Interaction of Plate, Mantle, core and the magmatism in the earth's history

我们对加拿大阿卡斯塔花岗岩杂岩进行了实地考察，这是世界上最古老的火成岩体，形成于4 Ga。根据锆石定年和地质资料，揭示了火成岩杂岩的形成顺序和时间。我们还在澳大利亚的皮尔巴拉克拉通进行了实地考察，这是最古老的花岗岩-绿岩地形之一，形成于2.8-3年。5 Ga。我们研究了那个时代洋中脊和辐合边缘的火成岩活动。结果表明，太古宙海水中含有大量的二氧化碳，并通过热液活动在洋壳中形成了相当比例的碳酸盐矿物。这种碳酸化地壳在会聚边缘俯冲，携带大量的碳进入深部。此外，对津巴布韦3.5 Ga科马地岩的熔体包裹体研究表明，当时的地幔柱中含有大量的水。为了研究下地幔的熔融过程，我们还使用kawai型仪器进行了高P-T实验。测定了软锰矿和玄武岩的熔融相关系，并对其微量元素分配进行了研究。这些实验结果表明casio_3 -钙钛矿在下地幔的微量元素分配中起主导作用，包括在核幔边界的熔融过程。在夏威夷和南太平洋羽流地幔的斜辉石捕虏体中发现了地幔底部熔融形成的微量元素特征模式，表明它们起源于该地区。我们进一步利用激光加热的金刚石砧细胞进行了超高P-T实验。结果表明，石英相在下地幔中经历了2次相变，α- pbo_2型相在下地幔条件下较为稳定。

We made a fieldwork at Acasta granitic complex in Canada, which is the oldest igneous body in the world formed at 4 Ga. We revealed the sequence and timing of formation of igneous complex on the basis of zircon dating and geological evidences. We made a fieldwork also at Pilbara craton in Australia, which is one of the oldest granite-greenstone terrain formed at 2.8-3. 5 Ga. We investigated igneous activities both at mid-oceanic ridges and convergent margins at that age. Results indicate that Archean seawater included large amounts of carbon-dioxide, and it formed significant proportions of carbonate minerals in oceanic crust through hydrothermal activities. Such carbonated crust subducted at convergent margins carrying large amount of carbon into the deep interior. In addition, melt inclusion studies of 3.5 Ga komatiites from Zimbabwe revealed that plume mantle included lots of water at that time. We also performed high P-T experiments using Kawai-type apparatus in order to investigate the melting processes in the lower mantle. Melting phase relations both of pyrolite and basalt compositions were determined, and trace element partitioning were investigated. These experimental results suggest that CaSiO_3-perovskite plays predominant roles in the partitioning of trace elements in the lower mantle including melting process at the core-mantle boundary. The characteristic pattern of trace elements expected to be formed by melting at the bottom of the mantle is found in the xenolith clinopylroxenes in the plume mantle at Hawaii and south Pacific, suggesting that they originated from that region. We further performed ultra-high P-T experiments using laser-heated diamond anvil cell. We revealed that silica phase undergoes phase transition twice in the lower mantle, and α-PbO_2-type phase is stable at the lowermost mantle conditions.