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New important discoveries of hydrothermal deposits at the Mid-Atlantic Ridge
Interest in submarine hydrothermal systems has led to the discovery of new hydrothermal fields in all the oceans. Three large hydrothermal fields (Ashadze, Krasnov and 13-31 N) were discovered by Russian geologists during last five years at the segment of Mid Atlantic Ridge (MAR) between 13 and 17 degrees N. Taking into account Logatchev field which was discovered earlier, the average frequency of occurrence could be estimated as one hydrothermal field per 100 km at this segment of the MAR structure. The similar distribution of hydrothermal sites occurs in the northern segment of MAR between 36 and 38 degrees N as well as to the south from equator near the Ascension Island between 5 and 9 degrees S. These three clusters of deposits demonstrate high metallogenic potential of the MAR structure which could be compared with the Pacific spreading centers potential.

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Cayman Trough
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Scientists are set to explore the world's deepest undersea volcanoes, which lie 6km down in the Caribbean.
Delving into uncharted waters to hunt for volcanic vents will be Autosub6000, Britain's new autonomously controlled, robot submarine.
Once found, the life, gas and sediment around the vents - the world's hottest - will be sampled and catalogued.

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Even Jules Verne did not foresee this one. Deep down at the very bottom of the Atlantic Ocean, geochemist Andrea Koschinsky has found something truly extraordinary: "It's water," she says, "but not as we know it."

At over 3 kilometres beneath the surface, sitting atop what could be a huge bubble of magma, it's the hottest water ever found on Earth. The fluid is in a "supercritical" state that has never before been seen in nature.
The fluid spews out of two black smokers called Two Boats and Sisters Peak.

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U.S. marine biologists have discovered thousands of new kinds of microbes at two deep-sea hydrothermal vents in the Pacific Ocean off the Oregon coast.
The discovery was made by scientists from the Marine Biological Laboratory in Woods Hole, Maine, and the University of Washington's Joint Institute for the Study of Atmosphere and Ocean.
Using a new analytical technique called 454 tag sequencing, the scientists surveyed 1 million DNA sequences of bacteria and archaea. The DNA was taken from samples collected from two hydrothermal vents on the Pacific deep-sea volcano, Axial Seamount.
The researchers discovered that while there might be as few as 3,000 different kinds of archaea at those sites, the bacteria exceed 37,000 different kinds.
Most of these bacteria had never been reported before, and hundreds were so different from known microbes that we could only identify them to the level of phylum, said lead author Julie Huber of the MBL. Clearly, additional sampling of these communities will be necessary to determine the true diversity.
The research is reported in journal Science.

Source UPI


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Thousands of new kinds of marine microbes have been discovered at two deep-sea hydrothermal vents off the Oregon coast by scientists at the MBL (Marine Biological Laboratory) and University of Washingtons Joint Institute for the Study of Atmosphere and Ocean. Their findings, published in the October 5 issue of the journal Science, are the result of the most comprehensive, comparative study to date of deep-sea microbial communities that are responsible for cycling carbon, nitrogen, and sulphur to help keep Earth habitable.

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Hot vents deep in the ocean harbour thousands of previously unknown microorganisms, scientists report. By examining the DNA of microbes taken from two hydrothermal vents off the coast of Oregon, researchers identified as many as 37,000 different kinds of bacteria and 3,000 archaea, a type of microorganism distinct from bacteria, according to researchers from the Marine Biological Laboratory at Woods Hole, Mass. and the University of Washington.
Their findings are reported in Friday's edition of the journal Science.

"Most of these bacteria had never been reported before. Clearly, additional sampling of these communities will be necessary to determine the true diversity" - lead author Julie Huber, MBL

The researchers also reported that the populations living at the two vents differed because of different chemical environments.
The research was funded by the NASA Astrobiology Institute, National Research Council, L'Oreal USA, the Alfred P. Sloan Foundation and the W.M. Keck Foundation.

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Exotic creatures that live at deep-sea vents will not be immune to the effects of climate change, a UK scientist says.
It was thought that life at these fiercely hot volcanic fissures was so independent from the world above that the habitat would prove a safe haven.
But new work finds that some of the animals are reliant on food sources from sea surface level, which could be affected by a change in climate.
The findings are presented at the BA Festival of Science in York.

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Title: Prolonged Exposure of Basement Edifices caused by Dissolution of Biogenic Ooze by Hydrothermal Venting
Authors: Bekins, B. A.; Spivack, A. J.; Davis, E. E.; Mayer, L. A.

Seafloor hydrothermal convection may continue for millions of years, but if the sediment cover is sufficiently thick, recharge of seawater diminishes, effectively reducing the water/rock ratio and causing changes in fluid composition that reflect more extensive reaction with host rocks. Outcrops formed by basement edifices provide sites for recharge and discharge, enhancing off-axis ventilation of the crust by relatively unaltered seawater; but their life-time as a conduit is thought to end once the seafloor sediment thickness exceeds their maximum height. A recent and exciting discovery is the widespread occurrence of closed depressions in biogenic oozes in the Equatorial Pacific. The position of these features overlying basement edifices, suggests that they are formed by sediment dissolution due to venting fluids. We computed the calcium carbonate precipitated by a fluid of bottom water composition at a range of basement temperatures; and assume this fluid has an equivalent carbonate dissolution potential during subsequent cooling and discharge. For a basement temperature of ~25° C dissolution can outpace moderate Equatorial Pacific carbonate mass accumulation rates of 1-5 g cm2/ky if fluid fluxes exceed 2- 10 m/yr respectively. This range of fluid fluxes is consistent with the regional heat flow deficit and basement permeability. Lower basement temperatures require either higher fluid flux or lower sedimentation rates to produce the dissolution features. By maintaining sediment-free basement outcrops, this process is self- sustaining and promotes wide-spread circulation of relatively unaltered seawater in the basement in an area where the average sediment thicknesses of 300-500 meters would otherwise create an impermeable cap. This dynamic relationship between enhanced ventilation, dissolution and permeability explains several previous observations in this region, including the existence of the closed sediment depressions, the long-standing puzzle of very low heat flow in this region, the presence of relatively unaltered seawater in the basement, and the existence of aerobic and nitrate-reducing microbial activity in the deepest section of the sediment where it would not otherwise exist.

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Ophiolites
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Within sight of the Great Wall of China, about 250 kilometres northeast of Beijing, are remnants from an ocean that no longer exists. Wedged between two slabs of earth that closed in on each other is a jumble of oceanic rocks and minerals that Chinese and American scientists working together have identified as an ophiolite. The discovery of this complete ophiolite complex dating back to the Archean, 2.5 billion years ago, is a major coup for geophysicists. Until now it was questionable whether ophiolites that old even existed

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blackrock_e1
This long, vertical black smoker chimney was found in the Wutai Mountains, North China Craton. It is part of a 2.5-billion-year old black smoker chimney-hydrothermal seafloor vent system, discovered in the upper portions of a fragment of Archean oceanic crust. The oceanic crust is now part of the Central Orogenic belt.
Photo courtesy of Jianghai Li.

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