大西沟—银洞子矿田滑塌构造的发现及其地质意义

大西沟－银洞子矿田由两个相邻的大型矿床组成，西部为大西沟菱铁矿矿床，东部为银洞子银－铅多金属矿床。在两个矿床接合部位的１１号矿体中，发现一套典型的小型滑塌构造，其变形层为薄层菱铁矿，非变形层为条带状重晶石岩，两者均为海底喷流成因的水沉积而成。滑混构造的发现表明，在成矿作用过程中两个矿床接合部位存在着一个近南北向水下高地，将沉积盆地分割成两个次级沉积洼地。该水下高地控制着两个洼的沉积环境和成矿条件，

DISCOVERY AND GEOLOGICAL SIGNIFICANCE OF SLUMP STRUCTURE IN THE DAXIGOU-YINDONGZI OREFIELD

Daxigou-Yindongzi orefield consists of two neighboring large deposits. The Daxigou siderite deposit is located in the western part of the orefield and the Yindongzi silver-lead polymetallic deposit is located in the eastern part of the orefield. Typical slump structure was found in orebody No, 11 at the juncture of the two deposits. The deformed bed is marked by a thin siderite bed and the nondeformed bed is represented by beded barite rock, both being hot-water sedimentary rocks.Discovery of the slump structure indicates that there would be an underwater highland in the juncture between the two deposits, which divides the sedimentary basin into two depressions and controls the sediemntary environments and mineralization conditions of the two depressions. Theeastern depression is possibly deeper, in which hot brine may be divided into two parts-theupper and lower brine layers. The upper brine layer probably belongs to weaker oxidation-reduction sedimentary environment, forming barite-siderite orebodiee formed. The lower brine layer belongs to strong reduction sedimentary environment, in which silver-lead polymetallic sulfide orebodies formed. The depth of the western depression is believed to be comparatively shallow and the sedimentary environment may be similar to that of the upper brine layer in eastern depression , in which barite-siderite/magnetite orebodies are formed, Shaanxi Province.