| 海相火山-沉积建造铁铜矿床类型及地质特征 |
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| 关键词:Fe-Cu deposit zonation of deposit mineralization setting volcano-ex-halative genesis |
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| Types and Characteristics of Fe-Cu Deposits in Marine Volcano-Sedimentary Formation |
| Fe-Cu deposits are one of major geologic-industrial types. In theis paper, the term Fe-Cu deposit is refered as volcanic-exhalative deposits occur in volcano-sedi-mentary seies.
The recent studies and examples show that Cu deposits are commonly associated with Fe deposits in the world.Fe-Cu deposits are not bound by the time, which range in age from Early Proterozoic to Carboniferous. These deposits occur within lavas, pyroclastic rocks and subvolcnaic rocks or contact between the sub-volcnaic rocks and sedimentray rocks. The recently discovered Fe-Cu deposits such as Jingtieshan of Gansu occured in Pro-terozoic basement metamorphic series are indicated that the Proterozoic is a major mineral-ization episodes in Western Part of North Qilianshan, and break te past framework which is shortage of copper deposits in the area.
Jingtieshan iron mining district consists mainly of Heigou and Huashugou deposits, and was discovered in 50's. In mid-80's, the Cu orebodies were discovered below the iron horizon. The reginal strata belong to a flyshcoid formation consisting of interbeded slight-ly metamorphic shallow marine sediment and deep marine sediment. The deposits are host-ed within Proterozoic Jingtieshan Group. The lower part of the Group comprises interme-diate-basic volcanic rocks and acidic rocks with minor sandslates. The mid-upper part con-sists of sand-mud slates in tercalated with siliceous rock, limestone and pyroclastic rocks, which contain Cu and Fe orebodies.
Iron orebody exhibits stratiform and coincides with the occurence of wall rocks.Iron ores consist of banded siderite, hematite (including specularite), jasper, barite with minor pyurite, chalcopyrite quartz, sericite and chlorite. Copper beds underlie iron orebody and are dominated by pyrite, chalcopyrite, whith subordinate chalcocite and minor tetrahedrite, bornite, covellite and malachite. There are some massive sulfide pods besides the dissemi-nated orbodies. The massive sulfide ores are compared with the typical massive sulfide noes.
Chenjiamiao Fe-Cu deposit is located in the basement uplefted ancient massif. The hsot rock series belong to metamorphic volcano-sedimentary formation. Iron orebodies ex-hibit sharp contact with the enclosing rocks, btu copper orbodies and pyrite orebodies show transitional relation with wall rocks. From top to bottom, the deposit shows the zonation wit magnetite-hematite to magnetite to pyrite to chalcomyrite ores.
Tongchang Fe-Cu deposit occurs in contacts between Poroterozoic Bikou Group meta-morphic volcano-sedimentary series and quartz diorite bodies. Iron orebodies are dominat-ed by magnetite with minor pyrite, pyrrhotite and chalcopyrite. Cu orebodies underlying Fe orebodies, contain mainly chalcopyrite, with subordinate pyrite and pyrrhotite.
The present writers consider that the deposits are formed by volcanic-exhalative pre-cipitation in analogy with volcanogenic massive sulfide deposits on the basis of the follow-ing facts: (1) The ore horizon conicides with a volcano-sedimentary interface. (2)The de-posit shows a stratiform zone overlying a stockowrk or stringer zone.(3)The deposit dis-plays the vertical zonation from a Cu-rich base to a Fe-rich top.(4)Alternation is mainly confined to the footwall rocks. |
| Yu Pusheng,Wu Jieren.1996.Types and Characteristics of Fe-Cu Deposits in Marine Volcano-Sedimentary Formation[J].Acta Geoscientica Sinica,17(z1):50-56. |
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