depleted mantle source for the ulungur river a type granites from north xinjiang china geochemistry and nd sr isotopic evidence and implications for phanerozoic crustal growth abstract the ulungur river granites from north xinjiang china display two petrological trends 1 a peralkaline trend composed of alkali amphibole and alkali pyroxene bearing granites and dykes and 2 an aluminous trend represented by alkali granites monzogranites and aluminous granite dykes within the peralkaline granites rb sr whole rock isochron dating yielded an age of 300 ma for the emplacement of the peralkaline granites and 270 ma for the aluminous granites the ulungur river granites share all the geochemical features common to a type granites of the world the ulungur river granites are post orogenic and emplaced in a post collisional extensional environment the peralkaline and aluminous rocks have indistinguishable nd isotopic compositions they have unusually positive and relatively uniform nd t values ranging from 5 1 to 6 7 for the peralkaline rocks at 300 ma and from 5 5 to 5 9 for the aluminous rocks at 270 ma the initial 87sr 86sr ratios cannot be determined precisely by the whole rock isochron technique mainly because most samples are highly radiogenic and have high rb sr ratios in addition the large variation in sr isotopic compositions can partly be explained by crustal contamination during magma differentiation the nd isotopic data clearly indicate that both the peralkaline and aluminous rocks were derived from a long lived depleted mantle reservoir the formation of the ulungur river a type granites is hypothesized as follows 1 a depleted mantle was first metasomatised then subjected to partial melting leading to the generation of basic magmas now represented by the kalatongke mafic ultramafic complex in the ulungur river area 2 the basic magmas have undergone high degrees of fractional crystallisation with separation of biotite hornblende plagioclase potassium feldspar and other accessory phases such as apatite and ilmenite with the residual magmas forming the peralkaline granites during the magmatic differentiation the liquids were probably contaminated by crustal materials as evidenced by nb depletion and nd sr isotopic systematics on the other hand the formation of aluminous granites involved a replenishment of new mantle derived magmas into the differentiating magma chamber and followed by fractional crystallisation with retention of hydrous phases hornblende and biotite the petrological evolution of the ulungur river granites is thus from peralkaline to calc alkaline and not from calc alkaline to peralkaline as more often observed elsewhere the ulungur river granites in common with the voluminous granitoids occurring in the central asian orogenic belt represent a significant juvenile addition of the continental crust in the phanerozoic

geochemistry and zircon geochronology of the permian a type hasanrobat granite sanandaj sirjan belt a new record of the gondwana break up in iran the sanandaj sirjan metamorphic plutonic belt ssb in west central iran is a polyphase metamorphic terrain composed of dominantly greenschist grade metasedimentary and metavolcanic rocks and felsic to mafic plutons of neoproterozoic phanerozoic ages the hasanrobat granite in central ssb occurs as a single pluton 20 km 2 surface area with relatively consistent mineralogy and chemistry quartz alkali feldspars microcline and perthite sodic plagioclases and biotite are the main constituents commonly associated with minor amphibole accessory phases include zircon allanite apatite and magnetite the country rocks are upper carboniferous lower permian sandstones and dolomitic limestones scattered patches of skarn type assemblages dominated by tremolite and talc occur in the dolomitic limestones and sandstones are recrystallized to a coarse grained quartzite at contact with the granite the granite is metaluminous to slightly peraluminous and is distinguished by high feo t mgo ratios typical of ferroan a type granites the a type affinity is also reflected by high na 2o k 2o high ga al ratios high contents of large ion lithophile elements lile high field strength elements hfse and rare earth elements ree as well as low contents of sr and distinct negative eu anomalies the biotites are aluminous fe rich and plot near the siderophyllite corner in the quadrilateral biotite diagram they are further distinguished by high fluorine contents 0 61 to 1 33 wt amphibole is ferrohastingsite in composition ion microprobe analyses of zircon grains separated from a representative granite sample yielded concordant u pb ages with weighted mean 206 pb 238 u age of 288 3 3 6 ma the granite and the country rocks are cut by a set of mafic dykes with asthenosphere like geochemical signatures such association suggests anorogenic intraplate magmatism in lower permian in the region this provides further evidence for and significantly constrains timing of a major extension in upper paleozoic in iran previously inferred from the rock record the extension led to the gondwana break up and the opening of neotethys ocean between sanandaj sirjan and zagros in permian

residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

active faults in the zagros and central iran abstract active tectonic movements in the northwestern zagros include right lateral slip at the rate of about 10 mm a along the main recent fault which inherits the position of the main thrust now inactive and active thrusting and accompanying folding distributed between several zones southwest of the main recent fault in the southeastern zagros the fars province there are several right lateral faults that extend n s obliquely to the overall trend of the zagros fault and fold belt these may be either branches of the main recent fault or faults accommodating relative broadening of the outer zagros in its southeastern segment the main thrust in the southeastern zagros also remains inactive the ipak north tehran and mosha fault zones and several minor structures in the eastern alborz form the e w trending active fault system with combined reverse and left lateral slip on the ipak and mosha zones lateral movements with the late quaternary mean rate exceeding 1 mm a dominate over vertical fault movements together with right lateral faults stretching northeast of zagros the faults of the alborz may accommodate east directed motion of the iranian microplate

probabilistic formulation of avo modeling and avo attribute based facies classification using well logs we have developed a probabilistic formulation to derive the probability density function of amplitude variation with offset avo attributes given the distribution of elastic properties in the context of avo analysis of well log data the proposed probabilistic formulation includes the analytical expression of the posterior distribution and contributes to the correct propagation of the uncertainty through the avo model when this analysis is performed in each facies the resulting posterior probability density functions of avo attributes conditioned by the elastic attributes and the underlying log facies classification can be used in a bayesian inversion workflow to obtain the avo attribute based facies classification this classification is then compared with the petrophysical log facies profile and can be extended to the entire reservoir model if inverted seismic attributes are available we demonstrate the methodology on a data set from an onshore tight sand gas reservoir in texas the main results of the application are the set of probability distributions of avo properties as a function of elastic attributes in each facies and the corresponding avo based facies profile at the well location a comparison of different statistical assumptions and a sensitivity analysis on the resolution of the elastic data set are presented

petrogenesis of post collisional a type granitoids from the urumieh dokhtar magmatic assemblage southwestern kerman iran constraints on the arabian eurasian continental collision abstract three plutons deh siahan bande bagh and baghe khoshk sharghi collectively referred to as the dbb hereafter in southwestern kerman in the southeastern part of the urumieh dokhtar magmatic assemblage udma of the zagros orogenic belt differ from the typical calc alkaline metaluminous i type intrusions of the region the dbb intrusions have a distinct lithological assemblage varying from diorite through monzogranite and monzonite to alkali feldspar syenite and alkali granite the dbb granitoids are metaluminous to slightly peraluminous alkaline to shoshonitic in composition and have high total alkali contents with k2o na2o high feot mgo values and low cao and mgo contents they are enriched in some liles such as rb and th and hfses such as zr y and rees except eu and depleted in sr and ba relative to primordial mantle and have low concentrations of transitional metals these features along with various geochemical discriminant diagrams suggest that the dbb granitoids are post collisional a type granitoids which had not been recognized previously in the udma the chondrite normalized ree patterns of the dbb granitoids show slightly enriched light rees la sm n 2 26 4 13 negative eu anomalies eu eu n 0 19 0 74 and flat heavy ree patterns gd yb n 0 80 1 87 the negative eu anomaly indicates an important role for plagioclase and or k feldspar during fractional crystallization whole rock rb sr isotope analysis yields an isochron age of 33 1 ma with an initial 87sr 86sr value of 0 7049 0 0001 whole rock sm nd isotope analysis gives endt values from 2 56 to 3 62 at 33 ma the positive endt and low isr values of the dbb granitoids together with their tdm of 0 6 0 7 ga suggest their formation from partial melting of a lithospheric mantle source modified by fluids or melts from earlier subduction processes melting of lithospheric mantle occurred via a dehydration melting process at pressures below the garnet stability field as a consequence of lithospheric mantle delamination or break off of a subducted slab and melting of the lithospheric mantle by upwelling of hot asthenosphere on the basis of rb sr age dating and the post collisional geochemical signatures of the dbb granitoids along with extensive pre collisional volcanic eruptions in middle eocene we suggest late eocene for the time of collision between the arabian and central iranian plates this also implies that the calc alkaline i type intrusions in the southwestern kerman and in other parts of the udma may have formed in a post collisional context

the southern caspian a compressional depression floored by a trapped modified oceanic crust the south caspian intracontinental depression floored by oceanic basement is a relatively stable block with minor deformation surrounded by active fold thrust belts of arcuate form talesh alborz and kopeh dagh mountains which have undergone intense late cainozoic crustal shortening the basin is interpreted as a neogene quaternary compressional depression bounded by multi role mountain bordering reverse faults and apparently floored by a late paleozoic triassic or late mesozoic early tertiary modified oceanic crust trapped along an old geosuture it may be a relic of an old paleozoic triassic ocean or else a marginal sea developed behind a mesozoic paleogene ocean and analysis of geological and geophysical data enables a scheme to be suggested the general arcuate shape of the alborz and the talesh bordering mountain belts follows the pattern of the supposed rigid and thickened ocean crust of south caspian depression a tectono sedimentary study of the south caspian region coupled w

