Protolith ages and timing of peak and retrograde metamorphism of the high-pressure granulites in the Shandong Peninsula,eastern North China Craton

High-pressure （HP） granulites widely occur as enclaves within tonalite-trondhjemite- granodiorite （TTG） gneisses of the Early Precambrian metamorphic basement in the Shandong Peninsula, southeast part of the North China Craton （NCC）. Based on cathodoluminescence （CL）, laser Raman spec- troscopy and in-situ U-Pb dating, we characterize the zircons from the HP granulites and group them into three main types： inherited （magmatic） zircon, HP metamorphic zircon and retrograde zircon. The inher- ited zircons with clear or weakly defined magmatic zoning contain inclusions of apatites, and 207pb/206pb ages of 2915--2890 Ma and 2763--2510 Ma, correlating with two magmatic events in the Archaean base- ment. The homogeneous HP metamorphic zircons contain index minerals of high-pressure metamor- phism including garnet, clinopyroxene, plagioclase, quartz, rutile and apatite, and yield 207pb/2066pb ages between 1900 and 1850 Ma, marking the timing of peak HP granulite facies metamorphism. The retrograde zircons contain inclusions of orthopyroxene, plagioclase, quartz, apatite and amphibole, and yield the youngest 207pb/206pb ages of 1840-1820 Ma among the three groups, which we correlate to the medium to low-pressure granulite facies retrograde metamorphism. The data presented in this study suggest subduction of Meso- and Neoarchean magmatic protoliths to lower crust depths where they were subjected to HP granulite facies metamorphism during Palaeoproterozoic （1900-1850 Ma）. Subse- quently, the HP granulites were exhumated to upper crust levels, and were ovel-printed by medium to low-pressure granulite and amphibolite facies retrograde event at ca. 1840--820 Ma.

Experimental and Finite Element Analysis of Corroded High-Pressure Pipeline Repaired by Laminated Composite

Repairs of corroded high-pressure pipelines are essential for fluids transportation under high pressure.One of the methods used in their repairs is the use of layered composites.The composite used must have the necessary strength.Therefore,the experiments and analytical solutions presented in this paper are performed according to the relevant standards and codes,including ASME PCC-2,ASME B31.8S,ASME B31.4,ISO 24817 and ASME B31.G.In addition,the experimental tests are replicated numerically using the finite element method.Setting the strain gauges at different distances from the defect location,can reduce the nonlinear effects,deformation,and fluctuations due to the high pressure.The direct relationship between the depth of an axial defect and the stress concentration is observed at the inner side edges of the defect.Composite reparation reduces the non-linearities related to the sharp variation of the geometry and a more reliable numerical simulation could be performed.

Polymetamorphism of the ultrahigh-temperature granulites in the Rauer Group,East Antarctica:new evidence from zircon SHRIMP U-Pb ages

The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz Belt.Thus,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating.The results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,respectively.These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.

Metamorphic characteristics and geotectonic implications of the high-pressure granulites from Namjagbarwa, eastern Tibet

A large area of high-pressure garnet-kyanite granulite is exhumed in the Namjagbarwa area, which provides a window for observing the deep crust rocks and structures of the Tibetan Plateau. Three mineral assemblages can have been distinguished in the garnet-kyanite HP granulites by petrography, i.e. M1. Mus+Bi+P1+Q, M2. Gt+Ky +perphite/antiperphite+Rt+Q, M3. Gt+Sill+Cord+Sp+Ilm±Opx. Metanmrphic conditions of the peak granulite assemblages （M2） formatted by thickening of crusts, with available isotopic ages of 45-69 Ma, are at 1.4-1.8 Gpa and 750--850℃ . Their retrograde assemblages overprinted by deconpressure during the uplift, with available isotopic ages of 18-23 Ma, were formed at 0.60-0.70 Gpa, 621-726℃ . The thermobarometric evaluation, petrogenetic grid and corresponding isotopic ages indicate a clockwise isothermal decompression metamorphic path. The HP granulite metamorphic history indicates that the collision of the Indian Plate with the Eurasian Plate had begun at 70 Ma, far earlier

Sm-Nd age dating of high-pressure granulites and amphi-bolite from Sanggan area,North China craton

The high pressure (HP) metamorphic age has been dated to HP rocks from the Sanggan area, North China craton. We have got garnet+whole rock isochron ages of (1 842±38) Ma for HP granulite, and (1 856± 26) Ma for HP amphibolite. The Sm-Nd whole rock isochron of HP granulites give out an age of (1870±150) Ma with Nd depleted mantle model age of (2402-2 482) Ma. Considering the Nd isotope homogenization during the peak metamorphism of the HP granulite, Sm-Nd closure temperature and the retention of Nd isotopic memory in garnets partially broken down during decompression, all these isochron ages are thought to be HP metamorphic age. Furthermore, we proposed that the HP metamorphism took place at the end of Paleoproterozoic during the large-scale collision and assembly of the North China craton.

