Melange- and sediment-hosted gold-bearing quartz veins, Hodgkinson gold field, Queensland, Australia

Gold-bearing quartz veins in the Hodgkinson gold field are hosted in subgreenschist facies Siluro-Devonian sandstone, conglomerate, carbonaceous shale, clast-in-matrix rock, chert, and spilite. Mineralization occurs in brittle to brittle-ductile shear zones which crosscut two previous deformations and melange. Vein systems are isolated in distinct structural and lithologic domains by postmineralization faulting. The gold quartz vein textural types are ribbon, buck, breccia, assimilation textured, and comb quartz. Multiple injection of quartz and multiple shear zone movement have produced complex zones of quartz separated by seams of gouge. Measured and calculated stable isotope compositions of the fluid depositing gold quartz are δO = 10 ± 2 per mil, δD = -100 ± 20 per mil. Although meteoric water contributions cannot be discounted, geologic characteristics, isotopic data, quartz types, sulfide mineralogy, and or controls favor gold deposition from an upwardly migrating, homogeneous, metamorphic, or distal magmatic fluid. -from Authors