Abstract: Laozuoshan gold deposit in Heilongjiang Province is a large-scale gold deposit located in the north-central part of Jiamusi block, Xing-Meng orogenic belt. The ore bodies are closely related to skarn, and hosted in the contacting belt between granodiorite and calcium marble and gneiss schist of Mashan Group, as well as in the ore-controlling structures such as the NW and NWW-trending extensional fractures. The studies of deposit geology, petrography, zircon U-Pb isotope chronology and geochemical characteristics reveal that Laozuoshan gold deposit develops two superimposed mineralization stages, including the skarn-type mineralization in late Middle Permian of Variscan and the hydrothermal mineralization in Yanshan Peried. The skarn-type mineralization during the main metallogenic period is closely related to the granodiorite, and its diagenetic age is (262.6±3.9) Ma. The Variscan granodiorite in this deposit is a kind of weak peraluminous and high potassium calc-alkaline rock series, characterized by high w(SiO2), low Mg# value and MgO, with features of enrichment of large ion lithophile elements and light rare earth elements, while depletion of high field strength elements and heavy rare earth elements, showing the characteristics of I-type granite, and the magma source originates from partial melting of crustal materials. The comprehensive studies show that the Variscan skarn-type mineralization and magmatism occurred during the transition period of the tectonic regime from ocean-continent subduction to continental collision, and the granodiorite is the product of partial melting of crustal materials.

Key words:  , Laozuoshan gold deposit, granodiorite, zircon U-Pb chronology, geochemistry, metallogenesis, petrogenesis