To study the characteristics of mineralization zone of lode gold in Phuoc Son area; To select resource assessment models for lode gold ores and associated minerals, as a contribution to exploration methods using newly developed scientific and technological advances.
MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF MINING AND GEOLOGY LE VAN LUONG RESEARCH ON THE SELECTION OF MODELS FOR MINERAL RESOURCE ASSESSMENT OF LODE GOLD DEPOSITS AT PHUOC SON – QUANG NAM SUMMARY OF TECHNICAL DOCTORAL THESIS Ha Noi - 2014 The study was completed at: Drilling and Production Department, Petroleum Faculty, Ha noi University of Mining and Geology Advisors: Prof Dr Truong Xuan Luan Prof Dr Nguyen Phuong Reviewer 1: Prof Dr Đo Đinh Toat Reviewer 2: Dr Hoang Van Khoa Reviewer 3: Dr Bui Tat Hop The thesis will be defended in Assessment Committee of University level which meeting at Hanoi University of Mining and Geology in time hour date month year 2014 References to thesis at library: National library or Hanoi University of Mining and Geology library INTRODUCTION Rationale of research: The Phuoc Son area, of Quang Nam province, has complex geological structures and rich in mineral resources, especially, lode gold deposits However, research issues on mineralization characteristics and the selection of mineral resource assessment (MRA) models are not thoroughly studied To elucidate the characteristics of lode gold occurrences; especially to select the appropriate models for mineral resource assessment and reserve calculations, forming a basis for the exploration and exploitation periods os a necessary task The disertation “Research on the selection of mineral resource assessment models for lode gold ores at Phuoc Son area, Quang Nam province” is prepared from actual requirements of mining activities in study area Objectives of the study: To study the characteristics of mineralization zone of lode gold in Phuoc Son area; To select resource assessment models for lode gold ores and associated minerals, as a contribution to exploration methods using newly developed scientific and technological advances Objects and scopes of the study: The ore bodies and mineralization zone of lode gold at Phuoc Son region, especially in the Dak Sa area Research contents: Data collection, investigation of previous studies and data analysis for geological and mineral resource information Additional research material composition to elucidate the characteristics of the original gold ore Determine the partition base and prospect base area Phuoc Son gold Studies shed light on the nature and characteristics of transformation parameters geological ore body serves exploration, resource evaluation, gold reserves Application of geographic information system (GIS) software dedicated especially Surpac 5.1 software to build a database, resource assessment, the original gold reserves Study selection model awareness mineralization characteristics and change selected resource assessment methods, appropriate reserves root Phuoc Son gold ore types Research methods: Collect, synthesize, geological data processing of minerals; Additional research material composition of ore; Building a database (the database) geological mineral form of tables on the basis of Surpac software applications and databases in GIS to manage digital map; The study used models: statistical (oneway and two-way), the structure function (Variogram), mine geometry, geological cross-sections for modeling objects as the basis for the research methodology selection resource prices, original gold reserves; Research using the Kriging method, inverse distance weighting to calculate reserves, resources and methodology determined according to mineralization straight to forecast resource undetermined Significance scientific and practical values: - Scientific significance: the thesis contributes additional evidence on a more comprehensive understanding of the material composition of ore, mineralization characteristics and spatial variations of the geological parameters of the original gold ore bodies investigated Research; Contributing to complete exploration methodology; Research focus is on selecting the appropriate model for resource assessment, the original gold reserves - Practical significance: to give managers and enterprise database geological mineral Phuoc Son Gold root zone to ensure reliability, the references in the search and navigation, exploration and mining; Provide production base methodology to enhance the reliability of resource assessment, reserve; Selecting the appropriate network probe with original style Phuoc Son gold ore and other areas where geological conditions similar minerals New achievements of the disertation: - Phuoc Son Gold of the original style quartz - sulphide polymetallic - typically yellow, two-stage mineralization with complex symbiosis is characterized