Stages Of Collision Research Articles

Geochemistry and depositional environment of black shale beds of the Belata Formation, Peninsular Malaysia

Shale deposits from Belata Formation outcrops were examined geochemically and mineralogically to establish their paragenesis and, subsequently, to identify factors that govern their depositional environment. Fifty representative samples were examined through SEM/EDX, XRD and XRF. The findings show the mineralogical composition was abundant in quartz, with pyrite and calcite in trace amount. Zr–TiO2 bivariate diagram showed predominantly felsic and intermediate igneous rocks, suggesting that the shales may be coming from the hidden basement rocks of Peninsular Malaysia. The diagenetic controls on the geochemistry are suggested by the changes in compositional trends. The samples exhibit CIA values ranging from 62.2 to 80.2, and PIA values ranging from 65 to 100. According to the V/Ni, Ni/Co, and V/Cr ratios, these black shales were formed in a suboxic environment. Additionally, the high V/Ni ratios (1.47) point to a marine source for the organic content that gives the shales their dark color. The paleoclimate during deposition was interpreted to be semiarid to warm. The black shale samples are inferred to have originated from a passive margin tectonic setting that followed continental collision and rifting stages of the foreland basin development phase of Peninsular Malaysia based on geochemical proxies and associated diagrams.

Late Paleoproterozoic collision-related granitic magmatism in the Cuoke Complex, SW China: New evidence for the early evolution of the Yangtze Block

The Paleoproterozoic tectonic evolution of the southwestern Yangtze Block has been ambiguous due to the scarce preservation of geological records, confusing the history of the entire Yangtze Block in the Nuna supercontinent. We here report an integrated study involving petrology, whole-rock geochemistry, zircon U-Pb geochronology and Hf-Nd isotopes of the recently identified late Paleoproterozoic granitoids from the Cuoke Complex in the southwestern Yangtze Block. LA-ICP-MS zircon U-Pb dating reveals three episodes of granitic magmatism at ca. 1.94 Ga, 1.89 Ga, and 1.85 Ga. Geochemically, the ca. 1.94 Ga albite granites (AGs) and ca. 1.89 Ga and 1.85 Ga monzogranites (MGs) exhibit features of I-type granite, while the ca. 1.85 Ga AGs display characteristics of A-type granite. The zircon εHf(t) values range from −13.0 to −8.1 for the 1.94–1.89 Ga granitoids and from −8.9 to −7.2 for the ca. 1.85 Ga granitoids, with two-stage model ages of 3.3–3.1 Ga and ca. 3.0 Ga, respectively, indicative of their derivation from remelting of Mesoarchean crustal materials. The relatively low heavy rare earth elements (HREEs) (e.g., Yb < 1.9 ppm) and Y (<18 ppm) contents, and moderately negative Eu anomalies of the ca. 1.94–1.89 Ga granitiods suggest they may have been produced in a late collisional or earliest post-collisional setting. The ca. 1.85 Ga AGs and MGs were probably formed in a post-collisional setting indicated by their high HREE (e.g., Yb > 1.9 ppm) and Y (>18 ppm) contents and strongly negative Eu anomalies. Combined with available data, we provisionally divided the tectonic evolution of the southwestern Yangtze Block into four stages: 1) ca. 2.01 Ga subduction, 2) ca. 1.97–1.95 Ga metamorphism associated with collision events, 3) ca. 1.94–1.89 Ga late collisional or earliest post-collisional stage, and 4) ca. 1.85 Ga post-collisional extensional stage. The subduction and collision of the southwestern Yangtze Block initiated slightly later than the northern part, but their near-synchronous tectonic process since ca. 1.97 Ga suggest they may have collaged together at that time. The ca. 1.94–1.89 Ga and ca. 1.85 Ga late collisional to post-collisional granitic magmatism likely recorded the convergence of discrete Archean rock provinces of the Yangtze Block during the Nuna supercontinent assembly.

