Abstract:
[Objective] The western Shandong region is located in the core area of eastern North China Craton and represents typical Archean basement exposure. It distributes as an overall NW–SE trending linear belt. This area not only preserves multiple phases of magmatic records spanning the early to late Neoarchean but also retains abundant anatexis–rheological structures and overprinted ductile deformational fabrics. These features are of great significance for understanding the Neoarchean tectonic evolution of the North China Craton. The Culaishan region is one of the most promising areas for such geological studies. It is situated in the core of the tectonic B belt of the western Shandong, characterized by well-developed anatexis and ductile deformation, making it an ideal location to investigate the spatial and temporal relations between the crustal anatexis and ductile deformation. [Methods] In this study, we selected the representative migmatite outcrop at the Huangshiya Village and conducted systematic field structural analysis, petrographic observation, and LA-ICP-MS zircon U-Pb geochronology. [Results] Field observations show that the structural lineaments in this region exhibit an overall NW–SE orientation. Numerous felsic melts are developed within the amphibolites, mainly banded along the foliation, with a few occurring in a network-like or disseminated pattern. Flow folds are well-developed. Petrographic observations demonstrate that quartz grains are distributed along the irregular, corroded boundaries of K-feldspar and plagioclase, containing small melt pockets, bead-like textures, and melt films. These features collectively indicate intense anatexis in the region. The newly generated melts reduced the overall rock strength, making it more susceptible to subsequent ductile deformation. Concurrently, NE–SW oriented horizontal compressive stress further promoted NW–SE regional extension, consistent with the nearly vertical foliation and sub-horizontal mineral stretching lineations observed in the amphibolite, suggesting near-oblate strain dominated deformation regime. To constrain the timing of regional deformation, we conducted LA-ICP-MS zircon U-Pb dating on representative pre-, syn- and post-tectonic samples of the area. The results indicate that the residual amphibolite records a melt crystallization age of ~2503 Ma, representing the timing of regional anatexis event. The syn-tectonic monzogranite yields a crystallization age of ~2497 Ma, reflecting the syn-tectonic magmatic event, while the undeformed pegmatite veins formed at ~2465 Ma, thereby bracketed the regional ductile deformation at 2497-2465 Ma. [Conclusion] In summary, the western Shandong region experienced intense anatexis in the late Neoarchean, which was rapidly overprinted by near-oblate strain dominated shortening deformation under NE–SW-oriented horizontal compressive stress. The anatexis further facilitated the development of NW–SE-directed ductile deformation. The superimposition of these two events ultimately shaped the structural pattern of the Neoarchean crust of the western Shandong region. [Significance] This study provides new constraints on further understanding the Neoarchean tectonic framework and structural pattern of the Western Shandong region.