cooling rates of lunar orange glass beads abstract it is widely accepted that the apollo 17 orange glass beads are of volcanic origin the degree of degassing of the glass beads depends on their cooling rates so the estimation of volatile contents in the parental magmas of these lunar pyroclastic glasses also depends on the cooling rates the cooling rate can be estimated using the calorimetric properties of the glass across the glass transition in this study a series of heat capacity measurements were carried out on hand picked lunar volcanic orange glass beads during several cycles of heating to temperatures above their glass transition using a differential scanning calorimeter the cooling rate of orange glass beads sample 74220 867 was calculated to be 101 k min using the correlation between glass cooling rates and fictive temperatures estimated from their heat capacity temperature paths this cooling rate is close to the lower end of the range that best fits the diffusion profiles of several volatile species in the glass beads and at the upper end of the cooling rate range recorded in glasses quenched subaerially on earth the cooling rate is likely to be controlled by the cooling environment cooling medium such that the lunar volcanic glass beads could have been cooled in a gaseous medium released from volcanic eruptions on the moon but not during free flight in vacuum the existence of a gas medium suggests in turn that there may have been at least a short lived or episodic atmosphere on the early moon at around 3 5 ga

microseismicity and seismotectonics of the south caspian lowlands ne iran this paper is concerned with the microseismicity and seismotectonics of the eastern south caspian sea region where the east alborz mountains descend to meet the south caspian lowlands of ne iran to better understand the present day tectonics and seismicity of this region which includes the cities of gorgan and gonbad e qabus combined population 500 000 we installed a temporary local seismic network across the area for 6 months between 2009 and 2010 we analysed the seismicity and focal mechanisms together with data from the permanent networks of the institute of geophysics university of tehran igut and the international institute of earthquake engineering and seismology iiees based in tehran microseismicity is focused primarily on the shahrud fault system which bounds the east alborz range to the south relatively few earthquakes are associated with the khazar thrust fault which bounds the north side of the range a cluster of shallow microseismicity 15 km depth occurs 40 km north of the khazar fault within the south caspian lowlands scl an area typically thought to be non deforming this area coincides with the location of three relatively deep thrust earthquakes m w 5 3 5 5 which occurred in 1999 2004 and 2005 inversion of teleseismic body waveforms allows us to constrain the depth of these earthquakes at 26 29 km although significant sedimentation throughout the scl obscures any expression of recent fault activity at the surface focal mechanisms of well located events from the shallow cluster of micro seismicity show a significant component of left lateral strike slip motion assuming slip occurs on ne sw fault planes typical of active faults in the region as well as a small normal component inversion of traveltimes for well located events in our network yields a velocity structure for the region and a moho depth of 41 km the pattern of deep thrust and shallow normal seismicity could be explained by bending of the rigid south caspian crust as it underthrusts the east alborz mountains and central iran late quaternary reorganization of drainage systems in the scl may be the result of shallow normal fault activity within the scl

inversion styles in the songliao basin northeast china and estimation of the degree of inversion abstract two inversion patterns fault reactivated and cover folded inversions are recognized in the songliao basin of northeastern china mild inversion with a reactivated fault showing normal separation in all synrift beds moderate partial inversion and total inversion are the common styles of fault reactivated inversion the magnitude of extension by rifting as well as orientation of the synrift faults in relation to the compressional direction during inversion significantly controlled the inversion structures the same amount of shortening may produce a moderate inversion style where the normal slip during the rifting was large but a total inversion in which the initial normal slip was small the cover folded inversions in the songliao basin have either no normal faults or have one or more normal faults that occurred prior to inversion and remained dormant during the inversion the geometry of cover folded inversion may be controlled by deep faults in the basement a graben like basement fault assemblage can result in an antiformal geometry while a horst like basement fault assemblage may control a synformal cover folded inversion an inversion with antiformal geometry of the sedimentary sequences is the major style in the songliao basin a new method of estimating the degree of fault inversion is discussed the degree of fault inversion is the ratio between reverse slip during inversion and normal slip during extension both measured along the fault it can be estimated in most fault reactivated inversions where the top of the basement or the floor of the synrift deposits does not fold during the inversion the horizontal inversion ratio represents the relative amount of shortening and extension of a structure or basin it can be used to analyse the degree of inversion of complex structures or basins however both fault inversion and horizontal inversion ratios are primarily influenced by the amount of extension if undergoing same amount of shortening a structure with a small amount of extension may have a much greater inversion ratio than one with a large amount of extension

microseismicity in the region of tehran we record and analyze small earthquakes around tehran iran using the permanent seismological network of the institute of geophysics of the university of tehran and two temporary dense seismological networks installed for several weeks during 1999 and 2000 regional seismicity is distributed throughout central alborz extending from the caspian sea to the iran plain with the highest level of activity east of tehran related to the mosha and to the garmsar faults which both dip northward and have had strong historical earthquakes our focal mechanisms the first for these faults confirm a left lateral strike slip motion

the continental margin of the mesozoic tethys in the western alps abstract most of the structural units of the western alps were derived from the european continental margin of the ligurian ocean a segment of the mesozoic tethys ocean their mesozoic palaeotectonic and stratigraphic evolution bears witness of the following main stages 1 deposition of the triassic platform carbonates essentially prerift but nevertheless bearing the imprint of some extensional movements 2 the liassic middle jurassic rifting corresponds to the creation of a horst and graben system with especially tilted blocks and hence a shoal and basin palaeogeography but without a preliminary doming event 3 the late jurassic early cretaceous opening and spreading of the ligurian ocean began with a general collapse of the continental margin thermal subsidence latest middle jurassic and earliest late jurassic in this paper emphasis is given to the refting derived structures more especially to the major tilted crustal blocks a few tens of kilometres wide which can be either reconstructed or directly observed the rifting stage lasted roughly 40 m y with the alternation of extensional tectonic phases and of relatively quiet periods during the extensional phases movements along fault planes and related episodes of tilting were followed by sudden and rapid episodes of subsidence the latter may be interpreted as resulting from the isostatic and thermal readjustment that follows a phase of stretching of the crust and of the lithosphere the tectonic evolution of the margin continued but decreased during the late jurassic early cretaceous oceanspreading stage tectonic activity resumed in the late cretaceous this probably resulting from the beginning of contraction of both the ocean and the continental margin leading progressively to the continental collision in the tertiary

inversion of field data in fault tectonics to obtain the regional stress iii a new rapid direct inversion method by analytical means summary a new method for determining the reduced stress tensor with four degrees of freedom the orientations of the three principal stress axes as well as the ratio of principal stress differences using fault slip data or focal mechanisms of earthquakes is presented from a computational point of view the inversion of fault slip data is made in a direct way by purely analytical means as a result the determination process is extremely fast and adaptable on small microcomputers from a physical point of view the method aims at simultaneously i minimizing the angles between theoretical shear stress and actual slip vector and ii having relative magnitudes of shear stress large enough to induce slip despite rock cohesion and friction examples of application to actual fault slip data sets with good or poor variety of fault slip orientations are shown the double significance of the basic criterion adopted results in a more realistic solution of the inverse problem than the single minimization of the shear stria angle

petrogenesis and tectonic implications of late carboniferous a type granites and gabbronorites in nw iran geochronological and geochemical constraints abstract carboniferous igneous rocks constitute volumetrically minor components of iranian crust but preserve important information about the magmatic and tectonic history of sw asia ghushchi granites and gabbronorites in nw iran comprise a bimodal magmatic suite that intruded ediacaran cambrian gneiss and are good representatives of carboniferous igneous activity precise sims u pb zircon ages indicate that the gabbronorites and granites were emplaced synchronously at 320 ma ghushchi granites show a type magmatic affinities with typical enrichments in alkalis ga zr nb and y depletion in sr and p and fractionated ree patterns showing strong negative eu anomalies the gabbronorites are enriched in lrees nb ta and other incompatible trace elements and are similar in geochemistry to oib type rocks granites and gabbronorites have similar e nd t 1 3 to 3 4 and 0 1 to 4 4 respectively and zircon e hf t 1 7 to 6 2 and 0 94 to 6 5 respectively the similar variation in bulk rock e nd t and zircon e hf t values and radiometric ages for the granites and gabbronorites indicate a genetic relationship between mafic and felsic magmas either a crystal fractionation or silicate liquid immiscibility process further work is needed to resolve petrogenetic details the compositional characteristics of the bimodal ghushchi complex are most consistent with magmatic activity in an extensional tectonic environment this extension may have occurred during rifting of cadomian fragments away from northern gondwana during early phases of neotethys opening

stochastic reservoir characterization using prestack seismic data reservoir characterization must be based on information from various sources well observations seismic reflection times and seismic amplitude versus offset avo attributes are integrated in this study to predict the distribution of the reservoir variables i e facies and fluid filling the prediction problem is cast in a bayesian setting the a priori model includes spatial coupling through markov random field assumptions and intervariable dependencies through nonlinear relations based on rock physics theory including gassmann s relation the likelihood model relating observations to reservoir variables including lithology facies and pore fluids is based on approximations to zoeppritz equations the model assumptions are summarized in a bayesian network illustrating the dependencies between the reservoir variables the posterior model for the reservoir variables conditioned on the available observations is defined by the a priori and likelihood models this posterior model is not analytically tra

