Collision Phase Research Articles

The Mekkam Inlier (Eastern Morocco): A Magmatic Domain with Mixed Characteristics: Contribution of Petrographic and Geochemical Data

The Mekkam inlier is located 50 km southeast of the town of Taourirt, in northeastern Morocco. It offers a great opportunity for the study of Variscan magmatism in Morocco. This inlier is punctuated by small magmatic bodies which we will characterize through a petrographic and geochemical study to situate this inlier in its geotectonic context. The petrographic study revealed the existence of three trends: acidic, intermediate, and basic, which are represented by facies ranging from granites to basanites, including andesites, rhyolites, trachytes, dacites, quartz microdiorites, Aplite and microgranites. All these facies have a mineralogical assemblage dominated by quartz, plagioclase, oligoclase, potassium feldspar, pyroxene, and biotite; the most abundant accessory minerals are zircon and apatite. Green hornblende is found in microdiorites and dacites. The geochemical analysis, conducted through the examination of major elements, trace elements, and rare earth elements, has uncovered the presence of two distinct magmatic series: a calc-alkaline series of the island arc type or active continental margin, and another alkaline series of syn-collision. Based on this combined data, we propose that the Mekkam sector represents a magmatic arc developed within a compressional tectonic regime located above a subduction zone, which was later followed by an intracontinental collision phase.

Effects of different tennis racket string tension on forehand stroke effect and racket dynamic impact.

This study investigates the effect of varying tennis racket string tension on stroke effect and the dynamic response of the racket. Using the YSV dynamic acceleration signal acquisition system and a portable radar speed gun collect data on racket acceleration, stress-strain signals, and ball speed from 15 male athletes. Stroke accuracy and depth were assessed according to the International Tennis Number. The recorded stroke speeds were 108.87±13.57 km/h, 111.83±16.34 km/h, and 107.76±12.53 km/h for the low, medium, and high tension, respectively. A significantly higher ball speed was observed at 54lbs compared to both 48lbs and 60lbs (P <0.05). Control scores were 4.90±0.61,5.46±0.84, and 4.64±0.69 for the respective tensions. The control at 54lbs was significantly higher than at 60lbs (P<0.05). Deformation measurements were 18.53±4.90με, 16.31±4.42με, and 20.90±3.53με, with significantly lower deformation at 54lbs compared to 60lbs (P<0.05). The impact forces recorded were 381.81±48.51m/s2, 380.53±50.47m/s2, and 380.04±53.70m/s2, with no significant effect of string tension on impact force. Racket vibration frequencies were 44.14±0.48Hz, 44.08±0.35Hz, and 44.14±0.25Hz, with no significant difference among three string tensions. Rackets with three string tensions showed significantly higher vibration frequencies during the collision phase compared to before or after (P<0.01). In conclusion, string tension affect the stroke effect, racket strung at medium tension can optimize stroke effect while got milder dynamic impact, suggesting that racket strung at medium tension is recommended for tennis enthusiasts to enhance stroke performance and to decrease the risk of resonance damage in the forearm soft tissues.

Glasma phase of relativistic heavy-ion collisions

Glasma phase of relativistic heavy-ion collisions

Strange Resonances and Exotic States

In these proceedings, I discuss how strange resonances and exotic states are used as unique probes in the field of ultrarelativistic heavy-ion physics. These particles can be used to study the properties of the hadronic phase of ion-ion collisions, the hadrochemistry of the system, flow and vorticity in the hot and dense medium, and the structures of the hadrons themselves. I provide an overview of recent results to illustrate these concepts.

