Study on the Physical and Chemical Conditions of Ore Formation of Hetai Ductile Shear Zone

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Vo1.21 No.1 CHINESE JOURNAL OF GE0CHEMISTRY 2002 

Study on the Physical and Chemical Conditions 

of Ore Formation of Hetai Ductile Shear 

Zone-Hosted Gold Deposit and Discovery 

of Melt Inclusions 

LI ZFLa ̄OLIN(李兆麟) ,ZHAIWEI(翟伟) , ,LIWEN(李文) SHIGUIYONG(石贵勇)”.MqDWENYON ̄UN(文拥军) / 

1I(DepartT ̄nt ofEarth Sciences.Zhongshan Uni ̄rsity,Gwlngzhou 510275, t ) 2)(State bzboratory of Jldetallogenesis.% ing Uni ̄sqty,Na ing 210093.CAina) 

Abstract:The Hera[ductile shear mne-hosted gold deposit o2curs in the deep—seated fault my— Ionite zone of the Sinian Silurian metamorphic rock series In this study there have been discov ered melt inclusions,fluid—melt inclusions and organic inclusions in ore-bearing quartz veins of the ore deposit and mylonite for the first time.The homogenization temperatur ̄of the various types of inclusions are 160℃,180—350℃,530℃and 870℃for organic inclusions,liquid in— clusions.two-phase jmmiscible 1iqnid indusions and mdt inclusions.respectively Ore fl d js categorized the neutralto basic K .Ca2 .Mg2 一Na—s0;一HCO;一CI system The con— tents of trace gases foflow a descending order of H2O>C02>c >(or<) >CO>c2 > >02>N2 The concentrations ofK一,Ca2一,s ,HcO .CI, O and in fluid Lnclusions are related to the contents of gold and the Au/Ag ratios in ores from different 1evels of the gold deposit Th is significanl for deep ore prospecting in the region Daughter minerals in melt inclusions were analyzed msing SEM Quartg,orthoclase,wollastonite and other silicate minerals were identified.They%vere formed in difforent mineral assemblages T s analysis further proves the existence of melt inclusions in ore veins Sedimentary nlet ̄.一 morphic rocks could form silicate melts dunng metamorphic anatexis and dynamic metamor— phism.which possess melt-solution characteristics.Ore formation is related to the multi-stage forrnin ̄g process of silicatemeh andfluid 

Key words:gold dep ̄it;ductile shear zone physical-chemical condition;melt inclusion fluid-melt inclusion;melt and flnid metallogenesis;Hetai 

The Hetai gold deposit is a typical ductile shear zone—type gold deposit,and it occurs in the Hetai ductile shear zone The gold deposit is situated on the northwestern side of the Sihui— 

Wuchuan fault and in the middle of the Guangning—Luoding fault.()re—bearing rocks belong to the 

Sinian Yunkai Group.and show a gradational relation to mylonite,migmatite.and migmatic granite.Orebodies are strictly controlled by the mylonite zone.Well developed in the mining dis— 

trict 3re Caledonian and Hercynian granites. WangHenian(1989)。He Shaoxun(1996)and Ling Jingshen et a1.(1988)conducted alot of re9earch on the characteristics of ore fluids and their relations with gold mineralization of the mylonite—type gold deposits hosted in the ductile shear zone,and thus have laid down a sound 

lSSN l000.9426 This…h pmJ ̄t was supported by the National Nat ̄ai Science Foundation of China(Nos 49873018,49673189)and the State Key Laboratory for Miner ̄]Deposiu ̄Re ̄ch,Na刊ing Universi

ty 维普资讯 http://www.cqvip.com No.1 CHINESE J0URNAL OF GEOCHEMISTRY 41 

foundation for the present studv Previous studies were restricted to the surface or sub—surface samples.for no deep exploitation was undertaken in the mining area at that time.A1l the data ob 

tained could not reflect vertical variations in this ductile shear zone This study is focused on the 

properties of ore fluids and their relations to gold mineralization in the Hetai gold deposit under the action of ductile shearing on the basis of systematic.sampling of orebodies at different levds(0 

—160 m)in the vertical direction,so as to provide new clues to ore prospecting 

Characteristics of Inclusions in Minerals of Ore-Bearing Quartz Veins and in the Mylonite Zone 

On the basis of thin section observations,temperature measurements and the analysis of 

properties of ore fluids for inclusions in mineralized quartz veins and the mylonite zone at 160 irl, 

80 m and 0 m levels,there have been found gaseous—liquid inclusions,fluid—melt inclusions and 

melt inclusions in quartz veins and mylonites at different levels Of the inclusions,fluid—melt in— clusions and melt inclusions have been found for the first time in this region The characteristics of 

the various types of fluid inclusions are described in Table 1. 

Table 1.Characteristics of fluid inclusions in minerals frmn the Hetai gold d 

L:hq山d G_ ;A衄。 h ;C 雌; kⅡ i s: ̄mte;LI.L2: pI】{雠tmmisdble hqdd md a :。r Ⅱ 曲n 

Liquidinclusions(L+G,Ll+L z+G,』 l+L2) 

Liquid inclusions are widespread in auriferous quartz veins at various levels,usually small in 

volume(n×n gm)and commonly associated with melt inclusions,belonging to the products of branch melting of melts Of the different levels.the 160 rn level is one where liquid inclusions are