Multiple Emplacement and Exhumation History of the Late Mesozoic Dayunshan–Mufushan Batholith in Southeast China and Its Tectonic Significance: 1. Structural Analysis and Geochronological Constraints

The South China Block (SCB) experienced a polyphase reworking by the Phanerozoic tectonothermal events. To better understand its Late Mesozoic tectonics, an integrated multidisciplinary investigation has been conducted on the Dayunshan–Mufushan composite batholith in the north‐central SCB. This batholith consists of two major intrusions that recorded distinct emplacement features. According to our structural analysis, two deformation events in relation to batholith emplacement and subsequent exhumation are identified. The early one (D 1 ) was observed mostly at the southern border of the batholith, characterized by a top‐to‐the‐SW ductile shearing in the early‐stage intrusion and along its contact zone. This deformation, chiefly associated with the pluton emplacement at ca. 150 Ma, was probably assisted by farfield compression from the northern Yangtze foreland belt. The second but main event (D 2 ) involved two phases: (1) ductile shearing (D 2a ) prominently expressed along the Dayunshan detachment fault at the western border of the batholith where the syntectonic late‐stage intrusion and minor metasedimentary basement in the footwall suffered mylonitization with top‐to‐the‐NW kinematics; and (2) subsequent brittle faulting (D 2b ) further exhumed the entire batholith that behaved as rift shoulder with half‐graben basins developed on its both sides. Geochronological constraints show that the crustal ductile extension occurred during 132–95 Ma. Such a Cretaceous NW–SE extensional tectonic regime, as indicated by the D 2 event, has been recognized in a vast area of East Asia. This tectonism was responsible not only for the destruction of the North China craton but also for the formation of the so‐called “southeast China basin and range tectonics.”