the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

fluid inclusion and h o isotope evidence for immiscibility during mineralization of the yinan au cu fe deposit shandong china abstract the fluid inclusion and h o isotope studies have provided the evidences for the source of ore forming fluids and helped to recognize two types of immiscibility and their relationships with mineralization hydrogen and oxygen isotopic geochemistry shows that the earlier ore forming fluids during the anhydrous skarn stage i and the hydrous skarn magnetite stage ii were mainly derived from magmatic water while the later fluids during the quartz sulfide stage iii and the carbonate stage iv were mainly from magmatic water mixed with small amounts of meteoric water various types of fluid inclusions including abundant vapor or liquid rich two phase aqueous inclusions daughter minerals bearing multiphase inclusions co2 h2o inclusions and less abundant liquid inclusions vapor inclusions and melt inclusions are present in hydrothermal minerals of different stages the liquid vapor fluid inclusions are mainly composed of h2o with significant amounts of co2 and a small amount of ch4 in the opaque bearing fluid inclusions the hematite and fahlore tetrahedrite were identified the homogenization temperature of the aqueous fluid inclusions decreases from stage i 520 410 c through stage ii 430 340 c and iii 250 190 c to stage iv 190 130 c the coexistence of melt inclusions with simultaneously trapped vapor or liquid rich two phase aqueous inclusions and daughter minerals bearing multiphase inclusions in garnet diopside and epidote of stages i and ii suggests an immiscibility between silicate melt and hydrothermal fluid it is an effective mechanism on scavenging and transporting ore forming components from magmas the aqueous fluid inclusions with various vapor liquid ratios from 65 commonly coexist with simultaneously trapped liquid inclusions vapor inclusions daughter minerals bearing multiphase inclusions and co2 h2o inclusions in the quartz of stage iii and the different kinds of the fluid inclusions have similar homogenization temperatures this indicates that the boiling another kind of immiscibility widely took place during stage iii it resulted in the precipitation and enrichment of gold copper and iron

synthetic fluid inclusions in natural quartz iii determination of phase equilibrium properties in the system h2o nacl to 1000 c and 1500 bars phase equilibria in the system h2o nacl have been determined to 1000 c and 1500 bars using synthetic fluid inclusions formed by healing fractures in inclusion free brazilian quartz in the presence of the two coexisting immiscible h2o nacl fluids at various temperatures and pressures petrographic and microthermometric analyses indicate that the inclusions trapped one or the other of the two fluids present or mixtures of the two salinities of the two coexisting phases were obtained from heating and freezing studies on those inclusions which trapped only a single homogeneous fluid phase results of the present study are consistent with previously published data on the h2o nacl system at lower temperatures and pressures and indicate that the two phase field extends well into the p t range of most shallow magmatic hydrothermal activity as a consequence chloride brines exsolved from many epizonal plutons during the process of second boiling should immediately separate into a high salinity liquid phase and a lower salinity vapor phase and produce coexisting halite bearing and vapor rich fluid inclusions this observation is consistent with results of numerous fluid inclusion studies of ore deposits associated with shallow intrusions particularly the porphyry copper deposits in which halite bearing and coexisting vapor rich inclusions are commonly associated with the earliest stages of magmatic hydrothermal activity

kiruna type deposits their origin and relationship to intermediate subvolcanic plutons in the great bear magmatic zone northwest canada magnetite apatite actinolite rocks similar to those at kiruna sweden and the st francois mountains missouri are associated with seven epizonal plutons that intrude andesitic stratovolcanoes of a broadly folded early proterozoic continental magmatic arc located in the northwestern canadian shield the plutons mainly medium grained quartz monzonite monzodiorite diorite iugs sheets and laccoliths 5 to 25 km in diameter are spatially temporally and compositionally related to host andesitic stratovolcanoes they were emplaced at 2 to 3 km depth are compositionally heterogeneous metasomatically altered and had plagioclase as the liquidus phase in addition they have kilometer wide alteration halos comprising an inner zone of nearly complete wall rock albitization an intermediate zone of magnetite apatite actinolite veins pods breccias and wall rock replacement and an outer zone of disseminated sulfides one pluton balachey has a halo that is more or less completely outside the body but another rainy lake has a halo that is partly superimposed over it separation of iron phosphate and silicate melts by liquid immiscibility is not supported by 1 the gradual replacement of plagioclase by chessboard albite toward the roof of the rainy lake pluton 2 the chemical trends in the rainy lake intrusion 3 the mineralogical zoning low temperature mineralogy and replacement textures of the magnetite apatite actinolite and 4 the relationship of the magnetite apatite actinolite veins and bodies to the plutons however all available data are compatible with a deuteric origin it is concluded that high temperature low initial water content and shallow level emplacement by intermediate plutons are necessary for the development of kiruna type deposits

