Mineralogía y geoquímica de las menas de óxidos de Fe-Ti en la anortosita de Don Dieguito, Sierra Nevada de Santa Marta, Colombia

Fe-Ti oxide ores are commonly associated with Proterozoic massif-type anorthosite bodies emplaced during the Grenville orogeny (~1.2-1.0 Ga). Some of these anorthositic bodies occur in the northernmost part of the Santa Marta Massif, Colombia. They locally contain crosscutting Fe-Ti(-V) ore bodies between the El Hierro creek and the Don Dieguito river. We have distinguished two types of Fe-Ti(-V) ores: i) oxide-apatite norite (fine grained ilmenite and magnetite disseminated in an assemblage of apatite, amphibole, chlorite, rutile and sericitized plagioclase) and ii) banded nelsonite (coarser grained ilmenite, magnetite and apatite distributed in bands, with minor baddeleyite, srilankite and högbomite). Ilmenite in the two ore types display distinct hematite exsolution features: a) needle-like in the oxide-apatite norite ore; and b) two generations of exsolutions in the banded ore. Magnetite shows similar Ti and V contents in both ore types (0.4 wt % TiO2 and 0.5 wt % V2O3 on average in the oxide-apatite norite ore, 0.5 wt % TiO2 and 0.4 wt % V2O3 in the banded ore), whereas ilmenite has higher hematite, pyrophanite and geikielite components in the banded ore. The ores might have formed from the combination of fractional crystallization and magma mixing, with exsolution occurring probably at 575-600°C. This first detailed mineralogical and textural study of Fe-Ti(-V) oxide ores in anorthosite massifs from Colombia suggests that the Santa Marta Massif is an interesting target for future research.Las mineralizaciones de óxidos de Fe-Ti se asocian comúnmente a complejos anortosíticos proterozoicos (massif-type) emplazados durante la orogenia Grenvilliana (~1.2-1.0 Ga). Algunos de estos cuerpos anortosíticos se encuentran en la parte septentrional del Macizo de Santa Marta, en Colombia. Localmente, éstos contienen cuerpos de óxidos de Fe-Ti(-V) entre la quebrada El Hierro y el río Don Dieguito. Se han distinguido dos tipos de mineralizaciones de Fe-Ti(-V): i) norita con óxidos y apatito (ilmenita y magnetita de grano fino diseminadas en una asociación de apatito, anfíbol, clorita, rutilo y plagioclasa sericitizada); y ii) nelsonita bandeada (ilmenita, magnetita y apatito de grano grueso, distribuidos en bandas, con cantidades menores de baddeleyita, srilankita y högbomita). Las ilmenitas en los dos tipos de mineralizaciones muestran diferentes exsoluciones de hematites: con forma de aguja en la mena diseminada; y dos generaciones de exsoluciones en la mena bandeada. La magnetita presenta contenidos en Ti y V similares en ambas mineralizaciones (un promedio de 0.4 wt % TiO2 y 0.5 wt % V2O3 en la diseminada, 0.5 wt % TiO2 y 0.4 wt % V2O3 en la bandeada), mientras que la ilmenita tiene mayor componente hematites, pirofanita y geikielita en la mena bandeada. Las menas se podrían haber formado por la combinación de cristalización fraccionada y mezcla de magmas, y la exsolución tendría lugar probablemente a 575-600°C. Esta primera caracterización mineral y textural de los óxidos de Fe-Ti(-V) en macizos anortosíticos en Colombia indica que la Sierra de Santa Marta es un objetivo interesante para investigaciones futuras

Multiple veining in a paleo–accretionary wedge: The metamorphic rock record of prograde dehydration and transient high porefluid pressures along the subduction interface (Western Series, central Chile)

