Interaction and compositional change between unsolidified sediments and magma

从该研究项目中获得的结果总结如下。侵入沉积物与玄武质岩浆的相互作用可分为两种类型。第一种为扩散型，主要表现在黑页岩被粗玄岩岩床侵入时;第二种为黑页岩与玄武质岩互夹时的相互作用型。第一种类型发生在较高的温度和较低的水/岩比条件下比第二种类型。第一类黑色页岩沿与粗粒岩岩床接触部位硅化，富SiO_2，而K_2O和Rb则完全亏损，可能转化为粗粒岩。而粗玄岩的SiO_2含量基本不变。与K_2O和Rb相反，CaO从粗玄岩中排出，并在接触面附近的黑色页岩中略有富集。然而，浓缩程度与排出量不平衡，表明CaO被移出系统。在第二种类型中，尽管黑色页岩变得发白，但在焙烧的沉积物中没有发生硅化。白色是由于页岩中大量方解石沉淀。而K_2O和Rb则与第一种类型一样被完全去除。玄武岩中浸出的MgO、FeO等元素可能富集在混合页岩中。这种相互作用的不同表现是受热岩浆侵入使沉积物脱水而形成的热液作用控制的。

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.