granite ascent and emplacement during contractional deformation in convergent orogens based on a case study in the central maine belt of west central maine u s a it is proposed that crustal scale shear zone systems provide an eaective focussing mechanism for transfer of granite melt through the crust in convergent orogens during contractional deformation flow of melt in crustal materials at depths below the brittle plastic transition is coupled with plastic deformation of these materials the flow is driven by pressure gradients generated by buoyancy forces and tectonic stresses within the oblique reverse central maine belt shear zone system stromatic migmatite and concordant to weakly discordant irregular granite sheets occur in zones of higher strain which suggests percolative flow of melt to form the migmatite leuco somes and viscous flow of melt channelized in sheet like bodies possibly along fractures cyclic fluctuations of melt pressure may cause instantaneous changes in the eaective permeability of the flow network if self propa gating melt filled tensile and or dilatant shear fractures are produced due to melt enhanced embrittlement in homogeneous migmatite and schlieric granite occur in zones of lower strain which suggests migration of partially molten material through these zones en masse by granular flow and channelized flow of melt carrying entrained residue founded on the central maine belt case study we develop a model of melt extraction and ascent using the driving forces stress conditions and crustal rheologies in convergent especially transpressive orogens ascent of melt becomes inhibited with decreasing depth as the solidus is approached for intermedi ate a h2o muscovite dehydration melting the water saturated solidus occurs between 400 and 200 mpa near the brittle plastic transition during high t low p metamorphism where the balance of forces favors sub horizontal fracture propagation emplacement of melt may be accommodated by ductile flow and or stoping of wall rock and inflation may be accommodated by lifting of the roof at shallower crustal levels and or sink ing of the pluton floor the resultant plutons have sub horizontal tabular geometries with floors that slope down to the ascent conduits although these plutons may have locally discordant relations with country rock structures when viewed at the crustal scale granite ascent and emplacement in convergent orogens are syn tec tonic processes 1998 elsevier science ltd all rights reserved

geochemistry origin and accumulation of petroleum in the eocene wenchang formation reservoirs in pearl river mouth basin south china sea a case study of hz25 7 oil field abstract the pearl river mouth basin in the south china sea has accumulated 2 km of eocene sediments in its deep basin and has become the exploration focus due to the recent discoveries of the hz25 7 oil field in the eocene wenchang e 2 w formation in this study the geochemical characteristics of potential source rocks and petroleum in the hz25 7 oil field are investigated and the possible origins and accumulation models developed the analytical results reveal two sets of potential source rocks e 2 w and enping e 2 e formations developed in the study area the semi deep to deep lacustrine e 2 w source rocks are characterized by relatively low c 29 steranes low c 19 c 23 tricyclic terpane 24 tetracyclic terpane c 30 hopane trans trans trans bicadinane t c 30 hopane most 30 4 methyl sterane c 29 sterane 0 2 ratios in contrast the shallow lacustrine and deltaic swamp plain e 2 e source rocks are characterized by relatively high c 29 steranes high c 19 c 23 tricyclic terpane 0 6 high c 24 tetracyclic terpane c 30 hopane 0 1 variable yet overall high t c 30 hopane and low c 30 4 methyl sterane c 29 sterane 19 c 23 tricyclic terpane ratios mean value 0 39 low c 24 tetracyclic terpane c 30 hopane ratios mean value 0 07 high c 30 4 methyl sterane c 29 sterane ratios mean value 1 14 and relatively high c 27 regular sterane content of petroleum in the hz25 7 oil field indicate that the petroleum most likely originated from the e 2 w formation mudstone in the huizhou depression one stage of continuous charging is identified in the hz25 7 oil field oil injection is from 16 ma to present and peak filling occurs after 12 ma thin sandstone beds with relatively good connectivity and physical properties porosity and permeability in the e 2 w formation are favorable conduits for the lateral migration of petroleum this petroleum accumulation pattern implies that the e 2 w formation on the western and southern margins of the huizhou depression are favorable for petroleum accumulation because they are located in a migration pathway thus exploration should focus in these areas in the future

petroleum generation and charge history of the northern dongying depression bohai bay basin china insight from integrated fluid inclusion analysis and basin modelling abstract the petroleum generation and charge history of the northern dongying depression bohai bay basin was investigated using an integrated fluid inclusion analysis workflow and geohistory modelling one and two dimensional basin modelling was performed to unravel the oil generation history of the eocene shahejie formation es3 and es4 source rocks based on the reconstruction of the burial thermal and maturity history calibration of the model with thermal maturity and borehole temperature data using a rift basin heat flow model indicates that the upper interval of the es4 source rocks began to generate oil at around 35 ma reached a maturity level of 0 7 ro at 31 30 ma and a peak hydrocarbon generation at 24 23 ma the lower interval of the es3 source rocks began to generate oil at around 33 32 ma and reached a maturity of 0 7 ro at about 27 26 ma oil generation from the lower es3 and upper es4 source rocks occurred in three phases with the first phase from approximately 30 20 ma the second phase from approximately 20 5 ma and the third phase from 5 ma to the present day the first and third phases were the two predominant phases of intense oil generation samples from the es3 and es4 reservoir intervals in 12 wells at depth intervals between 2677 7 m and 4323 0 m were investigated using an integrated fluid inclusion workflow including petrography fluorescence spectroscopy and microthermometry to determine the petroleum charge history in the northern dongying depression abundant oil inclusions with a range of fluorescence colours from near yellow to near blue were observed and were interpreted to represent two episodes of hydrocarbon charge based on the fluid inclusion petrography fluorescence spectroscopy and microthermometry data two episodes of oil charge were determined at 24 20 ma and 4 3 ma respectively with the second episode being the predominant period for the oil accumulation in the northern dongying depression the oil charge occurred during or immediately after the modelled intense oil generation and coincided with a regional uplift and a rapid subsidence suggesting that the hydrocarbon migration from the already overpressured source rocks may have been triggered by the regional uplift and rapid subsidence the expelled oil was then charged to the already established traps in the northern dongying depression the proximal locations of the reservoirs to the generative kitchens and the short oil migration distance facilitate the intimate relationship between oil generation migration and accumulation

first palaeomagnetic results from the cycladic massif greece and their implications for miocene extension directions and tectonic models in the aegean abstract the aegean region is characterised by major fault bound blocks with markedly contrasting structural trends recent models account for these variations either through differential block rotation or through a process of radial extension the cycladic massif in the back arc region to the hellenic trench represents a critical area where apparently divergent extension directions are observed this contribution provides the first palaeomagnetic results from this area magnetic remanence and ams data are presented for middle miocene granodiorites on the islands of mykonos and naxos these rocks are exposed in the footwalls of major extensional detachments within the metamorphic core complexes that characterise the cycladic massif a clear correlation between the orientation of an l s fabric developed within the intrusions and the magnetic fabric data is observed demonstrating the presence of a normal magnetic fabric of extensional origin the mean extension directions inferred from the orientations of the maximum axes of the magnetic susceptibility ellipsoids are markedly divergent at 064 mykonos and 351 naxos northeasterly in situ magnetic remanences are observed on mykonos whereas those on naxos are directed to the nnw neither direction corresponds to the appropriate palaeomagnetic reference direction for the miocene standard palaeomagnetic tilt corrections cannot be applied at these sites because of the lack of palaeohorizontal markers deviations of in situ remanences away from the reference direction are potentially due to rotation around any one of an infinite number of net tectonic rotation axes each of these may be arbitrarily decomposed into components of tilting and vertical axis rotation geologically realistic solutions which restore the in situ magnetisations back to the reference direction may be found by consideration of regional structural trends assuming that tilting is controlled by the major block bounding faults these solutions indicate significant components of differential vertical axis rotations across the cyclades mykonos is bound by nw se trending regional faults and is shown to have rotated clockwise by ca 22 in contrast naxos is bound by ene wsw trending structures and has rotated anticlockwise by ca 33 the apparent divergence of extension directions inferred from both the magnetic anisotropy and structural data is resolved by correcting the mean ams data for subsequent rotation using the rotation solutions derived from the magnetic remanence data the data imply that the primary middle miocene extension direction in the cycladic massif was nearly uniform along a nne ssw azimuth we consider that the uniform extension direction and opposing senses of block rotation determined for this portion of the cycladic massif are most consistent with a recent model describing deformation within the aegean in terms of a system of broken fault bounded slats within this scenario mykonos occupies a position on a clockwise rotating slat which continues northwest at least as far as evvia a major ene wsw trending fault between the islands previously identified on shallow seismic sections separates this domain from an anticlockwise rotating slat which includes naxos

strain localization within a syntectonic intrusion in a back arc extensional context the naxos monzogranite greece although fundamental to the understanding of crustal dynamics in extensional setting the relationships between the emplacement of granitic intrusions and activity of detachments still remain very elusive through a multi scale approach we here document a continuous deformation history between the monzogranitic intrusion of naxos and the naxos paros detachment system cyclades greece field observations first show an early magmatic deformation followed by solid state ductile and then brittle deformation when approaching the detachment zone as evidenced by the overprinting of mylonites by cataclastes and pseudotachylites from these observations we define six strain facies that characterize a positive strain gradient from core to rim of the naxos monzogranite based on field pictures x ray tomography and electron backscatter diffraction ebsd analyses along the strain gradient we then quantify the intensity of mineralogical fabrics in 2d and 3d and better characterize the deformation mechanisms our measured shape variations of the strain ellipsoid corroborate the large scale strain gradient showing a good correlation between qualitative and quantitative studies in addition ebsd data indicate that dislocation creep was predominant during cooling from more than 500 c to temperature conditions of the ductile to brittle transition however 1 a weakening of quartz lattice preferred orientation with increasing strain and 2 evidence of numerous four grain junctions in high strain shear bands also indicate that grain boundary sliding significantly contributed to the deformation although the source of grain boundary sliding remains to be constrained it provides a consistent approach to account for strain localization in naxos

structure and kinematics of upper cenozoic extensional detachment on naxos and paros cyclades islands greece this paper presents a study of the ductile and brittle deformation on naxos and paros islands cyclades greece previous maps and studies of the two islands have shown that a major low angle fault zone separates surface rocks above the contact from an initially deep seated unit below showing a metamorphic evolution from high to low pressures structural analysis as well as available stratigraphical metamorphic and geochronological data taken together demonstrate that this fault zone is a major normal sense detachment zone dipping to the north rapid denudation of footwall rocks subsequent to high temperature metamorphism at an estimated rate of 1 8 9 5 mm yr attests for tectonic unroofing during regional scale top to the north ductile shearing the change from ductile to brittle behavior of the footwall rocks together with a progressive localization of high strain intensity deformations just below the hangingwall is explained by the progressive cooling of the uprisen footwall of the detachment mio pliocene clastic sediments in the hangingwall represent the infilling of half grabens opened in between major normal faults that are synthetic to the underlying ductile shear zone these sediments are as old as aquitanian 25 ma or younger than the earliest recognized evidence of ductile extension in the footwall this provides a minimum age for the onset of extension in the cyclades which appears significantly older than maximum ages reported up to now 13 5 ma structural data strongly suggest that the detachment fault was initially rather low dipping 35 an evolutionary model is proposed in which migmatite domes in the footwall correspond to the uprise of the lower ductile crust between two separating upper crustal blocks during a process of asymmetric boudinage of the crust this detachment model applies to a previously thickened continental lithosphere which then suffers thermal relaxation and weakening allowing extensional deformation to reach a climax during and subsequent to high temperature metamorphism in the cyclades crustal scale extension started after early cenozoic thrusting while the crust was still thick or less likely before late underthrusting below the present surface

