Differential crustal rotation and its control on giant ore clusters along the eastern margin of Tibet

Abstract

Abstract Controls on the formation and distribution of mineralization in continental collisional settings remain unclear. However, our synthesis of diverse geophysical data sets from the eastern margin of Tibet revealed that differential crustal rotation played a key role in the production of a variety of mineralization types. Due to Cenozoic continental collision between India and Eurasia, the elongated continental blocks in the eastern margin of Tibet were extruded and reoriented. Prior to block extrusion in the Eocene, two giant porphyry-skarn ore clusters formed at the boundaries between the central segment and both the northern and southern segments of the Jinshajiang-Ailaoshan suture zone. These crustal segment boundaries displayed counterclockwise rotation, due to clockwise rotation of the central segment relative to both the essentially immobile northern and southern segments, combined with crust-mantle decoupling. This is considered to have induced crustal friction and resultant generation of fertile magmas that formed the porphyry-skarn Cu-Au deposits. During Oligocene–Miocene block extrusion, differential rotation of upper crust occurred on the western and eastern sides of the north-northwest–trending Central Axis fault in the Lanping-Simao basin. Two Oligocene–Miocene Mississippi Valley–type ore clusters occur on fault segments with anomalous differential rotation of 70° to 80°, suggesting that this differential rotation resulted in local extension with consequent ore-fluid influx.