geology geochronology fluid inclusion and h o isotope geochemistry of the luoboling porphyry cu mo deposit zijinshan orefield fujian province china abstract the luoboling cu mo deposit in the zijinshan orefield fujian province southeastern china is a large porphyry deposit hosted by the sifang granodiorite and the luoboling granodiorite porphyry the largest cu mo orebody is saddle shaped with various types of hydrothermal veinlets intensive hydrothermal alteration in the deposit is characterized by outward zoning from potassic overprinted by phyllic alteration to phyllic and alunite dickite alteration based on the mineral assemblages and crosscutting relationships of veins the ore forming process can be divided into three stages namely an early stage k feldspar quartz magnetite molybdenite veins associated with potassic alteration a middle stage quartz molybdenite chalcopyrite pyrite veins in phyllic zone and a late stage quartz gypsum veins in the phyllic and alunite dickite alteration zones six molybdenite separates yield a re os isochron age 104 6 1 0 ma which is identical to the age of emplacement of the sifang and luoboling granodiorite porphyries three types of fluid inclusions fis were observed at the luoboling deposit 1 nacl h 2 o aqueous 2 daughter mineral bearing and 3 co 2 h 2 o fluid inclusions fis of the early and middle stages are predominantly vapor rich aqueous and daughter mineral bearing inclusions together with minor co 2 rich and liquid rich aqueous inclusions whereas the late stage minerals only contain liquid rich aqueous inclusions homogenization temperatures and salinities of fis trapped in the early stage minerals range from 420 to 540 c and 0 4 to 62 9 wt nacl equiv respectively fis of the middle stage yield homogenization temperatures of 340 to 480 c and salinities of 0 5 to 56 0 wt nacl equiv co 2 content and the oxygen fugacity indicated by daughter minerals of fis trapped in middle stage minerals are lower than those in the early stage the liquid rich aqueous inclusions of the late stage homogenize at temperatures of 140 to 280 c yielding salinities of 0 4 to 8 4 wt nacl equiv the minimum estimated pressures of the three stages are 30 70 mpa 10 40 mpa and 1 10 mpa respectively corresponding to minimum ore forming depths of 1 2 8 km fluids trapped in early middle and late stages yield d values of 67 to 54 54 to 70 and 62 and 18 o values of 5 4 to 6 7 2 8 to 4 2 and 2 1 respectively fluid boiling which resulted in the formation of stockworks and the precipitation of sulfides occurred in the early and middle stages the fluids subsequently evolved into a low temperature low salinity system in the late stage along with an input of meteoric water the luoboling porphyry cu mo system was developed in a transition from continental arc to back arc extension region which was related to the westward subduction of the paleo pacific plate beneath the huanan orogen

a practical suggestion regarding the use of scandinavian and russian palaeomagnetic data to determine the palaeo position of baltica in ordovician time abstract there is a discrepancy between ordovician palaeomagnetic pole positions from the russian plate and from scandinavia however it is clear from faunal and tectonic evidence that the two regions were parts of a single continent through palaeozoic time data from both regions are few in number and some are controversial in nature therefore it is suggested that the palaeomagnetic discrepancy merely reflects the incomplete nature of the palaeomagnetic dataset for baltica it is notable that palaeolatitudes for baltica derived from the scandinavian dataset are confirmed by other lines of geological evidence it is therefore concluded that the scandinavian dataset offers the most reliable palaeomagnetic controls on the lower palaeozoic drift history of baltica placing it in mid southerly latitudes in early ordovician time rotated clockwise through at least 50 relative to its present orientation

origin and evolution of hydrothermal fluids in the taochong iron deposit middle lower yangtze valley eastern china evidence from microthermometric and stable isotope analyses of fluid inclusions abstract the middle lower yangtze river valley is one of the most important metallogenic belts in china hosting numerous cu fe au mo deposits the taochong deposit is located in the northern part of the fanchang iron ore district of the middle lower yangtze river metallogenic belt the fe orebody is hosted by middle carboniferous to lower permian limestones skarns and fe orebodies occur as tabular bodies along interlayer gliding faults at some distance from the inferred granitic intrusions field evidence and petrographic observations indicate that the three stages of hydrothermal activity the skarn iron oxide main mineralization stage and carbonate stages all contributed to the formation of the taochong iron deposit the skarn stage is characterized by the formation of garnet and pyroxene with high temperature hypersaline hydrothermal fluids with isotopic compositions similar to those of typical magmatic fluids these fluids were probably generated by the separation of brine from a silicate melt instead of the product of aqueous fluid immiscibility the iron oxide stage coincides with the replacement of garnet and pyroxene by actinolite chlorite quartz calcite and hematite the hydrothermal fluids at this stage are represented by saline fluid inclusions that coexist with vapor rich inclusions with anomalously low d values 66 to 94 the decrease in ore fluid 18 o water with time and decreasing depth is consistent with the decreases in fluid salinity and temperature the fluid d values also show a decreasing trend with decreasing depth both fluid inclusion and stable isotopic data suggest that the ore fluid during the main period of mineralization was evolved by the boiling of various mixtures of magmatic brine and meteoric water this process was probably induced by a drop in pressure from lithostatic to hydrostatic the carbonate stage is represented by calcite veins that cut across the skarn and orebody locally producing a dense stockwork this observation indicates the veins formed during the waning stages of hydrothermal activity the fluids from this stage are mainly represented by a variety of low salinity fluid inclusions as well as fewer high salinity inclusions these particular fluids have the lowest 18 o water values 2 2 to 0 4 and a wide of range of d values 40 to 81 which indicate that they were originated from a mixture of residual fluids from the oxide stage various amounts of meteoric water and possibly condensed vapor low temperature boiling probably occurred during this stage we also discuss the reasons behind the anomalously low d values in fluid inclusion water extracted by thermal decrepitation from quartz at high temperatures and suggest that calcite data provide a possible benchmark for adjusting low d values found in quartz intergrown with calcite

