lower permian paleomagnetism of the tarim block northwestern china we collected 262 samples at 39 sites in three thick lower permian sections along the northwestern margin of the tarim block the lower permian sections are basalts interbedded with limestones or sandstones or shallow marine limestones and sandstones alone all with biostratigraphic age control alternating field af and thermal demagnetization experiments remove small secondary components and reveal characteristic magnetizations reversed directions consistent with the kiaman reversed interval similar directions between basalts sandstones and limestones a positive fold test and apparent polar wander and polarity changes recorded in underlying devonian sediments all attest to the primary nature of the remanence two paleomagnetic poles one from the limestone section 65 1 n 162 5 e k 128 a95 4 1 n 11 sites and the other from the two basalt sections 54 5 n 172 3 e k 66 a95 4 0 n 21 sites differ primarily in colatitude 8 1 6 5 suggesting a difference in magnetization age permian paleomagnetic poles from tarim siberia north china and south china all differ significantly suggesting substantial post permian relative motions

physical properties of tuffs from a scientific borehole at alban hills volcanic district central italy recent seismic swarms and hydrothermal activity suggest that the quaternary volcanic complex of the alban hills may pose a threat to the city of rome a 350 m scientific borehole was therefore drilled into this volcanic area to elucidate its inner structure for the first time wire line logs were run in the borehole in order to characterize the physical properties of the rocks and their variations with depth in particular a detailed sonic log was run to measure the p wave velocity from the well head down to 110 m to further investigate velocity changes we carried out laboratory measurements of p and s elastic wave velocities and fluid permeability at effective pressures up to 70 mpa during both increasing and decreasing pressure cycles on selected core samples representative of the main volcanic units specifically we studied samples from two pyroclastic units representative of two classes of volcanic deposits that are representative of the whole succession i a coarse grained well lithified facies pozzolane rosse unit containing abundant mm to cm lava clasts and crystals and ii a fine grained matrix supported pyroclastic deposit tufo pisolitico di trigoria unit with rare lithic lava clasts and sparse pumice elastic wave velocities reveal significant differences between units and indicate how within the same lithology the different degree of lithification and presence of clasts can affect significantly physical property values the mean laboratory value of the p wave velocity for pozzolane rosse and tufo pisolitico di trigoria units is respectively of 3 75 and 3 2 km s at an effective pressure equivalent to that at the depth at which the sonic velocity was measured under increasing effective pressure a profound influence on the transport properties is observed permeability ranges from the order of 10 18 m 2 for the pozzolane rosse unit to the order of 10 15 m 2 for the tufo pisolitico di trigoria unit in good agreement with the shallow aquifer circulating in the shallower units c 2008 elsevier b v all rights reserved

first early permian paleomagnetic pole for the yili block and its implications for late paleozoic postorogenic kinematic evolution of the sw central asian orogenic belt we conducted a paleomagnetic study on the early permian volcanic and sedimentary rocks and the neoproterozoic mafic dikes in the yili block nw china magnetite and hematite were proven to be the principal magnetic remanence carriers demagnetizations revealed stable characteristic remanence magnetizations with a sole reversed magnetic polarity the magnetic remanence of only the early permian strata turned out to be primary based on positive fold tests meanwhile the magnetic remanence age of the mafic dikes is ambiguous accordingly the first early permian paleomagnetic pole for the yili block is calculated at 81 5 n 256 5 e n 11 and a95 10 9 comparisons of this new pole with published ones from the yili tarim and south junggar blocks provide new quantitative constraints on late paleozoic kinematic evolution of the sw central asian orogenic belt 1 between the yili and tarim blocks significant relative movement took place along major strike slip faults during the late carboniferous to early permian 580 290 km and the early to late permian 585 340 km and the displacement rate increased from the late carboniferous to early permian 19 3 9 7 mm yr to the early to late permian 29 3 17 0 mm yr 2 a significant relative rotation of 28 3 18 3 in the late permian and a lateral displacement of 630 295 km after the late permian occurred between the yili and south junggar blocks the significant strike slip movements played an important role in the formation of the central asian orogenic belt and should be considered with great attention in tectonic and paleogeographic reconstructions

the fold test in palaeomagnetism summary the fold test suggested by mcelhinny is shown to be inappropriate more correctly one should determine whether the mean direction of a group of sites from one limb of a fold may be distinguished statistically from the mean direction of a group of sites from another limb details of the application of this test are given with examples it is shown that the test indicates significance under far less severe folding than does the test suggested by mcelhinny

three dimensional seismic tomography from p wave and s wave microearthquake travel times and rock physics characterization of the campi flegrei caldera 1 the campi flegrei cf caldera experiences dramatic ground deformations unsurpassed anywhere in the world the source responsible for this phenomenon is still debated with the aim of exploring the structure of the caldera as well as the role of hydrothermal fluids on velocity changes a multidisciplinary approach dealing with three dimensional delay time tomography and rock physics characterization has been followed selected seismic data were modeled by using a tomographic method based on an accurate finite difference travel time computation which simultaneously inverts p wave and s wave first arrival times for both velocity model parameters and hypocenter locations the retrieved p wave and s wave velocity images as well as the deduced v p v s images were interpreted by using experimental measurements of rock physical properties on cf samples to take into account steam water phase transition mechanisms affecting p wave and s wave velocities also modeling of petrophysical properties for site relevant rocks constrains the role of overpressured fluids on velocity a flat and low v p v s anomaly lies at 4 km depth under the city of pozzuoli earthquakes are located at the top of this anomaly this anomaly implies the presence of fractured overpressured gas bearing formations and excludes the presence of melted rocks at shallow depth a high v p v s anomaly located at 1 km suggests the presence of rocks containing fluids in the liquid phase finally maps of the v p v s product show a high v p v s horseshoe shaped anomaly located at 2 km depth it is consistent with gravity data and well data and might constitute the on land remainder of the caldera rim detected below sea level by tomography using active source seismic data

palaeomagnetic constraints on the collision and rotation of north and south china the eastern half of china is dominated by the north china block ncb and south china block scb separated by a complex fold system that trends roughly east west interpretation of the geology of this fold belt has led to a variety of estimates of the age of amalgamation of these two blocks1 7 palaeomagnetic results are few and have also been subject to conflicting interpretations8 11 here we present our own palaeomagnetic results for late permian rocks for both the scb and ncb and summarize other relevant palaeomagnetic data by reinterpreting the polarity given in some previous studies we are able to synthesize the results for the widespread emeishan basalts of the scb and to suggest a new model for the collision and relative rotation of the two blocks

modeling of surface deformation in volcanic areas the 1970 1972 and 1982 1984 crises of campi flegrei italy campi flegrei is a densely inhabited volcanic area within a caldera 12 14 km in diameter immediately west of naples italy in 1970 1972 and in 1982 1984 campi flegrei experienced considerable ground surface deformation producing a bulge about 3 5 m high at its peak in the two inflation episodes the point of maximum uplift did not change coinciding with the caldera center about which the displacements exhibited radial symmetry the 1982 1984 uplift was accompanied by considerable seismic activity gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion volcanological petrological and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera we assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber static deformation is calculated by using a finite element method assuming axial symmetry around a vertical axis through the caldera center the role played by various components of the model geometry boundary conditions elastic properties is analyzed it is shown that models assuming uniform elasticity are inadequate therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account the results of various more complex models are presented it is suggested that a progressively fractured zone whose size and shape depend also on the possible occurrence of magmatic intrusions may explain the observed surface displacements and the other data collected at campi flegrei it is suggested that the 1970 1972 uplift was possibly accompanied by larger scale changes in the stress field

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

basin evolution within and adjacent to the tien shan range nw china two late palaeozoic collisions produced the ancestral tien shan range extension following the younger collision preceded a phase of thermal subsidence associated with fluvial and lacustrine sedimentation throughout the jurassic cretaceous and early tertiary this thermal subsidence was interrupted by renewed movement on palaeozoic reverse faults caused by the mesozoic collisions at the southern margin of asia the india asia collision in the early tertiary has produced widespread thrusting in the tien shan which in turn is responsible for the formation of active foreland basins at the southern and northern margins of the range and similar basins within the range itself this compression produced uplift and relief and consequent erosion gave rise to alluvial fans braidplains and ephemeral lakes in an extremely arid environment

the volcanic and geothermally active campi flegrei caldera an integrated multidisciplinary image of its buried structure the campi flegrei caldera in southern italy is one of the greatest geohazard areas on earth evidence of an active magmatic and geothermal system is provided by ongoing ground uplift with volcano tectonic and long period lp seismicity the persistent degassing of 1500 tonnes of co2 per day the presence of hot fumaroles at temperatures of 90 150 c brine rich aquifers with total dissolved solids up to 33 g l 1 and high thermal gradients in the crust with temperatures reaching 420 c at 3 050 m b s l since the 1940s more than 100 exploratory boreholes have been drilled in the area to depths of 80 3 100 m by the azienda geologica italiana petroli agip and the societa anonima forze endogene napoletane safen to date however no systematic reanalysis of the drilling data has been carried out and the buried volcanic structure has not been updated using the most recent scientific results and previous findings by integrating unpublished data from the agip and safen reports with published information from geological volcanological petrological petrophysical and geophysical studies this paper presents an improved picture of the campi flegrei caldera that will be useful for volcanic hazard assessment and mitigation in the naples area and for future research planning the results suggest that intra caldera activity has been influenced by how the magmatic system at depths greater than about 4 km has determined the transfer of magma volatiles and heat to the overlying geothermal system and ultimately to the surface in particular intriguing is that the most volcanically active central eastern sector of the caldera which is subject to intense bradyseismic ground movement and gas emission coincides with a structurally delimited subsurface rock volume characterized by an uprising of the 100 c isotherm a deep water supply to the shallower aquifer the early disappearance of secondary calcite lp seismicity and high seismic s wave attenuation in this area we also document evidence of repeated injection at depths of c 1 5 3 0 km of isolated and small volume batches of magma where occurred their crystallization and degassing shallow intrusions and degassing of magma are thus identified as two of the key processes that drive unrest in campi flegrei

