Deciphering magmatic processes in calc-alkaline plutons using trace element zoning in hornblende

Abstract The origin of the large diversity of rock types erupted along the subduction-related Trans-Mexican Volcanic Belt (TMVB) remains highly debated. In particular, several hypotheses have been proposed to explain the contemporary eruption of calc-alkaline and alkaline magmas along the belt. The Michoacán-Guanajuato Volcanic Field (MGVF) is an atypical, vast region of monogenetic activity located in the western-central part of the TMVB. Here we present new petrographic, geochemical, and isotopic (Sr–Nd–Pb–Os) data on recent volcanics in the Jorullo-Tacámbaro area that is the closest to the oceanic trench. TMVB-related volcanics in this area are Plio-Quaternary (<5 Ma) and mainly form a calc-alkaline series from basalts to dacites, with rare (<5 vol. %) alkaline rocks that range from trachybasalts to trachydacites, and transitional samples. Crystal textures are consistent with rapid crystallization at shallow depth and processes of mixing of similar magma batches (magma recharge). All of the samples exhibit an arc-type trace element pattern. Alkaline and transitional magmas have higher Na2O and K2O, lower Al2O3, and higher concentrations in incompatible elements (e.g. Sr, K, Ba, Th, Ce, P) compared to calc-alkaline rocks. Calc-alkaline rocks are similar isotopically to transitional and alkaline samples, except for a few low 87Sr/86Sr samples. Sr, Nd and Pb isotopes do not correlate with MgO or 187Os/188Os, indicating that they were not significantly influenced by crustal contamination. Isotopic and trace-element systematics suggest that the Tacámbaro magmas are produced by melting of a mantle wedge fluxed by fluids derived from a mixture of subducted sediments and altered oceanic crust. Alkaline and transitional magmas can be derived from a lower degree of partial melting of a similar source to that of the calc-alkaline rocks, whereas the few low 87Sr/86Sr calc-alkaline rocks require a lower proportion of fluid derived from oceanic sediments and crust. Volcanism at the trenchward edge of the MGVF was thus driven purely by subduction during the last 5 Ma, hence discarding slab rollback in this sector of the TMVB.

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Zircon Petrochronology of the Meghri-Ordubad Pluton, Lesser Caucasus: Fingerprinting Igneous Processes and Implications for the Exploration of Porphyry Cu-Mo Deposits

Economic Geology ◽

10.5382/econgeo.4671 ◽

2019 ◽

Vol 114 (7) ◽

pp. 1365-1388 ◽

Cited By ~ 4

Author(s):

Hervé Rezeau ◽

Robert Moritz ◽

Jörn-Frederik Wotzlaw ◽

Samvel Hovakimyan ◽

Rodrik Tayan

Keyword(s):

Trace Element ◽

Mineral Exploration ◽

Porphyry Copper ◽

Trace Element Composition ◽

Element Composition ◽

Porphyry Copper Deposits ◽

Copper Deposits ◽

Magmatic Processes ◽

Lesser Caucasus ◽

Intrusive Suite

Abstract The trace element composition of zircon, especially in tandem with U-Pb geochronology, has become a powerful tool for tracing magmatic processes associated with the formation of porphyry copper deposits. However, the use of the redox-sensitive Eu and Ce anomalies as a potential mineral exploration proxy is controversial. This study presents a comprehensive, temporally constrained data set of zircon trace element compositions (n = 645) for three compositionally distinct magmatic series identified in the Meghri-Ordubad pluton, southernmost Lesser Caucasus. The 30 million years of Cenozoic magmatism in the Meghri-Ordubad pluton are associated with several ore-forming pulses leading to the formation of porphyry copper deposits and epithermal-style mineralization. Our zircon geochemical data constrain the thermal and chemical evolution of this complex intrusive suite and allow an evaluation of the usefulness of zircon as a mineral exploration proxy for porphyry copper deposits. Our results combined with Rayleigh fractionation modeling indicate that the trace element composition of zircon (Th/U, Hf, Ti, YbN/DyN, Eu anomalies) is influenced by the composition and the water concentration of the parental magma, as well as by co-crystallizing titanite and apatite. In contrast, the variations of Ce anomalies remain difficult to explain by magmatic processes and could rather be ascribed to relative fluctuations of the redox conditions. In the Meghri-Ordubad pluton, we do not observe any systematic patterns between the trace element composition in zircons and the different ore-forming pulses. This questions the reliability of using the trace element composition in zircon as an exploration mineral proxy, and it rather emphasizes that a good knowledge of the entire magmatic evolution of a metallogenic province is required.

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Phlogopite/matrix, clinopyroxene/matrix and clinopyroxene/phlogopite trace-element partitioning in a calc-alkaline lamprophyre: new constrains from the Křižanovice minette dyke (Bohemian Massif)

Journal of Geosciences ◽

10.3190/jgeosci.160 ◽

2014 ◽

pp. 87-96 ◽

Cited By ~ 8

Author(s):

L. Krmíček ◽

M. Halavínová ◽

R.L. Romer ◽

M. Vašinová Galiová ◽

T. Vaculovič

Keyword(s):

Trace Element ◽

Bohemian Massif ◽

Calc Alkaline ◽

Trace Element Partitioning ◽

Element Partitioning

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Nature des sources des composants andesitiques des Gres du Champsaur et des Gres de Taveyannaz; implications dans l'evolution des Alpes occidentales au Paleogene

BSGF - Earth Sciences Bulletin ◽

10.2113/172.4.487 ◽

2001 ◽

Vol 172 (4) ◽

pp. 487-501 ◽

Cited By ~ 19

Author(s):

