reflectance of dispersed vitrinite in palaeozoic rocks with and without cleavage implications for burial and thermal history modeling in the devonian of rursee area northern rhenish massif germany abstract vitrinite reflectance is used as coalification parameter in coals and as maturity and palaeotemperature indicator in sedimentary rocks in high grade diagenetic rocks i e rocks at the boundary between diagenesis and metamorphism vitrinites become increasingly anisotropic therefore it has been suggested to study maximum minimum reflectance instead of mean reflectance for rocks which reached this stage in the present study vitrinite reflectance data from a folded sequence of the northern rhenish massif germany are combined with microtectonic study of thin sections in samples in which both bedding and cleavage are present we show that vitrinites in different microtectonic domains cleavage domains and microlithons show significant differences in both maximum vitrinite reflectance and vitrinite reflectance anisotropy this behaviour is due to a strong partitioning of deformation in cleavage domains as compared to microlithons so that vitrinite reflectance is controlled by the thermal and deformation history accordingly estimation of maximum palaeotemperatures during burial should be based on vitrinite reflectance measurements in microlithons unaffected by deformation after maximum burial based on this finding burial and temperature history of the rursee area in the eastern rhenish massif is reconstructed numerical simulations indicate a maximum burial at the siegen ems boundary of about 5000 m and a maximum burial temperature of about 220 c

formation and evolution of the tancheng lujiang wrench fault system a major shear system to the northwest of the pacific ocean abstract in the northwestern peri pacific tectonic belt on the continental margin of east asia there is a series of major faults trending ne nne i e the tancheng lujiang wrench fault system this fault system extends more than 5000 km with a width of 800 1000 km in the continent and a general strike of n30 e on the basis of the results of special research on the major faults and a lot of new information about the fault system the authors discuss early mesozoic triassic jurassic period sinistral transcurrent faulting in the different regions it is suggested that in the eastern continent of east asia the e w trending tectonic pattern of the paleozoic and beginning of the mesozoic appear in the nuclei of the sino korean continent massif and the yangtze continent massif these ancient continent massifs accreted both southwards and northwards which finally led to their collision and suturing to the angura continent massif later this tectonic framework was changed greatly by the tancheng lujiang wrench fault system along which left lateral horizontal displacement of 1000 1500 km took place since the mesozoic the dislocation and deformation of horizontal displacement of the tancheng lujiang fault system produced a series of structures trending ne nne in the continental margin which have greatly transformed the ancient structures of the preceding mesozoic this is an important diktyogenese in the continent of east asia during the horizontal displacement motion of these faults the folds nappes and decollement structures pull apart basins and subductions within the continent occurred in the continent at the same time some large sinistral ductile shear zones of horizontal displacement appeared the depth of the deformed horizon of ductile shear which belongs to simple shear was controlled by the tectonic element and distance away from the continental margin whilst the ductile shear deformation occurred the fault dynamo thermal metamorphism and the fault remelting took place and magma activity appeared within the continent in the mesozoic the fault zones used to be high energy zones and recently became the seismic belts within the continent formation of the tan lu fault system was due to the collision between the southern and northern blocks its large sinistral horizontal displacement in the mesozoic was closely related to the kula plate moving northwards therefore the continent disintegrated by shearing which produced some new terranes the shear edge belt was formed between the continent and ocean the change of relative motion between the continent and pacific ocean plate transformed the tan lu fault system into first extension and then compression clarifying the characteristics of the tan lu fault system is an important key in understanding the evolution of the east asia continent since the mesozoic

plate tectonic history basin development and petroleum source rock deposition onshore china abstract china comprises a mosaic of distinct continental fragments separated by fold belts these fold belts are suture zones resulting from the accretion of various fragments formerly separated by intervening areas of oceanic crust the major sedimentary basins onshore china can be classified into four groups those in western china are flexural developing as a result of north south compression in contrast those in the east are extensional and related to development of the pacific oceanic margin in central china basins have a more problematic origin those of north central china ordos sichuan are flexural basins controlled by eastward directed thrusting along their western margin in contrast basins further south chuxiong shiwandashan are predominantly extensional and related to major strike slip movements by synthesizing basin stratigraphies across china in tectonostratigraphic terms and in particular comparing the nature and timing of unconformities it is possible to formulate a coherent model for the palaeoreconstruction of china we identify five major tectonostratigraphic breaks which equate with the collision of the following continental fragments tarim north china carboniferous permian south china block permian triassic qiantang late triassic early jurassic lhasa block late jurassic early cretaceous and india early tertiary prior to permian times the southern margin of eurasia ran approximately along the northern border of modern china the late carboniferous collision of tarim north china with eurasia resulted in the development of a flexural basin junggar and deposition of non marine clastics to the south of the suture shallow marine deposition continued in the late permian early triassic the progressive collision from east to west of the south china block with the north china block resulted in a change to fluvial lacutrine sedimentation across the entire north china tarim block open marine carbonate deposition in the north of the south china block passed southward into a deeper marine clastic sequence deposited in a backarc basin further south a subduction zone existed along the southeastern margin of the south china block in western china northward subduction throughout the triassic resulted in the development of the songban ganzi accretionary prism with retroarc thrusting resulting in flexure and the first development of the tarim basin oblique collision of the qiantang block in the late triassic along the east of the south china block resulted in east west directed thrusting which initiated the suchuan and ordos basins continued strike slip deformation along the south western margin of the south china block resulted in the development of basins with a significant extensional component such as chuxiong the collision of the qiantang block with the southern edge of the tarim basin early jurassic resulted in a renewed clastic influx in both the tarim and junggar basins along the eastern pacific margin a compressional arc and retroarc basin in the south passed northwards into an extensional arc system subduction rollback of the extensional arc initiated rifting in the late jurassic in the eren and songliao basins the late jurassic early cretaceous collision of the lhasa block in the west rejuvenated the thrust systems bordering the western basin and resulted in a renewed clastic influx in the southeast the compressional arc phase culminated in widespread thrusting and folding of early cretaceous age in the northeast extension continued with the progressive migration of the rift system southward with time the arrival of the indian block in the early tertiary rejuvenated the bounding thrust belts of all the western basins in the east the change in convergence of the pacific plate to a more westerly direction is marked by extension and widespread rifting along the entire length of eastern china throughout most of china mesozoic and cenozoic deposition occurred in predominantly non marine environments source rocks in such settings comprise principally mudstones deposited in lakes organic rich mudstones these can accumulate in both deep and shallow lakes in order to accumulate substantial volumes the lake must be significant in space and time in china lacustrine orms occur in both rift and flexural basins lacustrine orms deposited under humid climatic conditions are restricted to the period of maximum tectonic subsidence in the flexural basins of western china source rock deposition follows basin initiation by 20 30 ma in the extensional basins of eastern china source rock deposition takes place 5 15 ma after basin initiation by contrast semi arid and arid climate lacustrine orms whilst being best developed during the period of maximum tectonic subsidence occur at all stages in the basin history

paleogene sediment provenance and paleogeographic reconstruction of the south yellow sea basin east china constraints from detrital zircon u pb geochronology and heavy mineral assemblages abstract this study presents new zircon u pb geochronological and heavy mineral assembly data from paleogene rocks to constrain the provenance and paleogeographic evolution of the south yellow sea basin sysb east china heavy minerals are mainly ilmenite garnet epidote zircon and pyrite detrital zircon ages from the paleocene funing to eocene sanduo formations can be grouped into five major populations 100 300 ma 400 500 ma 600 900 ma 1700 2100 ma and 2300 2700 ma paleocene funing sediments mainly contain zircons of 220 ma 760 ma 1850 ma and 2500 ma consistent with zircons from the daibie sulu orogen the south china craton and the north china craton lower eocene dainan sediments show different detrital zircon ages and heavy mineral assemblages indicating a change in sediment sources the daibie sulu orogen served as a major source for the north depression sediments of the southern segment of the south depression were derived mainly from the daibie sulu orogen and the north china craton from the west while sediments of the northern segment of the south depression received a southwestward supply from the central uplift with detrital zircon peak ages of 440 ma detrital zircon age spectra of sanduo samples resemble those of dainan samples with peaks at 120 ma 220 ma 440 ma 800 ma 1850 ma and 2500 ma suggesting that they share common sources the results allow the reconstruction of an updated paleogeographic model for the paleogene of the south yellow sea basin

