fluid compositions and p t conditions of vein type uranium mineralization in the beaverlodge uranium district northern saskatchewan canada the beaverlodge district in northern saskatchewan is known for vein type uranium mineralization most of the uranium deposits are spatially related to major structures and hosted by ca 3 2 1 9 ga granitic rocks and albitite derived from them and by ca 2 33 ga murmac bay group amphibolite all of which are unconformably overlain locally by deformed but unmetamorphosed redbeds of the ca 1 82 ga martin group and by the flat lying ca 1 75 1 5 ga athabasca group the uranium mineralization is mainly hosted in fault rocks breccias and carbonate quartz albite veins referred to as breccia style and vein style mineralization respectively with the latter being the focus of this study most of the mineralized veins occur in the basement rocks although some crosscut the martin group this study examines the field petrographic fluid inclusion and c o isotope characteristics of mineralized and non mineralized veins from 19 deposits occurrences as well as from the martin group with an aim to better understand the mineralizing environment and processes the coexistence of liquid dominated l v vapour dominated v l and vapour only v fluid inclusions within individual fluid inclusion assemblages fias in the veins suggests fluid immiscibility and heterogeneous trapping the l v inclusions with the lowest homogenization temperatures th within individual fias are interpreted to represent homogeneous trapping of the liquid phase which yield th values from 78 to 330 c mainly 100 to 250 c and salinities from 0 2 to 30 8 wt nacl equivalent mass spectrometric analysis of bulk fluid inclusions shows that the volatiles are dominated by h2o average 97 2 mol with minor amounts of co2 ch4 h2 o2 n2 ar and he fluid pressures were estimated to be 200 bars based on the inference of fluid immiscibility fluid temperatures of 100 to 250 c and low concentrations of non aqueous volatiles 3 mol the 18ovpdb and 13cvpdb of carbonate minerals associated with mineralization range from 20 5 to 8 9 and 10 1 to 0 9 respectively the 18ovsmow values of the parent fluids calculated using the th values range from 9 6 to 17 0 with the majority from 0 to 5 0 o isotopes of paired equilibrium quartz and calcite analyzed by secondary ion mass spectrometry sims yield temperatures from 161 to 248 c which are consistent with the fluid inclusion data the new fluid inclusion and stable isotope data are inconsistent with a metamorphic or magmatic hydrothermal model as proposed in some previous studies for breccia style and vein style mineralization but rather support a model in which the vein type uranium mineralization took place at relatively low temperature 100 to 250 c and shallow 2 km conditions with fluid pressure fluctuating between hydrostatic and sub hydrostatic regimes possibly related to episodic faulting the mineralizing fluids were mainly sourced from the martin lake basin and uraninite was precipitated as a result of mixing between this basin derived fluid and fluids carrying reducing agents fe2 ch4 derived from the basement although fluid rock reactions and fluid immiscibility may have also played a role

ore forming fluids and mineralization mechanism of laoshankou fe cu au deposit in northern margin of junggar the laoshankou ore district is located in the northern margin of junggar basin the fe cu au minerals mainly occur in the massive lumpy veinlike brecciaed and veinlet disseminaed forms in the diorite porphyrite and basaltic volcanic rocks garnets of the skarn period are characterized by the development of melt inclusions and fluid inclusions fluid inclusions in epidote of the retrogressive metamorphism stage are liquid inclusions fluid inclusions in calcite of the quartz sulfide carbonate period mostly contain liquid inclusions daughter mineral bearing inclusions and three phase co2 bearing inclusions homogenization temperatures of fluid inclusions at the early skarn stage vary from 212 to 550 and are even higher than 550 mostly in the range from 220 to 470 salinity w nacleq ranges from 7 02 to 17 96 ore fluid density ranges from 0 60 g cm3 to 1 00 g cm3 homogenization temperatures of fluid inclusions at the retrogressive metamorphism stage vary from 212 to 510 with the peak around 220 salinity w nacleq ranges from 6 16 to 21 04 ore fluid density ranges from 0 60 g cm3 to 0 95 g cm3 fluid inclusions in the quartz sulfide carbonate period have homogenization temperatures from 150 to 380 with the peaks around 160 and 220 salinity w nacleq ranges from 13 4 to 18 47 ore fluid density ranges from 0 75 g cm3 to 1 10 g cm3 the 18osmow values of garnet and calcite range from 5 2 to 17 8 with the corresponding 18oh2o values between 2 4 and 3 5 and dsmow values of fluid inclusions between 144 0 and 84 0 these isotopic data imply that the ore forming fluids were mainly derived from magmatic fluids and meteoric water the 13cpdb values of calcite define a narrow range of 6 8 to 3 5 and dsmow values of fluid inclusions vary between 11 6 and 17 8 indicating that the carbon in the ore fluids was mainly derived from the diorite magma closely related to the ore bodies with a minor part from carbonate rock the 34s values of pyrite mainly range from 0 to 3 indicating that the sulfur was derived from diorite magma closely related to the ore bodies in combination with the geological characteristics of the laoshankou deposit the authors hold that the ore forming process was related to the retrogressive metamorphism of the skarn

