摘要
砂金富集规律可归纳为五条:(1)砂金比重大,体积小,一般下沉于砂砾层底部基岩之上,形成富矿带。(2)河流流速减缓处是砂金富集之场所,如河流内湾处;两河会流处;河谷由宽突变窄处;河谷由窄突变宽处。(3)河床起伏不平是砂金富集之主要条件。最理想的河床是软硬相间之岩层,如砂页岩互层,且走向横穿河谷,倾斜较陡,这样,便形成具有无数隔梁与隔槽的起伏不平的河床,砂金受阻,易于停积。(4)位于谷旁之古老河床沉积阶地是无水患的易采砂金矿床,不容忽视。(5)红黄杂色铁砂及石英碎屑常为砂金富集标志。
The West Sichuan Plateau belongs to the eastern marginal part of the Qinghai-Xizang Plateau. From east to west there are 3 large rivers, Dadu, Yalong and Jinsha rivers running through from north to south. The topography of the plateau is sufferec to the deep erosion by these rivers and their tributaries.The stratigraphy in this region chiefly represents the flysch type deposits of sandstone and shale formations of the Triassic age. It was strongly folded and abundant granites have emplaced of the Indosinian-Yanshanian Cycle outcroped along the flanks of on the anti-clinoria. The gold bearing quartz veins which are related genetically with the grauites are widely distributed every where. They are usually in the short lenticular forms scattered here and there controlled by the abundant irregular fissures in the rocks. After the weasthering and erosion of the veins the materials as the residual and slope deposits were formed and then became the fluvial placer gold deposits with economic values through the transportation by the brooks and rivers.Five regularities of formation of the placer gold deposits may be summarized as the following which may be useful for the exploration and mining of the placer gold in any places.1. The characteristic of the gold bearing gravel bed. The gold is large in specific gravity and small in size. It usually sinks down to the bottom of the gravel bed above the bedrock forming the rich ore zones or pay streaks which are the target beds for the exploration of the sand gold with a thickness of 0.5-5m. Some muddy layers of lenticular form are usually included in the middle parts of the gravel bed acting as a local pseudo-bedrock and some local ore deposits formed upon it.2. The regions where the rivers are reduced in flow velocity are the ones of rich accumulation of the placer gold. It includes 4 kinds of regions: 1) the inner bank of the sinuous river, 2) the confluence of two rivers, 3) the section of the river where it is suddenly narrowed. 4) the section of the river where it is sudde
出处
《地质科学》
CAS
CSCD
北大核心
1989年第4期308-313,共6页
Chinese Journal of Geology(Scientia Geologica Sinica)
关键词
砂金矿床
形成规律
川西高原
west Sichuan plateau, placer gold deposit, the law of formation
