http://www.sciencedirect.com/science/article/pii/S1674987111000272

We present here a thermodynamic model for predicting multi-phase equilibrium of methane hydrate liquid and vapor phases under conditions of different temperature,pressure,salinity and pore sizes.The model is based on the 1959 van der Waals—Platteeuw model,angle-dependent ab initio intermolecular potentials,the DMW-92 equation of state and Pitzer theory.Comparison with all available experimental data shows that this model can accurately predict the effects of temperature,pressure, salinity and capillary r...     

Dating of zircon from high-grade rocks： Which is the most reliable method？

Magmatic zircon in high-grade metamorphic rocks is often characterized by complex textures as revealed by cathodoluminenscence （CL） that result from multiple episodes of recrystallization, over- growth, Pb-loss and modifications through fluid-induced disturbances of the crystal structure and the original U-Th-Pb isotopic systematics. Many of these features can be recognized in 2-dimensional CL images, and isotopic analysis of such domains using a high resolution ion-microprobe with only shallow penetration of the zircon surface may be able to reconstruct much of the magmatic and complex post- magmatic history of such grains. In particular it is generally possible to find original magmatic domains yielding concordant ages. In contrast, destructive techniques such as LA-ICP-MS consume a large volume, leave a deep crater in the target grain, and often sample heterogeneous domains that are not visible and thus often yield discordant results which are difficult to interpret. We provide examples of complex magmatic zircon from a southern Indian granulite terrane where SHRIMP lI and LA-ICP-MS analyses are compared. The SHRIMP data are shown to be more precise and reliable, and we caution against the use of LA-ICP-MS in deciphering the chronology of complex zircons from high-grade terranes.     

A review of the ～1600 Ma sedimentation, volcanism, and tectono-thermal events in the Singhbhum craton, Eastern India

The Palaeoproterozoic–Mesoproterozoic transition (～1600 Ma) is a significant event in the Earth history as a global thermal perturbation affected the pre-1600 Ma landmasses. Like other cratonic blocks of the world, lithospheric thinning, sedimentation, magmatism, metamorphism and crustal melting/anatexis are associated with this significant geological event in the Singhbhum cratonic province of India. This paper is a review of sedimentological, magmatic and tectono-thermal events in the Singhbhum craton at ～1600 Ma. The Palaeo-Mesoproterozoic sedimentation and volcanism in the Singhbhum craton took place in a terrestrial intracontinental rift setting. The available geochronological data are indicative of late Palaeoproterozoic to Neoproterozoic tectono-thermal events in the Chhotanagpur Granite Gneissic Complex (CGGC), an east–west trending arcuate belt of granite gneisses, migmatites and metasedimentary rocks. A detailed multidisciplinary geo-scientific investigation of the Dalma volcanic belt and the area to its north (Chandil Formation) and further north in CGGC will enable us to constrain the extant surface processes and crust-mantle interactions, the collision events between the North and South Indian cratonic blocks, and the position of India in the Columbia supercontinent.     

http://www.sciencedirect.com/science/article/pii/S1674987114000437

The Pranhita-Godavari Basin in central eastern India is one of the Proterozoic "Purana" basins of cratonic India.New geochronology demonstrates that it has a vast depositional history of repeated basin reactivation from the Palaeoproterozoic to the Mesozoic.U-Pb laser ablation inductively coupled plasma mass spectrometry dating of detrital zircons from two samples of the Somanpalli Group—a member of the oldest sedimentary cycle in the valley-constrains its depositional age to ~1620 Ma and demonstrates a tripartite age provenance with peaks at ~3500 Ma,~2480 Ma and ~1620 Ma,with minor age peaks in the Eoarchaean(~3.8 Ga) and at ~2750 Ma.These ages are consistent with palaeocurrent data suggesting a southerly source from the Krishna Province and Enderby Land in East Antarctica.The similarity in the maximum depositional age with previously published authigenic glauconite ages suggest that the origin of the Pranhita-Godvari Graben originated as a rift that formed at a high angle to the coeval evolving late Meosproterozoic Krishna Province as Enderby Land collided with the Dharwar craton of India.In contrast,detrital zircons from the Cycle III Sullavai Group red sandstones yielded a maximum depositional age of 970±20 Ma and had age peaks of ~2550 Ma,~1600 Ma and then a number of Mesoproterozoic detrital zircons terminating in three analyses at ~970 Ma.The provenance of these is again consistent with a southerly source from the Eastern Ghats Orogen and Antarctica.Later cycles of deposition include the overlying Albaka/Usur Formations and finally the late Palaeozoic to Mesozoic Gondwana Supergroup.     

