late paleozoic closure of the ob zaisan ocean along the irtysh shear zone nw china implications for arc amalgamation and oroclinal bending in the central asian orogenic belt the largest accretionary orogen in the world the central asian orogenic belt has evolved through the assembly of various oceanic and continental blocks understanding the processes associated with the development of this orogenic belt relies on precise recognition of the boundaries between various terranes one such major suture zone which records the collisional history of the siberian marginal arc system chinese altai with intra oceanic arc systems east west junggar is the irtysh shear zone in nw china the spatial continuity and the tectonic nature of this shear zone are still poorly understood but its development has supposedly made a significant impact on the architecture of the western central asian orogenic belt and the formation of the kazakhstan orocline here we provide new insight into the evolution of this shear zone based on detrital zircon ages hf isotope composition structural data and ar ar age constraints on the timing of deformation our results show a major discrepancy in detrital zircon populations and hf model ages across the southern chinese altai and the northern east west junggar thus allowing us to map the exact location of the tectonic boundary detrital zircon data constrain the initial closure of the ob zaisan ocean to the late carboniferous 323 ma and new structural and ar ar geochronological data shed light on the subsequent collisional processes we propose that the collisional zone between the chinese altai and the east west junggar was initially subjected to crustal thickening at ca 323 295 ma followed by orogen parallel extension ca 295 ma and transpressional deformation ca 286 253 ma the closure of the ob zaisan ocean in nw china postdates the initial phase of oroclinal bending in the western central asian orogenic belt thus indicating that oroclinal bending initiated during subduction based on our new constraints and other available geological data we suggest that the early stage of oroclinal bending was likely driven by slab rollback

an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

contrasting styles of mineralization in the chinese altai and east junggar nw china implications for the accretionary history of the southern altaids abstract the chinese altai east junggar collage in the southern altaids hosts three metallogenic belts which are from north to south 1 a volcanogenic massive sulphide vms cu pb zn belt 2 a belt of shear zone related gold deposits 3 a porphyry cu au mo belt the vms deposits formed in two pulses c 405 ma and c 375 ma in the chinese altai arc the porphyry deposits developed in three pulses in the east junggar arc the first two synchronous with the vms mineralization and the third at c 330 ma the shear zone related gold deposits developed in the late carboniferous to permian at the contact between the chinese altai and east junggar arcs time space distributions of diverse ore deposits across the altai east junggar collage indicate that the collage developed from two independent arcs the chinese altai and the east junggar the vms and porphyry deposits developed in the chinese altai and east junggar arcs respectively the chinese altai arc is interpreted to be a japanese type arc and the east junggar arc a mariana type arc during the latest palaeozoic the two arcs were juxtaposed by the erqis fault when many shear zone related lode gold deposits were emplaced these metallogenic distributions were a likely response to spatially localized mechanisms of crust growth and to the tectonic evolution of the altai east junggar collage and they are consistent with interpretation of the altaids as a multiple subduction accretion collage

transpressional deformation strain partitioning and fold superimposition in the southern chinese altai central asian orogenic belt transpressional deformation has played an important role in the late paleozoic evolution of the western central asian orogenic belt caob and understanding the structural evolution of such transpressional zones is crucial for tectonic reconstructions here we focus on the transpressional irtysh shear zone with an aim at understanding amalgamation processes between the chinese altai and the west east junggar we mapped macroscopic fold structures in the southern chinese altai and analyzed their relationships with the development of the adjacent irtysh shear zone structural observations from these macroscopic folds show evidence for four generations of folding and associated fabrics the earlier fabric s 1 is locally recognized in low strain areas and is commonly isoclinally folded by f 2 folds that have an axial plane orientation parallel to the dominant fabric s 2 s 2 is associated with a shallowly plunging stretching lineation l 2 and defines similar to nw se tight close upright macroscopic folds f 3 with the doubly plunging geometry f 3 folds are superimposed by similar to nnw sse gentle f 4 folds the f 3 and f 4 folds are kinematically compatible with sinistral transpressional deformation along the irtysh shear zone and may represent strain partitioning during deformation the sub parallelism of f 3 fold axis with the irtysh shear zone may have resulted from strain partitioning associated with simple shear deformation along narrow mylonite zones and pure shear dominant deformation f 3 in fold zones the strain partitioning may have become less efficient in the later stage of transpressional deformation so that a fraction of trans current components was partitioned into f 4 folds c 2016 elsevier ltd all rights reserved

early diagenesis of bone and tooth apatite in fluvial and marine settings constraints from combined oxygen isotope nitrogen and ree analysis abstract fossil bones and teeth of late pleistocene terrestrial mammals from rhine river gravels rs and the north sea ns that have been exposed to chemically and isotopically distinct diagenetic fluids fresh water versus seawater were investigated to study the effects of early diagenesis on biogenic apatite changes in phosphate oxygen isotopic composition 18opo4 nitrogen content wt n and rare earth element ree concentrations were measured along profiles within bones that have not been completely fossilized and in skeletal tissues bone dentine enamel with different susceptibilities to diagenetic alteration early diagenetic changes of elemental and isotopic compositions of apatite in fossil bone are related to the loss of the stabilizing collagen matrix the ree concentration is negatively correlated with the nitrogen content and therefore the amount of collagen provides a sensitive proxy for early diagenetic alteration ree patterns of rs and ns bones indicate initial fossilization in a fresh water fluid with similar ree compositions bones from both settings have nearly collagen free ree u f and sr enriched altered outer rims while the collagen bearing bone compacta in the central part often display early diagenetic pyrite void fillings however ns bones exposed to holocene seawater have outer rim 18opo4 values that are 1 1 to 2 6 higher compared to the central part of the same bones 18opo4 18 2 0 9 n 19 surprisingly even the collagen rich bone compacta with low ree contents and apatite crystallinity seems altered as ns tooth enamel 18opo4 15 0 0 3 n 4 has about 3 lower 18opo4 values values that are also similar to those of enamel from rs teeth therefore ree concentration n content and apatite crystallinity are in this case only poor proxies for the alteration of 18opo4 values seawater exposure of a few years up to 8 kyr can change the 18opo4 values of the bone apatite by 3 therefore bones fossilized in marine settings must be treated with caution for palaeoclimatic reconstructions however enamel seems to preserve pristine 18opo4 values on this time scale using species specific calibrations for modern mammals a mean 18oh2o value can be reconstructed for late pleistocene mammalian drinking water of around 9 2 0 5 which is similar to that of late pleistocene groundwater from central europe

interplay between fluid flow and fault fracture mesh generation within underthrust sediments geochemical evidence from the chrystalls beach complex new zealand the chrystalls beach complex in the otago schist on the south island of new zealand is a melange comprising sheared trench fill sediments and fragments of oceanic crust it represents an exhumed analogue for underthrust sediments actively deforming along modern subduction thrust interfaces the melange is cross cut by a fault fracture mesh comprising subvertical extension veins and subhorizontal slickenfibre coated shear surfaces both shear and extension veins have a crack seal microstructure indicating episodic growth shear veins are associated with pressure solution selvages along the shear surface whereas wall rock alteration is not observed adjacent to extension veins electron microprobe analyses of selvage seams indicate dissolution of silica from the immediate surroundings of slickenfibre shear veins and therefore these slickenfibres probably grew by local dissolution precipitation of silica on the contrary no depletion or addition of silica is detected around extension veins indicating these veins grew by precipitation from advecting fluids oxygen isotope ratios measured in vein quartz show that shear and extension veins both precipitated from an aqueous fluid with 7 18o 10 consistent with a fluid derived from low grade metamorphic dehydration reactions fluid pressure therefore probably increased as fluids were introduced to a relatively impermeable melange with increasing metamorphic grade and decreasing porosity fault fracture mesh generation therefore involved localized shear assisted by dissolution precipitation creep and concomitant extension fracturing this led in turn to transient permeability associated with a fluid pressure drop allowing episodic vein growth this process may be analogous to geophysically observed episodic tremor and slow slip which also involves a mixture of deformation styles that put together achieve shear slip along the subduction thrust interface

thermal maturity of carbonaceous material in conodonts and the color alteration index independently identifying maximum temperature with raman spectroscopy abstract the color alteration index cai of conodont specimens is commonly used for identifying the maximum temperature to which units of sedimentary rock particularly carbonates have been heated observable color variations in these fossils are thought to be a result of the thermally induced structural evolution of organic carbonaceous matter cm such temperature history information is extremely valuable for applications in hydrocarbon exploration as well as for constraining other temperature related geological processes in sedimentary systems however the identification of cai depends on the qualitative visual assessment of color which along with a host of other potential complications may yield inaccurate determinations of maximum temperature raman spectroscopy allows thermally induced structural changes in cm to be quantified and it has been used to estimate the thermal maturity in metasedimentary rocks for almost two decades here we use raman spectroscopy of carbonaceous material rscm in conodont specimens and their mississippian to upper triassic host rocks from british columbia canada to estimate maximum temperatures based on the transformation structural reorganization of disordered carbon to graphite this study demonstrates that the maximum temperatures experienced by conodont specimens as calculated from rscm using the iterative fitting of raman spectra ifors technique correlate well with cai but lie outside the suggested ranges in some instances this may be due to complex thermal histories of these conodont specimens or the influence of diagenetic alteration not thermal histories on conodont color we recommend the application of raman spectroscopic analyses of cm in conodonts and their host rocks to obtain more confident accurate and precise estimations of maximum temperature that are independent of cai

variscan veins record of fluid circulation and variscan tectonothermal events in upper palaeozoic limestones of the moravian karst czech republic numerous variscan syntectonic calcite veins cross cut palaeozoic rocks in the moravian karst a structural petrographic and stable isotopic analysis of the calcite veins and a microthermometric study of fluid inclusions in these vein cements have been carried out to determine the origin of the variscan fluids and their migration during burial and deformation the isotopic parameters of white older more deformed and rose younger calcites are 87 sr 86 sr is between 0 7078 and 0 7082 white and 0 7086 rose 18 o is between 17 7 and 26 1 white and between 14 8 and 20 7 smow rose 13 c ranges from 0 1 to 2 5 white and from 0 3 to 1 6 v pdb rose the isotopic signatures point to precipitation in an older fluid system buffered by the host rock white calcites and to an open younger fluid dominated system rose calcites parent fluids h 2 o nacl system had salinities between 0 35 and 17 25 eq wt nacl the pressure corrected and confined homogenization temperatures suggest formation of the calcite veins from a fluid with a temperature between 120 and 170 c a pressure of 300 880 bar at a depth between 2 1 and 3 2 km the fluids were most likely confined to a particular sedimentary bed as a bed scale fluid migration white older calcite veins or later to a pile of palaeozoic sediments as a stratigraphically restricted fluid flow rose younger calcite veins the low temperatures and pressures during precipitation of calcites which took place close to a peak of burial deformation confirm the distal position of the moravian karst region within the variscan orogen

