胶东大庄子构造角砾岩型金矿床地质地球化学特征及成矿流体来源探讨

Geological and geochemical characteristics and origin of ore-forming fluids in Dazhuangzi tectonic breccia type gold deposit,eastern Shandong Peninsula

大庄子金矿受胶莱盆地边缘发育于荆山群内的顺层状低角度断裂带控制,以大理岩质碎裂岩及角砾岩等张性构造岩胶结物发生矿化为特点。容矿岩石与成矿流体具有强烈的物质交换,矿化与SiO2、Fe2O3、Na2O及As、Cd、Hg、Cu、Pb等元素关系密切。矿石具有富集轻稀土元素、铕正异常的特征,其稀土元素特征和基性脉岩具有一定的相似性,又具有原岩的一些特点,表明容矿岩石受到了深部成矿流体的影响。硫、铅、碳-氧及氢-氧等同位素地球化学及流体包裹体研究显示,成矿物质较复杂,成矿流体来源于地壳深部或上地幔的岩浆热液,在成矿作用中,萃取了部分围岩,并与围岩发生了强烈反应。

The Dazhuangzi gold deposit is controlled by a low-angle fault zone along the marble strata of the Jingshan Group in the margin of the Jiaolai Basin.Gold mineralization occurs in the cements of the siliceous marble tectonic breccias and cataclastic rocks within the ore-controlling fault structure.Geochemical characteristics fully imply strong exchange of materials between the host rocks and the ore-forming fluid.Gold mineralization is closely related to SiO2,Fe2O3, Na2O and such elements as As,Cd,Hg,Cu and Pb.Ores assume LREE enrichment and Eu positive anomaly.REE values have some similarities between the mafic dikes and show ore inheriting characteristics of the protolith.These features suggest that the host rocks were affected by deep fluid.S,Pb,C-O and H-O isotopes and fluid inclusions indicate that ore-forming materials were derived from the upper mantle and the lower crust,which exhibit features of multiple sources.Ore-forming solutions originated mainly from magmatic water and were accompanied by the participation of meteoric water.The ore-forming solutions there experienced strong deep fluid-wall rock interaction during the mineralization.The deep fluid extracted partial materials from the wall rocks to participate in mineral fluid circulation.