Precambrian crustal evolution: Seismic constraints from the Canadian Shield
Precambrian crustal evolution: Seismic constraints from the Canadian Shield
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DOI：
10.1016/j.epsl.2010.07.021
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发表时间：
2010-09
影响因子：
5.3
通讯作者：
D. Thompson;I. Bastow;G. Helffrich;J. Kendall;J. Wookey;D. Snyder;D. Eaton
中科院分区：
文献类型：
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作者：
D. Thompson;I. Bastow;G. Helffrich;J. Kendall;J. Wookey;D. Snyder;D. Eaton
板块构造过程是否作用于一个更年轻、更热的地球上仍然不清楚。来自加拿大地盾哈德逊湾地区新网络的地震数据为解决这一问题提供了新的空间，该地区的前寒武纪地质记录跨越了20亿年。利用接收函数分析，我们表明，Rae域的地壳，表现出的年龄为古-新太古代（3.9-2.7Ga），可能是长英质到中间的成分（平均Vp/Vs<1.73）和地震透明与尖锐的莫霍面。现代风格的板块构造的证据很少，基于长英质地壳的简单性和空间范围，有利于垂直构造过程，如地壳分层或羽活动的模型似乎更适合的结果。赫恩域的数据显示，广泛的~2.7Ga花岗岩和绿岩地质，显示出更复杂的地壳具有更高的Vp/Vs比，与更大的镁铁质成分一致。外哈得逊造山带（Trans-Hudson Orogen，THO）被认为是古元古代的喜马拉雅造山带，形成于上级板块和丘吉尔板块的~1.8Ga碰撞过程中。THO的魁北克-巴芬岛段的结果似乎绘制出了下冲上级板块的一阶形状，Vp/Vs比值升高可能代表了上级克拉通的裂谷边缘。在巴芬岛中部和南部（~ 43 km）观察到一致的较厚地壳，与广泛的高级变质地表地质相一致。这些特征可以解释为陆-陆碰撞过程中，由于增生的碎屑堆积而导致的地壳增厚，类似于今天的青藏高原，随后发生侵蚀。根据地质记录中的年龄和成分限制进行回顾时，我们的地震观测结果表明，在古元古代，地壳从古到中太古代的非板块构造演化为完全发育的现代板块构造。
Whether or not plate tectonic processes operated on a younger, hotter Earth remains ambiguous. Seismic data from new networks in the Hudson Bay region of the Canadian Shield, where the Precambrian geological record spans more than 2 billion years, offer fresh scope to address this problem. Using receiver function analyses we show that the crust of the Rae domain, which exhibits ages of Paleo- to Neoarchean (3.9–2.7Ga), is likely felsic-to-intermediate in composition (average Vp/Vs<1.73) and seismically transparent with a sharp Moho. There is little evidence for modern-style plate tectonics, and based on the simplicity and spatial extent of the felsic crust, models favouring vertical tectonic processes such as crustal delamination or plume activity appear better suited to the results. Data from the Hearne domain, which exhibits widespread ~2.7Ga granite-and-greenstone geology, show a more complex crust with higher Vp/Vs ratios, consistent with a greater mafic component. The Trans-Hudson Orogen (THO), proposed to be a Himalayan-scale mountain belt during the Paleoproterozoic, is thought to have formed during the ~1.8Ga collision of the Superior and Churchill plates. Results from the Quebec–Baffin Island segment of the THO appear to map out the first-order shape of the underthrusting Superior plate, with elevated Vp/Vs ratios likely representing the rifted margin of the Superior craton. Consistently thicker crust is observed beneath central and southern Baffin Island (~43km), coincident with widespread high-grade metamorphic surface geology. These features can be explained by crustal thickening due to stacking of accreted terranes during continent–continent collision, analogous to the present-day Tibetan Plateau, followed by erosion. When reviewed in light of age and compositional constraints from the geological record, our seismic observations point towards secular crustal evolution from non-plate tectonic during the Paleo- to Mesoarchean evolving towards fully-developed modern-style plate tectonics during the Paleoproterozoic.