Thaïs Hyppolito is acknowledged for sharing her knowledge about local geology. Anne Verlaguet, Hugues Raimbourg, and James Connolly are also acknowledged for insightful discussions on fluid-rock metamorphic processes. Ralf Halama and two anonymous reviewers are warmly acknowledged for insightful comments. Mauricio Calderón, Francisco Fuentes, and the Earth Sciences department at Universidad Andrés Bello (Santiago, Chile) are thanked for their technical assistance. A.C. acknowledges the research grant provided by the Alexander von Humboldt Foundation for a post-doctoral fellowship at Ruhr-Universität Bochum.High pressure–low temperature metamorphic rocks from the late Paleozoic accretionary wedge exposed in central Chile (Pichilemu region) are characterized by a greenschist-blueschist lithological association with interbedded metasediments that reached peak burial conditions of ~400 °C and 0.8 GPa during late Carboniferous times. We herein combine new extensive field observations, structural measurements, and geochemical and petrological data on vein and matrix material from Pichilemu transitional greenschist-blueschist facies rocks. The studied veins were first filled by albite, followed by quartz and calcite as well as glaucophane and winchite. Field, structural, and microscopic zoning patterns show that these rocks underwent a protracted sequence of prograde vein-opening events, which have been largely transposed to the main foliation before and during underplating in the basal accretion site near 25–30 km depth. While some of the earliest albite-filled vein sets may have formed after prograde breakdown of sub–greenschist facies minerals (<250 °C), our thermodynamic modeling shows that relatively minor amounts of fluid are produced in the subducted pile by dehydration reactions between 250 and 400 °C along the estimated geothermal gradient. It also confirms that the formation of interlayered blueschist and greenschist layers in Pichilemu metavolcanics is a consequence of local bulk composition variations, and that greenschists are generally not formed due to selective exhumation-related retrogression of blueschists. The early vein sets are a consequence of prograde internal fluid production followed by sets of hydrofractures formed at near-peak burial that are interpreted as a record of external fluid influx. We postulate that such a fractured sequence represents a close analogue to the high-Vp/Vs regions documented by seismological studies within the base of the seismogenic zone in active subduction settings.This work has been funded by an Initiative D’EXcellence (IDEX) grant 16C538 to S.A. The University of Granada is acknowledged for partial funding. Part of this work was also supported by the TelluS Program of CNRS/INSU. This is Institut de Physique du Globe de Paris contribution 4124

Diamond forms during low pressure serpentinisation of oceanic lithosphere

Diamond is commonly regarded as an indicator of ultra-high pressure conditions in Earth System Science. This canonical view is challenged by recent data and interpretations that suggest metastable growth of diamond in low pressure environments. One such environment is serpentinisation of oceanic lithosphere, which produces highly reduced CH4-bearing fluids after olivine alteration by reaction with infiltrating fluids. Here we report the first ever observed in situ diamond within olivine-hosted, CH4-rich fluid inclusions from low pressure oceanic gabbro and chromitite samples from the Moa-Baracoa ophiolitic massif, eastern Cuba. Diamond is encapsulated in voids below the polished mineral surface forming a typical serpentinisation array, with methane, serpentine and magnetite, providing definitive evidence for its metastable growth upon low temperature and low pressure alteration of oceanic lithosphere and super-reduction of infiltrated fluids. Thermodynamic modelling of the observed solid and fluid assemblage at a reference P-T point appropriate for serpentinisation (350 °C and 100 MPa) is consistent with extreme reduction of the fluid to logfO2 (MPa) = −45.3 (ΔlogfO2[Iron-Magnetite] = −6.5). These findings imply that the formation of metastable diamond at low pressure in serpentinised olivine is a widespread process in modern and ancient oceanic lithosphere, questioning a generalised ultra-high pressure origin for ophiolitic diamond.European Union (EU)Spanish Projects CGL2015-65824 RTI2018-099157-A-I00 PID2019-105625RB-C21 A.RNM.186.UGR18Spanish Government RYC-2015-17596Mexican research program CONACYT-Ciencia Basica A1-S-14574Mexican research program UNAM-PAPIIT IA-10141

