Snapshots of primitive arc magma evolution recorded by clinopyroxene textural and compositional variations: The case of hybrid crystal-rich enclaves from Capo Marargiu Volcanic District (Sardinia, Italy)

2018 ◽  
Vol 103 (6) ◽  
pp. 899-910 ◽  
Author(s):  
Vanni Tecchiato ◽  
Mario Gaeta ◽  
Silvio Mollo ◽  
Olivier Bachmann ◽  
Albrecht von Quadt ◽  
...  
Keyword(s):  
Magma Evolution ◽  
Compositional Variations ◽  
Arc Magma

scholarly journals Multi-stage arc magma evolution recorded by apatite in volcanic rocks

Geology ◽  
2020 ◽  
Vol 48 (4) ◽  
pp. 323-327 ◽  
Author(s):  
Chetan L. Nathwani ◽  
Matthew A. Loader ◽  
Jamie J. Wilkinson ◽  
Yannick Buret ◽  
Robert H. Sievwright ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Volcanic Rocks ◽  
Explosive Volcanism ◽  
Ore Deposits ◽  
Magma Evolution ◽  
Arc Magmas ◽  
Deep Crust ◽  
Multi Stage ◽  
Novel Approach ◽  
Arc Magma

Abstract Protracted magma storage in the deep crust is a key stage in the formation of evolved, hydrous arc magmas that can result in explosive volcanism and the formation of economically valuable magmatic-hydrothermal ore deposits. High magmatic water content in the deep crust results in extensive amphibole ± garnet fractionation and the suppression of plagioclase crystallization as recorded by elevated Sr/Y ratios and high Eu (high Eu/Eu*) in the melt. Here, we use a novel approach to track the petrogenesis of arc magmas using apatite trace element chemistry in volcanic formations from the Cenozoic arc of central Chile. These rocks formed in a magmatic cycle that culminated in high-Sr/Y magmatism and porphyry ore deposit formation in the Miocene. We use Sr/Y, Eu/Eu*, and Mg in apatite to track discrete stages of arc magma evolution. We apply fractional crystallization modeling to show that early-crystallizing apatite can inherit a high-Sr/Y and high-Eu/Eu* melt chemistry signature that is predetermined by amphibole-dominated fractional crystallization in the lower crust. Our modeling shows that crystallization of the in situ host-rock mineral assemblage in the shallow crust causes competition for trace elements in the melt that leads to apatite compositions diverging from bulk-magma chemistry. Understanding this decoupling behavior is important for the use of apatite as an indicator of metallogenic fertility in arcs and for interpretation of provenance in detrital studies.

Back-arc magma processes in the Okinawa Trough: new insights from textural and compositional variations of plagioclase in basalts

2016 ◽  
Vol 51 ◽  
pp. 346-356 ◽  
Author(s):  
Zhiqing Lai ◽  
Guangtao Zhao ◽  
Zongzhu Han ◽  
Bo. Liu ◽  
Xuejiao Bu ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
The Okinawa Trough ◽  
Compositional Variations ◽  
Back Arc ◽  
Arc Magma

Amphibole fractionation—A constraint on the depth of arc magma evolution?

2006 ◽  
Vol 70 (18) ◽  
pp. A130
Author(s):  
J.P. Davidson ◽  
A. Dosseto ◽  
S.P. Turner
Keyword(s):  
Magma Evolution ◽  
Arc Magma ◽  
Amphibole Fractionation

scholarly journals The Choiyoi Group in the Cordón del Plata range, western Argentina: structure, petrography and geochemistry

2020 ◽  
Vol 24 (2) ◽  
pp. 121-132
Author(s):  
Amancay Martinez ◽  
Adrian Gallardo ◽  
Laura Giambiagi ◽  
Laura Tobares
Keyword(s):  
Mantle Wedge ◽  
Structural Data ◽  
Calc Alkaline ◽  
Magma Evolution ◽  
High Potassium ◽  
Geological Evolution ◽  
Compositional Variations ◽  
Thin Crust ◽  
San Rafael ◽  
Felsic Rocks

