structural evolution of the central part of the krusne hory erzgebirge mountains in the czech republic evidence for changing stress regime during variscan compression abstract in the central part of the krusne hory erzgebirge mountains the parautochthonous metasedimentary basement has been overthrust by a crustal nappe of fine and coarse grained orthogneisses the thrust boundary is defined by the presence of mafic eclogites with preserved subduction related fabric westward thrusting of an allochthonous unit is associated with the development of the main metamorphic foliation and lineation in non eclogitic lithologies buttressing of the allochthonous body from the west is responsible for the development of late large scale folds with n s trending hinges and vertical axial planes subsequent n s compression leads to large scale folding of both the parautochthonous and allochthonous units this deformation produces km scale antiforms with hinges plunging to the west and is associated with the development of the e w stretching lineation as a result of complete reworking of earlier fabric in the limb zones n s shortening is also associated with the development of small scale folds and brittle ductile kink bands suggesting a decrease in temperature and thus uplift of the whole studied area during this event the last stage of deformation is characterised by the development of kink band folds and a crenulation cleavage these structures suggest a sub vertical direction of principal compression developed exclusively in those parts of the area in which the n s compression produced steep planar fabric

dating reservoir filling a case history from the north sea abstract secondary petroleum inclusions in reservoir sandstones in the froy field and the rind discovery are used in combination with burial history modelling reservoir oils and core extracts to shed light on how and when these structures received their hydrocarbon charges analysis of normal alkane and biomarker distributions in these three data sets fluid inclusions core extracts and drill stem tests dsts provide information on the changes in organic facies and maturity of petroleum in the various reservoir strata over time the geochemistry of core extracts and dst oils in rind and froy reveal that the maturity of the rind petroleum system is higher and also of slightly less anoxic facies compared to the oil present in the froy system biodegraded oil is found today in a small sub compartment of the froy field using the burial history of the froy and the assumption that biodegradation effectively comes to a halt at 70 80 c we tentatively conclude that the filling of this sub compartment and the biodegradation of the oil must have occurred earlier than 30 40 m y b p and before oil from the upper jurassic draupne shales more recently homogeneously filled the main froy structure at 30 40 m y b p the froy structure was at a depth of 1 5 2 km compared to the present depth of 3 5 4 km and it is more than likely that neither the heather nor the draupne formations were mature in the paleo drainage area of the field at this time still the stratigraphically deeper dunlin formation could have been mature and the geochemical signatures of the now biodegraded oil correlates with known signatures from the dunlin formation in this region in the rind discovery no fluorescent petroleum inclusions are observed in k feldspar overgrowths however the number of inclusions in quartz and plagioclase is larger than that observed in the shallower froy field from the mean homogenization temperatures of the petroleum inclusions which are close to the present reservoir temperature filling of the froy field and main rind structure is suggested to have been a recent event a presently dry compartment penetrated by well 25 2 15r2 in the rind discovery contains high residual oil saturations indicating loss of oil from this structure either by direct cap rock leakage or displacement of oil by gas and subsequent cap rock leakage numerous petroleum and coexisting water inclusions were found in the presently dry overpressured structure and it is clear from measurements of homogenization temperatures that the water and the petroleum inclusions are not both saturated with respect to gas due to the lower solubility of hydrocarbon gas in water compared to in oil it is more likely that water inclusions are closer to saturation than are the petroleum inclusions using the difference in homogenization temperatures in these two systems and the burial history we tentatively suggest that the cap rock leakage occurred later than 10 m y b p such information on time for reservoir filling and seal failure when used to calibrate basin modelling should facilitate better models for understanding movement of hydrocarbon fluids in basins

crossing the several scales of strain accomplishing mechanisms in the hinterland of the central andean fold thrust belt bolivia depictions of structures at outcrop regional and tectonic scales enforce horizontal shortening and vertical thickening as the predominant style of deformation at all scales within the hinterland of the central andean fold thrust belt outcrop scale structures document a progression of strain that created 1 flexural slip folds 2 fold flattening via axial planar cleavage 3 vertical stretching via boudinage and late stage faulting and finally 4 kink folding these examples of intraformational deformation are generally concentrated just beyond the tip lines of thrust faults where fault propagation folds and related structures are well developed fault propagation folding accommodated the accrual of strain indicated by outcrop scale structures while the structures themselves indicate how deformation developed within each individual fold fault propagation fold geometries at a regional scale emerge from the construction of regional balanced cross sections the sections were drawn with careful attention to 1 known map relationships 2 field inspection of key contacts 3 bedding orientation data 4 local seismic control and 5 principles of balance the pervasive ese wnw shortening and vertical elongation seen at the outcrop and regional scales developed during the formation of the central andean backthrust belt in the hinterland of the andes the central andean backthrust belt is a large scale west vergent thrust system along the western side of the eastern cordillera in the generally east vergent andean fold thrust belt of bolivia strain accrual within this west verging zone of deformation is proposed to be a taper building mechanism that allowed the fold thrust belt to continue propagating eastward

a soft linkage between major seismogenic fault systems in the central southern apennines italy evidence from low magnitude seismicity abstract we investigate the transfer zone and linkage between divergent extensional seismogenic fault systems on the border amid the central and southern apennines central italy these regional nw se striking sets include large seismogenic sources that caused major historical earthquakes m w 7 the faults in the northern part of the study area dip to the southwest those in the southern part dip to the northeast the sw dipping system abruzzi apennines terminates with the aremogna cinque miglia source the ne dipping system southern apennines terminates with the boiano basin source to test whether the transfer zone model applies to the central southern apennines border we analyzed and relocated seismicity that occurred from 2007 to 2011 between the aremogna cinque miglia and boiano basin sources where we expect the transfer zone seismicity is made of independent events md the spatial distribution of seismicity the geometry and kinematics of active faulting in the region and the results from previous geophysical studies allow us to contend the existence of a transfer zone between these seismogenic normal fault systems our data also allow us to recognize the activity of such transfer along the central part of the ortona roccamonfina line we infer that reverse in dip polarity between the two normal fault systems could also result from the passage between the diverse tectonic units composing the border between central and southern apennines

the vertical chloride ion profile at the iodp site c0002 kumano basin off coast of japan abstract the vertical profiles of chloride ion cl concentration and oxygen and hydrogen isotopic ratios in pore fluids of basin fill sediments in the southern kumano basin were examined a model has been proposed to explain those profiles in conjunction with published data by invoking diffusion and advection of freshwater from methane hydrate dissolution the model requires a low initial cl concentration in the old accretionary prism below the basin before the basin began to fill with sediments it also requires little or no methane hydrate formation in the old accretionary prism given these requirements an upward fluid advection rate of 1 10 12 m s has been estimated which is very low compared to other accretionary prisms our data suggests that the tectonic compaction of the basin filling sediments and fault activity under the basin sediments have not been that active recently in the kumano basin

conical drag folds as kinematic indicators for strike slip fault motion abstract conical drag folds are developed in the vicinity of faults where rock sequences with significantly different mechanical properties are subjected to oblique shear the drag folds formed by passive rotation of a competent bed surrounded by flowing incompetent media mesoscale conical drag folds can serve as kinematic indicators the conical fold axis coincides with the rotation axis of slip and the angle between the small circle of poles to bedding and the conical axis is equal to the angle between the pole to tilted bedding and the rotation axis of slip the sense of asymmetry of the drag fold reflects the sense of shear the relationship between conical folding and sense of shear established for the mesoscale can be applied to larger fault zones for example the geometry of conical drag folds along with other fault related structures reveal sinistral strike slip motion in the mount arif area of the negev

thermal diffusivity measurements of porous methane hydrate and hydrate sediment mixtures 1 an experiment has been constructed to measure thermal diffusivity of methane hydrate and methane hydrate sand sediment mixtures thermal diffusivities of porous methane hydrate 40 pore space filled with methane gas and mixtures of methane hydrate with platte valley sand and blake ridge sediment have been measured between the temperature range 265 k and 281 k at pressures between 4 35 and 7 65 mpa thermal diffusivities of porous methane hydrate ranged between 3 1 10 7 and 3 3 10 7 m2 s thermal diffusivity of 0 4 porosity methane hydrate was found to have inverse dependence on temperature whereas the thermal diffusivity of methane hydrate sediment sand mixtures has positive temperature dependence thermal diffusivity of methane hydrate sand sediment mixtures increased with increasing hydrate volume fraction to a maximum between about 30 and 35 vol in sand and between about 20 and 40 vol in sediment after the maxima the thermal diffusivities decreased with increasing hydrate volume fraction

mechanics of kink bands during torsion deformation of muscovite aggregate abstract the growth geometry and bulk mechanical behavior of grain scale kink bands were investigated during layer parallel non coaxial deformation torsion of synthetic polycrystalline aggregates of muscovite at constant displacement rate 3 10 4 s 1 and various confining pressures cp 50 300 mpa temperatures t 300 800 c and finite shear strains 0 2 5 0 the kink instabilities were observed during elastic to plastic transition yield at finite shear strain of ca 0 2 the shear stress required to form the kinks is a function of pressure and temperature and range from ca 20 to 90 mpa within the experimental conditions the kink bands formed in non coaxial torsion tests are asymmetric involve strain partitioning show complex microstructures with increased deformation and have a limited lifetime as the structure is destroyed at ca 5 these results suggest a domain of pressure and temperature conditions where kink band structures should be common results obtained from torsion experiments are compared to those of layer parallel axial compression conducted with the same displacement rate at 600 c and 300 mpa for 5 10 and 17 bulk shortening combining microstructures viewed on surfaces parallel and perpendicular to the torsion plane a 3d geometrical model is constructed to discuss the kink mechanism the microstructural evolution and the mechanical behavior

india national gas hydrate program expedition 02 operational and technical summary abstract the india national gas hydrate program is being steered by the government of india s ministry of petroleum and natural gas mopng with participation of directorate general of hydrocarbons dgh oil and natural gas corporation limited ongc and the national oil companies and research institutes of india the india national gas hydrate program expedition 01 nghp 01 established the presence of gas hydrate in the krishna godavari kg and mahanadi basins and in the offshore area of the andaman sea basin however the gas hydrates discovered during nghp 01 were mainly distributed as fracture filling material in fine grained clay rich sediments the india national gas hydrate program expedition 02 nghp 02 was carried out with an objective to discover gas hydrate in sand rich sediment along the eastern offshore margin of india ongc planned and executed nghp 02 on the behalf of the mopng nghp 02 started on march 3 2015 and was completed on july 28 2015 total 147 days using the japanese scientific drilling vessel chikyu d v chikyu during nghp 02 42 holes at 25 sites were drilled cored and or surveyed with downhole logging tools these sites were located in four areas along the eastern margin of india and formally named area a mahanadi basin three sites area b northern part of the kg basin twelve sites area c central part of the kg basin six sites and area e southern part to the kg basin four sites all 25 sites established during nghp 02 were first drilled and logged with logging while drilling lwd tools and an additional 17 holes were then drilled and or cored with conventional coring tools hpcs escs or pressure coring tools pctb wireline logging was conducted in 10 holes and formation tests using a dual packer modular formation dynamics tester mdt tool were carried out in two holes the onboard science team used the laboratory facilities on the d v chikyu to examine and analyse the physical properties geochemistry and sedimentology of all the cores collected during the expedition core samples were also analysed in additional post expedition shore based studies conducted in numerous domestic and international gas hydrate research laboratories the nghp 02 sediment cores were archived at the national gas hydrate core repository in mumbai india which is associated with the ongc gas hydrate research and technology centre ghrtc the necessary data for characterizing the occurrence of gas hydrate such as interstitial water chlorinities core derived gas chemistry physical and sedimentological properties thermal images of the recovered cores pressure core and downhole measured logging data lwd and or conventional wireline log data were obtained from most of the drill sites established during nghp 02 almost all the drill sites yielded evidence for the occurrence of gas hydrate however the inferred in situ concentration of gas hydrate varied substantially from site to site for the most part the interpretation of downhole logging data core thermal images interstitial water analyses and pressure core images from the sites established during nghp 02 indicate that the occurrence of concentrated gas hydrate is mostly associated with coarser grained sand rich sediments this paper presents the operational and technical summary of nghp 02