denudation history of eastern indian peninsula from apatite fission track analysis linking possible plume related uplift and the sedimentary record abstract the late archaean early proterozoic 2 5 ga eastern dharwar craton edc eastern india which underlies much of the drainage basins of the krishna and godavari rivers has undergone an erosionally controlled evolution since the pan african event 500 550 ma this evolution has been responsible for the sedimentation and overall development of the krishna godavari kg sedimentary basin in order to reconstruct the denudation history of the edc which forms the hinterland to the petroliferous kg basin we report apatite fission track aft data from 41 samples thermal history modelling suggests that little denudation occurred before mid cretaceous time however during the late cretaceous accelerated cooling commenced from a temperature range of 60 75 c assuming a low palaeogeothermal gradient of 10 c km similar to that of the present day cooling of the edc translates to 0 5 2 km of denudation during the late cretaceous and a total of 4 km since that time the denudation history is closely related to the sedimentary record in the kg basin the episode of accelerated cooling in the late cretaceous is interpreted as a geomorphic response to uplift of the indian peninsula possibly resulting from an ascending mantle plume which produced the voluminous deccan traps at the k t boundary the denudation history coupled with previous palaeocurrent studies in the kg basin suggest that the krishna godavari drainage system was established in late cretaceous time

basin modeling meets rift analysis a numerical modeling study from the jeanne d arc basin offshore newfoundland canada abstract the jeanne d arc basin on the grand banks offshore newfoundland is a confined failed rift basin its initial development and burial history were controlled by crustal stretching and thinning this study provides a detailed analysis of the heat flow tectonic subsidence stretching factor maturation and temperature history based on 44 1d models and one full 4d space and time model in basin models the heat flow history is usually calculated from vitrinite reflectance vrr data however this causes uncertainties and reflects only the periods of sedimentation which where penetrated by wells therefore other methods should be used to reconstruct the early heat flow history not recorded by sediments in this study a discontinuous pure shear stretching model including radioactive heat production reflecting the timing and magnitude of stretching factors of crust and lithospheric mantle was applied to a 4d numerical model for the jeanne d arc basin it is the first time that this new technique is shown on a real case scenario and it gives new insights into the regional geodynamics results show that to understand the thermal evolution of the jeanne d arc sedimentary basin completely it is crucial to consider the triassic rift system this first rift generated the structural framework of the basin where most of the sediments were deposited the second extension in the cretaceous represents most likely an ultra slow extension phase with a heat impulse too weak to leave any thermal record this study demonstrates that the entire evolution of the jeanne d arc basin can be reconstructed assuming just one single triassic thermal rift additionally it shows the effects of a lateral heat transfer on the determination of stretching factors and thus on tectonic subsidence and the resulting heat flow history

fission track analysis of basement apatites at the western margin of the gulf of suez rift egypt evidence for synchroneity of uplift and subsidence fifty six apatite fission track ages and 52 horizontal confined track length measurements are reported from precambrian crystalline rocks along the western margin of the gulf of suez egypt ages fall in the range of ca 11 385 m y and older ages often occur within very close geographic proximity to younger ones indicating non uniform uplift the wide range in ages is accompanied by a systematic variation in the distribution of horizontal confined fission track lengths on the basis of apatite fission track ages and their length distributions data fall into three distinct groups group i ages ranging from 43 to 385 m y length distributions are all positively skewed and with decreasing age become progressively broader with shorter mean track length group ii ages ranging from 23 to 31 m y length distributions are negatively skewed with either a distinct tail or a small peak of short tracks group iii ages ranging from 11 to 20 5 m y length distributions are al unimodal narrow negatively skewed and have the longest mean lengths among samples studied apatite ages from groups i and ii are interpreted as mixed ages as a result of cooling during uplift from different levels within the apatite partial track annealing zone ages from group iii are interpreted as cooling ages due to uplift from the apatite total track annealing zone with minor partial annealing correcting the ages of the two oldest samples in this group for track length reduction yields ages of21 2 2and23 1 5m y it is proposed that the onset of rift flank uplift in the gulf of suez northern red sea area occurred between 21 and 23 m y ago fission track analysis in combination with subsidence data from the gulf of suez basin indicate that commencement of basement uplift postdate the start of rifting and is interpreted as evidence for passive rifting at the gulf of suez furthermore this uplift is contemporaneous with and is directly related to the process of extension and subsidence at the gulf of suez

cretaceous and cenozoic non marine deposits of the northern south yellow sea basin offshore western korea palynostratigraphy and palaeoenvironments abstract palynological analyses of two wells haema 1 and kachi 1 located in two sub basins of the northern south yellow sea basin have been carried out in order to establish a palynostratigraphic breakdown of the sedimentary succession and to determine environments of deposition seven assemblage zones and two assemblage subzones have been erected on the basis of frequency variations in and occurrences of biostratigraphically significant palynomorphs as follows classopollis ephedripites assemblage zone az barremian albian alisporites aquilapollenites penetetrapites az which is subdivided into an alisporites rugubivesiculites assemblage subzone cenomanian lower maastrichtian and an aquilapollenites penetetrapites assemblage subzone upper maastrichtian momipites coryluspollenites az paleocene caryapollenites inaperturopollenites az lower middle eocene quercoidites pinuspollenites az upper eocene liquidambarpollenites fupingopollenites magnastriatites az lower middle miocene graminidites persicarioipollis az pliocene the depositional environments represented by the well sections are considered to have been generally fluvio lacustrine and the climate to have varied between semi arid and wet and subtropical and warm temperate except during the late eocene and pliocene when a cool temperate climate prevailed six stages in the development of the sub basins are recognised these are 1 initial stage of rift or pull apart basin formation during the late jurassic cretaceous 2 subsidence from the paleocene to middle eocene 3 alternation of uplift and subsidence in the late eocene 4 synrift inversion and erosion through the oligocene 5 uplift during the early miocene and 6 widespread subsidence from the middle miocene onwards apart from during the early pliocene when the region was subjected to uplift once more

a flexural isostatic model of lithosphere shortening and foreland basin formation application to the eastern cordillera and subandean belt of nw argentina a numerical model of lithosphere shortening has been developed to combine flexural isostatic and structural balancing this allows us to quantitatively reconcile lithosphere shortening thrust sheet emplacement and foreland basin formation lithosphere shortening is accommodated by thrusting in the upper crust and by distributed deformation in the lower crust and the lithospheric mantle this leads to loading by thrust sheet emplacement crustal thickening and thermal perturbation additional loading and unloading are generated by sedimentation and erosion respectively the model is kinematically controlled each fault having its position geometry and movement prescribed the model is applied to the subandean late oligocene to recent foreland fold and thrust belt of nw argentina at 22 15 s the subandean belt of nw argentina contains three major stratigraphic units the lower middle and upper terciario subandino formations by modelling these formations we attempt to determine whether the terciario subandino group can be explained as a foredeep fill in response to thrust sheet loading and if so what is the required effective elastic thickness a successful model must predict not only foreland stratigraphy but also exhumation topography and crustal thickness we see a change in the wavelength of sedimentary deposition in the subandean basin through time that can be accounted for by a change in flexural rigidity accommodation space for the lower terciario subandino formation can be generated using an elastic thickness of 70 km for the middle upper terciario an elastic thickness of 15 km produces the correct basin geometries shortening estimates of 110 km have proved sufficient to generate the observed foreland stratigraphy bouguer anomaly and topography across the subandean belt and eastern cordillera however an additional 140 km of shortening is required to generate the observed bouguer anomaly and topography across the western andes this discrepancy could be due to earlier shortening in the western andes or to crustal thickening by magma addition

fluid inclusion technique for determining maximum temperature in calcite and its comparison to the vitrinite reflectance geothermometer theory laboratory experiments and empirical observation suggest that many aqueous fluid inclusions in calcite reequilibrate during overheating and therefore some homogenization temperatures t h record a temperature close to the maximum reached by the rock this characteristic suggests that aqueous fluid inclusions in calcite can be used to establish maximum temperature t peak to test this hypothesis we have compiled fluid inclusion t peak mean random vitrinite reflectance r m and present day t peak from 46 diverse geologic systems that have been at t peak from 10 4 to 10 6 yr present t peak ranged from 65 to 345 c t h modes and means ranged from 59 to 350 c and r m data ranged from 0 4 to 4 6 spanning the temperature and thermal maturity range associated with burial diagenesis hydrothermal alteration and low grade metamorphism plots of t h and t peak data for systems thought to be currently at maximum temperature demonstrate close agreement between t h and present t peak in sedimentary basins although caution should be applied the relation suggests that t h of aqueous fluid inclusions in calcite may be a useful measure of maximum temperature this study also compares t h to mean random vitrinite reflectance r m to offer further support for the use of t h as a measure of t peak and to provide a better understanding of r m t h correlates well with r m and results in a curve similar to r m vs t peak calibrations determined by other workers the strong correlation correlation coefficient r 0 93 between t peak and r m in these systems suggests that maximum temperature is the major control on thermal maturation

