Phosphate Mineral Associations from the Tres Arroyos Aplite-Pegmatites (Badajoz, Spain): Petrography, Mineral Chemistry, and Petrogenetic Implications

2021 ◽  
Author(s):  
Idoia Garate-Olave ◽  
Encarnación Roda-Robles ◽  
Pedro Pablo Gil-Crespo ◽  
Alfonso Pesquera
Keyword(s):  
Mineral Chemistry ◽  
Chemical Compositions ◽  
Granite Pegmatite ◽  
System P ◽  
Phosphate Mineral ◽  
Mineral Associations ◽  
Low Degree ◽  
History Of ◽  
Granitic Batholith ◽  
Tres Arroyos

ABSTRACT In the Tres Arroyos granite-pegmatite system (Badajoz, Spain) a zoned aplite-pegmatite field occurs, with poorly evolved, intermediate, and Li-rich dikes intruded into metasediments, close to the contact with the Nisa-Alburquerque granitic batholith. A large variety of Fe-Mn phosphate minerals occur in the poorly evolved aplite-pegmatites; Al-phosphates occur mainly in the intermediate and Li-rich dikes. The Fe/(Fe + Mn) ratio of the Fe-Mn phosphates is the highest reported for aplite-pegmatite fields in the Central Iberian Zone, suggesting a low degree of fractionation for the poorly evolved aplite-pegmatites that host these minerals. In contrast, the high F contents observed in crystals of the amblygonite–montebrasite series from the intermediate and Li-rich aplite-pegmatites indicates a higher fractionation degree for these dikes. The relatively common occurrence of phosphate minerals in the three types of aplite-pegmatites from Tres Arroyos attests to a significant availability of P in the pegmatitic melt. In this granite pegmatite system, P first started behaving as a compatible element, thus favoring the crystallization of discrete phosphates, during the crystallization of the poorly evolved aplite-pegmatites. In more fractionated melts, where Fe-Mn-(Mg) contents were extremely depleted, P was still available, allowing the crystallization of the Al-phosphates, mainly of the amblygonite–montebrasite series, in the more evolved intermediate and Li-rich aplite-pegmatites. Subsolidus replacement of the early phosphate phases, such as those of the amblygonite–montebrasite series, by lacroixite, together with the presence of late Ca- and Sr-bearing phosphates such as jahnsite-(CaMnFe), whiteite-(CaFeMg), mitridatite, and goyazite, attest to a high activity of metasomatic fluids in the Tres Arroyos granite-pegmatite system. Consequently, variations in the phosphate mineral associations and in their chemical compositions reflect well the fractional crystallization processes suffered by the pegmatitic melts from the poorly evolved up to the Li-rich dikes, as well as the subsolidus history of the Tres Arroyos system.

scholarly journals Petrology, mineral chemistry, and geochemistry of Late Triassic Ni–Cu ore-bearing mafic–ultramafic intrusions, Hongqiling, northeastern China: petrogenesis and tectonic implications

2019 ◽  
Vol 56 (2) ◽  
pp. 111-128
Author(s):  
Ai Li ◽  
Jian Wang ◽  
Yue Song
Keyword(s):  
Crustal Contamination ◽  
Parental Magma ◽  
Mineral Chemistry ◽  
Late Triassic ◽  
Sulfide Deposit ◽  
Chemical Compositions ◽  
Tholeiitic Magma ◽  
Average Value ◽  
Central Asian ◽  
History Of