diagenetic alteration of the structure and δ18o signature of palaeozoic fish and conodont apatite potential use for corrected isotope signatures in palaeoenvironmental interpretation abstract the oxygen isotopic compositions of carboniferous conodonts and fish microfossils ichthyoliths from identical samples were analysed in tandem in order to test whether these phosphatic media can be reliably used for palaeoclimatic reconstruction the structure of conodonts and of most ichthyoliths analysed are somewhat analogous to the enamel and dentine bone tissue respectively of modern mammals therefore the diagenetic susceptibilities of the taxa analysed may provide important clues to other palaeoclimatic studies utilising a variety of biogenic apatite thermal maturation indices and scanning electron microscopy were used to characterise the preservation of biogenic apatite despite a high conodont colour alteration index cai of 5 5 conodont elements appear to have been only mildly affected by diagenetic alteration in contrast ichthyoliths were commonly recrystallised and exhibited diagenetic apatitic overgrowths containing amorphous pyrolytic carbon interpreted as indicating that at least some overgrowth material derived from the original biogenic apatite diagenetic alteration has resulted in ichthyolith 18 o values being systematically lower by on average 2 9 1 0 3 relative to conodont apatite conodont samples yielded regionally correlatable isotope values which can be interpreted in terms of more palaeoenvironmentally sensible palaeotemperatures relative to ichthyolith values densely crystalline enamel like conodont elements are interpreted as the more robust phosphatic medium to preserve original isotopic compositions the strong correlation r 0 8 of the 18 o values of the more structurally pristine conodont and commonly recrystallised ichthyolith apatite indicates that i despite diagenetic lowering of absolute isotope values original palaeoenvironmental records may be preserved and ii diagenetic overprinting may result in a stable offset and therefore be correctable locally

late palaeozoic to mesozoic kinematic history of the talas ferghana strike slip fault kyrgyz west tianshan as revealed by 40ar 39ar dating of syn kinematic white mica abstract the nw trending talas ferghana fault tff in kyrgyzstan central asia is one of the largest intracontinental strike slip faults in the world it extends over a distance of more than 2000 km from southern tourghai to western tarim and exhibits a maximum dextral offset of 200 km during the late palaeozoic to present the history of the fault provides important insights for the understanding of the evolution of southern central asia but remains poorly constrained due to lack of reliable geochronological data we present new ar ar ages and structural data from the kyrgyz west tianshan that elucidate the kinematic history of the tff in the palaeozoic and mesozoic 40ar 39ar ages on mylonitic white micas document a deformational history consisting of several episodes a late carboniferous age of 312 4 ma point to initiation of top to the south and dextral transpressional deformation during a metamorphic overprint in precambrian and palaeozoic rocks along the northern compartment of the tff the main phase of dextral motion along the entire fault occurred in the permian as suggested by minimum ages of 260 290 ma obtained at two different locations in the nw and central parts of the tff partial isotopic resetting occurred between 240 and 210 ma and younger ages of the ar ar mineral ages and structural data argue for a major phase of dextral shearing affecting the entire region from the west tianshan to mongolia in the late permian and leading to formation of almost equally spaced major nw trending dextral strike slip faults the uniform character of this deformation indicates that the process of amalgamation in this part of the caob ended prior to the late permian and central asia evolved as a single coherent continental block since that time

physical properties geochemistry and diagenesis of xenarthran teeth prospects for interpreting the paleoecology of extinct species abstract xenarthrans also called edentates include modern armadillos sloths and numerous extinct clades e g glyptodonts and ground sloths that lack enamel on their teeth in contrast to mammals with tooth enamel which oftentimes preserves geochemical proxy data paleoecological interpretations of xenarthrans based on geochemical analyses e g stable isotopes have been limited xenarthrans have evolved a distinctive outer dentine layer that seems to be the functional analog of enamel here we evaluate the physical and chemical properties of xenarthran outer dentine to understand its potential use for investigating geochemical proxies the mean hardness h of xenarthran outer dentine 3 8 is significantly less than that of enamel 5 7 and there is no difference in h between the two main groups i e armadillos cingulates and pilosans sloths although the mean h does not change significantly during diagenesis its range increases indicating the replacement of secondary minerals e g carbonate representing the lower range within the original hydroxylapatite mineral lattice results of ft ir analyses indicate that xenarthran outer dentine has a high degree of organics and h2o similar to normal dentine and its crystallinity index and carbonate content are affected in varying degrees during diagenesis thus although xenarthran outer dentine functions like enamel it retains compositional similarities to dentine the uptake of rare earth elements ree was analyzed from three late neogene localities in florida as a proxy for understanding diagenesis in xenarthrans as compared to other mammals relative to modern specimens the fossils have about two orders of magnitude higher concentrations of ree uptake rates vary significantly among different dental tissues i e bone dentine both inner and outer enamel ree concentrations of fossil vertebrate specimens vary significantly between different localities the ree index ratio of outer dentine bone or enamel bone for a given specimen is proposed here to evaluate relative diagenesis in xenarthrans and other mammals respectively other non xenarthran mammals tend to have a lower ree index interpreted to represent less diagenesis nevertheless many xenarthrans likewise have a low ree index relative to other mammals at the same locality indicating a similar degree of diagenesis while the ree index will likely be a reliable indicator of relative diagenesis in xenarthrans the outer dentine provides challenges to the ultimate goal of interpreting proxy geochemical e g stable isotope data from these extinct mammals

crystallinity and diagenesis of sedimentary apatites the crystallinity of sedimentary apatites was determined by fourier transform infrared spectroscopy ft ir using the splitting of a triply degenerate antisymmetric bending vibration of orthophosphate the crystallinity indices of recent marine apatites are low 3 0 3 6 while those of onland ancient apatites are high 4 5 7 8 indicating post depositional recrystallization the infrared spectra reveal that recrystallization is associated with a decrease in carbonate content substituting for po43 and an increase in fluoride order within the apatite structure the relationship between the crystallinity index and po43 18o suggests alteration of the primary isotopic composition by exchange reactions between po43 oxygens and surrounding waters the monterey samples have a large range of crystallinity index that reflects a set of complex and highly variable diagenetic conditions this demonstrates the use of ft ir criteria for differentiating between pristine and altered apatites and as a consequence for relating geochemical markers to formation or diagenetic environments it is suggested that only those samples that have low crystallinity indices c i 3 8 should be considered as pristine apatite spectra of fish remains indicate that differences in rare earth element ree patterns correspond to variations in crystallinity carbonate content and f order in the apatite lattice the fact that crystallinity is not correlated with geologic age suggests that environmental factors such as accumulation rate and pore water chemistry govern the recrystallization process in general sr content decreases and 18op exhibits high variability with increasing crystallinity

chemistry microstructure petrology and diagenetic model of jurassic dinosaur bones dinosaur national monument utah abstract the fossil bone mineral in dinosaurs from the morrison formation is well crystallized stoichiometric francolite the closely packed subparallel francolite crystals have equidimensional cross sections mostly 10 40 nm wide in contrast crystallites in unaltered mammal bone tissue are poorly crystallized nonstoichiometric carbonate hydroxyapatite a few nanometers thick and plate rod or needle shaped the diagenetic francolite crystals are elongated in the c axis direction as are bone tissue crystallites along permeable cracks francolite crystals grew to 250 nm wide compared to unaltered crystallites in mammal bones the francolite has higher concentrations of ba ce cr f la mn ni pb rb sr th u v and y and perhaps zr na and mg are lower in concentration diagene ic francolite grew from groundwater enriched in ions from silicic ashes in the brushy basin member and from dissolution of bone tissue crystallites after burial francolite grew on crystallite seeds filling the space formerly occupied by collagen perhaps half the tissue volume and dissolved crystallites the micron scale structures such as haversian canals and laminae are preserved because the diagenetic francolite retains the orientations of the seeds the laminae 1 10 m thick commonly preserve an orthogonal plywood structure the diagenetic growth of francolite during this type of bone fossilization implies that oxygen isotopic ratios measured in dinosaur bones even those that appear fresh and unaltered may dominantly reflect groundwater temperature rather than dinosaur body temperature trace element concentrations in the francolite may reflect groundwater composition rather than dinosaur diet pore filling cements precipitated in the sands and bones at shallow burial depths as evidenced by the 35 52 minus cement porosities of the sandstones and numerous uncompacted oversize pores filled by cements gypsum and calcite were precipitated from shallow alkaline groundwater as the groundwater became increasingly dominated by ions from silicic ash argentite chalcopyrite native gold native silver tiemannite and uraninite replaced areas of bone a few microns to tens of microns in size along cracks a thin chlorite crust commonly mantled francolite crystals along bone cracks and lined openings in bones and sandstones pervasive precipitation of a chalcedony crust followed with pseudomorphs of chalcedony after gypsum in larger cancellous openings the remaining space was fi led by the various forms of silica the bones are brown due to goethite filled cracks that cut pore filling minerals

the effect of diagenesis on oxygen isotope ratios of biogenic phosphates the effect of diagenesis on the oxygen isotope composition of ancient biogenic phosphates was evaluated by measuring different types of material from middle triassic localities in the southern alps dentin bone and tooth enamel of different taxa hosted by different rock types and metamorphosed to differing degrees were analyzed for their 18 o and 13 c values using a new microanalytical gc irmms technique the 18 o values of the majority of bone and bulk tooth samples were 18 to 19 permil smow with three samples below this range and one close to 20 permil in contrast samples of tooth enamel were 19 4 to 20 7 permil significantly higher than bone and bulk tooth without the enamel data the 18 to 19 permil data could be misinterpreted as primary only when the higher 18 o values of the enamel are considered is it apparent that the bulk data have undergone diagenesis and temperature estimates are 5 c lower than would otherwise be calculated alteration of bulk tooth is also seen in a miocene shark tooth where 18 o values of enamel are 3 permil higher than those of bulk tooth although enamel is routinely analyzed for paleoclimate work of herbivorous mammals bulk bone teeth or shells are almost exclusively used for older marine samples the results of the present study indicate that bulk data should be treated with caution

litho stratigraphic effect on variscan fluid flow within the prague synform barrandian evidence based on c o sr isotopes and fluid inclusions the palaeozoic sedimentary sequence of the prague synform ordovician devonian in the centre of the bohemian massif underwent variscan deformation and thermal overprint events variscan veins widespread throughout the sedimentary strata have precipitated from syntectonic aqueous and hydrocarbon rich fluids homogenization temperatures of aqueous inclusions increased from 70 up to 226 degc in the cambrian rocks underlying the prague synform seawater modified due to intensive water rock interaction was the main fluid component fluid flow was limited and restricted to the lithostratigraphic compartments forming a rock buffered system stable isotopic modelling c o and final interpretations of the confined hydrostratigraphic fluid migration was supported by the 87sr 86sr ratio in veins and wall rocks siliciclastic cambrian and ordovician rocks and the associated intersecting veins yielded similar isotopic signatures and consequently the fluid migration is restricted to layer and formation scales gradually downwards increasing fluid temperature and compositional changes reflect burial at oil window conditions an open fluid system could be expected in proximity of major faults of the prague syncline and at the top of the sedimentary sequence

screening in situ bone and teeth preservation by atr ftir mapping abstract bones and teeth are highly hierarchically structured and hererogeneous materials and post mortem processes can reinforce this heterogeneity it is therefore important to consider this heterogeneity to better understand diagenetic processes in this study atr ftir mapping was applied to several heated and un heated archaeological samples and to similar modern references in order to test the potential of this method atr ftir mapping can provide spatially resolved information on alteration state of mineral and organic matter this technique allowed to describe the spatial distribution of organic and mineral matter preservation in unheated palaeolithic bones bize tournal france characterized by a better preservation in the centre of the cortical bone spatial variations in the chemical composition of an archaeological heated bone abri pataud france compared to a modern reference suggested taphonomical uptake of carbonate in the most external part this pattern could correspond to a process of re carbonatation of the calcined mineral matter in the outermost part of the sample due to combustion in a co2 rich atmosphere ftir atr is a powerful tool that allows for identifying and characterizing local heterogeneities in bone preservation this technique open new prospects to reconstruct the taphonomical history of ancient samples

