geochemical and mineralogical evidence for a coal hosted uranium deposit in the yili basin xinjiang northwestern china abstract the petrological geochemical and mineralogical compositions of the coal hosted jurassic uranium ore deposit in the yili basin of xinjiang province northwestern china were investigated using optical microscopy and field emission scanning electron microscopy in conjunction with an energy dispersive x ray spectrometer as well as x ray powder diffraction x ray fluorescence and inductively coupled plasma mass spectrometry the yili coal is of high volatile c b bituminous rank 0 51 0 59 vitrinite reflectance and has a medium sulfur content 1 32 on average fusinite and semifusinite generally dominate the maceral assemblage which exhibits forms suggesting fire driven formation of those macerals together with forms suggesting degradation of wood followed by burning the yili coals are characterized by high concentrations of u up to 7207 g g se up to 253 g g mo 1248 g g and re up to 34 g g as well as as up to 234 g g and hg up to 3858 ng g relative to the upper continental crust the rare earth elements rees in the coals are characterized by heavy or and medium ree enrichment the minerals in the yili coals are mainly quartz kaolinite illite and illite smectite as well as to a lesser extent k feldspar chlorite pyrite and trace amounts of calcite dolomite amphibole millerite chalcopyrite cattierite siegenite ferroselite krutaite eskebornite pitchblende coffinite silicorhabdophane and zircon the enrichment and modes of occurrence of the trace elements and also of the minerals in the coal are attributed to derivation from a sediment source region of felsic and intermediate petrological composition and to two different later stage solutions a u se mo re rich infiltrational and a hg as rich exfiltrational volcanogenic solution the main elements with high enrichment factors u se as and hg overall exhibit a mixed organic inorganic affinity the uranium minerals pitchblende and coffinite occur as cavity fillings in structured inertinite macerals selenium as and hg in high pyrite samples mainly show a sulfide affinity

structure of a frontal cyclone a diagnostic study of a mid latitude cyclone has been carried out using routinely available numerical weather prediction model products and imagery the cyclone was intense but not exceptionally so and the results are believed to have some generality the detailed description of the cyclone structure just before it began to deepen rapidly integrates concepts from a number of researchers into a common framework a dominant feature of the cyclone close to its centre was the cloud head a region of cloud with a sharp convex outer edge which formed poleward of the main polar front cloud band the cloud head was caused by two flows that entered it from the east ascending and fanning out within it one flow the cold conveyor belt brought low wet bulb potential temperature w air back into the cloud head from low levels ahead of the warm front the other flow was due to high w air that peeled off from the base of the main warm sector airflow i e part of the warm conveyor belt and travelled in the boundary layer back towards the cyclone centre first undercutting dry air that had earlier descended from the upper troposphere called a dry intrusion and then ascending at the upper boundary of the cloud head above the cold conveyor belt the transverse circulation that gave the ascent within the cloud head also led to the cold front fracturing along its length into two separate sharp surface cold fronts with a more diffuse frontal region in between frontal fracture the two sharp surface cold fronts were associated with narrow cold frontal rainbands line convection one of the line convection segments forming the southern edge of the cloud head the overrunning of the dry intrusion in the region of the frontal fracture led to a structure known as a split front in which an upper level humidity front began to run ahead of the position of the surface cold front a feature of the cyclone at this intermediate stage in its evolution was that a large proportion of the precipitation was being generated by ascent of relatively cold air the cold conveyor belt in the cloud head as part of the thermally indirect circulation at the left exit of a developing secondary upper level jet

mid paleozoic arc granitoids in sw japan with neoproterozoic xenocrysts from south china new zircon u pb ages by la icp ms abstract the kurosegawa belt in sw japan preserves fragments of early middle paleozoic granitoids traditionally called the mitaki igneous rocks and previously dated ca 470 435 ma by several isotope analyses such as rb sr k ar and u pb together with high grade metamorphic rocks and silurian strata in a narrow belt however the timing of the oldest arc related plutonism in japan is constrained by laser ablation inductively coupled plasma mass spectrometry la icp ms u pb ages of zircon from mitaki granitoids in 3 areas in sw japan i e kyushu shikoku and kii peninsula weighted mean u pb ages of these zircons are 431 8 3 9 for a granodiorite from the mt mitaki area in shikoku 444 1 5 8 ma for a granodiorite from kuraoka area in central kyushu and 444 5 7 6 ma for a quartzdiorite from the nabaenohana area in western kii peninsula respectively these ages confirm that the mitaki igneous rocks have ca 445 435 ma late ordovician to mid silurian ages they are some of the oldest subduction related plutonic rocks in sw japan particularly noteworthy is a tonalite from the nabaenohana area which has a unique spectrum of zircon u pb ages with distinct 3 clusters ca 700 500 ma neoproterozoic cambrian ca 1350 830 ma meo neoproterozoic and ca 3230 1560 ma paleoarchean mesoproterozoic of the 44 dated zircon grains the youngest possibly xenocrystic grains are ca 500 ma older zircon grains with ages 500 ma range up to 3230 ma and are interpreted as inherited xenocrysts in the tonalite the mitaki igneous rocks are interpreted to have been derived by melting of post 500 ma terrigenous sedimentary rocks that yielded a unique tonalitic s type granitoid magma from the presence of abundant 1350 700 ma meso to neoproterozoic zircon grains in the tonalite we conclude that during the early paleozoic proto japan was located close to the cathaysian margin of south china

active thrusting and folding along the northern tien shan and late cenozoic rotation of the tarim relative to dzungaria and kazakhstan we have studied geometries and rates of late cenozoic thrust faulting and folding along the northern piedmont of the tien shan mountain belt west of urumqi where the m 8 3 manas earthquake occurred on december 23 1906 the northern range of the tien shan rising above 5000 m overthrusts a flexural foredeep filled with up to 11 000 m of sediment of the dzungarian basement our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front within a 200 km long zone of neogene quaternary anticlines fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range in all the valleys the scarps offset vertically the highest terrace surface by the same amount 10 2 0 7 m inferring an early holocene age 10 2 kyr for this terrace which is continuous with the largest recent fans of the piedmont yields a rate of vertical throw of 1 0 0 3mm yr on the main active thrust at the surface a quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5 5 2 5 m 2 kyr a rather fresh surface scarp 0 8 0 15 m high that is unlikely to result from shallow earthquakes with 6 m 7 in the last 230 years is visible at the extremities of the main fold zone we associate this scarp with the 1906 manas earthquake and infer that a structure comprising a deep basement ramp under the range gently dipping flats in the foreland and shallow ramps responsible for the formation of the active fault propagation anticlines could have been activated by that earthquake if so the return period of a 1906 type event would be 850 380 years the small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth 2 3 is taken up by incremental folding near the surface comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising quaternary ranges such as the san gabriel mountains in california or the mont blanc aar massifs in the alps we estimate the finite cenozoic shortening of the folded dzungarian sediments to be of the order of 30 km and the cenozoic shortening rate to have been 3 1 5 mm yr assuming comparable shortening along the tarim piedmont and minor additional active thrusting within the mountain belt we infer the rate of shortening across the tien shan to be at least 6 3 mm yr at the longitude of manas 85 5 e a total shortening of 125 30 km is estimated from crustal thickening assuming local airy isostatic equilibrium under the same assumption serial n s sections imply that cenozoic shortening across the belt increases westwards to 203 50 km at the longitude of kashgar 76 e as reflected by the westward increase of the width of the belt this strain gradient implies a clockwise rotation of tarim relative to dzungaria and kazakhstan of 7 2 5 around a pole located near the eastern extremity of the tien shan west of hami 96 e 43 5 n comparable to that revealed by paleomagnetism between tarim and dzungaria 8 6 8 7 a 6 mm yr rate of shortening at the longitude of manas would imply a rate of rotation of 0 45 m y and would be consistent with a shortening rate of 12 mm yr north of kashgar taking such values to be representative of late cenozoic rates would place the onset of reactivation of the tien shan by the india asia collision in the early to middle miocene 16 22 9 m y in accord with the existence of particularly thick late neogene and quaternary deposits such reactivation would thus have started much later than the collision roughly at the time of the great mid miocene changes in tectonic regimes denudation and sedimentation rates observed in southeast asia the himalayas and the bay of bengal and of the correlative rapid change in seawater sr isotopic ratio 20 to 15 ma like these other changes the rise of the tien shan might be a distant consequence of the end of indochina s escape

the improve 1 storm of 1 2 february 2001 part i development of a forward tilted cold front and a warm occlusion abstract analysis of observations and the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 are used to study the development of a forward tilted cold front off the coast of washington state the vertical velocity associated with the cold front produced a wide cold frontal rainband in the early stage of development the midtropospheric baroclinic zone or upper cold front moved forward with time over the warm sector to produce a structure similar to a split front the movement of the upper cold front was due to horizontal transport and frontogenetical propagation the frontogenetical propagation was produced by a combination of tilting and diabatic frontogenesis which resulted in a negative positive couplet of frontogenesis straddling the baroclinic zone the lower tropospheric cold front eventually caught up with the warm front to form a classical warm occlusion in the initial occluding process the converging frontal zones tilted i

a growing sandstone type uranium district in south yili basin nw china as a result of extension of tien shan orogen evidences from geochronology and hydrology abstract the mesozoic yili basin of nw china represents the largest known concentration of u deposits in china and contains five major deposits namely from west to east the 512 kujie ertai 513 511 510 mengqiguer and 509 deposits pre mining resources within the explored sandstone type uranium deposits in this area are reportedly as much as 20 000 t contained u the mineralization is hosted by the middle lower jurassic shuixigou group which from base to top is divided into the badaowan sangonghe and xishanyao formations the u pb isotopic analysis of ores from the kujie ertai and mengqiguer deposits indicate that they contain high and variable amounts of initial common pb meaning that the only possible way to date these deposits is by using u pb isochrons two major stages of uranium mineralization have been identified by the u pb isotope dating of uranium ores in this region the kujie ertai deposit apparently formed between 23 4 3 3 and 20 18 0 49 ma corresponding to a period of crustal thickening and uplift within the tien shan orogen this event 35 21 ma accommodated the majority of the strain generated by the northward collision of the indian plate with the asian plate however the dating of samples from the mengqiguer deposit yielded much younger ages between 0 61 0 24 and 0 347 0 0048 ma the western tien shan mountains expanded until the pliocene as a result of the far field influence of continuous penetration of the indian plate into the asian plate this activated reverse faults and folds in the piedmont of the tien shan mountains and caused the continuous uplift of the southern flank of the yili basin the uplift caused the erosion of anticline hinge zones introducing significant amounts of oxidizing water into the shuixigou group generating a second stage of uranium mineralization hydrological sampling also suggests that the mengqiguer deposit continues to grow indicating a possible third stage of uranium mineralization 0 ma this also indicates that the u within these deposits is derived not only from u bearing sediments but from the tien shan mountains as a result of groundwater cycling the evolution of the u contents of groundwater that was initially derived from cold springs that flow into the mineralized units indicates that these cold springs have an essential role in mobilizing u from the tien shan mountains with rivers flowing through areas of outcropping mineralized units acting as a source of mineralizing fluids during the formation of the mengqiguer deposit

