Jiaodong is located at the junction of Tethys, Paleo-Asian and Pacific Oceans. Their interaction and intracontinental process affect the magma-tectonic events and metallogenic dynamics in the Jiaodong area. The tectonic system transformation in the Mesozoic, the destruction and reconstruction of the craton, and the strong lithospheric thinning in eastern China are the main causes of the Mesozoic gold mineralization burst. The Sanshandao fault zone, the Jiaojia fault zone and the Zhaoping fault zone are the main ore control structures in the Jiaodong area. The amount of gold in these three structural zones has reached 3317t as proved by exploration. The Xiadian gold deposit is a large gold deposit located in the footwall of the Zhaoping fault zone and distributed along the contact zone between the Linglong granite and the basement rocks in Jiaodong. The ore bodies are mainly hosted in pyrite sericite cataclasite and pyrite sericite within 80 m of the footwall of the Zhaoping fault zone. They are vein like and layered, with slow wave-like changes along the strike and trend, with feature of branches, complex, expansion, sharp extinguish and reappearance. The metallogenic geological environment, deposit characteristics, inclusions and trace element geochemical characteristics of the Xiadian gold deposit have been studied by predecessors. Based on geochemical data of main elements, trace elements and rare earth elements of granite, structural cataclasite and gold ore in the periphery of the Xiadian gold deposit, this article studies the changes in chemical composition, trace elements and rare earth elements in different rocks and ores to obtain a preliminary understanding. In terms of main elements, SiO2, Fe2O3, K2O, Na2O, CaO, MgO, MnO and P2O5 in the peripheral biotite monzogranite are lower than the average value of the Linglong granite, but the overall petrochemical characteristics are consistent; SiO2 and K2O in cataclastic rocks of the Zhaoping fault zone show a large increase, while Al2O3, Fe2O3, K2O, Na2O, CaO, MgO, MnO, TiO2 and P2O5 are relatively lower, especially Fe2O3, Na2O and CaO. The change in chemical composition reflects the occurrence of silicification and potassification in the ore-forming period. The chemical composition of ore is closely related to the original rock. The SiO2 content is 42.06%~81.29%. SiO2, Al2O3 and Fe2O3 have a double change characteristics of increasing and decreasing greatly, especially the increase in the proportion of iron, potassium, calcium and magnesium is relatively high, which indicates that the widely developed pyritization in ore leads to an increase in iron. The increase of K2O content in the ore is 30% higher than the average content of the Linglong granite, indicating that large-scale potassium mineralization is a prelude to gold mineralization and provides material preparation for the formation of gold deposits. In terms of trace elements, the content of Au in the wall rock of the Xiadian gold deposit is generally lower than that of the Linglong granite. However, the content of Ag, W are generally higher, 3-10 times of the average value, and other elements are similar to the average value. The structural geochemical elements show that Au, Cu, Pb, Zn and Ag are the main enrichment elements. The sulfophilic elements Ag, Cu, Pb and Zn in the cataclastic rocks of the Zhaoping fault zone are obviously increased, especially Ag and Zn are 2.79 times and 2.09 times higher than those in the Linglong granite, showing a close relationship between the sulfophilic elements and the mineralization of gold deposits. The ferriophilic elements Cr, Co, Ni, Mo, Au, Sn and W are generally higher. The large ion lithophile elements Li, Be, Rb, Zr, Nb, W, Sr, Ba, As are mostly depleted, only Rb is enriched. In the ore, Au, Ag, W, Cu are highly enriched, while Bi, Mo, As, Pb, Zn are less enriched. Au is enriched 381.40 times, W is enriched 3961.23 times, Ag is enriched 254.16 times, Cu is enriched 116.19 times, while Bi, Mo, As, Pb, Zn are between 3-20 times lower. There is very high enrichment of W in both wall rock, fracture alteration zone and gold ore, which shows that the Zhaoping fault zone has a unique metallogenic geochemical premise. In terms of rare earth elements, the ΣREE of wall rock, structural alteration cataclasite and gold ore in the Xiadian gold deposit are 78.82×10-6, 27.15×10-6 and 102.43×10-6 respectively. LREE are 74.92×10-6, 4.23×10-6 and 94.52×10-6 respectively. HREE are 3.88×10-6, 2.91×10-6 and 7.91×10-6 respectively. LREE/HREE ratio is 19.3, 8.46 and 12.66, and the ΣREE, LREE and HREE of gold ore is relatively high, but the LREE/HREE ratio is similar. The altered cataclasite in the Zhaoping fault zone has a lower ΣREE, while the gold ore has a relatively higher ΣREE, which indicates that the addition of foreign materials in the mineralization process changes the content and ratio of REEs. It is also an important geochemical indicator to identify ore from wall rock. The REE distribution pattern of ore in the Xiadian gold deposit is similar to that of the Linglong granite and altered rock in fracture zone. It is generally right dipping type with low ΣREE, characterized by enriched LREE and depleted HREE. The δEu of wall rock, structural alteration cataclasite and gold ore are 1.88, 1.49 and 0.83; the Eu/Sm ratios are 1.57, 2.05 and 0.69; the Ce/Yb ratios are 25.15, 5.33 and 12.86 respectively. The internal fractionation of LREE and LREE is relatively small and the metallogenic environment is weakly oxidized. The increasing REE in ore is a reflection of fluid system carrying REE into the ore-forming process. According to the results of rock-mineral identification, the pyrites formed in early stage of gold mineralization process are generally fragmentary and cracks developed. The chalcopyrites are filled in the cracks of pyrites and coexists with gold, indicating that the native gold is formed in the same period with chalcopyrites, but later than pyrites. © 2021, Science Press. All right reserved.
