Precambrian metamorphic crustal basement cannot provide much gold to form giant gold deposits in the Jiaodong Peninsula, China.

• Crustal xenoliths trapped by Guojialing granodiorites display rather low Au contents. • The Precambrian metamorphic outcrop rocks also show low Au contents. • The metal contents are consistent with the metamorphic devolatilization model. • The Precambrian basement was not the main Au source for Jiaodong giant gold deposits. The Jiaodong gold deposits, eastern China define a giant gold province in the Precambrian high-grade metamorphic crustal basement. Given the early metamorphism, the crustal basement would have been so depleted in gold that cannot be the main source for the later Mesozoic gold deposits. However, previously reported gold contents from crustal rocks were variably high (e.g., >5–10 ppb) and often interpreted to reflect the contribution of crustal basement. In this study, after careful field sampling, we obtained high-precision Au and S contents (with Cu and Ag for many samples) to solve the controversial issue. The Au contents were determined by internal standardization to platinum which was obtained from isotope dilution via high-sensitivity Element XR, and/or another independent method by GFAAS after polyurethane foam pretreatment. These methods achieved low procedural blanks (<0.02 ppb) and reliable analyses of low-Au samples. The analyzed metamorphic crustal rocks are from surface outcrops (n = 30) and crustal xenoliths (n = 10) in the Jiaobei terrane, where hosts the predominant Jiaodong gold resources (>85% of 5000 t). The Archean and Paleoproterozoic metamorphic outcrop rocks were sampled far from gold deposits and faults with the minimum effect of ore-forming fluids, and they display overall low Au contents (0.20 ± 0.18 ppb and 0.47 ± 0.29 ppb, respectively). More importantly, the crustal xenoliths trapped in pre-mineralization Guojialing granodiorites were not affected by hydrothermal overprint and better reflect the pristine features of the metamorphic basement. Although the crustal xenoliths contain variable sulfides with a wide range of Cu, Ag and S contents, they show rather low Au contents (0.18 ± 0.15 ppb). These results indicate the strong depletion of Au contents in the Precambrian crustal basement, consistent with the metamorphic devolatilization model. The Precambrian metamorphic crustal basement thus was rather difficult as the main gold source for the Jiaodong gold deposits, suggesting alternative sources. [ABSTRACT FROM AUTHOR]