Xuting granite is located in the Zanhuang Complex, western Zanhuang County, Hebei Province. It intrudes theNeoarchean TTG gneisses and metamorphic sequence as stocks, with a total area of 160km2. The pluton is not homogeneous and mainly consists of K-feldspar granite and monzonite in which rare melanocratic dioritic enclaves are present, but few xenoliths of the wall rocks have been observed. SHRIMP dating of zircon from the granite yielded an age of 2090 ± lOMa. The granite is high in SiO2( ＞75％ ) and K2O + Na2O (ALK=6.90％ ～8.75％) and low in Al2O3(10.32％～11.64％), TiO2(0.26％ ～0.36％), CaO (0.18％ ～ 0.48％), MgO (0.16％ ～0.40％) and Fe2O3T(2. 58％～3.46％), belonging to high K calc-alkaline series with metaluminous to slightly peraluminous feature. It is high in total REE contents (293. 8 × 10 -6 ～ 702. 8 × 10-6), and shows obvious negative Eu anomaly (Eu/Eu * = 0. 1 ～ 0. 35). In trace element distribution pattern diagram, the granite shows enrichment in large-ion lithophile (LIL) elements (Rb, Th and U) and depletion in Ti, Sr and P. In addition, it has high Rb/Sr and Ga/Al ratios of 1.45～ 7. 52 and 3. 04 ～ 10-6 ～4. 08 × 10-6. The rock has high εNd(t) value ranging from -14.29 to -0.29. The Xuting granite shows compositional characteristics of A-type granite formed by anatexis of the Neoarchean TTG with involvement of minor older materials in an extensional setting, probably resulted from the 2.1Ga basic magma underplating. Combined with regional data, the ~2. 1Ga metalkaline potassic granites in the Zanhuang, Fuping and Wutai regions were formed in an extensional setting in the North China Craton uniformed.%许亭花岗岩出露于赞皇杂岩中,位于河北省赞皇县西部山区,呈岩基状侵入新太古代TTG片麻岩和变质地层中,SHRIMP锆石U-Pb年龄为2090±10Ma.岩体主要由钾长-二长花岗岩组成,无暗色包体,偶见围岩的捕掳体.岩体组成不均匀,局部含石英和少量钾长石斑晶,构成似斑状结构.主要的矿物组合为石英+钾长石+斜长石+黑云母+绿帘石±白云母±角闪石,含萤石副矿物.岩石具有高硅(SiO2>75%)、富碱(ALK=6.90%-8.75%)、低铝(A12O3 =10.32%-11.64%)、钛(TiO2 =0.26%-0.36%)和贫钙(CaO =0.18%-0.48%),镁(MgO=0.16%-0.40%)、铁(Fe2OT3=2.58%-3.46%)的特征,为偏铝质到弱过铝质的高钾钙碱性系列.岩石的稀土总童较高(293.8x10-6～702.8x10-6),轻稀土相对富集,有明显的负Eu异常(Eu/Eu=0.1-0.35),微量元素中,富Zr、Nb和Y,而贫Ba、Sr和P等元素,Rb/Sr比值较高,介于1.45-7.52之间,平均4.31.岩石还具有高的Ga/AJ值(3.04×10-6～4.08×10-6),具有A型花岗岩特征.在同位素组成方面,具有较低的εNd(t)值(-14.29 ～-0.29,平均为-5.58).许亭花岗岩具有板内花岗岩特征,可能与2.1 Ga时岩浆板底垫托,导致新太古代TTG岩石部分熔融,并可能有少量古老地壳物质加入.根据岩体性质及岩石组合等特征推测赞皇、阜平、五台等地区的2.1 Ga岩浆活动形成于统一的拉张裂解环境.
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