interactions between plutonism and detachments during metamorphic core complex formation serifos island cyclades greece in order to better understand the interactions between plutonic activity and strain localization during metamorphic core complexes formation the miocene granodioritic pluton of serifos cyclades greece is studied this pluton 11 6 9 5 ma intruded the cycladic blueschists during thinning of the aegean domain along a system of low angle normal faults belonging to the south dipping west cycladic detachment system wcds based on structural fieldwork together with microstructural observations and anisotropy of magnetic susceptibility ams we recognize a continuum of deformation from magmatic to brittle conditions within the magmatic body this succession of deformation events is kinematically compatible with the development of the wcds the architecture of the pluton shows a marked asymmetry resulting from its interaction with the detachments we propose a tectonic scenario for the emplacement of serifos pluton and its subsequent cooling during the aegean extension 1 a first stage corresponds to the metamorphic core complex initiation and associated southwestward shearing along the meghalo livadhi detachment 2 in a second stage the serifos pluton has intruded the dome at shallow crustal level piercing through the ductile brittle meghalo livadhi detachment southwest directed extensional deformation was contemporaneously transferred upward in the crust along the more localized kavos kiklopas detachment 3 a third stage was marked by syn magmatic extensional deformation and strain localization at the contact between the pluton and the host rocks resulting in narrow shear zones nucleation which 4 continued to develop after the pluton solidification

molecular isotopic characterisation of hydrocarbon biomarkers in palaeocene eocene evaporitic lacustrine source rocks from the jianghan basin china immature organic matter in lacustrine source rocks from the jianghan basin eastern china was studied for distributions and stable carbon isotopic compositions 13 c of hydrocarbon biomarkers all of the bitumens contain isorenieratane 13 c ca 17 indicating the presence of chlorobiaceae and thus periods of euxinic conditions extended into the photic zone aliphatic hydrocarbon fractions are dominated by pristane and phytane and contain relatively low amounts of 4a and 4 methylsteranes c 30 13 c ca 16 believed to originate from 4 methylsterols in dinoflagellates 13 c values of gammacerane ca 24 and c 30 17 21 h hopane ca 23 are consistent with an origin from bacterivorous ciliates that fed on chlorobiaceae the bitumens contain low relative amounts of organo sulphur compounds one rock contains c 37 and c 38 n alkanes 13 c ca 36 derived from alkadienes and alkenones of prymnesiophytes the distributions of hydrocarbon biomarkers suggest that they were initially sulphurised during early diagenesis and later released during early thermal maturation

evolution of boudins under progressively decreasing pore pressure a case study of pegmatites enclosed in marble deforming at high grade metamorphic conditions naxos greece during ductile deformation of marbles under high grade metamorphic conditions on naxos greece pegmatites enclosed in the marbles were deformed in a brittle fashion forming blocky boudins with quartz crystallized in the interboudin zones we studied the three dimensional geometry of the boudins in the field and in two large samples the first sample was serially sectioned to observe the structural and microstructural evolution in the second sample we mapped the surface morphology of the deformed pegmatite in profile the boudins can be classified as symmetric torn type boudins evolving towards asymmetric boudins with a later domino boudin component in three dimensions however the morphology of the boudinaged pegma tite is a simple set of normal faults with mode i fractures in the fault tips and rotation of the fault blocks to accommodate the extension in the marble deformation history was constrained by petrology and microstructures in combi nation with simple order of magnitude calculations of both the cooling and pore fluid pressure evolution the dynamically recrystallized coarse grained calcite of the marble provides clear evidence that after the pegmatite intruded the marble and solidified it was deformed at peak conditions of m2b metamorphism 670 c and 0 6 gpa such pegmatitic melts contain 10 percent h2o which is released during crystalliza tion we infer that after crystallization of the pegmatite the pore fluid pressure in the pegmatite remained close to lithostatic due to the very low permeability of the surrounding marble and the pegmatite was deformed at very low effective stress which led to brittle deformation of feldspar and mode i fracturing of the pegmatite forming torn type boudins with time the pore fluid pressure slowly decreased increasing the effective stress ongoing n s extension thus resulted in slip along the quartz filled interboudin zones and in block rotation producing domino boudins

is there a link between faulting and magmatism in the south central aegean sea a distinct spatial relationship between surface faulting magmatic intrusions and volcanic activity exists in the aegean continental crust in this paper we provide detailed structural observations from key onshore areas as well as compilations of lineament maps and earthquake locations with focal plane solutions from offshore areas to support such a relationship although pluton emplacement was associated with low angle extensional detachments the nne to ne trending strike slip faults also played an important role in localizing the middle miocene plutonism providing ready pathways to deeper magma batches and controlling the late stage emplacement and deformation of granites in the upper crust additionally the linear arrangements of volcanic centres from the quaternary volcanoes along the active south aegean volcanic arc are controlled primarily by ne trending faults and secondarily by nw trending faults these volcanic features are located at several extensional settings which are associated with the main ne trending faults such as i in the extensional steps or relay zones between strike slip and oblique normal fault segments ii at the overlap zones between oblique normal faults associated with an extensional strike slip duplex and iii at the tip zone of a ne trending divergent dextral strike slip zone the ne trend of volcano tectonic features such as volcanic cone alignments concentration of eruptive centres hydrothermal activity and fractures indicates the significant role of tectonics in controlling fluid and magma pathways in the aegean upper crust furthermore microseismicity and focal mechanisms of earthquakes in the area confirm the activity and present kinematics of these ne trending faults

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

paleoenvironmental reconstruction of the late santonian songliao paleo lake the late cretaceous is often characterized as having a variable greenhouse climate however the relatively few continental sites preserving geologic records from this time exist limiting information on terrestrial climate and environments worldwide the songliao basin slb of northeastern china is one of the largest cretaceous age continental rift basins thus this well preserved lacustrine deposit provides a unique record of terrestrial paleoenvironmental conditions during the cretaceous here we report organic geochemical data from late cretaceous age lacustrine deposits lower nenjiang formation from the eastern side of the slb outcrop samples were collected from the houjingou section and the following analyses were performed 1 total organic carbon toc content and isotopic composition 2 biomarker distribution including the identification and determination of relative amounts of both aliphatic and aromatic hydrocarbons and steranes and 3 compound specific stable carbon and hydrogen isotopic compositions of n alkanes the biomarker distribution and stable carbon isotopic values 13c of the toc indicate organic matter om from the uppermost section of the first member of the nenjiang formation upper k2n1 was mainly sourced from aquatic macrophytes and land plants in the lower part of the second member of the nenjiang formation lower k2n2 the biomarker distribution and 13c of both the toc and n alkanes indicate that om was sourced from a mixture of algae bacteria and higher plants as a result of marine transgression seawater incursions indicated by the presence of 24 n propyl cholestanes and 24 iso propyl cholestanes occurred episodically in lower k2n2 the negative hydrogen isotopic composition 2h of short chain n alkanes in lower k2n2 indicates an extremely humid environment and it is likely that an influx of freshwater caused large scale flooding of the songliao paleo lake high resolution biomarker and stable isotope records from the houjingou section demonstrate abrupt environmental changes in the songliao paleo lake following seawater incursions during the late cretaceous

stockwork tungsten scheelite molybdenum mineralization lake george southwestern new brunswick scheelite molybdenite stockwork mineralization constitutes one component of the lake george polymetallic sb w mo au base metal deposit a complex hydrothermal center of late silurian ca 412 m y age in the fredericton trough of the northern appalachians the stockwork hosted by silurian graywackes in part calcareous is spatially and temporally related to a postkinematic cupola of biotite monzogranite and its formation overlapped in time with the emplacement of monzogranitic porphyry dikes mineralogical and textural evidence indicates that contact metamorphism associated with the cupola had ceased before the initiation of w mo mineralization and that it occurred at pressures of less than 1 75 kb in two stages a peak stage t 600 degrees c evident only in rocks of pelitic composition and a lower temperature reequilibration t 500 degrees c recorded in rocks of both pelitic and marly compositions the w mo deposit comprises three different scheelite and or molybdenite bearing veinlet types type 1 bodies the earliest formed are calc silicate granditic garnet wollastonite clinopyroxene and calcic amphibole quartz veinlets with ubiquitous ca and h metasomatic alteration envelopes mineralogical and fluid inclusion relationships indicate that the fluids ranged in temperature from 550 degrees to 228 degrees c and that temperature decreased away from the cupola the succeeding type 2 veinlets comprise quartz and lesser amounts of perthitic alkali feldspar muscovite calcite scheelite molybdenite and pyrite fluid inclusion evidence shows that mineralization dominantly occurred from 400 degrees to 175 degrees c under a confining pressure of 1 3 kb higher grade scheelite and molybdenite deposition was focused in a lower temperature zone to the north of the cupola in which co 2 effervescence occurred type 3 veinlets the last to form consist of prehnite molybdenite and quartz and represent a volumetrically minor mineralization type in both type 1 and 2 systems scheelite and molybdenite deposition appears to have been controlled by decreasing temperature and increasing ph temperature was a function of distance from the cupola for both veinlet types but the controls on ph were specific to each thus the ph of type 1 fluids was controlled by wall rock interaction h metasomatism whereas that of type 2 fluids was controlled by co 2 effervescence the economic stibnite quartz veins scratch et al 1984 occupy fractures which transect and therefore postdate all stages of w mo mineralization

the north cycladic detachment system low angle normal faults accommodate a large part of continental post orogenic extension besides the intrinsic rheological characteristics of the continental crust that may lead to the formation of shallow dipping shear zones at the brittle ductile transition the role of pre existing low angle structures such as large thrusts has been proposed by several authors we explore this question with the example of the north cycladic detachment system ncds that is composed of a series of distinct detachments cropping out on the islands of andros tinos and mykonos separating the cycladic blueschists in the footwall from the upper cycladic nappe in the hanging wall we show that these extensional structures are part of a single large scale structure more than 200 km along strike that reactivates the vardar suture zone it extends eastward on ikaria and westward offshore evia and thessalia where it probably connects to recent shallow dipping normal faults evidenced on published seismic reflection profiles the ncds started its activity in the oligocene concommitantly with the aegean extension and was still active in the late miocene it has exhumed a series of metamorphic domes from southern evia to mykonos below low angle detachment systems made of low angle normal faults and low angle ductile shear zones the ductile shear zones and the faults were created with a low dip and they kept the same attitude throughout their exhumation we identify three main detachments that are part of a continuum of extension on the ncds tinos detachment livada detachment and mykonos detachment a fourth detachment vari detachment is the reactivation of an eocene exhumation related structure deformation in the footwall is characterized by intense stretching and flattening using the spatial evolution observed along strike from andros to mykonos we construct a history of formation of the ncds starting with the reactivation of former thrusts leading to the exhumation of high temperature metamorphic domes the aegean example shows that reactivation of earlier shallow dipping discontinuities can play a fundamental role in continental post orogenic extension