a 2d mechanical thermalfluid dynamical model for geothermal systems at calderas an application to campi flegrei italy abstract a finite difference method has been developed to simulate water flow in a 2d porous medium with boundary conditions specified in terms of pressure and temperature the method computes steady state solutions for temperature pressure and fluid velocities with an appropriate choice for boundary conditions it is possible to simulate the behaviour of a geothermal system with an incremental pressure and or temperature applied to a finite part of the base pressure and temperature changes produce a change in the fluid flow regime leading to different final temperatures pressures and fluid velocities steady state the method is particularly suitable for simulating the coupled mechanical and thermalfluid dynamical effects at calderas when increases in pressure and heat flow from a magma chamber perturb the conditions of the uppermost aquifer system several tests performed with realistic values for the parameters of the porous medium show that increases of pressure at the base are efficiently propagated in the upper medium by water flow so that the effective centre of overpressure is shifted to considerably shallower levels this effect can strongly modify the shape of ground deformations at calderas and strongly amplify the peak values the proposed method has been applied to the explanation of the very peculiar ground deformation observed at campi flegrei during 1982 1984 which showed very high uplifts 1 8 m and a strong concentration in a small area 3 3 km 2 an integrated mechanical thermalfluid dynamical model for this caldera is proposed which could be generalised to other areas

apparent polar wander paths of the major chinese blocks since the late paleozoic toward restoring the amalgamation history of east eurasia abstract high quality paleomagnetic poles a k a paleopoles are essential for quantitative lithospheric plate reconstruction however the current paleomagnetic database of the major chinese blocks including the north china block ncb the south china block scb and the tarim block tb since the late paleozoic era contain outdated and low quality data here we update the database by adding recently published high quality paleopoles and rejecting low quality outdated ones the database includes 288 paleopoles published 1980 2014 90 of them published after 2000 following the van der voo selection criteria 75 paleopoles each with a quality factor q smaller than 4 were rejected in the first round of selection we then removed another 59 paleopoles that have been locally rotated or shallowed since the acquisition of stable remanence eventually 154 paleopoles were selected and adopted to calculate the new apparent polar wander paths apwps for the major chinese blocks we found comparable clastic and igneous paleopoles at intervals when a quantitative comparison was available as such comparison was not possible during most periods epochs our conclusions reflect an unclear extent of inclination errors in chinese clastic paleopoles new models of the chinese apwps with and without inclination error corrections were computed from carefully selected paleopoles version 1 running mean v1rm paths were calculated at the period epoch level version 2 running mean v2rm paths were computed in a set sliding time window of 20 or 30 myr spline paths were calculated with the same time windows along with a smoothing parameter of 50 using a recent global reconstruction model and up to date geological observations new models of the chinese apwps allowed us to re evaluate the coalescence history of east eurasia since the late paleozoic era four major tectonic events were confirmed 1 the tb accreted with the kazakhstan orocline during amalgamation of the west altaids during the middle late permian period ca 265 250 ma 2 the suturing of the ncb and the scb likely occurred in a scissor like pattern and had been accomplished no later than the middle jurassic period ca 180 160 ma 3 the amalgamation between the ncb and the tb along with the microblocks between the two might have been achieved during the late jurassic early cretaceous periods ca 160 140 ma 4 the mongol okhotsk ocean should have been closed no later than the early cretaceous period ca 140 120 ma

speculations on the mesozoic plate tectonic evolution of eastern china several orogenic belts transecting eastern china are the sites of former convergent plate margins although there have been varying views on the collisional framework of individual continental blocks styles of convergence at these zones and the timing of respective collisions a tectonic study of eastern china mongolia and the southern soviet far east indicates the collision of the south china block with a combined north china northeast china fold zone block in the late triassic early jurassic their collective suturing to eurasia in the late jurassic early cretaceous followed by the sikhote alin japan block in the mid to late cretaceous the evidence is as follows 1 a linear belt of late triassic early cretaceous granites and granodiorites trends east from the qinlingshan through the dabieshan to the huaiyang massif ophiolites flysch subduction zone melange a paired metamorphic belt indicating north dipping subduction and marine strata of carboniferous to late triassic age from the qinlingshan define the suture between the north and south china blocks 2 a sinuous belt of ultramafics blueschists silicic to intermediate magmatism and west and north vergent folds and thrusts trend from the west margin of the ordos basin through central inner mongolia and along the east great khingan range to the amur river coupled with a mid jurassic early creataceous unconformity a suturing of eastern chinese blocks to eurasia along this zone is suggested 3 a fold and thrust belt with ultramafics flysch blueschists and subduction zone melange along the ussuri river in northeast china indicates the suturing of the sikhote alin japan block to eurasia along a west dipping subduction zone in the mid to late cretaceous similarly a tectonic study of southern china and southeast asia has revealed a complex regional mosaic of suture bounded terrains which nucleated about the eastern western and southern margins of the yangtze craton during the late triassic and early jurassic the evidence is as follows 4 a north south trending belt of ophiolites blueschists calc alkaline volcanics and subduction zone melange including granites granodiorites and strongly deformed marine strata all of late triassic age exposed in the longmenshan of sichuan merge with the kekexilishan ophiolite zone into the ailaoshan tengtiaohe ophiolite and blueschist belt in central yunnan along which the songban ganzi complex and the shan thai malaya block join the craton and 5 a southeastern prolongation of the ailaoshan tengtiaohe belt bifurcates into the southeast trending konvoi zone of northern vietnam and the north south trending pak lay luang prabang zone of laos and eastern thailand zones of ophiolite calc alkaline volcanics and strong late triassic deformation they separate the indosinia and shan thai malaya blocks from the craton respectively these findings differ significantly from previous interpretations of a late paleozoic consolidation of south eastern asia as well as disputing the existence of a true pangea

accurate fault mechanism determinations for a 1984 earthquake swarm at campi flegrei caldera italy during an unrest episode implications for volcanological research we have analyzed 42 microearthquakes 1 ml 3 that occurred at campi flegrei volcanic area during an intense swarm like activity more than 500 events in half a day in the last period of strong ground uplift 1982 1984 focal mechanisms of these earthquakes have been computed by a probability method which uses p wave polarity and s wave polarization data composite focal mechanisms for different groups of earthquakes have also been computed by the same technique results show a well defined fault plane in agreement with the elongation of the epicentral pattern the orientation and dip of this fault plane together with other observations about hypocenter locations and focal mechanisms of the whole seismicity accompanying the ground uplift episode suggest the presence of an elliptical fracture system at the caldera center this fracture system dipping toward the center of the caldera should represent the limit of the most recent caldera collapse which is also indicated by a negative bouguer gravity anomaly moreover an important differential feature among various groups of earthquakes has been shown namely a rotation up to about 30 of the strike of the compressive stress axis between the easternmost and the westernmost events the resulting pattern indicates that the axis is always oriented towards the town of pozzuoli which roughly represents the very center of the caldera and also the center of symmetry of the ground deformation these observations strongly suggest that earthquakes are generated by the variation of the stress field associated with the deformation along prefractured zones because of their greater weakeness this study provides then the first direct evidence that both seismicity and ground deformations have a common origin

late paleozoic polar wander path for the tarim platform and its tectonic significance abstract stepwise thermal and a f demagnetizations have been carried out on 518 samples 47 sites from the sishichang section across the akesu area in the tarim basin the results lead to a discussion on some problems concerning the tectonic history of the tarim platform and adjacent blocks during the late paleozoic from the late carboniferous until the early permian the tarim platform collided with the kazakhstan block siberian platform and russian platform no large displacements have occurred between these blocks since the mesozoic however the permian pole position of the tarim platform obviously differs from that for the sino korea platform the difference in paleolatitude between the tarim and sino korea platforms in the permian was about 10 their orientations were also different the paleomagnetic result is in contrast to the geologically accepted idea that the two platforms in question occur as a whole in the late paleozoic

reply to comment by jose pujol on laboratory measurements of ultrasonic wave velocities in rocks from the campi flegrei volcanic system and their relation to other field data

continental growth of northwest china the northwest corner of china is the most interior part of central asia and includes parts of the siberian tarim and kazakhstan plates where the junggar and tarim basins are separated by the east west trending tianshan range a preliminary terrane map divides the area into thirteen separate areas which are classified into four types l continental 2 oceanic crust 3 island arc 4 composite the boundaries for these terranes are faults that have been previously defined either by geologic mapping or holocene activity passive consolidation of the southern margin of paleo asia is marked by accretion and subduction of the paleo tethys oceanic basins and by development of volcanic arcs paleomagnetic data indicate that the major plates and associated smaller terranes did not reach final consolidation until the permian or later the stratigraphic record reveals development of intracontinental basins in the late carboniferous followed by the pan asian thermal event that gave rise to widespread intrusion of a type granites of late paleozoic age the frontal collision of india along the southern border of asia in the paleocene reactivated nearly all of the older major strike slip and thrust faults formed during the late paleozoic consolidation of paleo asia the complex nature of the continental growth of central asia has produced and destroyed many varieties of sutures and reconstruction of the original plate and terrane configurations therefore is enigmatic

paleomagnetic results from the triassic of the yangtze platform two widely separated localities have been sampled from triassic formations of the yangtze platforms the first is from the border area between sichuan and guizhou provinces where the early triassic yelang formation was sampled at 15 sites located on both flanks of an anticline characteristic high temperature components were isolated from nine sites the remainder were severely overprinted by a recent field two polarities are present one directed toward the northeast with shallow positive inclinations and the other to the southwest with almost horizontal inclinations the northeast group passes the fold test at the 95 level the second area of study was from the city of nanjing jiangsu province where 19 sites were drilled from three formations ranging in age from the lower to upper triassic the samples are severely overprinted with a component that is almost vertical and whose origin is unclear however in 23 of the samples a high temperature component was isolated directed to the northeast and positive and to the southwest and negative the fold test is indeterminate the pole positions from the two localities are sichuan

paleo heat flow evolution of the tabei uplift in tarim basin northwest china abstract the paleo heat flow evolution of the tabei uplift in the tarim basin is investigated based on burial and thermal history reconstruction of 14 wells and using basin modeling numerous geological parameters such as temperature data and missing sediment thickness by erosion were used in the modeling the basin model was calibrated using 460 measured vitrinite reflectance vr o and vitrinite like maceral reflectance vlmr o values to constrain the validity of the maturity model the heat flow history of the tabei uplift tarim basin shows the following characteristics 1 the highest paleo heat flow was predicted to have occurred in the early ordovician as 65 5 mw m 2 and gradually decreased to 55 5 mw m 2 during the late carboniferous 2 a thermal kick was modeled to have occurred in the permian as suggested by an abrupt rise in the heat flow 3 the heat flow gradually decreased since the triassic 4 the present day heat flow was predicted to be as low as 38 mw m 2 this heat flow history honors the geologic and tectonic evolution history of the tabei uplift and is suggested as the best case heat flow model

