古元古代全球静寂期岩浆活动——以华北克拉通南缘中条山~2.3 Ga横岭关花岗岩为例

The Magmatic Activity in Paleoproterozoic Global Magmatic Quiescence: Take the ~2.3 Ga Henglingguan Granites from Zhongtiao Mountains in the Southern North China Craton as an Example

在全球岩浆活动静寂期,人们在华北克拉通内相继识别出大量~2.3 Ga的地质体,对探讨华北克拉通古元古代地质演化过程具有十分重要的意义.选择中条山地区横岭关二长花岗岩进行了地球化学、锆石U-Pb年代学和Hf同位素研究.横岭关二长花岗岩LA-ICPMS锆石U-Pb年龄结果为2 308±12 Ma,代表岩体的形成时代.横岭关二长花岗岩高硅、高钾、高铝、富碱,贫钙、低钠和低钛,A/CNK主要集中在1.0~1.1之间,为高钾钙碱性偏铝-过铝质花岗岩系列.岩石的稀土元素含量相对高,轻重稀土元素分异强烈,并具有明显的Eu负异常.高场强元素Nb、Ta、Zr、Hf、U和大离子亲石元素Rb等相对富集,亏损V、Cr、Co、Ni等相容元素,具有I型花岗岩的特征.横岭关二长花岗岩锆石εHf(t)为0.52~6.24,平均值为2.06,单阶段和两阶段模式年龄分别为2 419~2 642 Ma和2 438~2 738 Ma.横岭关二长花岗岩具有同碰撞花岗岩的特征,推测来源于~2.5 Ga古老地壳岩石在挤压碰撞环境下的部分熔融,揭示了华北克拉通在古元古代全球岩浆静寂期并不静寂.

A large number of ~2.3 Ga geologic bodies have been identified in the North China Craton(NCC) in global magmatic quiescence, which is vital for unveiling the Paleoproterozoic geological evolution on the NCC. This paper presents the whole rock geochemical data, zircon U-Pb ages and Hf isotopes of the Henglingguan monzogranite in Zhongtiao mountains area. LA-ICPMS dating of zircon from the Henglingguan monzogranite yields an age of 2 308±12 Ma. The Henglingguan monzogranite is high in SiO2, K2O, Al2O3 and alkali, and low in CaO, NaO and TiO2, with A/CNK concentrated between 1.0 and 1.1, which belongs to high-K calc-alkaline and metaluminous-peraluminous series. The monzogranite is high in total REE contents, showing strong fractionation of LREE and HREE and obvious negative Eu anomaly. As to the trace elements, the monzogranite shows enrichment in Nb, Ta, Zr, Hf, U and Rb, and depletion in V, Cr, Co and Ni, which is consistent with characteristics of I-type granite. Zircons in the Henglingguan monzogranite have εHf(t) values ranging from 0.52 to 6.24, with an average of 2.06, and Hf model TDM1 age of 2 419-2 642 Ma and TDM2 age of 2 438-2 738 Ma. The Henglingguan monzogranite shows the features of syncollision granites originated from partial melting of the ~2.5 Ga ancient crust in collision environment, which shows the NCC was not quiet during the Paleoproterozoic global magmatic quiescence.