Research on the Application of Electromagnetic Method in the Exploration of Altered Rock-type Gold Deposits in the East Kunlun Metallogenic Belt

Introduction The East Kunlun Orogenic Belt is located in the northeastern part of the Qinghai–Tibet Plateau(Li et al.,2007),stretching from the East Kunlun to the Elashan area in an east–west direction(Guo et al.,2018).It is an important part of the Central Orogenic Belt(Xiong et al.,2023).It is considered one of the important gold mineralization regions in the Tethys tectonic domain(Norbu et al.,2023)and an essential potential base for mineral resources in China.Wulonggou and Gouli gold mines have been discovered successively,earning the reputation of the"Golden Belt of Qinghai Province"(Feng et al.,2004;He et al.,2023).

Cassiterite U-Pb dating of the Yelonggou pegmatite-type lithium deposit in western Sichuan and its metallogenic age constraints

1.Objective Pegmatite hosts important resource of rare metals,e.g.,lithium(Li)and beryllium(Be).In recent years,increasingly more studies were dedicated to characterize and unravel the formation of pegmatite-type deposits,for which accurate dating of pegmatite formation and mineralization is essential.The Songpan-Ganzi orogenic belt is a major rare metal metallogenic belt in China,hosting many important pegmatite-type Li deposits,including the Lijiagou,Dangba,Jiajika,Yelonggou,Cuola,and Declalongba.Radiometric age data(mica Ar-Ar and zircon/cassiterite U-Pb)from these Li deposits are sparse,ranging from 210 to 152 Ma.However,obtaining reliable zircon U-Pb dates can be a challenge due to the strong decidualization in pegmatites.As a result,the formation and mineralization ages of these rare metal pegmatites remain controversial,which hampers the development of pegmatite-type metallogenic model for the Songpan-Ganzi orogenic belt.

Genesis, metallogenic model, and prospecting prediction of the Nibao gold deposit in the Guizhou Province, China

Southwestern Guizhou province is one of China’s most important distribution areas of Carlin-type gold deposits. The Nibao deposit is a typical gold deposit in southwestern Guizhou. To elucidate the genesis of the Nibao gold deposit, establish a metallogenic model, and guide prospecting prediction, we systematically collected previously reported geological, geochemical, and dating data and discussed the genesis of the Nibao gold deposit,based on which we proposed the metallogenic model.Earlier works show that the Nibao anticline, F1 fault, and its hanging wall dragged anticline(Erlongqiangbao anticline) were formed before or simultaneously with gold mineralization, while F2, F3, and F4 faults postdate gold mineralization. Regional geophysical data showed extensive low resistivity anomaly areas near the SBT(the product of tectonic slippage and hydrothermal alteration)between the P2/P3 and the strata of the Longtan Formation in the SSE direction of Nibao anticline in the lower plate of F1 and hanging wall dragged anticline(Erlongqiangbao anticline), and the anomaly areas are distributed within the influence range of anticlines. Simultaneously, soil and structural geochemistry show that F1, Nibao anticline,Erlongqiangbao anticline, and their transition areas all show good metallogenic elements(Au, As, and S) assemblage anomalies, with good metallogenic space and prospecting possibilities. There are five main hypotheses about the source of ore-forming fluids and Au in the Nibao gold deposit:(1) related to the Emeishan mantle plume activity;(2) source from the Emeishan basalt;(3) metamorphic fluid mineralization;(4) basin fluid mineralization;(5) related to deep concealed magmatic rocks;of these, the mainstream understanding is the fifth speculation. It is acknowledged that the ore-forming fluids are hydrothermal fluids with medium–low temperature, high pressure, medium–low salinity, low density, low oxygen fugacity, weak acidity, weak reduction, and rich in CO_(2)and CH_(4). The fluid pressure is 2–96.54 MPa, corresponding to depths of 0.23–3.64 km. The dating results show that the metallogenic age is ~141 Ma, the extensional tectonic environment related to the westward subduction of the Pacific Plate. Based on the above explanation, the genetic model related to deep concealed magmatic rocks of the Nibao gold deposit is established, and favorable prospecting areas are outlined;this is of great significance for regional mineral exploration and studying the genesis of gold deposits.