http://www.sciencedirect.com/science/article/pii/S1674987111001046

The role played by Paleoproterozoic cratons in southern South America from the Mesoproterozoic to the Early Cambrian is reconsidered here.This period involved protracted continental amalgamation that led to formation of the supercontinent Rodinia.followed by Neoproterozoic continental break-up,with the consequent opening of Clymene and Iapetus oceans,and finally continental re-assembly as Gondwana through complex oblique collisions in the Late Neoproterozoic to Early Cambrian.The evidence for this is based mainly on a combination of precise U-Pb SHRMP dating and radiogenic isotope data for igneous and metamorphic rocks from a large area extending from the Rio de la Plata craton in the east to the Argentine Precordillera in the west and as far north as Arequipa in Peru.Our interpretation of the paleogeographical and geodynamic evolution invokes a hypothetical Paleoproterozoic block(MARA) embracing basement ultimately older than 1.7 Ga in the Western Sierras Pampeanas(Argentina),the Arequipa block(Peru),the Rio Apa block(Brazil),and probably also the Paraguaia block(Bolivia).     

http://www.sciencedirect.com/science/article/pii/S1674987113000297

This paper compiles lithostratigraphic and geochronological data obtained for the Palaeoproterozoic glacial diamictite-bearing successions,and thereby provides insights into understanding the geological processes causing the Huronian Glaciation Event.The majority of evidence for appearances of this glaciation event can be related to the Kenorland supercontinent breakup,allied to significant atmospheric change,as well as blooms of biogeochemical oxygenic photosynthesis.In this paper,the Huronian Glaciation Event is constrained to have occurred synchronously during 2.29-2.25 Ga,accompanied by dramatic environmental changes characteristic of the Great Oxidation Event which includes the pre- 2.3 Ga hydrosphere oxidation and the post-2.3 Ga atmosphere oxygenation.     

http://www.sciencedirect.com/science/article/pii/S1674987114000887

The increasing number of fossil pterosaur eggs sheds light on nesting environments and breeding be- haviors of these extinct flying reptiles. Here we report the first partial three-dimensional egg of the pterosaur, Pteroduustro guinazui, from central Argentina. The specimen was discovered from the same Albian deposits as the exceptional R guinazui embryo described in 2004. Microscopic characterizations indicate a pristine preservation of the 50 Bm thick calcium carbonate, which differs significantly from the soft shell of Chinese pterosaur eggs. Estimate of the eggshell conductance implies that the nest had a minimum moisture content of 75%. This moisture estimate, combined with geological and taphonomical data, suggests that P. guinazui may have adopted a nesting strategy similar to those of grebes and flamingos rather than being buried on land, as previously hypothesized. Moreover, our results demon- strate that the nesting paleoenvironment of this pterosaur species was closely linked to a mesohaline lacustrine ecosystem in a basin governed by regional tectonic subsidence, a setting characteristic for the feeding and reproduction of modern flamingos.     

http://www.sciencedirect.com/science/article/pii/S1674987113001333

The basement of the Romanian Carpathians is made of Neoproterozoic to early Paleozoic periGondwanan terranes variably involved in the Variscan orogeny,similarly to other basement terrains of Europe.They were hardly dismembered during the Alpine orogeny and traditionally have their own names in the three Carpathian areas.The Danubian domain of the South Carpathians comprises the Dragsan and Lainici-Paius peri-Amazonian terranes.The Dragsan terrane originated within the ocean surrounding Rodinia and docked with Rodinia at ~800 Ma.It does not contain Cadomian magmatism and consequently it is classified as an Avalonian extra-Cadomian terrane.The Lainici-Paius terrane is a Ganderian fragment strongly modified by Cadomian subduction-related magmatism.It is attached to the Moesia platform.The Tisovita terrane is an ophiolite that marks the boundary between Dragsan and Lainici-Paius terranes.The other basement terranes of the Romanian Carpathians originated close to the Ordovician NorthAfrican orogen,as a result of the eastern Rheic Ocean opening and closure.Except for the Sebes-Lotru terrane that includes a lower metamorphic unit of Cadomian age,all the other terranes(Bretila,Tulghes,Negrisoara and Rebra in the East Carpathians,Somes,Biharia and Baia de Aries in the Apuseni mountains,Fagaras,Leaota,Caras and Pades in the South Carpathians) represent late Cambrian—Ordovician rock assemblages.Their provenance,is probably within paleo-northeast Africa,close to the Arabian-Nubian shield.The late Cambrian-Ordovician terranes are defined here as Carpathian-type terranes.According to their lithostratigraphy and origin,some are of continental margin magmatic arc setting,whereas others formed in rift and back-arc environment and closed to passive continental margin settings.In a paleogeographic reconstruction,the continental margin magmatic arc terranes were first that drifted out,followed by the passive continental margin terranes with the back-arc terranes in their front.They accreted to Laurussia during the Variscan orogeny.Some of them(Sebes-Lotru in South Carpathians and Baia de Aries in Apuseni mountains) underwent eclogite-grade metamorphism.The Danubian terranes,the Bretila terrane and the Somes terrane were intruded by Variscan granitoids.     

