petedunnite caznsi2o6 stability and phase relations in the system cao zno sio2 the phase relations of petedunnite caznsi2o6 pd were determined experimentally at p t conditions up to 2 5 gpa and 1100 c single phase petedunnite is formed at high pressures p 0 8 gpa reversed experiments show that at lower pressures and temperatures 650 c petedunnite decomposes to willemite zn2sio4 wil hardystonite ca2znsi2o7 har and quartz sio2 qtz according to the reaction 4 pd wil 2 har 3 qtz the boundary curve for this equilibrium reaction is given by p gpa 0 093 0 029 0 0014 0 0003 t c by disregarding the phase transition of quartz the stability field of wil har qtz is restricted toward lower temperatures by zinc feldspar caznsi3o8 zfsp according to the known reaction wil 2 har 7 qtz 4 zfsp these reactions intersect at 650 1 c 0 78 0 01 gpa generating an invariant point i pd additionally petedunnite breakdown reaction is intersected by the low high quartz phase transition curve generating an invariant point i pdqtz at 840 c 1 04 gpa at temperatures 650 c further reactions occur in the system cao zno sio2 including the doubly degenerate reaction zfsp pd qtz and 3 pd har wil zfsp which also intersect the invariant point i pd all reactions involving petedunnite display shallow positive slopes within the p t field indicating that the crystallization of petedunnite is highly pressure sensitive over a wide temperature range this means that an increasing petedunnite component in pyroxene shifts its stability field to higher pressures similar to the effect of a jadeitic component the study of natural clinopyroxene and the correlation of its zinc content with published p t conditions of these mineral assemblages confirmed a significant relationship between extraordinary high zinc concentrations in pyroxene and high metamorphic pressure conditions in addition the petedunnite component is obviously sensitive to the prevailing fluid conditions in terms of the fugacity ratio f s2 f o2 furthermore a distinct temperature dependency of the zinc component was observed in the range of trace element concentration in consequence zn turns out to be a key element with regard to its implementation as a sophisticated petrogenetic indicator of metamorphic conditions therefore routine measurement of zinc in element analyses of clinopyroxenes is strongly recommended

uppermost mantle structure and its relation with seismic activity in the central tien shan 1 using arrival data from ghengis and kyrgyz network knet stations we determined the uppermost mantle structure of the central tien shan from pn tomography pn velocities in the north central tien shan are slower than normal for stable lithosphere they are very slow in the south central tien shan where a hot mantle previously has been postulated the pn velocity variation correlates well with seismicity most earthquakes are concentrated in the north central tien shan but almost no earthquakes in the south central tien shan even though both geologic and gps observations show active convergence there this correlation suggests a genetic relationship between seismicity and the state of lithospheric mantle specifically we propose that the very slow pn velocity beneath the south central tien shan is caused by high temperatures produced by heating from mantle upwelling and that this heat has conducted well up into the crust inducing a ductile rheology that prevents significant seismicity

the influence of microstructure on seismic wave speed anisotropy in the crust computational analysis of quartz muscovite rocks summary we study the influence of microstructural variables on seismic wave speed anisotropy in crustal rocks the bulk elastic properties and corresponding wave velocities are calculated for synthetic rock samples with varying amounts of muscovite and quartz different muscovite and quartzgrainorientationsandvaryingspatialdistributionsofthemuscovitegrainstoinvestigate the sensitivity of seismic wave speed anisotropy on these characteristics the asymptotic expansionhomogenizationmethodcombinedwithfiniteelementmodellingisusedtocalculate bulk stiffness tensors for representative rock volumes and the wave velocities are obtained from these tensors using the christoffel equation the aim of this paper is to 1 demonstrate how wave speeds computed from the rigorous asymptotic expansion homogenization method compare with those generated using stiffness tensors derived from commonly applied analytic estimates and 2 explore how different microstructural variables influence seismic wave speeds our results show that the muscovite grain orientations have a significant influence on the wave speeds increasing the modal fraction and alignment of muscovite grains leads to greater seismic anisotropy of the rock the p wave speed at an incidence angle of 45 between the

models of the upper mantle beneath the central north island new zealand from speeds and anisotropy of subhorizontal p waves pn 1 the central north island of new zealand shows significant variations in pn wave speeds over small distances ranging from 8 5 0 2 km s to 7 4 0 1 km s over a distance of 150 km a combination of national network seismometers local volcanic seismic monitoring networks and temporary deployments are used to collect arrival times from local events during the period of 1990 2006 the data set consists of approximately 11 200 pn observations from 3000 local earthquakes at 91 seismograph sites we have created a method that allows us to model the predominant wavelength features of p wave speeds in the uppermost mantle as well as estimating values of mantle anisotropy and irregularities in the crust beneath stations using least squares collocation the resulting model shows distinct variations in uppermost mantle pn velocities velocities of less than 7 5 km s are found beneath the back arc extension region of the central volcanic region and under the taranaki volcanic region indicating the presence of water and partial melt the region to the east shows extremely high velocities of 8 3 8 5 km s where the p waves are traveling within the subducting pacific slab slightly lower than normal mantle velocities of 7 8 8 1 km s are found in the western north island suggesting a soft mantle pn anisotropy estimates throughout the north island show predominately trench parallel fast directions ceasing to nulls in the west anisotropy measurements indicate the strain history of the mantle null anisotropy measurements suggest an undisturbed mantle suggesting that mantle beneath the western north island is young

lithospheric density structure beneath the tarim basin and surroundings northwestern china from the joint inversion of gravity and topography abstract intraplate strain generally focuses in discrete zones but despite the profound impact of this partitioning on global tectonics geodynamics and seismic hazard the processes by which deformation becomes localized are not well understood such heterogeneous intraplate strain is exemplified in central asia where the indo eurasian collision has caused widespread deformation while the tarim block has experienced minimal cenozoic shortening the apparent stability of tarim may arise either because strain is dominantly accommodated by pre existing faults in the continental suture zones that bound it essentially discretizing eurasia into microplates or because the lithospheric scale strength i e viscosity of the tarim block is greater than its surroundings here we jointly analyze seismic velocity gravity topography and temperature to develop a 3 d density model of the crust and upper mantle in this region the tarim crust is characterized by high density v s v p and v p v s consistent with a dominantly mafic composition and with the presence of an oceanic plateau beneath tarim low density but high velocity mantle lithosphere beneath southern southwestern tarim underlies a suite of permian plume related mafic intrusions and a type granites sourced in previously depleted mantle lithosphere we posit that this region was further depleted dehydrated and strengthened by permian plume magmatism the actively deforming western and southern margins of tarim the tien shan kunlun shan and altyn tagh fault are underlain by buoyant upper mantle with low velocity we hypothesize that this material has been hydrated by mantle derived fluids that have preferentially migrated along paleozoic continental sutures such hydrous material should be weak and herein strain focuses there because of lithospheric scale variations in rheology rather than the pre existence of faults in the brittle crust thus this world class example of strain partitioning arises not simply from the pre existence of brittle faults but from the thermo chemical and therefore rheological variations inherited from prior tectonism

