Geochemical Mapping——Evolution of Its Aims, Ideas and Technology

The development of geochemical mapping progressed from local geochemical prospecting through regional geochemical exploration and regional geochemical mapping to national and global geochemical mapping. This paper discusses the evolution of aims, ideas and methodology of geochemical mapping in Western countries, Russia and China. The sophistication of geochemical mapping methodology will make great contributions to solving resources and environmental problems in the 21st century.     

Geochemical Mapping——Evolution of Its Aims,Ideas and Technology

The development of geochemical mapping progressed from local geochemical prospecting through regional geochemical exploration and regional geochemical mapping to national and global geochemical mapping.This paper discusses the evolution of aims,ideas and methodology of geochemical mapping in Western countries,Russia and China.The sophistication of geochemical mapping methodology will make great contributions to solving resources and environmental problems in the 21~(st) century.     

Geochemical Behavior of Manganese in Weathering Environments and Its Significance in Exploration

Under and climate conditions the chemical weathering of manganese ores is govermed by the fugacities of O2,CO2 and S2 in the atmosphere and soils.Manganese minerals exhibit solid phase transformations without migration of Fe and Mn.Under tropical and subtropical humid climate condi-tions low-valent Mn is instable and apt to be oxidized into high valency state.High-valent Mn miner-als are stable and easy to form secondary high-grade Mn ores.Secondary concentration is possible for Mn ores in carbonate formations,while those in clastic rocks tend to migrate and may be washed away.Such differences are the main obstacles in prospecting Mn ore deposits.     

REE Geochemical Evolution and Its Significance of Early Precambrian Metamorphic Terrain,Wuyang,Henan

The supracrustal rocks of the Wuyang metamorphic terrain are divided into the Zhao anzhuang,Tieshanmiao and Yangshuwan Formations.These three Formations were dated at 3000-2550Ma,2550-2300Ma and 2300-2200Ma,respectively.∑REE and La/Yb)n of the Zhao anzhuang Formation volcanic rocks are obviously higher than those of the Tiesanmiao Formation equivalents,suggesting a sedimentary gap(2550 Ma boundary)between these two formations,The Zhao‘anzhuang Formation is older than the Tieshanmiao Formation.The sediments of these two Formations show no obvious differences in REE and are generally characterized by low ∑REE and positive Eu anomalies.On the contrary,the sediments of the Yangshuwan Formation are characterized by high ∑REE and negative Eu anomalies.Detailed discussions demonstrate that the Yangshuwan Formation was deposited in an oxidizing environment whereas the other two formations were formed in a reducing environment.At the end of the evolution of the Tieshanmiao Formation about 2300 Ma ago,the sedimentary environment was transformed from reducing to oxidizing .On the basis of the SHAB (soft/hard acid and base)theory,an oxidation-reduction model for sedimentary REE evolution has been established .It is proposed that the mantle tends to become gradually depleted in REE.especially in LREE,and the indices ∑REE and La/Yb) n of mantle-dervived volcanic rocks also tend to become lower and lower.     

Geochemical Evolution and Environmental Changes of Qinghai—Xizang Plateau Since Late Cenozoic

Long-and short-term climatic curves were preliminarily established based on the comprehensive analysis of geochemical information since the Late Cenozoic in the Qinghai Xizang(Qinghai-Tibet)Plateau.The curves show that the climate in the plateau was alternatively dry-warm and cold-wet during the period of 30-3.4 Ma when the plateau was not uplifted to an enough altitude and the monsoon was not completely formed either,In the period of 3.4-0.73 Ma.the climate fluctuated between dry-cold and wet-warm when the plateau was rapidly uplifted and the Asian monsoon was consequently formed.Since 0.73 Ma.the climate became even drier when the plateau continuously rose.In the Holocene period.the climate alternatively changed with a complex model of being cool-dry,warm-wet and cold-wet.     