origin and evolution of ore forming fluids in the hemushan magnetite apatite deposit anhui province eastern china and their metallogenic significance abstract the middle lower yangtze river metallogenic belt in the northern yangtze block is one of the most important economic mineral districts in china the hemushan deposit is a medium class fe deposit located in the southern part of the ningwu iron ore district of the middle lower yangtze river metallogenic belt the fe orebodies are mainly hosted in the contact zone between diorite and triassic marble the actinolite phlogopite apatite magnetite ore shows metasomatic filling textures and disseminated mesh vein structures based on evidences and petrographic observations the ore forming process can be divided into three distinct periods the early metallogenic period albite diopside stage the middle metallogenic period magnetite stage and hematite stage and the late metallogenic period quartz pyrite stage and carbonate stage fluid inclusion studies show four types of inclusions type i daughter mineral bearing three phase inclusions l v s type ii vapor rich two phase inclusions l v type iii liquid rich two phase inclusions l v and minor type iv liquid phase inclusions l apatites from the magnetite stage contain type i type ii and type iii inclusions anhydrites from the hematite stage mainly contain abundant type ii inclusions and relatively less type i inclusions quartz and calcite from the late metallogenic stage are mainly characterized by type iii inclusions laser raman spectroscopy and microthermometry of fluid inclusions show that the ore forming fluids broadly correspond to unsaturated nacl h2o system from the magnetite stage to the carbonate stage the ore forming fluids evolved from moderate high temperature average 414 c moderate salinity average 25 01 wt nacl equiv conditions to low temperature average 168 c low salinity average 6 18 wt nacl equiv conditions hydrogen and oxygen isotopic studies indicate that the ore forming fluid during the early stage of middle metallogenic period was mainly of magmatic water and mixing of the ore fluids with meteoric water took place during the late phase during this evolution water rock interaction and boiling and mixing of the ore fluids with meteoric water occurred the boiling of fluids was a potential mechanism for the formation of magnetite

the source scanning algorithm mapping the distribution of seismic sources in time and space summary we introduce a new method which we call the source scanning algorithm ssa for imaging the distribution of seismic sources in both time and space using trial locations and origin times the method calculates the brightness function by summing the absolute amplitudes observed at all stations at their respective predicted arrival times the spatial and temporal distribution of sources is then identified by a systematic search throughout the model space and time for the maximum brightness the greatest advantages of this method are that 1 it exploits waveform information both arrival times and relative amplitudes without the need to calculate highfrequency synthetic seismograms and 2 it requires neither pre assembled phase picking data nor any a priori assumptions about the source geometry a series of tests using synthetic data have shown that this method is robust and can faithfully recover the input source configuration to within 1 grid interval finally we demonstrate the value of the algorithm by locating a typical tremor event with emergent waveforms that occurred during the recent episodic tremor and slip ets sequence in the northern cascadia subduction zone

review of geology alteration and origin of iron oxide apatite deposits in the cretaceous ningwu basin lower yangtze river valley eastern china implications for ore genesis and geodynamic setting abstract in the cretaceous ningwu volcano sedimentary basin in the yangtze river valley metallogenic belt eastern china there are three areas with a dense distribution of magnetite or hematite deposits the meishan deposit in the north washan nanshan and taocun deposits in the center and the zhongjiu and gushan deposits in the south the mineralization in the ningwu basin is associated mainly with subvolcanic intrusions consisting of gabbro diorite porphyry and or gabbro diorite alteration zoning of these deposits is pronounced and includes 1 an upper light colored zone of argillic kaolinite silica carbonate and pyritic alteration 2 a middle dark colored zone of diopside fluorapatite magnetite phlogopite and garnet with fluorapatite magnetite 3 a lower light colored zone of extensive albitic alteration however at the gushan iron deposit the lower light colored zone and the middle dark colored zone are absent whereas the principal alteration is represented by silicification kaolinization and carbonatization the iron oxide apatite deposits in the ningwu basin are typically magmatic metasomatic origin and are similar to the kiruna type deposits in scandinavia particularly with respect to mineral assemblages fabric and structure of the iron ores occurrence of the orebodies and wall rock alteration the iron oxide apatite deposits of the ningwu basin contain magnetite and or hematite with diopside or actinolite and apatite gangue they were formed in a rift or extensional environment and the mineralization is associated with alkaline magmatism the time interval between magmatism and related mineralization is very short

geology and geochronology of magnetite apatite deposits in the ning wu volcanic basin eastern china the ning wu volcanic basin is an important part of the middle lower yangtze river valley metallogenic belt in eastern china where magnetite apatite deposits are common these magnetite apatite deposits can be classified into two types the first type includes the washan taocun heshangqiao and dongshan deposits which are hosted in diorite porphyry and adjacent volcanic rocks the second type includes gushan baixiangshan and hemushan deposits developed at the contact between gabbro diorite and sedimentary rocks we used 40ar 39ar dating on phlogopite and u pb la icp ms dating of zircon in ore related diorite porphyry and gabbro diorite to determine the timing of iron mineralization in the basin the ages of the magnetite apatite deposits such as washan taocun heshangqiao gushan baixiangshan hemushan deposits are from 130 ma to 131 ma thus the magnetite apatite deposits in the ning wu volcanic basin all formed at about 130 ma later than the skarn and porphyry cu au deposits in the adjacent fault uplift areas such as edongnan jiu rui anqing guichi and tongling clusters that are between 146 ma and 135 ma based on available petrological and geochemical data the magnetite apatite deposits in the ning wu volcanic basin are interpreted to have formed under regional lithospheric extension and thinning and ore forming elements were derived from basaltic melts sourced from enriched lithospheric mantle and the crust

paleomagnetics of ringerike old red sandstone and related rocks southern norway implications for pre carboniferous separation of baltica and british terranes abstract paleomagnetic study of two stratigraphic sections of the upper silurian lower devonian ringerike sandstone oslo area norway indicate a straightforward multicomponent nrm for these rocks a lower temperature magnetization component gives a southwest and up reversed polarity in situ direction yields a negative fold test i e post folding at the 99 confidence level and is nearly identical to directions obtained from overlying permo carboniferous lavas a high temperature magnetization component exhibits both normal and reversed polarity directions passes a fold test at the 95 confidence level and is supported by a baked contact test which indicates a pre intrusion age of magnetization this characteristic high temperature component was successfully isolated in 79 samples from 19 sites within the ringerike succession results indicate a tilt corrected characteristic magnetic direction of declination 26 inclination 16 which is consistent with earlier work this direction corresponds to a time integrated paleopole position of 19 n latitude 164 longitude d p 4 8 d m 9 3 when compared to previous results from rocks of similar age from the british isles an approximately 20 latitudinal displacement between britain and baltica during late silurian early devonian time is suggested