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

the 1 october 1995 dinar earthquake sw turkey the dinar earthquake ms 6 1 usgs pde of 1 october 1995 occurred on the nwse trending dinar fault the earthquake is associated with a 10 km long surface rupture with predominantly normal faulting the mainshock was preceded by a series of foreshocks that started 6 days before the mainshock and included two md 4 5 events the mainshock source mechanism derived from the inversion of broad band p waves revealed that two sub events occurred on a nw se trending normal fault with a small strike slip component according to the source model estimated in this study the first rupture started at a depth of about 8 km and reached to a depth of about 12 km propagating north west the total seismic moment found from the inversion of p waveforms is 2 0 times 10 18 nm the seismic moment of the second sub event was about four times larger than the first one field observations gps measurements and slip vector obtained from the inversion of broad band p waveforms suggest that the nw se trending dinar fault is due to the internal deformation of sw anatolia moving south westwards

lithospheric heterogeneity in the kyrgyz tien shan imaged by magnetotelluric studies 1 a 450 km long north south magnetotelluric profile spanning the tien shan from kazakhstan to western china reveals lateral variations in the resistivity of the mantle lithosphere to depths of 140 km minimum changes of one order of magnitude in this depth range result from variations in temperature or composition or both higher resistivities beneath a central portion of the range where the moho is half as deep as elsewhere in the tien shan indicate a strong lithospheric block we propose that this block protects this region of thin crust from appreciable deformation and instead transmits stresses due to india asia plate convergence from the southern to the northern parts of the range

tomographic inversion of pn travel times in china 1 pn travel times are useful for studying crustal and uppermost mantle structure and regional tectonics because they are affected by crustal velocity and thickness as well as uppermost mantle velocity and anisotropy we obtained 57 740 pn travel time picks from 5433 earthquakes and 307 stations from chinese national and provincial earthquake bulletins and the international seismological center bulletins to invert for pn velocity variation and anisotropy and station delays in china our inversion reveals significant features that correlate with surface geology the main results are as follows 1 the pn velocities show a mosaic of very fast and very slow anomalies mirroring the heterogeneous geology of china at the surface the pn velocities are high beneath the major basins in the west sichuan qaidam west tarim tulufan and junggar and low in areas of active volcanoes myanmar and western yunnan and quaternary volcanism in northern tibet in seismically active areas in north china and tien shan and in the southern part of south china the hainan plume 2 the pn anisotropy beneath the major basins in the west is generally weak strong anisotropy is found beneath high deformation regions the tibetan plateau southeastern margin of the tibetan plateau western tien shan and part of north china suggesting the anisotropy is likely related to recent large scale tectonic activity 3 a large area of north china shows prominent low pn velocity beneath archean basement with thin crust our observations are consistent with rifting lithospheric thinning and mantle upwelling in the region the pn anisotropy is consistent with a dextral simple shear in the nne direction in the lithosphere mantle during the last and ongoing major deformation period 4 the pn velocity in northern tibet is generally lower than that in the south southern tibet has significant e w structure low velocity anomalies can be traced from northern tibet across southwestern tibet and south central tibet to near the india plate anisotropy is absent beneath much of the himalaya block but consistent anisotropy with e w fast direction is present beneath the lhasa block and large anisotropy up to 4 is observed in low velocity regions of the northern and western tibet complex station delays in the eastern margin of the plateau suggest that the whole crust may be highly deformed the anisotropy pattern in the southeastern margin of the tibetan plateau suggests a mantle lithospheric deformation similar to the clockwise rotation of material observed at the surface 5 crustal thicknesses inferred from our station delays are consistent with previous models which correlate well with surface topography

seismic tomographic imaging of the crust and upper mantle under the central and western tien shan orogenic belt 1 detailed 3 d tomographic images of p and s wave velocity vp vs and poisson s ratio under the central and western tien shan orogenic belt are determined by using a large number of high quality p and s wave arrival times from local earthquakes the results show that under the tien shan orogenic belt high vp high vs and low anomalies are revealed in the upper and middle crust possibly indicating the existence of the paleozoic crystalline basement rocks while low vp low vs and high anomalies appear in the lower crust and upper mantle perhaps suggesting that the hot and wet material is upwelling under the tien shan orogenic belt from the mantle some high vp high vs and low anomalies are tilted toward the tien shan along with the seismicity these are found in the collision zones between the tien shan and the tarim basin in the south and the kazakh shield in the north and suggest the underthrusting of the tarim and kazakh lithosphere beneath the tien shan meanwhile some low vp low vs and high anomalies are imaged in other parts of these collision zones perhaps indicating the intrusion of the hot and wet material into the crust from the upper mantle these results indicate that both the upwelling of the hot and wet material and the underthrusting of the tarim and kazakh lithosphere may have played an important role in the mountain building under the tarim and fergana basins low vp low vs and high anomalies are revealed in the upper crust while high vp high vs and low anomalies are visible in the lower crust and upper mantle these may reflect the existence of less compacted sedimentary material in the shallow crust and more highly compacted craton like structures in the deeper crust and upper mantle under the basins the talas fergana fault shows an obvious tectonic boundary between central and western tien shan the central tien shan displays high vp high vs and low anomalies in the upper and middle crust while western tien shan exhibits low vp low vs and high anomalies however the pattern of seismic structure between central and western tien shan reverses in the lower crust such a correlation may extend down to the upper mantle suggesting that the talas fergana fault may be a lithospheric scale boundary additionally a columnar low vp and low vs anomaly is clearly observed around the turning point of the talas fergana fault from the nwn to nww trending orientations and may indicate that the fault provides a channel for the hot and wet material upwelling from the mantle to the surface

attenuation of high frequency p and s waves in the crust of central and western tien shan in order to better understand the attenuation characteristics in the crust of the central and western tien shan orogenic belt we investigate both qp and qs values by applying the extended coda normalization method we estimate the frequency dependent attenuation of both p and s waves in the frequency band of 1 0 20 0 hz using data from local networks the average frequency relations of qp and qs have been derived as qp 61 9 f 1 21 0 08 and qs 77 6 f 1 11 0 04 by fitting a power law frequency dependence model for the study region the low q0 and high values indicate that the central and western tien shan is a tectonically and seismically active region we also find lateral variations of both qp s and qs qp values reflecting complex tectonic structures in the study area in general the relatively high attenuation areas corresponding to tectonically active regions are found beneath mountainous ranges in the central tien shan whereas the relatively low attenuation areas are associated with stable regions such as fergana basin and issyk kul lake besides regions in the central tien shan with qs qp 1 are likely partially saturated with fluids or rich in scattering heterogeneities whereas regions in the western tien shan display qs qp 1 possibly suggesting almost complete fluid saturation

