Two alkaline plutons occurred in the eastern part of Guyang County, Inner Mongolia. Recent Isotopic chronology study shows that two alkaline plutons formed respectively at the Early Mesoproterozoic and Early ( -Middle ) Devonian, the zircon SHRIMP U-Pb age of the Wayao quartz-syenite is 1702 ± 32Ma (2σ) , and of the Gaojiacun syenite is 399 ± 7. 4Ma ( 2σ) . The Wayao quartz-syenite are characterized by low Ca, Sr, and High ratios of Rb/Sr, TiO2/MgO, FeOT/MgO and Ga/Al, low ratio of Sm/Nd and 143Nd/ 144 Nd, with a negative Eu-anomaly and negative εNd(t) ( -6. 2 ~ -6. 5), which indicate the quartz-syenite similar to the aluminous A-type granite and derived from the partial melting of upper crust under extensional tectonic setting. The Gaojiacun syenite have high alkali content (K2O + Na2O = 10. 92% -11.67%) , low Rb/Sr ratio and relatively low Sm/Nd and !43Nd/144Nd ratios, with positive Sr-anomaly, weak positive Eu-anomaly and negative εNd(t) ( - 14. 4 ~ - 14. 9) , which imply the magma of the syenite derived from deep crust, and formed in the early stage of post-orogenic collapse. The emplaced time of two alkaline plutons correspond respectively with of the Mesoproterozoic anorogenic igneous suite (anorthosites-syenite-rapakivi granites) and Late-Paleozoic Shuiquangou syenite in the northern part of Hebei Province, that display two alkaline intrusion belt extending to hundreds of kilometers on the northern margin of North China Craton. The Mesoproterozoic alkaline intrusion belt indicates the rifting event after assembly of North China Craton at Late-Paleoproterozoic, the one of Early (-Middle) Devonian implies the post-collisional extension event after the Early-Paleozoic arc-continental collision in the northern margin of North China Craton.%在内蒙古固阳县东部出露了两个碱性岩体,最近的年代学研究显示这两个碱性侵入体分别形成于中元古代早期和晚古生代早期,瓦窑石英正长岩的锆石SHRIMP U-Pb年龄为1702±32Ma,高家村角闪正长岩的SHRIMP年龄为399±7Ma,TIMS法锆石U-Pb为389.9 ±4.7Ma.瓦窑石英正长岩相对贫Ca、贫Sr、高TiO2/MgO和FeOT/MgO、高Ga/A1,Eu负异常；岩石高87 Sr/86 Sr比值、低143Nd/144 Nd比值、εNd(t)为-6.2～ -6.5,地球化学特点显示铝质“A”型花岗岩性质,岩浆源区为大陆上部地壳,是拉张低压背景下部分熔融的产物.高家村角闪正长岩高碱(K2O+ Na2O为10.92％～ 11.67％),Sr正异常,弱正铕异常,具有较低的87 St/86 Sr比值、适中的143Nd/144 Nd比值,εNd(t)为-14.4～ -14.9,具有高压型正长岩的特征,岩石应形成于大陆下部地壳,属后造山崩塌早期阶段的产物.这两个岩体的形成时代分别与冀北地区的中元古代非造山岩浆岩组合(斜长岩-正长岩-环斑花岗岩组合)和晚古生代的水泉沟正长岩相对应,有可能构成华北克拉通北缘两条延伸数百千米的碱性侵入岩带.中元古代早期的碱性侵入岩带代表着华北克拉通在古元古代末汇聚造山后的裂解事件；而早(-中)泥盆世的碱性侵入岩带则代表着华北克拉通北缘早古生代末弧-陆拼合造山后的伸展事件.
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