textures and geochemistry of magnetite indications for genesis of the late paleozoic laoshankou fe cu au deposit nw china abstract laser ablation inductively coupled plasma mass spectrometry la icp ms and electron probe x ray microanalysis epma have been employed to determine major and trace elemental concentrations in magnetite from different ores in the laoshankou deposit which is the most important fe cu au deposit in the northern margin of east junggar two magnetite associated paragenetic sequences have been defined in laoshankou including amphibole epidote magnetite alteration mineralization stage ii and pyrite chalcopyrite mineralization stage iii b on the basis of the magnetite textures and chemical compositions we have identified six generations of magnetite from three types of ores rocks including the high ti inclusion rich m 1 a and inclusion free m 1 b in massive magnetite epidote amphibole ores type h1 from stage ii the low ti high si inclusion rich m 1 c in massive magnetite sulfide ores type h2 from stage ii the ubiquitous low ti m 2 and pristine low ti low si m 3 in both h1 and h2 types and m 4 within massive chalcopyrite magnetite ores type h3 from stage iii b the discriminations of v versus ti ca mn al versus ti v and fe versus v ti as well as mineral assemblages and trace element concentrations of cr

coseismic and postseismic stress changes in a subducting plate possible stress interactions between large interplate thrust and intraplate normal faulting earthquakes 1 a large intraplate normal faulting earthquake mw 7 5 occurred in 1999 in the subducting cocos plate below the downdip edge of the ruptured thrust fault of the 1978 oaxaca mexico earthquake mw 7 8 this situation is similar to the previous case of the 1997 normal faulting event mw 7 1 that occurred beneath the rupture area of the 1985 michoacan mexico earthquake mw 8 1 we investigate the possibility of any stress interactions between the preceding 1978 thrust and the following 1999 normal faulting earthquakes for this purpose we estimate the temporal change of the stress state in the subducting cocos plate by calculating the slip distribution during the 1978 earthquake through teleseismic waveform inversion the dynamic rupture process and the resultant coseismic stress change together with the postseismic stress variations due to plate convergence and the viscoelastic relaxation process to do this we calculate the coseismic and postseismic changes of all stress components in a three dimensional space incorporating the subducting slab the overlying crust and uppermost mantle and the asthenosphere for the coseismic stress change we solve elastodynamic equations incorporating the kinematic fault slip as an observational constraint under appropriate boundary conditions to estimate postseismic stress accumulations due to plate convergence a virtual backward slip is imposed to lock the main thrust zone the effects of viscoelastic stress relaxations of the coseismic change and the back slip are also included the maximum coseismic increase in the shear stress and the coulomb failure stress below the downdip edge of the 1978 thrust fault is estimated to be in the range between 0 5 and 1 5 mpa and the 1999 normal faulting earthquake was found to take place in this zone of stress increase the postseismic variations during the 21 years after the 1978 event modify the magnitude and patterns of the coseismic stress change to some extent but are not large enough to overcome the coseismic change these results suggest that the coseismic stress increase due to the 1978 thrust earthquake may have enhanced the chance of occurrence of the 1999 normal faulting event in the subducting plate if this is the case one of the possible mechanisms could be static fatigue of rock materials around preexisting weak planes involved in the subducting plate and it is speculated that that one of these planes might have been reactivated and fractured because of stress corrosion cracking under the applied stress there for 21 years

gps constraints on the 2011 2012 oaxaca slow slip event that preceded the 2012 march 20 ometepec earthquake southern mexico

mineralization and ore genesis of the qiaoxiahala fe cu au deposit in the northern margin of east junggar terrane central asian orogenic belt constraints from fluid inclusions and stable isotopes abstract the qiaoxiahala fe cu au deposit 1 44 mt ore 43 53 fe 0 55 2 21 cu and 0 13 2 4 g t au is located in the northern margin of east junggar terrane nw china the deposit is hosted in the upper part of the middle devonian beitashan formation mafic and felsic volcanic rocks and sedimentary interbeds and is spatially closely related to local fractures six hypogene hydrothermal stages have been identified including stage i early skarn stage ii late skarn stage iii magnetite mineralization stage iv magnetite pyrite mineralization stage v chalcopyrite mineralization and stage vi late veins these six stages include three major mineralization events as represented by the stage iii magnetite epidote k feldspar quartz calcite stage iv magnetite pyrite garnet quartz calcite and stage v chalcopyrite chlorite assemblages the stage iii magnetite mineralization fluids were likely of high temperature 354 386 c low medium salinity 9 9 14 7 wt nacl equiv mg fe rich and organic rich with lithostatic pressure of 1 3 1 5 kbar and corresponding depth of 4 3 4 8 km oxygen and hydrogen isotopes showed that the 18o rich 9 7 11 2 and d rich 26 3 fluids were possibly modified from the early carboniferous seawater interacting with the beitashan formation organic rich limestone or tuff in comparison the stage iv magnetite pyrite mineralization fluids were likely of medium high temperature 272 453 c low medium salinity 2 9 19 5 wt nacl equiv mg fe rich with pressure of 0 8 1 2 kbar and corresponding depth of 2 6 4 0 km the stage v chalcopyrite mineralization fluids were likely of low medium temperature 186 270 c low medium salinity 1 4 21 8 wt nacl equiv ca or na rich with pressure of 0 4 0 6 kbar and corresponding depth of 1 2 km hydrogen and oxygen isotopic compositions stage iv dwater 141 to 92 18owater 8 9 11 1 stage v dwater 104 18owater 7 2 suggest that the ore fluids were of connate marine origin furthermore stage iv 13cwater values 0 6 to 0 also indicate interactions between seawater and sedimentary wall rocks the negative sulfur isotopic compositions of chalcopyrite and pyrite 4 2 to 0 2 may demonstrate a biogenic sulfur source compared with the arc related iocg deposits in the central andean orogen the qiaoxiahala fe cu au deposit shares many common features in geology mineralization alteration and various sources of fluids indicating a possible iocg like mineralization style and potential to discover other late paleozoic arc related iocg deposits in east junggar