vs30 mapping and soil classification for seismic site effect evaluation in dinar region sw turkey summary the dinar earthquake m s 6 1 of 1995 october 1 killed 90 people and destroyed more than 4000 buildings despite the moderate size of the earthquake the level of damage was extremely high which led to many studies that were carried out in the region the majority of these studies concluded that the main reasons for the damage were the construction errors and the poor soil conditions however at that time no appropriate soil condition map based on extended high density measurements was available shear wave velocity is an important parameter for evaluating the dynamic behaviour of soil in the shallow subsurface thus site characterization in calculating seismic hazards is usually based on the near surface shear wave velocity values the average shear wave velocity for the top 30 m of soil is referred to as v s 30 for earthquake engineering design purposes both the uniform building code ubc and eurocode 8 ec8 codes use v s 30 to classify sites according to the soil type the v s 30 values calculated by using multichannel analysis of surface waves masw were used to create a new soil classification map of the dinar region surface seismic measurements were carried out at 50 locations mostly in dinar city and its surroundings the dispersion data of the recorded rayleigh waves were inverted using a genetic algorithm ga method to obtain shear wave velocity profiles of the investigated sites thus the derived v s 30 map of the dinar region was transformed to the ubc and ec8 standards soil classification results show that most parts of the region located in alluvial basin have low shear wave velocity values these values are within the range of 160 240 m s 1 and thus fall into the s d and s e categories according to the ubc and the c and d categories according to ec8 within the region some parts located on the hill zone and the transition zone have better soil conditions corresponding to s c ubc and b ec8 categories and have comparatively high shear wave velocities in the range of 500 740 m s 1 and 350 450 m s 1 respectively v s 30 and soil classification maps were compared with the damage distribution associated with the earthquake in possession of a detailed shear wave velocity map of dinar city in general the results show that there is a correlation between the v s 30 values and the damage distribution of the region in addition to the low v s 30 values the likely causes of the damage were investigated and it is observed that one of the major factors for high levels of damage is 3 d variations of geological structures

tomographic inversion for three dimensional velocity structure at mount st helens using earthquake data tomographic inversion is applied to 17 659 p phase observations at 21 stations from 2023 earthquakes in the vicinity of mount st helens to study the three dimensional velocity structure block size for the inversion is 2 km horizontally and 2 km or more vertically locations of hypocenters are assumed known and are based on a reference one dimensional layered velocity structure a conjugate gradient technique lsqr is used to invert the large sparse system of equations augmented by regularization with a laplacian roughening matrix resolution is estimated by computing the impulse response of the inversion for various critical locations and uncertainties of the estimates are determined by a jackknife approach the results of the inversion show a remarkable correlation with known geological and geophysical features the spirit lake and spud mt plutons are characterized by high velocity regions extending to approximately 9 km depth the st helens seismic zone a band of diffuse seismicity extending nnw from the volcano is evident as a prominent low velocity lineation the change in character of the velocity anomalies south of st helens corresponds well with the near cessation of seismic activity there a low velocity anomaly beneath the crater from 6 to 16 km depths may represent modern magma accumulations

origin of fluids in the hetaoping pb zn deposit baoshan narong dongzhi block metallogenic belt yunnan province sw china abstract the hetaoping skarn type pb zn deposit is located in the baoshan narong dongzhi block metallogenic belt bnd belt a belt between the tengchong terrane and the lanping basin the deposit is hosted by marble of the upper cambrian hetaoping formation and there are no outcrops of plutonic rocks present this deposit is one of two large pb zn deposits recently discovered in the bnd belt the hetaoping deposit is a high mn skarn four types of fluid inclusions were recognized in quartz from the deposit vapor rich inclusions type i liquid rich inclusions type ii pure vapor inclusions type iii and pure fluid inclusions type iv the coexistence of type i and type iii inclusions in stage i pre ore stage and stage ii main ore stage shows evidence of fluid boiling quartz hosted fluid inclusions stage i and stage ii display high homogenization temperatures and salinities 134 315 c 3 7 18 6 wt nacl equivalent but calcite hosted fluid inclusions in stage iii post ore stage record lower homogenization temperatures and salinities 85 214 c 0 5 5 4 wt nacl equivalent these data suggest a possible mixing between primary magmatic water and meteoric water based on chromatography data the fluid inclusions in quartz contain abundant co2 and o2 and subordinate co ch4 and c2h2 c2h4 suggesting an oxidizing environment based on their na k and cl so4 ratios fluids contained in fluid inclusions are similar to volcanic spring waters the low na k ratios 0 40 1 34 of the ore forming fluids may have resulted from interaction with a deep alkaline intermediate acid intrusion hydrogen and oxygen isotope determinations on quartz from different ore stages show low 18o and d values relative to vsmow 4 3 to 2 3 109 to 91 indicating that the ore forming fluids were diluted by external fluid sources as the skarn system cooled overall geological and geochemical interpretations suggest that the hetaoping deposit is a distal manganese skarn pb zn deposit related to concealed intrusions

lithosphere and asthenosphere of the tien shan imaged by s receiver functions 1 the s receiver function technique was applied to the recordings from 36 broad band stations in the tien shan the results reveal a pronounced difference in the properties of the lithosphere asthenosphere of the tien shan and those of the neighboring platforms beneath the tien shan an upper mantle lid with an s velocity of about 4 5 km s is underlain at a depth of about 90 km by a low velocity zone where the s velocity drops to 4 1 4 2 km s trends of p and s travel time residuals are consistent with the presence of melt or other liquids in this zone there is no evidence of any similar layer beneath the platforms the crust is 55 65 km thick beneath most of the tien shan and 45 km below the platforms although it thins to about 45 km near the naryn basin in the central tien shan

shear wave splitting at central tien shan evidence for rapid variation of anisotropic patterns at active collisional belts the fast polarization axis of shear wave splitting is generally aligned parallel to the strike of the belt which has been proposed to indicate mantle strain that is coherent with crustal deformation a notable exception is central tien shan where anomalous patterns of splitting have previously been observed we here analyze shear wave splitting of sks phases across north central tien shan using digital data from the kyrgyzstan broadband seismic network knet we find a pattern of short wavelength anisotropic heterogeneity that supports complex mantle flow due to small scale convection the along strike variations in mantle structure contrast with the coherent pattern of crustal shortening and indicate that mantle flow is not directly coupled to crustal deformation in this region

