- Email: [email protected]
Sixty years of exploration geochemistry in China
Sixty years of Exploration Geochemistry in China Xuejing Xie, Hangxin Cheng PII: DOI: Reference:
S0375-6742(13)00128-3 doi: 10.1016/j.gexplo.2013.06.013 GEXPLO 5189
To appear in:
Journal of Geochemical Exploration
Received date: Accepted date:
2 April 2013 24 June 2013
Please cite this article as: Xie, Xuejing, Cheng, Hangxin, Sixty years of Exploration Geochemistry in China, Journal of Geochemical Exploration (2013), doi: 10.1016/j.gexplo.2013.06.013
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Sixty years of Exploration Geochemistry in China Xuejing Xie, Hangxin Cheng
PT
Key Laboratory of Geochemical Cycling of Carbon and Mercury in the Earth’s
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Critical Zone, Institute of Geophysical and Geochemical Exploration, Chinese
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Corresponding author: Xuejing Xie,
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Academy of Geological Sciences, Langfang 065000, China.
MA
Phone: +86-10-62915583; Fax: +86-10-62915583.
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Email address: [email protected]
TE
Abstract: This paper provides a history of the development of Exploration Geochemistry in China. Over the past sixty years, geochemists in China have made
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great efforts to develop geochemical exploration methods to cover large areas and even all of China or the whole world, as well as to more elements with emphasis on high sensitivity and accuracy. The new innovative exploration concept and strategies established by the Chinese geochemists have greatly contributed to discoveries of the mineral deposits and to the environmental regulations. Key Words: Exploration geochemistry; China; History; Geochemical methodology; Exploration strategy
1. Introduction Exploration geochemistry was initiated in China in the year 1951 when Xie and Xu carried out the first experiment in Yueshan, Anqing, Anhui province. Rocks, soils and
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ACCEPTED MANUSCRIPT stream sediments were sampled and analyzed by the dithiazone method for Cu, in situ. A Cu indicator plant Elsholtzia haichowensis Sun was discovered (Xie and Xu, 1952).
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Most of the results except the Cu indicator plant were not published.
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From 1951 to 1978, Exploration geochemistry in China was developed slowly with
SC
many difficulties from a lack of confidence by those engaged in the work, a lack of support from the geological circle in China and also greatly influenced by Mao's
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political movements of class struggle and isolation from international scientific
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activities. After Mao's death and the arrest of the gang of four, the first author began to advance the Regional Geochemistry – National Reconnaissance (RGNR) Program
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(Wang et al., 2007; Xie et al., 2008).
2. Methodology development
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The advancement of this large science program was greatly influenced by the publication of the Provisional Geochemical Atlas of Northern Ireland (Webb et al., 1973). After the approval of this program by the National Geological Bureau (the former of Ministry of Land and Resources), Xie (1979) made important modifications to geochemical methodology on the basis of approaches of the Western countries. These modifications include: (1) Because of the complicated landscapes in China, a map showing the different physiographic regions was compiled at the beginning of the program for developing different sampling methods for each region (Fig. 1) (Xie et al., 1997; Xie and Ren, 1991). In regions of low mountain and hills of China proper, standard stream sediment sampling methods were used. For desert, semi–desert, karst, and high mountain zones, 2
ACCEPTED MANUSCRIPT the sampling methods developed were proved by large–scale practice to be very successful. For other regions, more studies should be carried out in the future
PT
especially the deep-penetrating techniques and the overburden drilling methods
RI
should be tested, and resampling by more effective methods should be done.
SC
(2) Cell sampling. The stream sediment sampling advanced by Webb and others was a great contribution to exploration geochemistry. Sampling a bottom sediment sample
NU
from a river can predict the average values of element concentration in the upstream
MA
basin. When a large area is sampled along streams，the sampling sites will become inhomogeneous and cause difficulties for the construction of geochemical maps. In
D
our method, the samples were not collected along streams but in cells of 1 × 1 km.
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Within each 1 ×1 km cell, 1 or 2 samples are collected in the extreme downstream
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locations of the cell. The element concentrations of the samples will represent the average values of this cell. With cell sampling the sample distribution is more homogenous, and more feasible for map construction than Webb's original approach of sampling along streams.
(3) Sampling coding system. This coding system is in accordance with cell sampling. The coding numbers of an analytic cell (4 km2) are marked from 1 to n from top left to top right and then from top to bottom. The four (1 km2) sampling cells in an analytical cell are marked with A, B, C, D (Fig. 2). This sampling coding system is made on a 1:200,000 topographic map before the field work (Xie and Ren, 1991; Xie et al., 2011a). (4) Global comparability of data. Systematic analytical errors or bias of analytical
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ACCEPTED MANUSCRIPT data obtained from the different laboratories should be eliminated or reduced to a minimum. Poor comparability between the results of different laboratories is one of
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the greatest unresolved problems in regional geochemistry (Reimann and de Caritat,
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2012). In China the analytical work in RGNR program has been conducted by many
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laboratories in the Geological Bureaus of different provinces. So we were the first in the world to understand the serious bias of this problem. Twelve standard reference
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samples GSD1 – 12 were prepared, certified values for different elements were
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obtained by the effort of cooperation of many laboratories in China (Xie et al., 1989a; Xie et al., 1989b; Xie et al., 1985). An analytical quality control system was then
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analytical bias.