The first discovery of Xinlong epithermal gold deposit in southern margin of the Bangonghu-Nujiang metallogenic belt: A new expansion of gold prospecting in Northern Tibet

The Xinlong gold deposit is located in Niyma County,Naqu area of Tibet and was discovered by the Institute of Mineral Resources,Chinese Academy of Geological Sciences through the 1∶50000 mineral geological survey.The ore bodies occur in the Zenong Group volcanic rocks in the middle section of the central Lhasa subterrane and are structurally controlled by the NNW-striking faults.Four ore bodies have been found,exhibiting cloddy,dense-sparse,disseminated,and breccia structures.The ore minerals are mainly tetrahedrite group minerals,and other ore minerals include pyrite,chalcopyrite,nevskite,bornite,anglesite,native gold,and silver-gold bearing selenide,etc.The types of alteration are dominated by silicification,as well as middle-and high-graded argillization.The alteration mineral assemblages contain quzrtz,pyrophyllite,and kaolinite.The Zaliela Formation volcanic rocks of Zenong Group are silicified by later hydrothermal fluid with vuggy quartz in some fractured zones.The middle-and high-graded argillization are characterized by pyrophyllitization and kaolinization.The Xinlong gold deposit shows great metallogenetic potentiality and has been revealed by 1∶10000 geological mapping,IP sounding,and trial trenching in the mining area.Combined with the regional metallogenic geological setting,we suppose that a potential epithermal gold belt probably exists in the middle of the Lhasa terrane.The discovery of the Xinlong gold deposit opens a new chapter for the gold prospecting in Northern Tibet.

Outline of Metallogenic Regularity of Bauxite Deposits in China

Among the abundant aluminum ore resources in China, bauxite is dominated, which is mainly distributed in 19 provinces and regions, including Shanxi, Henan, Guizhou and Guangxi. The major deposit type of bauxite is paleo-weathering crust sedimentary type, and the other one is the accumulation type. The main metallogenic period is the late Paleozoic Era followed by the Cenozoic Era. The metallogenic tectonic background is characterized by a cratonic environment. This paper summarizes the bauxite metallogenic regularity based on the characteristics of bauxite resources, bauxite deposit type, bauxite metallogenic belt and metallogenic series in China, and 15 bauxite metallogenic belts, 8 bauxite metallogenic series and 7 bauxite ore concentrated areas were identified in the study. This paper also provides a theoretical basis for the evaluation of the potential of bauxite resources.

Geological characteristics,metallogenic regularity,and research progress of lithium deposits in China

China is rich in abundant lithium resources characterized by considerable reserves and a concentrated distribution of metallogenic zones or belts,with proven reserves of 4046.8×10^(3) t(calculated based on Li_(2)O)by 2021.China is also a big consumer of lithium.By 2019,China’s lithium consumption in the battery sector alone had reached 99×10^(3) t,with an average annual growth rate of nearly 26%.China has become the world’s largest importer of lithium resources,showing a severely unbalanced relationship between supply and demand for lithium resources.Therefore,there is an urgent need for the prospecting,exploitation,and study of lithium resources in China.This study collected,organized,and summarized the data on the major lithium deposits in China,analyzed and compared the spatial-temporal distribution patterns,geological characteristics,and metallogenic regularity of these lithium deposits,and summarized the prospecting and research achievements over the last decade.The major lithium deposits in China are distributed in provinces and regions such as Qinghai,Jiangxi,Sichuan,Tibet,and Xinjiang.These deposits are mostly small in scale.According to different genetic types,this study divided lithium deposits into granitic pegmatite type,granite type,saline lake brine type,underground brine type,and sedimentary type,as well as new types including hot spring type and magmatic-hydrothermal type,and summarized the characteristics and key metallogenic factors of these different types of deposits.Sixteen metallogenic prospect areas of lithium deposits were delineated according to the deposit types and the distribution patterns of metallogenic belts.The paper introduced the research progress in major metallogenic models and lithium extraction techniques made over the past decade.Based on the comprehensive analysis of the prospecting potential of lithium deposits,the authors concluded that the future prospecting of lithium resources in China should focus on lithium metallogenic belts,the deep and peripheral areas of currently determined large-scale pegmatite-type lithium deposits,geophysical-geochemical anomalous areas with mineralization clues,and areas with developed large-scale low-grade associated granite-type and sedimentary lithium resources.The study aims to serve as a guide for the future prospecting of lithium deposits in China.