the ms 7 3 1992 suusamyr kyrgyzstan earthquake 1 constraints on fault geometry and source parameters based on aftershocks and body wave modeling we investigated the suusamyr kyrgyzstan earthquake of 19 august 1992 using aftershock data teleseismic body wave modeling and field observations aftershocks were recorded by the iris kyrgyzstan broadband network a temporary six station aftershock network and a regional network operated by the kyrgyz institute of seismology the aftershocks which range in depth from the surface to 18 km defined a 50 10 km long rupture zone that dips 50 13 to the south and strikes roughly east west the base of the eastern end of the aftershock zone shallowed to the east along strike and may represent a lateral ramp the surface ruptures also had an east west strike and dipped south but the total length less than 4 km was much shorter than the aftershock zone a teleseismic body wave inversion using a point source and a directivity correction yields a focal mechanism with a strike of 221 dip of 46 and a slip of 43 we obtained a moment of 4 1 1019 n m with a centroid depth between 5 and 21 km the rupture propagated along an azimuth of 330 60 which matches the relative location of the mainshock with respect to the aftershock zone the results of the aftershock study and teleseismic inversion yield a clear picture of the fault geometry of a large thrust earthquake

influence of station topography and moho depth on the mislocation vectors for the kyrgyz broadband seismic network knet deviations of slowness and backazimuth from theoretically calculated values the so called mislocation vectors are measured for the kyrgyz broadband seismic network knet in the tien shan region 870 events have been analysed for arrivals of p and pkp waves from all azimuths the deviations of slowness and backazimuth show a strong trend with values up to 1 s deg 1 for slowness values for waves arriving from the north and south and backazimuth deviations of in some cases more than 10 degrees for waves arriving from the east and west calculating the traveltime deviations of the stations for topography of the tien shan region and moho depth values appropriate for this area shows that most slowness and backazimuth deviations can be reduced to very small values the remaining mislocation vectors show no strong trends and are on average smaller than 0 2 s deg 1 for slowness and 2 degrees for backazimuth values which is within the error bars of these measurements results from array methods that rely on the knowledge of the backazimuth values show much improved resolution after the correction of the mislocation vectors which shows the importance of knowing and correcting for structures directly beneath arrays

three dimensional elastic wave velocity structure of the western and central tien shan arrival times of compressional p and shear s waves generated by earthquakes at local and teleseismic distances and recorded by seismographs located in the western and central tien shan are used to determine one and three dimensional elastic wave velocity structures of the crust and upper mantle beneath the mountain belt the best fit one dimensional structures suggest that the average depth of the mohorovicic discontinuity in this area is 50 km the three dimensional structure of the upper crust reveals thick sediments within each of the major depressions in the region a 7 km thick wedge of sediment beneath the chu depression is outlined at depth by a south dipping plane of seismic activity suggesting the presence of an active decollemont these low velocities extend continuously to the southeast toward issyk kul suggesting a structural relationship between the two however rather than being consumed it appears that issyk kul is overthrusting the surrounding ranges the low velocity sediments in the fergana basin reach depths of 10 km and are bounded on three sides by amorphous bands of seismicity velocities at midcrustal depths generally are lower beneath the central tien shan than beneath the western tien shan this pattern becomes more evident in the uppermost mantle with p velocity contrasts of as much as 10 across a boundary that corresponds roughly to the geographical position of the talasso fergana fault the low velocities beneath the central tien shan exceed 150 km depth but do not appear to be deeper than 300 km depth there is no evidence for a lithospheric root beneath this part of the range rather the low velocities imply the presence of a positive buoyancy force uplifting the mountains evidence that this low velocity region existed before the collision suggests that the tien shan may not owe its rejuvenation simply to its location at the northern edge of a strong tarim basin but rather to an anomalous upper mantle that was easier to deform than the surrounding lithosphere

zinc lead skarn deposits of the nakatatsu mine central japan several zoned skarns are found in the nakatatsu mine which consists of several zinc lead skarn deposits in the vicinity of the contact between the paleozoic fujikuradani formation and granite porphyry intrusions of tertiary age the skarns are mainly composed of manganoan hedenbergite of limestone origin and grandite andradite of dolerite and limestone origin clinopyroxene was altered in the vicinity of the orebodies to nontronite and clinopyroxene in the same skarn below the orebodies was transformed into garnet thus the relationship between skarns and ores seems to be one of the key points in considering a possible mechanism for ore formation the mode of occurrence of the ores the mineral compositions and the estimated physicochemical environment during ore formation suggest that the principal causes of ore formation are a reduction of the ore forming fluid and a decrease in temperature

receiver function tomography of the central tien shan abstract to obtain an image of the deep structure of the tien shan in central asia we invert p and s receiver functions jointly for almost 40 local broad band seismograph stations the inversion is performed using a simulated annealing technique the combined inversion is an improvement on earlier studies where p and s receiver functions were inverted separately using this approach we deal with structural imaging problems that are usually investigated with teleseismic body wave and surface wave tomography techniques we demonstrate that the uppermost mantle in the north of the central tien shan is composed of a high velocity lid a few tens of kilometers thick above a pronounced low velocity zone the crustal structure in this region provides evidence of magmatic underplating these features are likely related to a small plume that is manifested by basaltic eruptions of cretaceous paleogene age the low velocity layer is also found in a southeast trending corridor which may correspond to the bachu uplift in the tarim basin crustal thickness beneath the orogen varies from about 45 to about 70 km the smallest values most likely inherited from the pre orogenic era are found in a neighborhood of the talas fergana fault similar values are characteristic of the kazakh shield in the north and the tarim basin in the south the largest values are found beneath the bounding ranges we infer that uplift of the central tien shan is unlikely to be caused by crustal shortening alone

sources of fluids and metals and evolution models of skarn deposits in the qimantagh metallogenic belt a case study from the weibao deposit east kunlun mountains northern tibetan plateau abstract the weibao cu pb zn deposit is typical of skarn deposits in the qimantagh metallogenic belt qmb east kunlun mountains northern tibetan plateau it comprises three ore blocks from west to east known as weixi main and weidong mineralization in the weibao deposit is intimately related to late triassic intrusions occurring at weixi and weidong and orebodies are predominantly hosted by the langyashan formation marine carbonate rocks and to a lesser extent the devonian volcanic rocks skarns from weixi and weidong are characterized by a high garnet pyroxene ratio and diopside and andradite rich composition of pyroxenes and garnets indicating a proximal oxidized type in contrast skarn mineralogy of main indicates a slightly reduced condition typical of pb zn skarn deposits at least five hydrothermal mineralization stages can be identified and the microthermometric study indicates a general trend of cooling and dilution of the magmatic hydrothermal fluids significant precipitation of cu fe sulfides commenced from the fluid with the temperature of 340 448 c and the salinity of 2 1 15 0 wt nacl equiv pb zn sulfides however mainly precipitated when the temperatures declined to

