high temperature mylonitization of quartzofeldspathic gneisses example from the schirmacher hills east antarctica abstract in the schirmacher hills most of the ductile shearing took place under high to medium grade amphibolite facies metamorphism the microstructure of the mylonites shows characteristic features of high temperature deformation and thus gives us an idea of deformation mechanisms of the constituent minerals at great crustal depth the variation in microstructure of the sheared rock is partly due to heterogeneity of the intensity of strain from domain to domain producing protomylonites orthomylonites and ultramylonites however a large part of the microstructural variation has resulted from syn to post tectonic recrystallization and grain growth of constituent minerals both quartz and feldspar have deformed by crystal plastic processes with dominant grain boundary migration the present aspect ratio of the feldspar grains is a result of various degrees of dynamic recrystallization along the grain boundary the ratio varies between 1 5 and 2 presence of exsolution lamellae in perthites and formation of myrmekite at the strained grains of k feldspar suggest diffusion assisted dislocation creep these mylonites are characterized by the presence of weakly strained or unstrained long quartz ribbons the development of quartz ribbons with the absence of significant strain suggests grain recovery and grain growth during high temperature mylonitization the growth of quartz ribbons took place by coalescing neighbouring grains both along and across the ribbon length at the ultramylonite stage the fine grained matrix of quartz and feldspar mostly accommodates the bulk strain

u pb geochronology of vms mineralization in the iberian pyrite belt a geochronology study using u pb isotope dilution tims analyses of zircon has been conducted to determine the ages of volcanic associated massive sulfide vms deposits in the iberian pyrite belt ipb the world s most prolific vms province ages have been determined for host rocks to four vms systems that span the ipb the giant rio tinto and aljustrel districts in the central region lagoa salgada to the west and las cruces to the east a sample of chloritized quartz porphyritic dacite rhyolite in the footwall of the san dionisio massive sulfide deposit of the rio tinto district is 349 76 0 90 ma this is taken as the best age estimate of the mineralization in the rio tinto district probably the world s largest volcanogenic massive sulfide system two xenocrystic zircons from the same sample yielded 207pb 206pb ages of 414 and 416 ma which provide a minimum estimate for the age of the inherited component a biotite tonalite from the campofrio area 3 5 km north of the center of the rio tinto district is chemically similar to the felsic host rock protolith at rio tinto the campofrio sample has an age of 346 26 0 81 ma slightly younger and outside of the 2 error for the rio tinto age therefore this phase of this intrusion was not a heat source for the hydrothermal system that formed the deposits of the rio tinto district the campofrio sample also has three zircon analyses with 207pb 206pb minimum ages of 534 536 and 985 ma indicating inheritance from ordovician and neoproterozoic sources in the aljustrel vms district a u pb zircon age of 352 9 1 9 ma characterizes the altered green tuff host rock of the algares deposit which is slightly older than the rio tinto age two zircons with 207pb 206pb ages of 531 and 571 ma from this sample indicate inheritance from a cambrian or older source the age of mineralization at lagoa salgada is given by essentially identical ages of 356 21 0 73 and 356 4 0 8 ma for footwall and hanging wall samples respectively the hanging wall sample has two zircon analyses with 207pb 206pb ages of 464 and 466 ma indicating inheritance from an ordovician or older source the age for an altered dacite tuff sample from the hanging wall of the las cruces deposit is 353 97 0 69 ma one zircon analysis from the las cruces sample has a 207pb 206pb age of 1048 ma indicating inheritance from a neoproterozoic source these u pb ages refine the ipb geochronology provided by previous studies and they suggest that either volcanism progressed toward the center of the ipb or that volcanism was broadly static and the strata were progressively rifted to the margins during transtensional basin formation the zircon inheritance provides direct evidence for proterozoic to ordovician sources reflecting either basement rocks beneath the phyllite quartzite group during vms formation in late tournaisian times or a proterozoic to ordovician detrital component in phyllite quartzite group source rocks the presence of an older crustal component is consistent with vms formation during rift development at a continental margin

geochemistry and u pb geochronology of the wagone and hermyingyi a type granites southern myanmar implications for tectonic setting magma evolution and sn w mineralization abstract tin tungsten associated granites occur widely in the dawei region of the southeast asian tin belt in this contribution we present a detailed study of zircon u pb geochronology and whole rock and zircon elemental geochemistry for the wagone and hermyingyi granites in southern myanmar with the aim of determining their petrogenesis mineralization associations and tectonic setting these granitic rocks which belong to the high k calc alkaline series a2 type granites are characterized by high concentrations of sio2 75 2 82 5 rb 264 927 ppm th 18 4 58 3 ppm u 10 4 18 3 ppm and y 33 5 212 ppm but low contents of tfeo 0 57 3 45 cao 0 23 0 86 mgo 0 02 0 19 mno 0 01 0 38 tio2 0 01 0 10 p2o5 0 003 0 012 ba 3 162 ppm and sr 4 3 34 4 ppm hydrothermal zircons from the mineralized wagone pluton show an anomalous lack of zoning and vermicular spongy internal structures and they contain high concentrations of ti y u and light rees but low th u ratios mostly

developments in the characterization of complex rock slope deformation and failure using numerical modelling techniques recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms processes involved and the associated risk this paper illustrates how rock slope analyses may be undertaken using three levels of sophistication level i analyses include the conventional application of kinematic and limit equilibrium techniques with modifications to include probabilistic techniques coupling of groundwater simulations and simplistic treatment of intact fracture and plastic yield such analyses are primarily suited to simple translational failures involving release on smooth basal rear and lateral surfaces where the principle active damage mechanisms are progressive failure and or asperity breakdown level ii analyses involve the use of continuum and discontinuum numerical methods in addition to simple translation level ii techniques can be applied to complex translational rock slope deformations where step path failure necessitates degradation and failure of intact rock bridges along basal rear and lateral release surfaces active damage processes in this case comprise not only strength degradation along the release surface e g asperity breakdown but also a significant component of brittle intact rock fracture level iii analyses involve the use of hybrid continuum discontinuum codes with fracture simulation capabilities these codes are applicable to a wide spectrum of rock slope failure modes but are particularly well suited to complex translation rotational instabilities where failure requires internal yielding brittle fracturing and shearing in addition to strength degradation along release surfaces through a series of rock slope analyses the application of varied numerical methods are discussed particular emphasis is given to state of the art developments and potential use of level iii hybrid techniques d 2005 elsevier b v all rights reserved

double vein ore bearing vs ore free structures in the xitian ore field south china implications for fluid evolution and mineral exploration abstract two types of spatially and temporally associated hydrothermal veins ore bearing and ore free occur as double vein structures in the xitian ore field south china here we investigated the genetic relationship material provenance fluid properties and prospecting significance of the co developed veins in the granite related fault controlled vein type xiangdong w goudanlan w chaling pb zn and xinggao fluorite deposits of the xitian ore field focusing on two common minerals quartz and zircon petrographic cl microthermometric and h o isotopic analyses of stage i and stage ii quartz in both the ore bearing and ore free veins of these deposits document two episodes of hydrothermal activity the first episode involved a high temperature up to 370 high salinity up to 28 nacl equiv high 18o 2 1 to 7 2 and high 2h 82 to 54 mean 68 n 13 fluid that corresponds to the main magmatic hydrothermal stage of the deposits and the second episode involved a low temperature down to 90 low salinity down to 1 nacl equiv low 18o 8 8 to 5 3 and low 2h 83 to 60 mean 73 n 6 fluid that represents an accessary mineralization stage variations in fluid inclusion types and compositions indicate that the processes of fluid mixing boiling cooling and degassing played important roles in mineralization and that magmatic fluid became less important than meteoric water along during the formation of ore free veins la icpms u pb dating reveals totally different age populations for these veins zircons from the ore bearing quartz veins yield older and more variable ages pre devonian 400 ma n 68 that are similar to that of the local basement sedimentary rocks whereas zircons from the ore free quartz veins yield younger and less variable ages triassic 250 200 ma n 31 and jurassic 170 140 ma n 13 that are identical to those of the host granite zircons in addition the ore free veins show lower temperatures salinities and total rees as recorded by quartz but greater alteration as reflected by cl and trace element features of hydrothermally altered zircons and wider vein size than the ore bearing veins we propose a mineral water separation model to explain the formation of the double vein structures in this model ore bearing veins and ore free veins formed in succession during faulting events ore bearing veins formed first in the smaller fractures and were the dominant sites of mineralization whereas the ore free veins served as dissipating passageways for residual water and silica in larger fractures we suggest that the mineral water separation model has good application prospects in mineral exploration and that zircons can be applied as an indicative mineral to differentiate the mineralization potential of different types of quartz veins

