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de Abrisqueta A.,Instituto Nacional Of Geologia Y Mineria | Lopez L.,Institute Ciencias Of La Tierra | Lo Monaco S.,Institute Ciencias Of La Tierra | Rojas H.,Central University of Venezuela
Acta Microscopica | Year: 2010

The study of chemical elements behavior in the depositational environmental and the relation between them, allows to infer the physical-chemical paleoenvironmental conditions, besides, it is used for study of hydrocarbon source-rock, and understanding primary migration. Therefore, the aim of this work is the study of spatial distribution and the association of the major (C, S, Si, Fe, K, Mg, P and Al) and trace (V, Ni, Zn) elements, with organic matter (accumulate in fracture during primary migration) and inorganic phases (minerals), by means of electron probe microanalysis (EPMA). The results shows that only elements associate to organic matter (found it in fractures and fossils) were S, Ni and V. The fractures are the principal route of migration; this is demonstrated by the association between the C, S, V and Ni. Additionally were found some elemental relation that it allowed to infer paleoenviromental conditions.

Research carried out within the project entitled "Integrated risk management in urban areas (Mérida Phase)" framed in Science Mission project, had as main objective (geological - geotechnical- geomorphological component) produce a map susceptibility to mass movements in the metropolitan area of Libertador Municipality of Mérida, which resulted from the integration of five conditions to the stability variables: slope, vegetation, geomorphology, kinematics and ground units and surface lithology. For purposes of the article will present one of the main variables used, the map units of soil and surface lithology. This map represents a proposal to be included within the susceptibility maps, allowing mapping the distribution area of surface geological materials based on their physical and geomechanical state, condition not considered in the classical analysis. Based on this new method, it was possible to characterize seventeen units surface material, considering: resistance, degree of fracturing, weathering and geomechanical behavior of materials, also establishing levels of propensity to instability.

De Abrisqueta A.,Instituto Nacional Of Geologia Y Mineria | De Abrisqueta A.,Central University of Venezuela | Urbani F.,FUNVISIS | Urbani F.,Central University of Venezuela | And 5 more authors.
Revista de la Facultad de Ingenieria | Year: 2011

The Las Mercedes Schist is the more extensive geological unit of the Coastal Cordillera and is characterized by graphite schist/phyllite usually cut by numerous carbonate veins. During the weathering process the phyllite changes from black to white and the white veins change to reddish and orange colors. Mineralogical and geochemical studies were carried out to understand the processes acting in these color changes. Under SEM, the unaltered graphite phyllite is highly conductive and texturally homogeneous, while the altered whitish side contains numerous pores and steps and losses electrical conductivity. It is interpreted that during the advance of the weathering front, the rock undergoes a partial or total loss of graphite, which affects the color and conductivity. Both the reddish and white fractions of the carbonate veins were identified as pure calcite, but the concentrations of Fe and Mn are significantly higher in the reddish fraction. The analysis by infrared spectroscopy ruled out the influence of organic compounds in the reddish fraction so a sample was added to HCL (10%) and the resultant insoluble residue was identified by X-ray diffraction as goethite. Consequently it is interpreted that the advance of the colored front is due to the deposit of microparticles of goethite, as aqueous solutions permeate the vein through intergranular surfaces and structural defects in the calcite. Goethite comes from the oxidation of pyrite and other primary minerals of the bedrock. Field observations clearly show that in both cases the color variations are due to weathering processes.

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