An analytical method for evaluating the structural resistance of plate structures under in-plane impact load in ship-side collision scenarios

Ship collision accidents occur occasionally and it is of great significance to develop rapid prediction method for structural response. This paper proposes a new analytical method to predict the crushing resistance of the deck and bulkhead under head-on and oblique collision scenarios by a raked bow. The structural deformation modes of them are studied firstly through the numerical simulations and the analytical models are then established, respectively. In the analytical model, the deck structure is divided into four types of components and corresponding formulas are derived based on the upper-bound theorem of plastic deformation analysis. On the basis of theoretical analysis and statistical studies, a semi-analytical formula is also developed for predicting the structural resistance of the bulkhead under in-plane impact loads. The analytical method developed in this paper considers the damage evolution in different collision stages and the coupling effects from stiffeners. Through the comparative verification of multiple collision scenarios, the results of the newly proposed analytical method and semi-analytical formula are in good agreement with the numerical results. The research outcomes could highly benefit the engineering application for the damage assessment of plate structures in the case of head-on and oblique collision.

Nuclear viscosity estimated by dynamics of neck formation in the early stage of nuclear collision

The very early stage of the coalescence of two nuclei is studied and used to estimate the nuclear viscosity. The time evolution of the neck region has been simulated by the unified Langevin equation method, which is used in the analysis of heavy-ion collisions from the approaching stage to the fusion-fission stage. It is found that the transition from viscous to inertial coalescence that appeared in the neck growth of macroscopic drops can also be seen in the present simulation in nucleus–nucleus collisions. The dynamics of neck growth is analyzed in terms of the hydrodynamical formula and the viscosity coefficient of nuclear matter is estimated using the analogy of macroscopic drops.

The photon production and collective flows from magnetic induced gluon fusion and splitting in early stage of high energy nuclear collision

We present an event-by-event study of photon production in early stage of high energy nuclear collisions, where the system is dominant by highly occupied of gluons and initialized by McLerran-Venugopalan model. The photons are produced through the gluon fusion and splitting processes when strong magnetic field is included. We study the spectra and collective flows of the photons and show their dependence on transverse momentum qT. It is found that in our approach the photons from boost invariant evolving glasma provide visible enhancement on spectrum and obvious contribution on v2 of the total direct photons. The results, by weighting on top of parton-hadron-string dynamics (PHSD) model, agree even better with experiment measurements in Au-Au 20%-40% centrality collisions at sNN=200 GeV.

Kahi mélange complex in Kurram and Waziristan, NW Pakistan: An integrated approach for tectonic implications to India–Afghan suturing

The Kahi mélange complex in the Waziristan and Kurram sector (N–W Pakistan) is one of the several Neotethyan ophiolite–mélange complexes exposed along the westernmost margin of the Indian plate, preserving significant information on pre, syn and post–collision tectono–stratigraphic evolution of collision tectonics between the Indian plate and the Afghan block. It consists of highly dismembered ophiolitic and sedimentary units. Petrographic and field observations of mafic and ultramafic rocks within the ophiolitic unit, reveal a complete, but dismembered ophiolite suite similar to the Waziristan Ophiolite (WO) to its southwest. The sedimentary units consist of syn–orogenic deposits, turbidites and slope sediments of Campanian age as constrained by the Late Cretaceous radiolarians (Stichomitra communis Squinabol) and planktonic foraminifera (Rodotruncana Calcarata). From the structural point of view, the dismembered ophiolitic units represents the highest tectonic edifice. It’s overthrusting onto the Campanian sedimentary unit constraints the onset of the collision between the Indian plate and Afghan block to the Late Cretaceous. The subsequent obduction of combined ophiolite–sedimentary units over the brecciated Late Paleocene Lockhart Formation of Indian plate margin constraints the time of the end of the collisional stage. The unconfirmable deposition of the marine Patala Formation, Late Paleocene–Early Eocene in age, above the Kahi mélange complex documents the closure of Neotethys in the Early Eocene. In conclusion, our findings document that the Kahi mélange complex represents a typical polygenetic mélange formed by the superposition of two different dismembered units (the ophiolitic and the sedimentary units) coupled as a result of at least two tectonic events in a subduction–accretion setting related to the collision between the Indian plate and the Afghan block.

