Check the front page of El País, national edition of September 8, 2012 »<br />MINING: search and exploratio... - 0 views
started by Romigi Atkinson on 12 Sep 12
started by Romigi Atkinson on 12 Sep 12
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Individual searches. The most easily identifiable and accessible deposits of long open. In addition to the traditional tools geologist search engine - Kyle and tray wash samples - in today need a Geiger counter or scintillator, if the search is conducted radioactive minerals, instruments UV finding fluorescent minerals berillometr (devices detecting beryllium exposure by radioactive rocks isotopes) in the exploration of beryllium ores.
Intelligence Brigade. Modern mining companies to find mineral hire intelligence brigade, equipped with all-wheel drive vehicles and vehicles on tracks, small aircraft and helicopters, as well as geophysical instruments, chemical and micro-chemical laboratories, portable drilling rigs. Sometimes for channel sampling study areas and obtain representative samples reconnaissance party used earth moving equipment.
Territory, promising to explore. Each year, the problem of choosing the site for exploration with the probability of success is above average is more complicated. A significant role in this is the element of chance.
Many economically important deposits have been discovered in the vicinity of the old operating mines. They usually lie deeper exploited deposits.
As the surface of the earth is 71% covered by water, became objects of research as sea water and the ocean floor. Now recovered from sea water magnesium. The discovery of manganese nodules on the ocean floor is required to focus on the development of methods for their production. Planned more detailed underwater research to find other valuable materials. In the future it may expand the work to extract useful components from metal-bearing sludges, covering vast areas of the Pacific Ocean, and from highly mineralized water of the Red Sea.
Exploration methods. Choice of research methods is often determined by the shape and mode of occurrence of the ore body. If the flat-lying ore deposit formation is presented, for use of its intelligence network of vertical wells. Similarly, studying the massive deposits of disseminated ores. If the deposit is steep, then to delineate the deposit at a depth of drill deviated wells. Pipeline or lenticular ore zones in the veins require more careful selection of the location of the drill holes. Usually deep-seated mineral deposits are not subject to study simple methods, and require detailed and complex investigations.
First, studies the Earth's surface, where you can find search features hidden in the depths of the ore bodies. Areas of red rock or soil ("iron hat") are related to the oxidation of iron-bearing minerals, and are often a sign of ores of iron, gold, lead, zinc and bauxite. To indicate the presence of manganese black or brown spots (so-called "desert tan"). Light yellow color may indicate the presence of uranium, green or blue - copper, pale green - nickel or arsenic. Easily recognizable black weathered outcrops of coal.
As a result of weathering of the host rock in a number of minerals which can be dissolved, leaving small cavities or "core" (rocks, filling the internal cavity), preserving the form of leached mineral. These rocks with honeycomb structure serve as indicators of underlying ore zones. In addition, the signs are favorable search zone of strongly altered basement rocks or broken, where the displacement of the earth's crust formed positive and negative forms of relief.
Geophysical surveys. During the exploration of the ore areas of a sensitive instrument that registers changes in gravitational and magnetic fields, electrical and other physical properties of the rocks of the crust. Geophysical equipment (magnetometers to search for magnetic ores and gravimeters to detect differences in rock density) can be hand-held or mounted on vehicles and aircraft. The use of aircraft airborne geophysical devices greatly accelerated the process of exploration and increase its efficiency.
Microchemical, geobotanical and biogeochemical methods. Microchemical analysis of relatively small quantities to a large number of samples used for the detection of metals present in minor amounts. Generalization of the results of quantitative research allows further identify clusters of minerals by geophysical methods.
Methods geobotanical indication, based on the effects of certain minerals in the different plants, were developed in the early 1940's. They are the most widely used in the Soviet Union, where since 1955 have become common in the exploration parties. Plants growing in soils of high salinity anomalies are different color, shape and height. In order to identify the areas within which the indicator plants react to the presence of certain minerals that are used in conjunction aerial and ground control. "Universal" indicator is a plant that always respond to the presence of the element, and the "local" - those which operate only within a limited area. Thus, an indicator of zinc are certain types of mustard and cloves, although still in their presence were not open new zinc deposit. The indicators highlighted copper plants of the family Caryophyllaceae, different kinds of mint and moss. In Sweden, based on the study of mosses found three copper deposit. For some species of Astragalus and other legumes - indicators of selenium - in the U.S. was discovered uranium ore deposits on the Colorado Plateau. In bioindication important features are the anomalies of plant morphology and their phenological cycles. The presence of aluminum in the soil leads to a shortening of roots, wilting and leaf spot, and nickel - to the appearance of white spots on the dead leaves.
Biochemical analysis of plants is particularly useful when the zone of mineralization located deep. Samples of plants (herbs, shrubs, trees) are usually studied by colorimetric or spectrographic methods for the determination of micro-doses of the various elements and identify deviations from the norm of their content. Choose plants for chemical analysis by the depth and power of their root system, age, height, and "accumulation factor", which shows how much more the mineral is absorbed by plants that grow within the area of the ore body, compared to those that grow in different soil conditions .
