同位素填图与深部物质探测(Ⅰ):揭示岩石圈组成演变与地壳生长

Isotopic mapping and deep material probing (Ⅰ):revealing the compositional evolution of the lithosphere and crustal growth processes

固体地球科学的一个重要任务是探测地球深部过程与不同圈层协同演变。深部物质探测、地球物理结构探测和深钻一起构成深部探测的三大途径。岩浆岩“探针”及区域同位素(如全岩Nd、锆石Hf)示踪填图是深部物质探测的主要手段,可以用来揭示深部物质组成特征及时空变化,确定不同类型地壳省,划分大地构造边界,估算大陆地壳生长量、方式,分析区域成矿规律。这一技术广泛应用后,有望实现深部结构探测与物质探测结合,开展深部物质填图。中国大陆是深部物质探测的良好实验室,需要解决的重大问题包括:多块体拼合的岩石圈及陆壳深部物质组成架构,不同类型造山带地壳生长与深部物质组成结构,不同构造单元深部物质组成与成矿作用及其浅部成矿制约。文中重点总结和探讨了岩浆岩全岩Sr-Nd同位素和锆石Lu-Hf同位素区域填图以及捕获锆石信息填图的思路、方法和注意的问题,以及可以解决的重大地质问题,并探索性提出今后开展的重点研究方向。

One of the important tasks of solid-earth science is to detect deep earth processes and co-evolution of different layers.Deep material probing,geophysical structural probing and deep drilling are the three main approaches in deep-earth exploration."Magmatic rock probe"or lithospheric probe,and isotopic mapping (such as by whole rock Nd and zircon Hf) are powerful tools for deep material probing.This method has been used to reveal deep composition and structure and their spatio-temporal evolution,determine different crust provinces (ancient or juvenile),delineate terrane boundary,estimate mechanisms and degree of continental crust growth,and analyze regional metallogenesis.Their increasing application can lead to deep material mapping through a combination of deep structural and material probing.The Chinese mainland and adjacent areas are good testing ground for deep material probing.The major unsolved problems include compositions and structures of the lithosphere and continental crust made up of multiple blocks,crustal growth processes and compositions and structures of different types of orogenic belts,and compositions of different tectonic units and their constrains on mineralization.In this paper,we reviewed and discussed research ideas,methods and focuses related to regional isotopic mapping (using whole-rock SrNd and zircons Lu-Hf isotopic probes) and xenocrystic and inherited zircon mapping.We also discussed future key research areas and directions.