Gluon radiation from a classical point particle: recoil effects

The gluon radiation spectrum of a classical particle struck by a sheet of colored glass, is a key ingredient in understanding the distribution of energy and baryon density in the fragmentation region, particularly in the initial stages of heavy ion collisions. However, the currently known classical spectrum has a troublesome high-momentum tail (Kajantie et al. in Phys. Rev. D 100(5):054011, 2019; Phys Rev D 101(5):054012, 2020). By comparing tree-level bremsstrahlung of a spin-less quark to the above-mentioned known result, we propose an interpolating formula that takes into account the recoil of the struck particle, and therefore produces the correct perturbative behaviour at high momentum of the radiated gluon.

Ore genesis of the Mengya'a distal Pb–Zn deposit in the Lhasa terrane, Tibet, China: Constraints from in situ garnet U–Pb dating and C–H–O–Sr isotopes

A large amount of distal skarn Pb–Zn deposits without any causative intrusions exposed have been discovered along the eastern Nyainqêntanglha metallogenic belt (NMB) in the Gangdese region, Tibet, China. As a typical distal skarn Pb–Zn deposit in the east of NMB, the Mengya'a deposit is adjacent to the Longmala Pb–Zn ± Cu ± Fe deposit. However, the linkage between these two deposits is not unclear due to the chaotic dating results. In situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) U–Pb dating of reddish‐brown and yellow‐green garnet from Mengya'a yielded lower intersect ages of 53.6 ± 3.1 and 52.4 ± 4.4 Ma, respectively, indicating that Pb–Zn mineralization took place during the main collision stage of the India–Asia plates. The δDSMOW values of garnet, quartz and calcite vary from −148.4‰ to −140.4‰, −123.5‰ to −115.3‰ and −127.9‰ to −121.3‰, with the δ18OH2O values ranging from 5.8‰ to 6.6‰, 0.4‰ to 3.7‰ and 1.0‰ to 1.7‰, respectively. The δ13CV‐PDB and δ18OSMOW values of calcite range from −8.2‰ to −4.7‰ and 9.8‰ to 18.6‰, respectively. These C–H–O isotopic compositions of hydrothermal minerals indicate that the ore‐forming fluids were initially derived from the magmatic water with progressive input of meteoric water from the prograde stage to the retrograde stage. The 87Sr/86Sr(53 Ma) ratios of sphalerite (0.72321–0.73474) are consistent with those of Ando gneiss in the Lhasa‐Golmud area, indicating that the basement gneiss makes a great contribution for the source of ore‐forming materials. The newly obtained garnet U–Pb ages at Mengya'a are consistent with those of mineralization and causative intrusion in the Longmala Pb–Zn ± Fe ± Cu deposit, suggesting that the Mengya'a and Longmala deposits constitute an integrated distal skarn‐type system. This proposed hypothesis suggests that the Fe–Cu ± Pb ± Zn mineralization within the contact zone should focus on the locations beneath the identified Pb–Zn orebodies at Longmala and Pb‐21 orebody at Mengya'a.

Impact of a Water Microjet on a Microfiber

The transverse impact of a pulsed water microjet on individual cylindrical fibers is studied. The stages of ejection, breakup, and collision of the microjet were recorded by high-speed photography. A significant deceleration of the microjet by the fiber and its splitting into two parts were revealed. The mechanisms of the observed phenomena and the influence of various factors are discussed.