shear wave splitting and small scale convection in the continental upper mantle the deformation of the upper mantle beneath a collisional belt is key to the dynamics of the belt but this deformation is difficult to observe seismic azimuthal anisotropy manifested by shear wave splitting provides the best geophysical evidence of deformation in the upper mantle here we use observations of shear wave splitting to investigate deformation in the upper mantle beneath the tien shan in central asia we find that underneath most of the tien shan the fast direction of azimuthal anisotropy is roughly parallel to the axis of the belt but it deviates by nearly 90 where the upper mantle is anomalously hot the former relationship previously observed in other collisional belts seems to be usual for this environment the anomalous directions however provide evidence of a rising plume beneath the range suggesting more generally that the along strike flow of the mantle beneath collisional belts is a reflection of thermally driven convection

source parameters of moderate sized earthquakes in the tien shan central asia from regional moment tensor inversion we estimate faulting geometry depth and seismic moment of 32 moderate sized earthquakes in the tien shan by matching observed and synthetic seismograms recorded at regional distances the moment tensor compression axes are oriented in the direction 170 350 consistent with the orientation of india eurasia convergence this compression is manifested in reverse faulting on roughly east west trending fault planes faults within the mountain system have moderate to steep dips but range bounding faults appear to dip more gently earthquake source depths are in the range 5 25 km consistent with those determined from local earthquake studies the distribution and mechanism of earthquakes in the tien shan suggests that a significant proportion of the active deformation in the tien shan is absorbed by shortening across intramontane basins the absence of strike slip earthquake mechanisms associated with the talas ferghana fault suggests that the fault is presently locked with deformation accommodated on neighboring compressional structures

uppermost mantle velocities beneath china and surrounding regions 1 seismic p wave velocity variations in the uppermost mantle beneath china are tomographically imaged using pn wave travel time data the average velocity of the mantle lid beneath china is 8 05 km s with a range from 0 30 km s to 0 35 km s eastern china has slower mantle velocities and a thinner crust than western china different inversions performed for shorter ray path and longer ray path data sets separated the shallow and deep structure within the mantle lid velocities in the lower lid are no more than 0 2 km s faster than at the top the fastest velocities are beneath cratons which remained relatively undeformed despite orogenic events around their margins the pn velocity beneath southern tibet is faster than that beneath northern tibet suggesting that this contrast delineates the northern edge of the indian lithosphere on the southeastern margin of the tibetan plateau the panxi rift slow pn velocity exists in the lithosphere due to the transextensional tectonic environment in eastern china extension of the north china block produced a series of nne ssw trending rifts that cause slow mantle lid velocities these slow velocities extend to the base of the mantle lid suggesting that late cenozoic pacific subduction drove the rifting both high temperature and hydration may contribute to these low uppermost mantle velocities the shanxi rift along the east margin of the ordos platform is characterized by a slow mantle velocity in contrast the yinchuan rift on the west margin does not show any uppermost mantle velocity anomaly

shear wave splitting beneath the central tien shan and tectonic implications 1 shear wave splitting analyses were performed at 30 seismic stations in the central tien shan and its vicinity fast orientation at most of the stations on the tien shan range is ene wsw parallel to the strike of the tien shan it largely reflects a coherent deformation of the lithosphere in response to the ns shortening anisotropy with nne ssw fast axes is observed within adjacent basins around the issyk kul and near the northwestern tarim where the lithosphere is presumably strong less deformed the nne ssw orientation which coincides with the surface velocity of the central tien shan can be best explained by shear between the lithosphere and asthenosphere on a regional scale rather than small scale convection as proposed in previous studies the dextral talasso fergana fault seems to have little effect on anisotropy at its nearby stations suggesting this fault is probably confined to the shallow part of the lithosphere

three dimensional seismic velocity structure of the crust beneath the central tien shan kyrgyzstan implications for large and small scale mountain building abstract the central tien shan kyrgyzstan is located approximately 2000 km from the main collisional suture between india and eurasia and is sandwiched between the kazakh shield to the north and the tarim basin to the south a three dimensional 3 d seismic velocity structure of the crust beneath the central tien shan was estimated to a depth of 50 km by means of seismic tomography using arrival time data of p and s waves from local earthquakes recorded by a temporary seismic network of the tien shan during 1998 2000 velocity structure images show a good correlation with the subsurface geology at shallow depths a low velocity zone is distributed beneath the basins probably due to the cenozoic deposition whereas a high velocity zone is visible beneath the mountain ranges likely due to paleozoic crystalline basement rocks at the surface layer results obtained at greater depths revealed the following features 1 a low velocity zone is clearly observed in the middle to lower crust and is probably caused by melt and or fluids conveyed through the flow of mantle upwelling 2 both north dipping and south dipping low velocity zones were imaged at locations where the kazakh shield and the tarim basin underthrust beneath the tien shan respectively and are probably caused by mantle materials somehow being intruded into the crust 3 the lateral variation of high and low velocity zones seen in the middle to lower crust beneath basins and surrounding mountain ranges respectively seems to be caused by melt and or fluids vertically penetrated and or laterally spread all these findings suggest that in process northward shortening and crustal thickening owing to collision and mantle convective motion i e upwelling and as a consequence partial melting are work horses in the mountain building beneath the tien shan

microtremor measurements for the microzonation of dinar the geotechnical site conditions in dinar town located in western turkey were investigated after the 1995 dinar earthquake based on borings in situ penetration tests seismic wave velocity measurements and microtremor records the variation of damage distribution within the town was evaluated with respect to 23 district damage ratios calculated based on the detailed damage survey conducted by the general directorate of disaster affairs site amplifications were estimated from microtremor spectral ratios and microzonation was performed using a gis methodology the results of in situ penetration tests and seismic wave velocity measurements as well as the damage distribution were compared with the amplification zonation obtained from microtremor records the results indicate the applicability of microtremor spectral ratios for assessing the local site conditions and site amplifications

anisotropic pn tomography in the western united states pn travel times are affected not only by lateral variations in crust and mantle velocity but also by significant amounts of laterally varying anisotropy to investigate uppermost mantle anisotropy a tomography algorithm was reformulated to include lateral variations in both velocity and horizontal anisotropy and it was applied to pn travel time data from the western united states results show that anisotropy is as important in explaining the travel time residuals as are the velocity variations a detailed resolution study examined the trade off between the velocity variations and the anisotropy variations and showed that both could be resolved for regions with good ray path coverage pn anisotropy beneath the western united states has maximum amplitudes of 0 3 km s 7 5 when resolved on a length scales of around 3 the orientations of pn anisotropy often correlate well with those inferred from shear wave splitting results this correlation suggests that orientation of mantle anisotropy does not change significantly with depth for many regions the orientation of the pn anisotropy can be correlated with some of the tectonic processes which occur within the western united states for example the fast direction of pn anisotropy parallels the northeast direction of subduction of the juan de fuca plate beneath the northwest pacific coast suggesting that there the anisotropy is related to subduction driven deformation the fast direction of pn anisotropy also parallels the strike of the san andreas fault system in central california indicating that shear strains along the plate boundary may be responsible for the anisotropy there within the great basin the pn anisotropy varies substantially and both partial melting and small scale convection within the uppermost mantle could be responsible for these anisotropy variations