overpressure retardation of organic matter maturation and petroleum generation a case study from the yinggehai and qiongdongnan basins south china sea three superimposed pressure systems developed in the yinggehai basin south china sea as indicated by seismic data well logs and direct pressure measurements the organic maturation profile is nonlinear with three nonparallel segments that correspond to the shallow normal pressured system the intermediate overpressured system and the deep strongly overpressured system respectively the intermediate and deep overpressured systems have abnormally low r0 gradients the organic maturity of these overpressured rocks is significantly lower than the maturity of normal pressured source rocks in nearby wells with similar thermal histories and does not match the thermal histories of the rocks such an organic maturity anomaly is distinctly different from those aused by variation in activation energies conductivity contrasts and hydrologic effects and is confirmed to be the result of overpressure retardation the degree to which the organic matter maturation is retarded expressed as the difference between predicted and measured vitrinite reflectance increases exponentially with increasing fluid pressure confirming that pressure increases the activation energies of organic matter maturation reactions overpressure retardation has been proven to be conditional and quite important for clearly understanding petroleum generation migration and accumulation in overpressured sedimentary basins

interpreting magmatic fabric patterns in plutons abstract most plutons have widespread magmatic fabrics the interpretation of which remains controversial we propose a method to constrain likely causes of fabric patterns the application of which indicates the following 1 preserved fabric patterns often form after chamber construction and only rarely provide information about ascent or emplacement 2 fabrics are poor recorders of total strain and are easily reset preserving only the last increment of strain during crystallization 3 in magmatic systems mechanically decoupled from host rocks patterns may result from strain during internally driven flow filter pressing or porous flow in relatively static chambers or by final increments of strain during emplacement 4 with greater emplacement depths fabric patterns increasingly reflect strain caused by regional deformation and 5 given that magmatic fabrics are easily reset and reflect only the last increment of strain of comparatively weak materials they may provide a relatively direct record of paleostress in orogenic belts

variations in abundances and distributions of isoprenoid chromans and long chain alkylbenzenes in sediments of the mulhouse basin a molecular sedimentary record of palaeosalinity abstract the abundances and distribution patterns of mono di and trimethylated 2 methyl 2 4 8 12 trimethyltridecyl chromans mttcs and long chain alkylbenzenes in extracts of marl 66 samples anhydrite 15 and halite 1 strata of the salt iv formation of the oligocene mulhouse basin are reported the distributions of the methylated mttcs indicate salinity changes of the upper part of a density stratified water column of the basin these variations are explained by a tectonically or climatically induced change in the supply of water of relative lower salinity to form a layer overlying the deeper water brine hence it is suggested that mesohaline 3 5 15 conditions in the surface waters were established as a result of periodic incursions of marine water and subsequent evaporation conversely during periods when the surface water was derived mainly from fresh water from the hinterland lower average salinity in the surface layer resulted the distributions of long chain alkylbenzenes also appear to record these changes

kinematics of rock flow in a crustal scale shear zone implication for the orogenic evolution of the southwestern hellenides combined shear sense criteria finite strain data and vorticity analyses were used to study the deformation path in a curved crustal scale shear zone phyllite quartzite series of the southwestern hellenides the results are combined with data on the structural evolution of a cover nappe pindos thrust belt to provide new insights into the orogenic evolution of this region ductile deformation within the phyllite quartzite series was associated with a top to the west southwest shearing and was partitioned into two structural domains a root zone and a frontal domain the root zone is characterized by vertical coaxial stretching high strain and upward movement of the material while the frontal domain comprises simple shear deformation at the base and pure shear at the top this pattern suggests superposition of pure shear on simple shear deformation and implies tectonic extrusion of the material from the root zone the initiation of brittle deformation in the pindos thrust belt was associated with westward translation above the sub horizontal pindos thrust later as the mountain range elevated normal faulting at high altitudes and migration of thrusting to the west occurred while east directed folding and thrusting in the belt started to the east according to the proposed model crustal thickening was taking place throughout the oligocene and early miocene including the subduction of the apulian beneath the pelagonian microcontinent and the intracontinental subduction of the phyllite quartzite series during the lower miocene vertical buoyancy forces led to the successive steepening of the shear zone and the simultaneous duplexing of its basement facilitating tectonic extrusion of the material from its root zone finally an indentation process caused vertical expulsion of the orogenic wedge and gravity collapse in the brittle crust

granitoid rocks of the southern menderes massif southwestern turkey field evidence for tertiary magmatism in an extensional shear zone recent field campaign in the southern menderes massif in southwestern turkey revealed that the so called core of the massif comprises two distinct types of granitoid rocks an orthogneiss traditionally known as augen gneisses and leucocratic metagranite where the latter is intrusive into the former and the structurally overlying cover schists these differ from one another in intensity of deformation degree of metamorphism and kinematics the orthogneiss display penetrative top to the n nne fabrics formed under upper amphibolite facies conditions during the eocene main menderes metamorphism mmm whereas foliation and stretching lineation exists in the leucocratic metagranites but are not strongly developed the leucocratic metagranites show evidence of syn to post emplacement deformation in a series of weakly developed top to the s ssw fabrics formed under lower greenschist facies conditions leucocratic metagranite bodies occur all along the augen gneiss schist contact in the southern menderes massif they are emplaced as sheet like bodies into country rocks previously deformed and metamorphosed during a top to the n nne alpine orogeny along a ductile extensional shear zone located between orthogneisses and metasediments which was possibly active during emplacement the data presently available indicate that emplacement and associated ductile extensional deformation occurred during late oligocene early miocene time these results confirm previous contentions that there are tertiary granites in this part of the menderes massif

palaeoenvironmental conditions during deposition of the upper cretaceous oil shale sequences in the songliao basin ne china implications from geochemical analysis abstract excellent hydrocarbon source rocks oil shales containing type i organic matter om were deposited in the continental songliao rift basin during the late cretaceous a major contribution of aquatic organisms dinoflagellates green algae botryococcus and minor input from macrophytes and land plants to om accumulation is indicated by n alkane distribution steroid composition and 13 c values of individual biomarkers microbial communities included heterotrophic bacteria cyanobacteria and chemoautotrophic bacteria as well as purple and green sulfur bacteria the presence of methanotrophic bacteria is indicated by 13 c depleted methyl hopane the sediments were deposited in a eutrophic alkaline palaeolake highly reducing saline bottom water conditions and a stratified water column existed during om accumulation of the qingshankou formation and member 1 of the nenjiang formation this is indicated by low pristane phytane gammacerane index and mttc ratios and the presence of carotane and aryl isoprenoids however an abrupt change in environmental conditions during deposition of member 2 of the nenjiang formation is indicated by significant changes in salinity and redox sensitive biomarker ratios a freshwater environment and suboxic conditions in the deep water prevailed during this period higher input of terrigenous om occurred during deposition of the upper nenjiang formation good oil to source rock correlation was obtained using biomarker fingerprints of oil stained sandstone from the quantou formation and oil shales from the qingshankou formation based on the extent of isomerisation of c 31 hopanes the oil was most probably derived from oil shales of the qingshankou formation in deeper parts of the basin

the late alpine evolution of an extensional shear zone naxos greece the mid miocene structural evolution of the metamorphic complex on naxos involved deformation in a kilometre scale low angle ductile shear zone the structures described are consistent with exhumation of the metamorphic complex during crustal extension after and possibly during localized high temperature barrovian style metamorphism non coaxial fabrics developed throughout the structural history indicate that upper levels were transported to the north during ductile extension this shear sense is opposite that inferred previously for the development cordilleran style metamophic core complexes in the cvclades ductile deformation was accompanied during its later stages by e w directed compression

40ar 39ar dating of white micas from an alpine high pressure metamorphic belt on naxos greece the resetting of the argon isotopic system overprinting of white micas from high pressure low to medium temperature m1 metamorphic assemblages in pelitic schists on naxos during subsequent thermal dome m2 metamorphism ranges from minor in the southeast of the island to complete recrystallization in the amphibolite facies rocks near the migmatites in the centre of the dome the original m1 minerals are phengites si4 6 7 7 0 and the overprinting minerals are muscovites si4 6 0 6 45 40ar 39ar step heating analyses of white mica separates from rocks in the area where phengite and muscovite occur together yield complex age spectra characterized by low apparent ages in the first and the last stages of gas release and high apparent ages in between these upward convex age spectra are shown to be caused by mixing of two generations of micas each of which has a different age spectrum and argon release pattern seemingly good plateaus in some age spectra from white micas of the area must be interpreted as providing meaningless intermediate ages further the upward convex age spectra have been used to trace the isotopic signature of phengites toward increasing m2 metamorphic grade and suggest that as long as phengites can be observed in the rocks upward convex age spectra occur on naxos crystallization of muscovite at the expense of phengite appears to be the main mechanism of resetting argon isotopic ages in white micas however there is also good evidence for argon loss by volume diffusion from phengites simple diffusion calculations suggest that the m2 metamorphism was caused by a shortlived heat source

miocene south directed low angle normal fault evolution on kea island west cycladic detachment system greece 1 new structural petrologic and thermochronologic data from kea west cyclades define a crustal scale ductile shear zone and ductile brittle low angle normal fault lanf system both the greenschist facies shear zone forming the footwall and the overlying lanf zone formed during constrictional strains with a consistent top to sw s shear sense with increasing finite strains toward higher structural levels but decreasing temperatures from footwall to hanging wall the tectonostratigraphy comprises a 450 m thick footwall of shallowly dipping schists and calcite marbles representing the intermediate unit of the attic cycladic crystalline acc above the footwall is a 60 m thick highly strained lanf zone consisting of phyllonites cataclastic schists ultramylonitic calcite marbles proto mylonitic calcite marbles and cohesive cataclasites that arch over the whole island these fault rocks exhibit multistage lanfs evolving from ductile to brittle conditions an up to 50 m thick brecciated limestone and dolostone sequence forms the unmetamorphosed hanging wall which is most probably part of the upper unit of the acc multiequilibrium p t estimates on chlorite white mica pairs in the footwall yield 7 5 5 kbar 360 c 450 c for inclusions in albite and epidote 5 5 3 kbar 400 c 350 c for the main foliation and 3 2 kbar 350 c 280 c in localized shear bands c and c foliations the 40ar 39ar white mica footwall cooling ages demonstrate that greenschist facies retrogression occurred between 21 and 17 ma localized late decimeter thick shear zones were active and dynamically recrystallized before 15 to 13 ma the lanf on kea together with similar structures in south attica and the west cyclades define the west cycladic detachment system characterized by ductile to brittle top sw s shear sense

