本文選題：龍首山地區(qū) + 堿交代型鈾釷礦化�。� 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：龍首山地區(qū)是我國重要的花崗巖型鈾釷成礦帶,至少包括新水井、芨嶺、革命溝、紅石泉、金邊寺等5個鈾礦床/點(diǎn)。本文重點(diǎn)對芨嶺與新水井兩個典型堿交代型鈾(釷)礦床開展了詳細(xì)研究,試圖查明礦床地質(zhì)特征及成礦流體性質(zhì)以及流體來源。區(qū)內(nèi)主要賦礦巖石為加里東期中粗粒似斑狀花崗巖(芨嶺巖體),花崗巖地球化學(xué)特征表明其為是華北陸塊南緣上地殼熔融的產(chǎn)物,形成于加里東晚期,北祁連洋殼板塊與其北側(cè)華北板塊碰撞后擠壓向伸展轉(zhuǎn)變的構(gòu)造背景之下。該期花崗巖普遍具有較高鈾、釷含量,是本地區(qū)合適的鈾源和釷源。芨嶺和新水井礦床為典型的堿交代熱液型鈾(釷)礦床,熱液蝕變發(fā)育廣泛,由早至晚包括:礦化前期鉀長石化;礦化期鈉長石化、方解石化、赤鐵礦化、綠泥石化、高嶺石化、硅化;礦后期褐鐵礦化等。礦化期蝕變可劃分兩期:即早期強(qiáng)堿性鈉交代期,該期特征是花崗巖完全鈉長石化,并伴隨蝕變礦物系列有碳酸鹽化、綠泥石化和微量的銳鈦礦、赤鐵礦和黃鐵礦形成。在礦床堿交代早期、交代巖鈾含量有所增加。礦床晚期圍巖蝕變屬于鈣、鎂交代期,此時熱液堿度明顯減弱,向弱酸性轉(zhuǎn)變,交代礦物組合是方解石(碳酸鹽化)、鐵綠泥石、赤鐵礦、膠狀磷灰石和鈣蒙脫石等,礦床鈾、釷礦化在該期產(chǎn)生。通過系統(tǒng)流體包裹體研究,獲得芨嶺和新水井礦床成礦流體溫度為130℃~150℃。包裹體主要為水溶液包裹體和CO2-H2O溶液包裹體,激光拉曼檢測到包裹體氣相普遍發(fā)育CO2及H2等氣體,暗示鈾、釷可能主要以揮發(fā)份絡(luò)合物形式搬運(yùn)(如鈾酰碳酸離子等)為主。流體包裹體均一溫度-鹽度分布表明中低溫低鹽度流體與中低溫中鹽度流體混合可能為本區(qū)重要的礦質(zhì)沉淀機(jī)制。通過C-O同位素的研究,認(rèn)為鈾釷礦化的成礦流體應(yīng)為大氣降水與巖漿水混合而成。推測該地區(qū)鈾礦化主要受堿交代巖、構(gòu)造破碎帶、巖性接觸帶控制,區(qū)內(nèi)廣泛發(fā)育的堿交代作用完成了鈾的初步預(yù)富集,后期酸性含鈾熱液與大氣降水匯合,發(fā)生減壓沸騰作用,在構(gòu)造有利部位及巖性接觸界面附近發(fā)生鈾的沉淀、富集成礦。
[Abstract]:Longshoushan area is an important granitic uranium-thorium metallogenic belt in China, including at least five uranium deposits / sites, such as Xinshui well, Jiling, Chuanggou, Red Shi Quan and Phnom Pensi. In this paper, two typical alkaline metasomatic uranium (thorium) deposits in Jiling and Xinshui are studied in detail, and the geological characteristics, ore-forming fluid properties and fluid sources of the deposits are attempted to be ascertained. The main ore-bearing rocks in the area are Caledonian coarse-grained porphyry granites (Jieling granite). The geochemical characteristics of the granites indicate that they are the product of the melting of the upper crust in the southern margin of the North China continental block and formed in the late Caledonian period. The northern Qilian oceanic crust plate collided with the North China plate in the tectonic setting of compressional to extensional transition. The granites in this period generally have high uranium and thorium contents, which are suitable uranium and thorium sources in this area. The Jiling and Xinshui deposits are typical alkali-metasomatic hydrothermal uranium (thorium) deposits with extensive hydrothermal alteration and development, including: early to late mineralization of potassium feldspar; mineralization of albite, calcite, hematitization, green-mud fossilization. Kaoling Petrochemical, silicification, late ore limonitization, etc. The mineralization period can be divided into two periods: the early strongly alkaline sodium metasomatism period, which is characterized by the complete albite of granite, accompanied by carbonation of altered mineral series, green mud petrifaction and trace anatase, hematite and pyrite formation. During the early alkali metasomatism, the uranium content of metasomorphic rocks increased. The late metamorphism of the surrounding rock belongs to calcium and magnesium metasomatism, at which the hydrothermal basicity is obviously weakened and the metasomatic mineral assemblage is calcite (carbonation), iron chlorite, hematite, colloidal apatite and calcium montmorillonite. Thorium mineralization occurred during this period. Through systematic fluid inclusion study, the ore-forming fluid temperature of Jiling and Xinshui deposits is 130 鈩，

本文編號：2102349