Summary
Adoptive T‐cell therapy, where anti‐tumor T cells are first prepared in vitro, is attractive since it facilitates the delivery of essential signals to selected subsets of anti‐tumor T cells ...without unfavorable immunoregulatory issues that exist in tumor‐bearing hosts. Recent clinical trials have demonstrated that anti‐tumor adoptive T‐cell therapy, i.e. infusion of tumor‐specific T cells, can induce clinically relevant and sustained responses in patients with advanced cancer. The goal of adoptive cell therapy is to establish anti‐tumor immunologic memory, which can result in life‐long rejection of tumor cells in patients. To achieve this goal, during the process of in vitro expansion, T‐cell grafts used in adoptive T‐cell therapy must be appropriately educated and equipped with the capacity to accomplish multiple, essential tasks. Adoptively transferred T cells must be endowed, prior to infusion, with the ability to efficiently engraft, expand, persist, and traffic to tumor in vivo. As a strategy to consistently generate T‐cell grafts with these capabilities, artificial antigen‐presenting cells have been developed to deliver the proper signals necessary to T cells to enable optimal adoptive cell therapy.
One extremely young volcano (0.05–1 Ma) and other young volcanoes (1.8, 4.2, 6.0, and 8.5 Ma) composed of strongly alkaline magma were recently discovered on the abyssal plain of the Early Cretaceous ...(135 Ma) Pacific Plate. These volcanoes were dubbed “petit-spots”. The petit-spot volcanic province represents more than 8 Myr of activity over a large area (~600 km along the direction of plate motion), but with a relatively small volume of magma production, thus indicating a small supply of heat inconsistent with a hotspot. The low-flux petit-spot volcanoes may be related to the occurrence of a tensional field of lithosphere caused by plate flexure, with the ascending melt derived from a mantle source susceptible to partial melting. Rock samples from the young volcanoes are highly vesicular (up to 60%) despite high hydrostatic pressures at 6000 m water depth, indicating volatile-rich magmas. The depleted heavy rare earth elements and high radiometric isotopic ratios of noble gases indicate the magma was derived from upper mantle. Nevertheless, the low 143Nd/144Nd, high 87Sr/86Sr, low 206Pb/204Pb, and low 207Pb/204Pb ratios are similar to enriched or fertile compositions such as oceanic island basalts. These apparently conflicting data are explained by the extremely small degree of partial melting of recycled materials in the degassing mantle of the asthenosphere, probably with carbonate in the source. The petit-spot volcanoes, therefore, provide a unique window into the nature of the oceanic plate and underlying asthenosphere prior to subduction.
We report new noble gas isotopic compositions of submarine basaltic glasses sampled from two seamounts discovered offshore of Chile, and inferred to have erupted as petit-spot volcanoes near the Juan ...Fernández hotspot. The samples have 3He/4He of 1–15 times atmosphere (Ra). Their neon isotope compositions are similar to those of the Hawaiian Islands and Réunion Island. Their 40Ar/36Ar range from atmospheric to 2300. Although the lavas are likely to be influenced by a hotspot-related component, the cause of the 3He/4He variation must be clarified to ascertain the mantle source. Variations in 3He/4He are not attributable to processes occurring at the Earth's surface such as degassing fractionation, mixing with atmosphere dissolved in seawater, or in-situ post-eruptive addition of 4He. A combination of the Ne-Ar isotope ratios corrected for atmospheric influence and He isotope ratios indicates that the noble gas isotopes of the lavas are a mixture of a hotspot magma, MORB-source, and radiogenic components. The lower 3He/4He are attributed to assimilation with the oceanic lithosphere, suggesting that the pristine 3He/4He of the lavas is hotspot-like. These features can be interpreted as indicating that part of the Juan Fernández plume infiltrated the lithosphere–asthenosphere boundary (LAB), and that the ponding magma has erupted as petit-spot volcanoes because of plate bending. The noble gas data indicate that LAB can be a reservoir for exotic melts, which might have lubricated plate tectonics.
•We analyzed noble gas isotopes of basaltic glasses from central Chile trench.•They show hotspot-like noble gas isotopic signatures.•It demonstrates the possibility of exotic melt ponding in the LAB.
