西南地区黑色岩系铀成矿作用及成因模式探讨

Uranium Metallogenesis and Ore Genesis of the Rich-Large Black Rock Series-Type Uranium Deposits in Southwest China

西南地区广泛分布黑色岩系,主要分布于上震旦统—下寒武统、志留系、二叠系和三叠系,其中以上震旦统—下寒武统为主,次为志留系。西南地区黑色岩系中分布有众多的铀矿床、铀矿点和铀矿化点,但铀矿床相对较少。西南地区黑色岩系中典型的矿床有四川若尔盖铀矿床(510)、贵州白马硐铀矿床(504)和广西大新铀矿床(373)。这3个富大铀矿床具有许多相似的特点,与深大断裂有关,也与岩性有关,同时还与岩浆—流体活动有关。西南地区黑色岩系沉积和成岩期初步富集较高含量的铀,是西南地区黑色岩系铀成矿的前奏。后期改造作用和叠加成矿的方式及规模,是西南地区黑色岩系中铀矿大矿和富矿形成的必要条件。西南地区黑色岩系中形成富大铀矿需要经过"三部曲":①前奏:沉积作用形成铀含量高值区(铀异常),②改造:浅源流体改造形成铀的再富集(出现铀矿点、小型或中型矿床),③叠加:深源流体叠加和改造形成富大矿(大型铀矿床)。

Black rock series,which are widely distributed in Southwestern China,Distribute mainly in the upper Sinian-Lower Cambrian,Silurian system,Permian and Triassic.Among them,the major strata is the upper Sinian-lower Cambrian,followed by silurian system.In the black rock series in Southwestern China,there are many typical deposits,with many similar characteristics,has close relationship with the regional deep fault,lithology,magmatism-fluid activity.Numerous Uranium deposits,uranium occurrences and mineralized spots are widely distributed in the black rock series.In the black rock series in Southwestern China,there are many typical deposits,such as Zoige deposit（510） of Sichuan,Baimadong deposit in（504） Guizhou and Daxin deposit（373）of Guangxi.In Southwestern China,higher concentration of uranium in black rock series by sedimentation and Diagenetic stage is the prelude of the black rock series-type uranium deposits.The metallogenic way and scale of reformation and superposition are essential condition for the formation of rich and large deposit in black rock series.A necessary ＂trilogy＂ to the formation of rich and large deposit in Southwestern China： Prelude： High value area of uranium content by sedimentation（uranium mineralized spots and ＂abnormal area＂ of uranium）;Reformation： Second uranium enrichment by the transformation of shallow-sourced fluid（small or medium-sized uranium deposits,uranium occurrences）;Superposition： Formation of rich and large deposit by the superposition of deep-sourced fluid（large-scale uranium deposits）.