METALLOGENIC EVOLUTION AND MODEL OF MANZHOULI-XINBAERHU METALLOGENIC PROVINCE

This area is a superlarge potentiality metallogenic province of multimetal resource,belonging to Ergun accretionary fold system of early Caledonian.The regional basement(Neoproterozoic-Lower Cambrian Series)is the outer extent of the Siberian craton margin,and the metallization in this area was affected intensely by Pacific plate tectonics.The NE trending Ergun-Hulun deep-seated fracture controls the giant volcano-magmatic activty and mineralization in this area.NW cross trending tenso-shear fractures control the formation of ore cluster in this area.The major types of ore deposits in this area are porphyry type,subvolcanic hydrothermal vein type and skarn type.They are the products of different depths and environments as genetically-related,which can be collectively regarded as porphyry copper-multimetal metallogenic series.

Re-Os geochronology of Cu and W-Mo deposits in the Balkhash metallogenic belt,Kazakhstan and its geological significance

The Central Asian metallogenic domain （CAMD） is a multi-core metallogenic system controlled by boundary strike-slip fault systems. The Balkhash metallogenic belt in Kazakhstan, in which occur many large and super-large porphyritic Cu--Mo deposits and some quartz vein- and greisen-type W-Mo deposits, is a well-known porphyritic Cu--Mo metallogenic belt in the CAMD. In this paper 11 molybdenite samples from the western segment of the Balkhash metallogenic belt are selected for Re--Os compositional analyses and Re--Os isotopic dating. Molybdenites from the Borly porphyry Cu deposit and the three quartz vein-greisen W--Mo deposits--East Kounrad, Akshatau and Zhanet--all have relatively high Re contents （2712--2772 μg/g for Borly and 2.267--31.50 μg/g for the other three W-Mo deposits）, and lower common Os contents （0.670-2.696 ng/g for Borly and 0.0051--0.056 ng/g for the other three）. The molybdenites from the Borly porphyry Cu--Mo deposit and the East Kounrad, Zhanet, and Akshatau quartz vein- and greisen-type W-Mo deposits give average model Re--Os ages of 315.9 Ma, 298.0 Ma, 295.0 Ma, and 289.3 Ma respectively. Meanwhile, molybde- nites from the East Kounrad, Zhanet, and Akshatan W-Mo deposits give a Re--Os isochron age of 297.9 Ma, with an MSWD value of 0.97. Re--Os dating of the molybdenites indicates that Cu-W-Mo metallogenesis in the western Balkhash metallogeuic belt occurred during Late Carboniferous to Early Permian （315.9--289.3 Ma）, while the porphyry Cu--Mo deposits formed at ~316 Ma, and the quartz vein-greisen W--Mo deposits formed at ~298 Ma. The Re--Os model and isochron ages thus suggest that Late Carboniferous porphyry granitoid and pegmatite magmatism took place during the late Hercy- nian movement. Compared to the Junggar-East Tianshan porphyry Cu metallogenic belt in northwestern China, the formation of the Cu-Mo metallogenesis in the Balkhash rnetallogenic belt occurred between that of the Tuwu-Yandong in East Tianshan and the Baogutu porphyry Cu deposits in West Junggar. Collectively, the large-scale Late Carboniferous porphyry Cu-Mo metallogenesis in the Central Asian metallogenic domain is related to Hercynian tectono-magmatic activities.

A Preliminary Review of Metallogenic Regularity of Copper Deposits in China

Copper resources in China are rich, but imported copper products are still required. Researches on metallogenic regularity of major types of copper deposits by geologists have involved in worldwide classification, significant copper belts, representative copper deposits, etc. Studies on metallogenic regularity of copper deposits in China also have made achievements with a long-term work. Combined with latest exploration advances obtained in recent ten years, this review aims to conclude the achievements of researches on copper metallogenic regularity in China. Based on data of 814 copper deposits and other ore （mineralized） occurrences, ten prediction types of copper deposits have been suggested. Porphyry and skarn copper ores are taken as the key targets. Porphyry copper deposits are the most important one which concentrate in Gangdese, Changdu-Sanjiang, Dexing and East Tianshan. The Cenozoic and Mesozoic are the major metallogenic epochs. Four main metallogenic epochs are been studied based on the copper ore geochronological data including Precambrian Era （Archean and Proterozoic）, Paleozoic Era, Mesozoic Era and Cenozoic Era. Based on the study of metallogenic series of ore deposits in China, twenty-seven metallogenic series of copper deposits are proposed. This is suggested to deepen the study of metallogenic regularity of copper ore and provide the theory guide for copper resources prediction in China.

