Four issues of Thinking geochemical prospecting

[Abstract] Over the years, geochemical prospecting can distinguish between different ore bodies and mineralization, geochemical anomaly model and many other issues with the practical application of geochemical prospecting work is the difficult core issues, the paper analyzes the geochemistry from multiple perspectives Exploration of the four basic issues to geochemical prospecting for future work to lay a good foundation.

[Keywords:] Thoughts on geochemical prospecting

A, geochemical prospecting Several issues

1. Deposit abnormal differentiation and mineralization, geochemical exploration work over the years the most important issue, using the current world's advanced geochemical survey methods can be classified as a metal deposits geochemical anomalies. The problem of finding metal deposits , it comes down to looking for this geochemical anomaly. geochemical survey with a variety of methods to identify geochemical anomalies. but the anomalies found in the number of deposits have to exceed the industry many times, and because the deposits occur geological conditions and the geochemical conditions of the different landscapes, often there will be little unusually large or large mineral ore small abnormal situation. In individual cases, the kind of small (weak) exception can also be natural and technological interference cover. This requires identification of a certain size and output by the conditions of deposit, in the geochemical anomalies generated field and from the discovery of a large number of exceptions, those who carved out a small amount of the deposit with the industrial exception. This is the Earth Evaluation of chemical abnormalities.

Evaluation of geochemical anomalies are: (1) qualitative, that is, to determine the nature of an exception, identify anomalies and non-ore mineral anomaly. Non-mineral anomalies, mainly in abnormal mineralization, that is, reach the demands of industry caused by the mineralization exception. (2) position, which determine the spatial anomalies and the relationship between ore bodies. (3) quantification of the estimated depth of the ore body, size, occurrence, morphology, mineral composition, genetic type and so on. These three , the first is the fundamental problem of anomaly evaluation, it has two kinds of knowledge: one view is that the geochemical anomalies to distinguish between ore and mineralization. The reason is that elements are concentrated to a certain extent became ore body, element association and content changes and differences in the nature of mineralization should be. alleged that the Soviet Union to resolve the anomaly assessment of this critical issue. The criteria are: a. mineralized halo components in the simple than the ore body, and scattered isolated anomaly , there is no center, no obvious banding. b. combination (additive or multiplies) the curve halo index value in the horizontal direction to make mineralization, can not form a distinct maximum. c. in similar geological conditions, the mineralization small exception. In addition, combining structure, lithology, alteration of this and other methods to effectively identify ore bodies and mineralization abnormalities. geochemical barrier study may also contribute to such identification work. The other view , the elements are concentrated to what extent even the ore body, is based on the current mining, elections, the rule by the people to determine the level of technology, today belongs to the mineralization and will be counted as ore bodies, mineralization and ore body that is not considered essential differences between the two can not distinguish between abnormal. For example, porphyry copper deposit, the average Cu content of the mineralized porphyry 0.2, and 0.4 porphyry copper deposits, largely based on geochemical data can not distinguish. such as the distinction between ore bodies and mineralization in theory is not possible exception, but we insist on the distinction between practical application but it was in vain. but if a distinction, and people do not distinguish between the idea, that is conservative, so this is a well worth exploring.

2. Geochemical anomaly model and practical application of
Explore the setting and geochemical anomalies in the model to be used in practice is an effective way to achieve this goal. In recent years, domestic and international cases through the preparation of the case, the establishment of a series of GEOCHEMICAL model, this model is the genesis an important component of the model is the object of mineralization. It is the actual data from a large number of elements drawn from common characteristics of geochemical anomalies, expressed the general elements or compounds in the different regions and different types of metal deposits, and in the surrounding space and temporal changes in regularity. It expresses: (1) the geometry of geochemical anomalies (abnormal geometry, and large ore body or mineralized zone with consistent form), directly reflects the formation of ore bodies or control of the mineralized zone or halo factor. (2) Components and zoning, that is, for all types of deposits in the primary halo, halo components consistent with the mineral component, and has significant sub-vertical and horizontal zoning, objectively reflect the mineral composition and spatial distribution of minerals. (3) element concentration zoning characteristics, the concentration of elements in the halo away from the ore body with, deposit, mine field and even the belt, generally shows decreasing The law, which reflects the gradient element content can be used to determine the mineralization center, and identification of high-grade ore and dispersion of mineralization.

Established model of geochemical anomalies, geochemical data for the comprehensive analysis and summary, is an ideal means of expression. It is simple, intuitive, easy to understand and easy to use. Because of data limitations, the new model may be not established small gaps, which need to be updated with the information in the future, to modify the original conclusion, which is the normal process of scientific reasoning. and because the complexity of geological conditions. different regions, different types of deposits. geochemical anomaly is not completely consistent with the model in different parts of the same type of deposits, geochemical anomalies and often do not meet the (return). so. in practice, in the exception received by the unknown area. As long as consistent with the model of certain aspects of the composite, can be bold proposed verification opinion. for full compliance, composite, in the present is impossible.

Links to Research Papers Download http://www.hi138.com 3. Test the importance of survey work
What is the experimental measurement refers to the start of production in an area before choosing the best sampling methods and analysis programs is necessary. It is by choice and are looking for the deposit type, geological and geochemical landscape conditions as similar to the known test to determine the deposit. This is the test measurements.