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worked out (Xie et al., 1989a) to monitor the between-batch and between-laboratory
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(5) Detection limits. The most important modification for the methodology of geochemical mapping is the requirement that the detection limits for trace and subtrace elements be lowered to below their crustal abundances (Xie, 1995). This requirement is somewhat similar to the requirement that at least 80 – 100% of the samples has reportable values if the crustal abundances of some sub-trace elements (such as Au) published in the literature are modified by more modern and sensitive analytical methods. In order to meet these analytical requirements, a multi-instrument, multi-method analytical scheme was developed (Table 1 and Table 2). (6) Gold exploration. Gold was excluded in the list of elements analyzed in the early geochemical mapping programs by Webb et al. (1973), and others (Bolivar, 1980; Bowie and Plant, 1978a, b; Coker et al., 1981) because of the doubtful results of
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ACCEPTED MANUSCRIPT anomalies obtained due to the nugget effect of gold. Nichol et al. (1989) suggested to take large samples (200 – 800 g) for gold analysis to reduce the error caused by the
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nugget effect of gold. Our approach in RGNR program was to take a small sample (5
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– 10 g) for analysis with a very sensitive method (i.e. detection limit 1 – 0.3 ppb),
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defined 2 ppb as anomalous values provided such values are continuous over a large area (Xie and Wang, 1991). With this approach, the error caused by the nugget effect
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is bypassed during interpretation.
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(7) Streamline operations of sample analysis. In order to increase the cost-effectiveness when such a vast amount of samples are analyzed, operations were
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streamlined inspired by Ford's innovative idea of mass production in the automobile
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industry. The analytical procedures were divided into various kinds of operations,
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such as weighing, digestion, dilution filtering, addition of reagents and measuring by different instruments etc. These operations were separately carried out by individual analysts and streamlined on a large scale.
3. Innovative concept
Until 2000 more than about six million analytical values for each of the 39 dements were produced by laboratories involved in the RGNR programs. The vast amount of data obtained is becoming a treasure for further studies. For example, the innovative concept of geochemical blocks was resulting from utilizing
this information (Xie et
al., 2004). Geochemical blocks were formed as the net result of inhomogeneity caused by earth formation and the gradual build-up of metal concentrations afterward by a series of geological processes. The geochemical block concept could be used to 5
ACCEPTED MANUSCRIPT predict the existence of large ore deposits and to predict their tonnages. So during mineral exploration one could not only rely on dispersion patterns formed after the
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deposits were formed but also distribution patterns (geochemical locks) formed
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before the formation the mineral deposit by wide-spaced sampling using floodplain
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sediment as the sampling medium (Xie and Cheng, 1997).
The idea of flood plain sampling was developed before 1997. The Global
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Geochemical Baseline program was approved by IGCP as IGCP 360. China was
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ahead of this global program by carrying out two projects in China. One is the "Environmental Geochemical Monitoring and Dynamic Geochemical Mapping"
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(EGMON) project which used nearly 500 floodplain samples to cover the whole of
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China (Cheng et al., 1997). Another, more comprehensive project, i.e. the "National
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Geochemical Baseline project", used approximately 1400 cells involving the sampling of rocks, overbank and flood plain sediments (Wang, 2012). During the implementation of the RGNR program, the authors got the idea that geochemical mapping will be further developed to analyze all or most of the elements in the periodic table. This idea has fostered the idea to develop analytical methods for many difficult elements in the periodic table. Such efforts finally caused the establishment of the projects for geochemical mapping of 76 elements in SW and SE China (76GEM). The 76 elements included the 71 elements recommended by IGCP 259/360 plus Os, Ir, Ru, Rh and Re (Table 2). An important achievement by the 76 GEM program was the advancement of the Virtualized Reference maps concept to replace the Standard Reference Samples
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ACCEPTED MANUSCRIPT concept in monitoring not only the data quality, but also the map quality as a whole.
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4. Contribution to the mineral exploration In 2000, the RGNR program had been conducted for 20 years and covered more than
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6.6 million km2 of China's territory. Most of the ore deposits discovered (especially
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large amount of Au deposits) during these 20 years contributed to the information
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obtained by this program. The potential economic value of these discoveries reached 600 billion Chinese Yuans (Xie et al., 2011a). Also in this period, most of the
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colleagues working on the implementation of this program are now retired, but the
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new generation of geochemists in China are now active in China.
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From 2000 to 2011 more large copper-lead-zinc base metals, tungsten, tin and molybdenum deposits have been found, amounting to economic value estimated to be
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more than 1000 billion Chinese Yuans. Due to the language barrier and other reasons the case histories of these discoveries had not been published in English even in the present special volume. For remediation purpose, we would like to publish a map of China showing the locations of all the newly discovered large and giant ore deposits attributed to the information from the RGNR program (Fig. 3).
5. Deep penetrating Geochemistry During the 20th century, the deep penetration techniques first proposed by Cameron in 1997 (Cameron, 1998) were widespread. In western countries, most of the work was confined to detailed or semi-detailed surveys to test the results of geophysical surveys or geological prediction of buried mineral deposits by exogenic cover and
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ACCEPTED MANUSCRIPT their techniques were all weak selective extraction of the mobile phase of metals from depth. In China we have developed regional deep-penetration techniques to cover
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large exogenic or volcanic areas (Wang, 1998a, b; Xie, 1998). Only more recently we
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have developed several more strong selective extraction techniques to overcome the
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defects of weak selective extraction techniques (Wang et al., 2011; Xie et al., 2011b)
in nanoscale forms (Wang and Ye, 2011).
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6. New Programs
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and discovered by experiment that the deep penetration mobile phases of metals were
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Several new programs of nationwide and global scale exploration geochemistry have
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been planned in China including " Surface Geochemistry for Oil and Gas", "National Reconnaissance for Ore Tailing Dumps", "National Geochemical Survey and
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Geochemical Evaluation of Soil Quality", and "Global scale Geochemistry".
7. Conclusions
From the above, it can be seen that China has made great effort to develop geochemical exploration methods to cover large areas and even all of China or the whole world and to analyze more elements with emphasis on high sensitivity and accuracy. The possibility of mobilize the geochemists of the whole nation to use unified and standard method in big mapping program lays on the wise utilization of China's political system. These efforts have resulted in a new strategy for mineral exploration, i. e. "Quickly control the overall situation and gradually reduce the target areas". This strategy could be applied equally well in environmental monitoring and
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ACCEPTED MANUSCRIPT there after scale-chosen area and scale-up sample density to identify problem areas. The enormous amount of information produced in China by these large science
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programs will provide basic information for the newly born science: "Applied
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to mineral exploration and environmental regulations.
