花岗岩可否分离结晶,有堆晶花岗岩吗?——评学术界最近的一些争论

Can granite be formed by fractional crystallization?Is there any cumulate granite?Comment on some recent debates in academic circles

花岗岩能否分离结晶?世界上有没有堆晶花岗岩?这是学术界长期争论的问题。从近期发表的文献判断,上述争论已经从国际学术界转入国内学术界。国际学术界一直坚持花岗岩能够分离结晶,笔者一直持反对意见。最近,关于堆晶花岗岩的说法突然盛行起来。什么是堆晶岩?堆晶与堆积是一回事吗?斜长石是堆晶矿物吗?这些问题都是需要认真讨论的。众所周知,玄武岩有堆晶岩,花岗岩则主要呈晶粥状态出现,这是两种岩浆粘性不同的表现。花岗岩由于粘性大,晶出的矿物不能下沉,与其晶出的岩浆一起构成类似粥状的面貌,故称为“晶粥”。玄武岩粘性低,晶出的矿物可以下沉离开其结晶的部位在岩浆房底部堆积形成堆晶岩,故玄武岩不形成晶粥。花岗岩形成晶粥后,由于冷却、固结而不可能再次升温熔融造成“晶”与“粥”分离的可能。因此,关于上有高分异花岗岩(或流纹岩),下有堆晶的花岗岩的说法是不可能成立的。堆晶岩、堆晶结构等,统统是外国学者创造的。毋庸置疑,外国学者对花岗岩研究有很大的贡献,现今花岗岩理论的成果基本上都是外国学者提出来的,我们只是在学习、仿效和跟踪。然而,花岗岩研究中也有许多错误的理论、模型、假说,毫无疑问也是外国学者提出来的。面对上述情况,我们只有一个办法:独立思考。学习是必须的,但是,要批判地学,要仔细地鉴别,取其精华,去其糟粕。这样,我们才能更快地进步,才能不至于跟着外国学者犯错误。

Whether granite can be formed by fractional crystallization?Is there any cumulate granite in the world?This is a long?debated issue in academia.There have been some recent signs that the debate has shifted away from international academia and towards China,which has become the focus of international granite research in a way,and that I could not have imagined.The international academic community has always insisted that granite can be formed by fractional crystallization,I've always disagreed with that.Recently,there has been a lot of researches and papers about cumulate granite.Is this new and the academic frontier?Or is it old and a conservative concept?What is the definition of cumulate rocks?Is cumulation the same as aggregate?Can plagioclase cumulate?These are all issues that need to be seriously discussed.As is known to all,there are cumulate rocks in basalts,and granite is mainly in the state of crystal mush.This makes sense,as the two types of magma show different viscosities.Because of the high viscosity,the earlier crystallized minerals in the mush cannot settle down,so together with the magma as a mush,they move together.Once the mush has cooled and consolidated,there is no chance of heating up again and melting causing the crystal and magma to separate.Relatively,because of the low viscosity of basaltic magma,crystallized minerals can settle down to the bottom of the magma chamber from where they crystallized,so that cumulate rocks are common in basalts.Therefore,it is untenable to say that the upper part of the magma chamber forms highly differentiated granite and the lower part forms cumulate granite.Cumulate rocks and cumulate texture were proposed by foreigners.There is no doubt that foreigners have made great contributions to the study of granite.The achievements of modern granite theory are basically put forward by foreigners.We are just learning to imitate and follow up.However,there are many wrong theories,models and hypotheses in granite study,which is undoubtedly the problem of foreigners.How do we deal with this?There is only one way:think for yourself.It is necessary to study foreign countries,but we should study them critically,identify them carefully,take the essence and discard the dross.In this way,we can make progress faster and not make mistakes with foreigners.