中、西太平洋多金属结壳生长速率变化与制约因素

Variation in growth rate of polymetallic crusts in the central and western Pacific Ocean and its constraining factors

  • 摘要: 多金属结壳在不同生长区域、层位存在生长速率的差异,这在一定程度上反映了其生长条件的优劣,说明其受到了诸多海洋要素的制约。本研究在总结生长速率变化与结壳生长区域、年代和结构构造的关系的同时,分析生长间断发生与生长速率变化的关系,并尝试对多金属结壳生长环境条件的转变进行探讨。多金属结壳的生长速率随采样海山区位置由东向西(莱恩海山区—麦哲伦等海山区)、结构构造由致密到疏松再到较致密和生长期由老到新由高至低变化。最低含氧带之下合适的深度、较强的氧化性、较丰富的陆源物质供给和海洋中较高的碳酸钙溶解率有利于结壳的生长,使其具有较大的生长速率。多金属结壳生长间断的发生对应3种生长速率变化情形:①在生长速率由低升高前,主要对应65~60 Ma的间断期,此时水动力条件不佳,结壳因生长环境过差而间断,由差转好时复生长;②生长速率由高转低时,主要对应51~42 Ma和40~35 Ma的两次间断期,此时气候回暖同时陆源风尘供应水平较低,结壳在生长环境变差时间断,稍好时复生长;③生长速率持续偏低时,对应28~18 Ma的间断期,此时大洋CaCO3溶解率持续偏低,结壳在长时间较差的生长环境中断续生长。

     

    Abstract: The growth rate of polymetallic crust varies in different growing areas and layers, constrained by some marine factors. In this paper, the polymetallic crust growth rate and its variation with growth region, age and structures are studied, in addition to the relationship between growth discontinuity and growth rate change. It is found that from east to west of the study area, i.e. from the Line Seamounts to Magellan Seamounts, the growth rate of polymetallic crusts decreases as the crusts change from dense to loose to sub-dense in layers, from old to young in ages and from high to low in topography. The areas below OMZ, where it is strong in oxidability, abundant in terrigenous materials supply and high in dissolution rate of calcium carbonate, are the areas favorable to the growth of crusts. Hiatus of crusts corresponding to three types of growth rate changes are observed in the study area: a) before the growth rate turned from low to high, which mainly corresponds to the hiatus of 65~60 Ma, the hydrodynamic condition of the environment is not good enough to crust growth, so the crust stopped growing and the crust could only resume growing when conditions were improved. b) when the climate warmed up and the supply of continental-derived wind dust remain low, the growth rate of crust would drop from high, which mainly corresponds to the two hiatuses during 51~42 Ma and 40~35 Ma. The crusts stopped growing when the environment became severe, and could only resume growing when it was slightly getting better. c) the growth rate remained low, which corresponded to the hiatus of 28-18 Ma, while the dissolution rate of CaCO3 in the ocean was low. The crusts grew intermittently if the growth environment remained poor.

     

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