نتایج جستجو برای: Carbonates
تعداد نتایج: 9055 فیلتر نتایج به سال:
Different carbonates have been detected on Ceres, and their abundance and spatial distribution have been mapped using a visible and infrared mapping spectrometer (VIR), the Dawn imaging spectrometer. Carbonates are abundant and ubiquitous across the surface, but variations in the strength and position of infrared spectral absorptions indicate variations in the composition and amount of these mi...
Suk, D. Van der Voo, R. and Peacor, D.R., 1992. SEM/STEM observation of magnetic minerals in presumably unremagnetized Paleozoic carbonates from Indiana and Alabama. Tecfonop!tysics, 215: 255-272. The Silurian Wabash Formation in Indiana and the Mississippian Pride Mountain Formation in Alabama appear not to have been affected by a late Paleozoic remagnetization event. In an attempt to characte...
Data recorded of the Mormon Mesa by the airborne hyperspectral imaging spectrometer SEBASS show that some massive carbonates exhibit dramatically reduced spectral contrast for the strong carbonate bands at 6.5 and 11.25 μm. If carbonates are present on Mars, this type of reduced spectral contrast in massive carbonates could explain why they have not been detected using remotely sensed thermal i...
Carbonate oxygen isotope paleoaltimetry is based on analysis of the dO value of carbonate precipitated from surface water. Deciphering the diagenetic history is important for establishing whether particular carbonates are accurate recorders of paleosurface waters, which reflect paleoelevation. This study provides examples from southern, east–central, and northeastern Tibet of approaches aimed a...
It is well known that carbonates inhibit heavy metals transferring from soil to plants, yet the mechanism is poorly understood. Based on the Yangtze River delta area, we investigated bioaccumulation of Ni and Cd in winter wheat as affected by the presence of carbonates in soil. This study aimed to determine the mechanism through which soil carbonates restrict transport and plant uptake of heavy...
Carbonates are key minerals for understanding ancient Martian environments because they are indicators of potentially habitable, neutral-to-alkaline water and may be an important reservoir for paleoatmospheric CO2. Previous remote sensing studies have identified mostly Mg-rich carbonates, both in Martian dust and in a Late Noachian rock unit circumferential to the Isidis basin. Here we report e...
The ruthenium-catalyzed oxidative allylation of aromatic and α,β-unsaturated carboxamides with allylic carbonates is described. These transformations proceed readily with complete linear γ-selectivity of substituted allylic carbonates.
Carbonates. The dominant aqueous deposits in ALH 84001 are carbonate minerals, which form ellipsoids, discs, and other space-filling shapes, Figure 1 [1,4,5,6 etc]. These deposits are chemically zoned, nearly continuously from calcitic and ankeritic cores to magnesite-siderite compositions ranging from nearly pure magnesite to ~Mg45Fe45Ca10 (Fig. 2); hydromagnesite is not reported. The carbonat...
this study was conducted to characterize the reactivity of carbonates in the surface horizons of 20 soils (entisols and aridisols) from central region of iran. the samples were analyzed for calcium carbonate equivalent (cce), active calcium carbonate equivalent (acce), non-active calcium carbonate equivalent (n.acce), carbonate mineralogy and surface area of carbonates (ssa) through n2 adsorpti...
The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aero...
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