Fluorite deposits in China:Geological features,metallogenic regularity,and research progress

Fluorite is one of the important mineral raw materials in the industry.In China,it is mainly distributed in the provinces and regions such as Hunan,Zhejiang,Jiangxi,Inner Mongolia,Fujian,and Henan provinces,boasting huge reserves and large numbers of deposits.However,most of the fluorite deposits are on a small or medium scale.The main fluorite deposits in China were studied in this paper.Their geological features and metallogenic regularity were summarized and compared.Meanwhile,based on their main genetic factors including metallogenic fluid sources and main metallogenic geological processes,they were divided into two groups,namely meso-epithermal deposits and magmatic-hydrothermal deposits.Furthermore,based on the prospecting achievements and research progress obtained in fluorite deposits in recent years,prospecting potential predictions were made for the metallogenic prospect areas and major prospecting areas of fluorite in China.This aims to provide a theoretical basis and direction for future fluorite prospecting in China.

Uranium Metallogenic Regionalization and Resource Potential in China

This paper is comprehensively involved in main types of uranium deposits and their general metallogenic characteristics, metallogenic fields, provinces, regions and belts, and uranium resources potential evaluation. Generally speaking, there are favorable conditions and good uranium resources potential for uranium mineralization in China.

Metallogenic Systems on the Paleocontinental Margin of the North China Craton

The North China Craton (NCC) is one of the largest blocks composing the continent. Different types of continental margins well developed around the NCC, along with lots of metallogenic systems of different metals and different times. Based on the study on the structural evolution of the NCC, the authors made a new division of tectonic units of the NCC. Through an analysis of the data of 1:25000 geochemical survey on stream sediments, regional geochemical features of main ore-forming elements including Au, Ag, Cu, Pb, Zn, W, Ni, Co and Mo of the NCC are discussed in the paper. Then different metallogenic systems and their forming processes and geodynamics are discussed in detail. At last, temporal and spatial distribution regularities are summarized and ten favorable ore-control factors on the paleocontinental margins are put forward, including (1) abundance of ore sources; (2) rendezvous of ore-forming fluids; (3) high thermo-dynamic anomaly; (4) remarkable Earth crust-mantle interaction; (5) cluster of macroscopic structures and their long activities; (6) diversity of ore-forming environments; (7) long geohistory; (8) multiforms of critical transitional ore-forming mechanisms; (9) multi-staged and superimposed ore-formation; and (10) suitable preservation condition.

Field analysis of metallogenic information and its application

Focusing on the issue to deal with inadequate extraction of metallogenic information especially geological information,a new method of extracting metallogenic information based on field model,i.e.the field analysis method of metallogenic information,was proposed.In addition,a case study by using the method of the extraction of metallogenic information from the west Guangxi and southeast Yunnan district as an example was performed.The representation method for the field models of metallogenic information,including the metallogenic influence field model and the metallogenic distance field model,was discussed by introducing the concept of the field theory,based on the characteristic analysis of the distance gradualness and the influence superposition of metallogenic information.According to the field theory superposition principle and the spatial distance analysis method,the mathematical models for the metallogenic influence field and the metallogenic distance field of point,line and area geological bodies were derived out by using parameter equation and calculus.Based on the metallogenic background analysis,the metallogenic information field models of synsedimentary faults and manganese sedimentary basins were built.The relationship between the metallogenic information fields and the manganese mineralization distribution was also investigated by using the method of metallogenic information field analysis.The instance study indicates that the proposed method of metallogenic information field analysis is valid and useful for extracting the ore-controlling information of synsedimentary faults and manganese sedimentary basins in the study area,with which the extraction results are significant both statistically and geologically.

