摘要
Bigrlyi铀矿床位于澳大利亚北领地Ngalia盆地北缘,主要由A2/A3矿体、A4矿体、A7矿体、A15矿体等四个矿体组成,是一个典型的砂岩型铀矿床。Ngalia盆地为一个北陡南缓的不对称型山间残留盆地,盆地盖层主要由上元古界(~850 Ma)和古生界陆相沉积物组成,受晚奥陶世~晚石炭世Alice Springs造山运动(ASO)的影响,盆地内泥盆~石炭系Mount Eclipse组砂岩与下伏所有地层均呈不整合接触,是盆地内砂岩型铀成矿的主要含矿层位。Mount Eclipse组砂岩沉积于前陆盆地环境,发育河流、(扇)三角洲和湖泊沉积体系,含矿岩石主要为位于C单元的灰色长石砂岩及杂砂岩,铀矿物主要为沥青铀矿和铀石,脉石矿物为石英、钾长石及少量的黏土矿物。盆地砂岩型铀成矿作用主要受铀源、沉积、构造等因素的控制,其中在沉积成岩期的构造挤压与基底抬升不仅沉积了一套有利的含矿岩系,而且在该岩层内形成了铀的初始预富集及局部铀矿化,在沉积期后的持续挤压作用与逆冲推覆作用下,使得含矿岩系抬升并出露地表,接受来自蚀源区含铀含氧水的渗入,并在氧化还原过渡带内形成似卷状或“板状”富铀矿体。
Bigrlyi Uranium Deposit is located in the northern margin of Ngalia Basin,Northern Territory,Australia and it is a typical sandstone-hosted uranium deposit,which consists mainly of orebodies A2/A3,A4,A7 and A15.The Ngalia Basin is an asymmetrical residual intermontane basin of steep in the north and gentle in the south with the basin cover composed dominantly of Neoproterozoic(-850 Ma)and Palaeozoic terrestrial sedimentary successions.The Mount Eclipse Sandstone of Devonian to Carboniferous age lies unconformably on the underlying stratigraphy in response to the Alice Springs Orogeny(ASO)of Late Ordovician to Late Carboniferous age and it is the primary orebearing horizon for the sandstone-hosted mineralization in the Ngalia Basin.The Mount Eclipse Sandstone is deposited in the environment of foreland basin,where the fluvial,fan delta or delta and lake sedimentary systems are developed.The ore-bearing rocks are composed dominantly of grey arkosic sandstone and greywacke in the unit C of Mount Eclipse Sandstone with uranium minerals consisting dominantly of pitchblende and coffinite and with gauge minerals consisting of quartz,K-feldspar and a small amount of clay minerals.The sandstone-hosted uranium mineralization in the Ngalia Basin is controlled dominantly by the uranium source,depositional environment and structure.The compressional tectonics and basement uplift during the depositional and diagenetic period resulted in the formation of a set of ore-bearing horizons favorable for the uranium mineralization,where uranium is enriched initially and participated locally to form the uranium mineralization.The orebearing horizons are uplifted and exposed at the surface due to the post-depositional continuous compression and thrusting and the uranium and oxygen bearing water from the provenance area infiltrated into these horizons to form roll-like or“tabular”uranium-enriched orebodies in redox transition zones.
作者
董文明
肖树青
马汉峰
邓平
蔡兴琪
DONG Wenming;XIAO Shuqing;MA Hanfeng;DENG Ping;CAI Xingqi(CGN Uranium Resources Company,Beijing 100029,China)
出处
《中国矿业》
2023年第8期180-188,共9页
China Mining Magazine
基金
中央地质勘查基金项目资助(编号:10252B001)。
