There are two industrial types of chrysotile deposits: magnesium carbonate type and magnesium ultrabasic rock type. The surrounding rocks of magnesium carbonate deposits are mostly dolomite and dolomite limestone, which are small in scale and poor in grade. For example, asbestos mines such as Jinzhou in Liaoning and Laiyuan in Hebei belong to this type. The parent rocks of magnesium ultrabasic rock deposits are magnesium-rich and mafic ultrabasic rocks, mostly plagioclase peridotite and peridotite. This kind of deposit is generally large in scale, rich in grade and good in fiber quality. For example, the asbestos mines such as Mangya in Qinghai and Asbestos in Sichuan belong to this type.
According to Code for Geological Exploration of Glass Silica Raw Materials, Decorative Stone, Gypsum, Chrysotile, Wollastonite, Talc and Graphite (DZ/T0207-2002), the general industrial indexes of chrysotile ore are shown in Table 17- 10.
Table 17- 10 general industrial indicators of chrysotile ore
Two. Classification and basis of exploration types of mineral deposits
Asbestos geological exploration mainly finds out the shape and occurrence of ore bodies and their changes along strike and dip through various means. The mineralogical characteristics, physical and chemical properties, grade, type and washability of ore minerals are comprehensively studied. For areas with complex hydrogeological conditions, corresponding hydrogeological exploration work must also be carried out. Finally, according to the control degree of exploration engineering on the deposit, different reserves are divided and their reserves are calculated. Cotton content (grade) and fiber length are the main factors in evaluating asbestos deposits. At the same time, we should also pay attention to the physical and chemical properties of asbestos and the beneficial and harmful associated minerals, and make a comprehensive evaluation of the deposit.
1. Basis for classification of exploration types
(1) orebody scale
1) The extension length of the main ore body of a large deposit is generally more than 2000m m.
2) The extension length of main ore bodies in medium-sized deposits is generally 2000 ~1000m.
3) The extension length of the main ore body of a small deposit is generally less than1000m.
(2) Morphology and internal structure of main ore bodies
1) regular-simple, the main ore bodies are mostly layered, layered or lenticular, with regular boundaries, single ore type (variety, grade) or regular distribution of main ore types (varieties), no discontinuous interlayer, and the stone content is generally less than 10%.
2) Regular-medium, the main ore bodies are mostly layered and lenticular, with regular boundaries, regular distribution of main ore types (varieties and grades), and many discontinuous stone inclusions, and the stone inclusion rate is generally 10% ~ 30%.
3) Irregular-complex, the main ore bodies are mostly small lenticular or irregular bodies or ore bodies with irregular boundaries, and the main ore types (varieties and grades) are irregularly distributed, mostly discontinuous stone inclusions, and the stone inclusion rate is generally greater than 30%.
(3) Thickness stability of main ore body
1) is stable, the thickness of the main ore body changes little or regularly, and the coefficient of thickness variation is generally less than 40%.
2) Relatively stable, the thickness of the main ore body changes little or regularly, and the thickness variation coefficient is generally 40% ~ 70%.
3) Unstable, the thickness of the main ore body changes greatly or the change law is not obvious, and the thickness change coefficient is generally greater than 70%.
(4) Stability of ore quality
1) is stable, the ore grade or its performance in the main ore body changes little or regularly, and the coefficient of grade change is generally less than 40%.
2) Relatively stable, the ore grade or its performance of the main ore body changes little or regularly, and the coefficient of grade change is generally 40% ~ 70%.
3) Unstable, the ore grade or its performance of the main ore bodies changes greatly or the change law is not obvious, and the grade change coefficient is generally greater than 70%.
(5) The influence and damage degree of ore structure, magmatic rocks and karst on ore bodies.
1), the ore body is monocline or open anticline, faults, magmatic rocks and karst are undeveloped, and the ore body is unaffected or damaged, or only slightly affected and damaged.
2) Medium, the ore body has secondary folds or local folds are relatively tight, faults, magmatic rocks and karst are relatively developed, and the ore body is affected and destroyed.
3) The folds of ore bodies are dense and complex, faults, magmatic rocks and karst develop, and the ore bodies are strongly affected and destroyed.
2. Exploration types of mineral deposits
According to the specifications, it is generally divided into three types of exploration (see table 17- 1 1).
Table 17- 1 1 exploration types of asbestos deposits
Three, different types of exploration engineering spacing
Generally speaking, the exploration method of chrysotile ore is mainly drilling. When terrain conditions permit, pit exploration or the method of combining pit exploration with drilling can also be adopted. When drilling holes, effective measures should be taken to prevent selective wear. Strive for a complete and clean core. The core recovery rate of the surrounding rock of the roof and floor of the ore body is not less than 75%; Core recovery rate is not less than 90%. The principle of drilling diameter is to meet the sampling quality of a single sample. Magnesium ultrabasic rock deposits are generally not less than 75mm, and magnesium carbonate deposits are generally not less than 91mm. If the thickness of ore body is thin, large-diameter drilling should be used. Except the core recovery rate, the drilling quality standard shall be implemented according to the Core Drilling Regulations (1982). See table 17- 12 for the spacing of mineral resources/reserves exploration projects to be controlled.
Table 17- 12 mineral resources/reserves exploration project spacing unit: m.
Four, sampling, sample processing and analysis, testing
1. sampling
There are two sampling methods for asbestos samples: surface grooving method and core drilling method. According to different ore types and cotton content, surface grooving method is adopted for sampling. When sampling, the continuous grooving method is adopted. The cross section of the tank is 20cm× 30cm, and the sample length is 4 ~ 6m. ..
