喀麦隆南部姆巴拉姆铁矿区 Metzimevin高品位铁矿的块体地球化学、Rb-Sr、Sm-Nd 和稳定 O-H 同位素系统学研究

IF 1.4 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Samndong Cyril Tufoin, Cheo Emmanuel Suh, Tabod Charles Tabod, George Lemewihbwen Ngiamte
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引用次数: 0

摘要

首次报道了刚果克拉通(CC)西北部带状铁矿(BIF)-高品位铁矿的块体地球化学、Sr、Nd 和 O-H 同位素系统学。Metzimevin 铁矿位于喀麦隆南部姆巴拉姆(Mbalam)铁矿区,是一个赤铁矿-磁铁矿 BIF 系统,主要成分为 SiO2 + Fe2O3(97.1-99.84 wt%),碎屑元素(如 Al2O3、TiO2 和 HFSE)含量较低,是一种近乎纯净的化学沉淀物。铁矿床的 REE + Y 特征显示出强烈的正 Eu 异常、强烈的负 Ce 异常和软玉质到超软玉质的 Y/Ho 比率,表明是在氧化环境中由海水-高温热液混合流体形成的。BIF的87Sr/86Sr比值高于所有Archean储层(块状硅酸盐土、Archean地壳和Archean海水)的最大87Sr/86Sr演化曲线,表明在BIF形成和蚀变过程中有大陆衍生成分的参与。ƐNd(t)(+ 2.26 至 + 3.77)和 Nd 模型年龄表明,BIF 的化学成分来自 3.002 至 2.88 Ga 之间的未分化地壳源。多变而多样的 O 和 H 同位素数据(分别为-1.9‰至 17.3‰和-57‰至 136‰)表明,Metzimevin 铁矿最初由岩浆羽流形成,后经岩浆-变质-改质流体富集。质量平衡计算表明,矿化是通过浸出和沉淀相结合的方式进行的,平均铁富集系数为 >2.67,二氧化硅贫化系数为 >0.99。这与总体积减少 28.27% 有关,反映了 BIF 原岩的净沥滤和体积塌陷。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Bulk geochemistry, Rb–Sr, Sm–Nd, and stable O–H isotope systematics of the Metzimevin high-grade iron ore deposit, Mbalam iron ore district, southern Cameroon

Bulk geochemistry, Sr, Nd, and O–H isotope systematics are reported for the first time on banded iron formation (BIF)-hosted high-grade iron ore at the north-western segment of Congo Craton (CC). Located in Mbalam iron ore district, Southern Cameroon, Metzimevin iron ore deposit is a hematite-magnetite BIF system, dominated by SiO2 + Fe2O3 (97.1 to 99.84 wt%), with low concentrations of clastic elements e.g., Al2O3, TiO2, and HFSE, depicting a nearly pure chemical precipitate. The REE + Y signature of the iron deposit displays strong positive Eu anomaly, strong negative Ce anomaly, and chondritic to superchondritic Y/Ho ratios, suggestive of formation by mixed seawater-high temperature hydrothermal fluids in oxidising environment. The 87Sr/86Sr ratios of the BIF are higher than the maximum 87Sr/86Sr evolution curves for all Archean reservoirs (bulk silicate earth, Archean crust and Archean seawater), indicating involvement of continentally-derived components during BIF formation and alteration. The ƐNd(t) (+ 2.26 to + 3.77) and Nd model age indicate that chemical constituents for the BIF were derived from undifferentiated crustal source, between 3.002 and 2.88 Ga. The variable and diverse O and H isotope data (− 1.9‰ to 17.3‰ and − 57‰ to 136‰ respectively) indicate that the Metzimevin iron ore formed initially from magmatic plumes and later enriched by magmatic-metamorphic-modified meteoric fluids. Mass balance calculations indicate mineralisation by combined leaching and precipitation, with an average iron enrichment factor of > 2.67 and SiO2 depletion factor of > 0.99. This is associated with an overall volume reduction of 28.27%, reflecting net leaching and volume collapse of the BIF protholith.

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来源期刊
Acta Geochimica
Acta Geochimica GEOCHEMISTRY & GEOPHYSICS-
CiteScore
2.80
自引率
6.20%
发文量
1134
期刊介绍: Acta Geochimica serves as the international forum for essential research on geochemistry, the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth‘s crust, its oceans and the entire Solar System, as well as a number of processes including mantle convection, the formation of planets and the origins of granite and basalt. The journal focuses on, but is not limited to the following aspects: • Cosmochemistry • Mantle Geochemistry • Ore-deposit Geochemistry • Organic Geochemistry • Environmental Geochemistry • Computational Geochemistry • Isotope Geochemistry • NanoGeochemistry All research articles published in this journal have undergone rigorous peer review. In addition to original research articles, Acta Geochimica publishes reviews and short communications, aiming to rapidly disseminate the research results of timely interest, and comprehensive reviews of emerging topics in all the areas of geochemistry.
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