regional implications of geochemistry and style of emplacement of miocene i type diorite and granite delos cyclades greece abstract the miocene plutons of the cyclades were emplaced in a subduction setting during regional back arc extension of continental crust that led to flat lying mid crustal detachment faulting mapping of the island of delos shows that quartz diorite and tonalite were emplaced as dykes in country rock of schist and marble within shear zones parallel to the extension direction mafic magmas were followed by numerous small batches of felsic magma with magmatic and ductile deformation synchronous with magma emplacement late granite dykes occupy brittle fractures in the more deformed rocks mafic and intermediate rocks show a bimodal distribution of incompatible trace elements with one group of broadly tholeiitic character and the other with substantial enrichment in sr nb and hfse but low th and ba these differences appear to be inherited from two distinct mafic sources that are different from the mafic source for the plutons of the eastern cyclades voluminous granodiorite results from these mafic magmas fractionating and or mixing with felsic crustal material some of which was derived by anatexis of a sedimentary protolith indicated by high b and mn some late granites appear derived from partial melting of hercynian paragneiss regionally the shear zones appear to be feeders to more extensive granitic plutons located at space produced at ramps in detachment fault zones the shear zones parallel the mid cycladic lineament a broad zone of displacement between two crustal blocks rotating in opposing directions as rollback took place at the hellenic subduction zone distinctive geochemical features in miocene igneous rocks suggests that these two blocks had quite different geological histories the localisation of plutonism and core complexes near the mid cycladic lineament suggests that this crustal scale shear played a role in bringing subduction derived magmas to mid crustal levels the heat supplied by the mafic magmas promoted ductile deformation high in the crust where extension was concentrated leading to the formation of core complexes the regional extension resulted in progressive shallowing of the position of the granite solidus within the crust leading to welding of the mid cycladic lineament which is no longer seismically active

pluton emplacement by wall rock thrusting hanging wall translation and extensional collapse latest devonian plutons of the cobequid fault zone nova scotia canada

fluid inclusion study of the bournac polymetallic sb as pb zn fe cu vein deposit montagne noire france mineralogical studies demonstrate that the hercynian polymetallic antimony rich deposit of bournac can be described by four stages of ore deposition and one of partial ore remobilization fluid inclusion data permit calculation of the composition and temperature of the fluids associated with each stage of hydrothermal mineralization and concomitant wall rock alteration stages i and ii fe as and zn are represented by moderate salinity h2o co2 nacl inclusions which correlate closely with early carbonate deposition stage iii fluids which are responsible for the deposition of pb sb ores are characterized by low salinity h2o nacl inclusions during the final stage of mineralization iv corresponding to the main phase of stibnite deposition abundant aqueous inclusions confirm the continued involvement of low salinity fluids and the intense development of potassic clays and secondary silica in the wall rocks homogenization temperatures suggest that the whole cycle of mineralization took place during a gradual decrease in fluid temperature of 380 140 c stibnite deposition is restricted to the interval of 230 140 c thus confirming an essentially epithermal environment stage v partial remobilization is distinguished by the presence of high salinity cacl2 rich inclusions which are tentatively related to triassic barite mineralization in the region and therefore postdate the bournac antimony ores homogenization temperatures for this stage range 140 60 c

a comparison of geodetic and finite strain pattern in the aegean geodynamic implications abstract a comparison of the active strain pattern of the aegean constrained by global positioning system measurements and the oligo miocene finite strain field shows some striking similarities in terms of direction and rates of extension the geometry of extension at crustal scale is also very similar with north dipping normal faults connecting near the brittle ductile transition to shallow north dipping shear zones this pattern of extension is not significantly modified by the recent extrusion of the motion of anatolia and aegea the persistence over more than 25 myr of the same pattern of extension suggests that the cause for extension resides within the aegean lithosphere gravitational collapse allowed by extensional boundary conditions after 30 ma slab retreat is the primary cause for post orogenic extension in the aegean and western anatolia

late eocene marine incursion in north western south america article i nfo during the late eocene in the colombian subandean basins one of the most important oil bearing rocks of the country was deposited the mirador formation palaeogeographical models have interpreted a typically fluvial environment for the lower mirador formation and marginal to marine environments for its upper layers the potential of marine influence in the upper mirador beds and the overlying lower carbonera formation as a correlation tool and the palaeogeographic distribution of the event have not yet been defined in order to determine the palaeogeography of this probable incursion 80 wells and four sections were analysed using palynological techniques the presence of a marine influence in the sediments was determined by using a salinity index si that describes the negative relationship between continental and marine palynomorphs the marine influence has been recognized in two areas the first in the putumayo basin and the second in the eastern cordillera and central llanos foothills in the putumayo basin the salinity index pattern reveals a southern provenance of the marine incursion flooding the colombian territory in a south north trend through the ecuadorian coast the marine influence of the eastern cordillera and the central eastern llanos foothills is more difficult to explain we propose a possible corridor through the proto lower magdalena valley that connected the caribbean sea and the central llanos foothills palaeogeographic models for the late eocene of north western south america should consider this marine incursion and its geographical distribution published by elsevier b v

mylonite fabric development on naxos greece abstract the miocene structural evolution of the metamorphic complex on naxos occurred within a mid to lower crustal sub horizontal shear zone the deformation style and the regional stress field in the aegean during the miocene are consistent with exhumation of the metamorphic complex during ductile crustal thinning deformation in this shear zone initiated possibly before and continued after the peak of localized high temperature barrovian style metamorphism kinematic indicators in non coaxial fabrics indicate that upper structural levels were displaced to the nne throughout the miocene structural history of the metamorphic complex this displacement was accompanied during its latter stages by compression in an e w direction

the lateral boundary of a metamorphic core complex the moutsounas shear zone on naxos cyclades greece we describe the structure microstructures texture and paleopiezometry of quartz rich phyllites and marbles along n trending moutsounas shear zone at the eastern margin of the naxos metamorphic core complex mcc fabrics consistently indicate a top to the nne non coaxial shear and formed during the main stage of updoming and exhumation between ca 14 and 11 ma of the naxos mcc the main stage of exhumation postdates the deposition of overlying miocene sedimentary successions and predates the overlying upper miocene pliocene conglomerates detailed microstructural and textural analysis reveals that the movement along the moutsounas shear zone is associated with a retrograde greenschist to subgreenschist facies overprint of the early higher temperature rocks paleopiezometry on recrystallized quartz and calcite yields differential stresses of 20 77 mpa and a strain rate of 10 15 10 13 s 1 at 350 c for quartz and ca 300 c for calcite chlorite geothermometry of the shear zone yields two temperature regimes 300 360 c and 200 250 c the lower temperature group is interpreted to result from late stage hydrothermal overprint

fault structure and related basins of the north aegean sea and its surroundings 1 fault structure and basin evolution in the northern aegean sea and its surroundings have been investigated using bathymetry available onshore and offshore seismic profiles onshore fault patterns from ne greece nw turkey three islands in the aegean sea surface ruptures associated with the 1978 thessaloniki earthquakes gps measurements from north aegean islands and a number of earthquake focal plane solutions and historic seismicity bathymetric and isopach data show that the north aegean trough can be divided into the sporades basin and the saros trough post miocene sediment thickness differences in these basins offset of distinct horizons and frequent seismicity along basin bounding faults indicate that sediment accumulation in the area is fault controlled offshore seismic profiles show that the basin bounding faults are dominantly characterized by apparent normal components as well as strike slip components inferred from typical fault zone profiles additional evidence for existence of strike slip faulting comes from earthquake focal plane solutions we refined the pattern and kinematics of the faults controlling the basins and classified them into two major groups the faults in the first group trend ne sw and ene wsw and are here interpreted to be dominantly right lateral strike slip with normal or reverse components these faults accommodate a similar amount of deformation like the ganos fault and thus represent the westernmost extension of the north anatolian fault zone the faults in the second group trend nw se and are dominantly normal faults with an occasional left lateral component these faults are believed to manifest the termination of the north anatolian fault zone because of the segmentation of the right lateral strike slip faults and the preexisting ne trending tectonic grain the basins are compartmentalized into smaller depocenters basins are orientated with their long axes either parallel to the ne sw to ene wsw trending echelon strike slip faults or in the zone north of the strike slip faults parallel to the nw se trending normal faults the interpretations regarding the kinematics of the faults are consistent with the data compiled from the islands near the faults and from the land in ne greece and nw turkey the northern aegean basins and their spatial relationships to the fault architecture representing the diffused termination of the north anatolian fault system are consistent with the mechanical principles of the strike slip tectonics

lacustrine source rock deposition in response to co evolution of environments and organisms controlled by tectonic subsidence and climate bohai bay basin china three paleogene syn rift intervals from the bohai bay basin the most petroliferous basin in china were analyzed with sedimentological and geochemical techniques to characterize the lateral source rock heterogeneities to reveal the environmental and ecological changes through geologic time and to construct depositional models for lacustrine source rocks under different tectonic and climatic conditions the third es3 and first es1 members of the eocene shahejie formation and the oligocene dongying formation ed display widely variable total organic carbon contents hydrogen indices and visual kerogen compositions suggesting changes in organic facies from deep to marginal sediments carefully selected deep lake facies samples from any interval however display fairly uniform biomarker composition these three intervals have distinctly different biomarker assemblages which indicate weakly alkaline freshwater lakes with a moderately deep thermocline during es3 deposition alkaline saline lakes with shallow chemocline during es1 deposition and acidic freshwater lakes with deep unstable thermocline during the deposition of the dongying formation such environmental changes corresponded to changes in subsidence rate and paleoclimate from rapid subsidence and wet climate during es3 deposition through slow subsidence and arid climate during es1 deposition to rapid subsidence and wet climate during ed deposition and resulted in synchronous changes in terrigenous organic matter input phytoplankton community and primary productivity the co evolution of environments and organisms controlled by tectonic subsidence and climate accounted for the deposition and distribution of high quality lacustrine source rocks with distinctly different geochemical characteristics most rift basins experienced changes in subsidence rates and possibly changes in climates during their syn rift evolutions the models constructed in this paper may have important implications for source rock prediction in other lacustrine rift basins

modelling petroleum formation from heterogeneous source rocks the influence of frequency factors on activation energy distribution and geological prediction abstract the application of basin modelling programs permits the prediction of organic matter transformation to oil and gas under variable geological conditions simplified kinetic models are commonly applied with a distribution of activation energies and a single average frequency factor here it will be shown that such simplified kinetic models are not sufficient to correctly predict organic matter transformation in heterogeneous kerogens under geological conditions in the present paper individual pairs of frequency factors and activation energies were calculated from the temperature shift of nine different levels of organic matter transformation ranging from 0 1 to 0 9 tr at different heating rates 0 1 0 7 and 5 0 k min this type of extended kinetic evaluation has been applied on samples from the green river shale the toarcian shale the duvernay formation the draupne formation a type ii s source rock petroleum asphaltenes and a tertiary coal from the mackenzie delta respectively for terrestrial and heterogeneous marine source rocks the frequency factors systematically increase with increasing level of transformation while such an increase was insignificant or absent when homogeneous source rocks were studied by applying geological heating rates it was possible to illustrate the significance of the extended calculation of individual frequency factors the predicted onset temperature of petroleum formation was displaced to 60 70 c in case of lignites coals and type ii s source rocks which was up to 30 40 c lower than predicted by the use of a conventional single frequency factor model to a lesser extend such a shift was also documented for some marine shales e g draupne formation and the duvernay formation the reason for this phenomenon is that an average single frequency factor suppresses the initial formation of petroleum at geological heating rates because high activation energies are needed to maintain the kinetic equation at low generation temperatures in contrast correct activation energies derive from individual frequency factors which keep the activation energies low at low levels of organic matter transformation and result in a more reliable description of the low energy bonds in the heterogeneous organic matter types