a cretaceous pole from south china and the mesozoic hairpin turn of the eurasian apparent polar wander path to contribute to the apparent polar wander path apwp of the south china block and eurasia in general we collected paleomagnetic samples from mesozoic red beds around the city of ya an 30 n 103 e in the western tip of the sichuan basin in this paper we present the results from 373 oriented cores taken from one section representing 3 km of sedimentary rocks the section is dated with continental ostracods and with a magnetostratigraphic correlation between a densely sampled 272 m sequence and the polarity time scale giving an upper jurassic to upper cretaceous or lower tertiary age the remanent direction is remarkably stable throughout the section d 2 0 i 34 2 k 63 1 95 3 6 n 26 28 sites while this fact might suggest that the section has been remagnetized paleomagnetic and rock magnetic tests indicate that the remanence is primary the pole position 78 6 n 273 4 e dp 2 4 dm 4 1 corresponds to a rather low paleolatitude 18 8 2 4 but is consistent with other cretaceous poles from china if one accepts the eurasian apwp of irving and irving 1982 this result would imply that more than 1000 km of shortening took place between south china and eurasia following the acquisition of the remanence however there is no geological evidence for this large shortening we propose that the remanence was acquired within the time corresponding to the tip of the hairpin turn 150 50 ma in the revised apwp of besse and courtillot this issue the local geology suggests that the syncline from which the samples were taken has been rotated by 15 5 counterclockwise which is reflected in a similar discrepancy between the measured paleodeclination and that predicted by the besse and courtillot this issue eurasian apwp after correcting for this rotation the pole position is 70 9 n 225 2 e dp 2 4 dm 6 5 we conclude that eurasia was fully assembled by the end of the jurassic and that the mesozoic eurasian hairpin turn is a real feature

glacial geomorphology and glacial history of the muzart river valley tianshan range china abstract the muzart river originates on the southeastern slope of tumur peak the largest center of modern glaciation in the tianshan range glacial landforms and sediments indicate that there are four major quaternary glaciations in this drainage the glacial landforms contain considerable information about the changes of the ancient glaciers dating the landforms allows the temporal and spatial variations of the ancient glaciers in this valley to be understood and provides essential information in reconstructing the paleoenvironment in this region electron spin resonance esr dating of a well exposed section the multiple end moraines of the pochengzi glaciation the third set of moraines and the local outwash and fluvial sediments on the kezibulake glacial plain the fourth set of moraines was carried out using germanium ge centers in the glacial quartz grains which are sensitive to both sunlight and grinding eleven depositional ages have been determined based on the dating results the principle of superposition and the glaciations pattern reported in the adjacent valley the pochengzi end moraines were determined to be deposited during the major glacial intervals that are equivalent in age to marine oxygen isotope stages mis 2 mid mis 3 and mis 4 and the kezibulake glacial deposits were determined to be equivalent in age to mis 6 furthermore the tugaibieliqi end moraine the second set of moraines was deposited during the neoglaciation a cold period between 3 and 4 ka and the 3 4 end moraines located at the terminuses of the modern glacier were deposited during the little ice age the ages of the pochengzi glacial deposits can be subdivided into three clusters they are 13 6 25 3 ka 39 5 40 4 ka and 64 2 71 7 ka respectively the largest local last glacial maximum lgm l occurred during mis 4 rather than the global last glacial maximum lgm g of mis 2 furthermore a glacier that is slightly larger than that of mis 2 developed in this drainage during mid mis 3 the ancient muzart glaciers were compound valley glaciers during the neoglaciation mis 2 and mid mis 3 and piedmont glaciers during mis 4 and mis 6

a review of cold fronts with prefrontal troughs and wind shifts the conceptual model of a classical surface based cold front consists of a sharp temperature decrease coincident with a pressure trough and a distinct wind shift at the surface many cold fronts however do not conform to this model time series at a single surface station may possess a pressure trough and wind shift in the warm air preceding the cold front hereafter called a prefrontal trough and prefrontal wind shift respectively although many authors have recognized these prefrontal features previously a review of the responsible mechanisms has not been performed to date this paper presents such a review ten disparate mechanisms with different frontal structures have been identified from the previous literature these mechanisms include those external to the front i e those not directly associated with the cold front itself synoptic scale forcing interaction with lee troughs drylines interaction with fronts in the mid and upper troposphere and frontogenesis associated with inhomogeneities in the prefrontal air mechanisms internal to the front i e those directly associated with the structure and dynamics of the front include the following surface friction frontogenesis acting on alongfront temperature gradients moist processes descent of air ascent of air at the front and generation of prefrontal bores gravity waves given the gaps in our knowledge of the structure evolution and dynamics of surface cold fronts this paper closes with an admonition for improving the links between theory observations and modeling to advance understanding and develop better conceptual models of cold fronts with the goal of improving both scientific understanding and operational forecasting

velocity field in asia inferred from quaternary fault slip rates and global positioning system observations we perform a joint inversion of quaternary strain rates and 238 global positioning system gps velocities in asia for a self consistent velocity field the reference frames for all geodetic velocity observations are determined in our inversion procedure india in moves relative to eurasia eu about a pole of rotation at 29 78 n 7 51 e 0 353 myr 1 which yields a velocity along the himalaya within india that is 73 76 of the magnitude of the in eu nuvel 1a velocity and a vector azimuth that is 8 10 clockwise of nuvel 1a in eu vector azimuth relative to eurasia south china moves at 9 11 mm yr in the direction 110 120 with a pole position 64 84 n 156 74 e 0 12 myr 1 amurian block motion has a pole position in a similar location but at a slower rate 64 61 n 158 23 e 0 077 myr 1 and most of the amurian eurasia motion is accommodated by extension across lake baikal tarim basin moves relative to eurasia about a pole of rotation at 39 24 n 98 2 e 0 539 myr 1 and 16 18 mm yr of shortening is accommodated across the west central tien shan there is distributed e w extension throughout both southern and north central tibet within southern tibet between the longitudes of 77 e to 92 e the deformation field accommodates 16 19 mm yr of e w extension we compare predicted seismic moment rates with those observed in this century in asia total observed seismic moment rates within the entire area of central and east asia 2 2 107 km2 in this century are 2 26 0 7 1020 n m yr 1 as compared with a predicted total rate of 2 03 0 066 1020 n m yr 1 comparisons between observed and predicted moment rates within 42 subregions reflect the generally unstable process of inferring long term seismic moment rates from a catalog of limited duration 94 years an observation period of 10 000 years would be required to reduce uncertainties in observed seismic moment rate to the same size as the uncertainties in model tectonic moment rates inferred from the joint inversion of gps and quaternary rates of strain we show that in general a better correlation with model tectonic moment rate is inferred from the seismicity catalog by considering the numbers of earthquakes above a cutoff magnitude mb 5 0 for the period january 1 1965 to january 1 1999

palaeozoic collisional tectonics and magmatism of the chinese tien shan central asia abstract the chinese tien shan range is a palaeozoic orogenic belt which contains two collision zones the older southern collision accreted a north facing passive continental margin on the north side of the tarim block to an active continental margin on the south side of an elongate continental tract the central tien shan collision occurred along the qinbulak qawabulak fault southern tien shan suture the time of the collision is poorly constrained but was probably in in the late devonian early carboniferous we propose this age because of a major disconformity at this time along the north side of the tarim block and because the youshugou ophiolite is imbricated with middle devonian sediments a younger probably late carboniferous early permian collision along the north tien shan fault northern tien shan suture accreted the northern side of the central tien shan to an island arc which lay to its north the north tien shan arc this collision is bracketed by the middle carboniferous termination of arc magmatism and the appearance of late carboniferous or early permian elastics in a foreland basin developed over the extinct arc thrust sheets generated by the collision are proposed as the tectonic load responsible for the subsidence of this basin post collisional but palaeozoic dextral shear occurred along the northern suture zone this was accompanied by the intrusion of basic and acidic magmas in the central tien shan late palaeozoic basic igneous rocks from all three lithospheric blocks represented in the tien shan possess chemical characteristics associated with generation in supra subduction zone environments even though many post date one or both collisions rocks from each block also possess distinctive trace element chemistries which supports the three fold structural division of the orogenic belt it is unclear whether the chemical differences represent different source characteristics or are due to different episodes of magmatism being juxtaposed by later dextral strike slip fault motions because the southern collision zone in the tien shan is the older of the two the tarim block sensu stricto collided not with the eurasian landmass but with a continental block which was itself separated from eurasia by at least one ocean the destruction of this ocean in late carboniferous early permian times represented the final elimination of all oceanic basins from this part of central asia

the sting at the end of the tail damaging winds associated with extratropical cyclones strong surface winds often accompany the low level jets that occur along the cold fronts of extratropical cyclones but there is evidence that the strongest surface winds occur in a distinctly different part of a certain class of cyclone the most damaging extratropical cyclones go through an evolution that involves the formation of a bent back front and cloud head separated from the main polar front cloud band by a dry slot when the cyclone attains its minimum central pressure the trailing tip of the cloud head bounding the bent back front forms a hook which goes on to encircle a seclusion of warm air the most damaging winds occur near the tip of this hook the sting at the end of the tail observations of the great storm of october 1987 in south east england are re examined in some detail to study this phenomenon the cloud head is shown to have a banded structure consistent with the existence of multiple mesoscale slantwise circulations air within these circulations leaves the hooked tip of the cloud head and enters the dry slot much faster than the rate of travel of the cloud head tip implying rapid evaporation and diabatic cooling immediately upwind of the area of damaging surface winds the circumstantial evidence from the observational study leads one to hypothesize that the mesoscale circulations and the associated evaporative heat sinks may play an active role in strengthening the damaging winds regardless of how important this role may be the evolution of the cloud pattern seen in satellite imagery is a useful tool for nowcasting the occurrence and location of the worst winds copyright 2004 royal meteorological society