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Geochemistry" to carry out more in-depth studies for solving various problems related
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References
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Bolivar, S.L., 1980. An overview of the National Uranium Resource Evaluation Hydrogeochemical and Stream Sediment Reconnaissance Program: Los Alamos.
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Bowie, S.H.U., Plant, J., 1978a. Regional Geochemical Atlas, Orkney. Inst. Geol. Sci., London.
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Bowie, S.H.U., Plant, J., 1978b. Regional Geochemical Atlas, Shetland. Inst. Geol. Sci., London.
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Cameron, E.M., 1998. Deep-Penetrating Geochemistry: Unpublished Report of the Canadian Mining Industry Research Organization (CAMIRO), p. 177. Cheng, H., Shen, X., Yan, G., Gu, T., Lai, Z., Xie, X., 1997. Wide- spaced floodplain sediment sampling covering the whole of China: pilot survey for international geochemical mapping, in: Xie, X. (Ed.), Proc. 30th int. Geol. Congr., Geochemistry. International Science Publishers, Utrecht,Netherlands, Tokyo, pp. 89-109. Coker, W.B., Maurice, Y.T., Ellwood, D.J., Canada, G.S.o., Canada. Dept. of Energy, M., Resources, 1981. National Geochemical Reconnaissance, Baffin Island, Northwest Territories (27B and Part of C; 37A,D). Geological Survey of Canada. Nichol, I., Closs, L.G., Lavin, O.P., 1989. Sample representativity with reference to gold exploration, Proceedings of Exploration '87,
9
ACCEPTED MANUSCRIPT . Ont. Geol. Surv., Ont, pp. 609-624. Reimann, C., de Caritat, P., 2012. New soil composition data for Europe and Australia: Demonstrating
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comparability, identifying continental-scale processes and learning lessons for global geochemical
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mapping. Science of The Total Environment 416, 239-252.
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Wang, X., 1998a. Leaching of mobile forms of metals in overburden: development and application. Journal of Geochemical Exploration 61, 39-55.
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Wang, X., 1998b. Principle and practice of exploration geochemistry in searching and discriminating
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concealed large and giant mineral deposits. Geophysical and Geochemical Exploration 22, 81-89 (in Chinese with English Abstract).
(in Chinese with English abstract).
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Science Frontiers 19, 7-18
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Wang, X., 2012. Global geochemical baselines: understanding the past and predicting the Future. Earth
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Wang, X., Xu, S., Zhang, B., Zhao, S., 2011. Deep-penetrating geochemistry for sandstone-type uranium deposits in the Turpan–Hami basin, north-western China. Applied Geochemistry 26, 2238-2246.
Wang, X., Ye, R., 2011. Findings of Nanoscale Metal Particles: Evidence for Deep-penetrating Geochemistry. Acta Geoscientica Sinica 32, 7-12. (in Chinese with English Abstract). Wang, X., Zhang, Q., Zhou, G., 2007. National-Scale Geochemical Mapping Projects in China. Geostandards and Geoanalytical Research 31, 311-320. Webb, J.S., Nichol, I., Forster, R., Lowenstein, P.L., Howarth, R.J., 1973. Provisional geochemical atlas of Northern Ireland. Applied Geochemistry Research Group, Technical Communication, 60:30. Xie, X., 1979. Regional geochemical surveys. Geological publishing house, Beijing. Xie, X., 1995. Perspective. Analytical requirements in international geochemical mapping. Analyst 120,
10
ACCEPTED MANUSCRIPT 1497-1504. Xie, X., 1998. Strategic and tactic deep-penetrating geochemical surveys. Earth Science Frontiers 5,
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171-183 ( in Chinese with English Abstract).
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Xie, X., Cheng, H., 1997. The suitability of floodplain sediment as a global sampling medium:
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evidence from China. Journal of Geochemical Exploration 58, 51-62.
Xie, X., Liu, D., Xiang, Y., Yan, G., Lian, C., 2004. Geochemical blocks for predicting large ore
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deposits—concept and methodology. Journal of Geochemical Exploration 84, 77-91.
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Xie, X., Mu, X., Ren, T., 1997. Geochemical mapping in China. Journal of Geochemical Exploration 60, 99-113.
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Xie, X., Ren, T., 1991. A decade of regional geochemistry in China - the national reconnaissance
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project. Trans. Inst. Min. Metal.. Sect. B. Appl. Earth Sci. 100, 57-65.
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Xie, X., Sun, H., Ren, T., 1989a. Regional geochemistry-national reconnaissance project in China. Journal of Geochemical Exploration 33, 1–9. Xie, X., Wang, X., 1991. Geochemical exploration for gold: a new approach to an old problem. Journal of Geochemical Exploration 40, 25-48. Xie, X., Wang, X., Cheng, H., Cheng, Z., Yao, W., 2011a. Digital Element Earth. Acta Geologica Sinica (English edition) 85, 1-16. Xie, X., Wang, X., Zhang, Q., Zhou, G., Cheng, H., Liu, D., Cheng, Z., Xu, S., 2008. Multi-scale geochemical mapping in China. Geochemistry: Exploration, Environment, Analysis 8, 333-341. Xie, X., Xu, B., 1952. A Cu indicator plant Elsholtzia haichowensis. Acta Geologica Sinica 32, 360-368 (in Chinese). Xie, X., Yan, M., Wang, C., Li, L., Shen, H., 1989b. Geochemical standard reference samples GSD
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ACCEPTED MANUSCRIPT 9–12, GSS 1–8 AND GSR 1–6. Geostandards Newsletter 13, 83–179. Xie, X.J., Yan, M.C., L.Z., L., Shen, H.J., 1985. Usable values for Chinese standard reference samples
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of stream sediments, soils, and rocks: GSD 9-12, GSS 1-8 and GSR 1-6. Geostandards Newsletter 9,
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277-280.
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Xie, X.X., Lu, Y., Yao, W., Bai, J., 2011b. Further study on deep penetrating geochemistry over the
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Spence porphyry copper deposit, Chile. Geoscience Frontiers. 2, 303-311.