the timing of partial melting barrovian metamorphism and granite intrusion in the naxos metamorphic core complex cyclades aegean sea greece abstract the relationship between partial melting and granite intrusion in a classic barrovian metamorphic terrane has been assessed thirteen samples were dated by shrimp u pb zircon geochronology from the island of naxos greece one of the aegean metamorphic core complexes the effect of partial melting during peak barrovian metamorphism on naxos is recorded by fine

fracture controlled antimony quartz mineralization lake george deposit new brunswick mineralogy geochemistry alteration and hydrothermal regimes veins are of two orientations 000 degrees 35 degrees e lawrence vein and 090 degrees 33 degrees n hibbard and prout veins to date approximately 1 million short tons of ore grading 3 0 to 3 5 percent sb have been mined from hibbard the dominant vein two way chemical mass balance reveals that wall rock alteration accompanying stibnite quartz vein emplacement involved major additions of sb as s and volatiles with minor introduction of k 2 o rb and si fe 2 o 3 mgo cao and na 2 o along with co ni ba and zn were stripped whereas sc ti and al behaved essentially isochemically the argillic alteration developed at 360 degrees to 490 degrees c from fluids with a delta 18 o 10 per mil the hibbard vein was precipitated at 325 degrees to 350 degrees c from a saline hydrothermal fluid with a delta 18 o value of 11 to 12 per mil and a delta d value of 20 to 30 per mil undergoing transient boiling at a pressure of 270 to 420 bars salinity is estimated at 38 to 40 weight percent nacl hematitic alteration was formed at 200 degrees to 350 degrees c in the presence of a fluid with a delta 18 o value of 2 to 8 per mil the ore forming solutions may have been a late stage magmatic fluid evolved off a high 18 o granitic intrusion modified journal abstract

emplacement and geochemical evolution of highly evolved syenites investigated by a combined structural and geochemical field study the lujavrites of the ilimaussaq complex sw greenland abstract structural mapping and the combined study of magmatic to solid state deformation textures and mineral compositions in highly evolved nepheline syenites lujavrites of the alkaline to peralkaline ilimaussaq complex south greenland reveal detailed insight into the emplacement and geochemical evolution of the melts they crystallized from based on magmatic to solid state flow textures such as foliations and lineations we propose that the investigated rock sequence forms a sill like structure with a steep feeder zone that flattens out over a short distance and intrudes into less evolved overlying units as sub horizontal sheets by roof uplift systematic compositional variation of early magmatic eudialyte group minerals egm in the investigated rock sequence monitors the geochemical evolution of the lujavrite forming melt s the chlorine contents of egm decrease successively upwards within the rock sequence which probably indicates a successive increase of water activity during differentiation consistent with a change from sodic pyroxene aegirine to sodic amphibole arfvedsonite in the mineral assemblage both ree contents and fe mn ratios of egm are promising differentiation indicators which increase and decrease respectively upwards within the sequence due to fractional crystallization this closed system evolution is interrupted by a shift towards less evolved melt compositions in one lujavrite unit for which we assume magma recharge our study demonstrates the strength of a combined structural and petrological approach to understand the petrogenesis of an igneous body in more detail and highlights their close connection

petrographic and geochemical characterization of microfacies in a lacustrine shale oil system in the dongying sag jiyang depression bohai bay basin eastern china abstract petrology and rock eval analyses have been conducted in the lower third and upper fourth members lower es3 and upper es4 of the shahejie fm source rock intervals in well fanye1 in the dongying sag jiyang depression bohai bay basin eastern china the organic matter in rocks intersected by this well is dominated by lamalginite and bituminite and most samples contain type i or ii kerogen microfacies a h has been identified according to their organic mineral composition and structure using polished thin sections under microscopy the form and location of hydrocarbon residue occurrences mainly as solid bitumen with fluorescence are different in those microfacies microfacies a which is dominant in well fanye 1 is calcareous mudstone without lamination and the hydrocarbon residue is dispersed through the rock with some being present in subtle microfractures microfacies b and f are mostly composed of shale with adsorbed hydrocarbon indicated by fluorescence along mineral grains microfacies c is laminated argillaceous carbonate with hydrocarbon residue mainly occurring in thin microfractures along the bedding plane microfacies d and e are mainly carbonate and microfacies d is laminated with micrite and sparite and hydrocarbon residue occurrence is not only in the microfractures along the bedding but also in the micropores among the grains in the sparite layers which is the main place for hydrocarbon residue occurrence in microfacies type e without lamination microfacies g and h are both micrite microfacies g shows bioturbation and hydrocarbon residue occurs within small irregular microfractures along the bedding planes and pores only a little solid bitumen without fluorescence has been observed in microfacies h the rock eval oil saturation index osi s1 100 toc value is variable because of the different characteristics of these hydrocarbon residue occurrences osi values in microfacies a are normally high 74 8 242 8 mg hc g toc average of 117 2 mg hc g toc and likely much higher if microfractures develop 200 mg hc g toc osi values averaging 43 7 mg hc g toc are lowest in microfacies f because of adsorption on the shales and osi values are the highest in microfacies d 371 3 mg hc g toc and e 199 9 mg hc g toc since the hydrocarbon residues are stored both in microfractures and pores between the grains both osi values are high in microfacies g and h because of low toc content the combination of petrographic and osi analysis appear to be a promising tool for characterizing shale oil systems

the role of dextral transpressional faulting in the evolution of an early carboniferous mafic felsic plutonic and volcanic complex cobequid highlands nova scotia canada abstract the wentworth plutonic complex consisting of gabbro and granite was emplaced in the earliest carboniferous in the cobequid shear zone of the northern appalachians the plutonic complex is coeval with a 5 km thick pile of volcanic rocks early alkalic a type granite correlates with thick felsic pyroclastics and minor basalt which are overlain by 1 5 km thick basalts that correlate with a large gabbro pluton that is intruded in turn by late granites the basalt and gabbro are fe rich tholeiites the geochemistry of the late granites suggests that they formed by differentiation of a granodioritic magma resulting from assimilation of early granite by the gabbroic magma the wentworth plutonic complex lies on the north side of the dextral rockland brook fault near the western tip of wedge shaped basement block of the avalon terrane field observations of mesoscopic structures and map contacts show that the plutonic bodies at all structural levels are related to transpressive strike slip faults dykes parallel to the mylonitic foliation in the rockland brook fault zone and at the contacts between igneous phases suggest that the plutons developed largely through dyke to pluton construction the plutonism was initiated by dyking related to major faults under transpression that was partitioned into shear zone bounded blocks while the sinking of those blocks finally provided the space for mafic magma emplacement dyking was active over at least a 10 ma time period the overall location of plutonism in the cobequid shear zone appears related to its position at the intersection of the shear zone bounding the southwestern margin of the magdalen basin and the e w transpressional contact of the avalon and meguma terranes magmatism enabled thermomechanical softening of the crust and the vertical and lateral extrusion of the wedge shaped basement blocks whose movement controlled the localisation of the voluminous magmatic activity

geology compositional heterogeneities and geochemical origin of the yacheng gas field qiongdongnan basin south china sea the yacheng gas field is located in the footwall of the no 1 fault the boundary fault between the yinggehai and qiongdongnan basins the main reservoir is the fan delta sandstones in the lingshui formation the seals are meishan for m ation shales near the no 1 fault and lingshui formation shales away from the no 1 fault all strata are normally pressured in the gas field except for the meishan formation the meishan formation is overpressured near the no 1 fault in the gas field and in the adjacent yinggehai basin away from this fault into the qiongdongnan basin the overpressure diminishes an obvious thermal anomaly occurs below 3600 m in the gas field this anomaly characterized by an abrupt increase in drill stem test and fluid inclusion homogenization temperatures vitrinite reflectance ro and rock eval tmax and by an abnormally low temperature ro tmax gradient diminishes away from the yinggehai basin the gases and condensates have abnormally high aromatic hydrocarbon contents and show obvious heterogeneities away from the no 1 fault the c2 hydrocarbon content and c2 scn increase carbon dioxide content decreases d13c values for methane ethane and carbon dioxide become lighter the heptane and isoheptane values decrease and the relative contents of aromatic hydrocarbons both in c6 c7 light hydrocarbons and in the condensates decrease such heterogeneities reflect the reservoir filling process and origin of the gas field the gas field was charged from both the qiongdongnan and the yinggehai basins hydrocarbons sourced from the qiongdongnan basin have relatively low maturities whereas hydrocarbons from the yinggehai basin have relatively higher maturities and seem to have been in association with hydrothermal fluids the hydro thermal fluids from the yinggehai basin in which methane ethane carbon dioxide and especially aromatic hydrocarbons dissolved under the high temperature and high pressure subsurface conditions migrated along the no 1 fault and caused the abnormally high concentration of aromatic hydrocarbons as well as the thermal anomalies in the gas field especially near the no 1 fault

emplacement of the miocene west naxos pluton aegean sea greece a structural study synmagmatic and solid state structures within the naxos pluton and its rim may provide insight into the interplay between plutonism and regional deformation at upper crustal level within the hornblende biotite granite of western naxos synmagmatic foliations display two distinct patterns onion skin in the north and tangential to the rim in the south the two areas are separated by the ne trending glinadon fault deformed mafic enclaves in the pluton are prolate with their long axes parallel to the synmagmatic lineation in contrast phenocryst distribution analysis using the fry method defines an apparent oblate strain with a horizontal stretching lineation planar markers within the pluton progressively steepen through the vertical at the east pluton border several lines of evidence such as dykes intruding axial areas of rim parallel folds foliated or folded aplite veins folds and spaced cleavage in the mollase and inverted stratigraphy suggest pluton emplacement and deformation during transpressional deformation a northward divergent flow regime with magma spreading out mainly from the naxos fault and the deflection of both the synmagmatic foliation pattern and the flow lines at the glinadon fault suggest that the ne sw and n s trending faults were active during pluton formation in the south the pluton has grown by the expansion of dykes occupying p shear positions with respect with the naxos fault in the north a piecemeal block down drop complements this process and favours voluminous magma concentration during the late evolutionary stages of pluton construction the magma chamber was compartmentalized into ne trending sectors affected by block rotation in an anticlockwise manner understanding the role of faults in the emplacement of the naxos pluton is important for understanding emplacement of other plutons in the aegean sea region since most of them are controlled by n s ikaria pluton or ne tinos serifos and delos plutons trending faults

transpression and transtension within different structural levels in the central aegean region in the central aegean region shortening structures within the miocene molasse arc known since long ago nevertheless recently most authors have recognized extensional structures within middle to upper miocene granitoids proposing a basin and range type model for the late cenozoic evolution of the area to resolve this problem structural mapping and mesoscopic analysis of 900 faults sampled from 12 islands have been carried out late orogenic uplift of the central aegean region is the result of a continuous convergence and indentation of the pelagonian plate by the apulian plate that took place throughout the miocene formation of core complexes can be associated with a large oblique upthrusts b steeply dipping strike slip faults and c low angle normal faults the latter are produced by low multidirectional extension which has affected small crustal regions as adjacent areas underwent transpression in the late stages of collision the overthickened crust began to collapse due to transtension which was replaced by extension caused by the roll back of the hellenic subduction zone in the lower pliocene time this extensional regime has lasted until the present day