post accretionary permian granitoids in the chinese altai orogen geochronology petrogenesis and tectonic implications the altai orogen is an important constituent of the central asian orogenic belt caob the main orogenic processes occurred mainly in the early to middle paleozoic and involved a series of northward subduction and terrane accretion however termination of the accretionary and post accretionary processes remains poorly defined the chinese altai is located in the southern part of this orogeny which is widely intruded by permian granitic plutons these plutons are approximately circular in shape free of deformation and generally cutting pre permian structures suggesting a post tectonic formation we report the results of geochronological and geochemical data from five specific granitic plutons buerjin xibodu daqiaonan aweitan and adenbluk which all yielded magmatic zircon u pb ages of about 270 ma these plutons are composed of high k calc alkaline rocks including k feldspar megaphyric granite biotite granite and monzogranite that have metaluminous to weakly lree enriched coupled with negative eu anomalies significant negative anomalies of ba sr p and ti are also observed in the primitive mantle normalized diagram they have positive whole rock end t 1 3 to 7 2 and zircon ehf t values 5 6 to 12 9 yielding sm nd model ages of 0 9 ga therefore these granitoids are proposed to have been generated by differentiation of mantle derived magmas with variable crustal contamination in view of the field occurrence structural analysis regional tectonics and geochemical characteristics these permian plutons are concluded to be post accretionary or post collisional asthenospheric upwelling after the collision and amalgamation of the altai and junggar blocks could have caused the mantle derived magmas that evolved to form the granitoids we note that permian intrusions are not only widespread but also voluminous in the caob they mostly are post collisional products and some of them might have been related to the large igneous province activity in the tarim block

potential relations between caloris basin and mercury s sodium exosphere we have developed a 1d thermal model of mercury s regolith in order to simulate the heat diffusion in the upper subsurface first 10 m we assume in our model that the thermophysical properties of the hermean regolith are similar to those of the lunar regolith we apply our thermal model to the caloris basin which slopes induce distortions of the surface temperature compared to results obtained for a perfect spherical planet this thermal model is then coupled with a 3d monte carlo model of mercury s sodium exosphere leblanc f johnson r e 2003 icarus 164 261 281 leblanc f delcourt d johnson r e 2003b j geophys res 108 e12 doi 10 1029 2003je002151 5136 in order to describe the signatures of caloris basin on mercury s sodium exosphere in term of temporal and spatial variabilities in particular we find a motion of the maxima of sodium density in the exosphere towards the northern hemisphere similar to the one observed by potter et al potter a e morgan t h killen r m 1999 planet space sci 47 1441 1449 but did not reproduce the observed change of the emission brightness the main conclusion of this study is that the caloris basin exosphere relations might be observable from the earth which we hope will motivate new observations of mercury s exosphere

the retention of primary oxygen isotope compositions of fossil elephant skeletal phosphate fossil elephant remains from sediments of plio pleistocene age in the vicinity of lake turkana kenya provide insights into the ability of the phosphate oxygen system to preserve original 18o values 18op in the depositional environment individual fossil specimens exhibit systematic variations in the 18op values of their various tooth and bone components differences in 18op values between these skeletal components can be as high as 3 6 despite the fact that equivalent phases for individual modern elephants have 18op values which vary by less than 0 6 xrd traces of the different skeletal phases of modern and fossil samples also infer differential preservation of primary apatite crystallinities among the various fossil phases fossil samples of dentine cementum and bone have x ray spectra with sharper and more intense peaks compared to their modern counterparts but little change in crystallinity is observed for fossil enamel samples a model based on the premise that the enamel phase preserves primary isotope signatures and that the accompanying skeletal phases are partially re equilibrated with the fluids associated with the microbial decomposition of the elephant s carcass is consistent with the features of the 18op dataset this isotopic evidence in conjunction with the physical and chemical attributes of enamel has led us to postulate that enamel could be preserving primary isotope signatures while other skeletal components are affected to varying degrees by alteration processes in the burial environment

a comment on the insolation at mercury e van hemelrijck and j vercheval icarus 48 167 179 1981 presented calculations of the insolation at mercury and venus which neglect the finite angular size of the sun to determine the temperature structure in the subsurface a more accurate calculation is needed especially at longitudes 90 on mercury where the sun takes 18 days to rise or set these calculations are presented here

isotopic composition of recent shark teeth as a proxy for environmental conditions abstract the o c and sr isotope compositions of teeth from ten species belonging to five families and three orders of sharks were measured to determine the influence of habitat diet and possible species specific fractionation effects on the isotopic composition of biogenic phosphate from fish the sharks were recently caught in subtropical waters off the kwazulu natal kzn coast of south africa as well as from cold waters in prince william sound pws alaska and victor bay vb nunavut canada 18 o values of tooth phosphate 18 o p range from 20 9 to 23 5 for the kzn sharks for most species the range in measured 18 o p values is about 0 6 but it may be as high as 1 1 for different teeth from a single shark dentine and enameloid within individual teeth have no apparent differences in 18 o p values the 18 o p values of the kzn shark teeth reflect the typical habitat of the studied species primarily the thermal structure of the water column off kzn at depths between 20 and 280 m the 18 o p values of teeth from different greenland sharks from vb and pacific sleeper sharks from pws are very homogeneous averaging 25 8 and 24 7 respectively these values appear to be in equilibrium with deep 500 m ocean waters in each case at temperatures of about 0 3 c or less there is little discernable evidence for species specific fractionation effects for the oxygen isotope composition of phosphate in the studied marine fish the oxygen isotope composition of carbonate in apatite averages about 9 1 higher than corresponding 18 o p values in agreement with equilibrium fractionation between carbonate and phosphate but with a large variance 1 1 5 18 o c values also vary by up to 1 between enameloid and dentine within single teeth but in a non systematic way differences in 13 c values between carbonate in enameloid and dentine is also large up to 8 but the 13 c values vary systematically enameloid is always enriched in 13 c compared to dentine and the 13 c content increases with developmental stage of the teeth 13 c values measured for enameloid 1 6 to 4 8 appear to approach equilibrium with dissolved inorganic carbon in seawater in contrast 13 c values for dentine range from 6 4 to 2 3 for kzn sharks and 9 0 to 10 8 for the cold water sleeper sharks and are compatible with a predominantly dietary carbon source the 87 sr 86 sr ratios of teeth from kzn sharks as well as those from pws and vb are uniform averaging 0 709167 sr content varies from 1270 to 2100 ppm a range that is similar to that in well preserved fossilized teeth seawater sr is thus clearly incorporated in vivo concentrations of sm and nd are in the ppb range and contrast the ppm range in fossilized teeth indicating a postmortem incorporation of rare earth elements in apatite of the teeth

structural evolution of the irtysh shear zone northwestern china and implications for the amalgamation of arc systems in the central asian orogenic belt the nw se irtysh shear zone is a major tectonic boundary in the central asian orogenic belt caob which supposedly records the amalgamation history between the pen siberian orogenic system and the kazakhstan south mongolia orogenic system however the tectonic evolution of the irtysh shear zone is not fully understood here we present new structural and geochronological data which together with other constraints on the timing of deformation suggests that the irtysh shear zone was subjected to three phases of deformation in the late paleozoic d 1 is locally recognized as folded foliations in low strain areas and as an internal fabric within garnet porphyroblasts d 2 is represented by a shallowly dipping fabric and related similar to nw se stretching lineations oriented sub parallel to the strike of the orogen d2 foliations are folded by similar to nw se folds f 3 that are bounded by a series of mylonite zones with evidence for sinistral reverse kinematics these fold and shear structures are kinematically compatible and thus interpreted to result from a transpressional deformation phase d 3 two samples of mica schists yielded youngest detrital zircon peaks at similar to 322 ma placing a maximum constraint on the timing of d 1 d 3 deformation a similar to ne sw granitic dyke swarm similar to 252 ma crosscuts d 3 fold structures and mylonitic fabrics in the central part of the shear zone but is displaced by a mylonite zone that represents the southern boundary of the irtysh shear zone this observation indicates that the major phase of d 3 transpressional deformation took place prior to similar to 252 ma although later phases of reactivation in the mesozoic and cenozoic are likely the late paleozoic deformation d 1 d 3 at similar to 322 252 ma overlaps in time with the collision between the chinese altai and the intra oceanic arc system of the east junggar we therefore interpret that three episodes of late paleozoic deformation represent orogenic thickening d 1 collapse d 2 and transpressional deformation d3 during the convergence between the chinese altai and the east junggar on a larger scale late paleozoic sinistral shearing d3 together with dextral shearing farther south accommodated the eastward migration of internal segments of the western caob possibly associated with the amalgamation of multiple arc systems and continental blocks during the late paleozoic c 2015 elsevier ltd all rights reserved

mineral microbial structures in a bone of the late cretaceous dinosaur saurolophus angustirostris from the gobi desert mongolia a raman spectroscopy study abstract bones while buried undergo diagenetic transformations the intensity of which depends on a variety of geochemical factors microbial degradation is one of the main processes acting on bones during early diagenesis we present mineral microspheres formed during bone diagenesis from the inner walls of the left tibia of the late cretaceous dinosaur saurolophus angustirostris from the gobi desert mongolia the microspheres occur either as individual bodies from a few micrometers to about 70 m in diameter or aggregated in clusters micro raman analysis shows that the microspheres are composed of various fe oxides mostly hematite and goethite that form regular reddish brown rings with organic matter at their cores the bone itself is composed for the most part of diagenetically transformed carbonate fluorapatite calcite cement was identified around the spheres and at points of contact with bone tissue negative ce anomalies indicative of ce iv in the diagenetic environment indicate oxic burial conditions all the size distribution of the microspheres their mode of occurrence and the presence of organic matter in cores surrounded by concentric fe oxide envelopes indicate early diagenetic microbially mediated mineralization in aerobic conditions the presence of microspheres and other mineral phases in the studied bone gives evidence of at least two mineralization episodes 1 fe oxide formation during an early diagenetic microbial attack on the bone and 2 later calcite barite gypsum cementation