Correlation of heavy-flavour hadron production and charged-particle multiplicity in pp collisions measured by ALICE

Heavy-flavour (HF) quarks, i.e. charm and beauty, are produced in the early stages of ultra-relativistic collisions via hard scattering processes. The measurement of heavy flavour as a function of charged-particle multiplicity not only provides information on how the production mechanisms are influenced by the event activity, but can also be considered as a tool to test the role of multiple parton interactions. Furthermore, charged-particle multiplicity studies are essential for reference measurements, to tune theoretical models and to provide information on the global characteristics of events. In ALICE, charged-particle multiplicity and heavy-flavour production in the hadronic and electronic decay channels are measured at central rapidity while HF-decay muons and J/ψ → μ + μ − are measured at forward rapidity. In this contribution, results will be presented on relative J/ψ, average D-mesons and leptons from HF hadron decay yields as a function of charged-particle multiplicity in proton-proton (pp) collisions at , 7, 8 and 13 TeV. These results will also be compared to theoretical model calculations.

Recent ALICE results on quarkonium production in nuclear collisions

Quarkonium production has long been regarded as a potential probe of deconfinement in nucleus-nucleus collisions. Recently, the production of J/ψ via regeneration within the quark-gluon plasma (QGP) or at the phase boundary has been identified as an important ingredient for the interpretation of quarkonium production results from lead-lead collisions at the Large Hadron Collider (LHC). Quarkonium polarization could also be used to investigate the properties of the hot and dense medium created at LHC energies, as well as the initial stages of the heavy-ion collision. In this contribution, the latest ALICE quarkonium results are presented and discussed. These include, among others, the nuclear modification of (prompt, non-prompt and inclusive) J/ψ, the ψ(2S) production, and the J/ψ polarization, all measured in lead-lead collisions at the LHC. The results are compared with available theoretical model calculations.

Jet polarisation in an anisotropic medium

We study the evolution of an energetic jet which propagates in an anisotropic quark-gluon plasma, as created in the intermediate stages of ultrarelativistic heavy-ion collisions. We argue that the partons of the jet should acquire a non-zero average polarisation proportional to the medium anisotropy. We first observe that the medium anisotropy introduces a difference between the rates for transverse momentum broadening along the two directions perpendicular to the jet axis. In turn, this difference leads to a polarisation-dependent bias in the BDMPS-Z rates for medium-induced gluon branching. Accordingly, the daughter gluons in a branching process can carry net polarisation even if their parent gluon was unpolarised. Using these splitting rates, we construct kinetic equations which describe the production and transmission of polarisation via multiple branching in an anisotropic medium. The solutions to these equations show that polarisation is efficiently produced via quasi-democratic branchings, but then it is rapidly washed out by the subsequent branchings, due to the inability of soft gluons to keep trace of the polarisation of their parents. Based on that, we conclude that a net polarisation for the jet should survive in the final state if and only if the medium anisotropy is sizeable as the jet escapes the medium.

Geochronology, Petrogenesis and Tectonic Setting of the Late Jurassic I‐type Granites in the North Qinling Orogenic Belt, Central China

