Transition Of Regime Research Articles

Multiple temporalities of knowing in academic research

Based on ethnographic research at five Czech universities from 2011 to 2013, this article explores how academics make sense of and claims to three qualitatively distinct temporal regimes in which their activities as knowledge producers are inscribed: disciplinary time, career time and project time. This conceptual framework, a modification of Shinn’s distinction between disciplinary, transitory and transversal knowledge-production regimes, seeks to replace images of competition and succession between regimes with images of their recombination and intersection. It enables an interpretation of the empirical findings beyond the indigenous complaint that excessive speed is compromising the quality of knowledge production. The relationship between projects, careers and disciplines emerges from the study as problematic rather than synergistic. In this respect the paper does not contradict the claim by critical theorists that we are witnessing the disintegration of what used to be a functional relationship between the multiple temporalities of academic knowledge production based on standardized career scripts, nor the related claim that this may reflect a deeper crisis of modernity as a predictive regime for the production of futures. It proposes, however, that transversal projects can still be mediators of ‘disciplinary respiration’ insofar as their timeframes are available for variable calibration commensurate with the increasingly heteronomous ways of knowing and knowledge routines that academic researchers practise.

Dynamic Transition of the Exchange Rate Regime in the People's Republic of China

This paper analyzes the optimal transition of the exchange rate regime in the People’s Republic of China (PRC). How the PRC can successfully reach the desired regime — whether a basket peg or floating regime — from the current dollar-peg regime remains a major question. To answer it, we develop a dynamic small open-economy general equilibrium model. We construct four transition policies toward the basket-peg or floating regime and compare the welfare gains of these policies to those of maintaining the dollar-peg regime. Quantitative analysis using PRC data from Q1 1999 to Q4 2010 leads to two conclusions. First, a gradual adjustment toward a basket-peg regime seems the most appropriate option for the PRC, and would minimize the welfare losses associated with a shift in the exchange rate regime. Second, a sudden shift to a basket peg is the second-best solution. This is preferable to a sudden shift to a floating regime, since it would enable the authorities to implement optimal weights efficiently in order to achieve policy goals once a decision has been made to adopt a basket-peg regime.

Short-time heat impulse intensification of heat transfer in liquid nitrogen

The cryogenic technology deals with fluids produced from gases after liquefaction. Boiling of cryogenic fluids is frequently characterized by a hysteresis of their boiling curve. The present experimental work demonstrates an opportunity to intensify heat transfer in those fluids by means of short-term heat impulsion from a heater. The intensification takes place due to the impulse-induced transition of heat transfer regime from natural convection towards nucleate boiling. The process takes place when the impulse magnitude overcomes certain minimum value that was quantified experimentally. We also propose a theoretical expression for the minimum energy that is in agreement with the experimental data.

Experimental study on diesel fuel injection characteristics under cold start conditions with single and split injection strategies

Studies on fuel flow characteristics under both room temperature (25°C) and low temperature (−18°C) were carried out under a wide range of injection pressures and back pressures using a long tube real-time fuel flow rate measuring instrument. Both single and split injection strategies were employed. Several modified correlations were proposed to analyze fuel injection characteristics. It was found that low fuel temperature caused longer injection delay, shorter injection duration, lower mass flow rate and less injected fuel mass. The injector discharge coefficient was affected more by fuel viscosity changes due to low temperature than by the geometric structure of the injector. Cold start conditions effectively limited the inception of cavitation as seen in the flow rate/pressure dependence and accelerated the transition of flow regime from cavitation to turbulent and laminar flow with the decrease of injection pressure. This contributed to increased chances for the existence of laminar flow and thus to reduction of the discharge coefficient. Besides, low fuel temperature significantly weakened the degree of interaction between individual parts of split injection and split mass flow rate shapes became much less continuous than those under room temperature. These findings are of great importance for engine cold start studies.