geochemistry and geochronology of zircons from granite hosted gold mineralization in the jiaodong peninsula north china implications for ore genesis abstract large scale quart vein and structurally controlled gold mineralization is intensely developed in the jiaodong peninsula north china craton and is typified by the linglong and jiaojia deposits respectively in this work zircons from typical gold bearing ores of the sanshandao northern sea sns jiuqu jq and canzhuang cz gold deposits were compared in terms of texture u pb age trace element content and hf isotopic signatures in order to discern whether zircon from ore samples can be used as an indicator of ore genesis and grade most studied zircons are magmatic in origin with a hydrothermal overprint i e zircons with core rim assemblages fractured dissolution textures and hydrothermal activity related fluid mineral inclusions three zircon age clusters were differentiated 120 ma 150 ma and 2000 ma the 120 ma zircons show evidence of hydrothermal alteration dark in cathodoluminescent images with hydrothermal rim textures and are characterized by high lree p ti and ehf t 21 to 15 and young tdmc 2100 2500 ma this suggests an interaction between the mantle and crust at the magma source and that a p ti rich al poor high temperature high fo2 wet late stage residual granitic melt and intense hydrothermal alteration played an important role in the formation of gold mineralization the 150 ma zircons have high y nb ta and u contents low ehf t 26 to 20 and old tdmc 2300 3000 ma ages and hree enriched patterns with pronounced ce and eu anomalies these features indicate a reduced cool and al rich magma which did not favor gold mineralization even though it was highly evolved this also implies that the degree of magma differentiation is not the key factor that led to gold mineralization in the jiaodong gold province the 2000 ma zircons are primarily limited to gold ores with high pb contents hree enriched patterns and variable ce and eu anomalies indicating that they were inherited from the paleoproterozoic 2000 2200 ma basement in addition the sns high grade ores yielded zircon with the greatest u pb age range mainly 110 180 ma and the most pronounced hydrothermal overprinting indicating that large scale mineralization resulted from multi stage granitic intrusion with intense fluid dissolution and metasomatism this research highlights that correlations between zircon age populations hf isotope signatures internal structures and trace element patterns can provide insights into ore genesis and fluid evolution in gold mineralization systems

comparison of the implementation of rock engineering system and analytic hierarchy process methods upon landslide susceptibility mapping using gis a case study from the eastern achaia county of peloponnesus greece as landslides are very common in greece causing serious problems to the social and economic welfare of many communities the implementation of a proper hazard analysis system will help the creation of a reliable susceptibility map his will help local communities to define a safe land use and urban development the purpose of this study is to compare the implementation of two semi quantitative landslide assessment approaches using landslide susceptibility maps compiled in a gis environment the compared methods are rock engineering system res and the analytic hierarchy process ahp for the landslide susceptibility analysis the northeastern part of the achaia county was examined this area suffers from many landslides because of its neighborhood with the tectonically active corinthian gulf and its geological setting neogene sediments flysch and other bedrock formations with local overthrusts ten parameters were used in both methodologies and each one was separated into five categories ranging from 0 to 4 representing their specific conditions derived from the investigation of the landslides in the western part of the study area ranking area a layer map was generated for each parameter using gis while the weighting coefficients of each methodology were used for the compilation of res and ahp final maps of the eastern part of the study area validating area by examining these two maps it is revealed that even though both correctly show the landslide status of the second site the res map reveals a better behavior in the spatial distribution of the various landslide susceptibility zones

genesis of the xianghualing sn pb zn deposit south china a multi method zircon study abstract the xianghualing sn pb zn deposit is situated near the center of the world class nanling w sn ore belt associated with the highly evolved laiziling granite of jurassic age previous studies focused mainly on geochemical and geochronological features of the mineralization related granite whereas research on the source evolution and geochronology of the ore forming fluids has been limited we carried out precise u pb dating trace element and hf isotopic analyses on magmatic and hydrothermally altered zircons from the skarn stage and sulfide stage ores in the xianghualing deposit zircon u pb dating results from the two ore forming stages show distinct geochronological populations the skarn stage ores contain mainly magmatic and hydrothermally altered zircons in three age clusters 150 ma 220 ma and 420 ma whereas the sulfide stage ores are characterized by abundant old detrital zircons ranging from 497 to 3409 ma with a peak at 800 1000 ma this pattern may indicate that magmatic hydrothermal events in the silurian and triassic were precursors to the main sn mineralization event in the jurassic when circulation of evolved fluids through older sedimentary rocks led to pb zn mineralization the jurassic zircons exhibit high trace element contents e g hf p y nb ta th u and low ti contents eu anomalies nb ta and th u ratios which imply that the laiziling magma experienced significant plagioclase biotite and muscovite fractional crystallization and that it interacted extensively with post emplacement f rich hydrothermal fluids the positive ce anomalies of these zircons ce ce 1 0 226 indicate that the magmatic hydrothermal fluids that led to the jurassic sn mineralization event were reducing the less negative ehf t values of triassic zircons 18 7 to 2 6 compared to the silurian zircons 14 6 to 2 3 suggest more limited interaction between the mantle and the magma source region the jurassic magmatic zircons in the skarns exhibit even more negative ehf t values 30 7 to 6 7 along with tdmc model ages ranging from 1627 to 3134 ma indicating that the jurassic magma was derived from partial melting of old continental crustal basement based on the combined study of zircons in the skarns and sulfide ores we propose a three stage ore genetic model for the xianghualing sn pb zn deposit

the assessment of rock slope instability along the khosh yeylagh main road iran using a systems approach the slope instability is connected to a large diversity of causative and triggering factors ranging from inherent geological structure to the environmental conditions thus assessment and prediction of slope failure hazard is a difficult and complex multi parametric problem in contrast to the analytic approaches the systems approaches are able to consider infinite number of affecting parameters and assess the interactions of each couple of the parameters in the system this paper presents a complete application of the rock engineering systems approach in prediction of the instability potential of rock slopes in 15 stations along a 20 km section of the khosh yeylagh main road iran as the case study of the research in this research the main objective has been defining the principal causative and triggering factors responsible for the manifestation of slope instability phenomena quantify their interactions obtain their weighted coefficients and calculate the slope instability index which refers to the inherent potential instability of each slope of the examined region the final results have been mapped to highlight the rock slopes susceptible to instability finally as a preliminary validation on the utilization of systems approach in the study region the stability of investigated rock slopes were analyzed using an empirical method and the results were compared the comparisons showed a rather good coincidence between the given classes of two methods

geology age and fluid inclusions of the tanjianshan gold deposit western china two orogenies and two gold mineralizing events abstract the tanjianshan gold deposit located at the tectonic boundary between the oulongbuluk block ob and north qaidam orogenic belt nqo on the northern margin of the qaidam basin nmqb western china underwent early palaeozoic and late palaeozoic to early mesozoic multiple accretions and collisional orogenies it is a typical example of a deposit resulting from two gold mineralizing events related to two collisional orogenies two phases of ore controlling nw trending shear zones have been identified in the deposit dextral brittle ductile shear deformation during the late early palaeozoic collisional orogeny and sinistral strike slip shear deformation during the late palaeozoic early mesozoic orogeny n s trending folds developed in the nw trending shear zone and resulting from sinistral strike slip motion of the shear zone are nose shaped in plan view and control most gold orebodies in the deposit the major gold orebodies trend nne and are concentrated in the hinge zones of these n s trending folds occurring along the fault zones parallel to both limbs of these folds these gold orebodies composed of altered mylonite schist type ore and altered dyke type gold ore occur as saddle shaped bodies beds and lenses mainly within altered carbonaceous quartz sericite mylonite schist of a highly strained zone and locally in altered igneous dykes of the highly strained zone alteration related to gold mineralization includes silicification pyritization and sericitization a progressive increase of sio 2 s au ag as and sb from unaltered or weakly altered rocks through altered rocks to gold ore is consistent with progressively enhanced silicification and pyritization suggesting the flow of mineralizing fluids along the nw trending shear zone and n s trending folds native gold and electrum are present as very fine grains mainly enclosed in disseminated pyrite or occurring in fractures within the pyrite three generations of pyrite and associated hydrothermal quartz are observed the fabrics of gold ore generations of auriferous pyrite field relationship between multiple ore controlling structures and gold mineralization and the bimodal distribution of ore elements in the gold district suggest the occurrence of two main hydrothermal and mineralizing events the first event marked by a mineral assemblage of first generation quartz qz 1 and first generation pyrite py 1 was restricted to the carbonaceous mylonite schist within the nw trending shear zone sericite from the ore controlling nw trending shear zone gave a 40 ar 39 ar age of 409 4 ma which is consistent with the age of the regional late early palaeozoic collisional orogeny in the region the second event marked by a mineral assemblage of second generation quartz qz 2 and second generation pyrite py 2 occurred within the n s trending folds and was related to late palaeozoic orogeny in the region we have obtained a k ar age of 268 9 4 3 ma and an rb sr isochron age of 288 9 7 ma for hydrothermal minerals from gold ores the latter age is closer to the age of this event of gold mineralization mineralization of this event was superimposed onto gold mineralization of the early phase and formed most of the gold orebodies in the deposit the distribution and microthermometric data of fluid inclusions indicate that late early palaeozoic ore fluids belong to the h 2 o co 2 ch 4 nacl fluid system formed at 186 to 250 c whereas late palaeozoic fluids comprise two kinds of immiscible fluid a h 2 o nacl fluid with salinity of 1 6 to 10 8 wt nacl equiv which probably formed at temperatures of 381 to 449 c and and h 2 o co 2 nacl fluids with salinities of 1 8 to 7 9 wt nacl equiv which are genetically the product of evolution of former immiscible magmatic fluids and which formed at temperatures of 274 to 410 c