http://www.sciencedirect.com/science/article/pii/S1674987112000564

High-pressure（HP） granulites widely occur as enclaves within tonalite-trondhjemitegranodiorite （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 spectroscopy 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 inherited 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 basement. The homogeneous HP metamorphic zircons contain index minerals of high-pressure metamorphism including garnet,clinopyroxene.plagioclase,quartz,rutile and apatite,and yield ²⁰⁷Pb/²⁰⁶Pb ages between 1900 and 1850 Ma,marking the timing of peak HP granulite fades 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 fades 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）.Subsequently, the HP granulites were exhumated to upper crust levels,and were overprinted by medium to low-pressure granulite and amphibolite facies retrograde event at ca.1840—820 Ma.     

http://www.sciencedirect.com/science/article/pii/S1674987110000149

The structural stability of manganese titanate MnTiO3 at high pressure was investigated by X-ray diffraction and Raman spectroscopy with diamond anvil cells. Ilmenite-type MnTiO3 is stable at least to 26.6 GPa, and lithium niobate type MnTiO3 reversibly transforms at room temperature to perovskite at 2.0 GPa. Bulk moduli (K300) of ilmenite, lithium niobate and perovskite are 174(4) GPa, 179(8) GPa, and 208(5) GPa, respectively (at fixed first pressure derivative K′ = 4). The Grüneisen parameter γ has been estimated to be 1.28 for ilmenite and 1.75 for perovskite. In ilmenite phase, TiO6 octahedra become more regular with increasing pressure. In perovskite phase structural distortion increases with pressure increase.     

http://www.sciencedirect.com/science/article/pii/S1674987112001545

The presence of natural voids and cavities in subsurface karstic limestones causes severe problem for civil engineering and environmental management.The presence of such features hinders the extension of urbanizations particularly in the new metropolitan.The eastern part of Saudi Arabia contains various types of karstic limestone,sinkholes,solution cavities and voids.In this context,geophysical methods particularly electrical resistivity technique is used as a cost-effective solution for investigating subsurface caves,voids,and shallow weathered zones.2-D electrical resistivity data sets have been acquired along seven profiles in the new urbanization at Al Hassa area.Data processing has been carried out taking into consideration the response of synthetic models,which simulates physical models of the most common karstic features in the area.The results are very useful to determine the extension of shallow weathered zones and to locate different cavities underneath them.The hard limestone bedrock can also be detected and traced along the surveyed profiles.     

http://www.sciencedirect.com/science/article/pii/S1674987114000334

The Musgrave Province developed at the nexus of the North,West and South Australian cratons and its Mesoproterozoic evolution incorporates a 100 Ma period of ultra-high temperature(UHT) metamorphism from ca.1220 to ca.1120 Ma.This was accompanied by high-temperature A-type granitic magmatism over an 80 Ma period,sourced in part from mantle-derived components and emplaced as a series of pulsed events that also coincide with peaks in UHT metamorphism.The tectonic setting for this thermal event(the Musgrave Orogeny) is thought to have been intracontinental and the lithospheric architecture of the region is suggested to have had a major influence on the thermal evolution.We use a series of two dimensional,fully coupled thermo-mechanical-petrological numerical models to investigate the plausibility of initiating and prolonging UHT conditions under model setup conditions appropriate to the inferred tectonic setting and lithospheric architecture of the Musgrave Province.The results support the inferred tectonic framework for the Musgrave Orogeny,predicting periods of UHT metamorphism of up to 70 Ma,accompanied by thin crust and extensive magmatism derived from both crustal and mantle sources.The results also appear to be critically dependent upon the specific location of the Musgrave Province,constrained between thicker cratonic masses.     