The Choiyoi Group from the Permo-Triassic, is one of the most conspicuous volcano-sedimentary suites of southern South America, considered critical to understand the geological evolution of the western margins of Gondwana.  In this regard, petrography, geochemistry, and structural data were examined to better elucidate the physical character and emplacement conditions of the unit in the Cordon del Plata range, within the Frontal Cordillera of Mendoza, Argentina.  The site is representative of the magmatism and deformation through different Andean cycles.  Results of the study indicate three lithological facies of increasing acidity upwards.  Mafic units consist of basalts, andesite and andesitic breccias at the base of the sequence.  Felsic rocks such as rhyodacites, granites and welded tuffs are predominant above.  The fault zone of La Polcura – La Manga is the most prominent structural feature in the region, which presumably controlled the emplacement of breccias and ignimbrites within the middle and upper members.  These compositional variations suggest a magma evolution from subduction to a rifting environment after the San Rafael orogeny in the Late Palaeozoic.  In this line, the Lower Choiyoi was observed to overlie the San Rafael structures indicating thus, that compression ceased before the volcanic extrusion.  Geochemistry data indicate that mafic rocks are mostly high-potassium, calc-alkaline volcanics derived from the mantle wedge above the subduction zone.  In contrast, the felsic rocks range from high-potassium rhyolites to shoshonites, typically depleted in Eu.  This indicate partial melting of a lithospheric mantle in an average to thin crust. 

scholarly journals Multi-stage arc magma evolution recorded by apatite in volcanic rocks

2020 ◽  
Author(s):  
Chetan Nathwani ◽  
Matthew Loader ◽  
Jamie Wilkinson ◽  
Yannick Buret ◽  
Robert Sievwright ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Host Rock ◽  
Lower Crust ◽  
Magma Evolution ◽  
Deposit Formation ◽  
Ore Deposit ◽  
Arc Magmas ◽  
Multi Stage ◽  
Shallow Crust ◽  
Arc Magma

<p>The chemical diversity observed in the rock record of volcanic arcs is determined by a multitude of processes operating between the magma source region and the surface. A fundamental step in producing this variability is fractional crystallisation, assimilation and melting in the lower crust which drives magmas to more evolved and hydrous compositions. During extensive fractionation of hydrous magmas in the lower crust, amphibole (± garnet) is stabilized in the fractionating assemblage and plagioclase is suppressed resulting in melts with elevated Sr, an absence of strong negative Eu anomalies (both elements being compatible in plagioclase), and depleted Y (compatible in amphibole and garnet). The high Sr/Y values that result can be used to provide insights into arc magma evolution, evaluate whether a magmatic system has the potential to form a porphyry-related ore deposit and track crustal thickness. However, this deep fractionation history may be obscured due to differentiation and mixing upon ascent to the shallow crust. Since arc rocks are a product of this multi-stage, polybaric process, unravelling the complete history of magmatic evolution using bulk-rock chemistry alone can be challenging. However, accessory minerals such as apatite, are capable of capturing discrete periods of melt evolution during differentiation [1]. For example, apatite has been shown to record the Sr content of the melt at the time of its crystallization which has been used to reconstruct host rock compositions in provenance studies [2, 3].</p><p>Here, we use a novel approach to track the petrogenesis of arc magmas using apatite trace element chemistry in volcanic formations from the Cenozoic arc of Central Chile. These rocks formed during magmatism that culminated in high Sr/Y magmas and porphyry ore deposit formation in the Miocene. We use Sr/Y, Eu/Eu* and Mg in apatite to demonstrate that apatite tracks the multi-stage differentiation of arc magmas. We apply fractional crystallization modelling to show that early crystallizing apatite inherits a high Sr/Y and Eu/Eu* melt chemistry signature that is predetermined by amphibole-dominated fractional crystallization in the lower crust. Our modelling shows that crystallisation of the in-situ host rock mineral assemblage in the shallow crust causes competition for trace elements in the melt that leads to apatite compositions diverging from bulk magma chemistry. Understanding this decoupling behaviour is important for the use of apatite as an indicator of metallogenic fertility in arcs and for interpretation of provenance in detrital studies. We suggest our approach is widely applicable for unravelling the composite evolution of arc magmas and studying magmatic processes conducive to porphyry ore deposit formation.</p><p>References</p><p>[1] Miles, A.J., Graham, C.M., Hawkesworth, C.J., Gillespie, M.R., and Hinton, R.W., 2013, Evidence for distinct stages of magma history recorded by the compositions of accessory apatite and zircon: Contributions to Mineralogy and Petrology.</p><p>[2] Jennings, E.S., Marschall, H.R., Hawkesworth, C.J., and Storey, C.D., 2011, Characterization of magma from inclusions in zircon: Apatite and biotite work well, feldspar less so: Geology.</p><p>[3] Bruand, E., Storey, C., and Fowler, M., 2016, An apatite for progress: Inclusions in zircon and titanite constrain petrogenesis and provenance: Geology, v. 44, p. 91–94.</p>