mineral quartz - pyrite II - the first gold and quartz - pyrrhotite II - Gold II - galena - sphalerite (possible electrum); - Content of Au and associated elements (Ag, Pb and Zn) in the root zone of gold ore bodies may inductive study of the standard logarithmic distribution function, we have the relationship between correlated from relatively tight to close tightly - Characteristics of Au transformed space can function modeled by model type bridge structure, Au concentrations have local variability and weak anisotropy, can basically see as isotropic in space This feature is the scientific foundation for network exploration using squares and equilateral triangles, rhombus - The results of the study with the help of software Surpac Vietnam confirmed the superiority of the model structure and function Kriging method in resource assessment, the original gold reserves Phuoc Son - The study results suggested resource assessment process, the original gold reserves Phuoc Son ensure reliability, utility and mining exploration Theoretical points of dissertation: Thesis 1: Using modeling solution components reflected by the quality of the original gold complex statistical models (onedimensional, two-dimensional) structure and function (Variogram) has contributed to a more comprehensive awareness of mineralization characteristics; Au content in two dimensions (in strike and dip of ore body) local variation, weak anisotropy, can be considered as isotropic This is a scientific foundation for network application suitable for ore exploration area Phuoc Son gold original Thesis 2: Resource Assessment, the original gold reserves according to the research proposed in the thesis (Figure 2:11); Kriging method which is key to ensure the reliability and utility for use in planning material exploration and mining Basis Document The work geologic mapping area ratio 1:200.000, 1:50,000; Report the results of exploration, gold mining and the original subdivision Bai Bai Dat Type the Phuoc Son; Documents in the thematic studies, surveys, original gold exploration in the region; The resources of gold and foreign origin 10 Place this research The thesis was completed at the Department Search and Exploration, Department of Geology, University of Mining and Geology under the scientific guidance of Prof Truong Xuan Luan, Prof Nguyen Phuong NCS is pleased to express deep gratitude for the guidance and help of the dedicated science instructor NCS received attention, facilitated by the Department of exploration, backroom University, University of Mining and Geology, Office Leadership Board of Assessment national mineral reserves The teachers, scientists in and outside the University of Mining and Geology NCS would like to express gratitude! CHAPTER OVERVIEW OF THE STUDY AREA 1.1 STRUCTURAL CHARACTERISTICS OF REGIONAL GEOLOGY PHUOC SON 1.1.1 Position in the scheme of the study area structure Phuoc Son region has an area of approximately 100km2, located north of Kontum massif, terrane of South Asia Ngai 1.1.2 History of geological and mineral research - Before 1975: Geological studies document the left is a representative profile Fromaget, JH Hofet (1933-1941), La Croix A, Tran Huynh Anh (1932-1968) - After 1975: Works geological mapping and mineral ratio of 1:500.000 Tran Duc Luong and Nguyen Xuan Bao co-editor (1976) Geological and mineral maps Bana ratio 1:200.000 sheets are vetted Nguyen Duc Thang 2006; The East team to Tam Ky - German Association of Koliada A A et al (1990); A group of northern forms of Bui The Vinh Hoi et al (2011); To the south is the newspaper group Dak Glei - Do Kham Duc Van Chi et al (1997) The search for the 1:10,000 scale gold Phuoc Son has done in areas: Banana Beach, K7, Longjing Tea - Spring Tree, Butterfly Beach, Golden Light, Wind and Mountain Gold Beach Sa Dak area has been explored 1.1.3 An overview of the stratigraphy NCS uses geological map scale 1: 25,000 of Le Van Hai et al, combined with vetted results geological and mineral maps 1:200.000 sheets Bana rate of Nguyen Duc Thang et al, topographic maps mineral ratio 1:50,000 sheets A group of Bui The Vinh Hoi et al include the following formations: + Kham Duc Formation, middle tier module (PR2-3kd2) consists of quartz-biotite schist, quartz-chlorite, quartz-biotite schist containing garnet + Breast Mountain Formation, the upper sub (PR3-€ 1nv2) occupies the largest area distribution center in the study area Lithological composition includes quartz schist - biotite, actinolite albite, actinolite - chlorite, limestone and shale of lime blossom The rocks are strongly modified, common slope angle 30-500 During the oral argument breaks, fractures of the quartz schist - biotite, calcareous shale, distribution of ore bodies of gold polymetallic sulfide quartz vein, network circuit, circuit lens Thickness of about 1,300 meters floor modules + A