Geochemical Characteristics and Genesis Analysis of Deju Basalt in Midu County, Western Yunnan

摘要

Deju basalts is a characteristic volcanic association and was first founded in the 1 : 50 000 regional geological survey. There is no previous study. The basalts' characteristics and genesis are systematically studied from the geochemistry. It is showed that the basalts's w(SiO2) = 50.61-54.54%, w(K2O + Na2O) = 0.15-5.96%, w(P2O5) = 0.18-0.45%, w(TiO2) = 1.82-3.58%, belong to sub alkaline basalt series. Chondrite-normalized REE patterns indicate the basalts are relatively rich in LREE but deficient in HREE (LREE/HREE = 5.81-6.51), and have a similar mantle source with WPB and OIB. The mantle source have a characteristics of GP. The discrimination diagrams of basalt tectonic setting reflect the basalts in Deju belongs to continental intraplate basalt, formed in a continental rift stretching environment, and during the diagenesis process, the magma source was contaminated by the crust and oceanic crust subducted materials.