A Preliminary Review of the Metallogenic Regularity of Nickel Deposits in China

The nickel deposits mainly distributed in 19 provinces and autonomous regions in China are 339 ore deposits/occurrences, including 4 super large-scale deposits, 14 large-scale deposits, 26 middle- scale deposits, 75 small-scale deposits, and 220 mineralized occurrences. The prediction types of mineral resources of nickel deposits are magmatic type, marine sedimentary type and regolith type. The formation age is from the Neoarchean to the Cenozoic with two peaks in the Neoproterozoic and the late Paleozoic. The nickel deposits formed in the Neoproterozoic are located on the margin of the North China Block and Yangtze Block, and those formed in the late Paleozoic are mainly distributed in the Central Asian Orogenic Belt （CAOB）, Emeishan and the Tarim Large Igneous Provinces （LIPs）. Magmatic nickel deposits are mainly related with broken-up continental margin, post-collision extension of the orogenic belt and mantle plume. According to different tectonic backgrounds and main characteristics of magmatism, the Ni-Cu-Co-PGE metallogenie series types of ore deposits related with mantle-derived mafic-ultramafic rocks can be divided into 4 subtypes： （1） the Ni-Cu-Co- PGE metallogenic series subtype of ore deposits related with mantle-derived mafic-ultramafic rocks in the broken-up continental margin, （2） the Ni-Cu-Co-PGE metallogenic series subtype of ore deposits related with mantle-derived mafic-ultramafic rocks in mantle plume magmatism, （3） the Ni-Cu-Co- PGE metallogenic series subtype of ore deposits related with mantle-derived mafic-ultramafic rocks in the subduction of the orogenic belt, and （4） the Ni-Cu-Co-PGE metallogenic series subtype of ore deposits related with mantle-derived mafic-ultramafic rocks in post-collision extension of the orogenic belt. We have discussed in this paper the typical characteristics and metaliogenic models for Neoproterozoic Ni-Cu-（PGE） deposits related with broken-up continental margin, Cambrian marine sedimentary Ni-Mo-V deposits related with black shale, early Permian Ni-Cu deposits related with post-collision extension of the orogenic belt, late Permian Ni-Cu-（PGE） deposits related with Large Igneous Provinces （LIPs）, and Cenozoic Ni-Au deposits related with regolith. The broken-up continental margin, mantle plume and post-collision extension of the orogenic belt are important ore- forming geological backgrounds, and the discordogenic fault, mafic-ultramafic intrusion, high MgO primitive magma （high-MgO basaltic magma）, deep magmatism, sulfur saturation and sulfide segregation are 6 important geological conditions for the magmatic nickel deposits.

A Preliminary Review of Metallogenic Regularity of Tin Deposits in China

China is rich in tin resources,and contains many types of tin deposits.Among the tin deposit types,the cassiterite-sulfide type,skarn type and quartz vein type occupy a large proportion of tin resources and reserves.From the aspect of exploitation and utilization,the most important types are cassiterite-sulfide type and quartz vein type.The cassiterite-sulfide type tin deposits are mainly located in Northern Guangxi and Eastern Yunnan,skarn type deposits are mainly distributed in the ore-concentration areas of South Hunan in Middle Nanling,and the quartz vein type tin deposits are mainly distributed in South China,such as Western Fujian,Middle Jiangxi,Northern Guangzhou and Southern Hunan.The most important metallogenic epoch for tin deposits is the Mesozoic era.The metallogenic geotectonic background is mainly continental environments after orogeny process,with strong tectonic changes,interlaced deep fracture and frequent magmatism.And the most distinctive feature is the well developed Mesozoic granites,which have a close relationship with tin mineralization.Based on the detailed study of the data from 873 tin deposits in China,this paper summarized the metallogenic regularity of tin deposits,classified 20 important metallogenic series of tin or tin-associated deposits,and inferred that the cassiterite-sulfide type,skarn type,quartz vein type and greisen type are the main prediction types of tin resources.Forty-four tin-mineralization belts were divided,among which,19 belts are the most important.In addition,a series of maps about tin metallogenic belts and tin metallogenic regularity were compiled,aiming to provide theoretical basis for potential estimation and prediction of tin mineral resources.

