CENOZOIC BASALTS AND THEIR VOLCANISM IN TIANMA-NIUTOU SHAN AREA,FUJIAN PROVINCE
福建天马山—牛头山新生代玄武岩及其火山作用

The Cenozoic basalts of Futan Group controlled by the named Changle-Nanao deep fault are found in Tianma-Niutou Mrs area of Longhai county,Fujian Province. Niutoushan crater is a lava lake formed from three different types of basalts. The basalts and volcanic breccia occur on Tianma Mr. The volcanism is characterized by multiple and discontinuous extrusions, which produced the basalts and volcanic breccia. The volcanic rocks are distinguished into sixteen layers in strata and to be of four stages. The basalts in thefirst and third stages belong to tholeiitic series, consisting of quartz-tholeiite and olivine tholeiite (the latter only occurs in the third stage). The alkaline olivine basalt and olivine basalt belong to alkaline basalt series in the second stage. The altered basalt in the fourth stage is only exposed in Niutoushan lava lake. The tholeiitic and alkaline basalts occur closely in the studied area. The quartz tholeiite and olivine tholeiite consist essentially of labrador, orthopyroxene, clinopyroxene, olivine(only in olivine basalt), magnetite, and ilmenite. The alkaline olivine basalt and olivine basalt are mainly composed of labrador-andesine, olivine, Ca-rich clinopyroxene, magnetite and ilmenite. But the tholeiitic basalts are chemically lower in (K_2O+NaO), LREE, P and Ti than the alkaline basalts.