@phdthesis{oai:air.repo.nii.ac.jp:00003209,
 author = {李, 宏斌 and Li, Hongbin},
 month = {Mar},
 note = {The North China Craton is one of important regions for precious metal resources in China. Eastern Hebei Province in the craton has a long history regarding supply of gold for royal dynasties for thousands of years. The exploration of gold resource has been focused on the granite porphyry for a long time in the North China Craton. The Xiajinbao gold deposit is located in Yanshan district of the Craton. It is located in the northeast part of Beijing, and about 210 km away from the Beijing. Granite porphyry (Ilmenite-series) and diorite are present in the Xiajinbao deposit. The orebody predominantly is hosted in the granite porphyry. In the Xiajinbao deposit, previous researches also suggested that the granite porphyry is the source of the gold mineralization based on the similar ages between the granite porphyry and mineralization. However, the gold mineralization of the Xiajinbao deposit is thought to be formed by oxidized magmatism such as diorite based on the data in this study.
The orebodies of the Xiajinbao deposit, composed of aggregates of large number of veins and veinlets having width from 5cm to 1mm, occur mainly in the granite porphyry within an area of 800m by 300m. Base on cross-cutting relationships, the veins are classified into pyrite-quartz veins, pyrite-chalcopyrite quartz veins, and sphalerite-galena quartz veins from earlier to later. Pyrite quartz veins are composed of large amounts of quartz and pyrite with trace amounts of chalcopyrite and electrum. Pyrite-chalcopyrite quartz veins are composed of large amounts of quartz, pyrite, and chalcopyrite. Sphalerite-galena quartz veins are composed of large amounts of quartz, sphalerite and galena, small amounts of pyrite and chalcopyrite, and trace amounts of native bismuth, tetrahedrite and electrum. Quantity of electrum in sphalerite-galena quartz veins are larger than that of electrum in the pyrite quartz vein and pyrite-chalcopyrite quartz veins.
The granite porphyry consists of quartz, orthoclase, plagioclase and biotite as phenocrysts with trace amounts of ilmenite, zircon, rutile and apatite without magnetite. On the other hand, the diorite consists of plagioclase, amphibole and biotite with small amounts of apatite, magnetite, hematite, ilmenite and pyrite. The magnetic susceptibility of granite porphyry is generally Akita University lower than 0.1×10⁻³ SI unit while the diorite have much higher magnetic susceptibility from 30 to 60 ×10⁻³ SI unit in the Xiajinbao deposit. The igneous activity of Xiajinbao mining area is characterized by bimodal igneous activity. The distribution of diorite dike accords with the distribution in areas having high Au content. Au rich part (approx. 220ppm) is present near the diorite dike in the underground workings of the Xiajinbao deposit. These geological features indicate that mineralization has relationship with those diorite dikes in space.
The SiO₂ and TiO₂ contents of granite porphyry are around 70 wt% and 0.2 wt%, respectively. The Al₂O₃ contents of granite porphyry range from 13.9 to 14.3 wt%. The T-Fe₂O₃ contents of granite porphyry range from 1.9 to 2.5 wt%. The Na₂O and K₂O contents of granite porphyry range from 2.3 to 2.9 wt% and 4.6 to 6.1 wt%, respectively. The aluminum saturation index of granite porphyry ranges from 1.12 to 1.28. These features suggest that the granite porphyry belongs to the ilmenite-series granitic rocks. The granite porphyry was formed by reduced magma. On the other hand, the SiO₂ and Al₂O₃ contents of diorite dikes are 49.1 to 51.1 wt% and 13.7 to 16.3 wt%, respectively. The TiO₂ content of diorite dikes ranges from 1.0 to 3.1 wt%. The T-Fe₂O₃ content of diorite dikes is 7.3 to 11.5 wt%. The Na₂O and K₂O contents of diorite dikes are 3.3 to 4.1wt% and 2.4 to 2.9wt%, respectively. The Zr/TiO₂ ratios of granite porphyry and quartz porphyry dikes are both around 770 while the Zr/TiO₂ ratios of diorite dikes in the underground and outcrop are approximately 150 and 60. These ratios indicate that the characteristics of magma of granite porphyry and quartz porphyry dikes are similar. On the other hand, these are different from the characteristics of magma of diorite dikes.
The sulfur fugacity of sphalerite-galena quartz vein is estimated to be around 10⁻¹² atm. The formation environment of the sphalerite-galena quartz vein of the Xiajinbao deposit is similar to the environment of zoned base metal veins associated with oxidized magma. The δ³⁴S values of sulfide minerals of the Xiajinbao deposit range from -3 to +8 ‰ with a mode of +4 ‰. The distribution of sulfur isotopic ratios of the sulfide minerals of the Xiajinbao deposit are similar to the distribution of δ³⁴S of ores associated with oxidized magmas. The formation environment of gold-bearing sphalerite-galena-quartz veins of the Xiajinbao deposit is different from formation environment of hydrothermal activities associated with reduced granitic magma. The oxygen and hydrogen isotopic ratios of hydrothermal solution in equilibrium with quartz from the sphalerite-galena quartz vein range from +3.3 to +5.5 ‰ and -38 to -41‰, respectively. The oxygen and hydrogen isotopic ratios suggest hydrothermal solution of the pyrite quartz veins, pyrite-chalcopyrite quartz veins and sphalerite-galena quartz veins was magmatic origin.
Based on the geological, geochemical and isotopic data, Au mineralization of the Xiajinbao deposit is thought to have intimate relation with oxidized magma such as diorite.},
 school = {秋田大学},
 title = {Geology and geochemical characteristics of the Xiajinbao Au deposit in Hebei Province, China},
 year = {2018}
}