mesozoic paleomagnetic results of the tarim craton tertiary relative motion between china and siberia paleomagnetic poles from two late jurassic to late cretaceous stratigraphic sections on the northern boundary of the tarim craton in western china are concordant with poles of similar age from eastern china when combined with previously published data these new results suggest that the major tectonic blocks which comprise china the tarim yangtze and sino korean cratons have been arranged in approximately their present relative configuration since cretaceous times the averaged cretaceous paleomagnetic pole for china is significantly different from the averaged cretaceous pole for siberia the difference may reflect significant relative post cretaceous motion between the composite china terrane and the siberian craton alternatively the cretaceous pole for siberia may not be reliable

palynology and the eco plant model of peat forming wetlands of the upper triassic haojiagou formation in the junggar basin xinjiang nw china abstract terrestrial deposits of the triassic jurassic transition are well developed in the junggar basin located in the haojiagou valley of urumqi xinjiang uygur autonomous region of northwest china this paper describes the palynology of a 10 m thick lignite bed from the upper triassic haojiagou formation rhaetian with the aim of reconstructing the palaeovegetation and palaeoenvironment of a peat forming wetland near the triassic jurassic boundary the palynoflora contains both eurasian and gondwanan elements and is dominated by the spores and pollen of bennettitales corystospermales ginkgoales and gleicheniales at the triassic jurassic boundary hettangian the palynoflora significantly changes as cyatheales spores become the dominant elements we analyze assemblages in terms of an eco plant model which assigns the parent plants of the palynomorphs into five groups based on humidity and four groups based on temperature and uses multivariate statistical analyses to infer palaeoclimate and palaeoenvironmental conditions results suggest that the palaeoclimate of the rhaetian was generally wet and subtropical with short seasonal drought periods our analysis shows that an eco plant model may be a useful tool to reveal past vegetation patterns and climate changes applicable to other mesozoic assemblages

eruptive versus non eruptive behaviour of large calderas the example of campi flegrei caldera southern italy caldera eruptions are among the most hazardous of natural phenomena many calderas around the world are active and are characterised by recurrent uplift and subsidence periods due to the dynamics of their magma reservoirs these periods of unrest are in some cases accompanied by eruptions at campi flegrei caldera cfc which is an area characterised by very high volcanic risk the recurrence of this behaviour has stimulated the study of the rock rheology around the magma chamber in order to estimate the likelihood of an eruption this study considers different scenarios of shallow crustal behaviour taking into account the earlier models of cfc ground deformation and caldera eruptions and including recent geophysical investigations of the area a semi quantitative evaluation of the different factors that lead to magma storage or to its eruption such as magma chamber size wall rock viscosity temperature and regional tectonic strain rate is reported here for elastic and viscoelastic conditions considering the large magmatic sources of the cfc ignimbrite eruptions 400 2 000 km3 and a wall rock viscosity between 1018 and 1020 pa s the conditions for eruptive failure are difficult to attain smaller source dimensions a few cubic kilometres promote the condition for fracture eruption rather than for the flow of wall rock we also analyse the influence of the regional extensional stress regime on magma storage and eruptions and the thermal stress as a possible source of caldera uplift the present study also emphasises the difficulty of distinguishing eruption and non eruption scenarios at cfc since an unambiguous model that accounts for the rock rheology magma source dimensions and locations and regional stress field influences is still lacking

new paleomagnetic data from the mongol okhotsk collision zone chita region south central russia implications for paleozoic paleogeography of the mongol okhotsk ocean we present a reconnaissance paleomagnetic study of rocks from several formations of the chita region of south central russia representative location 51 n 116 e within the mongol okhotsk collision zone sections of siltstone and fine grained sandstone dated using fossils as bashkirian to moscovian epochs ussr carboniferous system middle carboniferous early permian late permian and triassic in age were sampled the resulting collection from five stratigraphic sections is a total of 319 oriented samples from 51 sites generally 5 to 10 samples per site were collected sample orientation was determined using both magnetic and sun shadow azimuths all paleomagnetic measurements were completed in the paleomagnetic laboratory at the university of pittsburgh using a 3 component 2g superconducting rock magnetometer srm in a magnetically shielded room thermal demagnetization was completed using between 12 to 20 heating steps up to temperatures of 685 c principal component analysis of the demagnetization data was successful in isolating two characteristic remanent magnetizations the lower unblocking temperature component component a fails the fold test is always of downward directed magnetic inclination and may record the present day earth s pdf magnetic field pdf i 69 4 d 351 8 component a ig 65 1 dg 356 5 95 6 2 n sites 50 the higher unblocking temperature magnetic component b was observed in the triassic bt n 3 late permian blp n 14 early permian bep n 5 and bashkirian to moscovian epochs of the late carboniferous bmc n 8 sections the b component differs significantly from component a and is recorded by sites of both downward and upward directed magnetic inclinations in the late permian and bashkirian to moscovian epoch sections component bmc and blp may represent primary remanent magnetizations the bashkirian to moscovian epochs of the late carboniferous mean paleolatitude is mc 19 9 14 8 and the late permian mean paleolatitude is lp 19 6 14 5 both are similar to that expected from reference paleomagnetic poles from the north china block but significantly different from paleolatitudes calculated using reference poles from the siberian or european plates we interpret the results of this study to suggest that the sampled sections were located near or associated with the north china block during their deposition

the campi flegrei deep drilling project cfddp new insight on caldera structure evolution and hazard implications for the naples area southern italy the 501 m deep hole of the campi flegrei deep drilling project located west of the naples metropolitan area and inside the campi flegrei caldera gives new insight to reconstruct the volcano tectonic evolution of this highly populated volcano it is one of the highest risk volcanic areas in the world but its tectonic structure eruptive history and size of the largest eruptions are intensely debated in the literature new stratigraphic and 40ar 39ar geochronological dating allow us to determine for the first time the age of intracaldera deposits belonging to the two highest magnitude caldera forming eruptions i e campanian ignimbrite ci 39 ka and neapolitan yellow tuff nyt 14 9 ka and to estimate the amount of collapse tuffs from 439 m of depth yield the first 40ar 39ar age of ca 39 ka within the caldera consistent with the ci volcanic rocks from the nyt were moreover detected between 250 and 160 m our findings highlight i a reduction of the area affected by caldera collapse which appears to not include the city of naples ii a small volume of the infilling caldera deposits particularly for the ci and iii the need for reassessment of the collapse amounts and mechanisms related to larger eruptions our results also imply a revaluation of volcanic risk for the eastern caldera area including the city of naples the results of this study point out that large calderas are characterized by complex collapse mechanisms and dynamics whose understanding needs more robust constraints which can be obtained from scientific drilling

physical and transport property variations within carbonate bearing fault zones insights from the monte maggio fault central italy the physical characterization of carbonate bearing normal faults is fundamental for resource development and seismic hazard here we report laboratory measurements of density porosity vp vs elastic moduli and permeability for a range of effective confining pressures 0 1 100 mpa conducted on samples representing different structural domains of a carbonate bearing fault we find a reduction in porosity from the fault breccia 11 7 total and 6 2 connected to the main fault plane 9 total and 3 5 connected with both domains showing higher porosity compared to the protolith 6 8 total and 1 1 connected with increasing confining pressure p wave velocity evolves from 4 5 km s to 5 9 km s in the fault breccia is constant at 5 9 km s approaching the fault plane and is low 4 9 km s in clay rich fault domains we find that while the fault breccia shows pressure sensitive behaviour a reduction in permeability from 2 10 16 m2 to 2 10 17 m2 the cemented cataclasite close to the fault plane is characterized by pressure independent behaviour permeability 4 10 17 m2 our results indicate that the deformation processes occurring within the different fault structural domains influence the physical and transport properties of the fault zone in situ vp profiles match well the laboratory measurements demonstrating that laboratory data are valuable for implications at larger scale combining the experimental values of elastic moduli and frictional properties it results that at shallow crustal levels m 1 earthquakes are less favoured in agreement with earthquake depth distribution during the l aquila 2009 seismic sequence that occurred on carbonates

constraining the intracontinental tectonics of the sw central asian orogenic belt by the early permian paleomagnetic pole for the turfan hami block in order to better understand the kinematics and geodynamics of the late paleozoic to early mesozoic transition from accretionary to intracontinental tectonics in the southwest central asian orogenic belt we performed a paleomagnetic study on lower permian strata in the turpan hami basin nw china magnetite and hematite are shown to be the principal magnetic remanence carriers a typical sedimentary fabric that has not been modified by postdepositional deformation is recognized via magnetic fabric study stable characteristic remanent magnetizations all of reverse magnetic polarity are revealed by step demagnetizations remanence age is determined to be of early permian affinity based on a fold test remanence behavior of minerals and geochronologic data with inclination shallowing corrections the first early permian paleomagnetic pole for the turpan hami block is acquired as 75 7 n 276 3 e a 95 5 7 and n 10 sites comparisons of this new pole with published ones from neighboring cratonic blocks provide kinematic constraints on the tectonic transition and subsequent intracontinental tectonics of this region the turpan hami and yili blocks have kept their relative positions since the early permian significant latitudinal movement of 14 7 7 2 occurred between the turpan hami and south junggar blocks and could be mainly accommodated by late paleozoic crustal shortening of at least 530 km across an intra arc basin in the bogda belt the turpan hami block has experienced large magnitude relative rotations of 41 1 7 1 a nd 21 2 9 4 with respect to tarim and south junggar since the early permian respectively corresponding to dominant intracontinental tectonics characterized by large magnitude strike slip displacements along megashear zones

understanding the seismic velocity structure of campi flegrei caldera italy from the laboratory to the field scale we report laboratory measurements of p and s wave velocities on samples of tuff from campi flegrei italy and a new tomographic velocity map of the campi flegrei caldera laboratory measurements were made in a hydrostatic pressure vessel during both increasing and decreasing effective pressure cycles selected samples were also thermally stressed at temperatures up to 600 c to induce thermal crack damage acoustic emission output was recorded throughout each thermal stressing experiment and velocities were measured after thermal stressing laboratory p and s wave velocities are initially low for the tuff which has an initial porosity of 45 but both increase by between 25 and 50 over the effective pressure range of 5 to 80 mpa corresponding to a decrease of porosity of 70 marked velocity hysteresis due to inelastic damage processes is also observed in samples subjected to a pressurization depressurization cycle tomographic seismic velocity distributions obtained from field recordings are in general agreement with the laboratory measurements integration of the laboratory ultrasonic and seismic tomography data indicates that the tuffs of the campi flegrei caldera can be water or gas saturated and shows that inelastic pore collapse and cracking produced by mechanical and thermal stress can significantly change the velocity properties of campi flegrei tuffs at depth these changes need to be taken into account in accurately interpreting the crustal structure from tomographic data

