岩石大地构造学说的兴起、没落与新生

在板块构造环境中形成的岩石组合(rock assemblages)被称为岩石大地构造组合(petrotectonic assemblages)。岩石大地构造学说创立于20世纪70~80年代,经历了兴起、没落与新生的曲折过程。研究表明,由Pearce等学者创立的岩石大地构造学说的理论基本正确,概括来说,洋中脊、洋岛和岛弧三大构造背景的源区是不同的,这是玄武岩判别图的理论基础。目前的情况是,三大构造背景源区不均一性可能比早先认为的更复杂。由于不同构造环境源区的复杂性,早先的玄武岩判别图采用的是抽样数据、典型地区、精确数据,显然不适合全球数据海量积累的情况,遂使玄武岩判别理论遇到了瓶颈。我们的研究发现,不同构造背景的所有岩石、矿物(包括玄武岩、苦橄岩、辉长岩、堆晶岩、橄榄石、单斜辉石、尖晶石等)几乎都保留了不同构造背景的“基因”信息,并且大多可采用大数据方法予以识别,遂使岩石大地构造学说焕发了青春。虽然本文提出了不同构造环境存在不同“基因”的假说,按照大数据方法判别的效果显著增加了。但是,这个不同构造背景的“基因”究竟是什么仍然不清楚。此外,上述“基因”假说的理论解释还非常不足,需要今后进一步探讨。

The Rise,Fall and Reborn of the Petrotectonic Theory

The rock assemblages formed in modern plate tectonic environments are called petrotectonic assemblages.Founded in the 1970s and 1980s,the theory has undergone a complicated process of rise,fall and reborn.This research showed that the theory of petrotectonics established by Pearce and other scholars is basically correct.In a word,the source areas of magmas in the three kind of tectonic settings including the mid-ocean ridge,oceanic island and island arc are substantially different.Indeed,the heterogeneity of the sources in the three tectonic settings may be much complex than previously thought of.Due to the complexity of source areas in the different tectonic settings and the fact that the diverse sampling protocols,regions,and accuracy of the data,the massive accumulation of global data may not suitable for basalt discrimination.Our study revealed that rocks as well as minerals within them(including basalt,picrite,gabbro,cumulate rocks,olivine,monoclinic pyroxene,spinel,etc.)may bear the“genes”of their tectonic settings,and big data method can be used to identify most of them.This may be a rebirth of the petrotectonic theory.Although specific“genes”for igneous rocks of different tectonic settings await further investigation,big data method can significantly improve the validity of geochemical discrimination.In addition,the theoretical explanation of the above gene hypothesis is still inadequate,and needs further investigation.