Preliminary research on data mining of N-MORB and E-MORB: Discussion on method of the basalt discrimination diagrams and the character of MORB' s mantle source

MORB can be divided into N-MORB and E-MORB, N-MORB is LREE depleted and E-MORB is enriched. Studies on MORB have greatly boosted the fundamental theories of basalts. N-MORB and OIB are generally believed to be two separate end members, and E-MORB is mixed by N-MORB and OIB in varying degrees. The diagrams for discriminating tectonic settings of basalts were established during the 1970s and 1980s, which are tremendous progress for analyzing earth dynamics and tectonic background of basalts and has thrived for decades especially in China. We have compiled more than 50000 MORB data in PetDB database for tectonic setting discrimination diagrams. The plotting diagrams applying whole samples exhibit more accurate and reliable results than that of using representative samples. Therefore, previous discrimination diagrams of major and trace elements require reexamination. Our study indicates that MORB can be either LREE depleted or enriched, and the degree of depletion or enrichment is in large difference from previous definition, which reflect that the mantle beneath ocean ridge is more heterogeneous in composition than previous understanding. In general, our study provides new, different insights to basalts, and we propose multi-dimension, high-confidence level discrimination system to be established for more research on the origin of magmas.