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

a hadean to paleoarchean geodynamo recorded by single zircon crystals knowing when the geodynamo started is important for understanding the evolution of the core the atmosphere and life on earth we report full vector paleointensity measurements of archean to hadean zircons bearing magnetic inclusions from the jack hills conglomerate western australia to reconstruct the early geodynamo history data from zircons between 3 3 billion and 4 2 billion years old record magnetic fields varying between 1 0 and 0 12 times recent equatorial field strengths a hadean geomagnetic field requires a core mantle heat flow exceeding the adiabatic value and is suggestive of plate tectonics and or advective magmatic heat transport the existence of a terrestrial magnetic field before the late heavy bombardment is supported by terrestrial nitrogen isotopic evidence and implies that early atmospheric evolution on both earth and mars was regulated by dynamo behavior

lithology color coded seismic sections the calibration of avo crossplotting to rock properties in the late 1960s several oil companies noticed that in environments of young clastic sediments large seismic amplitudes were associated with gas saturated sands this method of correlating lithology to normal incidence ni reflectivities was appropriately named the bright spot technique however it quickly became apparent that not all large amplitudes were necessarily associated with gas reservoirs and much to our chagrin not all gas reservoirs had large amplitudes for the next decade geophysicists tried numerous techniques to resolve the ambiguity associated with lithologic identification by means of the seismic attribute ni this met with various degrees of success finally ostrander s work on amplitude variation with offset avo led to the development of another seismic attribute s which improved our discrimination of lithologies see plane wave reflection coefficients for gas sands at nonnormal angles of incidence geophysics 1984 but proper application of this new attribute along wit

probabilistic petrophysical properties estimation integrating statistical rock physics with seismic inversion a joint estimation of petrophysical properties is proposed that combines statistical rock physics and bayesian seismic inversion because elastic attributes are correlated with petrophysical variables effective porosity clay content and water saturation and this physical link is associated with uncertainties the petrophysical properties estimation from seismic data can be seen as a bayesian inversion problem the purpose of this work was to develop a strategy for estimating the probability distributions of petrophysical parameters and litho fluid classes from seismics estimation of reservoir properties and the associated uncertainty was performed in three steps linearized seismic inversion to estimate the probabilities of elastic parameters probabilistic upscaling to include the scale changes effect and petrophysical inversion to estimate the probabilities of petrophysical variables andlitho fluid classes rock physics equations provide the linkbetween reservoir properties and velocities and lin

sr nd isotope geochemistry and tectonomagmatic setting of the dehsalm cu mo porphyry mineralizing intrusives from lut block eastern iran the dehsalm cu mo bearing porphyritic granitoids belong to the lut block volcanic plutonic belt central eastern iran these rocks range in composition from gabbro diorite to granite with dominance of monzonites and quartz monzonites and have geochemical features of high k calc alkaline to shoshonitic volcanic arc suites primitive mantle normalized trace element spider diagrams display strong enrichment in large ion lithophile elements such as rb ba and cs and depletions in some high field strength elements e g nb ti y and hree chondrite normalized plots display significant lree enrichments high lan ybn and a lack of eu anomaly high sr y and la yb ratios of dehsalm intrusives reveal that despite their k rich composition these granitoids show some resemblances with adakitic rocks a rb sr whole rock feldspar biotite age of 33 1 ma was obtained in a quartz monzonite sample and coincides within error with a previous geochronological result in chah shaljami granitoids further northwest within the lut block 87sr 86sr i and endi isotopic ratios range from 0 70481 to 0 70508 and from 1 5 to 2 5 respectively which fits into a supra subduction mantle wedge source for the parental melts and indicates that crustal contribution for magma diversification was of limited importance sr and nd isotopic compositions together with major and trace element geochemistry point to an origin of the parental magmas by melting of a metasomatized mantle source with phlogopite breakdown playing a significant role in the geochemical fingerprints of the parental magmas small amounts of residual garnet in the mantle source also help to explain some trace element patterns geochemical features of dehsalm porphyries and its association with cu mo mineralization agree with a mature continental arc setting related to the convergence of afghan and lut plates during oligocene

lunar volcanism produced a transient atmosphere around the ancient moon abstract studies of the lunar atmosphere have shown it to be a stable low density surface boundary exosphere for the last 3 billion years however substantial volcanic activity on the moon prior to 3 ga may have released sufficient volatiles to form a transient more prominent atmosphere here we calculate the volume of mare basalt emplaced as a function of time then estimate the corresponding production of volatiles released during the mare basalt forming eruptions results indicate that during peak mare emplacement and volatile release 3 5 ga the maximum atmospheric pressure at the lunar surface could have reached 1 kpa or 1 5 times higher than mars current atmospheric surface pressure this lunar atmosphere may have taken 70 million years to fully dissipate most of the volatiles released by mare basalts would have been lost to space but some may have been sequestered in permanently shadowed regions on the lunar surface if only 0 1 of the mare water vented during these eruptions remains in the polar regions of the moon volcanically derived volatiles could account for all hydrogen deposits suspected to be water currently observed in the moon s permanently shadowed regions future missions to such locations may encounter evidence of not only asteroidal cometary and solar wind derived volatiles but also volatiles vented from the interior of the moon

onset of subduction as the cause of rapid pliocene quaternary subsidence in the south caspian basin backstripping a representative stratigraphic column from the northwest of the south caspian basin shows that 2 4 km of tectonic subsidence has occurred since ca 5 5 ma at 1 5 10 times the rate recorded in typical foreland basins roughly half the basin s sedimentary thickness of 20 km has accumulated in this time while the upper part of the succession has begun to deform by buckle folding the south caspian basement appears to be either thick oceanic crust or thinned high velocity continental crust seismicity and gravity data indicate that the basement is in the initial stages of subduction under the middle caspian region to the north we propose that basement subduction began ca 5 5 ma to create the major pliocene quaternary subsidence subduction may have been triggered by a regional reorganization in the arabia eurasia collision at that time possibly following the construction of the turkish iranian plateau

characterization and origin of aluminous a type granites from the lachlan fold belt southeastern australia the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are a distinctive group of igneous rocks on the basis of chemical and mineralogical criteria those granites that contain 65 72 sio2 can be distinguished from other types on the basis of higher abundances of fetotal fetotal mg high field strength elements trivalent rare earth elements ga and zn mineralogically they contain fe rich hydrous mafic minerals and primary ilmenite and hence are reduced relative to the ni nio buffer however the extremely felsic a type granites sio2 72 have the same chemical and mineralogical characteristics as felsic fractionated i type granites recent analyses indicate that the lachlan fold belt a type granites have sc f alkali element trace transition element and h2o contents similar to those of other unfractionated i type granites rb sr and nd sm isotopic compositions are highly variable probably reflecting source region heterogeneity the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are distinct from peralkaline rocks in terms of chemical composition petrography and field associations although these rocks have been grouped together as a single type in current classification schemes we propose that the metaluminous to weakly peraluminous a type granites such as those of the lachlan fold belt should be defined as aluminous a type granites and should not be grouped with peralkaline granites the lachlan fold belt aluminous a type granites have relatively high calculated zircon saturation temperatures we suggest that these granites were produced by high temperature partial melting of a felsic infracrustal source

probabilistic approach to rock physics modeling abstractrock physics modeling aims to provide a link between rock properties such as porosity lithology and fluid saturation and elastic attributes such as velocities or impedances these models are then used in quantitative seismic interpretation and reservoir characterization however most of the geophysical measurements are uncertain therefore rock physics equations must be combined with mathematical tools to account for the uncertainty in the data we combined probability theory with rock physics modeling to make predictions of elastic properties using probability distributions rather than definite values the method provided analytical solutions of rock physics models in which the input is a random variable whose exact value is unknown but whose probability distribution is known the probability distribution derived with this approach can be used to quantify the uncertainty in rock physics model predictions and in rock property estimation from seismic attributes examples of fluid substitutio

a rock physics strategy for quantifying uncertainty in common hydrocarbon indicators we present a strategy for quantifying uncertainties in rock physics interpretations by combining statistical techniques with deterministic rock physics relations derived from the laboratory and theory a simple example combines gassmann s deterministic equation for fluid substitution with statistics inferred from log core and seismic data to detect hydrocarbons from observed seismic velocities the formulation identifies the most likely pore fluid modulus corresponding to each observed seismic attribute and the uncertainty that arises because of natural variability in formation properties in addition to the measurement uncertainties we quantify the measure of information in terms of entropy and show the impact of additional data about s wave velocity on the uncertainty of the hydrocarbon indicator in some cases noisy s data along with noisy p data can convey more information than perfect p data alone while in other cases s data do not reduce the uncertainty we apply the formulation to a well log example for detecting the most likely pore fluid and quantifying the associated uncertainty from observed sonic and density logs the formulation offers a convenient way to implement deterministic fluid substitution equations in the realistic case when natural geologic variations cause the reference porosity and velocity to span a range of values

