壳-幔演化和板块俯冲作用过程中的硼同位素示踪

硼同位素是近年来发展起来的一门新兴的稳定同位素地球化学方法。硼有两个稳定同位素 :10 B和11B。硼同位素组成自然界变化十分大 ,δ11B值为 - 37‰～ +58‰。对地幔岩石的硼同位素研究表明 ,原始地幔的δ11B值为 - 10‰± 2‰ ,B的质量分数估算为 (0 2 5± 0 1)×10 -6。相对而言 ,地壳岩石的B含量和δ11B值均较高。由于壳、幔岩石具有不同的B含量和δ11B值 ,硼同位素已被广泛应用于研究壳幔演化和板块俯冲作用过程 ,用于示踪俯冲板块中大洋沉积物和蚀变洋壳在地幔中的循环。

BORON ISOTOPE AS A TRACER IN THE STUDY OF CRUST-MANTLE EVOLUTION AND SUBDUCTION PROCESSES

Boron isotope method is a recently developed innovative geochemical technique.Boron has two stable isotopes, 10 B and 11 B,and its ratio varies a lot in nature ( δ 11 B=-37‰～+58‰).The primitive mantle has a δ 11 B value of -10‰±2‰ with an estimated B content of (0 25±0 1)×10 -6 ,which is in sharp contrast with the crust rocks of higher B and δ 11 B values.Boron isotope has already been used in the study of crust\|mantle evolution and subduction processes,in particular as a sensitive tracer for the recycling of marine sediments and altered oceanic crust in the deep mantle.