molybdenite re os and albite 40ar 39ar dating of cu au mo and magnetite porphyry systems in the yangtze river valley and metallogenic implications abstract the area of the middle lower yangtze river valley eastern china extending from wuhan hubei province to western zhenjiang jiangsu province hosts an important belt of cu au mo and fe deposits there are two styles of mineralization i e skarn porphyry stratabound cu au mo fe deposits and magnetite porphyry deposits in several nne trending cretaceous fault bound volcanic basins the origin of both deposit systems is much debated we dated 11 molybdenite samples from five skarn porphyry cu au mo deposits and 5 molybdenite samples from the datuanshan stratabound cu au mo deposit by icp ms re os isotope analysis nine samples from the same set were additionally analyzed by ntims on re os results from the two methods are almost identical the re os model ages of 16 molybdenite samples range from 134 7 2 3 to 143 7 1 6 ma 2 the model ages of the five samples from the datuanshan stratabound deposit vary from 138 0 3 2 to 140 8 2 0 ma with a mean of 139 3 2 6 ma their isochron age is 139 1 2 7 ma with an initial os ratio of 0 7 8 1 mswd 0 29 these data indicate that the porphyry skarn systems and the stratabound deposits have the same age and suggest an origin within the same metallogenic system albite 40 ar 39 ar dating of the magnetite porphyry deposits indicates that they formed at 123 to 125 ma i e 10 20 ma later both mineralization styles characterize transitional geodynamic regimes i e the period around 140 ma when the main ns trending compressional regime changed to an ew trending lithospheric extensional regime and the period of 125 115 ma of dramatic ew trending lithospheric extension

optimizing multi station earthquake template matching through re examination of the youngstown ohio sequence abstract a series of earthquakes in 2011 near youngstown oh has been a focal point for discussions of seismicity induced by a nearby wastewater disposal well utilizing an efficient waveform template matching procedure the optimal correlation template to study the youngstown sequence was identified by varying parameters such as the stations utilized frequency passband and seismogram length a catalog composed of 566 events was identified between january 2011 and february 2014 double difference relocation refines seismicity to a 800 m linear streak from the northstar 1 injection well to the wsw along the same strike as the fault plane of the largest event calculated gutenberg richter b values are consistent with trends observed in other regions with seismicity induced by fluid injection

raman microspectrometry of fluid inclusions abstract for many kinds of fluid inclusions the coupling of microthermometry and raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions a review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation analytical conditions and methodology of the application of raman microspectrometry to gaseous aqueous and hydrocarbon inclusions and their daughter minerals

complex precambrian crustal evolution beneath the northeastern yangtze craton reflected by zircons from mesozoic volcanic rocks of the fanchang basin anhui province abstract our knowledge of the precambrian accretion and reworking history of deep crust beneath the northeastern yangtze craton is still sparse zircons from volcanic rocks can not only give accurate crystallization ages for zircons within the host magmas but also provide unique information on the history of deep crustal rocks sampled during magma ascent in situ u pb ages and hf isotopes were analyzed on zircons from two trachyandesites from the late mesozoic zhongfencun and kedoushan formations in the fanchang basin anhui province the zircons exhibit relatively complex internal structures four zircons in the zhongfencun trachyandesite yield a lower intercept 206 pb 238 u age of 133 0 3 2 ma with hf model ages of 2 8 2 4 ga t crust and significantly negative hf t 25 15 to 18 72 demonstrating that this lava formed in early cretaceous time zircons in the kedoushan biotite trachyandesite yield a 206 pb 238 u age of 126 1 ma as well as negative but relatively high hf t values up to 4 34 revealing it formed roughly coeval with the cretaceous a type granites and bimodal magmatism in this region more significantly u pb ages and hf isotopes for proterozoic zircon xenocrysts in the fanchang volcanic rocks reveal that the northeastern yangtze deep crust probably contains unexposed archean e g 3 4 2 9 ga and 2 8 2 5 ga components rarely identified from the outcrops in this area and has undergone complex evolutional history including the addition of juvenile mantle derived materials at 3 4 2 9 ga ca 2 65 ga and ca 0 8 ga and reworking of the precambrian crust at ca 2 0 1 8 ga ca 0 8 ga and 133 126 ma the history of the continental crust s accretion and reworking of the northeastern yangtze craton may not fully coincide with the major episodes of crustal evolution in the wider yangtze craton especially during the archean to paleoproterozoic periods