late permian to late triassic palaeomagnetic data from iran constraints on the migration of the iranian block through the tethyan ocean and initial destruction of pangaea summary a palaeomagnetic study of late permian to early jurassic rocks from the alborz and sanandaj sirjan zones in iran and a compilation of selected palaeopoles from the carboniferous to the present provide an updated history of the motion of the iranian block within the tethys ocean the iran assemblage part of gondwana during the palaeozoic rifted away by the end of the permian we ascertain the southernhemisphere palaeoposition of iran at that time using magnetostratigraphy and show that it was situated close to arabia near to its relative position today a northward transit of this block during the triassic is shown with an estimated expansion rate of the neotethyan ridge of 100 140 km myr 1 the northward convergence with respect to eurasia ended during the ladinian middle triassic and is marked by a collision in the northern hemisphere with the turan platform which was the southern margin of the eurasian continent at that time no north south component of shortening is evidenced north of iran afterwards an analysis of the declinations from the late permian to the present shows diverent large rotations emphasizing the important tectonic phases suvered since the triassic finally we propose palaeomagnetic reconstructions of the tethys area during the late permian and the late triassic showing that the palaeotethys ocean was narrower than previously thought and did not widen its gate to the panthalassa before the triassic period

the lunar dynamo background it is unknown whether the moon has a fully differentiated and melted structure with a metallic core or retains a partially primordial unmelted interior the differentiation history of the moon is manifested by its record of past magnetism paleomagnetism although the moon today does not have a global magnetic field the discovery of remanent magnetization in lunar rocks and in the lunar crust demonstrated that there was a substantial lunar surface field billions of years ago however the origin intensity and lifetime of this field have been uncertain as a result it has been unclear whether this magnetization was produced by a dynamo in the moon s advecting metallic core or by fields generated externally to the moon establishing whether the moon formed a core dynamo would have major implications for understanding its interior structure thermal history and mechanism of formation as well for our understanding of the physics of planetary magnetic field generation the interior structure of the moon and the lunar dynamo new magnetic measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its advecting liquid metallic core innermost red shell this dynamo may have been driven by convection possibly powered by crystallization of the core innermost red sphere and or stirring from the solid mantle thick green shell the magnetic field was recorded as magnetization by rocks on the lunar surface image created by hernan canellas the interior structure of the moon and the lunar dynamo new magnetic measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its advecting liquid metallic core innermost red shell this dynamo may have been driven by convection possibly powered by crystallization of the core innermost red sphere and or stirring from the solid mantle thick green shell the magnetic field was recorded as magnetization by rocks on the lunar surface image created by hernan canellas advances a new generation of laboratory magnetic studies of lunar rocks and spacecraft measurements of lunar crustal magnetic fields have produced major advances in our understanding of the evolution of ancient magnetic fields on the moon it has now been established that a dynamo magnetic field likely existed on the moon from at least 4 5 billion to 3 56 billion years ago with an intensity similar to that at the surface of earth today the field then declined by at least an order of magnitude by 3 3 billion years ago the early epoch of high field intensities may require an exceptionally energetic power source such as mechanical stirring from mantle precession the extended history of the lunar dynamo appears to demand long lived power sources such as mantle precession and core crystallization outlook measurements of the intensity of the ancient lunar dynamo have shown that it was surprisingly intense and long lived the next phase of lunar magnetic exploration will be to obtain more accurate measurements of field paleointensities and to determine when the dynamo initiated and finally disappeared this will be coupled with the continued development of magnetohydrodynamic models for characterizing mechanical and other unusual dynamo mechanisms and further investigations into the thermal structural and geodynamical history of the lunar core and mantle the eventual availability of absolutely oriented samples and in situ spacecraft measurements of bedrock should enable the first measurements of the paleo orientation of lunar magnetic fields such directional data could determine the lunar field s geometry and reversal frequency as well as constrain ancient local and global scale tectonic events

mapping lithofacies and pore fluid probabilities in a north sea reservoir seismic inversions and statistical rock physics reliably predicting lithologic and saturation heterogeneities is one of the key problems in reservoir characterization in this study we show how statistical rock physics techniques combined with seismic information can be used to classify reservoir lithologies and pore fluids one of the innovations was to use a seismic impedance attribute related to the vp vs ratio that incorporates far offset data but at the same time can be practically obtained using normal incidence inversion algorithms the methods were applied to a north sea turbidite system we incorporated well log measurements with calibration from core data to estimate the near offset and far offset reflectivity and impedance attributes multivariate probability distributions were estimated from the data to identify the attribute clusters and their separability for different facies and fluid saturations a training data was set up using monte carlo simulations based on the well log derived probability distributions fluid substitution by ga

a hybrid origin for the qianshan a type granite northeast china geochemical and sr nd hf isotopic evidence abstract major and trace element whole rock sr and nd isotope and zircon hf isotope data are reported for a suite of a type granites and mafic microgranular enclaves from the early cretaceous 126 2 ma qianshan pluton liaodong peninsula northeast china with the aim of investigating the sources and petrogenesis of a type granites the qianshan pluton includes hornblende alkali feldspar granite graphic biotite granite and mafic microgranular enclaves the hornblende alkali feldspar granites have high sio 2 fe 2 o 3t mgo k 2 o na 2 o rb zr and lree contents and low ba and sr concentrations with strongly negative eu anomalies their high rb sr 87 rb 86 sr 16 76 24 15 and initial 87 sr 86 sr ratios 0 7215 to 0 7283 negative e nd t values 14 1 to 16 5 and zircon e hf t values 18 9 to 11 5 indicate they were mainly derived from a crustal source but with involvement of high e nd t and e hf t materials graphic biotite granites have similar geochemical features and sr nd hf isotopic compositions to enclaves indicating they were the result of crystal fractionation of evolved mafic magmas but with involvement of low e nd t and e hf t materials the mafic enclaves have an igneous texture and contain acicular apatite suggesting quenching of mafic magmas that have co mingled with the host granites they have low initial 87 sr 86 sr ratios 0 7097 0 7148 negative e nd t 14 5 to 11 9 and zircon e hf t 17 1 to 6 9 values and are enriched in liles and lrees and depleted in hfses when coupled with the high mgo mg up to 54 this indicates derivation from an enriched lithospheric mantle source but contaminated by crustal materials geochemical and sr nd and zircon hf isotopic compositions rule out simple crystal liquid fractionation or restite unmixing as the major genetic link between enclaves and host rocks instead magma mixing of mantle derived mafic and crustal derived magmas coupled with crystal fractionation is compatible with the data this example shows that at least some a type granites formed through a complex process involving mantle and crustal derived magma mixing crystal fractionation and infracrustal melting

seismic inversion combining rock physics and multiple point geostatistics a novel inversion technique combines rock physics and multiple point geostatistics the technique is based on the formulation of the inverse problem as an inference problem and incorporates multiple point geostatistics and conditional rock physics to characterize previously known geologic information the proposed implementation combines elements of sampling from conditional probabilities and elements of optimization the technique provides multiple solutions all consistent with the expected geology well log data seismic data and the local rock physics transformations a pattern based algorithm was selected as the multiple point geostatistics component rock physics principles are incorporated at the beginning of the process defining the links between reservoir properties e g lithology saturation and physical quantities e g compressibility density making it possible to predict situations not sampled by log data results for seismic lithofacies inversion on a synthetic test and a real data application demonstrate the validity and applicability of the proposed inversion technique

long term evolution of the geomagnetic dipole moment abstract the geomagnetic field intensity measured at the surface of the planet is a potential indicator of the dynamo activity in the conducting liquid core of the earth rapid field variations must be generated by the rapid fluid motions within the core whereas long term changes could be associated with other processes such as changes in boundary conditions at the core mantle interface and or at the outer liquid inner solid core boundary for about 50 years paleomagnetists gathered records of absolute paleointensity using the magnetization of lava flows distributed over the globe in order to reconstruct the field intensity changes during the past 3000 ma despite recent acquisition of paleointensity records the temporal distribution of the results remains limited except within a few time intervals to extract coherent features of the time averaged field intensity over periods of a few million years however significant informations can be gained from the recent updated paleointensity database by averaging the virtual dipole moment over very long time intervals the results suggest the existence of a long term evolution of the dipole field intensity during the past 3 billion years from 3 1022 a m2 at 1000 2000 ma to 8 1022 a m2 at present times

