Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the 24 site of a ... more Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the 24 site of a major and still ongoing eruption, located at 3.5 km depth bsl on a WNW-ESE 25 volcanic ridge. Oceanographic cruises carried out to monitor this seismo-volcanic crisis 26 allowed us to determine that this volcanic ridge is built by a bimodal sodic alkaline magmatic 27 series that includes basanites and phonolites. A petrological study of dredged samples allowed 28 us to image the magmatic system feeding the volcanic ridge and to determine the link 29 between basanitic and phonolitic magmas. The magmatic system feeding the volcanic ridge 30 comprises multiple levels of magma storage. Basanitic magmas generated at 80-100 km 31 mantle depth are stored in one or more deep reservoir(s) (≥ 37 km) and then in shallower 32 Manuscript Click here to access/download;Manuscript;Manuscript.pdf Click here to view linked References-2-basanitic and phonolitic lenses located close to the Moho interface before rising the surface. 33 This study identifies three possible scenarios: (1) the deep basanitic magma rises directly and 34 quickly to the surface from the deep mantle reservoir (as is currently happening 60 km 35 offshore), (2) the basanitic magma stalls in a shallower reservoir near the Moho before 36 resuming its ascent toward the surface and erupting as porphyritic basanite, (3) the basanitic magma stops and evolves to phonolite in these sub-crustal reservoirs. The phonolitic lavas are 38 produced by approximately 80% fractional crystallization (34% clinopyroxene, 30% 39 anorthoclase feldspar, 15.5% magnetite, 12.5% olivine, 5% apatite and 4% ilmenite) of a 40 hydrous basanitic magma at mantle depths (P > 0.6 GPa) under reduced oxygen fugacity 41 (~FMQ-1). In this third scenario, the phonolitic magma might be reactivated by the arrival of 42 a new batch of deeper basanitic magma. 43 44 1. Introduction 45 46 The deepest part (3.5 km bsl) of the eastern submarine flank of Mayotte is the site of a 47 long lasting and still ongoing (as of January 2021) effusive volcanic activity that followed an 48
The stable isotopic composition of insoluble, refractory elements such as titanium (Ti) or zircon... more The stable isotopic composition of insoluble, refractory elements such as titanium (Ti) or zirconium (Zr), which are modified by magmatic differentiation but, a priori, are poorly affected by weathering or diagenesis, serve as powerful potential proxies to reconstruct the compositional evolution of the continental crust. Here we present the evolution of the Zr stable isotopic compositions (δ 94/90 Zr IPGP-Zr , per mille suggest a Zr-weighted δ 94/90 Zr IPGP-Zr value of 0.077 ± 0.058‰ (2SD, n = 44) for the UCC, which is statistically distinct (t test, p value = 2.88×10-10) and higher than that of the mantle (0.040 ± 0.044‰, n = 72). Combining the δ 94/90 Zr IPGP-Zr values of different terrestrial reservoirs, the δ 94/90 Zr IPGP-Zr of the BSE and bulk Earth is constrained to be 0.041 ± 0.041‰.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A new olivine reference material-MongOl Sh11-2-forin-situanalysis has been prepared from a centra... more A new olivine reference material-MongOl Sh11-2-forin-situanalysis has been prepared from a central portion of a large (20X20X10 cm) mantle peridotite xenolith from a ~0.5 Ma old basaltic breccia at Shavaryn-Tsaram, Tariat region, central Mongolia. The xenolith is a fertile mantle lherzolite with minimal signs of alteration during and after its transport to the surface. Around 10 grams of 0.5 to 2 mm gem quality olivine fragments were separated under binocular microscope and analysed by EPMA, LA-ICP-MS, SIMS and bulk analytical methods (ID ICP-MS for Mg and Fe, XRF, ICP-MS) in six Institutions worldwide for major, minor and trace elements. The results show that the olivine fragments are sufficiently homogeneous in respect to major (Mg, Fe, Si) and minor and trace elements. Significant inhomogeneity revealed only for phosphorus (homogeneity index of 12.4 (e.g. Boyd et al. 1967)), while Li, Na, Al, Sc, Ti and Cr show minor inhomogeneity (homogeneity index between 1-2). The possible presence of some mineral and fluid-melt micro-inclusions is probably responsible for the inconsistency in concentration obtained by local and bulk analytical methods for Al, Cu, Sr, Zr, Ga, Dy and Ho.Here we report reference and information concentrations for Si,
Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the 24 site of a ... more Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the 24 site of a major and still ongoing eruption, located at 3.5 km depth bsl on a WNW-ESE 25 volcanic ridge. Oceanographic cruises carried out to monitor this seismo-volcanic crisis 26 allowed us to determine that this volcanic ridge is built by a bimodal sodic alkaline magmatic 27 series that includes basanites and phonolites. A petrological study of dredged samples allowed 28 us to image the magmatic system feeding the volcanic ridge and to determine the link 29 between basanitic and phonolitic magmas. The magmatic system feeding the volcanic ridge 30 comprises multiple levels of magma storage. Basanitic magmas generated at 80-100 km 31 mantle depth are stored in one or more deep reservoir(s) (≥ 37 km) and then in shallower 32 Manuscript Click here to access/download;Manuscript;Manuscript.pdf Click here to view linked References-2-basanitic and phonolitic lenses located close to the Moho interface before rising the surface. 33 This study identifies three possible scenarios: (1) the deep basanitic magma rises directly and 34 quickly to the surface from the deep mantle reservoir (as is currently happening 60 km 35 offshore), (2) the basanitic magma stalls in a shallower reservoir near the Moho before 36 resuming its ascent toward the surface and erupting as porphyritic basanite, (3) the basanitic magma stops and evolves to phonolite in these sub-crustal reservoirs. The phonolitic lavas are 38 produced by approximately 80% fractional crystallization (34% clinopyroxene, 30% 39 anorthoclase feldspar, 15.5% magnetite, 12.5% olivine, 5% apatite and 4% ilmenite) of a 40 hydrous basanitic magma at mantle depths (P > 0.6 GPa) under reduced oxygen fugacity 41 (~FMQ-1). In this third scenario, the phonolitic magma might be reactivated by the arrival of 42 a new batch of deeper basanitic magma. 43 44 1. Introduction 45 46 The deepest part (3.5 km bsl) of the eastern submarine flank of Mayotte is the site of a 47 long lasting and still ongoing (as of January 2021) effusive volcanic activity that followed an 48
The stable isotopic composition of insoluble, refractory elements such as titanium (Ti) or zircon... more The stable isotopic composition of insoluble, refractory elements such as titanium (Ti) or zirconium (Zr), which are modified by magmatic differentiation but, a priori, are poorly affected by weathering or diagenesis, serve as powerful potential proxies to reconstruct the compositional evolution of the continental crust. Here we present the evolution of the Zr stable isotopic compositions (δ 94/90 Zr IPGP-Zr , per mille suggest a Zr-weighted δ 94/90 Zr IPGP-Zr value of 0.077 ± 0.058‰ (2SD, n = 44) for the UCC, which is statistically distinct (t test, p value = 2.88×10-10) and higher than that of the mantle (0.040 ± 0.044‰, n = 72). Combining the δ 94/90 Zr IPGP-Zr values of different terrestrial reservoirs, the δ 94/90 Zr IPGP-Zr of the BSE and bulk Earth is constrained to be 0.041 ± 0.041‰.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A new olivine reference material-MongOl Sh11-2-forin-situanalysis has been prepared from a centra... more A new olivine reference material-MongOl Sh11-2-forin-situanalysis has been prepared from a central portion of a large (20X20X10 cm) mantle peridotite xenolith from a ~0.5 Ma old basaltic breccia at Shavaryn-Tsaram, Tariat region, central Mongolia. The xenolith is a fertile mantle lherzolite with minimal signs of alteration during and after its transport to the surface. Around 10 grams of 0.5 to 2 mm gem quality olivine fragments were separated under binocular microscope and analysed by EPMA, LA-ICP-MS, SIMS and bulk analytical methods (ID ICP-MS for Mg and Fe, XRF, ICP-MS) in six Institutions worldwide for major, minor and trace elements. The results show that the olivine fragments are sufficiently homogeneous in respect to major (Mg, Fe, Si) and minor and trace elements. Significant inhomogeneity revealed only for phosphorus (homogeneity index of 12.4 (e.g. Boyd et al. 1967)), while Li, Na, Al, Sc, Ti and Cr show minor inhomogeneity (homogeneity index between 1-2). The possible presence of some mineral and fluid-melt micro-inclusions is probably responsible for the inconsistency in concentration obtained by local and bulk analytical methods for Al, Cu, Sr, Zr, Ga, Dy and Ho.Here we report reference and information concentrations for Si,
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