Active Arc Research Articles

Insights Into Magma Storage Beneath a Frequently Erupting Arc Volcano (Villarrica, Chile) From Unsupervised Machine Learning Analysis of Mineral Compositions

AbstractA key method to investigate magma dynamics is the analysis of the crystal cargoes carried by erupted magmas. These cargoes may comprise crystals that crystallize in different parts of the magmatic system (throughout the crust) and/or at different times. While an individual eruption likely provides a partial view of the subvolcanic plumbing system, compiling data from multiple eruptions can build a picture of a whole magmatic system. In this study, we use machine learning techniques to analyze a large (>2,000) compilation of mineral compositions from a highly active arc volcano: Villarrica, Chile. Villarrica's postglacial eruptive activity (14 ka–present) displays large variation in eruptive style (mafic ignimbrites to Hawaiian style effusive eruptions), yet its eruptive products have a near constant basalt‐basaltic andesite bulk‐rock composition. What therefore, is driving explosive eruptions at Villarrica and can differences in storage dynamics be related to eruptive style? Here, we use a hierarchical cluster analysis to detect previously unseen structure in the composition of olivine, plagioclase and clinopyroxene crystals erupted at Villarrica, revealing the presence of compositionally distinct clusters within each crystal population. Using rhyolite‐MELTS thermodynamic modeling, we related these clusters to intensive magmatic variables: temperature, pressure, water content, and oxygen fugacity. Our results provide evidence for the existence of multiple discrete (spatial and temporal) magma reservoirs beneath Villarrica where melts differentiate and mix with incoming more primitive magma. The compositional diversity within an erupted crystal cargo strongly correlates with eruptive intensity, and we postulate that mixing between primitive and differentiated magma drives explosive activity at Villarrica.

SANTORY: SANTORini’s Seafloor Volcanic ObservatorY

Submarine hydrothermal systems along active volcanic ridges and arcs are highly dynamic, responding to both oceanographic (e.g., currents, tides) and deep-seated geological forcing (e.g., magma eruption, seismicity, hydrothermalism, and crustal deformation, etc.). In particular, volcanic and hydrothermal activity may also pose profoundly negative societal impacts (tsunamis, the release of climate-relevant gases and toxic metal(loid)s). These risks are particularly significant in shallow (<1000m) coastal environments, as demonstrated by the January 2022 submarine paroxysmal eruption by the Hunga Tonga-Hunga Ha’apai Volcano that destroyed part of the island, and the October 2011 submarine eruption of El Hierro (Canary Islands) that caused vigorous upwelling, floating lava bombs, and natural seawater acidification. Volcanic hazards may be posed by the Kolumbo submarine volcano, which is part of the subduction-related Hellenic Volcanic Arc at the intersection between the Eurasian and African tectonic plates. There, the Kolumbo submarine volcano, 7 km NE of Santorini and part of Santorini’s volcanic complex, hosts an active hydrothermal vent field (HVF) on its crater floor (~500m b.s.l.), which degasses boiling CO2–dominated fluids at high temperatures (~265°C) with a clear mantle signature. Kolumbo’s HVF hosts actively forming seafloor massive sulfide deposits with high contents of potentially toxic, volatile metal(loid)s (As, Sb, Pb, Ag, Hg, and Tl). The proximity to highly populated/tourist areas at Santorini poses significant risks. However, we have limited knowledge of the potential impacts of this type of magmatic and hydrothermal activity, including those from magmatic gases and seismicity. To better evaluate such risks the activity of the submarine system must be continuously monitored with multidisciplinary and high resolution instrumentation as part of an in-situ observatory supported by discrete sampling and measurements. This paper is a design study that describes a new long-term seafloor observatory that will be installed within the Kolumbo volcano, including cutting-edge and innovative marine-technology that integrates hyperspectral imaging, temperature sensors, a radiation spectrometer, fluid/gas samplers, and pressure gauges. These instruments will be integrated into a hazard monitoring platform aimed at identifying the precursors of potentially disastrous explosive volcanic eruptions, earthquakes, landslides of the hydrothermally weakened volcanic edifice and the release of potentially toxic elements into the water column.

