Multiple Emplacement and Exhumation History of the Late Mesozoic Dayunshan‐Mufushan Batholith in Southeast China and Its Tectonic Significance: 2. Magnetic Fabrics and Gravity Survey

Abstract

AbstractThe Late Mesozoic magmatic province is a prominent feature of the South China Block (SCB). However, the tectonic regimes associated with the magmatism are still elusive. A combined anisotropy of magnetic susceptibility and gravity study has been carried out to determine the fabric patterns and shape at depth of the Dayunshan‐Mufushan composite batholith in the north‐central SCB. This is a companion paper to Part 1 that presented the structural and geochronological data of this batholith. The magnetic fabrics in the batholith interior predominantly reflect magma flow structures. Two distinct patterns of the magnetic lineations are defined, around NNE‐SSW and WNW‐ESE trends for the early‐stage and late‐stage intrusions of the batholith, respectively. The gravity survey reveals that the early‐stage intrusion has a main feeder zone located below its northern part, while several linear feeder zones trending NNE‐SSW are inferred for the late‐stage intrusion. Integrating all results, a two‐stage construction of the batholith with distinct tectonic regimes has been established. It is concluded that the early‐stage intrusion experienced a southward magma transport during its emplacement, partially assisted by far‐field compression from the north at ca. 150 Ma. Conversely, the emplacement and exhumation of the late‐stage intrusion was accommodated by a NW‐SE crustal stretching involving a lateral magma expansion above the multiple feeder zones (likely corresponding to extensional fractures) and ductile shearing during 132–95 Ma localized mainly along the Dayunshan detachment fault. Finally, we discuss the geodynamic linkage between the paleo‐Pacific subduction and the Late Mesozoic tectonomagmatism in the SCB.