Study Of Metallogenic Regularity And Prospecting Direction Of Iron Deposits In Taxkorgan Area,Xinjiang Province

The study area is located in Taxkorgan landmass at west section of Karakorum orogenic belt, east adjacent the western Kunlun orogenic belt, and east adjacent the mingtiegai landmass.The region has undergone complex tectonic evolution and deformation and metamorphic features so that it has superior ore-forming geological conditions.The region has become a important iron ore belt of southwest Xinjiang,because a series of iron deposits of quite large scale have been reported in there as the result of the land and resources survey and prospecting boom,such as Laobing iron deposit,Qiaopukalimo iron deposit,Jiertiekegou iron deposit,Yelike iron deposit,etc in recent years.Based on the sufficient study and exhaustive field geological survey, combining previous research results and indoor analysis work,this paper mainly study ore genesis and metallogenic model of the iron deposits in the study area, summarizes metallogenic regularity and prospecting model of iron deposits, evaluate prospecting potential,and the next prospecting direction of iron deposits is also pointed out in the study area. The main conclusions in this paper are as follows:1.Based on the systemic analyses of previous research results, the regional tectonic units are further divided. The Taxkorgan landmass was divieded into three second order tectonic units which contained Taheman to Xindi volcanic-sedimentary basin, Taxkorgan to Waqia uplift belt, and Ta’axi to Tatulugou volcanic-sedimentary basin.A number of present already relatively large-scale iron deposits have been discovered in Ta’axi to Tatulugou volcanic-sedimentary basin. The mineralization of iron deposits was closely related to formation and evolution of the basin. The recent studies show that the age of sources in iron-bearing series is mainly focused on530Ma, which had always been belonged to paleoproterozoic Bulunkuole Group.It has characteristics of cap rock, so it should be saparated out from Bulunkuole Group.These iron-bearing series are divided into three lithology segment combinations,they are marble and quartz schist segment, gypsum (anhydrite)-magnetite segment,and quartz-mica schist segment,iron orebodys exist in second lithology segment combination.2. It’s the first time to get a systematic analysis on the geological features of Laobing iron deposit,Qiaopukalimo iron deposit,etc, and found that different types of iron-bearing minerals and magnetite ore bodies degree of the iron deposits have the obvious zoning characteristics in the space,where the lower iron-bearing segment is mainly magnetite and the scale of magnetite ore bodies is large, the upper iron-bearing rocks is mainly pyrite and the scale of magnetite ore bodies is small.The iron formations include gypsum-anhydrite-iron formation,quartz-magnetite formation, and pyrite-magnetite formation. Among them, the gypsum-anhydrite-iron formation has a unique feature, the mineral assemblage is magnetite+pyrite+anhydrite+gypsum. This discovery of the iron formation will lays a foundation for further study and prospecting work of iron deposits in the area.3. Based on the systematic research on geological features of ore deposit, geochemical characteristics of rock and ore, isotope geochemical characteristics, trace elements and rare earth elements characteristics of magnetite monomineral,etc, shows that genetic type of ore deposits which is the type of marine volcanic sedimentary iron deposits in the study area and the magnetite is mainly primary sedimentary cause. Although these deposits by limited regional metamorphism and magmatic hydrothermalism process at later stage, but these effects are relatively limited, which has revised the previous understanding about that the ore genesis has long been thought sedimentary-metamorphic iron deposits (BIF)4.Through LA-ICP-MS zircon U-Pb dating determining ages of detrital zircons of felsic schists and biotite quartz schist of iron-bearing segment in Laobing mining area, the result shows that the of age of detrital zircons mainly concentrated in510Ma～540Ma, combined the metamorphic age of strata definition from predecessors, and metallogenic epoch of iron deposits is early Paleozoic which was clearly first put forward, which has revised the previous understanding about that the metallogenic epoch of iron deposits was precambrian (palaeoproterozoic)5.Established the metallogenic model of marine volcanic sedimentary iron deposits in Taxkorgan area. Process of forming iron deposits in here has been through the sedimentary mineralization period, the reformation period of regional metamorphism,and the reformation period of magmatic hydrothermalism. Magnetite is formed in the the sedimentary mineralization period. The period of regional metamorphism and magmatic hydrothermalism mainly worked on the superimposed reformation part for the layered magnetite orebodies of deposition, but the influence is also limited.6. The iron deposits’characteristics in the area are similar. They are formed in early paleozoic, ore-hosting rocks are mainly made up of biotite quartz schist and metamorphic fine sandstone(metamorphic siltstone), iron minerals are mainly made up of magnetite of original sedimentary and features with the syngenetic minerals of magnetite, pyrite, anhydrite, and gypsum. The iron deposits in that area is quite different from any other sedimentary iron deposits in the world, whether in the geologic feature, nor the metallogenic epoch so this paper has been initiatively named iron deposits as "Pamir-type" iron deposits in Taxkorgan area (previously openly published on publishing magazine)7.Analysing ore-controlling factors, which as the formation, structure, magmatism, lithofacies paleogeography, metamorphism,etc. Summary regularity spatial and temporal distribution, regularity of ore-forming material source,and regularity of mineral association about iron deposits in the study area, raise the idea that these iron deposits in the study area are mainly hosted in the early paleozoic strata, and they are mainly controlled by the stratigraphic horizon and lithology and the lithofacies paleogeography factors of the volcanic-sedimentary basin; The evolution time of the mineralization can be described as follows:sedimentary mineralization in early paleozoicâ†'metamorphic mineralization in late Caledonian to Indo-chinese epochâ†'magmatic hydrothermal mineralization in Yanshanian. The forming of the iron deposits are mainly formed in the sedimentary mineralization of early paleozoic. Later effects of metamorphism and magmatic hydrothermalism has little influence for the formation and enrichment of magnetite, and it has more effect in the local superimposed reformation for early-formed magnetite orebodies;The iron deposits are distributed in the volcanic-sedimentary basin margin; The orebodies were controlled by the volcao-sedimentary cycles so that there are more multilayer magnetite orebodies in space and the types of iron mineralization and mineralizing degree has the obvious zoning characteristics;The metallogenic material of the iron doposits comes from the submarine volcanic activities; There are mineral association of gypsum-anhydrite-iron formation,quartz-magnetite formation, and pyrite-magnetite formation in the deposits.8.Get a comprehensive conclusion of ore-prospecting criteria for iron deposits, and establish a prospecting model of the marine volcanic sedimentary iron deposits in the study area. In particular, it’s the first time to describe the prospecting model of the iron deposits using graphics and tables,which offers reference for prospecting work of similar iron deposits.9. Based on systematical study and works of predecessors, this paper evaluates prospecting of iron deposits. It shows that the metallogenic conditions in littoral-neritic sea of Taaxi to Tatulugou volcanic-sedimentary basin are hopeful and have the great metallogenic potential so these place are preferable ore-finding area for searching iron deposits. Outline three prospecting areas, they are Sawuziale area,the northwestward Laobing iron deposit area,and the north Maeryang government area.