昆明理工大学Xu, Xiao-Fei在燕永锋教授指导下，在研究扬子地块西南缘大红山群石榴石-黑云母片岩变质P-T条件及时代中取得新进展。相关论文于2024年5月5日发表在《地球化学学报》杂志上。

研究人员采用岩石学分析、相平衡模拟、锆石U-Pb定年相结合的研究方法，对大红山群老厂河组石榴子石—黑云母片岩进行了研究。片岩主要由石榴子石、黑云母、斜长石、石英、金红石、钛铁矿组成。相平衡模型揭示了8-9kbar和635-675℃的峰值变质条件。研究进一步整合石榴子石的进阶变质剖面和地温压结果，构建了顺时针的P-T变质演化路径，其中包括进阶阶段温度和压力的升高。

LA-ICP-MS锆石U-Pb定年和锆石Ti测温确定了峰后变质年龄为831.2±7.2 Ma。综合前人研究结果，扬子地块西南缘在新元古代(890-750 Ma)经历了一次与碰撞造山过程有关的大规模区域变质作用。这可能与罗迪尼亚超大陆后期的拼合有关，也可能与罗迪尼亚超大陆解体期间的局部挤压和俯冲作用有关。

据悉，大红山群位于扬子地块西南缘，是该区一个以变质程度较高为特征的地质单元。

附：英文原文

Title: Metamorphic P–T conditions and ages of garnet-biotite schists in the Dahongshan Group from the southwestern Yangtze Block

Author: Ma, Jun-xiao, Yang, Guang-shu, Yan, Yong-feng, Xu, Xiao-Fei, Ren, Yun-hua, Zhao, Hui, Zheng, Xiao-jun, Qin, Yuan

Issue&Volume: 2024-05-05

Abstract: The Dahongshan Group, situated at the southwestern margin of the Yangtze Block, represents a geological unit characterized by relatively high-grade metamorphism in the region. This paper investigates the garnet-biotite schist from the Laochanghe Formation of the Dahongshan Group, employing an integrated approach that includes petrological analysis, phase equilibrium modeling, and zircon U–Pb dating. The schist is mainly composed of garnet, biotite, plagioclase, quartz, rutile, and ilmenite. Phase equilibrium modeling revealed the peak metamorphic conditions of 8–9 kbar and 635–675 °C. By further integrating the prograde metamorphic profile of garnet and geothermobarometric results, a clockwise P–T metamorphic evolution path is constructed, which includes an increase in temperature and pressure during the prograde stage. LA–ICP–MS zircon U–Pb dating and zircon Ti thermometry constrains the post-peak metamorphic age of 831.2±7.2 Ma. Integrated with previously reported results, it is revealed that the southwestern margin of the Yangtze Block experienced a large-scale regional metamorphism during the Neoproterozoic (890–750 Ma), which is related to the collisional orogenic process. This may be associated with the late-stage assembly of the Rodinia supercontinent or with local compression and subduction processes during the breakup of the Rodinia supercontinent.

DOI: 10.1007/s11631-024-00693-3

Source: https://link.springer.com/article/10.1007/s11631-024-00693-3