Prospecting methods and techniques
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1. Geological mapping method The geological mapping method is a technique that employs basic geological theories to carry out comprehensive and systematic geological and mineralogical surveys and studies. It enables the identification of the basic geological characteristics of strata, rocks, structures, and minerals in a study area, helps to understand the laws of mineral formation, and utilizes various types of information for mineral exploration. Its working process involves plotting geological features on topographic maps at a scale that is appropriate, which is why it is called geological mapping. Since the geological and mineralogical aspects reflected in this method are comprehensive and systematic, it is the most fundamental method for prospecting. Geological mapping must be carried out under any geological conditions, regardless of the minerals being sought. Therefore, geological mapping is a strategically important geological exploration task. The quality of geological mapping has a direct impact on the effectiveness of mineral exploration. In 1996, detailed geological mapping in the Camerda area of Australia revealed a nickel sulfide deposit with reserves of over 20 million tons, having an average grade of 3.4%. This mining area was originally an old gold mine with a history of 80 years. In 1962, detailed geological mapping (at a scale of 1:7200) was carried out in this area to further search for gold, and through this geological mapping, the stratigraphic sequence and structure were accurately determined. In 1964, some limonite samples were collected from the waste rock piles in an old gold mine. Analysis showed that they contained 1% nickel. Field investigations revealed some small, isolated iron deposits, and further mapping work indicated that these limonite deposits were located at the contact zone between ultramafic rocks and the metamorphosed basalt beneath them. This contact zone was approximately 20 kilometers long and had a dome-like structure. Beneath the limonite layers, there was nickel-bearing limonite in a disseminated form, which led to the speculation that primary sulfide mineralization might exist at greater depths. Therefore, excitation polarization potential measurements, magnetic surveys, and geochemical surveys were conducted, revealing numerous excitation polarization anomalies and nickel geochemical anomalies, which led to prompt drilling. In 1966, a nickel ore body of about 3 meters thick composed of massive sulfides was discovered, containing 8.3% nickel. Subsequently, many promising nickel deposits were identified and discovered in the surrounding area; the total reserves of ores with a nickel content of over 0.6% amount to about 100 million tons. It was considered a sensational event that shocked the Western world at the time. 2. Heavy mineral prospecting method The heavy mineral method is a prospecting technique with a long history. It was used to wash out gold dust as early as 2000 BC. Because of its simplicity, cost-effectiveness, and effectiveness, it remains an important method for mineral exploration to this day. It can be used not only to locate ores and sand deposits as well as primary minerals with relatively stable physicochemical properties (such as native gold, native platinum, wolframite, scheelite, cassiterite, cinnabar, magnetite, rutile, chromite, tantalite, niobite, beryl, zircon, monazite, yttrium phosphate, and other metallic, precious, rare, and rare-earth metal minerals, as well as non-metallic minerals such as diamonds, corundum, topaz, and apatite), but also to find sulfide deposits such as galena, chalcopyrite, molybdenite, and sphalerite in the vicinity of primary ore deposits. Strata can be classified through the study of artificial heavy mineral ores, rock bodies can be compared, the genesis of ore deposits and the occurrence states of metallogenic elements can be investigated to understand the regional metallogenic characteristics, thereby enabling mineral resource prediction. It is applied in mineral surveys, deposit exploration, and deposit research, yielding significant results. For example, in 1967, gravimetric surveys of water systems at a scale of 1:50000 were conducted in a certain area (with sampling intervals of 300–500 meters). Two particles of native gold were found at sampling site No. 06, which is located on a tributary of the river; several particles of native gold were also discovered in the gravimetric samples from sampling site No. 12. Following up by moving upstream, 11 particles of native gold were found at sampling site No. 13, located downstream of the confluence point where the stream meets the tributary, and ore-bearing quartz breccias were also observed there. Continuing the tracking downstream along the stream, an increase in the number of natural gold particles and an increase in their size were observed at sampling sites 14 and 16; moreover, there were more quartz cobbles containing loss holes. At sampling site No. 17 near the source of the stream, there were over 20 particles of natural gold in the heavy sand, along with a small amount of chalcopyrite (which had partially transformed into malachite). Through the aforementioned exploration efforts, primary gold deposits were found beneath the colluvial and residual deposits in the vicinity of that location. Subsequent trenching, shallow wells, and drilling confirmed that the gold-bearing quartz veins A and B represent large-scale industrial gold deposits. 