Person:
Ortega Menor, Lorena

First Name

Lorena

Last Name

Ortega Menor

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Mineralogía y Petrología

Area

Cristalografía y Mineralogía

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Now showing 1 - 10 of 62

Distribution of platinum-group and chalcophile elements in the Aguablanca Ni–Cu sulfide deposit (SW Spain): Evidence from a LA-ICP-MS study
(Elsevier Science B.V., Amsterdam., 2012) Piña García, Rubén; Gervilla, Fernando; Barnes, Sarah-Jane; Ortega Menor, Lorena; Lunar Hernández, Rosario
The 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.
Estudio Mineralógico del Depósito de Zn-Pb- Ag de Patricia (Paguanta, NE de Chile)
(Sociedad Española de Mineralogía, 2012-06) Chinchilla-Benavides, Darío; Piña García, Rubén; Merinero, Raul; Ortega Menor, Lorena; Quesada, Cecilio; Valverde, Antonio; Lunar Hernández, Rosario
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, Magdalena
Partition Coefficients of Platinum Group and Chalcophile Elements Between Arsenide and Sulfide Phases as Determined in the Beni Bousera Cr-Ni Mineralization (North Morocco)
(Society of Economic Geologists (U.S.), 2013) Piña García, Rubén; Gervilla, Fernando; Barnes, Sarah-Jane; Ortega Menor, Lorena; Lunar Hernández, Rosario
The partition coefficients of platinum group elements (PGE) and chalcophile elements Au, Re, Ag, Se, Bi, Te, and Sb, between arsenide and sulfide phases (DAs/sulf) have been estimated by measuring in situ concentrations of these elements using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in coexisting arsenide and sulfide minerals from the Beni Bousera Cr-Ni mineralization (North Morocco). Previous experimental studies and observations on the distribution of PGE in a number of As-rich, Ni-Cu-PGE ore deposits have shown that arsenide minerals may play an important role controlling the distribution of these metals in magmatic sulfide systems. However to date, there is no comprehensive study quantifying the partitioning behavior of these elements when arsenide minerals crystallize either directly from a sulfide melt or from an arsenide melt previously segregated by immiscibility from a sulfide melt. The Beni Bousera mineralization represents an excellent natural laboratory to evaluate these partition coefficients because maucherite (Ni11As8) coexists in equilibrium with pyrrhotite, pentlandite, and chalcopyrite in form of globules mostly associated with pyrrhotite, and arsenide and sulfide minerals account for the bulk of the PGE (with the exception of Pt) and chalcophile elements in the samples. The laser ablation analyses reveal that maucherite is strongly enriched in all chalcophile elements, except Se, relative to sulfide minerals. The calculated DPGEAs/sulf are the following: DIrAs/sulf = 920 DRhAs/sulf = 620, DPtAs/sulf = 330, DPdAs/sulf = 250, DOsAs/sulf = 140, and DRuAs/sulf = 50. For the rest of elements, the obtained values are the following: DSbAs/sulf = 890, DTeAs/sulf = 190, DBiAs/sulf = 50, DReAs/sulf = 6, DAuAs/sulf = 310, DAgAs/sulf = 4, and DSeAs/sulf = 0.6. These results clearly highlight the strong affinity of PGE for arsenide phases and the importance of these phases as potential carriers of PGE in Ni-Cu-PGE ore deposits.
Origin and emplacement of the Aguablanca magmatic Ni-Cu-(PGE) sulfi de deposit, SW Iberia: A multidisciplinary approach
(Geological Society of America, 2010-05) Piña García, Rubén; Romeo Briones, Ignacio; Ortega Menor, Lorena; Lunar Hernández, Rosario; Capote del Villar, Ramón; Gervilla, Fernando; Tejero López, Rosa; Quesada Ochoa, Cecilio
A model is proposed for the origin and emplacement of the ca. 341 Ma Aguablanca magmatic Ni-Cu-(platinum group element [PGE]) sulfi de deposit (SW Iberia) integrating petrological, geochemical, structural, and geophysical data. The Aguablanca deposit occurs in an unusual geodynamic context for this ore type (an active plate margin) as an exotic , magmatic subvertical breccia located at the northern part of the coeval gabbronorite Aguablanca stock (341 ± 1.5 Ma). Structural and gravity data show that mineralized breccia occurs inside the inferred feeder zone for the stock adjacent to the Cherneca ductile shear zone, a Variscan sinistral transpressional structure. The orientation of the feeder zone corresponds to that expected for tensional fractures formed within the strain fi eld of the adjacent Cherneca ductile shear. Two distinctive stages are established for the origin and emplacement of the deposit: (1) initially, the ore-forming processes are attributed to magma emplacement in the crust, assimilation of crustal S, and segregation and gravitational settling of sulfi de melt (a scenario similar to most plutonic Ni-Cu sulfi de ores), and (2) fi nal emplacement of the Ni-Cu sulfi de-bearing rocks by multiple melt injections controlled by successive opening events of tensional fractures related to the Cherneca ductile shear zone.
Mineralogy and geochemistry of platinum group elements in the Aguablanca Ni-Cu deposit (SW Spain)
(Springer Science Business Media, 2007) Piña García, Rubén; Gervilla, Fernando; Ortega Menor, Lorena; Lunar Hernández, Rosario
The 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.
Análisis de la evolución en la adquisición de competencias específicas y transversales en los Grados de Geología e Ingeniería Geológica
