scholarly journals Geochemical and isotopical variations within the Campanian Comagmatic Province: implications on magma source composition

2021 ◽  
Vol 47 (4) ◽  
Author(s):  
Monica Piochi ◽  
Lucia Pappalardo ◽  
Gianfilippo De Astis
Keyword(s):  
Mantle Source ◽  
Lithospheric Mantle ◽  
Campi Flegrei ◽  
Magma Source ◽  
Isotopic Ratios ◽  
Italian Peninsula ◽  
Mantle Sources ◽  
Compositional Variations ◽  
Volcanic Islands ◽  
Lithospheric Mantle Source

A spatial variation in chemical and isotopical composition is observed between the volcanoes belonging to the Campanian Comagmatic Province. At a given MgO content, magmas from volcanic islands (Procida and Ischia) are enriched in Ti, Na, depleted in La, Ba, Rb, Sr, Th, K contents, and shows lower LREE/HFSE (e.g., La/Nb = = 1-2), lower Sr-Pb isotopic ratios and higher Nd isotopic ratios with respect to magmas from volcanoes locat- ed inland (Campi Flegrei and Somma-Vesuvius). The observed compositional variations are explained involving two different mantle sources in the genesis of the magmas erupted in this region: a deeper asthenospheric man- tle source, from which the Tyrrhenian magmas also derived and a lithospheric mantle source enriched by slab- derived fluids. The contribution of the enriched-lithospheric mantle became more pronounced moving from the Tyrrhenian abyssal plain through the Italian Peninsula where it dominates, likely in response to the thickening of the lithosphere observed under the Peninsula

scholarly journals Deep Crustal Contamination of the Lithospheric Mantle Source to Variscan Ultrapotassic Magmas – Geochemical and Geodynamic Consequences

2020 ◽  
Author(s):  
Vojtěch Janoušek ◽  
John Milan Hora ◽  
Yulia Erban Kochergina ◽  
Simon Couzinié ◽  
Tomáš Magna ◽  
...  
Keyword(s):  
Mantle Source ◽  
Lithospheric Mantle ◽  
Crustal Contamination ◽  
Lithospheric Mantle Source

scholarly journals Calcium isotopic evidence for the mantle sources of carbonatites

2020 ◽  
Vol 6 (23) ◽  
pp. eaba3269 ◽  
Author(s):  
Elsa Amsellem ◽  
Frédéric Moynier ◽  
Hervé Bertrand ◽  
Amaury Bouyon ◽  
João Mata ◽  
...  
Keyword(s):  
Mantle Source ◽  
Igneous Rocks ◽  
Isotopic Ratios ◽  
Carbonate Minerals ◽  
Isotopic Evidence ◽  
Calcium Isotopes ◽  
Mantle Sources ◽  
Marine Carbonates ◽  
Carbonate Materials ◽  
Silicate Rocks

The origin of carbonatites—igneous rocks with more than 50% of carbonate minerals—and whether they originate from a primary mantle source or from recycling of surface materials are still debated. Calcium isotopes have the potential to resolve the origin of carbonatites, since marine carbonates are enriched in the lighter isotopes of Ca compared to the mantle. Here, we report the Ca isotopic compositions for 74 carbonatites and associated silicate rocks from continental and oceanic settings, spanning from 3 billion years ago to the present day, together with O and C isotopic ratios for 37 samples. Calcium-, Mg-, and Fe-rich carbonatites have isotopically lighter Ca than mantle-derived rocks such as basalts and fall within the range of isotopically light Ca from ancient marine carbonates. This signature reflects the composition of the source, which is isotopically light and is consistent with recycling of surface carbonate materials into the mantle.

scholarly journals Petrology and origin of the Lar igneous complex of the Sistan suture zone, Iran

Geologos ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 51-64
Author(s):  
Mohammad Boomeri ◽  
Rahele Moradi ◽  
Sasan Bagheri
Keyword(s):  
Partial Melting ◽  
Mantle Source ◽  
Lithospheric Mantle ◽  
Crustal Contamination ◽  
Suture Zone ◽  
Fractional Crystallisation ◽  
Igneous Rocks ◽  
Positive Anomaly ◽  
Igneous Complex ◽  
Lithospheric Mantle Source

AbstractThe Oligocene Lar igneous complex is located in the Sistan suture zone of Iran, being emplaced in Paleocene to Eocene flysch-type rocks. This complex includes mainly intermediate K-rich volcanic (trachyte, latite and andesite) and plutonic (syenite and monzonite) rocks that belong to shoshonitic magma. The geochemical characteristics of the Lar igneous complex, such as an enrichment of LREE and LILE relative to HREE and HFSE, respectively, a negative anomaly of Ti, Ba and Nb and a positive anomaly of Rb and Th are similar to those of arc-type igneous rocks. Tectonic discrimination diagrams also show that rocks of the Lar igneous complex fall within the arc-related and post-collisional fields and K-enrichment of these rocks confirm the post-collisional setting. Based on geochemical features, the Lar igneous complex magma was derived from partial melting of a phlogopite-bearing, enriched and metasomatised lithospheric mantle source and the magma was affected by some evolutionary processes like fractional crystallisation and crustal contamination.

scholarly journals The enriched Variscan lithosphere of NE Iberia: data from postcollisional Permian calc-alkaline lamprophyre dykes of Les Guilleries