the pelagonian zone in greece a polyphase deformed fragment of the cimmerian continent and its role in the geotectonic evolution of the eastern mediterranean data from macedonia greece correlated with those reported from the pontides turkey indicate that the pelagonian zone of the hellenides represents a fragment of the cimmerian continent which separated the paleo tethys and neo tethys oceans a permo triassic age is suggested for separation of the paleozoic continent and initial rifting in the two oceanic basins as the pelagonian zone represented the northwestern european end of the cimmerian continent the paleo tethys and the northern branch of neo tethys would have been very close to each other on either side of this zone thus both oceans at their european end closed within a short time of each other in the late jurassic early cretaceous the sequential development of the two oceans outlines a model for the geotectonic evolution of the internal hellenides in which a correlation of thrusting and folding phases is also given

ductile and brittle shortening extension parallel folds and maintenance of crustal thickness in the central aegean cyclades greece in contrast to previous studies that concentrated on the two dimensional crustal strain in the central aegean region cyclades it is shown that nne ssw extension via ductile and brittle stretching and low angle detachments was accompanied and or alternated with horizontal shortening perpendicular to the stretching direction since at least the early miocene roughly e w directed ductile shortening produced large scale overturned and upright folds having axes parallel or slightly oblique to the stretching lineation upright folding and arching of low angle normal faults occurred above the brittle ductile transition and brittle e w compression culminated with vertical axis block rotations strike slip faults and minor thrusts since at least the early miocene the structure of the cycladic massif evolved through alternating and or coeval increments of horizontal shortening and vertical thinning associated with an approximately constant nne ssw stretching exact magnitudes of the vertical and horizontal deformational components are difficult to assess nevertheless we note that extensional tectonics that affected the cyclades during the last 15 20 m y have produced no net crustal thinning we suggest that crustal thickness was maintained by extension parallel folds which represent true contractional structures and that crust was fed into the extended region from its margins

petrology mineral chemistry and sr nd pb isotopic compositions of granitoids in the central menderes metamorphic core complex constraints on the evolution of aegean lithosphere slab abstract plutonic associations in the central menderes metamorphic core complex are suitable rocks in order to understand the magma forming processes in extended terrains syn extensional salihli and turgutlu granitoids have granodioritic composition and contain monzonitic and monzodioritic microgranular enclaves they are transitional metaluminous peraluminous and high k calc alkaline in character and are located on i and s type transition salihli and turgutlu granodiorites are geochemically similar to each other while their microgranular enclave chemistry is in contrast with low sio2 and high mg values mineral chemistry data from granodiorites and mafic microgranular enclaves confirm their shallow emplacement at about 7 km geochemical modelling suggests that syn extensional granitoids were derived from the mixing of mantle and lower crustal components which were finally modified by a significant amount of upper crustal contamination and fractional crystallization processes at shallow crustal levels early middle miocene syn extensional granitoids across the aegean region form a magmatic belt associated with roll back of the aegean lithosphere slab roll back induced magmatism together with ductile deformation in western turkey ceased after cooling of the salihli granodiorites at 12 2 ma but core complex related magmatism was continuous in the cycladic metamorphic core complex during late miocene and was followed by an active arc volcanism in the southern aegean such abrupt change from ductile to brittle mode of extension in western turkey can be explained by opening of a slab window on the aegean lithosphere slab which would lead to upwelling of fertile subslab asthenospheric mantle forming transitional and finally oib type basalts

synextensional granitoids and detachment systems within cycladic metamorphic core complexes aegean sea greece toward a regional tectonomagmatic model within deforming continental regions where metamorphic core complexes mccs and synextensional granitoids are closely associated deciphering the link between detachment faulting and magmatism often remains complex as 1 the rheological weakness of magma may stimulate mechanisms of strain localization and conversely 2 tectonic processes may open close drains where magmas can intrude here we tackle this issue by focusing on the cyclades with the comparison of five granitoid cored mccs tinos mykonos ikaria naxos and serifos and their flanking detachment systems in this region granitoids were emplaced into the middle upper crust over a relatively short time period 15 9 ma while metamorphic domes were largely exhumed after more than 10 myr of extension none of those intrusions thereby proves to be a real candidate for the genesis of mccs but would rather be a consequence of a warmer regime during lithospheric thinning however all collected structural and kinematic data converge toward a regional scheme in which magmatic activity played a more pivotal role than previously postulated indeed late evolution stages of mccs were dynamically impacted by intrusions along which local and transient heterogeneities of the mechanical strength occurred interfering with the sequential development of detachments during their tectonically controlled emplacement magmatic products intruded already formed detachments at depth locally inhibiting their activity associated with a contemporaneous upward migration of extensional deformation that tended to localize through time within intrusion roofs along rheological discontinuities the newly formed detachments are expressed within granitoids through a continuum of deformation from comagmatic to ductile conditions followed by cataclasis along detachments

low grade retrogression of a high temperature metamorphic core complex naxos cyclades greece retrogressive deformation and metamorphism are often reported from the main low angle shear zones and detachments of metamorphic core complexes but their importance is not sufficiently emphasized for the footwall interior in order to contribute to a better understanding of exhumation related retrogression processes within and at the top of metamorphic core complexes an integrated detailed microstructural textural 40 ar 39 ar geochronological and thermobarometric study on the naxos metamorphic core complex within the aegean sea is presented that provides a new perspective on low grade retrogression during exhumation through shallow ductile levels we found variable retrogressive deformation within the naxos metamorphic core complex which even pervasively affected significant portions of the migmatite grade metamorphic core and remnant high pressure areas of the metamorphic core complex where retrogression led to pervasive formation of new fabrics within greenschist facies metamorphic conditions during brittle ductile transition within a continuum of retrogression 40 ar 39 ar white mica dating allowed us to deduce three retrogressive ages at 16 52 0 39 ma within the naxos metamorphic core complex 12 6 0 28 ma moutsounas detachment shear zone on the eastern boundary of the metamorphic core complex and 10 43 0 44 ma to 8 40 0 76 ma last ductile activity along the naxos paros shear zone to the north of the metamorphic core complex a further stage of retrogression at 12 11 ma occurred along distinct low angle normal faults within the middle miocene naxos granite retrogressive microstructures low temperature calcite fabrics in marbles and chloritization in metapelites at temperatures of 350 130 c in the metamorphic core complex core resulted mainly from late stage e w shortening and folding late stage flow of hydrous fluids resulted in resetting of fabrics and enhancement of ductile deformation the middle late miocene retrogression events are also reflected by a similarly aged tectonic collapse basin in the hanging wall unit above the detachment the wide temporal range of retrogression within the naxos metamorphic core complex coincides in age with retrogressive deformation within other metamorphic core complexes of the aegean sea we interpret the long temporal range of retrogression to reflect outward southwestward retreat of the subduction and sequential activation of major detachment zones

rapid extension recorded by cooling age patterns and brittle deformation naxos greece the metamorphic core complex exposed as the island of naxos in the aegean sea records an unusually complete sequence of structures developed as a result of continental extension the structures formed during miocene rise and cooling from ductile upper amphibolite facies and anatectic conditions to brittle near surface conditions beneath the naxos detachment fault top to the north ductile fabrics in the footwall which initially developed during amphibolite facies prograde metamorphism were overprinted by a succession of north directed normal sense lower temperature brittle structures as the footwall was tectonically unloaded and unroofed pseudotachylite and cataclasite formation brittle faulting alteration and erosion of the footwall occurred during continued slip and tectonic denudation neogene conglomerate and megabreccia in part derived from exhumation of this footwall lie structurally above the peripheral naxos fault published k ar and 40ar 39ar ages for hornblende white mica and biotite in the footwall decrease northwestward apparent ages 17 50 ma in the southeast correspond to areas of low metamorphic grade where preextension argon was partially retained published ages 16 10 ma in higher grade rocks of the domal core in the north are cooling ages that for each of the three minerals show a component of younging in the nne direction of extension assuming this is the direction of unroofing we interpret the rate of this younging as the fault slip rate as the footwall rocks moved 20 km ssw relative to their hanging wall along the base of the naxos detachment fault the calculated rates of slip average 5 8 mm yr comparable to maximum rates reported in the basin and range province

algal bloom episodes and the formation of bituminite and micrinite in hydrocarbon source rocks evidence from the devonian and mississippian northern williston basin canada organic petrology incident light microscopy of middle devonian inter reef laminates and devonian mississippian epicontinental black shales williston basin canada indicates that algal bloom episodes and consequential bacterial activity played a significant role in the accumulation of amorphous bituminite iii rich organic microfacies corpohuminite like algal akinete cells produced by filamentous algae during algal bloom periods are persistent maceral inclusions within the potential hydrocarbon source rock intervals these cells ro mean range 0 24 0 90 are regarded as positive indicators of stressful palaeoenvironmental conditions unicellular tasmanites and leiosphaeridia marine alginite and variably degraded alginite remnants ghosts within the amorphous kerogen may be products of cell lysis photo oxidation and microbial alteration these processes are characteristic of algal bloom periods minute ca 1 m spheroidal and coccoidal bacteria like macerals are dispersed throughout the bituminite iii network attesting to the importance of microbial activity within the water column and sediment during and after organic matter accumulation dispersed granules laminations and replacement textures of micrinite like macerals within bituminite iii are interpreted as remnants of microbial alteration rather than a residual product of thermal maturation and hydrocarbon generation

the type section of the maikop group oligocene lower miocene at the belaya river north caucasus depositional environment and hydrocarbon potential the type section of the oligocene to lower miocene maikop group considered the main source rock in the eastern paratethys has been studied using geochemical proxies to gain insights into depositional setting and hydrocarbon potential the maikop group at the type section is approximately 600 m 2000 ft thick deposition commenced after a major late eocene sea level drop and a subsequent early oligocene sea level rise the maikop group is composed mainly of carbonate free pelitic rocks calcareous rocks are limited to the lower oligocene succession including the polbian bed that forms a basin wide marker horizon deposited during a time with significantly decreased salinity solenovian event anoxic conditions prevailed and were only interrupted for longer periods during deposition of the lower part of the lower oligocene pshekha formation the polbian bed and the lower miocene olginskaya formation total organic carbon toc contents range up to 3 5 wt hydrogen index values are typically less than 300 mg hydrocarbons hc g toc but reach 420 mg hc g toc in black shales overlying the polbian bed lower morozkina balka formation organic richness of this level approximately 10 m 33 ft thick is controlled by low salinity and high bioproductivity the maikop group could generate approximately 2 0 t hc m2 surface area a significant part 0 45 t m2 comes from the lower morozkina balka formation which generates a high wax paraffinic naphthenic aromatic mixed oil the pshekha upper morozkina balka and batalpashinsk formations would generate low wax oil or condensate the hydrocarbon generation potential of the overlying formations is minor overall the generation potential of the maikop group is surprisingly low