the rudbar tarom earthquake of 20 june 1990 in nw persia preliminary field and seismological observations and its tectonic significance abstract the rudbar tarom earthquake of 20 june 1990 in nw persia m s 7 7 m b 6 4 m w 7 3 killed approximately 40 000 people left more than 500 000 homeless destroyed three cities rudbar manjil and lowshan and 700 villages and slightly damaged another 300 villages in the densely populated area of the western alborz mountains southwest of the caspian sea both faulting and folding associated with the earthquake were observed in the epicentral area co seismic surface faulting was associated with at least three main discontinuous complex fault segments with a total length of more than 80 km these three main fault segments are arranged in a right stepping en echelon pattern and are separated by gaps in the observed surface ruptures each segment has a strike of 95 to 120 with oblique left lateral and reverse motion on faults that are subvertical or have steep dips to the s or ssw maximum surface displacements were 60 cm horizontal left lateral and 95 cm vertical south side up bedding plane slip in a reverse or thrust sense was also observed at the surface following the earthquake and may have occurred during co seismic folding seismic body waves of the mainshock confirm the left lateral nature of the faulting and show that slip occurred in three main subevents that may correspond to the fault segments seen at the surface the focal mechanism obtained from broadband body waves is almost pure strike slip with little evidence of the vertical component of motion seen at the surface there were numerous aftershocks one of which had a thrust faulting mechanism different from that of the mainshock the complex system of surface faults on which the rudbar tarom earthquake occurred had not previously been identified as active the lack of obvious quaternary scarps on the faults that moved in 1990 suggests that return periods for earthquakes of this type are relatively long but this is difficult to quantify as erosion rates are high although the persian seismic network has insufficient coverage to locate small earthquakes with enough precision to identify active faults there is much modern and historical seismicity in the area and abundant geomorphological evidence of rapid active tectonic processes previous studies of focal mechanisms and active faulting had emphasized the reverse faulting and folding that are undoubtedly the main processes that build the alborz mountain belt the 1990 earthquake provided the first evidence that the belt also undergoes left lateral shear on the southern edge of the alborz mountains the slip direction in earthquakes is approximately ne and occurs on oblique faults we suspect that in the high alborz where the amount of shortening and the topography are greater this oblique convergence between persia and the southern caspian sea is partitioned into essentially pure reverse motion and left lateral strike slip

southern borderland of triassic laurasia in north east iran results obtained by iranian and european geoscientists in the critical area to the north east of the north iran suture east of mashhad are desribed and discussed a slightly metamorphosed ophiolite belt outcropping as the south easterly continuation of the previously known ophiolites of mashhad along the north eastern perimeter of the fariman torbat e jam depression proved to be either the remnant of a permian ocean floor or more likely the remnant of a narrow ocean trough there is as yet no proof of a triassic age for this ophiolitic belt to the north of this ophiolitic belt an epicontinental triassic sequence is exposed at the southern edge of laurasia in the erosional window of aghdarband this is the result of intermittent sedimentation in a pull apart basin along sinistral strike slip faults the triassic of aghdarband has much in common with other deposits of the triassic tethys however it shows a few unique features e g the early anisiannicomedites fauna of a palaeobiogeographic north tethyan subprovince or volcanogenic sedimentation during the late anisian and the entire ladinian

is avo the seismic signature of lithology a case history of ship shoal south addition many times we ve heard i ve tried amplitude versus offset avo and it doesn t work in my area before casting avo aside let s look at the process one more time avo analysis is actually a two step process the first step relates the seismic response cdp gather to the rock s velocity density and poisson s ratio the second step relates these rock properties to the lithologies sand shale etc

a review of the relationships between granitoid types their origins and their geodynamic environments abstract granitoids are divided into several types according to their mineral assemblages their field and petrographical features and their chemical and isotopic characteristics this typology complements most of the recent classifications because it is not based solely on chemical and isotopic criteria but also on the field petrographical and mineralogical criteria it thus has the advantage of distinguishing the various granitoid types in the field in most cases the proposed classification shares many similarities with the twenty most used genetic classifications of granitoids both types of peraluminous granitoids are of crustal origin the tholeiitic alkaline and peralkaline granitoids are of mantle origin and both types of calc alkaline granitoids are of mixed origin and involve both crustal and mantle materials each granitoid type is generated and emplaced in a very specific tectonic setting each stage of the wilson cycle is characterised by typical associations of granitoids well typed and precisely dated granitoids can then complement structural approaches and indicate on the geodynamic environment with reference to some case studies the use of granitoids as tracers of the geodynamic evolution is also proposed and discussed

analogue and geophysical modelling of the garmsar salt nappe iran constraints on the evolution of the alborz mountains summary the alborz mountains are forming a 100 km wide east west trending orogenic belt that stretches 2000 m across northern iran south of the caspian sea the alborz mountains consist of salt bearing neogene sediments which are folded and cut by faults global positioning system studies indicate n s directed shortening across the alborz range which is accommodated by right and left lateral strike slip along ese wnw and ene wsw trending faults respectively a 20 km 10 km 03 km sheet of salt extruded over the central plateau of iran arising at the front of the advancing alborz mountains the extruded salt forms the eyvanekey plateau between eyvanekey and garmsar which is now known as the garmsar salt nappe to get more insights in the evolution of the garmsar salt nappe analogue modelling has been carried out using pdms as salt analogue and sand as analogue for the brittle overburden the structures produced consist of folds and thrusts which were formed while the salt analogue pdms was rising up the modelling results are compatible with our interpretation that the deformation front of the alborz mountains advanced ssw when overriding a salt sequence in the garmsar area depth estimations using the gravity and magnetic fields suggest that the salt in the garmsar salt nappe extruded from a depth less than 2000 m

the present day deformation of the central zagros from gps measurements 1 in 1997 and in 2000 we measured the distances between 14 geodetic benchmarks across the central zagros mountain belt the results show that about 10 mm yr of shortening in the central zagros is distributed across the mountain belt this shortening corresponds to roughly 50 of the total convergence between arabia and eurasia and is consistent in direction the persian gulf does not deform significantly the main zagros reverse fault is not an active kinematic boundary the internal deformation of the folded belt is rather homogeneous at the scale of our survey which does not allow us to detect any individual active blind fault however the strain pattern suggests that n s dextral strike slip faults may accommodate part of the deformation

petrogenesis and tectonic setting of the tuyeh darvar granitoid northern iran constraints from zircon u pb geochronology and sr nd isotope geochemistry abstract tuyeh darvar granitoid which outcrop ca 45 km sw of damghan city in the eastern alborz zone comprise mainly the pluton emplaced into the barut formation of lower cambrian ages zircon u pb ages show carboniferous ages 325 3 ma for the formation of this granitoid the granitoid is mostly metaluminous ferroan and alkalic monzonite to monzodiorite these rocks have high values of feot mgo and ga al high concentrations of k2o na2o low abundances of mgo and transitional elements plots normalized to chondrite and primitive mantle compositions show strong enrichments of lree relative to hree and of lile relative to hfse accompannied by negative anomalies of nb and sr they contain fe rich hydrous mafic minerals and magnetite these features are typical of a type granites sr nd isotopic geochemistry with initial nd values from 1 1 to 1 5 and initial 87sr 86sr ratios between 0 70562 and 0 70678 are consistent with magmatic differentiation from mafic melts produced from an enriched mantle source however other models such as melting of mafic crust or mixing of components from depleted mantle and continental crust cannot be discarded on the basis of the u pb zircon age 325 3 ma and the known magmatic tectonic regime in iran during the paleozoic it is suggested that the pluton formed in a rift environment related to extensional structures of the alborz block in early carboniferous time

late cenozoic deformation in the south caspian region effects of a rigid basement block within a collision zone abstract active deformation in the south caspian region demonstrates the enormous variation in kinematics and structural style generated where a rigid basement block lies within a collision zone rigid basement to the south caspian basin moves with a westward component relative both to stable eurasia and iran and is beginning to subduct at its northern and western margins this motion is oblique to the approximately north south arabia eurasia convergence and causes oblique shortening to the south and northeast of the south caspian basin thrusting in the alborz and kopet dagh is accompanied by range parallel strike slip faults which are respectively left and right lateral there are also arcuate fold and thrust belts in the region for two principal reasons firstly weaker regions deform and wrap around the rigid block this occurs at the curved transition zone between the alborz and talysh ranges where thrust traces are concave towards the foreland secondly a curved fold and thrust belt can link a deformation zone created by movement of the basement block to one created by the regional convergence west to east thrusts in the eastern talysh represent underthrusting of the south caspian basement but pass via an arcuate fan of fold trains into ssw directed thrusts in the eastern greater caucasus which accommodates part of the arabia eurasia convergence each part of the south caspian region contains one or more detachment levels which vary dependent on the pre pliocene geology buckle folds in the south caspian basin are detached from older rocks on thick mid tertiary mudrocks whereas thrust sheets in the eastern greater caucasus detach on mesozoic horizons in the future the south caspian basement may be largely eliminated by subduction leading to a situation similar to archaean greenstone belts of interthrust mafic and sedimentary slices surrounded by the roots of mountain ranges constructed from continental crust

seismic inversion for reservoir properties combining statistical rock physics and geostatistics a review there are various approaches for quantitative estimation of reservoir properties from seismic inversion a general bayesian formulation for the inverse problem can be implemented in two different work flows in the sequential approach first seismic data are inverted deterministically or stochastically into elastic properties then rock physics models transform those elastic properties to the reservoir property of interest the joint or simultaneous work flow accounts for the elastic parameters and the reservoir properties often in a bayesian formulation guaranteeing consistency between the elastic and reservoir properties rock physics plays the important role of linking elastic parameters such as impedances and velocities to reservoir properties of interest such as lithologies porosity and pore fluids geostatistical methods help add constraints of spatial correlation conditioning to different kinds of data and incorporating subseismic scales of heterogeneities

