Further evidence for ∼8 kbar amphibolite facies metamorphism in the Marymia Inlier,Western Australia

Pressure estimates for amphibolite-facies metamorphism at Plutonic Gold Mine (Plutonic), Marymia Inlier, Western Australia, were recently revised significantly upwards from ～4 ± 2 kbar/550–600°C to ≥8 kbar/～600°C, based on the calculated stability fields for mineral assemblages in garnet-free mafic rocks. These conditions are anomalous in the context of the Yilgarn Craton. Here, we present new mineral equilibria calculations for rare garnet-bearing rock types from Plutonic that confirm those higher pressure estimates, and provide confidence that the determinations of metamorphic conditions based only on results from metamorphosed mafic rocks are robust and reliable. Taken together, the new estimates (7.3–8.2 kbar/580–590°C) from the garnet-bearing rocks, and the existing results from the mafic rocks, provide evidence that, most probably during the late Archean, rocks now exposed along the northern margin of the Yilgarn Craton underwent substantial increases in pressure, which was likely followed by rapid exhumation.     

长江上游安宁河流域主要生态环境地质问题及其效应

通过对安宁河流域生态环境地质现状全面深入地调查，结合大量前人资料和多时段的遥感解译成果综合研究，作者从区域稳定性问题、水土流失、泥石流、滑坡、水土污染、矿山开采、重大工程活动等方面系统全面地分析了安宁河流域存在的主要生态环境地质问题，并分析探讨了其产生的生态环境效应，阐明了地质环境条件对生态环境的影响和控制作用。为安宁河流域的生态地质环境合理开发与保护，以及流域经济可持续发展规划提供了科学依据。研究成果表明：安宁河并不安宁，流域新近构造活动强烈，泥石流、崩塌、滑坡、水土流失等多种外动力地质现象极为发育，不合理人类工程活动导致的生态环境地质问题也表现得十分突出，加强流域生态地质环境保护和恢复刻不容缓。