中西太平洋富鈷結(jié)殼Os同位素年代學(xué)研究及古海洋學(xué)意義
發(fā)布時間：2018-07-29 20:20
【摘要】：中、西太平洋海山區(qū)是全球富鈷結(jié)殼最富集的區(qū)域，本文對該地區(qū)7座海山的8個樣品進行分析，從空間和時間兩個方面對研究區(qū)的樣品進行研究，，取得如下認(rèn)識： 1.中西太平洋海山區(qū)富鈷結(jié)殼以水成成因為主，個別海山上出現(xiàn)混合成因結(jié)殼。作為富鈷結(jié)殼中的主要元素，Mn與Fe一般構(gòu)成此消彼長的反相關(guān)關(guān)系；但MP3D22樣則展示一個值得關(guān)注的特殊現(xiàn)象：新生代之前，在早期形成的結(jié)殼圈層中Mn和Fe呈明顯正相關(guān)，反相關(guān)關(guān)系的出現(xiàn)則須推遲至45Ma之后。這一情況暗示，中生代后期富鈷結(jié)殼中的Mn和Fe的來源可能均以內(nèi)源為主，始新世之后的Fe可能主要來自陸源輸入，而Mn依然以內(nèi)源為主。 2.精細(xì)的Os同位素年代學(xué)表明，研究區(qū)富鈷結(jié)殼樣品的187Os/188Os分布特征基本服從太平洋地區(qū)的演化樣式，可以據(jù)之構(gòu)建樣品生長-間斷的年代框架。其中，西側(cè)麥哲倫海山的MS-1樣始發(fā)育于56Ma，在53Ma發(fā)生沉積間斷，直到晚始新世即~36Ma復(fù)繼續(xù)生長，一直延續(xù)到當(dāng)代；而偏于太平洋中部萊恩海山群的MP海山的MP3D22樣則發(fā)育于距今72Ma的白堊紀(jì)晚期，在65Ma即中新生代界線附近產(chǎn)生間斷，在晚始新世即~38Ma恢復(fù)沉積，在早漸新世即~28Ma停止生長，裸存至今。上述兩種生長-間斷模式與已知的各種模式均存在一定差異，反映出鮮明的區(qū)域特色，其緣由有待深入分析。 3.富鈷結(jié)殼樣品中的Os同位素變化明顯受控于陸源物質(zhì)對太平洋的輸入，187Os/188Os隨生長層的波動不僅具有年代學(xué)意義，同時也反映海洋環(huán)境的深刻變化。始新世-漸新世界面附近187Os/188Os的不斷升高反映出亞洲大陸對太平洋沉積物質(zhì)的影響增強，可能與東特提斯海道的徹底關(guān)閉改變了北太平洋的環(huán)流模式以及青藏高原的加速隆升存在較密切的關(guān)聯(lián)。 4.富鈷結(jié)殼MS-1樣的古海洋學(xué)研究表明，56Ma左右時，陸源輸入較少而海底火山活動頻繁，結(jié)殼生長速率較慢但品位較高。25Ma左右南極底層流退縮，導(dǎo)致對氧與成礦物質(zhì)的傳輸速度減弱，結(jié)殼生長速率進入最慢期；從15Ma開始，隨著太平洋環(huán)流與南極底流的加強，陸源物質(zhì)輸入增加，結(jié)殼生長速率明顯加快，但品位亦隨之下降。
[Abstract]:In this paper, 8 samples of 7 seamounts in the western Pacific Ocean are analyzed, and the samples of the study area are studied from space and time. Gain the following knowledge: 1. Co-rich crusts in the western and western Pacific Ocean mountains are formed by water because of the main, mixed genetic crusts appear on individual seamounts. As the main element in cobalt-rich crusts, mn and Fe generally form a negative correlation, but MP3D22 patterns show a special phenomenon worthy of attention: prior to the Cenozoic, mn and Fe were positively correlated in the early crusts. The emergence of anti-correlation should be delayed until after 45Ma. This situation suggests that the origin of mn and Fe in the late Mesozoic cobalt-rich crusts may be mainly endogenous, and the Fe after Eocene may be mainly derived from land-based inputs, while mn is still mainly endogenous. Fine Os isotopic chronology shows that the 187Os/188Os distribution characteristics of cobalt-rich crusts in the study area are basically adapted to the evolution pattern of the Pacific region, according to which a growing and discontinuous chronological framework of the samples can be constructed. The MS-1 pattern of the western Magellanic seamounts began to develop at 56 Ma and was interrupted in 53Ma until the late Eocene, i.e., 36 Ma, and continued to grow until the present age. On the other hand, the MP3D22 pattern of MP seamounts in the central Pacific Ryan seamounts group developed in the late Cretaceous period of 72Ma, and was interrupted near the boundary of 65Ma, that is, Mesozoic and Cenozoic, and was restored to sediments at 38 Ma in the late Eocene, and ceased to grow at 28 Ma in the early Oligocene. Naked to this day. There are some differences between the above two growth and discontinuous models and the known models, which reflect the distinct regional characteristics, and the reasons need to be further analyzed. The variation of Os isotopes in cobalt-rich crusts is obviously controlled by the fluctuations of 187Os-188Os from terrestrial sources in the Pacific Ocean with the growth layer, which is not only of chronological significance, but also reflects the profound changes in the marine environment. The increasing 187Os/188Os near the Eocene-Oligocene interface reflects the increasing influence of the Asian continent on the Pacific sedimentary material. It is possible that the complete closure of the Eastern Tethys Seas changed the circulation model of the North Pacific Ocean and the accelerated uplift of the Qinghai-Xizang Plateau. Paleoceanographic studies of MS-1 samples of cobalt-rich crusts show that at about 56Ma, the continental source input is less, the submarine volcanic activity is frequent, the crust growth rate is slower but the lower Antarctic bottom current recovers at about 0.25 Ma or so, which results in the weakening of the transfer speed of oxygen and ore-forming materials. The crust growth rate entered the slowest stage, and with the enhancement of the Pacific circulation and the Antarctic bottom current, the terrestrial source material input increased, the crusting growth rate accelerated obviously, but the grade also decreased with the increase of the Pacific circulation and the Antarctic bottom current.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)（北京）
