dichotomy in mode propagation of coseismic ionospheric disturbance observations from 11 april 2012 indian ocean earthquake the ionosphere response to the great intraplate indian ocean earthquake of 11 april 2012 mw 8 6 and its largest aftershock mw 8 2 is analyzed using gps aided total electron content tec measurements data from the dense gps networks sugar sumatran gps array and the permanent andaman nicobar array formed the near field observations at distances 250 1200 km from the epicenter stations such as iisc dgar and few others provided measurements over 2000 km from the epicenter the coseismic ionospheric disturbances cids with a propagation velocity of 930 1262 m s equals the speeds of the shock acoustic waves arrive within 10 18 min after the earthquake occurrence the observed phenomenon of cid splitting into two modes north and south of the epicenter is akin to the well documented effects of anisotropy on wave propagation closer to the epicenter to its south the propagation velocity of cid is 1 km s and farther southeast of the network the velocity reduces to 500 600 m s in contrast toward andaman in the north the cid propagation velocity increases to 2 3 5 km s the zenith angle of the line of sight between the gps receiver and satellite appears to influence the amplitude of the tec fluctuations the anomalous azimuthal variation of the rayleigh wave radiation pattern best explains the observed n s asymmetry of cid

mesozoic cenozoic tectonic evolution and metallogeny in myanmar evidence from zircon cassiterite u pb and molybdenite re os geochronology abstract it is well known that there are many sn w mo and cu au metal resources in myanmar however the absence of precise mineralization ages for these deposits significantly hinders to understand the close genetic relationship among metallogeny ore bearing intrusions and tectonic evolution in this study two groups of consistent molybdenite re os and zircon u pb ages indicate that the dapingba mo w deposit in northern myanmar tengchong terrane formed at early cretaceous 119 ma and 114 ma the dapingba ore bearing granitic magmas were mainly derived from melting of ancient tengchong crust on the basis of zircon hf isotopic compositions ehf t 9 3 to 2 5 moreover the first reported cassiterite u pb ages of 60 ma for the bawapin and kalonta sn w deposits in southern myanmar western sibumasu terrane suggest that the two deposits formed at paleocene whereas the precise molybdenite re os age for the shangalon porphyry cu au deposit in the west burma terrane indicates that this deposit formed at eocene 39 ma importantly combined with previous studies on tectonic evolution and magmatic petrogenesis in myanmar and southwest china a comprehensive mesozoic cenozoic tectono magmatic and metallogenic model are proposed two periods of early cretaceous 120 114 ma and late cretaceous 75 70 ma crust derived felsic melts and related mo sn w deposits from the tengchong and western sibumasu terranes likely formed in a continental arc during subduction of the meso and neo tethys oceanic lithosphere respectively subsequently paleocene eocene 60 50 ma sn w deposits and coeval ore bearing granites in the western sibumasu terrane possibly formed during roll back of the neo tethys oceanic slab after 50 ma india asia collision eocene 41 39 ma porphyry cu au west burma terrane and sn w deposits western sibumasu terrane likely formed during the neo tethys oceanic slab tear and break off in a collisional setting whereas miocene 19 14 ma high sulfidation epithermal cu deposit in the west burma terrane possibly formed in an arc setting during oblique subduction of the indian oceanic lithosphere

two mode ionospheric response and rayleigh wave group velocity distribution reckoned from gps measurement following mw 7 8 nepal earthquake on 25 april 2015 the coseismic induced ionospheric total electron content tec perturbations were analyzed following the mw 7 8 nepal earthquake 28 147 n 84 708 e depth 15 km that occurred on 25 april 2015 at 06 11 26 utc the ionospheric response is due to both the modes i e shock acoustic waves slow mode and rayleigh wave induced fast mode the continuous global positioning system gps data at about 60 sites from various gps networks have been used in the present study all the sites within epicentral distance of 2400 km and 70 170 azimuth recorded the rayleigh wave induced tec response while the sites within 400 2200 km in the same azimuth recorded the response from both the modes the maximum coseismic induced peak to peak tec amplitude is 1 2 total electron content unit 1 tecu 1016 el m 2 from hodochron plot the apparent rayleigh wave velocity has been determined as 2400 m s on the average and the acoustic wave velocity as 1180 m s both these waves being discernible beyond 1200 km of epicentral distance as also evident from hodochron plot and wavelet spectrographs we reckoned the rayleigh wave group velocities using ionospheric response at selected radial pairs of stations and validated the ionospheric response distribution seen mainly depending on the epicentral distance satellite geometry directivity of radiation pattern and the upper crustal heterogeneity this study highlights the characteristics of ionospheric response consequent to the 2015 nepal earthquake

the modi taung nankwe gold district slate belt central myanmar mesothermal veins in a mesozoic orogen abstract the recently discovered quartz gold veins comprising the modi taung nankwe gold district in central myanmar are largely hosted by mudstones of the late palaeozoic slate belt mesozoic rocks of the paunglaung mawchi zone separate the slate belt from the shan scarp and shan plateau to the east at modi taung 5 km of exploration adits indicate that the veins within steeply dipping oblique reverse slip shear zones are displaced by movements along the shears intruded by late jurassic calc alkaline dykes and offset on conjugate cross faults drill intercepts show that mineralization extends vertically for more than 500 m coarse visible gold book and ribbon texture and stylolitic laminations and trace metal values are consistent with mineralization at mesothermal depths of several kilometres in the brittle ductile regime our field observations suggest that mineralization took place in the early jurassic following collision of myanmar on the passive western margin of a greater shan thai continental block with an oceanic arc on the overriding plate to the west collision generated intra continental thrusting in and east of the paunglaung mawchi zone metamorphism of plateau rocks thrust west beneath the slate belt to form the mogok metamorphics and ascent of mineralizing fluids expelled from dehydrating underthrust rocks reversal in orogenic polarity initiated late jurassic eastward subduction of oceanic crust beneath myanmar and generation of a magmatic arc with dykes cutting the quartz gold veins renewed east directed thrusting translated the slate belt over arc clastics and probably resulted in exhumation of the mogok metamorphics and offsets of the veins on conjugate faults young k ar rb 87 sr 86 and ar 40 ar 39 ages on the mogok metamorphic belt imply renewed tertiary uplift and possibly intrusion of mid tertiary or palaeogene granites

