陕西省旬阳地区汞锑金矿床成矿条件

THE MINEROGENETIC CONDITIONS FOR THE Hg-Sb-Au DEPOSITS IN XUNYANG DISTRICT, SHAANXI PROVINCE

陕西省旬阳地区位于南秦岭南东端，区内广布一套古生代（主要为晚古生代）浅变质细碎屑岩－碳酸盐岩地层．其中蕴藏着丰富的汞锑金等多金属矿产资源，它们明显受中晚古生代沉积盆地的控制．尤其是与盆地边缘同生断裂有关的海底热液喷流作用，对成矿起着至关重要的作用．本区沉积盆地的规模对矿床规模的控制十分明显，概括地说）即大盆拄大矿，小盆控小矿，改造成富矿．旬阳地区汞锑金等多金属成矿系列似有先张后压的两阶段成矿模式．首先，中晚古生代，尤其是自志留－泥盆纪起，为一裂解扩张构造体制的成矿阶段．此时在区域上，旬阳－商县－洛南北东向基底走滑与盆地边缘断裂活动一起，构成海底热液喷流作用的构造驱动力和主要热流循环通道，使得大量的深源成矿物质进入沉积盆地，为其后的矿产资源储备了丰富的成矿物质——形成汞锑金等矿源层其二，印支一燕山期，本区进入块体拼接－推覆挤压构造体制的成矿阶段，随着地史演化，华北、扬子两大陆块的拼接，多次发生逆冲推覆活动，产生不同规模的褶皱及顺层滑动等剪切构造，使地层、岩石中的各种流体和大气降水混和并循环流动，形成具有高盐度的热卤水．其中携带有大量的Ｈｇ、Ｓｂ、Ａｓ、Ｐｂ、Ｚｎ、Ａｕ、Ａｇ、Ｗ等有用元素，在适宜环境沉淀成矿．

Xunyang district is situated at the southeast end of the South Qinling Mts., where are broadly developed Palaeozoic metamorphic microclastic rock and carbonate rock strata which contain abundant multi-metallic minerals, such as Hg, Sb, Au etc. The deposits are obviously controlled by Middle-Late Palaeozoic sedimentary basin, especially the seabed hydrothermal spurt related to the contemporaneous faults in basin fringes. The scales of the deposits was correlated to the dimensions of the sedimentary basins, that is, the larger the sedimentary basin is, the larger the deposit is. The reformation produced shoots. In Xunyang area, the multi-metallic metallogenetic series seem to undergo two stages of mineralization. The first was split extensional structure stage in Middle-Late Palaeozoic, especially Silurian-Devonian period. At that time, the Xunyang-Shangxian-Luonan northeast-trending basement strike-slip fault, together with the faults in the basin fringes, formed the structural drive and the chief hydrotheraml circulation channel for the hydrothermal spurt at the sea bottom. Amounts of anatectic minerogenetic material entered the sedimentary basin, forming of source bed for the multi-metals of Hg, Bb, Au etc. The second stage, during Indosinian-Yanshanian period, was a block mergence-compressive nappe structure mineralization stage. Along with the collision of the North China block and Yangtse block, this area developed many thrust nappings, and various scales of folds, bed- ding-slip shear structures and so on. Various fluids from the strata and rocks blended with precipitated water and circulated, forming high salinity hot brine which contained amounts of Hg, Sb, As, Pb, Zn, Au, Ag, W etc. and depositted in appropriate environment.