Tracing leakage flux. Leakage fluxes call rejection debris and mineral components made by erosion of the deposit. When you find some useful components, then trace their way down to the source (Fig. 1). The most successful, this method is used in arid areas. However, it is extremely difficult to implement in the tropics, where lush vegetation and soil cover securely powerful camouflage initial deposit. Sometimes, where erosion completely destroyed zone of mineralization, the only thing left on the field, this is the leakage flux of useful components.
In prospecting for gold samples are taken sequentially along the watercourse upstream. Thus the search is conducted other heavy minerals (in Russia this method is called schlich sampling). When the particles of gold found in the stream beds, the adjacent slopes planned system of perpendicular lines, which are located at the same distance from each other. Samples taken at the nodes of the uniform grid, washed, and the number of gold particles counted in order to find the root of the source of their origin. Primary deposits from the surface reveal the trenches or ditches, and in depth - the galleries, pits and shafts. Then count the stock and determine the value of the deposit.
Testing. In unconsolidated sediments overlying the ore vein sampling are pits or trenches. When these surface rocks show signs of mineralization, fresh walls ditches and pits are selected more representative sample.
When coring sampling the soil at regular intervals, often by hand, hammered by the Boers - pipe sections of 2.5 or 5 cm with a sharp cutting edge. Then we study the selected drill samples. This method is applicable only in the study of unconsolidated sediments containing no stones or boulders. In Russia, the known method "move aside" encountered boulders or acute-angled debris. For a more complete and reliable information on the power and features of deposits, leaving the surface, conduct comprehensive testing by pits, trenches and manual core drilling.
Drilling. Where the test site blocked with sediment thickness or hard rock, you need to drill holes (Fig. 2) using a different rig - screw, cable-, rotational, and machines "Empire."
Auger drilling units are used for soft soils. The rotation of the screw by hand, or with the use of horse traction or mechanical means. Auger drilling is mainly down to a depth of approx. 200 m
Machines "Empire" is widely used to drill to a depth of unconsolidated deposits 9-12 m in the exploration of bauxite and laterite deposits of other origins. The main part of the unit is heavy casing with a cutting shoe on the bottom and a circular steel platform on the top. The platform with the casing could be rotated, it is mounted swivel arm. In the case of soft soil pipe under the weight of a person standing on the platform, is pressed into the soil. In clay and other more tight additional dent provide driving force plungers, which can be raised and reset. Loose material that accumulates inside the casing, diluted with water.
Installation cable drilling consists of a heavy chisel, drill stem, drummers and castle, to which is attached a rope. For driving the drill rig is used with the power plant, lift and reset the working body. Scattered masses extracted from wells Bailer or coil. When cable drilling wells rarely straight, and sampling - accurate. As the rock in which hammers drill, shot, it is often difficult to get a clear idea of their genesis. Despite the fact that the current cable drilling is rare, it has played an important role in the practice of exploration and preparation for operation of many mineral deposits.
Installing rotary drilling provide low cost full-hole drilling in unproductive deposits. Coring conducted only in the pay zone. Some of the design of such facilities are designed for directional drilling at any angle. The deepest hole in the world (12 066 m, the Kola Peninsula) was drilled with rotary drilling.
Different size rigs - from small machines, installation and managed in underground mines can carry two people to large, mounted on steel towers and serviced by a team of qualified drillers. There mounted assembly chassis or skids. Rotary drilling oil and gas wells (rotary) is also carried out by the special courts and fixed offshore platforms. Until recently, the use of steel drill rod, so the maximum depth of drilling machine determines the power that holds the drill string. The appearance of aluminum rods, although more expensive than steel, allowed to drill deeper wells.
When installing rotary drilling used for coring, at the end of the core barrel is screwed drill bit, reinforced diamond or hard metal, such as tungsten carbide (pobeditom). In this system, the hollow drill rods held drill chuck attached to the end of the hollow core barrel equipped with a thread. The drilling fluid under pressure is fed down the hollow rods to cool the bit and remove the fragmented mass and sludge. As we move into the crown core receiver core barrel shaped cylinder of undisturbed rock (core). When the crown is to deepen a distance equal to the length of the core barrel (1.5 to 3.6 m), the column rods, core barrel and crown removed from wells, and core - from the core barrel. Then he goes on all sorts of tests.
When drilling Full-Hole rotational units (rotary drilling) studied the scattered masses of mud and made with compressed air or mud through the hollow drill rods. Typically, rotary drilling faster and cheaper core. Total depth of wells drilled per shift, can vary widely, depending on the geological conditions and the size of holes - from a few hundred meters to 1.5-3 m in the rocks.
Drilling rigs with diamond drill bits are used for hole depths of up to 3 km. Some of these units are equipped with special auger that retrieve a core rod with a rope. Installation of this type can reach higher speeds with less drilling costs vremennh core recovery without raising the surface of all the drill string.
For sinking drilling relatively shallow shafts are special installation rotary drilling with carbide crown or crowns shot drilling diameter of 1 m or more. Installation of this type are also used in some systems development for the drilling penetration treatment of mine workings (eg in underground potash).
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For alot more detail about this subject go to: mineral occurrence.