人工重砂在蚀变岩金矿勘查中的应用——以宁夏树龙沟金矿为例被引量：4

Application of Placer in Exploration of Altered Rock Type Ore Deposit——A Case Study of the Shulonggou Gold Deposit

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摘要蚀变岩型金矿床中金常以"大颗粒金"形式存在,但针对其在蚀变矿化带中分布规律的研究相对缺乏。而且,采样及分析化验方法选择不当会导致测试结果与真实情况存在较大偏差,影响客观准确地评价找矿潜力。本文对宁夏树龙沟金矿床开展人工重砂研究,以期确定金的赋存状态、研究自然金的分布规律,以此指导区内相关勘查工作的具体部署。树龙沟金矿床为蚀变岩型金矿,受区内NE向断裂构造控制,从蚀变中心向两侧分别发育石英黄铁矿化带-伊利石黄铁矿化带-伊利石绿泥石化带,蚀变带宽度累计约10~20 m。采集的101件人工重砂样品中含自然金样品共计74件,其中粗粒金(>0.07 mm)样品总量达62.4%。通过区内各类蚀变(矿化)相关的矿物与金含量关系的系统对比后发现:(1)自然金含量与褐铁矿呈正相关关系,与石英呈负相关关系,与黄铁矿的关系复杂;(2)伊利石黄铁矿化带中的自然金含量高于石英黄铁矿化带和伊利石绿泥石化带;(3)矿区基性岩脉与金无成因联系,基性脉岩及其后期破碎为金矿化提供了构造通道。本文认为在该区找矿工作中应该将伊利石黄铁矿化及石英黄铁矿化作为重要的找矿标志。本矿床自然金属于粗粒-巨粒,矿石中金含量的测定应选用针对明金的过筛火试金等分析方法。 Gold often occurs as visible native gold in altered rock type gold deposits, however, distribution of native gold in the altered belts is not well-documented. Chemical analyses of gold often yield biased results due to improper selection of sampling and analysis methods, which may lead to poor evaluation of prospecting potential. The artificial placer is a useful method in prospecting by select heavy minerals from rocks or ores. In order to determine the occurrence and distribution of native gold, and guide the exploration, artificial placer study was carried out in the Ningxia Shulonggou gold deposit. The Shulonggou gold deposit is an altered rock type gold deposit, controlled by NE-trend fault structures. The width of alteration belts is about 10-20 m. The alteration types change successively from the center of the alteration belt to either side with the quartz-pyritization belt in the central part, the illitic-pyritization belt and the illitic-chloritization belt in the margin. 74 of 101 samples have native gold, and the content of coarse-grained gold is up to 62.4%. The contents of native gold is positively correlated with limonite, and negatively correlated with quartz. The illitic-pyritization belts have more native gold than the quartz-pyritization belts. The mafic dikes in this deposit have no genetic relationship with gold mineralization, but may provide tectonic channels for gold mineralization. So we suggest the illitic-pyritization and quartz-pyritization are important indicators of ore expecting. Due to the coarse-grained nature of the native gold in the ores, it should be very cautious in method selection for chemical analyses of gold contents in geological prospecting.