CHARACTERISTICS, MINERALIZATION AND RESOURCE POTENTIAL OF ENDOGENOUS GOLD DEPOSITS IN LIAODONG PENINSULA

Liaodong Peninsula is an important part of North China Craton, where intense tectonic movement, magmatic activities and gold mineralization occurred in Mesozoic, and gold deposits of different scales are distributed with typical regional characteristics. Through the systematic summary of basic characteristics such as spatial distribution, ore-bearing wall rock, ore-controlling structures and mineralized alteration, as well as the metallogenesis of gold deposits, the paper analyzes the resources potential of gold deposits in Liaodong Peninsula. According to the spatial distribution of gold deposits, four gold deposit concentration areas are divided, including Maoling, Baiyun-Qingchengzi, Wulong-Sidaogou and Xinfang gold deposit concentration areas. The ore-bearing wall rocks of Maoling and Baiyun-Qingchengzi concentration areas are Paleoproterozoic sedimentary metamorphic rock series, with the mineralization of altered rock type and quartz vein type, and the orebodies mainly controlled by low-angle interlayer faults. The wall rocks of Wulong-Sidaogou concentration area are Middle Jurassic gneissic biotite granite and Paleoproterozoic sedimentary metamorphic rock series respectively, with the main mineralization of quartz vein type, followed by altered rock type, and the orebodies controlled by high-angle fault and low-angle interlayer fault. The wall rocks of Xinfang concentration area are Archean gneisses and Neoproterozoic Qingbaikouan metamorphic sandstone, granulite and marble, with the mineralization of quartz vein type and altered rock type. The orebodies are mostly in veins and controlled by the ductile-brittle secondary faults developed in the foot wall of metamorphic core complex detachment fault and by the structural fractures in the Neoproterozoic Qingbaikouou cap rock. The geochronological study shows that the gold mineralization epoch can be divided into Late Triassic (~220 Ma), Early Jurassic (~190 Ma) and Early Cretaceous (~120 Ma). The study on fluid inclusions indicates that fluid immiscibility is the main mechanism of gold mineralization. The H-O isotopes reveal the ore-forming fluid mainly comes from magmatic water, with atmospheric precipitation added in later period. The He-Ar isotopes show that the ore-forming fluid is mainly derived from crustal source and a little from mantle source. The S-Pb-Sr isotopes indicate that the metallogenic materials mainly come from the Mesozoic magma. Besides, the ore-bearing strata play an indispensable role. The geological characteristics and isotopic data show that the gold deposits in Liaodong Peninsula are of magmatic hydrothermal origin. Combined with regional tectonic evolution, it is believed that the Late Triassic gold deposits in the area are related to the deep subduction of Yangtze plate to North China plate, the Early Jurassic gold deposits related to the subduction and compression of Paleo-Pacific plate to Eurasian plate, and the Early Cretaceous gold deposits were formed in the subduction and exhumation extensional setting of Paleo-Pacific plate to Eurasian plate. According to the geological, regional geochemical and geophysical characteristics of typical deposits, 23 prospecting targets are delineated and 2 414.56 t of gold resources at 3 000 m below surface are predicted.