The Jurassic Laberge Group in the Whitehorse Trough of the Canadian Cordillera: Using Detrital Mineral Geochronology and Thermochronology to Investigate Tectonic Evolution

The Laberge Group is an Early to Middle Jurassic sequence of mostly siliciclastic sedimentary rocks that were deposited in a marginal marine environment in the northern Canadian Cordillera. It forms a long narrow belt with a total thickness of 3–4 km extending for more than 600 km across southern Yukon and northwestern British Columbia. These sedimentary rocks overlap the Yukon-Tanana, Stikinia and Cache Creek terranes that form the main components of the Intermontane superterrane. The Laberge Group contains a record of the erosion of some of these terranes, and also offers some constraints on the timing of their amalgamation and accretion to the Laurentian margin. The Laberge Group was deposited with local unconformity on the Late Triassic Stuhini Group (in British Columbia) and correlative Lewes River Group (in Yukon), both of which are volcanic-rich, and assigned to the Stikinia terrane. The Laberge Group is in turn overlain by Middle Jurassic to Cretaceous clastic rocks, including the Bowser Lake Group in BC and the Tantalus Formation in Yukon. Clast compositions and detrital zircon populations within the Laberge Group and between it and these bounding units indicate major shifts in depositional environment, basin extent and detrital sources from Late Triassic to Late Jurassic. During the Early Jurassic clast compositions in the Laberge Group shifted from sediment- and volcanic-dominated to plutonic-dominated, and detrital zircon populations are dominated by grains that yield ages that approach or overlap their inferred depositional ages. This pattern is consistent with progressive dissection and unroofing of (an) active arc(s) to eventually expose Triassic to Jurassic plutonic suites. Detrital rutile and muscovite data from the Laberge Group indicate rapid cooling and then exhumation of adjoining metamorphic rocks during the Early Jurassic, allowing these to contribute detritus on a more local scale. The most likely source for such metamorphic detritus is within the Yukon-Tanana terrane, and its presence in the Laberge Group may constrain the timing of amalgamation and accretion of the Yukon-Tanana and Stikinia terranes. Thermochronological data also provide new insights into the evolution of the Laberge Group basin. Results from the U–Th/(He) method on detrital apatite suggest that most areas experienced post-depositional heating to 60°C or more, whereas U–Th/(He) results from detrital zircon show that heating to more than 200°C occurred on a more local scale. In detail, Laberge Group cooling and exhumation was at least in part structurally controlled, with more strongly heated areas situated in the footwall of an important regional fault system. The thermochronological data are preliminary, but they suggest potential to eventually constrain the kinematics and timing of inversion across the Laberge Group basin and may also have implications for its energy prospectivity. In summary, the Laberge Group is a complex package of sedimentary rocks developed in an active, evolving tectonic realm, and many questions remain about the details of its sources and evolution. Nevertheless, the available information demonstrates the potential of combined geochronological and thermochronological methods applied to detrital minerals to unravel links between regional tectonics, basin development and clastic sedimentation.

Reconstructive Timing of Nail Preserved Fingertip Injury With Reverse Digital Artery Island Flap.

This study aimed to compare the outcomes of reverse digital artery island flap (RDAIF) in primary and secondary reconstruction after failed replantation or composite graft method. This study retrospectively analyzed 42 patients that underwent RDAIF (18 primary and 24 secondary). Preoperative details (demographics, injury details, and waiting days) and postoperative outcomes (active arc of proximal interphalangeal [PIP] and distal interphalangeal (DIP) joints, extension loss of PIP, flexion arc of metacarpophalangeal joint, total active motion, flap sensation, the presence of numbness, Tinel's sign and cold intolerance) were evaluated. Quick Disabilities of the Arm, Shoulder, and Hand score (Quick-DASH) and patient satisfaction were also statistically compared between the 2 groups. There was no significant difference in patient demographics between the 2 groups in sex, age, smoking and diabetic history, affected hand and finger, injury type and level, and flap area. The only difference was in waiting days. Similar sensory recovery and patient satisfaction were found in both groups. Range of motion in the DIP and PIP joints, extension loss of PIP, total active motion, and Quick-DASH were superior in the primary coverage group. Increasing age, subzone III injury, and secondary reconstruction were found to be the factors that adversely affected the postoperative range of motion. Secondary reconstruction was more likely to result in joint contracture. In the event of a damaged fingertip amputation in older patients, primary flap reconstruction should be considered as the initial treatment of choice, with regard to the ultimate range of motion.

Magmatic water content controls the pre-eruptive depth of arc magmas.

