Research on Metallogenetic Regularity and Prospective of Taohua Hematite Deposit in Wushan County,Chongqing
Mineral resource is the material basis for human being’s existence and development.There are more than 300 kinds of iron-bearing minerals in nature.Hematite,the product of sedimentation,is one of the most widely-spreading iron ore in the crust,which is mainly applied to the iron and steel industry.There are two typical sedimentary hematite deposits in China,Ningxiang sedimentary ore deposit which is occurred in Devonian Series in South China and Xuanlong iron ore deposit in North China platform.The Taohua hematite mine in Wushan County is the only known large-scale sedimentary iron deposit having been explored in Chongqing in recent years.Yet,due to the poor geological exploration technology and difficulties in beneficiation and metallurgy in the early years,no systematic research has been done to uncover its geological characteristics and how it formed.Recently,with the increasing demand for iron resources and the development in exploration,there is an urge for systematic research in geological characteristics and comparison with adjacent areas.The author should summarize the metallogenetic regularity and ore genesis,analyze prospecting potential,promote the previous exploration results,and provide theoretical support for further exploration.The paper,based on the previous exploration and research results,is guided by the theory and methods of sedimentary geology,Sedimenttary facies paleogeography,metallogenetic regularity and prognosis.The author considers Taohua hematite mine in Wushan as our research object.The author finds the factors and laws by doing the analysis of the regional geological background,geological features of deposit and controlling factors of Taohua hematite mine.Moreover,the author summarizes the cause and sedimentary mineralization process of Taohua hematite ooid.Finally,the author analyzes the genetic type of mineral deposits and the prospecting potential.The main research results of the paper are as follows:(1)To systematically analyze the geological background and characteristics of the Taohua hematite deposit,and indicate the deposit distribution is severely influenced by sedimentary formation as well as the north-east anticline of this region.The Taohua hematite deposit,adjacent to the Ningxiang hematite zone on the east,sits in the south bank of Wu Gorge,which straddles eastern Chongqing and western Hubei province.The deposit also falls along the belt of the Yangtze platform-the upper Yangtze River Block-the carbonate platform in the south-the fold structure in Wulong.The Qiyao Mountain Fault Zone to the west of the mining zone which separates this area from the foreland basin in central Sichuan,is believed to be the center of the Palaeozoic depression sedimentation in upper Yangtze River Block.Sedimentary strata are formed broadly in Early Palaeozoic,large amount of marine growth.During Devonian-Carboniferous period,sea water erodes strata,so only remaining the strata of Upper Devonian and middle Carboniferous.Middle-late Permian sedimentary carbonate construction,iron and coal construction,Early Triassic sedimentary carbonate construction,all end with the sedimentary history of Early Triassic.The NE fold structure in the northern region is formed by combined action since late Yanshan period and later the Himalaya period.Taohua hematite deposit is controlled by Hejiaping anticline belt.Taohua hematite deposit occurs in huangjiadeng formation in Upper Devonian.The ore-bearing rocks are composed of red-purple siltstone with iron.At the bottom of the stratum is formed with the quartz sandstone construction of Yuntaihuan group in middle Devonian.At the roof of the stratum is the politic carbonate construction of Huanglong group in middle Carboniferous.The shape of ore is layered and stratiform-like.The length of the ore is 6300 m,single layered stratiform’ thick is 0.38-5.29m(averagely 2.81m).98﹪ of the mineral rock is hematite with siderite,pyrite and magnetite in less.The dominant gangue mineral is quartz,followed by calcite,dolomite,chlorite,hydromica and collophanite.The single sample of TFe is 4.49-56.80﹪,with the single mining section of TFe content among 25.61-51.59﹪(averagely 39.91﹪).The single mining section of P is 0.22-1.28﹪(average 0.75﹪).The relationship between P content and TFe content is significantly positive correlation(correlation coefficient 0.76).Ore texture mainly is oolite and bean granular.Ore structure is compact massive and streaked structure,belonging to Hi-P,Lo-S oolite hematite ore.(2)The environment of the study area is litho-paleogeography,surrounding by weathering denudation old land,which provide rich Fe,P,Al,Si,etc.minerals resources for formation of various paleontology,and has favorable condition to form oolite.The study indicates:(1)the study area is rich in clastic grain which is necessary for building core.(2)there are enough hydrodynamic condition.(3)seawater enriched ferruginous colloid or suspension.(4)the study area locats in shallow water environment near provenance.(5)pelitic hematite crystal,surrounding by core partical,sedimented in the way of colloidal chemistry and formed hematite oolith.(6)Hematite oolith with concentric rings are true oolitc.(3)The analyzing on the characteristics of the sedimentary facies as well as the mineral components leads to the conclusion that the ore-forming materials left over through weathering of surrounding rocks since ancient time were deposited in the semi-closed basin of shallow inland after the action of colloidal agglutination.Research indicates that:(1)Iron formation produced in the following Caledonian transgression program in sedimentary rocks.(2)The suggestion of ore genesis show that it has at least 50 Ma of weathering demudation of old land which formed in transgression sedimentary rocks system after Caledonian movement.(3)Mining area is located in half closed inland Taohua sea basin no deep than 60 m.(4)Full of oxygen gas in oxidizing milieu,having sufficient hydrodynamic condition.(5)Having enough hydrodynamic conditions,oolitic hematite colloid chemical deposition,oolitic band retains fiber floc structure of condensation of ferric hydroxide colloid solution and transportation and transformation of deposition and enrichment process experience.(6)Corals and brachiopods creatures flourished in the environment of normal salinity warm water,providing amounts of organic and P element source.(4)The study on the deposit characteristics and the ore-controlling factors enables the author to point out for the first time that the Taohua hematite deposit could be generally categorized into the Ningxiang iron deposit of syndepositional type.Research indicates that:(1)The ore is located between the iron clastic rocks and argillaceous carbonate rock construction.(2)Its natural type is hematite ooid while the industrial type is high phosphorus acidic sulfur ore.(3)The Taohua hematite deposit could be generally categorized into the Ningxiang iron deposit of syndepositional type.(4)With obvious prospecting criteria,the Taohua hematite deposit has great prospecting potential either at the center or around the mine.(5)The author uses various information technology in the research to compare the mineralization factors and metallogenetic model of the Taohua hematite deposit in Wushan County,from which the author summarizes the mineralization factors and metallogenetic model of this region,hence the resource potential evaluation factors of typical deposits and an evaluation model to assist further thorough exploring in Taohua and adjacent iron ore zones.For the first time,the resource potential evaluation of Taohua hematite deposit was carried out and revealed that this area is of great prospecting potential.Apart from a measured reserve,over 410 million tons of iron ore was discovered in the Taohua deposit,which provides theoretical and technical support for the municipal strategic action plan in mineral exploration breakthrough,the carryout of iron ore resources exploration project of Chongqing City and the Chong qing Iron and Steel(Group)Co.,Ltd in mine construction.