Person: Lunar Hernández, María Del Rosario
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First Name
María Del Rosario
Last Name
Lunar Hernández
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Cristalografía y Mineralogía
Identifiers
5 results
Search Results
Now showing 1 - 5 of 5
Item Origen de los fragmentos máficos-ultramáficos de la brecha mineralizada del yacimiento de Ni-Cu-EGP de Aguablanca (Badajoz)(Macla, 2004) Piña García, Rubén; Lunar Hernández, María Del Rosario; Ortega Menor, Lorena; Gervilla, F.; Alapieti, T.; Martínez, C.Item Detachment faulting and late Paleozoic epithermal Ag-basemetal mineralization in the Spanish central system(Geology, 1988) Doblas Lavigne, Miguel Manuel Delas; Oyarzun Muñoz, Roberto; Lunar Hernández, María Del Rosario; Mayor, Nicolás; Martínez, JesusHydrothermal activity during late Hercynian time resulted in epithermal silver-base-metal (Pb-Zn-Cu) vein formation in the eastern part of the Spanish central system. During the Hercynian orogeny, the central Iberian crust was thickened by compressional tectonics, heated, weakened, and subsequently overthickened by massive late Hercynian granitic intrusions. Subsequently, the central Iberian crustal welt underwent extensional collapse through lithosphere-scale, low-angle detachment faulting. The detachment systems evolved through tectonic denudation, isostatic rebound, and upward arching to define an extensional province much like the U.S. Basin and Range. Andesitic volcanism and hydrothermal activity occurred during extension, inducing epithermal-type hydrothermal convecting systems that leached, transported, and precipitated silver and base metals along fractures crosscutting the Hiendelaencina Metamorphic core complex.Item Zoned chromite records multiple metamorphic episodes in the Calzadilla de los Barros ultramafic bodies (SW Iberian peninsula)(European Journal of Mineralogy, 2014) Merinero Palomares, Raúl; Lunar Hernández, María Del Rosario; Ortega Menor, Lorena; Piña García, Rubén; Monterrubio Pérez, Serafín; Gervilla, FernandoPodiform chromitites occurring in the ultramafic bodies of Calzadilla de los Barros, in the Ossa-Morena zone of the Iberian Massif (SW Iberian Peninsula), were deformed and metamorphosed together with their host rocks, leading to the development of variably complex patterns of zoning in chromite grains. These patterns consist of cores with variable composition surrounded by thin rims of porous chromite. Two types of zoned chromite are observed in chromitites: (1) crystals with zoned cores characterised by progressive Mg# [¼Mg/(Mg þ Fe2þ)] decrease from inner to outer core, surrounded by Fe2O3-poor, porous rims, and (2) crystals showing the opposite chemical trend in cores (progressive Mg# increase from inner to outer core) and Fe2O3-rich porous rims. Mgrich chlorite is the only silicate mineral forming the matrix of all chromitites and filling most pores in chromite rims. Accessory chromites in dunites show complete transformation to ferrian chromite and Cr-rich magnetite. However, some of them exhibit complex chemical and textural zoning with three concentric zones (from inner to outer core and to inner rim) characterised by progressive Mg# increase and Cr# [¼Cr/(Cr þ Al)] decrease, surrounded by an outer rim with almost the same composition as the inner core. Some chromite grains from massive chromitites (defined here as higher than 85 vol.% chromite) still preserve inner core compositions unaffected by metamorphic transformation. These inner cores show high-Al composition (Cr# ¼ 0.48–0.52) with Mg# ranging from 0.65 to 0.70. These compositions resemble those reported for Al-rich, podiform chromitites in ophiolites elsewhere and indicate that chromitites from Calzadilla de los Barros derived from a MORB melt type in a MORB or supra-subduction zone setting. The chemical and textural variations in zoned chromite from chromitites and dunites can be interpreted in terms of a multistage process characterised by two episodes of retrograde metamorphism separated by a high-temperature heating event. This interpretation suggests a correlation with the tectono-metamorphic evolution of the Neoproterozoic basement of the Ossa-Morena zone.Item Dating of alteration episodes related to mercury mineralization in the Almaden district, Spain(Earth and Planetary Science Letters, 1997) Hall, Cris M.; Higueras, Pablo; Kesler, Stephen E.; Lunar Hernández, María Del Rosario; Dong, Hailing; Halliday, Alex N.The Almaden mercury deposits represent one of the largest geochemical anomalies on Earth, but the mode and timing of their formation remains a matter of controversy. There are two main possibilities: hydrothermal solutions associated with alkali basalt volcanism in the Silurian