The Hongqiling magmatic Ni–Cu sulfide deposit, situated on the southern margin of the eastern Central Asian Orogenic Belt (CAOB), is composed of over 30 mafic–ultramafic intrusions. These ore-bearing intrusions are composed mainly of harzburgite, lherzolite, websterite, orthopyroxenite, and norite (gabbro). The constituent minerals are olivine, diopside, bronzite, calcic-hornblende, plagioclase, and spinel with orthopyroxene as a dominant mineral in these intrusions. These ore-bearing intrusions are not Alaskan-type complexes. Spinel and clinopyroxene both exhibit different chemical compositions from those in the Alaskan-type complexes. The rocks that make up the intrusions have high contents of MgO (average value = 25.20 wt.%) and low TiO2 (average value = 0.58 wt.%). The high MgO contents of the minerals and the high Mg# (71) of the calculated melt in equilibrium with olivine demonstrate that the parental magma of the Hongqiling mafic–ultramafic intrusions was a high-Mg tholeiitic magma. The Hongqiling ore-bearing mafic–ultramafic intrusions and the calculated “trapped liquids” for the olivine-orthopyroxene cumulate rocks are all enriched in large-ion lithophile elements and depleted in high field strength elements. The Ce/Pb, Ta/La, Th/Yb, and (La/Sm)PM values and the depletion of Nb and Ta suggest that the magma experienced crustal contamination. The Hongqiling ore-bearing intrusions display many similarities with mafic–ultramafic intrusions that formed in a post-collisional extensional environment in the western CAOB (e.g., Huangshanxi). Common features include their whole-rock compositions and mineral chemistry. Combined with the evolutionary history of the eastern segment of the CAOB, we believe that the Late Triassic Hongqiling mafic–ultramafic intrusions formed in a post-collisional extensional environment.

Conclusion: What is Speculative Empiricism?

2018 ◽  
Author(s):  
Didier Debaise
Keyword(s):  
Social Groups ◽  
Speculative Philosophy ◽  
System P ◽  
History Of ◽  
Selection Of

Process and Reality ends with a warning: ‘[t]he chief danger to philosophy is narrowness in the selection of evidence’ (PR, 337). Although this danger of narrowness might emerge from the ‘idiosyncrasies and timidities of particular authors, of particular social groups, of particular schools of thought, of particular epochs in the history of civilization’ (PR, 337), we should not be mistaken: it occurs within philosophy, in its activity, its method. And the fact that this issue arises at the end of Process and Reality reveals the ambition that has accompanied its composition: Whitehead has resisted this danger through the form and ambition of his speculative construction. The temptation of a narrowness in selection attempts to expel speculative philosophy at the same time as it haunts each part of its system.

Drifting Through a Planetary System

2018 ◽  
Author(s):  
Karel Schrijver
Keyword(s):  
Seventeenth Century ◽  
Solar System ◽  
Virtual Worlds ◽  
Planetary System ◽  
System P ◽  
History Of ◽  
Or Team ◽  
Water Contents

This chapter describes how the first found exoplanets presented puzzles: they orbited where they should not have formed or where they could not have survived the death of their stars. The Solar System had its own puzzles to add: Mars is smaller than expected, while Venus, Earth, and Mars had more water—at least at one time—than could be understood. This chapter shows how astronomers worked through the combination of these puzzles: now we appreciate that planets can change their orbits, scatter water-bearing asteroids about, steal material from growing planets, or team up with other planets to stabilize their future. The special history of Jupiter and Saturn as a pair bringing both destruction and water to Earth emerged from the study of seventeenth-century resonant clocks, from the water contents of asteroids, and from experiments with supercomputers imposing the laws of physics on virtual worlds.

Digitally Mediated Identity in the Cases of Two Sámi Artists

2017 ◽  
Author(s):  
Ann Werner
Keyword(s):  
Cultural Issues ◽  
Global Media ◽  
Dominant Form ◽  
Industry Studies ◽  
Media System ◽  
Internet Users ◽  
System P ◽  
Music Consumption ◽  
History Of ◽  
Streaming Services

This chapter explores identity issues in commercial streaming services, which have grown steadily in the 2010s to become the dominant form of music consumption in the Nordic countries, with about 60% of all Internet users in 2015. The chapter offers an alternative to the dominant trend in music industry studies by focusing not on the industry’s interests but instead on broader cultural issues. The chapter presents case studies of two female Sámi artists and their representations on Spotify, YouTube, MySpace, and artists’ websites, taking various aspects of the services into account, including the interface and the algorithm-based recommendations. Informed by feminist cultural studies, the argument is that the industry continues a history of reinforcing stereotypes of ethnicity, indigeneity, and femininity. Thus, commercial streaming is not only making music available to global audiences, it is also selling images of Otherness within an unequal capitalist global media system.