AbstractThe North Qinling Orogenic Belt (NQOB) is a composite orogenic belt in central China. It started evolving during the Meso–Neoproterozoic period and underwent multiple stages of plate subduction and collision before entering intra‐continental orogeny in the Late Triassic. The Meso–Cenozoic intra‐continental orogeny and tectonic evolution had different responses in various terranes of the belt, with the tectonic evolution of the middle part of the belt being particularly controversial. The granites distributed in the Dayu and Kuyu areas in the middle part of the NQOB can provide an important window for revealing the geodynamic mechanisms of the NQOB. The main lithology of Dayu and Kuyu granites is biotite monzogranite, and the zircon U‐Pb dating yielded intrusive ages of 151.3 ± 3.4 Ma and 147.7 ± 1.5 Ma, respectively. The dates suggest that the biotite monzogranite were formed at the end of the Late Jurassic. The whole‐rock geochemistry analysis shows that the granites in the study areas are characterized by slightly high SiO2 (64.50–68.88 wt%) and high Al2O3 (15.12–16.24 wt%) and Na2O (3.55–3.80 wt%) contents. They are also enriched in light rare earth elements, large ion lithophile elements (e.g., Ba, K, La, Pb and Sr), and depleted in high field strength elements (HFSEs) (e.g., Ta, Nb, P and Ti). Additionally, the granites have weakly negative–slightly positive Eu anomalies (δEu = 0.91–1.19). Zircon Lu‐Hf isotopic analysis showed εHf(t) = –6.1—‐3.8, and the two‐stage model age is T2DM(crust) = 1.5–1.6 Ga. The granites in the study areas are analyzed as weak peraluminous high‐K calc‐alkaline I‐type granites. They formed by partial melting of the thickened ancient lower crust, accompanied by the addition of minor mantle‐derived materials. During magma ascent, they experienced fractional crystallization, with residual garnet and amphibole for a certain proportion in the magma source region. Comprehensive the geotectonic data suggest that the end of the Late Jurassic granite magmatism in the Dayu and Kuyu areas represents a compression–extension transition regime. It may have been a response to multiple tectonic mechanisms, such as the late Mesozoic intra‐continental southward subduction of the North China Craton and the remote effect of the Paleo‐Pacific Plate subduction.

Formation of authigenic grey monazite: A palaeo-thermal anomaly marker in very-low grade metamorphic rocks?

Reassessment of France’s rare earth element (REE) potential led us to investigate REE behaviour in the black shales of the Middle Ordovician Angers-Traveusot Formation in central Brittany (France). This study focuses on the distribution of nodular grey monazite (up to 200 g/t) within the shales, which formed in response to the diagenetic and low-grade metamorphic evolution of the studied area. Whole rock geochemistry, rock–eval pyrolysis and evolution of clay mineral crystallinity were firstly used to determine temperature and mass transfer conditions in the black shales. Then, monazite texture, composition and U–Pb in-situ dates were determined, and correlated with the diagenetic/anchimetamorphic conditions. Nodular monazite appears in the Ordovician black shales at the transition between high-grade diagenesis and the anchizone metamorphic facies, in response to processes controlled by competing influences such as organic matter maturation, Fe oxide/hydroxide reduction and clay transformation with accompanying fluid release. Monazite occurs mainly as elongated nodules, up to 2 mm in diameter that are characterised by their grey colour caused by an abundance of host-rock mineral inclusions. Monazite nodule compositions are zoned with Nd and middle REE-rich cores surrounded by Ce-rich rims, with no evidence of inherited domains. Ce-monazite also occurs as a replacement of nodular monazite or in late-stage fractures. Zoned nodular grey monazites were dated at ca. 403.6 ± 2.9 Ma, which is proposed to record the high heat flux that led to the anchimetamorphic conditions found at the base of the Angers-Traveusot formation, prior to the Variscan deformation. Crystallisation of the metamorphic Ce-monazite occurred at two periods, dated at 382.6 ± 2.9 Ma and 349.6 ± 6 Ma, which correspond to pre-collisional and collisional tectono-metamorphic stages respectively. Nodular grey monazite constitutes an interesting alternative economic solution because of its very low content in both Th (X¯=2160 ppm) and U (X¯=145 ppm) and negligible radiological impact if mined. However, placers currently display a limited economical interest.