rupture characteristics of major and great mw 7 0 megathrust earthquakes from 1990 to 2015 2 depth dependence depth varying characteristics of high frequency seismic radiation for megathrust earthquakes have been inferred from several recent giant earthquakes and large tsunami earthquakes to quantify any depth dependence more extensively we analyzed 114 m w 7 0 thrust faulting earthquakes with centroid depths from 5 to 55 km on circum pacific megathrusts using teleseismic body wave finite fault inversions and source spectrum determinations large tsunami earthquakes and some other shallow events at depths less than about 18 km have unusually long source durations and low values of static stress drop e v r 3 e and apparent stress with relatively depleted high frequency radiation deeper events have no clear global trend with source depth for moment normalized centroid time or total duration static stress drop moment scaled radiated energy apparent stress or radiation efficiency regional behavior among the 17 sampled subduction zones generally conforms to the global composite the source spectra have high frequency logarithmic spectral decay slopes averaging 1 6 there is relative enrichment in high frequency spectral levels with increasing source depth manifested in reduced high frequency spectral decay slope the ratio of high frequency 0 3 1 hz radiated energy to total energy increases correspondingly these observations suggest that overall dynamic rupture processes are relatively insensitive to source depth but varying scale lengths of megathrust heterogeneity may contribute to modest enrichment of high frequency seismic radiation for events deeper on the megathrust a weak correlation of higher estimated average megathrust temperature at 30 km depth with higher spectral decay rate indicates that the depth varying pattern may in part result from frictional properties being influenced by temperature variations or by systematic reduction of average attenuation with increasing depth along the megathrust

intraslab rupture triggering megathrust rupture coseismically in the 17 december 2016 solomon islands mw 7 9 earthquake the 17 december 2016 solomon islands earthquake m w 7 9 initiated 103 km deep in the subducting solomon sea slab near the junction of the solomon islands and new britain trenches most aftershocks are located near the solomon islands plate boundary megathrust west of bougainville where previous large interplate thrust faulting earthquakes occurred in 1995 m w 7 7 and 1971 m w 8 0 teleseismic body wave modeling and aftershock relocations indicate that the initial 30 s of the 2016 rupture occurred over depths of 90 to 120 km on an intraslab fault dipping 30 to the southwest almost perpendicular to the dipping slab interface the next 50 s of rupture took place at depths of 32 to 47 km in the deeper domain c portion of the overlying megathrust fault dipping 35 to the northeast high susceptibility to triggering in the region accounts for this compound rupture of two separate fault planes

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

the zihuatanejo mexico earthquake of 1994 december 10 m 6 6 source characteristics and tectonic implications summary an analysis of the zihuatanejo mexico earthquake of 1994 december 10 m 6 6 based on teleseismic and near source data shows that it was a normal faulting intermediate depth h 50 k 5 km event it was located about 30 km inland within the subducted cocos plate the preferred fault plane has an azimuth of 130 a dip of 79 and a rake of 86 the rupture consisted of two subevents which were separated in time by about 2s with the second subevent occurring downdip of the first the measured stress drop was relatively high requiring a acr of about a kilobar to explain the high frequency level of the near source spectra a rough estimate of the thickness of the seismogenic part of the oceanic lithosphere below zihuatanejo based on the depth and the rupture extent of this event is 40 km this event and the oaxaca earthquake of 1931 january 15 m 7 8 are the two significant normal faulting intermediate depth shocks whose epicentres are closest to the coast both of these earthquakes were preceded by several large to great shallow lowangle thrust earthquakes occurring updip the observations in other subduction zones show just the opposite normal faulting events precede not succeed updip thrust shocks indeed the thrust events soon after their occurrence are expected to cause compression in the slab thus inhibiting the occurrence of normal faulting events to explain the occurrence of the zihuatanejo earthquake we note that the cocos plate after an initial shallow angle subduction unbends and becomes subhorizontal in the region of the unbending the bottom of the slab is in horizontal extension we speculate that the large updip seismic slip during shallow low angle thrust events increases the buckling of the slab resulting in an incremental tensional stress at the bottom of the slab and causing normal faulting earthquakes this explanation may also hold for the 1931 oaxaca event

