本文關(guān)鍵詞： 重晶石礦床 鋇冰長石 微量元素 稀土元素 S同位素 有機地球化學(xué) 新晃 天柱　出處：《南京大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：重晶石是一種重要的含鋇礦物,在多個工業(yè)部門廣泛應(yīng)用,是人類社會不可缺少的一種重要的非金屬礦產(chǎn)資源。目前重晶石的主要用途是用于石油天然氣鉆探的泥漿加重劑。我國揚子地臺東南緣湘西-黔東交界處的新晃貢溪-天柱大河邊地區(qū)的早寒武世重晶石礦床是世界上最大的沉積型重晶石成礦帶,在世界范圍內(nèi)極具代表性,對其進行研究具有重要的科學(xué)意義。本文在查閱了大量相關(guān)文獻(xiàn)的基礎(chǔ)上,對新晃-大柱地區(qū)重晶石礦床進行了電子探針的礦物學(xué)研究以及礦床礦石與圍巖的微量稀土元素對比研究、重晶石礦石的主量元素研究、硫同位素特征的分析研究和有機地球化學(xué)研究,討論其形成環(huán)境和成礦過程,為該地區(qū)重晶石礦床的成礦理論提供一定的依據(jù)。主要得到了以下認(rèn)識：(1)電子探針礦物分析中環(huán)帶鋇冰長石的發(fā)現(xiàn)表明了海底富鋇熱液流體對重晶石礦床的形成有較大貢獻(xiàn),而且是一個幕式、逐漸的過程；(2)微量元素V/Cr、U/Th等地球化學(xué)指標(biāo)表明重晶石礦床形成時處于缺氧環(huán)境,稀土元素具有明顯的Ce負(fù)異常,及較高的Y/Ho比值,重晶石礦石具有明顯的Eu正異常,這些特征反映了成礦過程受到了較強的海底熱液物質(zhì)的影響,表明鋇可能主要來自于海底熱液噴流物質(zhì)；(3)新晃-天柱重晶石礦石的主量元素分析n(SiO2)/n(Al2O3)、n(Al2O3)/n(Al2O3+Fe2O3)、n(Al)/n(Al+Fe+Mn)、n(Si)/n(Si+Al+Fe)值表明了重晶石礦石的形成環(huán)境為在大陸邊緣并受到熱水物質(zhì)影響。(4)重晶石的δ34S值主要分布在+40‰～45‰,表現(xiàn)出重硫富集的特征,且重晶石硫同位素呈塔式分布,表明硫源來源單一,主要來自同期海水硫酸鹽。黃鐵礦634S值低于同期海水硫同位素組成,表明生物細(xì)菌對海水硫酸鹽的還原起到了很大作用,并且反映了礦床形成于海水交換有限的滯留的海盆系統(tǒng)。(5)重晶石含礦巖系有機質(zhì)的Ro值都大于2%,氯仿瀝青“A”和有機轉(zhuǎn)化率、Ts/(Ts+Tm)比值、C29TS/(C29H+C29TS)、甾烷的異構(gòu)化指數(shù)等的結(jié)果也都表明了有機質(zhì)達(dá)到了過成熟階段,經(jīng)歷了較高的熱演化階段,熱液可能對有機質(zhì)的成熟起到了促進作用。正構(gòu)烷烴和類異戊二烯的碳數(shù)分布、Pr/Ph比值、伽馬蠟烷、C30*/C29Ts值等都表明了重晶石含礦巖系的有機質(zhì)母質(zhì)來源為海相低等的菌藻類等生物,并在還原環(huán)境下沉積形成。有機質(zhì)為重晶石的形成提供了一定的能量,菌藻類生物對重晶石的形成起到了提供生成空間和加快晶體生長的作用。綜合以上分析認(rèn)為重晶石成礦時期為缺氧還原環(huán)境、海底熱液活動頻繁、封閉-半封閉的臺地瀉湖環(huán)境,生物-有機質(zhì)對重晶石礦床的形成起到了重要的作用。
[Abstract]:Barite is an important barium bearing mineral, which is widely used in many industrial sectors. Barite is an indispensable nonmetallic mineral resource in human society. At present, the main use of barite is mud aggravation for oil and gas drilling. Xinhuang at the junction of west Hunan and east Guizhou on the southeast margin of Yangtze platform. The early Cambrian barite deposit in the Gongxi-Tianzhu River area is the largest sedimentary barite metallogenic belt in the world. It is of great scientific significance to study it on the basis of consulting a large number of relevant literature. The mineralogy of barite deposits in Xinhuang-Dazhu area is studied by electron probe, the trace rare earth elements of ore and surrounding rock are compared, and the principal elements of barite ores are studied. The characteristics of sulfur isotopes and organic geochemistry are analyzed, and the formation environment and metallogenic process are discussed. It provides a basis for the metallogenic theory of barite deposits in this area. The following conclusions are obtained: 1) the discovery of barium ice feldspar in Central Zone by electron probe mineral analysis shows that the hydrothermal fluid rich in barium on the sea floor has a great contribution to the formation of barite deposits. Moreover, it is a series and gradual process. The geochemical indexes such as trace element V / Cr ~ (2 +) / T _ h indicate that the barite deposit was formed in anoxic environment, the rare earth element has obvious negative ce anomaly, and the ratio of Y / Ho is relatively high. The barite ore has obvious positive EU anomaly, which reflects that the ore-forming process is influenced by strong submarine hydrothermal material. The main element analysis of Xinhuang-Tianzhu barite ore indicates that barium may mainly come from submarine hydrothermal jet. The main element analysis of Xinhuang-Tianzhu barite ore shows that the formation environment of barite ore is that the barite ore was formed on the continental margin and was influenced by hot water matter. The value of Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3 shows that the barite ore is formed in the continental margin and under the influence of hot water matter in the formation environment of the barite ore, which is composed of Al / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3. The 未 34s value of the barite is mainly distributed in 40 鈥，

本文編號：1522622