Ultramafic-hosted volcanogenic massive sulfide deposits from Cuban ophiolites

Ultramafic-hosted volcanogenic massive sulfide deposits (UM-VMS) located in the Havana-Matanzas ophiolite (Cuba) are the only known example of this type of mineralization in the Caribbean realm. UM-VMS from Havana- Matanzas are enriched in Cu, Ni, Co, Au, and Ag. The mineralization consists of massive sulfide bodies mostly composed of pyrrhotite and hosted by serpentinized upper mantle peridotites. Chemical composition of unaltered cores in Cr-spinel grains found within the massive sulfide mineralization and in the peridotite host indicates formation in the fore-arc region of the Greater Antilles volcanic arc. A first stage of serpentinization probably took place prior to the sulfide mineralization event. The UM-VMS mineralization formed by the near-complete replacement of the silicate assemblage of partially serpentinized peridotites underneath the seafloor. The sequence of sulfide mineralization has been divided into two stages. The first stage is characterized by a very reduced hydrothermal mineral assemblage consisting of pyrrhotite, Co–Ni–Fe diarsenides, chalcopyrite, Co-rich pentlandite, and electrum. In the second stage, pyrite and Co–Ni–Fe sulfarsenides partially replaced pyrrhotite and diarsenides, respectively, under a more oxidizing regime during the advanced stages of ongoing serpentinization. The proposed conceptual genetic model presented here can be useful for future exploration targeting this type of deposit in the Caribbean region and elsewhere.Spanish Government PI0975CAP Investigacion PUCP-2022 Program PID 2019- 105625RB-C21MCIN/AEI PRE 2020-092140 2022-A- 004

A track record of Au–Ag nanomelt generation during fluid‑mineral interactions

This research was financially supported by Grant PID 2019-105625RB-C21 funded by MCIN/AEI/10.13039/501100011033, by Grant 2021 SGR 00239 funded by Gestió d’Ajuts Universitaris i de Recerca de Catalunya. Additional funding was provided by a “Ayudas predoctorales 2020” number PRE 2020-092140 PhD grant to DD-C by the Spanish Ministry of Science and Innovation and the Proyecto de Excelencia de la Junta de Andalucía (Spain), PROYECTEXCEL_00705 to JMGJ. Laura Casado (Instituto de Nanociencia de Aragón (INA)—University of Zaragoza) and María del Mar Abad (CIC, University of Granada) are acknowledged for her assistance with FIB and HRTEM respectivelyThe online version contains supplementary material available at https:// doi. org/ 10. 1038/ s41598- 023- 35066-yRecent studies have reported the significant role of Au-bearing nanoparticles in the formation of hydrothermal gold deposits. Despite the ever-increasing understanding of the genesis and stability of Au-bearing nanoparticles, it is still unknown how they behave when exposed to hydrothermal fluids. Here, we study the nanostructural evolution of Au–Ag nanoparticles hosted within Co-rich diarsenides and sulfarsenides of a natural hydrothermal deposit. We use high-resolution transmission electron microscopy to provide a singular glimpse of the complete melting sequence of Au–Ag nanoparticles exposed to the hydrothermal fluid during coupled dissolution–precipitation reactions of their host minerals. The interaction of Au–Ag nanoparticles with hydrothermal fluids at temperatures (400–500 ºC) common to most hydrothermal gold deposits may promote melting and generation of Au–Ag nanomelts. This process has important implications in noble metal remobilization and accumulation during the formation of these deposits.MCIN/AEI/10.13039/501100011033, PID 2019-105625RB-C21Gestió d'Ajuts Universitaris i de Recerca de Catalunya 2021 SGR 00239Ministerio de Ciencia e Innovación PRE 2020-092140 PhDProyecto de Excelencia de la Junta de Andalucía PROYECTEXCEL_00705Instituto de Nanociencia de Aragón (INA)-Universidad de ZaragozaComisión de Investigaciones Científicas (CIC), Universidad de Granad

Costarican Precolumbian social jade: A review of petrographic diversity, raw material sources and potential exchange routes