metal rich fluid inclusions provide new insights into unconformity related u deposits athabasca basin and basement canada the paleoproterozoic athabasca basin canada hosts numerous giant unconformity related uranium deposits the scope of this study is to establish the pressure temperature and composition p t x conditions of the brines that circulated at the base of the athabasca basin and in its crystalline basement before during and after uo2 deposition these brines are commonly sampled as fluid inclusions in quartz and dolomite cementing veins and breccias associated with alteration and u mineralization microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms data from five deposits rabbit lake p patch eagle point millennium and shea creek complement previously published data for the mcarthur river deposit in all of the deposits investigated fluid inclusion salinity is between 25 and 40 wt nacl equiv with compositions displaying a continuum between a nacl rich brine end member cl na ca mg k and a cacl2 rich brine end member cl ca mg na k the cacl2 rich brine has the highest salinity and shows evidence for halite saturation at the time of trapping the continuum of compositions between the nacl rich brine and the cacl2 rich brine end members combined with p t reconstructions suggest anisothermal mixing of the two brines nacl rich brine 180 30 c and 800 400 bars cacl2 rich brine 120 30 c and 600 300 bars that occurred under fluctuating pressure conditions hydrostatic to supra hydrostatic however because the two brines were u bearing and therefore oxidized brine mixing was probably not the driving force for uo2 deposition several scenarios are put forward to account for the cl na ca mg k composition of the brines involving combinations of seawater evaporation halite dissolution mixing with a halite dissolution brine mg ca exchange by dolomitization na ca exchange by albitization of plagioclase na k exchange by albitization of k feldspar and mg loss by mg rich alteration finally the metal concentrations in the nacl rich and cacl2 rich brines are among the highest recorded compared to present day sedimentary formation waters and fluid inclusions from basin hosted base metal deposits up to 600 ppm u 3000 ppm mn 4000 ppm zn 6000 ppm cu 8000 ppm pb and 10 000 ppm fe the cacl2 rich brine carries up to one order of magnitude more metal than the nacl rich brine though the exact origin of major cations and metals of the two brines remains uncertain their contrasting compositions indicate that the two brines had distinct flow paths and fluid rock interactions large scale circulation of the brines in the athabasca basin and basement was therefore a key parameter for metal mobility including u and formation of unconformity related u deposits

post taltson sedimentary and intrusive history of the southern rae province along the northern margin of the athabasca basin western canadian shield abstract the southern rae province of the western canadian shield underwent extensive reworking during paleoproterozoic time widespread granitic plutonism and poorly defined metamorphism resulting from the ca 2 5 to 2 3 ga arrowsmith orogen was followed by more intense thermotectonic overprints attributed to the 1 99 1 92 ga taltson orogen in the west and ca 1 91 1 90 ga tectonic activity associated with the snowbird tectonic zone in the east the thluicho lake group is a fining upwards conglomerate arkose argillite succession deposited in an intermontane setting towards the end of the taltson orogen following deposition the thluicho lake group underwent two phases of regional folding and greenschist facies metamorphism marking the latest taltson and snowbird overprints respectively prior to the emplacement of extensive 1 82 ga mafic dykes these depositional constraints support correlation of the thluicho lake group with the lithologically similar nonacho group in the northwest territories whereas petrological similarities and coeval emplacement ages indicate that the mafic dykes represent a southeastward extension of the sparrow dykes mafic volcanic rocks geochemically linked to the dykes are intercalated within the martin group a continental redbed succession deposited in trans tensional basin settings indicating that deposition was ongoing at 1 82 ga similarities in age lithological association and depositional setting suggest that the martin group is broadly correlative with the baker lake group of the lower dubawnt supergroup in nunavut widespread lamprophyre dykes of the type that fed minette volcanic rocks of the christopher island formation in the baker lake group are also spatially associated with the martin group the broadly coeval hudson granites which extend over much of the same ground as the lamprophyres in nunavut also appear to have analogs in the southern rae province the formation of widespread trans tensional basins together with extensive dyke emplacement implies a period of intense brittle to brittle ductile deformation throughout the western churchill province at about 1 83 1 82 ga this deformation is attributed to a broadly east west stress regime imposed by accretion of the nahanni fort simpson terrane to the west combined with terminal collision in the trans hudson orogen to the east

global ubiquity of dynamic earthquake triggering surface waves that were generated by 12 out of 15 earthquakes with magnitudes greater than 7 since 1990 led to a global increase in the number of small earthquakes this suggests that dynamic triggering of earthquakes is common and is independent of the tectonic environment earthquakes can be triggered by local changes in the stress field static triggering1 2 3 4 5 6 7 due to nearby earthquakes or by stresses caused by the passage of surface rayleigh and love waves from a remote large earthquake dynamic triggering8 9 10 11 12 13 14 15 16 17 18 however the mechanism frequency controlling factors and the global extent of dynamic triggering are yet to be fully understood because rayleigh waves involve compressional and dilatational particle motion volumetric changes as well as shearing whereas love waves only involve shearing triggering by either wave type implies fundamentally different physical mechanisms here we analyse broadband seismograms from over 500 globally distributed stations and use an automated approach to systematically identify small triggered earthquakes the low amplitude signals of such earthquakes would normally be masked by high amplitude surface waves our analysis reveals that out of 15 earthquakes studied of magnitude m greater than 7 0 that occurred after 1990 12 are associated with significant increases in the detection of smaller earthquakes during the passage of both the love and rayleigh waves we conclude that dynamic triggering is a ubiquitous phenomenon that is independent of the tectonic environment of the main earthquake or the triggered event