architecture and mineral deposit settings of the altaid orogenic collage a revised model abstract the altaids are an orogenic collage of neoproterozoic paleozoic rocks located in the center of eurasia this collage consists of only three oroclinally bent neoproterozoic early paleozoic magmatic arcs kipchak tuva mongol and mugodzhar rudny altai separated by sutures of their former backarc basins which were stitched by new generations of overlapping magmatic arcs in addition the altaids host accreted fragments of the neoproterozoic to early paleozoic oceanic island chains and neoproterozoic to cenozoic plume related magmatic rocks superimposed on the accreted fragments all these assemblages host important many world class late proterozoic to early mesozoic gold copper molybdenum lead zinc nickel and other deposits of various types in the late proterozoic during breakup of the supercontinent rodinia the kipchak and tuva mongol magmatic arcs were rifted off eastern europe siberia and laurentia to produce oceanic backarc basins in the late ordovician the siberian craton began its clockwise rotation with respect to eastern europe and this coincides with the beginning of formation of the mugodzhar rudny altai arc behind the kipchak arc these earlier arcs produced mostly cu pb zn vms deposits although some important intrusion related orogenic au deposits formed during arc arc collision events in the middle cambrian and late ordovician the clockwise rotation of siberia continued through the paleozoic until the early permian producing several episodes of oroclinal bending strike slip duplication and reorganization of the magmatic arcs to produce the overlapping kazakh mongol and zharma saur valerianov beltau kurama arcs that welded the extinct kipchak and tuva mongol arcs this resulted in amalgamation of the western portion of the altaid orogenic collage in the late paleozoic its eastern portion amalgamated only in the early mesozoic and was overlapped by the transbaikal magmatic arc which developed in response to subduction of the oceanic crust of the paleo pacific ocean several world class cu mo porphyry cu pb zn vms and intrusion related au mineral camps which formed in the altaids at this stage coincided with the episodes of plate reorganization and oroclinal bending of magmatic arcs major pb zn and cu sedimentary rock hosted deposits of kazakhstan and central asia formed in backarc rifts which developed on the earlier amalgamated fragments major orogenic gold deposits are intrusion related deposits often occurring within black shale bearing sutured backarc basins with oceanic crust after amalgamation of the western altaids this part of the collage and adjacent cratons were affected by the siberian superplume which ascended at the permian triassic transition this plume related magmatism produced various deposits such as famous ni cu pge deposits of norilsk in the northwest of the siberian craton in the early mesozoic the eastern altaids were oroclinally bent together with the overlapping transbaikal magmatic arc in response to the northward migration and anti clockwise rotation of the north china craton the following collision of the eastern portion of the altaid collage with the siberian craton formed the mongol okhotsk suture zone which still links the accretionary wedges of central mongolia and circum pacific belts in the late mesozoic a system of continent scale conjugate northwest trending and northeast trending strike slip faults developed in response to the southward propagation of the siberian craton with subsequent post mineral offset of some metallogenic belts for as much as 70 400 km possibly in response to spreading in the canadian basin india asia collision rejuvenated some of these faults and generated a system of impact rifts

structural evolution of the eastern segment of the irtysh shear zone implications for the collision between the east junggar terrane and the chinese altai orogen northwestern china the tectonic evolution of the central asian orogenic belt caob involved multiple episodes of arc accretions collisions but the reconstruction of these tectonic processes remains relatively poorly constrained evidence for a collision between the intra oceanic island arc system of the east junggar terrane and the active margin of the siberian craton chinese altai orogen is recorded in the eastern segment of the irtysh shear zone northwestern china field observations from the qinghe area show that this segment of the irtysh shear zone consists of four nw se sinistral mylonitic zones and domains bounded by these mylonitic zones show variable fold patterns in the northern part of the irtysh shear zone southern chinese altai orogen three generations of structures d d are recognized the earliest generation of foliation s is only recognized locally and is transposed to the orientation of the dominant d foliation s the latter is associated with a shallowly plunging stretching lineation which is sub parallel to the nw se hinge of d folds these third generation folds d show a steeply dipping axial plane trending nw se in the southern part of the irtysh shear zone northern east junggar terrane the structural pattern is simpler and only involves a single generation of penetrative foliation s new u pb detrital zircon and ar ar data provide constraints on the timing of collision and deformation these results suggest that the collision occurred after the early carboniferous with the timing of sinistral shearing constrained to the early middle permian the combination of sinistral shearing and nw se d folds likely represents an episode of transpressional deformation which was driven by oblique collision between the east junggar terrane and the chinese altai orogen during the early middle permian the occurrence of original sub horizontal s foliation and associated orogen parallel stretching lineation might indicate that following the initial collision after the early carboniferous the southern chinese altai orogen was subjected to orogen parallel extension in a larger scale context sinistral kinematics along the irtysh shear zone in northwestern china and northeastern kazakhstan together with coeval dextral strike slip deformation farther south might reflect an eastward escape of orogenic materials possibly in response to the permian convergence of the siberian baltic and tarim cratons

regional δ18o gradients and fluid rock interaction in the altay accretionary complex northwest china the 18 o values in syntectonic gold bearing quartz veins hosted by schist mylonite gneiss and migmatite from the altay accretionary prism xinjiang province northwest china range from 3 4 17 8 along a 20 km traverse plots of 18 o values in veins hosted by schist across several thrust sheets display a sawtooth pattern in which isotopic values decrease with increasing metamorphic grade across each thrust sheet and show abrupt increases of 5 3 to 6 8 across faults in the hanging wall models in which the host schist or clays buffer the isotopic composition of the veins provide a poor fit to the data on the other hand a fluid buffered model with 18 o fluid 0 to 2 standard mean ocean water smow provides a good fit to the data over a 5 10 km depth interval 150 300 c posttectonic normal reactivation of the thrusts with offsets averaging 5 km explains the abrupt increase in 18 o across the faults in the hanging wall a model in which seawater is tectonically ingested into the accretionary prism to a depth of 5 to 10 km followed by hydraulic fracturing and advection of hot fluid back to the sea floor along high permeability pathways is presented

stable isotope geochemistry of the archean val d or canada orogenic gold vein field a systematic study of the auriferous quartz veins of the val d or vein field abitibi quebec canada demonstrates that the c o s isotope composition of silicate carbonate borate oxide tungstate and sulphide minerals have a range in composition comparable to that previously determined for the whole superior province the oxygen isotope composition of quartz from early quartz carbonate auriferous veins ranges from 9 4 to 14 4 whereas later quartz tourmaline carbonate veins have 18oquartz values ranging from 9 2 to 13 8 quartz carbonate veins have carbonate 18o 6 9 12 5 13c 6 2 1 9 and pyrite 34s 1 2 and 1 9 isotope compositions comparable to those of quartz tourmaline carbonate veins 18o 7 9 11 7 13c 8 0 2 4 34s 0 6 6 0 18oquartz values in quartz tourmaline carbonate veins have a variance comparable to analytical uncertainty at the scale of one locality irrespective of the type of structure the texture of the quartz or its position along strike across strike or down dip a vein in contrast the oxygen isotope composition of quartz in quartz tourmaline carbonate veins displays a regional distribution with higher 18o values in the south central part of the vein field near the cadillac tectonic zone and which 18o values decrease regularly towards the north another zone of high 18o values in the northeast corner of the region and along the trace of the senneville fault is separated by a valley of lower 18o values from the higher values near the cadillac tectonic zone oxygen isotope isopleths cut across lithological contacts and tectonic structures this regional pattern in quartz tourmaline carbonate veins is interpreted to be a product of reaction with country rocks and mixing between 1 a deep seated hydrothermal fluid of metamorphic origin with minimum 18o 8 5 13c 0 6 and 34s 0 4 and 2 a supracrustal fluid most likely archean seawater with a long history of water rock exchange and with maximum 18o 3 9 13 c 5 6 and 34s 5 0

elemental and sr nd pb isotopic geochemistry of late paleozoic volcanic rocks beneath the junggar basin nw china implications for the formation and evolution of the basin basement the basement beneath the junggar basin has been interpreted either as a micro continent of precambrian age or as a fragment of paleozoic oceanic crust elemental and sr nd pb isotopic compositions and zircon pb pb ages of volcanic rocks from drill cores through the paleo weathered crust show that the basement is composed mainly of late paleozoic volcanic rock with minor shale and tuff the volcanic rocks are mostly subalkaline with some minor low k rocks in the western kexia area some alkaline lavas occur in the central luliang uplift and northeastern wulungu depression the lavas range in composition from basalts to rhyolites and fractional crystallization played an important role in magma evolution except for a few samples from kexia the basalts have low la nb 1 4 typical for oceanic crust derived from asthenospheric melts zircon pb pb ages indicate that the kexia andesite with a volcanic arc affinity formed in the early carboniferous 345 ma whereas the luliang rhyolite and the wucaiwan dacite with syn collisional to within plate affinities formed in the early devonian 395 and 405 ma respectively positive end t values up to 7 4 and low initial 87sr 86sr isotopic ratios of the intermediate silicic rocks suggest that the entire junggar terrain may be underlain by oceanic crust an interpretation consistent with the juvenile isotopic signatures of many granitoid plutons in other parts of the central asia orogenic belt variation in zircon ages for the silicic rocks different ba p ti nb or th anomalies in the mafic rocks and variable nb y and la nb ratios across the basin suggest that the basement is compositionally heterogeneous the heterogeneity is believed to reflect amalgamation of different oceanic blocks representing either different evolution stages within a single terrane or possibly derivation from different terranes

diagenetic effects on the oxygen isotope composition of bones of dinosaurs and other vertebrates recovered from terrestrial and marine sediments assessing effects of diagenesis on oxygen isotope composition of bone is essential to its use in reconstructing habitats and lifestyles of ancient vertebrates these effects are a matter of controversy particularly in the case of extinct animals such as dinosaurs to investigate the effects of diagenesis on isotopic composition of fossil bone bone samples from both marine and terrestrial campanian sediments from alberta canada have been analysed the isotopic compositions of oxygen 18 o smow were determined in bones sampled from articulated skeletons of exclusively terrestrial animals recovered from the terrestrial dinosaur park formation and compared with bones from the marine bearpaw formation the articulated skeleton of an exclusively terrestrial dinosaur hadrosaur found in marine sediments yielded similar 18 o values for both structural carbonate and phosphate fractions mean 18 o smow values 22 6 and 16 9 respectively in bone to marine reptiles mosasaurs recovered from the same locality mean 18 o smow values 24 2 and 17 3 respectively the isotopic composition of both skeletons recovered from marine sediments was significantly more positive than that of articulated hadrosaur skeletons recovered from contemporaneous terrestrial sediments mean phosphate 18 o smow value 12 9 and outside the range of phosphate 18 o smow values previously reported for terrestrial dinosaur skeletons c 9 14 these data suggest that the isotopic composition of oxygen in the phosphate and structural carbonate ions in the bone apatite was altered during diagenesis and can be used for neither palaeoclimate nor physiological reconstruction

