نتایج جستجو برای: geochemical anomalies
تعداد نتایج: 57431 فیلتر نتایج به سال:
Regional exploration and identification of anomalies can be done by geochemical data resulted from stream sediments. In this paper, fractal methods of concentration-number and concentration-area were used for regional studies, and abnormalities of elements including gold, arsenic, bismuth and mercury were studied. Statistical processing of these elements took place with the help of 1063 samples...
Mantle plumes are hypothetical hot, narrow mantle upwellings that are often invoked to explain hotspot volcanism with unusual geophysical and geochemical characteristics. The mantle plume is a well-established geological structure in computer modeling and laboratory experiments but an undisputed seismic detection of one has yet to be made. Vertically continuous low shear velocity anomalies in t...
[1] Seismically, the African superplume is known to have a sharp lateral transition in VS and an interface between seismic anomalies with high relief. Such a structure is usually unstable in conventional thermo-chemical convection models. Using a compressible thermo-chemical convection model in which each material has a distinct equation of state, we find an expanded regime of metastable superp...
The stratigraphy of the South-Pole Aitken basin (SPA) interior is consistent with that of a massive impact melt sheet that differentiated to form cumulates. Spectroscopic and geophysical constraints on the stratigraphy of SPA suggest a 12.5 km thick layer of norite above ultramafic pyroxenite and dunite layers. A similar stratigraphy is produced from differentiation by crystal settling of a 50 ...
As human impact have been increasing strongly over the last decades, it is crucial to distinguish human-induced dust sources from natural ones in order to define the boundary of a newly proposed epoch - the Anthropocene. Here, we track anthropogenic signatures and natural geochemical anomalies in the Mukhrino peatland, Western Siberia. Human activity was recorded there from cal AD 1958 (±6). An...
New occurrences of free gold were identified during fieldwork at outcrops located in the western part of the Castro Basin, state of Paraná. These are associated with silicified and sulfide-rich zones in hydrothermally-altered volcanic rocks. The aerogeophysical data indicate that the areas of the new targets show high K and eU relative to eTh, suggesting intense hydrothermal alteration. The str...
the closed nature of geochemical data has been proven in many studies. compositional data have special properties that mean that standard statistical methods cannot be used to analyse them. these data imply a particular geometry called aitchison geometry in the simplex space. for analysis, the dataset must first be opened by the various transformations provided. one of the most popular of the a...
The Robat-Paein barite deposit is located about 30 Km northwest of Khomein city, in the Sanandajـ Sirjan zone. The Lower Cretaceous carbonate sequences are the host rock of barite mineralization in the Robat-Paein deposit. These carbonate sequences consist mainly of massive bedded orbitolina-bearing limestone (undergone dolomitization in some areas) as well as marl, shale and thinly bedded l...
The Neoproterozoic witnessed several low latitude glaciations (i.e., the Sturtian, Marinoan and Gaskiers glaciations) geodynamic reorganization of cratonic blocks after breakup Rodinia. Trace element stable isotope geochemistry from approximately coeval carbonate deposits on continental marginal sea foreland basins (Yangtze Platform, China; Otavi Nama Groups, Namibia) have shown fluctuating oxy...
The inexpensive geochemical exploration technique based on broadspaced deflation lag sampling played a key role in the discovery of the Babel and Nebo ortho-magmatic Ni–Cu–platinum group elements (PGE) deposits. An area of 1100 km in the western Musgrave Block in central Australia was explored using deflation lag samples collected on a 1 km 0.5 km grid. A total of 35 elements were determined us...
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