dynamic modelling of the subduction zone of central mexico summary in central mexico some significant normal faulting events have occurred within the subducted oceanic cocos plate just below or near the down dip edge of the strongly coupled interface these normal faulting shocks followed large shallow thrust earthquakes in other subduction zones such events generally precede the up dip thrust events a vertical 2 d finite element modelling has been used to simulate the subduction of the cocos plate beneath the north american plate when the slab is driven by an active convergence velocity or slab pull we find that the latter mechanism plays only a minor role due to shallow subduction the modelling results show that the stress pattern is very sensitive to the geometry of the plates in particular normal faulting earthquakes that follow large thrust events can be explained on the basis of the flexural response of the overriding and subducting plates to the peculiar geometry of this subduction zone where the subducting slab becomes horizontal at about 100 km from the trench this horizontal part of the subducting plate down dip with respect to the main thrust zone is under an extensional stress field this provides an alternative explanation to the slab pull for the occurrence of normal faulting intraplate earthquakes in order for normal faulting earthquakes to occur in the early part of the seismic cycle it is necessary that the large up dip thrust events have a partial stress drop we find that for small fractional stress drop a wide region of extension remains below the down dip edge of the main fault plane following a large thrust earthquake thus the main thrust earthquakes do not invert the polarity of the active stress field which is compressional and extensional up dip and down dip respectively with respect to the main thrust fault larger fractional stress drops result in larger delays in the occurrence of normal faulting events after the main thrust events

iron oxide copper gold mineralization of the devonian laoshankou deposit xinjiang nw china in the central asian orogenic belt abstract the laoshankou iron oxide cu au iocg deposit 41 km southwest of qinghe city xinjiang nw china is the most important magnetite deposit with economic cu and au metal reserve 3 26 mt fe 33 5 36 4 9 8 kt cu 0 2 0 4 and 0 14 t au 0 5 1 3 g t in the east junggar terrane of the central asian orogenic belt caob the deposit is hosted by volcanic rocks of the middle devonian beitashan formation in this study four hypogene hydrothermal alteration stages have been identified including the ca silicate alteration stage i amphibole epidote magnetite alteration mineralization stage ii pyrite chalcopyrite mineralization stage iii and late hydrothermal veining stage iv mineralogical fluid inclusion including laser raman spectroscopy and mineral sulfur oxygen hydrogen and carbon isotope analyses were carried out to elucidate the nature and origin of the hydrothermal fluids at laoshankou stage i hydrothermal fluids were likely derived from a 590 c magmatic fluid with 18 o water 9 2 9 7 subsequently the magnetite epidote amphibole assemblage may have precipitated from the fluids 530 c formed by the mixing of high temperature magmatic fluids with the seawater that reacted with 18 o rich wall rocks the fluid rock reactions are reflected from the 18 o water 9 6 10 7 and d water 25 5 23 8 values the sub economic stage iii a pyrite epidote quartz garnet mineralization likely occurred at 415 c and was formed by fluids with 34 s fluid 3 7 0 5 d water 110 94 and 18 o water 7 92 8 9 the lower temperature and presence of organic matter of the stage iii a fluids may have reflected the involvement of meteoric water and organic matter from the wall rocks the economic cu mineralization stage iii b was probably formed by the mixing of a meteoric water dominated fluid medium temperature low salinity and na dominated and a ca rich formation water in equilibrium with the volcanic wall rocks medium temperature medium salinity and ca fe mg dominated with 34 s fluid 2 6 18 o water 5 6 5 8 13 c water 3 3 3 1 and d water 92 95 towards the end of the fluid evolution meteoric water incursion may have continued and generated the ore barren low temperature low salinity and na dominated fluids although the laoshankou deposit contains distinct skarn alteration the ore mineral assemblage and ore fluid features indicate that it is not a typical skarn deposit but share many similarities with many central andean iocg deposits we conclude that the iocg ore forming setting in the devonian east junggar was analogous to the cretaceous central andes in that they both occurred during basin inversion in a volcanic arc setting

rapid postseismic transients in subduction zones from continuous gps 1 continuous gps time series from three of four recently measured large subduction earthquakes document triggered rapid postseismic fault creep representing an additional moment release upward of 25 over the weeks following their main shocks data from two mw 8 0 and mw 8 4 events constrain the postseismic centroids to lie down dip from the lower limit of coseismic faulting and show that afterslip along the primary coseismic asperities is significantly less important than triggered deep creep time series for another mw 7 7 event show 30 postseismic energy release but here we cannot differentiate between afterslip and triggered deeper creep a fourth mw 8 1 event which occurred in the broad chilean seismogenic zone shows no postseismic deformation despite coseismic offsets in excess of 1 m for the three events which are followed by postseismic deformation stress transferred to the inferred centroids at 34 60 and 36 km depths by their respective main shock asperities increased reverse shear stress by 0 5 0 8 and 0 2 bar with a comparatively small decrease in normal stress 0 01 bar constraining the coulomb stress increase required to force slip along the metastable plate interface deep triggered slip of this nature is invisible without continuous geodesy but on the basis of these earthquakes would appear to constitute an important mode of strain release from beneath the seismogenic zones of convergent margins these events captured by some of the first permanent gps networks show that deep moment release is often modulated by seismogenic rupture updip and underscore the need for continuous geodesy to fully quantify the spectrum of moment release in great earthquakes index terms 7209 seismology earthquake dynamics and mechanics 3040 marine geology and geophysics plate tectonics 8150 8155 8157 8158 8150 tectonophysics plate boundary general 3040 7230 seismology seismicity and seismotectonics keywords subduction zone earthquake postseismic moment release