alteration of monazite and zircon and lead migration as geochemical tracers of fluid paleocirculations around the oklo okelobondo and bangombe natural nuclear reaction zones franceville basin gabon abstract large scale light rare earth element lree uranium lead and phosphorus migration has been evidenced in the fa lower proterozoic sandstones of the franceville basin gabon hosting oklo natural nuclear reaction zones rz in relation with extensive accessory mineral alteration by highly saline diagenetic brines 28 7 wt nacl eq to 30 wt cacl2 eq at about 140 c and 1 kbar monazite is the most severely altered accessory mineral in the coarse grained sandstones of the basal fa formation detrital monazite crystals are altered to th oh silicate microcrystalline phase with very low concentrations of u and lree the th la ratio increase from non altered th la 0 27 to altered sandstones th la 1 14 shows that about 76 of the lree was leached this corresponds to the leaching of 2 01 109 metric tons at the scale of the fa formation in the franceville basin similarly the th u increase from monazite th u 18 6 to the th silicate phase th u 88 7 is interpreted as a result of an alteration by oxidizing brines with leaching of u together with lree and p it corresponds to the leaching of 9 06 106 metric tons of uranium this amount of uranium largely exceeds the known uranium reserves from the franceville basin in zircon crystals the cores are generally homogeneous weakly fractured and well preserved as attested by the archean ages 2867 24 and 2865 51 ma obtained by ionic microprobe analysis on zircon of the fa formation respectively from the marginal and central parts of the basin their composition corresponds to the pure end member zr hf sio4 poor in th and u th u 1 at the contrary their rims which present several growth zones with cracks fillings are enriched in ree p th and u with higher th u ratios 5 10 both altered monazite and altered zircon contain galena as numerous inclusions in the outer growth zones and as crack fillings for example in zircon the pb of galena crystals 3 23 wt largely exceeds the amount of pb maximum 0 1 wt that would have been produced in situ by radioactive decay in this mineral nearly all the lead were introduced into altered zones of accessories dissolution of accessory minerals occurred at 2000 ma producing a porous and distorted crystal structure which has allowed a later incorporation of pb galena inclusions in altered zircons located in the vicinity of reactor zones have radiogenic lead compositions altered zircon rims and galena inclusions in altered zircon located far from reactor zones have non radiogenic pb isotopic compositions confirming the external origin of lead pb isotopic evolution models indicate a crystallization age sometime after 1000 ma both for galena located close to and far from u mineralizations and reactor zones which may be synchronous with a regional extension event contemporaneous with intrusion of dolerite dyke swarms between 1000 and 750 ma at the scale of the franceville basin the present study also illustrates the different retention capacities of accessory mineral for elements representing analogs of the radiotoxic nuclides in the relatively extreme natural conditions created by the circulation of moderately hot and chloride rich fluids during the diagenesis of a sedimentary basin

continuous mixing of crystal mush and replenished magma in the ongoing unzen eruption zoning profiles of magnetite phenocrysts in the successively effused dacite of the ongoing unzen eruption from 1991 wereanalyzed to estimate the time scale of magma mixing the dacite was formed by mixing of relatively high and low temperature t end member magmas the magnetite phenocrysts derived from the low t magma are reversely zoned by the mixing with high t magma a diffusion calculation for reequilibration of the reverse zonings gives the time interval from magma mixing to quenching for the mixed dacite erupted from may 1991 to may 1993 the typical diffusion time was estimated to be a few months regardless of the effused sequence for 2 yr this indicates that the mixing was continuous during the effusion the invariability of the other mixing signatures such as the thickness of reaction rims around biotite phenocrysts also supports the continuous mixing model low t end member magma is estimated by mass balance calculation to be a crystal rich mush of dacitic composition these observations lead to a model wherein the highly crystallized remnant magma of the preceding activity has been mixed with the newly injected hot magma of similar bulk composition just prior to the effusion the proposed mechanism implies that this type of magma mixing is an inevitable process in periodically erupting polygenetic volcanoes

zircon geochemistry records the action of metamorphic fluid on the formation of ultrahigh pressure jadeite quartzite in the dabie orogen abstract a combined study of mineral inclusions u pb ages trace elements and hf o isotopes was carried out for zircons from a coesite bearing jadeite quartzite in the dabie orogen the results provide insights into the action of ultrahigh pressure uhp metamorphic fluids during continental deep subduction to a mantle depth and thus constraints on the origin of the jadeite quartzite in the continental subduction zone the zircons mostly show core rim structures in cathodoluminescence images the overgrown rims contain rare mineral inclusions and exhibit concordant u pb ages of 225 to 246 ma and flat hree patterns with negligible eu anomalies in contrast the relict cores contain uhp metamorphic mineral inclusions such as coesite jadeite and rutile and show discordant u pb ages ranging from 983 to 2045 ma and steep ree patterns with significant negative eu anomalies the u pb isotope data for the all cores and rims define an apparent discordia line with upper and lower intercept ages of 2000 43 ma and 234 18 ma respectively we interpret the rims with triassic ages as the new growth of metamorphic origin and the cores with precambrian ages as the protolith relics of magmatic origin the relict magmatic zircons underwent two subtypes of metamorphic recrystallization i e solid state transformation and metasomatic alteration the solid state recrystallized zircons exhibit slightly discordant u pb ages close to the protolith age steep mree hree patterns and almost unchanged hf isotope ratios these observations point to the lowest degree of resetting to the geochemical composition of protolith zircons in contrast the metasomatically recrystallized zircons exhibit partial resetting in protolith zircon ree composition and u pb and lu hf isotopic systems all of the zircon domains regardless of the rims and cores show relatively consistent 18 o values of 4 0 0 2 such a consistency indicates not only that the metamorphic fluids are of internal origin from the deeply subducted continental crust but also that the oxygen isotope composition of protolith zircons was reequilibrated with the uhp metamorphic fluids of triassic age the metasomatic recrystallization of protolith zircons is indicated by the occurrence of uhp inclusion minerals such as coesite rutile and jadeite in sealed microcracks in this regard the fluid metasomatism firstly took place along fractures of the relict zircons during prograde subduction of the continental crust and then experienced the metamorphic recrystallization to result in sealing of the fractures under the uhp conditions as such the metasomatic recrystallization has heterogeneously reset the u pb and lu hf isotope systems of protolith zircons the composition of inclusion minerals within the relict zircon cores suggests that the metamorphic fluids were rich in si ti na and al these elements would be acquired by the metamorphic fluids through metasomatic reaction of metagreywackes overlying the granitic orthogneiss therefore the jadeite quartzite would be precipitated from the uhp metamorphic fluids that were derived from dehydration of the underlying basement orthogneiss but reacted with the metagreywackes during the continental subduction zone metamorphism

island arc volcanic rocks in the north qaidam uhp belt northern tibet plateau evidence for ocean continent subduction preceding continent continent subduction abstract a suite of early paleozoic island arc volcanic rocks consisting mainly of basaltic lavas and some intermediate silicic rocks crops out in the north qaidam basin northeastern tibet plateau these rocks have been extensively metamorphosed under greenschist facies conditions and hence differ from the older proterozoic intermediate mafic volcanic rocks which have generally experienced amphibolite facies metamorphism the early paleozoic volcanic rocks are divided into three groups based on their geochemical characteristics 1 vtg i consists of island arc tholeiitic basalts basaltic andesites and andesites that crop out in jilusu and shuangkoushan 2 vtg ii which are high al alkaline and sub alkaline basalts in jilusu and 3 vtg iii an assemblage of highly depleted morb type basalts andesites and dacites that occurs mostly in shuangkoushan groups vtg i and ii are considered to be the products of mature island arcs produced in two stages in the first stage following initiation of ocean continent subduction the island arc tholeiites were generated by partial melting of the subsiding oceanic crust and mantle wedge beneath the island arc as subduction progressed and accelerated calc alkaline and high al basalts were formed and the crust beneath the island arc was thickened the highly depleted morb type lavas vtg iii have boninitic affinities and are believed to have been generated from depleted mantle material modified by subduction zone fluids possibly in the fore arc region the island arc tholeiites are dated at 514 2 8 5 ma whereas uhp eclogite in the north qaidam belt has been dated at 494 ma these ages suggest that ocean continent subduction took place in the north qaidam basin in the early paleozoic and was followed shortly by continent continent collision and subduction which produced the uhp rocks

petrology and u pb geochronology of footwall porphyritic rhyolites from the wolverine volcanogenic massive sulfide deposit yukon canada implications for the genesis of massive sulfide deposits in continental margin environments porphyritic rhyolite sills form an important component of the footwall of the wolverine volcanogenic massive sulfide vms deposit yukon canada and occur proximal to mineralization in the immediate deposit area wolverine lynx zone and at similar stratigraphic levels along strike fisher puck and sable zones porphyritic rhyolites are of two types an older quartz feldspar porphyritic qfp rhyolite suite and a younger feldspar porphyritic fp suite both the qfp and fp suites of intrusions are semiconcordant suggesting a silllike morphology and are altered and crosscut by veinlet mineralization suggesting that they are pre to synmineralization the margins of qfp suite of intrusions contain minor xenoliths of surrounding shales and poorly developed chilled margins suggesting emplacement into partially consolidated sedimentary rocks whereas the fp suite of intrusions shows well developed chilled margins indicative of emplacement into fully solidified sedimentary rock these features suggest that the qfp suite of intrusions represents an older phase of rhyolitic magmatism whereas the fp suite represents a younger event this is supported by u pb zircon ages which indicate a 352 4 1 5 ma emplacement age for the fp suite and a 347 to 346 ma emplacement for the fp suite two ages at 347 8 1 3 and 346 0 2 2 ma both suites of porphyries have inherited proterozoic zircon and have ratios of la smucn 1 and nb thucn 1 ucn upper continental crust normalized indicating derivation from and or extensive interaction with ancient upper continental crustal materials the fp suite however has elevated high field strength element hfse and rare earth element ree contents high zircon saturation temperatures and higher nb ta ratios and lower ti sc ratios than the qfp suite these features are interpreted to reflect that the fp suite of magmas was hotter 900 c melts with a greater mantle component in their genesis both suites however are interpreted to have formed due to basaltic upwelling crustal melting and crust mantle mixing during ensialic back arc basin activity the presence of mantle heat within the wolverine basin from 352 to 347 to 346 ma a minimum of 5 m y suggests that sustained mantle heat flow was critical to the genesis of the wolverine porphyries it is also suggested that this sustained mantle heat was responsible for the wolverine hydrothermal system and that upwelling mantle may be essential in providing the heat to drive hydrothermal systems even in continental margin type vms environments e g bathurst iberian pyrite belt the wolverine porphyries are among the most hfse and ree enriched felsic rocks associated with vms mineralization globally the high hfse and ree concentrations in these rocks are interpreted to be due to

