The continental record and the generation of continental crust
The continental record and the generation of continental crust
复制标题
DOI：
10.1130/b30722.1
复制
发表时间：
2013-01-01
影响因子：
4.9
通讯作者：
Dhuime, B.
中科院分区：
文献类型：
--
作者：
Cawood, P. A.;Hawkesworth, C. J.;Dhuime, B.
大陆地壳是地球历史的档案。地球记录的岩石单元和事件的空间和时间分布是不均匀的；例如，火成岩结晶、变质作用、大陆边缘、矿化以及海水和大气代理的年龄分布在一系列波峰和波谷周围。这种分布反映了不同构造环境中生成的岩石的不同保存潜力，而不是活动的基本脉冲，并且年龄的峰值与超大陆聚集的时间相关。锆石的物理化学弹性及其主要源自长英质火成岩意味着它们是地壳记录的重要指标。此外，对一系列烃源岩进行取样的碎屑锆石提供了比直接分析火成岩中颗粒更具代表性的记录。对碎屑锆石的分析表明，至少类似于目前大陆地壳体积的 60%-70% 是由 3 Ga 生成的。这种估计试图考虑到沉积记录中旧地壳物质代表性不足的程度，并且它们意味着太古宙中大陆地壳的体积比根据碎屑锆石和沉积物的成分推断出的体积要大。大陆地壳的生长是一个连续的过程，而不是间歇性的过程，但在大约 10 世纪，地壳生长速度明显下降。 3 Ga，这可能与显着的地壳再循环的开始有关，可能是通过会聚板块边缘的俯冲而发生的。冥古宙和早太古代大陆记录保存较差，其特征是双峰 TTG（英闪长岩、长斜长岩和花岗闪长岩）和绿岩组合，这与较年轻的记录不同，后者可能与板块构造体系更直接相关。由于早期记录的缺乏，导致出现了一些相互竞争且模棱两可的模型，这些模型援引了板块构造和地幔柱主导的过程。估计 3 Ga 时存在的大陆地壳目前体积的 60%-70% 与
Continental crust is the archive of Earth history. The spatial and temporal distribution of Earth's record of rock units and events is heterogeneous; for example, ages of igneous crystallization, metamorphism, continental margins, mineralization, and seawater and atmospheric proxies are distributed about a series of peaks and troughs. This distribution reflects the different preservation potential of rocks generated in different tectonic settings, rather than fundamental pulses of activity, and the peaks of ages are linked to the timing of supercontinent assembly. The physio-chemical resilience of zircons and their derivation largely from felsic igneous rocks means that they are important indicators of the crustal record. Furthermore, detrital zircons, which sample a range of source rocks, provide a more representative record than direct analysis of grains in igneous rocks. Analysis of detrital zircons suggests that at least similar to 60%-70% of the present volume of the continental crust had been generated by 3 Ga. Such estimates seek to take account of the extent to which the old crustal material is underrepresented in the sedimentary record, and they imply that there were greater volumes of continental crust in the Archean than might be inferred from the compositions of detrital zircons and sediments. The growth of continental crust was a continuous rather than an episodic process, but there was a marked decrease in the rate of crustal growth at ca. 3 Ga, which may have been linked to the onset of significant crustal recycling, probably through subduction at convergent plate margins. The Hadean and Early Archean continental record is poorly preserved and characterized by a bimodal TTG (tonalites, trondhjemites, and granodiorites) and greenstone association that differs from the younger record that can be more directly related to a plate-tectonic regime. The paucity of this early record has led to competing and equivocal models invoking plate-tectonic- and mantle-plume-dominated processes. The 60%-70% of the present volume of the continental crust estimated to have been present at 3 Ga contrasts markedly with the