ROW: Composition and Evolution of the Lower Crust and Crust-Mantle Boundary of the Basin and Range-to-Colorado Plateau Transition Zone

大陆地壳演化的模拟需要更好地了解下层地壳岩石的类型、成分和结构。最近在盆地和山脉以及盆地和山脉到科罗拉多高原(BR-CP)过渡带的地球物理断面提出了关于该地区下地壳和壳幔边界的性质和发展的问题。盆地和山脉下方平坦的莫霍面地貌，以及盆地和山脉和BR-CP过渡带之下的多个亚水平莫霍面反射体，表明玄武岩底侵作用在新生代伸展期间盆地和山脉下地壳和壳幔边界的发育中发挥了重要作用。来自亚利桑那州Wikieup的捕虏体提供了来自BR-CP过渡带下方壳幔边界的实际岩石样品。包体中含有丰富的与下地壳辉长岩和麻粒岩接触的上地幔橄榄岩的复合结核。将使用完整的岩相学和成分分析(矿物、全岩主要、微量和稀有元素、同位素)来确定下地壳岩石类型的岩石成因。捕虏体温压计将提供对该地区下地壳热状态的估计。将完整的岩石学数据与现有的地球物理数据结合起来，将能够评估玄武岩底侵作用等过程在盆地和山脉、下地壳和壳幔边界发展过程中的作用。

Modeling of continental crustal evolution requires improved understanding of lower crustal rock types, compositions, and structure. Recent geophysical transects in the Basin and Range and the Basin and Range-to-Colorado Plateau (BR-CP) transition zone have raised questions about the nature and development of the lower crust and the crust-mantle boundary in this region. Flat Moho topography beneath the Basin and Range, and multiple, sub-horizontal Moho reflectors beneath the Basin and Range and the BR-CP transition zone have lead to suggestions that basaltic underplating played an important role in the development of the Basin and Range lower crust and crust-mantle boundary during Cenozoic extension. Xenoliths from Wikieup, Arizona provide actual rock samples from the crust-mantle boundary beneath the BR-CP transition zone. This xenolith suite includes abundant composite nodules of upper mantle peridotite in contact with lower crustal gabbro and granulite. Complete petrographic and compositional analysis (minerals, whole rock major, trace, and rare elements, isotopes) will be used to determine the petrogenesis of lower crustal rock types. Xenolith thermobarometry will provide estimates of the thermal state of the lower crust in this region. Integration of complete petrologic data with existing geophysical data will allow evaluation of the role of processes such as basaltic underplating in the evolution of the Basin and Range lower crust and the development of the crust-mantle boundary.