Structure, vein paragenesis, and alteration in the Al Wajh gold district, Saudi Arabia

The Al Wajh gold district contains small deposits of gold-bearing quartz veins located in sheared and altered Neoproterozoic mafic lavas and volcaniclastic sandstone and siltstone. The veins formed during multiple episodes of deformation and have structual and mineralogic features characteristic of mesothermal, low sulfide, gold-bearing quartz veins. Three early deformation episodes (D₁, D₂, D₃) are interpreted as progressive phases of a major deformation event that culminated about 660 Ma; episode D₄ makes up part of a later event about 620 Ma. The bulk of the gold-bearing veins in the district are located in D₂ and D₃ structures. D₁ veins consist of thin quartz veins in phyllite, D₂ veins are located in throughgoing, steeply dipping sinistral shear zones and in the crests of folds along the shears. D₃ veins, typically associated with carbonate alteration, are concentrated in small thrust faults that in places modify earlier D₂ shears. -from Authors