| Dabaoshan polymetallic deposit is one of well-known deposits in China. Studies of the deposit have focused on geological characteristics, mineralizing conditions and mechanism, and metallogenic models. However, there are still some key issues unresolved, such as the ages of magmatism and mineralization, the relationship between the subdacite porphyry and granodiorite porphyry and their metallogenic implication, as well as genesis of copper polymetallic ore bodies occurred in the Donggangling Formation as stratiform to stratoid, which constrain to set up the metallogenic model and prospecting model. In this study, after the extensive field work and the results of zircon U-Pb and molybdenite Re-Os geochronology, petrographic study, whole-rock geochemistry, isotopic geochemistry and fluid inclusion, we attempt to investigate the source and petrogenesis of the porphyries, source of ore and ore-bearing fluid evolvement, the ages of magmatism and mieralization, and geodynamic setting of this deposit. Furthermore, combining with the previous data of geology, geophysical and geochemical exploration, and remote sensing, we propose the metallogenic model and prospecting direction. The main results and conclusions are summarized as the follows:The results of zircon U-Pb dating, combining with the intrusive-contact relationship of the porphyries, show that the magma crystallization ages of the subdacite porphyry and granodiorite porphyry are about 175 Ma, but the subdacite porphyry intruded a little early. The results of molybdenite Re-Os dating suggest that the ages of porphyry-type and skarn-type Mo deposits are about 165 Ma, which are consistent with a molybdenite Re-Os model age (164.7±3 Ma) for the stratiform Cu-Pb-Zn sulfide orebody. It implied that both Mo deposit and strataform Cu-Pb-Zn deposit in the ore district could be the products of same mineralization event.The petrochemical diagrams of Rb-Y+Nb and Rb/30-Hf-Ta×3 show that the two type porphyries both formed in post-collisional lithosphere extension. In addition, the ages of magmatism and mieralization are consistent with the other Mo polymetallic deposits in the Nanling Region. Combining with previous studies, we interpret the Daobaoshan ore deposit and the porphyries as related to emplacement in an extensional setting due to post-collisional lithosphere extension.The major elements geochemical data show that the subdacite porphyry and granodiorite porphyry both are high-K calc-alkaline rock, with the character of high SiO2, enrich in K2O and Na2O, high K2O/Na2O, peraluminous and moderate fractionation. These rocks have similar major element composition and geochemical parameters, and there is a good linear relationship between SiO2 and the other oxide, indicating that they were derived from the same magma source. They are enriched in large ion lithophile elements (LILE, e.g., Rb, Th, U, La, Ce, Pb) and light rare earth elements (LREE; ((La/Yb)N=6.01-0.82), depleted in Sr, Ba and heavy rare earths (HREE). Combining with the whole-rock Sr and O isotopic data, we proposed that these rocks are between I-type and S-type granites (mixed with crust and mantle components), i.e., the deep material contained mantle components resulted in the partial melting in the deep crust, simultaneity occured the crustal contamination.The 818O values range from-4.42%o to 8.05‰andδD values from-56.1‰to-50.7‰in fluid inclusions from this deposit. On the basis of this data, we proposed that the ore-forming fluids were derived from mixed source of magmatic and meteoric waters. Furthermore, most of the 834S values of the sulfide ores from the deposit are from-2.00‰to 3.00‰, which is similar to magmatic sulphur. Most of lead isotope data fall on the magmatism-lead zone, indicating that the lead source of ores was related to the Yanshanian magmatisim. These isotope data support a genetic relationship between the Dabaoshan polymetallic deposit (including porphyry-type and skarn-type Mo deposits and strataform Cu-Pb-Zn deposit) and the two type porphyries.Fluid inclusions data show that ore-forming temperatures range from 410℃-174℃, Mineralization occurs mainly in middle to low temperature phase, molybdenum mineralization could be divided into two phases:i.e.,320℃-240℃and 220℃-170℃. Ore-forming fluids are rich in halogens and alkali, belonging to CaCl2 (MgCl2)-NaCl-KCl-H2O fluid system. Fluid salinity and density vary from 2wt%-17wt% and 0.67-0.98g/cm3, respectively. Instantaneous homogeneous pressure of fluid inclusions range from 8.4×106-169.4×106Pa, the ore-forming pressure of Cu-Pb-Zn deposit and Mo-W deposit vary from 50×106-70×106Pa and 40×106-50x106Pa, respectively. The intrusive depth of porphyries and mineralization is approximately 1.5-4 km.During the post-collisional lithosphere extension setting that may have began as early as the Early Jurassic (190-180 Ma) in the Nanling Region, the NE-trending and near SN-trending faults acted as the main structural controls for the magmatism and mineral deposits in the North Guangdong Province. The secondary faults of the NE-trending fault and the intersections of its branches were the elementary conduits for magmatism and ore-bearing fluid. The secondary faults of the main fracture, folds and the interlayer fracture zone lead the ore-bearing fluid and provided ore-forming space.These mineralizations, Mo-W mineralization and Cu-Pb-Zn mineralization in relation to the granodiorite porphyry and subdacite porphyry, consist of the porphyry-skarn-type magmatic hydrothermal ore-forming system in the Dabaoshan ore district. The Dabaoshan deposit, associated with the polymetallic Mo deposits distributed in the early to middle the Yanshannian related to the mixed crust-mantle magmatism, formed in the similar lithosphere extension setting, and constituted a region ore-forming system (magmatic hydrothermal deposits).In the early Yanshanian (about 175 Ma) the subdacite porphyry intruded along the north-northwest-trending fault, the granodiorite porphyry was subsequently following. The post-magmatic hydrothermal, rich in ore-forming materials, intruded into the interlayer fractured zone of the Donggangling Formation and formed the stratiform to stratoid skarn-type copper-lead-zinc deposits due to the metasomatism with carbonate rock, the later ore-bearing fluid formed vien-type copper deposit. Almost at the same time, the post-magmatic hydrothermal of the granodiorite porphyry reacting with carbonate rock in the Chuandu district formed the skarn-type Mo-W deposits, that reacting with clastic strata and the subdacite porphyry formed the porphyry-type Mo deposits along the contact zone. The ore-forming stage can be divided into the follows:skarn stage, molybdenum mineralization stage, copper and lead-zinc mineralization stage, chlorite-carbonate stage, supergene oxidation stage. The time of molybdenum, copper and lead-zinc mineralization stages was consistent with each other, maybe occured overlap.The district with the following conditions is favorable to form the Mo deposit, i.e., with the subdacite porphyry and granodiorite porphyry of the early Yanshanian stage, carbonate rock and clastic rock, the wall-rocks were subjected to the hydrothermal alteration, mainly including the greisenization, sericitization, skarnization and grammatite-actinolitization; Combining with multiple faults intersection and associated with secondary faults, folds, interlayer fractured zone; With pyrite, molybdenite, scheelite, wolframite; In addition, with CSAMT low resistivity anomaly, weakly positive and negative magnetic anomalies, Mo-W and other elements geochemical anomalies.In the Dabaoshan ore district, the north-east area of the Dabaoshan porphyry-type Mo deposit in the north contact zone with the subdacite porphyry is a good exploration prospect; The Daobaoshan and Chuandu granodiorite porphyries were divided by the post-mineraliton fault, the faulted space is also one of the most important next exploring direction of Mo-W, as well as the deep space of known Mo ore body.
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