magmatic hydrothermal albite actinolite apatite rich rocks from the cloncurry district nw queensland australia abstract albite quartz actinolite apatite rich rocks with accessory titanite form a carapace that caps a small dome like intrusion of roxmere pluton and provide evidence of the accumulation and release of magmatic fluids that may have contributed to regionally extensive na ca alteration in the proterozoic cloncurry district australia the roxmere pluton was emplaced after the peak amphibolite facies metamorphism and into psammitic metasedimentary rocks that are stratigraphically younger and overlie the calc silicate rich mary kathleen group na ca hydrothermal assemblages closely spatially related to the roxmere pluton suggest that na ca alteration in this case is inconsistent with excepted up temperature metamorphic fluid circulation models the carapace rocks comprise two variants aplite and pegmatite both of which were affected by alteration and brecciation aplitic material predominates and the carapace has a brecciated top and a distinct textural zonation from an aplite rich pegmatite poor base to a relatively aplite poor pegmatite rich top this zonation is interpreted to represent the progressive accumulation of volatile phases toward the top of the carapace which culminated in fluid overpressuring and brecciation of the granitoid stock the convoluted and ptygmatic habit of the aplitic and pegmatitic material within the carapace is similar in nature to the comb quartz unidirectional solidification textures that are developed in the roof zones of some porphyry stocks these complex textures are interpreted to have formed from a single phase of fluid saturation the roxmere pluton or a deeper equivalent has a na mg and ca rich composition and a clinopyroxene amphibole rich mineralogy that is consistent with the formation of the contained albite actinolite apatite rich phases however the source of the rocks within the carapace is equivocal given that their contact relationships are obscured the 18 o composition of minerals within the carapace has the following ranges albite 7 1 8 7 actinolite 8 0 8 5 and quartz 8 9 11 4 albite and quartz 18 o equilibria suggest that these minerals in the pegmatitic and aplitic components formed at temperatures of 510 c to 540 c the calculated 18 o composition of a fluid in equilibrium with these minerals 6 0 to 8 0 at temperatures between 450 c and 550 c is consistent with a magmatic origin these estimated temperatures and 18 o fluid composition are comparable to estimates for regional na ca alteration in contrast d analysis of actinolite 136 to 150 within the carapace demonstrates that these fluids have a significantly lower d signature compared to na ca alteration assemblages associated with regional alteration 70 to 90 the low values in the carapace could either be interpreted as being produced from meteoric fluids or from degassed magmatic fluids although a meteoric fluid model is deemed improbable as meteoric fluids in the district have a documented d composition of ca 0 0 as a consequence an open system degassed magmatic hydrothermal fluid origin is considered to be the most plausible explanation for the low isotopic signatures and is also consistent with the complex textural relationships described within the carapace

palaeomagnetism of the kvanishesten and hornelen old red sandstone basins western norway summary folded old red sandstone in western norway records at least four magnetization events which testify to a prolonged thermochemical history spanning mid palaeozoic to mesozoic time sediments in the hornelen and kvamshesten basins carry a post tectonic remanence which is correlated with the late palaeozoic kiaman superchron many of the overprints carried by mid and lower palaeozoic rocks in norway are reported to be significantly younger than this and might be related to mesozoic fault activity in the area a second overprint identified locally in the kvamshesten basin adjacent to one of the present margin faults supports the assertion a further remanence the integrity of which has not been previously recognized is probably devonian in age its precise age in relation to late caledonian folding is uncertain and therefore various geological models based on the data are offered the simplest of these is that the remanence is post tectonic and that britain and norway attained their present relative configuration in devonian times nevertheless much of the recently obtained middle palaeozoic palaeomagnetic data for norway perpetuate the longstanding discrepancy between norwegian and british apparent polar wander apw uncertainty in time calibration of the paths cannot be the sole explanation for this the difference might be founded in post mid devonian tectonism in norway or perhaps more likely in our understanding of the detailed apw of the relevant continents

the lower changjiang yangzi yangtze river metallogenic belt east central china intrusion and wall rock hosted cu fe au mo zn pb ag deposits abstract the lower valley of changjiang from wuhan of the hubei province in the west to zhenjiang of the jiangsu province in the east contains more than 200 polymetallic cu fe au mo zn pb ag deposits and is one of the most important metallogenic belts in china this metallogenic belt situated at the northern margin of the yangzi craton and bordered by the dabieshan ultrahigh pressure metamorphic belt to the north consists mainly of cambrian triassic marine clastic sedimentary rocks and carbonate and evaporite rocks which overlay a precambrian basement and are intruded by yanshanian 205 to 64 ma granitoid intrusions and subvolcanic complexes repeated tectonism from late proterozoic to triassic resulted in extensively developed networks of faults and folds involving the cambrian triassic sedimentary strata and the precambrian basement the yanshanian granitoid intrusions and subvolcanic complexes in the lower changjiang metallogenic belt are characterized by whole rock 18 o of 8 to 10 initial 87 sr 86 sr of 0 704 to 0 708 and ndt from 10 to 17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials also the yanshanian granitoids exhibit eastward younging and increase in alkalinity i e from older calc alkaline in the west to younger subalkaline alkaline in the east which are related to oblique collision between the yangzi and sino korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes most polymetallic deposits in the lower changjiang metallogenic belt are clustered in seven districts where the yanshanian magmatism is particularly extensive from west to east edong jiurui anqing guichi luzhong tongling ningwu and ningzhen mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits orebodies in yanshanian granitoid intrusions skarn orebodies at the contact zones between the yanshanian intrusions and late paleozoic early mesozoic sedimentary rocks and stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata the most important host sedimentary strata are the middle carboniferous huanglong formation lower permian and lower middle triassic carbonate and evaporite rocks the intrusion hosted and skarn orebodies exhibit well developed zonation in alteration assemblages metal contents and isotopic compositions within individual deposits and apparently formed from hydrothermal activities related to the yanshanian magmatism the stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano sedimentary exhalative processes in shallow marine environments however extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization on the basis of geological relationships and isotope geochemical characteristics we propose a carbonate hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies this model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the yanshanian intrusions with carbonate and evaporite wall rocks mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion hosted orebodies the stratabound massive sulfide deposits of the lower changjiang metallogenic belt share many features with the well studied high temperature carbonate hosted replacement deposits of northern mexico and western united states particularly with respect to association with small shallow granitoid complexes structural and stratigraphic controls on mineralization alteration assemblages geometry of orebodies metal association metal zonation and isotopic systematics