constraining the source of the m w 8 1 chiapas mexico earthquake of 8 september 2017 using teleseismic and tsunami observations the september 2017 chiapas mexico normal faulting intraplate earthquake mw 8 1 occurred within the tehuantepec seismic gap offshore mexico we constrained the finite fault slip model of this great earthquake using teleseismic and tsunami observations first teleseismic body wave inversions were conducted for both steep np 1 and low angle np 2 nodal planes for rupture velocities vr of 1 5 4 0 km s teleseismic inversion guided us to np 1 as the actual fault plane but was not conclusive about the best vr tsunami simulations also confirmed that np 1 is favored over np 2 and guided the vr 2 5 km s as the best source model our model has a maximum and average slips of 13 1 and 3 7 m respectively over a 130 km 80 km fault plane coulomb stress transfer analysis revealed that the probability for the occurrence of a future large thrust interplate earthquake at offshore of the tehuantepec seismic gap had been increased following the 2017 chiapas normal faulting intraplate earthquake

mechanisms of retrograde changes in oxide minerals from the proterozoic serrote da laje deposit northeastern brazil retrograde textural and chemical changes in oxide minerals from the proterozoic serrote da laje deposit northeastern brazil have been investigated the deposit is situated in a mafic ultramafic layered sill oxidation and cooling leading to successively decreasing diffusion rates resulted in disequilibrium on the microscale pleonaste in particular shows a rapid change in composition between a coarse grains in a granoblastic magnetite host indicating metamorphic peak conditions b coarse lamellae in magnetite indicating commencement of exsolution and c composite pleonaste ilmenite lamellae in magnetite which indicate oxidation exsolution barren rock layers cooled under more oxidized conditions compared with oxide rich layers formation of pleonaste and ilmenite lamellae in magnetite and ilmenite hematite relations are discussed

the role of seismic and slow slip events in triggering the 2018 m7 1 anchorage earthquake in the southcentral alaska subduction zone

coseismic slip of two large mexican earthquakes from teleseismic body waveforms implications for asperity interaction in the michoacan plate boundary segment teleseismic body waves recorded for the october 25 1981 playa azul and september 21 1985 zihuatanejo earthquakes in western mexico were inverted to derive the distributions and depths of coseismic slip broadband p wave displacements and intermediate period records were included to incorporate a wide frequency band in the analysis for the zihuatanejo earthquake digital sh records located away from the nodal directions were used in the inversion process nonnodal sh waveforms were not available for the playa azul earthquake but additional azimuthal coverage was obtained by including selected worldwide analog p wave records the results for the playa azul earthquake indicate that rupture occurred in two separate zones both updip and downdip of the point of initial nucleation with the majority of the slip concentrated in a circular region 15 km radius downdip from the hypocenter the maximum slip in this downdip region exceeds 3 6 m and is at a depth of about 16 km the computed seismic moment is 7 14 1026 dyn cm coseismic slip is observed to occur entirely within the area of reduced slip separating the two main shallow sources of the michoacan earthquake that occurred almost 4 years later on september 19 1985 for the zihuatanejo earthquake the p and sh data suggest rupture over a larger area 30 km radius with a lower peak slip 2 m and encompassing depths between 12 and 26 km slip is concentrated in an area adjacent to one of the major sources of the michoacan earthquake and represents the southeastern continuation of rupture along the cocos north america plate boundary the corresponding seismic moment is 1 35 1027 dyn cm the zones of peak slip observed for the playa azul zihuatanejo and michoacan earthquakes are interpreted as asperity regions that control the cessation and generation of large earthquakes within the michoacan segment of the plate boundary the stress drops within each of these asperities are observed to be very similar and may reflect a characteristic asperity strength for this portion of the subduction zone

experimental exsolution textures in the system bornite chalcopyrite genetic implications concerning natural ores textural interpretation of ore mineral assemblages such as bornite chalcopyrite bn cpy intergrowths should be based on definite experimentation appropriate exsolution and coarsening experiments were performed using sealed evacuated silicaglass tubes synthetic bn cpy solid solutions were annealed between 100 and 350 c for times of 20 min to 10 weeks early formed textures develop through nucleation and growth and depend on the initial degree of supersaturation and the metal diffusivities final textures due to additional growth and coarsening are very sensitive to temperature and may serve as geothermometers mutual boundary textures which form above 250 c can originate by 1 simultaneous precipitation 2 exsolution during slow cooling from above the solvus and 3 metamorphism to temperatures above about 250 c widmanstatten textures are not compatible with slow cooling but indicate 1 low temperature replacement of bn or 2 exsolution of cpy lamellae from anomalous bn heated to around 200 250 c during mild metamorphism