from magmatic generation to uhp metamorphic overprint and subsequent exhumation a rapid cycle of plate movement recorded by the supra subduction zone ophiolite from the north qaidam orogen abstract the rapid subduction and exhumation of high pressure hp and ultrahigh pressure uhp rocks exposed in collisional belts play a critical role in understanding the evolution of geodynamics and plate tectonics in subduction zone environments herein ophiolitic fragments eclogites and amphibolites from a subduction channel exposed in the dulan terrane north qaidam orogen were investigated garnet compositional zoning from the studied eclogites records only a single cycle of subduction and exhumation new uranium lead u pb zircon ages of the current study combined with previous rutile u pb ages from eclogites indicate a rapid cycle of events starting with the generation of the magmatic protolith at ca 446 ma its subsequent subduction reaching a depth of ca 100 110 km at ca 435 ma and its exhumation into shallow portions of the crust which occurred at ca 416 ma thus a rapid 30 million years myr protolith generation subduction exhumation cycle could be recorded according to an ophiolitic rock association with island arc basalt iab like and mid ocean ridge basalt morb to ocean island basalt oib like trace element compositions the slab derived components determined by sr nd hf isotopes and the short time span of only about 11 myr between photolith generation and uhp metamorphism in eclogites the protolith of eclogite is best explained as a supra subduction zone ophiolite this finding likely records the closure of the south qilian ocean and the initiation of a continent arc collision at ca 446 ma furthermore starting with subduction erosion during continent arc collision in the early palaeozoic ophiolitic and arc related materials become subducted in the north qaidam it was inferred that such a rapid succession of events from protolith formation to uhp overprint and final exhumation could be explained by movements of rock material in a subduction channel thus this study provides a new view in understanding the mechanics of different episodes of subduction systems in north qaidam uhp metamorphic belt

classification of slopes and prediction of factor of safety using differential evolution neural networks slope stability analysis is one of the most important problems in geotechnical engineering the development in slope stability analysis has followed the development in computational geotechnical engineering this paper discusses the application of different recently developed artificial neural network models to slope stability analysis based on the actual slope failure database available in the literature different ann models are developed to classify the slope as stable or unstable failed and to predict the factor of safety the developed ann model is found to be efficient compared with other methods like support vector machine and genetic programming available in literature prediction models are presented based on the developed ann model parameters different sensitivity analyses are made to identify the important input parameters

radar enabled recovery of the sutter s mill meteorite a carbonaceous chondrite regolith breccia doppler weather radar imaging enabled the rapid recovery of the sutter s mill meteorite after a rare 4 kiloton of tnt equivalent asteroid impact over the foothills of the sierra nevada in northern california the recovered meteorites survived a record high speed entry of 28 6 kilometers per second from an orbit close to that of jupiter family comets tisserand s parameter 2 8 0 3 sutter s mill is a regolith breccia composed of cm mighei type carbonaceous chondrite and highly reduced xenolithic materials it exhibits considerable diversity of mineralogy petrography and isotope and organic chemistry resulting from a complex formation history of the parent body surface that diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to c class asteroids are interpreted

detrital zircon as a proxy for tracking the magmatic arc system the california arc example coupled age and trace element geochemical analyses of detrital zircons provide criteria that may be applied to describe average melt compositions through virtually the entire history of a long lived magmatic arc detrital zircon data suggest that the california western united states cordilleran arc was characterized by five mean magmatic states three geochemically distinct pulses were characterized by high th u and progressively heavy rare earth element hree depleted melts the first and last pulses were also characterized by higher than average u yb suggesting that progressive crustal thickening coupled with variable fluid inputs from the subducting slab modulated pulse volumes lulls between pulses were states generally characterized by low magmatic volumes and low th u and u yb suggesting fluid poor conditions with minimized crustal involvement in magmatism

neural network based model for assessing failure potential of highway slopes in the alishan taiwan area pre and post earthquake investigation abstract this paper is aimed at creating an empirical model for assessing failure potential of highway slopes with a special attention to the failure characteristics of the highway slopes in the alishan taiwan area prior to and post the 1999 chi chi taiwan earthquake the basis of the study is a large database of 955 slope records from four highways in the alishan area artificial neural network ann is utilized to learn from this database the developed ann model is then used to study the effect of the chi chi earthquake on the slope failure characteristics in the alishan area significant changes in the degrees of influence of several factors variables are found and possible reasons for such changes are discussed the novelty of this paper lies in the fact that the developed ann models are used as a tool to investigate the slope failure characteristics before and after the chi chi earthquake

zircon upb age constraints on the mid cretaceous hkamti amber biota in northern myanmar abstract hkamti amber contains exquisite fossils but the age of the amber biota is unclear in this study we documented the characteristics of fossils hosted in the amber and we present zircon u pb ages of tuff layers from the kachin and hkamti sites i e the new mine we also present a compilation of arthropod and echinoderm syn inclusions from the mid cretaceous hkamti amber of myanmar indicating a humid tropical or subtropical forest paleo environment zircon analyses n 143 of four tuff samples that host the amber deposit in different pits yielded a weighted mean age of 109 7 0 4 ma zircon rare earth element data demonstrate the zircons are of igneous origin therefore the age of the cretaceous amber biota from hkamti is ca 110 ma this means that the hkamti assemblage should be treated as distinct from other burmese amber collections as it represents a significantly older source within a different depositional environment the commercial sources of burmese amber are variable and encompass multiple mining regions which makes maintaining distinctions between deposits important if their faunal contents are to be studied in a proper temporal or ecological context the refined understanding of amber deposits in myanmar highlights the importance of distinguishing sources but it also offers an opportunity to study a series of deposits from 110 to 72 ma instead of just one snapshot of terrestrial ecology around 99 ma

epidote amphibolite to amphibolite facies transition in the southern appalachian piedmont p t conditions across the garnet and cale silicate isograds amphibolites occur in three distinct localities hudson rapids davis mill and lindsey creek in the west central georgia part of the uchee belt southern appalachian piedmont epidote amphibolite facies assemblage plagioclase an24 36 hornblende epidote sphene quartz at the davis mill occurrence gives way to the amphibolite assemblage calcic plagio clase an33 88 hornblende garnet epidote ilmenite quartz at hudson rapids mineral chemistries indicate that the transition was controlled by increasing pressure and unusual bulk compositions equilibrium mineral assemblages record temperatures ranging from 610 to 780 c at the garnet isograd and from 570 to 634 c close to the calc silicate isograd estimated pressures range from 7 to 9 25 2 kbar these p t conditions are consistent with a thickened crustal section caused by emplacement of the piedmont allochthon followed by isobaric cooling or isothermal compression and the formation of symplectites of epidote amphibole around plagioclase clinopyroxene

alteration and remelting of nascent oceanic crust during continental rupture evidence from zircon geochemistry of rhyolites and xenoliths from the salton trough california abstract rhyolite lavas and xenoliths from the salton sea geothermal field southern california provide insights into crustal compositions and processes during continental rupture and incipient formation of oceanic crust salton buttes rhyolite lavas contain xenoliths that include granophyres fine grained altered rhyolites felsite and amphibole bearing basalts zircon is present in lavas and xenoliths surprisingly even in the basaltic xenoliths where it occurs in plagioclase rich regions interpreted as pockets of crystallized partial melt zircons in the xenoliths are exclusively late pleistocene holocene in age and lack evidence for inheritance u th isochron ages are 20 5 1 2 1 2 ka granophyres 18 3 3 5 3 6 ka felsite 30 1 12 4 14 1 ka and 9 2 6 6 7 0 ka basalts all errors 1 the dominant zircon population in the rhyolite lavas yielded u th ages between 18 and 10 ka with few pre quaternary xenocrysts present 18ozircon values are lower than typical crustal basement values thus ruling out rhyolite genesis by melting of continental crust moreover 18ozircon values are 0 5 1 0 lower than compositions achievable by zircon crystallization from residual melt in equilibrium with unaltered mid ocean ridge basalt suggesting that basaltic crust and silicic plutons in the subsurface of the salton sea geothermal field isotopically exchanged with meteoric waters this is evidence for deep reaching hydrothermal circulation and indicates rhyolite genesis by episodic remelting of altered basalts instead of fractional crystallization of unaltered basaltic magma