fluid inclusion and stable isotope study of the esfordi apatite magnetite deposit central iran a reply sir we are pleased that our recent paper in economic geology jami et al 2007 presenting the geologic setting a description of the mineralization fluid inclusion and o isotope analyses of the esfordi p fe oxide deposit in central iran has been of interest to aftabi and his colleagues aftabi et al 2009 the opportunity to discuss further some aspects of our paper is appreciated including support for a hydrothermal dominated depositional model for esfordi aftabi et al 2009 focus their comments on the question of the affinity of the esfordi p fe oxide deposit in particular they argue that esfordi and by inference other diverse fe oxide deposits within the bafq district of central iran should be considered rapitan type banded iron formations i e bif klein 2005 rather than kiruna type hitzman 2000 in discussing our results and conclusions in the light of previous work particularly forster and jafarzadeh 1994 aftabi et al 2009 have misconstrued our interpretation of some of the textural and isotopic data as providing support for an orthomagmatic model for the esfordi p fe oxide deposit based on the structure relationships between mineralization and host rocks fluid inclusion and isotopic data we concluded that esfordi exhibits strong evidence of hydrothermal origin though we did not preclude some component of precursor orthomagmatic processes in formation of the p fe mineralisation it is noted that some examples of the kiruna end member of the continuum of fe oxide deposits discussed by hitzman 2000 are controversial particularly in regard to their evolution sillitoe and burrows 2002 henriquez et al 2003 we have shown that esfordi has a number of features typical of the kiruna type deposits and does not exhibit features consistent with an affinity to rapitan type fe oxide deposits this evidence will be discussed briefly with further data

the palaeogeographic evolution of southern britain during early palaeozoic times a reconciliation of palaeomagnetic and biogeographic evidence abstract palaeomagnetic biogeographic and palaeoclimatic evidence together suggest that in the early ordovician southern britain lay off the west african margin of gondwana at around 60 s the combination of these disciplines reduces latitude uncertainties to around 5 to 10 degrees rifting of avalonia from gondwana was followed during most of the ordovician by northward drift as avalonia and baltica converged with subduction of tornquist sea crust both continents had similar moderate northward drift rates 3 6 cm yr so their convergence probably had a considerable longitudinal component silurian and early devonian data indicate that northward drift of avalonia and baltica continued after their collision and that southern britain reached a latitude of around 20 s by c 400 ma

gushan magnetite apatite deposit in the ningwu basin lower yangtze river valley se china hydrothermal or kiruna type abstract the gushan deposit is one of the typical magnetite apatite deposits associated with dioritic porphyries in the lower yangtze river valley belt of the eastern yangtze craton the origin of this deposit is still uncertain and remains a controversial issue divergent opinions are centered on whether the iron deposits are magmatic or hydrothermal in origin however our field observations and mineralogical studies combined with previous published petrological and geochemical features strongly suggest that the main ore bodies in the gushan magnetite apatite deposit are magmatic specific evidence includes the existence of gas bubbles tubes and miarolitic and amygdaloidal structures melt flow banding structure and the presence of ore breccia new electron microprobe analyses of the pyroxene phenocrysts of the dioritic porphyry genetically associated with the gushan magnetite apatite deposit show that the fe contents in the evolving magma dramatically decrease and then gradually increase because there is no evidence of mafic magma recharge this scenario decreasing fe could be plausibly interpreted by fe rich melts separated from fe poor silicate melts i e liquid immiscibility was triggered by minor addition of phosphorus by crustal contamination the occurrence of massive iron ore bodies can be satisfactorily explained by the immiscible fe rich melt with enormous volatile contents was driven to the top of the magma chamber due to the low density the hot and volatile rich iron ore magma was injected along fractures and spaces between the dioritic intrusions and wall rocks and led to an explosion near the surface resulting in the immediate fragmentation of the roof of the intrusion and wall rocks forming brecciated ores moreover other types of ores can be considered as a result of post magmatic hydrothermal activities our proposed metallogenic model involving the kiruna type mineralization is consistent with the observed phenomenon in the gushan deposit

palaeomagnetism of the lower ordovician orthoceras limestone st petersburg and a revised drift history for baltica in the early palaeozoic summary palaeomagnetic investigation of lower ordovician limestone in the vicinity of st petersburg yields a pole position at latitude 34 7 n longitude 59 1 e dp dm 5 7 6 4 a probable primary remanence origin is supported by the presence of a field reversal the limestone carries one other remanent magnetization component associated with a mesozoic remagnetization event an apparent polar wander path is compiled for baltica including the new result ranging in age from vendian to cretaceous ages of the published lower to midpalaeozoic palaeomagnetic pole positions are adjusted in accordance with the timescale of tucker mckerrow 1995 the new arenig result is the oldest of a series of ordovician and silurian palaeomagnetic pole positions from limestones in the baltic region there are no data to constrain apparent polar wander for the tremadoc cambrian and latest vendian if the fen complex results previously taken to be vendian in age c 565 ma are reinterpreted as permian remagnetizations an early ordovician cambrian vendian cusp in the polar wander path for baltica is eliminated the apparent polar wander curve might then traverse directly from poles for vendian dykes on the kola peninsula c 580 ma towards our new arenig pole c 480 ma the consequence of this change in terms of the motion of baltica in cambrian times is to reduce significantly a rotational component of movement the new arenig pole extends knowledge of ordovician apparent polar wander an increment back in time and confirms the palaeolatitude and orientation of baltica in some published palaeogeographies exclusion of the fen complex result places baltica in mid to high southerly latitudes at the dawn of the palaeozoic consistent with faunal and sedimentological evidence but at variance with some earlier palaeomagnetic reconstructions

