Assimilation and mixing of crystal-bearing magmas in the Snake River Plain, NW United States: rheological timescales for magmatism of large silicic provinces

斯内克河平原（Snake River Plain， SRP）为研究热异常对大陆地壳的影响以及由此产生的岩浆储层动力学提供了独特的机会。深层的、源自地幔的基性熔体穿过地壳上升，吸收邻近的岩石，混合并演化。这些过程，连同原始岩浆的组成，控制着冷却和结晶动力学，因此构成了岩浆分异的基本贡献。沿SRP的成分多样性表明了其物理化学的复杂性，从而为这些岩浆的演化提供了一个锁眼。岩心流纹岩中岩浆混合的结构证据和沉积岩与火成岩的地层交替表明，流纹岩（也是地壳衍生的）与玄武岩熔体岩浆混合存在。为了首次研究结晶对岩浆混合的影响，提出了一系列实验的延续。本研究旨在(1)表征已知端元的组成（如间隙熔体组成、挥发物和晶体含量）；(2)在对比晶体和/或挥发物含量下限制混合的性质和时间尺度；(3)将结果与SRP单元进行比较，特别是在对比端元（玄武岩-流纹岩；玄武岩-沉积物）界面上发现的SRP单元，如在Kamama和Mountain Home钻孔。

The Snake River Plain (SRP) represents a unique opportunity to study the impact of a thermal anomaly on continental crust and the resulting dynamics in magma reservoirs. Deep, mantle-derived mafic melts ascend through the crust, assimilate adjacent country rock, mix and evolve. These processes, along with the composition of the primitive magma, govern the cooling and crystallisation dynamics and thus constitute a fundamental contribution to magmatic differentiation. The diversity of compositions along the SRP demonstrates the physico-chemical complexities and thus provides a keyhole to the evolution of these magmas. The textural evidence for magma mixing in core rhyolite and the stratigraphic alternation of sediments with igneous rocks in the SRP drill log indicate the occurrence of magma mixing of rhyolite (also crustally derived) and basalt melts. The continuation of a series of experiments is proposed to investigate, for the first time, the influence of crystals on magma mixing. The present proposal aims to (1) characterize the composition of recognized end-members (e.g. interstitial melt compositions, volatile and crystal content), (2) constrain the nature and timescales of mixing under contrasting crystal and/or volatile contents, and (3) compare the results to SRP units, especially those found at the interface between contrasting end-members (basalt-rhyolite; basalt-sediment), such as at the Kamama and Mountain Home drillholes.