Insights into the mechanisms and timescales of pluton assembly from deformation patterns of mafic enclaves
Insights into the mechanisms and timescales of pluton assembly from deformation patterns of mafic enclaves
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DOI：
10.1029/2012jb009325
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发表时间：
2012-11
影响因子：
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通讯作者：
L. Caricchi;C. Annen;A. Rust;J. Blundy
中科院分区：
文献类型：
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作者：
L. Caricchi;C. Annen;A. Rust;J. Blundy
[1]我们提出了一种新的方法来约束侵入体的时间尺度和组合风格，利用花岗岩的常见成分基性包体记录的应变。结合岩石学、热模拟和岩浆流变学，研究了以不同岩浆输入速率生长的岩体碎片组合过程中包裹体记录的应变演化。寄主岩浆和包裹体的不同组成（以及相应的相关系）限制了这两种物质在有限的温度范围内的均匀变形，我们称之为“相互变形的窗口”。在这些窗口之外，只有粘性较低的宿主花岗岩记录了任何明显的变形，而包裹体主要作为刚性物体运输。相互变形窗口的时空发展反映了岩浆侵入岩体的速度。因此，包体记录的径向应变分布可以提供岩浆体在构造过程中的热流变演化的图像。我们的方法应用于意大利阿达梅洛地块Lago della Vacca杂岩（LVC）的基性包裹体的变形模式，以估计岩体侵位的时间尺度。我们的计算表明，总侵位时间尺度为50 ~ 150ky，与最近LVC锆石的高精度放射性定年非常吻合。
[1] We propose a novel method to constrain both timescales and assembly styles of intrusive bodies using the strain recorded by mafic enclaves, a common component of granitic rocks. Petrology, thermal modeling, and magma rheology are combined to investigate the evolution of strain recorded by enclaves during the piecemeal assembly of a pluton growing at various rates of magma input. The different compositions (and hence phase relations) of host magma and enclaves limits homogeneous deformation of these two materials to restricted temperature ranges, which we term “windows of mutual deformability.” Outside these windows only the less viscous host granite records any appreciable deformation and enclaves are mainly transported as rigid objects. The temporal and spatial development of the windows of mutual deformability reflects the emplacement rate of magmas into the pluton. Consequently, the radial distribution of strain recorded by enclaves can provide a picture of the thermal and rheological evolution of a magmatic body during its construction. Our approach is applied to deformation patterns of mafic enclaves in the Lago della Vacca Complex (LVC) of the Adamello Massif (Italy), to estimate the timescales of pluton emplacement. Our calculations suggest total emplacement timescales of the order 50 to 150 ky, in excellent agreement with recent high precision radiometric dating of zircons from the LVC.