大兴安岭北部诺敏河地区早石炭世A型花岗岩的年代学、地球化学及Hf同位素研究
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本文为中国地质调查局项目(编号DD20160047- 03)资助的成果。


The Early Carboniferous A- type granite in Nuominhe area,northern Da Hing’an Mountains:geochronology, geochemistry and Hf isotope studies
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    摘要:

    大兴安岭北部诺敏河地区碱长花岗岩锆石呈自形—半自形短柱状—板状,具有结构清晰的振荡生长环带和较高的Th/U比值(1. 10~2. 18),指示其为典型岩浆成因锆石。LA- ICP- MS U- Pb年代学研究显示岩石形成于早石炭世杜内期(352. 9 ± 3. 3 Ma)。岩石地球化学研究显示,岩石属于准铝质—弱过铝质高钾钙碱性岩石,富硅(SiO 2 =73. 25%~77. 01%)、富碱(Na 2 O+K 2 O=7. 72%~9. 48%)、富铁(Fe 2 O 3 =2. 06%~2. 97%,Fe 2 O 3 +FeO=2. 32%~3. 33%),贫镁(MgO=0. 08%~0. 26%)。根据强烈亏损Sr、Eu、Ba、Ti、P等元素,REE分布曲线为右倾式海鸥型和明显的Eu负异常( δ Eu=0. 26~0. 31)的岩石地球化学特征,判断碱长花岗岩属于A型花岗岩。锆石 176 Yb/ 177 Hf值为0. 03778~0. 133612, 176 Lu/ 177 Hf值为0. 001095~0. 004155, 176 Hf/ 177 Hf值为0. 282824~0. 282863。对应的锆石U- Pb年龄计算出锆石 ε Hf ( t )=8. 9~10. 6,一阶段Hf模式年龄为 t DM1 =560~658 Ma,两阶段Hf模式年龄 t DM2 =815~974 Ma,指示其源于新元古代源岩的部分熔融。与额尔古纳地块早石炭世A型花岗岩的对比表明,在兴蒙造山带东北部古亚洲洋盆的闭合发生在早石炭世;结合内蒙古中部地区古亚洲洋盆闭合时代为晚石炭世,表明古亚洲洋盆的闭合是东早西晚的“剪刀状”发展过程。

    Abstract:

    The zircons of alkali- feldspar granite in Nuominhe area, Northern Da Hing’an Mountains are self- shaped—semi- self- shaped short column—plate- like, with a well- structured oscillation growth zone and a high Th/U ratio (1.10~2.18). It is a typical magma- forming zircon. The LA- ICP- MS U- Pb geochronology study showed that the rock was formed in the Early Carboniferous Duinian period (352.9 ± 3.3 Ma). Rock geochemical studies show that the rock belongs to quasi- aluminum- weak aluminous high- potassium- calcium- alkaline rock, rich in silicon (SiO 2 =73.25%~77.01%), alkali- rich (Na 2 O+K 2 O=7. 72% ~9.48%), rich Iron (Fe 2 O 3 =2.06%~2.97%, Fe 2 O 3 + FeO=2.32%~3.33%), magnesium deficiency (MgO=0.08%~0.26%). Strongly depleted Sr, Eu, Ba, Ti, P and other elements, the REE distribution curve is right- winged seagull type and obvious Eu negative anomaly ( δ Eu=0.26~0.31), and the rock is judged to be A- type granite. Lu- Hf isotope analysis based on zircon U- Pb isotopic dating.The sample 176 Yb/ 177 Hf value was 0.03778~0.133612, the 176 Lu/ 177 Hf value was 0.001095~0.004155, and the 176 Hf/ 177 Hf value was 0. 282824~0.282863. The corresponding zircon U- Pb age calculated zircon ε Hf ( t )=8. 9 ~10.6, the first- stage Hf mode age was t DM1 =560~658 Ma, and the two- stage Hf mode age t DM2 =815~974 Ma, indicating that it originated from Partial melting of the Neoproterozoic source rocks. Our study and the development of the Early Carboniferous A- type granite in the Erguna block indicate that the closure of the Paleo- Asian ocean basin in the northeastern part of the Xingmeng orogenic belt occurred in the Early Carboniferous. Combined with the closure of the Paleo- Asian Ocean basin in the central part of Inner Mongolia, it is the Late Carboniferous, indicating that the closure of the ancient Asian ocean basin is a “scissor- like” development process in the east, west and west.

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吴子杰,汪洋,崔培龙,邱隆伟,王海鹏,仲米山.2020.大兴安岭北部诺敏河地区早石炭世A型花岗岩的年代学、地球化学及Hf同位素研究[J].地质学报,94(8):2200-2211.
WU Zijie, WANG Yang, CUI Peilong, QIU Longwei, WANG Haipeng, ZHONG Mishan.2020. The Early Carboniferous A- type granite in Nuominhe area, northern Da Hing’an Mountains:geochronology, geochemistry and Hf isotope studies[J]. Acta Geologica Sinica,94(8):2200-2211.

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  • 收稿日期:2019-07-08
  • 最后修改日期:2019-10-10
  • 录用日期:2019-12-17
  • 在线发布日期: 2019-12-17
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