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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Lahar deposits generated after the Millennium eruption of the Changbaishan Tianchi volcano in the Erdaobaihe River system, China
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Lahar deposits generated after the Millennium eruption of the Changbaishan Tianchi volcano in the Erdaobaihe River system, China

机译：在中国埃尔达比海河系统中千年山脉毫年爆发后产生的拉哈尔矿床

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摘要

After the Plinian Millennium Eruption (including the ME-I and ME-II eruptive stages) of Changbaishan Tianchi volcano in 969 +/- 20 CE, two large-volume lahars were deposited mainly on the northern flank of the Erdaobaihe River, which flows through the only outlet from Tianchi Lake: (1) a lahar deposit containing gray and black pumice (Lahar ((G&B)) (P)) and (2) a lahar deposit containing lithic particles (Lahar (L)). Based on the sedimentary characteristics of lahar outcrops and grain-size and compositional analyses performed using standard dry sieving techniques, examination of thin sections and geochemical analyses, the origins, transport and deposit processes and fluid phase variations of the two lahar deposits are studied. These two lahar deposits are fan-like in the flat medial area (23-60 km from the crater) and fill channels in the distal mountainous area (60 km from the crater). Lahar (L) in the medial area represents a complete composite lahar flow deposit with a frontal debris head (very coarse gravel texture, extremely poor sorting, massive and matrix-supported structure) and a hyperconcentrated fluid phase body and tail (coarse sandy texture, very poor sorting, faint horizontal stratification with thin lenses of gravel, clast-supported structure). Lahar (L) in the distal area represents the material that passed the debris flow head, and the fluid phase changes from debris flow to hyperconcentrated (poor sorting, clear thin horizontal stratification) downcurrent. The fluid phase of Lahar ((G&B)) (P) changes from debris flow in the medial area (medium gravel to fine sand, very poor sorting, thick horizontal stratification with floating pumice on each unit surface) to hyperconcentrated flow (poor sorting, thin horizontal stratification, clear normal graded bedding) and to stream flow (moderate sorting, cross-bedding) in the distal area. Lahar ((G&B)) (P) was likely formed by the mixing of water from Tianchi lake and pyroclastic flows of ME-II Lahar (L) was likely triggered by a sudden release (dam break) from Tianchi Lake. An assessment of the risk posed to the stability of Tianchi Lake is as important as an assessment of the eruption risk. (C) 2019 Elsevier B.V. All rights reserved.
机译：在969年+/-20 CE中的昌巴西天池火山的Plinian千年爆发（包括Me-I和Me-I和Me-II和Me-II和Me-II爆发阶段）之后，主要在埃尔达比海河的北侧沉积两批大型拉哈尔，流过Tianchi Lake的唯一出口：（1）含有灰色和黑色浮石的拉哈尔矿床（拉哈尔（（G＆B））（P））和（2）含有岩石颗粒的拉哈尔矿床（拉哈尔（L））。基于使用标准干筛分技术进行的拉哈尔露头和晶粒尺寸和组成分析的沉积特性，研究了两种拉哈尔沉积物的薄片和地球化学分析的检查，起源，运输和沉积过程以及两种拉哈尔沉积物的流体相变。这两个拉哈尔沉积物在扁平内侧区域（距离火山口23-60公里），并填充远侧山区（距离火山口60公里）。中间区域的拉哈尔（L）代表完整的复合拉哈尔流量沉积物，具有正面碎片头（非常粗糙的砾石纹理，极差的分类，巨大和矩阵支撑的结构）和过浓度的流体相体和尾部（粗砂质，非常差的分类，微弱的水平分层，具有薄镜片的砾石，夹层支撑的结构。远端区域中的拉哈尔（L）表示通过碎屑流动头的材料，并且流体相位从碎片流动变化到过浓度（分选差，清晰的薄水平分层）流动。拉哈拉尔（（G＆B））（P）的流体阶段（P）从内侧区域（中砾至细砂，分类非常差，在每个单元表面上的漂浮水平分裂，厚水平分层厚的水平分层）变为超级浓度的流量（差分类，薄的水平分层，透明正常分级床上用品，并在远端区域流（中等分选，交叉床上用品）。拉哈尔（（G＆B））（P）可能是通过来自天池湖的水混合来形成ME-II拉哈尔（L）的突然释放（坝爆）的突然释放（坝爆）引发。评估天池湖泊稳定的风险与对爆发风险的评估一样重要。 （c）2019 Elsevier B.v.保留所有权利。

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