Interaction and compositional change between unsolidified sediments and magma

点击翻译按钮获取中文摘要

The results obtained from this research project are summarized as follows. Two types were distinguished in the interaction between intruded sediments and basaltic magmas. The first type is diffusional one which appears in black shale intruded by dolerite sill, and the second is interaction when black shale and basaltic rocks are intrmingled . The first type occurs under higher temperature and lower water/rock ratio conditions than the second type. In the first type, black shales are silicified and enriched in SiO_2along the contact with dolerite sill, whereas they are completely depleted in K_2O and Rb, which are probably transferred into dolerites. On the other hand, SiO_2 contents of dolerite are constant. In contrast to K_2O and Rb, CaO are expelled from dolerite and slightly concentrated in black shale near the contact. However, the degree of concentration is not balanced with the expelled amount, suggesting that the CaO are removed outside of the system . In the second type, no silicification occurs in baked sediments, although the black shales became to whitish. The white color is due to abundant precipitation of calcite in the shale . However, K_2O and Rb are completely removed from the sediments as the same as the first type . Some elements such as MgO and FeO leached from basalts may be concentrated in the intermingled shale. The different behavior of the interaction is controlled by hydrothermal solution caused by dehydration of sediments by intrusion of hot magma.