The paper summarizes major, trace, and Sm-Nd isotopic data on metabasites of the Urik greenstone belt (GB) (Sharyzhalgai uplift, southwestern Siberian craton). The Archean metabasalts (amphibolites and garnet amphibolites) of the supracrustal complex and sheeted bodies represent four geochemical types. The first type includes low-Ti amphibolites of the Urik area. Their characteristic features are a clear LREE depletion ((La/Sm)_n = 0.8–1.1), the absent negative Nb anomaly, and positive ε_Nd(t) values (up to +4.1). The second type corresponds to moderate-Ti amphibolites of the Urik area. They differ from the rocks of the first type in the higher (La/Sm)_n ratio (1.0–1.5), Th, Zr, Nb, Y contents, and lower ε_Nd(t) values (+0.4…–1.6), but, like the low-Ti amphibolites, they do not show Nb depletion. The third type includes amphibolites of the Tagna area, which show an increase in the concentrations of TiO₂, LREE, Th, Zr, and Nb with a decrease in Mg# and have ε_Nd(t) values from +1.3 to –0.5. They are characterized by the elevated (La/Sm)_n ratio (1.1–2.3) and Zr and Nb contents and the presence of a clear Nb minimum. The fourth type includes all high-Ti amphibolites of sheeted bodies, which are enriched in LREE ((La/Sm)_n = 1.9–3.4), Th, Zr, and Nb, have an increased (Gd/Yb)_n (1.4–2.0), a sharp Nb depletion, and negative ε_Nd(t) values. Geochemical modeling coupled with trace element and isotopic composition indicates the formation of the low- and moderate-Ti metabasalts of the Urik area from weakly depleted and nearly primitive mantle sources, respectively. Their protoliths were oceanic basalts. The metabasalts of the Tagna area were formed from a weakly depleted and hydrated mantle source contaminated with crustal material. The enrichment of the source with incompatible elements could be caused by sediment subduction shortly before basalt formation. The metabasalts of the fourth type originated from a long-lived enriched source such as subcontinental lithospheric mantle. They resemble the present-day intraplate continental basalts. None of the three dominant types of metabasalts of the Urik GB shows signatures of sharply depleted or sharply enriched mantle sources, which indicates a weak differentiation of the mantle by the Meso- Neoarchean boundary (~2.8 Ga). The formation of a subduction-modifed lithospheric mantle (hydrated mantle) has only occurred since ~ 2.8 Ga. Different compositional and isotopic characteristics of the metabasalts of the Urik GB suggest that the Bulun terrane was formed by accretion and tectonic juxtaposition of fragments of the oceanic crust, an oceanic island arc, and an older TTG continental crust at ~ 1.86 –1.82 Ga.

该论文总结了 Urik 绿岩带 (GB)（Sharyzhalgai 隆起，西伯利亚克拉通西南部）变碱岩的主要、痕量和 Sm-Nd 同位素数据。上地壳复合体和片状体的太古代变玄武岩（角闪岩和石榴石角闪岩）代表四种地球化学类型。第一种类型包括 Urik 地区的低钛角闪岩。它们的特征是明显的 LREE 消耗（(La/Sm) _n = 0.8–1.1）、不存在负 Nb 异常和正 ε _Nd (t) 值（高达 +4.1）。第二种类型对应于 Urik 地区的中钛角闪岩。它们与第一类岩石的不同之处在于较高的 (La/Sm) _n比 (1.0–1.5)、Th、Zr、Nb、Y 含量和较低的 ε _Nd(t) 值 (+0.4…–1.6)，但是，与低钛角闪石一样，它们不显示 Nb 耗尽。第三种类型包括 Tagna 地区的角闪岩，随着 Mg# 的减少，TiO ₂、LREE、Th、Zr 和 Nb 的浓度增加，ε _Nd (t) 值从 +1.3 到 –0.5。它们的特点是 (La/Sm) _n比率升高 ( 1.1–2.3) 以及 Zr 和 Nb 含量以及存在明显的 Nb 最小值。第四类包括所有片状体的高钛角闪岩，它们富含轻稀土元素（(La/Sm) _n = 1.9–3.4）、Th、Zr 和 Nb，具有增加的 (Gd/Yb) _n (1.4– 2.0)，急剧的 Nb 耗尽，以及负的 ε _Nd(t) 值。结合微量元素和同位素组成的地球化学模型表明，Urik 地区的低钛和中钛变玄武岩分别由弱耗竭和近原始地幔源形成。它们的原岩是大洋玄武岩。Tagna 地区的变玄武岩是由被地壳物质污染的弱耗竭和水合地幔源形成的。不相容元素源的富集可能是由玄武岩形成前不久的沉积物俯冲引起的。第四类变玄武岩起源于次大陆岩石圈地幔等长寿命富集源。它们类似于当今的板内大陆玄武岩。Urik GB 的三种主要变玄武岩类型均未显示出地幔源急剧枯竭或富集的特征，这表明中新太古代边界（~2.8 Ga）对地幔的微弱分化。俯冲改造的岩石圈地幔（水合地幔）的形成仅发生于~2.8 Ga。Urik GB 变玄武岩的不同成分和同位素特征表明布伦地体是由海洋碎片的增生和构造并置形成的地壳、一个大洋岛弧和一个较老的 TTG 大陆地壳，约 1.86 –1.82 Ga。