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ACCEPTED MANUSCRIPT Table 1 Analytical scheme of 39 elements (Xie, 1995).
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Table 2
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The Analytical Scheme for 76 elements.
Fig. 1. Different regolith/landform/climate zones of China distinguished to optimize
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the sampling method (Xie and Ren, 1991; Xie and Ren, 1993).
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Fig. 2. Example for coding of sampling cells and the analytical cell (Xie, 1979). Fig. 3. Distribution of large and giant ore deposits discovered by geochemical
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exploration in China.
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Table 1 Analytical scheme of 39 elements (Xie, 1995) Al (0.05)*, Ba (50), Ca (0.05), Co (1), Cr (15), Cu (1), X-ray fluorescence spectrometry
Fe (0.05), K (0.05), La (30), Mg (0.05), Mn (30), Na
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(0.05), Nb (5), Ni (2), P (100), Pb (2), Si(0.1), Sr (5), Th (4), Ti (100), V (20), Y (5), Zn (10), Zr (10) As (1), Sb (0.1), Bi (0.1), Hg (0.0005)
Atomic absorption spectrometry
Ag (0.02), Cd (0.05), Li (5)
Atomic emission spectrometry
Ag (0.02), B (5), Be (0.5), Sn (1)
Catalytic polarography
W (0.5), Mo (0.4)
Ionic selection electrometry
F (100)
Colorimetry or laser catalytic fluorescence
U (0.5)
Graphite fumace atomic absorption spectrometry
Au (0. 0003)
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Atomic fluorescence spectrometry
– number enclosed in brackets is the detection limit; unit of Al, Ca, Fe, K, Mg, Na, Si is %, other element is µg/g.
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*
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ACCEPTED MANUSCRIPT Table 2
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XRF
DF-ICPMS VOL DF-ICPES XRF FU-I-ICPMS DF-ICPMS FU-ICPMS XRF XRF DA-ICPMS DA-ICPMS FU-I-ICPMS XRF FU-I-ICPMS FA-ICPMS FU-ICPMS XRF DF-ICPMS DF-ICPMS HG-AFS XRF FU-I-ICPMS AES XRF DF-ICPMS FU-I-ICPMS DF-ICPMS DF-ICPMS XRF DF-ICPMS FU-I-ICPMS DF-ICPMS XRF DF-ICPMS FU-I-ICPMS FU-I-ICPMS XRF
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0.02 ppm 20 ppm 0.01% 1ppm 0.05 ppm 0.6 ppm 0.01 ppb 10 ppm 2 ppm 0.2 ppb 0.2 ppb 0.01 ppm 1 ppm 0.05ppb 0.01 ppb 0.01 ppb 7 ppm 0.02 ppm 0.6ppm 0.01 ppm 0.01% 0.015 ppm 0.2 ppm 1.5ppm 0.005 ppm 0.01ppm 5ppb 0.003ppm 10ppm 0.003ppm 0.003 ppm 0.01 ppm 5 ppm 0.02 ppm 0.12 ppm 0.015 ppm 1 ppm 1 ppm
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Mo N Na2O Nb Nd Ni Os P Pb Pd Pt Pr Rb Re Rh Ru S Sb Sc Se SiO2 Sm Sn Sr Ta Tb Te Th Ti Tl Tm U V W Y Yb Zn Zr
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AES XRF HG-AFS DA-GFAAS AES XRF DF-ICPES DF-ICPMS XRF VOL XRF DF-ICPMS FU-I-ICPMS XRF DF-ICPMS XRF DF-ICPMS DF-ICPES FU-I-ICPMS FU-I-ICPMS FU-I-ICPMS ISE XRF DF-ICPES FU-I-ICPMS HG-AFS DF-ICPMS CV-AFS FU-I-ICPMS CF-COL DF-ICPMS FA-ICPMS DF-ICPES FU-I-ICPMS DF-ICPES FU-I-ICPMS DF-ICPES
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0.01 ppm 0.01% 0.2 ppm 0. 1ppb 0.5 ppm 9 ppm 0.2 ppm 0.015 ppm 0.8 ppm 0.04% 0.01% 0.02 ppm 0.12ppm 7 ppm 0.02 ppm 3 ppm 0.003 ppm 1 ppm 0.015ppm 0.015 ppm 0.004 ppm 20 ppm 0.01% 2 ppm 0.015 ppm 0.02 ppm 0.015 ppm 0.3ppb 0.004 ppm 0.5 ppm 0.002 ppm 0.01 ppb 0.01% 0.12 ppm 0.06 ppm 0.004 ppm 0.01% 10 ppm
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Ag Al2O3 As Au B Ba Be Bi Br C CaO Cd Ce Cl Co Cr Cs Cu Dy Er Eu F Fe2O3 Ga Gd Ge Hf Hg Ho I In Ir K2O La Li Lu MgO Mn
Analytical Method
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The Analytical Scheme for 76 elements. Component Detection Analytical Component Determined Method Limited limit
XRF
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ACCEPTED MANUSCRIPT Decomposition Method: DA, digestion with aqua regia; DF, digestion with aqua regia and hydrofluoric acid; FU, alkaline fusion or fusion with Eschka mixture; FA, enrichment of assay; and I, ion exchange resin preconcentration. Determined Method: ICP-MS, inductively coupled plasma mass spectrometry; ICP-ES, inductively couple plasma
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atomic emission spectrometry; XRF, X-ray fluorescence spectrometry; GFAAS, graphite furnace atomic absorption spectrometry; AFS, atomic fluorescence spectrometry; VOL, volumetry; COL, colorimetry; ISE, ionic selection
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electrometry; and AES, atomic emission spectrometry.
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Fig. 1
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ACCEPTED MANUSCRIPT
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Fig. 2
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Fig. 3
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ACCEPTED MANUSCRIPT Highlights 1. Sixty years of Exploration Geochemistry in China are reviewed
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2. China has made great effort to develop geochemical exploration methods.
