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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The upper crustal magma plumbing system of the Pleistocene Apacheta-Aguilucho Volcanic Complex area (Altiplano-Puna, northern Chile) as inferred from the erupted lavas and their enclaves
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The upper crustal magma plumbing system of the Pleistocene Apacheta-Aguilucho Volcanic Complex area (Altiplano-Puna, northern Chile) as inferred from the erupted lavas and their enclaves

机译：从喷发的熔岩及其飞地推断，更新世的阿帕奇塔-阿吉卢乔火山复杂地区（智利北部的Altiplano-Puna）的上地壳岩浆管道系统

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The evolution of the magma plumbing system of the Pleistocene Apacheta-Aguilucho Volcanic Complex area (Altiplano-Puna Volcanic Complex, northern Chile) was investigated through petrographic, geochemical and isotopic studies of representative lavas and related enclaves. Updated available dates of these products, both from the Apacheta and Aguilucho stratovolcanoes and nearby domes, allow us to define the activity during the last 1 Ma. This investigation shows that the andesitic magmas were affected by processes of Assimilation plus Fractional Crystallization (AFC, with a significant role played by amphibole fractionation) during their ascent through the upper crust, presumably by the interaction with the Altiplano-Puna Magma Body (15-20 km). These andesitic magmas were erupted with no or minor additional contamination at shallower levels, or experienced plagioclase-dominated Fractional Crystallization (FC) to dacite within shallower crustal magma chambers (4-8 km depth). The constructional phase of the Apacheta and Aguilucho stratovolcanoes (= 1 to ca. 0.6 Ma) reflect a transition from high-flux (i.e. flare-ups) to steady state magmatism, as also documented in other Pleistocene volcanic complexes of the Altiplano-Puna Volcanic Complex. During this stage the mafic magma recharge was high enough to permit a large spectrum of hybridization of the resident magmas in the upper crust to form the abundant andesites and dacites lavas. In contrast, at similar to 150-100 ka, the magmatism turned to a new stage of recharge (waning stage?) and the episodic intrusion of small-volumes of andesitic magmas permitted the remobilization of the crystal-rich dacites, triggering the extrusions of the Chanka, Chac-Inca and Cerro Pabellon domes. The andesitic enclaves in the domes studied here represent a snapshot of the magmatic processes of interaction that occurred in the shallower reservoir at the interface of the resident dacite with the ascending andesitic magma. Nevertheless, as there are no dated volcanic products from the area between 0.6 and 0.1 Ma, the youngest dacitic domes could also be interpreted as the beginning of a new magmatic pulse of the Altiplano-Puna Volcanic Complex. Independently from the significance of the mafic recharge at 150-100 ka (waning stage vs. new pulse) the youngest investigated domes share similar geochemical features and crustal depth constraints (4-8 km) with the ignimbrites of the Altiplano-Puna Volcanic Complex, therefore suggesting that the remobilized magmas erupted as the domes are possibly remains of older plumbing systems left over from the last magmatic flare-up of the Altiplano-Puna Volcanic Complex. (C) 2019 Elsevier B.V. All rights reserved.
机译：通过对代表性熔岩和相关飞地的岩石学，地球化学和同位素研究，研究了更新世的阿帕奇塔-阿吉卢乔火山复合体地区（智利北部的高原-普纳火山复合体）的岩浆管道系统的演化。这些产品的更新可用日期（包括来自Apacheta和Aguilucho地层火山以及附近圆顶的可用日期）使我们能够定义最近1 Ma内的活动。这项调查表明，安第斯岩浆通过上地壳上升过程中受同化加分形结晶作用（AFC，由闪石分馏起着重要作用）的过程影响，大概是与Altiplano-Puna岩浆体相互作用造成的（15- 20公里）。这些安山岩浆在较浅的水平喷发时没有或有轻微的附加污染，或者在较浅的地壳岩浆室内（4-8 km深度）经历了斜长石为主的分形结晶（FC）凝结。 Apacheta和Aguilucho平流层火山的构造阶段（> = 1到大约0.6 Ma）反映了从高通量（即爆发）到稳态岩浆的过渡，这在Altiplano-Puna的其他更新世火山复合体中也有记载火山综合体。在这个阶段，镁铁质岩浆充填量足够高，可以使上地壳中的常驻岩浆发生大范围的杂化，从而形成丰富的安山岩和Dacites熔岩。相反，在接近150-100 ka时，岩浆活动进入了一个新的补给阶段（减弱阶段？），小批量安第斯岩浆的偶发性侵入使得富晶体的静水分子得以移动，从而触发了岩浆的挤出。 Chanka，Chac-Inca和Cerro Pabellon圆顶。此处研究的穹顶中的安山岩飞地代表了岩浆相互作用过程的快照，该岩浆作用发生在常绿达克特岩与上升安山岩浆的交界处的浅层储层中。然而，由于在0.6至0.1 Ma之间没有过时的火山产物，因此，最年轻的datictic穹顶也可以解释为Altiplano-Puna火山群新岩浆脉的开始。独立于150-100 ka镁铁质补给的意义（逐渐减弱的阶段与新的脉动），研究最年轻的穹顶与Altiplano-Puna火山群的火成岩具有相似的地球化学特征和地壳深度限制（4-8 km），因此，这表明由于穹顶喷发而来的复垦岩浆可能是Altiplano-Puna火山群最后一次岩浆爆发留下的较旧管道系统的残骸。 （C）2019 Elsevier B.V.保留所有权利。

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