strain and stress field in taiwan oblique convergent system constraints from gps observation and tectonic data abstract this paper focuses on the stress and strain rate field of the taiwan area the strain rate field in the taiwan region is studied qualitatively and quantitatively based on the gps observation in 1990 1995 it reflects the accommodation of the ongoing lithospheric deformation within the seismogenic portion of lithosphere and exhibits zones with contrasting deformation modes and amounts we then compare the obtained strain rate field with the tectonic information provided by studies of borehole breakouts and earthquake focal mechanisms for the present and by fault slip data analyses for the quaternary period in the first approximation the stress and strain rate fields show spatial similarity the orientation of principal shortening is generally consistent with the compressive stress orientation that reflects the oblique indentation of the luzon arc into the eurasian continental margin in more detail significant anomalies in the deformation pattern deserve consideration in that they may reveal ongoing stress accumulation despite the short term variations related to the earthquake cycle some major features of the strain rate field including the distribution of extension and compression highlight the long term tectonic behavior of the mountain belt at the lithospheric scale the time and space variations of strain should be a function of local heterogeneity and be transferred between interseismic and coseismic periods

structures of the zagros fold thrust belt in iran the zagros fold thrust belt in iran forms the external part of the zagros active orogenic wedge it includes a sequence of heterogeneous latest neoproterozoic phanerozoic sedimentary cover strata 7 to 12 km thick and composed of alternating incompetent and competent layers overlying precambrian crystalline basement with a complex pre zagros structural fabric balancing structures of the cover statigraphic units in the zagros fold thrust belt requires in sequence and out of sequence involvement of the precambrian basement in the deformation six detailed balanced and retrodeformable cross sections which are constructed based on geological and geophysical data across various sectors of the belt show fault bend and fault propagation folds interpreted to have formed by slip on their subjacent thrusts out of sequence basement rooted thrusts as the interpretations in the constructed cross sections suggest have breached the cover basement interface and using incompetent cover strata for propagation cut across the cover structures and have created associated new folds superimposed upon the pre existing structures this style of deformation which has resulted in structural complexity of the belt characterizes a 200 to 300 km wide zone of distributed partly synchronous deformation with along strike and across strike variations it also implies that the zagros fold thrust belt as the external part of the orogenic wedge is still in its subcritical condition with internal deformation to achieve a critical taper in creating structural complexity in addition to out of sequence thrusting mechanically weak layers evaporites and mudstones of the cover strata have played a significant role by providing several detachment horizons shortening estimates across the belt are variable based on the constructed cross sections and their restorations minimum shortening estimates range from 16 percent to 30 percent in different sectors of the belt

the petrogenesis of a type magmas from the amram massif southern israel the 550 530ma alkaline magmatic suite of the amram massif southern israel was emplaced during the transition from an orogenic to an intra plate tectonic setting in the northeastern arabian nubian shield ans the suite ranges from 45 6t o 788 wt sio2 and consists of rhyolites alkali quartz syenites quartz syenites monzonites and co magmatic mafic to felsic alkaline dikes these rocks define a continuous chemical evolutionary trend and reveal a correlation between decreasing stratigraphic age and increasing silica content the felsic members of the suite display a type characteristics and are genetically linked through fractionation to the more mafic ones moderately positive initial end values a2 05 low initial 87 sr 86 sr values 07036 2 high mgo and fe2o3 concentrations 410 895 and 100 125 wt respectively and relatively flat rare earth element patterns la yb na 64 09 in the amram mafic dikes 456 495 wt sio2 suggest their derivation from the sub continental lithospheric mantle above the garnet stability zone the melts program was used to quantitatively model the chemical evolution of the suite extensive anhydrous fractionation 490 of plagioclase alkali feldspar clinopyroxene olivine and minor timagnetite and apatite from parental mafic magmas represented by the amram mafic dikes produced the rhyolitic compositions as well as the intermediate members of the suite this suggests the presence of a large unexposed body of cumulate rocks at depth as well as fusion of a large source region equivalent to an 5km layer in the lithospheric mantle regarded as a representative example for similar a type outcrops in this region this petrogenetic model further suggests that neoproterozoic early cambrian a type magmatism in the northeastern ans represents a significant post orogenic addition of mantlederived material to the juvenile crust this magmatic episode was of a similar magnitude to that of the cenozoic extensionrelated alkaline volcanism of the arabian plate

a tectonic origin of magnetic fabric in the shemshak group from alborz mts northern iran abstract the magnetic lineation observed in undeformed sedimentary units has been interpreted either as an indication of paleoflow direction or as a result of tectonic overprint which progressively modifies the original sedimentary fabric related to compactional processes distinguishing between the two processes is not always easy in fact most studies of the anistropy of magnetic susceptibility ams of undeformed sequences have been carried out in fine grained sediments from foredeep sequences which are characterized by sedimentary flow directions which are almost parallel to the main deformation structures like thrust faults and folds in the alborz mts the upper triassic lower jurassic shemshak group was deposited in a foreland to molassic basin of the eo cimmerian orogen and now outcrops in several folds which are oriented parallel to the curved chain paleoflow directions are generally oblique to the main tectonic structures being directed ssw to sse and showing negligible changes in their orientation along the alborz mountains we have therefore the opportunity to distinguish between tectonic or sedimentary related origins of the magnetic lineation the ams results show that magnetic lineations of the shemshak group are oriented almost parallel to the main fold axes and thrust structures which follow the alborz mts curved trend suggesting that magnetic lineation is of tectonic origin in fine to medium grained mostly massive sandstones and confirming that ams is a valuable tool to study deformation processes in sedimentary rocks

normal faults in thrust sheets pre orogenic extension post orogenic extension or both abstract in fold and thrust belts that experienced both pre orogenic and post orogenic extension it may be difficult to establish whether observed normal faults pre dated post dated or were synchronous with thrusting geometrical structural patterns may be insufficient to constrain the relative chronology of extensional and contractional deformations the systematic use of kinematic criteria makes it possible to unequivocally define the timing relationships of reverse and normal fault development and hence to correctly unravel complex structural evolutions kinematic analysis in the southernmost umbria marche apennines of italy where both normal and thrust faults are present revealed a history of repeated tectonic inversion characterised by two distinct stages of extension separated by an episode of folding and thrusting structural overprinting relationships observed at thrust normal fault intersections were useful for i removing sequentially younger deformations and hence ii separating and quantifying the effects of orogenic contraction from those of both pre orogenic and post orogenic extension

pervasive remagnetization of detrital zircon host rocks in the jack hills western australia and implications for records of the early geodynamo it currently is unknown when earth s dynamo magnetic field originated paleomagnetic studies indicate that a field with an intensity similar to that of the present day existed 3 5 billion years ago ga detrital zircon crystals found in the jack hills of western australia are some of the very few samples known to substantially predate this time with crystallization ages ranging from 3 0 4 38 ga these zircons might preserve a record of the missing first billion years of earth s magnetic field history however a key unknown is the age and origin of magnetization in the jack hills zircons the identification of 3 9 ga i e hadean field records requires first establishing that the zircons have avoided remagnetization since being deposited in quartz rich conglomerates at 2 65 3 05 ga to address this issue we have conducted paleomagnetic conglomerate baked contact and fold tests in combination with u pb geochronology to establish the timing of the metamorphic and alteration events and the peak temperatures experienced by the zircon host rocks these tests include the first conglomerate test directly on the hadean zircon bearing conglomerate at erawandoo hill although we observed little evidence for remagnetization by recent lightning strikes we found that the hadean zircon bearing rocks and surrounding region have been pervasively remagnetized with the final major overprinting likely due to thermal and or aqueous effects from the emplacement of the warakurna large igneous province at 1070 million years ago ma although localized regions of the jack hills might have escaped complete remagnetization there currently is no robust evidence for pre depositional 3 0 ga magnetization in the jack hills detrital zircons

early middle permian post collisional granitoids in the northern beishan orogen northwestern china evidence from u pb ages and sr nd hf isotopes the geochemistry and sr nd isotope zircon u pb and zircon hf isotope compositions are reported for monzogranites and granodiorites from the hazhu area in the northern beishan orogen northwestern

dome and basin refolding and transpressive inversion along the karatau fault system southern kazakstan the karatau fault system of southern kazakstan forms a crustal scale zone of strike slip dominated transpressional tectonics which has undergone multiple phases and styles of deformation during a protracted history of reactivation from the neoproterozoic to the cenozoic ductile fabrics associated with dextral kinematic indicators are present in amphibolites along the main karatau fault the ages of the possibly ophiolitic protoliths and the ductile fabrics are not well constrained but they are plausibly pre late riphean late ordovician granites stitch thrusts and folds which deform late riphean to llanvirn clastics preserved beneath a regional late devonian angular unconformity this deformation may be related to a contemporary continental collision ne of the karatau two phases of late palaeozoic deformation affected the upper devonian and carboniferous carbonate succession the first phase is related to sinistral transpression along the karatau fault system the second to dextral transpressional reactivation the combination of these events produced a regional scale dome and basin fold interference pattern similar polyphase deformation appears to have affected large areas of central asia and was possibly caused by the late palaeozoic orogenies at asia s margins such as the accretion of tarim and the east european craton to asia and the closure of the kazakstan orocline normal faults in the karatau are related to the formation of the leontiev graben south turgay basin and the yarkand fergana basin in the early to mid jurassic during renewed dextral slip along the karatau talas fergana fault late cenozoic deformation is minor and resulted in the uplift and incision of a cretaceous palaeogene peneplain without a major tectonic overprint reversals in the sense of strike slip dominated transpressive deformation across major fault systems results in transpressive inversion this represents an ideal process with which to generate overprinting orthogonal fold systems resulting in classic dome and basin interference patterns on a regional scale