response of the columbia river fluvial system to holocene climatic change abstract an understanding of the response of a fluvial system to past climatic changes is useful for predicting its response to future shifts in temperature and precipitation to determine the response of the columbia river system to previous climatic conditions and transitions a well dated sequence of floodplain development in the wells reservoir region was compared with the paleoenvironmental history of the columbia river basin results of this comparison indicate that aggradation episodes occurring approximately 9000 8000 7000 6500 4400 3900 and 2400 1800 yr b p coincided with climatic transitions that share certain characteristics the inferred climates associated with aggradation had at least moderate rates of precipitation that occurred mainly in winter coupled with moderate winter temperatures such conditions would have resulted in the buildup of snowpacks and a high frequency of rain on snow events the warming and precipitation increases predicted for the pacific northwest under most co2 doubling scenarios are likely to repeat these conditions which could increase the frequency of severe sediment laden floods in the columbia river basin

interaction of a warm season frontal system with the coastal mountains of the western united states part i prefrontal onshore push coastal ridging and alongshore southerlies abstract observational analyses and numerical simulations are used to investigate the interaction between a warm season frontal system trough and the complex terrain of the western united states prior to frontal landfall synoptically driven offshore flow was associated with the northward development of a thermal trough and a coastal pressure ridge and associated southerly winds moved northward along the coasts of northern california oregon washington and southwestern british columbia this coastal pressure ridge coupled with the subsequent weakening of the offshore flow resulted in the onshore push of cool marine air approximately 24 h before frontal passage the onshore surge of cool marine air into warm dry continental air associated with the thermal trough produced a mesofront that moved over the coastal and cascade mountains diagnosis of a realistic simulation of the event shows that both solar heating and adiabatic warming from downslope flow over the rockies and the cascade mountains are i

authigenic carbonate formation and its impact on the biomarker inventory at hydrocarbon seeps a case study from the holocene black sea and the plio pleistocene northern apennines italy carbonates are widespread at methane and petroleum seeps and are often precipitated as consequence of an alkalinity increase due to the anaerobic oxidation of methane aom or less often reported of higher hydrocarbons these carbonates are taphonomic windows into earth s history because they excellently protect the in situ formed microbial signatures e g lipid biomarkers from diagenetic destruction a complication for paleoreconstructions however is that seep carbonates also encapsulate variable amounts of allochthonous organic matter sometimes even completely obscuring authigenic microbial signatures seep carbonates from the holocene black sea the pleistocene enza river and the pliocene san lorenzo both northern apennines italy provide hints to better understand i the importance of processes other than aom for the formation of seep carbonates and ii the controls of allochthonous and autochthonous contribution of biomarkers to organic matter in seep carbonates biomarker distributions in different parts of a black sea carbonate clearly demonstrate that high allochthonous organic matter is entrapped if aom carbonates are formed intrasedimentary particularly if methane supply is relatively low and external organic matter input high high allochthonous contributions were also found in the biomarker inventory of ancient seep carbonates from the italian northern apennines enza river and san lorenzo pointing at their precipitation within the sediment specific and complex conditions were indicated from our data for the enza river location carbonate facies and particularly biomarker compositions with abundant signatures of sulfate reducing bacteria suggest that sulfate reduction using alkaline and eventually sulfate and higher hydrocarbon enriched fluids triggered the growth of these seep carbonates our and other data suggest that this process has to be more considered if interpreting seep settings particularly where microbial processes rely on rising fluids from deep petroleum reservoirs

petrological mineralogical and geochemical compositions of early jurassic coals in the yining coalfield xinjiang china abstract the petrological geochemical and mineralogical compositions of 10 coal seams early jurassic from an exploratory borehole hole zkj502 in the jieliangzi mining area of the yining coalfield xinjiang uygur autonomous region china were investigated using optical microscopy and field emission scanning electron microscopy in conjunction with an energy dispersive x ray spectrometer fe sem eds as well as x ray powder diffraction xrd x ray fluorescence xrf and inductively coupled plasma mass spectrometry icp ms the yining coals are of subbituminous to highly volatile c bituminous in rank vitrinite reflectance average 0 49 and are characterized by low sulfur content average 0 45 low ash yield average 4 10 high volatile matter average 38 82 high proportion of inertinite average 49 5 and low concentrations of most trace elements relative to the upper continental crust the rare earth elements and yttrium in the yining coals are mainly characterized by light and heavy rey enrichment the minerals in the yining coals are dominated by quartz kaolinite and siderite followed by pyrite bassanite and hexahydrite along with small proportions of illite calcite dolomite gorceixite goyazite ankerite marcasite diaspore florencite hematite and millerite the similarity between the yining coals and the magmatic rocks from the peripheral mountain area of the basin in terms of the al 2 o 3 tio 2 ratio the rey enrichment type the rey distribution patterns and the eu anomalous fractionation suggest that the sediment source region was mainly carboniferous volcanic rocks andesite and basalts on peripheral mountains the acid conditions and lowered water table during peat accumulation may have caused detrital minerals to be leached leading to the relatively low ash yield another reason for the low ash yield may be the simple coalfield structure and poor groundwater migration channels in the rocks and coal seams in the central zone of the basin which would limit the minerals carried by the groundwater into coals a number of authigenic minerals quartz kaolinite siderite and gorceixite occur as cell fillings and elevated concentrations of li be sc v cr co ni cu zn ga rb zr nb mo cs hf w pb th and rey occur in nos 26 and 27 coals indicating that there was an injection of a small scale solution

an excellent fossil wood cell texture with primary uranium minerals at a sandstone hosted roll type uranium deposit nw china abstract a fossil wood cell texture with pitchblende and coffinite found at a sandstone hosted roll type uranium deposit xinjiang nw china is first reported here for the country in the mineralized sandstone detrital grains consisting of quartz feldspar rock fragments carbonaceous trashes mica and accessory minerals were deposited in early turassic time and were cemented by clays and minor authigenic calcite and quartz pitchblende and minor coffinite are principal ore minerals at the deposit and selectively replaced carbonized fossil wood remnants or filled fossil wood cells an excellent fossil wood cell texture with primary uranium minerals formed replacement of organic debris by primary uranium minerals may be due to a local reducing environment resulting from the production of ch 4 h 2 s or h 2 so 3 in its decomposition and a biochemical reaction indicated by the common presence of framboidal pyrite

the effect of large scale flow on low level frontal structure and evolution in midlatitude cyclones abstract observational and modeling studies documented in the literature indicate that the large scale flow has an important effect on the structure and evolution of low level fronts in midlatitude cyclones the purpose of this paper is to address the role of the large scale flow on low level cyclone frontal structure and evolution through a combined observational and idealized modeling approach analyses of two observed cyclone cases embedded in large scale diffluence and confluence respectively are presented to illustrate two possible cyclone frontal structures and evolutions specifically the cyclone moving into a diffluent high amplitude ridge becomes meridionally elongated and possesses a strong meridionally oriented cold front and a weak warm front the cold front rotates into the warm front forming an occluded front in the manner of the norwegian cyclone model as indicated by the narrowing of the thermal ridge connecting the warm sector to the cyclone center in contrast the cyclone moving i

quaternary climate change and the formation of river terraces across growing anticlines on the north flank of the tien shan china nested stream terraces warped upward over actively growing anticlines along the north flank of the tien shan in western china appear to record alternating phases of valley widening and incision differences of relative heights between remnants of four separate strath terraces along one river and between two such terraces along another reach 100 to 120 m over the crests of the anticlines we infer that this spacing is due to alternating stages of valley widening and rapid incision associated with climate changes with a periodicity of 100 kyr the crests of the anticlines appear to emerge from the aggrading flanks of the anticlines at an average rate of about 1 mm a the maximum heights of 25 and 35 10 m for the lowest terraces above their projected initial profiles imply ages of roughly 25 kyr and 35 kyr 10 kyr hence they suggest that flood plains which were abandoned to form the terraces developed adjacent to active stream beds during the last glacial period when climates were relatively

quasigeostrophic forcing of ascent in the occluded sector of cyclones and the trowal airstream a numerical model based analysis of the quasigeostrophic forcing for ascent in the occluded quadrant of three cyclones is presented based upon a natural coordinate partitioning of the q vector into its along and acrossisentrope components qs and qn respectively the qn component describes the geostrophic contribution to the rate of change of the magnitude of pu traditional frontogenesis whereas the qs component describes the geostrophic contribution to the rate of change of direction of pu rotational frontogenesis it is shown that convergence of qs simultaneously creates the isobaric thermal ridge characteristic of the thermal structure of occluded cyclones and provides the predominant dynamical support for ascent within the occluded quadrant the absence of significant qn convergence there suggests that quasigeostrophic q g frontogenesis plays a subordinate role both in forcing vertical motions and in affecting three dimensional structural changes in the occluded sector of post mature phase midlatitude cyclones a cyclonically ascending cloud and precipitation producing airstream that originates in the warm sector boundary layer and flows through the trowal portion of the occluded structure is supported by the upward vertical motions implied by the identified q g forcing this airstream is referred to as the trowal airstream and it is shown to be responsible for the production of the wrap around cloud and precipitation commonly associated with occluded systems the relationship of the trowal airstream to previously identified cloud and precipitation producing airflows in cyclones is discussed

alluvial sequence in the north piedmont of the chinese tian shan over the past 550 kyr and its relationship to climate change abstract a new division of middle and late pleistocene alluvial sequence in the north piedmont of the chinese tian shan based on geomorphologic stratigraphic and chronologic criteria provides a framework for examining their relationship to climate change during glacial interglacial transitions over the past 550 kyr at least four major alluviation episodes occurred within the piedmont along the major river valleys in this region each episode of alluvial fan deposition morphologically correlates with a major river terrace these correlations create a regionally applicable framework for subdivision of the quaternary alluvial sequence in the study area where seven stepped river terraces are defined our new chronology of this fluvial sequence suggests that following intervals of aggradation three highest river terraces and equivalent alluvial fans were abandoned at 530 ka 300 ka and 10 ka respectively paleosols at the base of the loess sequences that directly overlie the older terraces and fans suggest that episodes of aggradation occurred late in the glacial cycles the subsequent incision that caused abandonment stabilization of these terraces and fans occurred near to glacial interglacial transitions a relatively high degree of synchrony in major river incision events across the piedmont despite disruption by several discrete structure zones with asychronous tectonic activities supports the dominant control exerted by climatic conditions on alluvial deposition and terrace creation during the quaternary across the north piedmont of the chinese tian shan