Tracking a magmatic arc within a confined orogen: New evidence from the Araçuaí orogen (SE Brazil)

By comparison with igneous rock assemblages of well-exposed modern magmatic arcs and their typical calc-alkaline, magnesian, I-type signatures, many deeply eroded magmatic arcs have been characterized worldwide, unraveling ancient plate margins. Since the 1980's, different assemblages of Ediacaran to Cambrian magmatic rocks have been systematically mapped and characterized according to their distinctive petrographic, structural, lithochemical, geochronologic, and isotopic features, allowing to establish the pre-collisional, collisional, and post-collisional stages of the Araçuaí orogen (SE Brazil). Among them, the tonalitic-granodioritic batholiths and stocks with calc-alkaline, magnesian, I-type signatures, rich in dioritic to mafic enclaves, and related metavolcano-sedimentary successions compose a magmatic arc formed in the early Ediacaran, the Rio Doce magmatic arc. Extending for more than 1000 km along the Araçuaí-Ribeira Orogenic System (AROS), the Rio Doce arc shows a hybrid isotopic signature and crustal inheritance, compatible with modern magmatic arcs built on continental active margins. We present new field, petrographic, and lithochemical studies, coupled with U–Pb (LA-ICPMS) geochronology and isotopic (in-zircon Lu–Hf and whole-rock Sm–Nd) analysis, unraveling the least evolved isotopic signatures ever found for tonalitic-granodioritic plutons of the Rio Doce magmatic arc, and a comprehensive data comparison with modern magmatic arcs. The studied Santa Tereza and Jequitibá suites comprise tonalitic-granodioritic and Opx-bearing charnockitic rocks, with calcic-to-alkali-calcic-magnesian I-type signature, associated with gabbroic rocks. Zircon U–Pb data yielded Concordia ages of 612 ± 3 Ma (Santa Tereza) and 594 ± 3 Ma (Jequitibá) for magmatic crystallization, and 580 ± 5 Ma to 571 ± 3 Ma for metamorphic recrystallization, with associated εNd(612Ma) values from −0.06 to −7.05 (TDM model ages: 1.4–2.04 Ga), and εNd(594Ma) values from −6.67 to −8.8 (TDM model ages: 1.64–1.87 Ga). The zircon εHf(t) (+2.3 to −4.8) and Hf TDM model ages (1.33–1.65 Ga) assigned a moderately juvenile to evolved signature for the Santa Tereza suite, while the Jequitibá suite (εHf(t): −1.7 to −36.4; TDM model ages: 1.33–3.21 Ga) shows a more evolved signature. Altogether, data from the Rio Doce arc are similar to typical continental-margin magmatic arcs with the involvement of mantle melts and/or melting of juvenile crust, suggesting a westward slab retreat during ocean-floor subduction within the Araçuaí confined orogen.

Numerical constraints on the one‐stage and two‐stage Greater India collision models

AbstractIndia‐Asia collision is generally believed to have collided since 55 ± 5 Ma, with a total amount of convergence of 2900–4400 km. Besides the overriding Tibetan lithospheric shortening, a large amount of convergence has to be accommodated by the subducting plate of Greater India. Three typical India‐Asia collision models have been proposed, including the Greater Indian Continent (GIC) model, Intra‐Oceanic Arc model and Greater Indian Oceanic Basin model. In this study, a large‐scale 2D numerical model, driven by the reconstruction‐based India‐Asia convergence rate, have been conducted to evaluate these three major models. The model results indicate that the one‐stage GIC model favours later initial collision at ≤50 Ma. For the two‐stage collision, the large amount of convergence can be easily accommodated by modifying the length of oceanic subduction after the first stage of continental collision. This study provides systematic numerical constraints for the favourable conditions of each model.

Detrital zircon U–Pb-Hf isotopes-based reconstruction of the depositional history of (ultra)high-temperature metamorphic rocks from the Socorro-Guaxupé Nappe (southern Brasília orogen, Brazil)