Genesis and Geological—Geochemical Characters of the ushan Gold Deposit,Shandong,China

The Rushan gold deposit, explored in recent years in the Jiaodong area, Shandong Province, is a quartz vein-type gold deposit hosted in granite. The temperature of its major mineralization episode is between 220°C and 280°C. The salinity of the ore-forming fluid is 5 % to 9% NaCl equivalent, with H₂O and CO₂ as the dominant gas constituents. The fluid is rich in Na⁺, Ca²⁺ and Cl⁻, but relatively impoverished in K⁺ and F⁻, characterized by either Ca²⁺ > Na⁺ > K⁺ (in three samples) or Na⁺ > Ca²⁺ > K⁺ (in six samples). Hydrogen and oxygen isotopes in the ore-forming fluid are highly variable with δ¹⁸ ranging between − 7.70‰ and 5. 97‰ and between − 128‰ and − 71‰. The possibility of lamprophyre serving as the source of gold can be excluded in view of its low gold content on the order of 2.5 × 10⁻⁹. Rb-Sr isochron ages of the deposit and the host Kunyushan granite are ( 104.8 ± 1.5) Ma and 134.6 Ma respectively with the respective initial Sr ratios of 0. 71307 and 0.7096. It is considered that the emplacement of the lamprophyre under a tensile environment had provided sufficient heat energy to facilitate deep circulation of meteoric water by which ore metals were extracted from the Kunyushan granite through long-term water-rock reaction. This project was financially supported by the National Natural Science Foundation of China.     

Geological and Geochemical Characteristics and Genesis of “Dolomite” at Bayan Obo, China

白云鄂博“白云岩”位于华北板块的北缘,宽沟背斜的南翼.蕴藏着世界最大的稀土矿床,还是大型—超大型铌、铁和钍等矿床赋存母岩.“白云岩”不是层状岩石,无明显的层理和固定的层位,而是一套大小不等,串珠状的”白云岩”带.“白云岩”与围岩呈明显的侵入关系.表现在“白云岩”切割H4石英砂岩、H5板岩和花岗岩脉,并有许多分枝脉插入到H4石英砂岩和H5板岩中.“白云岩”中存在H4石英砂岩的残留顶盖相,捕获了H4石英砂岩和H5板岩的捕掳体,并引起围岩的强烈蚀变.板岩的黑云化,石英砂岩的钠闪石化,花岗岩的碱交代.“白云岩”含有大量铌、稀土、钍等岩浆岩中常见的矿物晶体.硫、碳、氧、锶和铁等同位素组成都具有深源特征.说明白云鄂博“白云岩”不是沉积岩,而是岩浆碳酸岩.     

Chemistry and Evolution of Fergusonite—Group Minerals,Bayan Obo,Inner Mongolia

A new classification scheme of the fergusnoite-group minerals is suggested on the basis of mineral chemistry and high temperature XRD. A number of new varieties such as M-thorian fergusonite-(Ce). M-neodymian fergusonite-(Ce). T-titanian fergusonite-(Nd) and T-yttrian fergusonite-(Nd) have been recognized in the light of detailed chemical studies, particularly with reference to REE, SRE and solid solution relationship. The results indicate strong REE and SRE differentiation and evolution in the fergusonite group, which can be interpretated by differences in the stability of various REE complexes in response to variations in physicochemical conditions during the multi-stage mineralization process in the Bayan Obo ore deposit. The crystallization of the minerals is closely related to hydrolysis of REE and Nb complexes. REE (OH)₃ Nb(OH)₅ coprecipitation, dehydration, polymerization and nucleation.The significance of SRE (Eu)in the western part of the deposit is emphasized. This project was finantially supported by the National Natural Science Foundation of China.     

Mineralogy, geochemistry and release of heavy metals in wastes from indigenous zinc smelting in Northwest Guizhou

Environmental impact resulting from mining activities is serious and ubiquitous all over the world, and it has become one of the important aspects in environmental geochemistry. The environment was seriously damaged by wastes from historical zinc smelting in Northwest Guizhou. The geochemical distributions of Pb and Zn in the different grain-size fractions of wastes indicate that the coarser particles show similar or even higher heavy metal concentrations than finer ones in the samples, although the concentrations of heavy metals tend generally to increase as the size fractions get finer. The heavy metal contents are very high, with maximum values of 31631, 57178, 2367 and 311.5 mg/kg for Pb, Zn, Cu and Cd, respectively. It is also shown that the residual fraction of Pb is less than that of Zn, accounting for 0.39%-15.75% and 14.3%-46.2%, respectively, of the total, and this is likely relative to Zn-silicate minerals formed from smelting. Although the relative partitioning of Pb and Zn is very low （0.03%- 1.3.% for Pb; 0.03% -3.3% for Zn）, the exchangeable fraction of the waste contains large amounts of heavy metals （1.5%-385 μg/g for Pb; 3-590 μg/g for Zn）. Heavy metals in exchangeable forms have the highest solubility to give the highest potential bioavailability in contrast to other chemical forms. Mineralogical study indicates that the wastes were found to be highly heterogeneous materials, dominated by quartz, feldspar, carbonatite, iron or/and aluminum vitric compounds and a few secondary mineral phases, and their contents vary with the type of smelting wastes. The secondary minerals formed from smelting and sequentially weathering are the major chemical phase for heavy metals. Complex composition of many phases and substitution of elements suggested that many of the phases were found to be non-stoichiometric compounds. Pb was found to be the main Pb phase in the wastes by precipitation or/and adsorption.     