deformation in neogene sediments of the sorbas and vera basins se spain constraints on simple shear deformation and rigid body rotation along major strike slip faults abstract detailed structural analyses are presented of the neogene sorbas basin adjacent to the e w striking gafarillos fault zone and the vera basin adjacent to the 020 striking palomares fault zone in southeastern spain a stress regime with an e w oriented subhorizontal maximum principal stress 1 existed in pre tortonian 11 3 ma time a strike slip regime with nw se oriented compression during tortonian and earliest messinian time caused dextral displacement along the e w trending gafarillos fault of approximately 10 km structural analysis indicates that most displacement took place in the early tortonian deformational patterns within the adjacent pull apart basin reflect a dextral simple shear zone of at least 500 m width kinematical analysis of folds in the sorbas basin suggests however that rotational effects are largely caused by rigid body rotation without much internal deformation sinistral strike slip displacements occurred along the palomares fault zone under the influence of the same stress regime an abrupt change in the orientation of the stress field to n s directed compression in earliest messinian time 6 5 ma caused the termination of displacements along the gafarillos fault zone whereas the 020 trending palomares fault zone continued to accumulate sinistral strike slip displacements of about 25 km volcanism occurred along splays of the fault zone a wider shear zone of a few kilometers width evolved in which considerable anti clockwise rotation of folds occurred kinematic analysis of these folds shows that these rotational effects are again dominantly rigid body rotations assuming rotations are merely caused by simple shear deformation overestimates the amounts of strain a better way to deal with simple shear deformation is to compare observed shortening caused by folding with the magnitude of rotation of fold hinges

intersections of remanence small circles new tools to improve data processing and interpretation in palaeomagnetism summary intersections of remanence small circles are increasingly used in palaeomagnetism to determine the palaeofield direction from synfolding remanences the approach small circle intersection sci method presupposes that remanence small circles from sites tilted to different directions intersect in a common point which is assumed to represent the palaeofield direction the sci method is not restricted to synfolding remanences it can be applied also to derive the palaeofield direction from pre folding remanences in addition to tilt correction and as a cross check for fold tests however the sci method has specific requirements and does not work in all cases the suitability of data sets and reliability of palaeofield estimates have to be assessed carefully and always against the background of local geology this paper examines the occurrence and distribution of sci as a tool of judgement first a data set is most suitable and a palaeofield estimate by sci most reliable when most of the theoretically possible intersections are realized and in addition clearly grouping in a narrow region second the small circles that greatly determine the result of sci are identified by the highest number of intersections they have with the others these criteria allow a systematic investigation of sci estimates upon stability and dependencies moreover scis can be an indicator of irregular unexpected tectonic settings when the intersections disperse strongly although significant bedding strike differences are given relative rotations or other unexpected displacements are likely to have occurred if so the sci estimate will be invalid and probably biased however also fisher mean calculation and most fold tests will be affected in this case the scis can help to separate the data into subsets valid for fisher statistics and sci methods the other possibility is to use tentative reconstructions to infer the true sequence of tilts and rotations and correct the data adequately

a 3d study of aligned porphyroblast inclusion trails across shear zones and folds inclusion trails si within 741 equant garnet porphyroblasts show a consistent orientation across a 100 m2 outcrop of precambrian metapelite with later d2 folds and shear zones in posio finland variation in si orientations is not systematic with respect to these later folds and shear zones but instead represents microfolding and warping of s1 before the formation of d2 structures the development of the d2 folds and shear zones is investigated by comparing the pattern of si in the outcrop to those predicted for porphyroblasts in tangential longitudinal strain axial slip flexural flow pure shear partitioned flexural flow and partitioned pure shear folds si patterns are also compared with models for non coaxial and coaxial shear zones along with corroborating evidence from structures in the outcrop and matrix the comparisons indicate that d2 folds and shear zones in the outcrop formed in response to nw se axially symmetric shortening during which garnet porphyroblasts did not rotate relative to each other the axial plane of f2 folds and d2 shear zone boundaries

emplacement of the santa rita flat pluton as a pluton scale saddle reef regional mapping indicates that the middle jurassic santa rita flat pluton exposed in the inyo range of eastern california is situated within the core of a south plunging synform defined by bedding in the surrounding metasedimentary wall rocks which dip beneath the pluton however bedding in rocks preserved above the pluton defines a south plunging antiform anisotropy of magnetic susceptibility analysis revealed that magnetic foliation within the pluton also defines a south plunging antiform and the accompanying magnetic lineation plunges subparallel to the axis of this antiform our data indicate that the pluton was initially intruded as a sill in the hinge zone of the enveloping synform subsequent vertical inflation of the sill resulted in upward doming of the overlying roof and formation of the antiform now observed at the current erosion level in the pluton and preserved roof rocks emplacement of the pluton at 164 1 5 ma u pb zircon age overlaps in time with regional thrust faulting and folding ca 185 148 ma recognized in the southern inyo range we speculate that space for initial emplacement of the pluton was produced during folding by layer parallel slip and hinge zone dilation producing a saddle reef like structure

geochemistry and correlation of crude oils from reservoirs and source rocks in southern biyang sag nanxiang basin china abstract the paleogene hetaoyuan formation a sequence of gray to dark calcareous mudstone and dolomitic mudstones is the main source rock and reservoir in the biyang sag nanxiang basin eastern china organic geochemical analysis study performed on 57 source rock samples from the hetaoyuan formation demonstrates poor to abundant organic matter content ranging from 0 24 5 4 wt toc content characterized by oil prone type ii kerogen eleven crude oil samples from the hetaoyuan formation in southern biyang sag were analyzed using bulk properties and molecular methods to determine their maturity and origin the results suggest that the crude oils exhibit different maturity and source organic matter three groups of oils were identified by integrated analysis of gas chromatography gas chromatography mass spectrometry stable carbon isotope physical properties and gross composition of crude oil group a oils defined as low mature oil are characterized by high density viscosity sulfur content and low saturated hydrocarbon content this group of oils has relatively high values of ph n c 18 c 24 c 26 and gammacerane index indicating that the original organic matter had more contribution from terrigenous plants and was deposited in saline and stratified water columns under anoxic conditions group b oils defined as normal maturity oil are characterized by moderate density viscosity sulfur content and moderate saturated hydrocarbon content this group of oils has relatively low values of ph n c 18 c 24 c 26 and gammacerane index and displays a slight predominance of c 29 steranes indicating that the original organic matter had more contribution from marine algae and was deposited under sub oxic to anoxic conditions with low salinity group c oils defined as light oil are characterized by low density viscosity and abundant saturated hydrocarbons representative source rock samples were selected for further correlation the results of oil source rock correlation suggest that crude oils from the eh 2 member of hetaoyuan formation are mixture derived from source rocks in the eh 2 member and upper layer of the eh 3 member while oils from the upper and lower layer of the eh 3 member correlate with source rocks in the upper and lower layers of the eh 3 member respectively

kinematic and geochronological constraints on shear deformation in the ferriere mollieres shear zone argentera mercantour massif western alps implications for the evolution of the southern european variscan belt in the western alps a steeply dipping km scale shear zone the ferriere mollieres shear zone cross cuts variscan migmatites in the argentera mercantour external crystalline massif structural analysis joined with kinematic vorticity and finite strain analyses allowed to recognize a high temperature deformation associated with dextral transpression characterized by a variation in the percentage of pure shear and simple shear along a deformation gradient u th pb dating of syn kinematic monazites was performed on mylonites the oldest 340 ma ages were obtained in protomylonites whereas ages of 320 ma were found in mylonites from the core of the shear zone these ages indicate that the ferriere mollieres shear zone is a still preserved variscan shear zone ages of 320 ma obtained in this work are in agreement with ages of the dextral transpressional shear zones occurring in the maures tanneron massif and corsica sardinia however transpression in the argentera mercantour massif started earlier than in other sectors of the southern variscan belt this is possibly caused by the curvature of the belt triggering the progressive migration of shear deformation our data allow a correlation between the argentera mercantour massif and other segments of the southern european variscan belt in particular with maures tanneron massif and corsica sardinia and contribute to fill a gap in the age of activity and in the kinematics of the flow of the system of dextral shear zones of the southern portion of the evsz

petroleum accumulation and leakage in a deeply buried carbonate reservoir nispero field mexico abstract the filling history of the nispero deeply buried lower cretaceous carbonate reservoir below 4000 m from the south part of gulf of mexico was studied using a combination of data from petrography stable isotopes and fluid inclusions and compared with a one dimensional burial model to derive timing a combination of techniques such as microthermometry confocal laser scanning microscopy clsm and raman microspectroscopy have been used to characterize the different fluid inclusion assemblages and discriminate between the reequilibrated and the preserved fluid inclusions the nispero reservoir is composed of a fractured finely crystalline replacement dolostone a first generation of fractures is filled by a non planar dolomite cement and a second generation by a planar e dolomite cement and a blocky sparite the reservoir is lastly stylolitised dolomite has 13c values between 0 9 and 4 0 pdb and 18o values between 4 5 and 10 8 pdb calcite has 13c values between 3 8 and 4 4 pdb and 18o values between 4 9 and 5 5 pdb these values suggest that the calcite represents a change in water composition and that dolomite and calcite cements do not precipitate from petroleum derived fluids however geological fluids are trapped as aqueous and oil inclusions in the calcite cements three petroleum aqueous inclusion assemblages were identified pseudo primary brown oil paired with brine inclusions and pseudo primary yellow oil paired with low salinity water inclusions distributed in local concentrations and secondary colourless oil paired with low salinity aqueous inclusions distributed in healed microfractures the burial model calibrated with bottom hole temperatures has been calculated using petromod 1d to generate the rock pt history under hydrostatic and lithostatic regimes reconstructed temperatures of initial trapping of fluid inclusion and calculated temperatures from 18o measured in dolomite and calcite cements are in good agreement data suggests that the reservoir was being filled at 97 c 315 bar by heavy black oils accompanied by high salinity water during the miocene period 11 6 m y the maximum estimated pressure of 700 bar at 130 c is reconstructed by petroleum inclusions trapping black oil and associated low salinity aqueous inclusions these pt conditions were reached during the pliocene 3 2m y present day reservoir conditions of 145 c and 500 bar are recorded by reequilibration of most of the fluid inclusions of the two assemblages and correspond to hydrostatic pressure the drop of pressure from 700 bar to 500 bar may be an explanation for the late stylolitisation

multi measurement approach for establishing the base of gas hydrate occurrence in the krishna godavari basin for sites cored during expedition nghp 02 in the offshore of india abstract the 2015 national gas hydrate program of india s second expedition nghp 02 acquired logging and coring datasets for constraining the base of the gas hydrate occurrence zone deepest gh and the theoretical base of gas hydrate stability zone bghs these data are used here for two primary goals to constrain the deepest occurrence of gas hydrate relative to predicted stability limits and the observed bsr and to characterize the nature of the contact between gas hydrate bearing sediment and the underlying gas hydrate free sediment a consensus depth for the deepest gh is derived for each nghp 02 coring site from downhole indicators of gas hydrate occurrence obtained from well log electrical resistivity and acoustic data pressure core compressional wave velocity measurements and conventional core measurements of anomalously low temperatures to establish the theoretical bghs models of gas hydrate phase stability with depth are compared with downhole temperature profiles derived from 1 assuming a constant geothermal gradient consistent with downhole temperature measurements and 2 assuming constant heat flow using a geotherm through the downhole temperature measurements and incorporating thermal conductivity calculated from borehole logging data although the deepest nghp 02 gh occurrences are controlled at several sites by a lithologic boundary most sites have deepest gh occurrences within a single coarse grained lithology cutoffs within a single coarse grained lithology which occur for the primary nghp 02 area b gas hydrate reservoir will inhibit pore pressure drawdowns used to extract methane from gas hydrate as an energy resource

