白云鄂博矿床成矿构造环境分析

白云鄂博矿床是世界著名的超大型铁铌稀土矿床,但因为其成因和形成时代的证据复杂多样,其成因、形成时代及其形成的大地构造环境均有多种不同认识。笔者等曾对赋矿白云岩成因、成矿时代及赋矿地层白云鄂博群的年代这两个关键问题进行了系统的地质、地球化学研究,获得了一系列关键证据,并对前人资料进行了系统地梳理,论证了白云鄂博矿床赋矿白云岩为一大型微晶丘,而微晶丘是热水沉积形成;确定其成矿时代及白云鄂博群的年代均为早古生代。本文进一步报道了在与白云鄂博群下部相当的腮林忽洞群中发现了宏体化石海绵和腹足类,在白云鄂博群中发现了与腮林忽洞群中相同的振动液化脉和振动液化角砾岩。从而笔者等认为,白云鄂博矿床成矿和白云鄂博群的沉积环境是早古生代被动大陆边缘。

Analysis of Ore-Forming Tectonic Settings of the Bayan Obo REE Deposit

The Bayan Obo deposit is a giant Fe-Nb-REE deposit famous in the world. But its genesis, ore-forming time and ore-forming tectonic settings are in dispute because of complex evidences. Having reviewed comprehensively the published data, studied systematically in geology and geochemistry on the two key problems, the genesis of the ore-bearing dolostone and the time of ore-forming of the Bayan Obo deposit and the sedimentation of the Bayan Obo Group, writers derived a series of key evidences, and concluded that the ore-bearing dolostone should be mudmounds, formed by hydrothermal sedimentation, and that the ore-forming time should be Early Paleozoic. In this paper, it is reported that a specimen with a fossil of gastropods and a spongia simultaneously is discovered in the Sailinhudong Group which is correlated to the lower part of the Bayan Obo Group and that carbonates with veins and breccia formed by liquefaction in earthquake are discovered in the Bayan Obo Group in the orefield and adjacent area. So, writers believe that the tectonic settings of sedimentation of the Bayan Obo Group and ore formation of the Bayan Obo deposit should be passive continental margin.