Great Formation (€ 2-O1av) consists of schist quartz - biotite, quartz - biotite-chlorite, sericite - quartz, slate coal-rich material 1.1.4 Overview of intrusive Mainly granodiorit, granite - biotite phase complexes Ben Giang - Que Son distributed in the west of the original gold-related areas, less than olivinit rock, pyroxenite Hiep Duc complex, in addition to the majority circuit unknown age 1.1.5 An overview of structural features, tectonic The west fault Kham Duc, Dak Po Ko, K7, K7 which faults and anticlines Song Giang distribution of quartz - sulphide polymetallic gold on the southwest side These are favorable conditions for root in the area, looking for gold In a nutshell: the Phuoc Son geological structure complicated, distributed mainly metamorphosed sedimentary Breast Mountain Formation, upper level modules The sulfide ore bodies of gold in quartz schist quartz - biotite, alternating calcareous shale files related to faulting K7 and distribution wing Giang River anticline This is the basis of delimitation, the area of the original gold prospects in the region 1.2 Features gold mineralization awkward angle Phuoc Son areas identified primary gold ore distribution includes: Dak Sa, Banana Beach, K7, Longjing Tea - Spring Tree, Butterfly Beach, Golden Light, Wind and Mountain Gold Beach In which the Dak Sa has been explored in two zones (2 mines), the other new zones meticulous search 1.2.1 Characteristics of the mineralization zone The gold mineralization zone containing the main northeast southwest, longitude, northwest - southeast, length 200 - 1,500 mm, width - 30 m depth is estimated at 45 - 100m On the Au: 0.1 to 98.16 g / t; deep, Au: 0.1 to 69.7 g / t, averaging 0.5 to 3.27 g / T 1.2.2 Characteristics of ore bodies Sa Dak region, including two sub-areas and grounds timber yard - Beach Land Division Main orebody (BDMQ) accounting reserves mainly in zones, quartz schist in practice - biotite Small ore bodies (BDUQ) located on a thickness small, discontinuous distribution, of little value - Classification Type Beach area have been beam control including SERP itself, BGUQ, SC2, MB2, BGLQ, QTZ4 and 02 single body SC3, MB1 In particular ore body QTZ3 (under the beam itself BGLQ) accounts for the reserves in subdivisions distributed in quartz schist episode - biotite calcareous shale alternating sets Comment: in the Dak Sa, the original gold ore bodies form circuits, network circuits, circuit lenses, fill the cup surface layer of the developing northeast - southwest, is the less than or west longitude north - SE Part of the wall is often distributed collection of flowers limestone, calcareous shale alternating quartz schist episode - biotite, usually cylindrical quartz schist - biotite, the boundary between the rocks surrounding the ore body is relatively clear 1.2.3 Characteristics of material composition The thesis focused research, describe, calculate parameters Sa Dak mineralization zones, as the basis of interpretation of ore characteristics and model selection evaluation resources reserve - Mineral components: Beach Land subdivision mainly pyrrhotite, pyrite, galena, sphalerite and native gold (electrum can be) filled cracks form, accounting for ÷ 65% In that little sphalerite from 50% to 12% less galena, pyrite from less to 2%, from less than 1% pyrrhotite; Subdivision consisting of pyrrhotite timber yards, pyrite, sphalerite, galena and native gold (electrum can be); total sulfide minerals ÷ 15%, locally up to 45% + Main mineralogical characteristics: native gold (Au) exist are varied and plentiful including generations scattered disseminated in quartz; IC form filling cracks; and disseminated sphalerite and gelenit (image 1.3, 1:16) Gold particle size from 0.01 to 0.2 mm, from relatively isometric (photo 1.3) to the distorted grain (photo 1.5) or granular particles to form larger neighbor (photo 1:16), in the form spontaneous encounter Au system flat contact with galena, sphalerite (Image 1.3); with galena, sphalerite and pyrite II (picture 1:16) Photo 1.3 Model LV1, floor furnace 1, China BDMQ Native gold, isometric particles in contact with galena and sphalerite Picture Flat 1.5 Model LV2-2, 2-story fireplace, China BDMQ Extends native gold grains disseminated in accordance with the microchip micro cracks 1:16 Picture: BG 7.3 (oven 1) China QTZ3, native gold (Au) (≈ 0.2 mm) created THCSKV with sphalerite, galena, pyrrhotite II Non-ore minerals are mainly quartz, dolomite, calcite (less sericite and chlorite) - Chemical composition of ore + Key Element In the mineralization zone, on the Au concentration: 0.1 to 98.16 g / T (K7); deep Au: 0.1 to 69.7 g / T; zone average 0.5 to 3.27 g / T In Au grade ore bodies BDMQ: 0.13 ÷ 76g / t (sample handling characteristics were high), average 18.65 g / t; levels of change are extremely uneven (Vc = 267%); QTZ3 relative Au concentration: 0.11 ÷ 48g / t (sample handling characteristics were high), average: 9.57 g / T; levels of change are extremely uneven (Vc = 206%) + The accompanying elements including Ag, Pb and Zn recovery value - Composition characteristics, architecture ore: in the main drive form, fill cracks, chips form The ore mineral particles to form larger tha picture, particle lasts, sometimes relatively isometric particles, angular - Mineral Complex symbiotic stage mineralization In the region there are main stages of ore formation; with the mineralogical characteristics: Stage 1: quartz, pyrrhotite I, pyrite I; Stage 2: quartz, pyrite II, gold I; Stage 3: quartz, pyrrhotite II, II gold, galena, sphalerite (possible electrum) In this present gold mineralization in two phases and - Feature change surrounding rocks Transform ice thickness around 0.1 ÷ 0.3 m, disseminated gold at low levels, fail to achieve the industry Mineralization accompanying phenomenon mainly of quartz, dolomite is less of goods and calcite Slate quartz - biotite quartz is the mineral of ore containing up to 10% (Bai Dat and Bai Go), dolomite chemical, chemical calcite mineral ore containing less than 2% of, (K7, Tra Long - Stream Tree) , chlorite chemical (Long Tea - Spring Tree, Bai pump), sericitization phenomenon is limited Picture 1:22 Quartz biotite schist are quartz ore Picture of 1:23 Quartz biotite schist are quartz, dolomite, chemical, ore 1:24 Image Of dolomite rock is talc, magnesite of disseminated ore - Identify the source of the original gold ore From the results of additional studies, combined with previous literature (Tran Trong Hoa, Le Van Hai, Vinh Bui et al) allow to draw: original gold zones Sa Dak derived average temperature hydrothermal , medium low (300-1800) 1.3 DIVISION REGIONAL PERSPECTIVE 1.3.1 Establishments partition prospects - Premise: is the collective slate quartz - biotite, calcareous shale of Breast Mountain Formation, the upper sub; Phase complexes Ben Giang - Que Son; tectonic breccia zones related to faults and anticlines K7 Giang River - Signs of search: the ore outcrop, handmade exploitation work, the alteration zones of dolomite, quartz and calcite of goods; Geochemical dispersion haloes of primary Pb, Zn and Ag, the boulder zone containing sulfide minerals, geophysical anomalies 1.3.2 Promising Results partition Results were divided: very promising area (A) as follows: Sa Dak area: 0.5 km2 (outside the area explored); Banana Beach: 0.112 11 Today, with the help of computers, geostatistical methods are considered as key method in spatial forecasting The method has closely algorithmic, ability to forecast reliability, is not affected by the shape, size of probe network, overcoming the drawbacks that other methods can not calculator such as remove the local errors in calculation Input data volume is large enough, the result is high reliability; on the other hand the method also shows the error in calculation according to the Kriging variance By Kriging we could calculate reserves, resources each block of small size even if no work in block, and very useful for design mining engineering, mining directing, supporting for the other methods such as establishing contour maps, etc 2.2.5 Research Surpac software application 5.1 Surpac software to handle geological data, modeling ore body and calculator resource reserves of deposit Design, establishment and database management geology mining, modeling and evaluate original gold resources reserves 2.3 Select model and method for resources and reserves original gold accessment in Phuoc Son area 2.3.1 The factor affect model sellection Factors of mineralization controlling; shape, size of ore bodies; distribution of beneficial components in the ore body; shape exploration networks affect model selection 2.3.2 Select model + The search: document is preliminary, Postgraduate use vetically calculation method based on mineralization parameters for forecasting Au resource, correlation function model (regression) to predict useful accompanied element (Ag, Pb and Zn) + The exploration zone * Controlling mineralization factor: Bai Dat zone, the main ore body (BDMQ) distributes in the surface separated-layers of shale quartz - biotite Bai Go zone, QTZ3 ore body distributes in the surface separated-layers of quartz - biotite shale, calcareous shale * Ore body shape and size: BDMQ ore body extends to the north-east - south-west about 250m, plug direction to the Northwest 12 120 - 300 m, average slope angle of about 30°, the variation coefficient of contour perimeter is 1.23, type of simplified QTZ3 ore body extends to the NNE - SSW 450m, plug direction to the west northwest of 1,200 m, with an average slope angle of 35o, the variation coefficient of contour perimeter of 1.62, kind of complicated * The distribution of beneficial components in ore body: BDMQ body has Au ore grade: 