En este trabajo se revisa la información mineralógica-petrológica-geológica disponible sobre jade social (rocas “verdes”) utilizado en Costa Rica en época precolombina. Aproximadamente, el 55 % o más del jade social precolombino costarricense pudo elaborarse con fuentes locales (lutitas y areniscas verdosas, serpentinita, jaspes y otros pedernales y cuarzos), pero el restante al parecer tiene por fuente rocas y minerales foráneos (i.e., jadeitita, onfacitita, cloromelanita, mármol, dolomía, talco) que no se encuentran en Costa Rica del todo, donde las condiciones geológicas en el pasado no favorecieron la formación de jadeitita ni de las otras rocas y minerales citados. Por lo tanto, los jades sociales de rocas y minerales no presentes en Costa Rica deben de provenir de regiones metamórficas presentes desde el norte de Nicaragua hasta México. La jadeíta con toda probabilidad proviene de Guatemala. Las fuentes conocidas de jade de las Antillas Mayores (Cuba y República Dominicana) podrían haber estado involucradas, si bien los argumentos antropológicos y geológicos convergen en sugerir que existe una fuente “perdida” de jadeíta, que podría encontrarse en el norte de Venezuela. Analizando todas las evidencias arqueológicas (incluyendo el material lapidario, alfarería y orfebrería) de una forma sinóptica, se apoya fuertemente la idea de una importante red comercial desde México hasta el istmo de Panamá, llegando incluso hasta el norte de Colombia y Venezuela y las Antillas. Estudios petrológicos y geoquímicos de detalle de las piezas de jade y rocas asociadas costarricenses son requeridos, en particular si se quiere avanzar en comprender mejor la intrincada red económica y cultural de las sociedades precolombinas mesoamericanas y antillanas.In this paper we review the mineralogical-petrological-geological information relevant for social jade (greenstone) used in Costa Rica during Pre-Columbian times. Around 50 % or even more of the pre- Columbian social jade artifacts in Costa Rica may have been produced using local sources (green lutlte and green sandstone, serpentinite, jasper and other types of flint and quartz), but the rest of recovered samples seem to have been manufactured with material imported from external sources (i.e., jadeitite, omphacitite, chloromelanite, dolostone, marble and talc), for they are not present in Costa Rica. The geological evolution in the past did not favor the formation of jadeitite and other mentioned materials in Costa Rica. Hence, social jade made of material not present in Costa Rica must have been sourced from metamorphic regions from north Nicaragua to Mexico. Jadeitite and associated rocks (omphacitite, chloromelanite mineral) was most probably sourced from Guatemala. Known sources of jadeitite in the Greater Antilles (Cuba and Dominican Republic) may have been also involved in the trade of jade finally arriving at Costa Rica. However, geological and anthropological arguments can be raised in favor of a “lost” source of jade in northern Venezuela. In a synoptic view, archaeological evidence, including lapidary, pottery and precious-metal craftwork, point to a strong commercial pre-Columbian network from México to Panamá isthmus reaching further East to the north of Colombia and Venezuela and the Antilles. Detailed petrological/geochemical studies of jade (and related rocks) artifacts in Costa Rica are needed in order to move forward in the knowledge of the complex economic and cultural networks of Mesoamerica-Antillean pre-Columbian societies

Vetas de cromitita en ortopiroxenita anómalamente enriquecidas en minerales del grupo del platino de la ofiolita Habana-Matanzas, Cuba