geology alteration age and origin of iron oxide apatite deposits in upper eocene quartz monzonite zanjan district nw iran iron oxide apatite deposits are present in upper eocene pyroxene quartz monzonitic rocks of the zanjan district northwestern iran mineralization occurred in five stages 1 deposition of disseminated magnetite and apatite in the host rock 2 mineralization of massive and banded magnetite ores in veins and stockwork associated with minor brecciation and calcic alteration of host rocks 3 deposition of sulfide ores together with potassic alteration 4 formation of quartz and carbonate veins and sericite chlorite epidote silica carbonate and tourmaline alteration and 5 supergene alteration and weathering u pb dating of monazite inclusions in the apatite indicates an age of 39 99 0 24 ma which is nearly coeval with the time of emplacement of the host quartz monzonite supporting the genetic connection fluid inclusions in the apatite have homogenization temperatures of about 300 c and oxygen isotopic compositions of the magnetite support precipitation from magmatic fluids late stage quartz resulted from the introduction of a cooler less saline and isotopically depleted fluid the iron oxide apatite deposits in the tarom area of the zanjan district are typical of a magmatic hydrothermal origin and are similar to the kiruna type deposits with respect to mineral assemblages fabric and structure of the iron ores occurrence of the ore bodies and wall rock alteration

a tectono genetic model for porphyry skarn stratabound cu au mo fe and magnetite apatite deposits along the middle lower yangtze river valley eastern china abstract the middle lower yangtze river valley metallogenic belt yrb situated along the northern margin of the yangtze craton is characterized by porphyry skarn stratabound cu au mo fe deposits in the areas of uplift and magnetite apatite deposits in cretaceous fault basins following detailed field investigations and a review of published data we recognize two episodes of magmatism and mineralization in the yrb 1 156 137 ma high k calc alkaline granitoids associated with 148 135 ma porphyry skarn stratabound cu au mo fe deposits and 2 135 123 ma shoshonitic series associated with 134 9 122 9 ma magnetite apatite deposits a type granitoids and associated alkaline volcanic have a small age range from 126 5 to 124 8 ma and are temporally spatially and genetically associated with the second episode the geodynamic history of the yrb did not experience the paleozoic to mesozoic lithospheric thickening that took place in the north china craton this process is inferred to be linked to partial melting of the delaminated lower crust at high pressures resulting in the development of c type adakitic rocks the petrochemical and sr nd isotopic data show that both the shoshonitic series and a type granitoids are quite different from adakites with only some of the k calc alkaline granitoids having adakitic signatures previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono thermal evolution from 150 to 100 ma all data obtained for the middle lower yangtze river region consistently show that the tan lu regional strike slip fault zone initiated at 233 6 to 225 6 ma from the collision between the north china and yangtze cratons and was reactivated at ca 160 ma the tan lu fault was caused by the oblique subduction of the izanagi plate which along the yrb the low angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks the high k calc alkaline granitoids magmas were derived from melting of the subducted slab with some input of crustal material these magmas were emplaced at the intersections between ne and ew trending faults and formed porphyry skarn stratabound cu au mo fe deposits between 156 and 137 ma after 135 ma the subducted plate changed its direction of motion to northeast now running parallel to the eurasian continental margin and leading to large scale continental extension the shoshonitic series and subsequent a type granitoids magmatism and the development of magnetite apatite ores in the yrb took place in both fault basins and ne trending rifts between 135 and 124 ma

pushing the limit of earthquake detection with distributed acoustic sensing and template matching a case study at the brady geothermal field template matching has been widely applied in the detection of earthquakes and other seismic events due to its power in detecting weak signals recent studies using synthetics have shown that application of template matching to large n arrays can potentially detect earthquakes substantially below the noise level here we apply template matching to the distributed acoustic sensing das data recorded in the brady hot springs geothermal field nevada using 5 catalogued events we detect 116 events and find 68 of them well below the noise level we confirm 112 events are true earthquakes by examining the patterns of their sensor to sensor cross correlation sections this demonstrates that the combination of das and template matching has capability to detect microseismicity below the noise level which is unusual for conventional seismic arrays and methods with the updated catalogue we observe a surge of earthquakes during the shutdown of a geothermal power plant nearby in addition the rapid increases in the downhole pressure record coincide with intense swarms of earthquakes these observations show a strong correlation between the seismicity frequencies and the downhole pressure changes finally we investigate several factors that may affect the detection performance and compare different strategies for spatial down sampling in order to provide helpful insights for future large n design and data processing

crustal evolution of fennoscandia palaeomagnetic constraints abstract palaeomagnetic poles from fennoscandia ranging in age from archaean to tertiary are compiled and graded using a modified briden duff classification scale an new filtering technique is applied to select only the most reliable poles for analysis the filtering takes into account the following information 1 1 source block of rock unit 2 2 age of rock 3 3 age of magnetization component 4 4 scatter of palaeomagnetic directions 5 5 information from multicomponent analysis of natural remanent magnetization nrm 6 6 whether the pole considered belongs to a cluster or subcluster of poles 7 7 magnetic polarity and 8 8 the author s original assignment of results data are still insufficient for the drawing of separate apparent polar wander paths apwp for different blocks or cratons of fennoscandia treating fennoscandia as a single plate a new apwp from archaean to permian is constructed from the five previously drawn apwp loops or hairpins only one the jatulian loop 2200 2000 ma disappears in filtering the loops during 1925 1700 ma and during 1100 800 ma ago are linked to svecofennian and sveconorwegian orogenies respectively palaeomagnetic data support the concept that these orogenies took place episodically three distinct orogenic pulses early middle and late can be distinguished in the cluster plots of palaeopoles the drift history of fennoscandia from archaean to permian is presented during most of geological history fennoscandia has occupied low to moderate latitudes and undergone considerable latitudinal shifts and rotations the svecofennian and sveconorwegian orogenies have different kinematic characteristics during the svecofennian orogeny fennoscandia drifted slowly while rotating a large amount in an anticlockwise sense during the sveconorwegian orogeny it drifted rapidly and rotated first clockwise and then anticlockwise the most striking feature in the drift velocity curves is however the pronounced maxima in the latitudinal drift and rotation rates 9 cm yr and 0 8 ma respectively during the late subjotnian jotnian anorogenic magmatism and rifting phase 1450 1250 ma ago possibly reflecting the passage of fennoscandia across a thermal upwelling hotspot at equatorial latitudes the use of palaeomagnetism in delineating and dating movements between blocks is demonstrated with three examples from the polar profile area the northernmost section of the european geotraverse

