Die Entwicklung des Krusten Mantel Systems im Früharchaikum

早太古代地幔系统的发育

• 批准号: 57914783
• 负责人: Professor Dr. Carsten Münker
• 金额: --
• 依托单位: Institut für Geologie und Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/57914783?language=en
• 关键词: Die; Entwicklung; des; Krusten; Mantel

The evolution of the Earths depleted upper mantle in the Hadean and Early Archean Eons is still a contentious issue. There are competing models, one claiming an early depletion by 4.4 Ga, whereas others argue for late depletion, significantly after 3.5 Ga. To test these models, we propose to perform trace element and isotope measurements on fresh, 3.8 Ga old ultramafic rocks from the Isua region in southern West Greenland, interpreted as the oldest preserved mantle rocks on Earth. The Early Archean (3.6 to 3.8 Ga) old greenstones and tonalite-trondhjemite-granodiorite (TTG) suite rocks from the Isua region are worldwide unique in that they represent a nearly complete and well preserved re-cord of Early Archean crust-mantle evolution. Combining radiogenic isotope and trace elements systematics in these rocks provides a unique opportunity to get insights geological processes active during the earliest evolution of the silicate Earth. In the first phase of our project, we performed state of the art isotope and trace element measurements on 3.70 to 3.85 Ga old amphibolite-facies green-stones and TTGs from the region. We could show that (1) some of the greenstones (originated from highly depleted mantle sources formed in the Hadean, and (2) that there is a decoupling of Hf-Nd isotope signatures in tholeiitic greenstones that reflects the presence of subduction zone processes as early as 3.8 Gyrs ago. Moreover, we found strong evidence that TTGs associated with the Isua greenstones originated from melting of thickened mafic arc crust and not from subducted oceanic crust. During the second phase of the project as proposed here, we intend to gain new insight into the evolution of the early silicate Earth, by directly studying early Archean mantle rocks that were just recently discovered in the region south of Isua. These lithologies are preserved as fresh enclaves in TTGs. During a reconnaissance sample campaign we have collected ca. 40 samples from ultramafic enclaves where fresh olivine and pyroxenes are preserved. By preparing mineral separates from these samples, it will be possible to perform robust measurements of trace elements and radiogenic isotope compositions (Sr-Nd-Pb-Hf-Os) that will for the first time permit to directly characterize the trace element and radiogenic isotope inventory of early Archean mantle. In addition, the different models for the evolution of radiogenic isotope compositions in the silicate Earth can then be directly tested, contributing to a better understanding of the evolution of silicate reservoirs on Earth as found at present day.

地球上地幔在冥宙和早太古代的演化仍然是一个有争议的问题。有一些相互竞争的模型，一种模型声称早期损耗为 4.4 Ga，而其他模型则主张晚期损耗，明显在 3.5 Ga 之后。为了测试这些模型，我们建议对来自 3.8 Ga 的新鲜超镁铁质岩石进行微量元素和同位素测量。西格陵兰岛南部的伊苏阿地区，被解释为地球上保存最古老的地幔岩石。伊苏阿地区的早太古代（3.6 至 3.8 Ga）老绿岩和英闪长岩-长花岗岩-花岗闪长岩（TTG）套件岩石在世界范围内是独一无二的，因为它们代表了早太古代壳幔演化的近乎完整且保存完好的记录。将这些岩石中的放射性同位素和微量元素系统学相结合，为了解硅酸盐地球最早演化期间活跃的地质过程提供了独特的机会。在项目的第一阶段，我们对该地区的 3.70 至 3.85 Ga 老角闪岩相绿岩和 TTG 进行了最先进的同位素和微量元素测量。我们可以证明 (1) 一些绿岩（源自冥古宙形成的高度贫化的地幔源，以及 (2) 拉斑斑岩绿岩中的 Hf-Nd 同位素特征存在解耦，这反映了俯冲带过程的存在：此外，我们发现了强有力的证据表明与 Isua 绿岩相关的 TTG 起源于加厚的镁铁质弧地壳的熔化，而不是来自于。在此处提出的项目的第二阶段中，我们打算通过直接研究最近在伊苏阿以南地区发现的早期太古代地幔岩石，获得对早期硅酸盐地球演化的新见解。在一次勘探取样活动中，我们从保存有新鲜橄榄石和辉石的超镁铁质飞地中收集了约 40 个样品。从这些样本中，将有可能对微量元素和放射性同位素成分（Sr-Nd-Pb-Hf-Os）进行可靠的测量，这将首次允许直接表征早期太古代的微量元素和放射性同位素库存地幔。此外，可以直接测试硅酸盐地球中放射性同位素成分演化的不同模型，有助于更好地了解目前在地球上发现的硅酸盐储层的演化。

项目成果

Petrogenesis of plagiogranites from the Troodos Ophiolite Complex, Cyprus

• DOI: 10.1007/s00410-019-1569-3
• 发表时间: 2019-04
• 期刊: Contributions to Mineralogy and Petrology
• 影响因子: 3.5
• 作者: C. Marien;J. Hoffmann;C. Garbe-Schönberg;C. Münker

Sm-Nd and Lu-Hf isotope and trace-element systematics of Mesoarchaean amphibolites, inner Ameralik fjord, southern West Greenland

• DOI: 10.1180/minmag.2015.079.4.02
• 发表时间: 2015-08
• 期刊: Mineralogical Magazine
• 影响因子: 2.7
• 作者: K. Szilas;J. Hoffmann;Christina Hansmeier;J. Hollis;C. Münker;S. Viehmann;H. Kasper

Combined bulk-rock Hf- and Nd-isotope compositions of Mesoarchaean metavolcanic rocks from the Ivisaartoq Supracrustal Belt, SW Greenland: Deviations from the mantle array caused by crustal recycling

• DOI: 10.1016/j.chemer.2016.09.004
• 发表时间: 2016-12
• 期刊: Chemie Der Erde-geochemistry
• 作者: K. Szilas;J. Hoffmann;T. Schulz;Christina Hansmeier;A. Polat;S. Viehmann;H. Kasper;C. Münker

Hafnium isotope constraints on the origin of Mesoarchaean andesites in southern West Greenland, North Atlantic Craton

• DOI: 10.1144/sp449.2
• 发表时间: 2016-09
• 期刊: Special Publications
• 作者: K. Szilas;J. Tusch;J. Hoffmann;A. Garde;C. Münker

Earth’s oldest mantle peridotites show entire record of late accretion

• DOI: 10.1130/g39709.1
• 发表时间: 2018-03
• 期刊: Geology
• 影响因子: 5.8
• 作者: J. V. D. Löcht;J. Hoffmann;C. Li;Ze‐Zhou Wang;H. Becker;M. Rosing;R. Kleinschrodt;C. Münker