The Geological Characteris-ticsand Genesisof Depositof Caodi Gold Deposit At Jiuzhaigou In Sichuan, China

Caodi gold deposit located in the northwest trigile gold belt which tie threeprovinces of Shanxi，Gansu and Sichuan.Caodi gold deposit is the typicalmicro-disseminated gold deposits.the gold deposit not only has the classicalcharacteristic of Carlin-type gold deposit,but also has the characteristic ofOrogenic-type gold deposit.And in addition to this characteristics similar Carlin-typegold deposit and Orogenic-type gold deposit, but also has its owncharacteristics.Through the study of the deposit,understanding the genesis for theYangshan gold belt of mineralization, mineralization pattern and deep prospectingwork has positive significance.The paper obtained the following results:1）The ore control regularity of this deposit are three. Songbo-Liping fault and itssecondary structure controled the mineralization distribution. Bikou Group,Devonianand Carboniferous sedimentary metamorphic provides a fluid and material sources forCaodi. There has relatively close spatial relationship between Acidic dykes and themineralization of Caodi,but the magmatism was earlier than the mineralization.2）The mineralization of Caodi gold ddeposit can be divided into sedimentarydiagenesis stage, hydrothermal mineralization stage and supergene oxidation stage.The hydrothermal mineralization stage of gold is the most important stage which canbe further divided into early stage, main (middle) stage and the late stage. In the earlystage, it formed quartz-sericite-pyrite combination. In the main stage, it formedquartz-sulphides combination, enrichment of gold occurs mainly in the stage. Thereis a characteristic that the carbonates is more development and more transparentwhich filled along the fracture mostly and have a comb or vugs tectonic filled alongthe tensional fractures,and have no mineralization in the late stage.3）The Th in the late ore stage is271.7~288.3℃, and the salinity is2.95wt%NaCl, with pressure of2.948kbar.4) The ore-forming fluid is due to the influence by the regional metamorphicrock work, and from the formation of gold, arsenic, sulfur release elements,ore-forming fluids along tectonic fissures migrated and enriched in the favourableplace of sedimentary formation of gold, pyrite and arsenopyrite.5）Compared with the typical orogenic gold deposits and the Carlin-type gold deposits, the Caodi gold deposit is a orogenic gold deposit with disseminatedmineralization.