stress transfer and seismic phenomena in coupled subduction zones during the earthquake cycle an elementary mechanical model of a coupled subduction zone is presented it is used to study the transfer of extensional stresses along the underthrusting plate and shear stress interactions between the plate itself and its thrust contact zone with the overriding plate during the earthquake cycle the model assumes an elastic plate which deforms one dimensionally has shear drag interactions treated approximately by the elsasser procedure with a maxwellian viscoelastic mantle and is subject to steady gravitational sinking forces great thrust earthquakes are simulated as sudden stress relieving displacements at the contact zone between the slab and overriding plate the model allows analysis of the space and time variable stresses in the main thrust zone the adjacent oceanic plate and the subducting slab over each earthquake cycle stress variations leading to outer rise events are discussed as well as stress changes responsible for intraplate seismicity downdip from the main thrust zone based on simulations of periodic great earthquakes the results of simulated slow progression of deformation slip from below into the thrust contact zone are also presented such preslip occurring over a time scale that is small in comparison with the whole seismic cycle e g of the order of a tenth or so is shown to transiently slow the rate of buildup of or even relieve extensional stresses in the slab in the absence of preslip those stresses build up steadily in time during the latter part of the cycle the results have implications for induction of sesimic quiescence as well as for explaining patterns of seismicity in relation to spatial position along the underthrusting plate and to time throughout the cycle correlations are reported between the model simulations and seismicity observations from coupled subduction zones around the world the observations include tensional outer rise events after large subduction earthquakes and compressional ones in the latter parts of the cycle normal tensional intraplate earthquakes preceding the main thrust events and positioned downdip from the thrust zones and interlaced periods of seismic activity in the lower part of the main thrust zone and in the descending slab

distinguishing intraplate from megathrust earthquakes using lacustrine turbidites subduction zone seismicity arises from megathrust crustal and intraslab earthquakes and understanding the recurrence patterns of each type is crucial for hazard assessments lake sediments can record earthquakes from all three seismogenic sources here we studied the turbidite record of lo encanado an andean lake located in central chile we show that lo encanado turbidites can be attributed to 1 subaquatic slope failure by earthquake shaking coseismic phase 2 floods or human impact and 3 postseismic catchment response all historical events with shaking intensities vi modified mercalli intensity have triggered coseismic turbidites but only the intraplate earthquakes triggered subaerial slope failures followed by postseismic turbidites we argue that this contrasting result is due to different spectra of seismic waves from these earthquake sources higher frequency accelerations from intraplate earthquakes are hardly attenuated in rocks around the lake whereas lower frequency accelerations from megathrust earthquakes are amplified in soft lake sediments we tested our findings by comparing acceleration response spectra of recent and historical intraslab and megathrust earthquakes along a longitudinal profile results suggest that the location of andean lakes is ideal to distinguish earthquake sources

testing earthquake links in mexico from 1978 to the 2017 m 8 1 chiapas and m 7 1 puebla shocks

rare earth elements and carbon oxygen isotopes of calcite from the tongjiachong cu deposit south china implications for fluid source and mineral precipitation abstract calcite is a major gangue mineral in many types of hydrothermal deposits and its chemical and carbon oxygen isotopic signatures can shed light on the metallogenic evolution the tongjiachong cu deposit located in the northern margin of the yangtze block in south china is hosted by dolostone of the ediacaran doushantuo formation empirical geothermometric calculation indicates that the pre ore chlorite was formed at 265 305 c copper mineralization occurs mainly as veinlets in a calcite chalcopyrite bornite ankerite assemblage exsolution lamellae of chalcopyrite from bornite indicate that both minerals were formed coevally at 200 250 c mineral chemical analysis on the syn ore hydrothermal calcite from tongjiachong suggests that all the calcite samples are enriched in rare earth elements and yttrium reys rey 53 7 119 9 ppm they have similar y ho 38 3 42 3 and varying la ho 21 8 86 7 and display consistent convex paas normalized rey patterns the distinct positive eu anomalies 2 38 3 45 and lack of yb anomalies 0 92 1 05 suggest initial fluid temperatures of 250 to 420 c and calcites deposition temperatures of dolomite samples from the dolostone ore host show a marine carbonate c o isotopic affinity 13cpdb 4 0 to 2 7 18osmow 19 8 to 20 2 comparatively the hydrothermal calcite contains lower 13cpdb 7 4 to 6 1 and 18osmow 14 1 to 14 8 and display a positive 13cpdb vs 18osmow correlation simulated calculations of water rock w r interactions and ore geological constraints suggest that the initial fluids were likely originated from organic rich formation water we proposed that w r reactions may have been the main drive for calcite precipitation at tongjiachong whilst decreasing temperature and w r reactions may have led to the chalcopyrite precipitation

low detection capability of global earthquakes after the occurrence of large earthquakes investigation of the harvard cmt catalogue summary we investigated the detection capability of global earthquakes immediately after the occurrence of a large earthquake we stacked global earthquake sequences after occurrences of large earthquakes obtained from the harvard centroid moment tensor catalogue and applied a statistical model that represents an observed magnitude frequency distribution of earthquakes to the stacked sequence the temporal variation in model parameters which corresponds to the detection capability of earthquakes was estimated using a bayesian approach we found that the detection capability of global earthquakes is lower than normal for several hours after the occurrence of large earthquakes for instance the duration of lowered detection capability of global earthquakes after the occurrence of an earthquake with a magnitude of seven or larger is estimated to be approximately 12 hr

