黑龙江省东部梧桐河—都鲁河流域流水成因砂金矿特点

梧桐河-都鲁河流域是我国主要砂金富集区之一.区内以流水成因河漫滩砂金矿和阶地砂金矿为主.砂金矿的分布,明显地受矿质来源、新构造运动、水动力条件和沉积环境的控制.砂金矿体多呈带状、条带状赋存于河谷堆积物的底部,在矿体中经常出现一至几个富矿地段.砂金粒度为0.03-3.5mm.区内砂金矿的找矿前景好,主要找矿标志是旧采金迹、金矿化异常区和老变质岩分布区.根据砂金矿的分布和富集规律,可在五号山、小梧桐河北支沟、西梧桐河二支沟一带寻找岩金矿.

ALLUVIAL GOLD PLACER IN WUTONGHE-DULUHE DRAINAGE AREA OF EASTERN HEILONGJIANG PROVINCE

Wutonghe- Duluhe drainage area is one of the major concentration area of gold placers in China. In this area, the metamorphic rock series of Lower Proterozoic Heilongjiang group, Mashan group and Cretaceous volcanic rocks are widespread, Late Proterozoic migmatitic granite and Variscan granite cover a large area and Yanshanian granite, granitic-porphyry are mostly small stock. are S-N faults the major structures in this area and NE- and NW- trending faults are also developed and charactreistic of muitiple activity. This area is a low mountain- hilly geomorphic country with dendritic drainage of Wutonghe-Duluhe river system.The gold background value of the metamorphic rock series of the Heilongjiang and Mashan groups is high and gold content of altered granite, andesite, quartz vein, pegmatite and altered kataclastic zone is also high, up to 32.34g/t in maximum with phaneromerous gold. These rocks provided abundant ore materials for the formation of gold placer.The major types of gold piacer in this area are alluvial valley flat and terrance gold placer. The distribution and concentration of gold placers are controlled obviously by source of ore materials, neotectonic movement, hydrodynamic condition and sedimentary environment. Gold placer orebodies are mostly bended and striped form and occurs in sandy gravel bed and sandy-gravel debris bed in the bottom of river valley accumulation.One or several bonanzas may be present in a gold placer body beacause of difference of feeder provenance and river valley geomorphy.Gold content in the botton of a gold placer body is several times, tens times or even a thousand times as high as in the upper portion.The valley flat gold placer orebody is obviously wider than the present river bed and the width of a gold placer orebody has no certain proportion relation to its length.The grains of placer gold is dominently 0.3-3.5mm in size, and the intergrowth of gold grain and vein mineral is common. Generally, gold grain size is bigger in the head and bottom and smaller in the tail and top of a gold placer orebody, and bigger in metamorphic rocks area and smaller in volcanics area. Gold grains are mainly granular, flaky and scaly and abraded, The fineness of gold is generally 620-870‰.The prospect of gold placer is good in this area. The main prospecting criteria is mining traces of gold placers, old metamorphic rocks and anomaly of mineralizations. According to the distribution and concentration regularity of gold placer, primary gold deposits might be searched for in Wuhao mountain, the northern branches of Xiao Wutong river and the NO.2 branch of Xiwutong river etc.