【作者】 刘章月；

【导师】 秦明宽；

【作者基本信息】 核工业北京地质研究院 ， 矿产普查与勘探， 2008， 硕士

【摘要】 本论文针对沙瓦布齐地区铀矿地质研究程度较低和铀成矿受构造活动影响较大等特点,从塔北中新生代构造背景、天山隆升期次、铀成矿基本特征及成矿时代等方面入手,以构造演化为主线,对本区构造特征及其与铀矿化关系进行探讨,最后提出沙瓦布齐地区构造—铀成矿模式。塔里木盆地北缘现今地表由西向东分为柯坪冲断带、乌什冲断带和库车冲断带,各带具不同的展布方向和构造特征。而这三个构造带的形成和演化与塔北的断裂分布密切相关。整个断裂体系可分为两组,一组为具逆冲性质的东西—近北东东向断裂系统;另一组为北西向断裂系统,具走滑性质。前者控制构造的南北分带性,在塔北地区形成隆凹相间的构造格局:后者控制塔北东西向构造格局,使塔北东西部构造变形程度产生明显的变化。而这些断裂系统均为塔北南北向挤压构造应力场作用下的产物。研究表明喜山期构造应力场最强,对塔北的影响最大。通过对塔里克、沙瓦布齐和巴什布拉克地区磷灰石裂变径迹年龄的测试与隆升热历史的模拟,并结合前人的数据,得出天山中新生代经历了四个阶段的隆升,即:第一阶段隆升:135～145Ma(侏罗纪末);第二阶段隆升:75～40Ma(白垩纪末—始新世末);第三阶段隆升:25～10Ma(中新世);第四阶段隆升:4.0Ma～现今(上新世末—现今)。计算出三个地区不同阶段的隆升速率,其中沙瓦布齐地区山体隆升速率最大,为889.7～991.4m/Ma。本区于上新世末进入新构造运动强烈变形阶段。由于存在基底卷入式断裂,将水平挤压构造应变量转换为垂直隆升量,本区铀矿体遭受抬升、剥失,并接受地表水的改造;另一方面,矿床南部山体的隆升,使铀矿体免遭进一步剥失,具有保矿作用。侏罗纪,塔北地区进入应力松驰的断陷盆地演化阶段,在沙瓦布齐地区沉积了一套近山前的含煤粗碎屑岩有利建造。根据沉积旋回和沉积相特征,将含矿目的层中下侏罗统铁米尔苏组分为两个岩性段,四个岩性亚段。铀矿体主要产于该组上段辫状河三角洲相砂体中。铀矿体产状陡立,呈板状、层状和透镜体状。铀主要以铀矿物、吸附态铀及类质同像(含量甚微)三种方式存在。赋矿砂体中有机质和S的含量均较高,且两者具正相关性。从Fe元素的变化特征可知铀矿体在后期遭受了地表水的淋滤。本区铀成矿伴随Cd、Mo和Re元素的富集,具有典型层间氧化带砂岩型铀矿化微量元素富集的一般规律。经稀土元素配分曲线的对比和花岗岩体隆升热历史的模拟,发现本区西北部早二叠世火山岩系既是侏罗系的物源,也与下寒武统碳硅泥岩系一同为铀成矿提供铀源。利用微粒铀矿石U—Pb定年技术,测出本区主要一期铀矿化发生于39.0Ma,即始新世。此时,本区侏罗系有利建造在山前断裂的影响下发生掀斜:古气候条件已从温湿转变为干热;天山地区早二叠世火山岩和下寒武统碳硅泥岩系于古新世开始较大幅度的隆升,并为铀成矿提供外部铀源。在诸多有利因素的控制下形成了砂岩型铀矿化。最后,在综合分析本区及天山构造演化与铀成矿特点的基础上,建立了沙瓦布齐地区构造—铀成矿模式。更多还原

