Stratigraphic Sequence And Mineralization Process Of The Huo Geqi No.2 Deposit Of Langshan District In Inner Mongolia

The Huogeqi copper-polymetallic deposit is one of the representative deposits in langshan metallogenic belt which is located in the western segment of the northern margin of North China Craton.Different viewpoints on ore genesis and definite ore-forming process had been put forward in previous studies.This paper mainly focuses on the scientific problem of stratigraphic sequence of No.2 iron deposit of Huogeqi ore field.Firstly,based on the fundamental sedimentary and metamorphic characteristics of langshan group,1:10000 geological mapping of mine district and surrounding area were carried out,and distinct contact metamorphism characteristics was found in the contact zone,such as the andalusite-mica schist,between Langshan group and magmatic rocks,in the southwestern of Huogeqi ore district.Meanwhile,the protolith of the mainly metamorphic rocks outcropped in mining area were restored by petrography and rock geochemistry analysis.The feature of stratigraphic sequence was built by detail drilling lithological columns,petrology and micropetrography studies.Surface profile measure,drilling rock core documentation and open mining pit observation,especially the observation of the contact relationship between different strata and mineralization characteristics,were implemented as supplementary studies.Besides,geochemical data of surrounding rocks and ore minerals were collected for regional background research.Furthermore,Superimposition and mineral transformation were observed in thin section from the cores of No.2 deposit of Huogeqi.Tremolite schist is the mainly country rock of iron ore body,besides phyllite and banded quartzite in some parts of Fe-2 ore body.The floor rocks of No.2 deposit are biotite-quartz-schist or phyllite,and the roof rocks are two-mica quartz schist or muscovite-quartz-schist.The ore-bearing rocks sequence is tremolite schist-carbonaceous slat-lower banded quartzite-tremolite schist-up banded quartzite.While to the east of23 st exploration line,carbonaceous slat and banded quartzite are thin out,the ore-bearing rocks sequence is tremolite schist-phyllite.The major iron ore mineral in No.2 deposit is magnetite which was transformed from siderite or iron-bearing carbonate,formed in the exhalative sedimentation period.Based on the previous work,stratigraphic sequence of No.2 deposit of Huogeqi is established and ore forming procession can be concluded that Huogeqi deposit is an exhalative sedimentary deposit which was reformed by late regional metamorphism and magmatic hydrothermalism.