development of a model for analysis of slope stability for circular mode failure using genetic algorithm slope stability estimation is an engineering problem that involves several parameters the interactions between factors that affect slope instability are complex and multi factorial so often it is difficult to describe the slope stability mathematically this paper proposes the use of a genetic algorithm ga as a heuristic search method to find a regression model for analyzing the slope stability for this purpose an evolutionary algorithm based on ga was used to develop a regression model for prediction of factor of safety fs for circular mode failure the proposed ga uses the root mean squared error as the fitness function and searches among a large number of possible regression models to choose the best for estimation of fs from six geotechnical and geometrical parameters for validation of the model and checking its efficiency a validation dataset was used to evaluate fs using the proposed model and a previously developed mathematical ga based model in the literature results have shown that the presented model in this study was capable of evaluating fs at a higher level of confidence regarding the other model r 0 89 for presented model in this study comparing r 0 78 for the other model and can be efficient enough to be used as a simple mathematical tool for evaluation of factor of safety for circular mode failure especially in preliminary stages of the designing phase

magma mixing recharge and eruption histories recorded in plagioclase phenocrysts from el chichon volcano mexico operative throughout the 200 ky history of the el chichon magma consistent core to rim decreases of sr sr ratios and coincident system increases in sr concentrations in plagioclase phenocrysts of varying size 1 cm to 2 mm are reported from samples of the 1982 and pre 1982 200 ka eruptions of el chichon volcano maximum sr sr ratios of 0 7054 significantly higher than the wholerock isotopic ratios 0 7040 0 7045 are found in the cores

uranium series accessory crystal dating of magmatic processes complex and protracted crystallization histories over geologic timescales are recorded in accessory minerals e g zircon allanite although magmatic crystallization was traditionally assumed to occur essentially instantaneously for the purposes of interpreting mineral geochronometers with low absolute time resolution for ancient samples it emerged relatively recently that magmatic crystallization can occur over extended durations this discovery arose from applying high spatial resolution accessory mineral dating techniques for uranium series isotopes to young volcanic and cognate plutonic rocks the emerging pattern from these studies is that individual crystals and crystal populations record crystallization episodes lasting from 1 000 to many hundreds of thousands of years accessory mineral dating of volcanic rocks and cognate plutonic xenoliths opens new research avenues for crystal age fingerprinting that correlates pyroclastic deposits lavas and plutonic rocks by using characteristic age dis

zircon indicators of fluid sources and ore genesis in a multi stage hydrothermal system the dongping au deposit in north china abstract the syenite hosted dongping gold deposit represents the largest gold deposit on the northern margin of the north china craton here we present new u pb age trace element concentration and hf isotope data from magmatic and hydrothermal zircons to better constrain the timing and genesis of gold mineralization geochronological data combined with field and petrologic results document two mineralization events the earlier event in the mid devonian 380 ma was associated with the intrusion of the shuiquangou syenite whereas the later event in the early cretaceous 140 ma was related to the emplacement of the shangshuiquan granite devonian hydrothermal zircons extracted from gray auriferous quartz veins were formed via metasomatic alteration of magmatic zircons derived from the syenite by an oxidizing f rich fluid in contrast cretaceous hydrothermal zircons hosted in the altered shangshuiquan granite and milky gold rich quartz ores were precipitated directly from a high temperature zr saturated aqueous fluid that was contaminated by basement materials possessing a substantially different hf isotopic composition from the contemporaneous magmatic zircons we propose that the devonian au mineralization event at dongping involved a magmatic fluid and auto metasomatism during crystallization of the shuiquangou syenite complex whereas the cretaceous au mineralization event involved a fluid exsolved from the shangshuiquan alkaline pluton results from this study highlight the potential utility of zircons as indicators of fluid sources and ore genesis in a multi stage hydrothermal system

the influence of grain boundary fluids on the microstructure of quartz feldspar mylonites quartz rich domains in pre alpine water deficient amphibolite facies 510 580 c 250 450 mpa pegmatite mylonites from mont mary mm western alps preserve a fine dynamically recrystallized grain size without significant annealing despite the high synkinematic temperatures and subsequent static greenschist facies alpine overprint the microstructure is dramatically different from more typical water rich amphibolite facies mylonites such as from the simplon fault zone in the central alps where the recrystallized grain size is on the millimetre scale the difference reflects the dominant strain induced recrystallization mechanism 1 progressive subgrain rotation and grain boundary bulging for the dry mm examples and 2 fast grain boundary migration for the wet simplon examples the grain boundary microstructure imaged with sem is also very different with most grain boundaries in the dry mm samples lacking porosity whereas grain boundaries in the wet samples are decorated by a multitude of pores quartz grain boundaries from both wet and dry samples are locally coated by thin 100 s of nanometres possibly amorphous silica films despite the differences in microstructure the crystallographic preferred orientations cpos of quartz rich domains from both areas are very similar water deficient conditions hinder grain boundary mobility and thereby modify the dominant recrystallization mechanism s but apparently have little influence on the intracrystalline slip systems as reflected in the cpos strong c axis y maxima in mm mylonites both k feldspar and plagioclase an33 38 dynamically recrystallize consistent with the inferred metamorphic conditions under water deficient conditions mid to lower crustal rocks can deform heterogeneously under transitional ductile brittle conditions at high differential stress for mm ca 300 500 mpa as estimated for dry mohr coulomb failure and preserve this high stress microstructure because of the low mobility of dry grain boundaries

modelling progressive failure in fractured rock masses using a 3d discrete element method instabilities in rock structures involve coupled mechanisms related to both deformations along existing discontinuities and brittle fracture of intact rock conventional kinematic and limit equilibrium techniques used to study rock slope stability suffer from oversimplifications mass strength degradation and progressive failure mechanisms in rock bridges cannot be ignored and must be considered to predict the overall slope behaviour a 3d numerical model based on the discrete element method has been developed to overcome these limitations pre existing discontinuities as a discrete fracture network dfn can be initially plugged into a set of discrete elements combined with the use of a modified contact logic which provides an explicit representation of joints both fracturing of intact material and yielding within discontinuities can therefore be reproduced depending on the loading conditions and material strength simulations of referenced experimental tests are presented here to show the capabilities of the model in tackling the failure mechanisms of intact rock in the presence of pre existing discrete fractures with an emphasis on the initiation and propagation processes this model proves to be a promising tool in understanding and predicting instabilities that could lead to the failure of fractured rock slopes

timescales of crustal magma reservoir processes insights from u series crystal ages the dynamic processes operating within crustal magma reservoirs control many aspects of the chemical composition of erupted magmas and crystals in volcanic rocks provide a temporally constrained archive of these changing environments in this review i compile 238 u 230 th ages of accessory phases and 238 u 230 th 226 ra ages of bulk mineral separates of major phases these data document that crystals in individual samples can have ages spanning most of the history of a volcanic centre age populations for accessory phases show protracted pre eruptive crystal residence times but few crystals predate magmatic activity at a given centre these data have been interpreted in the context of residence times of the host magmas or timescales of the storage of crystals within a largely crystalline portion of the reservoir system in contrast less than half of the bulk separate 238 u 230 th 226 ra ages for major phases are more than 10 kyr older than the eruption many of these apparently conflicting observations of ages of major and accessory phases can be reconciled within the context of a model where a crystal mush was remobilized during processes leading to eruption overall the compiled data show that crystals contain rich archives of magmatic processes in crustal reservoirs especially when combined with other crystal scale geochemical data

petrology and geochemistry of high niobium eclogite in the north qaidam orogen western china implications for an eclogite facies metamorphosed island arc slice abstract to better understand the evolution of the north qaidam orogen eclogite that forms lens like bodies in granitic gneiss was studied in the luliangshan terrane north qaidam ultrahigh pressure uhp metamorphic belt petrographic and mineralogical studies as well as pressure temperature calculations showed that the eclogite underwent at least three metamorphic stages peak eclogite facies metamorphism at 647 768 c and 3 0 gpa was followed by high pressure hp granulite facies metamorphism at 815 929 c 1 61 1 75 gpa and cooling to amphibolite facies metamorphism at 606 720 c 0 41 0 56 gpa three age groups can be identified via la icp ms zircon u pb eclogite dating 1 an eclogite facies metamorphic age of ca 432 428 ma 2 an hp granulite facies retrograde age of ca 424 420 ma and 3 ages of 415 382 ma which constrained the timing of amphibolite facies metamorphism the studied eclogite is characterized by high field strength element enrichment particularly in nb content 57 8 124 ppm and flat rare earth element patterns similar to high nb island arc basalts described in many modern arcs that feature subduction of oceanic slabs the samples have positive end t values 2 1 to 5 1 and positive ehf t values 4 9 to 10 0 indicating that the protolith of the high nb eclogite was directly derived from the depleted mantle with little crustal contamination these island arc basalts have been interpreted to have arisen from the partial melting of mantle wedge garnet amphibole or garnet peridotite metasomatized by slab dehydrated melts of a subducted oceanic slab they were emplaced onto the continental block by arc magmatism prior to the main collision event then the island arc materials were dragged into the subduction channel with eclogite facies metamorphism via subduction of the qaidam block

