http://www.sciencedirect.com/science/article/pii/S1674987112000035

The well SK-I in the Songliao Basin is the first scientific borehole targeting the continental Cretaceous strata in China.Oval concretions,thin laminae and beds of dolostone are found intercalated within mudstone and organic-rich black shale in the Nenjiang Formation of Campanian age.Low ordered ferruginous dolomite is composed of euhedral-subhedral rhombs with cloudy nucleus and light rims formed during the diagenesis.which are typical features of replacement.The heavy carbon isotopes (δ¹³C_PDB-1.16-16.0) are results of both the fermentation of organic matter by microbes and degassing of carbon dioxide during the period of diagenesis,and the presence of light oxygen isotopes(δ¹⁸O_Pdb- 18.53～-5.1) is a characteristic feature of fresh water influence which means the carbonate may have been altered by ground water or rainwater in the late diagenesis.Marine water incursions into the normally lacustrine basin have been proved by both the salinity of Z value and the occurrence of foraminifera in the same strata where dolomite occurs.Pyrite framboids observed by SEM are usually enclosed in the dolomite crystals or in the mudstones,supporting the sulfate reducing bacteria（SRB）.The formation of both dolomite and pyrite are associated with marine water incursions,which not only supply magnesium ion for dolomite,but also result in limited carbonate precipitation in the basin.The presence of pyrite tramboids indicates the development of an anoxic environment associated with salinity stratification in the lake.The dolomite in the Nenjiang Formation is the results of marine water incursions,diagenetic replacement of calcareous carbonate and sulfate reducing bacteria（SRB）.     

http://www.sciencedirect.com/science/article/pii/S1674987112000345

Holocene environmental change and environmental archaeology are important components of an international project studying the human-earth interaction system.This paper reviews the progress of Holocene environmental change and environmental archaeology research in the Yangtze River Valley over the last three decades,that includes the evolution of large freshwater lakes.Holocene transgression and sea-level changes,Holocene climate change and East Asian monsoon variation,relationship between the rise and fall of primitive civilizations and environmental changes,cultural interruptions and palaeoflood events,as well as relationship between the origin of agriculture and climate change.These research components are underpinned by the dating of lacustrine sediments,stalagmites and peat to establish a chronology of regional environmental and cultural evolution.Interdisciplinary and other environment proxy indicators need to be used in comparative studies of archaeological site formation and natural sedimentary environment in the upper,middle and lower reaches of the Yangtze River Valley.Modern technology such as remote sensing,molecular bioarchaeology,and virtual reality,should be integrated with currently used dating,geochemical,sedimentological.and palaeobotanical methods of analysis in environmental archaeology macro- and micro-studies,so as to provide a greater comprehensive insight into Holocene environmental and cultural interaction and change in the Yangtze River Valley area.     

