138 resultados para Formaldehyde-assisted isolation of regulatory elements


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The comparison of Mn/Fe, Co/Ni, Co/Fe, Ni/Mn, and Cu/Fe ratios is presented and it is noticed that Co/Ni and Ni/Mn ratios of nodules fairly coincide with those of coexisting sediments. This agreement suggests that Mn, Ni, and Co are accumulated in both nodules and sediments at about the same rates. According to the calculation of Somayajulu et al. similar consideration is also applicable to Cu. Results are, however, implying that Cu co-precipitates with Fe, rather than Mn.

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Trace-element content in igneous quartz from granitoids of different geochemical types from Bohemian Massif (Central Evrope) was investigated using the laser ablation ICP-MS technique. Two laboratories (Geological Survey of Norway, Trondheim, and Institute of Geology of the Academy of Science of Czech Republic, Praha) were involved in the trace-element (Li, Be, B, Mn, Ge, Rb, Ba, Pb, Mg, Al, P, Ca, Ti, Fe, and Sn) analyses of quartz (altogether, ~300 analyses of 17 rock samples). About 200 representative analyses of quartz are given in Tables 1 and 2.

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Petrographic and geochemical analyses of basaltic rocks dredged from the first segment of the Southwest Indian Ridge near the Rodriguez Triple Junction have been completed in order to investigate water-rock interaction processes during mid-ocean ridge (MOR) hydrothermal alteration in the Indian Ocean. In the study area, we have successfully recovered a serial section of upper oceanic crust exposed along a steep rift valley wall which was uplifted and emplaced along a low angle normal fault. On the basis of microscopic observation, dredged samples are classified into three types: fresh lavas, low-temperature altered rocks, and high-temperature altered rocks. The fresh lavas have essentially the same chemical composition as typical N-MORB, although LILE and Nb are slightly enriched and depleted, respectively. Low temperature alteration brought about the enrichment of K2O, Rb, and U due to the presence of K-rich celadonite and U-adsorption onto Fe-oxyhydroxide and clay minerals. On the other hand, chloritization, albitization, and addition of base metals by high temperature hydrothermal alteration result in enrichments of MnO, MgO, Na2O, Cu, and Zn and depletions of CaO, K2O, Cr, Co, Ni, Rb, Sr, and Ba. In addition, U-enrichment is also observable in the high temperature altered rocks probably due to the decrease of uranite solubility in the reducing high-temperature hydrothermal solution. These petrological and geochemical features are comparable to those of the volcanic zone to transition zone rocks in the DSDP/ODP Hole 504B, indicating that our samples were recovered from the upper ~1000 m section of the oceanic crust. Only the alteration minerals related to off-axis alteration are absent in our samples dredged from near the spreading axis. The similarity of alteration between our samples from the Indian Ocean and the Hole 504B rocks from the Pacific Ocean suggests that MOR hydrothermal systems are probably similar across all world oceans.