Vanguard efforts in forecasting volcanic eruptions are turning to physics-based models, which require quantitative estimates of magma conditions during pre-eruptive storage. Below active arc volcanoes, observed magma storage depths vary widely (~0 to 20 kilometers) and are commonly assumed to represent levels of neutral buoyancy. Here we show that geophysically observed magma depths (6 ± 3 kilometers) are greater than depths of neutral buoyancy, ruling out this commonly assumed control. Observed depths are instead consistent with predicted depths of water degassing. Intrinsically wetter magmas degas water and crystallize deeper than dry magmas, resulting in viscosity increases that lead to deeper stalling of ascending magma. The water-depth relationship provides a critical constraint for forecasting models by connecting depth of eruption initiation to its volatile fuel.

Testing less-conventional methods to date a late-pleistocene to Holocene eruption: Radiocarbon dating of paleosols and 36Cl exposure ages at Pelado volcano, Sierra Chichinautzin, Central Mexico

Despite their significance for estimating hazards and forecasting future activity, dating young volcanic deposits and landforms (<50,000 yrs old) remains a challenge due to the limitations inherent to the different isotopic chronometers used. The Trans-Mexican Volcanic Belt is one of the most active and populated continental arcs worldwide, yet its temporal pattern of activity is poorly constrained. Such deficiency is particularly problematic for the Sierra Chichinautzin Volcanic Field (SCVF) that is located at the doorstep of Mexico City and Cuernavaca and is hence a major source of risk for these cities. Existing ages for this area derive mostly from either radiocarbon on charcoal, which is rare and may be contaminated, or 40 Ar/ 39 Ar on rock matrix, which is poorly precise for this time period and rock type. Here, we focus on the Pelado monogenetic volcano, which is located in the central part of the SCVF and erupted both explosively and effusively, producing a large lava shield and a widespread tephra blanket. This unique eruptive event was previously dated at ∼12 calibrated (cal) kyrs BP, using radiocarbon dating on charcoal from deposits related to the eruption. To test alternative dating approaches and confirm the age of this significant eruption, we applied two less conventional techniques, radiocarbon dating of bulk paleosol samples collected below the complete tephra sequence at nine sites around the shield, and in-situ 36 Cl exposure dating of two samples of an aphyric lava from the base of the shield. Radiocarbon paleosol ages span a continuous time interval from 13.2 to 20.2 cal kyrs BP (2σ), except for one anomalously young sample. This wide age spread, along with the low organic contents of the paleosols, may be due to erosive conditions, related to the sloping topography of the sampling sites and the cool and relatively dry climate of the Younger Dryas (11.7–12.9 ka), during which the Pelado eruption probably occurred. The two 36 Cl-dated lava samples have consistent ages at 1σ analytical errors of 15.5 ± 1.4 ka and 13.2 ± 1.2 ka, respectively, yielding an average age of 14.3 ± 1.6 ka for this lava flow. The high full uncertainty in 36 Cl ages (24%) is due to high rock Cl content. We conclude that paleosol radiocarbon dating is useful if numerous samples are analyzed and climatic and relief conditions at the time of the eruption and at the sites of tephra deposition are considered. The 36 Cl dating technique is an alternative method to date volcanic eruptions, as it gave consistent results, but in the specific case of Pelado volcano, the high Cl content in the analyzed rocks increases the age uncertainties. • Catalogue of recent eruptions in Trans-Mexican Volcanic Belt is incomplete. • 14 C on paleosol and 36 Cl dating are used on a previously dated monogenetic volcano. • New ages are coherent with previous 14 C charcoal age. • Spread in paleosol ages likely due to erosive conditions at time of eruption. • 36 Cl ages are statistically consistent but poorly precise, due to high Cl in rock.

Post-collisional extension of the South Altun subduction-collision belt, northern Tibetan Plateau: Insight from phase equilibria modeling and zircon geochronology of pelitic migmatites