http://www.sciencedirect.com/science/article/pii/S1674987112000643

Incipient charnockites represent granulite formation on a mesoscopic scale and have received considerable attention in understanding fluid processes in the deep crust.Here we report new petrological data from an incipient charnockite locality at Rajapalaiyam in the Madurai Block,southern India,and discuss the petrogenesis based on mineral phase equilibrium modeling and pseudosection analysis. Rajapalaiyam is a key locality in southern India from where diagnostic mineral assemblages for ultrahigh-temperature（UHT） metamorphism have been reported.Proximal to the UHT rocks are patches and lenses of charnockite（Kfs + Qtz + Pl + Bt + Opx + Grt + Ilm） occurring within Opx-free Grt-Bt gneiss（Kfs + Pl + Qtz + Bt + Grt + Ilm + Mt） which we report in this study.The application of mineral equilibrium modeling on the charnockitic assemblage in NCKFMASHTO system yields a p-T range of～820℃and～9 kbar.Modeling of the charnockite assemblage in the MnNCKFMASHTO system indicates a slight shift of the equilibrium condition toward lower p and T（～760℃and～7.5 kbar）. which is consistent with the results obtained from geothermobarometry（710—760℃,6.7—7.5 kbar）. but significantly lower than the peak temperatures（>1000℃） recorded from the UHT rocks in this locality,suggesting that charnockitization is a post-peak event.The modeling of T versus molar H₂O content in the rock（M（H₂O）） demonstrates that the Opx-bearing assemblage in charnockite and Opxfree assemblage in Grt-Bt gneiss are both stable at M（H₂O） = 0.3 mol%-0.6 mol%.and there is no significant difference in water activity between the two domains.Our finding is in contrast to the previous petrogenetic model of incipient charnockite formation which envisages lowering of water activity and stabilization of orthopyroxene through breakdown of biotite by dehydration caused by the infiltration of CO₂-rich fluid.T-X_Fe³⁺（= Fe₂O₃/（FeO + Fe₂O₃） in mole） pseudosections suggest that the oxidation condition of the rocks played a major role on the stability of orthopyroxene:Opx is stable at X_Fe³⁺ <0.03 in charnockite.while Opx-free assemblage in Grt-Bt gneiss is stabilized at X_Fe³⁺ >0.12.Such low oxygen fugacity conditions of X_Fe³⁺ <0.03 in the charnockite compared to Grt-Bt gneiss might be related to the infiltration of a reduced fluid（e.g.,H₂O + CH₄） during the retrograde stage.     

http://www.sciencedirect.com/science/article/pii/S1674987114000024

We propose that the brittle-ductile transition(BDT) controls the seismic cycle.In particular,the movements detected by space geodesy record the steady state deformation in the ductile lower crust,whereas the stick-slip behavior of the brittle upper crust is constrained by its larger friction.GPS data allow analyzing the strain rate along active plate boundaries.In all tectonic settings,we propose that earthquakes primarily occur along active fault segments characterized by relative minima of strain rate,segments which are locked or slowly creeping.We discuss regional examples where large earthquakes happened in areas of relative low strain rate.Regardless the tectonic style,the interseismic stress and strain pattern inverts during the coseismic stage.Where a dilated band formed during the interseismic stage,this will be shortened at the coseismic stage,and vice-versa what was previously shortened,it will be dilated.The interseismic energy accumulation and the coseismic expenditure rather depend on the tectonic setting(extensional,contractional,or strike-slip).The gravitational potential energy dominates along normal faults,whereas the elastic energy prevails for thrust earthquakes and performs work against the gravity force.The energy budget in strike-slip tectonic setting is also primarily due elastic energy.Therefore,precursors may be different as a function of the tectonic setting.In this model,with a given displacement,the magnitude of an earthquake results from the coseismic slip of the deformed volume above the BDT rather than only on the fault length,and it also depends on the fault kinematics.     

http://www.sciencedirect.com/science/article/pii/S1674987114001649

Hydrocarbon production from shale has attracted much attention in the recent years. When applied to this prolific and hydrocarbon rich resource plays, our understanding of the complexities of the flow mechanism(sorption process and flow behavior in complex fracture systems- induced or natural) leaves much to be desired. In this paper, we present and discuss a novel approach to modeling, history matching of hydrocarbon production from a Marcellus shale asset in southwestern Pennsylvania using advanced data mining, pattern recognition and machine learning technologies. In this new approach instead of imposing our understanding of the flow mechanism, the impact of multi-stage hydraulic fractures, and the production process on the reservoir model, we allow the production history, well log, completion and hydraulic fracturing data to guide our model and determine its behavior. The uniqueness of this technology is that it incorporates the so-called "hard data" directly into the reservoir model, so that the model can be used to optimize the hydraulic fracture process. The "hard data" refers to field measurements during the hydraulic fracturing process such as fluid and proppant type and amount, injection pressure and rate as well as proppant concentration. This novel approach contrasts with the current industry focus on the use of "soft data"(non-measured, interpretive data such as frac length, width,height and conductivity) in the reservoir models. The study focuses on a Marcellus shale asset that includes 135 wells with multiple pads, different landing targets, well length and reservoir properties. The full field history matching process was successfully completed using this data driven approach thus capturing the production behavior with acceptable accuracy for individual wells and for the entire asset.     

