發(fā)布時間：2018-03-21 00:35

  本文選題：銅鎳硫化物礦床　切入點：地球化學(xué)　出處：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：本次工作研究的對象為楊柳坪銅鎳硫化物礦床。本文緊扣巖漿硫化物礦床的幾個關(guān)鍵性問題:礦床的年代學(xué)研究、巖漿源區(qū)的性質(zhì)、是否有同化混染作用及混染程度等,通過巖石學(xué)、礦物學(xué)、元素地球化學(xué)以及同位素地球化學(xué)方法對巖體進行系統(tǒng)研究,主要獲得以下幾方面的成果:(1)前人通過測試縣城北邊殘坡積層中弱變質(zhì)的基性超基性巖中的金云母,獲得的等時線年齡為40Ar/39Ar坪年齡250.2±1.9Ma,推測該礦床為二疊紀(jì)峨眉地幔柱的產(chǎn)物。但本次工作通過對楊柳坪銅鎳硫化物礦石中磁黃鐵礦進行Re-Os同位素測年,獲得等時線年齡數(shù)據(jù)為375±63Ma(MSWD=9.2),該數(shù)據(jù)表明與峨眉山大火成巖省主噴發(fā)期不同,推測為一次獨立的成礦事件。根據(jù)其年齡及其微量元素構(gòu)造環(huán)境判別圖初步推斷該礦床的形成環(huán)境為島弧環(huán)境。(2)SiO2與氧化鈣(CaO)、全堿(Na2O+K2O)以及氧化鋁(Al2O3)、氧化鈦(TiO2)呈正相關(guān)關(guān)系,與氧化鎂(MgO)和氧化鐵(TFeO)呈負相關(guān)關(guān)系,反映出發(fā)生了斜長石、單斜輝石、橄欖石的分離結(jié)晶作用;δEu與氧化鈣(CaO)、氧化鋁(Al2O3)、鍶(Sr)呈正相關(guān)關(guān)系表明巖漿演化過程中斜長石的分離結(jié)晶作用;MgO與各主要氧化物的相關(guān)性表明超鎂鐵單元應(yīng)該發(fā)生了橄欖石的分離結(jié)晶作用,而鎂鐵單元則發(fā)生了少量斜方和單斜輝石的分離結(jié)晶。(3)S同位素組成變化范圍比較小,說明成礦物質(zhì)的均一化程度很高。S同位素變化范圍為-2~+2‰,其特征表明成礦物質(zhì)為幔源硫;87Sr/86Sr初始比值較高,187Os/188Os初始比值為0.1469±0.0037,γOs值介于26~46之間,206Pb/204Pb和207Pb/204Pb比值比較一致,208Pb/204Pb比值變化比較大,巖體的Nb/U值為1.2~30.7,平均為17.8;Ce/Pb值為0.59~10.124,平均為3.65等特征表明發(fā)生了地殼物質(zhì)的同化混染作用。
[Abstract]:The object of this work is Yangliuping copper-nickel sulfide deposit. This paper focuses on several key problems of magmatic sulfide deposit, such as the chronological study of the deposit, the nature of the magma source, whether there is assimilation and the degree of the mixed contamination, etc. Through petrology, mineralogy, element geochemistry and isotopic geochemistry, a systematic study of the rock mass was carried out. The main achievements are as follows: 1) by testing the biotite in the weakly metamorphosed basic ultrabasic rocks in the residual slope accumulation in the north of the county town, The isochron age of 40Ar39 ar plateau is 250.2 鹵1.9Ma. it is assumed that the deposit is a product of the Permian Emei mantle plume. However, the Re-Os isotopic dating of pyrrhotite in Yangliuping copper-nickel sulfide ore is carried out in this work. The isochron age data obtained is 375 鹵63 Ma MSWDX 9.2g, which indicates that the age data are different from the main eruption period of Emeishan great igneous rock province. It is inferred that the formation environment of the deposit is a positive correlation between the island arc environment, CaOO _ 2, Na2OK _ 2O _ 2 and Al _ 2O _ 3, TIO _ 2 and TIO _ 2, according to the age and trace element tectonic environment discriminant diagram of the deposit, which is supposed to be an independent metallogenic event, and the formation environment of the deposit is positively correlated with the CaOO _ 2, Na _ 2O _ 2, Al _ 2O _ 3 and Ti _ 2O _ 2. There is a negative correlation with MgO and TFeO, which indicates that plagioclase, clinopyroxene and clinopyroxene occur. The separation and crystallization of olivine and the positive correlation between 未 EU and Cao, Al _ 2O _ 3, Sr ~ (2 +) indicate that the separation and crystallization of plagioclase and the correlation between MgO and major oxides during magmatic evolution indicate that ultramagnesia-iron unit should occur. The separation and crystallization of olivine, On the other hand, a small amount of clinopyroxene and clinopyroxene occur in the magnesium-iron unit, and the variation range of the isotopic composition is relatively small, indicating that the degree of homogenization of the ore-forming material is very high. The variation range of S isotope is -2 ~ 2 鈥，

本文編號：1641488