Combustion regime classification of HCCI/PCCI combustion using Lagrangian fluid particle tracking

A new combustion regime classification method is proposed for HCCI/PCCI combustion based on Lagrangian fluid particle tracking. The performance of the present method is demonstrated with the time trace of net heat conduction to local mixture which is one of the quantities best representing the phenomena. Local combustion regimes are classified based on magnitudes of the maximum and minimum heat conduction on each fluid particle throughout the combustion process into autoignition, flame propagation and flame enclosing. Direct numerical simulations (DNS) of turbulent HCCI/PCCI combustion are conducted with different initial temperature fluctuations. A detailed kinetic mechanism including 53species and 325elementary reactions is used for methane–air reaction and a reduced kinetic mechanism including 37species and 61reactions is adopted for n-heptane–air reaction. The present DNS results show that the combustion process is highly sensitive to initial temperature fluctuations. The proposed method is applied to DNS results and the characteristics of fluid element classified into each combustion regime are investigated. By adopting appropriate threshold for the maximum and minimum heat conduction to local mixture, the contributions of three combustion regimes to whole fuel consumption can be discussed. The autoignition regime is dominant for lower temperature fluctuation case. However, the flame propagation and flame enclosing regimes turn to be significant for higher temperature fluctuation case where the autoignition regime is less than 20% and only triggers combustion start. Such qualitative tendency is confirmed in two fuel species. However, quantitatively, the transition of dominant combustion regime from autoignition to flame propagation/flame enclosing takes place at lower temperature fluctuation for the n-heptane–air mixture case. The proposed classification method effectively characterizes the turbulent combustion process in HCCI/PCCI engines. This classification method can be extended to quantify reaction mechanisms by tracking representative quantities such as the mole fraction of key intermediates.

CRGD-directed, NIR-responsive and robust AuNR/PEG–PCL hybrid nanoparticles for targeted chemotherapy of glioblastoma in vivo

cRGD-directed, NIR-responsive and robust AuNR/PEG–PCL hybrid nanoparticles (cRGD-HNs) were designed and developed for targeted chemotherapy of human glioma xenografts in mice. As expected, cRGD-HNs had excellent colloidal stability. The in vitro release studies showed that drug release from DOX-loaded cRGD-HNs (cRGD-HN-DOX) was minimal under physiological conditions but markedly accelerated upon NIR irradiation at a low power density of 0.2W/cm2, due to photothermally induced phase transition of PCL regime. MTT assays showed that the antitumor activity of cRGD-HN-DOX in αvβ3 integrin over-expressed human glioblastoma U87MG cells was greatly boosted by mild NIR irradiation, which was significantly more potent than non-targeting HN-DOX counterpart under otherwise the same conditions and was comparable or superior to free DOX, supporting receptor-mediated endocytosis mechanism. The in vivo pharmacokinetics studies showed that cRGD-HN-DOX had much longer circulation time than free DOX. The in vivo imaging and biodistribution studies revealed that cRGD-HN-DOX could actively target human U87MG glioma xenograft in nude mice. The therapeutic studies in human U87MG glioma xenografts exhibited that cRGD-HN-DOX in combination with NIR irradiation completely inhibited tumor growth and possessed much lower side effects than free DOX. The Kaplan–Meier survival curves showed that all mice treated with cRGD-HN-DOX plus NIR irradiation survived over an experimental period of 48days while control groups treated with PBS, cRGD-HN-DOX, cRGD-HNs with NIR irradiation, free DOX, or HN-DOX with NIR irradiation (non-targeting control) had short life spans of 15–40days. Ligand-directed AuNR/PEG–PCL hybrid nanoparticles with evident tumor-targetability as well as superior spatiotemporal and rate control over drug release have emerged as an appealing platform for cancer chemotherapy in vivo.

Dynamics of step-emulsification: From a single to a collection of emulsion droplet generators