Maud Boyet ◽

Henriette Lapierre ◽

Marc Tardy ◽

Delphine Bosch ◽

Rene Maury

Keyword(s):

Trace Element ◽

Western Alps ◽

Northern Italy ◽

Calc Alkaline ◽

Magmatic Source ◽

Isotopic Compositions ◽

Alpine Zone ◽

Internal Zone ◽

Isotopic Geochemistry

Abstract Paleogene magmatism is widespread in the western Alps and its origin is still a matter of debate. It consists of calc-alkaline and shoshonitic suites with mainly granodioritic intrusions in the Internal Zone (northern Italy), andesitic volcanism in the Delphino-Helvetic Zone (French-Swiss domain) and the Esterellite intrusions in Provence. In the External Alpine Zone, the Taveyannaz Sandstones and the Champsaur Sandstones preserve andesitic pebbles and mineral fragments dated at 32 Ma. On the basis of trace-element and isotopic geochemistry (Sr, Nd, Pb and O) of mineral separates (amphibole, pyroxene and plagioclase) and andesitic clasts, we characterise the nature of magmatic source(s) and compare the isotopic compositions of the andesites with those of well known Paleogene igneous suites.

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Pluton source varition over two magmatic pulses in the white-inyo range, central-eastern California : implications for paleozoic and mesozoic tectonic reconstructions

10.32469/10355/70686 ◽

2018 ◽

Author(s):

◽

Elizabeth M Kenderes

Keyword(s):

Trace Element ◽

North American ◽

Oceanic Island ◽

Island Arc ◽

Calc Alkaline ◽

Isotopic Data ◽

Regional Study ◽

University Of Missouri ◽

Tectonic Model ◽

Central Eastern

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This dissertation uses compositions of plutons in the White-Inyo Range (WIR) of central-eastern California, which is an important tectonic boundary as it is the easternmost extent of the Mesozoic Cordilleran arc and the western edge of Basin and Range extension. The main goal of this dissertation is to understand the lithospheric structure of this area in relation to the broader regional tectonics. Chapters 2 and 3 specifically investigate the Eureka Valley-Joshua Flat-Beer Creek (EJB) composite arc pluton, from its source to emplacement. The EJB pluton is one of a small number of monzonitic plutons cotemporally emplaced with the primarily calc-alkaline North American Mesozoic Cordilleran arc. Mineral major and trace element compositions are used to show the crystallization sequence and pressures and temperatures of mineral crystallization. These data are used to make interpretations about the EJB pluton's formation from source to emplacement. Additionally, whole rock major and trace element compositions and isotopic data show that the EJB pluton has a unique source from the calc-alkaline plutons: an underplated, eclogitized oceanic island arc. Chapter 4 is a regional study of the WIR, and it includes whole rock major and trace element and isotopic data to interpret the three distinct sources of plutons: (1) the eclogitized oceanic island arc, (2) enriched lithospheric mantle, and (3) Proterozoic North American basement. Recognizing the timing of the generation of these plutons in relation to their sources is crutial to understanding the tectonic history of the WIR area. This dissertation presents tectonic model for western North America from the Early Proterozoic to Late Cretaceous

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The Alkaline Lamprophyres of the Dolomitic Area (Southern Alps, Italy): Markers of the Late Triassic Change from Orogenic-like to Anorogenic Magmatism

Journal of Petrology ◽

10.1093/petrology/egz031 ◽

2019 ◽

Vol 60 (6) ◽

pp. 1263-1298 ◽

Cited By ~ 6

Author(s):

Federico Casetta ◽

Ryan B Ickert ◽

Darren F Mark ◽

Costanza Bonadiman ◽

Pier Paolo Giacomoni ◽

...

Keyword(s):

Trace Element ◽

Southern Alps ◽

Late Triassic ◽

Small Scale ◽

Main Process ◽

Calc Alkaline ◽

Isotopic Signatures ◽

Systematic Uncertainties ◽

High K ◽

Magmatic Event

AbstractWe present the first complete petrological, geochemical and geochronological characterization of the oldest lamprophyric rocks in Italy, which crop out around Predazzo (Dolomitic Area), with the aim of deciphering their relationship with Triassic magmatic events across the whole of the Southern Alps. Their Mg# of between 37 and 70, together with their trace element contents, suggests that fractional crystallization was the main process responsible for their differentiation, together with small-scale mixing, as evidenced by some complex amphibole textures. Moreover, the occurrence of primary carbonate ocelli suggests an intimate association between the alkaline lamprophyric magmas and a carbonatitic melt. 40Ar/39Ar data show that the lamprophyres were emplaced at 219·22 ± 0·73 Ma (2σ; full systematic uncertainties), around 20 Myr after the high-K calc-alkaline to shoshonitic, short-lived, Ladinian (237–238 Ma) magmatic event of the Dolomitic Area. Their trace element and Sr–Nd isotopic signatures (87Sr/86Sri = 0·7033–0·7040; 143Nd/144Ndi = 0·51260–0·51265) are probably related to a garnet–amphibole-bearing lithosphere interacting with an asthenospheric component, significantly more depleted than the mantle source of the high-K calc-alkaline to shoshonitic magmas. These features suggest that the Predazzo lamprophyres belong to the same alkaline–carbonatitic magmatic event that intruded the mantle beneath the Southern Alps (e.g. Finero peridotite) between 190 and 225 Ma. In this scenario, the Predazzo lamprophyres cannot be considered as a late-stage pulse of the orogenic-like Ladinian magmatism of the Dolomitic Area, but most probably represent a petrological bridge to the opening of the Alpine Tethys.

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