2021 ◽  
Vol 19 ◽  
pp. 1-23
Author(s):  
Esteban Mellado ◽  
Mercè Corbella ◽  
Didac Navarro ◽  
Andrew Kylander
Keyword(s):  
Mantle Source ◽  
Lithospheric Mantle ◽  
Subcontinental Lithospheric Mantle ◽  
Volatile Content ◽  
Calc Alkaline ◽  
Geochronological Data ◽  
Metamorphic Basement ◽  
Lithospheric Mantle Source ◽  
Porphyritic Texture ◽  
Alkaline Lamprophyres

Post-collisional mafic dykes crosscut the Paleozoic metamorphic basement and late-Variscan plutons in Les Guilleries massif (Catalan Coastal Ranges, NE Iberia). The predominance of mafic phenocrysts, porphyritic texture, abundant amphibole, high MgO and volatile content, together with crustal-like trace-element patterns indicate that the dykes correspond to calc-alkaline lamprophyres, mainly spessartites. Their enrichment in LILE, HFSE and REE and initial Sr-Nd isotopic compositions (87Sr/86Sri between 0.70851 and 0.71127, epsilon Ndi between -5.23 and -4.63) are consistent with an enriched subcontinental lithospheric mantle source. U-Pb ages of matrix titanite crystals yield concordia ages of 262±7Ma, congruent with crosscutting relationships. Postmagmatic processes are evidenced by intense chloritization and albitization of the lamprophyres, together with systematic variations of Na2O vs SiO2, K2O, CaO, Ba, Rb, Cs, Pb, Sr, Tl, and Zn, and possibly the removal of F. The geochemical and geochronological data support an orogenic geochemical affinity, in accordance with the transitional tectonic regime between Variscan compression/transpression and post-collisional transtension/extension, related to the fragmentation of Pangea and thinning of the lithosphere. The lamprophyre dykes studied could represent the youngest pulse of Variscan orogenic magmatism and, therefore, mark its end in NE Iberia before the onset of the generalized Triassic extension.

Petrogenesis of pleistocene basalts from the Western snake river plain, Idaho

2020 ◽  
Author(s):  
Tiffany A Rivera ◽  
Craig M White ◽  
Mark D Schmitz ◽  
Brian R Jicha
Keyword(s):  
Fractional Crystallization ◽  
Mantle Source ◽  
Lithospheric Mantle ◽  
Snake River Plain ◽  
Snake River ◽  
Isotopic Ratios ◽  
Isotopic Signatures ◽  
The North ◽  
North American Craton ◽  
River Plain

Abstract We present new geochemical, Sr, Nd, and Pb isotope, and 40Ar/39Ar data from Pleistocene basalts of the Western Snake River Plain (WSRP), Idaho, USA to explore their petrogenesis and to investigate the nature of the lithosphere at the western boundary of the North American craton. The basalts are divided into three groups based on their geochemical and isotopic characteristics. Prior to ∼1 Ma, volcanoes in the WSRP erupted iron-rich tholeiites (FeB1), but subsequent volcanism was dominated by concurrent eruptions of mildly alkaline, alumina-rich lavas (AlB) and iron-rich tholeiites (FeB2) with isotopic signatures similar to the AlB lavas. New 40Ar/39Ar dates of AlB and FeB2 basalts range from 0.920 ± 0.049 Ma to 0.287 ± 0.014 Ma. MELTS models of FeB1 differentiation trends indicate that the range of compositions in this suite can be produced by 10–15% crystallization of olivine and plagioclase at low pressure using the least evolved FeB1 composition as a parental magma; isotopic ratios can be produced via combined assimilation of a Miocene rhyolite and fractional crystallization. Additional modeling suggests that parental magmas at AlB centers were produced by 3–12% equilibrium melting of a garnet-spinel enriched mantle source, slightly different to that proposed for the youngest mildly alkaline lavas of the eastern and central Snake River Plain. Our new geochemical, isotopic, and geochronologic data of the FeB2 basalts suggests they are related to AlB-type magmas via a combination of fractional crystallization and assimilation of evolved mafic crust. MELTS models suggest that crystallization of an AlB parental melt at a depth of 6–8 km (2.5 kb) could produce residual liquids having many of the major oxide characteristics of FeB2 ferrobasalts. Sr-Nd-Pb isotopic signatures of these three suites indicate a dominant contribution from an enriched plume source. FeB1 lavas are likely products of mixing between melts of an enriched plume mantle source (represented by Imnaha and Steens Basalts of the Columbia River Basalt Group) and isotopically heterogeneous sub-continental lithospheric mantle (SCLM) that has been isolated from the convecting mantle since the Archean. Isotopic ratios of FeB2 and AlB lavas capture mixing between enriched plume mantle and a more isotopically homogeneous ancient SCLM domain characteristic of the eastern and central Snake River Plain, with a coupled decrease in lithospheric contribution and degree of partial melting through time to the present. Mixtures of enriched asthenospheric reservoirs with lithospheric mantle have been proposed for neighboring volcanic fields to the east along the strike of the Yellowstone-SRP hotspot track, and to the west due to differences in the mantle underlying the boundary of the North American craton and accreted terranes. Our petrogenetic model for the Pleistocene WSRP basalts suggests that there is also a lateral, across strike gradient in the geometry and interaction of enriched plume mantle and ancient lithosphere. We reiterate suggestions that the WSRP is a lithosphere-scale conduit connecting initial plume head impingement in east-central Oregon with the subsequent Yellowstone-SRP hotspot plume tail track.

Sign in / Sign up

Export Citation Format

Share Document