crust and upper mantle structure beneath western china from p wave travel time tomography 1 three dimensional velocity images of the crust and upper mantle beneath western china are obtained through seismic tomography by using p wave arrival times of local regional and teleseismic events recorded in chinese and kyrgyzstan seismic networks at shallow depths most mountain belts and tectonically elevated areas are imaged as higher velocities relative to adjacent sediment filled basins and foreland depressions with lower velocities at mid lower crust depths the kyrgyz tian shan is underlain by lower velocity material and a distinct low velocity zone in the south north direction is observed between the eastern and western parts of the chinese tian shan the moho of the southern tarim basin has a greater depth over 50 km in front of the western kun lun compared to the northern and western tarim basin lateral heterogeneity within the upper mantle is apparent at depths from 71 to 571 km the uppermost mantle beneath the kyrgyz tian shan altay qi lian and eastern kun lun is characterized by low velocity material that is probably related to the upwelling of hot mantle the lithospheric thickness varies from 120 to 170 km beneath the chinese tian shan and northern tibetan plateau to 200 250 km beneath the tarim basin deep coupling pattern of the chinese tian shan with adjacent provinces can be classified into the embedding detaching and sinking and underthrusting of lithospheric roots in addition the lithosphere of the northern edge of the tibetan plateau seems to be thickened in contrast to the central part of the northern plateau north dipping low velocities exist in the upper mantle between the tibetan plateau and provinces to its north which might indicate mantle flow from the tibetan plateau toward surrounding areas but it has been blocked by the thick tarim lithosphere

pn anisotropic tomography under the entire tienshan orogenic belt abstract we present a new anisotropic tomography of the uppermost mantle under the tienshan orogenic belt and surrounding regions using a number of pn arrival time data hand picked from portable seismic stations and chosen from the xinjiang provincial observation bulletins and the ehb datasets our results exhibit prominent lateral heterogeneities in the study region distinct low velocity anomalies are visible under the tectonically active regions such as the tienshan orogenic belt and western kunlun mountains whereas pronounced high velocity anomalies are imaged beneath the stable blocks such as the kazakh shield the junggar tarim qaidam and turpan hami basins and the tajik depression most strong earthquakes ms 7 0 are mainly distributed along the transition zone of high to low velocity anomalies suggesting a possible correlation between the strong earthquakes and the upper mantle structure the fast directions of pn anisotropy beneath the tienshan orogenic belt are generally parallel to its striking orientation whereas those beneath pamir show a northward arc shaped distribution the pn fast velocity directions on the boundaries of the kazakh shield and the tarim and junngar basins are approximately perpendicular to the strike of the tienshan orogenic belt by integrating with previous findings our results suggest that the tarim and kazakh lithospheric materials could have underthrusted beneath the tienshan orogenic belt that leads to the hot mantle material upwelling under the tienshan orogenic belt which is attributable to the indo asian collision these dynamic processes could play important roles in the tienshan mountain building

analysis of seismic activity in the crust from earthquake relocation in the central tien shan using p and s wave arrivals from local earthquakes recorded by a temporary broadband seismic network ghengis and a kyrgyzstan broadband seismic network knet we determined the source parameters of 1938 earthquakes occurring from 1997 to 1998 in the central tien shan and adjacent areas based on one dimensional and three dimensional velocity models the results indicate that seismic activity is not restricted to only central tien shan but also penetrates into the edges of the kazakh platform and the tarim basin to the north and south respectively it implies that most range bounding faults in the central tien shan are active and they play a significant role in the tectonic activity of the mountain belt however seismic activity of the talas fergana fault in the study area is different its central segment seems more active than its eastern segment we infer that this part of the fault may be activated by neighboring faults whereas its eastern segment could be temporally locked the earthquakes at the depths of 30 40 km beneath the east central tien shan reveal an interaction between the upper and mid lower crust this suggests that brittle failure is possible to greater depth within the crust another possibility is that the seismic activity in the mid lower crust is affected by a positive buoyancy force created by mantle upwelling of this area these observations indicate that dynamic processes such as small scale mantle convection or mantle upwelling which resulted in lithospheric thinning or removal still occur beneath the central tien shan

three dimensional velocity structure and earthquake locations beneath the northern tien shan of kyrgyzstan central asia we used the arrival times of local earthquakes and quarry blasts recorded by the kyrgyzstan broadband network knet to obtain three dimensional 3 d p and s wave velocity models of the upper crust beneath an actively deforming mountain front and its associated foreland in the kyrgyz tien shan the continuous velocity models described by cubic b spline interpolation of the squared slowness over a regular 3 d grid were computed by simultaneous inversion of hypocenter and medium parameters exact ray tracing was done in the smooth 3 d medium by shooting rays from the sources to the stations by an analytical perturbation method based on the paraxial ray theory the deduced large sparse linear system was solved using the damped iterative least squares algorithm lsqr the stability and resolution of the result was qualitatively tested by two synthetic tests the spike test and the checkerboard resolution test we found that the models are well resolved up to a depth of 27 km for most parts of our image domain the p and s wave velocity models are consistent with each other and provide evidence for marked heterogeneity in the upper crustal structure beneath the northern tien shan at shallower depths 7 km the sediment filled foreland is imaged as a relatively lower velocity feature compared to the mountains which are cored by crystalline basement rocks in contrast at midcrustal depths the mountains are underlain by relatively lower velocity materials compared to the foreland a distinct contrast in velocity structure is also observed between the eastern and western parts of the kyrgyz range at midcrustal depths with the presence of relatively higher velocities toward the east the seismicity is concentrated near the traces of major active faults and extends deeper beneath the foreland compared to the mountains the regional compression in the tien shan is accommodated along a series of high angle reverse faults distributed throughout the orogenic system that extend from the surface down to midcrustal depths the range bounding fault zone can be identified by a sharp lateral gradient in seismic velocities with a pronounced southward dip combined with a zone of seismicity that also deepens to the south and reverse fault source mechanisms from moderate sized events a pronounced low velocity zone lvz is imaged in the p wave field at midcrustal depths beneath the western part of the kyrgyz range this lvz is presumably correlatable with reported high conductivity zones in this region that have been proposed to mark active fault zones along which fluid migration occurs the location of the lvz which is closely coincident with the depth of maximum earthquake generation might imply that it is a crustal decoupling zone at the brittle ductile transition

