Deep-sea Basalt Research Articles

A New Find of Anorthoclase Crystals-lined Vug in a Deep-sea Basalt, Central Indian Ocean Basin

ABSTRACT We detail a new and first find of a vug in a deep-sea basalt that is lined with well-formed anorthoclase crystals. The specimen was dredged from the seafloor (water depth 4,440 m) near a seamount in the Central Indian Ocean Basin. The basalt has a thin veneer of glass covered with ferromanganese (FeMn) oxides while the interior is quite fresh. The geochemical analysis of the basalt depicts different degrees of alteration that vary from the outermost layer with FeMn oxides to the interior of the specimen. In general, the TiO2 (<1.5 wt%) and MgO (~5 wt%) contents are low while CaO, Na2O, K2O and P2O5 contents change within the specimen. The FeMn oxides have Fe2O3 (21 wt%) and MnO (8–27 wt%) and appear as botryoids and occur near and/or over the anorthoclase crystals. The trace and rare earth elements do not show significant variations from the outer to the interior of the specimen. Microscopy (binocular and scanning electron) and energy dispersive spectrometry of the vug revealed a dominance of drusy anorthoclase crystals. The formation of the anorthoclase crystals is ascribed to precipitation from hydrothermal solutions that seeped into the basalt through cracks. This is attested by the co-existing crystals of phillipsite and feldspar and FeMn oxides.

Size matters at deep-sea hydrothermal vents: different diversity and habitat fidelity patterns of meio- and macrofauna.

Species with markedly different sizes interact when sharing the same habitat. Unravelling mechanisms that control diversity thus requires consideration of a range of size classes. We compared patterns of diversity and community structure for meio- and macrofaunal communities sampled along a gradient of environmental stress at deep-sea hydrothermal vents on the East Pacific Rise (9° 50′ N) and neighboring basalt habitats. Both meio- and macrofaunal species richnesses were lowest in the high-stress vent habitat, but macrofaunal richness was highest among intermediate-stress vent habitats. Meiofaunal species richness was negatively correlated with stress, and highest on the basalt. In these deep-sea basalt habitats surrounding hydrothermal vents, meiofaunal species richness was consistently higher than that of macrofauna. Consideration of the physiological capabilities and life history traits of different-sized animals suggests that different patterns of diversity may be caused by different capabilities to deal with environmental stress in the 2 size classes. In contrast to meiofauna, adaptations of macrofauna may have evolved to allow them to maintain their physiological homeostasis in a variety of hydrothermal vent habitats and exploit this food-rich deep-sea environment in high abundances. The habitat fidelity patterns also differed: macrofaunal species occurred primarily at vents and were generally restricted to this habitat, but meiofaunal species were distributed more evenly across proximate and distant basalt habitats and were thus not restricted to vent habitats. Over evolutionary time scales these contrasting patterns are likely driven by distinct reproduction strategies and food demands inherent to fauna of different sizes.

Exploring the vents, ridges, rocks, and geothermal spas of the Reykjanes Peninsula

Renting a submarine to explore the deepsea basalt lava flows of the Mid‐Atlantic Ridge is a pricey proposition. But on a field trip to Iceland's Reykjanes Peninsula following the Chapman Conference on Volcanism and the Atmosphere, participants were able to stay on dry land to explore the volcanic features of the ridge where the Eurasian and North American plates are spreading apart. “If you're interested in ocean ridge basalt, the Reykjanes Ridge is your place,” said Karl Grönvold, a geochemist with the Institute of Earth Sciences at the University of Iceland. Grönvold led the daylong field trip to geologic sites of interest in southwest Iceland, including the ridge, fumaroles, boiling hot pots, and the geothermal spa and power plant at the Blue Lagoon.

Bacterial and Archaeal DNA Extracted from Inoculated Experiments: Implication for the Optimization of DNA Extraction from Deep-Sea Basalts

Difficulties in efficient DNA extraction from deep-sea volcanic basalt, due to high metal concentration, complex organic matter, or sometimes the low biomass, have hampered the understanding of the significant biosphere both at and below the sea floor. In order to optimize the DNA extraction from basaltic rocks, sterilized basalts with different particle sizes and chemically synthesized goethite were inoculated with an iron oxidizer Marinobacter aquaeolei and an extreme halophilic archaeon Halobaculum gomorrense respectively, and extracted with several methods. Large variations in DNA yields by different extracting methods including FastDNA® spin for soil kit, GeneClean® for ancient DNA kit, UltraClean™ and traditional phenol-chloroform methods. Among the commercially available kits tested here, FAST spin kit and GeneClean® for ancient DNA kit yield 10 times more DNA than the UltraClean™ kit used. In combination with FAST spin kit, skim milk greatly enhanced the archaeal DNA yields. DNA extracting efficiency was low with the cell number lower than 1 × 106 cells, but reached as high as 88% with a cell number of 1 × 108 cells. On these points, different strategies should be taken into consideration for the DNA extraction from basalts, depending on original biomass and cell types anticipated. FAST spin kit could provide high quality bacterial DNA for downstream PCR whilst the combination of FAST spin kit with skim milk would greatly enhance the archaeal DNA yields. GeneClean® for ancient DNA kit is also recommended for archaeal DNA extraction from deep sea basalt due to its high yield.