The Addition of Felsic Sediments to the Lower Continental Crust During the Variscan Orogeny

AbstractLower crustal metasedimentary xenoliths (garnet‐sillimanite granulites) from the Bournac breccia pipe in the Massif Central, France, provide a robust example of sediments transported to depth and incorporated into stable lower continental crust during a collisional orogeny. Dates for detrital igneous zircon range from the Archean (up to 3,300 Ma) to the Devonian and record sedimentation prior to the onset of the collisional phase of the Variscan orogeny. Metamorphic zircon and monazite document the presence of the metasediments in the lower crust by ca. 330 Ma during the later phase of Variscan collision. Zircon and monazite crystallization continued within the lower crust until ca. 265 Ma, corresponding to a period of slow cooling following an episode of ultra‐high temperature (UHT) metamorphism that peaked at 313 Ma. Zr‐in‐rutile thermometry and GASP barometry applied to these samples record conditions of 0.63–0.77 GPa and 830–910°C, which correspond to Ti‐in‐zircon temperatures from the latter part of the Variscan orogeny and geotherms in excess of typical continent‐continent collisions. Rutile in these samples remained open to Pb loss until their eruption at ca. 11.6 Ma, providing an indirect date of the Bournac eruption. These rocks record the incorporation of felsic sedimentary material into the stable deep continental crust during a collisional orogen and their residence there for over 300 Ma. More broadly, the addition of sediments to stable lower crust contributes to changes in crustal composition and has significant implications for the heterogeneity of the deep continental crust, as well as overall crustal heat production and mantle heat flow.

The structure of the f0(980) from system size dependent hadronic resonance ratios in p + p, p + Pb, and Pb + Pb collisions at the LHC

It is shown that the hadronic phase in ultra-relativistic heavy ion collisions can be used to understand the properties of the f0(980) resonance. In particular it is shown that the centrality dependence of the f0(980)/π and f0(980)/ϕ ratios depends strongly on the f0(980)→K¯+K branching ratio and whether the f0(980) is produced as a q¯q or s¯s state. These conclusions are drawn from calculations within the partial chemical equilibrium of the HRG model within Thermal-FIST as well as with the fully non-equilibrium hybrid-transport approach UrQMD. Our findings show how the hadronic phase in heavy ion collisions can be used for studies of exotic hadron properties otherwise possible only in dedicated experiments such as PANDA.

The catalogue of 1987–2023 earthquakes in the western (French) Alps north of 43.5°N

The western Alpine belt is the focal point of moderate but constant seismic activity. Numerous geodynamic and seismological studies underline the many scientific questions linked to Alpine dynamic processes and the associated rate of deformation resulting from late continental collision phases, and the assessment of seismic hazard and its associated risks. Seismic monitoring in the northern French Alps was launched in 1987 with the installation of the first seismological network, hosted by the Earth Science Observatory at Grenoble Alpes University. Since then, the network has been updated over the years, keeping pace with technical developments in seismic instrumentation, monitoring and data management. The homogenization of information described in this scientific data paper is motivated by the need for a single instrumental seismic catalogue, consisting in arrival times picks and hypocenters using the same velocity model. The final catalogue SISMalp-1987–2023 (CC-BY-4.0) contains 50,822 weak-to-moderate earthquakes with local magnitude between −1.8 and 5.0; it can serve as a basis for all general seismotectonic and risk assessment studies in the region.

Thermal and burial history of the axial Arcabuco-Floresta segment, Eastern Cordillera basin, Colombia: evidence from low-temperature thermochronology and numerical modelling

The axial Arcabuco-Floresta segment of the Eastern Cordillera basin, Colombia exhibits a complex geological history characterized by both along and across strike variations in deformation and exhumation, as well as magmatic activity, all of which provide valuable insights into the broader tectono-thermal evolution of the Andean region. In this study, we combine existing thermochronological data, with 16 new zircons (U-Th)/He and 9 new fission-track dates, and numerical modeling to investigate the thermal history in response to such anomalies across the axial Arcabuco-Floresta segment. Single grain ZHe data from Devonian to Lower Cretaceous strata range from 74 to 20 Ma. ZFT data from the same samples show a broader age distribution ranging from 200 to 70 Ma. The integration of different inverse modeling approaches suggests that cooling, here interpreted as exhumation, occurred in three distinct episodes which can each be linked to different regional tectonic interactions since the Late Cretaceous. Over this time, exhumation commenced in the northern and western parts of the basin and extended progressively through to the eastern and southern parts. The first episode, from the Late Cretaceous to Eocene is related to the accretion of different oceanic terranes related to Farallon Plate. The second, from the Oligocene to Middle Miocene, is interpreted as a probable compressional response to accretion of the Panamá-Chocó Arc, Nazca Plate and the Gorgona Terrane. The third, extending from the Middle Miocene to Pleistocene, may be associated with exhumation driven by far-field deformation resulting from the final collision phase of the Panamá-Chocó block with South America and its interaction with the Nazca and Caribbean plates. This last phase led to the complete emergence of the Eastern Cordillera and its development as an orographic barrier. No evidence was found suggesting any possible influence of thermal overprinting on the thermochronological data in the basin.

