The Cougar Point Tuff: Implications for Thermochemical Zonation and Longevity of High-Temperature, Large-Volume Silicic Magmas of the Miocene Yellowstone Hotspot
The Cougar Point Tuff: Implications for Thermochemical Zonation and Longevity of High-Temperature, Large-Volume Silicic Magmas of the Miocene Yellowstone Hotspot
复制标题
美洲狮点凝灰岩：对中新世黄石热点地区高温大体积硅质岩浆热化学分带和寿命的影响
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
B. Nash
中科院分区：
文献类型：
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作者：
H. Cathey;B. Nash
美国爱达荷州南部12.7-10.5 Ma的美洲狮点凝灰岩由10个大体积（每个>10²-10 km ³）、高温（800-1000 °C）流纹质灰流凝灰岩组成，喷发自黄石热点的Bruneau-Jarbidge火山中心。这些凝灰岩提供的证据，成分和热分带在喷发前的流纹岩岩浆，并建议存在一个长寿的水库，是由许多大型爆炸性喷发。辉石组合物表现出离散的组成模式，相对于铁和镁，定义了一个线性光谱打断了明显的差距。空气降落的玻璃成分也聚集成模式，并且多种模式的存在表明在喷发的早期阶段有不同的岩浆体积。利用褐变岩和普通辉石的平衡组合来重建喷发前储层的成分梯度和热梯度。相同的成分模式和矿物对在连续的喷发单位在高温下平衡的复发是一致的，其各自的液体在岩浆库中的持久性。相同的模式的复发间隔范围从0.3到0.9万年，并建议可能的岩浆停留时间相似的持续时间。喷发年龄，岩浆温度，钕同位素，辉石和玻璃成分是一致的，一个长期的，动态演变的岩浆库，化学和热分区，并由多个离散的岩浆体积。
The 12.7-10.5 Ma Cougar Point Tuff in southern Idaho, USA, consists of 10 large-volume (>10²-10³ km³ each), high-temperature (800-1000 °C), rhyolitic ash-flow tuffs erupted from the Bruneau-Jarbidge volcanic center of the Yellowstone hotspot. These tuffs provide evidence for compositional and thermal zonation in pre-eruptive rhyolite magma, and suggest the presence of a long-lived reservoir that was tapped by numerous large explosive eruptions. Pyroxene compositions exhibit discrete compositional modes with respect to Fe and Mg that define a linear spectrum punctuated by conspicuous gaps. Airfall glass compositions also cluster into modes, and the presence of multiple modes indicates tapping of different magma volumes during early phases of eruption. Equilibrium assemblages of pigeonite and augite are used to reconstruct compositional and thermal gradients in the pre-eruptive reservoir. The recurrence of identical compositional modes and of mineral pairs equilibrated at high temperatures in successive eruptive units is consistent with the persistence of their respective liquids in the magma reservoir. Recurrence intervals of identical modes range from 0.3 to 0.9 Myr and suggest possible magma residence times of similar duration. Eruption ages, magma temperatures, Nd isotopes, and pyroxene and glass compositions are consistent with a long-lived, dynamically evolving magma reservoir that was chemically and thermally zoned and composed of multiple discrete magma volumes.