Rapid incremental assembly of the Monte Capanne pluton (Elba Island, Tuscany) by downward stacking of magma sheets
Rapid incremental assembly of the Monte Capanne pluton (Elba Island, Tuscany) by downward stacking of magma sheets
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DOI：
10.1130/b30112.1
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发表时间：
2010-09-01
影响因子：
4.9
通讯作者：
Westerman, David S.
中科院分区：
文献类型：
--
作者：
Farina, Federico;Dini, Andrea;Westerman, David S.
晚中新世Monte Capanne岩体（意大利厄尔巴岛）的特点是自形钾长石巨晶的广泛出现，其大小和丰度的变化已在392个站点确定。巨晶分布的可变性定义了三个主要相，其特征在于低（San Piero相）、高（Sant' Andrea相）和中等（San Francesco相）巨晶丰度。这三个相显示出轻微的，但系统的差异，在整个岩石的主要和微量元素含量，同位素组成，和黑云母矿物化学，化学变异和巨晶丰度之间没有可检测的联系。这些结果沿着对结晶序列的重建，表明这些相在深部形成为具有独特地球化学特征的岩浆批次，并在上升侵位后得以保存。因此，基于钾长石巨晶分布的新地质图揭示了该岩体的复合结构，这种复合结构是由三个略有不同的岩浆批次向下叠加而逐渐形成的，导致中浅地壳中的席状岩体。这三个岩浆批次侵位在一个很短的时间序列，阻碍了地质年代学的努力，以解开内部相之间的年龄差异。
The late Miocene Monte Capanne pluton (Elba Island, Italy) is characterized by the widespread occurrence of euhedral K-feldspar megacrysts, for which variations in size and abundance have been determined at 392 stations. The variability of megacryst distribution defines three main facies characterized by low (San Piero facies), high (Sant' Andrea facies), and intermediate (San Francesco facies) megacryst abundance. The three facies show minor yet systematic differences in whole-rock major- and trace-element contents, isotopic composition, and biotite mineral chemistry, with no detectable link between chemical variabilities and megacryst abundance. These results, along with the reconstruction of the crystallization sequence, suggest that the facies formed at depth as distinct magma batches with their own peculiar geochemical features, which were preserved after ascent and emplacement. The new geological map based on K-feldspar megacryst distribution thus reveals the composite structure of the pluton, which was built up incrementally by downward stacking of three slightly different magma batches, resulting in a sheeted pluton in the intermediate-shallow crust. The three magma batches were emplaced in a short time sequence hampering geochronological efforts to unravel age differences between internal facies.