http://www.sciencedirect.com/science/article/pii/S1674987111000247

Recent advances in modeling of tornadoes and twisters consist of significant achievements in mathematical calculation of occurrence and evolution of a violent F5-class tornado on the Fujita scale, and four-dimensional mathematical modeling of a tornado with the fourth coordinate time multiplied by its characteristic velocity.Such a tornado can arise in a thunderstorm supercell filled with turbulent whirlwinds.A theory of the squall storms is proposed.The squall storm is modeled by running perturbation of...     

http://www.sciencedirect.com/science/article/pii/S1674987111000478

Convective heat transfer associated with the circulation of pore-fluid in porous rocks and fractures within the upper crust of the Earth is substantial when the temperature gradient is sufficiently high.In order to understand the process of Sn-polymetallic mineralization in the Dachang ore district of Guangxi,a finite element method has been used in this study to simulate both pore-fluid flow and heat transfer in this district.On the basis of related geological,tectonic and geophysical constraints,a computational model was established.It enables a computational simulation and sensitivity analysis to be carried out for investigating ore-forming pore-fluid flow and other key factors that may affect hydrothermal ore genesis in the district.The related simulation results have indicated that:(1) permeable fault zones in the Dachang ore district can serve as preferential pathways for pore-fluid flow on a regional-scale;and(2) the pore-fluid flow can affect the salinity distribution.This latter factor is part of the reason why Sn-polymetallic mineralization has taken place in this district.     

Petrology and phase equilibrium modeling of sapphirine ＋ quartz assemblage from the Napier Complex,East Antarctica： Diagnostic evidence for Neoarchean ultrahigh-temperature metamorphism

A synthesis of the petrological characters of granulite facies rocks that contain equilibrium sapphirine ＋ quartz assemblage from two localities （Tonagh Island （TI） and Priestley Peak （PP）） in the Napier Complex,East Antarctica,provides unequivocal evidence for extreme crustal metamorphism possibly associated with the collisional orogeny during Neoarchean.The reaction microstructures associated with sapphirine ＋ quartz vary among the samples,probably suggesting different tectonic conditions during the metamorphic evolution.Sapphirine and quartz in TI sample were probably in equilibrium at the peak stage,but now separated by corona of Grt ＋ Sil ＋ Opx suggesting near isobaric cooling after the peak metamorphism,whereas the Spr ＋ Qtz ＋ Sil ＋ Crd ＋ Spl assemblage replaces garnet in PP sample suggesting post-peak decompression.The application of mineral equilibrium modeling in NCKFMASHTO system demonstrated that Spr ＋ Qtz stability is lowered down to 930 ℃ due to small Fe3＋ contents in the rocks （mole Fe2O3/（FeO ＋ Fe2O3） =0.02）.The TI sample yields a peak p-T range of 950-1100 ℃ and 7.5-11 kbar,followed by cooling toward a retrograde stage of 800-950 ℃ and 8-10 kbar,possibly along a counterclockwise p-T path.In contrast,the peak condition of the PP sample shows 1000-1050 ℃ and ＞12 kbar,which was followed by the formation ofSpr ＋ Qtz corona around garnet at 930-970 ℃ and 6.7-7.7 kbar,suggesting decompression possibly along a clockwise p-T trajectory.Such contrasting p-T paths are consistent with a recent model on the structural framework of the Napier Complex that correlates the two areas to different crustal blocks.The different p-T paths obtained from the two localities might reflect the difference in the tectonic framework of these rocks within a complex Neoarchean subduction/collision belt.     

http://www.sciencedirect.com/science/article/pii/S1674987110000320

The self-similar is a common phenomena arising in the field of geology.It has been shown that geochemical element data,mineral deposits,and spacial distribution conform to a fractal structure.A fractal distribution requires that the number of objects larger than a specified size have a power-law dependence on size.This paper shows that a number of distributions,including power-function,Pareto, lognormal,and Zipf,display fractal properties under certain conditions and that this may be used as the mathemat...     

