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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The Carran-Los Venados volcanic field and its relationship with coeval and nearby polygenetic volcanism in an intra-arc setting
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The Carran-Los Venados volcanic field and its relationship with coeval and nearby polygenetic volcanism in an intra-arc setting

机译：弧内背景下的Carran-Los Venados火山场及其与近代和近代多生火山的关系

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Understanding the relationship between monogenetic and polygenetic volcanism has been a long-standing goal in volcanology, especially in cases where these two styles of volcanism are coeval and geographically adjacent. We studied the Carran-Los Venados (CLV) volcanic field and made comparisons with published data on CLV's polygenetic neighbor Puyehue-Cordon Caulle (PCC) in the Southern Andean arc, using quantitative tools and recent numerical simulations of magma reservoir formation. CLV is a basaltic to basaltic andesitic volcanic field composed of 65 post-glacial scoria cones and maars and a 1-km-high Pleistocene stratovolcano, whereas PCC is a basaltic to rhyolitic composite volcano. Our results point to three main differences between CLV and PCC: (1) the CLV magmas differentiate at low-crustal reservoirs, followed by rapid ascent to the surface, while the PCC magmas stagnate and differentiate in lower- and upper-crustal reservoirs; (2) CLV is elongated in the NE direction while FCC is elongated in the NW direction. Under the current stress field (N60 degrees sigma(Hmax)), these two volcanic alignments correspond, respectively, to local extensional and compressive deformation zones within the arc; and (3), the post-glacial CLV magma flux was estimated to be 3.1 +/- 1.0 km(3)/ky, which is similar to the average magma flux estimated for KC; however, the FCC magma flux is estimated at approximately twice this value during peak eruptive periods (5.5 +/- 1.1 km(3)/ky). Based on numerical simulations, CLV is in a limit situation to create and sustain a mush-type upper-crustal reservoir containing highly crystalline magma, which is however not eruptible. The FCC volcanic system would have been able to create a stable reservoir containing eruptible silicic magma during periods of peak magma flux. We postulate that monogenetic volcanism occurs at CLV due to both low magma flux and an extensional/transtensional regime that favors rapid magma rise without storage and differentiation in stable upper-crustal reservoirs. However, the CLV system seems to be at an inflection point, and could become polygenetic if magma flux increases. For PCC, high magma flux during some periods together with compressive deformation would have led to the construction of one or several stable upper-crustal magma reservoirs, with subsequent silicic volcanism and construction of central conduits for magma extrusion, resulting in polygenetic volcanism with evolved compositions. In this model, monogenetic volcanic systems can become polygenetic despite extensional regime if magma flux increases sufficiently to create and sustain a stable upper-crustal magma reservoir. (C) 2015 Elsevier B.V. All rights reserved.
机译：理解单基因和多基因火山之间的关系一直是火山学的长期目标，尤其是在这两种类型的火山同时存在并在地理上相邻的情况下。我们研究了Carran-Los Venados（CLV）火山场，并使用定量工具和近期岩浆储层形成的数值模拟，与南安第斯山弧中CLV的多基因近邻Puyehue-Cordon Caulle（PCC）的已发表数据进行了比较。 CLV是一个由玄武岩到玄武岩的火山场，由65个冰川后的火山灰锥和Maars和一个1 km高的更新世地层火山组成，而PCC是玄武岩到流纹岩复合火山。我们的结果指出了CLV和PCC之间的三个主要区别：（1）CLV岩浆在低地壳储层中分化，然后迅速上升到地表，而PCC岩浆在上，下地壳储层中停滞并分化。 （2）CLV在NE方向上拉长，而FCC在NW方向上拉长。在当前应力场（N60度sigma（Hmax））下，这两个火山路线分别对应于弧内的局部拉伸变形区域和压缩变形区域。 （3）冰川后CLV的岩浆通量估计为3.1 +/- 1.0 km（3）/ ky，与KC估计的平均岩浆通量相似；但是，在峰值喷发期（5.5 +/- 1.1 km（3）/ ky），FCC岩浆通量估计约为该值的两倍。基于数值模拟，CLV处于极限状态，无法建立和维持一个包含高结晶岩浆的糊状上地壳储层，但是这种储层是不可爆发的。 FCC火山系统本来可以在岩浆峰值流量期间建立一个稳定的储层，其中包含可喷发的硅岩浆。我们假设由于低岩浆通量和有利于岩浆快速上升而没有在稳定的上地壳储层中储存和分化的伸展/张性体系，CLV发生了单相火山作用。但是，CLV系统似乎处于拐点，如果岩浆通量增加，可能会成为多基因的。对于PCC，某些时期的高岩浆通量以及压缩变形将导致一个或几个稳定的上地壳岩浆储层的建设，随后形成硅质火山作用和用于岩浆挤压的中央管道的建设，从而导致多成岩火山岩具有演化的成分。在该模型中，如果岩浆通量增加到足以形成并维持稳定的上地壳岩浆储集层，那么尽管有扩张机制，但单相火山系统仍会变成多岩性。 （C）2015 Elsevier B.V.保留所有权利。

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