In-situ monazite geochronology with modelling of Barrovian-type metasediments was carried in the Burd Gol zone, NE Baidrag block. The peak recorded by Grt−Sil migmatite is ∼780 °C, 7.5 kbar; by Grt–St–Ky gneiss ∼690 °C, 10 kbar and by Grt schist ∼590 °C, 8 kbar. Monazite ages related to metamorphic peaks indicate diachronous burial events, c. 570–565 Ma for the Grt–Sil migmatite, c. 565–560 Ma for the Grt–St–Ky gneiss, and at c. 538 Ma for the Grt schist. Tonian Grt–St schist recorded new monazite crystallization at c. 546–543 Ma. By c. 545–542 Ma, the Grt–Sil migmatite and Grt–St–Ky gneiss experienced exhumation to ∼5 kbar, while the Grt schist underwent burial. Further exhumation is dated by xenotime, rutile and monazite alteration down to c. 515 Ma. The data suggest a prolonged orogenic cycle initiated by burial of distal orogenic core to the depths of ∼35 km at c. 570–565 Ma while the proximal continental margin was buried at c. 545–538 Ma. The higher-grade core was subsequently exhumed to the middle crust at c. 550–540 Ma and the orogenic activity ceased at c. 515 Ma. The difference in metamorphic gradients around 570–560 Ma, with ∼27–28 °C/km for the Grt–Sil migmatite and ∼18–19 °C/km for the Grt–St–Ky gneiss suggests lateral variations as a result of localized juxtaposition of migmatite-magmatite lower-middle crust with colder regions. A new model shows the Burd Gol zone as a progressively thickened and exhumed continental back-arc system beneath the supracrustal 590–570 Ma continental back-arc represented by the adjacent Ulziit Gol unit. The data provide important constraint on the timing and mechanisms of orogenic Baikal cycle at the margin of the Siberian Craton.

中文翻译：

---

大陆弧后的超俯冲增厚：拜德拉格地块东北部的埃迪卡拉纪-早寒武世（贝加尔纪）变质作用（蒙古拼贴画）


在 Baidrag 地块东北部的 Burd Gol 地区进行了原位独居石地质年代学研究，并模拟了巴罗夫型变质沉积岩。 Grt−Sil 混合岩记录的峰值为 ∼780 °C, 7.5 kbar； Grt–St–Ky 片麻岩 ∼690 °C, 10 kbar 和 Grt 片岩 ∼590 °C, 8 kbar。与变质峰相关的独居石年龄表明了历时埋藏事件，c。 Grt-Sil 混合岩，约 570–565 Ma，c. Grt-St-Ky 片麻岩为 565–560 Ma，c. 538 Ma为Grt片岩。 Tonian Grt-St片岩在c.记录了新的独居石结晶。 546–543 马。由c。 545–542 Ma，Grt-Sil 混合岩和 Grt-St-Ky 片麻岩经历了剥露至 ∼5 kbar，而 Grt 片岩经历了埋藏。进一步的挖掘工作通过磷钇矿、金红石和独居石蚀变来确定年代，可追溯到公元 100 年。 515马。数据表明，由远端造山核心埋藏至大约 35 公里深处而引发了一个延长的造山周期。 570–565 Ma，而近端大陆边缘被埋藏于 c. 545–538 马。随后，较高品位的岩心在 c 时被挖掘到中地壳。 550–540 Ma，造山活动在 c. 停止。 515马。 570-560 Ma 左右的变质梯度差异，Grt-Sil 混合岩为 ∼27-28 °C/km，Grt-St-Ky 片麻岩为 ∼18-19 °C/km，这表明横向变化是由于混合岩-岩浆岩中下地壳与较冷地区的局部并置。一个新模型显示，Burd Gol 地带是一个在表层 590-570 Ma 大陆弧后（以邻近的 Ulziit Gol 单元为代表）下方逐渐增厚和挖出的大陆弧后系统。这些数据对西伯利亚克拉通边缘造山贝加尔旋回的时间和机制提供了重要的约束。