http://www.sciencedirect.com/science/article/pii/S1674987115001334

The Hongyanjing inter-arc basin,is located at the central part of Beishan Orogenic College(BOC),Gansu Province,northwest China.Thick sequences of Permian sediments were strongly folded,forming extremely spectacular superposed folds.To better understand the thermal history of Hongyanjing interarc basin and to potentially constrain the timing of deformation,apatite fission track thermochronology method was applied on two superposed folds in the Hongyanjing Basin.Samples from the basin,yield central AFT ages ranging from-206 to 118 Ma.AFT peak ages were largely consistent between samples and can divided into three groups:245,204-170 and 112-131 Ma.Subsequent thermal history modeling of the samples from the Hongyanjing Basin can be summarized as follows:(1) thermal reheating by sedimentary burial at ~ 260 to-220 Ma;(2) major cooling from-220 to- 180 Ma;(3) an episode of very slow subsequent cooling from ~180 to 65 Ma(-80 ℃) to present-day outcrop temperatures.Sediments in the Hongyanjing Basin were folded forming F_1 fold during the early to late Triassic(-240-~220 Ma),by regional stress,and at the time that the adjacent Xingxingxia shear zone started to become active.It is further suggested that the F_2 folding occurred at ~225-219 Ma.The deformation age of F_2 should be extended to 180 Ma based on our thermal history modeling for the Hongyanjing Basin,which show a rapid exhumation and cooling at the late Triassic to early Jurassic(-220-~180 Ma).In our interpretations,the F_1 folding is therefore thought to be related to the final closure of the Paleo-Asian Ocean,while the F_2 folding occurred at ~225-180 Ma associated with a major pulse of orogenesis in the BOC.     

http://www.sciencedirect.com/science/article/pii/S1674987111000491

Based on the interpretations of three seismic profiles and one wide-angle seismic profile across the Northwest Sub-basin, South China Sea, stratigraphic sequences, deformation characteristics and an extension model for this sub-basin have been worked out. Three tectonic-stratigraphic units are determined. Detailed analyses of extension show that the event occurred mainly during the Paleogene and resulted in the formation of half-grabens or grabens distributed symmetrically around the spreading center. Sediments are characterized by chaotic and discontinuous reflectors, indicating clastic sediments. Farther to the southwest, the sub-basin features mainly continental rifting instead of sea-floor spreading. The rifting would have been controlled by the shape of the massif and developed just along the northern edge of the Zhongsha-Xisha Block, rather than joined the Xisha Trough. After 25 Ma, a southward ridge jump triggered the opening of the Southwest Sub-basin. The NW-directed stress caused by the sea-floor spreading of the Northwest Sub-basin may have prevented the continuous opening of the sub-basin. After that the Northwest Sub-basin experienced thermal cooling and exhibited broad subsidence. The deep crustal structure shown by the velocity model from a wide-angle seismic profile is also symmetrical around the spreading center, which indicates that the Northwest Sub-basin might have opened in a pure shear model.     

