柴北缘地区古层间氧化作用及古层间氧化带型铀矿化

The Paleo-interlayer Oxidation and the Paleointerlayer Oxidation Type Uranium Mineralization in the North Area of Qaidam Basin

古层间氧化作用是发育于盆地地质构造演化过程某一阶段的层间氧化作用,由此所形成并被保存的铀矿床被称为"古层间氧化带型铀矿床"。柴北缘地区中、下侏罗统含煤岩系的广泛发育,为古层间氧化带的发育及相应类型铀矿化的形成奠定了基础。早白垩世晚期—古近纪早期的强烈隆升剥蚀是层间氧化带及相应类型铀矿化的发育期。喜山期大规模逆冲推覆构造使原层间氧化带及相应成矿系统遭受强烈改造,保存并形成古层间氧化带和古层间氧化带型铀矿化。古层间氧化带型根据其改造、破坏或保存特点的不同,划分为褶-坳保存型、褶-断保存型和抬升破坏型3种改造亚型。褶-坳保存和褶-断保存2种亚型使得古层间氧化带砂岩型铀矿体能以盲矿形式有效保存,是今后重点找矿方向,如北大滩和冷湖石地26铀矿点。抬升破坏亚型使得古层间氧化带砂岩型铀矿体呈残留状或被剥蚀掉,找矿潜力不大。在总结不同改造亚型地质构造特点和找矿标志的基础上,建立了典型古层间氧化带砂岩型铀矿化成矿模式,并综合分析了其成矿特点。

The paleo-interlayer oxidation is an interlayer oxidation that it formed at a certain stage of basin geological tectonic evolution process. The uranium deposit formed and preserved by this interlayer oxida- tion is called paleo-interlayer oxidation zone type uranium deposit. Middle-lower Jurassic coal-bearing rock series grown widely for paleo-interlayer oxidation forming and relevant type uranium mineralization grow- ing founded basis. Badly uplift denudation at early Cretaceous period late-stage to Palaeogene period early- stage is the formation period of interlayer oxidation zone and relevant type uranium mineralization. Large- scale reverse thrust tectonic causes interlayer oxidation zone and relevant type metallogenic system havebeen altered badly, paleo-interlayer oxidation zone and relevant type uranium mineralization formed an~ preserved. On the basis of its difference of alteration, destroy and conservation, the paleo-interlayer oxida- tion type sandstone-hosted uranium mineralization can be divided into 3 sub-type： folding-downed con~ served, folded-faulting conserved and structure-uplifted destroy sub-type. The folding-downed conservea and folded-faulting conserved two sub-type cause paleo-interlayer oxidation zone sandstone uranium ore body can conserve well for blind ore, which is a key prospecting directiort in future, its example are Beida- tan and Lenghu Shide 26 uranium ore spot. Structure-uplifted destroy sub-type cause paleo-interlayer oxi- dation zone sandstone uranium ore body shows residual state or denuded. On the base of geological struc- tural feature and prospecting criteria of different reformation subtype, and then synthetically analyzed its metallogenc characteristics, the metallogenic model of typical paleo-interlayer oxidation type sandstone- hosed uranium mineralization is established.