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首页> 外文期刊>Contributions to Mineralogy and Petrology >Enrichments of the mantle sources beneath the Southern Volcanic Zone (Andes) by fluids and melts derived from abraded upper continental crust
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Enrichments of the mantle sources beneath the Southern Volcanic Zone (Andes) by fluids and melts derived from abraded upper continental crust

机译：南部火山带磨蚀产生的流体和熔体丰富了南部火山区（安第斯山脉）下方的地幔源

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摘要

Mafic basaltic-andesitic volcanic rocks from the Andean Southern Volcanic Zone (SVZ) exhibit a northward increase in crustal components in primitive arc magmas from the Central through the Transitional and Northern SVZ segments. New elemental and Sr-Nd-high-precision Pb isotope data from the Quaternary arc volcanic centres of Maipo (NSVZ) and Infemillo and Laguna del Maule (TSVZ) are argued to reflect mainly their mantle source and its melting. For the C-T-NSVZ, we identify two types of source enrichment: one, represented by Antuco in CSVZ, but also present northward along the arc, was dominated by fluids which enriched a pre-metasomatic South Atlantic depleted MORB mantle type asthenosphere. The second enrichment was by melts having the characteristics of upper continental crust (UCC), distinctly different from Chile trench sediments. We suggest that granitic rocks entered the source mantle by means of subduction erosion in response to the northward increasingly strong coupling of the converging plates. Both types of enrichment had the same Pb isotope composition in the TSVZ with no significant component derived from the subducting oceanic crust. Pb-Sr-Nd isotopes indicate a major crustal compositional change at the southern end of the NSVZ. Modelling suggests addition of around 2 % UCC for Infernillo and 5 % for Maipo.
机译：来自安第斯南部火山带（SVZ​​）的镁铁质玄武质-安第斯火山岩的原始弧岩浆中的地壳成分向北增加，从中部到过渡带和北部SVZ段。迈坡（NSVZ）第四纪弧火山中心和Infemillo和Laguna del Maule（TSVZ）的新元素和Sr-Nd高精度Pb同位素数据被认为主要反映了它们的地幔来源及其融化。对于C-T-NSVZ，我们确定了两种类型的震源富集：一种是由Antuco在CSVZ中代表的，但也沿弧线向北存在，其流体主要是富集了代交叠前南大西洋贫化的MORB地幔型软流圈。第二次富集是通过具有上陆壳（UCC）特征的熔体，与智利海沟沉积物明显不同。我们认为，随着汇聚板块向北逐渐增强的耦合作用，花岗岩通过俯冲侵蚀进入了地幔。两种富集类型在TSVZ中具有相同的Pb同位素组成，而没有明显的成分来自俯冲洋壳。 Pb-Sr-Nd同位素表明NSVZ南端的主要地壳组成变化。模型表明，Infernillo的UCC约为2％，Maipo的UCC为5％。

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