Deciphering the provenance of paraderived rocks that underwent high-to ultrahigh (HT-UHT) temperature metamorphism is a challenging task. Such metamorphic conditions can generate protracted zircon U–Pb age records of unclear meaning. However, the combination of U–Pb and Lu–Hf in zircon geochronology might be used as a powerful tool in order to retrieve the geological significance of geochronological data and track the signature of possible protosources. Six samples of ortho- and paraderived rocks from the São João da Mata complex in the Socorro-Guaxupé Nappe (SE Brazil), a section mainly containing a continental magmatic arc built at the margins of the Paranapanema paleocontinent affected by HT-UHT metamorphism have been investigated. U–Pb and Lu–Hf isotopic analyses were carried out to evaluate disturbances in the U–Pb system, identify minimum crystallization ages and the Lu–Hf signatures of protosources and protoliths. Five protosources were identified, being four showing crustal Hf signatures (εHf(804-776) = −16 to −2) and minimum U–Pb ages between ca. 804 Ma and ca. 776 Ma, and one with a moderately juvenile Hf signature (εHf(816) = +3 to +9) and a minimum U–Pb age of ca. 816 Ma. The moderately juvenile signature suggests contribution of an island or continental arc-related source. The remaining protosources exhibit similar Lu–Hf signatures to those of orthoderived rocks found within the Socorro-Guaxupé Nappe. We propose that the analyzed paraderived rocks were deposited in a restricted, arc-related setting, that evolved through the following stages: i) an island to early-continental arc stage, with a maximum depositional age of ca. 816 Ma; ii) a continental arc setting, recorded by the protosources with crustal signatures and exhibiting a maximum depositional age of ca. 776 Ma; iii) HT-UHT metamorphism between ca. 690–630 Ma, with high temperature conditions lasting until the end collisional stage of the Orogen (ca. 630–610).

40Ar-39Ar dating, fluid inclusion, and isotopic constraints on the timing, fluid evolution, and deposition of the polymetallic Nuocang Pb–Zn deposit in the western Nyainqêntanglha belt

The Nyainqêntanglha polymetallic belt (NPB) is western China's foremost skarn Pb–Zn metallogenic belt. Significant progress has been made in determining these ore deposits' age and origin. However, the precipitation mechanisms and mineralization controls for these deposits remain unresolved. 40Ar/39Ar dating, fluid inclusion (FI), and H-O-S-Pb isotopic data are presented for the Nuocang deposit, a newly discovered polymetallic Pb-Zn skarn deposit in the western NPB, with the goal to trace age and, especially, the major fluid processes associated with hydrothermal evolution leading to the precipitation of ore. The muscovite yields an 40Ar-39Ar plateau age of 59.68 ± 0.60 Ma, which closely resembles typical skarn deposits within the NPB, indicating that it formed during the main collisional stage of the India–Eurasia continent. In the Nuocang base-metal skarn deposit, three ore-related stages can be discerned and subdivided: 1) the pre-ore stage, containing the prograde and early retrograde metasomatic skarn minerals, 2) the syn-ore stage, including the late retrograde metasomatic minerals and sulfides, and 3) the post-ore stage of quartz, calcite, and chlorite alteration. Correspondingly, three types of FI (L, V, and S type) have been identified. The ore-forming fluids evolved from moderate to high temperature between 340 and 440 °C primarily, but up to 571 °C, and moderate to high salinity (concentrated ∼8–18 wt% NaCl-equiv., but up to 48.1 wt% NaCl equiv.) in the pre-ore stage. During the syn-ore stage, the fluids were at low to moderate temperature (between 200 and 320 °C) and low salinity (∼2 to 12 wt% NaCl-equiv.) and developed in low temperature (∼120–200 °C) and low salinity (∼2–8 wt% NaCl equiv.) in the post-ore stage. The calculated δDH2O values of the transparent minerals were −180 to −106 ‰ during the pre-ore stage, −141 to −59 ‰ during the syn-ore stage, and −152 to −105 ‰ during the post-ore stage. The δ18OH2O values were −1.2 to 3.8 ‰ during the pre-ore stage, −4.7 to −2.3 ‰ during the syn-ore stage, and −10.9 to −5.0 ‰ during the post-ore stage, respectively.Based on these results, the magmatic fluids appeared to have gradually evolved into meteoric. Meteoric water is believed to play a significant role in metal deposition within magmatic-hydrothermal systems. Locally, boiling is also considered another key mechanism for ore precipitation. The S-Pb isotope values of the sulfide metals indicate that the metallogenic materials were predominantly derived from an upper crustal source mixing with minor amounts of mantle–derived components. This study suggests that the fluid mixing is related to geostatic pressure variations and infiltration of meteoric waters into the hydrothermal system and are key mechanisms triggering Pb-Zn ore deposition in the NPB.