assessment of mesozoic and upper paleozoic source rocks in the south yellow sea basin based on the continuous borehole csdp 2 abstract being lack of core data and measured data although the marine oil gas exploration in the south yellow sea basin has been going on for 57 years no commercial hydrocarbon reservoirs have been found so far the quantitative source rocks evaluation based on geochemical data and fluid inclusions containing hydrocarbon benefits from the completion of borehole csdp 2 in 2016 a continuous coring well of the chinese continental shelf drilling program csdp which indicates that the marine origin oil gas exploration in the south yellow sea basin enters into a new stage as revealed by the well csdp 2 three sets of effective hydrocarbon source rocks in the mesozoic and upper paleozoic have been identified which are distributed in the lower triassic qinglong formation t1q upper permian longtan dalong formation p3l d and middle permian gufeng qixia formation p2g q respectively among them organic rich source rocks mainly concentrate in the lower part of the p3l d and the middle upper part of the p2g q and the p3d mudstone also works as good source rock the p3l d mudstone with high organic abundance is the chief source rock in the south yellow sea basin whose maximum hydrocarbon generating intensity may reaches up to 795 09 104 t km2 and hydrocarbon expulsing intensity remains at the level of 165 03 104 t km2 a noteworthy feature of the p2g q source rocks is the strong vertical heterogeneity with the hydrocarbon expulsing intensity of the upper part being 34 14 104 t km2 while that of the lower part being 18 07 104 t km2 in contrast the organic abundance of argillaceous limestone in the t1q is mainly poor to medium and its hydrocarbon expulsing intensity is the weakest one in the three sets of hydrocarbon source rocks only about 12 7 104 t km2 taking into consideration the joint influence of depositional environment organic matter parent source and biological productivity the overall quality of source rocks in the south yellow sea basin is at the similar level to the lower yangtze subei basin but lower than that of the upper yangtze sichuan basin the most significant oil gas information is that multiple direct oil indications and high value abnormalities of gas logging have been discovered in the well csdp 2 moreover the mesozoic and upper paleozoic marine strata in the south yellow sea basin have experienced three hydrocarbon charging stages indicating a broad prospect of marine oil gas exploration

late cretaceous cenozoic tectonic sedimentary evolution and u enrichment in the southern songliao basin abstract late cretaceous cenozoic tectonic sedimentary evolution is fundamental to u uranium migration and u enrichment in the southern songliao basin northeast china to establish the genetic connection between tectonic sedimentary evolution and u enrichment this paper presents a mineralogical study apatite fission track aft analysis and sem cl analysis of quartz grains two stages of mineralization were proposed including the u pre enrichment stage during the late cretaceous and the ore forming stage during the cenozoic based on the density plots of the aft ages paleoclimate studies and sem cl analysis of quartz grains it is inferred that the u pre enrichment was closely related to the rapid uplift of the great xing an range and the zhangguangcai range and the o2 rich atmosphere during 97 90 ma in the southern songliao basin the o2 rich atmosphere increased u mobility and led to the formation of red beds during the late cretaceous which widely developed u pre enrichment in the basins of northeast china the mineralogical study reveals that the qianjiadian uranium deposit developed in two stages the diagenetic process experienced the transition from early alkaline to late acidic conditions to promote the stage i mineralization u pre enrichment the dominant occurrence spaces for u were the dissolution pores of quartz tightly packed with calcite cement u enrichment during alkaline ambient conditions was mainly via adsorption with the increase of the buried depth the early alkaline diagenesis returned to acidic conditions due to the abundant organic material u vi was reduced to pitchblende due to the reducing capacity of the organic matter om stage ii ore forming stage mineralization was strictly related to the hydrocarbon re concentration according to the thermal history study of the cc1 and q2 boreholes the southern songliao basin experienced four episodes of rapid uplift during the cenozoic at 83 80 ma 68 52 ma 33 23 ma and 8 ma respectively the cenozoic uplifts led to hydrocarbon migration at 65 ma 23 ma and present the re concentration of hydrocarbon prompted the u mineralization in the qianjiadian uranium deposit in the southern songliao basin during the stable period of tectonic movements the reducing conditions caused by hydrocarbons promoted u mineralization the dominant spaces of coffinite were intergranular dissolved pores formed during the transformation from the feldspar to the kaolinite under acidic conditions the post rift phase and structural inversion phase directly controlled the u pre enrichment stage and the ore forming stage respectively overall the tectonic sedimentary evolution played an important role in controlling the u leaching from granites the dominant occurrence spaces and u recycling

basin modeling of the late miocene zeit source rock in the sudanese portion of red sea basin implication for hydrocarbon generation and expulsion history abstract the late miocene zeit formation is exposed in the red sea basin of sudan and represents an important oil source rock in this study five 5 exploratory wells along red sea basin of sudan are used to model the petroleum generation and expulsion history of the zeit formation burial thermal models illustrate that the red sea is an extensional rift basin and initially developed during the late eocene to oligocene heat flow models show that the present day heat flow values in the area are between 60 and 109 mw m2 the variation in values of the heat flow can be linked to the raise in the geothermal gradient from margins of the basin towards offshore basin the offshore basin is an axial area with thick burial depth which is the principal heat flow source the paleo heat flow values of the basin are approximately from 95 to 260 mw m2 increased from oligocene to early pliocene and then decreased exponentially prior to late pliocene this high paleo heat flow had a considerable effect on the source rock maturation and cooking of the organic matter the maturity history models indicate that the zeit formation source rock passed the late oil window and converted the oil generated to gas during the late miocene the basin models also indicate that the petroleum was expelled from the zeit source rock during the late miocene 7 ma and it continues to present day with transformation ratio of more than 50 therefore the zeit formation acts as an effective source rock where significant amounts of petroleum are expected to be generated in the red sea basin

early cenozoic two phase extension and late cenozoic thermal subsidence and inversion of the bohai basin northern china abstract the bohai basin is one of a family of early cenozoic extensional basins that lie along the eastern margin of asia from russia to vietnam initial extension was probably triggered by subduction roll back of the oceanic pacific plate from the asian continent there were two phases in the bohai basin s rift history the earlier paleocene early eocene phase resulted in the deposition of the kongdian formation and the fourth lowest member of the shahejie formation in a series of elongate half grabens these half grabens have master faults with a nne ssw orientation secondary normal faults are typically clockwise oblique to the master faults indicating a component of dextral transtension deposition was focused in the west and south of the present basin these rocks are mainly alluvial fan and fluvial red beds the architecture of the basin underwent an important change at ca 43 45 ma middle eocene beginning with the deposition of the third member of the shahejie formation in part these sediments were deposited in the same half grabens as the kongdian formation but the bozhong depression in the central part of the basin originated at this time and became the major depocentre the bozhong depression superficially resembles a pull apart basin it formed when continued transtension of the earlier tertiary fault systems to the east and west created an extensional overlap between them during this phase the basin as a whole had a geometry with elements typical of both pull apart and transtensional basins regional extension in many east asian basins ended at the end of the oligocene probably because of the onset of transpression within eastern asia caused by the collision of australia with the philippine sea plate dextral transpression caused minor inversion of some of the earlier normal faults in bohai but as a whole the basin began to subside in a post rift phase of thermal subsidence that has lasted until the present day

timing of the north south china collision from new middle to late mesozoic paleomagnetic data from the north china block we collected paleomagnetic samples from 43 sites of middle and upper jurassic and cretaceous rocks along a 250 km wide east west trending belt located north of the suture between the north and south china blocks in each case laboratory treatment isolates dual polarity antipodal magnetizations that are demonstrably pre folding the paleomagnetic poles show very good coherence with coeval poles from other localities from the north china block ncb suggesting the apparent polar wander path apwp from the ncb is not distorted by post middle jurassic local vertical axis block rotations a comparison of the ncb apwp with that from the south china block suggests that collision continued after the early jurassic and ended no later than the late jurassic a cusp in the ncb apwp coincides with a marked angular unconformity that separates middle jurassic from upper jurassic and younger sediments together these observations indicate that the scissor like collision and associated deformation ceased at the middle to late jurassic boundary 159 ma the time of rapid 1 ma relative angular velocity between the two plates 225 to 190 ma coincides with a peak in u pb and ar ar dates obtained from metamorphic rocks in the suture the combined late jurassic and cretaceous paleomagnetic data from both blocks suggest that the united china plate traveled 2000 km north relative to eurasia during the late jurassic before docking in the cretaceous this younger collision event is also marked by a cusp on the cretaceous part of the eurasian apwp

