28. VOLCANIC ASH FROM LEG 112 OFF PERU 1
28. VOLCANIC ASH FROM LEG 112 OFF PERU 1
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28. 秘鲁 1 海域第 112 段的火山灰
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
P. D. Wever
中科院分区：
文献类型：
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作者：
A. Pouclet;H. Cambray;J. Cadet;J. Bourgois;P. D. Wever
在秘鲁外的112航次期间，记录了从始新世中期到全新世的火山物质。火山灰的岩石学和化学成分与安第斯火山弧的起源一致。火山灰层的数量和厚度为火山爆发的幕性提供了有价值的证据。火山活动的第一个迹象是在始新世中期的沉积物中发现的。三个火山脉冲可以追溯到中新世时期。上新世晚期和更新世至全新世发生了两次强烈事件。上新世-更新世火山灰仅限于南部上斜坡和大陆架，表明火山弧的移除和秘鲁北方火山的灭绝。安第斯山脉边缘的新生代构造阶段可能与112腿火山记录。演化的岩浆产物的爆炸性供应继承了印加和盖丘亚构造阶段。酸性玻璃与安山质和钾玄质两个系列有关。这些玻璃的钙碱性因子（CAF）在中新世中期和晚期表现出适度的岩浆变化。在上新世-更新世期间发生了一个戏剧性的变化，反映在强烈的CAF增加和钾的出现，h演化的钾玄质玻璃。这发生在纳斯卡海岭俯冲开始时。这种岩浆成因和分异条件的变化可能与上大陆板块的加厚和贝尼奥夫带的新构型有关。
During Leg 112 off Peru, volcanic material was recorded from middle Eocene to Holocene time. The petrographical and chemical composition of tephra is consistent with an origin from the Andean volcanic arc. The amount and thickness of ash layers provide valuable evidence for explosive volcanic episodicity. The first indication of volcanism was found in mid-Eocene sediments. Three volcanic pulses date from Miocene time. Two intense episodes took place in upper Pliocene and from Pleistocene to Holocene time. Pliocene-Pleistocene tephra are restricted to the southern upper-slope and shelf sites, indicating a removal of the volcanic arc and the extinction of the northern Peru volcanoes. The Cenozoic tectonic phases of the Andean margin may be correlated with the Leg 112 volcanic records. The explosive supply of evolved magmatic products succeeded the Incaic and Quechua tectonic phases. Acidic glasses are related to both andesitic and shoshonitic series. The calc-alkaline factor (CAF) of these glasses exhibited moderate magmatic variations during middle and late Miocene time. A dramatic change occurred during the Pliocene-Pleistocene, reflected in a strong CAF increase and the appearance of potassium-ric h evolved shoshonitic glasses. This took place when the Nazca Ridge subduction began. This change in the magma genesis and/or differentiation conditions is probably related to thickening of the upper continental plate and to a new configuration of the Benioff Zone.