Geochemical survey of the different methods, experimental measurement of the content is different. To sum up, its contents cover general is to understand the nature of rock properties, geological features, select the sampling media, determine the sampling density, grain size sample, the sample layer : To determine the sample preparation programs: choice of indicator elements: determination of mineralization were not affected or affected very little rock in the metal content to determine the regional background geochemical values, local background values and outliers; of geochemical characteristics, various effects , proposes prospecting, geochemical anomalies identified data interpretation and evaluation criteria, and so on.

Experimental measurements are based on the information in the past. Learn practical experience, focused manner. On the sample type, sample media, such as validation indicator elements is an important part of experimental measurements.

4. Geochemical exploration and applications based on the work
Through nearly two decades of the earth summary of the work of prospecting, geochemical exploration work I think that the work program are: an analysis of a sample of a processing order data of a validation exception of a checked exception. It can be seen, "authentication exception" before work, is the basis of work: I believe that the basic work of exploration, the most need to strengthen the following aspects should be.

(1) Geochemistry of theoretical work. Study of the various geochemical anomaly formation mechanism and influence factors, the most basic foundation work, which is to develop appropriate methods of geochemical reconnaissance basis for this work, one is actually the accumulation and summary information, on the other hand is an experiment, as for mineralization, as the geological and geochemical halo simulation and mathematical simulation. The main role in a variety of geological and geochemical processes, the elements of migration patterns, centralized environment, conditions and forms. The third aspect is the temperature and pressure geochemical study of these basic work. geochemical survey for developing methods to determine the correct sampling media, select a reasonable method to provide a theoretical basis.

(2) geological foundation work. Mainly on the structure, rock, alteration and mineralization observed understanding of the causes of mineralization and type of awareness and strengthening of petrology and mineralogy.

(3) to achieve standardization of catalog work.

(4) analysis of the basic work. To expand the range of elements, the future should strive to achieve an increase of 80 means, to come up with high sensitivity, high accuracy, high phase accuracy and the valence state analysis, and the amount of micro-micro analysis the establishment of a center for basic analysis of instrumentation and automation to improve quality.

(5) to develop rigorous sampling, processing, analysis, documentation, a set of quality control programs.

(6) to achieve standardization of documentation, the establishment of basic data. Which should include: a variety of rocks of the regional geochemical background values, a variety of media such as water, air, plants, soil, the average content of elements: the average of various magmatic rocks chemical composition of mineral inclusions in various types of deposits in the temperature, composition, salinity, isotopic data: The main indicator elements in a form; mineralization into the halo of the thermodynamic data: the raw data of various geochemical survey map, elements of the Earth Chemical maps, geochemical metallogenic forecasting plans, landscape plans, and other basic geochemical maps; report: geochemical anomalies of various models and mathematical models: a typical case and the exploration of cases of the case and other cases.

Establish the appropriate systems. Such as organization and management systems, central elements of the test system, petrological and mineralogical Center to test the system, geochemical data processing systems, is to achieve and strengthen the basic work of the organization guarantee.


Second, geochemical prospecting work on several technical supplement

1. Stratabound deposits in the stratigraphic section of the rock features are: a set of rocks is usually lower, upper part of the carbonate rocks, carbonate rock ore bodies normally present in the lower part. Lower clastic rocks (especially the fine clastic rock) of a riser, the upper aquifer carbonate rocks, the two sets of contact with the water content of different activities conducive to groundwater, provide water for the mineralization.

2. Stratabound deposits from the source of ore-forming materials, ore source may be some kind of initial enrichment of ore-forming elements, but more important is the source bed in the spread of substances can be "liberated" them into solution. Zhengru "two ore said," pointed out: "material of the glass state (volcanic glass) Cheng mixture of state (such as debris deposition), there is no chemistry between each component balance. These rocks in the torsional stress and heat-driven easy crystallization, the crystallization process, not easy to enter the crystal lattice of some metal elements are transferred to the formation of ore fluid solution, so in many cases, clastic and volcanic deposits are usually stratabound ore source bed for the mineralization the role of the source.

3. Stratabound ore deposits in the formation of industrial transformation enrichment remote control seam position can be divided into source bed and reservoir seam in two parts. One: bit lower layers of mineral resources, in many cases by the broken rocks and volcanic rocks Yong ; storage slightly higher ledge, often formed by the breaking of rock salt.

4. Produced in the thick-bedded limestone and dolomite in the ore layer thick, large irregular veins were tested, linear, bead-like output, form complex and difficult exploration; produced in the thin-bedded argillaceous limestone and thin-bedded limestone contact zone (or two lithologic mutation carriers) of the deposits, the general development of bedding, shape comparison rules, mostly stratiform and lens layer output, easy exploration. This phenomenon is explained To: thick layered limestone and thick-bedded dolomite reason not developed a single rock, in the torsional stress traction, and more have fractured and difficult to form a layer stripping, ore fluid can crack along the joint activities, difficult to concentrate, Ore Deposit complex, distributed; thin-bedded argillaceous limestone and thin-bedded limestone contact zone (or two lithologic mutation carriers), due to variations in lithology and bedding developed in the torsional stress traction, easy to produce fractured, but it is easier to form layer stripping, ore concentrate solution is easy, often forming large deposits developed bedding. shows lithologic control is when the deposit can not be ignored.


References:
[1] Geochemical Journal, 2005, (10).

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