http://www.sciencedirect.com/science/article/pii/S1674987114000243

We combine a geological, geochemical and tectonic dataset from 118 ophiolite complexes of the major global Phanerozoic orogenic belts with similar datasets of ophiolites from 111 Precambrian greenstone belts to construct an overview of oceanic crust generation over 4 billion years. Geochemical discrimi- nation systematics built on immobile trace elements reveal that the basaltic units of the Phanerozoic ophiolites are dominantly subduction-related （75%）, linked to backarc processes and characterized by a strong MORB component, similar to ophiolites in Precambrian greenstone sequences （85%）. The remaining 25% Phanerozoic subduction-unrelated ophiolites are mainly （74%） of Mid-Ocean-Ridge type （MORB type）, in contrast to the equal proportion of RiftlContinental Margin, Plume, and MORB type ophiolites in the Precambrian greenstone belts. Throughout the Phanerozoic there are large geochemical variations in major and trace elements, but for average element values calculated in 5 bins of 100 million year intervals there are no obvious secular trends. By contrast, basaltic units in the ophiolites of the Precambrian greenstones （calculated in 12 bins of 250 million years intervals）, starting in late Paleo- to early Mesoproterozoic （ca. 2.0-1.8 Ga）, exhibit an apparent decrease in the average values of incom- patible elements such as Ti, P, Zr, Y and Nb, and an increase in the compatible elements Ni and Cr with deeper time to the end of the Archean and into the Hadean. These changes can be attributed to decreasing degrees of partial melting of the upper mantle from HadeanJArchean to Present. The onset of geochemical changes coincide with the timing of detectible changes in the structural architecture of the ophiolites such as greater volumes of gabbro and more common sheeted dyke complexes, and lesser occurrences of ocelli （varioles） in the pillow lavas in ophiolites younger than 2 Ga. The global data from the Precambrian ophiolites, representative of nearly 50% of all known worldwide greenston     

http://www.sciencedirect.com/science/article/pii/S1674987113000558

Several stratigraphic breaks and unconformities exist in the Mesoproterozoic successions in the northern margin of the North China Block.Geologic characters and spatial distributions of fve of these unconformities,which have resulted from different geological processes,have been studied.The unconformity beneath the Dahongyu Formation is interpreted as a breakup unconformity,representing the time of transition from continental rift to passive continental margin.The unconformities beneath the Gaoyuzhuang and the Yangzhuang formations are considered to be the consequence of regional eustatic fuctuations,leading to the exposure of highlands in passive margins during low sea-level stands and transgressive deposition on coastal regions during high sea-level stands.The unconformity atop the Tieling Formation might be caused by uplift due to contractional deformation in a back-arc setting,whereas the uplift after the deposition of the Xiamaling Formation might be attributed to a continental collision event.It is assumed that the occurrences of these unconformities in the Mesoproterozoic successions in the northern margin of the North China Block had a close bearing on the assemblage and breakup of the Columbia and Rodinia supercontinents.     

http://www.sciencedirect.com/science/article/pii/S1674987114001285

<正>There are number of geoinformation approaches and modeling tools to the numerical measurement of natural hazards,including direct and indirect heuristic approaches,and deterministic,probabilistic,statistical and data mining approaches(Pradhan and Buchroithner,2012;Pradhan et al.,2012,2014;Pradhan,2013).In this thematic section of Geoscience Frontiers,a set of six contributions are assembled that provide a window on various parameters,     

http://www.sciencedirect.com/science/article/pii/S1674987114001340

Two amphiboles and a syn-metamorphic quartz vein from the Yuka terrane,North Qaidam,western China,have been analyzed by joint ~(40)Ar/~(39)Ar crushing in vacuo and stepwise heating techniques.The crushing in vacuo results provide information to directly constrain the timing of fluid activity and the age of amphibolite-facies retrogression.The stepwise heating results could further be used to decipher the thermal history of the UHP rocks.Amphiboles from amphibolites and quartz vein within garnetamphibolite lens analyzed by in vacuo crushing yield similarly shaped age spectra and exhibit relatively flat age plateaus for the last several steps.The characteristics of gas release patterns and geochronological data testify to the presence of significant excess ~(40)Ar within the fluid inclusions.The age plateaux with weighted mean ages(WMA) ranges from 488 to 476 Ma for amphiboles and 403 Ma for quartz(2σ).These data points constitute amphibole WMA yielding excellent isochrons with isochron ages of 469 and 463 Ma with initial ~(40)Ar/~(36)Ar ratios of 520 and 334,respectively.The isochron ages are interpreted to represent initial amphibolite-facies retrogression.The data points constituting the quartz age plateaux give an isochron age of 405 Ma with initial ~(40)Ar/~(36)Ar ratio of 295,recording a significant aqueous fluid flow episode during the early Devonian.Age spectra obtained by stepwise heating of amphibole residues remaining after crushing experiments are characterized by younger and relatively complex age spectra,which are probably influenced by the combined effects of resetting argon and/or mineral inclusions.Nevertheless,we note that the spectra shapes have features in common:excluding the last two steps,minimum apparent ages are found at temperatures of around 500 ℃,corresponding to319 and 249 Ma,perhaps representing the time of isotopic resetting or resulting from release gas from mineral inclusions of,e.g.,biotite or feldspar.Maximum apparent ages are obtained at temperatures of around 800℃,corresponding to 418 and 413 Ma,which probably reflect mixed ages of radiogenic resetting and original amphibole.These results indicate that the Yuka eclogites and their retrogressed equivalents were overprinted by multiple thermal events in the Silurian and possibly as young as the Triassic.     

