Crustal structure across the Costa Rican Volcanic Arc
Crustal structure across the Costa Rican Volcanic Arc
复制标题
哥斯达黎加火山弧的地壳结构
DOI：
10.1002/ggge.20079
复制
发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
C. Ramirez
中科院分区：
文献类型：
--
作者：
J. Hayes;W. Holbrook;D. Lizarralde;Harm J. A. Avendonk;A. Bullock;M. Mora;S. Harder;G. Alvarado;C. Ramirez
岛弧被认为是大陆地壳生长的重要组成部分；然而，岛弧和大陆在体积组成上是根本不同的：分别是基性和长质。形成弧的基底（大洋地壳vs大火成岩省）可能对地壳的形成有强烈的影响。我们提出了哥斯达黎加火山锋的跨弧广角地震测量结果，该结果验证了在该位置幼年大陆地壳正在活跃形成的假设。旅行时间层析成像将上弧的速度限制在~15 km的深度，平均速度<6.5 km/s。地壳上5公里的速度在4.0到5.5公里/秒之间，可能代表沉积物、火山碎屑、流动和小侵入。在5至15公里深度之间，速度从5.5公里/秒缓慢增加到6.5公里/秒。地壳厚度和下地壳速度大致受推断出的壳幔过渡带反射的约束。哥斯达黎加火山锋下的地壳厚度约为40 km，最合适的平均地壳下速度在6.8 ~ 7.1 km/s之间。总的来说，哥斯达黎加中部横跨弧的速度处于大陆地壳整体速度的高速极值，低于现代岛弧速度，这表明大陆成分是在这个位置形成的。这些数据表明，加勒比海大火成岩省先前存在的厚地壳对整体组成有可测量的影响。这种加厚的弧壳可能是基性物质的密度过滤器，从而支持向大陆成分的分化。
Island arcs are proposed to be essential building blocks for the crustal growth of continents; however, island arcs and continents are fundamentally different in bulk composition: mafic and felsic, respectively. The substrate upon which arcs are built (oceanic crust versus large igneous province) may have a strong influence on crustal genesis. We present results from an across‐arc wide‐angle seismic survey of the Costa Rican volcanic front which test the hypothesis that juvenile continental crust is actively forming at this location. Travel‐time tomography constrains velocities in the upper arc to a depth of ~15 km where average velocities are <6.5 km/s. The upper 5 km of crust is constrained by velocities between 4.0 and 5.5 km/s, which likely represent sediments, volcaniclastics, flows, and small intrusions. Between 5 and 15 km depth, velocities increase slowly from 5.5 to 6.5 km/s. Crustal thickness and lower crustal velocities are roughly constrained by reflections from an inferred crust‐mantle transition zone. Crustal thickness beneath the volcanic front in Costa Rica is ~40 km with best‐fit average lower‐crustal velocities between 6.8 and 7.1 km/s. Overall, velocities across the arc in central Costa Rica are at the high‐velocity extreme of bulk continental crust velocities and are lower than modern island arc velocities, suggesting that continental compositions are created at this location. These data suggest that preexisting thick crust of the Caribbean Large Igneous Province has a measurable effect on bulk composition. This thickened arc crust may be a density filter for mafic material and thereby support differentiation toward continental compositions.
影响因子：
64.8
作者：
Hoernle, Kaj;Abt, David L.;Strauch, Wilfried
通讯作者：
Strauch, Wilfried
影响因子：
3.9
作者：
Ivandic, Monika;Grevemeyer, Ingo;McIntosh, Kirk
通讯作者：
McIntosh, Kirk