Abstract Southeastern Papua New Guinea has hosted magmatism throughout the Cenozoic, with the latest phase being concurrent with active extension in the Woodlark Rift. There, the Suckling-Dayman metamorphic core complex (SDMCC) has exhumed middle-crustal rocks in the past few million years along a still-active low-angle normal fault, the Mai'iu Fault. Uplift of the SDMCC has exposed metasedimentary and metaigneous rocks of Late Cretaceous-Pleistocene age that record an evolution from oceanic spreading to subduction, to collision, and finally to subduction-inversion and extensional exhumation. We present new petrographic, whole-rock geochemical and geochronologic (outcrop and detrital zircon U Pb) data from the SDMCC to reconstruct its long-term evolution. The dominant footwall-lithology of the SDMCC, the Goropu Metabasalt, has a MORB composition. Detrital zircons from metasedimentary beds intercalated with these basalts yield U–Pb-based maximum estimates for deposition of ~103 and ~72 Ma, suggesting a Late Cretaceous spreading age of the oceanic protolith. Bulk compositions of low-grade tholeiitic meta-gabbroic and -tonalitic rocks (Yau Igneous Complex) that intrude the Goropu Metabasalt reveal both enriched and depleted light rare earth element patterns. Zircon U Pb ages from the Yau Igneous Complex range between ~60 and ~57 Ma, providing a minimum age for the formation of the Goropu Metabasalt. Much younger syn-extensional granitoids in the mafic footwall of the SDMCC have calc-alkaline to high-K compositions and U Pb ages on zircon between ~3.7 and ~2.0 Ma. Our data indicate that the Mai'iu Fault had re-activated a Paleogene thrust as an extensional detachment fault by 3.7 ± 0.2 Ma. U Pb ages of detrital zircons in modern streams draining the footwall of the SDMCC are essentially restricted to the ages revealed by the Paleocene and Plio-Pleistocene intrusions. Xenocrystic zircons in the Plio-Pleistocene granitoids imply that the crust underlying the metabasaltic carapace of the SDMCC consists chiefly of Australian-continent derived sedimentary rocks.

中文翻译：

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巴布亚新几内亚 Suckling-Dayman 变质核心杂岩中火成岩的岩石学、地质年代学和构造-岩浆环境

摘要 巴布亚新几内亚东南部在整个新生代都存在岩浆活动，最新阶段与伍德拉克裂谷的活动伸展同时发生。在那里，Suckling-Dayman 变质岩核杂岩体 (SDMCC) 在过去的几百万年里沿着仍然活跃的低角度正断层，即迈尤断层挖掘出中地壳岩石。SDMCC的隆升暴露了晚白垩世-更新世变沉积岩和变火成岩，记录了从海洋扩张到俯冲、碰撞，最后到俯冲反转和伸展折返的演化过程。我们提供了来自 SDMCC 的新的岩石学、全岩地球化学和地质年代学（露头和碎屑锆石 U Pb）数据，以重建其长期演化。SDMCC 的主要下盘岩性，Goropu 变玄武岩，具有 MORB 成分。来自变质沉积层的碎屑锆石夹在这些玄武岩中，产生了基于 U-Pb 的最大沉积估计值约为 103 和 72 Ma，表明大洋原岩处于晚白垩世扩张时代。侵入 Goropu 变玄武岩的低品位拉斑变辉长岩和偏辉长岩（Yau 火成岩杂岩）的整体成分显示出富含和耗尽的轻稀土元素模式。来自 Yau 火成岩复合体的锆石 U Pb 年龄范围在 ~60 到 ~57 Ma 之间，为 Goropu 变玄武岩的形成提供了最低年龄。SDMCC 镁铁质下盘中更年轻的同延花岗岩具有钙碱性到高 K 成分，锆石 U Pb 年龄在~3.7 到~2.0 Ma 之间。我们的数据表明，麦 iu 断层重新激活了古近系逆冲断层 3.7 ± 0.2 Ma。从 SDMCC 下盘流出的现代溪流中碎屑锆石的 U Pb 年龄基本上限于古新世和上新世侵入体揭示的年龄。上新世-更新世花岗岩中的异晶锆石表明 SDMCC 变玄武质甲壳下面的地壳主要由澳大利亚大陆衍生的沉积岩组成。