Geology, mineralization, zircon U-Pb geochronology and Hf isotopes of Serenu porphyry copper prospect, Kerman Cenozoic magmatic arc, southeastern Iran

Serenu porphyry copper prospect is situated 22 km northwest of the Meiduk copper mine, Kerman Cenozoic magmatic arc in southeastern Iran. The study area is characterized by a simple lithology including Eocene volcanic and volcaniclastics, Neogene sediments, and sub-volcanic rocks (Hezar complex) which is intruded by a late Miocene porphyry diorite to quartz-diorite stock that has developed alteration and mineralization in the area. Phyllic, argillic, and propylitic alteration types are well-distributed in the Serenu prospect; potassic alteration is only locally observed. Hypogene mineralization occurs in the Serenu porphyry and the host Eocene volcanic rocks as scattered vein-veinlets, stockworks, and disseminated mineralization related to potassic and phyllic alteration types.The mineralogy and cross-cutting relationships, allow the vein-veinlets to be classified into five groups including (I) magnetite ± quartz, (II) quartz ± magnetite ± chalcopyrite ± pyrite ± chlorite ± anhydrite (III) quartz ± pyrite ± chalcopyrite ± anhydrite, (IV) pyrite, and (V) quartz ± calcite veinlets. Oxide and supergene enriched ores are poorly developed in the area. Zircon U-Pb dating on two samples from the Serenu porphyry provided consistent ages at 9.83 ± 0.4 Ma and 10.2 ± 0.17 Ma (±2σ) indicative of late Miocene emplacement of the intrusion. The zircons are characterized by positive εHf (t) values of 8.52 to 12.27 and TDM of 200–370 Ma and a TCDM of 310–590 Ma indicating that they originated from a juvenile mafic and thickened lower crust and depleted mantle-derived magma.The late Miocene age determined for the Serenu porphyry copper prospect is consistent with the ages reported for many other shallow intrusions related to porphyry-type mineralization in the Kerman belt and further emphasizes the Miocene metallogenic epoch as the preferred time for porphyry Cu-Mo-Au mineralization in this belt, coinciding with a significant stage of continental collision between the Arabian and Iranian plates. The results of this study reveal that the juvenile mafic lower crust together with input from a depleted mantle and older subduction-related magma has a very significant impact on the formation of the Serenu porphyry host magma.

FIRST LA-ICP-MS APATITE FISSION-TRACK AGES FROM THE SIBERIAN PLATFORM BASEMENT (NEPSKO-BOTUOBINSKAYA ANTECLISE)

We present the first results of LA-ICP-MS apatite fission-track dating (AFT) from nine core samples from wells, that exposed the top of the crystalline basement of the Siberian platform within the Nepsko-Botuobinskaya anteclise on the ~2 km depth. Obtained AFT ages belong to three clusters with mean values of 200, 140, and 60 Ma. A thermal event of ~200 Ma is widespread throughout almost the entire Siberian platform and reflects the stage of its Early Jurassic uplift. Reset of the fission-track geochronometer in apatite ~140 Ma correlates with tectono-thermal event marking the final stage of the Mongol-Okhotsk fold belt collision. The youngest AFT ages of ~60 Ma, on the one hand, may reflect the early (crypto) stage of the Baikal rifting, and, on the other hand, be a consequence of the high content of uranium in apatite.