ENRICHING MECHANISM OF MINERALIZING ELEMENTS IN CO-RICH CRUST ON ALLISON SEAMOUNT, CENTRAL PACIFIC OCEAN
-
摘要: 以中太平洋阿利森海山的Al-l富Co结壳为研究对象,在其结构观察、年龄标定和生长世代确定的基础上,平均按1.3mm间隔取样,测定各分层常微量元素含量,计算了结壳中各元素的富集系数和分布系数。结合元素富集系数、分布系数和特征元素对比值,探讨了古环境演化对结壳中元素富集的制约。研究表明,结壳中富集的元素正是那些在海水中滞留时间较短的元素;结壳是海洋中"清扫"型元素重要的"汇";元素在海水的行为是其在结壳中富集的内因。碳酸盐的溶解导致的Fe、Ba的释放有利于结壳的生长,但却"稀释"了Mn、Co、Ni等元素的累积;最低含氧带的发育和南极底层水活动的加强利于Mn、Co等元素的氧化和"清扫"。结壳的生长间断是南极底层流活动减弱和活动模式发生根本转变的结果;火山活动沉积抑制了结壳的生长;6.8Ma是结壳从快速生长到缓慢生长发生转变的关键时期。Abstract: Based on its structure, growth age and growth generations, the crust A1-1 from the Allison seamount of the Central Pacific Ocean was sub-sampled at an average interval of 1.3 mm in order to measure the concentrations of major and trace elements for each layers and subsequently to calculate the enrichment coefficient and distribution coefficient of the mineralizing elements of the crust. According to the coefficients and special element ratios, the constraint of paleo-environment on the enrichment of mineralizing elements in the crust was discussed. The study shows that the elements enriched in the crust are just those that have shorter resistant time in seawater. The crust is an important "sink" for the elements that are easily scavenged. The element behaviors in seawater are the intrinsic causation for their enrichment in crust. The release of iron and barium resulted from the dissolution of carbonate is favorable for crust growth, but dilutes the accumulation of manganese, cobalt and nickel. The development of Minimum Oxygen Zone and the strengthening of Antarctic Bottom Water are favorable for the oxidation and scavenging of manganese and cobalt. The growth hiatus occurring in crust is resulted from weakening and ultimate change of Antarctic Bottom Water. Volcanic ash restrains crust growth. It was at 6.8 Ma when the crust grew from rqpid to slow rake.
-
-
[1] Aplin A C, Cronan D S. Ferromanganese oxide deposits from Central Pacific Ocean. I:Encrustations from the Line Island Archipelago[J]. Geochim Cosmochim Acta, 1985, 49:427-436.
[2] De Carlo E H, Pennywell P A, Fraley C M. Geochemistry of ferromanganese deposits from Kiribati and Tuvalu Region of West Central Pacific Ocean[J]. Marine Mining, 1987, 6:301-321.
[3] Halbach P, Puteanus D. The influence of the carbonate dissolution rate on the growth and composition of Co-rich ferromanganese crusts from Central Pacific seamount areas[J]. Earth Planet Sci. Lett, 1984, 68:73-87.
[4] Alvarez R, De Carlo E H, Cowen J, et al. Micromorphological characteristic of a marine ferromanganese crust[J]. Marine Geology, 1990, 94:239-249.
[5] De Carlo E H. Paleoceanographic implication of rare earth elements variability in a marine Fe-Mn crust from the Hawaiian Archipelago[J]. Marine Geology, 1991, 98:449-467.
[6] Hein J R, Bohrson W A, Schulz M J. Variation in the fine-scale composition of a central Pacific ferromanganese crust:Paleoceanographic implications[J]. Paleoceanography, 1992, 7:63-77.
[7] McMurtry G M, Vonderhaar D L, Eisenhauer A, et al. Cenozoic accumulation histry of a Pacific ferromanganese crust[J]. Earth Planet Sci. Lett, 1994, 125:365-384.
[8] Neumann T, Stueben D. Detailed geochemical study and growth histry of ferromanganese crusts from the Tuamotu Archipelago[J]. Marine Mining, 199110:29-48.
[9] Wen X Y, De Carlo E H. A comparative study of the geochemistry and internal structure of seamount ferromanganese crusts. EOS Trans[J]. Am. Geophs. Union, 1994, 74:78.
[10] 孟宪伟, 石学法, 杜安道, 等. 中太平洋Allison海山富Co结壳Os同位素组成及其生长间断与生长年代的确定[J]. 中国科学D辑, 2008, 38(6):1130-1135.
[MENG Xianwei, SHI Xuefa, DU Andao, et al. Determine Osisotopic Composition and gronth of intermittent and grwh period in Co-rich Crust from ALLison Seamount, central Pacific Ocean[J]. Science in China (Series D), 2008, 38(6):1130-1135.]
[11] Wen X, De Carlo E H, Li Y H. Interelement relationships in ferromanganese crusts from the central Pacific ocean:Their implications for curst genesis[J]. Marine Geology, 1997, 136:277-297.
[12] Halbach P, Manheim F T, Otten P. Co-rich ferromanganese deposits in the Marginal seamount regions of the Central Pacific Basin-results of the Midpac'81[J]. Erzmetall, 1982, 35:447-453.
[13] Segl M, Mangini A, Bonani G, et al. 10Be-dating of a manganese crust from Central North Pacific and implications for ocean palaeocirculation[J]. Nature, 1984, 309:540-543.
-
计量
- 文章访问数: 956
- PDF下载数: 4
- 施引文献: 0
下载: