Submarine hydrothermal vent systems: the relevance of dynamic systems in chemical evolution and prebiotic chemistry experiments

Since their discovery, submarine hydrothermal vent systems have been pointed out as important places where chemical evolution on Earth could have occurred; and their role in the process has been highlighted. Similarly, some hypotheses have considered these systems in origin of life scenarios. In this way, many experiments have been developed, and the knowledge about these systems has increased. Due to their complexity, many experimental simulations have only included a few of the geochemical variables present in these environments, pressure and temperature. Other main variables have hardly been included, such as mineralogy, thermal and pH gradients, dissolved ions and/or redox reactions. As it has been understood, the dynamism and heterogeneity of these environments are huge, and it comprises different scales, from single vents to full hydrothermal fields. However, the vast majority of experiments focus on a specific part of these systems and do not include salinity, mineralogy and pH gradients. For this reason, in this paper, we pointed out some considerations about how this dynamism can be interpreted, and included in some models, as well their importance in prebiotic chemistry experiments and their extrapolations regarding the hypothesis about the origins of life.

Some Studies of the Geology, Volcanic History, and Geothermal Resources of the Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

<p>Okataina Volcanic Centre is the most recently active of the four major rhyolite eruptive centres in the Taupo Volcanic Zone of New Zealand. Within the Centre lies Haroharo Caldera, a complex of overlapping collapse structures resulting from successive voluminous pyroclastic eruptions from the same general source area. At least four main and possibly two minor caldera-forming eruptions have occurred during the last 250,000 years, although poor exposure means that attempts to interpret the early structural history are highly speculative. Although there is no compelling evidence of structural updoming within Haroharo Caldera, magma resurgence has followed the last major caldera-forming eruption of the Rotoiti Breccia at [greater than or equal to] 42,000 years B.P. Eruption of this magma within the caldera has formed the two large rhyolite lava and pyroclastic piles of the Haroharo Volcanic Complex and Tarawera Volcanic Complex, plus two subsidiary adjacent complexes at Okareka and Rotoma. All these intracaldera eruptives are younger than 20,000 years B.P., with the most recent eruptions from Tarawera; of rhyolite at c. 700 years B.P., and of basalt in 1886 A.D. A considerable amount of earlier work carried out at Okataina was directed mainly at petrology and chemistry of the rhyolites forming the Tarawera and Haroharo Volcanic Complexes. The present study has arisen from a 1:50,000 mapping programme at Okataina and has sought to examine structures and volcanic history in greater detail, and to consider the resulting geological implications for geothermal resources. Caldera boundaries have been mapped, and two major vent lineations are defined, apparently related to fundamental basement fractures which have controlled location of the Tarawera and Haroharo Volcanic Complexes. An intracaldera ring fault is also suggested by the sub-circular arrangement of some young volcanic vents. The Haroharo and Tarawera Complexes are mapped, with locations of source vents, and dating of the major lavas and pyroclastic deposits. All the post-20,000 year eruptives are placed in four main emptive episodes at Haroharo, and five at Tarawera. The near-source pyroclastic surge and flow deposits are 14C dated, and with their associated widespread plinian fall deposits they provide time planes for dating the associated lavas. The emptive episodes generally appear to have been of much shorter duration than the intervening quiescent periods which lasted for thousands of years. All the eruptive episodes at Haroharo involved multiple eruptions from vents spread out over several kilometres along the vent lineations. Similar multiple vent eruptions can be demonstrated for some of the Tarawera eruptive episodes. More than 500 km3 of magma has been erupted from Haroharo Caldera during the last 250,000 years, 80 km3 of which was erupted in the Last 20,000 years. This history suggests that a large magmatic heat source should continue to underlie the Okataina Volcanic Centre. However, very little surface hydrothermal activity occurs within Haroharo Caldera. It is suggested that the large external hydrothermal fields at Tikitere, Waimangu-Waiotapu-Waikite, and possibly Kawerau, are related to Haroharo Caldera heat sources. Presently available data are summarized for hydrothermal fields in and adjacent to Haroharo Caldera, and new analyses are presented for some warm springs discovered within the caldera. Estimates and measurements of chloride fluxes in lakes and rivers are reported. The chloride flux values suggest the occurrence of larger hydrothermal heat flows into lakes and rivers than are apparent at the surface. Measurements of chloride flux in the Tarawera River showed that 280 g s-1 of chloride is added to the river within Haroharo Caldera below the Lake Tarawera outlet. Only 80 g s-1 of this chloride comes from known geothermal sources. A total chloride flux of 760 g s-1 in the Tarawera River passing out of the Okataina Volcanic Centre indicates a minimum geothermal heat flow of 600 MW. Estimates of heat flows in other drainage paths from Haroharo Caldera suggest that minimum total heat flow from the caldera may exceed 1500 MW. A large heat flow from the caldera would appear consistent with the volcanic history. Some suggestions are made for further investigation of the geothermal resources</p>

