Crustal structure of the Kermadec arc from MANGO seismic refraction profiles
Crustal structure of the Kermadec arc from MANGO seismic refraction profiles
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DOI：
10.1002/2016jb013194
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发表时间：
2016-10
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通讯作者：
D. Bassett;H. Kopp;R. Sutherland;S. Henrys;A. Watts;C. Timm;M. Scherwath;I. Grevemeyer;C. D. Ronde
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文献类型：
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作者：
D. Bassett;H. Kopp;R. Sutherland;S. Henrys;A. Watts;C. Timm;M. Scherwath;I. Grevemeyer;C. D. Ronde
三个有源地震折射剖面与形态和位场数据相结合，对Kermadec俯冲带的结构进行了第一次区域限制。这些观测结果被用来测试对比构造模型，以确定边缘结构中沿沿着的过渡，这一过渡以前被称为南纬32度边界。我们使用剩余水深来约束这个边界的几何形状，并提出中央Kermadec不连续（CKD）的名称。在CKD以北，被掩埋的汤加海脊占据了弧前，VP为6.5-7.3 km s−1，剩余的自由空气重力异常限制了其纬度范围（30.5°S以北），宽度（110 ± 20 km）和走向（25°S以南~005°）。在CKD以南，弧前是结构均匀的下倾，VP为5.7-7.3 km s−1。在哈弗尔海槽弧后，CKD以南的地壳厚度为8-9 km，比北方哈弗尔海槽薄4 km，比南方哈弗尔海槽至少薄1 km。我们认为始新世弧并没有沿着汤加-克马德克海沟的当前长度延伸。始新世弧最初与三王岭相连，CKD可能是在渐新世早期始新世弧基底分离和向东平移期间形成的。我们认为，沿着Kermadec弧的一级地壳厚度变化是从新近纪之前继承的，反映了中生代地壳结构、汤加-Kermadec-Hikurangi边缘的新生代演化以及弧火山作用持续时间内沿着走向的变化。
Three active‐source seismic refraction profiles are integrated with morphological and potential field data to place the first regional constraints on the structure of the Kermadec subduction zone. These observations are used to test contrasting tectonic models for an along‐strike transition in margin structure previously known as the 32°S boundary. We use residual bathymetry to constrain the geometry of this boundary and propose the name Central Kermadec Discontinuity (CKD). North of the CKD, the buried Tonga Ridge occupies the fore‐arc with VP 6.5–7.3 km s−1 and residual free‐air gravity anomalies constrain its latitudinal extent (north of 30.5°S), width (110 ± 20 km), and strike (~005° south of 25°S). South of the CKD the fore‐arc is structurally homogeneous downdip with VP 5.7–7.3 km s−1. In the Havre Trough back‐arc, crustal thickness south of the CKD is 8–9 km, which is up to 4 km thinner than the northern Havre Trough and at least 1 km thinner than the southern Havre Trough. We suggest that the Eocene arc did not extend along the current length of the Tonga‐Kermadec trench. The Eocene arc was originally connected to the Three Kings Ridge, and the CKD was likely formed during separation and easterly translation of an Eocene arc substrate during the early Oligocene. We suggest that the first‐order crustal thickness variations along the Kermadec arc were inherited from before the Neogene and reflect Mesozoic crustal structure, the Cenozoic evolution of the Tonga‐Kermadec‐Hikurangi margin and along‐strike variations in the duration of arc volcanism.