Abstract The Charters Towers Province, of the northern Thomson Orogen, records conversion from a Neoproterozoic passive margin to a Cambrian active margin, as characteristic of the Tasmanides. The passive margin succession includes a thick metasedimentary unit derived from Mesoproterozoic rocks. The Cambrian active margin is represented by upper Cambrian–Lower Ordovician (500–460 Ma) basinal development (Seventy Mile Range Group), plutonism and metamorphism resulting from an enduring episode of arc–backarc crustal extension. Detrital zircon age spectra indicate that parts of the metamorphic basement of the Charters Towers Province (elements of the Argentine Metamorphics and Charters Towers Metamorphics) overlap in protolith age with the basal part of the Seventy Mile Range Group and thus were associated with extensional basin development. Detrital zircon age data from the extensional basin succession indicate it was derived from a far-field (Pacific-Gondwana) primary source. However, a young cluster (<510 Ma) is interpreted as reflecting a local igneous source related to active margin tectonism. Relict zircon in a tonalite phase of the Fat Hen Creek Complex suggests that active margin plutonism may have extended back to ca 530 Ma. Syntectonic plutonism in the western Charters Towers Province is dated at ca 485–480 Ma, close to timing of metamorphism (477–467 Ma) and plutonism more generally (508–455 Ma). The dominant structures in the metamorphic basement formed with gentle to subhorizontal dips and are inferred to have formed by extensional ductile deformation, while normal faulting developed at shallower depths, associated with heat advection by plutonism. Lower Silurian (Benambran) shortening, which affected metamorphic basement and extensional basin units, resulted in the dominant east–west-structural trends of the province. We consider that these trends reflect localised north–south shortening rather than rotation of the province as is consistent with the north–south paleogeographic alignment of extensional basin successions. KEY POINTS Northern Tasmanide transition from passive to active margin tectonic mode had occurred by ca 510 Ma, perhaps as early as ca 530 Ma. Cambro-Ordovician active margin tectonism of the Charters Towers Province (northern Thomson Orogen) was characterised by crustal extension. Crustal extension resulted in the development of coeval (500–460 Ma) basin fill, granitic plutonism and metamorphism with rock assemblages as exposed across the Charters Towers Province developed at a wide range of crustal levels and expressing heterogeneous exhumation. Protoliths of metasedimentary assemblages of the Charters Towers Province include both Proterozoic passive margin successions and those emplaced as Cambrian extensional basin fill.

中文翻译：

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塔斯曼尼德北部的同期盆地形成、深成体作用和变质作用：查特斯塔省的伸展寒武纪-奥陶纪构造作用

摘要 汤姆森造山带北部的查特斯塔省记录了从新元古代被动边缘到寒武纪活动边缘的转变，这是塔斯曼尼德山脉的特征。被动边缘序列包括源自中元古代岩石的厚变沉积单元。寒武纪活动边缘以上寒武统-下奥陶统（500-460 Ma）盆地发育（七十英里山脉群）、由弧后地壳伸展的持久事件引起的深成作用和变质作用为代表。碎屑锆石年龄谱表明查特斯塔省变质基底的部分（阿根廷变质岩和查特斯塔变质岩的元素）在原岩时代与七十英里山脉群的基底部分重叠，因此与伸展盆地发育有关。来自伸展盆地序列的碎屑锆石年龄数据表明它来自远场（太平洋-冈瓦纳）主要来源。然而，一个年轻的星团（<510 Ma）被解释为反映了与活动边缘构造活动相关的局部火成岩源。Fat Hen Creek 杂岩体的辉绿岩相中的残余锆石表明，活跃的边缘深成岩作用可能已经扩展到约 530 Ma。查特斯塔省西部的同构造岩体作用时间约为 485-480 Ma，接近于变质作用时间 (477-467 Ma) 和更普遍的深成作用时间 (508-455 Ma)。变质基底中的主导构造形成为平缓至近水平倾角，推测是由伸展延性变形形成的，而正断层则在较浅的深度发育，与深成作用的热平流有关。下志留统（Benambran）缩短影响变质基底和伸展盆地单元，导致该省主要的东西结构趋势。我们认为这些趋势反映了局部南北缩短而不是该省的旋转，这与伸展盆地序列的南北古地理排列一致。要点 北塔斯马尼德从被动到主动边缘构造模式的转变发生在大约 510 Ma，可能早在大约 530 Ma。查特斯塔省（汤姆森造山带北部）的寒武纪活动边缘构造以地壳伸展为特征。地壳伸展导致了同期（500-460 Ma）盆地充填的发展，花岗岩的深成体作用和变质作用以及在查特斯塔省暴露的岩石组合在广泛的地壳水平上发展并表现出异质的挖掘。查特斯塔省变沉积组合的原岩包括元古界被动边缘序列和作为寒武纪伸展盆地填充的那些。