origin ore forming fluid evolution and timing of the logrosan sn w ore deposits central iberian zone spain the logrosan sn w ore deposits in the metallogenic sn w province of the european variscan belt consist of endo and exogranitic greisen type and quartz cassiterite veins associated with a s type granite mineral characterization fluid inclusion study isotope geochemistry and ar ar geochronology have been combined in order to reconstruct the conditions for sn w mineralization the endo and exogranitic mineralization must have been developed in a relatively long lived system 308 303 ma during or soon after the emplacement of the logrosan related granite at ca 308 ma the mineralizing fluids are characterized by complex aqueous and volatile h2o n2 co2 ch4 nacl fluid inclusions microthermometry and raman analyses indicate that fluid composition evolved from n2 ch4 to n2 rich followed by co2 rich fluids with varying amounts of h2o the presence of n2 and ch4 suggests the interaction with fluids derived from the nearby metasedimentary host rocks a model of host rock interaction assimilation and mixing of metamorphic and magmatic fluids resulting in change of the redox conditions is proposed for tin deposition later sulfide minerals were precipitated as a result of pressure and temperature release

tin metallogenesis associated with granitoids in the southwestern sanjiang tethyan domain nature deposit types and tectonic setting article i nfo tin mineralization in the southwestern sanjiang tethys sn metallogenic domain extends from the southeast asia tin belt in the south the eastern part of the domain does not contain significant sn deposits whereas the central part of the domain composed of the changning menglian sn belt and related to ca 239 178 ma s type granitoids generated by the collision between tengchong baoshan and simao blocks carries wide spread the hydrothermal vein type mineralization the western part of the domain composed of the tengchong baoshan sn metallogenic belt is related to both 136 113 ma and 89 52 ma s type granitoids the former granitoids resulted from the collision between western burma and tengchong baoshan blocks and generated skarn type tin deposits the younger groups correspond to the india asia continental collision and are associated with the xiaolonghe and lailishan greisen type sn deposits

directivity and apparent velocity of the coseismic ionospheric disturbances observed with a dense gps array abstract coseismic disturbances in ionosphere have been observed after recent thrust earthquakes off the pacific coast of japan with a dense global positioning system array positive pulses in electron content as large as several times 10 15 electrons m 2 and as long as 4 5 min emerge 10 min after earthquakes and propagate horizontally with apparent velocity of 1 km s close to the sound velocity at the ionospheric height they may have been excited by coseismic uplifts of the sea surface initially as upward propagating compressive pulses of atmosphere which were gradually refracted to propagate horizontally in ionosphere the propagation has strong north south asymmetry and interaction between the movements of charged particles in acoustic waves and geomagnetic fields might have selectively attenuated the northward propagating disturbances

stable isotope and geochronological study of the mawchi sn w deposit myanmar implications for timing of mineralization and ore genesis myanmar is endowed with abundant sn w mineralization pre eminent amongst which is the world class mawchi deposit in the mawchi area n s trending vertical or steeply dipping quartz veins are hosted by both eocene granite and carboniferous to early permian metasediments three stages of ore formation are recognized i tourmaline cassiterite stage ii main ore stage and iii sulfide stage tourmaline cassiterite and pyrite i are early formed minerals and are representative of the first stage their deposition continued together with wolframite scheelite molybdenite arsenopyrite pyrite ii fluorite and danalite which form the second stage this was followed by the successive deposition of sulfides such as chalcopyrite sphalerite galena and pb bi sulfides a 40ar 39ar magmatic biotite plateau age of 41 50 0 16 ma mswd 2 5 is determined for the mawchi biotite granite which we interpret as the time the granite cooled through the biotite blocking temperature and is consistent with a previously reported la icp ms u pb zircon concordia age of 42 72 0 94 ma mswd 2 a molybdenite re os model age of 42 4 1 2 ma indicates that sn w mineralization was synchronous with late eocene granitic magmatism our 40ar 39ar hydrothermal muscovite plateau ages from the tourmaline granite 40 14 0 14 ma mswd 1 48 and quartz vein selvages 40 80 0 12 ma mswd 0 47 define the timing of hydrothermal alteration and simultaneous veining that accompanied the late stage of ore forming at mawchi fluid inclusion microthermometry from cassiterite scheelite quartz and fluorite reveals that ore fluids in the cassiterite tourmaline stage and main ore stage are characterized by moderate homogenization temperatures th 260 345 c and salinities 4 5 15 7 wt nacl equiv while the sulfide stage is characterized by lower temperatures th 175 260 c and moderate to low salinity 2 5 13 wt nacl equiv the mean 34s of all sulfides is 2 9 2 9 which is suggestive that the overall system is dominated by magmatic sulfur the similarity of 34s values in galena and pb bi sulfides 1 3 2 7 suggest that sulfur and inference the pb and bi were transported by a common fluid probably of magmatic origin the calculated 18oh2o of the hydrothermal fluid associated with cassiterite and tourmaline is 7 3 to 8 4 scheelite and quartz deposition is characterized by lighter 18oh2o values 2 1 to 4 9 indicating that the ore fluid might be mixed with another source of water perhaps meteoric hydrogen isotopic compositions d 51 to 121 again indicate that origin of the ore fluid is magmatic but d 120 is low enough to support the 18oh2o data that suggests in part a meteoric water component to the hydrothermal fluids at mawchi

ionospheric holes made by ballistic missiles from north korea detected with a japanese dense gps array 1 a dense array of global positioning system gps receivers is a useful tool to study ionospheric disturbances here we report observations by a japanese gps array of ionospheric holes i e localized electron depletion they were made by neutral molecules in exhaust plumes e g water of ballistic missiles from north korea taepodong 1 and 2 launched on 31 august 1998 and 5 april 2009 respectively negative anomaly of electron density emerged 6 min after the launches in the middle of the japan sea and extended eastward along the missile tracks by comparing the numerical simulation of electron depletion and the observed change in ionospheric total electron content we suggest that the exhaust plumes from the taepodong 2 second stage effused up to 1 5 1026 water molecules per second the ionospheric hole signature was used to constrain the taepodong 2 trajectory together with other information e g coordinates of the launch pad time and coordinates of the first stage splashdown and height and time of the second stage passage over japan the taepodong 2 is considered to have reached the ionospheric f region in 6 min flown above northeastern japan 7 min after the launch and crashed to the pacific ocean without attaining the first astronautical velocity the ionospheric hole in the 1998 taepodong 1 launch was much less in size but it is difficult to compare directly the thrusts of the two missiles due to uncertainty of the taepodong 1 trajectory