Some Studies of the Geology, Volcanic History, and Geothermal Resources of the Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

<p>Okataina Volcanic Centre is the most recently active of the four major rhyolite eruptive centres in the Taupo Volcanic Zone of New Zealand. Within the Centre lies Haroharo Caldera, a complex of overlapping collapse structures resulting from successive voluminous pyroclastic eruptions from the same general source area. At least four main and possibly two minor caldera-forming eruptions have occurred during the last 250,000 years, although poor exposure means that attempts to interpret the early structural history are highly speculative. Although there is no compelling evidence of structural updoming within Haroharo Caldera, magma resurgence has followed the last major caldera-forming eruption of the Rotoiti Breccia at [greater than or equal to] 42,000 years B.P. Eruption of this magma within the caldera has formed the two large rhyolite lava and pyroclastic piles of the Haroharo Volcanic Complex and Tarawera Volcanic Complex, plus two subsidiary adjacent complexes at Okareka and Rotoma. All these intracaldera eruptives are younger than 20,000 years B.P., with the most recent eruptions from Tarawera; of rhyolite at c. 700 years B.P., and of basalt in 1886 A.D. A considerable amount of earlier work carried out at Okataina was directed mainly at petrology and chemistry of the rhyolites forming the Tarawera and Haroharo Volcanic Complexes. The present study has arisen from a 1:50,000 mapping programme at Okataina and has sought to examine structures and volcanic history in greater detail, and to consider the resulting geological implications for geothermal resources. Caldera boundaries have been mapped, and two major vent lineations are defined, apparently related to fundamental basement fractures which have controlled location of the Tarawera and Haroharo Volcanic Complexes. An intracaldera ring fault is also suggested by the sub-circular arrangement of some young volcanic vents. The Haroharo and Tarawera Complexes are mapped, with locations of source vents, and dating of the major lavas and pyroclastic deposits. All the post-20,000 year eruptives are placed in four main emptive episodes at Haroharo, and five at Tarawera. The near-source pyroclastic surge and flow deposits are 14C dated, and with their associated widespread plinian fall deposits they provide time planes for dating the associated lavas. The emptive episodes generally appear to have been of much shorter duration than the intervening quiescent periods which lasted for thousands of years. All the eruptive episodes at Haroharo involved multiple eruptions from vents spread out over several kilometres along the vent lineations. Similar multiple vent eruptions can be demonstrated for some of the Tarawera eruptive episodes. More than 500 km3 of magma has been erupted from Haroharo Caldera during the last 250,000 years, 80 km3 of which was erupted in the Last 20,000 years. This history suggests that a large magmatic heat source should continue to underlie the Okataina Volcanic Centre. However, very little surface hydrothermal activity occurs within Haroharo Caldera. It is suggested that the large external hydrothermal fields at Tikitere, Waimangu-Waiotapu-Waikite, and possibly Kawerau, are related to Haroharo Caldera heat sources. Presently available data are summarized for hydrothermal fields in and adjacent to Haroharo Caldera, and new analyses are presented for some warm springs discovered within the caldera. Estimates and measurements of chloride fluxes in lakes and rivers are reported. The chloride flux values suggest the occurrence of larger hydrothermal heat flows into lakes and rivers than are apparent at the surface. Measurements of chloride flux in the Tarawera River showed that 280 g s-1 of chloride is added to the river within Haroharo Caldera below the Lake Tarawera outlet. Only 80 g s-1 of this chloride comes from known geothermal sources. A total chloride flux of 760 g s-1 in the Tarawera River passing out of the Okataina Volcanic Centre indicates a minimum geothermal heat flow of 600 MW. Estimates of heat flows in other drainage paths from Haroharo Caldera suggest that minimum total heat flow from the caldera may exceed 1500 MW. A large heat flow from the caldera would appear consistent with the volcanic history. Some suggestions are made for further investigation of the geothermal resources</p>

Identification of Two New Hydrothermal Fields and Sulfide Deposits on the Mid-Atlantic Ridge as a Result of the Combined Use of Exploration Methods: Methane Detection, Water Column Chemistry, Ore Sample Analysis, and Camera Surveys