0.13 - 76g / T (solid samples have done), especially distributed unevenly (Vc = 267%); Au content of QTZ3 ore body: 0.11 - 48g / T (solid samples have done), distributed very unevenly (Vc = 206%) * Shape exploration network: Drilling construction works is not follow a geometric network Probe network equivalent to route by route about of (30 - 50) m and work on route is of (30 - 50) m Based on the analysis of related geological factors and mineralization control, relationships between the mineralization with surrounding rocks, shape, size, variation characteristics and the distribution of useful components, exploration system and the advantages and disadvantages of each model as described in the thesis, it is best to use the model to coordinate the geological section, mine geometry, statistics math, and structure function with structure function model is a key function 2.3.3 Factor affecting select evaluation method for resources, reserves The factors of shape, size, ore body lying; the distribution of elements in the ore body; exploration system, mining systems affect the selection of resources and reserves assessment method Geological cross method requires the exploration network have to layout in route that in many cases difficult to implement in field, canculating results is not exactly if the distances between the routes is long or ore body changes Geological block method does not depend on how the layout of the probe work, but not favorable for ore body has complex structure, sometimes is difficult in zoning off to ensure three uniformity factors in volume calculated resource, reserves Inverse distance method can be applied if network probe is sparser than size of influence zone and the ore body is isotropic Kriging method almost overcomes the disadvantages of the other methods, especially when a 13 number of exploration works is large enough and distances between the works is smaller than the size of the affected zone (Hm) 2.3.4 Selecting assessment process of original gold resources and reserves Figure 2.11 Assessment process of origin Au resources, reserves Studied object (TQ) Approach to relevant document Building geological-mineral database CSDL ĐC-KS Table Map, Chart in GIS Modelling ore body Type model of geological section Statistical model Mine geometric model Identify experimental [(h)] in the different direction Structure function model [(h)] Selecting size of affected zone, isotropic, anisotropic Selecting size for mini-block, elipsoid Selecting the method for calculating reserves and resources (Kriging, inverse distance, etc.) Result 14 CHAPTER RESULT AND DISCUSSION 3.1.1 Data base of geological – the original gold mineral of study region - Table data base: Data of Terrain mining, borehole data (coordinates of drill hole, stratigraphic drilling, drill sample results, drilling azimuth) - Data base in GIS: To manage information layers in Mapinfo and Autocad 3.1.2 Modelling characteristics of mineralization - Geological section model: Establishment of the geological section of ore bodies allows overview assessment about distribution characteristics, the relationship between ore bodies and surrounding rocks, it is the basis to implement of the next research - Isoline model: Based on sectional system was established to formed the cylindrical framework, closure framework, equal thickness framework by interpolation method (Kriging method is a key) * BĐMQ orebody is controlled by 57 boreholes including 190 core samples which is analysis Au, Ag, Pb and Zn component, the result is shown in table 3.6 (test the distribution model) Table 3.6 The analysis result of the statistical characteristics of Au, Ag, Pb and Zn content in TQ BĐMQ Element Au (g/T) Ag (g/T) Pb (%) Zn (%) Value sample 190 Min 0,13 0,1 0,0003 0,0001 Content Max 197,55 438 29,3 28,87 Average 18,31 26,53 1,750 1,753 tA tE 3,19 3,80 4,16 3,87 16,57 19,44 23,13 19,64 Comments: Both standard deviation of Au content |tA| = |A/A| and normal kurtosis |tE|= |E/E| more than 3; frequency nomogram deviates from the left So it did not satisfy the normal distribution, the useful elements Ag, Pb and Zn were similar Test the logarithmic distribution standard: By changing the initial value to the logarithmic values for statistical processing The synthesis results is shown in Table 3.9 15 Table 3.9 Statistical characteristics of Au, Ag and Zn content accroding to logarithmic distribution standard in TQ BĐMQ Content Element Sample value Au (g/T) Ag (g/T) Pb (%) Zn (%) 190 Error of mean square Min Max Average () -0,88 1,88 0,83 0,63 -1,00 2,16 0,68 0,8 -3,50 1,00 -0,79 1,1 -4 1,00 -0,98 1,2 tA tE -0,09 0,18 -0,11 0,11 2,21 2,10 2,01 1,97 Table 3.9 shows that the standard |tA|3; frequency nomogram deviates from the left So it did not satisfy the normal distribution Test the logarithmic distribution standard: Table 3.14 Statistical characteristics