Geological basis of large-scale and detailed forecast
Prediction objectives and tasks
Large-scale (1: 50000 1: 25000) predictive-mineragenic and detailed (1: 10000 ... 1: 2000) forecasting and prospecting studies are conducted in ore sites, ore fields and deposits. Geological surveys, prospecting and evaluation work are carried out. They complete the studies of each stage of the general geological prospecting process, systematically analyze the discovered prospective areas and structures of potential ore sites, ore fields, and areas of predicted deposits. Studies are the source of factual material on minerals, the patterns of their location and the conditions of localization of mineralization in ore fields. The new data obtained clarify the direction of further prospecting or evaluation work and determine a rational methodology for their implementation.
The purpose of a large-scale and detailed forecast is to identify and qualitatively quantify the industrial significance of ore-promising areas, structures, geophysical and geochemical anomalies in the ranks of the ore cluster, ore field, and the field site. Forecast resources are calculated by categories P? and P |. The tasks of predictive research are:
1) collection, generalization and analysis of the resulting materials for geological, geophysical, geochemical works; identification of the regularities of location and conditions for the formation of deposits, an assessment of the main ore-controlling and ore-localizing factors; development of the forecast object model on the basis of a set of search criteria and indications of industrially significant mineralization;
2) identify promising areas and structures, anomalies (in the system of their hierarchy), quantify the forecast resources and their geological and economic significance in a specific area;
3) determination of the path and rational set of methods, the amount of further exploration required to implement the forecast.
The methodological foundations for a large-scale and detailed forecast of ore-bearing areas are interrelated with the principles of regional mineralogical analysis of fold structures and sedimentary basins. Forecasting takes into account such data:
1) the objects of large-scale and detailed forecast are parts of ore regions, mineralogical zones, therefore they are applicable to the principles of historical and formation analysis with successive approximation of works on the basis of comparative study and comparison with reference objects of appropriate rank;2) ore sites and ore fields, deposits, ore bodies as objects of geological forecasting, represent areas of the earth's crust with the ultimate development of the inherited mineralogical processes characteristic of ore regions; 3) large-scale and detailed forecasting, even in well-studied regions, geological structures, should predict new types of ore objects, taking into account the opportunities in the mineral economy for involving in the development of poorer ores with large resources and metal reserves;
4) development of special methodical methods for performing tasks for calculating resources with changing scales of forecasting.
In contrast to small- and medium-scale mineralogical forecasting, detailed materials, other in terms of volume, content, depth of geological preconditions that correspond to areas of possible mineralization, are involved in the mineralogical analysis at this stage. For example, in the development of stratigraphic-lithological forecasting and search criteria, it becomes possible to switch from assessing the mineralization of the territory on the scale of the formation to individual ore-bearing suites, strata, rock horizons by revealing ore-bearing lithologic-stratigraphic levels, horizons, packs, and geological mineralization screens. In the magmatic group of criteria, the transition from ore-bearing formations as a whole to specific intrusive complexes, individual intrusions, volcanoplutonic bodies, their phases and facies can be carried out. In the structural-tectonic group of forecast criteria, a transition from regional block-folded zones, terranes, deep faults to individual folds, volcanic tectonic structures, higher-order discontinuities is possible. The possibility of wide use of products of contact and hydrothermal metasomatism, geophysical, schlich, geochemical data with detailed analysis of ore-bearing local structures in their volumetric expression is realized [Forecasting ..., 2008].
The depth of forecasting is determined by the type of raw material, the economic peculiarity of the area, the technical capabilities of the estimated and exploratory work of the ore objects being identified. In areas where there are mining enterprises, the depth of forecasting is 1-2 km, and in new areas - 300-500 m. The fulfilled forecasts should be involved in further more detailed studies during the first years, and in industrial development - within 7-10 years. The purpose of such studies is to identify and assess the prospects of the area under investigation with respect to the industrially interesting manifestations of minerals possible in such a geological environment. To achieve this goal, the following tasks are solved:
& gt; the construction of models for the deposits expected in the study area;
& gt; identification and analysis of patterns of placement of ore objects;
& gt; determination of mineralogical factors;
& gt; mineralogical zoning of the territory;
& gt; development of criteria for the forecast of mineralization;
& gt; identification and assessment of ore-promising areas and objects;
& gt; Assessment of the scale of possible mineralization;
& gt; evaluation of the quality of the mineral;
& gt; assessment of mining and geological conditions for future field operations.
