Study On The Characteristics Of Mineralization And Alteration Based On Infrared Spectroscopy Technology Of The Baijian Iron Deposit In Heibei

The Han-Xing area is located in the southern section of the Taihang Mountai(TM)in the central belt of the North China Block.It is one of the important skarn-type iron-rich ore concentration areas in China.With the development of a new round of prospecting breakthrough strategic action,new technical methods and prospecting concepts are urgently needed in this area.Skarn-type iron deposits have typical layered alteration zoning.Detailed determination of the species characteristics,combination types and distribution characteristics of altered minerals is helpful to improve the efficiency of prospecting and exploration and to understand the metallogenic mechanism.Infrared spectroscopy has significant advantages in rapid identification of mineral types and extraction of relative content,and has achieved certain working experience in geological prospecting worldwide.In this study,infrared spectroscopy(SWIR + TIR)was used to test seven cores such as ZK0805 in the Baijian mining area of Han-Xing area.A total of 10155 spectral data were obtained,and more than ten minerals such as sericite,chlorite and pyroxene were identified.Mineral assemblages and spatial distribution characteristics were determined in detail.Combined with petrographic identification and mineral chemical analysis,infrared spectral mapping,mineral characteristic spectral parameters and mineral element geochemistry were carried out to extract effective prospecting and exploration indicators,which established a multi-mineral and multi-parameter spectral exploration model of Baijian mining area.The mineral mapping work was carried out on seven cores such as ZK0805 by infrared spectroscopy.SWIR + TIR successfully interpreted ten types of minerals such as sericite,chlorite,feldspar and amphibole.The spatial distribution of various minerals is basically consistent with the drilling data.According to the relative content of minerals,five mineral assemblage zones are divided.From the surface to the direction of the intrusion,the sequence is quartz + feldspar + carbonate + kaolinite + sericite(Z1)→ carbonate +kaolinite minerals + sericite(Z2)→ carbonate + chlorite(Z3)→ amphibole + biotite +pyroxene + serpentine + carbonate + kaolinite + sericite + chlorite(Z4)→ feldspar +amphibole + biotite + sericite + chlorite(Z5).Among them,Z4 is the main ore-bearing area,and the mineral assemblage in this belt can be directly used as a prospecting indicator.The characteristic spectral parameters of the main altered minerals were statistically analyzed.The results show that :(1)The half-width of sericite Al-OH2200 FWHM changes from 24-29 in the Carboniferous-Triassic strata to 20-25 in the Middle Ordovician strata in the borehole,showing a decreasing trend from shallow to deep.(2)The characteristic absorption peak value of chlorite Fe-OH2250 Pos from intrusive rock→contact zone→distal surrounding rock shows a trend of slowly increasing first,then rapidly decreasing and finally increasing slowly.(3)The characteristic reflection peak value of carbonate minerals6500 Pos shows a fluctuating trend in the Middle Ordovician Cixian Formation and Fengfeng Formation when it skews to the shortwave direction in the marble area of the Majiagou Formation.Combined with the previous research results and geochemical analysis of mineral elements,the spectral law was analyzed.It is found that the decrease of sericite Al-OH2200 FWHM indicates that the spectral crystallinity of sericite increases gradually to the deep part,reflecting the higher temperature fluid environment in the deep part.The chlorite Fe-OH2250 Pos skews regularly in the borehole by the sodium iron removal in the pluton and the iron action in the oxidation unloading fluid of the gypsum in the Middle Ordovician strata.The fluctuating trend of the carbonate mineral 6500 Pos in the Cixian Formation and Fengfeng Formation is controlled by the relative content of dolomite and calcite in the tested area.The content of Fe O and Mn O in the carbonate minerals at the marbleized area of Majiagou Formation decreases gradually from the surrounding rock to the contact zone while the content of Mg O and Na2 O increases gradually,which is the main reason for the the carbonate mineral 6500 Pos skewing toward the shortwave direction.Based on the research of infrared spectrum mapping,mineral characteristic spectrum parameters and mineral element geochemistry,a spectral exploration model suitable for the Baijian mining area is constructed.In our study,the decrease of Al-OH2200 FWHM can effectively indicate the trend of environmental temperature,which has certain guiding significance for mineralized hydrothermal center and concealed plutons.Chlorite with low Fe-OH2250Pos(< 2245nm)and carbonate minerals with low 6500Pos(< 6450nm)in marbleized area are effective and universal prospecting indicators.The achievements mentioned above provide scientific basis for the mineral exploration in Baijian mining area.Meanwhile,new technology and new methods are established for prospecting of the same type of deposits in the region.