scholarly journals Geochemical evolution of a composite pluton: insight from major and trace element chemistry of titanite

2020 ◽  
Vol 114 (5) ◽  
pp. 375-401
Author(s):  
Katarzyna Gros ◽  
Ewa Słaby ◽  
Łukasz Birski ◽  
Gabriela Kozub-Budzyń ◽  
Jiří Sláma
Keyword(s):  
Trace Element ◽  
Geochemical Evolution ◽  
Magmatic Evolution ◽  
Magma Evolution ◽  
Rock Types ◽  
Trace Element Chemistry ◽  
Wide Range ◽  
Compositional Variations ◽  
Almost All ◽  
Ree Patterns

Abstract Titanite from various rocks of the Karkonosze granitoid pluton (South-Eastern Poland) was studied, in order to evaluate its precision in recording magma evolution processes. The rocks are of lamprophyric, dioritic, granodioritic and granitic composition, including hybrid structures such as microgranular magmatic enclaves and composite dykes. Based on textures, chemistry and Zr-in-titanite geothermometry, titanites can be divided into magmatic and post-magmatic populations. Late- to post-magmatic titanite is present in almost all rock types, especially in the most evolved ones (where magmatic titanite is absent) and can be characterized by low trace element and high Al and F contents. Magmatic titanite crystallized in temperatures between 610 and 870 °C, after apatite and relatively simultaneously with amphibole and zircon. Titanite from lamprophyre exhibits compositional features typical of titanites formed in mafic rocks: low Al and F, high Ti4+/(Al + Fe3+), LREE (light rare earth elemet)-enriched chondrite-normalized REE patterns, low Y/Zr, Nb/Zr, Lu/Hf, high (Ce + Nd)/Y, Th/U and Zr. Titanite from hybrid rocks inherited these characteristics, indicating major contribution of the mantle-derived magma especially during early stages of magmatic evolution. Titanite compositional variations, as well as a wide range of crystallization temperatures in hybrid granodiorites point to prolonged crystallization from distinct magma domains of variable mafic versus felsic melt proportions. The extent of compositional variations decreases through subsequent stages of magmatic evolution, and titanite with the least contribution of the mafic component is characterized by higher total REE, Al and F contents, lower Ti4+/(Al + Fe3+), (Ce + Nd)/Y and Th/U ratios, LREE-depleted chondrite-normalized REE patterns and higher Y/Zr, Nb/Zr and Lu/Hf ratios. Titanite composition from the intermediate and late stage hybrids bears signature of decreasing amount of the mafic melt and higher degree of its evolution, however, the exact distinction between the former and the latter is very limited.

scholarly journals Resolving tectono-magmatic processes that drive multi-Myr arc magma evolution in Central Chile

2021 ◽  
Author(s):  
Simon Large ◽  
Chetan Nathwani ◽  
Yannick Buret ◽  
Simon Tapster ◽  
Tom Knott ◽  
...  
Keyword(s):  
Magma Evolution ◽  
Central Chile ◽  
Magmatic Processes ◽  
Arc Magma
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