| 辽吉古元古代造山带的地层单元划分与构造属性 |
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| 关键词:North China Carton Paleoproterozoic Liao–Ji Orogen stratigraphic division back-arc basin |
| 基金项目:中国地质调查局地质调查项目“华北克拉通对哥伦比亚超大陆事件的响应与构造格架”(编号: 1212011120154);“华北克拉通变质基底构造分区及其对成矿作用的制约”(编号: 12120114034201); 国家自然科学基金重点项目(编号: 41430210) |
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| Stratigraphic Units and Tectonic Setting of the Paleoproterozoic Liao–Ji Orogen |
| Paleoproterozoic Liao–Ji orogen is located on the eastern margin of the North China Craton, and its sedimentary tectonic setting and stratigraphic framework are topics of much controversy. Recent studies indicate that the sedimentary environment of Paleoproterozoic Liao–Ji orogen was an active continental margin back-arc basin, which went through an evolutional process of early basin expansion and late contraction-orogeny. The lower North Liaohe Group (Lanzishan Formation and Lieryu Formation, including the Dataishan Formation of Laoling Group) and the lower South Liaohe Group (Lieryu Formation, including the Mayihe Formation of Jian Group) were formed in different tectonic environments simultaneously, the former was a suite of clastic sediments with a small amount of acidic volcanic rocks formed on the inland side of back-arc basin, whereas the latter was developed on the side of the magmatic arc with intense volcanism. The khondalite composed of the Ji'an Group (Huangchagou Formation and Dadongcha Formation) and the upper South Liaohe Group (Gaojiayu Formation and Dashiqiao Formation) was formed in an sedimentary environment similar to one of the fore-arc basin during contraction and subduction of the back-arc basin, which was subjected to ~1.9 Ga metamorphism and the intrusion of ~1.9 Ga garnet-bearing granite. The lower Dashiqiao Formation of North Liaohe Group in the Helan–Caohekou area, a metamorphic sedimentary formation composed of marble and mafic volcanic rocks, was formed also in a tectonic setting of back-arc basin, as shown by the fact that the metamorphic mafic volcanic rocks and metamorphic mafic dikes have geochemical characteristics of island-arc tholeiite. According to SHRIMP U-Pb zircon age (~1.87 Ga) of the tholeiite which is regarded as the magmatic crystallization age, the authors hold that the tholeiite was formed at the stage of back-arc basin contraction-subduction. Because the detrital zircons from the narrow sense Gaixian Formation and equivalent strata recorded plenty of Paleoproterozoic age information but only recorded less Archean information, the authors consider that the clastics were mainly from magmatic arc on the south side of Liao–Ji Orogen, and hence the Rangrim Block is basically a Paleoproterozoic magmatic arc rather than an Archean block. |
| WANG Hui-chu,REN Yun-wei,LU Song-nian,KANG Jian-li,CHU Hang,YU Hong-bin,ZHANG Chang-jie.2015.Stratigraphic Units and Tectonic Setting of the Paleoproterozoic Liao–Ji Orogen[J].Acta Geoscientica Sinica,36(5):583-598. |
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