a linkage between uranium mineralization and high diagenetic temperature caused by coal self ignition in the southern yili basin northwestern china abstract jurassic sediments in the southern yili basin of the xinjiang province northwestern china host several sandstone hosted uranium deposits the jurassic uranium enriched white sandstones are in the transitional zone between the oxidized and reduced zones in addition burnt rocks are common in nearby outcrops and occur occasionally in drill cores mineralogical and geochemical compositions of sediments from the oxidized the uranium enriched transitional and the reduced zones were measured using optical microscopy field emission scanning electron microscopy in conjunction with energy dispersive x ray spectrometry x ray powder diffraction and inductively coupled plasma mass spectrometry icp ms chromite limonite and ilmenite are the typical accessory minerals in the brown sandstones of oxidized zone whereas calcite and saddle dolomite are typical accessory minerals in the sandstones of transitional zone the suite of vitrinite reflectance ro illitic crystallinity and homogenization temperature for fluid inclusions in calcites indicates a relatively high diagenetic temperature 100 c in the jurassic sandstones from both the oxidized and transitional zones in the southern yili basin an interesting relationship was discovered between the diagenetic high temperature conditions and coal self ignition the anomalous uranium concentrations in the burnt claystone from a drill hole and in the altered coals 0 10 cm below the burnt rocks in an outcrop section imply a relationship between the coal self ignition and uranium mineralization in the southern yili basin one option to interpret the uranium mineralization is a supergene descending from surface hydrothermal fluid model in which the downwelling fluids were heated as they penetrated through the warm burnt rocks and then underwent a chemical reaction as they progressively cooled when they traversed down through the underlying permeable sandstone beds accordingly we establish the linkage between uranium mineralization and high diagenetic temperature caused by coal self ignition

mineral paragenesis and textures associated with sandstone hosted roll front uranium deposits nw china abstract we present a first paragenetic study of the wuyier wuyisan wuyiyi and shihongtan sandstone hosted roll front uranium deposits northwest china the mineralization is hosted by lower middle jurassic coarse to medium grained sandstones which are dark gray to black due to a mixture of ore minerals and carbonaceous debris the sandstone is alluvial fan braided river facies minerals associated with these deposits can be broadly categorized as detrital authigenic and ore stage mineralization ore minerals consist of uraninite and coffinite this is the first noted occurrence of coffinite in this type of deposit in china sulfide minerals associated with the uranium minerals are pyrite marcasite and less commonly sphalerite and galena the sulfide minerals are largely in textural equilibrium with the uranium minerals however these sulfide minerals occasionally appear to predate as well as postdate the uranium minerals this implies that there are multiple generations of sulfides associated with these deposits the ore minerals occur interstitially between fossilized wood cells in the sandstones as well as replace fossilized wood and biotite the deposits are generally low grade primary uranium minerals associated with the low grade deposits are generally too small ranging from 0 2 to 0 3 m in diameter to be observed by optical microscopy and are only observed by electron microscopy mineral paragenesis and textures indicate that these deposits formed under low temperature 30 50 c conditions

high resolution observations of the trowal warm frontal region of two continental winter cyclones abstract this paper compares the structure of the trough of warm air aloft trowal warm frontal region of two continental wintertime cyclones the cyclones were observed over the central great lakes region during the lake induced convection experiment snowband dynamics project field campaign the cyclones had different origins with the first forming east of the colorado rockies and the second forming over the gulf of mexico they were associated with different upper level flow regimes one located just north of a nearly zonal jet and the other located just west of a nearly meridional jet both storms produced heavy swaths of snow across the states of illinois wisconsin and michigan high resolution observations of frontal structure were made during flights of the national center for atmospheric research electra aircraft using dropsondes and the electra doppler radar tail radar system the high resolution observations suggest a different arrangement of air masses in the trowal region compared with the

the structure and evolution of a simulated midlatitude cyclone over land abstract using output from a mesoscale model simulation this paper describes the evolution of the three dimensional temperature and humidity structures of an intense cyclone that developed over the eastern half of the united states during 14 16 december 1987 some specific findings include the following the occlusion process at the surface appeared similar to the classical paradigm with the cold front catching up with the warm front aloft a warm type occlusion structure formed as an upper baroclinic zone merged with the surface based occluded front the frontogenesis associated with the cold and warm fronts was initially continuous but as the system evolved a break in the frontogenesis along the northern section of the cold front developed a single frontogenesis feature appeared to support both the warm and occluded fronts a quasi linear region of convective activity was observed in advance of the surface cold front this convective line was associated with an upper level humidity front wh

tectonic evolution of the south tianshan orogen and adjacent regions nw china geochemical and age constraints of granitoid rocks geochemical and geochronological evidence was obtained from granitoids of the south tianshan orogen and adjacent regions which consist of three individual tectonic domains the kazakhstan yili plate the central tianshan terrane and the tarim plate from north to south the central tianshan terrane is structurally bounded by the early paleozoic nikolaev line north nalati fault and late paleozoic atbashy inyl chek south nalati qawabulak fault zones against the kazakhstan yili and tarim plates respectively the meta aluminous to weakly peraluminous granitic rocks which are exposed along the kekesu river and the bikai river across the central tianshan terrane have a tholeiitic calc alkaline or high potassium calc alkaline composition i type geochemical trace element characteristics and the y versus rb nb or y versus nb discrimination diagrams favor a continental arc setting for these granitoid rocks shrimp u pb and la icp ms u pb zircon age data indicate that the magmatism started at about 480 ma continued from 460 to 330 ma and ended at about 275 ma the earlier magmatism 470 ma is considered to be the result of a simultaneous southward and northward subduction of the terskey ocean beneath the northern margin of the tarim plate and the kazakhstan yili plate respectively the later magmatism 460 330 ma is related to the northward subduction of the south tianshan ocean beneath the southern margin of the kazakhstan yili central tianshan plate the dataset presented here in conjunction with previously published data support a late paleozoic tectonic evolution of the south tianshan orogen not a triassic one as recently suggested by shrimp u pb zircon dating for eclogites

a lagrangian based analysis of extratropical cyclones ii a detailed case study a detailed case study analysis is undertaken of the occurrence of significant coherent ensembles of trajectories cets that accompany atlantic cyclogenesis the approach is based upon the lagrangian based analysis scheme introduced in part i the analysis reveals the existence of several distinct moist ascending and dry descending cets two types of moist ascending cets associated with strong condensational processes ascend from the boundary layer of the warm sector either in the close vicinity of the cyclone centre or in the trailing cold frontal region the latter is the main contributor to the precipitation along the cold front during the early phase of the development another type of moist cets distinguished by maximum water vapour flux travels at low levels through the warm sector and ascends to mid tropospheric levels in the warm frontal region where it produces strong precipitation around the time of maximum storm intensity cets with an upper level origin are linked to the classical dry intrusion different cets correspond to strong descent of upper level tropospheric air that penetrated to the lower troposphere the movement of stratospheric air toward the centre of the maturing cyclone and an event of stratosphere to troposphere exchange upstream of the upper level trough two different visualizations of time sequences of the moist ascending cets indicate that they represent well defined flexible tubes or airstreams that exist over a time period comparable with the duration of the main cyclone intensification they provide a translating flexible but coherent river bed for the quasi continuous ascent of moist boundary layer air to the upper troposphere these tubes are akin to the concept of warm conveyor belts and the present analysis method objectively diagnoses their geometrical and physical characteristics and potential vorticity pattern some consideration is also given to the relationship of cets and tropospheric rivers and to possible shortcomings of the approach

cretaceous paleogene basaltic rocks of the tuyon basin nw china and the kyrgyz tian shan the trace of a small plume abstract the tuyon basin nw china and the central portion of the kyrgyz tian shan preserve a volumetrically small series of basaltic extrusive and intrusive units emplaced primarily in mesozoic paleogene sedimentary rocks four units from the tuyon basin yield 40 ar 39 ar ages of 67 59 46 and between 110 and 120 ma major and trace element analysis combined with sr nd and pb isotopic data suggest that these units were derived from apparently ocean island basalts oib like mantle melts which have characteristics close to asthenospheric prema mixed with an enriched component in the continental mantle lithosphere or emplaced with some crustal contamination two basalts from kyrgyzstan were also dated by 40 ar 39 ar as 54 ma these results agree with previous k ar analysis which show that most kyrgyz basalts were emplaced during the eocene major element data from the kyrgyz basalts knauf et al 1980 fortuna et al 1994 show strong similarities with the tuyon data suggesting that the more extensive tuyon data can be taken as representative of the entire basaltic suite there is little geological data to support either late cretaceous paleogene rifting or the presence of a large plume beneath the region instead these magmas point to the presence of a small thermally anomalous region in the mantle beneath the central tian shan which might best be described as a small plume which probably rooted at a shallow level in the asthenosphere

hercynian post collisional magmatism in the context of paleozoic magmatic evolution of the tien shan orogenic belt abstract the hercynian tien shan tianshan orogen formed during late palaeozoic collision between the karakum tarim and the kazakhstan paleo continents in order to constrain timing of hercynian post collisional magmatism 27 intrusions were sampled for u pb zircon dating along a ca 2000 km long profile in uzbekistan and kyrgyzstan the samples were dated utilizing sensitive high resolution ion microprobe shrimp ii the obtained ages together with previously published age data allowed the timing of hercynian post collisional magmatism to be constrained and interpreted in the context of the paleozoic magmatic evolution of the region apart from hercynian post collisional magmatism two older magmatic episodes have been recognized and the following sequence of events has been established 1 approximately 10 ma after cessation of continuous caledonian magmatism a number of late silurian early devonian intrusions were emplaced in the middle and northern tien shan terranes between 420 and 390 ma the intrusions probably formed in an extensional back arc setting during coeval subduction under the margins of caledonian paleo kazakhstan continent 2 the next relatively short late carboniferous episode of subduction under paleo kazakhstan was registered in the kurama range of the middle tien shan calc alkaline volcanics and granitoids with ages 315 300 ma have distinct metallogenic affinities typical for subduction related rocks and are not found anywhere outside the middle tien shan terrane west of the talas farghona fault 3 the early permian hercynian post collisional magmatism culminated after the closure of the paleo turkestan ocean and affected the whole region across terrane boundaries the post collisional intrusions formed within a relatively short time span between 295 and 280 ma the model for hercynian post collisional evolution suggests that after collision the tien shan was affected by trans crustal strike slip motions which provided suitable conduits for ascending asthenospheric material and heat influx in the crust this produced both granitoid magmas and hydrothermal fluid flow as a result post collisional intrusions and orogenic au deposits known in the region formed coevally and were tectonically controlled 4 between 240 and 220 ma a triassic thermal event affected the region resulting in resetting and growth of new zircon grains which is detected on a regional scale probably the influx of heat into the crust during the triassic was tectonically focused and varied significantly in different terranes in the region under investigation the triassic thermal event was not accompanied by any significant magmatic activity thus after cessation of hercynian post collisional magmatism ca 280 ma ago there was a long magmatically quiet period in the tien shan