3. Geochemical prospecting, abbreviated as geochem prospecting, refers to the systematic measurement of geochemical properties in natural materials such as rocks, water, air, or organisms (such as trace amounts of certain elements), in order to identify geochemical anomalies associated with mineralization or ore deposits. Geochemical methods can be divided into rock geochemical surveys, soil geochemical surveys, hydrological geochemical surveys, water-land geochemical surveys, gas geochemical surveys, and plant geochemical surveys, among others. Geochemical exploration methods can be used to locate deposits of non-ferrous metals, rare and dispersed elements, radioactive elements, as well as oil and natural gas. In recent years, research on methods such as isotope geochemical prospecting, aerial geochemical prospecting, and marine geochemical prospecting has further **enriched and developed this discipline**. Geochemical prospecting has developed driven by near-geochemistry and trace analysis techniques. This method was first applied in the 1930s by the former Soviet Union and the Nordic countries** (Sweden, Norway). It was not until the mid-1940s to the 1950s that it attracted widespread attention around the world. Our country began establishing agencies for this purpose in 1952. At present, this method is in a stage of rapid development and has already achieved considerable results in mineral exploration. 4. Geophysical exploration methods, abbreviated as “geophysics,” refer to methods that utilize physical principles to study geological structures and address issues related to mineral exploration. It is based on the differences in physical properties such as density, magnetism, electrical properties, elasticity, and radioactivity of various rocks and ores. Different physical methods and geophysical instruments are used to detect changes in natural or artificial geophysical fields, and by analyzing the geophysical data obtained, geological structures and mineral distributions can be inferred and interpreted. The main geophysical exploration methods currently available include: gravity exploration, magnetic exploration, electrical exploration, seismic exploration, and radioactive geophysics. Depending on the workspace, it can be further divided into: geophysical exploration on land, aerial geophysical exploration, marine geophysical exploration, drilling geophysical exploration, etc. In the covered areas, it can compensate for the shortcomings of conventional surveying and exploration methods, serving for comprehensive mineral prospecting and geological mapping. The development of remote sensing and telemetry technologies has opened up new avenues for geophysical exploration. In recent years, some new geophysical exploration technologies and methods have emerged, such as ground-penetrating radar technology and nuclear magnetic resonance technology. 5. Remote sensing methods: These involve using various instruments to explore, measure, or monitor various phenomena and changes on Earth, in the atmosphere, and on other planets from great distances, either from high altitudes or from the ground. This method of obtaining information about a target without direct contact with it was first proposed by geographer Evelyn Pruitt. Remote sensing technology has developed rapidly since the 1960s, building on methods such as aerial photography and aeronautical geophysical surveys, and by integrating the latest advancements in interdisciplinary sciences, optics, electronics, and computer technology. At the current stage, remote sensing technology still focuses primarily on Earth (including the atmosphere) as its main object of study. It makes use of the ability of various objects to reflect or emit electromagnetic waves; sensors mounted on vehicles such as aircraft, rockets, artificial satellites, and spacecraft are used to receive or detect electromagnetic wave information from distant targets, thereby obtaining various types of data and information about their dynamics. Due to its advantages such as a large coverage area, fast information acquisition, minimal restrictions from ground obstacles, and the ability to conduct continuous and repeated observations over short periods of time, this method holds great practical value and broad prospects for development in areas such as the detection of natural resources, monitoring of environmental changes, meteorological observations, disaster prediction, and **reconnaissance. 