滇东北毛坪铅锌矿床的蚀变-矿化分带模式——蚀变-岩相填图证据

The alteration-mineralization zoning model for the Maoping lead-zinc deposit,northeastern Yunnan Province: Evidence from alternation-lithofacies mapping

昭通毛坪铅锌矿床是川滇黔铅锌成矿域之滇东北矿集区上又一个具有超大型成矿潜力的矿床,过去其矿床研究程度弱,特别是成因矿物学工作鲜有开展。本文以赋存于猫猫山倒转背斜西翼上泥盆统宰格组上段(D3zg3)中晶白云岩中层间断裂带内的I号矿体(群)为对象,开展了系统的立体蚀变-岩相填图研究,建立了蚀变-矿化分带模式。结果表明:从矿体中心向外,自下而上,蚀变呈现硅化→泥化→碳酸盐化的显著分带现象,矿化具有致密块状高品位Pb-Zn矿石→致密块状Py壳→浸染状、脉状、斑块状低品位Pb-Zn矿石→星点状Py壳的分带特点,相应的矿物组合依次为Sp+Gn(+Cpy)+Py+Mrc+Apy+Q+Cal组合、Py+Gn+Sp+Dol+Fe-Dol+Cal+Q+Ill组合、Py+Dol+Fe-Dol+Cal+Q+Sd组合和Dol+Cal组合;垂向分带不明显,横向分带显著,矿化分带性与含矿热液的浓度梯度、横向渗透扩散受岩性垂向物性变化影响密切有关;矿化作用可分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ等5个阶段,Py外壳是早期流体的产物,条带状矿石是热液叠加作用的产物,且784 m高程处已处在Ⅲ阶段成矿流体叠加的前锋,Ⅱ阶段成矿流体的温度较Ⅲ阶段高。该蚀变-矿化分带模式对川滇黔铅锌成矿域具有普遍的找矿指导价值,也有助于深入理解成矿流体运聚和富集成矿机制。

The Maoping Pb-Zn deposit,located in Zhaotong City of northeastern Yunnan Province,is a Pb-Zn polymetallic deposit with superlarge-sized potential in Sichuan-Yunnan-Guizhou metallogenic area.The previous studies of its mineralization was weak,and the mineralogical work was especially insufficient.The No. I ore body group occurs in the interformational fault zone of dolomite within upper Devonian Zaige Formation,lying in the west wing of Maomaochang inverted fold.In this paper,based on three-dimensional alternation-lithofacies mapping and petrographic studies of No.I ore body group,the authors established a mineralization-alteration zoning model.The results indicate that the alternation zoning is silicified zone,carbonation ＋ silicification ＋ argillation zone and carbonation zone from the center of ore bodies outwards.Correspondingly,the mineralization zoning changes from massive high grade ore to massive pyrite shell,disseminated-vein-patchy low-grade ore and starry pyrite shell.The mineral assemblage zoning can be divided into Sp＋Gn（＋Cpy）＋Py＋Mrc＋Apy＋Q＋Cal assemblage,Py＋Gn＋Sp＋Dol＋Fe-Dol＋Cal＋Q＋Ill assemblage,Py＋Dol＋Fe-Dol＋Cal＋Q＋Sd assemblage and Dol＋Cal assemblage.The vertical zoning is not significant,whereas the horizontal zoning is well developed,which is related to the effect of the concentration gradient of vertical physical changes of ore-bearing hydrothermal solution and lithology.Mineralization-alternation can be divided into five stages,i.e.,Ⅰ,Ⅱ,Ⅲ,Ⅳ and Ⅴstage.Pyrite shell is the product of early fluid,and banded ore is the product of hydrothermal superposition.The 784 meter level is the ore-forming fluid superimposed striker of Ⅲ stage.Ore-forming fluid temperature of Ⅱ stage is higher than that of Ⅲ stage.The alteration and mineralization zoning model is of great indicating significance for the prospecting of mineral resourcesg and the understanding of the migration,concentration and enrichment of ore-forming fluids.