In previous study,the maric dikes in Hengshan-Xuanhua-Xinghe area of North China have been thought as the production of rifting and extension;some papers have already claimed that those mafic dikes may be sanukitouids.Therefore,the definition of those maric dikes is of important significance to distinguish the tectonic background of subduction or extensional tectonic background.The hand specimens of rocks in Hengshan-Xuanhua-Xinghe area have typical ophitic texture.The mafic dikes in Hengshan area are made up of pyroxene with amphibole-symplektite,idiomorphic plagioclase and garnet;the mafic dikes in Xinghe area consist of andesine,amphibole and the amphibole fills into the triangle "skeleton" which is made up of plagioclase;and the mafic dikes in Xuanhua area without obvious ophitic texture consist of garnet,plagioclase,clinopyroxene,orthopyroxene and amphibole.Compared with the geochemistry standard of sanukitoids,the samples in Hengshan and Xuanhua areas are rich in FeOT,MgO and TiO2,lightly rich in both compatible and incompatible elements,and what's more,the contents of light rare earth elements are much more than those of heavy rare earth elements.However,the samples in Xinghe area,which are very different from sanukitoids,are also rich in FeOT and TiO2,and richer in incompatible elements,but with lower Mg#,and the compatible elements are not that rich.Therefore,those mafic dikes in Hengshan-Xuanhua-Xinghe area of North China are not typical sanukitoids,but belong to the ferrobasalts.They have experienced a degree of fractional crystallization and crustal contamination,and may be the production of intraplate rifting.%在以往的研究中,华北恒山—宣化—兴和地区基性岩墙所代表的是一种裂解伸展构造背景,但近年来有研究提出这些基性岩墙可能为赞岐岩,代表了俯冲汇聚构造背景,因此,广泛出露于恒山—宣化—兴和地区的大量元古代基性岩墙是否为赞岐岩,对于明确该地区在古元古代是汇聚还是伸展构造背景具有重要科学意义.恒山—兴和—宣化地区岩石手标本可见典型的辉绿结构.恒山地区岩墙岩石主要由具角闪石后成合晶的辉石、自形的斜长石和石榴石组成;兴和地区岩墙岩石主要由角闪石和中性斜长石组成,角闪石填充在斜长石组成的三角形“骨架”中;宣化地区样品岩石薄片镜下无明显的辉绿结构,由石榴石、斜长石、单斜辉石、斜方辉石、角闪石组成.恒山、宣化地区样品岩石主量元素特征为高铁高镁富钛,略富集相容元素和不相容元素,且轻稀土元素较重稀土元素富集,与赞岐岩的地球化学标准不尽相似.兴和地区样品Mg#值偏低,但同样富铁富钛,更富集不相容元素,未见明显富集相容元素,与赞岐岩的地球化学标准相差较大.因此,华北恒山—宣化—兴和地区基性岩墙不属于赞岐岩,而为高铁玄武岩,且经历了一定程度的结晶分离作用和地壳混染作用,很可能属于板内裂解的产物.
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