地球化学填图与地球化学勘查

在中国与西方国家，地球化学填图的目的与做法并不相同，西方的地球化学填图是由研究机构开展的，使用等离子焰光量计、X射线荧光光谱仪等大型仪器进行多元素分析，目的是取得多种元素在地球表层分布的基础性资料。地球化学勘查则由矿业公司主要分析少量成矿元素，目的是为了找矿。而中国的地球化学填图计划却做出了巨大努力，使地球化学填图取得的资料既有学术价值又对矿产勘查具有重大的实用意义。本文详细讨论了西方国家与中国地球化学填图与地球化学勘查的思路、方法与技术的演变，并瞻望了地球化学填图在21世纪的巨大发展前景。     

National-Scale Geochemical Mapping Projects in China

Regional, national and global scale geochemical mapping projects have been carried out in China since the late 1970s, due to the development of cost‐effective, low detection limit analytical methods. These projects have provided a huge mass of high‐quality, informative and comparable data for mineral resource exploration and are now making contributions to environmental assessment. In this paper, four national‐scale geochemical mapping projects are described. (1) The Regional Geochemistry‐National Reconnaissance Project (RGNR project), which is China's largest national geochemical mapping project, has covered 6 million km² of upland regions since 1978. Generally, stream sediment samples were collected at a density of 1/km² and four samples were composited into one sample and analysed for thirty‐nine elements. (2) The deep‐penetrating geochemical mapping project (DEEPMAP Project) has been conducted since 1994 in covered terrains, including sedimentary basins, at a density of 1 sample per 100 km² with thirty to seventy elements determined per sample. In the past 10 years, an area of approximately 800 000 km² has been covered and this project has played an important role in finding sandstone‐type uranium deposits in basins. (3) The seventy‐six geochemical element mapping project (76 GEM project) has been carried out since 1999 and involved the collection of stream sediment samples from the RGNR project targets which were analysed for seventy‐six elements. Samples from each 1:50 000 map sheet were composited into one analytical sample (approximately one composite sample per 400 km²). Approximately 1 million km² have been surveyed to date. (4) The multi‐purpose eco‐geochemical mapping project has been conducted since 1999 in Quaternary plain areas for environmental and agricultural applications. Surface soils (depths from 0–20 cm) were collected at a density of one sample per km², and four samples were composited into one for analysis. Deep soils (from a depth of 150 to 200 cm) were collected at a density of one sample per 4 km² and four samples were composited into one analytical sample. All the composite samples were analysed for fifty‐four elements.     

国际地球化学填图新进展

欧洲和中国在国际地球化学填图中起着积极而重要的作用,而且进展也是最显著的。欧洲地球化学基准值填图计划于1996年被欧洲26个国家地质调查局长论坛(FOREGS)正式批准。经过近10年的工作,于2005年出版了电子版欧洲地球化学图集。中国不仅自己开展了多层次地球化学填图计划,而且还与发展中国家合作开展了全球尺度和成矿带尺度地球化学填图合作。欧洲和中国无论是在全球尺度,还是在区域尺度地球化学填图做法上都存在较大的差异。在采样介质上中国使用统一的采样介质,在分析技术上中国使用几种大型设备作为骨干配合使用多方法分析系统;欧洲恰恰相反,欧洲在采样介质上趋向于多介质,而分析技术上只使用少数几种大型设备。欧洲的做法尽管使用多介质采样获得了元素在更多天然介质中的分布信息,但使用单一分析技术,使得很多关键元素没有分析出来,如贵金属元素Ag,Au,Ir,Os,Pd,Pt,Rh,Ru;卤族元素F,Cl,Br,I;分散元素Ge,In,Se,Te;与生命密切相关的元素N,S,B等。尽管欧洲强调以环境为目的,但很多与环境密切相关的元素都没有分析,所以欧洲的全球尺度地球化学填图的信息量大打折扣。这些不统一的做法,特别是在全球尺度地球化学填图不统一的做法,会影响到以后全球地球化学图的编制。     

