Petrogenesis of alkaline rift-related ring complexes constrained from combined Sr, Nd, Pb, and Hf isotopes and HFSE systematics

受 Sr、Nd、Pb 和 Hf 组合同位素和 HFSE 系统学约束的碱性裂谷相关环状复合体的岩石成因

• 批准号: 507434582
• 负责人: Professor Dr. Stefan Jung
• 金额: --
• 依托单位: Mineralogisch-Petrographisches Institut (MPI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/507434582?language=en
• 关键词: Petrogenesis; alkaline; rift; related; ring

The proposed project deals with the major and trace element geochemistry and isotope composition of alkaline plutonic rocks from the Messum alkaline ring complex in western Nambia. Based on the distinct geochemical compositions relative to the tholeiitic flood basalts from the Etendeka plateau, it can be suggested that the alkaline rocks originated from sources distinct to those envisaged for other Cretaceous igneous rocks from western Namibia (Walvis Ridge basalts and Etendeka flood basalt sequences). Primitive alkaline gabbros (theralites) probably represent melts of the subcrustal lithospheric mantle. Ne-normative syenites are either fractionation products of the theralites or represent also evolved melts from upper mantle sources. Qtz-normative syenites are likely AFC products of the ne-normative syenites. The rocks will be investigated for Nd, Sr, Pb, Hf whole rock isotopes and high-precision HFSE (High-Field-Strength Elements; Zr-Nb-Ta-Hf) abundances using state-of-the-art ICP-MS techniques. The results will place constraints on possible heterogeneities of the upper mantle in rift-related areas and can also be used to distinguish second-order processes (crustal contamination with or without fractional crystallization, magma mixing) from first-order processes (partial melting of enriched mantle sources). The project aims at understanding complex asthenosphere-lithosphere interactions and is therefore ideally suited to add knowledge on lithosphere dynamics in rift-related continental settings.

拟议项目研究纳米比亚西部 Messum 碱性环杂岩碱性深成岩的主量和微量元素地球化学和同位素组成。根据与埃滕德卡高原拉斑玄武岩不同的地球化学成分，可以认为碱性岩石的来源与纳米比亚西部其他白垩纪火成岩的来源不同（沃尔维斯岭玄武岩和埃滕德卡溢流玄武岩序列） 。原始碱性辉长岩（theralites）可能代表地壳下岩石圈地幔的熔体。新规范正长岩要么是角长岩的分馏产物，要么代表来自上地幔来源的演化熔体。 Qtz 标准正长岩很可能是新标准正长岩的 AFC 产物。将使用最先进的 ICP-MS 技术研究岩石的 Nd、Sr、Pb、Hf 全岩石同位素和高精度 HFSE（高场强元素；Zr-Nb-Ta-Hf）丰度。研究结果将对裂谷相关区域上地幔可能的异质性施加限制，也可用于区分二级过程（有或没有分异结晶的地壳污染、岩浆混合）和一级过程（富集岩浆的部分熔融）。地幔来源）。该项目旨在了解复杂的软流圈-岩石圈相互作用，因此非常适合增加有关裂谷相关大陆环境中岩石圈动力学的知识。