Crustal velocity structure across the eastern Snake River Plain and the Yellowstone swell
Crustal velocity structure across the eastern Snake River Plain and the Yellowstone swell
复制标题
蛇河平原东部和黄石隆起的地壳速度结构
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
E. Humphreys
中科院分区：
文献类型：
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作者：
Xiaohua Peng;E. Humphreys
遥测接收器功能被用来估计地壳结构下的36个站，500公里长，西北方向的线性阵列集中在东部蛇河平原和穿越黄石热点膨胀250公里的黄石西南。以前从广角反射数据中导出的该区域的结构被用作初始模型，并且该结构解释了在我们的接收器函数中观察到的大多数特征。根据正、反演的结果，我们的资料需要对初始结构进行几处修正：（1）蛇河平原大部分地区莫霍面深度为42 km，两侧变浅至37 km，西南怀俄明州以下突然增厚至47 km;（2）先前被解释为厚1.9km的辉长岩岩床的中地壳层在整个1.90km宽的斯内克河平原上是平顶的;蛇河平原东南下方存在低速层，可能是部分熔融的下地壳。利用地壳的地震结构来估计地幔上的地壳负荷，并假设当地的等电位线，我们计算出，黄石膨胀下面的地幔近似均匀地具有与1200万年前的海洋地幔一样的浮力，并且比邻近的怀俄明州地幔的浮力更大，相当于海拔1.5公里。这两个地幔差异很大的地区之间的过渡发生在一个主要的古生代边界上，该边界现在将盆地和山脉与落基山脉分开。
Teleseismic receiver functions are used to estimate the crustal structure beneath a 36-station, 500-km-long, NW oriented linear array centered on the eastern Snake River Plain and crossing the Yellowstone hotspot swell 250 km SW of Yellowstone. Structure derived previously for this region from wide-angle reflection data is used as an initial model, and this structure explains most features observed in our receiver functions. Based on a combination of forward and inverse modeling, our data require several modifications to the initial structure: (1) Moho depth is ∼42 km beneath most of the Snake River Plain, shallows to ∼37 km to either side, and thickens abruptly to ∼47 km beneath SW Wyoming; (2) a midcrustal layer interpreted previously as a ∼9-km-thick gabbroic sill is flat topped across the entire ∼90 km width of the Snake River Plain; and (3) a low-velocity layer is found beneath and southeast of the Snake River Plain, which probably is partially molten lower-most crust. Using the seismic structure of the crust to estimate the crustal load upon the mantle, and assuming local isostasy, we calculate that mantle beneath the Yellowstone swell is approximately uniformly as buoyant as 12-million-year-old ocean mantle, and more buoyant than the adjacent Wyoming mantle by an amount equivalent of ∼1.5 km of elevation. The transition between these regions of greatly different mantle occurs across a major Paleozoic boundary that now separates the Basin and Range from the Rocky Mountains.