In recent years there has been growing interest in the investigation of dyke emplacement processes, not only because dykes represent former conduits of magma from deeper levels of the Earth to the surface but also because dyke swarms give information about tectonic processes that deformed the lithosphere (Hou, et al., 2005). The flow of magma inside fractures is one issue of basic importance in understanding how continental swarms developed (Raposo, 1995). Magma flow directions are traditionally investigated by petrographic fabric, oriented vesicles and fingers, grooves or lineations.
Figure 1. Geological map of Western Shandong
Geological map of Western Shandong, EB of the NCC (compiled from Hou et al., 2005). Insets show the distribution of the Precambrian mafic dyke swarms of the NCC (compiled from Hou et al., 2006a)
As the other main cratons on earth, Precambrian mafic dyke swarms extensively occur in the NCC (Figure 1). They record regional rifting events and provide useful information for paleocontinental reconstruction and for the rotation of cratonic blocks (Hou, et al., 2006a). The NCC is composed of three Archean tectonic units: the Eastern Block (EB), the Western Block (WB), and the Central Orogenic Belt (COB) (Kusky and Li., 2003). Dyke swarms in the northern Shanxi and Luliang areas, WB have been researched variously, while those in the western Shandong, EB have not been researched enough.