The significance of the early deformation architecture in localizing “Carlin-like” gold mineralisation at the Jianchaling Gold deposit, Shaanxi province, Peoples Republic of China

Abstract

The Jianchaling (JCL) deposit is located on the northern edge of the South China Craton and is separated from the North China Craton by the ESE-WNW trending Qinling-Dabie orogenic belt. A recent structural geology study established a new deformation framework for the local mine area. Structural controls on the distribution of Carlin-style mineralisation developed during early ductile deformation that preceded gold mineralisation. Early ductile deformation saw the rotation of early shallow dipping thrust faults to upright attitudes during regional folding. Subsequent extension or gravitational collapse folded bedding and the F145 fault asymmetrically about shallow dipping axial planes, whereby one limb maintained a shallow north dip. These deformation events produced the critical structural architecture for the gold mineralising event. “Carlin type” gold mineralisation was synchronous with late reverse movement along the F145 fault that locally brecciated the shallow north dipping “heterogeneities” in the F145 fault geometry. These heterogeneities were a product of early folding of the F145 fault. The shallow dipping heterogeneities provided the zones of maximum dilation and fracture during the gold mineralising stage, resulting in shallow plunging ore shoots. Steeply plunging ore shoots developed at the intersections of cross cutting gold stage NW and NE striking faults with the ESE striking F145 fault.