本文選題：巖石地球化學　切入點：蝕變分帶　出處：《南京大學》2015年碩士論文　論文類型：學位論文

【摘要】：302鈾礦床位于粵北地區(qū)諸廣南部巖體東南部的花崗巖內(nèi),在大地構(gòu)造位置上處于閩贛粵后加里東隆起與湘桂粵北海西—印支坳陷結(jié)合部位。本文在野外地質(zhì)工作的基礎(chǔ)上,通過巖相學、巖石地球化學、LA-ICP-MS鋯石U-Pb定年、電子探針定性及定量分析、H-O同位素和Sr-Nd同位素分析等方法,對與礦化相關(guān)的新鮮的花崗巖、蝕變圍巖、蝕變礦物和副礦物等進行分析研究,以探討礦床的成因。巖石地球化學研究表明,長江巖體新鮮的中粒黑云母花崗巖具有高Si02含量(72.27～75.08 wt.%),和較高的堿含量(Na2O+K20=7.68～8.10 wt.%),屬于高鉀鈣堿系列。巖體A/CNK值為1.03～1.05,屬弱過鋁質(zhì)花崗巖,富集輕稀土元素((La/Yb)N=7.24～11.04),Eu負異常明顯(δEu=0.14～0.30),明顯富集Rb、Th和U,而強烈虧損Ba、Sr、P和Ti,并輕微虧損Nb。 LA-ICP-MS鋯石U-Pb定年結(jié)果表明,長江巖體的年齡為164±2 Ma(MSWD=6.3,N=13).圍巖蝕變研究表明,在水平方向上,由礦脈向外蝕變圍巖可依次分為4個帶,且距離礦脈由近到遠,蝕變程度逐漸減弱,總體表現(xiàn)為：硅化+紅化→絹云母化→綠泥石化+堿性長石化→弱蝕變或正�；◢弾r。U礦化與硅化和赤鐵礦化密切相關(guān)。蝕變分帶是在復(fù)雜的構(gòu)造背景條件下,由多期多階段的流體與巖石發(fā)生相互作用形成。蝕變圍巖中綠泥石絕大多數(shù)屬于鮞綠泥石和蠕綠泥石,以貧Si富Fe為特征,屬于礦前期中高溫熱液蝕變范圍。副礦物研究表明,蝕變圍巖中主要副礦物為鈾釷石、鋯石、磷釔礦、磷灰石、褐簾石和黃鐵礦等。鈾釷石是最重要的富鈾礦物。鋯石最常見,磷釔礦和磷灰石數(shù)量較少,褐簾石只出現(xiàn)在弱蝕變花崗巖或正�；◢弾r中。距離礦脈由近到遠,副礦物的組合可簡單概括為：鈾釷石+鋯石+磷釔礦→鋯石+褐簾石+磷灰石。石英的H-O同位素研究表明,成礦流體的δ18OH2O值為-7.09‰～3.24‰,δDH2O值為-105‰～63‰,是在強烈的構(gòu)造-巖漿活動的地質(zhì)背景下,由大氣降水在深循環(huán)過程中通過水-巖相互作用演化形成,δDH2O值的偏低可能由成礦流體經(jīng)歷了熱液沸騰作用和/或少量有機水的混入引起。螢石的微量元素和Sr-Nd同位素研究表明,成礦期螢石的εNd(t)值(平均值為-11.6)幾乎一致,與長江巖體的值(平均為-10.9)十分相似,與油洞巖體的值(平均為-13.2)也較接近,而與基性巖脈的值(平均為1.4)區(qū)別明顯；螢石的稀土元素配分模式也與長江巖體更為相似,與油洞巖體區(qū)別相對較明顯,反映成礦流體中的稀土元素主要來源于長江巖體。螢石的(87Sr/86Sr)i值介于賦礦圍巖長江巖體和基性巖脈的(87Sr/86Sr)i值之間,反映成礦流體中的Rb-Sr組分來源于兩者之間不同程度的混合。上述研究可能指示：成礦流體中的多數(shù)組分是在流體與圍巖(尤其是長江巖體)之間相互作用過程中獲得的。白堊紀以來,研究區(qū)內(nèi)構(gòu)造-巖漿活動十分強烈,粵北地區(qū)的陸殼處于伸展拉張期,大氣降水來源的氧化性流體沿斷裂構(gòu)造下滲循環(huán),在地溫升高、強烈構(gòu)造及巖漿活動的條件下溫度升高形成熱液,這種氧化性熱液在與花崗巖的水-巖反應(yīng)過程中溶解浸取花崗巖中的鈾等元素,隨著流體的運移,在有利的物理化學條件及構(gòu)造部位,鈾卸載富集成礦。
[Abstract]:302 uranium deposit is located in the north area of the Guangnan Department of southeast in the granite rock, the tectonic position in Fujian Guangdong Jiangxi and Guangdong Hunan Jialidonglong after the Hercynian Indosinian depression binding site. In this paper, on the basis of field geological work, through petrography, geochemistry, LA-ICP-MS zircon U-Pb dating and analysis the probe of qualitative and quantitative, H-O isotope and Sr-Nd isotope analysis method, and on the mineralization related to fresh granite, altered rocks, analysis of altered minerals and accessory minerals, the genesis of the deposit. The rock geochemical studies show that the Yangtze River Rock fresh medium grained biotite granite with high Si02 content (72.27 ~ 75.08 wt.%), the content of alkali and high (Na2O+K20=7.68 ~ 8.10 wt.%), which belongs to high potassium calc alkaline series. Rock mass A/CNK value from 1.03 to 1.05, is weakly peraluminous granite, enriched in light rare earth elements ( (La/Yb) N=7.24 ~ 11.04), obvious Eu negative anomaly (Eu=0.14 ~ 0.30), Th and U are significantly enriched in Rb, Sr, and strong depletion of Ba, P and Ti, Nb. LA-ICP-MS, and slight depletion of U-Pb zircon dating results show that the rock mass at the age of 164 + 2 Ma (MSWD=6.3, N=13) the wall rock alteration. Research shows that in the horizontal direction, from outward vein altered rocks can be divided into 4 zones, and the distance between the veins from near to far, the alteration degree gradually weakened, the overall performance is: + red, silicification sericitization, chloritization + alkali feldspar, weak alteration.U or normal granite mineralization and silicification and hematitization are closely related. The alteration zoning is in complicated tectonic background conditions, fluid and rock formed by multi-stage interaction. Chlorite in altered rocks belong to the vast majority of chamosite and ripidolite, with poor Si Fe rich features, belong to high temperature hot mineral liquid in the early Alteration of accessory minerals range. Research shows that the alteration of accessory mineral rock for uranium and thorium ore, zircon, xenotime, apatite, allanite and pyrite. Uranium thorium is the most important. The most common uranium rich mineral xenotime and zircon, apatite, allanite number only in the weakly altered granite or granite veins. Normal distance from near to far, combination of accessory minerals can be summarized as the following: uranothorite + + xenotime zircon, zircon and allanite + apatite. H-O isotope study of quartz indicate that the ore-forming fluid of delta 18OH2O value is -7.09% ~ 3.24. DH2O values for -105% ~ 63 per thousand, is the geological background in the intense tectonic magmatic activity, from atmospheric precipitation in the deep circulation process by water rock interaction and evolution, the low DH2O values may consist of the ore-forming fluid experienced mixed hydrothermal boiling and / or a small amount of organic water caused by fluorite. Trace elements and Sr-Nd isotopes indicate that the mineralization of fluorite Nd epsilon (T) values (mean -11.6) is almost the same, and the Yangtze River Rock value (average -10.9) are very similar, and the oil hole rock value (average -13.2) is relatively close, and the average value of mafic dikes (1.4) the difference is obvious; the distribution patterns of rare earth elements of fluorite and rock is more similar to the Yangtze River, and the difference between oil hole rock is relatively obvious, reflect the rare earth elements in ore-forming fluid mainly derived from the Yangtze river rock. Fluorite (87Sr/86Sr) I value between ore body and surrounding rock of the Yangtze River dikes (87Sr/86Sr) I between the values, reflect the Rb-Sr group in the ore forming fluid source between the two different degrees of mixing. The study may indicate: most groups in the ore forming fluid is in fluid and the surrounding rock (especially the Yangtze River Rock) interactions in the process of the research. Since the Cretaceous. The tectonic magmatic activity in the area is very strong, the continental crust in the north of Guangdong Province in the extension period, oxidizing fluid source of atmospheric precipitation infiltration along the tectonic cycle, in the temperature rise, strong tectonic and magmatic activities under the conditions of temperature rise of hydrothermal oxidation, the hydrothermal water and dissolved in granite rock reaction process of leaching uranium in granite and other elements, with the migration of fluid flow in the physical and chemical conditions, favorable tectonic position and uranium enrichment, unloading.

【學位授予單位】：南京大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P619.14

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