Rocks that make up the Mesoarchean (~3Ga) Buhwa greenstone belt (BGB) of the Zimbabwe craton divide into three associations: shelf, basinal, and transitional. Chert and iron formation exist within the three associations, allowing the unique opportunity to compare textural and geochemical attributes of iron- and silica-rich rocks from distinct positions within a single basin. We analyzed major-, trace-, and rare-earth-elements, and silicon and oxygen isotopes of chert and iron formation from the shelf, basinal, and transitional associations within the BGB. Samples possess elemental signatures consistent with formation from mixed seawater and hydrothermal fluids (La_SN/La_SN* > 1; Pr_SN/Yb_SN < 1; Y/Ho = 28.2–44.4; Eu_SN/Eu_SN* = 1.8–2.8). Oxygen isotope values broadly overlap for samples from different associations (ranging from δ¹⁸O_V-SMOW = 9.41 to 15.10‰ (2σ = 0.8‰)), with isotopic variation linked to the presence of oxide inclusions in some samples. Silicon isotope values by contrast, vary widely. Iron formations possess ³⁰Si-depleted silicon isotope signatures (δ³⁰Si_NBS-28 = −2.5 to −0.5‰ (2σ = 0.05‰)), in line with previous studies. Basinal and transitional cherts possess ³⁰Si-depleted silicon isotope signatures (δ³⁰Si_NBS-28 = −1.1 to −0.5‰ (2σ = 0.05‰)) that overlap with values measured from iron formation samples. Within the transitional association, cherts are not ³⁰Si-enriched compared to iron formation, while chert in the basinal association is ³⁰Si-enriched compared to iron formation. Depleted silicon isotope signatures could result from fractionation during adsorption, re-equilibration, post-depositional processes, or possibly microbial reduction processes. Silicon isotope heterogeneity recorded in chert preserved in different assemblages across the BGB may in part reflect a seawater signature. The range of silicon isotope values preserved within broadly co-eval rocks from the same assemblage may indicate that samples preserve local isotopic signatures of a heterogeneous reservoir. Future work focused on identifying basin-position dependent trends may inform interpretations of the compiled Precambrian silicon isotope record.

构成津巴布韦克拉通的Mesoarchean（〜3Ga）Buhwa绿岩带（BGB）的岩石分为三个关联：陆架，盆地和过渡带。在这三个联系中存在着t硅和铁的形成，这为比较单一盆地中不同位置的富含铁和二氧化硅的岩石的质地和地球化学属性提供了独特的机会。我们分析了BGB内陆架，盆地和过渡缔合的主要，微量和稀土元素，以及硅质和铁形成的硅和氧同位素。样品具有与混合海水和热液混合形成的元素特征（La _SN / La _SN *> 1； Pr _SN / Yb _SN  <1； Y / Ho = 28.2-44.4； Eu _SN）/ Eu _SN * = 1.8–2.8）。氧同位素的值大致重叠用于从不同的关联的样本（从δ ¹⁸ ö _V-SMOW  = 9.41到15.10‰（2σ= 0.8‰）），与链接到氧化物夹杂的一些样品中存在同位素变化。相比之下，硅同位素值差异很大。铁地层具有³⁰的Si-贫硅同位素签名（δ ³⁰的Si _NBS-28  = -2.5至-0.5‰（2σ= 0.05‰）），符合先前的研究。盆地和过渡硅质岩具有³⁰的Si-贫硅同位素签名（δ ³⁰的Si _NBS-28 = -1.1至-0.5‰（2σ= 0.05‰），与从铁形成样品测得的值重叠。内过渡关联，硅质岩不是³⁰相比铁形成的Si富集，而燧石在盆地关联是³⁰富硅相比铁形成。贫化的硅同位素特征可能来自吸附，重新平衡，沉积后过程或可能的微生物还原过程中的分馏过程。在整个BGB中以不同组合保存的石中记录的硅同位素异质性可能部分反映了海水特征。同一集合的广泛同价岩石中保存的硅同位素值范围可能表明样品保留了非均质储层的局部同位素特征。着眼于确定盆地位置相关趋势的未来工作可能会为已汇编的前寒武纪硅同位素记录提供解释依据。