http://www.sciencedirect.com/science/article/pii/S1674987114000231

The possibility of a net rotation of the lithosphere with respect to the mantle is generally overlooked since it depends on the adopted mantle reference frames,which are arbitrary.We review the geological and geophysical signatures of plate boundaries,and show that they are markedly asymmetric worldwide.Then we compare available reference frames of plate motions relative to the mantle and discuss which is at best able to fit global tectonic data.Different assumptions about the depths of hotspot sources(below or within the asthenosphere,which decouples the lithosphere from the deep mantle) predict different rates of net rotation of the lithosphere relative to the mantle.The widely used no-net-rotation(NNR) reference frame,and low(0.2°-0.4° /Ma) net rotation rates(deep hotspots source) predict an average net rotation in which some plates move eastward relative to the mantle(e.g.,Nazca).With fast(1° /Ma) net rotation(shallow hotspots source),all plates,albeit at different velocity,move westerly along a curved trajectory,with a tectonic equator tilted about 30° relative to the geographic equator.This is consistent with the observed global tectonic asymmetries.     

http://www.sciencedirect.com/science/article/pii/S1674987114001558

The "Arctic" region,where the North Pole occupies the center of the Arctic Ocean,has been affecting the environmental variation of the Earth from geological time to the present.However,the seismic activities in the area are not adequately monitored.Therefore,by conducting long term monitoring of seismic phenomenon as sustainable parameters,our understanding of both the tectonic evolution of the Earth and the dynamic interaction between the cryosphere and geosphere in surface layers of the Earth will increase.In this paper,the association of the seismicity and structure of the Arctic region,particularly focused on Eurasian continent and surrounding oceans,and its relationship with regional evolution during the Earth's history is studied.The target areas cover representative tectonic provinces in the Eurasian Arctic,such as the wide area of Siberia,Baikal Rift Zone.Far East Russia,Arctic Ocean together with Greenland and Northern Canada.Based on discussion including characteristics of seismicity,heterogeneous structure of the crust and upper mantle,tectonic history and recent dynamic features of the Earth's surface in the Arctic are summarized.     

http://www.sciencedirect.com/science/article/pii/S1674987112000667

The brackish-water bivalve Waagenopema Tokuyama,1959 is reported from the Lower Jurassic Badaowan Formation at four localities,along the southern margin and western margin of the Junggar Basin. Taphonomic features recorded in the field indicate that it occurs in autochthonous or parautochthonous assemblages.The autecology of Waagenopema therefore yields information on the palaeoenvironment of the area.The restriction of Waagenopema to marine and brackish-water settings suggests that the sea water once reached these areas during the Sinemurian.This paper discusses the palaeogeographic implications and suggests an ingression of the sea water from the west to the western and southern part of the Junggar Basin.Additionally,the two Waagenopema species collected from the Haojiagou section in the Junggar Basin are taxonomically documented.     

