Eoarchaean tectonics: New constraints from high pressure-temperature experiments and mass balance modelling
Eoarchaean tectonics: New constraints from high pressure-temperature experiments and mass balance modelling
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DOI：
10.1016/j.precamres.2019.02.006
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发表时间：
2019-06
影响因子：
3.8
通讯作者：
Precambrian Research;A. Hastie;J. Fitton
中科院分区：
文献类型：
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作者：
Precambrian Research;A. Hastie;J. Fitton
四十亿年前，地球第一个大陆地壳的形成和保存标志着地球长期地球化学演化的新阶段。这种大陆材料主要由富含斜长石的花岗岩组成，形成太古宙英闪长岩和特隆杰姆岩 (ETT) 岩石套件。有两种可能的总体模型可用于产生 ETT：通过各种板内熔融机制或通过原始俯冲的开始。在这里，我们使用质量平衡模型来表明，ETT只能来自会聚边缘镁铁质岩石的含水熔融。这些镁铁质源区可能由相对未贫化（类似海洋高原）的非弧变玄武岩组成，有或没有残留金红石。来自这些变玄武岩的熔体随后与板状相关成分混合形成 ETT 岩浆。此外，ETT 可以由具有类似于现代岛弧玄武岩地球化学亲和力的变玄武岩部分熔融形成。我们认为，板块构造的原始形式始于冥古宙岩浆洋的表面，与现代熔岩湖上观察到的板块运动类似，随后演变成今天的板块构造。俯冲玄武岩地壳的含水融化和原大陆ETT地壳的形成可能是在地球表面液态水开始积累之后发生的。
Four billion years ago the formation and preservation of the Earth’s first continental crust marked a new stage in the long-term geochemical evolution of our planet. This continental material is predominantly composed of plagioclase-rich granitoids that form Eoarchaean Tonalite and Trondjhemite (ETT) rock suites. There are two plausible overarching models for generating ETT: by a variety of intraplate melting mechanisms or through the onset of primitive subduction. Here we use mass balance modelling to show that ETT can only be derived from the hydrous melting of mafic rocks in convergent margins. These mafic source regions could be composed of relatively undepleted (oceanic plateau-like) non-arc metabasalts with or without residual rutile. Melts derived from these metabasalts subsequently mix with a slab-related component to form ETT magmas. Additionally, ETT can be formed from partial melting of metabasalts with geochemical affinities similar to modern island arc basalts. We propose that a primitive form of plate tectonics began on the surface of Hadean magma ocean(s), in a similar way to the plate-like motions observed on modern lava lakes, and subsequently evolved into the plate tectonics operating today. Hydrous melting of subducted basaltic crust and the formation of the proto-continental ETT crust would have followed the onset of accumulation of liquid water on the Earth’s surface.