exhumation of the west central alborz mountains iran caspian subsidence and collision related tectonics crystallization and thermal histories of two plutons in the west central alborz also elburz elburs mountains northern iran are combined with crosscutting relations and kinematic data from nearby faults to determine the cenozoic tectonic evolution of this segment of the youthful euro arabian collision zone u pb 40 ar 39 ar and u th he data were obtained from zircon biotite k feldspar and apatite the akapol pluton intruded at 56 2 ma cooled to 150 c by ca 40 ma and stayed near that temperature until at least 25 ma the nearby alam kuh granite intruded at 6 8 0 1 ma and cooled rapidly to 70 c by ca 6 ma these results imply tectonic stability of the west central alborz from late eocene to late miocene time consistent with miocene sedimentation patterns in central iran elevation correlated u th he ages from the akapol suite indicate 0 7 km m y exhumation between 6 and 4 ma and imply 10 km of alborz uplift that was nearly synchronous with rapid south caspian subsidence suggesting a causal relation uplift south caspian subsidence and subsequent folding reversal of alborz strike slip from dextral to sinistral and eastward extrusion of central iran coarse zagros molasse deposition dead sea transform reorganization red sea oceanic spreading and north and east anatolian fault slip all apparently began ca 5 2 ma suggesting a widespread tectonic event that we infer was a response to buoyant arabian lithosphere choking the neo tethyan subduction zone

tectonic control on sedimentary facies pattern and sediment accumulation rates in the miocene foreland basin of the southern alborz mountains northern iran 1 the southern alborz mountains of northern iran are an integral part of the arabia eurasia collision zone a magnetostratigraphic and rock magnetic investigation of the eyvanekey stratigraphic section in the southern alborz mountains reveals the spatiotemporal character of sedimentary facies migration in the alborz foreland basin the section constitutes three coarsening upward units units 1 2 and 3 comprising the upper red and hezardarreh formations our data reveal that the upper red formation was deposited between 17 5 and 7 5 ma while the depositional age of the top of the hezardarreh formation can be extrapolated to 6 2 ma slow sediment accumulation rates correlate with sedimentary facies comprising prograding coarsening upward units this is likely the result of intraforeland uplift units 1 and 2 and basin inversion probably associated with a growth syncline located in the proximal foreland unit 3 in contrast fine grained strata at the bottom of each cycle are associated with faster sediment accumulation rates testifying to enhanced flexural basin subsidence in the course of thrust loading progradation of coarse grained facies also occurred during relatively fast sediment accumulation top of unit 2 suggesting that the influx of coarse grained sediment outpaced the storage capacity of the proximal foreland thus despite an overall southward propagation of deformation into the southern alborz foreland the locus of active deformation must have migrated back and forth on a time scale of circa 0 7 to 2 ma

enhanced atmospheric oxygen outflow on earth and mars driven by a corotating interaction region 1 solar wind controls nonthermal escape of planetary atmospheric volatiles regardless of the strength of planetary magnetic fields for both earth with a strong dipole and mars with weak remnant fields the oxygen ion o outflow has been separately found to be enhanced during corotating interaction region cir passage here we compared the enhancements of o outflow on earth and mars driven by a cir in january 2008 when sun earth and mars were approximately aligned the cir propagation was recorded by stereo ace cluster and mars express mex during the cir passage cluster observed enhanced flux of upwelling oxygen ions above the earth s polar region while mex detected an increased escape flux of oxygen ions in the martian magnetosphere we found that 1 under a solar wind dynamic pressure increase of 2 3 npa the rate of increase in martian o outflow flux was 1 order higher than those on earth and 2 as a response to the same part of the cir body the rate of increase in martian o outflow flux was on the same order as for earth the comparison results imply that the dipole effectively prevents coupling of solar wind kinetic energy to planetary ions and the distance to the sun is also crucially important for planetary volatile loss in our inner solar system

structure of the intraplate eastern palmyride fold belt syria the palmyride fold belt is an aulacogen within the arabian plate linked to the levantine continental margin which contains 10 km of phanerozoic sediments inversion of this mesozoic basin began during late cretaceous time although most deformation was clearly post oligocene recent field mapping shows that almost all the structures have resulted from a phase of northwest southeast compression followed by major dextral transpression early northwest southeast compression resulted in northeast southwest aligned fold axes in the central and southeast palmyrides many of which were subsequently rotated by progressive dextral simple shear during neogene to recent time the north south aligned sinistral dead sea fault is the major wrench fault aligned at 45 to the maximum compressive stress the conjugate east west striking dextral jhar fault and the northwest southeast aligned bishri fault have accommodated limited dextral shear and clockwise rotation of northeast southwest aligned folds jebels mrah ash shaer in the northern palmyrides dextral strike slip faults aligned along reidel fractures r1 cut the flanks of earlier domal structures jebel abu rajmein subordinate antithetic r2 reidel shears aligned north northeast south southwest are trans tensional sinistral strike slip faults showing minor extension that cut through the earlier domal structures for example ras al hawa depression in jebel abu rajmein northwest southeast aligned faults for example jebel bilas cross trend faults show northeast southwest extension at right angles to the palmyride shortening direction this extension parallels the major euphrates graben trend in eastern syria and northwestern iraq and also parallels some aligned pliocene pleistocene volcanic rifts south of damascus and in the jebel druze jebel arab region of southern syria and northern jordan a regional palmyride strain ellipse is presented to explain the geometry of all these structures the ad daww depression is a northeast southwest aligned transpressional basin containing around 2 km thickness of tertiary sediments the basin is bounded to the west by a sinistral shear couple along the cherrife structural trend in the central palmyrides along the north by the dextral jhar fault and along the southeast by the compressional southeast palmyrides in the southeast palmyrides structural style is one of a series of northeast southwest aligned narrow anticlines in the mesozoic platform sediments with upright to north west dipping southeast facing axial planes shortening amounts are very small in the eastern palmyrides 1 km and taken up almost entirely by folding but these increase slightly toward the west to probably 20 km in the cherrife region tight box folds and slightly asymmetric folds in the southeast palmyrides have a localized basal detachment along the triassic gypsum horizon which in some examples flows into the fold core jebel hayyan there is no evidence for a major basal detachment underlying the palmyrides all folding and faulting can be related to disharmonic folding of the mesozoic sediments above a triassic evaporite sequence and subsequent dextral transpression the lack of overthrusting explains the absence of any foreland basin caused by lithospheric flexuring on the rutbah platform the major palmyride deformation in miocene pliocene times was concomitant with the opening of the red sea with the closing of the bitlis zagros suture zone in eastern turkey and central iran and with the main sinistral strike slip motion along the dead sea fault

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

sedimentary basin inversion and intra plate shortening abstract sedimentary basin inversion the shortening of formerly extensional basins is accommodated mainly by compressional reactivation of extant faults and fractures across a wide range of scales as such inversion is a large scale manifestation of byerlee friction the dynamic criterion for fault reactivation governing the effective shear strength of the shallow crust basin inversion generates distinctive deformational architecture and it is implicated strongly in sedimentary basin exhumation as a principal source of horizontal stress inversion drives significant sedimentary porosity reduction and resultant fluid flow upper crustal deformation is critically dependent on fluid overpressure i e pore fluid pressures greater than would be calculated from a hydrostatic gradient and perhaps more than in any other tectonic setting overpressures are potentially large during sedimentary basin inversion this review therefore includes discussion of the role of fluid overpressure in inversion and the evidence for it collectively inversion has profound implications good and bad for the prospectivity of many petroliferous sedimentary basins thus recognizing the evidence for basin inversion quantifying its magnitude and understanding the mechanisms that accommodate inversion and other phenomena affected by it have become essential components of the basin analyst s remit

fluid substitution in shaley sediment using effective porosity the traditional method of fluid substitution in porous rock requires the total porosity and the elastic modulus of the mineral phase as input and assumes that the fluid reaches instantaneous hydraulic equilibrium throughout the pore space this assumption may not be appropriate for shaley sediment because of the low permeability of shale and the resulting immobility of the water in it to address this problem we propose an alternative method that uses effective porosity instead of total porosity effective porosity is lower than total porosity if porous shale is present in the system a new composite mineral phase is introduced which includes the porous water saturated shale together with the nonporous minerals and whose elastic modulus is an average of those of its components including the porous shale this alternative method increases the sensitivity of the elastic properties of sediment to pore fluid changes and therefore may be used as a physics based theoretical tool to better explain and interpret seismic data during exploration as well as variations in seismic response as hydrocarbon production progresses