apatite fission track analysis apatite fission track aft analysis has been widely used during the past 30 years to constrain the low temperature thermal histories of many igneous metamorphic and sedimentary rocks in a wide range of geological settings applicable geological settings include orogenic belts rifted margins faults sedimentary basins cratons and mineral deposits the types of geologic problems that can be addressed include the timing and rates of tectonic events sedimentary basin evolution the timing of hydrocarbon generation and ore mineralization the absolute age of volcanic deposits the effects of major climatic changes on the near surface geothermal gradient and long term landscape evolution early work by naeser 1967 and wagner 1968 1969 first established the basic procedures that enabled the fission track dating method to be applied routinely to these geologic problems fleischer et al 1975 summarized the early studies of the broader discipline of nuclear track detection in different solid state materials more recent comprehensive overviews of fission track applications have been provided by naeser and mcculloh 1989 wagner and van den haute 1992 gallagher et al 1998 van den haute and de corte 1998 dumitru 2000 and gleadow et al 2002 etched natural fission tracks in several apatite grains are shown in figure 1 successful aft analysis is limited by the following 1 the availability of apatite from which useful aft data can be obtained often due to a lack of apatite of sufficient grain size and quality within available rock types or alternatively the lack of available rock samples due to minimal outcrop exposure or other reasons 2 economic considerations in terms of the time and money required to obtain sufficient aft data 3 the inherent limitations of aft data to resolve geological thermal history information often related to limited numbers of accumulated spontaneous fission tracks due to

interpretation of discontinuous vitrinite reflectance profiles time temperature modeling was used to examine the effects of reburial on vitrinite reflectance profiles associated with stratigraphic uncomformities offsets in reflectance data for shallow unconformities can in many cases be explained by erosion and may provide a minimum estimate of the amount of missing section as reburial progresses the offset in reflectance values at the unconformity decreases in accordance with the thermal energy required to activate reaction pathways in strata above and below the unconformity until no statistically significant difference exists in vitrinite reflectance across the stratigraphic boundary the reflectance profile is thus annealed when observed at great depths significant offsets in reflectance values typically require geologic lly unreasonable amounts of erosion alternate explanations for offsets at great burial depths include igneous and metamorphic events and complications associated with editing and interpreting vitrinite reflectance data

role of the plasmapause in dictating the ground accessibility of elf vlf chorus this study explores the manner in which the plasmapause is responsible for dictating which magnetospheric source regions of elf vlf chorus are able to propagate to and be received by midlatitude stations on the ground first we explore the effects of plasmapause extent on ground based observations of chorus via a 3 month study of ground based measurements of chorus at palmer station antarctica l 2 4 50 s geomagnetic latitude and data on the plasmapause extent from the image euv instrument it is found that chorus normalized occurrence peaks when the plasmapause is at l 2 6 somewhat higher than palmer s l shell and that this occurrence peak persists across a range of observed chorus frequencies next reverse ray tracing is employed to evaluate the portion of the equatorial chorus source region distributed in radial distance and wave normal from which chorus is able to reach palmer station via propagation in a nonducted mode the results of ray tracing are similar to those of observations with a peak of expected occurrence when the plasmapause is at l 3 the exact location of the peak is frequency dependent this supports the conclusion that the ability of chorus to propagate to low altitudes and the ground is a strong function of instantaneous plasmapause extent and that peak occurrence of chorus at a given ground station may occur when the l shell of the plasmapause is somewhat beyond that of the observing station these results also suggest that chorus observed on the ground at midlatitude stations propagates predominantly in the nonducted mode

discovery of late devonian plants from the southern yellow sea borehole of china and its palaeogeographical implications abstract late devonian plant remains species of archaeopteris and sublepidodendron and some representative miospores are recognized from silty mudstone borehole core well depth 2063 1 2068 8 m in the southern yellow sea china these plants have been thoroughly studied and are widely distributed in the upper devonian of southern china the plant fossil bearing borehole core correlates to the upper devonian famennian terrestrial to shallow marine wutung formation of southern china lower yangtze plate moreover the late devonian megaplant and miospore records palaeogeographically distinguish the sino korean and yangtze plates the northeastern boundary of the yangtze plate is discussed it is proposed that the northeastern end of the yangtze plate probably extends to the imjingang belt and the gyeonggi massif the central part of the korean peninsula

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

an overview of pre devonian petroleum systems unique characteristics and elevated risks abstract the radiation of land plants at the onset of the devonian resulted in a change in the character of available biomass which in turn introduced changes to the nature of petroleum systems this study examines the nature of pre devonian petroleum systems prior to this significant evolutionary event conventional hydrocarbon resources have been associated with pre devonian petroleum systems across the globe including the neoproterozoic infracambrian huqf supergroup of the oman basin the riphean vendian sequences of east siberia the cambrian of the murzuq basin the ordovician of the tarim basin and the silurian qusaiba of saudi arabia although individual accumulations can be quite significant e g hassi messaoud has ultimate recoverable reserves of 10 billion barrels the relative importance of pre devonian derived oils is thought to be limited compared to the global conventional resource base with growing interest in unconventional resources the relative importance of these systems is expected to increase as resource plays such as the ordovician utica shale of the appalachian basin the cambrian of china and possibly the silurian of central and eastern europe develop the advanced ages of these systems result in some unique properties and amplify risks that exist in younger petroleum systems differences in the nature of the biomass contributing to pre devonian source rocks may give rise to oils that display unique geochemical characteristics for example there are some precambrian oils where c 29 steranes dominate even though land plants were absent there are also ordovician source rocks dominated by gloeocapsamorpha prisca a primitive prokaryote which yield oils containing limited amounts of c 20 components and nearly lack pristane and phytane the potential for unconventional reservoirs in pre devonian systems may also be highly dependent upon the age of the system as biological evolution influences the availability and nature of biogenic silica an important factor controlling brittleness and fracability literature has shown that biogenic silica from different sources displays varying degrees of resistance to diagenesis which allows the formation of a silica network and influences brittleness for example radiolaria present during the cambrian are more resistant to diagenesis than diatoms which did not evolve until the jurassic risks associated with preservation of hydrocarbons are also amplified in pre devonian petroleum systems many such systems have been exposed to significant thermal stresses resulting in the cracking of oil and wet gas others have had complex tectonic histories potentially resulting in the breaching of seals or changes in pvt conditions that can result in gas loss gas loss may also occur through diffusion from these older reservoirs as a result of long residence times

mesozoic cenozoic denudation and thermal history in the central uplift of the south yellow sea basin and the implications for hydrocarbon systems constraints from the csdp 2 borehole abstract this study focuses on the mesozoic cenozoic tectono thermal events in the central uplift of the south yellow sea basin sysb based on the csdp 2 borehole csdp 2 is the first borehole to penetrate the integrated paleozoic mesozoic sedimentary strata and recovered approximately 2736 m of core the drilling results confirm a significant stratigraphic hiatus i e indosinian unconformity between the neogene quaternary and the underlying lower triassic the eroded thickness estimated from sonic log and vitrinite reflectance data range from 1200 to 1400 m multiple paleo thermometer data from the csdp 2 cores including vitrinite reflectance apatite zircon fission track aft zft and fluid inclusions were used to reconstruct the mesozoic cenozoic thermal history in the study area there was a continuous heating process during the early mesozoic the peak paleo temperature may have reached up to 160 c base permian during the late jurassic with the highest paleo geothermal gradient of approximately 58 8 c km 1 the tectono thermal evolution was dominated by the mesozoic intracontinental collision between the yangtze craton and the sino korean platform the heating process was mainly caused by rapid burial on the passive continental margin and igneous activities the paleo temperature significantly decreased following the late jurassic two rapid cooling processes ca 100 65 ma and ca 35 ma are suggested by the aft modeling results cooling history indicates that the tectonic uplift and denudation likely occurred from the early cretaceous to the miocene the reconstruction results of thermal evolution confirm that the mesozoic paleozoic source rocks are mature or even highly mature and hydrocarbon generation migration and charge undoubtedly occurred in the central uplift showing substantial hydrocarbon potential moreover the reconstruction of the tectono thermal history provides important constraints for regional tectonic studies

