Ore geology, fluid inclusion, and stable isotope constraints on the origin of the Damoqujia gold deposit, Jiaodong Peninsula, China

The Damoqujia gold deposit within the Zhaoping Fault Zone on Jiaodong Peninsula in eastern China is hosted primarily by Mesozoic granitoids and contains >60t of gold, making it an important gold producer. Three mineralization stages are distinguished (early, middle, and late): (K-feldspar)-sericite-quartz-pyrite, quartz - gold - polymetallic sulfides, and quartz--carbonate. Gold deposition occurred mainly in the middle stage. The primary fluid inclusions of three stages are mainly homogenized at temperatures of 236-389,191-346, and 104-251 [degrees]C, with salinities of 2.96-11.33,1.39-17.28, and 0.53-11.48 wt.% NaCl equivalent, respectively. Fluid inclusion studies indicate that the metallogenic system evolved from C[O.sub.2]-rich mesothermal homogeneous fluids to C[O.sub.2]-poor aqueous fluids due to inputs of meteoric waters. The gold was carried as a bisulfide complex in the ore-forming fluids. Precipitation of gold was caused by a combination of fluid immiscibility and water-rock interaction. Studies of the fluid inclusion characteristics (medium temperature, C[O.sub.2]-rich, and low salinity [H.sub.2]O--C[O.sub.2]-NaCl homogeneous system), hydrogen and oxygen isotopes ([mathematical expression not reproducible] = -1.0[per thousand] to 7.6[per thousand], [delta]D = -109[per thousand] to -77[per thousand]), sulfur values ([mathematical expression not reproducible] = 4.5[per thousand] to 8.5[per thousand]), and regional geological events show that the ore-forming fluids reservoir was likely metamorphic in origin. Based on the immiscibility of fluid inclusion assemblages, the estimated depth and pressure of trapping are 8.3-10.2 km and 83-276 MPa, respectively, corresponding to the depth and pressure of mineralization. Key words: fluid inclusion, fluid evolution, stable isotope geochemistry, Damoqujia gold deposit, Jiaodong Peninsula. Le gisement aurifere de Damoqujia, dans la zone de faille de Zhaoping, dans la peninsule de Jiaodong de l'est de la Chine git principalement dans des granitoides mesozoiques et contient >60 t d'or, ce qui en fait un important producteur aurifere. Trois phases de mineralisation sont relevees (precoce, intermediaire et tardive), a savoir : a (feldspath potassique)--sericite-quartz-pyrite, a quartz--or--sulfures polymetalliques, et a quartz-carbonate. Le depot de l'or a principalement eu lieu durant la phase intermediaire. Les temperatures des inclusions fluides primaires des trois phases sont generalement de 236-389, 191-346, et 104-251 [degrees]C, pour des salinites de 2,96-11,33,1,39-17,28, et 0,53-11,48 % en poids d'equivalents NaCl, respectivement. Les analyses des inclusions fluides indiquent que le systeme metallogenique est passe de fluides mesothermaux riches en C[O.sub.2] a des fluides aqueux pauvres en C[O.sub.2] en raison d'apports d'eaux meteoriques. L'or a ete transporte sous forme de complexe d'hydrogenosulfure dans les fluides mineralisateurs. La precipitation de l'or est le resultat d'une combinaison d'immiscibilite des fluides et d'interactions eau-roche. Des etudes des caracteristiques des inclusions fluides (systeme a [H.sub.2]O--C[O.sub.2]-NaCl homogene de faible salinite, riche en C[O.sub.2] et de temperature intermediaire), des isotopes de l'hydrogene et de l'oxygene ([mathematical expression not reproducible] = -1,0 a 7,6 [per thousand], [delta]D = -109 a -77 [per thousand]) et des isotopes du soufre ([mathematical expression not reproducible] = 4,5 a 8,5 [per thousand]) et les episodes geologiques regionaux indiquent que le reservoir de fluides mineralisateurs etait probablement d'origine metamorphique. A la lumiere de l'immiscibilite des assemblages des inclusions fluides, la profondeur et la pression de piegeage estimees sont de 8,3-10,2 km et 83-276 MPa, respectivement, correspondant a la profondeur et a la pression de mineralisation. [Traduit par la Redaction] Mots-cles: inclusion fluide, evolution des fluides, geochimie des isotopes stables, gisement aurifere de Damoqujia, peninsule de Jiaodong.
Introduction Jiaodong Peninsula, located in the southeastern part of the North China Craton (NCC; Fig. 1), is one of the most important gold mineralization belts in China (with gold reserves [...]