-gold (IOCG) deposits are major sources of Cu, contain abundant Fe oxides, and may contain Au, Ag, Co, rare earth elements (REEs), U, and other metals as economically important byproducts in some deposits. They form by hydrothermal processes, but the source of the metals and ore fluid(s) is still debated. We investigated the geochemistry of magnetite from the hydrothermal unit and manto orebodies at the Mina Justa IOCG deposit in Peru to assess the source of the iron oxides and their relationship with the economic Cu mineralization. We identified three types of magnetite: magnetite with inclusions (type I) is only found in the manto, is the richest in trace elements, and crystallized between 459° and 707°C; type Dark (D) has no visible inclusions and formed at around 543°C; and type Bright (B) has no inclusions, has the highest Fe content, and formed at around 443°C. Temperatures were estimated using the Mg content in magnetite. Magnetite samples from Mina Justa yielded an average δ56Fe ± 2σ value of 0.28 ± 0.05‰ (n = 9), an average δ18O ± 2σ value of 2.19 ± 0.45‰ (n = 9), and Δ’17O values that range between –0.075 and –0.047‰. Sulfide separates yielded δ65Cu values that range from –0.32 to –0.09‰. The trace element compositions and textures of magnetite, along with temperature estimations for magnetite crystallization, are consistent with the manto magnetite belonging to an iron oxide-apatite (IOA) style mineralization that was overprinted by a younger, structurally controlled IOCG event that formed the hydrothermal unit orebody. Altogether, the stable isotopic data fingerprint a magmatic-hydrothermal source for the ore fluids carrying the Fe and Cu at Mina Justa and preclude significant input from meteoric water and basinal brines.