Microfluidics has proven to be an efficient tool for making fine and calibrated emulsion droplets. The parallelization of drop makers is required for producing large amounts. Here, we investigate the generation of emulsion drops along a series of shallow microchannels emerging in a deep one, in other words the step-emulsification process. The dynamics of a single drop maker is first characterized as a function of interfacial tension and viscosities of both phases. The characteristic time scale of drop formation, namely, the necking time that finally sets drop size, is shown to be principally governed by the outer phase viscosity to interfacial tension ratio with a minor correction linked to the viscosity ratio. The step emulsification process experiences a transition of fragmentation regime where both the necking time and drop size suddenly raise. This transition, that corresponds to a critical period of drop formation and thus defines a maximum production rate of small droplets, is observed to be ruled by the viscosity ratio of the two phases. When drops are produced along an array of microchannels with a cross flow of the continuous phase, a configuration comparable to a one-dimensional membrane having rectangular pores, a drop boundary layer develops along the drop generators. In the small drop regime, the local dynamics of drop formation is shown to be independent on the emulsion cross flow. Moreover, we note that the development of the drop boundary layer is even beneficial to homogenize drop size along the production line. On the other hand, in the large drop regime, drop collision can trigger fragmentation and thus lead to size polydispersity.

Model experiments on growth modes and interface electronics of CuInS2 : Ultrathin epitaxial films on GaAs(100) substrates

The heterojunction formation between GaAs(100) and CuInS2 is investigated using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). Thin layers of CuInS2 films were deposited in a step-by-step process on wet chemically pre-treated GaAs(100) surfaces by molecular beam epitaxy (MBE) with a total upper thickness limit of the films of 60 nm. The film growth starts from a sulfur-rich GaAs(100) surface. XPS core level analysis of the substrate and film reveals initially a transitory growth regime with the formation of a Ga containing chalcopyrite phase. With increasing film thickness, a change in stoichiometry from Cu-poor to Cu-rich composition is observed. The evaluation of the LEED data shows the occurrence of a recrystallization process where the film orientation follows that of the substrate with the epitaxial relation GaAs{100}||CuInS2{001}. On the completed junction with a CuInS2 film thickness of 60 nm, the band discontinuities of the GaAs(100)/CuInS2 structure measured with XPS and UPS were determined as ΔEV = 0.1 ± 0.1 eV and ΔEC = 0.0 ± 0.1 eV, thus showing a type II band alignment.

An analytical approach to non‐linear dynamical model of a permanent magnet synchronous generator

AbstractThis paper proposes an analytical approach to investigate the transitory dynamic regime of a low‐power permanent magnet synchronous generator that works in an actual wind power station. The governing non‐linear differential equations are solved by means of the optimal homotopy asymptotic method, and explicit analytical solutions are obtained. Four cases are analysed for different moments of inertia and electrical resistances specific to sudden short circuit produced at the generator terminals and sudden change of load. The proposed procedure is highly efficient and controls the convergence of the approximate solutions, ensuring a very fast convergence. Such analytical approach allows modeling and simulating turbine generator systems for real‐time computations, offline applications or stability problems. Numerical investigations are also performed in order to validate the analytical results. Copyright © 2014 John Wiley & Sons, Ltd.

Transition of flow regime along a marine-terminating outlet glacier in East Antarctica

Abstract. We present results of a multi-methodological approach to characterize the flow regime of West Ragnhild Glacier, the widest glacier in Dronning Maud Land, Antarctica. A new airborne radar survey points to substantially thicker ice (>2000 m) than previously thought. With a discharge estimate of 13–14 Gt yr−1, West Ragnhild Glacier thus becomes of the three major outlet glaciers in Dronning Maud Land. Its bed topography is distinct between the upstream and downstream section: in the downstream section (<65 km upstream of the grounding line), the glacier overlies a wide and flat basin well below the sea level, while the upstream region is more mountainous. Spectral analysis of the bed topography also reveals this clear contrast and suggests that the downstream area is sediment covered. Furthermore, bed-returned power varies by 30 dB within 20 km near the bed flatness transition, suggesting that the water content at bed/ice interface increases over a short distance downstream, hence pointing to water-rich sediment. Ice flow speed observed in the downstream part of the glacier (~250 m yr−1) can only be explained through very low basal friction, leading to a substantial amount of basal sliding in the downstream 65 km of the glacier. All the above lines of evidence (sediment bed, wetness and basal motion) and the relatively flat grounding zone give the potential for West Ragnhild Glacier to be more sensitive to external forcing compared to other major outlet glaciers in this region, which are more stable due to their bed geometry (e.g. Shirase Glacier).

