THE PROCESS OF MAGMATIC ACTIVITY OF THE EQUATORIAL REGIONS IN THE EAST PACIFIC RISE

In order to understand the cause and origin of the basalt in the rapid expansion area, in this study 9 basalts samples near the East Pacific Rise (EPR) were analyzed to investigate the evolutionary process of basalts in this area. we analyzed the mineralogy, EPMA and Sr-Nd-Pb isotopic compositions. This field is made up of subalkaline basalt. The basalts were mantle-derived magmas with the fractional crystallization of olivine and plagioclase. There are many oscillation ring in plagioclases and the average temperature of the source area that we speculate by the plagioclase is 1247℃. It is shows that magma originated in spinel peridotite area. It is derived from the loss of the mantle, including NEPR basalt may be mixed with HIMU source area, SEPR basalt mixed with HIMU and a little EMⅡ. Through the above research , we can put forward the process of magmatic activity in the region.