Abstract This paper reports new petrological, geochemical and isotopic data for Carlsberg Ridge Basalts (CRB) of northwest Indian Ocean and evaluates their petrogenetic aspects in the context of the geochemical and tectonic evolution of the Indian Ocean mantle. The CRB samples exhibit tholeiitic to transitional composition of precursor melts derived by high degree, shallow level partial melting of a spinel peridotite mantle source. CRB reflects distinct E-MORB affinity with selective enrichment in incompatible trace elements. Higher values of Zr/Hf (33.8–47.3) and Zr/Sm (24.9–36.4) in conjunction with lower Nb/Ta (1.7–7.3) ratio corroborate their origin from an enriched mantle source. Negative Nb anomalies with lower Nb/Y (0.04–0.11) and Zr/Y (2.5–3.5) conform to a non-plume origin of these basalts. Higher Zr/Nb (25.5–71.5) and Th/Nb (0.6–0.42) compared to OIB substantiate contributions from recycled subduction-processed components in the source mantle. Lower Nb/U (6.2–37.9) values with higher Ba/Nb (6.1–21.9), Ba/Th (27.7–147.5), Zr/Nb (25.5–71.5) and Th/Nb (0.6–0.42) compared to OIB and N-MORB attest to role of a metasomatized oceanic lithosphere that recycled into the depleted upper mantle attributing to the source heterogeneity. Sr-Nd isotopic signatures (87Sr/86Sr: 0.702668 to 0.702841 and 143Nd/144Nd: 0.512972 to 0.513068) of CRB suggest a HIMU source component preserved in the northwest Indian Ocean Ridge mantle. The compositional diversity of the Indian Ocean mantle can be translated in terms of periodic refertilization of depleted N-MORB type mantle through delamination and recycling of oceanic (HIMU component) and continental lithosphere (EM I component) concurrent with Neoproterozoic-Palaeozoic amalgamation and Jurassic dispersal of Gondwana Supercontinent respectively. This study complies with the derivation of CRB from a geochemically heterogeneous Indian Ocean mantle that experienced a protracted residence beneath the Gondwana Supercontinent prior to the opening of Indian Ocean and trapped recycled metasomatized oceanic lithosphere genetically linked with multiple stages of paleo-ocean closure and continental convergence during Gondwana assembly.

中文翻译：

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印度洋异质地幔中古代再生海洋岩石圈的印记：来自西北印度洋嘉士伯岭玄武岩岩石成因的证据

摘要 本文报告了印度洋西北部嘉士伯岭玄武岩 (CRB) 的新岩石学、地球化学和同位素数据，并在印度洋地幔地球化学和构造演化的背景下评估了它们的岩石成因。CRB 样品表现出拉斑岩到过渡组成的前体熔体，这是由尖晶石橄榄岩地幔源的高度、浅层部分熔融产生的。CRB 通过选择性富集不相容的微量元素反映了独特的 E-MORB 亲和力。较高的 Zr/Hf (33.8–47.3) 和 Zr/Sm (24.9–36.4) 以及较低的 Nb/Ta (1.7–7.3) 比值证实了它们来自富集地幔源。具有较低 Nb/Y (0.04–0.11) 和 Zr/Y (2.5–3.5) 的负 Nb 异常符合这些玄武岩的非羽流起源。更高的 Zr/Nb (25.5–71.5) 和 Th/Nb (0.6–0. 42) 与 OIB 相比，证实了源地幔中回收的俯冲处理成分的贡献。与 OIB 相比，较低的 Nb/U (6.2–37.9) 值与较高的 Ba/Nb (6.1–21.9)、Ba/Th (27.7–147.5)、Zr/Nb (25.5–71.5) 和 Th/Nb (0.6–0.42)和 N-MORB 证明了交代化的海洋岩石圈的作用，该岩石圈循环到耗尽的上地幔中，这归因于来源的异质性。CRB 的 Sr-Nd 同位素特征（87Sr/86Sr：0.702668 至 0.702841 和 143Nd/144Nd：0.512972 至 0.513068）表明在西北印度洋洋脊地幔中保存了 HIMU 源组分。印度洋地幔的成分多样性可以通过与新元古代-古生代合并和侏罗纪扩散同时发生的大洋（HIMU 成分）和大陆岩石圈（EM I 成分）的分层和再循环来转化为耗尽的 N-MORB 型地幔的周期性再利用分别位于冈瓦纳超大陆。这项研究符合从地球化学异质性印度洋地幔中推导出 CRB 的结论，该地幔在印度洋开放之前在冈瓦纳超大陆下方长期居住，并被困在与古海洋闭合和大陆辐合的多个阶段遗传相关的再循环交代海洋岩石圈在冈瓦纳组装期间。