Velocity structure beneath the southern Puna plateau: Evidence for delamination
Velocity structure beneath the southern Puna plateau: Evidence for delamination
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DOI：
10.1002/ggge.20266
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发表时间：
2013-10
期刊：
影响因子：
3.7
通讯作者：
F. Calixto;E. Sandvol;S. Kay;P. Mulcahy;B. Heit;X. Yuan;B. Coira;D. Comte;P. Alvarado
中科院分区：
文献类型：
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作者：
F. Calixto;E. Sandvol;S. Kay;P. Mulcahy;B. Heit;X. Yuan;B. Coira;D. Comte;P. Alvarado
普那高原南部的高海拔、地壳的广泛熔融、中深部地震活动的空隙以及最近的褐沸石杂岩喷发，可以用其下面的岩石圈地幔拆沉来解释。为了验证这一假设，从2007年开始，在该地区部署了一个由73个宽带和短周期地震台站组成的阵列，为期两年。我们用两个平面波法对数据进行了反演，得到了一维和三维瑞雷波相速度。我们的频散曲线表明，在短周期(<；70 S)，相速度略高于青藏高原，低于安纳托利亚高原。在S 100140时，我们观察到一个低速带，可能是在一个平板(7-10 Ma)之下的残余热软流层。我们估计该地区的大陆岩石圈平均厚度在100至130公里之间。我们的三维瑞雷波相速度在低频(0.007、0.008和0.009赫兹)处显示出高速异常，其位置略在塞罗加兰以北。这将与拆沉的假说一致，即一块岩石圈已经分离，并导致热软流圈上涌，进而导致广泛的与碱性碰撞有关的火山活动。这一解释也被我们的横波速度模型所证实，其中130公里深的Cerro Galan北缘以下的高速异常被解释为俯冲纳斯卡板块顶部的拆离块体。
The high elevation of the southern Puna plateau, the widespread melting of its crust, the gap in intermediate depth seismicity and the recent eruptions of ignimbrite complexes can be explained by delamination of the lithospheric mantle beneath it. To test this hypothesis, an array consisting of 73 broad band and short period seismic stations was deployed in the region for a period of 2 years starting in 2007. We inverted the data using the two plane wave approach and obtained 1‐D and 3‐D Rayleigh wave phase velocities. Our dispersion curve shows that at short periods (<70 s) the phase velocities are slightly higher than those of the Tibetan plateau and lower than those of the Anatolian plateau. At periods of 100–140 s we observe a low velocity zone that might be remnant hot asthenosphere below a flat slab (7–10 Ma). We estimate the average continental lithosphere thickness for the region to be between 100 and 130 km. Our three‐dimensional Rayleigh wave phase velocities show a high velocity anomaly at low frequencies (0.007, 0.008, and 0.009 Hz) slightly to the north of Cerro Galan. This would be consistent with the hypothesis of delamination in which a piece of lithosphere has detached and caused upwelling of hot asthenosphere, which in turn caused widespread alkaline‐collision related volcanism. This interpretation is also corroborated by our shear wave velocity model, where a high velocity anomaly beneath the northern edge of Cerro Galan at 130 km depth is interpreted as the delaminated block on top of the subducting Nazca slab.