collision and rifting in the tethys ocean geodynamic implication abstract the tethys ocean was formed 250 m y ago when gondwana collided with laurasia since then and up to its closure about 40 50 m y ago the development of the ocean was dominated by repeated jumps of the spreading axes to the passive margin of gondwana splitting of microcontinents their transportation across the ocean and accretion to the active margin of eurasia it appears that jumps of the spreading centre and rifting of the passive margin coincided with periods of major collisions on the active margin several epochs of collision and rifting are described the late permian mid late triassic late jurassic early cretaceous end of the early cretaceous late eocene the simultaneous occurrence of rifting and collision has important geodynamic implications and it cannot be explained if only the forces applied to plate margins i e slab pull and ridge push are considered as the plate drying forces slab pull did not act in times of collision when the subduction zone was blocked by continental fragments and the ridge push creates compression but not extension on the passive margin it is suggested instead that the conveyor belt process of transportation of continental masses from the passive to the active margin of tethys was governed by north directed convective flow in the asthenosphere in times of collision when lithospheric plates were unable to move with the flow the latter created great tensile stresses in the overlying lithosphere that led to formation of rifts and then to new spreading centres

new cretaceous paleomagnetic poles from the tarim basin northwestern china most paleomagnetic studies of the tarim have been focused on the paleozoic with little data published for mesozoic rocks however the ancient configuration of this part of asia has been affected by the indian eurasian collision during the second french chinese karakorum expedition from kashkar to kunjerab in the autumn of 1990 we sampled about 500 cores from 53 sites of upper and lower cretaceous red sandstones from three areas near uytak yingjisha and wuqia 38 5 39 5 n 75 76 5 8 isothermal remanent magnetization acquisition indicates the presence of minerals with high magnetic coercivity stepwise thermal demagnetization confirms that hematite is the dominant carrier and allowed the separation of low temperature components ltc 600 c in most samples the mean direction of ltcs is aligned with that of the present earth field normal and reversed polarities have been found for the htcs of each age group htcs show positive fold tests for at least one sub study where the attitudes of bedding were sufficiently different to allow the test to be performed more important the four sub studies from yingjisha and wuqia give fully compatible results results from the uytak area show a wide dispersion in declinations as could be expected from the rather severe deformation and proximity to major thrust and strike slip faults data obtained in the kuche area from northern tarim by li and co workers and in southern junggar by chen and co workers are statistically identical to the new data from yingjisha and wuqia data from paicheng in northern tarim appear to have been subject to local rotation excluding those sites which appear from paleomagnetic study to have been significantly rotated we calculated a mean cretaceous pole for the tarim basin at 69 1 n 223 88 ass 3 5 n 5 this result indicates that the total post cretaceous rotation of tarim relative to junggar and to eurasia has been negligible 2 6 6 1 and 0 4 4 6 respectively continental shortening and rotation between tarim and junggar within the tien shan are not resolved by paleomagnetism although the values obtained 400 t 600 km 3 6 are compatible with tectonic models of the range a major discrepancy warranting further geological investigation is that between the tarim and north china block poles which would imply some 1400 1060 km of north south relative displacement

a model for earthquake generation during unrest episodes at campi flegrei and rabaul calderas we have analysed the seismicity that occurred at campi flegrei caldera italy in the period 1982 1984 during an unrest episode earthquake locations describe a system of inward dipping ring faults focal mechanisms of such events show a normal dip component which is not in agreement with the differential uplift of the inner caldera as defined by static ground deformations we have performed a simulation of the stress field generated by overpressure in a magma chamber in presence of lateral discontinuities using a boundary element method lateral discontinuities simulate the ring fault system marking the border of the inner caldera collapse results allow us to hypothesize that reverse fault slip on the ring fault is mainly aseismic and such aseismic movement is able to focus normal fault shear stress along the lateral discontinuities aseismic slip on the ring fault in response to static deformation is also supported by the low seismic moment released m0 1015 nm about two orders of magnitude lower than expected from the shear slip on the discontinuities needed to accomplish the total static surface deformation 1 8 m such results have been compared with observations at rabaul caldera during a similar unrest episode in this area the seismic moment release is in good agreement with shear slip produced on a system of outward dipping ring faults and seismicity is much more focused on the fault structures such a different behaviour can be interpreted in the framework of our model as due to the different sign of the stress normal to the ring faults for inward and outward dip the comparison between the two areas shed new light about the dynamics of earthquakes in calderas in terms of the role played by ring fault systems

deep earthquakes in the southwest pacific a tectonic interpretation this paper examines the spatial distribution of deep earthquakes in the tonga fiji new hebrides region of the southwest pacific our interpretation emphasizes the complex cenozoic tectonics of the pacific indo australian plate boundary as a primary control on the distribution and deformation of subducted lithosphere most deep earthquakes in the interarc region are associated with the contorted pacific plate lithosphere subducted at the tonga trench however anomalous groups of deep earthquakes located west of the tonga zone are unrelated to the present plate configuration tectonic reconstructions of the region to 8 m y b p provide circumstantial evidence that 1 the anomalous events west of the tonga zone occur in two pieces of detached lithosphere subducted at the vitiaz and proto new hebrides trenches during the late miocene 2 the flattening of the inclined seismic zone in northernmost tonga is related to the rapid opening of the lau basin since 4 m y b p and 3 the sharp westward curvature of the tonga seismic zone in this area coincides with a preexisting bend in the late miocene vitiaz arc the sharpness of its present curvature appears to be a secondary effect of shear flow in the lower mantle and compression between detached vitiaz and attached tonga lithosphere thus much of the contortion of the subducted lithosphere beneath tonga fiji may be produced by local tectonic interactions rather than collision of the slab with an impenetrable boundary in the midmantle

constraints on the shallow elastic and anelastic structure of mars from insight seismic data mars s seismic activity and noise have been monitored since january 2019 by the seismometer of the insight interior exploration using seismic investigations geodesy and heat transport lander at night mars is extremely quiet seismic noise is about 500 times lower than earth s microseismic noise at periods between 4 s and 30 s the recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground transferred wind generated lander noise here we constrain properties of the crust beneath insight using signals from atmospheric vortices and from the hammering of insight s heat flow and physical properties hp3 instrument as well as the three largest marsquakes detected as of september 2019 from receiver function analysis we infer that the uppermost 8 11 km of the crust is highly altered and or fractured we measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the moon which suggests that the crust contains small amounts of volatiles the crust beneath the insight lander on mars is altered or fractured to 8 11 km depth and may bear volatiles according to an analysis of seismic noise and wave scattering recorded by insight s seismometer

late orogenic large scale rotations in the tien shan and adjacent mobile belts in kyrgyzstan and kazakhstan abstract most of kazakhstan belongs to the central part of the eurasian paleozoic mobile belts for which previously proposed tectonic scenarios have been rather disparate of particular interest is the origin of strongly curved middle and late paleozoic volcanic belts of island arc and andean arc affinities that dominate the structure of kazakhstan we undertook a paleomagnetic study of carboniferous to upper permian volcanics and sediments from several localities in the ili river basin between the tien shan and the junggar alatau ranges in southeast kazakhstan our main goal was to investigate the permian kinematic evolution of these belts particularly in terms of rotations about vertical axes in the hope of deciphering the dynamics that played a role during the latest paleozoic deformation in this area this deformation in turn can then be related to the amalgamation of this area with baltica siberia and tarim in the expanding eurasian supercontinent thermal demagnetization revealed that most permian rocks retained a pretilting and likely primary component which is of reversed polarity at three localities and normal at the fourth in contrast most carboniferous rocks are dominated by postfolding reversed overprints of probably mid permian age whereas presumably primary components are isolated from a few sites at two localities mean inclinations of primary components generally agree with coeval reference values extrapolated from baltica whereas declinations from primary as well as secondary components are deflected counterclockwise ccw by up to 90 such ccw rotated directions have previously also been observed in other tien shan sampling areas and in the adjacent tarim block to the south however two other areas in kazakhstan show clockwise cw rotations of permian magnetization directions one area is located in the kendyktas block about 300 km to the west of the ili river valley and the other is found in the chingiz range to the north of lake balkhash and about 400 km to the north of the ili river valley the timing of the ccw as well as cw rotations is clearly later than the disappearance of any marine basins from northern tarim the tien shan and eastern kazakhstan so that the rotations cannot be attributed to island arc or andean margin plate settings instead we attribute the rotations to large scale east west present day coordinates sinistral wrenching in an intracontinental setting related to convergence between siberia and baltica as recently proposed by natal in and engor natal in b a and engor a m c 2005 late palaeozoic to triassic evolution of the turan and scythian platforms the pre history of the palaeo tethyan closure tectonophysics 404 175 202 our previous work in the chingiz and north tien shan areas on ordovician and silurian rocks suggested relative rotations of 180 whereas the permian declination differences are of the order of 90 between the two areas thus we assume that about 50 of the total post ordovician rotations are of pre late permian age with the other half of late permian earliest mesozoic age the pre late permian rotations are likely related to oroclinal bending during plate boundary evolution in a supra subduction setting given the calc alkaline character of nearly all of the pre late permian volcanics in the strongly curved belts

radon and thoron emission from lithophysae rich tuff under increasing deformation an experimental study 1 radon and thoron emissions from lithophysae rich tuff under increasing deformation are measured to determine how mechanical damage affects gas emission levels in tuffs mechanical properties of rocks under stresses should be carefully considered to properly interpret data from geochemical field monitoring two samples are uniaxially loaded up to failure while two others are unloaded at the end of the elastic phase in order to achieve the highest compaction of existing pores changes in the porosity of deformed samples are evidenced by helium pycnometer and microscopy analyses radon and thoron exhalation rates are measured on groups of two samples by alpha spectrometer technique results show that tuff samples are characterised by a dual porosity consisting of a macroporosity given by isolated large pores with sizes from mm up to cm scale and a microporosity ranging between microns to hundreds of microns at the end of the elastic phase pervasive pore collapse is observed due to the closure of the cm scale macropores this is mirrored by a significant decrease of radon and thoron release after failure a further reduction of porosity in the rock adjacent to the fault planes is observed due to extensive closure of both macropores and micropores at this stage radon and thoron emissions increase the formation of new exhaling surfaces is the main carrier of the bulk increase of radon and thoron exhalations strongly prevailing over the densification carried out from the compaction mechanisms in terms of volcanic hazard negative anomalies in radon emissions should be considered as indicators of forthcoming ruptures key words radon and thoron exhalation tuff deformation seismic precursor

comment on laboratory measurements of ultrasonic wave velocities in rocks from the campi flegrei volcanic system and their relation to other field data by m zamora g sartoris and w chelini

