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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The Hudson Volcano and surrounding monogenetic centres (Chilean Patagonia): An example of volcanism associated with ridge-trench collision environment
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The Hudson Volcano and surrounding monogenetic centres (Chilean Patagonia): An example of volcanism associated with ridge-trench collision environment

机译：哈德逊火山及其周围的单基因中心（智利巴塔哥尼亚）：与山脊海沟碰撞环境有关的火山作用的例子

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摘要

Hudson Volcano (45°54′S, 72°58′W) represents the southernmost central volcano of the South Andean Volcanic Zone (SVZ). It lies about 280 km east of Nazca-Antarctic-South American Plate Triple Junction, where the Chile spreading ridge enters the Chile Trench. Hudson is located on the border of a volcanic gap separating the Southern from the Austral Volcanic Zone (AVZ), which is commonly interpreted as linked to a slab window. The volcano is characterised by a volcano-tectonic depression about 10 km wide, set in a morphological high of the Patagonian Batholith. The scarce pre-caldera products are made up of mafic lavas interbedded with hyaloclastite. The majority of the volcanic products out from the caldera rims consist of thick deposits of lahars or hyaloclastitic breccias, subordinate lava flows and pyroclastic deposits linked to historical large explosive eruptions. Rough volume calculations on pre-caldera and post-caldera products suggest that the caldera formed in steps in the lifetime of the volcano and that it is mainly linked to a volcano-tectonic collapse during partial emptying of the magma chamber. The monogenetic cones surrounding Hudson (Rio Ibanez and Murta) erupted primitive basalts that gave important clues on magma sources. The volcanic products of Hudson, with composition ranging from basalts to dacites, have a calc-alkaline signature. Nevertheless, they have distinctly higher K_2O, TiO_2, Na_2O, LILE, HFSE and REE than the calc-alkaline rocks of SVZ. The basaltic lavas from the monogenetic cones show La/Nb, Ba/Nb and Th/Ta significantly lower than the calc-alkaline lavas. Furthermore, they have some ratios as Th/Yb and La/Yb remarkably low, with values approaching those of MORB-like basalts. All the geochemical characteristics of Rio Ibanez and Murta cones are very similar to those of the basalts dredged in the Chile Ridge. Geochemical modeling suggests that the Hudson basalts may derive from the basalts erupted at the Rio Ibanez centre through an assimilation plus fractional crystallisation process. On the basis of these data, we propose a geodynamical model. In correspondence to the monogenetic centres, close to the border of the incipient opening of the slab window, the magma features are still those of the depleted asthenosphere under the subducting ridge. In this zone, remnant fragments of subducted oceanic crust undergo partial melting processes, while the mantle wedge is deeply modified by subduction-related components. In correspondence to Hudson and the nearby monogenetic centres, the MORB-type primary source component is modified by altered oceanic crust and variably mixed with andesitic magmas having a calc-alkaline signature. A contribution from partial melting of the continental lithosphere may be present in the complex source mixing process at the border of the slab window.
机译：哈德逊火山（45°54′S，72°58′W）代表南安第斯火山区（SVZ）最南端的中央火山。它位于纳斯卡-南极-南美板块三重交界以东约280公里，智利的扩张脊进入智利的海沟。哈德逊位于火山间隙的边界上，该火山间隙将南部和南部火山带（AVZ）分开，通常将其解释为与板状窗相连。火山的特征是火山构造的洼地宽约10公里，位于巴塔哥尼亚岩基的形态高处。稀有的破火山口产品是由镁铁质熔岩与透明质岩交织而成的。破火山口边缘的大部分火山产物由浓厚的拉哈斯沉积层或玻璃质碎屑角砾岩，次要的熔岩流和与历史性大爆炸爆发有关的火山碎屑沉积物组成。对破火山口前和破火山口产品的粗略体积计算表明，火山口在火山的生命周期内逐步形成，并且主要与岩浆室部分排空期间的火山构造塌陷有关。哈德逊周围的单相锥（里瓦·伊瓦涅兹和穆尔塔）喷出了原始玄武岩，为岩浆源提供了重要线索。哈德逊火山的火山产品具有从碱性到碱性的特征。然而，它们比SVZ的钙碱性岩石具有明显更高的K_2O，TiO_2，Na_2O，LILE，HFSE和REE。来自单相球果的玄武岩熔岩显示出La / Nb，Ba / Nb和Th / Ta显着低于钙碱性熔岩。此外，它们具有一些比率，如Th / Yb和La / Yb极低，其值接近于MORB类玄武岩。 Rio Ibanez和Murta锥的所有地球化学特征都与在智利山脊中挖出的玄武岩非常相似。地球化学模型表明，哈德逊玄武岩可能是通过同化和分步结晶过程从里约伊瓦涅斯中心喷出的玄武岩中衍生出来的。在这些数据的基础上，我们提出了一个地球动力学模型。对应于单基因中心，靠近板状窗口的初始开口的边界，岩浆特征仍然是俯冲脊下方枯竭软流圈的特征。在该区域中，俯冲洋壳的残余碎片经历了部分融化过程，而地幔楔被俯冲相关的成分深深地改变了。与哈德逊及其附近的单基因中心相对应，通过改变海洋洋壳并与具有钙碱性特征的安山岩岩浆混合混合，改变了MORB型主要源组分。在平板窗口边界处的复杂震源混合过程中可能存在大陆岩石圈部分融化的作用。

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