Abstract The Bakoudou gold deposit, southern Gabon, is hosted in the Archean basement granitoids of the Chaillu Massif. These granitoids of the Bakoudou deposit are subdivided into two main groups: TTGs and porphyritic biotite granites. The TTGs show geochemical characteristics similar to those of other TTGs worldwide, such as high Al2O3 (13.49–18.93 wt%) and Na2O (3.27–4.66 wt%) and low K2O (1.01–1.98 wt%), with low K/Na (0.15–0.32) ratios. Their Mg# (Mg/(Mg + Fe)*100) values vary from 34.81 to 50.76, with low to moderate Nb/Ta and Zr/Sm ratios (7.03–23.43 and 19.13–75.25, respectively). They are characterized by moderate (La/Yb)N (6.70–41.71) and Sr/Y (20.80–72.13) ratios similar to those of adakites, negative Nb, Ta and Ti anomalies and LREE-enriched and HREE-depleted patterns, without significant Eu anomalies (Eu/Eu* = 0.93–1.11, average = 1.00). These geochemical characteristics suggest that the TTG rocks were formed by partial melting of hydrous basaltic crust, such as garnet-rich amphibolite. The porphyritic biotite granites show high-K calc-alkaline affinity. They are characterized by high SiO2 (71.01–74.86 wt%) and K2O (3.29–4.92 wt%) but relatively low MgO (0.38–0.92 wt%), with Mg# values varying between 31.78 and 40.27. The rocks show low to moderate Sr/Y (13.75–26.66) ratios and LREE-enriched and HREE-depleted patterns, with negative Eu anomalies (Eu/Eu* = 0.36–0.58, average = 0.47). These geochemical features indicate that the porphyritic biotite granites originated from partial melting of TTG lithologies. The orebody of the Bakoudou gold deposit occurs as quartz veins hosted in the TTG shear zones. Quartz is the main gangue mineral, with minor sulfides such as pyrite and chalcopyrite. Gold is present in solid solution (Au+1) and as nanoparticles of native gold (Au0) in pyrite and mostly as free gold. Pyrite samples analysed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) show high Ni (3.24–3600 ppm) and Co (4.68–4140 ppm) and low As (

中文翻译：

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Bakoudou TTGs 和高钾黑云母花岗岩的岩石成因和相关的金矿化，加蓬南部：斑岩-浅成热液过渡金系统的太古代例子

摘要 加蓬南部巴库杜金矿床赋存于Chaillu地块的太古代基底花岗岩中。八口斗矿床的这些花岗岩类分为两大类：TTGs 和斑状黑云母花岗岩。TTG 显示出与全球其他 TTG 相似的地球化学特征，例如高 Al2O3 (13.49–18.93 wt%) 和 Na2O (3.27–4.66 wt%) 和低 K2O (1.01–1.98 wt%)，以及低 K/Na ( 0.15–0.32) 比率。它们的 Mg# (Mg/(Mg + Fe)*100) 值从 34.81 到 50.76 不等，具有低到中等的 Nb/Ta 和 Zr/Sm 比率（分别为 7.03–23.43 和 19.13–75.25）。它们的特点是中等 (La/Yb)N (6.70–41.71) 和 Sr/Y (20.80–72.13) 比率与埃达克岩相似，负 Nb、Ta 和 Ti 异常以及富含 LREE 和 HREE 的模式，没有显着的 Eu 异常（Eu/Eu* = 0.93–1.11，平均值 = 1。00）。这些地球化学特征表明，TTG 岩石是由含水玄武岩地壳部分熔融形成的，如富含石榴石的角闪岩。斑状黑云母花岗岩显示出高钾钙碱性亲和力。它们的特点是高 SiO2 (71.01–74.86 wt%) 和 K2O (3.29–4.92 wt%) 但 MgO (0.38–0.92 wt%) 相对较低，Mg# 值在 31.78 和 40.27 之间变化。岩石显示出低至中等的 Sr/Y (13.75–26.66) 比率和 LREE 富集和 HREE 耗尽模式，具有负 Eu 异常（Eu/Eu* = 0.36–0.58，平均值 = 0.47）。这些地球化学特征表明斑状黑云母花岗岩起源于TTG岩性的部分熔融。八口斗金矿床的矿体以 TTG 剪切带中的石英脉形式出现。石英是主要的脉石矿物，含有少量硫化物，如黄铁矿和黄铜矿。金存在于固溶体 (Au+1) 中，并以天然金 (Au0) 的纳米粒子存在于黄铁矿中，主要以游离金的形式存在。通过激光烧蚀电感耦合等离子体质谱 (LA-ICP-MS) 分析的黄铁矿样品显示出高 Ni (3.24–3600 ppm) 和 Co (4.68–4140 ppm) 和低 As (