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

late paleozoic paleomagnetic results from the junggar block northwestern china we have obtained middle carboniferous to permian paleomagnetic results from the junggar block in order to test its tectonic coherence and to reconstruct its late paleozoic position from hoboksar on the northwestern margin of junggar a paleomagnetic pole from basic silicic flows yields p 299 e p 70 n n 15 sites k a95 36 6 4 in the same general area a pole from lava flows plutons and as well as from remagnetized limestones sandstones is at p 350 e p 69 n n 26 site k a95 15 7 5 farther to the southwest in keramayi a pole from late paleozoic dike swarms lies at p 230 e p 80 n n 23 sites k a 95 16 7 8 in the southern margin near urumqi from sedimentary rocks and volcaniclastics of the middle to upper carboniferous qijiagou and aoertu formations a pole is produced at p 7 e p 72 n n 15 sites k a95 28 7 4 from the middle carboniferous liushugou formation and dike swarms intruding into the formation two poles are located at p 231 e p 69 n n 4 sites k a95 46 13 7 and p 172 e p 55 n n 7 sites k a95 17 15 1 respectively though reliabilities of these two poles are in question magnetic polarities of all the poles in our study are exclusively reversed based on positive fold tests and a baked contact test we believe that these magnetizations were acquired during the kiaman reversed interval 250 320 ma more accurate ages of the magnetizations cannot be resolved at present despite widely separate locations the pole positions are roughly located on a small circle segment around the junggar block similar inclinations suggest a coherent junggar block since permian time based on the results of this study and other published paleomagnetic data a mean middle carboniferous to permian paleomagnetic pole is calculated at p 329 e p 82 n n 6 poles k a95 26 13 4 recognition of late paleozoic apparent polar wander for junggar is obscured by a lack of detailed geochronologic data and possible relative horizontal rotations around vertical axis the paleolatitude for the southern junggar predicted by this pole is only 4 south of the present latitude difference exists between the mean pole from junggar and permian poles from other tectonic units in asia tarim siberia kazakhstan and north and south china indicating post permian relative motions at the boundary between tarim and junggar this motion is likely to have a left lateral sense

recent ground movement and seismic activity in campi flegrei southern italy episodic growth of a resurgent dome leveling surveys in campi flegrei an active volcanic caldera in southern italy show that this caldera has undergone both subsidence and uplift of a few meters during the past 85 years a single source located at a depth of about 3 km beneath the center of the caldera can account for almost all elevation changes recorded in campi flegrei since the first leveling survey conducted in 1905 1907 this includes leveling surveys that span periods of subsidence such as between 1905 1907 and 1919 and between january 1985 and october 1986 and periods of rapid uplift between march 1970 and october 1971 and between january 1981 and december 1984 a possible geometry for the source of uplift and subsidence beneath campi flegrei is a rectangular horizontal sheet located at a depth of about 3 km and centered a few hundred meters east of the city of pozzuoli the horizontal dimensions of this sheet are about 1 5 km by 3 0 km the long axis is oriented n70 w this sheet lies adjacent to the most intense area of seismicity that occurred from mid 1983 to december 1984 during an uplift episode this sheet may represent the top of a magma body undergoing internal pressure changes possibly by intrusion of additional magma subsidence is caused by groundwater removal from the water saturated deposits that fill this caldera to a depth of a few kilometers a temporary increase in subsidence rate after an uplift episode is caused by increased rate of groundwater removal from newly fractured regions that lie immediately above the magma body the close proximity of this water saturated region and the magma body makes it impossible to separate the depth to these two sources from the results of leveling surveys two observations indicate that uplift has occurred in the center of campi flegrei for at least the past several thousand years first marine deposits in the center of campi flegrei were uplifted at least 40 m between 4000 and 8000 years ago second continuous seismic profiles of the undersea portion of campi flegrei have identified only one region where rocks are fractured and faulted adjacent to the uplifted marine deposits that surround the point of maximum uplift indicated by recent leveling surveys on the basis of these observations and the historical record of activity we suggest that campi flegrei caldera is in a stage of growing a resurgent dome the present diameter of the resurgent dome is about 4 km and the maximum amount of vertical uplift during the past 10 000 years has probably not exceeded 100 m the episodes of rapid uplift and shallow earthquake swarms during the past 20 years are probably related to the growth of this resurgent dome

new paleomagnetic results from northern china collision and suturing with siberia and kazakhstan abstract we report new results from our paleomagnetic studies of the inner mongolia autonomous region in northeastern china and the xinjiang autonomous region in northwestern china primary magnetizations are isolated in tertiary cretaceous late jurassic and late permian rocks and secondary components of magnetization of late jurassic and recent ages are seen in strata of inner mongolia western junggar basin and part of the tarim block suffered widespread complete tectono thermal remagnetization at about 280 ma permian the paleomagnetic evidence suggests that the sampled areas in inner mongolia have been part of the north china block at least since late permian time and the junggar block collided with the tarim block by late permian time our own paleomagnetic results together with available data from other parts of eastern eurasia suggest a tectonic model in which kazakhstan europe and siberia collided with each other and formed the europe siberia kazakhstan plate eur sib kaz in late permian time to the east mongolia outer mongolia inner mongolia and the north china block were also wedged together forming the mongolia north china plate mon nc by this time these two composite continental plates were not a stable unit in the late permian the geometrical relationship of the paleomagnetic poles for these two plates suggests that collision initially occurred in the late permian near the western end 50 n 75 e of the southern siberian fold belt and progressed eastward as the mon nc plate rotated and clockwise about 117 relative to the eur sib kaz plate during the early mesozoic suturing and rotation were probably complete by the late jurassic significant relative motion between the tarim and siberia blocks continued from early triassic to late jurassic as tarim moved northeastward 1400 km relative to siberia

an apparent polar wander path from the tarim block china abstract the apparent polar wander apw path from the tarim block consists of devonian 16 n 165 e a95 4 late carboniferous 41 n 160 e a95 4 permian 61 n 177 e a95 9 early triassic 69 n 183 e a95 11 and jurassic cretaceous 65 n 214 e a95 6 poles on the basis of this apw path we conclude that tarim rode on a plate subducting under the kazakhstan plate between devonian and permian times by the end of the permian subduction had almost finished early triassic poles from tarim siberia north china and south china are discordant indicating post early triassic relative motions among them cretaceous paleomagnetic poles from tarim north china and south china however are consistent suggesting that china has been a coherent tectonic unit since cretaceous time the shape of the apw path from tarim is similar to that of siberia except that tarim s apw path is systematically displaced to the east a 26 clockwise rotation of tarim s apw path about the euler pole 60 n and 14 e reconciles these two apw paths tarim has moved northeastward some 2000 km relative to a fixed siberia since the cretaceous this northeastward motion of tarim with respect to siberia agrees well with the overall cenozoic tectonic style of asia most of southern china has been pushed eastward to give way to the penetrating indian continent east west and northeast trending left lateral strike slip faults north of the tarim block have been documented however the exact amounts of displacement along these faults are not well known using paleomagnetic data from tarim we will also discuss the tectonic evolution of terranes in central asia and the amount of continental shortening in the tibetan plateau

a physical appraisal of a new aspect of bradyseism the miniuplifts 1 the campi flegrei caldera is characterized by well known episodes of fast uplift called bradyseism the last of which produced 1 8 m of maximum vertical displacement in the period 1982 1984 less known is a particular aspect of campi flegrei unrests detected only in the last 20 years namely the occurrence of miniuplift episodes characterized by relatively small positive vertical displacements in the range 0 03 0 11 m miniuplift episodes occurred in 1989 1994 and 2000 and probably one or two times in the period 1972 1982 these small ground uplifts were also accompanied by moderate seismicity each of them was followed by a short phase of relatively quick subsidence after which the previous rate of subsidence of the period was resumed an order of magnitude analysis of the forces energy and power that can cause the onset and determine the evolution of these events is derived on the basis of a thermal fluid dynamical approach it allows the quantitative correlation of the power input from the energy source with the rate of energy dissipation in the geologic system during the miniuplifts in order to assess the likelihood of our fluid dynamical model for these episodes theoretical ground displacements have been computed these displacements result from the changes in pressure as a function of depth predicted by the fluid dynamical model for reasonable perturbations of the geothermal system described as changes of the peclet number theoretical results agree extremely well with the observed amounts of the miniuplifts

depositional mechanisms and alteration processes in different types of pyroclastic deposits from campi flegrei volcanic field southern italy the campi flegrei volcanic field southern italy is composed of a large variety of pyroclastic deposits related to both magmatic and hydromagmatic activity in spite of similarities of composition grain size age and pre eruptive environment the various deposits exhibit great differences in terms of degree and type of alteration of the juvenile components in particular detailed analyses of pyroclasts collected in the numerous monogenetic volcanic cones show the broad range of alteration from fresh glass to complete replacement of the glass by the zeolites the comparative analysis of 17 different deposits has allowed us to conclude that the eruptive and emplacement conditions were the major controls on the zeolitization processes the relationships between volcanological features of deposits and secondary mineralization are consistent with the glass fluid phase reaction in a near closed post depositional system eruptions characterised by separation of water vapour from the pyroclastic particles produce unaltered or poorly altered deposits in contrast eruptions characterised by mechanisms that permit the capture and retention of pore water and water vapour produce zeolitized deposits according to these lines of evidence the zeolitization of pyroclastic products of campi flegrei took place immediately after emplacement during the cooling of wet deposits

late permian paleomagnetic pole from dikes of the tarim craton china we have obtained a late permian paleomagnetic pole from dikes in the tarim craton of china directions of magnetization from 21 mafic and ultramafic dikes at three localities pass a fold test at the 95 confidence level the new paleomagnetic pole lies at lat 66 n long 181 e n 21 k 61 and 95 3 9 on the basis of a comparison with paleomagnetic data from adjacent tectonic units we conclude that 1 the late permian paleolatitude of the tarim craton differs from that of the sino korean craton suggesting that the two cratons were distinct tectonic units in late permian time 2 there was relative motion between the tarim craton and the siberian craton after late permian time and 3 negligible relative motions have occured between different thrust sheets in the keping bachu area of the north western tarim craton

