中国若干钨矿床相平衡关系

PHASE EQUILIBRIA OF SEVERAL TUNGSTEN DEPOSITS IN SOUTHERN CHINA

This paper reviews the features of several tungsten ore deposits in southern China, including the Shezhuyuan, Yaogangxian, Xihuashan, Danping, Yiatang and Dajishan mines. The authors think that the formation depth of greisen-type deposits is intermediate between the depths of pegmatite- and porphyry- type deposits. Using phase diagrams of the model system K2O-AhO3-SiO2-H2O-HF, the formation mechanism of greisens has been argued. The variation of mineral assemblages from K-feldspar, muscovite to topaz reflects a gradual increase in acidity. This variation can be used as a criterion to appreciate the depth of mineralization. Equilibria of tungsten minerals in greisen and skarn deposits can be depicted on chemical potential diagrams of the model system CaO-FeO-WO3-CO2-F2O-1. The assemblage wolframite+fluorite is shown to have been transformed to scheelite+magnetite with decreasing μHP. Depending on CO2 activity in the fluids, there are two distinct phase diagrams.One shows that wolframite is incompatible with calcite, and the other demonstrates that scheelite is incompatible with rhodochrosite. On the phase diagrams of the model system FeO-MnO-WO3-F2S-1, huebnerite is transformed to ferberite with increasing μP1O-1orμF2S-1,During the replacement of wolframite by scheelite, the wolframite residue must have been enriched in Mn.

This paper reviews the features of several tungsten ore deposits in southern China, including the Shezhuyuan, Yaogangxian, Xihuashan, Danping, Piatang and Dajishan mines.The authors think that the formation depth of greisen-type deposits is intermediate between the depths of pegmatite- and porphyry- type deposits. Using phase diagrams of the model system KaO-Al2O3-SiO2-H2O-HF, the formation mechanism of greisens has been argued. The variation of mineral assemblages from K-feldspar, muscovite to topaz reflects a gradual increase in acidity. This variation can be used as a criterion to appreciate the depth of mineralization.Equilibria of tungsten minerals in greisen and skarn deposits can be depicted on chemical potential diagrams of the model system CaO-FeO-WO3-CO2-F2O-1. The assemblage wolframite + fluorite is shown to have been transformed to scheelite +magnetite with decreasing μHF. Depending on CO2 activity in the fluids, there are two distinct phase diagrams. One shows that wolframite is incompatible with calcite, and the other demonstrates that scheelite is incompatible with rhodochrosite. On the phase diagrams of the model system FeO-MnO-WO3-F2S-1, huebnerite is transformed to ferberite with increasing μF2O-1orμF2S-1 During the replacement of wolframite by scheelite, the wolframite residue must have been enriched in Mn.