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.

地球最古老的连续地壳的主要组成部分是Tonalite -t​​rondhjemite-粒状岩（TTG）系列的Sodic Rocks，它们是通过不同深度下的含水质量质量的部分熔化而形成的。然而，与TTG融化形成相关的过程仍存在争议，并且有关水在产生这种大量融化量的作用和来源的基本问题尚未得到回答。该项目旨在更好地表征自然含量及其在自然含量及其中的旋律中的旋律，以更好地表征型 - 置入时间（P -T -T -T）条件（P -T -T -T）条件。特别是，我们旨在研究部分熔化过程中水的作用和来源，以及镁铁质 - 硫酸含量原石和水的组成多样性如何控制产生的熔体的组成和体积。研究的样品完整的TTG和封闭的镁铁质粉状豆荚从一系列的大古迹地形上有所不同，这些豆荚在其拟议的地球动力学进化和年龄方面有所不同。相等的前向模型将用于限制部分熔化的条件和产生的熔体的组成。这些结果将与相关TTG片麻岩的痕量元素建模和块状岩石地球化学结合，以将建模的熔体组合物与天然TTG片麻岩样品的组成进行比较。此外，锆石的U – PB地球人数，痕量元素和氧同位素分析将用于i）锆石平衡的TTG熔体的临时和P – T约束，ii）提供有关融化深度的进一步信息，以及III的进一步信息，以确定水在甲壳层融化过程中的作用以及水的作用。这项研究的结果有可能显着促进对大帝TTGS石油发生的长期讨论，并且还可能提供对它们形成的地球动力学环境的进一步见解。