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

the isotopic composition and diagenesis of human bone from teotihuacan and oaxaca mexico we analyzed archaeological human bone from teotihuacan and oaxaca dating from about 300 bc to 750 ad to distinguish ethnic groups within teotihuacan using oxygen isotopes sixty eight analyses of bone phosphate 6180 were made of 64 individuals in addition to oxygen isotopic analysis the bones were examined using ftir spectra with some additional dnaa and icp ms analyses little change occurs in the bone apatite until the amount of collagen as combustible organics has been reduced considerably when the bone becomes softer and ftir crystallinity increases the 6180 of the phosphate p appears to be unaltered even after extensive diagenesis and probably solution on ftir plots the relative area of the carbonate peak to the main phosphate peak decreases with diagenetic level the bones absorb some metals rapidly after burial for example uranium which then leach out as diagenesis of the bone apatite progresses other metallic elements increase irregularly in concentration as alteration proceeds

early diagenetic evolution of bone phosphate an x ray diffractometry analysis abstract a new crystallinity index ci based on the x ray powder diffractometric pattern of fossil bone carbonate hydroxylapatite is defined this ci value provides a semi quantitative way to estimate the diagenetic changes in archaeological and palaeontological bone phosphate the studied samples are 71 human bones from the french merovingian cemetery of saint linaire 1200 1700 bp 37 human bones from two necropoleis in niger 1000 5000 bp two cave bear bones from aldene cave southern france around 70 000 bp five bones of miocene mammals and 14 bones of mesozoic reptiles the main results are that 1 there is no correlation between the increase in the ci and the age of the sample even in one given locality 2 the ci seems to be related to the taphonomical conditions in archaeological and fossil bones 3 an increase in the ci is correlated with a loss in organic matter in one archaeological site but the quality of preservation of organic matter in fossil bones does not depend on the changes in the ci 4 the correlation between the increase in the ci and the decrease of co3amount in bones from the niger necropolies suggests a possible mechanism for the increase in crystallinity the changes of crystallinity reflect early diagenetic changes and depend on the burial environments

near surface ice on mercury and the moon a topographic thermal model abstract a thermal model that can be easily adapted to craters of arbitrary shape is developed and applied to high latitude impact craters on mercury and the moon chao meng fu crater at 87 5 l on mercury an unnamed bowl shaped crater at 86 7 l on mercury and peary crater at 88 6 l on the moon for an assumed input topography and grid of surface elements the model computes for each element the irradiation from direct insolation and reflected and emitted radiation from other elements taking into account shadowing by the walls of the crater partial obscuration of the solar disk near the poles and the diurnal orbital and seasonal cycles temperatures are computed over the surface grid as functions of depth and time from the surface to a specified depth and over the pertinent astronomical cycles including the effects of direct and indirect surface irradiation infrared radiation heat conduction and interior heating vapor fluxes and ice recession times are computed as functions of ice depth over the surface grid temperatures profiles vapor fluxes and ice recession times were computed for flat surfaces not associated with craters near the poles of mercury and the moon it was found that water ice could have existed throughout geologic time within the maximum radar detection depth of recent observation of mercury j k harmon and m a slade 1992 science 258 640 643 poleward of 87 88 l on mercury and poleward of 73 l on the moon for chao meng fu crater it was found that 40 of the crater floor is permanently shadowed from direct solar insolation while the remainder of the crater floor is periodically illuminated by a partially obscured sun temperatures at the upper levels of the south wall can slightly exceed 550 k surface temperatures in the permanently shadowed region of the crater floor are under 130 k which could have allowed water ice to exist throughout geologic time within the radar detection depth of recent observation of mercury for the small bowl shaped crater on mercury it was found that most of the crater is permanently shadowed from direct solar radiation except for a narrow semicircular band bordering the north rim however temperatures in the permanently shadowed region periodically reach a maximum near 315 k due to efficient heating of the small crater by thermal emission and reflection from the small sunlit region which periodically reaches temperatures exceeding 630 k water ice could not have existed throughout geologic time anywhere in this crater within the radar detection depth for peary crater on the moon the entire crater floor is permanently shadowed from direct solar insolation with maximum temperatures under 120 k the upper level of the north wall periodically reaches a maximum temperature near 310 k the low temperatures on the crater floor would have allowed water ice to exist near the surface throughout geologic time provided that the moon s obliquity was always as low as it is at present

northwestern junggar basin xiemisitai mountains china a geochemical and geochronological approach abstract we report sims u pb zircon elemental and nd sr pb isotopic data for the volcanic rocks and their subvolcanic units from the xiemisitai mountains in the west junggar region xinjiang china aiming to determine their ages source regions and tectonic setting zircon u pb dating results of the volcanic rocks 422 5 1 9 ma 411 2 2 9 ma indicate that the volcanic strata occurred in the xiemisitai mountains at late silurian early devonian time rather than middle devonian as suggested previously they are probably the eastern extension of the early paleozoic cambrian silurian boshchekul chingiz volcanic arc of east kazakhstan in china the xiemisitai volcanic rocks include andesite rhyolite and their pyroclastic equivalents the subvolcanic units are felsite and granite porphyry andesite is moderately lree enriched with a marked negative nb anomaly and th yb enrichment rhyolite felsite and granite porphyry are enriched in lree and th and depleted nb the initial sr isotope values of the xiemisitai volcanic rocks and their subvolcanic units range from 0 702294 to 0 704456 e nd 420 ma from 0 19 to 1 88 with nd model ages ranging from 600 to 803 ma initial pb isotope ratios 206 pb 204 pb are 17 77 17 96 207 pb 204 pb are 15 49 15 54 and 208 pb 204 pb are 37 56 37 80 these features suggest that the xiemisitai volcanic rocks and their subvolcanic units derived from a mantle wedge significant mixed by subducted material emi in a subduction zone they also indicate significant involvement of neoproterozoic primitive crust in the formation of the xiemisitai magmatic arc these rocks are associated with a late silurian early devonian southward subduction of the oceanic lithosphere in the northern west junggar region this gives rise to an ew trending boshchekul chingiz volcanic arc and associated metallogenic belt in the northern west junggar region and adjacent kazakhstan

oxygen isotope analyses of co existing carbonate and phosphate in biogenic apatite a way to monitor diagenetic alteration of bone phosphate abstract the oxygen isotopic composition of phosphate 18 op and structural carbonate 18 oc of hydroxylapatite was determined in 31 bone and tooth samples of modern mammals from different countries these two variables are highly correlate r 2 0 98 and the calculated best fit of linear regression is very similar to the equation calculated from the phosphate and carbonate palaeotemperature equations 1 2 according to previous measurements 3 6 on fossils of different ages from different areas it seems quite improbable to find isotopically altered skeletal remains showing a good correlation between 18 op and 18 oc as is the case with modern samples it therefore seems possible at least in some cases to use these measurements for monitoring fossil bone and tooth diagenetic alteration when a set of points lie on the equilibrium line or close to it the 18 o values could be considered close to the original values in contrast when the points lie to the left or to the right of this line this probably means that the values are diagenetically modified due to interaction with meteoric water or 18 o enriched water respectively

geochemical study of vertebrate fossils from the upper cretaceous santonian csehbanya formation hungary evidence for a freshwater habitat of mosasaurs and pycnodont fish abstract the diverse vertebrate remains from the upper cretaceous freshwater settings at iharkut hungary contain two fossil groups pycnodontiformes fish and mosasauridae that are almost exclusively known from marine palaeo environments hence their appearance in alluvial sediments is very unusual trace element and isotope compositions of the remains have been analyzed to investigate the taphonomy and the ecological differences among the different fossil groups present at iharkut all examined fossils have undergone post depositional diagenetic alteration which resulted in high concentrations of ree u and fe together with almost complete homogenization of 18oco3 values similar ree patterns in different fossils suggest a common origin for all remains hence the discovered species most likely lived in the same local ecosystem despite partial diagenetic overprinting the 18opo4 values of the fossils indicate sufficient taxon specific isotopic diversity to permit some broad conclusions on the palaeo environment of the fossils in particular it is apparent that the isotopic composition of the pycnodontiformes fish and mosasauridae remains is most compatible with a freshwater palaeo habitat and incompatible with a marine palaeo environment in addition the sr concentration and isotope data indicate that the pycnodontiformes and mosasauridae likely lived predominantly in a freshwater environment and were not simply occasional visitors to the iharkut river ecosystem regarding other fossil groups high 18opo4 values of alligatoroidea and iharkutosuchus teeth suggest that these small crocodile species might have inhabited swamps and ponds where the water was relatively rich in 18o due to evaporation

junggar basin northwest china trapped late paleozoic ocean abstract the junggar basin originated during the late paleozoic as either a remnant lower to mid paleozoic ocean basin or a mid carboniferous back arc intra or inter arc basin bounded by emergent volcanic arcs south of the siberian craton the retreating junggar sea left behind a regressive sedimentary section comprising at least 3 4 km of marine volcaniclastics in the southern junggar area sandstones deposited in the junggar basin since the devonian are exclusively volcaniclastic demonstrating that precambrian basement rocks have never been exposed in the basin and supporting the hypothesis that the junggar is underlain by oceanic crustal materials the mid carboniferous junggar ocean may have been a remnant ocean basin of early to mid paleozoic age or alternatively may have been an extending intra or inter arc basin formed behind an emergent volcanic arc in the northern turpan region subsequent strike slip deformation and the general sparsity of geologic and geophysical data from the junggar area make it difficult to distinguish between these models late early permian through triassic sediments of the junggar basin are exclusively non marine deposited in a flexurally subsiding foreland basin during initial uplift of the ancestral tian shan mountains the sedimentary section deposited during the late permian early triassic appears to be inconsistent with a proposed rifting episode during this period

composition and structural features of two permian parareptile deltavjatia vjatkensis kotelnich site russia bone fragments and their alteration during fossilisation abstract the kotelnich vertebrate fossil site one of the richest of the permian period is characterised by the excellent preservation of fossil remains due to their burial in a silty anaerobic environment similar to modern peat bogs the aim of the work is to carry out a comprehensive study of the composition and structure of bone fragments of the permian parareptile deltavjatia vjatkensis as well as that of its embedding rocks to support further paleoecological and fossilisation reconstructions fossil bones and their surrounding strata were investigated using optical and scanning electron microscopy raman spectroscopy x ray diffraction and inductively coupled plasma mass spectrometry icp ms the carbonate rich composition of the sediment was found to favour the preservation of the bone apatite the mineral phase of the bone tissue corresponds to fluorapatite organic matrix vibration bands arising on the raman spectra correspond to c h vibrations of lipids and proteins and possibly cholesterol the obtained data indicate a high degree of integrity of both bone mineral phase and its organic proteinaceous residue white blood cell wbc like structures were detected which possibly could be interpreted as leukocytes elemental mapping of fossil bones was used to reveal element distribution features uniform or with zones of apparent enrichment depletion and secondary mineralisation zones ca p mg mn and s are uniformly distributed through the bone conversely elevated quantities of fe are assigned to cracks and large pores formed as a consequence of the decomposition of organic materials as compared to bone apatite the authigenic calcite filling of bone porosities is significantly depleted in terms of microelements the apatite rare earth element ree composition of bone tissue which is inherited from seawater can be used for paleoreconstructions of redox conditions and water composition la sm ratios 0 4 0 5 high y ho ratios high uranium content and high la yb ratios 2 3 in the bone apatite indicate the absence of recrystallisation during the late stages of diagenesis a positive cerium anomaly detected in the bones indicates the presence of an oxidising and possibly alkaline environment during the early stages of diagenesis in shallow coastal basin of the kotelnich paleolocality it is shown that 10 to 20 of ree in bone apatite is derived from seawater absorption hydrogenous source with the remainder having been derived from host rock lithogenic sources

modelling of the oxygen isotope evolution of seawater implications for the climate interpretation of the δ18o of marine sediments it is often argued that the 18o value of oceanic water was maintained close to 0 for hundreds of millions of years as a consequence of oxygen isotope exchange between oceanic crust and seawater however for several decades the interpretation of the biosedimentary oxygen isotope record has conflicted with the igneous record because with increasing age a general trend of decreasing 18o values about 6 is observed in most carbonates cherts and phosphates especially for the paleozoic and early mesozoic we developed a dynamical model of seawater crust interaction that computes the 18o value in these two reservoirs as function of time this model takes into account the continuous production of crust at oceanic ridges its expansion rate the permeability profile with space and time the mineralogical mode of the crust and the kinetics of oxygen isotope exchange between rock forming minerals and seawater the model indicates that the 18o value of seawater may vary by 2 with a time response ranging from 5 to 50 ma for expansion rates of 1 to 10 cm a 1 the variation of 2 is fixed by both integrated water rock ratio and closure time of the seawater crust system by sediments variations in the oxygen isotope ratio of seawater through time have important implications for the interpretation of the systematically low 18o values of pre jurassic marine sediments according to our model marine paleotemperatures could be up to 10 c lower than those expected when applying the classical hypothesis of an ice free ocean with a 18o value of 1