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P736;P597.3
[Abstract]:In this paper, 8 samples of 7 seamounts in the western Pacific Ocean are analyzed, and the samples of the study area are studied from space and time. Gain the following knowledge: 1. Co-rich crusts in the western and western Pacific Ocean mountains are formed by water because of the main, mixed genetic crusts appear on individual seamounts. As the main element in cobalt-rich crusts, mn and Fe generally form a negative correlation, but MP3D22 patterns show a special phenomenon worthy of attention: prior to the Cenozoic, mn and Fe were positively correlated in the early crusts. The emergence of anti-correlation should be delayed until after 45Ma. This situation suggests that the origin of mn and Fe in the late Mesozoic cobalt-rich crusts may be mainly endogenous, and the Fe after Eocene may be mainly derived from land-based inputs, while mn is still mainly endogenous. Fine Os isotopic chronology shows that the 187Os/188Os distribution characteristics of cobalt-rich crusts in the study area are basically adapted to the evolution pattern of the Pacific region, according to which a growing and discontinuous chronological framework of the samples can be constructed. The MS-1 pattern of the western Magellanic seamounts began to develop at 56 Ma and was interrupted in 53Ma until the late Eocene, i.e., 36 Ma, and continued to grow until the present age. On the other hand, the MP3D22 pattern of MP seamounts in the central Pacific Ryan seamounts group developed in the late Cretaceous period of 72Ma, and was interrupted near the boundary of 65Ma, that is, Mesozoic and Cenozoic, and was restored to sediments at 38 Ma in the late Eocene, and ceased to grow at 28 Ma in the early Oligocene. Naked to this day. There are some differences between the above two growth and discontinuous models and the known models, which reflect the distinct regional characteristics, and the reasons need to be further analyzed. The variation of Os isotopes in cobalt-rich crusts is obviously controlled by the fluctuations of 187Os-188Os from terrestrial sources in the Pacific Ocean with the growth layer, which is not only of chronological significance, but also reflects the profound changes in the marine environment. The increasing 187Os/188Os near the Eocene-Oligocene interface reflects the increasing influence of the Asian continent on the Pacific sedimentary material. It is possible that the complete closure of the Eastern Tethys Seas changed the circulation model of the North Pacific Ocean and the accelerated uplift of the Qinghai-Xizang Plateau. Paleoceanographic studies of MS-1 samples of cobalt-rich crusts show that at about 56Ma, the continental source input is less, the submarine volcanic activity is frequent, the crust growth rate is slower but the lower Antarctic bottom current recovers at about 0.25 Ma or so, which results in the weakening of the transfer speed of oxygen and ore-forming materials. The crust growth rate entered the slowest stage, and with the enhancement of the Pacific circulation and the Antarctic bottom current, the terrestrial source material input increased, the crusting growth rate accelerated obviously, but the grade also decreased with the increase of the Pacific circulation and the Antarctic bottom current.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)（北京）
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P736;P597.3
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