Lawsonite eclogite and garnet blueschist occur as metre‐scale blocks within serpentinite mélange in the southern New England Orogen (SNEO) in eastern Australia. These high‐P fragments are the products of early Palaeozoic subduction of the palaeo‐Pacific plate beneath East Gondwana. Lu–Hf, Sm–Nd, and U–Pb geochronological data from Port Macquarie show that eclogite mineral assemblages formed between c. 500 and 470 Ma ago and became mixed together within a serpentinite‐filled subduction channel. Age data and P–T modelling indicate lawsonite eclogite formed at ~2.7 GPa and 590°C at c. 490 Ma, whereas peak garnet in blueschist formed at ~2.0 GPa and 550°C at c. 470 Ma. The post‐peak evolution of lawsonite eclogite was associated with the preservation of pristine lawsonite‐bearing assemblages and the formation of glaucophane. By contrast, the garnet blueschist was derived from a precursor garnet–omphacite assemblage. The geochronological data from these different aged high‐P assemblages indicate the high‐P rocks were formed during subduction on the margin of cratonic Australia during the Cambro‐Ordovician. The rocks however now reside in the Devonian–Carboniferous southern SNEO, which forms the youngest and most outboard of the eastern Gondwanan Australian orogenic belts. Geodynamic modelling suggests that over the time‐scales that subduction products accumulated, the high‐P rocks migrated large distances (~>1,000 km) during slab retreat. Consequently, high‐P rocks that are trapped in subduction channels may also migrate large distances prior to exhumation, potentially becoming incorporated into younger orogenic belts whose evolution is not directly related to the formation of the exhumed high‐P rocks.

中文翻译：

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澳大利亚东部的钙钠榴石榴辉岩和石榴石蓝片岩的俯冲和堆积

钙钠榴石榴辉岩和石榴石blueschist发生在澳大利亚东部新英格兰造山带（SNEO）南部蛇纹岩混杂岩中的米级块体中。这些高磷碎片是东冈瓦纳以下古太平洋板块早古生代俯冲的产物。麦夸里港的Lu-Hf，Sm-Nd和U-Pb年代学数据表明，在c之间形成了榴辉岩矿物组合。500 Ma和470 Ma以前，并在蛇纹石填充的俯冲通道中混合在一起。年龄数据和对叔建模表明形成在〜2.7 GPA和590℃，在硬柱石榴℃。490 Ma，而blueschist中的石榴石峰在〜2.0 GPa和550°C的温度下形成。470毫安。尖晶石榴辉岩在峰后的演化与原始质钠钙榴石组合的保存和青光烷的形成有关。相比之下，石榴石blueschist源自石榴石-杂方岩的前体组合。这些不同年龄的高P组合的年代学数据表明，高P岩石是在坎布罗-奥陶纪期间在克拉通澳大利亚边缘俯冲过程中形成的。然而，这些岩石现在位于泥盆纪-石炭纪南部SNEO，它是冈瓦南东部澳大利亚造山带中最年轻，最外侧的部分。地球动力学模型表明，在俯冲产物积累的时间尺度上，高磷岩石迁移了很长的距离（〜 > 1,000公里）。因此，被困在俯冲通道中的高P岩石在发掘前也可能迁移很长一段距离，有可能被整合到年轻的造山带中，而其演化与被发掘的高P岩石的形成没有直接关系。