of Au, Ag and Zn content accroding to logarithmic distribution standard in TQ QTZ3 Content Element Error of mean square Sample value Min Au (g/T) Ag (g/T) Max Average tA tE () -0,88 1,88 0,83 0,63 -0,09 2,21 -1,00 2,16 0,68 0,8 0,18 2,10 -3,50 1,00 -0,79 1,1 -0,11 2,01 -0,98 1,2 0,11 1,97 190 Pb (%) Zn (%) -4 1,00 Table 3.14 shows that the standard of Au, Ag and Pb conten is |tA|60 335 0,40 0,90 65 (h) 0,40 0,50(1,5 h h 0,5 ) if h≤ 65 65 65 = 0,40+0,50=0,90 if h>65 20 0,53 1,21 70 (h) 0,53 0,68(1,5 h h 0,5 ) if h≤ 70 70 70 = 0,53+0,68=1,21 if h>70 65 0,5 0,99 65 (h) 0,5 0,49(1,5 h h 0,5 ) if h≤ 65 65 65 = 0,5+0,49=0,99 if h>65 + The QTZ3 orebody Starting from 2800 strike with the scan angle is 450; the next strike will be 3250, 100, 550 to 1000, left hemisphere have similar values (The results are shown in Figure 3:27) Comment: The QTZ3 orebody, structure functions have autofining effects and circle model which shows that special variation is not uniform, the most complex according to northwest - southeast direction 19 (100-2800) nearly coincides with azimuth of slope; simpler according to northeast – southwest direction (10-1900) nearly coincides with the strike of orebody; expression of local variation, anisotropic hole and weak anisotropy (anisotropy index 1.4); can be interpolated the ore body accroding to slope within from 50 to 55m; 55-70m along the strike; circle model be used to to determine the size of impact zone, the size of the micro block, Kriging method is executed to calculate reserves, resources Table 3.27 Table synthetic survey results of Variogram in the QTZ3 orebody parameters characteristics of (h) Survey Size of method Autofining Sill (and influence (degree) effects nugget) zone (m) 280 0,15 0,81 50 Model (h) 0,15 0,66(1,5 h h3 0,5 ) if h≤ 50 50 50 = 0,15+0,66=0,81 if h>50 325 0,16 0,103 55 (h) 0,16 0,87(1,5 h h 0,5 ) if h≤ 55 55 55 = 0,16+0,87=1,03 if h>55 10 0,01 0,72 70 (h) 0,01 0,71(1,5 h h 0,5 ) if h≤ 70 70 70 = 0,01+0,71 =0,72 if h>70 55 0,15 1,12 55 (h) 0,15 0,97(1,5 h h 0,5 ) if h≤ 55 55 55 = 0,15+0,97=1,12 if h>55 General Comments: From the Variogram survey results of the BDMQ orebody and the QTZ3 orebody given mineralization characteristics of Au element as follows: Au content on the BDMQ orebody shown no clearly anisotropy, anisotropy coefficient = 1.17 (long axis of ellipsoid extending to 200 strike, short axis accroding to 2900 strike) The QTZ3 orebody have weakly anisotropy with anisotropy coefficient Idh = 1.4 (long axis of ellipsoid extending to 100 strike, the short axis extending to 2800), can be considered isotropic Intensity mineralization of the orebody is quite high Intensity mineralization of the BDMQ orebody is higher Intensity mineralization of the QTZ3 orebody with the demand curve conversion coefficient ranging from 0.49 to 0.75; the QTZ3 orebody with the demand curve conversion coefficient ranging from 0.66 to 0.97 20 BDMQ orebody have high autofining effects, Co: from 0.28 to 0.53, QTZ3 orebody have low autofining effects, Co: from 0.01 to 0.16 Abiogenesis gold and high gold content on the BĐMQ orebody is larger abiogenesis gold and high gold content on the QTZ3 orebody That is consistent with mineralization in the orebody study, ore erasable, micro vein, infilling fractures in quartz vein All of variogram presents hole effects and local variation, indicated gold mineralization at the Dak Sa has least two - mineralization stages, consistent with the analysis of mineralography samples - Apply structure function model on calculating reserves and resources by setting ellipsoid + BDMQ Ore Body: Based on the survey results of the models (h), identify the main axis (major - axis) nearly coincides with the strike of ore body, direction 20-2000, size is of 70m, secondary axis (semi major - axis) nearly coincides with the pitch of the ore body, direction 290 - 1100 with a size of 60 meters, the shortest axis (minor axis) coincides with the thickness of the ore body + QTZ3 Ore Body: The main axis nearly coincides with the strike of ore body, direction 10-1900 is of 70m, the secondary axis nearly coincides with the pitch of the ore body, d irection 280-1000 is of 50m, the short axis coincides with the thickness of the ore body 3.1.3 Assement of reserves and identified resources - Kriging Method Steps to solve Kriging problem and choice size for mini-block logically are explained in detail in the thesis Fig 3.42a Chart of Kriging interpolation results for Au content TQ BDMQ Fig 3.43a Chart of Kriging interpolation results for Au content TQ QTZ3 Fig 3.43 Legend 21 Reserves and resources of Au calculated by Kriging method for ore bodies BDMQ and QTZ3 is total of 14,660 kg Au (detail in table 3:31) - Method of inverse distance weighting Reserves and resources of Au calculated by the inverse distance weighting method for ore bodies BDMQ and QTZ3 is total