中西太平洋富钴结壳Os同位素年代学研究及古海洋学意义
发布时间：2018-07-29 20:20
【摘要】：中、西太平洋海山区是全球富钴结壳最富集的区域，本文对该地区7座海山的8个样品进行分析，从空间和时间两个方面对研究区的样品进行研究，，取得如下认识： 1.中西太平洋海山区富钴结壳以水成成因为主，个别海山上出现混合成因结壳。作为富钴结壳中的主要元素，Mn与Fe一般构成此消彼长的反相关关系；但MP3D22样则展示一个值得关注的特殊现象：新生代之前，在早期形成的结壳圈层中Mn和Fe呈明显正相关，反相关关系的出现则须推迟至45Ma之后。这一情况暗示，中生代后期富钴结壳中的Mn和Fe的来源可能均以内源为主，始新世之后的Fe可能主要来自陆源输入，而Mn依然以内源为主。 2.精细的Os同位素年代学表明，研究区富钴结壳样品的187Os/188Os分布特征基本服从太平洋地区的演化样式，可以据之构建样品生长-间断的年代框架。其中，西侧麦哲伦海山的MS-1样始发育于56Ma，在53Ma发生沉积间断，直到晚始新世即~36Ma复继续生长，一直延续到当代；而偏于太平洋中部莱恩海山群的MP海山的MP3D22样则发育于距今72Ma的白垩纪晚期，在65Ma即中新生代界线附近产生间断，在晚始新世即~38Ma恢复沉积，在早渐新世即~28Ma停止生长，裸存至今。上述两种生长-间断模式与已知的各种模式均存在一定差异，反映出鲜明的区域特色，其缘由有待深入分析。 3.富钴结壳样品中的Os同位素变化明显受控于陆源物质对太平洋的输入，187Os/188Os随生长层的波动不仅具有年代学意义，同时也反映海洋环境的深刻变化。始新世-渐新世界面附近187Os/188Os的不断升高反映出亚洲大陆对太平洋沉积物质的影响增强，可能与东特提斯海道的彻底关闭改变了北太平洋的环流模式以及青藏高原的加速隆升存在较密切的关联。 4.富钴结壳MS-1样的古海洋学研究表明，56Ma左右时，陆源输入较少而海底火山活动频繁，结壳生长速率较慢但品位较高。25Ma左右南极底层流退缩，导致对氧与成矿物质的传输速度减弱，结壳生长速率进入最慢期；从15Ma开始，随着太平洋环流与南极底流的加强，陆源物质输入增加，结壳生长速率明显加快，但品位亦随之下降。
[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.
【学位授予单位】：中国地质大学（北京）
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：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.
【学位授予单位】：中国地质大学（北京）
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P736;P597.3
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