Progressive Interaction between Dry and Wet Mantle during High-temperature Diapiric Upwelling: Constraints from Cenozoic Kita-Matsuura Intraplate Basalt Province, Northwestern Kyushu, Japan
Progressive Interaction between Dry and Wet Mantle during High-temperature Diapiric Upwelling: Constraints from Cenozoic Kita-Matsuura Intraplate Basalt Province, Northwestern Kyushu, Japan
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DOI：
10.1093/petrology/egu020
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发表时间：
2014-06
影响因子：
3.9
通讯作者：
T. Sakuyama;S. Nakai;M. Yoshikawa;T. Shibata;K. Ozawa
中科院分区：
文献类型：
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作者：
T. Sakuyama;S. Nakai;M. Yoshikawa;T. Shibata;K. Ozawa
日本九州西北部北松浦地区的板内新生代火山活动表现出系统的地球化学时空变化，可以用上涌地幔的部分熔融和熔融分凝来解释。一个光谱的初始熔体的水含量估计范围为0·5至1·5重量%的基础上相结合的斜长石液体和橄榄石饱和液体地质湿度计和MELTS计算。在1.7 ~ 2.8GPa的压力下，在含水条件下，估计的熔体偏析温度范围为1330 ~ 1500 ℃。熔融温度和压力随时间的推移而下降，而初始熔体的水含量增加。高场强元素（HFSE）的丰度和HFSE/大离子亲石元素（LILE）的比例相应的时间减少需要渐进的熔体提取和聚合从熔融地幔与连续和逐渐增加的输入到熔融系统中的富H2O流体或熔体。流入流体的同位素组成估计位于菲律宾海板块的沉积物和蚀变洋壳之间的混合线上，与沉积物组成有很强的亲和力。根据岩浆的时间变化和熔融模型，我们提出了小尺度上升流（c。70公里直径）的干地幔橄榄岩，与上覆的湿地幔楔逐步相互作用。湿地幔楔以前水化的流体从俯冲的菲律宾海板块的沉积物，而深部和干燥的地幔可能是来自俯冲的太平洋板块通过板窗下的地幔。
Intra-plate Cenozoic volcanism in Kita-Matsuura, northwestern Kyushu, Japan, shows systematic spatio-temporal changes in geochemistry that can be explained by partial melting followed by melt segregation in a region of upwelling mantle.We have examined the thermal and melting history of the upwelling mantle by quantitatively estimating melt water contents and melting conditions. The water content of a spectrum of primary melts is estimated to range from 0·5 to 1·5 wt % based on a combination of a plagioclaseliquid and olivine-saturated liquid geohygrometers and MELTS calculations. The estimated melt segregation temperature ranges from 1330 to 15008C, at pressures from 1·7 to 2·8 GPa under hydrous conditions. Melting temperature and pressure decreased with time, whereas the water content of the primary melts increased. Corresponding temporal decreases in high field strength element (HFSE) abundances and HFSE/large ion lithophile element (LILE) ratios require progressive melt extraction and aggregation from a melting mantle with a continuous and gradually increasing input of H2O-rich fluid or melt into the melting system. The estimated isotope composition of influxed fluid lies on a mixing line between the sediment and altered oceanic crust of the Philippine Sea Plate, with strong affinity to the sediment composition. Based on the temporal variation of the magmas and the melting model, we propose small-scale upwelling (c. 70 km in diameter) of a dry mantle peridotite that interacts progressively with the overlying wet mantle wedge. The wet mantle wedge was previously hydrated by fluids from sediments from the subducted Philippine Sea Plate, whereas the deep and dry mantle could have been derived from the mantle beneath the subducted Pacific Plate through a slab window.