柞水银洞子银铅多金属矿床地球化学特征、成矿模式及找矿预测

柞水银洞子银铅多金属矿床岩、矿石稀土总量变化较大,稀土分配模式总体均为右倾型,富集轻稀土,重稀土分异不明显,重晶石脉、矿石皆呈负铈异常,铈亏损这一特征反映了成矿过程中的海底热水溶液作用。该矿床硫同位素组成变化范围大,且以重硫为主,主矿体含矿溶液总硫值与泥盆纪海水基本一致,反映硫源来自半封闭还原条件的泥盆纪海水。铅同位素分析表明矿床铅来源主要为深源,与海底火山活动存在一定关系。已有的同位素年龄数据和研究分析表明该矿床形成于中泥盆世,成矿作用与热水沉积成岩作用同时发生,相关证据也证明热水沉积作用是主要的成矿方式。研究认为,该矿床属热水喷流沉积成因,银洞子银铅多金属矿床的形成可以分为海底喷气沉积成矿和改造成矿期两个成矿期,前者是本矿床最主要的成矿期,形成了热水沉积岩(重晶石岩、硅质岩等)以及细粒金属矿物,建立了成矿模式。结合区内地质勘查工作,提出了5条找矿标志,并通过资料研究分析,从矿区外围找矿和新区找矿两个方面进行找矿预测,指出了8片预测靶区。这为深化认识柞水-山阳沉积盆地内成矿机理和指导找矿指明了方向。

Geochemical Characteristics Metallogenetic Model and Exploration Predicting of Yindongzi Ag Pb Polymetallic Deposit Zhashui County Shaanxi Province China

The REE content of rocks and ores range widely in Yindongzi Ag-Pb polymetallic deposit, REE distribution patterns dip to right, enrich LREE, and differentiates pooly for HREE, barite vein and ores have negative Ce anomaly, the depletion of Ce imply submarine hydrothermal process. The composition of S isotope has wide range in Yindongzi Ag-Pb polymetallic deposit, heavy S isotope predominates, δ34S value of main orebody ore-bear solution is similar with that of Devonian sea water, it indicate that sulfur derived form Devonian sea water in semi-enclosed reducing condition. Pb isotope analysis suggested that Pb mainly came from depth, related with volcanic activity in sea floor. It showed that the deposit formed in Middle Devonian era, and metallogensis happened simultaneously with hydrothermal sedimentary rock-forming process by isotopic date references and geologic study. It proved that hydrothermal sedimentary process was main ore-forming means by research. It proposed that the formation of this deposit divided into two stages, included submarine exhalation sedimentary ore-forming and reformed metallogensis stages, the former dominated and formed hydrothermal sedimentary rocks (baritic rock and silica rock, and so on) and fine metal minerals. The metallogenic model of this deposit is built, too. Combined with geological exploration work in Zha-Shan region, it summed up five prospecting criteria and took exploration prediction in surrounding ore field and new region, and delineated eight predicting targets by studying and analyzing relative references. These conclusion pointed direction for probing further mineralization mechanics and exploring in Zhashui-Shanyang sedimentary basin.