• Continental collision led to the burial of pelitic rocks in the South Altun. • Pelitic migmatites were formed under the conditions of ∼850–870 °C and 0.6–0.7 GPa. • High- T/P type metamorphism and migmatisation lasted for ∼10 Myr (457–447 Ma) • Continental subduction to post-collisional extension took place in ∼50 Myr. The South Altun subduction-collision belt in the northern Tibetan Plateau is one of the rare examples of ultradeep subduction (>350 km). In addition to subduction-related low-temperature/pressure ( T/P ) type metamorphic rocks, the belt also exposes high- T/P metamorphic rocks with well-developed migmatitic structures, which provide insight into the post-collisional process. Phase equilibria modeling of the Tula pelitic migmatites indicates peak conditions of ∼850–870 °C and 0.6–0.7 GPa for the high- T/P type metamorphism and migmatism. Phase equilibria modeling predicts this high temperature could result in the production of 10–20 vol% melt in metapelites, producing stromatic migmatites observed in multiple outcrops. Based on results of zircon U-Pb geochronology of granulite-facies migmatites, we interpret the supra-solidus conditions to last for ∼10 Myr (457–447 Ma), corresponding to short-lived granulite-facies metamorphism in post-collisional extension. The deposition of the protolith is inferred to occur immediately before the metamorphism on active continental arcs based on the youngest detrital and oldest metamorphic ages. Combined with studies on subducted-related metamorphic rocks, these findings suggest that the South Altun belt experienced the continental subduction (early collision) to the post-collisional extension within a period of ∼50 Myr. At the same time, the thermal regime of this orogenic belt evolved from low- T/P to high- T/P whereas the high- T/P regime predominates the orogenic belt towards the end of orogenic evolution, as evidenced by regional high- T/P type metamorphic rocks and overprinting on the ancient low- T/P regime of exhumed subduction-related rocks.

206 Longevity of Deep Brain Stimulation Batteries at a Tertiary Neurosurgical Centre

Abstract Introduction Deep brain stimulation (DBS) is a surgery used in the treatment of movement disorders. It involves surgical placement of electrodes in the brain that are connected to a battery-powered stimulator to regulate brain activity. DBS has been used successfully in the management of Parkinson's disease (PD). It has improved patients' movement and quality of life. However, one inconvenience is the limited battery life and the need for battery change to prevent deterioration in function. In this audit, we measured the longevity of DBS batteries in PD at a tertiary neurosurgical centre. Method A retrospective audit on the longevity of DBS batteries in 86 Patients with PD. We collected data on; date and position of device implant, type of battery used (rechargeable vs non-rechargeable), and the two most recent battery changes. We excluded battery changes that were due to infection. Results 86 patients had DBS batteries. 21 patients had rechargeable batteries (Abbot Brio, Medtronic Activa RC and Boston Gevia), and 65 had non-rechargeable batteries (Abbot Infinity, Abbot Libra XP, Medtronic Activa PC). 53 patients have undergone a battery change, 49 of those were non-rechargeable batteries. Average battery life of non-rechargeable batteries was 3.06 ± .55 years in Infinity (n = 16), 4.0 ± 1.7 years in Libra XP(n = 22), and 4.6± .9 years in Activa PC (n = 11). Conclusions All three types of non-rechargeable batteries are lasting less than five years. Activa PC batteries had the lengthiest battery life of 4.6± .9 years, while infinity had the shortest battery life of 3.06± .55 years.

Tektite glasses from Belize, Central America: Petrography, geochemistry, and search for a possible meteoritic component

The presence of tektite-like glasses from a geographically restricted area in Belize (Central America) has been known for several decades. We comprehensively studied 18 such Belize glasses by a variety of petrographic and geochemical methods, including major and trace element analysis, radiogenic isotopic composition (Rb-Sr, Sm-Nd, and Re-Os), water content, oxidation state, and cosmogenic radionuclides. The aims were to determine their compositional variation, their mode of formation and possible source rocks, and their relation to known tektites, and to search for evidence of an extraterrestrial component.In terms of petrography, the samples are similar to tektites from the four “classical” strewn fields, with the presence of lechatelierites, schlieren, and vesicles; these are also widely accepted indicators of an impact origin. No close similarities to volcanic glasses are evident. Water contents are very low, and iron oxidation states are mostly reduced, in both cases similar to observations for other tektites. The geochemical and isotopic data presented, such as Cr, Co and Ni elemental abundances and interelement ratios, as well as trace element patterns are typical for local and regional volcanics from the active Central American Arc. Particular similarities to material comparable to volcanic rocks from Honduras or Guatemala are noted. This is confirmed by Sr-Nd isotope signatures of the Belize glasses, showing close similarities to Central American volcanics in general, and Honduran and Guatemalan volcanic, in particular. Osmium concentrations and 187Os/188Os ratios are comparable to arc volcanics from world-wide locations, but - in a few of the samples - elevated Ir concentrations, near-chondritic Pt/Ir and 187Os/188Os ratios can also be interpreted with the admixture of a minor meteoritic component to some of the Belize samples. 10Be concentrations are consistent with values typical of both, young or deeply buried soils and with values for Central American volcanics, which carry subducted 10Be.Geochemical data clearly indicate a source different from that of the Australasian tektites. Both isotope data sets for the Belize glasses indicate a close relationship to local arc lavas, especially those from Guatemala and Honduras, suggesting that the glasses were not deposited very far from their source. The main evidence that the Belize glasses are of impact origin are their petrographic characteristics and low water content. The evidence from 10Be is consistent with, but does not require, a model of formation for the Belize glasses by an impact on loosely consolidated surface sediments exposed to rain. A probable meteoritic component is low and heterogeneously distributed.