late mesozoic and cenozoic tectono thermal history and geodynamic implications of the great xing an range ne china abstract the mesozoic cenozoic tectonics of northeastern china involves complex multistage interaction of different tectonic domains and has long been controversial the tectono thermal evolutionary history recorded by the widespread outcropped granitoids in the great xing an range gxr may provide significant constraints on the tectonics illuminating the deep geodynamic process here we present new low temperature thermochronology data from the gxr and thus reconstruct the detailed thermal history zircon fission track dating yielded a group of central ages ranging from 80 4 to 185 10 ma while apatite fission track ages range from 55 3 to 75 5 ma the modeled time temperature paths of all the samples reveal two relatively rapid cooling events at 100 60 ma and 50 0 ma and one intervening reheating episode at 60 50 ma the initial uplift exhumation and induced cooling events which represent strong orogenic activity are related mainly to closure of the mongol okhotsk ocean in the north and were subsequently influenced by the paleo pacific plate subduction in the east the evolution of the basin mountain system consisting of the songliao basin and gxr as well as the accretion metamorphism and magmatism at the northeast asian continental margin are all dominated or indirectly influenced by the paleo pacific subduction this indicates that the paleo pacific subduction had affected the evolution of the gxr to the west since the jurassic the significant reheating episode during the late paleocene to eocene may be related to the heat flux derived from asthenosphere upwelling and igneous activity

quantitative constraints on the rate of landform evolution derived from low temperature thermochronology in recent years the nature of the complex interactions between the solid earth and the overlying atmosphere has been the subject of much debate england and molnar 1990 whipple et al 1999 braun et al 1999 does erosion play an important role in the dynamics of mountain building is there a strong feedback into the balance of forces at the crustal scale from mass transport by erosional and depositional processes at the earth s surface or does erosion passively react to changes in the earth s surface topography to shape mountains with tectonic forces originating in the underlying convecting mantle dominating the dynamics of plate interactions and crustal deformation at convergent plate margins the answers to these fundamental questions lie in our ability to determine the rate at which surface processes can react to tectonic forcing whipple et al 1999 where erosion is efficient the coupling will be strong as the rate of change of surface loading by mass transport will be similar to the rate of creation of topography by crustal deformation this may lead to a concentration of deformation and thus exhumation in regions of intense erosion koons 1990 willett et al 1993 beaumont et al 2001 koons et al 2002 2003 braun and pauselli 2004 where erosion is relatively inefficient mountain building is the result of a balance between internal driving forces and those originating from the deflection of an upper free surface there is no feedback from erosional processes low temperature thermochronology such as u th he he or fission track ft dating in apatite and zircon provides information on the rate at which rocks cool as they are exhumed towards the cold earth surface duddy et al 1988 warnock et al 1997 farley 2000 reiners and farley 1999 because the

main controls and geological sweet spot types in paleogene shale oil rich areas of the jiyang depression bohai bay basin china abstract the shale oil wells drilled in the early stage of the jiyang depression have achieved industrial scale flow but the oil production in special exploration wells has been less than ideal the area of continental shale oil and gas accumulations has not been properly controlled and geological sweet sections and sweet areas need to be systematically studied in this study shale reservoir characteristics are analyzed in detail based on thin sections field emission scanning electron microscopy fe sem observations and mercury injection experiments of well core samples combined with x ray diffraction xrd and geochemical indicators key factors related to a high yield of shale oil are determined in addition to the shale oil production capacity and the types of shale oil sweet spots are classified while the sweet spot distribution pattern is determined the results show that the paleogene shale in the jiyang depression is rich in carbonate minerals mainly calcite and ferrocalcite followed by dolomite and ferrodolomite and has a low clastic content high organic carbon content 2 0 7 0 wt and medium maturity ro 0 51 1 1 an effective reservoir space assemblage usually has a three tier intercommunication form within the porosity fracture network laminar lithofacies that are rich in carbonates are the most favorable for containing continental shale oil reservoirs shale oil geological sweet spots can be roughly divided into matrix shale oil fracture shale oil interlayer shale oil and compound shale oil types the key focus in locating shale oil wells is to find geological sweet spots that have an appropriate organic matter om content interlayer development light oil and high pressure this study demonstrates that favorable sweet spots are found to have the following conditions a shale formation pressure coefficient of 1 2 shale total organic carbon content of 2 organic rich laminar lithofacies including interlayer and single interlayer thicknesses of 2 cm burial depth of 3200 m middle diagenetic stage b ro 0 7 and crude oil density of

crustal structure of the gunsan basin in the se yellow sea from ocean bottom seismometer obs data and its linkage to the south china block abstract two major tectonic units in ne asia are the sino korean or north china and south china blocks that collided in the permo triassic periods the south china block is suggested to extend eastward to the korean peninsula across the southern yellow sea the gunsan basin is a well defined fault bounded sedimentary basin in the se yellow sea and is regarded as a structural link of the south china block to the korean peninsula we collected deep seismic sounding data recorded on ocean bottom seismometers to investigate how the crustal structure and nature of the south china block vary in the gunsan basin toward the middle part of the korean peninsula the main part of the gunsan basin is underlain by relatively thin 10 km thick upper and much thicker 20 km thick lower crustal layers indicating a close affinity to the south china block whereas it shows distinction from the korean peninsula underlain by upper and lower crustal layers with equal 15 km thickness a change in crustal structure is recognized under the eastern margin of the gunsan basin toward the korean peninsula that features a transition to the korean peninsula the thick lower crustal layer in the gunsan basin appears to be inherited from the evolution of the south china block including crustal shortening associated with the assembly of rodinia in the neoproterozoic before the collision between the sino korean and south china blocks

detrital zircon u th he thermochronometry of the mesozoic daba shan foreland basin central china evidence for timing of post orogenic denudation abstract the timing of the transition of a peripheral foreland basin from underfilled to overfilled provides important insights into the post orogenic dynamics of its coupled orogenic wedge such information is lacking in the mesozoic foreland basins surrounding the qinling orogen central china such as the daba shan foreland basin dsfb the northeastern part of the sichuan basin in an effort to constrain the timing of maximum burial and onset of denudation we report detrital zircon u th he zhe data from four deep boreholes in the dsfb results show that zhe ages from the oldest foreland basin formations upper triassic lower middle jurassic are mostly younger than their depositional age whereas non reset zhe ages characterize younger strata this suggests that the oldest strata attained maximum temperatures between 130 c and 200 c zhe partial retention zone which is consistent with previous independent paleotemperatures organic matter reflectance and illite crystallinity reported in two of the boreholes and another nearby the fully reset ages apparently show the youngest peaks at 80 ma and 100 ma which are interpreted as the minimum constraints on the timing of maximum basinal burial and subsequent denudation considering that the regional deposition has lasted to aptian time it is proposed that the onset of the basin exhumation in the dsfb started at aptian albian time 100 125 ma heralding the termination of regional tectonic shortening in the hinterland southern qinling

reproducibility of apatite fission track length data and thermal history reconstruction abstract the ability to derive detailed thermal history information from apatite fission track analysis is predicated on the reliability of track length measurements however insufficient attention has been given to whether and how these measurements should be standardized in conjunction with a fission track workshop we conducted an experiment in which 11 volunteers measured 50 track lengths on one or two samples one mount contained durango apatite with unannealed induced tracks and one contained apatite from a crystalline rock containing spontaneous tracks with a broad length distribution caused by partial resetting results for both mounts showed scatter indicative of differences in measurement technique among the individual analysts the effects of this variability on thermal history inversion were tested using the hefty computer program to model the spontaneous track measurements a cooling only scenario and a reheating scenario more consistent with the sample s geological history were posed when a uniform initial length value from the literature was used results among analysts were very inconsistent in both scenarios although normalizing for track angle by projecting all lengths to a c axis parallel crystallographic orientation improved some aspects of congruency when the induced track measurement was used as the basis for thermal history inversion congruency among analysts and agreement with inversions based on data previously collected was significantly improved further improvement was obtained by using c axis projection differences among inversions that persisted could be traced to differential sampling of long and short track populations among analysts the results of this study while demonstrating the robustness of apatite fission track thermal history inversion nevertheless point to the necessity for a standardized length calibration schema that accounts for analyst variation