mass spectra of sn 2 hydroxyarchaeol a polar lipid biomarker for anaerobic methanotrophy 1 extremely 13c depleted sn 2 hydroxyarchaeol is widely observed at marine methane seep sites it is the first biosynthetic product that provides information about a previously unknown microorganism involved in anaerobic methanotrophy a process that occurs widely in marine sediments the mono and di tms derivatives of this compound yield sharply differing and distinctive mass spectra depending on reaction conditions either of these products can be formed in the course of conventional analyses

geochemistry of dissolved and suspended loads of the seine river france anthropogenic impact carbonate and silicate weathering this study focuses on the chemistry of the seine river system one of the major rivers in europe and constitutes the first geochemical investigation of both suspended and dissolved loads of this river the seine river drains a typical mesozoic cenozoic sedimentary basin the paris basin constituted of limestones mixed or interbedded with terrigenous sediments derived from the paleoreliefs bordering the mesozoic and cenozoic seas in the context of quantifying the global influence of carbonate and silicate weathering on atmospheric co2 consumption the seine river offers the possibility of examining weathering rates in a flat sedimentary environment under temperate climatic conditions one of the major problems associated with the seine river as with many temperate rivers is pollution we propose in this paper 2 approaches in order to correct the dissolved load of the seine river for anthropogenic inputs and to calculate weathering rates of carbonates and silicates the first uses the dissolved load of rivers and tries to allocate the different solutes to different sources a mixing model based on elemental ratios is established and solved by an inversion technique the second approach consists in using the suspended load geochemistry under steady state conditions we show that the geochemistry of suspended sediments makes it possible to estimate the amount of solutes released during the chemical weathering of silicates and thus to calculate weathering rates of silicates the total dissolved load of the seine river at paris can be decomposed into 2 of solutes derived from natural atmospheric sources 7 derived from anthropogenic atmospheric sources 6 derived from agriculture 3 derived from communal inputs and 82 of solutes derived from rock weathering during high floods the contribution of atmospheric and agriculture inputs predominates the weathering rate of carbonates is estimated to be 48 t km2 yr 25 mm 1000 yr only 10 of carbonates are transported in a solid form the rest being transported in solution co2 consumption by carbonate weathering approaches 400 103 mol km2 yr in the seine river at paris about 2 3 mg l of dissolved cations are found to originate from the chemical weathering of silicates by taking dissolved silica into accounts the total dissolved load derived from silicate weathering is about 6 7 mg l this value is minimal because biological uptake of silica probably occur in the seine river the chemical weathering rate of aluminosilicates is estimated to be 2 t km2 yr the ratio of physical over chemical weathering of silicates range between 1 and 3 and the total chemical and physical erosion rates of sedimentary silicates are about 2 3 mm kyr the co2 consumption by silicate weathering 15 24 103 mol km2 yr and is independent of dissolved silica concentration silicate consumption is thus 20 times less than carbonate consumption in the paris basin compared to the neighboring granitic areas the sedimentary region drained by the seine river has 2 to 3 times lower co2 consumption rates we attribute this difference to the cation depleted nature of the seine basin aluminosilicates which are of sedimentary origin at a world scale the chemical denudation rates found for the seine basin are very low and comparable to those given for tropical lowland rivers draining silicates such as the rivers of the congo and amazon basins in spite of huge climatic differences we attribute this similarity to the low mechanical denudation that characterizes these two types of regions

closing history of the southern tianshan oceanic basin western china an oblique collisional orogeny abstract the tianshan tien shan range is an important paleozoic collisional orogenic belt and the key to understand the central asia tectonic evolution this paper integrates our research results with the existing chinese and international literature on sedimentology geochemistry isotopic geochronology paleontonology and paleomagnetism of the tianshan and tarim regions to propose that the oblique collision may have played an important role in the late paleozoic closing of the southern tianshan oceanic basin as a result of the sinian latest proterozoic younger than 800 ma continental extension and rifting process the tarim and yili blocks separated from their parent continent in the late cambrian ordovician the southern tianshan oceanic crusts between the two blocks subducted northward beneath the southern margin of the yili block in the silurian during the devonian early carboniferous the tarim block rapidly drifted to the north and rotated about 46 clockwise this process induced the collision of the yili micro continent with the eastern segment present geographical position of the tarim continent in the late devonian and the southern tianshan oceanic crust evolved to be a west facing remnant oceanic basin during the late carboniferous early permian the tarim block located within an almost constant latitude range rotated about 26 clockwise with respect to the yili micro continent which ultimately closed the remnant oceanic basin in a scissors like manner from east to west and completed the tarim yili collision subsequent a type subduction of the tarim continental crust and lithosphere scale sinistral shearing generated a magmatic arc on the southern margin of the tarim yili suture zone the late permian early triassic clastics deposited in a peripheral foreland basin developed above the arc

provenance constraints on the xishanyao formation southern yili basin northwest china evidence from petrology geochemistry and detrital zircon u pb geochronology we conducted petrographic geochemical and new u pb laser ablation inductively coupled mass spectrometry analyses of detrital zircons in the sandstone samples from the important mengqiguer sandsto

the linkage between the warm and the cold conveyor belts in an idealized extratropical cyclone abstractthis study continues the investigation of airstreams in idealized moist baroclinic waves and addresses the formation of the cold conveyor belt ccb its linkage to the warm conveyor belt wcb and their impact on the development of a midlatitude cyclone the ccb is identified as a coherent bundle of trajectories characterized by weak ascent and a strong increase of potential vorticity pv along the flow in contrast to the wcb defined as the trajectories with maximum ascent the authors illuminate the role of the two conveyor belts in the formation of two strong pv anomalies that form in the upper wcb negative pv anomaly and lower troposphere ccb positive pv anomaly respectively and thereby establish a link between these airstreams and relevant aspects of the dynamics of extratropical cyclones the ccb moves close to the surface along the colder side of the bent back front and experiences a pv increase as it passes below a region of maximum latent heat release at midtropospheric level

trace element geochemistry of no 511 uranium ore deposit in xinjiang systematical studies of main and trace element geochemistry indicate that the no 511 uranium ore deposit in northwestern china is a sandstone type composite ore deposit characterized by multi element enrichment se re ga ge v and mo are concentrated to different extents in this deposit of which se re and ga are of economic significance se re ge mo v and other zones of these trace elements are recognized successively in the development direction of interlayer oxidation integration of these trace element data further shows that there exists a positive correlation between u and re suggesting that re and se may be important indicators of uranium ore deposits

the nuheting deposit erlian basin ne china synsedimentary to diagenetic uranium mineralization sedimentary units deposited during the post rift stage of the erlian basin located in northeast china present an alternation of sandstone and mudstone layers this sedimentological architecture is at the origin of confined permeable reservoirs hosting sandstone type uranium deposits the study of the nuheting deposit offered the opportunity to identify synsedimentary early diagenetic uranium concentrations and diagenetic mineralization hosted in mudstone dominated layers of the erlian formation indicating that a stock of uranium was present in the basin prior to the genesis of sandstone hosted uranium deposits therefore this pre existing stock may constitute a significant source of uranium for the formation of roll front deposits present in other parts of the erlian basin detailed petrographic and geochemical study of drill core samples from the nuheting deposit led to the characterization of different stages related to the formation of the uranium ore bodies and allowed to propose a new metallogenic model uranium mineralization of the nuheting deposit is mainly hosted in dark gray silty mudstone of wetland depositional environment of the late cretaceous erlian formation petrographic observations and emp analyses evidenced that a significant amount of uranium was associated with clay minerals interstratmed clays smectite chlorite palygorskyte illite and kaolinite either adsorbed on mineral surfaces as u vi ions or reduced mainly as uo2 nano to microcrystals disseminated in the clayey matrix which corresponds to synsedimentary early diagenetic concentrations trace elements on pyrite analyzed by la icpms petrographic observations and whole rock geochemical data led to the characterization of a diagenetic uranium mineralization high as 1 50 ppm mo 10 500 ppm and se concentrations in the whole rock and the incorporation of these elements in pyrite highlight reducing conditions within the host rocks during the diagenesis of the erlian formation during the early diagenetic stage uranium was either desorbed from clay minerals and organic materials to be reduced or directly reduced and precipitated as p rich coffinite and pitchblende on pyrite crystals during the late diagenetic stage uranium was redistributed in situ and locally deposited mainly as coffinite on pyrites finally an epigenetic stage of cementation was identified with sulfate and carbonate minerals which may enclose some uranium minerals this epigenetic stage of fluid circulation may be responsible for a minor uranium remobilization therefore the nuheting deposit experienced three main stages i a synsedimentary early diagenetic uranium concentration and mineralization ii a late diagenetic in situ uranium remobilization and deposition on pyrite and iii an epigenetic cementation rock eval pyrolysis indicates that the organic matter contained in host rocks of the nuheting deposit is of type iv inherited from land plant and do not contain free hydrocarbons very low s1 therefore our results do not support that migrated hydrocarbons were involved as a reducing agent for uranium mineralization

