岩墙群的岩石学、地球化学和几何学特征及其大地构造意义

对近几十年来岩墙群在构造环境、侵位模式、形成机制、岩相学、地球化学、同位素地质年代学、几何学和比较行星学等方面的研究成果进行了总结,为岩墙群的深入研究提供重要信息。岩墙群主要与伸展构造环境有关,是岩浆侵位事件(如地幔柱)造成上覆地壳形成裂隙系统,岩浆随后灌入而形成的。岩墙群的侵位模式主要有垂向和侧向两种,也可能是两种模式共同作用的结果。岩墙群的岩性多样,但主要是超基性-基性岩,说明其与深部岩浆作用密切相关。对岩墙群的地球化学研究可揭示岩浆事件的构造环境、岩浆演化过程以及源区特征。放射性岩墙群的几何学特征有重要的指示意义,其收敛中心被认为是地幔柱的中心位置。岩墙群是古陆重建十分重要的"契合点",对古陆重建研究十分有帮助。类地行星(金星)巨型放射状系统很可能是岩墙群系统,暗示了地球上也存在过这种完整的巨型放射状岩墙群系统。岩墙群对于古陆重建、地幔柱中心的指示、地幔源区示踪、火山机构以及区域岩浆演化的研究都有十分重要的意义,并将对地球科学的发展产生重要影响。

Petrological, geochemical and geometric characteristics of dyke swarms and their tectonic significance

Dyke swarms are important in geological investigation.In order to provide valuable information for future research,this paper summarized the multidisciplinary research conclusions about dyke swarms in such aspects as tectonic setting,emplacement mode,genetic mechanism,lithology,geochemistry,isotopic geochronology,geometry and comparative planetology.Dyke swarms were primarily formed in an extensional setting and resulted from magmatic emplacement along the fracture system in lithospheric crust which was caused by magmatic activities such as mantle plumes.The emplacement modes of dyke swarms are mainly vertical and lateral emplacements,and may also be the combination of these two emplacement modes.The lithologic characteristics are varied,with most of the dykes being ultrabasic-basic rocks,suggesting a significant relativity between dyke swarms and hypogene magmatism.The geochemical characteristics of dyke swarms show the tectonic environments,magmatic evolution and source types of magmatic events.Geometrical characteristics of radiating giant dyke swarms have important indicating significance and the center of radiating giant dyke swarms is considered to be the location of the head of mantle plumes.Dyke swarms are important ’piercing points’ and very helpful to the palaeocontinent reconstruction.The giant radiating system on the terrestrial planets(Venus) may be the dyke swarms and can imply that such a radiating system once existed in the earth.Dyke swarms have important research values and valuable geological significance in such aspects as paleocontinent reconstruction,implication of mantle plume center,tracing of mantle sources,volcanic edifices and evolvement of regional magmatism,thus playing a great role in geoscience.