Abstract High-Mg# (molar 100 × Mg/(Mg + Fe)) diorites can provide significant insights on mantle metasomatism under a subduction zone. Here we investigate the genesis of the Neoproterozoic Shuilu high-Mg# diorites in the western Yangtze Block to evaluate the role of subduction-related fluids and sediment melts acting on mantle sources during the subduction process. Zircon U–Pb dating results display new weighted mean 206Pb/238U ages of 850.1 ± 1.7 Ma, 840.9 ± 2.4 Ma, and 836.6 ± 1.9 Ma for these high-Mg# diorites. They are metaluminous and calc-alkaline rocks, and characterized by moderate SiO2 contents (57.08–61.12 wt%) and high MgO contents (3.36–4.30 wt%) and Mg# values (56–60). The relatively low initial 87Sr/86Sr ratios (0.703406 to 0.704157) and highly positive whole-rock eNd(t) (+3.26 to +4.26) and zircon eHf(t) values (+8.43 to +13.6) imply that these rocks were predominantly sourced from depleted lithospheric mantle. These high-Mg# diorites also show enrichment of light rare earth elements and large ion lithophile elements (e.g., Rb, Ba, K, and Sr) as well as depletion of high field strength elements (e.g., Nb, Ta, Zr, and Hf), resembling a typical arc magma affinity. The highly variable Ba contents and Rb/Y, Th/Ce, Th/Sm, Ba/La, and Th/Yb ratios indicate significant incorporation of subduction-related fluids and sediment-derived melts into the primary mantle source. We therefore propose that the ca. 850–835 Ma high-Mg# diorites investigated in this study were formed by partial melting of a metasomatized mantle source enriched by subduction fluids and sediment melts. Our new data, in conjunction with numerous studies of metasomatized mantle magmatism from the western Yangtze Block, suggest that the Neoproterozoic mantle sources beneath the western Yangtze Block were metasomatized by subduction-related compositions involving slab fluids, sediment melts, and oceanic slab melts during the subduction process.

中文翻译：

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约的创世纪。华南扬子地块西部850-835 Ma高镁#闪长岩：俯冲作用下地幔交代作用的意义

摘要 高 Mg#（摩尔 100 × Mg/(Mg + Fe)）闪长岩可以为俯冲带下地幔交代作用提供重要见解。在这里，我们研究了扬子地块西部新元古代水鹿高镁#闪长岩的成因，以评估俯冲过程中与俯冲相关的流体和沉积物熔体对地幔源的作用。锆石 U-Pb 测年结果显示，这些高镁 # 闪长岩的新加权平均 206Pb/238U 年龄分别为 850.1 ± 1.7 Ma、840.9 ± 2.4 Ma 和 836.6 ± 1.9 Ma。它们是金属铝质和钙碱性岩石，具有中等 SiO2 含量（57.08-61.12 wt%）和高 MgO 含量（3.36-4.30 wt%）和 Mg# 值（56-60）的特点。相对较低的初始 87Sr/86Sr 比率（0.703406 至 0.704157）和高正的全岩 eNd(t)（+3.26 至 +4.26）和锆石 eHf(t) 值（+8.43 至 +13）。6) 暗示这些岩石主要来源于枯竭的岩石圈地幔。这些高 Mg# 闪长岩还显示出轻稀土元素和大离子亲石元素（例如 Rb、Ba、K 和 Sr）的富集以及高场强元素（例如 Nb、Ta、Zr 和Hf)，类似于典型的弧岩浆亲合力。高度可变的 Ba 含量和 Rb/Y、Th/Ce、Th/Sm、Ba/La 和 Th/Yb 比率表明与俯冲相关的流体和沉积物衍生的熔体大量掺入了主要地幔源。因此，我们建议约。本研究中研究的 850-835 Ma 高镁 # 闪长岩是由富含俯冲流体和沉积物熔体的交代地幔源部分熔融形成的。我们的新数据，