layering of alpine‐Type peridotite and the segregation of partial melt in the upper mantle
layering of alpine‐Type peridotite and the segregation of partial melt in the upper mantle
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DOI：
10.1029/jb092ib05p03467
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发表时间：
1987-04
影响因子：
--
通讯作者：
M. Obata;Nobuhiko Nagahara
中科院分区：
文献类型：
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作者：
M. Obata;Nobuhiko Nagahara
为了更好地理解上地幔的部分熔融和熔融分凝过程，我们研究了日本北海道一个橄榄岩体的层状结构。分层的特点是波浪和振荡模式，无论是在散装岩石和矿物化学。从所观察到的线性趋势，在散装岩石化学，我们得出结论，这种分层是由地幔中的部分熔融分离。结合地质地球化学资料，提出了重力场作用下熔体偏析的物理模型。由于渗透流与固体蠕变和压实强烈耦合，岩浆波可能是由部分熔融的上升地幔中的流体动力学振荡产生的。因此，从一个均匀的地幔开始，可以得到一个垂直的化学分层。根据这一假说，亏损最严重的纯橄榄岩是部分熔融的残留物，亏损最少的斜长石二辉橄榄岩代表熔融物聚集区。所涉及的部分熔体的成分可能是苦味酸。
For better understanding of the partial melting and melt segregation processes in the upper mantle, we have studied the layered structure of a peridotite mass in Hokkaido, Japan. The layering is characterized by wavy and oscillatory patterns both in terms of bulk rock and mineral chemistry. From the observed linear trends in bulk rock chemistry, we have concluded that such layering was caused by segregation of partial melt in the mantle. Considering the geological and geochemical data, a physical model of melt segregation in the gravity field is put forward. Because permeable flow is strongly coupled with solid creep and compaction, magma waves may be generated by a fluid dynamic oscillation in a partially molten, ascending mantle. A vertical chemical stratification may thus be obtained, starting from a homogeneous mantle. According to the hypothesis, the most depleted part, dunite, is a residue of partial melting, and the least depleted part, plagioclase Iherzolite, represents a melt accumulation region. The partial melt involved was probably picritic in composition.