of 14.279 kg Au (detail in table 3:34) Table 3:31 Calculation result of Au reserves and resources using Kriging method Reserves and resources level 122 BĐMQ 333 Total 122 QTZ3 333 Total Ore body Ore reserves and resources (tonnes) 213.824 244.434 458.258 232.334 1.029.614 1.261.948 Au average content (g/T) 14,61 9,99 7,81 7,07 Au reserves and resources (kg) 3.124 2.442 5.566 1.815 7.279 9.094 Table 3:34 Calculation result of Au reserves and resources using inverse distance weighting method Reserves and resources level 122 BĐMQ 333 Total 122 QTZ3 333 Total Ore body Ore reserves and resources (tonnes) 213.379 169.577 382.956 232.312 1.047.788 1.280.100 Au average content (g/T) 15,1 10,51 7,72 7.14 Au reserves and resources (kg) 3.222 1.782 5.004 1.793 7.481 9.275 - Geological block method Table 3:35 Results of calculated Au reserves and resources using Geological block method (Le Van Hai et al, 2010) The result listed in Table 3:35 was approved by the National Council on evaluation of mineral reserves in 2010 Therefore, Postgraduate did not recalculate but using the result as the reference for comparison with the proposed method 3.1.4 Forecast undetermined resources Using the vertical caculation method based on mineralization parameters to forecast for the region need to explore meticulously The 22 result show that predicted resources is about 22,932 kg Au; Using the correlation function (regression) predicted for Ag: 20,668 kg, Pb: 381 537 tons and Zn: 368 182 tons in the remaining areas including Bai Chuoi, B, K7, Bai Gio, Tra Long – Suoi Cay, Vang Nhe and Bai Buom 3.1.5 Results comparison - Compared with the 6-122 block mining results Table 3:40 The table compares the results calculated reserves to the results 6-122 block mining TQ BDMQ Reserves block Result 6-122 Khai thác Comparation parameters The error between the methods (%) Inverse distance Geological Kriging weighting block Reserve (tons) -2,00 -2,07 +6,941 grade (g/T) +0,70 +2,60 +5,66 Notes: - decrease; + increase compare with 6-122 block Comparing result in Table 3:40 show the ore reserves and Au content calculated by Kriging method has the smallest error Comparing the results calculated by Kriging method with geological block for all reserves blocks at 122 level, reserves error in the blocks range from 0.3 to 18.5%, an average of about 4% - Comparing the sections Compare AA’ section made from the results of exploration and exploitation of TQ BDMQ shows that basically the shape of ore bodies is similar; Exploiting result discovered 01 small tranform zones, however, does not affect the form of the ore body; According to the result of expldoration and result of exploitation, the area of the ore body on the AA' section is different about 6% Conclusion: In order to fully understand the variation characteristics of primary gold mineralization, it is best to use statistical model (one-way, two-way), and mine geometric model and structure function model, focus on structure function model Using Kriging method, distance inverse weighting; focus on Kriging to evaluate resources and reserves and vertical calculation method according to mineralization parameters to forecast original gold ore resource in Phuoc Son area to ensure reliability 3.1.6 Orientation for exploration network and development of mines 23 According to geologists, to ensure reliability can probe the ore bodies in Dak Sa area according to networking = (2/3) Hm (Hm, influenced size): Table 3:45 exploration Network is based on survey results Variogram Ore body Strike (m) Pitch (m) BĐMQ 40-50 40-45 QTZ3 35-50 30-35 Table 3:46 Exploration Network convert to square network Ore body Strike (m) Pitch (m) BĐMQ 40-47 40-47 QTZ3 32-41 32-41 3.2 DISCUSSION Regard to rare minerals, in addition to applying a statistical model to use the structure function model, allowing full understand the variation, affect size, anisotropy, isotropic of the parameters of orebody to interpreter exploration network, and applying Kriging on resources, reserves assessment Kriging method should be applied as a key method in assessing resources, reserves; particularly for rare minerals CONCLUSIONS AND RECOMMENDATIONS Conclusions 1.1 Phuoc Son region located in the north of Kontum block, belongs to Nam Ngai area Region has complex geological structures, distributed mainly metamorphosed sedimentary of Nui Vu formation, upper sub-layer and intrusive phase of Ben Giang - Que Son complex In contact position of metamorphosed sedimentary of formations Nui Vu and intrusive of Ben Giang - Que Son complex distributes the quartz - sulfide polymetallic - gold ore bodies 1.2 The original gold ore bodies in Phuoc Son are mainly the vein, circuits network, circuits lens, distributed in the separated-layer of quartz - biotite shale, calcareous shale of formations Nui Vu, the 24 upper sub-layer; developed mainly in the northeast - southwest, longitude and less than in the north west - south east, have relatively clear boundaries with surrounding rocks 1.3 The ore mineralogy is not complicated, consists of pyrite, pyrrhotite, galena, sphalerite, (possible electrum) and native gold; but the spatial variation is complex Symbiotic combination of minerals containing gold: quartz - pyrite II - Gold I and quartz - pyrrhotite II Gold II - galena - sphalerite (possible electrum) are typical The variation of the surrounding rocks is the phenomenon of silification, dolomitization, calcitization and sometimes chloritization, sericitization, etc 1.4 Au concentrations and associated elements (Ag, Pb and Zn) in the ore body accordance with the standard logarithmic distribution function, can be modeled on the spherical structure, has native effect Au content in the ore bodies shows the local variation and weak anisotropy can be considered as isotropic in space This is a scientific foundation for applying square exploration network, equilateral triangle, and rhombus Au correlated with Ag, Pb and Zn, however, the relationship between the ore body with zones, subdivisions has a little differences 1.5 Result of the model application: Mathematics statistics, mine geometry (contours), specially is function structures (Variogram) allows comprehensive assessment of mineralization variability and are the basis for selection an accordant assessment of resource, reserves 1.6 To assess the original gold resources and reserves of the Phuoc Son region according to procedure proposed in Figure 2:11, the combination of statistical model (one-dimensional, two-dimensional) with mine geometric model and structure function (Variogram ) plays a key role to realize the mineralization variation Using Kriging method, distance inverse weighting; focus on Kriging to calculator identified-resources will ensure the reliability and utility for exploration and mining Applying the method of vertical calculation based on mineralization parameters for forecast-resource assessment of original gold ore in the search-areas ensures reliability and consistent with mineralization zone in region 25 Recommendations The selected model to evaluate the original gold resources and reserves in the Phuoc Son region is consistent with studied object; can apply this model for mineral similar characteristics LIST OF PUBLICATION Nguyen Mai Quan, Le Van Luong, Do Ngoc Trung (2008), "Using Surpac 5.1 software to evaluate soild mineral resources reserves and apply to caculate coastal titanium placer ore reserves ", Journal of Geology, Series A, No 307, 7-8/2008 Nguyen Mai Quan, Le Van Luong (2008), " Using Surpac 5.1 software to evaluate soild mineral resources reserves and applying to material - cement clay mine, Phong Xuan commune, Phong Dien district, Thua Thien Hue Province", Report on the 18th Scientific conference, Hanoi University of Mining and Geology, Hanoi, 14/11/2008 Le Van Luong, Do Van Dinh (2010), "Using a specific model method in modeling cement limestone ore body in Thanh Nghi district, Ha Nam Province", Journal of Geology, Series A, No 320, - 10/2010 Truong Xuan Luan, Duong Thi Tam, Le Van Luong (2010), "Quantitive research of parameters reflected the quality of the ore Applying for bauxite ore body in lateritic weathered crust", Journal of Geology, Series A No 316/1-2/2010 Le Van Luong, Do Van Dinh (2010), "The selection method of modeling orebody to evaluate resources and reserves of lead-zinc mine Ban Bo, Cao Bang Province", Report on the 18th Scientific conference at Hanoi University of Mining and Geology, 11/11/2010 Le Van Luong, Truong Xuan Luan, Do Van Dinh (2013), "Some geological information methods be used in the mineral resource assessment, appllying for origin Au mineral in Phuoc Son area, Phuoc Son district, Quang Nam province" Technological Science Magazine of Mining and Geology, Hanoi University of Mining and Geology, No 43/7-2013 Le Van Luong, Truong Xuan Luan, Nguyen Phuong (2014), "Research on applying mathematical statistics model to assess the distribution characteristics and relationships between gold with accompanied useful components of original gold ore in Dak Sa area, Phuoc Son district, Quang Nam province", Journal of Geology, series A, No 339/1-2/2 ... exploration and exploitation periods os a necessary task The disertation Research on the selection of mineral resource assessment models for lode gold ores at Phuoc Son area, Quang Nam province” is... subdivision Bai Bai Dat Type the Phuoc Son; Documents in the thematic studies, surveys, original gold exploration in the region; The resources of gold and foreign origin 10 Place this research The thesis... of mining activities in study area Objectives of the study: To study the characteristics of mineralization zone of lode gold in Phuoc Son area; To select resource assessment models for lode gold