chemical changes of fluid inclusion oil trapped during the evolution of an oil reservoir jabiru 1a case study timor sea australia abstract this study of the jabiru oil field timor sea australia shows how the variability of visual properties of fluid inclusions in palaeo oil zones can be mapped to identify internal structures that result from fluid interactions in the reservoir variability in the attributes of oil inclusion assemblages oias is greater within an inferred palaeo gas cap zone 1 and current residual zone zone 3 and less within the current oil zone zone 2 in zone 3 where water imbibed a higher proportion of oias with visual white fluorescing oil inclusions correlates with less mono aromatic compounds and a higher abundance of polar compounds determined on a bulk extract of inclusion oil using high performance liquid chromatography hplc the ch 2 ch 3 ratios and water contents determined by fourier transform infrared spectroscopy ft ir are higher in zone 1 where gas drained there is a higher proportion of oias with visual yellow fluorescing oil inclusions and these correlate with low hplc mono aromatic and moderate polar contents and low ft ir ch 2 ch 3 ratios and water contents interpretation of the grains with oil inclusions goi and pressure volume temperature composition pvtx fluid inclusion data suggests that a gas saturated blue fluorescing palaeo oil was present in the three zones at the same pressure temperature fluid inclusion forming event pt 1 lighter gas saturated blue fluorescing oil was present in zone 2 but was rarer in zones 1 and 3 at the later fluid inclusion forming event pt 2 the yellow and white inclusion oils trapped in zones 1 and 3 respectively are gas depleted and interpreted to result from the interaction between non movable residual oil around grains with the surrounding gas and water respectively comparison between the pvtx data and the published burial curve suggests that most of the fluid inclusions were trapped during two different hot fluid flow events the full oil column is interpreted to have been present during early mid tertiary the palaeo oil column was reduced during the late miocene by imbibition of water in the present residual zone and drainage of gas at the top of the reservoir

late stage deformation in a collisional orogen western alps nappe refolding back thrusting or normal faulting nappe refolding back thrusting and normal faulting frequently cause severe late stage overprinting of the architecture of an orogen a combined investigation of nappe stack polarity kinematics of shearing and metamorphic gradients in the western alps develops criteria for distinguishing between these three modes of late stage deformation this distinction is a prerequisite for any retro deformation necessary for understanding the main tectonic and metamorphic evolution of collisional orogens in the case of the western alps overprint was by mega scale nappe refolding in the oligocene this implies exhumation of the hp rocks prior to postnappe folding i e during nappe stacking and by foreland directed ascent within a subduction channel

multidisciplinary approach to constrain kinematics of fault zones at shallow depths a case study from the cameros demanda thrust north spain thrusting at shallow depths often precludes analysis by means of structural indicators effective in other geological contexts e g mylonites sheath folds shear bands in this paper a combination of techniques including structural analysis magnetic methods as anisotropy of magnetic susceptibility and paleomagnetism and paleothermometry is used to define thrusting conditions deformation and transport directions in the cameros demanda thrust north spain three outcrops were analyzed along this intraplate large scale major structure having 150 km of outcropping length 30 km of maximum horizontal displacement and 5 km of vertical throw results obtained by means of the different techniques are compared with data derived from cross sections and stratigraphic analysis mixed layer illite smectite and vitrinite reflectance indicating deep diagenetic conditions and mature stage of hydrocarbon generation suggests shallow depths during deformation thus confirming that the protolith for most of the fault rocks is the footwall of the main thrust kinematic indicators foliation s c structures and slickenside striations indicate altogether a dominant nnw movement of the hanging wall in the western zone and ne in the eastern zone of the thrust thus implying strain partitioning between different branches of the main thrust the study of ams in fault rocks nearly 400 samples of fault gouge breccia and microbreccia indicates that the strike of magnetic foliation is oblique to the transport direction and that the magnetic lineation parallelizes the projection of the transport direction onto the k max k int plane in sites with strong shear deformation paleomagnetism applied to fault rocks indicates the existence of remagnetizations linked to thrusting in spite of the shallow depth for deformation and a strong deformation or scattering of the magnetic remanence vectors in the fault zone the application of the described techniques and consistency of results indicate that the proposed multidisciplinary approach is useful when dealing with thrusts at shallow crustal levels

development of igneous layering during growth of pluton the tarcouate laccolith morocco abstract we discuss the significance of igneous layering with respect to pluton growth processes the case study is the tarcouate laccolith morocco whose core consists of modally layered hornblende granodiorites with high amount of monzodioritic enclaves contrasting with peripheral non layered biotite granodiorites with low amount of enclaves rhythmic layering with modal grading cross stratification and trough layering is associated with monzodioritic layers and wraps around mafic enclaves its steep dips 45 result from tilting that occurred above solidus conditions as indicated by sub vertical and synmagmatic granite aplite and monzodiorite dykes cutting across the layering the systematic association of igneous layering with mafic enclaves in calc alkaline plutons suggests that layering originates from recurrent injection of mafic magma viscosity calculations suggest that the physicochemical properties of magma alone cannot account for the presence of layering in the central hornblende granodiorite and its coeval absence in the peripheral biotite granodiorite of the tarcouate laccolith intermittent pulses of hot mafic magma into crystallizing granodiorite likely produced thermal perturbations able to trigger local convection formation of mafic enclaves and development of igneous layering through protracted crystallization

quaternary reactivation of flexural slip folds by diapiric activity example from the western ebro basin spain in the western sector of the ebro basin two types of structures deform the quaternary terraces and pediments developed by the ebro river and its tributaries 1 folds up to 10 km long in the lower levels of fluvial terraces and 2 normal listric faults that produce tilting and rollover anticlines of the quaternary deposits both types of structures are linked to the geometrical and lithological features of the tertiary beds that underlie the quaternary deposits quaternary folds whose axes are parallel to the strike of the tertiary beds are the result of reactivation of tertiary large scale 60 km long folds due to diapirism of their gypsum cores where the gypsum units reach a maximum thickness of 3 000 m this reactivation produced flexural slip in some beds on the limbs of the folds bringing about the folding of the overlying quaternary terraces the mechanism of quaternary folding involves layer parallel shear in alternating tertiary units and folding linked to detachments and reverse layer parallel faults normal listric faults are widespread throughout the studied area they are partly parallel to low dipping tertiary beds and are the result of a nne ssw tectonic extension compatible with minor structures and focal mechanisms of recent earthquakes the relationship between the two kinds of quaternary structures indicates that diapirism of the gypsum cores of the anticlines was activated by extensional tectonics

characteristics and dynamic origin of the large scale jiaoluotage ductile compressional zone in the eastern tianshan mountains china abstract the jiaoluotage ductile compressional zone jdcz in the eastern tianshan mountains china developed in volcanic and sedimentary rocks that were deposited in a carboniferous back arc basin situated between the jungar plate and middle tianshan terrane the ductile compressional zone 500 km long and 20 50 km wide consists of a number of east trending vertical foliation zones that display an augen geometry in plan view and a fan like geometry in transverse profiles ductile compressional deformation has produced pervasive foliation radial stretching lineations contemporaneous folds and various macroscopic to microscopic symmetric structures within the jdcz rotations of most clasts and porphyroclasts are bidirectional the preferred orientation patterns of the optical axes of calcite and quartz display axial or orthorhombic symmetry three kinds of strain patterns have been determined in the jdcz apparent flattening plane strain and apparent constriction the overall strain character of the jdcz is cream cake style the volcanic and sedimentary rocks within the jdcz were metamorphosed into greenschist facies with temperature of 400 600 c and pressure of 300 400 mpa development of the jdcz is interpreted as due to n s coaxial compression caused by the collision between the tarim plate and the middle tianshan arc jiaoluotage basin jungar plate system during the permian between 270 and 290 ma

scale integrated architecture of a world class gold mineral system the archaean eastern yilgarn craton western australia abstract world class mineral systems such as those found in the archaean eastern yilgarn craton are the product of enormous energy and mass flux systems driven by lithospheric scale processes these processes can create big footprints or signatures in the lithosphere which can be observed at a range of scales and via a variety of methods including geophysics isotopes tectonostratigraphy and geochemistry we use these datasets to describe both the architecture structure of world class gold systems of the yilgarn craton and the signatures of their formation by applying an understanding of the most critical elements of the process and their signatures new areas especially undercover may be targeted more predictably than before knowledge of the major architectural elements of the yilgarn craton has increased greatly over the last decade through the collection of a wide range of geophysical geochemical and isotopic data these data range in scale from 1 lithospheric scale which provide information on the entire craton and their underlying volumes down to depths in excess of 350 km through 2 regional scale which provide information at the province scale and to depths of 30 40 km to 3 mine and camp scale which provide information on the top few kilometres of the crust the architecture structure in the upper mantle and lower crust can be inferred from broadband seismic tomography and analysis of long wavelength gravity data geophysical data such as magnetotellurics and deep crustal reflection seismic also provide evidence for the signatures of the flow of fluids through this architecture the pathways and they illustrate that the scale of the system is many orders of magnitude larger than the immediate deposit itself of particular importance is the role of deep crustal penetrating shear zones or faults which link the mantle with domes in the upper crust together these data provide first order insights into the physical and chemical properties of the yilgarn craton these insights provide geodynamic clues and constraints as to why the yilgarn is so well endowed in metals such as gold groves et al 1989 the intersection of favourable architectural features provides connections between the mantle and the upper crust in the kalgoorlie region possibly explaining why this area is so well endowed in comparison to others

the role of fluid pressure in the formation of bedding parallel thrust hosted gold deposits sabie pilgrim s rest goldfield eastern transvaal abstract shallowly dipping thrust hosted gold veins occur within the paleoproterozoic transvaal supergroup rocks in the eastern transvaal of south africa internally the veins record episodic events of fluid infiltration and subsequent mineral deposition within discrete local scale thrust faults evidence also exists for subvertical dilation within the individual veins and textures which record open space filling are preserved the probable depth of formation suggests lithostatic pressures in excess of 2 2 kbar and the vein textures indicate numerous reactivation events associated with individual thrust faults occurring in a terrain characterised by low levels of preserved strain fault reactivation may have occurred under conditions of low differential stress in the presence of high pressure fluids with p fluid approaching or exceeding lithostatic levels

partitioned transtension an alternative to basin inversion models inversion structures e g folds reverse faults spatially associated with basin bounding faults are very widely recognised in rift basins in both onshore and offshore settings worldwide the great majority of such structures are attributed to local or regional crustal shortening events there is however an alternative which is investigated in this paper inversion could reflect a horizontal shortening component of deformation formed during progressive and partitioned transtension a case study from the carboniferous northumberland basin shows that shortening structures can also form in obliquely divergent rifts if the bulk strain undergoes kinematic partitioning into distinct regions of wrench and extension dominated transtension such strain partitioning appears to be particularly favoured in basins where fault localisation is strongly influenced by pre existing basement structures this may occur because the pre existing anisotropies are zones of long lived weakness that lie in an orientation particularly favourable to the preferential accommodation of either strike slip or dip slip displacements our strain analysis applied to the northumberland basin traditionally considered as a classic example of a variscan inverted basin reduces the deformation history to a single kinematically partitioned phase of dextral transtension during the late carboniferous early permian our findings have profound implications for the interpretation of inversion structures in any rift basin where the direction of extension may be significantly oblique to the basin margins

inversion of needle probe data for sediment thermal properties of the eastern flank of the juan de fuca ridge 1 an estimation method is introduced for measuring thermal conductivity thermal diffusivity and heat capacity of sediment from temperatures using a needle probe this method is based on the continuous cylindrical heat source model thermal conductivity is estimated from needle probe temperature data using asymptotic approximation of the model heat capacity is then inverted from early time temperature data using a complete form of the model finally thermal diffusivity is calculated from the estimated thermal conductivity and heat capacity numerical experiments with synthetic temperature data indicate that the estimation error of the sediment s heat capacity is 12 the error of thermal diffusivity is thought to be greater than that of heat capacity we apply the method to needle probe temperature data obtained during integrated ocean drilling program expedition 301 carried out on the eastern flank of the juan de fuca ridge and estimate the sediments thermal properties the results indicate that thermal properties of sediments are strongly dependent on lithology and porosity examination results of the relations of heat capacity and thermal diffusivity to thermal conductivity show that these relations depend on the amount of quartz the empirical formulas for these relations are provided and they differ from those which are commonly used in thermal conductivity reduction schemes