Multicyclic Phanerozoic orogeny recorded in the Qaidam continent, northern Tibet: Implications for the tectonic evolution of the Tethyan orogenic system

The growth and evolution of the Eurasian continent involved the progressive closure of major ocean basins during the Phanerozoic, including the Tethyan and Paleo-Asian oceanic realms. Unraveling this complicated history requires interpreting multiple overprinted episodes of subduction-related magmatism and collisional orogeny, the products of which were later affected by the Cenozoic construction of the Himalayan-Tibetan orogen due to the India-Asia collision. In particular, the tectonic evolution of northern Tibet surrounding the Cenozoic Qaidam Basin is poorly resolved due to several phases of Phanerozoic orogeny that have been reactivated during the Cenozoic deformation. In this study, we investigated the geology of the northern Qaidam continent, which experienced Paleozoic−Mesozoic tectonic activity associated with the development of the Eastern Kunlun orogen to the south and the Qilian orogen to the north. We combined new and published field observations, geochronologic and thermochronologic ages, and geochemical data to construct regional tectonostratigraphic sections and bracket phases of Paleozoic−Mesozoic magmatism associated with oceanic subduction and continental collision. Results suggest that the Qaidam continent experienced two major phases of subduction magmatism and collision. First, a Cambrian−Ordovician magmatic arc developed in the northern Qaidam continent due to south-dipping subduction. This phase was followed by the closure of the Qilian Ocean and the collision of the North China craton and Qaidam continent, resulting in Silurian−Devonian orogeny and the development of a regional unconformity across northern Tibet. A subsequent Permian−Triassic magmatic arc developed across the northern Qaidam continent due to north-dipping subduction. This phase was followed by the closure of the Neo-Kunlun Ocean and the collision of the Songpan Ganzi terrane in the south and Qaidam continent. These interpretations are incorporated into a new and comprehensive model for the Phanerozoic formation of northern Tibet and the Eurasia continent.

Topography Response to Horizontal Slab Tearing and Oblique Continental Collision: Insights From 3D Thermomechanical Modeling

AbstractThe horizontal propagation of slab detachment (slab tearing) is known to control lateral migration of the mountain uplift along the collisional belt. However, along‐strike differential collision due to an oblique passive margin geometry can make the topography response more complex. In this study, we employ 3D thermomechanical modeling to distinguish between the lateral migration of the mountain topography driven by slab tearing and oblique continental collision itself. In our models, slab breakoff is triggered by the transition from oceanic to continental subduction, occurring earlier on one side of the passive margin than on the other due to the initial oblique configuration. However, once slab breakoff has begun, it spreads horizontally in the form of tearing at high velocity (∼38–118 cm yr−1), and associated topographic uplift also propagates with the same velocity. In contrast, the along‐strike migration of subsequent continental collision and related topographic uplift propagation is typically much slower (∼2–34 cm yr−1). Similarly, the vertical magnitude of surface uplift caused by slab tearing is higher (up to 10 mm yr−1) than the following collision phase (&lt;4 mm yr−1). The parametric analysis reveals that slab tearing velocity and the associated horizontal propagation of mountain uplift depends on obliquity angle and slab age, whereas the migration of collision‐induced topographic growth is controlled by the convergence velocity and obliquity angle. Finally, we show that presence of microcontinental block detached from the passive margin leads to spatial and temporal transition from horizontal to vertical slab tearing and more intense syn‐collisional mountain building.