【Abstract】 Due to characteristics of low degree of uranium geological research and sandstone type uranium mineralization, which controlled by tectonic in Shawabuqi area, this dissertation discuss structural characteristics and the relationship between tectonic and uranium mineralization, finally propose tectonic-metallogenetic model of sandstone type uranium deposit in Shawabuqi area, mainly by study on tectonic evolution, Mesozoic and Cenozoic regional tectonic background of northern Trim Basin, uplifting epochs of Tianshan, basic characteristics of uranium ore-formation and the age of uranium ore-formation.From the west to east, the northern peripheral earth’s surface of Tarim Basin contain Keping thrust belt, Wushi thrust belt, and Kuqa thrust belt, each has its own orientation and structural characteristics. But the formation and evolution of these thrust belts are related with distribution of faults. All faults are divided into two group, one group has thrust characteristic and its orientation is east-west or nearly north-east, it controls south-north distribution of folds, as a result, alternate appearances of uplift and depression in northern periphery of Tarim Basin, the other has strike-slip characteristic and its orientation is north-west, it controls east-west structural pattern, as a result, western structural deformation characteristics are different form eastern. The two group faults systems were formed in the condition of south-east compressed tectonic stress, result of research indicates that Himalayan epoch tectonic stress field made great influence on northern periphery of Tarim Basin.Apatite fission tracks of the samples from Talike, Shawabuqi and Bashibulake in southern Tianshan area, were measured and analyzed. Using the measurement data of whole Tianshan area, four uplifting epochs, which are 135～145Ma(latest Jurassic); 75～40Ma(latest Cretaceous-latest Eocene); 25～10Ma(Miocene); 4.0Ma～0(latest Pliocene-now), were founded in southern Tianshan aera, and thermal uplifting history were simulated in these three areas, we calculate uplifting speed of each epoch from the simulated map, find that Shawabuqi area has highest uplifting speed of 889.7～991.4m/Ma.Shawabuqi area entered into the evolution stage of Neotectonic activity in late Pliocene. Vertical uplift is main structural pattern in this area, because of existence of basement thrust fault. Therefore, the uranium deposit suffered from being uplifted, eroded and Epigenetic reworked by shallow water; on the other hand, the southern uplifting mountain of uranium deposit, which make the uranium bodies free of further erosion, is benefit for conservation of uranium bodies.Northern periphery of Tarim Basin enter into evolution stage of rift basin in Jurassic, coal-bearing coarse clastic rocks formation, which is benefit for interlayer oxidation zone sandstone type uranium mineralization, were deposited in Shawabuqi area. Based on analysis of cycles and facies of sedimentation, the Tiemiersu formation are divided into two lithology sects, and four lithology sub-sects. Uranium mineralization formed in sand bodies of braid delta facies in upper sect of this formation. Steep shapes of ore bodies show plank type, layer type and lentoid type. The most part of uranium element are absorbed, and the coffinite is primary uranium mineral, there are little isomorphism uranium.High content of Toc and S were measured in bearing ore sand bodies, they have positive correlation. The contents variety of Fe element in the different stone show that the uranium bodies undergone eluviation, variety of Cd, Mo and Re elements on drill show the distribution characteristic of rare elements in model interlayer oxidation zone sandstone type uranium mineralization.Using the REE distribution patterns of the rocks and thermal history simulation of granite uplift in Shawabuqi area, we find that the early Permian lava clastic rocks not only provide sediment, but also provide uranium element for Jurassic series with lower Cambrian.bedded chert.Main uranium ore-formation age of 39.0Ma is measured by "U-Pb" Dating Method. We find that, Jurassic benefit series were tilted by the great fault of Tianshan frontier, Paleo-climate turned to be dry and hot from warm and wet, early Permian lava clastic rocks and lower Cambrian.bedded chert, which have high uranium content, had uplifted already, uranium ore-formation occurred in Eocene, by the influence of all above factors.At last, according to analysis of tectonic evolution of Tianshan and uranium ore-formation, the author propose the tectonic-uranium ore-formation model of Shawabuqi area.更多还原