The Mai'iu Fault in the Woodlark Rift of southeastern Papua New Guinea is an active north-dipping low-angle normal fault (LANF) that has exhumed the spectacular Suckling-Dayman metamorphic core complex (SDMCC) in its footwall. While its youthful domal geomorphology suggests recent tectonic exhumation of the SDMCC, the cooling and exhumation history of this active metamorphic core complex have not been studied in detail before. Here we provide the first zircon and apatite fission-track (FT) and (U-Th)/He thermochronometric data on the SDMCC based on a suite of samples from slip-parallel footwall transects and syn-extensional alluvial deposits shed from the emerging dome. In addition, we double dated zircon using U–Pb LA-ICP-MS. These chronometric techniques are complemented by temperature and pressure estimates from Raman spectroscopy of carbonaceous material (RSCM) and Al-in-amphibole and Al-in-biotite barometry on footwall phyllites/schists and granitoids, respectively. The data indicate that slip on the Mai'iu Fault had initiated by ~4 Ma. We show that slip on the Mai'iu Fault has persisted at cm/year rates since the onset of extension, making it one of Earth's most rapidly slipping continental LANF. Integrating temperature estimates from FT and (U-Th)/He thermochronometry and RSCM, we calculated a down-dip, fault-parallel paleo-field temperature gradient along the now-exhumed part of the Mai'iu Fault of ~11 °C/km. For a likely range of pre-extensional geothermal gradients in the Woodlark Rift (10–20 °C/km), this paleo-field temperature gradient implies an average initial dip of the Mai'iu Fault of ~46°. Given the present dip of ~21° at the surface, the thermal data reinforce other evidence that the footwall of the Mai'iu Fault has been back-rotated to the south by ≥20° during progressive unroofing since fault inception, consistent with a rolling hinge style evolution of the SDMCC.

巴布亚新几内亚东南部伍德拉克裂谷的麦伊断裂是活跃的北倾低角度正断层（LANF），已挖掘出其下盘壁壮观的Suckling-Dayman变质核心复合体（SDMCC）。虽然其年轻的多角形地貌表明SDMCC近期已发掘出构造物，但该活跃的变质核心复合物的冷却和发掘史尚未进行过详细研究。在这里，我们基于滑移平行底壁断面和syn的一组样本，在SDMCC上提供了第一个锆石和磷灰石裂变径迹（FT）和（U-Th）/ He热计时数据。延伸的冲积沉积物从新兴的穹顶中脱落。此外，我们使用U–Pb LA-ICP-MS对锆石标上了日期。这些计时技术与碳质材料（RSCM）的拉曼光谱法以及分别在底壁网眼石/片岩和花岗石上的铝-闪石和铝-黑云母气压计估计的温度和压力相辅相成。数据表明，迈乌断层上的滑动是由约4 Ma引发的。我们显示，自延伸开始以来，迈乌断裂带的滑坡以厘米/年的速度持续存在，使其成为地球上滑坡最快的大陆LANF之一。结合FT和（U-Th）/ He热计时法和RSCM的温度估算值，我们沿着迈伊断层现出土的〜11°C /公里 对于可能的范围Woodlark裂谷（10–20°C / km）中存在伸展前的地热梯度，该古场温度梯度意味着Mai'iu断层的平均初始倾角约为46°。考虑到目前在地面上约21°的倾角，热数据进一步证明了迈乌断裂的下盘自断层开始以来在逐步顶顶过程中已经向南向后旋转了≥20°，这与滚动相一致。 SDMCC的铰链样式演变。