Videos by Ricardo A Valls
A series of webinars aimed to reduce the gap between the Academy and the Industry in Geology
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Papers by Ricardo A Valls
Journal of Geology & Geophysics, Jul 16, 2015
There is almost not a case in exploration geology, where the studied data doesn’t includes below ... more There is almost not a case in exploration geology, where the studied data doesn’t includes below detection limits and/or zero values, and since most of the geological data responds to lognormal distributions, these “zero data ” represent a mathematical challenge for the interpretation. We need to start by recognizing that there are zero values in geology. For example the amount of quartz in a foyaite (nepheline syenite) is zero, since quartz cannot co-exists with nepheline. Another common essential zero is a North azimuth, however we can always change that zero for the value of 360°. These are known as “Essential zeros”, but what can we do with “Rounded zeros ” that are the result of below the detection limit of the equipment? Amalgamation, e.g. adding Na2O and K2O, as total alkalis is a solution, but sometimes we need to differentiate between a sodic and a potassic alteration. Pre-classification into groups requires a good knowledge of the distribution of the data and the geochemic...
Todos los derechos reservados. Esta publicación está protegida por derechos de autor y el permiso... more Todos los derechos reservados. Esta publicación está protegida por derechos de autor y el permiso debe obtenerse de Valls Geoconsultant antes de cualquier reproducción prohibida, almacenamiento en un sistema de recuperación, o transmisión en cualquier forma o por cualquier medio, electrónico, mecánico, fotocopiado, grabación, o de la misma manera. Para obtener información sobre el permiso, escriba a Valls Geoconsultant al 1008-299 Glenlake Ave.
Ejemplos de aplicación de métodos artesanales a las investigaciones geológicas.
The Izabal Geosol is a new stratigraphic unit defined by the author within the Sierra de Santa Cr... more The Izabal Geosol is a new stratigraphic unit defined by the author within the Sierra de Santa Cruz (SSC) ophiolitic belt which is located to the north of Lake Izabal, in the east-central portion of Guatemala, some 140 km northeast from Guatemala City. The Geosol Izabal is composed of the following five pedosols: a. Gossan or Iron Cap (a.k.a. Ferricrete) b. Limonitic Horizon c. Stoneline Horizon d. Mottled Zone Horizon (a.k.a. Transition Zone) e. Saprolitic Horizon The Saprolitic Horizon lies over a Saprock Horizon, which, in turn, lies directly over a less weathered bedrock of the SSC ophiolitic belt. The most complete profiles are usually presented over weathered dunites and serpentinites, while on top of the less altered pyroxenites there usually forms only a limonitic horizon. The SSC ophiolitic belt overthrusted the Maya Block of the North American Continental Plate during the Early Tertiary period along a flat structure that outcrops at its base. The SSC is one of the five oph...
La determinación segura de la presencia de serpentinitas en los cortes estratigráficos de los poz... more La determinación segura de la presencia de serpentinitas en los cortes estratigráficos de los pozos de petróleo del yacimiento CANTEL es muy importante por ser las serpentinitas las principales colectoras de petróleo en esa zona en Cárdenas, Matanzas, Cuba.Para identificarlos, el geólogo cuenta como principal y casi única ayuda las muestras de canal, las cuales no son siempre fáciles de identificar visualmente.En el presente trabajo se ofrece una secuencia de análisis químicos que permiten la identificación de los tres componentes primarios de las serpentinitas (sílice, magnesio e hidroxilo), así como de los principales elementos acompañantes de la misma (níquel, cromo, aluminio, y hierro).Tanto la marcha analítica como los equipos y reactivos necesarios son suficientemente sencillos para que la misma pueda hacerse directamente en el pozo por los geólogos que atienden el mismo, permitiendo de esta forma la identificación inmediata de la presencia de serpentinitas con mayor seguridad.
La mayor utilidad del presente escrito es que sirva de modelo de cómo organizar una investigación... more La mayor utilidad del presente escrito es que sirva de modelo de cómo organizar una investigación científica de un tema en específico. Desde la formulación del problema a la recolección de información; de la generación de una hipótesis de alto nivel explicativo hasta la contrastación de los resultados para llegar finalmente a la presentación de la solución en forma de un reporte predictivo. Espero que el modelo le sea de utilidad en su trabajo investigativo.
El objetivo de este trabajo es la confección de una nueva clasificación geoquímica de los element... more El objetivo de este trabajo es la confección de una nueva clasificación geoquímica de los elementos que elimine las divergencias que existen entre las clasificaciones conocidas y que sea, al mismo tiempo, de utilidad práctica para el geólogo de campo. Como resultado, se obtuvo una clasificación geoquímica “unificada”, al reflejarse en la misma las clasificaciones preexistentes y la que se propone en este trabajo.