tectono thermal evolution of cambrian ordovician source rocks and implications for hydrocarbon generation in the eastern tarim basin nw china abstract the tectono thermal evolution is an important control on petroliferous basin development however this evolution is difficult to reconstruct in sedimentary basins subjected to multiple tectono thermal events the tarim basin is the largest petroliferous basin in northwestern china and hosts a complex oil gas system comprising several sets of source reservoir and cap rocks that have experienced multiple tectonic thermal and sedimentary events large oil and gas reserves have been discovered in the central and northern tarim basin during the last 30 years but none in the eastern part of the basin this is generally attributed to the high thermal maturity reached by source rocks during the late ordovician and subsequent hydrocarbon loss therefore reconstructing the cambrian ordovician tectono thermal evolution is critical in facilitating successful oil and gas exploration in this region we compiled equivalent vitrinite reflectance data n 178 of source rocks from seven wells in the tarim basin which for cambrian ordovician source rocks are 1 3 beyond the hydrocarbon generation threshold and in the main gas and dry gas generation stages the cambrian ordovician source rocks experienced rapid burial and heating during the caledonian period entered the hydrocarbon generation stage during the middle late ordovician and reached peak hydrocarbon generation at the end caledonian period they might have experienced secondary hydrocarbon generation after the jurassic homogenization temperatures of fluid inclusions n 616 from wells gc4 lx1 md1 and yd2 as well as the modeled thermal evolution reveal a main hydrocarbon generation event during the caledonian period and a secondary event in the yanshanian and himalayan period in other wells lx1 md1 and yd2 hercynian and indosinian uplift and exhumation in the eastern tarim basin controlled the main structures and faulting created favorable conditions for secondary hydrocarbon generation and migration at this time since the yanshanian and himalayan the tarim basin has experienced further sedimentation and heating and the tectono thermal evolution might have been related to the formation of the tibetan plateau in summary our reconstruction of the tectono thermal evolution of cambrian ordovician strata and the hydrocarbon generation history of the tarim basin suggests that the eastern tarim basin may also have hydrocarbon generation potential and can guide future oil and gas exploration

bedding parallel fibrous veins beef and cone in cone worldwide occurrence and possible significance in terms of fluid overpressure hydrocarbon generation and mineralization abstract bedding parallel fibrous veins are common worldwide in sedimentary basins especially within strata of low permeability the term beef refers to bedding parallel veins of fibrous minerals where the fibres are mutually parallel and have formed quasi vertically more complex on a smaller scale are cone in cone structures yet these are also common within bedding parallel veins for both beef and cone in cone we have compiled a worldwide catalogue 157 localities typically the veins consist mainly of white gangue minerals for example calcite gypsum or quartz but may also contain accessory minerals of economic interest for example bitumen sulphides emerald pitchblende or gold fluid inclusions may contain oil or gas calcite beef 110 localities is common in organic rich shale of marine carbonate origin especially of 1 cambrian ordovician 2 devonian carboniferous 3 early jurassic or 4 cretaceous to palaeogene ages gypsum beef 30 localities is common in evaporitic or lacustrine strata of continental origin especially of triassic or neogene ages quartz beef 17 localities is common within meta turbidite sequences especially of ordovician or proterozoic ages because these modal ages seem to reflect climatic controls we infer that the fibre forming mineral species have not travelled far vertically the same conclusion holds for accessory minerals typical temperatures of formation are 1 up to 60 c for gypsum beef 2 70 c to 120 c for calcite beef and 3 200 c to 350 c for quartz beef hydrocarbon bearing calcite beef may be a good indicator of a petroleum system in which oil or gas migrate together with aqueous solutions we argue that beef and cone in cone layers result from tensile fracturing and vertical dilation coeval with fibre growth possible causes are either 1 force of crystallization or 2 seepage forces due to fluid overpressure for layers that form at depths of several km fluid overpressure is the more likely cause

evidence for mesoarchean 3 2ga rifting of the pilbara craton the missing link in an early precambrian wilson cycle abstract a sequence of c 3 2 ga low grade sedimentary rocks bimodal volcanic rocks and subvolcanic layered mafic ultramafic sills and dykes occur in greenstone belts that flank the margins of the 3 51 3 24 ga east pilbara terrane of the pilbara craton western australia u pb shrimp zircon data and sm nd model age data suggest that these rocks represent juvenile addition of material to the margins of the craton during a period of major extension accompanied by the local emplacement of granitic rocks this extensional event is also represented in adjacent terranes by thick basalt flows with c 3 2 ga zircon and sm nd model ages and by granitic rocks based on the available age data geochemistry of basaltic rocks and the distribution of this event in space and time within the craton we interpret the c 3 2 ga rocks to reflect widespread rifting of the protocraton and associated thinning of the lithosphere this event resulted in separation of the flanking kurrana and karratha terranes from their parent east pilbara terrane which represents the ancient nucleus of the craton these terranes were then reassembled during subsequent accretion at 3 07 2 905 ga combined the data suggest the preservation of a mesoarchean wilson cycle in the pilbara craton

numerical modelling of porphyroclast and porphyroblast rotation in anisotropic rocks abstract the rotational behaviour of rigid objects in a weaker rock matrix during deformation has been the subject of many field experimental and numerical modelling studies often centred on the question whether objects rotate or not in non coaxial deformation with numerical studies gaining increasing popularity and importance we here provide an overview of the results published so far and provide new simulations originally shape and orientation were investigated while the emphasis shifted to rheology and slip between object and matrix in the nineties of the last century due to improved numerical techniques anisotropic rheology has become the focus of most recent studies indicating that it is a primary factor in the rotation behaviour of objects we present new simulations investigating the role of anisotropy on different scales relative to the object and show how this influences the rotation rate as well as the inclusion patterns in case of syntectonically growing porphyroblasts these simulations show that a variety of factors play a role to determine the rate and sense of rotation of objects the variability of the inclusion patterns that can develop necessitates extreme caution in the kinematic interpretation of these structures when observed in the field

petroleum inclusions in sedimentary basins systematics analytical methods and applications abstract fluid dynamics in sedimentary basins is of tremendous interest both from a scientific and an economic point of view integration between fluid inclusion and present day fluid data provides the time aspect necessary for reconstruction of fluid flow paths and can be used for mapping fluid dynamics both on a regional basin scale or on the more local scale of petroleum reservoirs this paper presents a review of analytical and modelling methods for petroleum in fluid inclusions essentially four types of data for petroleum inclusions can be established through analysis and modelling 1 textures which give indirect information of the time aspect 2 fluid composition 3 fluid properties and 4 pressure temperature of trapping during the last decade development of analytical methods for determination of inclusion fluid compositions has taken place traditional correlation studies for characterisation of maturity and source facies may now therefore include fluid inclusion data the development has also been directed towards an improved understanding of the physical properties of petroleum inclusions although these methods are in their early stages concerning precision and accuracy data necessary for fluid flow modelling such as fluid densities viscosities pressure and temperature can be estimated

diagenesis and origin of calcite cement in the flemish pass basin sandstone reservoir upper jurassic implications for porosity development abstract the flemish pass basin is a deep water basin located offshore on the continental passive margin of the grand banks eastern newfoundland which is currently a hydrocarbon exploration target the current study investigates the petrographic characteristics and origin of carbonate cements in the ti 3 member a primary clastic reservoir interval of the bodhran formation upper jurassic in the flemish pass basin the ti 3 sandstones with average q 86 0 f 3 1 r 10 9 contain various diagenetic minerals including calcite pyrite quartz overgrowth dolomite and siderite based on the volume of calcite cement the investigated sandstones can be classified into 1 calcite cemented intervals 20 calcite and 2 poorly calcite cemented intervals porous petrographic analysis shows that the dominant cement is intergranular poikilotopic 300 500 m calcite which stared to form extensively at early diagenesis the precipitation of calcite occured after feldspar leaching and was followed by corrosion of quartz grains intergranular calcite cement hosts all liquid inclusions mainly in the crystal core but rare primary two phase liquid and vapor fluid inclusions in the rims with mean homogenization temperature t h of 70 2 4 9 c and salinity estimates of 8 8 1 2 eq wt nacl the mean 18 o and 13 c isotopic compositions of the intergranular calcite are 8 3 1 2 vpdb and 3 0 1 3 vpdb respectively whereas fracture filling calcite has more depleted 18 o but similar 13 c values the shale normalized rare earth element ree sn patterns of calcite are generally parallel and exhibit slightly negative ce anomalies and positive eu anomalies fluid inclusion gas ratios co 2 ch 4 and n 2 ar of calcite cement further confirms that diagenetic fluids originated from modified seawater combined evidence from petrographic microthermometric and geochemical analyses suggest that 1 the intergranular calcite cement precipitated from diagenetic fluids of mixed marine and meteoric riverine waters in suboxic conditions 2 the cement was sourced from the oxidation of organic matters and the dissolution of biogenic marine carbonates within sandstone beds or adjacent silty mudstones and 3 the late phases of the intergranular and fracture filling calcite cements were deposited from hot circulated basinal fluids calcite cementation acts as a main controlling factor on the reservoir quality in the flemish pass reservoir sandstones over 75 of initial porosity was lost due to the early calcite cementation the development of secondary porosity mostly enlarged moldic pores and throats by later calcite dissolution due to maturation of organic matters e g hydrocarbon and coals was the key process in improving the reservoir quality

origin of low chloride fluid in sediments from the eastern continental margin of india results from the national gas hydrate program expedition 02 abstract national gas hydrate program expedition 02 was conducted in 2015 by d v chikyu in the western bay of bengal india analyses of interstitial water in sediment from four drilling sites along the eastern and western transect in the krishna godavari basin show that dissolved chloride cl concentrations decreased with depth from seawater values 550 mm near the sediment surface to 300 400 mm at 350 400 m below seafloor mbsf suggesting the upward advection of low cl fluid excursions of cl concentrations toward low values in gas hydrate zones were attributed to the presence of fresh water released by dissociation of gas hydrate during core recovery at sites in the western transect cl concentrations below the gas hydrate reservoir around 280 mbsf were ca 60 mm and ca 45 mm lower than those from above the reservoir and 18o and d values were 1 2 and 0 7 1 3 higher than those from above the reservoir respectively these results suggest that a fraction of migrating low cl fluid is trapped in the gas hydrate zone causing decreases of 18o and d in the residual water due to isotopic fractionation during gas hydrate formation from mass balance calculations we estimated that 10 20 of the advected fluid is trapped at the gas hydrate zone at all sites the 18o and d values below the gas hydrate zone representing relatively unaltered low cl fluid were 0 5 1 higher and ca 13 15 lower than those of seawater respectively this trend is consistent with water derived from the dehydration of clay minerals which generally occurs in deeply buried sediments the contribution of clay mineral dehydration is relatively large at the western transect compared to that in the eastern transect our results imply that fluid advection contributes to the accumulation of gas hydrate in the study area

scaling properties of thrust fault traces in the himalayas and inferences on thrust fault growth abstract map traces of thrust faults in the himalaya show a conspicuous cuspate lobate pattern i e broad lobes joined by sharp angular cusps for each lobe we can draw a chord by joining the apices of two adjacent cusps and define amplitude a by perpendicular distance of apex of the lobe from its chord the lobes show a linear scaling defined by the relationship a cl where l is the chord length and c is a constant the l a ratio remains nearly constant over about 1 71 orders of magnitude spread of the l values of the sampled lobes suggesting that a is proportional to l the trace pattern indicates that the thrust surfaces are laterally curved due to the growth of fault segments from multiple nuclei along concave upward laterally curved trajectories the propagating surfaces coalesce along sharp angular ridges this lateral curvature gives a furrow like shape to each segment and a fluted appearance to the thrust surfaces the invariant nature of the l a ratio supports self similarity and is manifest as a linear scaling of a against l of the lobes the self similarity further suggests the possibility of thrust fault growth along a characteristic curved surface

fluid inclusion constraints on petroleum pvt and compositional history of the greater alwyn south brent petroleum system northern north sea abstract pressure volume temperature pvt simulation of individual petroleum inclusions that are trapped in source rocks migration pathways and reservoirs is when combined with standard inclusion analytical techniques a useful tool for the quantitative estimation of paleopressures paleotemperatures and changes in petroleum compositions over time this study presents the results from the application of these techniques to determine the evolution of the petroleum trapped through time as maturation and migration progress within the greater alwyn south brent petroleum system of the northern north sea the results for the brent reservoir from the six study fields indicate that the petroleum inclusions recorded a wide range of compositions during the filling history of the reservoir the methane concentrations and gas oil ratios of included petroleum are lower than those presently within the reservoir the fluid inclusion data suggest that changes in petroleum compositions through time can be interpreted in terms of gradual mixing of earlier reservoired oil with later migrated more mature and gas rich fluids fields nearest the kitchen area appear to have been more severely affected by the emplacement of increasingly mature petroleum phase separation during vertical migration may also occur but is thought to be a volumetrically minor process the estimated paleopressures mostly correspond to the current pressure regime which is slightly higher than hydrostatic and lower than lithostatic combining fluid inclusion results with thermal burial models suggests that petroleum migration began at approximately 55 64 ma in the area this study provides quantitative limits on and confirms the value of fluid inclusion technology in such applications as evaluating oil compositions migration timing trap fill history paleopressures and in constraining the outputs of basin modeling

