Characterising early Precambrian collisional orogens: A metamorphic perspective from the Lüliang Complex and the Trans-North China Orogen
Characterising early Precambrian collisional orogens: A metamorphic perspective from the Lüliang Complex and the Trans-North China Orogen
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DOI：
10.1016/j.earscirev.2023.104566
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发表时间：
2023-09
影响因子：
12.1
通讯作者：
Chengsen Lu;J. Qian;C. Yin;Jian Zhang;Peng Gao;Minjie Guo
中科院分区：
文献类型：
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作者：
Chengsen Lu;J. Qian;C. Yin;Jian Zhang;Peng Gao;Minjie Guo
华北横贯造山带是一个典型的古元古代大陆碰撞造山带，它见证了东西陆块拼合形成华北陆块的过程，可与世界上许多早前寒武纪碰撞造山带相媲美。吕梁杂岩是华北造山带的重要组成部分，由一系列绿片岩-麻粒岩相变质岩石组成，是研究华北造山带构造演化和揭示早前寒武纪碰撞造山带典型变质模式的理想靶区。在吕梁杂岩西北部采集了石榴角闪岩样品，以确定该地区的变质特征。对岩相学、矿物化学和相平衡模型的综合研究表明，岩石记录了顺时针P-T路径，热峰为8.5-9.5 kbar和800-860 °C。代表性样品的锆石U-Pb年龄为1901 ± 17 Ma。锆石的稀土元素配分模式为左斜型，重稀土元素富集，结晶温度较低，为614-695 °C，表明变质作用的退变质阶段。结合吕梁杂岩中其他地区的变质特征，可以推断吕梁杂岩经历了中压相系列变质作用，中部为绿片岩-角闪岩相，西北部和东南部为角闪岩-麻粒岩相。这种变质结构与恒山-五台-阜平地区以及TNCO中的其他杂岩相似，表明造山带的变质模式具有扇型特征，中部为中低品位岩石，两翼为中-高级岩石。综合TNCO的P-T-t数据反映，NCC中部存在一个漫长的（>100 Ma）造山演化，包括1.97-1.93（~1.95）Ga的主要地壳增厚，随后是1.92 - 1.85（1.80）Ga的隆升-冷却。通过与世界上其他造山带构造变质演化的对比，指出了前进变质作用和长寿命的P-T演化可能是早前寒武纪碰撞造山带的两个共同特征。
The Trans-North China Orogen (TNCO) is a typical Paleoproterozoic continental collisional orogen, which witnessed the amalgamation of the Eastern and Western blocks to form the North China Craton (NCC) and is comparable with many other early Precambrian collisional orogens in the world. As an important part of the TNCO, the Lüliang Complex comprises a series of greenschist to granulite facies metamorphosed rocks and is an ideal target for decoding the tectonic evolution of the TNCO and revealing the typical metamorphic pattern of early Precambrian collisional orogens. Garnet amphibolite samples were collected from the northwestern part of the Lüliang Complex to determine the metamorphic characteristic of the region. An integrated investigation of petrography, mineral chemistry and phase equilibria modelling suggests that the rocks have recorded clockwiseP–Tpaths with thermal peaks of 8.5–9.5 kbar and 800–860 °C. Zircon U-Pb dating of a representative sample yields a metamorphic age of 1901 ± 17 Ma. The zircon grains show left-inclined REE patterns with HREE enrichment and low crystallization temperatures of 614–695 °C, indicating that the obtained metamorphic age should represent the retrograde stage of metamorphism. Combined with the metamorphic characteristics of other regions in the Lüliang Complex, it can be inferred that the Lüliang Complex has experienced medium-pressure facies series metamorphism, with greenschist to amphibolite facies in the middle and amphibolite to granulite facies in the northwest and southeast. Such a metamorphic framework is similar with that in the Hengshan-Wutai-Fuping area as well as other complexes in the TNCO, indicating that the metamorphic pattern of the orogen is characterized by a fan shape, with low- to medium-grade rocks in the middle and medium- to high-grade rocks on the flanks. SynthesizedP–T–tdata from the TNCO reflect that there exists a protracted (>100 Ma) orogenic evolution in the central NCC, including a main crustal thickening at 1.97–1.93 (~1.95) Ga followed by uplifting-cooling from 1.92 to 1.85 (1.80) Ga. Comparison of tectono-metamorphic evolution between the TNCO and other cases in the world indicates that progressive metamorphism and long-livedP–T–tevolution may be two common characteristics for early Precambrian collisional orogens.