paleomagnetism and tectonics of the southern tarim basin northwestern china we report late carboniferous permian and early tertiary paleomagnetic data from the southern tarim basin prefolding magnetizations were isolated in each case the late carboniferous permian and early tertiary poles lie at 64 6 n 166 5 e a95 6 3 and 58 1 n 202 0 e a95 12 7 respectively the late jurassic to early tertiary j3 e1 paleolatitudes of tarim and several basins throughout central asia are similar yet significantly 10 to 20 shallower than those predicted by the eurasian apparent polar wander path resolving this discrepancy remains a major problem in asian paleomagnetism discordance of the late paleozoic poles from tarim and siberia suggest that tarim has rotated about 30 counterclockwise with respect to siberia since the permian where paleomagnetic samples of both late carboniferous to early triassic c3 t1 and j3 e1 ages were collected from the same area of tarim a great circle passes through the means of the poles and the sampling locality this suggests that 1 only a difference in inclination and not declination distinguishes the two data sets and 2 vertical axis block rotations of the c3 e1 strata occurred after e1 although based on data of lesser quality the mean early to middle jurassic j1 2 pole from tarim differs significantly from the eurasian reference pole requiring radical tectonic solutions to resolve them the tarim j1 2 pole is indistinguishable from both the mean j3 e1 and c3 t1 poles the similarity of all the poles and the analogous tectonic setting of present day central asia to that of the late paleozoic in eastern north america raises the question whether all the data from tarim are overprinted

the evolution of elastic moduli with increasing crack damage during cyclic stressing of a basalt from mt etna volcano article i nfo volcanic edifices such as mt etna italy are commonly subject to repeated cycles of stress over time due to the combination of magma emplacement from deep reservoirs to shallow depths and superimposed tectonic stresses such repeated stress cycles lead to anisotropic deformation and an increase in the level of crack damage within the rocks of the edifice and hence changes to their elastic moduli which are a key parameter for reliable modelling of deformation sources we therefore report results of changes in elastic moduli measured during increasing amplitude cyclic stressing experiments on dry and water saturated samples of etna basalt in all experiments the young s modulus decreased by approximately 30 over the total sequence of loading cycles and the poisson s ratio increased by a factor of approximately 3 0 5 microseismicity in terms of acoustic emission ae output was also recorded throughout each experiment our results demonstrate that ae output only re commences during any loading cycle when the level of stress where ae ceased during the unloading portion of the previous cycle is exceeded a manifestation of the kaiser stress memory effect in cycles where no ae output was generated we also observed no change in elastic moduli this result holds for both mechanical and thermal stressing our results are interpreted in relation to measurements of volcano tectonic seismicity and deformation at mt etna volcano

permo triassic magnetostratigraphy in china northern tarim abstract the upper boundary of the permo carboniferous reversed polarity superchron has been identified in a palaeomagnetic study of the permo triassic of the northern part of the tarim basin china this boundary serves as an important marker horizon for correlation with other permo triassic sequences both in china and world wide a permo triassic palaeomagnetic pole for the tarim block is estimated to be at 71 8 n 187 6 e comparison with similar age poles from the adjacent blocks of china and asia suggests that the tarim was widely separated from the sino korean block in permo triassic times but was not yet sutured to kazakhstan

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

new cambrian and ordovician paleomagnetic poles for the north china block and their paleogeographic implications multicomponent magnetization has been revealed in several cambrian and ordovician sedimentary units from localities in hebei and shandong provinces of the north china block ncb a well defined component with lower unblocking temperature is characterized by northerly declination and moderate to steep inclination with both polarities and postdates the late cretaceous folding the pole position derived from the overprinted directions is close to both the cretaceous pole for the ncb as well as the present north pole the overprint is not a simple thermal remanent magnetization but is probably a chemical remanent magnetization imposed at moderately elevated temperature during the major episode of regional deformation in the late mesozoic the higher unblocking temperature characteristic components pass reversal baked contact and fold tests and are internally consistent with rocks of different lithologies from widely distributed localities moreover the data exhibit an overall similarity in the magnetic polarity pattern in the stratigraphic sequence at sampled localities hence the high unblocking temperature characteristic component was probably acquired at or near the time of deposition the cambrian and ordovician paleopoles are somewhat different from the other coeval poles for the ncb which are based on much less data and do not pass as many reliability tests but all imply that the ncb was in the equatorial zone in the early paleozoic

ground deformations in collapsed caldera structures abstract a method is presented to analyze the effect of stress strain discontinuities on the ground deformations generated by a pressure source this is meant to simulate the effects due to caldera structures likely to present fractured zones at the borders of the collapsed area a method originally developed by crouch 1976 to solve plane strain problems has been used to simulate deformation curves for several source and discontinuity geometries the main result is that the location of the discontinuities controls the extension of the deformed zone and always reduces it with respect to a continuous medium with respect to a homogeneous medium the presence of lateral discontinuities also acts towards lowering the overpressure required to produce a given amount of deformation these results indicate that when analyzing ground deformations in calderas the use of classical methods involving continuous media should be avoided or at least taken with caution these methods in fact assume that the extension of the deformed zone is only linked to the source depth some examples of ground deformations in active calderas have been analyzed in the framework of the results obtained from theoretical modeling four calderas recently affected by ground deformations have been considered rabaul new guinea campi flegrei italy long valley and yellowstone u s a the effects of collapsed structures on the deformation field are possibly evidenced for all the four calderas at rabaul and campi flegrei the fracture systems mainly affecting the ground deformations probably represent younger innermost collapses and are well evidenced by seismicity studies ground deformations are here concentrated in an area much smaller than the one enclosed by geologically visible caldera rims in particular at rabaul the effect of the innermost collapse can explain the high concentration of the uplift in the period 1971 1985 previously modeled by a very shallow source 1 3 km in terms of overpressure in the main magma chamber probably located at 4 5 km of depth

a geomagnetic polarity timescale for the permian calibrated to stage boundaries the reverse polarity kiaman superchron has strong evidence for at least three or prob ably four normal magnetochrons during the early permian normal magnetochrons are during the early asselian base ci1r 1n at 297 94 0 33 ma late artinskian ci2n at 281 24 2 3 ma mid kungurian ci3n at 275 86 2 0 ma and roadian ci3r an at 269 54 1 6 ma the mixed polarity illawarra superchron begins in the early wordian at 266 66 0 76 ma the wordian capitanian interval is biased to normal polarity but the basal wuchiapingian begins the beginning of a significant reverse polarity magnetochron lp0r with an overlying mixed polarity interval through the later lopingian no significant magnetostratigraphic data gaps exist in the permian geomagnetic polarity record the early cisuralian magnetochrons are calibrated to a succession of fusulinid zones the later cisuralian and guadalupian to a conodont and fusulinid biostratigraphy and lopingian magnetochrons to conodont zonations age calibration of the magnetochrons is obtained through a bayesian approach using 35 radiometric dates and 95 confidence intervals on the ages and chron durations are obtained the dating control points are most numerous in the gzhelian asselian wordian and changhsingian intervals this significant advance should provide a framework for better correlation and dating of the marine and non marine permian

probabilistic location of seismic sequences in heterogeneous media we have developed a method for the bayesian location of seismic sequences in 3d heterogeneous velocity models the method is based on a bayesian algorithm for single earthquake location joint location of seismic sequences is performed by summing the probability density functions for individual earthquake locations one of the main features of the method is the ability to accumulate travel times in the heterogeneous model as a function of both the seismic stations and the grid points simulating the seismogenic volume the ability to compute travel times just once separately from the location process allows for fast 3d locations this is a very attractive feature for real time monitoring probabilistic location of seismic sequences visualized in terms of contours of earthquake density moment and energy release etc can be obtained to give a much more seismotectonic insight than classical location algorithms the continuous character of the output quantities is particularly indicated for seismic network testing purposes it is in fact possible to compute the response of the location procedure given the seismic network geometry to various input earthquake distributions some applications of the method are also shown in this work both to the location of synthetic earthquakes and of real sequences seismic sequences at vesuvius and campi flegrei volcanic areas southern italy have been located by the probability algorithm allowing a better picture of the primary seismogenic structures we also apply the method to assess the resolution of the operating monitoring networks at the two areas

the effect of collapse structures on ground deformations in calderas ground deformations related to unrest episodes in calderas are generally interpreted like in other volcanic environments in terms of increased pressure within a magma chamber embedded in a continuous elastic medium in this framework the depth of the pressure source is inferred from the size of the deformed area this scheme works quite well for individual volcanoes for instance hawaiian shields where a good correspondence between inflation events and eruptive episodes has been observed ground deformation in calderas however show unusual features that are difficult to interpret within such a scheme because considerable positive deformation in the order of several meters and microfracturing i e intense seismicity may occur without eruptions altough the estimated depth for the magma source is sometime very shallow less than 1 2 km it has been recently suggested that the contact zones at the border of collapsed calderas could act as stress strain discontinuity zones and thus bias modeling results obtained for continuous elastic media we use both observations and theoretical modeling based on 3 d finite element techniques to show that ground deformations in collapsed calderas are strongly influenced by the caldera structure giving a new perspective in related geological and geophysical observations in such areas

a probability method for local earthquake focal mechanisms we propose a method for obtaining focal mechanisms of earthquakes recorded on a local network it is based on the non linear estimation of the probability function for strike dip and slip of the focal mechanism from p polarities s polarizations and s p amplitude ratios the method is shown to be effective for the analysis of small earthquakes recorded by local networks in particular the s p amplitude ratios bring strong constraints on fault parameters even if large errors are present an application to a small earthquake recorded at the volcanic zone of campi flegrei naples italy during a seismic outburst is presented

preliminary phanerozoic polar wander paths for the north and south china blocks polar wander paths for the north and south china blocks suggest that 1 both were parts of gondwana in the palaeozoic 2 the north china block accreted to siberia in the late permian and 3 the south china block accreted to the north china block in the middle triassic to the early jurassic comparison of the polar wander path for the south china block with that for northern eurasia suggests that relative motion of over 4 000 km has occurred between them