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

rare earth element distributions among minerals in a granodiorite and their petrogenetic implications a study of the distribution of lanthanide rare earths in a granodiorite from the eastern peninsular ranges batholith southern california reveals that a large fraction of the ree in this rock resides in the accessory phases sphene and allanite the minerals plagioclase alkali feldspar biotite epidote and apatite each contribute approximately 1 or less of each ree to the whole rock with the exception of eu for which plagioclase contributes 7 sphene and allanite together contain 80 to 95 of each ree each of these phases is zoned in ree concentration with substantial decreases from core to margin textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma ree zoning trends in sphene and allanite and unexpectedly low ree concentrations in largely later crystallizing minerals such as feldspar indicate that the precipitation of sphene and allanite significantly reduced ree concentrations in residual melts these results illustrate the potential that sphene and allanite have for controlling the behavior of ree in granitic magmas available information collectively suggest that the sampled granodiorite existed as a complete melt that the ree contained in the assemblage of phases were derived by direct crystallization from the melt and that the melt behaved essentially as a closed system once crystallization of the phases now present began close correspondences between the major and trace element chemistries of the granodiorite and phenocryst poor lavas from similar tectonic settings support these conclusions the ree pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism the high liquidus temperature of a granodiorite melt 1000 c indicates the importance of mantle derived components within the sources of batholithic magmas in the peninsular ranges

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

the drift history of iran from the ordovician to the triassic new late ordovician and triassic palaeomagnetic data from iran are presented these data in conjunction with data from the literature provide insights on the drift history of iran as part of cimmeria during the ordovician triassic a robust agreement of palaeomagnetic poles of iran and west gondwana is observed for the late ordovician earliest carboniferous indicat ing that iran was part of gondwana during that time data for the late permian early early tri assic indicate that iran resided on subequatorial palaeolatitudes clearly disengaged from the parental gondwanan margin in the southern hemisphere since the late early triassic iran has been located in the northern hemisphere close to the eurasian margin this northward drift brought iran to cover much of the palaeotethys in approximately 35 ma at an average plate speed ofc 7 8 cm year 21 and was in part coeval to the transformation of pangaea from an irvin gian b to a wegenerian a type configuration

inversion tectonics in central alborz iran abstract structural analyses carried out in the southern central alborz iran have shown that the evolution of this belt has been strongly conditioned by the inversion of pre existent extensional faults inversion tectonics has been identified especially in the southern part of the belt and it is related to the reactivation of grabens formed in the foreland of the late triassic eo cimmerian orogen resulting from the accretion of the iranian block to eurasia three main associations of structures active during the late cenozoic have been distinguished 1 e w thrust faults and folds followed by the activation of 2 e w right lateral strike slip faults associated to large ene wsw trending en echelon folds and finally 3 ese wnw to se nw thrust faults and left lateral strike slip faults inverting in some cases previous e w right lateral faults central alborz is strongly controlled by the geometry of pre existing tectonic discontinuities which are responsible for strain partitioning between strike slip and reverse faults during convergence these results provide new insights on the style and evolution of this complex intracontinental belt which can be considered a significant example of transpressive tectonics

quantifying arabia eurasia convergence accommodated in the greater caucasus by paleomagnetic reconstruction since the late eocene convergence and subsequent collision between arabia and eurasia was accommodated both in the overriding eurasian plate forming the greater caucasus orogen and the iranian plateau and by subduction and accretion of the neotethys and arabian margin forming the east anatolian plateau and the zagros to quantify how much arabia eurasia convergence was accommodated in the greater caucasus region we here provide new paleomagnetic results from 97 volcanic sites 500 samples in the talysh mountains of nw iran that show 15 net clockwise rotation relative to eurasia since the eocene we apply a first order kinematic restoration of the northward convex orocline that formed to the south of the greater caucasus integrating our new data with previously published constraints on rotations of the eastern pontides and lesser caucasus this suggests that north of the talysh 120 km of convergence must have been accommodated north of the eastern pontides and lesser caucasus this is significantly more 200 280 km our reconstruction independently confirms previous caucasus convergence estimates moreover we show for the first time a sharp contrast of convergence between the lesser caucasus and the talysh this implies that the ancient paleozoic mesozoic transform plate boundary preserved between the iranian and east anatolian plateaus was likely reactivated as a right lateral transform fault since late eocene time

stratigraphy and structure of eastern syria across the euphrates depression abstract a n s crustal scale geotransect across the northern arabian platform in eastern syria reveals an alternating series of basement uplifts and basins separated by predominantly transpressional fault zones above an effectively uniform crust four major tectonic provinces are crossed along a 325 100 km corridor that extends from the iraqi border in the south to the turkish border in the north the rutbah uplift the euphrates depression the abd el aziz structural zone and the qamichli uplift these features are the manifestations of reactivated pre cenozoic structures that responded to forces acting along nearby arabian plate boundaries particularly cenozoic convergence and collision along the margins of the northern arabian platform i e the bitlis suture and the east anatolian fault in southern turkey and the zagros suture in iran and iraq the database for this study consists of 3000 km of industry seismic reflection data 28 exploratory wells and geologic and bouguer gravity maps the deep crustal structure and in part the basement geometry along this transect are inferred from two dimensional modeling of bouguer gravity whereas the shallow about 8 km structure is constrained primarily by well and seismic data features of the geotransect reveal 1 1 a relatively uniform crustal column approximately 37 km thick with only minor crustal thinning beneath the euphrates crustal thinning may be slightly more pronounced beneath the euphrates about 35 km to the southeast of the transect where the bouguer gravity anomaly is slightly higher 2 2 along the euphrates depression ongoing subsidence which began during the late cretaceous resulted in the deposition of at least 3 km of late cretaceous and cenozoic rocks the structural complexity of the paleozoic and most of the mesozoic sedimentary sections along the transect contrasts markedly with a relatively simple flat lying cenozoic section along most of the transect a notable exception is the abd el aziz uplift where cenozoic rocks are strongly deformed 3 3 while euphrates subsidence continued throughout the cenozoic the inversion of the e w trending abd el aziz structure into a fault bounded tilted block began in the miocene perhaps as a response to the last episode of intense miocene collision along the nearby bitlis and zagros suture zones

a type granites in northeastern china age and geochemical constraints on their petrogenesis abstract a type granites are widely distributed in northeastern china ne china they were emplaced during three major episodes the permian late triassic to early jurassic and early cretaceous and evolved in different tectonic regimes according to their mineralogical and geochemical characteristics two subgroups of a type granites aluminous and peralkaline can be recognized the peralkaline subgroup contains alkali mafic minerals such as riebeckite arfvedsonite and sodic pyroxene while the aluminous subgroup contains annite and fe rich calcic or sodic calcic amphibole with respect to the aluminous subgroup the peralkaline granites contain higher rb ga and total rare earth elements ree but lower mgo cao al 2 o 3 ba and sr based on the discrimination criteria of eby geology 20 1992 641 the permian and late triassic to early jurassic a type granites belong to the a 2 post orogenic type whereas the early cretaceous granites are of the a 1 anorogenic type nd isotopic compositions of these a type granites indicate their derivation from a dominantly juvenile crustal source their origin is thought to have involved partial melting of an underplated lower crustal source because the generation of a type granites requires high melting temperature we propose models involving slab break off lithospheric delamination and extension the permian a type granites have the same age range as those in eastern junggar southern mongolia and central inner mongolia they occur along a major suture and form a narrow belt between the north china and siberian cratons we suggest that their formation was associated with post collisional slab break off the late triassic to early jurassic a type granites are likely to be the product of lithospheric delamination after the final collision of the major crustal blocks in the late paleozoic to early triassic the early cretaceous a type granites have an anorogenic affinity and were possibly associated with rifting in eastern china at this time associated with the onset of paleo pacific subduction consequently we conclude that the a type granites in ne china were generated at three different times involving multiple processes operative in different tectonic environments

early carboniferous back arc rifting related magmatism in southern tibet implications for the history of the lhasa terrane separation from gondwana

oxygen escape from the earth during geomagnetic reversals implications to mass extinction abstract the evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field intensity oxygen can escape into interplanetary space as ions after gaining momentum from solar wind but earth s strong dipole field reduces the momentum transfer efficiency and the ion outflow rate except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes mars like in morphology the newest databases available for the phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of years we propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level which is known to be a cause of mass extinction we simulated the oxygen ion escape rate for the triassic jurassic event using a modified martian ion escape model with an input of quiet solar wind inferred from sun like stars the results show that geomagnetic reversal could enhance the oxygen escape rate by 3 4 orders only if the magnetic field was extremely weak even without consideration of space weather effects this suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass extinction therefore if this causal relation indeed exists it should be a many to one scenario rather the previously considered one to one and planetary magnetic field should be much more important than previously thought for planetary habitability

deciphering oblique shortening of central alborz in iran using geodetic data the alborz is a narrow 100 km and elevated 3000 m mountain belt which accommodates the differential motion between the sanandaj sirjan zone in central iran and the south caspian basin gps measurements of 12 geodetic sites in central alborz between 2000 and 2002 allow to constrain the motion of the belt with respect to western eurasia one site velocity on the caspian shoreline suggests that the south caspian basin moves northwest at a rate of 6 2 mm year with respect to western eurasia north south shortening across the alborz occurs at 5 2 mm year to the south deformation seems to extend beyond the piedmont area probably due to active thrusting on the pishva fault we also observe a left lateral shear of the overall belt at a rate of 4 2 mm year consistent with the geological motion observed along e w active strike slip faults inside the belt e g the mosha fault