The work includes geological (GS-50, GPD-50, GGK-50), hydrogeological, ecology-geological surveys, advanced, accompanying remote and ground geophysical, geochemical, geomorphological, prognostic-mineragenic and other studies. The study of the distribution of mineral resources is carried out. The nature of the revealed geophysical and geochemical anomalies is established. New parameters are determined or the parameters of known ore-bearing areas and prospective areas are calculated with the calculation of the forecast resources of the category P 2 . The final documents of the geological study of subsurface resources of scale 1: 50000 are a set of compulsory and special geological maps, a comprehensive assessment of the prospects of the studied territory with the separation of ore fields.
Local forecasting is performed on the exploratory, evaluation and exploration stages of the general geological exploration process. Its purpose is to isolate the potential ore field or deposit in the search stage; deposits - at the evaluation stage; separate ore sites, ore bodies, ore columns and their delineation on flanks and deep horizons - in exploration stages. The calculated forecast resources must meet the category P |. For a quantitative assessment of the resources of this category, geologically sound ideas about the size, conditions of occurrence of ore zones, bodies are used. For this, the results of detailed geological, geophysical, geochemical studies of surface excavations and structural search wells are used [Forecasting ..., 2008].
All methods of local forecasting are divided into research and technological ones. Research methods are developed by employees of scientific and production organizations. The tasks of research methods are:
1) prediction of specific ore objects in addition to technological methods;
2) the development of new methods, techniques and transfer them to technological;
3) study of the structure of ore fields, deposits, ore bodies;
4) creation and improvement of models of ore objects on the basis of their typification and ore-forming analysis;
5) elucidation of the role of the host environment, magmatism, metamorphism, metasomatism, hypergenesis, geological-structural, lithological environments of ore formation;
6) determination of geochemical, physico-chemical parameters of ore-forming systems and processes.
Technological methods are united by those that have prerequisites for rapid study and development of mineral raw materials. The tasks of local prediction are the study of geological, structural and material indexes of mineralization [Criteria for predictive evaluation ..., 1986]. Here are the main properties of objects, which are the basis for geological forecasting.
1. Zonation of ore-bearing metasomatites.
2. Mineralogical-geochemical zoning:
a) zoning of ore and non-metallic minerals;
b) the sequence of formation and patterns of distribution of mineral associations.
3. Spatial variability of crystal morphology, physical and chemical properties of minerals:
a) zoning of distribution of microimpurities in minerals;
b) variations in the chemical composition of minerals;
c) crystal morphology of minerals;
d) thermo-emf, microhardness, density, thermoluminescence, minerals decrepitation.
4. Variations of ore formation conditions:
a) thermobarogeochemical parameters of melts, solutions;
b) Conditions for the formation of minerals of variable composition.
5. Zoning of endogenous geochemical halos:
a) composition and structure of geochemical anomalies;
b) zonal distribution of coefficients of accumulation (Kc) elements in ores and okolary ore metasomatites;
c) additive and multiplicative indicators, pair relationships of elements.
6. The ratio of predicted resources and reserves in ore bodies with the productivity of secondary geochemical halos.
7. Lateral zoning of petrophysical properties and gas saturation of rocks.
8. Structural factors of ore mineralization:
a) dynamic stresses and pathways of mineral-forming solutions;
b) morphostructural features of ore fields, deposits, ore bodies, ore columns.
9. Lithology of ore-bearing rocks:
a) lithologic-facies control of mineralization;
b) the morphology of the screening horizons.
10. The facies of metamorphism;
a) the real composition of metamorphites;
b) rock resistance to dynamic loads.
11. Morphology and location of ore-forming intrusions.
12. Geophysical fields and anomalies.
13. Complex interpretation of data on the sum of features - a quantitative forecast of mineralization.
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