Early Mesozoic subduction of the Mongol‐Okhotsk Ocean and its effect on the central Great Xing'an Range: Insights from the monzodiorite in the Erdaohe deposit,Geological Journal

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Early Mesozoic subduction of the Mongol‐Okhotsk Ocean and its effect on the central Great Xing'an Range: Insights from the monzodiorite in the Erdaohe deposit
Geological Journal ( IF 1.4 ) Pub Date : 2020-10-11 , DOI: 10.1002/gj.4002
Jun‐Sheng Yang ₁ , Xin‐Biao Lü _{1,

2} , Min‐Shan Gun _{2,

3} , Chao Chen ₁

Affiliation

Stuck in the middle of the Mongol‐Okhotsk Ocean and the Palaeo‐Asian Ocean, the tectonic background of the Great Xing'an Range is ambiguous, especially with the tectonic transition in Early Mesozoic. Previous studies showed a major influence by the closure of the Palaeo‐Asian Ocean and the onset of the Mongol‐Okhotsk Ocean subduction on the southern and northern part of the Great Xing'an Range, respectively. However, the Early Mesozoic tectonic setting of the central Great Xing'an Range still needs further discussion. New zircon ages, whole‐rock geochemical data for monzodiorite in the Erdaohe deposit, central Great Xing'an Range, are presented. Zircon U–Pb dating yields a Triassic age of 226 Ma. Monzodiorite displays metaluminous and high‐K calc‐alkaline affinity evidenced by petrologic and geochemical studies. A mixed source of juvenile lower crust with mantle material of the monzodiorite is indicated by its high Mg^# (44–61), low SiO₂ (50–53 wt%) contents, depletion in Nb and Ta, positive ε_Nd(t) (+2.5 ± 3.0) and zircon ε_Hf(t) (+6.8 ± 8.9), and low I_Sr values (0.70322–0.70432). Our new geochronological and geochemical data with compiled data of previous research on magmatism from the Xing'an Block and adjacent areas indicate new insights into the Triassic tectonic evolution of the central Great Xing'an Range. The Triassic magmatism in this region is intimately associated with the flat‐slab subduction and slab break‐off of the Mongol‐Okhotsk Ocean.

中文翻译：

蒙古鄂霍次克海早期中生代俯冲及其对大兴安岭中部的影响：二道河矿床的辉闪闪岩的见解

大兴安岭地陷在蒙古鄂霍次克海和古亚洲洋之间，特别是中早生代的构造过渡。先前的研究表明，古亚洲洋的关闭和蒙古-鄂霍次克海俯冲作用分别在大兴安岭的南部和北部产生了重大影响。然而，大兴安岭中部的早中生代构造环境仍需进一步讨论。给出了大兴安岭中部二道河矿床的新锆石年龄，全闪闪岩的全岩石地球化学数据。锆石U–Pb测年产生的三叠纪年龄为226 Ma。岩石和地球化学研究表明，Mondiodiorite具有金属和高K的钙碱性亲和力。^＃（44-61），低的SiO ₂（50-53重量％）的含量，在耗尽Nb和Ta，正ε_钕（吨）（2.5±3.0）和锆石ε_铪（吨）（6.8±8.9），并且I _Sr值较低（0.70322-0.70432）。我们的新的地球化学和地球化学数据，加上以前对兴安地块及邻近地区岩浆作用研究的数据汇编，表明对兴安大中部山脉的三叠纪构造演化有了新的认识。该地区的三叠纪岩浆作用与蒙古-鄂霍次克海的平板俯冲和平板断裂密切相关。

更新日期：2020-10-11

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