The Alaska Wrangell Arc: ~30 Ma of subduction‐related magmatism along a still active arc‐transform junction
The Alaska Wrangell Arc: ~30 Ma of subduction‐related magmatism along a still active arc‐transform junction
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DOI：
10.1111/ter.12369
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发表时间：
2018-12
期刊：
影响因子：
2.4
通讯作者：
M. Brueseke;J. Benowitz;J. Trop;Kailyn N. Davis;S. Berkelhammer;P. Layer;B. K. Morter
中科院分区：
文献类型：
--
作者：
M. Brueseke;J. Benowitz;J. Trop;Kailyn N. Davis;S. Berkelhammer;P. Layer;B. K. Morter
渐新世至今的Wrangell火山带(WVB)在火山弧转换交界处横跨美国阿拉斯加中南部延伸至加拿大，全长约500公里。以前，地球化学记录了12 Ma WVB火山岩中的地幔楔形和板缘熔融；新的地球化学表明，同样的过程表征了阿拉斯加约18-30 Ma的WVB岩浆活动。新的40Ar/39Ar年龄表明，阿拉斯加的WVB岩浆活动开始于~30 Ma，这是由于雅库塔特微板块的平板俯冲，此时右行的Totschunda断裂是活动的。我们的研究结果结合前人的研究表明，阿拉斯加WVB岩浆作用主要是由于俯冲作用而发生的，应该被认为是火山弧(例如朗格尔弧)。WVB提供了俯冲、走滑和岩浆作用的长期地质记录。板片边缘上涌、平板散焦流体流动和充当岩浆管道的断层可能是造成格外大的火山和兰格尔弧高喷发率的原因。
The Oligocene to Present Wrangell Volcanic Belt (WVB) extends for ~500 km across south‐central Alaska (USA) into Canada at a volcanic arc‐transform junction. Previously, geochemistry documented mantle wedge and slab‐edge melting in <12 Ma WVB volcanic rocks; new geochemistry shows that the same processes characterized ~18–30 Ma WVB magmatism in Alaska. New 40Ar/39Ar ages demonstrate that WVB magmatism in Alaska initiated at ~30 Ma due to flat‐slab subduction of the Yakutat microplate and that the dextral Totschunda fault was active at this time. Our results, together with prior studies, show that Alaskan WVB magmatism occurred chiefly due to subduction and should be considered a volcanic arc (e.g. the Wrangell Arc). The WVB provides a long‐term geological record of subduction, strike‐slip and magmatism. Slab‐edge upwelling, flat‐slab defocused fluid‐flux and faults acting as magma conduits are likely responsible for the exceptionally large volcanoes and high eruption rates of the Wrangell Arc.