felsic metavolcanic rocks related to the broken hill pb zn ag orebody australia geology depositional age and timing of high grade metamorphism two key issues related to the origin of the massive broken hill pb zn ag orebody are the genesis of its host rocks and their depositional age these granulite facies layered gneisses have been ascribed alternately to volcanic and nonvolcanic regimes determination of the depositional age of the sequence has never been seriously addressed north of broken hill amphibolite facies precursors to the granulite facies gneisses show compelling evidence of a volcanic origin in their texture chemistry and zircon morphology these felsic metavolcanic rocks are in the upper part of the broken hill group stratigraphically equivalent to the broken hill orebody the present work traces textural zircon morphological and isotopic changes across the amphibolite to granulite facies transition in order to determine the primary depositional age of this supracrustal sequence and the timing of highgrade regional metamorphism ion microprobe shrimp u pb data on zircons from the lower grade amphibolite facies felsic metavolcanic rocks define a major magmatic population at 1690 or 5 ma this is considered to be the age of zircon crystallization and eruption of felsic volcanics in this part of the broken hill group these shrimp data clarify inheritance and discordance problems that had plagued conventional multigrain u pb analyses zircon results from granulite facies stratigraphic equivalents of these rocks near southern cross and at broken hill have patterns similar to those of the amphibolite facies rocks including igneous relics that provide the same primary age additionally zircon in the highest grade granulite facies rocks approximately 800 degrees c forms metamorphic overgrowths surrounding the magmatic relics these younger zircon selvedges have a pooled age of 1600 or 8 ma which determines the timing of this granulite facies event consistent u pb monazite results yield this same age 1599 or 9 ma suggesting that the monazite blocking temperature is close to that of zircon or that cooling to 725 degrees c was achieved relatively rapidly this is some 60 m y younger than the previously accepted age for high grade metamorphism at broken hill irrespective of metamorphic grade in the gneisses all biotite rb sr ages have been reset to approximately 480 ma a reflection of early paleozoic delamerian orogenesis inherited zircon grains interpreted as xenocrysts and in some cases mantied by 1690 ma igneous rims have older proterozoic to late archcan ages 1780 2700 ma the presence of xenocrystic zircon components points to an ensialic tectonic setting for the broken hill block and reflects accidental incorporation in the felsic volcanic protoliths of lithic fragments and or complex igneous sources such as found in crust exposed in the gawler craton to the west the 1690 or 5 ma depositional age determined here provides a firm chronologic tie between the early proterozoic sequences enclosing major stratiform pb zn ag orebodies at broken hill mount isa 1670 or 19 ma and mcarthur river 1690 or 27 ma in northern australia in light of the uncertainties over timing and mode of origin of these deposits the similar ages of their host sequences have important implications for early proterozoic tectonics and metallogeny

the geodynamic setting of dulan eclogite type rutile deposits in the north qaidam orogen western china abstract abundant eclogite type rutile deposits have recently been discovered along the north qaidam ultrahigh pressure uhp metamorphic belt in china the identified titanium reserves exceed 3 million tons and range in grade from 1 0 to 4 5 the rutile deposits of economic interest are found within two types of eclogite however the origin and original geodynamic setting of the two types of rutile bearing eclogites remain controversial this study therefore investigates ore and mineralization bodies belonging to the two types by way of detailed field work and geochronological geochemical and sr nd hf isotopic compositional analysis taking the dulan eclogite type rutile deposit as its case study type 1 rutile bearing eclogites enclosed in granitic gneisses are found to have neoproterozoic protolith ages of 845 4 ma and an eclogite facies metamorphic age of ca 433 ma their high tio2 tfe2o3 and p2o5 contents cannot have been produced by rutile formation during uhp metamorphism but could have arisen through the accumulation of ilmenite and apatite in a high ti protolith they have ocean island basalt oib like trace element patterns with enrichment in light rare earth elements lrees and high field strength elements hfses nb ta zr and hf the hf isotopic compositions of the residual magmatic zircon cores in type 1 rutile bearing eclogites ehf 845 1 4 to 6 0 tdm 1 2 1 5 ga indicate that their parental magmas were derived from the proterozoic mantle however they show initial 87sr 86sr values of 0 71059 0 71326 and end 845 values of 1 5 to 2 5 suggesting significant crustal contamination thus the type 1 rutile bearing eclogites may have originated through partial melting of an oib type mantle plume source during the neoproterozoic rifting of the rodinia supercontinent in contrast the type 2 rutile bearing eclogites which are hosted in a mafic ultramafic ophiolitic complex have protolith ages of 449 3 ma and eclogite facies metamorphic ages of ca 435 433 ma correlations between the whole rock mgo and the major and trace element contents of type 2 rutile bearing eclogites suggest that they are derived from cumulates with alternating olivine and pyroxene rich and ilmenite rich layers they have mid ocean ridge basalt morb and oib like trace element patterns indicating extensive fractional crystallization and the possibility that there were multiple injections of magma during the formation of the protolith meanwhile the 0 6 to 4 3 end 449 values and 1 8 to 11 8 ehf 449 values of the type 2 rutile bearing eclogites indicate that the protoliths may have been generated by partial melting of a mantle wedge source metasomatized by slab derived components the short interval ca 14 my between magma generation and eclogite facies metamorphism in combination with the type of rock assemblage within which they are found indicates that the type 2 rutile bearing eclogites originated in a supra subduction zone ssz ophiolite type 1 and type 2 rutile bearing eclogites have similar eclogite facies metamorphic ages of ca 435 433 ma indicating that the type 1 and ssz related type 2 protoliths were incorporated into a subduction melange that was dragged down the subduction channel and underwent eclogite facies metamorphism via subduction of the qaidam block eventually forming eclogite type rutile deposits

zircons reveal multi stage genesis of the xiangdong dengfuxian tungsten deposit south china abstract as a typical tungsten deposit of the xitian ore field nanling range south china the xiangdong deposit is a quartz vein type w deposit related to a triassic jurassic granitic complex with total ore reserves of 7 mt wo3 30 kt in this study zircon cl and bse imaging la mc icp ms u pb dating trace element and hf isotopic analyses were carried out on the fluid altered granites and related w ores in the xiangdong deposits aiming to reveal the genesis of the deposit zircon u pb dating yielded three age clusters pre triassic 250 ma n 19 triassic 227 214 ma or 220 ma n 111 and jurassic 159 149 ma or 150 ma n 27 zircon morphology and geochemistry suggest that triassic granites and jurassic quartz veins experienced stronger influences from high temperature hydrothermal fluids than other geological bodies in the deposit high contents of p y pb and u are found in triassic granite zircons whereas high concentrations of nb and ta occur in jurassic quartz vein zircons indicating different hydrothermal fluid systems during the triassic and jurassic the triassic and jurassic zircons yield high y ho ratios up to 35 representing fractionated non chondritic compositions which are indicative of a late stage residual melt that co existed with f rich fluids decreases in zircon ce ce and eu eu ratios from the triassic to the jurassic suggest a decline in fo2 that is likely to have facilitated large scale jurassic w mineralization high 176yb 177hf and 176lu 177hf ratios in the hydrothermally altered jurassic zircons indicate intense fluid exsolution from the source magma whereas the more variable 176hf 177hf ratios and hf model ages of the triassic zircons suggest multiple fluid sources and more complex alteration processes a new ore genesis model is proposed for the xiangdong w deposit initial enrichment of ore materials during the late triassic followed by large scale tungsten precipitation during the late jurassic the triassic granite provided the initial w source whereas granite derived fluids successively formed magma differentiated ore veins and infilling metasomatic ore veins during the jurassic

volcanism mineralization and metamorphism at the xitieshan pb zn deposit nw china insights from zircon geochronology and geochemistry abstract the footwall volcanic rocks of the ordovician tanjianshan group in the world class xitieshan pb zn deposit have experienced prolonged arc volcanism followed by strong metamorphism and deformation this has resulted in a complex thermal history and led to ambiguity in interpretation of zircon geochronological results an integrated study involving textural characterization cl imaging trace element analysis ti in zircon thermometry and la icpms u pb dating has provided tight constraints on the age and genesis of the zircon groups in the volcanic rocks the temperature of metamorphism and deformation indicated by metacryst minerals and micro structures in the volcanic rocks ranges from 550 to 650 c which partially overlaps with the lower temperature range of zircon crystallization 600 750 c calculated using the ti in zircon thermometer cathodoluminescence images and trace element compositions confirm a magmatic origin for the zircons which have also been variably altered by metamorphic fluids two ranges of u pb ages 475 470 ma and 460 450 ma have been obtained on typical magmatic zircons and are interpreted to represent pre mineralization arc volcanism in the xitieshan deposit a younger age group of 440 430 ma for the fluid modified zircons is considered to record post ore metamorphism during the north qadaim orogeny thus we propose that the original exhalative ores at the xitieshan pb zn deposit formed at 450 440 ma

fluid zircon interaction during low temperature hydrothermal processes implications for the genesis of the banxi antimony deposit south china abstract fluid zircon interaction in hydrothermal systems may provide key information on fluid characterization and ore precipitation in this study in situ analyses of hf isotopes in zircon combined with u pb ages and major and trace element data provide new insights into fluid genesis at the banxi antimony deposit the zircons separated from typical quartz stibnite ores and altered wall rocks have undergone fluid modification to different degrees showing hydrothermal overprints in reflected transmitted light back scattered electron bse and cathodoluminescence cl images and variable concentrations of si zr hf u th pb ti nb ta p f y and rare earth elements they possess identical u pb ages to the banxi group and underlying lengjiaxi group clastic rocks but distinct 176hf 177hf 176lu 177hf and 176yb 177hf ratios indicating the possible changing of lu hf systematics during the hydrothermal alteration the evidence suggests a contribution of ore material from the banxi group and a deeper fluid source derived from the lengjiaxi group and the crystalline basement beneath it a fluid mixing model is proposed wherein the deep sourced high radiogenic hf fluid mixed with circulating near surface meteoric component dominated fluid triggering antimony precipitation the u pb chronometer was not reset during this low temperature mineralization event whereas the lu hf systematics in the fluid altered zircons show evidence of lattice breakdown of the old zircons during fluid mixing coupled with external input of highly radiogenic hf from the crystalline basement this research highlights the potential to use zircon structure and geochemistry in tracing complex fluid evolutionary processes