composition and evolution of the lunar crust in the descartes highlands apollo 16 samples from the north ray crater ejecta blanket apollo 16 were investigated by petrographic microscope electron microprobe instrumental neutron activation and xray fluorescence analyses and 40ar 39ar and rb sr dating techniques nine major groups of monomict and polymict breccias were defined on the basis of microscopic texture and these were further subdivided into chemical subgroups on the basis of characteristic elements such as al mg fe cr ree ni and co the polymict breccias fragmental breccias granulitic breccias and impact melt breccias are the result of multiple impact induced mechanical mixing and melting and of thermal and impact metamorphism of rock and mineral clasts derived from primordial igneous crustal rocks for calculations of mixing models it was found that end members consisting of the pristine igneous rock components present as discrete samples at the apollo 16 site and supplemented by kreep dunite and a meteoritic component yield the best fits for the composition of polymict breccias the end member rocks a re ferroan anorthosite various magnesian gabbronorites including sodic ferrogabbro and feldspathic lherzolite and spinei troctolite the following model is proposed for the composition and stratigraphy of the target for north ray crater the lower section of the stratigraphy is composed of a megabreccia with clasts of highly feldspathic polymict breccias kreep free old eastern highland rock suite interpreted as nectaris ejecta descartes formation the top section contains kreep bearing polymict breccias kreep bearing young western highland rock suite and appears to be similar to the lithologies found in the cayley plains this material interpreted as cayley formation may be a distant facies of imbrium basin ejecta deposits of the imbrium basin the petrographic differences between these two major selenographic units the descartes and the cayley formations in the apollo 16 area are more distinct than the chemical differences the petrographic and chemical composition of the primordial igneous upper crust in the regions of the nectaris and imbrium basins has been calculated by subtraction of the kreep and meteoritic components from the bulk composition of the descartes and cayley materials the nectaris crust which is better constrained consists of 86 87 a northosite 4 sodic ferrogabbro 0 5 1 3 feldspathic lherzolite 6 8 regular magnesian gabbronorite 1 8 2 8 dunite and 0 1 spinel troctolite a model for the evolution of the upper lunar crust in the descartes highlands is proposed on the basis of isotope ages and clast matrix relationships of polymict breccias essential features of this model in sequenial order are 1 development of multiple layers of kreep free early feldspathic fragmental megabreccias and impact melt sheets on the primordial crust in the time period from 4 4 aeons to the time of the nectaris impact which could have occurred as late as 3 85 aeons ago 2 excavation of these megabreccias by the nectaris event and deposition of a nectarian feldspathic fragmental megabreccia in the descartes area 3 introduction of kreep basaltic material into the upper crust mainly west and northwest of the descartes site and formation of kreepy impact melt sheets most probably from 4 05 to 3 80 aeons ago 4 imbrium impact at 3 8 aeons ago and deposition of kreep bearing imbrian feldspathic fragmental breccias at the descartes site which form the cayley formation and 5 redeposition mixing and melting of all preexisting breccias yielding kreep bearing and kreep poor post cayley fragmental breccias and melt ejecta glass bombs as the result of small impacts craters 1 5 km in diameter in the cayley plains and the descartes mountains respectively

oxygen isotope compositions of phosphate from middle miocene early pliocene marine vertebrates of peru phosphatic remains of marine vertebrates recovered from five fossil sites of the pisco formation ranging from the latest middle earliest late miocene ca 11 13 ma to the early pliocene ca 3 5 ma have been analysed for their oxygen isotope compositions 18op coexisting seals dolphins whales penguins and sharks from each locality have distinct 18op values reflecting ecology and physiology differences ranging from 18 2 to 21 4 for marine mammals from 19 5 to 21 5 for marine birds and from 20 9 to 23 1 for sharks systematic offsets observed between dolphin teeth and bones as well as between dolphin and whale bones indicate that the fractionation equation established by using data from extant cetaceans may not be directly applicable to miocene cetaceans in order to estimate water 18ow values assuming that polar ice caps were not totally developed during this time interval marine palaeotemperatures ranging from 13 0 1 3 c to 17 2 1 3 c were estimated comparison of our results with those obtained in other world s areas suggests that the oxygen isotope ratios of pisco vertebrates reflect the influence of both global and local events such as the setting of the atacama desert the cold humboldt current or the global phases of ice cap growth and decay

measurement and analysis of lunar basin depths from clementine altimetry altimetric profiles from the clementine lidar are used to calculate the depths of 29 large craters and basins on the moon plotting the depths of the best preserved structures together with values for simple and complex craters measured in pre clementine studies reveals an inflection in the depth diameter d d curve in addition to the one revealed by pre clementine data this inflection occurs in the diameter range that corresponds to the morphologic transition from complex crater to basin the best empirical power law fit for basin depths is log10 d 0 41 log10 d 0 57 this relationship is characterized by a lower slope than that for complex craters demonstrating that this morphologic transition corresponds to a further decrease in the depth of an impact structure relative to its diameter with increasing size qualitative consideration of possible causes for the second inflection leads to the conclusion that it is most likely a consequence of a short term modification mechanism that influences fundamental crater morphology such as the increasing influence of gravity with diameter thicknesses of maria in the major basins are calculated by assuming that their unfilled depths would follow thed drelation results are compared with previous estimates and yield thicknesses that are generally greater than those determined by studies of flooded craters and less than those obtained from analysis of gravity

geometry kinematics and tectonic models of the kazakhstan orocline central asian orogenic belt abstract the central asian orogenic belt caob is one of the largest accretionary orogens on earth and is characterized by the occurrence of tight oroclines kazakhstan and tuva mongolian oroclines the origin of these large scale orogenic curvatures is not quite understood but is fundamentally important for understanding crustal growth and tectonic evolution of the caob here we provide an outline of available geological and paleomagnetic data around the kazakhstan orocline with an aim of clarifying the geometry kinematics and geodynamic origin of the orocline the kazakhstan orocline is evident in a total magmatic image and can be traced by the continuation of high magnetic anomalies associated with the devonian volcanic belt and the late devonian to carboniferous balkhash yili arc paleomagnetic data show 112 126 clockwise rotation of the northern limb relative to the southern limb in the late devonian to early carboniferous as well as 15 28 clockwise rotation of the northern limb and 39 40 anticlockwise rotation of the southern limb relative to the hinge of the orocline during the late carboniferous to permian we argue that the kazakhstan orocline experienced two stage bending with the early stage of bending late devonian to early carboniferous 112 126 driven by slab rollback and the later stage late carboniferous to permian 54 68 possibly associated with the amalgamation of the siberian tarim and baltic cratons this new tectonic model is compatible with the occurrence of rift basins the spatial migration of magmatic arc and the development of large scale strike slip fault systems during oroclinal bending

nd sr isotopic mapping of the chinese altai and implications for continental growth in the central asian orogenic belt article i nfo the chinese altai orogen is a typical domain of the central asian orogenic belt and in previous syntheses was divided into six tectonic units or terranes in this paper 41 new and 36 published whole rock nd and sr isotopic data for granitoid intrusions and mafic dykes within units 2 and 3 of the central altai and units 4 to 6 of the southern altai were used for isotopic mapping the age of the samples used is known from u pb zircon dating end t values range from 4 to 2 in the central altai units 2 and 3 and from 1 4 to 6 in the southern altai units 4 and 5 and up to 8 4 in unit 6 correspondingly nd model ages tdm decrease from 1 6 1 1 ga in the central altai to 1 0 0 5 ga in the southern altai except for a continental fragment in unit 4 isr is elevated in the central units decreasing to b0 705 in the southern units 5 and 6 these results demonstrate that the central altai contains widespread old crustal components in its basement whereas the southern altai comprises a higher proportion of juvenile crust when integrated with published u pb zircon ages our data show that new crust grew southwards in the chinese altai in addition our data suggest that units 2 and 3 are a single tectonic unit whereas the southern altai unit 4 which previously was regarded as a single young accretionary terrane should be subdivided into two units a younger arc and an older continental fragment the granitoids in the chinese altai can be divided into syn and post non orogenic groups the syn orogenic granitoids have ca 50 80 mantle derived component whereas the post non orogenic granitoids contain ca 70 90 the generation of syn and post non orogenic granitoids represents horizontal lateral and vertical crustal growth which contributed ca 18 28 and 7 8 respectively to the area of the chinese altai this work shows that isotopic mapping is an effective approach to elucidate terrane composition in the central asian orogenic belt and thereby better constrain palaeozoic crustal growth

raman spectral elemental crystallinity and oxygen isotope variations in conodont apatite during diagenesis abstract conodont apatite has long been used in paleoenvironmental studies often with minimal evaluation of the influence of diagenesis on measured elemental and isotopic signals in this study we evaluate diagenetic influences on conodonts using an integrated set of analytical techniques a total of 92 points in 19 coniform conodonts from ordovician marine units of south china were analyzed by micro laser raman spectroscopy m lrs laser ablation inductively coupled plasma mass spectrometry la icp ms high resolution x ray microdiffraction hxrd and secondary ion mass spectrometry sims each conodont element was analyzed along its full length including the albid crown hyaline crown and basal body in either a whole specimen i e reflecting the composition of its outer layer or a split specimen i e reflecting the composition of its interior in the conodonts of this study the outer surfaces consist of hydroxyfluorapatite and the interiors of strontian hydroxyfluorapatite ionic substitutions resulted in characteristic raman spectral shifts in the position ss1 and width ss2 of the 1 po43 stretching band although multiple elements were enriched sr2 mg2 and depleted fe3 mn2 ca2 during diagenesis geochemical modeling constraints and known raman spectral patterns suggest that sr uptake was the dominant influence on diagenetic redshifts of ss1 all study specimens show lower ss2 values than modern bioapatite and synthetic apatite suggesting that band width decreases with time in ancient bioapatite possibly through an annealing process that produces larger more uniform crystal domains most specimens consist mainly of amorphous or poorly crystalline apatite which is inferred to represent the original microstructure of conodonts in a subset of specimens some tissues especially albid crown exhibit an increased degree of crystallinity developed through aggrading neomorphism however no systematic relationship was observed between crystallinity and raman spectral or elemental parameters oxygen isotopes show substantial variation within the conodont study specimens albid crown is on average 0 28 0 32 more depleted in 18o equivalent to 1 2 1 4 c higher temperatures than hyaline crown and basal body and the interiors of conodont elements are 1 08 0 37 more depleted in 18o equivalent to 3 0 6 4 c higher temperatures relative to their outer layers although albid crown is widely regarded as better preserved than other conodont tissue types its 18o depleted composition and greater development of secondary crystallinity suggest that in fact it may be the most strongly altered tissue type we conclude that raman spectral la elemental and hxrd microstructural data can provide useful information about the extent of diagenetic alteration of conodont elements and that such information should be taken into consideration in using conodont elemental and oxygen isotope data in paleoenvironmental studies