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3. Mapping programs try to cover large area and even whole China or whole world
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4. Analytical systems had been devised for nearly all elements in periodic table.
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5. Innovative geochemistry concept and exploration strategies are introduces.
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S0375-6742(13)00128-3 doi: 10.1016/j.gexplo.2013.06.013 GEXPLO 5189
To appear in:
Journal of Geochemical Exploration
Received date: Accepted date:
2 April 2013 24 June 2013
Please cite this article as: Xie, Xuejing, Cheng, Hangxin, Sixty years of Exploration Geochemistry in China, Journal of Geochemical Exploration (2013), doi: 10.1016/j.gexplo.2013.06.013
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Sixty years of Exploration Geochemistry in China Xuejing Xie, Hangxin Cheng
PT
Key Laboratory of Geochemical Cycling of Carbon and Mercury in the Earth’s
RI
Critical Zone, Institute of Geophysical and Geochemical Exploration, Chinese
NU
Corresponding author: Xuejing Xie,
SC
Academy of Geological Sciences, Langfang 065000, China.
MA
Phone: +86-10-62915583; Fax: +86-10-62915583.
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Email address: [email protected]
TE
Abstract: This paper provides a history of the development of Exploration Geochemistry in China. Over the past sixty years, geochemists in China have made
AC CE P
great efforts to develop geochemical exploration methods to cover large areas and even all of China or the whole world, as well as to more elements with emphasis on high sensitivity and accuracy. The new innovative exploration concept and strategies established by the Chinese geochemists have greatly contributed to discoveries of the mineral deposits and to the environmental regulations. Key Words: Exploration geochemistry; China; History; Geochemical methodology; Exploration strategy
1. Introduction Exploration geochemistry was initiated in China in the year 1951 when Xie and Xu carried out the first experiment in Yueshan, Anqing, Anhui province. Rocks, soils and
1
ACCEPTED MANUSCRIPT stream sediments were sampled and analyzed by the dithiazone method for Cu, in situ. A Cu indicator plant Elsholtzia haichowensis Sun was discovered (Xie and Xu, 1952).
PT
Most of the results except the Cu indicator plant were not published.
RI
From 1951 to 1978, Exploration geochemistry in China was developed slowly with
SC
many difficulties from a lack of confidence by those engaged in the work, a lack of support from the geological circle in China and also greatly influenced by Mao's
NU
political movements of class struggle and isolation from international scientific
MA
activities. After Mao's death and the arrest of the gang of four, the first author began to advance the Regional Geochemistry – National Reconnaissance (RGNR) Program
TE
D
(Wang et al., 2007; Xie et al., 2008).
2. Methodology development
AC CE P
The advancement of this large science program was greatly influenced by the publication of the Provisional Geochemical Atlas of Northern Ireland (Webb et al., 1973). After the approval of this program by the National Geological Bureau (the former of Ministry of Land and Resources), Xie (1979) made important modifications to geochemical methodology on the basis of approaches of the Western countries. These modifications include: (1) Because of the complicated landscapes in China, a map showing the different physiographic regions was compiled at the beginning of the program for developing different sampling methods for each region (Fig. 1) (Xie et al., 1997; Xie and Ren, 1991). In regions of low mountain and hills of China proper, standard stream sediment sampling methods were used. For desert, semi–desert, karst, and high mountain zones, 2
ACCEPTED MANUSCRIPT the sampling methods developed were proved by large–scale practice to be very successful. For other regions, more studies should be carried out in the future
PT
especially the deep-penetrating techniques and the overburden drilling methods
RI
should be tested, and resampling by more effective methods should be done.
SC
(2) Cell sampling. The stream sediment sampling advanced by Webb and others was a great contribution to exploration geochemistry. Sampling a bottom sediment sample
NU
from a river can predict the average values of element concentration in the upstream
MA
basin. When a large area is sampled along streams，the sampling sites will become inhomogeneous and cause difficulties for the construction of geochemical maps. In
D
our method, the samples were not collected along streams but in cells of 1 × 1 km.
TE
Within each 1 ×1 km cell, 1 or 2 samples are collected in the extreme downstream
AC CE P
locations of the cell. The element concentrations of the samples will represent the average values of this cell. With cell sampling the sample distribution is more homogenous, and more feasible for map construction than Webb's original approach of sampling along streams.
(3) Sampling coding system. This coding system is in accordance with cell sampling. The coding numbers of an analytic cell (4 km2) are marked from 1 to n from top left to top right and then from top to bottom. The four (1 km2) sampling cells in an analytical cell are marked with A, B, C, D (Fig. 2). This sampling coding system is made on a 1:200,000 topographic map before the field work (Xie and Ren, 1991; Xie et al., 2011a). (4) Global comparability of data. Systematic analytical errors or bias of analytical
3
ACCEPTED MANUSCRIPT data obtained from the different laboratories should be eliminated or reduced to a minimum. Poor comparability between the results of different laboratories is one of
PT
the greatest unresolved problems in regional geochemistry (Reimann and de Caritat,
RI
2012). In China the analytical work in RGNR program has been conducted by many
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laboratories in the Geological Bureaus of different provinces. So we were the first in the world to understand the serious bias of this problem. Twelve standard reference
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samples GSD1 – 12 were prepared, certified values for different elements were
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obtained by the effort of cooperation of many laboratories in China (Xie et al., 1989a; Xie et al., 1989b; Xie et al., 1985). An analytical quality control system was then
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analytical bias.
