Geochronology and geochemistry of Early Cretaceous granitic plutons in northern Great Xing’an Range, NE China, and implications for geodynamic setting
Geochronology and geochemistry of Early Cretaceous granitic plutons in northern Great Xing’an Range, NE China, and implications for geodynamic setting
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中国东北大兴安岭北部早白垩世花岗岩体的年代学和地球化学及其对地球动力学环境的影响
DOI：
10.1515/geo-2022-0422
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发表时间：
2022-01
期刊：
影响因子：
2
通讯作者：
Niangang Luo;Lian-feng Gao;Jing Zhang;Zhenguo Zhang;Junfei Wu;Jianyu Cui;Jie Xing
中科院分区：
文献类型：
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作者：
Niangang Luo;Lian-feng Gao;Jing Zhang;Zhenguo Zhang;Junfei Wu;Jianyu Cui;Jie Xing
摘要大兴安岭早白垩世花岗岩广泛分布。然而，它们的确切年龄和构造演化仍然存在争议。本文研究了大兴安岭北部兴安地块伊犁地区花岗质岩体的锆石U-Pb、Lu-Hf及全岩地球化学资料。研究的目的是破译大兴安岭晚中生代大规模岩浆活动的构造-热史，进一步认识大兴安岭晚中生代大规模岩浆活动的地球动力学背景。锆石U-Pb年龄测定表明，这些岩体形成于早白垩世，年龄为132.2 ~ 130.1 Ma。岩体具有相似的地球化学特征，SiO2、Na2O + K2O含量高，P2O5、CaO、MgO、TFe2O3含量低。岩体富集轻稀土元素和大离子亲石元素，贫重稀土元素和高场强元素。这些特征表明该岩体分选程度高，具有i型花岗岩亲和作用。结合岩体ε Hf(t)值为+ 5.25 ~ + 8.28，两阶段模式年龄（t DM2）为661 ~ 855 Ma，表明该区原生岩浆来源于新元古代积累的幼玄武质地壳物质的部分熔融。这些结果结合区域地质演化表明，大兴安岭北部早白垩世岩体的形成可能与蒙古-鄂霍次克洋闭合引起的碰撞后引力坍缩和随后的伸展密切相关。它们的形成还叠加了古太平洋俯冲板块收缩引起的弧后伸展。
Abstract Early Cretaceous granitic rocks are widely distributed in the Great Xing’an Range, northeast China. However, their precise age and tectonic evolution remain controversial. This study presents new zircon U–Pb, Lu–Hf, and whole-rock geochemical data for the granitic plutons in the Yili area, Xing’an Massif, northern Great Xing’an Range. The aim of this study was to decipher the tectono-thermal history and obtain further understanding of the geodynamic setting of the large-scale Late Mesozoic magmatism in the Great Xing’an Range. Zircon U–Pb age dating indicated that the plutons were emplaced during the Early Cretaceous, with ages of 132.2–130.1 Ma. The plutons showed similar geochemical features, characterized by high concentrations of SiO2 and Na2O + K2O and low concentrations of P2O5, CaO, MgO, and TFe2O3. The plutons were enriched in light rare earth elements and large ion lithophile elements and depleted in heavy earth elements and high-field-strength elements. Such features indicate that the plutons are highly fractionated with I-type granite affinity. These findings, combined with pluton ε Hf(t) values of + 5.25 to + 8.28 and two-stage model ages (t DM2) of 661–855 Ma, indicate that the primary magmas originated from partial melting of juvenile basaltic crustal material accreted during the Neoproterozoic. These results combined with regional geological evolution indicated that the generation of Early Cretaceous plutons in the northern Great Xing’an Range might be closely related to the post-collisional gravitational collapse and subsequent extension resulting from the closure of the Mongolia-Okhotsk Ocean. Their generation also superimposed the back-arc extension resulting from retraction of the Paleo-Pacific subduction plate.