Surface and mantle records reveal an ancient slab tear beneath Gondwana
Surface and mantle records reveal an ancient slab tear beneath Gondwana
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DOI：
10.1038/s41598-019-56335-9
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发表时间：
2019-12-24
影响因子：
4.6
通讯作者：
Spagnotto, Silvana
中科院分区：
文献类型：
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作者：
Gianni, Guido M.;Navarrete, Cesar;Spagnotto, Silvana
垂直板片撕裂已被广泛报道，在现代会聚设置深刻影响俯冲和地幔动力学。然而，在海洋板块俯冲和地质记录有限的古代会聚环境中评估类似的影响仍然具有挑战性。在这项研究中，我们相关的下地幔结构，保留了过去的俯冲配置，与上板块的地质记录显示深板破裂解释为一个大规模的撕裂事件，在中生代早期冈瓦纳西南部。为此，我们整合了地质年代学和地质数据集与P波全球地震层析成像和板块运动学重建。晚三叠世-早侏罗世板块撕裂幕的发展支持（i）下地幔深处的板块缺口，（ii）对比鲜明的时空岩浆演化，（iii）弧活动的平静，（iv）内乌肯和科罗拉多盆地的板内伸展和岩浆活动。这一发现不仅对确定过去形成俯冲带的基本过程的例子有意义，而且还说明了触发板片撕裂的另一种机制，其中板片断裂是由板片段的反向旋转引起的。
Vertical slab-tearing has been widely reported in modern convergent settings profoundly influencing subduction and mantle dynamics. However, evaluating a similar impact in ancient convergent settings, where oceanic plates have been subducted and the geological record is limited, remains challenging. In this study, we correlate the lower mantle structure, which retained the past subduction configuration, with the upper-plate geological record to show a deep slab rupture interpreted as a large-scale tearing event in the early Mesozoic beneath southwestern Gondwana. For this purpose, we integrated geochronological and geological datasets with P-wave global seismic tomography and plate-kinematic reconstructions. The development of a Late Triassic-Early Jurassic slab-tearing episode supports (i) a slab gap at lower mantle depths, (ii) a contrasting spatiotemporal magmatic evolution, (iii) a lull in arc activity, and (iv) intraplate extension and magmatism in the Neuquen and Colorado basins. This finding not only has implications for identifying past examples of a fundamental process that shapes subduction zones, but also illustrates an additional mechanism to trigger slab-tearing in which plate rupture is caused by opposite rotation of slab segments.