Teleseismic tomography of the southern Puna plateau in Argentina and adjacent regions
Teleseismic tomography of the southern Puna plateau in Argentina and adjacent regions
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DOI：
10.1016/j.tecto.2012.11.016
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发表时间：
2013-02
期刊：
影响因子：
2.9
通讯作者：
M. Bianchi;B. Heit;A. Jakovlev;X. Yuan;S. Kay;E. Sandvol;R. Alonso;B. Coira;Lawrence D. Brown;R. Kind;D. Comte
中科院分区：
文献类型：
--
作者：
M. Bianchi;B. Heit;A. Jakovlev;X. Yuan;S. Kay;E. Sandvol;R. Alonso;B. Coira;Lawrence D. Brown;R. Kind;D. Comte
我们使用阿根廷普纳高原和邻近地区的临时地震阵列记录的地震事件，进行了一次地震P波层析成像研究。层析图像显示，在阵列下方20- 300公里的深度范围内存在一些正异常和负异常。这些异常中最突出的对应于一个位于地壳中的低速体，在东部的Cerro Peinado火山、Cerro布兰科破火山口和Farallon Negro之间的阵列中心（南纬27°，西经67°）处看得最清楚。该异常（南部普纳岩浆体）从阵列的北方大部分延伸，并沿着测站密度最高的线向南延伸，在那里变小。它的两侧分别是西部和东部的高速。在西部，高速度可能与纳斯卡板块俯冲有关。在东北部的高速块与Hombre Muerto盆地在地壳中的位置相吻合，并可能表明岩石圈分层的区域，我们检测到一个高速块在100公里深的东部边界的普纳高原，北部的加兰。该地块可能与普纳和东科迪勒拉交界处的古生代变质岩厚壳区的拆沉事件有关。在阵列的中心，南部普纳岩浆体两侧也是高速的，但最突出的区域位于东部，被解释为具有高速的Sierras Pampeanas岩石圈的一部分。Sierras Pampeanas地质区的位置是该地区的关键，因为它似乎限制了高原向南的延伸。
We performed a teleseismic P wave tomography study using seismic events at both teleseismic and regional distances, recorded by a temporary seismic array in the Argentine Puna Plateau and adjacent regions. The tomographic images show the presence of a number of positive and negative anomalies in a depth range of 20–300km beneath the array. The most prominent of these anomalies corresponds to a low-velocity body, located in the crust, most clearly seen in the center of the array (27°S, 67°W) between the Cerro Peinado volcano, the Cerro Blanco caldera and the Farallon Negro in the east. This anomaly (southern Puna Magmatic Body) extends from the northern most part of the array and follows the line with the highest density of stations towards the south where it becomes smaller. It is flanked by high velocities on the west and the east respectively. On the west, the high velocities might be related to the subducted Nazca plate. On the northeast the high velocity block coincides with the position of the Hombre Muerto basin in the crust and could be indicating an area of lithospheric delamination where we detected a high velocity block at 100km depth on the eastern border of the Puna plateau, north of Galan. This block might be related to a delamination event in an area with a thick crust of Paleozoic metamorphic rocks at the border between Puna and Eastern Cordillera. In the center of the array the Southern Puna magmatic body is also flanked by high velocities but the most prominent region is located on the east and is interpreted as part of the Sierras Pampeanas lithosphere with high velocities. The position of the Sierras Pampeanas geological province is key in this area as it appears to limit the extension of the plateau towards the south.