Study On Enrichment Regularities And Genesis Of Xicha Gola-silver Deposit In Jilin Province

Xicha gold-silver deposit located in the eastern section of the northern margin ofNorth China, east of the Pacific plate, the north Siberian plate, tectonic positions inthe the eastern of Tianshan-Xingmeng orogenic belt. It is close to the Yalu Riverfault zone, the mineralization time is late Yanshan.The strata outcropped in the miningarea is Paleoproterozoic Ji’an Qinghe group. Ore body is controlled by the Yanshantectonic and magmatic activity. Deposits are strictly controlled by the NE-trendingfault structure, the mechanical properties,occurrence and scale of the fault structurecontrol the morphology, occurrence and size of the ore body, as well assub-enrichment patterns. The region has a multi-stage magmatic intrusions, mainlythe Yanshanian Zhengcha granite porphyry（porphyritic granite）,Fuxingtun porphyriticgranite,Fuxingtun diorite and Xicha amphibolite gabbro. Sodium feldspar porphyry isthe main dike.10ore bodies are found in the mine, gold-silver ore body including1,3,4,5,9,12ore body, a total of six, lead-zinc ore body including20,21,23,25ore body, a total offour and some mineralized bodies. Ore types contain structure altered rock type andhydrothermal breccia type which is found this time. Ore minerals are electrum, silver,pyrite, arsenopyrite and minor pyrargyrite. Gangue minerals are mainly composed ofcalcite, sericite, chlorite. Ore textures contains anhedral granular textures, euhedral-hypidiomorphic textures, account textures, skeletal textures, crushing textures andcontaining textures. Ore structure contains massive structure, veinlet constructedbanded structure, lumpy structure, and brecciated structure. alteration consist ofsilicification, carbonation, sericition and chlorition. The mineralization period can be divided into three phases: quartz-pyrite mineralization stage, quartz polymetallicsulphide mineralization stage, carbonate-pyrite formation stage.Pyrite contains Au, Ag, As, Sb, Bi, Se, Co, Ni and other trace elements analyzedby electron probe test. The pyrite with high Au in it is the main gold carrier ofminerals. Pyrite, Au/Ag ratio of3.481to6.200is much larger than0.5, the Co/Niratio ranging from1to5show magmatic hydrothermal origin. Se content of pyriteand S/Se ratio results also reflect the magmatic hydrothermal origin. Enrichment ofCo and Ni indicates that the fluid is from the mantle source or mafic metamorphicdehydration. Described above indicates ore-forming fluids comes mainly from themagma fluid and part of the mantle-derived fluid added.Quartz fluid inclusion homogenization temperature of276.0℃³71.9℃,mainly at280℃to320℃, salinity of7.72to17.74wt%NaCl, density of0.731to0.893g/cm³in the main mineralization stage. Raman analysis of fluid composition, the gas phasecomposition of the ore-forming fluids mainly H₂O, followed for N₂is a H₂O-N₂system.In deep mine the data of the primary halo and peripheral soil secondary halo datacarried out the element correlation analysis, factor analysis, as well as the elements ofabnormal figure drawing, combined with comprehensive information on geology thatin the area of the deep mine and D abnormal Ⅷ has good potential formineralization.Study on the genesis of the Xicha Gold Mine, mineralization time should bemid-late Yanshanian （Early Cretaceous） tectonic regime from compression toextension in conversion period, the mineralization period should be slightly later thanalbite porphyry of the emplacement of time.Xicha gold-silver mine in the genesis have a similar basic characteristics withorogenic gold deposit. Tectonic setting is continental arc orogenic environment. Thegenetic type is mesozonal orogenic gold deposit.