In 2018–2020 the research vessel (R/V) Professor Logachev (cruises 39 and 41) carried out geological and geochemical studies in the bottom waters of the Mid-Atlantic Ridge hydrothermal fields at 14°45’ N, 13°07’ N, and 13°09’ N. Two new hydrothermal fields were discovered—the Molodezhnoye and Koralovoye. Standard conductivity, temperature, and depth (CTD) sounding with a methane sensor was accompanied by video surveillance and sampling of rocks and water. The rocks were characterized by a zonal composition with opal and sulfides of copper and zinc. An increase in methane concentration values was accompanied by CTD anomalies in the bottom waters. The methane anomaly was formed within the hydrothermal plume of both high-temperature and low-temperature systems. Methane was almost absent in the plume of neutral buoyancy and was associated in all the studied manifestations with the ascending flow of hot waters over the hydrothermal vents. The hydrothermal plumes were characterized by increased Cu, Zn, and Fe concentrations at background Mn concentrations. Signs of low-temperature hydrothermal activity were also observed. Different sources and mechanisms are required to explain the elevated concentrations of base metals and methane in the hydrothermal plumes.

Paleofluid flow: answers in the quartz.

The search for carbon-free energy sources is at the heart of our concerns. It has become necessary to develop our capacities to harness the active energy flows of our environment while trying to have the lowest possible impact. Among these flows, one of the most stable is that linked to terrestrial thermal anomalies. Geothermal energy is an attractive option due to its regularity and the development of knowledge is encouraged, in France, by the national research funding agency. Geothermal systems are mainly associated with active hydrothermal circulations, fluids can be considered as a source of heat but also of metals. However, fluid circulation within active hydrothermal fields occurs at considerable depths and cannot be observed directly. In this study we propose a method for reconstructing the paleo-flow velocities recorded by quartz. The relative thickness of quartz growth bands is used to deduce the sense and velocity of the paleofluid flow. This contribution highlights the paleofluid flows velocities and the recharge/discharge area in the Limagne Basin geothermal province, which is currently under investigation. Finally, this study provides a tool to be used to study fossil hydrothermal systems containing quartz veins with comb textures.

Paleofluid flow: answers in the quartz.

The search for carbon-free energy sources is at the heart of our concerns. It has become necessary to develop our capacities to harness the active energy flows of our environment while trying to have the lowest possible impact. Among these flows, one of the most stable is that linked to terrestrial thermal anomalies. Geothermal energy is an attractive option due to its regularity and the development of knowledge is encouraged, in France, by the national research funding agency. Geothermal systems are mainly associated with active hydrothermal circulations, fluids can be considered as a source of heat but also of metals. However, fluid circulation within active hydrothermal fields occurs at considerable depths and cannot be observed directly. In this study we propose a method for reconstructing the paleo-flow velocities recorded by quartz. The relative thickness of quartz growth bands is used to deduce the sense and velocity of the paleofluid flow. This contribution highlights the paleofluid flows velocities and the recharge/discharge area in the Limagne Basin geothermal province, which is currently under investigation. Finally, this study provides a tool to be used to study fossil hydrothermal systems containing quartz veins with comb textures.

Mercury concentrations in thermal waters of the Bolshoi Semyachik hydrothermal system, Russia, Kamchatka.

&lt;p&gt;The study of mercury receipt within volcanic activity zones and large hydrothermal systems recently causes the big interest connected with attempts of an estimation of volumes of natural mercury receipt on a daily surface.&lt;/p&gt;&lt;p&gt;The hydrothermal system connected with volcanic massif Big Semyachik is one of the largest on the territory of Kamchatka peninsula. On the surface, the hydrothermal system is manifested by three large hydrothermal fields - the Verhnee Field, the parychay Dolina, and the Northern Crater of the Central Semyachik, the heat export from which is estimated at 300 MW (Vakin, 1976). On the surface of the thermal fields hot thermal waters and powerful steam-gas jets are unloaded.&amp;#160; At the same time, due to the inaccessibility of thermal fields remain poorly studied, and in particular, there is no information on the concentrations of mercury in hydrothermal solutions.&lt;/p&gt;&lt;p&gt;During fieldwork in 2020 all types of thermal waters were sampled, chemical types of waters were established, concentrations of mercury in hydrothermal solutions: for hot thermal waters the average value of mercury was - 0.44 mcg / L, and in steam-gas jets - the average value of mercury was - 4.60 mcg / L.&lt;/p&gt;&lt;p&gt;Thus, in the course of the work the data on concentrations of mercury in hydrothermal solutions of one of the largest hydrothermal systems of Kamchatka were received for the first time.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;