新疆北部构造特征与火山岩型铀矿成矿规律

Tectonic Characteristics and Metallogenic Regularity of Volcanic Rock Type Uranium Deposit in Northern Xinjiang

结合北天山、西准噶尔、东准噶尔、阿尔泰等地区火山岩型铀成矿区的地质工作成果,讨论了新疆北部构造断裂特征和侵入岩分布特征,通过进行火山岩型铀矿成矿条件、控矿条件对比分析,讨论了与火山岩型铀成矿有关的地质构造特征对火山岩型铀矿化的控制作用。研究表明:(1)火山岩型铀矿主要产出于岛弧带、裂陷槽和残余洋盆中,部分弧后盆地、弧前盆地、外弧带、弧间裂陷盆地也有产出,含矿主岩时代由晚志留世延续至古近纪,以泥盆纪、石炭纪、二叠纪火山岩铀矿化最为发育,其中二叠纪火山岩为铀成矿的主体,石炭纪—二叠纪火山岩与潜火山岩、浅成侵入岩的叠加为富矿形成的主要因素;(2)铀矿化受区域断裂带和火山机构的联合控制,两者的复合部位为铀成矿的主要地段,多期次、多旋回的火山活动为铀成矿的基础,断裂(特别是张性断裂)叠加及引起的蚀变为铀成矿的前提,中—酸性火山岩中叠加多期中—基性热液活动、中—基性火山岩中叠加中—酸性热液活动为形成富大铀矿体的关键因素;(3)赋存铀矿化的构造通常为区域大型断裂侧翼的次级断裂及其破碎带,有多方向、多期次破碎带叠加,以张性构造为主或处于压性构造旁侧的局部张性环境中,铀矿体赋存于更次一级的裂隙和节理中。上述分析对于进一步分析该区火山岩型铀矿成矿条件及开展铀矿找矿勘探工作有一定的借鉴价值。

Based on the geological working results of the volcanic rock type uranium metallogenic area of the Northern Tianshan, West Junggar, East Junggar, Altai and other regions, the tectonic fracture characteristics and intrusive rock distribution characteristics in Northern Xinjiang are discussed, by con- ducting comparison and analysis of metallogenic conditions and ore-controlling conditions, the controlling action of geological structural characteristics related to volcanic rock type uranium metallogenic to volcanic rock type uranium mineralization is analyzed in depth. The study results show that：①the volcanic rock type uranium deposit is mainly occurred in island arc belt, chasmic trough and residual ocean basin, part of the uranium deposits are occurred in the part of the back-arc basin, fore-arc basin, outer arc zone and crack basin between arcs, the ore-bearing main area era is from late Silurian epoch to Paleogene, the vol- canic uranium mineralization of Devonian, Carboniferous and Permian are mostly developed, Permian vol- canic rocks is the main body of uranium mineralization, the superposition of the volcanic rock and subvol- canic rock and hypabyssal intrusive rocks of Carboniferous-Permian is the main factor of the formation of rich uranium deposits;②the uranium mineralization are controlled by regional faults and volcanic institu tions jointly, the composite parts of them is the main section of uranium mineralization, the multi-stages and multi-cycle volcanic activities are the basic conditions of uranium mineralization, the superposition of fractures （ especially for tensile fractures） and the alteration caused by them are the premise conditions of uranium metallogenic, the multi-stages medium-basic hydrothermal activities superposed in medium-acid volcanic rock and the medium-acid hydrothermal activities superposed in medium-basic volcanic rock are the key influences factors of the formation of large and rich uranium ore-bodies;③the structures that the uranium mineralized is occurred are the wing secondary fractures and fracture zones of regional large faults, the above faults are superposed by multi-directions and multi-stages fracture zones, the tectonic en- vironment of uranium mineralization is mainly for tensional tectonic or the local tensional environment near the compression tectonic, the uranium ore-bodies are occurred in the inferior cracks and joints. The above analysis results can provide some reference for analyzing the metallogenic conditions of uranium de- posit and conducting prospecting and exploration work of the uranium deposits in the area.