A new geological map of the Lau Basin (southwestern Pacific Ocean) reveals crustal growth processes in arc-backarc systems

A 1:1,000,000-scale lithostratigraphic assemblage map of the Lau Basin (southwestern Pacific Ocean) has been created using remote predictive mapping (RPM) techniques developed by geological surveys on land. Formation-level geological units were identified in training sets at scales of 1:100,000–1:200,000 in different parts of the basin and then extrapolated to the areas where geological data are sparse. The final compilation is presented together with a quantitative analysis of assemblage-level crustal growth based on area-age relationships of the assigned units. The data sets used to develop mapping criteria and an internally consistent legend for the compilation included high-resolution ship-based multibeam, satellite- and ship-based gravity, magnetics, seafloor imaging, and sampling data. The correlation of units was informed by published geochronological information and kinematic models of basin opening. The map covers &amp;gt;1,000,000 km2 of the Lau-Tonga arc-backarc system, subdivided into nine assemblage types: forearc crust (9% by area), crust of the active volcanic arc (7%), backarc rifts and spreading centers (20%), transitional arc-backarc crust (13%), relict arc crust (38%), relict backarc crust (8%), and undivided arc-backarc assemblages (&amp;lt;5%), plus oceanic assemblages, intraplate volcanoes, and carbonate platforms. Major differences in the proportions of assemblage types compared to other intraoceanic subduction systems (e.g., Mariana backarc, North Fiji Basin) underscore the complex geological makeup of the Lau Basin. Backarc crust formed and is forming simultaneously at 12 different locations in the basin in response to widely distributed extension, and this is considered to be a dominant pattern of crustal accretion in large arc-backarc systems. Accelerated basin opening and a microplate breakout north of the Peggy Ridge has been accommodated by seven different spreading centers. The result is an intricate mosaic of small intact assemblages in the north of the basin, compared to fewer and larger assemblages in the south. Although the oldest rocks are Eocene (~40 m.y. old basement of the Lau and Tonga Ridges), half of the backarc crust in the map area formed within the last 3 m.y. and therefore represents some of the fastest growing crust on Earth, associated with prolific magmatic and hydro-thermal activity. These observations provide important clues to the geological evolution and makeup of ancient backarc basins and to processes of crustal growth that ultimately lead to the emergence of continents.

Latest Triassic–Early Jurassic Stikine–Yukon-Tanana terrane collision and the onset of accretion in the Canadian Cordillera: Insights from Hazelton Group detrital zircon provenance and arc–back-arc configuration

AbstractThe Hazelton Group is a Rhaetian–Bajocian (uppermost Triassic–Middle Jurassic) volcano-sedimentary sequence that represents both the last pre-accretionary arc volcanic cycle of Stikinia and its early synaccretionary aftermath. Hazelton magmatism of central Stikinia succeeded the Late Triassic (mainly Carnian–Norian) Stuhini arc, which ceased activity as a result of end-on collision with the pericratonic Yukon-Tanana terrane. The Hazelton volcanic belt lies to the south along strike with the coeval Whitehorse trough, the synorogenic clastic basin that developed on top of the Stikinia–Yukon-Tanana collision zone. Whereas the sources of voluminous clastic sediments in the Whitehorse trough were its rapidly exhuming shoulders, the thin clastic intervals in the Hazelton Group in northwestern British Columbia were derived from local to subregional block uplifts that supplied mainly ca. 230–215 Ma zircons eroded from the plutonic roots of the Stuhini arc. Lesser components include late Paleozoic (ca. 350–330 Ma) zircons from Stikinia's basement and penecontemporaneous (ca. 205–172 Ma) zircons from Hazelton volcanic/subvolcanic sources. Reexamination of the four main volcanic fields that make up the lower Hazelton Group suggests that the main Hazelton volcanic belt formed a southward-convex magmatic arc from eastern Stikinia across the Skeena arch, including the Toodoggone and Telkwa belts, with the Spatsizi and Stewart-Iskut regions of northwestern British Columbia in its back-arc. The Whitehorse trough and Hazelton belt represent a collision zone to active arc pair. Southward advance of the arc and counterclockwise rotation of the Stikinia microplate contributed to closure against the Quesnellia arc and assembly of the inner Canadian Cordilleran terrane collage.