hydrogeology and mechanics of subduction zone forearcs fluid flow and pore pressure at subduction zones fluid flow pore pressure and tectonic processes are tightly interconnected excess pore pressure is driven by tectonic loading and fluids released by mineral dehydration and it has profound effects on fault and earthquake mechanics through its control on effective stress the egress of these overpressured fluids which is in part governed by the presence of permeable fault zones is a primary mechanism of volatile and solute transport to the oceans recent field measurements new constraints gained from laboratory studies and numerical modeling efforts have led to a greatly improved understanding of these coupled processes here we summarize the current state of knowledge of fluid flow and pore pressure in subduction forearcs and focus on recent advances that have quantified permeability architecture fluxes the nature and timing of transience and pressure distribution thus providing new insights into the connections between fluid metamorphic mechanical and fault slip proc

thermochronology of the needle falls shear zone a post collisional high strain zone of the trans hudson orogen the needle falls shear zone is a major paleoproterozoic discontinuity separating an archean craton from accreted paleoproterozoic terranes in the western trans hudson orogen it is a 1 km wide subvertical mylonite zone forming the southwestern sector of a northeast trending shear system extending for more than 400 km kinematic data indicate oblique east side up dextral strike slip displacement throughout its evolution from ductile through late brittle deformation for most of its exposed length it marks the northwestern margin of the wathaman batholith the oldest pb evaporation ages of zircons from mylonite average 1857 ma consistent with published zircon ages of the wathaman batholith confirming the batholith is protolith for much of the shear zone the synkinematic metamorphic assemblage of amphibole biotite quartz feldspar signifies deformation under amphibolite facies conditions 500 630 c oxygen isotope fractionations between quartz hornblende and quartz biotite pairs in textural equilibrium

extrapolation of the kinetics of oil and gas formation from laboratory experiments to sedimentary basins it is generally accepted that the formation of oil and gas from sedimentary organic matter or kerogen is adequately described by kinetic models based on first order kinetics with rate constants obeying an arrhenius equation these models which are extensively used in oil exploration to assess the petroleum potential of sedimentary basins are based on geological observations1 2 3 4 5 6 but are formally quite similar to models designed to simulate oil shale pyrolysis7 8 9 or coal processing10 11 12 the idea of blending these two approaches is not new see for example ref 2 but until now the most sophisticated attempts reproduced only the gross features of kerogen cracking on a geological timescale5 or were uncontrolled by geochemical measurements13 14 here we show that the kinetic parameters determined from the laboratory pyrolysis of an immature kerogen sample apply to the conditions of sedimentary basins altough the time and temperature scale are completely different

pluton accommodation at high strain rates in the upper continental crust the example of the central extremadura batholith spain abstract emplacement in the tensional bridge of a stepped dextral shear zone system is proposed for the central extremadura batholith spain the country rocks show a pervasive anisotropy that conditioned the style of the structures developed as a consequence of the transference of displacement from the stepped shear zones to the releasing area the kinematic evolution of the resulting megakink fold provided the volume increase necessary for the granite emplacement thermal and kinematic models suggest that the growth of individual plutons took place in periods of no more than several hundred to a few thousand years fast strain rates 10 10 10 11 s 1 must concentrate in local structures e g initiation of kink folds even in zones deforming as a whole under typical strain rates 10 14 1 s 1 granite plutons might be used as strain rate gauges for syn plutonic structures

emplacement of synkinematic plutons in the variscan odenwald germany controlled by transtensional tectonics in the odenwald area sw germany an intermediate level of variscan magmatic arc is exposed between 360 and 335 ma the neunkirchen intrusive complex intruded into an active ne sw trending zone of ductile divergent strike shear after the thermal peak of metamorphism but before the emplacement of the magmatic rocks shear zones developed in the wall rocks the microfabrics of these zones infer plastic deformation of feldspar hornblende and quartz and an increasing degree of postkinematic annealing towards the intrusive complex during emplacement and solidification the magmatic rocks experienced bulk strain the intrusive complex locally crosscut the shear zones of the wall rocks but show magmatic and also mylonitic foliations which parallel these zones a change from plastic to brittle behavior of feldspar and amphibole and a varying degree of postkinematic annealing of quartz suggest that in the intrusive complex strike shear continued during cooling in wall rocks and plutonic rocks kinematic indicators imply sinistral displacement in the wall rocks adjacent to the intrusive complex strike shear was combined with normal displacement this suggests that a component of horizontal extension which was associated with strike shear transtension facilitated ascend and emplacement of the magma transtension occurred at the same time when the schwarzwald vosges area in the south of the odenwald was subjected to nw se compression transtension was probably initiated by lateral escape of crustal fragments during overall convergent plate movements transtension is also supposed to be associated with significant uplift of metamorphic rocks

a model of hydrocarbon generation from type i kerogen application to uinta basin utah we have developed a computer model that can predict when and how much oil and gas are generated from a source rock during its burial and later uplift kinetic parameters for the oil and gas generation reactions are obtained from high pressure pyrolysis experiments carried out over a wide range of heating rates and temperatures in our kinetic model which applies only to green river shale we use a single activation energy of 52 4 kcal mole and different pre exponential factors for different products of primary pyrolysis which allows us to extrapolate laboratory derived kinetics to geologic heating rates this model is in contrast to the wide distributions of activation energies or artificially low apparent activation energies used in some models of petroleum formation hen extrapolated to geologic heating rates on the order of 10 c m y our kinetics show that the temperature of the maximum rate of oil generation tp changes by about 15 c when the heating rate is changed by an order of magnitude changes in pressure have relatively minor effects on the kinetics of oil generation but are important for gas generation reactions we used geophysical data from oil fields in the uinta basin of utah to develop a thermal history model of green river formation source rocks this time temperature history was used to predict the maturation level of the kerogen at a given depth and to predict changes in the compositional characteristics of the oil the shape of calculated oil generation rate curves as a function of depth in the basin mimics the shape of the overpressure curves this similarity suggests that oil gas generation may be an important cause of overpressuring maturation levels and compositional characteristics of the oil predicted by our model agree very well with characteristics of the oil recovered from the basin

europa s ice tectonics new insights from physical wax experiments with implications for subduction initiation and global resurfacing processes abstract jupiter s moon europa has one of the youngest geological surfaces in our solar system with an age of 40 90 ma implying an intense history of resurfacing the surface of europa indeed shows abundant evidence of tectonic deformation related to extension strike slip and shortening however observed features related to shortening are scarce compared with pervasive extensive extensional features such as dilational bands and do not suffice as the sole mechanism for recycling aging terranes recently evidence for potential plate tectonics associated with subduction zones has been discovered on europa this could be responsible for recycling most of europa s surface however basic physical parameters needed to initiate subduction on europa such as thickness of the brittle layer deformation rates and orientation of pre existing zones of weakness at which subduction could start are not well understood here we aim to better understand the process and the conditions that could lead to initiation of subduction on europa through physical experiments using wax to simulate europa s two layered i e convective icy crust by deforming the wax strain on europa s surface possibly caused by diurnal tides or its nonsynchronous rotation is simulated our results indicate that subduction could initiate over a broad range of surface thicknesses and deformation rates above a minimum conductive layer thickness but is strongly dependent on the orientation of the pre existing zones of weakness very thin conductive layer experiments however result in a previously undescribed process that we term ductile rolldown which creates surface features similar to double ridges observed on europa thus subduction and ductile rolldown represent physically plausible mechanisms that could play a critical role in resurfacing europa throughout its geologic history these results could yield significant implications for europa s thermal history and evolution habitability and future spacecraft missions

stratigraphy and tectonics of an internal unit of the southern apennines implications for the geodynamic evolution of the peri tyrrhenian mountain belt the parasicilide succession is a key element of the southern apennine orogen being originally located in the distal portion of the apulian palaeomargin at the neotethys ocean continent transition the succession presently included in the upper nappe complex of the thrust belt has been described elsewhere as a broken formation however detailed investigations carried out in the sele valley point out that there the parasicilide unit is characterized by a coherent stratigraphy therefore in the study area these rocks form a coherent sheet of distal continental margin oceanic sedimentary cover material included within the peri tyrrhenian mountain belt stratigraphic and structural constraints obtained from both pre and synorogenic deposits the latter including both foredeep and thrust top basin sediments suggest that the pre orogenic part of the parasicilide succession subsided into the apennine foredeep in the first part of the burdigalian the studied rocks were then involved in thrusting prior to late burdigalian early langhian times

scale dependence strain compatibility and heterogeneity of three dimensional deformation during mountain building a discussion plate motion at convergent margins causes crustal shortening and orogenic thickening relative motion that is oblique to the plate margins is an inevitable consequence of plate kinematics on a sphere and results in non coaxial three dimensional deformation that cannot be approximated to simple shear models of mountain building that include a smoothly varying component of pure shear shortening allow strain compatibility to be maintained by deforming the upper free surface of the earth without disrupting the material continuum however such models do not reflect accurately the nature of deformation in many areas of high strain in the upper crust which are characterized by interconnected arrays of kinematically linked faults that can be active on several scales of magnitude simultaneously as brittle deformation increases the coherence of the material continuum is highly reduced in such situations strain compatibility is maintained by partitioning the deformation amongst structures of varying kinematic significance over a wide range of scales and not by smooth variations in strain magnitude acting on a single scale across a material continuum there is a marked tendency for such partitioned domains to be oriented parallel or sub parallel to the orogenic grain alignment of domains in this way represents a strong structural anisotropy which acts as a highly significant boundary condition that controls deformation at subordinate scales finite strain observed within an individual domain at a given scale need not therefore display the same magnitude or orientation as bulk finite strain at the plate scale and consequently data must be collected from as large an area as possible to relate outcrop scale structures to global scale tectonics

recasting historical earthquakes in coastal areas gargano promontory italy insights from marine paleoseismology uf was financially supported by miur italian ministry of education and research firb project airplane this research has also benefited from funding provided by the italian presidenza del consiglio dei ministri dipartimento della protezione civile dpc scientific papers funded by dpc do not represent its official opinion and policies this is ismar bologna contribution n 1720

dynamics and seismotectonics of the west alpine arc abstract in this paper we present a comparative review of structural seismic and focal mechanism data from the west alpine arc in the western alps seismic activity is concentrated along an external belt corresponding to the penninic front and an internal belt corresponding to the austro alpine front and its southern extension these seismic belts are connected in the ne by a seismic lineament corresponding to the simplon and centovalli line and in the south by the e w trending seismic stura couloir located between the argentera and dora maira massifs the simplondashcentovalli tonale system and the stura couloir are dextral and sinistral strike slip systems respectively this implies a westward translation of the west alpine arc and the po plain based on these observations a seismotectonic model is proposed in which the frontal penninic thrust and the basal surface of the accretionary wedge corresponding to the penninic sole thrust are reactivated activity along the frontal thrust increases the arcuate shape of the western alps and disengages them from the central and the ligurian alps along the tear faults of the simplondashcentovalli tonale system and the stura couloir respectively in the wider framework of northern italy the sector of the eastern alps north of the gailtal line is moving in an orogendashparallel direction towards the east areas with lateral escape in opposite directions towards the west for the po plain and towards the east for the eastern alps north of the gailtal line are separated by the south alpine atesine indenter a model postulating a double lateral escape and a central indenter matches most of the features of the models of poinconnement the seismic features of northern italy agree with the seismicity of the stable sector of northern europe up to the north sea this area is fragmented into blocks bounded by seismic bands some of which probably reactivate pre existing structures the overall stress field of cratonic europe is dominated by ndashnw directed trajectories of maximum horizontal compression the seismicity of the european alpine foreland is interpreted as the response of a stable block to the same stress field of northern italy which is induced by the ondashgoing nw se africa europe convergence we suggest that the westward translation of the west alpine arc continues at present and is the driving mechanism of the observed seismicity

a reevaluation of the position of the baie verte brompton line in the quebec appalachians the influence of middle devonian strike slip faulting in gaspe peninsula the baie verte brompton line bbl the surface expression of the taconian suture in the canadian appalachian orogen extends from southern quebec to the northeast end of newfoundland in the que