The Metasomatized Mantle beneath the North Atlantic Craton: Insights from Peridotite Xenoliths of the Chidliak Kimberlite Province (NE Canada)

2019 ◽  
Vol 60 (10) ◽  
pp. 1991-2024 ◽  
Author(s):  
M G Kopylova ◽  
E Tso ◽  
F Ma ◽  
J Liu ◽  
D G Pearson
Keyword(s):  
North Atlantic ◽  
Thermal State ◽  
Mineral Chemistry ◽  
Mantle Metasomatism ◽  
Labrador Sea ◽  
The North ◽  
Rock Types ◽  
History Of ◽  
The North Atlantic ◽  
North Atlantic Craton

Abstract We studied the petrography, mineralogy, thermobarometry and whole-rock chemistry of 120 peridotite and pyroxenite xenoliths collected from the 156–138 Ma Chidliak kimberlite province (Southern Baffin Island). Xenoliths from pipes CH-1, -6, -7 and -44 are divided into two garnet-bearing series, dunites–harzburgites–lherzolites and wehrlites–olivine pyroxenites. Both series show widely varying textures, from coarse to sheared, and textures of late formation of garnet and clinopyroxene. Some samples from the lherzolite series may contain spinel, whereas wehrlites may contain ilmenite. In CH-6, rare coarse samples of the lherzolite and wehrlite series were derived from P = 2·8 to 5·6 GPa, whereas predominant sheared and coarse samples of the lherzolite series coexist at P = 5·6–7·5 GPa. Kimberlites CH-1, -7, -44 sample mainly the deeper mantle, at P = 5·0–7·5 GPa, represented by coarse and sheared lherzolite and wehrlite series. The bulk of the pressure–temperature arrays defines a thermal state compatible with 35–39 mW m–2 surface heat flow, but a significant thermal disequilibrium was evident in the large isobaric thermal scatter, especially at depth, and in the low thermal gradients uncharacteristic of conduction. The whole-rock Si and Mg contents of the Chidliak xenoliths and their mineral chemistry reflect initial high levels of melt depletion typical of cratonic mantle and subsequent refertilization in Ca and Al. Unlike the more orthopyroxene-rich mantle of many other cratons, the Chidliak mantle is rich (∼83 vol%) in forsteritic olivine. We assign this to silicate–carbonate metasomatism, which triggered wehrlitization of the mantle. The Chidliak mantle resembles the Greenlandic part of the North Atlantic Craton, suggesting the former contiguous nature of their lithosphere before subsequent rifting into separate continental fragments. Another, more recent type of mantle metasomatism, which affected the Chidliak mantle, is characterized by elevated Ti in pyroxenes and garnet typical of all rock types from CH-1, -7 and -44. These metasomatic samples are largely absent from the CH-6 xenolith suite. The Ti imprint is most intense in xenoliths derived from depths equivalent to 5·5–6·5 GPa where it is associated with higher strain, the presence of sheared samples of the lherzolite series and higher temperatures varying isobarically by up to 200 °C. The horizontal scale of the thermal-metasomatic imprint is more ambiguous and could be as regional as tens of kilometers or as local as <1 km. The time-scale of this metasomatism relates to a conductive length-scale and could be as short as <1 Myr, shortly predating kimberlite formation. A complex protracted metasomatic history of the North Atlantic Craton reconstructed from Chidliak xenoliths matches emplacement patterns of deep CO2-rich and Ti-rich magmatism around the Labrador Sea prior to the craton rifting. The metasomatism may have played a pivotal role in thinning the North Atlantic Craton lithosphere adjacent to the Labrador Sea from ∼240 km in the Jurassic to ∼65 km in the Paleogene.