ionospheric effects of the solar eclipse of march 9 1997 as deduced from gps data this paper presents data from first measurements of total electron content tec and its gradient during the solar eclipse of march 9 1997 obtained with the gps radio interferometer at irkutsk the interferometer consists of three receivers one turbo rogue snr 8000 and two ashtech z 12 located at the vertices of a triangle and spaced by about 3 5 km the measured tec variations are indicative of profound changes in the ion production process in the ionosphere attendant on the solar eclipse simultaneously in a large volume of space with a radius of at height 300 km at 300 km altitude the delay of a minimum value of tec with respect to the maximum phase of eclipse at 300 km altitude was about 10 min and the depression depth of tec growth varies from l 3 1016m 2 by analyzing the data on tec gradient variations one is led to conclude that the depression of tec growth during the eclipse is essentially independent of the longitude and of the latitude within the observation ranges 52 6 n and 104 11 e

from sumatra 2004 to tohoku oki 2011 the systematic gps detection of the ionospheric signature induced by tsunamigenic earthquakes the recent tsunamigenic earthquake in tohoku 11 march 2011 strongly affirms one more time after the sumatra event 26 december 2004 the necessity to open new paradigms in oceanic monitoring detection of ionospheric anomalies following the sumatra tsunami demonstrated that ionosphere is sensitive to the tsunami propagation observations supported by modeling proved that tsunamigenic ionospheric anomalies are deterministic and reproducible by numerical modeling via the ocean neutral atmosphere ionosphere coupling mechanism in essence tsunami induces internal gravity waves propagating within the neutral atmosphere and detectable in the ionosphere most of the ionospheric anomalies produced by tsunamis were observed in the far field where the tsunami signature in the ionosphere is clearly identifiable in this work we highlight the early signature in the ionosphere produced by tsunamigenic earthquakes and observed by gps measuring the total electron content close to the epicenter we focus on the first hour after the seismic rupture we demonstrate that acoustic gravity waves generated at the epicenter by the direct vertical displacement of the source rupture and the gravity wave coupled with the tsunami can be discriminated with theoretical support we illustrate the systematic nature of those perturbations showing several observations nominally the ionospheric perturbation following the tsunamigenic earthquakes in sumatra on 26 december 2004 and 12 september 2007 in chile on 14 november 2007 in samoa on 29 september 2009 and the recent catastrophic tohoku oki event on 11 march 2011 based on the analytical description we provide tracks for further modeling efforts and clues for the interpretation of complex and thus often misleading observations the routine detection of the early ionospheric anomalies following the rupture highlights the role of ionospheric sounding in the future ocean monitoring and tsunami detection

depth of emplacement fluid provenance and metallogeny in granitic terranes a comparison of western thailand with other tin belts the most important tin mineralization in thailand is associated with the late cretaceous to middle tertiary western thai granite belt a variety of deposit types are present in particular pegmatite vein and greisen styles of mineralization a feature common to most of the deposits is that they are associated with granites that were emplaced into the khang krachan group which consists of poorly sorted carbonaceous pelitic metasediments most of the deposits contain low to moderately saline aqueous fluid inclusions and aqueous carbonic inclusions with variable ch4 co2 ratios low salinity aqueous inclusions represent trapped magmatic fluid in at least one case the nong sua pegmatite based on their occurrence as primary inclusions in magmatic garnet aqueous carbonic inclusions are commonly secondary and neither the co2 nor nacl contents of these inclusions decrease in progressively younger inclusions implying that they are not magmatic in origin reduced carbon is depleted in the metasediments adjacent to granites and the d values greisen muscovites are variable but are as low as 134 per mil indicative of fluid interaction with organic graphitic material this suggests that the aqueous carbonic fluid inclusions represent fluids that were produced at least in part during contact metamorphism metasomatism by comparing the western thai belt with other sn w provinces it is evident that there is a strong correlation between fluid composition and pressure in general low to moderately saline aqueous inclusions and aqueous carbonic inclusions are characteristic of mineralization associated with relatively deep plutonic belts mineralized pegmatites are also typically of deeper plutonic belts and pegmatite hosted deposits may contain cassiterite that is magmatic crystallized from granitic melt or is orthomagmatic hydrothermal crystallized from aqueous or aqueous carbonic fluids in origin the magmatic aqueous fluids those that were exsolved from granitic melts are interpreted to have had low salinities as a consequence of the low salinities tin is partitioned in favour of the melt on vapour saturation thus with a high enough degree of fractionation the crystallization of a magmatic cassiterite or different sn phase such as wodginite is inevitable because tin is not partitioned in favour of the vapour phase upon water saturation of the granitic melts it is proposed that relatively deep vein and greisen systems tend to form by remobilization processes in addition many deeper greisen systems are hosted in part by carbonaceous pelitic metasediments and the reduced nature of the metasediments may play a key role in remobilizing tin sub volcanic systems by contrast are characterized by high temperature high salinity fluids owing to the high chlorinity tin is strongly partitioned in favour of the vapour and cassiterite mineralization can form by of orthomagmatic hydrothermal processes similar relationships between the depth of emplacement and fluid composition also appear to apply to other types of granite hosted deposits such as different types of molybdenum deposits

