(China Geo University (Beijing))
This paper summarizes Comrade Zhu Xun's "prospecting" theory, the practical achievements of genetic understanding and scientific research of Shizishan ore field in Tongling ore concentration area, Anhui Province, and the experience of sustainable mining of crisis mines.
Key words: prospecting methods based on the understanding of the genesis of Shizishan ore field
1982 In May, Comrade Zhu Xun's On Prospecting was published in the Journal of Geology. In the past 30 years, the viewpoint of this paper has been verified and cited many times in prospecting practice, which has far-reaching guiding significance for geological exploration.
Tongling, Anhui Province is a famous copper capital, and the history of copper mining can be traced back to 3000 years ago. The territory is rich in mineral resources, and as one of the national key prospecting areas, it has great prospecting potential. Tongling area is an important ore concentration area of iron, copper and gold polymetallic metallogenic belt in the middle and lower reaches of the Yangtze River. At present, the proven deposits are mainly distributed in five ore fields: Tongguan Mountain, Lion Mountain, Xinqiao Mountain, Phoenix Mountain and Shatanjiao. The ore field is a typical large-scale copper-gold ore field with various types, unique spatial distribution and large and wide metallogenic depth. Since the founding of New China, many famous geological exploration units and geologists at home and abroad, such as No.32 1 Geological Team of Anhui Bureau of Geology and Mineral Resources, No.1 Geophysical Exploration Team of the former Ministry of Geology and Mineral Resources, and No.812 Geological Team of East China Metallurgical Geological Exploration Bureau, have done a lot of systematic research in the ore field and completed1:200,000 and/KLOC. Among them, the large porphyry Pb-Zn-Cu deposit discovered by East China Metallurgical Geological Exploration Bureau in Yaojialing, the periphery of Tongling, has tested and proved the theory of "in-situ prospecting" in practice, and also increased the public's confidence in prospecting in this area and its deep and periphery.
1. The genesis of Shizishan ore field in Tongling ore concentration area is considered to be gradual development.
In the late 1950s and early 1960s, scholars such as Guo (1957) and Guo (1957, 1963) thought that these deposits were skarn hydrothermal deposits related to granite. In the following decades, the understanding of the genesis of the deposit developed step by step, and developed circularly according to the process of practice-understanding-practice-understanding, and the understanding was continuously expanded and enriched on a ladder. From the 1990s to the early 20th century, a large number of scholars emerged, who believed that the deposits in this mining area were closely related to Yanshanian magmatism (Zhai Yusheng et al., 1992, 1995,1996; Tang Yongcheng et al.,1998; Xing et al.,1999; Deng et al., 2002; Mao Jingwen et al., 2005). However, with the discovery of massive sulfide ore bodies in sedimentary strata, Meng Xianming (1963) put forward the viewpoint of syngenesis. As early as the end of 1970s, Xu Keqin et al. (1978) put forward the viewpoint that marine sediments were superimposed on Mesozoic hydrothermal fluids. Since the end of 1970s, the debate on the genesis of mineral deposits has never stopped. Most scholars believe that the deposit is caused by the Hercynian submarine jet deposition superimposed by Yanshanian magmatic hydrothermal transformation, but some scholars believe that it should be defined as a stratabound skarn deposit (Changyin, 1983,1991; Wu Yanchang, 1992), although these layered deposits have some characteristics of syngenetic deposits, they always appear around Mesozoic granite bodies and are closely associated with skarn-porphyry ore bodies, so they are suggested to be stratabound skarn deposits. The understanding of the genesis of the deposit is rising, and it is more and more comprehensive and objective. Through the summary and study of typical deposits, the prospecting scope has been expanded, and then a large deposit-Yaojialing copper mine has been discovered in the deep and periphery of the old mine. The theory of "prospecting" has been tested by practice and achieved fruitful results.
Comprehensive information analysis on the genesis of Shizishan ore field.
With the deepening of the understanding of the genesis of Shizishan ore field, new requirements are put forward for the scientific research methods of the genesis of the ore deposit. What kind of research methods and scientific means can be the most authoritative and convincing has become the direction for geologists at home and abroad to strive for development. Taking Dongguashan copper mine as an example, a number of scientific research topics and projects have been carried out from the aspects of deposit geochemistry, isotope geochemistry, rock geochemistry, geochronology, fluid inclusion, mineralogy, petrography and so on, which have continuously filled the gaps in this field and provided new genetic evidence.