paleomagnetic investigation of upper permian sediments in the south junggar basin china lacustrine organic rich mudstones of the upper permian lucaogou formation are a significant petroleum source bed throughout most of the junggar basin in northwest china and paleomagnetic data may provide insight into tectonic conditions prevalent during their deposition secondary magnetizations were removed from 180 samples from 29 sites within the south junggar basin characteristic magnetizations of these samples were either revealed directly during thermal demagnetization or were calculated from great circle trajectories the primary nature of the characteristic magnetization is attested to by a positive fold test by exclusively reversed magnetizations which are consistent with the mid carboniferous to late permian kiaman reversed interval for the geomagnetic field and by relatively low levels of thermal maturity found in the mudstones tectonically corrected remagnetization circles and direct observations combined give a steep direction i 61 9 d 163 0 k 17 n 78 specimens the steep mean inclination recorded within the lacustrine organic rich mudstones suggests that junggar was situated near its present day latitude during deposition of the mudstones in late permian times consistent with the marginal ocean basin origin for junggar that has been proposed based upon stratigraphic relationships our data suggest that junggar may always have been associated with the northern continents of laurasia initially as a pre permian marginal ocean basin north of the tethys and subsequently as a permian mesozoic and cenozoic nonmarine foreland basin

paleomagnetism of upper cretaceous rocks from south china paleomagnetic study of upper cretaceous redbeds from two areas in south china was undertaken in an effort to constrain better the history of tectonic movements in southeastern asia from the nanjing area 32 n l19 e high temperature characteristic directions which pass a fold test were obtained from ten sites 43 samples in the upper cretaceous puko and yanzijing formations the paleomagnetic pole position 76 3 n 172 6 e a95 10 3 agrees well with a late cretaceous reference pole for eurasia and thus confirms that this part of south china was fully sutured to eurasia by the end of the cretaceous with no paleomagnetically resolvable subsequent relative rotation in western sichuan 26 5 n 102 3 e high temperature characteristic directions of normal and reverse polarity were obtained from twelve samples 48 specimens in the upper cretaceous to lower paleocene xiaoba and leidashu formations a provisional paleomagnetic pole position 80 9 n 296 8 e a95 7 7 differs significantly from a late cretaceous eurasia reference pole in terms of apparent tectonic movement the difference in paleopole positions would indicate a 13 10 3 northward translation and 22 11 2 counterclockwise rotation of western sichuan relative to eurasia confirmation of this reconnaisance result which would suggest that western sichuan was pushed ahead of an impinging india is needed

modelling gravity variations consistent with ground deformation in the campi flegrei caldera italy abstract in recent years 1970 72 and 1982 84 two inflation episodes took place in the campi flegrei caldera italy characterized by significant ground uplift and gravity variations an elastic half space model with vertical density stratification is employed to compute the displacement field and the gravity variations produced by the deformation of buried layers following the inflation of a spherically symmetric deformation source contributions to gravity variations are produced by dilation contraction of the medium by the displacements of density interfaces the free surface and subsurface layers and of source boundaries and possibly by new mass input from remote distances into the source volume three cases were examined in detail in case i the magma chamber is identified as the deformation source and volume and pressure increase in the magma chamber is due to input of new magma from remote distances in case ii deformation is due to magma differentiation within the magma chamber deformation source with constant mass in case iii the geothermal system is identified as the deformation source and a pressure increase possibly driven by the exsolution of high temperature and high pressure volatiles in the magma chamber is assumed to play a dominant role from the comparison between measured and computed gravity residuals free air corrected gravity variations we can assess that in case i an inflation source with constant density would predict gravity residuals compatible with observations whereas an expansion at constant mass case ii would predict gravity residuals much lower than observed the resolving power of gravity data however prevents accurate assessment of the density of the emplaced material in case iii the pervasive density increase of the geothermal fluids induced by pressure increase is assumed to be the main source of gravity variations the average porosity value required for this model to match both the ground deformation and the gravity residuals is found to be 10 a value which is compatible with measured porosity values at campi flegrei in deep wells the subsidence phases following both inflation episodes and the gravity residuals during subsidence lead us to consider case iii as more plausible even if a suitable combination of cases i and iii cannot be discarded

laboratory measurements of ultrasonic wave velocities in rocks from the campi flegrei volcanic system and their relation to other field data the campi flegrei caldera located near the city of naples italy has shown signs of unrest characterized by large ground deformation seismic activity and changes in the hydrothermal system since 1970 any attempt to model the processes giving rise to these phenomena requires some knowledge of the subsurface structure and of the physical properties of the rocks at depth in this study we report the results of laboratory measurements of ultrasonic compressional and shear wave velocities in rock samples cored in 4 different geothermal wells reaching a maximun depth of 3 km the wells are located in the san vito sv and mofete mf areas at about 3 km north and 4 km west respectively from the center of the caldera we selected 10 core samples 7 from the sv wells and 3 from the mf wells the attention being focused on the most important rock formations underneath campi flegrei and on the lower sections of the wells where data had been lacking the measurements involved the transmission of ultrasonic waves along three orthogonal directions through dry and water saturated rocks at room conditions the samples are only moderately anisotropic 13 for one sv sample and 8 for all the other samples wave velocities generally increase with the depth of the sample the range of velocities is 3 5 4 km s 1 for p waves and 1 5 2 9 km s 1 for s waves for the sv samples water saturation generally implies slightly larger 10 vp values and smaller 20 vs values as compared with dry velocities for the mf samples water saturation implies both higher vp and vs velocities up to 35 and 18 respectively these results may be explained by the different type of porosity of the sv samples vesicular and the mf samples fissurai the ultrasonic measurements on water saturated samples are slightly higher than the available in situ vp sonic measurements 25 for one sv sample and 15 for all the other samples these differences can be explained by velocity dispersion between ultrasonic and sonic frequencies and by the different pressure temperature conditions existing at depth

upper crustal structure seismicity and pore pressure variations in an extensional seismic belt through 3 d and 4 d vp and vp vs models the example of the val d agri area southern italy 1 we use local earthquake tomography and background seismicity to investigate static and transient features of the crustal velocity structure in the val d agri southern apennines italy one of the regions in central mediterranean with the highest seismogenic potential the upper crust is dominated by two broad high velocity anticlines of the buried apulia carbonate platform ramping on two parallel high angle thrusts interpreted as preexisting inverted normal faults the deep core of the anticlines consists of very high vp up to 6 9 km s and low vp vs rocks suggesting the involvement of the apulian crystalline basement in the apennine belt these results provide valuable constraints on the apennine belt tectonic evolution supporting a thick skinned interpretation for the pliocene terminal phase of the compressional tectonics the geometry of the val d agri quaternary basin is controlled by these inherited compressive features whereas the presently active extensional tectonics barely reworked the structure we find inconsistency between the structure of the apulia carbonate platform and the location and geometry of the quaternary normal faults mapped at the surface this suggests either the immaturity of the normal faults or their secondary role in accommodating the extension we observe spatiotemporal 4 d changes of vp and vp vs models defining transient variations of pore fluid pressure in the upper crust a strong change in the vp vs ratio heralds a raise in the seismicity rate that can be related to large water level changes in a nearby artificial lake this evidence is consistent with a mechanism of reservoir induced seismicity by fluid pressure increase and pore pressure diffusion the 4 d velocity variations are confined in the shallow portion of the upper crust 3 6 km depth where fluids are stored in a highly fractured medium pore pressure fluctuations can affect the strength of fault segments favoring seismicity rate changes along the active faults and possibly promoting large future earthquakes

magma system beneath tengchong volcanic zone inferred from local earthquake seismic tomography abstract the tengchong volcanic zone tcvz located in the southeastern part of the india eurasia collision zone is characterized by large scale volcano groups significant thermal activities and active seismicity to reveal the magma system we present new 3 d models of vp vs and vp vs ratio to 10 km depth beneath the tcvz based on the tomographic inversion of p and s wave arrival times from local earthquakes recorded by 10 broadband seismic stations we use arrival times to construct a reference velocity model checkerboard and jackknife tests are carried out to assess the reliability of the inversion results at shallow depths we suggest that the complex distribution of high vp vs ratio is the result of a combination of water and magmatic activity at depth of 10 km only three areas show obvious high vp vs ratio corresponding to areas of high relative geothermal value observed through hot springs at the surface we suggest that the three high vp vs ratio areas are magma chambers the upwelling volatiles heat the water in the shallow layer inducing the corresponding high relative geothermal value at the surface meanwhile the magma chamber beneath rehai spring which corresponds to high he3 he4 ratio may be fed by mantle magma we suggest that the heikongshan volcano and dayingshan volcano are fed by the magma chambers and that maanshan volcano is separated from the magma we also infer that the significant geothermal activity and active seismicity beneath rehai spring are the result of interaction between the magma and hot water reservoir

paleomagnetic study on the permian rocks of the indochina block and its implications for paleogeographic configuration and northward drifting of cathaysialand in the paleo tethys

fragmentation of asia in the permian asia is a composite continent formed by the accretion of crustal blocks1 3 a likely sequence of events is that siberia collided with a kazakhstan block which together then collided with europe along the urals in permo triassic times2 this was followed by the sucessive accretion of various blocks of south and east asia to siberia culminating in the collision of india with asia during the cenozoic palaeomagnetic data have already demonstrated that the kolyma and sikhote alin blocks of eastern asia collided with the main continent along the late mesozoic fold belts of verkhoyansk and sikhote alin4 furthermore results from the malay peninsula5 and japan6 suggest that south east asia and japan were situated near the equator in permian times and were therefore separated from the asian continent we report here some palaeomagnetic results from the permian of the sino korean and yangtze blocks of china that show they were also situated near the equator were not in their present relationship to one another and were widely separated from siberia

relating seismic velocities thermal cracking and permeability in mt etna and iceland basalts we report simultaneous laboratory measurements of seismic velocities and fluid permeability on lava flow basalt from etna italy and columnar basalt from seljadur iceland measurements were made in a servo controlled steady state flow permeameter at effective pressures from 5 80 mpa during both increasing and decreasing pressure cycles selected samples were thermally stressed at temperatures up to 900 degrees c to induce thermal crack damage acoustic emission output was recorded throughout each thermal stressing experiment at low pressure 0 10 mpa the p wave velocity of the columnar seljadur basalt was 5 4 km s while for the etnean lava flow basalt it was only 3 0 3 5 km s on increasing the pressure to 80 mpa the velocity of etnean basalt increased by 45 60 whereas that of seljadur basalt increased by less than 2 furthermore the velocity of seljadur basalt thermally stressed to 900 degrees c fell by about 2 0 km s whereas the decrease for etnean basalt was negligible a similar pattern was observed in the permeability data permeability of etnean basalt fell from about 7 5 x 10 16 m 2 to about 1 5 x 10 16 m 2 over the pressure range 5 80 mpa while that for seljadur basalt varied little from its initial low value of 9 x 10 21 m 2 again thermal stressing significantly increased the permeability of seljadur basalt whilst having a negligible effect on the etnean basalt these results clearly indicate that the etnean basalt contains a much higher level of crack damage than the seljadur basalt and hence can explain the low velocities 3 4 km s generally inferred from seismic tomography for the mt etna volcanic edifice c 2005 elsevier ltd all rights reserved

