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Thermal maturation of a complete magmatic plumbing system at the Sierra de Velasco, Northwestern Argentina
Geological Magazine ( IF 2.0 ) Pub Date : 2020-08-14 , DOI: 10.1017/s0016756820000692
Marcos Macchioli Grande , Pablo Alasino , Juan Dahlquist , Matías Morales Cámera , Carmen Galindo , Miguel Basei

The formation of magmatic plumbing systems in the crust involves mass and heat transfer from deep to shallow levels. This process modifies the local geotherm and increases the thermal maturation of the crust, affecting the rheological state of the host rock and the composition of magma. Here, we report a petrological, geochemical, isotopic and geochronological integrated study of the Huaco (354 Ma) and Sanagasta (353 Ma, from a new U–Pb zircon age) units from the Carboniferous (Lower Mississippian) Huaco Intrusive Complex, NW Argentina. Similar values of ϵNdt and δ18O, of −3.2 ± 0.7 and +11.2‰ ± 0.3‰ (V-SMOW), respectively, for both units indicate that they shared the same source, as a result of mixing and later homogenization of a crustal component at the Late Devonian (378 to 366 Ma), with metasomatized mantle-derived melts. Slightly higher contents of TiO2, FeO, MgO, CaO and rare earth elements for the Sanagasta unit in comparison with the Huaco unit suggest an increase in the degree of partial melting, which may have been caused by a higher temperature at the lower crust. In addition, the previous structural model of the Huaco Intrusive Complex points to an increase in thermal maturation in the upper crust, which drives a change in the emplacement style from tabular subhorizontal (Huaco) to vertically elongated (Sanagasta) bodies. Therefore, the evolution of the intrusive complex may reflect a generalized thermal maturation of the complete magmatic column, at both upper and lower crustal levels.

中文翻译:

阿根廷西北部 Sierra de Velasco 完整岩浆管道系统的热成熟

地壳中岩浆管道系统的形成涉及从深层到浅层的质量和热传递。这一过程改变了当地的地热,增加了地壳的热成熟,影响了母岩的流变状态和岩浆的组成。在这里,我们报告了对来自阿根廷西北部石炭纪(下密西西比)Huaco 侵入杂岩的 Huaco(354 Ma)和 Sanagasta(353 Ma,来自新的 U-Pb 锆石年龄)单元的岩石学、地球化学、同位素和地质年代学综合研究. 类似的值ε和δ18O,分别为 -3.2 ± 0.7 和 +11.2‰ ± 0.3‰ (V-SMOW),这两个单元表明它们共享相同的来源,这是晚泥盆世地壳成分混合和后来均质化的结果( 378 至 366 Ma),具有交代的地幔衍生熔体。TiO含量略高2、Sanagasta 单元的 FeO、MgO、CaO 和稀土元素与 Huaco 单元相比表明部分熔融程度增加,这可能是由于下地壳温度较高所致。此外,先前的华科侵入杂岩结构模型表明上地壳热成熟度增加,这推动了就位方式从板状亚水平(Huaco)体向垂直拉长体(Sanagasta)的变化。因此,侵入杂岩的演化可能反映了整个岩浆柱在上地壳和下地壳水平上的普遍热成熟。
更新日期:2020-08-14
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