The Havana–Matanzas Ophiolite contains one of the few examples of ophiolitic platinum group minerals (PGM)-rich chromitites associated with orthopyroxenites in the mantle section of ophiolitic complexes. The chromitites occur as veins hosted by orthopyroxenite bands within mantle peridotites. The peridotites are mostly harzburgites and their accessory chromite shows high-Al compositions (Cr# [Cr/(Cr+Al), atomic ratio] = 0.39–0.50), which are typical of spinels in abyssal peridotites. Conversely, chromite from the chromitite veins and their host orthopyroxenite are high-Cr (Cr# = 0.72–0.73 and 0.62–0.69, respectively), with lower Mg# [Mg/(Mg+Fe2+), atomic ratio]. This suggests that both the chromitite and the orthopyroxenite formed from melts with boninitic affinity. The abundant PGM inclusions found in the chromitites are mainly Os-rich laurite grains, which is also characteristic of chromitites formed from magmas with boninitic affinity. Therefore, we propose that the chromitite veins and the orthopyroxenite bands probably formed contemporaneously in the fore-arc setting of an intra-oceanic arc during subduction. The chromitite-orthopyroxenite pair of the Havana-Matanzas Ophiolite could form after the reaction of a Si-rich melt with boninitic affinity and mantle harzburgite, with the orthopyroxenite bands preserving fingerprints of the infiltration of boninitic- affinity melts within the mantle. The small volume of forming chromitite could maximize the efficiency for the mechanical collection of the PGM forming in the parental melt of these rocks, resulting in the anomalous enrichment of primary PGM in the chromitites.La ofiolita de Habana-Matanzas contiene uno de los pocos ejemplos de cromititas ricas en minerales del grupo del platino (MGP) asociadas a ortopiroxenitas de la sección mantélica de complejos ofiolíticos. Las cromititas ocurren como venas encajadas en bandas de ortopiroxenita dentro de la peridotita mantélica. Las peridotitas son mayoritariamente harzburgitas con cromita accesoria rica en Al (#Cr [Cr/(Cr+Al), cociente atómico] = 0.39–0.50), lo cual es típico de espinelas en peridotitas abisales. Por otro lado, la cromita perteneciente a las venas de cromitita y a la ortopiroxenita encajante es rica en Cr (#Cr = 0.72–0.73 y 0.62–0.69, respectivamente) y con bajo #Mg [Mg/(Mg+Fe2+), cociente atómico]. Esto sugiere que tanto las venas de cromitita como la ortopiroxenita se formaron a partir de fundidos de afinidad boninítica. Las abundantes inclusiones de MGP encontradas en las cromititas son principalmente granos de laurita ricos en Os, lo cual también es propio de cromititas formadas a partir de magmas con afinidad boninítica. Por lo tanto, proponemos que las venas de cromitita y las bandas de ortopiroxenitas se formaron contemporáneamente en un contexto de ante-arco en un arco intra-oceánico durante el proceso de subducción. El conjunto cromitita-ortopiroxenita de la ofiolita de Habana- Matanzas se formó por la reacción de fundidos ricos en Si con afinidad boninítica y la harzburgita mantélica. Las bandas de ortopiroxenitas sería la huella química que habrían dejado estos fundidos boniníticos al infiltrarse por el manto. El volumen reducido de las cromititas que se formaron maximizó la eficiencia del proceso de recolección mecánica de los MGP que se formaban en el fundido parental, dando lugar al enriquecimiento de MGP primarios como inclusiones en las cromititas

Piedra artificial porosa a partir de residuos de rocas ornamentales adaptable a obras de construcción y restauración patrimonial

The technique of volumetric reintegration in severely deteriorated stone materials is of major importance for the restoration of architectural heritage. In using mortars for restoration it is important to control aspects such as the colour and textural similarity in relation to the adjacent stone, minor or equal strength and equal or greater porosity/permeability with respect to the original stone. This latter aspect is of particular complexity because the percentage distribution of pore-size ranges should not differ from that of the original stone material. The invention patent (with numbers of publication ES2187245 A1 and B1 16. 06. 2004), owned by the University of Granada, allows the production of excellent porous stones for decorative work in construction and mortar for restoration of stone materials with controlled porosity. Both materials consist of ornamental rock waste, so that a particular recycling purpose is given to this type of material which is difficult to reuse. In this paper we present the manufacturing process of these artificial stones and porous mortars with decorative and restorative purposes, from the controlled mixture of aggregates of ornamental rocks, organic and inorganic binders and generators of porosity. Once the curing and hardening has been done it is worth noting that one of the most important aspects of the product is the generation of a complex connected porous system as a result of the incorporation of crushed expanded polystyrene, which is activated after hardening through the application of organic solvents.Grupo de Investigación: MATERIALES AVANZADOS PARA APLICACIONES TECNICAS Y ARTISTICAS Y SU CONSERVACION-RESTAURACION (Cod.: HUM629) y Research Group RNM302 Petrogenesis and lithospheric processe

Melting Relations of MORB-Sediment Mélanges in Underplated Mantle Wedge Plumes; Implications for the Origin of Cordilleran-type Batholiths