zircon geochronology and geochemistry of the xianghualing a type granitic rocks insights into multi stage sn polymetallic mineralization in south china abstract highly evolved sn polymetallic mineralization related granites are intensively developed in the nanling range of south china in this study two types of granitic rocks albite granite and greisenized granite from the laiziling pluton in the xianghualing area were studied to elucidate magma evolution and the genesis of mineralization the a type xianghualing granitic rocks are characterized by high sio2 69 16 85 04 rb 759 2110 ppm ta 17 2 50 8 ppm nd 2 8 82 4 ppm and 87sr 86sr 0 907275 4 181262 and low mgo 0 01 0 98 tio2 0 01 0 03 sr 1 4 70 2 ppm ba 1 4 132 5 ppm eu 0 03 0 21 ppm and 143nd 144nd 0 512283 0 512326 the whole rock end t values range from 6 3 to 6 0 with t2dm ages of 1426 1454 ma the zircon ehf t values mostly range from 10 to 5 with dominant tdmc values of 1400 1800 ma this suggests that the xianghualing granitic rocks were derived from partial melting of mesoproterozoic basement rocks in the cathaysian block in a lithospheric extension setting zircon u pb dating yielded five age clusters proterozoic 900 ma n 9 silurian 430 ma n 4 triassic 220 ma n 16 jurassic 150 ma n 62 and cretaceous 80 ma n 28 zircon internal textures trace element contents and hf isotopic compositions indicate that they formed from a range of sources including residual zircons from the magma source region detrital zircons from local sediments zircons captured from pre existing magmatic rocks with obvious mantle signatures magmatic and fluid altered zircons and late stage hydrothermal zircons this suggests significant fractional crystallization weak wall rock assimilation contamination and intense fluid differentiation metasomatism during the genesis of the xianghualing granitic rocks m type ree tetrad effects are seen not only in bulk rock compositions but also in individual zircon grains indicating that highly fractionated and reduced f rich fluids played an important role in the formation of sn polymetallic mineralization guided by the major mesozoic w sn ore forming events occurring in the cathaysian block of south china a multi stage genetic model is proposed for the xianghualing granitic minerogenic system initial enrichment of w sn in the triassic 220 ma dominant sn polymetallic metal precipitation in the jurassic 150 ma and superimposed mineralization in the cretaceous 80 ma

genesis of the giant shizhuyuan w sn mo bi pb zn polymetallic deposit south china constraints from zircon geochronology and geochemistry in skarns abstract the giant shizhuyuan w sn mo bi pb zn polymetallic skarn type deposit which lies in the world famous nanling w sn metallogenic belt has a close affinity with the qianlishan granite complex previous studies focused on the qianlishan granitoids rather than relevant skarns where the evolutionary processes of skarn forming fluids mineralized fluids and sources of metals are debated this study carried out systematic epma and la icpms zircon u pb dating major and trace element and lu hf isotopic analyses for three types of skarns ore free greisen stockwork and sulfide bearing skarns at shizhuyuan the whole skarn zircons were classified into six age clusters 125 187 ma 235 ma 345 509 ma 677 772 ma 811 921 ma and 1000 ma and three genetic types detrital magmatic and hydrothermally altered among them the majority of the skarn zircons are of detrital origin 345 to 2225 ma peaking at 410 ma 710 ma and 905 ma and showing a wide range of th u ratios 0 05 7 09 they share similar characteristics of zircons hosted by devonian strata in south china suggesting the inheritance from wall rock the magmatic zircons in skarns can be further subdivided into two clusters triassic 235 ma and jurassic 150 ma which are derived from the corresponding granite ore free skarn contains only detrital zircons that have experienced the weakest alteration indicating the minor participation of granitic fluid the greisen stockwork skarn consists of both detrital zircons and jurassic magmatic hydrothermal zircons implying that granitic and stratigraphic materials may both contribute greatly to the w sn polymetallic mineralization sulfide bearing skarn includes abundant detrital zircon a few of triassic zircons but no jurassic zircons indicating that the latest sulfide mineralization was dominated by sediments rather than granitic rocks the two mineralized skarn zircons display elevated concentrations of most trace elements e g u ree ti y p nb and ta coupled with decreased si and zr which reflects strong fluid rock reaction the lowest ratios of ce ce 1 22 89 78 mean 24 13 in greisen stockwork skarn zircons reveal the most reducing environment for the main w sn mineralizing event jurassic zircons are homogeneous in 176hf 177hf 0 282352 0 282454 and ehf t 11 58 to 7 27 in well accord with local granitic rocks triassic zircons have variable ehf t 9 5 to 1 6 values suggesting more mantle input of precursor pluton before the jurassic main mineralization event based on the zircon geochronology in skarns we speculate that concealed triassic magmatism exists in the deep shizhuyuan area consequently a three stage ore forming model was established for the giant shizhuyuan deposit this study further illustrates that zircon can be used as an important indicator for ore genesis in complex metallogenic systems

carbonate abundances and isotopic compositions in chondrites we report the bulk c abundances and c and o isotopic compositions of carbonates in 64 cm chondrites 14 cr chondrites 2 ci chondrites lew 85332 c2 kaba cv3 and semarkona ll3 0 for the unheated cms the total ranges of carbonate isotopic compositions are 13c 25 75 and 18o 15 35 and bulk carbonate c contents range from 0 03 to 0 60 wt there is no simple correlation between carbonate abundance and isotopic composition or between either of these parameters and the extent of alteration unless accretion was very heterogeneous the uncorrelated variations in extent of alteration and carbonate abundance suggests that there was a period of open system behavior in the cm parent body probably prior to or at the start of aqueous alteration most of the ranges in cm carbonate isotopic compositions can be explained by their formation at different temperatures 0 130 c from a single fluid in which the carbonate o isotopes were controlled by equilibrium with water 18o 5 and the c isotopes were controlled by equilibrium with co and or ch4 13c 33 or 20 for co or ch4 dominated systems respectively however carbonate formation would have to have been inefficient otherwise carbonate compositions would have resembled those of the starting fluid a quite similar fluid composition 18o 5 5 and 13c 31 or 17 for co or ch4 dominated systems respectively can explain the carbonate compositions of the cis although the formation temperatures would have been lower 10 40 c and the relative abundances of calcite and dolomite may play a more important role in determining bulk carbonate compositions than in the cms the cr carbonates exhibit a similar range of o isotopes but an almost bimodal distribution of c isotopes between more 13c 65 80 and less altered samples 13c 30 40 this bimodality can still be explained by precipitation from fluids with the same isotopic composition 18o 9 25 and 13c 21 or 8 for co or ch4 dominated systems respectively if the less altered crs had higher mole fractions of co2 in their fluids semarkona and kaba carbonates have some of the lightest c isotopic compositions of the meteorites studied here probably because they formed at higher temperatures and or from more co2 rich fluids the fluids responsible for the alteration of chondrites and from which the carbonates formed were almost certainly accreted as ices by analogy with cometary ices co2 and or co would have dominated the trapped volatile species in the ices the chondrites studied are too oxidized for co dominated fluids to have formed in their parent bodies if ch4 was the dominant c species in the fluids during carbonate formation it would have to have been generated in the parent bodies from co and or co2 when oxidation of metal by water created high partial pressures of h2 the fact that the chondrite carbonate c h2o mole ratios are of the order predicted for co co2 h2o ices that experienced temperatures of 50 100 k suggests that the chondrites formed at radial distances of 4 15 au

global comparisons of volcanic associated massive sulphide districts although volcanic associated massive sulphide vms deposits have been studied extensively the geodynamic processes that control their genesis location and timing remain poorly understood compar

whole rock and zircon geochemistry of the xiaoliugou granites north qilian orogen nw china implications for tectonic setting magma evolution and w mo mineralization abstract ordovician w mo polymetallic mineralization related granites are widely developed in the western section of the north qilian orogen nw china in order to shed light on the tectonic setting magma evolution and genesis of mineralization in the orogeny highly evolved granitic rocks monzogranites from the qibao and qiqing deposits in the xiaoliugou ore field were studied typical of subduction related a type granites the xiaoliugou granitic rocks are enriched in sio2 rb th u ta nd zr and hf but relatively depleted in ba sr p and eu the variable initial whole rock 87sr 86sr ratios 0 62937 0 70543 and wide range of zircon ehf t values 18 to 6 suggesting mantle crust interaction and mixing of depleted mantle and deep crust in the source area whole rock elemental and rb sr isotopic geochemistry suggest slow cooling significant fractional crystallization weak wall rock assimilation contamination and intense fluid differentiation metasomatism during the genesis of the xiaoliugou granitic rocks zircon u pb dating yielded three age clusters precambrian 540 ma n 32 ordovician 450 ma n 40 and cretaceous 135 ma n 18 zircon internal textures indicate a range of sources including residual detrital zircons from the magma source region and local sediments magmatic and fluid altered zircons and late stage hydrothermal zircons zircon trace element and lu hf isotopic compositions suggest fluid metasomatism during granite emplacement in the ordovician and overprinting by a more evolved oxidized fluid in the cretaceous involvement of a late high temperature highly fractionated f rich fluid could have enhanced w mo mineralization consequently a two stage genetic model is proposed for the xiaoliugou granitic minerogenic system involving primary mineralization in the ordovician 450 ma followed by a cretaceous magmatic hydrothermal overprint 135 ma