first report of coupled early permian paleomagnetic and geochronologic data from the dunhuang block nw china and implications for the tectonic evolution of the paleo asian ocean abstract in order to better understand the tectonic relationship between the dunhuang block dhb and its adjacent blocks and to constrain the timing of the closure of the paleo asian ocean a combined geochronologic and paleomagnetic investigation has been undertaken on early permian tuff basalt flows and sandstones from the shuangbaotang formation in the northwestern part of the dhb u pb zircon dating indicates that the age of the strata is between 280 6 2 9 ma and 291 4 2 6 ma thermal demagnetization of a three component isothermal remanent magnetization irm and curie point experiment suggest that magnetite dominates in the rock samples analyzed in addition there is a minor amount of hematite in some sandstones stepwise thermal demagnetization successfully isolated stable characteristic remanent magnetization chrm from 11 tuff layers two lava flows and nine sandstone beds two components were isolated from all samples a lower temperature component ltc and a higher temperature component htc the ltc is near the direction of the present day geomagnetic field and produced a negative fold test indicating it is a viscous remanent magnetization in the present day geomagnetic field most of the htc are reverse polarity normal 4 reverse 158 which is in accordance with the kiaman reversed superchron that spans the late carboniferous permian interval in addition the htc of all studied sites passed the fold and reverse tests suggesting that they likely represent primary remanent magnetization the tilt corrected mean direction from all sites tuff basalts and sandstones is ds 1 7 is 43 1 ks 403 95 1 5 n 22 the mean paleopole of the site mean direction corresponded vgps lies at 74 5 n 268 5 e with a95 1 6 considering the consistent inclination values recorded among the studied tuff basalts and sandstones and the low degrees of anisotropy within all samples we suggest that there is no significant inclination shallowing caused by depositional compaction in the sedimentary layers of the studied section taking into account the results from this study as well as previous late paleozoic paleomagentic studies from adjacent tectonic blocks we conclude that the dhb formed part of the amalgamated dunhuang north china alxa qaidam mega block during the early permian but was separated from the tarim block by a small ocean here named the qiemo xingxingxia paleo ocean at this time a comparison of the early permian paleolatitudes of these and other adjacent blocks suggest that the paleo asian ocean sensu lato was still open at this time combined with other geological evidence a paleogeographic reconstruction of the paleo asian ocean has been reconstructed for the early permian

genesis and evolution of unrest episodes at campi flegrei caldera the role of thermal fluid dynamical processes in the geothermal system we develop a model for describing water flow in a porous medium under the effect of thermal and pressure gradients the model simulates geothermal systems in calderas given the boundary conditions and the fluid dynamical properties of the medium the model allows computation in fluid dynamical stationary states of parameters characterizing the flow such as flow velocity and temperature and pressure distributions at depth the model is applied to investigate the effects of the local geothermal system on the unrest episodes at campi flegrei caldera using experimentally determined fluid dynamical parameters for the caldera rocks we show that changes of water flow in shallow aquifers under the effect of pressure and or temperature variations within the geothermal system can be very important in the genesis and evolution of unrest crises in particular they can strongly amplify the effect of pressure increase in the magma chamber on ground uplift they can also explain the timescales of evolution of ground movements in terms of transit times of the water front and of the connected temperature fronts due to advective transport on such grounds an integrated mechanic thermal fluid dynamical model was built allowing us to give a semiquantitative global explanation to the genesis and evolution of unrest phenomena results obtained here can be generalized to other similar calderas

a new paleogeographic configuration of the eurasian landmass resolves a paleomagnetic paradox of the tarim basin china 1 new paleomagnetic data from permian red beds and middle jurassic limestones from the tarim basin pose a paradox their declinations are similar to upper carboniferous to neogene rocks collected from the same sections and their inclinations parallel present values when assuming that lower than expected inclinations in continental sedimentary rocks arise from inclination shallowing effects then the paleolatitudes of all upper carboniferous to present rocks from tarim are indistinguishable local vertical axis block rotations occurring in the last 20 million years explain why declinations vary at different localities in the basin our middle jurassic data positions tarim 23 6 8 4 farther south than that predicted from the coeval reference pole for eurasia however no geologic argument exists to support the closure of a large ocean basin between tarim and siberia since the middle jurassic thus the paradox are the rocks from tarim totally overprinted or is the middle mesozoic part of the reference eurasian apparent polar wander path erroneous several lines of evidence suggest the tarim rocks are not remagnetized we conclude that tarim has experienced little or no apparent polar wander since the carboniferous moreover our middle mesozoic reconstruction of eurasia using the new middle jurassic pole from tarim results in a more geologically compatible solution for the eastern asian blocks over previous reconstructions

late paleozoic tectonic amalgamation of northwestern china sedimentary record of the northern tarim northwestern turpan and southern junggar basins sedimentary rocks contained in basins adjacent to the tian shan provide a long and complex record of the late paleozoic continental amalgamation of northwestern china complementing that provided by rocks preserved within the range this record which comprises dramatic changes in sedimentary facies sediment dispersal patterns sandstone provenance and basin subsidence rates broadly supports previous interpretations of a two part evolution of the tian shan late devonian to early carboniferous collision of the tarim continental block with the central tian shan followed by collision of this combined block with island arcs in the north tian shan and bogda shan in late carboniferous early permian times the first collision resulted in widespread angular unconformities within the tarim basin continued convergence following the collision created a long lived flexural foredeep along the northern margin of the tarim block which received at least 2000 m of lower carboniferous through lower permian fluvial and marine sediment derived from the interior of tarim subsequent early permian continental extension of the northern tarim basin resulted in the deposition of interbedded nonmarine siliciclastic sedimentary rocks and mafic to felsicvolcanic rocks sandstone within this interval was derived from the paleo tian shan and is composed predominantly of lithic volcanic grains similar to the rhyolite in contrast to the tarim basin calc alkaline volcanic rocks and volcanogenic sedimentary rocks dominated carboniferous and permian sedimentation in the northern turpan and northwestern junggar basins volcanic arcs remained active in the north tian shan and bogda shan through the early late carboniferous depositing a kilometers thick interval of deep marine sediment gravity flows in the northwestern junggar basin major arc magmatism ceased in the late carboniferous in response to closure of the oceanic basin between the combined tarim central tian shan block and the north tian shan bogda shan arcs upper carboniferous through lower permian rocks in the northwestern junggar basin compose the sedimentary fill of a bathymetric basin of oceanic depth on the northern side of the volcanic arcs culminating in a 1000 m thick marine regressive sequence middle to upper permian sandstones were derived from the uplifted paleo tian shan and bear the distinctive provenance imprint of granitic rocks presently exposed within the range late permian subsidence of the junggar basin accommodated 5 km of nonmarine sediments however the cause of this subsidence and its relationship to regional tectonic events remain controversial

ultrasonic and x ray computed tomography characterization of progressive fracture damage in low porous carbonate rocks abstract this paper studies the fracturing process in low porous rocks during uniaxial compressive tests considering the original defects and the new mechanical cracks in the material for this purpose five different kinds of rocks have been chosen with carbonate mineralogy and low porosity lower than 2 the characterization of the fracture damage is carried out using three different techniques ultrasounds mercury porosimetry and x ray computed tomography the proposed methodology allows quantifying the evolution of the porous system as well as studying the location of new cracks in the rock samples intercrystalline porosity the smallest pores with pore radius

structural geometry and evolution of an intracratonic strike slip fault zone a case study from the north sb5 fault zone in the tarim basin china abstract the north sb5 fault zone nsb5fz in the tarim basin experienced a multistage tectonic evolution thereby displaying complex structural features three dimensional seismic data were utilized to document the structural geometry and evolution of the fault zone comprehensive analysis of the seismic data suggests that the nsb5fz is a strike slip fault zone and it slipped right laterally during the early paleozoic with a varying slip azimuth three different types of responses of the late structural deformation to the pre existing structures exist on the nsb5fz in its evolution during the early paleozoic the nsb5fz has experienced at least three strike slip movements 1 induced by the first strike slip movement the lower middle cambrian strata were folded and positive flower structures occurred 2 during the second strike slip movement period several faults were produced and arranged both left and right stepping the traces of these faults were right above the faults or anticline axes at depth sequentially positive and negative relief occurred right above the left and right stepovers respectively 3 induced by the third strike slip movement a series of en echelon normal faults developed above the nsb5fz while the contractional deformation in the stepovers at depth has not ceased but propagated upward

ultrasonic velocity measurements in volcanic rocks correlation with microtexture summary this paper summarizes results of a study of porosity permeability microstructure and acoustic properties of volcanic and pyroclastic rocks from campi flegrei cf and mt etna et italy we have measured the hydraulic transport and acoustics properties of 28 room dry samples at ambient conditions 25 room dry samples under confining pressure up to 60 mpa and 5 brine saturated samples under pressure up to 45 mpa effective pressure we established the following range of porosity permeability and vp and vs variations as functions of mineralogy and differential pressure in cf and et lithologies 1 porosity cf pyroclastic rocks 30 60 per cent cf and et lava rocks 2 20 per cent 2 permeability cf pyroclastic rocks 10 1000 md cf and et lava rocks 0 01 100 md 3 velocity and quality factor cf pyroclastic rocks vp 2 3 km s x1 vs 1 2 km s x1 qp 5 80 cf and et lava rocks vp 3 5 5 5 km s x1 vs 2 3 km s x1 qp 10 115 mineralogy and microstructure govern the acoustic and petrophysical properties of these rocks under pressure in pyroclastic rocks changes in acoustic response are directly related to presence of zeolites and pumice and their reactions with the pore fluid in dry conditions collapse of the internal texture of pumice leads to decreasing velocity with pressure in saturated conditions the water zeolite interactions compete with effects due to collapsing internal textures and so velocity change with pressure is not as pronounced the microstructural changes were confirmed by analyses of optical hydraulic and transport properties after pressure ct scans show a macroscopically more compact structure under optical microscopy pumice and zeolitized pumice appear shredded a significant reduction in porosity and permeability is measured after pressurization in lava rock samples acoustic velocities increase in function of pressure and the velocity pressure relationships are characteristic of samples with rounded pores our results emphasize the importance of conducting velocity measurements at simulated in situ conditions by constraining the computations using site and depth specific rock physics properties differences between ground deformation models in volcanic areas can be assessed and predicted more reliably thus reducing volcanic hazard