Biofuels Barrier Properties of Polyamide 6 and High Density Polyethylene

In this paper, a comparison of the biofuels barrier properties of PolyAmide 6 (PA6) and High Density PolyEthylene (HDPE) is presented. Model fuels were prepared as mixtures of toluene, isooctane and ethanol, the ethanol volume fraction varying between 0% and 100%. Barrier properties were determined at 40°C by gravimetric techniques or gas chromatography measurements, and it was shown that polyamide 6 permeability is lower than that of polyethylene on a wide range of ethanol contents up to 85% of ethanol (E85) in the biofuel, permeability of PA6 being 100 times lower than that of HDPE for low ethanol content fuels (E5, E0). The time-lags were also compared, and on the whole range of ethanol contents, HDPE permeation kinetics appears to be much faster than that of PA6, the time lag for a 1 mm thick specimens in presence of E10 being 50 days for PA6 and 0.5 days for HDPE. The compositions of the solvent fluxes were analyzed by FID gas chromatography, and it turned out that the solvent flux was mainly made up of ethanol (minimum 95%) in the case of PA6, whereas in the case of HDPE, solvent flux was mainly made up of hydrocarbons. The implication of this difference in the solvent flux composition is discussed in the present article, and a side effect called the “fuel exhaustion process” is presented. The influence of the sample thickness was then studied, and for the different biofuels compositions, the pervaporation kinetics of polyamide 6 appeared to evolve with the square of the thickness, a long transitory regime being highlighted in the case of PA6. This result implies that the time needed to characterize the steady state permeability of thick PA6 parts such as fuel tanks can be very long (one year or more), this duration being far superior to the Euros 5 or Euro 6 standard emission measurements time scale. The influence of temperature on the permeability was finally assessed, and the activation energy that is the signature of the temperature dependence of the barrier property turned out to be similar for the different biofuels compositions.

Dynamic Transition of Exchange Rate Regime in China

AbstractThe paper considers the optimal transition path for China's exchange rate regime. How can China successfully make the shift from the current dollar peg regime to a more desirable regime, whether a basket peg or a floating regime? To answer this question, we develop a dynamic small open economy general equilibrium model. We construct four transition policies based on a basket peg or a floating regime and compare the welfare gains of these policies relative to maintaining the dollar peg regime. Two main results are derived from the quantitative analysis using Chinese data from 1999Q1 to 2010Q4. First, following a gradual adjustment to a basket peg regime is the most appropriate path for China to take, with minimal welfare losses associated with the shift in the exchange rate regime. Second, a sudden shift to the basket peg is the second best solution, and is superior to a sudden shift to floating because the monetary authority can efficiently determine optimal weights to attach to currencies in the basket to achieve policy goals once they adopt a basket peg regime.

Role of ion sources for spacer charging in SF6 gas insulated HVDC systems

Stationary DC electric fields are determined by the resistivity distribution of the insulation materials. In the presence of interfaces between different insulation materials, charge accumulation at these boundary layers may have a significant influence on the electric field distribution and with it on the breakdown strength of the arrangement. In many previous works, surface charging of model spacers was investigated. However, the ion flow problem to properly account for the electric conduction in the gas has not yet been solved. The role of different ion sources and the behavior of the resulting ion currents in the gas phase on the charge accumulation process have to be investigated in more detail. In this paper, the transient charge accumulation process on a PTFE spacer surface with a focus on charges originating from the gas phase is investigated experimentally and by simulations. These charges are produced by natural radiation. The transition of the ohmic conduction regime in the gas to a saturated ion current with increasing voltage is analyzed. Furthermore, the importance of additional charge sources like partial discharges and field emission from the electrodes is highlighted. The experimental results indicate that additional charges are generated already at voltage levels significantly below the measured PD inception voltage. These charges originate from micro discharges on the electrodes and have to be taken into account when designing HVDC GIS applications.

