本文選題：小花岔鈾礦床 + 花崗偉晶巖��； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：陜西小花岔鈾礦床是一個(gè)典型的偉晶巖型鈾礦床,位于北秦嶺丹鳳鈾礦成礦區(qū)的東北部,是近年來新發(fā)現(xiàn)的一個(gè)鈾礦床類型。本文在詳細(xì)野外地質(zhì)基礎(chǔ)上,通過對礦床野外地質(zhì)特征、礦區(qū)花崗質(zhì)巖石巖相學(xué)特征、巖漿巖年代學(xué)、巖石地球化學(xué)特征和同位素地球化學(xué)的綜合研究獲得以下認(rèn)識:礦床賦存于古元古界秦嶺群地層中,其礦體產(chǎn)生在黑云母花崗偉晶巖和黑云斜長片麻巖的接觸帶同化混染區(qū)。鈾的賦存形式主要以晶質(zhì)鈾礦為主,晶質(zhì)鈾礦主要以分散狀或浸染狀分布于產(chǎn)鈾花崗偉晶巖中,位于黑云母包晶、斜長石、更長石和黃鐵礦的粒間,并與鋯石、磷灰石、獨(dú)居石等副礦物共生,其周圍常常有金紅石和鈦鐵礦等金屬氧化物產(chǎn)生,少量的晶質(zhì)鈾礦生長在礦物中心。礦區(qū)出露的花崗質(zhì)巖石如花崗閃長巖、二長花崗巖等均屬于鈣堿性系列;弱過鋁質(zhì)-過鋁質(zhì)的中酸性巖漿巖;礦區(qū)巖漿巖均投點(diǎn)于花崗巖類;在巖漿巖分類中投點(diǎn)于I型花崗巖區(qū)域中。本文對區(qū)內(nèi)出露的花崗巖、花崗偉晶巖進(jìn)行了LA-ICP-MS鋯石U-Pb定年,結(jié)果表明:灰池子花崗巖的形成年齡為444±4.0Ma;高山溝花崗巖的形成年齡為422±0.82Ma;產(chǎn)鈾黑云母花崗偉晶巖的形成年齡為417±2.6Ma;非礦黑云母花崗偉晶巖形成年齡為413±1.8Ma。花崗質(zhì)巖石的Lu-Hf同位素二階段模式年齡平均為1.4Ga,花崗巖和花崗偉晶巖具有相似的Hf同位素特征(εHf(t)值分別為-0.48與-0.40),表現(xiàn)有明顯的同源性。產(chǎn)鈾黑云母花崗偉晶巖由于同化混染作用和圍巖的元素交換等原因,其基性組分(Fe、Mg)和揮發(fā)分(F)含量較高,并且富集大離子親石元素LILE(Rb、Ba、K),虧損高場強(qiáng)元素HFSE(Nb、Ta)。在偉晶巖-片麻巖的接觸帶發(fā)生化學(xué)組分的元素交換,使得巖漿中U-F絡(luò)合物發(fā)生分解,并且在良好的成礦條件下(圍巖的鈾含量較高、較好的構(gòu)造環(huán)境)使得U飽和沉淀形成現(xiàn)有的鈾礦物如晶質(zhì)鈾礦等。小花岔鈾礦床的形成受到了偉晶巖、圍巖成分、巖漿熱液中的揮發(fā)分共同的作用,最終導(dǎo)致了鈾礦床的形成。
[Abstract]:Xiaohuacha uranium deposit in Shaanxi Province is a typical pegmatite type uranium deposit located in the northeast of Danfeng uranium deposit in North Qinling Mountains. It is a newly discovered uranium deposit type in recent years. On the basis of detailed field geology, this paper analyzes the field geological characteristics of ore deposits, the petrographic characteristics of granitic rocks, the geochronology of magmatic rocks. A comprehensive study of petrogeochemical characteristics and isotopic geochemistry shows that the deposit occurred in the Paleoproterozoic Qinling Group and its orebody occurred in the contact zone of biotite granitic pegmatite and biotite obliquity gneiss. The main forms of uranium occurrence are crystalline uranium deposits, which are mainly dispersed or disseminated in uranium-producing granitic pegmatite, located in the intergranular areas of biotite peritectic, plagioclase, more feldspar and pyrite, and associated with zircon, apatite, zircon, apatite. The secondary minerals such as monazite are symbiotic, and there are some metallic oxides such as rutile and ilmenite around them, and a small amount of uranite grows in the mineral center. The granitic rocks, such as granodiorite and monzogranite, all belong to calc-alkaline series, weakly peraluminous and peraluminous intermediate-acid magmatic rocks, magmatic rocks of mining area are all located in granites; In the classification of magmatic rocks, the input point is in the I type granite area. LA-ICP-MS zircon U-Pb dating of granitic pegmatite and granitic pegmatite has been performed in this paper. The results show that the age of formation of Liqizi granite is 444 鹵4.0 Ma, that of Gaosanggou granite is 422 鹵0.82Ma, that of uranium-producing biotite granitic pegmatite is 417 鹵2.6 Ma, and that of non-mineral biotite granitic pegmatite is 413 鹵1.8 Ma. The average age of Lu-Hf isotopic two-stage model of granitic rocks is 1.4Ga.The granite and granitic pegmatite have similar HF isotopic characteristics (蔚 HF (t) = -0.48 and -0.40, respectively), showing obvious homology. The uranium biotite granitic pegmatite is characterized by assimilation mixing and element exchange of surrounding rock, which results in higher content of basic component (Feo mg) and volatile fraction (F), and enrichment of large ion lithophile element Lile (RbPe BaK) and depletion of high field strength element HFSE (NbTa). In the contact zone between pegmatite and gneiss, element exchange of chemical components occurs, which results in the decomposition of U-F complex in magma and the higher uranium content in the surrounding rock under good metallogenic conditions. The better tectonic environment causes U saturation precipitation to form existing uranium minerals such as crystalline uranium deposits and so on. The formation of Xiaohuacha uranium deposit was influenced by pegmatite, composition of surrounding rock and volatile matter in magmatic hydrothermal solution, which resulted in the formation of uranium deposit.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P619.14
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本文編號：2089334