SHRIMP U-Pb zircon geochronology and Hf isotope analyses of Middle Permian–early triassic intrusions in southern Manzhouli area, Northeast China: implications for the subduction of Mongol-Okhotsk plate beneath the Erguna massif
SHRIMP U-Pb zircon geochronology and Hf isotope analyses of Middle Permian–early triassic intrusions in southern Manzhouli area, Northeast China: implications for the subduction of Mongol-Okhotsk plate beneath the Erguna massif
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DOI：
10.1080/00206814.2019.1622458
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发表时间：
2020-03
影响因子：
2.6
通讯作者：
Kui-Feng Mi;Zhicheng Lü;Tingjie Yan;Shengjin Zhao;Haifei Yu
中科院分区：
文献类型：
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作者：
Kui-Feng Mi;Zhicheng Lü;Tingjie Yan;Shengjin Zhao;Haifei Yu
满洲里地区南部三个花岗岩的SHRIMP U-Pb年龄和锆石原位Hf同位素研究结果，为认识蒙古-鄂霍次克板块向额尔古纳造山带俯冲的过程提供了新的资料。细颗粒二长花岗岩SHRIMP锆石U-Pb年代学结果为265.5Ma（中二叠世）。早-中三叠世岩石主要为花岗闪长岩（247.4 ± 4.6和249.3 ± 4.9Ma），花岗岩SiO2 = 60.0- 77.4wt.%，Al2O3 = 12.3-16.8wt.% Na_2O/K_2O = 0.7 ~ 1.9。在化学上，它们是偏铝质到过铝质的，属于高钾钙碱性系列。大离子亲石元素的富集（例如，Rb、Ba和K）和高场强元素（例如，Nb、Ta和Ti）是这些岩石类型的典型代表。二长花岗岩（~265 Ma）和花岗闪长岩（~247 Ma）含有锆石，εHf（t）值分别为6.3-8.5和5.1-7.9，分别得到888-752和958-774 Ma的TDM 2模式年龄。这些地球化学和锆石Hf同位素数据表明，中二叠世-早三叠世花岗岩的原生岩浆结晶于新元古代地壳物质生成的原生岩浆，形成于活动大陆边缘环境。葛格瑙堡组安山岩与伊豆-小笠原-马里亚纳弧相似，与俯冲起始有关。根据研究区安山岩和花岗岩类岩石的出露特征和锆石U-Pb年龄，推断蒙古-鄂霍次克板块俯冲至额尔古纳造山带之下的起始时间可能为早-中二叠世。
ABSTRACT The results of SHRIMP U-Pb ages and in situ Hf isotope of zircons from three granites in the southern Manzhouli region of northeast China, provide new data to understand the subduction process of Mongol-Okhotsk Plate beneath the Erguna massif. SHRIMP U-Pb zircon geochronology results yield an age of 265.5 Ma (middle Permian) for fine-grained monzogranite. Rocks from the Early–Middle Triassic are mainly granodiorite (247.4 ± 4.6 and 249.3 ± 4.9 Ma), the granites are with SiO2 = 60.0–77.4 wt.%, Al2O3 = 12.3–16.8wt.% and Na2O/K2O = 0.7–1.9. Chemically, they are metaluminous to peraluminous and belong to the high-K calc-alkaline series. Enrichments in the large ion lithophile elements (e.g., Rb, Ba, and K) and depletions in the high field strength elements (e.g., Nb, Ta, and Ti) are typical for these rock types. The monzogranite (~265 Ma) and granodiorite (~247 Ma) contain zircons with εHf(t) values of 6.3–8.5 and 5.1–7.9, yielding TDM2 model ages of 888–752 and 958–774 Ma, respectively. These geochemical and zircon Hf isotopic data indicate that primary magmas for Middle Permian–Early Triassic granites crystallized from primary magmas generated by Neoproterozoic crustal materials, formed in an active continental margin setting. The andesite of the Gegenaobao formation is similar with the Izu–Bonin–Mariana arc, relating to subduction initiation. Based on the characteristics of exposed rocks and zircon U-Pb ages of andesite and granitoid rocks in the study area, we conclude the onset subduction of Mongol-Okhotsk Plate beneath the Erguna massif may occur at early-middle Permian.