Metamorphism and zircon U-Pb dating of high-pressure pelitic granulites from glacial moraines in the Grove Mountains, East Antarctica

The Grove Mountains are an inland continuation of the Prydz Belt in East Antarctica. Detailed metamorphic petrological and zircon U-Pb geochronological studies are performed on the high-pressure （HP） pelitic granulites from glacial moraines in the Grove Mountains. The metamorphic peak mineral assemblage of the HP pelitic granulites is characterized by garnet ＋ kyanite ＋ K-feldspar ＋ biotite ＋ plagioclase ＋ quartz, and the subsequent medium-pressure （MP） granulite facies retrogression is characterized by sillimanite replacing kyanite, the formation of the biolite ＋ sillimanite symplectite in the matrix. These mineral assemblages and their P-T estimates based on the P-T pseudosection constructed in MnNCKFMASHT system define a clockwise P-T path involving metamorphic peak of 11.6–13.6 kbar at 817–834°C followed by a near-isothermal decompression of 6.7–7.5 kbar at 806–828°C, comparable with those of associated HP mafic granulites from glacial moraines in the Grove Mountains. Zircon U-Pb dating, coupled with available metamorphic age data obtained for HP mafic granulites, reveals HP metamorphism occurred at 540–545 Ma. Combining the previous research results, the HP pelitic granulites and contemporary HP mafic granulites were widely distributed in glacial moraines from the Grove Mountains, suggesting at least part of the Grove Subglacial Highlands underwent Pan-Afrian HP granulite facies metamorphism, which provides new evidence for a collisional tectonic setting of the Pan-Afrian Prydz Belt.

Geochronological Study of Caledonian Granulite and High-Pressure Gneiss in the Dabie Mountains

Using the single—zircon evaporation technique and U—Pb method, the authors have conducted an isotope geochonological study of the Huilanshan granulite and Shima garnet-bearing plagioclase gneiss (“country rocks” of the Shima eclogite) in the Dabie Mountains. The study shows that these rocks have peak metamorphic ages of 443–455 Ma, which are essentially consistent with that of the Caledonian high—ultrahigh pressure eclogites. This indicates the existence of the Caledonian collisional orogeny in the Dabie Mountains.

Tectonic Evolution of an Early Precambrian High-Pressure Granulite Belt in the North China Craton

A large-scale high-pressure granulite belt (HPGB), more than 700 km long, is recognized within the metamorphic basement of the North China craton. In the regional tectonic framework, the Hengshan-Chengde HPGB is located in the central collision belt between the western block and eastern block, and represents the deep crustal structural level. The typical high-pressure granulite (HPG) outcrops are distributed in the Hengshan and Chengde areas. HPGs commonly occur as mafic xenoliths within ductile shear zones, and underwent multipile deformations. To the south, the Hengshan-Chengde HPGB is juxtaposed with the Wutai greenstone belt by several strike-slip shear zones. Preliminary isotopic age dating indicates that HPGs from North China were mainly generated at the end of the Neoarchaean, assocaited with tectonic assembly of the western and eastern blocks.

A new transition metal diphosphideα-MoP_(2) synthesized by a high-temperature and high-pressure technique

Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a temperature between 1100℃and 1200℃.The structure ofα-MoP_(2) and its relationship to other transition metal diphosphides are discussed.Surprisingly,the ambient pressure phase orthorhombicβ-MoP_(2)(space group Cmc21)is denser in structure thanα-MoP_(2).Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition fromβ-MoP_(2) to α-MoP_(2),suggesting thatα-MoP_(2) is a stable phase at ambient conditions;this is also supported by the total energy and phonon calculations.