Zeng Pusheng et al. (2005), through detailed field observation and indoor analysis and comparison, think that Dongguashan deposit is a large copper deposit formed by the superposition of massive sulfides deposited by Hercynian and Yanshan magmatic mineralization. In terms of deposit geology, Liu Jinghua et al. (2009) found that the Dongguashan layered copper deposit was formed by superimposed mineralization of Yanshanian magmatic hydrothermal solution on the basis of primary ore embryo deposition, and the mineralization went through two stages: the early stage was a massive sulfide deposit formed by jet deposition from Devonian to Carboniferous, and the late stage was a hydrothermal metasomatic deposit formed by magmatic transformation in Yanshan period. Guo Weimin et al. (20 10) hold that the formation of Dongguashan deposit has gone through several stages, such as syngenetic deposition, thermal metamorphism and hydrothermal metasomatism, which supports the view of syngenetic deposition-superimposed transformation. With regard to fluid inclusions, Chen Bangguo et al. (2002) considered that the Dongguashan superimposed layered copper deposit has both sedimentary characteristics and hydrothermal transformation characteristics. The carbon isotope study shows that the oxygen and hydrogen isotopes in the fluid are close to those of magmatic water, so it is inferred that the hydrothermal transformation fluid mainly comes from magma. Ling Qicong et al. (2003) studied the mineral fluid inclusions in Dongguashan stratabound skarn copper deposit, and the results showed that mineralization occurred under acidic and reducing conditions. Ore-forming fluid is provided by magma source and strata, which is a typical stratabound skarn deposit with multi-source ore-forming materials, multi-metallogenic stages and multi-ore-controlling factors. In terms of rock geochemistry, Li Hongyang et al. (2006) considered that Dongguashan copper deposit was caused by submarine hot water jet deposition through a series of geological and geochemical characteristics such as petrochemistry, trace elements, rare earth elements, isotope geochemistry and fluid inclusion homogenization temperature determination. In terms of stable isotopes, Xu et al. (2000, 2007) analyzed the hydrogen and oxygen isotopes of vein inclusions, and the results showed that the source of ore-forming fluid may be magmatic water, and vein ore bodies may be formed by the superposition of magmatic hydrothermal solution; However, the sulfur isotope is close to the δ43S value of massive sulfide deposits in the middle and lower reaches of the Yangtze River, indicating that the sulfur in the ore does not come from strata, so it is inferred that the Dongguashan copper-gold polymetallic deposit belongs to the sedimentary-hydrothermal superimposed transformation type. Lu Jianjun et al. (2008) pointed out that the copper in Dongguashan deposit comes from magmatic rocks, and the superimposed ore-forming fluid is mainly magmatic fluid, and put forward that Dongguashan deposit belongs to the jet deposition-magmatic hydrothermal superimposed ore-forming model. In the Late Carboniferous, massive sulfide deposits were formed by submarine jet mineralization, and the ore components were mainly sulfur and iron. On the one hand, magmatic hydrothermal solution transformed Yanshanian massive sulfide deposits and enriched copper and other ore-forming materials. Multi-angle and multi-level scientific research continuously enriches the geological data of mining areas. Through these technical methods, we can further guide the change of understanding. The epistemology and methodology of prospecting complement each other. The theory of "prospecting by ore" needs the guidance of advanced geological theory and the support of advanced technology. The continuous scientific research of old mines is an important means to guide the prospecting.
Third, some experiences of sustainable mining in crisis mines.
By summarizing the genesis and scientific research methods of Shizishan ore field in Tongling ore concentration area, it is enough to clarify the value and position of "prospecting theory" in the current mineral resources development. With the rapid development of national economy, the demand for resources is also expanding day by day, which puts forward higher requirements for prospecting. How to maximize the development and utilization of resources has become the focus of public attention. The sustainable mining of crisis mines has the following two experiences:
(1) For the old mines that have been mined, increase the research and investment in deep and peripheral prospecting. In recent years, the theory of "prospecting by ore" has been put into practice and achieved remarkable results. In addition to Tongling ore concentration area, Xiaoqinling gold mine in western Henan, Xiongershan gold mine, Sanshandao gold mine in Shandong, Hongtoushan copper mine in Liaoning, Tongkeng tin mine in Nandan County, Guangxi, etc. Breakthrough progress has been made in the exploration of replacement resources in crisis mines, which brings new hope to the national energy strategy.
(2) Improve smelting technology, reduce cut-off grade and expand resource reserves. Technological innovation can bring new economic benefits. With the innovation and improvement of mineral processing technology, low-grade ores are continuously mined and smelted, the selection range of ore bodies is continuously expanded, the calculable resource reserves are also continuously increased, and the cut-off grade is repeatedly reduced, which provides a basic guarantee for national economic construction.
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