genesis of a magmatic metamorphic hydrothermal system the sn w polymetallic deposits at pilok thailand cassiterite wolframite and base metal mineralization in the pilok area are hosted by veins and stockworks in the apical portion of leucocratic granite stocks close to their contacts with pelitic metasedimentary rocks a minimum pressure of emplacement of approximately 1 500 bars is indicated by the presence of two coexisting feldspars in the granites and a moderate depth is supported by a lack of coeval volcanism and absence of porphyritic textures that characterize hypabyssal intrusions a contact metamorphic metasomatic aureole in the surrounding pelitic metasediments consists of tourmaline biotite and muscovite zones that are superimposed on muscovite chlorite zone regional metamorphism whole rock carbon analyses demonstrate a volatilization of graphite in the metasediments as a function of distance from the intrusion and the presence of andalusite in the aureole constrains the maximum pressure to approximately 3 800 bars the earliest mineralization is late magmatic to early postmagmatic wolframite cassiterite intergrown with li and f rich muscovite in pegmatite pods the bulk of the wolframite mineralization was subsequently deposited in veins with potassic alteration which could have originated either by orthomagmatic or remobilization processes finally cassiterite and sulfides chalcopyrite sphalerite were deposited in association with greisen alteration and formed as a result of the remobilization of tin from the host granite fluid inclusion and stable isotope data indicate the involvement of at least four fluid types a moderately saline fluid of presumed magmatic origin aqueous carbonic metamorphic fluids low temperature and low salinity meteoric fluids and high salinity formational or metamorphic fluids the isotopic compositions of waters calculated from delta o 18 analyses of quartz muscovite and cassiterite and delta d analyses of muscovite range from 1 4 to 9 4 and 63 to 118 per mil respectively these are consistent with the mixing of magmatic and organic rich metamorphic fluids oxygen isotope thermometry indicates temperatures of 350 degrees to 500 degrees c for cassiterite mineralization the oldest preserved fluid inclusions are primary aqueous carbonic inclusions from wolframite and cassiterite mineralization both the homogenization of the carbonic phase and the bulk

short and long wavelength tids generated by the great american eclipse of 21 august 2017 on the 21 august 2017 the eclipse shadow drastically changed the state of the ionosphere over the united states this effect on the ionosphere is visible in the total electron content measured by global navigation satellite systems gnss the shadow moved with the supersonic speed of 1 000 m s over oregon to 650 m s over south carolina in order to exhaustively explore the ionospheric signature of the eclipse we use data of total electron content from 3 000 gnss stations seeing multiple global positioning system gps and global navigation satellite system glonass satellites to visualize the phenomena this tremendous dataset allows high resolution characterization of the frequency content and wavelengths using an omega k analysis based on 3 d fast fourier transform of the eclipse signature in the ionosphere in order to fully identify traveling ionospheric disturbances tids we confirm the generation of tids associated with the eclipse including tids interpreted as bow waves in previous studies additionally we reveal for the first time short 50 100 km and long 500 600 km wavelength tids with periods between 30 and 65 min the sources of the revealed short wavelength tids are co located with the regions of stronger gradient of the euv related to sunspots our work confirms and describes physical properties of the waves observable in the ionosphere during the great american eclipse

a sporadic low velocity layer atop the western u s mantle transition zone and short wavelength variations in transition zone discontinuities teleseismic receiver function analysis of data from six dense arrays in the western u s is used to investigate mantle transition zone mtz discontinuities and the prevalence of a low velocity layer atop the 410 km discontinuity 410 lvl negative polarity ps arrivals indicative of a low velocity layer with a top 25 60 km above the 410 are identified in 8 11 out of 18 stacks of receiver functions from highly sampled back azimuth corridors the 410 lvl is interpreted as partial melt resulting from upwelling of hydrated mantle across a water solubility contrast at the 410 the 669 km mean depth of the 660 km discontinuity 660 and the magnitude of 660 topography suggest variable hydration locally approaching saturation in addition to 150 k lateral temperature variations beneath five arrays mean amplitudes of p410s and p660s increase monotonically with period from 2 to 10 s however greater variations are observed in the frequency dependence of p410s compared to p660s implying 410 thickness is more heterogeneous variable 410 thickness is attributed to changes in hydration modulating the width of the olivine to wadsleyite transition interval frequency dependence of p660s amplitudes suggests a broad velocity gradient consistent with multivariate phase changes in the olivine and garnet systems sporadic detection of the 410 lvl the magnitude and length scales of mtz discontinuity topography and inferred variations in hydration support the occurrence of vigorous small scale convection in the western u s mantle comparison of receiver functions with body wave tomography suggests small scale convection driven by sinking slab segments and lithospheric instabilities contributes to the intermittent nature of the 410 lvl

trace element geochemistry by laser ablation icp ms of micas associated with ta mineralization in the tanco pegmatite manitoba canada in the tanco pegmatite one of the world s major ta deposits tantalum mineralization shows a complexity that reflects the complex petrogenesis of its host pegmatite micas are common in most of the pegmatite units and are intimately associated with the successive stages of ta mineralization from the wall zone to the central zones where micaceous replacement is pervasive different generations of micas both primary and secondary associated with ta oxides were selected for electron microprobe and laser ablation icp ms investigation their chemical trends are used to constrain the magmatic versus hydrothermal processes that played a role in their crystallization and their associated ta mineralization micas range from dioctahedral muscovite to trioctahedral lepidolite through al li substitution unexpectedly the most evolved compositions low k rb ratios and high li contents occur in the wall zone they are interpreted to reflect nonequilibrium crystallization from an undercooled melt with or without boundary layer effects in the central zones the fine grained mica quartz assemblage hosts some coarser grained li muscovite which has the highest ta contents up to 400 ppm these li f a rich micas are interpreted to originate from a magmatic metasomatic event which was also at the origin of the mqm style ta mineralization at tanco however the li ta poor muscovite end member compositions of fine grained alteration micas suggest crystallization from an aqueous fluid during a metasomatic hydrothermal event involving late pegmatitic fluids the low ta concentrations around 50 ppm of this fine grained muscovite suggest that this fluid transported at least small amounts of ta

effects of rayleigh taylor instability and ionospheric plasma bubbles on the global navigation satellite system signal abstract ionospheric disturbances induced by various natural e g earthquakes volcanic eruption thunderstorms meteorite showers solar eclipses or anthropogenic e g nuclear explosions launching of space shuttles processes can be detected through change in total electron content tec in the f layer these ionospheric perturbations can be captured by worldwide expanding geodetic gnss networks mainly during the day time when the solar radiation ionizes the air molecules however during post sunset period strong ionospheric irregularities known as equatorial plasma bubbles epbs develop due to the classical configuration for the rayleigh taylor r t instability that diffracts navigation and communication signals here we use various instances of ionospheric disturbances triggered by natural processes e g earthquakes and volcanic eruption in the recent decade to investigate the spatiotemporal and seasonal effects of ionospheric irregularities on the gnss signals our study suggests that in the low latitudinal region e g sumatra mexico such ionospheric irregularities can mask the ionospheric perturbations due to the higher production rate of epbs hence detection of such co seismic tec anomaly becomes difficult however in the high latitudinal region e g iceland alaska due to the lower production rate of epbs ambient ionospheric irregularities are insignificant and hence coseismic tec anomalies can be captured even during night time we argue that the production rate of epbs further depends upon seasonal and longitudinal parameters on the globe