http://www.sciencedirect.com/science/article/pii/S1674987112000424

Subcooled liquid solubility is the water solubility for a hypothetical state of liquid.It is an important parameter for multicomponent nonaqueous phase liquids(NAPLs) containing polycyclic aromatic hydrocarbons(PAHs),which can exist as liquids even though most of the solutes are solid in their pure form at ambient temperature.So far,subcooled liquid solubilities were estimated from the solid water solubility and fugacity ratio of the solid and(subcooled) liquid phase,but rarely derived from experimental data.In our study,partitioning batch experiments were performed to determine the subcooled liquid solubility of PAHs in NAPL-water system.For selected PAH,a series of batch experiments were carried out at increased mole fractions of the target component in the NAPL and at a constant NAPL/ water volume ratio.The equilibrium aqueous PAH concentrations were measured with HPLC and/or GCMS. The subcooled liquid solubility was derived by extrapolation of the experimental equilibrium aqueous concentration to a mole fraction of unity.With the derived subcooled liquid solubility,the fugacity ratio and enthalpy of fusion of the solute were also estimated.Our results show a good agreement between the experimentally determined and published data.     

http://www.sciencedirect.com/science/article/pii/S1674987112001053

Massif anorthosites form when basaltic magma differentiates in crustal magma chambers to form low-density plagioclase and a residual liquid whose density was greater than that of enclosing crustal rocks. The plagioclase and minor pyroxene crystallized in-situ on the floor of the magma chamber to produce the anorthosite complex, and the residual liquid migrated downwards, eventually to solidify as dense Fe-rich cumulates some of which were removed to the mantle. These movements were facilitated by high temperatures in Proterozoic continental crust, thus explaining the restriction of large anorthosite massifs to this period in Earth history.     

http://www.sciencedirect.com/science/article/pii/S1674987112001260

Archaea have unique glycerol dialkyl glycerol tetraether (GDGT) lipids that can be used to develop paleotemperature proxies such as TEX₈₆. This research is to validate proposed GDGT-proxies for paleotemperature determination in the South China Sea (SCS). Samples were collected from core-top sediments (0–5 cm) in the northern SCS. Total lipids were extracted to obtain core GDGTs, which were identified and quantified using liquid chromatography-mass spectrometry (LC-MS). The abundance of isoprenoidal GDGTs (iGDGTs) ranged from 271.5 ng/g dry sediment to 1266.3 ng/g dry sediment, whereas the branched GDGTs (bGDGTs), supposedly derived from terrestrial sources, ranged from 22.2 ng/g dry sediment to 56.7 ng/g dry sediment. The TEX₈₆-derived sea surface temperatures ranged from 20.9 °C in the coast (water depth < 160 m) to 27.9 °C offshore (water depth > 1000 m). TEX₈₆-derived temperatures near shore (<160 m water depth) averaged 23.1 ± 2.5 °C (n = 4), which were close to the satellite-derived winter mean sea surface temperature (average 22.6 ± 1.0 °C, n = 4); whereas the TEX₈₆-derived temperatures offshore averaged 27.4 ± 0.3 °C (n = 7) and were consistent with the satellite mean annual sea surface temperature (average 26.8 ± 0.4 °C, n = 7). These results suggest that TEX₈₆ may record the sea surface mean annual temperature in the open ocean, while it likely records winter sea surface temperature in the shallower water.     

http://www.sciencedirect.com/science/article/pii/S1674987112001259

The eastern Pontides orogenic belt provides a window into continental arc magmatism in the Alpine-Himalayan belt.The late Mesozoic-Cenozoic geodynamic evolution of this belt remains controversial.Here we focus on the nature of the transition from the adakitic to non-adakitic magmatism in the Kale area of Gumushane region in NE Turkey where this transition is best preserved.The adakitic lithologies comprise porphyries and hyaloclastites.The porphyries are represented by biotite-rich andesites,hornblende-rich andesite and dacite.The hayaloclastites represent the final stage of adakitic activity and they were generated by eruption/intrusion of adakitic andesitic magma into soft carbonate mud.The non-adakitic lithologies include basaltic-andesitic volcanic and associated pyroclastic rocks. Both rock groups are cutting by basaltic dikes representing the final stage of the Cenozoic magmatism in the study area.We report zircon U-Pb ages of 48.71±0.74 Ma for the adakitic rocks,and 44.68±0.84 Ma for the non-adakitic type,suggesting that there is no significant time gap during the transition from adakitic to non-adakitic magmatism.We evaluate the origin,magma processes and tectonic setting of the magmatism in the southern part of the eastern Pontides orogenic belt.Our results have important bearing on the late Mesozoic-Cenozoic geodynamic evolution of the eastern Mediterranean region.     

