The Origin of Bimodal Volcanic Suites: A Study of Newberry Volcano, Oregon

双峰式火山作用的起源一直是一个特别的 火成岩岩石学中一个长期存在的问题。 本项目谋求 了解双峰的岩石学过程 玄武岩-流纹岩火山岩套 一些岩石成因研究表明， 假设这些火山岩套是由一种 单一的、大型的、长寿的岩浆房， 需要过程来解释成分变化， 双峰套房。 在这里，建议双峰套房是 由镁铁质岩浆反复注入地壳而形成。 这些小体积的天体导致地壳部分熔融。 玄武岩流纹岩岩浆是由一系列小的， 不相连的水库 熔岩在一个区域内的大片区域爆发 时间短可能只与它们共同的起源有关。 镁铁质岩浆的反复注入， 熔融和熔融结晶会产生显著的变化 长期火山活动下地壳的特征 系统. 最近的地球物理研究和优秀的地质 限制使这座火山成为测试这一提议的理想选择。 模型 全新世熔岩将被用来测试 这套火山岩群是由互不相连的小岩浆房组成的。 然后 地壳蒸馏模型的适用性 通过对比全新世和更新世的差异 以确定熔岩的时间变化 特征与预测一致。 确认这一 模型可能会极大地影响岩石学家对 岩浆房与地球化学数据定量模拟 从时间和空间上相关的熔岩。

The origin of bimodal volcanism has been a particularly persistent problem in igneous petrology. This project seeks to understand the petrologic processes responsible for bimodal basalt-rhyolite volcanic suites. Some petrogenetic studies have assumed such volcanic suites formed by mechanisms operating in a single, large, long-lived magma chamber, where complex AFC processes are required to explain the compositional variations in bimodal suites. Here it is suggested that bimodal suites are produced by repeated injection of mafic magma into the crust. These small volume bodies cause partial melting of the crust. Basalt-rhyolite magmas are generated in a series of small, unconnected reservoirs. Lavas erupted over a large area within a short time may be related only by their common anatectic origin. Repeated injection of mafic magma, and subsequent crustal partial fusion and melt crystallization will generate significant changes in the character of the crust beneath long-lived volcanic systems. Recent geophysical studies and excellent geologic constraints make this volcano ideal for testing this proposed model. Holocene lavas will be used to test the generation of this volcanic suite in small unconnected magma chambers. Then the applicability of the crustal distillation model will be tested by comparing differences in the Holocene and Pleistocene volcanic suites to determine if temporal changes in lava characteristics agree with predictions. Confirmation of this model could dramatically affect petrologists' perceptions of magma chambers and quantitative modelling of geochemical data from temporally and spatially related lavas.