CAJ | 학술논문

西秦岭造山带东段西成矿田内发育一系列泥盆纪的喷流沉积型（SEDEX）铅锌矿床，甘肃徽县洛坝铅锌矿床就是其中的代表型矿床之一。它产于中泥盆统安家岔组焦沟层上部，矿体分布受洛坝背斜和南、北两翼断裂控制，与地层产状基本一致，矿石主要为纹层状、层状、浸染状、块状构造。经过详细的显微构造和 SEM 扫描电镜分析，鉴定出与喷流沉积有关的通道构造、淬火构造等。矿床地球化学分析显示，该矿床赋矿围岩的 Ba、As、Sb、B、Ag、Hg 等喷流沉积指示元素值均较高，且两者均具有 LREE 相对富集、明显的 Eu 正异常和中等 Ce 正异常特征，对比表明，成矿流体中的 REE 主要继承赋矿围岩（硅质岩）。矿床包裹体及硫同位素分析表明：成矿温度为168～350℃，以中、高温为主；早期矿化硫化物的δ34 S 值（平均9．8‰）明显大于晚期矿化硫化物的δ34 S 值（平均5．6‰），说明后期改造作用中有地层硫的参与。综合研究表明，该矿床为热水喷流沉积型铅锌矿床，后期又受到海西期印支期的叠加改造，并确定该矿床为秦岭后造山期板内伸展热水喷流的产物，最后建立了洛坝铅锌矿床热水喷流沉积成矿模式。
서진령조산대동단서성광전내발육일계렬니분기적분류침적형（SEDEX）연자광상，감숙휘현락패연자광상취시기중적대표형광상지일。타산우중니분통안가차조초구층상부，광체분포수락패배사화남、북량익단렬공제，여지층산상기본일치，광석주요위문층상、층상、침염상、괴상구조。경과상세적현미구조화 SEM 소묘전경분석，감정출여분류침적유관적통도구조、쉬화구조등。광상지구화학분석현시，해광상부광위암적 Ba、As、Sb、B、Ag、Hg 등분류침적지시원소치균교고，차량자균구유 LREE 상대부집、명현적 Eu 정이상화중등 Ce 정이상특정，대비표명，성광류체중적 REE 주요계승부광위암（규질암）。광상포과체급류동위소분석표명：성광온도위168～350℃，이중、고온위주；조기광화류화물적δ34 S 치（평균9．8‰）명현대우만기광화류화물적δ34 S 치（평균5．6‰），설명후기개조작용중유지층류적삼여。종합연구표명，해광상위열수분류침적형연자광상，후기우수도해서기인지기적첩가개조，병학정해광상위진령후조산기판내신전열수분류적산물，최후건립료락패연자광상열수분류침적성광모식。
A series of Devonian SEDEX deposits occur at the Xicheng ore field in east section of the Western Qinling orogenic belt,and the Luoba Pb Zn ore deposit in Hui County of Gansu Province is a typical one.The Luoba deposit is hosted in the upper section of the Jiaogou Layer in the Anjiacha Formation (Middle Devonian period)and controlled by Luoba anticline and fractures developing in its north and south wings.The ore bodies are accordant with the hosting strata in occurrence.The predominately ore structures include lamellar,layered,disseminated and massive structures.Channel and quenching structures,commonly related to SEDEX,are identified by the analysis of microstructure and SEM.Ba,As,Sb,B,Ag and Hg contents in the ore and wall-rock are relatively high and LREE are enriched.Obvious positiveδEu and medium positiveδCe imply that the REE in the ores inherited from the wall-rocks (chert).Fluid inclusions studies show that the mineralizing temperature ranged from 168 ℃ to 350 ℃.Theδ34 S values of the early sulfides (averaged at 9.8‰)are significantly higher than those of the late ones (averaged at 5.6‰),which indicates that the strata sulfur was involved in the late reconstruction processes.Authors suggest that the Luoba Pb Zn ore deposit belong to the SEDEX type,and be reformed by Late Hercynian-Indosinian metamorphism.It was derived from the hydrothermal fluid at the later Qinling orogenic intraplate extension stage.A metallogenic model for the Luoba SEDEX lead-zinc deposit is also given in this paper.