Abundant large and medium size iron deposits were hosted in the Carboniferous volcanic sedimentary rocks in the East Tianshan of NW China,among which the Baishanquan iron deposit is one of the important deposits.However,its genesis was poorly understood.In this paper,detailed petrographic,mineralogical and Nd isotope studies have been carried out on samples from the Baishanquan iron deposit.The results show that the Baishan-quan iron orebody is stratiform,and the iron ores show disseminated and banded structure,mainly composing of magnetite,quartz and iron silicate minerals,with minor plagioclase and apatite.Magnetite is relatively pure,mainly composed of TFeO,and the contents of other major oxides are less than 0.1％,This suggests that it is of chemical sedimentary origin,but significantly affected by submarine volcanism.EPMA analysis shows that horn-blende belongs to actinolite,magnesium hornblende and tremolite,biotite belongs to magnesium biotite and pla-gioclase is mainly albite.These minerals are of metamorphic origin,suggesting that the Baishanquan iron ore has experienced greenschist facies metamorphism.According to the Hbl-Pl geothermometer and biotite Ti geother-mometer(calculated according to the average value),the metamorphic temperature is 412～488℃.εNd(t)values of iron ores range from-2.44 to-6.11,which suggest that iron is derived from submarine hydrothermal fluid,but mixed with clastic materials.Through detailed comparison with Precambrian iron formations(IFs)and submarine volcanic-hosted type iron ores,we proposed that the Baishanquan iron ores share the same volcanic system with other types of submarine volcanic-hosted iron ores,which may be the Phanerozoic analogue of Precambrian IFs.This study further establishes the relationship between the Precambrian IFs and submarine volcanic-hosted type iron ores.
关键词
Nd同位素/火山作用铁矿/海相火山岩型铁矿/铁建造/东天山
Key words
Nd isotope/volcanism iron deposit/submarine volcanic-hosted iron ores/iron formations/eastern Tianshan
维普
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