Nontronite-bearing tubular hydrothermal deposits from a Galapagos seamount
Date of Original Version
A telepresence-enabled cruise using remotely operated vehicle (ROV) exploration discovered an unusual tubular deposit of Fe-rich hydrothermal nontronite on a young seamount, Mashi, of the Wolf-Darwin lineament in the Galápagos Islands. X-ray diffraction, ICP-MS, ICP-AES, and SEM-EDS analyses show that this deposit is chemically and mineralogically similar to other deep-sea hydrothermal nontronites, indicating a likely formation temperature of about 30° to 50 °C by diffuse hydrothermal activity. These deposits contain mixtures of Fe-rich, Al-poor nontronite and poorly crystalline Fe-Si-oxyhydroxides with bulk compositions of 38–51 wt% SiO2 and 40–50 wt% Fe2O3*. The presence of filamentous and spherical structures in the samples suggests that mineral deposition was in part facilitated by chemosynthetic microbes. Although hydrothermal nontronite has been sampled at a number of seafloor sites by coring and dredging, this is the first in situ documentation of its unusual sinuous, tubular structure, on the seafloor. Quantitative image-analysis of ROV imagery indicates that hydrothermal fluid pathways, developed through an underlying pillow lava sequence, likely control the distinctive sinuous morphology.
Deep-Sea Research Part II: Topical Studies in Oceanography
Lubetkin, Megan, Steven Carey, Katherine A. Kelley, Geneviève Robert, Winton Cornell, Nicole Raineault, Jacob Balcanoff, Robert D. Ballard, and Pelayo Salinas-de-León. "Nontronite-bearing tubular hydrothermal deposits from a Galapagos seamount." Deep-Sea Research Part II: Topical Studies in Oceanography 150, (2018): 181-194. doi:10.1016/j.dsr2.2017.09.017.