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在甘肃北山勒巴泉一带赋存一套变质侵入岩。岩性主要为闪长质片麻岩、石英闪长质片麻岩、英云闪长质片麻岩、花岗闪长质片麻岩及二长花岗质片麻岩。Rb-Sr全岩等时线定年获得似斑状中细粒花岗闪长质片麻岩年龄值727±50Ma,锆石Pb-Pb定年获得中细粒花岗闪长质片麻岩年龄值766±49Ma,结合其与围岩的接触关系及强变形变质特征,形成时代为南华纪中晚期。其岩石地球化学特点为:岩石A12O3>CaO+Na2O+K2O,A/CNK=1.30~1.38,属过铝质类型;σ=2.08~3.78,NK/A=0.32~0.61,属钙碱性系列。在微量元素组成上,富集LREE和大离子亲石元素(LILE),而亏损HREE、高场强元素(Nb、Ta、Yb),Eu异常具弱—明显Eu负异常—弱的Eu正异常(δEu=0.24~1.20)。这些花岗岩类总体具有俯冲的构造背景,岩浆的产生可能与北山地区在新元古代末古陆壳裂解作用有关。
A metamorphic intrusive rock was hosted in Lebaquan, Beishan, Gansu Province. The main lithology is dioritic gneisses, quartz dioritic gneisses, dacite diorites, granodioritic gneiss and monzonitic granite gneiss. The Rb-Sr whole-rock isochronal dating attained the age of the fine-grained granodiorite gneiss of 727 ± 50 Ma and the age of fine grained granodiorite gneiss of Pb-Pb dating of 766 ± 49Ma, combined with its contact with the surrounding rock and strong deformation metamorphism, the formation of the South China Century Middle Age. Its lithogeochemical characteristics are as follows: rock A12O3> CaO + Na2O + K2O, A / CNK = 1.30-1.38, belonging to the peraluminous type; σ = 2.08-3.78 and NK / A = 0.32-0.61. In the trace element composition, LREE and LILE are enriched and depleted in HREE and high field strength elements (Nb, Ta, Yb), Eu anomaly is weak - obvious Eu anomaly - weak Eu positive anomaly (δEu = 0.24 ~ 1.20). These granites generally have subducted tectonic setting. The magmatic generation may be related to the late Neoproterozoic Paleo-continental crust faulting in the Beishan area.