a new devonian palaeomagnetic pole for the russian platform and baltica and related apparent polar wander summary of published palaeomagnetic data from the russian platform and britain for mid palaeozoic times places an ocean between the two of the order of 2000 km latitudinal width this contradicts geological evidence which favours contiguity between the two continental units by devonian times we propose that this discrepancy can be attributed to the incorrect dating of palaeomagnetic remanence we strove to remedy this situation by conducting a new palaeomagnetic investigation of silurian and devonian sediments in west ukraine ussr latitude 48 7 n longitude 26 e that investigation uncovered a pervasive upper palaeozoic remagnetization corresponding to a palaeomagnetic pole at lat 45 8 s long 348 2 e dpldm 1 6 3 1 n 25 sites reversed polarity a second primary or near primary devonian remanence was identified with pole at lat 3 7 n long 325 5 e dpldm 5 2 8 7 n 25 samples mixed polarity the age determination for this devonian result is based on its dual polarity evidence for a detrital remanent mode and early host mineral phase haematite the new devonian result for the russian platform is conformable with the devonian parts of the british apparent polar wander paths and therefore eliminates the aforementioned discrepancy between palaeomagnetic and geological evidence for the timing of assembly of the old red continent

the relationship of mantle derived fluids to gold metallogenesis in the jiaodong peninsula evidence from d o c s isotope systematics abstract the largest gold district in china is the jiaodong peninsula where three types of gold deposits are recognized quartz vein fracture altered and breccia types the first two developed along a group of ne trending faults and are hosted by granitic intrusions dated at 160 to 150 ma biotite granite and 130 to 126 ma granodiorite and by metamorphic rocks of the precambrian crystalline basement the breccia type gold system is mainly located around the northern margin of the jiaolai cretaceous basin where mineralisation is controlled by both detachment fractures and ne trending faults this study is based on stable isotope determinations from ten gold deposits including linglong jiaojia sanshandao cangshang wang ershan dayigezhuang denggezhuang pengjiakuang fayunkuang and dazhuangzi as well as the linglong jurassic biotite granite guojialing cretaceous granodiorite and archean gneiss the stable isotope systematics reflect the style of the three types of gold deposits but also show that they belong to the same metallogenic system in which the hydrothermal fluids were derived from a mantle fluid reservoir and mixed with crustal fluids the ore forming age is later than both the jurassic biotite granite and cretaceous granodiotite but overlaps with the 121 to 114 ma ages of lamprophyre and diabase dykes the hydrothermal fluids that were responsible for both gold mineralisation and the retrograde alteration of the diabase and lamprophyre dykes are similar and represent a co 2 and potassium rich system this fluid system is interpreted to be the consequence of cretaceous lithospheric thinning asthenospheric upwelling and mantle degassing in eastern china

late mesozoic magmatism of the jiurui mineralization district in the middle lower yangtze river metallogenic belt eastern china precise u pb ages and geodynamic implications abstract the middle lower yangtze river metallogenic belt mlyrmb extending from daye in hubei province in the west to zhenjiang in jiangsu province in the east hosts a number of large polymetallic cu au mo fe zn pb and ag deposits and constitutes one of the most important metallogenic belts in china the cu au mo deposits in the jiurui district are an important component of the mlyrmb in this study we carried out precise and detailed zircon u pb dating for all types of magmatic rocks from the wushan ore deposit in the jiurui district three samples of cu au mo related porphyries from different ore belts at wushan were analyzed and yielded zircon u pb ages of 148 0 1 0 ma 145 4 0 9 ma and 147 3 0 9 ma respectively a series of dykes were emplaced immediately following the cu au mo related porphyries at wushan a dark colored basic dyke which intruded into the granodiorite porphyry at wujia gold deposit near wushan was dated at 144 5 1 2 ma two lamprophyre dykes taken from the north ore belt at wushan underground mining stops were dated at 143 6 0 9 ma and 144 3 0 9 ma respectively a late stage dyke which was also taken from the wushan north ore belt yielded an age of 142 6 1 0 ma and might represent the end of magmatism in the wushan ore deposit these new geochronological data demonstrate that the time range of magmatism in the wushan ore deposit is approximately between 148 ma and 143 ma showing that the magmatic activity at wushan was rapid and intensive the ages of cu au mo related porphyries from other areas in the jiurui district such as the dongleiwan yangjishan and chengmenba ore deposits were also measured and yielded zircon u pb ages of 141 5 1 7 ma 143 4 1 4 ma and 146 6 1 0 ma respectively combined with those previously reported zircon u pb age results from the jiurui district the present age data set demonstrates that extensive magmatism in the jiurui district was coeval and intensive marked by a magmatic activity in the age range of 148 to 138 ma and peaked between 148 ma and 142 ma according to the statistics of all those precise zircon u pb ages the cu au mo related porphyries in the edong and tongling districts in the mlyrmb show similar ages and they have a slightly younger peak age and a longer duration than that of the jiurui district the geographic shape of the mlyrmb in the cretaceous shows an arcuate structure the jiurui district is located at the transitional point of the arcuate structure and the edong and tongling districts are situated on both sides of the arcuate structure considering that the jiurui district has a slightly older peak age and a shorter duration of magmatic activity than that in the edong and tongling districts it seems that the arcuate structure of the mlyrmb played an important role in the formation of these cu au mo related porphyries consequently we suggest that the genesis of the late mesozoic magmatic rocks along the mlyrmb may have been due to a tectonic activity developed from southeast to northwest which probably has a close relationship with the subduction of the paleo pacific plate beneath the eurasian plate in mesozoic times