unraveling the early middle paleozoic paleogeography of kazakhstan on the basis of ordovician and devonian paleomagnetic results abstract it is a common concept that different tectonic units in the western part of the central asian orogenic belt were united into the landmass of the kazakhstania continent in the paleozoic but many important details of its history remain enigmatic and controversial recently published paleomagnetic data from this region demonstrate that the 2000 km long horseshoe shaped devonian volcanic belt was created by oroclinal bending of an originally rectilinear active margin of kazakhstania still the silurian and devonian paleomagnetic results which this interpretation is based upon are limited and unevenly spread along the belt and additional middle paleozoic data are highly desirable accordingly we studied three mid paleozoic objects from different segments of this volcanic belt two of the three new objects yielded paleomagnetic directions that fit perfectly into the oroclinal scenario whereas the third one provided no interpretable data the earlier history of kazakhstania however remains misty we obtained three new ordovician results in north central kazakhstan and found similar inclinations but widely dissimilar declinations previously published data show a large scatter of ordovician declinations in south kazakhstan and kyrgyzstan as well we analyzed all seven middle late ordovician paleolatitudes and came to the conclusion that a nearly e w trending active margin of the kazakhstania landmass had existed at low 10 s latitudes at that time we hypothesize that this margin of the kazakhstania landmass collided with another island arc called baydaulet akbastau and with the aktau junggar microcontinent by the ordovician silurian boundary as a result of this collision subduction ceased and regional deformation magmatism and rotations of crustal fragments took place in most of kazakhstania in silurian time kazakhstania moved northward crossing the equator and rotating clockwise by 45 this changed the orientation of the kazakhstania to nw se and thereby established the rectilinear predecessor of the modern curved devonian volcanic belt

raman spectroscopy of fossil bioapatite a proxy for diagenetic alteration of the oxygen isotope composition abstract fossil bioapatite may yield biogeochemical signals of paleoenvironments captured by living organisms bioapatite may be diagenetically altered however with ions added or removed post mortem such change is typically assessed using destructive and demanding techniques here raman spectroscopy is used as a rapid and non destructive way to identify significant diagenetic alteration of fossil bioapatite we found spectral parameters of phosphate symmetric stretching 1 po43 to be very sensitive to variations in apatite chemistry particularly with respect to common diagenetic components co32 f sr2 the raman spectral parameters were subsequently applied to a set of modern biogenic and geologic magmatic apatite samples as potential endmembers for diagenetic alteration raman spectra were also collected from enamel and dentin respectively resistant vs alteration prone of fossil teeth phosphate oxygen isotopic values from the same enamel dentin samples were used as an index of alteration and provided definition of raman spectral parameters as relates to diagenetic alteration diagenetically altered samples were characterised by spectra with 1 po43 widths at half maximum height less than 13 0 cm 1 and 1 po43 band positions greater than 964 7 cm 1 raman spectroscopy is shown to have potential as a tool for pre screening fossil apatite samples before further analyses

late paleozoic faults of the altai region central asia tectonic pattern and model of formation abstract the present kinematic and dynamic analysis of large scale strike slip faults which enabled the formation of a collage of altai terranes as a result of two collisional events the late devonian early carboniferous collision of the gondwana derived altai mongolian terrane and the siberian continent resulted in the formation of the charysh terekta system of dextral strike slip faults and later the kurai and kuznetsk teletsk bashkauss sinistral strike slip faults the late carboniferous permian collision of the siberian and kazakhstan continents resulted in the formation of the chara irtysh and north east sinistral strike slip zones the age of deformation of both collisional events becomes younger toward the inner areas of the siberian continent in the same direction the amount of displacement of strike slip faulting decreases from several thousand to several hundred kilometers the width of the late paleozoic zone of deformation reaches 1500 km these events deformed the accretion collision continental margins and their primary paleogeographic pattern

accretionary orogenesis of the chinese altai insights from paleozoic granitoids zircon u pb dating and whole rock major oxide trace element and nd sr isotope compositions have been determined for four representative granitic intrusions in the sw chinese altai in order to understand the orogenesis and history of crustal growth in the central asian orogenic belt caob the ashile and halatas bodiesare relatively small intrusions formed in the late carboniferous 318 6ma andpermian 267 4ma respectively thelargertarlang tb andkeketuohaibatholiths kb havemagmaticagesof 359 to 412 ma the granitoids consist chiefly of tonalite granodiorite and granite and are metaluminous to weakly peraluminous in composition asi 0 8 1 1 the ashile pluton is characterized by relatively high mgo 2 73 3 54 wt and sr 395 456 ppm contents with low k2o na2o ratios 0 31 0 42 and mantle like nd sr isotopic compositions endt 2 85 to 3 26 initial 87 sr 86 sr 0 7047 0 7051 it probably formed by fractional crystallization of a mantle derived magma with limited assimilation of oldcrustalmaterial theotherintrusionshavenear zeroornegative endtvalues 0 67to 4 41 andhighersrisotopiccompositions initial 87 sr 86 sr 0 7067 0 7092 indicating a mixture of juvenile and old components in their genesis these intrusions are characterized by relatively low k rb cs contents and low rb sr ratios mostly b0 6 and generally exhibit moderate to high heavy rare earth element hree concentrations ybn 8 26 and weak hree fractionation dy ybnb1 5 with or without negative europium anomalies eu eu 0 5 1 0 these characteristics are consistent with an origin by dehydration melting of a hornblendebearing mid crustal source above the garnet stability field dominated by mafic to intermediate rocks this suggests that the deep crust of the chinese altai may contain a considerable proportion of juvenile material mantle derived magmatism probably in an active extensional continental margin setting played an important role in the formation of the chinese altai acting not only as a heat sourceforcrustalmeltingbutasasourceofjuvenilecomponents therelativelysmallvolumesanddistinctgeochemicalcompositions of the ashile and halatas plutons may imply a substantial change in the geodynamic setting in the late paleozoic 2007 elsevier b v all rights reserved

evolution of cenozoic seaways in the circum antarctic region abstract a complete circum antarctic seaway did not open until both the south tasman rise cleared the oates land coast of east antarctica and drake passage opened between the southern tip of south america and the northern end of the antarctic peninsula major plate motions based on dated seafloor spreading anomalies and distinct fracture zone lineations constrain the age of the opening of a seaway between the south tasman rise and antarctica as very close to the eocene oligocene boundary with an unrestricted opening deeper than 2000 m dating from 32 ma timing of the opening of drake passage is more circumstantial because the exact motions of certain micro continental fragments are not known the motion of africa with respect to south america as well as the motion of east antarctica with respect to africa are well constrained for the cenozoic these major plate motions are used with the reasonable assumption of no cenozoic motion of the antarctic peninsula with respect to east antarctica to constrain the location of the antarctic peninsula with respect to the southern tip of south america for the critical period of late eocene to late oligocene uncertainty of motion of the south georgia and south orkney microcontinents and other possible continental fragments make an exact time for opening of drake passage difficult to ascertain even so the early oligocene position of the antarctic peninsula with respect to south america requires a through going deep water seaway to have been open at drake passage prior to 28 ma even given the unconstrained motion of various high standing crustal fragments in the scotia sea with reasonable assumptions concerning motion of the crustal fragments in the western and central scotia sea it is likely that drake passage or passage through powell basin was open to deep water circulation by 31 2 ma

isotope tracking of pore water freshening in the fore arc basin of the japan trench abstract pore waters of sediments in convergent zones typically show a decrease in chloride cl concentrations with depth that suggests the advection of chloride depleted fluids studies from odp leg 186 indicate that sediments accumulated in the fore arc of the japan trench also exhibit a freshening of pore waters with depth here the oxygen 18 o and hydrogen d isotopic composition of pore waters from site 1150 were determined to investigate the source of cl depleted fluids whereas the upper 100 m of sediments have pore waters exhibiting an increase in both 18 o and d values with depth the remaining 1000 m of studied sediments have pore waters exhibiting an overall decreasing trend in isotope values with depth dissociation of gas hydrates is a likely explanation for the elevated isotope values for pore waters in the upper 100 m in contrast the overall decreasing trend in isotope values probably resulted from the advection of cl depleted fluids exhibiting low 18 o and d values depletion of cl 18 o and d likely resulted from the diagenetic transformation of hydrous minerals and the subsequent precipitation of carbonates or other 18 o enriched minerals generation of cl depleted fluids did not occur within the studied depth interval but rather at deeper possible over pressured sites thereby pointing to the significance of deep seated fluid flow in fore arc basins

geodynamics of the western part of the mongolia okhotsk collisional belt trans baikal region russia and mongolia abstract after the western edge of the mongolian microcontinent joined the siberian continent in the region of central mongolia in the earliest permian these two continental blocks remained turned at an angle of about 120 with respect to each other and separated on greater extent of their present day boundary by an enormous gulf of the paleopacific called the mongolia okhotsk ocean closure of this ocean at the early middle jurassic boundary led to the complete collision of siberia and mongolia which by then had already become part of the mongolia north china continent this main collisional episode which lasted through the middle and late jurassic involved thrusting folding and magmatism and produced the mongolia okhotsk belt the onon island arc which was located in the mongolia okhotsk ocean was squeezed between the two major continents inasmuch as the third element the island arc was involved in the collision it is reasonable to distinguish two branches of the mongolia okhotsk suture these branches control the spatial distribution of gold mineralization in the trans baikal region on the southeastern periphery of siberia the crust thickened considerably after the collision and a plateau like uplift formed in the early cretaceous when compression ceased the collisional uplift collapsed and the thrusts were transformed into low angle normal faults the motions on which were responsible for the formation of rift basins and exhumation of metamorphic core complexes

mesozoic tertiary exhumation history of the altai mountains northern xinjiang china new constraints from apatite fission track data abstract this study uses apatite fission track ft analysis to constrain the exhumation history of bedrock samples collected from the altai mountains in northern xinjiang china samples were collected as transects across the main structures related to palaeozoic crustal accretion events ft results and modeling identify three stages in sample cooling history spanning the mesozoic and tertiary stage one records rapid cooling to the low temperature part of the fission track partial annealing zone circa 70 10 c stage two records a period of relative stability with little if any cooling taking place between 75 and 25 20 ma suggesting the altai region had been reduced to an area of low relief support for this can be found in the adjacent junngar basin that received little if any sediment during this interval final stage cooling took place in the miocene at an accelerated rate bringing the sampled rocks to the earth s surface this last stage linked to the far field effects of the himalayan collision most likely generated the surface uplift and relief that define the present day altai mountains

paleozoic accretionary orogenesis in the paleo asian ocean insights from detrital zircons from silurian to carboniferous strata at the northwestern margin of the tarim craton a detrital zircon u pb and lu hf isotopic study was carried out in the middle silurian to late carboniferous sedimentary strata of the northwestern tarim craton in order to understand accretionary processes in the southern part of the central asian orogenic belt detrital zircons from these strata yielded u pb ages clustering around 2 8 2 3 ga 2 0 1 7 ga 1 3 0 9 ga 880 600 ma and 500 400 ma with age populations and hf isotopic signatures matching those of magmatic rocks in the tarim craton and the central tianshan block abundant 500 400 ma detrital zircons most likely reflect deposition in a retroarc foreland basin inboard of an andean type magmatic arc to the north supporting the northern tarim central tianshan connection during early paleozoic time the absence of 380 310 ma zircon population in the carboniferous siliciclastic rocks suggests that the central tianshan block may have been separated from the tarim craton in the early devonian caused by the interarc back arc opening of the south tianshan ocean we propose an accretionary orogenic model switching from advancing to retreating mode during paleozoic time in the southwestern part of the paleo asian ocean this transition most likely occurred coevally with the rifting of southeast asian blocks from the northeastern margin of gondwana