Role of ion sources for spacer charging in SF<sub>6</sub> gas insulated HVDC systems

Stationary DC electric fields are determined by the resistivity distribution of the insulation materials. In the presence of interfaces between different insulation materials, charge accumulation at these boundary layers may have a significant influence on the electric field distribution and with it on the breakdown strength of the arrangement. In many previous works, surface charging of model spacers was investigated. However, the ion flow problem to properly account for the electric conduction in the gas has not yet been solved. The role of different ion sources and the behavior of the resulting ion currents in the gas phase on the charge accumulation process have to be investigated in more detail. In this paper, the transient charge accumulation process on a PTFE spacer surface with a focus on charges originating from the gas phase is investigated experimentally and by simulations. These charges are produced by natural radiation. The transition of the ohmic conduction regime in the gas to a saturated ion current with increasing voltage is analyzed. Furthermore, the importance of additional charge sources like partial discharges and field emission from the electrodes is highlighted. The experimental results indicate that additional charges are generated already at voltage levels significantly below the measured PD inception voltage. These charges originate from micro discharges on the electrodes and have to be taken into account when designing HVDC GIS applications.

Transition of Aid Regime Since the 1980s and the Post-MDGs

Transition of Aid Regime Since the 1980s and the Post-MDGs

Paleoproterozoic tectonic transition from collision to extension in the eastern Cathaysia Block, South China: Evidence from geochemistry, zircon U–Pb geochronology and Nd–Hf isotopes of a granite–charnockite suite in southwestern Zhejiang

The Badu complex and associated Paleoproterozoic granitoids are among the oldest known rocks in the Cathaysia Block in South China. The Paleoproterozoic units of the Badu complex are dominantly composed of metapelitic rocks and meta-greywackes. Here we report LA-SS-ICP-MS (laser ablation-split-stream inductively coupled plasma-mass spectrometry) zircon U–Pb data from a newly discovered garnet-bearing granite which show an emplacement age of 1929±15Ma and metamorphism at 1872±34Ma. We also report U–Pb ages of 1886±16Ma, 1858±7Ma, 1848±11Ma from a gneissic granodiorite, and two charnockites respectively. The garnet-bearing granite is peraluminous with A/CNK range from 1.1 to 1.3. The rock shows relatively high SiO2, K2O and Rb contents, and low total REE, Sr, CaO and ferromagnesian components, typical of leucogranites. The whole rock Nd two-stage model age(TDM2(Nd)) of this rock is ca. 2.7Ga, zircon Hf crustal model ages(TDMC(Hf)) peak at about 2.7Ga, and abundant inherited zircons occur with U–Pb ages in the range of 2044 to 2803Ma. Evidences from zircon U–Pb age and Hf isotope compositions, whole rock Nd isotopes and whole rock major and trace elements suggest a metasedimentary protolith, and that the garnet-bearing granite (leucogranite) was derived by partial melting in a thickened crust at about 1.93Ga. The gneissic granodiorite and charnockites show indistinguishable major and trace element features, as well as zircon Hf and whole rock Nd isotope compositions, indicating that they were generated from the same source rocks. The gneissic granodiorite and charnockites are ferroan, calc-alkalic and metaluminous with A/CNK range from 0.80 to 0.98. They display relatively low SiO2 contents and Ga/Al ratios, suggesting their A-type affinity. Their zircon TDMC(Hf) age-peak is 2.9Ga and whole rock TDM2(Nd) ages range from 2.8 to 2.9Ga. These high temperature rocks were generated possibly through the partial melting of ancient amphibolites (2.9Ga), with heat input from asthenosphere upwelling and magmatic underplating in an extensional setting at about 1.85–1.88Ga.Combined with data from previous studies, we suggest three episodes of major crustal growth in this region at 1.8–1.9Ga, ~2.7Ga and ~2.9Ga. During the 1.8–1.9Ga event, extensive reworking also took place. From the 1.93Ga syn-collision leucogranite (garnet-bearing granite), the 1.88–1.85Ga post-collision A-type granites and charnockites (the granite–charnockite suite), and the1.85–1.77Ga intraplate basaltic rocks (Li 1997 and Xiang et al. 2008) in the region, a Paleoproterozoic orogenic cycle can be deciphered in the Cathaysia Block. The rapid transition of tectonic regime from collision to post-collisional extension can be correlated to the assembly of the supercontinent Columbia.

