Prograde metamorphism in the ~1.9 Ga Jiao–Liao–Ji orogenic belt of NE China Craton: implications for orogenic crustal thickening

The complete evolutionary process of orogenesis can be deciphered by studying metamorphic rocks at middle and lower crustal depths of orogens. Recent studies have suggested that granulite-facies metamorphic rocks in the Paleoproterozoic Jiao–Liao–Ji orogenic belt experienced clockwise pressure–temperature (<i>p</i>–<i>T</i>) paths. However, due to the effects of high temperature, the prograde metamorphic processes are poorly constrained. The question could be solved by studying the Barrovian series rocks, because some garnet growth zoning has been preserved in the lower grade rocks. A Barrovian series from garnet to kyanite-sillimanite zones has been recognized in the Liaodong Peninsula. Based on petrology and mineral chemistry, each metamorphic rocks in metamorphic zone are divided into prograde, peak, and retrograde metamorphic stages. Pseudosection modelling constrains the peak metamorphic conditions at ~568°C and ~5.8 kbar for the garnet zone, ~585°C and ~6 kbar for the staurolite zone, and ~670°C and ~8.2 kbar for the kyanite-sillimanite zone. All Barrovian series rocks have clockwise <i>p</i>–<i>T</i> paths, implying crustal thickening during prograde metamorphism. LA-ICP-MS monazite and zircon U–Pb dating suggest that peak Barrovian metamorphism occurred at ca. 1.92–1.91 Ga. Combining our results of the Barrovian series with studies on granulite-facies metamorphic rocks, we suggest that the Jiao–Liao–Ji belt experienced crustal thickening from 1.95 to 1.90 Ga, inducing Barrovian metamorphism and granulite-facies metamorphism in the middle and lower crust, respectively. Subsequently, rocks located at the different crustal levels were exhumed during post-orogenic extension.

通过对造山带中下地壳深度变质岩的研究，可解译造山作用的完整演化历程。近期研究表明，古元古代胶辽吉造山带（Jiao–Liao–Ji orogenic belt）内的麻粒岩相变质岩呈现顺时针压力-温度（p-T）轨迹。但受高温作用影响，其进变质作用过程的约束证据较为匮乏。针对巴罗式变质相系岩石（Barrovian series rocks）的研究可解决这一问题，因为低品级变质岩中保存有部分石榴石生长环带。辽东半岛已识别出从石榴石相至蓝晶石-矽线石相的巴罗式变质相系。基于岩石学与矿物化学分析，各变质相带内的变质岩可划分为进变质、峰期变质以及退变质三个阶段。伪截面模拟（pseudosection modelling）限定：石榴石相带的峰期变质条件约为568℃、5.8 kbar，十字石相带约为585℃、6 kbar，蓝晶石-矽线石相带约为670℃、8.2 kbar。所有巴罗式变质相系岩石均呈现顺时针p-T轨迹，指示进变质作用过程中发生了地壳增厚。激光剥蚀电感耦合等离子体质谱（LA-ICP-MS）独居石与锆石U-Pb定年结果显示，巴罗式峰期变质作用发生于约1.92~1.91 Ga。结合本次巴罗式变质相系研究成果与麻粒岩相变质岩相关研究，我们认为胶辽吉造山带在1.95~1.90 Ga期间经历了地壳增厚，分别于中下地壳引发巴罗式变质作用与麻粒岩相变质作用。随后，不同地壳深度的岩石在造山后伸展过程中发生折返。

搜集汇总

背景与挑战

背景概述

该数据集包含中国东北Jiao–Liao–Ji造山带约1.9 Ga前的变质岩石研究数据，通过岩石学、矿物化学和伪截面建模揭示了地壳增厚过程，并提供了独居石和锆石U–Pb测年数据，支持了从1.95到1.90 Ga的地壳演化模型。