相山花岗斑岩和中基性脉岩特征及其与铀成矿关系

发布时间：2018-07-09 15:23

本文选题：脉岩侵入作用系列 + 花岗斑岩　；参考：《核工业北京地质研究院》2015年硕士论文

【摘要】：相山铀矿田是我国迄今为止发现的最大的火山岩型铀矿田。矿田内产出的花岗斑岩、中基性脉岩与铀成矿存在较为密切的时空关系,但关于这类岩石的地质特征、形成机制及其与铀成矿等问题缺乏系统研究。本文初步查明了花岗斑岩、中基性脉岩分布范围、规模、产状特征,系统开展岩石学和矿物学、岩石地球化学、同位素年代学和Sr-Nd同位素特征等研究,结合矿床地质特征、矿床地球化学特征等,探讨了研究区花岗斑岩、中基性脉岩与铀成矿作用的时空及成因关系,取得了以下几点认识:(1)在前人工作基础上,依据岩浆岩的产状、成岩年龄及成因,将相山火山盆地岩浆岩划分为流纹英安岩-碎斑流纹岩-环形花岗斑岩火山作用系列和脉状花岗斑岩-辉绿岩-煌斑岩脉岩侵入作用系列,把花岗斑岩划分为早期沿火山构造侵入的环形花岗斑岩和晚期沿盆地中断裂构造充填形成的脉状花岗斑岩。(2)同位素年代学研究表明,环形花岗斑岩形成于134~132Ma,居隆庵矿区其中一期煌斑岩年龄在87Ma左右。根据盆地内已有的中基性脉岩年龄数据,初步将中基性脉岩划分为128~125Ma、109Ma以及87~85Ma三期。其中,87~85Ma可能代表了火山盆地内中基性脉岩集中侵入的主要时期。(3)岩石地球化学及Sr、Nd同位素组成表明,花岗斑岩属于钾玄质、过铝质S型花岗岩系列,为上地壳物质部分熔融形成,成岩过程中有少量幔源物质参与;中基性脉岩主要为同一地幔源区不同程度部分熔融形成。(4)矿石微量元素研究,S、Pb、C-O、He-Ar多元同位素示踪研究表明,相山矿田铀成矿物质和成矿流体来源于壳幔混合作用体系,幔源流体在铀成矿过程中具有重要意义。(5)花岗斑岩、中基性脉岩与铀成矿时空关系研究表明,花岗斑岩、中基性脉岩在空间上与铀矿关系密切,花岗斑岩、中基性脉岩可作为铀成矿重要识别标志。脉状花岗斑岩、中基性脉岩侵入年龄(85~128Ma)与矿田内两期成矿年龄较为相近,这与该时期我国南方大规模火山侵入活动后,地壳区域伸展拉张引起的深源断裂活动时间基本一致。在白垩纪强烈伸展拉张构造环境下,深源流体携带部分成矿物质并交代萃取富铀地壳形成富铀热液,并上升迁移至浅部,与火山盆地花岗斑岩、中基性脉岩定位于同构造中,在适宜的温度、压力等物理化学条件下,含铀热液沉淀、富集成矿。
[Abstract]:Xiangshan uranium ore field is the largest volcanic type uranium deposit discovered in China so far. There is a close temporal and spatial relationship between granitic porphyry and uranium mineralization in the ore field, but there is no systematic study on the geological characteristics, formation mechanism and uranium mineralization of these rocks. In this paper, the distribution range, scale, occurrence characteristics of granitic porphyry and intermediate basic dike rocks have been preliminarily identified. Systematic studies on petrology and mineralogy, rock geochemistry, isotopic chronology and Sr-Nd isotopic characteristics have been carried out, combined with geological characteristics of the deposit. Based on the geochemical characteristics of ore deposits, the spatio-temporal and genetic relationships between granitic porphyry, intermediate basic dike rocks and uranium mineralization in the study area are discussed. The results are as follows: (1) on the basis of previous work, according to the occurrence of magmatic rocks, diagenetic age and genesis, The magmatic rocks in the Xiangshan volcanic basin are divided into the series of fluid-striated dolomite, plaster rhyolite and annular granitic porphyry volcanism and the series of vein granitic porphyry diabase lamprophyry dike intrusions. Granitic porphyry is divided into annular granitic porphyry intrusive along volcanic structure and vein granitic porphyry formed in late period along the middle fault structure of basin. (2) Isotope chronological study shows that, The annular granitic porphyry was formed in 134N 132Ma.The first stage lamprophyre age of Julongan mine is about 87Ma. According to the existing age data of mesobitic dikes in the basin, the middle basic-dike rocks are preliminarily divided into three stages: 128- 125Ma-109Ma and 87-85Ma. Among them, Yi-87-85 Ma may represent the main period of concentrated intrusion of meso-basic-dike rocks in the volcanic basin. (3) the petrogeochemistry and Sr-nd-isotopic composition indicate that granitic porphyry belongs to the kalitic and peraluminous S-type granite series, and that the granitic porphyry belongs to the K-type, peraluminous S-type granite series. In the process of diagenesis, a small amount of mantle-derived materials are involved in the diagenetic process, and the intermediate basic dike rocks are mainly formed by partial melting in the same mantle source. (4) the trace element study of ores shows that the trace elements of ore are SbPbCC-OOHe-Ar multicomponent isotopic tracer. Uranium ore-forming materials and ore-forming fluids in Xiangshan Orefield are derived from the mixed crust and mantle systems, and mantle-derived fluids play an important role in the uranium mineralization process. (5) the temporal and spatial relationship between granitic porphyry, intermediate basic dike rocks and uranium mineralization shows that granitic porphyry, and granitic porphyry, Middle-base dikes are closely related to uranium deposits in space. Granitic porphyry and medium-basic dikes can be used as important indicators for uranium mineralization. The intrusive age of the vein granitic porphyry (85 ~ 128 Ma) is similar to that of the two stages in the ore field, which is consistent with the time of the deep fault activity caused by the extensional extension of the crust after the large-scale volcanic intrusions in the southern part of China during this period. In the Cretaceous strongly extensional tectonic environment, the deep source fluids carried some ore-forming materials and metasomatically extracted the uranium-rich crust to form uranium-rich hydrothermal solution, and migrated upward to the shallow, which was located in the same structure as the granitic porphyry in the volcanic basin and the middle basic dike rock. Under the suitable physical and chemical conditions, such as temperature and pressure, uranium-bearing hydrothermal precipitates and enriched ore-forming.
【学位授予单位】：核工业北京地质研究院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.14;P588.1

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