【作者】 韦龙明；

【导师】 郑明华；

【作者基本信息】 成都理工大学 ， 矿物学岩石学矿床学， 2004， 博士

【摘要】 位于陕甘交界的凤县八卦庙金矿床是迄今发现的,产于秦岭地区泥盆系沉积岩中规模最大的金矿床。金矿床的含矿地层为下泥盆统星红铺组,容矿岩石为浅变质细碎屑岩系,其中发育有海底热水沉积成因的条带状的钠钙硅质岩和纹层状钠长石岩。 条带状钠-钙-硅质岩呈纹层、条带状构造,在走向上与千枚岩渐变过渡。条带宽度多<1cm,少数达几cm,岩性类型包括（含）铁碳酸盐硅质岩、含铁碳酸盐钠长石硅质岩、石英钠长石岩、（含）石英铁碳酸盐岩。剖面上出现条带岩带→斑点板岩带→含碳质千枚岩带的沉积旋回;薄片下常见到富硅质纹层（或富钠长石纹层）→富铁碳酸盐纹层→泥质纹层的沉积韵律,纹层厚度0.1～1.2mm不等。 位于矿区北部的钠长石岩呈透镜状产出,岩石纹层构造发育,Sr/Ba值均<1,属沉积成因而非侵入成因。 上述两类岩石的Fe₂O₃/FeO、SiO₂/Al₂O₃、SiO₂/MgO、SiO₂/（Na₂O+K₂O）等比值均与秦岭泥盆纪铅锌矿的热水沉积岩及现代海底热泉沉积物的组成一致,在Fe-Mn-（Co+Ni+Cu）×10三角图解上的投影点均落在现代海底热水沉积物区和秦岭泥盆纪铅锌矿的热水沉积岩分布区内,通过稀土元素及氢、氧、碳、硅同位素等综合研究,表明它们属于热水沉积成因。随着泥盆纪秦岭裂陷槽的形成,伴随凤太裂陷海盆边缘的同生断裂活动,形成金丰度较高的热水沉积岩系,它们与金矿化关系密切。 八卦庙矿床的金矿体主要沿褶皱构造破碎带分布,形态为大的透镜状、似层状,其产状与围岩产状基本一致。已鉴定出的矿物有30余种,常见矿物仅10余种,金属矿物总量一般<3%,以磁黄铁矿、黄铁矿、自然金最为常见,还见有白铁矿、黄铜矿、方铅矿、闪锌矿、钛铁矿等,脉石矿物中绢云母和白云母占30-50%,石英占10-25%,碳酸盐矿物占12-20%。元素组合为Au—Hg—Ag—B—Zn—Cu—Pb—Sb—As组合,以Au—Ag组合关系最为密切。矿床以具有独特的磁黄铁矿和黄铁矿组合、围岩蚀变褪色、斑点构造及发育顺层、穿层石英脉为特征。就其容矿岩石性质、矿物组合、元素组合及成矿机制等,均与典型的卡林型金矿床存在差异。 八卦庙矿区的金矿物主要以独立矿物形式产出,绝大部分为自然金,呈中细粒金—显微金为主,多以粒间金的形式存在,其次是裂隙金和包裹金,主要载金矿物为石英、磁黄铁矿和黄铁矿。矿石的金品位与其石英脉带的发育程度和揉皱（破碎）程度、共生硫化物的含量成正比,与脉体的厚度、共生硫化物的粒度成反比;节理脉的含金量比顺层脉的含金量高;石英细脉的含金量高于脉旁围岩的含更多还原

【Abstract】 The Baguamiao is the largest gold deposit found so far in Devonian sediments in Qinling Region, which located in Fengxian, Shaanxi near Gansu province. The Baguamiao deposit is hosted in the Xinghongpu group of lower Devonian, which consists low-grade fined-grained clasts, with striped Na- and Ca-bearing silicates and laminated albite. It is showed to be hydrothermal sediments on seabed.The natrium- calcium-silicalites with strip structure is gradually changing into phyllite. The thickness of the rocks is thinner than 1 cm in general and the minority reaches several cm. The rock types include the iron-bearing carbonate silicalite, the iron-bearing carbonate albite silicalite, and quartz albite, quartz- and iron-bearing carbonate. On the section in the field, there is depositional cycle with the change of the strip rock zone → the spot slate zone → carbon-bearing phyllite from the bottom upward.. There is a series of lamina change interbedded by iron-riching carbonate lamina, albite-bearing lamina and argillaceous lamina in thin section. The thickness of the lamina is from 0.1 to 1.2 mm.The albite, shaped in lense, is located in the northern of the deposit and the ratio of Sr/Ba is smaller than 1, which was identified to be sedimentary genesis rather than intrude.The ratios of Fe₂O₃/FeO, SiO₂/Al₂O₃, SiO₂/ MgO and SiO₂/（Na₂O+K₂O） of the two type rocks above are similar to those of the hydrothermal sedimentary rock of the lead-zinc deposits in Devonian, Qinling and the hydrothermal sediments on the sea floor. The projection pots locate in the area of the lead-zinc deposits in Devonian, Qinling and the modern hydrothermal sediment on the sea floor in the triangle diagrammatize of Fe-Mn- （Co+Ni+Cu）× 10. According to the synthesis study by their REE element and H, O, C, Si isotope, they belong to the hydrothermal sedimentary origin. Along with forming of the Qinling crack and sink trough in Devonian and the movement of the syngenetic rupture, the hydrothermal sedimentary rock series with gold-riching are formed, which is close relative to gold mineralization.The orebodies in Baguamiao gold deposit occurred as lens-like and bed-like orebodies along the fault zone with showing approximately comfortable attitudes with the host rocks. There are 30 various minerals about in ores. Of which, about 10 various minerals are common. The metal minerals less than 3%. Pyrotite, pyrite and native gold are common. Binerite, chalcopyrite, galena, sphalerite and ilmenite can be seen also. The element assemblage is Au-Hg-Ag-B-Zn-Cu-Pb-Sb -As, in which the Au-Ag assemblage is the most important. Baguamiao gold deposit is characteristic with the alone pyrotite and pyrite assemblage, altered and depigment of wall rock, spot structure and the quartz veins occur along or cut the stratum, which is different with the typical Carlin type or similar Carlin type gold deposits.The gold mineral of Baguamiao gold deposit is independent gold. The gold is usually in middle-, fine and micro- size. Gold is mainly occurred as intercrystal—gold and Crach—gold, and inclusion—gold is little. The gold mainly hosted in quartz, pyrotite and pyrite. It is shown by the gold ore selectation that Baguamiao gold deposit can be developed and utilized. The gold content in Baguamiao giant gold deposit is in direct proportion to the development and folded broken degree of quartz vein and to the content of co-existed sulphide, and is in inverse proportion to vein thickness and the grain size of co-existed sulphide. The gold content in joint vein is higher than that in bedding vein.the gold content is several to more than ten times of the content in surrounding rock nearby. Nevertheless industrial ore body isn’t alone consisted of gold-quartz vein. In view of the points mentioned above, the authors put forward that the gold mineralization type is更多还原