late cenozoic tectonics of the kepingtage thrust zone interactions of the tien shan and tarim basin northwest china the kepingtage kalpin thrust zone northwest china is an actively deforming part of the india asia collision system it lies south of the tien shan has an area of 16 000 km2 and consists of arcuate emergent imbricates overall vergence is toward the interior of the tarim basin to the south thrust sheets typically expose upper cambrian to permian platformal strata thrusting is largely thin skinned thin upper cambrian evaporites are likely to be the main decollement horizon the kepingtage thrust zone is the only margin of the tarim basin to deform in this style in the cenozoic it is replaced to the east and west by thrust zones which have propagated shorter distances into the interior of the tarim basin thick up to 10 km mesozoic and cenozoic clastic successions are present and deformed in these regions such successions are not present in the kepingtage thrust zone or the adjacent bachu uplift within the tarim basin because of episodic activity on steep northwest southeast trending thrusts which define the margins of the bachu uplift these mesozoic cenozoic strata may have suppressed the ability of regions along strike from the kepingtage thrust zone to deform by thin skinned thrusting utilizing the upper cambrian decollement the along strike variation in active thrusting at the southern margin of the tien shan is an example of syntectonic sedimentation controlling thrust belt deformation style a balanced section across the thrust zone indicates 28 shortening equivalent to 35 km this is equivalent to an average slip rate of 1 8 mm yr 1 and a strain rate of 4 4 10 16 s 1 assuming deformation began at circa 20 ma active deformation is focused along the frontal thrust the kepingtage fault the northern boundary of the kepingtage thrust zone is formed by the south tien shan fault this major north dipping thrust is seismically active with published earthquake focal depths at midcrustal levels 14 and 18 km it juxtaposes upper carboniferous sedimentary rocks of different facies and different paleozoic deformation histories speculatively it represents a reactivation of a late paleozoic thrust which originated at the boundary between the platformal interior of the tarim block and a deeper water foreland basin to its north

organization and structure of clouds and precipitation on the mid atlantic coast of the united states part vii diagnosis of a nonconvective rainband associated with a cold front aloft abstract a numerical simulation using the pennsylvania state university national center for atmospheric research fifth generation mesoscale model mm5 was run on a rainband associated with a cold front aloft cfa in a warm occluded structure on the u s east coast the storm originally developed in the lee of the rocky mountains as a pacific cold front overtook a rocky mountain lee trough this formed a warm type occluded structure that was essentially maintained as the storm proceeded to the east coast the cfa was a thermal front and therefore dynamically active the prominence of the cfa in the equivalent potential temperature field was due primarily to the strong upward transport of water vapor from lower levels in the updraft associated with the cfa the baroclinic zone was characterized by a tipped forward lower region where the cfa coincided with a maximum in potential temperature and a tipped backward upper region where the cfa coincided with the leading warm side edge of a zone of enhance

primary carboniferous and permian paleomagnetic results from the yili block nw china and their implications on the geodynamic evolution of chinese tianshan belt in order to better understand the tectonic role of the yili block on the paleozoic evolution of the chinese tianshan belt we performed a primary paleomagnetic study on carboniferous and permian rocks from different areas in the yili block nw of china more than 320 sedimentary and volcanic samples were collected from 39 sites except for the ordovician samples showing a weak and unstable magnetic remanence the majority of this collection presents characteristic remanent magnetization carried by magnetite and hematite in the study area though positive fold test has been observed on the early carboniferous rocks a general remagnetization of these rocks has been identified and attributed to the late carboniferous magmatism moreover all early and late carboniferous samples from the interior of the yili block yield stable and coherent magnetic directions with exhaustively reverse magnetic polarity the late carboniferous c2 is considered as the magnetic remanence age since these rocks are covered or intruded by synchronous magmatic rocks of the yili arc which lasted until to 310 ma the c2 paleomagnetic pole is therefore calculated at 68 6 n 290 6 e with 95 6 4 and n 15 the late carboniferous rocks located close to a deformation zone present a consistentmagnetic inclination but significant different declination with respect to other areas and are suspected to have probably experienced a local rotation although no fold test can be performed due to the monoclinal bedding stable magnetic components are isolated from late permian p2 red beds in the interior of the yili block with also a solo reverse magnetic polarity the p2 paleomagnetic pole of the yili block has been therefore calculated from the characteristic remanent magnetization 79 7 n 172 0 e with 95 11 3 and n 5 keeping important uncertainties in mind comparisons of the c2 and p2 paleomagnetic poles of the yili block with available coeval poles of junggar tarim and siberia indicate 1 no significant relative motion between the yili and junggar blocks since the late carboniferous 2 no significant or weak latitudinal relative motion occurred since the late carboniferous among these blocks but 3 the 46 2 15 1 and the 31 6 15 1 counterclockwise rotations of the yili junggar blocks with respect to tarim and siberia took place during c2 to p2 these rotations are accommodated by the permian dextral strike slip faults along the northern and southern sides of tianshan belt and sinistral strike slip faulting along the erqishi fault of altay belt resulting in about 1000 km and 600 km lateral displacements in the tianshan and altay belts respectively

multiple environmental and ecological controls on archaeal ether lipid distributions in saline ponds abstract the distribution of archaeal ether lipids is thought to be governed by salinity in hypersaline and marine environments due to differences in their biological sources however little is known about their source and relationship with salinity in lacustrine environments to explore this we analyzed the distribution of specific archaeal lipids isoprenoid gdgts and diethers of 11 ponds along a salinity gradient 0 8 to 279 in inner mongolia ne china functional gene mcra and compound specific stable carbon isotope data were used to explore the biological source s of archaeal diether and tetraether lipids both lipid and dna based methods showed methanogens to be abundant in ponds which is consistent with the dominance of gdgt 0 relative to other isoprenoid gdgts as well as the occurrence of archaeol c20 c20 dgd hydroxyarchaeol and the mcra gene however the occurrence of the extended archaeol c20 c25 dgd also suggests the presence of halobacteriales non halophilic methanogens and halophilic methanogens this means that the biological sources of archaeal diethers and tetraethers are complicated we subsequently evaluated the applicability of tex86 temperature and ace salinity proxies in these settings however due to the mixed sources of archaeal diethers and tetraethers these proxies are not applicable in these ponds and it appears that salinity is not the dominant control on archaeal ether lipid distributions in these saline ponds

the structure and evolution of a continental winter cyclone part i frontal structure and the occlusion process the frontal structure and occlusion process in a cyclone of moderate intensity that affected the central united states in january 1995 is examined the deep warm frontal zone associated with this cyclone had a lateral extension to the southwest of the sea level pressure minimum that although characterized by cold air advection near the surface had many of the characteristics of a warm front aloft in fact this feature had a structure similar to the so called bent back fronts previously documented only in association with explosively deepening maritime cyclones the development of a warm occluded structure was investigated with the aid of a numerical simulation of the event performed using the university of wisconsin nonhydrostatic modeling system the development of the warm occluded structure was asynchronous in the vertical occurring first at midtropospheric levels and later near the surface in contrast to the classical occlusion process near the surface the warm occluded front was formed as the warm front was overtaken by the frontogenetically inactive portion of the historical coldfrontal zone at midtropospheric levels the warm occluded structure formed as a result of the cold frontal zone approaching and subsequently ascending the warm frontal zone in accord with a component of the classical occlusion mechanism the observed asynchronous evolution of the occluded structure is proposed to result from the vertical variation in vortex strength associated with the upper level potential vorticity pv anomaly that controls the cyclogenesis it is suggested that the occlusion process begins aloft where the associated vortex strength is greatest and gradually penetrates downward toward the surface during the cyclone life cycle additionally a characteristic treble clef shape to the upper level pv anomaly is shown to be a sufficient condition for asserting the presence of a warm occluded structure in the underlying troposphere

observations of the mesoscale sub structure in the cold air of a developing frontal cyclone observations from 58 dropwindsondes released in a mesoscale array during the fronts 92 experiment are interpreted in the context of satellite imagery to derive the mesoscale structure and evolution of parts of a frontal cyclone developing over the eastern north atlantic a conceptual model involving the intertwining of dry intrusion and cloud head flows is corroborated and is used to provide the framework for interpreting the detailed mesoscale behaviour in the cold air two distinct dry intrusions were responsible for two cold fronts trailing south westwards from the tip of the cloud head both were surface features at the beginning of our study but the leading one evolved into an upper front with mid level convection as the dry intrusion responsible for it overran the warm sector areas of both high and low potential vorticity were indicated within the dry intrusions upon encountering a critical level of zero system relative velocity at the top of the moist boundary layer the dry intrusions arrival was associated with the development of multiple dry and moist laminae near the top of the boundary layer the vertical wavelength of the laminae was about 1 km and they extended over 200 km in the front normal direction with a slope of typically 1 in 60 although most parts of the laminae were subsaturated their circulations combined with the double structure of the dry intrusions to produce multiple shallow cloud lines within the boundary layer these formed as an extension of the south western tip of the cloud head associated with the developing cyclone possible mechanisms for generating the observed structures are discussed

archaeal and bacterial lipids in authigenic carbonate crusts from eastern mediterranean mud volcanoes abstract we investigated the distributions and 13 c values of lipid biomarkers in authigenic methane related carbonate crusts formed on eastern mediterranean mud volcanoes a highly diverse suite of microbial membrane lipids was detected strongly 13 c depleted lipids diagnostic for archaea include isoprenoid glycerol diethers isoprenoid glycerol dialkyl glycerol tetraethers and several c 20 c 35 isoprenoid hydrocarbons bacterial lipids mainly consist of dialkyl glycerol diethers branched fatty acids and hopanoids showing important 13 c depletions albeit less than archaeal lipids the data provide further evidence for the involvement of archaea and bacteria in the anaerobic oxidation of methane aom and in the sequestration of methane derived carbon in authigenic carbonate crusts varying distributions and isotopic compositions of 13 c depleted lipids argue for heterogeneous aom related microbial consortia expanding on existing work at cold seeps distinctive biomarker features and inferred microbial assemblages are observed in these crusts in agreement with available phylogenetic data for the samples our results support the potential of lipids for distinguishing methanotrophic communities despite the observed variances conservative features in the abundances and isotopic offsets of microbial biomarkers occur likely reflecting the overall relationships between archaea and bacteria and the nature of carbon flow between them

