The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust

At global scale, prominently mineralized porphyry copper systems (>40 Mt Cu) are located exclusively along thick crustal segments (>~40 km) of active continental margins. These magmatic-hydrothermal systems accumulate sulfide ore involving huge anomalies of Cu, Au and Mo in the shallow crust (...

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Autor: Salas-Reyes, Pablo Antonio
Tipo de recurso: tesis doctoral
Estado:Versión publicada
Fecha de publicación:2020
País:Chile
OAI Identifier:oai:repositorio.anid.cl:10533/253021
Acceso en línea:https://hdl.handle.net/10533/253021
Access Level:acceso abierto
Palabra clave:Ciencias Naturales
Otras Ciencias Naturales
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dc.title.es_CL.fl_str_mv The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
El estado redox y la contribución de metales y volátiles a partir de magmas primitivos de arco: implicancias en la formación de sistemas porfídicos mineralizados en la corteza somera
title The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
spellingShingle The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
Salas-Reyes, Pablo Antonio
Ciencias Naturales
Otras Ciencias Naturales
title_short The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
title_full The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
title_fullStr The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
title_full_unstemmed The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
title_sort The redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crust
dc.creator.none.fl_str_mv Salas-Reyes, Pablo Antonio
author Salas-Reyes, Pablo Antonio
author_facet Salas-Reyes, Pablo Antonio
author_role author
dc.contributor.advisor.none.fl_str_mv Rabbia-Dalmasso, Osvaldo
dc.contributor.institution.es_CL.fl_str_mv UNIVERSIDAD DE CONCEPCION
dc.subject.oecd1n.es_CL.fl_str_mv Ciencias Naturales
topic Ciencias Naturales
Otras Ciencias Naturales
dc.subject.oecd2n.es_CL.fl_str_mv Otras Ciencias Naturales
description At global scale, prominently mineralized porphyry copper systems (>40 Mt Cu) are located exclusively along thick crustal segments (>~40 km) of active continental margins. These magmatic-hydrothermal systems accumulate sulfide ore involving huge anomalies of Cu, Au and Mo in the shallow crust (<10 km depth). The specific processes that allow the large-scale transport of sulfur (S) and metals (Cu-Au) to the upper crust remain unclear, however, the redox conditions in the primitive basaltic melts intruding the deep crust exert a first-order control on the behavior of these metals through the speciation of sulfur. The basic causes of the more oxidized character of arc basalts compared with basalts from other tectonic settings is debated between two contrasting hypotheses. One of these postulates that the higher oxidation reflects the mantle source condition, whereas the other attributes the magma oxidation to intra-crustal processes during the ascent. In the first case, the crystallization of magmatic sulfides would be efficiently inhibited given that S+6 (sulfate) is the dominant S specie. This allows to S and metal to be transported to higher crustal levels. Conversely, in the second case, the precipitation of magmatic sulfides in the mid to deep crust would be dominant during the early stages of differentiation (S-2, sulfide), depleting in metal and sulfur the residual magmas that later can reach the high crust. This research explore into the redox conditions of a primitive arc magma at Los Hornitos, a pair of mafic monogenetic vents in the Central-South Andes (35.5°S), where magnesian olivines (Fo90-92; Ni ~3800 ppm) host quenched melt inclusions that were analyzed by a combination of microanalitycal techniques (μ- XANES, EPMA, SIMS & LA-ICP-MS), allowing the determination of Fe speciation (Fe+3/ƩFe) and the major, minor and trace element composition during the early stages of this arc melts in a metallogenetic fertile segment of the Andes. In addition, the examination of textural features and fine-scale zoning of a large amount of crystals, allows to establish the textural and volumetric evolution of v olivine during episodes of rapid growth, where phenocryst-size olivines results of the progressive growth of concentric open structured “crystal frames” that leave behind compositional boundary layers. This challenge the reliability of melt inclusions as indicator of equilibrium conditions as an implicit rule. Results indicate that the primitive basaltic melts (1250°C-1GPa) intruding the deep crust, present a fO2 equivalent to NNO+1 to +1.7, allowing to dissolve up to ~50% of the sulfur cargo as sulfate. This value is considerably higher compared with other arc magmas that only dissolve as much as ~5% of S. Therefore, it is possible to establish that the metallogenetic fertile nature of arc magmas above mature subduction zones relies in the comparatively more oxidized character of the melts intruding the crust from the subarc mantle. In addition, the contribution in volatile and metal of these melts is 3 wt% of H2O, 4000 ppm of S, 1300 ppm of Cl and 200 ppm of Cu.
