Person: Ortega Menor, Lorena
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First Name
Lorena
Last Name
Ortega Menor
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
MineralogÃa y PetrologÃa
Area
CristalografÃa y MineralogÃa
Identifiers
25 results
Search Results
Now showing 1 - 10 of 25
Item La actividad metalogénica durante el TardihercÃnico en el centro de España: una visión desde cinco localidades tipo(Geogaceta, 1996) Lillo Ramos, F. Javier; Oyarzun, Roberto; Ortega Menor, Lorena; Gallego, M.The most outstanding metallogenic period in central Spain took place during the so-cal/ed lateHercynian episode. This episode was characterized by widespread extensional conditions resulting from the collapse of an overthickened and overheated Hercynian orogen. A combination of magmatic activity and favorable structures induced hydrothermal activity leading to Sn-W, Pb-Zn, Ag-base metals, base metals-Ba-(F) and Sb-(Au) deposition. Five ore deposits/districts: El Trasquilón (Sn), Linares-La CarolinaTorrecillas (Pb-Zn-Ba-[Ag]), Sierra de Guadarrama (Ba-(F)-[base metals]), El Juncalón (Sb-[Au]), and Hiendelaencina (Ag-base metals) allow characterization of the main geologic features of this metallogenic episode.Item Evidencias de fraccionación en el yacimiento intramagmático de Ni-Cu-EGP de Aguablanca (Badajoz)(Cuadernos do Laboratorio Xeolóxico de Laxe, 2000) Ortega Menor, Lorena; Lunar Hernández, Rosario; GarcÃa Palomero, F.; MartÃn Estévez, J.R.Item The manto-type gold deposits of Andacollo (Chile) revisited(Economic geology and the bulletin of the Society of Economic Geologists, 1996) Oyarzun, Roberto; Ortega Menor, Lorena; Sierra, Josefina; Lunar Hernández, RosarioItem Conditions of graphite precipitation in the volcanic-hosted deposits at Borrowdale (Cumbria, UK)(2009) Ortega Menor, Lorena; Luque del Villar, Francisco Javier; Barrenechea, Edurne; Beyssac, Olivier; Huizenga, Jan-Marten; Millward, D.; Rodas, MagdalenaItem Edades de cristalización U-Pb en circones del complejo Ãgneo de Santa Olalla de Cala: implicaciones en la edad del yacimiento d e Ni-Cu-EGP de Aguablanca (Badajoz)(Macla, 2004) Rombo, I.; Lunar Hernández, MarÃa Del Rosario; Capote Del Villar, Ramón; Quesada, C.; Dunning, G. R.; Piña GarcÃa, Rubén; Ortega Menor, Lorena; Sociedad Española de MineralogÃaItem Fluid composition and reactions of graphite precipitation in the volcanic-Hosted deposit at Borrowdale (NW England): evidence from fluid inclusions(Macla, 2008) Ortega Menor, Lorena; Luque del Villar, Francisco Javier; Fernández Barrenechea, José MarÃa; Millward, David; Beyssac, Olivier; Hizenga, Jan Marten; Rodas, MagdalenaItem Cu, Mn, and Ag mineralization in the Quebrada Marquesa Quadrangle, Chile: the Talcuna and Arqueros districts(Mineralium deposita, 1998) Oyarzun, Roberto; Ortega Menor, Lorena; Sierra, Javier; Lunar Hernández, Rosario; Oyarzun, RobertoThe Quebrada Marquesa Quadrangle in Chile exhibits a series of mineralizations comprising manto-type manganese and copper deposits of Lower Creta-ceous age, and copper and silver veins of Tertiary age. The deposits are hosted by volcanic and volcaniclastic units of the Arqueros (Hauterivian-Barremian) and Quebrada Marquesa (Barremian-Albian) Formations. Three episodes of manganese mineralization (Mn1-3) are recognized within the study area. Hydrothermal activity leading to episodes 1 and 3 was of minor importance, while the second one (Mn2) gave rise to major manto-type deposits of both manganese and copper in the Talcuna mining district. Extensional faulting during Tertiary time resulted in block faulting and the unroofing of the oldest andesitic volcanics and marine sediments (Arqueros Formation). This episode was accompanied by magmatic and hydrothermal activity leading to vein formation in the Arqueros (Ag) and Talcuna (Cu) districts. The latter veins cross-cut the previous manto-type copper deposits. Ore mineralogy is similar in both styles of mineralization (manto- and vein-type) and consists mainly of chalcopyrite and bor-nite, with variable amounts of galena, tetrahedrite (vein-related), chalcocite, sphalerite, pyrite, hematite, digenite and covellite. Alteration processes at Talcuna can be divided into two categories, those related to the Lower Cretaceous manto-type episode (LK alteration: chlorite-epidote-calcite-albite, prehnite, zeolite), and those associated with the locally mineralized normal faults of Tertiary age (Tt alteration: chlorite-calcite, sericite). The Arqueros silver veins display an ore mineralogy consisting of arquerite, argentite, native silver, polybasite, cerargyrite and pyrargyrite-proustite; associated altera-tion includes strong chloritization of the country rock. The manto-type deposits formed from fluids of salinity between 11 and 19 wt.