揭示三维岩石圈物质架构的技术方法体系框架

The methodological framework for deciphering 3-demensional material architecture of the lithosphere

长期以来,岩石圈深部探测主要依赖地球物理手段和深部钻探,缺乏深部物质探测技术。对深部物质的了解也主要局限于两种途径:一类是地球物理推测方法,依据地表获得的深部岩石的物性测定,解释或推测深部物质的某些特征;另一类是捕虏体方法(Xenolith-based methodology),直接获取深部物质信息。本文重点探索的第三种途径,即充分利用地表出露的岩浆岩,通过岩石探针和同位素填图,示踪深部物源(物质)特征。特别是利用大数据分析和数字填图,了解深部物质三维架构及四维演变。在此基础上,总结上述三种途径,构建较完整的以岩石探针和同位素填图为核心的揭示岩石圈三维物质组成架构的方法体系。研究显示,在岩相学研究的基础上,通过系统开展Sr、Nd、Hf、Pb等多元同位素示踪填图,结合地球物理资料,可有效揭示岩石圈深部物质组成架构。通过中亚增生造山带(北疆)、青藏高原碰撞造山带(冈底斯-三江)和华北-扬子克拉通三个典型大地构造单元关键地区的实践,显示多元同位素示踪深部物质的一致性和有效性,以及同位素填图结果与地球物理探测结果的对应性。基于这些成果,笔者初步提出了揭示岩石圈三维物质组成架构的方法体系框架。该方法体系具有良好应用前景,有望成为与地球物理探测相结合和匹配的深部物质架构探测技术,为规范开展深部物质架构探测、物质演变过程及深部动力学过程研究提供技术支撑。

To date,our understanding concerning materials in the deep lithosphere relies primarily on two ways:(1)a geophysics-based methodology(in which geophysical features of deep components are speculated according to those of exposed rock);(2)a xenolith-based methodology.In this study,we explore the third way,a methodology that employs rock probe and multi-proxy isotopic mapping as the core.Combined with synthetical petrographic and petrogenetic studies on magmatic rocks derived from multiple sources at different depths,rock probe and multi-proxy isotopic mapping can be a suite of valuable tools in deciphering the 3-D lithospheric material architecture and its 4-D evolutionary history.Based on this,we attempt to incorporate the three methodologies into a novel methodological system for exploring the lithospheric material architecture.This will shed new light on the detection of the deep lithosphere.Previous studies have revealed that,based on petrographic observations,isotopic mapping by integrating Sr,Nd,Hf,Pb and other isotopes,combined with geophysical results,is capable of unraveling the material architecture of the deep lithosphere.These advances demonstrate the consistency and effectiveness of multi-proxy isotopic systems in tracing deep materials and the correspondence between the isotopic mapping and geophysical detection results.Therefore,we propose a methodological framework for deciphering the 3-D material architecture of the lithosphere.The application of this methodology in the Central Asian Orogenic Belt(accretionary orogen),Tibet Plateau(collisional orogen),and the North China and Yangtze cratons has yielded some encouraging advances,indicating the significant application potential of this methodology.The achievements documented in this paper suggest that a novel methodological system has been prepared for deciphering the deep lithospheric materials and elucidating the architectures of crust and mantle.