gps detection of ionospheric perturbations following the january 17 1994 northridge earthquake sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce pressure waves that propagate at infrasonic speeds in the atmosphere at ionospheric altitudes low frequency acoustic waves are coupled to ionospheric gravity waves and induce variations in the ionospheric electron density using global positioning system gps data recorded by the permanent gps network operating in southern california we computed ionospheric electron content time series for several days preceding and following the january 17 1994 mw 6 7 northridge earthquake we observe an anomalous signal beginning several minutes after the earthquake with time delays that increase with distance from the epicenter the signal frequency and phase velocity are consistent with results from numerical models of atmospheric ionospheric acoustic gravity waves excited by seismic sources as well as previous electromagnetic sounding results we believe that these perturbations are caused by the ionospheric response to the strong ground displacement associated with the northridge earthquake

gnss observations of ionospheric variations during the 21 august 2017 solar eclipse u s national science foundation grant nasa grant nasa lws funding support muri grant onr

atmospheric resonant oscillations by the 2014 eruption of the kelud volcano indonesia observed with the ionospheric total electron contents and seismic signals abstract acoustic waves from volcanic eruptions are often observed as infrasound in near fields part of them propagate upward and disturb the ionosphere and can be observed with total electron content tec data from global navigation satellite system gnss receivers here we report tec variations after the 13 february 2014 plinian eruption of the kelud volcano east java indonesia observed with regional gnss networks significant disturbances in tec were detected with six gnss satellites and wavelet analysis showed that harmonic oscillations started at 16 25 ut and continued for 2 5 h the amplitude spectrum of the tec time series showed peaks at 3 7 mhz 4 8 mhz and 6 8 mhz long wavelength standing waves with a wide range of wavelength trapped in the lower atmosphere are excited by the plinian eruption amplitude spectra of the ground motion recorded by seismometers however had frequency components at discrete wave periods the condition for the resonant oscillations between the atmosphere and the solid earth is satisfied only at these discrete wave period and horizontal wavelength pairs therefore efficient energy transfer from the atmospheric standing waves to the solid earth rayleigh waves occurred at discrete periods and resulted in the harmonic ground motion

lithosphere atmosphere ionosphere coupling after the 2003 explosive eruption of the soufriere hills volcano montserrat resonant coupling between the earth and the atmosphere at frequencies where the solid earth modes overlap the fundamental modes of the atmosphere allows for the triggering of oscillatory acoustic perturbations by ground excitation and vice versa here we describe oscillatory perturbations observed in the solid earth from volumetric borehole strainmeter data and in the atmosphere from gps derived ionospheric total electron content following the july 13 2003 soufri ere hills volcano explosion montserrat lesser antilles spectral analysis shows an amplitude peak at 4 mhz for both datasets with similar waveforms and signal duration using a normal mode summation technique we show that both signals are explained by a single explosive source in the atmosphere similarities in waveforms in particular a double wave train also reported after several other explosion triggered atmospheric perturbations result from the superposition of the dominant fundamental atmospheric modes that trigger resonant coupling with the solid earth around 4 mhz

coseismic ionospheric disturbance of the large strike slip earthquakes in north sumatra in 2012 mw dependence of the disturbance amplitudes we studied ionospheric responses to the 2012 april 11 mw8 6 north sumatra earthquake using total electron content tec measurements with the regional global navigation satellite system gnss network this earthquake ruptured the oceanic lithosphere off the indian ocean coast of north sumatra and is known as the largest strike slip earthquake ever recorded coseismic ionospheric disturbances cid with rapid tec enhancement of a few tec units propagated northward with a speed of acoustic waves 1 km s resonant atmospheric oscillation with a frequency 4 mhz have been found as monochromatic oscillation of tec lasting for an hour after the main shock and the largest aftershock we compared cid amplitudes of 21 earthquakes worldwide with moment magnitudes mw 6 6 9 2 they roughly obeyed a law such that cid amplitude increases by two orders of magnitude for the mw increase of three the 2012 north sumatra earthquakes slightly deviated negatively from the trend possibly reflecting their strike slip mechanisms i e small vertical crustal movements for their magnitudes

ionospheric disturbances triggered by the 25 april 2015 m7 8 gorkha earthquake nepal constraints from gps tec measurements the ionosphere response to the april 11 2015 mw 7 8 gorkha earthquake occurring in the himalayan arc is analysed using gps total electron content tec measurements from gps sites in nepal and india situated both close to and far from the epicentre in the near field the coseismic ionospheric disturbance cid following the earthquake rupture propagation arrive east of the epicentre within 5 7 min with a propagation velocity of 980 m s equal to the speed of the shock acoustic waves at the ionospheric heights and on to the west with a reduced speed of 650 m s within 8 11 min after the earthquake occurrence the phenomenon of cid splitting into two modes east and west of the epicentre is observed in the far field region up to epicentral distances of 2200 km rayleigh wave induced ionospheric disturbance are recorded with a propagation speed of 2 6 km s higher tec amplitude of 0 2 1 5 tecu is observed east of the epicentre compared to the west with 0 1 0 3 tecu the characteristics of this dip slip earthquake are well projected in the tec waveforms the ambient magnetic field in the mid latitudes prohibited the propagation of ionospheric disturbance in the northward direction in the present study the observed primary cid is essentially in congruence with the rupture propagation of the earthquake in e se direction

