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北京裂谷是古元古代晚期（１．８５～１．６０Ｇａ）在华北克拉通太古代基底上直接发育的初生夭折裂谷。Ｕ－Ｐｂ年龄表明，位于裂谷的断陷台阶至断陷中的四条平行的东西向岩带是同时的岩套。这包括北部大庙斜长（苏长）岩－纹长二长岩杂岩体（Ｓｍ－Ｎｄ１７３５Ｍａ）；赤城—古北口岩带的斜长岩、含橄石英正长岩（１６９７Ｍａ）及富钾和环斑花岗岩（１７０２～１６９６Ｍａ）；沙厂环斑花岗岩杂岩体（１７１５～１６８３Ｍａ）及南部平谷—蓟县火山岩带（１６２５Ｍａ）。在裂谷作用晚期诱发的双峰式岩浆活动具有被动式裂谷模式。大致与裂谷阶梯状向南断陷过程相配合的，从铁镁质向硅铝质岩浆转化的侵位序列及初始Ｓｒ０组成，反映了一个从地幔派生至下地壳深熔作用的连续熔融事件。以长期低Ｓｍ／Ｎｄ和Ｒｂ／Ｓｒ比及大为推迟的Ｐｂ同位素演化为特征的环斑花岗岩，具有一个纯粹的太古代母岩来源，在全球已知环斑花岗岩中是唯一不与古元古代造山地壳相联系的典型。在岩浆侵位前至少８００Ｍａ，其太古代母岩已从地幔分离出来，使本区成为非造山花岗岩的一个最佳实例。全部Ｓｍ／Ｎｄ比演化反映了极低部分熔融程度，不但双峰式岩石具显著钾质碱性地球化学特征，而且超钾质碱性火山岩在全球该岩
The rift in Beijing is a newborn premature rift developed directly on the Archean base of North China Craton in the late Paleoproterozoic (1.85 ~ 1.60Ga). The U-Pb ages indicate that the four parallel east-west stratigraphic rocks located in the rift-rift step to rift are contemporaneous rock sets. This includes the northern part of the Great Miaoping (Changchang) rock-monzogranite complex (Sm-Nd1735Ma) in the northern part of the Great Wall, plagiogranites in the Chicheng-Gubeikou belt, olivine syenite (1697Ma) And Ruanban granite (1702 ~ 1696Ma); the Shachang ringed granite complex (1715 ~ 1683Ma) and the Pinggu-Jixian volcanic belt (1625Ma) in the south. The bimodal magmatic activity induced late in rifting has a passive rift pattern. The emplacement sequence and initial Sr0 composition from the magnesian to sialon magmatic rocks, roughly in line with the southern rift ladder rifting process, reflects a continuous melting event derived from the mantle to the deep crust . Ringed granite, characterized by long-term low Sm / Nd and Rb / Sr ratios and greatly delayed Pb isotopic evolution, has a pure source of Archean origin and is uniquely not associated with ancient yuan Typical of the relationship between ancient orogenic crust. At least 800 Ma prior to the emplacement of the magma, its Archean mother rock has been separated from the mantle, making the area a non-orogenic granite a best example. The whole Sm / Nd ratio evolution reflects the very low degree of partial melting. Not only the bimodal rocks have significant potassic alkaline geochemical characteristics, but also the ultra-potassic alkaline volcanic rocks in the world