scholarly journals Geochemical signatures of mineralizing events in the Juomasuo Au–Co deposit, Kuusamo belt, northeastern Finland

2021 ◽  
Author(s):  
Mikael Vasilopoulos ◽  
Ferenc Molnár ◽  
Hugh O’Brien ◽  
Yann Lahaye ◽  
Marie Lefèbvre ◽  
...  
Keyword(s):  
Trace Element ◽  
Sulfur Isotope ◽  
Mineral Chemistry ◽  
Chemical Compositions ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Icp Ms ◽  
Stage 1 ◽  
Host Rocks ◽  
Relationship Of

AbstractThe Juomasuo Au–Co deposit, currently classified as an orogenic gold deposit with atypical metal association, is located in the Paleoproterozoic Kuusamo belt in northeastern Finland. The volcano-sedimentary sequence that hosts the deposit was intensely altered, deformed, and metamorphosed to greenschist facies during the 1.93–1.76 Ga Svecofennian orogeny. In this study, we investigate the temporal relationship between Co and Au deposition and the relationship of metal enrichment with protolith composition and alteration mineralogy by utilizing lithogeochemical data and petrographic observations. We also investigate the nature of fluids involved in deposit formation based on sulfide trace element and sulfur isotope LA-ICP-MS data together with tourmaline mineral chemistry and boron isotopes. Classification of original protoliths was made on the basis of geochemically immobile elements; recognized lithologies are metasedimentary rocks, mafic, intermediate-composition, and felsic metavolcanic rocks, and an ultramafic sill. The composition of the host rocks does not control the type or intensity of mineralization. Sulfur isotope values (δ34S − 2.6 to + 7.1‰) and trace element data obtained for pyrite, chalcopyrite, and pyrrhotite indicate that the two geochemically distinct Au–Co and Co ore types formed from fluids of different compositions and origins. A reduced, metamorphic fluid was responsible for deposition of the pyrrhotite-dominant, Co-rich ore, whereas a relatively oxidized fluid deposited the pyrite-dominant Au–Co ore. The main alteration and mineralization stages at Juomasuo are as follows: (1) widespread albitization that predates both types of mineralization; (2) stage 1, Co-rich mineralization associated with chlorite (± biotite ± amphibole) alteration; (3) stage 2, Au–Co mineralization related to sericitization. Crystal-chemical compositions for tourmaline suggest the involvement of evaporite-related fluids in formation of the deposit; boron isotope data also allow for this conclusion. Results of our research indicate that the metal association in the Juomasuo Au–Co deposit was formed by spatially coincident and multiple hydrothermal processes.

scholarly journals Petrogenetic and Compositional Features of Rare Metal Pan-African Post-Collisional Pegmatites of Southwestern Nigeria; A Status Review

2018 ◽  
Vol 7 (2) ◽  
pp. 166-187
Author(s):  
Abiola Oyebamiji ◽  
Adeniyi JohnPaul Adewumi ◽  
Tehseen Zafar ◽  
Adegbola Odebunmi ◽  
Philips Falae ◽  
...  
Keyword(s):  
Mineral Chemistry ◽  
Rare Metal ◽  
Border Zone ◽  
Chemical Compositions ◽  
Molten Material ◽  
Southwestern Nigeria ◽  
Pan African ◽  
Opening And Closing ◽  
High Degree ◽  
Rare Metal Pegmatite