minor and trace elements in bornite and associated cu fe sulfides a la icp ms studybornite mineral chemistry abstract in situ laser ablation inductively coupled mass spectroscopy la icp ms has been used to provide a baseline dataset on the minor element contents in hypogene bornite and accompanying cu sulfides from 12 deposits with emphasis on syn metamorphic cu vein systems in norway and skarn porphyry and epithermal systems in se europe bornite contains significant concentrations of both ag and bi especially in the vein and skarn deposits studied and has the potential to be a major ag carrier in such ores concentrations of up to 1 wt of both elements are documented measured concentrations appear to be independent of whether discrete ag and or bi minerals are present within the analyzed sulfide where bornite and chalcocite or mixtures of cu sulfides coexist ag is preferentially partitioned into chalcocite over co existing bornite and bi is partitioned into the bornite bornite is a relatively poor host for au which mimics ag by being typically richer in coexisting chalcocite most anomalous au concentrations in bornite can be readily tracked to micron and submicron scale inclusions but bornite and chalcocite containing up to 3 and 28 ppm au in solid solution can be documented selenium and te concentrations in bornite may be as high as several thousand ppm and correlate with the abundance of selenides and tellurides within the sample selenium distributions show some promise as a vector in exploration offering the possibility to track a fluid source bornite and chalcocite are poor hosts for a range of other elements such as co ni ga and ge etc which have been reported to be commonly substituted within sulfides hypogene bornite and chalcocite may have significantly different trace element geochemical signatures from secondary supergene bornite

global omori law decay of triggered earthquakes large aftershocks outside the classical aftershock zone 1 triggered earthquakes can be large damaging and lethal as evidenced by the1999 shocks in turkey and the 2001 earthquakes in el salvador in this study earthquakes with ms 7 0 from the harvard centroid moment tensor cmt catalog are modeled as dislocations to calculate shear stress changes on subsequent earthquake rupture planes near enough to be affected about 61 of earthquakes that occurred near defined as having shear stress change 0 01 mpa the ms 7 0 shocks are associated with calculated shear stress increases while 39 are associated with shear stress decreases if earthquakes associated with calculated shear stress increases are interpreted as triggered then such events make up at least 8 of the cmt catalog globally these triggered earthquakes obey an omori law rate decay that lasts between 7 11 years after the main shock earthquakes associated with calculated shear stress increases occur at higher rates than background up to 240 km away from the main shock centroid omori s law is one of the few time predictable patterns evident in the global occurrence of earthquakes if large triggered earthquakes habitually obey omori s law then their hazard can be more readily assessed the characteristic rate change with time and spatial distribution can be used to rapidly assess the likelihood of triggered earthquakes following events of ms 7 0 i show an example application to the m 7 7 13 january 2001 el salvador earthquake where use of global statistics appears to provide a better rapid hazard estimate than coulomb stress change calculations

nonvolcanic tremor along the oaxaca segment of the middle america subduction zone 1 the oaxaca subduction zone is an ideal area for detailed studies of plate boundary deformation as rapid convergent rates shallow subduction and short trench to coast distances bring the thermally defined seismogenic and transition zones of the plate interface over 100 km inland previous analysis of slow slip events in southern mexico suggests that they may represent motion in the transition zone defining the downdip edge of future megathrust earthquakes a new deployment consisting of broadband seismometers distributed inland along the oaxaca segment provide the means to examine whether nonvolcanic tremor nvt signals can also be used to characterize the boundary between the seismogenic and transition zones in this study we established that nvt exists in the oaxaca region based on waxing and waning of seismic energy on filtered day long seismograms that were correlated across neighboring stations and were further supported by appropriate relative time moveouts in record sections and spectrograms with narrow frequency bands eighteen prominent nvt episodes that lasted upwards of a week were identified during the 15 months analyzed june 2006 to september 2007 recurring as frequently as every 2 3 months in a given region we analyze nvt envelope waveforms with a semiautomated process for identifying prominent energy bursts and analyst refined relative arrival times are inverted for source locations nvt burst epicenters primarily occur between the 40 50 km contours for depth of the plate interface except in eastern oaxaca where they shift toward the 30 km contour as the slab steepens nvt hypocenters correlate well with a high conductivity zone that is interpreted to be due to slab fluids nvt is more frequent shorter in duration and located further inland than gps detected slow slip while the latter is associated with a zone of ultra slow velocity interpreted to represent high pore fluid pressure this zone of slow slip corresponds to approximately 350 c 450 c with megathrust earthquakes microseismicity and strong long term coupling occurring immediately updip from it this leaves nvt primarily in a region further inland from the thermally defined transition zone suggesting that transition from locking to free slip may occur in more than one phase

the 2017 mw 8 2 chiapas mexico earthquake energetic slab detachment on 8 september 2017 a great m w 8 2 normal faulting earthquake ruptured within the subducting cocos plate 70 km landward from the middle american trench beneath the tehuantepec gap iterative inversion and modeling of teleseismic and tsunami data and prediction of gps displacements indicate that the steeply dipping rupture extended 180 km to the northwest along strike toward the oaxaca coast and from 30 to 70 km in depth with peak slip of 13 m the rupture likely broke through the entire lithosphere of the young subducted slab in response to downdip slab pull the plate boundary region between the trench and the fault intersection with the megathrust appears to be frictionally coupled influencing location of the detachment comparisons of the broadband body wave magnitude m b and moment scaled radiated energy e r m 0 establish that intraslab earthquakes tend to be more energetic than interplate events accounting for strong ground shaking observed for the 2017 event

independent component analysis and parametric approach for source separation in insar time series at regional scale application to the 2017 2018 slow slip event in guerrero mexico