Person:
Ortega Menor, Lorena

First Name

Lorena

Last Name

Ortega Menor

URI

https://hdl.handle.net/20.500.14352/75233

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 29

The Patricia Zn–Pb–Ag epithermal ore deposit: An uncommon type of mineralization in northeastern Chile
(Ore Geology Reviews, 2016) Chinchilla Benavides, Darío; Ortega Menor, Lorena; Piña García, Rubén; Merinero Palomares, Raúl; Moncada, Daniel; Bodnar, Robert J.; Quesada Ochoa, Cecilio; Valverde, Antonio; Lunar Hernández, Rosario
The 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.
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; García Palomero, F.; Martín Estévez, J.R.
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, Rosario
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, Roberto
The 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.
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 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 petrológico y mineralógico de la mineralización de Cu-(Ag) de tipo manto del prospecto Shaft 40 (Proyecto Minero Picachos, Chile)
(Macla, 2018) 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.
Mineralogy and geochemistry of platinum group elements in the Aguablanca Ni-Cu deposit (SW Spain)
(Mineralogy and petrology, 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.
Estudio Mineralógico del Depósito de Zn-Pb- Ag de Patricia (Paguanta, NE de Chile)
(Macla, 2012) Chinchilla-Benavides, Darío; Piña García, Rubén; Merinero, Raul; Ortega Menor, Lorena; Quesada, Cecilio; Valverde, Antonio; Lunar Hernández, Rosario
Petrology and Geochemistry of Mafic-Ultramafic Fragments from the Aguablanca Ni-Cu Ore Breccia, Southwest Spain
(Economic geology and the bulletin of the Society of Economic Geologists, 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.
Partition Coefficients of Platinum Group and Chalcophile Elements Between Arsenide and Sulfide Phases as Determined in the Beni Bousera Cr-Ni Mineralization (North Morocco)
(Economic geology and the bulletin of the Society of Economic Geologists, 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.