From “Vent” to “Volcanic Field” and “Volcanic Province”: Pivotal terms in volcanology that require formal definitions

Magma storage and degassing beneath the youngest volcanoes of the Massif Central (France): Lessons for the monitoring of a dormant volcanic province

Long-lasting widespread volcanism contributed to heavily shaping the surface of Mars. In fact, the Tharsis volcanic province is one of the largest volcanic provinces with the largest shield volcanoes of the Solar System, Mount Olympus and the NE-SE trending Tharsis Montes, namely Ascareaus, Pavonis and Arsia Mons.However, volcanism on Mars is characterized also by the presence of wide volcanic fields, either in form of small shields or monogenic cones. The region of Syria Planum (SP), located eastern to the Tharsis province and encompassed between Noctis Labyrinthus on the North and Claritas Fossae on the southwest, is an example of diffuse volcanism. SP presents hundreds of small edifices which insist on top of a large bulge roughly 300x200 km in size.New chronological results pointed out a complex magmatic history and volcano-tectonic evolution of the whole Tharsis and SP area spanning from the early-Noachian to the more recent times such as the 130 Ma of the Arsia Mons’ single caldera and the 140 Ma for the Pavonis Mons’ composite calderas. Although through the years SP has been considered the by-product of the enormous volcano-tectonic activity forming the Tharsis, it has been shown that this magmatic complex could be related to large multiple episodes of mantle upwelling forming minor edifices that do not necessarily overlap with the major volcanic centres. Moreover, the NW-SE elongated SP volcanic field grew just south of the Noctis Labyrinthus canyon systems that form a dissected highland and is located at the western tip of the Valles Marineris.In this work, we investigate the geometry of the plumbing system of the SP volcanic field as well as the structures (vent elongation and vent alignment) that fed the magma to forward a possible tectonic and volcanic evolution of the area. The spatial distribution of vents and the overall shape of the volcanic field have been studied in terms of vent clustering and spatial distribution. Moreover, analyzing the lineament pattern on SP and surrounding areas possible links with the formation and evolution of the Noctis Labyrinthus graben, the Valles Marineris and the Tharsis province are forwarded.

Endogenous versus exogenous factors: What matters for vent mussel communities?

Basaltic Volcanic Fields (BVFs) occur on all continents, in all tectonic environments and host a diverse range of small scale basaltic volcanoes, which include the most numerous types of volcanic edifices on Earth. They are associated with small, often monogenetic, eruptions with long periods of quiescence. BVF are poorly studied compared with more obviously threatening, and high eruptive flux volcanic systems (volcanic arcs, mid-ocean ridges, continental rifts, and mantle plumes). The range of models used to explain what drives volcanism at the dozens of BVFs studied globally, stems from the variety of tectonic settings in which they occur. The complexity and inconsistency between the various models accounts for the need for further research on how these fields develop and the hazards they pose to society. BVFs that have been studied in detail are predominantly geometrically smaller examples, with characteristics that suggest relationships with local tectonic processes. The Newer Volcanics Province (NVP) is an expansive Pliocene to Recent intraplate basaltic plains province, located in south-eastern Australia. The NVP has several aspects that make it an interesting and unique BVF to study. It is not readily relatable to any tectonic processes expressed at the surface, it occurs in a compressional lithospheric stress field setting, and it is host to some of the world’s largest maar volcanoes. The NVP therefore provides an ideal case study for larger end-member examples of both volcanoes and BVFs. The NVP as a whole, and many of its volcanoes, have been the subject of geochemical, deep geophysical imaging, physical volcanology, and limited age dating studies over the past half century. Despite this, there are significant gaps in understanding what controls on volcanism in a compressive stress regime, and the formation of very large maar volcanoes. Potential field modelling and spatial analysis methods are proven effective methods in studying basaltic volcanoes and volcanic fields. Hence, they are used in this thesis to investigate the aforementioned unique aspects of the NVP, with the implications being relevant to cases of basaltic volcanoes and BVFs worldwide. Lake Purrumbete Maar (LPM) is a ~50 ka yrs old, large maar volcano with a crater that is up to 2,800 m in diameter. Despite its age, Lake Purrumbete’s near circular crater is well preserved, having undergone only minor erosion and is. It is one of a number of maar volcanoes of the NVP that rank amongst the largest examples in the world. Forward and inverse potential field modelling is used to constrain the subsurface structures related to the maar to assist in determining the factors that control the formation of such a large maar. Results show that LPM is the result of at least four coalesced vents that have produced a large shallow bowl shaped diatreme system, and not a deep conical feature. This is consistent with features typical of maars hosted in unconsolidated sediments, which is suggested for LPM by the occurrence of irregular marl lithic clasts with peperitic textures in the tephra ring deposits. Geometry inversions of the magnetic data indicate that the vents extend to a greater depth than inferred by accidental lithics present in the volcanic deposits (1472 boreholes. Results show the NVP is large (23,100±530 km2) voluminous (680–900 km3 DRE) and high-flux (0.15–0.2 km3/ka) example relative to comparable low-flux IBVFs (0.0001 – 0.1 km3/ka). All the BVFs used for comparison have eruptive fluxes an order of magnitude or more less than examples of plume related volcanoes (Kilauea) and BVFs (Eastern Snake River Plains). Most lower flux BVFs also show no systematic age migration pattern in volcanism suggestive of a fixed mantle plume, and those with detailed geochronology and volume data often show a correlation between their eruptive flux and the rate of local tectonic processes. It is suggested that the NVP and most low- and high-flux BVFs are the result of upwelling occurring in the asthenosphere, related to tectonic processes; without requiring additional thermal input from a deep mantle source, as is inferred for several cases. Considering a control on volcanism by tectonic processes, the range of eruptive flux of tectonically controlled BVFs is related to variations in the rate of the effecting tectonic process, mantle composition, and the size of the mantle source zone where melt generation and accumulation is taking place.