gps tec response to the 22 july 2009 total solar eclipse in east asia 1 the longest total solar eclipse of this century occurred in east and south asia on 22 july 2009 the eclipse was accompanied with a medium magnetic storm whose main phase onset occurred 27 min after the passage of the moon s umbral shadow using tec data from 60 gps stations we construct differential tec maps to investigate the ionosphere response to the solar eclipse in central china in the range of 26 n 36 n 108 e 118 e i e the magnetic latitude 15 n 25 n during the eclipse s totality a shadow in the ionosphere shown as tec depletion area was formed 100 km south of the moon s umbral path with a maximum decrease of 5 tecu the tec depletion area moved eastward following the movement of the totality area with a time lag of 10 min enhancements of tec due to the storm are observed after the main phase onset the relative drop of tec due to the solar eclipse is evidently larger at lower latitudes than that at higher ones and around noontime than that in the morning by modeling work we find that the latitudinal dependence of the tec response may result from latitudinal variation of magnetic inclination which influences the diffusion of ionization among different layers besides the local time dependence of tec response is closely related to the local time variation of background atmosphere density which affects the electron loss efficiency in the ionosphere

tracing metal sources in peribatholitic hydrothermal w deposits based on the chemical composition of wolframite the example of the variscan french massif central abstract we present a complete dataset for major minor and trace elements in wolframite fe mn wo4 based on the example of several peribatholitic hydrothermal w deposits located in the variscan french massif central fmc the wolframite samples were characterized down to the micrometer scale by combining scanning electron microscopy observations and in situ chemical analysis by electron probe microanalyzer and laser ablation inductively coupled plasma mass spectrometry most samples are fe dominated wolframites and are characterized by variable fe fe mn values for the studied deposits from 0 36 to 0 86 without significant alteration features wolframites present intracrystalline variations for concentrations of several minor and trace elements principally for nb ta and sn which reflect growth zoning the minor and trace element compositions of the different wolframite samples show at first order similar enrichments in ta nb sn zn and in as well as depletions in lree li th ti zr hf pb v co and mg compared to the upper continental crust second order compositional variations are observed between the studied deposits which can be separated in four main regional geochemical groups this work highlights that the chemical composition of wolframite is controlled by both the crystallochemical parameters and the composition of the primary hydrothermal fluid the regional variations observed in the geochemical signatures of wolframite reflect local variations in the composition of the hydrothermal fluid i e variable metal sources therefore this suggests that the minor and trace element contents in wolframite likely represent direct markers of the source of the hydrothermal fluid and ultimately of the metals the comparison between the trace element compositions of wolframite with the compositions of regional granitic rocks and worldwide shales suggests that evolved peraluminous granites represent the main source of metals in peribatholitic hydrothermal w deposits from the fmc whereas metasedimentary rocks have a limited to no influence on the metal budget

combined zircon molybdenite and cassiterite geochronology and cassiterite geochemistry of the kuntabin tin tungsten deposit in myanmar

metal source and wolframite precipitation process at the xihuashan tungsten deposit south china insights from mineralogy fluid inclusion and stable isotope abstract the xihuashan tungsten deposit hosted in the late jurassic granitic pluton in the nanling range of south china has a total resource of about 81 300 tonnes of wo 3 with an average ore grade of 1 08 wo 3 wolframite is the dominant ore mineral and intergrown with quartz in the main mineralization stage ore forming fluids trapped in wolframite have d and 18 o values from 82 to 64 and 7 4 to 8 8 respectively those in quartz have similar d 72 to 58 and 18 o 6 8 to 8 0 values indicative of a magmatic fluids simultaneously trapped by quartz and wolframite la icp ms analyses for individual fluid inclusion show that this mineralizing fluid contains measurable li rb cs k na ti cu zn as and w 1 to 125 ppm with average of 19 ppm while depleted in fe and mn the wolframite from the xihuashan tungsten deposit contains high feo 10 9 to 17 7 wt and mno 5 9 to 12 7 wt contents with fe fe mn atomic ratio of 0 46 to 0 75 thus requires the availability of external fe and mn we detect that the fe and mn contents in mica from the greisen are remarkably lower than primary mica from granite some magmatic micas were observed in greisen and were subjected to hydrothermal alteration compared to the core the rim of these micas depleted in fe mn f and na the siderite and pyrophanite are formed along cleavage planes of altered magmatic mica that are evidence to be due to fe and mn release during granite alteration thus we demonstrate quantitatively that magmatic fluids at xihuashan provide w in solution whereas the hosted granite alteration contributes fe and mn to precipitate wolframite it is also supported by wolframites have trace and rare earth elements characteristics similar to those of granite and some characteristics similar to the greisen therefore the ore forming fluids has components derived from the last highly evolved residual granitic melt and components acquired by releasing through the hosted granite alteration fluid rock interaction exert a principle control on wolframite precipitation based on mineralogy fluid inclusion and stable isotope we proposed three stage process to illustrate the genetical link between tungsten mineralization and granite

age and origin of the bulangshan and mengsong granitoids and their significance for post collisional tectonics in the changning menglian paleo tethys orogen the subduction and collision tectonics in the sanjiang region provide important insights into the evolution of the paleo tethyan orogen here we present la icp ms zircon u pb ages sm nd and lu hf isotopic data whole rock major and trace element compositions of the late triassic magmatic rocks from the mengsong and bulangshan granitoids in this region zircon u pb dating of the bulangshan and mengsong granitoids yields crystallization age of 216 228 ma with zircon ehf t values ranging from 15 2 to 1 5 these granitoids are high k calc alkaline and muscovite bearing the rocks show peraluminous nature and are enriched in large ion lithophile elements rb k u and th and depleted in high field strength elements nb and ti they also display enrichment in light rare earth elements with strong negative eu anomalies eu 0 16 the geochemical and isotopic features suggest that the primary magma of the bulangshan and mengsong granitoids most likely originated from partial melting of the underlying proterozoic metasedimentary rocks the granitoid magmatism is correlated with post collisional tectonics and provides important constraints on the timing of closure of the paleo tethyan ocean