Numerical Simulation Analysis of the Transformer Fire Extinguishing Process with a High-Pressure Water Mist System under Different Conditions

To thoroughly study the extinguishing effect of a high-pressure water mist fire extinguishing system when a transformer fire occurs,a 3D experimental model of a transformer is established in this work by employing Fire Dynamics Simulator(FDS)software.More specifically,by setting different parameters,the process of the highpressure water mist fire extinguishing system with the presence of both diverse ambient temperatures and water mist sprinkler laying conditions is simulated.In addition,the fire extinguishing effect of the employed high-pressure water mist system with the implementation of different strategies is systematically analyzed.The extracted results show that a fire source farther away fromthe centerline leads to a lower local temperature distribution.In addition,as the ambient temperature increases,the temperature above the fire source decreases,while the temperature and the concentrationof theupperflue gas layer bothdecrease.Interestingly,after thehigh-pressurewatermist sprinkler begins to operate,both the temperature distribution above the fire source and the concentration of the flue gas decrease,which indicates that the high-pressure water mist system plays the role of cooling and dust removal.By comparing various sprinkler laying methods,it is found that the lower sprinkler height has a better effect on the temperature above the fire source,the temperature of the upper flue gas layer,and the concentration of the flue gas.Moreover,when the sprinkler is spread over thewhole transformer,the cooling effect on both the temperature above the fire source and the temperature of the upper flue gas layer is good,whereas the change in the concentration of the flue gas above the fire source is not obvious compared to the case where the sprinkler is not fully spread.

High-pressure new phases of V–N compounds

The high-pressure diagram of V–N compounds is enriched by proposed seven new stable high-pressure phases.The P-1-VN_4with the armchair N-rich structure may be quenched to ambient conditions.The formed N–N covalent bond plays an important role for the structural stability of N-chain.The charge transfer results in a V–N ionic bond interaction,which further improves the stability of N-chain structure.The P-1-VN_4,P4mnc-VN_8,and Immm-VN_(10)with the outstanding detonation properties have potential application in explosive field.

The discovery of TiO_(2)-Ⅱ,the α-PbO_(2)-structured high-pressure polymorph of rutile,in the Suizhou L6 chondrite

We report the discovery of TiO_(2)-Ⅱ in the unmelted rock of the shocked Suizhou L6 chondrite.Natural TiO_(2)-Ⅱ was previously found in ultrahigh-pressure metamorphic and mantle-derived rocks,terrestrial impact structures,and tektite.Our microscopic,Raman spectroscopic,electron microprobe and transmission electron microscopic investigations have revealed:(1) All observed TiO_(2)-Ⅱ grains are related with ilmenite and pyrophanite;(2) TiO_(2)-Ⅱ occurs as needle-and leaf-shaped inclusions in llmenite and patch-,tape-shaped body in pyrophanite;(3)The composition of TiO_(2)-Ⅱ is identical with that of its precursor rutile;(4) The Raman spectrum of TiO_(2)-Ⅱ is in good agreement with that of natural and synthesized α-PbO_(2)-type TiO_(2);(5) TiO_(2)-Ⅱ occurs mainly in the form of well-ordered nano-domains and small mis-orientation among the domains can be observed.(6) All electron diffraction reflections from TiO_(2)-Ⅱ can be indexed to α-PbO_(2)structure in space group Pbcn with lattice parameters of a=4.481 ?,b=5.578 A and c=4.921 A;(7) The exsolution inclusions of rutile from host ilmenite are mostly connected with an alternation process along the lamellar twinning plane of ilmenite induced by shockinduced high pressure and high temperature;(8) The P-T regime of 20-25 GPa and 1000 ℃ estimated for the Suizhou unmelted rock is suitable for phase transition of rutile into TiO_(2)-Ⅱ phase.

Adakitic Rocks Resulting from Partial Melting of Metabasite at High-Pressure Granulite-Facies Condition during Continental Collision

Objective Previous studies on adakitic rocks with high Sr/Y and La/Yb ratios have established that such rocks may form in a variety of tectonic settings through different petrogenetic processes including： （1） partial melting of subducted young （〈25 Ma）, hot and hydrated oceanic slab; （2） partial melting of thickened lower crust; （3） assimilation and fractional crystallization processes involving basaltic magma; （4） partial melting of delaminated lower crust; and （5） partial melting of hydrous garnet peridotite. The various origins for adakites provide important constraints on crustal growth and evolution throughout the Earth＇s history.