6. Statistical prediction methods for mineral deposits Everyone wants to be the one to discover a mineral deposit, but some succeed while others always miss out; the difference lies in their approach to thinking. The statistical prediction method for mineral deposits is a scientific approach to mineral exploration. It includes the following four aspects: (1) Theoretical prospecting. This is in contrast to the \"empirical prospecting\" and \"technical\" prospecting that have been used for a long time in the past. As the difficulty of mineral exploration increases, it is no longer possible to rely solely on experience or technology; instead, geological theories must be used as a guide in carrying out mineral deposit exploration. (2) Comprehensive prospecting Includes comprehensive methods, comprehensive information, and comprehensive mineral types; special attention should be paid to the indirect role of comprehensive information in prospecting (its function in identifying geological bodies and tracing geological boundaries). (3) 3D prospecting To locate hidden ore deposits, it is necessary to determine the variations of mineralization signs in three-dimensional space in order to increase the depth of prospecting. (4) Quantitative mineral exploration Predicting and evaluating deposits by establishing various mathematical models is one of the three main components of statistical methods for deposit prediction. (5) The three major theories of deposit prediction The theory of similar analogy forms the basis of deposit prediction; it requires us to have a thorough understanding of, and extensive knowledge of, the mineralization conditions, characteristics of, and exploration indicators of various known deposits both domestically and internationally ； The theory of difference is at the core of deposit prediction; it requires, on the basis of similar analogies, paying attention to identifying differences at various levels or scales, as well as different types of geological anomalies ； The quantitative combined ore-control theory serves as the basis for deposit prediction; it requires an understanding of all geological, chemical, and biological processes that are related to the genesis of deposits, as well as a grasp of all factors associated with mineralization and their manifestations. The theory of similar analogies guides us in comparing mineralization environments, thereby allowing us to identify the most likely mineralization environments across a wide range of crustal areas, or to determine the minerals that can be sought for and predicted in a given area based on its geological conditions. The theory of differentiation guides the analysis of the metallogenic background field, thereby enabling the selection of target areas for prediction within defined favorable metallogenic environments or sites. The quantitative combined ore-control theory guides the analysis of the probability of mineralization and the degree of its excellence, thereby enabling one to evaluate and select the areas most likely to develop mineralization, or the optimal sites for mineralization, within identified prospective areas
Plants in nature contain rich mineralization information. If you don’t believe me, let me tell you a story first! In the Americas, there is a mysterious valley with fertile soil, beautiful scenery, and a pleasant climate. But most of the people who lived there died for no apparent reason. Over time, it became a valley with no inhabitants, and the local Indians called it “Valley of Death”. Later, immigrants from Europe discovered this charming valley and settled there, tilling the land and sowing seeds, reaping bountiful harvests. However, the good times did not last long; a strange and mysterious disease filled them with fear. Those suffering from this disease gradually lose their vision, their hair falls out over time, and eventually they die from exhaustion. What’s going on? Is there a ghost? It was not until after World War II, when geologists went there to search for minerals, that this ancient mystery was solved. It turns out that the rocks and soil there are rich in selenium but deficient in sulfur; in order to grow properly, plants absorb selenium, which has properties similar to sulfur, from the soil to compensate for the lack of sulfur. Selenium is an element that is toxic to the human body; foods containing high levels of selenium can cause poisoning if consumed, leading to death from this strange disease. After uncovering the true nature of \"Death Valley,\" geologists were greatly inspired to realize that plants can not only help people locate minerals but also assist in extracting useful elements. In practice, it has been found that many plants can be used as indicators for mineral exploration, giving rise to a new discipline—bioexploratory geochemistry. The iron birch has very hard wood; even nails have difficulty being driven into it. This is because the iron birch has absorbed a large amount of silicon. Silicon mines can be found in areas where iron birches grow abundantly, such as in the border region between our country and Korea. Haizhou Elsholtzia