This paper gives the results of a set of laboratory experiments designed to analyse the petrological implications of mantle wedge plumes—large buoyant structures predicted by thermomechanical numerical modelling of subduction zones. A particular design of layered capsule was used to simulate the complex multilayer formed by intense flow within the mantle wedge as predicted by numerical models. A basaltic [mid-ocean ridge basalt (MORB)-derived amphibolite] component was sandwiched between two adjacent layers of a sedimentary (Bt-rich metagreywacke) component. Conditions were fixed at temperatures of 1000-1200°C at pressures of 1·5-2·0 GPa. Our results suggest that significant volumes of hybrid, Cordilleran-type granodioritic magmas can be generated by sub-lithospheric partial melting of a mechanically mixed source. Partial melting of the end-members is not buffered, forming granitic (melting of metasediment) and trondhjemitic (melting of MORB) melts in high-variance assemblages Melt + Grt + Pl and Melt + Grt + Cpx, respectively. However, the composition of melts formed from partial melting of metasediment-MORB mélanges is buffered for sediment-to-MORB ratios ranging from 3:1 to 1:3, producing liquids of granodiorite to tonalite composition along a cotectic with the lower-variance phase assemblage Melt + Grt + Cpx + Pl. Our model explains the geochemical and isotopic characteristics of Cordilleran batholiths. In particular, it accounts for the observed decoupling between major element and isotopic compositions. Large variations in isotopic ratios can be inherited from a compositionally heterogeneous source; however, major element compositions are more strongly dependent on the temperature of melting rather than on the composition of the sourc

Glaucony authigenesis, maturity and alteration in the Weddell Sea: An indicator of paleoenvironmental conditions before the onset of Antarctic glaciation

This research used samples from the ODP. We thank the staff at the Gulf Coast core repository for assistance in ODP Leg 113 core handling and shipping.We acknowledge the help of Dr. María del Mar Abad, Dr. Isabel Sánchez Almazo, Dr. Miguel Angel Hidalgo, Dr. Miguel Angel Salas, and Isabel Nieto (Scientific Instrumentation Center of the University of Granada, CIC) for their help along different phases of the laboratory work. We also acknowledge the constructive comments of two anonymous reviewers that have helped to improve this paper. We wish to thank Prof. C. Hans Nelson for their constructive comments and improvement of our English, which contributed greatly toward clarification of the text. Thanks are also given to Dr. Francisco J. Lobo and Dr. Fernando Bohoyo for their helpful comments related to the study area and regional tectonics.Three types of glaucony grains were identified in the late Eocene (~35.5–34.1 Ma) sediments from Ocean Drilling Program (ODP) Hole 696B in the northwestern Weddell Sea (Antarctica). The grains are K2O-rich (~7 wt%) and formed by smectite-poor interstratified ~10 Å glauconite-smectite with flaky/ rosette-shaped surface nanostructures. Two glaucony types reflect an evolved (types 1 and 2 glaucony; less mature to mature) stage and long term glauconitization, attesting to the glaucony grains being formed in situ, whereas the third type (type 3 glaucony) shows evidences of alteration and reworking from nearby areas. Conditions for the glaucony authigenesis occurred in an open-shelf environment deeper than 50 m, under sub-oxic conditions near the sediment-water interface. These environmental conditions were triggered by low sedimentation rates and recurrent winnowing action by bottomcurrents, leading to stratigraphic condensation. The condensed glaucony-bearing section provides an overview of continuous sea-level rise conditions pre-dating the onset of Antarctic glaciation during the Eocene-Oligocene transition. Sediment burial, drop of O2 levels, and ongoing reducing (postoxic to sulphidic) conditions at Hole 696B, resulting in iron-sulphide precipitation, were a key limiting factor for the glauconitization by sequestration of Fe2+.Funding for this research is provided by the Spanish Ministry of Science and Innovation (grants CTM2014-60451-C2-1-P and CTM2017-89711-C2-1-P, CGL2016-75679P) cofunded by the European Union through FEDER funds and RNM-208 group (Discontinuidades estratigráficas, Junta de Andalucía, Spain)