and Devonian; or regional hydrothermal activity during later Hercynian metamorphism. Although these models can be distinguished by determining the age of ore deposition, no suitable isotopic method had been applied to the problem prior to this study. We report here on vacuum encapsulated and more traditional laser 40Ar / 39Ar dating performed on illite concentrates and Cr-rich micas that are intimately associated with mercury mineralization in both Devonian and Silurian host rocks. Illite is associated with a later stage of Hg mineralization (cinnabar + kaolinite + pyrophyllite + chlorite) which locally replaces an earlier episode associated with carbonates and Cr-mica. The dating results from illite separates suggest that the later stages of Hg mineralization or remobilization occurred about 360 Ma, which is about 20 Ma younger than any mercury-hosting rocks in the district and coincides with the onset of regional deformation during the Hercynian orogeny. Cr-mica ages are variable and range from 365 Ma to 427 Ma. This age range spans the period between the deposition of the Criadero quartzite (the oldest sedimenta.~·y unit hosting mercury), and the later episode of mineralization. This suggests that mineralization started at least by the mid to lower Silurian and the younger argon ages for Cr-mica could represent partial to nearly total argon loss, caused by the Hercynian metamorphic event. It appears that both postulated styles of mercury mineralization occurred, separated in time by up to 80 million years.Item Internal features, mineralogy and geochemistry of ferromanganese nodules from the Gulf of Cadiz: The role of the Mediterranean Outflow Water undercurrent(Journal of marine systems, 2010) González, F.J.; Somoza Losada, Luis; Lunar Hernández, María Del Rosario; Martínez Frías, Jesús; Martín Rubí, Juan Antonio; Torres, Trinidad; Ortiz, J.E.; Díaz del Río, VíctorA large suite of Fe–Mn nodules (561 samples) were recovered during the Anastasya 2001 cruise (TASYO project) along the continental margin of the Gulf of Cadiz (Eastern Central Atlantic), at the confluence of the Mediterranean Sea with the Atlantic Ocean, where extensive nodule fields were discovered. Based on wide previous studies that included swath bathymetry, multi-channel and very high-resolution seismic reflection, gravimetry, magnetism, heat flow probes and underwater photography surveys, nodules were collected at water depths ranging from 850 to 1000 m, associated with hydrocarbon-derived Mg-calcite, ankerite and dolomite chimneys and crusts. Forty-six selected samples among the various morphological types were used for the laboratory analysis of physical properties (morphology, color, surface texture, sphericity, weight and size), mineralogy (XRD, optical and electronic microscopy), geochemistry (XRF, AAS, ICP-MS, ICP-AES, EPMA, and GC-MS) and stable isotopes. The nodules show a wide range of sizes, densities, weights and morphologies. They are formed by multiple millimeter-thick layers of Fe and Mn oxyhydroxides surrounding the nucleus composed of Early–Middle Miocene plastic marl and sediment, which were derived from underlying units by fluid venting. Massive, laminated, detrital and mottled to dendritic textural features were developed by the Fe and Mn oxyhydroxide layers. The main components are Goethite, lepidocrocite, Mn oxides (7 Å manganates and 10 Å manganates), quartz, and phyllosilicates. Accessory minerals are calcite, dolomite, siderite, rhodochrosite, kutnahorite, pyrite, chalcopyrite, potassium feldspar, zircon, rutile, ilmenite and chlorite. Fe–Mn carbonates from the siderite–rhodochrosite continuous series are the principal constituent of the nuclei. Framboidal, filamentous and globular textures are observed in Fe–Mn oxides and pyrite, suggesting biogenic origin. The nodules show a high mean abundance of Fe (38.6%), moderate Mn (6.0%) and low contents of trace metals and REEs compared to the average content of deep-seabed polymetallic nodules from other oceanic areas. The Mn/Fe ratio ranges from 0.07 to 0.25. The studied nodules hold hydrocarbons (n-alkanes) derived from marine bacterial activity in their oxide layers, with the presence of aromatic hydrocarbons as phenanthrene as well, characteristic of mature petroleum. The structure, mineralogy and chemical composition in the studied nodules are more similar to those of diagenetic–hydrogenetic continental margin nodules rather than deep-sea nodules. We suggest that the formation of this type of nodule could respond to a combined diagenetic–hydrogenetic growth process, where the fluid venting from deep-seated hydrocarbon reservoirs, the bio-mineralization processes and the bottom currents erosion and chemistry could have played an important role.