Abstract
Petit-spot volcanoes provide a unique opportunity to directly examine the structure and geochemical composition of the lithospheric and asthenospheric mantle beneath the subducting oceanic ...crust. Currently, petit-spot volcanos—formed in response to the flexure of subducting oceanic plates—are known to exist off the Japan, Java, Chile and Mariana trenches, however, the difficulties associated with detecting them leaves the possibility that they may be more widespread along outer rise of plates. Investigation of the lavas and xenolithic material erupted from petit-spot volcanos has suggested that the suboceanic lithosphere is largely metasomatized by numerous ascending petit-spot melts. This somewhat contradicts previous understanding which indicated that the oceanic lithosphere has a depleted mantle composition. The ultimate source and geodynamic processes that lead to the formation of petit-spot melts remain ambiguous, however, possibilities include that the lavas originate from incipient asthenospheric carbonatitic or carbonated silicate melts that are characteristically depleted in zirconium and hafnium. Typical geochemical trends in petit-spot lava fields off Japan trench indicate elemental partitioning through the immiscible separation of carbonate and silicate melts.
A dense field of ferromanganese (Fe-Mn) nodules was discovered on a seamount approximately 300 km east of Minamitorishima Island, in the Japanese Exclusive Economic Zone. To evaluate its potential as ...a resource for critical metals, we describe results of a geological survey using the SHINKAI 6500 submersible (dive No. 6K 1207) during cruise YK10-05 of R/V Yokosuka in 2010, and geochemical analyses of collected samples. Submersible observations showed that spherical nodules 5–10 cm in diameter almost fully cover the region of high acoustic reflectivity. The large nodules generally consist of three concentric layers: the outermost mottled (sediment-filled) layer L0, the massive black layer L1, and the innermost porous (sediment-filled) layer L2. Elements including Fe, Ti, Co, As, rare earth elements other than Ce, Th, U, and Pb are concentrated in the nodule rim rather than the center. In contrast, Mn, Al, P, Ca, Ni, Zn, Y, Mo, Ce, and W are concentrated in the center, and decrease toward the rim. Geochemical and structural features indicate that the nodules are compositionally and morphologically similar to Fe-Mn crusts, suggesting that they owe their origin solely to prolonged hydrogenetic precipitation of Fe-Mn-(oxyhydr)oxides. As the nodules include metals of economic interest, especially Co, Ni, Mo, and W, this deposit should have high potential for future mining. The changes in nodule composition from the center to the rim may yield information on paleoceanographic events since early Oligocene time.
A discontinuity in the seismic velocity associated with the lithosphere-asthenosphere interface, known as the Gutenberg discontinuity, is enigmatic in its origin. While partial mantle melts are ...frequently suggested to explain this discontinuity, it is not well known which factors critically regulate the melt production. Here, we report geochemical evidence showing that the melt fractions in the lithosphere-asthenosphere boundary were enhanced not only by accumulation of compacted carbonated melts related to recycled ancient marine sediments, but also by partial melting of a pyroxene-rich mantle domain related to the recycled oceanic eclogite/pyroxenites. This conclusion is derived from the first set of Mg isotope data for a suite of young petit-spot basalts erupted on the northwest Pacific plate, where a clearly defined Gutenberg discontinuity exists. Our results reveal a specific linkage between the Gutenberg discontinuity beneath the normal oceanic regions and the recycling of ancient subducted crust and carbonate through the deep Earth.
Abstract
The deep carbon cycle plays an important role on the chemical differentiation and physical properties of the Earth’s mantle. Especially in the asthenosphere, seismic low-velocity and high ...electrical conductivity due to carbon dioxide (CO
2
)-induced partial melting are expected but not directly observed. Here we discuss the experimental results relevant to the genesis of primitive CO
2
-rich alkali magma forming petit-spot volcanoes at the deformation front of the outer rise of the northwestern Pacific plate. The results suggest that primitive melt last equilibrated with depleted peridotite at 1.8–2.1 GPa and 1,280–1,290 °C. Although the equilibration pressure corresponds to the pressure of the lower lithosphere, by considering an equilibration temperature higher than the solidus in the volatile–peridotite system along with the temperature of the lower lithosphere, we conclude that CO
2
-rich silicate melt is always produced in the asthenosphere. The melt subsequently ascends into and equilibrates with the lower lithosphere before eruption.
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