(2019-06-28) García Lorenzo, Mari Luz; Abati Gómez, Jacobo; Orejana García, David; Castiñeiras García, Pedro; Crespo Feo, María Elena; Piña García, Rubén; García Romero, Emilia; Granja Bruña, José Luis; López García, José Ángel; Fernández Barrenechea, José María; Arribas Mocoroa, María Eugenia; Ortega Menor, Lorena; Pérez Moreno, Elisa María; Benito Moreno, María Isabel
Petrology and Geochemistry of Mafic-Ultramafic Fragments from the Aguablanca Ni-Cu Ore Breccia, Southwest Spain
(Society of Economic Geologists (U.S.), 2006) Piña García, Rubén; Lunar Hernández, Rosario; Ortega Menor, Lorena; Gervilla, F.; Alapieti, T.; Martínez, C.
Aguablanca (southwest Spain) is the first economic Ni-Cu-(PGE) deposit found in southern Europe. Two features make it an unusual example of magmatic sulfide ore: it is related to the development of an Andeantype continental magmatic arc, and it is hosted by a subvertical magmatic breccia. The structural style and the geodynamic context of the deposit contrast with most plutonic Ni-Cu-PGE deposits elsewhere, which occur at specific levels of layered mafic intrusions in rift environments. The Ni-Cu deposit is hosted by the Aguablanca intrusion, a mafic body composed of gabbronorite and minor quartz-diorite, gabbro, and norite. Sulfides are concentrated in a gabbronorite matrix along a subvertical (dipof 70º–80º N), funnel-like magmatic breccia that contains barren or slightly mineralized ultramafic-mafic cumulate fragments. Modal compositions of the fragments reflect a wide variety of rock types, including peridotite (hornblende-rich werhlite, dunite, and hornblende-rich harzburgite), pyroxenite (ortho- and clinopyroxenite), gabbro (gabbro, gabbronorite, and hornblende gabbro), and anorthosite. The primary silicate assemblage includes olivine (Fo91–Fo79), orthopyroxene (Mg no. 0.85–0.73), clinopyroxene (Mg no. 0.93–0.62), plagioclase (An99–An38), amphibole (Mg no. 0.87–0.68) and phlogopite (Mg no. 0.89–0.64). The wide range of rock types and the Fe-enrichment trends in the primary ferromagnesian silicates suggest magmatic differentiation processes from the parent melts, with the fragments representing different stages of cumulate formation. The ore-bearing breccia contains both semimassive and disseminated sulfides in the gabbronorite matrix. Textures vary between meso- and orthocumulate, and the rock-forming magmatic silicates are orthopyroxene (Mg no. 0.83–0.74), clinopyroxene (Mg no. 0.89–0.78), plagioclase (An50-An77), and intercumulus amphibole (Mg no. 0.86–0.70), phlogopite (0.84–0.69) and minor quartz. The gabbronorite in the matrix of the breccia is petrographically and chemically very similar to that of the unmineralized parts of the main Aguablanca intrusion and exhibits a similar differentiation trend, suggesting that the matrix of the ore-bearing breccia and the unmineralized rocks belong to a same magmatic suite. The local presence of mafic-ultramafic fragments in the barren Aguablanca intrusion supports this suggestion. The presence of highly Ni depleted olivine, whole-rock Cu/Zr ratios below 1, and the local occurrence of disseminations of magmatic sulfides in the peridotite fragments point to sulfide segregation before and/or during the formation of the peridotite cumulates. Mantle-normalized incompatible trace element patterns of the fragments along with published sulfur isotope data are consistent with crustal contamination, suggesting that addition of crustal sulfur from pyrite-bearing black slates led to sulfide saturation. These results support a model in which sulfides segregated and settled during the differentiation of an unexposed mafic-ultramafic complex, now sampled as fragments in the breccia, whereas the overlying silicate magma, most probably fed by successive fresh magma injections, underwent fractional crystallization, giving rise to this cumulate sequence. The emplacement of the ore breccia took place at temperatures above the (monosulfide solid solution (mss) solidus but below the olivine and pyroxene solidus, likely owing to the explosive injection of a new pulse of magma into the chamber, which mingled with the sulfide liquid and disrupted the overlying cumulate sequence. As a consequence, fragments reached their current position in the breccia, injected along with the sulfide and the silicate melts, which subsequently formed the sulfide-rich gabbronorite.
Contrasting Mineralizing Processes in Volcanic-Hosted Graphite Deposits
(The Economic Geology Research Unit, 2009) Luque del Villar, Francisco Javier; Barrenechea, José F.; Ortega Menor, Lorena; Rodas, Magdalena; Millward, David; Williams, Jean-Pierre
The 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.
Estudio petrológico y mineralógico de la mineralización de Cu-(Ag) de tipo manto del prospecto Shaft 40 (Proyecto Minero Picachos, Chile)
(Sociedad Española de Mineralogía, 2018-07) Baza, Andrea; Piña García, Rubén; Ortega Menor, Lorena; Lunar Hernández, Rosario
El Proyecto Minero de Picachos (IV Región, Coquimbo, Chile) es una mineralización de Cu-(Ag) de tipo manto localizada en la Franja Cretácica de los Andes Centrales, y constituye un proyecto de exploración minera desarrollado por la empresa Herencia Resources. Cubre una superficie de unas 410 Ha y hasta la fecha se han definido 5 prospectos de Cu-(Ag), donde la mineralización de sulfuros y sulfosales tiene un claro control litológico y estructural, y aparece como cuerpos diseminados y vetas (Fig. 1a). Actualmente, en la zona se están llevando a cabo trabajos de explotación minera a pequeña escala, con una producción mensual que oscila entre 4000 y 10000 toneladas.