| 其他摘要 | The Yaogangxian
tungsten deposit, tectonically located in the intersection part of the post-Caledonian uplift and the Hercynian-Indosinian depress belt, is a typical quart-vein tungsten deposit in the Nanling region, South China. On the base of detailed field investigation, a systematic study on helium and argon isotope and carbon, oxygen and sulfur stable isotope has been carried out, and the sources of ore-forming fluid and the relationship between granite intrusion and tungsten mineralization are discussed. Finally, a possible genetic model is proposed. The main conclusions are listed as follows:
(1) The helium and argon isotopic compositions of fluid inclusions in different sulfides collected from the Yaogangxian deposit have been analyzed. It is shown that, 3He/4He ratios of fluid inclusions in arsenopyrite are 0.58~2.60 Ra, 0.41~1.26 Ra in pyrite, 0.37~0.43 Ra and 0.05~0.49 Ra in chalcopyrite and wolframite, respectively, obviously higher than that of the crust. 40Ar/36Ar ratios of fluid inclusions in arsenopyrite are 309.94~454.39, 409.12~1822.31 in pyrite, 672.87~885.67 and 324.81~903.09 in chalcopyrite and wolframite, respectively, which are obviously higher than that of air-saturated meteoric water. The above helium and argon isotope values indicate that the ore-forming fluid in this deposit is a mixture between mantle- and crustal-derived fluids. Combined with the regional tectonic evolution and geochronological data, it is concluded that the ore-forming fluid in this deposit is a mixture of mantle fluid and crustal fluids; the former is of magmatic origin, differentiated from the Yaogangxian granite and enriched in mantle-source helium, the latter is of meteoric origin.
(2) Carbon and oxygen isotopic compositions of calcite and argentine indicated that, the 13CPDB values of calcite range from -2.2‰ to -7.0‰ (averaging -4.8‰) and the 18OSMOW values of calcite vary between 5.6‰ and 14.4‰ (averaging 11.3‰); the 13CPDB values of argentine range from -2.2‰ to -7.0‰ (averaging -5.8‰) and the 18OSMOW values of argentine range from 5.6‰ to 14.4‰ (with an average of 13.8‰). The above carbon and oxygen isotope data coincides well with those of calcite and argentine in the Xihuashan deposit, southern Jinagxi. The result show that the ore-forming fluid is mainly derived form the magma, and meteoric water take part in the tungsten mineralization at the late mineralization stage.
(3) The δ34S values of different sulfides collected from the Yaogangxian mining district show a relatively narrow range, varying from -2.0‰ to -1.5‰, and display obvious tower distribution. It is suggested that the sulfur mainly comes from magma.
(4) The Yaogangxian granite was considered as one of typical S-type granite, but it is revealed in this dissertation that the granite usually contains mantle-origin helium. Combined with the regional tectonic setting, we can confirm that this so-called S-type granite actually resulted from the geologic setting of lithospheric extension and crust-mantle interaction, mantle-source substance and energy play an important role during granite intrusion.
（5）The Yaogangxian tungsten deposit has a close temporal, spatial and genetic relationship with the granite complex in the mining district. Moreover, the granite has predominately provided the ore-forming fluid and metallogenic materials for tungsten mineralization, thus both are genetically associated. |
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