青海省都兰县诺木洪河东地区1∶2.5万地球化学测量在找矿中的应用

An Application of 1∶25,000 Geochemical Survey in Prospecting in Nuomuhonghe East area, Dulan County, Qinghai Province

青海省都兰县诺木洪河东地区位于柴达木盆地的南缘,诺木洪镇南部昆仑山东段布尔汗布达山,地貌总体表现为中部高,南北部低,地形多变,变化跨度大,因水系总体不发育,具有严重的风成物干扰现象,采用1∶25万、1∶5万等小比例尺化探水系测量对区内地质勘查找矿工作影响较严重。该区1∶2.5万地球化学测量工作,平均的采样密度为每平方千米21个点,采样介质多为水系沉积物,少量为残坡积碎屑物质,采样粒级一般为-10~+60目截取粒级。通过区内地球化学特征、元素的富集与离散特征、主要成矿元素组合特征和空间分布特征总结分析,明确了研究区内主要的成矿元素是Sn、W、Bi、Au、As、Cu。Sn、W、Bi富集成矿,与中酸性花岗岩侵入岩和碳酸盐岩接触带有关;Au、As、Cu富集成矿与昆中断裂附近韧性剪切带及北西西向断裂有关。在研究区内圈出的锡、金异常内已圈出多条锡、金矿体。说明1∶2.5万地球化学测量的化探找矿方法有效,对诺木洪河东地区地质勘查找矿有较好的指导作用。

The east area of Nuomuhong River in Dulan County of Qinghai Province is located in the southern margin of Qaidam Basin, and Buerhanbuda Mountain of the east section of Kunlun Mountain of the south of Nuomuhong Town. The landform is generally high in the middle and low in the south and north. The terrain is variable and the variation span is large. The small scale geochemical drainage survey, such as 1∶250 000 and 1∶50 000, has a serious impact on the geological exploration and prospecting work in the area. The work of 1∶25 000 geochemical survey in this area shows the average sampling density is 21 points per square kilometer. Most of the sampling media are stream sediments and there are small amount in residual slope debris. The sampling particle size is generally 250~1 700 μm. The main metallogenic elements in the study area are Sn, W, Bi, Au, As and Cu. The analysis shows the geochemical characteristics, elements enrichment and dispersion characteristics in assemblage characteristics and spatial distribution characteristics of main metallogenic elements. Sn, W, Bi enrichment is related to the contact zone between intermediate-acid granite intrusive rocks and carbonate rocks. The enrichment and mineralization of Au, As and Cu are related to the ductile shear zone near kunzhong fault and NWW trending fault. Several tin and gold ore bodies have been enclosed in the tin and gold anomalies in the research area. The results show that the geochemical prospecting method of 1∶25 000 geochemical survey is effective. It has a good guiding role for geological exploration and prospecting in the east nuomuhonghe area.