migration of igneous activities related to ridge subduction in southwest japan and the east asian continental margin from the mesozoic to the paleogene abstract in the inner zone of southwest japan the northern part of the median tectonic line mtl granites and their volcanic equivalents were formed in large quantities during the late cretaceous to early tertiary migration of magmatic activity related to ridge subduction is proposed to explain the widely distributed magmatism and its tectonics for this purpose the ages of granitic rocks were carefully inspected according to the criteria of the dating methods and procedures concerned and compiled with the sampling localities they clearly show a trend in rock ages along the mtl in agreement with the general direction of strikes in southwest japan from the trend of the ages and the cooling histories of the bodies it was concluded that the magmatism migrated eastward along the mtl with a rate of 30 km m y this migration concept is extended to the mesozoic igneous rocks of the east asian continental margin there two magmatic belts ranging in age from mesozoic to paleogene are found to become younger northeastward along the margins which is ascribed to the subduction of the farallon izanagi and kula pacific ridges

origin and migration pathway of biodegraded oils pooled in multiple reservoirs of the chepaizi uplift junggar basin nw china insights from geochemical characterization and chemometrics methods abstract the chepaizi uplift possesses three sets of oil bearing reservoirs six sets of source intervals multiple episodes of hydrocarbon charging and variable physical properties of crude oils in this study based on geochemical characterization source intervals and the biodegradation rank of the crude oils four oil populations named as group a b c and d d1 d2 were defined the combined results of q cluster analysis qca and discriminant analysis da indicate that group a occurred mainly in lower neogene shawan formation n1s in the western chepaizi uplift and were primarily derived from the middle lower jurassic xishanyao badaowan sangonghe formations j2x j1b j1s and a little of paleogene anjihaihe formation e2 3a of the sikeshu sag group b occurred essentially in upper carboniferous xibeikulasi formation c2x of the western chepaizi and originated mainly from the j1b mudstone of the shawan sag in addition the crude oils of group c occurred mainly in the lower cretaceous tugulu group k1tg of the eastern chepaizi and were primarily derived from carboniferous sourced oil from the chepaizi uplift the crude oils of groups d d1 and d2 are mixed with permian p1f and p2w of shawan sag and carboniferous sourced oil from the chepaizi uplift based on the reconstruction of the migration history the oils of group a in the n1s formation of western chepaizi migrated predominantly from the south sikeshu sag to the north and northeast with wells su1 2 and c27 as the initial filling points the oils of group b in the n1s formation of the western chepaizi travelled predominantly from the southeast shawan sag to the north and northwest the oils of group d1 in the c2x formation of eastern chepaizi migrated mainly from the northeast and southeast shawan sag to the west with well p661 as the initial filling point wells sm011 and c64 are the initial filling points of the k1tg group in the hongche fault belt crude oils of group c in the k1tg group travelled predominantly from the southeast shawan sag and northeast to the west into the eastern chepaizi and from well p68 to the southwest according to the paleo oil preferential filling orientations and paleogeomorphology some favourable targets for petroleum exploration of the chepaizi uplift are forecast in this study

annealing kinetics of fission tracks in zircon an experimental study a series of laboratory annealing experiments on zircon fission tracks has been carried out under heating conditions of 350 750 c for 10 1 103 hr i e 4 5 min 40 days variation in the confined lengths of spontaneous fission tracks was determined using zircon grains from nisatai dacite the fading contours of normalized mean track length r on the arrhenius diagram showed as sets of straight lines we performed a series of model fittings called the parallel and fanning models in order to describe the decrease in r with increasing temperature or heating time the lowest temperature limit of the zircon partial annealing zone zpaz was defined as r 0 95 and the highest as r 0 4 which approximately corresponded to the total fading of surface tracks extrapolation of the results of the laboratory experiments to the geological timescale gives for a heating duration of 106 yr estimated values of the zpaz of 210 320 c 60 c 2 with the parallel model 190 350 c 50 c 2 with the fanning model critical temperature t0 and 170 390 c 50 c 2 with the fanning model t0 the temperatures of the zpaz decrease by 20 c for an annealing duration that is an order of magnitude longer because the estimated closure temperature of zircon fission track analysis approximately corresponds to the middle of the zpaz these results support the previously estimated closure temperature of 240 c by varying the etching time it was revealed that significant removal of radiation damage occurs at r 0 93

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

a field based estimate of the zircon fission track closure temperature abstract a field based estimate of the zircon fission track closure temperature is proposed from 13 zircon fission track cooling ages of the gold butte block se nevada using previously published and new thermochronological data the thermal history of the gold butte block is re evaluated resulting in a geothermal gradient estimate of 20 3 c km and a slow cooling rate of 0 55 0 02 c m y from the late jurassic to the early miocene before onset of rapid miocene cooling the rapidly cooled part of the gold butte block provides a slip rate of 10 5 km m y of the hanging wall that caused the miocene exhumation of this crustal section assuming these thermal conditions are correct the closure temperature of the zircon fission track system is determined at 205 18 c which is in good agreement with previous field based estimates because of the variation in zircon fission track annealing behavior with radiation damage field studies are a suitable way to calibrate the closure temperature of the zircon fission track system

late paleogene sinistral strike slip system along east qinling and in southern north china implications for interaction between collision related block trans rotation and subduction related back arc extension in east china abstract we present in this paper a compilation of paleogene rift and strike slip structures in east qinling and southern north china based on a synthesis of published stratigraphic structural and thermochronological data which aids in delineating a broad 500 km wide kinematically interlinked eocene oligocene transtensional system this transtensional system was bifurcated from two discrete strike slip fault zones in ne tibetan plateau the overall fault patterns indicate a clockwise rotation of south china relative to north china during the cenozoic possibly driven by dextral shearing along the eastern tibetan margin this collision related trans rotation of south china occurred coevally with late paleogene intracontinental rifting and volcanism in east china in a subduction related back arc extensional setting these two tectonic processes interacted with each other giving birth to cenozoic rift systems and contrasting morpho structural features in east asia

current plate motions across the red sea summary a new objective method is used to estimate precisely 64 rates of seafloor spreading since chron 2a 3 2 ma from all the red sea magnetic profiles available from 15 9 to 26 n the fastest spreading rate 16 mm yr 1 occurs near 18 n whereas the slowest rate 10 mm yr 1 occurs at 25 5 n and is consistent with the rate predicted from arabia nubia data to the south the standard deviation of the spreading rates is 0 8 mm yr 1 much smaller than the median standard deviation of 4 mm yr 1 previously assigned to spreading rates in the global plate motion model nuvel 1 demets et al 1990 the fit to the spreading rates as well as the locations of earthquakes in and near the red sea indicate that spreading south of approximately 17 7 n is less than the full rate of spreading between the arabian and nubian plates the red sea spreading centre is instead usefully interpreted as the boundary between the arabian plate and a danakil microplate that includes the subaerial danakil block and a larger oceanic portion of lithosphere despite the absence of reliable azimuths of transform faults in the red sea all components of the angular velocity of arabia relative to nubia are usefully constrained from just the 45 relevant spreading rates the new compact 95 per cent confidence region of the angular velocity excludes prior estimates based on only four and two spreading rates by chase 1978 and jestin et al 1994 respectively 19 spreading rates in the southern red sea are used to estimate the angular velocity between the danakil microplate and arabia an approach based on singular value decomposition shows that without slip vectors only two of the three components of the angular velocity of the danakil microplate relative to arabia or nubia are usefully constrained but that all three components are usefully constrained if one earthquake slip vector is included

tectonic and paleogeographic controls on development of the early middle ordovician shanganning carbonate platform ordos basin north china lower middle ordovician platform carbonates are important oil and gas reservoir rocks in the ordos basin of the north china craton ncc in recent years numerous cores have been recovered from these units but the depositional environments and facies architecture of this large carbonate platform system have not yet been reported in detail this study integrates sedimentological and magnetic fabric data collected from outcrops and cores to document variation in microfacies and facies associations within the shanganning carbonate platform scp infer paleowind directions and the paleogeographic location of the scp and evaluate tectonic and paleogeographic controls on platform development this analysis documented 25 microfacies belonging to 7 microfacies fabric and sediment types carbonate mudstone wackestone packstone grainstone evaporite bindstone framestone siliciclastics and dolostone microfacies can be grouped into facies associations that represent tidal flat open platform restricted platform evaporite platform platform margin slope and deep basinal depositional environments these environments are mainly distributed zonally around the l shaped qingyang paleo uplift on the western and southern margins of the scp anisotropy of magnetic susceptibility measurements at five platform margin locales yielded paleocurrent directions of all approximately 318 348 51 81 42 72 80 110 and 54 84 from paleo north after correction for a 120 150 clockwise rotation of the ncc since the ordovician the depositional architecture of the scp depended on a combination of tectonic and paleogeographic wind influences local tectonic movements controlled the spatial distribution of facies associations around the qingyang paleo uplift which was characterized by open restricted and evaporite platform facies in the platform interior and mainly slope and basinal facies on the outer platform margin to the west and south of the qingyang paleo uplift vertical tectonic movements resulted in cyclic submergence and emergence of the platform over its approximately 20 m y long formation history paleo trade winds influenced aspects of facies zonation across the platform including growth of metazoan reefs on the windward platform margin and formation of oolitic grainstone and microbial reefs on the leeward platform margin the facies model for the scp developed in this study should provide a useful reference framework for future carbonate oil and gas exploration in lower middle ordovician units of the ordos basin furthermore this study makes innovative use of magnetic anisotropy data in combination with standard petrographic core and field data to discern facies patterns and controls on a paleo carbonate platform which is an integrated methodology that may serve as a model for future studies of other carbonate platforms