volume loss and deformation around conjugate fractures comparison between a natural example and analogue experiments abstract in well stratified sedimentary rocks measurement of the bedding offsets along fractures gives a value for the relative displacement at each location to restore the undeformed geometry of the layers the offset along each fracture must be cancelled restoration of the geometry enables the location of places where shortening is concentrated to be established namely at the fracture intersection and at fracture tips slow displacement during deformation is demonstrated by the growth of fibres on the fault surfaces pressure solution inside the layers is responsible for the internal strain with associated volume loss this mechanism is compatible with low strain rates giving aseismic displacements along the fractures to model rock rheology dominated by pressure solution a viscous material paraffin wax has been employed in the analogue model volume loss in nature is represented by area changes during the analogue experiments in the experiments shortening is concentrated around the fractures in exactly the same geometrical positions as in nature when the amount of displacement is different on each of the two fractures one of the fractures is observed to offset its conjugate fracture when this is the case relative timing of displacement along conjugate fractures cannot be determined without ambiguity from the observation of fracture offsets

experimental deformation of a single layer anhydrite in halite matrix under bulk constriction part 1 geometric and kinematic aspects a new deformation apparatus has been used to model the internal kinematics of salt diapirs composite natural samples consisting of a single layer of anhydrite embedded in halite matrix were constrictionally deformed at temperature t 345 c strain rate 10 7 s 1 maximum viscosity 2 1013 pa s and maximum finite strain ex 122 the anhydrite layer oriented parallel to the major stretching axis x was deformed by fracturing whereas halite behaved viscously at advanced state of constriction ex 90 a strong increase in strain hardening of halite led to a transient tension fracture that healed up and was shortened by folding during the final phase of viscous deformation tiny prismatic anhydrite inclusions disseminated inside the halite matrix were reoriented during constriction resulting in a linear grain shape fabric 3d images of the anhydrite layer based on computer tomography revealed rare kink folds with axes subparallel to x and boudins which result from tension fracture with increasing layer thickness hi the width of boudins wa increases linearly wa 0 3 1 3 hi the normalized width of boudins wd wa hi is almost constant at 1 5 1 0 these geometrical parameters can be used to reveal fracture boudinage under bulk constriction the oblique orientation of most of the boudins with respect to the principal strain axes results from folding of the boudins by a second generation of folds the latter with axes subperpendicular to the layer

warm humid paleoclimate control of salinized lacustrine organic rich shale deposition in the oligocene hetaoyuan formation of the biyang depression east china abstract lacustrine organic rich shales are widely developed within the oligocene biyang depression in the nanxiang basin in east china and across southeast asia these shales have been proven as hydrocarbon source rocks of crude oil as well as sources and reservoirs of shale oil understanding the deposition of these shales is essential to reconstruct the paleoenvironment and paleoclimate during the oligocene in east china as well as target the potential shale oil resources based on x ray diffraction organic and inorganic petrologic organic and inorganic geochemical and stable isotopic analyses paleoenvironment paleoclimate and hydrocarbon potential of the lacustrine organic rich shales in the oligocene hetaoyuan formation were investigated the mineral composition of hetaoyuan formation organic rich shales is dominated by clay minerals followed by quartz plagioclase calcite dolomite pyrite and gypsum six lithotypes are identified including siltstone silty shale clay shale calcareous shale dolomite shale and massive mudstone the organic matter om of the organic rich shales is dominated by type i kerogen lamalginite maturity parameters tmax biomarker ratios and calculated vitrinite reflectance suggest that the om enters the oil window maturity high toc and generative potential together with high contents of brittle minerals including quartz plagioclase and carbonates reveal the oligocene hetaoyuan formation hold good to very good potential of shale oil exploitation six organic rich shale layers have been identified in the hetaoyuan formation shale layer 1 to 6 from top to bottom among them shale layers 5 and 3 hold the best shale oil potential and therefore be investigated in the present paper shale layer 5 was deposited in a semi deep lacustrine environment under the moderately warm humid paleoclimate further dividing into lower middle and upper units relatively low toc contents av 2 6 wt in the lower unit are probably caused by high sedimentation rate high bioproductivity under favorable preservation conditions led to relatively high toc contents av 3 6 wt in the middle unit less reducing conditions together with moderate low bioproductivity resulted in relatively low toc contents av 2 6 wt in the upper unit warm humid paleoclimate prevailed during deposition of shale layer 3 deepened water depth and formed a deep lacustrine environment the stratified water column led to stable anoxic condition and photic zone euxinia in the saline deep lacustrine environment which enabled the accumulation of high amounts of om av 4 9 wt toc under excellent preservation av hi 710 mg hc g toc the results of core scanning analysis indicate that formation of the laminated shales probably controlled by seasonal fluctuations of paleoclimate

fibrous calcite veins overpressures and primary oil migration the fibrous calcite veins found parallel to the bedding of certain shales may have been formed during burial as a consequence of overpressuring their presence could even be indicative of former overpressures this suggestion if it can be upheld carries implications for theories of primary oil migration

a gravity profile across southern saganash lake fault implications for the origin of the kapuskasing structural zone a high resolution gravity profile with station elevations and locations determined by a differential global positioning system shows that the saganash lake fault that defines the northwestern boundary of the southern kapuskasing structural zone ksz is southeast dipping and of reverse type previous interpretations of a normal fault caused by crustal collapse following east verging thrusting along the ivanhoe lake fault that forms the southeastern boundary of the ksz are no longer tenable instead the reverse nature of the saganash lake fault is more in harmony with a model of the kapuskasing zone whereby its fault bounded uplifted blocks are positive flower structures formed by dextral shear along a zone of left stepping en echelon faults

integrated fluid inclusion analysis and petrography constraints on the petroleum system evolution of the central and southern biyang sag nanxiang basin eastern china abstract we combine integrated fluid inclusion analysis petrography and burial thermal hydrocarbon generation history modeling to delineate multiple generation expulsion charge episodes within the central and southern biyang sag nanxiang basin eastern china basin models suggest the main phase of oil generation occurred between the late eocene and early miocene this period generally corresponds to the three oil expulsion episodes ca 37 5 ma 33 1 ma and 23 0 ma recorded in petroleum inclusions that are hosted in fibrous calcite veins in organic rich shales based on fluorescence spectrum parameters and the api gravities of a set of crude oils used as a calibration the oils expelled during the three expulsion episodes were determined to have been heavy black and light oils fluorescence correlations indicate that the three types of oil inclusions found in the source rocks correspond well with those detected in the reservoirs the first episode of heavy oil emplacement occurred prior to quartz overgrowth whereas the second episode of black oil emplacement was synchronous with quartz overgrowth ferrodolomite and ankerite cements were deposited this being accompanied by a second phase of quartz grain overgrowth dissolution the last episode of light oil emplacement was coincident with the precipitation of ankerite by integrating fluid inclusion th burial thermal models and constraints from oil expulsion timing the timings of the three episodes of oil charge were estimated to be 35 3 ma 31 9 ma and 20 8 ma tectonic deformation related to horizontal compression facilitated trap formation this is thought to be the reason behind the observation that only light oil related to the third charging episode accumulated in the reservoirs

book review the techniques of modern structural geology volume 2 folds and fractures john g ramsay and martin i huber academic press london 1987 xi 309 398 pp price stg17 50 us 34 50 paperback

mineralogy porosity and fluid control on thermal conductivity of sedimentary rocks summary estimates of thermal conductivity of the main non clay and clay sedimentary minerals are presented especially for the case of argillaceous ones these estimates are averaged estimates based on the interpretation of laboratory conductivity porosity and mineralogy measurements performed on small volumes of the order of 100cm3 of water saturated moist and air saturated samples the sampling is representative of the main sedimentary rocks sandstones carbonates evaporites and shales and it is composed of samples considered as structurally isotropic material first we experimentally verify the first order control of mineralogy porosity and fluid content on bulk conductivity and we demonstrate that such influences may be predicted accurately using a geometric mean model as long as isotropic samples are used then we interpret the data using an inverse method in order to estimate the average mineral conductivities of the main non clay and clay minerals which give the best fit to the individual laboratory measurements through the geometric mean model the analysis is based on measurements on 82 non clay samples and 29 clay samples taken on oil well cores or cuttings on outcrops and on artificially recompacted samples estimates of average mineral conductivities returned by the inversion process for the main non clay minerals are similar to generally admitted values 7 7 w m k for quartz 3 3 w m i k for calcite 5 3 w m l k for dolomite and 6 3 w m k for anhydrite values obtained for the clay minerals are systematically lower than those obtained for non clay ones they are of the order of 1 9 w m k for illite and smectite 2 6 w m k for kaolinite and 3 3 w m l k for chlorite these estimates combined with porosity and mineralogy data are used with the geometric mean model in order to verify its first order validity for predicting thermal conductivity of small volumes of porous isotropic sedimentary rocks the bulk conductivity is predicted with an accuracy of the order of f10 per cent for moist or water saturated samples and of the order of f20 per cent for air saturated samples

the effects of sedimentation and compaction on oceanic heat flow summary the estimation of environmental effects forms an important part of the interpretation of oceanic heat flow measurements in particular the perturbations associated with sedimentation and surface temperature changes must be taken into account analytical solutions can be obtained only for individual simplified versions of these problems whereas any real example is complicated by the process of sediment compaction which changes the bulk thermal properties with depth a physical model is developed which uses sediment porosity trends to predict the thermal parameters and material advection rates for an evolving sediment basement system these values are then used in a numerical solution to the heat flow equation to give estimates of the perturbed surface heat flux through time in addition to variations in sedimentation rate sediment type radioactive heat production and surface temperature changes are considered heat flow corrections may vary by up to a factor of 2 according to sediment type while radioactive heat production can offset the effects of sedimentation by as much as 40 per cent the results also indicate that alterations determined from simple analytical models tend to over estimate the true perturbation to the flux

a modified version of archie s law to estimate effective diffusion coefficients of radionuclides in argillaceous rocks and its application in safety analysis studies abstract because of the very low hydraulic conductivity of clay rocks molecular diffusion is the main process responsible for the transport of radionuclides released from the waste matrix into the host rock diffusion values are thus important input parameters in safety analyses because diffusion measurements are very time consuming it is impossible to measure diffusion coefficients for all radionuclides of interest it is therefore important to develop procedures for doing reliable estimates of diffusion coefficients diffusion data of mainly tritiated water hto and anions i cl measured in different sedimentary rocks were taken from the literature the effective diffusion coefficient could be related to the transport porosity by an extended version of archie s law e archie d e d w e m 1 b e m 2 the extended version deviates from the classical law at porosity values below ca 0 1 effective diffusion coefficients of hto 36cl and 22na were measured for a series of swiss clay rocks brauner dogger effingen member opalinus clay and helvetic marls and for one hungarian rock boda claystone formation and could be satisfactorily described by the extended version of archie s law bounded by an upper and a lower curve a method was developed based on e archie for estimating effective diffusion coefficients for a series of radionuclides important input parameters are the accessible porosity of the rock and the diffusion coefficient of the radionuclide in water in case of cations showing surface diffusion a correction term was introduced based on the work of gimmi and kosakowski 2011

geometrical similarity in successively developed folds and sheath folds in the basement rocks of the northwestern indian shield an intensely deformed gneiss migmatite terrane and a relatively undeformed granulite granitoid terrane constitute the bulk of precambrian basement in the northwestern indian shield this article traces the structural evolution in the gneiss migmatite terrane where traditional methods of structural analysis are difficult to apply and shows how successively developed folds can assume identical geometry and orientation at an advanced stage of progressive ductile shearing the gneiss migmatite terrane exemplifies a regional scale ductile shear zone that preserves the history of polyphase folding and sheath folding geometrical similarity between individual domain scale sheath folds and mesoscopic regional scale folds implies that sheath folding is common at all scales in the gneiss migmatite terrane as the mylonite foliation that traces successive folds is curviplanar the successively initiated hinge lines were curvilinear from their inception in the shear zone at the advanced stage of ductile shearing the hinge line curvatures were accentuated due to their rotation towards subvertically directed maximum stretching x and variably oriented fold axial planes were brought into approximate parallelism with the upright principal plane xy of the bulk strain ellipsoid eventually all the folds irrespective of their relative order of development became strongly non cylindrical extremely tight isoclinal and approximately co planar with respect to each other it is due to the above geometrical modifications during ductile shearing that folds irrespective of their order of development now appear identical with respect to isoclinal geometry axial plane orientation and hinge line curvilinearity evidence from the fold orientations the deformed lineation patterns and the sheath fold geometry suggest that the shearing occurred in a general shear type of bulk strain and nnw sse directed subhorizontal compression resulted in subvertically directed stretching in the gneiss migmatite terrane