distinct deformational history of two contrasting tectonic domains in the chinese altai their significance in understanding accretionary orogenic process abstract the chinese altai a key component of the western central asian orogenic belt is considered to be formed through multiple accretions of different terranes however the deformational histories of each terrane tectonic domain i e structural records before and after the accretion are rarely studied which has hindered our understanding of the accretionary processes to fill the gap a systematic macro and microscopic structural analysis was carried out on two contrasting litho tectonic units i e the early paleozoic low grade alegedayi ophiolitic complex aoc juxtaposed to the high grade tarlang granitic massif tgm selected rock samples were analyzed using zircon u pb isotopic dating to constrain the timing of polyphase deformation our structural and geochronological data suggest that the two litho tectonic units were initially detached and located in different crustal levels and experienced distinct phases of deformation under contrasting p t conditions they were mutually accreted with each other in the early devonian and jointly underwent a wnw ese directed shortening deformational event d 1 at 390 ma the change of tectonic regime was further enhanced by a subsequent nne ssw directed shortening deformation d 2 after 380 ma the shortening process ended before the crustal scale sinistral strike slip shearing deformation along the erqis fault zone at 290 240 ma results of this study provide solid field based evidence for a model that the chinese altai initially underwent a nearly e w oriented subduction accretional event in the middle paleozoic before it was reoriented to a nearly n s oriented convergence

quartz vein formation by local dehydration embrittlement along the deep tremorgenic subduction thrust interface hydrothermal quartz veins are ubiquitous in exhumed accretionary complexes including the namibian damara belt here subduction related deformation occurred at temperatures 550 c and vein geometry is consistent with plate interface shear low effective normal stresses and mixed mode deformation quartz vein 18o values relative to standard mean ocean water smow range from 9 4 to 17 9 n 30 consistent with precipitation from metamorphic fluids a dominant subset of quartz veins away from long lived high strain zones and basaltic slivers have 18o values in a smaller range of 14 9 1 requiring precipitation from a fluid with 18o of 12 1 at 470 550 c this uniform fluid isotope value is consistent with progressive local breakdown of chlorite allowing extensive hydrofracture at temperatures typical of the plastic regime in active subduction zones brittle deformation within the plastic regime is inferred from observations of tectonic tremor a noise like seismic signal including overlapping low and very low frequency earthquakes which occurs below the seismogenic zone both tremor and hydrothermal veins correlate with zones of inferred high fluid pressure could represent a mixture of shear and dilatant failure and may therefore be controlled by episodic hydrofracturing within a dominantly plastic and aseismic regime

late paleozoic strike slip shear zones in eastern central asia nw china new structural and geochronological data 1 new structural studies and 40ar 39ar dating in northwest china provide information about late paleozoic strike slip motions subsequent to accretional events which built eastern central asia during the paleozoic two principal areas were affected by these large transcurrent motions first in the tianshan range main east west ductile shear zones are dextral and coeval with an eastward decreasing greenschist retrograde metamorphism associated biotites give ages ranging from 290 ma to 245 ma the earlier n110 shearing occurred in western tianshan while the last one dextral in whole tianshan occurred 250 245 myr ago second in the chinese altay region several nw se shear zones structured the area the main motion is sinistral and occurred along the erqishi zone at 280 290 ma it is followed by a complex succession of dextral and sinistral shearing episodes leading to the northwestward structuring dated at 245 ma of a metamorphic zone that was folded during a compressive event

evaluating the impact of acetic acid chemical pre treatment on old and cremated bone with the perio spot technique and perios endos profiles abstract the impacts of diagenesis on archaeological and palaeontological bone complicate investigations of in vivo chemical and isotopic characteristics such bone is often pre treated in an attempt to remove diagenetic alteration prior to trace element or isotopic analyses although very few standardized approaches exist for evaluating pre treatment effectiveness in this pilot study we characterize the diagenetic alteration and assess the impact of acetic acid chemical pre treatment on the trace element and structural characteristics of four bones from belgium including an early medieval cremated bone from broechem and three representative old bones of different ages ca 40 130 ka from the late pleistocene sedimentary sequence of scladina cave each bone was analyzed before and after acetic acid pre treatment using the perio spot technique and perios endos profiles we measured trace element concentrations with laser ablation inductively coupled plasma mass spectrometry la icp ms and micro x ray fluorescence spectroscopy xrf structural characteristics were investigated with raman spectroscopy and fourier transform infrared spectroscopy ftir our results indicate that chemical pre treatment had little to no significant impact on the trace element content of the early medieval cremated bone had the most impact on the youngest bone from scladina cave and had less impact on the trace element content of two older bones from scladina cave this suggests that the effectiveness of acetic acid chemical pre treatment is greater for bones undergoing early diagenetic processes has minimal impact on highly crystalline cremated bone and may preferentially leach in vivo signatures from bones undergoing later diagenesis the weights of leachates removed from each bone also correspond well with their hypothetical diagenetic states indicating that researchers could potentially assess the diagenetic state of bones by weighing the leachates produced during acetic acid pre treatment therefore our new approach may provide a valuable step toward effectively and consistently differentiating among in and ex vivo trace element signatures and by proxy those of their isotopes in archaeological and palaeontological bone

the preservation of glacial interglacial climatic signatures in the oxygen isotopes of elephant skeletal phosphate abstract phosphate 18o values 18op of modern elephant bone and teeth are found to vary linearly according to the 18o of local meteoric water 18omw a parameter with close ties to regional and local climatic conditions enamel dentine cementum and bone separates from individual fossil elephant specimens of late pleistocene age have op values which vary by up to elephant specimens the larger spread in the 18op values of the various skeletal phases for the fossil samples is interpreted as evidence for post depositional alterantion of primary 18op signatures of some if not all of these fossil skeletal components in the fossil samples investigated enamel and dentine phases have systematically lower 18o values than associated bone and cementum phases differential re equilibration with soil waters either by the wholesale replacement of primary apatite or by processes of isotopic exchange is suggested as a mechanism to account for the observed spread in the fossil phosphate 18o data

palaeozoic tectonics of the south western chinese tianshan new insights from a structural study of the high pressure low temperature metamorphic belt the south western chinese tianshan orogenic belt is famous for its omphacite bearing blueschists and associated eclogite facies metavolcanic rocks although numerous petrologic geochemical and geochronological studies are available structural data and interpretations are still rare this paper provides new structural data including bulk geometry of structures and kinematic analyses based on field and laboratory studies along the akyazhi keburt and muzaert rivers the study area is divided into three tectonic units namely 1 a southern unit composed of weakly metamorphosed sedimentary rocks of silurian age 2 a central hp lt unit composed of blueschist eclogite facies metamorphic rocks derived from basalts pelites and volcaniclastic rocks 3 a northern unit which consists of a carboniferous magmatic arc developed upon an amphibolite facies metamorphic continental basement our structural analysis documents a polyphase deformation the main event d1 is reflected by devonian to carboniferous top to the northwest ductile shearing coeval with hp lt metamorphism this is followed by north directed thrusting d2 of the southern unit over the central hp lt unit coeval with retrogression of the high pressure rocks a top to the s se deformation d3 overprints the earliest events and is observed in the northern and central units lastly permian dextral ductile brittle wrenching d4 overprints the older flat lying fabrics d4 is conspicuous along the nalati fault that separates the northern unit from the central hp lt unit the absolute timing of these deformation events is discussed in the light of available radiometric dating the structural metamorphic and geochronological data are integrated into a geodynamic model of the south western chinese tianshan that emphasizes south directed subduction of microcontinents located between tarim and junggar

diagenesis and the reconstruction of paleoenvironments a method to restore original δ18o values of carbonate and phosphate from fossil tooth enamel abstract intra tooth 18 o variations within the carbonate 18 oc and phosphate 18 op components of tooth apatite were measured for miocene and pliocene hypsodont mammals from afghanistan greece and chad in order to evaluate the resistance of enamel to diagenetic alteration application of water apatite interaction models suggest that the different kinetic behaviours of the phosphate water and carbonate water systems can be used to detect subtle oxygen isotope disequilibria in fossil enamel when intra individual variations are considered selective alteration of the oxygen isotope composition from the carbonate component of afghan and greek enamels suggests inorganic isotopic exchange processes microbially induced isotopic exchange for phosphate is demonstrated for the first time in enamel samples from chad in association with extensive recrystallization in chad 18 op values were derived from partial isotopic exchange with fossil groundwater during early diagenesis mass balance calculations using average carbonate content in enamel as a proxy for recrystallization and the lowest 18 op value of dentine as a proxy for the isotopic composition of the diagenetic fluid indicate that diagenesis can alter 18 op by as much as 3 in some enamel samples this diagenetic alteration is also responsible for a decrease in intra individual variations of up to 1 in affected specimens the effects of diagenesis on 18 op values of fossil enamel are not systematic however and can only be estimated if sequential 18 op and 18 oc analyses are performed on fossil enamel and dentine reconstruction of large temporal or spatial scale paleoclimates based on 18 op analyses from mammalian teeth cannot be considered valid if enamel has been affected by bacterial activity or if the data cannot be corrected for diagenetic effects

petrography and geochemistry of lower carboniferous greywacke and mudstones in northeast junggar china implications for provenance source weathering and tectonic setting abstract northeast junggar occupies an important position that links east junggar and chinese altai numerous magmatic and sedimentary rocks of the paleozoic in this area recorded the final amalgamation processes of east junggar and chinese altai this study analyzes the petrological and geochemical characteristics of sandstones and mudstones from the early carboniferous nanmingshui formation in northeast junggar the provenance and tectonic setting of these clastic rocks are discussed petrography indicates that the composition and texture maturity of the sandstones are low the components of the sandstones are mainly volcanic fragments 61 87 feldspars 9 30 and monocrystalline quartz 2 18 with a few polycrystalline quartz and other minerals slice observation indicates that the majority of the volcanic fragments of sandstones are basic intermediate volcanic rocks with a few dacite and felsic plutonic fragments the detrital modes of the sandstones reflect that these sandstones are derived from undissected arcs a low to moderate chemical index of alteration and the al2o3 cao na2o k2o diagram reflect a low to moderate weathering degree in the source area trace and rare earth element e g la th hf sc cr co and eu contents and their ratios suggest that the source rocks of the clastic rocks are intermediate basic rocks with some felsic rocks compared with sandstones the source rocks for mudstones are more felsic the petrography and geochemistry characteristics of the clastic rocks suggest that the proximal dulate arc should be the primary source area mixing calculations based on ree data suggest that approximately two thirds of the sandstone fragments are intermediate basic volcanic rocks the contents of the major and trace elements as well as the stratum features of the clastic rocks manifest that these clastic rocks resemble sedimentary rocks in a back arc basin the formation of this back arc basin is caused by the southward subduction of the zaysan erqis ocean

oxygen and strontium isotopes from fossil shark teeth environmental and ecological implications for late palaeozoic european basins article i nfo fossil shark remains occur in both marine and nonmarine late palaeozoic deposits therefore their palaeo ecology is controversial the oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth scales and spines predominantly of hybodontid lissodus and xenacanthiform orthacanthus xenacanthus bohemiacanthus triodus sharks from various late carboniferous moscovian to early permian artinskian basins of europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa the 18 op values of the different shark teeth range from 11 7 to 20 2 within the different basins with mean values of 16 9 0 5 for the bohemian massif 16 2 0 8 for eastern germany 18 2 1 0 for southwestern germany 18 5 0 7 for southern central spain 17 6 0 4 for