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北京裂谷北缘的赤城－古北口深断裂，是硅铝质（石英正长岩、富钾／环斑花岗岩）与铁镁质（斜长岩、辉长岩、辉绿岩）的双峰式深成岩带。Ｕ／Ｐｂ一致性年龄为１６９７±０．９Ｍａ，其岩石组合可与河北大庙斜长（辉长）岩－二长岩杂岩体类比，但铁镁质岩石较少。主体硅铝质岩石的富钾、富铁暗色矿物及钾质Ａ型花岗岩地球化学均与世界各地及密云沙厂环斑花岗岩一致。含铁橄榄石石英正长岩，代表了岩浆分离结晶初期还原条件下，太古代母岩派生的初始岩浆组成。该岩带的确定是将裂谷不同构造部位的四条东西向岩带与裂谷作用联系的关键。伴随裂谷作用拉张断裂向南呈台阶状断陷下沉，由隆起区向断陷区顺序形成了深成至浅成侵入，以至火山喷发的非造山岩浆活动。
The Chichen-Gubeikou deep fault in the northern margin of the Beijing Rift is a bimodal area of Si-Al (quartz syenite, potassium-enriched / annular granite) and mafic (plagioclase, gabbro, diabase) Deep plutonic belt. The U / Pb coincidence age is 1697 ± 0.9Ma. Its rock assemblage can be compared with the diaphanous (gabbro) -degranite complex in Hebei Daping, but less Fe-Mg rock. The potassium-rich, iron-rich dark-colored minerals and potash-type A-type granites of the host Si-Al rock are consistent with those from around the world and the Miyun Sand Factory. Fe olivine quartz syenite, representing the initial magma separation crystallization initial reduction conditions, the Archean parent rock derived initial magmatic composition. The identification of the rock zone is the key to the connection of the four east-west rock zones and the rifting in different structural parts of the rift. Along with rifting, extensional faults are stepped southward with step-like fault subsidence, and non-orogenic magmatism from deep to shallow intrusive to volcanic eruption is formed in sequence from uplifted area to fault-depression area.