http://www.sciencedirect.com/science/article/pii/S1674987113000091

The current lithospheric geodynamics and tectonophysics in the Baikal rift are discussed in terms of a nonlinear oscillator with dissipation.The nonlinear oscillator model is applicable to the area because stress change shows up as quasi-periodic inharmonic oscillations at rifting attractor structures （RAS）.The model is consistent with the space-time patterns of regional seismicity in which coupled large earthquakes,proximal in time but distant in space,may be a response to bifurcations in nonlinear resonance hysteresis in a system of three oscillators corresponding to the rifting attractors.The space-time distribution of coupled MLH ＞ 5.5 events has been stable for the period of instrumental seismicity,with the largest events occurring in pairs,one shortly after another,on two ends of the rift system and with couples of smaller events in the central part of the rift.The event couples appear as peaks of earthquake ‘migration＇ rate with an approximately decadal periodicity.Thus the energy accumulated at RAS is released in coupled large events by the mechanism of nonlinear oscillators with dissipation.The new knowledge,with special focus on space-time rifting attractors and bifurcations in a system of nonlinear resonance hysteresis,may be of theoretical and practical value for earthquake prediction issues.Extrapolation of the results into the nearest future indicates the probability of such a bifurcation in the region,i.e.,there is growing risk of a pending M ≈ 7 coupled event to happen within a few years.     

http://www.sciencedirect.com/science/article/pii/S1674987111000387

Fluid flow is an integral part of hydrothermal mineralization,and its analysis and characterization constitute an important part of a mineralization model.The hydrodynamic study of mineralization deals with analyzing the driving forces,fluid pressure regimes,fluid flow rate and direction,and their relationships with localization of mineralization.This paper reviews the principles and methods of hydrodynamic studies of mineralization,and discusses their significance and limitations for ore deposit studies and mineral exploration. The driving forces of fluid flow may be related to fluid overpressure,topographic relief,tectonic deformation, and fluid density change due to heating or salinity variation,depending on specific geologic environments and mineralization processes.The study methods may be classified into three types,megascopic(field) observations, microscopic analyses,and numerical modeling.Megascopic features indicative of significantly overpressured (especially lithostatic or supralithostatic) fluid systems include horizontal veins,sand injection dikes,and hydraulic breccias.Microscopic studies,especially microthermometry of fluid inclusions and combined stress analysis and microthermometry of fluid inclusion planes(FIPs) can provide important information about fluid temperature,pressure,and fluid-structural relationships,thus constraining fluid flow models.Numerical modeling can be carried out to solve partial differential equations governing fluid flow, heat transfer,rock deformation and chemical reactions,in order to simulate the distribution of fluid pressure, temperature,fluid flow rate and direction,and mineral precipitation or dissolution in 2D or 3D space and through time.The results of hydrodynamic studies of mineralization can enhance our understanding of the formation processes of hydrothermal deposits,and can be used directly or indirectly in mineral exploration.     

http://www.sciencedirect.com/science/article/pii/S1674987111000788

This paper presents numerical investigation on the ore-forming fluid migration driven by tectonic deformation and thermally-induced buoyancy force in the Chanziping ore district in South China. A series of numerical scenarios are considered to examine the effect of meteoric water precipitation, the dip angle of the faults, unconformity surface, and thermal input on the ore genesis. Our computations reveal that the downward basinal fluid flow driven by extensional stress mixes with the upward basal fluid driven by the thermal input from depth at the junction of two faults at a temperature of about 200 C, triggering the precipitation of the Chanziping uranium deposit.     

http://www.sciencedirect.com/science/article/pii/S1674987114000449

We review petrologic observations of reaction textures from high-grade rocks that suggest the passage of fluids with variable alkali activities. Development of these reaction textures is accompanied by regular compositional variations in plagioclase, pyroxenes, biotite, amphibole and garnet. The textures are interpreted in terms of exchange and net-transfer reactions controlled by the K and Na activities in the fluids. On the regional scale, these reactions operate in granitized, charnockitized, syenitized etc. shear zones within high-grade complexes. Thermodynamic calculations in simple chemical systems show that changes in mineral assemblages, including the transition from the hydrous to the anhydrous ones, may occur at constant pressure and temperature due only to variations in the H2O and the alkali activities. A simple procedure for estimating the activity of the two major alkali oxides, K2O and Na2O, is imple- mented in the TWQ software. Examples of calculations are presented for well-documented dehydration zones from South Africa, southern India, and Sri Lanka. The calculations have revealed two end-member regimes of alkalis during specific metamorphic processes： rock buffered, which is characteristic for the precursor rocks containing two feldspars, and fluid-buffered for the precursor rocks without K-feldspar. The observed reaction textures and the results of thermodynamic modeling are compared with the results of available experimental studies on the interaction of the alkali chloride and carbonate-bearing fluids with metamorphic rocks at mid-crustal conditions. The experiments show the complex effect of alkali activities in the fluid phase on the mineral assemblages. Both thermodynamic calculations and experiments closely reproduce paragenetic relations theoretically predicted by D.S. Korzhinskii in the 1940s.