Petrogenesis and tectonic setting of the Pan-African Deng-Deng intrusive complex in the Lom series, Eastern Cameroon

The Deng-Deng intrusive complex belongs to the Central African Fold Belt (CAFB) in eastern Cameroon and includes granodiorite and diorite. Both rocks are classified as metaluminous to slightly peraluminous, high-K calc-alkaline, and I-type granitoids (A/CNK <1.1). Primitive mantle-normalized trace-element patterns display large-ion lithophile elements (LILE) enrichment, such as Rb, Cs, Ba and K, and depletion in high-field-strength elements (HFSEs), such as Nb, Ti, Ta and P. The studied rocks are enriched in LREEs relative to HREEs and exhibit weak negative Eu anomalies (Eu/Eu* = 0.61–0.92 and 0.59–0.67 for the granodiorite and diorite, respectively), suggesting active continental margin arc affinity. The emplacement temperatures of these granitoids are estimated between 775 and 806 °C. Combined with their diagnostic ratios (e.g., Th/Ta, Rb/Sr, Nb/La, and La/Sm), we propose that the Deng-Deng granitoids were sourced by mixing between mafic magma derived from the lithospheric mantle and felsic magma derived from partial melting of a lower crust in a convergent margin setting.

Distribution Network Voltage Arc Suppression Method Based on Flexible Regulation of Neutral Point Potential of the New Grounding Transformer

Aiming at the problems that the existing arc suppression cabinet technology cannot adjust the zero sequence voltage flexibly and the control and hardware implementation of active arc suppression equipment based on power electronics are difficult, a new method of voltage arc suppression in the distribution network based on the flexible regulation of the neutral point potential of the new grounding transformer is proposed. From the perspective of the sequence component, the variation law of the neutral point voltage before and after the closing of the tapped grounding branch of the new grounding transformer is analyzed. By selecting the appropriate initial tap position of the tap-to-ground switch, the fault phase voltage is flexibly controlled so that the fault phase voltage is reduced to below the reignition voltage to quickly solve the influence of the single-phase grounding fault, and the risk of non-fault phase insulation breakdown is reduced to ensure the stable operation of the distribution network. According to the ratio of the fault phase current to the zero sequence voltage before and after the gear inputs, whether the arc suppression of the single-phase grounding fault is completed is judged. Compared with power electronic products, the new grounding transformer has the advantages of high reliability, long service life, and low cost and has strong economy and applicability in engineering. The single-phase grounding fault model of the 10kV distribution network is built in the PSCAD/EMTDC simulation environment, and the new method of the distribution network voltage arc suppression based on the flexible regulation of neutral point potential of the new grounding transformer is verified. The simulation results show that the proposed method can effectively reduce the fault phase voltage to achieve the reliable arc suppression of the single-phase grounding fault.

Characterization of organic matter from the Cretaceous sedimentary and volcano-sedimentary strata from Livingston Island, Antarctic Peninsula: Insights from organic petrology, molecular proxies and carbon and hydrogen isotopes

Rock samples from the Early to Late Cretaceous marine and non-marine strata of Livingston Island, South Shetland Islands, Antarctica, were studied. Organic matter (OM) originates predominantly from terrestrially-derived organic particles. Mostly highly fragmented plant remains, and locally vitrinite/semifusinite as part of plant compressions/imprints or thin vitrain/fusain lenses, are present. Bulk geochemical results indicate Type III kerogen with poor hydrocarbon generation potential. Tmax and molecular proxies (i.e hopane and sterane isomerization ratios, MPI-1, etc.), together with the local presence of oily droplets, argue for an early oil window maturity, probably caused by regional volcanic activity. In contrast to the results of petrography and Rock-Eval pyrolysis, molecular composition of extractable OM is dominated by short-chain n-alkanes, saturated fatty acids (FAs) and n-alkanols implying a major contribution of autochthonous OM. This contradiction is most likely caused by decomposition of OM from plant tissues, the predominance of wood remains (i.e., xylites) and the low input of FAs from cuticular waxes. The presence of terrestrial OM is indicated by plant wax-derived lipids and resinous compounds. Prominent even carbon number predominance in the short-chain n-alkane range argue for deposition/decomposition under reducing environmental settings, most probably caused by high sedimentation rates and quick burial. Terpenoid biomarker compositions indicate contribution from conifers, whereas input from phytoplankton/algal organic matter is evidenced by C27 steroids, the presence of 4-methyl steranes and dinosterol. Low concentrations of hopanoids and C15 and C17 branched n-FAs argue for limited bacterial input. Only in one sample from Hannah Point, a difference between the δ13C values of the short-chain versus long-chain n-alkanes was obtained, arguing for mixed OM sources (i.e., autochthonous input, land plants). The presence of charred organic matter in most of the studied samples, together with the considerable concentrations of combustion-derived PAHs, argue for the common occurrence of wildfires within the terrestrial environments. Despite the active volcanic arc settings, the compound specific carbon and hydrogen isotopes do not record significant changes in climatic/hydrological conditions, although some short-term events cannot be ruled out. Instead, the δ13C and δ2H isotopic fractionation is most likely caused by the specific biosynthetic mechanisms of the plants and the global carbon and hydrogen cycles.