Variscan lithotectonic units of the Suchý massif in the Strážovské vrchy Mts., Western Carpathians – products of sedimentary, tectonometamorphic and granite forming processes

The present geological investigation of the Pre-Alpine structure of the western part of Strážovské vrchy Mts (the Suchý massif; Western Carpathians) has distinguished three lithologically distinct Variscan lithotectonic units, which originated (1) in the deeper parts of oceanic basin (prevailingly metapelites with different content of organic matter, metabasalts, metacarbonates?); (2) sediments of the continental slope (flyschoid sediments with a predominance of greiwacke sediments; both VmD0); (3) a unit of continent basement primarily of pre-VmD0 granitic composition (orthogneiss). These rock sequences of differing geotectonic provenances were amalgamated and metamorphosed in the pre-intrusive (Pre-Mississipian) stage; pre-VmD2). Regarding the Variscan polyorogenic evolution, Variscan processes in Tatricum represent the Meso-Variscan evolution (VmD). The maximum P-T conditions of orogenic (regional) metamorphism (up to 610 °C and 7.5–8.5 kbar) were not sufficient for more extensive anatexis. Field observations indicated that the production of a limited volume of granitoid melts occurred mainly at the contacts of amalgamated lithotectonic units. Probably due to the heat, produced by the hot line below the collisional orogen and contributing also to unroofing processes (in orogenic phase VmD2) there started new granitization process. This stage of Mississippian VmD2 granite formation is associated with the emplacement of various types of granitoid magma, encompassing the oldest granodiorites with frequent schliers, representing a poorly differentiated and poorly mobile crystal slurry (present in the SE part of the territory). In the highly evolved collision phase, masses of leucogranites intruded comformably with the deformation plan in the metamorphic complexes, interacting with surrounding metamorphic rocks in shallower crustal conditions and causing their contact metamorphic overprint (up to 590 °C and 3–4 kbar). The syn-deformation character of leucocratic granites is proved by the orientation of biotite flakes parallel to the deformation plane of surrounding metamorphites. Part of leucogranites, especially in the central parts of the bodies, is omnidirectional. The stress field acted not only during the intrusion of the leucogranite magma, but also in the subsolidus stage. The final stage of this process is the formation of large bodies of pegmatites in extensional VmD2 fractures oriented at a large angle to the main stress component. The texture of the grey blocky K-feldspar pegmatites and the lack of H2O-bearing minerals point to pneumatolytic fracturing in a subsequently opened environment in VmD2. The final stage of VmD2 is represented by intrusions of I-type granodiorites with indications of magma mixing, or mingling. The chemical dating of monazites in granitoids allowed to date individual phases of granitization process in the range of 360–345 Ma, which youngest ages correspond with the formation of pegmatites. Dating of monazite in metamorphic rocks points to their thermal overprint during granitization process (360–350 Ma), having already earlier metamorphic overprint (380–370 Ma). The scenario of placement of granitoid intrusions is consistent with the decompression regime (in VmD2) after the end of VmD1c crustal thickening until the fracturing of the crustal block with of I-type magma intrusions of deeper origin. After this period, the exhumation of crystalline blocks, partial diaphtoresis and later surface erosion continue until the Lower Triassic. The re-submergence of the crystalline complexes is associated with a low degree of Alpine metamorphic reworking.

Geochronology and Sr-Nd-Pb-Hf-O isotopes of Neoproterozoic orthogneisses in the Jiamusi Block, NE China: Implications for tectonic origin and secular crustal evolution

