本文關鍵詞：北京密云條帶狀鐵建造的鋯石SHRIMP U-Pb年齡及其地質意義　出處：《中國地質大學(北京)》2017年碩士論文　論文類型：學位論文

  更多相關文章： 條帶狀鐵建造(BIF) 鋯石SHRIMP U-Pb定年 變質事件 形成時代 構造環(huán)境 北京密云

【摘要】：前寒武紀條帶狀硅鐵建造(BIF)是全球范圍內(nèi)重要的鐵礦資源類型,在世界上分布廣泛。BIF作為一種早前寒武紀特殊化學沉積建造類型,其在形成的過程中經(jīng)歷了復雜的變質變形作用,在反演地球早期構造(地幔柱與早期板塊構造)演化方面有重要作用。北京密云地區(qū)位于華北克拉通北緣,該區(qū)在古太古代到早中元古代經(jīng)歷了復雜的構造變質事件,在此過程中形成了大量的大中型沉積變質鐵礦床。本文主要通過對該區(qū)馮家峪鐵礦、沙廠鐵礦和放馬峪鐵礦等典型BIF型鐵礦床的磁鐵石英巖及其附近含鐵巖系共4件樣品進行SHRIMP鋯石U-Pb測年研究,得到的年齡數(shù)據(jù)如下:(1)馮家峪鐵礦的含云母閃石類磁鐵石英巖(MF01)的變質鋯石207Pb/206Pb年齡主要集中在1777±9 Ma和2456±8 Ma;(2)沙廠鐵礦的透閃石化磁鐵石英巖(MY01)的變質鋯石定年結果為1806±13 Ma和2469±21 Ma,碎屑鋯石的207Pb/206Pb年齡為2517±12 Ma。侵入礦體中的長英質輝石角閃巖(SY01)的變質鋯石207Pb/206Pb年齡為1798±15 Ma,具有明顯韻律環(huán)帶的捕獲鋯石的年齡為2531±7 Ma。從而限定首云鐵礦BIF建造的沉積時代為可能2469±21 Ma到2517±12 Ma之間;(3)放馬峪鐵礦的含磁鐵礦石榴子石二長片麻巖(MFM01)的變質鋯石測年結果分別為1817±13 Ma和2456±6 Ma,碎屑鋯石207Pb/206Pb年齡為2529±8 Ma。由此間接限定了放馬峪條帶狀鐵建造的形成時代約為2456±6 Ma到2529±8 Ma,根據(jù)前人研究,最可能為太古代晚期。密云BIF型鐵礦指示了該區(qū)在華北克拉通新太古代晚期的一次重要的BIF成礦事件。由年齡數(shù)據(jù)結合其野外勘查情況及樣品巖相學和鋯石陰極發(fā)光圖表明該區(qū)兩組變質鋯石年齡即分別代表了該區(qū)條帶狀鐵建造的變質年齡,這兩期變質年齡時間基本上與之前已提出的華北克拉通在古元古代時期的兩次變質事件(2.44Ga和1.82 Ga)相一致。因此我們推測該區(qū)BIF的變質成礦作用與整個華北克拉通東部陸塊在古元古代發(fā)生的兩次大的構造熱事件有密切成因關系,二者在時間上是一個連續(xù)的過程。結合華北克拉通的構造演化史,我們推測密云地區(qū)BIF建造可能形成于島弧構造環(huán)境。
[Abstract]:The Precambrian banded iron formation (BIF) is an important type of iron ore resources in the global scope, wide distribution of.BIF as an early Precambrian sedimentary formation of special chemical type in the world, it has experienced complex metamorphic deformation in the process of formation, in the early tectonic inversion (mantle plume and ball the early plate tectonics) plays an important role in evolution. Beijing Miyun area is located in the northern margin of the North China Craton, the area in the Archean to early Proterozoic metamorphic complex experienced tectonic events, formed in this process a large number of large and medium-sized sedimentary metamorphic iron deposit. This paper is mainly based on the study of the Fengjiayu iron ore, iron ore sand plant and the Fangmayu iron mine and other typical BIF type iron ore deposits of magnetite quartzite and nearby iron rocks a total of 4 samples of SHRIMP zircon U-Pb dating, the age data obtained are as follows: (1) oxybiotite Feng Jiayu ore Amphibole magnetite quartzite (MF01) metamorphic zircon 207Pb/206Pb age mainly concentrated in the 1777 + 9 and 2456 + 8 Ma Ma; (2) sand plant iron ore flash Petrochemical magnetite quartzite (MY01) metamorphic zircon dating results for 1806 Ma + 13 and 2469 + 21 Ma, detrital zircon 207Pb/206Pb years at the age of 2517 + 12 Ma. intrusive orebody in felsic pyroxene amphibolite (SY01) metamorphic zircon 207Pb/206Pb age of 1798 + 15 Ma, zircon has obvious oscillatory zoning at the age of 2531 + 7 Ma. to limit the deposition time of Shouyun Iron Mine BIF built for 2469 + 21 to 2517 + 12 Ma Ma between; (3) magnetite garnet gneiss containing two Fangmayu iron mine (MFM01) of the metamorphic zircon dating results were 1817 + 13 and 2456 + 6 Ma Ma, detrital zircon 207Pb/206Pb age of 2529 + 8 Ma. indirectly defines Ma Yu banded iron formation formation era about 2456 + 6 Ma 2529 + 8 Ma, according to previous research, most likely for the late Archean Miyun. BIF type iron ore indicates an important BIF mineralization events in the region through late Neoarchean in the North China Craton. Exploration and sample petrography and zircon cathodoluminescence shows that the metamorphic age of the metamorphic zircon age is two group on behalf of the banded iron formation by age data combined with the field, the two metamorphic age time basically and has been proposed before the North China Craton in the two Paleoproterozoic metamorphic event period (2.44Ga and 1.82 Ga) are consistent. So we speculate that the metamorphic mineralization in this region has a close genetic BIF the relationship with the two major tectonic thermal events throughout the eastern North China Craton landmass in the early Proterozoic occurred, the two is a continuous process in time. The combination of the North China Craton tectonic evolution history, we speculate that the Miyun. The formation of BIF in the region may be formed in the island arc tectonic environment.

【學位授予單位】：中國地質大學(北京)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P597.3;P618.31

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