柿竹园钨锡多金属矿床矽卡岩中碱交代脉研究

柿竹园钨锡多金属矿床地处南岭中段,矿种多、规模大、共生组分丰富,是世界罕见的超大型钨锡钼铋多金属矿床。区内发育有大量不同类型的脉体,包括酸性岩浆岩脉、云英岩脉、碱交代脉等,其中发育于矽卡岩中的碱交代脉是矿区规模最大、分布最广的矿体。本文通过详实的野外地质调研、显微镜下岩相学鉴定以及电子探针测试分析,发现大部分碱交代脉中以钾长石、斜长石、石英、萤石为主,白云母含量较少,一般小于3%,含少量黄玉、电气石等矿物,并非前人所称的"云英岩脉"或"云英岩网脉",脉体外侧发育较多的石榴子石、透辉石等矽卡岩类矿物,脉体及其两侧含有较多的白钨矿、磁铁矿等氧化物。从矿物组合和矿化特点上分析,碱交代脉总体碱质成分含量较高,发生了较强的碱交代作用,脉体的形成与矽卡岩演化关系密切,可进一步分为:早期阶段碱交代脉,富斜长石、黑钨矿,形成矽卡岩,对应矽卡岩演化的矽卡岩阶段,是黑钨矿的主成矿期;晚期阶段碱交代脉,富钾长石、白钨矿、磁铁矿,表现为交代矽卡岩,对应矽卡岩演化的退变质阶段,是白钨矿的主成矿期。综上,柿竹园矿床矽卡岩中碱交代脉,制约和影响着矽卡岩的形成与成矿,贯穿矽卡岩演化过程的矽卡岩阶段和退变质阶段,其形成的矿体为矽卡岩型矿体。

Research on the alkali metasomatic veins in skarn of the Shizhuyuan W-Sn polymetallic deposit

The Shizhuyuan W-Sn polymetallic deposit in the middlel of Nanling region is a superlarge W-SnMo-Bi polymetallic deposit rarely seen in the world,characterized by multi-mineral resources,large size and rich associated components.It has numerous veins of different types,composed mainly of acid magmatic dikes,greisen veins and alkali metasomatic veins in the skarns,with the alkali metasomatic veins comprising the largest and most widely distributed ore bodies.Based on detailed field investigation,microscopic petrographic analysis and EPA analysis,the authors found that the main minerals in the veins are potassium feldspar,plagioclase,quartz and fluorite,the muscovite content is small(<3%),and topaz,tourmaline content is rare.They hence do not belong to the "greisen veins" or "greisen stockwork".The vein body has extensively developed some skarn minerals,and the vein body and its both sides contain more tungsten and magnetite.On the whole,the alkali composition in the alkali metasomatic vein is relatively high,and has experienced strong alkali metasomatism.The vein bodies can be divided into two types,i.e.,the early alkali metasomatic vein and the late alkali metasomatic vein.The early alkali metasomatic vein contains more plagioclase and wolframite,which is the main ore-forming period of the wolframite in accord with the evolution of the skarn.The late alkali metasomatic vein contains more potassium feldspar,tungsten and magnetite,which is the main ore-forming period of the scheelite in accord with degradation metamorphic stage.The authors thus hold that the alkali metasomatic veins in skarn of the Shizhuyuan ore district restricted and affected the formation of skarns and the ore-forming process,and their evolution passed through the skarn stage and the degradation metamorphic stage.The alkali metasomatic veins belong to the skarn type ore bodies.