Geochronology of age-progressive volcanism of the Oregon High Lava Plains : implications for the plume interpretation of Yellowstone
Geochronology of age-progressive volcanism of the Oregon High Lava Plains : implications for the plume interpretation of Yellowstone
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DOI：
10.1029/2003jb002776
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发表时间：
2004-10
影响因子：
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通讯作者：
B. Jordan;A. Grunder;R. Duncan;A. Deino
中科院分区：
文献类型：
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作者：
B. Jordan;A. Grunder;R. Duncan;A. Deino
[1]高熔岩平原省(HLP)是位于俄勒冈州东南部盆岭省北缘的晚新生代双峰火山田，其硅质火山活动具有向西年轻的趋势，粗略地反映了硅质火山活动沿黄石-蛇河平原(YSRP)向东北方向的迁移。给出了19个流纹岩穹隆、5个流纹岩灰流凝灰岩和34个玄武岩熔岩的40Ar/39Ar年龄。证实了以前发现的HLP流纹岩向西迁移的趋势。传播速度为∼33公里/英里/年。从10 Ma到5 Ma，减慢到∼13公里/英里。在5 Ma之后。任何地点的硅质火山活动的持续时间都是∼2 m.y。三个较老的高位英安岩穹隆的∼年龄为15.5 Ma。玄武岩不随年龄增长。我们确定了在7.5-7.8 Ma、5.3-5.9 Ma和2-3 Ma期间玄武岩活动增加的几个幕，较年轻的幕可能持续到最近。HLP和YSRP趋势出现在中新世中新世哥伦比亚河玄武岩和斯蒂恩斯玄武岩的轴线上。我们提出了一个模型：(1)中新世泛滥玄武岩和广泛分布的硅质岩是在克拉通边缘附近侵位的热柱头部的结果，并通过沿克拉通边缘岩石圈底部的地形梯度向上流动而增强；(2)HLP趋势是起源于克拉通边缘的西向流动的结果；(3)YSRP趋势是北美板块在热柱尾部上方运动的痕迹。
[1] The High Lava Plains province (HLP) is a late Cenozoic bimodal volcanic field at the northern margin of the Basin and Range province in southeastern Oregon that hosts a westward younging trend of silicic volcanism that crudely mirrors northeastward migration of silicic volcanism along the Yellowstone–Snake River Plain (YSRP) trend. We present 40Ar/39Ar ages for 19 rhyolite domes, 5 rhyolite ash flow tuffs, and 34 basaltic lavas from the HLP. The previously identified trend of westward migration of HLP rhyolites is confirmed. The rate of propagation is ∼33 km/m.y. from 10 to 5 Ma, slowing to ∼13 km/m.y. after 5 Ma. The duration of silicic volcanism at any locus is ∼2 m.y. Three older HLP dacite domes yielded ages of ∼15.5 Ma. Basalts are not age progressive. We identify several episodes of increased basaltic activity at 7.5–7.8, 5.3–5.9, and 2–3 Ma, with the younger episode likely continuing into the Recent. The HLP and YSRP trends emerged from the axis of middle Miocene basaltic volcanism of the Columbia River and Steens basalts. We propose a model in which (1) Miocene flood basalts and widespread silicic rocks are the result of emplacement of a plume head near the craton margin, enhanced by flow up a topographic gradient along the base of the lithosphere at the craton margin; (2) the HLP trend is the result of westward flow originating at the craton margin; and (3) the YSRP trend is the trace of the motion of the North American plate over the tail of the plume.