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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Geochemical and isotopic profile of Pico de Orizaba (Citlaltepetl) volcano, Mexico: Insights for magma generation processes
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Geochemical and isotopic profile of Pico de Orizaba (Citlaltepetl) volcano, Mexico: Insights for magma generation processes

机译：墨西哥皮科德奥里扎巴火山（Citlaltepetl）的地球化学和同位素剖面：岩浆生成过程的见解

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摘要

Pico de Orizaba or Citlaltepetl volcano is the easternmost and highest stratovolcano of the subduction-related Mexican Volcanic Belt (MVB) located >400 km NNE of the Middle America Trench. This active volcano comprises four evolutionary stages, ranging in age from 0.65 Ma to the Holocene, and is surrounded by Quaternary monogenetic scoria cones and maar volcanoes. Magmatic products of the stratocone range from basaltic andesites to rhyolites and the cinder cones erupted basalts and basaltic andesites. All rock compositions form a continuous calc-alkaline suite. Petrogenetic processes involved in magma generation and evolution include fractional crystallization and mid-crustal assimilation. Trace element patterns with elevated Ba/Nb, positive Pb spikes, and Th enrichments indicate contributions from subducted sediment. Low Ba/Th ratios suggest melting of hydrous sediment without significant loss of fluid-mobile elements prior to melting. Sr-Nd isotopic ratios of Pico de Orizaba and cinder cones are nearly chondritic and are located on a mixing curve between Pacific MORB and Paleozoic crust of SE Mexico. However, vertical Nd distributions in an ~(87)Sr/~(86)Sr vs. sNd diagram cannot be explained by crustal assimilation and indicate contributions of a sedimentary component with unradiogenic Nd. In contrast to other eastern MVB volcanic centres, Pico de Orizaba magmas are derived almost exclusively from a depleted mantle source. Compared to other MVB stratocones, Pico de Orizaba shows the least radiogenic Nd isotope ratios at nearly identical~(87)Sr/~(86)Sr. Steep trends in a ~(206)Pb/~(204)Pb vs.~(207)Pb/~(204)Pb diagram favour the involvement of young, ~(207)Pb-enriched oceanic sediments in magma generation processes of Pico de Orizaba volcano. The Pb isotope data do not support any assimilation of lower crustal Grenvillian basement.
机译：Pico de Orizaba火山或Citlaltepetl火山是俯冲相关的墨西哥火山带（MVB）的最东端和最高的平流火山，位于中美洲海沟NNE大于400公里处。这座活火山包括四个演化阶段，年龄从0.65 Ma到全新世，并被第四纪单相角屑锥和Maar火山包围。层状锥的岩浆产物范围从玄武安山岩到流纹岩，煤渣锥喷出玄武岩和玄武安山岩。所有岩石成分组成一个连续的钙碱性套件。涉及岩浆生成和演化的岩石成因过程包括部分结晶和中地壳同化。 Ba / Nb升高，Pb尖峰正和Th富集的痕量元素模式指示了俯冲沉积物的贡献。低的Ba / Th比值表明含水的沉积物熔化，而在熔化之前没有大量的流动元素损失。皮科·德·奥里萨巴（Pico de Orizaba）和煤渣锥的Sr-Nd同位素比率几乎是软骨状的，位于墨西哥太平洋MORB和东南墨西哥古生代地壳之间的混合曲线上。但是，〜（87）Sr /〜（86）Sr对sNd图中的垂直Nd分布不能通过地壳同化来解释，并且不能指示沉积组分与非放射源Nd的关系。与其他东部MVB火山中心相反，Pico de Orizaba岩浆几乎完全来自枯竭的地幔源。与其他MVB平流圆锥相比，Pico de Orizaba在几乎相同的〜（87）Sr /〜（86）Sr处显示出最低的放射性Nd同位素比。 〜（206）Pb /〜（204）Pb与〜（207）Pb /〜（204）Pb图的陡峭趋势有利于年轻，〜（207）Pb富集的海洋沉积物参与皮克岩浆形成过程德奥里扎巴火山。铅同位素数据不支持下地壳格林维尔基底的任何同化作用。

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