LAUSR

The Haoyaoerhudong gabbro is a mafic intrusion located in the Haoyaoerhudong gold deposit, which is a giant gold deposit (148 t Au) hosted in Proterozoic strata on the northern margin of the North China Craton. In this paper, we present integrated SHRIMP U–Pb, geochemical and Sr–Nd isotopic data from gabbro of the Haoyaoerhudong gold deposit to reveal the magmatic processes behind its origin. SHRIMP zircon U–Pb dating constrains the timing of crystallization of the Haoyaoerhudong gabbro to 278.8 ± 0.81 Ma. Whole-rock geochemical results indicate that the Haoyaoerhudong gabbro has calc-alkaline features with enrichments of large-ion lithophile elements (LILE) and light rare-earth elements (REE) as well as depletions of high-field strength elements (HFSE). The relatively high (87Sr/86Sr)i (0.7053 to 0.7078) and low εNd(t) (−4.6 to −15.1) values of the gabbro indicate the involvement of crustal materials. Low Ce/Pb ratios (1.35 to 7.38), together with nearly constant La/Sm and Th/Yb ratios and variable Ba/Th and Sr/Nd ratios, suggest that the ancient mantle was modified by slab dehydration fluids. Based on new geochemical data and regional geological investigations, we propose that both the Haoyaoerhudong gold deposit and the Haoyaoerhudong gabbro formed in a post-orogenic extensional setting.