Structure of the crust and the lithosphere beneath the southern Puna plateau from teleseismic receiver functions
Structure of the crust and the lithosphere beneath the southern Puna plateau from teleseismic receiver functions
复制标题
DOI：
10.1016/j.epsl.2013.10.017
复制
发表时间：
2014
影响因子：
5.3
通讯作者：
B. Heit;M. Bianchi;X. Yuan;S. Kay;E. Sandvol;Prakash Kumar;R. Kind;R. Alonso;Lawrence D. Brown;D. Comte
中科院分区：
文献类型：
--
作者：
B. Heit;M. Bianchi;X. Yuan;S. Kay;E. Sandvol;Prakash Kumar;R. Kind;R. Alonso;Lawrence D. Brown;D. Comte
我们利用普纳高原最南端及邻近地区临时被动震源地震台阵的资料，对远震P和S接收函数进行了研究。P接收函数图像显示了该区地壳厚度和Vp/V S比值的分布。在普纳高原南部的大部分地区，地壳厚度为50-55公里，而在西部，在安第斯火山弧地区的大部分下面可以观察到更厚的地壳(∼60-75公里)。从普那向南，越过高原边界(S 28°以南)的地壳厚度变化不大。在潘皮亚山脉，地壳向东逐渐变薄，厚度为35-40公里。普那高原南部总体上具有低的地壳Vp/V S比值(<1.7)，表明地壳成分为长英质。在塞罗加兰火山中心下方观测到的异常高的Vp/V S比值为1.87，该地区在∼10公里以下发现了一个明显的地壳低速带，可能延伸到下地壳。在Cerro Galan地区(59公里)下确定的地壳厚度与普纳南部其他地区的地壳厚度接近。加兰火山口下方存在明显的高Vp/V S比值和低速带，暗示存在部分熔融带或岩浆房，这与岩石圈拆沉假说相一致。在普纳南部大部分地区下方观察到的广泛的地壳低速层，与远震层析成像观测到的地壳低速异常有很好的相关性。P和S接收函数在70-90公里深度都能清楚地观测到台阵下方的岩石圈-软流圈边界，这与以往的研究结果一致，表明高海拔高原之下存在较薄的岩石圈。地幔过渡带的不连续面出现在预期深度。
We present a teleseismic P and S receiver function study using data from a temporary passive-source seismic array in the southernmost Puna plateau and adjacent regions. The P receiver function images show the distribution of crustal thickness and V p/V s ratio for this area. Over much of the southern Puna plateau, the crustal thickness is 50–55 km, whereas to the west a thicker crust (∼ 60 to 75 km) is observed beneath much of the Andean volcanic arc region. From the Puna southward, there is little obvious change in the crustal thickness across the border of the plateau (south of 28° S). The crust is seen to progressively thin towards the east in the Pampean Ranges where it is 35–40 km thick. The southern Puna plateau is characterized overall by a low crustal V p/V s ratio (less than 1.70), implying a felsic crustal composition. An anomalously high V p/V s ratio of 1.87 is observed beneath the Cerro Galan volcanic center, in the region where a prominent crustal low-velocity zone identified below∼ 10 km depth probably extends into the lower crust. The crustal thickness determined under the Cerro Galan area (59 km) is close to that of the rest of the southern Puna. The prominent high V p/V s ratio and low-velocity zone beneath the Galan region implies the presence of a zone of partial melt or a magma chamber is consistent with hypothesis calling for lithospheric delamination beneath the Galan caldera. A widespread crustal low-velocity layer observed beneath much of the southern Puna, correlates well with crustal low-velocity anomalies observed by teleseismic tomography. The lithosphere–asthenosphere boundary beneath the array can be clearly observed by both P and S receiver functions at depths of 70–90 km in agreement with previous studies suggesting a thin lithosphere beneath the high elevated plateau. The mantle transition zone discontinuities appear at expected depths.