Tracking fluid flow during deep crustal anatexis: metasomatism of peridotites (Naxos, Greece)
Tracking fluid flow during deep crustal anatexis: metasomatism of peridotites (Naxos, Greece)
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追踪深地壳深熔过程中的流体流动：橄榄岩的交代作用（希腊纳克索斯岛）
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
M. Spicuzza
中科院分区：
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作者：
Y. Katzir;J. Valley;A. Matthews;M. Spicuzza
抽象的。超镁铁质透镜体的视野变质与主机长英质片麻岩在上角闪岩相的条件下，在M2事件的纳克索斯岛，希腊。同运动峰M2的主要，混合岩相关，超镁铁质层（MUH）的Ol-Opx-Hbl-Chl-Spl组合保留地幔样的化学和氧同位素组成，因此没有证据表明从寄主岩石的流体渗透。MUH变质橄榄岩中的氧同位素Opx-Ol温度测量给出了温度的双峰分布，分组为700和1，200 °C，并表明M2叠加在先前的地幔分馏期间的部分氧交换。阿吉亚超镁铁质层（AUH）是一种粗粒无叶理橄榄岩，产于纳克索斯西北部的硅线岩片麻岩中，含有滑石顽火辉石和橄榄石域。在富硅、高δ 18 O流体的峰后M2渗透期间，AUH橄榄岩的再结晶作用表现为缺乏变形、稳定滑石-顽火辉石组合所需的二氧化硅活性增加、Ol和Opx的极高δ 18 O值以及520-650 °C的Δ 18 O（Opx-Ol）温度。这些流体的来源被推断为细晶岩和伟晶岩脉来自Naxos的混合岩核，侵入AUH。在M2温度峰值和片麻岩深熔过程中，流体体积较小，在Naxos剖面较深处局部缓冲了流体成分。在AUH中观察到，混合岩核内的熔体结晶释放硅质流体，并在上覆序列中引发了一段退水变质作用。
Abstract. Horizons of ultramafic lenses were metamorphosed with host felsic gneisses at upper amphibolite facies conditions during the M2 event on the island of Naxos, Greece. The synkinematic peak M2 Ol–Opx–Hbl–Chl–Spl assemblage of the Main, migmatite-associated, Ultramafic Horizon (MUH) retains mantle-like chemical and oxygen isotope compositions and thus shows no evidence of infiltration of fluids from the host rocks. A bimodal distribution of temperatures, grouped at 700 and 1,200 °C, is given by oxygen isotope Opx–Ol thermometry in the MUH meta-peridotites and indicates partial oxygen exchange during M2 superposed over previous mantle fractionation. The Agia Ultramafic Horizon (AUH), a coarser-grained and unfoliated peridotite, occurs within sillimanite gneisses in northwest Naxos and contains talc–enstatite and olivine domains. Recrystallization of the AUH peridotite during post-peak M2 infiltration of silica-rich, high δ18O fluids is indicated by lack of deformation, increased activity of silica required to stabilize the talc–enstatite assemblage, extremely high δ18O values of Ol and Opx and Δ18O(Opx–Ol) temperatures of 520–650 °C. The source for these fluids is inferred to be aplitic and pegmatitic dikes emanating from the migmatitic core of Naxos and intruding the AUH. At peak M2 temperatures and during anatexis of gneisses, volumes of fluid were small and fluid composition was locally buffered in the deeper part of the Naxos section. Crystallization of melts within the migmatitic core released siliceous fluids and initiated an episode of retrograde hydrous metamorphism in the overlying sequences, as observed in the AUH.