Oxygen Isotope Geochemistry as a Tool in the Exploration for BIF-hosted Iron Ore Occurrences within the Precambrian Mineral Belt of Southern Cameroon, Northwestern Margin of the Congo Craton: A Review

IF 0.8 4区地球科学 Q3 GEOLOGY

Geology of Ore Deposits Pub Date : 2024-01-09 DOI:10.1134/s1075701523060077

G. L. Ngiamte, O. A. Okunlola, C. E. Suh, D. C. I. Ilouga, R. B. Ngatcha, N. Y. Njamnsi, N. A. Afahnwie, S. C. Tufion

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Abstract

As a method for discovering the footprint of concealed iron ore enrichments, oxygen isotopes have revealed hydrothermal fluid sources and processes in Banded Iron Formation (BIF)-hosted iron ore provinces worldwide. This paper reviews the role oxygen isotopes play in exploring BIF-hosted iron ore bodies and discusses their application in southern Cameroon’s Precambrian mineral belt as an auxiliary exploration technique. Oxygen isotope analysis of iron ore species (e.g., BIFs, itabirites, and jaspilites) showed that the least altered BIFs had higher δ¹⁸O values than enriched ores. In the Nyong complex BIF sequence of southern Cameroon, δ¹⁸O_mag values range from –3 to –1.8, while δ¹⁸O_qtz values range from 6.8 to 10.6, indicating a discernible shift between the δ¹⁸O_mag-qtz values. Much higher δ¹⁸O_mag values (2.89 to 9.30‰) have been observed for magnetite gneisses suggesting an evolved magmatic-hydrothermal fluid source. Quartz veins associated with early-stage hematite ores in the adjacent Ivindo basement complex display higher δ¹⁸O values (4.7 to 8.1%) than those associated with late-stage magnetite ores (–2.3 to –1.5%). It is evident from these values that there is an isotopic shift between early-stage and late-stage iron ores, supporting the relevance of oxygen isotope to understanding iron ore signatures within the NW margin of the Congo craton. However, since the Congo Basin is characterised by inaccessible equatorial vegetation cover and lacks superficial exposures, high-precision oxygen isotopes (δ¹⁸O and δ¹⁷O) in conjunction with other isotopic techniques (e.g., δ⁵⁶Fe) and lithogeochemistry, will be more useful in constraining the isotopic signature of the BIF mineralisation.

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以氧同位素地球化学为工具，勘探刚果克拉通西北边缘喀麦隆南部前寒武纪矿产带中的 BIF 赋存铁矿：综述

摘要作为发现隐蔽铁矿富集区足迹的一种方法，氧同位素揭示了世界各地带状铁地层（BIF）铁矿区的热液来源和过程。本文回顾了氧同位素在勘探带状铁成藏铁矿体中发挥的作用，并讨论了氧同位素作为一种辅助勘探技术在喀麦隆南部前寒武纪矿带中的应用。对铁矿石物种（如 BIF、itabirites 和 jaspilites）进行的氧同位素分析表明，蚀变程度最小的 BIF 比富矿具有更高的δ18O 值。在喀麦隆南部的 Nyong 复杂 BIF 序列中，δ18Omag 值从 -3 到 -1.8 不等，而δ18Oqtz 值从 6.8 到 10.6 不等，表明δ18Omag-qtz 值之间有明显的变化。在磁铁矿片麻岩中观察到的δ18Omag值要高得多（2.89 至 9.30‰），这表明岩浆-热液流体来源已经发生变化。在邻近的伊文多基底复合体中，与早期赤铁矿相关的石英脉显示的 δ18O 值（4.7%至 8.1%）高于与晚期磁铁矿相关的石英脉（-2.3%至-1.5%）。从这些数值可以明显看出，早期铁矿石和晚期铁矿石之间存在同位素转变，这证明氧同位素对于了解刚果克拉通西北边缘的铁矿特征具有重要意义。然而，由于刚果盆地的特点是难以进入赤道植被覆盖区，且缺乏表层暴露，高精度氧同位素（δ18O 和 δ17O）与其他同位素技术（如 δ56Fe）和岩石地球化学相结合，将更有助于确定 BIF 矿化的同位素特征。

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来源期刊

Geology of Ore Deposits 地学-地质学

CiteScore

1.10

自引率

14.30%

发文量

审稿时长

6-12 weeks

期刊介绍： Geology of Ore Deposits is a periodical covering the topic of metallic and nonmetallic mineral deposits, their formation conditions, and spatial and temporal distribution. The journal publishes original scientific articles and reviews on a wide range of problems in theoretical and applied geology. The journal focuses on the following problems: deep geological structure and geodynamic environment of ore formation; distribution pattern of metallogenic zones and mineral deposits; geology and formation environment of large and unique metallic and nonmetallic deposits; mineralogy of metallic and nonmetallic deposits; physicochemical and isotopic characteristics and geochemical environment of ore deposition; evolution of ore-forming systems; radiogeology and radioecology, economic problems in exploring, developing, and mining of ore commodities.