The genesis of the slab window-related Arzular low-sulfidation epithermal gold mineralization （eastern Pontides, NE Turkey）

The Arzular mineralization is one of the best examples of epithermal gold deposits in the eastern Pontides orogenic belt.The mineralization is hosted by the subduction-related basaltic andesites and is mainly controlled by E-W and NE-SW trending fracture zones.The main ore minerals are galena, sphalerite,pyrite.chalcopyrite.tetrahedrite and gold.Homogenization temperatures of fluid inclusions are between 130 and 295℃ for quartz and between 90 and 133℃ for sphalerite.Sulphur isotope values obtained from pyrite,galena and sphalerite vary between 1.2‰ and 3‰.indicating that sulphur belongs to magmatic origin and was derived from the Lutetian non-adakitic granitic intrusions in the region.Oxygen isotope values are between 15.0‰ and 16.7‰ and hydrogen isotope values are between -87‰ and -91‰ The sulphur isotope thermometer yielded temperatures in the range of 244-291℃ for the ore formation.Our results support the hypothesis that the Arzular mineralization is a low-sulfidation epithermal gold deposit associated with non-adakitic subduction- related granitic magmas that were generated by slab window-related processes in a south-dipping subduction zone during the Lutetian.     

http://www.sciencedirect.com/science/article/pii/S1674987111000843

We report equilibrium sapphirine t quartz assemblage in biotiteeorthopyroxeneegarnet granulites from a new locality in Panasapattu of Paderu region in the Eastern Ghats granulite belt, which provide new evidence for ultrahigh-temperature (UHT) metamorphism at 1030e1050 C and 10 kbar in this region. The development of migmatitic texture, stabilization of the garneteorthopyroxenee plagioclaseeK-feldspar association, prograde biotite inclusions within garnet and sapphirine as well as sapphirine and cordierite inclusions within garnet in these granulites indicate that the observed peak assemblages probably formed during prograde dehydration melting of a BteSilleQtz assemblage, and constrain the prograde stage of the PeT path. The core domains of orthopyroxene porphyroblasts have up to wt(Al2O3) 9.6%, which suggest that the temperatures reached up to 1150 C suggesting extreme crustal metamorphism. These conditions were also confirmed by the garneteorthopyroxene thermobarometery, which yields a PeT range of 1012e960 C and 9.4 kbar. The PeT phase topologies computed using isochemical sections calculated in the model system Na2OeCaOeK2OeFeOeMgOeAl2O3eSiO2 eH2O (NCKFMASH) for metapelites, garnet-free sapphirine granulites and garnet-bearing sapphirine granulites match the melt-bearing assemblages observed in these rocks. Isochemical sections constructed in the NCKFMASH system for an average sub-aluminous metapelite bulk composition, and contoured for modal proportions of melt and garnet, as well as for the compositional isopleths of garnet, predict phase and reaction relations that are consistent with those observed in the rocks. Garnet and orthopyroxene contain Ti-rich phlogopite inclusions, suggesting formation by prograde melting reactions at the expense of phlogopite during ultrahigh-temperature conditions. These PeT results underestimate ‘peak’ conditions, in part as a result of the modification of garnet compositions in the domains where some melt was retained. The post-peak evolution is constrained by a succession of melt-present reactions that occur at P < 10 kbar, inferred from micro-structural relations among various minerals. After high-temperature decompression from the metamorphic peak, the PeT path followed a near isobaric cooling stage to T < 900 C. The UHT rocks investigated in this study occur within a continental collision suture which witnessed prolonged subductioneaccretion history prior to the final collision. We correlate the extreme metamorphism and the stabilization of UHT mineral assemblages to heat and volatile input from an upwelled asthenosphere during subductionecollision tectonics in a Proterozoic convergent plate margin.