Magma sources and tectonic setting of Central Andean andesites (25.5–28°S) related to crustal thickening, forearc subduction erosion and delamination
Magma sources and tectonic setting of Central Andean andesites (25.5–28°S) related to crustal thickening, forearc subduction erosion and delamination
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DOI：
10.1144/sp385.11
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发表时间：
2013-08
期刊：
影响因子：
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通讯作者：
S. Kay;C. Mpodozis;M. Gardeweg
中科院分区：
文献类型：
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作者：
S. Kay;C. Mpodozis;M. Gardeweg
安第斯山脉中部边缘是弧安山岩的典型产地，也是安山岩名称的起源地。从25.5°S到28.2°S喷发的<25 Ma的中高钾安山岩在微量元素和同位素比值上表现出很大的变化，反映了在一个不断发展的板片上形成，地壳增厚到65-75 km，以及一个向东迁移的前缘弧。向东45 km，约为8-3 Ma。28-26.8°S处的安山岩具有最易变和极端的重稀土元素（REE）、高场强元素（HFSE）和Ba/La比以及wt% Na 2 O，其中随着前锋弧迁移和板片变浅而喷发的安山岩的值最高。向南。所需的石榴石轴承，无辉长岩残留物中产生的厚地壳和地幔楔，其中地壳注入弧前俯冲侵蚀的高峰弧迁移。普纳高原以东25.5-26.8°S处的安山岩，其下的板片在18-7 Ma变浅，然后随着岩石圈拆沉发生而变陡，通常缺乏极端的REE和HFSE比值。它们的上地壳状特征反映了在混合应力状态下的喷发，以及从东部广泛的深地壳熔融区域向西流动的放射性地壳的合并。
Abstract The Central Andean margin, where the name andesite originated, is the type locality for arc andesites erupted through thick continental crust. The <25 Ma mid to high K2O andesites erupted from 25.5°S to 28.2°S exhibit a large variation in trace element and isotopic ratios, reflecting formation over an evolving slab, a crust thickening to 65–75 km and a frontal arc that migrated c. 45 km eastward at 8–3 Ma. Andesites at 28–26.8°S have the most variable and extreme heavy rare earth element (REE), high field strength element (HFSE) and Ba/La ratios and wt% Na2O, with the highest values in those erupted as the frontal arc migrated and the slab shallowed to the south. The required garnet-bearing, feldspar-free residue is generated in both the thick crust and the mantle wedge, into which crust was injected in a peak of forearc subduction erosion as the arc migrated. Andesites at 25.5–26.8°S, east of the Puna plateau under which the slab shallowed at 18–7 Ma and then steepened as lithospheric delamination occurred, generally lack extreme REE and HFSE ratios. Their upper crust-like features reflect eruption in a mixed stress regime and incorporation of westward-flowing radiogenic crust from a region of extensive deep crustal melting to the east.