Native aluminium in metalliferous sediments from the East Pacific Rise axial zone (21°S)

Discovery of native aluminum and its possible origin from prospective gas hydrate areas in the South China Sea

“…The unit cell edge a calculated by the eight d ranges from (4.028±0.003)×10 −1 nm to (4.059±0.05)×10 −1 nm (Table 2), similar to those from the East Pacific Rise (a = 4.048×10 −1 −4.060×10 −1 nm) [14]. In addition, the value of a is also close to those from other locations such as in the rocks of basites (4.023×10 −1 nm) [1] and kimberlite pipe "Leningrad" (4.052×10 −1 nm) [2], in gibbsite-alunite-halloysite rocks near Lake Baikal (4.03×10 −1 -4.04×10 −1 nm) [19], in the oxidation zone in Getang, Guizhou Province (4.051×10 −1 nm) [9] and Table 2 X-ray diffraction data for native A1° particles from the SCS and synthetic Al in the Lianhuashan Tungsten Deposit, Guangdong Province (4.044×10 −1 nm) [8].…”

“…The Al° particles vary from 50 to 1100 μm in length and 10 to 50 μm in width. This size is almost identical to that of Al° grains in metalliferous sediments from the East Pacific Rise [14], but larger than that from the Central Indian Basin sediments [17]. Typical shapes of Al° particles are presented in Figure 2.…”

“…The chemical characteristics are similar to those from the Central Indian Basin (Al 2 O 3 =84.65%-99.11%) [17] and East Pacific Rise (Al=98%-99%) [14], but are distinctly different from those in basites on the Siberian Platform [1] and the tungsten deposit, Guangdong Province [7], where Al concentration is in a range of 48%-98% and 82.39%-100%, respectively. It implies that the formation environment of the studied Al° particles is almost identical to those from the Central Indian Basin [17] and the East Pacific Rise [14], suggesting Al° particles from the SCS are also formed in aqueous environments. Figure 3 shows the relationship of element concentration between Al and the other elements, except for Cr, Mn and P because there were fewer than five measurements for them.…”

“…Up to date hydrothermal activities and oceanic volcano eruption have not been reported at the areas of Al° particle occurrence, thus Al° origin differs from that in the East Pacific Rise [14] or the Central Indian Basin [17] where Al° was associated with hydrothermal activities. Similarly the studied Al° particles could not form in high temperature conditions like mantle ophiolites [10], kimberlite pipe [2] or magma basites [1].…”

“…Up to date, more than twenty discoveries of Al° have been reported such as in olivine kimberlitic tube [2], mud volcano [3], ore deposits [4][5][6][7], beresitization zone [8], jarositized quartzitic rock [9], ophiolitic chromitites [10], and potash rhyolites [11]. In addition, Al° was also discovered in sediments from the Pacific Ocean [12][13][14][15], the Atlantic Ocean [16], the Indian Ocean [17] as well as from the Red Sea [18] and the Lake Baikal [19]. These findings indicate that Al° can be formed and preserved in various geological settings, characterized by a considerable genetic diversity.…”