le chaˆtelet gold bearing arsenopyrite deposit massif central france mineralogy and geochemistry applied to prospecting abstract the abundant data available on the geochemistry and mineralogy of the herynian gold deposit of le cha telet massif central france formed the basis for an analysis of the complex signature of a gold deposit and its hydrothermal alteration haloes this study describes the deposit and its environment at various scales the sulfide paragenesis of the le cha telet deposit resulted from several stages one of which was an event responsible for the deposition of au bearing arsenopyrite quartz veins the au is contained within the arsenopyrite lattice hydrothermal activity associated with these veins produced two superimposed alteration haloes an outer halo of kaolinite tosudite siderite alteration that developed at the expense of the plagioclase minerals and an inner halo of illite siderite alteration that affected all the minerals the hydrothermal alteration was followed by silicification of the wall rocks and then deposition of the au bearing arsenopyrite the hydrothermal alteration related to the event also generated geochemical signatures such as li b lree as sb au and w anomalies mineralogical studies and geochemical analyses of the hydrothermal facies show that 1 the anomalous li is trapped mainly in the tosudite lattice and to a lesser degree in the illite lattice and 2 the b is probably located in tosudite and illite lattices arsenic sb and au are contained in the arsenopyrite lattice during weathering the lithochemical signatures determined by the analytical techniques used in this study lose some of their specific characteristics depending on the original concentrations at deposit scale 0 25 1 0 km 2 b and li in the soill profiles indicate zones of hydrothermal alteration whereas as and au indicate zones of mineralization at a regional scale the association of au li and b in stream sediments is characteristics of this type of mineralization therefore in the hydrothermal setting described at le cha telet au as li and b appear at all scales to be dependable pathfinders for au bearing hydrothermal systems of possible economic interest

oil families and their source rocks in the weixinan sub basin beibuwan basin south china sea abstract thirty one crude oils and 15 source rocks were selected for molecular geochemical and isotopic analyses in order to establish the genetic relationships between discovered oils and petroleum source rocks in the weixinan sub basin beibuwan basin south china sea three groups of oils were recognized group i oils are only found in the upper section of the liusagang formation with a moderate abundance of c 30 4 methylsteranes low oleanane contents and lighter 13 c values showing a close relation to the shale occurring in the upper section of the liusagang formation group ii is represented by the majority of the discoveries and is distributed in multi sets of reservoirs having different ages the oils are characterized by a high abundance of c 30 4 methylsteranes low to moderate abundance of oleanane and heavy 13 c values and shows a good correlation with the lacustrine shale and oil shale in the middle section of the liusagang formation group iii oils occurred in the lower section of the liusagang formation the oils have a lower concentration of c 30 4 methylsteranes relatively high abundance of oleananes and their 13 c values are intermediate oils of this group correlated well with the shallow lake delta mudstone of the lower section of liusagang formation these oil source genetic relationships suggest a strong source facies control on the geographic distribution of oil groups within the weixinan sub basin the geochemical data indicate shale in the middle section of the liusagang formation has an excellent oil generation potential and the lower and upper sections contain dark shale and mudstone with good to fair oil potential future exploration or assessment of petroleum potential of the sub basin could be improved by considering the proposed genetic relationship between the oil types and source rocks as well as their distribution

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin

impact of marine incursions on lacustrine source rocks organic matter quantity quality and kinetics in the paleocene south yellow sea basin offshore eastern china abstract the impact of marine incursions during transgression on the quantity and quality of organic matter in lacustrine source rocks is critical to understanding their source rock properties and therefore on their hydrocarbon generation potential but is also challenging and controversial here we examine this issue based on a case study in the south yellow sea basin sysb offshore eastern china addressing organic matter om quantity quality and petroleum generation kinetics a total of 139 lacustrine source rock samples was collected from the fourth member of the paleocene funing formation e1f4 in the sysb and investigated for organic petrographic and geochemical characteristics the samples are immature to early oil window mature and the om in all samples is dominated by terrigenous material as shown by the organic petrography relatively low hydrogen indices and biomarker distributions the sediments are classified as inert to gas prone however the presence of marine fossils red and brown algae coccolithophores and probably neomonoceratinabullata and the biomarker results suggest that marine incursions occurred during the deposition of the lower unit of the e1f4 e1f4l the samples from this unit display higher hi values and more depleted 13corg ratios but lower toc and s1 s2 contents than the upper unit of the e1f4 e1f4u source rocks without marine influence this suggests that marine incursions primarily improved the quality rather than quantity of organic matter bulk kinetics indicated that marine incursions also led to a more homogenous om and compositional kinetics and phase properties suggest that black oil is generated throughout the process of kerogen conversion thus our data suggest that marine incursions had a positive effect on the om quality and oil generation potential of these lacustrine source rocks therefore the impact of marine incursions should be fully considered during source rock evaluation of coastal lacustrine basins especially during high sea level stages in addition the greatest hydrocarbon exploration potential is observed in the south 4th sag of the southern depression and thus this study provides valuable data for shaping regional exploration strategy in the sysb

shallow structure and recent evolution of the aegean sea a synthesis based on continuous reflection profiles abstract a dense grid of continuous seismic reflection profiles partly calibrated with drilling results has allowed construction of a structural outline of the entire aegean sea in the north aegean we observe a clear difference between the thickly sedimented northern margin basins and the steep slopes of the trough margin of the southern north aegean the trough itself comprises a series of separate tectonic depressions resulting from an apparent transtensional motion the central aegean consists of a complex tectonic puzzle caused by the prevailing extension incipient strike slip faulting sub parallel to the north aegean trough trend may however affect its eastern anatolian domain three main structural areas characterize the southern aegean comparable structural directions cut across this chiefly extensional basin but one fault system may be prevailing over the others depending on the area the central cretan sea results from the interaction of at least two distinct extensions these were superimposed on previous mostly e w structural trends generated during the inception of the southern hellenic subduction and led to the present day predominant sw ne trending extension as a hypothesis we propose that the overall late miocene present evolution of the aegean sea is directly dependent on two geodynamic processes to the southeast of the area collision between arabia and turkey leads to the lateral westward expulsion of the aegean continental crust and to the west hellenic subduction is still active

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

the geological signature of a slab tear below the aegean in this paper we explore the geology of the aegean region in the miocene to identify the geological signature of a first order slab tear observed in all tomographic models from 15 to 8 ma the tear is associated spatially and timely with a fast clockwise rotation of the external hellenides alkaline volcanism high temperature metamorphic domes with a predominance of north dipping detachments and south westward migration of granitoid intrusions these features suggest a warmer geodynamic environment during the rotation and the impact of a hot mantle flow associated with the tear the 8 ma duration between the first high temperature metamorphic domes in the centre of the archipelago and the beginning of the fast rotation may correspond to the time needed for the slab to bend stretch and finally tear

the micro scale simulation of maturation outline of a new technique and its potential applications a micro analytical technique has been developed for artifically maturing sedimentary organic matter and then quantifying the major components generated during this process in a single analytical step such a capability is well suited for examining the compositional relationships between kerogens and petroleums determining reaction kinetics and making precursor product mass balances according to this technique simulations are made using sealed glass capillary tubes heated here for three days at 300 c 330 c and 350 c pyrolysis products are then released directly into a combined thermovaporisation pyrolysis gc instrument and the major components of the entire c1 yto c35 range can be quantified in a single step using gas chromatography alkene yields are very low and pyrolysates are oil like this is exemplified by the fact that then c9 c19 alkane distribution range of simulated whole petroleum chromatograms from originally immaturegloeocapsamorpha typz alginite a resembles that seen in crude oils generated from this same kerogen type in nature sealed tube experiments usingbotryococcus type alginite a generated a high wax pyrolysate the relative abundance ofn alkanes in the c2 c32 range of many kerogen pyrolysates does not appear to change significantly despite an approximately fifteen fold difference inn alkane yield between the 300 c and 350 c experiments kerogens which are paraffinic oil prone and whose pyrolysates are very rich inn alkanes might therefore generate petroleums in nature with a fixed wet gas c2 c4 to oil c5 ratio alginite b in a greenland shale is much more thermally labile than eitherbotryococcus type alginite a orgloeocapsamorpha type alginite a the mass balance capabilities of the technique have been tested using alum shale kerogen two gas chromatograms were obtained one for the free compounds generated during simulation and one for the high temperature pyrolysate of the kerogen residue for each heating experiment precursor product relationships were qualitatively assessed and dead carbon formation was quantified in this exercise

depositional environment of the late santonian lacustrine source rocks in the songliao basin ne china implications from organic geochemical analyses abstract the songliao basin slb located in northeastern china is one of the largest cretaceous continental sedimentary basins in the world the slb is filled with sediments deposited in the upper jurassic the lower cretaceous and the upper cretaceous epochs the nenjiang formation k2n is subdivided into five members where member 2 k2n2 was deposited in the late santonian in the lower part of the nenjiang formation this member is characterized by a thick succession of organic rich source rocks however the complexity of the depositional environment raises questions about the specific factors that drove this accumulation of organic material here we present data on the total organic carbon toc contents and their stable carbon isotope values 13corg as well as biomarker data from 50 outcrop samples collected from the yuewangcheng ywc section in the southeastern slb according to the variations of the bulk organic parameters toc and 13corg and biomarker indices the profile could be divided into three stages stages i iii the distribution of biomarkers n alkanes steranes and hopanes and 13corg values indicate that the organic matter om in the lower k2n2 is derived largely from algae and macrophytes with a minor input from bacteria and land plants the water column was stratified as indicated by the presence of gammacerane variations in the pristane phytane pr ph and aryl isoprenoids relative to phenanthrene ratio a i p suggest that bottom waters were anoxic during stage i 31 5 26 0 m and stage ii 26 0 16 3 m with the anoxic layer impinging on the euphotic zone and a relative oxic environment at stage iii 16 3 0 m this brackish environment persisted in the water over the interval represented by the section as reflected by methytrimethyltridecyl chromans mttcs index mttci and mttc mttc ratios marine transgressions with subsequent seawater incursions can be detected with the presence of 24 n propyl cholestanes and 24 isopropyl cholestanes in the lower k2n2 sediments especially during stage i these seawater incursions are closely correlated with anoxic conditions and the deposition of organic rich source rocks

from petroleum type organofacies to hydrocarbon phase prediction the organic facies concept states that kerogen abundance and composition are relatable to depositional settings this link has been extended using open system pyrolysis methods to include major petroleum types whose gross compositions are inherently defined by source rock kerogens and hence to petroleum composition which directly controls the physical response of fluids to changing pressure and temperature conditions during secondary migration the possibility to model petroleum composition during hydrocarbon generation as well as the phase behavior of the fluids during migration is now available in modern basin modeling software however whereas pyrolysis methods can accurately reconstruct hydrocarbon gas oil ratios and liquid compositions they are inherently incapable of correctly reproducing the gas composition of natural fluids and because the gas composition dominantly controls the phase behavior of petroleums multicompound compositional kinetic predictions based on pyrolysis results alone are inappropriate for the prediction of phase behavior the new phasekinetics approach described here combines open and closed system pyrolysis techniques to characterize the compositional evolution of the fluids generated as a function of increasing thermal stress as well as correcting experimentally determined gas compositions and therefore overcomes these deficiencies it has been used to develop compositional kinetic schemes capable of predicting natural petroleum phase behavior for different organofacies types the methodology uses a compositional description of the generated fluids similar to that used in pressure volume temperature pvt simulation selected studies in the norwegian north sea brazil and mexico demonstrate the quality of the tuned compositional predictions for different organic facies types

