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
62 results
Search Results
Now showing 1 - 10 of 62
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 The Patricia Zn–Pb–Ag epithermal ore deposit: An uncommon type of mineralization in northeastern Chile(Ore Geology Reviews, 2016) Chinchilla Benavides, DarÃo; Ortega Menor, Lorena; Piña GarcÃa, Rubén; Merinero Palomares, Raúl; Moncada, Daniel; Bodnar, Robert J.; Quesada Ochoa, Cecilio; Valverde, Antonio; Lunar Hernández, RosarioThe Patricia ore deposit represents an unusual example of economic Zn–Pb–Ag mineralization at the northernmost end of the Late Eocene–Oligocene metallogenic belt in Chile. It is hosted by volcano-sedimentary units, which are typically tuffaceous and andesitic breccias. The ore body consists of a set of subvertical E-W vein systems developed under a sinistral strike-slip regime that included transtensive domains with generalized extensional structures where the ores were deposited. The deposit is divided into two blocks by a set of NNW-ESE-trending reverse faults, which uplifted the eastern block and exhumed thicker and deeper parts of the deposit. At least 200 m of volcano-sedimentary pile hosting the mineralization has been eroded in this block. By contrast, the western block exposes a shallower part of the system where cherts, amorphous silica and jasperoids occur. Three main stages of mineralization have been defined: (1) pre-ore stage is characterized by early quartz, pyrite and arsenopyrite, (2) base-metal and silver stage; characterized by sphalerite (6 to 15 mol% FeS), galena, chalcopyrite, pyrrhotite and Ag-bearing minerals (freibergite, polybasite, stephanite, pyrargyrite, freieslebenite and acanthite) and (3) post-ore stage; characterized by late quartz, kutnohorite and minor sulfides (arsenopyrite, sphalerite, pyrite, galena, Ag-bearing minerals and Pb-sulfosalts). Whole-ore geochemistry shows two groups of elements that are positively correlated; 1) Ag–Cd–Cu–Pb–Zn related to the base metal sulfides and 2) Au–As–Ge–Sb–W related to arsenopyrite and pyrite. Hydrothermal alteration is pervasive in the outcropping mineralized areas, including silicification and locally, vuggy silica textures. At depth, chloritic and sericitic alteration is developed along vein selvages and is superimposed to the regional propylitic alteration. Fluid inclusions indicate that the base-metal ores were deposited from 250 to 150 °C moderate salinity fluids (1–9 wt.% NaCl). The pre-ore stage is characterized by a saline fluid (6–22 wt.% NaCl) and between 210 and 250 °C whereas the post-ore stage has salinity of 4–8 wt.% and temperature from 175 to 215 °C. Cooling was the mechanism of ore mineral precipitation in the Patricia deposit, although mixing of fluids could have occurred in the pre-ore stage. Mineralogical, geochemical and fluid inclusion evidence is consistent with an intermediate sulfidation (IS) epithermal deposit type. This study highlights the high potential for hidden economic mineralization at depth in the western block and for extension of the ore body both to the south and to deeper levels in the eastern block of the Patricia ore deposit. To a larger extent, the implications of finding such polymetallic epithermal style of mineralization in the northern Chile Precordillera is relevant both to the regional metallogenic perspective and to the exploration potential of the region, where the late Eocene–early Oligocene metallogenic belt apparently disappears.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 The role of crustal contamination in the genesis of Ni-Cu sulfide ores from the Cortegana Igneous Complex (SW Spain)(Let's Talk Ore Deposits: Proceedings of the Eleventh Biennial SGA Meeting, Antofagasta, Chile, 26-29 September 2011, 2011) Piña GarcÃa, Rubén; Gervilla, Fernando; Ortega Menor, Lorena; Lunar Hernández, MarÃa Del RosarioCrustal contamination of mafic magmas with S-rich country rocks is believed to play a critical role in the formation of Ni-Cu sulfide ores in SW Spain. Whereas this process has been well recognized in the Aguablanca Ni-Cu deposit (the only economic ore of this type in SW Europe), no data existed in other less mineralized, mafic-ultramafic intrusions of the region, such as the Tejadillas prospect in the Cortegana