is a perennial herbaceous plant. The grass stems are square in shape and highly branched. In autumn, it blooms with blue or azure flowers that are stunningly beautiful and emit a delightful fragrance. The flower is shaped like half a toothbrush, hence it is commonly known as toothbrush grass. The color of the Haeju elsholtzia is dyed with copper. Elsholtzia haizhouensis has a strong tendency to absorb copper ions; once these ions are absorbed into the plant and form copper compounds, they cause the flowers to turn blue. Thus, Haizhou Elsholtzia earned the fragrant name of copper grass. Why can Elsholtzia haizhouensis indicate the presence of copper mines underground? This is because it prefers to grow in acidic soil containing large amounts of copper; in such soil, it absorbs copper ions, and its flowers turn blue or azure due to the effect of these copper ions. If a chemical analysis of the rhizomes of Elsholtzia halimifolia is conducted, each kilogram of the rhizomes contains one gram of copper. Zambian copper flower has upright branches, opposite leaves, and blue flowers. Where copper flowers grow in large numbers, high-quality copper mines may be present. This kind of copper grass also exists in Yunnan. If artemisia (pigtail grass) grows in ordinary soil, its plants grow tall ； When grown in soil rich in boron, it turns into a little dwarf old man. Based on the development of the mugwort, boron deposits can be located. When plants absorb excessive ions of transition metals, their normal color of leaves, flowers, and stems changes; therefore, minerals can be detected by observing such abnormal colors in plants. For example, copper can make the flowers of plants appear blue, such as in wild roses ； Manganese can make a plant’s flowers turn red ； Uranium can turn the flowers of Chinese milk vetch light red ； Zinc can make the blue, yellow, and white colors of violet flowers more vivid ； Manganese can also cause the flowers of plants to lose their color. Because plants have the unique ability to concentrate mineral elements from soil or water within their bodies, they are used not only for mineral exploration but also for mining. In nature, some minerals are scattered widely, and the concentration of certain ores is very low, making extraction difficult and requiring substantial costs for development; therefore, people use plants to assist in mining. For example, after geologists uncovered the secrets of selenium, they planted alfalfa. Clover absorbs large amounts of selenium from the soil and stores it in its body; thereafter, it is harvested, dried, burned to ashes, and selenium is extracted from those ashes. It is said that two kilograms of selenium can be obtained per hectare of alfalfa. In the Minas Gerais region of Brazil, there grow many small, dark-red grasses. These grasses have a strong affinity for iron; they accumulate large amounts of iron in their tissues, with an iron content that is even higher than that of iron ore of the same weight. That’s why they are called iron grasses. By harvesting this grass and refining it, high-quality iron can be obtained. There is also a type of zinc grass that thrives in soils rich in zinc; its roots absorb zinc from the soil and store it within the plant. Zinc is extracted using zinc grass; 294 grams of zinc can be obtained from the ashes of each kilogram of zinc grass after combustion. By planting corn in areas containing gold mines, it is possible to extract gold from the corn plants; Czech scientist Babicika obtained 10 grams of gold from one kilogram of corn ash. Japanese geologists discovered a deciduous shrub from the Verbenaceae family called Subaish, which has an extremely strong ability to absorb gold; therefore, gold can be extracted from it. Alfalfa has the ability to accumulate tantalum; it is planted in soil containing tantalum, and 200 grams of tantalum can be extracted from approximately 40 hectares of alfalfa. There is another type of flax plant whose ash, after combustion, can contain up to 52% lead oxide, making it practically a plant ore. Aquatic plants can also be used to mine from water or recover precious metals from wastewater. For example, kelp that grows in the sea is able to accumulate large amounts of iodine from seawater; therefore, it is used as a useful tool for obtaining iodine from the sea. For example, water hyacinth can absorb heavy metals such as gold, silver, mercury, and lead from wastewater. It has been determined that one mu of water hyacinth can extract 75 grams of mercury from wastewater every four days. Therefore, paying attention to vegetation, interacting more with plants, listening to their ‘voices’, and understanding their properties is highly beneficial for people looking to discover minerals and extract useful elements! Who says vegetation has no feelings? Thousands of flowers and plants surround the mine!
I know there are plants that grow in areas rich in copper ions; they prefer to thrive in such places, and I’ve seen that these plants indeed grow abundantly where there are copper mines