Durante la década de los ochenta, se desarrollaron en Cuba investigaciones dirigidas a la búsqued... more Durante la década de los ochenta, se desarrollaron en Cuba investigaciones dirigidas a la búsqueda de gemas, piedras semipreciosas y ornamentales con vistas a obtener nuevas fuentes de materias primas nacionales necesarias para el desarrollo económico del país.Con esta publicación se pretende alertar a los especialistas y técnicos del ramo, sobre la posibilidad de descubrir yacimientos de crisoprasas en las cortezas de intemperismo niquelíferas de Cuba.Acá se exponen las principales propiedades físicas, ópticas y químicas de dicha gema, así como sus peculiaridades geológicas y económicas. Se caracteriza la composición química de las cortezas de intemperismo niquelíferas de Cuba Oriental. Por último, se incluyen criterios geológicos, mineralógicos y geoquímicos para facilitar la búsqueda de esta gema.
Si el estudio de los procesos geoquímicos en condiciones tropicales es aún joven en países tropic... more Si el estudio de los procesos geoquímicos en condiciones tropicales es aún joven en países tropicales, menos todavía se conoce acerca de dichos procesos en las grutas y cavernas. El estudio de los procesos espelogeoquímicos es importante ya que muchas grutas representan zonas de debilidad tectónica y por ende son más propensos a los procesos hidrotermales-metasomáticos. Además, por su morfología y posición topográfica, las espeluncas son en ocasiones depositarias de importantes acumulaciones de minerales útiles, tal como la bauxita, el caolín, la fosforita, algunas piedras preciosas, el manganeso, y otros.En ocasiones son los mismos procesos geoquímicos los que conllevan a la formación de importantes minerales en las grietas.En este reporte se analizan estos procesos geoquímicos y se propone un plan de observaciones espelogeoquímicas factibles de ser desarrollados inclusos por aficionados sin preparación geológica especial.
Enzyme selective extractions (ESE) aids in the detection of mineral deposits at depths ranging fr... more Enzyme selective extractions (ESE) aids in the detection of mineral deposits at depths ranging from a few meters to 800 metres and sometimes more. This selective extraction technique was developed over the past 25 years and it has been utilized successfully to locate many types of mineral deposits. Ore bodies are indicated by a host of elements that are distributed into positive and negative patterns at surface, above and around the margins of mineral deposits. Trace elements become trapped at parts-per-billion and parts-per-trillion levels within amorphous oxide coatings on sand and silt grains in the soil or sediment in the near-surface environment. Selective extraction by Enzyme Leach of amorphous MnO within these coatings and subsequent analysis for up to 68 trace and major elements by ICP-Mass Spectrometry reveals repeatable patterns that indicate blind mineral bodies. One big advantage of this method is the simplicity of the sampling procedure and the small amount of material ...
Golden Software Inc. included the method of cokriging in the newest version of SURFER 17. This ha... more Golden Software Inc. included the method of cokriging in the newest version of SURFER 17. This has opened a new tool for interpreting geochemical data. We can use cokriging in SURFER 17 to improve the quality of maps and to predict similar targets in nearby areas. We use cokriging when we want to process data from different datasets. One dataset is always smaller than the other. Here, I first tasted the method with a hypothetical geochemical model combining a smaller dataset of FA gold results with a larger dataset of ICP-MS multi-elements. Later, I applied this method to real data from a soil sampling project in Mozambique. I tested a known mineralized target and also an extended area to predict gold targets. I also had the gold results for the extended area. They allowed me to confirm the effectiveness of cokriging in predicting the new targets. There are many opportunities where we can apply cokriging as a prediction tool. One situation is when an initial sampling returned a grou...
Alicanto Mining Corp. through its fully owned Colombian subsidiary Alicanto Colombia S.A.S., has ... more Alicanto Mining Corp. through its fully owned Colombian subsidiary Alicanto Colombia S.A.S., has applied for two licenses in the Rionegro Project, northwest of Bucaramanga, and encompassing disseminated gold mineralization in a marine basin. Within Rionegro II, the Client owns the exploitation area contract JG3-1392 (Mina Guayos) with 7.65 km2. Within the Rionegro applications there is an exploitation contract IH8-11141 of 4 km2 and the application license GEG-154A of 0.2 km2 located within the Mina Guayos exploitation contract that do not belong to the Client. Besides the known placers in the river, there is a clear potential for paleo placers associated to a Jurassic marine basin in the area, as well as gold associated to a sequence of Tertiary conglomerates. There is also the potential for a Carlin type of mineralization in the bituminous-rich limestones, as well as gold associated to a tonalite intrusive. All exploration permits have been obtained and are in order, and to the ex...
