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
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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.
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.
引文
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耿元生,周喜文,王新社,任留东.2009.内蒙古贺兰山地区古元古代晚期的花岗岩浆事件及其地质意义:同位素年代学的证据.岩石学报,25(8):1830-1842.
黄智龙.2001.幔源岩浆活动过程中的去气作用.矿物岩石地球化学通报,20(1):1-5.
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李红宇,宋新华,郭合伟,孙文坤,谷守江,张连昌,黄世武,陈志广.2010.宁夏贺兰山北段牛头沟金矿地质地球化学特征和矿床成因探讨.地质与勘探,46(6):1036-1044.
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谭俊.2009.胶东郭城断裂带脉岩岩浆演化过程:对岩石圈演化及金成矿的制约.武汉:中国地质大学博士学位论文:102-104.
谭俊.2013.宁夏贺兰山北段金成矿类型及构造控矿规律.黄金,34(12):9-14.
万宏.1989.铜陵桃园铁帽型金矿床氧化带与金的赋存特征.地质找矿论丛,4(2):28-41.
王鹤年,储同庆.1982.金的赋存形式及其有关地球化学问题.矿物岩石,(1):84-95.
王玉明,陈小明.1996.石英中金的赋存状态研究.地质地球化学,(5):5-8.
许庄.2008.重砂的鉴定方法及其指示作用.化学工程与装备,(4):79-81.
Dan W,Li X H,Guo J,Liu Y and Wang X C.2012.Integrated in situ zircon U-Pb age and Hf-O isotopes for the Helanshan khondalites in North China Craton:Juvenile crustal materials deposited in active or passive continental margin?Precambrian Research,222:143-158.
Golding S D,Mc Naughton N J,Barley M E,Groves,D I,Ho S E,Rock N M S and Turner J V.1989.Archean carbon and oxygen reservoirs:Their significance for fluid sources and circulation paths for Archean mesothermal gold deposits of the Norseman?Wiluna Belt,Western Australia.Economic Geology Monograph,6:376-388.
Morton A,Hallsworth C,Kunka J,Laws E,Payne S and Walder D.2010.Heavy mineral stratigraphy of the Clair Group(Devonian?Carboniferous)in the Clair Field,West of Shetland,UK//Ratcliffe K T and Zaitlin B A.Modern Alternative Stratigraphic Techniques:Theory and Case Histories.Society of Economic Paleontologists and Mineralogists Special Publication,94:183-201.
Okay N and Ergün B.2005.Source of the basinal sediments in the Marmara Sea investigated using heavy minerals in the modern beach sands.Marine Geology,216(1):1-15.
Rock N M and Groves D I.1988.Do lamprophyres carry gold as well as diamonds?Nature,332:253-255.
Wyman D and Kerrich R.1988.Lamprophyres a source of gold.Nature,332:209-210.
Yin C,Zhao G,Guo J,Sun M,Xia X,Zhou X and Liu C.2011.U-Pb and Hf isotopic study of zircons of the Helanshan Complex:Constrains on the evolution of the Khondalite Belt in the Western Block of the North China Craton.Lithos,122(1):25-38.
耿元生,周喜文,王新社,任留东.2009.内蒙古贺兰山地区古元古代晚期的花岗岩浆事件及其地质意义:同位素年代学的证据.岩石学报,25(8):1830-1842.
黄智龙.2001.幔源岩浆活动过程中的去气作用.矿物岩石地球化学通报,20(1):1-5.
黄智龙,王联魁.1995.云南老王寨金矿区煌斑岩成因讨论.岩石矿物学杂志,14(4):313-324.
李红宇,宋新华,郭合伟,孙文坤,谷守江,张连昌,黄世武,陈志广.2010.宁夏贺兰山北段牛头沟金矿地质地球化学特征和矿床成因探讨.地质与勘探,46(6):1036-1044.
李厚民,沈远超,胡正国,汤红云,钱壮志,刘继庆,孙继东.2001.青海五龙沟金矿床矿石、矿物含金性及金的赋存状态.矿物学报,21(1):89-94.
宁夏回族自治区地质矿产局.1990.宁夏回族自治区区域地质志.北京:地质出版社:7-18.
宋新华,李红宇,郭合伟,张连昌,孙文坤,谷守江,陈志广,张晓静.2010.贺兰山北段牛头沟金矿区围岩的原岩恢复、时代及其地质意义.岩石学报,26(5):1625-1632.
谭俊.2009.胶东郭城断裂带脉岩岩浆演化过程:对岩石圈演化及金成矿的制约.武汉:中国地质大学博士学位论文:102-104.
谭俊.2013.宁夏贺兰山北段金成矿类型及构造控矿规律.黄金,34(12):9-14.
万宏.1989.铜陵桃园铁帽型金矿床氧化带与金的赋存特征.地质找矿论丛,4(2):28-41.
王鹤年,储同庆.1982.金的赋存形式及其有关地球化学问题.矿物岩石,(1):84-95.
王玉明,陈小明.1996.石英中金的赋存状态研究.地质地球化学,(5):5-8.
许庄.2008.重砂的鉴定方法及其指示作用.化学工程与装备,(4):79-81.
Dan W,Li X H,Guo J,Liu Y and Wang X C.2012.Integrated in situ zircon U-Pb age and Hf-O isotopes for the Helanshan khondalites in North China Craton:Juvenile crustal materials deposited in active or passive continental margin?Precambrian Research,222:143-158.
Golding S D,Mc Naughton N J,Barley M E,Groves,D I,Ho S E,Rock N M S and Turner J V.1989.Archean carbon and oxygen reservoirs:Their significance for fluid sources and circulation paths for Archean mesothermal gold deposits of the Norseman?Wiluna Belt,Western Australia.Economic Geology Monograph,6:376-388.
Morton A,Hallsworth C,Kunka J,Laws E,Payne S and Walder D.2010.Heavy mineral stratigraphy of the Clair Group(Devonian?Carboniferous)in the Clair Field,West of Shetland,UK//Ratcliffe K T and Zaitlin B A.Modern Alternative Stratigraphic Techniques:Theory and Case Histories.Society of Economic Paleontologists and Mineralogists Special Publication,94:183-201.
Okay N and Ergün B.2005.Source of the basinal sediments in the Marmara Sea investigated using heavy minerals in the modern beach sands.Marine Geology,216(1):1-15.
Rock N M and Groves D I.1988.Do lamprophyres carry gold as well as diamonds?Nature,332:253-255.
Wyman D and Kerrich R.1988.Lamprophyres a source of gold.Nature,332:209-210.
Yin C,Zhao G,Guo J,Sun M,Xia X,Zhou X and Liu C.2011.U-Pb and Hf isotopic study of zircons of the Helanshan Complex:Constrains on the evolution of the Khondalite Belt in the Western Block of the North China Craton.Lithos,122(1):25-38.
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