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worked out (Xie et al., 1989a) to monitor the between-batch and between-laboratory
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(5) Detection limits. The most important modification for the methodology of geochemical mapping is the requirement that the detection limits for trace and subtrace elements be lowered to below their crustal abundances (Xie, 1995). This requirement is somewhat similar to the requirement that at least 80 – 100% of the samples has reportable values if the crustal abundances of some sub-trace elements (such as Au) published in the literature are modified by more modern and sensitive analytical methods. In order to meet these analytical requirements, a multi-instrument, multi-method analytical scheme was developed (Table 1 and Table 2). (6) Gold exploration. Gold was excluded in the list of elements analyzed in the early geochemical mapping programs by Webb et al. (1973), and others (Bolivar, 1980; Bowie and Plant, 1978a, b; Coker et al., 1981) because of the doubtful results of
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ACCEPTED MANUSCRIPT anomalies obtained due to the nugget effect of gold. Nichol et al. (1989) suggested to take large samples (200 – 800 g) for gold analysis to reduce the error caused by the
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nugget effect of gold. Our approach in RGNR program was to take a small sample (5
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– 10 g) for analysis with a very sensitive method (i.e. detection limit 1 – 0.3 ppb),
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defined 2 ppb as anomalous values provided such values are continuous over a large area (Xie and Wang, 1991). With this approach, the error caused by the nugget effect
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is bypassed during interpretation.
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(7) Streamline operations of sample analysis. In order to increase the cost-effectiveness when such a vast amount of samples are analyzed, operations were
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streamlined inspired by Ford's innovative idea of mass production in the automobile
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industry. The analytical procedures were divided into various kinds of operations,
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such as weighing, digestion, dilution filtering, addition of reagents and measuring by different instruments etc. These operations were separately carried out by individual analysts and streamlined on a large scale.
3. Innovative concept
Until 2000 more than about six million analytical values for each of the 39 dements were produced by laboratories involved in the RGNR programs. The vast amount of data obtained is becoming a treasure for further studies. For example, the innovative concept of geochemical blocks was resulting from utilizing
this information (Xie et
al., 2004). Geochemical blocks were formed as the net result of inhomogeneity caused by earth formation and the gradual build-up of metal concentrations afterward by a series of geological processes. The geochemical block concept could be used to 5
ACCEPTED MANUSCRIPT predict the existence of large ore deposits and to predict their tonnages. So during mineral exploration one could not only rely on dispersion patterns formed after the
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deposits were formed but also distribution patterns (geochemical locks) formed
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before the formation the mineral deposit by wide-spaced sampling using floodplain
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sediment as the sampling medium (Xie and Cheng, 1997).
The idea of flood plain sampling was developed before 1997. The Global
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Geochemical Baseline program was approved by IGCP as IGCP 360. China was
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ahead of this global program by carrying out two projects in China. One is the "Environmental Geochemical Monitoring and Dynamic Geochemical Mapping"
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(EGMON) project which used nearly 500 floodplain samples to cover the whole of
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China (Cheng et al., 1997). Another, more comprehensive project, i.e. the "National
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Geochemical Baseline project", used approximately 1400 cells involving the sampling of rocks, overbank and flood plain sediments (Wang, 2012). During the implementation of the RGNR program, the authors got the idea that geochemical mapping will be further developed to analyze all or most of the elements in the periodic table. This idea has fostered the idea to develop analytical methods for many difficult elements in the periodic table. Such efforts finally caused the establishment of the projects for geochemical mapping of 76 elements in SW and SE China (76GEM). The 76 elements included the 71 elements recommended by IGCP 259/360 plus Os, Ir, Ru, Rh and Re (Table 2). An important achievement by the 76 GEM program was the advancement of the Virtualized Reference maps concept to replace the Standard Reference Samples
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4. Contribution to the mineral exploration In 2000, the RGNR program had been conducted for 20 years and covered more than
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6.6 million km2 of China's territory. Most of the ore deposits discovered (especially
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large amount of Au deposits) during these 20 years contributed to the information
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obtained by this program. The potential economic value of these discoveries reached 600 billion Chinese Yuans (Xie et al., 2011a). Also in this period, most of the
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colleagues working on the implementation of this program are now retired, but the
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new generation of geochemists in China are now active in China.
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From 2000 to 2011 more large copper-lead-zinc base metals, tungsten, tin and molybdenum deposits have been found, amounting to economic value estimated to be
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more than 1000 billion Chinese Yuans. Due to the language barrier and other reasons the case histories of these discoveries had not been published in English even in the present special volume. For remediation purpose, we would like to publish a map of China showing the locations of all the newly discovered large and giant ore deposits attributed to the information from the RGNR program (Fig. 3).
5. Deep penetrating Geochemistry During the 20th century, the deep penetration techniques first proposed by Cameron in 1997 (Cameron, 1998) were widespread. In western countries, most of the work was confined to detailed or semi-detailed surveys to test the results of geophysical surveys or geological prediction of buried mineral deposits by exogenic cover and
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ACCEPTED MANUSCRIPT their techniques were all weak selective extraction of the mobile phase of metals from depth. In China we have developed regional deep-penetration techniques to cover
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large exogenic or volcanic areas (Wang, 1998a, b; Xie, 1998). Only more recently we
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have developed several more strong selective extraction techniques to overcome the
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defects of weak selective extraction techniques (Wang et al., 2011; Xie et al., 2011b)
in nanoscale forms (Wang and Ye, 2011).
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6. New Programs
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and discovered by experiment that the deep penetration mobile phases of metals were
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Several new programs of nationwide and global scale exploration geochemistry have
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been planned in China including " Surface Geochemistry for Oil and Gas", "National Reconnaissance for Ore Tailing Dumps", "National Geochemical Survey and
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Geochemical Evaluation of Soil Quality", and "Global scale Geochemistry".
7. Conclusions
From the above, it can be seen that China has made great effort to develop geochemical exploration methods to cover large areas and even all of China or the whole world and to analyze more elements with emphasis on high sensitivity and accuracy. The possibility of mobilize the geochemists of the whole nation to use unified and standard method in big mapping program lays on the wise utilization of China's political system. These efforts have resulted in a new strategy for mineral exploration, i. e. "Quickly control the overall situation and gradually reduce the target areas". This strategy could be applied equally well in environmental monitoring and
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programs will provide basic information for the newly born science: "Applied
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to mineral exploration and environmental regulations.
