Cratonic granulite, pyroxenite and eclogite xenoliths: Archives of continental crust evolution and terrestrial trace element cycling

克拉通麻粒岩、辉石岩和榴辉岩捕虏体：大陆地壳演化和陆地微量元素循环档案

基本信息

批准号：
243877522
负责人：
Dr. Sonja Aulbach
金额：
--
依托单位：
Abteilung Petrologie und Geochemie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/243877522?language=en
关键词：
Cratonic granulite pyroxenite eclogite xenoliths

项目摘要

The processes of forming, stabilising, modifying and recycling continental crust (CC) through time are fundamental to understanding the differentiation of the Earth, global geochemical cycling and geodynamics. While the composition and origin of the upper CC are reasonably well known, those of the largely inaccessible lower CC remain enigmatic. Granulites and pyroxenites are actual samples of cratonic lower CC that are sporadically entrained as xenoliths during rare kimberlite or basaltic magmatism. Moreover, some mantle eclogites may represent residues complementary to the early upper CC, while others crystallised near the crust-mantle boundary from mafic melts during later events. Thus, all these lithologies offer important insights into processes attending the formation and modification of the CC, such as crustal differentiation and mass transfer between the crust and mantle at the Moho. I propose to comprehensively study the major-element, trace-element and isotopic composition (U-Pb, Hf-Nd-Sr, O and multiple S isotopes) and redox state of granulite, pyroxenite and eclogite xenoliths from four cratons to constrain (1) the processes, sources, conditions and timing of lower CC formation, modification and growth; (2) the thermophysical properties of granulites and pyroxenites and the resultant thermal and gravitational stability of lower CC; (3) the role of cratonic mantle eclogites in continent formation and their relationship to the lower CC; (4) the abundances, distribution and mobility of high field-strength, chalcophile and siderophile elements, with a focus on accessory rutile, ilmenite and sulphide. Taken together, these studies will have implications for Archaean geodynamics, terrestrial trace-element cycling, and geochemical processes relevant to continent formation.

随着时间的推移形成，稳定，修饰和回收大陆地壳（CC）的过程对于理解地球的区分，全球地球化学循环和地球动力学的分化至关重要。虽然上CC的组成和起源是相当众所周知的，但在很大程度上无法访问的下部CC的组成和起源仍然存在神秘性。颗粒和辉石是在稀有的金伯利岩或玄武岩岩浆中偶发地作为异种石的实际样品。此外，某些地幔eclogites可能代表了早期CC的残留物，而另一些地幔则代表了在以后的事件中与镁铁质融化的地壳甲壳边界附近结晶的残留物。因此，所有这些岩性都为参加CC的形成和修饰的过程提供了重要的见解，例如地壳分化以及Moho的地壳和地幔之间的质量转移。我建议全面研究主要元素，痕量元素和同位素组成（U-PB，HF-ND-SR，O和多个S同位素）和颗粒状，辉石和粘岩的氧化还原状态。（2）颗粒和辉石的热物理特性以及较低CC的最终热和重力稳定性；（3）克拉托式地幔eclogites在大陆形成中的作用及其与较低CC的关系；（4）高场强，豆科植物和辅助元素的丰度，分布和迁移率，重点是辅助金红石，iLmenite和硫化物。综上所述，这些研究将对古细菌学，陆地痕量元素循环以及与大陆形成相关的地球化学过程有影响。