A global assessment of deep-sea basalt sites for carbon sequestration

Abstract Deep-sea basalt aquifers have been identified for geological CO 2 sequestration in worldwide locations and offer vast reservoir capacities, permanent geochemical trapping potential, and other deep-sea protections that significantly reduce the risk of post- injection leakage. Using site-specific criteria, we target basalt aquifers along seismic and aseismic oceanic ridges, and calculate the injection volume potential for each. Results indicate that these aquifers occur in many oceans and could sequester 2.3–11.5 Tt-C along seismic ridges and 5.9–29.6 Tt-C along aseismic ridges. The enormous size of these potential reservoirs warrants further research and pilot experiments in each geographic setting.

A global assessment of deep-sea basalt sites for carbon sequestration

AbstractIn recent years, the debate over the most effective means to stabilize greenhouse gas concentrations in the atmosphere has endorsed multiple approaches and a variety of technologies. Assuring secure storage of anthropogenic carbon dioxide is one of our most pressing global scientific challenges that may contribute to achieving a stable solution over the next several decades. Geological sequestration by injection into deep-sea basalt formations provides unique and significant advantages over other potential storage options, including: (a) vast reservoir capacities with high porosity and permeability, sufficient to accommodate centuries-long U.S. production of fossil fuel CO~2~ at locations within a few hundreds of kilometers of populated areas; (b) chemical reactivity of CO~2~ with basalt and in situ fluids to produce stable, non-toxic carbonates; and (c) significant risk reduction for post-injection leakage by geological, gravitational, and mineral trapping mechanisms. We compare independent trapping mechanisms available in deep-sea basalts to those in saline aquifers, which have also been proposed as potential storage environments for anthropogenic carbon dioxide. We suggest that deep-sea basalts offer significant advantages over saline aquifers, in terms of reduced risk of post-injection leakage and storage capacity. Using a global site assessment strategy to highlight the most secure oceanic basalt sites that provide all trapping mechanisms, we initially identify potential target regions that occur in deep-sea basalt and calculate the potential injection volume for each. The largest volumes and most secure basalt sites occur in regions adjacent to intermediate- to fast-spreading seismic ridges as well as deep aseismic ridges. We then use site-specific criteria, such as abundance of ODP and IODP drill sites with basement penetration, permeability and/or porosity data, to refine volume calculations and to prioritize these target regions as promising locations to securely accommodate carbon dioxide injection. Pilot injection studies in deep-sea basalts are necessary to establish the viability of these reservoirs for future CO~2~ sequestration. We suggest that basaltic crust at deep ocean sites offers vast capacity and potential for permanent sequestration of carbon dioxide to mitigate atmospheric build-up of this greenhouse gas.

A global assessment of deep-sea basalt sites for carbon sequestration

Abstract Deep-sea basalt aquifers have been identified for geological CO 2 sequestration in worldwide locations and offer vast reservoir capacities, permanent geochemical trapping potential, and other deep-sea protections that significantly reduce the risk of post- injection leakage. Using site-specific criteria, we target basalt aquifers along seismic and aseismic oceanic ridges, and calculate the injection volume potential for each. Results indicate that these aquifers occur in many oceans and could sequester 2.3–11.5 Tt-C along seismic ridges and 5.9–29.6 Tt-C along aseismic ridges. The enormous size of these potential reservoirs warrants further research and pilot experiments in each geographic setting.

Fine-scale vertical distribution of bacteria in the East Pacific deep-sea sediments determined via 16S rRNA gene T-RFLP and clone library analyses

Although the deep-sea sediments harbor diverse and novel bacteria with important ecological and environmental functions, a comprehensive view of their community characteristics is still lacking, considering the vast area and volume of the deep-sea sedimentary environments. Sediment bacteria vertical distribution and community structure were studied of the E272 site in the East Pacific Ocean with the molecular methods of 16S rRNA gene T-RFLP (terminal restriction fragment length polymorphism) and clone library analyses. Layered distribution of the bacterial assemblages was detected by both methods, indicating that the shallow sediments (40 cm in depth) harbored a diverse and distinct bacterial composition with fine-scale spatial heterogeneity. Substantial bacterial diversity was detected and nine major bacterial lineages were obtained, including Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Nitrospirae, Planctomycetes, Proteobacteria, and the candidate divisions OP8 and TM6. Three subdivisions of the Proteobacteria presented in our libraries, including the α-, γ- and δ-Proteobacteria. Most of our sequences have low similarity with known bacterial 16S rRNA genes, indicating that these sequences may represent as-yet-uncultivated novel bacteria. Most of our sequences were related to the GenBank nearest neighboring sequences retrieved from marine sediments, especially from deep-sea methane seep, gas hydrate or mud volcano environments. Several sequences were related to the sequences recovered from the deep-sea hydrothermal vent or basalt glasses-bearing sediments, indicating that our deep-sea sampling site might be influenced to certain degree by the nearby hydrothermal field of the East Pacific Rise at 13°N.

