论文部分内容阅读
利用Os同位素地层学方法结合钴含量经验公式,确定了分布于太平洋海山的两个富钴结壳的生长年龄,其中MHD79自距今75Ma开始生长,经历了4次生长间断,分别在63~59,51~42,38~33和25~11Ma.MP3D10推测于距今62Ma以前开始生长,其间经历了5次生长间断,分别在62~59,51~40,38~33,23~11和8~4Ma.通过与前人的研究成果包括ODP144航次以及中太平洋海山的结壳CD29-2,N5E-06和N1-15进行对比研究,发现它们比较一致的5个生长与间断时期与新生代海洋演化过程存在着密切的关系.古新世碳同位素最高期(PCIM)全球海洋生产力上升,刺激了海山结壳的生长,富钴结壳的第一个生长间断(Ⅰ)结束.古新世-始新世最暖期(PETM),虽然海水的垂直交换减弱,但强烈的陆地化学风化致使大量的陆源营养物质输入,生物生产率上升,没有发生结壳的生长间断.而早始新世气候最佳期(EECO)距今52~50Ma,两极温暖,纬向温度梯度小,风驱海洋循环及上升流活动微弱,陆地风化作用亦减弱,开放大洋的生物生产力下降,富钴结壳再次出现生长间断(Ⅱ).中始新世早期-始新世晚期、渐新世是一个长期渐进的变冷过程,海洋循环和上升流活动增强导致的生物生产力上升,并由此造成水成成因元素Fe,Mn和Co及生物成因元素Cu和Zn含量增加,是研究区最有利于富钴结壳生长的阶段(生长期Ⅲ,Ⅳ),其间的间断期Ⅲ对应于始新世-渐新世界线,推测与始新世-渐新世之交的全球气候转型、天体撞击事件有关.中新世早至中期研究区富钴结壳经历的一次较大规模的生长间断(间断期Ⅳ),推测与中新世早期短暂的气候回暖,南极底流的暂时退缩有关.其后南极冰盖扩展,底层水环流增强,大洋肥力增加,一度中断的结壳于中新世晚期又继续生长(生长期Ⅴ).
Based on the empirical formula of Os isotope stratigraphy combined with cobalt content, the growth ages of two cobalt-rich crusts distributed in seamounts in the Pacific Ocean were determined. The MHD79 began to grow from 75 Ma up to now and experienced 4 growth discontinuities, ranging from 63 to 59 , 51 ~ 42,38 ~ 33 and 25 ~ 11Ma.MP3D10 was estimated to grow 62Ma ago, during which 5 growth discontinuities occurred, ranging from 62 to 59, 51 to 40, 38 to 33, 23 to 11, and 8 ~ 4Ma. By comparing with the predecessor’s research results including ODP144 voyage and the crusts of the Central Pacific seamounts CD29-2, N5E-06 and N1-15, it is found that their relatively five growth and discontinuity periods and the Cenozoic ocean And the evolutionary process is closely related.The rise of global marine productivity in PCIM at the highest stage of the Pliocene accelerated the growth of seamounts and ended the first growth of cobalt-rich crust (Ⅰ) In the Eocene warm-up period (PETM), although the vertical exchange of seawater weakened, strong terrestrial chemical weathering led to the input of a large amount of terrigenous nutrients, which led to the increase of biological productivity and the absence of crustal growth. Good times (EECO) 52 ~ 50Ma, bipolar warm, latitudinal temperature gradient is small, The marine circulation and upwelling activities are weak, and the weathering of the terrestrial is weakened. The biological productivity of the open ocean is declining, and the growth of cobalt-rich crusts is intermittent again (Ⅱ). In the middle of Eocene-Late Eocene, Oligocene is a Long-term and gradual cooling process, increased biological productivity due to enhanced marine circulation and upwelling activities resulted in the increase of water-forming genetic elements Fe, Mn and Co and biogenic elements Cu and Zn, which is the most favorable for the study area The phases of the growth of cobalt crusts (growth stages III, IV), the interphase III corresponds to the Eocene-Oligocene line, and the correlation with the global climate change during the Eocene-Oligocene transition and the collision with celestial bodies A larger episode of intergrowth (discontinuity IV) experienced by cobalt-rich crusts in the early to mid-Miocene study area was postulated to be related to the brief warming of the Antarctic ice and the temporary retreat of the Antarctic ice in the early Miocene Cover expansion, bottom water circulation enhancement, increased ocean fertility, once interrupted crusts continue to grow in late Miocene (growth period Ⅴ).