There is a considerable debate as to when and how the continental crust has evolved to its present state. Existing studies of crustal evolution have focused on large cratons, whereas microcontinents within accretionary orogenic belts have been conspicuously neglected. The controversial definition of tectonic origins and lack of Precambrian basement rocks of microcontinents, lead to an equivocal issue of their secular crustal evolution processes. Here we present zircon U-Pb ages and Hf-O isotopes, as well as whole-rock elemental and Sr-Nd-Pb-Hf isotopic data for the newly discovered Neoproterozoic orthogneisses from the Jiamusi Block of NE China in the easternmost Central Asian Orogenic Belt (CAOB). LA-ICP-MS U-Pb dating of zircons from the orthogneisses recorded two episodes of magmatism at 896–886 Ma and 752–726 Ma. Combined with zircon Hf-O isotopes and REE patterns, the peak of the late Pan-African metamorphism is proved to occur at 566–565 Ma, demonstrating the linkage between the Jiamusi Block and the Kuunga-Pinjarra interior orogen of East Gondwana. In conjunction with compiled zircon U-Pb-Hf isotopic data of Neoproterozoic-Mesozoic granitoids, a new crustal evolution model has been established for the Jiamusi Block, which defines a continuous rather than an episodic crustal growth pattern during the Neoarchean to Neoproterozoic, as well as four stages of crustal reworking at 940–880 Ma, 780–660 Ma, 560–460 Ma, and 340–240 Ma. The enhanced and reduced rates of crustal growth during the progressive period are related to the assembly-breakup and collision phases of supercontinent cycles, respectively. Our study along with previous researches on eastern CAOB not only highlights that the Phanerozoic accretionary orogen underwent diverse forms of crustal growth with most of the continental crust formed during the Precambrian, but also provides an example to show the heterogeneity of the lower continent and the complexity of global secular crustal evolution.

Performance analysis of a collision channel with abandonments

We consider a Markovian retrial queueing system with customer collisions and abandonment in the context of carrier-sense multiple access systems. Using z-transform techniques, we find a set of first-order differential equations for the probability generating functions of the orbit size when the server is empty, busy, or in the collision phase. We then rely on series expansion techniques to extract approximations for relevant performance measures from this set of differential equations. More precisely, we construct a numerical algorithm to calculate the terms in the series expansions of various factorial moments of the orbit size. To improve the accuracy of our series expansion approach, we apply Wynn’s epsilon algorithm which not only speeds up convergence, but also extends the region of convergence. We illustrate the accuracy of our approach by means of some numerical examples, and find that the method is both fast and accurate for a wide range of the parameter values.

The distribution and formation of mine body in Tibet

The Gangdise metallogenic belt has been a popular mineral mine since it was discovered due to its various types of mineral elements, such as copper, iron, zinc, molybdenum, silver, gold, and bismuth, attracting millions of researchers. Moreover, the possible copper output that has been indicated here has already reached 3,000,000 tons. The deposit here is a typical skarn type ore rich in garnet. The article mainly introduces how the minerals in Gangdise metallogenic belt is distributed and investigates how the Gangdise metallogenic belt is formed. Some hypotheses in this article refer to previous investigations in the Gangdise metallogenic belt. This paper concludes that the reasons for the formation of the major ore deposit in Gangdise metallogenic can be regarded as the movement of the Eurasian Plate and India Plate, which can also be defined as the main collision phase, though other geologic changes altered the distribution of the ore body later.

Walking control of semi-passive robot via a modified Q-learning algorithm

The analysis and control of stability of passive biped robot has been the subject of an in-depth study because of its unique characteristics. This work gives a new perspective aiming at a force applied on foot of collision phase of walking process of passive robot, which is a completely new way of applying impulse force that is different from the previous. Therefore, the new equation has been derived due to this force which is not parallel to the support leg to provide further analysis for the study. Besides, this paper combines the characteristics of passive walking with the process of reinforcement learning, and an improved algorithm thus was designed to calculate the value of the control force. The simulation results show that control method designed in this article can not only make the unsteady passive robot achieve stable walking, but also have a quick control speed. Furthermore, the selection range of initial values is expanded by using this method, which provides a convenient reference for the later research work.

Stability of initial glasma fields

A system of gluon fields produced in the earliest phase of relativistic heavy-ion collisions, which is called , can be described in terms of classical fields. Initially there are chromoelectric and chromomagnetic fields along the collision axis. A linear stability analysis of these fields is performed, assuming that the fields are space-time uniform and using the SU(2) gauge group. We apply Milne coordinates and the gauge condition, which are usually used in studies of glasma. The chromoelectric field is in the Abelian configuration with the corresponding potential linearly depending on coordinates, but the chromomagnetic field is in the non-Abelian configuration generated by the potential of noncommuting components. The chromomagnetic field is found to be unstable, and the growth rate of the unstable mode is derived. Our findings are critically debated and confronted with the numerical simulations by Romatschke and Venugopalan, who found that the evolving glasma is unstable due to the Weibel instability, which is well known in electromagnetic plasma. Published by the American Physical Society 2024

