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大兴安岭地区晚中生代的大地构造背景一直存在争议,通过对内蒙古巴林右旗胡都格绍荣岩体进行锆石U-Pb测年、岩石地球化学以及锆石Lu-Hf同位素分析,探讨其形成时代及构造背景.胡都格绍荣岩体主体岩性为似斑状黑云母二长花岗岩,LA-ICP-MS锆石U-Pb测年确定其加权平均年龄为129.9±1.4Ma(MSWD=0.91),指示其侵位于早白垩世.花岗岩具有高SiO_2、Na_2O、K_2O含量,低CaO、MgO含量,富集Cs、Rb、K、Th、U、Zr,亏损Ba、Sr、P、Ti,轻稀土富集,具明显Eu负异常(δEu=0.35~0.44),10 000×[w(Ga)/w(Al)]为2.08~3.05,表明其为典型的A型花岗岩.Hf同位素分析结果显示,锆石具有正的ε_(Hf)(t)值(2.24~9.41),Hf两阶段模式年龄为1 030~570Ma,平均为809Ma,结合其微量元素特征,认为岩浆来源于新元古代地壳的部分熔融.胡都格绍荣花岗岩指示研究区在早白垩世为伸展构造背景,可能与蒙古-鄂霍茨克洋闭合关系更为密切.
The Mesozoic tectonic setting in the Daxinganling area has been controversial for a long time. Based on U-Pb zircon dating, lithogeochemistry and Lu-Hf isotopic analysis of zircons from the Hudugeshurong in Balin You Banner, Inner Mongolia, And tectonic setting.The lithology of the Hudu Geshao rond body is plagioclase-biotite monzogranite, and its weighted average dating age is 129.9 ± 1.4Ma (MSWD = 0.91) by LA-ICP-MS zircon U-Pb dating. , Indicating that they invaded the Early Cretaceous.The granites have high content of SiO_2, Na_2O, K_2O, low content of CaO and MgO, enrichment of Cs, Rb, K, Th, U, Zr, loss of Ba, Sr, P, Ti, (ΔEu = 0.35 ~ 0.44) and 10 000 × [w (Ga) / w (Al)] ranged from 2.08 to 3.05, indicating that it is a typical A-type granite.The results of Hf isotope analysis show that, Zircon has a positive ε_ (Hf) (t) value (2.24 ~ 9.41). The Hf two-stage model has an age of 1030 ~ 570Ma and an average of 809Ma. Combined with its trace element characteristics, the magma is thought to be derived from part of the Neoproterozoic crust Melting. The Hudu Geshurong granite indicates that the study area was an extensional tectonic setting during the Early Cretaceous and may be more closely related to the Mongolia-Okhotsk Ocean.