The role of mafic-ultramafic bodies in the origin of the early continental crust

镁铁质-超镁铁质体在早期大陆地壳起源中的作用

• 批准号: 504307867
• 负责人: Professorin Dr. Annika Dziggel
• 金额: --
• 依托单位: Institut für Geologische Wissenschaften
• 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/504307867?language=en
• 关键词: role; mafic; ultramafic; bodies; origin

Major components of the Earth’s oldest continental crust are sodic rocks of the tonalite– trondhjemite–granodiorite (TTG) series, which formed through partial melting of hydrous metabasalts at different depths. However, the processes associated with TTG melt formation are still debated, and fundamental questions regarding the role and source of water in the production of such voluminous amounts of melts have yet to be answered.This project aims to better characterize the pressure–temperature–composition–time (P–T– X–t) conditions during partial melting of natural Archean mafic–ultramafic protoliths and their role in the generation of TTG melts. In particular, we aim to investigate the role and source of water during partial melting, and how the compositional diversity of the mafic–ultramafic protoliths and water availability control the composition and volume of the melts produced. The investigated samples comprise pairs of TTGs and enclosed mafic-ultramafic pods from a range of Archean terrains that differ in terms of their proposed geodynamic evolution and age. Phase equilibrium forward-modelling will be used to constrain the conditions of partial melting and the compositions of the melts produced. These results will be combined with trace element modelling and bulk-rock geochemistry of the associated TTG gneisses to compare the modelled melt compositions with those of the natural TTG gneiss samples. Additionally, U–Pb geochronology, trace element and oxygen isotope analysis of zircon will be used to i) integrate temporal and P–T constraints of the zircon-equilibrated TTG melt, ii) to provide further information on the depth of melting, and iii) to determine the source and the role of water during crustal melting. The results of this study have the potential to significantly contribute to the long-lasting discussion on Archean TTGs petrogenesis and may also provide further insights into the geodynamic setting(s) in which they formed.

最古老的大陆地壳的主要组成部分是Tonalite -Granodiolite（TTG）的Sodic Rocks，在不同depther处有液压metabasalts的部分融化，该过程与TTG Meleltatill辩论有关的过程。熔体的大量融化尚未得到回答。该元素在天然天生镁铁质的部分熔化过程中的压力 - 温度 - 分配 - 时间（P -T -X -T）条件 - 硫酸含量 - 硫酸含量 - 硫酸含量 - 硫酸含量 - 硫酸含量 - 硫酸含量 - 硫酸含量 - 硫酸含量质石和TTG融化的产生部分熔化期间的水，以及粉料的组成多样性 - 粉状质量和水的供应能力。在其提出的地球动力学进化和部分融化的条件下，这些融化和产生的融化。样品。将使用锆石的痕量元素和氧同位素分析，将使用TTG熔体，ii）提供有关熔化深度的进一步信息，以及III），以确定在地壳熔化中的水源和作用TTGS石油发生，也可能在其形成的地球动力学环境中进一步提供。