Reappraisal of the significance of volcanic fields

The Parana Volcanic Province follows Siberia as the second largest in the continents and offers a unique opportunity to study the hydrothermal relationship between basalt-rhyodacite lavas and buried erg-turned aquifer in an intraplate setting. Injected sand fluidized after basalt sealing and was succeeded by amethyst and agate geode opening and filling. Excellent exposures in the Herveiras cuesta, southern Brazil, allow the comparison of processes over long distances (1500 km) in the volcanic group. Fieldwork and basalt chemistry led to the identification of three hydrothermal processes-amygdales filling (H1), sand injection (H2) and amethyst geodes formation (H3). Sand injection was triggered by high temperature (150 ℃) and seismicity. These low-temperature processes identified in the Herveiras cuesta demonstrate the homogeneity of relationships between the paleoerg, giant aquifer and intraplate volcanic rocks across the volcanic province.

The eruptive history of the Pátzcuaro Lake area in the Michoacán Guanajuato Volcanic Field, central México: Field mapping, C-14 and 40Ar/39Ar geochronology

Overview and plumbing system implications of monogenetic volcanism in the northernmost Andes' volcanic province

Deep and shallow crustal structure control on the late-stage volcanism in Syria Planum (Mars)

Petrogenesis of primitive lavas from the Toro Ankole and Virunga Volcanic Provinces: Metasomatic mineralogy beneath East Africa's Western Rift

Almost three quarters of known volcanic activity on Earth occurs in underwater locations. The presence of active hydrothermal vent fields in such environments is a potential natural hazard for the environment, the society, and the economy. Despite its importance for risk assessment and risk mitigation, monitoring of the activity is impeded by the remoteness and the extreme conditions of underwater volcanoes. The large difference of population present on Santorini between the winter and summer seasons, all within a partially enclosed system, make the Santorini-Kolumbo volcanic field, an ideal place for detailed exploration. In 2017, GEOMAR in collaboration with the National and Kapodistrian University of Athens (mission: POS-510 ANYDROS), used an Autonomous Underwater Vehicle (AUV) to map the NE–trending Santorini–Kolumbo line, where it also collected CTD data. Here we present the preliminary results from the 15-hour survey held on the 25th March 2017, during the POS-510 expedition targeting the vent field which is located in the North Basin of Santorini Caldera. Detailed CTD 3D profiles have been reconstructed from the raw data of Santorini’s vent field. An anomaly emerges at the depth of 350 m in the Conductivity and Salinity depth profiles, as the CTD sensor is placed directly above the vent sources. Anomalies were evident in the 3D maps reconstructed, showing for the first time a rather weak, but underlying hydrothermal vent activity at various locations. As the present results are the first ones produced from this expedition, further investigation is required incorporating the full dataset. Based on those results, the impact of developing appropriate mechanisms and policies to avoid the associated natural hazard is expected to be immense.