zircon u pb ages in myanmar magmatic metamorphic events and the closure of a neo tethys ocean abstract previous isotopic age studies have concluded that the main metamorphism in the mogok metamorphic belt mmb in myanmar was tertiary and caused by collision with or underthrusting by india we present here results of zircon u pb age determinations on 18 samples from myanmar largely on intrusive rocks from the north trending 550 km long shan scarps segment of the sickle shaped mmb the oldest determination is 491 ma on orthogneiss north of mandalay interpreted as a protolith age and similar to the stratigraphic age of the bawdwin volcanics augen gneiss at kyaukse has a 114 ma protolith age our zircon u pb ages on undeformed intrusive rocks in the mmb range from cretaceous to miocene the oldest 128 ma on a diorite near yebokson implies an earliest cretaceous minimum age for regional metamorphism here younger ages on undeformed intrusions include 91 ma on diorite at mokpalin 72 ma on the weakly foliated garnet bearing nattaung granite 44 and 48 ma respectively on the mec and sedo granites and 17 20 ma on granite dykes for the 128 ma diorite sr and nd isotopes indicative of a continental crust component and mapped continuity of metamorphic host rocks suggest correlation with mid early cretaceous plutons in the eastern transhimalayas zircon u pb ages for the mec sedo and other granites within the mmb and slate belt help to define a late cretaceous to early eocene age range for mostly ilmenite series peraluminous granites within the western granite belt and more restricted western tin belt of myanmar and southern thailand in the wuntho popa arc west of the dextral sagaing fault our new u pb zircon age of 105 ma on diorite at salingyi supports previous k ar ages 106 93 ma for pre tertiary intrusions in the cretaceous this arc may have occupied the andaman sea and continued northwards through the mokpalin diorites and west of the mmb to the 103 80 ma i type plutons in the gandise batholith of southern tibet we interpret the mmb and slate belt as part of a western myanmar block separated in the jurassic from the shan plateau to the east by the southwestward continuation of the bangong nujiang luxi neo tethys i ocean we relate most intrusive and metamorphic events in and near the mmb to westward subduction of this ocean and end jurassic collision of the plateau with the overriding western myanmar slate belt block to orogenic polarity reversal and early cretaceous westward translation of the plateau sequence over the suture zone and to eastward subduction of the ancestral indian ocean or neo tethys ii beneath myanmar with generation of the wuntho popa arc beginning before the late cretaceous the mmb includes meta plateau rocks near mandalay but meta slate belt rocks to the north and south within the mmb previous monazite xenotime thorite ages of eocene oligocene and oligocene early miocene cooling ages on micas with no deformation in eocene granites suggest a high temperature thermal event related to intrusion of these and other granites during a previously proposed regional extension our data imply that the main fabric forming metamorphic event in the mmb pre dated the india asia collision

ionospheric total electron content response to solar eclipses on october 24 1995 and march 9 1997 two solar eclipse events occur it is therefore of interest to investigate how the ionosphere responded to the eclipses five global positioning system gps ground based receivers are specifically designed to observe large scale ionospheric variations over the geomagnetic equatorial equatorial anomaly crest and midlatitude regions two dimensional images of ionospheric total electron content tec during the two eclipse periods are constructed the deviations in the tec images on eclipse days from those on reference days show that during the eclipse days the ionosphere experienced some large scale changes four features of the tec deviations pre ascension pa major depression md sunset ascension sa and secondary depression sd have been observed a detailed study shows that in geomagnetic low latitudes pas are possibly related to the locations of the equatorial anomaly crest the latitudinal location amplitude and occurrence time of mds suggest that the fountain effect is essential sas and sds occurring in geomagnetic equatorial and low latitudes and appearing respectively before around and after local sunset indicate that the prereversal enhancement plays an important role

three dimensional and trans hemispheric changes in ionospheric electron density caused by the great solar eclipse in north america on 21 august 2017

geology mineralization and fluid inclusion characteristics of the skrytoe reduced type w skarn and stockwork deposit sikhote alin russia the skrytoe deposit 145 kt wo3 average grade 0 449 wo3 in the sikhote alin orogenic system eastern russia is situated in a metallogenic belt of w sn w au and au w deposits formed in a late to post collisional tectonic environment after cessation of active subduction it is localized within a mineralized district of reduced type skarn w and veined au w deposits and occurrences related to the early cretaceous ilmenite series plutonic suite the deposit incorporates large stockworks of scheelite bearing veinlets related to propylitic amphibole chlorite quartz and phyllic quartz sericite albite apatite and carbonate hydrothermal alteration the stockwork cuts flat lying mafic volcanic rocks and limestone partially replaced by pyroxene skarn that host the major w orebodies scheelite is associated with pyrrhotite and or arsenopyrite with minor chalcopyrite and other sulfide minerals the late phyllic stage assemblages hosts bi and au mineralization the fluid evolution included low salinity moderate temperature moderate pressure 370 390 c 800 bars methane dominated carbonic aqueous fluids that formed post skarn propylitic alteration assemblages then at the phyllic stage there has been an evolution from methane dominated moderate temperature 330 360 c low salinity 12 3 wt nacl equiv fluids forming the early quartz sericite albite arsenopyrite assemblage through lower temperature 290 330 c methane dominated low salinity 9 10 wt nacl equiv fluids forming the intermediate quartz sericite albite scheelite pyrrhotite assemblage to yet lower temperature 245 320 c co2 dominated carbonic aqueous low salinity 1 7 wt nacl equiv fluids forming the late quartz sericite sulfide bi au assemblage recurrent fluid immiscibility phase separation and cooling probably affected w solubility and promoted scheelite deposition the stable isotope data support a sedimentary source of carbon 13cfluid 21 to 10 a magmatic source for water 18oh2o 7 4 to 7 7 and dominantly crustal derived source of sulfur 34s 4 6 to 2 9 in the hydrothermal fluids this is consistent with the development of larger longer crystallizing crustal intermediate to felsic magma chambers in the late to post collisional tectonic environment with their protracted magmatic evolution advancing magmatic differentiation and partitioning of w into magmatic hydrothermal fluid the dominating role of the crustal derived magmatic water sulfur and carbon appears to be an important feature of reduced w skarn deposits related to ilmenite series granitoids

