甘肃塔-尕地区大河坝组地球化学特征及成矿远景分析

Geochemical characteristics and metallogenic potential analysis of Daheba formation in Ta-Ga area of Gansu Province

西秦岭造山带西北缘为我国构造域复合叠加部位,成矿条件优越,甘肃塔-尕地区大河坝组为重要的金含矿层位,研究其地球化学特征对于判别沉积物源、构造环境和分析成矿远景有重要意义。通过采集大河坝组砂岩岩石全分析样品、基岩光谱样品并进行地球化学特征分析,结果表明,区内样品的主微量元素含量、比值特征、稀土元素配分模式等均具有典型壳源成因特征,w(Al_(2)O_(3))/w(TiO_(2))和w(Cr)/w(Zr)值指示成岩物质来源于长英质源区,综合La/Th-Hf图解确定其物源来自上地壳中的长英质岩石;从TiO_(2)-(Fe_(2)O_(3)+MgO)、(K_(2)O+Na2O)-SiO_(2)和Th-Co-Zr/10构造判别图解中判定其沉积构造环境为大陆岛弧;基岩光谱样品分析结果显示塔-尕地区大河坝组地层在提供金矿成矿物质来源方面存在优势,且较好的地层渗透性有利于成矿物质富集,综合判定该地层具有良好的金矿成矿远景。

The northwest margin of the western Qinling orogenic belt is the superposition site of China’s tectonic domain,and is superior in metallogenic conditions.The Daheba formation in the Ta-Ga area of Gansu Province is an important metallogenic horizon.This paper analyzes its geochemical characteristics which is significant to discriminate source of sedimentary materials and analysis of ore potential.Bulk analysis samples of sandstone and spectral samples of bedrock are collected and analyzed and tested.Results are geochemically analyzed showing that the main trace element content and their ratio characteristics and REE distribution pattern of the samples are characteristic of typical crustal genesis.w(Al_(2)O_(3))/w(TiO_(2))and w(Cr)/w(Zr)values indicate that the rock-forming maerials come from the felsic source area,La/Th-Hf diagrm from felsic rocks in upper crust.The Al2O3/TiO2 and Cr/Zr values indicate that the the sedimentary environment rock-forming materials comes from the Felsic source area.According to the La/Th-Hf diagram,the provenance is determined to be felsic rocks in the upper cruts.According to the structural discrimination diagrams of TiO_(2)-(Fe_(2)O_(3)+MgO),(K_(2)O+Na_(2)O)-SiO_(2) and Th-Co-Zr/10 structures,it is determined that the sedimentary tectonic environment is continental island arc.The results of the bedrock spectral samples show that the Daheba formation in Ta-Ga area has advantages in providing the source of gold ore-forming minerals,and its better permeability is beneficial to the enrichment of ore-forming materials.According to the comprehensive judgment,the stratum is potential for Au prospecting.