evidence for significant granite space creation by the ballooning mechanism the example of the ardara pluton ireland the emplacement mechanism of the ardara granite a caledonian pluton located on the northwestern seaboard of ireland has been a widely cited and a key point of reference in the debate about the granite space problem for nearly half a century early models related its subcircular tailed shape concentric foliation pattern and concentrically deformed envelope to diapirism it was subsequently reinterpreted using strain data as a ballooning pluton that was created by 70 in situ expansion at the emplacement site and was later cut by a regional shear zone recently it was the leading example in a wide ranging review of forcefully emplaced plutons of this type and was reinterpreted as a series of nested diapirs associated with only modest amounts 30 of forceful space creation but a large component of inferred early block stoping we report the results of the complete remapping and extensive collection of new structural data from this 8 km diameter normally zoned three phase calc alkaline pluton we confirm the existence of the steeply inclined internal foliation pattern and that it was formed in the magmatic state although this and the outline of the pluton are modified by late stage high temperature solid state regional transcurrent shear zones along two of the pluton contacts structural mapping has failed to identify a macroscopic lineation in the magmatic foliation planes and this is confirmed by strain determinations using mafic enclave populations and magmatic crystal separations for the magmatic state deformation that show nearly pure flattening type strains k 0 strains measured by these techniques show an apparently smooth gradient increasing outward toward the pluton contacts from an inner low strain zone we argue that these features together with the simple normal petrographic zonation a lack of small scale structures that would indicate the pluton had moved up relative to the wall rocks and an exposure level that is not in the roof zone are inconsistent with diapirism either singly or multiply but are most easily explained by a ballooning emplacement mechanism synmagmatic shear sense data from both the pluton and the adjacent country rocks indicate however that within the overall context of radial ballooning there was a limited amount of late stage nonradial northward injection of magma an inversion of the deformed enclave and crystal spacing strain determinations and strain determinations within the country rocks suggest that more than 80 of the volume of the pluton was accommodated by the ballooning mechanism

tectonic significance of synextensional ductile shear zones within the early miocene alacamdag granites northwestern turkey synextensional granitoids may have significant structural features leading to the understanding of the evolution of extended orogenic belts one of the highly extended regions the aegean region includes a number of metamorphic core complexes and synextensional granitoids that developed following the alpine collisional events the alacamdag area in northwestern turkey is one of the key areas where miocene granites crop out along the boundary of various tectonic units structural data from the early miocene alacamdag granites demonstrated two different deformation patterns that may provide insights into the development of granitic intrusions and metamorphic core complexes 1 steeply dipping ductile shear zones caused emplacement of syn tectonic granite stocks they include kinematic indicators of a sinistral top to the sw displacement this zone has also juxtaposed the izmir ankara zone and the menderes massif in the west and east respectively 2 gently dipping ductile shear zones have developed within the granitic stocks that intruded the schists of the menderes massif on the structurally lower parts kinematic data from the foliated granites indicate a top to the ne displacement which can be correlated with the direction of the hanging wall movement documented from the simav and kazdag metamorphic core complexes the gently dipping shear zones indicate the presence of a detachment fault between the menderes massif and the structurally overlying izmir ankara zone mesoscopic to map scale folds in the shallow dipping shear zones of the alacamdag area were interpreted to have been caused by coupling between ne sw stretching and the accompanying nw se shortening of ductilely deformed crust during early miocene times one of the ne trending shear zones fed by granitic magmas was interpreted to form the northeastern part of a sinistral wrench corridor which caused differential stretching between the cycladic and the menderes massifs this crustal scale wrench corridor the izmir balikesir transfer zone may have controlled the asymmetrical and symmetrical extensions in the orogenic domains the combination of the retreat of the aegean subduction zone and the lateral slab segmentation leading to the sinistral oblique slip tearing within the eurasian upper plate appears to be a plausible mechanism for the development of such extensive ne trending shear zones in the aegean region

synkinematic granite emplacement in a shear zone the pleasant hills pluton canadian appalachians the 361 356 ma late devonian pleasant hills pluton comprises a series of sheets of mafic felsic and hybrid intermediate plutonic rocks that were emplaced along a positive flower structure associated with the crustal scale cobequid fault zone this dextral strike slip fault zone forms the boundary of the meguma and avalon terranes the sequence of emplacement is inferred from crosscutting structures radiometric dating shows that the pluton was crystallized within a few million years gabbroic magma was probably derived from partial melting of the mantle beneath the extensional magdalen basin and successive batches of mafic magma were progressively richer in h 2 o ti zr and nb felsic magmas were probably derived by partial melting of the lower crust small batches of felsic magma show differing trace element evolution that reflects changes in magma temperature and type of volatiles younger magmas being generally richer in high field strength elements and fluorine rapakivi textured granite is common heat transfer and mass transfer along the fault zone resulted in thermal softening and lubrication of all branches of the flower structure so that there was repeated magma flow through each branch the presence of magma controlled the localization of strain which is expressed as synmagmatic deformational structures and deformation continued under solid state conditions to produce mylonitic fabrics each branch of the flower structure acted as a pathway for many magma batches and only small volumes of magma reached the highest structural levels the pluton was emplaced by progressive widening of and magma emplacement along branches of the flower structure as a result of country rock translation this translation involved both lateral and upward movement of blocks within the cobequid fault zone dextral slip is recognized on the southern margin of the escaping block and reverse oblique sinistral slip on its northern margin the pleasant hills pluton shows progressive creation of space for magma along branches of the flower structure and gradual expansion of the pluton from a series of dike like bodies to a larger composite pluton through the emplacement of numerous small geochemically distinct magma batches

block rotations and continental extension in the central aegean sea palaeomagnetic and structural evidence from tinos and mykonos cyclades greece abstract the aegean sea floored by an attenuated continental crust is a mediterranean type back arc basin formed above the subducting african plate we investigated post 12 ma block rotation in relation to back arc extension in the area of the western cyclades central aegean sea on tinos island nw trending dacitic dikes and a miocene monzogranite penetrated an alpine metamorphic series k ar analyses of 6 dike samples yielded an average age of 11 5 0 4 ma the palaeomagnetic analyses of the dikes and the monzogranite reveal 23 vertical axis clockwise rotation we assume that the dacitic dikes intruded vertical as they are today and that no tilt correction is required this is supported by the fact that no inclination anomaly is revealed when the palaeomagnetic data is compared with a tilt corrected pole position from kimi evia the absence of tilting implies that post 12 ma crustal thinning in the area of tinos island was minor on mykonos a low angle normal fault dipping 30 to the ne juxtaposes a series of oligo miocene molasse sediments above a 10 12 ma granite published palaeomagnetic data revealed a considerable amount of inclination flattening and 22 clockwise rotation of the footwall granite we show that tilting predated vertical axis rotation and that the now low angle normal fault originated steeper dipping ca 54 planar rotational fault geometry indicates extension of ca 60 in spite of the significant variations in the magnitude of post 12 ma upper crustal extension across the tinos mykonos transect crustal thickness below the entire area changes only slightly this indicates that upper crustal levels were decoupled from the lower crust the widespread middle miocene granitic magmatism in the cyclades suggests that flow in the lower crust may have had a dominant role in maintaining the smooth moho assuming that the western cyclades constitute a set of nw striking crustal blocks it is estimated that vertical axis rotations increased the n s dimension of the area by ca 31 e g 25 km the exact timing of this clockwise rotation is not well constrained but it postdated the formation of low angle normal faults and tilting and may have taken place in the late miocene

marine incursion events in the late cretaceous songliao basin constraints from sulfur geochemistry records abstract songliao basin in ne china developed the most productive oilfield in the world sourced from terrestrial rocks the main source rock of the basin includes member 1 of the qingshankou k2qn1 and members 1 and 2 of the nenjiang formation k2nj1 2 however the exact reasons for the formation of the source rock especially the k2qn1 are still controversial former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of k2qn1 but further geochemical evidence is needed this paper explores the distinct sulfate levels that distinguish marine from fresh waters of the songliao paleo lake we undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the quantou formation k1q4 to top of member 1 of the qingshankou k2qn1 the ratio of organic carbon to the pyrite sulfur toc pys proved the previously suggested saline conditions during the deposition of k2qn1 and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for k2qn1 but also for top of k1q4 the exact time for the beginning of marine incursion is to be determined the marine incursion within k2qn1 is not strong and partially controlled by the fluctuation of paleo lake level the present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the songliao paleo lake although further studies are still needed

the emplacement of the rieserferner pluton eastern alps tyrol constraints from field observations magnetic fabrics and microstructures abstract within the alpine chain several tertiary intrusions e g bergell adamello intruded along the periadriatic lineament this study attempts to show how the rieserferner pluton vedrette di ries is related to the defereggen antholz vals dav line for a survey of the fabric pattern over the pluton the anisotropy of the magnetic susceptibility ams was determined on nearly 170 samples low bulk susceptibilities of k vol 6 si and a total degree of anisotropy p

hydrocarbon potential of the lower cretaceous mudstones in coastal southeastern china the cretaceous hosts the highest hydrocarbon potential among all geological stratigraphic sequences worldwide and the lower cretaceous in coastal southeastern china with the development of black mudstones and shales has potential for hydrocarbon generation this potential therefore is of significance to regional hydrocarbon exploration both onshore and offshore however it has not been investigated in detail here we address this issue based on the results of integrated organic geochemistry and petrology of four representative outcrop sections in the region results show that there are two possible source rock sequences in the lower cretaceous of coastal southeastern china that is a lower sequence represented by the bantou formation black mudstones in the fujian province and an upper interval represented by the guantou formation black mudstones or calcareous mudstones in the zhejiang province the organic matter abundance of these two formations reaches levels of poor to good source rocks the kerogen is dominated by type iii whereas type ii can also be found locally in the northwestern fujian province most samples are highly mature to overmature except for the samples with less influence of volcanism in the northern guangdong province comparatively the organic matter abundance of the early stage source rocks is higher than for the late stage rocks and the kerogen type is less favorable however the maturity shows little correlation with age and is largely related to volcanism therefore the lower cretaceous in coastal southeastern china seems to have hydrocarbon potential gas in particular in local areas including the northern guangdong province and its analog in offshore basins for the early stage and the northwestern fujian province and its analog in offshore basins for the late stage these results and understanding provide insights for expanding new hydrocarbon exploration targets in southeastern china both onshore and offshore and may also have implications for understanding the regional cretaceous geology

observations from the floor of a granitoid pluton inferences on the driving force of final emplacement an east west profile across the tilted bergell pluton exposes a 10 km thick interval in terms of crustal depth consequently the floor as well as the root and side of the main intrusive body of the pluton crop out at the surface and a tentative three dimensional geometry is constructed at the highest crustal level the geometry and deformation features at the margin of the pluton indicate ballooning whereas the folded floor of the main intrusive body indicates synmagmatic shortening related to regional deformation these contrasting features are best explained by shortening of the base of the pluton which caused an expansion at a higher crustal level final emplacement of the pluton into higher crustal levels was therefore not driven primarily by buoyancy but rather by regional deformation within deeper levels of the crust