在地球化学填图计划中3种多元素配套分析方案的概述

本文在总结我国地球化学填图分析方法的基础上,概括并阐述了地球化学填图计划中3种多元素配套分析方案。对指导、优化我省乃至全国地球化学样品分析方法具有重要的现实意义。     

Outlines of New Global Geochemical Mapping Program

<正>Since 1988,great efforts and enthusiasm had been paid by applied geochemists in the implementation of global geochemical mapping through the International Geological Correlation Program's Projects 259 and 360,and the Task Group on‘Global Geochemical Baselines' established by the International Union of Geological Sciences(IUGS),in collaboration with the International Association of Geochemistry(IAGC).But how to use extremely low-density sampling to obtain a global picture of the distribution of most elements in the periodic table in a reasonably short time is still a great challenge faced by the applied geochemistry community.It will depend on the continuous development of new mapping concept,and the advisable and courageous innovation of methodology for searching other suitable sample media and sampling layout.Based on the encouragement results obtained from the representativeness study of delta sediments conducted at the mouth of Yangtze River,and at the mouths of its four major tributary,it is expected to broadly apply the geochemical fractal self-similarity nature to main rivers and their estuaries with catchments up to hundreds of thousands or over a million square kilometers in the world.With this new mapping concept,a new outlines of a Global Geochemical Mapping Program was advanced and the establishment of an International Research Center of Global Geochemical Mapping was also suggested to facilitate the programs implementations.     

老挝全国地球化学填图与成矿远景区预测

随着国家"一带一路"倡议的推进,在中国地质调查局的资助下,开展了老挝境内21万km^2的国家尺度(1:100万)地球化学填图工作,本次工作填补了老挝国家尺度地球化学填图的空白,为老挝基础地质、矿产开发、环境保护、农业生产等多个方面提供了基础地球化学保障。本次共采集老挝境内地球化学样品1905件,使用多种测试手段分析了71种元素的含量,并据此制作了这些元素的地球化学图和地球化学异常图。通过对老挝Au、Cu、Ni、Co、Mn、Zn、Ag、As、Sb、Pb、Bi和Sn的地球化学参数及其相关性的研究发现:这些元素的中位值均小于我国热带雨林区水系沉积物元素含量,而且这些元素的中位值均小于其平均值,As、Au、Bi、Pb和Sb在老挝境内的分布十分不均,元素局部富集明显。通过R型聚类分析,我们将上述元素分为Au;Cu;Ni、Co;Mn、Zn;Ag、As、Sb、Pb、Bi、Sn等5个簇群,并根据元素的地球化学分布特征及综合异常特征,在老挝划分了7个地球化学成矿远景区。     

中国与欧洲全球尺度地球化学填图分析方法的对比

实施国际地球化学填图项目最关键的是分析问题。欧洲和中国在全球尺度地球化学填图做法上存在较大的差异。中国使用统一的采样介质,即泛滥平原沉积物,并使用几种大型设备作为骨干配合使用多方法分析系统,分析76种元素,这是人类历史上首次制作了元素周期表上除惰性气体元素和人工元素以外的几乎所有元素地球化学图。欧洲恰恰相反,欧洲在采样介质上趋向于多介质,而分析技术上只使用少数几种大型设备;分析方法的单一,使得很多关键元素没有分析出来,如贵金属元素Ag,Au,Ir,Os,Pd,Pt,Rh,Ru;卤族元素F,Cl,Br,I;分散元素Ge,In,Se,Te;与生命密切相关的元素K,N,S,B等。尽管欧洲强调以环境为目的,但很多与环境密切相关的元素都没有分析,所以欧洲的全球尺度地球化学填图的信息量大打折扣。这些不统一的做法,将会制约全球地球化学图的编制。     

地球化学背景与地球化学基准

探讨了地球化学背景和地球化学基准的概念、含义和确定方法.认为随着地球化学的发展,地球化学背景的概念和含义都发生了很大的变化,由初期的注重其“量”到目前的关注其“质”,研究的目的不同,背景值的确定途径也不同.无论是地球化学背景还是地球化学基准,共同之处在于它们独特的参考功能,正是这种参照性质使地球化学背景和地球化学基准的研究在进行环境质量评价和环境立法时具有重要的理论意义和实用价值.