The final assembly of the Mesoproterozoic supercontinent Nuna was marked by the collision of Laurentia and Australia at 1.60 Ga, which is recorded in the Georgetown Inlier of NE Australia. Here, we decipher the metamorphic evolution of this final Nuna collisional event using petrostructural analysis, major and trace element compositions of key minerals, thermodynamic modelling, and multi‐method geochronology. The Georgetown Inlier is characterised by deformed and metamorphosed 1.70–1.62 Ga sedimentary and mafic rocks, which were intruded by c. 1.56 Ga old S‐type granites. Garnet Lu–Hf and monazite U–Pb isotopic analyses distinguish two major metamorphic events (M1 at c. 1.60 Ga and M2 at c. 1.55 Ga), which allows at least two composite fabrics to be identified at the regional scale—c. 1.60 Ga S1 (consisting in fabrics S1a and S1b) and c. 1.55 Ga S2 (including fabrics S2a and S2b). Also, three tectono‐metamorphic domains are distinguished: (a) the western domain, with S1 defined by low‐P (LP) greenschist facies assemblages; (b) the central domain, where S1 fabric is preserved as medium‐P (MP) amphibolite facies relicts, and locally as inclusion trails in garnet wrapped by the regionally dominant low‐P amphibolite facies S2 fabric; and (c) the eastern domain dominated by upper amphibolite to granulite facies S2 foliation. In the central domain, 1.60 Ga MP–medium‐T (MT) metamorphism (M1) developed within the staurolite–garnet stability field, with conditions ranging from 530–550°C at 6–7 kbar (garnet cores) to 620–650°C at 8–9 kbar (garnet rims), and it is associated with S1 fabric. The onset of 1.55 Ga LP–high‐T (HT) metamorphism (M2) is marked by replacement of staurolite by andalusite (M2a/D2a), which was subsequently pseudomorphed by sillimanite (M2b/D2b) where granite and migmatite are abundant. P–T conditions ranged from 600 to 680°C and 4–6 kbar for the M2b sillimanite stage. 1.60 Ga garnet relicts within the S2 foliation highlight the progressive obliteration of the S1 fabric by regional S2 in the central zone during peak M2 metamorphism. In the eastern migmatitic complex, partial melting of paragneiss and amphibolite occurred syn‐ to post‐ S2, at 730–770°C and 6–8 kbar, and at 750–790°C and 6 kbar, respectively. The pressure–temperature–deformation–time paths reconstructed for the Georgetown Inlier suggest a c. 1.60 Ga M1/D1 event recorded under greenschist facies conditions in the western domain and under medium‐P and medium‐T conditions in the central domain. This event was followed by the regional 1.56–1.54 Ga low‐P and high‐T phase (M2/D2), extensively recorded in the central and eastern domains. Decompression between these two metamorphic events is ascribed to an episode of exhumation. The two‐stage evolution supports the previous hypothesis that the Georgetown Inlier preserves continental collisional and subsequent thermal perturbation associated with granite emplacement.

中文翻译：

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多个P–T–d–t路径揭示了澳大利亚东北部最终努纳议会的演变

中古生代超大陆努纳的最终组装以劳伦西亚和澳大利亚在1.60 Ga处发生的碰撞为标志，这在澳大利亚东北部的乔治敦Inlier记录。在这里，我们使用岩石结构分析，关键矿物的主要和微量元素组成，热力学模拟以及多方法地质年代学，来解释最后的努纳河碰撞事件的变质演化。乔治敦Inlier的特征是变形和变质的1.70–1.62 Ga沉积岩和镁铁质岩，被c侵入。1.56 Ga老的S型花岗岩。石榴石路-Hf和独居石的U Pb同位素分析区分两种主要变质事件（M1在Ç。1.60 Ga和M2在Ç。1.55 Ga），这样至少可以在区域范围内识别出两种复合面料-c。1.60 Ga S1（由织物S1a和S1b组成）和c。1.55 Ga S2（包括织物S2a和S2b）。此外，还区分了三个构造变质域：（a）西部域，S1由低磷（LP）绿片岩相组合定义；（b）中央区域，其中S1织物保留为中P（MP）角闪石相遗迹，局部保留在石榴石中的包裹痕迹中，被区域优势低磷包裹闪石相S2织物; （c）东部地区以上两面闪石为主，至粒相S2片层。在中央结构域，1.60镓MP-介质-T（MT）变质（M1）的十字石石榴石稳定性领域内开发，与条件范围从530 - 550℃，在6 - 7千巴（石榴石芯）到620 - 650在8 – 9 kbar（石榴石边缘）下为°C ，它与S1织物相关。1.55 Ga LP–高T（HT）变质作用（M2）的开始是用红柱石（M2a / D2a）代替星形石，随后由硅线石（M2b / D2b）伪变质，那里有大量花岗岩和蒙脱石。M2b硅线石阶段的P–T条件范围为600至680°C和4–6 kbar。S2叶片内的1.60 Ga石榴石遗迹突出显示了在M2高峰期变质过程中，中央区域的S2逐渐消灭了S1织物。在东部混合岩复杂，副片麻岩和闪岩的部分熔融发生顺后- S2，在730-770℃下和6-8千巴，并在750-790℃下和6千巴，分别。为Georgetown Inlier重建的压力-温度-变形-时间路径表明c。在西部地区的绿片岩相条件下以及在中P和中T下记录到1.60 Ga M1 / D1事件中央领域的条件。此事件之后是区域1.56–1.54 Ga低磷和高T相（M2 / D2），广泛记录在中部和东部地区。这两个变质事件之间的减压归因于发掘出尸体。这两个阶段的演化支持先前的假设，即乔治敦内里尔（Georgetown Inlier）保留了与花岗岩沉积有关的大陆碰撞和随后的热扰动。