source of copper in the giant shimensi w cu mo polymetallic deposit south china constraints from chalcopyrite geochemistry and oxygen fugacity of ore related granites abstract porphyry type copper mineralization is generally considered to be related to ore forming fluid exsolution from oxidized magnetite bearing intermediate to felsic magmas however copper deposits associated with ilmenite bearing per aluminous evolved granites also exist and their origin remains obscure the shimensi w cu mo polymetallic deposit located in the northern segment of the jiangnan orogen south china composed mainly of the neoproterozoic shuangqiaoshan group meta sediments volcanic rocks and biotite granite is one of the largest tungsten deposits in the world the w cu mo polymetallic orebodies occur at the contact zone between the mesozoic ilmenite bearing fluorite bearing f rich highly fractionated granite and the neoproterozoic granite the reason for the accompanying cu mineralization within ilmenite bearing granites is unclear in this paper we present a detailed study of chalcopyrite geochemistry including s pb isotopes trace elements and nd isotopes and oxygen fugacity fo2 of ore related granites in the shimensi deposit to constrain the origin of copper sulfur isotope values of the sulfides give a narrow 34s interval of 3 3 to 0 5 mean 1 5 n 32 suggesting the ore forming fluid is of magmatic origin the similarity of pb isotopes of the majority of sulfides and k feldspars from mesozoic granites indicates their genetic relationship however chalcopyrite samples show a wider range of pb isotopic compositions than that of k feldspars suggesting an extra source for the ore forming fluids chalcopyrite from the ore deposit show features of lree enriched patterns variable eu negative anomalies eu eu 0 26 0 75 and la sm n values 0 77 5 93 while the two figures for the mesozoic f rich evolved granites are eu eu 0 18 0 45 and la sm n 2 42 4 09 this along with and the larger range of end values 12 4 to 2 7 of the chalcopyrites than for the mesozoic granites and neoproterozoic granite therein 8 6 to 6 2 suggest that the ore forming fluids cannot be attributed to the mesozoic granites alone the local cu enriched neoproterozoic shuangqiaoshan group rocks should have contributed to the mineralization the low bulk rocks fe3 fe2 ratios 0 02 1 00 average 0 22 fe2 enriched biotite compositions fe2 fe3 5 64 143 average 22 combined with the low ce4 ce3 ratios 3 509 average 142 negative eu anomalies eu eu 0 05 0 56 average 0 25 and low fo2 fmq 3 4 1 9 fmq 1 5 1 7 for the mesozoic magmatic zircons suggest that the granites in the shimensi deposit are relatively reduced the low oxygen fugacity below nno of granites is favorable for significant tungsten mineralization accompanying by minor cu mineralization

ore genesis of the zhuxi supergiant w cu skarn polymetallic deposit south china evidence from scheelite geochemistry abstract scheelite is the main ore mineral in skarn type tungsten deposits which can be used to track the ore forming processes and sources the zhuxi w cu deposit 3 44 mt wo3 at 0 54 and 0 10 mt cu at 0 57 located in the northern part of the jiangnan orogen is one of the largest tungsten deposits in the world skarn and orebodies occur mainly within the contact zone between the mesozoic highly fractionated intrusions and carboniferous carbonate sediments huanglong and chuanshan formations our data reveal that the rees of scheelite are mainly controlled by the substitution mechanism 3ca2 2ree3 ca scheelites from the zhuxi deposit show negative eu anomalies in the prograde skarn stage but positive eu anomalies in the retrograde skarn stage in the chondrite normalized ree patterns variation of eu anomalies recorded the ore forming processes the negative eu anomalies were inherited from the mesozoic granites and the positive ones formed under more reduced redox conditions the decrease of mo concentrations along with increase of eu and ce of scheelite from prograde to retrograde skarn stage support a temporal decrease in oxygen fugacity of the mineralization fluids the scheelites from the zhuxi deposit are characterized by low end t values 10 1 to 7 0 and high initial 87sr 86sr ratios 0 71231 0 72371 which are different from the scheelites hosted in vein type au w deposits contributed mainly by mantle the nd sr isotopes of scheelites are consistent with the results of the three mesozoic granites indicating their genetic relationship however the scheelites show variable nb ta compositions which straddle between the values of mesozoic granites and the country rock of shuangqiaoshan group meta sedimentary rocks indicating the shuangqiaoshan group also has contributed to mineralization this is different from a commonly accepted model that the ore forming fluids and metals were exsolved exclusively from the granite plutons

granite related tin metallogenic events and key controlling factors in peninsular malaysia southeast asia new insights from cassiterite u pb dating and zircon geochemistry

multistage deformation of au quartz veins laurieras french massif central evidence for late gold introduction from microstructural isotopic and fluid inclusion studies abstract the relative chronology of fluid migration quartz and au deposition in a silicified fault from the main au district laurieras st yrieix district from northern french massif central has been determined from microstructural fluid inclusion isotopic and ore mineral evidences three main stages of fluid circulation microfracturing and quartz crystallization and ore deposition were distinguished on the basis of textural relationships and the pressure temperature and composition of the palaeo fluids 1 a series of early fluid events was responsible for the localized drainage of retrograde metamorphic fluids along the main fault and the subsequent sealing by milky and microcrystalline quartz preceeded the main au ore stages early fluids were aqueous carbonic trapped under lithostatic to sublithostatic pressures at temperatures in the range 350 500 c subsequently several types of microstructures were developed in the early quartz matrix 2 ns microfractures filled by clear quartz arsenopyrite and boulangerite i contain significant refractory gold concentrations clear quartz formed from aqueous carbonic fluids of lower densities than those of the earlier fluids significant pressure drops down to pressures around 55 mpa were responsible for a local immiscibility of the aqueous carbonic fluids at temperatures of 340 20 c 3 the main ore stage is characterized by the formation of dense sets of sub vertical ew microfractures healed fluid inclusion planes in quartz and filled by ore minerals native gold galena and boulangerite ii when they crosscut earlier sulfides the fluids are aqueous with low and decreasing salinity and probable trapping temperatures around 230 c isotopic data obtained on microfissured quartz indicate these dilute aqueous fluids may be considered as meteoric waters that deeply infiltrated the crust late microfissuring of a mesothermal quartz vein originally barren only with pyrite and arsenopyrite appears to be the main factor controlling gold enrichment it can be related to late hercynian deformational stages disconnected from the early fault formation and silicification these late stages which affected the hercynian basement during its uplift are of critical importance for the formation of au ores we concluded that this type of au ore formed under rather shallow conditions is distinct from those generally described in most mesothermal au veins