Older crust underlies Iceland
Older crust underlies Iceland
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冰岛的地壳较古老
DOI：
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发表时间：
2006
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影响因子：
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通讯作者：
G. Foulger
中科院分区：
文献类型：
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作者：
G. Foulger
冰岛西北部最古老的岩石出露年龄为1.16亿年，冰岛东部为1.13亿年。在新生代期间，该地区的板块扩张速率为1.2cm a −1，因此这些岩石预计将被分离1.290 km。然而，它们相距500公里。结论是不可避免的，一片约210公里宽的古老地壳位于冰岛之下，淹没在年轻的熔岩之下。这一结论是独立的任何考虑有关蔓延脊迁移，跳跃，同时存在多个活动的山脊，三维，或熔岩桩的沉降。这种复杂性影响了老地壳的分布和年龄，但与它的存在或宽度无关。如果它完全是海洋性的，它的最大年龄很可能是26 - 37 Ma。它在南北方向至少有150公里，但可能逐渐变细并延伸到冰岛南部。它的一部分可能是大陆--扬马延马延微大陆向南的延伸。这一较老的地壳对冰岛下方的地壳厚度有很大贡献，因此，地震测量的1040公里的局部厚度可能高估了冰岛现今稳定状态的地壳生产。
SUMMARY The oldest rocks outcropping in northwest Iceland are ∼16 Myr old and in east Iceland ∼13 Myr. The full plate spreading rate in this region during the Cenozoic has been ∼ 2c m a −1 , and thus these rocks are expected to be separated by ∼290 km. They are, however, ∼500 km apart. The conclusion is inescapable that an expanse of older crust ∼210 km wide underlies Iceland, submerged beneath younger lavas. This conclusion is independent of any considerations regarding spreading ridge migrations, jumps, the simultaneous existence of multiple active ridges, three-dimensionality, or subsidence of the lava pile. Such complexities bear on the distribution and age of the older crust, but not on its existence or its width. If it is entirely oceanic its maximum age is most likely 26‐37 Ma. It is at least 150 km in north‐south extent, but may taper and extend beneath south Iceland. Part of it might be continental—a southerly extension of the Jan Mayen microcontinent. This older crust contributes significantly to crustal thickness beneath Iceland and the ∼40 km local thickness measured seismically is thus probably an overestimate of present-day steady-state crustal production at Iceland.