Since the grade I reservoir in Changshen volcanic gas field has high natural deliverability. Horizontal wells completed with screen pipe were applied to develop this type of reservoir. However, the severe mud pollution during drilling badly damaged the formation, which reduced the well deliverability greatly. In order to remove the mud cake near well bore and restore the reservoir permeability, a new plugging relief technology of biological enzyme was developed. According to the situation of screen completed horizontal wells and the degradation characteristics of the enzyme, laboratory experiments and field applications were conducted. The results show that biological enzyme can remove the reservoir pollution and recover the natural production of screen completed horizontal wells in Jilin volcanic gas field. It provided a new way to develop the grade I reservoir in Changshen volcanic rock gas field. Introduction Changshen gas field is located in the center of the Changling fault depression which lies in the south of Songliao basin. As it kept uplift status during the Yingcheng Sedimentary period, its formation was controlled by dual mechanisms of volcanic activity and tectonic movement. In September 2005, well Changshen X was drilled in this area, which showed that the Yingcheng volcanic layer group has a long gassy well section and that the physical property and gas abundance was good near the crater. The drill stem test(DST) got such a high production as 46×104m3/d in this well. Following evaluation wells, control wells and exploration wells all received success. These indicate that the exploration and development of Changling faulted structure has a good prospect. Screen completed horizontal wells was applied to develop the grade I volcanic gas reservoir of Yingcheng layer group. The total measure depth of well CS- X was 4360.41m. Volcanic reservoir layer was discovered while drilling to 3616 m. gas survey showed that gas bearing formation became good in 3669 m. The main lithology of the reservoir was in-situ dissolution breccia and stomatal rhyolite. The reservoir types were fracture, pore or pore-fracture. The core analysis data showed that the reservoir porosity was 5.3–21.4%, average 13.1%. The permeability was 0.09–1.77 mD average 0.565 mD. It was also indicated that the in-situ dissolution breccia was the best reservoir type in Yingcheng volcanic group, which comprise the grade I reservoir. Since it had a high productivity, screen completed horizontal wells were adopted. The well configuration schematic diagram of well CSP1 is shown in figure 1, which has a screen pipe completed section length of 735.3 m. With intensive fracture development, reservoir invasion by drilling fluid was serious in Changshen gas reservoirs. Thus thick mud cake could form near well bore, which caused reservoir pollution and productivity decrease. This paper developed a bio-enzyme technology to remove plugging of screen completed horizontal well in volcanic gas reservoir. According to the situation of screencompleted horizontal wells and the degradation characteristics of the enzyme, laboratory experiments and field applications were conducted. Both laboratory experiments and field applications received success. Reservoir pollutions were relieved and well deliverability got recovered. It provided a new way to develop the grade I reservoir in Changshen volcanic rock gas field.

Non-equilibrium fractionation of stable carbon isotopes in chemosynthetic mussels

Paleomagnetic study of Tres Vírgenes Volcanic Complex, Baja California, Mexico

<p>The Mt. Melbourne field is interpreted as a quiescent volcanic complex, located in Northern Victoria Land, Antarctica, at the boundary between the Transantarctic Mountains (TAM) and the West Antarctic Rift System (WARS). It is one of the handful Antarctic volcanoes with the potential for large–scale explosive eruptions [1], with resulting key effects on the local environment and potentially on climate.</p><p>The geological and geophysical structure of this volcanic field remains poorly known, despite its key relevance to better comprehend the Cenozoic tectonic and geodynamic processes responsible for the opening of the WARS and the uplift of the TAM rift flank.</p><p>Here we present results derived from a novel high–resolution aeromagnetic dataset, collected in the austral summer 2002/2003 during the XVIII Italian Expedition, with the aim of investigating the geophysical structure of the main volcanic centres of the field.</p><p>Aeromagnetic data were processed and Digital Enhancement and Depth to Magnetic Source analysis performed to reveal the distribution of the main fault systems affecting the Mt. Melbourne volcanic field, particularly beneath the ice–covered areas. The results highlight NNE–SSW, NW–SE and E–W trending structural systems, in agreement with the available tectonic information for the study area [2, 3]. Furthermore, similar NNW–SSE trending pervasive negative anomalies are detected beneath both the Mt. Melbourne edifice and Cape Washington, superimposed by positive ones forming radial patterns.</p><p>With the aid of laboratory magnetic susceptibility data from rock samples collected in the field [4], we carried out forward and inverse modeling across the volcanic centres in order to image their subglacial internal structure.</p><p>Based on our results, considering the ambiguity and narrowness of the available geochronological data [1, 5, 6], we propose two (non–mutually exclusive) interpretative models to explain the evolution steps of the Mt. Melbourne volcanic complex. In the former, a major volcanic phase responsible for building of the inner part of the main volcanic centres likely occurred prior to the last magnetic polarity reversal (i.e. before 0.78 Ma, Matuyama Chron), explaining the negative anomalies detected as due to remnant magnetisation. During the Pleistocene–Holocene period, a following second volcanic phase put in place at shallower levels, primarily with present–day magnetization. In the alternative model, magma pulses originated at the lithospheric step between the thick East Antarctic craton and the thinner Ross Sea crust [7] caused i) widespread volcanism at the surface of the volcanic complex, particularly with the building up of the Mt. Melbourne edifice, and ii) a regional upward of the Curie isotherm at depth, causing partial de–magnetisation of the underlying volcanic rocks.</p><p><strong>