Carbon dioxide sequestration in deep-sea basalt

Developing a method for secure sequestration of anthropogenic carbon dioxide in geological formations is one of our most pressing global scientific problems. Injection into deep-sea basalt formations provides unique and significant advantages over other potential geological storage options, including (i) vast reservoir capacities sufficient to accommodate centuries-long U.S. production of fossil fuel CO2 at locations within pipeline distances to populated areas and CO2 sources along the U.S. west coast; (ii) sufficiently closed water-rock circulation pathways for the chemical reaction of CO2 with basalt to produce stable and nontoxic (Ca(2+), Mg(2+), Fe(2+))CO(3) infilling minerals, and (iii) significant risk reduction for post-injection leakage by geological, gravitational, and hydrate-trapping mechanisms. CO2 sequestration in established sediment-covered basalt aquifers on the Juan de Fuca plate offer promising locations to securely accommodate more than a century of future U.S. emissions, warranting energized scientific research, technological assessment, and economic evaluation to establish a viable pilot injection program in the future.

Total nitrogen content of deep sea basalts

Various models have been suggested concerning the origin and evolution of the earth's atmosphere. An estimate of the nitrogen content of the mantle could further constrain atmospheric models. Total nitrogen content was determined by thermal neutron activation analysis via 14N(n,p) 14C. The 14C was converted to carbon dioxide and counted in miniature low level proportional counters. The total nitrogen content of U.S.G.S. standards BCR-1 and G-2 as determined by different laboratories is variable, probably due to atmospheric adsorption by the finely ground samples. Total nitrogen content was determined in deep sea basalt glasses from three regions: East Pacific Rise ( 15 ± 4, 18 ± 4, and 7 ± ppm2 N ), Mid-Atlantic Rift (FAMOUS Region: 22 ± 5, 18 ± 3, and 10 ± 2 ppm N ) and the Juan de Fuca Ridge ( 17 ± 4 ppm N ). Matrix material from the same samples as the glasses was available from the East Pacific Rise ( 37 ± 6, 26 ± 4, and 34 ± 6 ppm N ) and the Mid-Atlantic Rift ( 39 ± 4 ppm N ) which are about 50 to 100% greater than the associated glasses. The increased matrix abundance may be due to incorporation of chemically bound nitrogen from sea water rather than dissolved molecular nitrogen. The nitrogen content of the FAMOUS samples are inconsistent with the model of Langmuir et al. (1977) for petrogenesis based on trace element data. Factors which can affect the observed nitrogen content in the basalts and the interpretation in terms of the mantle nitrogen abundance are discussed ( e.g. partial melting and degassing of the basalts). A lower limit of about 2 ppm N in the mantle can be estimated.

Decorated vesicles in deep-sea basalt glass, eastern Pacific

Microprobe and scanning electron microscope (SEM) examination of small vesicles found in glassy selvages of tholeiitic basalt shows that some vesicle walls are decorated with evenly spaced spherules 0.5–4 μm across. Some are iron sulfides with high concentrations of Cu and Ni and are set in hemispherical pits in vesicle walls. Other spherules are not sulfides and appear to be aggregates of plates in microvesicular vesicle walls; these may be oxidized spherules accompanied by palagonitized glass. Other decorations include plates, grooves, and whiskers; the chemical nature of these features is not known. The spherical shape of sulfide spherules is distorted by secondary crystal growth into the vesicle, presumably due to reequilibration during cooling or to alteration. Loss of sulfide spherules during degassing may be an additional mechanism by which metals enter seawater near a rise crest.

Excess Argon in Submarine Basalt Pillows

Four deep-sea basalt pillows from near the axis of the East Pacific Rise were investigated for the presence of excess radiogenic argon. Excess argon in the rocks is verified by the presence of an argon gradient. The highest concentrations of radiogenic argon occur in the pillow margins, and at depths of 5 to 8 cm within the pillows, no radiogenic argon can be measured. The complete degassing of the insides of deep-sea pillow basalts suggests that K-Ar ages of deep-sea rocks may be valid if large samples are used.

Petrology of deep-sea basalt near Hawaii : Moore James G., 1965. Am. J. Sci., 263 (1): 40–52

Petrology of deep-sea basalt near Hawaii : Moore James G., 1965. Am. J. Sci., 263 (1): 40–52

Petrology of deep sea basalt near Hawaii

Dredge samples collected from the submarine part of the east rift zone of Kilauea Volcano consist of glassy, tholeiitic pillow basalts containing vesicles whose volume and size decrease systematically with depth. Basalt dredged from seamounts near the Island of Hawaii is weathered, and the large volume of vesicles indicates that the seamounts have submerged as much as 1,700 m since their lava was extruded. Close chemical similarity between the glassy crust of submarine pillows and subaerial lava of the same rift zone indicates that exchange does not take place between sea water and deep sea basalt at the time of eruption. There is no evidence that spilite forms at the time of eruption.