广西东平沉积锰矿地球化学特征及成矿物质来源研究

Geochemistry characteristics and the ore material source of Dongping sedimentary manganese deposit in Guangxi

东平沉积锰矿为桂西南的一个中大型锰矿床,大地构造位置处于滇桂地洼系,主要的含矿层位是下三叠统北泗组,沉积相主要为浅海陆棚相。本文通过研究东平锰矿矿床地球化学特征,结合东平锰矿的岩相古地理、含锰岩系、矿石矿物等特征,阐明矿床成因及成矿物质来源。测试结果表明,含锰岩系富集Co、Ni、Ba、Sr、Ti、V等元素,w(Ba)/w(Sr)值在3~7之间,N(Fe)/N(Ti)、N(A1)/N(Al+Fe+Mn)值分别为6~59、0.26~0.66,w(Co)/w(Ni)值在0.4~1之间;w(ΣREE)为36.9×10^(-6)~774.1×10^(-6)之间,w(Nb)/w(Ta)值为9~22(平均13),w(Y)/w(Ho)值为26~35,HREE与LREE分馏不明显;微量元素的图解均显示成矿过程中有海底热液的加入,说明矿床的形成受稳定的大地构造环境与局部海底火山热液喷流活动的控制。

Dongping sedimentary manganese deposit is a medium-large deposit in the southwest Guangxi. Geotectonically it occurs in Diangui Diwa region. Beisi Formation of Lower Triassic series, the shallow sea-shelf sedimentary facies is the major ore-bearing horizon. Based on geochemical characteristics, lithofacies and paleogeographic condition, the ore-bearing sequence and mineralogy is expounded the genesis and ore material source of the deposit. The analytical results：enrichment of Co、Ni、Ba、Sr、Ti、V in the Mn-bearing sequence, w（Ba）/w（Sr）, 3~7, N（Fe）/N（Ti）, 6~59, N（A1）/N（Al＋Fe＋Mn）, 0.26~0.66, w（Co）/w（Ni） 0.4~1; w（ΣREE）, 36.9×10-6~774.1×10-6, w（Nb）/w（Ta）, 9~22（averagely13, w（Y）/w（Ho）, 26~35 without evident fractionation of HREE and LREE show that submarine hydrothermal fluid incorporated in the metallogenic process and the deposit is controlled by stable geotectonic environment and local Sedex condition.