Iron from continental weathering dictated soft‐part preservation during the Early Ordovician

AbstractThe Fezouata Shale in Morocco is the most diverse Lower Ordovician unit yielding soft‐tissue preservation. Iron played a crucial role in the preservation of soft parts in this formation through the damage of bacterial membranes under oxic conditions and the pyritization of soft parts under the activity of bacterial sulphate reduction. However, the origin of Fe in this formation remains largely speculative. Herein, trace and rare earth elements were investigated in drilled‐core sediments from the Fezouata Shale. It is shown that a correlation exists between Fe and Al suggesting that most Fe has a detrital source. Elemental concentrations in the Fezouata Shale are most comparable to rivers and are the least similar to loess and sediments deposited near active island arcs. In this sense, continental weathering and its related Fe in river fluxes dictated occurrences of exceptional fossil preservation in the Fezouata Shale.

Analysis on the operation reliability of active intervention type arc extinguishing device

With the increase of urban power grid scale, the requirement of power supply reliability has been improved, and the active intervention type arc extinguishing device (AIT-AED) has been paid more and more attention to. As one of the effective means of grounding fault arc extinguishing, the AIT-AED has a high demand on the operation reliability, but the operation experience of AIT-AED is insufficient. Hence, the pilot application of this device was carried out and its operation situations were investigated in this paper. It is found that the setting value, control logic, accessories quality and artificial operation are the main influencing factors of operation reliability and the corresponding improved measures were proposed, which could provide references for the operation and maintenance of AIT-AED.

Age, chemistry, and tectonic setting of Miramichi terrane (Early Paleozoic) volcanic rocks, eastern and east-central Maine, USA

Volcanic rocks in the Miramichi inlier in Maine occur in two areas separated by the Bottle Lake plutonic complex: the Danforth segment (Stetson Mountain Formation) north of the complex and Greenfield segment to the south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, and rhyolite tuffs and subordinate lavas, breccias, and agglomerates. Rare basaltic tuffs and a small area of basaltic tuffs, agglomerates, and lavas are restricted to the Greenfield segment. U–Pb zircon geochronology dates Greenfield segment volcanism at ca. 469 Ma, the Floian–Dapingian boundary between the Lower and Middle Ordovician. Chemical analyses reveal a calc-alkaline suite erupted in a continental volcanic arc, either the Meductic or earliest Balmoral phase of Popelogan arc activity. The Maine Miramichi volcanic rocks are most likely correlative with the Meductic Group volcanic suite in west-central New Brunswick. Orogen-parallel lithologic and chemical variations from New Brunswick to east-central Maine may result from eruptions at different volcanic centers. The bimodal Poplar Mountain volcanic suite at the Maine–New Brunswick border is 10–20 myr younger than the Miramichi volcanic rocks and more likely an early phase of back-arc basin rifting than a late-stage Meductic phase event. Coeval calc-alkaline arc volcanism in the Miramichi, Weeksboro–Lunksoos Lake, and Munsungun Cambrian–Ordovician inliers in Maine is not consistent with tectonic models involving northwestward migration of arc volcanism. This &gt;150 km span cannot be explained by a single east-facing subduction zone, suggesting more than one subduction zone/arc complex in the region.