carbonate formation by anaerobic oxidation of methane evidence from lipid biomarker and fossil 16s rdna carbonate chimneys and other carbonate structures occur widespread in the gulf of cadiz and probably reflect the presence of cold seeps and associated release of methane in the geological past possibly in the early pleistocene but it is unclear under what conditions and by which processes these carbonates were formed we studied a fossil methane related carbonate crust collected from the kidd mud volcano in the gulf concentrations of microbial lipids their stable carbon isotope composition sequences of fossil 16s rrna genes of anaerobic methanotrophic archaea in combination with mineralogical and carbon and oxygen isotopic composition of carbonate were obtained for seven different horizons of the crust this combination of organic and inorganic geochemical techniques with molecular ecological methods gave a consistent view on processes resulting in the formation of the crust and indicated that it took place in two phases and in a downward direction archaeal lipid biomarkers and fossil 16s rrna gene sequence data revealed the dominance of archaeal anme 2 group and elevated methane partial pressures during the formation of the top part of the crust the lower part of the carbonate was likely formed in an environment with reduced methane fluxes as revealed by the dominance of fossil remains of anme 1 archaea the combination of these methods can be used as an effective tool to reconstruct in unprecedented detail the palaeo biogeochemical processes resulting in the formation of carbonate fabrics this interdisciplinary strategy may also be applied for other fossil methane derived carbonates generating new concepts and knowledge about past methane related carbonate systems

u pb ages of uranium ores in the churchrock uranium district new mexico examines samples from the largest us uranium producing region in order to determine ages of mineralization of different orebodies uranium from this area has come mainly from arkosic and subarkosic sandstones of the upper jurassic morrison formation several lines of evidence suggest that ages range from late jurassic or early cretaceous to at least as young as tertiary geologic observations indicate that the oldest primary orebodies are tabular in shape and rich in amorphous organic material whereas the youngest orebodies tend to be poor in amorphous organic material display roll front geometry and are commonly spatially associated with laramide or younger faults both types of ore were formed by relatively lowtemperature dilute fluids that were essentially ground water in nature concludes that the 0 to 1 m y u pb apparent ages of the united nuclear corporation church rock mine relate to redistribution by roll front processes of earlier formed ores by oxidizing pleistocene ground waters perhaps those that resulted in the present day limonitic zone of the westwater canyon member suggests that the 10 m y apparent age of sample km 17 1 may represent an earlier phase of redistributed ore formation perhaps related to the tertiary oxidation front that resulted in the present day hematitic zone of the westwater canyon member

the structure and evolution of a continental winter cyclone part ii frontal forcing of an extreme snow event abstract the production of a narrow heavy occasionally convective snowband that fell within a modest surface cyclone on 19 january 1995 is examined using gridded model output from a successful numerical simulation performed using the university of wisconsin nonhydrostatic modeling system it is found that the snowband was produced by a thermally direct vertical circulation forced by significant lower tropospheric warm frontogenesis in the presence of across front effective static stability differences as measured in terms of the equivalent potential vorticity pve the sometimes convective nature of the snowband resulted from the development of freely convective motions forced by frontal lifting of the environmental stratification model trajectories demonstrate that a stream of warm moist air ascended through the trowal portion of the warm occluded structure that developed during the cyclone life cycle the lifting of air in the trowal was in this case forced by lower tropospheric frontogenesis occ

reexamining the cold conveyor belt abstract despite the popularity of the conveyor belt model for portraying the airflow through midlatitude cyclones questions arise as to the path of the cold conveyor belt the lower tropospheric airflow poleward of and underneath the warm front some studies beginning with carlson s analysis of the eastern u s cyclone of 5 december 1977 depict the cold conveyor belt moving westward reaching the northwest quadrant of the storm turning abruptly anticyclonically rising to jet level and departing the cyclone downstream hereafter the anticyclonic path other studies depict the cold conveyor belt reaching the northwest quadrant turning cyclonically around the low center and remaining in the lower troposphere the cyclonic path to clarify the path of the cold conveyor belt the present study reexamines carlson s analysis of the cold conveyor belt using an observational and mesoscale numerical modeling study of the 5 december 1977 cyclone this reexamination raises several previously unappreciated

the evolution of a terrace sequence along the manas river in the northern foreland basin of tian shan china as inferred from optical dating abstract the tian shan range lies in the actively deforming part of the india asia collision zone the uplift rate and deformation pattern of the tian shan are important for understanding the dynamics of crustal deformation in the region the river terraces in northern tian shan provide key records of past changes in climate and or regional tectonics in this study a terrace sequence along the manas river in a tectonically active zone in the northern foreland basin of tian shan is investigated six river terraces were identified and dated using optically stimulated luminescence osl the results show that the six terraces were abandoned at 0 5 ka 1 4 ka 3 1 ka 4 0 ka 12 4 ka and 19 9 ka respectively together with high resolution global positioning system gps measurements on the terrace treads the fluvial history of manas river is reconstructed from 20 ka to 4 8 ka the height of the fluvial bed of manas river decreased at an average rate of 2 2 0 6 mm yr from 4 8 ka to the present the height of the fluvial bed decreased at an average rate of 13 5 0 6 mm yr corresponding to intensified incision of manas river during the late holocene this accelerated incision is very likely caused by the tectonic forces rather than climatic influences alone suggesting that the tectonic uplift activity was significantly intensified since 4 8 ka in the northern piedmont of tian shan other controlling factors on the incision of manas river are also discussed

mesoscale dynamics of the trowal and warm frontal regions of two continental winter cyclones abstract the dynamic and thermodynamic structure and associated frontal circulations within the trowal and warm frontal regions of two extratropical winter cyclones are examined using numerical simulations in each cyclone the warm moist airstream originating in the warm sector was found to bifurcate upon reaching the warm front one branch of the flow turned anticyclonically eastward corresponding to the warm conveyor belt while the second branch turned cyclonically westward becoming the trowal airstream the dynamic forcing of vertical motion within the two airstreams was investigated using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model mm5 both from an analysis of the sawyer eliassen se equation in two dimensions and from complete model solutions shearing deformation associated with the jet stream and the low level cyclonic flow dominated confluent deformation near the trowal in both cases the shearing deformation was accompanied

biomarker and 16s rdna evidence for anaerobic oxidation of methane and related carbonate precipitation in deep sea mud volcanoes of the sorokin trough black sea many mud volcanoes were recently discovered in the euxinic bottom waters of the sorokin trough ne black sea three of them i e nioz odessa and kazakov were selected for a detailed biogeochemical investigation four methane related carbonate crusts covered with microbial mats and sediments dmud brecciat from these mud volcanoes were collected during the 11th training through research cruise ttr 11 in 2001 the first finding of methanotrophic microbial mats associated with authigenic carbonates in the deep black sea we measured the concentrations and 13c values of methane and specific archaeal and bacterial lipids and determined archaeal and bacterial 16s rrna gene sequences the 13c of the microbial lipids reflected the carbon isotopic values of the methane indicating that methane was the main carbon source for microorganisms inducing carbonate formation anaerobic oxidation of methane aom in these settings was performed by archaea affiliated with the so called anme 1 group none of the identified archaeal sequences were closely related to known methanogens the combined 16s rrna gene sequence and biomarker data revealed a distinct difference in archaeal assemblage between the carbonate crusts and mud breccias besides gene sequences of sulfate reducing bacteria dna analysis of bacterial communities revealed a diversity of bacteria with apparent contrasting metabolic properties the methane utilization via aom processes was detected in the uppermost sediments where it subsequently induces authigenic carbonate precipitation most probably below seafloor the results of integrated biomarker and 16s rrna gene study reveal a crucial role of aom processes in formation of authigenic carbonates in methane seep environments

magnetochronology of the upper cenozoic strata in the southwestern chinese tian shan rates of pleistocene folding and thrusting abstract the southwestern chinese tian shan of central asia is an actively deforming part of the indian asian collision system paleomagnetic investigations of two plio pleistocene terrestrial successions provide the first detailed magnetostratigraphy for the upper cenozoic strata in this region paleomagnetic samples were collected from 358 sites within the atushi formation and xiyu formation across the atushi talanghe anticline near atushi thermal demagnetization behavior reversal and fold tests of paleomagnetic stability indicate that the characteristic remanence directions were acquired before tilting and folding of the strata a composite magnetostratigraphic section for this sequence correlates with the mammoth subchron to the jaramillo subchron between 3 3 and 1 07 myr of the geomagnetic polarity timescale of cande and kent j geophys res 100 1995 6093 6095 the mean declination 349 3 in the boguzihe section indicates a counterclockwise vertical axis rotation 11 2 during the past 1 4 myr the conglomeratic xiyu formation is time transgressive along its progradational contact with the underlying atushi formation across a map distance of 6 km the basal contact ranges from less than 1 0 myr in the ganhangou section to 1 9 myr in the boguzihe section to the southwest and to 2 8 myr on the northwest limb of the anticline northeastward lateral propagation and growth of the atushi talanghe anticline initiated at 1 4 myr in the boguzihe and 1 2 myr in the ganhangou the cross section in the boguzihe provides a conservative maximum estimate of shortening rate of 3 3 4 4 mm yr and uplift rate of 3 mm yr this rate represents about half of the geodetically determined shortening rate between the northern tarim basin and the kyrgyz tian shan wang et al acta seismol sin 22 2000 263 270 reiger et al earth planet sci lett 191 2001 157 165 during fold growth over the past 1 4 myr the crest of the atushi talanghe anticline eroded at an average rate of 2 6 2 7 mm yr

characterization of ore forming fluids in the tamusu sandstone type uranium deposit bayingobi basin china constraints from trace elements fluid inclusions and c o s isotopes abstract the tamusu deposit is a large sandstone type uranium deposit discovered in recent years in the bayingobi basin inner mongolia hydrothermal activity was recorded by veins in this deposit but its relationship with uranium mineralization has not been clarified in this study petrographic observations chemical composition of u minerals whole rock geochemistry fluid inclusions and c o s stable isotope studies of sandstone and veins were integrated to characterize the mineralizing fluids and mineralization conditions we found uranium minerals generally co exist with pyrite occurring in interstitial pores or on detrital grains in sandstone the main ore mineral is pitchblende and minor ore minerals include brannerite and coffinite pitchblende coexists with subhedral pyrite whereas brannerite and coffinite coexist with cubic pyrite and calcite calcite also occurs in veins together with gypsum fluid inclusions from calcite and gypsum in the veins have homogenization temperatures ranging from 124 c to 326 c with salinities of 5 7 17 2 wt nacl equivalent the c o and s isotopes of the vein minerals suggest that the hydrothermal fluids were derived from circulated formation water trace element analysis shows that the u bearing sandstone is commonly enriched in v re and mo while the high grade uranium ores are further enriched in zn co ni and cu the ree patterns and eu values in the high grade u bearing sandstone are similar to those in the veins which are characterized by high lree and low eu suggesting that the high grade u bearing sandstone is related to hydrothermal activity the mineral assemblages temperatures trace elements and isotopes indicate that the tamusu deposit was affected by two distinct types of fluids supergene diagenetic alkaline oxidizing fluids and acidic reducing hydrothermal fluids the oxidizing fluids started to be involved after the deposition of the ore hosting upper bayingobi formation forming a large amount of low grade u bearing ores the hydrothermal fluids occurred in association with the eruption of basalt in the overlying suhongtu formation the involvement of hydrothermal fluids changed the ph and eh conditions superimposed and reformed the low grade uranium ores forming high grade uranium ores and finally fixed the position of the uranium orebodies therefore the tamusu deposit experienced four main stages i sedimentary and early diagenetic uranium concentration ii oxidation and ore forming stage iii hydrothermal alteration and superimposed mineralization and iv post ore stage

