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首页> 外文期刊>Bulletin of Volcanology >Rhyolitic ignimbrites in the Rogerson Graben, southern Snake River Plain volcanic province: volcanic stratigraphy, eruption history and basin evolution
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Rhyolitic ignimbrites in the Rogerson Graben, southern Snake River Plain volcanic province: volcanic stratigraphy, eruption history and basin evolution

机译：蛇河平原南部火山省罗杰森·格拉本的流纹质火成岩：火山地层，喷发历史和盆地演化

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摘要

The 80 km long NNE-trending Rogerson Graben on the southern margin of the central Snake River Plain, Idaho, USA, hosts a rhyolitic pyroclastic succession, 200 m thick, that records a period of successive, late-Miocene, large-volume explosive eruptions from the Yellowstone–Snake River Plain volcanic province, and contemporaneous extension. The succession, here termed the Rogerson Formation, comprises seven members (defined herein) and records at least eight large explosive eruptions with numerous repose periods. Five high-grade and extremely high-grade ignimbrites are intercalated with three non-welded ignimbrites and two volcaniclastic deposits, with numerous repose periods (palaeosols) throughout. Two of the ignimbrites are dominantly rheomorphic and lava-like but contain subordinate non-welded pyroclastic layers. The ignimbrites are typical Snake River Plain high-silica rhyolites, with anhydrous crystal assemblages and high inferred magmatic temperatures (≤ 1,025°C). We tentatively infer that the Jackpot and Rabbit Springs Members may have been emplaced from the Bruneau–Jarbidge eruptive centre on the basis of: (1) flow lineation trends, (2) crystal assemblage, and (3) radiometric age. We infer that the overlying Brown’s View, Grey’s Landing, and Sand Springs Members may have been emplaced from the Twin Falls eruptive centre on the basis of: (1) kinematic indicators (from the east), and (2) crystal assemblage. Furthermore, we have established the contemporaneous evolution of the Rogerson Graben from the emplacement of the Jackpot Member onwards, and infer that it is similar to younger half-graben along the southern margin of the Snake River Plain, formed by local reactivation of Basin and Range structures by the northeastwardly migration of the Yellowstone hot-spot.
机译：位于美国爱达荷州中部蛇河平原南缘的长达80公里的NNE趋势罗杰森·格拉本（Rogerson Graben）拥有200 m厚的流纹质火山碎屑演替，记录了一段连续的，中新世晚期，大爆发性爆发来自黄石-斯内克河平原的火山省，并同时扩展。此系列称为罗杰森组，由7个成员（在此定义）组成，并记录至少8次具有多个休止期的大型爆炸爆发。五个高级和极高级的火成岩与三个非焊接型火成岩和两个火山碎屑沉积物相插，整个过程中有许多静止期（古土壤）。其中两个火成岩主要为变质和熔岩状，但包含从属的非焊接热碎屑层。这些火成岩是典型的蛇河平原高硅流纹岩，具有无水晶体组合和较高的推断岩浆温度（≤1,025°C）。我们初步推断，可能是由于（1）流线趋势，（2）晶体组合和（3）辐射年龄而从布鲁诺–贾比德火山喷发中心安置了大奖和兔子泉成员。我们推断，可能是由于以下原因而从双子瀑布喷发中心安置了上覆的布朗观点，灰色着陆点和沙泉成员：（1）运动学指标（来自东部），以及（2）晶体组合。此外，我们从累积奖金成员的位置开始就建立了罗杰森·格拉本的同时演变过程，并推断它类似于斯纳克河平原南缘的年轻半graben，由盆地和山脉的局部活化形成结构由黄石热点向东北迁移。

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