Numerical study of horizontal pneumatic conveying: Effect of material properties

This paper presents a numerical study of the effects of friction and restitution coefficients of particles on horizontal pneumatic conveying by a combined approach of computational fluid dynamics for gas and discrete element method for particles. The flow behaviours are analysed in terms of particle flow pattern, gas pressure drop, solid concentration, particle velocity and transition of flow regime. The results show that in the slug flow regime, an increased friction coefficient or a decreased restitution coefficient results in longer slugs but no change in slug shape. Slug flow cannot be obtained at a low friction coefficient. In the stratified and dispersed flow regimes, the transition between the two regimes and formation of clusters occur due to the changes of friction and/or restitution coefficient. These two coefficients also affect the pressure drop, particle velocity and solid concentration. The resulting effects vary with flow regime. Overall, the effect of restitution coefficient is less significant than that of friction coefficient. It is also found that when gas velocity is varied from high to low values, three flow transition modes may occur depending on friction and restitution coefficients. They are respectively represented by Mode I for dilute-phase only, Mode II for unsmooth transition from dilute-phase to unstable-zone, and finally to slug-flow, and Mode III for smooth transition from dilute-phase to slug-flow. Based on the numerical results, a diagram is established to predict these transition modes as a function of friction and restitution coefficients.

Mid-crustal emplacement and deformation of plutons in an Andean-style continental arc along the northern margin of the North China Block and tectonic implications

Abstract Outcrop mapping and thermobarometrical, thermochronological and microstructural analyses in five Late Carboniferous–Early Permian arc plutons in the northern North China Block (NCB) indicate a transition of tectonic regime from arc-perpendicular contraction to transpression and successive uplift and exhumation of the crustal rocks during magma emplacement and construction of the continental arc system. The early emplaced Daguangding and Boluonuo plutons (324–302 Ma) display well-developed, penetrative, moderately to steeply dipping magmatic foliations and high-temperature sub-solidus foliations that are parallel to host rock foliation near the contact. Widespread high-temperature sub-solidus foliations in these plutons indicate that they are syn-tectonic with N–S, arc-perpendicular shortening and record arc construction at a convergent continental margin. However, the late emplaced Tianqiao and Xianghuangqi–Wudaoyingzi plutons (288–274 Ma) display relatively weak magmatic fabrics at their margins and lack sub-solidus foliations and pluton-related ductile deformation of the contact host rocks. These structural differences likely reflect a kinematic transition from early arc-perpendicular contraction to late sinistral transpression during continental arc formation. Aluminum-in-hornblende barometry shows that their estimated emplacement depths decrease gradually from the Late Carboniferous (18.7 ± 0.8 km) to Early Permian (13.8 ± 0.9 km), indicating successive exhumation of the crustal rocks at an average rate of ca. 123 mm/ka over 40 million years of arc formation. 40 Ar/ 39 Ar thermochronological results show that cooling of the continental crust was very slow (4.9 °C/Ma) during arc construction in the Late Carboniferous–Late Permian but increased significantly during the Late Permian–Middle Triassic after arc termination. The mid-crust of the northern NCB remained very hot (> 530 °C) during arc construction and emplacement of the arc batholiths. Combined with emplacement depth estimated by aluminum-in-hornblende barometry, paleogeothermal gradients of 42.8–46.5 °C/km were estimated in mid- to upper-crustal levels (0–19 km). Hot mid-crust and high mid–upper crust geothermal gradients resulted from magmatic advection are likely the most important reasons for crust thickening and uplift during construction of Andean-style continental arcs and largely influenced the rheological behavior of continental crust.

Stress magnitude and orientation in the Potiguar Basin, Brazil: Implications on faulting style and reactivation