tomographic image of the crust and upper mantle beneath the western tien shan from the manas broadband deployment possible evidence for lithospheric delamination abstract we combine teleseismic p arrival times from the recent manas deployment of broadband sensors with p and s arrival times from local events recorded by the genghis deployment and analog observations from the kyrgyz institute of seismology to generate a high resolution 20 km image of elastic wavespeeds in the crust and upper mantle beneath the western tien shan the total data set consists of 29 006 p and 21 491 s arrivals from 2176 local events recorded at 144 stations along with 5202 p arrivals from 263 teleseismic events recorded at 40 stations the most significant feature in our image of the mantle beneath the tien shan is a pair of large elongated high wavespeed regions dipping in opposite directions from the near surface to depths of at least 400 km these regions appear to be continuous and extend upwards to bounding range fronts where the tarim basin is being overthrust by the kokshal range on the south side and the kazach shield underthrusts the kyrgyz range on the north side while it is tempting to interpret these high wavespeed anomalies as evidence for contemporary subduction of continental lithosphere such a scenario is difficult to reconcile with both the timing of the orogen and the size of the wavespeed anomaly we suggest instead that they represent downwelling side limbs of a lithospheric delamination beneath the central part of the tien shan possibly by siphoning of the bordering continental lithosphere as the central part descends

the influence of meteoric water on skarn formation and late stage hydrothermal alteration at the evciler skarn occurrences kazdag nw turkey abstract skarn ore deposits are generally characterized by two distinctly different alteration styles an early prograde stage with anhydrous minerals such as garnet grossular andradite and pyroxene diopside hedenbergite which forms in the presence of relatively high temperature fluid and a later retrograde stage with hydrous minerals such as epidote amphibole actinolite and chlorite from most to least abundant plus sulfides which forms in the presence of the lower temperature fluid these two alteration stages commonly have been thought to reflect a dominance of magmatic and meteoric water respectively with relevance to the source of ore metals we report data from the evciler au cu skarn deposit kazdag nw anatolia the aim of the analyses was to determine temperatures of formation the extent of equilibration among the mineral phases and or of possible alteration through fluid mineral isotopic exchange stable isotope compositions of anhydrous and hydrous alteration minerals indicate that garnet grossular andradite pyroxene diopside hedenbergite skarn prograde stage was produced by predominantly magmatic fluids during initial skarn forming metasomatism in the study area and actinolite epidote rich skarn retrograde stage was formed by magmatic water mixed with meteoric water the 18 o values of garnet from the evciler district range from 4 6 to 8 2 mean 6 7 18 o values of pyroxene range from 6 2 to 10 3 mean 8 2 18 o values of amphibole range from 6 3 to 8 2 mean 7 4 and the 18 o values of epidote range from 3 3 to 5 1 mean 0 9 however the d values of retrograde alteration minerals such as amphibole and epidote indicate both magmatic and lighter values for evciler skarn deposit that could be explained by mixing with meteoric water we conclude that the isotopic evolution of the hydrothermal fluid can be accounted for by circulation of meteoric water through a convection system heated by the evciler granitoid causing exchange of oxygen isotopes with the granitoid and country rock and possibly involving some admixture of magmatic water

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

crustal radial anisotropy across eastern tibet and the western yangtze craton 1 phase velocities across eastern tibet and surrounding regions are mapped using rayleigh 8 65 s and love 8 44 s wave ambient noise tomography based on data from more than 400 program for array seismic studies of the continental lithosphere and chinese earthquake array stations a bayesian monte carlo inversion method is applied to generate 3 d distributions of vsh and vsv in the crust and uppermost mantle from which radial anisotropy and isotropic vs are estimated each distribution is summarized with a mean and standard deviation but is also used to identify highly probable structural attributes which include 1 positive midcrustal radial anisotropy vsh vsv across eastern tibet spatial average 4 8 1 4 that terminates abruptly near the border of the high plateau 2 weaker 1 0 1 4 negative radial anisotropy vsh vsv in the shallow crust mostly in the songpan ganzi terrane 3 negative midcrustal anisotropy 2 8 0 9 in the longmenshan region 4 positive midcrustal radial anisotropy 5 4 1 4 beneath the sichuan basin and 5 low vs in the middle crust 3 427 0 050 km s of eastern tibet midcrustal vs 3 4 km s perhaps consistent with partial melt is highly probable only for three distinct regions the northern songpan ganzi the northern chuandian and part of the qiangtang terranes midcrustal anisotropy provides evidence for sheet silicates micas aligned by deformation with a shallowly dipping foliation plane beneath tibet and the sichuan basin and a steeply dipping or subvertical foliation plane in the longmenshan region near vertical cracks or faults are believed to cause the negative anisotropy in the shallow crust underlying tibet

relatively recent construction of the tien shan inferred from gps measurements of present day crustal deformation rates the tien shan a high seismically active intracontinental mountain belt 1 000 2 000 km north of the himalaya has grown as a result of india s collision with asia1 the crustal shortening 200 50 km refs 2 3 and thickening that gave rise to the tien shan accommodates only a small fraction of india s total penetration into asia 2 000 3 000km and the temporal relationship of deformation in this belt to the india asia collision remains unclear here we report geodetic measurements of the tien shan using the global positioning system gps that indicate that the current crustal shortening rate is nearly half of india s convergence rate with eurasia in this area4 we infer a total shortening rate for the tien shan of 20 mm yr 1 which is approximately twice that inferred previously from the extrapolation of slip rates in the holocene3 and earthquake induced displacements during this century5 suggesting that the rate of mountain building in this region has accelerated several fold since the onset of collision 50 55 myr ago6 7 if as we argue the current shortening rate can be extrapolated to geological timescales then our results suggest that most of the tien shan has been constructed during the past 10 myr perhaps in response to an increased horizontal force following an abrupt rise of the tibetan plateau8 9