Abstract This research reviews the geology, petrogenesis, compositional trends and geochronology of the rare-metal pegmatite of southwestern Nigeria. The source of these pegmatites is still presently debated which have been explained as either product of highly fractionated molten material or anatexis of the local crust. However, published works of past authors have been compiled to give a detailed understanding of the formation of the mineral deposits. The basement complex of southwestern Nigeria comprises of Precambrian rocks of amphibolite, the hornblende gneiss and the granite gneisses which were formed as a result of the opening and closing of the ensialic basin with significant, extensive subduction during the Pan-African orogeny. The pegmatites in this region have shown internal zoning and a high degree of evolution from the border zone to the core zone during the crystallization and solidification of the felsic granite to pegmatite melt. The rare-metal pegmatites have distinct chemical compositions and mineralogy, containing quartz, biotite, muscovite, microcline, garnet with localized tourmaline, tantalite and columbite. These pegmatites vary significantly by their bulk-rock and mineral chemistry which indicates a more peraluminous attribute and enrichments of lithophile elements of Rb, Cs, Ta and Ba. Previous K/Ar isotopic ages (502.8±13.0 Ma and 514.5±13.2 Ma) suggest that the pegmatites are related to the post-collisional phase of intensive metasomatism. Adopted from previous studies, a five-stage conceptual model of evolution which is widely accepted have been proposed for the origin of the pegmatites.

The Next Space Patrons

2017 ◽  
Author(s):  
Alexander MacDonald
Keyword(s):  
Solar System ◽  
Political History ◽  
Space Exploration ◽  
Development Program ◽  
The Political ◽  
Early American ◽  
Long Run ◽  
Space Race ◽  
System P ◽  
History Of

Mankind will not remain forever confined to the Earth. In pursuit of light and space it will, timidly at first, probe the limits of the atmosphere and later extend its control to the entire solar system. —Konstantin Tsiolkovsky, Letter to B. N. Vorobyev, 1911 What do we learn from this long-run perspective on American space exploration? How does it change our understanding of the history of spaceflight? How does it change our understanding of the present? This book has provided an economic perspective on two centuries of history, with examinations of early American observatories, the rocket development program of Robert Goddard, and the political history of the space race. Although the subjects covered have been wide-ranging, together they present a new view of American space history, one that challenges the dominant narrative of space exploration as an inherently governmental activity. From them a new narrative emerges, that of the Long Space Age, a narrative that in the ...

scholarly journals Different Tectonic Evolution of Fast Cooling Ophiolite Mantles Recorded by Olivine-Spinel Geothermometry: Case Studies from Iballe (Albania) and Nea Roda (Greece)

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 64
Author(s):  
Micol Bussolesi ◽  
Giovanni Grieco ◽  
Alessandro Cavallo ◽  
Federica Zaccarini
Keyword(s):  
Tectonic Evolution ◽  
Early Stage ◽  
Mineral Chemistry ◽  
Northern Greece ◽  
Present Contribution ◽  
Cooling Rates ◽  
History Of ◽  
Ferrian Chromite ◽  
Fast Cooling ◽  
Subduction Setting

Mg-Fe2+ diffusion patterns in olivine and chromite are useful tools for the study of the thermal history of ultramafic massifs. In the present contribution, we applied the exponential modeling of diffusion patterns to geothermometry and geospeedometry of chromitite ores from two different ophiolite contexts. The Iballe ophiolite (Northern Albania) hosts several chromitite pods within dunites. Primary and re-equilibrated Mg#, estimated by using an exponential function, provided re-equilibration and primary temperatures ranging between 677 and 996 °C for chromitites and between 527 and 806 °C for dunites. Cooling rates for chromitites are higher than for dunites, suggesting a different genesis for the two lithologies, confirmed also by spinel mineral chemistry. Chromitites with MORB affinity formed in a SSZ setting at a proto-forearc early stage, explaining the higher cooling rates, while dunites, with boninitic affinity, were formed deeper in the mantle in a more mature subduction setting. At the Nea Roda ophiolite (Northern Greece) olivine in chromitites do not show Mg-Fe variations, and transformation into ferrian chromite produced “fake” diffusion patterns within chromite. The absence of diffusion patterns and the low estimated temperatures (550–656 °C) suggest that Nea Roda chromitites were completely re-equilibrated during an amphibolite-facies metamorphic event that obliterated all primary features.

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