preservation and exhumation history of the harizha halongxiuma mining area in the east kunlun range northeastern tibetan plateau china abstract the extent to which ore bodies are preserved in orogenic belts remains a poorly understood area of ore deposit research using zircon and apatite fission track analysis together with apatite u th he dating we constrained the erosion history of the ore bodies in the harizha halongxiuma mining area of the east kunlun range northern tibetan plateau china apatite fission track ages range from 114 8 to 87 6 ma with mean track lengths varying from 11 4 1 9 to 12 9 2 0 m zircon fission track ages vary from 205 14 to 142 7 ma in addition apatite u th he dating yielded ages of 60 56 ma the thermal history of jiapigou was modelled based on the apatite fission track data including ages and track lengths with constraints of zircon fission track ages and u th he ages the exhumation history of the harizha halongxiuma mining area was reconstructed with these age data revealing that since the early mesozoic the area has undergone three cooling stages 1 rapid cooling from 175 30 ma to 100 10 ma with a cooling rate and inferred exhumation of 2 0 0 8 c myr and 4 3 1 7 km respectively 2 a relatively stable stage from 100 10 ma to 40 10 ma with a cooling rate and inferred exhumation of 0 3 0 1 c myr and 0 5 0 2 km respectively and 3 rapid cooling since 40 10 ma with a cooling rate and inferred exhumation of 1 2 0 6 c myr and 1 4 0 4 km respectively this exhumation history is consistent with the subduction process of pacific plate and the strike slip movements of dunmi fault the total exhumation after main mineralization is calculated to be 7 6 3 2 km suggesting that ore bodies in the harizha halongxiuma mining area remain partially preserved

structural development and tectonic evolution of gunsan basin cretaceous tertiary in the central yellow sea abstract this study analyzes the structural development of the gunsan basin in the central yellow sea based on multi channel seismic reflection profiles and exploratory well data the basin comprises three depressions the western central and eastern subbasins filled with a thick ca 6000 m cretaceous to paleogene nonmarine succession it was initiated in the early cretaceous due to intracontinental extension caused by oblique subduction of the izanagi plate under the eurasian plate and sinistral movement of the tan lu fault the basin appears to have undergone transtension in the late cretaceous eocene caused by dextral movement of the tan lu and its branching faults the transtension was accommodated by oblique intra basinal normal faults and strike slip or oblique slip movement of a ne trending bounding fault in the northern margin of the central subbasin the entire basin was deformed ne sw contraction in the oligocene when tectonic inversion occurred possibly due to the changes in strike slip motion from right to left lateral of the tan lu fault during the early miocene extension resumed by reactivation of the pre existing normal and transpressional faults a combination of extension uplift and erosion resulted in differential preservation of the early miocene succession at the end of the early miocene extension ceased with mild contraction and then the basin thermally subsided with ensued rise in sea level

initial constraints on the timing of granitic magmatism in north korea using u pb zircon geochronology abstract the geology of north korea is very poorly known in this paper twenty seven granitic samples from the tumangang belt and the rangnim massif including diorite granodiorite and monzogranite were selected for in situ zircon u pb isotopic dating in the tumangang belt granites formed mainly in the jurassic with one sample giving a triassic age this is contrary to previous views that considered the granites to be permian to triassic in age in the rangnim massif precambrian granitic magmatism mainly took place at 2 1 and 1 9 1 8 ga no archean emplacement ages have been documented in this study although some inherited discordant zircon may be of this age mesozoic magmatism in this area can be divided into three stages with ages of 234 213 173 and 114 109 ma the triassic granites are mostly exposed in the north and the early cretaceous ones in the west the distribution of jurassic granites is less well documented and only one sample was identified in this study however previous data indicate they are more widely distributed in the area the 2 1 and 1 9 1 8 ga precambrian ages are comparable to paleoproterozoic magmatism in northeastern china indicating that the rangnim massif was most likely part of the north china craton during that time however the absence of 2 5 ga granites and the occurrence of 1 2 ga granites indicate that the rangnim massif was probably at the margin of the north china craton and affected by mesoproterozoic magmatism the similarity in age patterns of the mesozoic granites in north korea to surrounding areas of south korea and the liaodong peninsula of northeastern china indicate that they were controlled by subduction of the pacific ocean under eastern asia however roll back or retreat of the subduction zone resulted in a younging trend from northwest to southeast during the cretaceous

modeling of gas generation from the barnett shale fort worth basin texas the generative gas potential of the mississippian barnett shale in the fort worth basin texas was quantitatively evaluated by sealed gold tube pyrolysis kinetic parameters for gas generation and vitrinite reflectance ro changes were calculated from pyrolysis data and the results used to estimate the amount of gas generated from the barnett shale at geologic heating rates using derived kinetics for ro evolution and gas generation quantities of hydrocarbon gas generated at ro 1 1 are about 230 l t 7 4 scf t and increase to more that 5800 l t 186 scf t at ro 2 0 for a sample with an initial total organic carbon content of 5 5 and ro 0 44 the volume of shale gas generated will depend on the organic richness thickness and thermal maturity of the shale and also the amount of petroleum that is retained in the shale during migration gas that is reservoired in shales appears to be generated from the cracking of kerogen and petroleum that is retained in shales and that cracking of the retained petroleum starts by ro 1 1 this result suggests that the cracking of petroleum retained in source rocks occurs at rates that are faster than what is predicted for conventional siliciclastic and carbonate reservoirs and that contact of retained petroleum with kerogen and shale mineralogy may be a critical factor in shale gas generation shale gas systems together with overburden can be considered complete petroleum systems although the processes of petroleum migration accumulation and trap formation are different from what is defined for conventional petroleum systems

shrimp u pb dating and geochemistry of the cretaceous plutonic rocks in the korean peninsula a new tectonic model of the cretaceous korean peninsula abstract the cretaceous tectonomagmatism of the korean peninsula was examined based on geochemical and geochronological data of the cretaceous plutonic rocks along with distribution of volcano sedimentary nonmarine n to ne trending fault bounded sedimentary basins we conducted sensitive high resolution ion microprobe shrimp zircon u pb ages and whole rock geochemical compositions of 21 cretaceous plutonic rocks together with previously published data from the central to southern korean peninsula four age groups of plutonic rocks were identified group i ca 119 106 ma in the northern to central area group ii ca 99 87 ma in the central southern area group iii ca 85 82 ma in the central to southern area and group iv ca 76 67 ma in the southernmost area these results indicate a sporadic trenchward younging trend of the cretaceous magmatism in the korean peninsula the group i ii and iii rocks are dominated by high k calc alkaline i type rocks with rift related a type granitoids in contrast the group iv rocks are high k calc alkaline i type plutonic rocks with no a type rocks the geochemical signatures of the entire groups indicated lrees light rare earth elements enrichments and negative nb ta and ti anomalies indicating normal arc magmatism a new tectonic model of the cretaceous korean peninsula was proposed based on temporal and spatial distribution of the cretaceous plutons represented by four age groups 1 magmatic quiescence throughout the korean peninsula from ca 160 to 120 ma 2 intrusions of the i and a type granitoids in the northern and central korean peninsula group i plutonic rocks from ca 120 to 100 ma resulted from the partial melting of the lower continental crust due to the rollback of the izanagi plate expressed as the conversion from flat lying subduction to normal subduction the gyeongsang nonmarine sedimentary rift basin in the korean peninsula and adakite magmatism preserved in the present day japanese islands supported the slab rollback followed by steepening of the izanagi plate with an injection of upwelling of the hot asthenosphere into the mantle wedge 3 alternating shallow from 100 to 85 ma to steep from 85 to 65 ma subduction resulted in the migration of the normal arc magmatism in the southern korean peninsula expressed as the intruded i and a type group iii and i type granitoids group iv respectively the tectonomagmatism of the korean peninsula showed the unique style of evolution different from those of south china and japanese islands

