Geochemical Characteristics And Genesis Of The Tonglushan Cu-Fe Deposit In Hubei Province

Located in the southeastern Hubei metallographic province of the Middle-LowerYangtze River Fe-Cu metallogenic belt,the Tonglushan Cu-Fe deposit is a typicalskarn Cu-Fe deposit in the southeastern Hubei province. The ore bodies,in thelenticular forms, occur in the contact zone between the marble of4th-7th M embersof the Lower Triassic Daye Group. This paper mainly studied S,H,O,C,Pb isotopiccompositions, geochemistry of rare earth elements and trace elements, analyzed theindicative meaning of these isotopes to the ore fluids and the sources of theore-forming materials and intrusions to to provide basis for study of deposit genesis.The results show that Tonglushan rock body has the characteristics of highsilicon, low magnesium, rich alkali (mainly sodium). The REE distribution curves areof right inclination which indicates they are relative enrichment of LREE, relativedepletion of HREE. The rocks are highly enriched in the large ion lithophile elements(LILE) such as Rb, Ba, Th, U, K, Sr but strongly depleted in the high field strengthelements(HFSE)such as Nb,Ta and Ti.The magmatic rock,skarn,ore have similar REE distribution curves that they areall relative enrichment of LREE and the LREE part of the curves is steeper，whilethe HREE part is flatter shows that deposit has a close relation with the magma.Ore fluids were most likely composed of magmatic water at the earlyore-forming stage and mixed with much meteoric water at the late ore-forming stage;Sulfur and carbon isotopic data suggest that the ore forming materials were mainlyderived from the deep magma and the carbon derived subordinately from thedissolution of wall rocks or the mantle. The Pb isotopic composition of ore sulfidesare stable and they are ordinary common lead. Ore lead derived from mantle magmawhich was subjected to the hybridization of crust materials in the course of intrudedupward.The U-Th-Pb harmonic age of the rock body is141±1.1Ma,measured byLA-ICP-MS.The data indicate that the age of Tonglushan rock body are almostidentical to the mineralization age （137～140Ma） from previous researches. Tonglushan deposit has a close relation with the rock body in space time and genesis.