Eclogite-High-Pressure Granulite Belt in Northern Edge of the Archean North China Craton

The discovery of retrograded eclogites and high pressure basic granulites in the joining region of Hebei Shanxi Inner Mongolia (HSIM) abandon the old thoughts that Archean granulites in the North China craton are of middle or low pressure facies and promote the reconsideration of Early Precambrian cratonization tectonic process, and reveal the geological fact that the scale, rigid behavior and geological structure of Archean cratonic blocks have strong similarities to the present fundamental plate tectonics, which suggest new tectonic mechanism to understand the early continental evolution of the North China craton. (1) The retrograded eclogites and high pressure granulites constitute a ENE NE striking structure rock zone termed as the Sanggan structural belt. (2) The retrograded eclogites are closely associated with high pressure granulites. We can call this belt a transitional eclogite granulite facies metamorphic belt. Petrographically three metamorphic stages, at least, in the retrograded eclogite can be distinguished. ① The main mineral assemblage is composed of garnet+clinopyroxene+quartz+rutile. The mineral inclusions in garnet are fine grained quartz, rutile and small inclusions of fine grained second stage mineral aggregate. This aggregate consists of hypersthene+albite, and has the typical texture of small hypersthene core surrounded by albite micro grained grains. ② The second mineral assemblage is represented by corona of garnet and symplectite of clinopyroxene. The corona of garnet is composed of hypersthene+plagioclase+clinopyroxene+a minor amount of quartz and magnetite. The symplectite of clinopyroxene is composed of hypersthene + albite+clinopyroxene. The secondary mineral assemblage along boundaries between quartz and garnet (or clinopyroxene) is fine grained aggregate of hypersthene and clinopyroxene. ③ The third retrograded metamorphic minerals are mainly amphiboles replacing pyroxenes and plagioclases replacing garnets. The estimated metamorphic temperature and pressure of symplectitic minerals are 850-900 ℃ and 1.1-1.2 GPa, and those of the third stage are 600-700 ℃ and 0.6-0.7 GPa. They indicate a decompressional pTt path. (3) Geochemically, the compositions of the retrograded eclogites and high pressure basic granulites are the same as those of tholeiite and olivine tholeiite, which are Fe rich and show the differentiation tendency of tholeiitic cumulate rocks. Connecting with isotopic data, we can prove that the original rocks of retrograded eclogites and high pressure basic granulites were formed by partial melting of depleted mantle ( ε (Nd) =1.2-3.6) in the age of about 2 650-2 510 Ma. It might be formed in the lowermost crust by underplating and underwent high pressure metamorphism afterwards.

Zircon U-Pb Dating of Yushugou Terrain of High-Pressure Granulite Facies in Southern Tianshan Mountain and Its Geological Significance

The Yushugou terrain of high\|pressure granulite facies in southern Tianshan Mountain is composed mainly of an ophiolite suite. Most selected zircons are round or elliptical in shape, and some are of tetragonal prism with round edges. The granulometric analyses show that they are well sorted in sedimentation. ZrO\-2/HfO\-2 ratios in zircons range from 45 to 57. These characters, together with the petrologic and geochemical characters of plagioclase\|garnet\|orthopyroxenite bearing zircons, indicate that the protolith of plagioclase\|garnet\|orthopyroxenite may be derived mainly from volcanic base surge sedimentary debris in oceanic islands and from clays formed by seafloor weathering. Zircons are simply of pyroclastic debris. The ophiolite formation age of (440±18) Ma and the first\|stage metamorphic age (amphibolite or granulite facies) of (364±5) Ma were obtained with a method of multiple grains in different groups and a method of concordia plot. These ages provide important information on the temporal and spatial occurrence of southern Paleozoic Tianshan Ocean, the subduction rate of the oceanic crust and the formation mechanism of ophiolite of granulite facies.

The Metamorphism of High-Pressure Basic Granulite in Laixi District, East Shandong, China

A high pressure basic granulite ultramafics belt is found in the late Archaean gneisses of Laixi Laiyang Qixia district, east Shandong. This belt has previously been considered as another eclogite belt in Sulu ultra high pressure(UHP) terrain. The typical high P granulite is characterized by mineral assemblages of three generations formed in different metamorphic episode respectively. The mineral assemblage of first episode is Grt(core)+Cpx+Pl, that of the second episode is Grt(rim)+Cpx+Opx+Pl+Amp+Q+Mt and that of the third episode is Cpx+Pl+Amp+Q+Mt. In first assemblage, the garnet porphyroblast is rich in grossular and pyrope component, and the coexisting Cpx is Al rich. Using mineral thermobarometer and Berman’s (1991) TWQ program, the P T conditions of three episodes are established, i.e. T=840℃～860℃, P>1.4GPa for first episode; T=720℃～780℃,P=0.8～1.2GPa for second episode and T=600℃～800℃,P=0.5～0.7GPa for the third episode.Considering the reaction texture, mineral Chemistry and PT estmations, a clockwise PTt path can be constructed, which shows post peak isothermal decompression at first and followed by a process of pressure and temperature decreasing. The mineral wholerock Sm Nd isochron age of the granulite is 1752Ma, which indicates its last thermal event during early middle Proterozoic stage. Therefore, it is concluded that the high pressure granulite and ultramafics of this belt represents the lower continental curst of the North China Craton during early Precambrian without any relationship to tectonic process of the Sulu UHP terrain.