magnetostratigraphy and luminescence dating on a sedimentary sequence from northern east china sea constraints on evolutionary history of eastern marginal seas of china since the early pleistocene owing to the large and increasing population density in low lying coastal regions even small changes in sea level can have substantial societal and economic impacts alternations of terrestrial and marine sediments deposited in coastal areas or continental shelves are important and effective indicators of sea level changes and thus have been widely studied in the marginal seas of china over the past 30 years however sea level change results from not only eustatic factors but also tectonic activity the zhe min or zhejiang fujian uplift zmu was such an important factor in geomorphology and formed a barrier preventing entry of sea water into the northern marginal seas of china but its quaternary history is poorly known

onshore offshore structure and hydrocarbon potential of the south yellow sea abstract recent high resolution airborne gravity data taken over the south yellow sea and its western onshore offshore transition zone combined with ground gravity data taken over the onshore area subei basin china show that the south basin of the south yellow sea and the subei basin correspond to the same gravity low anomaly magnetic data also support our interpretations both areas have similar strata structures and hydrocarbon potential and form a large cenozoic terrestrial sedimentary basin controlled by the tanlu fault cenozoic terrestrial strata are well developed in the south basin of the south yellow sea and thick meso paleozoic marine strata are preserved in the central uplift area future hydrocarbon exploration in the south yellow sea should focus on the cenozoic continental sequence especially the paleogene in the south basin as well as the meso paleozoic marine rocks in the central uplift area the western part of the middle depression and middle and western parts of the north depression in the south basin of the south yellow sea have the greatest potential for hydrocarbon accumulation

the sedimentary succession of the last 3 50 myr in the western south yellow sea paleoenvironmental and tectonic implications abstract the south yellow sea sys basin which is part of the west pacific continental margin began to form in the late mesozoic to early cenozoic as a result of regional tectonic activity in asia the pre middle pleistocene sedimentary history of the area remains poorly understood or controversial mainly due to a lack of long borehole cores penetrating pre quaternary strata borehole core csdp 1 300 10 m long the longest sediment core recovered thus far from the sys was drilled in 2013 in the western sys recently a reliable timescale for the core for the last 3 50 myr was obtained by magnetostratigraphy liu et al 2016a here we report the results of integrated analyses of the core including sedimentary characteristics downcore changes in environmental proxies benthic foraminifera and ostracods and accelerator mass spectrometry 14c and optically stimulated luminescence dates in addition we analyze 546 km of single channel seismic profiles and 50 km of a boomer seismic profile around the core site and correlate the regional stratigraphy the core sedimentary succession contains 17 depositional units lithofacies associations corresponding to three major seismic units reflecting a variety of depositional environments during the last 3 50 myr our results show that fluvial environments prevailed in the western sys from 3 50 to 1 66 ma followed by alternations of tidal flat to shallow subtidal environments with fluvial environments from 1 66 to 0 83 ma and alternations of modern like marine environments and fluvial environments from 0 83 ma to the present day in response to glacio eustatic sea level cycles the depositional succession during the last 3 50 myr was dominantly controlled by tectonism and glacio eustatic sea level cycles the presumed first marine transgression since the neogene in the western sys at 1 66 ma is interpreted to suggest that sea water could partially flood the zhe min uplift zmu into the sys due to tectonic subsidence and further subsidence of the zmu and the sys shelf is inferred to have resulted in establishment of normal marine environments in the sys during the highstands of glacio eustatic sea level cycles since 0 83 ma the average subsidence rates in the western sys were 120 165 m myr during the last 1 66 myr the sedimentary succession comprises fifth and fourth order sequences which are interpreted to have been driven by the 20 kyr or 41 kyr and by the 100 kyr glacio eustatic sea level cycles respectively since the late pliocene the sequences deposited since the late pleistocene are relatively complete recording deposits from mis 5 to mis 1 however the pre upper pleistocene sequences show significant stratigraphic hiatuses presumably caused by fluvial erosion during the glacial sea level lowstands and subsequent transgressive erosion this type of significant discontinuity in the sedimentary record can be considered to be diagnostic of shelf sequences controlled by glacio eustatic sea level cycles

mantle dynamics of western pacific and east asia insight from seismic tomography and mineral physics abstract recent results of high resolution seismic tomography and mineral physics experiments are used to study mantle dynamics of western pacific and east asia the most important processes in subduction zones are the shallow and deep slab dehydration and the convective circulation corner flow processes in the mantle wedge the combination of the two processes may have caused the back arc spreading in the lau basin affected the morphology of the subducting philippine sea slab and its seismicity under southwest japan and contributed to the formation of the continental rift system and intraplate volcanism in northeast asia which are clearly visible in our tomographic images slow anomalies are also found in the mantle under the subducting pacific slab which may represent a small mantle plumes b upwellings associated with the slab collapsing down to the lower mantle or c sub slab dehydration associated with deep earthquakes caused by the reactivation of large faults preserved in the slab combining tomographic images and earthquake hypocenters with phase diagrams in the systems of peridotite water we proposed a petrologic model for arc volcanism arc magmas are caused by the dehydration reactions of hydrated slab peridotite that supply water rich fluids to the mantle wedge and cause partial melting of the convecting mantle wedge a large amount of fluids can be released from hydrated morb at depths shallower than 55 km which move upwards to hydrate the wedge corner under the fore arc and never drag down to the deeper mantle along the slab surface slab dehydration reactions at 120 km depth are the antigorite related 5 reactions which supply water rich fluids for forming the volcanic front phase a and mg surssasite breakdown reactions at 200 and 300 km depths below 700 c cause the second and third arcs respectively moreover the dehydration reactions of super hydrous phase b phases d and e at 500 660 km depths cause the fluid transportation to the mantle boundary layer mbl 410 660 km depth the stagnant slabs extend from japan to beijing china for over 1000 km long indicating that the arc trench system covers the entire region from the japan trench to east asia we propose a big mantle wedge bmw model herein where hydrous plumes originating from 410 km depth cause a series of intra continental hot regions fluids derived from mbl accumulated by the double sided subduction zones rather than the india asia collision and the subsequent indentation into asia are the major cause for the active tectonics and mantle dynamics in this broad region

thermal control on post orogenic extension in collision belts abstract intracontinental extension develops in two different ways in the rhine graben the baikal or the east african rifts it is localized in a long and narrow zone along a few normal faults which often delineate a single graben in contrast in the basin and range province or the tibetan plateau it is distributed over a much broader area up to more than 1000 km across this difference arises from differences in rheology and applied forces widespread extension probably reflects the thinning of a previously thickened crust geological observations indicate that only wide orogenic belts undergo late or post orogenic thinning a related fact is that anatectic granites seem to be most abundant in wide orogenic belts the general correlation between belt width and occurrence of both extension and anatectic granites suggest that it reflects in part the characteristics of horizontal heat transfer between thickened crust and surroundings in wide orogenic plateaux the large amount of heat produced in the crust by radioactive decay and lack of erosion leads to high temperatures in narrow mountain belts horizontal heat transfer and high erosion rates concur to prevent temperatures from rising to values at which the crust may yield in extension we have tested this hypothesis using transient two dimensional numerical models of orogenic belts focussing on the effects of the shortening rate the final width of the belt and the rate of crustal radiogenic heat production in the range of geological values the shortening rate has little influence on the results crustal temperatures increase as a function of belt width we find that the sensitivity of crustal temperatures to belt width is most pronounced in the 100 300 km width range and for large values of crustal heat generation the pressure temperature paths followed by geological formations depend on the belt width which is consistent with available data the integrated shear strength of the lithosphere decreases with time as the belt is being built and then eroded this evolution is sensitive to belt width if extension occurs when the integrated shear strength drops below a critical value our results yield a framework for comparing different orogenic belts we predict that extension starts late in the history of wide belts and never occurs in narrow belts a final implication of this study is that the average rate of crustal heat production is probably close to 1 1 10 6 w m 3 which is in the upper range of possible values we present a simple and convenient diagram summarizing the thermal characteristics of orogenic belts as a function of width and shortening rate