五十年代以来,一般认为,从非碱性玄武岩质岩浆(拉斑玄武岩质岩浆)产生的偏长英质火成岩,根据其化学成分变化的特点,可有两种不同的类型。一种是,随着从镁铁质岩石向偏长英质岩石的过渡,SiO_2含量递增不明显,而 FeO(FeO 表示全铁量,以 FeO+0.9Fe_2O_3计)或 FeO/Mgo 值递增。另一种是,随着从镁铁质岩石向偏长英质岩石的过渡,SiO_2含量逐渐增大,而 FeO 含量逐渐减少。 Since the 1950s, it is generally believed that the late-type igneous igneous rocks from non-alkaline basaltic magmatic (tholeiitic basaltic magma) can be classified into two different types based on their chemical composition. One is that with the transition from mafic to overblown quartz, the content of SiO 2 increases little, but FeO (FeO means total Fe, FeO + 0.9Fe_2O_3) or FeO / Mgo increases. The other is that with the transition from mafic to overlying quartzitic rocks, the SiO 2 content gradually increases and the FeO content decreases gradually.