玄武岩类形成的大地构造环境的Th/Hf-Ta/Hf图解判别

Th/Hf-Ta/Hf identification of tectonic setting of basalts.

Th,Ta,Hf是一组耐熔强亲岩浆元素 ,由于地球化学性质的相似性 ,其相互之间的比值关系能将深部作用的地球化学过程较好地恢复出来。玄武岩类 ,特别是原始玄武岩浆形成的岩石的 Ta/ Hf及 Th/ Hf比值 ,能较好地反映其源区的 Th、Ta、Hf之间的分异特征 ,在一般情况下 ,这一特征与某种确定的大地构造环境有密切关系和确定的因果联系 ,可用来判别玄武岩类形成的大地构造环境及其源区 Th、Ta、Hf分异特征。本文根据典型大地构造环境玄武岩类的 Th、Ta、Hf数据 ,提出了玄武岩类形成的大地构造环境判别的 Th/ Hf- Ta/

Th, Ta and Hf are refractory strong magmatophile elements. Because that the geochemical behavior of Th, Ta and Hf is similar during magmatic action, the ratios of Th, Ta and Hf could restore processes of mantle partial, magmatic fractional crystallization, mantle fractionation and so on. The Th/Hf and Ta/Hf ratios of basalts, especially primary one, reflect the differentiation of Th, Ta and Hf of its source region. In general, there is a close relationship between these characteristics and tectonic setting. Based on the ratios among Th, Ta and Hf of basalts formed from typical tectonic setting of the world, we propose a new tectonic identification scheme of basalts on the Th/Hf and Ta/Hf double logarithmic plot. Key words Basalt, Tectonic setting, Th/Hf-Ta/Hf identification diagram.