geology mineralogy geochemistry and zonation of the bajiazi dolostone hosted zn pb ag skarn deposit liaoning province china abstract the bajiazi zn pb ag skarn deposit is located in northwest liaoning province china the orebodies occur in a contact zone between yanshanian 170 177 4 ma quartz monzodiorite and middle proterozoic dolomitic marble of the gaoyuzhuang formation as well as along the nw and ns trending fault systems in carbonate wall rocks metasomatic mineralization zoning in the deposit is very pronounced from the intrusive contact zone to dolomitic marble along the nw trending fault system three ore bearing skarn zones may be distinguished magnesian skarn zone fe mo manganoan magnesian skarn zone cu s fe pb zn ag manganoan skarn zone zn pb ag magnesian skarn is composed of diopside forsterite tremolite spinel phlogopite chondrodite and serpentine accompanied by magnetite pyrite and molybdenite manganoan magnesian skarn consists mainly of manganoan diopside manganoan tremolite mangano anthophyllite and manganocummingtonite with minor spessartine and pyroxmangite the associated ore minerals are pyrite pyrrhotite and chalcopyrite with subordinate magnetite sphalerite galena and ag bearing minerals manganoan skarn is composed chiefly of spessartine pyroxmangite magnesian rhodonite manganocummingtonite and manganopyrosmalite with the associated ore minerals sphalerite galena alabandite and ag bearing minerals studies of fluid inclusions and s pb o and h isotopic compositions suggest that ore bearing fluids flowed from the deep contact zone of the intrusion in the southeast to the shallow depth in the northwest with decreasing temperatures oxidation state and increasing ph when the ore bearing fluids migrated their frontal part constantly reacted with the dolomitic carbonate wall rocks to form different types of skarn and mineralization sulfur and lead zinc were mainly derived from the deep lower crust while the middle proterozoic wall rocks may have provided most al si mg ca and mn for the formation of skarns the zonal model reflecting the variations in metallization assemblage skarn mineralogy composition 34 s isotope values and fluid inclusion characteristics can be used as a guide to exploration for zn pb ag skarn deposits

stable isotope thermometry at high temperatures determination of accurate temperatures for geological events has been the grail of stable isotope geochemistry since the seminal 1947 paper by urey in theory this should be simple calibrated mineral pairs are common analysis is rapid and there is no significant pressure correction however in spite of widespread application the promise of reliable thermometry has been elusive stable isotope temperatures in metamorphic and igneous rocks are often controversial is the fractionation between two phases a thermometer speedometer rate dependant hygrometer p h2o dependant or chimera a number of factors have contributed to this uncertainty including incomplete and sometimes conflicting calibration of isotope fractionation factors limited understanding of the kinetics of mineral exchange and the lack of microanalytical techniques this situation has improved dramatically over the past decade permitting reliable and detailed thermal histories to be inferred in a landmark paper bottinga and javoy 1975 empirically calibrated the oxygen isotope fractionation factors among ten rock forming minerals at t 500 c their compilation shows that 84 of analyzed samples contain at least three minerals meeting a concordance test for equilibrium they concluded the great majority of igneous and metamorphic rocks has conserved a state of oxygen isotope exchange equilibrium if correct this bodes well for thermometry however this conclusion was contested by deines 1977 who critically examined the existing data and concluded that less than half of the rocks analyzed to date would yield concordant 18o derived temperatures while seeming irreconcilable both conclusions are based on fact all rocks contain some degree of disequilibrium but many also preserve a thermometric record it is the purpose of this review to discuss the new strategies for reliable isotope thermometry and to explore disequilibrium processes so they may be recognized and properly interpreted the organization of this paper will be to discuss the assumptions

mineralization of luziyuan pb zn skarn deposit baoshan yunnan province sw china evidence from petrography fluid inclusions and stable isotopesy l yang and othersmineralization process of luziyuan pb zn skarn deposit the luziyuan pb zn skarn deposit located in the baoshan narong dongzhi block metallogenic belt in sw china is hosted by marble and slate in the upper cambrian shahechang formation three skarn zones have been identified from the surface 1495 m above sea level asl to a depth of 1220 m asl zone 1 consists of chlorite actinolite calcite quartz zone 2 of rhodonite actinolite fluorite quartz calcite and zone 3 contains garnet rhodonite actinolite fluorite quartz calcite the deposit formed in four distinct mineralization stages an early anhydrous skarn garnet rhodonite and bustamite stage stage 1 a hydrous skarn actinolite and chlorite stage stage 2 an early quartz coarse barren quartz veins stage stage 3 and a late sulphide forming fine sulphide bearing quartz veins stage stage 4 the stage 1 skarn forming fluid temperature was at least 500 c according to the geothermometer with rhodonite bustamite trace elements measured by laser ablation inductively coupled plasma mass spectrometry la icp ms a decrease in ore fluid temperatures with time is consistent with the decreases in the 18 o fluid and d fluid values from stage 3 to 4 this trend suggests that the ore fluid was mainly derived from magmatic water and mixed with large amounts of meteoric water during mineralization the 34 s values of stage 4 chalcopyrite sphalerite and galena are similar to those of an ordovician gypsum layer and together with the high salinity fluids in stage 4 indicate the dissolution of evaporites in the luziyuan region overall the results of this study suggest that the luziyuan deposit is a distal pb zn skarn deposit that formed in response to multi stage alteration associated with a combination of magmatic water and meteoric water

receiver functions for the tien shan analog broadband network contrasts in the evolution of structures across the talasso fergana fault we determined the structure of the crust beneath the central and western tien shan by analyzing broadband 1 20 s analog seismograms of converted p sv phases generated by earthquakes at teleseismic distances and recorded by 14 seismograph stations the one dimensional structures that best explain the waveforms reveal pronounced differences in crustal velocities east and west of the talasso fergana fault specifically the transition zone between the crust and the mantle east of the fault is about 2 times broader than that west of the fault also velocities at depths between 10 and 35 km are about 10 lower in the east although the depth range of these lower velocities is not well resolved the talasso fergana fault is an important boundary for other observables in addition to the structural discontinuities observed at the surface the areas east of the talasso fergana fault are associated with abnormally low mantle velocities outcrops of basalt low q and short wavelength variations in anisotropy integrating these observations we interpret the broad mantle gradient as being due to vertical intrusions of mantle material into the lower crust likewise the low velocities in the midcrust could be thermally induced or due to the introduction of magmatically derived fluids the gross contrast in structure east and west of the talasso fergana fault could reflect a contrast in the dynamics of mountain building in these two regions we postulate that while crustal shortening is the dominant mechanism controlling topography west of the talasso fergana fault vertical uplift caused by a mass deficiency in the upper mantle may contribute significantly to the generation and maintenance of the high elevations east of the fault

a low velocity belt beneath northern and eastern tibetan plateau from pn tomography 1 new pn tomography on tibetan plateau tp and neighboring region is conducted with data assembled from various sources the improved pn tomographic image delineates several distinct geophysical regimes that are approximately separated by geological boundaries at surface dense distribution of the stations in the eastern half of the plateau allows us to infer a 3d view of crustal thickness variation of the region the most striking feature is the bended low velocity belt lvb which extends from west to east beneath qiangtang block and songpan ganzi fold belt sgfb in northern tp and then turns consistently southward with sgfb beneath eastern tp and further south to indo china the consistency between geological boundaries on surface and sharp velocity contrast boundaries in uppermost mantle may suggest strong deformation coupling between crust and at least uppermost mantle if not whole lithosphere a north south striking lvb is also observed cutting through the southern tp coinciding with the yadong gulu rift at surface our tomographic results are generally consistent with dynamic models that involve with underthrusting in the southern tp shortening in the northern tp and extrusion to the east and the southeast furthermore our results suggest significant east west variations in the structure and dynamics