2 research outputs found
Evidence for mantle exhumation since the early evolution of the slow-spreading Gakkel Ridge, Arctic Ocean
We study the basement configuration in the slow-spreading Eurasia Basin, Arctic Ocean. Two multichannel seismic (MCS) profiles, which we acquired during ice-free conditions with a 3600 m long streamer, image the transition from the North Barents Sea Margin into the southern Eurasia Basin. The seismic lines resolve the up to 5000 m thick sedimentary section, as well as the crustal architecture of the southern Eurasia Basin along 120 km and 170 km, respectively. The seismic data show large faulted and rotated basement blocks. Gravity modeling indicates a thin basement with a thickness of 1–3 km and a density of 2.8*103 kg/m3 between the base of the sediments and the top of the mantle, which indicates exhumed and serpentinized mantle. The Gakkel spreading ridge, located in northern prolongation of the seismic lines is characterized by an amagmatic or sparsely magmatic segment. From the structural similarity between the basement close to the ultra-slow spreading ridge and our study area, we conclude that the basement in the Eurasia Basin is predominantly formed by exhumed and serpentinized mantle, with magmatic additions. An initial strike-slip movement of the Lomonosov Ridge along the North Barents Sea Margin and subsequent near-orthogonal opening of the Nansen Basin is supposed to have brought mantle material to the surface, which was serpentinized during this process. Continuous spreading thinned the serpentinized mantle and subsequent normal faulting produced distinct basement blocks. We propose that mantle exhumation has likely been active since the opening of the Eurasia Basin
Calcium-Induced Molecular Rearrangement of Peptide Folds Enables Biomineralization of Vaterite Calcium Carbonate
Proteins
can control mineralization of CaCO<sub>3</sub> by selectively
triggering the growth of calcite, aragonite or vaterite phases. The
templating of CaCO<sub>3</sub> by proteins must occur predominantly
at the protein/CaCO<sub>3</sub> interface, yet molecular-level insights
into the interface during active mineralization have been lacking.
Here, we investigate the role of peptide folding and structural flexibility
on the mineralization of CaCO<sub>3</sub>. We study two amphiphilic
peptides based on glutamic acid and leucine with β-sheet and
α-helical structures. Though both sequences lead to vaterite
structures, the β-sheets yield free-standing vaterite nanosheet
with superior stability and purity. Surface-spectroscopy and molecular
dynamics simulations reveal that reciprocal structuring of calcium
ions and peptides lead to the effective synthesis of vaterite by mimicry
of the (001) crystal plane