Preliminary Statistics of Temperatures and Pressures for Formation of Eclogites,Granulites and Peridotites in China

The rock forming temperatures and pressures represent the p T points of the local regions in the lithosphere at a certain age, providing some important information on rock formation. Based on the preliminary statistics on the temperatures and pressures for the formation of eclogites, granulites and peridotites in China, the variant ranges are given, in this paper, of temperatures, pressures and linear geothermal gradients of eclogites, granulites and peridotites. In addition, since the eclogite is different from granulite and peridotite in the p T diagram, these three rocks can be classified into two groups: the first group includes eclogites and the second group granulites and peridotites. Then, the p T correlation functions of these two groups of rocks are provided. Finally, the two groups of rocks have different geothermal gradients at the same pressure gradient or have different pressure gradients at the same geothermal gradient. The temperatures and pressures for the formation of the rocks can be calculated from the mineral chemical compositions, but the depths ( H ) for the rock formation can be calculated only under the hypotheses of given p H (or T H ) correlation functions. The explanations for the ultrahigh pressure metamorphism vary obviously with different hypotheses.

A study of hydrate plug formation in a subsea natural gas pipeline using a novel high-pressure flow loop

The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages in the pipeline occur occasionally. To maintain the natural gas flow in the pipeline, we proposed a method for analyzing blockages and ascribed them to the hydrate formation and agglomeration. A new high-pressure flow loop was developed to investigate hydrate plug formation and hydrate particle size, using a mixture of diesel oil, water, and natural gas as experimental fluids. The influences of pressure and initial flow rate were also studied. Experimental results indicated that when the flow rate was below 850 kg/h, gas hydrates would form and then plug the pipeline, even at a low water content （10%） of a water/oil emulsion. Furthermore, some practical suggestions were made for daily management of the subsea pipeline.

Effect of high-pressure homogenization on stability of emulsions containing zein and pectin

The aim of this study was to investigate the effect of high-pressure homogenization on the droplet size and physical stability of different formulations of pectin–zein stabilized rice bran oil emulsions. The obtained emulsions, both before and after passing through highpressure homogenizer, were subjected to stability test under environmental stress conditions,that is, temperature cycling at 4 °C/40 °C for 6 cycles and centrifugal test at 3000 rpm for 10 min. Applying high-pressure homogenization after mechanical homogenization caused only a small additional decrease in emulsion droplet size. The droplet size of emulsions was influenced by the type of pectin used;emulsions using high methoxy pectin(HMP) were smaller than that using low methoxy pectin(LMP). This is due to a greater emulsifying property of HMP than LMP. The emulsions stabilized by HMP–zein showed good physical stability with lower percent creaming index than those using LMP, both before and after passing through high-pressure homogenizer. The stability of emulsions after passing through high-pressure homogenizer was slightly higher when using higher zein concentration, resulting from stronger pectin–zein complexes that could rearrange and adsorb onto the emulsion droplets.

Mechanisms and capacity of high-pressure soaking after hydraulic fracturing in tight/shale oil reservoirs

Huff-n-puff by water has been conducted to enhance oil recovery after hydraulic fracturing in tight/shale oil reservoirs.However,the mechanisms and capacity are still unclear,which significantly limits the application of this technique.In order to figure out the mechanisms,the whole process of pressurizing,high-pressure soaking,and depressurizing was firstly discussed,and a mechanistic model was established.Subsequently,the simulation model was verified and employed to investigate the significances of high-pressure soaking,the contributions of different mechanisms,and the sensitivity analysis in different scenarios.The results show that high-pressure soaking plays an essential role in oil production by both imbibition and elasticity after hydraulic fracturing.The contribution of imbibition increases as the increase in bottom hole pressure(BHP),interfacial tension,and specific surface area,but slightly decreases as the oil viscosity increases.In addition,it first decreases and then slightly increases with the increase in matrix permeability.The optimal soaking time is linear with the increases of both oil viscosity and BHP and logarithmically declines with the increase in matrix permeability and specific surface area.Moreover,it shows a rising tendency as the interficial tension(IFT)increases.Overall,a general model was achieved to calculate the optimal soaking time.