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.

地球亏损上地幔在冥古宙和早太古代的演化至今仍是一个有争议的问题。有相互竞争的模型，一个声称早期耗尽4.4 Ga，而其他人则认为晚期耗尽，明显在3.5 Ga之后。为了测试这些模型，我们建议进行微量元素和同位素测量新鲜，3.8 Ga老超镁铁岩从Isua地区在西格陵兰岛南部，解释为地球上保存最古老的地幔岩。Isua地区早太古代（3.6 ~ 3.8Ga）的古老绿岩和英云闪长岩-奥长花岗岩-花岗闪长岩（TTG）套岩石是世界上独一无二的，它们代表了几乎完整和保存完好的早太古代壳幔演化记录。结合这些岩石中的放射性同位素和微量元素系统学，为深入了解硅酸盐地球早期演化过程中活跃的地质过程提供了一个独特的机会。在我们项目的第一阶段，我们对该地区3.70至3.85 Ga的角闪岩相绿岩和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（起源于形成于冥古宙的高度亏损的地幔源），以及（2）拉斑玄武岩绿岩中存在Hf-Nd同位素特征的去耦，反映了早在3.8 Gyrs前俯冲带过程的存在。此外，我们发现了强有力的证据表明，TTG与Isua绿岩起源于加厚的镁铁质弧地壳的熔融，而不是从俯冲洋壳。在这里提出的项目的第二阶段，我们打算通过直接研究最近在Isua南部地区发现的早期太古代地幔岩，对早期硅酸盐地球的演化有新的认识。这些岩性在TTG中作为新鲜包体保存。在一次侦察抽样活动中，我们收集了大约。超镁铁质包体中保存有新鲜橄榄石和辉石的40个样品。通过从这些样品中制备矿物分离物，将有可能对微量元素和放射性同位素组成（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地幔的微量元素和放射性同位素库存。此外，硅酸盐地球中放射性同位素组成演化的不同模型可以直接测试，有助于更好地了解地球上硅酸盐储层的演化。

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

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

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

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

Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa)

巴伯顿绿岩带（南非）Onverwacht 群下部变玄武岩和变科岩岩的岩石成因演化

• DOI: 10.1016/j.chemgeo.2019.02.020
• 发表时间: 2019
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Schneider;Hoffmann;Münker;Patyniak;Sprung;Roerdink;Garbe Schönberg;Kröner
• 通讯作者: Kröner