% NaCl equivalent and temperatures between 120 and 205 °C. Mineralizing fluids during the vein-type stage circulated at lower temperatures, between 70 and 170 °C, with salinity values in a wide range from 3 to 27 wt.% NaCl equivalent. This distribution of salinities is interpreted as the result of the complex interplay of two diferent processes: boiling and fluid mixing; the former is considered to control the major mineralogical, textural and fluid inclusion features of the vein-type deposits. We suggest that the Lower Cretaceous mineralization (manto-type stage) developed in response to widespread hydrothermal activity (geothermal field-type) involving basinal brines.Item Contrasting Mineralizing Processes in Volcanic-Hosted Graphite Deposits(Smart Science for Exploration and Mining, Proceedings of the Tenth Biennial SGA Meeting, 2009) Luque del Villar, Francisco Javier; Barrenechea, José F.; Ortega Menor, Lorena; Rodas, Magdalena; Millward, David; Williams, Jean-PierreThe only two known graphite vein-deposits hosted by volcanic rocks (Borrowdale, United Kingdom, and Huelma, Southern Spain) show remarkable similarities and differences. The lithology, age of the magmatism and geodynamic contexts are distinct, but the mineralized bodies are controlled by fractures. Evidence of assimilation of metasedimentary rocks by the magmas and hydrothermal alteration are also common features to both occurrences. Graphite morphologies at the Borrowdale deposit vary from flakes (predominant) to spherulites and cryptocrystalline aggregates, whereas at Huelma, flaky graphite is the only morphology observed. The structural characterization of graphite indicates a high degree of ordering along both the c axis and the basal plane. Stable carbon isotope ratios of graphite point to a biogenic origin of carbon, most probably related to the assimilation of metasedimentary rocks. Bulk į13C values are quite homogeneous in both occurrences, probably related to precipitation in short time periods. Fluid inclusion data reveal that graphite precipitated from C-O-H fluids at moderate temperature (500 ºC) in Borrowdale and crystallized at high temperature from magma in Huelma, In addition, graphite mineralization occurred under contrasting fO2 conditions. All these features can be used as potential exploration tools for volcanic-hosted graphite deposits.Item Mineralogy and geochemistry of platinum group elements in the Aguablanca Ni-Cu deposit (SW Spain)(Mineralogy and petrology, 2007) Piña GarcÃa, Rubén; Gervilla, Fernando; Ortega Menor, Lorena; Lunar Hernández, RosarioThe Aguablanca Ni-Cu-(PGE) magmatic sulphide deposit is associated with a magmatic breccia located in the northern part of the Aguablanca gabbro (SW, Iberia). Three types of ores are present: semi-massive, disseminated, and chalcopyrite-rich veined ore. The principal ore minerals are pyrrhotite, pentlandite and chalcopyrite. A relatively abundant platinum-group mineral (PGM) assemblage is present and includes merenskyite, melonite, michenerite, moncheite and sperrylite. Moreover, concentrations of base and precious metals and micro-PIXE analyses were obtained for the three ore-types. The mineralogy and the mantlenormalised chalcophile element profiles strongly suggest that semi-massive ore represents mss crystallisation, whereas the disseminated ore represents an unfractionated sulphide liquid and the chalcopyrite-rich veined ore a Cu-rich sulphide liquid. Palladium-bearing minerals occur commonly enclosed within sulphides, indicating a magmatic origin rather than hydrothermal. The occurrences and the composition of these minerals suggest that Pd was initially dissolved in the sulphides and subsequently exsolved at low temperatures to form bismutotellurides. Negative Pt and Au anomalies in the mantle-normalised chalcophile element profiles, a lack of Cu-S correlation and textural observations (such as sperrylite losing its euhedral shape when in contact with altered minerals) suggest partial remobilisation of Pt, Au and Cu by postmagmatic hydrothermal fluids after the sulphide crystallisation.Item Origen de los fragmentos máficos-ultramáficos de la brecha mineralizada del yacimiento de Ni-Cu-EGP de Aguablanca (Badajoz)(Macla, 2004) Piña GarcÃa, Rubén; Lunar Hernández, MarÃa Del Rosario; Ortega Menor, Lorena; Gervilla, F.; Alapieti, T.; MartÃnez, C.