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.

拟议的项目涉及来自西南比亚市中心碱性环复合体碱性岩石岩石的主要和痕量元素地球化学和同位素组成。基于与埃特内卡高原（Etendeka Plateau）的Tholeiitic洪水底层相关的不同地球化学成分，可以建议碱性岩石起源于来自西部纳米比亚（Walvis Ridge Basalts and Etendeka Floodeka Floodeka Floodeka Floodeka Basalt序列）所设想的碱性岩石的来源。原始碱性gabbros（theralites）可能代表亚质岩石圈地幔的熔体。 NE-Normatorative Syenites要么是theralites的分级产物，要么代表上地幔源的进化熔体。 QTZ定义的syenite可能是NE-Normatorative Syenite的AFC产品。使用最先进的ICP-MS技术，将研究岩石的ND，SR，PB，HF全岩同位素和高精度HFSE（高场强元件； ZR-NB-TA-HF）丰度。结果将在与裂谷相关区域的上地幔的可能异质性上施加限制，还可以用来区分二阶过程（具有或不具有分数结晶的地壳污染，岩浆混合）与一阶过程（部分融化的岩浆混合）（富含地形源的局部融化）。该项目旨在理解复杂的软磷 - 斜圈相互作用，因此非常适合在与裂谷相关的大陆环境中增加有关岩石圈动力学的知识。