New geochemical constraints on the development of active continental margin in Southeast China during the Middle Permian and its tectonic implications

Two competing hypotheses that passive or active continental margins developed in South China during the Late Paleozoic are still under debate. Previous studies were mainly focused on the remnant magmatic rocks, but little attention has been paid to the contemporary sediments deposited in the back-arc basin. Therefore, a deeper knowledge of the tectonic link between the continental arc and regional basins is not only vital for understanding their tectono-sedimentary evolution, but also provide the potential to evaluate these hypotheses. Here two Middle Permian sections of bedded chert-mudstone sequence (Gufeng Formation) and an overlying siliciclastic succession (Yinping Formation) from the Lower Yangtze region, were analyzed to understand their provenance, tectonic and depositional setting, and to provide new constraints on the Late Paleozoic tectonics of the South China. Discrimination of tectonic setting indicates that the Middle Permian sedimental source rocks of the Lower Yangtze basin probably originated in a transitional setting from continental island arc to active continental margin, consistent with the development of an active margin magmatic arc along Southeast China during that time. Provenance analysis also showed that, the Gufeng Formation was mainly derived from an Andesitic arc source with mixed mafic and felsic source, whereas the Yinping Formation received detritus from a more felsic source. This provenance switching could reflect a possible tectonic transition related to the continental arcs’ evolution that from Andean-type normal/high-angle subduction to flat-slab subduction, which weakened the arc volcanism and intensified the bedrock uplift in South China. The depositional environments of the Lower Yangtze basin also evolved from an open deep ocean environment to a continental margin setting during the deposition of Gufeng Formation, and then transformed into a coastal/neritic shallow water setting during the deposition of Yinping Formation. This sedimentary evolution can be attributed to the tectonic transition during the Middle Permian.

DBS treatment in an 18-year-old with refractory dystonia due to DYT1 mutation: a case report

Introduction: The term dystonia may be defined by abnormal involuntary movements or postures due to sustained or intermittent muscle contractions. One of the most common aetiologies of isolated dystonia is due to the mutation in DYT1 gene, resulting in a disorder of abnormal regulation of gene transcription and neuronal circuit development. Of all the patients with this mutation, about 30-40% will develop symptoms of the disease. Typically, the clinical manifestation of this type of dystonia will begin from the first to third decade of life, with generalized distribution, and involving more likely the lower limbs or, less frequently, the upper limbs and trunk. Objective: To present a case of an infrequent refractory dystonia due to DYT1 gene mutation in an 18-year-old male patient that was later treated with Deep Brain Stimulation (DBS). Case report: Here we report about the case of a 18-year-old male patient affected by torsion dystonia of the neck and a segment of the upper limbs. He first exhibited symptoms when he was 15 years old and, since then, has had a series of complications, such as severe pain and recurrent pneumonia. Genetic analysis identified a DYT1 gene superexpression mutation. Previous therapies had included physiotherapy, botulinum toxin injections, drugs such as primidone and clonazepam, but all with little improvement. Due to the patient's severe torsion dystonia on his right side, it was decided to implant a DBS only in the left internal globus pallidus (GPi) posteromedial area, in a brain surgery with general anesthesia that took place in March 2018. After 10 months, the same procedure was made in the right GPi, at the subthalamic nucleus, aiming to treat his dystonic tremors located in the left part of the body. The electrodes inserted were Medtronic® 3389 and the generator was Activa RC rechargeable, with 0.5 mm spacing. The following programming was set: current of 3 mA, frequency of 130 Hz and pulse width of 90 μs. The battery of the electrode was inserted in the right side of the chest due to the patient's more severe torsion. The post-operative (PO) was successful, without any deficit, being discharged from the hospital at the PO day 4 in the first surgery and day 2 and in the second. After a 2-year follow-up period, the patient presents a normal life compared to the average of his age, without any of the symptoms or complications he had before. He regularly attends physiotherapy and fitness centres to maintain muscle training.

Active arc suppression device based on voltage‐source convertor with consideration of line impedance in distribution networks

In the non-effectively grounding distribution system, residual current under single-line-to-ground (SLG) fault threatens the safety of human being and power supply equipment. Active arc suppression device has been proved to be effective for SLG fault arc suppression when the line impedance is ignored. However, in practice, line impedance varies with the fault location and the load current flowing through the impedance brings about additional voltage drop, which increases the fault current and is not dealt with by the conventional methods. To achieve accurate SLG fault arc suppression with the existence of line impedance, the neutral-to-ground voltage reference for full ground-fault current compensation is firstly derived and a detection method is then proposed. The pre-fault and post-fault line currents are used to eliminate the influence of load current on the line impedance voltage drop. A dual-loop voltage and current controller is then designed. The prototype of active arc suppression device was developed. The results of simulation and prototype experiment validate the effectiveness of the proposed method.