from carbonate sulphate interbeds to carbonate breccias the role of tectonic deformation and diagenetic processes cameros basin lower cretaceous n spain interpreting the origin of carbonate breccias requires a detailed analysis because they may be the result of a wide variety of processes that produce similar features this is the case of the lower cretaceous carbonate breccias of the cameros basin previously interpreted as slump or collapse breccias whose origin is interpreted after performing a detailed sedimentary petrographic and tectonic study the studied carbonate breccias consist of angular carbonate mudstone fragments floating in a matrix of calcite and quartz crystals the breccias are interbedded with and laterally associated to alternating layers of carbonate mudstone and calcite and quartz pseudomorphs after gypsum which show strong similirities to the breccia fragments and matrix respectively suggesting that the brecciated beds were originally composed of identical alternating carbonate mudstone and gypsum layers as the unbrecciated layers the breccias are associated with frequently polyharmonic deformation structures which are similarly oriented as the regional tectonic structures indicating that they are related with the alpine contractional deformation of this area of the cameros basin all these features suggest that the carbonate breccias were formed by tectonic deformation of alternating layers of carbonate mudstone and calcium sulphate which have very different rheological behaviours as a result during tectonic deformation sulphate flowed and carbonate layers were broken and displaced producing a breccia of carbonate fragments within a sulphate groundmass afterwards the sulphate groundmass was replaced by quartz and calcite and the breccia acquired its final composition

growth of the central andean plateau by tectonic segmentation is controlled by the gradient in crustal shortening abstract crustal deformation orocline formation and growth of the central andean plateau as well as the mutual relations of these processes with climate are a matter of international debate earthquake focal mechanism fault kinematic paleomagnetic and cross section balancing data are paramount for understanding the morphotectonic evolution of this noncollisional orogen but collectively await an explanation in terms of a comprehensive kinematic model we offer such a model that approximates simple shear in plan view and that predicts the kinematics of first order fault zones in the southern central andes the model indicates that segmentation of the upper crust into rhomb shaped domains confined by transpressive ranges resulted from the decrease in crustal shortening with distance to the central bend of the andes an anastomosing network of kinematically coupled reactivated orogen parallel and newly formed ne trending deformation zones encompassing components of sinistral and dextral strike slip res

experimental investigation of thermal maturation on shale reservoir properties from hydrous pyrolysis of chang 7 shale ordos basin abstract thermal maturity has a significant impact on hydrocarbon generation and the storage capacity within shales but explicit and quantitative characterization of that impact on continental shales is scarce to better understand how thermal maturation affects the organic and inorganic changes of the continental shale reservoirs hydrous pyrolysis was performed to simulate the maturation process toc rock eval and adsorption isotherms tests were used to obtain various geochemical parameters of the shale solid residues the results indicate that with pyrolysis temperature increasing from ambient temperature to 550 c the vitrinite reflectance increases from 0 5 to 2 5 ro and the toc total organic carbon loss weight reaches 25 regarding porosity the fraction of micro to meso pores in the shale increases with an increase in the pyrolysis temperature whereas the macro pores do not change significantly the total amount of gas adsorption does not necessarily increase as the toc is consumed but the gas adsorption capacity per unit of toc increases with increasing thermal maturity our finding provides theoretical modelling for identifying shale gas development prospective zones according to thermal maturity mapping and for predicting quantitatively the geochemical and inorganic changes that occur with thermal evolution

using petroleum inclusions to trace petroleum systems a review abstract petroleum bearing fluid inclusions are small encapsulations of oil and gas that offer an invaluable opportunity to better constrain the evolution of petroleum systems insights into palaeo fluid compositions complement observations on present day fluid compositions which represent only the end point of complex cumulative processes throughout basin history in this contribution we review a wide range of approaches used to extract geochemical information from petroleum inclusions and how these can be used to better constrain petroleum systems these techniques can be grouped into optical spectrographic and thermometric non destructive methods or destructive chemical analyses of bulk samples or individual inclusions typically optical methods documenting the distribution and visual properties of petroleum inclusions are used to provide petrographic context for subsequent specialised geochemical analyses of petroleum inclusions additional non destructive techniques such as raman spectroscopy can then be applied to provide some further insights into the composition of the trapped fluids although the complex nature of petroleum generally requires direct access to the fluid for a more complete understanding of geochemical aspects a variety of destructive techniques have been developed initially to analyse bulk samples released by mechanical crushing and more recently through ablation type techniques that allow the composition of individual inclusions to be characterised screening geochemical techniques that utilise mechanical crushing of bulk samples to analyse petroleum inclusions using mass spectrometry without prior chromatographic separation have become routine analyses other geochemical techniques more geared towards detailed molecular information such as biomarkers utilise chromatographic separation prior to mass spectrometry evaluation of the isotopic composition of petroleum inclusions is also possible for both bulk samples and compound specific analyses the use of lasers to open individual inclusions allows the released contents to be analysed by thermal extraction gas chromatography mass spectrometry gc ms or mass spectrometric mapping of minerals using time of flight secondary ion mass spectrometry tof sims a surface sensitive analytical method that uses ion beams to ablate into minerals the continued evolution of techniques to analyse the incredibly small volume of hydrocarbons trapped within fluid inclusions has progressed to a point where there is little that can be done to evaluate a live oil or gas sample that cannot be achieved for a fluid inclusion sample the full power for tracing petroleum systems is however only realised where there is an effective integration of fluid inclusion data with a more conventional approach to petroleum systems analysis

episodic gravitational collapse and migration of the mountain chain during orogenic roll on in the himalayas an w e belt of maximum bulk horizontal shortening the orogen core moved north relative to the overlying crust to form the himalayan syntaxes due to roll on of this portion of the indian plate this displacement occurred below a lengthy succession of gently dipping decollements that formed episodically at a depth of 30 km along the orogen core due to numerous periods of gravitational collapse and spreading of the overlying ductile crust successively developed basal decollements were deformed when continued bulk horizontal shortening of the orogen core below reasserted dominance over the effects of gravitational collapse above causing refolding about steeply dipping axial planes this resulted in northwards migration of the orogen core above depths of 30 km causing rocks metamorphosing at depths of 22 km on the north side of the orogen core to be moved to its south side with no change in depth as roll on progressed garnet porphyroblasts record this lengthy history of lateral migration across the orogen within their inclusion trails the 6 4 kbar average pressures accompanying it were obtained from the mn fe and ca contents of successive garnet cores garnet grew at depths of 22 km until movement towards the surface initiated on successively developed decollements that accommodated the volume constraints of gravitational collapse and spreading on both sides of the orogen the speed of extrusional displacement increased the further the rocks migrated from the orogen core developing mylonitic schists around the porphyroblasts this truncated inclusion trails against all matrix foliations as the porphyroblasts were carried towards the surface indeed these rocks were multiply deformed during at least four distinct periods of deformation after mylonitization began and prior to exposure above the main central thrust mct three or more sub vertical and sub horizontal foliations were formed during each of the five changes in fia trend foliation inflection intersection axes in porphyroblasts preserved in these rocks the inclusion trail asymmetries and p t of garnet core growth accompanying each fia reveal that the first four changes in fia trend which define periods of tectonism about one direction of horizontal bulk shortening relative plate motion occurred on the north side of the orogen core the fifth occurred on the south side of the orogen core and the switch in shear sense on gently dipping foliation planes that resulted from this shift to the south eventually led to the development of the mct when magnetic anomaly 22 that formed in the southern indian ocean ridge is taken into account these five changes in fia trend correlate markedly with changes in the motion of india relative to a constant eurasia from 50 to c 25 ma they reveal that eurasia moved nnw during fias 1 3 and 4 and sse during fia 5 when the shear sense on gently dipping foliations switched to top to the s they suggest collision of india with eurasia took place at 50 ma immediately prior to the development of fia 1

constraints on the fluid supply rate into and through gas hydrate reservoir systems as inferred from pore water chloride and in situ temperature profiles krishna godavari basin india abstract we estimate the rate of upward pore fluid flow and chlorinity cl concentrations at depth through a joint analysis of cl concentration and temperature versus depth profiles obtained from gas hydrate related test sites drilled and cored in the krishna godavari basin off the eastern coast of india cl measured on conventional core samples decreases with depth at all sites but some of the cl profiles show a prominent convex shape whereas in situ temperature profiles obtained by the advanced piston coring temperature probe are mostly linear at all sites established during the national gas hydrate program 02 expedition nghp 02 assuming a one dimensional time dependent model for the advection of pore fluid including the sedimentation effect and depth dependent diffusivity we estimate darcy velocity and the cl concentrations at depth the best fit darcy velocity of 1 2 1 6 10 11 m s was estimated for the sites along the crest of the regional anticlinal structure in the nghp 02 area b which was significantly faster than those on the flanks of the anticline because the thermal diffusion coefficient is much larger than the chloride ion diffusion coefficient estimated darcy velocities are not great enough to generate nonlinear temperature profiles with depth which is consistent with observed linear thermal profiles

large magnitude continental extension an example from the central mojave metamorphic core complex the central mojave metamorphic core complex is defined by a belt of miocene brittle ductile extension and coeval magmatism the brittle ductile fault zone defines a basin and dome geometry that results from the interference of two orthogonal fold sets that we infer to have formed by mechanically independent processes one fold set contains axes that lie parallel to the extension direction of the shear zone and has a maximum characteristic wavelength of about 10 km the axial surfaces of these folds can be traced from the footwall mylonites through the brittle detachment and into hanging wall strata however folds of mylonitic layering have smaller interlimb angles than those of the brittle detachment suggesting that the folds began to form during ductile shearing and continued to amplify in the brittle regime possibly after movement across the fault zone ceased mesoscopic fabrics related to the transport parallel fold set indicate that the folds record true crustal shortening perpendicular to the extension direction we interpret these folds to form in response to elevated horizontal compressive stress perpendicular to the extension direction and suggest that this stress regime may be a natural consequence of large magnitude extension the other fold set has axes perpendicular to the extension direction and a characteristic maximum wavelength of about 50 km mesoscopic fabrics related to these folds include northwest striking joints kink bands and en echelon tension gash arrays these fabrics formed after mylonitization and record both layer parallel extension and northeast side up subvertical shear the postmylonitic fabrics are kinematically compatible with rolling hinge style isostatic rebound of the footwall following tectonic denudation the relative timing of extension related magma intrusion and ductile deformation varies through the central mojave metamorphic core complex on the scale of the small mountain ranges that make up the central mojave metamorphic core complex no correlation was observed between either shear zone thickness or intensity of ductile deformation and either the proximity or relative volume of extension related igneous rocks this suggests that models that invoke a single upper crustal genetic relationship such as magmatism triggering extension or vice versa do not apply to the central mojave metamorphic core complex systematic variation in the relative timing of dike emplacement and mylonitization suggests that at the time of dike emplacement rocks in the mitchel range were below the brittle ductile transition while those in the hinkley hills were above it the hinkley hills and mitchel range are separated by 2 km in the dip direction of the fault zone which suggests that the vertical thickness of the brittle ductile transition probably was between 100 and 950 m

dike propagation and magma flow in a glassy rhyolite dike a structural and kinematic analysis exhumed magma conduits provide important evidence of the development and evolution of subvolcanic plumbing systems we use a 5 14 m thick flow banded rhyolite dike in arran scotland to present the first reconstruction of the directions and styles of initial propagation and subsequent magma flow based on mesoscale kinematic indicators the dike has concave inward dike margin segments with plumose like structures that record vertical and horizontal propagation of lobes which inflated and linked to form a through going sheet devitrified rhyolite zones at the dike margins show gentle to open folds in contrast glassy central parts of the dike are flow laminated and preserve folded and refolded isoclinal curvilinear folds and sheath folds that record sustained progressive deformation the inner interface between the glassy and devitrified facies is abrupt and marked by elongation lineations and mullions in the dike center fold axes plunge 27 ne along the dike and parallel to elongation lineations combined with shear sense indicators and objects sheared vesicles and asymmetric folds these features indicate that magma flow was obliquely upward to the southwest and locally 60 to the propagation direction of the dike the distribution of structures within the rhyolite indicates local accretion of the now devitrified material to the margins with localization of flow into the center of the dike we find that the initial magma flow direction was controlled by fracture propagation and interaction with the subsequent flow record controlled by accretion and flow localization in the conduit this study demonstrates that analysis of mesoscopic structural and kinematic features several of which have not previously been reported from dikes is a powerful tool that can be used to reconstruct the complex evolution of conduit initiation and magma flow processes