evidence of uranium biomineralization in sandstone hosted roll front uranium deposits northwestern china we show evidence that the primary uranium minerals uraninite and coffinite from high grade ore samples u3o8 0 3 in the wuyiyi wuyier and wuyisan sandstone hosted roll front uranium deposits xinjiang northwestern china were biogenically precipitated and psuedomorphically replace fungi and bacteria uranium vi which was the sole electron acceptor was likely to have been enzymically reduced post mortem accumulation of uranium may have also occurred through physio chemical interaction between uranium and negatively charged cellular sites and inorganic adsorption or precipitation reactions these results suggest that microorganisms may have played a key role in formation of the sandstone or roll type uranium deposits which are among the most economically significant uranium deposits in the world

a cyclone phase space derived from thermal wind and thermal asymmetry abstract an objectively defined three dimensional cyclone phase space is proposed and explored cyclone phase is described using the parameters of storm motion relative thickness asymmetry symmetric nonfrontal versus asymmetric frontal and vertical derivative of horizontal height gradient cold versus warm core structure via the thermal wind relationship a cyclone s life cycle can be analyzed within this phase space providing substantial insight into the cyclone structural evolution an objective classification of cyclone phase is possible unifying the basic structural description of tropical extratropical and hybrid cyclones into a continuum stereotypical symmetric warm core tropical cyclone and asymmetric cold core extratropical cyclone life cycles are illustrated using 1 navy operational global atmospheric prediction system nogaps operational analyses and 2 5 ncep ncar reanalyses the transitions between cyclone phases are clearly illustrated within the phase space including extratro

the formation of a forward tilting cold front with multiple cloud bands during superstorm 1993 abstract a mesoscale model simulation is used to examine the evolution of the cold front and accompanying cloud bands in eastern mexico associated with superstorm 1993 12 14 march the simulated cold front differed in structure and evolution from a classical cold front in agreement with evidence from observations and european centre for medium range weather forecasts analyses the surface cold front as defined by the leading edge of strong northerlies and cold advection initially possessed a rearward tilt with height over southern texas within 6 h the leading edge of the front moved equatorward and developed a large scale forward tilt of greater than 200 km in the horizontal from the surface to 700 hpa this forward tilt occurred as a mid to upper tropospheric baroclinic zone arrived from over the sierra madre descended into eastern mexico and interacted with the surface cold front embedded within this large scale forward tilt was a locally enhanced horizontal potential temperature gradient tha

u pb zircon geochemical and sr nd hf isotopic constraints on age and origin of jurassic i and a type granites from central guangdong se china a major igneous event in response to foundering of a subducted flat slab abstract the mesozoic geology of se china is characterized by widespread jurassic to cretaceous igneous rocks consisting predominantly of granites and rhyolites and subordinate mafic lithologies however the tectonic regime responsible for the inland jurassic granites remains controversial we report here u pb zircon ages geochemical and sr nd hf isotopic data for the nankunshan alkaline granite and the fogang granitic batholith in central guangdong mineralogical and geochemical features suggest that the fogang and nankunshan rocks are i and aluminous a type granites respectively shrimp u pb zircon analyses yield consistent ages ranging from 159 3 ma to 165 2 ma for four samples from the fogang batholith and an age of 158 5 ma for the nankunshan granite the fogang granites having i sr 0 7098 0 7136 e nd t 4 3 to 12 2 and e hf t 11 5 to 3 1 for the magmatic zircons were derived from paleoproterozoic mafic intermediate igneous protolith with minor addition of mantle derived magmas the nankunshan rocks have relatively lower i sr 0 706 0 708 higher e nd t 0 3 to 2 4 and e hf t 5 7 to 1 1 for the magmatic zircons and some oib like trace element ratios they were likely generated through extensive fractional crystallization of mantle derived alkaline parental magma associated with crustal assimilation these 160 ma i and a type granites in central guangdong were emplaced coeval with the widespread 165 155 ma i and a type granites and syenites following the initiation of intraplate basaltic and or bimodal igneous magmatism at 180 170 ma in the adjacent regions we interpret these jurassic igneous rocks as anorogenic magmatism formed during a major igneous event in response to foundering of an early mesozoic subducted flat slab beneath se china continent

molecular and isotopic analysis of anaerobic methane oxidizing communities in marine sediments convergent lines of molecular carbon isotopic and phylogenetic evidence have previously indicated hinrichs k u hayes j m sylva s p brewer p g delong e f 1999 methane consuming archaebacteria in marine sediments nature 398 802 805 that archaea are involved in the anaerobic oxidation of methane in sediments from the eel river basin offshore northern california now further studies of those same sediments and of sediments from a methane seep in the santa barbara basin have confirmed and extended those results mass spectrometric and chromatographic analyses of an authentic standard of sn 2 hydroxyarchaeol hydroxylated at c 3 in the sn 2 phytanyl moiety have confirmed our previous tentative identification of this compound but shown that the previously examined product was the mono tms rather than di tms derivative further analyses of 13 c depleted lipids appreciably more abundant in samples from the santa barbara basin have shown that the archaeal lipids are accompanied by two sets of products that are only slightly less depleted in 13 c these are additional glycerol ethers and fatty acids the alkyl substituents in the ethers mostly monoethers with some diethers are non isoprenoidal the carbon number distributions and isotopic compositions of the alkyl substituents and of the fatty acids are similar suggesting strongly that they are produced by the same organisms their structures n alkyl and methyl branched n alkyl require a bacterial rather than archaeal source the non isoprenoidal glycerol ethers are novel constituents in marine sediments but have been previously reported in thermophilic sulfate and nitrate reducing organisms which lie near the base of the rrna based phylogenetic tree based on previous observations that the anaerobic oxidation of methane involves a net transfer of electrons from methane to sulfate it appears likely that the non archaeal 13 c depleted lipids are products of one or more previously unknown sulfate reducing bacteria which grow syntrophically with the methane utilizing archaea their products account for 50 of the fatty acids in the sample from the santa barbara basin at all methane seep sites examined the preservation of aquatic products is apparently enhanced because the methane oxidizing consortium utilizes much of the sulfate that would otherwise be available for remineralization of materials from the water column

paleozoic accretion and cenozoic redeformation of the chinese tien shan range central asia the tien shan range in central asia contains two late paleozoic sutures the older southern suture marks the collision of a passive margin at the north of the tarim block and an active continental margin subduction under the latter was to the north the younger northern suture separates a northern carboniferous island arc from an active continental margin developed over a south dipping subduction zone the subduction direction under the island arc is unknown mesozoic elastics were deposited over the doubly sutured orogen rate and energy of sedimentation waned until deposition of oligocene conglomerates above a regional unconformity interpreted as marking the onset of deformation induced by the india asia collision molasse deposition accelerated in pliocene and quaternary time and deposition continues today as active thrusts generate relief paleozoic structures control the gross divergence of cenozoic thrusts across the orogen

a three dimensional upb discordia plane to evaluate samples with common lead of unknown isotopic composition abstract the concordia method introduced by g w wetherill or in a modified fashion by f tera and g j wasserburg which can only be applied to the radiogenic leead fraction of u containing minerals can be extended to the measured total pb isotope ratios by a three dimensional discordia plane the three dimensional model does not require knowledge of the isotope ratios of the common pb used for correction if the assumption of only one type of common pb with an a priori unknown isotopic composition for the investigated samples is justified the theory is derived and formulae for calculation of best fit plane parameters as well as for their errors are derived with one synthetic set of data the applicability of the method is demonstrated

the 1993 superstorm cold surge frontal structure gap flow and tropical impact in the wake of the eastern united states cyclone of 12 14 march 1993 a cold surge originating over alaska and western canada brought northerlies exceeding 20 m s21 and temperature decreases up to 158c over 24 h into mexico and central america this paper addresses the multiscale aspects of the surge from the planetary scale to the mesoscale focusing on 1 the structure and evolution of the leading edge of the cold surge 2 the reasons for its extraordinary intensity and equatorward extent and 3 the impact of the surge on the tropics specifically on the strength of the trade winds and on the sea surface temperature in the eastern pacific the cold surge was initiated as a developing cyclone over the gulf of mexico and an upstream anticyclone east of the rockies caused an along barrier pressure gradient to form forcing topographically channeled northerlies along the rocky and sierra madre mountains to transport cold air equatorward on the mesoscale the leading edge of the cold surge possessed nonclassical frontal structure for example as the cold surge entered mexico the coldest air and the strongest wind arrived at about 900 hpa before affecting the surface suggestive of a tipped forward leading edge to the surge also satellite imagery and surface observations indicate that the leading edge appeared to be successively regenerated in the warm presurge air the cold surge had characteristics reminiscent of a kelvin wave a tipped forward cold front a pressure jump line a bore and a gravity current but none of these conceptual dynamical models was fully applicable associated with the cold surge gap winds up to 25 m s21 were observed in the gulfs of tehuantepec a tehuantepecer fonseca papagayo and panama owing to the strong cross mountain pressure gradient in the case of the tehuantepecer a rope cloud emanated from the isthmus of tehuantepec and turned anticyclonically consistent with an inertial oscillation on the synoptic and planetary scales the extraordinary equatorward extent of the cold surge was aided by topographic channeling similar to cold air damming by a low latitude upper tropospheric trough and by the lower branch of the secondary circulation associated with a confluent jet entrance region aloft the cold surge also impacted the tropical atmosphere and ocean by contributing to the strengthening of the northeast trade winds over the eastern pacific ocean and by inducing local cooling of the sea surface temperature in the gulfs of tehuantepec and papagayo by about 48 88c