本文選題：偉晶狀白崗巖 + 熱液蝕變　； 參考：《東華理工大學(xué)》2015年碩士論文

【摘要】：紅石泉偉晶狀白崗巖型鈾礦床地處甘肅省山丹縣境內(nèi),是我國最為典型的白崗巖型鈾礦床。本區(qū)研究工作主要完成于上世紀八十年代及之前,對與鈾礦化關(guān)系密切的蝕變礦物的研究較為薄弱。本文通過對紅石泉偉晶狀白崗巖型鈾礦床蝕變巖開展系統(tǒng)研究,在厘定其特征基礎(chǔ)上,探討熱液蝕變的形成環(huán)境、物質(zhì)來源及與鈾成礦的關(guān)系。研究發(fā)現(xiàn),該區(qū)鈾礦主要賦存在偉晶狀白崗巖與圍巖交界附近的蝕變帶中。鈾礦化類型可歸納為兩種,一為黑色富含綠泥石化黑云母的黑化礦石;另一種為紅色與鈉長石化、赤鐵礦化關(guān)系密切的紅化礦石。兩者疊加存在,一般在富鈾礦體中心,綠泥石化發(fā)育最強,赤鐵礦化、鈉長石化、鉀長石化次之,絹云母化最次。相較于正常偉晶狀白崗巖,主量元素方面,蝕變巖的Si、K組分減少,TFe、Mg、Mn、Ti組分增多,且Fe價態(tài)發(fā)生了變化。微量元素方面,蝕變巖的U、Th、Pb、Mo、Li、Ti明顯偏高,尤其是U、Mo增高數(shù)倍;Th*均值為5.84,增加明顯,而Sr*均值為0.83,降低明顯;微量元素蛛網(wǎng)圖總體上呈“W”分布模式,大離子親石元素Rb、Th、U、Pb相對富集及高場強元素Ti、P、Cr相對虧損,與正常巖石一致。稀土元素方面,蝕變巖的ΣREE含量(均值為88.412)增加明顯,尤其HREE,在稀土元素分配模式上表現(xiàn)為蝕變巖更趨于水平,負δEu(均值為0.856)異常稍弱些,而δCe值十分接近1,呈較弱的負異常與正常巖性基本一致。成礦元素方面,蝕變巖的U含量增加明顯,Th變化不大。研究表明,本區(qū)熱液蝕變形成于中低溫度、低氧逸度、低PH值及富含鐵鎂質(zhì)組分環(huán)境。蝕變作用一方面能夠改變巖石的物理性質(zhì),形成有利于鈾成礦的空間條件,另一方面又能夠促進鈾的活化轉(zhuǎn)移與沉淀。蝕變可分成三個階段,第一階段發(fā)生在偉晶狀白崗巖成巖晚期,以黑云母綠泥石化為主,部分晶質(zhì)鈾礦析出分布在蝕變礦物的邊緣或裂隙中,鈾初步富集;第二階段主要表現(xiàn)為堿交代,蝕變以鈉長石化、鉀長石化為特征,鈾進一步富集成貧礦石;第三階段為酸交代,綠泥石化蝕變強烈,赤鐵礦化蝕變中等,鈾富集成富礦石,是紅石泉鈾礦化主成礦期。綠泥石化、鈉交代、赤鐵礦化等熱液蝕變可作為該區(qū)重要找礦標志。
[Abstract]:The Shi Quan pegmatite Baigang type uranium deposit is located in Shandan County Gansu Province and is the most typical Baigangyan type uranium deposit in China. The research work in this area was mainly completed in the 1980s and before, but the study of altered minerals which are closely related to uranium mineralization is relatively weak. Based on the systematic study of altered rocks in the Shi Quan pegmatite Baigangyan type uranium deposit, the forming environment, material source and the relationship between hydrothermal alteration and uranium mineralization are discussed on the basis of the determination of its characteristics. It is found that the uranium deposits in this area are mainly located in the altered zone near the boundary between pegmatite and surrounding rock. The uranium mineralization types can be divided into two types, one is black rich in chlorite biotite, the other is red and albite, the red ore is closely related to hematitization. They are superimposed, generally in the center of the uranium rich body, with the strongest development of green mud fossilization, hematitization, albite, potassium feldspar, sericite, and sericite. Compared with the normal pegmatite, the Si-K component of the altered rock decreases and the Fe valence state changes as compared with the normal pegmatite. In respect of trace elements, the Uttrium, PbPbPbMoMoLiOTi in altered rocks is obviously higher, especially the average value of Th* is 5.84, the average value of Sr* is 0.83, and the distribution pattern of trace element cobwebs is "W" pattern in general, the average value of Th* is 5.84, and the average value of Sr* is 0.83.The trace element cobweb pattern shows a "W" distribution pattern in general. The relative enrichment of the heavy ion lithophile element RbBX and the relative depletion of the high field strength element TiOPU Cr are consistent with that of the normal rocks. For rare earth elements, the 危 REE content (mean value is 88.412) of altered rocks increases obviously, especially HREE, which shows that the REE distribution model shows that the altered rocks tend to be more horizontal, and the negative EU 未 (mean 0.856) anomaly is slightly weaker. The 未 ce value is very close to 1, and the weak negative anomaly is basically consistent with the normal lithology. In terms of ore-forming elements, the increase of U content in altered rocks has little change in Th. The results show that the hydrothermal corrosion in this area is formed in the environment of low temperature, low oxygen fugacity, low PH value and rich in ferromagnesia components. On the one hand, alteration can change the physical properties of rocks and form the space conditions conducive to uranium mineralization, on the other hand, it can promote the activation, transfer and precipitation of uranium. The alteration can be divided into three stages. The first stage occurs in the late diagenetic period of pegmatite bhagite, mainly in biotite greenstone, and some of the uraniferous uranium deposits are precipitated and distributed in the edge or fissures of altered minerals, and the uranium is initially enriched. The second stage is mainly characterized by alkali metasomatism, albite and potassium feldspar, and uranium is further enriched and integrated into poor ore, while in the third stage, acid metasomatism, strong alteration of green-mud petrifaction, moderate alteration of hematite and uranium rich ore are the main features. It is the main metallogenic period of red Shi Quan uranium mineralization. The hydrothermal alteration, such as green mud fossilization, sodium metasomatism and hematitization, can be used as an important prospecting marker in this area.
【學(xué)位授予單位】：東華理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P619.14

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本文編號：1938148