The San José de Las Malezas quartz-gold deposit is located on the North side of the Cuban Ophioli... more The San José de Las Malezas quartz-gold deposit is located on the North side of the Cuban Ophiolitic Complex, within the Structural-Facial Zone "Zaza", Province of Villa Clara, Cuba. In the area of the deposit there is a well developed listwanite zone that begins with (i) massive and relatively little altered serpentinites that pass into (ii) iron-altered serpentinites which are in gradational contact with (iii) completely carbonatized rocks and (iv) a core of silicified rocks and quartz veins. Copper and gold mineralization are associated with these quartz bodies, but binary correlation analysis of geochemical data suggests that the ores are genetically independent of one another. In concordance with the proposed genetic model supported by thermodynamic calculations and field observations, copper is thought to be introduced by a hydrothermal process, whereas gold was leached from the serpentinites. The evolution of manganese minerals from anaerobic to aerobic species prov...
A geological reconnaissance at an approximated scale of 1:100000 was done over 112 km2, between t... more A geological reconnaissance at an approximated scale of 1:100000 was done over 112 km2, between the townships of Roche Platte to the West, Jasquezyl to the North, Grand Basin to the East, and Perches to the South. A total of 56 points were described for an average of one geological observation per two square kilometers.Also, 18 grab samples were taken from mineralized showings, as well as three heavy mineral concentrates and two samples for whole rock analysis.All the collected information was kept in a database created on MS Access by the author of this report. The database, including the results of the analysis, can be consulted on Mendeley at doi:10.17632/b35fmjntnr.1.A model for the regional geological evolution of the area is presented, as well as a proposal for the denomination of the three basic geological structures found in the area, The Douvray Volcanic Group, the Grand Basin Magmatic Complex, and the Bercera Volcanic Formation, which the author interpreted as the last vol...
The geology of Northern Haïti corresponds to a volcanic arc of Meso-Cenozoic Age that can be trac... more The geology of Northern Haïti corresponds to a volcanic arc of Meso-Cenozoic Age that can be traced from Central Cuba, through the Dominican Republic and forms part of the mountains of the Massif du Nord Group in Haïti oriented NW-SE. This group is composed of volcanic tuffs and lavas from the volcanic belt, ranging in composition from felsic, through intermediate, to mafic and ultramafic rocks. The belt is composed of numerous lenticular bodies of lavas and pyroclastic material of felsic composition, varying from dacite to rhyolite, embedded in a thick series of andesites with lesser amounts of basalts and with numerous intercalations of radiolarians cherts, carbonate rocks, and tuffs. Copper and gold are the two main ore types in the area. Copper is usually found associated with the porphyritic facies, the apophyses microtonalitics, and the silicified zones, filling fissures and fractures, as well as disseminated. Within the quartz vein systems, the copper is contained in the chal...
We studied an outcrop of massive iron-copper-zinc sulphides in Cretaceous volcanogenic intermedia... more We studied an outcrop of massive iron-copper-zinc sulphides in Cretaceous volcanogenic intermediate to felsic rocks, located to the south of the village Los Tramojos, in the province of Sancti Spiritus, in Central Cuba. It is an artificial cut of dacitic tuffs and volcanic breccias with a strong mineralized area, dark in color, containing pyrite, magnetite, barite, sphalerite, bornite and others copper sulphides, as well as apatite, galenita and chalcopyrite. This area includes another tectonic zone with limonitic, hematitic, zeolitic and chloritic alterations, in contact with tuffs and non-mineralized and fresh volcanic breccias. It is a manifestation of a submarine volcanic-exhalative type. The mineralized area described above are very like the so call "Black Ores" of the Kuroko type of deposits. We investigated an area of 3,000 m2 using a soil grid of 25 x 10 meters, with some lithogeochemical samples. This study allowed to determine the correlation coefficients charact...
A main limitation of geochemistry is that we never know whether a low value of gold in sample X i... more A main limitation of geochemistry is that we never know whether a low value of gold in sample X is there because there is no gold or because the source of mineralization is too deep for the technique used. In geochemical surveys, the actual value of a sample is not as important as its difference with other surrounding samples. This difference is known as gradient, a term more frequently used by geophysicists.I present here a simple method to quickly identify gradient areas that may be due to the presence of a true geochemical anomaly using Excel.
Existen varios métodos para el análisis de los minerales. Entre los más exactos tenemos las secci... more Existen varios métodos para el análisis de los minerales. Entre los más exactos tenemos las secciones delgadas o los microscopios electrónicos. Pero estos métodos sólo pueden utilizados en instalaciones especiales y requieren, generalmente, de una preparación más profesional.También las propiedades físicas de un mineral a veces bastan para identificarlo.En cambio, hay minerales que presentan propiedades físicas muy semejantes, pero que se diferencian radicalmente por su composición química. En esos casos tenemos que recurrir a los análisis químicos para poder identificar el mineral estudiado.Con este artículo quiero ofrecerle al aficionado a la geología una segura guía para que logre identificar cuarenta y tres de los elementos más comunes para que de esta forma esté preparado para identificar el mineral que está estudiando. En negritas están señalados los elementos de importancia industrial más comunes.Para realizar estos experimentos no son necesarios equipos especiales, por lo qu...
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Videos by Ricardo A Valls
Papers by Ricardo A Valls