publishDate 2020
dc.date.issued.es_CL.fl_str_mv 2020
dc.date.accessioned.none.fl_str_mv 2021-11-02T14:01:57Z
2022-08-23T03:11:07Z
dc.date.available.none.fl_str_mv 2021-11-02T14:01:57Z
2022-08-23T03:11:07Z
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identifier_str_mv 21161063
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spelling UNIVERSIDAD DE CONCEPCIONSalas-Reyes, Pablo Antonio2020https://hdl.handle.net/10533/253021http://purl.org/coar/access_right/c_abf2Otras Ciencias NaturalesCiencias NaturalesThe redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crustRabbia-Dalmasso, OsvaldoUNIVERSIDAD DE CONCEPCIONChileSalas-Reyes, Pablo Antonio2021-11-02T14:01:57Z2022-08-23T03:11:07Z2021-11-02T14:01:57Z2022-08-23T03:11:07Z2020At global scale, prominently mineralized porphyry copper systems (>40 Mt Cu) are located exclusively along thick crustal segments (>~40 km) of active continental margins. These magmatic-hydrothermal systems accumulate sulfide ore involving huge anomalies of Cu, Au and Mo in the shallow crust (<10 km depth). The specific processes that allow the large-scale transport of sulfur (S) and metals (Cu-Au) to the upper crust remain unclear, however, the redox conditions in the primitive basaltic melts intruding the deep crust exert a first-order control on the behavior of these metals through the speciation of sulfur. The basic causes of the more oxidized character of arc basalts compared with basalts from other tectonic settings is debated between two contrasting hypotheses. One of these postulates that the higher oxidation reflects the mantle source condition, whereas the other attributes the magma oxidation to intra-crustal processes during the ascent. In the first case, the crystallization of magmatic sulfides would be efficiently inhibited given that S+6 (sulfate) is the dominant S specie. This allows to S and metal to be transported to higher crustal levels. Conversely, in the second case, the precipitation of magmatic sulfides in the mid to deep crust would be dominant during the early stages of differentiation (S-2, sulfide), depleting in metal and sulfur the residual magmas that later can reach the high crust. This research explore into the redox conditions of a primitive arc magma at Los Hornitos, a pair of mafic monogenetic vents in the Central-South Andes (35.5°S), where magnesian olivines (Fo90-92; Ni ~3800 ppm) host quenched melt inclusions that were analyzed by a combination of microanalitycal techniques (μ- XANES, EPMA, SIMS & LA-ICP-MS), allowing the determination of Fe speciation (Fe+3/ƩFe) and the major, minor and trace element composition during the early stages of this arc melts in a metallogenetic fertile segment of the Andes. In addition, the examination of textural features and fine-scale zoning of a large amount of crystals, allows to establish the textural and volumetric evolution of v olivine during episodes of rapid growth, where phenocryst-size olivines results of the progressive growth of concentric open structured “crystal frames” that leave behind compositional boundary layers. This challenge the reliability of melt inclusions as indicator of equilibrium conditions as an implicit rule. Results indicate that the primitive basaltic melts (1250°C-1GPa) intruding the deep crust, present a fO2 equivalent to NNO+1 to +1.7, allowing to dissolve up to ~50% of the sulfur cargo as sulfate. This value is considerably higher compared with other arc magmas that only dissolve as much as ~5% of S. Therefore, it is possible to establish that the metallogenetic fertile nature of arc magmas above mature subduction zones relies in the comparatively more oxidized character of the melts intruding the crust from the subarc mantle. In addition, the contribution in volatile and metal of these melts is 3 wt% of H2O, 4000 ppm of S, 1300 ppm of Cl and 200 ppm of Cu.A escala global, los sistemas de pórfidos cupríferos de alto tonelaje (>40 Mt de Cu) se ubican exclusivamente a lo largo de segmentos de corteza gruesa (>~40 km) en márgenes continentales activos. Estos sistemas magmáticoshidrotermales acumulan mena sulfurada que constituye grandes anomalías de Cu, Au y Mo en la corteza somera (<10 km). Los procesos específicos que controlan el transporte a gran escala de azufre (S) y metales (Cu-Au) hacia la corteza somera no se conocen con exactitud, sin embargo, las condiciones redox en los fundidos basálticos primitivos que intruyen la corteza profunda, ejercen un control de primer orden en el comportamiento de dichos metales a través de la especiación de S. La causa basal del carácter más oxidado de los basaltos de arco, comparado con basaltos de otros