The Zanhuang Massif, the second and eastern suture zone of the Paleoproterozoic Trans-North China Orogen

This paper presents a reappraisal of the tectonic evolution of the Zanhuang Massif that lies at the eastern margin of the Trans-North China Orogen, a continent–continent collision belt that marked the amalgamation of the North China Craton in Late Paleoproterozoic. Detailed field work with focus on geometries of structures and kinematics was performed. This was completed with LA-ICP-MS U–Pb analyses on zircon, EPMA U–Th/Pb dating on monazite and 40Ar/ 39Ar dating on amphibole. These studies led us to propose a new three-fold litho-tectonic subdivision of the massif: The Western Zanhuang Domain (WZD) made of TTG, migmatite and pink anatectic granite is correlated to the Fuping Massif that crops out to the north-west. Both areas represent a continental block, called the Fuping Block, which acquired most of its architecture around 2100 Ma ago. The Eastern Zanhuang Domain (EZD) made of TTG and migmatite represents the western edge of an Eastern Neoarchean Block. In between, the Central Zanhuang Domain (CZD) is a NE–SW trending stack of supracrustal, gneiss and mafic magmatic rocks thrust sheets displaced toward the ESE upon the Eastern Block. The lithological features suggest that the CZD represents the remnant of an oceanic basin, called the Taihang Ocean that closed during the amalgamation of the Eastern Block and the Fuping Block around 1880–1850 Ma. In agreement with recent work done along the western margin of the belt, in the Lüliang Massif, this study documents the amalgamation of the North China Craton in response to the closure of two oceanic basins, namely the Lüliang Ocean and the Taihang Ocean. West-dipping subductions and collisions involving three distinct continental blocks, called the Western, the Fuping and the Eastern Blocks, took place around 1880–1850 Ma.