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Geochemistry" to carry out more in-depth studies for solving various problems related
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References
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Bolivar, S.L., 1980. An overview of the National Uranium Resource Evaluation Hydrogeochemical and Stream Sediment Reconnaissance Program: Los Alamos.
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Bowie, S.H.U., Plant, J., 1978a. Regional Geochemical Atlas, Orkney. Inst. Geol. Sci., London.
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Bowie, S.H.U., Plant, J., 1978b. Regional Geochemical Atlas, Shetland. Inst. Geol. Sci., London.
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Cameron, E.M., 1998. Deep-Penetrating Geochemistry: Unpublished Report of the Canadian Mining Industry Research Organization (CAMIRO), p. 177. Cheng, H., Shen, X., Yan, G., Gu, T., Lai, Z., Xie, X., 1997. Wide- spaced floodplain sediment sampling covering the whole of China: pilot survey for international geochemical mapping, in: Xie, X. (Ed.), Proc. 30th int. Geol. Congr., Geochemistry. International Science Publishers, Utrecht,Netherlands, Tokyo, pp. 89-109. Coker, W.B., Maurice, Y.T., Ellwood, D.J., Canada, G.S.o., Canada. Dept. of Energy, M., Resources, 1981. National Geochemical Reconnaissance, Baffin Island, Northwest Territories (27B and Part of C; 37A,D). Geological Survey of Canada. Nichol, I., Closs, L.G., Lavin, O.P., 1989. Sample representativity with reference to gold exploration, Proceedings of Exploration '87,
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ACCEPTED MANUSCRIPT . Ont. Geol. Surv., Ont, pp. 609-624. Reimann, C., de Caritat, P., 2012. New soil composition data for Europe and Australia: Demonstrating
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comparability, identifying continental-scale processes and learning lessons for global geochemical
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mapping. Science of The Total Environment 416, 239-252.
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Wang, X., 1998a. Leaching of mobile forms of metals in overburden: development and application. Journal of Geochemical Exploration 61, 39-55.
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Wang, X., 1998b. Principle and practice of exploration geochemistry in searching and discriminating
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concealed large and giant mineral deposits. Geophysical and Geochemical Exploration 22, 81-89 (in Chinese with English Abstract).
(in Chinese with English abstract).
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Science Frontiers 19, 7-18
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Wang, X., 2012. Global geochemical baselines: understanding the past and predicting the Future. Earth
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Wang, X., Xu, S., Zhang, B., Zhao, S., 2011. Deep-penetrating geochemistry for sandstone-type uranium deposits in the Turpan–Hami basin, north-western China. Applied Geochemistry 26, 2238-2246.
Wang, X., Ye, R., 2011. Findings of Nanoscale Metal Particles: Evidence for Deep-penetrating Geochemistry. Acta Geoscientica Sinica 32, 7-12. (in Chinese with English Abstract). Wang, X., Zhang, Q., Zhou, G., 2007. National-Scale Geochemical Mapping Projects in China. Geostandards and Geoanalytical Research 31, 311-320. Webb, J.S., Nichol, I., Forster, R., Lowenstein, P.L., Howarth, R.J., 1973. Provisional geochemical atlas of Northern Ireland. Applied Geochemistry Research Group, Technical Communication, 60:30. Xie, X., 1979. Regional geochemical surveys. Geological publishing house, Beijing. Xie, X., 1995. Perspective. Analytical requirements in international geochemical mapping. Analyst 120,
10
ACCEPTED MANUSCRIPT 1497-1504. Xie, X., 1998. Strategic and tactic deep-penetrating geochemical surveys. Earth Science Frontiers 5,
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171-183 ( in Chinese with English Abstract).
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Xie, X., Cheng, H., 1997. The suitability of floodplain sediment as a global sampling medium:
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evidence from China. Journal of Geochemical Exploration 58, 51-62.
Xie, X., Liu, D., Xiang, Y., Yan, G., Lian, C., 2004. Geochemical blocks for predicting large ore
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deposits—concept and methodology. Journal of Geochemical Exploration 84, 77-91.
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Xie, X., Mu, X., Ren, T., 1997. Geochemical mapping in China. Journal of Geochemical Exploration 60, 99-113.
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Xie, X., Ren, T., 1991. A decade of regional geochemistry in China - the national reconnaissance
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project. Trans. Inst. Min. Metal.. Sect. B. Appl. Earth Sci. 100, 57-65.
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Xie, X., Sun, H., Ren, T., 1989a. Regional geochemistry-national reconnaissance project in China. Journal of Geochemical Exploration 33, 1–9. Xie, X., Wang, X., 1991. Geochemical exploration for gold: a new approach to an old problem. Journal of Geochemical Exploration 40, 25-48. Xie, X., Wang, X., Cheng, H., Cheng, Z., Yao, W., 2011a. Digital Element Earth. Acta Geologica Sinica (English edition) 85, 1-16. Xie, X., Wang, X., Zhang, Q., Zhou, G., Cheng, H., Liu, D., Cheng, Z., Xu, S., 2008. Multi-scale geochemical mapping in China. Geochemistry: Exploration, Environment, Analysis 8, 333-341. Xie, X., Xu, B., 1952. A Cu indicator plant Elsholtzia haichowensis. Acta Geologica Sinica 32, 360-368 (in Chinese). Xie, X., Yan, M., Wang, C., Li, L., Shen, H., 1989b. Geochemical standard reference samples GSD
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ACCEPTED MANUSCRIPT 9–12, GSS 1–8 AND GSR 1–6. Geostandards Newsletter 13, 83–179. Xie, X.J., Yan, M.C., L.Z., L., Shen, H.J., 1985. Usable values for Chinese standard reference samples
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of stream sediments, soils, and rocks: GSD 9-12, GSS 1-8 and GSR 1-6. Geostandards Newsletter 9,
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277-280.
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Xie, X.X., Lu, Y., Yao, W., Bai, J., 2011b. Further study on deep penetrating geochemistry over the
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Spence porphyry copper deposit, Chile. Geoscience Frontiers. 2, 303-311.
