Significant Increase of Continental Freeboard During the Early Paleoproterozoic: Insights From Metasediment‐Derived Granites
Significant Increase of Continental Freeboard During the Early Paleoproterozoic: Insights From Metasediment‐Derived Granites
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DOI：
10.1029/2021gl096049
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发表时间：
2021-11
影响因子：
5.2
通讯作者：
Guimei Lu;C. J. Spencer;Yang Tian;Wei Wang
中科院分区：
文献类型：
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作者：
Guimei Lu;C. J. Spencer;Yang Tian;Wei Wang
亚大陆地壳在调节海洋、大气和生物圈的组成方面发挥着重要作用，但大陆出现在海平面以上的时间和速度仍不清楚。本文利用扬子地块西南部古元古代早期变质沉积岩型花岗岩类的锆石氧同位素组成，对大陆出露的快速性进行了研究。对编制的火山岩和碎屑岩锆石氧同位素数据库的统计分析表明，锆石δ18O在1.236Ga时迅速增加。我们认为，这种同位素变化最好的解释是，由于自晚太古代以来大陆岩石圈强度的增加，大陆干舷在2.43至2.36 Ga之间显著增加，同时产生了高δ 18 O沉积储层。这些高δ 18 O沉积物在各种构造体制下的后续熔融导致高锆石δ 18 O。
Subaerial continental crust plays a fundamental role in modulating the composition of the ocean, atmosphere, and biosphere, but the timing and rate of continental emergence above sea level remain unclear. Here, we use the zircon oxygen isotopic compositions of early Paleoproterozoic metasediment‐derived granitoids from the southwestern Yangtze Block to constrain the rapidity of continental emergence. Statistical analyses of compiled igneous and detrital zircon oxygen isotopic database show a rapid increase in zircon δ18O at ∼2.36 Ga. We suggest that this isotopic shift is best explained by a significant increase of continental freeboard between ∼2.43 and ∼2.36 Ga due to the increasing strength of the continental lithosphere since the late Archean, concomitantly yielding a high‐δ18O sedimentary reservoir. Subsequent melting of these high‐δ18O sediments in a variety of tectonic regimes results in high zircon δ18O.