甘肃鹿儿坝金矿床金赋存状态研究

The Occurrence State of Gold in the Luerba Gold Deposit,Gansu Province

甘肃鹿儿坝金矿处在西秦岭“岷礼金矿带”上,是我国卡林型金矿“西北金三角”组成部分。该矿床赋存于洮河复向斜北东翼之中三叠统浅变质浊积岩建造中,矿体受NWW向断裂构造控制明显,矿石以中-低温热液蚀变矿物组合为特征,是一个正在开发但难选的大型金矿床。为了解金的赋存状态,文章通过中-高倍矿相显微镜、金化学物相分析及电子探针(EMPA)测试等手段,研究了金在矿石中的赋存状态。结果表明,三类矿石中金的分布型式基本一致,载金矿物主要为毒砂、石英、黄铁矿和铁白云石;金以矿物包裹金为主,总占比达96.31%,其中硫化物包裹的金占61.45%~89.01%、硅酸盐中的金占有率为7.28%~25.49%,独立存在的金矿物较少,占1.03%~9.01%;独立金矿物主要以矿物粒间单体金形式存在,金成色987.05‰,为自然金,粒度以0.0009 mm×0.0061 mm~0.0078 mm×0.0114 mm为主。这为矿床研究提供了基础信息,并为改善矿山生产提供了一定的理论依据。

The Luerba gold deposit in Gansu Province,a part of the Northwest Gold Triangle of Carlin-type gold deposits in China,is located in the Minxian-Lixian gold ore belt in the West Qinling.The deposit occurs in the Middle Triassic shallow metamorphic turbidite formation in the northeast wing of the Taohe synclinorium.Its ore bodies are obviously controlled by NWW trending fault structure.The ore is characterized by medium-low-temperature hydrothermal alteration mineral assemblage.It is a large-scale gold deposit under development but its ore is difficult to sort.The purpose of this work is to clarify the occurrence state of gold in the ore of this deposit by means of medium-high power mineralogical microscope,gold chemical phase analysis and EMPA.Results show that the distribution patterns of gold in three kinds of ores are basically the same:gold wrapped in minerals accounts for 96.31%,among which gold wrapped by sulfide accounts for 61.45%~89.01%and gold in silicate accounts for 7.28%~25.49%.Independent gold mineral is less,accounting for only 1.03%~9.01%,which mainly exists in the form of monomer gold between mineral grains.The gold fineness is 987.05‰,which is native gold,with particle size of 0.0009mm×0.0061mm~0.0078mm×0.0114mm.These results provide basic information for further research of the deposit as well as a theoretical basis for improving mine production.