AbstractWe analyzed borehole breakout data and drilling‐induced tensile fractures derived from resistivity image logs run at 10 oil wells to derive the orientation of the maximum horizontal stress SHmax from the Potiguar Basin in the continental margin of Brazil. Stress magnitudes are derived from density logs for the vertical stress, mini‐frac tests for the minimum horizontal stress Shmin, and rock strength laboratory analysis to estimate the SHmax magnitudes. We compared these results with the stress regime and SHmax orientation derived from nine earthquake series located in the crystalline basement, where seismicity is concentrated, and previous breakout data from the basin. In the basin, the SHmax gradient is 20.0 MPa/km, and the SHmax/Shmin ratio is 1.154, indicating a normal tectonic stress regime from 0.5 to 2.0 km, whereas the SHmax gradient of 24.5 MPa/km and SHmax/Shmin ratio of 1.396 indicate a transition from a normal to strike‐slip stress regime at 2.5 to 4.0 km. The deeper stress regime in the basin is similar to that in the basement at 1–12 km depth. This transition of the tectonic stress regime is consistent with an incipient tectonic inversion in the basin. We note that the SHmax orientation rotates from NW–SE in the western part of the Potiguar Basin to E–W in its central and eastern parts, roughly following the shoreline geometry, indicating that local features such as flexural stresses influence the local (scale < 100 km) stress pattern. We also conclude that the basement is critically stressed, but not the basin.

Geochronology and fluid inclusion study of the Yinjiagou porphyry–skarn Mo–Cu–pyrite deposit in the East Qinling orogenic belt, China

The Yinjiagou Mo–Cu–pyrite deposit of Henan Province is located in the Huaxiong block on the southern margin of the North China craton. It differs from other Mo deposits in the East Qingling area because of its large pyrite resource and complex associated elements. The deposit’s mineralization process can be divided into skarn, sulfide, and supergene episodes with five stages, marking formation of magnetite in the skarn episode, quartz–molybdenite, quartz–calcite–pyrite–chalcopyrite–bornite–sphalerite, and calcite–galena–sphalerite in the sulfide episode, and chalcedony–limonite in the supergene episode. Re–Os and 40Ar–39Ar dating indicates that both the skarn-type and porphyry-type orebodies of the Yinjiagou deposit formed approximately 143Ma ago during the Early Cretaceous. Four types of fluid inclusions (FIs) have been distinguished in quartz phenocryst, various quartz veins, and calcite vein. Based on petrographic observations and microthermometric criteria the FIs include liquid-rich, gas-rich, H2O–CO2, and daughter mineral-bearing inclusions. The homogenization temperature of FIs in quartz phenocrysts of K-feldspar granite porphyry ranges from 341°C to >550°C, and the salinity is 0.4–44.0wt% NaCl eqv. The homogenization temperature of FIs in quartz–molybdenite veins is 382–416°C, and the salinity is 3.6–40.8wt% NaCl eqv. The homogenization temperature of FIs in quartz–calcite–pyrite–chalcopyrite–bornite–sphalerite ranges from 318°C to 436°C, and the salinity is 5.6–42.4wt% NaCl eqv. The homogenization temperature of FIs in quartz–molybdenite stockworks is in a range of 321–411°C, and the salinity is 6.3–16.4wt% NaCl eqv. The homogenization temperature of FIs in quartz–sericite–pyrite is in a range of 326–419°C, and the salinity is 4.7–49.4wt% NaCl eqv. The ore-forming fluids of the Yinjiagou deposit are mainly high-temperature, high-salinity fluids, generally with affinities to an H2O–NaCl–KCl±CO2 system. The δ18OH2O values of ore-forming hydrothermal fluids are 4.0–8.6‰, and the δDV-SMOW values are between −64‰ and −52‰, indicating that the ore-forming fluids were primarily magmatic. The δ34SV-CDT values of sulfides range between −0.2‰ and 6.3‰ with a mean of 1.6‰, sharing similar features with deeply sourced sulfur, implying that the sulfur mainly came from the lower crust composed of poorly differentiated igneous materials, but part of the heavy sulfur came from the Guandaokou Group dolostone. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of sulfides are in the range of 17.331–18.043, 15.444–15.575, and 37.783–38.236, respectively, which is generally consistent with the Pb isotopic signature of the Yinjiagou intrusion, suggesting that the Pb chiefly originated from the felsic–intermediate intrusive rocks in the mine area, with a small amount of lead from strata. The Yinjiagou deposit is a porphyry–skarn deposit formed during the Mesozoic transition of a tectonic regime that is EW-trending to NNE-trending, and the multiepisode boiling of ore-forming fluids was the primary mechanism for mineral deposition.