Yanshanian Magma-Tectonic-Metallogenic Belt in East China of Circum-Pacific Domain(Ⅱ): Lithosphere-Asthenosphere System and Metallogenic Environment

This paper shows that the catastrophe of lithosphere asthenosphere system (LAS) is developed for the Yanshanian metallogenic belt in the East China. Two types of Yanshanian disturbed LAS and metallogenesis in the East China are recognized: great lithosphere thinning and thickening in the compressional orogenic environment, and the related Andes type and Hercyn type metallogenesis, respectively. Great amount of the juvenile and hot mantle materials and the reactivated hot lower crustal materials replaced, heated and injected into the cold lithosphere and crust are believed to be a fundamental source and a basic deep environment for the Yanshanian metallogenic explosion. Reactivated and active discontinuities on the lithosphere scale are considered to be the main ore storing space of the metallogenic zone. Large magma tectonic metallogenic system is necessary for the formation of large cluster area of ore deposit. The eastern China is believed to have large potential for prospecting of ore deposits in terms of the metallogenic environment.

Metallogenic Dynamics of Zhashui Ag－Pb Polymetallic Ore Deposit in Shaanxi，China

Zhashui Ag-Pb polymetallic ore deposit is located in northern Qinling geosyncline. In this paper, its geological features and metallogenic background are introduced. The volcanic dynamics,physical-chemical conditions of metallogeny and ore-forming experimental simulation are discussed in detail. Based on the existence of paleovolcanic activity, the protolith characters and geochemistry of ore-bearing rock series, the authors study the law of volcanic activity in Middle Devonian period. The Physical-chemical conditions of metallogeny. including temperature, pressure, pH and Eh of mineralizing solution, are also determined. The evolution of salinity, f(O2), pH, M (H2S), M(SO2-4) (M is mole fraction of certain component ), t (temperature) and a(ionic activity)of mineralizing solution suggests that the mineralization was a long-term dynamic process. Finally, the metallogenic pattern is established.

^40Ar/^39Ar and Rb-Sr Ages of the Tiegelongnan Porphyry Cu-(Au)Deposit in the Bangong Co-Nujiang Metallogenic Belt of Tibet,China:Implication for Generation of Super-Large Deposit

The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate-felsic intrusions（ca. 123–120 Ma）. Various epithermal ore and gangue mineral types were discovered in the middle-shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite（potassic zone）, sericite（phyllic zone）, and alunite（advanced argillic zone） in/around the ore-bearing granodiorite porphyry yielded 121.1±0.6 Ma（1σ）, 120.8±0.7 Ma（1σ） and 117.9±1.6 Ma（1σ）, respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb-Sr dated to be 117.5±1.8 Ma（2σ）, representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic-hydrothermal system. The Tiegelongnan super-large Cu-（Au） deposit may have undergone a prolonged magmatichydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.

Origin and Superposition Metallogenic Model of the Sandstone-type Uranium Deposit in the Northeastern Ordos Basin,China

This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been established due to complex uranium mineralization processes with superposition of oil-gas reduction and thermal reformation.

Metallogenic mechanism of Pingguo bauxite deposit,western Guangxi,China:Constraints from REE geochemistry and multi-fractal characteristics of major elements in bauxite ore

Major and REE geochemistry and multi-fractal analysis of two types of bauxite(primary bauxite and accumulated bauxite) ores were studied in Pingguo bauxite orefield in western Guangxi,China.The results of geochemical data show that the accumulated bauxite has a feature of high Al_2O_3 whereas relative low Fe_2O_3 and SiO_2 contents compared to the primary bauxite.The similar chondrite-normalized rare earth element(REE) patterns illustrate that they have a cognate relationship.However,the negative Ce anomalies of primary bauxite and positive Ce anomalies of accumulated bauxite indicate that the ore-forming system changed from reducing environment to oxidation environment.The results of multi-fractal spectrum and parameters of Al_2O_3,Fe_2O_3 and SiO_2 between primary bauxite and accumulated bauxite show that the distinct multi-fractal spectrum parameters reflect the different grade distribution between accumulated and primary bauxite ores.Metallogenic process from primary bauxite to accumulated bauxite is accompanied by the loss of diffluent elements(e.g.,Si and S) and enrichment of stable elements(e.g.,Al and Fe) in the surface environment.Among the rest,the migration mechanism of iron during the evolutionary process from primary ore to accumulated ore can be described as combined leaching and chemical weathering action with participation of sulfur.