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ACCEPTED MANUSCRIPT Table 1 Analytical scheme of 39 elements (Xie, 1995).
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Table 2
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The Analytical Scheme for 76 elements.
Fig. 1. Different regolith/landform/climate zones of China distinguished to optimize
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the sampling method (Xie and Ren, 1991; Xie and Ren, 1993).
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Fig. 2. Example for coding of sampling cells and the analytical cell (Xie, 1979). Fig. 3. Distribution of large and giant ore deposits discovered by geochemical
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exploration in China.
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Table 1 Analytical scheme of 39 elements (Xie, 1995) Al (0.05)*, Ba (50), Ca (0.05), Co (1), Cr (15), Cu (1), X-ray fluorescence spectrometry
Fe (0.05), K (0.05), La (30), Mg (0.05), Mn (30), Na
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(0.05), Nb (5), Ni (2), P (100), Pb (2), Si(0.1), Sr (5), Th (4), Ti (100), V (20), Y (5), Zn (10), Zr (10) As (1), Sb (0.1), Bi (0.1), Hg (0.0005)
Atomic absorption spectrometry
Ag (0.02), Cd (0.05), Li (5)
Atomic emission spectrometry
Ag (0.02), B (5), Be (0.5), Sn (1)
Catalytic polarography
W (0.5), Mo (0.4)
Ionic selection electrometry
F (100)
Colorimetry or laser catalytic fluorescence
U (0.5)
Graphite fumace atomic absorption spectrometry
Au (0. 0003)
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Atomic fluorescence spectrometry
– number enclosed in brackets is the detection limit; unit of Al, Ca, Fe, K, Mg, Na, Si is %, other element is µg/g.
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XRF
DF-ICPMS VOL DF-ICPES XRF FU-I-ICPMS DF-ICPMS FU-ICPMS XRF XRF DA-ICPMS DA-ICPMS FU-I-ICPMS XRF FU-I-ICPMS FA-ICPMS FU-ICPMS XRF DF-ICPMS DF-ICPMS HG-AFS XRF FU-I-ICPMS AES XRF DF-ICPMS FU-I-ICPMS DF-ICPMS DF-ICPMS XRF DF-ICPMS FU-I-ICPMS DF-ICPMS XRF DF-ICPMS FU-I-ICPMS FU-I-ICPMS XRF
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0.02 ppm 20 ppm 0.01% 1ppm 0.05 ppm 0.6 ppm 0.01 ppb 10 ppm 2 ppm 0.2 ppb 0.2 ppb 0.01 ppm 1 ppm 0.05ppb 0.01 ppb 0.01 ppb 7 ppm 0.02 ppm 0.6ppm 0.01 ppm 0.01% 0.015 ppm 0.2 ppm 1.5ppm 0.005 ppm 0.01ppm 5ppb 0.003ppm 10ppm 0.003ppm 0.003 ppm 0.01 ppm 5 ppm 0.02 ppm 0.12 ppm 0.015 ppm 1 ppm 1 ppm
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Mo N Na2O Nb Nd Ni Os P Pb Pd Pt Pr Rb Re Rh Ru S Sb Sc Se SiO2 Sm Sn Sr Ta Tb Te Th Ti Tl Tm U V W Y Yb Zn Zr
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AES XRF HG-AFS DA-GFAAS AES XRF DF-ICPES DF-ICPMS XRF VOL XRF DF-ICPMS FU-I-ICPMS XRF DF-ICPMS XRF DF-ICPMS DF-ICPES FU-I-ICPMS FU-I-ICPMS FU-I-ICPMS ISE XRF DF-ICPES FU-I-ICPMS HG-AFS DF-ICPMS CV-AFS FU-I-ICPMS CF-COL DF-ICPMS FA-ICPMS DF-ICPES FU-I-ICPMS DF-ICPES FU-I-ICPMS DF-ICPES
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0.01 ppm 0.01% 0.2 ppm 0. 1ppb 0.5 ppm 9 ppm 0.2 ppm 0.015 ppm 0.8 ppm 0.04% 0.01% 0.02 ppm 0.12ppm 7 ppm 0.02 ppm 3 ppm 0.003 ppm 1 ppm 0.015ppm 0.015 ppm 0.004 ppm 20 ppm 0.01% 2 ppm 0.015 ppm 0.02 ppm 0.015 ppm 0.3ppb 0.004 ppm 0.5 ppm 0.002 ppm 0.01 ppb 0.01% 0.12 ppm 0.06 ppm 0.004 ppm 0.01% 10 ppm
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Ag Al2O3 As Au B Ba Be Bi Br C CaO Cd Ce Cl Co Cr Cs Cu Dy Er Eu F Fe2O3 Ga Gd Ge Hf Hg Ho I In Ir K2O La Li Lu MgO Mn
Analytical Method
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The Analytical Scheme for 76 elements. Component Detection Analytical Component Determined Method Limited limit
XRF
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ACCEPTED MANUSCRIPT Decomposition Method: DA, digestion with aqua regia; DF, digestion with aqua regia and hydrofluoric acid; FU, alkaline fusion or fusion with Eschka mixture; FA, enrichment of assay; and I, ion exchange resin preconcentration. Determined Method: ICP-MS, inductively coupled plasma mass spectrometry; ICP-ES, inductively couple plasma
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atomic emission spectrometry; XRF, X-ray fluorescence spectrometry; GFAAS, graphite furnace atomic absorption spectrometry; AFS, atomic fluorescence spectrometry; VOL, volumetry; COL, colorimetry; ISE, ionic selection
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electrometry; and AES, atomic emission spectrometry.
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Fig. 1
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Fig. 2
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Fig. 3
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ACCEPTED MANUSCRIPT Highlights 1. Sixty years of Exploration Geochemistry in China are reviewed
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2. China has made great effort to develop geochemical exploration methods.
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3. Mapping programs try to cover large area and even whole China or whole world
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4. Analytical systems had been devised for nearly all elements in periodic table.
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5. Innovative geochemistry concept and exploration strategies are introduces.
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