安徽新桥块状硫化物矿床地球化学特征

GEOCHEMICAL FEATURES OF THE XINQIAO MASSIVE SULFIDE DEPOSIT IN ANHUI PROVINCE

新桥块状硫化物矿床发育双层结构,地球化学特征也呈现出明显的“二元性”和垂向变化。下部网脉状蚀变矿化岩石SiO2、Al2O3、K2O和Na2O等含量较高,上部层状块状矿石和含矿岩石Fe2O3、FeO、CaO、MgO及SiO2等明显富集。稀土含量相对较低,上部层状块状矿层平均值为10.73×10-6,下部通道相蚀变矿化岩石平均值为126.1×10-6。重晶石δ34S值为+16.2‰,硬石膏δ34S值为+11.2‰,黄铁矿δ34S值为+1.5‰～+4.7‰。含矿硅质岩δ18O为+12.0‰～+13.9‰,下部通道相含黄铁矿石英脉δ18O值为+13.3‰～+18.6‰。自下部网脉状矿化到上部层状块状矿层,从粗晶细晶到变胶状胶状黄铁矿,δ34S、δ18O和δ30Si值逐渐降低,206Pb/204Pb、207Pb/204Pb和208Pb/204Pb平均值逐渐增高。

The Xinqiao massive sulfide deposit had a two-layer texture, whose geochemical features were presented by a “ binary ability”and a vertical change. The contents of SiOz ,Al2O3 ,TiO2 , K2O and Na2O were higher in the lower altered and mineralized rocks, while the Fe2O3 ,FeO, CaO,MgO and SiO2 were richer in the upper stratiform and massive ore beds and ore-bearing rocks. The REE contents, relatively enriched in HRR, were lower, with the average REE of the upper stratiform and massive ore beds being 10.73×10^-6, and that of the lower channelway phase altered and mineralized rocks being 126.1×10^-6, respectively. The δ^34S value of barite was 16.2‰, that of anhydrite was ＋ 11.2‰, the δ^34S values of pyrite ranged from ＋ 1.5‰ to ＋ 4.7‰. The δ^18O values of ore-bearing silicalite ranged from ＋ 12. 3‰ to ＋ 13.9‰, those of pyrite-bearing quartz vein in the lower channelway phase from ＋ 13.3‰ to ＋ 18. 6‰. The average δ^34S, δ^18O and δ^30 Si decreased progressively with ^206Pb/^204 Pb, ^207Pb/^204Pb and ^208Pb/^204Pb increasing gradually from the lower stockwork mineralization to the upper stratiform massive ore bed, following descending crystallization of coarse-fine-metacollo-form-colloform pyrite.