In chrysotile mine, according to the appearance characteristics, color, length, alteration and deterioration degree, cleavability and firmness of asbestos fibers, representative unweathered primary structural fibers should be collected respectively, and pure asbestos and unselected primary fibers selected by microscope should be tested by X-ray diffraction, and multi-element analysis should be carried out. The number of samples is generally 2 ~ 3 pieces.
The second step process
Asbestos ore samples are treated by air separation method to replace the original geological samples and ore samples. Implement unified processing flow, processing equipment and grading standards. The technological process realizes the mechanization and miniaturization of processing equipment, which is similar to the technology and equipment of mine mineral processing production and is beneficial to the protection of asbestos fiber. The accuracy of asbestos sample test results in cotton content, fiber quality and fiber classification should be guaranteed.
Field treatment and indoor treatment stages of geological treatment of asbestos ore samples;
On-site sample processing Sample processing flow: Weigh and sieve the sample, manually crush the ore to the granularity requirement corresponding to the quality with a hammer, and sieve to make it pass the specified granularity control sieve. When the sample quality is large, it needs to be reduced. Tapering the sample repeatedly for 3 ~ 5 times by moving the pile, then flattening the sample into a pie shape, and dividing it by quartering. Weighing after each division, the relative error of the two masses shall not exceed 5%, otherwise it shall be re-divided. If the heavy part is used as the normal sample for the first time, and the light part is used as the normal sample after the second shrinkage, it is selected alternately in turn. The mass of the sample after shrinkage should be greater than or equal to 50kg.
Indoor treatment of samples Indoor treatment of samples should be carried out according to the air separation process of asbestos samples: the samples should be weighed to make their mass greater than or equal to 50kg (the fiber mass of treated mineral samples should be greater than or equal to 500g). Generally, tailings, coarse concentrate, bag recyclables, fibers sorted and graded at all levels and fibers to be inspected should be weighed before and after drying, before and after shrinkage, roughing and cleaning.
3. Analysis and testing
The multi-element analysis items are generally SiO2, TiO2, Al2O3, Fe2O3, FeO, MnO, MgO, Cao, NiO, Na2O, K2O, P2O5, Cr2O3, V2O5, H2O+, F, Cl, CO2, SO3, loss on ignition, etc.
The physical performance test of chrysotile fiber mainly tests the unweathered fiber, and appropriately tests the cotton affected by alteration and weathering. Samples used for tensile strength test are not allowed to damage asbestos fibers. The number of samples of each type is 2-3; The physical properties of samples used for chemical multi-element analysis should be tested at the same time. If necessary, appropriately increase the number of certain items and samples. The sample quality depends on the test requirements.
The determination of the volume mass (weight) of chrysotile mineral depends on the uniformity of cotton vein distribution and fiber type. The transverse fiber-type ore is sampled and determined by the small volume mass (weight) method, and the longitudinal fiber-type ore is determined by the cotton measuring tank sample. Generally, samples with large mass (weight) should be taken for comparison, and the specification is 100cm × 100cm ×50cm. The samples should be representative, with 3-5 pieces, and the samples with mass (weight) should be inspected.
Determination of cotton content in chrysotile mineral: the surface and tunnel of samples with cotton content in chrysotile mineral are sampled by grooving method, and the grooving profile is generally: magnesium carbonate type deposit (10 ~15) cm× (10 ~15) cm, and magnesium ultrabasic rock type deposit. In-situ shrinkage of notched specimens is carried out according to Chechott formula, and the shrinkage coefficient k is generally 0.2. If it is necessary to change the value of k, it should be tested. The relative error of field calibration is less than 3%. When collecting slotted samples, the specifications of slotted section should be guaranteed to prevent foreign impurities from being mixed. The quality of grooving samples sent to the laboratory should be not less than 50kg, and the sample particle size should be less than 15mm. Core samples were collected by the whole heart method. The same samples should be taken under the conditions that the actual core diameter is the same, the recovery rate is basically the same and the ore type is the same. The length of core sample depends on mineralization characteristics and sampling quality requirements, and is generally 2 ~ 10m, so as to ensure that the quality of samples sent to the laboratory is not less than 40kg. For magnesium carbonate deposits with little change in grade, the sampling quality should be not less than 25kg.
The quality inspection of chrysotile fiber is to select a representative part of finished cotton from the samples with cotton content and send it to the quality inspection room for inspection. The sample quality is determined according to the inspection requirements. The inspection contents include: determination of hand-selected cotton fiber length and sand content, determination of asbestos specific surface area, wet and rapid wet determination of asbestos fiber, determination of dust content of-0.075mm, determination of sand particles and undissociated asbestos in asbestos, determination of asbestos moisture, etc. Inspection items and methods shall be carried out in accordance with Test Methods for Chrysotile Asbestos (GB 6646. 1 ~ 6646.6—86). Number of samples to be tested: in addition to measuring the specific surface area, 5% ~ 10% of samples above the cut-off grade should be sampled in batches or stages for testing; When determining the specific surface area of machine-selected cotton, 5 ~ 10 pieces should be tested according to different fiber grades. After inspection, if the processed finished cotton does not meet the index of finished cotton, the processing equipment should be checked in time or the processing flow should be adjusted.
Verb (abbreviation of verb) comprehensive evaluation method
Serpentine in serpentine asbestos deposit is an important raw material for producing calcium magnesium phosphate and can also be used as refractory. In some mining areas, serpentine is often associated with nickel, chromium, cobalt, platinum, magnesite, talc, jadeite and nephrite. Pay attention to comprehensive evaluation. Some amphibole asbestos deposits are also accompanied by tiger eye stone (silicified asbestos). Bright colors can be used as craft stones, and attention should be paid to the evaluation.