record of multiple stage channelized fluid and melt activities in deeply subducted slab from zircon u pb age and hf o isotope compositions abstract geochemical features of island arc rocks require two slab derived components of a melt and a fluid added to their sources these two liquids may unite to an intermediate aqueous melt at the base of volcanic arc direct evidence of this process has been scarce yet here we present an integrated study of in situ u pb age trace element and o hf isotope for zircons from a suite of a quartz vein a felsic vein their host eclogite and surrounding gneiss at the xitieshan uhp terrane of the north qaidam metamorphic belt nqmb oscillatory zoned zircons from the quartz vein are enriched in u li nb and ree with a formation age of 442 6 ma consistent with the timing of the peak uhp metamorphism this demonstrates there is no temporal gap between the uhp metamorphism and fluid flow in the xitieshan terrane in particular the oscillatory zoned zircons of the quartz vein have similar hf isotope compositions to zircons from the surrounding gneiss but variable o isotope compositions between the host eclogite and surrounding gneiss the fluid from surrounded gneiss was thus an aqueous melt with high transport ability for lu and hf and o while the fluid from the host eclogite was an aqueous fluid only with the ability to transport o according to the similar behaviors of granitic rock and sediment it is inferred that a channelized hydrous melt can be formed in the downgoing sediment layer where an aqueous fluid can be formed from underlying basalt and or peridotite layers at the sub arc depth the two types of fluid are fed to the overlying mantle wedge from subducting slab to form island arc rock by contrast the zircons in the felsic vein yield a weighted mean 206pb 238u age of 420 4 ma which can be regard as the timing of partial melting during the exhumed stage for the xitieshan uhp rocks the zircon o and hf isotopic features of the felsic vein are between the country gneiss and host eclogite compatible with their emanating from hydrous melt of both the eclogite and gneiss during the exhumation stage of the uhp rocks this indicates that hydrous melt would be released from both the sediment and basalt or peridotite layers of the subducting slabs at relatively shallow depth

effusive eruption of viscous silicic magma triggered and driven by recharge a case study of the cerro chascon runtu jarita dome complex in southwest bolivia the cerro chascon runtu jarita complex is a group of ten late pleistocene 85 ka lava domes located in the andean central volcanic zone of bolivia these domes display considerable macroscopic and microscopic evidence of magma mixing two groups of domes are defined chemically and geographically a northern group the chascon consists of four lava bodies of dominantly rhyodacite composition these bodies contain 43 48 phenocrysts of plagioclase quartz sanidine biotite and amphibole in a microlite poor rhyolitic glass rare mafic enclaves and selvages are present mineral equilibria yield temperatures from 640 to 750 c and log o2 of 16 geochemical data indicate that the pre eruption magma chamber was zoned from a dominant volume of 68 to minor amounts of 76 sio2 this zonation is best explained by fractional crystallization and some mixing between rhyodacite and more evolved compositions the mafic enclaves represent magma that intruded but did not chemically interact much with the evolved magmas a southern group the runtu jarita is a linear chain of six small domes 1 km3 total volume that probably is the surface expression of a dike the five most northerly domes are composites of dacitic and rhyolitic compositions the southernmost dome is dominantly rhyolite with rare mafic enclaves the composite domes have lower flanks of porphyritic dacite with 35 vol phenocrysts of plagioclase orthopyroxene and hornblende in a microlite rich rhyodacitic glass sieve textured plagioclase mixed populations of disequilibrium plagioclase compositions xenocrystic quartz and sanidine with ternary composition reaction rims indicate that the dacite is a hybrid the central cores of the composite domes are rhyolitic and contain up to 48 vol phenocrysts of plagioclase quartz sanidine biotite and amphibole this is separated from the dacitic flanks by a banded zone of mingled lava macroscopic microscopic and petrologic evidence suggest scavenging of phenocrysts from the silicic lava mineral equilibria yield temperatures of 625 727 c and log o2 of 16 for the rhyolite and 926 1000 c and log o2 of 9 5 for the dacite the rhyolite is zoned from 73 to 76 sio2 and fractionation within the rhyolite composition produced this variation most of the 63 73 sio2 compositional range of the lava in this group is the result of mixing between the hybrid dacite and the rhyolite eruption of both groups of lavas apparently was triggered by mafic recharge a paucity of explosive activity suggests that volatile and thermal exchanges between reservoir and recharge magmas were less important than volume increase and the lubricating effects of recharge by mafic magmas for the runtu jarita group the eruption is best explained by intrusion of a dike of dacite into a chamber of crystal rich rhyolite close to its solidus the rhyolite was encapsulated and transported to the surface by the less viscous dacite magma which also acted as a lubricant simultaneous effusion of the lavas produced the composite domes and their zonation reflects the subsurface zonation the role of recharge by hotter more fluid mafic magma appears to be critical to the eruption of some highly viscous silicic magmas

oxygen isotopic ratios of primordial water in carbonaceous chondrites abstract in this work i estimate the 18 o and 17 o values of primordial water in cm chondrites to be 55 13 and 35 9 respectively based on whole rock o and h data also i found that the o and or h data of antarctic meteorites are biased which is attributed to terrestrial weathering this characteristic o isotopic ratio of water together with corresponding water abundances in cm chondrites are consistent with the origin of water as ice processed by photochemical reactions at the outer regions of the solar nebula where mass independent o isotopic fractionation and water destruction may have occurred another possible mechanism to produce the inferred o isotopic ratio of water would be o isotopic fractionation between water vapor and ice which likely occurred near the condensation front of h2o snow line in the solar nebula the inferred o isotopic ratio of water suggests that carbonate in cm chondrites formed at low temperatures of

zircon morphology geochronology and trace element geochemistry of the granites from the huangshaping polymetallic deposit south china implications for the magmatic evolution and mineralization processes abstract the huangshaping polymetallic deposit is a large scale deposit located in the central nanling region south china different types of mineralization have been classified in the area which are attributed to three types of granitoids from the composite granitic pluton quartz porphyry granophyre and granite porphyry in order to study the magmatic genesis and evolutionary process as well as constrain the crystallization and mineralization events 100 zircon separates from different intrusive stages of the pluton have been analyzed for trace element contents and u pb isotopic concentrations the results show that zircons from the huangshaping granitoids are enriched in th u hf ti ree and other trace elements indicating hydrothermal fluid alteration and transformation additionally there is a large variation between different types of granitoids in terms of trace element concentrations compared to the zircons from the quartz porphyry and the granophyre zircons from the granite porphyry are more enriched in th u hf ti and p but strongly depleted in eu this suggests that the magma that formed the granite porphyry possessed higher temperatures possibly experienced stronger crystal fractionation and originated from a more evolved complex magmatic source region with higher degree of crustal maturity combined with characteristics of crystal morphology and internal texture hydrothermal zircons were distinguished from magmatic zircons in each granitoid to reveal mineralization processes the u pb geochronology results show that there are two major stages of mineralization 190 ma weak cu pb zn mineralization related to the quartz porphyry and the granophyre and 155 ma strong w sn mo pb zn mineralization associated with the granite porphyry compositions of these hydrothermal zircons suggest that the earlier stage mineralization could be close to single relatively cold reduced and quickly ascended fluids whereas the later stage might be related to hot oxidized strongly fractionated and highly evolved mixed fluids this study also indicates that hydrothermal zircons from typical composite granitic plutons could be a good tool to reveal the multi stage magmatic and mineralization process in middle to late jurassic south china

re os and u pb geochronology of the shazigou mo polymetallic ore field inner mongolia implications for permian triassic mineralization at the northern margin of the north china craton abstract the recently discovered polymetallic shazigou mo w pb zn ore field is located at the northern margin of the north china craton this integrated metallogenic system is comprised of quartz vein mineralization in three deposits shazigou mo w jindouzishan pb zn and mantougou pb zn the total reserves are estimated to be 50 kt mo 626 t wo3 244 kt pb and 150 kt zn molybdenite re os dating of five quartz vein type ores yielded a mean model age of 243 8 1 6 ma mswd 0 81 and hydrothermal zircons yielded a concordant u pb age of 245 2 6 ma mswd 0 65 these results suggest that the mineralization was formed in the early triassic and could be related to paleo asian ocean subduction microthermometry and quartz fluid inclusion compositions indicate that fluids related to the mo w mineralization were mainly derived from magmatic sources and precipitated under relatively high temperature 280 340 c and salinity conditions 6 9 wt nacl equiv whereas subsequent pb zn mineralization related fluids may have been modified by metamorphic and meteoric waters the discovery of the shazigou ore field suggests conditions may be favourable for more extensive mineralization in the western xilamulun mo metallogenic belt at the northern margin of the north china craton

stability analysis of rock slope based on an abstraction ant colony clustering algorithm the study of the stability of rock slope is very important because its instability can cause large disasters because the main influence factor of the stability of rock slope is the geological environment the engineering experience analogy method is a practical and extensively applied method the main feature of the engineering analogy method is the cluster based on the analysis of a dataset of rock slope samples and using the engineering analogy method in relation to the abstraction ant colony clustering algorithm a new method for rock slope stability analysis is proposed using this method rock slopes can be automatically clustered to obtain the stability status of rock slopes in one class therefore the class rating can represent the stability status of rock slopes some real engineering examples are used to verify the computing effect of the new algorithm engineering applications prove that this new algorithm can automatically estimate the stability of rock slope with high validity its robustness surpasses the robustness of traditional algorithms and its application is more convenient than that of traditional algorithms however as a heuristic algorithm the selection of algorithm parameters is sometimes challenging and the computation effect for a highly complex problem is not satisfactory therefore this practical method of slope stability analysis should be popularized