First results of the upgraded ALICE Inner Tracking System in LHC Run 3

Major upgrades of the ALICE experiment at CERN were completed during the LHC Long Shutdown 2 (2019–2021). The ALICE detector is currently taking data and has been doing so from the start of the third period of operation of the LHC (Run 3) on July 5th, 2022. One key part of these upgrades is the new Inner Tracking System (ITS2), a full silicon-pixel vertexing and tracking detector constructed entirely with CMOS monolithic active pixel sensors (ALPIDE). The ITS2 consists of three inner layers (50 μm thick sensors) and four outer layers (100 μm thick sensors) covering 10 m2 and containing 12.5 billion pixels with a pixel pitch of 27 μ m × 29 μm. It offers a significant improvement in impact-parameter resolution and tracking efficiency, thanks to the increased granularity, the very low material budget (0.35% X0 /layer in the inner barrel) as well as a smaller beam pipe radius.The ITS2 was successfully installed in the ALICE experiment in May 2021, followed by a period of comprehensive on-site commissioning, before starting data taking in July 2022. In this paper, the detector construction and commissioning will be introduced briefly. The performance results from the first phase of proton-proton collisions recorded to date in LHC Run 3 will be discussed in detail, which include detector calibration, long-term evolution of the ALPIDE sensor threshold and noise, and the first measurement of the impact parameter.

Exploring the hadron gas phase of relativistic heavy-ion collisions at the LHC

The lifetimes of hadronic resonances are comparable to the one of the hadron gas phase created in the late stages of high-energy nuclear collisions. Therefore, a significant fraction of resonances decay inside a high-density medium and their decay daughters rescatter with nearby hadrons destroying their initial kinematic correlations. The competing effect of resonance regeneration via pseudo-elastic interactions of hadrons interplays between the rescattering effect, modifying the measured yields and transverse-momentum spectra of hadronic resonances. These effects are studied by measuring the production yield ratio of resonances to the corresponding long-lived particle as a function of the hadronic lifetime, i.e. charged-particle multiplicity. In addition, measurements of the differential yields of resonances with different masses, quark content, and quantum numbers help in understanding particle production mechanisms, strangeness production, and parton energy loss. This article reports recent ALICE measurements on resonances and the use of the experimental input in a partial chemical equilibrium-based thermal model to constrain the kinetic freezeout temperature. This is a novel procedure that is independent of assumptions on the flow velocity profile and the freeze-out hypersurface.

The Earliest Phase of Relativistic Heavy-ion Collisions

The Earliest Phase of Relativistic Heavy-ion Collisions

Effect of pre-stress on dynamic finite element analysis of the temporomandibular joint

The pre-stress of the temporomandibular joint (TMJ) at the intercuspal position (ICP) was often neglected, which would cause errors in the finite element analysis. The purpose of this study was to investigate the effect of pre-stress on dynamic finite element analysis of the TMJs. One healthy female adult was recruited for medical imaging and motion data acquisition of the reference position (RP) to the ICP and the clicking teeth. The three-dimensional maxillofacial model including the maxilla, mandible, articular cartilages, discs, and discal attachments was reconstructed. Motion from the RP to the ICP was simulated to obtain pre-stress at the ICP. Two groups of the clicking teeth were simulated: (1) the group without pre-stress (GWoP); (2) the group with pre-stress (GwP). Significant differences were found between the two groups at the initial moment of movement, during the open-mouth phase, and during the collision phase between the upper and lower teeth. The maximum difference in the discal contact stress between both groups was even more than double. The relaxation of the TMJ at the beginning of the mouth opening was simulated in the GwP. In addition, an increase in the TMJ stress during teeth tapping was simulated in the GwP. These were not reflected in the GWoP. If pre-stress at the ICP was not considered, part of the true results would be lost. It is necessary to consider pre-stress in the dynamic finite element analysis of the TMJ.