ambientes tectónicos, se debate entre dos visiones contrastantes. Una de ellas postula que la más alta oxidación refleja las condiciones de la fuente del manto, mientras que la otra atribuye la oxidación a procesos intracorticales durante el ascenso. En el primer caso, la precipitación de sulfuros magmáticos sería eficientemente inhibida debido a que el S+6 (sulfato) es la especie de S dominante. Esto permite que el S y los metales sean transportados a niveles corticales más altos. Por el contrario, en el segundo caso, la precipitación de sulfuros magmáticos (S-2, sulfuro) en la corteza mediaprofunda sería el proceso dominante, deprimiendo en metales y S a los magmas residuales que posteriormente alcanzan niveles corticales más altos. Esta investigación explora las condiciones redox de un magma de arco primitivo en Los Hornitos, un par de volcanes monogenéticos máficos en los Andes Centrales-del Sur (35.5°S), donde olivinos magnesianos (Fo90-92; Ni ~3800 ppm) contienen inclusiones vítreas que fueron analizadas por una combinación de técnicas microanalíticas (μ-XANES, EPMA, SIMS & LA-ICP-MS), permitiendo la determinación de la especiación del Fe (Fe+3/ƩFe) y la composición en iii elementos mayoritarios, minoritarios y trazas durante las etapas tempranas de estos fundidos de arco, en un segmento andino metalogenéticamente fértil. Adicionalmente, el análisis de las características texturales y de zonación química a pequeña escala en un gran número de cristales, permitió establecer la evolución textural y volumétrica durante episodios de crecimiento rápido, donde un fenocristal de olivino resulta del crecimiento concéntrico progresivo de estructuras abiertas denominadas “crystal frames”. Esto implica el desarrollo de capas límites composicionales, lo cual desafía la fiabilidad de las inclusiones de fundido como indicadores de condiciones en equilibrio como una regla implícita. Los resultados indican que los fundidos basálticos primitivos (1250°C-1GPa) que intruyen la corteza profunda presentan una fO2 equivalente a NNO+1 a +1.7, permitiendo que hasta un ~50% del total de azufre se disuelva como sulfato. Este porcentaje es considerablemente mayor al de otros magmas de arco, que pueden disolver sólo hasta un ~5% de S. Por lo tanto, es posible establecer que la naturaleza metalogenéticamente fértil de los magmas de arco en zonas de subducción maduras, radica en el carácter comparativamente más oxidado de los fundidos que intruyen la corteza desde el manto bajo el arco. Adicionalmente, la contribución en volátiles y metales de aquellos fundidos es 3 wt% de H2O, 4000 ppm de S, 1300 ppm de Cl y 200 ppm de Cu.21161063https://hdl.handle.net/10533/253021instname: Conicytreponame: Repositorio Digital RI2.0info:eu-repo/grantAgreement//21161063info:eu-repo/semantics/dataset/hdl.handle.net/10533/93488info:eu-repo/semantics/openAccessAttribution-NonCommercial-NoDerivs 3.0 Chilehttp://creativecommons.org/licenses/by-nc-nd/3.0/cl/Ciencias NaturalesOtras Ciencias NaturalesThe redox state and metal-volatile budget of primitive arc magmas: implications in the formation of ore-mineralized porphyry systems in the shalow crustEl estado redox y la contribución de metales y volátiles a partir de magmas primitivos de arco: implicancias en la formación de sistemas porfídicos mineralizados en la corteza somerainfo:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersionTesisTesishttps://hdl.handle.net/10533/25302178abe9ac-2395-4827-8d27-49df24fb47b8virtual::63463-178abe9ac-2395-4827-8d27-49df24fb47b8virtual::63463-1THUMBNAILTesis_Pablo_Salas.pdf.jpgIM Thumbnailimage/jpeg3809https://repositorio.anid.cl/bitstreams/31a38915-2343-40cf-b420-2441ef31ffb6/downloadfa44d989f0168bc837f337f2fdc37ca7MD51TEXTTesis_Pablo_Salas.pdf.txtExtracted texttext/plain356622https://repositorio.anid.cl/bitstreams/606526cd-b8f4-4a8f-88b1-d7029e50459d/downloadff5503f756e56baafa9abaa46d4b9fdeMD52CC-LICENSElicense_rdfapplication/octet-stream1232https://repositorio.anid.cl/bitstreams/c3e70ee8-2780-4428-aa2d-ba5e3b0a163c/downloadf97bcfdf58f3e17b5cec231112dab5b1MD53LICENSElicense.txttext/plain1779https://repositorio.anid.cl/bitstreams/ed79b565-a70f-48b4-a3d1-3ea83a4fc65a/download593a6e7305c66c56041a9f9e15a649c1MD54ORIGINALTesis_Pablo_Salas.pdfapplication/pdf8416662https://repositorio.anid.cl/bitstreams/baa67315-0330-46f0-9376-3f81d300f8a5/download9801cb97222e399111240f0b7ef241ceMD5510533/253021oai:repositorio.anid.cl:10533/2530212023-07-24 13:17:01.438http://creativecommons.org/licenses/by-nc-nd/3.0/cl/info:eu-repo/semantics/openAccesshttps://repositorio.anid.clRepositorio ANIDaletelier@anid.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