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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.

大陆地壳（CC）的形成，稳定，修改和再循环过程是理解地球分异，全球地球化学循环和地球动力学的基础。虽然上CC的组成和起源是相当众所周知的，但那些基本上无法进入的下CC仍然是谜。麻粒岩和辉石岩是在罕见的金伯利岩或玄武岩浆作用期间作为捕虏体零星夹带的低CC的实际样品。此外，一些地幔榴辉岩可能代表残留物的补充早期上CC，而其他结晶附近的壳幔边界的镁铁质熔体在后来的事件。因此，所有这些岩性都为CC的形成和改造过程提供了重要的见解，例如莫霍面的地壳分异和壳幔之间的质量传递。笔者建议综合研究其常量元素、微量元素和同位素组成（U-Pb，Hf-Nd-Sr，O和多种S同位素）和氧化还原状态，以制约（1）下CC形成、变质和生长的过程、物质来源、条件和时间;（2）麻粒岩和辉石岩的热物理性质及其引起的低CC的热稳定性和重力稳定性：（3）地幔榴辉岩在大陆形成中的作用及其与低CC的关系;（4）高场强、亲硫、亲铁元素的丰度、分布和活动性，重点是副金红石、钛铁矿和硫化物。总之，这些研究将有意义的西太平洋地球动力学，陆地微量元素循环，地球化学过程相关的大陆形成。