Igneous Complex. The Tejadillas prospect is composed of igneous cumulates similar to those of Aguablanca, but their incompatible trace element abundances show more primitive patterns than those of Aguablanca. In contrast, incompatible trace element ratios of the Aguablanca rocks are much closer to the contaminant country rocks than those of Tejadillas. Therefore, we suggest that the small volume of sulfide mineralization observed at Tejadillas was the consequence of low degrees of contamination of its parental magma by S-rich country rocks. This suggest that assimilation of S-rich country rocks by mafic magmas is the key factor for the genesis of economic Ni-Cu sulfide ores in SW Spain.Item 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 Distribution of platinum-group and chalcophile elements in the Aguablanca Ni–Cu sulfide deposit (SW Spain): Evidence from a LA-ICP-MS study(Chemical geology, 2012) Piña GarcÃa, Rubén; Gervilla, Fernando; Barnes, Sarah-Jane; Ortega Menor, Lorena; Lunar Hernández, RosarioThe concentrations of platinum-group elements (PGE) and chalcophile elements Ni, Co, Au, Ag, Se, Re, Cd, Bi, Te and As have been determined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) in base metal sulfide minerals (BMS) from the Aguablanca Ni–Cu deposit, SW Spain. The main aim was to constrain the role played by the BMS as hosts of PGE as this reveals important information regarding the processes controlling the distribution of these elements in the deposit. The BMS (pyrrhotite, pentlandite, chalcopyrite and minor pyrite) occur as semi-massive, disseminated and minor chalcopyrite-veined ores. On the basis of whole rock metal abundances and BMS mineralogy, these ore types have been interpreted to be the result of the fractionation and crystallization of an immiscible sulfide liquid. Platinum-group and chalcophile element concentrations vary as a function of the BMS and ore types. The partitioning behavior of some of these metals during the fractional crystallization of the sulfide liquid largely governed their distribution in the ore. Rhenium, Os, Ir, Ru, and Rh occur mostly in solid solution in pyrrhotite and pentlandite from the semi-massive ore which has been interpreted to represent monosulfide solid solution (mss) cumulates. The mss crystallization gave rise to minor Cu-rich sulfide liquid in the form of chalcopyrite veinlets with relatively Pd-, Au- and Ag-enriched chalcopyrite, and minor Re-, IPGE- and Rhdepleted pyrrhotite and pentlandite. Platinum-group element contents in the BMS from the disseminated ore, interpreted to represent an original unfractionated sulfide melt, are approximately intermediate to the semimassive and chalcopyrite-veined ores. Palladium and Pt occur mostly associated with Bi, Te, and As forming platinum-group minerals (PGM, Pd–Pt bismuthotellurides and Pt arsenides) within individual BMS grains. This preferential location along with the textures adopted (usually rounded grains and laths) and the temperatures of crystallization (inferred below 500 °C) suggests that Pd and Pt, initially dissolved in the BMS, were exsolved along with Bi, Te and As to form the PGM assemblage present in the ore. Some Pd (approximately 30% of the bulk) remains in solid solution in pentlandite for the three ore types. The presence of Pd in pentlandite is likely a combined effect of limited sulfide fractionation with some of Pd remaining in mss and Pd diffusion into pentlandite from the mss and Curich portions on cooling. Two textural types of pyrite hosting distinct PGE concentrations have been described: (1) large idiomorphic pyrite and (2) ribbon-like pyrite. Idiomorphic pyrite is the unique BMS hosting Pt (with contents as high as 15 ppm) and also contains relatively high Rh concentrations (4–31 ppm). By contrast, ribbon-like pyrite has no Pt and hosts similar Os, Ir, Ru and Rh concentrations (30–360 ppb) to those of the host pyrrhotite to that it replaces. The origin of the idiomorphic grains, whether exsolution products from mss or alteration products of pyrrhotite, is not well known and further work will be necessary to constrain this point. Nevertheless, the presence of PGE hosted by pyrite reveals that this sulfide should not be overlooked as a potential carrier of PGE in Ni–Cu–(PGE) ore deposits.