primary and tectonic fabric intensities in mudrocks abstract in this paper we present a summary of quantitative measurements of the preferred orientation of phyllosilicate grains in a variety of tectonically weakly deformed to undeformed fine grained pelitic rocks we also briefly examine a small amount of data on clay fabrics in deep sea cores and compare them to fabrics in deformed equivalents from the mariposa formation and calaveras complex sierra nevada california the measured fabric ellipsoids support the following conclusions 1 a bedding parallel foliation forms in pelitic rocks during compaction that in our samples is associated with shortening between 3 and 74 2 the amount of compaction is in part controlled by the quartz feldspar content interbedded sandy layers undergo little to no compaction and do not develop bedding parallel foliations and 3 it is impossible to determine precisely the amounts of compaction horizontal shortening and later tectonic strain in deformed samples because of the variability of initial compactions our data and results presented by others indicate that strain paths in pelitic rocks always include early compaction followed by an episode of simultaneous compaction and plane strain in accretionary wedges and by a variety of other types of strain in other settings

combined use of confocal laser scanning microscopyand pvt simulation for estimating the composition andphysical properties of petroleum in fluid inclusions we present a method to determine the composition and pvt properties of petroleum inindividual petroleum fluid inclusions confocal laser scanning microscopy is used to generatethree dimensional images of single petroleum inclusions because liquid petroleum fluorescesunder the laser the images readily distinguish the liquid and vapour within the inclusion and canbe used to determine the inclusions volumetric liquid vapour ratio using pvt modellingsoftware the liquid vapour ratio is used along with the homogenisation temperature to determinethe bulk composition phase envelope isochore and a range of physical properties of the includedpetroleum this is done using an iterative series of pvt calculations which match twoparameters 1 the molar volume of the petroleum at room and homogenisation temperatures 2 the liquid vapour ratio of the inclusion at room temperature key uncertainties in the methodare explored including the accuracy with which the liquid vapour ratio can be determined thecomposition of the titrant gas used in the iterative procedure and the composition of thepetroleum chosen to model the physical properties of the included petroleum data from coevalinclusions suggest that the saturation pressure gas oil ratio viscosity molar volume densityand surface tension of included petroleum are determined with a precision of a few percent confirmation of the accuracy of the method awaits tests using inclusions grown in the laboratoryunder carefully controlled pvtx conditions however it is likely that the physical properties ofincluded petroleums are more accurately modelled by fluids which are genetically related tothem if proven to be accurate the method will provide a routine method for determiningpalaeopressure in petroleum systems finally we present data from a central north sea examplewhich are geologically realistic and which for the first time record the evolution of fluid pressureand petroleum composition in a petroleum reservoir

practical kinetic modeling of petroleum generation and expulsion abstract models for petroleum generation used by the industry are often limited by a sub optimal laboratory pyrolysis methods for studying hydrocarbon generation b over simple models of petroleum generation c inappropriate mathematical methods to derive kinetic parameters by fitting laboratory data d primitive models of primary migration expulsion and its coupling with petroleum generation and e insufficient use of subsurface data to constrain the models problems a b and c lead to forced compensation effects between the activation energies and frequency factors of reaction kinetics that are wholly artificial and which yield poor extrapolations to geological conditions simple switch or adsorption models of expulsion are insufficient to describe the residence time of species in source rocks yet the residence time controls the thermal stresses to which the species are subjected for cracking to lighter species the shellgenex model for petroleum generation and expulsion has been developed since 1988 in this multi species model the rate limiting step of primary migration is treated as the slow diffusion of the petroleum through the kerogen itself other key aspects of the model are the reaction and transport behaviour of the heavy compounds the role of free radicals in the cracking kinetics of hydrocarbon species in the model and the evolving free volume of the kerogen the last of these has a particularly strong effect on the primary migration of the generated petroleum molecules some implications of this model are that a compositions of expelled petroleum vary more strongly than the standard parallel reaction model suggests and b expulsion is not immediately extinguished by waning temperatures and pressures but continues with decreasing gor of the expelled petroleum and increasing density of the expelled oil

geochemical comparison of oil bearing fluid inclusions and produced oil from the toro sandstone papua new guinea abstract a detailed study was carried out to compare the geochemistry of the crude oil in the lower cretaceous toro sandstone reservoir in the iagifu 7x well with oil trapped in fluid inclusions in this sandstone in the iagifu 7x and p nyang 2x wells in the papuan fold belt the drill stem test dst oils and the oils trapped in fluid inclusions show different source and maturity dependent geochemical parameters biomarkers suggest that the dst oils at iagifu 7x were derived from clay rich mixed marine terrestrial source rocks deposited under oxic conditions probably middle to late jurassic mudstones the fluid inclusion oils were derived from a less terrestrially influenced marine source rock deposited under less oxic conditions the fluid inclusion oils contain 1 2 7 trimethylnaphthalene and oleanane biomarkers indicative of angiosperm input and a cretaceous or younger source rock these oils are more mature calculated reflectance rc 1 02 than the reservoired oil at iagifu 7x rc 0 84 and condensate at p nyang 2x rc 0 84 source and thermal maturity parameters for all three fluid inclusion samples are similar suggesting that they were derived from similar source rock facies furthermore samples with predominantly blue vs white fluorescing oil inclusions have no discernible geochemical maturity difference suggesting that the use of fluorescence colours as a qualitative guide to the maturity of the trapped oil is not valid in this case fluid inclusion oils were trapped prior to charge of the reservoir with oil at the iagifu 7x and gas condensate at the p nyang 2x wells the fluid inclusion oils therefore represent an early oil charge from a deeply buried probably cretaceous source rock which started migrating into the toro sandstone during the miocene at iagifu this early oil was probably diluted by a larger volume of jurassic oil generated at the end of the miocene the absence of fluid inclusions with compositions like the currently reservoired oil is interpreted to be due to oil charging an already oil saturated zone when diagenesis is likely to have been inhibited at the p nyang well the transition from oil as represented by the oil inclusions to gas condensate was most likely caused by gas displacement

structural metamorphic evolution of the tia complex new england fold belt thermal overprint of an accretion subduction complex in a compressional back arc setting rocks in the tia complex underwent a simple clockwise p t t deformation path moving from mid crustal levels at blueschist facies conditions d1 d2 6 kbar 200 c to upper crustal levels at high t amphibolite facies conditions d4 d5 2 5 kbar 600 c in a relatively short time 15 ma the rocks remained under these conditions for approximately 40 ma d6 before they cooled and were brought to the surface d7 d8 during d6 permian rift basins were opening as thermal gradients in the tia complex reached a maximum d1 2 deformation was associated with accretion subduction processes and was followed by progressively less intense mainly e w oriented compression and uplift during d3 5 bringing the rocks to within 2 kbars of the surface d6 is characterized by limited extensional deformation and final uplift took place during d7 8 along shear zones that have orientations similar to d3 5 thrusts the shift from subduction dominated processes to thermally dominated processes occurred during d3 4 uplift of 4 kbar around 310 300 ma this coincided with a change in tectonic setting of the tia complex from an accretionary prism to a back arc position as the subduction zone stepped eastward an increased heat flow associated with back arc processes gradually caused thermal weakening of the lithosphere which due to external subduction related compressive forces resulted in uplift d3 with continued heating of the crust thermal doming resulted and uplift stopped d4 5 whilst thermal weakening led to limited crustal collapse as permian basins opened d6 the extremely high heat flow that was maintained for 40 ma suggests a heat source external to the crust possibly associated with thermal relaxation dehydration and detachment of the remnant stab left beneath the new england orogen after the subduction zone shifted east a stable crustal thermal structure was re established by 260 ma as the crust strengthened and could further support subduction induced compressional structures d7 8

effects of tectonic compression on petroleum accumulation in the kelasu thrust belt of the kuqa sub basin tarim basin nw china abstract the kelasu thrust belt is a favorable hydrocarbon accumulation zone in the kuqa sub basin with several known giant gas fields including the dabei and kela 2 gas fields as well as the dawanqi oil field the origin and accumulation process of the hydrocarbons were investigated through an integrated petroleum geochemistry and fluid inclusion analysis and basin modeling geochemical parameters indicate that the light oils from the dawanqi oil field and dabei gas field were generated from different sources as compared with light oils from the kela 2 gas field light oils from the dawanqi oil field and dabei gas field are primarily derived from the terrestrial mudstones in the jurassic qiakemake j2q formation with a maturity level of 1 4 1 6 ro whereas light oils from the kela 2 gas field are mainly derived from the terrestrial mudstones in the triassic huangshanjie t3h with a maturity level of 1 6 1 8 ro gases in the kelasu thrust belt are dominated by coal type gas and are primarily generated from the jurassic coal measures carbon isotope ratios suggest that gases in the dawanqi oil field and dabei gas field were generated at a thermal maturity level of 1 6 2 3 ro while gas in the kela 2 gas field was generated at a thermal maturity level of 2 1 2 5 ro two episodes of oil and one episode of gas charge were delineated in the dabei gas field the second episode of oil charge occurred around 5 4 ma while gas charge occurred around 3 2 ma three episodes of oil and one episode of gas charge were identified in the kela 2 gas field the latter two episodes of oil charge occurred around 5 5 4 5 ma and the gas charge occurred around 3 2 ma the timing of the petroleum charge was also confirmed by the correlation between the maturity of the source rocks during the times of charge and the maturity levels of the light oil and gas in the reservoirs the later oil and gas charge occurred at the same period in both the dabei and kela 2 gas fields possibly relating to structural reactivation caused by regional tectonic compression because intense tectonic compression and rapid uplift of the tianshan mountains occurred during the same period which may have caused thrust fault activation and opening hydrocarbon expulsion from the source rocks during the period was possibly also related to the regional tectonic movement providing hydrocarbon sources for the reservoirs

superposed buckle folding in the eastern iberian chain spain abstract the aliaga area eastern iberian chain shows large scale examples of buckle superposition developed during tertiary folding in most cases ene trending folds overprint earlier nnw sse trending ones the resulting structures are mapped analysed and genetically classified by comparison with analogue models described by several authors the following types are found standard type 1 1a dome and basin structure 1b unequal wavelength overprinted folds modified type 1 1c t shaped joined folds 1d t shaped abutting folds 1e l shaped folds 1f snake like folds standard type 2 2a non cylindrical buckling of earlier axial surfaces involving hinge replacement different superposed sets of flexural slip striations record successive folding episodes in snake like folds and hinge replacement in the case of type 2a superpositions types 1 and 2 apparently develop where the earlier folds have interlimb angles over and below 90 respectively which fits the results of analogue modelling and theoretical analysis by previous authors types 1b and 1d are associated with higher w1 w2 wavelength ratios than types 1a and 1c other controlling factors are viscosity contrast and erosion processes specifically erosion of competent limestone beds in the hinge zone of a nnw sse trending anticline allowed the near vertical eastern limb to be refolded into snake like folds

strain and possible volume loss in a high grade ductile shear zone small scale ductile shear zones in high grade metagabbros from the caledonides of northern sweden provide a good opportunity for examining the development of fabric and strain in rocks undergoing progressive non coaxial deformation the rocks contain strain markers in the form of aggregates of plagioclase feldspar a selected shear zone is analyzed assuming monoclinic symmetry which requires for the zone as a whole variable simple shear variable volume change or variable simple shear and volume change plus a homogeneous deformation both size of the feldspar aggregates and aspect ratio of the aggregates plotted against orientation indicate significant volume decrease in excess of 50 and perhaps as much as 80 towards the centers of the zones the data are broadly consistent with a deformation path involving constant shear strain across the zone followed by variable volume change or by a path of progressive loss of volume with increasing shear strain followed by a homogeneous strain they are not consistent with a single path involving rates of shear strain and volume loss that are in constant proportions there is little difference in chemical composition between the shear zone and the surrounding rock an analysis of the concentrations of elements in the shear zone and wall rock suggests that volume changes were slight 15 the discrepancy between the values of volume change estimated from strain analysis and geochemical analysis may be resolved either by geochemical equilibration being attained after deformation or by a departure from the geometric constraints of the monoclinic band model for shear zones modification of marker particle size and shape during dynamic recrystallization may also partly account for the apparent volume loss