摘要
本文根据若干产于钙质围岩中钨矿脉的矿物组合特征和热力学计算结果,证明了在富钙环境中,如果热液同时富含F^-、Fe^(2+)、Mn^(2+),且具酸性还原条件,则可以形成黑钨矿,而不是一定形成白钨矿。所以在富钙环境中形成黑钨矿不能否定矿脉与围岩的物质交换,也不能否定钙以络合物的形式迁移。
In some deposits, wolframite-quartz veins occur within calcium-rich wall rocks including limestone, marble or skarn. Looking into their mineral associations, the author found that when wolframite appears, fluorite is surely existent but no minerals formed in oxidation environment (such as magnetite and barite) can be observed. On the other hand, in case when wolframite fails to appear, either magnetite or barite might be seen or no ferromanganese-bearing minerals are present.In the WO_4~2-(Mn^(2+), Fe^(2+)) -Ca^(2+)-F^-CO_(?)~2-O_2-H_2O system, there exist complex relation between the ions and the minerals, and different environments are characterized by different reactions. When the hydrothermal solutions are . rich in F^-, Fe^(2+) , Mn^(2+) and are in an acidic-reducing environment, the following reaction will take place:nMn^(2+)+ (1-n)Fe^(2+)+ 2F^- + CaWO_4(?)CaF_2 + (Mn_(?), Fe_(1-n)) WO_4 The thermodynamic calculation demonstrates that the reaction is favorable for the formation of fluorite-wolframite association.It is concluded from the above discussion that only if the hydrothermal solutions are rich in F^- ,Fe^(2+) and Mn^(2+) and under the acidic reducing condition can wolframite be formed in a calcium-rich environment, and that the occurrence of wolframite quartz veins in limestone, marble or skarn can neither negate the existence of material exchange between the hydrothermal solutions and the wall rocks nor confirm the migration of tungsten in the form of wolframite particles.
出处
《矿床地质》
CAS
CSCD
北大核心
1989年第1期65-69,共5页
Mineral Deposits
