纳米比亚金刚石矿床地质特征、矿床成因及找矿模型

Geological characteristics,genesis and prospecting model of diamond deposits in Namibia

纳米比亚金刚石资源丰富且品质优良,矿床类型以次生砂矿为主。文章对前人的大量研究成果进行分析总结,概述了纳米比亚金刚石矿床的区域地质背景,分析了金刚石矿床的地质特征及矿床成因。对纳米比亚金刚石包裹体氩-氩法定年分析发现,80%的包裹体熔蚀年龄〈300Ma,表明大部分纳米比亚碎屑金刚石源自Dwyka期（〈300Ma）以后的金伯利岩;纳米比亚金刚石以橄榄岩型（占比46%）和榴辉岩型（占比41%）为主,其余为二辉岩型或介于橄榄岩型-二辉岩型之间;纳米比亚橄榄岩型金刚石包裹体中石榴石-橄榄石平衡矿物的温度为961~1 223℃,平均（1 107±98）℃;石榴石-斜方辉石的平衡压力多为4.5~6.0GPa。纳米比亚金刚石的找矿有利地区主要为奥兰治河沿线及Oranjemund、卢得立次海岸地区,以次生金刚石砂矿为主。

Namibia is abundant with placer-dominated and quality diamond resources.The authors analyze a lot of previous research results and summarize the regional geological background and characteristics and genesis of the deposits.40 Ar/39 Ar dating data show fusion ages300 Ma for 80% of the inclusions and indicate that most of Namibian detrital diamonds derive from kimberlites of Dwyka（300 Ma）Period.Namibian diamond is mainly peridotitic type（about 46%）and eclogitic type（41%）.The rest is websteritic type and the type between peridotitic and websteritic type.Garnet-olivine equilibrated at temperature 961-1 223 ℃（the average 1 107±98℃）.The equilibrium pressure of garnet-orthopyroxene is generally 4.5-6.0GPa.The best prospecting areas of diamond in Namibia are located mainly along the Orange River and Oranjemund,Luderitz coast area and focused on placer diamond.